Interpretation of the spatial and spectral intensities of optically thick resonance lines emitted from a spherical laser-heated plasma

Abstract

We present interpretations of computed spatial and spectral intensities of the principal resonance lines emitted from a spherical laser‐heated aluminum plasma. Our interpretations are based upon frequency‐by‐frequency solutions for the radiation transport equation which are coupled to a spherically symmetric time‐dependent aluminum plasma model. This model solves the coupled equations for ion and electron temperatures and densities, atomic level populations, and fluid velocities for varying assumptions of energy deposition within the plasma. We find that the HeK_α and HK_α resonance line profiles and intensities of the Al XII and Al XIII ions emitted during deposition are sensitive to the spatial plasma heating profile. By solving for the emitted H‐like K_α line intensities along various lines of sight we generate theoretical ’’pinhole photographs’’ of the emission of this line. These spatial H‐like K_α profiles are also very sensitive to the assumed laser deposition distribution. We have also compared our numerical results with those given by the escape‐factor formula of Holstein, and we present an escape formula which is more accurate than Holstein’s for large optical depths when the photon sources are approximately uniformly distributed in the plasma sphere.