X射线探测用SSPA器件的数据采集系统

Data Acquisition System of SSPA for X-Ray Detection

设计了一种供 X射线 SSPA(Self scanned photodiode array)器件使用的 8位高速数据采集系统。X射线 SSPA的视频信号是窄脉冲 ,所以必须采用峰值保持 ,同时为了在同一系统中测量多路信号 ,设计了一多路开关。在使用 X射线 SSPA器件时需对视频信号进行逐位高速采集 ,因此所有视频信号在一次逐位转换完毕 ,存储在帧存储器中 ,然后再逐位读出。所以本系统主要包括多通道开关、峰值保持、高速 A/D、帧存储器、内地址发生器和时序及逻辑控制等几部分。该系统带有帧存储 RAM,对 SSPA的视频信号采集速度可达 1MHz以上。由于 X射线 SSPA器件的信号移出原理与可见光 SSPA相同 ,所以也适用于可见光 SSPA器件。

A high speed data acquisition system of self scanned photodiode array (SSPA) used for X ray detection is designed. The video signal of SSPA is in narrow pulses, so peak value holding is necessary for sampling. To measure several channel signals in the same system, a multiple channel switching system is designed. When using the X ray SSPA, the video signal must be sampled at a high speed, so all the video signals are converted from analog to digital and memorized in order at a time, and then the data from the frame memory are accessed. Therefore the data acquisition system includes mainly a multiple channel switch, a peak value holding circuit, a high speed A/D converter, a frame memory, an address generator, a sequence and logic control circuit. An 8 KB static RAM is adopted so that the acquisition speed of the SSPA video signal exceeds 1 MHz. Because the principle of shifting video signals of a visible light SSPA deviceis is the same as an X ray SSPA, this system can also be used for visible light SSPA devices.