A Dual-Frequency Mode Converter for a 70/105 GHz Gyrotron

The VGE-8071A gyrotron, currently in fabrication, is designed to produce 600 kW of continuous RF output power in a Gaussian output beam at either 70 GHz or 105 GHz. The gyrotron circuit employs the TE
11,3
interaction mode at 70 GHz, or the TE
14,5
interaction mode at 105 GHz. To facilitate conversion of either operating mode into a Gaussian output beam, a dual-frequency internal converter is employed, consisting of a numerically optimized dimpled-wall launcher, two phase correcting mirrors, and a final toroidal mirror to direct the RF beam through the gyrotron output window. An external 2-mirror matching optics unit couples either output beam to an external transmission line system, using frequency-specific swappable mirrors for precise alignment and optimal coupling of the beam to the transmission line.