Keyword: simulation
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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 icon 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 icon 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 icon 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 icon 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 icon 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 icon 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 icon 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 icon 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 icon 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
    IPN, 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 icon 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 icon 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 icon 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 icon 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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