DESIGN OF A HIGH-RESOLUTION EXTREME-ULTRAVIOLET IMAGING SPECTROMETER WITH ABERRATION-CORRECTED CONCAVE GRATINGS

A high-resolution extreme-ultraviolet imaging spectrometer is designed for the Japanese solar mission Solar-B. A spherical varied-line-space (SVLS) grating and a toroidal uniform-line-space (TULS) grating are c hosen as candidates for use in the spectrometer to yield high spectral and spatial resolution within the spectral range 25-29 nm. The spectr al image-focusing properties and the mechanical tolerances for fabrica tion and alignment are compared for the two types of grating. The SVLS design is found to be superior to the TULS design for off-plane spect ral images and in ease of fabrication and optical alignment. (C) 1998 Optical Society of America.