Advances in HYDRA and its applications to simulations of inertial confinement fusion targets

Abstract

A new set of capabilities has been implemented in the HYDRA 2D/3D multiphysics inertial confinement fusion simulation code. These include a Monte Carlo particle transport library. It models transport of neutrons, gamma rays and light ions, as well as products they generate from nuclear and coulomb collisions. It allows accurate simulations of nuclear diagnostic signatures from capsule implosions. We apply it to here in a 3D simulation of a National Ignition Facility (NIF) ignition capsule which models the full capsule solid angle. This simulation contains a severely rough ablator perturbation and provides diagnostics signatures of capsule failure due to excessive instability growth. 1. INTRODUCTION Simulations of indirect drive ignition target designs for the National Ignition Facility (NIF) must model asymmetries originating from a wide variety of sources. These include intrinsic drive asymmetries due to the illumination geometry, and extrinsic asymmetries resulting from pointing and power balance errors between the beams. Roughness on the shell surfaces seed hydrodynamic instabilities which can also degrade capsule performance. These include discrete features such as ice grooves, dust grains, unusually large isolated bumps and the fill tube used to inject fuel into the capsule. The growth factors due to hydrodynamic instabilities are sufficiently large that perturbations progress into the nonlinear saturated regime. Experiments and simulations have established that larger saturation amplitudes are obtained by symmetric 3D perturbation shapes (1-10). In addition the various asymmetries can combine in a capsule implosion so that accurate treatment of the phases between them is essential. Treating accurately the effects of these asymmetries on capsule performance and their manifestation in simulated diagnostics requires 3D simulation (11). Previously we reported results from 3-D integrated simulations of the full ignition target and high resolution simulations of a capsule over a limited solid angle (12-14). Here we report the first high resolution 3D simulation of a full implosion of a NIF ignition capsule carried out over the full 4 solid angle. The simulation includes a Monte Carlo treatment of the burn product transport, enabling simulation of neutron diagnostics.