ELECTRIC-FIELD IN THE EDGE LAYER OF FIELD-REVERSED CONFIGURATIONS

A particle-tracing routine is used to find the boundary surface of the confinement region in velocity space. This numerical boundary surface is then imposed on the distribution function to calculate the electric potential profile around the X point in field-reversed configurations (FRC's). The model eliminates the original assumptions of the fast loss of the unconfined particles and free end-throat electric field in deriving the analytical confinement criteria in the velocity-space particle loss (VSPL) model. Electric potential profiles over the whole region with different particle-tracing times are presented. According to the calculated results, a new hypothetical electrostatic confinement in the edge layer is proposed. Effects resulting from this electrostatic confinement are investigated. It is found that several physical issues in the edge layer can be explained by this hypothetical electrostatic confinement.