硅光电倍增管探测器的脉冲宽度调制方法研究

Silicon photomultipliers (SiPM) has shown a trend to replace traditional photomultipliers for its high gain, compact structure and insensitivity to magnetic field. However, SiPM’s internal quenching resistance and junction capacitance result in long recovering time and wide signal width, which will influence detector’s dead time, time resolution and energy measurement, like bringing needless noise and background light to Cherenkov telescope. Some solution could reduce the pulse width through high pass filter, while it is mainly suitable for time measurement but energy measurement, since the high pass filter will attenuate pulse amplitude. This project intends to simulate SiPM’s physical process on generating the signal pulse from a photon and analyze the key points that could affect SiPM’s pulse shape; study the optimal response time for SiPM when taking the incident light time into account; research the method to assist SiPM finish its internal quenching process faster based on high speed analog switch and leading edge timing; according to incident light time, modulate SiPM’s output pulse width and make it under 10ns without losing signal amplitude. This project aims at promoting SiPM to play a greater role in the particle detection field.

硅光电倍增管（SiPM）增益大、结构紧凑、抗磁场干扰，大有取代传统光电倍增管之势。然而受内部大阻值淬灭电阻和结电容影响，SiPM雪崩淬灭恢复时间长、输出脉冲宽度大；这不仅会影响SiPM探测器的时间分辨和探测死时间，也会为能量测量引入过多噪声和背景光干扰；而以损失脉冲幅度为代价的高通滤波方案仅适用于时间测量，不适合能量测量。本项目拟通过模拟SiPM信号产生物理过程，研究影响SiPM脉冲形状的关键节点；研究入射光时间特性，针对性分析SiPM输出脉冲对入射光强度和时间特性的响应效果，明确与入射光时间特性相匹配的SiPM脉冲时间调制参数；基于高速模拟开关、低噪声快放大技术和前沿触发技术研究加快SiPM内部物理淬灭的方法；根据入射光时间特性，针对性调制SiPM探测器输出脉冲宽度，在不损失脉冲幅度的条件下使SiPM输出脉冲宽度达到10ns以下，推动SiPM在粒子探测领域发挥更大的作用。

硅光电倍增管具有工作电压低、增益高、量子效率大、结构紧凑、对磁场不敏感、抗曝光损伤等优势，在核医学、核安全、高能物理实验和宇宙线天文物理实验等领域已经成为新一代粒子探测器研制的关键光电部件。本项目基于C/C++编程对SiPM-APD微元的“雪崩倍增-淬灭放电”物理过程进行了模拟，物理模拟程序输出的脉冲形状与实际相符；利用电路仿真软件multisim搭建了SiPM等效电路模型，仿真电路模型输出的脉冲形状与实际相符。本项目基于COSIKA和C/C++编程对外天空伽马射线广延大气簇射次级粒子所辐射出的大气切伦科夫光的时间特性进行了模拟分析，并阐述分析了皮秒脉冲激光和LYSO闪烁光的发光机制和时间特性，对光电器件读出脉冲时间特性的调制成形具有指导意义。本项目基于不同入射光源耦合单片SiPM读出和3×3 SiPM合并读出，针对性设计了SiPM脉冲调制成形电路，最终实现SiPM耦合皮秒脉冲激光光源＜10ns的脉冲时间宽度、耦合大气切伦科夫光＜50ns的脉冲时间宽度。此外，SiPM信号经脉冲调制成形电路读出后，信号线性度与原初信号保持一致，信噪比提升1.6倍。本项目针对SiPM输出脉冲的时间特性调制成形研究，使单片SiPM读出和3×3SiPM合并读出脉冲成功匹配采样深度有限的国产/商用ASIC；为研制新一代高角分辨、多像素、大面积、高集成度大气切伦科夫成像望远镜相机打下了技术基础。