Abstract. The H-mode like discharges induced by tangential compact torus (CT) injection in the STOR-M tokamak and by other techniques, such as by a short current pulse and electrode/limiter biasing, are commonly characterized by an increase in the electron density, significant reduction in the H radiation level, and steepening of the edge density profile. The H-modes induced by negative biasing and edge heating via a short current pulse result in large negative electric potential biasing, formation of a strong poloidal velocity shear, and slowdown of the toroidal flow. In contrast, in the H-modes induced by positive biasing and CT injection, only moderate positive electric potential biasing occurs. Formation of a strong poloidal velocity shear is absent, but the toroidal flow velocity increases. A plausible mechanism that does not require strong velocity shear itself to suppress the long wavelength turbulence is attributed to the stabilizing role of the curvature in the toroidal velocity profile.
IAEA 2001