An SLAC-like Compact Linac installed on the HUST THz-FEL has been used as an injector to produce high power THz radiation. In order to produce the terahertz radiation with high monochromaticity and repeatability continuously, the beam parameters should be stabilized rigorously. Therefore, by using beam-dynamic calculation and simulation, the stability targets for RF system have been proposed on basis of analyzing the influence of RF jitter. Furthermore, to meet the requirements for the RF stability, a digital-LLRF control system has been designed, both the system stability and the response rate of the feedback loop has been enhanced by suitable PI coefficients. In experiments, the instability of the RF power fed into the accelerator have been measured. And an LLRF system based on FPGA has been constructed and added to present RF system. The preliminary measurement results show that the LLRF system is effective to suppress jitter and the targets of RF stability is achieved.

安装在 HUST THz-FEL 上的类似 SLAC 的紧凑型直线加速器已用作注入器以产生高功率太赫兹辐射。为了连续产生具有高单色性和重复性的太赫兹辐射，必须严格稳定光束参数。因此，通过波束动力学计算和仿真，在分析射频抖动影响的基础上，提出了射频系统的稳定性目标。此外，为了满足射频稳定性的要求，设计了数字-LLRF控制系统，通过适当的PI系数提高了系统稳定性和反馈回路的响应速度。在实验中，已经测量了馈入加速器的射频功率的不稳定性。并构建了一个基于FPGA的LLRF系统并将其添加到现有的RF系统中。