  Using high-resolution X-ray scattering techniques, we measure the variation,
q(x), of the position in reciprocal space of the CDW satellite, in the sliding
state, along the length of NbSe_3 whiskers. We show that structural defects and
intentionally X-ray radiation-damaged regions increase locally the CDW pinning
force, and induce CDW phase distortions which are consistent with those
observed near contacts. Using the semi-microscopic model from Brazovskii
describing the normal-condensed carrier conversion, with spatially varying
parameters, we account for the experimental spatial dependence of the CDW phase
gradient near both types of defects.
