Edge electric-field profiles of H-mode plasmas in the JFT-2M tokamak

Abstract

The structure of the edge radial electric field ${\mathit{E}}_{\mathit{r}}$ inferred from the poloidal rotation velocity is compared with that of the particle and thermal transport barrier for H-mode plasmas in JFT-2M. Both ${\mathit{E}}_{\mathit{r}}$ and its gradient \ensuremath{\partial}${\mathit{E}}_{\mathit{r}}$/\ensuremath{\partial}r in the thermal transport barrier are found to become more negative at the L-H transition. On the other hand, \ensuremath{\partial}${\mathit{E}}_{\mathit{r}}$/\ensuremath{\partial}r is more positive outside of the separatrix. The shear of the radial electric field and poloidal rotation velocity in the H mode is localized within the order of an ion poloidal gyroradius near the separatrix, in the region of ion collisionality ${\ensuremath{\nu}}_{\mathrm{*}\mathit{i}}$\ensuremath{\approxeq}20--40.