Study of ohmic loss of high power polarizers at 170 GHz for ITER

Kashiwa, Yoshinori*; Saigusa, Mikio*; Takahashi, Koji; Oishi, Shimpei*; Hoshi, Yuki*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi

An electron cyclotron current drive (ECCD) system is, especially, necessary to suppress the neoclassical tearing mode instability in ITER. The polarizers are one of the important components in the ECCD system, to generate optimum polarization for an efficient ECCD. An ohmic loss of the polarizers is evaluated, when 170GHz, high power RF wave taransmits, in oreder to investigate its performance. The maximum temperature increase on the back plate of the deep grooved and the conventinal type were 65C and 30C, respectively. RF power and pulse were 441kW and 6sec, respectively. The dependence of temperature increase on the plolarizer angle obtained in the experiment agrees with the calculation, qualitatively. It was also found that the significant reduction of ohmic loss on the polarizers was achievable with the optimized rotation angle of the linearly polarized incident wave.