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The properties of large volume cylindrical 3.5" x 8" (89 mm x 203 mm) LaBr 3 :Ce scintillation detectors coupled to the Hamamatsu R10233-100SEL photo-multiplier tube were investigated. These crystals are among the largest ones ever produced and still need to be fully characterized to determine how these detectors can be utilized and in which applications. We tested the detectors using monochromatic ray sources and in-beam reactions producing  rays up to 22.6 MeV; we acquired PMT signal pulses and calculated detector energy resolution and response linearity as a function of -ray energy. Two different voltage dividers were coupled to the Hamamatsu R10233-100SEL PMT: the Hamamatsu E1198-26, based on straightforward resistive network design, and the "LABRVD", specifically designed for our large volume LaBr 3 :Ce scintillation detectors, which also includes active semiconductor devices. Because of the extremely high light yield of LaBr 3 :Ce crystals we observed that, depending on the choice of PMT, voltage divider and applied voltage, some significant deviation from the ideally proportional response of the detector and some pulse shape deformation appear. In addition, crystal non-homogeneities and PMT gain drifts affect the (measured) energy resolution especially in case of high-energy  rays. We also measured the time resolution of detectors with different sizes (from 1"x1" up to 3.5"x8"), correlating the results with both the intrinsic properties of PMTs and GEANT simulations of the scintillation light collection process. The detector absolute full energy efficiency was measured and simulated up to -rays of 30 MeV

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Abstract-CeBr 3 crystals have been studied to assess their utility as potential gamma ray spectrometers for future ESA planetary missions. Pulse height spectra, scintillation time profiles, X-ray excited emission spectra, and photoluminescence spectra have been recorded as a function of temperature between 78 and 600 K. In addition, the influence of exposing CeBr 3 to various doses of gamma rays from a strong 60 Co source on its scintillation performance has been investigated.