Evaluation of cosmogenic production of  ³⁹Ar and  ⁴²Ar for rare-event physics using underground argon

Journal Article · 20 May 2022 · Astroparticle Physics

DOI: https://doi.org/10.1016/j.astropartphys.2022.102733 · OSTI ID:1976881

Zhang, C. ^[1]; Mei, D. -M. ^[2]

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1. Mount Marty University, Yankton, SD (United States); OSTI
2. University of South Dakota, Vermillion, SD (United States)

Underground argon (UAr) with lower cosmogenic activities of ³⁹Ar and ⁴²Ar has been planned as a detector in detecting scintillation light and charge collection using time projection chambers for dark matter searches and as a veto detector in suppressing backgrounds for neutrinoless double beta decay (0$vββ$ ) experiments. Long-lived radioactive isotopes, ³⁹Ar and ⁴²Ar, can also be produced on the surface when UAr is pumped out from a deep well. Understanding the production of long-lived isotopes in Ar is important for utilizing UAr for dark matter and 0$vββ$ experiments in terms of its production, transportation, and storage. Ar exposure to cosmic rays at sea-level is simulated using Geant4 for a given cosmic ray muon, neutron, and proton energy spectrum. Here we report the simulated cosmogenic production rates of ³⁹Ar, ⁴²Ar, and other long-lived isotopes at sea-level from fast neutrons, high energy muons, and high energy protons. Total production rates of 938.53/kg_Ar day and 5.81 × 10^-3/kg_Ar day for ³⁹Ar and ⁴²Ar are found from our simulation. Utilizing these production rates, we set a time limit of 954 days constrained by the production of ³⁹Ar for UAr to be on the surface before it compromises the sensitivity for a dark matter experiment. Similarly, a time limit of 1702 days constrained by the production of ⁴²Ar is found for a 0$vββ$ experiment.

• Research Organization: University of South Dakota, Vermillion, SD (United States)
• Sponsoring Organization: National Science Foundation (NSF); State of South Dakota; USDOE; USDOE Office of Science (SC); University of South Dakota
• Grant/Contract Number: SC0004768
• OSTI ID: 1976881
• Journal Information: Astroparticle Physics, Journal Name: Astroparticle Physics Journal Issue: C Vol. 142; ISSN 0927-6505
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English