Hybrid PIC acceleration schemes for discharges

Summary for only given, as follows. Kinetic simulation of plasmas in which equilibrium occurs over ion timescales poses a computational challenge due to the disparate timescales of the electron plasma frequency (/spl sim/10/sup 9/), the ion plasma frequency (/spl sim/10/sup 7/), and the ionization frequency (/spl sim/10/sup 7/). Hybrid electrostatic PIC algorithms are presented in which the electrons reach thermodynamic equilibrium with the ions each time step. There are three different approximations for the electrons. First, the nonlinear Boltzmann relationship for the electrons can be applied to the bulk of a plasma. Second there is a truncated Maxwellian which is used in undriven sheaths; this approximation truncates the electron distribution at the wall potential. The last method used the steady-state electron distribution function in a DC electric field, with elastic collisions between electrons and neutral gas atoms. The collision frequency, /spl nu//sub m/(/spl upsi/), can be a tabulated or fitted function; the method is implemented using argon cross-sections. These approximations neglect effects faster than the ion time-scales, decreasing the computer time used by over an order of magnitude; however, they increase the complexity of the boundary conditions, and the simulation is no longer self-consistent. Theoretical ramifications of these approximations are examined, and results are compared with full PIC simulations of undriven sheaths, ion acoustic waves and DC discharges (PDP).