Hot-spot mix in large-scale HDC implosions at NIF

Abstract

Mix of high-Z material from the capsule into the fuel can severely degrade the performance of inertial fusion implosions. On the Hybrid B campaign, testing the largest high-density-carbon capsules yet fielded at the National Ignition Facility, several shots show signatures of high levels of hot-spot mix. We attribute a ∼40% yield degradation on these shots to the hot-spot mix, comparable to the level of degradation from large P2 asymmetries observed on some shots. A range of instability growth factors and diamond crystallinity were tested and they do not determine the level of mix for these implosions, which is instead set by the capsule quality.