Near-field speckle in coherent X-ray scattering

A coherent X-ray beam produces a speckle pattern when it impinges on a sample. Usually the size and shape of the speckle do not depend on the sample at all, but a group led by Professor M. Giglio (Universita degli Studi di Milano, Italy) recently found significant effects, observed when the detector is placed in the near field. Conventional far-field techniques, because of the van Cittert and Zernike theorem, have limitations in the statistical analysis of speckles, but it has now become possible to generate static and dynamic X-ray-scattering data. In addition, the present technique permits an increase of around four orders of magnitude in beam size and power. The measurements were done at BM05, European Synchrotron Radiation Facility (ESRF) in Grenoble, France. The peak energy was 12 keV and the beam size at the sample position was 1 mm × 1 mm. For more information, see the paper, "X-ray-scattering information obtained from near-field speckle", R. Cerbino et al., Nature Physics, advanced online publication, DOI: 10.1038/nphys837