High-power microwave source based on an unmagnetized backward-wave oscillator

A unique, high-power microwave source, called PASOTRON (Plasma-Assisted Slow-wave Oscillator), has been developed. The PASOTRON utilizes a long-pulse E-gun and plasma-filled slow-wave structure (SWS) to produce high-energy microwave pulses from a simple, lightweight device that utilizes no externally-produced magnetic fields. The novel E-gun employs a low-pressure glow discharge to provide a stable, high current-density electron source. A high-perveance, multi-aperture electron accelerator produces an E-beam that is operated in the ion-focused regime; where the beam-produced plasma filling the SWS space-charge neutralizes the beam, and the self-pinch force compresses the beamlets to provide propagation through the SWS. The PASOTRON E-gun has produced beams with voltages of up to 220 kV and currents in excess of 1 kA for pulse lengths of over 100 μsec. The PASOTRON HPM source normally operates in the TM₀₁ mode, and a unique mode converter has been developed to efficiently produce a TE₁₁ output mode with fixed polarization, The PASOTRON also has the ability to directly produce TE-mode radiation with a rotating output polarization, PASOTRON HPM sources have operated in L, S, C and X-bands, and have produced output powers in the 1 to 5 MW range in C-band at about 20% efficiency with pulse lengths of over 100 μsec