宇宙・素粒子分野における，極微量元素除去技術を応用したシンチレータの高純度化技術

抄録

  The high purity of inorganic crystals is one of the most important properties for radiation measurement in nuclear and particle physics. The dark matter search project needs a low background rate of less than 1 keV⁻¹kg⁻¹day⁻¹ and energy of less than 10 keV. The neutrinoless double beta decay experiment needs less than one event per one ton of detector in one year. The radioactive impurities in an inorganic crystal suffer its sensitivity to dark matter and neutrinoless double beta decays. We aim to reduce the concentrations of uranium and thorium series impurities in the crystals to less than one ppt. The purification method should be optimized for both water-soluble and water-insoluble materials. This review report describes the purification methods. The measurement technique for tiny amounts of impurity is described. ICP-MS and radiation measurements should be applied to get precise contamination information. The prospects for the dark matter search and double beta decay experiments by inorganic crystals are discussed.