The collider RF parameters listed in Table 1 were chosen to meet the baseline luminosity requirement for each operating energy. During W and Z operations, part of the Higgs cavities will be used in each RF section, and the electron or positron beams will go through only one of the two RF stations of a RF section.
Electron or positron beams go through the two RF stations in each RF section for Higgs operation. This common cavity scheme reduces the total number of cavities, cryomodules, and cryogenics by half compared to that of a usual double ring with separate cavities for the two rings. The collider is a double-ring with shared cavities for Higgs operation and separate cavities for W and Z operations, as shown in Fig. 1. CEPC will use a 650 MHz radiofrequency (RF) system with 240 cavities for the collider and a 1300 MHz RF system with 96 cavities for the booster. A conceptual design report (CDR) for CEPC was published in August 2018 and describes the parameters and lattice design for the collider. The HOM damping results for a real 650 MHz two-cell cavity were also measured and compared with the damping requirements.Ĭircular Electron Positron Collider (CEPC) has a circumference of 100 km and operates at a center-of-mass energy of 90–240 GeV for Z, W, and Higgs bosons. To validate the design, a prototype of the HOM coupler and a coaxial line test bench were fabricated and tested, and the test results agreed well with the simulation results. This paper presents the design process of the HOM coupler: the RF design, thermal analysis, and mechanical aspects. Each cavity has two detachable coaxial HOM couplers mounted on the cavity beam pipe with a HOM power handling capacity of 1 kW. A double-notch coupler was chosen because of its wide bandwidth for the fundamental mode. This study examined the impedance budget and HOM damping requirements for the CEPC ring to keep the beam stable, and a coaxial HOM coupler was considered for extracting the beam-induced HOM power.
The higher order modes (HOMs) excited by the intense beam bunches must be damped to avoid additional cryogenic loss and multi-bunch instabilities. The collider will be a double ring with shared cavities for Higgs operation and separate cavities for W and Z operations. CEPC will use a 650 MHz radiofrequency (RF) system with 240 two-cell cavities. A conceptual design report (CDR) for the Circular Electron Positron Collider (CEPC) was published in September 2018.
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