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 Facility.This paper introduces the basic principles,system setup,data processing method,and preliminary experimental results of this system.The systematic measurement error introduced by the limited system bandwidth,bunch length,and bunch charge variation was studied using simulation data.The random measurement uncertainty was evaluated using experimental beam data.The experimental result shows that the longitudinal phase resolution of this system is better than 1.0 ps.The 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.
针对自由电子激光装置(Free Electron Laser,FEL)对束流位置测量的需求,研制了可同时用于条带束流位置检测器(Stripline Beam Position Monitor,SBPM)和腔式束流位置检测器(Cavity Beam Position Monitor,CBPM)信号处理的数字化束流位置信号处理器(Digital Beam Position Measurement processor,DBPM)。该处理器为一体化的嵌入式结构,以现场可编程逻辑门阵列(Field Programmable Gate Array,FPGA)为系统核心,采用分布式的实验物理及工业控制系统(Experiment Physics and Industrial Control System,EPICS)进行远程数据交互。处理器对SBPM和CBPM系统的测试分辨率在0.5 n C流强时分别达到4μm和0.4μm,达到设计指标,成功应用于大连相干光源(Dalian Coherent Light Source,DCLS),并将应用于上海软X射线自由电子激光装置(Shanghai X-ray Free Electron Laser,SXFEL),是国内首台自主研制成功并实现工程应用的DBPM处理器。
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 ns.The 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.
In building Shanghai Synchrotron Radiation Facility(SSRF), in order to reduce or eliminate the unnecessary sources of beam motion, the precise and stable beam position measurement system in the feedback system was required. In this study, we focused on theoretical analysis of the electrode of beam position monitor(BPM).Simulations, including analytic derivations of the propagation impedance and the distribution inductance, were performed. The BPM was designed based on the results and the acceptance measurements of the impedance and the inductance by using the time domain reflection(TDR) with a network analyzer. It has been proved in years of operations that the BPM system meets the requirement of the resolution of sub-micron.
In this paper, we report the development of a bunch-by-bunch beam position acquisition system.Through 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.
The injection performance of the storage ring is one of the most important factors to consider at a synchrotron radiation facility, especially in the top-up mode. To evaluate the injection performance of the storage ring at the Shanghai Synchrotron Radiation Facility, we have built a bunch-by-bunch position measuring system based on an oscilloscope Input/Output Controller. Accurate assessment of energy mismatching, distribution of residual oscillation, and angle error of injection kickers can be achieved by this system.
