Triplet lifetime in gaseous argon
The MiniCLEAN is a single-phase liquid argon dark matter experiment. During the initial cooling phase, impurities within the cold gas ( $<140 K$) were monitored by measuring the scintillation light triplet lifetime, and ultimately a triplet lifetime of $3.480±0.001(stat.) ±0.064(sys.)$ μs was obtained, indicating ultra-pure argon. This is the longest argon triplet time constant ever reported. The effect of quenching of separate components of the scintillation light is also investigated.