Development of photon beam position feedback system based on two PBPMs at HLS

In this paper,in order to stabilize the position and angle of the light source point,a new photon beam position feedback system based on the Photon Beam Position Monitors was developed on Hefei Light Source,and used to correct the position drift and angle variation of the light source at the same time.On introducing the feedback principle,the transfer function matrix is calibrated,indicating that the new system is workable and effective.

Design and measurement of signal processing system for cavity beam position monitor

In this paper,in order to achieve the output signal processing of cavity beam position monitor(CBPM),we develop a digital intermediate frequency receiver architecture based signal processing system,which consists of radio frequency(RF) front end and high speed data acquisition board.The beam position resolution in the CBPM signal processing system is superior to 1μm.Two signal processing algorithms,fast Fourier transform(FFT) and digital down converter(DDC),are evaluated offline using MATLAB platform,and both can be used to achieve,the CW input signal,position resolutions of 0.31μm and 0.10μm at -16 dBm.The DDC algorithm for its good compatibility is downloaded into the FPGA to realize online measurement,reaching the position resolution of 0.49μm due to truncation error.The whole system works well and the performance meets design target.

Alignment of beam position monitors in cryomodule of CADS injector Ⅱ

Significant temperature difference(300-77 K or even 4 K) can cause large deformations and displacements of the beam position monitors(BPMs),which affect BPMs measurement resolution or even cause their malfunction in cryogenic situations.In this paper,to check the offset from the mechanical to electrical center in low temperature(77 K),Fourier's law and finite element method are used to simulate cryo-deformation.Laser tracker and micro-alignment telescope are employed in combined BPM calibration,installation and monitoring.The calibration error is<0.02 mm,and the installation and monitoring precision are 0.06 mm and 0.01 mm,respectively.The monitored cryo-deformation agrees well with the simulation results.These indicate that the combined alignment can improve performance of the BPM system.All these guaranteed the success of running the 9.55 MeV@2.14 mA cw protons.

Strip line beam position monitor for HLS LINAC

The parameters of beam transverse positions at HLS 200 MeV LINAC are very important to injection ef-ficiency. We have designed a new non-interceptive strip line beam position monitor (BPM) as a substitution for the original interceptive fluorescent target. This paper gives out the theoretical analysis and bench test result of the strip line BPM. The BPM has a characteristic impedance of (50±5)?, a reflection coefficient of less than –4 dB, a band-width of 400 MHz, a coupling coefficient of less than -15 dB, and a sensitivity of 1.16 dB/mm. Additionally, the strip line BPM has a good linearity.

Beam position monitor troubleshooting by using principal component analysis in Shanghai Synchrotron Radiation Facility

Beam position monitors(BPMs)have been widely used in all kinds of measurement systems,feedback systems and other areas in particle accelerator field these days.The malfunction of a single BPM can cause serious consequences such as the failure of the orbit feedback and the transverse feedback.A troubleshooting has been made to prevent the defective BPMs from affecting the accuracy and stability of the storage ring in Shanghai Synchrotron Radiation Facility(SSRF).Different types of malfunctions have been successfully identified by using the idea of principal component analysis(PCA).

Beam position monitors as precise phase pickups for beam energy measurement at the Compact Pulsed Hadron Source

The 13-MeV proton linac of the Compact Pulsed Hadron Source(CPHS) at Tsinghua University, China,is composed of a 50-keV electron cyclotron resonance proton source, a 3-MeV four-vane-type radio-frequency quadrupole(RFQ) accelerator, and a drift tube linac(DTL). Precise measurement of the beam energies at the exit of the RFQ and the DTL is critical for DTL commissioning. Two button-type beam position monitors(BPMs) installed downstream of the RFQ are used to perform the measurement using a time-of-flight method. The effects of several factors on phase measurement accuracy are analyzed. The phase measurement accuracy of the BPMs at CPHS is better than ± 1.03° at 325 MHz after corrections,corresponding to an energy measurement error of± 0.07%. The beam energy measured at the exit of the RFQ is 2.994 ± 0.0022 MeV,which is consistent with the design value.

Development of a PSD-based photon beam position measurement system

As an important part of the beam diagnostic system, the synchrotron light beam position measurement has a very high value in the high quality and high stability light source applied research. A new photon beam position monitor based on position-sensitive detector (PSD) has been developed to measure the photon beam position in vertical and horizontal directions at the same time at HLS (Hefei Light Source). The new PBPM based on the PSD has fast response speed, high sensitivity and wide dynamic range. This PBPM system also includes the C4674 signal processing circuit, NI USB-9215 data acquisition device and the LABVIEW data acquisition program. This PBPM system has been calibrated vertically and horizontally on-line, and then has been applied in the beam line B3EA of HLS to measure the position of the synchrotron light. As the results shown, the resolution of the system is better than 3 mm.

Implementation and integration of a systematic DBPM calibration with PLL frequency synthesis and FPGA

Beam current dependence resulted from nonlinearity and asymmetry of the four channels of digital BPM(Beam Position Monitor) processor deteriorates the BPM performance.A systematic solution based on signal source calibration tactics has been carried out to rectify this defect.It is optimized for implementation in FPGA.Mathematical illustrations of the calibration method,hardware and software design and implementation are presented.A signal source circuit using frequency synthesis technique is designed as calibration standard.Data acquisition system using JAVA web technology and Ethernet is introduced.Integrated FPGA implementation code architecture is presented,and experimental test results show that the method implemented in FPGA is feasible.Compared to other methods,our approach can rectify the nonlinearity and asymmetry simultaneously.The whole solution is integrated into the DBPM processor and can be executed online.

Research into the sampling methods of digital beam position measurement

A fully digital beam position monitoring system(DBPM) has been designed for SSRF(Shanghai Synchrotron Radiation Facility). As analog-to-digital converter(ADC) is a crucial part in the DBPM system, the sampling methods should be studied to achieve optimum performance. Different sampling modes were used and compared through tests. Long term variation among four sampling channels, which would introduce errors in beam position measurement, is investigated. An interleaved distribution scheme was designed to address this issue. To evaluate the sampling methods, in-beam tests were conducted in SSRF. Test results indicate that with proper sampling methods, a turn-by-turn(TBT) position resolution better than 1 μm is achieved, and the slow-acquisition(SA) position resolution is improved from 4.28 μm to 0.17 μm.

新型数字BPM信号处理器研制进展

介绍了采用Arm微处理器技术、FPGA数字信号处理技术、高速带通欠采样技术的新型BPM信号处理器研制进展情况;对两类主要的原理样机进行了评估测试。信号处理算法评估样机基于商业评估板搭建,用于测试包含数字下变频、低通滤波、抽取降速等信号处理算法功能模块。自主开发的硬件评估样机用于测试不同硬件功能模块及整机集成后的硬件性能。在上海光源储存环上进行的束流实验表明,两个样机的逐圈位置分辨率均好于2μm,可正确获取包含束流实时信息的逐圈位置信号,可用于相关机器研究。

数字BPM时钟锁相电路的设计与实现

为实现数字BPM时钟系统的锁相,设计了一种基于锁相环同步原理的低抖动、低相位噪声的时钟同步系统。根据锁相环电路工作原理,对数字BPM时钟同步系统的硬件及固件程序进行了设计,实现了外部输入时钟信号与系统内部产生的主工作时钟信号的锁相,并且时钟信号输出的频率及相位均可调整以满足后端ADC采样的要求。测试结果表明,设计可以完成对一定频率范围内变化的外部输入时钟信号的锁相,输出时钟信号抖动满足束流实验要求,为数字BPM后续算法研究提供了基础。

数字BPM信号处理算法研究

束流位置检测器(BPM)系统是加速器监测系统的重要组成部分,其中涉及的信号处理算法是该系统的关键,因而该算法的研究对研制数字BPM系统有极其重要的意义。本文采用GE公司开发的商业数字信号处理板ICS-1554A-002,采集实验室信号发生器和储存环原始的A、C两路数据,基于软件无线电原理,利用Matlab对数据进行离线分析。重点设计并讨论了获取逐圈(TBT)束流位置信号的三种数字信号处理算法:多级滤波抽取算法、单级抽取算法,以及应用快速傅里叶变换(FFT)算法。对各算法的原理、结果及优劣进行了分析,找到性能及FPGA实现都较好的信号处理方法。

北京同步辐射1W2B生物大分子束线双丝型BPM实时跟踪监测系统

同步辐射光束位置稳定性对光束强度至关重要,直接会影响到实验数据的质量,因此需要在实验过程中对光束位置进行实时监测.在同步辐射光束线上一般会使用双丝型的光束位置监测器(beam position monitor,BPM)扫描光束,获得光束的截面分布,同时在固定位置的双丝会对光束位置进行静态的实时监测.但是这种监测方式对于入射光束分布有特殊的要求,当光束较大地偏离原有位置时会对双丝BPM造成损伤的危险.北京同步辐射1W2B生物大分子实验站通过采用双丝型BPM实时动态跟踪监测方式,有效地解决了常规监测方式带来的光束分布和光敏丝损伤问题,为实验光束的稳定性研究提供了基础.

BPM技术用于环形电子束位置测量的可行性分析

为了对传输管道半径24mm,电子束半径19mm,厚度3mm的环形电子束位置开展非阻拦测量,选择了BPM技术方案。对比研究了真空管道中环形电子束与位于束团中心的实心束在管道壁上产生的场分布,证明BPM测量技术可以用于电流密度均匀分布的环形电子束。采用点密度不均匀性模型,分析了环形电子束角向不均匀性对测量精度的影响。结果显示,当环形电子束电流密度不均匀性应为10%时,对位置分辨率精度的影响为0.1mm。

Diagnostic Method for Beam Position Monitor Based on Clustering by Fast Search and Find of Density Peaks

Beam position monitors(BPMs)are important to monitor the beam moving steadily.Keeping the beam's normal motion is an important mission for Shanghai Synchrotron Radiation Facility.Effective diagnostic analysis is an important way to accomplish this task.This paper develops a new method based on clustering analysis to diagnose the healthy of BPMs with basic running data,i.e.,the β oscillation of X and Y directions and noise data.The analysis results showed that all beam position monitors(140 BPMs)can be classified into three groups:normal group,worse performance group,and fault group,respectively.In addition,the abnormal BPMs(including worse performance)could be marked.The new method showed its ability to handle faulty BPMs and it could instruct daily maintenance.On the other hand,it will be a useful supplement for data analysis in accelerator physics.

Libera Photon处理器在上海光源XBPM中的应用研究

上海光源X射线位置探测器(X-ray Beam Position Monitor,XBPM)用于束线X光位置的测量,本文简述了该探测器在升级改造中对其数据采集设备更新的考虑,选用了新一代数字信号处理器Libera Photon,它的测量分辨率最高可达0.01μm;该电子学设备可实现快慢两种数据采集方式,其数据采样率分别为10 kHz和10 Hz,快信号能捕获2 ms的状态变化,可用于输出光斑的稳定反馈控制,慢信号可用做输出光斑的长期稳定性监测等。同时给出了使用该探测器所需修改的部分EPICS接口控制程序,以及Libera Photon在上海光源光束线站中的应用结果。

西安质子应用装置BPM设计及测试结果

西安质子应用装置(XiPAF)中能传输段设有6个束流位置探测器(BPM)用于测量束流位置及相位,要求位置和相位测量分辨率分别好于0.1mm和1°,绝对位置测量准确度好于±0.5mm。本文从理论上分析了纽扣型BPM位置测量分辨率与电极长度及电极张角的关系,并结合CST模拟得到最优值,设计分辨率达24.5μm。离线测试结果表明,BPM样机的电极电容、灵敏度及电极间耦合度均与设计值相符。利用旋转法测量得到BPM样机水平和竖直方向电中心与机械中心的偏差分别为(0.04±0.05)mm和(-1.53±0.05)mm。样机安装在清华大学微型脉冲强子源(CPHS)高能传输段进行测试,测试结果表明,XiPAF BPM位置测量分辨率好于60μm,相位测量分辨率好于0.74°,绝对位置测量准确度为±0.35mm。该设计满足西安质子应用装置的要求。

基于单个四条带BPM的非拦截式能散度测量方法

能散度是反映束流品质的重要参数,采用传统测量方法测量时打到靶上的束流不能得到利用,测得的数据也是多个宏脉冲的平均值,利用该方法的测量结果进行束流调节时,要等待荧光靶从束流轨道中反复插入和提出,调节时间很长。基于单个四条带束流位置检测器,结合发射度测量的方法,实现了非拦截式能散度测量方法。该方法能在不加入额外设备的情况下对每个束流宏脉冲的能散度进行测量,测量结果与传统的拦截式测量方法结果相吻合。进行了误差分析,指出为了减小测量系统误差,需要尽可能使束流通过束流位置检测器中心。

Calibration method for electrode gains in an axially symmetric stripline BPM

The four electrodes in the stripline beam position monitor(BPM) for Hefei Light Source(HLS II) storage ring are of axially symmetric type. We have derived a new calibration method of electrode gains for this type stripline BPM. The gain fit error of different data grids was analyzed, and the ±5 mm by ±5 mm grid is the best.The electrode gains of two stripline BPMs(HLS II SR-BD-STLB1 and HLS II SR-BD-STLB2) were obtained based on offline calibrated data. The results show that data after fitting gains are improved, with the electrode gains being between 0.94 and 1.15.

A real-time online data acquisition system for Dragon-I linear induction accelerator

An extensible high-speed accelerator data acquisition system(ADAS) for the Dragon-I linear induction accelerator has been developed. It comprises a ⅤⅪ crate, a controller, four data acquisition plug-ins, and a host computer. A digital compensation algorithm is used to compensate for the distortion of high-speed signals arising from longdistance transmission. Compared with the traditional oscilloscope wall, ADAS has significant improvements in system integration, automation, and reliability. It achieves unified management of data acquisition and waveform monitoring and performs excellently with a 107-ps high-accuracy trigger and 32-channel signal monitoring. In this paper, we focus on the system architecture and hardware design of the ADAS,realization of the trigger, and digital compensation algorithm.