INTERNAL ELECTRIC-FIELD STRUCTURE OF LAUNCHED FAST MAGNETOSONIC WAVESIN THE DIII-D TOKAMAK

Results are obtained, for the first time in a major tokamak plasma, of the spatial electric field structure of a launched fast magnetosonic wave (FW). The FW launch directionality necessary for current drive ha s been confirmed at a position close to the FW antenna. The FW electri c field profile is determined using X-mode reflectometry. Electric fie ld profiles, calculated using a full-wave numerical code, exhibit many features common to the experimental results. However, differences rem ain regarding density dependence that suggest alternative damping mech anisms may exist.