Development of new radon monitoring systems in the Kamioka mine

Abstract

Radioactivity from radon is a major threat for high-precision low energy physics experiments like the ones in the Kamioka Mine. We developed a new high sensitive radon monitoring system and conducted systematic radon concentration measurements for the first time in Kamioka. The system consists of portable radon detectors with a capacity of 1 L and new electronics based on Raspberry Pi. These radon detectors measure the radon in air with electro-static collection and a PIN photodiode. We measured the absolute humidity dependence of the 1-L radon detector for air to be $C_F(A_H)=(12.86\pm 0.40)-(1.66\pm 0.19)\sqrt{A_H}$ $(counts/day)/(Bq/{\mathrm{m}}^3)$. The background level of the 1-L radon detector is $0.65\pm 0.15$ (stat.) count/day. This corresponds to a detection limit of $\sim 0.4$ Bq/m${}^3$ in a one-day measurement. Data was collected for a period of more than one year with twenty one 1-L radon detectors in the Kamioka mine. They indicate seasonal and day-night variations in radon concentration within the mine. These results also allow us to confirm the stability of the new Raspberry Pi electronics.

arXiv comment21 pages, 22 figures, to be published in PTEP Erratum on 2019/03/06: Figures 15 and 16 were corrected, this doesn't change our conclusions

References in corpus (4)

• Limit on Neutrinoless ββ Decay of Xe-136 from the First Phase of KamLAND-Zen and Comparison with the Positive Claim in Ge-76
• XMASS detector
• Neutrino-less Double Beta Decay of 48Ca studied by CaF2(Eu) Scintillators
• Measurement of Radon Concentration in Super-Kamiokande's Buffer Gas

Cited by in corpus (4)

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