Radon mitigation during the installation of the CUORE 0νββ decay detector

CUORE—the Cryogenic Underground Observatory for Rare Events—is an experiment searching for the neutrinoless double-beta (0νββ) decay of ¹³⁰Te with an array of 988 TeO₂ crystals operated as bolometers at ∼10 mK in a large dilution refrigerator. With this detector, we aim for a ¹³⁰Te 0νββ decay half-life sensitivity of 9×10²⁵ y with 5 y of live time, and a background index of ≲ 10⁻² counts/keV/kg/y. Making an effort to maintain radiopurity by minimizing the bolometers' exposure to radon gas during their installation in the cryostat, we perform all operations inside a dedicated cleanroom environment with a controlled radon-reduced atmosphere. In this paper, we discuss the design and performance of the CUORE Radon Abatement System and cleanroom, as well as a system to monitor the radon level in real time.