Long-pulse improved central electron confinement in the TCV tokamak with electron cyclotron heating and current drive

Current profile tailoring by electron cyclotron heating (ECH) and current d rive (ECCD) is used to improve central electron energy confinement in the T CV tokamak. Counter-ECCD on axis alone achieves this goal in a transient ma nner only. A stable scenario is obtained by a two-step sequence of err-axis ECH, which stabilizes magnetohydrodynamics modes, and on-axis counter-ECCD , which generates a flat or inverted current profile. This high-confinement regime, with central temperatures up to 9 keV (at a. normalized beta (N) s imilar to 0.6), has been sustained for the entire duration of the heating p ulse, or over 200 electron energy confinement times and 5 current redistrib ution times.