Investigations of Hot-Pressed 6LiInSe2 as a Ceramic Scintillator
The shortage of 3He has driven a worldwide search for solid-state neutron detection devices. The detector materials for these devices respond to incident radiation by either producing photons through scintillation mechanisms or an electrical current in a semiconductor mode. Lithium-based chalcogenides such as 6LiInSe2 have been researched extensively because of their ability to operate in both scintillator and semiconductor modes. These materials have many uses in the nuclear-science field, including nuclear-material detection for national security, space applications and medical imaging. This dissertation is motivated by national security issues, such as nuclear nonproliferation. In particular, it presents a comparative study between polycrystalline and monocrystalline 6LiInSe2 radiation detectors with the aim of understanding the photon interactions within the polycrystalline 6LiInSe2. High-resolution, single-crystal scintillators provide adequate light yield and decay times to prove useful for neutron detection in real world applications, but in some situations growth and fabrication costs are of concern. In the case of 6LiInSe2, for example, it can take upwards of 40 days to synthesize a charge of the crystal components, grow a crystal and fabricate a detector. Polycrystalline radiation detectors are a solution for this long route of preparation while also removing the size restrictions that monocrystalline detectors face. This dissertation describes how using a polycrystalline 6LiInSe2 instead of a single crystal significantly decreases the time required to make a detector. In the present work, polycrystalline wafers can be formed using a mechanical press equipped with a heating attachment. After annealing, the resulting polycrystalline wafer has a significant increase in radiation detection efficiency while performing similarly to a slow-growth single crystal 6LiInSe2 when used in the scintillator mode.