Nonequilibrium effects in high-gain inertial confinement fusion.

Abstract

Recent experimental demonstrations of ignition and target gain in inertial confinement fusion (ICF) have stimulated interest in exploring the fundamental physics of violent deuterium-tritium (DT) burn in high-gain ICF targets. A significant DT-burn fraction is a necessary condition for high energy gain and large neutron yields (>100MJ). Using classical molecular-dynamics (MD) simulations and a hybrid fluid-kinetic model, we examine how a large fraction of low-energy α particles can kick D and T ions out of equilibrium in high-gain ICF targets. The MD results suggest that (1) temperatures of T_{D} and T_{T} can differ by as much as ∼20% of their mean temperature and (2) the deviation of the DT energy distribution from the Maxwell-Boltzmann function can exceed ∼30%. Some of these MD observations, such as the preferential heating of D ions by low-energy α particles and the temperature separation, can be explained by a proposed hybrid fluid-kinetic model. The implication of such nonequilibrium effects on the DT reactivity is also discussed.