J. Chen, S.S. Cao, F.Z. Chen, B. Gao, L.W. Lai, Y.B. Leng, T. Wu, X.Y. Xu, R.X. Yuan, Y.M. Zhou
SSRF, Shanghai, People’s Republic of China
Precise bunch charge measurement is the fundamental of charge feedback, beam lifetime measurement, beam loss monitor, as well as the basis of the related interlocking work. Beam position monitor (BPM) is often used for high-precision bunch charge measurement due to its superior performance. In this paper, the pros and cons of different types of BPM for measurement of bunch charge in storage ring and free electron laser (FEL) will be discussed. The related simulations, beam experiment and signal processing methods are also mentioned. The beam experiments results show that the relative bunch charge resolution of the Button BPM can reach 0.02％ in SSRF, 0.073％ and 0.021％ of the SBPM and CBPM in SXFEL, respectively. Besides, based on the method of beam experiments, we systematically studied the position dependence of BPM pickup and related compensation algorithms for high-precision bunch charge measurement.
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B. Gao, S.S. Cao, Y.B. Leng
SSRF, Shanghai, People’s Republic of China
L.W. Lai, X.Q. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China
SSRF is currently working on the beam line phase-II project, which has moved toward laser/x-ray pump-probe experiments. In order to quantify the bunch pattern and charge purity of the probe pulse, a bunch purity monitor based on the time-correlated single-photon counting system has been installed. This system has very good time resolution of 22ps, and high dynamic range of more than seven orders of magnitude. In this paper, system setup, system evaluation and optimization process，a series of experimental studies and initial application will be described.
Prototype Design of Bunch Arrival Time Measurement System Based on Cavity Monitor for SHINE
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Y.M. Zhou, S.S. Cao, J. Chen, Y.B. Leng
SSRF, Shanghai, People’s Republic of China
The Shanghai high repetition rate XFEL and extreme light facility (SHINE) is planned to be built into one of the most efficient and advanced free-electron laser user facilities over the world to provide a unique tool for kinds of cutting-edge scientific research. The measurement of bunch arrival time is one of the key issues to optimize system performance. This is because the FEL facility relies on the synchronization of electron bunch and seeded lasers. Currently, there are mainly two methods to measure the bunch arrival time: the electro-optical sampling method and the RF cavity-based method. Considering the latter one has a simpler system and lower cost, the method has been adopted by SXFEL. The previous results show that the measurement uncertainty of bunch arrival time has achieved to be 45 fs, which can be further optimized. For SHINE, the bunch arrival time resolution is required to be better than 25 fs@100pC, and 200 fs@10 pC. The RF cavity-based method will also be applied. This paper will present the system prototype design and related simulation results.
