Application of Milne condition diffusive radiation transport in Mach2 to wire implosions on Saturn

Summary form only given. Generally no prescribed radiation temperature boundary condition in the region exterior to a PRS can be specified and the radiation diffusion problem is thus ill-posed. A flux based or gradient boundary condition within the radiating material, such as the Milne condition, establishes a self consistent gradient in the radiation temperature based on local opacities at the radiating surface and therefore removes the ambiguity. We establish a gradient or Milne condition in the radiation diffusion methods of Mach2 and couple it with LTE source terms. The implications for the global energy balance in r-z cylindrical pinch radiation sources are examined using Mach2. Benchmark studies of the method as implemented in Mach2 are followed by simulations of recent wire implosions on the Saturn accelerator in long pulse mode.