Coincidence summing correction methods and influence factors of γ spectrum

Abstract

BackgroundIn the radiation environmental quality measurement or emergency measurement, one of the factors that influence the measurement results of γ spectrum activity is the cascade coincidence summing effect of multienergy nuclides.PurposeThis study aims to verify the accuracy of coincidence summing correction and analyze its influencing factors.Methods152Eu nuclide was taken as an example object, the peak-to-total fitting formula of the detector was obtained according to the invariance characteristics of peak-to-total ratio. Combined with the coincidence summing correction formula and the full energy peak efficiency formula, and the coincidence summing correction factors of 152Eu nuclide were calculated, and the Genie 2000 Monte Carlo program was used to correct 152Eu nuclide of the bulk samples.ResultsThe experimental results show that the relative deviation between the result and the true value is less than 6% of point source, and the relative deviation between the corrected results and the reference values is within ±4% of bulk samples. Through the linear relationship between the point source coincidence summing correction factor and the distance from the source to the detector, the minimum measurement distance with negligible coincidence summing effect can be obtained. The results of coincidence summing correction of bulk samples show that the higher the sample height is, the smaller the coincidence summing correction factor is.ConclusionsThe numerical correction method combining peak-to-total ratio invariance and decay scheme, which does not require measurement of the point source total efficiency at different locations. Compared with the Monte Carlo program method, this method does not require factory characterization of the detector, nor does the parameters of the bulk sample such as medium, density and shape after abandoning the energies with serious cascade coincidence, hence be used for the coincidence summing corrections of the environmental emergency samples. In the low energy part, the self-absorption effect has a great influence on the effective solid angle of the sample, so that affecting the coincidence summing correction factor of the sample.

Keywords

• coincidence summing correction
• γ spectrum
• peak-to-total ratio