Modeling of current profile evolution and equilibria in negative central shear discharges in the DIII-D experiment

摘要

Recent DIII-D advanced tokamak experiments with negative central shear (NCS) have resulted in operation at high normalized (beta), (beta)(sub N)=(beta)/(I/aB), to 4.2, confinement enhancement factors to H=4 (H=(tau)(sub E)/(tau)ITER-89P), and record neutron rates for DIII-D to 2.4X10(sup 16) neutrons/sec. These data were obtained during high triangularity, single and double null diverted operation with peaked (L-mode) and broad (H-mode) pressure profiles. We are modeling the spatial and temporal current profile evolution for these discharges using Corsica, a predictive 1-1/2 D equilibrium and transport code. Current profile evolution is self-consistently determined by including current diffusion resulting from current drive due to early neutral beam injection during the ohmic current ramp-up phase of the discharge and the bootstrap current drive associated with pressure profile evolution.