Growth and characterization of isotopically enriched ~(40)Ca ~(100)MoO_4 single crystals for rare event search experiments

摘要

Calcium molybdate is considered as a very promising scintillator material for experimental studies of rare processes. This paper reports on the production and characterization of a ~(40)Ca~(100)MoO_4 scintillator. Using the Czochralski technique, a crystal of high optical quality with total mass 0.55 kg, 42 mm diameter (minimum) and 53 mm 1ength of the cylindrical section was produced from isotopically enriched raw materials, containing 96.1% of ~(100)Mo and 99.964% of ~(40)Ca. To satisfy the requirement of low intrinsic radioactivity the purity of the materials was monitored at different stages of the production process and it is shown that the concentration of ~(238)U and ~(232)Th in the final crystal does not exceed 0.05 ppb. The scintillation properties of ~(40)Ca ~(100)MoO_4 were measured over the 8 - 300 K temperature range and it is found that the light yield of the ~(40)Ca ~(100)MoO_4 crystal is very similar to that of the CaMoO _4 reference scintillator.