Electron heat transport studies

Electron transport in fusion plasmas is intensively studied in coordinated experiments and great progress in physics understanding has been achieved during the past years. A threshold in normalized gradient explains most of the observations, both in steady-state and transient conditions. The results convincingly suggest that trapped electron modes (TEM) dominate electron transport at low and moderate collisionality, with electron heating. The stabilization of these modes at high collisionality predicted by theory is found in the experiments. Electron transport is then driven by the ion temperature gradient modes. At low collisionality, if TEM are stabilized by negative shear and Shafranov shift effects, electron internal transport barriers may develop.