Enhanced detection limits for radiokrypton analysis

We present a method for improving detection limits of Atom Trap Trace Analysis for the krypton radioisotopes 85Kr and 81Kr. For the case of 85Kr this work demonstrates that systematic use of isotopically depleted gas for calibration and extended conditioning of the instrument results in a detection limit of 900 85Kr atoms per 11 µl of Kr gas, equivalent to a 85Kr/Kr isotopic abundance of 3 × 10–15. This improvement of roughly two orders of magnitude over previously reported limits will help to expand the reach of radiokrypton dating towards longer age ranges where most of the radioisotopes have decayed. Additionally, the method offers an opportunity to investigate radiokrypton production via spontaneous fission within naturally occurring minerals to understand potential underground production of these isotopes.