Long term measurement of the 222Rn concentration in the Canfranc Underground Laboratory

Abstract

We report the results of 6 years (2013–2018) of measurements of 222Rn air concentration, relative humidity, atmospheric pressure and temperature in the halls A, B and C of the Canfranc Underground Laboratory (LSC). We have calculated all the Pearson correlation coefficients among these parameters and we have found a positive correlation between the 222Rn concentration and the relative humidity. Both correlated variables show a seasonal periodicity. The joint analysis of laboratory data and 4 years (2015– 2018) of the meteorological variables outside the laboratory shows the correlation between the 222Rn concentration and the outside temperature. The collected information stresses the relevance of designing good Rn-mitigation strategies in current and future experiments at LSC; in particular, we have checked for two years (2017–2018) the good performance of the mitigation procedure of the ANAIS-112 experiment. Finally, we have monitored (2019–2021) for 2 years of live time, the radon-free air provided by the radon abatement system installed in the laboratory.