Abstract: Semiconductor crystals for use, for example, in the manufacture of integrated circuits are required to be inspected for crystal lattice perfection before any subsequent circuit processing. This can be done by X-ray diffraction in which the crystal is curved so that a divergent beam irradiates all points of the crystal surface at the same angle and simultaneously. The difficulty is however, in holding the crystal in the appropriately curved form while at the same time not obstructing the passage of X-rays from the front or back of the crystal and so enable topographs to be obtained by both reflection and transmission. According to the invention, in such a system the crystal is attached to a flat, X-ray transparent plate by pneumatic X-ray transparent means, and the plate is deformed to the required curvature, carrying the crystal with it.