Influence of mass ablation on the ignition threshold in layered fusion capsules

The ignition physics for layered fusion capsules involves a complex interplay between the dynamically forming hot spot and the dense surrounding fuel. Recent analysis has demonstrated [1] that the mass ablation rate into the hot spot depends sensitively upon the temperature of the dense fuel. This produces an enthalpy flux into the hot spot which plays a critical role in controlling the hot spot temperature and the ignition threshold. In this presentation, we demonstrate that net influence of mass ablation on the ignition threshold is regulated by a dimensionless parameter which depends upon the temperature of the dense fuel. As a consequence, the ignition threshold is sensitive to any mechanism that heats the dense fuel, such as neutrons or radiation emitted from the hot spot. These predictions are confirmed using radiation hydrodynamic simulations for a series of capsules near ignition conditions. These results may have relevance for understanding the variable performance of recent experiments and for guiding new capsule designs toward higher fusion yields.



[1] Daughton et al, https://arxiv.org/abs/2207.00093