基于高能γ源的CdZnTe成像探测器极化效应研究  

Polarization Effect of CdZnTe Imaging Detector Based on High Energy γ Source

作　　者：黎淼[1] 肖沙里[1] 王玺[1] 曹玉琳[2] 陈宇晓[2] 沈敏[1] 张流强[1] 

机构地区：[1]重庆大学光电技术及系统教育部重点实验室,重庆400030 [2]中国工程物理研究院电子工程研究所,四川绵阳621900

出　　处：《原子能科学技术》2011年第8期1005-1010,共6页Atomic Energy Science and Technology

基　　金：国家自然科学基金委员会与中国工程物理研究院联合基金资助项目(10876044);中央高校基本科研业务费资助项目(CDJXS11122219)

摘　　要：应用第一类边界条件泊松方程,推导了碲锌镉(CdZnTe)探测器晶体内部电势分布,研究了CdZnTe探测器在137 Cs高能γ源成像探测过程中的极化效应。数值计算与实验结果表明:在低辐射注量率条件下,即CdZnTe晶体内部载流子电荷密度较低时,内部电势分布主要受外加偏压影响,晶体内部电势与偏压为线性关系,电场呈均匀分布。在高辐射注量率条件下,即晶体内部载流子电荷密度较高时,内部电势分布出现极化区域,电场分布发生扭曲,电子载流子向辐照区域外侧迁移,形成辐照中心无信号而辐照边缘区域仍有响应信号的极化探测图像。极化效应造成CdZnTe探测器探测性能严重退化,辐照边缘区域像素事件计数下降约70%。The inner electric potential distribution of CdZnTe detector was derived by applying poisson equation with the first type boundary condition,and the polarization effect of CdZnTe pixellated detector for imaging 137 Csγsource was investigated.The results of numerical calculation and experiment indicate that electric potential distribution is mainly influenced by applied bias for low charge density in CdZnTe crystal and, in turn,there is linear relationship between electric potential distribution and applied bias that induces uniform electric field under low irradiated flux.However,the electric potential appears polarization phenomenon,and the electric field in CdZnTe crystal is distorted when CdZnTe detector is under high irradiated flux.Consequently,charge carriers in CdZnTe crystal drift towards the edge pixels of irradiated region,and hence, the shut-off central pixels are surrounded by a ring of low counting pixels.The polarization effect indeed deteriorates the performance of CdZnTe detector severely and the event counts of edge pixels for irradiated region reduce about 70%.

关 键 词：辐射成像探测 半导体探测器 CDZNTE 极化效应 像素阵列 

分 类 号：TL816[核科学技术—核技术及应用]