Normal-incidence efficiencies of multilayer-coated laminar gratings for the extreme-ultraviolet imaging spectrometer on the solar-B mission.

The normal-incidence efficiencies of two laminar gratings and the reflectances of two parabolic mirrors with matching multilayer coatings were measured by monochromatic synchrotron radiation and were compared with modeling calculations. These optics were developed for the Extreme-Ultraviolet Imaging Spectrometer to be launched on the Japanese Solar-B mission. Each optic has two sectors coated with Mo/Si multilayers that reflect the 17-21-nm and 25-29-nm wave bands at normal incidence. The measured peak grating efficiencies are in the 8%-12% range and are in good agreement with efficiency calculations that account for the effects of groove profile and the microroughness as determined by atomic force microscopy.