An online radon monitor for low-background detector assembly facilities

Abstract Backgrounds from long-lived radon decay products are often problematic for low-energy neutrino and rare-event experiments. These isotopes, specifically $${}^{210}\hbox {Pb}$$ 210 Pb , {Bi}$$ Bi {Po}$$ Po easily plate out onto surfaces exposed to radon-loaded air. The alpha emitter is particularly dangerous detectors searching weakly-interacting dark matter particles. Neutrons produced via ( $$\upalpha $$ ? n) reactions in detector materials are, some cases, a residual background that can limit the sensitivity of experiment. An effective solution reduce $${}^{222}\hbox {Rn}$$ 222 Rn activity air contact with components during fabrication, assembly, commissioning, operation. We present design, construction, calibration procedures performance an electrostatic made monitor two radon-suppressed clean rooms built DARKSIDE-50 A dedicated data acquisition system immune harsh operating conditions also described. record detection specific achieved by device $$0.05\,\hbox {mBqm}^{-3}$$ 0.05 mBqm - 3 (STP). concentration different samples collected measured presented.