Computer Simulation of a 5.7GHz, 110kW Transit-Time Oscillator

A high-power transit-time oscillator producing 110kW at 5.7GHz in the TM₀₁₀ cavity mode is described. The device comprises a temperature-limited diode electron gun operating at 40A in the range from 28kV to 35kV and an intermediate coaxial cavity from which the microwave power is extracted through a TEM coaxial guide. The diode serves also as a resonant cavity, where electromagnetic oscillations are grown from noise. The effect of the applied voltage on both the output microwave power and the instability saturation time has been investigated leading to an optimal diode voltage of 33kV.     

An Axial Monotron with Rippled Wall Resonator

With application to centimeter-wave monotron oscillators, the present work proposes a rippled wall cylindrical cavity that provides efficient coupling to a coaxial output circuit. Driven by a centered, solid 50 A, 34 keV electron beam, the corrugated cavity thus designed operates at 10.5 GHz in the 2-mode with two radial variations. The monotron operation is examined through 2.5D particle-in-cell simulation giving 260 kW average power output. This corresponds to 15.3 percent overall efficiency at the theoretical limit of 20.0% percent electronic effciency as predicted by one-dimensional analysis.