Comparison of LaBr/sub 3/:Ce and NaI(Tl) scintillators for radio-isotope identification devices

LaBr₃:Ce scintillators offer significantly better resolution (<3% at 662 keV) relative to NaI(Tl) and have recently become commercially available in sizes large enough for the handheld, radio-isotope identification device (RIID) market. Drawbacks to lanthanum halide detectors, however, include internal radioactivity contributing to spectral counts, and a low-energy response which can cause detector resolution to be worse than that of NaI(Tl) below 100 keV. To study the potential of this new material for RIIDs we performed a series of measurements comparing a 1.5"times1.5" LaBr₃:Ce detector with an Exploranium GR-135 RIID, which contains a 1.5"times2.2" NaI(Tl) detector. Measurements were taken for short timeframes, as typifies RIID usage. Measurements included examples of naturally occurring radioactive material (NORM), typically found in cargo, and special nuclear materials. Some measurements were non-contact, involving short distances or cargo shielding scenarios. To facilitate direct comparison, spectra from the different detectors were analyzed with the same isotope-identification software (ORTEC ScintiVision)