Session RP1 - Poster Session VIII.
POSTER session, Thursday afternoon, October 30
Fran Hill Southeast Exhibit Hall, ACC
JET operation with reverse B changes the NBI heating to counter injection, while the normal field has co-NBI. One consequence is to change NBI induced rotation and its effect upon MHD has been studied. Shorter sawtooth periods were obtained with counter-NBI. With co-NBI, the sawtooth period increased with power, while with counter-NBI, the sawtooth period reduced to a minimum at 4 MW. A candidate mechanism consistent with the salient features of this trend is the dependence of kinetic internal kink stabilization on sheared toroidal rotation and central energetic ion penetration in reverse B plasmas. ELMs and Washboard modes in high density ELMy H-mode plasmas, as well as edge MHD modes in the quiescent H-mode (QHM) regime were studied. Although the QHM was not obtained, an edge continuous n=1 mode (with several harmonics) was observed during ELM-free phases. The edge MHD features were similar to the "edge harmonic oscillation" of DIII-D and also similar to earlier JET counter-NBI experiments where the n=1 external kink (outer mode) was found to be more unstable than with co-NBI.