Steady-state hollow electron temperature profiles in the Rijnhuizen Tokamak Project.

In the Rijnhuizen Tokamak Project steady-state hollow electron temperature ({ital T}{sub {ital 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}{sub {ital e}}{sup {ital pb}}) is close to neoclassical in high density plasmas. For medium density, {chi}{sub {ital e}}{sup {ital 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 {ital T}{sub {ital e}} gradient. {copyright} {ital 1996 The American Physical Society.}