Sagittal X-ray beam deviation at asymmetric inclined diffractors

A new approach to focusing X-ray optics based on asymmetric inclined (or rotated inclined) diffraction has been experimentally studied. Using a linear longitudinal W-groove cut into the surface of an asymmetric silicon (111) diffractor perpendicularly to the line of intersection of its surface and crystallographic (111) planes, the out-of-diffraction-plane (or sagittal) deviation of the X-ray diffracted beam has been measured for three angles of asymmetry and constant angle of inclination on BM5 at the ESRF for a wavelength of 0.1 nm. It has been demonstrated that in the grazing-emergence case the sagittal deviation increases with increasing asymmetry angle. A discrepancy with the theoretical value for the largest asymmetry angle and inhomogeneities in the contrast of the diffraction spot have been discussed.