A Change of H-Mode Dynamics due to Edge Electric Field Shear

Abstract

An extended model theory for Edge Localized Modes (ELMs) is presented with inclusion of the effects of the radial electric field shear, E_r^′, for high temperature plasmas in tokamaks. The dynamic model consists of an electric bifurcation model for the L/H transition, which contains a hysteresis characteristic due to E_r^′, and of a dynamic transport equation for the plasma gradient parameter. The self-generated oscillation is found to occur even if the effects of E_r^′ are included: in addition to those of the radial electric field.The condition for the occurrence of a self-generated oscillation is examined. The wider region in the parameter space is found for the case with a negative electric field shear than for the case with a positive one.