Phased Antenna Arrays Based on Vircators: Numerical Experiments

We present the results of numerical simulation of two different design schemes for phased antenna arrays (PAAs) based on vircators, i.e., microwave oscillators with virtual cathodes. The active and passive schemes of PAA design are analyzed separately. It is shown that in the case of an active PAA scheme, the degree of tuning the vircator to the master oscillator increases with increasing power of the latter, while in the case of a passive PAA scheme, the coherence degree of two vircators due to waveguide coupling increases with increase in the coupling coefficient.     

Interpretation of ion-acoustic solitons of unusual form in experiments in SF6-Ar plasma

The emergence in SF₆-Ar plasma of ion-acoustic solitons with angular profiles or profiles with several maxima has been explained. It has been shown that the cause of these profiles is that the phase trajectories of the solitons of this type in the phase portrait cover one or more separatrices, which in turn can appear only in plasma with a complex chemical composition.     

Simulation of the Formation of the Squeezed State of an Electron Beam with a Sublimiting Beam Current in a Closed Drift Tube

Technical Physics - The dynamics of formation of a virtual cathode and the squeezed beam state (SBS) in a setup with a sublimiting relativistic electron beam under repeated input of the electron...     

Generalized bohm criterion for a multicomponent plasma

We have formulated the generalized Bohm criterion regulating the existence of a stationary charged near-electrode sheath in a multicomponent plasma with an infinitely large number of ion species. The criterion has the form of a set of inequalities one of which coincides with the Bohm criterion for a two-component plasma.     

Can ion-acoustic waves in plasma be backward waves?

The dispersion relation for ion-acoustic waves in plasma with ion flow has been analyzed. It is shown that these waves may exist (under certain conditions) in the form of backward waves with antiparallel group and phase velocities. The range of ion flow velocities allowing implementation of backward ion-acoustic waves is found.     

Tunable source of terahertz radiation based on the difference-frequency generation in a GaP crystal

A tunable source of terahertz (1–4 THz) radiation with a line width of 12 GHz is created on the basis of difference- frequency generation in a GaP crystal. Radiation of a pulsed Nd:YAG laser with a wavelength of 1064 nm and a tunable optical parametric oscillator is used as the pump. The radiation is generated in 10-ns-duration pulses with a pulse repetition rate of 10 Hz. The pulsed radiation power is about 15 mW.     

Nonlinear adiabatic models of ion-acoustic waves in dust plasma

Nonlinear adiabatic models of ion-acoustic waves in a dust plasma are developed. The problem of the structure of subsonic periodic and supersonic solitary ion-acoustic waves is exactly solved analytically under the assumption of a constant charge of dust particles; the critical Mach numbers for the solitary wave are determined. The problem of the wave structure is solved numerically for the case when the charge of dust particles was assumed to be variable.     

Generation of soft X rays in a vircator with exploding anode foil

A soft X-ray generator is designed on the basis of a vircator the plasma anode of which is formed by electrical explosion of anode foil. The intensity of soft X-ray radiation (E _γ > 20 eV) produced by vircators with a metal and plasma anode is measured. Microwave pulses indicating the presence of a virtual cathode in the plasma beam are detected.     

Mikhel’son effect in a plasma

An analysis is made of the parametric frequency shift of an electromagnetic wave traveling in a plasma (isotropic collisionless, isotropic collisional, and magnetized collisionless) with time-varying parameters (Mikhel’son effect). Different situations corresponding to the growth of plasma concentration, a change of collision frequency, and a change of magnetic field are considered.