Design of Valid Line Spacing Holographic Grating with High Groove Density and Multilayered Laminar-Type Grooves for Flat Field Spectrometer Optimized for 200‒900 eV Region

Iron is one of the most important transition elements and abundant in the sun and other celestial bodies e.g., iron occupies about 5% of the earth\u27s crust. Therefore, iron is an important indicator element to investigate the constitution and origin of celestial bodies by spectroscopic studies. We have performed feasibility study to enhancement diffraction efficiency and resolving power of diffraction grating optimized for Fe-L (705 eV) emission spectrum, simultaneously. The optimized structural parameters of laminar-type grating are a nominal groove density of 3,200 lines/mm, groove depth of 5.0 nm, and duty ratio of 0.46. As the results of numerical calculations of the multilayer grating coated with of a few pairs of C/W layers on Au layer provides the maximum diffracting efficiency of over 10 % at 705 eV and a practical diffraction efficiency of 2% or more in a wide energy range of ca. 200 eV to 900 eV. Furthermore, resolution power of the designed aberration-corrected flat field varied-line-spacing holographic diffraction grating evaluated by means of ray tracing showed a resolving power of ca. 800.The 15th Symposium on X-ray Imaging Optic