As part of its mission, the Transportation Security Laboratory (TSL) of the Department of Homeland Security (DHS) Science and Technology Directorate (S&T) develops methods for characterizing materials that are of interest to transportation security and first responders. For emerging technologies, new metrics that meaningfully differentiate materials must be identified and evaluated. Although X-ray diffraction (XRD) is an established technique for identifying solid crystalline materials, the ability to complement the current generation of X-ray-based threat detection using XRD is still being investigated. The TSL has constructed a high-energy X-ray diffraction system to measure a material’s scattering signature, which can vary based on the presence of organic and inorganic materials, solid crystals, and water or other liquids within a sample. Measurements have been performed on a wide range of household items as well as explosives and other threats. The scattering intensity as a function of momentum transfer was examined for each material to identify several potential metrics for distinguishing threats from inert substances.
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