Author: Leng, Y.B.
Paper Title Page
MOOC03 The Removal of Interference Noise of ICT using the PCA Method 22
 
  • J. Chen, Y.B. Leng, L.Y. Yu
    SINAP, Shanghai, People's Republic of China
  • N. Zhang
    SSRF, Shanghai, People's Republic of China
 
  The measurement of beam charge is a fundamental re-quirement to all particle accelerators facility. Shanghai soft X-ray free-electron laser (SXFEL) started construc-tion in 2015 and is now in the commission phase. Al-though integrated current transformer (ICT) were installed in the entire FEL for the measurement of the absolute beam charge, the accurate measurement becomes difficult in the injector and the main accelerator section due to the noise interference from external factors such as klystron modulator. The evaluation of the source of noise signals and the procession of noise reduction using the principal component analysis (PCA) are proposed in this paper. Experiment results show that PCA method can effectively remove the interference of lower frequency noise from the klystron modulator and it can also improve the resolution of the ICT system. Detailed experiment results and data analysis will be mentioned as well.  
slides icon Slides MOOC03 [2.520 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOOC03  
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MOPB14 SSRF Beam Operation Stability Evaluation Using Bunch by Bunch Beam Position Method* 104
 
  • N. Zhang
    SSRF, Shanghai, People's Republic of China
  • Y.B. Leng, Y.M. Zhou
    SINAP, Shanghai, People's Republic of China
 
  Funding: * Work supported by National Natural Science Foundation of China (No.11575282 No.11375255 No.11305253)
In order to improve the efficiency and quality of light in top-up mode at SSRF, disturbance caused by leakage fields mismatch during injection should be minimized and stable. This could be evaluated by analysis of bunch by bunch residual betatron oscillation data, using this method, instability of tune distribution and damping repeatability could also be calculated. So we could evaluate the beam operation stability by the data analysis and discuss in the paper.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPB14  
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MOPC02 Identification of Faulty Beam Position Monitor Based Clustering by Fast Search and Find of Density Peaks 114
 
  • R. Jiang, Y.B. Leng
    SSRF, Shanghai, People's Republic of China
  • F.Z. Chen, Z.C. Chen, Y.B. Leng
    SINAP, Shanghai, People's Republic of China
 
  The accuracy and stability of beam position moni-tors(BPMs) are important for all kinds of measurement systems and feedback systems in particle accelerator field. A proper method detecting faulty beam position monitor or monitoring their stability could optimize accel-erator operating conditions. With development in ma-chine learning methods, a series of powerful analysis approaches make it possible for detecting beam position monitor's stability. Here, this paper proposed a clustering analysis approach to detect the defective BPMs. The method is based on the idea that cluster centres are char-acterized by a higher density than their neighbours and by a relatively large distance from points with higher densi-ties. The results showed that clustering by fast search and find of density peaks could classify beam data into dif-ferent clusters on the basis of their similarity. And that, aberrant data points could be detected by decision graph. So the algorithm is appropriate for BPM detecting and it could be a significant supplement for data analysis in accelerator physics.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPC02  
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TUPB09 The Evaluation of Beam Inclination Angle on the Cavity BPM Position Measurement 278
 
  • J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu, R.X. Yuan
    SINAP, Shanghai, People's Republic of China
 
  Cavity beam position monitor (CBPM) is widely used to measure the transverse position in free-electron laser (FEL) and international linear collider (ILC) facilities due to the characteristic of high sensitive. In order to study the limiting factors of the position resolution of cavity BPM, the influence of beam inclination angle on the measure-ment of CBPM position and the direction of beam deflec-tion was analyzed. The simulation results show that the beam inclination angle is an important factor limiting the superiority of CBPM with extremely high position resolu-tion. The relative beam experiments to change the relative inclination angle between the cavity and the electron beam based on a 4-dimension moveable platform were performed in Shanghai Soft X-ray FEL (SXFEL) facility, the experiment results will also be mentioned as well.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPB09  
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WEOA04 The Application of Beam Arrival Time Measurement at SXFEL 342
 
  • S.S. Cao, J. Chen, Y.B. Leng, R.X. Yuan
    SINAP, Shanghai, People's Republic of China
 
  Shanghai soft X-ray free electron laser (SXFEL) is able to generate high brightness and ultra-short light pulses. The generation of the light sources relies on the synchronization between seeded laser and electron bunch. Beam arrival time play an important role to keep the synchronization. For the SXFEL, a beam arrival time resolution under 100 fs is required. In this paper, the application of beam arrival time measurement scheme on SXFEL has been presented. The whole BAM system consists of four parts: beam arrival time monitor, electronic front-end, signal acquisition system, and high-level signal processing and presentation. Currently, four sets of beam arrival time monitors (BAMs) have been installed in the SXFEL and distributed in four different locations. The relevant beam arrival time experiment and beam flight time experiment based on the dual-cavities mixing method have also been performed so as to evaluate and analyze the beam status.  
slides icon Slides WEOA04 [4.588 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEOA04  
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WEPA13 Electro-Optic Modulator Based Beam Arrival Time Monitor for SXFEL* 396
 
  • X.Q. Liu, L.F. Hua, L.W. Lai, Y.B. Leng, R.X. Yuan
    SINAP, Shanghai, People's Republic of China
  • N. Zhang
    SSRF, Shanghai, People's Republic of China
 
  Beam arrival time monitor (BAM) is an important tool to investigate the temporal characteristic of elec-tron bunch in free electron laser (FEL) like Shanghai soft X-ray Free Electron Laser (SXFEL). Since the timing jitter of electron bunch will affect the FEL's stability and the resolution of time-resolved experi-ment at FELs, it is necessary to precisely measure the electron bunch arrival time so as to reduce the timing jitter of the electron bunch with beam based feedback. The beam arrival time monitor based on electro-optic modulator (EOM) is already planned and will be de-veloped and tested at SXFEL in the next three years. Here the design and preliminary results of the EOM based beam arrival time monitor will be introduced in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA13  
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WEPC15 Machine Learning Applied to Predict Transverse Oscillation at SSRF 512
 
  • B. Gao, J. Chen, Y.B. Leng, Y.M. Zhou
    SINAP, Shanghai, People's Republic of China
 
  A fast beam size diagnostic system has been developed at SSRF (Shanghai Synchrotron Radiation Facility) storage ring for turn-by-turn and bunch-by-bunch beam transverse oscillation study. This system is based on visible synchrotron radiation direct imaging system. Currently, this system already has good experimental results. However, this system still has some limitations, the resolution is subject to the point spread function and the speed of online data processing is limited by the complex algorithm. We present a technique that applied machine learning tools to predict transverse oscillation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPC15  
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MOPC11 Data Acquisition System for Beam Instrumentation of SXFEL and DCLS 137
 
  • Y.B. Yan
    SINAP, Shanghai, People's Republic of China
  • J. Chen, L.W. Lai, Y.B. Leng, C.L. Yu, L.Y. Yu, H. Zhao, W.M. Zhou
    SSRF, Shanghai, People's Republic of China
 
  The high-gain free electron lasers have given scientists hopes for new scientific discoveries in many frontier research areas. The Shanghai X-Ray Free-Electron Laser (SXFEL) test facility is commissioning at the SSRF campus. The Dalian Coherent Light Source (DCLS) has successfully commissioned in the northeast of China, which is the brightest vacuum ultraviolet free electron laser facility. The data acquisition system for beam instrumentation is based on EPICS platform. The field programmable gate array (FPGA) and embedded controller are adopted for the signal processing and device control. The high-level applications are developed using Python. The details of the data acquisition system will be reported in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPC11  
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MOPC16 The Development and Applications of Digital BPM Signal Processor on SSRF 147
 
  • L.W. Lai, F.Z. Chen, Y.B. Leng, Y.B. Yan, N. Zhang, W.M. Zhou
    SSRF, Shanghai, People's Republic of China
 
  The development of Digital BPM Signal Processors (DBPM) for SSRF started from 2008. The first prototype for SSRF storage ring was completed in 2012, with turn-by-turn resolution better than 1μm. From 2016 to 2017, SSRF successively constructed two FEL facilities in China, DCLS and SXFEL test facilities. The second ver-sion DBPM was developed and used in large scale during this period to meet the requirements of signal processing for stripline BPMs and cavity BPMs. After that, we turned to the development of DBPM for SSRF storage ring based on the second version hardware, including FPGA firmware, EPICS IOC, EDM control panel. The development was completed and tests were carried out in early 2018. Test results showed that the position data is accurate and can monitor beam movement correctly, and online turn-by-turn position data resolution reaches 0.46μm. This paper will introduce the design of DBPM for the SSRF storage ring and the tests carried out to verify the data accuracy and evaluate the system performance.  
poster icon Poster MOPC16 [1.372 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPC16  
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MOPC17 On-line Crosstalk Measurement and Compensation Algorithm Study of SXFEL Digital BPM System 150
 
  • F.Z. Chen, L.W. Lai, Y.B. Leng, T. Wu, L.Y. Yu
    SSRF, Shanghai, People's Republic of China
  • J. Chen, R.X. Yuan
    SINAP, Shanghai, People's Republic of China
 
  Shanghai soft X-ray Free Electron Laser (SXFEL) has acquired the custom designed Digital BPM processor used for signal processing of cavity BPMs and stripline BPMs. In order to realize monitor the beam position accurately, it has high demand for DBPM system performance. Considering the crosstalk may introduce distortion and influence beam position resolution, it is important to analyze and compensate the crosstalk to improve the resolution. We choose the CBPM signal to study the crosstalk for its narrowband and sensitive for phase. The main experiment concept is successive accessing four channels to form a signal transfer matrix, which including amplitude frequency response and phase response information. And the compensation algorithm is acquire four channel readouts, then using the signal transfer matrix to reverse the true signal to ensure the accurate beam position measurement. This concept has already been tested at SXFEL and hopeful to compensate the crosstalk sufficiently.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPC17  
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TUPC05 Influence of Sampling Rate and Passband on the Performance of Stripline BPM 307
 
  • T. Wu, S.S. Cao, F.Z. Chen, Y.B. Leng, Y.M. Zhou
    SSRF, Shanghai, People's Republic of China
  • J. Chen, L.W. Lai
    SINAP, Shanghai, People's Republic of China
 
  It is obviously that the property of SBPM is influenced by data acquisition system, but how the procedure of data acquisition and processing takes effect is still room for enquiring into it. This paper will present some data simulation and experiment results to discuss the function between resolution and pass band, sampling rate or other influence factor. We hope that this paper would give some advice for building up data acquisition system of SBPM.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPC05  
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THOB01 Injection Transient Study Using 6-Dimensional Bunch-by-bunch Diagnostic System at SSRF* 542
 
  • Y.M. Zhou, Y.B. Leng, N. Zhang
    SSRF, Shanghai, People's Republic of China
  • B. Gao
    SINAP, Shanghai, People's Republic of China
 
  Beam instability often occurs in the accelerator and even causes beam loss. The beam injection transient process provides an important window for the study of beam instability. Measurement of the bunch-by-bunch dynamic parameters of the storage ring is useful for accelerator optimization. A 6-dimensional bunch-by-bunch diagnostic system has been successfully implemented at SSRF. The measurements of transverse position and size and longitudinal phase and length are all completed by the system. Button BPM is used to measure beam position, phase, and length, and the synchrotron radiation light is used to beam size measurement. Signals are sampled simultaneously by a multi-channel acquisition system with the same clock and trigger. Different data processing methods are used to extract the 6-dimensional information, where the delta-over-sum algorithm for beam position extraction, the Gaussian fitting algorithm for beam size extraction, zero-crossing detection algorithm for beam phase extraction and the two-frequency method for bunch length extraction. The system set up and performance will be discussed in more detail in this paper.  
slides icon Slides THOB01 [7.413 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-THOB01  
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