Research On Key Technology Of Digital Multi-channel Pulse Amplitude Analyzer Based On FPGA

In the field of radiation detection,multi-channel pulse amplitude analysis technology is currently one of the main methods for obtaining nuclear energy spectrum information.Traditional analog multi-channel pulse amplitude analyzers mainly rely on analog circuits to process the nuclear pulse signals collected by the detector.The simulation of multi-channels is mostly implemented by hardware as a whole,and the system stability is poor and the dead time is too long,so that the optimal energy spectrum analysis result cannot be obtained,and the performance index is low.With the continuous improvement of semiconductor manufacturing technology and digital signal processing technology in recent years,the digital multi-channel pulse amplitude analyzer has gradually replaced the position of analog multi-channel with its advantages of fast processing speed,strong functional adaptability,stable overall performance and high portability.In the field of radiation detection,multi-channel pulse amplitude analysis technology is currently one of the main methods for obtaining nuclear energy spectrum information.Traditional analog multi-channel pulse amplitude analyzers mainly rely on analog circuits to process the nuclear pulse signals collected by the detector.The simulation of multi-channels is mostly implemented by hardware as a whole,and the system stability is poor and the dead time is too long,so that the optimal energy spectrum analysis result cannot be obtained,and the performance index is low.With the continuous improvement of semiconductor manufacturing technology and digital signal processing technology in recent years,the digital multi-channel pulse amplitude analyzer has gradually replaced the position of analog multi-channel with its advantages of fast processing speed,strong functional adaptability,stable overall performance and high portability.In recent years,the development of energy spectrum measuring instruments based on digital multi-channel pulse analysis technology in western developed countries has reached a considerable height,and there is still a significant gap in research and investment in this area in my country.Therefore,the research on the hardware composition circuit and software processing algorithm of the digital multi-channel pulse amplitude analyzer has positive engineering significance.The main research work of this subject is divided into three parts.First,the working principle of nuclear detectors and the characteristics of nuclear detection output signals are analyzed,and the basic structure of the multi-channel system and the main factors affecting system performance indicators are summarized;The signal processing method after digitization is researched and improved.Through the analysis of the existing digital signal processing algorithms such as filter shaping,baseline estimation and amplitude extraction and Matlab simulation,the trapezoidal algorithm based on Z domain transformation is selected,and the interpolation is determined.The baseline solution method of the fitted average method and the amplitude extraction method of the direct comparison method.Finally,a digital multi-channel pulse analyzer hardware board with FPGA as the logic control core was developed to complete the hardware circuit design and the software design of the FPGA internal logic function modules.It can realize a series of processing operations from signal conditioning and sampling to baseline subtraction,trapezoid formation,accumulation judgment and rejection,and peak extraction output.In order to realize the real-time display of the energy spectrum image and the effective test of the system performance indicators,the energy spectrum analysis software was developed using the C# language,which can realize the display of the spectrum and the function of spectrum analysis.The system test results show that the system not only has a relatively good linear index and spectral effect,the energy resolution of the system reaches 7.04% in the measurement of 137Cs radioactive source,the characteristic peak spectrum is drifted within 3 channels,and the performance is relatively stable.Compared with traditional analog multi-channel,the performance is significantly improved.