title: Characterization of windows and filters for coherent X-ray beamlines.
abstract: Beryllium windows and graphite heat absorbers used in coherent X-ray beamlines must be optically flat. If the optical path through the window varies by more than lambda/4, the X-ray wave front will be distorted after passing through the window, and the divergence of the X-ray beam may be increased. This reduces the beam coherence. Beryllium, graphite and Kapton films have been tested using ultra-small-angle X-ray scattering. Wave-front distortion was also directly observed by means of phase-contrast X-ray microradiography. The measured increase of angular divergence is about 4 micro rad. The wave-front distortion is larger than 2pi (optical path difference of lambda). These are serious problems for utilizing coherent X-ray beams.
authors.affiliation: Advanced Research Laboratory, Hitachi Ltd, Hatoyama, Saitama 350-03, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Suzuki
authors.forename: A
authors.initials: A
authors.lastname: Momose
authors.forename: H
authors.initials: H
authors.lastname: Sugiyama