The performance of RF power couplers with capacitive coupling for SRF accelerators

Different from common coaxial couplers used for superconducting radio frequency (SRF) accelerators, power couplers with capacitive coupling in which the inner conductor is separated into two unconnected parts on both sides of the cold ceramic window transmit RF power by capacitive coupling. Capacitive coupling type power couplers have the advantages of easy fabrication of ceramic window, reduced thermal conduction from room temperature side to the cryogenic system, and convenient assembling to cryomodule. To further investigate the performance of this type of RF power couplers, an upgraded power coupler with capacitive coupling has been designed and fabricated at Peking University. The high-power test demonstrated that RF power up to 15 kW in continuous wave (CW) mode can be transmitted steadily. In this paper, the structure, simulation, and high-power test results of this power coupler are presented in detail.