Saturated tabletop lasers having increased output energy and operating at
5 Hz repetition rate, were demonstrated at wavelengths about 18.9 nm for
molybdenum targets, 16.4 nm for ruthenium targets, 14.7 nm for palladium
targets, 13.9 nm for silver targets, and 13.2 nm for cadmium targets in
transitions of nickel-like ions. The results were obtained using a
sequence of two, plasma-generating pre-pulses, each having sub-Joule
energy followed after a selected delay period by picosecond laser plasma
excitation pulses having with an energy of about 1 J at angles of
incidence optimized for maximum energy deposition.