DIII-D Electron Cyclotron Heating and Current Drive Systems Status and Plans for Expansion to 10 Gyrotrons

The ECH/ECCD systems on DIII-D currently comprise five non-depressed and one depressed collector 110 GHz CPI gyrotrons. The combined total injected power is 3.4 MW into the DIII-D plasma via four dual-launchers with steerable mirrors that are mounted above the mid-plane at 240°, 255°, 270° and 285° in DIII-D port coordinates. A seventh CPI gyrotron is expected later this year to bring the total injected power to approximately 4 MW. An 8-gyrotron (8-G) project is ongoing to install two new Thales TH1512 depressed collector 117.5 GHz gyrotrons (replacing one) that will use existing waveguides and launchers to establish eight systems with injected power of approximately 5.2 MWs by 2026. Another 10-gyrotron (10-G) project is ongoing to install two additional ITER-like 1 MW gyrotrons from Kyoto Fusioneering. These operate at 104, 137 and 170 GHz, though this variant will be tuned for optimal power at the 104 and 137 GHz frequencies, closer to the optimum frequencies for DIII-D rather than the ITER 170 GHz need. Two new transmission lines and dual-launcher will inject power from below the mid-plane at 255° symmetrically with the existing launchers. The 8-G and 10-G projects will bring the DIII-D ECH/ECCD capability to 10 systems with injected power approaching 7 MW by the beginning of the FY2026 plasma experimental campaign. We describe the latest status of operational systems and power calibration method; along with the plans and progress of the expansion projects.