Electromagnetic-field distribution measurements in the soft s-ray range : full characterization of a soft x-ray laser beam
We report direct measurement of the electromagnetic-field spatial distribution in a neonlike Ar capillary discharge-driven soft x-ray laser beam. The wave front was fully characterized in a single shot using a Shack-Hartmann diffractive optics sensor. The wave front was observed to be dependent on the discharge pressure and capillary length, as a result of beam refraction variations in the capillary plasma. The results predict ~70% of the laser beam energy can be focused into an area 4 times the size of the diffraction-limited spot, reaching intensities of ~4 × 1013 W/cm2.