An x-ray beam with energy of 20.5 keV has been efficiently focused down to a spot size as small as 90 nm390 nm by a Kirkpatrick–Baez reflecting mirrors device. The first mirror, coated with a graded multilayer, plays both the role of vertical focusing device and monochromator, resulting in a very high flux s231011 photons/sd and medium monochromaticity sDE /E,10−2d. Evaluation of the error cont...