Fast optimization of a bimorph mirror using x-ray grating interferometry.

An x-ray grating interferometer was employed for in situ optimization of an x-ray bimorph mirror. Unlike many other at-wavelength techniques, only a single interferogram image, captured out of the focal plane, is required, enabling the optical surface to be quickly optimized. Moiré fringe analysis was used to calculate the wavefront slope error, which is proportional to the mirror's slope error. Using feedback from grating interferometry, the slope error of a bimorph mirror was reduced to <200  nrad (rms) in only two iterations. This technique has the potential to create photon beams with spatially homogeneous intensities for use in synchrotron and free electron laser beam lines.