Gettering of Hydrogen and Methane from a Helium Gas Mixture using SAES St 175 ® Getters

An approach developed previously using commercially available SAES St 172® getters was successfully implemented with titanium based SAES St 172® getters to accurately quantify the helium content in a gas mixture. The gas mixture contained mostly hydrogen with small fractions of methane and helium. The approach used allows for multiple measurements to be made quickly with accuracy better than 1%. Both H2 and CH4 were removed simultaneously from the mixture using two SAES St 175® getters operating at different temperatures. A capacitance manometer was then used to measure the remaining He. Optimum performance was achieved by operating one getter at 500°C to decompose the methane, and the second at 100°C to remove the hydrogen. This gettering approach is also useful for quantifying the He-3 in mixtures that include tritium, tritiated methane, and helium-3.