Design Of Digital Multichannel Pulse Amplitude Analyzer Based On FPGA

Multichannel pulse amplitude analysis technology is one of the main methods to obtain nuclear information in the field of nuclear detection.With the development of digital signal processing and semiconductor technology,digital multichannel pulse amplitude analyzer has been widely applied to many fields due to its sensitivity and accuracy.In order to improve the performance of multichannel pulse amplitude analyzer,the hardware structure and software algorithm of multichannel pulse amplitude analyzer were studied in this paper,and a digital multichannel pulse amplitude analyzer based on FPGA was designed.In this paper,Xilinx's SPARTAN-6 XC6SLX25 chip is used as the master of the digital multichannel pulse amplitude analyzer and peripheral circuits include the LM318 chip as the core of the amplifier circuit,the AD9226 chip as the core of the ADC acquisition circuit and the CY7C68013A chip as the core of the USB data transmission circuit.The multichannel pulse amplitude analyzer of this kind of structure has the characteristics of fast operation speed,strong real-time transmission capability,and high integration degree.In this paper,designning the internal logic of FPGA with the aid of the System Generator tool based on Verilog HDL language in the ISE environment,including the ADC sampling control,filtering,trapezoidal shape,piling up discriminant,peak extraction,energy spectrum information storage,USB data transfer and other functions.According to the characteristics of the output pulse of the NaI?Tl?crystal detector,the trapezoidal shaping algorithm uses a double exponential pulse trapezoidal shaping filtering algorithm.This algorithm has a short time to eliminate ballistic deficit and can improve the accuracy of peak extraction and the energy resolution of the system.In this paper,the upper monitor of multichannel pulse amplitude analyzer is designed by LabVIEW software.The upper monitor can control the running state of FPGA and read spectrum information through the USB data transmission circuit.At the same time,the upper monitor can process the energy spectrum data in real time and has the functions of the spectrum display,energy calibration,net area calculation,data storage.Becase of LabVIEW software is easy to learn,so the development cycle of the system can be shortened by using LabVIEW software to design upper momitor of multichannel pulse amplitude analyzer.Through the system test,the trapezoid shaping effect of the multichannel pulse amplitude analysis system is consistent with the theoretical analysis,and the feasibility of the trapezoid shaping algorithm is verified.The multiple parameters of the multichannel system meet the requirements of the national standard for the main performance of the multichannel pulse amplitude analyzer.The gamma ray spectra of the ¹³⁷Cs source had good energy resolution by the actual measurement under the NaI?Tl?crystal detector.It is proved that the algorithm and hardware structure designed of this paper have the advantages of good optimal dffect on the performance of the multichannel pulse amplitude analysis system.