Correction And Total Spectral Quantitative Analysis Of NaI? Spectra

Gamma-ray spectrometry is one of the main techniques for analyzing radioactivity,and it is widely used in the fields of environmental radioactive pollution monitoring,nuclear facilities monitoring,etc.The types and activities of the radioactive isotopes in the samples to be analyzed can be achieved by gamma spectrum analysis.However,during the collection of gamma spectra,the instability of gamma spectrometer caused by ambient temperature always results in spectral drift,deformation,or even distortion,making it difficult to analyze gamma spectra,thus reducing the quantitative analysis accuracy of radioactive isotopes.To solve this problem,a new method for correcting NaI(Tl)gamma spectra based on the transformation theory of system was proposed,which treats the measurement of gamma spectra as a no-linear system transformation,and the deposition energy in the detector as the random input signal of the spectrometer system,and the channel address in MCA corresponding to the deposition energy as the random output signal of the system,the energy-calibration function as the transformation function of spectrometer system.By the system inverse transformation theory of random signals,the actually measured spectra are transformed into energy domain from channel domain,thus the spectral drifts caused by the instabilty of gamma spectrometer parameters and the spectral distortion caused by the system parameters themselves are all eliminated,laying a foundation for improving the analysis accuracy of NaI(Tl)gamma spectra.The contents of the research are as follows :(1)Simulation study on the feasibility of the correction method.Firstly,a series of NaI(Tl)gamma spectra with drifts and without drifts are obtained under certain different system parameters by Monte Carlo simulation technique.Secondly,all these simulated NaI(Tl)gamma spectra are corrected using the above correction method,eliminating the influence of the spectrometer system parameters by system inverse transformation;Finally,these spectra were quantitatively analyzed with the full spectrum analysis method before and after correction to verify the feasibility of the proposed correction method.(2)Experimental study on the availability of the correction method.Firstly,a series NaI(Tl)gamma spectra without drifts were measured using the NaI(Tl)gamma spectrometer under certain parameters of the spectrometer system,and those with drifts were also measured by changing the amplifier gain value of the spectrometer system.Secondly,all the gamma spectra were corrected using the above correction method.Finally,the spectra were quantitatively analyzed with the full spectrum analysis method before and after correction to validate the correction method.The results show that the correction method of NaI(Tl)gamma spectra based on the system transformation theory of random signals can effectively correct the horizontal spectra;drifts and longitudinal spectral intensity variation,and it has a strong correction ability,thus effectively improving the quantitative analysis accuracy of NaI(Tl)gamma spectra.In principle,by the proposed methid,the spectra data can be shared among different spectrometer systems.