Traditionally, depth resolution in diffraction experiments is obtained by inserting pinholes in both the incoming and diffracted beam. For materials science investigations of local strain and texture properties this leads to very slow data-acquisition rates, especially when characterization is performed on the level of the individual grains. To circumvent this problem a conical slit has been manufactured by wire-electrodischarge machining. The conical slit has six 25 microm-thick conically shaped openings matching six of the Debye-Scherrer cones from a face-centred-cubic powder. By combining the slit with a microfocused incoming beam of hard X-rays, an embedded gauge volume is defined. Using a two-dimensional detector, fast and complete information can be obtained regarding the texture and strain properties of the material within this particular gauge volume. The average machining and assemblage errors of the conical slit are found both to be of the order of 5 microm. An algorithm for alignment of the slit is established, and the potential of the technique is illustrated with an example of grain mapping in a 4.5 mm-thick Cu sample.

Section topographs recorded at different spatial locations and at different rocking angles of a highly oriented pyrolytic graphite (HOPG) crystal allow three-dimensional maps of the local angular-dependent scattering power to be obtained. This is performed with a direct reconstruction from the intensity distribution on such topographs. The maps allow the extraction of information on local structural parameters such as size, form and internal mosaic spread of crystalline domains. This data analysis leads to a new method for the characterization of mosaic crystals. Perspectives and limits of applicability of this method are discussed

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Highly oriented pyrolytic graphite is a very efficient and well-known X-ray and neutron monochromator that is obtained by thermal cracking of a hydrocarbon gas and a subsequent graphitization treatment. Its microstructure is still, however, a matter of controversy. Several samples of different quality were extensively studied by X-ray diffraction topography. The contrast obtained on OOL reflections is mainly explained in terms of 'primary extinction' and orientation contrast. This implies that the interlayer spacing of the graphite lattice planes remains constant over distances of several tens of micrometres. Graphitization mechanisms are discussed in the light of this interpretation. A microstructural model, closely related to that of as-deposited pyrolytic carbon, is proposed.

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