Abstract
We combine diffraction and absorption tomography by raster scanning samples through a hollow cone of pseudo monochromatic X-rays with a mean energy of 58.4 keV. A single image intensifier takes 90x90 (x,y) snapshots during the scan. We demonstrate a proof-of-principle of our technique using a heterogeneous three-dimensional (x,y,z) phantom (90x90x170 mm3) comprised of different material phases, i.e., copper and sodium chlorate. Each snapshot enables the simultaneous measurement of absorption contrast and diffracted flux. The axial resolution was ~1 mm along the (x,y) orthogonal scan directions and ~7 mm along the z-axis. The tomosynthesis of diffracted flux measurements enable the calculation of d-spacing values with ~0.1 Å full width at half maximum (FWHM) at ~2 Å. Thus the identified materials may be color-coded in the absorption optical sections. Characterization of specific material phases is of particular interest in security screening for the identification of narcotics and a wide range of homemade explosives concealed within complex "everyday objects." Other potential application areas include process control and biological imaging.
Highlights
Radiographic imaging and the structural analysis of materials using X-rays developed disparately soon after the discovery of X-rays in 1895 [1]
We report for the first time the combined application of tomosynthesis to absorption image contrast and X-ray diffraction (XRD) signals collected simultaneously via a single scanning hollow beam probe and planar detector
As predicted by our theory, where the same radial shift values are applied to both XRD and absorption the result is in-focus planes with one-to-one spatial (x,y,z) correspondence. This result is a function of the primary beam geometry i.e. encoding of position is nominally independent of the diffraction angle
Summary
Radiographic imaging and the structural analysis of materials using X-rays developed disparately soon after the discovery of X-rays in 1895 [1]. The spectroscopic analysis of the transmitted X-rays may provide some useful materials discrimination information [6]. Such approaches are limited fundamentally and cannot provide structural or ‘molecular resolution’ analysis. The common problem confronting all volumetric XRD scanning/imaging methods is the production and measurement of sufficient diffracted flux or signal photons to provide the desired scan speed at application dependent energies. These considerations are a significant hurdle in the ongoing development of practical high-energy XRD scanning technology. The many fields that would benefit from combining spatial imaging with structural characterization include material science, security screening and medicine
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