LiInP2Se6, a new semiconductor detector material for high resolution neutron imaging

High spatial resolution crystal diffractometers are important for Neutron single-crystal diffraction (SCD), which is a powerful tool to study the crystal structure and morphology of complicated organic and inorganic materials, and to address structural problems in diverse research areas including nano-structured materials, chemistry, earth sciences, materials science, engineering, and solid-state physics. Such studies are often limited by the capabilities of available detectors and would benefit from a more efficient high resolution neutron imaging detector technology. The goal of the proposed effort is to develop the semiconducting material, lithium indium phosphor selenide (LiInP2Se6), based neutron detection arrays. LiInP2Se6, has been recently discovered and exhibits an extremely high neutron detection efficiency, and great charge collection efficiency. The research is initially focusing on developing and optimizing the crystal growth processes needed to produce high quality crystals. Following that we will develop prototype detectors and detector modules for evaluation by scientists at ORNL. The research in Phase I focused on the materials science aspects of LiInP2Se6 and we investigated methods to synthesize and purify it and to grow high quality semiconductor crystals. Neutron detectors were fabricated and characterized. This research is being done in collaboration with Northwestern University, University of Tennessee, Knoxville, and Oak Ridge National Lab. In Phase II we will optimize the synthesis and growth of LiInP2Se6, scale up the size of the crystals, develop detectors with better than 300µm spatial resolution with a neutron detector efficiency of 60% and a gamma rejection ratio, GRR, of at least 10-6. We will construct a prototype neutron scatter detector module and demonstrate its capabilities at the ORNL neutron scattering research facilities. The prototype will be a module of 2×2 array of four LiInP2Se6 cross-strip detectors integrated with readout ASICs. In addition to neutron scattering, a system capable of high efficiency detection of neutrons with high spatial resolution and good GRR will find use in various other systems in research, homeland security, nuclear physics, medical imaging and material sciences.