EXPERIMENTAL AND THEORETICAL STABILITY LIMITS OF HIGHLY ELONGATED TOKAMAK PLASMAS

Stability limits of highly elongated, D-shaped plasmas have been measu red in the TCV (tokamak a configuration variable) tokamak. It is found that the plasma current is limited by kink-type disruptions, preceded by magnetohydrodynamic (MHD) mode activity. The mode structure has be en analyzed using magnetic fluctuation and soft x-ray diagnostics. Mod e numbers, growth rates, and experimental stability limits are consist ent with ideal and resistive MHD models, based on measured plasma shap es and profiles. These results provide the first experimental confirma tion of previously predicted stability limits at high elongation, kapp a less than or equal to 2.58.