用于现场X荧光分析的硅漂移探测器读出电路及数字处理算法研究

In-situ X-ray fluorescence detection is an important technical method in the field of nuclear geophysics exploration, and it plays an important role in the development of mineral resources. The traditional X-ray fluorescence detection instrument has the disadvantages of high detection limit, long dead time and significantly reduced energy resolution at high counting rates, which makes it impossible to shorten the measurement period by increasing the fluorescence yield, and it will be impossible to accurately achieve mineral accuracy or fast measurement. In response to this problem, this project is based on a new silicon drift detector to build a complete silicon drift X-ray fluorescence detection mathematical model and establish a detector energy response function, and it will study high-resolution silicon drift detector technology, fast low-noise readout technology, and all-digital high-speed nuclear pulse acquisition and processing technologies. Based on field programmable gate array chip (FPGA), a flat top forming algorithm with optimal filtering shaping effect and a symmetrical zero area forming algorithm with low dead time pulse processing effect are realized in parallel, and ultimately meet the requirements of the detection system for measurement speed and measurement accuracy, so as to provide a theoretical basis for the optimal design of the in-site X-ray detector based on the silicon drift detector, and provides technical support for the accurate and rapid investigation of field mineral resources.

现场X荧光探测作为核地球物理勘探领域的重要技术方法，在地质矿物资源开发中发挥着重要的作用。由于传统的X荧光探测仪具有检出限高、死时间长、在高计数率条件下系统能量分辨率显著下降的缺点，因此无法通过增加荧光产额的方法缩短测量周期，无法对矿物实现精确快速测量。针对该问题，本项目拟基于新型硅漂移探测器，构建完整的硅漂移X荧光探测数学模型，建立探测器能量响应函数，对高分辨率硅漂移探测器技术、高速低噪声信号读出技术、全数字化高速核脉冲采集处理技术进行研究，并基于现场可编程门阵列芯片（FPGA）并行实现具有最佳滤波成形效果的平顶成形算法和具有低死时间脉冲处理效果的对称零面积成形算法，最终使探测系统满足测量速度和测量精度的要求，从而为基于硅漂移探测器的现场X荧光探测仪的最优化设计提供理论依据，为野外矿产资源的精确快速勘察提供技术保障。

硅漂移探测器（SDD）是一种具有高能量分辨率和高脉冲通过率的半导体探测器，在现场X荧光探测领域中发挥着重要的作用。本项目针对SDD探测器能量沉积和载流子传输特点，开展了探测器前置读出电路、谱仪电路和数字核脉冲处理算法的设计。其中前置读出电路方面，分别研制了源级复位型电荷灵敏前置放大器、开关并联复位型电荷灵敏前置放大器、基于Cube ASIC的电荷灵敏前置放大器，实现硅漂移探测器高速、低噪声信号的读出；谱仪电路方面，研制了数字高速核脉冲处理器，其电路模拟带宽为100MHz、采样率为80MSPS，可实现核脉冲信号的低噪声、高通过率、高精度的测量；数字核脉冲处理算法方面，分别开展了适用于复位型前置读出电路的数字化预调理、数字化核脉冲信号最优滤波等算法的研究，并在嵌入式核脉冲处理器上实现了平顶成形、对称零面积成形、数字CR微分、数字极零相消、数字恒比定时、数字基线恢复等算法。基于上述读出电路、谱仪电路、核脉冲处理算法可实现硅漂移探测器快速、高精度的能谱测量，为高端国产核仪器装备的研制提供技术支撑。