闪烁体耦合SiPM测量γ能谱的模拟研究

硅光电倍增管(Silicon photomultiplier,SiPM)是一种新型的光电探测器件,由工作在盖革模式下的雪崩二极管阵列组成。利用GEANT4蒙特卡罗软件包对LaBr_3:10%Ce~(3+)、Na I(TI)闪烁晶体耦合SiPM测量γ射线能谱进行了细致的模拟,通过单色光LED光源照射SiPM,得到SiPM自身暗电流噪声经电子学放大后,与集成的盖革雪崩二极管之间的间隙引起吸收光子涨落对能谱的展宽。对模拟得到的662 keVγ射线能量分辨率进行修正,最后与实验结果对比能够很好地符合,还得到了一组对应闪烁晶体本征能量分辨率的程序参数Pr,s。结果验证了模拟程序设置的闪烁晶体与封装材料光学参数的合理性与可靠性,为闪烁体探测器设计提供了一套开发工具。

Simulation study of scintillation crystal photocoupling with SiPM for gamma spectrometry

Background:The silicon photomultiplier (SiPM) is a new type of photo detector consisting of avalanche photodiode arrays operated in Geiger mode.Its photocoupling performance with scintillation crystal is helpful for gamma spectrometry.Purpose:This study aims to provide a reliable tool for the design of scintillation detector photocoupling with SiPM to achieve effective gamma spectrometry with the GEANT4 code.Methods:GEANT4 toolkit is used to simulate NaI(TI) and LaBr3:10％Ce3+ scintillation crystal detect 662-keV γ-ray photocoupling with SiPM by building a complete Monte Carlo model of a scintillator includes ionizing particle and optical photon transport.Energy resolution of 662-keV gamma spectrum is modified with the contribution of dark current noise amplified by the electronic system and statistical fluctuation of optical photon absorbed by avalanche photodiode of SiPM which was previously illuminated with monochromatic LED light.Results:Simulation results show that energy resolution of 662-keV gamma spectrum is in accordance with the result of experimental measurement.A group of parameters (Pr,s) which corresponded to scintillation crystal intrinsic energy resolution is obtained simultaneously.Conclusion:The GEANT4 simulation of NaI(TI) and LaBr3:10％Ce3+ scintillation crystals photocoupling with SiPM for 662-keV γ-ray spectrometry results consistently with experimental energy spectrum,and confirms the reliability and rationality of material properties and parameters which set in GEANT4 toolkit.