Special complex open-cavity and low-magnetic-field high-power gyrotron

A theory is proposed for the special complex cavity; it is in the form of a single resonant circuit having a TE/sub 0n/ from or to TE/sub 0,n+p/ mode converter and it features excellent mode selectivity, high power capability, and an asymmetric triangle profile of the RF field that is favourable to efficient operation for a 35-GHz second-harmonic gyromonotron employing this complex cavity with TE/sub 03/ mode output are numerically illustrated and experimentally demonstrated. Power as high as 200 kW and efficiency as high as 30% have been obtained. These experimental results are record values for a gyrotron operating at the second-harmonic millimeter wavelength. Implications of the single-resonant complex cavity for the fundamental harmonic and third-harmonic high-average-power gyrotron design are discussed.< >