高空间分辨伽马成像用CdZnTe像素探测器研究

Gama imaging system, with large area, high efficiency and high space resolution, has shown important application prospects in nuclear diagnostic, nuclear medicine imaging and space science, etc. The high performance CdZnTe crystal serves as the important timbering materials for the development of room temperature high energy γ-ray detection and imaging technique. This project focus on the key specification of high image precision and high efficiency, systemically developing the research on the CdZnTe pixel detector design, preparation and gamma imaging algorithms, considering the edge effect and charge sharing effect of CdZnTe pixel detector. Main research proposals are as follows: (1) Developing a systematic study on the mechanism of surface processing, electrodes structure and γ-ray scattering on the edge effect of pixel detector. (2) An in-depth research will be given on the charge sharing effect and its physical process. Through the optimization of center weighted algorithm, detectors with the capability of sub-pixel positioning will be achieved. (3) Problems like lateral signal loss and interference of detectors will be solved through the investigation of crystal surface defects and processing procedure. Developing the detector packaging, integration and evaluation system. (4) On the basis of the above studies, the high spatial resolution gamma imaging technique will be realized, combining the algorithms of depth of interaction (DOI) extraction and angular resolution based on Compton scattering effect. Through the implementation of this project, we aim to develop the CdZnTe pixel detector for high spatial resolution gamma imaging detector and technique use, and to achieve its primary application.

大面积、高效率和高空间分辨的伽马成像系统在核辐射诊断、核医学成像、空间科学等领域具有重要的应用前景，CdZnTe像素探测器被认为是高能射线成像技术的重要支撑。本项目拟针对高成像精度、高探测效率等关键技术指标，重点围绕CdZnTe像素探测器的边缘效应和串扰效应，系统开展探测器的设计、制备以及成像算法研究。主要研究内容包括：（1）研究晶体表面处理、电极结构、射线散射等因素对像素探测器边缘效应的影响机理；（2）研究像素探测器电荷串扰机理及其基本物理过程，在此基础上通过中心权重优化算法实现探测器的“亚像素”位置分辨能力；（3）通过晶体表面缺陷态及处理工艺研究解决探测器侧向信号损失及干扰等问题，建立探测器封装、集成与测评体系；（4）结合DOI深度信息提取算法和康普顿散射效应的角度分辨算法实现高分辨伽马射线成像技术。通过本项目的实施，最终研制出高分辨的伽马成像用CdZnTe像素探测器，并实现初步应用。

高空间分辨、高能量分辨、高探测效率的CdZnTe像素探测器是实现高性能伽马射线探测和成像的关键。本项目以CdZnTe像素探测器为研究对象，研究并优化了CdZnTe像素探测器的制备工艺；开展了CdZnTe像素探测器边缘效应、电荷串扰（共享）等的物理本质及其影响机理研究；研究并提出了基于射线与CdZnTe相互作用的基本规律、CdZnTe载流子输运特性、器件结构设计优化伽马相机成像算法。主要研究内容包括：（1）采用模拟仿真方法，模拟研究了光子在CdZnTe中的能量沉积规律、模拟了不同探测器尺寸和电极设计对权重势、电场、电势的影响，进一步研究了电荷输运规律和边缘效应对器件性能的影响规律；（2）研究了载流子迁移率、射线能量、探测器尺寸、电极尺寸以及工作偏压等对电荷收集的影响，揭示了CdZnTe像素探测器电荷串扰的影响机理；（3）优化了CdZnTe晶体表面与侧面的处理工艺、电极光刻工艺、探测器封装结构设计和低温倒装焊接工艺，形成了完备的CdZnTe像素探测器制备和封装工艺；（4）研究了射线作用深度、电荷共享效应，提出了深度分辨算法、高能量分辨率高探测效率能谱修正算法以及亚像素分辨算法，开发出基于康普顿效应的图像重建算法，实现了高空间分辨率伽马成像。