Luminescence efficiency of CaF2:Eu single crystals: Temperature dependence

During the last decades, there is increasing interest in applications of scintillators at harsh environments (i.e., high temperatures or radiation fluxes), such as in geophysical detectors for deep geology boreholes, non-destructive testing (NDT) of pipelines in oil and gas industry, space and marine exploration, nuclear reactor monitoring, radiation chemistry, etc. To this aim, the current study is the first step towards the investigation of the luminescence efficiency dependence of single-crystal scintillators over wide temperature ranges. Calcium fluoride doped with europium (CaF2:Eu) was selected due to the fact that it has a high melting point at 1418°C and is also robust to mechanical and thermal shocks. The dimensions of the single-crystal sample were 10x10x10 mm3, and it was irradiated using typical X-ray radiographic exposures (90 kVp, 63mAs) in order to measure the light photon intensity dependence with temperature (22 to 128 °C). The luminescence efficiency was found maximum at the lowest examined temperature (22.01 efficiency units-E.U. at 22 °C-environmental). With increasing temperature, the luminescence efficiency decreased almost exponentially due to thermal quenching (4.43 efficiency units-E.U. at 128 °C).