A liquid-phase loop-mode argon purification system

Noble gas and liquid detectors rely on high chemical purity for successful operation. While gaseous purification has emerged as a reliable method of producing high-purity noble fluids, the requirement for large mass flows drives the development of liquid-phase purification. We constructed a medium-scale liquid argon (LAr) purification system based on a copper catalyst and 4 A molecular sieve capable of purifying 1 t of commercial LAr 5.0 to a long effective triplet lifetime of $\tau_3 \sim 1.3 \mu$s. We further demonstrate that a quenched effective triplet lifetime of $\tau_3 \sim 1 \mu$s, due to contamination by air, can be recovered in loop-mode purification to $\tau_3 \sim 1.3 \mu$s after > 20 volume exchanges.