Performance, heating and current drive scenarios of ASDEX Upgrade advanced tokamak discharges

Abstract

Various approaches to high performance and steady state operation are presented. Strong neutral beam heating in the current ramp leads to internal transport barriers (ITBs) in conjunction with negative central magnetic shear. To avoid the destabilization of external kink modes this regime is limited to L mode edge operation with βN < 1.7. In high poloidal β, βp, discharges, full non-inductive current drive has been achieved transiently. At Greenwald density, values of βp = 3.1, βN = 2.8 and HITER89-P = 1.8 have been reached simultaneously. In plasmas with ITBs and L mode edge, additional ECRH and ECCD facilitates high core confinement with Te ≈ Ti. Central ECCD has been applied in low density low current discharges. For ECCD in the co-current direction a current drive fraction of 82% is calculated. In the case of counter-ECCD, negative central shear with qmin > 1 leads to the formation of an electron ITB.