Calibration of the Angular Energy Efficiency of an in Situ Spectrometer Based on a LaBr 3 (ce) Detector

The angular response of an environmental γ-spectrometer equipped with a LaBr3(Ce) detector is characterized. The efficiency calibration was performed via mathematical and experimental methods and yielded three-dimensional maps of angle, energy, and efficiency. The applicability and limitation of the mathematical calibration were evaluated by relative uncertainty propagation. The uncertainty is in the range of 65 % for γ-rays with energies below 250 keV, up to 35 % in the range 250–550 keV, and approximately 10 % for other energies. These are acceptable levels of accuracy for environmental monitoring.