The Design And Implement Of Digital Multi-channelpulse Height Analyzer Based On FPRG

Multi-channel pulse height analyzer(MCA) is a key and important part of the ray spectra measurement technology. With the development of electronic technology, especially on the aspects of ADC(analog-to-digital converter) technology and integrated circuits, spectra measurement technology is moving in the digital direction. This design aims to realize a DMCA(Digital Multi-Channel Pulse Height Analyzer) based on FPGA(Field Programmable Gate Array), capable of sampling the fast and random pulse from the detector and converting these analog signal into the digital binary with the help of the high sampling rate ADC. Then DMCA gets the ray spectra through threshold identification and algorithms such as searching the amplitude.This DMCA mainly includes two parts--hardware and software. Hardware circuit is consisted of analog circuit, digital circuit and power supply circuit. Analog circuit completes the task of driving and amplifying the signal from the detector to meet the input requirement of the ADC converter. This design adopts AD9224 at the sample frequency of 40 MSPS as the high sampling rate ADC to complete the sample of nuclear pulse signal. Digital circuit uses EP3C40Q240C8 FPGA as the digital pulse processor to complete the goals of distracting the pulse amplitude, storing and transmitting spectral data, and communicating with PC and so on. Power conversion circuit solves the power supply problem, converting the input + 7 ~ + 12 V DC voltage into 1.2V, 2.5V, 3.3V and ±5V DC to meet the need of the printed circuit board.Software programs on the platform of Quartus II 8.1 software based on VHDL(Very-high-speed Integrated Circuit Hardware Description Language) aim to achieve the goal of getting the pulse signal’s amplitude. Embedded NIOS II soft-core based on the technology of SOPC(system on programmable chip) achieves the goal of storing and reading the spectral data, communicating with PC via RS485 serial communication. In addition, I also use Matlab software to simulate the trapezoidal shaping algorithm.I get the conclusion by actual test of137 Cs source and 232 Th,226Ra and 40 K that the digital multi-channel pulse height analyzer has a good linearity and a 6% ~ 8% energy resolution.