Research On Single-Photon-Counter System

Currently, the detection technology of the limit optical has become an important tool for scientific researches. In the field of biomedical, environmental monitoring, chemical analysis, radiation detection and laser measurement, single-photon-counting system has wide applications. The purpose of this study is to extract extremely weak signal from noise, and complete transformation and control of the signals.The design of single-photon-counting was completed using the following three aspects: the photo-detector, the external hardware and software design. The main course of this system is: PMT completes the conversion from photon to electric, amplifier and discriminator transform the electrical signals. Then, CPLD counts the signal, PC will displays and controls the data.This paper describes the design method of the PMT according to principle, the technical parameters and detection circuit. We chose MAX4144 as a high bandwidth gain amplifier, and low delay MAX9012 as discriminator to filter background noise, thus completing the photoelectric signal extraction. In the part of counting, EPM7128 of Altera Corporation is chosen as the core device and VHDL is used to program CPLD to complete the count and display. Then MCU will transmit the data from CPLD to PC. The CH372 interface chip was used to complete the communication between the PC and MCU. Finally, I prepare a graphical interface, draw the threshold curve by the measured data, judge the best threshold level and analyze the reasons for fluctuations in the data.The single-photon-counting system uses CPLD+MCU+USB chip model. It combines the MCU of strong logic control and data processing capabilities with the CPLD of high integration level, high reliability and speed, low cost and high performance.