Instrument aberrations in a 4-circle powder diffractometer

Abstract

A theoretical basis for the effects of instrument aberrations on the position of the diffraction peak in a 4-circle powder diffractometer is given. Peak shifts due to non-intersecting rotation axes, displacement of the incident beam and displacement of the specimen height are all described on the basis of pure analytical functions. These functions may be useful as software corrections on the measured peak positions in residual stress analysis. The theoretical derivation includes an analytical description of the position of the measurement spot in specimen coordinates. This may be useful for improving the instrument performance in micro-diffraction analysis.