Phonon-mediated crystal detectors with metallic film coating capable of rejecting $\alpha$ and $\beta$ events induced by surface radioactivity

Abstract

Phonon-mediated particle detectors based on single crystals and operated at millikelvin temperatures are used in rare-event experiments for neutrino physics and dark-matter searches. In general, these devices are not sensitive to the particle impact point, especially if the detection is mediated by thermal phonons. In this Letter, we demonstrate that excellent discrimination between interior and surface $\beta$ and $\alpha$ events can be achieved by coating a crystal face with a thin metallic film, either continuous or in the form of a grid. The coating affects the phonon energy down-conversion cascade that follows the particle interaction, leading to a modified signal shape for close-to-film events. An efficient identification of surface events was demonstrated with detectors based on a rectangular $20\times 20\times 10$ mm${}^3$ Li${}_2$MoO${}_4$ crystal coated with a Pd normal-metal film (10~nm thick) and with Al-Pd superconductive bi-layers (100~nm-10~nm thick) on a $20\times 20$ mm${}^2$ face. Discrimination capabilities were tested with ${}^{238}$U sources emitting both $\alpha$ and $\beta$ particles. Surface events are identified for energy depositions down to millimeter-scale depths from the coated surface. With this technology, a substantial improvement of the background figure can be achieved in experiments searching for neutrinoless double-beta decay.

References in corpus (21)

• Search for Majorana Neutrinos near the Inverted Mass Hierarchy Region with KamLAND-Zen
• Neutrinoless Double-Beta Decay: Status and Prospects
• Final Results of GERDA on the Search for Neutrinoless Double-$\beta$ Decay
• Semi-empirical calculation of quenching factors for ions in scintillators
• The event generator DECAY4 for simulation of double beta processes and decay of radioactive nuclei
• Neutrinoless double beta decay and neutrino mass
• Improved Limit on Neutrinoless Double-Beta Decay in ${}^{130}$Te with CUORE
• Scintillating double beta decay bolometers
• Evidence of a nonequilibrium distribution of quasiparticles in the microwave response of a superconducting aluminium resonator
• Development of ${}^{100}$Mo-containing scintillating bolometers for a high-sensitivity neutrinoless double-beta decay search
• The projected background for the CUORE experiment
• The CUPID-Mo experiment for neutrinoless double-beta decay: performance and prospects
• Quasiparticle relaxation in optically excited high-Q superconducting resonators
• Performance of the EDELWEISS-III experiment for direct dark matter searches
• Final result of CUPID-0 phase-I in the search for the ${}^{82}$Se Neutrinoless Double Beta Decay
• Low background techniques in bolometers for double-beta decay search
• Experimental searches for rare alpha and beta decays
• The $0\nu 2\beta$-decay CROSS experiment: preliminary results and prospects
• Charge-to-heat transducers exploiting the Neganov-Trofimov-Luke effect for light detection in rare-event searches
• Surface-sensitive macrobolometers for the identification of external charged particles
• The CROSS Experiment: Rejecting Surface Events by PSD Induced by Superconducting Films

Cited by in corpus (7)

• Test of ${}^{116}$CdWO${}_4$ and Li${}_2$MoO${}_4$ scintillating bolometers in the CROSS underground facility with upgraded detector suspension
• Twelve-crystal prototype of Li${}_2$MoO${}_4$ scintillating bolometers for CUPID and CROSS experiments
• Li${}_2$${}^{100\text{depl}}$MoO${}_4$ Scintillating Bolometers for Rare-Event Search Experiments
• A novel mechanical design of a bolometric array for the CROSS double-beta decay experiment
• An automated system to define the optimal operating settings of cryogenic calorimeters
• BINGO innovative assembly for background reduction in bolometric $0\nu \beta \beta$ experiments
• Development of large-volume ${}^{130}$TeO${}_2$ bolometers for the CROSS $2\beta$ decay search experiment