Line emission from hot, dense, aluminum plasmas

The radiation emission from dense, high-temperature aluminum plasmas has been studied to appraise the influence of photoexcitation on several spectral diagnostics currently used to determine average plasma parameters. The plasma state is described by a set of collisional-radiative rate equations characterizing the competing atomic processes occurring in a homogeneous plasma volume of constant density and temperature. Radiation is transported through the plasma by the method of frequency diffusion, a technique which employs collision times of the photons as they diffuse through the wings of a broadened line profile. Line spectra and line-intensity ratios for several pairs of emission lines of the $K$ shell are calculated in optically dense plasmas and compared with those obtained from the model within the optically thin approximation. The radiation-trapping effects are shown significantly to modify the behavior of the optically thin constant-density or constant-temperature line ratio curves, which become double valued in some cases. Comparisons of state populations obtained from this model and the local-thermodynamic-equilibrium model are also shown.