THERMAL-WAVE STUDIES OF ELECTRON-TRANSPORT USING MODULATED ECRH

Modulated ECRH has been used to study electron thermal transport in DITE. In most cases the spatial structure of the thermal waves produced is consistent with a simple diffusive transport model in which the heat flux is proportional to the electron temperature gradient, q = -ne?e ?Te. At low density (ne ? 1019 m-3) the values of electron thermal diffusivity deduced from modulation experiments (?emod) are ? 2.5 m2.s-1, similar to the values deduced from power balance analysis (?ePB and sawtooth heat pulse propagation (?est). At higher density (ne ? 3 × 1019 m-3) the interpretation of the modulation data is sensitive to details of the ECRH power deposition profile. The high density data are fitted best by assuming that approximately 30% of the ECRH power is deposited with a broad profile with the remainder more localized, in qualitative accordance with ray tracing code predictions. The values of ?emod deduced are then ? 1.3 m2.s-1, again similar to the values of ?ePB and ?est