Frequency dependent opacity of aluminium plasma using average atom model

Knowledge of radiative opacity of a material is essential in modeling the radiation hydrodynamics process occurring in inertial confinement fusion (ICF). It depends on the detailed internal structure of atoms and ions embedded in plasma. We have used screened hydrogenic model with 1-splitting in the average atom framework to obtain the energy levels, population and average ionization state of plasma. With this knowledge, we have calculated the frequency dependent opacity of aluminium plasma for different temperature and density. The results are compared with OPAL data and a reasonable agreement between the two is seen. We have also discussed the effect of density on the individual lines through pressure ionization and continuum lowering. The dependence of opacity on density and temperature is also investigated. It is observed that the plasma becomes more opaque as the density is increased, where as the transparency increases as we increase the temperature of plasma at a particular density. (author)