  Argon-37 is an environmental signature of an underground nuclear explosion.
Producing and quantifying low-level Ar-37 standards is an important step in the
development of sensitive field measurement instruments. This paper describes
progress at Pacific Northwest National Laboratory in developing a process to
generate and quantify low-level Ar-37 standards, which can be used to calibrate
sensitive field systems at activities consistent with soil background levels.
This paper presents a discussion of the measurement analysis, along with
assumptions and uncertainty estimates.
