Optimization and operation of a BBB X-ray interferometer

A special arrangement of Bonse-Hart X-ray interferometers, which uses the Bragg geometry of X-ray diffraction for the beam splitter, mirrors and the analyser (so-called BBB interferometers), has been designed and characterized both computationally and experimentally in different versions. The design includes wavelength-dependent optimization of transmission through the lamella, which is used both for beam splitting and for recombination. For characterization of the function of the instrument, interference patterns were evaluated from BBB interferograms, as well as from LLL (employing the Laue geometry for coherent beam splitting, reflecting and analysing) topograms and from interferograms resulting from a new combined geometrical layout. The influence of gravitation on the horizontally running diffraction planes was visible as a system of fringes in the interferograms, resulting from bending of the lamella under its own weight.