Nuclear Science and Techniques

《核技术》(英文版) ISSN 1001-8042 CN 31-1559/TL     2019 Impact factor 1.556

Nuclear Science and Techniques ›› 2015, Vol. 26 ›› Issue (3): 030106 doi: 10.13538/j.1001-8042/nst.26.030106


Digital LLRF controller for SSRF booster RF system upgrade

ZHANG Zhi-Gang,1, 2, 3 ZHAO Yu-Bin,1, 3 XU Kai,1, 3 ZHENG Xiang,1, 3 LI Zheng,1, 3 ZHAO Shen-Jie,1, 3 CHANG Qiang,1, 3 HOU Hong-Tao,1, 3 MA Zhen-Yu,1, 3 LUO Chen,1, 3 MAO Dong-Qing,1, 3 SHI Jing,1, 3 WANG Yan,1, 3 LIU Jian-Fei 1, 3   

  1. 1Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
    2University of Chinese Academy of Sciences, Beijing 100049, China
    3Shanghai Key Laboratory of Cryogenics & Superconducting RF Technology, Shanghai 201800, China
  • Contact: LIU Jian-Fei
  • Supported by:

    Supported by the National Natural Science Foundation of China (No. 11335014)

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ZHANG Zhi-Gang, ZHAO Yu-Bin, XU Kai, ZHENG Xiang, LI Zheng, ZHAO Shen-Jie, CHANG Qiang, HOU Hong-Tao, MA Zhen-Yu, LUO Chen, MAO Dong-Qing, SHI Jing, WANG Yan, LIU Jian-Fei . Digital LLRF controller for SSRF booster RF system upgrade.Nuclear Science and Techniques, 2015, 26(3): 030106     doi: 10.13538/j.1001-8042/nst.26.030106


The low level radio frequency (LLRF) system for booster accelerator at Shanghai Synchrotron Radiation Facility (SSRF) was upgraded by a digital controller based on field programmable gate array (FPGA) technology. Parameters of voltage, frequency and field flatness in the two 5-cell cavities are controlled to meet the requirements of booster. In this article, the ramping curve of cavity voltage, amplitude and phase control loop with vector sum of the two 5-cell cavities, tuning loop and field flatness loop are analyzed and discussed in detail. A different method in tuning loop is adopted due to the limitations of ADC channels. The function realizes energy ramping of electron beam from 150 MeV to 3.5 GeV with a repetition rate of 2 Hz. With the new LLRF controller, the phase stability at ramping mode in 10 hours long operation is improved from ±1.5° (RMS) with open loop to ±0.15° (RMS) with close loop, while the detuning phase and field flatness are maintained to within ±2° and ±1%, respectively.

Key words: LLRF control, Ramping, Amplitude and phase loop, Field flatness, Tuning loops