Research on the Competition Mode Suppression in Coaxial Extended Interaction Structure

Extended interaction klystrons operating in high-order mode can establish more sufficient axial electric field than the fundamental mode in a large size cavity. However, this structure suffers greatly from the mode competition because of the combination of axial and transverse modes. This paper presents the mode competition analysis of a coaxial extended cavity operating in ${TM}_{31}$ mode through particle-in-cell (PIC) simulation. Meanwhile, applying dielectric loads in the proper position can effectively suppress the mode competition of this structure, while the ${TM}_{31}$ mode has little interaction with the dielectric loads.