A phase-stabilized superradiant Ka-band oscillator driven by nanosecond voltage pulses with amplitude variations and reduced rise rates

This paper presents the results of experiments and a numerical simulation of the conditions for phase stabilization (standard deviation < 0.5 rad) of a subgigawatt relativistic superradiant Ka-band backward wave oscillator with the accelerating voltage amplitude varying within 15%. It is shown that phase stabilization can be achieved for the voltage rise rate (dU/dt)max ∼ 2 MV/ns by using our recently developed approach. Particular emphasis is given to the cases of substantially lower voltage rise rates at which stabilization of the microwave oscillation phase is also possible. The mode with (dU/dt)max ≪ 1 MV/ns is considered for specific voltage waveforms that ensure efficient kinematic peaking of the beam current. In this case, stabilization of the microwave oscillation phase can be achieved by initiating a voltage prepulse, provided that the accelerating pulse leading edge has a segment of stable rise rate and stable shape.