SRF2013 - List of Keywords (SRF)

Paper	Title	Other Keywords	Page
MOIOA04	SRF Challenges for Energy Recovery Linacs	cavity, 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]

MOIOB01	High Power Proton/Deuteron Accelerators	linac, proton, operation, cavity	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	cavity, cathode, laser, emittance	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, cavity, 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	controls, cavity, 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]

MOP004	The ESS Superconducting Linear Accelerator	cryomodule, linac, cavity, 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.

MOP007	The Status of Superconducting Linac and SRF Activities at the SNS	linac, cryomodule, cavity, operation	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.

MOP014	Cold Tests of SSR1 Resonators for PXIE	cavity, radiation, vacuum, cryomodule	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	cavity, cryomodule, linac, 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	cavity, 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	gun, electron, cavity, 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.

MOP024	Novel SRF Gun Design	gun, cathode, cavity, 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, cavity, cryomodule, 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.

MOP026	Emittance Compensation for an SRF Photo Injector	solenoid, gun, emittance, cathode	151
	H. Vennekate, A. Arnold, P.N. Lu, P. Murcek, J. Teichert, R. Xiang HZDR, Dresden, Germany P. Kneisel JLAB, Newport News, Virginia, USA I. Will MBI, Berlin, Germany
	Funding: European Community-Research Infrastructure Activity under the FP7 program (EuCARD, contract number 227579), German Federal Ministry of Education and Research grant 05 ES4BR1/8 A lot of the future electron accelerator projects such like ERLs, high power FELs and also some of the new collider designs rely on the development of particle sources which provide them with high average beam currents at high repetition rates, while maintaining a low emittance. SRF photo injectors represent a promising concept to give just that, offering the option of a continuous wave operation with high bunch charges. Nevertheless, emittance compensation for these electron guns, with the goal to reach the same level as normal conducting sources, is an ongoing challenge. The poster is going to discuss several approaches for the 3-1/2-cell SRF gun installed at the accelerator facility ELBE at the Helmholtz Center Dresden-Rossendorf including the installation of a superconducting solenoid within the injector’s cryostat and present the currently used method to determine the beam’s phase space.

MOP027	BNL SRF Gun Commissioning	gun, cathode, cavity, 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.

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, cavity, linac, 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.

MOP038	Series Production of EXFEL 1.3 GHz SRF Cavities at E. Zanon: Management, Infrastructures and Quality Control	cavity, 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.

MOP042	Quality Control and Processes Optimization for the EXFEL Superconducting Cavities Series Production at Ettore Zanon spa	cavity, controls, operation, vacuum	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.

MOP044	Performance Characteristics of Jefferson Lab’s New SRF Infrastructure	cavity, 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.

MOP052	RF Aspects of Quality Control for Industrial XFEL Cavities Fabrication	cavity, controls, background, 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	cavity, 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.

MOP059	Management for the Long-Term Reliability of the Diamond Superconducting RF Cavities	cavity, vacuum, 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, cryomodule, cavity	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	cavity, 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	operation, vacuum, cavity, 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.

MOP073	IHEP 1.3 GHz Low Loss Large Grain 9-cell Cavity Fabrication, Processing and Test	cavity, HOM, 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.

MOP086	Integration, Commissioning and Cryogenics Performance of the ERL Cryomodule Installed on ALICE-ERL Facility at STFC Daresbury Laboratory, UK	cryomodule, cryogenics, HOM, linac	349
	S.M. Pattalwar, R.K. Buckley, P.A. Corlett, P. Goudket, A.R. Goulden, A.J. May, P.A. McIntosh, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S.A. Belomestnykh BNL, Upton, Long Island, New York, USA A. Büchner, F.G. Gabriel, P. Michel HZDR, Dresden, Germany E.P. Chojnacki, J.V. Conway, R.G. Eichhorn, G.H. Hoffstaetter, M. Liepe, H. Padamsee, P. Quigley, J. Sears, V.D. Shemelin Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA M.A. Cordwell, T.J. Jones, L. Ma, A.J. Moss, J. Strachan STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom J.N. Corlett, D. Li, S.M. Lidia LBNL, Berkeley, California, USA T. Kimura Stanford University, Stanford, California, USA R.E. Laxdal TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada J.K. Sekutowicz DESY, Hamburg, Germany T.J. Smith SLAC, Menlo Park, California, USA
	On successful assembly and preliminary testing of an optimised SRF cryomodule for application on ERL accelerators, which is being developed through an international collaboration the cryomodule has been installed on the 35 MeV ALICE (Accelerators and Lasers in Combined Experiments) Energy Recovery Linac (ERL) facility at STFC Daresbury Laboratory. Existing cryogenic infrastructure has a capacity to deliver approximately 120 W cooling power at 2 K, but the HOM (Higher Order Mode) absorbers, the thermal intercepts for the high power RF couplers and the radiation shield in the cryomodule are designed to be cooled (to 5 K and 80 K) with gaseous helium instead of liquid nitrogen. As a result the cryogenic infrastructure for ALICE had to be modified to meet these additional requirements. In this paper we describe our experience with the process of integration and the cryogenic commissioning, and present some initial results.

MOP087	Conceptual Design of a Cryomodule for Compact Crab Cavities for Hi-Lumi LHC	cryomodule, cavity, cryogenics, 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.

TUIOA01	Influence of the Couldown at the Transition Temperature on the SRF Cavity Quality Factor	cavity, shielding, niobium, 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]

TUIOA05	New Insights Into Quench Caused by Surface Pits in SRF Cavities	cavity, niobium, laser, 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]

TUIOB01	R&D Progress in SRF Surface Preparation With Centrifugal Barrel Polishing (CBP) for both Nb and Cu	cavity, 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	cavity, niobium, 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]

TUIOC04	Analysis of Post-Wet-Chemistry Heat Treatment Effects on Nb SRF Surface Resistance	cavity, 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	cavity, induction, vacuum, niobium	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	cavity, niobium, electron, experiment	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]

TUP008	Models of the Magnetic Field Enhancement at Pits	cavity, 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)

TUP010	Simulation of Non-linear RF Losses Derived from Characteristic Nb Topography	cavity, simulation, niobium, 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.

TUP011	A Parametric Study of BCS RF Surface Impedance with Magnetic Field Using Xiao Code	impedance, niobium, superconductivity, survey	444
	C.E. Reece JLab, Newport News, Virginia, USA B. P. Xiao JLAB, Newport News, Virginia, USA B. P. Xiao BNL, Upton, Long Island, New York, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. A recent new analysis of field-dependent BCS RF surface impedance based on moving Cooper pairs has been presented.* Using this analysis coded in Mathematica™, survey calculations have been completed which examine the sensitivities of this surface impedance to variation of the BCS material parameters and temperature. The results present a refined description of the “best theoretical” performance available to potential applications with corresponding materials. * Xiao B. P. et al, Physica C: Superconductivity, 490, 2013, pp. 26–31

TUP015	Bitter Decoration Studies of Magnetic Flux Penetration Into Cavity Cutouts	experiment, cavity, 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	cavity, 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, cavity, 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, cavity, 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	cavity, 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.

TUP023	Evidence of Magnetic Breakdown on the Defects With Thermally Suppressed Critical Field in High Gradient SRF Cavities	site, superconducting-RF, superconductivity, niobium	472
	G.V. Eremeev, 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. At SRF 2011 we presented the study of quenches in high gradient SRF cavities with dual mode excitation technique[]. The data differed from measurements done in 80’s that indicated thermal breakdown nature of quenches in SRF cavities. In this contribution we present analysis of the data that indicates that our recent data for high gradient quenches is consistent with the magnetic breakdown on the defects with thermally suppressed critical field. From the parametric fits derived within the model we estimate the critical breakdown fields and RF resistances at the breakdown site. [] G. Eremeev et al.,. In Proceedings of the 15th Superconducting RF conference,pp. 746-749, July 2011.

TUP026	Performance of a FNAL Nitrogen Treated Superconducting Niobium Cavity at Cornell	cavity, niobium, 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	cavity, niobium, 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	cavity, resonance, superconducting-RF, 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	cavity, vacuum, 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, cavity, experiment, 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

TUP037	Dynamic Hardening Rule; a Generalization of the Classical Hardening Rule for Crystal Plasticity	experiment, simulation, controls, niobium	499
	A. Mapar, F. Pourboghrat MSU, East Lansing, USA T.R. Bieler Michigan State University, East Lansing, 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. The mechanical properties of a niobium (Nb) specimen can change with the orientation of the sheet. This anisotropy causes inhomogeneity in manufactured SRF cavities. Large grain Nb sheets are more anisotropic and less expensive than fine grain sheets. Designing a manufacturing process for large grain Nb sheets, however, is extremely complex, and requires using advance modeling techniques. A model capable of accurately predicting the deformation behavior of Nb can help improve the performance and reduce costs of a SRF cavity. Optimal design of the manufacturing of cavities with tube hydroforming process is possible with such a model. Crystal plasticity modeling of FCC materials has been very successful; however, there is still no model that can accurately predict the deformation behavior of BCC materials like the large grain Nb sheet. In this study, authors have proposed a dynamic hardening rule for crystal plasticity that significantly improves predictions of the model for large grain Nb. This model is the generalization of the classical hardening rule, and gives better control over the hardening rate. It also increases the stability of the model.

TUP043	Nanostructural TEM/STEM Studies of Hot and Cold Spots in SRF Cavities	niobium, cavity, electron, 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.

TUP046	Vertical Electropolishing of SRF Cavities and its Parameters Investigation	cavity, cathode, superconductivity, 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, simulation, cavity, 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.

TUP049	Cornell VEP Update, VT Results and R&D on Nb Coupon	cavity, cathode, 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.

TUP054	Electropolishing of Niobium SRF Cavities in Low Viscosity Aqueous Electrolytes Without Hydrofluoric Acid	cavity, niobium, 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	cavity, niobium, 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.

TUP058	Recent Findings on Nitrogen Treated Niobium	niobium, cavity, 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	cavity, vacuum, 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	cavity, niobium, 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	cavity, neutron, 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.

TUP063	Quench Studies and Preheating Analysis of Seamless Hydroformed Cavities Processed at Jefferson Laboratories	cavity, 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)	cavity, niobium, 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, cavity, 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, cavity, 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.

TUP068	Laser Polishing of Niobium for SRF Applications	laser, niobium, experiment, simulation	593
	L. Zhao, M.J. Kelley The College of William and Mary, Williamsburg, USA M.J. Kelley, J.M. Klopf, C.E. Reece JLAB, Newport News, Virginia, USA L. Zhao JLab, Newport News, Virginia, USA
	Smooth interior surfaces are desired for niobium SRF cavities, now obtained by buffered chemical polish (BCP) and/or electropolish (EP). Laser polishing is a potential alternative, having advantages of speed, freedom from chemistry and in-process inspection. Here we show that laser polishing can produce smooth topography with Power Spectral Density (PSD) measurements similar to that obtained by EP. We studied the influence of the laser power density and laser beam raster rate on the surface topography. These two factors need to be combined carefully to smooth the surface without damaging it. Computational modeling was used to simulate the surface temperature and explain the mechanism of laser polishing.
	Poster TUP068 [1.011 MB]

TUP070	Characterization of Superconducting Samples With SIC System for Thin Film Developments: Status and Recent Results.	niobium, cavity, ECR, 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.

TUP072	Quality Factor Measurements of the Ultramet 3 GHz Cavity Constructed Using Chemical Vapour Deposition	cavity, niobium, 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	cavity, niobium, vacuum, cathode	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.

TUP075	Design and Commissioning Status of New Cylindrical HiPIMS Nb Coating System for SRF Cavities	cavity, niobium, ion, cathode	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.

TUP077	Thin Film Coating Optimization for HIE-ISOLDE SRF Cavities: Coating Parameters Study and Film Characterization	cavity, cathode, niobium, hardware	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.

TUP079	ECR Nb Films Grown on Amorphous and Crystalline Cu Substrates: Influence of Ion Energy	ion, ECR, interface, electron	631
	A-M. Valente-Feliciano, G.V. Eremeev, H.L. Phillips, C.E. Reece JLAB, Newport News, Virginia, USA C. Cao Illinois Institute of Technology, Chicago, IL, USA Th. Proslier ANL, Argonne, USA J.K. Spradlin JLab, Newport News, Virginia, USA T. Tao UIC, Chicago, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. In the pursuit of niobium (Nb) films with similar performance with the commonly used bulk Nb surfaces for Superconducting RF (SRF) applications, significant progress has been made with the development of energetic condensation deposition techniques. Using energetic condensation of ions extracted from plasma generated by Electron Cyclotron Resonance, it has been demonstrated that Nb films with good structural properties and RRR comparable to bulk values can be produced on metallic substrates. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. Particular attention is given to the nucleation conditions to create a favorable template for growing the final surface exposed to SRF fields. The influence of the deposition energy for both hetero-epitaxial and fiber growth modes on copper substrates is investigated with the characterization of the film surface, structure, superconducting properties and RF performance.

TUP081	Chemical Vapor Deposition Techniques for the Multilayer Coating of Superconducting RF Cavities	niobium, cavity, 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	cavity, 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	cavity, niobium, cryogenics, 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.

TUP084	Reciprocal Space XRD Mapping with Varied Incident Angle as a Probe of Structure Variation within Surface Depth	lattice, software, survey, electron	651
	X. Zhao JLab, Newport News, Virginia, USA M. Krishnan AASC, San Leandro, California, USA C.E. Reece JLAB, Newport News, Virginia, USA F. Williams, Q.G. Yang NSU, 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 In this study, we used a differential-depth X-Ray diffraction Reciprocal Spacing Mapping (XRD RSM) technique to investigate the crystal quality of a variety of SRF-relevant Nb film and bulk materials. By choosing different X-ray probing depths, the RSM study successfully revealed the materials’ microstructure evolutions after different materials processes, such as energetic condensation or surface polishing. The RSM data clearly measured the materials’ crystal quality at different thickness. Through a novel differential-depth RSM technique, this study found: I. for a heteroepitaxy Nb film Nb(100)/MgO(100), the film thickening process, via a cathodic arc-discharge Nb ion deposition, created a near-perfect single crystal Nb on the surface’s top-layer; II. for a mechanic polished single-crystal bulk Nb material, the microstructure on the top surface layer is more disordered than that in-grain.

TUP086	Cryogen-Free RF System Studies Using Cryocooler-Cooled Magnesium Diboride-Coated Copper RF Cavities	cavity, niobium, cryomodule, 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	cavity, niobium, 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	cavity, 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.

TUP096	High Power Processing at a High Order Mode Frequency	HOM, cavity, gun, 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	cavity, niobium, 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).

TUP103	Calibration and Characterization of Capacitive OST Quench Detectors in SRF Cavities at IPN Orsay	detector, cavity, 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	cavity, detector, 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	cavity, 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.

TUP111	Experimental Investigations of the Quench Phenomena for the Quench Localization by the Second Sound Wave Method	cavity, 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	cavity, 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.

WEIOA01	HiPIMS: a New Generation of Film Deposition Techniques for SRF Applications	ion, cavity, 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]

WEIOA04	Nb3Sn for SRF Application	niobium, cavity, 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	cavity, 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, shielding, cavity, 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]

WEIOC02	Multilayers Activities at Saclay / Orsay	niobium, cavity, 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	niobium, cavity, 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]

THIOB02	High Q Cavities for the Cornell ERL Main Linac	cavity, linac, cryomodule, 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]

THIOC03	Superconducting Photonic Band Gap Structures for High-Current Applications	cavity, 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]

THIOD01	SRF Cavities for ADS Project in China	cavity, linac, 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]

THIOD03	Cavity Development for the Linear IFMIF Prototype Accelerator	cavity, niobium, cryomodule, simulation	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]

THP001	Development of a Prototype SRF Cavity for the Proton Beam Utilization Facility at Nanjing University	cavity, HOM, 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.

THP011	Improving Gradient of 9-cell SRF Cavities at Peking University	cavity, 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	cavity, cryomodule, operation, vacuum	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.

THP017	Mechanical Study on the Cavity Package of 1.3 GHz Superconducting Accelerating Unit at IHEP	cavity, simulation, cryomodule, 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.

THP019	1.3 GHz SRF Cavity Tests for ARIEL at TRIUMF	cavity, TRIUMF, HOM, linac	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.

THP026	Cage Cavity: A Low Cost, High Performance SRF Accelerating Structure	cavity, 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.

THP030	Superconducting RF Cavity Development With UK Industry	cavity, 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	cavity, 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.

THP035	Production of a 1.3 GHz Niobium 9-cell TRIUMF-PAVAC Cavity for the ARIEL Project	cavity, TRIUMF, ion, monitoring	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.

THP038	Development and Performance of a High Field TE-Mode Sample Host Cavity	cavity, niobium, simulation, resonance	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

THP040	3D MULTIPACTING STUDY FOR THE ROSSENDORF SRF GUN	electron, simulation, gun, cathode	991
	E.T. Tulu, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany A. Arnold HZDR, Dresden, Germany
	Funding: *This work is supported by Federal Ministry for Research and Education BMBF Electron multipacting is still observed in the Rossendorf SRF gun which limits the cavity fields (accelerating gradient). To better understand this process, a three-cell 1.3 GHz elliptical-shape cavity with cathode was modeled in CST Studio Suite® 2013 at the University of Rostock. All parameters are provided by Helmholtz-Zentrum Dresden-Rossendorf. The multipacting simulations have been performed with CST Microwave Studio® (CST MWS) [1] and CST Particle Studio® (CST PS) which is suitable and powerful for 3D electromagnetic designs and provides the most advanced model of secondary emission. The radio frequency fields are calculated using the frequency domain solver of CST MWS, whereas the CST PS is used for particle tracking simulation [2]. The purpose of these numerical simulations is to better comprehend multipacting in the Rossendorf SRF gun and make a detailed analysis. The midterm goal is to find a new cavity shape, which might suppress the electron amplification so that the SRF Gun will be able to operate up to an accelerating gradient of 50 MV/m. #eden.tulu@uni-rostock.de [1] CST AG, Bad Nauheimer Str. 19, D-64289 Darmstadt, Germany [2] F. Hamme, U. Becker and P. Hammes, Proc. of ICAP 2006, Chamonix, France

THP042	High Frequency SRF Cavity Study for Bunch Shortening in PEPX	cavity, HOM, 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.

THP053	Development of Quality Control Procedures for the Processing of ReA3 Copper Plated Fundamental Power Coupler	controls, cavity, detector, 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.

THP065	Design of 352.21 MHz RF Power Input Coupler and Window for the European Spallation Source Project (ESS)	operation, cavity, multipactoring, vacuum	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.

THP067	Testing of Copper Plating Quality on ReA3 Coupler Bellows and Approach to Improved Plating for FRIB Production	vacuum, experiment, cavity, 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.

THP078	Deformation Tuner Design for a Double Spoke Cavity	cavity, operation, cryomodule, 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.

THP095	Error Analysis for Vertical Test Stand Cavity Measurements at Fermilab	cavity, detector, resonance, simulation	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.

FRIOA02	Developing Quarter Wave SRF Cavities for Hadron Colliders	cavity, HOM, electron, collider	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	cavity, operation, coupling, niobium	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]

FRIOB01	SRF Cavities for Future Ion Linacs	cavity, cryomodule, linac, ion	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]

FRIOB03	Development of 650 MHz Cavities for the GeV Proton Accelerator in Project X	cavity, 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]

Paper

Title

Other Keywords

Page

MOIOA04

SRF Challenges for Energy Recovery Linacs

cavity, 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]

MOIOB01

High Power Proton/Deuteron Accelerators

linac, proton, operation, cavity

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

cavity, cathode, laser, emittance

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, cavity, 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

controls, cavity, 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]

MOP004

The ESS Superconducting Linear Accelerator

cryomodule, linac, cavity, 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.

MOP007

The Status of Superconducting Linac and SRF Activities at the SNS

linac, cryomodule, cavity, operation

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.

MOP014

Cold Tests of SSR1 Resonators for PXIE

cavity, radiation, vacuum, cryomodule

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

cavity, cryomodule, linac, 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

cavity, 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

gun, electron, cavity, 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.

MOP024

Novel SRF Gun Design

gun, cathode, cavity, 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, cavity, cryomodule, 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.

MOP026

Emittance Compensation for an SRF Photo Injector

solenoid, gun, emittance, cathode

151

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

Funding: European Community-Research Infrastructure Activity under the FP7 program (EuCARD, contract number 227579), German Federal Ministry of Education and Research grant 05 ES4BR1/8
A lot of the future electron accelerator projects such like ERLs, high power FELs and also some of the new collider designs rely on the development of particle sources which provide them with high average beam currents at high repetition rates, while maintaining a low emittance. SRF photo injectors represent a promising concept to give just that, offering the option of a continuous wave operation with high bunch charges. Nevertheless, emittance compensation for these electron guns, with the goal to reach the same level as normal conducting sources, is an ongoing challenge. The poster is going to discuss several approaches for the 3-1/2-cell SRF gun installed at the accelerator facility ELBE at the Helmholtz Center Dresden-Rossendorf including the installation of a superconducting solenoid within the injector’s cryostat and present the currently used method to determine the beam’s phase space.

MOP027

BNL SRF Gun Commissioning

gun, cathode, cavity, 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.

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, cavity, linac, 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.

MOP038

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

cavity, 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.

MOP042

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

cavity, controls, operation, vacuum

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.

MOP044

Performance Characteristics of Jefferson Lab’s New SRF Infrastructure

cavity, 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.

MOP052

RF Aspects of Quality Control for Industrial XFEL Cavities Fabrication

cavity, controls, background, 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

cavity, 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.

MOP059

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

cavity, vacuum, 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, cryomodule, cavity

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

cavity, 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

operation, vacuum, cavity, 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.

MOP073

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

cavity, HOM, 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.

MOP086

Integration, Commissioning and Cryogenics Performance of the ERL Cryomodule Installed on ALICE-ERL Facility at STFC Daresbury Laboratory, UK

cryomodule, cryogenics, HOM, linac

349

S.M. Pattalwar, R.K. Buckley, P.A. Corlett, P. Goudket, A.R. Goulden, A.J. May, P.A. McIntosh, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA
A. Büchner, F.G. Gabriel, P. Michel
HZDR, Dresden, Germany
E.P. Chojnacki, J.V. Conway, R.G. Eichhorn, G.H. Hoffstaetter, M. Liepe, H. Padamsee, P. Quigley, J. Sears, V.D. Shemelin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
M.A. Cordwell, T.J. Jones, L. Ma, A.J. Moss, J. Strachan
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
J.N. Corlett, D. Li, S.M. Lidia
LBNL, Berkeley, California, USA
T. Kimura
Stanford University, Stanford, California, USA
R.E. Laxdal
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
J.K. Sekutowicz
DESY, Hamburg, Germany
T.J. Smith
SLAC, Menlo Park, California, USA

On successful assembly and preliminary testing of an optimised SRF cryomodule for application on ERL accelerators, which is being developed through an international collaboration the cryomodule has been installed on the 35 MeV ALICE (Accelerators and Lasers in Combined Experiments) Energy Recovery Linac (ERL) facility at STFC Daresbury Laboratory. Existing cryogenic infrastructure has a capacity to deliver approximately 120 W cooling power at 2 K, but the HOM (Higher Order Mode) absorbers, the thermal intercepts for the high power RF couplers and the radiation shield in the cryomodule are designed to be cooled (to 5 K and 80 K) with gaseous helium instead of liquid nitrogen. As a result the cryogenic infrastructure for ALICE had to be modified to meet these additional requirements. In this paper we describe our experience with the process of integration and the cryogenic commissioning, and present some initial results.

MOP087

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

cryomodule, cavity, cryogenics, 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.

TUIOA01

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

cavity, shielding, niobium, 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]

TUIOA05

New Insights Into Quench Caused by Surface Pits in SRF Cavities

cavity, niobium, laser, 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]

TUIOB01

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

cavity, 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

cavity, niobium, 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]

TUIOC04

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

cavity, 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

cavity, induction, vacuum, niobium

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

cavity, niobium, electron, experiment

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]

TUP008

Models of the Magnetic Field Enhancement at Pits

cavity, 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)

TUP010

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

cavity, simulation, niobium, 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.

TUP011

A Parametric Study of BCS RF Surface Impedance with Magnetic Field Using Xiao Code

impedance, niobium, superconductivity, survey

444

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

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A recent new analysis of field-dependent BCS RF surface impedance based on moving Cooper pairs has been presented.* Using this analysis coded in Mathematica™, survey calculations have been completed which examine the sensitivities of this surface impedance to variation of the BCS material parameters and temperature. The results present a refined description of the “best theoretical” performance available to potential applications with corresponding materials.
* Xiao B. P. et al, Physica C: Superconductivity, 490, 2013, pp. 26–31

TUP015

Bitter Decoration Studies of Magnetic Flux Penetration Into Cavity Cutouts

experiment, cavity, 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

cavity, 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, cavity, 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, cavity, 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

cavity, 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.

TUP023

Evidence of Magnetic Breakdown on the Defects With Thermally Suppressed Critical Field in High Gradient SRF Cavities

site, superconducting-RF, superconductivity, niobium

472

G.V. Eremeev, 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.
At SRF 2011 we presented the study of quenches in high gradient SRF cavities with dual mode excitation technique[*]. The data differed from measurements done in 80’s that indicated thermal breakdown nature of quenches in SRF cavities. In this contribution we present analysis of the data that indicates that our recent data for high gradient quenches is consistent with the magnetic breakdown on the defects with thermally suppressed critical field. From the parametric fits derived within the model we estimate the critical breakdown fields and RF resistances at the breakdown site.
[*] G. Eremeev et al.,. In Proceedings of the 15th Superconducting RF conference,pp. 746-749, July 2011.

TUP026

Performance of a FNAL Nitrogen Treated Superconducting Niobium Cavity at Cornell

cavity, niobium, 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

cavity, niobium, 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

cavity, resonance, superconducting-RF, 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

cavity, vacuum, 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, cavity, experiment, 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

TUP037

Dynamic Hardening Rule; a Generalization of the Classical Hardening Rule for Crystal Plasticity

experiment, simulation, controls, niobium

499

A. Mapar, F. Pourboghrat
MSU, East Lansing, USA
T.R. Bieler
Michigan State University, East Lansing, 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.
The mechanical properties of a niobium (Nb) specimen can change with the orientation of the sheet. This anisotropy causes inhomogeneity in manufactured SRF cavities. Large grain Nb sheets are more anisotropic and less expensive than fine grain sheets. Designing a manufacturing process for large grain Nb sheets, however, is extremely complex, and requires using advance modeling techniques. A model capable of accurately predicting the deformation behavior of Nb can help improve the performance and reduce costs of a SRF cavity. Optimal design of the manufacturing of cavities with tube hydroforming process is possible with such a model. Crystal plasticity modeling of FCC materials has been very successful; however, there is still no model that can accurately predict the deformation behavior of BCC materials like the large grain Nb sheet. In this study, authors have proposed a dynamic hardening rule for crystal plasticity that significantly improves predictions of the model for large grain Nb. This model is the generalization of the classical hardening rule, and gives better control over the hardening rate. It also increases the stability of the model.

TUP043

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

niobium, cavity, electron, 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.

TUP046

Vertical Electropolishing of SRF Cavities and its Parameters Investigation

cavity, cathode, superconductivity, 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, simulation, cavity, 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.

TUP049

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

cavity, cathode, 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.

TUP054

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

cavity, niobium, 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

cavity, niobium, 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.

TUP058

Recent Findings on Nitrogen Treated Niobium

niobium, cavity, 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

cavity, vacuum, 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

cavity, niobium, 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

cavity, neutron, 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.

TUP063

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

cavity, 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)

cavity, niobium, 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, cavity, 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, cavity, 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.

TUP068

Laser Polishing of Niobium for SRF Applications

laser, niobium, experiment, simulation

593

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

Smooth interior surfaces are desired for niobium SRF cavities, now obtained by buffered chemical polish (BCP) and/or electropolish (EP). Laser polishing is a potential alternative, having advantages of speed, freedom from chemistry and in-process inspection. Here we show that laser polishing can produce smooth topography with Power Spectral Density (PSD) measurements similar to that obtained by EP. We studied the influence of the laser power density and laser beam raster rate on the surface topography. These two factors need to be combined carefully to smooth the surface without damaging it. Computational modeling was used to simulate the surface temperature and explain the mechanism of laser polishing.

Poster TUP068 [1.011 MB]

TUP070

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

niobium, cavity, ECR, 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.

TUP072

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

cavity, niobium, 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

cavity, niobium, vacuum, cathode

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.

TUP075

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

cavity, niobium, ion, cathode

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.

TUP077

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

cavity, cathode, niobium, hardware

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.

TUP079

ECR Nb Films Grown on Amorphous and Crystalline Cu Substrates: Influence of Ion Energy

ion, ECR, interface, electron

631

A-M. Valente-Feliciano, G.V. Eremeev, H.L. Phillips, C.E. Reece
JLAB, Newport News, Virginia, USA
C. Cao
Illinois Institute of Technology, Chicago, IL, USA
Th. Proslier
ANL, Argonne, USA
J.K. Spradlin
JLab, Newport News, Virginia, USA
T. Tao
UIC, Chicago, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In the pursuit of niobium (Nb) films with similar performance with the commonly used bulk Nb surfaces for Superconducting RF (SRF) applications, significant progress has been made with the development of energetic condensation deposition techniques. Using energetic condensation of ions extracted from plasma generated by Electron Cyclotron Resonance, it has been demonstrated that Nb films with good structural properties and RRR comparable to bulk values can be produced on metallic substrates. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. Particular attention is given to the nucleation conditions to create a favorable template for growing the final surface exposed to SRF fields. The influence of the deposition energy for both hetero-epitaxial and fiber growth modes on copper substrates is investigated with the characterization of the film surface, structure, superconducting properties and RF performance.

TUP081

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

niobium, cavity, 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

cavity, 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

cavity, niobium, cryogenics, 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.

TUP084

Reciprocal Space XRD Mapping with Varied Incident Angle as a Probe of Structure Variation within Surface Depth

lattice, software, survey, electron

651

X. Zhao
JLab, Newport News, Virginia, USA
M. Krishnan
AASC, San Leandro, California, USA
C.E. Reece
JLAB, Newport News, Virginia, USA
F. Williams, Q.G. Yang
NSU, 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
In this study, we used a differential-depth X-Ray diffraction Reciprocal Spacing Mapping (XRD RSM) technique to investigate the crystal quality of a variety of SRF-relevant Nb film and bulk materials. By choosing different X-ray probing depths, the RSM study successfully revealed the materials’ microstructure evolutions after different materials processes, such as energetic condensation or surface polishing. The RSM data clearly measured the materials’ crystal quality at different thickness. Through a novel differential-depth RSM technique, this study found: I. for a heteroepitaxy Nb film Nb(100)/MgO(100), the film thickening process, via a cathodic arc-discharge Nb ion deposition, created a near-perfect single crystal Nb on the surface’s top-layer; II. for a mechanic polished single-crystal bulk Nb material, the microstructure on the top surface layer is more disordered than that in-grain.

TUP086

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

cavity, niobium, cryomodule, 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

cavity, niobium, 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

cavity, 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.

TUP096

High Power Processing at a High Order Mode Frequency

HOM, cavity, gun, 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

cavity, niobium, 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).

TUP103

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

detector, cavity, 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

cavity, detector, 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

cavity, 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.

TUP111

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

cavity, 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

cavity, 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.

WEIOA01

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

ion, cavity, 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]

WEIOA04

Nb3Sn for SRF Application

niobium, cavity, 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

cavity, 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, shielding, cavity, 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]

WEIOC02

Multilayers Activities at Saclay / Orsay

niobium, cavity, 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

niobium, cavity, 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]

THIOB02

High Q Cavities for the Cornell ERL Main Linac

cavity, linac, cryomodule, 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]

THIOC03

Superconducting Photonic Band Gap Structures for High-Current Applications

cavity, 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]

THIOD01

SRF Cavities for ADS Project in China

cavity, linac, 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]

THIOD03

Cavity Development for the Linear IFMIF Prototype Accelerator

cavity, niobium, cryomodule, simulation

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]

THP001

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

cavity, HOM, 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.

THP011

Improving Gradient of 9-cell SRF Cavities at Peking University

cavity, 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

cavity, cryomodule, operation, vacuum

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.

THP017

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

cavity, simulation, cryomodule, 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.

THP019

1.3 GHz SRF Cavity Tests for ARIEL at TRIUMF

cavity, TRIUMF, HOM, linac

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.

THP026

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

cavity, 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.

THP030

Superconducting RF Cavity Development With UK Industry

cavity, 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

cavity, 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.

THP035

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

cavity, TRIUMF, ion, monitoring

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.

THP038

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

cavity, niobium, simulation, resonance

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

THP040

3D MULTIPACTING STUDY FOR THE ROSSENDORF SRF GUN

electron, simulation, gun, cathode

991

E.T. Tulu, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
A. Arnold
HZDR, Dresden, Germany

Funding: *This work is supported by Federal Ministry for Research and Education BMBF
Electron multipacting is still observed in the Rossendorf SRF gun which limits the cavity fields (accelerating gradient). To better understand this process, a three-cell 1.3 GHz elliptical-shape cavity with cathode was modeled in CST Studio Suite® 2013 at the University of Rostock. All parameters are provided by Helmholtz-Zentrum Dresden-Rossendorf. The multipacting simulations have been performed with CST Microwave Studio® (CST MWS) [1] and CST Particle Studio® (CST PS) which is suitable and powerful for 3D electromagnetic designs and provides the most advanced model of secondary emission. The radio frequency fields are calculated using the frequency domain solver of CST MWS, whereas the CST PS is used for particle tracking simulation [2]. The purpose of these numerical simulations is to better comprehend multipacting in the Rossendorf SRF gun and make a detailed analysis. The midterm goal is to find a new cavity shape, which might suppress the electron amplification so that the SRF Gun will be able to operate up to an accelerating gradient of 50 MV/m.
#eden.tulu@uni-rostock.de
[1] CST AG, Bad Nauheimer Str. 19, D-64289 Darmstadt, Germany
[2] F. Hamme, U. Becker and P. Hammes, Proc. of ICAP 2006, Chamonix, France

THP042

High Frequency SRF Cavity Study for Bunch Shortening in PEPX

cavity, HOM, 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.

THP053

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

controls, cavity, detector, 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.

THP065

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

operation, cavity, multipactoring, vacuum

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.

THP067

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

vacuum, experiment, cavity, 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.

THP078

Deformation Tuner Design for a Double Spoke Cavity

cavity, operation, cryomodule, 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.

THP095

Error Analysis for Vertical Test Stand Cavity Measurements at Fermilab

cavity, detector, resonance, simulation

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.

FRIOA02

Developing Quarter Wave SRF Cavities for Hadron Colliders

cavity, HOM, electron, collider

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

cavity, operation, coupling, niobium

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]

FRIOB01

SRF Cavities for Future Ion Linacs

cavity, cryomodule, linac, ion

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]

FRIOB03

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

cavity, 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]