Digital Gamma Spectrum Measurement System Based On FPGA

Nuclear energy spectrum measurement technology is an important method to study nuclear physics,heavy ion physics,high energy physics and nuclear application technology.As an important means of nuclear energy spectrum measurement,gamma spectroscopy is widely used in medicine,biology,physics,chemistry,geology and other fields.The traditional gamma spectroscopy measurement system performs the steps of filtering amplification,pulse shaping,baseline recovery,stacking discrimination,peak hold and low-speed ADC sampling on the pulse signal output from the gamma ray detector,and finally generates an energy spectrum curve.Due to the low sampling rate of the ADC,the system measures the dead time,making it difficult to measure the energy spectrum in a high-radiation environment.At the same time,because the pulse formed by the analog circuit is wide,it is easy to cause signal accumulation,and it is impossible to realize the processing of stacking pulse separation..The digital gamma spectroscopy system developed in recent years can directly sample the amplified ray pulse by high-speed digital processing chip?such as FPGA?and high-speed ADC,without pulse shaping,baseline recovery,and accumulation of analog circuits.Discriminating,peak-holding and other processing,directly by the high-speed digital processing chip to achieve similar functions,system adaptability and portability is stronger,but if the detector input ray pulse is wide,it is still unable to achieve energy spectrum measurement in high-radiation environment.The paper intends to use the high-performance LaBr3 detector to study the digital gamma spectroscopy measurement system based on FPGA to realize gamma spectroscopy measurement in high radioactive environment.Based on the basic theory of gamma spectroscopy,the paper analyzes the advantages and disadvantages of different gamma ray detectors and the principle of digital multi-channel pulse amplitude analysis,and studies the pulse digital gaussian forming algorithm and trapezoidal forming algorithm in gamma-ray spectrum measurement.algorithm.Based on this,a high-speed digital gamma spectroscopy measurement system based on FPGA is designed,which realizes full-pulse high-speed sampling,threshold discrimination,digital shaping and pulse stacking identification of high-performance LaBr3 detector input narrow pulse signals.Separation,post-forming pulse amplitude extraction,energy spectrum curve generation,etc.,and the energy spectrum curve is transmitted to the host computer through the serial port for energy spectrum analysis.In this paper,the energy spectrum of standard calibration source ¹³⁷Cs is measured and analyzed through the developed high-speed digital gamma energy spectrum measurement system based on FPGA,and the energy resolution performance of the system is verified.The energy spectrum measurement and analysis achieves the linear scale of the energy of the system.At the same time,the paper achieved the calibration efficiency of the system by using the standard calibration model of the basement uranium mine of East China University of Technology.The performance of the system in a highly radioactive environment was verified by a high-content uranium model.The high-speed digital gamma spectroscopy measurement system based on FPGA research solves the problem of the existing digital gamma spectroscopy measurement system by using the high-performance LaBr3 detector with narrow output pulse and the FPGA-based digital spectroscopy algorithm.Due to the serious pulse accumulation,the pass rate is low,the energy resolution is poor,and the effective separation of the pulse cannot be realized.The research results of the thesis aim to provide a method basis for the research of digital gamma spectroscopy measurement technology,and provide technical basis for the corresponding system development to meet the application requirements of digital gamma spectroscopy measurement in high radioactive environment.