Improvement of accuracy of efficiency extrapolation method in 4πβ—γ coincidence counting

A normalized efficiency function has been calculated (which includes the optimum upper limit of the fitting region, fitting order and γ gate setting) in order to determine the type B uncertainty introduced by extrapolating. The calculated results were applied in the efficiency extrapolation method. pe B uncertainty resulting from extrapolation can be eliminated including the components introduced by different γ gate settings and/or different fitting orders. This method has been applied to the efficiency trace technique, and the results are presented for 147Nd and 35S. The final uncertainties at the 99.7 confidence level were 0.1% and 0.5%, respectively.