NONLINEAR ION BERNSTEIN WAVE HEATING EXPERIMENT IN THE WT-3 TOKAMAK

Ion Bernstein wave (IBW) heating at ion cyclotron half-harmonic freque ncies was performed in hydrogen (H) discharges in the WT-3 tokamak. Th e bulk ion temperature increase was measured by a charge exchange anal yser and a spatially scanning polychrometer. The latter diagnostics ca n provide radial ion-temperature profiles. The incremental ion tempera ture has shown a peak at the exact location where the IBW frequency om ega equals 3/2 of the ion cyclotron frequency, indicating the nonlinea r direct acceleration of H ions. The wave electric field was measured by a Langmuir probe in the scrape-off layer. The electric field at the second harmonic of the excited IBW frequency was observed to vary dep ending on the power level and the toroidal magnetic field. These exper imental results are compared with the theoretical prediction of nonlin ear IBW damping. The measured dependences of the ion heating and the w ave amplitude at 2omega on the toroidal magnetic field are in reasonab le agreement with the prediction.