High-efficiency MoRu-Be multilayer-coated gratings operating near normal incidence in the 11.1-12.0-nm wavelength range

MoRu-Be multilayer coatings were applied to two diffraction gratings for th e purpose of enhancing their normal-incidence efficiency in the 11.1-12.0-n m wavelength range. The grating substrates were replicas of a holographic m aster grating that had a blazed groove profile with 2400 grooves/mm and a 2 -m radius of curvature. The relatively low average microroughness (0.8 nm) of the grating surfaces contributed to the relatively high groove efficienc y of the grating substrates and the reflectance of the MoRu-Be multilayer c oatings. The peak efficiency, measured with synchrotron radiation, was 10.4 % in the second diffraction order at a wavelength of 11.37 nm.