Recent activities on the study of mm-wave transmission for the ITER equatorial launcher and transmission line

Takahashi, Koji; Kajiwara, Ken; Oda, Yasuhisa; Kobayashi, Noriyuki*; Oshima, Katsumi; Sakamoto, Keishi

The mm-wave design of the EL to improve the shielding capability has been investigated and the modification of the mirror position is essential to obtain the effective shielding without degrading the mm-wave transmission capability. The torus diamond window prototype was manufactured and tested. The transmission of 0.74MW/100sec and of 0.52MW/172sec were demonstrated. Loss tangent of 5.54 10, which was the lowest value that had ever obtained, was measured. The characteristic temperature increase of the waveguides near and between the miter bends has been measured due to high order modes propagation or/and their modes trapping in the transmission line. The measurement shows that the HE11 mode purity was degraded by 10% and on the other hand, the mode content of LP11 mode was increased by 10% when the displacement of waveguides was 11.5mm. This result suggests that the effective cooling of the waveguide or the stiffness support structure for the transmission line component like the miter bend should be considered to minimize the degradation of HE11 mode purity.