Gyrokinetic Particle Simulation of a MultiIon Species Plasma.
Abstract
Particle and energy transport are studied for fusion plasmas using gyrokinetic particle simulation techniques. Interactions between plasma waves and plasma particles are considered in the lowfrequency limit (omega<< eB/m_{i}c). The ion temperature gradient (ITG) driven mode is simulated in the hot collisionless core tokamak plasma for both slab and toroidal geometries. Excellent agreement is found between the linear stage of the simulation and the complex eigenfrequencies and eigenmode structures predicted by linear gyrokinetic theory in the slab geometry. A nonlinear calculation of the saturation level of the electrostatic potential, Phi, in the 2D sheared slab geometry based on nonlinear mode coupling theory is carried out. Reasonable agreement is found between the numerical simulation and the predicted saturation level. GyroBohm scaling is observed for the thermal diffusivity, chi_{i} , in the 3D sheared slab geometry in contrast to the nongyroBohm scaling which has been observed in the full cross section toroidal simulation. Multiple ion species are included selfconsistently in the simulation. Impurity effects on the bulk ion modes are considered for Z _{eff}<=q2 for various impurity profiles. Significant concentrations of impurity ions are found to reduce the saturation level of Phi and the energy transport when the impurity density profile is inwardly peaked or flat. The inward pinch of impurity ions due to the ITG mode is investigated and found to be driven by the parallel acceleration of the impurity ions along the magnetic field. In the 3D sheared slab geometry it is determined that chi_ {i} for a pure tritum plasma is larger than chi_{i} for a pure deuterium plasma. In contrast, in the full cross section toroidal simulation it is found that chi _{i} for a pure tritium plasma is smaller than chi_{i} for a pure deuterium plasma. Deuteriumtritium plasmas are simulated in toroidal geometry using a wide range of D: T ratios and, for a given DT plasma, it is found that chi_{D} is larger than chi_{T}. It is also found that increasing T_{i }/T_{e} has a strong stabilizing effect on the ITG instability in toroidal geometry and reduces the saturation level of chi_ {i}. Finally, parallel algorithms for gyrokinetic particle simulation are discussed for the Cray C90 supercomputer and the TMC CM200 and CM5.
 Publication:

Ph.D. Thesis
 Pub Date:
 1994
 Bibcode:
 1994PhDT.......233S
 Keywords:

 Physics: Fluid and Plasma