Impact of areal-density asymmetries on the loss of confinement and ignition threshold in inertial confinement fusion capsules

Abstract

In inertial confinement fusion implosion experiments, variations in the shell areal density reduce the shell's inertia to confine the core pressure. Distorted capsules with large areal-density modulations decompress faster than uniform capsules in the disassembly phase. A simple 3D analytic hot-spot model is derived to include the effects of low-mode areal-density modulations in the ignition criterion. The generalized 3D ignition criterion for low modes is shown to depend on both the harmonic mean and the arithmetic mean of the areal density. The “thin spots” in the shell are shown to dominate the loss of confinement as reflected by the harmonic mean definition of areal densities.