  In anticipation of the increased use of coherent x-ray methods and the need
to upgrade beamlines to match improved source quality, we have characterized
the coherence properties of the x-rays delivered by beamline 12ID-D at the
Advanced Photon Source. We compare the measured x-ray divergence, beam size,
brightness, and coherent flux at energies up to 26 keV to the calculated values
from the undulator source, and evaluate the effects of beamline optics such as
a mirror, monochromator, and compound refractive lenses. Diffraction patterns
from slits as a function of slit width are analyzed using wave propagation
theory to obtain the beam divergence and thus coherence length. Imaging of the
source using a compound refractive lens was found to be the most accurate
method for determining the vertical divergence. While the brightness and
coherent flux obtained without a monochromator ("pink beam") agree well with
those calculated for the source, those measured with the monochromator were a
factor of 3 to 6 lower than the source, primarily because of vertical
divergence introduced by the monochromator. The methods we describe should be
widely applicable for measuring the x-ray coherence properties of synchrotron
beamlines.

Accelerator Physics