Comparative analysis on TM₁₁₀-2π-mode and TM₁₁₀-π-mode as the operating mode for W-band sheet beam klystron

Abstract

Multicavity multigap sheet beam klystron in W-band is an ideally portable coherent radiation source for nonlethal warfare system. In general, the beam–wave interaction circuit employs multigap structures operating with TM₁₁₀-2π-mode. In this paper, compared investigation of TM₁₁₀-2π-mode and TM₁₁₀-π-mode interacting with sheet beam is demonstrated. Analysis indicates that although TM₁₁₀-2π-mode has higher cavity impendence R/Q, TM₁₁₀-π-mode possesses wider frequency spacing interval with the adjacent competition modes, larger beam–wave coupling coefficient M and M²(R/Q), which is profitable to improve beam–wave interaction efficiency, reduce mode oscillation and shorten the circuit length. Furthermore, cold characteristics, including R/Q, M, M²(R/Q), operating frequency, and electric-field uniformity, with different gap distance and variable displacements along electron beam propagation and the perpendicular direction are explained in detail. It also turns out TM₁₁₀-π-mode is not sensitive to the fluctuations of cold characteristics as TM₁₁₀-2π-mode. This paper provides a confident evidence for TM₁₁₀-π-mode interacting with sheet beam in the WSBK design.

Acknowledgment

This work was supported by the National Natural Science Foundation of China under Grant No. G0501040161101040.