Gettering of Hydrogen and Methane from a Helium Gas Mixture

In this study, we developed an approach for accurately quantifying the helium content in a gas mixture also containing hydrogen and methane using commercially available getters. We performed a systematic study to examine how both H2 and CH4 can be removed simultaneously from the mixture using two SAES St 172$^{\textregistered}$ getters operating at different temperatures. The remaining He within the gas mixture can then be measured directly using a capacitance manometer. The optimum combination involved operating one getter at 650$^{\circ}$C to decompose the methane, and the second at 110$^{\circ}$C to remove the hydrogen. This approach eliminated the need to reactivate the getters between measurements, thereby enabling multiple measurements to be made within a short time interval, with accuracy better than 1{\%}. We anticipate that such an approach will be particularly useful for quantifying the He-3 in mixtures that include tritium, tritiated methane, and helium-3. The presence of tritiated methane, generated by tritium activity, often complicates such measurements.