NUMERICAL CALCULATION OF RADIAL Er PROFILES IN H-MODE TOKAMAK DISCHARGES BASED ON A REVISED NEOCLASSICAL THEORY

摘要

Under H-mode conditions a transport barrier is formed at the plasma edge characterized byrnsteep radial gradients of the plasma parameters just inside the separatrix. Gradient lengthsrnof the order of a few poloidal (main) ion Larmor radii are caused by a very localized strongrnnegative radial electric field accompanied by a strongly sheared electric drift velocity and arncorresponding largely reduced turbulence. H-mode discharges have been observed in a widerncollisionality range of the edge plasma. Although H-mode operation is also possible in the highrncollisionality regime of the thermal part of the edge plasma, a high energy tail of ions, leading torna loss-cone current into the scrape-off layer, seems to play an important role in the L-H transitionrn.