Development of Crystal Scintillators From Enriched Isotopes for Double $\beta$ Decay Experiments

Experiments to search for neutrinoless double beta decay are considered as an unique tool to study properties of neutrino and weak interactions. Scintillation detectors possess important properties required for high-sensitivity double beta decay experiments: presence of elements of interest, low level of intrinsic radioactivity, reasonable spectrometric characteristics, fast response, pulse-shape discrimination ability. Moreover, some crystal scintillators can be applied as cryogenic scintillating bolometers with high energy resolution and excellent particle discrimination. High concentration of isotope of interest and as low as possible radioactive contamination are important requirements to a scintillation material to be used in double beta decay experiments. Therefore development of radiopure crystal scintillators from isotopically enriched materials is required. Other important issues are maximal output of detectors and minimal loss of enriched materials. High quality, radiopure cadmium tungstate crystal scintillators were developed from enriched ¹⁰⁶Cd and ¹¹⁶Cd, while calcium molybdate scintillators were grown form calcium depleted in ⁴⁸Ca and molybdenum enriched in ¹⁰⁰Mo. Prospects of several scintillation materials, promising for double beta experiments, are discussed.