The determination of helium-3 in argon at levels of 10–12

Abstract

The helium in the argon is first concentrated by removing the argon on an activated charcoal trap at –190° C. The helium is then transferred to a modified A.E.I. Ltd., MS2 mass spectrometer equipped with a Vibron amplifier, in which the volume of the helium-3 (and helium-4) is measured. With 1-litre samples the limit of detection is approximately 2 × 10^–5 p.p.m. by volume.

Current experience on establishing the level of helium-3 in the argon blanket gas of the Dounreay Fast Reactor is outlined.