Oversized coaxial output cavity for Ka band relativistic klystron

In this study, an oversized coaxial output cavity is proposed for a Ka band relativistic klystron amplifier (RKA). It consists of a three-gap resonator and a coupler. To ensure the concentricity, the double-row supporting rods are used in the output cavity. The parameters of the output cavity are obtained through theoretical analysis and CST simulation. In addition, the authors evaluate the performance of the output cavity by using particle-in-cell software CHIPIC. They investigate the influences of the period length and the external quality factor on the output power. Furthermore, they study the effect of the overmoded ratio on power and electronic efficiency. The simulation shows that the output power reaches 1.08 GW and electronic efficiency is 36.0%. The simulated results indicate that the proposed output cavity can be used in the RKA with GW-level power at the Ka band.