On Simulating the Generation of a Ka-Band Subnanosecond Microwave Peak Train by a Relativistic Backward-Wave Oscillator in the Beam Current Modulation Regime

Abstract

We consider numerical models for generating sequences of subgigawatt microwave superradiance (SR) peaks in a relativistic Ka-band backward-wave oscillator (BWO) due to a deep periodic modulation of the electron beam current. In the first model, this regime is achieved by applying a sequence of trapezoidal accelerating pulses to the explosive-emission cathode with a certain delay. The delay duration determines the influence of the residual background of slow spent electrons on the dynamics of formation of the subsequent SR peak and the peak amplitude. In an alternative model, the injected beam current is continuous, but modulated by the preceding SR pulse, which generates strong electric fields in the radial gap near a coaxial insert used in the anode unit of the BWO instead of the resonant reflector. Here, the beam is periodically dumped onto the wall. In this case, unlike the first model, the electrons at the leading edge of the next beam segment have the maximum energy. Therefore, the excitation of subsequent SR pulses is less sensitive to residual slow electrons and occurs under reproducible conditions. The pulses have a short delay and close amplitudes.