  The DarkSide-50 experiment demonstrated the ability to extract and purify
argon from deep underground sources and showed that the concentration of
$^{39}$Ar in that argon was greatly reduced from the level found in argon
derived from the atmosphere. That discovery broadened the physics reach of
argon-based detector and created a demand for low-radioactivity underground
argon (UAr) in high-energy physics, nuclear physics, and in environmental and
allied sciences. The Global Argon Dark Matter Collaboration (GADMC) is
preparing to produce UAr for DarkSide-20k, but a general UAr supply for the
community does not exist. With the proper resources, those plants could be
operated as a facility to supply UAr for most of the experiments after the
DarkSide 20k production. However, if the current source becomes unavailable, or
UAr masses greater than what is available from the current source is needed,
then a new source must be found. To find a new source will require
understanding the production of the radioactive argon isotopes underground in a
gas field, and the ability to measure $^{37}$Ar, $^{39}$Ar, and $^{42}$Ar to
ultra-low levels. The operation of a facility creates a need for ancillary
systems to monitor for $^{37}$Ar, $^{39}$Ar, or $^{42}$Ar infiltration either
directly or indirectly, which can also be used to vet the $^{37}$Ar, $^{39}$Ar,
and $^{42}$Ar levels in a new UAr source, but requires the ability to separate
UAr from the matrix well gas. Finding methods to work with industry to find gas
streams enriched in UAr, or to commercialize a UAr facility, are highly
desirable.
