Nonextensive equation of state for NLTE plasmas with <i>κ</i> -Fermi distributed free electrons

A nonextensive statistical approach is developed to investigate the equations of state of partially ionized plasmas containing nonthermal free electrons. The average-atom model is adopted to simulate the plasma ionization balance, in which the κ-Fermi distribution is applied for the free electrons. We introduce a nonequilibrium kinetic temperature that consistently characterizes the electron mean kinetic energy. The κ-Fermi distribution substantially reduces the electron pressure and the average ionization degree of the plasma, which has a much more significant impact on high-Z plasmas than low-Z plasmas. This should influence the plasma hydrodynamics remarkably when nonthermal electrons are present, such as in the Hohlraum dynamics of laser-driven inertial confinement fusion.