The temperature-dependent luminescence efficiency of a hygroscopic cerium-doped lanthanum bromide (LaBr₃:Ce) single-crystal scintillator

Background. Scintillators are used in a variety of applications, including modalities in environmental conditions of extreme temperature or radiation flux. Thus, knowledge of their luminescence performance under the influence of temperature or radiation flux is of paramount importance. In this framework, the aim of this study was to examine the influence of temperature on the luminescence efficiency of a hygroscopic cerium-doped lanthanum bromide (LaBr₃:Ce) single-crystal scintillator. The crystal output was compared with a cerium-doped lanthanum chloride (LaCl₃:Ce) crystal scintillator of equal dimensions, in similar experimental conditions.

Materials and Methods. The experimental setup comprised a CPI series CMP 200 DR medical X-ray source set to a fixed high voltage (90kVp) to expose the sample to X-ray radiation under temperature conditions in the range of 23–154 ^oC. LaBr₃:Ce is an extremely efficient crystal, with a high light yield of 63,000 photons/MeV and a fast decay time (25ns). The crystal was removed from the protective aluminum encapsulation (thickness 0.7 mm). Heating was performed using a Perel 3700-9 2000W 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 LaBr₃:Ce decreases with increasing temperature, from 69.58 EU at 23.0^oC to 18.27 EU at 154^oC (EU is the S.I. equivalent μWm^-2/(mGy/s). The corresponding values for LaCl₃:Ce were 33.14 to 17.96 EU in the temperature range from 29 to 162 ^oC. The room-temperature absolute efficiency of LaBr₃:Ce, with the protective aluminum encapsulation, was 50.02 EU.

Conclusion. LaBr₃:Ce is an extremely efficient crystal scintillator and knowledge of its performance in various temperatures could be useful for various applications, from medical imaging to detectors for extreme environments.