Simulations of isolated defect evolution in direct-drive targets

Target imperfections come in many forms, all of which generate seeds for hydrodynamic instability growth that degrade implosion performance. Isolated defects, such as domes or divots on the surface of the outer-most plastic layer, have been shown to reduce areal density and potentially compromise shell integrity during shock-transit and shell acceleration. OMEGA cryogenic targets can have thousands of surface defects with dimensions ranging from sub-micron to several microns in size, due to permeation fill and cooling cycles. Simulating defects presents a significant challenge due to the fidelity required to capture hydrodynamic evolution at this scale. The multi-physics code Cygnus is being used to simulate defects with low-dissipation, high-order hydrodynamics to capture the propagation of characteristic waves throughout the target. This talk will present a discussion of the behavior of these defects in 2D and 3D and the evolution of hydrodynamic waves and corresponding seeding effects for Rayleigh-Taylor instability growth. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE- NA0004144.