Efficient sub 100 nm focusing of hard x rays

An x-ray beam with energy of 20.5 keV has been efficiently focused down to a spot size as small as 90 nm × 90 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 ( 2 × 10 11 photons ∕ s ) and medium monochromaticity ( Δ E ∕ E ∼ 10 − 2 ) . Evaluation of the error contributions shows that the vertical focus is presently limited by the mirror figure errors, while the horizontal focus is limited by the horizontal extension of the x-ray source. With a gain in excess of a few million, this device opens up new possibilities in trace element nanoanalysis and fast projection microscopy.