Studies of the New Series of Gyrotrons Installed in DIII-D Electron Cyclotron Heating and Current Drive System*

The DIII-D Electron Cyclotron Heating and Current Drive system (ECH/ECCD) recently added two 110 GHz gyrotrons in a new series produced by Communications and Power Industries, bringing the total number of installed gyrotrons to four. The performance of the new gyrotrons was studied. One of the new gyrotrons supports plasma experiments together with two other gyrotrons, while the other was installed and is in the process of being conditioned to long pulse and high power. We are presenting the results of the measurements of the generated frequency versus time and voltage, peak power density in the collector (less than 600 W/cm² limit), power loss in the collector support (less than 20 kW limit) and azimuthal distribution, quality of the generated RF beam, and mode content in the transmission line. The infrared (IR) image processing for mode content measurement was optimized.