X-ray luminescence efficiency of a Barium Fluoride (BaF₂) single-crystal scintillator: Temperature dependence

Background. Scintillators are used in a variety of applications, from medical imaging to detectors of extreme temperatures or radiation fluxes. In this sense, measurements on the luminescence output, using a range of temperatures or radiation flux, are useful. The aim of this study was to examine the influence of temperature on the luminescence efficiency of a barium fluoride (BaF₂) single-crystal scintillator. The crystal output was compared with a cerium fluoride (CeF₃) and a commercially available bismuth germanate (Bi₄Ge₃O₁₂-BGO) of equal dimensions in similar experimental conditions.

Materials and Methods. The experimental setup, which comprised a CPI series CMP 200 DR medical X-ray source, was set to a fixed high voltage (90kVp) to expose the sample to X-ray radiation under temperature conditions in the range of 19–174 ^oC. Barium fluoride has a fast decay component, at around 0.6–0.87 ns, and a slow one, at around 620–630 ns. The maximum emission of these two components is within the ultraviolet (UV) range of 310 nm (slow) to 225 nm (fast). Heating was performed using a Perel 3700–9 2000 W heating gun. The temperature on the crystal surface was monitored using an Agilent Technologies U1253A digital multimeter, coupled to a U1185A thermocouple (J-Type) with a temperature probe adapter.

Results. The luminescence efficiency of BaF₂ decreases with increasing temperature, between 1.56 EU at 19.5^oC and 0.32 EU at 174.2^oC (EU is an abbreviation for μWm^-2/(mGy/s)). The corresponding absolute efficiency values at 90 kVp for BGO and CeF₃, in room temperature, were 2.96 and 0.69 EU, respectively.

Conclusion. BaF₂ is an inorganic scintillator that balances luminescence performance, speed and resolution, especially for applications requiring fast materials. Knowledge of its performance under various temperatures could be useful for various applications, from medical imaging to detectors in extreme environments.