PERFORMANCE OF MULTILAYER COATED GRATINGS AT NEAR NORMAL INCIDENCE IN THE EXTREME ULTRAVIOLET

We report on the normal incidence performance of multilayer coated concave gratings in spectral regions where near normal incidence reflectivities of conventional coatings are calculated to be 10−4 to 10−5. These concave gratings were designed for use in a McPherson 225 Spectrometer and were tested for resolution in this instrument using a Garton flash tube source and a film detector. Efficiency measurements were obtained for both the gratings and flat multilayers fabricated at the same time using a Penning source and an incident beam monochromator to obtain spectral purity. The incident and diffracted beams were measured using the same microchannel plate based two dimensional photon counting detector. Experimental results are compared with scalar theory. © 1990 IOP Publishing Ltd.