Multi-port cavity model and Low-level RF Systems design for VHF gun

Kui Liu; Lin Li; Cheng Wang; Qiang Gu; Ming-Hua Zhao

doi:10.1007/s41365-019-0711-2

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Multi-port cavity model and Low-level RF Systems design for VHF gun

SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS | Updated：2021-01-26

- Multi-port cavity model and Low-level RF Systems design for VHF gun
- Nuclear Science and Techniques Vol. 31, Issue 1, Article number: 8(2020)
- Affiliations：
  
  1.Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
  2.University of Chinese Academy of Sciences, Beijing 100049, China
  3.Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China
- Author bio：
  
  Corresponding author, guqiang@sinap.ac.cn
  Corresponding author, minghuazhao@sinap.ac.cn
- Funds：
- DOI：10.1007/s41365-019-0711-2
  CLC：
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Kui Liu, Lin Li, Cheng Wang, et al. Multi-port cavity model and Low-level RF Systems design for VHF gun. [J]. Nuclear Science and Techniques 31(1):8(2020)
DOI：

Kui Liu, Lin Li, Cheng Wang, et al. Multi-port cavity model and Low-level RF Systems design for VHF gun. [J]. Nuclear Science and Techniques 31(1):8(2020) DOI： 10.1007/s41365-019-0711-2.

摘要

Abstract

Very high frequency (VHF) photocathode guns have excellent performance and are being increasingly selected as electron sources for high repetition rate X-ray free-electron lasers. As a high loaded quality factor cavity, the VHF gun requires high stability in the amplitude and phase of the cavity field. However, the gun is microwave powered by two solid-state power sources through two separate power couplers. The input difference between the two power couplers will influence the stability of the cavity field. To systematically study this influence and obtain measurement formulae, a multi-port VHF gun LCR circuit model is built and analyzed. During the warm-up condition, the cavity structure will be deformed due to the large-scale change in the cavity temperature. Then, the deformation will result in cavity resonant frequency changes. To prevent the mechanic tuner from suffering damages due to the frequent and long-distance movement for correcting the cavity resonant frequency, a self-excited loop (SEL) control system is considered for changing the loop phase and make the loop frequency follow the resonant frequency. In this study, a steady-state model of the VHF gun cavity is built for obtaining the optimal input coupler coefficient and the stability requirement of the forward voltage. Then, the generator-driven resonator (GDR) and SEL control system, which combine with the VHF multi-port modeling, are modeled and simulated. The simulated results show that the SEL system can perfectly operate in the process of condition and warm-up.

关键词

Keywords

VHF photocathode gunMulti-port modelingSelf-excited loopLLRF control

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