单光子计数型CCD的蒙特卡罗模拟

Monte Carlo simulation on single photon counting charge coupled device

建立了适用于研究PI-LCX:1300型单光子计数型CCD量子效率及多像素事件的蒙特卡罗模拟模型,采用蒙特卡罗程序Geant4对0.5～30.0keV能量区间的X射线在CCD芯片中的输运进行了模拟研究。研究了X射线在CCD芯片中的能量沉积谱,给出了CCD探测X射线的效率曲线,其结果与厂家提供的效率曲线一致。研究了Si片厚度对探测效率的影响,结果表明在有效探测范围内,Si片越厚探测效率越高,而对较高能量的X射线,此趋势不明显。研究了能量沉积分布在多个像素中的问题,结果表明周围像素中的能量沉积主要由中心像素的特征X射线及瑞利散射X射线所贡献,在5～30keV之间X射线能量越高,能量沉积效率越低,多像素污染效果越弱。

The Monte Carlo models for studying the quantum efficiency and the split pixel event of PI-LCX： 1300 charge coupled device （CCD） were set up. The X-ray transport in the CCD chips was simulated using the Monte Carlo code Geant4 in the energy range of 0.5-30.0 keV. The energy deposit spectra of X-ray in CCD chips were investigated, the subsequent quantum ef- ficiency obtained is in good agreement with that offered by the manufacturer. Simulation results show that the efficiency increase with increasing the thickness of the Si layer and this effect is not obvious for high energy X-rays. The deposited energy spread in mtilti-pixels was studied. It shows that the surrounding pixels split the incident photon energy by deriving from the characteristic and Rayleigh scattering X-rays, which are generated in the central pixel but escape from it. In the range of 5-30 keV, the energy deposit efficiency and the effect of the multi-pixel pollution decrease as the X-ray energy increases.