The Laboratorio Subterráneo de Canfranc (LSC) is the Spanish national hub for low radioactivity techniques and the associated scientific and technological applications. The concentration of the airborne radon is a major component of the radioactive budget in the neighborhood of the detectors. The LSC hosts a Radon Abatement System, which delivers a radon suppressed air with $1.1\pm 0.2$ mBq/m${}^3$ of ${}^{222}$Rn. The radon content in the air is continuously monitored with an Electrostatic Radon Monitor. Measurements with the double beta decay demonstrators NEXT-NEW and CROSS and the gamma HPGe detectors show the important reduction of the radioactive background due to the purified air in the vicinity of the detectors. We also discuss the use of this facility in the LSC current program which includes NEXT-100, low background biology experiments and radiopure copper electroformation equipment placed in the radon-free clean room.

We report on the development of scintillating bolometers based on lithium molybdate crystals that contain molybdenum that has depleted into the double-$\beta$ active isotope ${}^{100}$Mo (Li${}_2$${}^{100\mathrm{depl}}$MoO${}_4$). We used two Li${}_2$${}^{100\mathrm{depl}}$MoO${}_4$ cubic samples, each of which consisted of 45-millimeter sides and had a mass of 0.28 kg; these samples were produced following the purification and crystallization protocols developed for double-$\beta$ search experiments with ${}^{100}$Mo-enriched Li${}_2$MoO${}_4$ crystals. Bolometric Ge detectors were utilized to register the scintillation photons that were emitted by the Li${}_2$${}^{100\mathrm{depl}}$MoO${}_4$ crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc Underground Laboratory (Spain). We observed that the Li${}_2$${}^{100\mathrm{depl}}$MoO${}_4$ scintillating bolometers were characterized by an excellent spectrometric performance (∼3–6 keV of FWHM at 0.24–2.6 MeV $\gamma$s), moderate scintillation signal (∼0.3–0.6 keV/MeV scintillation-to-heat energy ratio, depending on the light collection conditions), and high radiopurity (${}^{228}$Th and ${}^{226}$Ra activities are below a few µBq/kg), which is comparable with the best reported results of low-temperature detectors that are based on Li${}_2$MoO${}_4$ using natural or ${}^{100}$Mo-enriched molybdenum content. The prospects of Li${}_2$${}^{100\mathrm{depl}}$MoO${}_4$ bolometers for use in rare-event search experiments are briefly discussed.