Spectral Deconvolution Uses Of Gaussian Fit Method In Gamma-ray Spectrometry

When we estimate radioactivity level in the environment of pollution of 137Cs inthe soil, we usually have airborne gamma-ray survey. The NaI(Tl) detector is mainlyused in in-situ multi-channel gamma-ray spectrometer. It is fast, economical andefficient. But it has the shortcoming of low resolute and so as too many peaks in lowenergy areas are overlapping. These peaks are the 609keV photopeak of ²¹⁴Bi(²³⁸Userial) and the 583keV photopeak of ²⁰⁸Tl(²³²Th serial). When the man-made nuclidepollutes soil, the overlapped peaks will appear a peak of 662keV of ¹³⁷Cs.The author uses Gaussian fit method to deconvolution the low energy absorbedpeaks based on the analyzing lots of literature about overlapped peaks in gamma-rayspectrometry. The method is using the Gaussian function to fit the peaks in thespectrum. The arithmetic is the square least. There are three parameters in theGaussian function, that is the peak value and the FWHM(full width of half theMaximum) and the central site of the peak(centroid). Firstly, you need to plot a scatterfigure of the data that you want to fit. Then you should study the scatter figure anddecide which mean of the background calculation: the linear background or theparabolic background. After that the net counts of ROI are calculate after backgroundsubtracted from the spectra in the last step. Following that you should get the peakvalue, the FWHM and the centroid. Now we can fit the spectrum of the peak with thesquare least arithmetic and get the two changing parameters they are peak value andthe peak's FWHM. Finally, we use the parameters to get the Gaussion function anduse it to calculate the fit curve. After that we have finished spectral deconvolution bythe Gaussian function.After processing of measured airborne gamma spectrometry data, the fitted netarea of the peak by Gaussian function is not more the 10% compared with measuredspectra. So Gaussian fit is feasible for spectral analysis in gamma-ray spectrometerwith NaI(Tl) detector. And the method is great important of studying and applyinggamma spectral method to estimate the pollution of 137Cs in ionized radiationenvironment.