Interferometric measurements with hard X-rays using a double slit

We report about interferometric measurements with X-rays of 1.24 Angstrom w avelength using a standard set-up of Young's double-slit interferometer. We could experimentally probe the spatial coherence of X-rays by measurement of the fringe visibility in the interference pattern. The interferometer wa s additionally used to determine the index of refraction of a thin silicon plate by measuring the fringe shift in the interference pattern. The set-up allowed to resolve path length differences of a tenth of the wavelength. ( C) 2001 Elsevier Science B.V. All rights reserved.