RF Helicity Injection and Current Drive

The relation between RF-driven current and wave helicity is analytically and numerically studied for a tokamak plasma. The helicity conversion coefficient from the wave to the plasma is generally obtained and numerically examined for the waves in the range of ion cyclotron frequency. The wave propagation equation which includes kinetic effects is solved as a boundary-value problem with one-dimensional inhomogeneities. It is shown that the wave helicity well satisfies the continuity equation. We confirm that the RF-helicity injection is not an identical phenomenon of the reduction of the one turn loop voltage due to the RF-driven current