On the Half-Life of ⁷¹Ge and the Gallium Anomaly

The Gallium Anomaly is based on the fact that several experiments have reported (ν_e,e-) reaction rates on ⁷¹Ga lower than expected. The vast majority of these reactions are thought to involve transitions between the ground states of ⁷¹Ga and ⁷¹Ge. The cross section for such reactions can be deduced from the known half-life of ⁷¹Ge of 11.43±0.03 days¹. This half life was last measured in 1985 and recently it was suggested that a somewhat larger value could reduce or eliminate this anomaly². As a result, we are remeasuring this important half life. We produced ⁷¹Ge at the McClellan Nuclear Research Center by irradiating samples of high-purity GeO₂ and detector grade Ge with thermal neutrons. After allowing approximately two weeks of cooling for short-lived activities to decay, we started three separate measurements using dedicated planar Ge detectors – one using ⁵⁵Fe as a standard, one using ⁵⁷Co as a standard, and one stand-alone measurement, collecting data in one-day time bins. Preliminary results from these three measurements yield half-lives consistent with the known value. Final results from this experiment will be presented in this talk.

¹ B. Singh and J. Chen, Nucl. Data Sheets 188 (2023) 1

² C. Giunti et al, arXiv:2212.09722 (2023)