高速紫外光子探测器位置读出电路的实现

High speed position readout circuit design for extreme ultraviolet photon-counting imaging detector

为了提高现有楔条形阳极的光子计数成像探测器的整体计数率,根据探测器输出信号的特点,研制了一个基于高速模数转换(A/D)芯片和现场可编程门阵列(FPGA)的位置读出电路。该电路采用高速A/D芯片(65 MHz采样频率)对整型放大器输出的高斯型脉冲信号逐点数据采样后获取其峰值的方法来代替原有的前端模拟电路中昂贵的峰值保持模块及NI公司的多道数据采集卡,采集的数据通过FPGA进行处理并且通过USB传输到计算机中进行解码,最终还原出图像。试验结果表明:由该电路获得的探测器图像在分辨率基本保持不变的条件下,整体计数率可以提高近一倍。

In order to raise the whole count rate of a wedge-strip anode＇s photon-counting imaging detector, according to the feature of the signal output from the detector, a position readout circuit was designed and developed. This circuit is based on high speed Analog-Digital （A/D） converters and a Field Programmable Gate Array （FPGA） chip. The circuit employs high speed A/D converters with 65 MHz sapling rate to transform the Gaussian pulse analog signal into digital series at every clock period and obtain the peak value of the pulse signal by a FPGA. It has the functions of peak hold module of voltage pulse and NI data collection card in the original circuit. The FPGS processes the received digital series according to certain rules and sends them to the computer by UBS data interface. The developed software can compute the coordinate position of every photon and display them on PC screen according to obtained 3-way data. The design of the circuit hardware and logic control is described in detail in this paper. Experiment results show that the designed circuit can get a 2D image with same position resolution and double count rate compared with the original circuit with peak hold and NI card.