Li${}_2$${}^{100\text{depl}}$MoO${}_4$ Scintillating Bolometers for Rare-Event Search Experiments

Abstract

We report on the development of scintillating bolometers based on lithium molybdate crystals containing molybdenum depleted in the double-${\hat{I}}^2$ active isotope ${}^{100}$Mo (Li${}_2$${}^{100\text{depl}}$MoO${}_4$). We used two Li${}_2$${}^{100\text{depl}}$MoO${}_4$ cubic samples, 45 mm side and 0.28 kg each, produced following purification and crystallization protocols developed for double-${\hat{I}}^2$ search experiments with ${}^{100}$Mo-enriched Li${}_2$MoO${}_4$ crystals. Bolometric Ge detectors were utilized to register scintillation photons emitted by the Li${}_2$${}^{100\text{depl}}$MoO${}_4$ crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc underground laboratory (Spain). We observed that the Li${}_2$${}^{100\text{depl}}$MoO${}_4$ scintillating bolometers are characterized by excellent spectrometric performance ($\sim$3--6 keV FWHM at 0.24--2.6 MeV ${\hat{I}}^3$'s), moderate scintillation signal ($\sim$0.3--0.6 keV/MeV depending on light collection conditions) and high radiopurity (${}^{228}$Th and ${}^{226}$Ra activities are below a few $\hat{I}¼$Bq/kg), comparable to the best reported results of low-temperature detectors based on Li${}_2$MoO${}_4$ with natural or ${}^{100}$Mo-enriched molybdenum content. Prospects of Li${}_2$${}^{100\text{depl}}$MoO${}_4$ bolometers for use in rare-event search experiments are briefly discussed.

Prepared for submission to MDPI Sensors; 16 pages, 7 figures, and 3 tables