PROCESSING OF COMPLEX ALPHA SPECTRA MEASURED USING LSC, PIPS, AND OTHER SPECTROMETERS

ABSTRACT. This paper is devoted to the problem of radionuclide identification in multilabel samples by mathematically decoding the complex alpha spectra measured using liquid scintillation (LS), PIPS, and other alpha spectrometers. An algo-rithm is proposed that models the sample spectrum using elementary spectra of individual radionuclides. Each energy line of the radionuclide is modeled by a function representing a combination of asymmetric normal distribution, exponent and hyper-bole, connected by the condition of the continuity of the function and its derivative. The algorithm is based on the minimiza-tion of the function characterizing the deviation between the model and the apparatus spectra. This minimization is carried out by a nonlinear optimization algorithm based on the exact penalty function method. We discuss the problems that have arisen when implementing the algorithm, and we propose methods for solving these problems. We also present methods for per-forming the correct estimation and minimization of measurement uncertainties. On the basis of this algorithm, the software SpectraDecAlpha was developed. This software allows for automatic, continuous processing of complex spectra, including spectra with poor statistics, bad resolution, and a high degree of overlapping. The areas of application include rapid analysis of radionuclide content in ecological and technological samples, processing of spectra of radiochemically separated fractions, precise determination of isotopic ratios in industrial uranium- and plutonium-containing materials, and many more. Some practical results of applying this software to decode the complex spectra are reported