Study of a Large CaF2(Eu) Scintillating Bolometer for Neutrinoless Double Beta Decay

Scintillating bolometer is a powerful tool to search neutrinoless double beta decay. We established a large scintillating bolometer using a 312 g CaF2(Eu) crystal with a readout technology of metallic magnetic calorimeters. A set of successful measurements were carried out for simultaneous detection for heat and light signals at 10-40 mK in an above-ground laboratory. We found large light signals with clear difference in scintillation yields between electron- and alpha-induced events. The comparison of relative amplitudes of heat and light signals obtained about 10 a discrimination power. We also found the heat signals experiencing strong position dependence from the event location. This position dependence can be interpreted by the spin-lattice interaction of paramagnetic Eu ions in the CaF2 crystal.