A Study of the Residual 39Ar Content in Argon from Underground Sources

TL;DR

This paper reports on the measurement of 39Ar levels in underground argon sources, demonstrating significantly reduced radioisotope content suitable for dark matter detection experiments.

Contribution

It introduces a low background liquid argon detector and provides the first measurement of 39Ar content in underground argon from a specific source.

Findings

Underground argon has less than 0.65% of atmospheric 39Ar activity.

The detector effectively measures low radioisotope levels in argon.

Results support underground argon as a promising material for dark matter experiments.

Abstract

The discovery of argon from underground sources with significantly less 39Ar than atmospheric argon was an important step in the development of direct-detection dark matter experiments using argon as the active target. We report on the design and operation of a low background detector with a single phase liquid argon target that was built to study the 39Ar content of the underground argon. Underground argon from the Kinder Morgan CO2 plant in Cortez, Colorado was determined to have less than 0.65% of the 39Ar activity in atmospheric argon.