Higher resolution alkali halide scintillators

High-resolution gamma-ray sensors are essential for non-proliferation monitoring of special nuclear materials. Today, commercially available detection systems are mostly based on either LaBr3:Ce or NaI:Tl scintillation crystals, which are at the opposite ends when it comes to the performance and price. The former has excellent energy resolution (~3%at 662 keV) but is high cost. The latter has poor energy resolution (~6-7%) but costs much less. Therefore, new high-resolution, affordable materials are urgently required. How the Problem is Addressed: From our recent studies, we have established that CsI(Tl) can achieve much better energy resolution benchmarks than typically assumed for this material to date. The growth techniques and co-doping with multivalent ions improved its non-proportionality and energy resolution to better than 5% at 662 keV. Therefore, optimized CsI has emerged as a very promising option for non-proliferation applications, due to its low intrinsic radiation background, good energy resolution, and low cost (comparable to NaI). The goal of this project is to scale-up our optimized CsI to larger sizes (up to 4 inch) and further improve its energy resolution (to 4% or better). Plans for Phase I: In Phase-I, we will work on the scale-up of our current optimized composition to develop a viable growth process for 2 inch diameter crystals. We will also work on additional material optimization to further improve the energy resolution beyond current limits (<5%FWHM at 662 keV with the goal of <4%). Commercial and Scientific Potential: Our improved CsI composition will find use in nuclear non-proliferation monitoring, homeland security, well-logging, non-destructive evaluation, particle physics and medical imaging. It may replace currently used NaI(Tl) scintillators.