Efficient keV x-ray generation from 50 mJ KrF laser plasmas

High efficiency generation of keV x‐rays from copper and iron targets has been studied using 50 mJ, 90 ps KrF laser pulses. By use of an aberration corrected 125 mm focal length lens conversion efficiencies of 9% and 10% into 800–1400 eV x‐rays have been obtained for copper and iron targets. This is a substantial increase over the 2%–3% previously measured in a similar experiment and is comparable to results obtained with much larger laser energies.