Grazing-incidence hyperboloid-hyperboloid designs for wide-field x-ray imaging applications

Optical design of type-1 x-ray telescopes and their application to STAR-X

An astronomical x-ray telescope's capability rests on the quality of its optics, which in turn rests on its point spread function (PSF), field of view (FOV), and photon-collecting area. The design and implementation of telescope optics must optimize these three parameters in the context of mathematical prescription, optical fabrication, engineering, and resources such as mass and cost constraints. In this paper, after reviewing important features of grazing incidence optics and the many different mathematical prescriptions in the literature, we quantitatively compare the advantages and disadvantages of these prescriptions, using detailed ray trace, to optimize the PSF and FOV for a given set of requirements. Then, we apply this approach to optimizing the designs for a proposed future x-ray telescope, Survey and Time-Domain Astrophysical Research eXplorer (STAR-X), a NASA Medium-Class (MIDEX) mission by optimizing the combination of PSF and FOV.

Equal-curvature grazing-incidence x-ray telescopes

We introduce a new type of x-ray telescope design, an equal-curvature telescope. We simply add a second-order axial sag to the base grazing-incidence cone-cone telescope. The radius of curvature of the sag terms is the same on the primary surface and on the secondary surface. The design is optimized such that the on-axis image spot at the focal plane is minimized. The on-axis rms spot diameter of two telescopes that we studied is less than 0.2 arc sec. The off-axis performance is comparable with that of equivalent Wolter type 1 telescopes.