The output unit of a high-power millimeter-wave gyrotron to convert the rotating TEn,3 mode into a Gaussian beam is elaborated. The improved construction of the converter permits one to combine it successfully with an electron-optical system of a gyrotron. The converter includes a waveguide launcher in the form of a stepwise cut of a conical waveguide and a system of mirrors. The measured efficiency of conversion of the operating mode into the Gaussian beam is 83% .
M. A. Shapiro, M. A. Shapiro,
"Built-in converter for high-power gyrotron", Proc. SPIE 1929, 17th International Conference on Infrared and Millimeter Waves, 19296T (14 December 1992); doi: 10.1117/12.2298362; https://doi.org/10.1117/12.2298362