Laser wire scanner system for Beijing Electron-Positron Collider Ⅱ

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 ColliderⅡ(BEPC Ⅱ) accelerator transport line in IHEP. The development of the system is explained in this paper, along with descriptions of its photon detector and laser system. Results of GEANT4 simulation about the process of interaction between laser photons and electron, Cerenkov radiation in different medium are presented. The parameters 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.