束流位置探测器自动标定系统研制

Development of an automatic calibration system for beam position monitor

为满足高能同步辐射光源(High Energy Photon Source,HEPS)和北京正负电子对撞机重大改造工程(Upgrade of Beijing Electron Positron Collider,BEPCII)等工程需求,研制了一套束流位置探测器(Beam Position Monitor,BPM)自动标定系统。标定系统主要包括模拟束流发生装置、精密运动机构、信号处理电子学以及系统软件等部分。利用标定系统,开展了BPM标定试验,采集了足量的原始数据。对这些数据进行分析,通过组合试验讨论了标定范围、标定点数目和拟合阶数对标定精度的影响。实验结果表明:在给定条件下,该系统能够全自动化地完成探头标定,满足应用需求,达到预期功能。在全部范围内标定,BPM精度可达40μm,在局部线性区标定,BPM精度可达7μm。

[Background]Beam position monitor(BPM)is an important beam measurement component of accelerators,and it generally needs to be calibrated before online operating.High energy photon source(HEPS)and upgrade of Beijing electron positron collider(BEPCII)will need a large amount of BPM,which brings challenges to the calibration work.[Purpose]This study aims to design and implement an automatic BPM calibration system for raising calibration efficiency and improving the accuracy of BPM measurement after calibration.[Methods]First of all,an analog beam generating device,precision motion and support device,signal processing electronics and industrial computer were employed to compose the hardware of the calibration system.Then,the control software was programmed by Python to realize automation of the calibration,and the binary polynomial regression algorithm was used to determine the probe calibration coefficient.Finally,the appropriate calibration parameters were optimized by the combination experiments with sufficient raw data,and the influence of calibration range,number of calibration points and fitting order on calibration accuracy were analyzed.[Results]The calibration system can automatically complete the BPM probe calibration.The BPM accuracy can reach 40μm over the entire calibration range,and 7μm in the local linear region.[Conclusions]The calibration system of this study meets application requirements and achieves the expected function.The measurement accuracy of the calibrated BPM is related to factors such as the order of the polynomial,the calibration range and the selection of calibration points.