We present the analysis of a microwave generator that uses two-spiral metamaterial (MTM) plates in a below cutoff WR340 waveguide that interacts with a high-power electron beam, motivated by recent results obtained by researchers at MIT. Particle-in-cell simulations using the MAGIC code demonstrated that power levels of 12 MW are achieved in a backward wave mode at a frequency of 2.47 GHz from an anomalous Doppler instability using a 1 μs pulsed electron beam of energy 400 keV, current 82 A in a 415 G magnetic field. In addition, a backward wave with 9 MW output power is achieved at a frequency of 2.54 GHz attributed to a Cherenkov instability using a 1 μs pulsed electron beam of energy 400 keV, current 82 A in a 1200 G magnetic field. MAGIC simulations demonstrate that the beam-wave interaction electronic efficiency can be as high as 27.4%. Nonlinear simulations indicate that beam interception leads to secondary electron emission from surfaces, which makes the anomalous Doppler instability and Cherenkov instability more complicated by a shift in frequency. This work seeks to clarify some discrepancy between particle-in-cell simulations and experiments at MIT over a range of guide magnetic field.
We describe a klystron-like oscillator operating at a frequency of 77.2 GHz (E-band) using particle-in-cell (PIC) simulations with the code MAGIC. It is shown that the klystron oscillator with one “buncher” cavity and one “catcher cavity” shaped like a “clamp” driven with an applied voltage U=20 kV−100 kV can operate with an electronic efficiency of above 11% with MW output power. To increase the electronic efficiency, we combined two clamp klystrons along the z-axis in a hybrid configuration between a klystron and the slow wave structure of a coupled-cavity TWT. PIC simulations demonstrate that when this hybrid design operates in the TE30 mode, its electronic efficiency can be as high as 28% with an output power as high as 1.35 MW. This article describes in detail this approach to the high power millimeter-wave source design.
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