On the structure of quasi-stationary laser ablation fronts in strongly radiating plasmas

The effect of strong thermal radiation on the structure of quasi-stationary laser ablation fronts is investigated under the assumption that all the laser flux is absorbed at the critical surface. Special attention is paid to adequate formulation of the boundary-value problem for a steady-state planar ablation flow. The dependence of the laser-to-x-ray conversion efficiency phi(r) on the laser intensity I-L and wavelength lambda(L) is analyzed within the non-equilibrium diffusion approximation for radiation transfer. The scaling of the main ablation parameters with I-L and lambda(L) in the strongly radiative regime 1 - phi(r) << 1 is derived. It is demonstrated that strongly radiating ablation fronts develop a characteristic extended cushion of "radiation-soaked" plasma between the condensed ablated material and the critical surface, which can efficiently suppress perturbations from the instabilities at the critical surface. (C) 2015 AIP Publishing LLC.