Half-life ofPu241

The half-life of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$ was determined by studying the ingrowth of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ by $\alpha$ spectrometry. A synthetic mixture was prepared by mixing was prepared by mixing different isotopes of plutonium so as to obtain a ${}_{}{}^{238}{}_{}{}^{}\mathrm{Pu}$/(${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$+${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$) $\alpha$ activity ratio of nearly 0.1 and an increase in the $\alpha$ activity ratio due to the ingrowth of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ of about 0.1 after a period of 30 days. This was done to get a desired change periodically in the $\alpha$ activity ratio and to measure this change with high precision and accuracy. The initial values of ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$/${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$ and ${}_{}{}^{240}{}_{}{}^{}\mathrm{Pu}$/${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$ atom ratios in the mixture were obtained by mass spectrometry. The ingrowth of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ was measured periodically by $\alpha$ spectrometry on electrodeposited sources using a silicon surface barrier detector. From the 80 $\alpha$ spectrometric measurements carried out on five electrodeposited sources over a period of 457 days, a value of 14.42±0.09 yr is obtained for the half-life of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Pu}$ using a value of 432.6 yr for the half-life of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$. The uncertainty quoted on the value is a combination of one standard deviation on the average value and the error evaluated from the estimate on various error components. The half-life obtained in this work is in good agreement with the preliminary results reported recently by CBNM (Geel), NBS (Washington), and AERE (Harwell) using different methods.