Temperature dependence of CaMoO4 scintillation properties

The perspective of using CaMoO4 as a scintillation target in cryogenic rare event searches has provided strong motivation for the optimisation of this material. A single crystal of CaMoO4, exhibiting high optical quality, was produced and its scintillation light response to particle excitation and its decay time constant were investigated over the 7–300 K temperature range. The scintillation at room temperature is strongly affected by thermal quenching. The main decay time constant is found to be 15.7±0.4 μs at T=300 K; cooling to 7 K increases the scintillation decay time constant to 380±20 μs. The scintillation efficiency of the CaMoO4 crystal was evaluated by comparison with a reference CaWO4 crystal measured under the same conditions; we estimate the light output of CaMoO4 to be 55±20% that of CaWO4 at 294 K and 95±30% at 7 K. The study confirmed that calcium molybdate optimised for high light yield is a very attractive material for use in cryogenic phonon-scintillation detectors in rare event searches.