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Employing asymmetric Bragg reflection at the monochromator we obtain a wide and practically parallel synchrotron‐radiation beam which, when combined with the use of a CCD detector, enables us to perform chemically specific, high‐speed and high‐resolution tomography. We present recent results obtained with this new method. The actual resolution achieved was determined from the measured line‐spread function of the complete detection system which includes the CCD, the fluorescent screen, and the lens used for optical magnification. The modulation‐transfer function (MTF) calculated from the line‐spread function shows that with only twofold magnification and at 3% contrast detectability about 28 line pairs per mm are resolved. Extrapolating from this result we find that with an optical magnification of 7:1 about 100 line pairs per mm should be resolved. Ways to optimize the method further are discussed.

This article describes a high‐resolution three‐dimensional CT system which has been tested on the new wiggler beamline X‐2 at the Stanford Synchrotron Radiation Laboratory. The present system is a rotate‐only design which uses a virtual phase CCD array camera optically coupled to a high‐resolution phosphor screen. The spatial resolution of this system is presently somewhat better than 10 μm (50 line pairs/mm at 20% contrast). This resolution is limited by the optical elements in the detector, and we are undertaking an effort to improve this resolution to 1 μm. Nevertheless, the spatial resolution offered by this design is sufficient to begin many studies of interest to materials research, such as, supported catalysts, composite materials, and crack growth and propagation.

Synchrotron microtomography is a new technique which is capable of elemental, chemical, and structure sensitive imaging in three dimensions at resolutions better than 15 μm. This paper describes the first application of this new technique to the investigation of the morphology and elemental distribution of a supported catalyst. Using this new tool it was possible to obtain three‐dimensional information from regions of the catalyst away from the vicinity of the damaged surface region of the sample. The technique allows the use of both computed tomographic (CT) cross sections as well as the development of a three‐dimensional rendering of elements in a material, each of which allows visualization of different areas that would go unnoticed in normal radiographic or CT investigations.

We describe an instrument for computerized x‐ray tomography which can provide fully three‐dimensional examination of small samples (a few millimeters to a few centimeters) with resolution variable from 5 to 100 μm. Elemental and chemical‐state distributions are obtained with high resolution by modulating the energy of the incident x‐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 x‐ray beam with small angle of divergence, and is cooled in a way that eliminates thermal and vibrational instabilities.