Design considerations for the high-power multicavity klystron

Abstract

A confined-flow large-signal formulation of the klystron interaction equations is presented and applied to the analysis of the multicavity klystron amplifier. The effects of cavity voltage, cavity phase, drift length, and beam parameters are studied. The two- and three-cavity amplifiers are studied in detail, and several numerical examples of four-cavity klystrons are also given. A significant second-harmonic component of velocity modulation is shown to improve the dc to RF conversion efficiency. Two methods of obtaining this modulation are discussed. The large-signal theory presented here has been used to design a five-cavity klystron which is 50 percent efficient and has a controllable power transfer curve. Theoretical and experimental power transfer curves are presented for several 1 1/4-MW klystrons; the calculated output power is between 4 and 10 percent greater than the experimental values.