Radiopurity of a kg-scale PbWO$_4$ cryogenic detector produced from archaeological Pb for the RES-NOVA experiment

TL;DR

This paper reports on the radiopurity of archaeological lead-based PbWO$_4$ cryogenic detectors, demonstrating their suitability for low-background neutrino detection in the RES-NOVA experiment, with promising results for future low-noise applications.

Contribution

It provides the first radiopurity measurements of archaeological PbWO$_4$ crystals for cryogenic detectors, supporting their use in low-background neutrino experiments like RES-NOVA.

Findings

Radioactive contaminations are below key thresholds for most isotopes.

The detector shows potential for low-background neutrino detection.

Strategies for further background reduction are discussed.

Abstract

RES-NOVA is a newly proposed experiment for the detection of neutrinos from astrophysical sources, mainly Supernovae, using an array of cryogenic detectors made of PbWO$_4$ crystals produced from archaeological Pb. This unconventional material, characterized by intrinsic high radiopurity, enables to achieve low-background levels in the region of interest for the neutrino detection via Coherent Elastic neutrino-Nucleus Scattering (CE$\nu$NS). This signal lies at the detector energy threshold, O(1 keV), and it is expected to be hidden by naturally occurring radioactive contaminants of the crystal absorber. Here, we present the results of a radiopurity assay on a 0.84 kg PbWO$_4$ crystal produced from archaeological Pb operated as a cryogenic detector. The crystal internal radioactive contaminations are: $^{232}$Th $<$40 $\mu$Bq/kg, $^{238}$U $<$30 $\mu$Bq/kg, $^{226}$Ra 1.3 mBq/kg and $^{210}$Pb 22.5 mBq/kg. We present also a background projection for the final experiment and possible mitigation strategies for further background suppression. The achieved results demonstrate the feasibility of realizing this new class of detectors.