Large mass bolometric detectors for double-beta decay experiments

TeO/sub 2/ bolometric detectors with masses of 5.5 g, 20.9 g, and 34 g have been developed. The latter have been operating for more than 440 h in the Gran Sasso underground laboratory, and a limit of 1.2*10/sup 20/ y for the half life of the neutrinoless double-beta decay of /sup 130/Te was reached. CaF/sub 2/ detectors for simultaneous detection of scintillating light and phonon signals are under development and will be used to search for double-beta decay of /sup 48/Ca. Scintillation of a CaF/sub 2/ crystal with 0.03% Eu doping was observed at 20 mK. A 2.1 g, 0.01% Eu doped crystal was used as a bolometer, and a resolution of 50 keV for the double escape peak of /sup 232/Th was obtained at 60 mK, showing a negligible contribution of the Eu atoms to the crystal heat capacity. Simultaneous detection of light and phonons will allow an efficient background rejection of the /sup 238/U to /sup 234/Th alpha decay from the /sup 238/U natural series occurring at almost the same energy of the /sup 48/Ca transition. Background rejection is necessary as even U contamination as low as 10/sup -10/ g/g would make the search impossible.<>