KEV X-RAY-PRODUCTION USING 50-MJ KRF LASER-PRODUCED PLASMAS AT 1-PS AND 100-PS

The emission of 800-1400 eV x rays from plasmas produced by KrF discharge laser pulses with durations in the range of 1 and 100 ps with energies up to 50 mJ has been studied using various metal targets. The emission spectra, angular distribution, and x-ray conversion efficiencies into 2pi Sr have been measured in vacuum. Peak conversion efficiencies of 10%-13% were obtained for Fe, Co, Ni, Cu, and Zn when a 90 ps, 50 mJ pulse was used. A 2 ps, 40 mJ pulse yielded efficiencies of 8%-10% with plasma reflectivity accounting for the reduction in conversion efficiency. An 850 fs, 35 mJ pulse gave reduced yields of 4% for Cu. In a background gas of 1 atm helium a reduction of conversion efficiency by 15% was observed for 90 ps pulses.