SRF2017 - List of Keywords (ion)

Paper	Title	Other Keywords	Page
MOXA02	The Commissioning of the European XFEL Linac and its Performance	MMI, FEL, linac, cavity	1
	D. Reschke, W. Decking, N. Walker, H. Weise DESY, Hamburg, Germany
	Funding: Presented on behalf of the XFEL Accelerator Consortium. Work supported by the respective funding agencies of the contributing institutes; for details see www.xfel.eu. The main linac of the superconducting accelerator of the European XFEL presently consists of 96 accelerator modules, each housing eight 1.3 GHz TESLA-type cavi-ties, with an average design gradient of 23.6 MV/m. The performance of each individual module has been tested after module assembly in the Accelerator Module Test Facility (AMTF) at DESY. The 2-year period of module installation to the accelerator tunnel was finished in August 2016. In order to recheck and re-establish the performance of the input power couplers, warm processing of nearly all installed modules was performed before the first cool-down during Dec 2016 / Jan 2017. Four consecutive modules are connected to one 10 MW klystron and form a so-called RF station, which is powered and controlled individually during operation. By June 2017 23 of 25 RF stations have been commissioned for beam acceleration including frequency tuning, various calibrations and LLRF adjustments. A preliminary beam energy of 14 GeV was achieved, which is sufficient for first lasing experiments. No significant performance degradation has been observed so far. The commissioning experience and the available RF performance data will be presented.
	Slides MOXA02 [6.896 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOXA02
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MOXA03	The 30MeV Stage of the ARIEL e-linac	cavity, linac, cryomodule, electron	6
	R.E. Laxdal, Z.T. Ang, T. Au, K. Fong, O.K. Kester, S.R. Koscielniak, A.N. Koveshnikov, M.P. Laverty, Y. Ma, D.W. Storey, E. Thoeng, Z.Y. Yao, Q. Zheng, V. Zvyagintsev TRIUMF, Vancouver, Canada
	A MW class cw superconducting electron linac (e-Linac) is being installed at TRIUMF as a driver for radioactive beam production as part of the ARIEL project. The e-linac final configuration is planned to consist of five 1.3GHz nine-cell cavities housed in three cryomodules with one single cavity injector cryomodule (EINJ) and two double cavity accelerating cryomodules (EACA, EACB) to accelerate in continuous-wave (cw) up to 10mA of electrons to 50MeV. The e-Linac is being installed in stages. A demonstrator phase (2014) consisting of a 300kV electron gun, EINJ, and a partially outfitted EACA with just one accelerating cavity was installed for initial technical and beam tests to 22.9MeV. A Stage 2 upgrade now installed has a completed EACA to reach an operational goal of 3mA of electrons to 30MeV for first science from the ARIEL ISOL targets. A single 290kW klystron is used to feed the two EACA cavities in vector-sum closed-loop control. The paper is focused on the SRF challenges: systems design, cavity and cryomodule performance, rf ancillaries preparation and performance, LLRF and RF system performance and final beam test results.
	Slides MOXA03 [13.981 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOXA03
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MOXA04	Superconducting Accelerator for ERL Based FEL EUV Light Source at KEK	cavity, HOM, linac, operation	13
	H. Sakai, E. Kako, T. Konomi, T. Kubo, K. Umemori KEK, Ibaraki, Japan T. Ota Toshiba, Yokohama, Japan M. Sawamura QST, Tokai, Japan
	An energy recovery linac (ERL)-based free electron laser (FEL) is a possible candidate of a tens of kW EUV source and open the era for next generation EUV-lithography. We have designed the 10 mA class ERL-based EUV-FEL source to generate more than 10 kW power. One of the key technologies is CW superconducting cavities to realize the energy recovery of high beam current of more than 10 mA by suppressing HOMs and high gradient acceleration of higher than 12 MV/m. This CW superconducting cavity had been developed through the construction of the Compact ERL facility in KEK and it successfully achieved the energy recovery of 1 mA CW beam until now. In this talk, first we express our design strategies of SRF cavities of the main linac of ERL-EUV light sources not only to suppress the HOMs but also to overcome the field emission problem by modifying the main linac cavity of Compact ERL more sophisticatedly. Next we show the recent development works for ERL-EUV superconducting cavity about HOM damper, cryomodule, and its clean string-assembly work by using horizontal test stand.
	Slides MOXA04 [5.938 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOXA04
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MOXA07	Development of the C-ADS SRF Accelerator at IHEP	cavity, linac, cryomodule, operation	19
	F. Yan, L. Bian, J.S. Cao, Y. Chen, Y.L. Chi, J.P. Dai, L. Dong, L.L. Dong, Y.Y. Du, H.F.S. Feisi, Y. Gao, R. Ge, H. Geng, D.Z. Guo, D.Y. He, J. He, T.M. Huang, X. Jing, B. Li, H. Li, L. Li, S.P. Li, H.Y. Lin, F. Liu, R.L. Liu, F. Long, Y.H. Lu, H.Z. Ma, Q. Ma, X. Ma, C. Meng, Z.H. Mi, H.F. Ouyang, W.M. Pan, S. Pei, Q.L. Peng, X.H. Peng, P. Sha, H. Shi, P. Su, Y.F. Sui, L.R. Sun, X.T. Sun, G.W. Wang, J.L. Wang, S.C. Wang, G. Wu, O. Xiao, X.C. Yang, Q. Ye, R. Ye, L. Yu, X.Y. Zhang, X.Y. Zhao, Y.L. Zhao, Y. Zhao, Z.H. ZhenHua, N. Zhou, Z.S. Zhou IHEP, Beijing, People's Republic of China H.Y. Zhu Institute of High Energy Physics (IHEP), People's Republic of China
	Funding: CAS Strategic Priority Research Program-Future Advanced Nuclear Fission Energy (Accelerator-Driven Sub-critical System) and National Natural Science Foundation of China, under contract NO. 11405190 The 10 MeV accelerator-driven subcritical system (ADS) Injector I test stand at Institute of High Energy Physics (IHEP) is a testing facility dedicated to demonstrate one of the two injector design schemes [Injector Scheme-I, which works at 325 MHz], for the ADS project in China. The ion source was installed since April of 2014, periods of commissioning are regularly scheduled between installation phases of the rest of the injector. Early this year, continuous wave (CW) proton beam has been successfully obtained with energy of 10MeV and average beam current around 2 mA, the single spoke cavities with smallest developed beta (βg=0.12) were applied and successfully commissioned. Single spoke cavities with higher beta (βg=0.21) were also adopted for the last cryomodule of 25MeV proton linac, and 170uA CW proton beam were shooting through recently. This contribution reports the details of the development of the C-ADS SRF accelerator at IHEP and the challenges of the CW machine commissioning
	Slides MOXA07 [5.605 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOXA07
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MOYA01	The Superconducting Accelerator for the ESS Project	cavity, cryomodule, SRF, linac	24
	F. Schlander, C. Darve, N. Elias, M. Lindroos, C.G. Maiano ESS, Lund, Sweden P. Bosland CEA/IRFU, Gif-sur-Yvette, France M. Ellis STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom P. Michelato INFN/LASA, Segrate (MI), Italy G. Olry IPN, Orsay, France R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden
	The European Spallation Source, ESS, is under construction in Lund since 2014. While the installation of the source and the normal conducting part will start in this autumn, the production and testing of cryomodules and cavities for the superconducting accelerator is in full swing at the partner laboratories. The spoke cavities and cryomodules will be provided by IPN Orsay and the testing of those modules will take place at Uppsala University. Prototyping and assembly of the elliptical cryomodules series is occurring at CEA Saclay, and the modules will be tested at a new test stand at ESS. The fabrication and test of the medium beta cavities is provided by INFN Milan and STFC Daresbury for the high beta cavities respectively. An overview of the current activities and test results will be presented in this talk.
	Slides MOYA01 [26.361 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOYA01
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MOYA02	BESSY VSR: SRF Challenges and Developments for a Variable-pulse Length Next-generation Light Source	cavity, HOM, SRF, synchrotron	29
	A.V. Vélez, H.-W. Glock, F. Glöckner, B.D.S. Hall, J. Knobloch, A. Neumann, P. Schnizer, E. Sharples HZB, Berlin, Germany A.V. Tsakanian Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
	The BESSY VSR project represents an exciting alternative to diffraction limited storage rings in the development of a next generation light source. Such a system should be capable to store "standard" (some 10 ps long) and "short" (ps and sub-ps long) pulses simultaneously in the storage ring opening the door to picosecond dynamic and high-resolution experiments at the same facility. This unique feature can be created by the introduction of the beating effects produced by higher harmonic SRF cavity systems (1.5 GHz & 1.75 GHz). The challenging design specifications as well as the technological demands on the SRF system make BESSY VSR a defiant project where non-standard techniques such as waveguide-damped cavities have been further developed. This talk focuses on the new SRF developments that includes wveguide-damped cavities, high-power couplers and higher-order mode absorbers that must handle nearly 2 kW of HOM power. The cryomodule design and its interaction with the beam will also be discussed. Comment: VSR concept was introduced at SRF15. Much development work has now been done. Here the focus is more one the technology of VSR and the talk could also be listed under "SRF technology R&D"
	Slides MOYA02 [7.961 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOYA02
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MOYA03	Progress of the RAON	cavity, cryomodule, quadrupole, rfq	36
	D. Jeon, B.H. Choi, C. Choi, J.W. Choi, C.O. Choi, S. Choi, I. Chun, I.S. Hong, M.O. Hyun, H. Jang, H.M. Jang, J.-H. Jang, S.C. Jeong, H. Jin, Y.W. Jo, J. Joo, M.J. Joung, H.C. Jung, I.I. Jung, Y. Jung, J. Kang, D.G. Kim, H. Kim, H.J. Kim, J.H. Kim, J.-W. Kim, W.K. Kim, Y. Kim, Y.K. Kwon, D.Y. Lee, J. Lee, K.W. Lee, M. Lee, S. Lee, S. Lee, S.H. Nam, B.-S. Park, M.J. Park, K.T. Seol, I. Shin, J.H. Shin, C.W. Son, K.T. Son, S.W. Yoon, A. Zaghloul IBS, Daejeon, Republic of Korea
	Funding: This work was supported by the Institute for Basic Science funded by the Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) under Contract 2013M7A1A1075764 Construction of the RAON heavy ion accelerator facility is in-progress in Korea. The driver linac is a superconducting linac with 200 MeV/u for uranium beam and 400 kW beam power. Prototyping of major components and their tests are proceeding including superconducting cavities, superconducting magnets and cryomodules. December 2016, the RFQ accelerated oxygen beam. Status report of the RAON accelerator systems is presented.
	Slides MOYA03 [10.275 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOYA03
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MOPB001	Concepts and Design for Beamline HOM Dampers for eRHIC	HOM, cavity, impedance, linac	39
	P. Kolb, Y. Gao, D. Holmes, K.S. Smith, W. Xu BNL, Upton, Long Island, New York, USA Y. Gao PKU, Beijing, People's Republic of China
	Funding: Work supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. In the design of eRHIC at BNL, HOM power plays a major role for the SRF installation. Depending on the final accelerator design and choice of cavity, up to 100kW of HOM power is estimated to be generated, presenting a big challenge for the HOM damping concept. Due to this high amount of HOM power, all current concepts for eRHIC would use room temperature beam line absorbers equipped with silicone-carbide dielectrics to absorb HOM power. Concepts, designs and simulations for these beam line absorbers will be presented.
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MOPB002	eRHIC Crab Cavity Choice for Ring-ring Design	cavity, luminosity, electron, impedance	43
	Q. Wu, I. Ben-Zvi, Y. Hao, S. Verdú-Andrés, B. P. Xiao BNL, Upton, Long Island, New York, USA
	Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The future electron ion collider eRHIC adopts large crossing angle (22 mrad) to allow fast separation of two beams in the ring-ring scheme. Crab cavities are required to recover the luminosity from geometric losses. Initial calculation shows that the frequency of the cavities for the ion beam is no more than 336MHz. In this paper, we discuss the crab cavity related lattice parameters for both ion and electron beams in ring-ring design, the frequency choice, and the cavity design considerations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB002
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MOPB003	A New High Resolution Optical System for Inspection of Gun-and Multi-cell Resonators in ISO-4 Cleanrooms	cavity, gun, SRF, MMI	47
	M. Schalwat, R. Bandelmann, A. Daniel, N. Krupka, A. Matheisen, S.T. Sievers DESY, Hamburg, Germany
	Optical inspection of the inner surface of superconducting resonators was established during European XFEL cavity production by usage of the so called OBACHT optical inspection. In addition to the surface inspection by OBACHT a new optical inspection system with integrated high resolution camera is set up at DESY. It allows inspection of multi-cell resonators as well as gun cavity resonators with only single side accessibility to the inner surface. A prototype was commissioned and optical inspections were done with OBACHT and the new system in parallel. Two SRF gun cavities were inspected by this optical system and origin of limitations of the resonators were identified.
	Poster MOPB003 [0.220 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB003
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MOPB004	Design of a RF Quadrupole Resonator for Landau Damping in HL-LHC	cavity, impedance, quadrupole, damping	51
	K. Papke, A. Grudiev CERN, Geneva, Switzerland
	The design and optimization of a quadrupole resonator for transverse Landau damping in the High Luminosity Large Hadron Collider (HL-LHC) is presented. Two different cavity types are considered whose shape is determined by quadrupolar strength, surface peak fields, and beam coupling impedance. The lower order and higher order mode (LOM and HOM) spectra of the optimized cavities are investigated and different approaches for their damping are proposed. Along an example, the required RF power and optimal external quality factor for the input coupler is derived.
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MOPB005	Beam Dynamics Simulations for the New Superconducting CW Heavy Ion Linca at GSI	cavity, linac, heavy-ion, accelerating-gradient	56
	M. Schwarz, M. Basten, M. Busch, H. Podlech, U. Ratzinger, R. Tiede IAP, Frankfurt am Main, Germany W.A. Barth, S. Yaramyshev MEPhI, Moscow, Russia W.A. Barth, M. Heilmann, S. Yaramyshev GSI, Darmstadt, Germany W.A. Barth, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu HIM, Mainz, Germany
	Funding: Work supported by BMBF contr. No. 05P15RFRBA For future experiments with heavy ions near the coulomb barrier within the super-heavy element (SHE) research project a multi-stage R&D program of GSI, HIM and IAP is currently in progress. It aims at developing a superconducting (sc) continuous wave (CW) LINAC with multiple CH cavities as key components downstream the upgraded High Charge Injector (HLI) at GSI. The LINAC design is challenging, due to the requirement of intense beams in CW-mode up to a mass-to-charge ratio of 6 while covering a broad output energy range from 3.5 to 7.3 MeV/u with minimum energy spread. After sucessful tests with the first CH cavity in 2016 demonstrated a promising maximum accelerating gradient of E_a = 9.6 MV/m, recently first beam tests have been started as next milestone at GSI, confirming its flawless functionality. W. Barth et al., Further Layout Investigations for a Superconducting CW-linac for Heavy Ions at GSI, 18th Int. Conf. on RF Superconductivity (SRF17), Lanzhou, China, July 2017, paper MOPB023.*
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MOPB007	Design of the Superconducting Quarter Wave Resonators for HIAF	cavity, linac, heavy-ion, ECR	59
	C. Zhang, L. Chen, Q.W. Chu, H. Guo, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, L. Li, Y.M. Li, F. Pan, T. Tan, R.X. Wang, A.D. Wu, Q.J. Wu, P.R. Xiong, W.M. Yue, S.H. Zhang, S.X. Zhang IMP/CAS, Lanzhou, People's Republic of China
	A heavy ion accelerator facility (HIAF) is under development in the Institute of Modern Physics. For the low energy superconducting accelerating section, two types of quarter wave resonators with frequency of 81.25 MHz and β of 0.05 and 0.10 have been proposed. The electro-magnetic design has been optimized in order to reach the high accelerating voltage, and the optimization also included the drift tube face tilting to compensate for the beam steering caused by the asymmetry in the quarter wave resonator geometry.
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MOPB008	Input Power Coupler for NICA Injector Coaxial Quater Wave SC Cavity	cavity, multipactoring, Windows, operation	61
	M.V. Lalayan, T.A. Bakhareva, M. Gusarova, S.V. Matsievskiy MEPhI, Moscow, Russia
	New coaxial power coupler research and development results are presented and discussed. Coupler is proposed for superconducting QWR cavities being under consideration now as option for planned Nuclotron-based Ion Collider fAcility (NICA) injector upgrade. The goal was to develop power coupler operating at 162 MHz and feeding SC cavity with about 20 kW RF power. It provides Qext tuning range (1.5-3)E5 by inner conductor movement. Conservative design with two identical disk ceramic windows was chosen. Electrodynamic, thermal and mechanical simulations were carried out.
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MOPB009	Progress of 650 MHz SRF Cavity for eRHIC SRF Linac	cavity, SRF, HOM, linac	64
	W. Xu, I. Ben-Zvi, Y. Gao, D. Holmes, P. Kolb, G.T. McIntyre, C. Pai, R. Porqueddu, K.S. Smith, R. Than, J.E. Tuozzolo, F.J. Willeke, A. Zaltsman BNL, Upton, Long Island, New York, USA I. Ben-Zvi Stony Brook University, Stony Brook, USA
	Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. eRHIC ERL SRF requires 160 5-cell 650 MHz SRF cavities. The 650 MHz cavity has been designed and two prototypes have been fabricated, one Cu cavity for HOM study and one Nb cavity for cavity performance study. This paper will describe cavity design and the progress of prototyping.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB009
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MOPB010	Design of the 2×4-cell Superconducting Cryomodule for the Free-electron Laser	cryomodule, shielding, cavity, radiation	67
	X. Luo, C.L. Lao, M. Li, L.J. Shan, X.M. Shen, H. Wang, X. Yang, K. Zhou CAEP/IAE, Mianyang, Sichuan, People's Republic of China X.Y. Lu, S.W. Quan, F. Wang PKU, Beijing, People's Republic of China
	A 2×4-cell superconducting linac module for the THz-FEL facility has been developed at the China Academy of Engineering Physics, which is expected to provide 6~8 MeV quasi-CW electron beams with an average current of 1~5 mA. The design of the cryomodule is presented in this paper. The dynamic and static heat load have been evaluated to reasonable level. The temperature distribution inside the cryomodule has been optimized by simulation, as well as mechanical structure and the magnetic shielding.
	Poster MOPB010 [1.019 MB]
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MOPB011	CEA Cryomodules Design for SARAF Phase 2	cavity, cryomodule, simulation, vacuum	70
	C. Madec CEA, Gif-sur-Yvette, France N. Bazin, D. Chirpaz-Cerbat, R. Cubizolles CEA/IRFU, Gif-sur-Yvette, France P. Brédy CEA/DSM/IRFU, France R. Bruce, P. Hardy, F. Leseigneur, Th. Plaisant, J. Plouin CEA/DRF/IRFU, Gif-sur-Yvette, France
	CEA is committed to delivering 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 in 4 cryomodules separated by warm diagnostics housing beam diagnostics. The first two identical cryomodules host 6 half-wave resonator (HWR) low beta cavities (β = 0.091), 176 MHz. The last two identical cryomodules are equipped with 7 HWR high-beta cavities (β = 0.181), 176 MHz. The beam is focused through superconducting solenoids located between cavities housing steering coils. A Beam Position Monitor is placed upstream each solenoid. A diagnostic box containing a beam profiler and a vacuum pump will be placed at the end of each cryomodule. The cryomodules and the warm sections are being designed. These studies will be presented in this poster.
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MOPB012	Status of the IFMIF LIPAc SRF Linac	cavity, cryomodule, SRF, operation	74
	N. Bazin, C. Boulch, A. Bruniquel, P. Carbonnier, J.K. Chambrillon, G. Devanz, F. Éozénou, P. Hardy, H. Jenhani, O. Piquet, J. Plouin, A. Riquelme, D. Roudier, C. Servouin CEA/DRF/IRFU, Gif-sur-Yvette, France P. Charon, S. Chel, G. Disset, L. Maurice, J. Relland, B. Renard CEA/IRFU, Gif-sur-Yvette, France P. Contrepois CEA/DSM/IRFU, France D. Regidor, F. Toral CIEMAT, Madrid, Spain
	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 and eight focusing solenoids. This paper presents the status of the IFMIF SRF Linac.
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MOPB013	European XFEL Input Coupler Experiences and Challenges in a Test Field	FEL, GUI, SRF, operation	78
	F. Hoffmann, D. Kostin, W.-D. Möller, D. Reschke, M. Wiencek DESY, Hamburg, Germany
	102 European XFEL accelerating modules with 816 superconducting cavities and main input RF power couplers were assembled and then tested at DESY prior to installation in the European XFEL tunnel. In the Accelerating Module Test Facility (AMTF) warm and cold RF tests were done. The test results went directly to the operational setup for the LINAC. Main input couplers did present several problems during the tests, resulting in some minor coupler design changes as well as in a few repair actions. The experience got from the said testing operation is worth to be shared and is presented here together with a discussion.
	Poster MOPB013 [0.648 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB013
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MOPB015	Accelerator Module Repair for the European XFEL Installation	FEL, cavity, vacuum, linac	82
	E. Vogel, S. Barbanotti, F. Hoffmann, K. Jensch, D. Kostin, L. Lilje, W.-D. Möller, M. Schmökel, H. Weise DESY, Hamburg, Germany S. Berry, O. Napoly CEA/DSM/IRFU, France M. Sienkiewicz, J. Świerbleski, M. Wiencek IFJ-PAN, Kraków, Poland
	Repair actions of different extent have been performed at 61 modules of the 100 accelerating series modules for the European XFEL to qualify them for the tunnel installation. Four modules could not be repaired in time. CEA Saclay managed to perform three major repairs in parallel to the series module integration, the residual repair actions took place at DESY Hamburg. In this paper we will give an overview on the various technical problems which required being fixed before the tunnel installation and on the repair actions performed.
	Poster MOPB015 [9.354 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB015
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MOPB016	Operation of Diamond Superconducting RF Cavities	cavity, vacuum, operation, GUI	87
	P. Gu, C. Christou, P.J. Marten, S.A. Pande, A.F. Rankin, D. Spink DLS, Oxfordshire, United Kingdom
	The Diamond Light Source storage ring has been in operation using superconducting RF cavities since 2007. Diamond has four superconducting cavity modules with two usually installed at any one time. The four cavities perform differently in many aspects such as reliable operating parameters and time in service, with the longest in continuous service for 7 years without failure and the shortest failing after only 8 months. All Diamond superconducting RF cavities suffered many fast vacuum trips in their early years, but after many years of efforts, the performance of the cavities have now been effectively managed by weekly conditioning, partial warm-up during shut down and cavity voltage level control. We will discuss our experience with superconducting RF cavities and our future plan.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB016
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MOPB017	Multiphysics Simulations of the Wide Opened Waveguide Crab-cavity	cavity, HOM, impedance, dipole	90
	K. Papke, A. Amorim Carvalho, A. Grudiev, C. Zanoni CERN, Geneva, Switzerland
	In the frame of a FCC study a first prototype of a compact superconducting crab-cavity, using Nb-on-Cu-coating technique is being manufactured and investigated. The design, which is based on the ridged waveguide resonator, is subjected to multipacting and pressure sensitivity simulations. First results of theses simulations are presented and compared to those of other SRF cavities. Furthermore, several aspects related to the design of the fundamental mode coupler and HOM dampers are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB017
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MOPB018	Testing of SRF Cavities and Cryomodules for the European Spallation Source	cavity, cryomodule, SRF, linac	95
	N. Elias, E. Asensi Conejero, C. Darve, N.F. Hakansson, W. Hees, C.G. Maiano, F. Schlander ESS, Lund, Sweden
	The European Spallation Source (ESS) is currently under construction in Lund, Sweden. The ESS linear accelerator aims to deliver a 62.5 mA , 2.86 ms long proton beam onto a rotating tungsten target, at 14 Hz repetition rate, thus achieving an energy of 2 GeV and 5 MW power. Most of the beam acceleration happens in the superconducting fraction of the linac, which is composed of three sectors of cryomodules named after the cavities housed within. The first sector of the SRF linac is composed of 13 Spoke cryomodules containing 2 double-spoke cavities with a geometric beta of 0.5, the second is composed of 9 medium beta cryomodules each housing four elliptical cavities (β=0.67) and finally 21 high beta cryomodules enclosing four elliptical cavities (β=0.86). ESS has strategically built up a SRF collaboration with other European institutions, these partners will deliver through In-Kind agreements cavities and cryomodules performing within the ESS specification. This article describes the process leading to the acceptance of cavities and cryomodules received from the different partners and the necessary testing required prior to the final installation in the ESS tunnel.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB018
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MOPB019	Interface Challenges for the SRF Cryomodules for the European Spallation Source	cryomodule, cavity, interface, ion-source	100
	F. Schlander, C. Darve, N. Elias, C.G. Maiano ESS, Lund, Sweden P. Bosland CEA/DSM/IRFU, France G. Olry IPN, Orsay, France
	The European Spallation Source is currently under construction in Lund in southern Sweden. The main part of the accelerator will consist of two different types of cryomodules housing three different types of cavities ' double spoke cavities and two different elliptical cavities. The spoke cavities as well as the cryomodules will be provided by IPN Orsay, thus the external interfaces to the other accelerator systems have to be verified. While the procurement and assembly of the elliptical cryomodules will be performed by CEA Saclay, the cavities will be provided by INFN Milano and STFC Daresbury. Thus in addition to the external cryomodule interfaces, also the internal interfaces between cavities and cryomodules have to be taken care of. This contribution presents the challenges related to this work.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB019
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MOPB020	An Optimal Procedure for Coupler Conditioning for ESS Superconducting Linac	cavity, vacuum, interface, controls	103
	H. Li Uppsala University, Uppsala, Sweden E. Asensi Conejero, C.G. Maiano, R. Zeng ESS, Lund, Sweden
	An optimal procedure for coupler and cavity conditioning is proposed for the ESS superconducting cavities, which is applicable for different test stands and following installation in the ESS tunnel. A preliminary procedure has been developed and successfully tested at FREIA facility, Uppsala. The preliminary procedure will now be improved by integrating it into LLRF and EPICS control. This will be a joint effort between FREIA and ESS and will be used at the test stands in Lund and on the couplers installed in the tunnel. Developing the conditioning procedures on a common platform offers ESS significant advantages by allowing the procedures to be reused at different sites and by recording data in a consistent format. The details of the procedure, its development and testing will be reported and the future activities will be described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB020
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MOPB023	Further Layout Investigations for a Superconducting CW-linac for Heavy Ions at GSI	linac, cavity, heavy-ion, SRF	108
	W.A. Barth, K. Aulenbacher, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu HIM, Mainz, Germany K. Aulenbacher IKP, Mainz, Germany W.A. Barth, M. Heilmann, S. Yaramyshev GSI, Darmstadt, Germany W.A. Barth, S. Yaramyshev MEPhI, Moscow, Russia M. Basten, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany
	Very compact accelerating-focusing structures, as well as short focusing periods, high accelerating gradients and very short drift spaces are strongly required for superconducting (sc) accelerator sections operating at low and medium beam energies. To keep the GSI-Super Heavy Element program competitive on a high level and even beyond, a standalone sc continuous wave Linac in combination with the GSI High Charge State injector, upgraded for cw-operation, is envisaged. The first LINAC section (financed by HIM and GSI) as a demonstration of the capability of 216 MHz multi gap Crossbar H-structures (CH) is still in the beam commissioning phase, while an accelerating gradient of 9.6 MV/m (4 K) at a sufficient quality factor has been already reached. Recently the overall Linac design, based on a standard cryomodule, comprising three CH cavities, a rebuncher section and two 9.3 T-solenoidal lenses, has to be fixed. This paper presents the status of the Linac layout studies as well as the integration in the GSI accelerator facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB023
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MOPB024	Steps Towards Superconducting CW-linac for Heavy Ions at GSI	cavity, linac, solenoid, heavy-ion	112
	M. Miski-Oglu, M. Amberg, K. Aulenbacher, W.A. Barth HIM, Mainz, Germany K. Aulenbacher IKP, Mainz, Germany W.A. Barth, V. Gettmann, M. Heilmann, S. Yaramyshev GSI, Darmstadt, Germany W.A. Barth, S. Yaramyshev MEPhI, Moscow, Russia M. Basten, M. Busch, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany
	A superconducting (sc) cw-Linac at GSI should ensure competitive production of Super Heavies in the future. Further R&D for this cw-Linac, a so called 'Advanced CW-Demonstrator', with maximal energy of 3.5 MeV/u is ongoing. As a first step, the demonstrator project with one sc CH-cavity is near its completion, the beam tests are scheduled for mid-summer 2017. The completion of the 'Advanced CW-Demonstrator' includes successive construction of two new cryogenic modules comprising four CH-cavities and two solenoids each. In this contribution the layout of the cryomodules and the Helium distribution system are presented.
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MOPB028	HOM Coupler Design for CEPC Cavities	HOM, cavity, damping, collider	115
	H.J. Zheng, F. Meng, J.Y. Zhai IHEP, Beijing, People's Republic of China
	Funding: This study was supported by National Key Programme for S&T Research and Development (Grant NO.: 2016YFA0400400) In this paper，it will be presented the higher order mode (HOM) coupler design for the Circular Electron-Positron Collider (CEPC) 650 MHz 2-cell cavity. 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. A double notch 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. This paper summarizes the RF design of the HOM coupler, tolerance analysis, thermal analysis as well as mechanical structures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB028
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MOPB031	Fabrication and Cold Test Result of FRIB β=0.53 Pre-production Cryomodule	cavity, cryomodule, solenoid, SRF	120
	H. Ao, J. Asciutto, B. Bird, N.K. Bultman, E.E. Burkhardt, F. Casagrande, C. Compton, K.D. Davidson, K. Elliott, A. Ganshyn, I. Grender, W. Hartung, L. Hodges, I.M. Malloch, S.J. Miller, D.G. Morris, P.N. Ostroumov, J.T. Popielarski, L. Popielarski, M.A. Reaume, K. Saito, M. Shuptar, S. Stark, J.D. Wenstrom, M. Xu, T. Xu, Z. Zheng FRIB, East Lansing, USA A. Facco INFN/LNL, Legnaro (PD), Italy
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 The driver linac for the Facility for Rare Isotope Beams (FRIB) comprises four kinds of cavities (β=0.041, 0.085, 0.29, and 0.53) and six types of cryomodules including matching modules. FRIB has completed the fabrication and the cold test of a β=0.53 pre-production cryomodule, which is the first prototype for a half-wave (β=0.29 and 0.53) cavity. This paper describes the fabrication and the cold test result of the β=0.53 pre-production cryomodule including lessons learned.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB031
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MOPB034	Selection of the Type of Accelerating Structures for the Second Group of Cavity SC Linac Nuclotron-NICA	cavity, linac, accelerating-gradient, multipactoring	125
	M. Gusarova, A.A. Gorchakov, M.V. Lalayan, D.V. Surkov, K.V. Taletskiy MEPhI, Moscow, Russia A.V. Butenko JINR/VBLHEP, Dubna, Moscow region, Russia D.A. Shparla Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus A.O. Sidorin, G.V. Trubnikov JINR, Dubna, Moscow Region, Russia
	The paper summorises the research results aimed on the choice of superconducting accelerating cavities for the second section of the SC linac Nuclotron-NICA injector project. This choice was based on comparative analysis of accelerating structures electrodynamic characteristics taking into account technological challenges of bulk niobium cavities production.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB034
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MOPB035	Cryogenic Probe Station at Old Dominion University Center for Accelerator Science	cavity, SRF, cryogenics, niobium	128
	J. Makita, J.R. Delayen, A.V. Gurevich ODU, Norfolk, Virginia, USA G. Ciovati JLab, Newport News, Virginia, USA
	With a growing effort in research and development of an alternative material to bulk Nb for a superconducting radiofrequency (SRF) cavity, it is important to have a cost effective method to benchmark new materials of choice. At Old Dominion University's Center for Accelerator Science, a cryogenic probe station (CPS) will be used to measure the response of superconductor samples under RF fields. The setup consists of a closed-cycle refrigerator for cooling a sample wafer to a cryogenic temperature, a superconducting magnet providing a field parallel to the sample, and DC probes in addition to RF probes. The RF probes will extract a quality factor from a sample patterned in a coplanar waveguide resonator structure on a 2' wafer. From the measured quality factor, the surface resistance and the penetration depth as a function of temperature and magnetic field will be calculated. This paper will discuss the design and measurement procedures of the current CPS setup.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB035
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MOPB036	The Study of Deposition Method of Nb3Sn Film on Cu Substrate	SRF, niobium, cavity, superconductivity	131
	L. Xiao, X.Y. Lu, W.W. Tan, D. Xie, D.Y. Yang, Y. Yang, Z.Q. Yang, J. Zhao PKU, Beijing, People's Republic of China
	Our work is mainly focused on the fabrication methods of Nb3Sn films on Cu substrates and film's properties. There are diffraction peaks of Nb3Sn in the X-ray diffraction patterns in which without diffraction peaks of copper compounds. Scanning electron microstructures of Nb3Sn film reflect its nice compactness and binding force between film and substrate.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB036
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MOPB037	Progress of the 2x4-Cell Superconducting Accelerator for the CAEP THz-FEL Facility	cavity, pick-up, cryomodule, cryogenics	134
	K. Zhou, C.L. Lao, M. Li, X. Luo, L.J. Shan, X. Shen, H. Wang, X. Yang CAEP/IAE, Mianyang, Sichuan, People's Republic of China X.Y. Lu PKU, Beijing, People's Republic of China
	The high average power THz radiation facility is now under construction in China Academy of Engineering Physics. The superconducting accelerator is one of the most important components for this facility, including two 4-Cell TESLA superconducting radio frequency cavities. The designed effective field gradients for both cavities are 10^-12 MV/m. This paper will present the progress of the 2x4-cell superconducting accelerator, mainly including its construction and cryogenic test in Chengdu. At 2 K state, the cryomodule works smoothly and stably. The effective field gradients of both cavities have achieved 10 MV/m. Further beam loading experiments are now in progress.
	Poster MOPB037 [5.124 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB037
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MOPB040	ESS High-beta Cavity Test Preparations at Daresbury Laboratory	cavity, niobium, LLRF, SRF	137
	P.A. Smith, L. Bizel-Bizellot, K.D. Dumbell, M. Ellis, P. Goudket, A.J. Moss, E.F. Palade, S.M. Pattalwar, M.D. Pendleton, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Science and Technology Facility Council is responsible for supplying, and testing 84 High beta elliptical SRF cavities, as part of the UK In Kind Contribution to the European Spallation Source (ESS). The High-β=0.86, cavities have been designed by CEA- Saclay and are a five cell Niobium cavity operating at 704.42 MHz. They are required to provide an accelerating gradient of 19.9 MV/m at an unloaded Q of 5x10⁹. Preparations are underway to upgrade the cryogenic and RF facilities at Daresbury laboratory prior to the arrival of the first cavities. As part of these arrangements, a niobium coaxial resonator has been manufactured, to validate the test facility. The design considerations, for the coaxial resonator are presented, along with preliminary results. The RF measurement system to perform the cavity conditioning and testing is also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB040
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MOPB041	Status of the SOLEIL Superconducting RF System	cavity, operation, SRF, GUI	141
	M. Diop, J.P. Baete, R.C. Cuoq, H.D. Dias, J.L. Labelle, L.R. Lopes, M. Louvet, P. Marchand, C.M. Monnot, S. Petit, F. Ribeiro, T. Ruan, R. Sreedharan, K.T. Tavakoli SOLEIL, Gif-sur-Yvette, France
	The 352 MHz SOLEIL SRF systems consist in two cryomodules, each containing a pair of SC Nb/Cu cavities, cooled with LHe at 4K from a single 350 W cryogenic plant. In order to store 500 mA, a power of 575 kW and an accelerating voltage of 3-4 MV are required. The RF power is provided by 4 SSPA's delivering up to 180 kW each. The original cavity input power couplers, which are LEP-type antennas designed to handle up to 200 kW, are being replaced by upgraded versions, able to operate at 300 kW CW. This will open the possibility to operate at full beam current with only one active cryomodule. The SRF system operational experience over the past ten years as well as the different upgrades will be reported here.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB041
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MOPB042	The TRIUMF/VECC Injector Cryomodule Performance	cavity, cryomodule, TRIUMF, linac	144
	Y. Ma, K. Fong, T. Junginger, D. Kishi, A.N. Koveshnikov, R.E. Laxdal, N. Muller, R.R. Nagimov, D.W. Storey, E. Thoeng, Z.Y. Yao, V. Zvyagintsev TRIUMF, Vancouver, Canada U. Bhunia, A. Chakrabarti, S. Dechoudhury, V. Naik VECC, Kolkata, India
	The collaboration on superconducting electron Linac for rare ion beam facilities ARIEL (Advanced Rare Iso-topE Laboratory) [1-4] and ANURIB [5] (Advanced Na-tional facility for Unstable and Rare Isotope Beams) has resulted in production of a superconducting Injector Cryomodule (VECC ICM) at TRIUMF for VECC. The cryomodule design utilizes a unique box cryomodule with a top-loading cold mass. The hermetic unit consists of a niobium cavity which operating at 1.3GHz and connected with two symmetrically opposed couplers which can deliver 100kW RF power to the beam. Liquid helium supplied at 4.4 K is converted to superfluid helium-II through a cryogenic insert on board which includes 4 K phase separator, 4K/2K heat exchanger and Joule-Thompson valve. In 2016, the VECC ICM has been tested at TRIUMF and demonstrated 10.5 MeV acceleration. A summary of the VECC ICM commissioning are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB042
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MOPB043	Pansophy, a JLab SRF Engineering Data Management System, Supporting Data Collection, Retrieval and Analysis Utilized by LCLS-II	cryomodule, cavity, database, status	148
	V.D. Bookwalter, M. Dickey, E.A. McEwen, M.G. Salvador JLab, Newport News, Virginia, USA
	Pansophy is an Engineering Data Management System that provides a comprehensive solution for managing information in the production and testing of cryomodules. It is especially suited to supporting the Data & Quality Management Systems for large projects like LCLS-II. With extensive amounts of data collected for an individual project, data retrieval to facilitate feedback and enhancement of production and processing activities is a high priority. The priority shares importance with the needs of managing the project, including production status, NCR, and Quality Management reports. Recent Pansophy enhancements have been to Data and Quality management reports and statistical analysis. Such enhancements include a database driven menu system, extended MSWord macro and preprocessing of travelers, and an extensive reporting system. The reporting system allows managers and group leaders to quickly respond to the needs of the project in areas of cavity and cryomodule production, data collection, NCR, Quality Management and schedule. Extensions include integration with the SRF inventory system PRIMeS, allowing traceability from receiving of manufactured parts to final cryomodule product.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB043
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MOPB044	Magnetic Hygiene Control on LCLS-II Cryomodules Fabricated at JLab	cavity, cryomodule, controls, shielding	153
	G. Cheng, E. Daly, G.K. Davis, J.F. Fischer, N.A. Huque, R.A. Legg, H. Park, K.M. Wilson, L. Zhao JLab, Newport News, Virginia, USA
	Funding: U.S. DOE Contract No. DE-AC05-06OR23177 and the LCLS-II project. Jefferson Lab (JLab) is in collaboration with Fermi Na-tional Accelerator Laboratory (Fermilab) to build 18 cryomodules to install at the SLAC National Accelerator Laboratory's tunnel as part of the Linac Coherent Light Source upgrade project (LCLS-II). Each LCLS-II cry-omodule hosts 8 superconducting niobium cavities that adopt the nitrogen doping technique, which aims to en-hance the cavity quality factor Qo to reduce the consumption of liquid helium used to cool down the cavities. It is known that the Qo of niobium cavities is affected by cavity surface magnetic field. Traditionally, magnetic shields made of high magnetic permeability mu-metals are employed as a passive shielding of the ambient magnetic fluxes. During the LCLS-II cryomodule development, magnetic hygiene control that includes magnetic shielding and demagnetization of parts and the whole-machine is implemented. JLab and Fermilab worked closely on developing magnetic hygiene control procedures, identifying relevant tools, investigating causes of magnetization, magnetic field monitoring, etc. This paper focuses on JLab's experiences with LCLS-II cryomodule magnetic hygiene control during its fabrication. Authored by Jefferson Science Associates, LLC. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for Government purposes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB044
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MOPB045	JLab New Injector Cryomodule Design, Fabrication and Testing	cavity, cryomodule, cryogenics, HOM	158
	G. Cheng, M.A. Drury, J.F. Fischer, R. Kazimi, K. Macha, H. Wang JLab, Newport News, Virginia, USA
	Funding: U.S. DOE Contract No. DE-AC05-06OR23177. A new Injector Cryomodule (INJ CM) aimed to replace the existing Quarter Cryomodule in the CEBAF tunnel has been developed at Jefferson Lab (JLab). It is sched-uled to be first tested in the Cryomodule Test Facility (CMTF) for module performance then the Upgraded Injector Test Facility (UITF) with electron beam. This new cryomodule, hosting a 2-cell and 7-cell cavity, is designed to boost the electron energy from 200 keV to 5 MeV and permit 380 uA - 1.0 mA of beam current. The 2-cell cavity is a new design whereas the 7-cell cavity is refurbished from a low loss cavity from the retired JLab Renascence Cryomodule. The INJ CM adopts quite a few designs from the JLab 12 GeV Upgrade Cryomodule (C100). Examples of this include having the cold mass hung from a spaceframe structure by use of axial and transverse Nitronic rods, cavities to be tuned by scissor-jack style tuners and the end cans are actually modified from C100 style end cans. However, this new INJ CM is not a quarter of the C100 Cryomodule. This paper focuses on the major design features, fabrication and alignment process and testing of the module and its components. Authored by Jefferson Science Associates, LLC. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for Government purposes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB045
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MOPB046	LCLS-II Cryomodule Production at JLab	cryomodule, cavity, vacuum, SRF	163
	R.A. Legg, G. Cheng, E. Daly, G.K. Davis, M.A. Drury, J.F. Fischer, T. Hiatt, N.A. Huque, L.K. King, J.P. Preble, A.V. Reilly, M. Stirbet, K.M. Wilson JLab, Newport News, Virginia, USA
	Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515. The LCLS-II cryomodule construction program leverages the mature XFEL cryomodule design to produce technologically sophisticated cryomodules with a minimum of R&D according to an accelerated manufacturing schedule. Jlab, as one of the partner labs, is producing 18 cryomodules for LCLS-II. To meet the quality and schedule demands of LCLS-II, many upgrades to the JLAB cryomodule assembly infrastructure and techniques have been made. JLab has installed a new cleanroom for string assembly and instituted new protocols to minimize particulate transfer into the cavities during the cryomodule construction process. JLab has also instituted a set of magnetic hygiene protocols to be used during the assembly process to minimize magnetic field impingement on the finished cavity structure. The goal has been to have gradients, both maximum and field emission onset, that do not degrade between the cavity vertical test and final cryomodule qualification, while maximizing the Q0 of each finished cavity. Results from the prototype cryomodule assembly are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB046
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MOPB049	Upgraded Cavities for the CEBAF Cryomodule Rework Program	cavity, HOM, cryomodule, GUI	168
	R.A. Rimmer, G. Cheng, G. Ciovati, W.A. Clemens, E. Daly, G.K. Davis, J. Follkie, D. Forehand, F. Fors, J. Guo, J. Henry, K. Macha, F. Marhauser, G.R. Myneni, L. Turlington JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The CEBAF cryomodule rework program has been a successful tool to recover and maintain the energy reach of the original baseline 6 GeV accelerator. The weakest original modules with eight five-cell cavities assembled in four 'pairs', with a specification when new of 20 MV per cryomodule (5 MV/m), are disassembled, re-cleaned with modern techniques and re-qualified to at least 50 MV (12.5 MV/m), (leading to the acronym 'C50'). The cost per recovered MV is much less than building new modules. However over time the stock of weak modules is being used up and the voltage gain per rework cycle is diminishing. In an attempt to increase the gain per cycle it is proposed to rework the cavities by replacing the original accelerating cells with new ones of an improved shape and better material. The original CEBAF HOM and FPC end groups are retained. The goal is to achieve up to 75 MV (18.75 MV/m) for the reworked module ('C75'). We report on the fabrication experience and test results of the first trial pair, containing two such reworked cavities.
	Poster MOPB049 [1.503 MB]
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MOPB050	Cavity Processing and Testing Activities at Jefferson Lab for LCLS-II Production	cavity, SRF, FEL, cryomodule	173
	L. Zhao, G.K. Davis, J. Follkie, D. Forehand, K. Macha, A.D. Palczewski, A.V. Reilly JLab, Newport News, Virginia, USA
	Funding: Work supported by Jefferson Science Associates, LLC under U.S. DOE Contracts DE-AC05-06OR23177 and DE-AC02-76SF00515 for the LCLS-II Project. Cryomodule production for LCLS-II is well underway at Jefferson Lab. This paper explains the process flow for production cavities, from being received at the Test Lab to being assembled onto cavity strings. Taking our facility and infrastructure into consideration, process optimization and process control are implemented to ensure high quality products.
	Poster MOPB050 [2.338 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB050
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MOPB052	Dual-ridge Waveguide Load Design for eRHIC	GUI, HOM, cavity, simulation	177
	P. Kolb, Y. Gao, C. Pai, R. Porqueddu, K.S. Smith, W. Xu BNL, Upton, Long Island, New York, USA Y. Gao PKU, Beijing, People's Republic of China
	Funding: Work supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. To increase the real estate gradient in the eRHIC electron accelerator waveguide HOM couplers are being considered. These significantly reduce the length of individual cavities and address inter-cavity trapped modes, allowing for an increased number of cavities per cryomodule, which would increase the real estate gradient. The choice of waveguide went to a dual ridge waveguide due to a smaller size compared to rectangular waveguides. The waveguide termination, to convert the RF energy into thermal energy, is a custom designed load based on a silicon carbide dielectric that is already being used in beamline absorbers. Simulations of the RF properties of the load are presented as well as first measurements on a prototype.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB052
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MOPB053	RF Energy Harvesting of HOM Power	GUI, HOM, cavity, distributed	180
	C. Xu, I. Ben-Zvi, Q. Wu, T. Xin BNL, Upton, Long Island, New York, USA I. Ben-Zvi Stony Brook University, Stony Brook, USA
	In an accelerator cavity, Higher Order Modes (HOM) are generated by the current of the beam. The HOM power can reach tens of kilowatts in a high current accelerator, depending on the details of the beam and cavity design. In this report, we propose a novel RF harvesting system to recover the HOM power into DC power which can further used for various purposes such as driving a solid state or klystron RF amplifier to supply fundamental RF power at other frequencies, charge batteries etc. The efficiency would be a product of the energy recovery and regeneration efficiencies, where the state of art is 90%. The proposed HOM power recycling system contains a multiple band harmonic RF coupler, broadband RF antenna system, a high power rectifier diode circuit and a DC load. 1) Collider-Accelerator Department, Brookhaven National Lab, Upton, NY 11973, USA 2) Physics & Astronomy Department, Stony Brook University, Stony Brook, NY 11794, USA
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB053
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MOPB054	Design of Fundamental Power Coupler for High Intensity Heavy-ion Accelerator	electron, cavity, simulation, multipactoring	183
	B. Bing, T.M. Huang, Q. Ma, F. Meng, W.M. Pan IHEP, Beijing, People's Republic of China K.X. Gu Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
	A single-window coaxial coupler at warm has been designed for high intensity heavy-ion accelerator. The coupler is designed to handle 100 kW CW power of 325 MHz and is currently being fabricated. T-bend transition and doorknob have been taken into account. The length of the T-bend short circuit is sensitive to S parameters and contributes to the online adjustment of VSWR in RF conditioning. The doorknob type is adopted to realize the transition from a half-height WR 2300 waveguide to a coaxial line ended with a coupling antenna. This paper describes the RF design, thermal stress and heat load analysis of the coupler as well as multipacting simula-tions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB054
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MOPB061	Quality Control of Copper Plating in STF-2 Input Power Couplers	cavity, vacuum, cryomodule, controls	186
	E. Kako, R. Ueki KEK, Ibaraki, Japan K. Hiroaki, J. Taguchi Nomura Plating Co, Ltd., Osaka, Japan K. Okihira, K. Sennyu MHI, Hiroshima, Japan F. Saito, H. Umezawa Tokyo Denkai Co., Ltd., Tokyo, Japan O. Yushiro Toshiba Electron Tubes & Devices Co., Ltd, Tokyo, Japan
	Purity of thin copper plating using in input power couplers for superconducting cavities is one of important characteristics for considering thermal losses at low temperature. Various samples of thin copper plating on stainless sheets was fabricated by three companies with their own plating techniques. The RRR values of the samples with different thickness of copper plating were compared in the condition before and after heat treatment at 800oC in a brazing furnace. Deterioration of the RRR was observed in all of samples after heat treatment. The results of the RRR measurements and sample analysis of impurities will be reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB061
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MOPB062	Development of HOM Absorbers for CW Superconducting Cavities in Energy Recovery Linac	HOM, cavity, superconducting-cavity, linac	191
	T. Ota, A. Miyamoto, K. Sato, M. Takasaki, M. Yamada Toshiba, Yokohama, Japan E. Kako, T. Konomi, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	Higher Order Modes (HOM) absorbers for superconducting cavities have been developing at TOSHIBA in collaboration with High Energy Accelerator Research Organization (KEK) since 2015. Prototype HOM absorbers for 1.3 GHz 9-cell superconducting cavity were fabricated. An AlN lossy dielectrics cylinder was brazed with a copper cylinder, and the cool-down tests by nitrogen gas was carried out. Copper cylinders and SUS flanges were joined by electron beam welding to fabricate a whole prototype HOM absorber. Fabrication process of the prototype HOM absorber will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB062
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MOPB063	Fundamental Studies for the STF-type Power Coupler for ILC	vacuum, FEL, cavity, SRF	194
	Y. Yamamoto, E. Kako, T. Matsumoto, S. Michizono, A. Yamamoto KEK, Ibaraki, Japan M. Irikura, M. Ishibashi, H. Yasutake Toshiba Electron Tubes & Devices Co., Ltd (TETD), Tochigi, Japan
	From the view point of mass-production for the power coupler in ILC, the fundamental studies for the STF-type power coupler are under progress by the collaboration between KEK and TETD. At present, there are various rinsing procedures for power coupler in the world-wide laboratories. In this R&D, the main topic is to investigate the various rinsing effects in the copper plating and the ceramic through the high power test. In this paper, the first results will be presented.
	Poster MOPB063 [2.237 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB063
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MOPB064	High Power Test for Plug-compatible STF-type Power Coupler for ILC	electron, vacuum, simulation, GUI	199
	Y. Yamamoto, E. Kako, T. Matsumoto, S. Michizono, A. Yamamoto KEK, Ibaraki, Japan C. Julie, E. Montesinos CERN, Geneva, Switzerland
	From the view point of plug-compatibility for the power coupler in the ILC, recommended by Linear Collider Collaboration in 2013, new STF-type power couplers with 40mm of input port diameter were re-designed, fabricated and successfully high-power-tested. Moreover, from the view point of the cost reduction for the ILC, another type of power couplers with TiN coating-free ceramic were also fabricated and high-power-tested by the collaboration between CERN and KEK. In this paper, the detailed results for the both power couplers will be presented.
	Poster MOPB064 [6.671 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB064
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MOPB065	Development of Hybrid Superconducting Photocathodes on Niobium Using High QE Coatings	cathode, electron, site, SRF	205
	M. Warren, A.R. Denchfield, N. Samuelson, J. Zasadzinski IIT, Chicago, Illinois, USA W. Gai, J.H. Shao, E.E. Wisniewski ANL, Argonne, Illinois, USA L.K. Spentzouris, Z.M. Yusof Illinois Institute of Technology, Chicago, Illinois, USA
	High power, low emittance electron beams require superconducting RF photoinjectors, typically made of pure Nb, and a superconducting photocathode is desired. However, superconductivity and high photocathode quantum efficiency (QE) are not compatible, e.g. QE for pure Nb is only 10^-5 at 260 nm wavelength. Here is presented the current status of the development of hybrid superconducting photocathodes by the deposition of thin films of a high QE metal or semiconductor on Nb. Nb plugs coated with 10-100 nm of Mg have been tested for adhesion and dark current under RF fields as high as 60MV/m. QE measurements show significant enhancements over Nb. In another test, ultra thin films of the high QE material Cs2Te deposited on Nb are reported. Using the standard deposition procedure, QE ~12% is found for films ~ 200Å. As the thickness is reduced QE maintains a high value ~ 6% for films as thin as 2.0 nm. These results are quite promising for future superconducting photocathodes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB065
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MOPB066	Development of 81.25 MHz 20 kW SSPA for RAON Accelerator	impedance, rfq, cavity, power-supply	210
	C.O. Choi, H. Jang, H.C. Jung, D.Y. Lee, K.T. Son IBS, Daejeon, Republic of Korea
	A heavy ion accelerator, RAON is under development in Daejeon, Korea by Rare Isotope Science Project (RISP). In this accelerator, 81.25 MHz Radio Frequency Quadrupole (RFQ) will be used for the acceleration of various ions from several tens of keV/u to about half MeV/u. For this system two 80 kW RF power sources are planned and RISP will develop them with a solid state power amplifier (SSPA) architecture. As a first step, a 20 kW SSPA was developed and its performance was tested. In this presentation the current status of developed SSPA and its test results will be presented
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB066
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MOPB068	Development of 4-way 81.25 MHz 20 kW High Power Combiner Using Parallel Plate Structure	simulation, cavity, rfq, impedance	213
	K.T. Son, C.O. Choi, H. Jang, H.C. Jung, D.Y. Lee IBS, Daejeon, Republic of Korea
	The recent development of semiconductor technology has proved that solid-state RF amplifier is a quite effective alternative high power RF source for numerous accelerator applications. To develop a high power SSPA system, high power combiner is required to combine the RF power from a lot of solid-state RF module. The parallel plate RF power combiner, which is designed to combine various high power modules, is developed for RAON(Rare the rare isotope accelerator complex for on-line experiment). In this presentation, the status of developed 81.25 MHz 20 kW power combiner will be described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB068
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MOPB069	Design of the High Power Input Coupler for CEPC Main Ring Cavity *	cavity, coupling, vacuum, cryogenics	216
	T.M. Huang, Q. Ma, J.Y. Zhai IHEP, Beijing, People's Republic of China K.X. Gu Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
	The main ring cavities of CEPC project are two-cell el-liptical superconducting cavities operating at 650 MHz in CW mode. Each cavity equips with one high power input coupler and each coupler has to deliver at least 300 kW of CW RF power to the beam. A variable coupling from 10⁵ to 2·10⁶ is required to meet different operation modes. Considering the cavities working with high quali-ty factor up to 2·10¹⁰, the coupler assembled with cavity in class 10 clean room is strongly recommended to protect the cavity from contamination. Also, low cryogenic heat loss is one of the important issues for a large scale CW operation machine. Some of the above requirements should be compromise. Therefore, it's a big challenge to design a high power input coupler fulfilling the above requirements simultaneously. A new coupler that employs 75 Ω coaxial line sections, a planar ceramic disk win-dow, a coaxial to waveguide transition and a coupling adjusting actuator has been designed. In this paper, the RF design, thermal stress analysis and preliminary me-chanical design of the coupler are presented.
	Poster MOPB069 [0.735 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB069
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MOPB070	The Improvement of the Power Coupler for CADS SC Spoke Cavities	cavity, electron, experiment, cryomodule	220
	T.M. Huang, B. Bing, X. Chen, H.Y. Lin, Q. Ma, F. Meng, W.M. Pan, G.W. Wang IHEP, Beijing, People's Republic of China K.X. Gu Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
	Twenty superconducting spoke cavities mounted in three cryomodules (CM1, CM2 and CM4) were in-stalled in the CADS, a test facility of 10 mA, 25 MeV CW proton linac. Each cavity was equipped with one coaxial type fundamental power coupler (FPC). Fatal window crack was observed during the test cryomod-ule (TCM) commissioning. A series of experiments were subsequently implemented and eventually at-tributed the window crack to the electron bombard-ment from cavity field emission (FE). Improvements covering the coupler cleaning and assembly proce-dure, the structure and position modifications were thus implemented, aiming to reduce the cavity contam-ination and avoid the window damaged by cavity FE electrons. This paper will describe how the coupler window damaged by cavity field emission and the improve-ments for cure. In addition, the performances of FPCs for CM1, CM2 and CM4 were compared.
	Poster MOPB070 [0.613 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB070
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MOPB071	The Recent Research of HOM Damper for Superconducting Cavity in IHEP	HOM, cavity, simulation, site	223
	F. Meng, T.M. Huang, H.Y. Lin, Q. Ma, W.M. Pan, J.Y. Zhai, P. Zhang, H.J. Zheng IHEP, Beijing, People's Republic of China
	Funding: This study was supported by National Key Programme for S&T Research and Development (Grant NO.: 2016YFA0400400) For high current accelerator, the efficient higher-order mode (HOM) damping is always an important issue. HOM damper with microwave absorbing material is a key component for high power and broadband HOM damping application. To pursue the high damping efficiency, some ideal material with good microwave absorbing capacity is essential during the RF design and fabrication phase. Sometimes the selection and test of material is the first step and also a long step. This paper will present the recent work on HOM dampers for BEPCII 500MHz cavity and CEPC 650MHz cavity in IHEP.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB071
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MOPB072	The Development of the LLRF Control System for the New High Power Test Stand of Couplers	vacuum, controls, LLRF, FPGA	227
	L. Chen, W. Chang, T.C. Jiang, C.L. Li, Y.M. Li, R.X. Wang, S.H. Zhang IMP/CAS, Lanzhou, People's Republic of China
	RF power conditioning is an effective way to suppress multipacting in fundamental mode power couplers. Room temperature test-stand conditioning is an essential step that can be hardly circumvented before couplers are installed on SC cavities. Based on our original one, a new test-stand has been designed and being assembled at IMP. It can work as a multi-task platform conditioning different couplers, including couplers for HWR010 cavities and HWR015 cavities. It is also featured with the capacity to flexibly change β according to different specifications. A variety of conditioning modes have been incorporated into the LLRF system, including frequency sweeping mode, amplitude sweeping mode, arbitrary-duty-cycle mode and triangle-wave mode. In addition, smartly-conditioning has been achieved because of the accomplishment of smart interlocks and automatic reset in the system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB072
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MOPB074	Analysis of Higher Order Modes of the Superconducting Cavities for the China-ADS Injector-II in IMP	dipole, HOM, cavity, higher-order-mode	231
	C. Zhang, L. Chen, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, Y.M. Li, F. Pan, R.X. Wang, A.D. Wu, Q.J. Wu, W.M. Yue, S.H. Zhang, S.X. Zhang IMP/CAS, Lanzhou, People's Republic of China
	Funding: funded by Natural Science Foundation of China， No.11505253 The influence of the higher order modes on the beam dynamics and the cryogenic losses has been studied for the superconducting section of the CIADS project in this paper. In addition, the necessity of HOM dampers in the Superconducting (SC) cavities is discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB074
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MOPB075	Quench Protection in Digital Power Supplies for Superconducting Magnets in ADS	controls, power-supply, superconducting-magnet, solenoid	233
	J. Zhao, S. Zhang, Z.Z. Zhou IMP/CAS, Lanzhou, People's Republic of China
	The front-end demo superconducting Linac for Chinese ADS (Accelerator Driven Sub-critical System) project is under construction at institute of modern physics(IMP) in Lanzhou. It will demonstrate the key technologies and the feasibility of a high power beam for the future national project " the Chinese Initiative Accelerator Driven Subcritical System(CIADS)". In this system, there are about 60 superconducting magnets, including solenoids, vertical correction and horizontal correction. They are utilized to focus and correct the proton beam. Quench protection of the superconducting magnets is key to reliability of the facility. A full digital power supply is developed and employed as excitation source for all of these superconducting magnets. In this paper, an FPGA-based quench protection plan implemented in the power supplies is mainly described. The commissioning results show that it is feasible.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB075
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MOPB076	Analysis of the Production, Installation and Commissioning of the European-XFEL Frequency Tuners	cavity, FEL, cryomodule, controls	235
	R. Paparella, A. Bosotti, D. Sertore INFN/LASA, Segrate (MI), Italy C. Albrecht, S. Barbanotti, A. Bellandi, J. Branlard, K. Jensch, L. Lilje DESY, Hamburg, Germany C. Cloué, T. Trublet CEA/IRFU, Gif-sur-Yvette, France C. Madec CEA, Gif-sur-Yvette, France
	In the European-XFEL superconducting linac, mechanical frequency tuners equipped with stepper motors and piezoelectric actuators provide cold tuning of each of the 768 1.3 GHz cavities. More than 820 complete tuning systems were fabricated and pre-assembled in industry, tested at several stages before and after assembly and successfully commissioned during cryo-module cold tests at AMTF (DESY). Quality control strategy adopted to preserve the well-assessed tuner reliability through such a large-scale industrial production is critically reviewed and the lessons learned are presented in this paper. The statistical analysis of the large set of data acquired up to the recent commissioning of the entire linac is then summarized.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB076
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MOPB077	Operational Experience of the European-XFEL 3.9 GHz Coaxial Tuners	cavity, FEL, operation, MMI	240
	R. Paparella, A. Bellandi, A. Bignami, A. Bosotti, D. Sertore INFN/LASA, Segrate (MI), Italy C.G. Maiano ESS, Lund, Sweden P. Pierini DESY, Hamburg, Germany
	The European-XFEL injector hosts a third-harmonic section composed by a module with eigth 3.9 GHz cavities equipped with a coaxial frequency tuner inspired by INFN-LASA Blade Tuner design. The 3.9 GHz tuning system met specifications during all the injector runs in 2016 up to the recent commissioning of the entire linac; it matched the required tuning range and frequency sensitivity although higher than expected cavity detuning was experienced during pressure transients in the cryogenic system. An analysis of all collected experimental data is reported in this paper together with the strategy developed to provide a sound and effective retuning routine to the control room operator.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB077
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MOPB078	Power Coupler Design for the LUCRECE Project	simulation, radiation, coupling, cavity	245
	H. Guler, D. Auguste, J. Bonis, O. Bouras, M. El Khaldi, W. Kaabi LAL, Orsay, France
	The LUCRECE project aims at developing an elementary RF system (cavity, power source, LLRF and controls) suitable for continuous (CW) operation at 1.3 GHz. This effort is made in the framework of the advanced and compact FEL project LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation), using superconducting linac technology for high repetition rate and multi-user operation (http://www.lunex5.com). In this context, based on its large experience on coupler design and RF conditioning, LAL Laboratory is in charge of the design and the fabrication of RF couplers that could operate at up to 15-20 kW in CW mode. For this purpose, couplers based on CORNELL 65kW CW couplers (RF power couplers for the Cornell ERL injector) are under consideration and will be adapted to the LUCRECE needs. Electromagnetic simulations and associated thermal heating will be discussed. Methods to decrease the thermal impact will be considered.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB078
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MOPB079	HOM Coupler Alterations for the LHC DQW Crab Cavity	cavity, HOM, impedance, simulation	249
	J.A. Mitchell Lancaster University, Lancaster, United Kingdom G. Burt, N.C. Shipman Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R. Calaga CERN, Geneva, Switzerland S. Verdú-Andrés, Q. Wu, B. P. Xiao BNL, Upton, Long Island, New York, USA
	As part of the High Luminosity Large Hadron Collider (HL-LHC) project, 16 crab cavities are to be installed in the LHC in 2025. The two crab cavity designs are the Double Quarter Wave (DQW) and Radio Frequency Dipole (RFD). Preliminary beam tests in the Super Proton Synchrotron (SPS) are planned for both cavity types, with the DQW scheduled for testing in 2018. In reference to to Higher Order Mode (HOM) damping, the DQW has three identical on-cell HOM couplers. These HOM couplers provide a band-stop response at the frequency of the fundamental mode and act as a transmission path for the cavity HOMs. For the SPS cavity design, several geometric constraints exist. These give rise to dimensional limitations which in-turn impose limitations on the RF performance of the HOM couplers. As such, for the LHC assembly, the HOM coupler design is re-visited to take into account the relaxed geometric limitations, hence allowing the feasibility of an increased RF performance to be investigated. In addition to the RF performance, several geometric alterations were incorporated to ease manufacturing processes, tolerances and costs.
	Poster MOPB079 [2.038 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB079
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MOPB080	The Stable Operation of MPG and Measurement of Output	electron, experiment, cavity, cathode	254
	B.T. Li, X.Y. Lu, L. Xiao, D.Y. Yang, Y. Yang, Z.Q. Yang, J. Zhao PKU, Beijing, People's Republic of China
	The concept of micro-pulse electron gun(MPG) was proposed decades ago. It can provide electron beam with high current, short pulse and low emittance. But it is still not put into practical use as electron source because of its unsteady operating state. This paper presents an experimental result of the steady running of MPG which can operate stably for more than ten hours. The energy spread of the electron beam is also measured, the peak is located at near 20eV and half width is less than 15eV .
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB080
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MOPB082	A Preliminary Scheme for X-ray Emission Based on Micro-pulse Electron Gun	electron, target, radiation, simulation	259
	Y. Yang, B.T. Li, X.Y. Lu, W.W. Tan, L. Xiao, D.Y. Yang, Z.Q. Yang, J. Zhao PKU, Beijing, People's Republic of China
	X-ray is now widely used in many areas of physics, biology, chemistry and materials. And how to achieve emission, monochrome, and focusing of x-ray is of great significance to study. Micro-pulse electron gun (MPG) is a new type of electron source, with characteristics of high repetition frequency, short-pulse and low cost. Generating x-ray with better monochromaticity is one of the potential applications of MPG. And a preliminary scheme of X-ray based on MPG is proposed in this paper. The scheme is designed by comparing different anode materials and the thickness of filters. The simulation results based on the software MCNP5 show that the proposed scheme can effectively improve the monotonicity of the generated X-rays.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB082
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MOPB086	First Results of the IFMIF/EVEDA-SaTHoRI Tests	cavity, SRF, controls, cryomodule	262
	O. Piquet, N. Bazin, P. Carbonnier, J.K. Chambrillon, M. Desmons, G. Devanz, H. Jenhani, C. Servouin CEA/DRF/IRFU, Gif-sur-Yvette, France P. Cara Fusion for Energy, Garching, Germany J.F. Denis, L. Maurice, J. Relland CEA/IRFU, Gif-sur-Yvette, France F. Éozénou, P. Hardy, E. Jacques, Y. Lussignol, P. Sahuquet CEA/DSM/IRFU, France D. Gex, A. Jokinen, G. Phillips F4E, Germany I. Moya, P. Méndez CIEMAT, Madrid, Spain
	The SaTHoRI test stand (Satellite de Tests Horizontal des Résonateurs IFMIF) aims to characterize a jacketed and fully dressed cavity with its coupler and tuner. A dedicated test cryostat has been manufactured and is connected to an existing horizontal test cryostat which provides the cryogenic coolant. A RF source ' provided by the IFMIF collaboration, one of the four RF sources which will be used for the cryomodule at Rokkasho ' has been installed and commissioned at CEA. This paper describes the test stand and presents the first results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB086
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MOPB087	Frequency Tuner Development and Testing at Cornell for the RAON Half-wave-resonator	cavity, cryogenics, SRF, cryomodule	266
	M. Ge, F. Furuta, J.E. Gillette, T. Gruber, S.W. Hartman, M. Liepe, 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 (HWRs) for the RAON project require a slow frequency tuner that can provide >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 optimized tuner design, prototype fabrication, test insert preparation, and cryogenic test results. The performance of the tuner is analysed in detail.
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MOPB088	Experience on In-situ Module Repair and Set Up of Non XFEL Cavity Strings at DESY	cavity, FEL, HOM, pick-up	269
	M. Schmökel, A. Daniel, N. Krupka, A. Matheisen, S. Saegebarth, M. Schalwat, P. Schilling DESY, Hamburg, Germany
	All components installed to the European XFEL cavity string modules underwent an intensive inspection and quality control before acceptance for installation to cavities or modules. Even though some RF feed throughs for HOM coupler- and Pick Up antennas showed leaks at the ceramic insulation after module test at 2 K. Due to time restriction and continuity of production the exchange of these parts needed to be done without reentering the cleanroom. Successful repair of these modules took place by setting up a local cleanroom onto the cavity string. In collaboration with Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a cavity string for the ELBE project was assembled at DESY and transported to HZDR for installation to the vacuum vessel. A spare module with 3.9 GHz Resonators for the European XFEL was set up at DESY and will be tested and qualified for the European XFEL. Due to delay in delivery of the power couplers, four power couplers were installed after string assembly.
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MOPB089	Characterisation of Magnetic Shielding Material for HL-LHC Crab Cavities	cavity, cryogenics, shielding, ECR	273
	K. Eiler, P. Arpaia, M.C.L. Buzio, O. Capatina, S.A.E. Langeslag, A. Parrella CERN, Geneva, Switzerland P. Arpaia, A. Parrella Naples University Federico II, Science and Technology Pole, Napoli, Italy A. Parrella IT, Lisboa, Portugal N. Templeton STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: CERN, 1211 Geneva 23 To guarantee optimum performance, the crab cavities for the high-luminosity upgrade of CERN's LHC need to be shielded from external magnetic fields. Consequently, they will be enclosed by two layers of magnetic shielding, of which the inner is immersed in superfluid helium at 2 K. A Ni-based high-permeability material with a tailored composition and a designated heat treatment is applied. Its magnetic properties at cryogenic temperature are however not yet fully assessed. Especially the effect of deformation on magnetic properties has not been thoroughly investigated, however strain effects may have severe consequences. A magnetic measurement set-up has been developed, and the magnetic permeability at room temperature and at cryogenic temperatures is evaluated, showing that the maximum relative permeability at 4 K exceeds the design criteria of 100, 000. Measurements of the magnetic permeability after introduction of uniaxial plastic deformation between 0% and 3% are conducted by means of an Epstein frame. Results show that deformation induces significant decrease of the magnetic performance, underlining that particular care must be taken during all stages of handling and operation. *konrad.eiler@cern.ch
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MOPB090	Sub-micro-Tesla Magnetic Shielding Design for Cryomodules in the High-gradient Program at CERN	shielding, cavity, cryomodule, simulation	278
	S. Papadopoulos, L. Dassa, F. Gerigk, F. Pillon, S. Ramberger, P. Yilmazer CERN, Geneva, Switzerland J. Dequaire Intitek, Lyon, France
	In the framework of the High-Gradient R\&D program at CERN a cryomodule, consisting of four superconducting 5-cell cavities, has been designed. In order to reduce flux trapping in the surface of the superconductor and to minimize Q degradation during a quench, highly effective magnetic shielding is needed. The solution proposed includes cold and warm passive shielding enhanced by four compensating coils. In this paper the magneto-static simulation results are presented illustrating different design considerations that led to a final design. Finally the shielding ability of the vacuum vessel is investigated experimentally through ambient magnetic field measurements.
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MOPB094	Commissioning of Demonstrator Module for CW Heavy Ion LINAC@GSI	cavity, linac, solenoid, heavy-ion	283
	V. Gettmann, K. Aulenbacher, W.A. Barth, F.D. Dziuba, T. Kürzeder, M. Miski-Oglu HIM, Mainz, Germany K. Aulenbacher IKP, Mainz, Germany W.A. Barth, M. Heilmann, S. Yaramyshev GSI, Darmstadt, Germany W.A. Barth, S. Yaramyshev MEPhI, Moscow, Russia M. Basten, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany
	The cw - Linac - demonstrator is a prototype of the first section of the proposed cw-LINAC@GSI, comprising a superconducting CH-cavity embedded by two superconducting solenoids. The sc CH-structure is the key component and offers a variety of research and development. The beam focusing solenoids provide maximum fields of 9.3 T at an overall length of 380 mm and a free beam aperture of 30 mm. The magnetic induction at the fringe is minimized to 50 mT at the inner NbTi-surface of the neighboring cavity. The fabrication of the key components is finished, as well as the cold performance testing of the RF cavity. The cryostat is ready for assembling and the test environment is completely prepared. After successful testing of the RF-Power coupler, the components will be assembled to the suspended frame under cleanroom conditions. Alignment, assembly, under cleanroom condition issues will be presented.
	Poster MOPB094 [2.881 MB]
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MOPB096	Estimation of Alignment Error by Measuring Higher-order-mode of Injector Superconducting Cavity at KEK-cERL	cavity, HOM, dipole, alignment	286
	Y. Honda, E. Kako, T. Konomi, T. Miyajima, T. Obina, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	Precise alignment of accelerator cavities is important in realizing a low emittance beam. Especially in the cases of superconducting cavities installed in a cryomodule, it is difficult to mechanically measure the position of the cavities. By measuring higher-order-modes (HOM) excited by a beam, the electrical center of the cavities can be estimated. We have developed a HOM measurement system for the injector superconducting accelerator cavities of KEK ERL test accelerator (cERL).Comparing the HOM signals of the three independent cavities in the cryomodule, we estimated the relative positioning errors of the three cavities.
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MOPB097	Degradation and Recovery of Cavity Performances in Compact-ERL Injector Cryomodule	cavity, operation, radiation, cryomodule	289
	E. Kako, T. Konomi, T. Miura, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	Injector cryomodule for cERL consists of three 2-cell cavities equipped with double-feeds input couplers, five antenna-type HOM couplers and a slide-jack tuner with two piezo actuators. After cryomodule assembly and first cool-down tests in 2012, the cERL injector cryomodule has been stably operated with beam for four years. Gradual increases of x-ray radiation levels due to field emission were observed during long term beam operation. High power pulsed RF conditioning as a cure method was applied in the cool-down period in 2016 and 2017, so that degraded cavity performances have almost recovered up to the original levels. Performance recovery status in three 2-cell cavities will be reported in this paper.
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MOPB099	Design of C-ADS Injector-I Cryomodule for 325MHz Cavities	cryomodule, cavity, linac, solenoid	294
	R. Ge, L. Bian, R. Han, S.P. Li, M.J. Sang, L.R. Sun, M.F. Xu, R. Ye, J.Q. Zhang, J.H. Zhang, X.Z. Zhang IHEP, Beijing, People's Republic of China
	Funding: Supported by Strategic Priority Research Program of CAS (XDA030213) The Chinese Accelerator Driven Sub-critical system (C-ADS) uses a high energy proton beam to bombard the metal target and generate neutrons to deal with the nuclear waste. The Chinese ADS proton linear has two 0~10 MeV injectors and one 10~1500 MeV superconducting linac. Injector-I is studied by the Institute of High Energy Physics (IHEP) under construction in the Beijing, China. The linear accelerator consists of two accelerating cryomodules operating at the temperature of 2 Kelvin. This paper describes the structure and thermal performances analysis of the cryomodule. The analysis takes into account all the main contributors (support posts, multilayer insulation, current leads, power couplers, and cavities) to the static and dynamic heat load at various cryogenic temperature levels. The thermal simulation analysis of the cryomodule is important theory foundation of optimization and commissioning.
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MOPB101	Cryomodule Fabrication and Modification for High Current Operation at the Mainz Energy Recovering Superconducting Accelerator MESA	cavity, cryomodule, operation, experiment	297
	T. Stengler, K. Aulenbacher, F. Hug, D. Simon IKP, Mainz, Germany K. Aulenbacher, T. Kürzeder HIM, Mainz, Germany
	Funding: This work is supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA" EXC 1098/2014} At Johannes Gutenberg-Universität Mainz, the Institute for Nuclear Physics is currently building the multiturn ERL 'Mainz Energy-Recovering Superconducting Accelerator' MESA. The §I{1.3}{\giga\hertz} cryomodules are based on the ELBE modules at Helmholtz Center Dresden-Rossendorf (HZDR) but are modified to suit the high current, energy recovering purposes of MESA. With two 9-cell TESLA cavities each, they shall provide §I{50}{\mega\electronvolt} energy gain per turn. The design and fabrication was done by Research Instruments GmbH, Bergisch Gladbach, Germany. The current status of the cryomodules, the test set up at the Helmholtz-Institute Mainz, the cavity properties and their tests will be discussed.
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MOPB102	Preliminary Design on the Cryomodule of the HWR for the Secondary Particle Generation at KOMAC	cryomodule, proton, linac, cavity	301
	H.-J. Kwon, Y.-S. Cho, J.J. Dang, H.S. Kim, K.H. Kim, S. Lee, Y.G. Song Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea
	Funding: This work has been supported through KOMAC (Korea of Multi-purpose Accelerator Complex) operation fund of KAERI by MSIP (Ministry of Science, ICT and Future Planning). A 100 MeV proton linac based on the radio frequency quadrupole and conventional drift tube linac has been operating for user service at KOMAC (Korea Multi-purpose Accelerator Complex). A superconducting linac based on the half-wave resonator is studied in order to increase the proton energy from 100 MeV to 160 MeV for secondary particle generation such as neutron. A cryomodule and its cryogenics were designed. The operating temperature of the HWR is 2 K. One cryomodule contains four HWR cavities and it didn't have superconducting solenoid because a doublet lattice using normal conducting magnet was considered as focusing elements. A thermal design was conducted and the structure was designed based on the existing well proven technologies. The results of the design on the cryomodule and cryogenics for KOMAC HWR are summarized and discussed in the conference.
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MOPB104	Development of a Novel Supporting System for High Luminosity LHC SRF Crab Cavities	cavity, cryomodule, SRF, interface	304
	T.J. Jones STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom K. Artoos, R. Calaga, O. Capatina, T. Capelli, M. Sosin, J.S. Swieszek, C. Zanoni CERN, Geneva, Switzerland G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom T.J. Jones Lancaster University, Lancaster, United Kingdom
	Compact SRF Crab Cavities are integral to the HL-LHC upgrade. This paper details the design of support structures within the SPS (Super Proton Synchrotron) Crab Cavity Cryomodule. For ease of alignment each cavity is supported with the mechanical tuner and RF Fundamental Power Coupler (FPC) via a common support plate. To reduce heat leak and remove bellows in the FPC it was determined that this would be the fixed support for the cavity (V. Parma, 2013). In addition, novel flexural blades were designed to give increased stiffness yet allow for thermal contraction of the cavity towards the fixed point of the FPC. This approach was superior when compared via simulation to several alternative techniques. A detailed simulation model was used for optimisation of directional stiffness, identification of vibration modes and minimising thermal stresses. A transmission matrix was developed in MS Excel to assess modal deflection for given ground vibration conditions. The spreadsheet gives an instantaneous yet comparable result to time consuming random vibration FE Analyses. The final engineering design of the supporting system is now complete and will also be described in this paper. References V. Parma, R. B. (2013). Status of the Superconducting Proton Linac (SPL) Cryomodule. SRF2013.
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MOPB105	Thermosiphon Cooling Loops for ARIEL Cryomodules	cryomodule, cavity, TRIUMF, linac	309
	Y. Ma, A.N. Koveshnikov, D. Lang, R.E. Laxdal, N. Muller TRIUMF, Vancouver, Canada
	Thermosiphon cooling loops have been used in ARIEL[1,2] cryomodules for 1.3GHz superconducting cavities cooling. It can deliver 4K liquid Helium from 4K phase separator to cavity thermal intercepts and return the vaporized liquid to the 4K phase separator as a refrigerator load. The design and test results are presented in this paper.
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MOPB106	Test Results of the European XFEL Serial-production Accelerator Modules	cavity, cryomodule, FEL, operation	312
	K. Kasprzak, M. Wiencek, A. Zwozniak IFJ-PAN, Kraków, Poland D. Kostin, D. Reschke, N. Walker DESY, Hamburg, Germany
	The serial-production tests of 100 cryomodules for the European XFEL have been finished. In this paper the statistics of the cold RF measurements in the AMTF (Accelerator Module Test Facility) are reported for all the modules. In addition comparison between the cavity vertical test results and module test results are presented.
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MOPB109	LCLS-II Cryomodule Transport System Testing	cavity, vacuum, cryomodule, ISOL	317
	N.A. Huque, E. Daly JLab, Newport News, Virginia, USA M.W. McGee Fermilab, Batavia, Illinois, USA
	The Cryomodules (CM) for the Linear Coherent Light Source II (LCLS-II) will be shipped to SLAC (Menlo Park, California) from JLab (Newport News, Virginia) and FNAL (Batavia, Illinois). A transportation system has been designed and built to safely transport the CMs over the road. It uses an array of helical isolator springs to attenuate shocks on the CM to below 1.5g in all directions. The system rides on trailers equipped with Air-Ride suspension, which attenuates vibration loads. The prototype LCLS-II CM (pCM) was driven 750 miles to test the transport system; shock loggers recorded the shock attenuation on the pCM and vacuum gauges were used to detect any compromises in beamline vacuum. Alignment measurements were taken before and after the trip to check whether cavity positions had shifted beyond the ± 0.2mm spec. Passband frequencies and cavity gradients were measured at 2K at the Cryomodule Test Facility (CMTF) at JLab to identify any degradation of CM performance after transportation. The transport system was found to have safely carried the CM and is cleared to begin shipments from JLab and FNAL to SLAC.
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MOPB110	Results of Accelerated Life Testing of LCLS-II Cavity Tuner Motor	cavity, cryomodule, operation, SRF	323
	N.A. Huque, E. Daly JLab, Newport News, Virginia, USA Y.M. Pischalnikov Fermilab, Batavia, Illinois, USA
	An Accelerated Life Test (ALT) of the Phytron stepper motor used in the LCLS-II cavity tuner has been conducted at JLab. Since the motor will reside inside the cryomodule, any failure would lead to a very costly and arduous repair. As such, the motor was tested for the equivalent of 30 lifetimes before being approved for use in the production cryomodules. The 9-cell LCLS-II cavity is simulated by disc springs with an equivalent spring constant. Plots of the motor position vs. tuner position ' measured via an installed linear variable differential transformer (LVDT) ' are used to measure motor motion. The titanium spindle was inspected for loss of lubrication. The motor passed the ALT, and is set to be installed in the LCLS-II cryomodules.
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Paper

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MOXA02

The Commissioning of the European XFEL Linac and its Performance

MMI, FEL, linac, cavity

1

D. Reschke, W. Decking, N. Walker, H. Weise
DESY, Hamburg, Germany

Funding: Presented on behalf of the XFEL Accelerator Consortium. Work supported by the respective funding agencies of the contributing institutes; for details see www.xfel.eu.
The main linac of the superconducting accelerator of the European XFEL presently consists of 96 accelerator modules, each housing eight 1.3 GHz TESLA-type cavi-ties, with an average design gradient of 23.6 MV/m. The performance of each individual module has been tested after module assembly in the Accelerator Module Test Facility (AMTF) at DESY. The 2-year period of module installation to the accelerator tunnel was finished in August 2016. In order to recheck and re-establish the performance of the input power couplers, warm processing of nearly all installed modules was performed before the first cool-down during Dec 2016 / Jan 2017. Four consecutive modules are connected to one 10 MW klystron and form a so-called RF station, which is powered and controlled individually during operation. By June 2017 23 of 25 RF stations have been commissioned for beam acceleration including frequency tuning, various calibrations and LLRF adjustments. A preliminary beam energy of 14 GeV was achieved, which is sufficient for first lasing experiments. No significant performance degradation has been observed so far. The commissioning experience and the available RF performance data will be presented.

Slides MOXA02 [6.896 MB]

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MOXA03

The 30MeV Stage of the ARIEL e-linac

cavity, linac, cryomodule, electron

6

R.E. Laxdal, Z.T. Ang, T. Au, K. Fong, O.K. Kester, S.R. Koscielniak, A.N. Koveshnikov, M.P. Laverty, Y. Ma, D.W. Storey, E. Thoeng, Z.Y. Yao, Q. Zheng, V. Zvyagintsev
TRIUMF, Vancouver, Canada

A MW class cw superconducting electron linac (e-Linac) is being installed at TRIUMF as a driver for radioactive beam production as part of the ARIEL project. The e-linac final configuration is planned to consist of five 1.3GHz nine-cell cavities housed in three cryomodules with one single cavity injector cryomodule (EINJ) and two double cavity accelerating cryomodules (EACA, EACB) to accelerate in continuous-wave (cw) up to 10mA of electrons to 50MeV. The e-Linac is being installed in stages. A demonstrator phase (2014) consisting of a 300kV electron gun, EINJ, and a partially outfitted EACA with just one accelerating cavity was installed for initial technical and beam tests to 22.9MeV. A Stage 2 upgrade now installed has a completed EACA to reach an operational goal of 3mA of electrons to 30MeV for first science from the ARIEL ISOL targets. A single 290kW klystron is used to feed the two EACA cavities in vector-sum closed-loop control. The paper is focused on the SRF challenges: systems design, cavity and cryomodule performance, rf ancillaries preparation and performance, LLRF and RF system performance and final beam test results.

Slides MOXA03 [13.981 MB]

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MOXA04

Superconducting Accelerator for ERL Based FEL EUV Light Source at KEK

cavity, HOM, linac, operation

13

H. Sakai, E. Kako, T. Konomi, T. Kubo, K. Umemori
KEK, Ibaraki, Japan
T. Ota
Toshiba, Yokohama, Japan
M. Sawamura
QST, Tokai, Japan

An energy recovery linac (ERL)-based free electron laser (FEL) is a possible candidate of a tens of kW EUV source and open the era for next generation EUV-lithography. We have designed the 10 mA class ERL-based EUV-FEL source to generate more than 10 kW power. One of the key technologies is CW superconducting cavities to realize the energy recovery of high beam current of more than 10 mA by suppressing HOMs and high gradient acceleration of higher than 12 MV/m. This CW superconducting cavity had been developed through the construction of the Compact ERL facility in KEK and it successfully achieved the energy recovery of 1 mA CW beam until now. In this talk, first we express our design strategies of SRF cavities of the main linac of ERL-EUV light sources not only to suppress the HOMs but also to overcome the field emission problem by modifying the main linac cavity of Compact ERL more sophisticatedly. Next we show the recent development works for ERL-EUV superconducting cavity about HOM damper, cryomodule, and its clean string-assembly work by using horizontal test stand.

Slides MOXA04 [5.938 MB]

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MOXA07

Development of the C-ADS SRF Accelerator at IHEP

cavity, linac, cryomodule, operation

19

F. Yan, L. Bian, J.S. Cao, Y. Chen, Y.L. Chi, J.P. Dai, L. Dong, L.L. Dong, Y.Y. Du, H.F.S. Feisi, Y. Gao, R. Ge, H. Geng, D.Z. Guo, D.Y. He, J. He, T.M. Huang, X. Jing, B. Li, H. Li, L. Li, S.P. Li, H.Y. Lin, F. Liu, R.L. Liu, F. Long, Y.H. Lu, H.Z. Ma, Q. Ma, X. Ma, C. Meng, Z.H. Mi, H.F. Ouyang, W.M. Pan, S. Pei, Q.L. Peng, X.H. Peng, P. Sha, H. Shi, P. Su, Y.F. Sui, L.R. Sun, X.T. Sun, G.W. Wang, J.L. Wang, S.C. Wang, G. Wu, O. Xiao, X.C. Yang, Q. Ye, R. Ye, L. Yu, X.Y. Zhang, X.Y. Zhao, Y.L. Zhao, Y. Zhao, Z.H. ZhenHua, N. Zhou, Z.S. Zhou
IHEP, Beijing, People's Republic of China
H.Y. Zhu
Institute of High Energy Physics (IHEP), People's Republic of China

Funding: CAS Strategic Priority Research Program-Future Advanced Nuclear Fission Energy (Accelerator-Driven Sub-critical System) and National Natural Science Foundation of China, under contract NO. 11405190
The 10 MeV accelerator-driven subcritical system (ADS) Injector I test stand at Institute of High Energy Physics (IHEP) is a testing facility dedicated to demonstrate one of the two injector design schemes [Injector Scheme-I, which works at 325 MHz], for the ADS project in China. The ion source was installed since April of 2014, periods of commissioning are regularly scheduled between installation phases of the rest of the injector. Early this year, continuous wave (CW) proton beam has been successfully obtained with energy of 10MeV and average beam current around 2 mA, the single spoke cavities with smallest developed beta (βg=0.12) were applied and successfully commissioned. Single spoke cavities with higher beta (βg=0.21) were also adopted for the last cryomodule of 25MeV proton linac, and 170uA CW proton beam were shooting through recently. This contribution reports the details of the development of the C-ADS SRF accelerator at IHEP and the challenges of the CW machine commissioning

Slides MOXA07 [5.605 MB]

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MOYA01

The Superconducting Accelerator for the ESS Project

cavity, cryomodule, SRF, linac

24

F. Schlander, C. Darve, N. Elias, M. Lindroos, C.G. Maiano
ESS, Lund, Sweden
P. Bosland
CEA/IRFU, Gif-sur-Yvette, France
M. Ellis
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
P. Michelato
INFN/LASA, Segrate (MI), Italy
G. Olry
IPN, Orsay, France
R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden

The European Spallation Source, ESS, is under construction in Lund since 2014. While the installation of the source and the normal conducting part will start in this autumn, the production and testing of cryomodules and cavities for the superconducting accelerator is in full swing at the partner laboratories. The spoke cavities and cryomodules will be provided by IPN Orsay and the testing of those modules will take place at Uppsala University. Prototyping and assembly of the elliptical cryomodules series is occurring at CEA Saclay, and the modules will be tested at a new test stand at ESS. The fabrication and test of the medium beta cavities is provided by INFN Milan and STFC Daresbury for the high beta cavities respectively. An overview of the current activities and test results will be presented in this talk.

Slides MOYA01 [26.361 MB]

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MOYA02

BESSY VSR: SRF Challenges and Developments for a Variable-pulse Length Next-generation Light Source

cavity, HOM, SRF, synchrotron

29

A.V. Vélez, H.-W. Glock, F. Glöckner, B.D.S. Hall, J. Knobloch, A. Neumann, P. Schnizer, E. Sharples
HZB, Berlin, Germany
A.V. Tsakanian
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany

The BESSY VSR project represents an exciting alternative to diffraction limited storage rings in the development of a next generation light source. Such a system should be capable to store "standard" (some 10 ps long) and "short" (ps and sub-ps long) pulses simultaneously in the storage ring opening the door to picosecond dynamic and high-resolution experiments at the same facility. This unique feature can be created by the introduction of the beating effects produced by higher harmonic SRF cavity systems (1.5 GHz & 1.75 GHz). The challenging design specifications as well as the technological demands on the SRF system make BESSY VSR a defiant project where non-standard techniques such as waveguide-damped cavities have been further developed. This talk focuses on the new SRF developments that includes wveguide-damped cavities, high-power couplers and higher-order mode absorbers that must handle nearly 2 kW of HOM power. The cryomodule design and its interaction with the beam will also be discussed.
Comment: VSR concept was introduced at SRF15. Much development work has now been done. Here the focus is more one the technology of VSR and the talk could also be listed under "SRF technology R&D"

Slides MOYA02 [7.961 MB]

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MOYA03

Progress of the RAON

cavity, cryomodule, quadrupole, rfq

36

D. Jeon, B.H. Choi, C. Choi, J.W. Choi, C.O. Choi, S. Choi, I. Chun, I.S. Hong, M.O. Hyun, H. Jang, H.M. Jang, J.-H. Jang, S.C. Jeong, H. Jin, Y.W. Jo, J. Joo, M.J. Joung, H.C. Jung, I.I. Jung, Y. Jung, J. Kang, D.G. Kim, H. Kim, H.J. Kim, J.H. Kim, J.-W. Kim, W.K. Kim, Y. Kim, Y.K. Kwon, D.Y. Lee, J. Lee, K.W. Lee, M. Lee, S. Lee, S. Lee, S.H. Nam, B.-S. Park, M.J. Park, K.T. Seol, I. Shin, J.H. Shin, C.W. Son, K.T. Son, S.W. Yoon, A. Zaghloul
IBS, Daejeon, Republic of Korea

Funding: This work was supported by the Institute for Basic Science funded by the Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) under Contract 2013M7A1A1075764
Construction of the RAON heavy ion accelerator facility is in-progress in Korea. The driver linac is a superconducting linac with 200 MeV/u for uranium beam and 400 kW beam power. Prototyping of major components and their tests are proceeding including superconducting cavities, superconducting magnets and cryomodules. December 2016, the RFQ accelerated oxygen beam. Status report of the RAON accelerator systems is presented.

Slides MOYA03 [10.275 MB]

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MOPB001

Concepts and Design for Beamline HOM Dampers for eRHIC

HOM, cavity, impedance, linac

39

P. Kolb, Y. Gao, D. Holmes, K.S. Smith, W. Xu
BNL, Upton, Long Island, New York, USA
Y. Gao
PKU, Beijing, People's Republic of China

Funding: Work supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
In the design of eRHIC at BNL, HOM power plays a major role for the SRF installation. Depending on the final accelerator design and choice of cavity, up to 100kW of HOM power is estimated to be generated, presenting a big challenge for the HOM damping concept. Due to this high amount of HOM power, all current concepts for eRHIC would use room temperature beam line absorbers equipped with silicone-carbide dielectrics to absorb HOM power. Concepts, designs and simulations for these beam line absorbers will be presented.

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MOPB002

eRHIC Crab Cavity Choice for Ring-ring Design

cavity, luminosity, electron, impedance

43

Q. Wu, I. Ben-Zvi, Y. Hao, S. Verdú-Andrés, B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The future electron ion collider eRHIC adopts large crossing angle (22 mrad) to allow fast separation of two beams in the ring-ring scheme. Crab cavities are required to recover the luminosity from geometric losses. Initial calculation shows that the frequency of the cavities for the ion beam is no more than 336MHz. In this paper, we discuss the crab cavity related lattice parameters for both ion and electron beams in ring-ring design, the frequency choice, and the cavity design considerations.

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MOPB003

A New High Resolution Optical System for Inspection of Gun-and Multi-cell Resonators in ISO-4 Cleanrooms

cavity, gun, SRF, MMI

47

M. Schalwat, R. Bandelmann, A. Daniel, N. Krupka, A. Matheisen, S.T. Sievers
DESY, Hamburg, Germany

Optical inspection of the inner surface of superconducting resonators was established during European XFEL cavity production by usage of the so called OBACHT optical inspection. In addition to the surface inspection by OBACHT a new optical inspection system with integrated high resolution camera is set up at DESY. It allows inspection of multi-cell resonators as well as gun cavity resonators with only single side accessibility to the inner surface. A prototype was commissioned and optical inspections were done with OBACHT and the new system in parallel. Two SRF gun cavities were inspected by this optical system and origin of limitations of the resonators were identified.

Poster MOPB003 [0.220 MB]

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MOPB004

Design of a RF Quadrupole Resonator for Landau Damping in HL-LHC

cavity, impedance, quadrupole, damping

51

K. Papke, A. Grudiev
CERN, Geneva, Switzerland

The design and optimization of a quadrupole resonator for transverse Landau damping in the High Luminosity Large Hadron Collider (HL-LHC) is presented. Two different cavity types are considered whose shape is determined by quadrupolar strength, surface peak fields, and beam coupling impedance. The lower order and higher order mode (LOM and HOM) spectra of the optimized cavities are investigated and different approaches for their damping are proposed. Along an example, the required RF power and optimal external quality factor for the input coupler is derived.

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MOPB005

Beam Dynamics Simulations for the New Superconducting CW Heavy Ion Linca at GSI

cavity, linac, heavy-ion, accelerating-gradient

56

M. Schwarz, M. Basten, M. Busch, H. Podlech, U. Ratzinger, R. Tiede
IAP, Frankfurt am Main, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia
W.A. Barth, M. Heilmann, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu
HIM, Mainz, Germany

Funding: Work supported by BMBF contr. No. 05P15RFRBA
For future experiments with heavy ions near the coulomb barrier within the super-heavy element (SHE) research project a multi-stage R&D program of GSI, HIM and IAP is currently in progress. It aims at developing a superconducting (sc) continuous wave (CW) LINAC with multiple CH cavities as key components downstream the upgraded High Charge Injector (HLI) at GSI. The LINAC design is challenging, due to the requirement of intense beams in CW-mode up to a mass-to-charge ratio of 6 while covering a broad output energy range from 3.5 to 7.3 MeV/u with minimum energy spread. After sucessful tests with the first CH cavity in 2016 demonstrated a promising maximum accelerating gradient of E_a = 9.6 MV/m, recently first beam tests have been started as next milestone at GSI, confirming its flawless functionality*.
W. Barth et al., Further Layout Investigations for a Superconducting CW-linac for Heavy Ions at GSI, 18th Int. Conf. on RF Superconductivity (SRF17), Lanzhou, China, July 2017, paper MOPB023.

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MOPB007

Design of the Superconducting Quarter Wave Resonators for HIAF

cavity, linac, heavy-ion, ECR

59

C. Zhang, L. Chen, Q.W. Chu, H. Guo, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, L. Li, Y.M. Li, F. Pan, T. Tan, R.X. Wang, A.D. Wu, Q.J. Wu, P.R. Xiong, W.M. Yue, S.H. Zhang, S.X. Zhang
IMP/CAS, Lanzhou, People's Republic of China

A heavy ion accelerator facility (HIAF) is under development in the Institute of Modern Physics. For the low energy superconducting accelerating section, two types of quarter wave resonators with frequency of 81.25 MHz and β of 0.05 and 0.10 have been proposed. The electro-magnetic design has been optimized in order to reach the high accelerating voltage, and the optimization also included the drift tube face tilting to compensate for the beam steering caused by the asymmetry in the quarter wave resonator geometry.

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MOPB008

Input Power Coupler for NICA Injector Coaxial Quater Wave SC Cavity

cavity, multipactoring, Windows, operation

61

M.V. Lalayan, T.A. Bakhareva, M. Gusarova, S.V. Matsievskiy
MEPhI, Moscow, Russia

New coaxial power coupler research and development results are presented and discussed. Coupler is proposed for superconducting QWR cavities being under consideration now as option for planned Nuclotron-based Ion Collider fAcility (NICA) injector upgrade. The goal was to develop power coupler operating at 162 MHz and feeding SC cavity with about 20 kW RF power. It provides Qext tuning range (1.5-3)E5 by inner conductor movement. Conservative design with two identical disk ceramic windows was chosen. Electrodynamic, thermal and mechanical simulations were carried out.

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MOPB009

Progress of 650 MHz SRF Cavity for eRHIC SRF Linac

cavity, SRF, HOM, linac

64

W. Xu, I. Ben-Zvi, Y. Gao, D. Holmes, P. Kolb, G.T. McIntyre, C. Pai, R. Porqueddu, K.S. Smith, R. Than, J.E. Tuozzolo, F.J. Willeke, A. Zaltsman
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
eRHIC ERL SRF requires 160 5-cell 650 MHz SRF cavities. The 650 MHz cavity has been designed and two prototypes have been fabricated, one Cu cavity for HOM study and one Nb cavity for cavity performance study. This paper will describe cavity design and the progress of prototyping.

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MOPB010

Design of the 2×4-cell Superconducting Cryomodule for the Free-electron Laser

cryomodule, shielding, cavity, radiation

67

X. Luo, C.L. Lao, M. Li, L.J. Shan, X.M. Shen, H. Wang, X. Yang, K. Zhou
CAEP/IAE, Mianyang, Sichuan, People's Republic of China
X.Y. Lu, S.W. Quan, F. Wang
PKU, Beijing, People's Republic of China

A 2×4-cell superconducting linac module for the THz-FEL facility has been developed at the China Academy of Engineering Physics, which is expected to provide 6~8 MeV quasi-CW electron beams with an average current of 1~5 mA. The design of the cryomodule is presented in this paper. The dynamic and static heat load have been evaluated to reasonable level. The temperature distribution inside the cryomodule has been optimized by simulation, as well as mechanical structure and the magnetic shielding.

Poster MOPB010 [1.019 MB]

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MOPB011

CEA Cryomodules Design for SARAF Phase 2

cavity, cryomodule, simulation, vacuum

70

C. Madec
CEA, Gif-sur-Yvette, France
N. Bazin, D. Chirpaz-Cerbat, R. Cubizolles
CEA/IRFU, Gif-sur-Yvette, France
P. Brédy
CEA/DSM/IRFU, France
R. Bruce, P. Hardy, F. Leseigneur, Th. Plaisant, J. Plouin
CEA/DRF/IRFU, Gif-sur-Yvette, France

CEA is committed to delivering 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 in 4 cryomodules separated by warm diagnostics housing beam diagnostics. The first two identical cryomodules host 6 half-wave resonator (HWR) low beta cavities (β = 0.091), 176 MHz. The last two identical cryomodules are equipped with 7 HWR high-beta cavities (β = 0.181), 176 MHz. The beam is focused through superconducting solenoids located between cavities housing steering coils. A Beam Position Monitor is placed upstream each solenoid. A diagnostic box containing a beam profiler and a vacuum pump will be placed at the end of each cryomodule. The cryomodules and the warm sections are being designed. These studies will be presented in this poster.

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MOPB012

Status of the IFMIF LIPAc SRF Linac

cavity, cryomodule, SRF, operation

74

N. Bazin, C. Boulch, A. Bruniquel, P. Carbonnier, J.K. Chambrillon, G. Devanz, F. Éozénou, P. Hardy, H. Jenhani, O. Piquet, J. Plouin, A. Riquelme, D. Roudier, C. Servouin
CEA/DRF/IRFU, Gif-sur-Yvette, France
P. Charon, S. Chel, G. Disset, L. Maurice, J. Relland, B. Renard
CEA/IRFU, Gif-sur-Yvette, France
P. Contrepois
CEA/DSM/IRFU, France
D. Regidor, F. Toral
CIEMAT, Madrid, Spain

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 and eight focusing solenoids. This paper presents the status of the IFMIF SRF Linac.

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MOPB013

European XFEL Input Coupler Experiences and Challenges in a Test Field

FEL, GUI, SRF, operation

78

F. Hoffmann, D. Kostin, W.-D. Möller, D. Reschke, M. Wiencek
DESY, Hamburg, Germany

102 European XFEL accelerating modules with 816 superconducting cavities and main input RF power couplers were assembled and then tested at DESY prior to installation in the European XFEL tunnel. In the Accelerating Module Test Facility (AMTF) warm and cold RF tests were done. The test results went directly to the operational setup for the LINAC. Main input couplers did present several problems during the tests, resulting in some minor coupler design changes as well as in a few repair actions. The experience got from the said testing operation is worth to be shared and is presented here together with a discussion.

Poster MOPB013 [0.648 MB]

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MOPB015

Accelerator Module Repair for the European XFEL Installation

FEL, cavity, vacuum, linac

82

E. Vogel, S. Barbanotti, F. Hoffmann, K. Jensch, D. Kostin, L. Lilje, W.-D. Möller, M. Schmökel, H. Weise
DESY, Hamburg, Germany
S. Berry, O. Napoly
CEA/DSM/IRFU, France
M. Sienkiewicz, J. Świerbleski, M. Wiencek
IFJ-PAN, Kraków, Poland

Repair actions of different extent have been performed at 61 modules of the 100 accelerating series modules for the European XFEL to qualify them for the tunnel installation. Four modules could not be repaired in time. CEA Saclay managed to perform three major repairs in parallel to the series module integration, the residual repair actions took place at DESY Hamburg. In this paper we will give an overview on the various technical problems which required being fixed before the tunnel installation and on the repair actions performed.

Poster MOPB015 [9.354 MB]

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MOPB016

Operation of Diamond Superconducting RF Cavities

cavity, vacuum, operation, GUI

87

P. Gu, C. Christou, P.J. Marten, S.A. Pande, A.F. Rankin, D. Spink
DLS, Oxfordshire, United Kingdom

The Diamond Light Source storage ring has been in operation using superconducting RF cavities since 2007. Diamond has four superconducting cavity modules with two usually installed at any one time. The four cavities perform differently in many aspects such as reliable operating parameters and time in service, with the longest in continuous service for 7 years without failure and the shortest failing after only 8 months. All Diamond superconducting RF cavities suffered many fast vacuum trips in their early years, but after many years of efforts, the performance of the cavities have now been effectively managed by weekly conditioning, partial warm-up during shut down and cavity voltage level control. We will discuss our experience with superconducting RF cavities and our future plan.

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MOPB017

Multiphysics Simulations of the Wide Opened Waveguide Crab-cavity

cavity, HOM, impedance, dipole

90

K. Papke, A. Amorim Carvalho, A. Grudiev, C. Zanoni
CERN, Geneva, Switzerland

In the frame of a FCC study a first prototype of a compact superconducting crab-cavity, using Nb-on-Cu-coating technique is being manufactured and investigated. The design, which is based on the ridged waveguide resonator, is subjected to multipacting and pressure sensitivity simulations. First results of theses simulations are presented and compared to those of other SRF cavities. Furthermore, several aspects related to the design of the fundamental mode coupler and HOM dampers are presented.

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MOPB018

Testing of SRF Cavities and Cryomodules for the European Spallation Source

cavity, cryomodule, SRF, linac

95

N. Elias, E. Asensi Conejero, C. Darve, N.F. Hakansson, W. Hees, C.G. Maiano, F. Schlander
ESS, Lund, Sweden

The European Spallation Source (ESS) is currently under construction in Lund, Sweden. The ESS linear accelerator aims to deliver a 62.5 mA , 2.86 ms long proton beam onto a rotating tungsten target, at 14 Hz repetition rate, thus achieving an energy of 2 GeV and 5 MW power. Most of the beam acceleration happens in the superconducting fraction of the linac, which is composed of three sectors of cryomodules named after the cavities housed within. The first sector of the SRF linac is composed of 13 Spoke cryomodules containing 2 double-spoke cavities with a geometric beta of 0.5, the second is composed of 9 medium beta cryomodules each housing four elliptical cavities (β=0.67) and finally 21 high beta cryomodules enclosing four elliptical cavities (β=0.86). ESS has strategically built up a SRF collaboration with other European institutions, these partners will deliver through In-Kind agreements cavities and cryomodules performing within the ESS specification. This article describes the process leading to the acceptance of cavities and cryomodules received from the different partners and the necessary testing required prior to the final installation in the ESS tunnel.

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MOPB019

Interface Challenges for the SRF Cryomodules for the European Spallation Source

cryomodule, cavity, interface, ion-source

100

F. Schlander, C. Darve, N. Elias, C.G. Maiano
ESS, Lund, Sweden
P. Bosland
CEA/DSM/IRFU, France
G. Olry
IPN, Orsay, France

The European Spallation Source is currently under construction in Lund in southern Sweden. The main part of the accelerator will consist of two different types of cryomodules housing three different types of cavities ' double spoke cavities and two different elliptical cavities. The spoke cavities as well as the cryomodules will be provided by IPN Orsay, thus the external interfaces to the other accelerator systems have to be verified. While the procurement and assembly of the elliptical cryomodules will be performed by CEA Saclay, the cavities will be provided by INFN Milano and STFC Daresbury. Thus in addition to the external cryomodule interfaces, also the internal interfaces between cavities and cryomodules have to be taken care of. This contribution presents the challenges related to this work.

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MOPB020

An Optimal Procedure for Coupler Conditioning for ESS Superconducting Linac

cavity, vacuum, interface, controls

103

H. Li
Uppsala University, Uppsala, Sweden
E. Asensi Conejero, C.G. Maiano, R. Zeng
ESS, Lund, Sweden

An optimal procedure for coupler and cavity conditioning is proposed for the ESS superconducting cavities, which is applicable for different test stands and following installation in the ESS tunnel. A preliminary procedure has been developed and successfully tested at FREIA facility, Uppsala. The preliminary procedure will now be improved by integrating it into LLRF and EPICS control. This will be a joint effort between FREIA and ESS and will be used at the test stands in Lund and on the couplers installed in the tunnel. Developing the conditioning procedures on a common platform offers ESS significant advantages by allowing the procedures to be reused at different sites and by recording data in a consistent format. The details of the procedure, its development and testing will be reported and the future activities will be described.

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MOPB023

Further Layout Investigations for a Superconducting CW-linac for Heavy Ions at GSI

linac, cavity, heavy-ion, SRF

108

W.A. Barth, K. Aulenbacher, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu
HIM, Mainz, Germany
K. Aulenbacher
IKP, Mainz, Germany
W.A. Barth, M. Heilmann, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia
M. Basten, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany

Very compact accelerating-focusing structures, as well as short focusing periods, high accelerating gradients and very short drift spaces are strongly required for superconducting (sc) accelerator sections operating at low and medium beam energies. To keep the GSI-Super Heavy Element program competitive on a high level and even beyond, a standalone sc continuous wave Linac in combination with the GSI High Charge State injector, upgraded for cw-operation, is envisaged. The first LINAC section (financed by HIM and GSI) as a demonstration of the capability of 216 MHz multi gap Crossbar H-structures (CH) is still in the beam commissioning phase, while an accelerating gradient of 9.6 MV/m (4 K) at a sufficient quality factor has been already reached. Recently the overall Linac design, based on a standard cryomodule, comprising three CH cavities, a rebuncher section and two 9.3 T-solenoidal lenses, has to be fixed. This paper presents the status of the Linac layout studies as well as the integration in the GSI accelerator facility.

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MOPB024

Steps Towards Superconducting CW-linac for Heavy Ions at GSI

cavity, linac, solenoid, heavy-ion

112

M. Miski-Oglu, M. Amberg, K. Aulenbacher, W.A. Barth
HIM, Mainz, Germany
K. Aulenbacher
IKP, Mainz, Germany
W.A. Barth, V. Gettmann, M. Heilmann, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia
M. Basten, M. Busch, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany

A superconducting (sc) cw-Linac at GSI should ensure competitive production of Super Heavies in the future. Further R&D for this cw-Linac, a so called 'Advanced CW-Demonstrator', with maximal energy of 3.5 MeV/u is ongoing. As a first step, the demonstrator project with one sc CH-cavity is near its completion, the beam tests are scheduled for mid-summer 2017. The completion of the 'Advanced CW-Demonstrator' includes successive construction of two new cryogenic modules comprising four CH-cavities and two solenoids each. In this contribution the layout of the cryomodules and the Helium distribution system are presented.

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MOPB028

HOM Coupler Design for CEPC Cavities

HOM, cavity, damping, collider

115

H.J. Zheng, F. Meng, J.Y. Zhai
IHEP, Beijing, People's Republic of China

Funding: This study was supported by National Key Programme for S&T Research and Development (Grant NO.: 2016YFA0400400)
In this paper，it will be presented the higher order mode (HOM) coupler design for the Circular Electron-Positron Collider (CEPC) 650 MHz 2-cell cavity. 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. A double notch 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. This paper summarizes the RF design of the HOM coupler, tolerance analysis, thermal analysis as well as mechanical structures.

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MOPB031

Fabrication and Cold Test Result of FRIB β=0.53 Pre-production Cryomodule

cavity, cryomodule, solenoid, SRF

120

H. Ao, J. Asciutto, B. Bird, N.K. Bultman, E.E. Burkhardt, F. Casagrande, C. Compton, K.D. Davidson, K. Elliott, A. Ganshyn, I. Grender, W. Hartung, L. Hodges, I.M. Malloch, S.J. Miller, D.G. Morris, P.N. Ostroumov, J.T. Popielarski, L. Popielarski, M.A. Reaume, K. Saito, M. Shuptar, S. Stark, J.D. Wenstrom, M. Xu, T. Xu, Z. Zheng
FRIB, East Lansing, USA
A. Facco
INFN/LNL, Legnaro (PD), Italy

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The driver linac for the Facility for Rare Isotope Beams (FRIB) comprises four kinds of cavities (β=0.041, 0.085, 0.29, and 0.53) and six types of cryomodules including matching modules. FRIB has completed the fabrication and the cold test of a β=0.53 pre-production cryomodule, which is the first prototype for a half-wave (β=0.29 and 0.53) cavity. This paper describes the fabrication and the cold test result of the β=0.53 pre-production cryomodule including lessons learned.

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MOPB034

Selection of the Type of Accelerating Structures for the Second Group of Cavity SC Linac Nuclotron-NICA

cavity, linac, accelerating-gradient, multipactoring

125

M. Gusarova, A.A. Gorchakov, M.V. Lalayan, D.V. Surkov, K.V. Taletskiy
MEPhI, Moscow, Russia
A.V. Butenko
JINR/VBLHEP, Dubna, Moscow region, Russia
D.A. Shparla
Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
A.O. Sidorin, G.V. Trubnikov
JINR, Dubna, Moscow Region, Russia

The paper summorises the research results aimed on the choice of superconducting accelerating cavities for the second section of the SC linac Nuclotron-NICA injector project. This choice was based on comparative analysis of accelerating structures electrodynamic characteristics taking into account technological challenges of bulk niobium cavities production.

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MOPB035

Cryogenic Probe Station at Old Dominion University Center for Accelerator Science

cavity, SRF, cryogenics, niobium

128

J. Makita, J.R. Delayen, A.V. Gurevich
ODU, Norfolk, Virginia, USA
G. Ciovati
JLab, Newport News, Virginia, USA

With a growing effort in research and development of an alternative material to bulk Nb for a superconducting radiofrequency (SRF) cavity, it is important to have a cost effective method to benchmark new materials of choice. At Old Dominion University's Center for Accelerator Science, a cryogenic probe station (CPS) will be used to measure the response of superconductor samples under RF fields. The setup consists of a closed-cycle refrigerator for cooling a sample wafer to a cryogenic temperature, a superconducting magnet providing a field parallel to the sample, and DC probes in addition to RF probes. The RF probes will extract a quality factor from a sample patterned in a coplanar waveguide resonator structure on a 2' wafer. From the measured quality factor, the surface resistance and the penetration depth as a function of temperature and magnetic field will be calculated. This paper will discuss the design and measurement procedures of the current CPS setup.

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MOPB036

The Study of Deposition Method of Nb3Sn Film on Cu Substrate

SRF, niobium, cavity, superconductivity

131

L. Xiao, X.Y. Lu, W.W. Tan, D. Xie, D.Y. Yang, Y. Yang, Z.Q. Yang, J. Zhao
PKU, Beijing, People's Republic of China

Our work is mainly focused on the fabrication methods of Nb3Sn films on Cu substrates and film's properties. There are diffraction peaks of Nb3Sn in the X-ray diffraction patterns in which without diffraction peaks of copper compounds. Scanning electron microstructures of Nb3Sn film reflect its nice compactness and binding force between film and substrate.

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MOPB037

Progress of the 2x4-Cell Superconducting Accelerator for the CAEP THz-FEL Facility

cavity, pick-up, cryomodule, cryogenics

134

K. Zhou, C.L. Lao, M. Li, X. Luo, L.J. Shan, X. Shen, H. Wang, X. Yang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China
X.Y. Lu
PKU, Beijing, People's Republic of China

The high average power THz radiation facility is now under construction in China Academy of Engineering Physics. The superconducting accelerator is one of the most important components for this facility, including two 4-Cell TESLA superconducting radio frequency cavities. The designed effective field gradients for both cavities are 10^-12 MV/m. This paper will present the progress of the 2x4-cell superconducting accelerator, mainly including its construction and cryogenic test in Chengdu. At 2 K state, the cryomodule works smoothly and stably. The effective field gradients of both cavities have achieved 10 MV/m. Further beam loading experiments are now in progress.

Poster MOPB037 [5.124 MB]

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MOPB040

ESS High-beta Cavity Test Preparations at Daresbury Laboratory

cavity, niobium, LLRF, SRF

137

P.A. Smith, L. Bizel-Bizellot, K.D. Dumbell, M. Ellis, P. Goudket, A.J. Moss, E.F. Palade, S.M. Pattalwar, M.D. Pendleton, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Science and Technology Facility Council is responsible for supplying, and testing 84 High beta elliptical SRF cavities, as part of the UK In Kind Contribution to the European Spallation Source (ESS). The High-β=0.86, cavities have been designed by CEA- Saclay and are a five cell Niobium cavity operating at 704.42 MHz. They are required to provide an accelerating gradient of 19.9 MV/m at an unloaded Q of 5x10⁹. Preparations are underway to upgrade the cryogenic and RF facilities at Daresbury laboratory prior to the arrival of the first cavities. As part of these arrangements, a niobium coaxial resonator has been manufactured, to validate the test facility. The design considerations, for the coaxial resonator are presented, along with preliminary results. The RF measurement system to perform the cavity conditioning and testing is also presented.

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MOPB041

Status of the SOLEIL Superconducting RF System

cavity, operation, SRF, GUI

141

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

The 352 MHz SOLEIL SRF systems consist in two cryomodules, each containing a pair of SC Nb/Cu cavities, cooled with LHe at 4K from a single 350 W cryogenic plant. In order to store 500 mA, a power of 575 kW and an accelerating voltage of 3-4 MV are required. The RF power is provided by 4 SSPA's delivering up to 180 kW each. The original cavity input power couplers, which are LEP-type antennas designed to handle up to 200 kW, are being replaced by upgraded versions, able to operate at 300 kW CW. This will open the possibility to operate at full beam current with only one active cryomodule. The SRF system operational experience over the past ten years as well as the different upgrades will be reported here.

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MOPB042

The TRIUMF/VECC Injector Cryomodule Performance

cavity, cryomodule, TRIUMF, linac

144

Y. Ma, K. Fong, T. Junginger, D. Kishi, A.N. Koveshnikov, R.E. Laxdal, N. Muller, R.R. Nagimov, D.W. Storey, E. Thoeng, Z.Y. Yao, V. Zvyagintsev
TRIUMF, Vancouver, Canada
U. Bhunia, A. Chakrabarti, S. Dechoudhury, V. Naik
VECC, Kolkata, India

The collaboration on superconducting electron Linac for rare ion beam facilities ARIEL (Advanced Rare Iso-topE Laboratory) [1-4] and ANURIB [5] (Advanced Na-tional facility for Unstable and Rare Isotope Beams) has resulted in production of a superconducting Injector Cryomodule (VECC ICM) at TRIUMF for VECC. The cryomodule design utilizes a unique box cryomodule with a top-loading cold mass. The hermetic unit consists of a niobium cavity which operating at 1.3GHz and connected with two symmetrically opposed couplers which can deliver 100kW RF power to the beam. Liquid helium supplied at 4.4 K is converted to superfluid helium-II through a cryogenic insert on board which includes 4 K phase separator, 4K/2K heat exchanger and Joule-Thompson valve. In 2016, the VECC ICM has been tested at TRIUMF and demonstrated 10.5 MeV acceleration. A summary of the VECC ICM commissioning are presented.

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MOPB043

Pansophy, a JLab SRF Engineering Data Management System, Supporting Data Collection, Retrieval and Analysis Utilized by LCLS-II

cryomodule, cavity, database, status

148

V.D. Bookwalter, M. Dickey, E.A. McEwen, M.G. Salvador
JLab, Newport News, Virginia, USA

Pansophy is an Engineering Data Management System that provides a comprehensive solution for managing information in the production and testing of cryomodules. It is especially suited to supporting the Data & Quality Management Systems for large projects like LCLS-II. With extensive amounts of data collected for an individual project, data retrieval to facilitate feedback and enhancement of production and processing activities is a high priority. The priority shares importance with the needs of managing the project, including production status, NCR, and Quality Management reports. Recent Pansophy enhancements have been to Data and Quality management reports and statistical analysis. Such enhancements include a database driven menu system, extended MSWord macro and preprocessing of travelers, and an extensive reporting system. The reporting system allows managers and group leaders to quickly respond to the needs of the project in areas of cavity and cryomodule production, data collection, NCR, Quality Management and schedule. Extensions include integration with the SRF inventory system PRIMeS, allowing traceability from receiving of manufactured parts to final cryomodule product.

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MOPB044

Magnetic Hygiene Control on LCLS-II Cryomodules Fabricated at JLab

cavity, cryomodule, controls, shielding

153

G. Cheng, E. Daly, G.K. Davis, J.F. Fischer, N.A. Huque, R.A. Legg, H. Park, K.M. Wilson, L. Zhao
JLab, Newport News, Virginia, USA

Funding: U.S. DOE Contract No. DE-AC05-06OR23177 and the LCLS-II project.
Jefferson Lab (JLab) is in collaboration with Fermi Na-tional Accelerator Laboratory (Fermilab) to build 18 cryomodules to install at the SLAC National Accelerator Laboratory's tunnel as part of the Linac Coherent Light Source upgrade project (LCLS-II). Each LCLS-II cry-omodule hosts 8 superconducting niobium cavities that adopt the nitrogen doping technique, which aims to en-hance the cavity quality factor Qo to reduce the consumption of liquid helium used to cool down the cavities. It is known that the Qo of niobium cavities is affected by cavity surface magnetic field. Traditionally, magnetic shields made of high magnetic permeability mu-metals are employed as a passive shielding of the ambient magnetic fluxes. During the LCLS-II cryomodule development, magnetic hygiene control that includes magnetic shielding and demagnetization of parts and the whole-machine is implemented. JLab and Fermilab worked closely on developing magnetic hygiene control procedures, identifying relevant tools, investigating causes of magnetization, magnetic field monitoring, etc. This paper focuses on JLab's experiences with LCLS-II cryomodule magnetic hygiene control during its fabrication.
Authored by Jefferson Science Associates, LLC. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for Government purposes.

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MOPB045

JLab New Injector Cryomodule Design, Fabrication and Testing

cavity, cryomodule, cryogenics, HOM

158

G. Cheng, M.A. Drury, J.F. Fischer, R. Kazimi, K. Macha, H. Wang
JLab, Newport News, Virginia, USA

Funding: U.S. DOE Contract No. DE-AC05-06OR23177.
A new Injector Cryomodule (INJ CM) aimed to replace the existing Quarter Cryomodule in the CEBAF tunnel has been developed at Jefferson Lab (JLab). It is sched-uled to be first tested in the Cryomodule Test Facility (CMTF) for module performance then the Upgraded Injector Test Facility (UITF) with electron beam. This new cryomodule, hosting a 2-cell and 7-cell cavity, is designed to boost the electron energy from 200 keV to 5 MeV and permit 380 uA - 1.0 mA of beam current. The 2-cell cavity is a new design whereas the 7-cell cavity is refurbished from a low loss cavity from the retired JLab Renascence Cryomodule. The INJ CM adopts quite a few designs from the JLab 12 GeV Upgrade Cryomodule (C100). Examples of this include having the cold mass hung from a spaceframe structure by use of axial and transverse Nitronic rods, cavities to be tuned by scissor-jack style tuners and the end cans are actually modified from C100 style end cans. However, this new INJ CM is not a quarter of the C100 Cryomodule. This paper focuses on the major design features, fabrication and alignment process and testing of the module and its components.
Authored by Jefferson Science Associates, LLC. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for Government purposes.

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MOPB046

LCLS-II Cryomodule Production at JLab

cryomodule, cavity, vacuum, SRF

163

R.A. Legg, G. Cheng, E. Daly, G.K. Davis, M.A. Drury, J.F. Fischer, T. Hiatt, N.A. Huque, L.K. King, J.P. Preble, A.V. Reilly, M. Stirbet, K.M. Wilson
JLab, Newport News, Virginia, USA

Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515.
The LCLS-II cryomodule construction program leverages the mature XFEL cryomodule design to produce technologically sophisticated cryomodules with a minimum of R&D according to an accelerated manufacturing schedule. Jlab, as one of the partner labs, is producing 18 cryomodules for LCLS-II. To meet the quality and schedule demands of LCLS-II, many upgrades to the JLAB cryomodule assembly infrastructure and techniques have been made. JLab has installed a new cleanroom for string assembly and instituted new protocols to minimize particulate transfer into the cavities during the cryomodule construction process. JLab has also instituted a set of magnetic hygiene protocols to be used during the assembly process to minimize magnetic field impingement on the finished cavity structure. The goal has been to have gradients, both maximum and field emission onset, that do not degrade between the cavity vertical test and final cryomodule qualification, while maximizing the Q0 of each finished cavity. Results from the prototype cryomodule assembly are presented.

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MOPB049

Upgraded Cavities for the CEBAF Cryomodule Rework Program

cavity, HOM, cryomodule, GUI

168

R.A. Rimmer, G. Cheng, G. Ciovati, W.A. Clemens, E. Daly, G.K. Davis, J. Follkie, D. Forehand, F. Fors, J. Guo, J. Henry, K. Macha, F. Marhauser, G.R. Myneni, L. Turlington
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The CEBAF cryomodule rework program has been a successful tool to recover and maintain the energy reach of the original baseline 6 GeV accelerator. The weakest original modules with eight five-cell cavities assembled in four 'pairs', with a specification when new of 20 MV per cryomodule (5 MV/m), are disassembled, re-cleaned with modern techniques and re-qualified to at least 50 MV (12.5 MV/m), (leading to the acronym 'C50'). The cost per recovered MV is much less than building new modules. However over time the stock of weak modules is being used up and the voltage gain per rework cycle is diminishing. In an attempt to increase the gain per cycle it is proposed to rework the cavities by replacing the original accelerating cells with new ones of an improved shape and better material. The original CEBAF HOM and FPC end groups are retained. The goal is to achieve up to 75 MV (18.75 MV/m) for the reworked module ('C75'). We report on the fabrication experience and test results of the first trial pair, containing two such reworked cavities.

Poster MOPB049 [1.503 MB]

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MOPB050

Cavity Processing and Testing Activities at Jefferson Lab for LCLS-II Production

cavity, SRF, FEL, cryomodule

173

L. Zhao, G.K. Davis, J. Follkie, D. Forehand, K. Macha, A.D. Palczewski, A.V. Reilly
JLab, Newport News, Virginia, USA

Funding: Work supported by Jefferson Science Associates, LLC under U.S. DOE Contracts DE-AC05-06OR23177 and DE-AC02-76SF00515 for the LCLS-II Project.
Cryomodule production for LCLS-II is well underway at Jefferson Lab. This paper explains the process flow for production cavities, from being received at the Test Lab to being assembled onto cavity strings. Taking our facility and infrastructure into consideration, process optimization and process control are implemented to ensure high quality products.

Poster MOPB050 [2.338 MB]

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MOPB052

Dual-ridge Waveguide Load Design for eRHIC

GUI, HOM, cavity, simulation

177

P. Kolb, Y. Gao, C. Pai, R. Porqueddu, K.S. Smith, W. Xu
BNL, Upton, Long Island, New York, USA
Y. Gao
PKU, Beijing, People's Republic of China

Funding: Work supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
To increase the real estate gradient in the eRHIC electron accelerator waveguide HOM couplers are being considered. These significantly reduce the length of individual cavities and address inter-cavity trapped modes, allowing for an increased number of cavities per cryomodule, which would increase the real estate gradient. The choice of waveguide went to a dual ridge waveguide due to a smaller size compared to rectangular waveguides. The waveguide termination, to convert the RF energy into thermal energy, is a custom designed load based on a silicon carbide dielectric that is already being used in beamline absorbers. Simulations of the RF properties of the load are presented as well as first measurements on a prototype.

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MOPB053

RF Energy Harvesting of HOM Power

GUI, HOM, cavity, distributed

180

C. Xu, I. Ben-Zvi, Q. Wu, T. Xin
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA

In an accelerator cavity, Higher Order Modes (HOM) are generated by the current of the beam. The HOM power can reach tens of kilowatts in a high current accelerator, depending on the details of the beam and cavity design. In this report, we propose a novel RF harvesting system to recover the HOM power into DC power which can further used for various purposes such as driving a solid state or klystron RF amplifier to supply fundamental RF power at other frequencies, charge batteries etc. The efficiency would be a product of the energy recovery and regeneration efficiencies, where the state of art is 90%. The proposed HOM power recycling system contains a multiple band harmonic RF coupler, broadband RF antenna system, a high power rectifier diode circuit and a DC load.
1) Collider-Accelerator Department, Brookhaven National Lab, Upton, NY 11973, USA 2) Physics & Astronomy Department, Stony Brook University, Stony Brook, NY 11794, USA

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MOPB054

Design of Fundamental Power Coupler for High Intensity Heavy-ion Accelerator

electron, cavity, simulation, multipactoring

183

B. Bing, T.M. Huang, Q. Ma, F. Meng, W.M. Pan
IHEP, Beijing, People's Republic of China
K.X. Gu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

A single-window coaxial coupler at warm has been designed for high intensity heavy-ion accelerator. The coupler is designed to handle 100 kW CW power of 325 MHz and is currently being fabricated. T-bend transition and doorknob have been taken into account. The length of the T-bend short circuit is sensitive to S parameters and contributes to the online adjustment of VSWR in RF conditioning. The doorknob type is adopted to realize the transition from a half-height WR 2300 waveguide to a coaxial line ended with a coupling antenna. This paper describes the RF design, thermal stress and heat load analysis of the coupler as well as multipacting simula-tions.

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MOPB061

Quality Control of Copper Plating in STF-2 Input Power Couplers

cavity, vacuum, cryomodule, controls

186

E. Kako, R. Ueki
KEK, Ibaraki, Japan
K. Hiroaki, J. Taguchi
Nomura Plating Co, Ltd., Osaka, Japan
K. Okihira, K. Sennyu
MHI, Hiroshima, Japan
F. Saito, H. Umezawa
Tokyo Denkai Co., Ltd., Tokyo, Japan
O. Yushiro
Toshiba Electron Tubes & Devices Co., Ltd, Tokyo, Japan

Purity of thin copper plating using in input power couplers for superconducting cavities is one of important characteristics for considering thermal losses at low temperature. Various samples of thin copper plating on stainless sheets was fabricated by three companies with their own plating techniques. The RRR values of the samples with different thickness of copper plating were compared in the condition before and after heat treatment at 800oC in a brazing furnace. Deterioration of the RRR was observed in all of samples after heat treatment. The results of the RRR measurements and sample analysis of impurities will be reported in this paper.

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MOPB062

Development of HOM Absorbers for CW Superconducting Cavities in Energy Recovery Linac

HOM, cavity, superconducting-cavity, linac

191

T. Ota, A. Miyamoto, K. Sato, M. Takasaki, M. Yamada
Toshiba, Yokohama, Japan
E. Kako, T. Konomi, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

Higher Order Modes (HOM) absorbers for superconducting cavities have been developing at TOSHIBA in collaboration with High Energy Accelerator Research Organization (KEK) since 2015. Prototype HOM absorbers for 1.3 GHz 9-cell superconducting cavity were fabricated. An AlN lossy dielectrics cylinder was brazed with a copper cylinder, and the cool-down tests by nitrogen gas was carried out. Copper cylinders and SUS flanges were joined by electron beam welding to fabricate a whole prototype HOM absorber. Fabrication process of the prototype HOM absorber will be presented in this paper.

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MOPB063

Fundamental Studies for the STF-type Power Coupler for ILC

vacuum, FEL, cavity, SRF

194

Y. Yamamoto, E. Kako, T. Matsumoto, S. Michizono, A. Yamamoto
KEK, Ibaraki, Japan
M. Irikura, M. Ishibashi, H. Yasutake
Toshiba Electron Tubes & Devices Co., Ltd (TETD), Tochigi, Japan

From the view point of mass-production for the power coupler in ILC, the fundamental studies for the STF-type power coupler are under progress by the collaboration between KEK and TETD. At present, there are various rinsing procedures for power coupler in the world-wide laboratories. In this R&D, the main topic is to investigate the various rinsing effects in the copper plating and the ceramic through the high power test. In this paper, the first results will be presented.

Poster MOPB063 [2.237 MB]

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MOPB064

High Power Test for Plug-compatible STF-type Power Coupler for ILC

electron, vacuum, simulation, GUI

199

Y. Yamamoto, E. Kako, T. Matsumoto, S. Michizono, A. Yamamoto
KEK, Ibaraki, Japan
C. Julie, E. Montesinos
CERN, Geneva, Switzerland

From the view point of plug-compatibility for the power coupler in the ILC, recommended by Linear Collider Collaboration in 2013, new STF-type power couplers with 40mm of input port diameter were re-designed, fabricated and successfully high-power-tested. Moreover, from the view point of the cost reduction for the ILC, another type of power couplers with TiN coating-free ceramic were also fabricated and high-power-tested by the collaboration between CERN and KEK. In this paper, the detailed results for the both power couplers will be presented.

Poster MOPB064 [6.671 MB]

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MOPB065

Development of Hybrid Superconducting Photocathodes on Niobium Using High QE Coatings

cathode, electron, site, SRF

205

M. Warren, A.R. Denchfield, N. Samuelson, J. Zasadzinski
IIT, Chicago, Illinois, USA
W. Gai, J.H. Shao, E.E. Wisniewski
ANL, Argonne, Illinois, USA
L.K. Spentzouris, Z.M. Yusof
Illinois Institute of Technology, Chicago, Illinois, USA

High power, low emittance electron beams require superconducting RF photoinjectors, typically made of pure Nb, and a superconducting photocathode is desired. However, superconductivity and high photocathode quantum efficiency (QE) are not compatible, e.g. QE for pure Nb is only 10^-5 at 260 nm wavelength. Here is presented the current status of the development of hybrid superconducting photocathodes by the deposition of thin films of a high QE metal or semiconductor on Nb. Nb plugs coated with 10-100 nm of Mg have been tested for adhesion and dark current under RF fields as high as 60MV/m. QE measurements show significant enhancements over Nb. In another test, ultra thin films of the high QE material Cs2Te deposited on Nb are reported. Using the standard deposition procedure, QE ~12% is found for films ~ 200Å. As the thickness is reduced QE maintains a high value ~ 6% for films as thin as 2.0 nm. These results are quite promising for future superconducting photocathodes.

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MOPB066

Development of 81.25 MHz 20 kW SSPA for RAON Accelerator

impedance, rfq, cavity, power-supply

210

C.O. Choi, H. Jang, H.C. Jung, D.Y. Lee, K.T. Son
IBS, Daejeon, Republic of Korea

A heavy ion accelerator, RAON is under development in Daejeon, Korea by Rare Isotope Science Project (RISP). In this accelerator, 81.25 MHz Radio Frequency Quadrupole (RFQ) will be used for the acceleration of various ions from several tens of keV/u to about half MeV/u. For this system two 80 kW RF power sources are planned and RISP will develop them with a solid state power amplifier (SSPA) architecture. As a first step, a 20 kW SSPA was developed and its performance was tested. In this presentation the current status of developed SSPA and its test results will be presented

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MOPB068

Development of 4-way 81.25 MHz 20 kW High Power Combiner Using Parallel Plate Structure

simulation, cavity, rfq, impedance

213

K.T. Son, C.O. Choi, H. Jang, H.C. Jung, D.Y. Lee
IBS, Daejeon, Republic of Korea

The recent development of semiconductor technology has proved that solid-state RF amplifier is a quite effective alternative high power RF source for numerous accelerator applications. To develop a high power SSPA system, high power combiner is required to combine the RF power from a lot of solid-state RF module. The parallel plate RF power combiner, which is designed to combine various high power modules, is developed for RAON(Rare the rare isotope accelerator complex for on-line experiment). In this presentation, the status of developed 81.25 MHz 20 kW power combiner will be described.

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MOPB069

Design of the High Power Input Coupler for CEPC Main Ring Cavity *

cavity, coupling, vacuum, cryogenics

216

T.M. Huang, Q. Ma, J.Y. Zhai
IHEP, Beijing, People's Republic of China
K.X. Gu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

The main ring cavities of CEPC project are two-cell el-liptical superconducting cavities operating at 650 MHz in CW mode. Each cavity equips with one high power input coupler and each coupler has to deliver at least 300 kW of CW RF power to the beam. A variable coupling from 10⁵ to 2·10⁶ is required to meet different operation modes. Considering the cavities working with high quali-ty factor up to 2·10¹⁰, the coupler assembled with cavity in class 10 clean room is strongly recommended to protect the cavity from contamination. Also, low cryogenic heat loss is one of the important issues for a large scale CW operation machine. Some of the above requirements should be compromise. Therefore, it's a big challenge to design a high power input coupler fulfilling the above requirements simultaneously. A new coupler that employs 75 Ω coaxial line sections, a planar ceramic disk win-dow, a coaxial to waveguide transition and a coupling adjusting actuator has been designed. In this paper, the RF design, thermal stress analysis and preliminary me-chanical design of the coupler are presented.

Poster MOPB069 [0.735 MB]

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MOPB070

The Improvement of the Power Coupler for CADS SC Spoke Cavities

cavity, electron, experiment, cryomodule

220

T.M. Huang, B. Bing, X. Chen, H.Y. Lin, Q. Ma, F. Meng, W.M. Pan, G.W. Wang
IHEP, Beijing, People's Republic of China
K.X. Gu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

Twenty superconducting spoke cavities mounted in three cryomodules (CM1, CM2 and CM4) were in-stalled in the CADS, a test facility of 10 mA, 25 MeV CW proton linac. Each cavity was equipped with one coaxial type fundamental power coupler (FPC). Fatal window crack was observed during the test cryomod-ule (TCM) commissioning. A series of experiments were subsequently implemented and eventually at-tributed the window crack to the electron bombard-ment from cavity field emission (FE). Improvements covering the coupler cleaning and assembly proce-dure, the structure and position modifications were thus implemented, aiming to reduce the cavity contam-ination and avoid the window damaged by cavity FE electrons. This paper will describe how the coupler window damaged by cavity field emission and the improve-ments for cure. In addition, the performances of FPCs for CM1, CM2 and CM4 were compared.

Poster MOPB070 [0.613 MB]

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MOPB071

The Recent Research of HOM Damper for Superconducting Cavity in IHEP

HOM, cavity, simulation, site

223

F. Meng, T.M. Huang, H.Y. Lin, Q. Ma, W.M. Pan, J.Y. Zhai, P. Zhang, H.J. Zheng
IHEP, Beijing, People's Republic of China

Funding: This study was supported by National Key Programme for S&T Research and Development (Grant NO.: 2016YFA0400400)
For high current accelerator, the efficient higher-order mode (HOM) damping is always an important issue. HOM damper with microwave absorbing material is a key component for high power and broadband HOM damping application. To pursue the high damping efficiency, some ideal material with good microwave absorbing capacity is essential during the RF design and fabrication phase. Sometimes the selection and test of material is the first step and also a long step. This paper will present the recent work on HOM dampers for BEPCII 500MHz cavity and CEPC 650MHz cavity in IHEP.

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MOPB072

The Development of the LLRF Control System for the New High Power Test Stand of Couplers

vacuum, controls, LLRF, FPGA

227

L. Chen, W. Chang, T.C. Jiang, C.L. Li, Y.M. Li, R.X. Wang, S.H. Zhang
IMP/CAS, Lanzhou, People's Republic of China

RF power conditioning is an effective way to suppress multipacting in fundamental mode power couplers. Room temperature test-stand conditioning is an essential step that can be hardly circumvented before couplers are installed on SC cavities. Based on our original one, a new test-stand has been designed and being assembled at IMP. It can work as a multi-task platform conditioning different couplers, including couplers for HWR010 cavities and HWR015 cavities. It is also featured with the capacity to flexibly change β according to different specifications. A variety of conditioning modes have been incorporated into the LLRF system, including frequency sweeping mode, amplitude sweeping mode, arbitrary-duty-cycle mode and triangle-wave mode. In addition, smartly-conditioning has been achieved because of the accomplishment of smart interlocks and automatic reset in the system.

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MOPB074

Analysis of Higher Order Modes of the Superconducting Cavities for the China-ADS Injector-II in IMP

dipole, HOM, cavity, higher-order-mode

231

C. Zhang, L. Chen, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, Y.M. Li, F. Pan, R.X. Wang, A.D. Wu, Q.J. Wu, W.M. Yue, S.H. Zhang, S.X. Zhang
IMP/CAS, Lanzhou, People's Republic of China

Funding: funded by Natural Science Foundation of China， No.11505253
The influence of the higher order modes on the beam dynamics and the cryogenic losses has been studied for the superconducting section of the CIADS project in this paper. In addition, the necessity of HOM dampers in the Superconducting (SC) cavities is discussed.

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MOPB075

Quench Protection in Digital Power Supplies for Superconducting Magnets in ADS

controls, power-supply, superconducting-magnet, solenoid

233

J. Zhao, S. Zhang, Z.Z. Zhou
IMP/CAS, Lanzhou, People's Republic of China

The front-end demo superconducting Linac for Chinese ADS (Accelerator Driven Sub-critical System) project is under construction at institute of modern physics(IMP) in Lanzhou. It will demonstrate the key technologies and the feasibility of a high power beam for the future national project " the Chinese Initiative Accelerator Driven Subcritical System(CIADS)". In this system, there are about 60 superconducting magnets, including solenoids, vertical correction and horizontal correction. They are utilized to focus and correct the proton beam. Quench protection of the superconducting magnets is key to reliability of the facility. A full digital power supply is developed and employed as excitation source for all of these superconducting magnets. In this paper, an FPGA-based quench protection plan implemented in the power supplies is mainly described. The commissioning results show that it is feasible.

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MOPB076

Analysis of the Production, Installation and Commissioning of the European-XFEL Frequency Tuners

cavity, FEL, cryomodule, controls

235

R. Paparella, A. Bosotti, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Albrecht, S. Barbanotti, A. Bellandi, J. Branlard, K. Jensch, L. Lilje
DESY, Hamburg, Germany
C. Cloué, T. Trublet
CEA/IRFU, Gif-sur-Yvette, France
C. Madec
CEA, Gif-sur-Yvette, France

In the European-XFEL superconducting linac, mechanical frequency tuners equipped with stepper motors and piezoelectric actuators provide cold tuning of each of the 768 1.3 GHz cavities. More than 820 complete tuning systems were fabricated and pre-assembled in industry, tested at several stages before and after assembly and successfully commissioned during cryo-module cold tests at AMTF (DESY). Quality control strategy adopted to preserve the well-assessed tuner reliability through such a large-scale industrial production is critically reviewed and the lessons learned are presented in this paper. The statistical analysis of the large set of data acquired up to the recent commissioning of the entire linac is then summarized.

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MOPB077

Operational Experience of the European-XFEL 3.9 GHz Coaxial Tuners

cavity, FEL, operation, MMI

240

R. Paparella, A. Bellandi, A. Bignami, A. Bosotti, D. Sertore
INFN/LASA, Segrate (MI), Italy
C.G. Maiano
ESS, Lund, Sweden
P. Pierini
DESY, Hamburg, Germany

The European-XFEL injector hosts a third-harmonic section composed by a module with eigth 3.9 GHz cavities equipped with a coaxial frequency tuner inspired by INFN-LASA Blade Tuner design. The 3.9 GHz tuning system met specifications during all the injector runs in 2016 up to the recent commissioning of the entire linac; it matched the required tuning range and frequency sensitivity although higher than expected cavity detuning was experienced during pressure transients in the cryogenic system. An analysis of all collected experimental data is reported in this paper together with the strategy developed to provide a sound and effective retuning routine to the control room operator.

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MOPB078

Power Coupler Design for the LUCRECE Project

simulation, radiation, coupling, cavity

245

H. Guler, D. Auguste, J. Bonis, O. Bouras, M. El Khaldi, W. Kaabi
LAL, Orsay, France

The LUCRECE project aims at developing an elementary RF system (cavity, power source, LLRF and controls) suitable for continuous (CW) operation at 1.3 GHz. This effort is made in the framework of the advanced and compact FEL project LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation), using superconducting linac technology for high repetition rate and multi-user operation (http://www.lunex5.com). In this context, based on its large experience on coupler design and RF conditioning, LAL Laboratory is in charge of the design and the fabrication of RF couplers that could operate at up to 15-20 kW in CW mode. For this purpose, couplers based on CORNELL 65kW CW couplers (RF power couplers for the Cornell ERL injector) are under consideration and will be adapted to the LUCRECE needs. Electromagnetic simulations and associated thermal heating will be discussed. Methods to decrease the thermal impact will be considered.

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MOPB079

HOM Coupler Alterations for the LHC DQW Crab Cavity

cavity, HOM, impedance, simulation

249

J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
G. Burt, N.C. Shipman
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Calaga
CERN, Geneva, Switzerland
S. Verdú-Andrés, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA

As part of the High Luminosity Large Hadron Collider (HL-LHC) project, 16 crab cavities are to be installed in the LHC in 2025. The two crab cavity designs are the Double Quarter Wave (DQW) and Radio Frequency Dipole (RFD). Preliminary beam tests in the Super Proton Synchrotron (SPS) are planned for both cavity types, with the DQW scheduled for testing in 2018. In reference to to Higher Order Mode (HOM) damping, the DQW has three identical on-cell HOM couplers. These HOM couplers provide a band-stop response at the frequency of the fundamental mode and act as a transmission path for the cavity HOMs. For the SPS cavity design, several geometric constraints exist. These give rise to dimensional limitations which in-turn impose limitations on the RF performance of the HOM couplers. As such, for the LHC assembly, the HOM coupler design is re-visited to take into account the relaxed geometric limitations, hence allowing the feasibility of an increased RF performance to be investigated. In addition to the RF performance, several geometric alterations were incorporated to ease manufacturing processes, tolerances and costs.

Poster MOPB079 [2.038 MB]

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MOPB080

The Stable Operation of MPG and Measurement of Output

electron, experiment, cavity, cathode

254

B.T. Li, X.Y. Lu, L. Xiao, D.Y. Yang, Y. Yang, Z.Q. Yang, J. Zhao
PKU, Beijing, People's Republic of China

The concept of micro-pulse electron gun(MPG) was proposed decades ago. It can provide electron beam with high current, short pulse and low emittance. But it is still not put into practical use as electron source because of its unsteady operating state. This paper presents an experimental result of the steady running of MPG which can operate stably for more than ten hours. The energy spread of the electron beam is also measured, the peak is located at near 20eV and half width is less than 15eV .

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MOPB082

A Preliminary Scheme for X-ray Emission Based on Micro-pulse Electron Gun

electron, target, radiation, simulation

259

Y. Yang, B.T. Li, X.Y. Lu, W.W. Tan, L. Xiao, D.Y. Yang, Z.Q. Yang, J. Zhao
PKU, Beijing, People's Republic of China

X-ray is now widely used in many areas of physics, biology, chemistry and materials. And how to achieve emission, monochrome, and focusing of x-ray is of great significance to study. Micro-pulse electron gun (MPG) is a new type of electron source, with characteristics of high repetition frequency, short-pulse and low cost. Generating x-ray with better monochromaticity is one of the potential applications of MPG. And a preliminary scheme of X-ray based on MPG is proposed in this paper. The scheme is designed by comparing different anode materials and the thickness of filters. The simulation results based on the software MCNP5 show that the proposed scheme can effectively improve the monotonicity of the generated X-rays.

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MOPB086

First Results of the IFMIF/EVEDA-SaTHoRI Tests

cavity, SRF, controls, cryomodule

262

O. Piquet, N. Bazin, P. Carbonnier, J.K. Chambrillon, M. Desmons, G. Devanz, H. Jenhani, C. Servouin
CEA/DRF/IRFU, Gif-sur-Yvette, France
P. Cara
Fusion for Energy, Garching, Germany
J.F. Denis, L. Maurice, J. Relland
CEA/IRFU, Gif-sur-Yvette, France
F. Éozénou, P. Hardy, E. Jacques, Y. Lussignol, P. Sahuquet
CEA/DSM/IRFU, France
D. Gex, A. Jokinen, G. Phillips
F4E, Germany
I. Moya, P. Méndez
CIEMAT, Madrid, Spain

The SaTHoRI test stand (Satellite de Tests Horizontal des Résonateurs IFMIF) aims to characterize a jacketed and fully dressed cavity with its coupler and tuner. A dedicated test cryostat has been manufactured and is connected to an existing horizontal test cryostat which provides the cryogenic coolant. A RF source ' provided by the IFMIF collaboration, one of the four RF sources which will be used for the cryomodule at Rokkasho ' has been installed and commissioned at CEA. This paper describes the test stand and presents the first results.

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MOPB087

Frequency Tuner Development and Testing at Cornell for the RAON Half-wave-resonator

cavity, cryogenics, SRF, cryomodule

266

M. Ge, F. Furuta, J.E. Gillette, T. Gruber, S.W. Hartman, M. Liepe, 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 (HWRs) for the RAON project require a slow frequency tuner that can provide >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 optimized tuner design, prototype fabrication, test insert preparation, and cryogenic test results. The performance of the tuner is analysed in detail.

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MOPB088

Experience on In-situ Module Repair and Set Up of Non XFEL Cavity Strings at DESY

cavity, FEL, HOM, pick-up

269

M. Schmökel, A. Daniel, N. Krupka, A. Matheisen, S. Saegebarth, M. Schalwat, P. Schilling
DESY, Hamburg, Germany

All components installed to the European XFEL cavity string modules underwent an intensive inspection and quality control before acceptance for installation to cavities or modules. Even though some RF feed throughs for HOM coupler- and Pick Up antennas showed leaks at the ceramic insulation after module test at 2 K. Due to time restriction and continuity of production the exchange of these parts needed to be done without reentering the cleanroom. Successful repair of these modules took place by setting up a local cleanroom onto the cavity string. In collaboration with Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a cavity string for the ELBE project was assembled at DESY and transported to HZDR for installation to the vacuum vessel. A spare module with 3.9 GHz Resonators for the European XFEL was set up at DESY and will be tested and qualified for the European XFEL. Due to delay in delivery of the power couplers, four power couplers were installed after string assembly.

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MOPB089

Characterisation of Magnetic Shielding Material for HL-LHC Crab Cavities

cavity, cryogenics, shielding, ECR

273

K. Eiler, P. Arpaia, M.C.L. Buzio, O. Capatina, S.A.E. Langeslag, A. Parrella
CERN, Geneva, Switzerland
P. Arpaia, A. Parrella
Naples University Federico II, Science and Technology Pole, Napoli, Italy
A. Parrella
IT, Lisboa, Portugal
N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

Funding: CERN, 1211 Geneva 23
To guarantee optimum performance, the crab cavities for the high-luminosity upgrade of CERN's LHC need to be shielded from external magnetic fields. Consequently, they will be enclosed by two layers of magnetic shielding, of which the inner is immersed in superfluid helium at 2 K. A Ni-based high-permeability material with a tailored composition and a designated heat treatment is applied. Its magnetic properties at cryogenic temperature are however not yet fully assessed. Especially the effect of deformation on magnetic properties has not been thoroughly investigated, however strain effects may have severe consequences. A magnetic measurement set-up has been developed, and the magnetic permeability at room temperature and at cryogenic temperatures is evaluated, showing that the maximum relative permeability at 4 K exceeds the design criteria of 100, 000. Measurements of the magnetic permeability after introduction of uniaxial plastic deformation between 0% and 3% are conducted by means of an Epstein frame. Results show that deformation induces significant decrease of the magnetic performance, underlining that particular care must be taken during all stages of handling and operation.
*konrad.eiler@cern.ch

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MOPB090

Sub-micro-Tesla Magnetic Shielding Design for Cryomodules in the High-gradient Program at CERN

shielding, cavity, cryomodule, simulation

278

S. Papadopoulos, L. Dassa, F. Gerigk, F. Pillon, S. Ramberger, P. Yilmazer
CERN, Geneva, Switzerland
J. Dequaire
Intitek, Lyon, France

In the framework of the High-Gradient R\&D program at CERN a cryomodule, consisting of four superconducting 5-cell cavities, has been designed. In order to reduce flux trapping in the surface of the superconductor and to minimize Q degradation during a quench, highly effective magnetic shielding is needed. The solution proposed includes cold and warm passive shielding enhanced by four compensating coils. In this paper the magneto-static simulation results are presented illustrating different design considerations that led to a final design. Finally the shielding ability of the vacuum vessel is investigated experimentally through ambient magnetic field measurements.

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MOPB094

Commissioning of Demonstrator Module for CW Heavy Ion LINAC@GSI

cavity, linac, solenoid, heavy-ion

283

V. Gettmann, K. Aulenbacher, W.A. Barth, F.D. Dziuba, T. Kürzeder, M. Miski-Oglu
HIM, Mainz, Germany
K. Aulenbacher
IKP, Mainz, Germany
W.A. Barth, M. Heilmann, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia
M. Basten, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany

The cw - Linac - demonstrator is a prototype of the first section of the proposed cw-LINAC@GSI, comprising a superconducting CH-cavity embedded by two superconducting solenoids. The sc CH-structure is the key component and offers a variety of research and development. The beam focusing solenoids provide maximum fields of 9.3 T at an overall length of 380 mm and a free beam aperture of 30 mm. The magnetic induction at the fringe is minimized to 50 mT at the inner NbTi-surface of the neighboring cavity. The fabrication of the key components is finished, as well as the cold performance testing of the RF cavity. The cryostat is ready for assembling and the test environment is completely prepared. After successful testing of the RF-Power coupler, the components will be assembled to the suspended frame under cleanroom conditions. Alignment, assembly, under cleanroom condition issues will be presented.

Poster MOPB094 [2.881 MB]

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MOPB096

Estimation of Alignment Error by Measuring Higher-order-mode of Injector Superconducting Cavity at KEK-cERL

cavity, HOM, dipole, alignment

286

Y. Honda, E. Kako, T. Konomi, T. Miyajima, T. Obina, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

Precise alignment of accelerator cavities is important in realizing a low emittance beam. Especially in the cases of superconducting cavities installed in a cryomodule, it is difficult to mechanically measure the position of the cavities. By measuring higher-order-modes (HOM) excited by a beam, the electrical center of the cavities can be estimated. We have developed a HOM measurement system for the injector superconducting accelerator cavities of KEK ERL test accelerator (cERL).Comparing the HOM signals of the three independent cavities in the cryomodule, we estimated the relative positioning errors of the three cavities.

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MOPB097

Degradation and Recovery of Cavity Performances in Compact-ERL Injector Cryomodule

cavity, operation, radiation, cryomodule

289

E. Kako, T. Konomi, T. Miura, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

Injector cryomodule for cERL consists of three 2-cell cavities equipped with double-feeds input couplers, five antenna-type HOM couplers and a slide-jack tuner with two piezo actuators. After cryomodule assembly and first cool-down tests in 2012, the cERL injector cryomodule has been stably operated with beam for four years. Gradual increases of x-ray radiation levels due to field emission were observed during long term beam operation. High power pulsed RF conditioning as a cure method was applied in the cool-down period in 2016 and 2017, so that degraded cavity performances have almost recovered up to the original levels. Performance recovery status in three 2-cell cavities will be reported in this paper.

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MOPB099

Design of C-ADS Injector-I Cryomodule for 325MHz Cavities

cryomodule, cavity, linac, solenoid

294

R. Ge, L. Bian, R. Han, S.P. Li, M.J. Sang, L.R. Sun, M.F. Xu, R. Ye, J.Q. Zhang, J.H. Zhang, X.Z. Zhang
IHEP, Beijing, People's Republic of China

Funding: Supported by Strategic Priority Research Program of CAS (XDA030213)
The Chinese Accelerator Driven Sub-critical system (C-ADS) uses a high energy proton beam to bombard the metal target and generate neutrons to deal with the nuclear waste. The Chinese ADS proton linear has two 0~10 MeV injectors and one 10~1500 MeV superconducting linac. Injector-I is studied by the Institute of High Energy Physics (IHEP) under construction in the Beijing, China. The linear accelerator consists of two accelerating cryomodules operating at the temperature of 2 Kelvin. This paper describes the structure and thermal performances analysis of the cryomodule. The analysis takes into account all the main contributors (support posts, multilayer insulation, current leads, power couplers, and cavities) to the static and dynamic heat load at various cryogenic temperature levels. The thermal simulation analysis of the cryomodule is important theory foundation of optimization and commissioning.

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MOPB101

Cryomodule Fabrication and Modification for High Current Operation at the Mainz Energy Recovering Superconducting Accelerator MESA

cavity, cryomodule, operation, experiment

297

T. Stengler, K. Aulenbacher, F. Hug, D. Simon
IKP, Mainz, Germany
K. Aulenbacher, T. Kürzeder
HIM, Mainz, Germany

Funding: This work is supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA" EXC 1098/2014}
At Johannes Gutenberg-Universität Mainz, the Institute for Nuclear Physics is currently building the multiturn ERL 'Mainz Energy-Recovering Superconducting Accelerator' MESA. The §I{1.3}{\giga\hertz} cryomodules are based on the ELBE modules at Helmholtz Center Dresden-Rossendorf (HZDR) but are modified to suit the high current, energy recovering purposes of MESA. With two 9-cell TESLA cavities each, they shall provide §I{50}{\mega\electronvolt} energy gain per turn. The design and fabrication was done by Research Instruments GmbH, Bergisch Gladbach, Germany. The current status of the cryomodules, the test set up at the Helmholtz-Institute Mainz, the cavity properties and their tests will be discussed.

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MOPB102

Preliminary Design on the Cryomodule of the HWR for the Secondary Particle Generation at KOMAC

cryomodule, proton, linac, cavity

301

H.-J. Kwon, Y.-S. Cho, J.J. Dang, H.S. Kim, K.H. Kim, S. Lee, Y.G. Song
Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea

Funding: This work has been supported through KOMAC (Korea of Multi-purpose Accelerator Complex) operation fund of KAERI by MSIP (Ministry of Science, ICT and Future Planning).
A 100 MeV proton linac based on the radio frequency quadrupole and conventional drift tube linac has been operating for user service at KOMAC (Korea Multi-purpose Accelerator Complex). A superconducting linac based on the half-wave resonator is studied in order to increase the proton energy from 100 MeV to 160 MeV for secondary particle generation such as neutron. A cryomodule and its cryogenics were designed. The operating temperature of the HWR is 2 K. One cryomodule contains four HWR cavities and it didn't have superconducting solenoid because a doublet lattice using normal conducting magnet was considered as focusing elements. A thermal design was conducted and the structure was designed based on the existing well proven technologies. The results of the design on the cryomodule and cryogenics for KOMAC HWR are summarized and discussed in the conference.

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MOPB104

Development of a Novel Supporting System for High Luminosity LHC SRF Crab Cavities

cavity, cryomodule, SRF, interface

304

T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
K. Artoos, R. Calaga, O. Capatina, T. Capelli, M. Sosin, J.S. Swieszek, C. Zanoni
CERN, Geneva, Switzerland
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
T.J. Jones
Lancaster University, Lancaster, United Kingdom

Compact SRF Crab Cavities are integral to the HL-LHC upgrade. This paper details the design of support structures within the SPS (Super Proton Synchrotron) Crab Cavity Cryomodule. For ease of alignment each cavity is supported with the mechanical tuner and RF Fundamental Power Coupler (FPC) via a common support plate. To reduce heat leak and remove bellows in the FPC it was determined that this would be the fixed support for the cavity (V. Parma, 2013). In addition, novel flexural blades were designed to give increased stiffness yet allow for thermal contraction of the cavity towards the fixed point of the FPC. This approach was superior when compared via simulation to several alternative techniques. A detailed simulation model was used for optimisation of directional stiffness, identification of vibration modes and minimising thermal stresses. A transmission matrix was developed in MS Excel to assess modal deflection for given ground vibration conditions. The spreadsheet gives an instantaneous yet comparable result to time consuming random vibration FE Analyses. The final engineering design of the supporting system is now complete and will also be described in this paper.
References
V. Parma, R. B. (2013). Status of the Superconducting Proton Linac (SPL) Cryomodule. SRF2013.

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MOPB105

Thermosiphon Cooling Loops for ARIEL Cryomodules

cryomodule, cavity, TRIUMF, linac

309

Y. Ma, A.N. Koveshnikov, D. Lang, R.E. Laxdal, N. Muller
TRIUMF, Vancouver, Canada

Thermosiphon cooling loops have been used in ARIEL[1,2] cryomodules for 1.3GHz superconducting cavities cooling. It can deliver 4K liquid Helium from 4K phase separator to cavity thermal intercepts and return the vaporized liquid to the 4K phase separator as a refrigerator load. The design and test results are presented in this paper.

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MOPB106

Test Results of the European XFEL Serial-production Accelerator Modules

cavity, cryomodule, FEL, operation

312

K. Kasprzak, M. Wiencek, A. Zwozniak
IFJ-PAN, Kraków, Poland
D. Kostin, D. Reschke, N. Walker
DESY, Hamburg, Germany

The serial-production tests of 100 cryomodules for the European XFEL have been finished. In this paper the statistics of the cold RF measurements in the AMTF (Accelerator Module Test Facility) are reported for all the modules. In addition comparison between the cavity vertical test results and module test results are presented.

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MOPB109

LCLS-II Cryomodule Transport System Testing

cavity, vacuum, cryomodule, ISOL

317

N.A. Huque, E. Daly
JLab, Newport News, Virginia, USA
M.W. McGee
Fermilab, Batavia, Illinois, USA

The Cryomodules (CM) for the Linear Coherent Light Source II (LCLS-II) will be shipped to SLAC (Menlo Park, California) from JLab (Newport News, Virginia) and FNAL (Batavia, Illinois). A transportation system has been designed and built to safely transport the CMs over the road. It uses an array of helical isolator springs to attenuate shocks on the CM to below 1.5g in all directions. The system rides on trailers equipped with Air-Ride suspension, which attenuates vibration loads. The prototype LCLS-II CM (pCM) was driven 750 miles to test the transport system; shock loggers recorded the shock attenuation on the pCM and vacuum gauges were used to detect any compromises in beamline vacuum. Alignment measurements were taken before and after the trip to check whether cavity positions had shifted beyond the ± 0.2mm spec. Passband frequencies and cavity gradients were measured at 2K at the Cryomodule Test Facility (CMTF) at JLab to identify any degradation of CM performance after transportation. The transport system was found to have safely carried the CM and is cleared to begin shipments from JLab and FNAL to SLAC.

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MOPB110

Results of Accelerated Life Testing of LCLS-II Cavity Tuner Motor

cavity, cryomodule, operation, SRF

323

N.A. Huque, E. Daly
JLab, Newport News, Virginia, USA
Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA

An Accelerated Life Test (ALT) of the Phytron stepper motor used in the LCLS-II cavity tuner has been conducted at JLab. Since the motor will reside inside the cryomodule, any failure would lead to a very costly and arduous repair. As such, the motor was tested for the equivalent of 30 lifetimes before being approved for use in the production cryomodules. The 9-cell LCLS-II cavity is simulated by disc springs with an equivalent spring constant. Plots of the motor position vs. tuner position ' measured via an installed linear variable differential transformer (LVDT) ' are used to measure motor motion. The titanium spindle was inspected for loss of lubrication. The motor passed the ALT, and is set to be installed in the LCLS-II cryomodules.

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MOPB111

European XFEL Linac RF System Conditioning and Operating Test

cavity, FEL, vacuum, MMI

328

D. Kostin, J. Branlard, A. Gössel, O. Hensler, M. Omet, D. Reschke, A.A. Sulimov, N. Walker, M. Wiencek
DESY, Hamburg, Germany

96 accelerating modules with 768 TESLA/European-XFEL type superconducting cavities were installed in the European XFEL LINAC tunnel (XTL) in the fall 2016. Warm conditioning of the RF system - High/Low Level RF System and main input couplers - begun even before finishing the accelerator installation works. All modules were conditioned and tested prior to the installation in the tunnel in the AMTF test stand at DESY. Nevertheless, due to some repair activities on warm input coupler parts, warm conditioning was needed on a few modules/couplers. Cooling down to 2K begun in December 2016 and was finished in January 2017. Since then cold conditioning and tests are running. Several cavities in a few modules did show the multipacting (MP) effects, mostly because a cavity vacuum was filled with a dry nitrogen for before mentioned repairs on couplers in some modules. Said MP effects were seen in AMTF as well. All MP effects were successfully conditioned until now. The warm/cold RF system conditioning and its results/experiences/limits are described and discussed.

Poster MOPB111 [1.267 MB]

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TUXAA01

CEPC SRF System Design and Challenges

cavity, SRF, HOM, cryomodule

332

J.Y. Zhai, Y.L. Chi, J. Dai, J. Gao, R. Ge, D.J. Gong, R. Han, T.M. Huang, S. Jin, Z.Q. Li, B. Liu, Z.C. Liu, Q. Ma, F. Meng, Z.H. Mi, G. Pei, Q. Qin, P. Sha, Q.Y. Wang, T.X. Zhao, H.J. Zheng
IHEP, Beijing, People's Republic of China
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

Funding: Work supported by National Key Programme for S&T Research and Development of China (Grant NO.: 2016YFA0400400)
CEPC is a 100 km circular electron positron collider operating at 90-240 GeV center-of-mass energy of Z, W and Higgs bosons. CEPC and its successor SPPC, a 100 TeV center-of-mass super proton-proton collider, will ensure the elementary particle physics a vibrant field for decades to come. The conceptual design report (CDR) of CEPC will be completed in the end of 2017 as an important step to move the project forward. In this contribution, CEPC SRF system CDR design and challenges will be introduced, including the system layout and parameter choices, configuration at different operation energies, transient beam loading and its compensation, cavity fundamental mode (FM) and higher order mode (HOM) induced coupled bunch instabilities (CBI) and the beam feedback requirement, etc. The SRF technology R&D plan and progress as well as the SRF infrastructure and industrialization plan are discussed at last.

Slides TUXAA01 [9.124 MB]

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TUXAA02

HIE Isolde Cavity Production & Cryomodule Commissioning, Lessons Learned

cavity, ISOL, cryomodule, linac

338

W. Venturini Delsolaro, K. Artoos, O. Brunner, O. Capatina, K.M. Dr. Schirm, Y. Kadi, Y. Leclercq, A. Miyazaki, E. Montesinos, V. Parma, G.J. Rosaz, A. Sublet, S. Teixeira Lopez, M. Therasse, L.R. Williams
CERN, Geneva, Switzerland

The lessons learned during the HIE Isolde Cavity Production, the Cryo Module Assembly and Commissioning will be presented

Slides TUXAA02 [8.191 MB]

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TUXAA03

Progress of FRIB SRF Production

cavity, cryomodule, SRF, linac

345

T. Xu, H. Ao, B. Bird, N.K. Bultman, F. Casagrande, C. Compton, K.D. Davidson, K. Elliott, A. Facco, V. Ganni, A. Ganshyn, W. Hartung, M. Ikegami, P. Knudsen, S.M. Lidia, E.S. Metzgar, S.J. Miller, D.G. Morris, P.N. Ostroumov, J.T. Popielarski, L. Popielarski, M.A. Reaume, K. Saito, S. Shanab, M. Shuptar, S. Stark, D.R. Victory, J. Wei, J.D. Wenstrom, M. Xu, Y. Xu, Y. Yamazaki
FRIB, East Lansing, Michigan, USA
A. Facco
INFN/LNL, Legnaro (PD), Italy
K. Hosoyama
KEK, Ibaraki, Japan
M.P. Kelly
ANL, Argonne, Illinois, USA
R.E. Laxdal
TRIUMF, Vancouver, Canada
M. Wiseman
JLab, Newport News, Virginia, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Facility for Rare Isotope Beams (FRIB), under construction at Michigan State University, will utilize a driver linac to accelerate stable ion beams from protons to uranium up to energies of >200 MeV per nucleon with a beam power of up to 400 kW. The FRIB linac consists of 46 cryomodules containing a total of 324 superconducting radio-frequency (SRF) resonators and 69 superconducting solenoids. The design of all six type cryomodules has been completed. The critical SRF components are tested as subsystem and validated in the pre-production cryomodules. The mass production of SRF cryomodules is underway. Here we report on the progress of the technical construction of FRIB superconducting linac.

Slides TUXAA03 [4.006 MB]

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TUXBA01

Low Temperature Doping of Niobium Cavities: What is Really Going on?

cavity, niobium, vacuum, background

353

P.N. Koufalis, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Initial work, first at Fermilab and subsequently at Cornell, has shown that low temperature heat treatments (120 - 160 C) in a low pressure atmosphere can lead to a 'Q-rise' and high quality factors similar to that of cavities nitrogen-doped at high temperatures (~800 C). It was suggested that the low-temperature baking effect is a result of nitrogen doping or 'infusion'. We conducted a systematic study of this effect, using both RF measurements of cavities treated at different doping temperatures as well as detailed SIMS analysis of the surface layer. We match RF performance and extracted material parameters (especially electron mean free path) to the measured doping concentration profiles. We conclusively show that the low-temperature baking is drastically lowering the mean free path in the penetration layer, and that this is not the result of nitrogen doping or infusion. Instead, other interstitial impurities (specifically oxygen and carbon) are diffused into the surface in the low temperature heat treatment and are the source of lowering of the mean free path and, thus, of the observed Q-rise.

Slides TUXBA01 [4.153 MB]

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TUYAA01

The Importance of the Electron Mean Free Path for Superconducting RF Cavities

cavity, niobium, electron, SRF

359

J.T. Maniscalco, P.N. Koufalis, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Theoretical results offer a potential explanation for the anti-Q-slope, the phenomenon of decreasing microwave surface resistance with increasing radiofrequency electromagnetic field strength. This effect has been observed in niobium doped with impurities, chiefly nitrogen, and has been put to use in the Linac Coherent Light Source II (LCLS-II) accelerator currently under construction. Our work, presented here, finds a strong link between the electron mean free path, the main measure of impurity doping, to the overheating of quasiparticles in the RF penetration layer. This is an important effect that adjusts the magnitude of the theoretical anti-Q-slope by providing a mechanism to counteract it and introduce a surface resistance that increases with field strength. We discuss our findings in a study of niobium cavities doped at high temperature (800-990 °C) as well as new analysis of low-temperature-doped cavities.

Slides TUYAA01 [6.988 MB]

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TUYAA02

Advancement in the Understanding of the Field and Frequency Dependent Microwave Surface Resistance of Niobium

cavity, ECR, niobium, resonance

364

M. Martinello, S. Aderhold, S.K. Chandrasekaran, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

The radio-frequency surface resistance of niobium resonators is incredibly reduced when nitrogen impurities are dissolved as interstitial in the material, conferring ultra-high Q-factors at medium values of accelerating field. This effect has been observed in both high and low temperature nitrogen treatments. As a matter of fact, the peculiar anti Q-slope observed in nitrogen doped cavities, i.e. the decreasing of the Q-factor with the increasing of the radio-frequency field, come from the decreasing of the BCS surface resistance component as a function of the field. Such peculiar behavior has been considered consequence of the interstitial nitrogen present in the niobium lattice after the doping treatment. The study here presented show the field dependence of the BCS surface resistance surface of cavities with different resonant frequencies, such as: 650 MHz, 1.3 GHz, 2.6 GHz and 3.9 GHz, and processed with different state-of-the-art surface treatments. These findings show for the first time that the anti Q-slope might be seen at high frequency even for clean Niobium cavities, revealing useful suggestion on the physics underneath the anti Q-slope effect.
*M. Martinello, A. Grassellino, M. Checchin, A. Romanenko, O. Melnychuk, D.A. Sergatskov, S. Posen, J. Zasadzinski App. Phys. Lett. 109, 6 (2016)

Slides TUYAA02 [4.342 MB]

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TUYBA01

Progress on Characterization and Optimization of Multilayers

SRF, cavity, site, niobium

368

C.Z. Antoine
CEA/DSM/IRFU, France
M. Aburas, A. Four
CEA/DRF/IRFU, Gif-sur-Yvette, France
H. Hayano, S. Kato, T. Kubo, T. Saeki
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan

Multilayers MgO/NbN/MgO/Nb with several thicknesses are being tested by local magnetometry, Scanning tunneling and various standard structural techniques experiment providing usefull information to compare experiments and recent theoretical advances proposed by A. Gurevich or T. Kubo.

Slides TUYBA01 [5.819 MB]

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TUYBA02

Thermal Boundary Resistance Model and Defect Statistical Distribution in Nb/Cu Cavities

cavity, interface, ISOL, feedback

374

R. Vaglio
UniNa, Napoli, Italy
V. Palmieri
INFN/LNL, Legnaro (PD), Italy

The ‘Q-slope' problem strongly limits the application of niobium thin film sputtered cavities in high field accelerators. Here we consider the hypothesis that the Q-slope is related to local enhanced of the thermal boundary resistance at the Nb/Cu interface, due to poor thermal contact between film and substrate. We introduce a simple model that directly connects the Q versus Eacc curves to the distribution function f(RNb/Cu) of RNb/Cu thermal contact at the Nb/Cu interface over the cavity surface. Starting from the experimental curves, using inverse problem methods, we deduce the distribution functions generating those curves. The technique has been applied to cavities by different groups, including LNL/INFN and ISOLDE/CERN. In all cases to explain the data it is sufficient to assume that only a small fraction of the film over the cavity surface is in poor thermal contact with the substrate. The distribution functions typically follow a simple power-law statistical distribution and are temperature independent. The full analysis supports the hypothesis that the main origin of the Q-slope in thin film cavities is indeed related to bad adhesion at the Nb/Cu interface.

Slides TUYBA02 [0.988 MB]

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TUYBA03

The Way of Thick Films toward a Flat Q-curve in Sputtered Cavities

cavity, niobium, interface, site

378

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

Thick films have bulk like properties. In this paper it is explored the possibility to sputter 70 micron thick films in order to get rid of the Q-slope in Niobium sputtered Cop-per Cavities. An innovative method based on the multi-layer deposition of zero-stress single layers is reported. The deposition of zero-stress thick films into 6 GHz Cop-per seamless cavities, has shown the possibility to obtain straight curves for the Q-factor versus accelerating fields
Work supported by the INFN V group experiment ISIDE and performed under the CERN-INFN-FTSC Agreement N. KE2722/BE/FCC

Slides TUYBA03 [4.935 MB]

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TUPB001

338 MHz Crab Cavity Design for the eRHIC Hadron Beam

cavity, proton, electron, HOM

382

S. Verdú-Andrés, I. Ben-Zvi, Q. Wu, B. P. Xiao
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA

Funding: Work supported by the US Department of Energy via Brookhaven Science Associates LLC under contract no. DE-AC02-98CH10886.
Crab crossing is an essential mechanism to restore high luminosity and avoid synchro-betatron resonances in the electron-hadron collider eRHIC. The current ring-ring eRHIC design envisages a set of crab cavities operating at 338 MHz. This set of cavities will provide the crabbing kick to the hadron beam of eRHIC. Double-Quarter Wave (DQW) cavities are compact, superconducting RF deflecting cavities appropriate for crab crossing. This paper summarizes the main design requirements and presents an optimized RF design of a DQW cavity for the crabbing system of the ring-ring eRHIC hadron beam.

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TUPB002

Novel HOM Damper Design for High Current SRF Cavities

HOM, GUI, cavity, SRF

385

W. Xu, I. Ben-Zvi, M. Blaskiewicz, Y. Gao, D. Holmes, P. Kolb, G.T. McIntyre, R. Porqueddu, K.S. Smith, R. Than, F.J. Willeke, B. P. Xiao, T. Xin, C. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA
Y. Gao
PKU, Beijing, People's Republic of China

Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
ERL-Ring eRHIC aims to build a new high current (50 mA), multi-pass (6 passes) ERL to provide 3-18 GeV electron beams to collide with proton beams from existing RHIC. One critical challenge for eRHIC is to damp HOMs. The average HOM power is up to 8 kW per cavity, and it will get worse when the electron beam spectrum overlaps with cavity HOM spectrum. A novel HOM damping scheme by employing ridge waveguides has been worked out at BNL, which is able to well damp both longitudinal and transversal modes. This paper will describe the design of the HOM damping scheme, including RF design, HOM damping results, progress of prototyping.

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TUPB004

HOM damping with an enlarged beam tube for HEPS 166.6 MHz SC cavities

HOM, cavity, damping, impedance

389

H.X. Hao, Z.Q. Li, F. Meng, P. Zhang, X.Y. Zhang
IHEP, Beijing, People's Republic of China

The 166.6 MHz superconducting cavities have been proposed for the High Energy Photon Source (HEPS) storage ring, which is initiated by the Institute of High Energy Physics in Beijing. Their higher order modes (HOMs) have to be damped sufficiently in order to limit coupled-bunch instabilities and parasitic mode losses. In order to keep the beam stable, the impedance budget and the HOM damping requirement are given. As one HOM damping option, an enlarged beam tube allows HOMs to propagate and subsequently be absorbed by downstream HOM dampers installed on the inner surface of the beam tube. And the conventional coaxial HOM coupler, which will be mounted on the big beam tube, is planned to extract the HOM power below the cut-off frequency of the beam pipe.

Poster TUPB004 [1.132 MB]

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TUPB005

Developed Spoke Cavity Module for Main Linac of China ADS HOM Simulations and Damping Scheme for CEPC Cavities

cavity, linac, SRF, niobium

393

Z.Q. Li, J.S. Cao, Y.L. Chi, F.S. He, S.P. Li, H.Y. Lin, Q. Ma, Z.H. Mi, W.M. Pan, P. Sha, B. Xu, J.Y. Zhai, X.Y. Zhang
IHEP, Beijing, People's Republic of China

During past five year, two kind of spoke of Beta equal 0.21 and 0.40 were developed at IHEP CAS, the spoke cavity of beta 0.21 was adopted to accelerate proton from 10 to 32MeV, and 32 to 160MeV for beta 0.40 spoke cavity. Up to now, two kind of naked spoke cavities have been test in vertical, also the module of beta 0.21 spoke cavity, which equipped the liquid helium jacket, magnetic shield layer and frequency tuner has been fulfilled and test, the performance of all of components reach the design requirements.

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TUPB008

Performance of SRF Half-wave-resonators Tested at Cornell for the RAON Project

cavity, radiation, SRF, multipactoring

396

M. Ge, F. Furuta, J.E. Gillette, T. Gruber, S.W. Hartman, M. Liepe, 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

Two prototype half-wave-resonators (HWR; 162.5MHz and β=0.12) for the RAON project were tested at Cornell University. In this paper, we report and analyse detailed results from vertical tests, including tests of the HWRs without and with helium tank. Surface preparation at Research Instruments is discussed, as well as the development of new HWR preparation and test infrastructure at Cornell.

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TUPB009

High-frequency SRF Cavities

cavity, cryogenics, SRF, ECR

400

T.E. Oseroff, D.L. Hall, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Historically, the frequency of SRF cavities has been limited by cryogenic power dissipation increasing rapidly with frequency, due to the BCS surface resistance having a quadratic dependence on frequency. Now, new SRF surfaces using doped niobium and compound superconductors like Nb3Sn can drastically reduce the BCS part of the surface resistance. The temperature independent part of the surface resistance (residual resistance) can therefore become dominant, and has its own, different frequency dependence. We have developed a model to analyze cryogenic cooling power requirements for SRF cavities as function of operating frequency, temperature, and trapped flux to evaluate the impact of the novel low-loss SRF surfaces on the questions of optimal operating frequency and frequency limit. We show that high-frequency SRF cavities now become a realistic option for future SRF driven accelerators. As the transverse cavity size decreases inversely with respect to its resonant frequency, such high-frequency SRF cavities could greatly reduce cost.

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TUPB010

Multipactor Study in the Coupler Region of the Diamond SCRF Cavities

cavity, pick-up, GUI, electron

405

S.A. Pande, C. Christou, P. Gu
DLS, Oxfordshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

The Diamond storage ring operates with two CESR-B type Superconducting RF cavities. The cavities suffer from trips with a sudden loss of accelerating field if operated above a certain voltage. Consequently the cavities are operated at voltages up to 1.4 MV for better reliability. These cavities are iris coupled and have fixed Qext. At these lower operating voltages, the optimum condition for beam loading is satisfied at powers around 100 kW. For operation at 300 mA with two cavities, the power needed per system exceeds 200 kW. Therefore 3 stub tuners are used to lower the Qext to move the optimum condition close to 200kW. Additionally, the step due to the difference in the height of the coupling waveguide on the cavity and that of the vacuum side waveguide on the window results in a standing wave between the cavity and the window even at matched operation. The 3 stub tuner further enhances this standing wave. Numerical simulation reveals that the standing wave field from the cavity penetrates into the coupling waveguide increasing the probability of multipactor and breakdown in the coupler region. The results of multipactor simulations in this region with CST Studio are discussed.

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TUPB013

Advanced Manufacturing Techniques for the Fabrication of Hl-LHC Crab Cavities at CERN

cavity, niobium, simulation, MMI

409

M. Garlaschè
CERN, Geneva, Switzerland

RF Crab Cavities are an essential part of the HL-LHC upgrade at CERN. Two concepts of such systems are being developed: the Double Quarter Wave (DQW) and the RF Dipole (RFD). The following paper describes the advanced manufacturing techniques developed for the fabrication of the DQW cavity prototype with an outlook on the upcoming RFD prototype production.

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TUPB014

In-situ Bulk Residual Resistivity Ratio Measurement on Double Quarter Wave Crab Cavities

cavity, niobium, luminosity, cryomodule

415

N.C. Shipman, A. Castilla, K.G. Hernández-Chahín, A. Macpherson
CERN, Geneva, Switzerland
I. Ben-Zvi
BNL, Upton, Long Island, New York, USA
G. Burt, N.C. Shipman
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
K.G. Hernández-Chahín
Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
N.C. Shipman
UMAN, Manchester, United Kingdom

A four wire measurement was used to measure the bulk RRR on two DQW Crab Cavities. The measurement procedure is explained and the values obtained for each cavity are compared together with the values obtained from Niobium samples of the same stock from which the cavities were manufactured. Measurement errors and carefully analysed and further improvements to the measurement procedure are suggested.

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TUPB016

Redesign of CERN's Quadrupole Resonator for Testing of Superconducting Samples

cavity, quadrupole, alignment, simulation

420

V. del Pozo Romano, R. Betemps, F. Gerigk, R. Illan Fiastre, T. Mikkola
CERN, Geneva, Switzerland

The Quadrupole Resonator (QPR) was constructed in 1997 to measure the surface resistance of niobium samples at 400 MHz, the technology and RF frequency chosen for the LHC. It allows measurement of the RF properties of superconducting films deposited on disk-shaped metallic substrates. The samples are used to study different coatings which is much faster than the coating, stripping and re-coating of sample cavities. An electromagnetic and mechanical re-design of the existing QPR has been done with the goal of doubling the magnetic peak fields on the samples. Electromagnetic simulations were carried out on a completely parameterized model, using the actual CERN's QPR as baseline and modifying its dimensions. The aim was to optimize the measurement range and resolution by increasing the ratio between the magnetic peak fields on the sample and in the cavity. Increasing the average magnetic field on the sample leads to a more homogenous field distribution over the sample, which in turn gives a better resolution. Some of the modifications were based on the work already done by Helmholtz-Zentrum-Berlin for their upgraded version of the QPR.

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TUPB020

Microphonics Passive Damping

cavity, SRF, simulation, operation

423

E.N. Zaplatin
FZJ, Jülich, Germany
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Different types of external loads on the resonator walls predetermine the main working conditions of the SRF cavities. The most important of them are very high electromagnetic fields that result in strong Lorentz forces and the pressure on cavity walls from the helium tank that also deforms the cavity shape. For pulsed operation, the Lorentz forces usually play the decisive role for the cavity design. For CW operation, the liquid helium vessel pressure instability even for 2K operations is the source of large microphonics. All deformations resulting from any type of external loads on cavity walls lead to shifts in the working RF frequency in the range of hundreds of kHz. Taking into account high Q-factor of SC cavities such a large frequency shift takes the cavity out of operation. Here we present and discuss the achievements and problems of microphonics passive damping in different type SRF cavities.

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TUPB021

First Considerations on HZB High Frequency Elliptical Resonator Stiffening

cavity, simulation, SRF, cryomodule

428

E.N. Zaplatin
FZJ, Jülich, Germany
H.-W. Glock, J. Knobloch, A. Neumann, A.V. Vélez
HZB, Berlin, Germany

There are two projects that currently are under development and construction at HZB which utilize high frequency elliptical resonators ' Energy Recovery Linac Prototype (BERLinPro, 7-cell, 1300 MHz, β=1) and BESSY Variable pulse-length Storage Ring (VSR, 5-cell, 1500/1750 MHz, β=1). A critical issue of both projects is small effective beam loading in cavities operating at high CW fields (Eacc of 20 MV/m) with a narrow band width. This necessitates precise tuning and therefore good compensation of microphonics and coupled Lorentz-force detuning driven instabilities. Here we present a conceptual study of an integrated SRF resonator and helium vessel structure design to ensure a reduced resonance frequency dependence on pressure and Lorentz forces to minimize their impact on the accelerating field profile.

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TUPB022

First Measurements of the Next SC CH-cavities for the New Superconducting CW Heavy Ion Linac at GSI

cavity, linac, heavy-ion, status

433

M. Basten, M. Busch, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
K. Aulenbacher, W.A. Barth, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, M. Heilmann, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia

In the future the existing GSI-UNILAC (Universal Linear Accelerator) will primarily be used to provide high power heavy ion beams at a low repetition rate for the FAIR project (Facility for Antiproton and Ion Research). To keep the ambitious Super Heavy Element (SHE) physics program at GSI competitive a superconducting (sc) continuous wave (cw) high intensity heavy ion LINAC is highly desirable to provide ion beams at or above the coulomb barrier [*]. The fundamental linac design composes a high performance ion source, a new low energy beam transport line, the High Charge State Injector (HLI) upgraded for cw, and a matching line (1.4 MeV/u) followed by the new sc-DTL LINAC for acceleration up to 7.3 MeV/u. The construction of the first demonstrator section has been finished in the 3rd quarter of 2016. It comprises the first crossbar-H-mode (CH) cavity with two sc 9.3 T solenoids and has been successfully tested in the end of 2016 [**]. Currently the next two sc 8 gap CH-cavities are under construction at Research Instruments (RI). First intermediate measurements during the fabrication process as well as the latest status of the construction phase will be presented.
*W. Barth et al., Further R&D for a new Superconducting cw Heavy Ion LINAC@GSI, IPAC2014, THPME004
**F. Dziuba et al., First cold tests of the superconducting cw demonstrator at GSI, RuPAC2016, WECBMH01

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TUPB023

Further Tests on the SC 325 MHz CH-cavity and Power Coupler Test Setup

cavity, linac, SRF, pick-up

437

M. Busch, M. Basten, H. Podlech, U. Ratzinger, M. Schwarz
IAP, Frankfurt am Main, Germany
W.A. Barth
MEPhI, Moscow, Russia
W.A. Barth
GSI, Darmstadt, Germany
W.A. Barth, F.D. Dziuba, V. Gettmann
HIM, Mainz, Germany

Funding: Work supported by BMBF contr. No. 05P15RFRBA
The 325MHz CH-cavity which has been developed and successfully vertically tested at the Institute for Applied Physics, Frankfurt, has has been welded to the helium vessel at the frontal joints of the cavity and further vertical and horizontal tests are in preparation. Finally a beam test with a 11.4 AMeV, 10 mA ion beam at GSI, Darmstadt is projected. Furthermore a newly developed, dedicated test stand for the 217 MHz power couplers has been set up for the cavities of the sc cw-LINAC project at GSI.

Poster TUPB023 [2.579 MB]

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TUPB024

Performance Tests of the Superconducting 217 MHz CH Cavity for the CW Demonstrator

cavity, linac, heavy-ion, operation

440

F.D. Dziuba, M. Amberg, K. Aulenbacher, W.A. Barth, V. Gettmann, M. Miski-Oglu
HIM, Mainz, Germany
M. Amberg, M. Basten, M. Busch, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany
K. Aulenbacher
IKP, Mainz, Germany
W.A. Barth, M. Heilmann, A. Schnase, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia

Regarding the future research program of super heavy element (SHE) synthesis at GSI, high intense heavy ion beams above the coulomb barrier and high average particle currents are highly demanded. The associated beam requirements exceed the capabilities of the existing Universal Linear Accelerator (UNILAC). Besides the existing GSI accelerator chain will be exclusively used as an injector for FAIR (Facility for Antiproton and Ion Research) providing high power heavy ion beams at a low repetition rate. As a consequence a new dedicated superconducting (sc) continuous wave (cw) linac is highly demanded to keep the SHE research program at GSI competitive on a high level. In this context the construction of the first linac section, which serves simultaneously as a prototype to demonstrate its reliable operability has been finished at the end of 2016. The so called demonstrator cryomodule comprises two sc 9.3 T solenoids and a sc 217 MHz crossbar-H-mode (CH) cavity with 15 equidistant accelerating gaps. Furthermore, the performance of the cavity has been successfully tested at cryogenic temperatures. The results of these tests are presented.

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TUPB028

Improvement of Magnetic Condition for KEK-STF Vertical Test Facility Toward High-Q Study

cavity, solenoid, SRF, controls

444

K. Umemori, T. Dohmae, E. Kako, T. Konomi, T. Kubo, M. Masuzawa, G.-T. Park, A. Terashima, K. Tsuchiya, R. Ueki
KEK, Ibaraki, Japan
T. Okada
Sokendai, Ibaraki, Japan

Improvement of unloaded Q-values of SRF cavities are important to reduce surface loss of cavity and heat loads of He refrigerators. R&D activities have been developed worldwide. We also started work toward high-Q, but soon realized that magnetic condition of KEK-STF vertical test facility was not good enough to carry out high-Q measurements. First, magnetized components were searched. Shafts to move variable coupler were found to be most magnetized one and exceed more than 1 Gauss. Magnetized components were exchanged to non-magnetized one. In order to further reduce remnant magnetic field, a solenoid coil was prepared and used to cancel it. To suppress flux trapping, a heater was located around an upper beampipe of cavity and made thermal gradient. Owing to these efforts, Q-value of more than 1x10¹¹ can be measured with a condition of residual resistance of ~3 nΩ. Clear flux expulsion signal can be also observed. In this presentation, we report about efforts to reduce ambient magnetic field and to realize high-Q measurements. Results of vertical tests, including flux expulsion measurements, are also presented.

Poster TUPB028 [1.961 MB]

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TUPB032

Study on 650MHz 5-cell Prototype Cavities at IHEP

cavity, HOM, SRF, simulation

448

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

CEPC Pre CDR pointed that the 650 MHz 5-cell SRF cavity could be a candidate for the main ring of the single-ring pretzel scheme at the Higgs energy in 2015. Then EM design of 5-cell cavities were published later. So, the study on the fabrication of a 5-cell prototype cavity with waveguide HOM couplers were carried on at IHEP. In the paper, we will mainly report the mechanical design and fabrication progress of the 5-cell prototype. Besides, fabrication of a bare 2-cell prototype cavity was also carried on according to the further study after Pre-CDR. Challenges and possible solutions for the prototypes development will also be discussed.

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TUPB033

Tests of the High Current Slotted Superconducting Cavity with Extremely Low Impedance

cavity, HOM, GUI, damping

451

Z.C. Liu, J. Gao, F.S. He, S. Jin, Z.H. Mi, T.X. Zhao, H.J. Zheng
IHEP, Beijing, People's Republic of China
F. Wang, D.H. Zhuang
PKU, Beijing, People's Republic of China

Slotted superconducting cavity is a novel structure with extremely low impedance and high BBU threshold. It can be used in various high current applications. A 1.3 GHz 3-cell slotted superconducting cavity was designed and tested. The room temperature test results show the cavity has an extremely low impedance. The vertical test results show the cavity gradient can reach several MV/m, but it was limited by the test end group made of steel.

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TUPB034

The 166.6 MHz Proof-of-principle SRF Cavity for HEPS-TF

cavity, HOM, storage-ring, SRF

454

P. Zhang, J. Dai, H.X. Hao, T.M. Huang, Z.Q. Li, H.Y. Lin, Q. Ma, F. Meng, Z.H. Mi, W.M. Pan, 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 also partly supported by Pioneer "Hundred Talents Program" of Chinese Academy of Sciences.
The 166.6 MHz superconducting RF cavities have been proposed for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale light source. The cavity is of quarter-wave type made of bulk niobium with β =1. Each cavity will be operated at 4 K providing 1.2 MV accelerating voltage and 145 kW of power to the electron beam. During the HEPS - Test Facility (HEPS-TF) phase, a proof-of-principle cavity of 166.6 MHz has been designed in IHEP and manufactured in Beijing. The subsequent BCP was conducted in Ningxia, while HPR, cleanroom assembly and 120 degree baking was done in IHEP. The cavity was finally vertical tested at both 4K and 2K in IHEP. The cavity Q0 at nominal gradient at 4 K was measured to be 2.4·10⁹ with Epeak of 42 MV/m and Bpeak of 65 mT. The maximum Epeak and Bpeak reached 86MV/m and 131 mT respectively at both 4 K and 2 K, and the corresponding Q0 was measured to be 5.10⁸ (4 K) and 3.3·10⁹ (2 K). The residual surface resistance was measured to be 2.3 nOhm.

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TUPB035

Frequency Pre-tuning of the 166.6 MHz Proof-of-principle SRF Cavity for HEPS-TF

cavity, simulation, SRF, target

459

P. Zhang, H.X. Hao, Z.Q. Li, X.Y. Zhang
IHEP, Beijing, People's Republic of China

Funding: This work has been supported by HEPS-TF project and also partly supported by Pioneer 'Hundred Talents Program' of Chinese Academy of Sciences.
A 166.6 MHz proof-of-principle SRF cavity has been designed for the High Energy Photon Source - Test Facility (HEPS) at IHEP in Beijing. The cavity is a β=1 quarter-wave resonator made of bulk niobium operating at 4 K. A pre-tuning scheme was made to accommodate the cavity frequency shift mainly due to mechanical tolerances during cavity production, the subsequent surface treatment and cooldown process. To this end, the length of the cavity outer conductor was chosen as a free parameter for the pre-tuning. The cavity frequency was carefully monitored during the production, post-processing steps and vertical test. The measurement results agree well with our calculations. It is worth noticing that the pre-tuning method only involves one-time measurement of the cavity resonant frequency and its outer conductor length.

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TUPB036

R&D of CEPC Cavity

cavity, cryomodule, SRF, experiment

463

P. Sha
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
B. Liu, Z.H. Mi, J.Y. Zhai, X.Y. Zhang, H.J. Zheng
IHEP, Beijing, People's Republic of China

Funding: This study was supported by National Key Programme for S&T Research and Development (Grant NO.: 2016YFA0400400) and National Natural Science Foundation of China (Grant NO.: 11505197)
CEPC will use 650 MHz cavities for the collider (Main Ring) and 1.3 GHz cavities for the Booster. Each booster cryomodule contains eight 1.3 GHz 9-cell cavities, which is similar as LCLS-II. Each collider cryomodule contains six 650 MHz 2-cell cavities, which is totally new. So our R&D of CEPC cavity mainly focuses on the 650 MHz 2-cell cavity. A cryomodule which consists of two 650 MHz 2-cell cavities has began in early 2017. In this thesis, the RF and mechanical design is displayed with Helium Vessel. Besides, multipacting is analyzed. In order to achieve high Q, N-doping is also studied.

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TUPB037

A 166.6 MHz Proof-of-principle SRF Cavity for HEPS-TF: Mechanical Design and Fabrication

cavity, SRF, storage-ring, superconducting-RF

466

X.Y. Zhang
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
H.X. Hao, Z.Q. Li, H.Y. Lin, Y. Sun, P. Zhang
IHEP, Beijing, People's Republic of China

166.6 MHz superconducting RF cavities operating at 4.2 K have been proposed by IHEP for the High Energy Photon Source - Test Facility (HEPS-TF). The cavity is a quarter wave resonator with beam going through the cavity inner conductor. The cavity and its stiffness were designed and optimized to meet pressure safety requirement and to reduce frequency sensitivity due to helium pressure fluctuations. Tuning sensitivity, Lorentz force detuning and microphonics were also simulated. Most calculations have been validated by experiments. This paper reports the mechanical design and fabrication details of the first proof-of-principle cavity.

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TUPB038

Mechanical Design of a 650 MHz Superconducting RF Cavity for CEPC

cavity, collider, SRF, positron

471

X.Y. Zhang
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
F.S. He, Q. Ma, Z.H. Mi, P. Sha, J.Y. Zhai
IHEP, Beijing, People's Republic of China

Funding: This study was supported by National Key Programme for S&T Research and Development (Grant NO.: 2016YFA0400400)
The 650 MHz superconducting RF cavities have been proposed by IHEP for the Circular Electron-Positron Collider (CEPC). The major components are a 2-cell elliptical cavity, end groups, stiffness and helium vessel, which have been optimized to meet the design requirement. The minimization of the Lorentz force detuning and the sensitivity of resonance frequency to Helium pressure variations was the main goal of the optimization. Also detailed stress analysis, tuning and microphonics performance of dresses cavity will be presented in this paper.

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TUPB039

Electropolishing of Niobium from Deep Eutectic Solvents Based on Choline Chloride

ECR, cavity, niobium, SRF

475

Q.W. Chu, H. Guo, Y. He, L. Li, P.R. Xiong, Z.M. You, S.H. Zhang
IMP/CAS, Lanzhou, People's Republic of China

Niobium (Nb) was successfully electropolished from a green ionic liquid, choline chloride/urea deep eutectic solvent (DES). This paper was to investigate the influence of various electropolishing parameters, including electropolishing time, temperature and voltage, on the electropolishing rate, surface roughness, glossiness and microstructure of Nb. The result showed that the electropolishing parameters had a significant impact on the performance of Nb. Based on surface analysis by scanning electron microscope (SEM) and atomic force microscope (AFM), smooth Nb can be achieved under properly controlled conditions.

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TUPB040

Design and Optimization of Medium and High Beta Superconducting Elliptical Cavities for the CW Linac in CIADS

cavity, HOM, multipactoring, linac

478

Y.L. Huang, L. Chen, Y. He, Y.M. Li, S.H. Zhang
IMP/CAS, Lanzhou, People's Republic of China

Superconducting technology is adopted in the main accelerating section of the CW Linac in China Initiative Accelerator Driven System (CIADS) to accelerate the 10 mA proton beam from 2.1 MeV up to 1.5 GeV. The high energy section of the superconducting linac is composed of two families of SC elliptical cavities with optimum beta 0.62 and 0.82 for the acceleration of proton beam from 178 MeV to 1.5 GeV. In this paper, the design and optimization of the 650 MHz medium and high beta elliptical cavities are discussed, including the RF design, multipacting analysis, high order modes (HOMs) analysis, generator RF power calculation, and the mechanical design.

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TUPB041

Design of a Triple Spoke Cavity for the HIF Demo Injector

cavity, heavy-ion, linac, simulation

481

W. Ma, L. Lu, L. Yang
IMP/CAS, Lanzhou, People's Republic of China

Funding: This work was supported by National Nature Science Foundation of China under Grant No. 11475232 and No. 11535016.
A 325 MHz triple spoke type superconducting cavity for lead beams with β=0.3 is designed for the heavy ion inertial fusion (HIF) Demo facility. The design and simulations of the triple spoke will be reported in this paper, including the electromagnetic (EM) design and mechanical study using CST microwave studio (MWS) and ANSYS workbench.

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TUPB046

Experience on Design, Fabrication and Testing of a Large Grain ESS Medium Beta Prototype Cavity

cavity, radiation, niobium, electron

484

M. Bertucci, 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

INFN-LASA built a complete Medium Beta cavity, based on the ESS prototype design, with novel large-grain material sliced in sheets from an ingot provided by CBMM manufacturing experience. Design and fabrication are reported as well as results on the physical and chemical analyses performed on samples at different cavity production stages. Results from the cold tests performed are also summarized and critically discussed in view of future R&D activities

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TUPB047

Passband Modes Excitation Triggered by Field Emission in ESS Medium Beta Cavity Prototype

cavity, site, electron, simulation

489

J.F. Chen, M. Bertucci, A. Bosotti, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
M. Eshraqi, M. Lindroos, S. Pirani
ESS, Lund, Sweden
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
T.P.Å. Åkesson
Lund University, Department of Physics, Lund, Sweden

During the first vertical test of ESS Medium Beta large-grain prototype cavity in INFN-LASA, a phenomenon of coexisting two passband-modes was observed – 4π/6 mode was excited spontaneously during the power rise of 3π/6 mode. This phenomenon is most likely due to the field-emission electrons that transfer their energy gained from the 3π/6 mode to the 4π/6 mode. In this paper, we present the experimental results, the excitation mechanism and the related simulation results.

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TUPB048

INFN- LASA Medium Beta Cavity Prototypes for ESS Linac

cavity, controls, niobium, vacuum

494

D. Sertore, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
S. Pirani
ESS, Lund, Sweden

INFN-LASA, in the framework of INFN contribution to the European Spallation Source, has developed, produced and tested 704.4 MHz Medium Beta (β = 0.67) cavities. Mode separation and avoidance of HOM excitation by machine line frequencies have driven the cavity design. The production at the industry, also in view of the INFN in-kind contribution of series cavities, has been done "build-to-print" and we have implemented our own quality control process, based on our XFEL experience, from raw material to cavity ready for test. The cavities have been then cold tested in our upgraded Vertical Test Facility. In this paper, we report on our experience on the different phases of the cavity production and test processes.

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TUPB049

Design Study on the Superconducting HWR for Secondary Particle Generation at KOMAC

cavity, proton, linac, SRF

499

H.S. Kim
KAERI, Daejon, Republic of Korea
Y.-S. Cho, J.J. Dang, H.S. Jeong, H.-J. Kwon, S. Lee
Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea

Funding: This work has been supported through KOMAC (Korea of Multi-purpose Accelerator Complex) operation fund of KAERI by MSIP (Ministry of Science, ICT and Future Planning).
A 100-MeV proton linac has been operated since 2013 at KOMAC (Korea Multi-purpose Accelerator Complex) and provides the accelerated proton beam to various users from the research institutes, universities and industries. To expand the utilization fields of the accelerator, we have a plan to develop a secondary particle utilization facility including a pulsed neutron source and radio-isotope beam based on the 100-MeV linac. According to the preliminary analysis, the neutron yields can be increased by about 2.5 times if the incident proton beam energy increases from 100 MeV to 160 MeV. Therefore, we carried out design study on the SRF linac based on half-wave resonator to increase the proton beam energy. Baseline design parameters include 350 MHz operating frequency, 2 K operation temperature, and peak electric field and magnetic field less than 35 MV/m and 70 mT, respectively. The available space at existing accelerator tunnel was also taken into consideration. Details on the design study on the SRF linac based on HWR cavity for the secondary particle utilization facility at KOMAC will be given in this presentation.

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TUPB052

Higher Order Modes Damping in 9-cell Superconducting Cavity with Grooved Beam Pipe

HOM, cavity, damping, quadrupole

502

A.M. Bulygin, R.V. Donetskiy, Ya.V. Shashkov
MEPhI, Moscow, Russia

This paper is focused on higher order modes (HOM) damping efficiency analysis in 9-cell superconducting cavities with HOM couplers and with grooved beam pipe. Comparison of two methods of HOM damping is presented. In order to increase efficiency of damping of trapped modes the end cells of the structure were modified.
Higher order modes, tesla, SRF

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TUPB053

Lessons Learned from RF-Dipole Prototype Cavities for LHC High Luminosity Upgrade

cavity, dipole, HOM, luminosity

506

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
H. Park
JLab, Newport News, Virginia, USA

The rf-dipole cavity has successfully demonstrated the principles of using a compact cavity operating in TE11-like mode in generating a transverse kick. Several proof-of-principle rf-dipole cavities have been fabricated and the rf tests have demonstrated high transverse gradients. The rf-dipole geometry has been adapted into a square-shaped geometry designed to meet the dimensional constraints for the LHC also maintaining crabbing in both horizontal and vertical planes. Recently, two prototype rf-dipole cavities intended for the test at SPS for have been completed that is designed to accommodate the FPC and HOM dampers. The performance during the rf tests have shown excellent results on achieving the design requirements of operation for the crab cavities for SPS. This paper presents the experiences and lessons learned during the cavity preparation and testing, including process validation, frequency tracking.

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TUPB054

RF Tests of RF-Dipole Prototype Crabbing Cavities for LHC High Luminosity Upgrade

cavity, dipole, HOM, luminosity

509

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
H. Park
JLab, Newport News, Virginia, USA

The superconducting rf-dipole crabbing cavity is one of the two crabbing cavity designs proposed for the LHC high luminosity upgrade. The proof-of-principle (P-o-P) rf-dipole cavity operating at 400 MHz has demonstrated 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. The crab cavities will be installed in the SPS beam line 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.

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TUPB055

Nb3Sn Thin Film Deposition On Copper By DC Magnetron Sputtering

target, SRF, cavity, niobium

512

W.W. Tan, B.T. Li, X.Y. Lu, L. Xiao, D. Xie, D.Y. Yang, Y. Yang, Z.Q. Yang, J. Zhao
PKU, Beijing, People's Republic of China

Nb3Sn for SRF cavities has been coated on copper samples by DC magnetron Sputtering. Pure Nb target and pure Sn target were installed separately in the magnetron sputtering device. Nb3Sn precursor was coated on copper in the Ar atmosphere of 0.5 Pa. The Nb3Sn precursor was annealed in the vacuum furnace whose pressure is 10^-4 Pa. The XRD results demonstrate the exist of Nb3Sn crystal, and MPMS results show superconductivity of Nb3Sn. The highest critical temperature obtained is 15K.

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TUPB056

Study on a Low Beta High Current Taper Type Superconducting Half Wave Resonator for BISOL

cavity, simulation, experiment, ISOL

516

F. Zhu, M. Chen, L.W. Feng, S.W. Quan, F. Wang, H.T.X. Zhong
PKU, Beijing, People's Republic of China

Funding: Work supported by National Basic Research Project (No. 2014CB845504)
Beijing isotope separation on line type rare ion beam facility (BISOL) for both basic science and applications is a project proposed by China Institute of Atomic Energy and Peking University. Deuteron driver accelerator of BISOL would adopt superconducting half wave resonator (HWR) with low beta and high current. For pre-research of BISOL, a β=0.09 162.5 MHz taper type HWR cavity has been designed for accelerating deuteron beam with several tens of mA. The Design, fabrication, post-processing and room temperature RF measurement of the HWR cavity will be presented in this paper.

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TUPB060

Innovative Cryogenic Test Facility for Testing SRF Cavity Series Production

cavity, SRF, operation, cryogenics

520

L. Bizel-Bizellot, M. Ellis, S.M. Pattalwar, M.D. Pendleton, P.A. Smith, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Testing SRF cavities in a vertical cryostat is the first step in qualifying the performance of SRF cavities before being integrated into a cryomodule. The European Spallation Source (ESS) requires 84 high-beta 5 cells, 704 MHz cavities which will be manufactured and qualified for their RF performance in a vertical cryostat at Science and Technology Facility Council (STFC) Daresbury Laboratory (United-kingdom). Taking a conventional approach each vertical test would require a large cryostat demanding more than 7000 litres of liquid helium per test for testing 3 cavities simultaneously. In order to reduce the overall operating cost, we plan to develop an alternative method to divide the liquid helium consumption by 5 by filling liquid helium only in each individual helium vessels enclosing each cavity placed horizontally in the cryostat. Therefore the test is performed in more realistic conditions such as in a cryomodule and reduces the operating time. This also reduces the mass flow-rate to be handled by a factor 10, leading to 2 g/s, thus reducing the size of the associated components such as the 2 K pumps, the safety device, the valves and transfer lines.

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TUPB063

Fabrication of a SRF Deflecting Cavity for the ARIEL-Linac

cavity, niobium, linac, TRIUMF

524

D.W. Storey, R.E. Laxdal, B. Matheson, N. Muller
TRIUMF, Vancouver, Canada
D.W. Storey
Victoria University, Victoria, B.C., Canada

A superconducting RF deflecting cavity has been designed and is being fabricated at TRIUMF to allow simultaneous beam delivery to both rare isotope production and an energy recovery linac. The 650 MHz cavity will operate in a TE-like mode in CW. The design has been optimised for high shunt impedance and minimal longitudinal footprint, reaching roughly 50% higher shunt impedance with 50% less length than comparable non-TM mode cavity geometries. Due to low power dissipation at 4K at the maximum required deflecting voltage of 0.6 MV, low cost manufacturing techniques have been employed in the construction of the cavity. These include the use of reactor grade Niobium and TIG welding in an inert atmosphere. Development of the manufacturing processes will be presented along with the status of fabrication.

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TUPB064

Operating Experience on Cavity Performance of ISAC-II Superconducting Heavy Ion Linac

cavity, ISAC, operation, linac

527

Z.Y. Yao, T. Junginger, A.N. Koveshnikov, R.E. Laxdal, Y. Ma, D.W. Storey, E. Thoeng, B.S. Waraich, V. Zvyagintsev
TRIUMF, Vancouver, Canada

ISAC-II is a superconducting heavy ion linac with 40 QWRs as an extension of ISAC facility for ISOL based on radioactive ion beam production and acceleration. Phase-I with twenty 106MHz cavities has been operating since 2006. The design spec was achieved with the completion of Phase-II with another twenty 141MHz cavities in 2010. The cavity performance statistics and operating experience have been accumulated over years. This paper will summarize the operating experience on cavity performance of ISAC-II.

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TUPB065

Design of Multi-frequency Coaxial Test Resonators

cavity, niobium, SRF, operation

531

Z.Y. Yao, T. Junginger, R.E. Laxdal, B. Matheson, B.S. Waraich, V. Zvyagintsev
TRIUMF, Vancouver, Canada

A significant issue in low beta resonators is medium field Q-slope (MFQS) at 4K. To study the MFQS and the field dependence of surface resistance in low beta resonators, a quarter-wave resonator (QWR) and a half-wave resonator (HWR) were designed to be tested at integer harmonic frequencies of 200MHz, and up to 1.2GHz. A series of chemistry and heat treatments will be applied to these cavities so that a systemic study on the surface resistance of the coaxial resonators associating with post-processing, RF field, and frequency can be done. The detail design of these cavities and the status of cavity fabrication will be reported in this paper.

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TUPB066

RF Results of Nb Coated SRF Accelerator Cavities via HiPIMS

cavity, SRF, lattice, site

535

M.C. Burton, M. Beebe, R.A. Lukaszew
The College of William and Mary, Williamsburg, Virginia, USA
A.D. Palczewski, H.L. Phillips, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: Jefferson Lab
Bulk Nb SRF cavities are the preferred method for acceleration of charged particles. However, bulk Nb cavities suffer from variable RF performance, high cost and impose material & design restrictions on other components of a particle accelerator. Since SRF is a shallow surface phenomena, a proposed solution is to deposit a Nb thin film on the interior of a cavity made of an alternative material such as Cu. While this approach has been attempted in the past, new energetic condensation techniques, such as High Power Impulse Magnetron Sputtering (HiPIMS), offer the opportunity to create Nb films with improved properties compared to traditional methods. To test HiPIMS, a study was performed in which Nb films were deposited on samples in multiple 'series' where only one parameter (Ion Fraction, Condensation Energy'etc.) is varied. Sample properties were then characterized using: XRD, AFM, SEM'etc., and correlations made between deposition parameters and film properties. Nb films were then deposited on 1.3GHz Cu cavities at select parameter sets and RF tested. Here we present the results from the Nb film studies and correlate the sample properties to RF results of Nb/Cu cavities.

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TUPB067

Insights into Formation of Nb3Sn Film During the Vapor Diffusion Process

niobium, experiment, cavity, SRF

539

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 DE-AC05-06OR23177 and Office of High Energy Physics under grant DE-SC-0014475.
The potential of Nb3Sn for SRF cavities is widely recognized and renewed R&D efforts continue to bring new insights about material structure and its properties. We have systematically coated niobium with Nb3Sn using "vapor diffusion" under varying coating conditions to elucidate the reaction of tin with niobium at the temperatures of interest. The analysis of the coated samples is revealing new understanding about the two-stage nucleation/deposition ("vapor diffusion") process that allows us to form a hypothesis regarding Nb3Sn formation mechanism. The essential aspect of nucleation is the deposition of a high coverage, nanoscale thin tin film with particle assemblage by decomposition of tin chloride on the niobium surface at temperatures sufficient for reduction of the thick niobium oxide film, usually at about 500°C. The deposition is followed by the reaction of tin from tin vapor with the niobium surface to form Nb3Sn at about 1200°C, where the surface and grain boundaries start to play key role in the formation process initiation and progression. These findings improve understanding of the Nb3Sn growth in the typical vapor diffusion process used for accelerator cavity coatings.

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TUPB069

Rigorous Data Processing and Automatic Documentation of SRF Cold Tests

LabView, SRF, software, cavity

543

K.G. Hernández-Chahín
Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
S. Aull, P.F. Fernández López, K.G. Hernández-Chahín, N. Schwerg, N. Stapley
CERN, Geneva, Switzerland

Performance curves for SRF cavities are derived from primary quantities which are processed by software. Commonly, the mathematical implementation of this analysis is hidden in software such as Excel or LabVIEW, making it difficult to verify or to trace, while text-based programming like Python and MATLAB require some programming skills for review and use. As part of an initiative to consolidate and standardise SRF data analysis tools, we present a Python program converting a module containing the collection of all commonly used functions into a \LaTeX (PDF) document carrying all features of the implementation and allowing for a review by SRF experts, not programmers. The resulting document is the reference for non-experts, beginners and test stand operators. The module is imported in any subsequent processing and analysis steps like the symbolic analysis of the measurement uncertainties or the study of sensitivities. As an additional layer of protection the functions can be further wrapped including assertions, type and sanity checks. This process maximises function reuse, reduces the risk of human errors and guarantees automatically validated and documented cold test results.

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TUPB070

INFN-LASA Cavity Design for PIP-II LB650 Cavity

cavity, HOM, coupling, operation

547

C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
S. Pirani
ESS, Lund, Sweden

INFN-LASA is going to join the international partnership for Fermilab PIP-II project and to provide a novel design for the 650 MHz cavity of the 0.61 beta linac section, plug compatible with the Fermilab Cryomodule design. This paper reports the cavity design features both from the electro-magnetic and mechanical aspects, with focus on the rationales at the basis of the choice of main parameters. Furthermore, the current plans for the future R&D activity are here reported, including the production of two single cells and two complete cavities.

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TUPB071

Test Result of 650 MHz, Beta 0.61 Single-cell Niobium Cavity

cavity, niobium, accelerating-gradient, electron

553

S. Seth, P. Bhattacharyya, A. Dutta Gupta, S. Ghosh, S. Ghosh, A. Mandal, S. Som
VECC, Kolkata, India
A. Grassellino, T.N. Khabiboulline, O.S. Melnychuk, C.S. Mishra, T.H. Nicol, A.M. Rowe, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
M.P. Kelly, T. Reid
ANL, Argonne, Illinois, USA
K.K. Mistri, P.N. Prakash
IUAC, New Delhi, India

VECC has been involved in the design, analysis and development of 650 MHz, beta 0.61 (LB650), elliptical Superconducting RF linac cavity, as part of research and development activities on SRF cavities and associated technologies under Indian Institutions Fermilab Collaboration (IIFC). A single-cell niobium cavity has been indigenously designed and developed at VECC, with the help of Electron Beam Welding (EBW) facility at IUAC, New Delhi. Various measurements, processing and testing at 2K in Vertical Test Stand (VTS) of the single-cell cavity was carried out at ANL and Fermilab, USA, with active participation of VECC engineers. It achieved a maximum accelerating gradient(Eacc) of 34.5 MV/m with Quality Factor of 2·10⁹ and 30 MV/m with Quality Factor of 1.5·10¹⁰. This is probably the highest accelerating gradient achieved so far in the world for LB650 cavities. This paper describes the design, fabrication and measurement of the single cell niobium cavity. Cavity processing and test results of Vertical Test of the single-cell niobium cavity are also presented.

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TUPB072

Investigation of BCP Parameters for Mastery of SRF Cavity Treatment

cavity, niobium, experiment, SRF

558

F. Éozénou
CEA/DSM/IRFU, France
E. Cenni, G. Devanz, T. Percerou, Th. Proslier, C. Servouin
CEA/DRF/IRFU, Gif-sur-Yvette, France
M.L.L. Nghiem
UPMC, Paris, France

Mastery of Standard Buffered Chemical Polishing (with mixture of hydrofluoric, nitric and phosphoric acids) is of paramount importance for the treatment of SRF resonators with complex geometry has IFMIF half-wave resonators, in order to control accurately their frequency evolution. Furthermore, strong and unexpected asymmetry in removals has recently been observed after BCP treatment of ESS-medium beta resonators. The goal of this study is to investigate accurately influence of parameters such as surface geometry and orientation, acid temperature, agitation and their coupling on the removal rate. We will also focus on the influence of by-products such has NOx on kinetics. The mixture used is HF(40%)- HNO3(65%)-H3PO4(85%) with ratio 1-1-2.4.

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TUPB073

Vertical Electro-polishing Collaboration Between Cornell, KEK, and Marui Galvanizing Co. Ltd

cathode, cavity, SRF, linac

563

F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, 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
H. Hayano, S. Kato, T. Saeki
KEK, Ibaraki, Japan

Cornell's SRF group, KEK, and Marui Galvanizing Co. Ltd (MGI) have collaborated since 2014 on Vertical Electro-Polishing (VEP) R&D as a part of a US/Japan Program for Cooperation in High Energy Physics. We have focused on an improvement of removal uniformity during the VEP process. MGI and KEK have developed their original VEP cathode named i-cathode Ninja®, which has four retractable wing-shape parts per cell. Cornell processed one single cell cavity with VEP using this cathode and performed a vertical test. KEK also provided one 9-cell cavity to Cornell. Cornell then performed surface treatments including Cornell VEP and RF test on this 9-cell cavity. The progress by the VEP collaboration and RF test results are presented in this paper.

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TUPB074

RF Performance of Multi-cell Scale Niobium SRF Cavities Prepared with HF Free Bipolar Electro-polishing at Faraday Technology

cavity, SRF, niobium, MMI

567

F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T.D. Hall, M.E. Inman, R. Radhakrishnan, S.T. Snyder, E.J. Taylor
Faraday Technology, Inc., Clayton, Ohio, USA

Cornell's SRF group and Faraday Technology, Inc. have been collaborating on two phase-II SBIR projects. One of them is the development and commissioning of a 9-cell scale HF free Bipolar Electro-Polishing (BEP) system. Faraday Technology had completed the proof of principle on BEP with single cell scale prior to the work reported here, and has now developed a new 9-cell scale BEP system. Cornell has fabricated three single cell cavities and has assembled them together as a 9-cell scale test string. The 9-cell scale test string has received BEP at Faraday Technology and RF testing has been performed on the three single cell cavities one-by-one at Cornell. Here we give a status update on the new 9-cell scale BEP system commissioning and on results from RF tests of the BEP cavities.

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TUPB075

Vertical Electro Polishing of Superconducting Single-and Multi Cell Gun Resonators

gun, cavity, SRF, cathode

571

N. Steinhau-Kühl, R. Bandelmann, A. Matheisen, S. Saegebarth, M. Schmökel
DESY, Hamburg, Germany
A. Arnold
HZDR, Dresden, Germany

At DESY activities on surface treatment of superconducting RF gun cavity resonators at 1.3 GHz are ongoing. Due to the small opening on the endplate for insertion of cathodes, no reasonable acid flow can be realized with the existing set up for horizontal electro polishing. To benefit from electro polishing of Niobium surfaces, an adapter to the existing horizontal electro polishing bench at DESY was set up and is in operation now. Vertical EP was applied on 1.3 GHz SRF gun resonators with 1.6 and 3.5 cell geometry. Work flow, process conditions as well as test results of gun cavities treated so far at DESY are described.

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TUPB078

SUBU Characterisation: Bath Fluid Dynamics vs Etching Rate

cavity, simulation, ISOL, software

575

A. Perez Rodriguez, L.M.A. Ferreira, A. Sublet
CERN, Geneva, Switzerland

The chemical polishing bath SUBU is widely used at CERN to prepare copper RF cavities surfaces before niobium thin film coating; examples are HIE-ISOLDE, LHC and future FCC accelerating cavities. The performance of the polishing process is affected by bath temperature and fluid dynamics. As part of on-going activities to characterise SUBU, the actual study was done to identify a correlation between the etching rate and physical parameters linked to the bath fluid dynamics. A first approach was made using experimental data from a simplified model setup, transposing them via numerical simulation to a real cavity geometry and verifying the agreement with an experiment in a real size (HIE-ISOLDE) mock-up. In a second approach to improve the accuracy of the calculation, the relation of the measured local etching rates, extracted from the mock-up, to flow dynamics quantities extracted from simulation was investigated. As a result, a correlation between the local etching rate and the turbulence kinetic energy was obtained. This correlation can be exploited to improve the polishing tools and so optimise the current process, as well as to predict the etching rate in other cavity geometries.

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TUPB082

Setup of a Spatially Resolving Vector Magnetometry System for the Investigation of Flux Trapping in Superconducting Cavities

cavity, SRF, niobium, superconducting-cavity

580

B. Schmitz, K. 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.

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TUPB083

Post Processing of a 166.6 MHz HEPS-TF Cavity at Institute of High Energy Physics

cavity, SRF, photon, target

583

J. Dai, Z.Q. Li, P. Zhang
IHEP, Beijing, People's Republic of China

Funding: Work supported by High Energy Photon Source Test Facility (HEPS-TF) project
A 166.667 MHz Proof-of-Principle (PoP) superconducting RF cavity has been fabricated by IHEP for the High Energy Photon Source Test Facility (HEPS-TF) [1]. After a series of post-processing including chemical etching (BCP), high temperature heat treatment, High Pressure water Rinsing (HPR) and 120°C baking, the cavity was cold RF tested and reached E_peak=86.5 MV/m and B_peak=132.1 mT with Q₀=5.1×〖10〗⁸ at 4.2K. The cavity was RF tested again at 2K, and reached E_peak=85.5 MV/m and B_peak=131.1 mT with Q₀=3.3×〖10〗⁹.
daijin@ihep.ac.cn

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TUPB084

EP System Development at IHEP

cavity, controls, cathode, SRF

586

S. Jin, J. Dai, J. Gao, D.J. Gong, F.S. He, Z.Q. Li, Z.C. Liu, P. Sha, J.Y. Zhai, P. Zhang, T.X. Zhao
IHEP, Beijing, People's Republic of China

Electropolishing (EP) System is a critical facility for SRF cavity treatment, especially for high performance cavities which are necessary for several great projects like LCLS-II, CEPC, Shanghai XFEL, and so on. So, an EP system was under development at IHEP. At this stage, we would like a horizontal EP facility. Main purpose is for elliptical SRF Nb cavities like 500MHz single cell cavities. Besides, it should be compatible for other frequency cavities, such as 650MHz and 1.3GHz cavities. In this paper, we will mainly report the preliminary design for the EP system. Several key points in the design will be also discussed.

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TUPB085

Quench Detection on Superconducting Cavity by Second Sound

cavity, detector, site, SRF

589

Z.C. Liu, J. Gao, F.S. He, H.Y. Lin, P. Zhang
IHEP, Beijing, People's Republic of China

High gradient is very important for superconducting cavity, however it may be limited by quench on the cavity high field region. Quench can be caused by various reasons. To locate the position is the key to reveal the mysteries of quench. OST sensor was widely used to locate the quench position. Now we are developing the quench position detection system by RTD sensors such as Cernox. In this paper, we will show the design of the second sound system and testing results on the QWR cavity.

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TUPB086

Study on Local Chemical Treatment for Recovery From Surface Oxidation by HPR Process on SRF Cavities

cavity, experiment, SRF, niobium

592

H. Guo, Y. He, Y.M. Li, T. Tan, A.D. Wu, P.R. Xiong, Z.M. You, W.M. Yue, S.H. Zhang
IMP/CAS, Lanzhou, People's Republic of China

High pressure rinsing (HPR) with ultra-pure water (UPW) is the last step which is commonly used for SRF cavities cleaning. The serious surface damage will be caused due to the failure of the distance control between the jet and cavity surface or the breakdown of the jet rotation. The surface of taper HWR cavities which are used for CIADS project was damaged in HPR process. Two methods were used for surface recovery and the result will be presented in this paper.

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TUPB087

Low Temperature and Low Pressure Plasma for the HWR Superconducting Cavity In-situ Cleaning

electron, plasma, cavity, experiment

595

A.D. Wu, W. Chang, H. Guo, Y. He, C.L. Li, Y.M. Li, P.R. Xiong, L. Yang, W.M. Yue, S.H. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China
F. Gou
Sichuan University, Chengdu, People's Republic of China

The glow discharge for low temperature and low pressures plasma were utilized for the half-wave resonator (HWR) superconducting cavity in-situ cleaning. The plasma was on ignition of the Argon/Oxygen mixture atmosphere, which was under the low pressure of 0.5 to 5.0 Pascal. Driven by the RF power with the frequency of the cavity fundamental mode, the plasma showed the typical characteristic of the typical RF glow discharge, which the temperature of the electrons about 1eV that diagnosed by the optical emission spectrum. The experimental parameters for the discharge were optimized to obtain the uniform plasma distribution on the HWR cavity, including the RF power, the atmospheric pressure and the oxygen proportion. At last, the vertical cryogenic test was completed to investigate the impact of active oxygen plasma cleaning on the HWR cavity performance recovery, which contaminated by hydrocarbons. The test proves that the glow plasma clean can relieve the x-ray radiation which caused by the field electron emission effect.

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TUPB090

Investigation of High Temperature Baking of Jacketed Quarter Wave Resonators

cavity, linac, niobium, SRF

598

A. Rai, D. Kanjilal, K.K. Mistri, P. Patra, P.N. Potukuchi, S.K. Sonti
IUAC, New Delhi, India

The Superconducting booster Linac at IUAC has been delivering accelerated beams for scheduled experiments since 2013. It has three accelerating modules with 8 Quarter Wave Resonators (QWR)in each. The QWRs for the first module were built at Argonne National Laboratory while those for the second and third modules have been built in-house. During the electropolishing of one of the indigenously built resonators (QWR # I03) the RF surface got spoiled due to a wrong acid mixture that was being used for etching. In subsequent cold tests of the cavity, its performance was poor (2.6 MV/m @ 4W). There was evidence of Q disease also, as the performance deteriorated further (~20%) when the cavity was held at 100-120K for ~8 hours .In an attempt to recover the cavity it was baked at 650 °C for 10 hours along with its stainless steel jacket. A series of tests were conducted thereafter wherein, a substantial improvement (factor of two) in the performance was observed. Encouraged with the results another QWR designed for a lower beta (β=0.05) was also heat treated identically. This paper presents the different treatments followed to enhance the cavity performance vis-à-vis the test results.

Poster TUPB090 [1.240 MB]

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TUPB091

Study on Vertical Electropolising of 9-cell Niobium Coupon Cavity

cavity, cathode, niobium, polarization

602

V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan

Authors report a study on vertical electropolishing (VEP) carried out for a 1.3 GHz 9-cell niobium (Nb) coupon cavity using a unique cathode namely 'Ninja Cathode'. The design of the cathode for VEP of a 9-cell cavity was based on the Ninja cathode used for 1-cell cavity since the 1-cell Ninja cathode was found effective to reduce longitudinal asymmetry in material removal and to obtain a smooth surface of a 1-cell cavity. Moreover, 1-cell Nb cavities after being treated in VEP using the Ninja cathode showed good performance in vertical RF tests. The 9-cell coupon cavity used in this study was designed to have totally nine coupons set on the iris and equator positions of the first, fifth and ninth cells. These three cells contain viewports as well at their upper and lower iris positions. Measurement of currents from the individual coupons and in-situ observation are possible using the cavity to understand EP phenomenon at different locations of the cavity. VEP results, which include removal thicknesses at different positions of the cavity and surface study of the coupons, are discussed.

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TUPB092

Analysis of Niobium Surface and Generated Particles in Vertical Electropolishing of Single-cell Coupon Cavity

cavity, experiment, cathode, niobium

607

V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan

In our previous studies, we have reported parameter investigation for vertical electropolishing (VEP) of 1-cell niobium (Nb) tesla/ILC type cavities using a Ninja cathode. A 1-cell coupon cavity containing six Nb disk coupons at its different positions was found effective to reduce time and cost to establish an optimized VEP recipe. In this work, we present surface analyses of VEPed Nb coupon surfaces using scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX) and x-ray photoelectron spectroscopy (XPS). Surfaces contained micro- and nano-sized particles which were found with random distributions and different number densities on the beam pipe and iris coupons. Surfaces of equator coupons were found to have relatively less number of particles or almost clean. To analyze particles, a few particles were picked-up from a coupon surface using a tungsten tip under SEM and analyzed with EDX while the coupon was moved out from the SEM chamber to avoid its effect in EDX spectra. The particles were confirmed as oxygen-rich niobium and contained fluorine and carbon also. XPS analysis of the coupon surfaces was also carried out for further study of surface chemistry.

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TUPB093

Nb Single-cell Cavity Vertical Electro-polishing with Ninja Cathode and Evaluation of its Accelerating Gradient

cavity, cathode, experiment, accelerating-gradient

612

K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
P. Carbonnier, Y. Gasser, L. Maurice
CEA/IRFU, Gif-sur-Yvette, France
F. Éozénou, C. Servouin
CEA/DSM/IRFU, France
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan
Th. Proslier
CEA/DRF/IRFU, Gif-sur-Yvette, France

Marui Galvanizing Co. Ltd. has been improving Vertical Electro-Polishing (VEP) technology for Nb superconducting RF cavity in collaboration with KEK. In this collaboration, we developed a unique cathode namely Ninja cathode for VEP treatment of Nb cavities. We have already reported that longitudinal symmetry in niobium removal and surface state of a single cell cavity were improved after VEP using the Ninja cathode. In this article, we report a result of accelerating gradient evaluation for 1.3 GHz single cell RF cavity after VEP with Ninja cathode in collaboration with KEK and CEA Saclay.

Poster TUPB093 [0.704 MB]

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TUPB095

Modeling the Hydroforming of a Large Grain Niobium Tube With Crystal Plasticity

cavity, niobium, experiment, SRF

616

A. Mapar
MSU, East Lansing, Michigan, USA
T.R. Bieler
Michigan State University, East Lansing, Michigan, USA
J.E. Murphy
University of Nevada, Reno, Reno, Nevada, USA
F. Pourboghrat
Ohio State University, Columbus, Ohio, USA

Current SRF cavities are made from fine grained polycrystalline niobium half-cells welded together. Hot spots are commonly found in the heat-affected zone, making seamless hydroformed cavities attractive. Large grain cavities usually perform as well as fine grain cavities, often having a higher Q, presumably due to fewer grain boundaries. Large grain Nb forms non-uniformly, which introduces problems in manufacturing. A model that could realistically predict the deformation response of large grain Nb could facilitate the design of large grain hydroformed tubes. To this end, a crystal plasticity model was developed and calibrated with tensile stress-strain data of Nb single crystals. A seamless large grain tube was made from rolling a fine grain sheet into a tube, welded, and heat treated to grow large grains. The heat treatment resulted in a large grain tube with a single grain orientation in the center. The tube was hydroformed until it cracked. The hydroforming process was simulated with the crystal plasticity model, which was able to predict the deformed shape of the tube, the location of the crack and other localized areas with heterogeneous strain.

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TUPB096

SRF Cavity Assembly in Clean Room with Horizontal Laminar Flow

cavity, GUI, SRF, cryomodule

620

A. Miyamoto, H. Hara, K. Sennyu, T. Yanagisawa
MHI-MS, Kobe, Japan

Mitsubishi Heavy Industries Mechatronics Systems(MHI-MS) has developed manufacturing process of superconducting cavitis for a long time. In this presentation, recent progress will be reported.

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TUPB097

R&D of Electro-polishing (EP) Process with HF-free Neutral Electrolyte by Bipolar-pulse (BP) Method

experiment, cavity, SRF, cathode

623

J. Taguchi, Y. Mochida, T. Nakajima
Nomura Plating Co, Ltd., Osaka, Japan
H. Hayano, T. Saeki
KEK, Ibaraki, Japan
S. Kakudo, M. Kunieda
The University of Tokyo, Tokyo, Japan

Currently the Electro-Polishing (EP) process of Superconducting Radio-Frequency (SRF) accelerating cavity is performed with the electrolyte that is the mixture of hydrofluoric and sulfuric acids. However, the electrolyte is very dangerous and the environmental load in the disposal process of electrolyte is very heavy. This is the reason why the high cost is necessary in the safe design of facility and the safe operation of process in the conventional EP method. In such situation, considering the reduction of cost and environmental load in the EP process, we performed the R&D of novel EP process with HF-free neutral electrolyte by Bipolar-Pulse (BP) method. In this presentation, we will report the removal rate, surface roughness and the results of surface analysis for the Nb-coupon samples that were processed by the BP-EP with HF-free neutral electrolyte.

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TUPB098

The Effect of Process Parameters on the Surface Properties of Niobium During Plasma Etching

plasma, cavity, experiment, SRF

628

J.J. Peshl, S. Popović, L. Vušković
ODU, Norfolk, Virginia, USA
J. Upadhyay
LANL, Los Alamos, New Mexico, USA
A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: This work is supported by the Department of Energy, Grant DE-SC0014397.
We have shown that plasma etching using an electronegative Ar/Cl2 discharge can effectively remove surface oxide layers on Nb samples as well as bulk Nb from single cell SRF cavities*. With accelerating fields on the order of wet etching processes and a decrease in field emission the use of plasma assisted etching for bulk Nb processing is a worthwhile endeavor. We are presenting the surface properties of plasma etched Nb. Cavity grade Nb coupons were made by water jet cutting, and then polished to achieve surface roughness equivalent to electropolishing (<1 micron). The coupons were plasma etched while process parameters (rf power, gas pressure, temperature and DC bias voltage) are varied. These samples are placed on the inner surface of the cylindrical cavity to be etched. The experimental setup is similar to the single cell cavity plasma etching setup. Each sample is weighed and scanned before and after plasma processing with an AFM, SEM, and digital optical microscope that provide both atomic composition and surface roughness profiles. Comparing the scans allows us to make conclusions about the effect of each parameter on the surface roughness.
J. Upadhyay et. al. 'Cryogenic rf test of the first plasma etched SRF cavity,' arXiv: 1605.06494 [physics.acc-ph] (2016).

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TUPB099

Vertical Test System for Superconducting RF Cavities at Peking University

cavity, shielding, radiation, controls

631

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

A new vertical test system (VTS) for superconducting RF cavities has been designed and constructed at Peking University. This facility is designed to operate at a temperature of 2K and with pumping speed of 10g/s for helium gas at 30 mbar. In this paper, we present the structure design, modification of 2K system, ambient magnetic field and radiation shielding, LLRF and the test run of this VTS.

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TUPB100

Determining BCP Etch Rate and Uniformity in High Luminosity LHC Crab Cavities

cavity, experiment, simulation, SRF

635

T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Calaga, O. Capatina, L.M.A. Ferreira, R. Leuxe
CERN, Geneva, Switzerland
T.J. Jones, J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
S.M. Pattalwar
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S. Verdú-Andrés, B. P. Xiao
BNL, Upton, Long Island, New York, USA

The compact SRF Crab Cavities required for HL-LHC have complex geometries making prediction of average and local BCP etch rates a difficult task. This paper describes a series of experiments and simulations used to determine the etch uniformity and rate within these structures. An initial experiment was conducted to determine the correlation between etch rate and flow rate in a Nb tube. These results were then incorporated into Computational Fluid Dynamics simulations of acid flow in the Double Quarter Wave (DQW) cavity to predict etch rates across the surface and allow optimisation of the BCP setup. There were several important findings from the work; one of which is that the flow rate in the relatively large body of the cavity is predominantly driven by natural convection due to the exothermic reaction. During BCP processing of the DQW cavity a significant difference in etching was observed between upper and lower horizontal surfaces which was mitigated by etching in several orientations. Two DQW cavities manufactured by CERN have received a heavy BCP of 200μm followed by 2 light BCPs of 30μm each with subsequent vertical cold tests showing performance exceeding specification.

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TUPB103

DC Magnetism of Niobium Thin Films

site, niobium, cavity, power-supply

640

S. Wilde, B. Chesca
Loughborough University, Loughborough, Leicestershire, United Kingdom
A.N. Hannah, O.B. Malyshev, N. Pattalwar, S.M. Pattalwar, B.S. Sian, R. Valizadeh, S. Wilde
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
B.S. Sian
UMAN, Manchester, United Kingdom
G.B.G. Stenning
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

Niobium thin films were deposited onto a-plane sapphire with varying kinetic energy and varying substrate temperature. There were no consistent trends which related the particle energy or substrate temperature to RRR. The sample which displayed the largest RRR of 229 was then compared to both a thin film deposited with similar conditions onto copper substrate and to bulk niobium. DC magnetometry measurements suggest that the mechanism of flux entry into thin film niobium and bulk niobium may vary due to differences in the volumes of both defects and impurities located within the grains. Results also suggest that magnetic flux may penetrate thin films at small fields due to the sample geometry.

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TUPB104

First Full Cryogenic Test of the SRF Thin Film Test Cavity

cavity, SRF, cryogenics, niobium

644

R. Valizadeh, L. Bizel-Bizellot, P. Goudket, L. Gurran, O.B. Malyshev, N. Pattalwar, S.M. Pattalwar
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt, L. Gurran
Lancaster University, Lancaster, United Kingdom
G. Burt, P. Goudket, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom
L. Gurran
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

A test cavity that uses RF chokes, rather than a physical seal, to contain the field is a promising method of SRF sample testing, especially in thin films research where the rate of sample production far outstrips that of full SRF characterisation. Having the sample and cavity physically separate reduces the complexity involved in changing samples - major causes of low throughput rate and high running costs for other test cavities - and also allows direct measurement of the RF power dissipated in the sample via power calorimetry. Choked test cavities operating at 7.8 GHz with three RF chokes have been designed and tested at Daresbury Laboratory. As part of the commissioning of this system, we performed the first full SRF test with a bulk Nb sample and we verified that the system would perform as required for future superconducting thin film sample tests.

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TUPB106

Standardized Beamline Particulate Characterization Analysis: Initial Application to CEBAF and LCLS-II Cryomodule Components

cavity, SRF, cryomodule, linac

647

C.E. Reece, J.K. Spradlin, O. Trofimova, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Despite continuously evolving efforts to minimize particulates in operational SRF accelerator systems, the presence of electron field emission from contaminating particulates on SRF surfaces with high surface electric fields remains a challenge. Jefferson Lab has recently initiated a standardized particulate sampling and characterization practice in order to gain more systematic knowledge of the particulates actually present. It is expected that patterns that emerge from such sampling will strengthen source attribution and guide improvement efforts. Initial samples were gathered from a cryomodule and adjoining warm girders removed from the CEBAF tunnel for reprocessing. The collection and analysis techniques were also used to characterize particulates on the inside of LCLS-II string components. Samples are transferred to clean industry-standard forensic GSR carbon tape spindles and examined via automated cleanroom SEM scanning for particle localization and sizing. The particulates are subsequently analyzed with EDS for elemental composition. A catalogue of particle types is being accumulated. The methods used and results obtained from these initial applications will be presented.

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TUPB108

Genesis of Topography in Buffered Chemical Polishing of Niobium for Application to Superconducting Radiofrequency Accelerator Cavities

niobium, cavity, electron, SRF

651

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

Funding: Supported by Office of High Energy Physics, U.S. Department of Energy, Grant SC0007907 to the College of William & Mary and by U.S. DOE Contract No. DE-AC05-06OR23177 to Jefferson Science Associates
Topography arising from the final etch step in preparing niobium superconducting radiofrequency (SRF) accelerator cavities is understood to significantly impact cavity performance at high field levels. This study investigated the effect of process temperature and time on the etch rate and topography arising from the widely-used buffered chemical polishing (BCP). This study aims to understand more thoroughly the genesis of topography in BCP of polycrystalline niobium, with the ultimate aim of finding a path to surface smoothness comparable to that obtained by electropolishing (EP). It was found that the etch process is controlled by the surface reaction; and that the etch rate varies with crystallographic orientation. The familiar micron-scale roughening necessarily results. Gas evolution has an impact, but is secondary. The major outcome is that surface smoothness comparable to EP appears to be inherently unachievable for polycrystalline niobium using BCP, setting an upper limit to the gradient for which it is useful.

Poster TUPB108 [3.782 MB]

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TUPB111

R&D Activities on Centrifugal Barrel Polishing of 1.3 GHz Niobium Cavities at DESY/University of Hamburg

cavity, niobium, ECR, laser

655

A.L. Prudnikava, B. Foster, Y. Tamashevich
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
A. Ermakov, B. Foster
DESY, Hamburg, Germany
Y. Tamashevich
HZB, Berlin, Germany

In this paper the status of research activities at ILC-HiGrade Lab (DESY/University of Hamburg) on Centrifugal Barrel Polishing (CBP) of 1.3 GHz Niobium Cavities is presented. We focus on CBP based on the polishing recipe reported by Fermi National Laboratory and Jefferson Lab*. The aim is to gain a better understanding of the limitations of this technique, detailed characterization of the treated surface after each polishing step using a "coupon" single cell cavity. Plastic deformations upon initial CBP steps, embedded polishing media and residual damage upon final polishing were investigated at different areas of the cavity.
* C. A. Cooper, L. D. Cooley, Supercond. Sci. Technol. 26 (2013) 015011

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TUPB112

First Test of Electropolishing System at IMPCAS

cavity, cathode, controls, SRF

660

L. Li, Q.W. Chu, H. Guo, Y. He, P.R. Xiong, Z.Q. Yang, Z.M. You, B. Zhang, S.H. Zhang, X. Zhu
IMP/CAS, Lanzhou, People's Republic of China

The first SRF cavity electropolishing system of China has been built by IMPCAS. We used two type of cathodes in different process parameters to test the typical Voltage-Current Density curves of 1.3GHz one-cell SRF cavity.

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TUPB113

Surface Characterization of Nitrided Niobium Surfaces

niobium, cavity, electron, experiment

663

A.L. Prudnikava, B. Foster
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
B. Foster
DESY, Hamburg, Germany
Y. Tamashevich
HZB, Berlin, Germany
Y. Tamashevich
University of Hamburg, Hamburg, Germany

Thermal treatment of niobium radio frequency cavities in nitrogen atmosphere is employed in ILCLS-II Project in order to improve the quality factor of Nb cavities. A so called "N-infusion" thermal treatment is applied without any post processing*, **, whereas "N-doping" requires the removal of the upper layer of 5-30 um. For better understanding the mechanism of such an improvement, a detailed characterization of the nitrided surface is necessary. Our studies are focused on characterization of the niobium surface subjected to such treatments (surface morphology, nitrogen concentration profile, hardness, phase composition). The sample preparation technique for studying the hydride precipitation in N-Nb system is presented, and current activities on studying of N-infused Nb samples by SQUID and PPMS are briefly discussed.
* A. Grassellino, et al, Supercond. Sci. Technol. 26 (2013) 102001.
** A. Grassellino, arXiv:1701.06077

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WEXA01

High Performance Nb3Sn Cavities

cavity, niobium, SRF, site

667

D.L. Hall, M. Liepe, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T. Arias, P. Cueva, D. Liarte, D.A. Muller, J.P. Sethna, N. Sitaraman
Cornell University, Ithaca, New York, USA

In recent years, 1.3 GHz single-cell cavities coated with Nb3Sn at Cornell University have repeatedly demonstrated quality factors of >10¹⁰ at 4.2 K and >15 MV/m. Ongoing research is currently focussed on the impact of intrinsic and extrinsic factors that limit the quality factor and quench field in these cavities. New single-cell cavities have been commissioned to enable further exploration of the coating parameter space. Experimental studies on both cavities and sample coupons have been supplemented by theoretical work done on layer growth, trapped vortex motion and flux entry. In this paper, we provide a comprehensive overview of the latest developments on Nb3Sn cavities, including work conducted in collaboration with the new NSF Centre for Bright Beams, with a brief summary on work being done in the field at large.

Slides WEXA01 [10.681 MB]

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WEXA03

High-performance Thin-film Niobium Produced via Chemical Vapor Deposition (CVD)

niobium, cavity, SRF, electron

674

R.D. Porter, D.L. Hall, M. Liepe, J.T. Maniscalco
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

Bulk niobium cavities have been the standard for superconducting particle accelerators for many years. However, the cost of high RRR niobium start materials makes them expensive. The use of Chemical Vapor Deposition (CVD) processing technologies to produce thin Nb films on low-cost substrates (e.g. copper) offers a method to significantly reduce the cost of accelerator cavity fabrication while increasing cavity performance capabilities. Recent optimization of CVD niobium processes for high RRR Nb films has led to RF performance approaching that of bulk Nb. In collaboration with Ultramet, Cornell continues to explore the potential of CVD techniques. This paper presents results from a detailed study of CVD thin film Nb materials produced by Ultramet on 5-inch diameter copper and molybdenum substrates, including RF performance results with T-mapping and detailed surface analysis of performance limiting regions. Our work shows that CVD-based cavity fabrication methods are a promising alternative to sheet-formed bulk cavities, and to other thin Nb film techniques, warranting further development. Additional results from the field will be discussed.

Slides WEXA03 [1.503 MB]

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WEYA02

Construction and Performance Tests of Prototype Quarter-wave Resonator and Its Cryomodule at RIKEN

cavity, cryomodule, linac, multipactoring

681

N. Sakamoto, O. Kamigaito, H. Okuno, K. Ozeki, K. Suda, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
H. Hara, K. Sennyu, T. Yanagisawa
MHI-MS, Kobe, Japan
E. Kako, H. Nakai, K. Umemori
KEK, Ibaraki, Japan
K. Okihira
MHI, Hiroshima, Japan

Funding: This research work was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).
This paper describes the development of a superconduct- ing quarter-wave resonator for use in an intense low-β-ion linear accelerator. The prototype cavity was fabricated from bulk Nb, inner cavity surface processing was per- formed, and vertical testing was carried out. In the vertical test, a Q-value of 8.7·10⁸ was obtained with an operating field gradient of 4.5 MV/m at a frequency of 75.5 MHz. Here, we describe the results of the performance tests and various phenomena we experienced during the tests. After the vertical tests, the helium vessel was assembled and the prototype resonator was integrated into a cryomodule. Initial cooldown testing results are described. Performance testing of the cryomodule is continuing. The situation of upgrade of the RIKEN heavy-ion RIKEN Linac (RILAC) is also reported.

Slides WEYA02 [7.751 MB]

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WEYA03

A Seamless Quarter-wave Resonator for HIE-ISOLDE

cavity, linac, ISOL, cryomodule

686

S. Teixeira Lopez, M.A. Fraser, M. Garlaschè, T. Mikkola, A. Miyazaki, A. Sublet, W. Venturini Delsolaro
CERN, Geneva, Switzerland

The superconducting linac booster for the HIE ISOLDE project, in operation at CERN, is based on NB/Cu coated Quarter Wave Resonators. The performance of the series cavities has been limited by defects in the copper substrates close to the EB weld. A novel cavity design has been developed and prototyped, in order to make it possible manufacturing of the resonators by machining them from the bulk, without any weld. The RF design was optimized for the customary figures of merit, and fully integrated in the HIE ISOLDE cryomodule. Mechanical tolerances were assessed in relation to the available range of pre tuning, and demonstrated on a dummy prototype. Beam dynamics simulations were carried out to check the effects on the beams when the new cavities will be installed in the high energy end of the linac. The presentation will cover the design and the first experimental results of the first Nb/Cu seamless QWR for HIE ISOLDE.

Slides WEYA03 [5.262 MB]

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WEYA05

Progress Toward 2 K High Performance Half-wave Resonators and Cryomodule

cavity, cryomodule, cryogenics, SRF

692

Z.A. Conway, B.M. Guilfoyle, M. Kedzie, M.P. Kelly, T. Reid
ANL, Argonne, Illinois, USA
H. Guo
IMP/CAS, Lanzhou, People's Republic of China

Funding: This material is based upon work supported by the U.S. DOE, Office of Science's Office of Nuclear Physics and Office of High Energy Physics, contract numbers DE-AC02-06CH11357 and DE-AC02-76CH03000.
Argonne National Laboratory is implementing a novel 2.0 K superconducting cavity cryomodule operating at 162.5 MHz. This cryomodule is designed for the acceleration of 2 mA H-/proton beams from 2.1 to 10.3 MeV as part of the Fermilab Proton Improvement Project-II (PIP-II). The 2.0 K cryomodule is comprised of 8 half-wave cavities operated in the continuous wave mode with 8 superconducting magnets, one in front of each cavity. In this paper we will review recent cavity results which demonstrate continuous-wave operated cavities with low-field residual resistances of 2.5 nΩ which achieve peak surface fields up to 134 MV/m and 144 mT, electric and magnetic respectively, with field emission onset fields greater than 70 MV/m in the production cavities following the prototyping effort.

Slides WEYA05 [1.967 MB]

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THXA03

Crab Cavities for the High-luminosity LHC

cavity, luminosity, cryomodule, HOM

695

R. Calaga
CERN, Geneva, Switzerland

Funding: This work has been supported by the HL-LHC project (and by DOE or any other collaborating institutes, when applicable).
As a first step towards the realization of crab crossing for HL-LHC, two superconducting crab cavities are foreseen to be tested with proton beams for the first time in the SPS. The progress on the cavity fabrication, RF test results, cryomodule development and integration into the SPS are presented. Some aspects of the beam tests with crab cavities in the SPS are outlined.

Slides THXA03 [12.629 MB]

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THXA04

Fabrication, Treatment and Test of Large Grain Cavities

cavity, SRF, superconducting-cavity, FEL

700

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

Development of SRF technology has been included in the project of Soft X-ray FEL (SXFEL) for a hard X-ray FEL plan in China which would be operated in CW mode. Six 9-cell TESLA type cavities as well as several single-cell cavities made of Ningxia large grain niobium material have been fabricated by Peking University for achieving high gradient and high intrinsic quality factor Q0. The measurements of gradient and Q0 have been carried out with a new vertical test system at PKU. The process of fabrication, surface treatment and test results of these large grain cavities will be presented.

Slides THXA04 [7.911 MB]

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THXA06

Advanced OST System for the Second-sound Test of Fully Dressed Cavities

cavity, power-supply, FEL, detector

703

Y. Tamashevich
HZB, Berlin, Germany
Y. Tamashevich
University of Hamburg, Hamburg, Germany

Cavities which exhibit a low field quench are normally discarded from usage in accelerator projects. However, they can be repaired if the exact location of the quench is known. Optical inspection alone cannot reliably locate the source of a quench. Methods that directly measure the quench, such as thermometry or second sound detection, could so far only be performed at undressed cavities. A new, specially designed, second-sound system for the first time allows the localization of the quench in multicell cavities equipped with a helium vessel. It can be easily installed in the helium pipe of the cavity. Information on the quench location can be acquired during a standard rf test. A new algorithm localizes the quench based on the real path of the second-sound wave around the cavity surface, rather than using simple triangulation. The implemented pathfinding method leads to a high precision and high accuracy of the quench location. This was verified by testing standard dressed 9-cell XFEL cavities. The system can be easily applied to other cavity shapes and sizes.

Slides THXA06 [9.681 MB]

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THXA08

Review of Heat Treatments for Low Beta Cavities : What's So Different from Elliptical Cavities

cavity, SRF, niobium, accelerating-gradient

708

D. Longuevergne
IPN, Orsay, France

Heat treatments done for low beta (low frequency) cavities are usually, due to the lack of feedback, inspired from elliptical (high frequency) cavity results. Is that still relevant now that experimental data are available thanks to the florishing business of low beta structures (Spiral2, ESS, FRIB, C-ADS, MYRRHA, PROJECTX, …). These 2 families are moreover not usually operating in the same resistance regime (BCS and residual). The paper will review procedures applied and results obtained on different type of cavities (Quarter-Wave resonator, Half-Wave resonator and Spoke) and different temperature treatments (low temperature baking, hydrogen degassing, nitrogen doping, …) and compare these to elliptical cavities.

Slides THXA08 [5.567 MB]

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THYA01

Performance Testing of FRIB Early Series Cryomodules

cavity, cryomodule, linac, SRF

715

J.T. Popielarski, C. Compton, A. Ganshyn, W. Hartung, D. Luo, S.J. Miller, D.G. Morris, P.N. Ostroumov, L. Popielarski, K. Saito, S. Shanab, S. Stark, T. Xu, S. Zhao, Z. Zheng
FRIB, East Lansing, USA

Funding: U.S. Department of Energy Office of Science under Cooperative Agreement DE SC0000661.
Construction of a new accelerator for nuclear physics research, the Facility for Rare Isotope Beams (FRIB), is underway at Michigan State University (MSU). The FRIB linac will use superconducting resonators at an operating temperature of 2 K to accelerate ions to 200 MeV per nucleon. The linac requires 10⁶ quarter wave resonators (80.5 MHz, β = 0.043 and 0.086) and 248 half wave resonators (322 MHz, β = 0.29 and 0.54), all made from sheet Nb. Production resonators being delivered to MSU by cavity vendors. At MSU, the resonators are etched, rinsed, and tested in MSU's certification test facility. Certification testing is done before the installation of the high-power input coupler and the tuner. After certification, the resonators are tested in the cryomodule before installation into the FRIB tunnel. The cryomodule test goals are to verify integrated operation of the resonators, RF couplers, tuners, RF controls, and superconducting solenoids. To date, 10 cryomodules out of 48 have been fabricated, and 8 of the cryomodules have been certified. Cryomodule test results are presented in this paper.

Slides THYA01 [31.165 MB]

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THYA02

Achievement of Stable Pulsed Operation at 36 MV/m in STF-2 Cryomodule at KEK

cavity, cryomodule, operation, accelerating-gradient

722

Y. Yamamoto, T. Dohmae, M. Egi, K. Hara, T. Honma, E. Kako, Y. Kojima, T. Konomi, T. Kubo, T. Matsumoto, T. Miura, H. Nakai, K. Nakanishi, G.-T. Park, T. Saeki, H. Shimizu, T. Shishido, T. Takenaka, K. Umemori
KEK, Ibaraki, Japan

In the Superconducting RF Test Facility (STF) in KEK, the cooldown test for the STF-2 cryomdoule with 12 cavities has been done totally three times since 2014. In 2016, the 3rd cooldown test for the STF-2 cryomodule including the capture cryomodule with 2 cavities was successfully carried out. The main achievement is the vector-sum operation with 8 cavities at average accelerating gradient of 31 MV/m as the ILC specification (2 of 8 cavities achieved 36 MV/m with piezo compensation), and the others are the measurement for Lorenz Force Detuning (LFD) and unloaded Q value, and Low Level RF (LLRF) study, etc. In this paper, the result for the STF-2 cryomodule in three cooldown tests will be presented in detail.

Slides THYA02 [4.042 MB]

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THYA05

Developments and Progress with ESS Elliptical Cryomodules at CEA-Saclay and IPN-orsay

cavity, cryomodule, cryogenics, vacuum

729

F. Peauger, C. Arcambal, F. Ardellier, S. Berry, P. Bosland, A. Bouygues, E. Cenni, J.-P. Charrier, G. Devanz, F. Éozénou, A. Gaget, D. Gevaert, A. Gomes, T. Hamelin, X. Hanus, P. Hardy, V.M. Hennion, T.J. Joannem, C. Marchand, O. Piquet, J.P. Poupeau, B. Renard, P. Sahuquet, T. Trublet
CEA/DRF/IRFU, Gif-sur-Yvette, France
C. Darve
ESS, Lund, Sweden
G. Olivier
IPN, Orsay, France

CEA Saclay in collaboration with IPN Orsay is in charge of the ESS elliptical cavities cryomodule design, prototyping and series production. Two cryomodule prototypes are being developed and will be tested at CEA Saclay before starting the series production. The main cryomodule design features are first reminded. We present the cavities and couplers test results and the achieved assembly sequences of the first medium beta cavities cryomodule demonstrator M-ECCTD. The progress on the preparation of the CEA cryomodule test station is given. The procurement status and development plan of the second high beta demonstrator H-ECCTD are also reported. Finally we give the components procurement progress and the assembly strategy of the 30 series cry-omodules to be integrated at CEA before delivery to ESS at Lund.

Slides THYA05 [11.226 MB]

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THYA06

Long-term Operation Experience with Beams in Compact ERL Cryomodules

cavity, operation, linac, cryomodule

736

K. Umemori, M. Egi, K. Enami, T. Furuya, Y. Honda, E. Kako, T. Konomi, H. Sakai
KEK, Ibaraki, Japan
T. Okada
Sokendai, Ibaraki, Japan
M. Sawamura
QST, Tokai, Japan

Compact ERL (cERL) was constructed at KEK as a prototype for 3GeV ERL light source. It consists of two types of SRF cavities. Three injector 2-cell SRF cavities and two main linac 9-cell SRF cavities. The beam operation started at 2013, with 100 nA (CW). Beam current increased step by step and currently reached to 1 mA (CW). Energy recovery has successfully achieved. Performance of the SRF cavities through long term beam operation has been investigated. With the beam induced HOMs, the beam position and the beam timing were studied. cERL has suffered from heavy field emissions in operation. Field emissions of the main linac cavity started just after module assembly work, and during beam operation, performances of both the main linac and the injector SRF cavities sometimes degraded. One reason of degradation was discharges occurred at beamline components due to charge up of electrons. Pulse aging technique helped to recover SRF performances. In this presentation, details of SRF beam operation, degradation, applied recovery methods are described.

Slides THYA06 [4.973 MB]

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THPB002

Role of Nitrogen on Hydride Nucleation in Pure Niobium by First Principles Calculations

niobium, site, cavity, electron

741

P. Garg, I. Adlakha, K.N. Solanki
Arizona State University, Tempe, USA
S. Balachandran, P.J. Lee
NHMFL, Tallahassee, Florida, USA
T.R. Bieler
Michigan State University, East Lansing, Michigan, USA

It is known that formation and growth of Nb hydride degrades superconducting radio frequency (SRF) properties of Nb cavities and the treatments that reduce H concentration improve quality factor. Recently it is has also been shown that addition of N through doping or infusion improves the quality factor. Thus, we probe role of N addition in Nb on hydride precipitation and stability through first principles calculations & compared with coupon samples. In presence of N, energetic preference for H to occupy interstitial sites in the vicinity of N is reduced. Furthermore, presence of N forces H to occupy interstitial octahedral site instead of a tetrahedral site. The thermodynamic stability of hydride is decreased in the presence of N in Nb.The quantum insights using charge transfer and density of states show a strong tendency of N to accumulate charge, thereby decreasing the bond strength of neighboring Nb and H atoms. These atomic scale results explain the lesser tendency of surface hydride formation in SRF Nb cavities in presence of N. These results are consistent with metallographic examination of N-treated Nb coupons, which show suppressed hydride formation near N-treated surface.

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THPB003

An Innovative Design of a Flexible Temperature-mapping System

cavity, SRF, electron, superconducting-cavity

746

M. Ge, F. Furuta, M. Liepe, P.J. Pamel
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

A temperature-mapping (T-Map) system is an essential tool for fundamental SRF research as it provides spatial information of RF power dissipation and so allows localizing hot-spots on a cavity surface at cryogenic temperatures. However, the temperature sensors are mounted on rigid boards in most current systems, so each can only work for one specific cavity size and shape. In this paper, we proposed a flexible design, which allows this temperature mapping system to work for different cavity shapes.

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THPB004

Impact of the Duration of Low Temperature Doping on Superconducting Cavity Performance

cavity, niobium, vacuum, superconducting-cavity

750

P.N. Koufalis, F. Furuta, J.J. Kaufman, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Low temperature treatments of superconducting cavities in a low pressure ambient atmosphere have been shown to introduce a 'Q-rise' up to moderate surface fields and an overall increase in quality factor. However, the effect of varying the doping time at a fixed temperature on cavity performance has not been systematically examined. We present results of such an investigation for cavities prepared at 120 and 160 C in a continuously flowing low pressure atmosphere for various amounts of time. We show that the introduction of impurities to the RF penetration layer can improve cavity performance and investigate the relationship between electron mean free path and the temperature-dependent component of the surface resistance.

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THPB005

Design Updates on Cavity to Measure Suppression of Microwave Surface Resistance by DC Magnetic Fields

cavity, niobium, SRF, experiment

754

J.T. Maniscalco, M. Liepe, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Our research has shown good agreement between experimental measurements of the anti-Q-slope in niobium SRF cavities and predictions from a recent theoretical model of the suppression of the microwave surface resistance with applied RF field. To confirm that this mechanism is indeed what causes the anti-Q-slope in impurity-doped niobium, it will be necessary to measure the theory's prediction that the same effect may be achieved by applying a constant (i.e. DC) magnetic field parallel to the RF surface. This will also allow for systematic studies of the proposed fundamental effect of the anti-Q-slope and of the behavior of the anti-Q-slope for many surface preparations and alternative materials, since it provides a cleaner measurement by eliminating the counteracting quasiparticle overheating and the complexifying oscillation of the screening currents. In this report we give an update on work at Cornell to design and build a coaxial cavity to measure this effect.

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THPB007

Nitrogen Infusion R&D on Single Cell Cavities at DESY

cavity, niobium, SRF, injection

759

M. Wenskat, D. Reschke, J. Schaffran
DESY, Hamburg, Germany
A.L. Prudnikava
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

A first series of single cell cavities underwent the "Nitrogen Infusion" treatment at DESY. Samples, which were in the furnace together with the cavities, underwent a series of SEM/EDX measurements and showed some unexpected structures. In parallel, the cavity performance deteriorated after the treatment. The furnace pressure and temperature and the residual gases during the treatment were analyzed and the possible cause for the deterioration has been found. Steps to prevent this deterioration in following treatments are discussed and first results are shown.

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THPB017

Investigation of Trapped Magnetic Flux in Superconducting Niobium Samples with Neutron Radiography

neutron, niobium, experiment, detector

762

O. Kugeler, T. Junginger, J. Knobloch, M.M. Krzyzagorski, J.M. Köszegi, L. Riik, W. Treimer, R.F. Ziesche
HZB, Berlin, Germany

The dynamics of flux expulsion in Nb samples during superconducting transition has been investigated with neutron radiography. Aiming at a reduction of the trapped flux with respect to obtaining a small residual resistance it was attempted to influence the expulsion by applying external AC magnetic fields. The results of these experiments are presented.

Poster THPB017 [1.528 MB]

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THPB018

Towards the Perfect Meissner State: A Magneto-Optical Study on Competing Pinning Centers in Niobium

niobium, cavity, SRF, background

766

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

Over the past years trapped magnetic flux has emerged as a main limiting factor of high quality factors in SRF cavities. Several studies investigated how the ambient magnetic field can be minimized or how the flux expulsion during the phase transition can be improved. We now present a study that targets the pinning centers which allow for the flux to remain inside the superconductor in the first place. Using magneto-optical imaging we were able to not only measure the amount of trapped flux but in addition we managed to image its distribution with a resolution below 10μm and correlate it with electron backscatter diffraction maps. As a result we found that the grain boundaries did not play a major role as pinning centers nor did the crystal orientation influence the amount of trapped flux signifi-cantly. Niobium hydrides which formed during the cool down to cryogenic temperatures however were found to enhance trapping.

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THPB019

Simulation of the Thermoelectrically Generated Magnetic Field in a SC Nine-cell Cavity

cavity, simulation, experiment, ECR

771

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 superconducting phase transition. The trapped flux causes additional dissipation during operation and can therefore significantly degrade the cavity's quality factor. We simulated the distribution of the generated magnetic field for different temperature distributions and compared the results to experimental findings. Furthermore, the impact of a growing superconducting area was investigated. The simulations complement the experimental studies because measurements were only feasible with a limited number of probes and restricted to selected locations and orientations. The simulations allow to analyze this data in the context of the whole system.

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THPB021

Trial of Nitrogen Infusion and Nitrogen Doping by Using J-PARC Furnace

cavity, niobium, controls, SRF

775

T. Konomi, T. Dohmae, Y. Hori, E. Kako, T. Kubo, G.-T. Park, H. Sakai, K. Umemori
KEK, Ibaraki, Japan
J. Kamiya, K. Takeishi
JAEA/J-PARC, Tokai-mura, Japan
T. Nagata
ULVAC, Inc., Tsukuba, Japan

KEK has been carrying out SRF cavity developments toward higher Q-values and higher accelerating gradients. In the past nitrogen-doping was tested using the KEK furnaces, but it did not succeed. This time nitrogen infusion and nitrogen doping are tested using the J-PARC's furnace, which has an oil-free pumping system and is mainly pumped by a 10000 L/s cryopump and three 3000 L/s turbo pumps. Nitrogen pressure is controlled by a variable leak valve and an additional turbo pump. To avoid performance degradation during heat treatment, flanges of cavities are covered by Nb caps and foils. Nitrogen infusion at 120 degrees was applied to a single cell cavity and cavity performance was measured by vertical tests after HPR and assembly. Nitrogen doping at 800 degrees is also applied to another single cell cavity. After applying EP and HPR, vertical tests were carried out. Nb samples were also installed into the furnace during heat treatment. Surfaces are analyzed by SIMS and XPS. In this presentation, we report procedure of nitrogen infusion and doping, vertical test results and results of surface analysis.

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THPB024

Investigation on Depth Profiling of Niobium Surface Composition and Work Function of SRF Cavities

niobium, cavity, electron, SRF

779

A.D. Wu, L. Chen, Q.W. Chu, H. Guo, Y. He, Y.M. Li, F. Pan, L. Yang, S.H. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China

The niobium samples were prepared by different surface treatments that commonly applied for the superconducting RF cavities preparation, as the following of electrochemical polishing, the buffered chemical polishing and high temperature annealing. In order to understand the property of niobium surface, especially the relationship between the composition and the work function value, the X-ray and ultraviolet photoelectron spectra depth profiling has been studied. The intensity photoelectrons signals of O1s, C1s and the Nb3d were identified for composition of the niobium oxide and the hydrocarbon contamination. And the work function of sample surface was measured via the means of the ultraviolet photoelectron spectra band width. To make a depth profiling, the sputtering of Argon ions was used to remove surface material gradually under by control the sputtering times. The results shown that the value of work function strongly depends on the chemical composition.

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THPB025

A Crystal Plasticity Study on Influence of Dislocation Mean Free Path on Stage II Hardening in Nb Single Crystals

experiment, simulation, cavity, niobium

783

T. Maiti, A. Chakrabarty, P. Eisenlohr
MSU, East Lansing, USA
T.R. Bieler, D. Kang
Michigan State University, East Lansing, Michigan, USA

Funding: Financial support from the Department of Energy through grant DE-SC0009962 is gratefully acknowledged. This work was supported in part by MSU through computational resources provided by the ICER.
Constitutive models based on thermally-activated stress-assisted dislocation kinetics have been successful in predicting deformation behavior of crystalline materials, particularly in face-centered cubic (fcc) metals. In body-centered cubic (bcc) metals, success has been more or less limited, owing to ill-defined nature of slip planes and non-planar spreading of 1/2\hkl<111> screw dislocation cores. As a direct consequence of this, bcc metals show a strong dependence of flow stress on temperature and strain rate, and violation of Schmid law. We present high-resolution full-field crystal plasticity simulations of single crystal Niobium under tensile loading with an emphasis on multi-stage hardening, orientation dependence, and non-Schmid behavior. A dislocation density-based constitutive model with storage and recovery rates derived from Discrete Dislocation Dynamics is used to model strain hardening in stage II. The influence of dislocation mean free path and initial dislocation content on stage II hardening is simulated and compared with in-situ tensile experiments.

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THPB026

Investigation of the Effect of Strategically Selected Grain Boundaries on Superconducting Properties of SRF Cavity Niobium

niobium, cavity, SRF, cryogenics

787

M. Wang, T.R. Bieler
Michigan State University, East Lansing, Michigan, USA
S. Balachandran, P.J. Lee
NHMFL, Tallahassee, Florida, USA
S. Chetri, A. Polyanskii
ASC, Tallahassee, Florida, USA
C. Compton
FRIB, East Lansing, Michigan, USA

Funding: Research supported by DOE/OHEP contracts DE-SC0009962, DE-SC0009960, NSF-DMR-1157490, and the State of Florida.
High purity Nb is commonly used for fabricating SRF cavities due to its high critical temperature and its formability. However, microstructural defects such as dislocations and grain boundaries in niobium can serve as favorable sites for pinning centers of magnetic flux that can degrade SRF cavity performance. In this study, two bi-crystal niobium samples extracted from strategically selected grain boundaries were investigated for the effect of grain misorientation on magnetic flux behavior. Laue X-ray and EBSD-OIM crystallographic analyses were used to characterize grain orientations and orientation gradients. Cryogenic Magneto-Optical Imaging (MOI) was used to directly observe magnetic flux penetration at about 5-8 K. Flux penetration was observed along one of the grain boundaries, as well as along a low angle boundary that was not detected prior to MOI imaging. Hydride scars on the sample surface after MOI were examined using atomic force microscopy (AFM) analysis. The relationships between dislocation content, cryo-cooling, flux penetration and grain boundaries are examined.

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THPB027

Characterization of Microstructural Defects in SRF Cavity Niobium using Electron Channeling Contrast Imaging

cavity, niobium, electron, SRF

792

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

Funding: Research supported by DOE/OHEP contract DE-SC0009962
Although the quality factor of niobium cavities has improved, performance variability arises from microstructural defects such as dislocations and grain boundaries that can trap magnetic flux, block heat transfer, and perturb superconducting currents. Microstructural defect evolution is compared in four samples extracted from a 2.8 mm thick large-grain niobium slice, with tensile axes chosen to generate desired dislocation structures during deformation. The four samples are 1) as-extracted, 2) extracted and annealed, 3) extracted and then deformed to 40% strain, and 4) extracted, annealed at 800 °C 2 hours, and deformed to 40% strain. Electron Channeling Contrast Imaging (ECCI) was performed on all samples to characterize initial dislocation density, dislocation structure evolution due to annealing and deformation, and related to the mechanical behavior observed in stress-strain curves. The orientation evolution and geometrically necessary dislocation (GND) density were characterized with electron backscattered diffraction (EBSD) maps. Fundamental understanding of dislocation evolution in niobium is necessary to develop models for computational cavity design.

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THPB028

Flux Pinning Study of OTIC Niobium Material

niobium, site, cavity, superconducting-cavity

797

S. Chen, J.K. Hao, L. Lin, K.X. Liu, S.W. Quan
PKU, Beijing, People's Republic of China

The performance of superconducting cavities is influenced by the trapped flux during the cooling down through critical temperature, especially for nitrogen doped cavities which are more sensitive to flux trapping. We have investigated the flux trapping of OTIC niobium samples with different grain size. Samples were prepared and heat treated at 800°C and 900°C, followed with different surface removal by BCP. A series of measurements, including MPMS, TOF-SIMS, were carried out on the niobium samples. The results and analysis will be presented.

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THPB029

XPS Studies of Nitrogen Doping Nb Samples before and after GCIB Etching

niobium, cavity, SRF, electron

802

Z.Q. Yang, X.Y. Lu, W.W. Tan, D.Y. Yang, Y. Yang, J. Zhao
PKU, Beijing, People's Republic of China

The surface chemical composition of nitrogen doping Nb samples used for the fabrication of superconducting radio frequency (SRF) cavities, followed by the subsequent successive EP with different amounts of material removal, has been studied by XPS. The chemical composition of Nb, O, C and N was presented before and after Gas Cluster Ion Beams (GCIB) etching. No signals of bad superconducting nitrides NbNx was found in any doped and un-doped samples before etching. However, in the depth range greater than 30nm, the content of N elements is below the XPS detection precision scope even in the samples directly after nitrogen doping treatment.

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THPB030

Direct Observation of Hydrides Formation of Nitrogen Doping Nb Samples

niobium, experiment, cavity, electron

805

Z.Q. Yang, X.Y. Lu, W.W. Tan, D.Y. Yang, Y. Yang, J. Zhao
PKU, Beijing, People's Republic of China

Direct observation of hydrides precipitates formation on both nitrogen doped and un-doped Nb samples at 80K has been carried out using Scanning Electron Microscope (SEM) with Cold Stand. We have found that, under our experimental conditions, when the subsequent EP removal is less than 7μm, the amounts of hydrides formed on the surface of doped samples can be effectively reduced. When the subsequent material removal is larger than 9μm, the amounts of precipitated hydrides increased with the EP removal. When the EP removal is 7-9μm, the amounts of hydrides can still be effectively reduced. Also, more hydrides were precipitated on the surface of un-doped samples. The amounts of hydrides of doped samples may be reduced to varying degrees with different amounts of material removal.

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THPB031

Magnetic Properties of Nitrogen Doping Niobium Samples

cavity, niobium, SRF, experiment

809

Z.Q. Yang, X.Y. Lu, W.W. Tan, D.Y. Yang, Y. Yang, J. Zhao
PKU, Beijing, People's Republic of China

Nitrogen doping study on Niobium samples used for the fabrication of superconducting radio frequency (SRF) cavities was carried out. The samples' surface treatments were attempted to replicate that of the cavities, which included heavy electropolishing (EP), nitrogen doping and the subsequent successive EP with different amounts of material removal. The magnetization curves of both doped and un-doped samples have been measured, from which the lower critical field Hffp (First Flux Penetration, ffp) and upper critical field Hc2 was extracted. The thermodynamic critical field Hc, superheating field Hsh and superconducting parameters of samples with different treatments was calculated from the determined reversible magnetization curves. Hsh of doped samples is obviously smaller than that of un-doped samples, which may be a possible reason for the reduction of achievable accelerating gradient in SRF niobium cavities after nitrogen doping treatments.

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THPB034

Development of High Purity Niobium Components and Cavities for SRF Accelerator

cavity, electron, SRF, niobium

814

T. Nagata, H. Masui, S. Shinozawa
ULVAC, Inc, Chiba, Japan
H. Inoue, E. Kako, M. Yamanaka
KEK, Ibaraki, Japan
M. Murakami
ULVAC, Inc., Tsukuba, Japan

Comprehensive cavity fabrication process from Niobium ingot was investigated. In order to purify ingots, A 600 kW electron beam furnace was introduced in ULVAC. It makes possible the stable quality of Niobium sheets and tubes. In evaluation of chemical components, mechanical properties, and RRR of our materials, all the value satisfies the ASTM Type 5 (superconducting grade) specification. In this study, we performed the trial manufacturing of welding-type and seamless-type cavities were made of our high purity Niobium ingots (RRR > 300). Accelerating gradient over 40 MV/m was shown in both cavities. We also tried to manufacture a 3-cell seamless cavity as scale up study. A seamless tube with a length of 830 mm, an inner diameter of 131 mm and a thickness of 3.5 mm was prepared. We succeed in direct forming from tube to cavity shape by using a hydroforming process. Cavity surface could be smoother than that of single cell cavity caused by small crystal grain size.

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THPB035

High Power Testing of the First ESS SPOKE Cavity Package

cavity, controls, accelerating-gradient, linac

817

H. Li, A.K. Bhattacharyya, L. Hermansson, M. Jobs, R.J.M.Y. Ruber, R. Santiago Kern
Uppsala University, Uppsala, Sweden

The first double spoke cavity for the ESS project was tested with high power in the HNOSS cryostat at the FREIA Laboratory. This cavity is designed for 325.21MHz, pulsed mode with 14 Hz repetition rate, up to a peak power of 360 kW. The qualification of the cavity package in a horizontal test, involving a superconducting spoke cavity, a fundamental power coupler (FPC), LLRF system and RF station, represents an important verification before the module assembly. This paper presents the test configuration, RF conditioning history and first high power performance of this cavity.

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THPB036

Fundamental SIMS Analyses for Nitrogen-enriched Niobium

niobium, cavity, interface, instrumentation

821

J. Tuggle, M.J. Kelley
Virginia Polytechnic Institute and State University, Blacksburg, USA
M.J. Kelley, U. Pudasaini
The College of William and Mary, Williamsburg, Virginia, USA
M.J. Kelley, A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA
F.A. Stevie
NCSU AIF, Raleigh, North Carolina, USA

Funding: Co-Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. W&M and VT work supported by the Office of High Energy Physics, U.S. DOE under grant DE-SC-0014475
In order to fully understand nitrogen addition techniques it is vital to have a full understanding of the material, including the content, location, and speciation of nitrogen contained in the treated Nb. In this work Secondary Ion Mass Spectrometry (SIMS) is used to elucidate content and location. Dynamic SIMS nitrogen analysis is reported, for the first time, for "as-received" cavity grade niobium from three separate suppliers. In addition, a number of method and instrumental issues are discussed including depth resolution, detection limit, and quantification.

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THPB037

Cavity Fundamental Mode and Beam Interaction in CEPC Main Ring

cavity, beam-loading, ECR, luminosity

825

D.J. Gong, J. Gao, D. Wang, J.Y. Zhai
IHEP, Beijing, People's Republic of China

Circular electron positron collider (CEPC) is design as a particle factory for Higgs, W and Z. The preliminary study is undertaken for CEPC cavity fundamental mode and beam interaction in this paper. The baseline of CEPC is DR scheme, the alternative is the APDR scheme. Beam loading effects and the corresponding longitudinal beam dynamics of both CEPC DR and APDR are elaborated in this article. The phase shift and voltage decrease are calculated by the analytic formula and the program. Furthermore, the longitudinal coupled-bunch instability is also studied. At last, the RF parameters are calculated for CEPC 100km APDR, in order to match the machine parameters and relieve the beam loading effects.

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THPB038

Local Magnetometer: First Critical Field Measurement of Multilayer Superconductors

experiment, cavity, ion-effects, vacuum

830

M. Aburas, C.Z. Antoine
CEA/IRFU, Gif-sur-Yvette, France
A. Four
CEA/DRF/IRFU, Gif-sur-Yvette, France

S-I-S (Superconductor-Insulator-Superconductor) nanometric superconducting multilayers have been proposed by Gurevich* to increase the maximum accelerating field of Nb RF cavities. This enhancement of HC1 may be done by coating Nb with thin layers of thickness less than the penetration depth. Therefore, it is necessary to find a particular tool, which allows us measuring HC1 directly. In fact, DC magnetometers (e.g. magnetometer SQUID) are largely used for magnetic measurements but these last are strongly influenced by orientation, edge and shape effects, especially in the case of superconductor thin films. For that reason, we developed at Saclay facilities a specific local magnetic measurement of first critical field HC1. The principle of our local magnetometer is based on the third-harmonic voltage method purposed by Claassen**, which is very useful to estimate the first critical field HC1 of superconducting multilayer samples with nondestructive and contactless, but more importantly, without demagnetization effects***. This paper will present the evolution of the magnetometer to overcome all types of difficulties.
* A. Gurevich, Appl. Phys. Lett. 88, 012511 (2006)
** J. H. Claassen et al., Review of Scientific Instruments 62, 996 (1991)
*** M. Aurino et al., Journal of Applied Physics 98, 123901 (2005)

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THPB040

SRF Theory Developments from the Center for Bright Beams

cavity, SRF, experiment, HOM

835

D. Liarte, T. Arias, M. Liepe, J.P. Sethna, N. Sitamaran
Cornell University, Ithaca, New York, USA
D.L. Hall
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A.R. Pack, M.K. Transtrum
Brigham Young University, Provo, USA

Funding: This work was supported by the US National Science Foundation under Award OIA-1549132, the Center for Bright Beams.
We present theoretical studies of SRF materials from the Center for Bright Beams. First, we discuss the effects of disorder, inhomogeneities, and materials anisotropy on the maximum parallel surface field that a superconductor can sustain in an SRF cavity, using linear stability in conjunction with Ginzburg-Landau and Eilenberger theory. We connect our disorder mediated vortex nucleation model to current experimental developments of Nb3Sn and other cavity materials. Second, we use time-dependent Ginzburg-Landau simulations to explore the role of inhomogeneities in nucleating vortices, and discuss the effects of trapped magnetic flux on the residual resistance of weakly-pinned Nb3Sn cavities. Third, we present first-principles density-functional theory (DFT) calculations to uncover and characterize the key fundamental materials processes underlying the growth of Nb3Sn. Our calculations indicate that the observed tin-depleted regions may be the direct result of an exothermic reaction between Nb3Sn and Nb at the growing Nb/Nb3Sn interface. We suggest new growth protocols to mitigate the formation of tin depleted regions.

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THPB041

Cavity Quench Studies in Nb3Sn Using Temperature Mapping and Surface Analysis of Cavity Cut-outs

cavity, detector, niobium, electron

840

D.L. Hall, M. Liepe, 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

Previous experimental studies on single-cell Nb3Sn cavities have shown that the cause of quench is isolated to a localised defect on the cavity surface. Here, cavity temperature mapping has been used to investigate cavity quench behaviour in an Nb3Sn cavity by measuring the temperature at the quench location as the RF field approaches the quench field. The heating profile observed at the quench location prior to quench appears to suggest quantised vortex entry at a defect. To investigate further, the quench region has been removed from the cavity and analysed using SEM methods. These results are compared to theoretical models describing two vortex entry defect candidates: regions of thin-layer tin-depleted Nb3Sn on the cavity surface that lower the flux entry field, and grain boundaries acting as Josephson junctions with a lower critical current than the surrounding material. A theoretical model of layer growth developed using density functional theory is used to discuss alterations to the coating process that could mitigate the formation of such defects.

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THPB042

Field-dependence of the Sensitivity to Trapped Flux in Nb3Sn

cavity, niobium, site, SRF

844

D.L. Hall, M. Liepe, R.D. Porter
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

The amount of residual resistance gained per unit of trapped flux ' referred to as the trapped flux sensitivity ' in Nb3Sn cavities has been found to be a function of the amplitude of the RF field. This behaviour is consistent with a scenario in which the trapped vortex dynamics are described by collective weak pinning. A model has been developed to describe this, and results in the observed linear dependence of trapped flux sensitivity with RF field. The model is used to discuss cavity preparation methods that might suppress this dependence, which would reduce the trapped flux requirements necessary to operate an Nb3Sn cavity at simultaneous high quality factors and accelerating gradients.

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THPB043

Effects of Chemical Treatments on the Surface Roughess and Surface Magnetic Field Ehancement of Niobium-3 Tin Films for Superconducting Radio-Frequency Cavities

cavity, niobium, SRF, linac

848

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

Current niobium-3 tin (Nb3Sn) films produced via vapor diffusion have rougher surfaces than typical electropolished niobium surfaces causing significantly enhancement of the surface magnetic fields. Reducing surface roughness of Nb3Sn surfaces may be necessary to achieve higher gradient accelerator cavities with high Q. Previous work at Cornell has shown the impact of several chemical treatments on the surface roughness of Nb3Sn films; however, it had not been evaluated how the changes in surface roughness impact the surface magnetic field enhancement. In this paper we present simulations of the surface field enhancement of oxipolished Nb3Sn, which was shown to be effective at reducing the surface roughness of Nb3Sn. The surface magnetic field enhancement data is compared to those of unetched Nb3Sn to find that the surface magnetic field enhancement (and surface roughness) has been roughly halved.

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THPB044

Update on Sample Host Cavity Design Work for Measuring Flux Entry and Quench Field

cavity, niobium, SRF, radio-frequency

851

R.D. Porter, M. Liepe, J.T. Maniscalco, R.A. Strauss
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

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 are capable of supporting higher surface magnetic fields. This necessitates measuring the quench fields of new materials in high power RF fields. Previous work at Cornell University has used electromagnetic simulations to optimize the shape of a dipole mode sample host cavity such that the surface magnetic fields on the sample are high compared to the energy inside the cavity and the surface magnetic field on the rest of the cavity. In this paper we present an update of the design that includes how to mount samples in the cavity and the addition of a low field chamber.

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THPB048

Double Cathode Configuration for the Nb Coating of HIE-ISOLDE Cavities

cathode, cavity, ISOL, simulation

854

A. Awais
NCP, Islamabad, Pakistan
A. Awais, A.J.G. Lunt, G.J. Rosaz, A. Sublet, M. Taborelli
CERN, Geneva, Switzerland

The Quarter Wave Resonator (QWR) cavities for HIE-ISOLDE project at CERN have entered their ending phase of production. Some R&D is still required to improve the uniformity of the Nb layer thickness on the cavity surface. In order to improve this behaviour one approach which has been proposed is to replace the single cathode with a double cathode and test the suitability of different deposition techniques. With this change it is possible to control the plasma and power distribution separately for the inner and outer part of cavity and thereby potentially improve film uniformity throughout the cavity and coating duration. In this study a comparison between the deposition rates obtained using a single cathode and a double cathode using Direct Current (DC)-bias diode sputtering, DC-magnetron sputtering (DCMS) and Pulsed DC-magnetron sputtering (PDCMS) is presented. The morphology of the thin film samples were compared using Focused Ion Beam (FIB) cross section milling and Scanning Electron Microscopy (SEM) analysis.

Poster THPB048 [3.715 MB]

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THPB052

Error Analysis of Surface Resistance Fits to Experimental Data

cavity, experiment, simulation, data-analysis

859

S. Keckert, J. Knobloch, O. Kugeler
HZB, Berlin, Germany

Funding: This work is part of EuCARD-2, partly funded by the European Commission, GA 312453.
Superconducting material properties such as energy gap, mean free path or residual resistance are commonly extracted by fitting experimental surface resistance data. Depending on the measurement setup, both, temperature range and the number of points are limited. In order to obtain significant results, systematic as well as statistical uncertainties have to be taken into account. In this contribution different classes of errors and their impact on systematic and statistical deviations of the fitted parameters are discussed. In particular, past measurements have yielded contradictory conclusions that, we believe, result from the use of insufficient data in the necessary temperature range. Furthermore, this study is applied to the boundary conditions of the Quadrupole Resonator and its measurement accuracy.

Poster THPB052 [1.034 MB]

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THPB053

Surface Resistance Characterization of Nb3Sn Using the HZB Quadrupole Resonator

SRF, quadrupole, cavity, niobium

863

S. Keckert, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
D.L. Hall, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work is part of EuCARD-2, partly funded by the European Commission, GA 312453.
Nb3Sn is a very promising candidate material for future SRF cavities. With a critical temperature more than twice as the one of bulk niobium, higher operational temperatures with still lower surface resistance are theoretically possible. A sample prepared by Cornell University was characterized towards its SRF properties using the HZB Quadrupole Resonator. In comparison to a coated cavity this device enables SRF measurements at an extended parameter space (frequency, temperature and RF field) and easy access to physical quantities such as critical field and penetration depth. In this contribution we present surface resistance and RF critical field measurements.

Poster THPB053 [2.725 MB]

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THPB054

Advanced Method to Extract the Surface Resistance From Q0 Measurements

cavity, factory, HOM, quadrupole

867

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

Funding: The research leading to these results has received funding from the European Commission under the FP7 Research Infrastructures project EuCARD-2, grant agreement No. 312453.
The quality factor of an RF cavity and the surface resistance are typically related with a constant geometry factor. The implicit assumption made is that the surface resistance is field independent, which is however not observed experimentally in superconducting cavities. The approximation error due to this assumption becomes larger the less homogeneous the magnetic field distribution along the cavity walls is. In this paper we calculate the surface resistance error for different cavity types. An iterative method to correct for this error is presented.

Poster THPB054 [0.196 MB]

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THPB055

Plasma-enhanced ALD System for SRF Cavity

cavity, niobium, plasma, SRF

870

S. Kato, H. Hayano
KEK, Ibaraki, Japan

Funding: This work was supported by Photon and Quantum Basic Research Coordinated Development Program by MEXT and partly by JST-CREST.
A remote PEALD (Plasma-enhanced Atomic Layer Deposition) system which would offer a high conformality and a low deposition temperature has been being developed for deposition of NbN on an SRF cavity. The deposition equipment consists of a deposition chamber, a remote plasma exciter, a precursor supply system, vacuum pumps, a quartz crystal microbalance (QCM) as a film growth rate meter, a detoxifying system and a safety system. An RF frequency of 13.56MHz was used for the inductively coupled plasma exciter of a reactant gas. The whole equipment is in a draft booth for operation safety. For ALD of an SRF cavity, the ALD system allows us to easily replace the deposition chamber with a single cell Nb cavity. The prepared precursors are tris[ethylmethylamido][tert-butylimido] niobium (TBTEMN) and trimethylaluminium (TMA). Ammonia, hydrogen and water are also prepared as reactants. We will report the ALD system design and result of the NbN deposition on sample coupons which are analysed with SEM, EDX and XPS.

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THPB057

Investigation of Nucleation Stage in Diffusion Coating of Nb3Sn on Nb

niobium, experiment, SRF, cavity

873

F. Pan
IMP/CAS, Lanzhou, People's Republic of China

Nb3Sn has the potential to improve properties of SRF cavities, such as the gradients and the working tempera-tures. Institute of Modern Physics has launched its Nb3Sn thin film coated SRF cavity project in 2016. Samples have been successfully coated to study the process of tin vapor diffusion. The main part of the deposition system is a tube furnace, which working temperature can reach 1100°C. Basic material characterization of the Sn-Nb film will be presented in this work.

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THPB058

R&D of Thin Film Coating on Superconductors

cryogenics, controls, embedded, FPGA

877

Y. Iwashita, 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 partially supported by 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.

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THPB059

Simulation and Measurements of Crab Cavity HOMs and HOM Couplers for HL-LHC

HOM, cavity, damping, simulation

881

J.A. Mitchell, T.J. Jones
Lancaster University, Lancaster, United Kingdom
R. Apsimon, G. Burt, N.C. Shipman
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
I. Ben-Zvi, S. Verdú-Andrés, B. P. Xiao
BNL, Upton, Long Island, New York, USA
R. Calaga, A. Castilla, A. Macpherson, N.C. Shipman, A. Zwozniak
CERN, Geneva, Switzerland
T. Powers, H. Wang
JLab, Newport News, Virginia, USA
N.C. Shipman
UMAN, Manchester, United Kingdom

Two Superconducting Radio-Frequency (SRF) crab cavities are foreseen for the High Luminosity LHC (HL-LHC) upgrade. Preliminary beam tests of the Double Quarter Wave (DQW) crab cavity will take place in the Super Proton Synchrotron (SPS) in 2018. For damping of the cavity's Higher Order Modes (HOMs) the DQW has three identical on-cell, superconducting HOM couplers. The couplers are actively cooled by liquid heluim. In this paper, electromagnetic simulations of the HOMs and HOM couplers are presented. A novel approach to pre-installation spectral analysis of the HOM couplers is then presented, detailing both simulated and measured data. Measurements of the cavity HOMs at warm and in Vertical Test Facilities (VTFs) at both JLAB and CERN are detailed, comparing the measured characteristics of each mode to that of the simulated data-sets. Finally, the measured cavity data is compared with the test box measurements to see by what extent any reduction in damping can be predicted.

Poster THPB059 [8.192 MB]

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THPB061

Effect Of Dislocations On the Thermal Conductivity Of Superconducting Nb

scattering, electron, ECR, cavity

886

P. Xu, N.T. Wright
MSU, East Lansing, Michigan, USA
T.R. Bieler
Michigan State University, East Lansing, Michigan, USA

Funding: This work is funded by DOE and OHEP through grant number DE-FOA-0001438.
The thermal conductivity of Niobium (Nb) often experiences a local maximum (a phonon peak) at a temperature between 1.8 and 3 K. While the magnitude of the phonon peak has been shown to be related to the dislocation density and may be influenced by manufacturing processes, little has been discussed as to the temperature at which the peak occurs. In examining these phenomena, it has been determined that more explicit accounting of phonon–dislocation scattering in a popular model better represents the thermal conductivity at temperatures colder than 3 K. Scaled sensitivity coefficients show this term to have similar influence as the phonon-electron and phonon-boundary scattering terms. Results using the enhanced model also show an apparent threshold of dislocation density below which there is little contribution to the thermal conductivity of Nb.

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THPB066

Introducing the Vertical High-temperature UHV Furnace of the S-DALINAC for Future Cavity Material Studies

niobium, vacuum, cavity, linac

891

R. Grewe, L. Alff, M. Arnold, J. Conrad, S. Flege, M. Major, N. Pietralla
TU Darmstadt, Darmstadt, Germany
F. Hug
IKP, Mainz, Germany

Funding: Work supported by the Federal Ministry of Education and Research through grant No. 05H15RDRBA.
Since 2005 the Institute for Nuclear Physics in Darmstadt operates a high temperature UHV furnace for temperatures of up to 1750°C. It has been used several times for hydrogen bake-out of the SRF cavities of the S-DALINAC with proven success. In 2013, studies at FNAL have shown that cavities treated with nitrogen reached an up to four times higher q-factor*. The cavities are exposed to N2 at 850°C at the end of the H2 bake-out. A thin layer of normalconducting hexagonal niobium nitride (NbN) forms at the surface which is removed by electropolishing while the higher quality factors are attributed to the N2 diffusion into the bulk Nb. At temperatures from 1300°C to 1700°C a thin layer of the superconducting cubic phase of NbN can be observed, e.g. delta-phase NbN**, which has a higher critical field and higher critical temperature and thus is very intereresting for applications for SRF cavities***. The UHV furnace has been prepared for future treatments of Nb samples and cavities in a N2 atmosphere at high temperatures for research on cubic NbN. The material properties of the samples will be analyzed at the ATFT group at the Department for Material Sciences of TU Darmstadt.
*Grasselino et al., Superconducting Science and Technology, 2013
**Hennessey et al., Oxidation of Metals, 1992
***Martienssen et al., Springer Handbook of Condensed Matter and Materials Data, 2005

Poster THPB066 [3.024 MB]

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THPB069

Surface Studies of Nb3Sn Coated Samples Prepared under Different Coating Conditions

experiment, cavity, SRF, site

894

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 DESC0014475.
The promise of better performance and significant cost reduction make Nb3Sn-coated Nb SRF cavities an attractive option when compared to traditional Nb SRF cavities. Historically, the vapor diffusion technique for coating Nb cavities with Nb3Sn has proven to be the most successful, and is currently practiced in several research facilities with minor variations. Using modern characterization tools, we examined the Nb3Sn coating prepared in different systems and/or under different conditions. Identically prepared high RRR (~ 300) Nb samples were coated using existing standard protocols at different coating facilities. The microstructure and composition of Nb3Sn coatings were found to be similar when examined with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Atomic force microscopy (AFM) was performed on each sample and the topographies of the samples were then compared in terms of power spectral densities (PSDs). Secondary ion mass spectrometry (SIMS) depth profiles revealed trace amounts of Ti in some of the samples.

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THPB070

Electrochemical Finishing Treatment of Nb3Sn Diffusion-coated Niobium

niobium, cavity, experiment, SRF

900

U. Pudasaini, M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece, H. Tian
JLab, Newport News, Virginia, 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 DESC0014475.
Nb3Sn cavities are now routinely prepared by depositing few micron thick Nb3Sn coatings on Nb cavities using tin vapor diffusion process. For the¬¬ case of niobium there is a significant improvement after electropolishing (EP), but electrochemical finishing treatment on Nb3Sn coatings has not been studied. Controlled removal of the first few layers could lead to a smoother and cleaner surface that is conducive to better RF performance. Several samples, which were coated with Nb3Sn by vapor diffusion process in a JLab sample chamber, were used to explore polishing parameters, such as I-V characteristics, removal rate, topography, etc. Preliminary results from the first runs are discussed here.

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THPB075

GaN-based Photocathodes for High Brightness Electron Beams

cathode, electron, target, experiment

906

M. Schumacher, X. Jiang, M. Vogel
University Siegen, Siegen, Germany

Funding: This research is funded by the Federal Ministry of Education and Research of Germany in the framework of HOPE II (project number 05K16PS1).
Prospective light sources requires photocathodes with high quantum efficiency (QE), long lifetime and minimized thermal emittance. One promising candidate meeting the aforementioned specifications is GaN. Due to its wide band gap (Eg = 3,4 eV), GaN can be excited by UV-light sources. Its thermal and chemical stability are added bonuses. In the framework of the present activity, the synthesis of GaN films on Si, Cu, Mo and Nb by means of rf magnetron sputtering is proposed. In this context, Ga, GaAs and GaN are suitable source material candidates, which are sputtered in a nitrogen/argon plasma discharge. The conductivity as well as the band-gap of the corresponding films can be modified by dopants like Mg and In, respectively. Standard materials science characterization techniques such as SEM, EDX, XRD or XPS are used to explore the growth mechanism of GaN alongside with a morphological and chemical examination. To assess and optimize the performance of the photocathode the abovementioned requirements are tested in an in-situ setup. In addition to the project outline, first experimental results of GaN coatings synthesized based on a GaAs source sputtered in pure N2 are presented.

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THPB076

Carbon-based Coatings for Electron Cloud Mitigation in SRF Photocathodes

SRF, gun, cathode, electron

910

M. Vogel, X. Jiang, C. Schlemper
University Siegen, Siegen, Germany

Funding: This research has been funded by the Federal Ministry of Education and Research of Germany in the framework of HOPE I (project number 05K13PS2).
During the past three years, we developed a coating along with a corresponding in-situ characterization process in order to realize SRF-gun surfaces featuring low secondary electron yield (SEY). Important aspects that have been accounted for are the homogeneity and adhesion of the coatings deposited on the cylindrical SRF-gun mantle. Furthermore, the correlation between SEY and crystallinity, morphology, and contamination was studied in detail. The SEY maximum can be tuned between 1.5 and less than 0.7 depending on the deposition conditions. In this work, we recap the results and present a general strategy for the effective mitigation of electron cloud multiplication.

Poster THPB076 [5.583 MB]

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THPB077

Design Study of Mushroom Shaped Cavity for Evaluation of RF Critical Magnetic Field of Thin-film Superconductor

cavity, electromagnetic-fields, target, insertion

914

H. Oikawa
Utsunomiya University, Utsunomiya, Japan
H. Hayano
KEK, Ibaraki, Japan
T. Higashiguchi
Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan

For future accelerator, superconducting RF cavity has high gradient of 45 MV/m or more is demanded. To obtain such a higher gradient, there has been proposed a method of increasing an RF critical magnetic field of the cavity inner surface by coating of multi-layer thin-film superconductor. Their thickness is close to the London penetration depth. By producing a multilayer film structure in cavity inner surface, it is believed to improve the RF critical magnetic field, and to connect directly to high gradient. To demonstrate a creation of a thin film on a surface of Nb samples, an RF cavity with a thin film coated Nb sample is needed to measure the RF critical field of the sample. To adapt it to the cavity, to cool to cryogenic temperature and to establish the sample to supply the RF power, it is necessary to design a cavity to produce a strong RF magnetic field parallel to the surface of the thin film sample. We designed a mushroom shaped cavity made of Nb and input coupler. Resonant frequency is 5.2 GHz by calculation. We calculated the resonant frequency and the field distribution, compared with the measured values for the model cavity.

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THPB078

Fabrication of Large-area MgB2 Films on Copper Substrates

cavity, niobium, SRF, radio-frequency

917

X. Guo, K.X. Liu, Z. Ni
PKU, Beijing, People's Republic of China
Q. Feng, C. Yang
Peking University, Beijing, People's Republic of China

Magnesium diboride (MgB2) is a promising candidate material for SRF cavities because of its higher transition temperature and critical field compared with niobium. To meet the demand of RF test devices, the fabrication of large-area MgB2 films on metal substrates is needed. In this work, MgB2 films with 50-mm diameter were fabri-cated on Cu substrates by using an improved HPCVD setups at Peking University. The transition temperatures of MgB2 film on Cu substrate and with Mo buffer layer on Cu substrate are 36.2 K and 36.5 K, respectively. The fabrication processes, surface morphology, superconduct-ing properties of these large-area MgB2 films are present-ed.

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THPB079

Simulations of RF Field-induced Thermal Feedback in Niobium and Nb3Sn Cavities

cavity, niobium, simulation, feedback

920

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

Thermal feedback is a known limitation for SRF cavities made of low-purity niobium, as the increased losses at higher temperature described by BCS theory create a feedback mechanism that can eventually result in a runaway effect and associated cavity quench. In a similar manner, niobium cavities coated with Nb3Sn may also be subject to increased losses from thermal feedback, as Nb3Sn is possessed of a much lower thermal conductivity than niobium, although this effect will be mitigated by the thin film nature of the coating. In order to better understand the degree to which thermal feedback plays a role in the performance of Nb3Sn cavities, it is necessary to understand how the various components of the problem play a role in the outcome. In this paper, we present the first results from simulations performed at Cornell University that model RF induced thermal feedback in both conventional niobium cavities and niobium cavities coated with a thin film of Nb3Sn. The impacts of layer thickness, niobium substrate thermal conductivity, and trapped flux on the performance of the cavity are discussed.

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THPB080

Measurement of Frequency, Temperature, RF Field Dependent Surface Resistance Using Superconducting Half Wave Cavity

cavity, experiment, SRF, factory

925

H. Park
JLab, Newport News, Virginia, USA
S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA

A theory of surface resistance of superconductor was rigorously formulated by Bardeen, Cooper, Schrieffer more than 50 years ago. Since then the accelerator community has been used the theory as a guideline to improve the surface resistance of the superconducting cavity. It has been observed that the surface resistance is dependent on frequency, temperature and rf field strength, and surface preparation. To verify these dependences, a well-controlled study is required. Although many different types of cavities have been tested, the typical superconducting cavities are built for specific frequencies of their application. They do not provide data other than at its own frequency. A superconducting half wave cavity is a cavity that enables us to collect the surface resistance data across frequencies of interest for particle accelerators and evaluate preparation techniques. This paper will present the design of the half wave cavity, its electromagnetic mode characteristics and experimental results.

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FRXAA01

Production Status of Superconducting Cryomodules for the Facility for Rare Isotope Beams

cryomodule, cavity, linac, vacuum

928

C. Compton, H. Ao, J. Asciutto, B. Bird, W. Hartung, S.J. Miller, J.T. Popielarski, L. Popielarski, M.A. Reaume, K. Saito, M. Shuptar, S. Stark, B.P. Tousignant, T. Xu
FRIB, East Lansing, USA

The Facility for Rare Isotope Beams (FRIB) is an SRF accelerator project in full production at Michigan State University (MSU). With the civil construction nearly complete, the installation of accelerator equipment into the tunnel has taken center stage. A total of 46 superconducting cryomodules are needed for the FRIB linac to reach 200 MeV per nucleon. The linac consist of four cavity types (β = 0.041, 0.085, 0.29, and 0.53) and 6 different cryomodule designs. Cryomodule assembly is done in 5 parallel bays, each one compatible with every cryomodule type. Completed cryomodules undergo full system testing in bunkers before being accepted and delivered to the tunnel. The current status of the cryomodule assembly effort will be presented, including lessons learned and overall experience to date.

Slides FRXAA01 [9.990 MB]

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FRXAA02

High-efficiency, High-current Optimized Main-linac ERL Cryomodule

cavity, linac, cryomodule, HOM

935

F. Furuta, N. Banerjee, A.C. Bartnik, J. Dobbins, R.G. Eichhorn, M. Ge, G.H. Hoffstaetter, M. Liepe, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The Main Linac Cryomodule (MLC) prototype is a key component of the Cornell-BNL ERL Test Accelerator (CBETA) project, which is a 4-turn FFAG ERL currently under construction at Cornell University. This novel cryomodule is the first SRF module ever to be fully optimized simultaneously for high efficient SRF cavity operation and for supporting very high CW beam currents. After a successful initial MLC testing, the MLC has now been moved into its final location for the CBETA ring. For a first beam test of the MLC and CBETA, the Cornell ERL high voltage DC gun and SRF injector cryomodule were connected to MLC via an entry beam line; a beam stop assembly was also installed at the exit line. In this paper, we summarize the performance of this novel ERL cryomodule including the results of the first beam test and the additional tests focused on RF field stability and cavity microphonics.

Slides FRXAA02 [8.792 MB]

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FRXBA01

LLRF Commissioning at the European XFEL

MMI, LLRF, FEL, cavity

941

M. Omet, V. Ayvazyan, J. Branlard, L. Butkowski, M. Fenner, M.K. Grecki, M. Hierholzer, M. Hoffmann, M. Killenberg, D. Kühn, F. Ludwig, U. Mavrič, S. Pfeiffer, H. Pryschelski, K.P. Przygoda, R. Rybaniec, H. Schlarb, Ch. Schmidt, B. Szczepanski, H.C. Weddig
DESY, Hamburg, Germany
W. Cichalewski, D.R. Makowski, F. Makowski, A. Mielczarek
TUL-DMCS, Łódź, Poland
K. Czuba, B. Gąsowski, S. Hanasz, P.K. Jatczak, D. Kolcz, T.P. Leśniak, D. Sikora
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

The European X-ray Free-Electron Laser (XFEL) at Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany is a user facility under commissioning, providing ultrashort X-ray flashes with a high brilliance in the near future. All LLRF stations of the injector, covering the normal conducting RF gun, A1 (8 1.3 GHz superconducting cavities (SCs) and AH1 (8 3.9 GHz SCs), were successfully commissioned by the end of 2015. The injector was operated with beam transmission to the injector dump since then. After the conclusion of the construction work in the XFEL accelerator tunnel (XTL), the commissioning of 22 LLRF stations (A2 to A23) started with the beginning of 2017. Every station consists of a semi-distributed LLRF system controlling 32 1.3 GHz SCs. Stable operation with beam transport to the main dump (TLD) was achieved. The commissioning procedure applied, experience gained and performance reached are described.

Slides FRXBA01 [2.159 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-FRXBA01

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FRXBA02

High Precision RF Control for SRF Cavities in LCLS-II

cavity, controls, LLRF, feedback

944

L.R. Doolittle, K.S. Campbell, Q. Du, G. Huang, J.A. Jones, C. Serrano, V.K. Vytla
LBNL, Berkeley, California, USA
S. Babel, A.L. Benwell, M. Boyes, G.W. Brown, D. Cha, J.H. De Long, J.A. Diaz Cruz, D.B. Greg, B. Hong, R.S. Kelly, A. McCollough, A. Ratti, C.H. Rivetta
SLAC, Menlo Park, California, USA
R. Bachimanchi, C. Hovater, D.J. Seidman
JLab, Newport News, Virginia, USA
B.E. Chase, E. Cullerton, J. Einstein, D.W. Klepec
Fermilab, Batavia, Illinois, USA

Funding: This work supported under DOE Contract DE-AC02-76SF00515
The unique properties of SRF cavities enable a new generation of X-ray light sources in XFEL and LCLS-II. The LCLS-II design calls for 280 L-band cavities to be operated in CW mode with a Q_L of 4x10⁷, using Single-Source Single-Cavity control. The target RF field stability is 0.01% and 0.01 degree for the band above 1 Hz. Hardware and software implementing a digital LLRF system has been constructed by a four-lab collaboration to minimize known contributors to cavity RF field fluctuation. Efforts include careful attachment to the phase reference line, and minimizing the effects of RF crosstalk by placing forward and reverse signals in chassis separate from the cavity measurement. A low-noise receiver/digitizer section will allow feedback to operate with high proportional gain without excessive noise being sent to the drive amplifier. Test results will show behavior on prototype cryomodules at FNAL and JLab, ahead of the 2018 final accelerator installation.

Slides FRXBA02 [3.425 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-FRXBA02

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