Development of linear motion antenna and 110 GHz gyrotron for 7 MW electron cyclotron range of frequency system in JT-60SA tokamak

A 110 GHz gyrotron featuring an improved mode convertor has started the conditioning operation aiming at 1 MW for 100 s as a power source of electron cyclotron range of frequency (ECRF) heating and current drive system in JT-60SA (super advanced) tokamak, by improving the original gyrotron achieved 1 MW for 5 s and 1.5 MW for 1 s in JT-60U. Remarkable reduction of diffraction loss was confirmed by temperature rise of the cooling water. An output power of 1 MW for 10 s was achieved in July 2009 and conditioning is ongoing. An unconventional linear motion (LM) antenna is designed having a linearly movable flat mirror and a fixed curved mirror for millimeter wave beam steering to control the position of heating or current drive in the plasma. This method has the advantage of reliable feeding of cooling water to the mirrors comparing to the conventional antenna having rotatable mirror. Low power measurement of the mockup antenna which is designed to be installed in 0.48 m times 0.48 m port showed satisfactory performance, e.g., 80 deg of steering range, 0.1 m of beam radius at the EC resonance in the plasma.