Structural formation induced by electrode biasing in tokamaks: Accessibility to a double-peaked E_r shear layer

Electrode biasing is one of the methods for controlling the radial electric field externally and can induce a transition to an improved confinement state. We have shown theoretically that a solitary E_r structure with a single peak is formed selectively by electrode biasing in our previous works. That a multiple-peaked E _r structure, which has a wider E × B flow shear region, can exist stably was also derived. In this paper, accessibility to a double-peaked E_r structure is demonstrated theoretically by double electrode biasing with an applied voltage ramp-up.