High‑power umbrella-shaped RF coupler for SC240 cyclotron

The high-power RF coupler is a critical component of RF cavity in cyclotron, not only serving as an impedance-matching device between RF cavity and rigid transmission line, but also acting as a vacuum barrier isolating RF coupler from atmosphere, and functioning as a feeder that delivers RF power into the cavity to achieve the accelerating voltage. RF window, however, is susceptible to damage from electron bombardment. To address this, an umbrella-shaped coupler has been developed to shield the ceramic from high-energy electrons emitted from Dee plate, while an optimized cooling design significantly reduces thermal stress on RF window. In this paper, the coupler’s reflection coefficient and the impedance matching of RF window have been described in detail. RF coupler has been validated on SC240 cyclotron, demonstrating stable operation at an average power of 60 kW. The design method of RF coupler will be meaningful for design reference in similar devices.