Temporal fluid simulation of plasma particle and energy confinement in GAMMA 10/PDX pellet injection experiments

Abstract

The pellet injection experiment in the tandem mirror device GAMMA 10/PDX is simulated with a plasma fluid model based on the anisotropic ion pressure (AIP model). A neutral gas shielding (NGS) model is implemented to model the pellet ablation rate. It is suggested that the energy loss due to charge exchange reactions promotes the axial particle loss from the main confinement region, i.e., the central cell. It is also found that the axial particle loss and energy loss owing to charge exchange reactions are the main contributors to the reduction in the stored energy in the central cell. To investigate the reason for the promotion of particle loss due to the charge exchange reaction, we analyze the force balance on the ion fluid. It is found that the particle flux at the edge of the central cell is determined by the pressure-gradient force, electric field force (in the direction of loss), and the mirror force (in the direction of confinement). In addition, it is shown that the mirror force decreases its absolute value more than the pressure-gradient force due to the energy loss caused by the charge exchange reaction, which enhances the particle loss from the central cell.