Fig. 3: Evaluated intensity distributions of focused beam.

The intensity distributions in the focal plane were measured using a knife-edge scanning method at an XFEL repetition rate of 30 Hz. The evaluated focal spot size was a 110 nm (full width at half-maximum (FWHM)) in the horizontal direction and b 60 nm (FWHM) in the vertical direction at scan steps of 25 and 15 nm, respectively. In a and b, intensities of 600 and 100 XFEL pulses were averaged for each data point, respectively.