Microwave generators with passive mode-locking

We present the results of experiments on the generation of periodical trains of subnanosecond Ka-band pulses in the electron generator, which is based on passive mode locking. The experimental scheme includes a helical-waveguide gyro-TWT and a saturable absorber which is based on cyclotron resonance interaction with an initially rectilinear electron beam. Saturation of absorption is caused by relativistic dependence of the gyrofrequency on electrons energy. In good agreement with theoretical predictions, periodical trains of 0.4 ns pulses with peak power of 100 kW and repetition period of 2.5 ns were measured. In addition, we describe an alternate scheme of the pulse generator with passive mode-locking which feature using of two parallel electron beams formed by a single cathode and transported in common vacuumized interaction space that should simplify the practical implementation.