An inversion decomposition method for better energy resolution of NaI(Tl) scintillation detectors based on a Gaussian response matrix

Abstract

NaI(Tl) scintillation detectors have been widely applied for gamma-ray spectrum measurements owing to advantages such as high detection efficiency and low price. However, the mitigation of the limited energy resolution of these detectors, which detracts from an accurate analysis of the instrument spectra obtained, remains a crucial need. Based on the physical properties and spectrum formation processes of NaI(Tl) scintillation detectors, the detector response to gamma photons with different energies is represented by photopeaks that are approximately Gaussian in shape with unique full-width-at-half-maximum (FWHM) values. The FWHM is established as a detector parameter based on resolution calibrations and is used in the construction of a general Gaussian response matrix, which is employed for the inverse decomposition of gamma spectra obtained from the detector. The Gold and Boosted Gold iterative algorithms are employed to accelerate the decomposition of the measured spectrum. Tests of the inverse decomposition method on multiple simulated overlapping peaks and on experimentally obtained U and Th radionuclide series spectra verify the practicability of the method, particularly in the low-energy region of the spectrum, providing for the accurate qualitative and quantitative analysis of radionuclides.