MULTILAYER COATED CONCAVE DIFFRACTION GRATING RESOLUTION AND EFFICIENCY IN THE EXTREME ULTRAVIOLET

Recent advances in multilayer structures for the extreme ultraviolet now make it possible to construct diffraction gratings in the wavelength range below 350 angstrom which can be used for precision measurements using normal incidence spectrometers. We report results from two such gratings, one with conventionally ruled blazed facets and the other with a holographically ruled sinusoidal surface. Both gratings are 1 m in radius, 1200 lines/mm coated with a molybdenum-silicon multilayer for use in the 150 angstrom wavelength region. A 1 m normal incidence spectrometer with a Garton flash tube source and a film detector was used to test the spectral resolution. Relative efficiency measurements were obtained by comparison to spectra produced by an osmium coated grating. Emission lines in the wavelength region of interest (characteristic of the source) are easily detected and well resolved with both multilayer coated gratings. Quantitative efficiency measurements were obtained using a Penning source coupled to a 1 m grazing incidence monochromator and an imaging photon counting detector.