ICRF CURRENT DRIVE AND HELICITY INJECTION

The relation between RF-driven current and wave helicity is analytically and numerically studied for a tokamak plasma. The helicity conversion ratio from the wave to the plasma is discussed and numerically examined for the waves in the range of ion cyclotron frequency in JT-60 plasma. The wave propagation equation which includes kinetic effects is solved as a boundary-value problem with one-dimensional inhomogeneities. Both the RF helicity-driven current and the RF momentum driven current are calculated. It is shown that the efficiency of the current drive by the wave helicity is small compared with the conventional scheme for the fast wave excitation of the present-day plasma parameters.