A generalized Wolter Type I design for wide-field X-ray imaging applications

Surface scatter effects are a dominant image degradation mechanism for very short X-ray wavelengths, even for state-of-the-art optical surfaces. And the severe off-axis aberrations of the classical Welter Type 1 grazing incidence X-ray telescope consisting of a confocal paraboloid and hyperboloid severely limit the useful angular field that can be imaged onto a flat detector. A new family of alternative designs based on two hyperboloids has been developed that improves the wide-field imaging performance by aberration balancing and a complete optical systems engineering analysis. A particular member of this family, designated as H-T#17, has been selected for use in the Solar X-ray Imager (SXI) instrument to be integrated into the NOAA GOES satellite. The development of the SXI optical prescription lid its defining parameters are first presented, then detailed image quality predictions, as degraded by diffraction effects, geometrical aberrations, surface scatter effects, and all other residual errors in the mirror manufacturers error budget tree are presented. This new optimized design yields an 80% increase in the number of spatial resolution elements over the full solar disc when compared to the classical Welter Type I design that was the SXI baseline design.