High-gradient aspherization of substrates with thin-film Al/Si coatings

The paper discusses the issues of film aspherization. A multilayer Al/Si structure has been proposed as an aspherizing coating. It was applied to a spherical surface. By selecting the ratio of materials in the period, a state was searched in which stresses in the multilayer structure were minimized. At the same time, the period of the structure of 9–10 nm corresponds to the mirrors of normal incidence for the wavelength range of 17–19 nm, which are of interest to solar astronomy. Using precision shaped diaphragms, an aspherical coating profile with a maximum height difference of $\sim$1.3 $\mu$m microns was formed between the magnetron and the substrate.