Kinetic Modeling of Magnetic Field Dynamics and Thermal Energy Transport in Inertial Fusion Energy Plasmas.

[摘要] In indirect-drive inertial-fusion experiments, a hohlraum converts laser energy into X-rays that heat an ablator material on a fuel capsule. The expansion of the ablator leads to implosion of the fuel capsule and fusion conditions in a hot spot, where alpha particles are produced and propagate a burn wave through the fuel. Accurate determination of the balance of energy fluxes in the hohlraum not only requires consideration of X-ray transport, but also needs careful treatment of electron transport, because laser energy is coupled primarily to the electrons in the plasma. The steep electron-thermal-energy gradients in this environment can lead to breakdown of diffusive heat-transport and introduce non-local effects. Additionally, the plasmas produced in such laser-plasma experiments are subject to the influence of self-generated magnetic fields. A kinetic formulation enables detailed calculations of thermal-energy transport and magnetic-field dynamics in these plasmas due to self-consistent inclusion of effects in electron transport that depend not only on details of the particle energy distribution but also on the electromagnetic fields in the plasma. The dissertation describes novel comparisons between Braginskii transport and kinetic modeling that quantify the importance of kinetic effects. In addition to the theoretical contributions and modeling results, the author was also responsible for the development of a ray-tracing module to model laser propagation.Through kinetic modeling, the heat flow near the laser heating region retains non-local effects. In the case of an externally applied magnetic field, non-local contributions to the Nernst effect increase the rate of field transport by the Nernst mechanism. The Nernst effect leads to significantly faster transport of the magnetic field to the hohlraum axis in comparison to field transport through plasma hydrodynamic motion only.The self-generated magnetic fields are oppositely aligned with respect to each other and and are subject to reconnection. The magnetic reconnection mechanism is, in this case, governed by heat flow that transports the magnetic field. This mechanism is prevalent in plasmas where the thermal energy density is higher than the magnetic energy density. Such an environment is present in hohlraums near the critical surface, where reconnection results in redistribution of the thermal energy.

[发布机构] University of Michigan

[效力级别] Magnetized Plasma Kinetic Simulation

[关键词] Inertial Confinement Fusion;Magnetized Plasma Kinetic Simulation;Electron Transport in Laser-produced Plasmas;Magnetic Field Generation;Physics;Science;Nuclear Engineering and Radiological Sciences