SRF2013 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOIOA01	The FRIB Project at MSU	cryomodule, linac, ion, operation	1
	M. Leitner, B. Bird, F. Casagrande, S. Chouhan, C. Compton, J.L. Crisp, K. Elliott, A. Facco, A.D. Fox, M. Hodek, M.J. Johnson, G. Kiupel, I.M. Malloch, D. Miller, S.J. Miller, D. Morris, D. Norton, R. Oweiss, J.P. Ozelis, J. Popielarski, L. Popielarski, A.P. Rauch, R.J. Rose, K. Saito, M. Shuptar, N.R. Usher, G.J. Velianoff, D.R. Victory, J. Wei, J. Whitaker, K. Witgen, T. Xu, Y. Xu, O. Yair, S. Zhao FRIB, East Lansing, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661. The Facility for Rare Isotope Beams (FRIB) is ready to start construction. The facility will utilize a high-intensity, heavy-ion driver linac to provide stable ion beams from protons to uranium up to energies of >200 MeV/u and at a beam power of up to 400 kW. The superconducting cw linac consists of 330 individual low-beta (β = 0.041, 0.085, 0.29, and 0.53 at 80.5 MHz and 322 MHz) cavities in 49 cryomodules operating at 2 K. This paper discusses the current development status of the project with emphasis on the linac SRF acquisition. SRF coldmass and cryomodule component designs are briefly summarized. A SRF production facility, currently under construction, is described.
	Slides MOIOA01 [9.804 MB]

MOIOA02	Status and Challenges of Spiral2 SRF Linac	cryomodule, linac, vacuum, ion	11
	R. Ferdinand, P.-E. Bernaudin, M. Di Giacomo GANIL, Caen, France P. Bosland CEA/IRFU, Gif-sur-Yvette, France Y. Gómez Martínez LPSC, Grenoble Cedex, France G. Olry IPN, Orsay, France
	GANIL is presently extending its experimental facility with the new SPIRAL2 project. It is based on a multi-beam Superconducting Linac Driver delivering 5 mA deuterons up to 40 MeV and 1 mA heavy ions up to 14.5 MeV/u. Several domains of research in nuclear physics at the limits of stability will be covered by this new accelerator. SPIRAL2 construction has two phases. SPIRAL2 phase 1 includes the superconducting accelerator driver, and the construction of the two research areas where the accelerated protons and deuterons will generate extremely intense neutron beams for fundamental physics experiments and numerous applications. SPIRAL2 will also accelerate stable heavy ion beams of very high intensity. The phase2 includes the RIB production building and links to the existing GANIL accelerator complex for RIB post acceleration. The Superconducting Linac incorporates many innovative developments of the Quarter-Wave resonators and their associated cryogenic and RF systems. The installation of the SPIRAL2 accelerator at GANIL has started. Status of the Spiral 2 SRF linac will be presented, focusing on the various SRF challenges met by this project and how/what solutions were chosen. * on behalf of the SPIRAL2 project and superconducting teams
	Slides MOIOA02 [87.841 MB]

MOIOA03	The Challenge and Realization of the Cavity Production and Treatment in Industry for the European XFEL	niobium, controls, superconductivity, HOM	18
	W. Singer, J. Iversen, A. Matheisen, H. Weise DESY, Hamburg, Germany P. Michelato INFN/LASA, Segrate (MI), Italy
	The main effort in production of 1.3 GHz cavities for the EXFEL was dedicated to transfer the superconducting technology to the industry. These know how transfer is executed by DESY and INFN/LASA team. The preparation phase based on prototype cavities covered: qualification of potential vendors for material and cavity fabrication; work out recipe and strategy for qualification of the infrastructure for cavity surface treatment at industry; definition of the quality management strategy, documentation and electronically data exchange. Production of 800 series cavities on the principle “build to print” is contracted to companies Research Instruments and Ettore Zanon. High purity niobium and NbTi for resonators provides DESY. The principles of the material and cavities production in conformity with European Pressure Equipment Directive are developed together with the notified body. New or upgraded infrastructure has been established at both companies. The first several tens of series cavities have been produced and treated. Most of the cavities handed over to DESY up to now fulfill immediately the EXFEL specifications. The cavity production for EXFEL will be finished mid of 2015.
	Slides MOIOA03 [7.394 MB]

MOIOA04	SRF Challenges for Energy Recovery Linacs	SRF, HOM, linac, operation	24
	A. Burrill HZB, Berlin, Germany
	Many of the challenges associated with operating a SRF ERL are independent of the choice of operating frequency, beam energy, and overall purpose of the machine. Worldwide there are an increasing number of ERLs in various stages of development and operation which are facing a number of similar challenges and often solving them in very different ways. In this talk I will seek to summarize the main challenges the community as a whole faces, address how different laboratories are working to solve these problems, and seek to identify areas of overlap where the community can work together to solve some of these common problems.
	Slides MOIOA04 [5.213 MB]

MOIOA05	SRF in Heavy Ions Projects	linac, ion, heavy-ion, cryomodule	30
	D. Jeon IBS, Daejeon, Republic of Korea
	SRF technologies are widely applied to heavy ion accelerator projects in the world such as the RAON, C-ADS, HIAF, FRIB, SPIRAL2, ISAC-II, HIE-ISOLDE etc. In this talk, status report, design choices and SRF challenges met in heavy ion machines are presented.
	Slides MOIOA05 [10.228 MB]

MOIOB01	High Power Proton/Deuteron Accelerators	linac, SRF, proton, operation	35
	J.-L. Biarrotte IPN, Orsay, France
	High power proton and deuteron linear accelerators can give rise to a large variety of scientific applications, useful for both fundamental and applied research. Thanks to the on-going efficient development of the superconducting RF technology, more and more projects based on such machines have emerged during the last 2 decades. This paper will review these existing high power proton/deuteron accelerator facilities or projects, trying in particular to emphasize in each case the various specificities and challenges related to the SRF technology.
	Slides MOIOB01 [4.474 MB]

MOIOB02	Towards a 100mA Superconducting RF Photoinjector for BERLinPro	cathode, laser, emittance, SRF	42
	A. Neumann, W. Anders, A. Burrill, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, P. Lauinger, A.N. Matveenko, M. Schmeißer, J. Völker HZB, Berlin, Germany G. Ciovati, P. Kneisel JLAB, Newport News, Virginia, USA R. Nietubyć NCBJ, Świerk/Otwock, Poland S.G. Schubert, J. Smedley BNL, Upton, Long Island, New York, USA J.K. Sekutowicz DESY, Hamburg, Germany V. Volkov BINP SB RAS, Novosibirsk, Russia I. Will MBI, Berlin, Germany E.N. Zaplatin FZJ, Jülich, Germany
	For BERLinPro, a 100 mA CW-driven SRF energy recovery linac demonstrator facility, HZB needs to develop a photo-injector superconducting cavity which delivers a at least 1mmmr emittance beam at high average current. To address these challenges of producing a high peak brightness beam at high repetition rate, at first HZB tested a fully superconducting injector with a lead cathode,followed now by the design of a SC cavity allowing operation up to 4 mA using CW-modified TTF-III couplers and inserting a normal conducting high quantum efficiency cathode using the HZDR-style insert scheme. This talk will present the latest results and an overview of the measurements with the lead cathode cavity and will describe the design and optimization process, the first production results of the current design and an outlook to the further development steps towards the full power version. *T. Kamps et al., Proceedings of the 2nd International Particle Accelerator Conference, San Sebastián, Spain, 2011.
	Slides MOIOB02 [7.574 MB]

MOIOB03	SRF Photoemission Electron Guns at BNL: First Commissioning Results	gun, SRF, electron, cathode	50
	S.A. Belomestnykh BNL, Upton, Long Island, New York, USA S.A. Belomestnykh Stony Brook University, Stony Brook, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE Two SRF photoemission electron guns are under development at BNL. The first gun operates at 704 MHz and is design to deliver high bunch charge and high average current beams for the R&D ERL accelerator. Its cavity is of an elliptical geometry. The gun cryomodule has been commission without a cathode up to the design voltage of 2 MV. The experiments with a copper cathode are underway. The second gun utilizes a quarter wave resonator geometry with coaxial cathode insert and beam tube RF power coupler. It will be used to produce high bunch charges, but low average beam currents for the coherent electron cooling proof-of-principle experiment. This 112 MHz SRF gun was first tested two years ago. Since then it was rebuilt in a new cryomodule and cryogenically re-tested in late 2012/early 2013, reaching the accelerating gap voltage of 0.9 MV. This paper describes main design features of two SRF guns, presents test results and discusses future plans.
	Slides MOIOB03 [3.431 MB]

MOIOB04	Commissioning and Operation of DC-SRF Injector	SRF, controls, LLRF, experiment	53
	K.X. Liu, J.E. Chen, L.W. Feng, J.K. Hao, S. Huang, L. Lin, S.W. Quan, F. Wang, Zh.W. Wang, X.D. Wen, H.M. Xie, K. Zhao, F. Zhu PKU, Beijing, People's Republic of China
	As a new and compact injector with medium beam current, the DC-SRF injector at Peking University has been upgraded recently mainly on DC part and heat loading. With a new 20kW solid state RF power source, an improved LLRF system and related diagnostic devices on the new beam line, a series of experiments have been carried out for stably operating the DC-SRF injector at 2K temperature. The description of the system, experiment process and results will be presented.
	Slides MOIOB04 [4.992 MB]

MOIOC01	Heat Transfer at the Interface Between Niobium and Liquid Helium for 6 GHz SRF Cavities	niobium, interface, coupling, operation	57
	V. Palmieri INFN/LNL, Legnaro (PD), Italy
	Cavity Thermal Boundary Resistance is something extremely complex and not completely understood by the theory. Often identified with the Kapitza resistance or with the Khalatnikov acoustic phonon mismatch at the interface metal-liquid Helium, it depends on so many different and uncontrolled parameters, that its interpretation is not covered by a complete treatise of the phenomenon. Therefore, 99% of the literature on superconducting cavities worries about the cavity interior surface state,while almost nothing is reported on treatments applied to the exterior. In the authors opinion, there is a lack in experimental data analysis due to the fact that the cavity is often considered as a whole adiabatic entity interacting only with RF fields. On the contrary, the cavity is immersed in liquid Helium and the cavity behavior cannot prescind from its thermal properties. Indeed in the normal state He-I has poor thermal conductivity and high specific heat. Moreover the heat exchange at HeII obeys to further mechanisms besides the phonon mismatch. Driven by the hypothesis that thermal losses are dominant for ultraclean cavities, we have collected a plethora of surprising experimental results.
	Slides MOIOC01 [15.558 MB]

MOIOC02	A New First-Principles Calculation of Field-Dependent RF Surface Impedance of BCS Superconductor	impedance, electron, niobium, superconductivity	63
	B. P. Xiao, C.E. Reece JLab, Newport News, Virginia, USA B. P. Xiao BNL, Upton, Long Island, New York, USA
	Funding: This manuscript has been authored in part by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. There is a need to understand the intrinsic limit of RF surface impedance that determines the performance of superconducting RF cavities in particle accelerators. Here we present a field-dependent derivation of Mattis-Bardeen theory of the RF surface impedance of BCS superconductors, based on the shifted density of states resulting from coherently moving Cooper pairs. Our theoretical prediction of the effective BCS RF surface resistance of niobium as a function of peak surface magnetic field amplitude agrees well with recently reported record low loss resonant cavity measurements from JLab and Fermi Lab with carefully prepared niobium material. The surprising reduction in resistance with increasing field is explained to be an intrinsic effect.
	Slides MOIOC02 [3.122 MB]

MOP001	CASCADE: a Cavity Based Dark Matter Experiment	experiment, photon, shielding, detector	66
	M.K. Kalliokoski, I.R. Bailey, N. Woollett Lancaster University, Lancaster, United Kingdom G. Burt, A.C. Dexter Cockcroft Institute, Lancaster University, Lancaster, United Kingdom S. Chattopadhyay Cockcroft Institute, Warrington, Cheshire, United Kingdom J.B. Dainton The University of Liverpool, Liverpool, United Kingdom P. Goudket, A.J. Moss, S.M. Pattalwar, T.T. Thakker, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	An experiment is proposed that uses a pair of RF cavities as a source and detector of hidden sector photons (HSP). HSP's are hypothetical low-mass dark matter candidates with coupling to ordinary photons. SRF cavities are favoured in this experiment as they are able to store a high number of photons for a given input power due to the high Q available. When powered, such a cavity will act as a source of HSPs, while an empty cavity will be able to capture any HSP's decaying back into RF photons. Such an experiment (CASCADE) is being developed at the Cockcroft Institute using single cell 1.3 GHz cavities previously utilised for manufacturing and BCP studies. The aims of the CASCADE project are detailed, along with the system specification.

MOP002	Conceptual Design for Replacement of the DTL and CCL with Superconducting RF Cavities in the Spallation Neutron Source Linac	linac, cryomodule, DTL, klystron	69
	M.S. Champion, M. Doleans, S.-H. Kim ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. The Spallation Neutron Source Linac utilizes normal conducting RF cavities in the low energy section from 2.5 MeV to 186 MeV. Six Drift Tube Linac (DTL) structures accelerate the beam to 87 MeV, and four Coupled Cavity Linac (CCL) structures provide further acceleration to 186 MeV. The remainder of the Linac is comprised of 81 superconducting cavities packaged in 23 cryomodules to provide a final beam energy of approximately 1 GeV. The superconducting Linac has proven to be substantially more reliable than the normal conducting Linac despite the greater number of stations and the complexity associated with the cryogenic plant and distribution. A conceptual design has been initiated on a replacement of the DTL and CCL with superconducting RF cavities. The motivation, constraints, and conceptual design are presented.

MOP003	Implications of Increased Beam Current for the Diamond Storage Ring RF System	storage-ring, operation, cathode, linac	73
	C. Christou, A. Bogusz, P. Gu, M. Maddock, P.J. Marten, S.A. Pande, A.F. Rankin, D. Spink, A.V. Watkins Diamond, Oxfordshire, United Kingdom
	Diamond Light Source presently operates for users with 300mA beam current and initial tests have begun to upgrade this current towards an ultimate goal of 500mA. The implications of such a beam current increase for the storage ring RF system will be significant, including the installation of a third superconducting cavity and a possible modification of the coupling parameters of the existing cavities. An overview of the planned enhancements of the RF system is presented, including an update of the procurement of a new CESR-design cavity and options for installation and operation of this cavity and supporting infrastructure.

MOP004	The ESS Superconducting Linear Accelerator	cryomodule, linac, SRF, lattice	77
	C. Darve, M. Eshraqi, M. Lindroos, D.P. McGinnis, S. Molloy ESS, Lund, Sweden P. Bosland CEA/IRFU, Gif-sur-Yvette, France S. Bousson IPN, Orsay, France
	The European Spallation Source (ESS) is one of Europe's largest planned research infrastructure. The collaborative project is funded by a collaboration of 17 European countries and is under design and construction in Lund, Sweden. The ESS will bring new insights to the grand challenges of science and innovation in fields as diverse as material and life sciences, energy, environmental technology, cultural heritage solid-state and fundamental physics. A 5 MW, long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle). The choice of SRF technology is a key element in the development of the ESS linear accelerator(linac). The superconducting linac is composed of one section of spoke cavity cryomodule (352 MHz) and two sections of elliptical cavity cryomodules (704 MHz). These cryomodules contain Niobium SRF cavities operating at 2 K. This paper presents the superconducting linac layout and its lifecycle.

MOP006	Status of the SC CW-Linac Demonstrator	linac, solenoid, status, emittance	80
	V. Gettmann, W.A. Barth, S. Jacke, S. Mickat, S. Mickat, A. Orzhekhovskaya GSI, Darmstadt, Germany M. Amberg, K. Aulenbacher, W.A. Barth, S. Jacke, S. Mickat HIM, Mainz, Germany M. Amberg, F.D. Dziuba, H. Podlech, U. Ratzinger IAP, Frankfurt am Main, Germany K. Aulenbacher IKP, Mainz, Germany
	The commissioning of the superconducting (sc) continuous wave (cw) LINAC Demonstrator, financed by the Helmholtz Institute Mainz (HIM) mainly, is planned in 2014. The aim is a “full performance test” at GSI-High Charge Injector (HLI) of a 217 MHz sc CH-Cavity, which is designed by the Institute of Applied Physics (IAP) of the University Frankfurt. Inside the cryostat a suspended frame supports the cavity embedded by two solenoids. All of these components are in fabrication. The testing environment is about to be completed. The radiation protection bunker, and the beam transport line straightforward to the GSI-HLI, comprising beam diagnostic components as well as focusing and steering magnets, has been mounted.

MOP007	The Status of Superconducting Linac and SRF Activities at the SNS	linac, cryomodule, operation, SRF	83
	S.-H. Kim, W. Blokland, M.S. Champion, A. Coleman, M.T. Crofford, M. Doleans, D.L. Douglas, T.V. Gorlov, M.P. Howell, Y.W. Kang, A.P. Shishlo, S.E. Stewart, W.H. Strong ORNL, Oak Ridge, Tennessee, USA R. Afanador, B. DeGraff, B.S. Hannah, S.W. Lee, C.J. McMahan, T.S. Neustadt, S.W. Ottaway, C.C. Peters, J. Saunders, D.M. Vandygriff ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. There have been substantial gains at the Spallation Neutron Source (SNS) in last 7 years in understanding pulsed superconducting linac (SCL) operation including system and equipment limiting factors and resolution of system and equipment issues. Significant effort and focus are required to assure ongoing success of the operation, maintenance and improvement of the SCL, and to address the requirements of the upgrade project in the future. The SNS is taking a multi-faceted approach to maintaining and improving its linac. A balanced set of facilities which support processing, assembly, repair, and testing of cavities/cryomodules are currently being placed into service. This paper summarizes the status of the SNS SCL and related superconducting radio-frequency (SRF) activities such as development of ASME code-stamped spare cryomodules, R&D activities for SRF cavity performance improvements, SRF cavity development for power upgrade project and SRF facility development/upgrade to support all required activities.

MOP008	SUPERCONDUCTING LINAC FOR THE RISP	linac, cryomodule, proton, ion	89
	H.J. Kim, H.J. Cha, M.O. Hyun, H.J. Jang, D. Jeon, J.D. Joo, M.J. Joung, H.C. Jung, Y. Jung, Y. Kim, M. Lee, G.-T. Park IBS, Daejeon, Republic of Korea
	The RISP (Rare Isotope Science Project) accelerator has been planned to study heavy ion of nuclear, material and medical science at the Institute for Basic Science (IBS). It can deliver ions from proton to Uranium. The facility consists of three superconducting linacs of which superconducting cavities are independently phased. Requirement of the linac design is especially high for acceleration of multiple charge beams. In this paper, we present the RISP linac design, the superconducting cavity, and cryomodule.

MOP009	A Summary of the Advanced Photon Source (APS) Short Pulse X-ray (SPX) R&D Accomplishments	cryomodule, LLRF, vacuum, laser	92
	A. Nassiri, N.D. Arnold, T.G. Berenc, M. Borland, B. Brajuskovic, D.J. Bromberek, J. Carwardine, G. Decker, L. Emery, J.D. Fuerst, J.P. Holzbauer, D. Horan, J.A. Kaluzny, J.S. Kerby, F. Lenkszus, R.M. Lill, H. Ma, V. Sajaev, B.K. Stillwell, G.J. Waldschmidt, M. White, G. Wu, Y. Yang, A. Zholents ANL, Argonne, USA J.M. Byrd, L.R. Doolittle, G. Huang LBNL, Berkeley, California, USA P. Dhakal, J. Henry, J.D. Mammosser, J. Matalevich, R.A. Rimmer, H. Wang, K.M. Wilson JLAB, Newport News, Virginia, USA Z. Li, L. Xiao SLAC, Menlo Park, California, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06H11357. The Advanced Photon Source Upgrade Project (APS-U) at Argonne will include generation of short-pulse x-rays based on Zholents’ [1] deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. Since early 2012, in collaboration with Jefferson National Laboratory, we have made significant progress prototyping and testing a number of single-cell deflecting cavities. We have designed, prototyped, and tested silicon carbide as damping material for higher-order-mode (HOM) dampers, which are broadband to handle the HOM power across the frequency spectrum produced by the APS beam. In collaboration with Lawrence Berkeley National Laboratory, we have developing a state-of-the-art timing and synchronization system for distributing stable rf signals over optical fiber capable of achieving tens of femtoseconds phase drift and jitter. Collaboration with the Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi- cavity geometries. This contribution provides a progress report on the current R&D status of the SPX project. [1] A. Zholents et al., NIM A 425, 385 (1999).

MOP010	Spiral2 Cryomodules B Tests Results	cryomodule, linac, operation, alignment	95
	G. Olry, F. Chatelet, C. Commeaux, N. Gandolfo, D. Grolet, C. Joly, J. Lesrel, D. Longuevergne, R. Martret, G. Michel, L. Renard, A. Stephen, P. Szott IPN, Orsay, France P.-E. Bernaudin, R. Beunard, R. Ferdinand, A. Lefevre GANIL, Caen, France Y. Gómez Martínez LPSC, Grenoble Cedex, France
	Assembly and tests of the SPIRAL2 superconducting linac's cryomodules at CEA/Saclay and IPN/Orsay have now reached cruising speed after having faced a series of problems, among them contamination. 19 cryomodules are composing the whole Linac and IPN Orsay is in charge of the 7 cryomodules B, housing two 88MHz, beta 0.12 Quarter-Wave Resonators. Two cryomodules have been successfully assembled and tested up to the nominal gradient of 6.5 MV/m for all cavities with also total cryogenic losses under specifications. One of them is fully qualified and has been already delivered to GANIL. The second one showed misalignment on one cavity which could lead to partial disassembly. This paper will present the results of those cryomodules tests as well as the status of the remaining ones.

MOP011	European XFEL 3.9 GHz System	linac, HOM, cryomodule, controls	100
	P. Pierini, M. Bertucci, A. Bosotti, C. Maiano, P. Michelato, L. Monaco, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy E. Vogel DESY, Hamburg, Germany
	The third harmonic system of the European XFEL is a joint INFN and DESY contribution to the project. Achievements, status and activity plan will be reviewed.

MOP013	SRF Developments at MSU for FRIB	solenoid, operation, shielding, cryomodule	106
	K. Saito, N.K. Bultman, F. Casagrande, S. Chouhan, C. Compton, K. Elliott, A. Facco, M.J. Johnson, S. Jones, M. Leitner, S.J. Miller, R. Oweiss, J.P. Ozelis, J. Popielarski, L. Popielarski, S. Shanab, J. Wei, T. Xu, Y. Yamazaki, Y. Zhang, Z. Zheng FRIB, East Lansing, Michigan, USA S.K. Chandrasekaran MSU, East Lansing, USA K. Hosoyama KEK, Ibaraki, Japan
	FRIB has built up a new SRF development group for future SRF research and development at MSU. This paper will report on the present status of development for fundamental couplers, pneumatic tuners for HWR, magnetic shielding and superconducting solenoids, barrel polishing techniques for HWR, a cavity steam cleaning method, and niobium material characterization efforts.

MOP014	Cold Tests of SSR1 Resonators for PXIE	radiation, vacuum, cryomodule, SRF	112
	A.I. Sukhanov, M.H. Awida, P. Berrutti, C.M. Ginsburg, T.N. Khabiboulline, O.S. Melnychuk, R.V. Pilipenko, Y.M. Pischalnikov, L. Ristori, A.M. Rowe, D.A. Sergatskov, V.P. Yakovlev Fermilab, Batavia, USA
	Fermilab is currently building the Project X Injector experiment (PXIE). PXIE linac will accelerate 1 mA H⁻ beam up to 30 MeV and serve as a testbed for validation of Project X concepts and mitigation of technical risks. A cryomodule of eight superconducting RF Single Spoke Resonators of type 1 (SSR1) cavities operating at 325 MHz is an integral part of PXIE. Ten SSR1 cavities were manufactured in industry and delivered to Fermilab. In this paper we discuss surface processing and tests of bare SSR1 cavities at the Fermilab Vertical Test Stand (VTS). We report on the measured performance parameters of nine cavities achieved during tests.

MOP015	Status of the SRF Development for the Project X	cryomodule, linac, SRF, proton	117
	V.P. Yakovlev, T.T. Arkan, M.H. Awida, P. Berrutti, E. Borissov, A.C. Crawford, M.H. Foley, C.M. Ginsburg, I.V. Gonin, A. Grassellino, C.J. Grimm, S.D. Holmes, S. Kazakov, R.D. Kephart, T.N. Khabiboulline, V.A. Lebedev, A. Lunin, M. Merio, S. Nagaitsev, T.H. Nicol, Y.O. Orlov, D. Passarelli, T.J. Peterson, Y.M. Pischalnikov, O.V. Pronitchev, L. Ristori, A.M. Rowe, D.A. Sergatskov, N. Solyak, A.I. Sukhanov, I. Terechkine Fermilab, Batavia, USA
	Project X is a high intensity proton facility being developed to support a world-leading program of Intensity Frontier physics over the next two decades at Fermilab. The proposed facility is based on the SRF technology and consists of two linacs: CW linac to accelerate beam from 2.1 MeV to 3 GeV and pulsed linac accelerate 5% of the beam up to 8 GeV. In a CW linac five families of SC cavities are used: half-wave resonators (162.5 MHz); single-spoke cavities: SSR1 and SSR2 (325 MHz) and elliptical 5-cell β=0.6 and β=0.9 cavities (650 MHz). Pulsed 3-8 GeV linac linac are based on 9-cell 1.3 GHz cavities. In the paper the basic requirements and the status of development of SC accelerating cavities, auxiliaries (couplers, tuners, etc.) and cryomodules are presented as well as technology challenges caused by their specifics.

MOP016	SRF Systems for the Coherent Electron Cooling Demonstration Experiment	SRF, gun, cryomodule, electron	123
	S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, Y. Huang, D. Kayran, V. Litvinenko, P. Orfin, I. Pinayev, T. Rao, B. Sheehy, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, Q. Wu, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, M. Ruiz-Osés, T. Xin Stony Brook University, Stony Brook, USA C.H. Boulware, T.L. Grimm Niowave, Inc., Lansing, Michigan, USA X. Liang SBU, Stony Brook, New York, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE A short 22-MeV linac under development at BNL will provide high charge, low repetition rate beam for the coherent electron cooling demonstration experiment in RHIC. The linac will include a 112 MHz SRF gun and a 704 MHz five-cell accelerating SRF cavity. The paper describes the two SRF systems, discusses the project status, first test results and schedule.

MOP017	SRF for Low Energy RHIC Electron Cooling: Preliminary Considerations	SRF, gun, electron, linac	126
	S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, A.V. Fedotov, D. Kayran, V. Litvinenko, Q. Wu, B. P. Xiao, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko Stony Brook University, Stony Brook, USA Z.A. Conway, M.P. Kelly, S.V. Kutsaev, B. Mustapha, P.N. Ostroumov ANL, Argonne, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE A search for the QCD Critical Point has renewed interest to electron cooling ion beams in RHIC at energies below 10 GeV/nucleon. The electron cooling will utilize bunched electron beams form an SRF linac at energies from 0.9 to 5 MeV. The SRF linac will consist of two quarter wave structures: a photoemission electron gun and a booster cavity. In this paper we present preliminary design consideration of this SRF linac.

MOP018	Design of the MYRRHA 17-600 MeV Superconducting Linac	linac, lattice, operation, simulation	129
	J.-L. Biarrotte IPN, Orsay, France F. Bouly CERN, Geneva, Switzerland J.-P. Carneiro Fermilab, Batavia, USA D. Uriot CEA/DSM/IRFU, France D. Vandeplassche SCK•CEN, Mol, Belgium
	Funding: This work is being supported by the European Atomic Energy Community’s (EURATOM) Seventh Framework Programme under grant agreement n°269565 (MAX project). The goal of the MYRRHA project is to demonstrate the technical feasibility of transmutation in a 100MWth Accelerator Driven System (ADS) by building a new flexible irradiation complex in Mol (Belgium). The MYRRHA facility requires a 600 MeV accelerator delivering a maximum proton flux of 4 mA in continuous operation, with an additional requirement for exceptional reliability. This paper will briefly describe the beam dynamics design of the main superconducting linac section which covers the 17 to 600 MeV energy range and requires enhanced fault-tolerance capabilities.

MOP021	Conceptual Design of SC Linac for RIBF-Upgrade Plan	linac, cryomodule, quadrupole, ion	137
	K. Yamada, O. Kamigaito, N. Sakamoto, K. Suda RIKEN Nishina Center, Wako, Japan
	For the intensity upgrade of very-heavy ions such as 238U and 124Xe at the RIKEN RI-Beam Factory (RIBF), a design study of new SC linac injector has started on. In the RIBF, the very-heavy ions are accelerated in a cascade of the injector linac (RILAC2), the RIKEN ring cyclotron (RRC), the fixed-frequency ring cyclotron (fRC), the intermediate-stage ring cyclotron (IRC), and the world's first superconducting ring cyclotron (SRC). We plan to substitute the SC linac for the RRC with respect to the very heavy ions, and to boost up the energy of ions with mass-to-charge ratio of 7 from 1.4 MeV/u to 11 MeV/u in the cw mode. The SC cavity is assumed to be a two gap QWR with an rf frequency of 73 MHz, that is twice the rf frequency of IRC and SRC. The cell parameters and number of cavity are determined by calculating the energy gain of synchronous ion by taking the rf phase at the center of gap into account. The transverse motion is calculated by the transfer matrix method and several types of lattice are studied. This contribution reports the progress of design study for the SC linac.

MOP022	Preliminary Design of CEPC RF Superconducting System	HOM, impedance, cryogenics, storage-ring	140
	H.J. Zheng, J. Gao, S. Jin, Y. Liu, Z.C. Liu, J.Y. Zhai, T.X. Zhao IHEP, Beijing, People's Republic of China
	In order to study Higgs Boson, scientists proposed to construct a Higgs factory. Chinese scientists are also actively involved in research of the construction of Higgs factory. Construction of a circular collider and several construction solutions were proposed. Electron and positron are eventually accelerated to the center of mass energy 240GeV. RF superconducting acceleration system is indispensable to ensure the normal operation of machine. This article mainly introduces the RF parameters in the design of 700MHz China Higgs Factory (CHF) system. It mainly includes choose of cavity type, couplers and relevant parameters of cryogenic system.

MOP024	Novel SRF Gun Design	gun, cathode, SRF, laser	145
	F. Marhauser Muons, Inc, Illinois, USA K.H. Lee, Z. Li SLAC, Menlo Park, California, USA
	Funding: Work supported under U.S. DOE Grant Application Number 98802B12-I A high brightness superconducting radio frequency (SRF) photoinjector gun cavity has been developed to a level ready for construction. The design aims to prevent operational limitations encountered with existing concepts.

MOP025	The SRF Photo Injector at ELBE – Design and Status 2013	solenoid, cryomodule, SRF, gun	148
	P. Murcek, A. Arnold, P.N. Lu, J. Teichert, H. Vennekate, R. Xiang HZDR, Dresden, Germany P. Kneisel JLAB, Newport News, Virginia, USA
	Funding: EuCARD, contract number 227579, German Federal Ministry of Education and Research grant 05 ES4BR1/8 In order to improve the gradient of the cavity and the beam quality of the gun, a new design for the SRF photo injector at the Helmholtz-Zentrum Dresden-Rossendorf has been developed. Apart from the special design of the cavity itself – as presented at SRF09, Berlin – the next update will include a separation of input and output of the liquid nitrogen supply system. This is supposed to increase the stability of the nitrogen pressure and enable a better monitoring of its temperature. The implementation of a superconducting solenoid inside the cryomodule is another major improvement. The position of this solenoid can be adjusted with a high precision using two independent step motors, which are thermally isolated from the solenoid itself. The poster will present the progress of turning the first design models into reality.

MOP027	BNL SRF Gun Commissioning	gun, SRF, cathode, insertion	155
	W. Xu, Z. Altinbas, S.A. Belomestnykh, I. Ben-Zvi, J. Dai, S. Deonarine, D.M. Gassner, H. Hahn, J.P. Jamilkowski, P. Kankiya, D. Kayran, N. Laloudakis, L. Masi, G.T. McIntyre, D. Pate, D. Phillips, T. Seda, K.S. Smith, A.N. Steszyn, T.N. Tallerico, R. Than, R.J. Todd, D. Weiss, A. Zaltsman BNL, Upton, Long Island, New York, USA I. Ben-Zvi, J. Dai Stony Brook University, Stony Brook, USA
	Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The 704 MHz superconducting RF gun for the R&D ERL project is under comissioning at BNL. Since last November, the SRF gun has been conditioned and demonstrated an operational accelerating voltage of 2 MV (an accelerating gradient of 23.5 MV/m). Preparations for the cathode insertion are in final stages and we expect the gun to generate the first electron beam this summer. This paper discusses the BNL SRF gun system,and the results of the SRF gun commissioning.

MOP031	Quality Control of the Vessel and Cold Mass Production for the 1.3 GHz XFEL Cryomodules	vacuum, controls, cryomodule, operation	168
	S. Barbanotti, H. Hintz, K. Jensch, W. Maschmann DESY, Hamburg, Germany
	The industrial production of one hundred cold masses and vacuum vessels for the 1.3 GHz XFEL cryomodules is now fully in operation. Quality checks at the companies and controls at DESY assure the quality level required for the cryomodule assembly. Verification of the main production steps, non-destructive tests, dimensional controls are performed by DESY personnel before accepting the components. This paper resumes the quality control strategy and the results for the first components produced by the companies.

MOP032	Statistic to Eddy-Current Scanning of Niobium Sheets for European XFEL	niobium, controls, survey, superconducting-RF	171
	A. Brinkmann, S. Arnold, A. Ermakov, J. Iversen, M. Lengkeit, A. Poerschmann, L. Schaefer, W. Singer, X. Singer DESY, Hamburg, Germany
	The fabrication experiences of superconducting cavities for FLASH have shown that eddy-current scanning of the Nb-sheets foreseen for half-cells reduces the cavity failures. New eddy current devices have been developed and build together with the industry for the production of 800 pieces 1.3 GHz superconducting niobium cavities for European XFEL. More than 15.000 Nb-sheets provided by three companies have been tested by eddy-current scanning. The sheets that demonstrated local deviations of the signal have been subsequently non-destructively examined by 3d-microscope and X-Ray element analysis. The surface defects (dents, holes, scratches) are the mainly detected flaws. In addition several types of foreign material inclusions observed. Statistic concerning eddy-current signal deviation and rejection rates for each supplier will be presented.

MOP033	Quality Assurance and Acceptance Testing of Niobium Material for Use in the Construction of the Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU)	niobium, linac, SRF, controls	174
	C. Compton, D. Miller FRIB, East Lansing, USA T.R. Bieler, D. Kang Michigan State University, East Lansing, USA S.K. Chandrasekaran, N.T. Wright MSU, East Lansing, USA
	Funding: Work supported by US DOE Cooperative Agreement DE-SC0000661 and Michigan State University Niobium is the current material of choice for the fabrication of superconducting radio frequency (SRF) cavities used in SRF based accelerators. Although niobium specifications for this application have been well established, material properties of as-received materials can still vary substantially. As required for the FRIB accelerator, large volumes (60,000 lbs) of niobium materials (sheet, tube, and flange) have been contracted to several niobium vendors. The FRIB cavity designs require very large niobium sheets, increasing the difficulty in fabrication and potential for contamination. FRIB has developed and initiated plans to control niobium specifications and perform incoming acceptance checks to ensure quality is maintained. Acceptance results from the first niobium shipment will be presented, looking at several production lots from the same vendor and across multiple vendors. Non-conforming results were observed and will be discussed including follow-up investigations and mitigation strategies to improve quality of future shipments.

MOP034	The Statistics of Industrial XFEL Cavities Fabrication at E.ZANON	target, controls, niobium, accelerating-gradient	180
	A. Gresele, M. Giaretta, A. Visentin Ettore Zanon S.p.A., Nuclear Division, Schio, Italy A.A. Sulimov, J.H. Thie DESY, Hamburg, Germany
	Serial production of superconducting cavities for European-XFEL was successfully started at E.ZANON at the end of last year. The production rate (3-4 cavities a week) allows us to summarize the results and present the statistics of industrial cavity fabrication. Many parameters have been traced during different steps of cavity production. The most interesting of them, as cavity length, frequency, field flatness and eccentricity, are presented and discussed. The last results of new preparation cycles development in the frame of E-XFEL projects is also included

MOP035	Using an Engineering Data Management System for Series Cavity Production for the European XFEL	controls, niobium, database, data-management	183
	J. Iversen, A. Brinkmann, J.A. Dammann, A. Poerschmann, W. Singer, J.H. Thie DESY, Hamburg, Germany
	For series production of 800 superconducting cavities for the European XFEL an Engineering Data Management System (EDMS) is in use as a tool for quality control and quality assurance. DESY is responsible for “in-time” supply of more than 24000 semi-finished products of niobium and niobium-titanium alloy. The EDMS as a main repository was set up to fulfill logistic requirements and to guarantee traceability and documentation issues according to the European pressure equipment directive (PED 97/23 EC). The main aspects consist of complete paperless documentation, fully automated transfer of quality management documents and data from vendor system to DESY’s EDMS, providing to industry an access to relevant documentation and processing of release procedures for acceptance levels and non-conformity reporting. A summary of documentation methods, procedures and first experiences will be presented.

MOP036	New Technique and Result of Laser Welded SCRF Cavity Developed at RRCAT	laser, vacuum, niobium, experiment	186
	P. Khare, R. Arya, J. Dwivedi, R. Ghosh, G. Gilankar, C. Gupta, P.D. Gupta, A. Jain, S.C. Joshi, G.V. Kane, R. Kaul, P.K. Kush, G. Mundra, S.M. Oak, C.K. Pithawa, P. Ram Sankar, S.B. Roy, V.C. Sahni, R.S. Sandha, P. Shrivastava, B.N. Upadhyay RRCAT, Indore (M.P.), India C.A. Cooper, C.M. Ginsburg, A. Grassellino, C.S. Mishra, A.M. Rowe Fermilab, Batavia, USA
	A new technique to fabricate SCRF cavities with the help of laser welding process has been developed at Raja Ramanna Centre for Advanced Technology RRCAT), Indore, Department of Atomic Energy, India. In this technique, a pulsed Nd:YAG laser has been used and welding was performed in inert gas environment, in a specially designed welding rig. The advantages of this technique are reduced cost, small heat affected zone, no necessity to weld in vacuum and enhanced rate of production. The paper describes the technique and fabrication method of a single-cell 1.3 GHz SCRF cavity which was fabricated at RRCAT with this new technique. It also discusses the test result of this cavity which was processed and tested at Fermilab. The cavity reached an Eacc of 17MV/m with a Q0 of 1.4 E +10 at 2K. The cavity is being barrel polished for further improvement.

MOP037	Test of the 1.3 GHz Superconducting Cavities for the European X-ray Free Electron Laser	HOM, vacuum, software, pick-up	191
	K. Krzysik DESY, Hamburg, Germany B. Dzieza, W. Gaj, D. Karolczyk, K. Kasprzak, L.M. Kolwicz-Chodak, A. Kotarba, A. Krawczyk, W. Maciocha, A. Marendziak, K. Myalski, S. Myalski, T. Ostrowicz, B. Prochal, M. Sienkiewicz, M. Skiba, J. Świerbleski, M. Wiencek, J. Zbroja, A. Zwozniak IFJ-PAN, Kraków, Poland
	The European X-ray Free Electron Laser (XFEL) is currently under construction in Germany in Hamburg area. A linear accelerating part of the XFEL is going to consist of 808 superconducting 9-cell Niobium cavities installed in 101 accelerating modules. Before assembly into modules the cavities are tested in a dedicated test facilities. The testing procedures are prepared based on DESY expertise and available software from Tesla Test Facility (TTF) Collaboration and Free electron LASer for Hamburg (FLASH). RF test provides the most important information about cavity performance: maximum available gradient and dependence of quality factor and radiation on the gradient. Results of the RF test determine, whether a cavity is shipped to CEA Saclay (France) to be assembled into a module or send for retreatment to improve its performance. In this paper we present the most important aspects of the cavity RF test procedure.

MOP038	Series Production of EXFEL 1.3 GHz SRF Cavities at E. Zanon: Management, Infrastructures and Quality Control	SRF, controls, niobium, cryogenics	194
	G. Massaro Ettore Zanon S.p.A., Nuclear Division, Schio, Italy G. Corniani, M. Festa, M. Maule Ettore Zanon S.p.A., Schio, Italy
	In this paper we report on the capability of Ettore Zanon S.p.A. (EZ) to implement a EXFEL 1,3 GHz SRF cavities production system. In order to assure the series efficient repeatability of the product, this system is based on work team, composed of people with different skills, qualified infrastructures and technical procedures. A detailed study of the different work phases of the production cycle has been performed in advance, highlighting the technical difficulties and the production constraints. Based on this result, infrastructures and processes have been optimized to grant the specified quality and time/cost requirements and procedures and operating instructions, where the most complexes and delicate phases as well as the responsibilities and acceptance criteria are investigated, have been introduced. Qualification operations and eight pre-series cavities have proven EZ capability of fulfilling the imposed requirements. The above described manufacturing system allows nowadays a production rate of 4 cavities per week. EZ future developments involve minimizing time and costs while keeping the highest quality standard.

MOP039	Strategy of Technology Transfer of EXFEL Preparation Technology to Industry	controls, status, hardware, linac	197
	A. Matheisen, J. Iversen, A. Schmidt, W. Singer DESY, Hamburg, Germany P. Michelato, L. Monaco INFN/LASA, Segrate (MI), Italy
	For the EXFEL a specification for the cavitiy preparation procedures (R1)was set up and handed to the industrial companies. Basing on this specification companies hard ware as well as process flows were set up. Beside this specified part of the preparation technique the companies personal needed to be educated and the processes ramped up. To check the quality of the infrastructure, status of education of personal and correct set up of process flows, so called Dummy (DCV) - , Reference (RCV ) and Pre-series (PCV) cavities were assigned. We report on the general strategy applied for the EXFEL technology transfer on cavity preparation and the results obtained on the qualification cavities. R1) Series Surface and acceptance test preparation of superconducting cavities for the European Xfel (XFEL/A - D) JUNE 30, 2009

MOP040	Industrialization of European XFEL Preparation Cycle “Final EP ” at Research Instruments Company	controls, acceleration, vacuum, radiation	201
	A. Matheisen, N. Krupka, M. Schalwat, A. Schmidt, M. Schmökel, W. Singer, B. van der Horst DESY, Hamburg, Germany P. Michelato, L. Monaco INFN/LASA, Segrate (MI), Italy M. Pekeler RI Research Instruments GmbH, Bergisch Gladbach, Germany
	In the Specification for XFEL Cavity preparation (R1) two different preparation sequences are presented. Research Instruments Company as one of the two companies contracted for XFEL cavity production and preparation has chosen the so called “final EP” cycle. Major infrastructure components like EP facility and the BCP facility were pre- qualified. This existing and the new set up areas like the cleanroom are distributed over the ground area of the industrial park Bergisch Gladbach. The process flow given in the DESY specification needed adaptation to this scenario. Additional infrastructure beside the once specified needed to be set up to ensure the same quality of processes even with a changed work flow. The general lay out of the facility, matched work flow of preparation and test results of resonators processed by RI company in their infrastructure will be reported. (R1) Series Surface and acceptance test preparation of superconducting cavities for the European Xfel (XFEL/A - D) JUNE 30, 2009

MOP042	Quality Control and Processes Optimization for the EXFEL Superconducting Cavities Series Production at Ettore Zanon spa	controls, operation, vacuum, SRF	208
	L. Facci, D. Rizzetto Ettore Zanon S.p.A., Nuclear Division, Schio, Italy G. Corniani Ettore Zanon S.p.A., Schio, Italy A. Matheisen DESY, Hamburg, Germany P. Michelato, L. Monaco INFN/LASA, Segrate (MI), Italy
	The construction of the European XFEL forced the first mass production of Niobium bulk SRF cavities. In this context Ettore Zanon S.p.A. built a fully new facility designed to produce four fully treated and He tank equipped cavities per week, ready to be tested at DESY. The facility already reached the foreseen production rate. The guarantee of the highest quality of the resonators produced requires a very strict quality control plan. At the same time, the requirements of the industrial production in terms of time, cost and productivity must be satisfied. As a consequence processes must be standardized and working times optimized. In the following, after the description of the production facility, we would like to highlight and discuss the strategies and arrangements adopted in the various critical fields (clean room, vacuum, etc.) to ensure the foreseen results. Moreover correlation between cavities performances and production cycle parameters will be investigated and discussed.

MOP043	ILC-HiGrade Cavities as a Tool of Quality Control for European XFEL	controls, radiation, feedback, framework	212
	A. Navitski, E. Elsen, B. Foster, J. Iversen, A. Matheisen, D. Reschke, W. Singer, X. Singer, L. Steder, M. Wenskat DESY, Hamburg, Germany R. Laasch, Y. Tamashevich University of Hamburg, Hamburg, Germany
	Funding: BMBF, Helmholtz Association, ILC-HiGrade, FP7 (CRISP), Alexander von Humboldt Stiftung/Foundation The EXFEL order for SRF cavities includes 24 cavities, which are part of the ILC-HiGrade program. Initially, these cavities serve as quality control (QC) sample extracted from the EXFEL cavities series production on a regular basis. The QC and quality assurance (QA) include all processing steps of the EXFEL cavities. To maximize the information from these so-called QC cavities, a surface mapping technique is applied in a second cold RF test. There the cavities delivered have experienced identical treatment of the inner surface with the exception of mounting of the Helium vessel. After the normal acceptance test at the cavity RF measurement facility, the cavities are removed from the production flow. Further quality assurance steps beginning with a detailed RF test with surface mapping followed by a high resolution optical inspection (OBACHT) are carried out to improve the understanding of defects in close collaboration with the standing experts engaged in the EXFEL production. Results of the first QC cavities tests as well as planned further R&D will be presented and discussed.

MOP044	Performance Characteristics of Jefferson Lab’s New SRF Infrastructure	SRF, cryomodule, cryogenics, vacuum	216
	C.E. Reece, P. Denny, A.V. Reilly JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. In the past two years, Jefferson Lab has reconfigured and renovated its SRF support infrastructure as part of the Technology and Engineering Development Facility project, TEDF. The most significant changes are in the cleanroom and chemistry facilities. We report the initial characterization data on the new ultra-pure water systems, cleanroom facilities, describe the reconfiguration of existing facilities and also opportunities for flexible growth presented by the new arrangement.

MOP045	Electropolishing for EXFEL Cavities Production at Ettore Zanon SpA	niobium, controls, cathode, superconductivity	220
	M. Rizzi Ettore Zanon S.p.A., Schio, Italy A. Gresele Ettore Zanon S.p.A., Nuclear Division, Schio, Italy A. Matheisen, N. Steinhau Kühl DESY, Hamburg, Germany P. Michelato INFN/LASA, Segrate (MI), Italy
	A new horizontal electropolishing (EP) facility has been implemented by Ettore Zanon SpA for the series production of the EXFEL cavities produced by the company. According to EXFEL specification a bulk EP of at least 100 micron is the first step of the surface treatment for high performances. Particular attention has been dedicated to find the best configuration during qualification of the system. Correlation between process variables, RF tests at room temperature at Zanon and vertical RF tests at 2 K at DESY have been investigated and the Niobium removal optimized. The facility has been designed for industrial scope, in order to guarantee the required quality and production rate of 4 cavities per week. One of the most important aspects has been the system automation to have complete control of the process.

MOP048	PED Requirements Applied to the Cavity and Helium Tank Manufacturing	niobium, linac, controls, operation	227
	A. Schmidt, J. Iversen, A. Matheisen, W. Singer DESY, Hamburg, Germany
	For the European XFEL more than 800 Cavities are manufactured by industrial partners. Each cavity is housed in an individual cryo vessel, the so called helium tank. All vessels are made from titanium and manufactured by industry as well. The cavity, welded into its helium tank, is a pressure loaded part and has to follow the pressure equipment directive - PED (97/23/EC). Setting up a series production of cavities and helium tanks by different vendors according given standards, was the task of the EXFEL WPG-1 LINAC-WP04. In cooperation with the TUEV-Nord as the notified body, DESY is responsible for the qualification of design, material in use and reasonable tests to get a certificate for pressure bearing parts.

MOP049	Progress and Experiences of Series Production of Helium Tanks With DESY as a Subcontractor for RI	controls, status, factory, data-management	231
	A. Schmidt, J.A. Dammann, A. Daniel, A. Matheisen DESY, Hamburg, Germany
	DESY acts as a subcontractor for helium tanks, for one of the cavity manufacturer in charge, for the EXFEL cavity production. Here the full responsibility of production, quality and warranty of these parts is at DESY. Therefore on 400 out of the total of 800 helium tanks, DESY has to set up a logistic of incoming inspection, documentation, storage and distribution. Special effort is made to archive a free of doubts interconnection and integration of the cavity into the helium tank. After more than 300 units produced a review and statistic is provided.

MOP051	The Statistics of Industrial XFEL Cavities Fabrication at Research Instruments	target, controls, status, vacuum	234
	A.A. Sulimov, J.H. Thie DESY, Hamburg, Germany M. Pekeler, D. Trompetter RI Research Instruments GmbH, Bergisch Gladbach, Germany
	Serial production of superconducting cavities for European-XFEL was successfully started at Research Instrument (RI) at the end of last year. The production rate (3-4 cavities a week) allows us to summarize the results and present the statistics of industrial cavity fabrication. Many parameters have been traced during different steps of cavity production. The most interesting of them, as cavity length, frequency, field flatness and eccentricity, are presented and discussed.
	Poster MOP051 [0.769 MB]

MOP052	RF Aspects of Quality Control for Industrial XFEL Cavities Fabrication	controls, background, SRF, pick-up	237
	A.A. Sulimov, V. Gubarev, S. Yasar DESY, Hamburg, Germany
	Quality control of XFEL serial cavities allows us not only except the using of reject cavities for linac, but also give a feedback to the industry in case of cavity parameters come to their limits. RF control assays not only the electro dynamical characteristics (as frequencies, Q-factors and fields), but also provide the mechanical revise with a very high accuracy. Automation of this quality control in XFEL data base gave us a powerful tool which is required for the big projects as European-XFEL.
	Poster MOP052 [1.178 MB]

MOP053	R&D on Cavity Treatments at DESY Towards the ILC Performance Goal	SRF, factory, controls, linear-collider	240
	A. Navitski, E. Elsen, B. Foster, D. Reschke, J. Schaffran, W. Singer, X. Singer DESY, Hamburg, Germany R. Laasch, Y. Tamashevich University of Hamburg, Hamburg, Germany
	Funding: BMBF, Helmholtz Association, ILC-HiGrade, FP7 (CRISP), Alexander von Humboldt Stiftung/Foundation The actual R&D program at DESY is derived from the global effort for the International Linear Collider (ILC) and is well in phase with effort elsewhere. The program aims at a solid understanding and control of the industrial mass-production process of the superconducting radio-frequency accelerating cavities, which are manufactured for the European X-ray Free Electron Laser (EXFEL) at DESY. The goal is to identify the gradient limiting factors and further refine the cavity treatment technique to provide gradients above 35 MV/m at >90% production yield. Techniques such as 2nd sound quench detection, OBACHT optical inspections, defect metrology using silicon replica as well as Centrifugal Barrel Polishing (CBP) and Local Grinding repair are foreseen as tools. Actual status, details, and first achievements of the program will be reported.

MOP054	Tests of the Accelerating Cryomodules for the European X-Ray Free Electron Laser	cryomodule, cryogenics, operation, radiation	244
	M. Wiencek, B. Dzieza, W. Gaj, D. Karolczyk, K. Kasprzak, L.M. Kolwicz-Chodak, A. Kotarba, A. Krawczyk, K. Krzysik, W. Maciocha, A. Marendziak, K. Myalski, S. Myalski, T. Ostrowicz, B. Prochal, M. Sienkiewicz, M. Skiba, J. Świerbleski, J. Zbroja, A. Zwozniak IFJ-PAN, Kraków, Poland
	The European X-ray Free Electron Laser (XFEL) is currently under construction in Germany in Hamburg area. A 2.1 km long superconducting linear accelerator, part of the XFEL, consists of 101 accelerating cryomodules. The XFEL cryomodule is assembled with eight superconducting RF cavities, one cold magnet and Beam Position Monitor (BPM). The cryomodules are tested in dedicated test facility before installation in the XFEL tunnel. The testing procedures for the cryomodules were prepared with use of DESY expertise from TTF (Tesla Test Facility) Collaboration and FLASH (Freie-Elektronen-Laser in Hamburg). This paper describes the full set of testing procedure and incoming and outgoing inspections as well.

MOP055	Status of the Superconducting Cavity Development for ILC	cryomodule, status, HOM, linac	247
	T. Yanagisawa, H. Hara, F. Inoue, K. Kanaoka, K. Sennyu MHI, Hiroshima, Japan
	MHI activities for ILC are reported. MHI had developed several procedure and method of cavity production for stable quality and cost reduction. And we are producing cryomodules too. These activities are reported in detail.

MOP057	Developments and Tests of a 700 MHz Cryomodule for the Superconducting Linac of MYRRHA	cryomodule, linac, vacuum, cryogenics	250
	F. Bouly CERN, Geneva, Switzerland S. Berthelot, J.-L. Biarrotte, M. El Yakoubi, C. Joly, J. Lesrel, E. Rampnoux IPN, Orsay, France A. Bosotti, R. Paparella, P. Pierini INFN/LASA, Segrate (MI), Italy
	Funding: This work is being supported by the European Atomic Energy Community’s EURATOM) Seventh Framework Programme under grant agreement n°269565(MAX project). The MYRRHA (“Multi-purpose Hybrid Research reactor for High-tech Applications”) project aims at the construction of a new flexible fast spectrum research reactor. This reactor will operate as an Accelerator Driven System demonstrator. The criticality will be sustained by an external spallation neutron flux; produced thanks to a 600 MeV high intensity proton beam. This CW beam will be delivered by a superconducting linac which must fulfil very stringent reliability requirements. In this purpose, the accelerator design is based on a redundant and fault-tolerant scheme to enable the rapid mitigation of RF failures. To carry out “real scale” reliability-oriented experiments a prototype of cryomodule was developed by INFN Milano and installed at IPN Orsay. The module holds a 700 MHz 5-cell elliptical cavity (βg = 0.47) equipped with its blade frequency tuner. Several tests were carried out to commission the experimental set-up. We review here the obtained results and the lessons learnt by operating this module, as well as the on-going developments.

MOP059	Management for the Long-Term Reliability of the Diamond Superconducting RF Cavities	vacuum, SRF, ion, electron	255
	P. Gu, C. Christou, M.P. Cox, S.A. Pande, A.F. Rankin, H.S. Shiers, A.V. Watkins Diamond, Oxfordshire, United Kingdom
	Diamond started operation with users in January 2007 and the Diamond storage ring superconducting RF cavities used to be the largest single contributor to unplanned beam trips. Extensive effort has been dedicated to understand and improve the long-term stability of the SRF cavities. Our experience shows that the long-term stability of superconducting RF cavities relies heavily on the surface conditions. Gases keep accumulating on the cold surfaces with time due to its huge cryo-pumping capacity. The integral effect will ultimately lead to fast vacuum trips during operation. In Diamond, we have developed a systematic approach to control the long-term stability of the SRF cavities. We will discuss here our approach and also present the future work that should be completed.

MOP061	75 mA Operation of the Cornell ERL Superconducting RF Injector Cryomodule	HOM, operation, SRF, cryomodule	259
	M. Liepe, B.M. Dunham, R.G. Eichhorn, G.H. Hoffstaetter, R.P.K. Kaplan, P. Quigley, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work is supported by the National Science Foundation (Grant No. DMR-0807731). Cornell University has developed a SCRF injector cryomodule for the acceleration of high current, low emittance beams in continuous wave operation. This cryomodule is based on 1.3 GHz superconducting RF technology, and has been tested extensively in the Cornell ERL injector prototype with world record CW beam currents exceeding 70 mA. High CW RF power input couplers and strong Higher-Order-Mode damping in the cavities are essential for high beam current operation. This paper summarizes the performance of the cryomodule during the high beam current operation.

MOP062	Production of 500 MHz SRF Modules the KEKB-type for Taiwan Photon Source	SRF, niobium, operation, vacuum	263
	Ch. Wang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, Z.K. Liu, C.H. Lo, M.H. Tsai, T.-T. Yang, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan T. Furuya, K. Hara, T. Honma, A. Kabe, Y. Kojima, S. Mitsunobu, Y. Morita, H. Nakai, K. Nakanishi, M. Nishiwaki, S. Takano KEK, Ibaraki, Japan F. Inoue, K. Sennyu, T. Yanagisawa MHI, Hiroshima, Japan
	The KEKB-type single-cell 500-MHz superconducting radio frequency (SRF) modules have been selected to power the 3 GeV, 500 mA, storage ring of the constructing Taiwan Photon Source (TPS) at National Synchrotron Radiation Research Center (NSRRC). The design target is to routinely deliver RF forward power up to 300 kW, CW, to single SRF module with highly reliable operation. Three sets of SRF modules have been successfully produced under a tight collaboration with High Energy Accelerator Research Organization (KEK) and Mitsubishi Heavy Industries Ltd. (MHI), after obtaining the technology transfer from KEK. MHI is responsible for the mechanical fabrication and cryo-module assembly, KEK for the surface and RF treatments of the niobium cavities, high power input couplers and HOM dampers and for the liquid-helium tests of the cryo-modules, and NSRRC for the electronic/diagnostic system, final assembly and system integration, high power horizontal test, and reliable test. This work reports the results obtained during the production of these three SRF modules at KEK and NSRRC.

MOP063	Mature Operation of CESR-Type 500-MHz SRF Module at Taiwan Light Source	SRF, operation, vacuum, cryogenics	266
	Ch. Wang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, Z.K. Liu, C.H. Lo, M.H. Tsai, T.-T. Yang, M.-S. Yeh, T.-C. Yu NSRRC, Hsinchu, Taiwan
	The Cornell-type 500-MHz SRF module has been routinely operated since the end of 2004 to power the 1.5 GeV Taiwan Light Source with 360 mA in top-up mode. A new record of SRF operation with mean time between failures (MTBF)up to 800 hr has been achieved in the 1st half of 2013 that is compatible with the best operational record of room temperature cavities ever made in the same machine. To meet the user’s strict requirements on highly operational reliability, developing in advanced diagnostic instrumentation together with user-friendly event logging software does never stop. Here, we review our SRF operational experience in last 9 years.

MOP064	Operational Experience with the SOLEIL Superconducting RF System	cryogenics, operation, HOM, vacuum	269
	P. Marchand, J.P. Baete, R.C. Cuoq, H.D. Dias, M. Diop, J.L. Labelle, R. Lopes, M. Louvet, C.M. Monnot, S. Petit, F. Ribeiro, T. Ruan, R. Sreedharan, K. Tavakoli SOLEIL, Gif-sur-Yvette, France
	In the SOLEIL storage ring, two cryomodules provide to the electron beam an accelerating voltage of 3-4 MV and a power of 575 kW at 352 MHz. Each cryomodule contains a pair of superconducting cavities, cooled with liquid Helium at 4K, which is supplied by a single 350 W cryogenic plant. The RF power is provided by 4 solid state amplifiers, each delivering up to 180 kW. The parasitic impedances of the high order modes are strongly mitigated by means of four coaxial couplers, located on the central pipe connecting the two cavities. Seven years of operational experience with this system as well as its upgrades are reported.

MOP065	Consolidated Design of the 17 MeV Injector for MYRRHA	proton, rfq, linac, cryomodule	274
	D. Mäder, D. Koser, H. Podlech, A. Schempp IAP, Frankfurt am Main, Germany
	Funding: Project supported by the EU, FP7 MAX, contract No. 269565 and BMBF, contract No. 06FY7102. The MYRRHA research reactor will be an Accelerator Driven System, which demands a 2.4 MW proton beam delivered by a 600 MeV cw operated linac. The beam dynamics design of the injector has been consolidated to fulfil the requirements with respect to beam losses and quality. After a 4-rod-RFQ, four 7-gap room temperature CH cavities with a constant phase and an effective voltage of 750 keV are used to reach 4.3 MeV. Then the proton beam is accelerated to 18 MeV using six superconducting 5-gap Nb CH structures with a constant beta profile. With reducing the gradient and adjusting the phase of the twelfth CH structure the originally demanded 17 MeV can be delivered, too. Every SC CH cavity is cooled down to 2K with liquid helium in a separate cryo module. The new geometric design of the SC CH cavities improves the rigidity and reduces the electric peak field.

MOP066	Development of Compact Cryomodules Housing HWRs for High-intensity SC CW Linacs	cryomodule, linac, niobium, proton	277
	P.N. Ostroumov, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.H. Kim, S.V. Kutsaev, R.C. Murphy, B. Mustapha, T. Reid ANL, Argonne, USA D. Berkovits Soreq NRC, Yavne, Israel S. Nagaitsev Fermilab, Batavia, USA
	Funding: This work was supported by the U.S. Department of Energy, under Contracts No. DE-AC02-06CH11357, DE-AC02-76CH03000 and ANL WFO No. 85Y47. Acceleration of high-intensity light-ion beams immediately after an RFQ requires a compact accelerating and focusing lattice with a high packing factor. We have developed a cryomodule which satisfies this requirement with eight accelerating-focusing periods for Project X at FNAL. Each focusing period consist of a 162.5-MHz SC HWR, a SC solenoid and a beam position monitor. The highly optimized EM parameters of the cavity were achieved by using double conical, hour glass like, inner and outer conductors. This design is also favorable for the beam dynamics because the short focusing periods which helps to better control the beam quality. All sub-systems of the cryomodule, except the vacuum-vessel, are in advanced stages of prototyping and testing. A similar concept has been developed for the design of several cryomodules for a 20 MeV/u proton/deuteron 200 kW linac at SNRC. These cryomodules house two types of 176 MHz half-wave resonators and require only modest modifications for the application. This paper will discuss the status of the FNAL cryomodule design and sub-system fabrication and its impact on future HWR cryomodule such as the SNRC project.

MOP067	Results From Initial Tests of the 1st Production Prototype β=0.29 and β=0.53 HWR Cavities for FRIB	linac, target, cryomodule, vacuum	280
	J.P. Ozelis, C. Compton, K. Elliott, M. Hodek, M. Leitner, I.M. Malloch, D. Miller, S.J. Miller, D. Norton, R. Oweiss, J. Popielarski, L. Popielarski, A.P. Rauch, K. Saito, G.J. Velianoff, D.R. Victory FRIB, East Lansing, USA
	Funding: Work supported by US DOE Cooperative Agreement DE-SC0000661 and Michigan State University The first prototypes of the β=0.53 and β=0.29 HWR production design cavities for FRIB were fabricated early this year by Roark Manufacturing Company and delivered to MSU. These cavities have undergone an extensive evaluation program to verify both mechanical and RF performance before proceeding with fabrication of a pre-production run of 10 cavities. Results from physical inspections, warm RF measurements, chemical processing, and cryogenic vertical testing will be presented.

MOP068	NGLS Linac Design	cryomodule, linac, cryogenics, controls	286
	R.P. Wells, J.M. Byrd, J.N. Corlett, L.R. Doolittle, P. Emma, A. Ratti LBNL, Berkeley, California, USA C. Adolphsen, C.D. Nantista SLAC, Menlo Park, California, USA D. Arenius JLAB, Newport News, Virginia, USA C.M. Ginsburg, T.J. Peterson Fermilab, Batavia, USA
	Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 The Next Generation Light Source (NGLS) is a design concept for a multibeamline soft x-ray FEL array powered by a CW superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. This paper describes the concepts for the cavity and cryostat design operating at 1.3 GHZ and based on minimal modifications to the design of ILC cryomodules, This leverages the extensive experience derived from R&D that resulted in the ILC design. Due to the different nature of the two applications, particular attention is given now to high loaded Q operation and microphonics control, as well as high reliability and expected up time. The work describes the design and configuration of the linac, including choice of gradient, possible modes of operation, cavity design and RF power, as well as the consequent requirements for the cryogenic system.

MOP069	Precise Measurement of Superconducting Cavity Movement in Cryomodule by the Position Monitor Using White Light Interferometer	target, cryomodule, linac, superconducting-cavity	291
	H. Sakai, T. Aoto, K. Enami, T. Furuya, M. Sato, K. Shinoe, K. Umemori KEK, Ibaraki, Japan E. Cenni Sokendai, Ibaraki, Japan K. Hayashi, K. Kanzaki Tokyo Seimitsu Co. Ltd, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	Alignment of Superconducting cavity is one of the important issues for linear collider and/or future light source like ERL and X-FEL. To measure the cavity displacement under cooling to Liq He temperature more precisely, we newly developed the position monitor by using white light interferometer. This monitor is based on the measurement of the interference of light between the measurement target and the reference point. It can measure the position from the outside of the cryomodule. We applied this monitor to the main linac cryomodule of Compact ERL and successfully measured the displacement during 2K cooling with the resolution of 10 micron

MOP070	Results on Quality Factors of 1.3 GHz Nine-Cell Cavities at DESY	factory, niobium, operation, linear-collider	297
	F. Schlander IKP, Mainz, Germany F. Schlander DESY, Hamburg, Germany
	Superconducting cavities made of niobium are the basis of many particle accelerators around the world. Besides the quest for high accelerating fields for projects like European XFEL and the International Linear Collider, the quality factor, a measure for the resistance and hence the ohmic losses, is of importance, as it eventually determines the cryoplant size and its costs of operation. Especially for accelerators operating in continuous wave mode, the dynamic heat load generated by cavity operation exceeds the static heat load by far and thus requires minimisation. To investigate the current quality factor performance of 1.3 GHz cavities at DESY, the test results of some 50 recent cavities with state-of-the-art treatment have been examined regarding surface treatment and material.
	Slides MOP070 [0.590 MB]

MOP071	Record Quality Factor Performance of the Prototype Cornell ERL Main Linac Cavity in the Horizontal Test Cryomodule	linac, cryomodule, experiment, higher-order-mode	300
	N.R.A. Valles, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Supported by NSF grant DMR-0807731 Future SRF linac driven accelerators operated in CW mode will require very efficient SRF cavities with high intrinsic quality factors Q at medium accelerating fields. Cornell has recently ﬁnished testing the fully equipped 1.3 GHz, 7-cell main linac cavity for the Cornell Energy Recovery Linac in a horizontal test cryomodule (HTC). Measurements characterizing the fundamental mode’s quality factor have been completed, showing record Q performance. In this paper, we present detailed quality factor vs gradient results for three HTC assembly stages. We show that the performance of an SRF cavity can be maintained when installed into a cryomodule, and that thermal cycling reduces residual surface resistance. We present world record results for a fully equipped multicell cavity in a cryomodule, reaching intrinsic quality factors at operating accelerating field of Q(E =16.2 MV/m, 1.8K) > 6·10¹⁰ and Q(E =16.2 MV/m, 1.6K) > 1.0·10¹¹, corresponding to a very low residual surface resistance of 1.1 nOhm.

MOP073	IHEP 1.3 GHz Low Loss Large Grain 9-cell Cavity Fabrication, Processing and Test	HOM, SRF, vacuum, niobium	305
	J.Y. Zhai, J. Gao, S. Jin, Z.Q. Li, Y. Liu, Z.C. Liu, Z.H. Mi, X.H. Peng, T.X. Zhao, H.J. Zheng IHEP, Beijing, People's Republic of China C.A. Cooper, C.M. Ginsburg, T.N. Khabiboulline, A.M. Rowe, D.A. Sergatskov Fermilab, Batavia, USA J.X. Wang, H. Yu, H. Yuan BIAM, Beijing, People's Republic of China
	The combination of the low-loss shape and large grain niobium material is expected to be the possible way to achieve higher gradient and lower cost for ILC 9-cell cavities, and will be essential for the ILC 1 TeV upgrade. As the key component of the “IHEP 1.3 GHz SRF Accelerating Unit Project”, a low-loss shape 9-cell cavity with full end groups using Ningxia large grain niobium (IHEP-02) was fabricated at IHEP in 2012. The cavity was processed (CBP and EP) and tested at FNAL. The cavity processing,test performance and gradient limitation is reported in this paper. We will weld the helium vessel, assemble the magnetic shield and install the cavity to IHEP ILC-TC1 cryomodule.

MOP077	Cryomodule Component Development for the APS Upgrade Short Pulse X-Ray Project	cryomodule, HOM, vacuum, alignment	314
	J.P. Holzbauer, J.D. Fuerst, A. Nassiri, Y. Shiroyanagi, B.K. Stillwell, G.J. Waldschmidt, G. Wu ANL, Argonne, USA G. Cheng, J. Henry, J.D. Mammosser, J. Matalevich, J.P. Preble, R.A. Rimmer, H. Wang, K.M. Wilson, M. Wiseman, S. Yang JLAB, Newport News, Virginia, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CHI1357 at ANL and under U.S. DOE Contract No. DE-AC05-06OR23177 at Jefferson Lab. The short pulse x-ray (SPX) part of the Advanced Photon Source Upgrade calls for the installation of a two-cavity cryomodule in the APS ring to study cavity-beam interaction, including HOM damping and cavity timing and synchronization. Design of this cryomodule is underway at Jefferson Lab in collaboration with the APS Upgrade team at ANL. The cryomodule design faces several challenges including tight spacing to fit in the APS ring, a complex set of cavity waveguides including HOM waveguides and dampers enclosed in the insulating vacuum space, and tight alignment tolerances due to the APS high beam-current (up to 150 mA). Given these constraints, special focus has been put on modifying existing CEBAF-style designs, including a cavity tuner and alignment scheme, to accommodate these challenges. The thermal design has also required extensive work including coupled thermal-mechanical simulations to determine the effects of cool-down on both alignment and waveguides. This work will be presented and discussed in this paper.

MOP078	Horizontal Testing of a Dressed Deflecting Mode Cavity for the APS Upgrade Short Pulse X-Ray Project	controls, operation, photon, vacuum	321
	J.P. Holzbauer, N.D. Arnold, T.G. Berenc, D.J. Bromberek, J. Carwardine, N.P. Di Monte, J.D. Fuerst, A.E. Grelick, D. Horan, J.A. Kaluzny, J.W. Lang, H. Ma, T.L. Mann, D.A. Meyer, M.E. Middendorf, A. Nassiri, Y. Shiroyanagi, J.H. Vacca, G.J. Waldschmidt, R.D. Wright, G. Wu, Y. Yang, A. Zholents ANL, Argonne, USA E.R. Harms, W. Schappert Fermilab, Batavia, USA J.D. Mammosser JLAB, Newport News, Virginia, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CHI1357. The short pulse x-ray (SPX) part of the Advanced Photon Source (APS) Upgrade is an effort to enhance time-resolved experiments on a few-ps-scale at the APS. The goal of SPX is the generation of short pulses of x-rays for pump-probe time-resolved capability using superconducting rf (SRF) deflecting cavities. These cavities will create a correlation between longitudinal position in the electron bunch and vertical momentum. The light produced by this bunch can be passed through a slit to produce a pulse of light much shorter (1-2 ps instead of 100 ps) than the bunch length at reduced flux. An SPX cavity has been tested with a helium vessel and tuner. In addition to studying rf performance with more realistic cooling, this test allowed integration and operation of many systems designed for SPX cryomodule in-ring operation. These systems included an APS-constructed 5 kW, 2.815 GHz amplifier, a digital low-level rf controller system designed and fabricated in collaboration with LBNL, a cavity tuner, and instrumentation systems designed for the existing APS infrastructure. Cavity performance and subsystem performance will be reported and discussed in this paper. A. Zholents et al., NIM A 425, 385 (1999). ** A. Nassiri et al., “Status of the Short-Pulse X-Ray Project at the Advanced Photon Source,” IPAC 2012, New Orleans, LA, May 2012.

MOP080	Design of a New Horizontal Test Cryostat for SCRF Cavities at the Uppsala University	cryomodule, radiation, operation, vacuum	328
	T. Junquera, P. Bujard, N.R. Chevalier, J.P. Thermeau Accelerators and Cryogenic Systems, Orsay, France L. Hermansson, M. Noor, R.J.M.Y. Ruber, R. Santiago Kern Uppsala University, Uppsala, Sweden H. Saugnac IPN, Orsay, France
	At Uppsala University, the FREIA facility for research and development of new accelerators and associated instrumentation, is presently in construction. Associated to a new Helium Liquefier, a Horizontal Test Cryostat will be used for high power RF tests of completely equipped SC cavities. This paper presents the main characteristics of the cryostat and the associated cryogenic distribution system. Two types of cavities have been considered for test purpose: SC elliptical cavities for future free electron lasers and SC cavities for high intensity proton accelerators (i.e. SC spokes). A special valve box including a subcooling stage and power coupler cooling with supercritical Helium supply have been designed, for temperature operation ranging from 2K to 4.2 K. This facility will play an essential role in the development and test of cavities, couplers and cryomodules for the ESS project. High power RF sources will be installed in order to allow unique and complete tests of spoke cavities and cryomodules at high nominal peak power.

MOP082	Development and Test of a New Cryostat Module for the Injector of the S-DALINAC*	electron, operation, vacuum, linac	334
	T. Kürzeder, J. Conrad, F. Hug, N. Pietralla, A. Richter, S.T. Sievers TU Darmstadt, Darmstadt, Germany R.G. Eichhorn Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: *This work is supported by the DFG through the Collaborative Research Center SFB 634. The present injector of the superconducting Darmstadt electron linear accelerator S-DALINAC provides an electron beam of up to 10 MeV kinetic energy and up to 60 μA current in continuous wave operation. A new cryostat module has been constructed to replace the actual one in order to provide higher beam energies of up to 14 MeV and currents of up to 250 μA for nuclear resonance fluorescence experiments at the Darmstadt High Intensity Photon Setup (DHIPS). As before two 20-cell superconducting microwave cavities will be operated at an acceleration frequency of 3 GHz in a liquid helium bath at 2 K. For the injector upgrade two new elliptical 20-cell niobium cavities were also manufactured and in addition a third spare one. The rf power is transferred to the cavities by an also newly developed waveguide-transition line and input couplers. We report on the construction of the cryostat module and its components and present the results of a first cooling-down procedure.

MOP083	Operational Experience With the SOLEIL Storage Ring RF Cryogenic Plant	cryogenics, controls, operation, HOM	337
	M. Louvet, H.D. Dias, M. Diop, P. Marchand SOLEIL, Gif-sur-Yvette, France
	In the Storage Ring of the Synchrotron SOLEIL light source, two cryomodules provide the required power of 575 kW at the nominal energy of 2.75 GeV with the full beam current of 500 mA and all the insertion devices. Each cryomodule contains a pair of 352 MHz superconducting cavities (Nb/Cu), cooled in a bath of liquid helium at 4.5 K. A single 350 W cryogenic system supplies the liquid helium for the two cryomodules. The seven years of operational experience with this cryogenic plant as well as its upgrades are reported.

MOP084	ESS Cryomodules for Elliptical Cavities	cryomodule, vacuum, cryogenics, operation	341
	G. Olivier, J.P. Thermeau IPN, Orsay, France P. Bosland CEA/IRFU, Gif-sur-Yvette, France C. Darve ESS, Lund, Sweden
	The European Spallation Source will be the world's most powerfull neutron source. IPN Orsay undertakes the development of the ESS linac cryomodules for both medium and high beta elliptical cavities which constitute the high energy section. A medium beta technical demonstrator will be built in a first time. The cryomodules are composed of 4 superconducting cavities cooled at 2K. The cold mass assembly is hanged in an intermediate structure located inside the vacuum vessel. A 50K fixed temperature is implemented by the mean of an aluminium shield. Each cryomodule is connected to the cryogenic distribution line. The vacuum vessel is 6.3m long and has a 1.2m diameter. The poster describes the general design,the solutions implemented, the characteristics of the main components and the mechanical/thermal calculations .

MOP085	Status of the Superconducting Proton Linac (SPL) Cryomodule	vacuum, cryogenics, operation, linac	345
	V. Parma, R. Bonomi, O. Capatina, J.K. Chambrillon, E. Montesinos, K.M. Schirm, A. Vande Craen, G. Vandoni, R. van Weelderen CERN, Geneva, Switzerland G. Devanz CEA/IRFU, Gif-sur-Yvette, France P. Duchesne, P. Duthil, S. Rousselot IPN, Orsay, France
	The Superconducting Proton Linac (SPL) is an R&D effort conducted by CERN in partnership with other international laboratories, aimed at developing key technologies for the construction of a multi-megawatt proton linac based on state-of-the-art SRF technology. Such an accelerator would serve as a driver in new physics facilities for neutrinos and/or radioactive ion beams. Amongst the main objectives of this effort, are the development of 704 MHz bulk niobium β=1 elliptical cavities (operating at 2 K and providing an accelerating field of 25 MV/m) and the test of a string of cavities integrated in a machine-type cryo-module. In an initial phase, only four out of the eight cavities of the SPL cryo-module will be tested in a half- length cryo-module developed for this purpose, which nonetheless preserves the main features of the full size machine. This paper presents the final design of the cryo-module and the status of the construction of the main cryostat parts. Preliminary plans for the assembly and testing of the cryo-module at CERN are presented and discussed.

MOP087	Conceptual Design of a Cryomodule for Compact Crab Cavities for Hi-Lumi LHC	cryomodule, cryogenics, SRF, luminosity	353
	S.M. Pattalwar, P.A. McIntosh, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt Cockcroft Institute, Warrington, Cheshire, United Kingdom G. Burt Lancaster University, Lancaster, United Kingdom O. Capatina CERN, Geneva, Switzerland B.D.S. Hall Cockcroft Institute, Lancaster University, Lancaster, United Kingdom T.J. Jones, N. Templeton STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom T.J. Peterson Fermilab, Batavia, USA
	A prototype Superconducting (RF) cryomodule, comprising multiple compact crab cavities is foreseen to realise a local crab crossing scheme for the “Hi-Lumi LHC”, a project launched by CERN to increase the luminosity performance of LHC. A cryomodule with two cavities will be initially installed and tested on the SPS drive accelerator at CERN to evaluate performance with high-intensity proton beams. A series of boundary conditions influence the design of the cryomodule prototype, arising from; the complexity of the cavity design, the requirement for multiple RF couplers, the close proximity to the second LHC beam pipe and the tight space constraints in the SPS and LHC tunnels. As a result, the design of the helium vessel and the cryomodule has become extremely challenging. This paper assesses some of the critical cryogenic and engineering design requirements and describes an optimised cryomodule solution for the tests with SPS.

MOP089	Design of the ESS Spoke Cryomodule	vacuum, cryomodule, operation, cryogenics	357
	D. Reynet, S. Bousson, S. Brault, P. Duchesne, P. Duthil, N. Gandolfo, G. Olry, E. Rampnoux IPN, Orsay, France
	The European Spallation Source (ESS) project brings together 17 European countries to develop the world’s most powerful neutron source feeding multidisplinary researches. The superconducting part of the linear accelerator consists in 59 cryomodules housing different superconducting radiofrequency (SRF) resonators among which 28 paired β=0.5 352.2 MHz SRF niobium double Spoke cavities, held at 2K in a saturated helium bath. A prototype Spoke cryomodule with two cavities equipped with their 300kW RF power couplers is now being designed and will be constructed and tested at full power by the end of 2015 for the validation of all chosen technical solutions. It integrates all the interfaces necessary to be operational within a linac machine. Its assembly requires dedicated tooling and procedures in and out of a clean room. The design takes into account an industrial approach for the management of the fabrication costs. This prototype will have to guarantee an accelerating field of 8MV/m while optimizing the energy consumption and will aim at assessing the maintenance operations issues. We propose to present the design of this cryomodule and its related tooling.

MOP092	Computation of Wakefields and HOM Port Signals by Means of Reduced Order Models	wakefield, impedance, HOM, operation	364
	J. Heller, T. Flisgen, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
	The investigation of wakefields is an important task in the design and operation of particle accelerators. Computer simulations are a reliable tool to extend the understanding of these effects. This contribution presents an application example of a new method to compute wakefields as well as parameters derived from those fields, such as higher order mode (HOM) port signals. The method is based on a reduced order model of the structure created by as set of 3D eigenmodes, a set of 2D waveguide port modes and the current density of the beam. In contrast to other wakefield computations, the proposed method operates directly on the reduced order model. Therefore, once having established this model, the beam-excited fields can be determined quickly for different beam parameters. As a matter of fact, only a small part of the reduced system has to be recomputed for every sweep point. From these advantages it is obvious, that the method is highly compatible for beam parameter studies. In a proof of principal the effectiveness of the method compared to established methods of wakefield computations in terms of computational time and accuracy is shown.

MOP093	Geometric Optics of Wake Fields of Very Short Bunches in Superconducting Cavities	wakefield, HOM, FEL, superconducting-cavity	367
	A. Novokhatski SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE-AC02-76SF00515 We study the wake potentials of very short bunches in a quasi periodic structure of superconducting cavities. We analyze the pattern of the electric force lines and the shape of a cavity. The behavior of electric force lines reflects irregularities of the shape structure of a cavity. Simulations were carried for different kind of cavities, including JLAB 7 cell cavity with application to future light sources.

TUIOA01	Influence of the Couldown at the Transition Temperature on the SRF Cavity Quality Factor	shielding, niobium, SRF, experiment	370
	O. Kugeler, J. Knobloch, J.M. Vogt HZB, Berlin, Germany
	The quality factor Q0 that can be obtained in a superconducting cavity is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We believe that cooling conditions have an additional impact, as they appear to influence the amount of trapped flux and hence the residual resistance. We constructed a test stand using a niobium rod shorted out by a titanium rod to mimic a cavity in its helium tank to study flux trapping. Here we can precisely control the temperature and measure the dynamics of flux trapping at the superconducting phase transition. We learned that magnetic flux can be generated when a temperature gradient exists along the rod and when the niobium transitions into the superconducting state it subsequently remains trapped. Furthermore, it was shown that the cooling rate during isothermal cooldown through the transition temperature can influence the amount of externally applied flux which remains trapped. The acquired knowledge may be used to modify the cooldown procedure of SRF cavities leading to a reduced level of trapped flux and hence operation closer to the BCS limit.
	Slides TUIOA01 [1.276 MB]

TUIOA02	High Q0 Research: The Dynamics of Flux Trapping in Superconducting Niobium	niobium, experiment, simulation, shielding	374
	J.M. Vogt HZB, Berlin, Germany J. Knobloch, O. Kugeler BESSY GmbH, Berlin, Germany
	The quality factor Q0 that can be obtained in a superconducting cavity is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We believe that cooling conditions have an additional impact, as they appear to influence the amount of trapped flux and hence the residual resistance. We have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and measure the dynamics of flux trapping at the superconducting phase transition. We learned that magnetic flux can be generated when a temperature gradient exists along the rod as the niobium transitions to the superconducting state, which subsequently remains trapped. It was also shown that the cooling rate can influence the amount of externally applied flux which is trapped. Furthermore, we also were able to demonstrate that flux lines become mobile if the superconductor is warmed close to below Tc. The acquired knowledge may be used to modify the cooldown procedure of SRF cavities leading to a reduced level of trapped flux and hence operation closer to the BCS limit.
	Slides TUIOA02 [5.774 MB]

TUIOA05	New Insights Into Quench Caused by Surface Pits in SRF Cavities	niobium, laser, SRF, feedback	378
	Y. Xie, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by NSF Career award PHY-0841213 and the Alfred P. Sloan Foundation. Surface defects such as pits have been identified as some of the main sources of limitations of srf cavity performance. A single cell cavity with 30 artificial pits in the high magnetic field region was made to gain new insight in how pits limit the cavity performance. The test of the pit cavity showed clear evidence that the edges of two of the largest radius pits transitioned into the normal conducting state at field just below the quench field of the cavity, and that the quench was indeed induced by these two pits. The pit geometrical information measured by laser confocal microscopy combined with a numerical finite element ring-type defect model will be compared with temperature mapping results. Insights about quench and non-linear rf resistances will be presented. Y. Xie, PhD thesis, Cornell University, 2013
	Slides TUIOA05 [3.101 MB]

TUIOA06	Research on Field Emission and Dark Current in ILC Cavities	electron, simulation, photon, detector	392
	Y.M. Li, K.X. Liu PKU, Beijing, People's Republic of China R.L. Geng, A.D. Palczewski JLAB, Newport News, Virginia, USA
	Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Field emission and dark current are issues of concern for SRF cavity performance and SRF linac operation. Complete understanding and reliable control of the issue are still needed, especially in full-scale multi-cell cavities. Our work aims at developing a generic procedure for finding an active field emitter in a multi-cell cavity and benchmarking the procedure through cavity vertical test. Our ultimate goal is to provide feedback to cavity preparation and cavity string assembly in order to reduce or eliminate filed emission in SRF cavities. Systematic analysis of behaviors of field emitted electrons is obtained by ACE3P developed by SLAC. Experimental benchmark of the procedure was carried out in a 9-cell cavity vertical test at JLab. The energy spectrum of Bremsstrahlung X-rays is measured using a NaI(Tl) detector. The end-point energy in the X-ray energy spectrum is taken as the highest kinetic electron energy to predict longitudinal position of the active field emitter. Angular location of the field emitter is determined by an array of silicon diodes around irises of the cavity. High-resolution optical inspection was conducted at the predicted field emitter location.
	Slides TUIOA06 [4.565 MB]

TUIOB01	R&D Progress in SRF Surface Preparation With Centrifugal Barrel Polishing (CBP) for both Nb and Cu	SRF, niobium, synchrotron, experiment	398
	A.D. Palczewski JLAB, Newport News, Virginia, USA B. Bullock Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA C.A. Cooper Fermilab, Batavia, USA S.C. Joshi RRCAT, Indore (M.P.), India A. Navitski DESY, Hamburg, Germany A.A. Rossi INFN/LNL, Legnaro (PD), Italy
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Centrifugal Barrel polishing (CBP) is becoming a common R&D tool for SRF cavity preparation around the word. During the CBP process a cylindrically symmetric SRF cavity is filled with relatively cheap and environmentally friendly abrasive and sealed. The cavity is then spun around the cylindrical axis at high speeds uniformly conditioning the inner surface. This uniformity is especially relevant for SRF application because many times a single manufacturing defects limits cavity’s performance well below it’s theoretical limit. In addition CBP has created surfaces with roughness’s on the order of 10’s of nm which create a unique surface for wet chemistry or thin film deposition. CBP is now being utilized at Jefferson Laboratory, Fermi Laboratory and Cornell University in the US, Ko Enerugi Kasokuki Kenkyu Kiku in Japan, Deutsches Elektronen-Synchrotron in Germany, Laboratori Nazionali di Legnaro in Italy, and Raja Ramanna Centre for Advanced Technology in India. In this talk we will present current CBP research from each lab including polishing recipes, equipment, post CBP chemistry/heat treatment, and subsequent cryogenic cavity tests on niobium as well as copper cavities.
	Slides TUIOB01 [2.204 MB]

TUIOC02	Bipolar EP: Electropolishing without Fluorine in a Water Based Electrolyte	niobium, SRF, experiment, controls	404
	A.M. Rowe, A. Grassellino Fermilab, Batavia, USA T.D. Hall, M.E. Inman, S.T. Snyder, E.J. Taylor Faraday Technology, Inc., Clayton, USA
	Funding: Operated by Fermi Research Alliance, LLC under contract No. De-AC02-07CH11359 with the United States Department of Energy For more than thirty years, preparing superconducting RF cavities for high performance has required the use of dangerous and ecologically damaging chemicals. Reducing the personnel and environmental risks associated with using these chemicals is a priority at Fermilab. Therefore, Fermilab pursued a project to adapt a non-hazardous and relatively benign bipolar electropolishing technique to SRF cavities that Faraday Technology, Inc. developed. Faraday initially developed this electropolishing technique to polish metal alloys used in automotive and semiconductor components as well as medical devices and implants. By modifying the cathodic/anodic interaction via a pulse forward/pulse reverse technique, Fermilab and Faraday Technology demonstrate the capability to polish 1.3 GHz single-cell cavities utilizing an aqueous 10% sulfuric acid electrolyte. We present the development of bipolar EP for single-cell 1.3 GHz cavities and show the results from vertical tests achieving gradients greater than 40 MV/m.
	Slides TUIOC02 [1.251 MB]

TUIOC03	Fluorine Free Ionic Liquid Electropolishing of Niobium Cavities	niobium, cathode, experiment, superconductivity	410
	V.B. Pastushenko, O.V. Malkova, V. Palmieri, A.A. Rossi, F. Stivanello, G. Yu INFN/LNL, Legnaro (PD), Italy G. Yu CIAE, Beijing, People's Republic of China
	Ionic liquids are an emerging breakthrough in green chemistry since the years 2000. In 2006, INFN-LNL was the first to apply a mixture of Choline Chloride and Urea to Niobium electropolishing. It was found that mirror like surfaces could be obtained at temperature higher than 120°C, with high throwing power. Subsequently the process was successfully applied to the electropolishing of a 6 GHz monocell cavity with the addition of sulphamic acid. In this work, we will report an intense investigation of the possible variants of the original recipe. We studied the influence on Niobium surface roughness of several parameters such as: other sulphamic, ammonium and carboxylic containing additives different than sulfamic acid, the possible substitution of Urea with ethylene glycol and malic acid, the current regime; the electrolyte temperature and the cathode shape, rotating horizontal electropolishing versus vertical electropolishing. Due to the cavity hollow cylindrical shape, the electrolyte temperature appeared to be the most crucial parameters among those above mentioned for a uniform dissolution of niobium.
	Slides TUIOC03 [14.464 MB]

TUIOC04	Analysis of Post-Wet-Chemistry Heat Treatment Effects on Nb SRF Surface Resistance	SRF, niobium, superconductivity, site	414
	P. Dhakal, G. Ciovati, P. Kneisel, G.R. Myneni JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Most of the current R&D in SRF is focused on ways to reduce the construction and operating cost of SRF-based accelerators as well as on the development of new or improved cavity processing techniques. The increase in quality factors is the result of the reduction of the surface resistance of the materials. A recent test [] on a 1.5 GHz single cell cavity made from ingot niobium of medium purity and heat treated at 1400 C in a ultra-high vacuum induction furnace resulted in a residual resistance of ~ 1nanoohm and a quality factor increasing with field up to ~ 5×10¹⁰ at a peak magnetic field of 90 mT. In this contribution, we present some results on the investigation of the origin of the extended Q0-increase, obtained by multiple HF rinses, oxypolishing and heat treatment of “all Nb” cavities. [] P. Dhakal et al., Phys. Rev. ST Accel. Beams 16, 042001 (2013).
	Slides TUIOC04 [4.838 MB]

TUIOC05	Purification of 6 GHz Cavities by Induction Heating	induction, vacuum, niobium, SRF	419
	A.A. Rossi, A. Battistello, M. Checchin, V. Palmieri, S. Stark, F. Stivanello, R.K. Thakur, G. Yu INFN/LNL, Legnaro (PD), Italy
	We have developed an innovative technique for purification of bulk-Nb 6GHz RF cavities under ultra-high vacuum (UHV) system. The main advantages of 6 GHz bulk-Nb cavities are saving cost, materials and time to collect statistics of surface treatments and RF test. Cavities are RF tested before and after high temperature treatment under UHV conditions. Induction heating method is used to anneal the cavity at temperatures higher than 2000°C and close to the melting point of Nb for less than a minute while few seconds at maximum temperature. Before RF test and UHV annealing, the surface treatment processes like tumbling, chemical, electro-chemical (such as BCP and EP), ultrasonic cleaning and high pressure rinsing (HPR) have been employed. This kind of Nb 6 GHz cavity purification allow to reduce hydrogen, oxygen and other elemental impurities content, which effects on cavity Q-factor degradation, by a rapid annealing over 2000°C and a subsequent rapid reduction at room temperature.
	Slides TUIOC05 [42.171 MB]

TUIOC06	Study on Optimum Electron Beam Welding Condition for Superconducting Accelerating Cavities	niobium, electron, experiment, SRF	424
	T. Kubo, Y. Ajima, H. Inoue, T. Saeki, K. Umemori, Y. Watanabe, S. Yamaguchi, M. Yamanaka KEK, Ibaraki, Japan T. Nagata ULVAC, Inc., Tsukuba, Japan
	Optimizations of electron beam welding conditions might solve the quench problems and improve the accelerating field of the superconducting radio-frequency cavity. As a first step toward optimum conditions, basic properties of weld beads are studied by using niobium test pieces. Effects of a combination of a beam generator position and a welding direction on geometries of weld bead are shown. Good parameter-regions for electron beam welding, which yield full penetration welds without holes or weld spatters, are surveyed. Microscopic structures, such as pits or bumps due to poor welds, have greater influence on cavity performances, which are also our research objects. We introduce a model of the magnetic field enhancement at pits, where a formula for a magnetic field enhancement factor is given as a function of parameters that express a geometry of pit. Comparisons between calculations and vertical test results are also shown.
	Slides TUIOC06 [15.958 MB]

TUP007	Vortex Penetration Field in the Multilayered Coating Model	vacuum, superconductivity, electromagnetic-fields	430
	T. Kubo, T. Saeki KEK, Ibaraki, Japan Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan
	A multilayered structure with a single superconductor layer and a single insulator layer deposited on a bulk superconductor is studied. General formulae for the vortex penetration-field of the superconductor layer and the magnetic field on the bulk superconductor which is shielded by the superconductor and insulator layers are derived with a rigorous calculation of the magnetic field attenuation in the multilayered structure. The formulae depend not only on the material and the thickness of the superconductor layer but also on the thickness of the insulator layer. The results can be applied to superconducting accelerating cavities with the multilayered structure. Using the formulae, a combination of the thicknesses of superconductor and insulator layers to enhance the RF breakdown field limits can be found for any given materials. (Submitted on 25 Apr 2013) T. Kubo, Y. Iwashita and T. Saeki, arXiv:1304.6876 [physics.acc-ph](Submitted on 25 Apr 2013); arXiv:1306.4823 [physics.acc-ph](Proc. of IPAC13); arXiv:1307.0583 [physics.acc-ph](Proc. of SRF2013)

TUP008	Models of the Magnetic Field Enhancement at Pits	SRF, experiment, laser, radio-frequency	433
	T. Kubo KEK, Ibaraki, Japan
	A simple model of the magnetic field enhancement at pits on the surface of superconducting accelerating cavity is proposed. The model consists of a two-dimensional pit with a slope angle, depth, width, and radius of round edge. An analytical formula that describes the magnetic field enhancement factor of the model is derived. The formula is given as a function of a slope angle and a ratio of half a width to a round-edge radius. Using the formula, the field at which vortices start to penetrate can be evaluated for a given geometry of pit. Takayuki Kubo, arXiv:1307.5943 [physics.acc-ph](Submitted on 23 Jul 2013)

TUP009	Magnetic Dependence of the Energy Gap: a Good Model to Fit Q Slope of Low Beta Cavities	superconductivity, experiment, niobium, simulation	438
	D. Longuevergne IPN, Orsay, France
	The reasons why the intrinsic quality factor (noted Qo) of a superconducting cavity drops with the accelerating field (noted Eacc) are still not well understood. In an effort to explain this phenomenon, mainly for high beta cavities, many models have been developed in the community but few of them could fit experimental data whatever the material treatment or surface conditioning. In the specific case of low beta cavities made of bulk Niobium (i.e Spiral 2 Quarter Wave Resonator), a model based on a magnetic field dependence of the energy gap has been developed to fit experimental data. The evolutions of the model input parameters depending on the cavity treatment or test conditions are consistent with the changes described in the literature. The model will be described and specific examples will be given.

TUP010	Simulation of Non-linear RF Losses Derived from Characteristic Nb Topography	simulation, niobium, SRF, interface	441
	C. Xu, M.J. Kelley JLAB, Newport News, Virginia, USA M.J. Kelley, C. Xu The College of William and Mary, Williamsburg, USA C.E. Reece JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. A simplified model has been developed to simulate non-linear rf losses on Nb surfaces due exclusively to topographical enhancement of surface magnetic fields. If local sharp edges are small enough, where local surface fields exceed Hc, small volumes of material may become normal conducting without thermal runaway leading to quench. These small volumes of normal material yield increases in the effective surface resistance of the Nb. Using topographic data from typical BCP’d and EP’d fine grain niobium, we have simulated field-dependent losses and find that when extrapolated to resulting cavity performance correspond well to characteristic BCP/EP high field Q0 performance differences for fine grain Nb. We will describe the structure of the model, its limitations, and the effects of this type of non-linear loss contribution to SRF cavities.

TUP014	Fast Table Top Niobium Hydride Investigations Using Direct Imaging in a Cryo-Stage	niobium, cryogenics, laser, vacuum	447
	F.L. Barkov, A. Grassellino, A. Romanenko Fermilab, Batavia, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. Performance of niobium SRF cavities can be strongly affected by hydrogen segregation into lossy niobium hydrides as known for "hydrogen Q disease" at higher concentration of dissolved H and may be a reason for the "high field Q slope" at lower concentrations. With the use of optical cryostat and laser confocal microscope we have developed a "table top technique" for direct observation of hydride precipitation, and studied formation, morphology, and time evolution of hydrides after different treatments used for cavities. Our results show that hydrides can form at the niobium surface at 90-180K depending mainly on H concentration and the cooldown rate. A lot of H is absorbed by bulk niobium during mechanical polishing, which leads to the formation of very large (>10 microns) hydrides. Both EP and BCP do not influence H concentration significantly provided that temperature during treatments is kept below 15C. 800C degassing reduces H concentration and precludes large hydride precipitation. 120C baking and mechanical deformation do not change H concentration but affect hydride precipitation through their influence on the number of nucleation centers and H binding defects.

TUP015	Bitter Decoration Studies of Magnetic Flux Penetration Into Cavity Cutouts	SRF, experiment, niobium, radio-frequency	451
	F.L. Barkov, A. Grassellino, A. Romanenko Fermilab, Batavia, USA L.Y. Vinnikov ISSP, Chernogolovka, Russia
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Magnetic flux penetration may produce additional losses in superconducting radio frequency cavities. All the existing models for flux penetration are based on the formation of Abrikosov vortices. Using high resolution Bitter decoration technique we have investigated magnetic flux distribution patterns in cavity cutouts at the perpendicular magnetic fields of 10-80 mT. At low fields <20 mT the magnetic field penetrates in the form of flux bundles and not Abrikosov vortices, the situation characteristic of type-I superconductors. With the increase of the magnetic field up to 30 mT "bundles" first merge into a connected structure and then break up into individual Abrikosov vortices at ~60 mT and a well-known intermediate mixed state is observed. Such magnetic field driven transition from type I to type II superconductivity has never been observed before in any existing superconductor. For the case of flat samples we have observed a coexistence of both "bundles" and Abrikosov vortices in one experiment. Our results show that high-purity cavity grade niobium is a "border-line" material and behaves as a type-I superconductor at lower fields and type-II at higher fields.

TUP016	Effects of Processing History on Damage Layer Evolution in Large Grain Nb Cavities	SRF, electron, niobium, radio-frequency	455
	D. Kang, T.R. Bieler Michigan State University, East Lansing, Michigan, USA C. Compton FRIB, East Lansing, Michigan, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics, through Grant No. DE-S0004222. Previous cavity tests identified a strong dependence of achievable accelerating gradients on the amount of material removed from the surface. Samples extracted from the iris and the equator of a half cell fabricated by Jefferson Lab using large grain Nb were examined to identify underlying mechanisms. Electron backscattered diffraction (EBSD) was used to measure the crystal orientations on the cross sections of the samples. Results demonstrated the presence of a surface damage layer, which contained higher dislocation content than the bulk due to the deep drawing process. The depth of the damage layer depends on crystal orientations, and damage to the iris is more severe than at the equator. From the EBSD data, the damage depth was estimated to be about 100 microns. The samples were then heat treated at 800°C and 1000°C, and the same areas were examined again for the effects of heat treatment on the healing of the damage layer. While the damage layer accounts for some of the performance gain from chemical surface removal, the depth of the damage layer in polycrystalline cavities remains an open question.

TUP017	Study of Slip and Dislocations in High Purity Single Crystal Nb for Accelerator Cavities	niobium, SRF, radio-frequency, factory	461
	D. Kang, D.C. Baars, T.R. Bieler Michigan State University, East Lansing, Michigan, USA C. Compton FRIB, East Lansing, Michigan, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics, through Grant No. DE-S0004222. SRF Cavities can be formed by deep drawing slices from Nb ingots with large grains. Crystal orientation dependent slip system activities affect the shape change of ingot slices during deep drawing, and form a dislocation substructure that affects subsequent recrystallization and ultimately, cavity performance. Two groups of single crystal tensile specimens with different orientations were extracted from a large grain ingot slice. The first group was deformed monotonically to 40% engineering strain. Analysis revealed that slip was preferred on {112} planes. The second group was heat treated at 800°C for two hours, and then deformed incrementally to 40% engineering strain using an in situ tensile stage. Crystal orientations and surface images were recorded at each increment of deformation. Results indicate that the heat treated group had lower yield strengths, and the details of slip activity differed in the annealed samples. Active slip systems were investigated and compared to the first group. Direct observations of dislocations were performed in selected specimens using electron channeling contrast imaging, to determine how slip affects the dislocation substructure.

TUP019	Probing Hot Spot and Cold Spot of SRF Cavities with Tunneling and Raman Spectroscopies	superconductivity, SRF, laser, electron	466
	C. Cao Illinois Institute of Technology, Chicago, IL, USA G. Ciovati JLAB, Newport News, Virginia, USA L.D. Cooley, A. Grassellino Fermilab, Batavia, USA N. Groll, Th. Proslier ANL, Argonne, USA J. Zasadzinski IIT, Chicago, Illinois, USA
	Point contact tunneling and Raman spectroscopies are presented on high purity Nb samples, including pieces from hot and col spot regions of tested SRF cavities and Nb coupons subject to similar treatment. High quality tunneling spectra were observed on cold spots, revealing the bulk Nb gap, indicating minimal surface contamination. Hot spots exhibit high smearing suggestive of pair breaking along with generally lower superconducting gap. In addition, pronounced zero bias conductance peaks were frequently observed indicative of spin-flip tunneling and thus magnetic impurities in the oxide layer. Optical microscopy reveals higher density of surface blemishes on hot spots. Raman spectra inside those blemishes show clear difference from surrounding areas, exhibiting enhanced intensity peaks identified as either amorphous carbon, hydrocarbons or the ordered NbC phase. The presence of surface NbC is consistent with TEM studies, and these inclusions exhibit enhanced second order phonon response. Such regions with high concentrations of impurities are expected to suppress the local superconductivity and may explain the formation of hot spots.

TUP022	Study of AC/RF Properties of SRF Ingot Niobium	SRF, niobium, radio-frequency, superconductivity	469
	P. Dhakal, G. Ciovati, G.R. Myneni JLAB, Newport News, Virginia, USA V.M. Genkin, M.I. Tsindlekht The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. In an attempt to correlate the SRF performance of niobium cavities with the superconducting properties, we present the results of the magnetization and ac susceptibility of the niobium used in the superconducting radiofrequency cavity fabrications which were subjected to buffer chemical polishing surface and high temperature heat treatments, typically applied to the SRF cavities fabrications. The analysis of the results show the different surface and bulk ac conductivity for the samples subjected to BCP and HT. Furthermore, the RF surface impedance is measured on the sample using the TE011 microwave cavity for a comparison to the low frequency measurements.

TUP026	Performance of a FNAL Nitrogen Treated Superconducting Niobium Cavity at Cornell	niobium, SRF, linac, superconductivity	475
	D. Gonnella, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A. Grassellino Fermilab, Batavia, USA
	Funding: NSF In many tests of superconducting cavities, the performance of the cavity in the medium field region will be limited by medium field Q slope. For projects such as the proposed Cornell Energy Recovery Linac, high Q operation at medium fields is necessary to meet specifications for efficient CW cavity operation. A single cell cavity was prepared by Fermilab by electropolishing it and baking it at 1000°C with 1x10^-2 Torr of Nitrogen, and subsequently tested at Cornell. The cavity displayed an increase in Q at medium fields between 5 and 20 MV/m at 2.0 K, opposite of the usual medium field Q slope. The material properties of this cavity were studied and correlated with performance. This analysis helps to better understand how to overcome medium field Q slope and improve cavity performance in future CW SRF machines such as the Cornell ERL.

TUP027	High Q0 Studies at Cornell	niobium, SRF, factory, linac	478
	D. Gonnella, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF The construction and preparation of superconducting RF cavities with very high quality factors is very advantageous for future particle accelerators operating in CW mode. Until recently, the highest quality factors measured in SRF cavities were on the order of 10¹¹. A Cornell ERL single-center-cell cavity was prepared with BCP and a five day heat treatment at 1000°C. Following this treatment, the cavity was tested and achieved a record high intrinsic quality factor of 2.9·10¹¹ at 1.4 K, corresponding to a very small residual resistance of (0.35±0.10) nOhm. This cavity was then given a series of BCP’s of 5, 75, and 200 μm and retested. Material properties were extracted from the data hinting at a very low mean free path of the niobium. In this paper we discuss the unusual material properties of the surface layer of the cavity and their implication for the RF performance of the cavity.

TUP028	Investigation of Spatial Variation of the Surface Resistance of a Superconducting RF Cavity	resonance, superconducting-RF, SRF, superconductivity	483
	D. Gonnella, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA R.E. French Corning Community College, Corning, USA
	Funding: NSF Cornell has recently completed a single cell temperature mapping system with a resolution of a few tenths of a millikelvin, corresponding to a surface resistance resolution of 1 nOhm. A superconducting RF cavity was tested using temperature mapping and the surface resistance was extracted from the temperature mapping data as function of position on the cavity surface. The surface resistance was profiled across the surface of the cavity between 5 and 35 MV/m and at different temperatures between 1.6 and 2.1 K. From BCS fitting of the local surface resistance, the spatial variation and the field dependence of the mean free path, energy gap, and residual resistance was found. These studies give interesting new insight into the degree of variation of the properties of the superconductor over the surface of the cavity.

TUP029	Heat Treatment of SRF Cavities in a Low-Pressure Atmosphere	vacuum, SRF, niobium, resonance	487
	D. Gonnella, F. Furuta, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF Recent results from FNAL on baking superconducting RF cavities at high temperatures in a low-pressure atmosphere of a few mTorr indicate that such treatments can increase the medium field quality factor. In this paper we report on studies from Cornell, giving new insight into the mechanism behind this effect.

TUP033	Magnetic Property Improvement of Niobium Doped with Rare Earth Elements	niobium, experiment, SRF, electron	490
	F.S. He, F. He, F. Jiao, X.Y. Lu, K. Zhao PKU, Beijing, People's Republic of China L. Chen NNIEC, Shizuishan City, Ningxia, People's Republic of China T.C. Jiang IMP, Lanzhou, People's Republic of China Y. You, H.Y. Zhao Ningxia Orient Tantalum Industry Co., Ltd., Dawukou District, Shizuishan city, People's Republic of China
	A new idea of modifying the raw niobium was proposed by PKU in 2010, by introducing rare earth elements of Sc and Y into Nb ingot during smelting process. Test results on small samples were very promising: the Tc was same as Nb, while the Hc1 and Hc2 were increased by 500-700 Oe and up to 4000 Oe, respectively. Recently one Nb ingot doped with Sc was successfully smelted under the collaboration of PKU and OSTEC at Ningxia, and two TESLA-type half cells were fabricated out of the new material by deep drawing. The Hc1 measured from the drop-off of the blanks were consistently high. The RRR was 127, while the mechanical properties met the ILC requirement. One single cell cavity is being fabricated, and vertical test is planned to study the SRF properties of the new material. There is a good chance that the quenching could be pushed to a higher gradient. Another innovative idea of doping only the surface layer of bulk Nb by ion implantation in the pelletron at PKU is also being investigated, in order to improve the SRF performance of the surface layer while maintaining the high thermal conductivity of bulk Nb. Some initial testing results of the new method will be reported as well. TTC2012 at JLab: https://www.jlab.org/indico/getFile.py/access?contribId=78&sessionId=8&resId=0&materialId=slides&confId=24

TUP035	Neutron Activation Analysis as a Foreign Intrusion Cavity DetectionTool	neutron, detector, radioactivity, background	495
	C. Maiano, P. Michelato INFN/LASA, Segrate (MI), Italy M. Clemenza Universita Milano Bicocca, MILANO, Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	Neutron Activation Analysis (NAA) is one of the currently available techniques used to determine contaminants in Nb superconducting cavities, allowing a non-destructive determination of foreign materials, provided they have radioactive isotopes with a sufficiently long half-life. We present the NAA technique application with the goal of contaminants determination, identification and localization for the European XFEL 3rd harmonic cavities (3.9 GHz). Irradiation and analysis has been performed in collaboration with the LENA nuclear reactor (Pavia, Italy) and the University of Milano Bicocca. The main difference respect to the measurements performed in the past is the goal to apply of the NNA directly to entire cavities and not to material samples. Currently nine samples were exposed to thermal and fast neutron flux and the resulting activity was measured with HPGe detectors.

TUP043	Nanostructural TEM/STEM Studies of Hot and Cold Spots in SRF Cavities	niobium, electron, SRF, vacuum	504
	Y. Trenikhina, J. Zasadzinski IIT, Chicago, USA A. Romanenko Fermilab, Batavia, USA
	Direct TEM/STEM imaging and spectroscopic chemical characterization by EELS/EDS of the surface of the SRF cavity cutouts before and after the treatments (e.g. in situ mild vacuum bake and rinsing with hydrofluoric acid) down to subnanometer scale is implemented to correspond the changes in niobium surface to the SRF performance of the cavities. We also report current results of the direct search, using cryogenic TEM stage, for suggested phase transformations in the niobium-hydrogen system* on “hot” and “cold” spot cavity cutouts, which may help clarifying the mechanism of the high field Q slope and its empirical cure. *A. Romanenko, F. Barkov, L. D. Cooley, A. Grassellino, Supercond. Sci. Technol. 26 (2013) 035003.

TUP044	Surface Processing Facilities for Spoke Cavities at IHEP	linac, recirculation, superconductivity, LLRF	508
	J.P. Dai, H. Li, L.H. Li, Q.Y. Wang, J. Zhang IHEP, Beijing, People's Republic of China P. Sha Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
	Funding: Work supported by the "Strategic Priority Research Program" of CAS, under Grant No. XDA03020600 The China ADS injector I program is building a CW 10MeV Superconducting proton linac at IHEP. To develop the superconducting spoke-type cavities incorporated in this linac, a set of new surface processing facilities were built and successfully used to treat the Spoke012 prototype cavities. In this paper, we present the design, fabrication and operation of these facilities, including BCP, HPR and UPW, etc.

TUP046	Vertical Electropolishing of SRF Cavities and its Parameters Investigation	cathode, superconductivity, SRF, experiment	514
	F. Eozénou, F. Ballester, Y. Boudigou, P. Carbonnier, J.-P. Charrier, Y. Gasser, D. Roudier, C. Servouin CEA/DSM/IRFU, France K. Muller Grenoble-INP Phelma, Grenoble, France
	Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP7 program (EuCARD, Contract No. 227579),and the support of the ‘‘Conseil General de l’Essonne’’(ASTRE) An advanced set-up for vertical electropolishing (VEP) of SRF niobium elliptical cavities is operating at CEA Saclay. Cavities are VEP’ed with circulating standard HF-H2SO4 electrolyte. Parameters such as voltage, cathode shape, acid flow and temperature were investigated. Low-voltage (<7V), high acid flow (25L/min) and low acid temperature (20°C) are considered as promising parameters. Such recipe was tested on single-cell and 9-cell ILC cavities with nice surface finishing. After 60 μm VEP on a HEP'ed single-cell, the cavity show similar performance at 1.6K compared to previous Horizontal EP: (Eacc > 41MV/m) limited by quench. Another cavity reaches 36MV/m after 300μm removal by VEP in spite of a pitted surface due to initial VEP treatment at higher temperature (> 30°C). The baking effect after HEP/VEP is similar. An asymmetric niobium removal is observed with faster polishing in the upper cell. Nice surface finishing as well as standard Q0 value are obtained at low/medium field on 9Cell but achieved performance is limited by Field Emission. F. Eozenou et al., PRST-AB, 15, 083501 (2012)

TUP047	Niobium Cavity Electropolishing Modelling and Optimisation	cathode, SRF, simulation, niobium	518
	L.M.A. Ferreira, S. Calatroni, S. Forel CERN, Geneva, Switzerland J.A. Shirra Loughborough University, Leicestershre, United Kingdom
	It’s widely accepted that electropolishing is the most suitable surface finishing process to achieve high performance bulk Nb accelerating cavities. At CERN, as part of the R&D studies for the 704 MHz high-beta SPL cavities, a new vertical electropolishing facility has been assembled and a study is on-going for the modelling of electropolishing on cavities with COMSOL software. In a first phase, the electrochemical parameters were taken into account for a fixed process temperature and flow rate, and are presented in this poster as well as the results obtained on a real SPL single cell cavity. The procedure to acquire the data used as input for the simulation is presented. The modelling procedure adopted to optimise the cathode geometry, aimed at a uniform current density distribution in the cavity cell for the minimum working potential and total current is explained. Some preliminary results on fluid dynamics and Joule effect are also briefly described.

TUP048	Preparations and VT Results of ERL7-cell at Cornell	cryomodule, vacuum, target, radiation	521
	F. Furuta, B. Bullock, R.G. Eichhorn, B. Elmore, A. Ganshin, G.M. Ge, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	We have fabricated 7 ERL 7-cell cavities for Cornell ERL project. 4 nu-stiffened and 3-stiffened cavities have been fabricated in house so far. Specification values of our 7-cell is 16.2MV/m with Qo of 2.0·10¹⁰ at 1.8K. In this report, we will describe our surface treatments recipe which is based on BCP and the results of vertical tests of these 7-cell cavities.

TUP049	Cornell VEP Update, VT Results and R&D on Nb Coupon	cathode, SRF, status	524
	F. Furuta, B. Elmore, G.H. Hoffstaetter, D.K. Krebs, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cornell's SRF group have been led development of Vertical Electro-Polishing(VEP) on SRF Nb Cavity. We have done many VEP on singel-/multi-cell cavities. We also have started VEP'ed Nb coupon surface analysis based on surface roughness measurement. In this report, we will describe our status of VEP R&D, the results of VEP'ed cavity vertical testing, and fundamental study on VEP using Nb coupons.

TUP051	Horizontal High Pressure Water Rinsing for Performance Recovery	cryomodule, vacuum, operation, factory	527
	Y. Morita, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, M. Nishiwaki KEK, Ibaraki, Japan
	Eight superconducting accelerating cavities were operated for more than ten years at the KEKB machine. Those cavities are also used at SuperKEKB. During the KEKB operation, Q values of some cavities were degraded. Cause of the degradation was contamination by air dusts at a repair of vacuum seals or a gasket replacement of input couplers. So far, those degradations are acceptable for the SuperKEKB operation, however, further degradation will make the operation unstable and, in the worst case, make it impossible. High pressure rinsing (HPR) is an effective method to clean the cavity surface. In order to apply HPR, however, the cavity has to be disassembled from a cryomodule. The disassembly takes time and costs. Furthermore, re-sealed vacuum flanges bring the risk of vacuum leakage again. Therefore we have developed a horizontal HPR. This method applies a high pressure water jet that is inserted horizontally into the cavity in the cryomodule. The wasted water is extracted with an aspirator. This method does not require the disassembly. We applied the horizontal HPR to our degraded cavity. Its RF performance has been successfully recovered.

TUP052	Study on Vertical Electro-Polishing by Cathode With Variable-Geometry Wings	experiment, cathode, scattering, niobium	530
	Y.I. Ida, K.N. Nii MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan K. Ishimi, Y.B. Iwabuchi MGI, Chiba, Japan
	We have been studying on Vertical Electro-Polishing (VEP) of Nb superconducting accelerator cavity for about one year with a view to the mass-production and cost-reduction of Electro-Polishing (EP) process. Marui Galvanizing Co. Ltd. has been in the EP business of various metals for long time and we have matured experience on EP processes. With being based on the experience, we thought that uniform electric-current on the surface of cavity and effective flow of electrolyte in the cavity are important factors. Moreover, we thought the most important effect is given if the cathode and the cavity surface (anode) are kept in a constant distance. Following these considerations, we invented VEP process by a cathode with variable-geometry wings. Using this cathode, we performed several experiments of VEP Nb single-cell cavities as well as fluid circulation test by plastic 9-cell mock-up. In this article, we will report this unique VEP process, which might be applicable to the mass-production process of International Linear Collider (ILC).

TUP053	Estimation of Small Geometry Deviation for TESLA-Shape Cavities Due to Inner Surface Polishing	superconductivity, coupling, factory, data-analysis	537
	A.A. Sulimov, G. Kreps, J.K. Sekutowicz DESY, Hamburg, Germany
	Two well know polishing methods are used for the inner surface cleaning of superconducting TESLA-shape cavities: electro-polishing (EP) or buffered chemical polishing (BCP). The amount of removed material is relatively small and varies from 10 till 140 um. The cavity after polishing is closed to prevent the scratches or dust appearing on its inner surface. The estimation of the removed material amount is possible by different criteria, for example by comparison of weight before and after cleaning, or by the time - cleaning procedure duration. Both calculations could give us only approximate average value of the removed material amount. We describe the method for estimation of small geometry deviation basing on RF frequency measurements, which allows calculating the different influence of surface treatment on the iris and equator areas.
	Poster TUP053 [0.785 MB]

TUP054	Electropolishing of Niobium SRF Cavities in Low Viscosity Aqueous Electrolytes Without Hydrofluoric Acid	niobium, SRF, experiment, controls	540
	E.J. Taylor, T.D. Hall, M.E. Inman, S.T. Snyder Faraday Technology, Inc., Clayton, USA A.M. Rowe Fermilab, Batavia, USA
	Funding: U.S. DOE Purchase order No. 594128 Electropolishing of niobium materials and cavities is conventionally conducted in high viscosity electrolytes consisting of concentrated sulfuric and hydrofluoric acid. The use of these dangerous and ecologically damaging chemicals requires careful attention to safety protocol to avoid harmful worker exposure and environmental damage. In this poster we present an approach based on bipolar voltage fields enabling the use of low viscosity water based electrolytes without hydrofluoric acid for electropolishing of niobium materials. The subtleties of the bipolar electropolishing process vis-a-vis conventional electropolishing will be presented.

TUP055	Electropolishing of the ANL Deflecting Cavity for the APS Upgrade	niobium, SRF, background, coupling	544
	Y. Yang, J.D. Fuerst, J.P. Holzbauer, J.A. Kaluzny, A. Nassiri, G. Wu ANL, Argonne, USA A.C. Crawford Fermilab, Batavia, USA P. Dhakal, J.D. Mammosser, H. Wang JLAB, Newport News, Virginia, USA Y. Yang TUB, Beijing, People's Republic of China
	Studies on the application of electropolishing (EP) of the ANL superconducting deflecting cavity have shown promising results. This cavity geometry is a squashed single-cell cavity with Y-end group waveguide as well as on-cell LOM damper. The cavity works at TM110-like deflecting mode, in which the iris between the cavity cell and the Y-end group is the highest magnetic field region. Before EP, the cavity had been chemically etched (BCP) several times. Forty-um EP processing was performed on one Mark II prototype deflecting cavity at Fermilab. No mild baking was performed before the cavity vertical test. The test showed that the low-field Q had improved from 2·10⁹ to 3·10⁹ and the high-field Q-slope had been successfully removed. The quench limit was slightly improved from 10⁶ mT to 113 mT. Fast T-mapping had detected a significant decrease of local temperature rise in the cavity iris. Optical inspection before EP found a lot of grooves around the iris, which might be related to the gas bubbles generated during BCP. This suggests that horizontal EP is a promising processing technique to remove the high-field Q-slope and improve the deflecting cavity performance.

TUP056	Industrialization of European XFEL Preparation Cycle “BCP Flash” at Ettore Zanon Company	controls, vacuum, acceleration, pick-up	547
	A. Matheisen, N. Krupka, M. Schalwat, A. Schmidt, W. Singer, N. Steinhau Kühl, B. van der Horst DESY, Hamburg, Germany G. Corniani Ettore Zanon S.p.A., Schio, Italy P. Michelato, L. Monaco INFN/LASA, Segrate (MI), Italy
	In the Specification for XFEL Cavity preparation (R1) two different preparation sequences are presented. Ettore Zanon Company as one of the two companies contracted for XFEL cavity production and preparation has chosen the so called BCP flash cycle. To fulfill the requested work flow and quality of infrastructure and processes, the company set up a complete new infrastructure in refurbished fabrication halls. The layout of the facility, set up of work flow of preparation and test results of resonators processed by E.Zanon in their infrastructure will be reported. (R1) Series Surface and acceptance test preparation of superconducting cavities for the European Xfel (XFEL/A - D) JUNE 30, 2009

TUP057	Plasma Processing R&D for the SNS Superconducting Linac RF Cavities	plasma, linac, cryomodule, niobium	551
	M. Doleans, W. Blokland, M.T. Crofford, D.L. Douglas, M.P. Howell, S.-H. Kim, P.V. Tyagi ORNL, Oak Ridge, Tennessee, USA R. Afanador, J.A. Ball, B. DeGraff, B.S. Hannah, S.W. Lee, C.J. McMahan, J. Saunders ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE The Spallation Neutron Source routinely operates with a proton beam power of 1 MW on its production target. A plan to reach the design 1.4 MW within a few years is in place* and relies on increasing the ion beam current, pulse length and beam energy in the linac. The increase in beam energy from the present 930 MeV to 1 GeV will require an increase of approximately 15% in the accelerating gradient of the superconducting linac high-beta cryomodules. In-situ plasma processing was identified as a promising technique** to reduce electron activity in the SNS superconducting cavities and increase their accelerating gradient. R&D on plasma processing aims at deploying the new in-situ technique in the linac tunnel by 2016. Overall plan and current status of the plasma processing R&D will be presented. * NScD Five year plan 2012-2016, SNS-NSCD-EXE-PN-0001, R00, ORNL ** S-H Kim et al., “R&D Status for In-Situ Plasma Surface Cleaning of SRF Cavities at Spallation Neutron Source”, PAC 2011 Proceedings

TUP058	Recent Findings on Nitrogen Treated Niobium	niobium, SRF, vacuum, solenoid	558
	R.G. Eichhorn, A. Ganshin, A. Holmes, J.J. Kaufman, S.R. Markham, S. Posen, E.N. Smith Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Recent findings on Nitrogen treated Niobiums Based on recent findings at Fermilab, Cornell investigated the role of Nitrogen being present during the cavity hydrogen degassing process. We treated several samples at different temperatures being exposed to nitrogen between 10 minutes and 3 hours at pressures around 15 mbar as well as single cell cavities. This contribution will summarize our findings from surface analysis, Tc measurements and cavity Qs, addressing the question, if such a process can form Niobium-Nitride.

TUP059	TM-Furnace Qualification at Cornell	vacuum, SRF, cryomodule	561
	F. Furuta, B. Bullock, R.G. Eichhorn, A. Ganshin, G.M. Ge, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cornell's SRF group had new vacuum furnace for hydrogen degassing of SRF Nb cavity. Systematic study and testing have been done to qualify this new furnace. We will report the results of those qualification tests include cavity bake and vertical testing.

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MOIOA01

The FRIB Project at MSU

cryomodule, linac, ion, operation

1

M. Leitner, B. Bird, F. Casagrande, S. Chouhan, C. Compton, J.L. Crisp, K. Elliott, A. Facco, A.D. Fox, M. Hodek, M.J. Johnson, G. Kiupel, I.M. Malloch, D. Miller, S.J. Miller, D. Morris, D. Norton, R. Oweiss, J.P. Ozelis, J. Popielarski, L. Popielarski, A.P. Rauch, R.J. Rose, K. Saito, M. Shuptar, N.R. Usher, G.J. Velianoff, D.R. Victory, J. Wei, J. Whitaker, K. Witgen, T. Xu, Y. Xu, O. Yair, S. Zhao
FRIB, East Lansing, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
The Facility for Rare Isotope Beams (FRIB) is ready to start construction. The facility will utilize a high-intensity, heavy-ion driver linac to provide stable ion beams from protons to uranium up to energies of >200 MeV/u and at a beam power of up to 400 kW. The superconducting cw linac consists of 330 individual low-beta (β = 0.041, 0.085, 0.29, and 0.53 at 80.5 MHz and 322 MHz) cavities in 49 cryomodules operating at 2 K. This paper discusses the current development status of the project with emphasis on the linac SRF acquisition. SRF coldmass and cryomodule component designs are briefly summarized. A SRF production facility, currently under construction, is described.

Slides MOIOA01 [9.804 MB]

MOIOA02

Status and Challenges of Spiral2 SRF Linac

cryomodule, linac, vacuum, ion

11

R. Ferdinand, P.-E. Bernaudin, M. Di Giacomo
GANIL, Caen, France
P. Bosland
CEA/IRFU, Gif-sur-Yvette, France
Y. Gómez Martínez
LPSC, Grenoble Cedex, France
G. Olry
IPN, Orsay, France

GANIL is presently extending its experimental facility with the new SPIRAL2 project. It is based on a multi-beam Superconducting Linac Driver delivering 5 mA deuterons up to 40 MeV and 1 mA heavy ions up to 14.5 MeV/u. Several domains of research in nuclear physics at the limits of stability will be covered by this new accelerator. SPIRAL2 construction has two phases. SPIRAL2 phase 1 includes the superconducting accelerator driver, and the construction of the two research areas where the accelerated protons and deuterons will generate extremely intense neutron beams for fundamental physics experiments and numerous applications. SPIRAL2 will also accelerate stable heavy ion beams of very high intensity. The phase2 includes the RIB production building and links to the existing GANIL accelerator complex for RIB post acceleration. The Superconducting Linac incorporates many innovative developments of the Quarter-Wave resonators and their associated cryogenic and RF systems. The installation of the SPIRAL2 accelerator at GANIL has started. Status of the Spiral 2 SRF linac will be presented, focusing on the various SRF challenges met by this project and how/what solutions were chosen.
* on behalf of the SPIRAL2 project and superconducting teams

Slides MOIOA02 [87.841 MB]

MOIOA03

The Challenge and Realization of the Cavity Production and Treatment in Industry for the European XFEL

niobium, controls, superconductivity, HOM

18

W. Singer, J. Iversen, A. Matheisen, H. Weise
DESY, Hamburg, Germany
P. Michelato
INFN/LASA, Segrate (MI), Italy

The main effort in production of 1.3 GHz cavities for the EXFEL was dedicated to transfer the superconducting technology to the industry. These know how transfer is executed by DESY and INFN/LASA team. The preparation phase based on prototype cavities covered: qualification of potential vendors for material and cavity fabrication; work out recipe and strategy for qualification of the infrastructure for cavity surface treatment at industry; definition of the quality management strategy, documentation and electronically data exchange. Production of 800 series cavities on the principle “build to print” is contracted to companies Research Instruments and Ettore Zanon. High purity niobium and NbTi for resonators provides DESY. The principles of the material and cavities production in conformity with European Pressure Equipment Directive are developed together with the notified body. New or upgraded infrastructure has been established at both companies. The first several tens of series cavities have been produced and treated. Most of the cavities handed over to DESY up to now fulfill immediately the EXFEL specifications. The cavity production for EXFEL will be finished mid of 2015.

Slides MOIOA03 [7.394 MB]

MOIOA04

SRF Challenges for Energy Recovery Linacs

SRF, HOM, linac, operation

24

A. Burrill
HZB, Berlin, Germany

Many of the challenges associated with operating a SRF ERL are independent of the choice of operating frequency, beam energy, and overall purpose of the machine. Worldwide there are an increasing number of ERLs in various stages of development and operation which are facing a number of similar challenges and often solving them in very different ways. In this talk I will seek to summarize the main challenges the community as a whole faces, address how different laboratories are working to solve these problems, and seek to identify areas of overlap where the community can work together to solve some of these common problems.

Slides MOIOA04 [5.213 MB]

MOIOA05

SRF in Heavy Ions Projects

linac, ion, heavy-ion, cryomodule

30

D. Jeon
IBS, Daejeon, Republic of Korea

SRF technologies are widely applied to heavy ion accelerator projects in the world such as the RAON, C-ADS, HIAF, FRIB, SPIRAL2, ISAC-II, HIE-ISOLDE etc. In this talk, status report, design choices and SRF challenges met in heavy ion machines are presented.

Slides MOIOA05 [10.228 MB]

MOIOB01

High Power Proton/Deuteron Accelerators

linac, SRF, proton, operation

35

J.-L. Biarrotte
IPN, Orsay, France

High power proton and deuteron linear accelerators can give rise to a large variety of scientific applications, useful for both fundamental and applied research. Thanks to the on-going efficient development of the superconducting RF technology, more and more projects based on such machines have emerged during the last 2 decades. This paper will review these existing high power proton/deuteron accelerator facilities or projects, trying in particular to emphasize in each case the various specificities and challenges related to the SRF technology.

Slides MOIOB01 [4.474 MB]

MOIOB02

Towards a 100mA Superconducting RF Photoinjector for BERLinPro

cathode, laser, emittance, SRF

42

A. Neumann, W. Anders, A. Burrill, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, P. Lauinger, A.N. Matveenko, M. Schmeißer, J. Völker
HZB, Berlin, Germany
G. Ciovati, P. Kneisel
JLAB, Newport News, Virginia, USA
R. Nietubyć
NCBJ, Świerk/Otwock, Poland
S.G. Schubert, J. Smedley
BNL, Upton, Long Island, New York, USA
J.K. Sekutowicz
DESY, Hamburg, Germany
V. Volkov
BINP SB RAS, Novosibirsk, Russia
I. Will
MBI, Berlin, Germany
E.N. Zaplatin
FZJ, Jülich, Germany

For BERLinPro, a 100 mA CW-driven SRF energy recovery linac demonstrator facility, HZB needs to develop a photo-injector superconducting cavity which delivers a at least 1mm*mr emittance beam at high average current. To address these challenges of producing a high peak brightness beam at high repetition rate, at first HZB tested a fully superconducting injector with a lead cathode*,followed now by the design of a SC cavity allowing operation up to 4 mA using CW-modified TTF-III couplers and inserting a normal conducting high quantum efficiency cathode using the HZDR-style insert scheme. This talk will present the latest results and an overview of the measurements with the lead cathode cavity and will describe the design and optimization process, the first production results of the current design and an outlook to the further development steps towards the full power version.
*T. Kamps et al., Proceedings of the 2nd International Particle Accelerator Conference, San Sebastián, Spain, 2011.

Slides MOIOB02 [7.574 MB]

MOIOB03

SRF Photoemission Electron Guns at BNL: First Commissioning Results

gun, SRF, electron, cathode

50

S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh
Stony Brook University, Stony Brook, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE
Two SRF photoemission electron guns are under development at BNL. The first gun operates at 704 MHz and is design to deliver high bunch charge and high average current beams for the R&D ERL accelerator. Its cavity is of an elliptical geometry. The gun cryomodule has been commission without a cathode up to the design voltage of 2 MV. The experiments with a copper cathode are underway. The second gun utilizes a quarter wave resonator geometry with coaxial cathode insert and beam tube RF power coupler. It will be used to produce high bunch charges, but low average beam currents for the coherent electron cooling proof-of-principle experiment. This 112 MHz SRF gun was first tested two years ago. Since then it was rebuilt in a new cryomodule and cryogenically re-tested in late 2012/early 2013, reaching the accelerating gap voltage of 0.9 MV. This paper describes main design features of two SRF guns, presents test results and discusses future plans.

Slides MOIOB03 [3.431 MB]

MOIOB04

Commissioning and Operation of DC-SRF Injector

SRF, controls, LLRF, experiment

53

K.X. Liu, J.E. Chen, L.W. Feng, J.K. Hao, S. Huang, L. Lin, S.W. Quan, F. Wang, Zh.W. Wang, X.D. Wen, H.M. Xie, K. Zhao, F. Zhu
PKU, Beijing, People's Republic of China

As a new and compact injector with medium beam current, the DC-SRF injector at Peking University has been upgraded recently mainly on DC part and heat loading. With a new 20kW solid state RF power source, an improved LLRF system and related diagnostic devices on the new beam line, a series of experiments have been carried out for stably operating the DC-SRF injector at 2K temperature. The description of the system, experiment process and results will be presented.

Slides MOIOB04 [4.992 MB]

MOIOC01

Heat Transfer at the Interface Between Niobium and Liquid Helium for 6 GHz SRF Cavities

niobium, interface, coupling, operation

57

V. Palmieri
INFN/LNL, Legnaro (PD), Italy

Cavity Thermal Boundary Resistance is something extremely complex and not completely understood by the theory. Often identified with the Kapitza resistance or with the Khalatnikov acoustic phonon mismatch at the interface metal-liquid Helium, it depends on so many different and uncontrolled parameters, that its interpretation is not covered by a complete treatise of the phenomenon. Therefore, 99% of the literature on superconducting cavities worries about the cavity interior surface state,while almost nothing is reported on treatments applied to the exterior. In the authors opinion, there is a lack in experimental data analysis due to the fact that the cavity is often considered as a whole adiabatic entity interacting only with RF fields. On the contrary, the cavity is immersed in liquid Helium and the cavity behavior cannot prescind from its thermal properties. Indeed in the normal state He-I has poor thermal conductivity and high specific heat. Moreover the heat exchange at HeII obeys to further mechanisms besides the phonon mismatch. Driven by the hypothesis that thermal losses are dominant for ultraclean cavities, we have collected a plethora of surprising experimental results.

Slides MOIOC01 [15.558 MB]

MOIOC02

A New First-Principles Calculation of Field-Dependent RF Surface Impedance of BCS Superconductor

impedance, electron, niobium, superconductivity

63

B. P. Xiao, C.E. Reece
JLab, Newport News, Virginia, USA
B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: This manuscript has been authored in part by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
There is a need to understand the intrinsic limit of RF surface impedance that determines the performance of superconducting RF cavities in particle accelerators. Here we present a field-dependent derivation of Mattis-Bardeen theory of the RF surface impedance of BCS superconductors, based on the shifted density of states resulting from coherently moving Cooper pairs. Our theoretical prediction of the effective BCS RF surface resistance of niobium as a function of peak surface magnetic field amplitude agrees well with recently reported record low loss resonant cavity measurements from JLab and Fermi Lab with carefully prepared niobium material. The surprising reduction in resistance with increasing field is explained to be an intrinsic effect.

Slides MOIOC02 [3.122 MB]

MOP001

CASCADE: a Cavity Based Dark Matter Experiment

experiment, photon, shielding, detector

66

M.K. Kalliokoski, I.R. Bailey, N. Woollett
Lancaster University, Lancaster, United Kingdom
G. Burt, A.C. Dexter
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
S. Chattopadhyay
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J.B. Dainton
The University of Liverpool, Liverpool, United Kingdom
P. Goudket, A.J. Moss, S.M. Pattalwar, T.T. Thakker, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

An experiment is proposed that uses a pair of RF cavities as a source and detector of hidden sector photons (HSP). HSP's are hypothetical low-mass dark matter candidates with coupling to ordinary photons. SRF cavities are favoured in this experiment as they are able to store a high number of photons for a given input power due to the high Q available. When powered, such a cavity will act as a source of HSPs, while an empty cavity will be able to capture any HSP's decaying back into RF photons. Such an experiment (CASCADE) is being developed at the Cockcroft Institute using single cell 1.3 GHz cavities previously utilised for manufacturing and BCP studies. The aims of the CASCADE project are detailed, along with the system specification.

MOP002

Conceptual Design for Replacement of the DTL and CCL with Superconducting RF Cavities in the Spallation Neutron Source Linac

linac, cryomodule, DTL, klystron

69

M.S. Champion, M. Doleans, S.-H. Kim
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
The Spallation Neutron Source Linac utilizes normal conducting RF cavities in the low energy section from 2.5 MeV to 186 MeV. Six Drift Tube Linac (DTL) structures accelerate the beam to 87 MeV, and four Coupled Cavity Linac (CCL) structures provide further acceleration to 186 MeV. The remainder of the Linac is comprised of 81 superconducting cavities packaged in 23 cryomodules to provide a final beam energy of approximately 1 GeV. The superconducting Linac has proven to be substantially more reliable than the normal conducting Linac despite the greater number of stations and the complexity associated with the cryogenic plant and distribution. A conceptual design has been initiated on a replacement of the DTL and CCL with superconducting RF cavities. The motivation, constraints, and conceptual design are presented.

MOP003

Implications of Increased Beam Current for the Diamond Storage Ring RF System

storage-ring, operation, cathode, linac

73

C. Christou, A. Bogusz, P. Gu, M. Maddock, P.J. Marten, S.A. Pande, A.F. Rankin, D. Spink, A.V. Watkins
Diamond, Oxfordshire, United Kingdom

Diamond Light Source presently operates for users with 300mA beam current and initial tests have begun to upgrade this current towards an ultimate goal of 500mA. The implications of such a beam current increase for the storage ring RF system will be significant, including the installation of a third superconducting cavity and a possible modification of the coupling parameters of the existing cavities. An overview of the planned enhancements of the RF system is presented, including an update of the procurement of a new CESR-design cavity and options for installation and operation of this cavity and supporting infrastructure.

MOP004

The ESS Superconducting Linear Accelerator

cryomodule, linac, SRF, lattice

77

C. Darve, M. Eshraqi, M. Lindroos, D.P. McGinnis, S. Molloy
ESS, Lund, Sweden
P. Bosland
CEA/IRFU, Gif-sur-Yvette, France
S. Bousson
IPN, Orsay, France

The European Spallation Source (ESS) is one of Europe's largest planned research infrastructure. The collaborative project is funded by a collaboration of 17 European countries and is under design and construction in Lund, Sweden. The ESS will bring new insights to the grand challenges of science and innovation in fields as diverse as material and life sciences, energy, environmental technology, cultural heritage solid-state and fundamental physics. A 5 MW, long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle). The choice of SRF technology is a key element in the development of the ESS linear accelerator(linac). The superconducting linac is composed of one section of spoke cavity cryomodule (352 MHz) and two sections of elliptical cavity cryomodules (704 MHz). These cryomodules contain Niobium SRF cavities operating at 2 K. This paper presents the superconducting linac layout and its lifecycle.

MOP006

Status of the SC CW-Linac Demonstrator

linac, solenoid, status, emittance

80

V. Gettmann, W.A. Barth, S. Jacke, S. Mickat, S. Mickat, A. Orzhekhovskaya
GSI, Darmstadt, Germany
M. Amberg, K. Aulenbacher, W.A. Barth, S. Jacke, S. Mickat
HIM, Mainz, Germany
M. Amberg, F.D. Dziuba, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
K. Aulenbacher
IKP, Mainz, Germany

The commissioning of the superconducting (sc) continuous wave (cw) LINAC Demonstrator, financed by the Helmholtz Institute Mainz (HIM) mainly, is planned in 2014. The aim is a “full performance test” at GSI-High Charge Injector (HLI) of a 217 MHz sc CH-Cavity, which is designed by the Institute of Applied Physics (IAP) of the University Frankfurt. Inside the cryostat a suspended frame supports the cavity embedded by two solenoids. All of these components are in fabrication. The testing environment is about to be completed. The radiation protection bunker, and the beam transport line straightforward to the GSI-HLI, comprising beam diagnostic components as well as focusing and steering magnets, has been mounted.

MOP007

The Status of Superconducting Linac and SRF Activities at the SNS

linac, cryomodule, operation, SRF

83

S.-H. Kim, W. Blokland, M.S. Champion, A. Coleman, M.T. Crofford, M. Doleans, D.L. Douglas, T.V. Gorlov, M.P. Howell, Y.W. Kang, A.P. Shishlo, S.E. Stewart, W.H. Strong
ORNL, Oak Ridge, Tennessee, USA
R. Afanador, B. DeGraff, B.S. Hannah, S.W. Lee, C.J. McMahan, T.S. Neustadt, S.W. Ottaway, C.C. Peters, J. Saunders, D.M. Vandygriff
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
There have been substantial gains at the Spallation Neutron Source (SNS) in last 7 years in understanding pulsed superconducting linac (SCL) operation including system and equipment limiting factors and resolution of system and equipment issues. Significant effort and focus are required to assure ongoing success of the operation, maintenance and improvement of the SCL, and to address the requirements of the upgrade project in the future. The SNS is taking a multi-faceted approach to maintaining and improving its linac. A balanced set of facilities which support processing, assembly, repair, and testing of cavities/cryomodules are currently being placed into service. This paper summarizes the status of the SNS SCL and related superconducting radio-frequency (SRF) activities such as development of ASME code-stamped spare cryomodules, R&D activities for SRF cavity performance improvements, SRF cavity development for power upgrade project and SRF facility development/upgrade to support all required activities.

MOP008

SUPERCONDUCTING LINAC FOR THE RISP

linac, cryomodule, proton, ion

89

H.J. Kim, H.J. Cha, M.O. Hyun, H.J. Jang, D. Jeon, J.D. Joo, M.J. Joung, H.C. Jung, Y. Jung, Y. Kim, M. Lee, G.-T. Park
IBS, Daejeon, Republic of Korea

The RISP (Rare Isotope Science Project) accelerator has been planned to study heavy ion of nuclear, material and medical science at the Institute for Basic Science (IBS). It can deliver ions from proton to Uranium. The facility consists of three superconducting linacs of which superconducting cavities are independently phased. Requirement of the linac design is especially high for acceleration of multiple charge beams. In this paper, we present the RISP linac design, the superconducting cavity, and cryomodule.

MOP009

A Summary of the Advanced Photon Source (APS) Short Pulse X-ray (SPX) R&D Accomplishments

cryomodule, LLRF, vacuum, laser

92

A. Nassiri, N.D. Arnold, T.G. Berenc, M. Borland, B. Brajuskovic, D.J. Bromberek, J. Carwardine, G. Decker, L. Emery, J.D. Fuerst, J.P. Holzbauer, D. Horan, J.A. Kaluzny, J.S. Kerby, F. Lenkszus, R.M. Lill, H. Ma, V. Sajaev, B.K. Stillwell, G.J. Waldschmidt, M. White, G. Wu, Y. Yang, A. Zholents
ANL, Argonne, USA
J.M. Byrd, L.R. Doolittle, G. Huang
LBNL, Berkeley, California, USA
P. Dhakal, J. Henry, J.D. Mammosser, J. Matalevich, R.A. Rimmer, H. Wang, K.M. Wilson
JLAB, Newport News, Virginia, USA
Z. Li, L. Xiao
SLAC, Menlo Park, California, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06H11357.
The Advanced Photon Source Upgrade Project (APS-U) at Argonne will include generation of short-pulse x-rays based on Zholents’ [1] deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. Since early 2012, in collaboration with Jefferson National Laboratory, we have made significant progress prototyping and testing a number of single-cell deflecting cavities. We have designed, prototyped, and tested silicon carbide as damping material for higher-order-mode (HOM) dampers, which are broadband to handle the HOM power across the frequency spectrum produced by the APS beam. In collaboration with Lawrence Berkeley National Laboratory, we have developing a state-of-the-art timing and synchronization system for distributing stable rf signals over optical fiber capable of achieving tens of femtoseconds phase drift and jitter. Collaboration with the Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi- cavity geometries. This contribution provides a progress report on the current R&D status of the SPX project.
[1] A. Zholents et al., NIM A 425, 385 (1999).

MOP010

Spiral2 Cryomodules B Tests Results

cryomodule, linac, operation, alignment

95

G. Olry, F. Chatelet, C. Commeaux, N. Gandolfo, D. Grolet, C. Joly, J. Lesrel, D. Longuevergne, R. Martret, G. Michel, L. Renard, A. Stephen, P. Szott
IPN, Orsay, France
P.-E. Bernaudin, R. Beunard, R. Ferdinand, A. Lefevre
GANIL, Caen, France
Y. Gómez Martínez
LPSC, Grenoble Cedex, France

Assembly and tests of the SPIRAL2 superconducting linac's cryomodules at CEA/Saclay and IPN/Orsay have now reached cruising speed after having faced a series of problems, among them contamination. 19 cryomodules are composing the whole Linac and IPN Orsay is in charge of the 7 cryomodules B, housing two 88MHz, beta 0.12 Quarter-Wave Resonators. Two cryomodules have been successfully assembled and tested up to the nominal gradient of 6.5 MV/m for all cavities with also total cryogenic losses under specifications. One of them is fully qualified and has been already delivered to GANIL. The second one showed misalignment on one cavity which could lead to partial disassembly. This paper will present the results of those cryomodules tests as well as the status of the remaining ones.

MOP011

European XFEL 3.9 GHz System

linac, HOM, cryomodule, controls

100

P. Pierini, M. Bertucci, A. Bosotti, C. Maiano, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
E. Vogel
DESY, Hamburg, Germany

The third harmonic system of the European XFEL is a joint INFN and DESY contribution to the project. Achievements, status and activity plan will be reviewed.

MOP013

SRF Developments at MSU for FRIB

solenoid, operation, shielding, cryomodule

106

K. Saito, N.K. Bultman, F. Casagrande, S. Chouhan, C. Compton, K. Elliott, A. Facco, M.J. Johnson, S. Jones, M. Leitner, S.J. Miller, R. Oweiss, J.P. Ozelis, J. Popielarski, L. Popielarski, S. Shanab, J. Wei, T. Xu, Y. Yamazaki, Y. Zhang, Z. Zheng
FRIB, East Lansing, Michigan, USA
S.K. Chandrasekaran
MSU, East Lansing, USA
K. Hosoyama
KEK, Ibaraki, Japan

FRIB has built up a new SRF development group for future SRF research and development at MSU. This paper will report on the present status of development for fundamental couplers, pneumatic tuners for HWR, magnetic shielding and superconducting solenoids, barrel polishing techniques for HWR, a cavity steam cleaning method, and niobium material characterization efforts.

MOP014

Cold Tests of SSR1 Resonators for PXIE

radiation, vacuum, cryomodule, SRF

112

A.I. Sukhanov, M.H. Awida, P. Berrutti, C.M. Ginsburg, T.N. Khabiboulline, O.S. Melnychuk, R.V. Pilipenko, Y.M. Pischalnikov, L. Ristori, A.M. Rowe, D.A. Sergatskov, V.P. Yakovlev
Fermilab, Batavia, USA

Fermilab is currently building the Project X Injector experiment (PXIE). PXIE linac will accelerate 1 mA H⁻ beam up to 30 MeV and serve as a testbed for validation of Project X concepts and mitigation of technical risks. A cryomodule of eight superconducting RF Single Spoke Resonators of type 1 (SSR1) cavities operating at 325 MHz is an integral part of PXIE. Ten SSR1 cavities were manufactured in industry and delivered to Fermilab. In this paper we discuss surface processing and tests of bare SSR1 cavities at the Fermilab Vertical Test Stand (VTS). We report on the measured performance parameters of nine cavities achieved during tests.

MOP015

Status of the SRF Development for the Project X

cryomodule, linac, SRF, proton

117

V.P. Yakovlev, T.T. Arkan, M.H. Awida, P. Berrutti, E. Borissov, A.C. Crawford, M.H. Foley, C.M. Ginsburg, I.V. Gonin, A. Grassellino, C.J. Grimm, S.D. Holmes, S. Kazakov, R.D. Kephart, T.N. Khabiboulline, V.A. Lebedev, A. Lunin, M. Merio, S. Nagaitsev, T.H. Nicol, Y.O. Orlov, D. Passarelli, T.J. Peterson, Y.M. Pischalnikov, O.V. Pronitchev, L. Ristori, A.M. Rowe, D.A. Sergatskov, N. Solyak, A.I. Sukhanov, I. Terechkine
Fermilab, Batavia, USA

Project X is a high intensity proton facility being developed to support a world-leading program of Intensity Frontier physics over the next two decades at Fermilab. The proposed facility is based on the SRF technology and consists of two linacs: CW linac to accelerate beam from 2.1 MeV to 3 GeV and pulsed linac accelerate 5% of the beam up to 8 GeV. In a CW linac five families of SC cavities are used: half-wave resonators (162.5 MHz); single-spoke cavities: SSR1 and SSR2 (325 MHz) and elliptical 5-cell β=0.6 and β=0.9 cavities (650 MHz). Pulsed 3-8 GeV linac linac are based on 9-cell 1.3 GHz cavities. In the paper the basic requirements and the status of development of SC accelerating cavities, auxiliaries (couplers, tuners, etc.) and cryomodules are presented as well as technology challenges caused by their specifics.

MOP016

SRF Systems for the Coherent Electron Cooling Demonstration Experiment

SRF, gun, cryomodule, electron

123

S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, Y. Huang, D. Kayran, V. Litvinenko, P. Orfin, I. Pinayev, T. Rao, B. Sheehy, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, Q. Wu, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, M. Ruiz-Osés, T. Xin
Stony Brook University, Stony Brook, USA
C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA
X. Liang
SBU, Stony Brook, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE
A short 22-MeV linac under development at BNL will provide high charge, low repetition rate beam for the coherent electron cooling demonstration experiment in RHIC. The linac will include a 112 MHz SRF gun and a 704 MHz five-cell accelerating SRF cavity. The paper describes the two SRF systems, discusses the project status, first test results and schedule.

MOP017

SRF for Low Energy RHIC Electron Cooling: Preliminary Considerations

SRF, gun, electron, linac

126

S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, A.V. Fedotov, D. Kayran, V. Litvinenko, Q. Wu, B. P. Xiao, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko
Stony Brook University, Stony Brook, USA
Z.A. Conway, M.P. Kelly, S.V. Kutsaev, B. Mustapha, P.N. Ostroumov
ANL, Argonne, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE
A search for the QCD Critical Point has renewed interest to electron cooling ion beams in RHIC at energies below 10 GeV/nucleon. The electron cooling will utilize bunched electron beams form an SRF linac at energies from 0.9 to 5 MeV. The SRF linac will consist of two quarter wave structures: a photoemission electron gun and a booster cavity. In this paper we present preliminary design consideration of this SRF linac.

MOP018

Design of the MYRRHA 17-600 MeV Superconducting Linac

linac, lattice, operation, simulation

129

J.-L. Biarrotte
IPN, Orsay, France
F. Bouly
CERN, Geneva, Switzerland
J.-P. Carneiro
Fermilab, Batavia, USA
D. Uriot
CEA/DSM/IRFU, France
D. Vandeplassche
SCK•CEN, Mol, Belgium

Funding: This work is being supported by the European Atomic Energy Community’s (EURATOM) Seventh Framework Programme under grant agreement n°269565 (MAX project).
The goal of the MYRRHA project is to demonstrate the technical feasibility of transmutation in a 100MWth Accelerator Driven System (ADS) by building a new flexible irradiation complex in Mol (Belgium). The MYRRHA facility requires a 600 MeV accelerator delivering a maximum proton flux of 4 mA in continuous operation, with an additional requirement for exceptional reliability. This paper will briefly describe the beam dynamics design of the main superconducting linac section which covers the 17 to 600 MeV energy range and requires enhanced fault-tolerance capabilities.

MOP021

Conceptual Design of SC Linac for RIBF-Upgrade Plan

linac, cryomodule, quadrupole, ion

137

K. Yamada, O. Kamigaito, N. Sakamoto, K. Suda
RIKEN Nishina Center, Wako, Japan

For the intensity upgrade of very-heavy ions such as 238U and 124Xe at the RIKEN RI-Beam Factory (RIBF), a design study of new SC linac injector has started on. In the RIBF, the very-heavy ions are accelerated in a cascade of the injector linac (RILAC2), the RIKEN ring cyclotron (RRC), the fixed-frequency ring cyclotron (fRC), the intermediate-stage ring cyclotron (IRC), and the world's first superconducting ring cyclotron (SRC). We plan to substitute the SC linac for the RRC with respect to the very heavy ions, and to boost up the energy of ions with mass-to-charge ratio of 7 from 1.4 MeV/u to 11 MeV/u in the cw mode. The SC cavity is assumed to be a two gap QWR with an rf frequency of 73 MHz, that is twice the rf frequency of IRC and SRC. The cell parameters and number of cavity are determined by calculating the energy gain of synchronous ion by taking the rf phase at the center of gap into account. The transverse motion is calculated by the transfer matrix method and several types of lattice are studied. This contribution reports the progress of design study for the SC linac.

MOP022

Preliminary Design of CEPC RF Superconducting System

HOM, impedance, cryogenics, storage-ring

140

H.J. Zheng, J. Gao, S. Jin, Y. Liu, Z.C. Liu, J.Y. Zhai, T.X. Zhao
IHEP, Beijing, People's Republic of China

In order to study Higgs Boson, scientists proposed to construct a Higgs factory. Chinese scientists are also actively involved in research of the construction of Higgs factory. Construction of a circular collider and several construction solutions were proposed. Electron and positron are eventually accelerated to the center of mass energy 240GeV. RF superconducting acceleration system is indispensable to ensure the normal operation of machine. This article mainly introduces the RF parameters in the design of 700MHz China Higgs Factory (CHF) system. It mainly includes choose of cavity type, couplers and relevant parameters of cryogenic system.

MOP024

Novel SRF Gun Design

gun, cathode, SRF, laser

145

F. Marhauser
Muons, Inc, Illinois, USA
K.H. Lee, Z. Li
SLAC, Menlo Park, California, USA

Funding: Work supported under U.S. DOE Grant Application Number 98802B12-I
A high brightness superconducting radio frequency (SRF) photoinjector gun cavity has been developed to a level ready for construction. The design aims to prevent operational limitations encountered with existing concepts.

MOP025

The SRF Photo Injector at ELBE – Design and Status 2013

solenoid, cryomodule, SRF, gun

148

P. Murcek, A. Arnold, P.N. Lu, J. Teichert, H. Vennekate, R. Xiang
HZDR, Dresden, Germany
P. Kneisel
JLAB, Newport News, Virginia, USA

Funding: EuCARD, contract number 227579, German Federal Ministry of Education and Research grant 05 ES4BR1/8
In order to improve the gradient of the cavity and the beam quality of the gun, a new design for the SRF photo injector at the Helmholtz-Zentrum Dresden-Rossendorf has been developed. Apart from the special design of the cavity itself – as presented at SRF09, Berlin – the next update will include a separation of input and output of the liquid nitrogen supply system. This is supposed to increase the stability of the nitrogen pressure and enable a better monitoring of its temperature. The implementation of a superconducting solenoid inside the cryomodule is another major improvement. The position of this solenoid can be adjusted with a high precision using two independent step motors, which are thermally isolated from the solenoid itself. The poster will present the progress of turning the first design models into reality.

MOP027

BNL SRF Gun Commissioning

gun, SRF, cathode, insertion

155

W. Xu, Z. Altinbas, S.A. Belomestnykh, I. Ben-Zvi, J. Dai, S. Deonarine, D.M. Gassner, H. Hahn, J.P. Jamilkowski, P. Kankiya, D. Kayran, N. Laloudakis, L. Masi, G.T. McIntyre, D. Pate, D. Phillips, T. Seda, K.S. Smith, A.N. Steszyn, T.N. Tallerico, R. Than, R.J. Todd, D. Weiss, A. Zaltsman
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi, J. Dai
Stony Brook University, Stony Brook, USA

Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 704 MHz superconducting RF gun for the R&D ERL project is under comissioning at BNL. Since last November, the SRF gun has been conditioned and demonstrated an operational accelerating voltage of 2 MV (an accelerating gradient of 23.5 MV/m). Preparations for the cathode insertion are in final stages and we expect the gun to generate the first electron beam this summer. This paper discusses the BNL SRF gun system,and the results of the SRF gun commissioning.

MOP031

Quality Control of the Vessel and Cold Mass Production for the 1.3 GHz XFEL Cryomodules

vacuum, controls, cryomodule, operation

168

S. Barbanotti, H. Hintz, K. Jensch, W. Maschmann
DESY, Hamburg, Germany

The industrial production of one hundred cold masses and vacuum vessels for the 1.3 GHz XFEL cryomodules is now fully in operation. Quality checks at the companies and controls at DESY assure the quality level required for the cryomodule assembly. Verification of the main production steps, non-destructive tests, dimensional controls are performed by DESY personnel before accepting the components. This paper resumes the quality control strategy and the results for the first components produced by the companies.

MOP032

Statistic to Eddy-Current Scanning of Niobium Sheets for European XFEL

niobium, controls, survey, superconducting-RF

171

A. Brinkmann, S. Arnold, A. Ermakov, J. Iversen, M. Lengkeit, A. Poerschmann, L. Schaefer, W. Singer, X. Singer
DESY, Hamburg, Germany

The fabrication experiences of superconducting cavities for FLASH have shown that eddy-current scanning of the Nb-sheets foreseen for half-cells reduces the cavity failures. New eddy current devices have been developed and build together with the industry for the production of 800 pieces 1.3 GHz superconducting niobium cavities for European XFEL. More than 15.000 Nb-sheets provided by three companies have been tested by eddy-current scanning. The sheets that demonstrated local deviations of the signal have been subsequently non-destructively examined by 3d-microscope and X-Ray element analysis. The surface defects (dents, holes, scratches) are the mainly detected flaws. In addition several types of foreign material inclusions observed. Statistic concerning eddy-current signal deviation and rejection rates for each supplier will be presented.

MOP033

Quality Assurance and Acceptance Testing of Niobium Material for Use in the Construction of the Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU)

niobium, linac, SRF, controls

174

C. Compton, D. Miller
FRIB, East Lansing, USA
T.R. Bieler, D. Kang
Michigan State University, East Lansing, USA
S.K. Chandrasekaran, N.T. Wright
MSU, East Lansing, USA

Funding: Work supported by US DOE Cooperative Agreement DE-SC0000661 and Michigan State University
Niobium is the current material of choice for the fabrication of superconducting radio frequency (SRF) cavities used in SRF based accelerators. Although niobium specifications for this application have been well established, material properties of as-received materials can still vary substantially. As required for the FRIB accelerator, large volumes (60,000 lbs) of niobium materials (sheet, tube, and flange) have been contracted to several niobium vendors. The FRIB cavity designs require very large niobium sheets, increasing the difficulty in fabrication and potential for contamination. FRIB has developed and initiated plans to control niobium specifications and perform incoming acceptance checks to ensure quality is maintained. Acceptance results from the first niobium shipment will be presented, looking at several production lots from the same vendor and across multiple vendors. Non-conforming results were observed and will be discussed including follow-up investigations and mitigation strategies to improve quality of future shipments.

MOP034

The Statistics of Industrial XFEL Cavities Fabrication at E.ZANON

target, controls, niobium, accelerating-gradient

180

A. Gresele, M. Giaretta, A. Visentin
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
A.A. Sulimov, J.H. Thie
DESY, Hamburg, Germany

Serial production of superconducting cavities for European-XFEL was successfully started at E.ZANON at the end of last year. The production rate (3-4 cavities a week) allows us to summarize the results and present the statistics of industrial cavity fabrication. Many parameters have been traced during different steps of cavity production. The most interesting of them, as cavity length, frequency, field flatness and eccentricity, are presented and discussed. The last results of new preparation cycles development in the frame of E-XFEL projects is also included

MOP035

Using an Engineering Data Management System for Series Cavity Production for the European XFEL

controls, niobium, database, data-management

183

J. Iversen, A. Brinkmann, J.A. Dammann, A. Poerschmann, W. Singer, J.H. Thie
DESY, Hamburg, Germany

For series production of 800 superconducting cavities for the European XFEL an Engineering Data Management System (EDMS) is in use as a tool for quality control and quality assurance. DESY is responsible for “in-time” supply of more than 24000 semi-finished products of niobium and niobium-titanium alloy. The EDMS as a main repository was set up to fulfill logistic requirements and to guarantee traceability and documentation issues according to the European pressure equipment directive (PED 97/23 EC). The main aspects consist of complete paperless documentation, fully automated transfer of quality management documents and data from vendor system to DESY’s EDMS, providing to industry an access to relevant documentation and processing of release procedures for acceptance levels and non-conformity reporting. A summary of documentation methods, procedures and first experiences will be presented.

MOP036

New Technique and Result of Laser Welded SCRF Cavity Developed at RRCAT

laser, vacuum, niobium, experiment

186

P. Khare, R. Arya, J. Dwivedi, R. Ghosh, G. Gilankar, C. Gupta, P.D. Gupta, A. Jain, S.C. Joshi, G.V. Kane, R. Kaul, P.K. Kush, G. Mundra, S.M. Oak, C.K. Pithawa, P. Ram Sankar, S.B. Roy, V.C. Sahni, R.S. Sandha, P. Shrivastava, B.N. Upadhyay
RRCAT, Indore (M.P.), India
C.A. Cooper, C.M. Ginsburg, A. Grassellino, C.S. Mishra, A.M. Rowe
Fermilab, Batavia, USA

A new technique to fabricate SCRF cavities with the help of laser welding process has been developed at Raja Ramanna Centre for Advanced Technology RRCAT), Indore, Department of Atomic Energy, India. In this technique, a pulsed Nd:YAG laser has been used and welding was performed in inert gas environment, in a specially designed welding rig. The advantages of this technique are reduced cost, small heat affected zone, no necessity to weld in vacuum and enhanced rate of production. The paper describes the technique and fabrication method of a single-cell 1.3 GHz SCRF cavity which was fabricated at RRCAT with this new technique. It also discusses the test result of this cavity which was processed and tested at Fermilab. The cavity reached an Eacc of 17MV/m with a Q0 of 1.4 E +10 at 2K. The cavity is being barrel polished for further improvement.

MOP037

Test of the 1.3 GHz Superconducting Cavities for the European X-ray Free Electron Laser

HOM, vacuum, software, pick-up

191

K. Krzysik
DESY, Hamburg, Germany
B. Dzieza, W. Gaj, D. Karolczyk, K. Kasprzak, L.M. Kolwicz-Chodak, A. Kotarba, A. Krawczyk, W. Maciocha, A. Marendziak, K. Myalski, S. Myalski, T. Ostrowicz, B. Prochal, M. Sienkiewicz, M. Skiba, J. Świerbleski, M. Wiencek, J. Zbroja, A. Zwozniak
IFJ-PAN, Kraków, Poland

The European X-ray Free Electron Laser (XFEL) is currently under construction in Germany in Hamburg area. A linear accelerating part of the XFEL is going to consist of 808 superconducting 9-cell Niobium cavities installed in 101 accelerating modules. Before assembly into modules the cavities are tested in a dedicated test facilities. The testing procedures are prepared based on DESY expertise and available software from Tesla Test Facility (TTF) Collaboration and Free electron LASer for Hamburg (FLASH). RF test provides the most important information about cavity performance: maximum available gradient and dependence of quality factor and radiation on the gradient. Results of the RF test determine, whether a cavity is shipped to CEA Saclay (France) to be assembled into a module or send for retreatment to improve its performance. In this paper we present the most important aspects of the cavity RF test procedure.

MOP038

Series Production of EXFEL 1.3 GHz SRF Cavities at E. Zanon: Management, Infrastructures and Quality Control

SRF, controls, niobium, cryogenics

194

G. Massaro
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
G. Corniani, M. Festa, M. Maule
Ettore Zanon S.p.A., Schio, Italy

In this paper we report on the capability of Ettore Zanon S.p.A. (EZ) to implement a EXFEL 1,3 GHz SRF cavities production system. In order to assure the series efficient repeatability of the product, this system is based on work team, composed of people with different skills, qualified infrastructures and technical procedures. A detailed study of the different work phases of the production cycle has been performed in advance, highlighting the technical difficulties and the production constraints. Based on this result, infrastructures and processes have been optimized to grant the specified quality and time/cost requirements and procedures and operating instructions, where the most complexes and delicate phases as well as the responsibilities and acceptance criteria are investigated, have been introduced. Qualification operations and eight pre-series cavities have proven EZ capability of fulfilling the imposed requirements. The above described manufacturing system allows nowadays a production rate of 4 cavities per week. EZ future developments involve minimizing time and costs while keeping the highest quality standard.

MOP039

Strategy of Technology Transfer of EXFEL Preparation Technology to Industry

controls, status, hardware, linac

197

A. Matheisen, J. Iversen, A. Schmidt, W. Singer
DESY, Hamburg, Germany
P. Michelato, L. Monaco
INFN/LASA, Segrate (MI), Italy

For the EXFEL a specification for the cavitiy preparation procedures (R1)was set up and handed to the industrial companies. Basing on this specification companies hard ware as well as process flows were set up. Beside this specified part of the preparation technique the companies personal needed to be educated and the processes ramped up. To check the quality of the infrastructure, status of education of personal and correct set up of process flows, so called Dummy (DCV) - , Reference (RCV ) and Pre-series (PCV) cavities were assigned. We report on the general strategy applied for the EXFEL technology transfer on cavity preparation and the results obtained on the qualification cavities.
R1) Series Surface and acceptance test preparation of superconducting cavities for the European Xfel (XFEL/A - D) JUNE 30, 2009

MOP040

Industrialization of European XFEL Preparation Cycle “Final EP ” at Research Instruments Company

controls, acceleration, vacuum, radiation

201

A. Matheisen, N. Krupka, M. Schalwat, A. Schmidt, M. Schmökel, W. Singer, B. van der Horst
DESY, Hamburg, Germany
P. Michelato, L. Monaco
INFN/LASA, Segrate (MI), Italy
M. Pekeler
RI Research Instruments GmbH, Bergisch Gladbach, Germany

In the Specification for XFEL Cavity preparation (R1) two different preparation sequences are presented. Research Instruments Company as one of the two companies contracted for XFEL cavity production and preparation has chosen the so called “final EP” cycle. Major infrastructure components like EP facility and the BCP facility were pre- qualified. This existing and the new set up areas like the cleanroom are distributed over the ground area of the industrial park Bergisch Gladbach. The process flow given in the DESY specification needed adaptation to this scenario. Additional infrastructure beside the once specified needed to be set up to ensure the same quality of processes even with a changed work flow. The general lay out of the facility, matched work flow of preparation and test results of resonators processed by RI company in their infrastructure will be reported.
(R1) Series Surface and acceptance test preparation of superconducting cavities for the European Xfel (XFEL/A - D) JUNE 30, 2009

MOP042

Quality Control and Processes Optimization for the EXFEL Superconducting Cavities Series Production at Ettore Zanon spa

controls, operation, vacuum, SRF

208

L. Facci, D. Rizzetto
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
G. Corniani
Ettore Zanon S.p.A., Schio, Italy
A. Matheisen
DESY, Hamburg, Germany
P. Michelato, L. Monaco
INFN/LASA, Segrate (MI), Italy

The construction of the European XFEL forced the first mass production of Niobium bulk SRF cavities. In this context Ettore Zanon S.p.A. built a fully new facility designed to produce four fully treated and He tank equipped cavities per week, ready to be tested at DESY. The facility already reached the foreseen production rate. The guarantee of the highest quality of the resonators produced requires a very strict quality control plan. At the same time, the requirements of the industrial production in terms of time, cost and productivity must be satisfied. As a consequence processes must be standardized and working times optimized. In the following, after the description of the production facility, we would like to highlight and discuss the strategies and arrangements adopted in the various critical fields (clean room, vacuum, etc.) to ensure the foreseen results. Moreover correlation between cavities performances and production cycle parameters will be investigated and discussed.

MOP043

ILC-HiGrade Cavities as a Tool of Quality Control for European XFEL

controls, radiation, feedback, framework

212

A. Navitski, E. Elsen, B. Foster, J. Iversen, A. Matheisen, D. Reschke, W. Singer, X. Singer, L. Steder, M. Wenskat
DESY, Hamburg, Germany
R. Laasch, Y. Tamashevich
University of Hamburg, Hamburg, Germany

Funding: BMBF, Helmholtz Association, ILC-HiGrade, FP7 (CRISP), Alexander von Humboldt Stiftung/Foundation
The EXFEL order for SRF cavities includes 24 cavities, which are part of the ILC-HiGrade program. Initially, these cavities serve as quality control (QC) sample extracted from the EXFEL cavities series production on a regular basis. The QC and quality assurance (QA) include all processing steps of the EXFEL cavities. To maximize the information from these so-called QC cavities, a surface mapping technique is applied in a second cold RF test. There the cavities delivered have experienced identical treatment of the inner surface with the exception of mounting of the Helium vessel. After the normal acceptance test at the cavity RF measurement facility, the cavities are removed from the production flow. Further quality assurance steps beginning with a detailed RF test with surface mapping followed by a high resolution optical inspection (OBACHT) are carried out to improve the understanding of defects in close collaboration with the standing experts engaged in the EXFEL production. Results of the first QC cavities tests as well as planned further R&D will be presented and discussed.

MOP044

Performance Characteristics of Jefferson Lab’s New SRF Infrastructure

SRF, cryomodule, cryogenics, vacuum

216

C.E. Reece, P. Denny, A.V. Reilly
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In the past two years, Jefferson Lab has reconfigured and renovated its SRF support infrastructure as part of the Technology and Engineering Development Facility project, TEDF. The most significant changes are in the cleanroom and chemistry facilities. We report the initial characterization data on the new ultra-pure water systems, cleanroom facilities, describe the reconfiguration of existing facilities and also opportunities for flexible growth presented by the new arrangement.

MOP045

Electropolishing for EXFEL Cavities Production at Ettore Zanon SpA

niobium, controls, cathode, superconductivity

220

M. Rizzi
Ettore Zanon S.p.A., Schio, Italy
A. Gresele
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
A. Matheisen, N. Steinhau Kühl
DESY, Hamburg, Germany
P. Michelato
INFN/LASA, Segrate (MI), Italy

A new horizontal electropolishing (EP) facility has been implemented by Ettore Zanon SpA for the series production of the EXFEL cavities produced by the company. According to EXFEL specification a bulk EP of at least 100 micron is the first step of the surface treatment for high performances. Particular attention has been dedicated to find the best configuration during qualification of the system. Correlation between process variables, RF tests at room temperature at Zanon and vertical RF tests at 2 K at DESY have been investigated and the Niobium removal optimized. The facility has been designed for industrial scope, in order to guarantee the required quality and production rate of 4 cavities per week. One of the most important aspects has been the system automation to have complete control of the process.

MOP048

PED Requirements Applied to the Cavity and Helium Tank Manufacturing

niobium, linac, controls, operation

227

A. Schmidt, J. Iversen, A. Matheisen, W. Singer
DESY, Hamburg, Germany

For the European XFEL more than 800 Cavities are manufactured by industrial partners. Each cavity is housed in an individual cryo vessel, the so called helium tank. All vessels are made from titanium and manufactured by industry as well. The cavity, welded into its helium tank, is a pressure loaded part and has to follow the pressure equipment directive - PED (97/23/EC). Setting up a series production of cavities and helium tanks by different vendors according given standards, was the task of the EXFEL WPG-1 LINAC-WP04. In cooperation with the TUEV-Nord as the notified body, DESY is responsible for the qualification of design, material in use and reasonable tests to get a certificate for pressure bearing parts.

MOP049

Progress and Experiences of Series Production of Helium Tanks With DESY as a Subcontractor for RI

controls, status, factory, data-management

231

A. Schmidt, J.A. Dammann, A. Daniel, A. Matheisen
DESY, Hamburg, Germany

DESY acts as a subcontractor for helium tanks, for one of the cavity manufacturer in charge, for the EXFEL cavity production. Here the full responsibility of production, quality and warranty of these parts is at DESY. Therefore on 400 out of the total of 800 helium tanks, DESY has to set up a logistic of incoming inspection, documentation, storage and distribution. Special effort is made to archive a free of doubts interconnection and integration of the cavity into the helium tank. After more than 300 units produced a review and statistic is provided.

MOP051

The Statistics of Industrial XFEL Cavities Fabrication at Research Instruments

target, controls, status, vacuum

234

A.A. Sulimov, J.H. Thie
DESY, Hamburg, Germany
M. Pekeler, D. Trompetter
RI Research Instruments GmbH, Bergisch Gladbach, Germany

Serial production of superconducting cavities for European-XFEL was successfully started at Research Instrument (RI) at the end of last year. The production rate (3-4 cavities a week) allows us to summarize the results and present the statistics of industrial cavity fabrication. Many parameters have been traced during different steps of cavity production. The most interesting of them, as cavity length, frequency, field flatness and eccentricity, are presented and discussed.

Poster MOP051 [0.769 MB]

MOP052

RF Aspects of Quality Control for Industrial XFEL Cavities Fabrication

controls, background, SRF, pick-up

237

A.A. Sulimov, V. Gubarev, S. Yasar
DESY, Hamburg, Germany

Quality control of XFEL serial cavities allows us not only except the using of reject cavities for linac, but also give a feedback to the industry in case of cavity parameters come to their limits. RF control assays not only the electro dynamical characteristics (as frequencies, Q-factors and fields), but also provide the mechanical revise with a very high accuracy. Automation of this quality control in XFEL data base gave us a powerful tool which is required for the big projects as European-XFEL.

Poster MOP052 [1.178 MB]

MOP053

R&D on Cavity Treatments at DESY Towards the ILC Performance Goal

SRF, factory, controls, linear-collider

240

A. Navitski, E. Elsen, B. Foster, D. Reschke, J. Schaffran, W. Singer, X. Singer
DESY, Hamburg, Germany
R. Laasch, Y. Tamashevich
University of Hamburg, Hamburg, Germany

Funding: BMBF, Helmholtz Association, ILC-HiGrade, FP7 (CRISP), Alexander von Humboldt Stiftung/Foundation
The actual R&D program at DESY is derived from the global effort for the International Linear Collider (ILC) and is well in phase with effort elsewhere. The program aims at a solid understanding and control of the industrial mass-production process of the superconducting radio-frequency accelerating cavities, which are manufactured for the European X-ray Free Electron Laser (EXFEL) at DESY. The goal is to identify the gradient limiting factors and further refine the cavity treatment technique to provide gradients above 35 MV/m at >90% production yield. Techniques such as 2nd sound quench detection, OBACHT optical inspections, defect metrology using silicon replica as well as Centrifugal Barrel Polishing (CBP) and Local Grinding repair are foreseen as tools. Actual status, details, and first achievements of the program will be reported.

MOP054

Tests of the Accelerating Cryomodules for the European X-Ray Free Electron Laser

cryomodule, cryogenics, operation, radiation

244

M. Wiencek, B. Dzieza, W. Gaj, D. Karolczyk, K. Kasprzak, L.M. Kolwicz-Chodak, A. Kotarba, A. Krawczyk, K. Krzysik, W. Maciocha, A. Marendziak, K. Myalski, S. Myalski, T. Ostrowicz, B. Prochal, M. Sienkiewicz, M. Skiba, J. Świerbleski, J. Zbroja, A. Zwozniak
IFJ-PAN, Kraków, Poland

The European X-ray Free Electron Laser (XFEL) is currently under construction in Germany in Hamburg area. A 2.1 km long superconducting linear accelerator, part of the XFEL, consists of 101 accelerating cryomodules. The XFEL cryomodule is assembled with eight superconducting RF cavities, one cold magnet and Beam Position Monitor (BPM). The cryomodules are tested in dedicated test facility before installation in the XFEL tunnel. The testing procedures for the cryomodules were prepared with use of DESY expertise from TTF (Tesla Test Facility) Collaboration and FLASH (Freie-Elektronen-Laser in Hamburg). This paper describes the full set of testing procedure and incoming and outgoing inspections as well.

MOP055

Status of the Superconducting Cavity Development for ILC

cryomodule, status, HOM, linac

247

T. Yanagisawa, H. Hara, F. Inoue, K. Kanaoka, K. Sennyu
MHI, Hiroshima, Japan

MHI activities for ILC are reported. MHI had developed several procedure and method of cavity production for stable quality and cost reduction. And we are producing cryomodules too. These activities are reported in detail.

MOP057

Developments and Tests of a 700 MHz Cryomodule for the Superconducting Linac of MYRRHA

cryomodule, linac, vacuum, cryogenics

250

F. Bouly
CERN, Geneva, Switzerland
S. Berthelot, J.-L. Biarrotte, M. El Yakoubi, C. Joly, J. Lesrel, E. Rampnoux
IPN, Orsay, France
A. Bosotti, R. Paparella, P. Pierini
INFN/LASA, Segrate (MI), Italy

Funding: This work is being supported by the European Atomic Energy Community’s EURATOM) Seventh Framework Programme under grant agreement n°269565(MAX project).
The MYRRHA (“Multi-purpose Hybrid Research reactor for High-tech Applications”) project aims at the construction of a new flexible fast spectrum research reactor. This reactor will operate as an Accelerator Driven System demonstrator. The criticality will be sustained by an external spallation neutron flux; produced thanks to a 600 MeV high intensity proton beam. This CW beam will be delivered by a superconducting linac which must fulfil very stringent reliability requirements. In this purpose, the accelerator design is based on a redundant and fault-tolerant scheme to enable the rapid mitigation of RF failures. To carry out “real scale” reliability-oriented experiments a prototype of cryomodule was developed by INFN Milano and installed at IPN Orsay. The module holds a 700 MHz 5-cell elliptical cavity (βg = 0.47) equipped with its blade frequency tuner. Several tests were carried out to commission the experimental set-up. We review here the obtained results and the lessons learnt by operating this module, as well as the on-going developments.

MOP059

Management for the Long-Term Reliability of the Diamond Superconducting RF Cavities

vacuum, SRF, ion, electron

255

P. Gu, C. Christou, M.P. Cox, S.A. Pande, A.F. Rankin, H.S. Shiers, A.V. Watkins
Diamond, Oxfordshire, United Kingdom

Diamond started operation with users in January 2007 and the Diamond storage ring superconducting RF cavities used to be the largest single contributor to unplanned beam trips. Extensive effort has been dedicated to understand and improve the long-term stability of the SRF cavities. Our experience shows that the long-term stability of superconducting RF cavities relies heavily on the surface conditions. Gases keep accumulating on the cold surfaces with time due to its huge cryo-pumping capacity. The integral effect will ultimately lead to fast vacuum trips during operation. In Diamond, we have developed a systematic approach to control the long-term stability of the SRF cavities. We will discuss here our approach and also present the future work that should be completed.

MOP061

75 mA Operation of the Cornell ERL Superconducting RF Injector Cryomodule

HOM, operation, SRF, cryomodule

259

M. Liepe, B.M. Dunham, R.G. Eichhorn, G.H. Hoffstaetter, R.P.K. Kaplan, P. Quigley, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work is supported by the National Science Foundation (Grant No. DMR-0807731).
Cornell University has developed a SCRF injector cryomodule for the acceleration of high current, low emittance beams in continuous wave operation. This cryomodule is based on 1.3 GHz superconducting RF technology, and has been tested extensively in the Cornell ERL injector prototype with world record CW beam currents exceeding 70 mA. High CW RF power input couplers and strong Higher-Order-Mode damping in the cavities are essential for high beam current operation. This paper summarizes the performance of the cryomodule during the high beam current operation.

MOP062

Production of 500 MHz SRF Modules the KEKB-type for Taiwan Photon Source

SRF, niobium, operation, vacuum

263

Ch. Wang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, Z.K. Liu, C.H. Lo, M.H. Tsai, T.-T. Yang, M.-S. Yeh, T.-C. Yu
NSRRC, Hsinchu, Taiwan
T. Furuya, K. Hara, T. Honma, A. Kabe, Y. Kojima, S. Mitsunobu, Y. Morita, H. Nakai, K. Nakanishi, M. Nishiwaki, S. Takano
KEK, Ibaraki, Japan
F. Inoue, K. Sennyu, T. Yanagisawa
MHI, Hiroshima, Japan

The KEKB-type single-cell 500-MHz superconducting radio frequency (SRF) modules have been selected to power the 3 GeV, 500 mA, storage ring of the constructing Taiwan Photon Source (TPS) at National Synchrotron Radiation Research Center (NSRRC). The design target is to routinely deliver RF forward power up to 300 kW, CW, to single SRF module with highly reliable operation. Three sets of SRF modules have been successfully produced under a tight collaboration with High Energy Accelerator Research Organization (KEK) and Mitsubishi Heavy Industries Ltd. (MHI), after obtaining the technology transfer from KEK. MHI is responsible for the mechanical fabrication and cryo-module assembly, KEK for the surface and RF treatments of the niobium cavities, high power input couplers and HOM dampers and for the liquid-helium tests of the cryo-modules, and NSRRC for the electronic/diagnostic system, final assembly and system integration, high power horizontal test, and reliable test. This work reports the results obtained during the production of these three SRF modules at KEK and NSRRC.

MOP063

Mature Operation of CESR-Type 500-MHz SRF Module at Taiwan Light Source

SRF, operation, vacuum, cryogenics

266

Ch. Wang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, Z.K. Liu, C.H. Lo, M.H. Tsai, T.-T. Yang, M.-S. Yeh, T.-C. Yu
NSRRC, Hsinchu, Taiwan

The Cornell-type 500-MHz SRF module has been routinely operated since the end of 2004 to power the 1.5 GeV Taiwan Light Source with 360 mA in top-up mode. A new record of SRF operation with mean time between failures (MTBF)up to 800 hr has been achieved in the 1st half of 2013 that is compatible with the best operational record of room temperature cavities ever made in the same machine. To meet the user’s strict requirements on highly operational reliability, developing in advanced diagnostic instrumentation together with user-friendly event logging software does never stop. Here, we review our SRF operational experience in last 9 years.

MOP064

Operational Experience with the SOLEIL Superconducting RF System

cryogenics, operation, HOM, vacuum

269

P. Marchand, J.P. Baete, R.C. Cuoq, H.D. Dias, M. Diop, J.L. Labelle, R. Lopes, M. Louvet, C.M. Monnot, S. Petit, F. Ribeiro, T. Ruan, R. Sreedharan, K. Tavakoli
SOLEIL, Gif-sur-Yvette, France

In the SOLEIL storage ring, two cryomodules provide to the electron beam an accelerating voltage of 3-4 MV and a power of 575 kW at 352 MHz. Each cryomodule contains a pair of superconducting cavities, cooled with liquid Helium at 4K, which is supplied by a single 350 W cryogenic plant. The RF power is provided by 4 solid state amplifiers, each delivering up to 180 kW. The parasitic impedances of the high order modes are strongly mitigated by means of four coaxial couplers, located on the central pipe connecting the two cavities. Seven years of operational experience with this system as well as its upgrades are reported.

MOP065

Consolidated Design of the 17 MeV Injector for MYRRHA

proton, rfq, linac, cryomodule

274

D. Mäder, D. Koser, H. Podlech, A. Schempp
IAP, Frankfurt am Main, Germany

Funding: Project supported by the EU, FP7 MAX, contract No. 269565 and BMBF, contract No. 06FY7102.
The MYRRHA research reactor will be an Accelerator Driven System, which demands a 2.4 MW proton beam delivered by a 600 MeV cw operated linac. The beam dynamics design of the injector has been consolidated to fulfil the requirements with respect to beam losses and quality. After a 4-rod-RFQ, four 7-gap room temperature CH cavities with a constant phase and an effective voltage of 750 keV are used to reach 4.3 MeV. Then the proton beam is accelerated to 18 MeV using six superconducting 5-gap Nb CH structures with a constant beta profile. With reducing the gradient and adjusting the phase of the twelfth CH structure the originally demanded 17 MeV can be delivered, too. Every SC CH cavity is cooled down to 2K with liquid helium in a separate cryo module. The new geometric design of the SC CH cavities improves the rigidity and reduces the electric peak field.

MOP066

Development of Compact Cryomodules Housing HWRs for High-intensity SC CW Linacs

cryomodule, linac, niobium, proton

277

P.N. Ostroumov, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.H. Kim, S.V. Kutsaev, R.C. Murphy, B. Mustapha, T. Reid
ANL, Argonne, USA
D. Berkovits
Soreq NRC, Yavne, Israel
S. Nagaitsev
Fermilab, Batavia, USA

Funding: This work was supported by the U.S. Department of Energy, under Contracts No. DE-AC02-06CH11357, DE-AC02-76CH03000 and ANL WFO No. 85Y47.
Acceleration of high-intensity light-ion beams immediately after an RFQ requires a compact accelerating and focusing lattice with a high packing factor. We have developed a cryomodule which satisfies this requirement with eight accelerating-focusing periods for Project X at FNAL. Each focusing period consist of a 162.5-MHz SC HWR, a SC solenoid and a beam position monitor. The highly optimized EM parameters of the cavity were achieved by using double conical, hour glass like, inner and outer conductors. This design is also favorable for the beam dynamics because the short focusing periods which helps to better control the beam quality. All sub-systems of the cryomodule, except the vacuum-vessel, are in advanced stages of prototyping and testing. A similar concept has been developed for the design of several cryomodules for a 20 MeV/u proton/deuteron 200 kW linac at SNRC. These cryomodules house two types of 176 MHz half-wave resonators and require only modest modifications for the application. This paper will discuss the status of the FNAL cryomodule design and sub-system fabrication and its impact on future HWR cryomodule such as the SNRC project.

MOP067

Results From Initial Tests of the 1st Production Prototype β=0.29 and β=0.53 HWR Cavities for FRIB

linac, target, cryomodule, vacuum

280

J.P. Ozelis, C. Compton, K. Elliott, M. Hodek, M. Leitner, I.M. Malloch, D. Miller, S.J. Miller, D. Norton, R. Oweiss, J. Popielarski, L. Popielarski, A.P. Rauch, K. Saito, G.J. Velianoff, D.R. Victory
FRIB, East Lansing, USA

Funding: Work supported by US DOE Cooperative Agreement DE-SC0000661 and Michigan State University
The first prototypes of the β=0.53 and β=0.29 HWR production design cavities for FRIB were fabricated early this year by Roark Manufacturing Company and delivered to MSU. These cavities have undergone an extensive evaluation program to verify both mechanical and RF performance before proceeding with fabrication of a pre-production run of 10 cavities. Results from physical inspections, warm RF measurements, chemical processing, and cryogenic vertical testing will be presented.

MOP068

NGLS Linac Design

cryomodule, linac, cryogenics, controls

286

R.P. Wells, J.M. Byrd, J.N. Corlett, L.R. Doolittle, P. Emma, A. Ratti
LBNL, Berkeley, California, USA
C. Adolphsen, C.D. Nantista
SLAC, Menlo Park, California, USA
D. Arenius
JLAB, Newport News, Virginia, USA
C.M. Ginsburg, T.J. Peterson
Fermilab, Batavia, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The Next Generation Light Source (NGLS) is a design concept for a multibeamline soft x-ray FEL array powered by a CW superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. This paper describes the concepts for the cavity and cryostat design operating at 1.3 GHZ and based on minimal modifications to the design of ILC cryomodules, This leverages the extensive experience derived from R&D that resulted in the ILC design. Due to the different nature of the two applications, particular attention is given now to high loaded Q operation and microphonics control, as well as high reliability and expected up time. The work describes the design and configuration of the linac, including choice of gradient, possible modes of operation, cavity design and RF power, as well as the consequent requirements for the cryogenic system.

MOP069

Precise Measurement of Superconducting Cavity Movement in Cryomodule by the Position Monitor Using White Light Interferometer

target, cryomodule, linac, superconducting-cavity

291

H. Sakai, T. Aoto, K. Enami, T. Furuya, M. Sato, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
K. Hayashi, K. Kanzaki
Tokyo Seimitsu Co. Ltd, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

Alignment of Superconducting cavity is one of the important issues for linear collider and/or future light source like ERL and X-FEL. To measure the cavity displacement under cooling to Liq He temperature more precisely, we newly developed the position monitor by using white light interferometer. This monitor is based on the measurement of the interference of light between the measurement target and the reference point. It can measure the position from the outside of the cryomodule. We applied this monitor to the main linac cryomodule of Compact ERL and successfully measured the displacement during 2K cooling with the resolution of 10 micron

MOP070

Results on Quality Factors of 1.3 GHz Nine-Cell Cavities at DESY

factory, niobium, operation, linear-collider

297

F. Schlander
IKP, Mainz, Germany
F. Schlander
DESY, Hamburg, Germany

Superconducting cavities made of niobium are the basis of many particle accelerators around the world. Besides the quest for high accelerating fields for projects like European XFEL and the International Linear Collider, the quality factor, a measure for the resistance and hence the ohmic losses, is of importance, as it eventually determines the cryoplant size and its costs of operation. Especially for accelerators operating in continuous wave mode, the dynamic heat load generated by cavity operation exceeds the static heat load by far and thus requires minimisation. To investigate the current quality factor performance of 1.3 GHz cavities at DESY, the test results of some 50 recent cavities with state-of-the-art treatment have been examined regarding surface treatment and material.

Slides MOP070 [0.590 MB]

MOP071

Record Quality Factor Performance of the Prototype Cornell ERL Main Linac Cavity in the Horizontal Test Cryomodule

linac, cryomodule, experiment, higher-order-mode

300

N.R.A. Valles, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Supported by NSF grant DMR-0807731
Future SRF linac driven accelerators operated in CW mode will require very efficient SRF cavities with high intrinsic quality factors Q at medium accelerating fields. Cornell has recently ﬁnished testing the fully equipped 1.3 GHz, 7-cell main linac cavity for the Cornell Energy Recovery Linac in a horizontal test cryomodule (HTC). Measurements characterizing the fundamental mode’s quality factor have been completed, showing record Q performance. In this paper, we present detailed quality factor vs gradient results for three HTC assembly stages. We show that the performance of an SRF cavity can be maintained when installed into a cryomodule, and that thermal cycling reduces residual surface resistance. We present world record results for a fully equipped multicell cavity in a cryomodule, reaching intrinsic quality factors at operating accelerating field of Q(E =16.2 MV/m, 1.8K) > 6·10¹⁰ and Q(E =16.2 MV/m, 1.6K) > 1.0·10¹¹, corresponding to a very low residual surface resistance of 1.1 nOhm.

MOP073

IHEP 1.3 GHz Low Loss Large Grain 9-cell Cavity Fabrication, Processing and Test

HOM, SRF, vacuum, niobium

305

J.Y. Zhai, J. Gao, S. Jin, Z.Q. Li, Y. Liu, Z.C. Liu, Z.H. Mi, X.H. Peng, T.X. Zhao, H.J. Zheng
IHEP, Beijing, People's Republic of China
C.A. Cooper, C.M. Ginsburg, T.N. Khabiboulline, A.M. Rowe, D.A. Sergatskov
Fermilab, Batavia, USA
J.X. Wang, H. Yu, H. Yuan
BIAM, Beijing, People's Republic of China

The combination of the low-loss shape and large grain niobium material is expected to be the possible way to achieve higher gradient and lower cost for ILC 9-cell cavities, and will be essential for the ILC 1 TeV upgrade. As the key component of the “IHEP 1.3 GHz SRF Accelerating Unit Project”, a low-loss shape 9-cell cavity with full end groups using Ningxia large grain niobium (IHEP-02) was fabricated at IHEP in 2012. The cavity was processed (CBP and EP) and tested at FNAL. The cavity processing,test performance and gradient limitation is reported in this paper. We will weld the helium vessel, assemble the magnetic shield and install the cavity to IHEP ILC-TC1 cryomodule.

MOP077

Cryomodule Component Development for the APS Upgrade Short Pulse X-Ray Project

cryomodule, HOM, vacuum, alignment

314

J.P. Holzbauer, J.D. Fuerst, A. Nassiri, Y. Shiroyanagi, B.K. Stillwell, G.J. Waldschmidt, G. Wu
ANL, Argonne, USA
G. Cheng, J. Henry, J.D. Mammosser, J. Matalevich, J.P. Preble, R.A. Rimmer, H. Wang, K.M. Wilson, M. Wiseman, S. Yang
JLAB, Newport News, Virginia, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CHI1357 at ANL and under U.S. DOE Contract No. DE-AC05-06OR23177 at Jefferson Lab.
The short pulse x-ray (SPX) part of the Advanced Photon Source Upgrade calls for the installation of a two-cavity cryomodule in the APS ring to study cavity-beam interaction, including HOM damping and cavity timing and synchronization. Design of this cryomodule is underway at Jefferson Lab in collaboration with the APS Upgrade team at ANL. The cryomodule design faces several challenges including tight spacing to fit in the APS ring, a complex set of cavity waveguides including HOM waveguides and dampers enclosed in the insulating vacuum space, and tight alignment tolerances due to the APS high beam-current (up to 150 mA). Given these constraints, special focus has been put on modifying existing CEBAF-style designs, including a cavity tuner and alignment scheme, to accommodate these challenges. The thermal design has also required extensive work including coupled thermal-mechanical simulations to determine the effects of cool-down on both alignment and waveguides. This work will be presented and discussed in this paper.

MOP078

Horizontal Testing of a Dressed Deflecting Mode Cavity for the APS Upgrade Short Pulse X-Ray Project

controls, operation, photon, vacuum

321

J.P. Holzbauer, N.D. Arnold, T.G. Berenc, D.J. Bromberek, J. Carwardine, N.P. Di Monte, J.D. Fuerst, A.E. Grelick, D. Horan, J.A. Kaluzny, J.W. Lang, H. Ma, T.L. Mann, D.A. Meyer, M.E. Middendorf, A. Nassiri, Y. Shiroyanagi, J.H. Vacca, G.J. Waldschmidt, R.D. Wright, G. Wu, Y. Yang, A. Zholents
ANL, Argonne, USA
E.R. Harms, W. Schappert
Fermilab, Batavia, USA
J.D. Mammosser
JLAB, Newport News, Virginia, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CHI1357.
The short pulse x-ray (SPX) part of the Advanced Photon Source (APS) Upgrade is an effort to enhance time-resolved experiments on a few-ps-scale at the APS. The goal of SPX is the generation of short pulses of x-rays for pump-probe time-resolved capability using superconducting rf (SRF) deflecting cavities*. These cavities will create a correlation between longitudinal position in the electron bunch and vertical momentum**. The light produced by this bunch can be passed through a slit to produce a pulse of light much shorter (1-2 ps instead of 100 ps) than the bunch length at reduced flux. An SPX cavity has been tested with a helium vessel and tuner. In addition to studying rf performance with more realistic cooling, this test allowed integration and operation of many systems designed for SPX cryomodule in-ring operation. These systems included an APS-constructed 5 kW, 2.815 GHz amplifier, a digital low-level rf controller system designed and fabricated in collaboration with LBNL, a cavity tuner, and instrumentation systems designed for the existing APS infrastructure. Cavity performance and subsystem performance will be reported and discussed in this paper.
* A. Zholents et al., NIM A 425, 385 (1999).
** A. Nassiri et al., “Status of the Short-Pulse X-Ray Project at the Advanced Photon Source,” IPAC 2012, New Orleans, LA, May 2012.

MOP080

Design of a New Horizontal Test Cryostat for SCRF Cavities at the Uppsala University

cryomodule, radiation, operation, vacuum

328

T. Junquera, P. Bujard, N.R. Chevalier, J.P. Thermeau
Accelerators and Cryogenic Systems, Orsay, France
L. Hermansson, M. Noor, R.J.M.Y. Ruber, R. Santiago Kern
Uppsala University, Uppsala, Sweden
H. Saugnac
IPN, Orsay, France

At Uppsala University, the FREIA facility for research and development of new accelerators and associated instrumentation, is presently in construction. Associated to a new Helium Liquefier, a Horizontal Test Cryostat will be used for high power RF tests of completely equipped SC cavities. This paper presents the main characteristics of the cryostat and the associated cryogenic distribution system. Two types of cavities have been considered for test purpose: SC elliptical cavities for future free electron lasers and SC cavities for high intensity proton accelerators (i.e. SC spokes). A special valve box including a subcooling stage and power coupler cooling with supercritical Helium supply have been designed, for temperature operation ranging from 2K to 4.2 K. This facility will play an essential role in the development and test of cavities, couplers and cryomodules for the ESS project. High power RF sources will be installed in order to allow unique and complete tests of spoke cavities and cryomodules at high nominal peak power.

MOP082

Development and Test of a New Cryostat Module for the Injector of the S-DALINAC*

electron, operation, vacuum, linac

334

T. Kürzeder, J. Conrad, F. Hug, N. Pietralla, A. Richter, S.T. Sievers
TU Darmstadt, Darmstadt, Germany
R.G. Eichhorn
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: *This work is supported by the DFG through the Collaborative Research Center SFB 634.
The present injector of the superconducting Darmstadt electron linear accelerator S-DALINAC provides an electron beam of up to 10 MeV kinetic energy and up to 60 μA current in continuous wave operation. A new cryostat module has been constructed to replace the actual one in order to provide higher beam energies of up to 14 MeV and currents of up to 250 μA for nuclear resonance fluorescence experiments at the Darmstadt High Intensity Photon Setup (DHIPS). As before two 20-cell superconducting microwave cavities will be operated at an acceleration frequency of 3 GHz in a liquid helium bath at 2 K. For the injector upgrade two new elliptical 20-cell niobium cavities were also manufactured and in addition a third spare one. The rf power is transferred to the cavities by an also newly developed waveguide-transition line and input couplers. We report on the construction of the cryostat module and its components and present the results of a first cooling-down procedure.

MOP083

Operational Experience With the SOLEIL Storage Ring RF Cryogenic Plant

cryogenics, controls, operation, HOM

337

M. Louvet, H.D. Dias, M. Diop, P. Marchand
SOLEIL, Gif-sur-Yvette, France

In the Storage Ring of the Synchrotron SOLEIL light source, two cryomodules provide the required power of 575 kW at the nominal energy of 2.75 GeV with the full beam current of 500 mA and all the insertion devices. Each cryomodule contains a pair of 352 MHz superconducting cavities (Nb/Cu), cooled in a bath of liquid helium at 4.5 K. A single 350 W cryogenic system supplies the liquid helium for the two cryomodules. The seven years of operational experience with this cryogenic plant as well as its upgrades are reported.

MOP084

ESS Cryomodules for Elliptical Cavities

cryomodule, vacuum, cryogenics, operation

341

G. Olivier, J.P. Thermeau
IPN, Orsay, France
P. Bosland
CEA/IRFU, Gif-sur-Yvette, France
C. Darve
ESS, Lund, Sweden

The European Spallation Source will be the world's most powerfull neutron source. IPN Orsay undertakes the development of the ESS linac cryomodules for both medium and high beta elliptical cavities which constitute the high energy section. A medium beta technical demonstrator will be built in a first time. The cryomodules are composed of 4 superconducting cavities cooled at 2K. The cold mass assembly is hanged in an intermediate structure located inside the vacuum vessel. A 50K fixed temperature is implemented by the mean of an aluminium shield. Each cryomodule is connected to the cryogenic distribution line. The vacuum vessel is 6.3m long and has a 1.2m diameter. The poster describes the general design,the solutions implemented, the characteristics of the main components and the mechanical/thermal calculations .

MOP085

Status of the Superconducting Proton Linac (SPL) Cryomodule

vacuum, cryogenics, operation, linac

345

V. Parma, R. Bonomi, O. Capatina, J.K. Chambrillon, E. Montesinos, K.M. Schirm, A. Vande Craen, G. Vandoni, R. van Weelderen
CERN, Geneva, Switzerland
G. Devanz
CEA/IRFU, Gif-sur-Yvette, France
P. Duchesne, P. Duthil, S. Rousselot
IPN, Orsay, France

The Superconducting Proton Linac (SPL) is an R&D effort conducted by CERN in partnership with other international laboratories, aimed at developing key technologies for the construction of a multi-megawatt proton linac based on state-of-the-art SRF technology. Such an accelerator would serve as a driver in new physics facilities for neutrinos and/or radioactive ion beams. Amongst the main objectives of this effort, are the development of 704 MHz bulk niobium β=1 elliptical cavities (operating at 2 K and providing an accelerating field of 25 MV/m) and the test of a string of cavities integrated in a machine-type cryo-module. In an initial phase, only four out of the eight cavities of the SPL cryo-module will be tested in a half- length cryo-module developed for this purpose, which nonetheless preserves the main features of the full size machine. This paper presents the final design of the cryo-module and the status of the construction of the main cryostat parts. Preliminary plans for the assembly and testing of the cryo-module at CERN are presented and discussed.

MOP087

Conceptual Design of a Cryomodule for Compact Crab Cavities for Hi-Lumi LHC

cryomodule, cryogenics, SRF, luminosity

353

S.M. Pattalwar, P.A. McIntosh, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Warrington, Cheshire, United Kingdom
G. Burt
Lancaster University, Lancaster, United Kingdom
O. Capatina
CERN, Geneva, Switzerland
B.D.S. Hall
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
T.J. Jones, N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
T.J. Peterson
Fermilab, Batavia, USA

A prototype Superconducting (RF) cryomodule, comprising multiple compact crab cavities is foreseen to realise a local crab crossing scheme for the “Hi-Lumi LHC”, a project launched by CERN to increase the luminosity performance of LHC. A cryomodule with two cavities will be initially installed and tested on the SPS drive accelerator at CERN to evaluate performance with high-intensity proton beams. A series of boundary conditions influence the design of the cryomodule prototype, arising from; the complexity of the cavity design, the requirement for multiple RF couplers, the close proximity to the second LHC beam pipe and the tight space constraints in the SPS and LHC tunnels. As a result, the design of the helium vessel and the cryomodule has become extremely challenging. This paper assesses some of the critical cryogenic and engineering design requirements and describes an optimised cryomodule solution for the tests with SPS.

MOP089

Design of the ESS Spoke Cryomodule

vacuum, cryomodule, operation, cryogenics

357

D. Reynet, S. Bousson, S. Brault, P. Duchesne, P. Duthil, N. Gandolfo, G. Olry, E. Rampnoux
IPN, Orsay, France

The European Spallation Source (ESS) project brings together 17 European countries to develop the world’s most powerful neutron source feeding multidisplinary researches. The superconducting part of the linear accelerator consists in 59 cryomodules housing different superconducting radiofrequency (SRF) resonators among which 28 paired β=0.5 352.2 MHz SRF niobium double Spoke cavities, held at 2K in a saturated helium bath. A prototype Spoke cryomodule with two cavities equipped with their 300kW RF power couplers is now being designed and will be constructed and tested at full power by the end of 2015 for the validation of all chosen technical solutions. It integrates all the interfaces necessary to be operational within a linac machine. Its assembly requires dedicated tooling and procedures in and out of a clean room. The design takes into account an industrial approach for the management of the fabrication costs. This prototype will have to guarantee an accelerating field of 8MV/m while optimizing the energy consumption and will aim at assessing the maintenance operations issues. We propose to present the design of this cryomodule and its related tooling.

MOP092

Computation of Wakefields and HOM Port Signals by Means of Reduced Order Models

wakefield, impedance, HOM, operation

364

J. Heller, T. Flisgen, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany

The investigation of wakefields is an important task in the design and operation of particle accelerators. Computer simulations are a reliable tool to extend the understanding of these effects. This contribution presents an application example of a new method to compute wakefields as well as parameters derived from those fields, such as higher order mode (HOM) port signals. The method is based on a reduced order model of the structure created by as set of 3D eigenmodes, a set of 2D waveguide port modes and the current density of the beam. In contrast to other wakefield computations, the proposed method operates directly on the reduced order model. Therefore, once having established this model, the beam-excited fields can be determined quickly for different beam parameters. As a matter of fact, only a small part of the reduced system has to be recomputed for every sweep point. From these advantages it is obvious, that the method is highly compatible for beam parameter studies. In a proof of principal the effectiveness of the method compared to established methods of wakefield computations in terms of computational time and accuracy is shown.

MOP093

Geometric Optics of Wake Fields of Very Short Bunches in Superconducting Cavities

wakefield, HOM, FEL, superconducting-cavity

367

A. Novokhatski
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE-AC02-76SF00515
We study the wake potentials of very short bunches in a quasi periodic structure of superconducting cavities. We analyze the pattern of the electric force lines and the shape of a cavity. The behavior of electric force lines reflects irregularities of the shape structure of a cavity. Simulations were carried for different kind of cavities, including JLAB 7 cell cavity with application to future light sources.

TUIOA01

Influence of the Couldown at the Transition Temperature on the SRF Cavity Quality Factor

shielding, niobium, SRF, experiment

370

O. Kugeler, J. Knobloch, J.M. Vogt
HZB, Berlin, Germany

The quality factor Q0 that can be obtained in a superconducting cavity is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We believe that cooling conditions have an additional impact, as they appear to influence the amount of trapped flux and hence the residual resistance. We constructed a test stand using a niobium rod shorted out by a titanium rod to mimic a cavity in its helium tank to study flux trapping. Here we can precisely control the temperature and measure the dynamics of flux trapping at the superconducting phase transition. We learned that magnetic flux can be generated when a temperature gradient exists along the rod and when the niobium transitions into the superconducting state it subsequently remains trapped. Furthermore, it was shown that the cooling rate during isothermal cooldown through the transition temperature can influence the amount of externally applied flux which remains trapped. The acquired knowledge may be used to modify the cooldown procedure of SRF cavities leading to a reduced level of trapped flux and hence operation closer to the BCS limit.

Slides TUIOA01 [1.276 MB]

TUIOA02

High Q0 Research: The Dynamics of Flux Trapping in Superconducting Niobium

niobium, experiment, simulation, shielding

374

J.M. Vogt
HZB, Berlin, Germany
J. Knobloch, O. Kugeler
BESSY GmbH, Berlin, Germany

The quality factor Q0 that can be obtained in a superconducting cavity is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We believe that cooling conditions have an additional impact, as they appear to influence the amount of trapped flux and hence the residual resistance. We have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and measure the dynamics of flux trapping at the superconducting phase transition. We learned that magnetic flux can be generated when a temperature gradient exists along the rod as the niobium transitions to the superconducting state, which subsequently remains trapped. It was also shown that the cooling rate can influence the amount of externally applied flux which is trapped. Furthermore, we also were able to demonstrate that flux lines become mobile if the superconductor is warmed close to below Tc. The acquired knowledge may be used to modify the cooldown procedure of SRF cavities leading to a reduced level of trapped flux and hence operation closer to the BCS limit.

Slides TUIOA02 [5.774 MB]

TUIOA05

New Insights Into Quench Caused by Surface Pits in SRF Cavities

niobium, laser, SRF, feedback

378

Y. Xie, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by NSF Career award PHY-0841213 and the Alfred P. Sloan Foundation.
Surface defects such as pits have been identified as some of the main sources of limitations of srf cavity performance. A single cell cavity with 30 artificial pits in the high magnetic field region was made to gain new insight in how pits limit the cavity performance*. The test of the pit cavity showed clear evidence that the edges of two of the largest radius pits transitioned into the normal conducting state at field just below the quench field of the cavity, and that the quench was indeed induced by these two pits. The pit geometrical information measured by laser confocal microscopy combined with a numerical finite element ring-type defect model will be compared with temperature mapping results. Insights about quench and non-linear rf resistances will be presented.
*Y. Xie, PhD thesis, Cornell University, 2013

Slides TUIOA05 [3.101 MB]

TUIOA06

Research on Field Emission and Dark Current in ILC Cavities

electron, simulation, photon, detector

392

Y.M. Li, K.X. Liu
PKU, Beijing, People's Republic of China
R.L. Geng, A.D. Palczewski
JLAB, Newport News, Virginia, USA

Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Field emission and dark current are issues of concern for SRF cavity performance and SRF linac operation. Complete understanding and reliable control of the issue are still needed, especially in full-scale multi-cell cavities. Our work aims at developing a generic procedure for finding an active field emitter in a multi-cell cavity and benchmarking the procedure through cavity vertical test. Our ultimate goal is to provide feedback to cavity preparation and cavity string assembly in order to reduce or eliminate filed emission in SRF cavities. Systematic analysis of behaviors of field emitted electrons is obtained by ACE3P developed by SLAC. Experimental benchmark of the procedure was carried out in a 9-cell cavity vertical test at JLab. The energy spectrum of Bremsstrahlung X-rays is measured using a NaI(Tl) detector. The end-point energy in the X-ray energy spectrum is taken as the highest kinetic electron energy to predict longitudinal position of the active field emitter. Angular location of the field emitter is determined by an array of silicon diodes around irises of the cavity. High-resolution optical inspection was conducted at the predicted field emitter location.

Slides TUIOA06 [4.565 MB]

TUIOB01

R&D Progress in SRF Surface Preparation With Centrifugal Barrel Polishing (CBP) for both Nb and Cu

SRF, niobium, synchrotron, experiment

398

A.D. Palczewski
JLAB, Newport News, Virginia, USA
B. Bullock
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
C.A. Cooper
Fermilab, Batavia, USA
S.C. Joshi
RRCAT, Indore (M.P.), India
A. Navitski
DESY, Hamburg, Germany
A.A. Rossi
INFN/LNL, Legnaro (PD), Italy

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Centrifugal Barrel polishing (CBP) is becoming a common R&D tool for SRF cavity preparation around the word. During the CBP process a cylindrically symmetric SRF cavity is filled with relatively cheap and environmentally friendly abrasive and sealed. The cavity is then spun around the cylindrical axis at high speeds uniformly conditioning the inner surface. This uniformity is especially relevant for SRF application because many times a single manufacturing defects limits cavity’s performance well below it’s theoretical limit. In addition CBP has created surfaces with roughness’s on the order of 10’s of nm which create a unique surface for wet chemistry or thin film deposition. CBP is now being utilized at Jefferson Laboratory, Fermi Laboratory and Cornell University in the US, Ko Enerugi Kasokuki Kenkyu Kiku in Japan, Deutsches Elektronen-Synchrotron in Germany, Laboratori Nazionali di Legnaro in Italy, and Raja Ramanna Centre for Advanced Technology in India. In this talk we will present current CBP research from each lab including polishing recipes, equipment, post CBP chemistry/heat treatment, and subsequent cryogenic cavity tests on niobium as well as copper cavities.

Slides TUIOB01 [2.204 MB]

TUIOC02

Bipolar EP: Electropolishing without Fluorine in a Water Based Electrolyte

niobium, SRF, experiment, controls

404

A.M. Rowe, A. Grassellino
Fermilab, Batavia, USA
T.D. Hall, M.E. Inman, S.T. Snyder, E.J. Taylor
Faraday Technology, Inc., Clayton, USA

Funding: Operated by Fermi Research Alliance, LLC under contract No. De-AC02-07CH11359 with the United States Department of Energy
For more than thirty years, preparing superconducting RF cavities for high performance has required the use of dangerous and ecologically damaging chemicals. Reducing the personnel and environmental risks associated with using these chemicals is a priority at Fermilab. Therefore, Fermilab pursued a project to adapt a non-hazardous and relatively benign bipolar electropolishing technique to SRF cavities that Faraday Technology, Inc. developed. Faraday initially developed this electropolishing technique to polish metal alloys used in automotive and semiconductor components as well as medical devices and implants. By modifying the cathodic/anodic interaction via a pulse forward/pulse reverse technique, Fermilab and Faraday Technology demonstrate the capability to polish 1.3 GHz single-cell cavities utilizing an aqueous 10% sulfuric acid electrolyte. We present the development of bipolar EP for single-cell 1.3 GHz cavities and show the results from vertical tests achieving gradients greater than 40 MV/m.

Slides TUIOC02 [1.251 MB]

TUIOC03

Fluorine Free Ionic Liquid Electropolishing of Niobium Cavities

niobium, cathode, experiment, superconductivity

410

V.B. Pastushenko, O.V. Malkova, V. Palmieri, A.A. Rossi, F. Stivanello, G. Yu
INFN/LNL, Legnaro (PD), Italy
G. Yu
CIAE, Beijing, People's Republic of China

Ionic liquids are an emerging breakthrough in green chemistry since the years 2000. In 2006, INFN-LNL was the first to apply a mixture of Choline Chloride and Urea to Niobium electropolishing. It was found that mirror like surfaces could be obtained at temperature higher than 120°C, with high throwing power. Subsequently the process was successfully applied to the electropolishing of a 6 GHz monocell cavity with the addition of sulphamic acid. In this work, we will report an intense investigation of the possible variants of the original recipe. We studied the influence on Niobium surface roughness of several parameters such as: other sulphamic, ammonium and carboxylic containing additives different than sulfamic acid, the possible substitution of Urea with ethylene glycol and malic acid, the current regime; the electrolyte temperature and the cathode shape, rotating horizontal electropolishing versus vertical electropolishing. Due to the cavity hollow cylindrical shape, the electrolyte temperature appeared to be the most crucial parameters among those above mentioned for a uniform dissolution of niobium.

Slides TUIOC03 [14.464 MB]

TUIOC04

Analysis of Post-Wet-Chemistry Heat Treatment Effects on Nb SRF Surface Resistance

SRF, niobium, superconductivity, site

414

P. Dhakal, G. Ciovati, P. Kneisel, G.R. Myneni
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Most of the current R&D in SRF is focused on ways to reduce the construction and operating cost of SRF-based accelerators as well as on the development of new or improved cavity processing techniques. The increase in quality factors is the result of the reduction of the surface resistance of the materials. A recent test [*] on a 1.5 GHz single cell cavity made from ingot niobium of medium purity and heat treated at 1400 C in a ultra-high vacuum induction furnace resulted in a residual resistance of ~ 1nanoohm and a quality factor increasing with field up to ~ 5×10¹⁰ at a peak magnetic field of 90 mT. In this contribution, we present some results on the investigation of the origin of the extended Q0-increase, obtained by multiple HF rinses, oxypolishing and heat treatment of “all Nb” cavities.
[*] P. Dhakal et al., Phys. Rev. ST Accel. Beams 16, 042001 (2013).

Slides TUIOC04 [4.838 MB]

TUIOC05

Purification of 6 GHz Cavities by Induction Heating

induction, vacuum, niobium, SRF

419

A.A. Rossi, A. Battistello, M. Checchin, V. Palmieri, S. Stark, F. Stivanello, R.K. Thakur, G. Yu
INFN/LNL, Legnaro (PD), Italy

We have developed an innovative technique for purification of bulk-Nb 6GHz RF cavities under ultra-high vacuum (UHV) system. The main advantages of 6 GHz bulk-Nb cavities are saving cost, materials and time to collect statistics of surface treatments and RF test. Cavities are RF tested before and after high temperature treatment under UHV conditions. Induction heating method is used to anneal the cavity at temperatures higher than 2000°C and close to the melting point of Nb for less than a minute while few seconds at maximum temperature. Before RF test and UHV annealing, the surface treatment processes like tumbling, chemical, electro-chemical (such as BCP and EP), ultrasonic cleaning and high pressure rinsing (HPR) have been employed. This kind of Nb 6 GHz cavity purification allow to reduce hydrogen, oxygen and other elemental impurities content, which effects on cavity Q-factor degradation, by a rapid annealing over 2000°C and a subsequent rapid reduction at room temperature.

Slides TUIOC05 [42.171 MB]

TUIOC06

Study on Optimum Electron Beam Welding Condition for Superconducting Accelerating Cavities

niobium, electron, experiment, SRF

424

T. Kubo, Y. Ajima, H. Inoue, T. Saeki, K. Umemori, Y. Watanabe, S. Yamaguchi, M. Yamanaka
KEK, Ibaraki, Japan
T. Nagata
ULVAC, Inc., Tsukuba, Japan

Optimizations of electron beam welding conditions might solve the quench problems and improve the accelerating field of the superconducting radio-frequency cavity. As a first step toward optimum conditions, basic properties of weld beads are studied by using niobium test pieces. Effects of a combination of a beam generator position and a welding direction on geometries of weld bead are shown. Good parameter-regions for electron beam welding, which yield full penetration welds without holes or weld spatters, are surveyed. Microscopic structures, such as pits or bumps due to poor welds, have greater influence on cavity performances, which are also our research objects. We introduce a model of the magnetic field enhancement at pits, where a formula for a magnetic field enhancement factor is given as a function of parameters that express a geometry of pit. Comparisons between calculations and vertical test results are also shown.

Slides TUIOC06 [15.958 MB]

TUP007

Vortex Penetration Field in the Multilayered Coating Model

vacuum, superconductivity, electromagnetic-fields

430

T. Kubo, T. Saeki
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan

A multilayered structure with a single superconductor layer and a single insulator layer deposited on a bulk superconductor is studied. General formulae for the vortex penetration-field of the superconductor layer and the magnetic field on the bulk superconductor which is shielded by the superconductor and insulator layers are derived with a rigorous calculation of the magnetic field attenuation in the multilayered structure. The formulae depend not only on the material and the thickness of the superconductor layer but also on the thickness of the insulator layer. The results can be applied to superconducting accelerating cavities with the multilayered structure. Using the formulae, a combination of the thicknesses of superconductor and insulator layers to enhance the RF breakdown field limits can be found for any given materials. (Submitted on 25 Apr 2013)
T. Kubo, Y. Iwashita and T. Saeki, arXiv:1304.6876 [physics.acc-ph](Submitted on 25 Apr 2013); arXiv:1306.4823 [physics.acc-ph](Proc. of IPAC13); arXiv:1307.0583 [physics.acc-ph](Proc. of SRF2013)

TUP008

Models of the Magnetic Field Enhancement at Pits

SRF, experiment, laser, radio-frequency

433

T. Kubo
KEK, Ibaraki, Japan

A simple model of the magnetic field enhancement at pits on the surface of superconducting accelerating cavity is proposed. The model consists of a two-dimensional pit with a slope angle, depth, width, and radius of round edge. An analytical formula that describes the magnetic field enhancement factor of the model is derived. The formula is given as a function of a slope angle and a ratio of half a width to a round-edge radius. Using the formula, the field at which vortices start to penetrate can be evaluated for a given geometry of pit.
Takayuki Kubo, arXiv:1307.5943 [physics.acc-ph](Submitted on 23 Jul 2013)

TUP009

Magnetic Dependence of the Energy Gap: a Good Model to Fit Q Slope of Low Beta Cavities

superconductivity, experiment, niobium, simulation

438

D. Longuevergne
IPN, Orsay, France

The reasons why the intrinsic quality factor (noted Qo) of a superconducting cavity drops with the accelerating field (noted Eacc) are still not well understood. In an effort to explain this phenomenon, mainly for high beta cavities, many models have been developed in the community but few of them could fit experimental data whatever the material treatment or surface conditioning. In the specific case of low beta cavities made of bulk Niobium (i.e Spiral 2 Quarter Wave Resonator), a model based on a magnetic field dependence of the energy gap has been developed to fit experimental data. The evolutions of the model input parameters depending on the cavity treatment or test conditions are consistent with the changes described in the literature. The model will be described and specific examples will be given.

TUP010

Simulation of Non-linear RF Losses Derived from Characteristic Nb Topography

simulation, niobium, SRF, interface

441

C. Xu, M.J. Kelley
JLAB, Newport News, Virginia, USA
M.J. Kelley, C. Xu
The College of William and Mary, Williamsburg, USA
C.E. Reece
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A simplified model has been developed to simulate non-linear rf losses on Nb surfaces due exclusively to topographical enhancement of surface magnetic fields. If local sharp edges are small enough, where local surface fields exceed Hc, small volumes of material may become normal conducting without thermal runaway leading to quench. These small volumes of normal material yield increases in the effective surface resistance of the Nb. Using topographic data from typical BCP’d and EP’d fine grain niobium, we have simulated field-dependent losses and find that when extrapolated to resulting cavity performance correspond well to characteristic BCP/EP high field Q0 performance differences for fine grain Nb. We will describe the structure of the model, its limitations, and the effects of this type of non-linear loss contribution to SRF cavities.

TUP014

Fast Table Top Niobium Hydride Investigations Using Direct Imaging in a Cryo-Stage

niobium, cryogenics, laser, vacuum

447

F.L. Barkov, A. Grassellino, A. Romanenko
Fermilab, Batavia, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
Performance of niobium SRF cavities can be strongly affected by hydrogen segregation into lossy niobium hydrides as known for "hydrogen Q disease" at higher concentration of dissolved H and may be a reason for the "high field Q slope" at lower concentrations. With the use of optical cryostat and laser confocal microscope we have developed a "table top technique" for direct observation of hydride precipitation, and studied formation, morphology, and time evolution of hydrides after different treatments used for cavities. Our results show that hydrides can form at the niobium surface at 90-180K depending mainly on H concentration and the cooldown rate. A lot of H is absorbed by bulk niobium during mechanical polishing, which leads to the formation of very large (>10 microns) hydrides. Both EP and BCP do not influence H concentration significantly provided that temperature during treatments is kept below 15C. 800C degassing reduces H concentration and precludes large hydride precipitation. 120C baking and mechanical deformation do not change H concentration but affect hydride precipitation through their influence on the number of nucleation centers and H binding defects.

TUP015

Bitter Decoration Studies of Magnetic Flux Penetration Into Cavity Cutouts

SRF, experiment, niobium, radio-frequency

451

F.L. Barkov, A. Grassellino, A. Romanenko
Fermilab, Batavia, USA
L.Y. Vinnikov
ISSP, Chernogolovka, Russia

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Magnetic flux penetration may produce additional losses in superconducting radio frequency cavities. All the existing models for flux penetration are based on the formation of Abrikosov vortices. Using high resolution Bitter decoration technique we have investigated magnetic flux distribution patterns in cavity cutouts at the perpendicular magnetic fields of 10-80 mT. At low fields <20 mT the magnetic field penetrates in the form of flux bundles and not Abrikosov vortices, the situation characteristic of type-I superconductors. With the increase of the magnetic field up to 30 mT "bundles" first merge into a connected structure and then break up into individual Abrikosov vortices at ~60 mT and a well-known intermediate mixed state is observed. Such magnetic field driven transition from type I to type II superconductivity has never been observed before in any existing superconductor. For the case of flat samples we have observed a coexistence of both "bundles" and Abrikosov vortices in one experiment. Our results show that high-purity cavity grade niobium is a "border-line" material and behaves as a type-I superconductor at lower fields and type-II at higher fields.

TUP016

Effects of Processing History on Damage Layer Evolution in Large Grain Nb Cavities

SRF, electron, niobium, radio-frequency

455

D. Kang, T.R. Bieler
Michigan State University, East Lansing, Michigan, USA
C. Compton
FRIB, East Lansing, Michigan, USA

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics, through Grant No. DE-S0004222.
Previous cavity tests identified a strong dependence of achievable accelerating gradients on the amount of material removed from the surface. Samples extracted from the iris and the equator of a half cell fabricated by Jefferson Lab using large grain Nb were examined to identify underlying mechanisms. Electron backscattered diffraction (EBSD) was used to measure the crystal orientations on the cross sections of the samples. Results demonstrated the presence of a surface damage layer, which contained higher dislocation content than the bulk due to the deep drawing process. The depth of the damage layer depends on crystal orientations, and damage to the iris is more severe than at the equator. From the EBSD data, the damage depth was estimated to be about 100 microns. The samples were then heat treated at 800°C and 1000°C, and the same areas were examined again for the effects of heat treatment on the healing of the damage layer. While the damage layer accounts for some of the performance gain from chemical surface removal, the depth of the damage layer in polycrystalline cavities remains an open question.

TUP017

Study of Slip and Dislocations in High Purity Single Crystal Nb for Accelerator Cavities

niobium, SRF, radio-frequency, factory

461

D. Kang, D.C. Baars, T.R. Bieler
Michigan State University, East Lansing, Michigan, USA
C. Compton
FRIB, East Lansing, Michigan, USA

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics, through Grant No. DE-S0004222.
SRF Cavities can be formed by deep drawing slices from Nb ingots with large grains. Crystal orientation dependent slip system activities affect the shape change of ingot slices during deep drawing, and form a dislocation substructure that affects subsequent recrystallization and ultimately, cavity performance. Two groups of single crystal tensile specimens with different orientations were extracted from a large grain ingot slice. The first group was deformed monotonically to 40% engineering strain. Analysis revealed that slip was preferred on {112} planes. The second group was heat treated at 800°C for two hours, and then deformed incrementally to 40% engineering strain using an in situ tensile stage. Crystal orientations and surface images were recorded at each increment of deformation. Results indicate that the heat treated group had lower yield strengths, and the details of slip activity differed in the annealed samples. Active slip systems were investigated and compared to the first group. Direct observations of dislocations were performed in selected specimens using electron channeling contrast imaging, to determine how slip affects the dislocation substructure.

TUP019

Probing Hot Spot and Cold Spot of SRF Cavities with Tunneling and Raman Spectroscopies

superconductivity, SRF, laser, electron

466

C. Cao
Illinois Institute of Technology, Chicago, IL, USA
G. Ciovati
JLAB, Newport News, Virginia, USA
L.D. Cooley, A. Grassellino
Fermilab, Batavia, USA
N. Groll, Th. Proslier
ANL, Argonne, USA
J. Zasadzinski
IIT, Chicago, Illinois, USA

Point contact tunneling and Raman spectroscopies are presented on high purity Nb samples, including pieces from hot and col spot regions of tested SRF cavities and Nb coupons subject to similar treatment. High quality tunneling spectra were observed on cold spots, revealing the bulk Nb gap, indicating minimal surface contamination. Hot spots exhibit high smearing suggestive of pair breaking along with generally lower superconducting gap. In addition, pronounced zero bias conductance peaks were frequently observed indicative of spin-flip tunneling and thus magnetic impurities in the oxide layer. Optical microscopy reveals higher density of surface blemishes on hot spots. Raman spectra inside those blemishes show clear difference from surrounding areas, exhibiting enhanced intensity peaks identified as either amorphous carbon, hydrocarbons or the ordered NbC phase. The presence of surface NbC is consistent with TEM studies, and these inclusions exhibit enhanced second order phonon response. Such regions with high concentrations of impurities are expected to suppress the local superconductivity and may explain the formation of hot spots.

TUP022

Study of AC/RF Properties of SRF Ingot Niobium

SRF, niobium, radio-frequency, superconductivity

469

P. Dhakal, G. Ciovati, G.R. Myneni
JLAB, Newport News, Virginia, USA
V.M. Genkin, M.I. Tsindlekht
The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In an attempt to correlate the SRF performance of niobium cavities with the superconducting properties, we present the results of the magnetization and ac susceptibility of the niobium used in the superconducting radiofrequency cavity fabrications which were subjected to buffer chemical polishing surface and high temperature heat treatments, typically applied to the SRF cavities fabrications. The analysis of the results show the different surface and bulk ac conductivity for the samples subjected to BCP and HT. Furthermore, the RF surface impedance is measured on the sample using the TE011 microwave cavity for a comparison to the low frequency measurements.

TUP026

Performance of a FNAL Nitrogen Treated Superconducting Niobium Cavity at Cornell

niobium, SRF, linac, superconductivity

475

D. Gonnella, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A. Grassellino
Fermilab, Batavia, USA

Funding: NSF
In many tests of superconducting cavities, the performance of the cavity in the medium field region will be limited by medium field Q slope. For projects such as the proposed Cornell Energy Recovery Linac, high Q operation at medium fields is necessary to meet specifications for efficient CW cavity operation. A single cell cavity was prepared by Fermilab by electropolishing it and baking it at 1000°C with 1x10^-2 Torr of Nitrogen, and subsequently tested at Cornell. The cavity displayed an increase in Q at medium fields between 5 and 20 MV/m at 2.0 K, opposite of the usual medium field Q slope. The material properties of this cavity were studied and correlated with performance. This analysis helps to better understand how to overcome medium field Q slope and improve cavity performance in future CW SRF machines such as the Cornell ERL.

TUP027

High Q0 Studies at Cornell

niobium, SRF, factory, linac

478

D. Gonnella, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF
The construction and preparation of superconducting RF cavities with very high quality factors is very advantageous for future particle accelerators operating in CW mode. Until recently, the highest quality factors measured in SRF cavities were on the order of 10¹¹. A Cornell ERL single-center-cell cavity was prepared with BCP and a five day heat treatment at 1000°C. Following this treatment, the cavity was tested and achieved a record high intrinsic quality factor of 2.9·10¹¹ at 1.4 K, corresponding to a very small residual resistance of (0.35±0.10) nOhm. This cavity was then given a series of BCP’s of 5, 75, and 200 μm and retested. Material properties were extracted from the data hinting at a very low mean free path of the niobium. In this paper we discuss the unusual material properties of the surface layer of the cavity and their implication for the RF performance of the cavity.

TUP028

Investigation of Spatial Variation of the Surface Resistance of a Superconducting RF Cavity

resonance, superconducting-RF, SRF, superconductivity

483

D. Gonnella, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
R.E. French
Corning Community College, Corning, USA

Funding: NSF
Cornell has recently completed a single cell temperature mapping system with a resolution of a few tenths of a millikelvin, corresponding to a surface resistance resolution of 1 nOhm. A superconducting RF cavity was tested using temperature mapping and the surface resistance was extracted from the temperature mapping data as function of position on the cavity surface. The surface resistance was profiled across the surface of the cavity between 5 and 35 MV/m and at different temperatures between 1.6 and 2.1 K. From BCS fitting of the local surface resistance, the spatial variation and the field dependence of the mean free path, energy gap, and residual resistance was found. These studies give interesting new insight into the degree of variation of the properties of the superconductor over the surface of the cavity.

TUP029

Heat Treatment of SRF Cavities in a Low-Pressure Atmosphere

vacuum, SRF, niobium, resonance

487

D. Gonnella, F. Furuta, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF
Recent results from FNAL on baking superconducting RF cavities at high temperatures in a low-pressure atmosphere of a few mTorr indicate that such treatments can increase the medium field quality factor. In this paper we report on studies from Cornell, giving new insight into the mechanism behind this effect.

TUP033

Magnetic Property Improvement of Niobium Doped with Rare Earth Elements

niobium, experiment, SRF, electron

490

F.S. He, F. He, F. Jiao, X.Y. Lu, K. Zhao
PKU, Beijing, People's Republic of China
L. Chen
NNIEC, Shizuishan City, Ningxia, People's Republic of China
T.C. Jiang
IMP, Lanzhou, People's Republic of China
Y. You, H.Y. Zhao
Ningxia Orient Tantalum Industry Co., Ltd., Dawukou District, Shizuishan city, People's Republic of China

A new idea of modifying the raw niobium was proposed by PKU in 2010, by introducing rare earth elements of Sc and Y into Nb ingot during smelting process. Test results on small samples were very promising*: the Tc was same as Nb, while the Hc1 and Hc2 were increased by 500-700 Oe and up to 4000 Oe, respectively. Recently one Nb ingot doped with Sc was successfully smelted under the collaboration of PKU and OSTEC at Ningxia, and two TESLA-type half cells were fabricated out of the new material by deep drawing. The Hc1 measured from the drop-off of the blanks were consistently high. The RRR was 127, while the mechanical properties met the ILC requirement. One single cell cavity is being fabricated, and vertical test is planned to study the SRF properties of the new material. There is a good chance that the quenching could be pushed to a higher gradient. Another innovative idea of doping only the surface layer of bulk Nb by ion implantation in the pelletron at PKU is also being investigated, in order to improve the SRF performance of the surface layer while maintaining the high thermal conductivity of bulk Nb. Some initial testing results of the new method will be reported as well.
* TTC2012 at JLab:
https://www.jlab.org/indico/getFile.py/access?contribId=78&sessionId=8&resId=0&materialId=slides&confId=24

TUP035

Neutron Activation Analysis as a Foreign Intrusion Cavity DetectionTool

neutron, detector, radioactivity, background

495

C. Maiano, P. Michelato
INFN/LASA, Segrate (MI), Italy
M. Clemenza
Universita Milano Bicocca, MILANO, Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

Neutron Activation Analysis (NAA) is one of the currently available techniques used to determine contaminants in Nb superconducting cavities, allowing a non-destructive determination of foreign materials, provided they have radioactive isotopes with a sufficiently long half-life. We present the NAA technique application with the goal of contaminants determination, identification and localization for the European XFEL 3rd harmonic cavities (3.9 GHz). Irradiation and analysis has been performed in collaboration with the LENA nuclear reactor (Pavia, Italy) and the University of Milano Bicocca. The main difference respect to the measurements performed in the past is the goal to apply of the NNA directly to entire cavities and not to material samples. Currently nine samples were exposed to thermal and fast neutron flux and the resulting activity was measured with HPGe detectors.

TUP043

Nanostructural TEM/STEM Studies of Hot and Cold Spots in SRF Cavities

niobium, electron, SRF, vacuum

504

Y. Trenikhina, J. Zasadzinski
IIT, Chicago, USA
A. Romanenko
Fermilab, Batavia, USA

Direct TEM/STEM imaging and spectroscopic chemical characterization by EELS/EDS of the surface of the SRF cavity cutouts before and after the treatments (e.g. in situ mild vacuum bake and rinsing with hydrofluoric acid) down to subnanometer scale is implemented to correspond the changes in niobium surface to the SRF performance of the cavities. We also report current results of the direct search, using cryogenic TEM stage, for suggested phase transformations in the niobium-hydrogen system* on “hot” and “cold” spot cavity cutouts, which may help clarifying the mechanism of the high field Q slope and its empirical cure.
*A. Romanenko, F. Barkov, L. D. Cooley, A. Grassellino, Supercond. Sci. Technol. 26 (2013) 035003.

TUP044

Surface Processing Facilities for Spoke Cavities at IHEP

linac, recirculation, superconductivity, LLRF

508

J.P. Dai, H. Li, L.H. Li, Q.Y. Wang, J. Zhang
IHEP, Beijing, People's Republic of China
P. Sha
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

Funding: Work supported by the "Strategic Priority Research Program" of CAS, under Grant No. XDA03020600
The China ADS injector I program is building a CW 10MeV Superconducting proton linac at IHEP. To develop the superconducting spoke-type cavities incorporated in this linac, a set of new surface processing facilities were built and successfully used to treat the Spoke012 prototype cavities. In this paper, we present the design, fabrication and operation of these facilities, including BCP, HPR and UPW, etc.

TUP046

Vertical Electropolishing of SRF Cavities and its Parameters Investigation

cathode, superconductivity, SRF, experiment

514

F. Eozénou, F. Ballester, Y. Boudigou, P. Carbonnier, J.-P. Charrier, Y. Gasser, D. Roudier, C. Servouin
CEA/DSM/IRFU, France
K. Muller
Grenoble-INP Phelma, Grenoble, France

Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP7 program (EuCARD, Contract No. 227579),and the support of the ‘‘Conseil General de l’Essonne’’(ASTRE)
An advanced set-up for vertical electropolishing (VEP) of SRF niobium elliptical cavities is operating at CEA Saclay*. Cavities are VEP’ed with circulating standard HF-H2SO4 electrolyte. Parameters such as voltage, cathode shape, acid flow and temperature were investigated. Low-voltage (<7V), high acid flow (25L/min) and low acid temperature (20°C) are considered as promising parameters. Such recipe was tested on single-cell and 9-cell ILC cavities with nice surface finishing. After 60 μm VEP on a HEP'ed single-cell, the cavity show similar performance at 1.6K compared to previous Horizontal EP: (Eacc > 41MV/m) limited by quench. Another cavity reaches 36MV/m after 300μm removal by VEP in spite of a pitted surface due to initial VEP treatment at higher temperature (> 30°C). The baking effect after HEP/VEP is similar. An asymmetric niobium removal is observed with faster polishing in the upper cell. Nice surface finishing as well as standard Q0 value are obtained at low/medium field on 9Cell but achieved performance is limited by Field Emission.
*F. Eozenou et al., PRST-AB, 15, 083501 (2012)

TUP047

Niobium Cavity Electropolishing Modelling and Optimisation

cathode, SRF, simulation, niobium

518

L.M.A. Ferreira, S. Calatroni, S. Forel
CERN, Geneva, Switzerland
J.A. Shirra
Loughborough University, Leicestershre, United Kingdom

It’s widely accepted that electropolishing is the most suitable surface finishing process to achieve high performance bulk Nb accelerating cavities. At CERN, as part of the R&D studies for the 704 MHz high-beta SPL cavities, a new vertical electropolishing facility has been assembled and a study is on-going for the modelling of electropolishing on cavities with COMSOL software. In a first phase, the electrochemical parameters were taken into account for a fixed process temperature and flow rate, and are presented in this poster as well as the results obtained on a real SPL single cell cavity. The procedure to acquire the data used as input for the simulation is presented. The modelling procedure adopted to optimise the cathode geometry, aimed at a uniform current density distribution in the cavity cell for the minimum working potential and total current is explained. Some preliminary results on fluid dynamics and Joule effect are also briefly described.

TUP048

Preparations and VT Results of ERL7-cell at Cornell

cryomodule, vacuum, target, radiation

521

F. Furuta, B. Bullock, R.G. Eichhorn, B. Elmore, A. Ganshin, G.M. Ge, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

We have fabricated 7 ERL 7-cell cavities for Cornell ERL project. 4 nu-stiffened and 3-stiffened cavities have been fabricated in house so far. Specification values of our 7-cell is 16.2MV/m with Qo of 2.0·10¹⁰ at 1.8K. In this report, we will describe our surface treatments recipe which is based on BCP and the results of vertical tests of these 7-cell cavities.

TUP049

Cornell VEP Update, VT Results and R&D on Nb Coupon

cathode, SRF, status

524

F. Furuta, B. Elmore, G.H. Hoffstaetter, D.K. Krebs, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell's SRF group have been led development of Vertical Electro-Polishing(VEP) on SRF Nb Cavity. We have done many VEP on singel-/multi-cell cavities. We also have started VEP'ed Nb coupon surface analysis based on surface roughness measurement. In this report, we will describe our status of VEP R&D, the results of VEP'ed cavity vertical testing, and fundamental study on VEP using Nb coupons.

TUP051

Horizontal High Pressure Water Rinsing for Performance Recovery

cryomodule, vacuum, operation, factory

527

Y. Morita, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, M. Nishiwaki
KEK, Ibaraki, Japan

Eight superconducting accelerating cavities were operated for more than ten years at the KEKB machine. Those cavities are also used at SuperKEKB. During the KEKB operation, Q values of some cavities were degraded. Cause of the degradation was contamination by air dusts at a repair of vacuum seals or a gasket replacement of input couplers. So far, those degradations are acceptable for the SuperKEKB operation, however, further degradation will make the operation unstable and, in the worst case, make it impossible. High pressure rinsing (HPR) is an effective method to clean the cavity surface. In order to apply HPR, however, the cavity has to be disassembled from a cryomodule. The disassembly takes time and costs. Furthermore, re-sealed vacuum flanges bring the risk of vacuum leakage again. Therefore we have developed a horizontal HPR. This method applies a high pressure water jet that is inserted horizontally into the cavity in the cryomodule. The wasted water is extracted with an aspirator. This method does not require the disassembly. We applied the horizontal HPR to our degraded cavity. Its RF performance has been successfully recovered.

TUP052

Study on Vertical Electro-Polishing by Cathode With Variable-Geometry Wings

experiment, cathode, scattering, niobium

530

Y.I. Ida, K.N. Nii
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan
K. Ishimi, Y.B. Iwabuchi
MGI, Chiba, Japan

We have been studying on Vertical Electro-Polishing (VEP) of Nb superconducting accelerator cavity for about one year with a view to the mass-production and cost-reduction of Electro-Polishing (EP) process. Marui Galvanizing Co. Ltd. has been in the EP business of various metals for long time and we have matured experience on EP processes. With being based on the experience, we thought that uniform electric-current on the surface of cavity and effective flow of electrolyte in the cavity are important factors. Moreover, we thought the most important effect is given if the cathode and the cavity surface (anode) are kept in a constant distance. Following these considerations, we invented VEP process by a cathode with variable-geometry wings. Using this cathode, we performed several experiments of VEP Nb single-cell cavities as well as fluid circulation test by plastic 9-cell mock-up. In this article, we will report this unique VEP process, which might be applicable to the mass-production process of International Linear Collider (ILC).

TUP053

Estimation of Small Geometry Deviation for TESLA-Shape Cavities Due to Inner Surface Polishing

superconductivity, coupling, factory, data-analysis

537

A.A. Sulimov, G. Kreps, J.K. Sekutowicz
DESY, Hamburg, Germany

Two well know polishing methods are used for the inner surface cleaning of superconducting TESLA-shape cavities: electro-polishing (EP) or buffered chemical polishing (BCP). The amount of removed material is relatively small and varies from 10 till 140 um. The cavity after polishing is closed to prevent the scratches or dust appearing on its inner surface. The estimation of the removed material amount is possible by different criteria, for example by comparison of weight before and after cleaning, or by the time - cleaning procedure duration. Both calculations could give us only approximate average value of the removed material amount. We describe the method for estimation of small geometry deviation basing on RF frequency measurements, which allows calculating the different influence of surface treatment on the iris and equator areas.

Poster TUP053 [0.785 MB]

TUP054

Electropolishing of Niobium SRF Cavities in Low Viscosity Aqueous Electrolytes Without Hydrofluoric Acid

niobium, SRF, experiment, controls

540

E.J. Taylor, T.D. Hall, M.E. Inman, S.T. Snyder
Faraday Technology, Inc., Clayton, USA
A.M. Rowe
Fermilab, Batavia, USA

Funding: U.S. DOE Purchase order No. 594128
Electropolishing of niobium materials and cavities is conventionally conducted in high viscosity electrolytes consisting of concentrated sulfuric and hydrofluoric acid. The use of these dangerous and ecologically damaging chemicals requires careful attention to safety protocol to avoid harmful worker exposure and environmental damage. In this poster we present an approach based on bipolar voltage fields enabling the use of low viscosity water based electrolytes without hydrofluoric acid for electropolishing of niobium materials. The subtleties of the bipolar electropolishing process vis-a-vis conventional electropolishing will be presented.

TUP055

Electropolishing of the ANL Deflecting Cavity for the APS Upgrade

niobium, SRF, background, coupling

544

Y. Yang, J.D. Fuerst, J.P. Holzbauer, J.A. Kaluzny, A. Nassiri, G. Wu
ANL, Argonne, USA
A.C. Crawford
Fermilab, Batavia, USA
P. Dhakal, J.D. Mammosser, H. Wang
JLAB, Newport News, Virginia, USA
Y. Yang
TUB, Beijing, People's Republic of China

Studies on the application of electropolishing (EP) of the ANL superconducting deflecting cavity have shown promising results. This cavity geometry is a squashed single-cell cavity with Y-end group waveguide as well as on-cell LOM damper. The cavity works at TM110-like deflecting mode, in which the iris between the cavity cell and the Y-end group is the highest magnetic field region. Before EP, the cavity had been chemically etched (BCP) several times. Forty-um EP processing was performed on one Mark II prototype deflecting cavity at Fermilab. No mild baking was performed before the cavity vertical test. The test showed that the low-field Q had improved from 2·10⁹ to 3·10⁹ and the high-field Q-slope had been successfully removed. The quench limit was slightly improved from 10⁶ mT to 113 mT. Fast T-mapping had detected a significant decrease of local temperature rise in the cavity iris. Optical inspection before EP found a lot of grooves around the iris, which might be related to the gas bubbles generated during BCP. This suggests that horizontal EP is a promising processing technique to remove the high-field Q-slope and improve the deflecting cavity performance.

TUP056

Industrialization of European XFEL Preparation Cycle “BCP Flash” at Ettore Zanon Company

controls, vacuum, acceleration, pick-up

547

A. Matheisen, N. Krupka, M. Schalwat, A. Schmidt, W. Singer, N. Steinhau Kühl, B. van der Horst
DESY, Hamburg, Germany
G. Corniani
Ettore Zanon S.p.A., Schio, Italy
P. Michelato, L. Monaco
INFN/LASA, Segrate (MI), Italy

In the Specification for XFEL Cavity preparation (R1) two different preparation sequences are presented. Ettore Zanon Company as one of the two companies contracted for XFEL cavity production and preparation has chosen the so called BCP flash cycle. To fulfill the requested work flow and quality of infrastructure and processes, the company set up a complete new infrastructure in refurbished fabrication halls. The layout of the facility, set up of work flow of preparation and test results of resonators processed by E.Zanon in their infrastructure will be reported.
(R1) Series Surface and acceptance test preparation of superconducting cavities for the European Xfel (XFEL/A - D) JUNE 30, 2009

TUP057

Plasma Processing R&D for the SNS Superconducting Linac RF Cavities

plasma, linac, cryomodule, niobium

551

M. Doleans, W. Blokland, M.T. Crofford, D.L. Douglas, M.P. Howell, S.-H. Kim, P.V. Tyagi
ORNL, Oak Ridge, Tennessee, USA
R. Afanador, J.A. Ball, B. DeGraff, B.S. Hannah, S.W. Lee, C.J. McMahan, J. Saunders
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE
The Spallation Neutron Source routinely operates with a proton beam power of 1 MW on its production target. A plan to reach the design 1.4 MW within a few years is in place* and relies on increasing the ion beam current, pulse length and beam energy in the linac. The increase in beam energy from the present 930 MeV to 1 GeV will require an increase of approximately 15% in the accelerating gradient of the superconducting linac high-beta cryomodules. In-situ plasma processing was identified as a promising technique** to reduce electron activity in the SNS superconducting cavities and increase their accelerating gradient. R&D on plasma processing aims at deploying the new in-situ technique in the linac tunnel by 2016. Overall plan and current status of the plasma processing R&D will be presented.
* NScD Five year plan 2012-2016, SNS-NSCD-EXE-PN-0001, R00, ORNL
** S-H Kim et al., “R&D Status for In-Situ Plasma Surface Cleaning of SRF Cavities at Spallation Neutron Source”, PAC 2011 Proceedings

TUP058

Recent Findings on Nitrogen Treated Niobium

niobium, SRF, vacuum, solenoid

558

R.G. Eichhorn, A. Ganshin, A. Holmes, J.J. Kaufman, S.R. Markham, S. Posen, E.N. Smith
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Recent findings on Nitrogen treated Niobiums Based on recent findings at Fermilab, Cornell investigated the role of Nitrogen being present during the cavity hydrogen degassing process. We treated several samples at different temperatures being exposed to nitrogen between 10 minutes and 3 hours at pressures around 15 mbar as well as single cell cavities. This contribution will summarize our findings from surface analysis, Tc measurements and cavity Qs, addressing the question, if such a process can form Niobium-Nitride.

TUP059

TM-Furnace Qualification at Cornell

vacuum, SRF, cryomodule

561

F. Furuta, B. Bullock, R.G. Eichhorn, A. Ganshin, G.M. Ge, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell's SRF group had new vacuum furnace for hydrogen degassing of SRF Nb cavity. Systematic study and testing have been done to qualify this new furnace. We will report the results of those qualification tests include cavity bake and vertical testing.

TUP060

Acid Free Extended Mechanical Polishing R&D

niobium, SRF, electron, radio-frequency

564

C.A. Cooper, A.C. Crawford, C.M. Ginsburg, A. Grassellino, R.D. Kephart, O.S. Melnychuk, A. Romanenko, A.M. Rowe, D.A. Sergatskov
Fermilab, Batavia, USA

We report the progress in the development of a centrifugal barrel polishing recipe which can lead to standard cavity performance without the need of any chemical treatments. Q ~ 10¹⁰ at 20 MV/m and gradients above 35 MV/m have already been demonstrated for cavities whose preparation sequence was CBP, degassing and no subsequent chemical treatments. Results of studies on the effect of different CBP media on RF performance will be reported, including full body T-map showing the distribution of RF losses.

TUP061

Update on Study of Welding Porosity in Nb EBW

neutron, SRF, target, superconducting-cavity

567

Y. Iwashita, Y. Fuwa, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
H. Hayano
KEK, Ibaraki, Japan

Voids have been found in the Nb EBW seams. Since the buried defects cannot be observed by the optical inspections, other techniques have to be applied to study their characteristics such as distributions. X-ray or neutron radiography have been tried for the purpose. The recent results will be presented.

TUP062

Application of In-Vacuum Infrared Pyrometry During Fabrication of European XFEL Niobium Cavities

vacuum, operation, electron, niobium

570

L. Monaco, P. Michelato, D. Sertore
INFN/LASA, Segrate (MI), Italy
V. Battista, G. Corniani, M. Festa
Ettore Zanon S.p.A., Schio, Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

A technique to measure the temperature of Niobium components in vacuum during Electron Beam Welding (EBW) operation is presented and results obtained on the large scale cavity production for the European XFEL are discussed. During the EBW process, the knowledge of the components temperature during the welding operation could help both for the better choice of the welding parameters and for the optimization of the production cycle. In collaboration with the Italian firm Ettore Zanon (EZ), we developed a system able to measure the temperature of Nb components in vacuum during EBW operation using a IR pyrometer placed outside the vacuum chamber through an appropriate vacuum viewport. In the paper the experience of this device during the production of Nb components for the XFEL 1.3 GHz cavity production is discussed.

TUP063

Quench Studies and Preheating Analysis of Seamless Hydroformed Cavities Processed at Jefferson Laboratories

SRF, electron, niobium, site

575

A.D. Palczewski, G.V. Eremeev, R.L. Geng
JLAB, Newport News, Virginia, USA
I. Jelezov
RAS/INR, Moscow, Russia
W. Singer, X. Singer
DESY, Hamburg, Germany

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
One of the alternative manufacturing technologies for SRF cavities is hydroforming from seamless tubes. Although this technology has produced cavities with gradient and Q-values comparable to standard EBW/EP cavities, a few questions remain. One of these questions is whether the quench mechanism in hydroformed cavities is the same as in standard electron beam welded cavities. Towards this effort Jefferson Lab performed quench studies on 4 different seamless hydroformed cavities. These cavities include DESY’s – Z163 and Z164 nine-cell cavities, and Black Laboratories nine-cell and two-cell TESLA shaped cavities, hydroformed at DESY. Initial results from the cavities and quench localization were published in SRF2011*. In this report we will present post JLAB surface retreatment quench studies for each cavity. The data will include OST and T-mapping quench localization as well as quench location preheating analysis comparing them to the observations in standard electron beam welded cavities.
*W. Singer, A. Ermakov, G. Kreps, A. Matheisen, X. Singer, K. Twarowski, I. Zhelezov, P. Kneisel, R. Crooks, Proceedings of SRF2011, TUPO026 2011.

TUP064

Exploration of Material Removal Rate of SRF Elliptical Cavities as a Function of Media Type and Cavity Shape on Niobium and Copper Using Centrifugal Barrel Polishing (CBP)

niobium, SRF, superconductivity, status

579

A.D. Palczewski, G. Ciovati, R.L. Geng, Y.M. Li
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Centrifugal barrel polishing (CBP) for SRF application is becoming more wide spread as the technique for cavity surface preparation. CBP is now being used in some form at SRF laboratories around the world. Before the process can become as mature as wet chemistry like eletro-polishing (EP) and buffered chemical polishing (BCP) there are many questions which remain unanswered. One of these topics includes the uniformity of removal as a function of cavity shape and material type. In this presentation we show CBP removal rates for various media types on 1.3 GHz TESLA and 1.5 GHz CEBAF large grain niobium cavities, 1.3 GHz TESLA fine grain niobium cavity, and 1.3GHz low surface field copper cavity. The data will also include calculated RF frequency shift modeling non-uniform removal as a function of cavity position and comparing them with CBP results.

TUP065

Chemical Structure of Niobium Samples Vacuum Treated in Nitrogen in Parallel With Very High Q0 Cavities

niobium, SRF, lattice, accelerating-gradient

583

Y. Trenikhina
IIT, Chicago, USA
A. Grassellino, A. Romanenko
Fermilab, Batavia, USA

XPS in combination with subsequent material removal via Ar sputtering as well as XRD are used for the surface analysis and bulk phase characterization of nitrogen treated samples processed parallel with SRF cavities. We investigated the surface chemistry of the samples treated with nitrogen in order to understand this treatment effect on SRF cavity performance for several baking temperatures and durations in order to find cost efficient post-furnace chemistry free procedures to enable high Q-values.

TUP066

Plasma Processing of Large Surfaces with Application to SRF Cavity Modification

plasma, SRF, experiment, niobium

586

J. Upadhyay, S. Popović, L. Vušković
ODU, Norfolk, Virginia, USA
D.S. Im
Old Dominion University, Norfolk, Virginia, USA
H.L. Phillips, A-M. Valente-Feliciano
JLAB, Newport News, Virginia, USA

Funding: Supported by DOE under grant no. DE-SC0007879. JU acknowledges support by JSA/DOE via DE-AC05-06OR23177
Plasma based surface modifications of SRF cavities present promising alternatives to the wet etching technology currently applied. To understand and characterize the plasma properties and chemical kinetics of plasma etching processes inside a single cell cavity, we have built a specially-designed cylindrical cavity with 8 observation ports. These ports can be used for holding niobium samples and diagnostic purposes simultaneously. Two frequencies (13.56 MHz and 2.45 GHz) of power source are used for different pressure, power and gas compositions. The plasma parameters were evaluated by a Langmuir probe and by an optical emission spectroscopy technique based on the relative intensity of two Ar 5p-4s lines at 419.8 and 420.07 nm. Argon 5p-4s transition is chosen to determine electron temperature in order to optimize parameters for plasma processing. Chemical kinetics of the process was observed using real-time mass spectroscopy. The effect of these parameters on niobium surface would be measured, presented at this conference, and used as guidelines for optimal design of SRF etching process.

TUP067

Hydrogen Saturation and the Thermal Conductivity of Superconducting Niobium

niobium, superconductivity, vacuum, lattice

589

S.K. Chandrasekaran
MSU, East Lansing, USA
T.R. Bieler
Michigan State University, East Lansing, USA
C. Compton
FRIB, East Lansing, USA
N.T. Wright
(MSU), East Lansing, USA

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics, through Grant No. DE-S0004222
The thermal conductivity k of Nb at less than 3 K is dominated by phonon transport. In Nb with sufficiently few lattice imperfections, a maximum in k occurs at 1.8 K, called the phonon peak (PP). A large PP is desired to reduce potential local hot spots and contributes to an increased Q factor. The magnitude of the PP is sensitive to SRF cavity manufacturing processes. The effect of interstitial hydrogen on the magnitude of the PP is examined by subjecting two bicrystal Nb specimens to 300 C for 1 h in a 75% H2, 25% N2 atmosphere at 0.5 atm. Prior to hydrogen infusion, specimen 1 was heated to 800 C for 2 h, while specimen 2 was heated to 1100 C for 4 h. Both specimens displayed a 25% reduction in the PP due to the additional hydrogen, independent of their crystal orientations and heat treatment histories. An 800 C vacuum heating for 2 h was found to be sufficient to recover the PP in specimen 1, while an 1100 C heating for 4 h was required to recover the PP in one of the grains of specimen 2. The results suggest that hydrogen trapped in the Nb lattice will degas when the Nb is heated to at least the temperature to which it was heated at prior to the hydrogen infusion step.

TUP069

The Copper Substrate Developments for the HIE-ISOLDE High-Beta Quarter Wave Resonator

electron, cryogenics, operation, linac

596

L. Alberty, G. Arnau-Izquierdo, I. Aviles Santillana, S. Calatroni, O. Capatina, A. D'Elia, G. Foffano, Y. Kadi, P. Moyret, K.M. Schirm, T. Tardy, W. Venturini Delsolaro
CERN, Geneva, Switzerland
A. D'Elia
UMAN, Manchester, United Kingdom

A new linac using superconducting quarter-wave resonators (QWR) is under construction at CERN in the framework of the HIE-ISOLDE project. The QWRs are made by Niobium sputtered on a bulk Copper substrate. The working frequency at 4.5 K is 101.28 MHz and they will provide 6 MV/m accelerating gradient on the beam axis with a total maximum power dissipation of 10 W. The properties of the cavity substrate have a direct impact on the final cavity performance. The Copper substrate has to ensure an optimum surface for the Niobium sputtered layer. It has also to fulfill the required geometrical tolerances, the mechanical stability during operation and the thermal performance to optimally extract the RF dissipated power on cavity walls. The paper presents the mechanical design of the high β cavities. The procurement process of the Copper raw material is detailed, including specifications and tests. The manufacture sequence of the complete cavity is then explained and the structural and thermo-mechanical behavior during the tests performed on a prototype cavity is discussed. The industrialization strategy is presented in view of final production of the cavities.

TUP070

Characterization of Superconducting Samples With SIC System for Thin Film Developments: Status and Recent Results.

niobium, ECR, SRF, network

599

G.V. Eremeev, H.L. Phillips, A-M. Valente-Feliciano
JLAB, Newport News, Virginia, USA
C.E. Reece
JLab, Newport News, Virginia, USA
B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Within any thin film development program directed towards SRF accelerating structures, there is a need for an RF characterization device that can provide information about RF properties of small samples. The current installation of the RF characterization device at Jefferson Lab is Surface Impedance Characterization (SIC) system. The data acquisition environment for the system has recently been improved to allow for automated quicker measurement, and the system has been routinely used for characterization of bulk Nb, films of Nb on Cu, MgB2, NbTiN, Nb3Sn films, etc. We present some of the recent results that illustrate present capabilities and limitations of the system.

TUP071

Development of Nb3Sn Cavity Vapor Diffusion Deposition System

niobium, vacuum, impedance, controls

603

G.V. Eremeev, W.A. Clemens, K. Macha, H. Park, R.S. Williams
JLAB, Newport News, Virginia, USA
H. Park
ODU, Norfolk, Virginia, USA

Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Alternative BCS superconductors with the superconducting critical temperature higher than that of niobium theoretically surpass the limitations of niobium. The feasibility of technology has been demonstrated at 1.5 GHz with Nb3Sn vapor deposition technique at Wuppertal University. The benefit at these frequencies is more pronounced at 4.2 K, where Nb3Sn coated cavities show RF resistances an order of magnitude lower than that of niobium. At Jefferson Lab we started the development of Nb3Sn vapor diffusion deposition system within an R&D development program towards compact light sources. Here we present the current progress of the system development.

TUP072

Quality Factor Measurements of the Ultramet 3 GHz Cavity Constructed Using Chemical Vapour Deposition

niobium, SRF, radio-frequency, operation

607

D.L. Hall, D. Gonnella, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V.M. Arrieta, S.R. McNeal
Ultramet, California, USA

Funding: US Department of Energy Phase 1 Small Business Innovation Research award to Ultramet
A seamless 3 GHz bulk niobium cavity constructed by Ultramet using rapid chemical vapor deposition (CVD) techniques has been tested on the vertical SRF test stand at Cornell. The cavity received a 25 um buffered chemical polish (BCP) and 700 C heat treatment for 4 days. First test results gave an intrinsic quality factor of Q0 = (1.55 ± 0.12) x 10⁷ and (2.00 ± 0.15) x 10⁷ at 4.2 K and 1.5 K, respectively. A second BCP removed 100 um of material, after which test results improved to Q0 = (7.59 ± 1.52) x 10⁷ and (4.16 ± 0.31) x 10⁸ at 4.2 K and 1.5 K. During the ﬁrst test poor coupling to the input ampliﬁer impeded tests at accelerating ﬁelds >0.2 MV/m, while during the second test the cavity quenched at 1.3 MV/m when operating at 1.5 K. An optical inspection of the cavity after the second test revealed the presence of at least 4 pits on the upper hemisphere suggesting an area of higher than average surface resistance that may have contributed to the low ﬁeld quench via thermal runaway. The potential of CVD as a construction method for SRF cavities is discussed.

TUP073

Niobium Coatings for the HIE-ISOLDE QWR Superconducting Accelerating Cavities

niobium, vacuum, cathode, SRF

611

N.M. Jecklin, S. Calatroni, L.M.A. Ferreira, I. Mondino, A. Sublet, M. Therasse, W. Venturini Delsolaro
CERN, Geneva, Switzerland
B. Delaup
EPFL, Lausanne, Switzerland

The HIE-ISOLDE project is the upgrade of the existing ISOLDE facility at CERN, which is dedicated to the production of a large variety of radioactive ion beams for nuclear physics experiments. A new linac made of 20 β=10.3% and 12 β=6.3% QWR superconducting accelerating cavities at 101 MHz will be built, and in a first phase two cryomodules of 5 high-beta cavities each are scheduled to accelerate first beams in 2015. The cavities are made of a copper substrate, with a sputter-coated superconductive niobium layer, operated at 4.5 K with an accelerating field of 6 MV/m at 10W RF losses (Q0=4.5e8) In this paper we will discuss the baseline surface treatment and coating procedure which allows obtaining the required performance, as well as the steps undertaken in order to prepare series production of the required number of cavities guaranteeing their quality and functionality.

TUP074

Development of an Optimized Quadrupole Resonator at HZB

quadrupole, niobium, resonance, focusing

614

R. Kleindienst, J. Knobloch, O. Kugeler
HZB, Berlin, Germany

Funding: EuCARD II
Current superconducting cavities are generally made of solid niobium. A possibility to reduce cost as well as increase accelerating fields and, essential for CW applications, the quality factor is to use thin-film coated cavities. Measuring and understanding the RF-properties of superconducting thin films, specifically the surface resistance at the operating field and frequency, is needed to drive forward this development. Presently, only few facilities exist capable of measuring the surface resistance of thin films samples with a resolution in the nano-ohm range at L-Band. We describe here a dedicated test stand consisting of a quadrupole resonator that was constructed at the Helmholtz Zentrum Berlin. Starting with 400-MHz quadrupole resonator developed at CERN, the design was adapted and optimized for resolution and reduced peak electric field to 433 MHz (making available the higher harmonic mode at 1,3GHz) using simulation data obtained with CST Microwave Studio as well as ANSYS. The relevant figures of merit have been improved, giving the possibility to perform measurements with high resolution at high field levels.

TUP075

Design and Commissioning Status of New Cylindrical HiPIMS Nb Coating System for SRF Cavities

niobium, ion, cathode, SRF

617

H.L. Phillips, K. Macha, A-M. Valente-Feliciano
JLAB, Newport News, Virginia, USA

Funding: † Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
For the past 19 years Jefferson Lab has sustained a program studying niobium films deposited on small samples in order to develop an understanding of the correlation between deposition parameters, film micro-structure, and RF performance. A new cavity deposition system employing a cylindrical cathode using the HiPIMS technique has been developed to apply this work to cylindrical cavities. The status of this system will be presented.

TUP076

Preliminary Results of Nb Thin Film Coating for HIE-ISOLDE SRF Cavities Obtained by Magnetron Sputtering

plasma, niobium, cathode, monitoring

620

A. Sublet, I. Aviles Santillana, S. Calatroni, A. D'Elia, N.M. Jecklin, I. Mondino, S. Prunet, M. Therasse, W. Venturini Delsolaro, P. Zhang
CERN, Geneva, Switzerland

Funding: Work supported in part by a Marie Curie Early Initial Training Network Fellowship of the European Community's 7th Programme under contract number PITN-GA-2010-264330-CATHI.
In the context of the HIE-ISOLDE upgrade at CERN, several new facilities for the niobium sputter coating of QWR-type superconducting RF accelerating cavities have been developed, built, and successfully operated. In order to further optimize the production process of these cavities the magnetron sputtering technique has been further investigated and continued as an alternative to the already successfully operational DC bias diode sputtering method. The purpose of this poster is to present the results obtained with this technique. The Nb thickness profile along the cavity and its correlation with the electro-magnetic field distribution inside the cavity are discussed. Film structure, morphology and Residual Resistivity Ratio (RRR) will be considered as well and compared with films obtained by DC bias diode sputtering. Finally these results will be compared with RF characterization and measurement of a production-like magnetron-coated cavity.

TUP077

Thin Film Coating Optimization for HIE-ISOLDE SRF Cavities: Coating Parameters Study and Film Characterization

cathode, niobium, hardware, SRF

623

A. Sublet, I. Aviles Santillana, S. Calatroni, P. Costa Pinto, N.M. Jecklin, S. Prunet, A. Sapountzis, W. Venturini Delsolaro, W. Vollenberg
CERN, Geneva, Switzerland

Funding: Work supported in part by a Marie Curie Early Initial Training Network Fellowship of the European Community's 7th Programme under contract number PITN-GA-2010-264330-CATHI.
The HIE-ISOLDE project at CERN requires the production of 32 cavities in order to increase the energy of the beam. The Quarter Wave Resonators (QWRs) cavities of complex cylindrical geometry (0.3m diameter and 0.8m height) are made of copper and are coated with a thin superconducting layer of niobium. In the present phase of the project the aim is to obtain a niobium film, using the DC bias diode sputtering technique, providing adequate high quality factor of the cavities and to ensure reproducibility for the future series production. After an overview of the explored coating parameters (hardware and process), the resulting film characteristics, thickness profile along the cavity, structure and morphology (SEM measurements) and Residual Resistivity Ratio (RRR) of the Nb film will be shown. The effect of the sputtering gas process pressure and configuration of the coating setup will be highlighted.

TUP078

Nb Coating Developments with HIPIMS for SRF Applications

target, plasma, cathode, niobium

627

G. Terenziani, I. Aviles Santillana, S. Calatroni, T. Junginger
CERN, Geneva, Switzerland
A.P. Ehiasarian
SHU, Sheffield, United Kingdom

In the last few years the interest of the thin film science and technology community on High Impulse Power Magnetron Sputtering (HIPIMS) coatings has steadily increased. HIPIMS literature shows that better thin film morphology, denser and smoother films can be achieved when compared with standard dc Magnetron Sputtering (dcMS) coating technology. Furthermore the capability of HIPIMS to produce a high quantity of ionized species can allow conformal coatings also for complex geometries. A study is under way at CERN to apply this technology for the Nb coating of SRF 1.3-1.5 GHz Cu cavities, and in parallel at SHU the plasma physics and its correlation with film morphology are being investigated. Recent results achieved with this technique are presented in the paper.

TUP081

Chemical Vapor Deposition Techniques for the Multilayer Coating of Superconducting RF Cavities

niobium, SRF, controls, experiment

635

F. Weiss, C. Jimenez, S. Pignard
Institut Polytechnique de Grenoble, Grenoble INP, Grenoble, France
C.Z. Antoine
CEA/IRFU, Gif-sur-Yvette, France
M. Benz, E. Blanquet, R. Boichot, A. Mantoux, F. Mercier
Laboratoire SIMAP, Grenoble-INP, CNRS, UJF, Saint Martin d'Hères, France

Issued from the recent development of thin films technologies, multilayer nanostructures face today very challenging questions in materials science: ultimate size reduction, process control at an atomic scale, new size driven properties and system characterisation. For superconducting RF technologies a significant breakthrough could arise from the use of multilayered structures deposited inside Nb cavities. These multilayer nanostructures are based on the use of some 10 nanometers thick superconducting layers (d<λL) with a higher Tc than in Nb, alternating with insulating layers, required to decouple the superconducting films. We present here our first studies devoted to nano-layered superconductors produced by Chemical Deposition techniques: CVD and ALD. The basic principles of CVD and ALD will be presented together with new developments of the coordination chemistry for the ALD precursors, which is key point for the optimization of the individual layers. First results concerning NbN films obtained by CVD as well as CVD and ALD results concerning insulating materials used for Superconducting/insulating (S/I/S/I) multilayers structures will be reported.

TUP082

Materials Analysis of CED Nb Films Being Coated on Bulk Nb Single Cell SRF Cavities

SRF, HOM, ion, cryogenics

638

X. Zhao, C.E. Reece
JLab, Newport News, Virginia, USA
G. Ciovati
Jefferson Lab, Newport News, Virginia, USA
I. Irfan, C. James, M. Krishnan
AASC, San Leandro, California, USA
A.D. Palczewski
JLAB, Newport News, Virginia, USA

Funding: This research is supported at AASC by DOE via Grant No. DE-FG02-08ER85162 and Grant No. DE-SC0004994 and by Jefferson Science Associates, LLC under U.S. DOE Contract No. DEAC05- 06OR23177
This study is an on-going research on depositing a Nb film on the internal wall of bulk Nb single cell SRF cavities, via an coaxial energetic condensation (CED) facility at AASC company. The motivation is to firstly create a homoepitaxy-like Nb/Nb film in a scale of a ~1.5GHz RF single cell cavity. Next, through SRF measurement and materials analysis, it might reveal the baseline properties of the CED-type homoepitaxy Nb films. Such knowledge of Nb-Nb homo-epitaxy is useful to create future realistic SRF cavity film coatings, such as hetero-epitaxy Nb/Cu Films, or template-layer-mitigated Nb films. One large-grain, and three fine grain bulk Nb cavity were coated. They went through cryogenic RF measurement. Preliminary results show that the Q0 of a Nb film at 2 K and low rf field, produced by CED, could be close to that of the pre-coated bulk Nb surface (being CBP'ed plus a light EP); but the quality drops rapidly for increasing rf field. We are investigating if the severe Q0-slope is caused by hydrogen incorporation before deposition, or is determined by some structural defects during Nb film growth.

TUP083

Film Deposition, Cryogenic RF Testing and Materials Analysis of a Nb/Cu Single Cell SRF Cavity

niobium, cryogenics, SRF, plasma

642

X. Zhao
JLab, Newport News, Virginia, USA
R.L. Geng, Y.M. Li, A.D. Palczewski
JLAB, Newport News, Virginia, USA
Y.M. Li
PKU, Beijing, People's Republic of China

Funding: The JLab effort was provided by Jefferson Science Associates, LLC under U.S. DOE Contract No. DEAC05- 06OR23177.
In this study, we present preliminary results on using a cathodic-arc-discharge Nb plasma ion source to establish a Nb film-coated single-cell Cu cavity for SRF research. The polycrystalline Cu cavity was fabricated and mirror-surface-finished by a centrifugal barrel polishing (CBP) process at Jefferson Lab. Special pre-coating processes were conducted, in order to create a template-layer for follow-on Nb grain thickening. A sequence of cryogenic RF testing demonstrated that the Nb film does show superconductivity. But the quality factor of this Nb/Cu cavity is low as a result of high residual surface resistance. We are conducting a thorough materials characterization to explore if some microstructural defects or hydrogen impurities, led to such a low quality factor.

TUP085

Study of NbTi Welded Parts

niobium, laser, plasma, linac

659

N. Bazin, C.Z. Antoine
CEA/DSM/IRFU, France
C. B. Baumier, G. Martinet
IPN, Orsay, France
F. F. Fortuna
CSNSM, ORSAY CAMPUS, France
J.-B. Sirven
Commisariat à l'Energie Atomique (CEA/DEN/DPC), Direction de l'Energie Nucléaire, Gif-sur-Yvette, France

Due to its properties, niobium-titanium alloy is widely used to manufacture the flanges of superconducting niobium accelerating cavities. The material hardness is compliant to provide UHV-tight connections with aluminum gaskets or spring-type gaskets (Helicoflex). And the alloy can be directly welded to the niobium. The paper will present the surface analysis made on NbTi samples after the chemical treatment and on a Nb / NbTi weld.

TUP086

Cryogen-Free RF System Studies Using Cryocooler-Cooled Magnesium Diboride-Coated Copper RF Cavities

niobium, cryomodule, SRF, accelerating-gradient

663

A. Nassiri, R. Kustom, Th. Proslier
ANL, Argonne, USA
T. Tan, X. Xi
TU, Philadelphia, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06H11357.
Studies on the application of magnesium diboride(MgB2)high-Tc superconducting films have shown promise for use with rf cavities. Studies are directed towards applying the films to niobium cavities with the goal to increase accelerating gradients to greater than 50 MeV/m. However, studies also have shown that MgB2 films, with a critical temperature over four times higher than Nb, have surface resistances equal, or nearly equal, at 8-12 K, to what is achieved with niobium at 4 K. It might be possible to design and operate cavity systems in the 8-12K temperature range with cryocoolers that are currently available. The current cryocoolers can remove as much as 20 watts per unit in the range of 8-12K. This suggests that helium-free superconducting RF systems are possible for future light sources and possible industrial and medical linear accelerators. Our current research is directed towards depositing MgB2 films onto copper, or other high thermal conductivity metal, substrates which would allow future cavities to be fabricated as film coated copper structures. We have started atomic layer deposition and Hybrid chemical vapor deposition studies of MgB2 on 2-inch copper coupons.

TUP087

RF Test Results of the first Nb3Sn Cavities Coated at Cornell

niobium, SRF, operation, linac

666

S. Posen, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

As an alternative material to niobium for SRF cavities in particle accelerators, Nb3Sn presents two significant advantages. With a Tc of 18 K, it has a very small surface resistance at a given temperature, leading to a significant reduction in cryogenic costs; and with a predicted Hsh of nearly 400 mT, it has the potential to produce cavities with higher gradients and therefore shorter high energy linacs. Recently, two 1.3 GHz cavities have been fabricated and coated with Nb3Sn at Cornell. Tests of these first cavities have produced encouraging results, including a very high Tc and some very high-performing surface regions. These cavity results as well as new results of samples studied using TEM will be presented.

TUP088

NbTiN Based SIS Multilayer Structures for SRF Applications

SRF, lattice, radiation, superconducting-RF

670

A-M. Valente-Feliciano, G.V. Eremeev, H.L. Phillips, C.E. Reece
JLAB, Newport News, Virginia, USA
A.D. Batchelor
NCSU AIF, Raleigh, North Carolina, USA
R.A. Lukaszew
The College of William and Mary, Williamsburg, USA
J.K. Spradlin
JLab, Newport News, Virginia, USA
Q.G. Yang
NSU, Norfolk, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
For the past three decades, bulk niobium has been the material of choice for SRF cavities applications. RF cavity performance is now approaching the theoretical limit for bulk niobium. For further improvement of RF cavity performance for future accelerator projects, Superconductor-Insulator-Superconductor (SIS) multilayer structures (as recently proposed by Alex Gurevich) present the theoretical prospect to reach RF performance beyond bulk Nb, using thinly layered higher-Tc superconductors with enhanced Hc1. Jefferson Lab (JLab) is pursuing this approach with the development of NbTiN and AlN based multilayer SIS structures via magnetron sputtering and High Power Impulse Magnetron Sputtering (HiPIMS). This paper presents the results on the characteristics of NbTiN and insulator films and the first RF measurements on NbTiN-based multilayer structure on thick Nb films.

TUP090

Thermal Simulations for the Multi-Layer Coating Model

simulation, feedback, electromagnetic-fields, superconducting-cavity

674

F. Meng
IHEP, Beijing, People's Republic of China
A. Romanenko
Fermilab, Batavia, USA
Y. Xie
Euclid TechLabs, LLC, Solon, Ohio, USA

Thermal simulations for the multi-layer coating model has been developed based on previous work of a finite difference thermal feedback code.* RF field-attenuation formula for the multi-layer coating model has also been included.** The temperature distribution along different superconducting layers under applied magnetic fields has been calculated with various superconducting material parameters.
*Y. Xie et.al., "Relationship between defects pre-heating and defects size", SRF2009.
**T. Kubo et.al.,"Rf field-attenuation formulae for the multilayer coating model", IPAC2013

TUP091

Field Emission Measure During cERL Main Linac Cryomodule High Power Test in KEK

radiation, electron, cryomodule, linac

678

E. Cenni
Sokendai, Ibaraki, Japan
K. Enami, T. Furuya, H. Sakai, M. Satoh, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

A compact Energy Recovery Linac (cERL) is under construction in KEK in order to proof the performance of the key components required for the future ERL project in KEK. The main linac L-band cavities were assembled and tested in the cryomodule under high power operation, during the test information concerning field emission were gathered by means of PIN diodes rings and NaI scintillator located at the cavities ends. The data were analyzed by means of simulations, taking into account the cavities operating conditions and interaction between the accelerated electrons and the cavity surface. The resulting information are used to deduce a possible emitter location, determining if there is any change in the cavities performance with respect to the last vertical test they undertook. With PIN diode is possible to observe the radiation pattern produced by field emission, inferring the meridian where the emitter belongs. On the other hand the bremsstrahlung spectra recorded with the scintillator allow an estimation of the cavity cell where the emitter is located.

TUP092

MUSICC3D: a Code for Modeling the Multipacting

electron, simulation, RF-structure, vacuum

683

T. Hamelin, M. Chabot, J.-L. Coacolo, J. Lesrel, G. Martinet
IPN, Orsay, France

IPNO has conducted an effort to develop a 3D code for modeling multipacting in RF structures. The MUSICC3D program is using particle in cell method. Based on Runge Kutta method and using relativistic equation of motion, it solves the trajectory of a particle (e-) in the RF field. The integrations over the multi differential Secondary Emission Yield (SEY) (E_in, Alpha_in ,E_out, Alpha_out)) is made with Montecarlo method. Two running modes are available. The first one is using a model of virtual particle (i.e. the charge of a unique particle “rebounding” in the interior of the cavity is made by the product of SEYs occurring at each interaction with the walls). The other one makes generation of a full cascade of individual electrons. Benchmarking calculations have been done with analytical calculations and 2D particle in cell code (MULTIPAC). In all these cases the effects of the different inputs for the multi differential SEY have been investigated. Its intend is to give a guide to determine which precision on the SEY is needed to perform accurate multipacting calculations. Benchmarking with real cavity has been recently started and results with QWR Spiral2 cavities are presented.
Hatch, Multipacting Modes etc., Physical Review.
Wood, Investigations into Multipactor Breakdown etc., ESA Journal.
Geng, Multipacting Simulations etc., Particule Accelerator Conference.

TUP094

Influence of Heat Treatments on Field Emitters on Nb Crystals

vacuum, site, status, power-supply

690

S. Lagotzky, G. Müller
Bergische Universität Wuppertal, Wuppertal, Germany
A. Matheisen, D. Reschke
DESY, Hamburg, Germany

Funding: Funding by HGF Alliance and the BMBF project 05H12PX6
Systematic investigations of the enhanced field emission (EFE) of HPR-cleaned large grain (LG) and single crystal (SC) Nb samples (Ra < 0.5μm) revealed an exponential increase of the emitter number density N with electric surface field Es and strong activation effects of the remaining particulates. Different types of EFE activation were observed: by high E partially combined with a micro-discharge or by heat treatments (HT) [1]. In cavities, EFE activation might also occur due to enhanced rf losses of particulates. Therefore, we have started a test series with two LG and two SC typically prepared Nb samples (40 μm BCP, 140 μm EP and HPR at DESY). At first all emitters (1 nA) up to Es = 160 MV/m were localized by means of correlated field emission microscopy (FESM). Then systematically varied in-situ HT between 122°C (24 h) and 400°C (2 h) were applied to investigate the activation of emitters due to the change of the natural Nb oxide. For all samples a significant increase of N with stronger HT up to 32 emitters/cm² at 400°C were obtained resulting in some activated emitters already at Es = 40 MV/m. Final SEM images of the activated emitters will also be discussed.
[1] A. Navitski et. al, subm. to PRSTAB 2013

TUP095

Field Emission and Consequences as Observed and Simulated for CEBAF Upgrade Cryomodules

neutron, electron, radiation, operation

694

F. Marhauser, R.P. Johnson, R. Rodriguez
Muons, Inc, Illinois, USA
P. Degtiarenko, A. Hutton, G. Kharashvili, C.E. Reece, R.A. Rimmer
JLAB, Newport News, Virginia, USA

High gamma and neutron radiation levels were monitored at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) after installation of new cavity cryomodules and initial test runs in the frame of the ongoing 12 GeV upgrade program. The dose rates scaled exponentially with cavity accelerating fields, but were independent of the presence of an electron beam in the accelerator. Hence, field emission (FE) is the source of origin. This has led to concerns regarding the high field operation (100 MV per cryomodule) in the future 12 GeV era. Utilizing supercomputing, novel FE studies have been performed with electrons tracked through a complete cryomodule. It provides a principal understanding of experimental observations as well as ways to mitigate FE as best as practicable by identification of problematic cavities.

TUP096

High Power Processing at a High Order Mode Frequency

HOM, gun, SRF, cathode

697

V. Volkov
BINP SB RAS, Novosibirsk, Russia
J. Knobloch, A.N. Matveenko, A. Neumann
HZB, Berlin, Germany

Regular High Power Processing (HPP) at fundamental frequency in a superconducting cavity usually carried out to increase maximal RF field in the cavity that is limited by Field Emission (FE). HPP at a High Order Mode (HOM) frequency allow significantly increasing FE threshold of fundamental RF field. In the paper we give proof of this prediction and give the concrete proposal of such HPP design for Rossendorf 3.5-cell RF gun structure. Expected RF over field is about 100% (from 17 up to 34 MV/m) as compared with a regular HPP.

TUP097

Study of the Temperature Interface Between Niobium and Superfluid Helium. Temperature Waves Measurements from Heat Sources

niobium, SRF, factory, radio-frequency

700

A. Ganshin, F. Furuta, D.L. Hartill, G.H. Hoffstaetter, K.M. Price, E.N. Smith
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work has been supported by NSF award PHY-0969959 and DOE award DOE/SC00008431.
One of the most important properties of Superconducting Radio Frequency (SRF) cavities is their ability to disperse generated heat from the internal cavity wall to the external super fluid helium bath. When the generated heat is not removed fast enough, an effect known as thermal feedback dominates, resulting in medium field Q-slope. This medium field Q-slope has the ability to reduce the Q factor should it become strong enough. To determine what physical factors affect the creation of the medium field Q-slope we will be computationally modeling the medium field Q-slope with varying parameters, such as Kapitza conductivity, wall thickness, RF frequency, bath temperature, residual resistivity ratio, residual resistance, and phonon mean path. Our results show that the medium-field Q slope is highly dependent on the Kapitza conductivity and that by doubling the Kapitza conductivity the medium field Q-slope reduces significantly. Understanding and controlling the medium ﬁeld Q-slope will benefit future continuous wave (CW) applications such as the Energy Recovery Linacs (ERL) where cryogenics costs dominate due to CW operation at medium ﬁelds (< 20 MV/m).

TUP100

Medium Field Q-Slope Studies in High Frequency Cavities

operation, superconductivity, niobium, factory

705

O.S. Melnychuk, A. Grassellino, A.I. Sukhanov
Fermilab, Batavia, USA

A phenomenon of Medium Field Q-Slope (MFQS) in superconducting RF cavities is of high importance because it occurs in the field range (5-20MV/m) that includes designed operation fields of future CW accelerators. MFQS impacts resistive losses in the cavity and, consequently, directly affects accelerator operation costs. We present studies of MFQS based on vertical test data for 1.3GHz nine-cell cavities and make comparisons of vertical test data from different laboratories.

TUP102

Quench Detection Diagnostics on 3.9 GHz XFEL Cavities

site, detector, diagnostics, superconductivity

710

M. Bertucci, A. Bosotti, L. Garolfi, P. Michelato, L. Monaco, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

This paper presents results of quench localization on 3.9 GHz XFEL prototype cavities tested at LASA vertical test facility. Cavities have been equipped with OST second sound detectors and thermometry sensors. A first guess for quench position has been obtained from modal analysis. Second sound sensors confirmed the quench position resolving also the symmetry degeneracy given by the RF mode pattern analysis. In a subsequent vertical test, second sound and temperature sensors have been installed nearby the suspect quench position. From Thermometry mapping, a sudden increase in cavity temperature within a small region is evident, therefore confirming that a local thermal breakdown due to defect heating occurs in the predicted quench point. The quench region deduced with the mentioned techniques is eventually compared with results of optical inspection.

TUP103

Calibration and Characterization of Capacitive OST Quench Detectors in SRF Cavities at IPN Orsay

SRF, detector, cryogenics, diagnostics

714

M. Fouaidy, F. Dubois, J.-M. Dufour, D. Longuevergne, A. Maroni, G. Michel, J.-F. Yaniche
IPN, Orsay, France

Funding: IPNO/IPN2P3/CNRS
The maximum RF surface magnetic field (Bs) achieved with SRF bulk Nb cavities is often limited by anomalous losses due to Joule heating of normal-resistive defects embedded onto the RF surface. At high BS (e.g Bs>50 mT), the defect temperature increases strongly with BS, leading to a thermal runaway of the cavity or quench. The unloaded quality factor Q0 of the cavity decreases suddenly and strongly due to superconducting to normal state phase transition of the hot spot area. Quench detectors, called Oscillating Superleak Transducer (OST) and sensing 2nd sound events in He II, have been recently used to study quench of SRF cavities. IPN developed his prototypes of OST quench detectors and a test stand for their calibration and characterization in the temperature range T0=1.6 K-2.2 K. This device allows precise and controlled experimental simulation of SRF cavity quench using pulsed heat sources. Experimental runs were performed to study the dynamic response of OST detectors when the heat source is subjected to a time varying heat flux q(t) as function of several parameters (T0, q(t) time structure and density, heat source size) and first experimental data are presented.

TUP104

Temperature Waves in SRF Research

detector, SRF, experiment, software

719

A. Ganshin, R.G. Eichhorn, D.L. Hartill, G.H. Hoffstaetter, E.N. Smith, N.R.A. Valles
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
X. Mi
Cornell University, Ithaca, New York, USA

Funding: This work has been supported by NSF award PHY-0969959 and DOE award DOE/SC00008431
Previously Cornell University developed Oscillating Superleak Transducers (OST) to locate quench spots on superconducting cavities in superfluid helium. This work builds upon this research and presents a technique to automatically visualize quench locations from OST data (1). This system is now fully automated. The current system consists of between 8 and 16 OSTs, a high gain low noise preamplifier, and a data acquisition card that can log up to 16 simultaneously recorded inputs. The developed software allows computing quench locations on various cavity geometries, adjustment of the location of each OST and a choice between several quench finding algorithms. Observed results are in excellent agreement with optical inspection and temperature map data.
1. http://newsline.linearcollider.org/2011/04/21/the-sound-of-accelerator-cavitie

TUP105

Investigation of the Surface Resistivity of SRF Cavities via the Heat and Srimp Program as Well as the Multi-Cell T-Map System

SRF, feedback, accelerating-gradient, electron

724

G.M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, H. Padamsee
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
F. Furuta
Cornell University, Ithaca, New York, USA

A high-sensitive temperature mapping system for multi-cell SRF cavities has been constructed at Cornell University. The resolution of the system is 1mK. Hence it’s able to detect small temperature increases when cavities reach at low accelerating gradients e.g. 3MV/m. The surface resistivity of superconductor under radio-frequency electromagnetic field can be calculated from the temperature increases. In this contribution, the surface resistance map of multi-cell SRF cavities is shown. The temperature mapping result is possible to establish a relationship between the surface resistivity and the magnetic field as well. Unlike the RF method which is average value of the surface resistance, the T-map results give local surface resistivity versus magnetic field. BCS theory assumes the surface resistivity is independent to the magnetic field. The T-map results, however, suggest that the surface resistance at high-loss region is field dependent and caused Q-slope.

TUP106

Second-Sound Measurements on a 3 GHz SRF Cavity at Low Acceleration Fields*

electron, operation, acceleration, scattering

728

S.T. Sievers, U. Bonnes, C. Burandt, F. Hug, T. Kürzeder, N. Pietralla, A. Richter
TU Darmstadt, Darmstadt, Germany

Funding: *This work is supported by the DFG through the Collaborative Research Center SFB 634.
The superconducting Darmstadt electron linear accelerator S-DALINAC uses 20-cell niobium cavities that are operated at a microwave frequency of 3 GHz in liquid helium at a temperature of 2 K. This operation temperature is well below TC = 9.25 K of niobium and guarantees superconducting condition in routine operation. Occasional surface impurities, in particular after venting the beamline following maintenance work, can lead to local quenches which destroy superconductivity of the cavity. In such events it is desirable to have a method for locating and eliminating these surface impurities. In order to locate quench sites in the superconducting cavities during operation in liquid helium a set-up of oscillating superleak transducers (OSTs) was tested in a vertical bath cryostat on a cavity known to quench at very small accelerating fields. Despite the low rf power of approximately 4 W needed to quench the cavity, we were able to identify the quench sites with the OST set-up. Subsequent optical inspection clearly showed surface damages at the determined positions. We will report on our set-up and the procedure.

TUP108

Study on Niobium Scratch and Tantalum or Carbonaceous Contamination at Niobium Surface with Field Emission Scanner

niobium, electron, site, controls

731

S. Kato, H. Hayano, T. Kubo, T. Noguchi, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan

It is mandatory to investigate field emission from niobium SRF cavity surface systematically since even small field emission often limits the cavity performance terribly. The field emission strength and the number of emission sites strongly depend on niobium surface properties which are determined by its surface treatment and handling. It was found that carbonaceous contamination including carbon, oxygen, sometimes, nitrogen often segregates at CPed or EPed surface with a size of several micron to several tens of micron-meters. There is a strong doubt that this contamination causes field emission from the surface. Newly developed field emission scanner (FES) allows us to measure a distribution of the field emitting sites over a sample surface at a given field strength along with its SEM (scanning electron microscope) observation and EDX (energy dispersive x-ray) analysis. This article describes results of the FES-SEM-EDX application to carbonaceous contamination at niobium surface.

TUP110

An X-Ray Fluorescence Probe for Defect Detection in Superconducting 1.3 GHz Cavities

niobium, detector, embedded, radiation

736

P. Michelato, M. Bertucci
INFN/LASA, Segrate (MI), Italy
A. Navitski, W. Singer, X. Singer
DESY, Hamburg, Germany
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
Y. Tamashevich
Uni HH, Hamburg, Germany

The aim of this project is to develop a system for defect detection by means of X-ray fluorescence (XRF) analysis. XRF is a high sensitivity spectroscopy technique allowing the detection of trace element content, such as the few microgram impurities, responsible for low cavity performances if embedded in the equatorial region during cavity manufacturing. The proposed setup is customized on 1.3 GHz TESLA-type niobium cavities: both the detector and the X-ray excitation source are miniaturized so to allow the probe to enter within the 70 mm iris diameter and aside of the HOM couplers. The detection-excitation geometry is focused on cavity cell equator surface located at about 10³ mm from the cavity axis, with an intrinsic spot-size of about 10 mm. The measuring head will be settled on a high angular resolution optical inspection system at DESY, exploiting the experience of OBACHT. Defect position is obtained by means of angular inner cavity surface scanning. A quantitative determination of defect content can also be carried out by means of fundamental parameters technique with a Niobium standard calibration.

TUP111

Experimental Investigations of the Quench Phenomena for the Quench Localization by the Second Sound Wave Method

SRF, niobium, controls, experiment

739

J. Plouin, J.-P. Charrier, C. Magne, J. Novo
CEA/DSM/IRFU, France
L. Maurice
CEA/IRFU, Gif-sur-Yvette, France

The quench localization by the second sound method is now widely used in many laboratories. This method avoids the complicated implementation of temperature arrays around the surface cavities. Instead, specific sensors are placed around the cavity and the time of arrival of the second sound wave generated by the quench is measured on each sensor; then the distance from sensors to quench is deducted from the theoretical second sound wave velocity. In principle, the quench position can be localized with a triangulation by a limited number of sensors. However, many measurements have shown that the time of arrival of the wave was not corresponding to the theoretical second sound wave velocity: the “measured” velocity is often 50% higher than the theory. At CEA-Saclay we performed several measurements on single cell cavities to investigate these phenomena. Several hypotheses are studied: large quench spot, heat propagation by another phenomenon than the second sound near to the cavity where the heat power density is very high. These results and the discussions on these hypotheses will be presented.

TUP112

Time-Resolved Measurements of High-Field Quench in SRF Cavities

SRF, niobium, simulation, accelerating-gradient

743

S. Antipov
University of Chicago, Chicago, Illinois, USA
E. Efimenko
MIPT, Dolgoprudniy, Moscow Region, Russia
A. Romanenko, D.A. Sergatskov
Fermilab, Batavia, USA

Fermilab’s temperature mapping system for SRF cavities has been improved to observe quench dynamics with 1ms time resolution. The increase in sampling rate was achieved by localizing the quench and then performing the measurements using a limited subset of thermometers. Implemented experimental procedure allowed to measure temperature distribution within quench spot, as well as the amount of stored energy, at the moment quench starts, during its growth, and decay. For three tested SRF cavities, quenching at fields 21.7 – 33 MeV/m, maximal radius of the normal zone was 40 – 65 mm; time to return to superconducting state: 90 – 250 ms. In the beginning of the process temperature increase rate in the center of the normal zone is as high as 2.5 K/ms, radius increase rate – 20 mm/ms. The described experimental procedure can be useful for investigating how different surface treatments affect the breakdown, understanding of the nature of high-field quench, improvement of quench detection techniques, and material science research for future SRF cavities.

TUP114

XT-map System for Locating SC Cavity Quench Position

cryogenics, survey, operation, accelerating-gradient

747

H. Tongu, Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
H. Hayano, Y. Yamamoto
KEK, Ibaraki, Japan

XT-map system under development in collaboration between Kyoto University and KEK is a combined system of the temperature mapping (T-map) and X-ray mapping (X-map). High resolution T-map at quench detection will give more information for improving yield in production of high performance SC Cavities. The high-density sensor distribution of the XT-map gives the high resolution. Because the huge amount of sensor lines are multiplexed at a hi-speed scanning rate in the vicinity of the sensors, the small number of signal lines makes the installation process easy and reduces the system complexity. The scanning test of this XT-map system has been performed in the vertical test at KEK. The detected quench events will be reported.

TUP116

Quench field and Location in Vertical Tests at KEK-STF

linear-collider, accelerating-gradient, linac, cryomodule

751

Y. Yamamoto, E. Kako, T. Shishido
KEK, Ibaraki, Japan

Many vertical tests have been done for the ILC and ERL at KEK-STF since 2008. T-mapping system (fixed type) was equipped at every vertical test, and quench location was identified completely. Every quench location at quench field will be presented in this paper.

WEIOA01

HiPIMS: a New Generation of Film Deposition Techniques for SRF Applications

ion, SRF, plasma, target

754

A-M. Valente-Feliciano
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Over the years, Nb/Cu technology, despite its shortcomings due to the commonly used magnetron sputtering, has positioned itself as an alternative route for the future of accelerator superconducting structures. Avenues for the production of thin films tailored for Superconducting RF (SRF) applications are showing promise with recent developments in ionized PVD coating techniques, i.e. vacuum deposition techniques using energetic ions. Among these techniques, High power impulse magnetron sputtering (HiPIMS) is a promising emerging technique which combines magnetron sputtering with a pulsed power approach. This contribution describes the benefits of energetic condensation for SRF films and the characteristics of the HiPIMS technology. It describes the on-going efforts pursued in different institutions to exploit the potential of this technology to produce bulk-like Nb films and go beyond Nb performance with the development of film systems, based on other superconducting materials and multilayer structures.

Slides WEIOA01 [12.446 MB]

WEIOA02

Energetic Condensation Growth of Niobium Films

ion, lattice, plasma, vacuum

761

M. Krishnan, I. Irfan
AASC, San Leandro, California, USA

Funding: The AASC research is supported by the US Department of Energy via several SBIR research grants
Energetic Condensation refers to thinfilm growth on a surface using ~100eV ions, versus lower energy deposition using sputtering (~1-10eV with no substrate bias) or still lower energy thermal evaporation. The relatively high incident energy of energetic condensation creates defects and vacancies within the first few atomic layers and enables diffusion to lower free-energy sites in the lattice. Shallow defects migrate to the heated surface and are annihilated, leading to low-defect crystal growth. It has been shown [1] that the purer the film, the closer are its superconducting parameters to those of the bulk metal. Use of cathodic arc plasmas was proposed in 2000 by Langner [TESLA Rep. 2000-15, Ed. D. Proch, DESY 2000], followed by detailed development of the process [2]. AASC picked up from the European Community-Research Infrastructure Activity and has demonstrated very high RRR=541 in Nb films grown on crystal substrates [3]. Ongoing work to coat 1.3GHz copper cavities using cathodic arc plasmas, as well as growth of higher temperature films such as NbTiN, Nb3Sn and MgB2 are described. A related technique for energetic condensation using an ECR plasma source is also described.
1. C. Benvenuti et al, IEEE Trans. Appl. Supercond. 9 (1999) 900
2. R. Russo et al, Supercond. Sci. Technol. 18 (2005) L41-L44
3. M. Krishnan et al, Supercond. Sci. Technol. 24, 115002 (2011)

Slides WEIOA02 [14.616 MB]

WEIOA03

Nb Sputtered Quarter Wave Resonators for the HIE-ISOLDE

cathode, niobium, vacuum, linac

767

W. Venturini Delsolaro, S. Calatroni, A. D'Elia, B. Delaup, N.M. Jecklin, Y. Kadi, P. Maesen, I. Mondino, A. Sublet, M. Therasse
CERN, Geneva, Switzerland
A. D'Elia
UMAN, Manchester, United Kingdom
D.A. Franco Lespinasse, G. Keppel, V. Palmieri, S. Stark
INFN/LNL, Legnaro (PD), Italy

The HIE-ISOLDE superconducting linac will be based on quarter wave resonators (QWRs), made by Niobium sputtering on Copper. The operating frequency at 4.5 K is 101.28 MHz and the required performance for the high beta cavity is 6 MV/m accelerating field for 10 W maximum power dissipation. These challenging specifications were recently met at CERN at the end of a vigorous development program. The paper reports on the progress of the cavity RF performance with the evolution of the sputtering process; it equally illustrates the parallel R&D which is ongoing at CERN and at INFN in the quest for even higher performances.

Slides WEIOA03 [14.564 MB]

WEIOA04

Nb3Sn for SRF Application

niobium, SRF, laser, vacuum

773

M. Liepe, S. Posen
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The superconductor Nb3Sn is a promising alternative to standard niobium for SRF applications for two reasons: Its larger superconducting energy gap results in significantly lower BCS surface resistance at typical SRF operating temperatures. Additionally, theoretical predictions suggest that the maximum operating field of Nb3Sn cavities could be twice that of niobium cavities. Early work on a small number of Nb3Sn coated cavities indeed showed 2K to 4.2K quality factors well above what is achievable with niobium, though at accelerating fields below ~10 MV/m only. After many years of worldwide inactivity, Cornell has taken the lead and initiated a new R&D program on Nb3Sn to explore its full potential for SRF applications. New facilities for coating cavities with Nb3Sn have been set up at Cornell, and 1.3 GHz single cell cavities have been coated and tested. This talk presents the Cornell Nb3Sn program, discusses first promising results obtained, and also gives an overview of other Nb3Sn SRF work worldwide.

Slides WEIOA04 [3.854 MB]

WEIOB01

Status of MgB2 Coating Studies for SRF Applications

SRF, controls, background, superconductivity

777

T. Tajima, L. Civale, D.J. Devlin, G.C. Martinez, R.K. Schulze
LANL, Los Alamos, New Mexico, USA

Funding: DOE Office of Science/Nuclear Physics
MgB2 has shown promising results on small samples and its coating development is entering into the stage to coat large samples and elliptical cavities. Several coating techniques that seem to be appropriate for cavity coating and their status will be shown together with some cavity measurement results with either 6 GHz or 1.3 GHz single-cell cavities. Other data such as RF surface resistance at low temperatures and vortex penetration fields with small samples will also be shown.

Slides WEIOB01 [2.183 MB]

WEIOB02

Proof of Concept Thin Films and Multilayers Toward Enhanced Field Gradients in SRF Cavities

impedance, SRF, shielding, radio-frequency

782

R.A. Lukaszew, D. Beringer, W.M. Roach
The College of William and Mary, Williamsburg, USA
G.V. Eremeev, A-M. Valente-Feliciano
JLAB, Newport News, Virginia, USA
C.E. Reece
JLab, Newport News, Virginia, USA
X. Xi
TU, Philadelphia, USA

Funding: Defense Threat Reduction Agency (DTRA)
Due to the very shallow penetration depth of the RF fields, SRF properties are inherently a surface phenomenon involving a material thickness of less than 1 micron thus opening up the possibility of using thin film coatings to achieve a desired performance. The challenge has been to understand the dependence of the SRF properties on the detailed characteristics of real surfaces and then to employ appropriate techniques to tailor these surface properties for greatest benefit. Our aim is to achieve gradients >100 MV/m and no simple material is known to be capable of sustaining this performance. A theoretical framework has been proposed which could yield such behavior [1] and it requires creation of thin film layered structures. I will present our systematic studies on such proof-of-principle samples. Our overarching goal has been to build a basic understanding of key nano-scale film growth parameters for materials that show promise for SRF cavity multilayer coatings and to demonstrate the ability to elevate the barrier for vortex entry in such layered structures above the bulk value of Hc1 for type-II superconductors and thus to sustain higher accelerating fields.
[1]. A. Gurevich, Appl. Phys. Lett. 88, 012511 (2006).

Slides WEIOB02 [15.612 MB]

WEIOC01

High Resolution Surface Resistance Studies

quadrupole, niobium, shielding, superconductivity

785

S. Aull, S. Döbert, T. Junginger
CERN, Geneva, Switzerland
S. Aull, J. Knobloch
University of Siegen, Siegen, Germany
J. Knobloch
HZB, Berlin, Germany

Funding: Work supported by the German Doctoral Students program of the Federal Ministry of Education and Research (BMBF).
The attempt to reach quality factors beyond 10¹¹ and pushing the accelerating gradients of SRF cavities to the theoretical limit, the treatment depending loss mechanisms in niobium need better understanding. CERNs Quadrupole Resonator enables sub-nΩ-resolution measurements of the surface resistance. The available parameters cover resonant modes at 400, 800 and 1200 MHz, any temperature up to 15 K and rf fields up to 60 mT. Recently the setup has been extended with a coil creating a dc magnetic field for trapped flux studies. Overall, much more information about the rf performance is accessible compared to regular cavity measurements. Since the samples are flat disks of 75 mm diameter geometric fabrication issues are simplified which makes the Quadrupole Resonator also the perfect tool to study alternative materials or new coating techniques. In this contribution in depth studies of a heat treated bulk niobium sample exploiting the complete parameter range of the setup are presented.

Slides WEIOC01 [2.724 MB]

WEIOC02

Multilayers Activities at Saclay / Orsay

niobium, SRF, vacuum, superconductivity

789

C. B. Baumier, G. Martinet
IPN, Orsay, France
C.Z. Antoine
CEA/IRFU, Gif-sur-Yvette, France
F. F. Fortuna
CSNSM, ORSAY CAMPUS, France
J.C. Villegier
CEA/INAC, Grenoble Cedex 9, France

In the investigations on the high gradient SRF cavities, the superconducting multilayer is a promising alternative. The predictions show that an SIS (Superconductor/Isolator/Superconductor) nano-composite could improve the efficiency limited by the bulk Nb it-self used today for accelerating cavities. We start, at the IPNO lab in collaboration with the CSNSM lab (CNRS) and Irfu lab (CEA), an experimental study to test the screening effect on multilayer assemblies. Based on 3rd harmonic magnetometer and a TE011 SRF cavity, measurements of first critical magnetic field HC1 and surface resistance of samples have been performed. Along with these first results, we are starting the development of a MBE deposition. This set-up is devoted to optimise the best organisation of the multilayer to produce the model sample, and to find, in a close future, a realistic solution to apply this technique on an accelerating SRF cavity.
Labex P2IO funding

Slides WEIOC02 [3.035 MB]

WEIOC04

Theoretical Field Limits for Multi-Layer Superconductors

SRF, niobium, experiment, superconductivity

794

S. Posen, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
G. Catelani
Forschungszentrum Jülich, Peter Gruenberg Institut (PGI-2), Jülich, Germany
J.P. Sethna
Cornell University, Ithaca, New York, USA
M.K. Transtrum
M.D.A.C.C., Houston, Texas, USA

With modern cavity preparation techniques, niobium SRF cavities reach surface magnetic fields very close to the fundamental limit of the superheating field of the material, and researchers are looking to alternative superconductors to sustain even higher fields. However, these materials may have an increased vulnerability to flux penetration at defects, even small ones, as a result of their short coherence lengths. A. Gurevich has proposed [1] a method of mitigating this vulnerability: coating a bulk superconducting cavity with a series of very thin insulating and superconducting films. In this work, we present a thorough mathematical description of the SIS thin films proposed by Gurevich in the language of the SRF community, to help researchers to optimize cavities made from alternative superconductors.
[1] A. Gurevich, Appl. Phys. Lett. 88, 012511 (2006)

Slides WEIOC04 [4.116 MB]

WEIOD01

Review of Magnetic Shielding Designs of Low-Beta Cryomodules

solenoid, cryomodule, shielding, linac

800

R.E. Laxdal
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

It is well known that superconducting cavities can trap magnetic flux while cooling through transition. The trapped flux adds to the residual rf surface resistance. For this reason magnetic shielding is added to the cryomodules to shield the cavities from the environmental magnetic field. The low beta portion of many superconducting hadron linear accelerators, either in operation or in production, includes cryomodules containing one or more high field superconducting solenoids. The operation of a high field solenoid in close proximity to a cavity adds a level of complexity to the cryomodule design considerations. The paper will summarize the various techniques that can be employed to reduce the risk of magnetic pollution from internal solenoids.

Slides WEIOD01 [10.342 MB]

THIOA01

Infrastructure, Methods and Test Results for the Testing of 800 Series Cavities for the European XFEL

coupling, operation, controls, feedback

812

D. Reschke
DESY, Hamburg, Germany

Funding: The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no 283745 (CRISP).
The main linac of the European XFEL will consist of 100 accelerator modules, i.e. 800 superconducting accelerator cavities operated at a design gradient of 23.6 MV/m. The fabrication and surface preparation of the cavities in industry is in full swing. This talk describes the infrastructure and procedures of the vertical acceptance test in the "Accelerator Module Test Facility AMTF" at DESY. The present status of the test results is given.

Slides THIOA01 [1.998 MB]

THIOA02

The Challenge to Assemble 100 Cryomodules for the European E-XFEL

cryomodule, controls, vacuum, linac

816

C. Madec
CEA, Gif-sur-Yvette, France
S. Berry, J.-P. Charrier, M. Fontaine, Y. Gasser, O. Napoly, C.S. Simon, T.V. Vacher, B. Visentin
CEA/DSM/IRFU, France
P. Charon, C. Cloué, G. Monnereau, J.L. Perrin, D. Roudier, Y. Sauce, T. Trublet
CEA/IRFU, Gif-sur-Yvette, France

As In-Kind contributor to the E-XFEL project, CEA is committed to the integration on the Saclay site of the 100 cryomodules (CM) of the superconducting linac as well as to the procurement of miscellaneous parts including 31 cold beam position monitors (BPM) of the re-entrant type. The assembly infrastructure has been renovated from the previous Saturne Synchrotron Laboratory facility: it includes a 200 m2 clean room complex with 112 m2 under ISO4, 1325 m2 of assembly platforms and 400 m2 of storage area. In parallel, CEA has conducted industrial studies and three cryomodule assembly prototyping both aiming at preparing the industrial file, the quality management system and the commissioning of the assembly plant, tooling and control equipment. In 2012, the contract of the integration has been awarded to ALSYOM. The first pre-series modules have been assembled and are being tested at DESY. This paper will present the challenges of the module integration from the preparation phase to the industrial phase.

Slides THIOA02 [17.641 MB]

THIOA03

Cavity Fabrication Study in CFF at KEK

niobium, electron, HOM, gun

821

M. Yamanaka, Y. Ajima, H. Inoue, T. Kubo, T. Saeki, Y. Watanabe, S. Yamaguchi
KEK, Ibaraki, Japan

The construction of new facility for the fabrication of superconducting RF cavity at KEK was completed in 2011. It is equipped with the following machines; an electron-beam welding (EBW) machine, a servo press machine and a CNC vertical lathe. A chemical etching apparatus is also equipped. The study on the fabrication of 9-cell cavity for International Linear Collier (ILC) has been started from 2009 using this facility. The study is focusing on the cost reduction with keeping high performance of cavity, and the goal is the establishment of mass-production procedure for ILC.

Slides THIOA03 [7.823 MB]

THIOA05

Optimization of SRF Linacs

cryomodule, linac, cryogenics, operation

830

T. Powers
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S.
This work describes preliminary results of a new software tool that allows one to vary parameters and understand the effects on the optimized costs of construction plus 10 year operations of an SRF linac, the associated cryogenic facility, and controls, where operations includes the cost of the electrical utilities but not the labor or other costs. It derives from collaborative work done with staff from Accelerator Science and Technology Centre, Daresbury, UK several years ago while they were in the process of developing a conceptual design for the New Light Source project. The initial goal was to convert a spread sheet format to a graphical interface to allow the ability to sweep different parameter sets. The tools also allow one to compare the cost of the different facets of the machine design and operations so as to better understand the tradeoffs. More recent additions to the software include the ability to save and restore input parameters as well as to adjust the Qo versus E parameters in order to explore the potential costs savings associated with doing so.

Slides THIOA05 [2.712 MB]

THIOB01

CEBAF Upgrade: Cryomodule Performance and Lessons Learned

cryomodule, linac, vacuum, controls

836

M.A. Drury, J. Hogan, C. Hovater, L.K. King, H. Park, J.P. Preble, R.A. Rimmer, H. Wang, M. Wiseman
JLAB, Newport News, Virginia, USA
G.K. Davis, C.E. Reece
JLab, Newport News, Virginia, USA
F. Marhauser
Muons, Inc, Illinois, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract DE-AC05-06OR23177.
The Thomas Jefferson National Accelerator Facility is currently engaged in the 12 GeV Upgrade Project. The goal of the 12 GeV Upgrade is a doubling of the available beam energy of the Continuous Electron Beam Accelerator Facility (CEBAF) from 6 GeV to 12 GeV. The increase in beam energy will largely be due to the addition of ten C100 cryomodules and the associated RF in the CEBAF linacs. These cryomodules are designed to deliver 100 MeV per cryomodule. Each C100 cryomodule contains a string of eight seven-cell, electro-polished, superconducting RF cavities. While an average performance of 100 MV is needed to achieve the overall 12 GeV beam energy goal, the actual performance goal for the cryomodules is an average energy gain of 108 MV to provide operational headroom. All ten of the C100 cryomodules are installed in the linac tunnels and are on schedule to be commissioned by September 2013. Commissioned performance has ranged from 104 MV to 118 MV. In May, 2012, a test of an early C100 achieved 108 MV with full beam loading. This paper will discuss the performance of the C100 cryomodules along with operational challenges and lessons learned for future designs.
The U.S. Govt. retains a non-exclusive, paid-up,irrevocable,world-wide license to publish or reproduce this manuscript.

Slides THIOB01 [2.534 MB]

THIOB02

High Q Cavities for the Cornell ERL Main Linac

linac, cryomodule, SRF, HOM

844

R.G. Eichhorn, B. Bullock, B. Clasby, B. Elmore, F. Furuta, A. Ganshin, G.M. Ge, D. Gonnella, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V.D. Shemelin, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

While SRF research for linear colliders was focused on achieving high gradients, Cornell’s proposal for an energy recovery linac (ERL) demanded for low cw losses. Starting several years ago, a high-Q R&D phase was launched that led to remarkable results recently: A fully dressed cavity (7 cells, 1.3 GHz) with side-mounted input coupler and beamline HOM absorbers achieved a Q of 3.5·10¹⁰ ((16 MV/m, 1.8 K). This talk will review the staged approach we have chosen in testing a single cavity in a horizontal short cryomodule (HTC), report results on each step and conclude on our findings about preserving high Q from vertical testing. We also discuss the production of six additional cavities as we progress toward constructing a full 6-cavity cryomodule as a prototype for Cornell’s main linac module

Slides THIOB02 [8.378 MB]

THIOC01

Low Beta Cavity Development for an ATLAS Intensity Upgrade

cryomodule, niobium, linac, ion

850

M.P. Kelly, Z.A. Conway, S.M. Gerbick, M. Kedzie, S.H. Kim, R.C. Murphy, B. Mustapha, P.N. Ostroumov, T. Reid
ANL, Argonne, USA

The set of seven new 72 MHz quarter wave SC (QWR) cavities has been completed and is being installed in the ATLAS heavy-ion accelerator at Argonne. The aim is to provide at least 17.5 MV accelerating potential with large acceptance and minimal beam losses for high intensity ion beams. The cavity electromagnetic design uses optimizations not used before with QWR including a large taper on both the inner and outer conductors in order to reduce surface fields and make efficient use of space along the beam line. Electropolishing (EP) on the finished cavities with integral helium jacket and no demountable RF joints has been performed, and is the first for any low beta SC cavity. This type of EP, adapted from Argonne systems for the linear collider effort, appears to have a large benefit in terms of the average quench field which range between 103-165 mT for five QWR tested to date. Cavity residual resistances at the proposed operating point of ~70 mT are low, clustering close to a value of ~2nOhm. Additional technical details including the almost exclusive use of wire EDM for niobium fabrication and a new CW 4 kW RF power coupler are presented.

Slides THIOC01 [10.152 MB]

THIOC02

High Power CW Tests of cERL Main-Linac Cryomodule

cryomodule, HOM, linac, alignment

855

H. Sakai, K. Enami, T. Furuya, M. Satoh, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

A main linac cryomodule have been constructed for Compact ERL project. It contains two 9-cell cavities, mounted with HOM absorbers and input couplers. After cavity string assembly, they were installed into the vacuum vessel of the cryomodule. It was placed inside radiation shield of cERL and connected to a refrigerator system. The cryomodule was successfully cooled down to 2K and low power and high power measurements were carried out.

Slides THIOC02 [12.842 MB]

THIOC03

Superconducting Photonic Band Gap Structures for High-Current Applications

SRF, HOM, accelerating-gradient, wakefield

860

E.I. Simakov, S. Arsenyev, W.B. Haynes, S.S. Kurennoy, D.Y. Shchegolkov, N.A. Suvorova, T. Tajima
LANL, Los Alamos, New Mexico, USA
C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA

Funding: This work is supported in parts by the U.S. DOE Early Career Research Program and by the DOD High Energy Laser Joint Technology Office through the Office of Naval Research.
We present the results of recent design and testing of several 2.1 GHz superconducting rf (SRF) photonic band gap (PBG) resonators. PBG cells have great potential for outcoupling long-range wakefields in SRF accelerator structures without affecting the fundamental accelerating mode. Using PBG structures in superconducting particle accelerators will allow operation at higher frequencies and moving forward to significantly higher beam luminosities thus leading towards a completely new generation of colliders for high energy physics. Here we report the results of our efforts to fabricate 2.1 GHz PBG cells with round and elliptical rods and to test them with high power at liquid helium temperatures. Two PBG cells with round rods were tested in spring of 2012 and achieved accelerating gradients of 15 MV/m at 2 Kelvin. Two PBG cells with elliptical rods will be tested in summer of 2013.

Slides THIOC03 [2.284 MB]

THIOC04

Demonstration of RF Stabilities in STF 9-cell Cavities Aiming for the Near Quench Limit Operation

operation, feedback, LLRF, controls

865

M. Omet
Sokendai, Ibaraki, Japan
T. Matsumoto, S. Michizono, T. Miura
KEK, Ibaraki, Japan

In preparation of ILC an operation of two superconducting cavities controlled by digital LLRF techniques at different gradients (16 MV/m, 24 MV/m) with flat flattops and a 6.4 mA beam was demonstrated, which is only possible by PkQL control (individual setting of driving power and loaded Q per cavity). The vector sum stabilities were ΔA/A = 0.009%rms and Δφ = 0.009°rms. Since in ILC the cavity gradient spread is large (31.5 MV/m±20%) the required range of loaded Q values is 3·10⁶ to 10⁷. High loaded Q operation with a 6.1 mA beam at 2·10⁷ was demonstrated. The stabilities were ΔA/A = 0.008%rms and Δφ = 0.014°rms. Furthermore a near klystron operation within 5% of saturation was performed with a 6.2 mA beam. The stabilities were ΔA/A = 0.010%rms and Δφ = 0.009°rms.

Slides THIOC04 [1.448 MB]

THIOD01

SRF Cavities for ADS Project in China

linac, SRF, proton, operation

868

Y. He, W.M. Yue, S.H. Zhang
IMP, Lanzhou, People's Republic of China
J.P. Dai, Z.Q. Li, Z.C. Liu, W.M. Pan
IHEP, Beijing, People's Republic of China
X.Y. Lu
PKU, Beijing, People's Republic of China

The driver linac for ADS project in China is full superconducting downstream of Radio Frequecy Quadrupole Accelerator. It is a key technology R&D stage of the project from 2011 to 2015. Superconducting HWR, Spoke, and elliptical cavities are all involved in the project. The prototypes of 162.5 MHz HWR010, 325 MHz Spoke012, 325 MHz Spoke021, 325 MHz Spoke040, and 650 MHz elliptical 063 are being developed at IMP and IHEP in China. A small number of HWR010 and Spoke012 have been produced and vertically tested. The first prototype of Spoke021 were tested too. The design, performances, fabrication, suface processing, and testing of all cavities will be presented in the talk. The design improvement of the cavities in the future will also be discussed.

Slides THIOD01 [13.465 MB]

THIOD02

Faced Issues in ReA3 Quarter-Wave Resonators and Their Successful Resolution

vacuum, linac, cryomodule, operation

873

A. Facco
NSCL, East Lansing, Michigan, USA
C. Compton, J.L. Crisp, K. Elliott, A. Facco, M. Hodek, M.J. Johnson, M. Leitner, I.M. Malloch, D. Miller, S.J. Miller, D. Morris, D. Norton, R. Oweiss, J.P. Ozelis, J. Popielarski, L. Popielarski, K. Saito, N.R. Usher, G.J. Velianoff, D.R. Victory, J. Wei, K. Witgen, Y. Xu, S. Zhao
FRIB, East Lansing, Michigan, USA
A. Facco
INFN/LNL, Legnaro (PD), Italy

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
The 80.5 MHz, β=0.085 QWR production cavities for the ReA3 project at MSU have initially shown puzzling behavior and unexpected lack of performance. This was due to a combination of design problems and subtle mechanical effects which have been pointed out during a brief but intense testing campaign made by the FRIB SRF group. The same cavities could be eventually refurbished and brought to performance well above original specifications. This work will be presented with emphasis to the technical problems encountered, their diagnosis and the adopted solutions.

Slides THIOD02 [8.256 MB]

THIOD03

Cavity Development for the Linear IFMIF Prototype Accelerator

niobium, cryomodule, simulation, SRF

878

N. Bazin, P. Carbonnier, G. Devanz, G. Disset, N. Grouas, P. Hardy, F. Orsini, D. Roudier
CEA/DSM/IRFU, France
J. Neyret
CEA/IRFU, Gif-sur-Yvette, France

The Linear IFMIF Prototype Accelerator (LIPAc), which is presently under design and realization, aims to accelerate a 125 mA deuteron beam up to 9 MeV. Therefore, a low-beta 175 MHz Half-Wave Resonator (HWR) was initially designed and manufactured with a tuning system based on a capacitive plunger located in the electric field region. Following the results of the vertical tests at 4.2K, this tuning system was abandoned and replaced by a conservative solution based on the HWR wall deformation using an external mechanical tuner. This paper will focus on the manufacturing of the prototype cavity, the studies realized to explain the first test results and the solutions taken to overcome the difficulties, leading to the validation of the prototype. Then, we will present the new cavity design.

Slides THIOD03 [8.845 MB]

THIOD04

A Cold Tuner System With Mobile Plunger

simulation, linac, insertion, cryomodule

884

D. Longuevergne, S. Blivet, S. Bousson, N. Gandolfo, G. Martinet, G. Olry, H. Saugnac
IPN, Orsay, France

Tuner systems for accelerating cavities are required to compensate static and dynamic frequency perturbations during beam operation. In the case of superconducting cavities, these are commonly tuned by deforming the cavity wall in specific places of the geometry. Nevertheless, considering the mechanical properties and frequency versus displacement sensitivity of some structures, tuning by deformation doesn’t allow to meet the requirements. In these specific cases, inspired from the “room temperature technology”, an alternative tuning technique by insertion of a helium-cooled superconducting plunger can be considered and has been studied for several projects (IFMIF, ESS-BILBAO). Advantages and drawbacks of such solution will be discussed and the successful results on SPIRAL2 cryomodule developed at IPNO will be presented.

Slides THIOD04 [4.938 MB]

THP001

Development of a Prototype SRF Cavity for the Proton Beam Utilization Facility at Nanjing University

HOM, SRF, proton, linac

889

S. An, P.P. Xue
PLAI, Nanjing, People's Republic of China
S.Q.X. Xu, H. Z. Zhang
ADS-SRF, People's Republic of China
P.P. Xue, L. Zhang
Chang’an University, Chang'an, People's Republic of China
Z.R. Zhang
Nanjing University of Aeronautics and Astronautics, Jiangning, People's Republic of China

Nanjing University has initiated the new technology development in the field of high-energy, charged-particle beam application and fundamental sciences. A high-current proton accelerator used for the new energy, new technology and fundamental science applications platform will be the near term goal at Nanjing University. For developing the superconducting RF linac for the proton beam utilization at Nanjing University, the first 6-cell, medium-beta prototype superconducting RF cavity has been fabricated and demonstrated using Chinese vendors only. The low-power test has been completed. The vertical test will be carried out soon.

THP002

Design of 3-Cell Travelling Wave Cavity for High Gradient Test

accelerating-gradient, feedback, pick-up, niobium

892

P.V. Avrakhov, A. Kanareykin, R.A. Kostin, Y. Xie
Euclid TechLabs, LLC, Solon, Ohio, USA
S. Kazakov, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, USA

Utilization of a superconducting traveling wave accelerating (STWA) structure with small phase advance per cell for future high energy linear colliders may provide accelerating gradient 1.2/1.4 times larger [1] than standing wave structure. However, the STWA structure requires a feedback waveguide [1]. Recent tests of 1.3 GHz model of a single-cell cavity with waveguide feedback demonstrated an accelerating gradient comparable to the gradient in a single-cell ILC-type cavity from the same manufacturer [2]. In the present paper a design for a STWA resonator with a 3-cell accelerating cavity for high gradient tests is considered. Methods to create and support the traveling wave in this structure are discussed. The results of detailed studies of the mechanical and tuning properties of the superconducting resonator with 3-cell traveling wave accelerating structure are also presented.

THP003

Cold Measurements on the 325 MHz CH-Cavity

linac, coupling, ion, operation

896

M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
M. Amberg
HIM, Mainz, Germany

Funding: GSI, BMBF Contr. No. 06FY7102, 06FY9089I
At the Institute for Applied Physics (IAP), Frankfurt University, a sc 325 MHz CH-Cavity has been designed and built. This 7-cell cavity has a geometrical beta of 0.16 corresponding to a beam energy of 11.4 AMeV. The design gradient is 5 MV/m. Novel features of this resonator are a compact design, low peak fields, easy surface processing and high power coupling. After successful tests at Research Instruments (RI) and in Frankfurt the cavity was processed and cleaned at RI and power tests at 4K have been performed at the cryo lab in Frankfurt. In this paper these measurements will be presented.

THP004

Design Progress of SSR1 Single Spoke Resonator for RAON

superconducting-cavity, simulation, acceleration, operation

899

H.J. Cha, D. Jeon, H.C. Jung, H.J. Kim, G.-T. Park
IBS, Daejeon, Republic of Korea
R.E. Laxdal, Z.Y. Yao, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

Funding: The Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) of the Republic of Korea under Contract 2011-032011
An advanced heavy ion accelerator for basic sciences and multiple applications, called “RAON”, is under construction in Daejeon, South Korea. The fabrication of prototypes for four different types of superconducting cavities, QWR, HWR, SSR1 and SSR2, is scheduled based on the on-going technical designs. In this paper, we present the electromagnetic and mechanical analyses for the SSR1 cavity (β=0.3 and f=325 MHz). Several variants have been considered and compared in terms of rf parameters, multipacting sensitivity, helium pressure sensitivity and ease of fabrication. This includes an analysis of stiffening rings and helium jacket design for stable operation. The progress towards the design of the SSR1 cavity will be given.

THP005

Characteristics and Fabrication of Spoke Cavities for High-Velocity Applications

vacuum, operation, target, superconductivity

902

C.S. Hopper, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
J.R. Delayen, H. Park
JLAB, Newport News, Virginia, USA

A 500 MHz, velocity-of-light, two-spoke cavity has been designed and optimized for possible use in a compact light source [1]. Here we present the mechanical analysis and steps taken in fabrication of this cavity at Jefferson Lab.
*[1] T. Satogata et al, “Compact Accelerator Design for a Compact Light Source,” IPAC13, Shanghai, China, May 2013.

THP006

A Superconducting 217 MHz CH Cavitiy for the CW Demonstrator at GSI

solenoid, linac, cryomodule, ion

906

F.D. Dziuba, M. Amberg, M. Busch, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher, W.A. Barth, V. Gettmann, S. Mickat
HIM, Mainz, Germany
K. Aulenbacher
IKP, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

Funding: Work supported by HIM, GSI, BMBF Contr. No. 05P12RFRBL
For a competitive production of new Super Heavy Elements (SHE) in the future a 7.3 AMeV superconducting (sc) continuous wave (cw) LINAC is planned at GSI. Currently, a cw demonstrator is going to be built up. The demonstrator consists of a sc 217 MHz Crossbar-H-mode (CH) cavity and two sc 9.5 T solenoids mounted in a horizontal cryostat. One major goal of the demonstrator project is to show the operation ability of sc CH cavity technology under a realistic accelerator environment. After first rf and cold tests the demonstrator will be tested with beam delivered by the GSI High Charge State Injector (HLI) in 2014.

THP007

Cornell's ERL Cavity Production

target, controls, linac, cryomodule

909

R.G. Eichhorn, B. Bullock, B. Clasby, B. Elmore, F. Furuta, G.H. Hoffstaetter, J.J. Kaufman, B.M. Kilpatrick, J. Sears, V.D. Shemelin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T. Kürzeder
TU Darmstadt, Darmstadt, Germany

The phase 1 R&D program launched in preparation to building a 5 GeV Energy Recovery Linac (ERL) at Cornell, a full main linac cryomodule is currently built, housing six 7-cell cavities. In order to control the beam break-up limit, the shape of the cavity was highly optimized and stringent tolerances on the cavity production were targeted. We will report on the details of the cavity production, the accuracy of the cups forming the individual cells, the trimming procedure for the dumbbells, the cavity tuning and final accuracy of the cavity concerning field flatness, resonant frequency and overall length within this small series production.

THP011

Improving Gradient of 9-cell SRF Cavities at Peking University

SRF, niobium, accelerating-gradient, electron

914

J.K. Hao, J.E. Chen, L. Lin, K.X. Liu, X.Y. Lu, S.W. Quan, F. Wang, H.M. Xie, B.C. Zhang, K. Zhao, F. Zhu
PKU, Beijing, People's Republic of China

Four 9-cell TESLA superconducting cavities have been fabricated with Ningxia OTIC niobium material, including two fine grain and two large grain niobium cavities. The cavities have been tested after post treatments. At the early stage (PKU1 and PKU2), the gradient was about 23 MV/m. The gradient of PKU3 reached 28.4 MV/m, but the Q is low. The newest large grain 1.3 GHz 9-cell TESLA type SRF cavity (PKU4) has been made with careful control of machining, and improved surface treatment and electron beam welding. The maximum of gradient is 32.4 MV/m and the intrinsic quality factor (Q0) is 1.3x10¹⁰, which meet the requirement for ILC both in accelerating gradient and intrinsic quality factor.

THP012

Rebuild of Capture Cavity 1 at Fermilab

cryomodule, operation, vacuum, SRF

917

E.R. Harms, T.T. Arkan, E. Borissov, N. Dhanaraj, A. Hocker, Y.O. Orlov, T.J. Peterson, K.S. Premo
Fermilab, Batavia, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The front end of the proposed Advanced Superconducting Test Accelerator at Fermilab employs two single cavity cryomodules, known as ‘Capture Cavity 1’ and ‘Capture Cavity 2’, for the first stage of acceleration. Capture Cavity 1 was previously used as the accelerating structure for the A0 Photoinjector to a peak energy of ~14 Mev. In its new location a gradient of ~25 MV/m is required. This has necessitated a major rebuild of the cryomodule including replacement of the cavity with a higher gradient one. Retrofitting the cavity and making upgrades to the module required significant re-design. The design choices and their rationale, summary of the rebuild, and early test results are presented.

THP013

A New Cavity Design for Medium Beta Acceleration

linac, cryomodule, target, impedance

920

F.S. He, R.A. Rimmer, H. Wang
JLAB, Newport News, Virginia, USA

Funding: Work supported by DOE
Heavy duty or CW, superconducting proton and heavy ion accelerators are being proposed and constructed worldwide. The total length of the machine is one of the main drivers in terms of cost. Thus HWR and spoke cavities at medium beta are usually optimized to achieve low surface field and high gradient. A novel accelerating structure at β=0.5 evolved from spoke cavity is proposed, with lower surface fields but slightly higher heat load. It would be an interesting option for pulsed and CW accelerators with beam energy of more than 200MeV/u.

THP016

DEVELOPMENT OF THE SUPERCONDUCTING HALF WAVE RESONATOR FOR INJECTOR II IN C-ADS

niobium, simulation, linac, proton

923

W.M. Yue, W. Chang, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, F.F. Wang, R.X. Wang, M.X. Xu, C. Zhang, S.H. Zhang, S.X. Zhang
IMP, Lanzhou, People's Republic of China

The Development of the Half Wave Resonator (HWR010) is based on the China ADS. The HWR010 operates at 162.5 MHz and can provide more than 0.78 MV of accelerating voltage per cavity for proton withβopt=0.10. We have designed the HWR010 in 2011. A copper model has been fabricated to test the HWR fabrication procedure. Five HWR010s have been fabricated in 2012. The HWR010s has finished the vertical testing and the Q0 is 4·10⁸ at Epeak = 45 MeV/m, and one of the HWR010s has been vertical tested with helium vessel. The slow tuner and high power coupler for this HWR have been developed and tested.

THP017

Mechanical Study on the Cavity Package of 1.3 GHz Superconducting Accelerating Unit at IHEP

simulation, cryomodule, SRF, operation

926

S. Jin, J. Gao, Z.C. Liu, J.Y. Zhai, H.J. Zheng
IHEP, Beijing, People's Republic of China

The program of 1.3GHz Superconducting RF (SRF) Accelerating Unit is under study at IHEP. A scheme of the unit structure is shown as fig. 1. In the unit, a 9-cell SRF cavity, tuner and a liquid helium (LHe) tank including a section of 50mm long, 0.3mm thick bellows will be welded and assembled together to form a relatively independent component called cavity package. In the study, mechanical analyses are carried out focusing on the package to assure its safety in the fabrications or other room temperature measurements. A commercial program of ANSYS Workbench is used.

THP018

Design of a Superconducting 352MHz Fully Jacketed Double-Spoke Resonator for the ESS-Bilbao Proton Linac

linac, cryomodule, simulation, DTL

929

T. Junquera
Accelerators and Cryogenic Systems, Orsay, France
F.J. Bermejo, J.L. Muñoz, A.V. Vélez
ESS Bilbao, Bilbao, Spain
P. Duchesne, G. Olry
IPN, Orsay, France

The baseline design for the ESS-Bilbao light-ion linear accelerator and neutron source (a facility compliant with the ESS-AB requirements) has been completed and the normal conducting section of the linac (RFQ and DTL) is at present under detailed design and construction. Starting at 50 MeV, it is proposed to follow this section with a superconducting section composed of double and triple spoke cavities grouped in cryomodules of 2 or 3 cavities reaching a maximum energy of 300 MeV. After an initial R&D program on spoke cavities with an aluminum model, detailed electromagnetic and mechanical studies of a beta 0.50, 352MHz, double spoke cavity were performed. The results of the calculations are presented in this paper. It is proposed to continue this development by the construction and test of the niobium cavities prototypes and initiating the study of a cryo-module with two cavities that could be tested with beam at the ESS-Bilbao facility.

THP019

1.3 GHz SRF Cavity Tests for ARIEL at TRIUMF

TRIUMF, HOM, linac, SRF

933

P. Kolb, P.R. Harmer, D. Kishi, A. Koveshnikov, C. Laforge, D. Lang, R.E. Laxdal, Y. Ma, B.S. Waraich, Z.Y. Yao, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

The 1.3 GHz cavity test program at TRIUMF for the ARIEL eLINAC progressed into its next stage: Going from single cell cavity tests to demonstrate the operating Q and gradient for ARIEL can be reached at TRIUMF to nine cell cavity tests for production cavities. Single cell cavity tests at TRIUMF showed a comparable performance to a characterization done on the same cavity at FNAL last year. These single cell tests showed that the operating point for ARIEL of Q0 > 10¹⁰ at 10 MV/m during 2 K operation can be reached and exceeded at TRIUMF. To prepare for the first ARIEL nine cell cavity, a test with a TESLA nine cell cavity was done. This included frequency and field tuning, etching via BCP, HPR and assembly in a class 10 clean environment as well as modifications to the cryo assembly and upgrades to the 2 K pumping system. The performance of this TESLA cavity and the performance of first ARIEL nine cell cavity produced by PAVAC will be shown.

THP020

Measuring the Higher Order Mode Spectrum of the TRIUMF 9-cell Cavity

dipole, HOM, TRIUMF, simulation

936

P. Kolb, B. Amini, R.E. Laxdal, Y. Ma, Z.Y. Yao, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

The ARIEL eLINAC consists of five nine cell cavities, produced by PAVAC, and will accelerate 10 mA electrons to 50 MeV. This 500 kW beam will be used for rare isotope production. Future upgrade plans include a recirculating beam line. Recirculating the beam, for either energy doubling or energy recovery to drive a FEL, brings the risk of multi-pass beam break up (BBU). Therefore it is necessary to avoid higher order modes (HOMs) with high shunt impedance. The goal of the cavity design is to reduce the highest shunt impedance of any dipole HOM to 1 *10⁶Ω or less. Measurements on the nine cell cavity with bead pulling have been done to identify dipole modes and their geometric shunt impedance R/Q as well as measurements at 2 K to estimate the quality factor of those HOMs. Results of these measurements will be shown and compared to computer simulations done with ACE3P.

THP021

Design of the SSR021 Cavity for the Proton Accelerator Main Linac of China ADS

linac, proton, simulation, target

939

Z.Q. Li, Y.L. Chi, Q. Ma, W.M. Pan, Y. Sun, J.Y. Tang, Q.Y. Wang, B. Xu, X.Y. Zhang
IHEP, Beijing, People's Republic of China
Y. He, C. Zhang, S.H. Zhang, S.X. Zhang
IMP, Lanzhou, People's Republic of China
H.Y. Lin, P. Sha
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

China ADS is a high intensity proton machine based on CW superconducting technology. It includes two injectors and one main linac. The Institute of High Energy Physics (IHEP) and the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS), are responsible for developing the main linac together. This paper introduces the physics and mechanical design of the single spoke resonator (SSR021, beta021 cavity), which is used for first section of the main linac.

THP022

DEVELOPMENT OF A VERY LOW BETA SUPERCONDUCTING SINGLE SPOKE CAVITY FOR CHINA-ADS LINAC*

accelerating-gradient, linac, LLRF, niobium

942

H. Li, J.P. Dai, L.H. Li, H.Y. Lin, Q. Ma, W.M. Pan, Y. Sun, Q.Y. Wang, J. Zhang
IHEP, Beijing, People's Republic of China
H. Huang, P. Sha
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

Twelve very low Beta superconducting single spoke cavities whose Beta is only 0.12 (Spoke012) operating at 325MHz, are adopted in Injector I for China-ADS linac. This type of spoke cavity is believed to be one of the key challenges for its very low geometric Beta. So far, collaborated with Peking University and Harbin Institute of Technology, IHEP has designed, fabricated and tested the spoke012 prototype cavity successfully. This paper presents the details of the design, fabrication and vertical test results for Spoke012 prototype cavity.

THP024

Lorentz Force Detuning Simulations of Spoke Cavities With Different Stiffening Elements

simulation, radiation, vacuum, operation

946

J.L. Muñoz, F.J. Bermejo
ESS Bilbao, Zamudio, Spain

Lorentz force detuning caused by radiation pressure on the Nb cavity walls is of concern in cavity design and operation since its magnitude can approach the cavity bandwidth. This effect can be reduced using pasive stiffening elements in the cavity. In this work, Lorentz force detuning has been studied by numerical simulations for spoke cavities. Different stiffening elements has been considered. Static and dynamic behaviour have been analyzed by means of 3D static and transient electromagnetic and mechanical coupled finite elements simulations.

THP026

Cage Cavity: A Low Cost, High Performance SRF Accelerating Structure

SRF, HOM, vacuum, simulation

950

J. Noonan, T.L. Smith, M. Virgo, G.J. Waldschmidt
ANL, Argonne, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

Funding: Funded by Office of Naval Research. Argonne National Laboratory is operated by UChicago-Argonne LLC for the Department of Energy
The Cage Cavity is a new SRF cavity technology using tubes formed into the shape of a solid wall cavity then assembled into a closed volume. The theory is that the cage cavity will form a resonant cavity at RF frequencies below a critical frequency at which the cage structure behaves as a solid structure. Several cage cavity structures have been fabricated and measured that demonstrate good RF properties. Comparison of simulations and measurements for these structures will be discussed. More importantly, simulations have identified a new cage cavity configuration in which an SRF cage cavity’s quality factor is greater than 10exp10. The cage cavity must operate in a vacuum vessel which is also an RF cavity. By choosing the cage cavity resonant frequency to be decoupled from the vessel higher order resonances, simulations show that the cage cavity Q is ~95% of a solid wall SRF cavity. The Cage Cavity design, fabrication costs, and high order mode behavior have a number of advantages over solid wall cavities. However, the cage cavity also has limitations. The design and properties of the cage cavity will be discussed and compared with existing SRF cavities.

THP027

Multipactor Analysis of the HWR at RISP

electron, simulation, resonance, coupling

955

G.-T. Park
IBS, Daejeon, Republic of Korea

We report on the progress of the HWR development at RISP. The multipaction of the HWR was studied using CST-PS (PIC) solver and multipacting band is predicted. Additional considerations were given to see the effects of the coupling ports and the coupler on the multipaction. We present the modified cavity design without multipaction at our operation accelerating voltage~1.2MV.

THP028

The Research on Spoke 0.40 Cavity

simulation, proton, linac, superconducting-cavity

959

P. Sha, H. Huang
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
W.M. Pan, X.Y. Zhang
IHEP, Beijing, People's Republic of China

Spoke superconducting cavity can be used in the low-energy section of the proton accelerator. It has many significant advantages: compact structure, high value of R/Q, etc. The Chinese ADS (Accelerator Driven System) project will adopt many spoke cavities with 3 different β values (0.12, 0.21, 0.40). Spoke040 cavities (β=0.40) are used to increase the proton energy from 34 MeV to 178 MeV. Now the physical design of spoke040 cavity has been finished, and the machining are going on right now. The vertical test would be held at the end of this year.

THP029

Simulation of Mechanical Resonances of SRF Cavities in Low Beam Current CW Operation

resonance, operation, simulation, cryomodule

962

N. Solyak, M.H. Awida, I.V. Gonin, T.N. Khabiboulline, Y.M. Pischalnikov, W. Schappert, V.P. Yakovlev
Fermilab, Batavia, USA

The low beam current for CW operation of the Project X requires cavities to be mechanically optimized to operate at a high loaded Q and thus, low bandwidth with higher sensitivity to microphonics. The essential source of microphonics detuning is fluctuations in the helium pressure df/dp. Last year’s several methods for reducing df/dp has been proposed. One of the other possible sources of RF frequency instability is mechanical resonances. The cavity could be driven out of operating frequency by the mechanical deformations due to vibrations caused by external factors. In this paper we present the COMSOL multiphysics algorithm developed for evaluation of operating frequency shift due to mechanical resonances in SC cavities. We discuss the results of simulations for 5-cell elliptical 650 MHz β=0.9 cavities. The comparison of COMSOL simulations and measurements of ILC type cavities in Horizontal Test Stand at Fermilab is presented.

THP030

Superconducting RF Cavity Development With UK Industry

SRF, multipactoring, accelerating-gradient, niobium

966

A.E. Wheelhouse, R.K. Buckley, L.S. Cowie, P. Goudket, A.R. Goulden, P.A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
C.A. Cooper, C.M. Ginsburg, A. Grassellino, O.S. Melnychuk, A.M. Rowe, D.A. Sergatskov
Fermilab, Batavia, USA
J.R. Everard, N. Shakespeare
Shakespeare Engineering, South Woodham Ferrers, Essex, United Kingdom

As part of a continuing STFC Innovations Partnership Scheme (IPS) grant, in support of enabling UK industry to address the large potential market for superconducting RF structures Daresbury Laboratory and Shakespeare Engineering Ltd are developing the capability to fabricate, process and test a niobium 9-cell 1.3 GHz superconducting RF cavity. A single-cell cavity fabricated under this grant was surface processed and tested at Fermilab, and achieved an accelerating gradient in excess of 40 MV/m at an unloaded quality factor in excess of 1.0 x 10¹⁰. This paper presents the results of the single-cell cavity testing and discusses the progress made to date in the development of the design and manufacture of a 9-cell niobium cavity, which Shakespeare Engineering Ltd will fabricate and which is anticipated to be qualified in 2014.

THP031

Superconducting Test of the 56 MHz SRF Quarter Wave Resonator for RHIC

SRF, electron, simulation, resonance

969

Q. Wu, S.A. Belomestnykh, I. Ben-Zvi, G.T. McIntyre, R. Porqueddu, S.K. Seberg, T. Xin
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
A 56 MHz superconducting RF cavity will be the first quarter wave resonator (QWR) installed in a high energy storage ring. It is expected to boost the luminosity of the Relativistic Heavy Ion Collider by more than 60% after installation. In this paper, we discuss the cavity parameters and design features. We report the results from the first vertical test of this cavity at 4 K.

THP033

Study of Balloon Spoke Cavities

TRIUMF, simulation, operation, proton

972

Z.Y. Yao, R.E. Laxdal, B.S. Waraich, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
R. Edinger
PAVAC, Richmond, B.C., Canada

A balloon geometry has been proposed to suppress multipacting for single spoke resonators. The design may find a useful application for proton and ion accelerator projects. TRIUMF has completed initial RF, mechanical, and fabrication studies on this special geometry for both low (β=0.12) and medium (β=0.3) β geometries. The RF properties are comparable with that of traditional spoke cavities but with improved RF efficiency in addition to the reduced multipacting. The results of electro-magnetic and structural design studies comparing the balloon geometry with traditional spoke geometries will be presented. We will also present optimization studies of the mechanical design, such as decreasing df/dp by EM field compensation as well as discussing tuning strategies and fabrication techniques.

THP034

Multipacting Suppression in a Single Spoke Cavity

electron, resonance, simulation, operation

975

Z.Y. Yao, R.E. Laxdal, V. Zvyagintsev
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
X.Y. Lu, K. Zhao
PKU, Beijing, People's Republic of China

Spoke cavities are good candidates for the low and medium β section of a high intensity proton or ion accelerator. For many high intensity accelerators, stability and reliability are the most important properties. Currently, one of the key issues of spoke cavity performance is multipacting, which may cause instability during operation. Multipacting in a spoke cavity has a troublesome characteristic as it presents a continual barrier over a wide gradient range, usually in the range of operation from 3MV/m to 15MV/m. A good surface processing can improve the secondary electron emission yield. However, the complex 3D structure makes it not easily achievable as with the elliptical cavity variants. Suppressing multipacting in the design stage is clearly advantageous. This paper will present a multipacting study based on the PKU-I spoke cavity. A systematic correlation between geometric parameters and multipacting behaviors is obtained. Based on this study a new geometry of single spoke cavity called the ‘balloon’ variant is proposed.

THP035

Production of a 1.3 GHz Niobium 9-cell TRIUMF-PAVAC Cavity for the ARIEL Project

TRIUMF, ion, monitoring, SRF

978

V. Zvyagintsev, B. Amini, P.R. Harmer, P. Kolb, R.E. Laxdal, Y. Ma, B.S. Waraich, Z.Y. Yao
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
R. Edinger, M.C. Leustean, R. Singh
PAVAC, Richmond, B.C., Canada

A nine-cell 1.3 GHz superconducting niobium cavity has been fabricated for the ARIEL project at TRIUMF. The cavity is intended to accelerate a beam current of 10 mA at an accelerating gradient of 10 MV/m. The beam loaded RF power of 100 kW is supplied through two opposed fundamental power couplers. The electromagnetic design was done by TRIUMF. The cavity final design and fabrication procedure have been developed in collaboration between TRIUMF and PAVAC Industries Inc. Several innovations in the cavity fabrication process were developed at PAVAC. Since the most important weld is at the equator this weld is done first to form a ‘smart-bell’ as the basic unit as opposed to welding first at the iris to form ‘dumb-bell’ units. Each half cell is pressed with a male die into a plastic forming surface to produce half-cells with less shape distortion and material dislocations. The cavity fabrication sequence including the frequency tuning steps and RF frequency modelling methods will be discussed.

THP036

Design of a 4 Rod Crab Cavity Cryomodule System for HL-LHC

cryomodule, HOM, luminosity, impedance

982

G. Burt, B.D.S. Hall
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
T.J. Jones, N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
P.A. McIntosh, S.M. Pattalwar, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
T.J. Peterson
Fermilab, Batavia, USA
L.A. Wright
CERN, Geneva, Switzerland

The LHC requires compact SRF crab cavities for the HL-LHC and 3 potential solutions are under consideration. One option is to develop a 4 rod cavity utilising for quarter wave rods to maintain a dipole field. The cavity design has been developed including power and LOM/HOM couplers have been developed, as well as a conceptual design of a complete cryomodule system including ancillaries and this is presented. The cryomodule is designed to allow easy access during testing and uses a novel support system and contains the opposing beamline section to fit inside the LHC envelope.

THP038

Development and Performance of a High Field TE-Mode Sample Host Cavity

niobium, simulation, resonance, SRF

985

D.L. Hall, M. Liepe, I.S. Madjarov, K.P. McDermott, N.R.A. Valles
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: US National Science Foundation Career award PHY-0841213
A TE-mode 4 GHz sample host cavity has been designed and constructed at Cornell for the purpose of testing wafers of niobium and other candidates for the construction of SRF cavities. Simulations made using CLANS and ACE3P indicate that the peak magnetic field on the sample plate will reach approximately 120 mT before a quench occurs on the surface of the cavity due to thermal runaway. This quench field can be further increased using a 1400 C treatment to improve the thermal conductivity of the niobium bulk and a 120 C treatment to minimise the BCS surface resistance of the cavity walls. Such an improvement would put peak fields of 170 mT within reach of this cavity. Results of the cavity design, fabrication and first vertical test are presented and discussed.
*Development of Superconducting RF Sample Host Cavities and study of Pit-Induced Cavity Quench, Yie Xie, PhD Thesis, Cornell University, Jan 2013

THP039

Design of a Triple-Spoke Cavity as a Rebuncher for RIKEN RI-Beam Factory

factory, heavy-ion, simulation, acceleration

988

L. Lu
RIKEN, Saitama, Japan
O. Kamigaito, N. Sakamoto, K. Suda, K. Yamada
RIKEN Nishina Center, Wako, Japan

A superconducting triple-spoke cavity as a rebuncher for very heavy ion beams such as uranium at β=0.303 for RIKEN RI-beam factory is designed. The required total gap voltage is 3 MV. In this design, thick ribs (25 mm) are placed on the both ends of cavity so that the deformation caused by pressure of liquid helium is less than 0.5 mm. A copper test model with one spoke is designed to be fabricated using the same technique as that for Nb cavity. The detailed design will be presented.

THP041

Optimization of the Double Quarter Wave Crab Cavity Prototype for Testing at SPS

HOM, interface, acceleration, luminosity

995

S. Verdú-Andrés, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
R. Calaga
CERN, Geneva, Switzerland
Z. Li
SLAC, Menlo Park, California, USA

Funding: Research supported by EU FP7 HiLumi LHC – No. 284404, and by US DOE through Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and the US LHC Accelerator Research Program (LARP).
The crab cavity program for LHC luminosity upgrade envisages the testing of at least one of the three competing crab cavities in the Super Proton Synchrotron (SPS) of CERN by 2016. This paper presents the design optimization of a Double Quarter Wave Crab Cavity (DQWCC) prototype suited for testing in SPS.

THP042

High Frequency SRF Cavity Study for Bunch Shortening in PEPX

HOM, SRF, FEL, simulation

998

L. Xiao, K.L.F. Bane, Y. Cai, X. Huang, C.-K. Ng, A. Novokhatski, L. Wang
SLAC, Menlo Park, California, USA

The proposed PEPX is a diffraction limited storage ring light source, or “ultimate storage ring (USR)”, which can be built in the PEP tunnel at SLAC. The 4.5GeV PEPX design based on the USR with a natural emittance about 10pm-rad can be used to drive a high-gain soft X-ray FEL. In order to achieve a desired high peak current over 300A for the FEL, the bunch length is reduced to 1ps from 10ps through a set of multi-cell SRF cavities working at 1.428GHz in CW mode, providing about 300MV RF gradient. In this paper, the 1.5GHz JLAB C100 cavity for the CEBAF upgrade and 1.3GHz Cornell ERL cavity are investigated for its application to PEPX-FEL. The simulation results show that the beam induced high order modes (HOM) in the C100 cavities will limit the threshold of the beam current for PEPX-FEL. And the same pass band modes (SPM) in the cavities are strongly trapped, and thus generate unacceptable beam power once they hit the beam resonances. Therefore, a 5-cell with a larger iris cavity design instead of the C100 7-cell design is proposed. Preliminary results on the rf parameters of the cavity, HOM damping and beam dynamics studies will be presented.

THP043

Design and Vertical Test of Double Quarter Wave Crab Cavity for LHC Luminosity Upgrade

cryogenics, simulation, pick-up, HOM

1002

B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, R. Calaga, C. Cullen, L.R. Hammons, J. Skaritka, S. Verdú-Andrés, Q. Wu
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with LARP and the U.S. DOE, and supported by EU FP7 HiLumi LHC - Grant Agreement 284404.
A proof of principle Double Quarter Wave Crab Cavity (DQWCC) was designed and fabricated for the Large Hadron Collider (LHC) luminosity upgrade. Vertical cryogenic test has been done in Brookhaven National Lab (BNL). We report the test results of this design.

THP044

Compact Higher Order Mode Filter for Crab Cavities in the Large Hadron Collider

HOM, luminosity, simulation, cryomodule

1006

B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, S. Verdú-Andrés, Q. Wu
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
R. Calaga
CERN, Geneva, Switzerland

Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with LARP and the U.S. DOE, and supported by EU FP7 HiLumi LHC - Grant Agreement 284404.
A double quarter wave crab cavity was designed for the Large Hadron Collider luminosity upgrade. Starting from the analytical calculation of simplified RLC circuit, a compact higher order mode filter is developed for this cavity. Finite element simulation results are presented. The design concept is generic and can easily be adapted to other cavities.

THP046

Magnetic Material Characterization & SC Solenoid Coil Package Design for FRIB

solenoid, shielding, operation, cryogenics

1009

K. Saito, S. Chouhan, C. Compton, J. DeKamp, M. Leitner, F. Marti, J.P. Ozelis, S. Shanab, G.J. Velianoff, X. Wu, Y. Yamazaki, A. Zeller, Y. Zhang, Q. Zhao
FRIB, East Lansing, Michigan, USA
S.K. Chandrasekaran
MSU, East Lansing, USA
K. Hosoyama
KEK, Ibaraki, Japan

To date SRF technology is extending to large scale heavy ion LINACs, where SRF cavities accelerate beams from very low energy to high energy. In this application, superconducting (SC) solenoids are installed inside the cryomodule to provide strong beam focusing with enhanced space efficiency. FRIB will use local magnetic shielding, where magnetic shielding by Cryoperm or A4K is located close to the cavity at 2K. In this scheme rather strong magnetic fringe fields from the SC solenoid expose the shielding material and will magnetize it. An efficient degaussing process is required as cure against such magnetization. Magnetic material characterization of magnetic shielding materials is very important to be able to plan effective degaussing procedures. The paper will also discuss the design of FRIB solenoids optimized for cost, reliability, and robust long-term operation. NbTi wire performance criteria are discussed in addition to solenoid operational margins.

THP047

Performance Degradation of a Superconducting Cavity Quenching in Magnetic Field

cryomodule, RF-structure, superconducting-RF, superconductivity

1013

I. Terechkine, T.N. Khabiboulline, D.A. Sergatskov
Fermilab, Batavia, USA

Although degradation of a superconducting RF (SRF) cavity performance induced by magnetic field trapped in its walls is a well understood phenomenon, a criterion for an acceptable level of magnetic field existing in the vicinity of an SRF cavity and generated after the cavity is cooled down has not been agreed upon. The bulk of superconducting Nb should protect the RF surface of the cavity from the magnetic field on the outside; nevertheless a failure mode exists when the cavity quenches while the external field is applied. The amount of trapped magnetic flux in this case depends on the size of normally conducting zone developed in walls of the cavity during quenching. Although propagation of the normally conducting zone in walls of a cavity can be modeled, no dedicated studies of this process that would include experimental verifications of its impact on the cavity performance could be found. We tried to address his issue in a special study by using as an example a superconducting coil mounted near a quenching cavity; the method and some results of the study can be applied to any RF structure and magnetic system.

THP048

The Influence of Tuners and Temperature on the Higher Order Mode Spectrum for 1.3 GHz SCRF Cavities

HOM, quadrupole, dipole, higher-order-mode

1016

R. Ainsworth
Royal Holloway, University of London, Surrey, United Kingdom
N. Baboi, M.K. Grecki, T. Wamsat
DESY, Hamburg, Germany
N. Eddy
Fermilab, Batavia, USA
S. Molloy
ESS, Lund, Sweden
P. Zhang
CERN, Geneva, Switzerland

Higher Order Modes are of concern for superconducting cavities as they can drive instabilities and so are usually damped and monitored. With special dedicated electronics, HOMs can provide information on the position on the beam. It has been proposed that piezo tuners used to keep the cavities operating at 1.3 GHz could alter the HOM spectrum altering the calibration constants used to read out the beam position affecting long term stability of the system. Also, of interest is how the cavity reacts to the slow tuner. Detuning and the retuning the cavity may alter the HOM spectrum. This is of particular interest for future machines not planning to use dedicated HOM damping as the tuning procedure may shift the frequency of HOMs onto dangerous resonances. The effect of temperature on the HOM spectrum is also investigated. An investigation of these effects has been performed at FLASH and the results are presented including numerical simulations used to predict the resulting cavity distortion.

THP049

SPL RF Coupler Cooling Efficiency

cryomodule, radiation, operation, framework

1019

R. Bonomi, O. Capatina, E. Montesinos, V. Parma, A. Vande Craen
CERN, Geneva, Switzerland

Energy saving has become an important challenge in accelerator design. In this framework, reduction of heat loads in a cryomodule is of fundamental importance due to the small thermodynamic efficiency of cooling at low temperatures. In particular, care must be taken during the design of its critical components (RF couplers, cold-warm transitions, ..). In this framework, the main RF coupler of the Superconducting Proton Linac cryomodule at CERN will not only be used for RF powering but also as the main mechanical support of the superconducting cavities. These two functions have to be accomplished while ensuring the lowest heat in-leak to the helium bath at 2 K. In the SPL design, the RF coupler outer conductor is composed of two walls and cooled by forced convection with helium gas at 4.5 K. Analytical, semi-analytical and numerical analyses are presented in order to defend the choice of gas cooling. Temperature profiles and thermal performance have been evaluated for different operating conditions; a sensitivity analysis of RF currents node position along the wall has also been performed. Finally, comparison with respect to other heat extraction methods is presented.

THP050

Development of Power Coupler for Superconducting Spoke Cavities for China ADS Proton Linac

vacuum, coupling, simulation, Windows

1024

X. Chen, T.M. Huang, H.Y. Lin, Q. Ma, F. Meng, W.M. Pan, Y.H. Peng
IHEP, Beijing, People's Republic of China

Abstract: The China-ADS proton linac adopts β=0.12 superconducting Spoke cavities. Each cavity is powered via a 325MHz coaxial power coupler. The coupler is to feed 6kW maximum power though it is designed to handle at 15kW .Two coupler sets have been made by IHEP so far, and a 10kW RF power in continuous travelling wave mode has passed through the coupler during high power test in late January 2013. An introduction of this coupler design and the room temperature test results are presented in this paper.

THP053

Development of Quality Control Procedures for the Processing of ReA3 Copper Plated Fundamental Power Coupler

controls, detector, SRF, operation

1031

R. Oweiss, J.L. Crisp, A. Facco, M. Leitner, D. Morris, J. Popielarski
FRIB, East Lansing, Michigan, USA
A. Facco
INFN/LNL, Legnaro (PD), Italy
L. Popielarski, J. Wenstrom
NSCL, East Lansing, Michigan, USA

The processing of copper plated fundamental power couplers (FPCs) has posed major risks to the successful performance of superconducting cavities. This paper discusses the lessons learnt throughout the development of quality control procedures for the ReA3 copper plated FPCs. Michigan State University (MSU) Re-Accelerator project (ReA3) utilizes eight copper plated coaxial FPCs to power the 80.5 MHz=0.085 quarter-wave resonators (QWRs) for which baseline quality control procedures are established. The effectiveness of visual inspection process using the microscope & borescope to qualify FPC components is evaluated. The adaptive use of quality control diagnostic devices as the liquid particle counter, surface particle detector & desiccator for the clean processing & assembly is assessed. A summary of the collaborative work to refine and optimize FPC design & processing in correlation to cavity performance and experimental results is presented.
*This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661.

THP054

Last Spiral 2 Couplers Preparation and RF Conditioning

vacuum, cryomodule, multipactoring, controls

1036

Y. Gómez Martínez, M.A. Baylac, P. Boge, T. Cabanel, P. De Lamberterie, M. Marton, R. Micoud
LPSC, Grenoble Cedex, France

Six crymodules are ready to be installed in the SPIRAL 2 LINAC. We present here the protocols used for the preparation and for the RF conditioning of the couplers and the obtained results.

THP055

Ferrite Covered Ceramic Break HOM Damper

gun, HOM, vacuum, damping

1040

H. Hahn, S.A. Belomestnykh, I. Ben-Zvi, L.R. Hammons, V. Litvinenko, R.J. Todd, D. Weiss, W. Xu
BNL, Upton, Long Island, New York, USA
A. Burrill
HZB, Berlin, Germany
J. Dai
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under contract no. DE-AC02-98CH10886 with the DOE.
The Brookhaven Energy Recovery Linac (ERL) is operated as R&D setup for high-current, high charge electron beams. It is comprised of a superconducting (SC) five-cell cavity and a half-cell SC photoinjector electron RF gun. Achieving the performance objectives requires effective HOM damping in the linac and gun cavity. Among the HOM dampers being developed is a beam-tube type HOM load for the electron gun consisting of a ceramic break surrounded by ferrite tiles. This design is innovative in its approach and achieves a variety of ends including broadband HOM damping and protection of the superconducting cavity from potential damage of the separately cooled ferrite tiles. The damper properties are described by the coupling impedance to a beam and the external Q to constrain the unloaded mode Q’s. Measured results for the gun damper at room and superconducting temperatures are presented

THP059

HOM Coupler Design Adjustment for CW operation of the 1.3 GHz 9-cell TESLA Type SRF Cavity

HOM, dipole, operation, simulation

1051

D. Kostin, W.-D. Möller, J.K. Sekutowicz
DESY, Hamburg, Germany

One of the key features of a modern research facility is its versatility, ability to adjust for a multitude of the applications and user needs. A challenge for the coming European XFEL is to become a multipurpose laboratory with a broad applications spectrum. Primarily, the XFEL is a pulsed machine. Encompassing the CW mode would be a worthy addition. CW operation of the 1.3GHz 9-cell TESLA Type SRF Cavity was performed several times at DESY and other Labs successfully. One of the difficulties was a heat load of the High Order Mode (HOM) couplers. To amend this HOM coupler design adjustement is proposed, simulated and modelled. Results are presented and discussed.

THP060

High Power RF Coupler for ADS Accelerating Cavities

simulation, operation, linac, Windows

1055

S.V. Kutsaev, M.P. Kelly, B. Mustapha, J.A. Nolen, P.N. Ostroumov
ANL, Argonne, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
Accelerator driven systems (ADS) require a high-power CW proton accelerator with proton beam energy near 1 GeV. High-gradient superconducting TEM-cavities are a natural choice for the front end of linac. This paper presents the design of superconducting low-beta half wave resonator operating at 162 MHz frequency for ADS, as well as a new 75 kW power coupler that has been designed at Argonne National Laboratory. This coupler would permit operations with an accelerating voltage of 3.0 MV with a beam current of 25 mA. The coupler includes a cold RF window which keeps the antenna at low temperature and a variable bellows section to adjust the coupling factor. The importance of these features for reliable operation will be discussed in detail.

THP061

Developments of HOM Dampers for SuperKEKB Superconducting Cavity

HOM, simulation, operation, factory

1058

M. Nishiwaki, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, Y. Morita
KEK, Ibaraki, Japan

Eight superconducting accelerating cavities were stably operated under a high beam current and a large beam induced HOM power in KEKB electron ring. The HOM power of 16 kW at the beam current of 1.4A was absorbed in two ferrite dampers attached to each cavity. In SuperKEKB, that is the upgrade machine of KEKB, the design beam current is 2.60 A. The HOM power of higher than 40 kW is expected to be induced. To cope with the large HOM power, precise evaluations of HOM power loads including HOM dampers were carried out. Then, new ferrite dampers with reinforced water cooling were developed and high-power tested. On the other hand, the evaluation indicated that an additional HOM damper can absorb significant amount of HOM power. Additional damper is effective to reduce each ferrite damper load. In this report, we will describe the results of high power tests of the new ferrite dampers, studies for additional dampers, and an installation plan for SuperKEKB.

THP062

Optimisation of the 3-Stub Tuner for Matching the Diamond SCRF Cavities

simulation, operation, coupling, storage-ring

1061

S.A. Pande, C. Christou, P. Gu, M. Jensen
Diamond, Oxfordshire, United Kingdom

The Diamond Storage Ring cavities are aperture coupled resulting in a fixed external Q. This results in the cavities being matched under certain conditions depending on the loss per turn, the beam current and the accelerating voltage. Operationally, there are advantages to limiting the accelerating voltage to improve reliability and lifetime, which at high beam current results in a mismatch and high reflected power. To match the cavities under such non-optimum operating conditions we use 3-stub tuners in the waveguide feeds. It has been observed, that certain configurations of the 3-stub tuners can improve the match of the cavity, but this can result in strong heating of the waveguide in the cryostat. Numerical simulations of the cavity along with the coupling waveguide and 3-stub tuners have been carried out using CST Studio for different beam loading conditions to optimise the 3-stub tuners for acceptable match and heating. In this paper we present the results of our simulations and comparisons with measurements for operation with different beam currents and cavity voltages.

THP064

HOM Couplers for CERN SPL Cavities

HOM, coupling, dipole, linac

1066

K. Papke, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
F. Gerigk
CERN, Geneva, Switzerland

Funding: Work supported by the Wolfgang-Gentner-Programme of the Bundesministerium für Bildung und Forschung (BMBF)
Higher-Order-Modes (HOMs) may affect beam stability and refrigeration requirements of superconducting proton linacs such as the SPL, which is studied at CERN as the driver for future neutrino facilities. In order to limit beam-induced HOM effects CERN considers the use of HOM couplers on the cut-off tubes of the 5-cell superconducting cavities. These couplers consist of resonant antennas shaped as loops or probes which are designed to couple to modes of a specific frequency range. In this paper the design process is presented and a comparison is made between various design options for the medium and high-beta SPL cavities, both operating at 704 MHz. The RF characteristics, thermal behaviour and multipacting sensitivity of the various designs are discussed and 2 options are presented, which will be tested as warm prototypes on 5-cell high-beta copper cavity models.

THP065

Design of 352.21 MHz RF Power Input Coupler and Window for the European Spallation Source Project (ESS)

operation, multipactoring, vacuum, SRF

1069

E. Rampnoux, S. Bousson, S. Brault, P. Duchesne, P. Duthil, G. Olry, D. Reynet
IPN, Orsay, France

A 352.21 MHz RF high power coupler window was designed by IPNO to meet the specification requirements for the ESS accelerator project. This designed is based on IPNO’s power coupler developments performed in the framework of the EURISOL Design Study project for which two power couplers using coaxial technology without chokes systems around the ceramic disc have been designed and tested successfully up to 20 kW RF power level in CW mode. For ESS project, the RF power input window was developed and designed to reliability operate at an average power level of 25 kW up to 300 kW in pulsed and continuous wave modes. This 352.21 MHz RF window was developed to remove the chocks usually used and provided the following advantages: more reliability, less expensive to manufacture, better vacuum, easier cleaning, less secondary electron-multipacting with specificity to present a bandwidth close to 1 GHz.

THP066

SARAF Phase-I HWR Coupler Cooling Design

simulation, operation, linac, proton

1073

J. Rodnizki, Y. Ben Aliz, I. Fishman, A. Grin, Z. Horvitz, B. Kaizer, L. Weissman
Soreq NRC, Yavne, Israel

The Soreq Applied Research Accelerator Facility (SARAF) design is based on a 40 MeV 5 mA light ions superconducting RF linac. Phase I of SARAF delivers up to 2 mA CW proton beam in an energy range of 1.5-4.5 MeV. The maximum beam power that we have reached is 4.5 kW. The warming of the SARAF linac RF couplers is currently the main limiting factor for reaching higher CW beam power. The coupler cooling configuration was optimized by increasing the cold window copper braid and adding a copper braid to the top end, using CST Multiphysics and ANSYS steady state and transient solvers. The study was conducted for the heat load generated by the surface currents of a matched 4 kW forward CW power, simulated by the CST MWS FD solver. Multipacting is a known potential heat source that overheats the coupler in the vicinity of the cold window. The coupler overheat phenomena was experimentally studied as a function of DC bias voltage, and it was found that a 900 V bias reduces significantly the heating rate. As a result we expect that the beam power can be significantly increased. The long overheat period implies that optimization of the cooling configuration is still needed.

THP067

Testing of Copper Plating Quality on ReA3 Coupler Bellows and Approach to Improved Plating for FRIB Production

vacuum, SRF, experiment, controls

1077

L. Popielarski, M. Goodrich, M. Hodek, I.M. Malloch, N.M. Nicholas, R. Oweiss, J. Popielarski, N. Putnam, K. Saito, D.R. Victory
FRIB, East Lansing, Michigan, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
The SRF community faces difficulties finding repeatable, quality copper plating for fundamental power coupler (FPC) components. The copper plating of ten small custom bellows of β=0.085 Quarter-Wave Resonator (QWR) variable couplers for the ReAccelerator project has presented technical challenges. An improvement plan has been established and includes: better defining plating requirements and specification, creating testing processes to assure plating quality (Acceptance Criteria Listing (ACL)), identify viable plating vendors, develop clean, robust plating fixtures, procedures and quality assurance steps with multiple vendors, and perform ACL testing on plated bellows. A total of 24 prototype and production plated bellows are analyzed through acceptance testing, which include a vacuum leak check, tape test, 1000 psi water rinse, thermal cycle at 77K, borescope inspection and final leak check. Select bellows have been processed and tested with a quarter-wave resonator. A summary of the plating improvement program, plated bellows acceptance statistics, and RF test results will be reported.

THP068

New Design of HOM Coupler Using Coaxial-like Rounded Waveguide

HOM, damping, simulation, operation

1081

M. Sawamura
Japan Atomic Energy Agency (JAEA), Gamma-ray Non-Destructive Assay Research Group, Tokai-mura, Ibaraki-ken, Japan
R. Hajima, R. Nagai, N. Nishimori
JAEA, Ibaraki-ken, Japan

It is important to damp higher-order modes (HOMs) of superconducting accelerators especially for energy-recovery linacs of high current operation. Though various types of HOM couplers, beam line HOM dampers and waveguide HOM couplers have been developed, there are some problems such as inner conductor heating of output connector for HOM couplers and low packing factor for beam line HOM dampers. We propose new design of HOM coupler. This coupler consists of a coaxial line coupled with a cavity or a beam pipe and a rounded waveguide which cuts off the accelerating mode. The rounded waveguide is similar to a coaxial line and the inner conductor and outer conductor are connected with a plate which corresponds to waveguide side wall. This enables the inner connector cooled down efficiently through the outer conductor. The calculation results of MW-STUDIO will be presented.

THP070

Analysis of High Order Modes in 1.3 GHz CW SRF Electron Linac for a Light Source

HOM, linac, dipole, emittance

1085

A.I. Sukhanov, A. Vostrikov, V.P. Yakovlev
Fermilab, Batavia, USA

Design of a Light Source (LS) based on the continuous wave superconducting RF (CW SRF) electron linac is currently underway. This facility will provide soft coherent X-ray radiation for a broad spectrum of basic research applications. Quality of the X-ray laser radiation is affected by the electron beam parameters such as the stability of the transverse beam position and longitudinal and transverse beam emittances. High order modes (HOMs) excited in the SRF structures by a passing beam may deteriorate the beam quality and affect the beam stability. Deposition of HOM energy in the walls of SRF cavities adds to the heat load of the cryogenic system and leads to the increased cost of building and operation of the linac. In this paper we evaluate effects of HOMs in an LS CW SRF linac based on Tesla-type 9-cell 1.3 GHz cavities. We analyze non-coherent losses and resonance excitation of HOMs. We estimate heat load due to the very high frequency HOMs. We study influence of the HOMs on the transverse beam dynamics.

THP071

HOM Studies of the Cornell ERL Main Linac Cavity in the Horizontal Test Cryomodule

HOM, linac, cryomodule, experiment

1090

N.R.A. Valles, R.G. Eichhorn, D.A. Goldman, G.H. Hoffstaetter, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Supported by NSF grant DMR-0807731
The Cornell energy recovery linac will accelerate a 100 mA beam to 5 GeV, while maintaining very low emittance (30 pm at 77 pC bunch charge). A major challenge to running such a large current continuously through the machine is the effect of strong higher-order modes (HOMs) in the SRF cavities that can lead to beam breakup. This paper presents the results of HOM studies for the prototype 7-cell cavity installed in a horizontal test cryomodule (HTC). HOM measurements were done for three HTC assembly stages, from initial measurements on the bare cavity to being fully outﬁtted with side-mounted RF input coupler and beam line HOM absorbers. We compare the simulated results of the optimized cavity geometry with measurements from all three HTC experiments, demonstrating excellent damping of all dipole higher order modes.

THP072

Input Coupler for Cornell ERL Main Linac

linac, cryomodule, vacuum, operation

1094

V. Veshcherevich, P. Quigley
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work is supported by the National Science Foundation grant DMR-0807731.
Each cavity of the Cornell ERL Main Linac has a single coaxial type input coupler with fixed coupling, Qext = 6.5×E7. The input coupler will operate at RF power up to 5 kW at full reflection. The coupler design is based on the design of TTF-III input coupler with appropriate modifications and with taking into account the Cornell experience with couplers for ERL Injector. Seven couplers have been fabricated by CPI, Beverly and tested at Cornell on the test stand up to 5 kW CW. No major issues were noticed during the test. One coupler was attached to the prototype linac cavity. The cavity was successfully tested with great results achieved inside the horizontal test cryomodule. Six other couplers will be installed in the Main Linac Cryomodule (MLC) Prototype.

THP073

HOM Dampers and Waveguide for the Short Pulse X-Ray (SPX) Project

HOM, cryomodule, vacuum, damping

1098

G.J. Waldschmidt, B. Brajuskovic, D.J. Bromberek, J.D. Fuerst, J.P. Holzbauer, A. Nassiri, Y. Shiroyanagi, G. Wu
ANL, Argonne, USA
V.D. Shemelin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The production of HOM dampers for the superconducting SPX cavities has been undertaken at the Advanced Photon Source. The dampers are vacuum compatible loads that utilize a four wedge design in WR284 rectangular waveguide. The rf lossy material consists of hexoloy silicon carbide (SiC) due to its suitable mechanical and electrical material properties. Issues regarding manufacturing consist of initial SiC material failure due to fabrication stresses as well as substandard soldering bonds of the SiC to the copper damper bodies. In addition, integration into the cryomodule consists of rf, thermal, and mechanical design considerations of the dampers and the waveguide transmission lines. An analysis of the manufacturing and integration issues and remedies are discussed further in this paper.

THP077

Coaxial Blade Tuner for European XFEL 3.9 GHz cavities

linac, operation, simulation, cryomodule

1101

R. Paparella, M. Bertucci, A. Bosotti
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

The European XFEL linac injector features a third harmonic section jointly realized by INFN and DESY and hosting a 3.9 GHz 9-cell cavities cryomodule. The cold tuning system, developed by INFN for these cavities, is inspired by the coaxial Blade Tuner already qualified for ILC cavities. Design, fabrication and room temperature qualification of first tuner units produced are reviewed in this paper.

THP078

Deformation Tuner Design for a Double Spoke Cavity

operation, cryomodule, SRF, linac

1104

N. Gandolfo, S. Bousson, S. Brault, P. Duchesne, P. Duthil, G. Olry, D. Reynet
IPN, Orsay, France

IPN Orsay is developing the low-beta double Spoke cavities cryomodule for the ESS. Based on previous successfully tested prototypes, a fast/slow tuner has been studied to compensate resonance frequency variations of the cavity during operation. The typical perturbations are coming from LHe pressure variations as well as microphonics and Lorentz force detuning (LFD). Two tuners are being built in order to validate both expected performances and series production feasibility. In this paper, the tuner design of the double Spoke cavity is presented.

THP079

Improvement of the Pneumatic Frequency Tuner of the Superconducting Resonators at IUAC

controls, linac, vacuum, feedback

1107

A. Pandey, G.K. Chaudhari, R.N. Dutt, S. Ghosh, D. Kanjilal, J. Karmakar, D.S. Mathuria, P. Patra, A. Rai, A. Roy, B.K. Sahu, S.K. Saini
IUAC, New Delhi, India

The existing phase locking scheme of the quarter wave resonators used in superconducting linear accelerator of Inter University Accelerator Centre consists of a fast (electronic) and a slow time scale (pneumatic) control. Presently, helium gas operated mechanical tuners are being used to phase lock the resonators against the master oscillator frequency and different ion beams have been accelerated and delivered to conduct experiments. The present pneumatic frequency tuner has two limitations: (a) no proportional flow control in vacuum condition (b) large hysteresis problem in the proportional valve responsible for gas flow control. Due to these limitations, the system becomes non-linear and the response time is very slow (~sec). Using the existing system, phase locking of a resonator becomes delicate and time consuming. In addition, it was found to be difficult to implement auto phase locking mechanism on the resonator. To overcome these problems and to improve the dynamics of the existing tuner, a new pneumatic tuning system has been adopted. Details of the existing tuning mechanism and the modified tuning system along with the test results will be presented in the paper.

THP080

SRF Cavity Tuning for Low Beam Loading

resonance, operation, cryomodule, vacuum

1110

N. Solyak, E. Borissov, I.V. Gonin, C.J. Grimm, T.N. Khabiboulline, R.V. Pilipenko, Y.M. Pischalnikov, W. Schappert, V.P. Yakovlev
Fermilab, Batavia, USA

The design of 5-cell elliptical 650 MHz β=0.9 cavities to accelerate H⁻ beam of 1 mA average current in the range 467-3000 MeV for the Project X Linac is currently under development at Fermilab. The low beam current enables cavities to operate with high loaded Q’s and low bandwidth, making them very sensitive to microphonics. Mechanical vibrations and the Lorentz force can drive cavities off resonance during operation; therefore the proper design of the tuning system is very important part of cavity mechanical design. In this paper we review the design, performance, operation, reliability and cost of fast and slow tuners for 1.3 GHz elliptical cavities. We also present a design of the slow and fast tuners for 650 MHz β=0.9 cavities based on this experience. The HV in the new design is equipped with the tuners located at the end of the cavity instead of the initially proposed blade tuner located in the middle. We will present the results of ANSYS analyses of mechanical properties of tuners.

THP081

Development of a Slow Tuner for the 162.5 MHz Superconducting Half-Wave Resonator in IMP

cryomodule, low-level-rf, controls, feedback

1115

S. He, Y. He, Y.L. Huang, L.B. Liu, F.F. Wang, R.X. Wang, X.W. Wang, W.M. Yue, S.H. Zhang, H.W. Zhao
IMP, Lanzhou, People's Republic of China

Funding: This work is supported by Strategic Priority Research Program of CAS (XDA0302)and National Natural Science Foundation of China (91026004)
Within the framework of the C-ADS project, IMP has proposed a 162.5MHz HWR Superconducting cavity for low energy section(β=0.09) of high power proton linear accelerators. A compact slow tuner has been developed for final tuning of the resonance frequency of the cavity after cooling down to operating temperature and to compensate microphonics and Lorentz force detuning. The slow tuner is driven by an external stepper motor and gear box for coarse cavity adjustment. To reduce the force requirements of the actuator, a lever arm and scissor jack mechanism have been applied. The tuner design and recent results of warm tests as the first prototype are presented.

THP082

Fast Detuning Experiment on an SRF Cavity

cryomodule, experiment, resonance, storage-ring

1118

G. Wu, N.D. Arnold, T.G. Berenc, J. Carwardine, A.R. Cours, J.D. Fuerst, J.P. Holzbauer, D. Horan, A. Nassiri
ANL, Argonne, USA
J. Matalevich
JLAB, Newport News, Virginia, USA
Y. Yang
TUB, Beijing, People's Republic of China

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Short Pulse X-ray beamlines occupy a limited number of sectors after the APS Upgrade. The majority of APS users will not participate in the SPX experiment. As user operation requires the best beam availability, it is important that any SPX-related circuit trip that requires the extinguishment of rf power should not affect overall beam availability. As such, it is necessary to de-couple the SRF cavities from beam when such an rf trip happens. An example of such trip is that the rf window arcing has to be stopped within 1 ms, before serious damage occurs to the ceramic. As the rf amplifier shuts down the rf output, beam-driven cavity power has to be reduced, too. If cavity can be detuned fast enough and far enough away from its resonance, the beam does not have to be aborted. The SPX0 tuner is equipped with a fast response Piezo actuator in the cavity tuner stack. Such a Piezo may be able to provide a quick jolt of the cavity to provide detuning capability for the purpose of maintaining the beam in the event of an rf trip. In this paper, we describe the experimental setup and results obtained, and discuss its effectiveness for beam operation.

THP084

The Tuning System for the HIE-ISOLDE High-Beta Quarter Wave Resonator

simulation, niobium, controls, LLRF

1121

P. Zhang, L. Alberty, L. Arnaudon, K. Artoos, S. Calatroni, O. Capatina, A. D'Elia, Y. Kadi, I. Mondino, T. Renaglia, D. Valuch, W. Venturini Delsolaro
CERN, Geneva, Switzerland
A. D'Elia
UMAN, Manchester, United Kingdom

Funding: Work supported in part by a Marie Curie Early Initial Training Network Fellowship of the European Community's 7th Programme under contract number PITN-GA-2010-264330-CATHI.
A new linac using superconducting quarter-wave resonators (QWR) is under construction at CERN in the framework of the HIE-ISOLDE project. The QWRs are made by Niobium sputtered on a bulk Copper substrate. The working frequency at 4.5 K is 101.28 MHz and they will provide 6 MV/m accelerating gradient on the beam axis with a total maximum power dissipation of 10 W on cavity walls. A tuning system is required in order to both minimize the forward power variation in beam operation and to compensate the unavoidable uncertainties in the frequency shift during the cool-down process. The tuning system has to fulfill a complex combination of RF, structural and thermal requirements. The paper presents the functional specifications and details the tuning system RF and mechanical design and simulations. The results of the tests performed on a prototype system are discussed and the industrialization strategy is presented in view of final production.

THP085

Equipping FLASH with MTCA.4-based LLRF System

LLRF, controls, cryomodule, feedback

1126

J. Branlard, V. Ayvazyan, L. Butkowski, M.K. Grecki, M. Hoffmann, F. Ludwig, U. Mavrič, S. Pfeiffer, K.P. Przygoda, H. Schlarb, Ch. Schmidt, H.C. Weddig
DESY, Hamburg, Germany
W. Cichalewski, D.R. Makowski, A. Piotrowski
TUL-DMCS, Łódź, Poland
K. Czuba, I. Rutkowski, D. Sikora, L. Zembala, M. Żukociński
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
I.M. Kudla
NCBJ, Świerk/Otwock, Poland
K. Oliwa, W. Wierba
IFJ-PAN, Kraków, Poland

The Free-Electron Laser in Hamburg (FLASH) is now equipped with a MicroTCA-based (MTCA.4) low-level radio frequency (LLRF) system, to replace the previous VME system and to serve as a test bench for the European X-ray Free Electron Laser (XFEL) LLRF system. This paper presents details on the new FLASH LLRF system setup, including installations inside the radiation prone tunnel environment. The benefits and preliminary results of the newly installed system are also given.

THP086

LLRF System Design and Performance for XFEL Cryomodules Continuous Wave Operation

operation, feedback, LLRF, cryomodule

1129

J. Branlard, V. Ayvazyan, L. Butkowski, K.P. Przygoda, H. Schlarb, J.K. Sekutowicz
DESY, Hamburg, Germany
W. Cichalewski, A. Piotrowski
TUL-DMCS, Łódź, Poland
W. Jałmużna
Embedded Integrated Control Systems GmbH, Hamburg, Germany
J. Szewiński
NCBJ, Świerk/Otwock, Poland

The Cryomodule Test Bench (CMTB) at DESY is equipped with a 100 kW Inductive Output Tube (IOT) allowing the test of superconducting cryomodules in continuous wave (CW) operation mode. Although significantly different from the nominal pulsed operation mode of the European X-Ray Free Electron Laser (XFEL), CW operation can be handled by the same Low-level Radio Frequency (LLRF) system, within minor firmware modifications. The hardware details of the LLRF setup at CMTB, the firmware and software architecture and performance results from the last CW test are presented in this contribution.

THP087

LLRF Tests of XFEL Cryomodules at AMTF: First Experimental Results

cryomodule, LLRF, resonance, operation

1132

J. Branlard, V. Ayvazyan, M.K. Grecki, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
W. Cichalewski, K. Gnidzińska, A. Piotrowski, K.P. Przygoda
TUL-DMCS, Łódź, Poland
W. Jałmużna
Embedded Integrated Control Systems GmbH, Hamburg, Germany

In preparation for the series production of cryomodules for the European X-ray Free Electron Laser (XFEL), three pre-series cryomodules and several prototypes have been produced and tested at the Cryomodule Test Bench (CMTB) and at the Accelerating Module Test Facility (AMTF) in DESY. Among the numerous tests performed on the modules, the low-level radio frequency (LLRF) tests aim at characterizing the performance of the modules from an RF controls perspective. These integration tests must take into account cavity tuners, cavity motorized couplers, quench gradients, microphonics, piezo control and the overall gradient performance of the cryomodule under test. In this paper, the LLRF-specific tests are summarized and the first experimental results obtained at CMTB and AMTF are presented.

THP093

Fundamental Mode Spectrum Measurement of RF Cavities with RLC Equivalent Circuit

cryomodule, software, electron, pick-up

1141

K. Kasprzak, M. Wiencek
IFJ-PAN, Kraków, Poland

The procedure of the cavity fundamental mode spectrum measurement consists of the following steps: scanning of the accelerating mode passband for any deviation from the standard one, determining all peaks in the accelerating mode passband and evaluating the mean spectrum frequency deviation. The upgrade of that procedure was proposed and successfully implemented. The cavity RLC equivalent circuit is used in order to predict the measured peaks. This method allows more quickly detects the peaks in the accelerating mode passband thereby reduce the time needed for test, which is crucial for serial production cavities testing. In this paper, an upgrade of the test procedure and its validation with measurements is presented. The method was validated with data taken during testing of the cavities installed in two pre-series XFEL cryomodules. This improvement of the test procedure is implemented into the testing software and it is successfully used for serial production cavities testing.

THP094

Beam Induced HOM Analysis in STF

HOM, dipole, alignment, cryomodule

1144

A. Kuramoto
Sokendai, Ibaraki, Japan
H. Hayano
KEK, Ibaraki, Japan

Requirements of superconducting cavity (SC) alignment for ILC are less than 300 μm offset and 300 μrad tilt with respect to cryomodule. It is necessary to measure their offset and tilt inside of cryomodule. Cavity offset has been already measured by using beam induced HOM at FLASH in DESY. Cavity deformation during assembly and by cooling contraction has not been examined yet. To detect their tilt and bending, we measured HOM signals with beam trajectory sweep. Our interesting modes are pi over nine mode in the first dipole passband (TE111-1) which is trapped mode has maximum radial electric field in the middle cell and beam pipe modes localized in the both end-group of the SC. These modes tell us electrical center of middle cell and electrical centers at both beam pipe. We can know cavity tilt and bending from combinations of them. The experiment to find these HOM was performed at STF accelerator. Electron beam extracted from the RF Gun was accelerated to 40 MeV by the SC cavities. We could find TE111-1 and beam pipe modes. These HOM signals were correlated with beam orbit, accelerating field gradient. The detailed data analysis is introduced in this paper.

THP095

Error Analysis for Vertical Test Stand Cavity Measurements at Fermilab

detector, resonance, simulation, SRF

1148

O.S. Melnychuk
Fermilab, Batavia, USA

Overview of Vertical Test Stand (VTS) facility at Fermilab is presented. Uncertainty calculations for the measurements of quality factor and accelerating field are described Sources of uncertainties and assumptions on their correlations are reviewed. VTS hardware components with non-negligible instrumental errors are discussed. Relative contributions of individual sources to the total uncertainties are assessed. Stability of VTS test results with respect to potential mismeasurements of calibration coefficients and decay constant are studied.

THP096

Recent Upgrade of Ultra-Broadband RF System for Cavity Characterization

controls, software, operation, pick-up

1151

S. Stark, V. Palmieri, A.M. Porcellato, A.A. Rossi
INFN/LNL, Legnaro (PD), Italy
V. Palmieri
Univ. degli Studi di Padova, Padova, Italy

The first computer controlled RF system for SC cavity characterization entered into operation at INFN-LNL in 1994. Since then it has been successfully used for testing SC cavities of different shapes and frequencies. Recently we performed an important upgrade on it in order to cover a wider frequency range and to take advantage of the better performance of nowadays electronic devices. The paper describes the present system layout, dedicated software, sequences of calibration and testing procedures and moreover discusses further upgrading possibilities.

THP097

Use of Waveguide Probes as Beam position and Tilt Monitoring Diagnostics with Baseline and Alternative Superconducting Deflecting Cavities for the APS Upgrade

monitoring, diagnostics, dipole, HOM

1155

X. Sun, G. Decker, G. Wu
ANL, Argonne, USA

Funding: *Work supported by U.S. Department of Energy, Office of Science, under Contract No. DE-AC-02-06CH11357.
A set of superconducting deflecting cavities were studied for the APS Upgrade. A TM-mode baseline deflecting cavity design has been developed and prototyped, while an alternative design based on a TE-like mode is being studied. Waveguide field probes associated with the baseline and alternative superconducting deflecting cavities are explored as beam position and tilt monitoring diagnostics. Microwave Studio was used to simulate the technique of detecting the fields excited by a Gaussian bunch passing through the cavities to determine beam position relative to the electrical center. Probes installed on the horizontal midplane in the beam pipe are promising diagnostics for monitoring beam position and tilt in both designs. The probes in the power coupler also work as beam position monitors for the alternative deflecting cavities.

THP098

LLRF and Data Acquisition Systems for Spoke012 Cavity Vertical Test at IHEP

LLRF, interface, LabView, data-acquisition

1158

J.P. Dai, H. Huang, H. Li, H.Y. Lin, P. Sha, Y. Sun, Q.Y. Wang, J. Zhang
IHEP, Beijing, People's Republic of China

Development of two Spoke 012 cavities and their vertical tests have been completed successfully at IHEP with a LLRF system and DAQ (data acquisition) system specially designed. The LLRF system is developed on the basis of the proven analog system used for the test of the BEPCII 500 MHz spare cavity. The Labview 2009-based DAQ system is in charge of the communications of the measuring instruments, the local machine and the remote machine. It also completes drawing the test curve online and obtaining the test result in real time. The data connection between Labview and EPICS is implemented. The vertical test result shows that the LLRF system and the DAQ system in operation perform stably and reliably as expected. This paper introduces the two systems and the general situation for Spoke 012 cavity vertical test.

FRIOA01

LHC Crab Cavity .Progress and Outlook

luminosity, cryomodule, dipole, operation

1161

R. Calaga, E. Jensen
CERN, Geneva, Switzerland

Three novel superconducting RF crab cavity designs proposed for the LHC luminosity upgrade have rapidly progressed. First Niobium prototypes are reaching close to the design performance and beyond. The highlights of the RF test results from the prototypes along with design modifications for initial beam tests in the SPS are presented. The status of the cryomodule development, integration into the SPS and the beam tests in view of validating the crab cavity system for LHC upgrade are addressed.

Slides FRIOA01 [12.063 MB]

FRIOA02

Developing Quarter Wave SRF Cavities for Hadron Colliders

HOM, electron, collider, SRF

1165

Q. Wu
BNL, Upton, Long Island, New York, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with LARP and the U.S. DOE
Quarter Wave Resonators (QWRs) have been widely used in low-beta accelerators around the world because of their compact size at low frequency. Recently, application of QWRs is carrying over into hadron colliders aiming at various goals. A 56 MHz superconducting QWR is under testing at Brookhaven National Lab (BNL). It will be installed in the Relativistic Hadron Ion Collider (RHIC) as a storage cavity, which would be the first QWR operating in a high energy storage ring. A Compact crab cavity using QWR concept is another active SRF project at BNL. This crab cavity is a candidate for the Large Hadron Collider HiLumi upgrade, as well as for the future electron-ion collider (eRHIC). We report the design, fabrication, and testing results for the QWRs for hadron colliders under development at BNL.

Slides FRIOA02 [10.542 MB]

FRIOA03

Fabrication and Testing of Deflecting Cavities for APS

operation, coupling, niobium, SRF

1170

J.D. Mammosser
JLab, Newport News, Virginia, USA
P. Dhakal, J. Henry, R.A. Rimmer, H. Wang, K.M. Wilson
JLAB, Newport News, Virginia, USA
J.F. Fuerst, J.P. Holzbauer, J.S. Kerby, A. Nassiri, G.J. Waldschmidt, G. Wu, Y. Yang
ANL, Argonne, USA
F. He
PKU, Beijing, People's Republic of China
Z. Li
SLAC, Menlo Park, California, USA

Abstract Jefferson Lab in Newport News, Virginia, in collaboration with Argonne National Laboratory, Argonne, Il, has fabricated and tested three production, 2.815 GHz crab cavities for Argonne’s Short-Pulse X-ray project. These cavities are unique in that the cavity and waveguides were milled from bulk large grain niobium ingot material directly from 3D CAD files. No forming of sub components was used with the exception of the beam-pipes. The cavity and helium vessel design along with the RF performance requirements makes this project extremely challenging for fabrication. Production challenges and fabrication techniques as well as testing results will be discussed in this paper.

Slides FRIOA03 [22.677 MB]

FRIOA04

Superconducting RF-Dipole Deflecting and Crabbing Cavities

dipole, HOM, impedance, luminosity

1176

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA

Recent interests in designing compact deflecting and crabbing structures for future accelerators and colliders have initiated the development of novel rf structures. The superconducting rf-dipole cavity is one of the first compact designs with attractive properties such as higher gradients, higher shunt impedance, the absence of lower order modes and widely separated higher order modes. Two rf-dipole designs of 400 MHz and 499 MHz have been designed, fabricated and tested as proof-of-principle designs of compact deflecting and crabbing cavities for the LHC high luminosity upgrade and Jefferson Lab 12 GeV upgrade. The first rf tests have been performed on the rf-dipole geometries at 4.2 K and 2.0 K in a vertical test assembly with excellent results. The cavities have achieved high gradients with high intrinsic quality factors, and multipacting levels were easily processed.

Slides FRIOA04 [6.218 MB]

FRIOB01

SRF Cavities for Future Ion Linacs

cryomodule, linac, ion, SRF

1183

Z.A. Conway, G.L. Cherry, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.H. Kim, S.V. Kutsaev, R.C. Murphy, B. Mustapha, P.N. Ostroumov, T. Reid
ANL, Argonne, USA

There is considerable interest worldwide in the applications of high-intensity (>5 mA) high-energy (>200 MeV) ion accelerators and the research which could be done with these machines. This presentation will present results of the three year ANL study funded specifically to make possible substantial reductions in the size and cost for future ion linacs in the region beta < 0.5. Applications include basic research, medical isotope production, and accelerator driven systems. High-performance low-beta resonators are key components of all of these machines. Recent 72.75 MHz, β = 0.077, quarter-wave resonator cold test results, designs and their impact on next generation ion accelerators are discussed. Peak fields in excess of 166 mT and 117 MV/m have been achieved and future work to improve upon this will be discussed.

Slides FRIOB01 [3.833 MB]

FRIOB02

Development and Performance of 325 MHz Single Spoke Resonators for Project X

operation, vacuum, niobium, electron

1187

L. Ristori, M.H. Awida, P. Berrutti, C.M. Ginsburg, I.V. Gonin, T.N. Khabiboulline, M. Merio, T.H. Nicol, D. Passarelli, A.M. Rowe, D.A. Sergatskov, A.I. Sukhanov, V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy.
Two types of single spoke resonators will be utilized for beam-acceleration in the low energy part of the Project X linac. SSR1 and SSR2 operate at 325 MHz and at an optimal beta of 0.22 and 0.51 respectively. After the initial phase of prototyping, a production run of 10 SSR1 resonators was recently completed in US industry. The qualification of this group of resonators in the Fermilab VTS is proceeding successfully and nearly complete. The first qualified resonator has been outfitted with a Stainless Steel helium vessel. Preliminary test results for the first jacketed SSR1 are presented. The first RF power couplers were ordered, the design of the double-lever tuning mechanism is almost complete.

Slides FRIOB02 [8.800 MB]

FRIOB03

Development of 650 MHz Cavities for the GeV Proton Accelerator in Project X

SRF, electron, HOM, proton

1193

S.S. Som, P. Bhattacharyya, A. Dutta Gupta, S. Ghosh, A. Mandal, S. Seth
VECC, Kolkata, India

Funding: DAE, Government of India
Project X is a GeV range high intensity proton linear accelerator being developed at Fermilab, USA in collaboration with various American and Indian laboratories as well. In stage-1 of the project, the CW linac structures with different velocity factor (beta) accelerate proton up to 3 GeV at an average beam current of 1 mA. For acceleration from 180 to 480 MeV,the development of 650 MHz, beta 0.61, 5-cell elliptical SRF cavities has been taken up by VECC. The EM design and analysis of this cavity, carried out using 2D and 3D codes, will be discussed along with its structural and mechanical modal analysis. This design has been compared with the designs made by JLab and Fermilab. The presence of higher order modes (HOMs)for the said cavity has been thoroughly examined. The multipacting analysis will be presented using 2D code and also 3D CST Particle Studio code with due consideration of Furman model for secondary electron emission comprising of true, elastic and rediffused secondary electrons. The prototype development and low power testing of this cavity will be discussed here. The talk will be concluded with the probable SRF challenges to be faced in the development of the cavity.

Slides FRIOB03 [39.119 MB]

FRIOB04

CERN Developments for 704 MHz Superconducting Cavities

niobium, operation, linac, proton

1198

O. Capatina, G. Arnau-Izquierdo, S. Atieh, I. Aviles Santillana, R. Bonomi, S. Calatroni, J.K. Chambrillon, R. Garoby, F. Gerigk, M. Guinchard, T. Junginger, M. Malabaila, L. Marques Antunes Ferreira, S. Mikulas, V. Parma, T. Renaglia, K.M. Schirm, T. Tardy, M. Therasse, A. Vacca, N. Valverde Alonso, A. Vande Craen
CERN, Geneva, Switzerland
F. Pillon
Kraftanlagen Nukleartechnik GmbH, Heidelberg, Germany

The Superconducting Proton Linac (SPL) is an R&D effort coordinated by CERN in partnership with other international laboratories. It is aiming at developing key technologies for the construction of a multi-megawatt proton linac based on state-of-the-art RF superconducting technology, which would serve as a driver in new physics facilities for neutrinos and/or Radioactive Ion Beam (RIB). Amongst the main objectives of this R&D effort, is the development of 704 MHz bulk niobium β=1 elliptical cavities, operating at 2 K with a maximum accelerating gradient of 25 MV/m, and the testing of a string of cavities integrated in a machine-type cryomodule. The cavity together with its helium tank had to be carefully designed in coherence with the innovative design of the cryomodule. New fabrication methods have also been explored. Five such niobium cavities and two copper cavities are in fabrication. The key design aspects are discussed, the results of the alternative fabrication methods presented and the status of the cavity manufacturing and surface preparation is detailed.

Slides FRIOB04 [8.677 MB]

FRIOC01

Design of the 352 MHz, Beta 0.50, Double-Spoke Cavity for ESS

cryomodule, simulation, operation, niobium

1212

P. Duchesne, S. Bousson, S. Brault, P. Duthil, G. Olry, D. Reynet
IPN, Orsay, France
S. Molloy
ESS, Lund, Sweden

The ESS proton accelerator contains a superconducting sector consisting in three families of superconducting radiofrequency (SRF) bulk niobium cavities, operating at a nominal temperature of 2K: a family of Spoke cavities for the medium energy section followed by two families of elliptical cavities for higher energies. The superconducting Spoke section, having a length of 58.6m, consists of 14 cryomodules, each of them housing two 352.2 MHz β=0.50 Double-Spoke Resonators (DSR). The operating accelerating field is 8MV/m. The choice of the Spoke technology is guided by the high performances of such structures. Benefitting from 10 years of extensive R&D experience carried out at IPNO, the electromagnetic design studies came out with a solution that fulfills requirements of beam dynamics analysis and manufacturing considerations. Pursuing the same objective, the mechanical design of the cavity and its helium vessel were optimized by performing intensive coupled RF-mechanical simulations. We propose to present a review of the RF and mechanical design studies of the Spoke cavity. We will conclude with the integration of the Spoke cavity with its ancillaries inside the cryomodule.

Slides FRIOC01 [6.321 MB]

FRIOC02

ESS Elliptical Cavities and Cryomodules

HOM, cryomodule, proton, cryogenics

1218

G. Devanz, P. Bosland, M. Desmons, P. Hardy, F. Leseigneur, M. Luong, F. Peauger, J. Plouin, D. Roudier
CEA/DSM/IRFU, France
N. Bazin
CEA/IRFU, Gif-sur-Yvette, France
G. Costanza
Lund University, Lund, Sweden
G. Olivier
IPN, Orsay, France

The accelerator of the European Spallation Source (ESS) is a 5 MW proton linac to be built in Lund Sweden. Its superconducting section is composed of 3 cavity families: double spoke resonators, medium beta and high beta elliptical multicell cavities. This paper presents the electromagnetic and mechanical design of the 704.42 MHz elliptical cavities. Both elliptical famillies are housed in 4-cavity cryomodules which share a common design and set of components which will be described here.

Slides FRIOC02 [3.475 MB]