Orateur
Description
The hydrodynamic stability of ablation flows is a key issue in laser-driven inertial confinement fusion (ICF) where a sufficiently symmetric implosion of a spherical capsule is expected to achieve thermonuclear burn. More recently, experimental and simulation results have pointed out that ablator internal perturbations could account for degraded capsule performances, emphasizing the need for a comprehensive understanding of associated perturbation growth mechanisms. In the present work, we apply a method of non-modal linear stability analysis for determining optimal density perturbations within a capsule ablator . The chosen base flow is relevant to the radiative ablation of a capsule shell during the transit of the first shock-wave within the ablator. Optimal longitudinal distributions of linear density perturbations that maximize the ablation front distortion at different times prior to the shock breakout are obtained for transverse wavelengths between 1 and 100 µm and longitudinal wavelengths in the full range 0.1-100 µm. Ablation front sensitivity is maximum for the longest transverse wavelengths with entropy perturbation amplification as the dominant destabilizing mechanism.