Development of a matching optics unit (MOU) for the coaxial ITER gyrotron at KIT

Closed corrugated waveguide transmission lines operating in the HE₁₁ mode will be used to transmit the powerful radiation from the coaxial-cavity gyrotrons to the ITER tokamak for Electron Cyclotron Resonance Heating (ECRH) and Current Drive (CD). A Match Optics Unit (MOU) has been developed to transform the gyrotron output into a Gaussian mode distribution with optimal parameters to maximize the coupling efficiency of the TEM₀₀ Gaussian distribution to the HE₁₁ mode of the corrugated waveguide. The calculation results reveal that the coupling efficiency of the Gaussian-mode like wave beam to the HE₁₁ mode is approximately 96.3%.