Search for Variations of Po-213 Half-Life

A device with the parent ${}^{229}$Th source was constructed to search for variations of the daughter ${}^{213}$Po half-life ($T_{1\mathrm{/}2}=4.2$ $\mu$s). A solar-daily variation with amplitude $A_{So}=(5.3\pm 1.1)\times {10}^{-4}$, a lunar-daily variation with amplitude $A_L=(4.8\pm 2.1)\times {10}^{-4}$, and a sidereal-daily variation with amplitude $A_S=(4.2\pm 1.7)\times {10}^{-4}$ were found upon proceeding the data series over a 622-day interval (from July 2015 to March 2017). The ${}^{213}$Po half-life mean value is found to be $T_{1\mathrm{/}2}=3.705\pm 0.001$ $\mu$s. The obtained half-life is in good agreement with some of the literature values obtained with great accuracy.