厚GEM探测器对γ射线探测效率的研究

作为一种新型微结构气体探测器(MPGD)，厚型气体电子倍增器（THGEM）用于较高能量光子探测是新的尝试。为了解其探测机理及探测效率的主要影响因素，利用多粒子输运软件、多物理耦合仿真软件及气体电离模拟软件，分别建立了光子与探测器相互作用模型、电子漂移扩散模型和气体电离模型。通过仿真得到了漂移极内表面和膜上电极的电子出射概率，¹³⁷Cs在漂移极内表面产生激发电子的能量分布和角分布。动态模拟了电子在特定电场中的漂移和横向扩散行为，定量计算了原初电子的入孔数量和入孔效率。最后通过实验验证，证明增大漂移区距离和提高THGEM膜间电压可显著提高THGEM对γ射线的探测效率。

Study on Detection Efficiency of Thick GEM Detector for Gamma Ray

As a new kind of micro-pattern gas detector (MPGD), the thick gas electron multiplier (THGEM) was investigated to detect higher energy photon in this paper. In order to understand the reaction mechanism and the main factor influencing detection efficiency, three models consisting of interaction model between photon and detector, drift and diffusion model of electron, and ionization model of gas were developed based on multi-particle transport software, multi-physical coupling simulation software, and the gas ionization simulation software respectively. The electron emission probability with energy and angular distributions from the inner surface of the drift and the electrode of the THGEM were simulated, and the drift and lateral diffusion behavior in the electric field was dynamically simulated. Especially, the amount and entering-hole efficiency of primary electrons were quantitatively calculated. It is proved that increasing the drift distance and the working voltage of THGEM can significantly improve the detection efficiency of gamma ray.