Growth and characterization of isotopically enriched ⁴⁰Ca ¹⁰⁰MoO₄ single crystals for rare event search experiments

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 ⁴⁰Ca¹⁰⁰MoO₄ 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 ¹⁰⁰Mo and 99.964% of ⁴⁰Ca. 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 ²³⁸U and ²³²Th in the final crystal does not exceed 0.05 ppb. The scintillation properties of ⁴⁰Ca ¹⁰⁰MoO₄ were measured over the 8 - 300 K temperature range and it is found that the light yield of the ⁴⁰Ca ¹⁰⁰MoO₄ crystal is very similar to that of the CaMoO ₄ reference scintillator.