Coupling characteristics of the ridged waveguide for ICRF heating

Ion cyclotron range of frequencies (ICRF) heating using fast wave has been recognized one of the most promising auxiliary heating methods of a tokamak plasma. Although loop antennas have been widely employed as the coupling structure of the ICRF heating, a waveguide launcher is more favourable from the point of view of the reactor engineering. In this paper, we calculate coupling characteristics of the T-shaped ridged waveguide for the JT-60 plasma. It is found that the ridged waveguide is not suitable for JT-60 ICRF heating (120MHz). However, it must be noted that the coupling characteristics are improved by connecting a different impedance line on the head of the launcher or by using loaded waveguide launcher. (author)