Europium-doped strontium and barium iodide are found to be readily growable by the Bridgman method and to produce high scintillation light yields. Sr12(Eu) emits into the Eu2+ band, centered at 435 nm, with a decay time of 1.2 ps and a light yield of -90 000 photons/MeV. It offers energy resolution better than 4% full width at half maximum at 662 keV, and exhibits excellent light yield proportionality. BaIz(Eu) produces >30 000 photons/MeV into the Eu2+ band at 420 nm (< 1 ps decay). An additional broad impurity-mediated recombination band is present at 550 nm (>3 ps decay), unless high-purity feedstock is used.

is the most promising. SrI 2 (Eu) emits into the Eu 2+ band, centered at 435 nm, with a decay time of 1.2 µs and a light yield of up to 115,000 photons/MeV. It offers energy resolution better than 3% FWHM at 662 keV, and exhibits excellent light yield proportionality. Transparent ceramics fabrication allows production of Gadolinium-and Terbium-based garnets which are not growable by melt techniques due to phase instabilities. While scintillation light yields of Cerium-doped ceramic garnets are high, light yield non-proportionality and slow decay components appear to limit their prospects for high energy resolution.We are developing an understanding of the mechanisms underlying energy dependent scintillation light yield non-proportionality and how it affects energy resolution. We have also identified aspects of optical design that can be optimized to enhance energy resolution.

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Transmission nuclear resonance fluorescence measurements were made on targets consisting of Pb and depleted U with total areal densities near 86 g/cm 2 . The 238 U content in the targets varied from 0 to 8.5% (atom fraction). The experiment demonstrates the capability of using transmission measurements as a non-destructive technique to identify and quantify the presence of an isotope in samples with thicknesses comparable to the average thickness of a nuclear fuel assembly. The experimental data also appear to demonstrate the process of notch refilling with a predictable intensity. Comparison of measured spectra to previous backscatter 238 U measurements indicates general agreement in observed excited states. Evidence of two new 238 U excited states and possibly a third state have also been observed.