Speaker
Description
The CUPID collaboration is advancing toward a next-generation cryogenic calorimetric experiment for neutrinoless double beta decay search $(0\nu\beta\beta)$, based on enriched Li$_{2}$$^{100}$MoO$_4$ scintillating crystals. To overcome the background-limited sensitivity of its predecessor, CUORE, CUPID will instead use scintillating absorbers. The purpose is to reduce the background from energy-degraded alpha particles by taking advantage of a dual readout approach, heat and light, which has been proven to allow a complete $\alpha$ vs $\beta/\gamma$ discrimination. Building on the experience of a first prototype, a new upgraded CUPID tower has been developed, featuring an upgraded mechanical structure to achieve a more uniform thermalisation along the array and to further mitigate the correlated noise among the light detectors.
The light detectors, thin germanium wafer-based cryogenic calorimeters, are now equipped with concentric Al-electrodes to take advantage of the Neganov-Trofimov-Luke amplification, thus boosting the light signal sensitivity. This advancement is crucial for enhancing the rejection of pileup events — a major challenge for CUPID due to the relatively high decay rate of Mo and the intrinsically slow thermal response of the calorimetric detectors. The tower is being operated deep underground in a wet cryostat at Laboratori Nazionali del Gran Sasso in Italy, and it is instrumented with optical fibres, dedicated thermometry, and vibrational sensors. These systems will enable a full characterisation of the thermal behaviour, optical performance, and vibrational noise. The prototype tower was built to mirror the baseline CUPID tower idea, made up by 28 Li$_{2}$$^{100}$MoO$_4$, 30 light detectors and with a periodical optical injection system serving for NTL regeneration, calibration and pile-up rejection power probing of the light detectors.
In this poster, we will present the tower design and results of this measurement, which are expected to be instrumental in validating the technological solutions for the final CUPID detector design.