Gamma ray spectroscopy with a O19/spl times/19 mm/sup 3/ LaBr/sub 3/:0.5% Ce/sup 3+/ scintillator

Pulse height spectra of various sources covering X-ray and gamma ray energies from 10 keV to 6.1 MeV were measured by the first large O19/spl times/19 mm/sup 3/ LaBr/sub 3/:0.5% Ce/sup 3+/ scintillator. The spectra are compared with that recorded with a same sized NaI:Tl/sup +/ scintillator. Excellent energy resolution pulse height spectra are obtained showing that the scaling up from a small (/spl ap/3/spl times/3/spl times/10 mm/sup 3/) sized LaBr/sub 3/:Ce/sup 3+/ scintillator studied initially up to an /spl ap/6 cm/sup 3/ scintillator does not lead to much deterioration of resolution and light output. Special attention is devoted to the nonproportionality in the response of LaBr/sub 3/:Ce/sup 3+/ and related energy resolution. At high energy LaBr/sub 3/:Ce/sup 3+/ is far superior above NaI:Tl/sup +/ in terms of energy resolution and scintillation speed. At energies below 100 keV, NaI:Tl/sup +/ shows a better energy resolution.