The design of the multilayer coatings and multilayer grating for the EIS spectrometer is presented. The grating substrate has a rectangular laminar groove profile with 4200 grooves/mm and a 58 angstrom groove depth. The grating and mirror have two multilayer coatings, each covering half of the areas of the grating and mirror, and with high reflectance in the two wavelength regions 170 - 210 angstrom and 250 - 290 angstrom. The reflectance of the multilayer coating and the efficiency of the multilayer grating were calculated using computer codes that were validated by comparison to reflectance and efficiency measurements performed using synchrotron radiation. The sensitivities of the calculated reflectance and grating efficiency to surface microroughness, layer interdiffusion, layer nonuniformity, illumination angle, grating groove variations, hydrocarbon contamination, and oxide buildup were analyzed.
John F. Seely, John F. Seely,
"Multilayer grating for the Extreme Ultraviolet Spectrometer (EIS)", Proc. SPIE 4138, X-Ray Optics, Instruments, and Missions IV, (28 November 2000); doi: 10.1117/12.407557; https://doi.org/10.1117/12.407557