Electron diode oscillators for high-power RF generation

Summary Form only given, as follows. Feedback oscillators have been extended to the regime of relativistic electron beam diodes. Such devices have potential application for the generation of high-power RF radiation in the range 50-250 MHz and 1-10 GW with 20-60% conversion efficiency. The relativistic feedback oscillator is based on a four-electrode foilless diode with magnetic insulation. The diode consists of an annular cathode, a magnetically insulated control electrode, a shielded anode and an inverse diode collector. The control electrode modulates the electron flow. The time-varying beam current at the inverse diode collector drives a high-vacuum output transmission line. Output waves on the line couple to a high-Q feedback resonator that drives the control electrodes. The results of a design study for the four-electrode diode show that good modulation of a 30-kA electron beam at 600 kV can be achieved with moderate field stress on the electrodes. The net power and harmonic purity of the oscillator output improve considerably with a tuning capacitance at the cathode and a resonant termination in the output transmission line. A 7.5-GW oscillator at 200 MHz with 25% conversion efficiency has been designed.<>