Half-life ofPu241

The half-life of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$ was determined by studying the ingrowth of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ in two independent sets of experiments: (i) by $\alpha$ spectrometry taking ${}_{}{}^{242}{}_{}{}^{}\mathrm{Pu}$ as well as ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ and ${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$ as reference isotopes, and (ii) by $\alpha$ proportional counting. In these experiments, separate synthetic mixtures, prepared by mixing different isotopes of plutonium, were used with an objective of obtaining periodically a desired change in the $\alpha$ activity ratio (as in $\alpha$ spectrometry) or in the total $\alpha$ activity (as in $\alpha$ proportional counting) and to measure this change with high precision and accuracy. In $\alpha$ spectrometry, from the 65 measurements carried out on five electrodeposited sources over a period of 574 days, a value of 14.37±0.09 yr was obtained for the half-life of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$. In the $\alpha$ proportional counting, from the 20 measurements carried out on five sources over a period of 704 days, a value of 14.50±0.08 yr was obtained. The average of these two independent determinations leads to a value of 14.44±0.06 yr for the half-life of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$. The uncertainty quoted on the values is a combination of one standard deviation on the average value and the error evaluated from estimates on various error components. The half-life obtained in this work is in good agreement with the results reported earlier from this laboratory by $\alpha$ spectrometry, taking ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ and ${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$ as reference isotopes as well as with the preliminary results reported by other laboratories using different methods.