The Hot and Energetic Universe: The Optical Design of the Athena+ Mirror
The Athena+ X-ray mirror will provide a collecting area of 2 m^2 at 1 keV and an angular resolution of 5 arc seconds Half Energy Width. The manufacture and performance of this mirror is of paramount importance to the success of the mission. In order to provide the large collecting area a single aperture of diameter ~3 m must be densely populated with grazing incidence X-ray optics and to achieve the high angular resolution these optics must be of extremely high precision and aligned to tight tolerances. A large field of view of ~40 arc minutes diameter is possible using a combination of innovative technology and careful optical design. The large collecting area and large field of view deliver an impressive grasp of 0.5 deg^2 m^2 at 1 keV and the angular resolution will result in a source position accuracy of better than 1 arc second. The Silicon Pore Optics technology (SPO) which will deliver the impressive performance of the Athena+ mirror was developed uniquely by ESA and Cosine Measurement Systems specifically for the next generation of X-ray observatories and Athena+ represents the culmination of over 10 years of intensive technology developments. In this paper we describe the X-ray optics design, using SPO, which makes Athena+ possible for launch in 2028.