Observation of Ion-Cyclotron-Frequency Mode-Conversion Flow Drive in Tokamak Plasmas

Strong toroidal flow (V_ϕ) and poloidal flow (V_θ) have been observed in D-³He plasmas with ion cyclotron range of frequencies (ICRF) mode-conversion (MC) heating on the Alcator C-Mod tokamak. The toroidal flow scales with the rf power P_rf (up to 30  km/s per MW), and is significantly larger than that in ICRF minority heated plasmas at the same rf power or stored energy. The central V_ϕ responds to P_rf faster than the outer regions, and the V_ϕ(r) profile is broadly peaked for r/a≤0.5. Localized (0.3≤r/a≤0.5) V_θ appears when P_rf≥1.5  MW and increases with power (up to 0.7  km/s per MW). The experimental evidence together with numerical wave modeling suggests a local flow drive source due to the interaction between the MC ion cyclotron wave and ³He ions.