Metrics for long wavelength asymmetries in inertial confinement fusion implosions on the National Ignition Facility

We investigate yield degradation due to applied low mode P2 and P4 asymmetries in layered inertial confinement fusion implosions. This study has been performed with a large database of >600 2D simulations. We show that low mode radiation induced drive asymmetries can result in significant deviation between the core hot spot shape and the fuel rho R shape at peak compression. In addition, we show that significant residual kinetic energy at peak compression can be induced by these low mode asymmetries. We have developed a metric, which is a function of the hot spot shape, fuel rho R shape, and residual kinetic energy at peak compression, that is well correlated to yield degradation due to low mode shape perturbations. It is shown that the rho R shape and residual kinetic energy cannot, in general, be recovered by inducing counter asymmetries to make the hot core emission symmetric. In addition, we show that the yield degradation due to low mode asymmetries is well correlated to measurements of time dependent shape throughout the entire implosion, including early time shock symmetry and inflight fuel symmetry. (C) 2014 AIP Publishing LLC.