The Photon Counting System Design Based On Photomultiplier Tube

Single photon detection is a technology that are widely used in the weak light inspection field, it is the use of weak light signal to present the particle and the technique is used in high energy physics, quantum key, chemiluminescence analysis, radiation detection, etc. In this paper, the single photon counting system is used to extract week light signal that produced by the chemiluminescence reaction and its wavelength is usually in the range of 300~650nm.By transforming the singal, we can achieve the function of single photon counting and if we record the number of photons per unit time, then we can get the concentration of the sample solution. The system is mainly composed of photomultiplier tubes, preamplifier, signal identifying and pulse counting.According to the realization principle of single photon detection technology, the paper first compare the working performance of several kinds of commonly used photoelectric detector, and finally choose the photomultiplier tube as the detector of this system. Then, according to the characteristics of photomultiplier tube’s output signal, the paper completes the hardware circuit design of subsequent signal transformation and pulse counting module. Because anode output of the photomultiplier tube is negative polarity pulse signal, so the selected amplifier and comparator should be dual polarity power supply. This paper selects THS3001 amplifier and MAX913 comparator to complete the transformation function of signal and converts the signal to the TTL standard square wave signal output that is suitable for counting. In pulse counting module, we select the freescale microcontroller MC9S12XS128 as main control chip. Because the input signal frequency is greater than 100 MHz, so we design a frequency division circuit what is composed of two pieces of 74F163 counter. Finally the data will be transferred via USB interface to computer and be displayed in the computer. Here we take a general interface chip of CH375 to implement the USB communication between the up and down machine.In the design of single photon counting system, the author completed the two aspects of hardware circuit and software design and achieved the simulation test and analysis for the whole system.