Keyword: damping
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THP071 HOM Measurement Results for CEPC 650 MHz 2-cell Cavity HOM, cavity, collider, cryomodule 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.  
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About • paper received ※ 19 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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