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Bunch-length measurement at a bunch-by-bunch rate based on time–frequency-domain joint analysis techniques and its application

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Nuclear Science and Techniques 2024年第4期35卷 165-175页

作者： Hong-Shuang Wang Xing Yang yong-bin leng Yi-Mei Zhou Ji-Gang Wang Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230026China Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201204China

This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage *** technique uses the time–frequency-domain joint analysis of the bunch signal to obtain bunch-by-bunch and turn-by-turn longitudinal parameters,such as bunch length and synchronous *** bunch signal is obtained using a button electrode with a bandwidth of several *** data acquisition device was a high-speed digital oscilloscope with a sampling rate of more than 10 GS/s,and the single-shot sampling data buffer covered thousands of *** bunch-length and synchronous phase information were extracted via offline calculations using Python *** calibration coefficient of the system was determined using a commercial streak ***,this technique was tested on two different storage rings and successfully captured various longitudinal transient processes during the harmonic cavity debugging process at the Shanghai Synchrotron Radiation Facility(SSRF),and longitudinal instabilities were observed during the single-bunch accumulation process at Hefei Light Source(HLS).For Gaussian-distribution bunches,the uncertainty of the bunch phase obtained using this technique was better than 0.2 ps,and the bunch-length uncertainty was better than 1 *** dynamic range exceeded 10 *** technology is a powerful and versatile beam diagnostic tool that can be conveniently deployed in high-energy electron storage rings.

关键词： Bunch-by-bunch diagnostic Bunch-length measurement Synchronous phase measurement Joint time–frequency-domain analysis Longitudinal instability

Ultrahigh spatiotemporal resolution beam signal reconstruction with bunch phase compensation

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Nuclear Science and Techniques 2024年第5期35卷 99-108页

作者： You-Ming Deng yong-bin leng Xing-Yi Xu Jian Chen Yi-Mei Zhou Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of the Chinese Academy of Sciences Beijing 100049China Shanghai Synchrotron Radiation Facility Chinese Academy of SciencesShanghai 201204China University of Science and Technology of China Hefei 230026China Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201204China

Various electromagnetic signals are excited by the beam in the acceleration and beam-diagnostic elements of a particle *** is important to obtain time-domain waveforms of these signals with high temporal resolution for research,such as the study of beam–cavity interactions and bunch-by-bunch parameter ***,a signal reconstruction algorithm with ultrahigh spatiotemporal resolution and bunch phase compensation based on equivalent sampling is proposed in this *** with traditional equivalent sampling,the use of phase compensation and setting the bunch signal zero-crossing point as the time reference can construct a more accurate reconstructed *** basic principles of the method,simulation,and experimental comparison are also *** on the beam test platform of the Shanghai Synchrotron Radiation Facility(SSRF)and the method of experimental verification,the factors that affect the reconstructed signal quality are analyzed and discussed,including the depth of the sampled data,quantization noise of analog-to-digital converter,beam transverse oscillation,and longitudinal *** results of the beam experiments show that under the user operation conditions of the SSRF,a beam excitation signal with an amplitude uncertainty of 2%can be reconstructed.

关键词： Turn-by-turn bunch phase compensation technique Equivalent sampling Signal reconstruction algorithm Ultrahigh spatiotemporal resolution SSRF

Optimization of the cavity beam-position monitor system for the Shanghai soft X-ray free-electron laser user facility

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Nuclear Science and Techniques 2022年第10期33卷 22-32页

作者： Jian Chen yong-bin leng Lu-Yang Yu Long-Wei Lai Ren-Xian Yuan Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201204China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China

To achieve high-efficiency operation of the highgain free-electron laser(FEL),the electron beams and radiated photon beams need to be overlapped precisely and pass through the entire undulator ***,a high-resolution beam-position monitor(BPM)is required.A cavity BPM(CBPM)with a resonant cavity structure was developed and used in the Shanghai Soft X-ray FEL(SXFEL)test facility and can achieve a position resolution of<1μ*** construction and operation of the SXFEL user facility also bring about higher requirements for beamposition *** this case,the factors that affect the performance of the CBPM system were further *** included the amplitude and phase stability of the local oscillator,stability of the trigger signal,performance of the radio frequency front-end,signal processing electronics,and signal processing *** on the upgrade and optimization of the system,a beam test platform was built at the end of the linear acceleration section of the SXFEL,and the experimental results show that the position resolution of the system can reach 177 nm at a bunch charge of 500 pC,and the dynamic range is controlled within±300μm,and the relative measurement uncertainty of the bunch charge can reach 0.021%,which are significant improvements compared to the attributes of the previous system.

关键词： Cavity BPM SXFEL System optimization Position resolution Measurement uncertainty Algorithm

Shape embedding and retrieval in multi-ﬂow deformation

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Computational Visual Media 2024年第3期10卷 439-451页

作者： Baiqiang leng Jingwei Huang Guanlin Shen bin Wang School of Software Tsinghua UniversityBeijingChina Huawei Technologies ShenzhenChina

We propose a uniﬁed 3D ﬂow frameworkfor joint learning of shape embedding and deformationfor different categories. Our goal is to recovershapes from imperfect point clouds by ﬁtting thebest shape template in a shape repository afterdeformation. Accordingly, we learn a shape embeddingfor template retrieval and a ﬂow-based network forrobust deformation. We note that the deformationﬂow can be quite different for different shapecategories. Therefore, we introduce a novel multi-hubmodule to learn multiple modes of deformation toincorporate such variation, providing a network whichcan handle a wide range of objects from differentcategories. The shape embedding is designed to retrievethe best-ﬁt template as the nearest neighbor in a latentspace. We replace the standard fully connected layerwith a tiny structure in the embedding that signiﬁcantlyreduces network complexity and further improvesdeformation quality. Experiments show the superiorityof our method to existing state-of-the-art methods viaqualitative and quantitative comparisons. Finally, ourmethod provides efficient and flexible deformation thatcan further be used for novel shape design.

关键词： deformation shape retrieval embedding reconstruction

Bunch-by-bunch beam size measurement during injection at Shanghai Synchrotron Radiation Facility

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Nuclear Science and Techniques 2018年第6期29卷 19-27页

作者： Han-Jiao Chen Jie Chen Bo Gao yong-bin leng Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China University of Chinese Academy of Sciences Beijing 100049China

Fast beam profile measurement is important in fast beam dynamic behavior investigations. A bunch-bybunch beam size measurement system, which is presently used to measure horizontal profile, has been developed at the Shanghai Synchrotron Radiation Facility(SSRF) and is capable of measuring bunches within a separation of 2 *** system is based on a direct-imaging optical system and high-speed photomultiplier array detector. A high-bandwidth linear signal amplifier and acquisition module have also been designed to process bunch-by-bunch multichannel signals from the detector. The software resampling technique and principal component analysis method were developed to obtain the synchronized data and enhance the signal-to-noise ratio. The fast injection of transients was successfully captured and analyzed. Moreover, the bunchby-bunch positions and sizes exhibited strong oscillation after the injection at the horizontal betatron oscillation frequency of the SSRF storage ring, and this demonstrated the bunch-by-bunch measurement capability of our system.

关键词：尺寸测量同步加速器放射设备横梁注射上海信号放大器测量系统

Injection transient study using a two-frequency bunch length measurement system at the SSRF

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Nuclear Science and Techniques 2017年第7期28卷 37-42页

作者： Li-Wu Duan yong-bin leng Ren-Xian Yuan Zhi-Chu Chen Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China Shanghai Synchrotron Radiation Facility Chinese Academy of Sciences Zhangjiang Campus Shanghai 201204 China

The bunch length can be measured by comparison of two frequency components of a synchrotron beam *** online bunch length measurement system has been implemented based on this *** frequencies of 3 GHz and 500 MHz were selected,and the raw data was acquired by digital oscilloscope and was resampled and analyzed using the MATLAB software platform at bunch-by-bunch *** constructed system was employed to study the bunch length synchronous oscillation phenomenon during *** beam experiments demonstrated a time resolution of less than 0.5 ps.

关键词：长度测量系统束团长度注射过程双频光源上海瞬态 Matlab

Dual-cavity beam arrival time monitor design for the Shanghai soft X-ray FEL facility

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Nuclear Science and Techniques 2019年第5期30卷 14-21页

作者： Shan-Shan Cao Ren-Xian Yuan Jian Chen yong-bin leng Shanghai Institute of Applied Physics Chinese Academy of Sciences University of Chinese Academy of Sciences

Free electron lasers provide high-power and ultrashort pulses with extreme brightness. In order to improve a facility's capabilities and explore the possibility of performing high-resolution time-resolved experiments, a beam arrival time resolution under 100 fs is required. In this article, a novel beam arrival time monitor(BAM)equipped with two cavities has been designed and a beam flight time measurement scheme based on the BAM prototype has been proposed to estimate phase jitter in the signal measurement system. The two BAM cavities work at different frequencies and the frequency difference is designed to be 35 MHz. Therefore, a self-mixing intermediate frequency signal can be generated using the two cavities. The measured beam flight time shows a temporal deviation of 37 fs(rms).

关键词： Beam arrival time monitor Dual-cavities Beam flight time Self-mixing

Development of the bunch-by-bunch beam position acquisition system based on BEEcube

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Nuclear Science and Techniques 2016年第2期27卷 86-91页

作者： yong Yang yong-bin leng Ying-bing Yan Wei-Min Zhou Ren-Xian Yuan Zhi-Chu Chen Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China University of Chinese Academy of Sciences Beijing 100049China

In this paper, we report the development of a bunch-by-bunch beam position acquisition *** a wideband synthesizer of PLL, the system realizes synchronous clock of bunch signal. Based on the highperformance FPGA hardware DAQ environment, fourchannel raw data of beam signal can be achieved. Test results in the SSRF storage ring show that the system can obtain beam position of single bunch with the resolution of10 lm and multi-bunch instability can be observed.

关键词：采集系统束流位置基础同步时钟数据采集 FPGA 原始数据合成器

Bunch-by-bunch longitudinal phase monitor at SSRF

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Nuclear Science and Techniques 2018年第8期29卷 149-154页

作者： Yi-Mei Zhou Han-Jiao Chen Shan-Shan Cao yong-bin leng Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai Synchrotron Radiation Facility Chinese Academy of Sciences

Beam signals captured from a button-type pickup contain multidimensional information including the bunch charge,transverse position,bunch length,and longitudinal phase.A bunch phase monitor,which retrieves longitudinal phase information from a pickup signal at a bunch-by-bunch rate,has been developed at the Shanghai Synchrotron Radiation *** paper introduces the basic principles,system setup,data processing method,and preliminary experimental results of this *** systematic measurement error introduced by the limited system bandwidth,bunch length,and bunch charge variation was studied using simulation *** random measurement uncertainty was evaluated using experimental beam *** experimental result shows that the longitudinal phase resolution of this system is better than 1.0 *** first application,measuring the relationship between the longitudinal phase and bunch charge to determine the energy loss factor,was implemented,and the preliminary result is also discussed.

关键词：监视器 SSRF 数据处理方法同步加速器试验性信号信息系统