Feasibility Study of the Poloidal Current Drive by Axial Neutral Beam Injection into a Field-Reversed Configuration

In order to generate a toroidal field in field-reversed configuration (FRC) plasma, a poloidal current drive by axial neutral beam injection (NBI) is investigated analytically and numerically. Species of neutral beam particle are hydrogen and helium. Feasibility for two types of injection geometry, injection along the geometric axis and to near the separatrix, is tested. Since all beam ions are lost directly through the device end, more than 12-kA beam current is needed to improve electron confinement near the separatrix. On the other hand, it is found that low energy (about 200 eV) beam ions can be confined for injection to near the separatrix. Present calculation of the beam ion orbit shows possibility of poloidal current drive and toroidal field generation by axial NBI into an FRC plasma.