Beam Instrumentation System for Shanghai Soft X-ray FEL Test Facility
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L.W. Lai, F.Z. Chen, J. Chen, J. Chen, W. Fang, C. Feng, B. Gao, R. Jiang, Y.B. Leng, Y.B. Yan, L.Y. Yu, R.X. Yuan, N. Zhang, W.M. Zhou, T. Shen
SSRF, Shanghai, People’s Republic of China
S.S. Cao, L.F. Hua
SINAP, Shanghai, People’s Republic of China
Shanghai Soft X-ray FEL (SXFEL) test facility was designed and built to demonstrate EEHG and HGHG schemes and verify key technologies for the future hard X-ray FEL facility (SHINE). After three years commissioning 8.8 nm FEL radiation with peak power of 1 MW had been achieved at the end of 2019. The design, fabrication, commissioning and operation of BI system including Stripline-BPM, Cavity-BPM, screen monitor, bunch length monitor, beam arrival monitor, bunch energy monitor, will be introduced in this paper. Several lessons learned during design stage and beam commissioning stage will be addressed as well.
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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.
S.S. Cao
Private Address, Zhangjiang, Shanghai, People’s Republic of China
R. Jiang, Y.B. Leng, R.X. Yuan
SSRF, Shanghai, People’s Republic of China
SHINE (Shanghai High repetition rate XFEL aNd Extreme light facility) is designed to be an extremely high-performance hard X-ray free-electron laser facility located at Zhangjiang, Shanghai. As one of the key parameters of the facility, the resolution of the beam position measurement in the undulator section is required to be under 200 nm at a low bunch charge of 100 pC and better than 10 um at 10 pC. To achieve this, a pre-study based on cavity beam position monitors is under development. Four sets of cavity monitors with different frequencies or load quality factors have been designed and are now manufactured by four different companies. It aims to select the cavity with the best performance and select the most capable company. This paper will briefly introduce the motivation, cavity design considerations, and cold test results.
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.
High-Accuracy Diagnostic Tool for Beam Position Monitor Troubleshooting in SSRF Based on Clustering Analysis
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R. Jiang, J. Chen, Y.B. Leng
SSRF, Shanghai, People’s Republic of China
Beam position monitors (BPMs) are important to monitor the beam moving steadily. In spite of some data is viewed and analysed, a large fraction of data has never been effectively analysed in accelerator operation. It lead to some useful information not coming to the surface during the beam position monitor troubleshooting processing. We will describe in this paper our efforts to use clustering analysis techniques to pull out new information from existing beam data. Our focus has been to look at malfunction of BPM, associating basic running data that is ß oscillation of X and Y directions, energy oscillation and doing predictive analysis. Clustering analysis results showed that 140 BPMs could be classify into normal group and fault group and abnormal BPM could be separated. Based on the results, the algorithm could locate fault BPM and it could be an effective supplement for data analysis in accelerator physics.
Beam Coupling Impedance Analyze Using Bunch-by-Bunch Measurement
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X.Y. Xu
University of Chinese Academy of Sciences, Beijing, People’s Republic of China
Y.B. Leng, X.Y. Xu
SSRF, Shanghai, People’s Republic of China
X.Y. Xu
SINAP, Shanghai, People’s Republic of China
Beam coupling impedance is very important parameters for advanced synchrotron radiation facilities. Till now there is no online method to measure beam impedance directly. But some beam parameters such as betatron tune amplitude and frequency, synchrotron phase, bunch lifetime and so on, can be modulated by beam impedance effects. So wake field and beam impedance information could be retrieved by measuring bunch-by-bunch beam 3D positions and analyzing bunch index dependency of above beam parameters. A bunch-by-bunch 3D positions and charge measurement system had been built at SSRF for this purpose and the performance is not good enough for beam impedance analyze due to cross talk between bunches. We upgraded the measurement system to minimize cross talk and improve resolution this year. New beam experiment results and corresponding analyze will be introduced in this paper.
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Development of Abnormal Beam State Monitoring Processor on SSRF Storage Ring
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L.W. Lai, Y.B. Leng, Y.B. Yan
SSRF, Shanghai, People’s Republic of China
An abnormal beam state monitoring processor has been developed on SSRF, which is based on the hardware of self-developed digital BPM processor. By applying digital signal processing algorithms in the on-board FPGA, the processor keeps monitoring the beam running state. Once abnormal event is detected, the processor will record the abnormal event type and store the turn-by-turn beam position data before and after the event for later analyzing. The abnormal events including beam loss and beam position jump.
J. Wan
SINAP, Shanghai, People’s Republic of China
F.Z. Chen, J. Chen, B. Gao, Y.B. Leng, K.R. Ye, L.Y. Yu, W.M. Zhou
SSRF, Shanghai, People’s Republic of China
SHINE is a high repetition rate XFEL facility, based on an 8 GeV CW SCRF linac, under development in Shanghai. In order to meet the requirements of measuring the beam profile of SHINE in real time and without obstruction, a new diagnostic instrument, wire scanner has been designed. This paper mainly describes the design of wire scanner in SHINE, and some simulation results are also shown and discussed.
