Skylab 3600 groove/mm replica grating with a scandium-silicon multilayer coating and high normal-incidence efficiency at 38-nm wavelength

A Sc-Si multilayer coating was applied to a replica of the 3600 groove/mm grating, developed for the SO82A spectroheliograph that flew on the Skylab mission, for the purpose of enhancing the normal-incidence efficiency in the extreme-ultraviolet region. The efficiency, measured at an angle of incidence of 6degrees with synchrotron radiation, had a maximum value of 7.2% at a wavelength of 38 nm and was a factor of 3 higher than the efficiency of the gold-coated Skylab grating. The measured efficiency of the Sc-Si grating was in good agreement with the efficiency calculated by use of the modified integral method.