The X-ray Evolving Universe Spectroscopy mission (XEUS) the X-ray mirror design and technology

To achieve the demanding aims of XEUS, which involve the detection of sources as faint as 10(-18) ergs cm(-2) s(-1) a large X-ray mirror will need to be developed. This core scientific aim implies that the XEUS mirror needs to have an effective collecting area at 1 keV of 30 m(2) coupled to a spatial resolution on-axis of between 2 and 5 arcsec (HEW), so as to avoid source confusion at these very faint flux levels. Finally a field of view of at least 5 arcmin must be covered so as to ensure that a significantly large population of high redshift x-ray sources can be observed in a single pointing over the energy band from 0.05 - 30 keV. Clearly the key characteristic of XEUS is the large X-ray mirror aperture coupled to the high spatial resolution. The XEUS mirror aperture of 10 m diameter is divided into annuli with each annulus subdivided into sectors. The basic mirror unit therefore consists of a set of heavily stacked thin mirror plates each retaining the correct geometry. This unit is known as a mirror petal and constitutes a complete free-standing calibrated part of the overall XEUS mirror.