Performance of ZnMoO₄crystal as cryogenic scintillating bolometer to search for double beta decay of molybdenum

Abstract

Zinc molybdate (ZnMoO4) single crystals were grown for the first time by the Czochralski method and their luminescence was measured under X-ray excitation in the temperature range 85-400 K. Properties of ZnMoO4 crystal as cryogenic low temperature scintillator were checked for the first time. Radioactive contamination of the ZnMoO4 crystal was estimated as <= 0.3 mBq/kg (Th-228) and 8 mBq/kg (Ra-226). Thanks to the simultaneous measurement of the scintillation light and the phonon signal, the alpha particles can be discriminated from the gamma/beta interactions, making this compound extremely promising for the search of neutrinoless Double Beta Decay of Mo-100. We also report on the ability to discriminate the alpha-induced background without the light measurement, thanks to a different shape of the thermal signal that characterizes gamma/beta and alpha particle interactions.