Study on Low-Level Control of the Buncher in the Hard X-ray Free Electron Laser Facility

Zhang Zhigang; Yang Wenfeng; Jiang Hongru; Xu Kai; Huang Xuefang; Yu Yuechao; Wu Hailong; Wu Hong; Chuang Qiang; Zheng Xiang; Zhao Yubin

doi:10.11884/HPLPB202537.250106

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Zhang Zhigang, Yang Wenfeng, Jiang Hongru, et al. Study on Low-Level Control of the Buncher in the Hard X-ray Free Electron Laser Facility[J]. High Power Laser and Particle Beams. doi: 10.11884/HPLPB202537.250106

Citation:

Zhang Zhigang, Yang Wenfeng, Jiang Hongru, et al. Study on Low-Level Control of the Buncher in the Hard X-ray Free Electron Laser Facility[J]. High Power Laser and Particle Beams. doi: 10.11884/HPLPB202537.250106

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Study on Low-Level Control of the Buncher in the Hard X-ray Free Electron Laser Facility

doi: 10.11884/HPLPB202537.250106

Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201800, China

Received Date: 2022-04-29
Accepted Date: 2025-07-16
Rev Recd Date: 2022-07-25

Available Online: 2025-08-13

Abstract

Abstract

Background
In the Hard X-ray Free Electron Laser (SHINE), the normal-conducting L-band buncher plays a critical role in the compression of electron bunches, significantly improving beam quality meeting the stringent injection requirements of low emittance and low energy spread.
Purpose
Due to its 2-cell structure, a dedicated digital low-level RF control system was developed.
Methods
This system, based on an architecture comprising FPGA and RF front-end boards, and adopts I/Q demodulation techniques. It incorporates amplitude and phase feedback, frequency tuning, and multi-motor coordinated for field flatness control.
Results
During 10 kW continuous-wave (CW) operation the amplitude stability (peak-to-peak) improved from ±0.17% in open-loop to within ±0.03% under closed-loop, while the phase stability (peak-to-peak) was controlled within ±0.05°, and field flatness was maintained within ±2%, fully meeting design specifications. Additionally, a radio-frequency (RF) power calibration method based on ADC acquisition of LLRF was proposed.
Conclusions
Experimental results showed calibration error within ±2% when compared with power meter, demonstrating this method’s reliability as an alternative solution for RF power calibration.
- digital low level radio frequency,
- buncher,
- cavity voltage stability,
- power calibration

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References(17)

References

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