Lower hybrid current drive and antenna coupling experiments on TdeV

摘要

At a coupled RF power density of 50 MW/m~2, the LHCD system installed on TdeV has achieved record performance at 3.7 GHz. With TdeV's unique set of RF diagnostics, lower hybrid wave coupling was found to be in agreement with the antenna modelling code SWAN. Discrepancies exist at high RF power but the launched spectra do not seem to be affected. Strong toroidal asymmetries in power deposition on divertor and first wall components during LHCD were observed and characterized. A possible mechanism for the power dissipation is described. Current drive experiments have been performed and comparison with codes is presnted. Resutls from a set of diagnostics suggest that the radial profile of suprathermal electrons is broader than code predictions. Furthermore, the velocty distribution extends well beyond the N_II resonance energics permitted by the LH wave accessibility. Large current profile modifications (-0.4 <= DELTAl_i <= 0.2) in steady state have been obtained by tailoring the power deposition of the lH wave in TdeV. These profile modifications have an impact on energy ocnfinement, as W_e~KIN/W_e~RL increases with DELTAl_i.