Nuclear Science and Techniques ›› 2019, Vol. 42 ›› Issue (4): 40101-040101.doi: 10.11889/j.0253-3219.2019.hjs.42.040101

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Study on precise bunch current measurement based on dual cavity monitor

Shanshan CAO1,2,Yongbin LENG1(),Renxian YUAN1,Longwei LAI1   

  1. 1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2018-12-20 Revised:2019-02-19 Online:2019-04-10 Published:2019-04-18
  • Contact: Yongbin LENG E-mail:leng@sinap.ac.cn
  • About author:<named-content content-type="corresp-name">CAO Shanshan</named-content>, female, born in 1992, graduated from University of Science and Technology of China in 2014, doctoral student, focusing on beam instrumentation|<named-content content-type="corresp-name">CAO Shanshan</named-content>, female, born in 1992, graduated from University of Science and Technology of China in 2014, doctoral student, focusing on beam instrumentation|LENG Yongbin, E-mail: <email>leng@sinap.ac.cn</email>
  • Supported by:
    Supported by National Key Research and Development Program (No.2016YFA0401903), National Natural Science Foundation of China(No.11575282)

Abstract: Background

The Shanghai synchrotron radiation facility (SSRF) is a third generation light source. It has been in operation for user experiment in decay mode since 2009. Meanwhile, the top-up operation is also under exploration in order to provide users with stable beam. A key technique for top-up mode is optimizing the injection efficiency by precisely controlling the injecting bunch charge. Therefore, it is essential to measure precisely the bunch charge at the high-energy transport line. The direct-current current transformers (DCCT) can measure the average beam current but can't measure the single bunch charge. Although the integrating current transformer (ICT) can measure the individual bunch charge, it is sensitive to different background noise with a resolution of less than 1% and even worse under low bunch charge case.

Purpose

This study aims to improve the measuring resolution for the injected individual bunch charge by using cavity charge monitor.

Methods

Since the cavity monitor has high sensitivity and high resolution, it will be used to extract the bunch charge information. Normally, the cavity monitor works at C-band frequency and the generated radio frequency signal (RF) has to be down-converted to intermediate frequency (IF) signal. Thus a dual-cavity monitor working at different frequencies was developed to realize the two RF signals self-mixing. Moreover, because of the limited signal sampling rate, the four channel signal splicing scheme with strict synchronous phase-locked sampling technique was addopted to further improve the sampling rate.

Results

The experimental results show that IF signal amplitude is linear to the bunch charge quantity. Moreover, the test results presents the measuring sensitivity is better than 0.03%.

Conclusion

The novel dual cavity bunch charge system works well and meets the requirement of injection bunch charge measurement.

Key words: SSRF, Dual-cavity bunch charge monitor, Precise bunch charge measurement, Signal acquisition

CLC Number: 

  • TL506.6