Numerical simulation of ion rings and ion beam propagation

This thesis presents the development of numerical simulation techniques for studying the physics of ion beams and rings in a background plasma as applicable to certain problems in magnetic and inertial confinement fusion. Two codes have been developed for these purposes: RINGA and CIDER. The 2 and 1/2-dimensional (r,z,v/sub r/, v/sub theta/, v/sub z/, par. delta/par. delta theta = 0) particle code RINGA follows the trajectories of ions in their self-consistent magnetic field. The code assumes strict charge neutrality and admits currents only in the azimuthal direction, i.e., PHI = J/sub r/ = J/sub z/ = 0. The injection and resistive trapping of ion rings has been studied with RINGA. The number of particles trapped as a fraction of the total number injected N is found to be strongly dependent upon (1) N (in the range 2.85 x 1016 - 3.99 x 1017) and (2) mirror ratios in the system (1.05 to 1.14), and more weakly dependent upon (3) wall resistance per unit length (0.72 Ω/cm - 1.80 Ω/cm) and (4) beam divergence (00 to 60). Fractions of trapped particles in excess of 0.9 have been observed. Modifications to RINGA to include finite pressure of confined plasma and beam ion-electron slowing down collisions are discussed. Finite plasma pressure leads to a diamagnetic current which increases the field reversal factor in ion ring equilibria, while causing the closed flux surfaces to expand outward