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 multila yer mirror. The energy densities significantly exceeded the thresholds for the ablation of metals. Single-shot laser ablation patterns were used in co mbination with ray-tracing computations to characterize the focused beam. T he radiation intensity within the 2-mu m-diameter central region of the foc al spot was estimated to be approximate to 10(11) W/cm(2), with a correspon ding energy density of similar to 100 J/cm(2). (C) 1999 Optical Society of America.