Gridless electrostatic field solver for particle simulation codes in cylindrical geometry.

摘要

A new gridless electrostatic field solver which utilities Fourier decomposition in the azimuthal coordinate has been developed and tested. The scaling with the number of simulation particles is N log N. This algorithm has been implemented in the BUCKSHOT code, which originally used a direct summation algorithm with N(sup 2) scaling. The Fourier decomposition in the new algorithm is done about the center of mass of each species, thus nonlinear ion hose physics is included in the m = O mode. Higher order modes describe non-axisymmetric profile changes. The breakeven point between the new solver and the direct summation algorithm is about N = 64 particles per species when up to m = 2 Fourier modes are kept. For a typical ion hose simulation with 256 particles per species the new solver is faster by a factor of about 2.7. 8 refs., 11 figs.