用于实现能量倍增器平顶输出的双环PI控制技术研究及验证  

Design and test of double PI-control loop to generate flat-top output of RF pulse compressor

作　　者：徐一茗 张俊强 肖诚成 方文程 XU Yiming;ZHANG Junqiang;XIAO Chengcheng;FANG Wencheng(Shanghai Institute of Applied Physics,Chinese Academy of Sciences,Shanghai 201800,China;University of Chinese Academy of Sciences,Beijing 100049,China;Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201204,China)

机构地区：[1]中国科学院上海应用物理研究所,上海201800 [2]中国科学院大学,北京100049 [3]中国科学院上海高等研究院,上海201204

出　　处：《核技术》2022年第6期11-18,共8页Nuclear Techniques

基　　金：国家自然科学基金(No.12105345)资助。

摘　　要：上海软X射线自由电子激光(Shanghai Soft X-ray Free-electron Laser,SXFEL)升级改造工程中,升级项目之一是使装置在双束团模式下运行,即在一个微波脉冲内加速得到两个相同能量的电子束团。为此设计开发了基于双环比例积分(Proportional Integral,PI)控制的微波低电平(Low Level Radio Frequency,LLRF)控制系统,用于调制微波脉冲能量倍增器的输出波形,使其变为平顶脉冲,以满足双束团模式的要求。该方法使用了两个反馈闭环分别控制输出脉冲整体的幅相稳定性和保持波形的平坦化。通过在微波实验平台上的连续测试,证明了双环PI控制法可以长时间维持能量倍增器输出脉冲的平坦度,并保证整体的幅相稳定性在0.09%和0.1°以内(均方根值),满足了设计要求。当对系统施加较大的外部干扰时,无需人为干预,算法能自动恢复平顶输出。[Background]Shanghai Soft X-ray Free-electron Laser(SXFEL)is upgrading and requires to operate in double-bunch mode instead of original mode to transport uniform energy along the bunch chain.[Purpose]This study aims to satisfy the requirement of double-bunch mode by designing and implementing low level radio frequency(LLRF)system to flatten the output of RF pulse compressor through amplitude modulation.[Methods]Based on double PI-control loops,the LLRF control system was designed and implemented with one PI-feedback loop for keeping the long-term stability of amplitude and phase,and the additional operating-outside-LLRF PIfeedback loop for flattening the output pulse shape.Furthermore,an experimental setup,including the compressor,was built for the verification of the above method.[Results]The 2-h continuous test results show that the double PI-control loops can flatten and keep the compressor output,and maintain the long-term stability of amplitude and phase within 0.09%and 0.1°(Root Mean Square,RMS)respectively.In addition,the algorithm can restore the flat-top output automatically when a large manual frequency offset occurs.[Conclusions]The double PI-control loop applied to the LLRF system preserves satisfactory static and dynamic behaviors,meeting the requirement of the SXFEL upgrade.

关 键 词：低电平控制系统 微波脉冲能量倍增器 PI控制 幅度调制 

分 类 号：TL54[核科学技术—核技术及应用]