Study On Time-division Dynamic Spectrum Stabilization Technology Of NaI（Tl）γ Spectra Based On System Transformation

γ spectrum analysis is an important technical means of radioactive analysis and identification,which has been widely used in nuclear safety detection,nuclear weapons verification in nuclear disarmament,aerospace and many other fields.However,γ spectral drift caused by ambient temperature changes often brings great difficulties to NaI（Tl）γ spectrum analysis and identification.In order to improve the analytical accuracy and recognition confidence of NaI（Tl）y spectrum,spectral stabilization or spectral drift correction must be carried out.A time-division dynamic spectrum stabilization technique based on system transformation was proposed in this thesis.Firstly,a γ spectrum measured for a long time was regarded as the linear superposition of a series of the time-division spectra measured for a short time.Secondly,the theoretical deposition spectra of time-division spectra in the detector,the corrected time-division spectra,were reversely derived by the systematic transformation method of random signals;Finally,the corrected time-division spectra were linearly superimposed to obtain the stabilized spectrum,thus achieving the goal of spectrum stabilization.Monte Carlo simulation technique and experimental measurement method were used to study the feasibility and effectiveness of spectral stabilization technique.The main research contents and steps are as follows:Firstly,time-division spectra with different drifts were obtained by simulation or experimental measurement;Secondly,the system transformation method was used to correct the time-division spectra;Finally,the time-division dynamic spectrum stabilization technique was used to linearly superposed the corrected time-division spectra to obtain the stabilized spectrum,which was then compared with the standard spectrum.The results show that,in the simulation experiment,Before spectral stabilization,the relative drift of peak position in superposition spectrum was 0.00%,the maximum relative deviation of peak height was 60.97%,and the maximum relative deviation of FWHM was greater than 173.03%.After spectral stabilization,the relative drift of the corrected spectrum peak position was 0.01%,and the relative deviations of peak height and that of FWHM were 0.00%.In the experimental measurement study,Before spectral stabilization,the maximum relative drift of peak position in superposition spectrum was 2.44%,the relative deviation of peak height was 16.97%,and the relative deviation of FWHM was 37.99%.After spectral stabilization,the maximum relative deviation between the peak positions in the stabilized spectrum and those in the standard spectrum was 0.00%,and the relative deviation of the peak height and that of FWHM were less than 0.50%.The results indicate that through the drift correction and linear superposition of time-division spectra,the technology achieved the purpose of stabilizing spectrum and effectively improved energy resolution of the NaI（Tl）gamma spectrum,laying the technical foundation for further improving the analysis precision of NaI（Tl）gamma spectrum and the recognition degree of confidence of NaI（Tl）gamma fingerprints,thus enlarging the range of NaI（Tl）gamma spectrum analysis technology laid the technical foundation.