Broadening of the scrape-off-layer by a plasma convection induced by toroidal asymmetries of the divertor plates and the gas-puff

Abstract

In the open field line region of the scrape-off layer (SOL), plasma potential is to a considerable degree determined by the boundary conditions on the divertor plates. By introducing toroidal asymmetries of the surface relief of the divertor plates or of their chemical composition, one can create toroidally asymmetric potential variations over the whole SOL and thereby induce convective plasma motion. This motion should lead to a broadening of the SOL and to reduction of heat load on the divertor plates. Convective motion can be induced also by a toroidally asymmetric gas-puff. In the present paper we consider all these techniques and evaluate the possible increase in the cross-field transport.