QN3D: A Three-Dimensional Quasi-Neutral Hybrid Particle-in-Cell Code with Applications to the Tilt Mode Instability in Field Reversed Configurations

摘要

The tilt mode instability of field reversed configurations (FRC) is discussed. Current numerical models do not properly explain the behavior of this mode. A particle-in-cell (PIC) model in cartesian coordinates is introduced with an explanation as to why it represents the physics of FRCs more closely. The model is presented by first simplifying Maxwell's equations using the Darwin limit. A final set of equations are derived by assuming the electrons to be an inertialess fluid with zero temperature. The PIC model is implemented in a FORTRAN code, QN3D. The major elements of this code are presented indicating the many techniques required for its optimization. Many of the major factors in optimization are dependent upon features of the Cray-2 Multiprocessor. Taking advantage of these new features is discussed in the text. Testing of the code is presented in three phases. First, single particle motion is analyzed. Next the normal modes are calculated and simulated. Finally, QN3D is applied to the rigid rotor problem. These tests indicate that the codes is suited to model plasma phenomena in the parameter regimes of interest. Lastly, two cases of the tilt mode problem are attempted. The results match current experiments and confirm initial hypothesis as to why other models are not adequate. (ERA citation 12:046996)