High-power microwave oscillator-amplifier systems

Experiments are described which employ backward-wave oscillators (BWO's), powered by high current relativistic electron beams, to drive traveling-wave tube amplifiers (TWT's) having outputs of a few hundred megawatts. Experimental results and a brief discussion of the pulse-shortening syndrome in oscillators are included. In a single-amplifier configuration the same electron beam passes through both slow-wave structures, with a small connecting pipe in which the EM waves are cut off. By operating the BWO at low power levels, the problem of pulse shortening is avoided, giving both high power output and long pulses. In a second configuration the BWO drives two TWT's, each having independent electron beams. The outputs from the two TWT's can be adjusted to have the same power level and a discrete phase relationship, conditions that are important for a phased antenna array or an electron accelerator.