Measurement of ambient radon progeny decay rates and energy spectra in liquid argon using the MicroBooNE detector

Abstract

We report measurements of radon progeny in liquid argon within the MicroBooNE time projection chamber (LArTPC). The presence of specific radon daughters in MicroBooNE's 85 metric tons of active liquid argon bulk is probed with newly developed charge-based low-energy reconstruction tools and analysis techniques to detect correlated ${}^{214}$Bi-${}^{214}$Po radioactive decays. Special datasets taken during periods of active radon doping enable new demonstrations of the calorimetric capabilities of single-phase neutrino LArTPCs for $\beta$ and $\alpha$ particles with electron-equivalent energies ranging from 0.1 to 3.0 MeV. By applying ${}^{214}$Bi-${}^{214}$Po detection algorithms to data recorded over a 46-day period, no statistically significant presence of radioactive ${}^{214}$Bi is detected, and a limit on the activity is placed at $<0.35$ mBq/kg at the 95% confidence level. This bulk ${}^{214}$Bi radiopurity limit -- the first ever reported for a liquid argon detector incorporating liquid-phase purification -- is then further discussed in relation to the targeted upper limit of 1 mBq/kg on bulk ${}^{222}$Rn activity for the DUNE neutrino detector.

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Cited by in corpus (5)

• The science and technology of liquid argon detectors
• 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
• Physics Prospects with MeV Neutrino-Argon Charged Current Interactions using Enhanced Photon Detection in Future LArTPCs
• Benchmarks and applications of the nuclear deexcitation event generator NucDeEx