On Equilibrium of a Current-Carrying Toroidal Plasma. II. Experiments with the Model C Stellarator

A series of experiments with the Model C stellarator showed that a previously detected asymmetry in the device could be removed by applying such a magnetic field BT, transverse to the main confining magnetic field, that an inherent lack of closure of the flux lines of the confining field was removed. The symmetrized stellarator was then used to demonstrate that an equilibrium (discussed theoretically elsewhere) could be achieved in the plasma by applying a uniform magnetic field transverse to the plane of the stellarator. With current IOH flowing toroidally in the plasma, the tendency for the toroid to expand, due to the hoop force and the U-bend drift, is counterbalanced by the IOH × BT force. The observed transverse field required for equilibrium is in good agreement with the value predicted theoretically. Improvement at equilibrium of such plasma parameters as electron temperature, particle confinement time, and energy replacement time is demonstrated.