Analysis of the 222Rn concentration in argon and a purification technique for gaseous and liquid argon

We present an investigation of the 222Rn concentration in argon with ultra-low background proportional counters. Argon purification tests by means of cryo-adsorption of radon on activated carbon were performed. For gaseous argon the purification process was found to be very efficient. Also in liquid phase the 222Rn concentration could be reduced significantly, however, the efficiency is lower than in the gas phase. We also have analyzed the initial 222Rn concentrations in commercial liquid argon. It was found to be significantly higher than in liquid nitrogen.