Design of soft x-ray laminar-type gratings coated with supermirror-type multilayer to enhance diffraction efficiency in a region of 2–4 keV.

This article focuses on the design and numerical evaluation of laminar-type soft x-ray diffraction gratings coated with supermirror-type multilayers to enhance diffraction efficiency in the 2–4 keV energy range. The optimized grating features a groove density of 3200 grooves/mm, a groove depth of 2.05 nm, and an incidence angle of 88.65°, with a multilayer structure composed of 11 pairs of B4C (boron carbide) and W (tungsten) layers, where the B4C thickness increases from bottom to top while the W thickness remains constant. Replacing the top tungsten layer with cobalt, chromium, or nickel yields smoother and higher diffraction efficiency curves, achieving an average efficiency of approximately 5.3%, nearly eight times greater than that of conventional gold-coated gratings. The design suppresses zeroth-order diffraction and enhances first-order diffraction, showing potential for practical application in soft x-ray spectrometers used in advanced materials research and emerging x-ray sources.