Coupling of gyrotron output with a small-sized circular waveguide

High frequency, medium power gyrotrons are being used as effective radiation sources in the submillimeter region of the electromagnetic spectrum. For some applications, it is necessary to focus the gyrotron radiation and transmit it through a small size waveguide. We have developed a transmission system consisting of a quasi-optical antenna and two novel focusing mirrors. The system converts the gyrotron output (TE0. mode, 301GHz) into a Gaussian-like beam with a small waist size. The Gaussian-like beam couples efficiently with the TE11 mode of a small size circular waveguide