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 promising candidate for improving confinement properties of a reversed field pinch. Ray-tracing calculations indicate that the wave will make a few poloidal turns while spiraling radially into a target zone inside the 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-dimensional resistive magnetohydrodynamic computation demonstrates that an additive poloidal current in this region will reduce the magnetic fluctuations and magnetic stochasticity.