First tungsten-based double shell implosions on the National Ignition Facility

Inertial Confinement Fusion Double Shell implosions rely on the efficient transfer of kinetic energy from an outer (ablator) shell to an inner shell to compress and heat its central DT fuel. Due to imperfections associated with the target and laser, ideal transfer of energy is never achieved; however, design choices and target advancements can reduce these losses. Reaching the ignition and burn with double shells at MJ-scale laser facilities requires the use of dense, high-Z metal inner shells due to their ability to undergo efficient shell collisions while maintaining compressibility and high work rate on the DT plasma. The ability of heavy metal shells to withstand imperfections, such as engineering features and low-mode asymmetries from the incoming ablator and hohlraum, has not previously been measured.

In this presentation we discuss the first energetics and implosion symmetry experiments using tungsten-based double shells, present first observations of W/Be gradient shell implosions that are predicted to enhance high-mode stability over bare W or W/Be bi-layer designs. Finally, we will present future plans and directions for high-Z double shells.