The Physics of Long- and Intermediate-Wavelength Asymmetries of the Hot Spot

The effect of asymmetries on the inertial confinement fusion implosion yield and stagnation pressure will be presented. The asymmetries are divided into low $\left( {\ell <6} \right)$ and intermediate $\left( {6<\ell <40} \right)$ modes by comparing the wavelength with the hot-spot radius. Long-wavelength modes introduce substantial nonradial motion, whereas intermediate-wavelength modes involve more cooling by thermal losses. It is found that for distorted hot spots, the measured neutron-averaged properties can be very different from the real hydrodynamic conditions. This is because mass ablation driven by thermal conduction introduces flows in the Rayleigh--Taylor bubbles that results in pressure variations, in addition to temperature variations between the bubbles and the neutron-producing region. The yield degradation---with respect to the symmetric case---results primarily from a reduction in the hot-spot pressure for low modes and from a reduction in burn volume for intermediate modes. A general expression is found relating the pressure degradation to the residual shell energy and the flow within the hot spot (i.e., the~total residual energy). This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and by the LLNL under subcontract B614207.