The Method Using Low Energy Characteristic Peaks To Determine The Contents Of U, Th, K

select Φ38mm × 38mm LaBr3(Ce) detectors, choose the energy range lower than 1500keV to do gamma spectrometry analysis, explore a new analysis method in low energy range. This paper provides a new way for small size detector for gamma-ray Spectrometry Technology, and is in favor of it’s application and promotion which using LaBr3(Ce) detector in the field of the ground y-ray spectrometry.Given the current development of y spectrometer trend towards more lightweight and flexible, researching small size scintillation crystals y ray spectrometry technology is imperative. For the small size of the crystals, the detection efficient for high energy gamma-ray is lower than low energy gamma-ray, so choose low energy range with high detection efficiencies to improve the efficiency of y-ray spectrometry. For LaBr3(Ce) scintillation crystal, its inherent radionuclides will have a serious impact on peaks, thus further affecting the accuracy of y spectrum analysis. So selecting the appropriate low-energy peaks to study of gamma spectrometry analysis method is very meaningful.Firstly introduced natural radiation and gamma-ray detector. Secondly, according to U and Th series radionuclides and their gamma photons, based on the principle of selecting characteristic energy, confirmed the characteristic energy optimization for this paper. For the gamma spectrometry analytical difficulties, such as spectrum smoothing, peak region determination, background reduction and solution of radionuclides, these issues were studied and verified. The main conclusions are as follows(1) The characteristic energy optimization:according to the principle of choicing y-ray spectrum characteristic energy, and compared with the measured gamma instrument, the characteristic energy optimization is confirmed,214Bi-1.120MeV, 228Ac-0.908MeV,40K-1.460MeV.(2) The spectral data smoothing:this paper focusing on the study of centroid method and least squares fitting method, at last, confirmed the best gamma spectrometry data smooth method, which is 5 points quadratic least-squares fitting using 500 times.(3) Peak region determination:Using full spectrum background deduction method for background deduction, get the selected fitting data, then fit them. Finally, get the gauss curve and calculate the peak area。(4) Background reduction:Using r(m) and t(m), evaluated the effect of these deduction method. The result is best, by using SNIP with 15 iterations.(5) The technology of parsing spectrum:it is possible to parse the K peak using Least-squares fitting method.(6) Using modified inverse matrix method to examine the observed spectral lines, the results show that using this method for calculating U, Th, K contents, errors are less than 10%, analysis accuracy requirements for exploration, this method is feasible.For ΦD38mm×38mm LaBr3(Ce) detectors, the method is feasible, which choosing 214Bi-1.120MeV,228Ac-0.908MeV and 40K-1.460MeV, as characteristic energy, by using improved matrix inversion method for confirming the contents of U, Th and K.