Speaker
Description
The Advanced Mo Based Rare Process Experiment (AMoRE) collaboration is searching for the neutrino less double beta decays (0ν2β) of 100Mo isotopes using CaMoO4 scintillating crystals operating at milli-Kelvin temperatures [1]. Due to the 2ν2β background caused by 48Ca and the limitation of calcium purification within an acceptable level [2], new molybdate-based scintillation crystals for the AMoRE in the phase-II are necessary. In this work we studied luminescence and scintillation properties of the novel Na2Mo2O7 crystals grown by using two different techniques, the conventional Czochralski and the low-temperature-gradient Czochralski techniques. The transmittances of Na2Mo2O7 crystals were measured at the room temperature. The luminescence properties and decay times of the crystals at room and low temperatures were measured by using a light emitting diode (LED) source of 280 nm wavelength. The crystals showed a red emission peak of 663 nm at 10 K. The scintillation decay time was short (2 µs) at the room temperature however it was ~750 µs at 10 K. Scintillation light yield of the scintillator was measured by a photon counting technique using 90Sr as the excitation source in the temperature range from 300 K to 10 K. This work reports on the light yields of Na2Mo2O7 crystals grown at two different institutes at various temperatures and compared with a CaMoO4 crystal. Results for thermoluminescence measurements will be presented, which is going to let us understand whether the main constraint of the scintillator performance at low temperature is due to the self-trapping of charge carriers or the trap level in the crystals by defects or impurities [3].
References
[1] V. Alenkov et al., arXiv:1512.05957v1, 18 Dec 2015.
[2] V.B. Mikhailik and H. Kraus, Phys. Status Solidi B, 247 (2010) 1583–1599.
[3] D.A. Spassky et al., Journal of Luminescence, 166 (2015) 195–202.
