An original interference effect observed in one-dimensional (1D) disordered conductors between X-ray
scattering due to the disorder and the charge density wave (CDW)- periodic lattice modulation (PLD) allows to
study the pinning of the modulation at local scale. We apply this effect to determine the phase of the CDW at the
pinning centres and to show that the response of the CDW to the impurity potential leads to the formation of Friedel
oscillations (FO). We report experimental determination and quantitative interpretation of the thermal evolution of
both features. The thermal dependence of the interference effect allows one to determine the pinning energy of the
2kF-CDW in the V-and W-doped blue bronzes. We show in particular that in these compounds the regular CDW is
pinned to the dopant dressed by its FO. In the organic charge transfer salts irradiation leads to an enhancement of
the 2kF and 4kF X-ray scattering that we show, by its thermal dependence, to be due to the formation of FO.
X-ray-scattering measurements of the transient structure of a driven charge-density wave
