Radio-frequency System of the High Energy Photon Source

Purpose High energy photon source is a 6 GeV diffraction-limited storage ring light source currently under construction in Beijing. A low-frequency fundamental radio-frequency (rf) system of 166.6 MHz was proposed to accommodate the accelerator physics design. Superconducting rf (srf) technologies were chosen for the storage ring rf accompanied by solid-state power amplifiers and digital low-level rf controls. The design of the rf system was completed, and the parameters are frozen. Elucidation of the rf design with key parameters is desired. Methods The requirements from the accelerator physics design will be presented followed by the detailed rf design. The logic behind the choice of key rf parameters is elaborated. The configuration of the entire rf system is presented. Results and conclusions The fundamental srf cavity of 166.6 MHz was designed to accelerate the ultrarelativistic electron beam. Heavy damping of higher-order modes in these cavities is required to avoid the coupled bunch instabilities. An active third harmonic srf of 499.8 MHz was adopted to realize the required rf gymnastics. Normal-conducting 5-cell cavities will be used for the booster rf. Solid-state amplifiers of 2.4 MW in total will be installed at HEPS to drive these cavities in the booster and the storage ring. A digital low-level rf system will be used to regulate rf field inside each cavity with high stabilities. The rf configuration during the commissioning and the operation scenarios are also presented.