A Medium Power Electrostatically Focused Multiple-Beam Klystron

This paper presents data on a new device, a 7-beam, electrostatically focused klystron oscillator/amplifier with planned output of 2-kW continuous wave (CW) at 5.8 GHz for an RF-excited ion thruster. An abridged presentation of this paper was given at the International Vacuum Electronics Conference/International Vacuum Electron Sources Conference (IVEC/IVESC) 2006 Conference in Monterey, CA. Advantages over conventional magnetic focusing are discussed. A tube was constructed that exhibited expected performance. It produced about 500 W with three beams at saturation and was operated as both an oscillator and an amplifier. DC beam transmission was 99% but degraded rapidly at saturation. We discuss ways to mitigate this problem. Cavity gaps were used as focus lenses by applying a dc voltage across them, and this improved overall beam focusing. A technique for splitting cavities without lowering Q is presented. An unconventional construction technology was employed and is described.