<title>Measuring reflected x-ray absorption fine structure in gold-coated x-ray mirrors</title>

Abstract

We describe an experiment to quantify reflected X-ray Absorption Fine Structure (XAFS) in the mirrors to be used on the Joint European X-ray Telescope (JET-X). This instrument is due to be launched on the Russian Spectrum-X platform into deep orbit in December 1995. As part of the calibration program, samples of the Wolter type I, X-ray mirrors were taken to the Synchrotron Radiation Source at the Daresbury Laboratory and exposed to monochromatic X- rays across the energy range of the gold M<SUB>I</SUB> - M<SUB>V</SUB> edges (2 keV to 3.5 keV). We outline our research program and present preliminary results of both direct and reflected XAFS measurements at a variety of incident angles. We find that, while the position of the M<SUB>II</SUB> edge occurs within 3 eV of its tabulated value, the M<SUB>I</SUB>, M<SUB>III</SUB>, M<SUB>IV</SUB> and M<SUB>V</SUB> edges are shifted to higher energies by approximately 10 eV, 13 eV, 40 eV and 40 eV, respectively. We attribute these discrepancies to inaccuracies in the field equations used to generate atomic and nuclear data tables.