Bragg diffraction in a coherent X-ray scattering experiment

The requirements of a small X-ray source size and large distance from the s ource which limit the coherence length in coherent X-ray scattering experim ents can be avoided by Bragg diffraction on perfect crystals. The coherence in setups which include crystal diffraction is investigated. The coherence length, limited by the extinction length of the Bragg diffraction, can be comparable or larger than the one typically obtained by wave propagation in free space. The increase of the coherence length is demonstrated in a labo ratory experiment on a periodic surface grating with variable period. (C) 2 000 Elsevier Science B.V. All rights reserved.