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تسجيل مستخدم جديدEnriched TeO$_2$ bolometers with active particle discrimination: towards the CUPID experiment
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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.
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Next-generation experiments searching for neutrinoless double-beta decay must be sensitive to a Majorana neutrino mass as low as 10 meV. CUORE, an array of 988 TeO$_2$ bolometers being commissioned at Laboratori Nazionali del Gran Sasso in Italy, fea
tures an expected sensitivity of 50-130 meV at 90% C.L, that can be improved by removing the background from $alpha$ radioactivity. This is possible if, in coincidence with the heat release in a bolometer, the Cherenkov light emitted by the $beta$ signal is detected. The amount of light detected is so far limited to only 100 eV, requiring low-noise cryogenic light detectors. The CALDER project (Cryogenic wide-Area Light Detectors with Excellent Resolution) aims at developing a small prototype experiment consisting of TeO$_2$ bolometers coupled to new light detectors based on kinetic inductance detectors. The R&D is focused on the light detectors that could be implemented in a next-generation neutrinoless double-beta decay experiment.
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