Effect of poloidal density asymmetries on shear flows and radial electric field at the plasma edge

Abstract

Mass flows and radial electric field driven by edge poloidal density asymmetries can be used as a highly effective control mechanism for the edge and thus the global confinement in tokamaks. The underlying physics can be demonstrated entirely within a simple magnetohydrodynamic equilibrium model that addresses the poloidal pressure asymmetry self-consistently. As an example, strong dependence of the low to high transition power threshold on the magnetic topology, an experimental observation still poorly understood, can be easily explained within this framework. Similar arguments indicate that the ITER fueling ports above the midplane may lead to higher input power requirements.