Plasma-hydro coupling in cassio, an Inertial Confinement Fusion Code from the Crestone Project

The Crestone Project at Los Alamos National Laboratory produces cassio, an ICF code. Currently cassio implements radiation hydrodynamics on an Eulerian AMR mesh along with a three temperature (3T) plasma physics model. A 3T model treats a plasma as a single species fluid with separate electron and ion temperatures, and uses a radiation diffusion model, where a radiation temperature characterizes the radiation energy density. The evolution equations for the electron and ion specific internal energies contain nonconservative products ($p\nabla \cdot u)$, which requires an assumption about shock jump conditions. Assuming an isentropic discontinuity in electron quantities at the shock permits semi-analytical solutions for simple fully ionized flows; these flows exhibit differential shock heating of the electrons and ions with relaxation to a common temperature. We have developed an Eulerian Godunov-based scheme for computing such shocks. We provide details for the model, method, and semi-analytic solutions, and compare results of the method to the semi-analytic solutions.