A windowless flow-type Geiger counter for the assay of solid materials containing soft β-emitting isotopes

Abstract
The construction of a windowless Geiger counter for the assay of soft [beta]-emitting isotopes is described. The counting gas mixture is arranged to flush air from a second sample while the first is being counted. The counter has a low background count rate; for C14 or S35 its efficiency is 3 to 4 times that of commercial thin-window Geiger counters, and it may also be used for measuring H3.