A multiscale analysis of the hotspot dynamics during the deceleration phase of inertial confinement capsules

This paper is devoted to the study of the deceleration phase of inertial confinement capsules. First the self-similar flow exhibited by Betti et al. [Phys. Plasmas 8, 5257 (2001)] is proved to be an attractor in the sense that arbitrary initial conditions converge towards this solution. The convergence rate depends on the ablation process and heat conductivity and it is shown to be a power law of the increase rate of the hotspot mass. Second the thin layer that separates the hotspot from the cold shell is described and it is shown that it also converges to a locally self-similar profile. By using and generalizing a shell model introduced by Betti et al. [Phys. Plasmas 9, 2277 (2002)] a closed system of ordinary differential equations for the main hydrodynamic variables is derived. Finally the linear growth rates of the deceleration phase Rayleigh–Taylor instabilities are computed taking into account ablation and spherical convergence. Significant differences are exhibited between directly and indirectly driven capsules.