Abstract: | The authors have developed bolometric detectors with masses of 5.5 g, 20.9 g, and 34 g using TeO2 crystals for the investigation of 130Te, and are developing CaF2 detectors for double-beta decay search in 48Ca, using the luminescence properties of the crystal to improve background rejection. Scintillation of a CaF2 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 232Th 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 238U to 234Th α decay from the 238U natural series occurring at almost the same energy of the 48Ca transition. Background rejection is necessary as even uranium contamination as low as 10m-10 g/g would make the search impossible |