Fast-neutron elastic-scatter imaging for material characterization

Abstract

Fast-neutron associated-particle imaging (API) using neutrons created via the deuterium-tritium (DT) fusion reaction is a powerful technique for imaging the internal geometry of target items, even if they contain large amounts of shielding. Although traditional neutron transmission radiography and tomography performed using API techniques provide detailed information about geometry, they provide little or no information about the materials in the items under inspection. Fortunately, material-specific information is available using neutrons that elastically scatter in the target and are subsequently detected. Because the API technique provides knowledge of the time and initial direction of 14 MeV neutrons produced in the DT reaction, the angular deviation and time of flight of detected neutrons are used to identify these elastically scattered neutrons. The most distinctive elastic-scatter signal exists for materials with low mass numbers (4), so initial development has focused on producing low-4 images. This paper describes the elastic-scatter imaging approach, describes the imaging system, describes analysis and image reconstruction approaches with a focus on elastic scatters from A = 1 nuclei, and presents the first elastic-scatter images from laboratory measurements.