Initial results from the multi-megawatt 110 GHz ECH system for the DIII-D tokamak

Summary form only given, as follows. The first of three MW-level 110 GHz ECH systems was operated on the DIII-D tokamak in late 1996. Two additional units will be commissioned during 1997. Each gyrotron is connected to the tokamak by a low-loss-windowless evacuated transmission line using circular corrugated waveguide carrying the HE/sub 11/ mode. The microwave beam spot is well focused with a spot size of approximately 6 cm and can be steered poloidally from the center to the outer edge of the plasma. The initial operation with about 0.5 MW delivered to a low density plasma for 0.5 s showed good central electron heating with peak temperature in excess of 10 keV. The system status is described and the initial physics results are presented, including heating efficiencies, power deposition profiles, and overall system performance.