基于微虾眼阵列的CdZnTe面元像素辐射探测技术研究

The development and mechanism research of the high performance CdZnTe detector will provide an important technological means to spectrum and imaging irradiation detections, and serve as the technological support for the high demands from national scientific facilities on nuclear diagnostic. Based on preceding researches, this project is the first to propose micro-lobster-eye array based pixellated CdZnTe detector. It will conduct an in-depth exploration into the impact principle of micro-lobster-eye array on the performance of detectors. And a systematic study on the impact of critical parameters, which means high aspect ratio and material etc., on the detector signal will be implemented. This project will be completed with the optimization of the detectors’ structure and fabrication of 8 × 8 pixellated CdZnTe detector based on the micro-lobster-eye array system. On its completion, the carrier transport equation will be derived and improved on the condition of high initial carrier concentration for each pixel location. And hence, multi-dimensional distribution characteristic and drifting discipline of detector carriers can be clarified based on the building of a multi-physics induced signal prediction model. By developing the multi-parameter anti-coincidence circuit for the edge pixels, this project will end up improving CdZnTe detector energy resolution performance. This project aims to provide insights into the CdZnTe detector technology, which can be used in wide-field low energy irradiation detection condition, and to give theoretical and technological suggestions to the research on the new CdZnTe detection system.

高性能CdZnTe探测器的开发及其机理研究可为射线能谱及成像探测提供重要技术手段，为满足国家大科学装置对核辐射诊断领域的重大需求提供技术支撑。本项目在前期研究基础上提出微虾眼阵列CdZnTe面元像素探测器结构，深入探讨微虾眼阵列光学系统对探测器性能的影响机理，系统研究虾眼栅格高宽比及材料等关键物理参数变化对探测器信号响应特性的影响；完成探测器结构优化设计，制备8×8微虾眼阵列CdZnTe面元像素探测器。针对像素单元高初始载流子浓度条件推导并改进载流子输运方程，建立多物理场耦合感应信号预测模型，明确探测器载流子多维耦合分布特征及迁移规律。建立探测器侧向电极边缘信号补偿技术，制备基于边缘像素不完全收集信号的反符合多参量分析电路，针对能量分辨率指标完成探测器性能优化设计。本项目旨在为解决大视场低能辐射CdZnTe探测器关键技术提供新思路，并为研制新型CdZnTe探测系统提供一些理论和技术建议。

作为II-VI族化合物半导体材料中的典型代表，碲锌镉(CdZnTe)晶体由于其高电阻率、高原子序数及常温下优异的能量分辨率性能，已经在核辐射能谱探测及成像探测领域引起了广泛的关注。具有小尺寸阳极单元的大面积面元像素阵列CdZnTe探测技术一直是X射线与伽玛射线辐射探测领域倍受关注的研究课题。虽然越来越小的电极尺寸决定了探测系统整体具备较高的直接成像分辨率，但像素单元较低的信噪比及较严重的像素间信号串扰也越来越明显。本项目探讨了微虾眼聚焦系统对入射X射线的作用机理，分析确定了栅格的通道长宽比，采用LIGA工艺设计并制备了微虾眼栅格阵列射线聚焦器件并完成了微虾眼栅格阵列聚焦性能测试，实验结果表明所制备的微虾眼射线聚焦系统视场角约为1.623。，低能X射线增益达到80，8 keV高能射线增益约为10。设计并建立像素阵列电极高初始载流子浓度分布的CdZnTe探测器三维模型，模拟并分析了晶体内部载流子分布特征及迁移规律，系统研究了不同物理阶段探测器内电场分布与初始载流子浓度分布变化的关系。此外，也研究并设计碲锌镉探测器边缘电极信号读出及处理电路，针对已封装了微虾眼栅格准直层的8×8像素阵列CdZnTe晶体制备了边缘电极信号读出及后续高增益处理电路，实验测试结果表明，探测器对Cs137伽玛源的能量分辨率达到0.3%。