基于硅光电倍增管的高时间分辨位置灵敏探测器研究

Compared with the traditional photomultiplier tubes, silicon photomultipliers showed significant advantage, which is triggering a revolution in core photoelectric converter of scintillation detectors. Recently, good results about the energy resolution and spatial resolution of SiPM detectors were reported. However, timing resolution of multichannel SiPM detector requires much improvement. After investigating the signal generation mechanism and the electrical characteristics of SiPM, key factors that determined the timing performance of SiPM will be analyzed. A scintillation detector based on single channel SiPM and the relevant electronics will be studied, aiming to obtain the timing resolution of 200 ps. During the study of multichannel SiPM detectors, the way to extract the timing signal without distortion will be studied. After that, two design proposal namely delay line circuit and charge multiplexing circuit will be studied to achieve position sensitive function. The designed timing resolution is 500 ps and the spatial resolution better than 2 mm, with high gamma ray stopping efficiency. The practicability of the detectors will promote its application in the fields of time of flight positron emission tomography, LIDAR and positron annihilation lifetime spectrometer。

新型光电器件硅光电倍增管（SiPM）与传统光电倍增管相比优势明显，正在引发探测器核心光电器件的变革。目前，基于SiPM的闪烁探测器在能量分辨及空间分辨研究方面已取得比较好的结果，但时间分辨研究仍有较大进步空间。针对科学研究与实际应用对高性能闪烁探测器的需求，本项目通过模拟分析SiPM信号产生机制及电气特性，分析决定其时间性能的关键因素；设计基于单通道SiPM和闪烁体的探测器及与之匹配的前端电子学，时间分辨率达到200ps以内；研究多通道SiPM读出电路，无失真的引出时间信号，设计延迟线电路和电荷分配电路两种方案实现位置灵敏闪烁探测器，时间分辨率达到500ps，同时空间分辨优于2mm，并具有较高的探测效率，推动其在ToF-PET、正电子湮没寿命谱仪、激光雷达等研究领域的应用。

本项目针对飞行时间正电子发射断层扫描成像等系统对高时间分辨、高空间分辨闪烁探测器的应用需求，研究了基于硅光电倍增管的单通道及阵列式位置灵敏型探测器。经过深入分析测试，筛选出光探测效率高、结电容小、渡越时间分散小、稳定性较高的硅光电倍增管作为光电转换器；根据硅光电倍增管信号特点，研究并实现了高速、高带宽、极小时间晃动的时间甄别电子学，精心设计芯片电源旁路滤波、走线、阻抗匹配，避免信号反射及震荡，减小延迟，建立符合时间分辨测量系统对两个单通道探测器模块进行测试，对511keV的光子符合时间分辨最佳值为131.6ps，单模块时间分辨则为93ps，优于项目研究目标提出的200ps；在此基础上，研究了基于肖特基二极管对各通道快信号隔离加和技术，实现了320ps的符合时间分辨；研制基于电荷分配电路的8×8通道硅光电倍增管大面积位置灵敏探测器及电子学模块，经耦合硅酸镥钇阵列测试，时间分辨365ps，空间分辨优于1.5mm，关键指标均优于项目研究目标，达到国际领先水平。本项目实现并掌握了闪烁探测器高精度空间分辨技术以及快定时关键技术，未来有望在飞行时间正电子发射断层扫描成像、正电子湮没寿命谱仪、激光雷达等研究领域得到应用。