Impact of Outer Shell Joint Morphology in Double Shell Capsule Designs*

Current double shell target fabrication requires mating two hemispheres with a machined equatorial joint to form an outer shell. Experimental radiographs from sub-scale double shell experiments at the National Ignition Facility (NIF) demonstrate that the morphology of the joint significantly impacts the implosion dynamics. Further, simulations demonstrate that the joint morphology can impart significant asymmetry in the outer shell and is a major factor in yield degradation. Therefore, understanding and mitigating the joint perturbation is important for improving performance. We present simulations of the double shell joint feature using xRAGE, an Eulerian radiation-hydrodynamics code with adaptive mesh refinement, which is well suited to modeling fine-scale engineering features. Post-shot modeling of the sub-scale experiments and preparatory simulations at full NIF energy are discussed. A nominal scale capsule in a cylindrical hohlraum is compared to larger variants designed for a rugby hohlraum, and a design study for a hydro-growth radiography platform to directly image the joint feature is presented.