Three-dimensional particle simulation of ion temperature gradient mode

Gyrokinetic particle simulations have proven to be a useful method for studying low frequency waves such as drift waves and the associated transport which may be responsible for the anomalous particle and energy transport in tokamaks. One can perform particle simulations with time steps longer than the cyclotron period and fewer particles than in conventional particle simulations because cyclotron motion of particles and fluctuations in the cyclotron frequency range are analytically eliminated while the finite Larmor radius effects are retained. At present, however, it still takes 50 to 100 hours of CPU time on a single processor of the Cray-2 to follow several oscillations of drift waves with a three-dimensional gyrokinetic electrostatic slab code. Clearly, it is necessary to improve the efficiency further. One approach to further efficiency gain is use of a massively parallel computer, and the other is to devise new algorithms that may allow even larger time steps in the simulation. The authors report their efforts and progress based on the first approach with a three-dimensional electrostatic slab code originally developed by Sydora. The goal is first to port the three-dimensional code to the Connection Machine-2, and then use the improved version to study ion temperature gradient mode with more realistic parameters such as scale lengths than have been used so far. The code at present employs adiabatic electrons and makes use of a multiple-scale expansion. The preliminary results indicate that the CM-2 code when run on 64k processors is 2 to 4 times faster than the Cray-2 code on a single processor. Further work is in progress to optimize the CM-2 code. They also present progress on implementation of the same three-dimensional code on a 128-node BBN TC2000. They use the PFC/PCP split-join parallel programming system, and they employ methods developed in their porting of a one-dimensional conventional PIC code to the machine. 2 refs