太阳X射线/伽玛射线探测用高分辨CdZnTe像素探测器的研究

Determination of the intensity, spectrum, timing, and location of accelerated electrons and ions emitted by the Sun, the energy transfer of solar flare and so on, are the research hotspots for the current solar observation. One important way to resolve the issues mentioned above is to detect the Sun bremsstrahlung X/γ-ray emission. Duo to the absence of proprietary satellites for solar exploration, however, the correlated original contribution in China was hampered. In this project, CdZnTe crystals with the thickness of 5~10 mm will be employed to fabricate the pixellated detectors, which applied in the energy range of 30 keV~1 MeV, with the energy resolutions of 4% @ 59.5 keV and 1.5% @ 662 keV. The main research proposals are as follows: (1) To optimize the structure and the dimension of the pixellated electrodes, the weighting potential and electric field strength distribution will be calculated using the finite element software COMSOL Multiphysics. The charge carrier collection and energy resolution will be also improved upon the simulation. (2) The deposition of metal composite electrode and high K dielectric layer will be explored, respectively. The flip chip of CdZnTe pixellated electrodes with the substrate will be resolved. Then the packaging of CdZnTe with multi-channel low-noise readout ASIC will be developed. (3) Finally, the key factors influencing the energy resolution and the response uniformity of CdZnTe pixellated modular will be concluded, in combine with the evaluation of material properties and detector configuration. We will investigate the feasibility of signal discrimination and response correction techniques to improve the energy resolution and the uniformities of CdZnTe pixellated detector. This project will offer new ideas and techniques for the utilization of CdZnTe pixellated detectors in the future Sun-observing mission.

关于太阳爆发能量释放的机理和粒子加速机制等问题一直是太阳研究的热点。通过对太阳辐射X射线/伽玛射线的精确观测是研究上述问题的一个重要途径。但由于缺少自主设计的太阳探测卫星，制约了我国在相关方面做出更多原创性贡献。本项目拟以5~10mm厚CdZnTe晶体制备像素探测器，实现观测能区在30 keV~1 MeV范围，能量分辨率优于4%@59.5keV和1.5%@662 keV。主要内容包括：(1)基于对权重势和电场分布的模拟，优化像素电极的形状和尺寸，提高电荷收集效率和能量分辨率；(2)完善复合电极和像素电极间高K栅介质层的制备技术，解决像素电极的倒装和与ASIC电路的集成封装问题；(3)结合材料物性表征和探测器结构特征，揭示影响CdZnTe像素探测器能量分辨率和均匀性的主要因素，并实现对信号的甄别与补偿。本项目的实施将为实现CdZnTe像素探测器在未来太阳观测计划中的应用提供理论和技术基础。

对太阳辐射出的X射线和伽马射线的流量、能谱等物理量进行高灵敏、高分辨的观测，有利于探索太阳爆发能量释放的机理和粒子加速的机制，同时对于理解恒星的形成和演化过程具有重要意义。但由于缺少自主设计的太阳探测卫星，制约了我国在相关方面做出更多原创性贡献。碲锌镉晶体作为一种室温化合物半导体探测材料，对能量10 keV-1 MeV范围的X /γ射线具有较高的能量分辨率，是制备太阳X /γ射线探测器的首选。.本项目针对太阳观测需求，基于本课题组生长的碲锌镉晶体，制备出高分辨X/γ射线像素探测器。(1) 阐明了退火过程中夹杂相和位错密度的变化规律，发明了移动循环退火方法，有效消除了晶体中的微米级夹杂相。(2) 完成了碲锌镉探测器辐射探测响应仿真程序的应用开发，研制了一款基于VATA450电荷测量芯片的多通道低噪声电子学测试系统。(3) 提出了采用氧化铟锡非金属电极替代传统的金属电极，探索了低温倒装焊材料，开发出碲锌镉像素探测器模块封装与测试技术。(4) 研究了晶体电学性能均匀性对探测器性能的影响，制备的碲锌镉像素探测器对241Am@59.5 keV能量分辨率达3.67%，137Cs@ 662 keV的分辨率达1.17%。.三年内发表SCI论文25篇，申请发明专利8项，授权3项。获2019年陕西省技术发明一等奖1项，以及2017年中国专利优秀奖和2018年陕西省专利奖一等奖各1项。所制备的碲锌镉像素探测器应用于中国原子能科学研究院和中科院合肥物质研究院等单位，开展“伽马相机”研制和“托卡马克实验”。.通过研制高性能碲锌镉像素探测器，为我国下一步开展太阳X/γ射线探测等天文计划提供理论和技术基础。同时，研究成果为发展其他空间观测用X/γ射线探测器提供借鉴。项目的实施对于发展我国的高能射线探测技术，提升我国在环境监测、核医学成像、工业无损检测、安全检查等领域的技术水平具有重要的战略意义。