Yu. F. Lonin

Auto-oscillation system based on dielectric resonator with “Whispering gallery” modes

A new method of microwave generation in a system with high-Q quasi-optical cylindrical dielectric resonator (CDR) excited by an azimuthal-periodic electron beam current is proposed. Characteristic parameters of a cylindrical fluoroplastic CDR have been determined. Data on microwave generation in a system based on a CDR with whispering-gallery eigenmodes excited by a relativistic azimuthal-periodic electron beam current are presented. Electromagnetic radiation of this system was measured using a detector for the 8-mm wavelength range.

Plasma travelling wave antenna

The possibility of using plasma column as linear travelling wave antenna is studied. It is shown that surface current waves propagating in plasma column of finite length are a source of paraxial electromagnetic radiation of decimeter band. Influence of dielectric waveguide, which surrounds cold isotropic plasma, on dispersion properties of plasma column is investigated. The corresponding dispersion equation for eigenwaves of circular dielectric waveguide filled with plasma is derived and solved numerically. Plasma and waveguide parameters are determined under which the surface wave slowing-down is close to unity leading to antenna’s radiation primarily in axial direction. It is shown that in case of plasma density around 1012−1013 cm−3 dispersion of the considered wave is close to dispersion of waves propagating in metal travelling wave antenna.

Axial-radiation plasma antenna

The possibility of applying a cylindrical isotropic collisionless plasma column with a thin dielectric shell as an antenna of strictly axial radiation is investigated. It is assumed that the phase velocity of radiated waves approaches the velocity of light and the radiated wavelength substantially exceeds the radius of the antenna. Radiation patterns of azimuthally symmetric and azimuthally nonsymmetric current waves are calculated. It is shown that, in contrast to the symmetric wave used in traditional traveling-wave antennas, the first harmonic of a nonsymmetric current wave in plasma is a source of radiation reaching its maximum at the zero angle to the antenna’s axis.

Microwave radiation of cylindrical plasma column

The travelling wave antennas representing a column of isotropic plasma and a plasma column placed into external infinitely large magnetic field have been theoretically and numerically investigated and compared. The relationships of radiation patterns as a function of the plasma density, geometrical parameters of the plasma cylinder and the radiation wavelength were also investigated. We considered both the linear antennas and the radiating antennas with wavelengths close to the antenna radius. An axially symmetric E-wave was studied. The need of taking into account the radial distribution of antenna current was shown. The dependence of normalized radiation patterns on the wave-slowing was analyzed. The characteristic value of plasma density was found; if this value is exceeded, the normalized radiation patterns are sharp directional and have the main lobe located at small angle towards the antenna axis. For the magnetized plasma this characteristic value of density is much smaller than for the isotropic one. With the rise of the plasma density the level of side lobes gets smaller.

Synchronization circuit with galvanic isolation for high-current accelerator REB of microsecond duration

Considered in this paper is the simple synchronization circuit with galvanic isolation. The main source of electromagnetic disturbances in high-current accelerator is ring current. Radical method of such interferences control is galvanic isolation

Formation and Emission of Intense Electromagnetic Pulses by Means of an Insulated Rod Antenna Excited by a Short-Duration High-Current Relativistic Electron Beam

The possibility of forming and emitting high-power electromagnetic pulses by means of an insulated rod antenna excited by a short-duration high-current electron beam is studied. It is found experimentally that the amplitude of the emitted pulses and their characteristic period depend on the antenna length. The potentialities of the method proposed as applied to the generation of intense videopulses are discussed.

Radiation-acoustic control over the thermal parameter of construction materials irradiated by intense relativistic electron beams

The characteristic manifestations of radiation-acoustic effects in metals and alloys under the irradiation of a high-current relativistic electron beam, leading to a melt surface with the partial removal of material from the surface, are studied in this paper. An increase in the acoustic emission in the samples when they are irradiated with a high-current electron beam is experimentally observed. It is shown that the primary mechanism for the generation of radiation-acoustic pulses in irradiated refractory metals is a stress-relieving mechanism. The amplitudes of the acoustic pulses after the second and subsequent electron pulses do not change, which indicates a correlation between the amplitude of the acoustic signal and the surface structure of the irradiated material.

Plasma antenna of traveling wave with axial radiation

The dispersion equations for azimuthally asymmetric slow waves propagating along the plasma column, located in the dielectric cylinder are derived and solved. These waves induce currents that lead to the radiation of electromagnetic waves into the surrounding space. The antenna, which is a hollow dielectric cylinder of finite length, filled with an isotropic cold collisionless plasma is considered. The formulas for the angular distribution of the radiation in the far-field for azimuthally asymmetric and azimuthally symmetric slow current waves propagating along the antenna are derived. They can be used for case when the antenna length is much greater than antenna transverse dimensions and the radiated wave length. At that antenna radius, the thickness of the dielectric tube and dielectric permittivity, plasma density, the phase velocity and the wave current frequency can be arbitrary. Practically interesting case of a linear antenna of a traveling wave, which phase velocity is close to the speed of light is considered. Asymmetrical current wave with m=1 has a particular place. For it the maximum of directional diagram (pattern), unlike the asymmetric waves (m>1) and the symmetric wave (m=0), accounts for the direction of the antenna axis, and the side-lobe level is much lower than for the symmetric wave. The width of the pattern is decreased with increasing the ratio of the antenna length to the radiated wave length L/λ and is 17° for L/λ=10 and 12° for L/λ=20. Thus, the plasma antenna operating in the regime of the asymmetric wave current with m=1, can serve as a source of strictly axial radiation. It is shown that a sufficiently thin dielectric shell does not influence on the normalized radiation pattern.

Microwave radiation of the column of isotropic and magnetized plasma

In this paper the antenna of a traveling wave, which represents a column of isotropic plasma or the plasma column, placed in an external infinitely large magnetic field is studied both theoretically and numerically and compared between them. Plasma is assumed cold and collisionless. The dependence of radiation patterns upon plasma density, geometric parameters of plasma cylinder and radiation wavelength is investigated. At that it is considered not only linear, but also short-wave antenna radiating wavelengths close to the antenna radius. In an isotropic plasma column (B0 = 0) and in the magnetized (B0 = ∞), there are only a slow plasma E-wave with frequencies lower the plasma frequency. We study axially symmetric E-wave. Solutions of the dispersion equations give the dependence of the frequency on the wavevector, necessary to calculate the radiation patterns. The wave in plasma cylinder induces a wave of current density. Knowing the current it is possible to calculate the radiation field in the far field and, accordingly, the normalized radiation pattern.

Electromagnetic wave generation in a cylindrical resonator by electrons orbiting in a radial electrostatic field

The mechanisms leading to the generation of microwaves by electrons orbiting in a radial electrostatic field produced by a positively charged filament on the axis of a cylindrical resonator are investigated theoretically. The dispersion relations describing the interaction of the waves with the electrons are obtained. It is shown that the generation of electromagnetic fields is possible on account of both Cherenkov and plasma resonances. The frequencies and growth rates of waves under Cherenkov resonance conditions and also plasma resonance conditions in uniform and nonuniform electron layers are found. The advantages and disadvantages of different generation mechanisms are determined.