Study On The Radiative Opacity Of Iron Plasmas Using A Model Based On The Detailed-Level-Accounting Approximation

The radiative opacity of iron plasmas is of great significance for application in research fields of inertial confinement fusion(ICF),astrophysics and radiation transport.In this work,two objectives are highlighted.First,atomic data are systematically calculated for all iron ions of 26 different ionization stages such as the energy levels,optical oscillator strengths and photoionization cross sections.These data are obtained by large-scale full relativistic configuration interaction method.Second,Rosseland and Planck mean opacity of iron plasmas are investigated in a wide region of temperature and density,which is essential for the application in radiation transport in plasmas.As a preliminary work for achieving the targets mentioned above,the radiative opacity of iron plasma is studied in this paper using a detailed level approximation(DLA) model and compared with the previous work,which showed that the present work is more reliable and accurate.The atomic data required in the calculation of radiative opacity are obtained in the following way.The energy levels and oscillator strengths are obtained using a large-scale multi-configuration Dirac-Fock method,where the configuration interaction(CI) is considered. The photoionization process is calculated using distorted wave approximation method.Total photoionization cross section for a particular charge state is obtained by summing all contributions from all bound energy levels of relevant ion.The CI effects on the energy levels and oscillator strengths are studied and the result shows it is very strong compared to the result of single configuration Hartree-Fock calculation.After taking CI effects into account,the energy levels are much closer to experimental data and the oscillator strengths are 30%smaller.For optical oscillator strengths,such a feature is consistent with the experimental observations.For photoionization,it is found that there exist differences between the results of detailed configuration approximation(DCA) model and DLA model and the discrepancy is becoming larger with the decrease of density.The transmission spectra of iron plasma under the temperature of 20 eV and density of 0.0001 g/cm~3 are obtained and compared with other theoretical models.A systematic study was carried out for spectrally resolved and Rosseland and Planck mean opacities for an iso-thermal,an iso-density and an iso-ionization degree sequence. The differences between different models were discussed.