EXPERIMENTAL SCALING LAWS FOR MASS-ABLATION RATE, ABLATION PRESSURE IN PLANAR LASER-PRODUCED PLASMAS WITH LASER INTENSITY, LASER WAVELENGTH, AND TARGET ATOMIC-NUMBER

Layered-target experiments at 1.06 mum for carbon and silicon materials have been carried out to measure mass-ablation rate m and ablation pressure P(a) as a function of absorbed laser intensity I(a), laser wavelength lambda(L), and target atomic number Z at irradiances of 10(13)-10(15) W/cm2. The results can be put in the forms m(kg/s cm2) congruent-to 55 [I(a)(W/cm2)/10(14)]1/3lambda L-4/3(mum) Z3/8 and P(a)(Mbar) congruent-to 7.4 [I(a)(W/cm2)/10(14)]2/3lambda L-2/3(mum) Z3/16. The experimental data are compared with one-dimensional hydrodynamic calculations (code MEDUSA) using different values of electron heat-flux limitation. An indication of laser intensity, target atomic number dependent on flux inhibition was found: 0.06 less-than-or-equal-to f less-than-or-equal-to 0.08 for silicon targets and f=0.015-0.03 for carbon targets. These flux limitations are discussed in terms of a small lateral transport and an eventual presence of intense magnetic fields.