Design of matching optics unit (MOU) for coaxial ITER gyrotron

The paper presents the design of a MOU for the coaxial ITER gyrotron. Corrugated waveguides are used to transmit the high power mm-waves generated by gyrotrons to the plasma for Electron Cyclotron Resonance Heating (ECRH) and Current Drive (CD). The MOU contains two focusing mirrors, which are used to convert the gyrotron output into a Gaussian distribution with optimal parameters to improve 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 beam to the HE₁₁ mode is approximately 96.33%.