Influence of the plasma edge on tokamak performance

A number of edge plasma physics phenomena are considered to determine tokam ak performance: transport barrier, edge MHD instabilities and plasma flow. These phenomena are thought to be causally related: a spontaneous increase in the plasma flow (actually, its radial variation) suppresses heat and par ticle fluxes at the plasma edge to form a transport barrier; the edge press ure gradient steepens until limited by MHD instabilities, resulting in a te mperature pedestal at the top of the steep gradient region; a number of cor e transport models predict enhanced confinement for higher values of the te mperature pedestal. The article examines these phenomena and their interact ion.