Application of the spectral determination method to unified gamma-ray singles and coincidence spectra

To analyze radioactive spectra, we have developed a simple algorithmic method of the Spectral Determination Method (SDM), which analyzes the entire spectrum, including continuum backgrounds and peaks. Since the SDM utilizes the total counts in a spectrum, the determination accuracy is theoretically at its highest. In previous studies, we applied this method to γ-ray spectra measured using a Ge detector and a NaI detector, as well as a liquid scintillation counter (LSC), demonstrating its versatility. Furthermore, we have extended the SDM from singles spectra to a unified spectrum created by combining a Ge detector spectrum with an LSC spectrum, resulting in improved determination accuracies for 40 medium-heavy nuclides. In the present study, we extended the SDM to a unified spectrum composed of a γ-ray singles spectrum and a γ-γ coincidence matrix. A database of these spectra was created through measurements with a compact γ-ray detector array as well as simulation calculations. We have developed an analysis code called SDM-GGG. By using this code, we studied the determination accuracies of the method and compared them to those of conventional peak analysis methods and previously developed SDM analysis for singles spectra. For a sample containing 22 radioactive nuclides, where each nuclide except137Cs has a rare abundance of 0.1% and137Cs accounts for the remainder, the determination accuracies are almost within several percent. Furthermore, the determination accuracies for 10 nuclides remain within several percent, even when the abundance of each nuclide, except for137Cs, is as low as 0.01%. We have demonstrated the superiority of the SDM-GGG analysis compared to previous methods.