Metal rings installed coaxial cavity for multiple-beam klystron

High-order operating mode is adopted to improve the performance of multiple-beam klystron. However, the frequency interval between high order operating mode and neighboring mode (spurious mode) is small, which easily interfere with the state of the operating mode. In the paper, the metal rings are installed in the coaxial cavity to enlarge the frequency interval. The equivalent circuit models are used to analyze the frequencies of operating mode TM₃₁₀ and neighboring modes TM₂₁₀ and TM^P₃₁₀ (the polarized degenerated mode of TM₃₁₀).