Neodymium-Containing Single Crystals for Neutrinoless Double Beta Decay Detection

The Neutrinoless Double Beta Decay Underground Detector for the determination of the neutrino mass has been identified by DOE as a high scientific priority. Unfortunately, the current generation of proposed experiments would require 500 kg of isotopically enriched germanium (Ge). The cost of this specialized Ge would exceed $100 million. 150Nd is an alternate parent isotope for neutrinoless double beta decay, which could substantially reduce the size and cost of cooling and detection infrastructure. However, the favorable theoretical decay rate of 150Nd can be exploited only by using a detector with high detection efficiency and excellent energy resolution. The only known approach for constructing such a detector is to construct a bolometer of a single crystal from a compound that contains a significant fraction of neodymium. Therefore, this project will develop technology for growing bulk crystals of a high-purity single-crystal neodymium-containing oxide optimized for bolometer applications. In Phase I, neodymium gallate was identified theoretically as the preferred compound for this application, and small cubes were fabricated for initial bolometer testing. In Phase II, the growth conditions identified in Phase I will be realized and scaled-up to produce high-yield optimum-size crystals, and cubes will be delivered for a prototype bolometer. Commercial Applications and other Benefits as described by the awardee: The primary application of single crystal neodymium-containing oxides would be for cryogenic bolometers for neutrinoless double beta decay. The value of the scientific goal of determining neutrino mass is inestimable. Neodymium gallate also should find use as a substrate for high temperature superconductors.