Nuclear Techniques ›› 2017, Vol. 40 ›› Issue (6): 60102-060102.doi: 10.11889/j.0253-3219.2017.hjs.40.060102


Linearization of the input and output characteristic curve of a klystron for SXFEL

SUN Sisi1,2, ZHANG Junqiang1, LI Lin1, LIU Yajuan1, GU Qiang1, HUANG Dazhang1, ZHAO Minghua1   

  1. 1 Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Jiading Campus, Shanghai 201800, China;
    2 University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2017-01-23 Revised:2017-03-21 Online:2017-06-10 Published:2017-06-06
  • About author:10.11889/j.0253-3219.2017.hjs.40.060102
  • Supported by:
    Supported by National Natural Science Foundation of China (No.11675248)

Abstract: Background: The output signal of klystrons for the soft X-ray free-electron laser (SXFEL) is processed by the low level radio frequency (LLRF) measurement and control system to ensure the stable operation of the amplitude and phase of the electric field of an radio frequency (RF) structure in the linear accelerator (LINAC). However, the nonlinearity of the input-to-output characteristic curve of the klystron makes the radio frequency regulation of the LLRF control system inefficient. Purpose: The study aims to design an online system to compensate the nonlinearity characteristic from klystrons in SXFEL. Methods: The online system uses the FPGA-based digital predistortion method, including three algorithms:third order polynomial, direct lookup table, and lookup table with linear interpolation. Results: In the on line experiment, the input-to-output characteristic curve of the klystron is linearized, and the system effectively compensates the nonlinearity characteristic introduced by the klystron. Conclusion: The online system improves the precision and accuracy of the LLRF control system, which meets the requirements of the SXFEL.

Key words: Klystron, Linearization, SXFEL

CLC Number: 

  • TL53