title: Echelle spectrographs at grazing incidence.
abstract: It is shown that by using the conical diffraction mount existing echelle gratings can be used at grazing incidence to achieve high spectral resolution in the extreme UV and soft x rays. Design considerations for grazing incidence echelle spectrographs are examined, and two sample designs are discussed. The first, for use in the extreme UV has a primary mirror and an entrance slit to the spectrograph. The system has resolution of 10(4), operates at any wavelength longward of 100 A, and covers 30% of the spectrum at a single setting. The x-ray spectrograph uses objective gratings to obtain spectral resolution of 2.8 x 10(4) over any factor of 2 in wavelength. It operates to wavelengths as short as 4 A.
authors.forename: W
authors.initials: W
authors.lastname: Cash