  Dynamical diffraction effects always play a role when working with perfect
single crystals. The penetration of X-rays respect to the surface normal during
diffraction (extinction depth, $1/\sigma_e$) in perfect single crystals does
not have a constant value. The value changes for different angular positions on
the crystal diffraction condition. For higher X-ray energies this value can
change from few micrometers to tens of millimeters for each different crystal
angular position in the small angular range of the diffraction condition. This
effect may spread a single point in the object (sample) as a line in the image
detector, especially if the crystal is set (or if the sample angularly deviates
the beam) at lower diffraction angle positions, where the surface component of
X-ray penetration can achieve huge values. Then, for imaging experiments where
the dynamical diffraction occurs, such intrinsic property can affect the image
resolution. We have modeled and experimentally checked such a dynamical
diffraction property using, as example, an Analyzer-based X-ray phase contrast
imaging setup (ABI) at two different X-ray energies: 10.7 keV and 18 keV. The
results show that our theoretical model is consistent with the measured
results. For higher energies the blur effect is enhanced and intrinsically
limits the image spatial resolution.

Instrumentation and Detectors