A. V. Gromov

Low-impedance relativistic backward wave oscillator

It is shown that the limiting electron-beam current in a relativistic backward wave oscillator (BWO) can be increased using a slow-wave system (SWS) in the form of a circular waveguide with shallow rectangular corrugation. This idea was checked both experimentally and numerically for a 3-cm BWO with a short homogeneously corrugated SWS and a resonance reflector-modulator. The experiments showed that the proposed BWO with an explosion-emission electron gun and said SWS can effectively operate on 60-Ohm electron beams at a gigawatt output power.

Relativistic backward wave oscillator with multijet electron beam

The influence of the multijet structure of an annular electron beam on the operation of a high-current relativistic backward wave oscillator (BWO) has been experimentally studied. Multijet annular electron beams were generated using graphite explosive-emission cathodes shaped as tubes with comb-shaped ridges. It is established that the BWO working characteristics are highly stable with respect to the multijet beam structure. Potential possibilities of using multijet electron beams in BWOs are pointed out.

Relativistic backward-wave tube with a smooth control over output radiation pulse duration

The effect of failure of oscillations in a low-impedance backward-wave tube is described and the possibility of using this effect for controlling the duration of output radiation pulses is considered.

Nonlinear Stationary Waves in Thin-Walled Electron Beams

Summary form only given. We analyze conditions under which a double-humped potential function of electron beam states is formed in a system of coordinates that is moving with the electrons. We show that periodic states with large amplitudes can exist. Such states can be used as the basis for microwave oscillators with a strong Doppler frequency shift. In addition, we predict the existence of solitary waves in thin-walled electron beams. The dependence of the velocity of such solitons on their amplitudes is obtained. Equations for various states of sheet electron beams, including states with two-dimensional solitons, are also presented.

On Bursian and Pierce Instabilities of Electron Beams Propagating in Weakly Irregular Channels

Summary form only given. The stability of stationary states of dense electron beams propagating in weakly irregular channels, in particular, in channels with non-deep periodically corrugated walls, is investigated using the method of coupled waves. We show that Bursians instability can develop, leading to the formation of virtual cathodes or their disruption. In unlimited channels, separate zones of absolute and convective instabilities on the omega-k plane (Brillouins diagram) are possible. In a channel of finite length, these zones are merged forming the well-known Bursians instability in a vacuum channel or Pierces instability when a space charge of electrons is neutralized by immobile ions. In addition, we investigate the influences of limited conductivity of channel walls, joined elements and other irregularities.

Relativistic BWO with Short Interaction Space

Summary form only given. The results of experimental investigations of two high power relativistic BWOs with short electrodynamic systems and input reflectors that convert an operating wave to a wave extracting radiation from the interaction space, and modulate the electron beam are presented. A variation of the quasi-static potential of the electron beam takes place in the section with deep corrugation of the waveguide wall. This variation significantly alters phase relations and the magnitude of coupling between interacting waves. In the experiments amplitude and phase relations are chosen by varying the length of the drift channel between the reflector and the interaction space and by applying resonant modulators. We have used a system of coupled cavities or a Bragg reflector as a resonant modulator. We also demonstrate that these gigawatt BWO-oscillators can work at high repetition rate and with low impedance (down to 50 Omega) electron beams.

I-V Characteristic of a High-Current Electron Gun with a Magnetically Insulated Thin Cathode

It is shown that the accelerating electric field has an integrable singularity-on the emitting edge of a thin-walled cathode. Therefore, emitted electrons accelerate with infinitely large acceleration from such a cathode either with limited electron emission or with the current of the magnetized electron beam limited by its own space charge. The impact of the singularity on the I-V characteristic of a coaxial electron gun is considered. In addition, we show that the same singularity is also realized in virtual cathodes appearing in thin-walled electron beams. This exerts a significant influence on conditions of the appearance and development of instabilities. We have qualitatively constructed I-V characteristics for a two-section channel. These characteristics allow us to determine reasons for and conditions of appearance of hysteresis transitions with associated instabilities and oscillatory regimes of electron beam motion.