High internal inductance improved confinementH-mode discharges obtained with an elongation ramp technique in the DIII-D tokamak

High confinement mode (H-mode) discharges with peaked toroidal current density profile (high internal inductance, ${\mathit{l}}_{\mathit{i}}$) and improved confinement are obtained in the DIII-D tokamak by dynamically varying the current profile using a rapid elongation ramp technique. The confinement improvement increases with ${\mathit{l}}_{\mathit{i}}$ and persists in the presence of edge-localized modes. The plasma toroidal rotation and the corresponding radial electric field component also increase with the peakedness of the current density profile.