Installation and Testing of a 110 GHz Gyrotron With Depressed Collector Potential on the DIII-D Tokamak

A single stage depressed collector gyrotron has been installed for testing on the DIII-D tokamak. The tube has operated at the 1.25~MW level at 44\% efficiency for short pulses and at 0.5~MW for 10~s pulses at CPI and now is being tested to full parameters at DIII-D. A two-stage mode conversion dummy load has been built to handle the higher ultimate power from this gyrotron for pulses up to 5~s in length. Modifications to the high voltage power supply system were required to provide 30~kV depression and sequencing of the application of the voltages.