Numerical simulation of an ICE target explosion in a stratified gas atmosphere

Two-dimensional radiation hydrodynamics simulations of a light-ion fusion target-generated microfireball in a stratified gas atmosphere have been performed. Target microexplosions of 200 and 800 MJ were investigated. The intent of this configuration was to determine if the stratified gas (with different opacities) could be used to reduce the overpressure on the diodes placed at the walls of the target chamber and also the diagnostic equipment placed below the target explosion position in the nitrogen layer. Nonspherical fireball propagation caused by venting of the fireball once its radiation front reached the N2/He interface was investigated. The interface is within the distance from the target where the fireball shock breaks away from the radiation diffusion wave. A two-dimensional radiation hydrodynamics code with a single radiation temperature and a single fluid temperature (ion and electron temperature were equal) was used to perform the calculations on a Cray-1 computer. The computational mesh had typically from 4000 to 10,000 mesh points in a cylindrical coordinate system