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| DC-SRF photo-injector, which can be operated in continuous wave (CW) and pulse mode, was firstly proposed and developed by Peking University. It combines a 1.3 GHz 3+1/2-cell superconducting cavity working at 2 K. Due to the thin walled structure and narrow bandwidth, the superconducting cavity is very susceptible to mechanical perturbations which induces significant amplitude and phase errors and resulting in electron beam quality degradation. In the paper, the parameters of the proportional-integral (PI) controller are optimized in MATLAB and a new controller is presented and simulated in Simulink to deal with the Lorentz force detuning during the filling stage of the cavity in pulse mode. The digital low level radio frequency (LLRF) control system is improved and accomplished based on the new controller, the amplitude and phase stability of the 3+1/2-cell superconducting cavity in pulse mode achieve 0.13% and 0.1 respectively, and it runs stably during the high repetition terahertz radiation experiments based on the DC-SRF photo-injector. |
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| Keywords:Particle accelerators; DC-SRF photo-injector; LLRF; pulse mode |
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