The deposition of a 30-Å-thick layer of iridium upon a 250-Å-thick osmium reflective layer for use as a diffraction grating in the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) satellite observatory has provided sufficient protection from an expected maximum orbital atomic-oxygen fluence of 1 × 10<sup>16</sup> atoms/cm<sup>2</sup>. The grating parameters of groove constant and depth, efficiencies of zeroth-order, first and second inside orders, and first inside-order efficiency positional uniformity as well as stray light near the first inside order of the Ir-Os-coated grating were measured within a CHIPS spectral bandpass of 90–260 Å. Stray-light measurements were also made near the first inside spectral order at 304, 584, and 1216 Å. The results make the Ir-Os coat an acceptable grating reflectivity layer for CHIPS and other spaceborne extreme-ultraviolet spectrometers that employ grazing-incidence reflection optics.
© 2003 Optical Society of America
(050.2770) Diffraction and gratings : Gratings
(290.5820) Scattering : Scattering measurements
(310.1620) Thin films : Interference coatings
(310.6860) Thin films : Thin films, optical properties
Richelieu Hemphill, Mark Hurwitz, and Maria G. Pelizzo, "Osmium atomic-oxygen protection by an iridium overcoat for increased extreme-ultraviolet grating efficiency," Appl. Opt. 42, 5149-5157 (2003)