We describe an instrument for computerized xhyphen;ray tomography which can provide fully threehyphen;dimensional examination of small samples (a few millimeters to a few centimeters) with resolution variable from 5 to 100 mgr;m. Elemental and chemicalhyphen;state distributions are obtained with high resolution by modulating the energy of the incident xhyphen;ray beam. An essential component is the monochromator we designed and optimized for chemical microtomography. It has a narrow energy bandpass and a large degree of harmonic suppression, provides a uniform xhyphen;ray beam with small angle of divergence, and is cooled in a way that eliminates thermal and vibrational instabilities.
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