Direct low-energy measurement of 37 Ar and 127 Xe in a radiotracer gas using low-background proportional counters

A radiotracer gas with a blend of 37 Ar and 127 Xe was created for a gas migration experiment and was characterized at Pacific Northwest National Laboratory using ultra-low-background proportional counters. This paper describes the direct low-energy measurement of 37 Ar and 127 Xe in a dual-isotope sample. Using this low-energy technique, the dual-isotope radiotracer gas was determined to have activity concentrations of 483 Bq/cc and 1435 Bq/cc for 37 Ar and 127 Xe, respectively, and a ratio of 1:3 on the reference date of 7/11/2016.