Lithium indium diselenide: A new scintillator for neutron imaging

Lithium indium diselenide, (6)LilnSe(2) or LISe, is a newly developed neutron detection material that shows both semiconducting and scintillating properties. This paper reports on the performance of scintillating LISe crystals for its potential use as a converter screen for cold neutron imaging. The spatial resolution of LISe, determined using a 10% threshold of the Modulation Transfer Function (MTF), was found to not scale linearly with thickness. Crystals having a thickness of 450 mu m or larger resulted in an average spatial resolution of 67 mu m, and the thinner crystals exhibited an increase in spatial resolution down to the Nyquist frequency of the CCD. The highest measured spatial resolution of 198 mu m thick LISe (27 gm) outperforms a commercial 50 mu m thick ZnS(Cu):(LiF)-Li-6 scintillation screen by more than a factor of three. For the LISe dimensions considered in this study, it was found that the light yield of LISe did not scale with its thickness. However, absorption measurements indicate that the Li-6 concentration is uniform and the neutron absorption efficiency of LISe as a function of thickness follows general nuclear theory. This suggests that the differences in apparent brightness observed for the LISe samples investigated may be due to a combination of secondary charged particle escape, scintillation light transport in the bulk and across the LISe-air interface, and variations in the activation of the scintillation mechanism. Finally, it was found that the presence of In-115 and its long-lived In-116 activation product did not result in ghosting (memory of past neutron exposure), demonstrating potential of LISe for imaging transient systems. (C) 2016 Elsevier B.V. All rights reserved.