BEPCⅡ上正在进行激光丝系统的研究。基于GEANT4对激光丝系统探测器进行了模拟。首先模拟了康普顿散射信号在探测器材料中电磁簇射的分布, 确定了探测器初始尺寸。之后模拟了不同尺寸下探测器的输出, 根据模拟结果确定了探测器的最终尺寸, 使得探测器在所确定的尺寸有较大的信号输出。还进行了不同康普顿散射位置时探测器的响应模拟, 结果表明束流管道的影响是不可忽略的, 是探测器响应非线性的主要原因, 预计该结果对束流截面测量有重要意义。最后简要介绍了BEPCⅡ几种可能的束流能量时, 探测器信号输出和能量泄漏的模拟结果。

A laser wire system is being developed in the electron beam transport line of BEPCⅡ. In this paper, the simulation based on GEANT4 is presented. Firstly, the electromagnetic shower distribution in detector material was simulated to choose an initial detector dimension for Cerenkov process simulation. Then detector responses for different dimensions, Compton signal positions and beam energy were obtained, and the most important result is that the detector dimension is determined at which an optimal signal output can be achieved. The results for different Compton signal positions show that the effect of the beam pipe is significant, which is expected to be important for the beam profile measurement. Furthermore, the simulation results of the detector response and electromagnetic shower energy leakage at different electron beam energy are presented.