Multicapillary optics for materials science studies

XRD patterns from a standard polycrystalline gold film, collected by a parallel beam goniometer equipped with a conventional cross-slits collimator were compared with those obtained by replacing the incident beam optics with a multicapillary collimator. Considerable improvements can be achieved by using the new optics: (a) a much higher fraction of the X-ray beam produced by a conventional sealed tube can be used to build the diffracted signal, provided that a sufficiently wide sample area is available for measurement (diameter> 1 mm); (b) the limited beam divergence (=0.3°) gives a good stability and precision, in terms of negligible systematic errors in peak position due to sample psi- and omega-tilting; (c) instrumnental profiles are much narrower than those obtained by the conventional cross-slits collimator; (d) width and shape of the instrumental profile are ahnost unaffected by sample tilting. The considerable interest in this device is increased by considering that features (b), (c) and (d) were verified also for relatively low 26 angles (30-40°): this is of great importance for thin film studies, where most of the available information comes from low diffraction order profiles; in addition, the increased signal intensity greatly helps to reduce measurement time (or to improve statistics). Advantages and drawbacks of the new optics are described in this paper, together with some practical examples of use.