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 = -n(e) chi(e) del T-e. At low density ((n) over bar(e) similar or equal to 10(19) m(-3)) the values of electron thermal diffusivity deduced from modulation experiments (chi(e)(mod)) are similar or equal to 2.5 m(2).s(-1), similar to the values deduced from power balance analysis (chi(e)(PB)) and sawtooth heat pulse propagation (chi(e)(st)). At higher density ((n) over bar(e) similar or equal to 3 x 10(19) 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 similar to 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 chi(e)(mod) deduced are then similar or equal to 1.3 m(2).s(-1), again similar to the values of chi(e)(PB) and chi(e)(st).