Critical velocity shear flow for triggering L-H transition and its parametric dependence in the HL-2A tokamak

The dynamics of shear flows and turbulence in the pedestal region during the L-H transition have been studied in the HL-2A tokamak. It has been shown that ion diamagnetic shear flow plays a key role in triggering the L-H transition. A critical E x B velocity shear has been found for the L-H transition. Statistical results indicate that the velocity shear threshold is independent of the plasma density and the total heating power.