Twin traveling-wave tube amplifiers driven by a relativistic backward-wave oscillator

Experiments demonstrate stable frequency and relative-phase angle output from twin traveling-wave tube (TWT) amplifiers driven with the redirected signal from a high-power backward-wave oscillator (BWO). The experimental X-band apparatus employs a single generator to produce three independent electron beams which simultaneously drive the BWO and TWT sources. The BWO spontaneously generates up to 14.1 MW peak, 25 to 15-ns long pulses over a current-tunable bandwidth of 9.6%. The BWO power extracted upstream is split and redirected into twin TWT's for amplification. The TWT's produce up to 9.0 MW pulses over an 800 MHz instantaneous bandwidth. Across the amplifier's full-width half-maximum pulse duration of 10 to 20 ns, a relative-phase angle of better than 15/spl deg/ is maintained between TWT's for an 11.0 to 11.7 GHz range. Experiments characterize the gain, relative-phase angle, and efficiency of twin-TWT output as a function of RF-drive frequency and beam current. These experiments are the first to demonstrate the feasibility of relativistic TWT's for phased-array applications, and increase the limited data base documenting relativistic-TWT operation.