Multifunctional Coaxial Insert With Distributed Impedance Corrugations for Cavities of Broadband Tunable Second-Harmonic Gyrotrons

A coaxial insert with distributed impedance corrugations for cavities of subterahertz second-harmonic gyrotrons is investigated. The insert is designed to serve multiple functions: suppression of all first- and second-harmonic competing modes, attainment of high peak power, and widening of continuous frequency tunability. In the design study, advantages are taken of distributed shallow and deep corrugations of the coaxial insert. The multifunctional corrugated insert for a coaxial cavity is used to improve performance of a second-harmonic 527-GHz gyrotron. It is shown that the designed insert enables stable single-mode operation of this gyrotron with peak output power of 66 W and frequency bandwidth of 3 GHz. The sensitivity of the gyrotron performance to machining errors in the multifunctional corrugated insert is discussed.