Li2100deplMoO4 Scintillating Bolometers for Rare-Event Search Experiments

Abstract

We report on the development of scintillating bolometers based on lithium molybdate crystals that contain molybdenum that has depleted into the double-𝛽 active isotope 100 Mo (Li2 100depl MoO4 ). We used two Li2 100depl MoO4 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-𝛽 search experiments with 100 Mo-enriched Li2 MoO4 crystals. Bolometric Ge detectors were utilized to register the scintillation photons that were emitted by the Li2 100depl MoO4 crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc Underground Laboratory (Spain). We observed that the Li2 100depl MoO4 scintillating bolometers were characterized by an excellent spectrometric performance (∼3–6 keV of FWHM at 0.24–2.6 MeV 𝛾 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 Li2 MoO4 using natural or 100 Mo-enriched molybdenum content. The prospects of Li2 100depl MoO4 bolometers for use in rare-event search experiments are briefly discussed.