Inward transport of energy during off-axis heating on the DIII-D tokamak

Inward transport of energy is observed on the DIII-D tokamak during off-axis electron cyclotron heating (ECH) experiments under a variety of operating conditions. Power balance analysis of steady state discharges shows that the electron heat flux can be negative (inward) interior to the ECH resonance location with a certainty of up to three times the experimental error bars. The ion heat flux is always positive (outward), as is the total heat flux. The electron heat flux becomes increasingly negative as the plasma density is increased. A detailed error analysis of the energy transport is performed as well as an independent verification of the measured plasma profiles. These results contradict purely diffusive models of radial heat transport, since energy in the electron channel is observed to flow in the direction of increasing temperature