Characterization of a Flat-Field Grazing-Incidence XUV Spectrometer.

We describe a XUV spectrometer for the study of dense hot microplasmas at wavelengths between ≈50 and ≈300 Å. It uses a commercially fabricated grazing incidence flat-field reflection grating with 1200 grooves per millimeter. The spectral resolution was optimized by imaging the source on a narrow slit with the help of a curved grazing incidence mirror. The instrument was tested with a laser-produced plasma as a source. The limit of the resolving power due to imaging aberrations of the flat-field grating ranges from 1500 at 50 Å to 3600 at 200 Å and has been achieved with a 5-μm slit. We also measured and calculated the grating efficiencies for the first to fifth diffraction order as a function of wavelength.