Behaviour of 222Rn at cryogenic temperatures

The behaviour of radon in a cryogenic environment is still not well known. Therefore, measured radon emanation rates at room temperature cannot be translated directly to cryogenic conditions. In this work we present a table-top experiment that provides a direct way of determining the behaviour of Rn-222 in cryogenic argon and helium at liquid argon temperature. We observe an increased emanation rate of Rn-222 atoms to liquid argon compared to the rate observed to helium at room temperature. We also find that Rn-222 atoms stick to cold metal surfaces when emanated to helium at liquid argon temperature but partly distribute in the liquid when emanated to cryogenic argon. Concluding, we give possible interpretations of the observations.