Direct comparison between circularly and linearly polarized RF field in ICRF heating of a toroidal plasma

ICRF heating of a toroidal plasma is performed using slow waves generated by the m = +-1 circularly polarized rf field and the m = +-1 linearly polarized rf field which is, in general, conventionally employed. From direct comparison between the two field-modes on wave generation, ion heating efficiency, and enhanced plasma loss, it is revealed that the circularly polarized field is far more effective than the linearly polarized field in both achieving higher heating efficiency and reducing enhanced plasma loss. The ion heating by the linearly polarized field is accompanied with the enhanced cross-field plasma loss, which may be qualitatively explained by the ion convection resulting from the ponderomotive force of the applied rf field. (author)