Aberration correction for hard x-ray focusing at the nanoscale

We developed a corrective phase plate that enables the correction of residual aberration in reflective, diffractive, and refractive X-ray optics. The principle is demonstrated on a stack of berylliumcompound refractive lenses with a numerical apertureof 0.49 10 -3 at three synchrotron radiation and x-ray free-electron laserfacilities, where we corrected spherical aberrationof the optical system. The phase plate improved the Strehl ratioof the optics from 0.29(7) to 0.87(5), creating a diffraction-limited, large aperture, nanofocusing optics that is radiation resistantand very compact.