Temperature Dependence of the Luminescence output of CdWO4 Crystal. Comparison with CaF2:Eu

Abstract

Scintillators are radiation converters applied in medical imaging detectors, in applications at harsh environments, including in geophysical detectors for deep geology boreholes, non-destructive testing (NDT) in gas and oil facilities, space, marine exploration, etc. In this study the luminescence efficiency dependence of single-crystal scintillators was examined with increasing temperature. Cadmium tungstate (CdWO4) was examined against calcium fluoride doped with europium (CaF2:Eu). The dimensions of the single crystals’ samples were 10x10x10 mm3 and were irradiated using X-ray radiographic exposures (90 kVp, 63mAs) to measure the light output with temperature (22 to 128 °C). The luminescence efficiency was found in both cases maximum at the lowest examined temperature (23.06 efficiency units-E.U for CdWO4 and 22.01 E.U. for CaF2:Eu, at 22 °C-environmental). With increasing temperature, the luminescence efficiency constantly decreased for both crystals due to thermal quenching (5.32 efficiency units for CdWO4 and 4.43 for CaF2:Eu, at 128 °C). In the mid-range (50-80 °C) CdWO4 shows increased differences compared to CaF2:Eu. CdWO4 has a higher density (7.9 g/cm 3) and luminescence signal than CaF2:Eu (3.18 g/cm 3), thus it is suitable, besides medical imaging, also for operation in harsh environments.