Molecular dynamics investigations of the ablator/fuel interface during early stages of inertial confinement fusion

Summary form only given. At the National Ignition Facility, high-powered laser beams are focused into a hohlraum, which in turn produces x-rays that heat and compress a small spherical target to generate fusion reactions. A critical issue in achieving this is the understanding of the mix at the ablator/fuel interface. Mixing occurs at various length scales, ranging from atomic inter-species diffusion to hydrodynamic instabilities. Because the ablator/fuel interface is preheated by energy from the incoming shock, it is important to understand the dynamics of the interface before the shock arrives. The interface is in the warm dense matter phase with a deuterium-tritium fuel mixture on one side and a plastic (H, C and O) mixture on the other. We would like to understand various aspects of the evolution of this warm dense mixture, including the state of the interface when the main shock arrives, the role of electric field generation at the interface, and the character and time scales for diffusive-like mixing. We present a molecular dynamics approach to model these processes, in which the ions are treated as classical point particles. Because we must reach extremely large length (many microns) and time scales (many picoseconds), we have also developed a simplified electronic structure model, which includes time- and space-dependent ionization levels, external heating and electron-ion energy exchange. Simulation results are presented and compared with other models and experiments.