Search for New Molybdenum-Based Crystal Scintillators for the Neutrino-Less Double Beta Decay Search Experiment

摘要

Studies of Li2O-MoO3, Cs2MoO4-MoO3, and Na2O-MoO3 phases have helped us to develop several new crystals such as Li2MoO4, Li4Mo5O17, Li2Mo4O13 Cs2MoO4, Cs2Mo2O7, Cs2Mo3O10 Na2Mo2O7, and Na6Mo11O36 grown by a Czochralski method. Syntheses of the polycrystalline materials are discussed based on the thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) analysis and the crystals' structures are reported based on the X-ray powder diffraction (XRD) analysis. Luminescence properties of the crystals from room temperature to 10 K are studied by exciting the crystal with a 280 nm light emitting diode (LED). The scintillation light yields of the crystals at different low temperatures are studied by exciting the crystal with strontium-90 (Sr-90) beta source. The developed crystals are not luminescent at room temperature. At cryogenic temperature, however, they become luminescent with longer decay times. This work also reports on the luminescence and scintillation properties of ZnMoO4, PbMoO4, Pb2MoO5, and CaMoO4 crystals which have been grown at other institutes. The newly developed crystals' results are compared with the result of a standard CaMoO4 crystal. Among the new Mo-based crystals, the Na2Mo2O7 crystal shows the most promising properties for the neutrino-less double beta decay (0 nu beta beta) search experiments at cryogenic temperature.