Measurements of mass ablation rate and pressure in planar targets irradiated by 0.27-μm laser light

Planar CH targets were irradiated by 400-ps and 1-ns pulses of 0.27-μm light at intensities of 5×1012–1014 W/cm2. The mass ablation rate obtained from time integrated x-ray line emission from layered targets was found to be ṁ=1.5×105(Ia/1013 W/cm2)0.5 g/cm2 s. Using this result and the ion blowoff velocity, the ablation pressure scaled as Pa=3.9 (Ia/1013 W/cm2)0.6 Mbar. Comparisons to similar experiments at 0.53 μm indicate that the mass ablation rate and pressure scale with laser wavelength as λ−1.4 and λ−0.9, respectively. The intensity and wavelength scalings are found to agree with analytic predictions for spherical geometry rather than planar models. Comparisons are also made with previously reported measurements at other wavelengths and geometries.