Upgraded Rubidium-Based Multilayer Mirrors for Operation in the Radiation Wavelength Range of 11.4–17 nm

The paper presents the theoretical modeling results of the reflectivity of multilayer mirrors based on rubidium and its compounds, designed to operate in the radiation wavelength range of 11.4–17 nm and of interest to modern lithography and X-ray astronomy. Using a genetic algorithm, the problem of optimizing the multilayer design of such mirrors to achieve maximum reflection is solved, and a comparison of the theoretical reflection coefficients obtained in this work with modern developments of multilayer X-ray mirrors in the characteristic radiation regions of 11.4, 13.5, and 17 nm is presented. Due to the high chemical activity of pure rubidium, it is proposed to use a more stable compound for the potential practical implementation of rubidium-containing mirrors. It is shown that the use of boron carbide between the main layers of the mirrors leads to a significant increase in their final reflection coefficient and can be considered a barrier method to prevent interdiffusion between materials; however, experimental verification of this hypothesis is required. The integral reflection of an optical system containing a few multilayer mirrors significantly depends on increasing the reflectivity of a single mirror, thus justifying the prospects of using the proposed mirrors in the optical system of a modern lithograph.