Experimental setup. (a) A monochromatic x-ray beam is focused by two KB mirrors onto the system of two crossed planar waveguides (WG) with a layered guiding core structure for optimized transmission. The sample (for an optical mircograph of the cells, see inset) is placed at a distance z
1 behind the WG exit. The area pixel detector is placed at a distance z
2 ≫ z
1 away from the sample to collect the diffraction pattern. (b) Logarithmic far-field intensity distribution of a 15 keV beam exiting the waveguide (scale bar 0.02 Å-1, 100 second dwell time), measured with a pixel detector (Pilatus) at a distance of 5.29 m behind the focus. The small focal width of the waveguide beam is evidenced by its large divergence angle, the relatively homogenous intensity distribution well suited for imaging (dashed rectangle) has a divergence angle of 5 mrad. (c) The near-field intensity distribution in the effective focal plane is obtained by inverting the diffraction pattern with the error reduction algorithm, shown in logarithmic scale, scale bar 20 nm. (d) Gaussian fits of the central peak along the horizontal and vertical direction give a width of 10 nm × 9.8 nm (FWHM), respectively.