Investigation of Transmission Characteristic in Corrugated Waveguide Transmission Lines for Fusion Application

A 170 GHz, high power and long pulse RF experiments of the ITER relevant transmission line consisting of 63.5 mm circular corrugated waveguides, bends, an in-line switch and etc... was, for the first time, carried out. The transmission efficiency of 92% from the inlet of the transmission line to the end, which is comparable to the specification value was successfully obtained. The anomalous incremental temperature between the bends or after/before the bend were observed. This result suggests that the bends generated the higher order modes and the modes are possibly trapped between them and reflect back to the direction propagating toward them.