Purification of CaF2 crystal for double beta decay experiments.

We report on inorganic crystal purification for the search for the neutrinoless double-beta decay of ⁴⁸Ca using CaF₂ crystals. We are working on the purification of CaF₂ crystal, which is made from water-insoluble raw materials. The goal of the purity in this crystal is ≤1 µBq/kg. We measured the impurities in the crucible and CaF₂ powder before we made a molten product of the CaF₂. We will consider the correlation between the purity contained in the materials around the crystal growth and the purity of the molten product. The material-selection policy and prospects for the large-volume detector system will be discussed. [ABSTRACT FROM AUTHOR]