Performance of the 1 MW, 110 GHz, 10 s gyrotrons recently installed in the DIII–D ECH system

ECH power has proven capabilities for both heating and current drive in energetic plasmas. For the second phase of ECH power on DIII–D, there will be three 1 MW sources added to the existing three systems for a total power generating capacity of 5.1 MW. This upgrade is based on the use of the single disc chemical vapor deposition (CVD) diamond window, 1 MW diode gyrotron, recently developed by CPI. All gyrotrons are connected to the tokamak via a low-loss, windowless, evacuated transmission line system, using circular corrugated waveguide for propagation in the HE11 mode. Each waveguide system incorporates an in-vessel two-mirror launcher. The newest launcher can steer the rf beam poloidally from the center to the outer edge of the plasma and toroidally for either co- or counter-current drive. An overview of the total system, its integration with the DIII–D tokamak, and recent results will be discussed. The various new aspects of the upgrade ranging from building modifications to the use of the new steerable launcher will also be addressed.