Software to Compensate Coincidence Losses in the Environmental Sample Analysis of a Digital Anti-Compton Spectrometer

Anti-Compton spectroscopy is a useful approach to analyze low-level contaminants in environmental samples that would otherwise be obscured by the Compton signal of the natural radionuclides present in the sample matrix. An example of this is the sensitive identification of 137Cs in soil samples. A challenge of the anti-Compton technique is that the anti-coincidence veto to remove Compton scattered photons also suppresses the identification of contaminant radionuclides that have cascade gamma emissions such as 60Co. This is a major limitation of the technique in environmental sample analysis. The time stamped pulse analysis method presented in this paper recovers the undesired full-energy-peak (FEP) coincidence losses for cascade radionuclides that trigger the anti-Compton spectrometer veto while retains suppression of true Compton events to keep the improved detection limit, thus extending the usefulness of the anti-Compton spectroscopy. In this study, the software has been used to analyse the radionuclides with a relative simple decay scheme, such as 22Na, 60Co and 88Y, and a complex decay scheme, such as 125Sb, 134Cs, 152Eu and 154Eu. The results have indicated that in the reconstruct anticoincidence spectra the FEP restoration efficiency, both for minor and major peaks, is near 100%.