Two normal incidence collimators designed for the calibration of the extreme ultraviolet explorer

Two Dall-Kirkham, normal incidence collimators have been designed to calibrate the imaging properties of the Extreme Ultraviolet Explorer over the wavelength region from 114 to 2000 Å. The mirrors of the short- wavelength, 25-cm diameter collimator are superpolished Zerodur which have been multilayer coated for optimal reflectivity at 114 Å. The mirrors of the long-wavelength, 41.25-cm diameter collimator are gold coated Zerodur for high reflectance above 300 Å. The design, performance, and future use of these collimators in the extreme ultraviolet is discussed. © 1988 SPIE.