LOWER-HYBRID POTENTIAL CURRENT DRIVE FOR FLUCTUATION REDUCTION IN A REVERSED-FIELD PINCH

Current drive using the lower-hybrid slow wave is shown to be a promis ing candidate for improving confinement properties of a reversed field pinch. Ray-tracing calculations indicate that the wave will make a fe w poloidal turns while spiraling radially into a target zone inside th e reversal layer. The poloidal antenna wavelength of the lower hybrid wave can be chosen so that efficient parallel current drive will occur mostly in the poloidal direction in this outer region. Three-dimensio nal resistive magnetohydrodynamic computation demonstrates that an add itive poloidal current in this region will reduce the magnetic fluctua tions and magnetic stochasticity.