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 / r on the laser intensity I L and wavelength k L is analyzed within the non-equilibrium diffusion approximation for radiation transfer. The scaling of the main ablation parameters with I L and k L in the strongly radiative regime 1 À / 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. V C 2015 AIP Publishing LLC. [http://dx.

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Abstract. Spectral properties of the x-ray pulses, generated by perfectly uniform cylindrical implosions of tungsten plasma with parameters typical of wire array zpinches, are investigated under the simplifying assumption that the final stage of the kinetic-to-radiant energy conversion is not affected by the magnetic field. The x-ray emission is shown to be generated within a narrow (sub-micron) radiationdominated stagnation shock front with a "supercritical" amplitude. The structure of the stagnation shock is investigated by using two independent radiation-hydrodynamics codes, and by constructing an approximate analytical model. The x-ray spectra are calculated for two values of the plasma column mass, 0.3 mg cm −1 and 6 mg cm −1 , with a newly developed two-dimensional radiation-hydrodynamics code RALEF-2D. The hard component of the spectrum (with a blackbody-fit temperature of 0.5-0.6 keV for the 6-mg cm −1 mass) originates from a narrow peak of the electron temperature inside the stagnation shock. The softer main component emerges from an extended halo, where the primary shock radiation is reemitted by colder layers of the imploding plasma. Our calculated x-ray spectrum for the 6-mg cm −1 tungsten column agrees well with the published Sandia experimental data (Foord et al 2004 Phys. Rev. Lett. 93, 055002).