TUPB —  Poster Session   (18-Jul-17   14:00—17:00)

Paper	Title	Page
TUPB001	338 MHz Crab Cavity Design for the eRHIC Hadron Beam	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB001
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TUPB002	Novel HOM Damper Design for High Current SRF Cavities	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB002
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TUPB004	HOM damping with an enlarged beam tube for HEPS 166.6 MHz SC cavities	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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB004
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TUPB005	Developed Spoke Cavity Module for Main Linac of China ADS HOM Simulations and Damping Scheme for CEPC Cavities	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB005
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TUPB008	Performance of SRF Half-wave-resonators Tested at Cornell for the RAON Project	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB008
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TUPB009	High-frequency SRF Cavities	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB009
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TUPB010	Multipactor Study in the Coupler Region of the Diamond SCRF Cavities	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB010
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TUPB013	Advanced Manufacturing Techniques for the Fabrication of Hl-LHC Crab Cavities at CERN	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB013
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TUPB014	In-situ Bulk Residual Resistivity Ratio Measurement on Double Quarter Wave Crab Cavities	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB014
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TUPB016	Redesign of CERN's Quadrupole Resonator for Testing of Superconducting Samples	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB016
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TUPB020	Microphonics Passive Damping	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB020
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TUPB021	First Considerations on HZB High Frequency Elliptical Resonator Stiffening	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB021
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TUPB022	First Measurements of the Next SC CH-cavities for the New Superconducting CW Heavy Ion Linac at GSI	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
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB022
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TUPB023	Further Tests on the SC 325 MHz CH-cavity and Power Coupler Test Setup	437
	M. Busch, M. Bastenpresenter, 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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB023
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TUPB024	Performance Tests of the Superconducting 217 MHz CH Cavity for the CW Demonstrator	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB024
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TUPB028	Improvement of Magnetic Condition for KEK-STF Vertical Test Facility Toward High-Q Study	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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB028
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TUPB032	Study on 650MHz 5-cell Prototype Cavities at IHEP	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB032
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TUPB033	Tests of the High Current Slotted Superconducting Cavity with Extremely Low Impedance	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB033
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TUPB034	The 166.6 MHz Proof-of-principle SRF Cavity for HEPS-TF	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB034
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TUPB035	Frequency Pre-tuning of the 166.6 MHz Proof-of-principle SRF Cavity for HEPS-TF	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB035
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TUPB036	R&D of CEPC Cavity	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB036
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TUPB037	A 166.6 MHz Proof-of-principle SRF Cavity for HEPS-TF: Mechanical Design and Fabrication	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB037
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TUPB038	Mechanical Design of a 650 MHz Superconducting RF Cavity for CEPC	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB038
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TUPB039	Electropolishing of Niobium from Deep Eutectic Solvents Based on Choline Chloride	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB039
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TUPB040	Design and Optimization of Medium and High Beta Superconducting Elliptical Cavities for the CW Linac in CIADS	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	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	484
	M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella, D. Sertorepresenter 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	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	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	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	502
	A.M. Bulygin, R.V. Donetskiy, Ya.V. Shashkovpresenter 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	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	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	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	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	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	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB063
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TUPB064	Operating Experience on Cavity Performance of ISAC-II Superconducting Heavy Ion 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	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	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	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB067
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TUPB069	Rigorous Data Processing and Automatic Documentation of SRF Cold Tests	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB069
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TUPB070	INFN-LASA Cavity Design for PIP-II LB650 Cavity	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	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	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB072
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TUPB073	Vertical Electro-polishing Collaboration Between Cornell, KEK, and Marui Galvanizing Co. Ltd	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB073
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TUPB074	RF Performance of Multi-cell Scale Niobium SRF Cavities Prepared with HF Free Bipolar Electro-polishing at Faraday Technology	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB074
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TUPB075	Vertical Electro Polishing of Superconducting Single-and Multi Cell Gun Resonators	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB075
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TUPB078	SUBU Characterisation: Bath Fluid Dynamics vs Etching Rate	575
	A. Perez Rodriguez, L.M.A. Ferreira, A. Subletpresenter 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB078
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TUPB082	Setup of a Spatially Resolving Vector Magnetometry System for the Investigation of Flux Trapping in Superconducting Cavities	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB082
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TUPB083	Post Processing of a 166.6 MHz HEPS-TF Cavity at Institute of High Energy Physics	583
	J. Dai, Z.Q. Li, P. Zhangpresenter 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 Epeak=86.5 MV/m and Bpeak=132.1 mT with Q0=5.1×〖10〗8 at 4.2K. The cavity was RF tested again at 2K, and reached Epeak=85.5 MV/m and Bpeak=131.1 mT with Q0=3.3×〖10〗9. daijin@ihep.ac.cn
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB083
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TUPB084	EP System Development at IHEP	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB084
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TUPB085	Quench Detection on Superconducting Cavity by Second Sound	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB085
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TUPB086	Study on Local Chemical Treatment for Recovery From Surface Oxidation by HPR Process on SRF Cavities	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB086
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TUPB087	Low Temperature and Low Pressure Plasma for the HWR Superconducting Cavity In-situ Cleaning	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB087
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TUPB090	Investigation of High Temperature Baking of Jacketed Quarter Wave Resonators	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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB090
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TUPB091	Study on Vertical Electropolising of 9-cell Niobium Coupon Cavity	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB091
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TUPB092	Analysis of Niobium Surface and Generated Particles in Vertical Electropolishing of Single-cell Coupon Cavity	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB092
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TUPB093	Nb Single-cell Cavity Vertical Electro-polishing with Ninja Cathode and Evaluation of its 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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB093
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TUPB095	Modeling the Hydroforming of a Large Grain Niobium Tube With Crystal Plasticity	616
	A. Mapar MSU, East Lansing, Michigan, USA T.R. Bielerpresenter 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB095
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TUPB096	SRF Cavity Assembly in Clean Room with Horizontal Laminar Flow	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB096
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TUPB097	R&D of Electro-polishing (EP) Process with HF-free Neutral Electrolyte by Bipolar-pulse (BP) Method	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB097
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TUPB098	The Effect of Process Parameters on the Surface Properties of Niobium During Plasma Etching	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).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB098
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TUPB099	Vertical Test System for Superconducting RF Cavities at Peking University	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB099
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TUPB100	Determining BCP Etch Rate and Uniformity in High Luminosity LHC Crab Cavities	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB100
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TUPB103	DC Magnetism of Niobium Thin Films	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. Valizadehpresenter, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB103
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TUPB104	First Full Cryogenic Test of the SRF Thin Film Test Cavity	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB104
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TUPB106	Standardized Beamline Particulate Characterization Analysis: Initial Application to CEBAF and LCLS-II Cryomodule Components	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB106
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TUPB108	Genesis of Topography in Buffered Chemical Polishing of Niobium for Application to Superconducting Radiofrequency Accelerator Cavities	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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB108
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TUPB111	R&D Activities on Centrifugal Barrel Polishing of 1.3 GHz Niobium Cavities at DESY/University of Hamburg	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
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB111
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TUPB112	First Test of Electropolishing System at IMPCAS	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB112
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TUPB113	Surface Characterization of Nitrided Niobium Surfaces	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
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB113
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