OBSERVATION AND EXPLANATION OF ONE-DIMENSIONAL X-RAY SPECKLE PATTERNSFROM SYNTHETIC MULTILAYERS

Using the new ''Troika'' x-ray undulator beamline at the European Sync hrotron Radiation Facility, we have succeeded in measuring coherent di ffraction (''speckle'') patterns from artificial multilayers. The patt erns are unusual in that they are unremarkable in the scan direction p erpendicular to the Bragg angle, showing a single peak of the width of the Fraunhofer maximum, but have dramatic structure in the direction of the Bragg angle. This is shown to be consistent with the extreme as ymmetry of the geometry that causes more than one well-ordered domain of the sample to fall within the coherently illuminated region. The pa tterns are sufficiently simple that we are able to model them reasonab ly well by fitting explicit phase parameters to a fixed number of illu minated ''blocks.'' Two fitting procedures are described that may have some general utility.