Design of a low level radio frequency control system for the direct current-superconductive photocathode injector at Peking University

A digital low level radio frequency (LLRF) control system based on a high precision field-programmable gate array (FPGA) is being developed for the stable operation of the upgraded direct current-superconductive (DC-SC) photocathode injector at Peking University. The design of this LLRF control system is described, including both the hardware and the internal algorithm. Analysis of disturbances shows that the system can achieve the requirement of +/- 0.1% for amplitude stability and +/- 0.1 degrees for phase stability. Through experiments, preliminary results are presented in the paper.