Description
The CROSS collaboration is developing a new technology of surface sensitive bolometers for low-background neutrinoless double beta decay searches. Efficient rejection of surface $\alpha$ and $\beta$ events will allow to reach a background level in the region of interest below 10$^{−4}$ cnts/keV/kg/yr. The investigated isotopes are $^{130}$Te and $^{100}$Mo. They will be embedded in bolometers based on enriched TeO$_2$ and Li$_2$MoO$_4$ crystals. The surface sensitivity is achieved thanks to the evaporation of thin metallic films on the crystal surfaces that modify the pulse shape of near-surface events. The results here presented show that in small scale prototypes an efficient tagging of surface $\alpha$ and $\beta$ events is achievable both for TeO$_2$ and Li$_2$MoO$_4$ using a coating based on a Pd-Al (10 nm - 100 nm) bi-layer. A large demonstrator with 48 crystals, containing 6.6 kg of $^{100}$Mo and 2.6 kg of $^{130}$Te, will be installed in the CROSS cryogenic facility in the Canfranc underground laboratory, in Spain. For redundancy in $\alpha$ background reduction and to control the background induced by pile-up, the demonstrator will be provided also with high-sensitivity light detectors. Small scale prototypes of the final CROSS demonstrator, containing up to 6 crystals, have been tested in Canfranc, showing an excellent bolometric performance.
| Collaboration | CROSS |
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