Non-focusing diffractometer for X-ray studies on weakly absorbing amorphous materials

One of the main sources of error when studying weakly absorbing materials using an X-ray diffractometer with Bragg-Brentano focusing geometry is specimen transparency. Its undesired effects (peak displacement and loss of intensity in the medium angular range) can be avoided by using a slab-like specimen in symmetrical transmission, in which case the type of diffractometer is more or less immaterial except that a non-focusing diffractometer offers a series of advantages, e.g. a very simple lining-up procedure and the possibility of using rod-like specimens. Such a diffractometer with a flat monochromator in the primary beam is described and both the equatorial aberration and the axial aberration are discussed.