  The use of coherent x-ray beams has been greatly developing for the past
decades. They are now used by a wide scientific community to study biological
materials, phase transitions in crystalline materials, soft matter, magnetism,
strained structures, or nano-objects. Different kinds of measurements can be
carried out: x-ray photon correlation spectroscopy allowing studying dynamics
in soft and hard matter, and coherent diffraction imaging enabling to
reconstruct the shape and strain of some objects by using methods such as
holography or ptychography. In this article, we show that coherent x-ray
diffraction (CXRD) brings a new insight in another scientific field: the
detection of single phase defects in bulk materials. Extended phase objects
such as dislocations embedded in the bulk are usually probed by electron
microscopy or X-ray topography. However, electron microscopy is restricted to
thin samples, and x-ray topography is resolution-limited. We show here that
CXRD brings much more accurate information about dislocation lines (DLs) in
bulk samples and opens a route for a better understanding of the fine structure
of the core of bulk dislocations.
