SRF2019 - List of Keywords (simulation)

Paper	Title	Other Keywords	Page
MOP015	RF Performance Sensitivity to Tuning of Nb₃Sn Coated CEBAF Cavities	cavity, SRF, experiment, factory	55
	G.V. Eremeev, W. Crahen, J. Henry, F. Marhauser, C.E. Reece JLab, Newport News, Virginia, USA U. Pudasaini The College of William and Mary, Williamsburg, Virginia, USA
	Funding: Co-Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics. Nb₃Sn has the potential to surpass niobium as the material of choice for SRF applications. The potential of this material stems from a larger superconducting energy gap, which leads to expectations of a higher RF critical field and a lower RF surface resistance. The appeal of better superconducting properties is offset by the relative complexity of producing practical Nb₃Sn structures, and Nb₃Sn sensitivity to lattice disorder challenges the use of the material for practical applications. Such sensitivity is indirectly probed during SRF cavity development, when the cavity is tuned to match the desired accelerator frequency. In the course of recent experiments we have coated and tuned several multi-cell cavities. Cold RF measurements before and after tuning showed degradation in cavity performance after tuning. The results of RF measurement were compared against strain evolution on Nb₃Sn surface during tuning based on CST and ANSYS models.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP015
About •	paper received ※ 26 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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MOP022	Superconducting RF Cavity Materials Research at the S-DALINAC	cavity, niobium, linac, SRF	74
	R. Grewe, L. Alff, M. Arnold, J. Conrad, S. Flege, M. Major, N. Pietralla TU Darmstadt, Darmstadt, Germany F. Hug IKP, Mainz, Germany
	Funding: Supported by BMBF Through 05H18RDRB2 Current state-of-the-art superconducting rf (srf) accelerators are mostly using cavities made of high RRR bulk niobium (Nb). The maximum field gradients and quality factors (Q₀) of these cavities are basically reached now. To further increase the srf cavity properties for future accelerator facilities, research of new materials for srf cavity applications is necessary. The current research at the S-DALINAC* is focused on the development of bake-out procedures of Nb samples and cavities in nitrogen (N) atmosphere of up to 100 mbar to nucleate the delta-phase (d-phase) of the Nb-N binary system. The d-phase has superconducting properties which exceed the properties of bulk Nb. This makes the d-phase attractive for srf applications. The vertical test cryostat (vt) at the S-DALINAC has been upgraded and recommissioned to allow investigations of the quality factor and accelerating field gradients of cavities before and after bake-out. The vt upgrade includes a newly developed variable input coupling to allow matching of the external q-factor (Qex) to Q₀. The results of the ongoing research of the nitrogen atmosphere bake-out procedures and the upgrade of the vt will be presented. *N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018)
	Poster MOP022 [1.759 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP022
About •	paper received ※ 21 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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MOP041	Comparison of the Lattice Thermal Conductivity of Superconducting Tantalum and Niobium	scattering, electron, lattice, niobium	148
	P. Xu, N.T. Wright MSU, East Lansing, Michigan, USA T.R. Bieler Michigan State University, East Lansing, Michigan, USA
	Funding: This work is supported by the U.S. Department of Energy, Office of High Energy Physics through Grant No. DE-FG02-13ER41974. The thermal conductivity k of superconducting Ta behaves similarly to that of superconducting Nb, albeit at colder temperatures. This shift is due to the superconducting transition temperature of Ta being 4.3 K, versus 9.25 K for Nb. For example, the temperature of the phonon peak of properly treated Ta is about 1 K as opposed to a phonon peak at about 2 K for Nb. The typical value of k of Ta is smaller than Nb with the value at the phonon peak for Ta being O(10) W/ m/ K. Like Nb, k is dominated by phonons at these temperatures. This lattice k can be modeled by the Boltzmann transport equation, solved here by a Monte Carlo method using the relaxation time approximation. Individual scattering mechanisms due to boundaries, dislocations, and residual normal electrons are examined, and the phonon dispersion relation is included. Differences in the thermal response of deformed Ta, as compared with Nb, may be attributed to differences in dislocation densities of the two metals following similar levels of deformation. Boundary scattering dominates at the coldest temperatures. The phonon peak decreases and shifts to warmer temperatures with deformation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP041
About •	paper received ※ 19 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP050	Modular Power Couplers for 217 MHz Superconducting CH-Cavities	cavity, Windows, linac, heavy-ion	168
	J. List, K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, M. Miski-Oglu HIM, Mainz, Germany K. Aulenbacher, W.A. Barth, C. Burandt, V. Gettmann, M. Heilmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, A. Schnase, S. Yaramyshev GSI, Darmstadt, Germany K. Aulenbacher, F.D. Dziuba, S. Lauber, J. List IKP, Mainz, Germany M. Basten, M. Busch, H. Podlech, M. Schwarz IAP, Frankfurt am Main, Germany
	The HELmholtz LInear ACcelerator (HELIAC) is being developed by a collaboration of HIM, GSI and the Goethe University of Frankfurt. It is a superconducting (sc), continuous wave (cw) heavy ion linac that comprises novel Crossbar H-mode (CH) cavities. In April 2017 and November/December 2018 the first sc CH-cavity of the linac was tested with beam. The first operations of the cavity showed, that the prototype of the rf power coupler needs to be further improved. A new version of the coupler is being designed at the HIM. Further development will mainly be focused on the heat input into the cryostat caused by the coupler. Also the coupler will have a modular design. This improves the accessibility and maintenance of the coupler. Various cryogenic and rf tests are foreseen, to provide a reliable, fail-safe coupler for the HELIAC. For an enhanced coupler test stand a movable reflector has been designed and built. With its movable semi-reflective element, it allows to operate the test stand in a resonance mode. In addition, the movable reflector can vary the coupling factor. This contribution discusses the recent coupler R&D for the HELIAC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP050
About •	paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP056	Surface Treatments for the Series Production of ESS Medium Beta Cavities	cavity, recirculation, SRF, niobium	188
	M. Bertucci, A. Bosotti, A. D’Ambros, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy D. Rizzetto, M. Rizzi Ettore Zanon S.p.A., Schio, Italy A. Visentin Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
	The surface treatment of ESS 704 MHz medium beta cavities consists of a bulk BCP 200 micron removal, a 10 h 600°C heat treatment and a final 20 micron BCP performed after tank integration. The facility currently employed for the BCP treatment, settled in Ettore Zanon SpA, is here presented, together with the results so far obtained on the first series cavities in terms of frequency sensitivity, removal rate and surface external temperature. The optimization of BCP treatment by a preliminary fluid-dynamical finite element model is also discussed. Some details about the visual inspection procedure and the furnace qualification are also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP056
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP070	Investigation of the Critical RF Fields of Superconducting Cavity Connections	cavity, vacuum, niobium, impedance	230
	J.C. Wolff, J.I. Iversen, D. Klinke, D. Kostin, D. Reschke, S. Sievers, A. Sulimov, J.H. Thie, M. Wiencek DESY, Hamburg, Germany R. Wendel, J.C. Wolff HAW Hamburg, Hamburg, Germany
	To optimise the length of the drift tube of a superconducting cavity (SC), it is required to know the critical value of the RF fields to prevent a potential early quench at the flange connection in case of a drift tube length reduction. To avoid changes on the SC which has been used for the tests, all RF cryogenic experiments have been carried out by using a cylinder in the center of a 1-cell cavity drift tube to increase the field magnitude at the connection. This cylinder has been designed and optimised by RF simulations to provide a field density at the connection twice as high as at a chosen reference point near the iris. Hence also a test SC with a comparatively low gradient can be used without causing field restrictions. In this contribution an approach to investigate the field limitations of 1.3 GHz TESLA-Shape SC connections and thereby the minimal drift tube length based on simulations will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP070
About •	paper received ※ 23 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019
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MOP073	The Study of High Power Couplers for CIADS	status, multipactoring, operation, experiment	241
	Z.Q. Lin, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, C.L. Li, Y.M. Li, M. Lu, F. Pan, T. Tan, R.X. Wang, Z. Xue, Z.Q. Yang, S.X. Zhang IMP/CAS, Lanzhou, People’s Republic of China
	High power couplers with high operation reliability are needed for the superconducting cavities used in the Linac of CiADS project at IMP. This paper will report two works on high power coupler. The DC bias structure of the coupler was optimized to suppress the multipacting effect, where the series resistors were introduced to the wire of the DC bias to reduce the field propagating along the DC bias¿s wire. For the purpose of significantly decreasing the power needed to condition the coupler, we designed a new RF conditioning scheme, in which the coupler served as a standing wave resonator, and the positions of the crests and troughs of the wave were tunable. The details of the design mentioned above will be depicted.
	Poster MOP073 [14.677 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP073
About •	paper received ※ 25 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP074	External Q Measurement for Quarter Wave Resonators in RISP	pick-up, cavity, cryomodule, coupling	245
	S. Lee, B.H. Choi, M.O. Hyun, Y. Jung, J.W. Kim, Y. Kim, J. Lee, K.T. Seol IBS, Daejeon, Republic of Korea
	A heavy-ion accelerator facility is under construction for Rare Isotope Science Project(RISP) in Korea. The super conducting cavity, quarter wave resonator(QWR) which consists of driver and post linear accelerator system, is now in the mass production phase. In order to develop the QWR cavity and cryomodule, the RF couplers are fabriacated and tested. In this paper, the study of external Q for QWR coupler will be described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP074
About •	paper received ※ 21 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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MOP075	Design of RF Power Coupler Transmitting both 162.5 MHz and 81.25 MHz Power to SRF Cavities for BISOL R&D Research	cavity, ISOL, RF-structure, Windows	249
	F. Zhu, M. Chen, A.Q. Cheng, J.K. Hao, S.W. Quan, F. Wang PKU, Beijing, People’s Republic of China
	Beijing isotope separation on line type rare ion beam facility (BISOL) is a proposed facility which has two superconducting RF linacs. One is a high intense driver linac which adopts half wave resonators (HWRs), and the other is the low current post-accelerator which includes quarter wave resonators (QWRs). For the pre-research of BISOL, a cryomodul which can do the horizontal test of both 81.25 MHz QWR for the post-accelerator and 162.5 MHz HWR for the driver accelerator with the proper external quality factor. For this purpose, Peking University are developing a coupler which can transfer 5 kW power to the 81.25 MHz QWR or cw 20 kW power to the 162.5 MHz HWR cavity. The electromagnetic optimization, Multipacting simulation, thermal analysis and detail structure of the coupler will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP075
About •	paper received ※ 21 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
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MOP076	Fundamental Power Coupler Design for a 325 MHz Balloon SSR Cavity	cavity, multipactoring, vacuum, cryogenics	252
	R.E. Laxdal, Y. Ma, B. Matheson, B.S. Waraich, Z.Y. Yao, V. Zvyagintsev TRIUMF, Vancouver, Canada
	TRIUMF has designed, fabricated and tested the first balloon variant of the single spoke resonator at 325 MHz and β=0.3. TRIUMF has also designed a 6 kW fundamental power coupler as part of the development. The design of the coupler will be presented.
	Poster MOP076 [1.282 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP076
About •	paper received ※ 24 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP078	Adjustable Power Coupler for NICA HWR Cavities	cavity, vacuum, coupling, collider	260
	S.V. Matsievskiy, M.V. Lalayan MEPhI, Moscow, Russia D. Bychanok INP BSU, Minsk, Belarus M. Gusarova JINR, Dubna, Moscow Region, Russia
	Current results on input power coupler development for Half-Wave superconducting accelerating cavity proposed for Nuclotron-based Ion Collider fAcility (NICA) collider injector upgrade are discussed. Two coupler designs are considered, first one is a low-power coupler for cavity tests and the second one is a high-power operational coupler. Both devices are of coaxial type with capacitive coupling; high-power coupler utilizes single ceramic vacuum window. NICA is designed to accelerate different types of ions. Due to the variable intensity of ion sources, beam current will vary in wide range. In order to ensure efficient acceleration, power coupler must be highly adjustable in terms of coupling coefficient. This introduces excessive mechanical stress in the ceramic RF window due to the bellows deformation. In order to mitigate this effect bellows were substituted with sliding contacts. This paper discusses new coupler design and its electrical, mechanical and thermal properties.
	Poster MOP078 [1.296 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP078
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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MOP089	Development of a Suspension System for the Road Transportation of Cryomodule SSR1 through a Multilevel Finite Element-Multibody Approach	ISOL, cavity, cryomodule, software	297
	P. Neri, F. Bucchi University of Pisa, Pisa, Italy D. Passarelli Fermilab, Batavia, Illinois, USA
	The on-road transportation of cryomodules (CM) is a critical phase during which the structure may be subject to relevant dynamic loading. Thus, an accurate design of Transportation Tool (TT), equipped with a proper suspension system, is mandatory. In this paper the TT design for the PIP-II proto SSR1 CM is presented. A finite element (FE) model was developed considering the main CM parts. However, the full model was not suited for the design of the suspension system because of its computational time. Thus, it was exported as a Modal Neutral File to a multibody (MB) software, where minor components were modeled as rigid bodies or lumped stiffnesses. The reduced MB model considerably shortened the computational time and it was exploited for the design of the TT, which includes helical isolators (HI) acting as a mechanical filter. A real 3D acceleration profile, acquired during the transportation of a LCLS-II CM from Fermilab to SLAC, was used to validate the TT effectiveness in reducing the vibrational loading. In addition, the results of the MB analysis were used to perform FE analysis of critical components, such as bellows.
	Poster MOP089 [0.995 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP089
About •	paper received ※ 29 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUFUB3	Mapping Flux Trapping in SRF Cavities to Analyze the Impact of Geometry	cavity, experiment, HOM, niobium	364
	F. Kramer, J. Knobloch, O. Kugeler, J.M. Köszegi HZB, Berlin, Germany J. Knobloch University of Siegen, Siegen, Germany
	A combined temperature and magnetic field mapping system was used to investigate the impact of an ambient field on trapped flux and on the resulting local surface resistance. For this, a 1.3 GHz TESLA single cell cavity was cooled through the superconducting transition at different magnetic field angles with respect to the cavity axis. The measurements suggest, that the field is trapped homogeneously over the cavity volume, without changing its orientation. Flux trapped perpendicular the surface contributed significantly more to the surface resistance, than trapped flux parallel to the surface.
	Slides TUFUB3 [12.777 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUB3
About •	paper received ※ 21 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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TUP008	HOMs Extraction Structure Design for HEPS 166.6 MHz Cavities	HOM, cavity, extraction, experiment	403
	X.R. Hao IHEP, Beijing, People’s Republic of China
	Higher order modes (HOMs) may af{}fect beam stability and refrigeration requirements of superconducting cavity such as the 166.6~MHz superconducting(SC) cavity, which is studied at IHEP. Under certain conditions beam-induced HOMs can accumulate suf{}f{}icient energy to destabilize the beam or quench the SC cavities. In order to limit these ef{}fects, we considers the use of coaxial HOM couplers on the cut-of{}f tubes of the SC cavity. However, HOMs cannot be ef{}fectively extracted by HOM couplers. Therefore, it is necessary to design a HOMs extraction structure to introduce the dangerous modes from the cavity into the bundle tube, which are designed to couple to potentially dangerous modes while suf{}ficiently rejecting the fundamental mode. The HOMs extraction structure consists of an enlarged tubes, a coaxial structure, and the petal. The extraction of the dangerous modes and the suppression of the fundamental mode are realized by the petal structure and the coaxial structure. In order to verify the designs, a rapid prototype for the favored structure was fabricated and characterized on a low-power test-stand.
	Poster TUP008 [1.665 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP008
About •	paper received ※ 22 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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TUP010	Mechanical Design and Horizontal Tests of a Dressed 166.6 MHz Quarter-wave β=1 SRF Cavity System	cavity, cryomodule, superconducting-cavity, SRF	408
	X.Y. Zhang, X.R. Hao, D.B. Li, Z.Q. Li, H.Y. Lin, Q. Ma, Z.H. Mi, Q.Y. Wang, P. Zhang IHEP, Beijing, People’s Republic of China
	Funding: This work has been supported by HEPS-TF project. A 166.6 MHz quarter-wave β=1 superconducting proof-of-principle cavity has been designed and recently been dressed with a helium jacket, fundamental power coupler and tuner. The cavity was subsequently installed in a modified cryomodule and tested in a horizontal manner at both 4.2 K and 2 K. The helium jacket was successfully developed with a focus on minimizing frequency shift due to helium pressure fluctuation while retaining a reasonable tuning range. The Lorentz force detuning (LFD) and microphonics were also optimized during the design. The df/dp and LFD coefficient were measured to be -3.1 Hz/mbar and -0.8 Hz/(MV/m)². These are in good agreement with simulations. Future work is mainly to reduce the stiffness of the cavity and further suppress the vibration mode of the inner conductor.
	Poster TUP010 [1.245 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP010
About •	paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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TUP011	QWR085 Design for Bisol Post Accelerator SCL2	ISOL, cavity, LEBT, niobium	413
	M. Chen, S. Chen, A.Q. Cheng, J.K. Hao, K.X. Liu, Y.Q. Liu, D.M. Ouyang, S.W. Quan, F. Zhu PKU, Beijing, People’s Republic of China Z. Peng CIAE, Beijing, People’s Republic of China
	BISOL(Beijing Isotope-Separation-On-Line Neutron-Rich Beam Facility) is a new generation radioactive ion beam(RIB) facility[1]. It consists a CARR nuclear reactor, a high intensity deuteron accelerator and a post accelera-tor. QWR085 cavity is supposed to be used in SCL2 of post accelerator. This paper mainly talks about the elec-tromagnetic design, mechanical design and vibration damper design of QWR085.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP011
About •	paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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TUP056	A First-Principles Study on Magnetic Flux Trapping at Niobium Grain Boundaries	niobium, electron, cavity, radio-frequency	565
	P. Garg, K.N. Solanki Arizona State University, Tempe, USA T.R. Bieler Michigan State University, East Lansing, Michigan, USA L.D. Cooley NHMFL, Tallahassee, Florida, USA
	Niobium is basis for all superconducting radio frequency cavities, a technology that accelerates charged particle beams to energy levels not possible by other means. When cavities are pushed to limits, significant heating appears at extended material defects, like grain boundaries. Therefore, it is crucial to understand how grain boundary (GB) structure and associated properties lead to trapping of magnetic field, and whether GB itself has any unusual magnetic behavior. Using first-principles calculations, external magnetic field along the GB plane was simulated within an all-electron full-potential linearized augmented plane-wave framework. A ground state with non-zero flux, indicative of flux trapping, was obtained at some grain boundaries, this outcome being influenced strongly by GB local structure. Furthermore, electronic density of states and charge-transfer calculations suggested non-zero spin polarization at grain boundaries, which may be consistent with recent observations of unusual paramagnetic magnetization as a function of specimen surface area for cavity-grade niobium.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP056
About •	paper received ※ 23 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019
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TUP080	Tuner Design and Test for 166.6 MHz SRF Cavity of HEPS	cavity, SRF, high-voltage, LLRF	642
	Z.H. Mi, Z.Q. Li, H.Y. Lin, W.M. Pan, Q.Y. Wang, P. Zhang, X.Y. Zhang, H.J. Zheng IHEP, Beijing, People’s Republic of China
	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 ¿=1. Each cavity will be operated at 4.2 K providing 1.2 MV accelerating. To compensate the frequency change due to manufacturing uncertainty, Lorentz force, beam loading, He pressure and microphonics the plunger tuner and gap tuner are chosen as options. Now the plunger tuner and low temperature gap tuner have been test with cavity, while the warm gap tuner is being designed. Details of the design and summary of the test results of the two type tuners with cavity are presented in this paper.
	Poster TUP080 [1.141 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP080
About •	paper received ※ 22 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUP086	Frequency Tuning System Based on Mobile Plungers For Superconductive Coaxial Half Wave Resonators	cavity, linac, SRF, vacuum	664
	D. Bychanok, S. Huseu, S.A. Maksimenko INP BSU, Minsk, Belarus A.V. Butenko, E. Syresin JINR, Dubna, Moscow Region, Russia E.A. Gurnevich Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk, Belarus M. Gusarova, M.V. Lalayan, S.M. Polozov MEPhI, Moscow, Russia
	The design of a prototype of the frequency tuning system (FTS) for superconductive coaxial half wave cavities (HWR) [1] developed for the Nuclotron-based Ion Collider fAcility (NICA) injector is presented. The proposed system is based on mobile plungers placed in the technological holes in the end caps of the resonator. The FTS allows controlling the penetration depth of plungers, which is monotonically related to the resonant frequency shift of the cavity. The developed FTS includes slow/fast tuner parts and is more compact and simple in comparison to traditional mechanical systems, which deform reversibly the HWR by applying an effort on the beam ports [2]. The similar plunger-based tuner design was considered for QWR cavities in [3]. The results of numerical simulations of the resonant frequency for a wide range of plunger parameters are presented and discussed. The most important parameters for effective frequency shift are estimated. [1] S. Matsievskiy et al., RuPAC’18. doi:10.18429/JACoW-RUPAC2018-WEPSB48 [2] N. Misiara et al., LINAC’16. doi:10.18429/JACoW-LINAC2016-MOPRC026 [3] D. Longuevergne et al., ‘‘A cold tuner system with mobile plunger’’, in Proc. SRF2013, paper THIOD04.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP086
About •	paper received ※ 22 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUP087	Development and Performances of Spoke Cavity Tuner for MYRRHA Linac Project	cavity, controls, linac, operation	667
	N. Gandolfo, S. Blivet, P. Duchesne, D. Le Dréan Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
	In the framework of the Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) 100 MeV linac construction, a fully equipped prototype cryomodule is being developed. In order to control the resonance frequency of the cavities during operation, a tuner has been studied with the specific requirements: high degree of reliability and high tuning speed. This paper reports the design consideration and the first performances measurement in vertical cryostat test at an early stage of the prototyping phase.
	Poster TUP087 [2.367 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP087
About •	paper received ※ 01 July 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019
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TUP106	Mechanical Tuner for a 325 MHz Balloon Single Spoke Resonator	cavity, cryomodule, linac, operation	730
	R.E. Laxdal, J.J. Keir, B. Matheson, N. Muller, Z.Y. Yao TRIUMF, Vancouver, Canada
	TRIUMF has designed, fabricated and tested the first balloon variant of the single spoke resonator at 325 MHz and β=0.3. TRIUMF has also designed and built a mechanical tuner as part of the development. The tuner employs a nutcracker lever pressing at the beam ports driven by a scissor jack. The scissor is actuated through a tube coupling to a warm ball-screw and servo-motor located outside the cryostat. The design and warm tests of the tuner will be presented.
	Poster TUP106 [1.089 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP106
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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WETEB8	The Fundamental Power Coupler for CEPC Booster Cavity	vacuum, cavity, booster, multipactoring	789
	T.M. Huang, F. Bing, R. Guo, H.Y. Lin, Q. Ma, W.M. Pan, J.Y. Zhai, Z. Zhang IHEP, Beijing, People’s Republic of China
	Funding: Supported by National natural Science Foundation of China ( 11475203) 96 Tesla type 1.3GHz 9-cell superconducting cavities, housed in eight 12m-long cryomodules, will be adopted for CEPC booster. Each cavity equips with one variable coupling, double-window fundamental power coupler (FPC). The FPC will operate at RF power up to 20 kW at quasi-CW mode. A variable coupling from 4·10⁶ to 10⁷ is required to meet different operation modes of Higgs, W and Z. A new coupler that employs a 50 Ω coaxial line with bellow structures, a cylindrical warm window, a coaxial planar cold window and a coupling adjusting actuator has been designed. Then two prototypes have been fabricated and high power tested up to CW 70 kW successfully. In this paper, the design, fabrication and high power test of the prototype FPCs will be presented.
	Slides WETEB8 [9.971 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-WETEB8
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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THP004	Design and Fabrication of a Quadrupole-Resonator for Sample R&D	quadrupole, cavity, SRF, niobium	838
	R. Monroy-Villa, D. Reschke, M. Wenskat DESY, Hamburg, Germany W. Hillert, R. Monroy-Villa, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Keckert, O. Kugeler, D.B. Tikhonov HZB, Berlin, Germany P. Putek, S.G. Zadeh, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany U. van Rienen University of Rostock, Rostock, Germany
	Being able to obtain BCS and material properties from the same surface is necessary to gain a fundamental understanding of the evolution of SRF surfaces. A test resonator which will allow to obtain BCS properties from samples is currently under development at the University of Hamburg and DESY and is based on the Quadrupole Resonators developed and operated at CERN and HZB. The current status of the necessary infrastructure, the procurement process and design considerations are shown. In addition, an outline of the planed R&D project with the Quadrupole Resonator will be presented and first RF measurements and surface analysis results of samples will be shown
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP004
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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THP012	Assessment of the Mechanical Properties of Ultra-High Purity Niobium After Cold Work and Heat Treatment With the HL-LHC Crab Cavities as Benchmark	cavity, ECR, operation, niobium	860
	A. Gallifa Terricabras, A. Amorim Carvalho, I. Aviles Santillana, S. Barrière, R. Calaga, E. Cano-Pleite, O. Capatina, M.D. Crouvizier, L. Dassa, M.S. Meyer, N. Valverde Alonso CERN, Geneva, Switzerland M. Benke, A.B. Palotas, G. Szabó, M. Szűcs University of Miskolc, Faculty of Materials Science and Engineering, Miskolc-Egyetemváros, Hungary A. Hlavács, G.J. Krallics, V. Mertinger, M. Sepsi University of Miskolc, Miskolc, Hungary
	The High Luminosity Large Hadron Collider (HL-LHC) is the upgrade of the world’s largest particle collider; it will allow the full exploitation of the LHC potential and its operation beyond 2025. An essential part of the HL-LHC project are the Crab Cavities, that are particle deflecting SRF cavities of non-axisymmetric shape made of bulk ultra-high purity Nb. Since the cavities are produced by complex metal sheet forming processes, followed by a heat treatment (HT) for H outgassing (650 °C, 24 h), there is uncertainty on their mechanical properties after manufacturing and in service conditions (2 K). Mechanical tests at room temperature have been conducted on RRR300 pure Nb samples. The samples were previously submitted, by cold cross-rolling, to different levels of plastic deformation representative of the effective plastic strain seen by the Nb sheets during forming operations. Moreover, a comparison of the mechanical properties of cold cross-rolled samples before and after HT has been established. Results of evolution of the microstructure and hardness are also presented. This study can be of interest for Nb cavities to be sub-mitted to HT at 650 °C, and may help to push the design of novel SRF cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP012
About •	paper received ※ 22 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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THP076	Simulation Analysis of Lorentz Force Induced Oscillations in RF Cavities in Vector Sum and Cw Operation	cavity, operation, controls, alignment	1078
	R. Leewe, K. Fong TRIUMF, Vancouver, Canada
	Within TRIUMFs electron LINAC, two TESLA type cavities are operated with a single klystron in CW mode. Vector sum control is applied for field stabilization and the resonance frequencies are individually tuned with a proportional feedback controller. First operational experiences showed that amplitude oscillations can start in both cavities, while the vector sum is perfectly stable. These instabilities occur at high operating fields and are driven by Lorentz force changes. This paper presents a simulation study of multiple cavities in vector sum operation with respect to Lorentz force oscillations. It will be shown that all cavities in operation have to be damped to guarantee system stability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP076
About •	paper received ※ 22 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
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THP095	Direct Measurement of Thermoelectric Currents During Cool Down	cavity, experiment, niobium, coupling	1139
	A.E. Ivanov, F. Gerigk, A. Macpherson CERN, Geneva, Switzerland
	In recent years there has been much discussion on thermoelectric effects and their role in flux expulsion during cool down of SRF cavities. Magnetic field is often measured to asses both flux expulsion as the cavity undergoes superconducting transition, and thermoelectric currents due to spatial thermal gradients. As a complementary view, in this paper we show direct measurement of the thermoelectric current independent from the expulsion measurement of the magnetic field. In our setup the azimuthally symmetric cavity is vertically installed and the thermal gradient is along the symmetry axis allowing to describe the cool down behavior of the thermoelectric current using simple coupled simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP095
About •	paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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FRCAB8	Systematic Studies of the Second Sound Method for Quench Detection of Superconducting Radio Frequency Cavities	cavity, radio-frequency, interface, diagnostics	1239
	L. Steder, B. Bein, D. Reschke DESY, Hamburg, Germany W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	DESY conducts R&D for SRF cavities, part of the manifold activities are vertical performance tests. Besides the determination of accelerating gradient and quality factor, additional sensors and diagnostic methods are used to obtain more information about the cavity behaviour and the test environment. The second sound system is a tool for spatially resolved quench detection via oscillating super-leak transducers, they record the second sound wave, generated by the quench of the superconducting Niobium. The mounting of the sensors was improved to reduce systematic uncertainties and results of a recent master thesis are presented in the following. Different reconstruction methods are used to determine the origin of the waves. The precision, constraints and limits of these are compared. To introduce an external reference and to qualify the different methods a calibration tool was used. It injects short heat pulses to resistors at exact known space and time coordinates. Results obtained by the different algorithms and measurements with the calibration tool are presented with an emphasis on the possible spatial resolution and the estimation of systematic uncertainties of the methods.
	Slides FRCAB8 [3.039 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB8
About •	paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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Paper

Title

Other Keywords

Page

MOP015

RF Performance Sensitivity to Tuning of Nb₃Sn Coated CEBAF Cavities

cavity, SRF, experiment, factory

55

G.V. Eremeev, W. Crahen, J. Henry, F. Marhauser, C.E. Reece
JLab, Newport News, Virginia, USA
U. Pudasaini
The College of William and Mary, Williamsburg, Virginia, USA

Funding: Co-Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
Nb₃Sn has the potential to surpass niobium as the material of choice for SRF applications. The potential of this material stems from a larger superconducting energy gap, which leads to expectations of a higher RF critical field and a lower RF surface resistance. The appeal of better superconducting properties is offset by the relative complexity of producing practical Nb₃Sn structures, and Nb₃Sn sensitivity to lattice disorder challenges the use of the material for practical applications. Such sensitivity is indirectly probed during SRF cavity development, when the cavity is tuned to match the desired accelerator frequency. In the course of recent experiments we have coated and tuned several multi-cell cavities. Cold RF measurements before and after tuning showed degradation in cavity performance after tuning. The results of RF measurement were compared against strain evolution on Nb₃Sn surface during tuning based on CST and ANSYS models.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP015

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paper received ※ 26 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

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MOP022

Superconducting RF Cavity Materials Research at the S-DALINAC

cavity, niobium, linac, SRF

74

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

Funding: Supported by BMBF Through 05H18RDRB2
Current state-of-the-art superconducting rf (srf) accelerators are mostly using cavities made of high RRR bulk niobium (Nb). The maximum field gradients and quality factors (Q₀) of these cavities are basically reached now. To further increase the srf cavity properties for future accelerator facilities, research of new materials for srf cavity applications is necessary. The current research at the S-DALINAC* is focused on the development of bake-out procedures of Nb samples and cavities in nitrogen (N) atmosphere of up to 100 mbar to nucleate the delta-phase (d-phase) of the Nb-N binary system. The d-phase has superconducting properties which exceed the properties of bulk Nb. This makes the d-phase attractive for srf applications. The vertical test cryostat (vt) at the S-DALINAC has been upgraded and recommissioned to allow investigations of the quality factor and accelerating field gradients of cavities before and after bake-out. The vt upgrade includes a newly developed variable input coupling to allow matching of the external q-factor (Qex) to Q₀. The results of the ongoing research of the nitrogen atmosphere bake-out procedures and the upgrade of the vt will be presented.
*N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018)

Poster MOP022 [1.759 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP022

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paper received ※ 21 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

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MOP041

Comparison of the Lattice Thermal Conductivity of Superconducting Tantalum and Niobium

scattering, electron, lattice, niobium

148

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

Funding: This work is supported by the U.S. Department of Energy, Office of High Energy Physics through Grant No. DE-FG02-13ER41974.
The thermal conductivity k of superconducting Ta behaves similarly to that of superconducting Nb, albeit at colder temperatures. This shift is due to the superconducting transition temperature of Ta being 4.3 K, versus 9.25 K for Nb. For example, the temperature of the phonon peak of properly treated Ta is about 1 K as opposed to a phonon peak at about 2 K for Nb. The typical value of k of Ta is smaller than Nb with the value at the phonon peak for Ta being O(10) W/ m/ K. Like Nb, k is dominated by phonons at these temperatures. This lattice k can be modeled by the Boltzmann transport equation, solved here by a Monte Carlo method using the relaxation time approximation. Individual scattering mechanisms due to boundaries, dislocations, and residual normal electrons are examined, and the phonon dispersion relation is included. Differences in the thermal response of deformed Ta, as compared with Nb, may be attributed to differences in dislocation densities of the two metals following similar levels of deformation. Boundary scattering dominates at the coldest temperatures. The phonon peak decreases and shifts to warmer temperatures with deformation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP041

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paper received ※ 19 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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MOP050

Modular Power Couplers for 217 MHz Superconducting CH-Cavities

cavity, Windows, linac, heavy-ion

168

J. List, K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, M. Miski-Oglu
HIM, Mainz, Germany
K. Aulenbacher, W.A. Barth, C. Burandt, V. Gettmann, M. Heilmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, A. Schnase, S. Yaramyshev
GSI, Darmstadt, Germany
K. Aulenbacher, F.D. Dziuba, S. Lauber, J. List
IKP, Mainz, Germany
M. Basten, M. Busch, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany

The HELmholtz LInear ACcelerator (HELIAC) is being developed by a collaboration of HIM, GSI and the Goethe University of Frankfurt. It is a superconducting (sc), continuous wave (cw) heavy ion linac that comprises novel Crossbar H-mode (CH) cavities. In April 2017 and November/December 2018 the first sc CH-cavity of the linac was tested with beam. The first operations of the cavity showed, that the prototype of the rf power coupler needs to be further improved. A new version of the coupler is being designed at the HIM. Further development will mainly be focused on the heat input into the cryostat caused by the coupler. Also the coupler will have a modular design. This improves the accessibility and maintenance of the coupler. Various cryogenic and rf tests are foreseen, to provide a reliable, fail-safe coupler for the HELIAC. For an enhanced coupler test stand a movable reflector has been designed and built. With its movable semi-reflective element, it allows to operate the test stand in a resonance mode. In addition, the movable reflector can vary the coupling factor. This contribution discusses the recent coupler R&D for the HELIAC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP050

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paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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MOP056

Surface Treatments for the Series Production of ESS Medium Beta Cavities

cavity, recirculation, SRF, niobium

188

M. Bertucci, A. Bosotti, A. D’Ambros, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
D. Rizzetto, M. Rizzi
Ettore Zanon S.p.A., Schio, Italy
A. Visentin
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy

The surface treatment of ESS 704 MHz medium beta cavities consists of a bulk BCP 200 micron removal, a 10 h 600°C heat treatment and a final 20 micron BCP performed after tank integration. The facility currently employed for the BCP treatment, settled in Ettore Zanon SpA, is here presented, together with the results so far obtained on the first series cavities in terms of frequency sensitivity, removal rate and surface external temperature. The optimization of BCP treatment by a preliminary fluid-dynamical finite element model is also discussed. Some details about the visual inspection procedure and the furnace qualification are also presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP056

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paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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MOP070

Investigation of the Critical RF Fields of Superconducting Cavity Connections

cavity, vacuum, niobium, impedance

230

J.C. Wolff, J.I. Iversen, D. Klinke, D. Kostin, D. Reschke, S. Sievers, A. Sulimov, J.H. Thie, M. Wiencek
DESY, Hamburg, Germany
R. Wendel, J.C. Wolff
HAW Hamburg, Hamburg, Germany

To optimise the length of the drift tube of a superconducting cavity (SC), it is required to know the critical value of the RF fields to prevent a potential early quench at the flange connection in case of a drift tube length reduction. To avoid changes on the SC which has been used for the tests, all RF cryogenic experiments have been carried out by using a cylinder in the center of a 1-cell cavity drift tube to increase the field magnitude at the connection. This cylinder has been designed and optimised by RF simulations to provide a field density at the connection twice as high as at a chosen reference point near the iris. Hence also a test SC with a comparatively low gradient can be used without causing field restrictions. In this contribution an approach to investigate the field limitations of 1.3 GHz TESLA-Shape SC connections and thereby the minimal drift tube length based on simulations will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP070

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paper received ※ 23 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019

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MOP073

The Study of High Power Couplers for CIADS

status, multipactoring, operation, experiment

241

Z.Q. Lin, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, C.L. Li, Y.M. Li, M. Lu, F. Pan, T. Tan, R.X. Wang, Z. Xue, Z.Q. Yang, S.X. Zhang
IMP/CAS, Lanzhou, People’s Republic of China

High power couplers with high operation reliability are needed for the superconducting cavities used in the Linac of CiADS project at IMP. This paper will report two works on high power coupler. The DC bias structure of the coupler was optimized to suppress the multipacting effect, where the series resistors were introduced to the wire of the DC bias to reduce the field propagating along the DC bias¿s wire. For the purpose of significantly decreasing the power needed to condition the coupler, we designed a new RF conditioning scheme, in which the coupler served as a standing wave resonator, and the positions of the crests and troughs of the wave were tunable. The details of the design mentioned above will be depicted.

Poster MOP073 [14.677 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP073

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paper received ※ 25 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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MOP074

External Q Measurement for Quarter Wave Resonators in RISP

pick-up, cavity, cryomodule, coupling

245

S. Lee, B.H. Choi, M.O. Hyun, Y. Jung, J.W. Kim, Y. Kim, J. Lee, K.T. Seol
IBS, Daejeon, Republic of Korea

A heavy-ion accelerator facility is under construction for Rare Isotope Science Project(RISP) in Korea. The super conducting cavity, quarter wave resonator(QWR) which consists of driver and post linear accelerator system, is now in the mass production phase. In order to develop the QWR cavity and cryomodule, the RF couplers are fabriacated and tested. In this paper, the study of external Q for QWR coupler will be described.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP074

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paper received ※ 21 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

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MOP075

Design of RF Power Coupler Transmitting both 162.5 MHz and 81.25 MHz Power to SRF Cavities for BISOL R&D Research

cavity, ISOL, RF-structure, Windows

249

F. Zhu, M. Chen, A.Q. Cheng, J.K. Hao, S.W. Quan, F. Wang
PKU, Beijing, People’s Republic of China

Beijing isotope separation on line type rare ion beam facility (BISOL) is a proposed facility which has two superconducting RF linacs. One is a high intense driver linac which adopts half wave resonators (HWRs), and the other is the low current post-accelerator which includes quarter wave resonators (QWRs). For the pre-research of BISOL, a cryomodul which can do the horizontal test of both 81.25 MHz QWR for the post-accelerator and 162.5 MHz HWR for the driver accelerator with the proper external quality factor. For this purpose, Peking University are developing a coupler which can transfer 5 kW power to the 81.25 MHz QWR or cw 20 kW power to the 162.5 MHz HWR cavity. The electromagnetic optimization, Multipacting simulation, thermal analysis and detail structure of the coupler will be presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP075

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paper received ※ 21 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

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MOP076

Fundamental Power Coupler Design for a 325 MHz Balloon SSR Cavity

cavity, multipactoring, vacuum, cryogenics

252

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

TRIUMF has designed, fabricated and tested the first balloon variant of the single spoke resonator at 325 MHz and β=0.3. TRIUMF has also designed a 6 kW fundamental power coupler as part of the development. The design of the coupler will be presented.

Poster MOP076 [1.282 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP076

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paper received ※ 24 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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MOP078

Adjustable Power Coupler for NICA HWR Cavities

cavity, vacuum, coupling, collider

260

S.V. Matsievskiy, M.V. Lalayan
MEPhI, Moscow, Russia
D. Bychanok
INP BSU, Minsk, Belarus
M. Gusarova
JINR, Dubna, Moscow Region, Russia

Current results on input power coupler development for Half-Wave superconducting accelerating cavity proposed for Nuclotron-based Ion Collider fAcility (NICA) collider injector upgrade are discussed. Two coupler designs are considered, first one is a low-power coupler for cavity tests and the second one is a high-power operational coupler. Both devices are of coaxial type with capacitive coupling; high-power coupler utilizes single ceramic vacuum window. NICA is designed to accelerate different types of ions. Due to the variable intensity of ion sources, beam current will vary in wide range. In order to ensure efficient acceleration, power coupler must be highly adjustable in terms of coupling coefficient. This introduces excessive mechanical stress in the ceramic RF window due to the bellows deformation. In order to mitigate this effect bellows were substituted with sliding contacts. This paper discusses new coupler design and its electrical, mechanical and thermal properties.

Poster MOP078 [1.296 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP078

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paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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MOP089

Development of a Suspension System for the Road Transportation of Cryomodule SSR1 through a Multilevel Finite Element-Multibody Approach

ISOL, cavity, cryomodule, software

297

P. Neri, F. Bucchi
University of Pisa, Pisa, Italy
D. Passarelli
Fermilab, Batavia, Illinois, USA

The on-road transportation of cryomodules (CM) is a critical phase during which the structure may be subject to relevant dynamic loading. Thus, an accurate design of Transportation Tool (TT), equipped with a proper suspension system, is mandatory. In this paper the TT design for the PIP-II proto SSR1 CM is presented. A finite element (FE) model was developed considering the main CM parts. However, the full model was not suited for the design of the suspension system because of its computational time. Thus, it was exported as a Modal Neutral File to a multibody (MB) software, where minor components were modeled as rigid bodies or lumped stiffnesses. The reduced MB model considerably shortened the computational time and it was exploited for the design of the TT, which includes helical isolators (HI) acting as a mechanical filter. A real 3D acceleration profile, acquired during the transportation of a LCLS-II CM from Fermilab to SLAC, was used to validate the TT effectiveness in reducing the vibrational loading. In addition, the results of the MB analysis were used to perform FE analysis of critical components, such as bellows.

Poster MOP089 [0.995 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP089

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paper received ※ 29 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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TUFUB3

Mapping Flux Trapping in SRF Cavities to Analyze the Impact of Geometry

cavity, experiment, HOM, niobium

364

F. Kramer, J. Knobloch, O. Kugeler, J.M. Köszegi
HZB, Berlin, Germany
J. Knobloch
University of Siegen, Siegen, Germany

A combined temperature and magnetic field mapping system was used to investigate the impact of an ambient field on trapped flux and on the resulting local surface resistance. For this, a 1.3 GHz TESLA single cell cavity was cooled through the superconducting transition at different magnetic field angles with respect to the cavity axis. The measurements suggest, that the field is trapped homogeneously over the cavity volume, without changing its orientation. Flux trapped perpendicular the surface contributed significantly more to the surface resistance, than trapped flux parallel to the surface.

Slides TUFUB3 [12.777 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUB3

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paper received ※ 21 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

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TUP008

HOMs Extraction Structure Design for HEPS 166.6 MHz Cavities

HOM, cavity, extraction, experiment

403

X.R. Hao
IHEP, Beijing, People’s Republic of China

Higher order modes (HOMs) may af{}fect beam stability and refrigeration requirements of superconducting cavity such as the 166.6~MHz superconducting(SC) cavity, which is studied at IHEP. Under certain conditions beam-induced HOMs can accumulate suf{}f{}icient energy to destabilize the beam or quench the SC cavities. In order to limit these ef{}fects, we considers the use of coaxial HOM couplers on the cut-of{}f tubes of the SC cavity. However, HOMs cannot be ef{}fectively extracted by HOM couplers. Therefore, it is necessary to design a HOMs extraction structure to introduce the dangerous modes from the cavity into the bundle tube, which are designed to couple to potentially dangerous modes while suf{}ficiently rejecting the fundamental mode. The HOMs extraction structure consists of an enlarged tubes, a coaxial structure, and the petal. The extraction of the dangerous modes and the suppression of the fundamental mode are realized by the petal structure and the coaxial structure. In order to verify the designs, a rapid prototype for the favored structure was fabricated and characterized on a low-power test-stand.

Poster TUP008 [1.665 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP008

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paper received ※ 22 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

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TUP010

Mechanical Design and Horizontal Tests of a Dressed 166.6 MHz Quarter-wave β=1 SRF Cavity System

cavity, cryomodule, superconducting-cavity, SRF

408

X.Y. Zhang, X.R. Hao, D.B. Li, Z.Q. Li, H.Y. Lin, Q. Ma, Z.H. Mi, Q.Y. Wang, P. Zhang
IHEP, Beijing, People’s Republic of China

Funding: This work has been supported by HEPS-TF project.
A 166.6 MHz quarter-wave β=1 superconducting proof-of-principle cavity has been designed and recently been dressed with a helium jacket, fundamental power coupler and tuner. The cavity was subsequently installed in a modified cryomodule and tested in a horizontal manner at both 4.2 K and 2 K. The helium jacket was successfully developed with a focus on minimizing frequency shift due to helium pressure fluctuation while retaining a reasonable tuning range. The Lorentz force detuning (LFD) and microphonics were also optimized during the design. The df/dp and LFD coefficient were measured to be -3.1 Hz/mbar and -0.8 Hz/(MV/m)². These are in good agreement with simulations. Future work is mainly to reduce the stiffness of the cavity and further suppress the vibration mode of the inner conductor.

Poster TUP010 [1.245 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP010

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paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

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TUP011

QWR085 Design for Bisol Post Accelerator SCL2

ISOL, cavity, LEBT, niobium

413

M. Chen, S. Chen, A.Q. Cheng, J.K. Hao, K.X. Liu, Y.Q. Liu, D.M. Ouyang, S.W. Quan, F. Zhu
PKU, Beijing, People’s Republic of China
Z. Peng
CIAE, Beijing, People’s Republic of China

BISOL(Beijing Isotope-Separation-On-Line Neutron-Rich Beam Facility) is a new generation radioactive ion beam(RIB) facility[1]. It consists a CARR nuclear reactor, a high intensity deuteron accelerator and a post accelera-tor. QWR085 cavity is supposed to be used in SCL2 of post accelerator. This paper mainly talks about the elec-tromagnetic design, mechanical design and vibration damper design of QWR085.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP011

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paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

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TUP056

A First-Principles Study on Magnetic Flux Trapping at Niobium Grain Boundaries

niobium, electron, cavity, radio-frequency

565

P. Garg, K.N. Solanki
Arizona State University, Tempe, USA
T.R. Bieler
Michigan State University, East Lansing, Michigan, USA
L.D. Cooley
NHMFL, Tallahassee, Florida, USA

Niobium is basis for all superconducting radio frequency cavities, a technology that accelerates charged particle beams to energy levels not possible by other means. When cavities are pushed to limits, significant heating appears at extended material defects, like grain boundaries. Therefore, it is crucial to understand how grain boundary (GB) structure and associated properties lead to trapping of magnetic field, and whether GB itself has any unusual magnetic behavior. Using first-principles calculations, external magnetic field along the GB plane was simulated within an all-electron full-potential linearized augmented plane-wave framework. A ground state with non-zero flux, indicative of flux trapping, was obtained at some grain boundaries, this outcome being influenced strongly by GB local structure. Furthermore, electronic density of states and charge-transfer calculations suggested non-zero spin polarization at grain boundaries, which may be consistent with recent observations of unusual paramagnetic magnetization as a function of specimen surface area for cavity-grade niobium.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP056

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paper received ※ 23 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019

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TUP080

Tuner Design and Test for 166.6 MHz SRF Cavity of HEPS

cavity, SRF, high-voltage, LLRF

642

Z.H. Mi, Z.Q. Li, H.Y. Lin, W.M. Pan, Q.Y. Wang, P. Zhang, X.Y. Zhang, H.J. Zheng
IHEP, Beijing, People’s Republic of China

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 ¿=1. Each cavity will be operated at 4.2 K providing 1.2 MV accelerating. To compensate the frequency change due to manufacturing uncertainty, Lorentz force, beam loading, He pressure and microphonics the plunger tuner and gap tuner are chosen as options. Now the plunger tuner and low temperature gap tuner have been test with cavity, while the warm gap tuner is being designed. Details of the design and summary of the test results of the two type tuners with cavity are presented in this paper.

Poster TUP080 [1.141 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP080

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paper received ※ 22 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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TUP086

Frequency Tuning System Based on Mobile Plungers For Superconductive Coaxial Half Wave Resonators

cavity, linac, SRF, vacuum

664

D. Bychanok, S. Huseu, S.A. Maksimenko
INP BSU, Minsk, Belarus
A.V. Butenko, E. Syresin
JINR, Dubna, Moscow Region, Russia
E.A. Gurnevich
Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk, Belarus
M. Gusarova, M.V. Lalayan, S.M. Polozov
MEPhI, Moscow, Russia

The design of a prototype of the frequency tuning system (FTS) for superconductive coaxial half wave cavities (HWR) [1] developed for the Nuclotron-based Ion Collider fAcility (NICA) injector is presented. The proposed system is based on mobile plungers placed in the technological holes in the end caps of the resonator. The FTS allows controlling the penetration depth of plungers, which is monotonically related to the resonant frequency shift of the cavity. The developed FTS includes slow/fast tuner parts and is more compact and simple in comparison to traditional mechanical systems, which deform reversibly the HWR by applying an effort on the beam ports [2]. The similar plunger-based tuner design was considered for QWR cavities in [3]. The results of numerical simulations of the resonant frequency for a wide range of plunger parameters are presented and discussed. The most important parameters for effective frequency shift are estimated.
[1] S. Matsievskiy et al., RuPAC’18. doi:10.18429/JACoW-RUPAC2018-WEPSB48
[2] N. Misiara et al., LINAC’16. doi:10.18429/JACoW-LINAC2016-MOPRC026
[3] D. Longuevergne et al., ‘‘A cold tuner system with mobile plunger’’, in Proc. SRF2013, paper THIOD04.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP086

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paper received ※ 22 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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TUP087

Development and Performances of Spoke Cavity Tuner for MYRRHA Linac Project

cavity, controls, linac, operation

667

N. Gandolfo, S. Blivet, P. Duchesne, D. Le Dréan
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

In the framework of the Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) 100 MeV linac construction, a fully equipped prototype cryomodule is being developed. In order to control the resonance frequency of the cavities during operation, a tuner has been studied with the specific requirements: high degree of reliability and high tuning speed. This paper reports the design consideration and the first performances measurement in vertical cryostat test at an early stage of the prototyping phase.

Poster TUP087 [2.367 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP087

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paper received ※ 01 July 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

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TUP106

Mechanical Tuner for a 325 MHz Balloon Single Spoke Resonator

cavity, cryomodule, linac, operation

730

R.E. Laxdal, J.J. Keir, B. Matheson, N. Muller, Z.Y. Yao
TRIUMF, Vancouver, Canada

TRIUMF has designed, fabricated and tested the first balloon variant of the single spoke resonator at 325 MHz and β=0.3. TRIUMF has also designed and built a mechanical tuner as part of the development. The tuner employs a nutcracker lever pressing at the beam ports driven by a scissor jack. The scissor is actuated through a tube coupling to a warm ball-screw and servo-motor located outside the cryostat. The design and warm tests of the tuner will be presented.

Poster TUP106 [1.089 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP106

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paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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WETEB8

The Fundamental Power Coupler for CEPC Booster Cavity

vacuum, cavity, booster, multipactoring

789

T.M. Huang, F. Bing, R. Guo, H.Y. Lin, Q. Ma, W.M. Pan, J.Y. Zhai, Z. Zhang
IHEP, Beijing, People’s Republic of China

Funding: Supported by National natural Science Foundation of China ( 11475203)
96 Tesla type 1.3GHz 9-cell superconducting cavities, housed in eight 12m-long cryomodules, will be adopted for CEPC booster. Each cavity equips with one variable coupling, double-window fundamental power coupler (FPC). The FPC will operate at RF power up to 20 kW at quasi-CW mode. A variable coupling from 4·10⁶ to 10⁷ is required to meet different operation modes of Higgs, W and Z. A new coupler that employs a 50 Ω coaxial line with bellow structures, a cylindrical warm window, a coaxial planar cold window and a coupling adjusting actuator has been designed. Then two prototypes have been fabricated and high power tested up to CW 70 kW successfully. In this paper, the design, fabrication and high power test of the prototype FPCs will be presented.

Slides WETEB8 [9.971 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-WETEB8

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paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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THP004

Design and Fabrication of a Quadrupole-Resonator for Sample R&D

quadrupole, cavity, SRF, niobium

838

R. Monroy-Villa, D. Reschke, M. Wenskat
DESY, Hamburg, Germany
W. Hillert, R. Monroy-Villa, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Keckert, O. Kugeler, D.B. Tikhonov
HZB, Berlin, Germany
P. Putek, S.G. Zadeh, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
U. van Rienen
University of Rostock, Rostock, Germany

Being able to obtain BCS and material properties from the same surface is necessary to gain a fundamental understanding of the evolution of SRF surfaces. A test resonator which will allow to obtain BCS properties from samples is currently under development at the University of Hamburg and DESY and is based on the Quadrupole Resonators developed and operated at CERN and HZB. The current status of the necessary infrastructure, the procurement process and design considerations are shown. In addition, an outline of the planed R&D project with the Quadrupole Resonator will be presented and first RF measurements and surface analysis results of samples will be shown

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP004

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paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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THP012

Assessment of the Mechanical Properties of Ultra-High Purity Niobium After Cold Work and Heat Treatment With the HL-LHC Crab Cavities as Benchmark

cavity, ECR, operation, niobium

860

A. Gallifa Terricabras, A. Amorim Carvalho, I. Aviles Santillana, S. Barrière, R. Calaga, E. Cano-Pleite, O. Capatina, M.D. Crouvizier, L. Dassa, M.S. Meyer, N. Valverde Alonso
CERN, Geneva, Switzerland
M. Benke, A.B. Palotas, G. Szabó, M. Szűcs
University of Miskolc, Faculty of Materials Science and Engineering, Miskolc-Egyetemváros, Hungary
A. Hlavács, G.J. Krallics, V. Mertinger, M. Sepsi
University of Miskolc, Miskolc, Hungary

The High Luminosity Large Hadron Collider (HL-LHC) is the upgrade of the world’s largest particle collider; it will allow the full exploitation of the LHC potential and its operation beyond 2025. An essential part of the HL-LHC project are the Crab Cavities, that are particle deflecting SRF cavities of non-axisymmetric shape made of bulk ultra-high purity Nb. Since the cavities are produced by complex metal sheet forming processes, followed by a heat treatment (HT) for H outgassing (650 °C, 24 h), there is uncertainty on their mechanical properties after manufacturing and in service conditions (2 K). Mechanical tests at room temperature have been conducted on RRR300 pure Nb samples. The samples were previously submitted, by cold cross-rolling, to different levels of plastic deformation representative of the effective plastic strain seen by the Nb sheets during forming operations. Moreover, a comparison of the mechanical properties of cold cross-rolled samples before and after HT has been established. Results of evolution of the microstructure and hardness are also presented. This study can be of interest for Nb cavities to be sub-mitted to HT at 650 °C, and may help to push the design of novel SRF cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP012

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paper received ※ 22 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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THP076

Simulation Analysis of Lorentz Force Induced Oscillations in RF Cavities in Vector Sum and Cw Operation

cavity, operation, controls, alignment

1078

R. Leewe, K. Fong
TRIUMF, Vancouver, Canada

Within TRIUMFs electron LINAC, two TESLA type cavities are operated with a single klystron in CW mode. Vector sum control is applied for field stabilization and the resonance frequencies are individually tuned with a proportional feedback controller. First operational experiences showed that amplitude oscillations can start in both cavities, while the vector sum is perfectly stable. These instabilities occur at high operating fields and are driven by Lorentz force changes. This paper presents a simulation study of multiple cavities in vector sum operation with respect to Lorentz force oscillations. It will be shown that all cavities in operation have to be damped to guarantee system stability.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP076

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paper received ※ 22 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

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THP095

Direct Measurement of Thermoelectric Currents During Cool Down

cavity, experiment, niobium, coupling

1139

A.E. Ivanov, F. Gerigk, A. Macpherson
CERN, Geneva, Switzerland

In recent years there has been much discussion on thermoelectric effects and their role in flux expulsion during cool down of SRF cavities. Magnetic field is often measured to asses both flux expulsion as the cavity undergoes superconducting transition, and thermoelectric currents due to spatial thermal gradients. As a complementary view, in this paper we show direct measurement of the thermoelectric current independent from the expulsion measurement of the magnetic field. In our setup the azimuthally symmetric cavity is vertically installed and the thermal gradient is along the symmetry axis allowing to describe the cool down behavior of the thermoelectric current using simple coupled simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP095

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paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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FRCAB8

Systematic Studies of the Second Sound Method for Quench Detection of Superconducting Radio Frequency Cavities

cavity, radio-frequency, interface, diagnostics

1239

L. Steder, B. Bein, D. Reschke
DESY, Hamburg, Germany
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

DESY conducts R&D for SRF cavities, part of the manifold activities are vertical performance tests. Besides the determination of accelerating gradient and quality factor, additional sensors and diagnostic methods are used to obtain more information about the cavity behaviour and the test environment. The second sound system is a tool for spatially resolved quench detection via oscillating super-leak transducers, they record the second sound wave, generated by the quench of the superconducting Niobium. The mounting of the sensors was improved to reduce systematic uncertainties and results of a recent master thesis are presented in the following. Different reconstruction methods are used to determine the origin of the waves. The precision, constraints and limits of these are compared. To introduce an external reference and to qualify the different methods a calibration tool was used. It injects short heat pulses to resistors at exact known space and time coordinates. Results obtained by the different algorithms and measurements with the calibration tool are presented with an emphasis on the possible spatial resolution and the estimation of systematic uncertainties of the methods.

Slides FRCAB8 [3.039 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB8

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paper received ※ 21 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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