Design of W-band sheet beam extended interaction cavity based on high-order mode

In millimeter band, the size of microwave vacuum device decreases rapidly with the increase of frequency, resulting in a significant reduction of output power of the device. In order to improve the power capacity of the extended interaction klystron, it is an effective way to combine sheet electron beam and high-order mode. In this paper, we propose a rapid design approach for the equivalent circuit based on
$\text{TM}_{31}-2\pi$
mode for the dumbbell-type extended interaction cavity. The method allows rapid adjustment of the characteristic impedance and mode interval of the cavity, which results in increased intensity of beam interactions and avoids mode competition.