Observation of Radon Mitigation in MicroBooNE by a Liquid Argon Filtration System

Abstract

The MicroBooNE liquid argon time projection chamber (LArTPC) maintains a high level of liquid argon purity through the use of a filtration system that removes electronegative contaminants in continuously-circulated liquid, recondensed boil off, and externally supplied argon gas. We use the MicroBooNE LArTPC to reconstruct MeV-scale radiological decays. Using this technique we measure the liquid argon filtration system's efficacy at removing radon. This is studied by placing a 500 kBq ${}^{222}$Rn source upstream of the filters and searching for a time-dependent increase in the number of radiological decays in the LArTPC. In the context of two models for radon mitigation via a liquid argon filtration system, a slowing mechanism and a trapping mechanism, MicroBooNE data supports a radon reduction factor of greater than 99.999% or 97%, respectively. Furthermore, a radiological survey of the filters found that the copper-based filter material was the primary medium that removed the ${}^{222}$Rn. This is the first observation of radon mitigation in liquid argon with a large-scale copper-based filter and could offer a radon mitigation solution for future large LArTPCs.

arXiv comment14 pages, 7 figures, accepted by the Journal of Instrumentation

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Cited by in corpus (4)

• Large Low Background kTon-Scale Liquid Argon Time Projection Chambers
• Measurement of ambient radon progeny decay rates and energy spectra in liquid argon using the MicroBooNE detector
• Demonstration of new MeV-scale capabilities in large neutrino LArTPCs using ambient radiogenic and cosmogenic activity in MicroBooNE
• Demonstration of neutron identification in neutrino interactions in the MicroBooNE liquid argon time projection chamber