Efficiency measurements at Mo/Si multilayer gratings and comparison with the model of radiating dipoles

Diffraction efficiencies of three different laminar multilayer gratings (333 lines/mm) were measured in the soft X-ray region with photon energies between 30 and 350 eV. The measurements are compared with calculations using a model based on a reasonable assumption for the electric field in the modulated area of the grating and applying the Ewald-Oseen theorem. The gratings differ in the line-width to groove-width ratio. The grating profiles have been characterized accurately by atomic force microscopy measurements. Moving sample and detector according to the grating equation provides continuous efficiency mapping for the different diffraction orders. These results display structures from which all the important parameters of the gratings can be deduced.