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

Sisi SUN; Junqiang ZHANG; Lin LI; Yajuan LIU; Qiang GU; Dazhang HUANG; Minghua ZHAO

doi:10.11889/j.0253-3219.2017.hjs.40.060102

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

SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS | 更新时间：2021-05-19

- Linearization of the input and output characteristic curve of a klystron for SXFEL
- NUCLEAR TECHNIQUES Vol. 40, Issue 6, Article number: 060102(2017)
- 作者机构：
  
  1.中国科学院上海应用物理研究所嘉定园区上海 201800
  2.中国科学院大学北京 100049
- 作者简介：
- 基金信息：
  
  National Natural Science Foundation of China
- DOI：10.11889/j.0253-3219.2017.hjs.40.060102
  CLC： TL53
- Received：23 January 2017，
  
  Revised：21 March 2017，
  
  Published：10 June 2017
- 稿件说明：
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Sisi SUN, Junqiang ZHANG, Lin LI, et al. Linearization of the input and output characteristic curve of a klystron for SXFEL[J]. Nuclear techniques, 2017, 40(6): 060102
DOI：

Sisi SUN, Junqiang ZHANG, Lin LI, et al. Linearization of the input and output characteristic curve of a klystron for SXFEL[J]. Nuclear techniques, 2017, 40(6): 060102 DOI： 10.11889/j.0253-3219.2017.hjs.40.060102.

摘要

在上海软X射线自由电子激光（Soft X-ray Free-electron Laser，SXFEL）中的微波低电平控制系统中，通过对各速调管的输出信号进行测量和控制，保证加速器的稳定运行并且达到技术指标。另一方面，SXFEL中的脉冲速调管的输入输出特性存在非线性的关系，这种电子管放大器不理想的非线性特性会导致微波低电平（Low Level Radio Frequency，LLRF）控制系统调节的效率降低。基于SXFEL装置，采用基于现场可编程门阵列（Field Programmable Gate Array，FPGA）的数字预失真方法，在LLRF控制系统中设计了一套实现高功率速调管放大器线性化的在线系统。S波段加速装置和其相应的东芝E3730A速调管及高压调制器和低电平系统实地测试结果表明，在LLRF控制系统中建立的在线系统能够有效补偿速调管带来的非线性问题，提高微波低电平控制系统的精度及准确性。

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.

关键词

Keywords

references

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Omet M, Michizono S, Matsumoto T, et al . Development of FPGA-based predistortion type linearization algorithms for klystrons within digital LLRF control systems for ILC-like electron accelerators[C] . Proceedings of LINAC 2014, Geneva, Switzerland, 2014.

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