Inward energy transport in tokamak plasmas

Abstract

Peaked electron temperature profiles are observed in the DIII-D tokamak during electron cyclotron heating despite the fact that >75% of the input power is deposited significantly off axis. Power balance analysis indicates a net inward flow of energy for electrons. An inward energy flow is not compatible with diffusive or critical gradient models. A time-dependent perturbation technique is employed to estimate the conductive loss and the nondiffusive part of the energy transport. The nondiffusive component of the transport appears only at radii smaller than that of the heating location.