THERMAL-WAVE STUDIES OF ELECTRON-TRANSPORT USING MODULATED ECRH

Modulated ECRH has been used to study electron thermal transport in DI TE. In most cases the spatial structure of the thermal waves produced is consistent with a simple diffusive transport model in which the hea t 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 1 0(19) m(-3)) the values of electron thermal diffusivity deduced from m odulation 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 den sity ((n) over bar(e) similar or equal to 3 x 10(19) m(-3)) the interp retation of the modulation data is sensitive to details of the ECRH po wer deposition profile. The high density data are fitted best by assum ing that similar to 30% of the ECRH power is deposited with a broad pr ofile with the remainder more localized, in qualitative accordance wit h 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 o f chi(e)(PB) and chi(e)(st).