X-ray and gamma-ray response of a 2″×2″ LaBr3:Ce scintillation detector

Advances in material growth techniques have recently made large volume LaBr3:Ce crystals commercially available. These scintillators are currently being assessed by ESA for use as remote sensing gamma-ray spectrometers on future planetary missions. In addition to their superior scintillation properties (high light output, fast time response and good stopping power), they offer significant benefits when designing gamma-ray detection systems for resource-limited spacecraft—not only in terms of resources but also in terms of reliability and robustness. We present the results of an investigation into the gamma-ray detection properties of a 2″×2″ LaBr3:Ce crystal, characterized using radioactive sources over the energy range 14–3220keV. The response of the crystal was found to be largely linear over the upper 95% of the dynamic range, the deviations at lower energies can be attributed to the shortcomings of the PMT. Compared to smaller volume crystals, no substantial degradation in light output, or alternately, energy resolution has been observed. For example, at 662keV, an energy resolution of 3% FWHM was measured. Experiments with monoenergetic protons show that they create approximately half the light output of gamma-rays.