Large mass bolometric detectors for double-beta decay experiments

The authors have developed bolometric detectors with masses of 5.5 g, 20.9 g, and 34 g using TeO/sub 2/ crystals for the investigation of /sup 130/Te, and are developing CaF/sub 2/ detectors for double-beta decay search in /sup 48/Ca, using the luminescence properties of the crystal to improve background rejection. Scintillation of a CaF/sub 2/ crystal with 0.03% of 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 uranium contamination as low as 10/sup m-10/ g/g would make the search impossible.<
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