28 November 2000 Grazing incidence flat-field spectrometer with spatial resolution capability for extended sources
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Abstract
The optical design for stigmatic grazing-incidence flat-field spectrometers with spatial resolution capability is presented. The spectral focal curve is almost a straight line by use of the flat-field focusing properties of spherical variable line- spaced gratings. The astigmatism in the plane perpendicular to the dispersion plane is corrected by a spherical mirror mounted with its sagittal plane coincident with the equatorial plane of the grating. The spectral and spatial focusing properties result almost fully uncoupled, so the ultimate spectral resolution depends only on the grating characteristics and on the detector pixel size and the spatial resolution depends only on the properties of the mirror. The image on the focal plane is stigmatic in the spectral direction both for on-plane and off-plane sources: no spectral broadening is observed for off-plane sources, maintaining therefore a constant spectral resolution also for extended sources. The resolution in the plane perpendicular to the plane of dispersion decreases for off-plane sources, depending on the incidence angle on the mirror and on the acceptance angle. Comparisons with optical performances of conventional stigmatic grazing-incidence spectrometers are presented.
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Luca Poletto, Luca Poletto, Giuseppe Tondello, Giuseppe Tondello, } "Grazing incidence flat-field spectrometer with spatial resolution capability for extended sources", Proc. SPIE 4138, X-Ray Optics, Instruments, and Missions IV, (28 November 2000); doi: 10.1117/12.407558; https://doi.org/10.1117/12.407558
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