Interaction of 1.3-μm laser radiation with thin foil targets

Comprehensive studies of the hydrodynamics and energy transport in laser-produced plasmas are presented. Thin low-$Z$ foil targets (${10}^{-5\mathrm{}}$—${10}^{-3\mathrm{}}$ g/${\mathrm{cm}}^2$) were irradiated with 300-ps pulses from the Asterix-III iodine laser ($\lambda =1.3\mathrm{}$ μm). Different diagnostics such as high-speed photography, plasma calorimetry, Ulbricht sphere for laser-light absorption measurements, and x-ray and ion techniques were used. Results on the velocity and energy of the accelerated foil, pressure, ablation rate, and lateral energy spread were obtained for a wide intensity range ${10}^{11}$—${10}^{16}$ W/${\mathrm{cm}}^2$. Pressures exceeding 10 Mbar and foil velocities of up to ${10}^8$ cm/se observed. The experimental data are compared with one-dimensional hydrodynamic calculations using different values of electron heat-flux limitation. An indication of intensity-dependent flux inhibition was found: $f\ge 0.1$ at intensities below ${10}^{13}$ W/${\mathrm{cm}}^2$, but $f=0.015-0.03\mathrm{}$ at intensities above ${10}^{14}$ W/${\mathrm{cm}}^2$.