Nonlinear dynamics of material interface perturbations initiated by high-density inclusions in the ablator of inertial confinement fusion implosions

We systematically investigate the influence of a high-density defect on the evolution of perturbations at the high-density carbon ablator-deuterium–tritium fusion fuel material interface under shock compression. The results show that the convergence geometry configuration induced by the interaction between the shock and the defect governs the development of interface perturbations, which manifest in two forms: expansion deformation caused by direct shock impact and a spike-like jet. The expansion deformation evolves through three stages: shock impact, vorticity dominance, and secondary shock interaction, its amplitude increasing with the local Atwood number At. The formation mechanism of a spike-like jet varies with At: after shock convergence, when Mach reflection forms upstream of the interface (typically lower At), vorticity-induced shear layer triggers spike formation; when Mach reflection occurs downstream (typically higher At), reverse vorticity deposited by the converging shock drives spike formation via axial compression. The transition range of At between these two mechanisms is identified. Furthermore, the secondary shock significantly enhances material mixing and seeds new perturbations. At low At, a spike–bubble inversion occurs, while at high At, the development of secondary spikes dominates; both phenomena are driven by baroclinic vorticity. Even small initial perturbations are markedly amplified by secondary shock effects.