Reflectance of a wideband multilayer x-ray mirror at normal and grazing incidences.

The reflectance of a W-B(4)C multilayer mirror, with a period thickness that increased with depth into the multilayer, was measured at near-normal incidence with synchrotron radiation and at grazing incidence with Cu Kα radiation. The period thickness increased linearly from 17.9 Å at the top of the multilayer structure to 21.9 Å at the substrate while the same ratio of nodal layer to period thickness was maintained. For a grazing angle of 80° (10° from normal incidence), the peak reflectance was 1.1% at a wavelength of 36 Å, and the reflectance profile was 1 Å wide. For Cu Kα radiation the reflectance peaked at a grazing angle of 2.4° and was 0.4° wide. Compared with a W-B(4)C multilayer mirror with a constant period thickness, the depth-graded multilayer mirror has wider reflectance profiles at near-normal and grazing incidences, resulting in larger integrated reflectances and wider fields of view.