The effect of surface residual stress on the performance of high quality x-ray mirrors
The use of high quality X-ray mirrors at synchrotron beamlines as low-energy bandpass, harmonic rejection and high
heat load optical elements has become routine. Nearly perfect optical surfaces generated on substrates and held in strain-free
fixtures are of paramount importance to their success. Production of these mirrors requires extensive care, yet the
effect of residual fabrication stress has not been closely studied. This paper examines the effect of surface and near-surface
residual stress on the performance of hard X-ray mirrors using topography and X-ray reflectivity techniques. The
present approach complements the information provided by standard optical metrology, giving a more comprehensive
understanding of polishing induced surface deformation on X-ray reflectivity. This information is invaluable for the
characterization of future, coherence preserving optics where scattering and evanescent sub-surface X-ray penetration
may impact beam quality.