High-Power Tests of a Remote-Steering Antenna at 140 GHz

This paper reports the results of the high-power tests of a remote-steering-launcher mock-up at 140 GHz, which were performed at the electron cyclotron resonance heating installation for the future stellarator Wendelstein 7-X (W7-X) at Max-Planck-Institut für Plasmaphysik, Greifswald. The mock-up test system consists of a 6.62-m-long square corrugated waveguide with a steerable optic at the entrance and various diagnostics at the exit of the waveguide. A straight launcher and a version with two integrated miter bends were investigated.The ohmic loss of the waveguide was measured via the temperature increase of the waveguide wall and was used to calibrate the calculated angular dependence of the total ohmic losses of the waveguide. Short-pulse radiation pattern measurements with thermographic recording show high beam quality and confirm the steering range of -12…12 deg. The version with two miter bends produces similar results but with an increased level of side lobes.Although the tests were performed under atmospheric pressure, no arcing was observed in the straight waveguide. In the version with the miter bends, however, arcing limited the power and pulse length.