Dual frequency gyrotron operating at 42/84 GHz for plasma fusion application

•Design and feasibility study of dual frequency gyrotron.•A procedure of mode selection for dual frequency gyrotron is established.•The magnetically tunable Magnetron Injection Gun is designed.•CVD diamond window for dual frequency is designed.

The design study of dual frequency gyrotron operating at 42/84 GHz frequencies with output power ∼500 kW is presented in this article. TE10,4 and TE6,2 are selected as the operating modes for 84 and 42 GHz operations of the device, respectively. The beam-wave interaction simulations are performed by using the Particle-in-Cell algorithm to evaluate the growth of RF power and frequency. Magnetically tunable magnetron injection gun is also designed to launch the electron beam at the radius of 6.2 mm (84 GHz) and 7.3 mm (42 GHz) in the interaction cavity. The CVD diamond RF window is also designed, which must be transparent for 42 GHz and 84 GHz frequencies. The design results of the dual frequency gyrotron confirm the growth of ∼500 kW power at 42/84 GHz.