Evidence of Relaxation and Spontaneous Transition to a High-Confinement State in High-β Steady-State Plasmas Sustained by Rotating Magnetic Fields

Evidence of relaxation has appeared, for the first time, in the extremely high-β, steady-state field-reversed configuration plasma states driven by rotating magnetic fields (RMF) in the translation, confinement, and sustainment experiment. The plasma self-organizes into a near-force-free state in the vicinity of the magnetic axis, with significant improvement in confinement. Associated with this change in magnetic topology is the appearance of an axial RMF component; this would, in turn, generate a current drive in the poloidal direction, thus sustaining the magnetic helicity. A newly developed two-dimensional 'equilibrium-lite' model is employed to analyze the magnetic properties of the final high-confinement state, and shows a large q and a significant magnetic shear in the core