Research progress on correction techniques for coincidence summing effect in γ-ray spectrometry

Abstract

As a passive nondestructive nuclear technique, gamma ray spectrometry is used in many radioactivity laboratories. Gamma-ray spectrometry enables the identification of radionuclides in a sample from their emitted photon energy and calculation of their activities from the number of photons collected for each energy. However coincidence summing effects will influence the reliability of both radionuclide identification and calculation of activity. Coincidence summing effects appear when sources emitting coincident gamma rays are measured via gamma-ray spectrometry. Those effects that result in losses from the full energy peaks and enhancement of sum peaks influence the accuracy of the spectral analysis. To eliminate this influence, many correction methods have been established. Research on the coincidence summing effect (CSE) originated in the 1960s. Subsequently, many algorithm-based generation mechanisms of CSE have been built together with the development of corresponding correction software. Massive amounts of technological information on and achievements about coincidence summing correction have been reported by researchers from different countries, hence several intercomparisons of these methods, and self-consistency testing of cascaded additive effect correction algorithm were organized by the International Committee for Radionuclide Metrology (ICRM). Based on a detailed summary of the development history of correction methods, the CSE mechanisms, correction algorithms, correction software, and application of correction techniques were reviewed in this paper. Cobalt-60 was taken as an example to illustrate the influence of the summing-in and summing-out effects, with correction equations based on different measurement geometries and considering the impact of angular correlations. Meanwhile, the performance of different algorithms and software were compared and analyzed. Combined with the current research status, some suggestions are presented for future research for domestic researchers on the coincidence summing effect correction. First, the efficiency must be accurately established for the geometrical conditions of the measurement. Second, the number of cascades in the algorithm must be taken into account owing to its influence on the results. Third, correction software with a user-friendly interface and database of accurate decay schemes should be developed.

Keywords

• coincidence summing effect
• gamma-ray spectrometry
• summing-out effect
• summing-in effect