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The design study of dual frequency gyrotron operating at 42/84 GHz frequencies with output power ∼500 kW is presented in this article. TE 10,4 and TE 6,2 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. [ABSTRACT FROM AUTHOR]

Highlights: [•] Design of triple frequency MW gyrotron. [•] The mode selection process for three frequency operation of MW gyrotron. [•] Design of magnetically tunable magnetron injection gun. [•] CVD diamond window design for triple frequency operation of gyrotron. [Copyright &y& Elsevier]

Abstract: The electrical design of different components of 1MW, 170GHz gyrotron such as, magnetron injection gun, cylindrical interaction cavity and collector and RF window is presented in this article. Recently, a new project related to the development of 170GHz, 1MW gyrotron has been started for the Indian Tokamak. TE34,10 mode is selected as the operating mode after studied the problem of mode competition. The triode type geometry is selected for the design of magnetron injection gun (MIG) to achieve the required beam parameters. The maximum transverse velocity spread of 3.28% at the velocity ratio of 1.34 is obtained in simulations for a 40A, 80kV electron beam. The RF output power of more than 1MW with 36.5% interaction efficiency without depressed collector is predicted by simulation in single-mode operation at 170GHz frequency. The simulated single-stage depressed collector of the gyrotron predicted the overall device efficiencies>55%. Due to the very good thermal conductivity and very weak dependency of the dielectric parameters on temperature, PACVD diamond is selected for window design for the transmission of RF power. The in-house developed code MIGSYN and GCOMS are used for initial geometry design of MIG and mode selection respectively. Commercially available simulation tools MAGIC and ANSYS are used for beam–wave interaction and mechanical analysis respectively. [Copyright &y& Elsevier]