Synchrotron powder diffraction measurements were obtained from a Co/Cu multilayer produced by low energy ion-assisted deposition. The experiment was carried out on the high resolution diffractometer on Station 2.3 at the SRS, Daresbury Laboratory. Exploiting the parallel beam optics, high photon flux and wavelength tunability of the instrument, the anomalous reflectivity method was used to examine the multilayer structure. With its inherent instrumental advantages, shifts in powder peak position have been measured using the sin 2 ψ diffraction technique, and the average in-plane stress present in the sample has been determined.