Performance and optimization of direct implicit particle simulation

Abstract

Performance characteristics obtained from particle simulations using the direct implicit method are presented. Parameter studies of simulation behavior for an expanding plasma slab have been made determining code performance as functions of ω pe Δt and Δx λ De , where ω pe is the plasma frequency, λ D e , is the electron Debye length, Δt is the time step, and Δx is the grid spacing. A range of time steps ω pe Δt ⩽ 200 and mesh sizes Δx λ rmDe ⩽ 100 were explored. Accurate results for low-frequency phenomena resolved by the time step can be obtained without limit on ω pe Δt in this range (and higher) with a careful choice of algorithms. This choice of algorithms defeats a potential nonlinear instability that occurs when ( ω pe Δt) 2 exceeds the number of particles per cell.