Introduction to Computed Microtomography and Applications in Earth Science
Computed X-ray tomography is a technique that produces cross sections of an object from a series of projections at different angles. The technique has found widespread use in medical CAT scanners, which typically have resolutions of ~1 mm. Microtomography is the extension of this technique to smaller spatial resolution down to <1 μm. In the last 15 years the development of high-brightness synchrotron X-ray sources, high resolution CCD detectors, and high-performance computing have allowed the field of microtomography to progress rapidly. It is now being applied widely in Earth and soil science, where it is used to image the 3-D distribution of minerals, fluids, and pores. By exploiting X-ray absorption edges, 3-D images of the distribution of specific chemical elements can be produced. This is used to image the distribution of aqueous and organic fluids that have been doped with contrast agents such as iodine and cesium. The method is also being used to locate trace-mineral phases containing high-atomic-number elements such as zirconium and cerium. With fluorescence tomography 3-D images of trace element abundances and even oxidation states can be produced. This is being applied to understand the chemical contamination and remediation by plants in the environment. Diffraction tomography images the 3-D distribution of crystalline phases based on their powder diffraction peaks, and is very useful for imaging materials with similar X-ray absorption and composition but different crystalline structures.
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This volume presents the majority of topics in synchrotron science that are of use to the clay science community. The chapters presented in this volume serve not only as significant statements on the state of these applications, but also as useful primers to potential new users of synchrotron facilities.