Numerical analysis of radon behavior in radon-suppressed clean room environments

Abstract

Radon-free clean rooms are essential for the production and assembly of components adopted in low-background experiments. In particular, long-lived radon decay products are often problematic for rare events searches, such as low energy neutrino interactions, direct dark matter detection, and neutrinoless double beta decay. These isotopes can easily deposit onto surfaces exposed to radon, leading to a residual background that can limit the sensitivity of experiments. In order to mitigate this background source, construction of detectors in radon-reduced environments is essential. In this framework, design and building of radon-suppressed clean rooms require a deep understanding of the radon behavior and the different sources of contamination. In the paper, computation fluid-dynamics (CFD) analyses of the radon-suppressed clean rooms built for the DarkSide-50 experiment are reported. The numerical model including the main radon contributions, such as structural materials, equipment, and operators activity, provides very promising results in a remarkable agreement with available experimental data, confirming the validity of the current modelling approach for future applications.