Transition radiation from relativistic electrons crossing a perfectly conducting conical surface: Calculation and experiment

The angular distributions of the transition radiation intensity when a charged particle passes through the vertex of a perfectly conducting conical surface have been calculated. The radiation generated both when the particle exits the conductor and when it falls on the conductor has been considered. The angular distributions of the intensity of the transition radiation generated by a bunch of relativistic electrons have been measured in the millimeter wavelength range. A microtron with a particle energy of 7.4 MeV was the source of electrons. The influence of the particle injection direction and the conical-surface opening angle on the angular distribution of the radiation intensity has been studied. The measurements have shown that the distribution of the radiation generated by a charge when it enters the horn differs significantly in pattern from the distribution when it exits the horn.     

Transition radiation in a dihedral angle formed by perfectly conducting planes

The spatial distribution of the field of transition radiation generated by a relativistic particle flying into a dihedral angle formed by perfectly conducting plane surfaces is determined. The cases when particles are injected from the edge and from a plane of the dihedral angle are considered. The angular distributions of radiation intensity in dihedral angles of different values are calculated.     

Transition and diffraction radiation from a charge on a perfectly conducting sphere

The problem of transition radiation from a charge on a perfectly conducting sphere and diffraction radiation from a charge flying near the same sphere is solved. The radiation energy, spectrum, and polarization are found. The result is obtained for the limiting case of dipole radiation and the trajectory of the charge passing through the center of the sphere.     

Transition radiation generated by a particle passing through the apex of a conducting cone

The spatial field distribution is determined for the transition radiation generated by a particle passing through the apex of a cone along its axis. Expressions for the angular distribution of the radiation intensity are obtained for apex angles between 0 and π. Characteristics of transition radiation emitted into a “funnel” and a dihedral angle are compared.     

Dipole radiation of a charged particle moving along a fractal trajectory

The dipole radiation of a charged particle moving along a closed fractal trajectory with constant velocity is studied. It is found that the spectrum intensity of the radiation is displaced to the high frequency region when reducing the spatial scale of the fractal trajectory and tends to zero if the trajectory is a true fractal.     

Diffraction of light by a perfectly conducting biaxial periodic surface

The Rayleigh theory is numerically implemented for a crossed sinusoidal grating. It is shown that the scattering pattern of such a structure can be very sensitive to the polarization of a normally-incident plane wave when the surface periodicities are of the order of the wavelength.     

Transient radiation induced by a modulated flow of charged particles on a perfectly conducting surface with random roughness

The excitation of surface waves by a modulated electron flow in a medium whose surface has random inhomogeneities is studied. It is shown that the energy flux density of a surface wave (polariton) exhibits oscillations determined by the ratio of the period of oscillations of the electron beam and the time of flight of a charged particle in the space between the beam modulation plane and the interface between the media.     

Hard X-radiation emitted by a charged particle moving in a carbon nanotube

We consider the radiation emitted by a charged particle propagating inside a single-layer carbon nanotube and interacting without delay with the screened charges of the nuclei of carbon atoms. It is shown, for example, that a beam of positrons with an energy of around 1 GeV and a divergence of some 10⁻⁴ rad is captured by the nanotube and emits hard X-rays with an energy of about 0.3 MeV in the direction of its propagation. The theoretical results obtained allow one to consider carbon nanotubes as a new source of hard X-radiation.     

Enhanced specular scattering by a single particle near a perfectly reflecting surface

The scattering of electromagnetic waves by a single particle situated randomly near a perfectly reflecting surface is considered in the dipole approximation with allowance for an infinite number of scatterings. It is shown that the rescattered waves lead to an increase in the effective scattering cross section and suppress the enhanced specular scattering of the p-polarized wave compared with the s-polarized wave. ISTOK, Fryazino, Moscow region; State Pedagogical Institute of Elabuga, Tatarstan, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 7, pp. 860–869, July, 1997.     

Cherenkov radiation by the charged particle moving in moving Hermitian medium

Detailed theoretical investigation and computer calculations on the Cherenkov radiation (CR) in moving Hermitian medium (CRMH) are presented in this paper. It has been found that, similar to that in stationary Hermitian medium (CRH) case, there are two modes in the CRMH; in general, only one of them is radiative mode, another one is local field, and the comparison of the two modes is given in the paper. The small absorption of CRMH mainly results in the Gaussian-like field intensity pattern. And the group velocity in the CRMH is always slower than the phase velocity in the moving HM, so the fine inner structure occurs. Comparing the behaviors of CRMH and CRH, we have found that the movement of the Hermitian medium (HM) brings significant influences on the CR, so there are some interesting characteristics of CRMH, such as in the CRMH; the radiation power of the “o” mode is much higher than that of “e” mode. And because of the relativistic Doppler effect, the frequency region where both modes are radiative becomes quite different from that for CRH.     

Doppler radiation emitted by an oscillating dipole moving inside a photonic band-gap crystal

We study the radiation emitted by an oscillating dipole moving with a constant velocity in a photonic crystal, and analyze the effects that arise in the presence of a photonic band gap. It is demonstrated through numerical simulations that the radiation strength may be enhanced or inhibited according to the photonic band structure, and anomalous effects in the sign and magnitude of the Doppler shifts are possible, both outside and inside the gap. We suggest that this effect could be used to identify the physical origin of the backward waves in recent metamaterials.     

Electromagnetic radiation from a conducting tether moving in the ionosphere

Summary We set up a model to compute electromagnetic radiation associated with the motion of a conductor through a magnetized plasma. Calculations are carried out, in the framework of cold-plasma theory, for radiation near the ion cyclotron frequency. Results are applied to the TSS (Tethered Satellite System) project presently under development.

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Riassunto S’imposta il formalismo generale per il calcolo della radiazione elettromagnetica associata con il moto di un conduttore in moto attraverso un plasma magnetizzato. I calcoli sono poi fatti specificamente per la radiazione nelle vicinanze della frequenza di ciclotrone degli ioni. I risultati sono applicati ai parametri del progetto spaziale TSS (Tethered Satellite System) che è attualmente in fase di sviluppo.

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Резюме Мы предлагаем модель для вычисления электромагнитного излучения, связанного с движением проводника через намагниченныю плазму. Вычисления проводятся в рамках теории холодной плазмы для изучения вблизи ионной циклотронной частоты. Полученные результаты применяются к ТСС (связанная система спутников), проект которой разрабатывается в настояцее время.

     

Cerenkov radiation of a spatially extended charged bunch moving along the axis of a cylindrical channel in a transparent medium

Relations are obtained which determine the electromagnetic field produced by an axially symmetric bunch of charged particles moving along the axis of a cylindrical channel in a transparent medium. The problem of the Cerenkov radiation of such a bunch is investigated and relations are obtained for the intensity of this radiation.In conclusion the author thanks Professor A. A. Sokolov for discussing the results.     

On the magnetic dipole absorption of electromagnetic radiation by a fine conducting particle

The cross section of absorption of electromagnetic radiation by a fine spherical conducting particle is estimated in terms of the classical kinetic theory of electrical conduction. The mixed diffuse-specular mechanism of charge carrier reflection from the sample boundary is considered. A correlation between the coefficient of specular reflection and the absorption cross section at different temperatures is analyzed.     

Transition radiation of a charged particle crossing the waveguide filled with a dispersive dielectric medium perpendicularly to the waveguide axis

The theory of charged particle transition radiation is developed for the case when the particle crosses the waveguide, which is filled with a piecewise-homogeneous dielectric, perpendicularly to the waveguide axis. The cases where the charged particle is flying between two dispersive plates and between two thin impedance films are considered.     

Polarization studies of radiation emitted by surface plasmons in silver

Measurements are reported on the polarization of radiation emitted by the roughness induced decay of nonradiative surface plasmons optically excited by light in thin Ag films. This radiation is of mixed polarization when the incident light is p-polarized. The s-polarized component of the radiation is observed to be considerably less intense than the p-polarized component.