Comparison of LaBr_3:Ce and NAI(Tl) scintillators for radio-isotope identification devices

摘要

Lanthanum bromide (LaBr_3:Ce) scintillators offer significantly better resolution (< 3 percent at 662 keV) relative to sodium iodide (NaI(Tl)) but contain internal radioactivity that contributes to spectral counts. LaBr_3:Ce has recently become available commercially in sizes large enough for the hand-held radio-isotope identification device (RIID) market. To study its potential for RIIDs, a series of measurements were performed comparing a 1.5 x 1.5-in. LaBr_3:Ce detector with an Exploranium GR-135 RIID, which contains a 1.5 x 2.2-in. NaI(Tl) detector. Measurements were taken for short time frames and included examples of naturally occurring radioactive material (NORM), typically found in cargo, and special nuclear materials. To facilitate direct comparison, spectra from the different detectors were analyzed with the same isotope identification software (ORTEC ScintiVision™). In general, the LaBr_3:Ce detector was able to find more peaks and find them faster than the NaI(Tl) detector. To the same level of significance, the LaBr_3:Ce detector was usually two to three times faster. The notable exception was for ~(40)K-containing NORM where interfering internal activity due to ~(138)La in the LaBr_3:Ce detector exists and NaI(Tl) consistently outperformed LaBr_3:Ce.