Low-Temperature Scintillation Properties of CaWO4 Crystals for Rare-Event Searches

In prospect of its application in cryogenic rare-event searches, we have investigated the low-temperature scintillation properties of CaWO4 crystals down to 3.4 K under α and γ excitation. Concerning the scintillation decay times, we observe a long component in the ms range which significantly contributes to the light yield below 40 K. For the first time we have measured the temperature dependence of the α/γ-ratio of the light yield. This parameter, which can be used to discriminate α and γ events in scintillating bolometers, is found to be ∼8%–15% smaller at low temperatures compared to room temperature.