FIVEFOLD CONFINEMENT TIME INCREASE IN THE MADISON SYMMETRICAL TORUS USING INDUCTIVE POLOIDAL CURRENT DRIVE

Current profile control is employed in the Madison Symmetric Torus [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] reversed field pinc h to reduce the magnetic fluctuations responsible for anomalous transp ort. An inductive poloidal electric-field pulse is applied in the sens e to fatten the parallel current profile, reducing the dynamo fluctuat ion amplitude required to sustain the equilibrium. This technique demo nstrates a substantial reduction in fluctuation amplitude (as much as 50%), and improvement in energy confinement (from 1 to 5 ms); a record low fluctuation (0.8%) and record high temperature (615 eV) for this device were observed simultaneously during current drive experiments. Plasma beta increases by 50% and the Ohmic input power is three times lower. Particle confinement improves and plasma impurity contamination is reduced. The results of the transient current drive experiments pr ovide motivation for continuing development of steady-state current pr ofile control strategies for the reversed field pinch. (C) 1997 Americ an Institute of Physics.