SRF Technology - Ancillaries
HOM coupler / dampers
Paper Title Page
THP068 Evaluation of Low Heat Conductivity RF Cables 1045
 
  • G. Cheng, G. Ciovati, M.L. Morrone
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
New potential applications of superconducting radio-frequency can be envisioned with conduction cooling of the cavities using cryocoolers. In this case, the total heat load to the cryocoolers have to be carefully managed to assure sufficient margin to operate the cavity at an acceptable accelerating gradient. The static and dynamic heat load from rf cables connected to the cavity can be a significant contribution to the total heat load. In this contribution we report the results from measurements of the temperature profile at 1.3 GHz for two low heat conductivity rf cables, as a function of the rf power and with one end of the cable in thermal contact with a liquid helium bath at 4.3 K. A parametric model of the two cables was developed with ANSYS to match the temperature profiles and calculate the heat load at the cold end of the cable.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP068  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP070 CEPC HOM Coupler R&D 1050
 
  • H.J. Zheng, F. Meng, P. Sha, J.Y. Zhai
    IHEP, Beijing, People’s Republic of China
 
  The conceptual design report (CDR) for the Circular Electron Positron Collider (CEPC) has been published in September 2018. In this talk, the CDR design and prototyping of the HOM coupler for the CEPC Collider ring cavity will be given. Each cavity has two detachable coaxial HOM couplers mounted on the cavity beam pipe with HOM power handling capacity of 1 kW. A double notch coupler is chosen due to its wide bandwidth for the fundamental mode. A prototype of this HOM coupler and a coaxial line test bench have been fabricated and tested under low power. The low power test results agree well with the simulation results. The high power test was also carried out in room temperature.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP070  
About • paper received ※ 19 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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THP071 HOM Measurement Results for CEPC 650 MHz 2-cell Cavity 1055
 
  • H.J. Zheng, F. Meng, J.Y. Zhai
    IHEP, Beijing, People’s Republic of China
 
  CEPC will use a 650 MHz RF system with 240 2-cell cavities for the Collider. The Collider is a double-ring with shared cavities for Higgs operation and separate cavities for W and Z operations. The higher order modes (HOM) excited by the intense beam bunches must be damped to avoid additional cryogenic loss and multi-bunch instabilities. In this paper, the impedance budget and HOM damping and HOM power requirement for the CEPC Collider ring are given. This HOM power limit and the fast-growing longitudinal coupled-bunch instabilities (CBI) driven by both the fundamental and higher order modes impedance of the RF cavities determine to a large extent the highest beam current and luminosity obtainable in the Z mode. Two prototypes of HOM coupler have been fabricated and installed on the 650 MHz 2-cell cavity. The higher order modes were verified by bead pulling method. The Qe for the HOMs were also measured. A test bench with two 2-cell cavities was used to measure the real damping results and HOM propagating properties for a cavity string.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP071  
About • paper received ※ 19 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP072 Development of HOM Absorbers for CW Superconducting Cavities in Energy Recovery Linac 1060
 
  • T. Ota, S. Nakamura, K. Sato, M. Takasaki
    Toshiba Energy Systems & Solutions Corporation, Keihin Product Operations, Yokohama, Japan
  • E. Kako, T. Konomi, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • A. Miyamoto
    Toshiba, Yokohama, Japan
 
  Higher Order Modes (HOM) absorbers for superconducting cavities have been developing at TOSHIBA in collaboration with High Energy Accelerator Research Organization (KEK) since 2015. A new prototype HOM absorber for 1.3 GHz 9-cell superconducting cavity was fabricated. An AlN lossy dielectrics cylinder was brazed with a thin copper plate, and the cool-down tests by nitrogen gas was carried out. The copper plate and a copper cylinder were joined by electron beam welding. SUS flanges were electron beam welded to both ends of the copper cylinder to fabricate a whole prototype HOM absorber. Fabrication process of the prototype HOM absorber will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP072  
About • paper received ※ 21 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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