COMMISSIONING AND OPERATION RESULTS OF 110 GHZ ECH SYSTEM IN KSTAR

A 110 GHz GYCOM gyrotron, which was loaned from DIII-D in General Atomics (GA) including a matching optics unit (MOU) and a magnet, was successfully commissioned and used for the second harmonic ECH-assisted startup in 2009 Korea Superconducting Tokamak Advanced Research (KSTAR) campaign. The gyrotron was aligned at the magnetic field axis of the magnet by adjusting aligners on top and bottom flanges of the magnet during the installation procedures. The measured images of the output beam profile at the window using a burn paper showed a good agreement with those measured in DIII-D. The maximum available RF power was just about 250 kW, which was measured at the terminal dummy load, due to the limitation of the existing power supply of which nominal beam voltage and current were 63 kV and 20 A, respectively. The 110 GHz, 250 kW EC wave, which corresponds to the second harmonic resonance wave to the toroidal field of 2 T, was injected to KSTAR for the plasma start-up and current ramp-up. The plasma start-up was successfully and reliably achieved through the second harmonic ECH pre-ionization. The injection mode was the X-mode with oblique launch angle to the toroidal magnetic field. This paper reports the initial commissioning and operation results of the 110 GHz ECH system. Moreover, the experimental results of the ECH-assisted start-up during the 2009 KSTAR campaign are presented and discussed.