07 Accelerator Technology
T07 Superconducting RF
Paper Title Page
MOOCA2 First Results From New Single-Cell Nb3Sn Cavities Coated at Cornell University 40
 
  • D.L. Hall, J.J. Kaufman, M. Liepe, R.D. Porter, J. Sears
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Cavities coated with Nb3Sn at Cornell University demonstrate quality factors of >1010 at 4.2 K, outperforming equivalent niobium cavities by a factor of >30 at these bath temperatures. These quality factors have been maintained up to fields of 17-18 MV/m without significant Q-slope. Recently, new single-cell cavities have been added to the Cornell Nb3Sn programme in an effort to improve statistics and allow further exploration of the available parameter space. In this paper we report on the first results of these new cavities, as well as the latest performance from other cavities already in use on the programme. Furthermore, continuing work to optimise the coating procedure is reported on, and the latest understanding of the ideal coating profile is discussed.  
slides icon Slides MOOCA2 [10.366 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOOCA2  
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MOPAB022 Fabrication Studies of a 650 MHz Superconducting RF Deflecting Mode Cavity for the ARIEL Electron Linac 120
SUSPSIK098   use link to see paper's listing under its alternate paper code  
 
  • D.W. Storey, R.E. Laxdal, B. Matheson, N. Muller
    TRIUMF, Vancouver, Canada
  • D.W. Storey
    Victoria University, Victoria, B.C., Canada
  
  A 650 MHz RF deflecting mode cavity is required for the ARIEL electron Linac to separate interleaved beams bound for either rare isotope production or a recirculation loop containing a Free Electron Laser. An RF separator will allow both modes to run simultaneously by imparting opposite transverse deflection to adjacent bunches at 1.3 GHz. The SRF cavity has been designed to provide up to 0.6 MV transverse voltage for operation with up to a 50 MeV CW electron beam. The design was optimised for compact geometry with high shunt impedance. Due to the low dissipated power, the cavity will operate at 4 K and allows for investigations into low cost fabrication techniques. The cavity is being machined from bulk reactor grade ingot Niobium and welds will be performed using TIG welding in an ultra-pure Argon chamber. Results of fabrication studies will be presented as well as measurements performed on a copper prototype cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB022  
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MOPVA038 Manufacturing Status of the IFMIF LIPAc SRF Linac 939
 
  • N. Bazin, P. Carbonnier, P. Contrepois, J. Plouin, B. Renard
    CEA/DSM/IRFU, France
  • C. Boulch, A. Bruniquel, J.K. Chambrillon, G. Devanz, P. Hardy, H. Jenhani, N. N'Doye, O. Piquet, A. Riquelme, D. Roudier
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • P. Charon, S. Chel, G. Disset, J. Relland
    CEA/IRFU, Gif-sur-Yvette, France
  • D. Regidor, F. Toral
    CIEMAT, Madrid, Spain
  
  This paper gives the fabrication status of the IFMIF cryomodule. This cryomodule will be part of the Linear IFMIF Prototype Accelerator (LIPAc) whose construction is ongoing at Rokkasho, Japan. It is a full scale of one of the IFMIF accelerator, from the injector to the first cryomodule. The cryomodule contains all the necessary equipment to transport and accelerate a 125 mA deuteron beam from an input energy of 5 MeV up to the output energy of 9 MeV. It consists of a horizontal vacuum tank of around 6 m long, 3 m high and 2.0 m wide, which includes 8 superconducting HWRs for beam acceleration, working at 175 MHz and at 4.45 K, 8 Power Couplers to provide RF power to cavities up to 70 kW CW in LIPAc case and 200 kW CW in IFMIF case, and 8 Solenoid Packages as focusing elements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA038  
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MOPVA039 Manufacturing and Validation Tests of IFMIF Low-Beta HWRs 942
 
  • G. Devanz, F. Éozénou, L. Maurice, P. Sahuquet, C. Servouin
    CEA/DSM/IRFU, France
  • N. Bazin, P. Carbonnier, P. Charon, G. Disset, P. Hardy, E. Jacques, O. Piquet, D. Roudier
    CEA/IRFU, Gif-sur-Yvette, France
  • J.K. Chambrillon, T. Percerou
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  
  The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy neutron flux to test samples as possible candidate materials to a full lifetime of fusion energy reactors. A prototype of the low energy part of the accelerator is under construction at Rokkasho in Japan. It includes one cryomodule containing 8 half-wave resonators (HWR) operating at 175 MHz .The first manufactured HWR has passed low power tests at 4.2K in vertical cryostat succesfully and exceeds the specifications. It has also been tested in the dedicated horizontal Sathori cryostat equiped with its cold tuning system. The serial production and qualification tests of the 8 cavities which will eventually equip the cryomodule are carried out in parallel. In this paper, we focus on the HWR preparation and test results and give a status of the manufacturing activities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA039  
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MOPVA040 Status of the ESS Elliptical Cryomodules at CEA Saclay 945
 
  • P. Bosland, C. Arcambal, F. Ardellier, S. Berry, A. Bouygues, A. Bruniquel, E. Cenni, J.-P. Charrier, C. Cloué, G. Devanz, F. Éozénou, T. Hamelin, X. Hanus, P. Hardy, C. Marchand, O. Piquet, J. Plouin, J.P. Poupeau, T. Trublet
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • G. Costanza
    Lund University, Lund, Sweden
  • C. Darve
    ESS, Lund, Sweden
  • P. Michelato
    INFN/LASA, Segrate (MI), Italy
  • G. Olivier
    IPN, Orsay, France
  • F. Peauger
    CEA/DSM/IRFU, France
  
  The first ESS prototype cryomodule with medium beta cavities named M-ECCTD is being assembled at CEA Saclay. The Q curves of the 4 cavities mounted inside the cryomodule are presented, and the four power couplers have been conditioned at high power before their assembly onto the cavity string. Completion of the M-ECCTD assembly outside clean room is in progress as well as the finalization of the RF power test stand preparation. RF power tests of the M-ECCTD will be performed during summer 2017. CEA is preparing the production of the ESS medium and high beta cryomodules of the series before the test of the M-ECCTD and the contracts for the procurement of the most critical components have already been signed  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA040  
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MOPVA041 Vertical Test Results on ESS Medium and High Beta Elliptical Cavity Prototypes Equipped with Helium Tank 948
 
  • E. Cenni
    CEA/IRFU, Gif-sur-Yvette, France
  • P. Bosland, G. Devanz, F. Éozénou, X. Hanus, L. Maurice, F. Peauger, J. Plouin, D. Roudier, C. Servouin
    CEA/DSM/IRFU, France
  • G. Costanza
    Lund University, Lund, Sweden
  • C. Darve
    ESS, Lund, Sweden
  
  The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity Linac) up to the final energy at 2 GeV. The last Linac optimization, called Optimus+, has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. This work presents the latest vertical test results on ESS medium and high beta elliptical cavity prototypes equipped with helium tank. We describe the cavity preparation procedure from buffer chemical polishing to vertical test.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA041  
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MOPVA042 CEA Preliminary Design of the Cryomodules for SARAF Phase II Superconducting Linac 951
 
  • R. Cubizolles, P. Brédy, D. Chirpaz-Cerbat, P. Hardy, F. Leseigneur, C. Madec, J. Plouin
    CEA/IRFU, Gif-sur-Yvette, France
  • N. Bazin
    CEA/DSM/IRFU, France
  • R. Bruce, Th. Plaisant
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  
  CEA is committed to deliver a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40.1 MeV. The SCL consists of 4 cryomodules and 4 warm sections with diagnostics at the end of each cryomodule. The first two identical cryomodules host 6 half-wave resonator (HWR) low-beta cavities (β = 0.091), 176 MHz, and 6 focusing superconducting solenoids. The last two identical cryomodule welcome 7 HWR high-beta cavities (β = 0.181), 176 MHz, and 4 solenoids. The paper will presents the preliminary design of the cryomodules.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA042  
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MOPVA043 Assembly Preparation of the IFMIF SRF Cryomodule 954
 
  • J.K. Chambrillon, N. N'Doye
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • N. Bazin, P. Charon, G. Devanz, P. Hardy, O. Piquet, J. Plouin
    CEA/IRFU, Gif-sur-Yvette, France
  • P. Contrepois, C. Servouin
    CEA/DSM/IRFU, France
  
  This article presents the preparation work performed by CEA for the assembly of the IFMIF Cryomodule. Before the shipping of the components to Japan many tests and trial assemblies has been realized on the CEA site of Saclay, France. The cryomodule, which is part of the Linear IFMIF Prototype Accelerator (LIPAc) under construction at Rokkasho in Japan, will be assembled there under the responsibility of F4E (Fusion for Energy) with CEA assistance. To fulfill the assembly of the cavity string, a cleanroom will be built at Rokkasho under the responsibility of QST.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA043  
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MOPVA044 Conditioning of the Power Couplers for the ESS Elliptical Cavity Prototypes 957
 
  • C. Arcambal, P. Carbonnier, M. Desmons, G. Devanz, T. Hamelin, C. Marchand, C. Servouin
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • C. Darve
    ESS, Lund, Sweden
  
  In the framework of the European Spallation Source (ESS), some power couplers have been designed and manufactured to supply, with RF power, the medium-beta (β=0.67) elliptical cavities of the cryomodule demonstrator. The power couplers work at 704.4 MHz and are tested up to 1.2 MW (repetition rate=14 Hz, RF pulse width close to 3.6 milliseconds). The CEA Saclay is in charge of the design, the manufacturing, the preparation and the conditioning of these power couplers. In this paper, after a general presentation of the power couplers used in the ESS LINAC and their characteristics, we give some détails about the manufacturing and then we describe the different steps of the preparation (cleaning), the assembly of the couplers on the coupling box in cleanroom, the baking of the couplers and the conditioning procedure. Finally, the experimental results obtained in travelling and standing waves on the first pairs of couplers will be shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA044  
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MOPVA046 120kW RF Power Input Couplers for BERLinPro 960
 
  • B.D.S. Hall, V. Dürr, F. Göbel, J. Knobloch, A. Neumann
    HZB, Berlin, Germany
  
  The 50-MeV, 100-mA energy-recovery-linac (ERL) demonstration facility BERLinPro is currently undergoing construction at HZB. The high power injection system, that will deliver a beam at 6.5MeV, is split into a 1.4 cell SRF Photo injector and three Cornell-style 2-cell boosters. The injector and two of the booster cavities will provide about 2MeV each and must handle up to 220 kW of beam loading. New, cERL-based 115-kW high power couplers needed for the cavities' twin coupler system have begun manufacture. The design, optimization and manufacturing considerations of these couplers are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA046  
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MOPVA047 Investigation of Trapped Magnetic Flux in Superconducting Niobium Samples with Polarized Neutron Radiography 964
 
  • O. Kugeler, J. Knobloch, M.M. Krzyzagorski, J.M. Köszegi, L. Riik, W. Treimer, R.F. Ziesche
    HZB, Berlin, Germany
  
  The dynamics of flux expulsion during superconducting transition and the influence of external AC magnetic fields on expulsion of trapped fields in Nb samples has been investigated with radiography using polarized neu-trons. Results of these experiments are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA047  
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MOPVA048 Simulation of the Thermoelectrically Generated Magnetic Field in a SC Nine-Cell Cavity 968
 
  • J.M. Köszegi, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  
  Several studies showed that thermocurrents generate a magnetic field in a horizontal cavity test assembly or cryomodul, which may get trapped during the supercon-ducting phase transition. The trapped flux causes additional dissipation in the order of 1 to 10 n' during operation and can therefore significantly degrade the quality factor in a TESLA cavity. We simulated the distribution of the generated magnetic field over the whole cavity-tank system for an asymmetric temperature distribution. The asymmetry allows the field to penetrate the RF surface which would be field free in the symmetric case. The calculated results complemented a direct measurement of trapped magnetic flux inside the cavity with a small number of field probes. Finally, the obtained data was combined with RF measurements in three passband modes to determine the overall distribution of trapped magnetic flux due to thermocurrents.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA048  
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MOPVA049 First Commissioning of an SRF Photo-Injector Module for BERLinPro 971
 
  • A. Neumann, A. Burrill, D. Böhlick, A.B. Büchel, M. Bürger, P. Echevarria, A. Frahm, H.-W. Glock, F. Göbel, S. Heling, K. Janke, T. Kamps, S. Keckert, S. Klauke, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, N. Ohm, E. Panofski, H. Plötz, S. Rotterdam, M. Schenk, M.A.H. Schmeißer, M. Schuster, H. Stein, Y. Tamashevich, J. Ullrich, A. Ushakov, J. Völker
    HZB, Berlin, Germany
  • A. Matheisen, M. Schmökel
    DESY, Hamburg, Germany
  
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association.
Helmholtz-Zentrum Berlin (HZB) is currently building an high average current superconducting ERL to demonstrate ERL operation with low normalized beam emittance of 1 mm·mrad at 100mA and short pulses of about 2 ps. For the injector section a series of SRF photoinjector cavities is being developed. The medium power prototype presented here features a 1.4 x λ/2 cell SRF cavity with a normal-conducting, high quantum efficiency CsK2Sb cathode, implementing a modified HZDR-style cathode insert. This injector potentially allows for 6 mA beam current at up to 3.5 MeV kinetic energy. In this contribution, the first RF commissioning results of the photo-injector module will be presented and compared to the level of performance during the cavity production and string assembly process. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA049  
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MOPVA050 Setup of a Spatially Resolving Vector Magnetometry System for the Investigation of Flux Trapping in Superconducting Cavities 975
SUSPSIK099   use link to see paper's listing under its alternate paper code  
 
  • B. Schmitz, K.Alomari. Alomari, J. Knobloch, O. Kugeler, J.M. Köszegi, Y. Tamashevich
    HZB, Berlin, Germany
  
  Flux trapping is the major contribution to the residual resistance of superconducting cavities. In order to gain a better understanding of the mechanisms involved and aiming at an eventual minimization of trapped flux, a measurement setup based on AMR sensors was devised that allows for monitoring the magnetic field vector at various positions near the cavity surface. First results of the efforts are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA050  
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MOPVA051 Design of the High Power 1.5 GHz Input Couplers for BESSY VSR 978
 
  • E. Sharples, M. Dirsat, J. Knobloch, A.V. Vélez
    HZB, Berlin, Germany
  
  The Variable pulse length Storage Ring (BESSY VSR) upgrade to BESSY II at Helmholtz-Zentrum Berlin (HZB) requires an upgrade on the RF systems in the form of high-voltage longitudinally focusing super conducting RF cavities of 1.5 GHz ad 1.75 GHz. For operation, coaxial RF power couplers capable of handling 13 kW peak power at standing wave operation are required for both the 1.5 GHz and 1.75 GHz cavities. The coupler is based on a design by Cornell University with modifications to suit frequency and coupling requirements. The coupler is intended to provide variable coupling with a range of Qext from 6x106 to 6x107 to allow flexibility to adjust to operating conditions of BESSY VSR. Here we present the RF design of the high-power coaxial coupler for BESSY VSR along with the design of the test stand for conditioning a pair of couplers.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA051  
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MOPVA052 Study on HOM Power Levels in the BESSY VSR Module 982
 
  • A.V. Tsakanian, H.-W. Glock, J. Knobloch, A.V. Vélez
    HZB, Berlin, Germany
  
  The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store of long (ca. 15ps) and short (ca. 1.5ps) bunches in the storage ring with the 'standard' user optics. This challenging goal requires installation of four new SRF cavities (2x1.5GHz and 2x1.75GHz) in a single module to minimize space requirements. These cavities are equipped with strong waveguide and beam tube HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete module. This study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. In the module different cavity arrangements are analyzed to reach the optimal operation conditions with equally distributed power portions in warm HOM loads and tolerable beam coupling impedance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA052  
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MOPVA053 The SRF Module Developments for BESSY VSR 986
 
  • A.V. Vélez, H.-W. Glock, F. Glöckner, B.D.S. Hall, J. Knobloch, A. Neumann, P. Schnizer, E. Sharples, A.V. Tsakanian
    HZB, Berlin, Germany
  
  Helmholtz-Zentrum Berlin is developing BESSY VSR, a novel upgrade of the BESSY II facility to provide highly flexible pulse lengths while maintaining the flux and brilliance. The project goal is to simultaneously circulate both standard (some 10 ps long) and short (ps and sub-ps long) pulses offering the BESSY user community picosecond dynamics and high-resolution experiments. The concept relies on the installation of high-voltage SRF cavities operating at the 3rd and 3.5th harmonic whereby the beating of the two frequencies provides RF buckets for long and short bunches. Since these cavities will operate in CW and with high beam current (Ib=300 mA), the cavity design represents a challenging goal. In addition the need to avoid coupled bunch instabilities (CBI's), the installation of the VSR Cryomodule must fit in one of the available 4-m long low beta straights. To address the technological and engineering challenges techniques such as waveguide-damped cavities have been developed. First prototypes have been produced. In this paper, the present SRF developments are presented, including the cavities, high power couplers, higher-order mode absorbers and the cryomodule design.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA053  
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MOPVA054 High Power RF Coupler for the CW-Linac Demonstrator at GSI 990
 
  • M. Heilmann, W.A. Barth, S. Yaramyshev
    GSI, Darmstadt, Germany
  • M. Amberg, M. Basten, R. Blank, M. Busch, F.D. Dziuba, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
  • K. Aulenbacher
    IKP, Mainz, Germany
  • K. Aulenbacher, W.A. Barth, V. Gettmann, M. Miski-Oglu
    HIM, Mainz, Germany
  • W.A. Barth, S. Yaramyshev
    MEPhI, Moscow, Russia
  
  The planned super-heavy element (SHE) research project investigates heavy ions near the coulomb barrier in future experiments. A superconducting (sc) continuous wave (cw) CH-Linac Demonstrator was developed and installed behind the High Charge State Injector (HLI) at GSI Darmstadt, Germany. In future the advanced cw-LINAC setup, with several CH-cavities, will accelerates the heavy ion beam from HLI with an energy of 1.4 MeV/u up to 3.5 - 7.3 MeV/u. The RF power of several kW will be coupled capacitively into the CH-cavities with minimal reflection at an operation frequency of 217 MHz. Two ceramic windows (Al2O3) are installed inside the RF coupler, to reduce the premature contamination of the cavity and as an additional vacuum barrier. The CH-cavity will be operated at cryogenic temperature (4 K) and will be increased to room temperature along the RF coupler. The optimally adapted RF coupler design, providing minimal RF losses and simultaneously maximal performance, was optimized by electromagnetic simulations. An RF coupler design with a reflection-free RF adaptor as well as the temperature distribution along the coupler will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA054  
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MOPVA055 Upgrade of the Capture Section of the S-DALINAC Injector 993
SUSPSIK100   use link to see paper's listing under its alternate paper code  
 
  • D.B. Bazyl, H. De Gersem, W.F.O. Müller
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  Funding: This work is supported by the DFG through GRK 2128.
In order to reduce the energy spread of the recirculated beam, the injector of the S-DALINAC needs to be optimized, because the non-isochronous recirculation cannot correct for errors originating from the injector linac. For the S-DALINAC, spatial restrictions suggest the use of SRF technology for the capture section. In this work, we consider various SRF cavities with an operating frequency of 3 GHz for a possible upgrade of the capture section of the S-DALINAC. The first results of the RF and beam dynamics simulations for the proposed options are presented in this paper. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA055  
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MOPVA057 Structural Investigations of Nitrogen-Doped Niobium for Superconducting RF Cavities 996
 
  • M. Major, L. Alff, M. Arnold, J. Conrad, S. Flege, R. Grewe, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
  
  Funding: Work supported by BMBF through 05H15RDRBA.
Niobium is the standard material for superconducting RF (SRF) cavities. Superconducting materials with higher critical temperature or higher critical magnetic field allow cavities to work at higher operating temperatures or higher accelerating fields, respectively. Enhancing the surface properties of the superconducting material in the range of the penetration depth is also beneficial. One direction of search for new materials with better properties is the modification of bulk niobium by nitrogen doping. In the Nb-N phase diagram the cubic delta-phase of NbN has the highest critical temperature (16 K). Already slight nitrogen doping of the alpha-Nb phase results in higher quality factors.* Nb samples will be N-doped at the refurbished UHV furnace at IKP Darmstadt. The first results on the structural investigations of the processed Nb samples at the Materials Research Department of TU Darmstadt are presented.
* Grassellino et al., Proc. SRF2015, MOBA06, 48. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA057  
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MOPVA058 Commissioning and Operation Experience of the 3.9 GHz System in the EXFEL Linac 999
 
  • C.G. Maiano, J. Branlard, M. Hüning, M. Omet, P. Pierini, E. Vogel
    DESY, Hamburg, Germany
  • A. Bosotti, R. Paparella, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  
  The European X-ray Free Electron Laser (EXFEL) injector linac hosts a 3.9~GHz module (AH1) for beam longitudinal phase space manipulation after the first acceleration stage, in order for the linac to deliver the high current beams with sufficiently low emittance for the production of 1 Angstrom FEL light to the experimental users. The module was technically commissioned in December 2015 and operated well above its nominal performances during the Injector Run from January to July 2016. Its operation has restarted in January 2017 with the startup of the whole facility, and the system met the design beam specifications after the bunch compression stages. A brief review of the commissioning and first operation experience of the RF system are presented here.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA058  
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MOPVA060 Fabrication and Treatment of the ESS Medium Beta Prototype Cavities 1003
 
  • L. Monaco, A. Bellandi, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • S. Pirani
    ESS, Lund, Sweden
  
  In view of the Medium Beta series cavities production at the industry for the European Spallation Source project, INFN Milano - LASA design prototypes have been fully produced at Ettore Zanon S.p.A. with our supervision. Based on our experience on the production of 1.3 GHz and 3.9 GHz E-XFEL series cavities, we set-up and applied an external quality control activity of the overall production of the prototype cavity, starting from the row materials to the ready to be tested cavity. In this paper, we report the strategy we have adopted on the overall production, mechanical and surface treatments, frequency measurement of subcomponents and cavities and the obtained results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA060  
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MOPVA061 Quench and Field Emission Diagnostics for the ESS Medium-Beta Prototypes Vertical Tests at LASA 1007
 
  • M. Bertucci, A. Bellandi, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • S. Pirani
    ESS, Lund, Sweden
  
  In order to investigate the possible causes of premature thermal breakdown and performance degradation, several diagnostic techniques have been employed during the vertical tests of the Fine and Large Grain ESS Medium Beta prototypes cavities. The whole equipment, which includes second sound, fast thermometry, photodiode x ray detectors and an external NaI scintillator, is here described and the results so far obtained during the vertical tests presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA061  
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MOPVA062 Test, Diagnostics and Computed Tomographic Inspection of a Large Grain 3.9 GHz Prototype Cavity 1011
 
  • M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • G. Ciovati, G.R. Myneni
    JLab, Newport News, Virginia, USA
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  
  A large grain 3.9 GHz prototype cavity made of RRR = 105 ±10 has been tested at LASA. The cavity suffered of quench at moderate levels of accelerating field, for all nine fundamental pass-band modes. Several diagnostic techniques have been employed to determine the quench positions, which occur close to significant grain-boundary steps, visible from the external cavity surface. The cavity has been scanned with a high resolution X-ray tomographic machine, confirming the existence of remarkable topographic features on the inner RF surface at the suspected quench positions. A strategy for a future surface treatment for recover the cavity performances is here presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA062  
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MOPVA063 Vertical Tests of ESS Medium Beta Prototype Cavities at LASA 1015
 
  • A. Bosotti, A. Bellandi, M. Bertucci, A. Bignami, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • S. Pirani
    ESS, Lund, Sweden
  
  In the framework of the INFN activity related to the European Spallation Source collaboration, the LASA infrastructure has been renewed to allow the qualification, in its vertical cryostat, of the 704 MHz medium beta cavity prototypes. A new cryogenic insert has been realized, fully equipped with dedicated mechanical supports, vacuum, thermal sensors and quench diagnostic systems. The RF test station has been upgraded as well with a new PLL electronics rack. The first beta 0.67 cavity prototype designed and produced by INFN Milano has been successfully cold tested at 2.0 K temperature, outperforming the ESS specifications. The technical features of LASA infrastructure, the design of novel components and the experimental results of cavities cold-tests are thoroughly described in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA063  
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MOPVA064 Multipacting Study in INFN-LASA ESS Medium-Beta Cavity 1019
 
  • J.F. Chen, M. Bertucci, A. Bosotti, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • S. Pirani
    ESS, Lund, Sweden
  
  We present Multipacting studies in ESS Medium-Beta cavities of INFN-LASA design with both simulation and experimental results. The simulation on the ideal cavity shape with both FishPact and MultiPac2.1 codes shows that multipacting appears in a very small region near equator where the weld seam exists. A simulation with more realistic cavity shape considering the weld seam at cell equators has also been done out showing similar results for end cell but a remarkable mitigation for inner cell. During the vertical tests at LASA, Multipacting is frequently observed but with no limitation to the cavity performance, which well confirms the MP predicted by the simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA064  
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MOPVA066 Limits for the Operation of the European XFEL 3.9 GHz System in CW Mode 1023
 
  • P. Pierini, A. Bosotti, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • J. Branlard, D. Kostin, C.G. Maiano, W.-D. Möller, P. Pierini, D. Reschke, J.K. Sekutowicz, E. Vogel
    DESY, Hamburg, Germany
  
  Future upgrades of the European XFEL (EXFEL) facility may require driving the linac at higher duty factor, possibly extending to CW mode at reduced gradients. A preliminary analysis for the accelerator modules has been presented in the EXFEL TDR, but no precise assessment has been performed so far for the present 3.9 GHz system design. By making use of data collected during the commissioning and operation phase of the EXFEL injector system, we discuss here an estimate for the limits of CW operation of the present system and a plan for its possible experimental verification with existing available cavities and the EXFEL spare module.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA066  
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MOPVA068 Experience on Design, Fabrication and Testing of a Large Grain ESS Medium Beta Prototype Cavity 1027
 
  • D. Sertore, A. Bellandi, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • S. Pirani
    ESS, Lund, Sweden
  
  We report on the design, fabrication and testing of an ESS Medium Beta prototype cavity made with Large Grain Niobium sheets sliced from an ingot provided by CBMM. The peculiar choices during the fabrication process related to the Large Grain Niobium material are described. We present also the results of the cavity test at cryogenic temperature and the dedicated quench diagnostic.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA068  
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MOPVA071 Press Forming Tests of Superconducting Spoke Cavity for Laser Compton Scattered Photon Sources 1031
 
  • M. Sawamura, R. Hajima
    QST, Tokai, Japan
  • H. Hokonohara, Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  
  We are developing the superconducting spoke cavity for laser Compton scattered (LCS) photon sources. We adopt the superconducting spoke cavity for electron beam drivers to realize a wide use of LCS X-ray and '-ray sources in academic and industrial applications. The spoke cavity can make the accelerator more compact than an elliptical cavity because the cavity size is small at the same frequency and the packing factor is good by installing couplers on outer conductor. Though our proposal design for the photon source consists of the 325 MHz spoke cavities in 4K operation, we are fabricating the half scale model of 650 MHz spoke cavity in order to accumulate our cavity production experience by effective utilization of our limited resources. Since the spoke has more complicated structure than an elliptical cavity, we performed press forming tests for the half spoke and estimated the formed shapes with 3-dimensional measurement.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA071  
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MOPVA073 Development of Peak Hold Module for Electron Emission in STF-Type Power Coupler for the ILC 1034
 
  • Y. Yamamoto, E. Kako, T. Shishido
    KEK, Ibaraki, Japan
  
  In STF, the RF conditioning for power coupler is done in several steps from 10 to 1650 μs as specified in TDR for the ILC. The most important signals during the RF conditioning are vacuum level, and electron emission by multipacting. The vacuum level changes continuously, and electron emission has pulse-like behavior, which has much faster response. Therefore, it was necessary to develop the peak hold and isolation modules to evaluate electron emission in short pulse width. This module has two kinds of feature. One is pulse height detection, and the other is total charge detection (integrated signal). During the RF conditioning for power couplers in STF-2 cryomodule, this module perfectly worked, and detected different trend between the pulse height and the total charge. In this paper, the detailed result for the peak hold module will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA073  
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MOPVA074 Fabrication of Superconducting QWR at MHI-MS 1037
 
  • N. Shigeoka, H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa
    MHI-MS, Kobe, Japan
  • O. Kamigaito, K. Ozeki, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada
    RIKEN Nishina Center, Wako, Japan
  
  Mitsubishi Heavy Industries Mechatronics Systems, Ltd. (MHI-MS), a subsidiary campany of MHI, took over MHI's accelerator business on October 1, 2015, and has been developing the business. MHI-MS is manufacturing the prototype Superconducting QWR for RIKEN Superconducting linac project. MHI-MS has dedicated surface treatment facilities for superconducting cavities, the QWR will be treated using this facilities. In this presentation, recent progress will be reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA074  
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MOPVA075 Development of High Sensitive X-Ray Mapping for SC Cavities 1040
 
  • H. Tongu, H. Hokonohara, Y. Iwashita
    Kyoto ICR, Uji, Kyoto, Japan
  • R.L. Geng, A.D. Palczewski
    JLab, Newport News, Virginia, USA
  • H. Hayano, T. Kubo, T. Saeki, Y. Yamamoto
    KEK, Ibaraki, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
  
  We developed an X-ray mapping system sX-map for superconducting cavities. The sensors are inserted under the stiffener rings between cavity cells, whose locations are close to the iris areas. The whole circuits are im-mersed in liquid He and the multiplexed signals reduces the number of cables to the room temperature region. sX-map has the advantages in its compact size, low cost and simple setup for nondestructive inspections. The sX-map system detected X-rays from field emissions in vertical RF tests of ILC 9-cell cavities at Jefferson Lab (JLab) and KEK. sX-map showed an excellent performance in the meas-urement test at JLab, it exhibited a high sensitivity com-pared with an the fixed diode rings colocated at irises and ion chamber located out side of the vertical test cryostat.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA075  
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MOPVA076 Measurement of Thin Film Coating on Superconductors 1043
 
  • Y. Iwashita, Y. Fuwa, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • H. Hayano, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • M. Hino
    Kyoto University, Research Reactor Institute, Osaka, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
  
  Funding: This research is supported by following programs: Grant-in-Aid for Exploratory Research JSPS KAKENHI Grant Number 26600142 and Photon and Quantum Basic Research Coordinated Development Program from the MEXT.
Multilayer thin film coating is a promising technology to enhance performance of superconducting cavities. Until recently, principal parameters to achieve the sufficient performance had not been known, such as the thickness of each layer. We proposed a method to deduce a set of the parameters to exhibit a good performances. In order to verify the scheme, we are trying to make some experiments on the subject at Kyoto. The sample preparation and the test setup for the measurement apparatus will be discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA076  
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MOPVA078 The Window Replacement and Q Recovery of BEPCII Storage Ring SCC 1046
 
  • T.M. Huang, J.P. Dai, R. Ge, S.P. Li, Z.Q. Li, H.Y. Lin, Q. Ma, W.M. Pan, Y. Sun, G.W. Wang
    IHEP, Beijing, People's Republic of China
  • P. Sha
    Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
  
  The storage ring RF system for the upgrade of the Beijing Electron Positron Collider (BEPCII) adopted two 500 MHz superconducting cavities: west for the positron ring (BPR); east for the electron ring (BER). The excessive heating of the west window was observed in Nov.2013, and not cured thoroughly*. After two years operation, the window cracked suddenly on Nov.18th, 2015. The replacement of the window was subsequently implemented in tunnel. However, the quality factor (Q) of the cavity decayed a lot after the window replacement. 90 degrees Celsius N2 gas baking of the outer surface of the cavity was carried out in situ and the Q recovered in a short time. This paper will present the process of the window replacement and the cavity Q recovery in detail.
* Tong-ming Huang et al., Chinese Physics C Vol. 40, No. 6 (2016) 067001 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA078  
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MOPVA079 A 166.6 MHz Superconducting RF System for the HEPS Storage Ring 1049
 
  • P. Zhang, H.X. Hao, T.M. Huang, Z.Q. Li, H.Y. Lin, F. Meng, Z.H. Mi, Y. Sun, G.W. Wang, Q.Y. Wang, X.Y. Zhang
    IHEP, Beijing, People's Republic of China
  
  Funding: This work has been supported by HEPS-TF project and partly by Pioneer 'Hundred Talents Program' of Chinese Academy of Science.
A superconducting 166.6 MHz quarter-wave β=1 cavity was recently proposed for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale light source. Four 166.6 MHz cavities will be used for main acceleration in the newly planned on-axis beam injection scheme realized by a double-frequency RF system. The fundamental frequency, 166.6 MHz, was dictated by the fast injection kicker technology and the preference of using 499.8 MHz SC RF cavity as the third harmonic. Each 166.6 MHz cavity will be operated at 4.2 K providing 1.2 MV accelerating voltage and 150 kW of power to the electron beam. The input coupler will use single-window coaxial type graded up to 200 kW CW power. Each cavity will be equipped with a 200 kW solid-state amplifier and digital low-level RF system. This paper will describe the 166.6 MHz RF system with a focus on the design and optimization of the RF cavity and its ancillaries, the LLRF system and the status of the solid-state amplifiers. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA079  
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MOPVA080 HOM Simulations and Damping Scheme for CEPC Cavities 1052
 
  • H.J. Zheng, J. Gao, F. Meng, P. Sha, J.Y. Zhai
    IHEP, Beijing, People's Republic of China
  
  In this paper, it will be presented that the higher order mode (HOM) analysis of the 650 MHz cavities for the Circular Electron-Positron Collider (CEPC). The higher order modes excited by the intense beam bunches must be damped to avoid additional cryogenic loss and multi-bunch instabilities. To keep the beam stable, the impedance budget and the HOM damping requirement are given. The conventional coaxial HOM coupler, which will be mounted on the beam pipe, is planned to extract the HOM power below the cut-off frequency of the beam pipe, and the propagating modes will be absorbed by the two HOM absorbers at room temperature outside the cryomodule.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA080  
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MOPVA082 PLASMA PROCESSING R&D OF THE 1.3 GHZ SINGLE-CELL SRF CAVITY AT IMP 1055
SUSPSIK101   use link to see paper's listing under its alternate paper code  
 
  • L. Yang, L. Chen, Y. He, S.C. Huang, C.X. Li, C.L. Li, Y.M. Li, L. Lu, A. Shi, L.P. Sun, A.D. Wu, S.H. Zhang
    IMP/CAS, Lanzhou, People's Republic of China
  
  The China-Accelerator Driven Sub-critical System (C-ADS) injector II has already commissioned with a CW 1 mA and a pulsed 10 mA proton beam. The beam energy achieved 10 MeV. The superconducting linac (SCL) is routinely operating at 4.7 MV/m average accelerating gradient in the low-beta cryomodules. Field emission and surface contaminants of the SCL limit the gradient in-crease in the beam commissioning. Hence, in order to increase the SCL accelerating gradient, reduce field emis-sion and remove surface pollutants, in-situ plasma pro-cessing R&D in a 1.3 GHz single-cell SRF cavity has being studied. In this paper, the current effort of plasma processing R&D in a 1.3 GHz single-cell SRF cavity will be presented in details and the future plan will be also reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA082  
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MOPVA087 Low Betta Superconducting Cavity for the New Injector Linac for Nuclotron-NICA 1058
 
  • M. Gusarova, T.A. Bakhareva, M.V. Lalayan, S.V. Matsievskiy, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy, V. Zvyagintsev
    MEPhI, Moscow, Russia
  • A.A. Bakinowskaya, V.S. Petrakovsky, A.I. Pokrovsky, D.A. Shparla
    Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
  • A.V. Butenko, G.V. Trubnikov
    JINR/VBLHEP, Dubna, Moscow region, Russia
  • V. Zvyagintsev
    TRIUMF, Vancouver, Canada
  
  The results of the RF, mechanical and multipactor discharge simulations of the 162 MHz quarter wave resonator (QWR) for New Superconducting Injector Linac for Nuclotron-NICA are presented. Cavity design in conjunction with manufacturing features is discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA087  
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MOPVA088 Medium Betta Superconducting Cavity for the New Injector Linac for Nuclotron-NICA 1061
 
  • M. Gusarova, M.V. Lalayan, N.P. Sobenin, D.V. Surkov, K.V. Taletskiy
    MEPhI, Moscow, Russia
  • A.A. Bakinowskaya, V.S. Petrakovsky, A.I. Pokrovsky, D.A. Shparla
    Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
  • A.V. Butenko, G.V. Trubnikov
    JINR/VBLHEP, Dubna, Moscow region, Russia
  
  The results of the electrodynamical and multipactor discharge simulations of the medium betta superconducting cavity for New Superconducting Injector Linac for Nuclotron-NICA are presented. Different designs of CH and Spoke cavities are compared and the optimal one is chosen.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA088  
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MOPVA089 The Cryomodule Test Stands for the European Spallation Source 1064
 
  • E. Asensi Conejero, W. Hees
    ESS, Lund, Sweden
  • K. Fransson, K.J. Gajewski, L. Hermansson, M. Jobs, H. Li, T. Lofnes, R.J.M.Y. Ruber, R. Santiago Kern, R. Wedberg
    Uppsala University, Uppsala, Sweden
  
  The European Spallation Source (ESS) is currently under construction in Lund, in southern Sweden. The superconducting section of the linear accelerator consists of three parts; 26 double-spoke cavities at 352.21 MHz gathered in 13 cryomodules, 36 medium beta elliptical cavities at 704.42 MHz gathered in 9 cryomodules and 84 high beta elliptical cavities also at 704.42 MHz gathered in 21 cryomodules. These cryomodules allow the acceleration of the beam from 90 MeV to 2.0 GeV. The cryomodules have to be tested in dedicated test facilities before installation in the ESS tunnel, the Test Stand 2 (TS2) in Lund and the FREIA Test Stand at Uppsala University, Sweden, which are dedicated to the tests of the medium and high beta elliptical cryomodules and the spoke cavity cryomodules, respectively, for the ESS linear accelerator. All cryomodules will go through their Site Acceptance Tests (SAT) on these dedicated test stands which will each consist of an RP bunker, a test stand cryoplant and RF power sources. Both test stands will allow the SAT of cryomodules with full cryogenic load at the final operating temperature and with full RF load on all cavities in parallel.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA089  
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MOPVA090 ESS Superconducting RF Collaboration 1068
 
  • C. Darve, H. Danared, N. Elias, N.F. Hakansson, M. Lindroos, C.G. Maiano, F. Schlander
    ESS, Lund, Sweden
  • F. Ardellier, P. Bosland
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • S. Bousson, G. Olry
    IPN, Orsay, France
  • M. Ellis, A.E. Wheelhouse
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • L. Hermansson, R.J.M.Y. Ruber
    Uppsala University, Uppsala, Sweden
  • P. Michelato, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  
  The European Spallation Source (ESS) project is a neutron-scattering facility, currently under construction by a partnership of at least 17 European countries, with Sweden and Denmark as host nations. The ESS was designated a European Research Infrastructure Consortium, or ERIC, by the European Commission in October of 2015. Scientists and engineers from 50 different countries are members of the workforce in Lund who participate in the design and construction of the European Spallation Source. In complement to the local workforce, the superconducting RF linear accelerator is being prototyped and will be constructed based on a collaboration with European institutions: CEA-Saclay, CNRS-IPN Orsay, INFN-LASA, STFC-Daresbury, Uppsala and Lund Universities. After a description of the ESS collaborative project and its in-kind model for the SRF linac, this article will introduce the linac component first results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA090  
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MOPVA091 Investigation of HOM Frequency Shifts Induced by Mechanical Tolerances 1071
 
  • S. Pirani, M. Eshraqi, M. Lindroos
    ESS, Lund, Sweden
  • A. Bosotti, J.F. Chen, P. Michelato, C. Pagani, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • T.P.Å. Åkesson
    Lund University, Department of Physics, Lund, Sweden
  
  We present Higher Order Mode (HOM) studies on ESS Medium-Beta cavity of INFN-LASA design, including both simulation and measurement results. Mechanical tolerances of the fabrication process might shift HOMs frequencies toward harmonics of the bunch frequency. Both simulation and measurements at room and cryogenic temperature show that INFN LASA cavity is fully compatible with ESS requirements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA091  
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MOPVA094 ESS Spoke Cavity Conditioning at FREIA 1074
 
  • H. Li, K.J. Gajewski, L. Hermansson, M. Jobs, R.J.M.Y. Ruber, R. Santiago Kern
    Uppsala University, Uppsala, Sweden
  
  The first ESS double spoke cavity installed with RF power coupler was tested in the HNOSS cryostat at the FREIA Laboratory. Power coupler and cavity conditioning have been optimized in order to reach high efficiency and high availability by reducing the time and effort of the overall conditioning process. Meanwhile, an optimal procedure for ESS conditioning is studied. This paper presents the study result and experience of the RF conditioning procedure for the first ESS double spoke cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA094  
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MOPVA095 First RF Performance Results for the DQW Crab Cavities to be Tested in the CERN SPS 1077
 
  • A. Castilla, R. Calaga, O. Capatina, K.M. Dr. Schirm, K.G. Hernández-Chahín, A. Macpherson, N.C. Shipman, K. Turaj
    CERN, Geneva, Switzerland
  • I. Ben-Zvi
    BNL, Upton, Long Island, New York, USA
  • G. Burt, J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
  • K.G. Hernández-Chahín
    DCI-UG, León, Mexico
  • N.C. Shipman
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • N.C. Shipman
    UMAN, Manchester, United Kingdom
  
  As part of the High Luminosity LHC (HL-LHC) project strategy, crab cavity correctors shall be installed around CMS and ATLAS experiments of the LHC. To accommodate the different crossing angle planes, two distinct cavity designs have been selected: the RF Dipole (RFD) and the Double Quarter Wave resonator (DQW). CERN has fabricated two double quarter wave resonators (DQWSPS), for validation with a proton beam at the CERN SPS accelerator. Standard superconducting rf surface preparation protocols have been applied to the two bulk niobium cavities, followed by cryogenic testing in a vertical cryostat at CERN's SM18 facility. The performance results obtained after the first bare cavity tests for cavities DQWSPS001 and DQWSPS002 are shown in this paper, and include Q0 vs Vt curves, Lorentz Force Detuning (LFD) analyses and pressure sensitivity of a higher order mode.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA095  
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MOPVA096 The Crab Cavities Cryomodule for SPS Test 1081
 
  • C. Zanoni, A. Amorim Carvalho, K. Artoos, S. Atieh, K. Brodzinski, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, T. Dijoud, K. Eiler, G. Favre, P. Freijedo Menendez, M. Garlaschè, L. Giordanino, S.A.E. Langeslag, R. Leuxe, H. Mainaud Durand, P. Minginette, M. Narduzzi, V. Rude, M. Sosin, J.S. Swieszek
    CERN, Geneva, Switzerland
  • T.J. Jones, N. Templeton
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  RF Crab Cavities are an essential part of the HL-LHC upgrade. Two concepts of such systems are being developed: the Double Quarter Wave (DQW) and the RF Dipole (RFD). A cryomodule with two DQW cavities is in advanced fabrication stage at CERN for their tests with protons in the SPS during the 2018 run. The cavities must be operated at 2 K, without excessive heat loads, in a low magnetic environment and in compliance with CERN safety guidelines on pressure and vacuum systems. A large set of components, such as a thermal shield, a two layers magnetic shield, RF lines, helium tank and tuner is required for the successful and safe operation of the cavities. The assembly of all these components with the cavities and their couplers forms the cryomodule. An overview of the design and fabrication strategy of this cryomodule is presented. The main components are described along with the present status of cavity fabrication and processing and cryomodule assembly. The lesson learned from the prototypes, the helium tank above all, and first manufactured systems is also included.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA096  
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MOPVA097 Finite Element Analysis on Helium Discharge from Superconducting RF in the Storage Ring Tunnel 1085
 
  • J.-C. Chang, F. Z. Hsiao, J.C. Huang, S.P. Kao, H.C. Li, W.R. Liao, C.Y. Liu, H.H. Tsai, Z.-D. Tsai
    NSRRC, Hsinchu, Taiwan
  
  Liquid helium for transferring cooling power from the cryogenic plant to the magnets and SRF cavities had been widely applied on the advanced large superconducting particle accelerators. For requirements of high stable and reliable operation, many efforts have been put into the improvement and modification of the cryogenic system. However, personnel safety is another critical issue of the cryogenic system. Once large liquid helium was released on the atmospheric tunnel, the volume of helium will expand several hundred times and cause oxygen deficiency in short time due to sudden change of helium density. In this study, we applied numerical simulation to analyze helium discharge through a SRF cavity in the TPS tunnel.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA097  
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MOPVA098 Strategy Towards Non-Interrupted Operation of Superconducting Radio Frequency Modules at NSRRC 1088
 
  • Ch. Wang, F.Y. Chang, L.-H. Chang, M.H. Chang, J. Chen, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
  
  Two modern 3rd generation light sources, the well-developed 1.5-GeV Taiwan Light Source (TLS) and the new constructed 3-GeV Taiwan Photon Source (TPS), are now in routine operation. Both storage rings are powered by the superconducting RF (cavity) modules, one CESR-type SRF module for the TLS since 2005 and two KEKB-type SRF modules for the TPS since 2014. Thanks to continuous efforts, the operational reliability of SRF modules at NSRRC is now compatible or better in comparison with the best operation record of room temperature cavities ever achieved at TLS (1992-2004). How to improve the long term availability but hold the achieved reliability of SRF modules such as to maximize the available annual user beam time, especially, under requirements on high RF power operation, become a new operational challenge, especially for the SRF modules at TPS which is now routinely operated with a forward RF power around 150-kW individually and expected to push to 300-kW in the coming future. Here we report our strategy and achievement to minimize long term interrupt of SRF operation owing to regular full-thermal cycling and annual maintenance of cryogenic plant.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA098  
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MOPVA099 The Study of Electromagnet Compensated High Power Ferrite Circulator Operation With Superconducting RF Cavity 1091
 
  • T.-C. Yu, F.Y. Chang, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.H. Tsai, Ch. Wang, M.-S. Yeh
    NSRRC, Hsinchu, Taiwan
  
  In a high power RF system for accelerator application, the circulator is very important for protecting klystron or IOT from damage due to high reflection power from the cavity. When there is no beam current passing through the superconducting RF cavity of the accelerator, almost 100% RF power will be reflected from the cavity even the cavity is on resonance. The circulator shall be able to forward the reflected power to the load and remain good matching and isolation condition between ports at klystron and the cavity. However, for a ferrite material based circulator, the magnetic field within circulator would be temperature dependent which would cause the variation of input return loss and isolation between ports. Additional DC current driving electromagnet field is thus re-quired for compensating the temperature variation. Even with the compensating DC current, the circulator is still not ideal for practical operation especially when the performance of the circulator is strongly phase dependent. The phenomenon observed in actual operation with one set of SRF systems in NSRRC is thus reported in this article.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA099  
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MOPVA100 Atomic Layer Deposition of Niobium Nitride from Different Precursors 1094
 
  • P. Pizzol, P. Chalker, J.W. Roberts, J. Wrench
    The University of Liverpool, Liverpool, United Kingdom
  • O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  Advancements in technology have taken bulk niobium cavities close to their theoretical operational limits of 45 MV/m, pushing the research to explore novel materials, such as niobium based alloys . Theoretical studies suggest that a composite material composed of alternative superconductor / insulator multilayers would surpass the bulk niobium limits. Chemical vapour deposition (CVD) can deposit mi-crons thick Nb films in less than an hour, at the expense of precise thickness control. Atomic layer deposition (ALD), instead, even if considerably slower than CVD can be used in applications where the thickness of the deposited layers needs to be controlled with a resolution down to the nanometer. This article presents the preliminary results obtained by using plasma assisted ALD techniques to deposit NbN based compounds starting from chlorinated precursors and organic ones, and the design for a new deposition system currently being built at the Daresbury Laboratories.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA100  
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MOPVA102 Modeling the Low Level RF Response on the Beam during Crab Cavity Quench 1098
 
  • R. Apsimon, G. Burt, A.C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • R.B. Appleby
    UMAN, Manchester, United Kingdom
  • P. Baudrenghien, K.N. Sjobak
    CERN, Geneva, Switzerland
  
  The High Luminosity Upgrade for the LHC (HL-LHC) relies on crab cavities to compensate for the luminosity reduction due to the crossing angle of the colliding bunches at the interaction points. In this paper we present the simulation studies of cavity quenches and the impact on the beam. The cavity voltage and phase during the quench is determined from a simulation in Matlab and used to determine the impact on the beam from tracking simulations in SixTrack. The results of this study are important for determining the required machine protection and interlock systems for HL-LHC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA102  
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MOPVA104 Physical Vapour Deposition of NbTiN Thin Films for Superconducting RF Cavities 1102
 
  • S. Wilde, B. Chesca
    Loughborough University, Loughborough, Leicestershire, United Kingdom
  • E. Alves
    Associação EURATOM/IST, Instituto de Plasmas e Fusão Nuclear, Lisboa, Portugal
  • N.P. Barradas
    Universidade de Lisboa, Instituto Superior Técnico, Bobadela, Portugal
  • A.N. Hannah, O.B. Malyshev, N. Pattalwar, S.M. Pattalwar, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • G.B.G. Stenning
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  The production of superconducting coatings for radio frequency cavities is a rapidly developing field that should ultimately lead to acceleration gradients greater than those obtained by bulk Nb RF cavities. The use of thin films made from superconductors with thermodynamic critical field, HC>HCNb, allows the possibility of multilayer superconductor ' insulator ' superconductor (SIS) films and accelerators that could operate at temperatures above the 2 K typically used. SIS films theoretically allow increased acceleration gradient due to magnetic shielding of underlying superconducting layers [1] and higher operating temperature can reduce cost [2]. High impulse magnetron sputtering (HiPIMS) and pulsed DC magnetron sputtering processes were used to deposit NbTiN thin films onto Si(100) substrate. The films were characterised using scanning electron microscopy (SEM), x-ray diffraction (XRD), Rutherford back-scattering spectroscopy (RBS) and a four-point probe.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA104  
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MOPVA106 Experimental Studies of Asymmetric Dual Axis Cavity for Energy Recovery LINAC 1105
 
  • I.V. Konoplev, A.J. Lancaster, K. Metodiev, A. Seryi
    JAI, Oxford, United Kingdom
  • R. Ainsworth
    Fermilab, Batavia, Illinois, USA
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  
  Funding: The Leverhulme Trust via International Network Grant (IN-2015-012).
Increasing the beam charge and repetition rate leads to appearance of beam break-up instabilities in conventional ERLs. At this stage the highest current, from the SRF ERL, is around 300mA. A single turn, dual axis, compact Asymmetric Energy Recovery LINAC (AERL) was proposed. The concept assumes the use of electron beams with energies up to 300 MeV and peak currents >1A, enabling the generation of high flux EUV/X-rays and THz radiation using conventional approaches. System allows beam to be transported through each stage i.e. the acceleration, interaction and deceleration only once partially removing the feedback thus increasing the instability start current. This further improved by tuning the individual cells allowing only operating mode to be uniform inside the cavity. We present the studies of 7 cells, aluminium alloy prototype of the cavity and discuss the experimental results. We show that HOMs excited on the different axis have different R/Q factors and show the field structures of operating mode and HOMs. The experimental results observed are in good agreement with theoretical predictions and the full scale copper prototype is demonstrated. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA106  
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MOPVA113 RF Quality Control of SRF Cavities for LCLS-II Cryo-Modules 1108
 
  • M.H. Awida, P. Berrutti, T.N. Khabiboulline, A. Lunin, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  
  Funding: *Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
LCLS-II project is gearing up to build 36 cryo-modules of the 1.3 GHz TESLA style cavities. Half of those cryomodules are being built at Fermilab, while JLAB is carrying the production of the other half. In this paper, we present the process of quality controlling the RF performance of cavities until they are qualified for the final string assembly at Fermilab. The RF quality control process includes monitoring the frequency spectrum of each cavity and tuning/adjusting of the notch frequencies before testing at the Vertical Test Stand (VTS). Measured data during income QC is presented and in addition we show the notch frequencies before and after testing at the VTS. Moreover, we report some of the RF measurements taken while the cavity is cooled down to 2K temperature. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA113  
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MOPVA114 Materials Characterization for SRF Cavities: Gaining Insight Into Nb3Sn 1111
SUSPSIK102   use link to see paper's listing under its alternate paper code  
 
  • J. Tuggle
    Virginia Polytechnic Institute and State University, Blacksburg, USA
  • G.V. Eremeev, A.D. Palczewski, C.E. Reece
    JLab, Newport News, Virginia, USA
  • M.J. Kelley, U. Pudasaini
    The College of William and Mary, Williamsburg, Virginia, USA
  
  Funding: JLab work supported by U.S. DOE Contract No. DE-AC05-06OR23177. Work at William & Mary and Virginia Tech supported by the Office of High Energy Physics, U.S. Department of Energy grant DE-SC-0014475
Although SRF accelerators are an invaluable research tool they can be painfully expensive to construct and operate at the current level of SRF technology. This cost is significantly due to the necessity to operate at a temperature of only 2K. Considerable research is currently underway into next generation SRF cavity technologies such as Ndoping and Nb3Sn coating. Both of these technologies will lower the cryogenic load of accelerators, correspondingly lowering both construction and operating costs. However, current understanding of either technology is incomplete and in order to elucidate the underlying mechanisms there is a need to push current characterization methods forward. In this work, ion beam techniques (e.g. focused ion beam (FIB)), and electron backscatter diffraction (EBSD) were applied to help understand Nb3Sn coating mechanisms. This presentation will focus on characterization, providing examples of EBSD work, along with discussion of some of the issues encountered while trying to produce high quality EBSD data. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA114  
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MOPVA115 Status and Challenges of Vertical Electro-Polishing R&D at Cornell 1115
 
  • F. Furuta, M. Ge, T. Gruber, D.L. Hall, J.J. Kaufman, M. Liepe, R.D. Porter, J. Sears
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • T.D. Hall, M.E. Inman, R. Radhakrishnan, S.T. Snyder, E.J. Taylor
    Faraday Technology, Inc., Clayton, Ohio, USA
  • H. Hayano, S. Kato, T. Saeki
    KEK, Ibaraki, Japan
  
  Advanced Vertical Electro-Polishing (VEP) R&D for SRF Niobium cavities continues at Cornell's SRF group. One focus of this work is new EP cathode development in collaboration with KEK and Marui Galvanizing Co. Ltd (Marui) in Japan, and another focus is on HF free or acid free VEP protocols in collaboration with Faraday Technology Inc. The outcomes of these activities could be a significant cost reduction and an environmentally-friendlier VEP, which would be a breakthrough for future large scale EP applications on SRF cavities. Here we give a status update and report latest results from these R&D activities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA115  
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MOPVA116 Quench Studies in Single-Cell Nb3Sn Cavities Coated Using Vapour Diffusion 1119
 
  • D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • P. Cueva, D. Liarte, D.A. Muller, J.P. Sethna
    Cornell University, Ithaca, New York, USA
  
  The superconductor Nb3Sn is known to have a superheating field, Hsh, of approximately 400 mT. This critical field represents the ultimate achievable gradient in a superconducting cavity, and is equivalent to an accelerating gradient of 90 MV/m in an ILC single-cell cavity for this value of Hsh. However, the currently best performing Nb3Sn single-cell cavities remain limited to accelerating gradients of 17-18 MV/m, translating to a peak surface magnetic field of approx. 70 mT. In this paper, we consider theoretical models of candidate quench mechanisms, and compare them to experimental data from surface analysis and cavity tests.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA116  
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MOPVA117 Performance of a SRF Half-Wave-Resonator Tested at Cornell for the RAON Project 1123
 
  • M. Ge, F. Furuta, T. Gruber, D.L. Hall, S.W. Hartman, C. Henderson, M. Liepe, S. Lok, T.I. O'Connell, P.J. Pamel, J. Sears, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin
    IBS, Daejeon, Republic of Korea
  
  A prototype half-wave-resonator (HWR) with frequency 162.5MHz and geometrical \beta=0.12 for the RAON project is currently undergoing testing at Cornell University. Detailed vertical performance testing includes (1) test of the bare cavity without the helium tank; (2) test of the dressed cavity with helium tank. In this paper, we report on the development of the test infrastructure, test results, and performance data analysis.  
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MOPVA118 Impact of Trapped Magnetic Flux and Thermal Gradients on the Performance of Nb3Sn Cavities 1127
SUSPSIK103   use link to see paper's listing under its alternate paper code  
 
  • D.L. Hall, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • D. Liarte, J.P. Sethna
    Cornell University, Ithaca, New York, USA
  
  Trapped magnetic flux is known to degrade the quality factor of superconducting cavities by increasing the surface losses ascribed to the residual resistance. In Nb3Sn cavities, which consist of a thin layer of Nb3Sn coated on a bulk niobium substrate, the bimetallic interface results in a thermal current being generated in the presence of a thermal gradient, which will in turn generate flux that can be trapped. In this paper we quantify the impact of trapped flux, from either ambient fields or thermal gradients, on the performance of the cavity. We discover that the sensitivity to trapped flux, a measure of the increase in residual resistance as a function of the amount of flux trapped, is a function of the accelerating gradient. A theoretical framework to explain this phenomenon is proposed, and the impact on the requirements for operating a Nb3Sn cavity in a cryomodule are considered.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA118  
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MOPVA119 Surface Analysis of Features Seen on Nb3Sn Sample Coupons Grown by Vapour Diffusion 1130
 
  • D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T. Arias, P. Cueva, D.A. Muller, N. Sitaraman
    Cornell University, Ithaca, New York, USA
  
  As a high-kappa superconductor with a coherence length of 7 nm, the superconductor Nb3Sn is highly susceptible to material features at the sub-micron scale. For niobium surfaces coated with a thin layer of Nb3Sn using the vapour diffusion method, the polycrystalline nature of the film grown lends to the possibility that performance-degrading non-uniformities may develop. In particular, regions of insufficiently thick coating and tin-depletion have been seen to occur in sample coupons. In the interests of understanding how to control the presence and nature of such features, it is necessary to know how they form. In this paper we stop the coating at defined instances to gain a stop-motion image of the growth of the layer, and use SEM and TEM techniques to image the development of the features seen in previously coated samples. We demonstrate that surface pre-anodisation can suppress the formation of thin film regions, and apply this technique to a single-cell cavity. Contemporarily, we use TEM with EDS mapping to monitor grain boundaries and tin-depleted regions within the layer.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA119  
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MOPVA121 Frequency Tuner Development at Cornell for the RAON Half-Wave-Resonator 1134
 
  • M. Ge, F. Furuta, T. Gruber, D.L. Hall, S.W. Hartman, C. Henderson, M. Liepe, S. Lok, T.I. O'Connell, P.J. Pamel, P. Quigley, J. Sears, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • B.H. Choi, J. Joo, J.W. Kim, W.K. Kim, J. Lee, I. Shin
    IBS, Daejeon, Republic of Korea
  
  The half-wave-resonators (HWR) for the RAON pro-ject require a slow frequency tuner that can provide at least 80 kHz tuning range. Cornell University is currently in the process of designing, prototyping, and testing this HWR tuner. In this paper, we present the tuner design, prototype fabrication, and first test results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA121  
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MOPVA122 Microphonics Studies of the CBETA Linac Cryomodules 1138
 
  • N. Banerjee, J. Dobbins, F. Furuta, D.L. Hall, G.H. Hoffstaetter, M. Liepe, 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 was performed through the support of NYSERDA (New York State Energy Research and Development Agency).
The Cornell BNL ERL Test Accelerator (CBETA) incorporates two SRF linacs; one for its injector and another for the energy recovery loop. Microphonics in both the cryomodules play a crucial role in determining the energy stability of the electron beam in high current operation. We have measured vibrations and frequency detuning of the SRF cavities and determined that the cryogenic system is the major source of microphonics in both cryomodules. In this paper we discuss these measurements and demonstrate an Active Microphonics Compensation system implemented using fast piezo-electric tuners which we incorporated in our Low Level RF control system to be used in routine operation. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA122  
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MOPVA123 Cornell Sample Host Cavity: Recent Results 1142
 
  • J.T. Maniscalco, D.L. Hall, M. Liepe, R.D. Porter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • V.M. Arrieta, S.R. McNeal, W.E. Williams
    Ultramet, Pacoima, California, USA
  
  Funding: NSF-PHY 1416318 NSF-PHY 1549132
The Cornell sample host cavity is a 3.9~GHz testing system for RF analysis of novel superconducting surfaces. The cavity applies fields up to 100~mT on a removable and replaceable 5-inch sample plate in order to measure the surface resistance of the material under investigation. The cavity also includes a temperature-mapping system for localization of quench events and surface defects. In this paper, we present recent experimental results from the host cavity of niobium deposited onto molybdenum and copper substrates using chemical vapor deposition, in collaboration with industry partner Ultramet. The results indicate low BCS resistance and good adhesion but also areas of high residual resistance due to chemical and morphological defects. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA123  
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MOPVA124 Effectiveness of Chemical Treatments for Reducing the Surface Roughness of Nb3Sn 1145
SUSPSIK104   use link to see paper's listing under its alternate paper code  
 
  • R.D. Porter, F. Furuta, D.L. Hall, M. Liepe, J.T. Maniscalco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: DOE DE-SC008431, NSF-PHY 1549132, NSF DMR-1120296
Current Niobium-3 Tin (Nb3Sn) superconducting radio-frequency (SRF) accelerator cavities have rougher surfaces than conventional electropolished Niobium accelerator cavities. The surface roughness can cause enhancement of the surface magnetic field, pushing it beyond the critical field. If this occurs over a large enough area it can cause the cavity to quench. The surface roughness may cause other effects that negatively impact cavity quality factor (Q) performance. Reducing surface roughness of Nb3Sn cavities may be necessary to achieve higher gradient with high Q. Current chemical treatments for reducing the surface roughness of Niobium are challenging for Nb3Sn: the Nb3Sn layer is only ~2 um thick while it is difficult to remove less than 1 mu uniformly with most chemical treatments. This paper presents measurements of the surface roughness before and after Buffered Chemical Polish, Electropolishing and oxipolishing. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA124  
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MOPVA126 Sample Host Cavity Design for Measuring Flux Entry and Quench 1149
 
  • R.D. Porter, M. Liepe, J.T. Maniscalco, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: NSF-PHY 1549132
Current state-of-the-art Niobium superconducting radio-frequency (SRF) accelerator cavities have reached surface magnetic field close to the theoretical maximum set by the superheating field. Further increasing accelerating gradients will require new superconducting materials for accelerator cavities that can support higher surface magnetic fields. This necessitates measuring the quench fields of new materials in high power RF fields. In this paper, we present designs and simulations of a sample host cavity. The cavity design is optimized to maximize the surface magnetic field achieved on the sample. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA126  
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MOPVA127 Vertical Test Results for the LCLS-II 1.3 GHz First Article Cavities 1152
 
  • A. Burrill, D. Gonnella, M.C. Ross
    SLAC, Menlo Park, California, USA
  • G.K. Davis, A.D. Palczewski, L. Zhao
    JLab, Newport News, Virginia, USA
  • A. Grassellino, O.S. Melnychuk
    Fermilab, Batavia, Illinois, USA
  
  The LCLS-II project requires 35 1.3 GHz cryomodules to be installed in the accelerator in order to deliver a 4 GeV electron beam to the undulators hall. These 35 cryomodules will consist of 8 1.3 GHz TESLA style SRF cavities, a design most recently used for the XFEL project in Hamburg, Germany. The cavity design has remained largely unchanged, but the cavity treatment has been modified to utilize the nitrogen doping process to allow for Quality factors in excess of 3x1010 at 16 MV/m, the designed operating gradient of the cavities in the CM. Two industrialized vendors are producing most of the SRF cavities for these cryomodules; and the performance of the first article cavities, 16 from each vendor, will be reported on in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA127  
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MOPVA128 RF Performance of Nitrogen-Doped Production SRF Cavities for LCLS-II 1156
 
  • D. Gonnella, A. Burrill, M.C. Ross
    SLAC, Menlo Park, California, USA
  • S. Aderhold, A. Grassellino, C.J. Grimm, T.N. Khabiboulline, O.S. Melnychuk, S. Posen, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  • E. Daly, G.K. Davis, F. Marhauser, K.M. Wilson
    JLab, Newport News, Virginia, USA
  
  Funding: DOE and the LCLS-II Project
The Linac Coherent Light Source II (LCLS-II) requires 280 9-cell superconducting RF cavities for operation in continuous wave mode. Two vendors have previously been selected to produce the cavities, Research Instruments GmbH and Ettore Zanon S.p.a. Here we present results from manufacturing and cavity preparation for the cavities constructed at these two vendors for LCLS-II. We show how the cavity preparation method has been changed mid-production in order to improve flux expulsion in the cavities and maintain high performance in realistic magnetic field environments (~5 mG). Additionally, we show that the nitrogen-doping process has been carried out successfully and repeatedly on over 70 cavities. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA128  
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MOPVA130 Development of Waveguide HOM Loads for BERLinPro and BESSY-VSR SRF Cavities 1160
 
  • J. Guo, F. Fors, J. Henry, R.A. Rimmer, H. Wang
    JLab, Newport News, Virginia, USA
  • H.-W. Glock, A. Neumann, A.V. Tsakanian, A.V. Vélez
    HZB, Berlin, Germany
  
  Two ongoing accelerator projects at Helmholtz-Zentrum Berlin (HZB), BERLinPro and BESSY-VSR, need to design three different SRF cavities, a 1.3GHz cavity in BERLinPro and 1.5GHz/1.75GHz cavities in BESSY-VSR. These cavities have adopted waveguide HOM dampers in their design, with a few tens of watts HOM power in each load for BERLinPro and a few hundred watts for BESSY-VSR. JLab is collaborating with HZB prototyping these HOM loads. In this paper, we will report on the integrated RF-thermal-mechanical design of the loads, as well as the fabrication and testing results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA130  
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MOPVA131 Status of the LCLS-II Accelerating Cavity Production 1164
 
  • F. Marhauser, E. Daly, J.A. Fitzpatrick, A.D. Palczewski, J.P. Preble, K.M. Wilson
    JLab, Newport News, Virginia, USA
  • A. Burrill, D. Gonnella
    SLAC, Menlo Park, California, USA
  • C.J. Grimm
    Fermilab, Batavia, Illinois, USA
  
  Funding: Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 with supplemental funding from the LCLS-II Project U.S. DOE Contract No. DE-AC02-76SF00515.
Cavity serial production for the LCLS-II 4 GeV CM SRF linac has started. A quantity of 266 accelerating cavities has been ordered from two industrial vendors. Jefferson Laboratory leads the cavity procurement activities for the project and has successfully transferred the Nitrogen-Doping process to the industrial partners in the initial phase, which is now being applied for the production cavities. We report on the results from vendor qualification and the status of the cavity production for LCLS-II. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA131  
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MOPVA132 Production of Copper-Plated Beamline Bellows and Spools for LCLS-II 1167
 
  • K.M. Wilson, B. Carpenter, E. Daly, N.A. Huque, T. Peshehonoff
    JLab, Newport News, Virginia, USA
  • T.T. Arkan, A. Lunin, K.S. Premo
    Fermilab, Batavia, Illinois, USA
  
  Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory is currently constructing a major upgrade to its accelerator, the Linac Coherent Light Source II (LCLS-II). Several Department of Energy national laboratories, including the Thomas Jefferson National Accelerator Facility (JLab) and Fermi National Accelerator Laboratory (FNAL), are participating in this project. The 1.3-GHz cryomodules for this project consist of eight cavities separated by bellows (expansion joints) and spools (tube sections), which are copper plated for RF conduction. JLab is responsible for procurement of these bellows and spools, which are delivered to JLab and FNAL for assembly into cryomodules. Achieving accelerator-grade copper plating is always a challenge and requires careful specification of requirements and application of quality control processes. Due to the demanding technical requirements of this part, JLab implemented procurement strategies to make the process more efficient as well as provide process redundancy. This paper discusses the manufacturing challenges that were encountered and resolved, as well as the strategies that were employed to minimize the impact of any technical issues. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA132  
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MOPVA133 Optimization of the RF Cavity Heat Load and Trip Rates for CEBAF at 12 GeV 1170
 
  • H. Zhang, A. Freyberger, G.A. Krafft, Y. Roblin
    JLab, Newport News, Virginia, USA
  • B. Terzić
    ODU, Norfolk, Virginia, USA
  
  Funding: Work supported by the Department of Energy under Contract No. DE-AC05-06OR23177
The Continuous Electron Beam Accelerator Facility at JLab has 200 RF cavities in the north linac and the south linac respectively after the 12 GeV upgrade. The purpose of this work is to simultaneously optimize the heat load and the trip rate for the cavities and to reconstruct the pareto-optimal front in a timely manner when some of the cavities are turned down. By choosing an efficient optimizer and strategically creating the initial gradients, the pareto-optimal front for no more than 15 cavities down can be re-established within 20 seconds. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA133  
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MOPVA135 Fabrication, Processing and RF Test of RF-Dipole Prototype Crabbing Cavity for LHC High Luminosity Upgrade 1174
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • H. Park
    JLab, Newport News, Virginia, USA
  
  The superconducting rf-dipole crabbing cavity is one of two crabbing cavity designs proposed for the LHC high luminosity upgrade. The proof-of-principle rf-dipole cavity operating at 400 MHz has demonstrated excellent performance exceeding the design specifications. The prototype cavity for SPS beam test has been designed to include the fundamental power coupler, HOM couplers, and all the ancillary components intended to meet the design requirements. A crabbing cavity system is expected to be installed in the SPS beam line and tested prior to the installation in LHC; this will be the first crabbing cavity operation on a proton beam. The fabrication of two prototype rf-dipole cavities is currently being completed at Jefferson Lab. This paper presents the details on cavity processing and cryogenic test results of the rf-dipole cavities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA135  
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MOPVA136 Higher Order Multipole Analysis for 952.6 Mhz Superconducting Crabbing Cavities for Jefferson Lab Electron-Ion Collider 1177
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • H. Park
    JLab, Newport News, Virginia, USA
  
  The proposed electron ion collider at Jefferson Lab requires a crabbing cavity system to increase the luminosity in the colliding beams. Currently several superconducting crabbing cavity designs are being reviewed as the design option for the crabbing cavity. Knowledge of higher order mode multipole field effects is important for accurate beam dynamics study for the crabbing system, in selecting the design that meets the design specifications. The multipole components can be accurately determined numerically using the electromagnetic field data in the rf structure. This paper discusses the detailed analysis of higher order multipole components for the operating crabbing mode and design modifications in reducing those components.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA136  
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MOPVA140 Multipacting Behavior Study for the 112 MHz Superconducting Photo-Electron Gun 1180
SUSPSIK105   use link to see paper's listing under its alternate paper code  
 
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
  • V. Litvinenko, G. Narayan, I. Pinayev, F. Severino, K.S. Smith
    BNL, Upton, Long Island, New York, USA
  • V. Litvinenko
    Stony Brook University, Stony Brook, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Superconducting 1.2 MV 112 MHz quarter-wave photo-electron gun (SRF gun) is used as a source of electron beam for the Coherent electron Cooling experiment (CeC) at BNL. During the CeC commissioning we encountered a number of multipacting zones in the gun. It was also observed that introduction of CsK2Sb photocathode creates additional multipacting zone. This paper presents numerical and experimental study of the multipactor discharge in the SRF gun. We also discuss ways of crossing the multipacting levels to the operational voltage. Finally, we compare the results of our numerical simulations of the multipactor discharge using ACE3P with experimental data. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA140  
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MOPVA141 Input RF Coupler Design for Energy Compensator Cavity in eRHIC 1184
 
  • C. Xu, S. Bellavia, I. Ben-Zvi, M. Blaskiewicz, Y. Hao, K.S. Smith, R. Than, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
This report gives a detail design of a 1.3 GHz input coupler for second harmonic cavity for eRHIC project. This coupler is designed to transmit 200KW CW RF to the cavity to compensate the synchrotron radiation loss. This report include RF and thermal simulation for this design. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA141  
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MOPVA143 Trim Tuning of SPS-Series DQW Crab Cavity Prototypes 1187
 
  • S. Verdú-Andrés, J. Skaritka, Q. Wu
    BNL, Upton, Long Island, New York, USA
  • S. Baurac, C.H. Boulware, T.L. Grimm, J.A. Yancey
    Niowave, Inc., Lansing, Michigan, USA
  • W.A. Clemens, E.A. McEwen, H. Park
    JLab, Newport News, Virginia, USA
  • H. Park
    ODU, Norfolk, Virginia, USA
  • A. Ratti
    LBNL, Berkeley, California, USA
  • A. Ratti
    SLAC, Menlo Park, California, USA
  
  Funding: Work partially supported by US DOE via BSA LLC contract No.DE-AC02-98CH10886 and by the US LARP program.
The final steps in the manufacturing of a superconducting RF cavity involve careful tuning before the final welds to match the target frequency as fabrication tolerances may introduce some frequency deviations. The target frequency is chosen based on analysis of the shifts induced by remaining processing steps including acid etching and cool down. The baseline fabrication of a DQW crab cavity for the High Luminosity LHC (HL-LHC) envisages a first tuning before the cavity subassemblies are welded together. To produce a very accurate final result, subassemblies are trimmed to frequency in the last machining steps, using a clamped cavity assembly for RF measurements. This paper will describe the trim tuning of one of the SPS prototype DQW crab cavities fabricated by Niowave. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA143  
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MOPVA144 Post-Processing of Nb3Sn Coated Nb 1190
SUSPSIK106   use link to see paper's listing under its alternate paper code  
 
  • U. Pudasaini, M.J. Kelley
    The College of William and Mary, Williamsburg, Virginia, USA
  • G.V. Eremeev, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
  • M.J. Kelley, J. Tuggle
    Virginia Polytechnic Institute and State University, Blacksburg, USA
  
  Funding: Supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE­AC05­06OR23177 and Office of High Energy Physics under grant SC00144475.
Practical SRF cavities may be subjected to one or more processes after nominally complete preparation. Successful implementation of such processes in Nb3Sn coated cavities requires the understanding of material's response to these treatments. SRF-grade Nb samples, coated with Nb3Sn by the widely used tin vapor diffusion process were subjected to one or more of the following: hydrofluoric acid (HF) rinsing, oxypolishing, buffered chemical polishing (BCP) or electrochemical treatment. They were examined by materials characterization tech-niques including scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and X-ray photoelectron spec-troscopy (XPS). The effects compared to niobium are different enough in most cases that further development is desirable to routinely obtain a favorable result. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA144  
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WEZB2
 Development and Testing of Spoke Cavities  
 
  • F.S. He
    IHEP, Beijing, People's Republic of China
  
  Several laboratories are developing and testing superconducting spoke cavities, including the first tests with beam. The speaker will present an overview of the ongoing developments and the plans and perspectives for the use of this type of cavities in present and future linac projects.  
slides icon Slides WEZB2 [6.710 MB]  
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THOBB2
 Plasma Processing R&D for LCLS-II Cavities  
 
  • M. Martinello, S. Aderhold, P. Berrutti, A. Grassellino, T.N. Khabiboulline
    Fermilab, Batavia, Illinois, USA
  • A. Burrill, D. Gonnella, G. Lanza, C.-K. Ng, M.C. Ross, L. Xiao
    SLAC, Menlo Park, California, USA
  • M. Doleans
    ORNL, Oak Ridge, Tennessee, USA
  
  Field emission is one the major limitations to the maximum usable accelerating gradient of SRF cavities in cryomodules. Taking advantage of the plasma chemistry, field emitting particles may be preferentially attacked with the purpose of modifying the work function, smoothing the particle shape or even removing completely the field emitter. Relying on this idea, a collaboration between FNAL, SLAC and ORNL was established with the purpose of building a plasma processing system as a tool capable to minimize and overcome the problem of field emission in LCLS-II cryomodules. The plasma processing system is inspired to the one already built at the Spallation Neutron Source (SNS), that is capable to process in-situ cavities from hydrocarbon contaminants, by means of a neon-oxygen reactive plasma mixture. Here we show an innovative RF design that has been optimized in order to ignite the plasma using a mixture of fundamental pass-band and high order modes. In addition, the first results obtained on contaminated samples and single-cell cavities are shown together with the future plan of the project.  
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THOBB3 ESS SRF Linear Accelerator Components Preliminary Results and Integration 3666
 
  • C. Darve, N. Elias, C.G. Maiano, F. Schlander
    ESS, Lund, Sweden
  • C. Arcambal, G. Devanz, F. Peauger
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • E. Cenni
    CEA/IRFU, Gif-sur-Yvette, France
  • G. Costanza
    Lund University, Lund, Sweden
  • P. Duthil, G. Olry, D. Reynet
    IPN, Orsay, France
  • L. Hermansson
    Uppsala University, Uppsala, Sweden
  • P. Michelato, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  
  The European Spallation Source (ESS) is a pan-European project and one of world's largest research infrastructures based on neutron sources. This collaborative project is funded by a collaboration of 17 European countries and is under construction in Lund, Sweden. The 5 MW, 2.86 ms long pulse proton accelerator has a repetition frequency of 14 Hz (4 % duty cycle), and a beam current of 62.5 mA. The Superconducting Radio-Frequency (SRF) linac is composed of three families of Superconducting Radio-Frequency (SRF) cavities, which are being prototyped, counting the spoke resonators with a geometric beta of 0.5, medium-beta elliptical cavities (betag=0.67) and high-beta elliptical cavities (betag=0.86). After a description of the ESS linear accelerator layout, this article will focus on the recent progress towards integration of the first test results of the main critical components to be assembled in cryomodules, then in the ESS tunnel.  
slides icon Slides THOBB3 [25.611 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THOBB3  
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THPVA069 NSC KIPT Experience in Use of Laser Tracker Leica at 401 in Equipment Alignment of 100 MeV/100 KW Electron Linear Accelerator of Neutron Source Driver 4604
 
  • M. Moisieienko, O. Bezditko, I.M. Karnaukhov, A. Mytsykov, A.Y. Zelinsky
    NSC/KIPT, Kharkov, Ukraine
  
  For successful operation of electron linear accelerator that is driver of NSC KIPT Neutron source it is necessary that all the acceleration sections and all the electromagnetic elements should be installed in design position according to the designed lattice. Accuracies of all electromagnetic elements installation are 150 mkm in transverse positions and 200 mrad for all three rotation directions. The whole process, fiducialization and developing of coordinate net, is controlled by Laser tracker Leica AT 401. Well-planned methods allow to realize uniform irradiation of neutron-generation target.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA069  
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