"Non-equilibrium physics in plasmas heated by intense laser beams
or otherwise"
Abstract:
Plasmas heated by lasers have important potential applications, for
nuclear fusion and as point-like ultra-short X-ray sources. As the laser
beams are very intense and short, the plasma is in a strongly
non-equilibrium state. Most notable among its properties are the
strongly non-Maxwellian electron energy distribution functions, caused
both by the heating itself and by very steep spatial gradients. These
non-Maxwellian distribution functions in turn affect strongly the energy
transport and the rates of ionization and excitation. Results from one
dimensional electron kinetic (Fokker-Planck) numerical simulations of
these physical effects will be shown, and some comparisons to
experiments. New formulas to correct classical fluid formulations were
developed, so that hydrodynamic codes may account for some of this
physics without the enormous computation cost of kinetic codes.
Similar physical effects also occur in other areas of plasma physics,
such as in the diverters of magnetic fusion devices, such as the planned
ITER experiment, but with a twist: the time and spatial scales are much
longer, but as the density is much lower, the collision times are also
longer, so that the dimensionless collisionality is again too small to
establish equilibrium. In the future, two dimensional simulations of
such non-equilibrium physics will require parallel computing.