Nonlinear stability of field-reversed configurations with self-generated toroidal field

The field-reversed configuration (FRC) is a high-beta compact toroidal plas ma confinement scheme in which the external poloidal field is reversed on t he geometric axis by azimuthal (toroidal) plasma current. A quasineutral, h ybrid, particle-in-cell (PIC) approach [Y. A. Omelchenko and R. N. Sudan, P hys. Plasmas 2, 2773 (1995)] is applied to study long-term nonlinear stabil ity of computational FRC equilibria to a number of toroidal modes, includin g the most disruptive tilt mode. In particular, a self-generated toroidal m agnetic field is found to be an important factor in mitigating the instabil ity and preventing the confinement disruption. This is shown to be a unique FRC property resulting from the Hall effect in the regions of vanishing po loidal magnetic field. The instability-driven toroidal field stabilizes kin k formation by increasing the magnetic field energy without destabilizing c urvature-driven plasma motion. Finally, the tilt instability saturates due to nonlinear, finite Larmor radius (FLR) effects and plasma relaxation to a quasisteady kinetic state. During this transition the FRC is shown to diss ipate a substantial amount of initially trapped flux and plasma energy. The se effects are demonstrated for kinetic and fluid-like, spherical and prola te FRCs. (C) 2001 American Institute of Physics.