Focusing of a tabletop soft-x-ray laser beam and laser ablation.

We focused the beam of a high-repetition-rate capillary-discharge tabletop laser operating at a wavelength of 46.9 nm, using a spherical Si/Sc multilayer mirror. The energy densities significantly exceeded the thresholds for the ablation of metals. Single-shot laser ablation patterns were used in combination with ray-tracing computations to characterize the focused beam. The radiation intensity within the 2-mum -diameter central region of the focal spot was estimated to be approximately 10(11)W/cm(2), with a corresponding energy density of ~100 J/cm(2).