北京正负电子对撞机二期工程激光扫描系统

Laser wire scanner system for Beijing Electron-Positron ColliderⅡ

为探索激光在束流截面测量上的应用,在北京正负电子对撞机二期工程(BEPCⅡ)的负电子传输线上建立了激光扫描系统。研究了激光扫描测量束流截面的相关计算方法。对激光和电子束相互作用、光子在介质中的切伦科夫辐射等过程进行了GEANT4模拟。对脉冲激光器进行了调试,测量了激光的脉宽、尺寸、功率等各项参数。设计并搭建了激光扫描系统的光路,编写了激光系统的机械扫描部件的控制软件。搭建了用于探测康普顿光子的契伦科夫探测器系统。激光的扫描、控制、以及激光参数的在线监测等系统工作正常,能满足激光扫描实验需要。

A laser-wire scanner which can measure the transverse charge profiles of an electron （or positron） beam has been constructed at the Beijing Electron-Positron Collider Ⅱ （BEPC Ⅱ ） accelerator transport line in IHEP. The development of the sys- tem is explained in this paper, along with descriptions of its photon detector and laser system. Results of GEANT4 simulation a- bout the process of interaction between laser photons and electron, Cerenkov radiation in different medium are presented. The pa- rameters of the laser pulse such as width, size and power are measured. Laser optical system and mechanical scanning system are designed and tested. The Cherenkov detector is set up for detecting the Compton photons. Mathematical processing methods of laser scanner are given. Measurement results show the laser transport and focus subsystem work in accordance with the design, and the stability of laser focus parameters can meet the requirement of beam profile measurement.