Optical design of the x-ray telescope for XEUS

Abstract

XEUS is a single focus X-ray telescope which will provide a collecting area of 10-20 m² at 1 keV with angular resolution 2-5 arc seconds. Such a large area can be achieved with low mass using pore optics manufactured from silicon. The aperture utilisation of the pore optics is ~ 0:5 and with an aperture diameter of 7 m and gold reflecting surfaces the effective area can be 14 m² at 1 keV and 1.5 m² at 8 keV, providing it is possible to launch the required mass. Diffraction imposes a limit on the angular resolution that can be obtained with pore optics. If the focal length is 30 m then the angular resolution limit would be ~ 1 arc second but the pore size must be 0.2 mm. If the pore size is limited by manufacturing to 0.6 mm then the goal of 2 arc seconds half energy width will require a focal length ≥ 40 m. The hard X-ray response can be extended using multilayer coatings on the innermost shells giving ~ 1270 cm² effective area at 40 keV for an increase in Si mass of ~ 96 kg.