Electron gun and collector design for 94-GHz gyro-amplifiers

This paper presents the electrical design of a magnetron injection gun and collector for high peak and average power TE₀₁ W-band gyro-amplifiers. The magnetron injection gun design employs an optimized double-anode geometry and a cathode angle of 500 to achieve superior beam optics that are relatively insensitive to electrode misalignments and field errors. A transverse relative velocity spread of 1.6% at a velocity ratio of 1.5 is obtained in simulations for a 6-A 65-kV beam. Cathode edge emission was modeled, found to produce a major effect on velocity spread, and will be eliminated by nonemissive cylinders affixed to the cathode. The collector, which also serves as the output waveguide, is designed to minimize the required collector length while avoiding excessive power loading on the collector surface. An average power density of less than 640 W/cm² on a 3.25-cm-diameter collector is achieved for 91-kW average beam power. Both the gun and collector are currently under construction