Performance of the Li6Eu(BO3)3 crystal as a scintillating bolometer for studies of rare processes

In this article we report on a detailed study of the internal radioactive and chemical contamination of the Li6Eu(BO3)3 scintillating crystal operated as a cryogenic scintillating bolometer over 359 h. The excellent discrimination power of the detector allows to distinguish effectively beta/gamma events from alpha events. Whilst a weak activity of daughter nuclides from U/Th chains at the level few mBq/kg was observed, this crystal was found to be significantly contaminated by 147Sm, an alpha-active nuclide, at the level of about 0.5 Bq/kg. The light yield for β/γ events was determined to be 7.4(6) keV/MeV. The light yield and quenching factor for alpha particles vary in the range of (0.5–1.2) keV/MeV and (0.07–0.17), respectively, due to energy dependence of the emitted scintillating light in the energy interval (2.0–7.0) MeV. The integral luminescence intensity of the Li6Eu(BO3)3 crystal increases by more than four times only at low temperatures, below 80 K. Therefore, the Li6Eu(BO3)3-based cryogenic scintillating bolometers can be attractive detectors for direct neutron flux monitoring, to search for rare alpha decays or solar axions.