Study of soft-x-ray generation by laser-heating solid and gaseous tantalum plasmas with subpicosecond pulses

The efficiency of x-ray emission in the 17–35 nm region from laser-heated solid and gaseous density Ta plasmas has been compared. An x-ray conversion efficiency of 0.4% from a solid density Ta plasma requires a laser fluence of 200 J/cm2 whereas the same efficiency in a gaseous Ta plasma with optimal density profile requires only 3 J/cm2 . This is due to ultrarapid thermal diffusion in the solid and to the shorter attenuation length and duration of x rays emitted from the heated solid density plasma.