Steady-State Hollow Electron Temperature Profiles in the Rijnhuizen Tokamak Project

In the Rijnhuizen Tokamak Project steady-state hollow electron temperature ( $T_e$) profiles have been sustained with strong off-axis electron cyclotron heating, creating a region of reversed magnetic shear. In this region the effective electron thermal diffusivity ( ${\chi }_e^{\mathrm{pb}}$) is close to neoclassical in high density plasmas. For medium density, ${\chi }_e^{\mathrm{pb}}$ is lower than neoclassical and may even be negative, indicating that off-diagonal elements in the transport matrix drive an electron heat flux up the $T_e$ gradient.