Fig. 3
From: In-situ monitoring of 3He/4He in summit gases of Kilauea Volcano (Hawaii) prior to the 2020 eruption
Schematic diagram of the portable field Helium Isotope Monitor (HIM), showing major vacuum components. Electronics and wiring are not shown for clarity. Pink areas indicate thermal insulation. A detailed description of the working procedure for this instrument can be found in the text and in McMurtry et al. (2019a, b)