Improved Energy Resolution in CsI Scintillator Material

The number of scintillators that allow the use of pulse shape discrimination (PSD) to distinguish between gamma-rays and charged particles is quite limited, and none of them offer good spectroscopic ability. CsI(Tl), which has good stopping power and can be grown in large boules, typically achieves a ¿E/E of 8% at 662 keV. Recent high resolution materials, such as LaBr3(Ce) and SrI2(Ce), have attained a better ¿E/E (<3%) at 662 keV, but they do not support PSD. Previous research on CsI(Tl) suggests that this material has not yet reached its intrinsic energy resolution; in fact, through careful growth techniques, the ¿E/E at 662 keV already has been reduced to 5.2%. This project will seek further progress by taking advantage of the fact that the non-proportionality curves (which generally correlate with attained energy resolution) for CsI(Tl) differ significantly from one sample to another. Phase I will investigate the sources of these variations as an approach to engineering non-proportionality, in order to achieve resolution well below 3%.Commercial Applications and other Benefits as described by the awardee The commercial applications for this technology should be diverse in the $1B/yr market for instruments based on scintillation detectors. Examples include nuclear particle detectors (which require improved measurement precision), medical gamma cameras (enhanced spatial resolution), and hand-held survey instruments for Homeland Security (increased sensitivity to special nuclear materials).