A massively parallel three-dimensional hybrid code for simulating ion-driven parametric instabilities

A massively parallel three-dimensional hybrid particle-in-cell (PIC) code, implemented on the CRAY-T3D, is presented. The code is based on a physical model described in a previous report where the electrons are modeled as an adiabatic fluid with an arbitrary ratio of specific heats gamma and the electromagnetic field model is based on a temporal Wentzel-Krammers-Brillouin (WKB) approximation. On a CRAY-T3D with 512 processors, the code requires about 0.6 mu s/particle/time step. The largest test problem performed with this code consists of a computational mesh of 4096 x 64 x 64 (16 million) cells, a total of 256 million particles, and corresponds to a plasma volume of 50 mu m x 20 mu m x 20 mu m (:approximately 150 lambda x 60 lambda x 60 lambda, where lambda is the laser's vacuum wavelength). We believe this code is the first PIC computational tool capable of simulating low-frequency ion-driven parametric instabilities in a large, three-dimensional plasma volume and offers a unique opportunity for examining issues that are potentially vital to inertial confinement fusion (ICF), e.g., nonlinear ion kinetic effects and their role in nonlinear saturation mechanisms in three dimensions. Test simulations of the self-focusing (SF) instability and of the self-focusing-induced deflection of a laser beam are presented. (C) 1998 Academic Press.