A conical slit for three-dimensional XRD mapping

Traditionally, depth resolution in diffraction experiments is obtained by i nserting pinholes in both the incoming and diffracted beam. For materials s cience investigations of local strain and texture properties this leads to very slow data-acquisition rates, especially when characterization is perfo rmed on the level of the individual grains. To circumvent this problem a co nical slit has been manufactured by wire-electrodischarge machining. The co nical slit has six 25 mu m-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 v olume is defined. Using a two-dimensional detector, fast and complete infor mation can be obtained regarding the texture and strain properties of the m aterial within this particular gauge volume. The average machining and asse mblage errors of the conical slit are found both to be of the order of 5 mu m. An algorithm for alignment of the slit is established, and the potentia l of the technique is illustrated with an example of grain mapping in a 4.5 mm-thick Cu sample.