Analysis and Design of the Resonator in a 110 GHz Gyrotron Oscillator

Abstract

Gyrotron oscillators are powerful millimeter, sub-millimeter and even potential THz wave sources, capable of reaching megawatt power levels. They are widely studied today to use for electron cyclotron resonance heating, current drive, stability control and active diagnostics of magnetically confined fusion plasmas. To suppress the parasitic modes and improve the efficiency of the over-mode resonator is a important object for the design of high power gyrotrons. On the basis of electron cyclotron resonance maser theory and generalized transmission line theory, we compiled programs to analyze the resonant cavity in a 110 GHz gyrotron. The results shows that the coupling coefficient to parasitic modes of gradually tapered cavity is obviously less than line-joint cavity. By calculating and studying different gradual-varying and line-joint resonant cavities, we designed a gradually tapered resonator for a 110 GHz gyrotron, which is good at suppressing the parasitic modes, improving the purity of the operating mode and the efficiency of the beam–wave interaction.