Spectral Measurements with Aligned and Misaligned Two-Crystal Spectrometers. II. Alignment

Abstract

Conditions for and methods of aligning a two-crystal spectrometer are discussed. These include the alignment of rotation axes, crystals, and x-ray beam. The results of a new nondispersive crystal alignment procedure are compared in detail with theory for a typical case of CuKα radiation and calcite crystals. This method is contrasted with other procedures which lead only to pseudo-alignments. It is shown that x-ray methods which are sensitive to vertical divergence do not lead to crystal alignment unless the beam is already perfectly aligned. It is concluded that the x-ray beam can be aligned only after the crystals have been aligned.