WEOCAV —  Wednesday Oral Cavities   (30-Jun-21   08:00—10:30)
Paper Title Page
High-Performance Large-Grain Cavities for the ILC  
  • K. Umemori
    KEK, Ibaraki, Japan
  Large-grain SRF cavities might offer performance and cost benefits for the ILC and other future accelerators. On the other hand, ununiformity of grains might sometimes give difficulties on fabrication. Varication of mechanical strength is also another issues related to high pressure gas safety. This contribution will present an overview of recent worldwide activities related to large grain cavities. Materials, fabrications and cavity performances will be discussed.  
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Development and Vertical Tests of a 166.6-MHz Proof-of-Principle Superconduting β = 1 Quarter-Wave Cavity for HEPS  
  • P. Zhang, J. Dai, L. Guo, T.M. Huang, Z.Q. Li, H.Y. Lin, Q. Ma, F. Meng, Z.H. Mi, Q.Y. Wang, X.Y. Zhang
    IHEP, Beijing, People’s Republic of China
  Funding: This work was supported by the High Energy Photon Source - Test Facility (HEPS-TF) project, HEPS project and Chinese Academy of Sciences.
Low-frequency superconducting cavities are needed in main accelerators for storage ring light sources with ultralow emittance. Therefore, a compact 166.6-MHz superconducting proof-of-principle cavity was designed for the High Energy Photon Source (HEPS) in China by adopting a quarter-wave geometry with β=1*. The cavity is compact in size yet possessing a low resonant frequency. The nearest higher order mode is significantly separated from the fundamental mode, making the cavity attractive for high-current accelerators such as HEPS. The achieved accelerating voltage of 3.0 MV is well beyond the designed 1.5 MV and high surface electromagnetic fields were reached with excellent RF and mechanical performances. Multipacting barriers were easily processed. This constitutes the first demonstration of a compact low-frequency β=1 superconducting cavity for HEPS. The design, fabrication, surface preparation, and cryogenic tests of the cavity will be presented.
* P. Zhang, et al., Review of Scientific Instruments 90, 084705 (2019).
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WEOCAV03 RF Dipole Crab Cavity Testing for HL-LHC 687
  • N. Valverde Alonso, R. Calaga, S.J. Calvo, O. Capatina, O. Capatina, A. Castilla, M. Chiodini, C. Duval, L.M.A. Ferreira, M. Gourragne, P.J. Kohler, T. Mikkola, J.A. Mitchell, E. Montesinos, C. Pasquino, G. Pechaud, N. Stapley, M. Therasse, K. Turaj, J.D. Walker
    CERN, Geneva 23, Switzerland
  • A. Castilla
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • A. Castilla
    Lancaster University, Lancaster, United Kingdom
  RF Crab Cavities are an essential element of the High Luminosity LHC (HL-LHC) upgrade at CERN. Two RF dipole crab cavity used for the compensation of the horizontal crossing angle were recently manufactured and integrated into Titanium Helium tank and RF ancillaries necessary for the beam operation. The two cavities will be integrated into a cryomodule in collaboration with UK-STFC and tested with proton beams in the SPS in 2023. This paper will highlight the RF measurements during the important manufacturing steps, surface preparation and cavity performance at 2K.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEOCAV03  
About • Received ※ 18 June 2021 — Revised ※ 07 September 2021 — Accepted ※ 16 September 2021 — Issue date ※ 22 November 2021
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WEOCAV04 Optimization of a Traveling Wave Superconducting Radiofrequency Cavity for Upgrading the International Linear Collider 694
  • V.D. Shemelin
    Valery D Shemelin, Freeville, USA
  • H. Padamseepresenter
    Cornell University, Ithaca, New York, USA
  • H. Padamseepresenter, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  The Standing Wave TESLA Niobium-based structure is limited to a gradient of about 50 MV/m by the critical RF magnetic field. To break through this barrier, we explore the option of Niobium-based traveling wave (TW) structures. Optimization of TW structures was done taking into account experimentally known limiting electric and magnetic fields. It is shown that a TW structure can have an accelerating gradient above 70 MeV/m that is about 1.5 times higher than contemporary standing wave structures with the same critical magnetic field. The other benefit of TW structures shown is R/Q about 2 times higher than TESLA structure that reduces 2 times the dynamic heat load. A method is proposed how to make TW structures multipactor-free. Some design proposals can be realized to facilitate fabrication. Further increase of the real-estate gradient (equivalent to 80 MV/m active gradient) is also possible by increasing the length of the accelerating structure because of higher group velocity and cell-to-cell coupling. Realization of this work opens paths to ILC energy upgrades beyond 1 TeV to 3 TeV in competition with CLIC. The paper will discuss corresponding opportunities and challenges.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEOCAV04  
About • Received ※ 15 June 2021 — Accepted ※ 24 October 2021 — Issue date; ※ 16 May 2022  
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WEOCAV06 Saraf-Phase 2 Low-Beta and High-Beta Superconducting Cavities Qualification 703
  • G. Ferrand, G. Jullien, S. Ladegaillerie, N. Misiara, N. Pichoff, C. Servouin
    CEA-IRFU, Gif-sur-Yvette, France
  • M. Baudrier, E. Fayette, L. Maurice
    CEA-DRF-IRFU, France
  • A. Navitski, L. Zweibaeumer
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  CEA is committed to delivering a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5 mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40 MeV. The SCL consists in four cryomodules. The first two identical cryomodules host 6 half-wave resonator (HWR) low beta cavities (β= 0.09) at 176 MHz. The last two identical cryomodules will host 7 HWR high-beta cavities (β = 0.18) at 176 MHz. The low-beta prototypes was qualified in 2019. Low-beta series manufacturing is on-going. The high-beta prototype was first tested in 2019 but failed. A new prototype was tested in the end of 2020. This contribution will present the results of the tests for low- and high-beta SARAF cavities, series and prototypes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEOCAV06  
About • Received ※ 21 June 2021 — Revised ※ 17 October 2021 — Accepted ※ 20 December 2021 — Issue date ※ 17 May 2022
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Damage Recovery for SRF Photoinjector Cavities  
  • Y. Tamashevich, A. Frahm, F. Göbel, S. Heling, A. Hellwig, K. Janke, S. Klauke, J. Knobloch, A.N. Matveenko, A. Neumann, H. Plötz, A.L. Prudnikava, S. Rotterdam, M. Schuster, J. Ullrich
    HZB, Berlin, Germany
  Two niobium elliptical 1.3 GHz SRF electron photoinjector cavities were successfully recovered after mechanical inner surface damage. Both injector cavities had deep imprints in critical high surface electric field area around the photoelectric cathode position. The repairing procedure, consisting of surface inspection, mechanical polishing and light chemical etching is described in detail. Subsequent cold RF tests demonstrate complete performance recovery.  
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