NLTE opacity calculations: C-Si and C-Ge mixtures

摘要

Abstract The opacity is an important issue in the knowledge of the radiative properties of ICF and astrophysical plasmas. We present the opacity of dopants (silicon, germanium) embedded in the ablator of some ICF capsules. In recent works, Hill and Rose calculated the opacity of silicon in LTE and non-LTE plasmas, while Minguez and co-workers focused on the opacity of carbon. We have used the Cowan code to calculate the atomic structure of carbon, silicon and germanium in various ionic stages. The cross-sections of atomic processes (collisional excitation, collisional ionization) are obtained by fitting the values given by the code FAC to the Van Regemorter-like formulas of Sampson and Zhang. A corrected Gaunt factor is then obtained. A collisional-radiative code was developed in order to obtain the ionic populations, the level populations and the opacity. Line broadening and line shift are taken into account. The ionization potential depression is included in our calculations. The effect of a radiation field on the opacity is examined. ]]>