A New Version of the Dipole Expansion Scheme

摘要

The report describes a modified version of the dipole expansion technique for particle simulation of plasmas. In this version the field calculations do not take significantly longer than in nearest-grid-point calculations. This is particularly important in two- and three-dimensional simulations. Also discussed is an optimization of the coding, particularly for the operations that must be done for each particle (computing its contribution to the charge density and updating its position and velocity). For example, this optimization has given a one-dimensional, nearest-grid-point code (lowest order in the multipole expansion scheme) that takes about 1.8 microsec/particle on the IBM 360/91. Finally, the value of the dipole correction is determined by comparing dipole and nearest-grid-point simulations. (Author)