Ka-Band Ultra-Short Pulse Oscillator with Helical-Waveguide Gyro-TWT and Cyclotron Resonance Absorber in the Feedback Loop

We present the results of first experiments on generation of trains of sub-nanosecond Ka-band pulses in the electron oscillator consisting of a helical-waveguide gyro-TWT and a saturable absorber based on cyclotron resonance interaction of radiation with initially rectilinear electron beam. The process of pulse formation is associated with the effect of passive mode locking which is well known in laser physics but has not yet been employed in high-power microwave electronics. In good agreement with the theoretical predictions, periodical trains of coherent (in-phase) 0.5 ns pulses with peak power of 100 kW and repetition period of 2.5 ns were measured.