Influence of radiative losses on the hydrodynamics of a laser plasma corona

A theoretical study is made of the steady-state flow of a laser plasma formed by the irradiation of a solid calcium target with q~10¹²–10¹³ W/cm². In the range ρ>ρ_cr the self-consistent hydrodynamic problem is solved numerically, with allowance for the electronic thermal conduction, the ionization, and the plasma radiation in the soft x-ray range. In that range, 5–30% of the laser energy may be reemitted from ρ>ρ_cr; the conversion efficiency depends on the saturated heat flux. It is shown that radiative energy losses together with saturation of the heat flux carried by the electrons cause a subsonic plasma flow in the supercritical part of the corona, leading to a rarefaction jump at the critical surface, a large difference between the electron temperature and the ion and ionization temperatures, elimination of the electronic thermal conduction by ionacoustic waves, and formation of satellites of the resonance helium-like ion line in ions with a lower degree of ionization, including the K_α line.