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In anticipation of the increased use of coherent x-ray methods and the needto upgrade beamlines to match improved source quality, we have characterizedthe coherence properties of the x-rays delivered by beamline 12ID-D at theAdvanced Photon Source. We compare the measured x-ray divergence, beam size,brightness, and coherent flux at energies up to 26 keV to the calculated valuesfrom the undulator source, and evaluate the effects of beamline optics such asa mirror, monochromator, and compound refractive lenses. Diffraction patternsfrom slits as a function of slit width are analyzed using wave propagationtheory to obtain the beam divergence and thus coherence length. Imaging of thesource using a compound refractive lens was found to be the most accuratemethod for determining the vertical divergence. While the brightness andcoherent flux obtained without a monochromator ("pink beam") agree well withthose calculated for the source, those measured with the monochromator were afactor of 3 to 6 lower than the source, primarily because of verticaldivergence introduced by the monochromator. The methods we describe should bewidely applicable for measuring the x-ray coherence properties of synchrotronbeamlines.

Characterization of the X-ray Coherence Properties of an Undulator Beamline at the Advanced Photon Source