Processes driving non-Maxwellian distributions in high energy density plasmas

摘要

The purpose of this thesis is to explore the driving of non-Maxwellian distributions of particles in high energy density plasmas in a few select cases, with particular reference to efforts to produce a net gain in energy via inertial confinement fusion (ICF). ududNon-Maxwellian distributions are typically short-lived, as distributions are forced toward equilibrium by collisions, and are rarely static as a net transfer of energy must occur to sustain them. This makes non-Maxwellian distributions challenging to study with conventional approaches to plasma physics. The strategy adopted in this work to understand their evolution, and their effects, is a kinetic approach in which particles are individually accounted for.ududThe specific cases presented are that of degenerate electrons during the heating of the cold fuel shell in hotspot ignition schemes, ion-ion inverse bremsstrahlung absorption of laser radiation, and large-angle Coulomb collisions. New computational algorithms based on the Monte Carlo technique are presented, and are capable of modelling the salient aspects of the phenomena explored. Important results which form part of this thesis include that conventional models underestimate degenerate electron temperatures long after the plasma ceases to be degenerate, that it may be possible to induce temperatures of keV in light-ion species with high power, short pulse lasers, and that consideration of large-angle collisions changes interactions in a plasma in several significant ways. Of most interest are the ability of large-angle collisions to decrease equilibration times, drive athermal tails on distribution functions, and increase the overall yield from fusion reactions relative to small-angle only simulations.