Enriched TeO$_2$ bolometers with active particle discrimination: towards the CUPID experiment

TL;DR

This study demonstrates that enriched TeO2 bolometers with Cherenkov light detection can effectively discriminate between beta/gamma and alpha events, advancing the development of neutrinoless double beta decay experiments like CUPID.

Contribution

The paper introduces a novel approach combining enriched TeO2 bolometers with Cherenkov light readout for active particle discrimination in neutrinoless double beta decay searches.

Findings

Achieved energy resolutions of 4.3 and 6.5 keV FWHM at 2615 keV.

Demonstrated 98.21% and 99.99% alpha rejection efficiency.

Measured low internal radioactive contamination levels.

Abstract

We present the performances of two 92% enriched $^{130}$TeO$_2$ crystals operated as thermal bolometers in view of a next generation experiment to search for neutrinoless double beta decay of $^{130}$Te. The crystals, 435 g each, show an energy resolution, evaluated at the 2615 keV $\gamma$-line of $^{208}$Tl, of 6.5 and 4.3 keV FWHM. The only observable internal radioactive contamination arises from $^{238}$U (15 and 8 $\mu$Bq/kg, respectively). The internal activity of the most problematic nuclei for neutrinoless double beta decay, $^{226}$Ra and $^{228}$Th, are both evaluated as $<$3.1 $\mu$Bq/kg for one crystal and $<$2.3 $\mu$Bq/kg for the second. Thanks to the readout of the weak Cherenkov light emitted by $\beta/\gamma$ particles by means of Neganov-Luke bolometric light detectors we were able to perform an event-by-event identification of $\beta/\gamma$ events with a 95% acceptance level, while establishing a rejection factor of 98.21% and 99.99% for $\alpha$ particles.