Multiband imaging at the diffraction limit using Fresnel x-ray telescopes

We present a diffractive-refractive x-ray telescope for simultaneous imaging in multiple energy bands.Based on segmented achromatic lenses, the system yields an angular resolution around 1 mas between 5 and 10 keV for a focal distance of a few 10 2 km.The total sensitivity, measured via the bandwidth-integrated effective area, reaches at least 10 3 cm 2 keV.Our arrangement exploits Fresnel lenses used in higher phase shift orders for orderly protection from scattered radiation as well as reduced refractive profiles for an enhanced throughput.The telescope, which has its focal plane detector on a separated spacecraft, may be reoriented to new astrophysical targets on short timescales.Scientific applications are briefly discussed for active galactic nuclei.