Gyrotron-backward-wave-oscillator experiments utilizing a high current, high voltage, microsecond electron accelerator

We report the first gyrotron-backward-wave-oscillator experiments to produce high power (tube power of ∼1–8 MW), long-pulse (0.3–1.2 μs) microwaves at high currents (0.1–2 kA) and high voltages (650–750 kV). Experiments were performed in the TE11 fundamental backward-wave mode, with efficiencies of ∼1%–2%. Mode competition was observed which is believed to originate from the TE21 absolute instability.