Simulation And Correction Of The Performance Of Gamma Spectrometer System

Gamma spectrum analysis technology and gamma spectrum fingerprint identification technology are important means of radioactivity analysis and nuclear material identification,and have been widely used in many fields,such as environmental radioactivity monitoring,nuclear facilities safety monitoring,nuclear terrorism prevention,nuclear weapons verification and cosmic ray detection.As a measuring tool of gamma-ray spectrum,the performance of gamma-ray spectrometer determines the accuracy of measured gamma-ray spectrum or fingerprints of gamma-ray spectrum.Therefore,to study the performance of the gamma spectrometer system and its influence on the measured gamma spectrum,and to modify it pertinently is of great practical significance to improve the accuracy of gamma spectrum analysis and the confidence of fingerprint identification of gamma spectrum.Because of the influence of the non-linearity,amplification effect,stability and statistical characteristics of various physical processes of the gamma spectrometer system,the measured gamma spectrum often has some problems like spectral intensity change,spectral line broadening,drift,spectral distortion and even distortion,which brings great difficulties to gamma spectrum analysis and gamma fingerprint identification.In order to solve this problem,the Monte-Carlo simulation method is used to study the influence of various factors on the gamma spectrum,and to propose the corresponding correction method.Finally,the method is verified by the modification of the simulated and measured gamma spectrum.This paper will study the following questions:(1)The influence of random noise in electronics and the statistical fluctuation of amplifier gain;(2)The influence of system nonlinearity and amplification effect of gamma spectrometer.On the basis of the above research,a method for the correction of gamma-ray spectra is proposed.(1)According to the theory of random signal,the gamma spectrum is modified by systematic transformation.The measurement process of gamma spectrometer is regarded as a non-linear transformation process of gamma spectrometer to depositional energy E.Through systematic transformation,the counting probability density of the road site is converted into depositional energy probability density,thus the depositional gamma spectrum is obtained.This revision method is also the innovation of this paper.(2)According to the deconvolution theory,the broadening of gamma spectrum is corrected.The results show that the system noise and the statistical fluctuation of amplifier gain mainly affect the peak height,half width and peak-to-Compton ratio,while the systemnonlinearity and amplification effect will cause spectral line drift,and have adverse effects on peak height,half-width,peak-to-Compton ratio and signal-to-noise ratio.The correction method based on random signal transformation theory can effectively eliminate the influence of system nonlinearity and amplification effect,and make the spectral line drift,peak height,peak-to-Compton ratio and half width corrected and restored reasonably and effectively.The deconvolution correction method can reduce the influence of system noise and the statistical fluctuation of amplifier gain,increase peak height,peak-to-Compton ratio,reduce half-width and keep peak area unchanged while improving energy resolution.Because deconvolution correction is equivalent to a non-linear transformation,the signal-to-noise ratio of gamma spectrum is reduced.