Instability growth seeded by DT density perturbations in ICF capsules

Abstract

Identifying and controlling hydrodynamic instabilities is vital to inertial confinement fusion. We use simulations to examine the growth of several defects seeded in the deuterium-tritium (DT) fuel layer. First, we examine the growth of bulk density fluctuations in a solid DT ice layer. These density perturbations grow with amplitudes similar to surface defects, however the high-mode (m > 40) growth structures differ. We also consider the wetted foam capsule design, where density perturbations can be seeded by foam inhomogeneity. Simulations show that foam-seeded perturbations grow similarly to pure DT density seeds at low modes (m < 40), but at higher modes, the foam seeds grow significantly more. Next, we simulate the growth of two common multimode ice defects, grooves, and bubbles, and find that bubbles are significantly less harmful than grooves of similar width. Finally, we explore shimming the ablator to counteract surface roughness and show that instability growth from low-mode roughness can be effectively mitigated.