Journal of Applied Crystallography

Volume 35, Part 5 (October 2002)

research papers

J. Appl. Cryst. (2002). 35, 565-570 [ doi:10.1107/S0021889802009780 ]

Simple optics to decrease beam divergence and improve energy resolution for laboratory X-ray sources

M. Kunz, P. Pattison and H. Reifler

Abstract: A combination of very simple and well known optical elements is presented, which allows characteristics such as monochromaticity and angular divergence of a sealed-tube Mo X-ray beam to be improved, while maintaining adequate intensity for high-pressure measurements of unit-cell volumes. This improvement is aimed at optimizing measurements of lattice compressibility by means of single-crystal diffraction, as commonly carried out in mineral physics. The experimental arrangement consists of an asymmetrically cut Ge(111) monochromator, a pair of Cr-coated mirrors and a simple blade to cut off the K [alpha] ₂ contribution. Tests with a ruby standard crystal show a decrease in the widths of the diffraction peaks by a factor of three and an improvement in the accuracy of the unit-cell volume determination by at least a factor of three, while maintaining sufficient intensity in the diffracted beam.

Keywords: X-ray optics; single-crystal diffractometry; compressibility; mineral physics.