基于示波器嵌入式IOC技术的逐束团位置监测系统研制

为研究尾场引起的束团不稳定性,本工作开发了基于高速宽带示波器嵌入式IOC的逐束团位置测量系统。该系统通过直接获取加速器储存环中钮扣型电极的原始束流信号,进行在线计算独立的水平和垂直方向的逐束团位置。介绍了此系统的需求分析、硬件结构以及嵌入式IOC软件结构。利用在上海光源储存环上获取的逐束团位置数据,对系统性能进行了评估。实验显示,不同束团感应到的工作点及横向振荡振幅与束团编号间的依赖关系,结果证明该系统是一个有效的机器研究工具。     

3D Position Information Extraction of Refilled Charge during Injection Process of Electron Storage Ring

The injection process of electron storage ring is a special transient process. The mismatch between the injector and the storage ring can be evaluated online by studying the 3D merging of refilled charge and stored charge. For the next-generation light source, it can lay a technical foundation for building a diagnostic system. The beam instrumentation group of the Shanghai Synchrotron Radiation Facility developed a 3D bunch-by-bunch diagnostic system based on button pick-up signal and high-speed acquisition boards to measure the beam transverse position and longitudinal phase. Extracting the 3D position information of the refilled charge during the injection process is the critical issue in this system. The charge-weighted average method was proposed to extract the transverse position and the proportional coefficient method was proposed to extract the longitudinal phase. The transverse betatron oscillation and longitudinal synchrotron oscillation of the refilled charge were analyzed. 3D position information of the refilled charge and several dynamic parameters of ring, such as longitudinal maximum oscillation amplitude, initial arrival time and synchrotron damping time, can be extracted during the user operation mode, which provides a strong toolkit for accelerator physics.     

电子储存环注入过程中补注电荷的三维位置信息提取

电子储存环的注入过程是特殊的瞬态过程，研究补注电荷和储存电荷的三维位置融合过程可在线评估注入器与储存环的匹配度，也可为下一代光源诊断系统的搭建奠定技术基础。目前，上海同步辐射光源束流检测组研发了一套基于纽扣电极拾取信号和高速采集板卡的三维逐束团诊断系统，可精确测量逐束团三维位置。注入过程中补注电荷的三维位置信息可通过电荷加权平均法和比例系数法分别提取。通过对补注电荷横向betatron振荡和纵向同步振荡的分析，可原位提取betatron振荡振幅、同步振荡振幅、初始到达时间、同步振荡阻尼时间等多个动态参数，不需提供特别的机器研究时间，为储存环动力学研究提供了有力工具。     

束流位置探头用于束团电荷量测量的数值仿真研究

加速器常用的束流位置探头为电磁耦合型,其输出信号包括束流位置信息和束团电荷量信息.本文采用数值仿真方法研究探头电极和信号与束流位置之间的关系,基于Matlab开发一个用于仿真计算探头电荷量标定系数的软件包.对上海光源储存环束流位置探头的仿真结果表明,探头流强标定系数在2.5 mm半径内差值小于千分之二,在此精度范围内可认为流强标定系数为常数.     

Bunch-by-bunch longitudinal phase monitor at SSRF

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.     

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

The bunch length can be measured by comparison of two frequency components of a synchrotron beam signal.An online bunch length measurement system has been implemented based on this method.Working 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 rate.The constructed system was employed to study the bunch length synchronous oscillation phenomenon during injection.The beam experiments demonstrated a time resolution of less than 0.5 ps.     

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

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.     

Development of Bunch-by-bunch Beam Position Measurement Electronics for High Energy Photon Source

A bunch-by-bunch beam position measurement (BPM) electronics for High Energy Photon Source (HEPS) storage ring was designed. The hardware of electronics consists of analog signal acquisition board and digital signal processing board. The software consists of underlying firmware and application software. The sampling frequency is 500 MHz, and the bandwidth is 1 GHz. The electronics digitizes four analog signals from BPM probe of storage ring, and obtains the amplitude of beam signal. ZYNQ chip was used to process the beam data and calculate the position of each bunch. Electronics test results in the laboratory is that the nonlinearity of ADC channels is less than 1% when the peak-to-peak value of input signal is less than 1.8 V, and spurious-free dynamic range is about 60 dB. When the sensitivity coefficient is 8.26 mm, the beam position resolution is less than 10 μm. The test results meet the needs of HEPS.     

高能同步辐射光源逐束团束流位置测量电子学研制

基于高能同步辐射光源（HEPS）储存环，研制了一套逐束团束流位置测量（BPM）电子学系统，电子学的硬件部分由模拟信号采集板卡和数字信号处理板卡组成，软件部分由底层固件和顶层应用软件组成。系统的采样频率为500 MHz，带宽为1 GHz，对来自储存环BPM探头的4路模拟信号进行数字化，得到束团幅度数据，利用ZYNQ芯片计算出每个束团在真空管道中的位置。逐束团BPM电子学在实验室的测试结果为：输入信号峰峰值小于1.8 V时ADC通道非线性度小于1%，无杂散动态范围约60 dB，灵敏度系数取8.26 mm时位置分辨率优于10 μm，测试结果满足HEPS逐束团BPM的需求。     

Touschek lifetime study based on the precise bunch-by-bunch BCM system at SSRF

Continuous tracking of bunch charges is the key to maintain stable operations in a storage ring in top-up mode. Recently, a precise bunch-by-bunch beam-current measurement(BCM) system has been developed at the Shanghai Synchrotron Radiation Facility. To avoid the influence of longitudinal oscillation on the amplitudes of the sampling points, a method called two-point equilibrium sampling is introduced. The results, obtained during routine operation time, show that the relative resolution of the measurement of the bunch charges is better than 0.02%.With this high resolution, the new BCM system is able to monitor the bunch-by-bunch beam lifetime. By using the filling pattern information, the Touschek lifetime and the vacuum lifetime can also be calculated. In this paper, the principle of the new method and the experiments is presented in detail.     

Cavity Beam Position Monitor System for Shanghai Soft X-ray Free Electron Laser

Shanghai Soft X-ray Free Electron Laser (SXFEL) requires a beam position monitor system with resolution of sub-micron, so the beam based alignment (BBA) method to achieve close coincidence of the electron beam and the photon beam in the undulator section can be used. A cavity beam position monitor (CBPM) system consisting of a C-band cavity probe, a RF front-end and a dedicated digital beam position monitor processor (DBPM) was developed. The system design, hardware and software structure, and system construction were introduced in this paper. Based on the three adjacent CBPM systems in the drift section, the online system performance evaluation was completed. And the experiment results show that the position resolution of 880 nm is obtained under the condition of the bunch charge of 500 pC and the dynamic range of the system of ±800 μm. This is also the first CBPM system with submicron position resolution that can be run online in China. In addition, the phase cavity of CBPM was used to measure the relative charge and the arrival time of the bunch. The evaluation results show that the performance is better than the design requirements of SXFEL.     

上海软X射线自由电子激光腔式束流位置测量系统

上海软X射线自由电子激光装置（Shanghai Soft X-ray Free Electron Laser, SXFEL）需1个分辨率达到亚μm量级的束流位置测量系统，并采用基于束流准直的方法实现波荡器段电子束与光子束的紧密重合。为此设计研制了1个由C波段腔式探头、单路混频至低中频的射频前端以及自主研发的专用数字信号束流位置处理器（digital beam position monitor processor, DBPM）构成的腔式束流位置测量（cavity beam position monitor, CBPM）系统。本文对系统的设计、软硬件结构、系统搭建进行了介绍，并基于漂移段搭建的3个紧邻的CBPM阵列完成了在线系统性能评估。束流实验结果表明，在束团电荷量为500 pC、系统动态范围在±800 μm的条件下，位置分辨率可达880 nm，这也是国内首次研制成功可在线运行的具有亚μm位置分辨率的CBPM系统。此外，采用CBPM的相位腔进行相对束团电荷量、束团到达时间的测量，其性能评估结果也均优于SXFEL设计要求。     

合肥光源谐波法束团长度测量系统研制

同步辐射光与束流信号具有相同的时间结构,测量同步辐射光并基于频域的信号处理方法可得到束团的长度。基于该原理,研制了采用谐波法测量束团长度的系统。该系统用高速光电接收器将同步光转换为电信号,然后采集该信号的四路频率分量,计算得到束团长度。阐述了该系统的软硬件设计,并应用该系统测量了束团长度随流强的变化规律,与条纹相机的测量结果相吻合。     

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

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.     

BEPCⅡ快亮度监测系统的信号处理

针对北京正负电子对撞机(BEPCⅡ)逐束团（bunch-by-bunch）亮度监测系统需求,设计了高速亮度信号的采集、存储和显示系统。实现了4ns束团间隔亮度信号的放大甄别、远距离传输、反符合判别,以及对应束团亮度信号的累加,利用乒乓存储技术解决了高数据产生率和CAMAC低数据读出率间的矛盾。测试结果表明,该设计能够满足BEPCⅡ4ns间隔的逐束团亮度监测系统的要求。     

Development of the bunch-by-bunch beam current acquisition system at SSRF

In this paper, we report the development of a bunch-by-bunch beam current acquisition system. Through a waveform-reconstruction algorithm, the system realizes high equivalent sampling rate with a relatively low inherent rate. Based on the EPICS environment, information communication with other systems can be achieved. Preliminary test results in commissioning the SSRF storage ring show that the system can reconstruct the beam waveform of single bunch, providing a convenient and reliable method for the top-up operation in the future.     

基于腔式探头的束团到达时间测量算法优化

腔式探头具有高信噪比和高灵敏度的特性,TM010模式下在近轴附近的腔体输出信号与束流横向位置无关,信号幅度与电荷量呈正比,信号相位由束团到达时间决定,因此非常适用于高分辨率的束团到达时间测量。上海硬X射线自由电子激光装置（SHINE）对束团到达时间的测量精度要求非常高,期望运用基于谐振腔的束团到达时间监测系统,可实现在100 pC电荷量下分辨率好于25 fs的技术指标。对于高Q的谐振腔信号,单点采样的信噪比随信号的衰减而降低,因此肯定存在一最佳的信号处理窗口。为分析最佳处理窗口与相关参数的定量关系,采用数值仿真和束流实验相结合的办法来研究这个问题。分析发现,存在最佳数据处理时间窗口,该参数只与信号衰减时间常数有关,而与系统采样率、系统信噪比、系统模拟带宽无关。在最佳数据处理时间窗口条件下,束流到达时间测量不确定性可获得最佳值。     

Space Charge De-Bunching in Charged-Particle Beams

One of the factors influencing the properties of a pulsed beam is the growth of the charge bunches due to space charge forces. The growth along the direction of motion of the bunch degrades the time-structure of the pulsed beam and the growth transverse to the direction of motion de-focuses the beam. Although the space charge effect is only important at high current densities, it must be considered a limiting factor in any pulsed beam system. A general method of obtaining the field in the bunch to second order in v/c was developed. From this the motion of charges in the bunch was obtained by numerical integration for the case of a Gaussian distribution of space charge under the assumption that the charge distribution remains Gaussian. Solutions are presented in a dimensionless, graphical form which can easily be scaled for a particular problem.     

腔式束流位置探测器的设计与实验研究

束流位置探测器对自由电子激光装置的研制和运行具有重要的意义。其中,腔式束流位置探测器(腔式BPM)又以其高精度、高分辨率的特点而得到广泛的应用。本文对应用于上海深紫外自由电子激光装置上的腔式BPM进行了理论分析、模拟计算和BPM腔的测量等方面的研究。     

兰州高能电子成像实验平台电子束团长度测量研究

为提高高能电子成像的时间和空间分辨率,实验需低能散、低发射度、短脉冲的高品质束流。本文利用相干渡越辐射能谱分析法测量基于热阴极微波电子枪的高能电子成像用直线加速器的电子束团长度。通过用迈克尔逊干涉仪测量太赫兹辐射能谱,利用自相关曲线拟合法得到电子束团长度。实验结果表明,当束流宏脉冲峰值强度约为24 mA,即电荷量约为15 pC时,电子束团均方根长度约为0723 5 ps。另外,用Kramers Kronig(K K)相位分析法可重建一种可能的电子束团纵向分布。电子束团长度测量的研究可优化束流品质,对后续高能电子成像实验有重要的参考意义。