Radiation Phenomena of Plasma Waves Part 3. Radiation from Finite Sources

Radiation phenomena of plasma waves has been reviewed in three parts, fundamental radiation theory, radiation from point sources, and radiation from finite sources. It is the author's impression that the theoretical prediction of the resonance cone by Kuehl (Phys. Fluids 5, 1095 [1962]) initiated much of the theoretical work. The experimental observation of the resonance cone by Fisher and Gould (Phys. Fluids 14, 857 [1971]) is an epoch-making work in the field of radiation problems from point sources. Although finite sources had been used for excitation of many plasma waves, the experimental confirmation of the radiation patterns from finite sources by Shen et al. (Rad. Sci. 5, 611 [1970]) has initiated much later work. Since thier investigations, radiation phenomena of plasma waves have been investigated and been made clear by many authors, as shown in this review paper Parts 1 - 3. The essential radiation phenomena from point sources have been clarified experimentally except for an observation of electromagnetic ion waves radiated from point sources. Radiation phenomena from finite sources will be investigated further because there are various sources required for various goals, e.g., for heating of plasma infusion devices, etc. These investigations will progress into nonlinear phenomena, instabilities, and inhomogenuous effects in plasmas. It is a great pleasure for the author of this review paper if he could give some insight or any help for further developments in plasma sciences.     

Solitary Surface Waves on a Plasma Confined by External Radiation

We consider the nonlinear surface deformation of a plasma which is confined by external fields. It then turns out that a perturbation of the plasma-vacuum boundary can propagate as a solitary wave with a velocity that depends on the external radiation intensity.     

Nonlinear Interaction of S-Polarized Incident Radiation and Surface Waves in Magnetoactive Plasma

The effect of an external magnetic field on the nonlinear interaction of S-polarized electromagnetic radiation incident on a S-polarized surface wave in a plasma layer was studied analytically. We have calculated the amplitudes of generated waves at combination frequencies. The generated waves are of P-polarization and can be either electromagnetic or surface waves, depending on the signal of the value=\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\chi '^2 = \frac{{k'^2 }}{{\varepsilon '}} - \frac{{\omega '^2 }}{{c^2 }} + k'\frac{\partial }{{\partial x}}\frac{{\varepsilon '_2 }}{{\varepsilon '\varepsilon '_1 }}} $\end{document}.     

Radiation technology in medicine: Part 1. medical accelerators

Ionizing radiation is widely used in medicine today. Sources of ionizing radiation include X-ray tubes, natural and artificial isotopes, and accelerators [1, 2]. This review describes the role of accelerator technology and nuclear physics methods in cancer treatment. It presents an analysis of the data that have been published in scientific articles and reports, materials of the IAEA, and other places over the course of the past 5 decades.     

Generation and Radiation of Waves at Combined Frequencies in a Warm Inhomogeneous Plasma Layer

We investigate generation and radiation of waves at combined frequencies from an arbitrary inhomogeneous, isotropic plasma layer, when electromagnetic waves are obliquely incident on it to interact with a surface wave at the plasma boundary. This interaction has been described for both S- and P-polarized waves. We consider a warm plasma layer with thickness very small as compared to the wavelengths of oscillations. It is shown that generated waves are strongly amplified, compared to cold plasma, when phase velocities of generated waves approaches the electron thermal velocity. Waves are not emitted when P-polarized waves are incident perpendicular onto the plasma layer.     

Quadrupole Radiation of Ion-Acoustic Waves

An experiment to measure the radiation of ion-acoustic waves from a quadrupole antenna is described. The quadrupole consists of 4 hemispherical grids located at the corners of a square structure. The results are contrasted with those obtained from an antenna with the 4 hemispheres excited in phase and compared with a fluid model prediction. Electrostatically coupled excitation of ion-acoustic waves from 3 hemispheres when only the fourth is excited is also observed in this experiment.     

On Diffraction Phenomena in Sensors of Surface Waves

The diffraction phenomena associated with the limited aperture size of an incident wave are considered on the basis of a theoretical method for studying the reflection of a plane electromagnetic wave from a plane-layered multifilm structure with homogeneous films. The proposed theory is applied to the analysis of the sensitivity of sensors based on surface waves.     

A Second-Order Theory for Electron Plasma Solitary Waves in a Cylindrical Waveguide

To describe the long time asymptotic behaviour of weakly nonlinear plasma waves propagating in a strongly magnetized plasmafilled cylindrical waveguide the usual KDV equation which is first order in wave amplitude is extended to second order including the effects of finite temperature, mobile ions and giving a proper treatment to the radial co-ordinate for all possible modes of propagation. The second-order effects on the first-order solitary wave profile, phase speed and first order correction to the wavelength are all determined and discussed.     

Plasma Maser Theory of Whistler Waves in the Presence of Ion Cyclotron Turbulence

In this paper we consider the plasma maser theory of whistler waves in the presence of ion cyclotron waves in a magnetized plasma. In a plasma with low frequency ion cyclotron turbulence and a high frequency test whistler wave, growth of the whistler wave takes place because of the turbulent bremsstrahlung interaction between the resonant electrons and the modulated electric fields. The growth rate of the whistler wave is calculated and the results discussed.     

Resonance Selective Excitation of Terahertz Plasma Waves in a Semiconductor Quantum Well Using Two-Color Laser Radiation

A new method of coherent resonance excitation of plasma instability in a 2D quantum well driven by twocolor laser radiation due to photoinduced generation of electron–hole pairs is proposed. It is shown that under the resonance condition, where the frequency and wavenumber of the beat wave obey the 2D plasmon dispersion relation, a spacecharge wave is excited efficiently. A selfconsistent treatment of the problem is presented and the smallsignal response of the 2D system in the THz frequency region is found. This new method provides the selective resonance excitation of plasmons, tuning of their frequency, and efficient control of plasma wave parameters crucial for THz semiconductor technology.     

Generalized Approximation of Strong Interaction of Waves in the Theory of High-Power Radiation Frequency Doubling

The approximation of strong interaction of waves is developed to analyze the generation of the second harmonic under the conditions of self-action. Based on this method, an approximate expression is obtained for the generation efficiency of the second harmonic with allowance for the effect of higher nonlinearities, depletion of pumping radiation, and linear phase detuning. The effect of phase detuning and change in the spatial distribution of the amplitude of the fundamental radiation on the efficiency of second-harmonic generation has been analyzed. Good agreement of the results of the developed approximate method with experimental data and numerical calculations is shown. The optimum conditions of the second-harmonic generation in a wide range of the laser system radiation intensities are determined.     

Nonlinear Theory of Backward and Oblique Ion-Acoustic Waves in Plasma with Unidirectionally Moving Ions

Technical Physics - Oblique ion-acoustic waves in plasma with unidirectionally moving ions are considered. Within the framework of the linear theory, a two-dimensional dispersion relation is...     

Nonlinear Dynamics of Cylindrical Plasma Waves

The nonlinear dynamics of Langmuir cylindrical waves in a collisionless plasma is studied. The possibility of energy transformation in such waves is considered.     

The Frequency of Nonlinear Plasma Waves

We study steady-state plane nonlinear plasma waves in a cold collisionless plasma in the absence of a magnetic field. The main conclusion following from the performed analysis is that allowance for the motion of the ion component of the plasma is of fundamental importance when studying nonlinear plasma waves. It is shown that, in general, the frequency of waves is essentially determined by the ion-component mass and depends equally on the velocity and amplitude of the waves. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 6, pp. 502–516, June 2005.     

Stability of Waves in Relativistic Plasma

The dispersion relation of electromagnetic waves propagating perpendicular to an applied uniform magnetic field B₀ in relativistic plasma is derived. Waves propagating perpendicular to the uniform applied magnetic field can be separated into two modes - one is the linearly polarized transverse wave and the other is a hybrid mode. In the present analysis, dispersion relation of the first mode i. e., for a pure transverse wave is analysed under the assumption that the wavelength is much longer than the cyclotron radii of the electrons. A stability criterion which limits the thermal energy of the electrons along B₀ is obtained.     

Heating of Low-Density Matter by Soft X-Ray Radiation and Radiation Waves

We investigate the nonlinear radiative thermal conductivity model, which is theoretically well substantiated and based on a small number of assumptions. We consider the spatial and temporal evolutions for a low-density polymer foam heated by radiation waves taking into account the dependence of the absorption coefficients on the quantum energy. The form of the radiation wavefront (its slope and speed of propagation) differs from the classical form by a low-temperature “tongue” penetrating deep into the plasma. The plasma in this segment of the wavefront is heated up to a temperature of 1–2 eV by photons in the hard part of the spectrum, with energies for which hν/kT?>?4. We simulate numerically the experiments at the PHELIX facility to heat a low-density cellulose triacetate (TAC, C₁₂H₁₆O₈) taking into account the radiation transfer. The energy and the spectral flux of radiation that passed through the TAC layer are satisfactorily consistent with the experimental results.