Alfven resonance mode conversion in the Phaedrus-T current drive experiments: modelling and density fluctuations measurements

Summary form only given, as follows. Current drive experiments on the Phaedrus-T tokamak (R/sub maj/=92 cm, r/sub min/=25.5 cm, B/sub t/=.6/spl rarr/1 T, I/sub p/<100 kA, n/sub e0/: 1.2/spl times/10/sup 12//spl rarr/1.5/spl times/10/sup 13/ cm/sup -3/, H plasma) performed with a low field side two-strap fast wave antenna at frequencies below /spl omega//sub cH/(f/spl sim/7 MHz, P/sub RF/<400 kW, poloidal extent: /spl plusmn/30/spl deg/, strap separation: /spl sim/15 cm) show loop volt drops of up to 30% with strap phasing (0,/spl pi//2). RF induced density fluctuations in the plasma core have also been observed with a microwave reflectometer. It is believed that they are caused by kinetic Alfven waves generated by mode conversion of fast waves at the Alfven resonance. Correlation of the observed density fluctuations with the magnitude of the /spl Delta/V/sub loop/ suggest that the /spl Delta/V/sub loop/ is attributable to current drive/heating due to mode converted kinetic Alfven waves. The toroidal cold plasma wave code LION is used to model the Alfven resonance mode conversion surfaces in our experiments while the cylindrical hot plasma kinetic wave code ISMENE is used to model the behavior of kinetic Alfven waves at the Alfven resonance location. Initial results obtained from limited density, magnetic field, antenna phase, and impurity scans show good agreement between the RF induced density fluctuations and the predicted behavior of the kinetic Alfven waves.