Interaction of an Electron Beam with Electromagnetic Waves in a Rectangular Plasma Waveguide

We study the interaction of a rectilinear nonrelativistic electron beam with a solid-state plasma in a rectangular metal waveguide, as well as wave processes in a plasma waveguide of rectangular cross section in the absence of an electron beam. It is shown that in such a system, space-charge waves of an electron beam, which propagate along a semiconductor boundary, become unstable in a wide frequency band.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 3, pp. 219–227, March 2005.     

Linear and Nonlinear Magnetic Electron Drift Waves in a Nonuniform Strong Magnetic Field

Linear and nonlinear propagation of magnetic electron drift vortex waves in a nonuniform magnetic field is investigated by means of a generalized adiabatic law which takes into account the effect of strong fields and reduces in the appropriate limits to several well known energy conservation equations in a collisionless plasma. In the linear limit, an instability is shown to exist, whereas in the nonlinear regime, steady-state dipole vortices associated with the electron drift vortex waves may appear. The anomalous electron energy transport associated with the unstable magnetic electron drift vortex waves is investigated by means of a quasilinear theory.     

Propagation and Absorption of ECR Waves in a Low Temperature Toroidal Plasma of Small Size and Magnetic Field

The propagation and absorption of ECR waves in a tokamak plasma with small size and low values of the electron temperature and the toroidal magnetic field is studied numerically. The cold plasma dispersion equation is solved and ray tracing calculations are performed to find the accessibility conditions and the optimal angle of wave launching for maximal ECR absorption. Absorption coefficients are computed in the high density approximation.     

Dust Lattice Waves of Dusty Plasma Chain with an External Magnetic Field

Dust lattice waves of a one-dimensional plasma crystal chain with an external magnetic field are investigated. When the magnetic field is in the vertical direction （θ- 0）, perpendicular to the chain, the vertical transverse mode is not affected, while the horizontal transverse mode is coupled with the longitudinal mode. In the high frequency range, we obtain an ‘upper-hybrid＇ dust lattice mode and in the low frequency range, we obtain a ＇lower-hybrid＇ dust lattice mode. Between the two modes, a ＇gap＇ is formed. When the magnetic field is oriented to the chain （0 = π/2）, the longitudinal mode is not affected while both the horizontal and vertical transverse modes are shifted due to the effect of the magnetic field.     

Electron Energy Distribution in a Nondegenerate Nonrelativistic Gas Polarized by a Magnetic Field

The effect of a strong magnetic field on the electron energy distribution for a nondegenerate, nonrelativistic magnetized electron gas is assessed in the context of the statistical thermodynamics of equilibrium systems in the general form and for the zero Landau level. The average energy for the level is calculated using the distribution obtained.     

Parametric Decay of Electron Electrostatic Waves Pumped by an Electromagnetic Wave

In a computer simulation study, we have observed the parametric decay of an electromagnetic wave propagating parallel to the DC magnetic field into two electron electrostatic waves. We have identified the mechanism as three-wave parametric interaction. The growth constants of the decay waves have been measured. After saturation, the decay waves are observed to trap electrons. Consequently, the velocity distribution function develops a high velocity tail. The details of these processes are discussed. We have found that the kinetic energy of the total assembly of electrons will increase by about a factor of four.     

Intensity Effects in Scattering of Electromagnetic Waves by Electrons Moving in External Magnetic Field

In this paper we consider the emission processes of a relativistic electron moving in the field of a plane electromagnetic wave and in a homogeneous magnetic field. A detailed analysis of the most important characteristics of the radiation properties for arbitrary values of the magnetic field, compared with \documentclass{article}\pagestyle{empty}\begin{document}$ [H_0 = \frac{{m^2 c^3}}{{e\hbar}}]$\end{document} = 4.41.10¹³ gauss, is presented.     

Finite Temperature and Wall Effects on the Absorption of Electron Cyclotron Waves in an EBT Plasma

The absorption of electron cyclotron waves propagating along an externally applied magnetic field in a uniform plasma surrounded by a cylindrical metallic cavity wall is studied. In the model, the cavity wall, the vacuum-plasma interface, and the effects of finite electron temperature are considered, and the dispersion relation for the wave propagation is derived. The results are then applied to the ELMO Bumpy Torus (EBT-I) plasma, and the propagation characteristics are computed. The wave absorption in the ordinary mode is found to be a result of the wall effects, which cannot be predicted with the infinite plasma theory. The loaded quality factor QL is also estimated from the model to be about 14, which is in good agreement with the experimentally observed value.     

A Particle in a Magnetic Field of an Infinite Rectilinear Current

We consider the Schrödinger operator H=(i+A)² in the space L ₂(R ³) with a magnetic potential A created by an infinite rectilinear current. We show that the operator H is absolutely continuous, its spectrum has infinite multiplicity and coincides with the positive half-axis. Then we find the large-time behavior of solutions exp(–i H t)f of the time dependent Schrödinger equation. Our main observation is that a quantum particle has always a preferable (depending on its charge) direction of propagation along the current. Similar result is true in classical mechanics.     

Momentum Space Diffusion from Spatially Amplified Waves in a Plasma in a Magnetic Field

Quasilinear equations for relativistic plasmas in external magnetic fields are derived for the case of spatially growing wave turbulence. This generalizes the well-known quasilinear approach to an amplifying relativistic plasma. The equations can be cast in condensed momentum-space diffusive form. The diffusion tensor is given. As a result an inhomogeneity is produced in the space charge distribution giving rise to the development of a second-order field-aligned dc electric field. A general formula for the electrostatic potential is presented, which is specialised to the case of ion-cyclotron turbulence. Here the field points out of the interaction region.     

Numerical Analysis of Symmetrical Waves Dispersion in a Nonisothermal Plasma Waveguide in a Magnetic Field

Dispersion equations of a nonisothermal plasma waveguide in a constant external magnetic field are derived, when the magnetic field intensity tends to infinity. The plasma electrons' thermal velocity are taken in mind. A numerical analysis of dispersion equations for the E- (TH-) and H- (TE-) waves is made. In the high-frequency range it shows the possibility of the slow E-waves exciting with a higher frequency than the electron Langmuir frequency. In the range near to the ion Langmuir frequency it shows the existence of waves with an anomalous dispersion. These waves are named low-frequency backward E-waves and it is shown, that in some frequency ranges they change the group velocity sign. The dispersion is investigated also in respect to the waveguide plasma filling.     

Solitary Waves in Relativistic Electromagnetic Plasma

Solitary waves in relativistic electromagnetic plasmas are obtained numerically. The longitudinal momentum of electrons has been taken into account in the problem. It is found that in the moving frame with electromagnetic field propagating the solitary waves can exist in both cases, where the vector potential frequency is larger or smaller than the plasma characteristic frequency.     

Oblique Electron Thermal Waves in a Magnetized Plasma

Propagations of an oblique electron thermal mode under the electron plasma frequency without boundary effects are investigated experimentally and theoretically in a magnetized plasma. The phase, ray, and group velocity surfaces of the electron thermal mode are obtained in a polar coordinate. The experimental observation of the electron mode radiated from a point source is found to be in fair accord with the theoretical wave fronts which are obtained from the ray velocity surface. Wave fronts and ray trajectories of an oblique electron thermal mode radiated from a point source are numerically obtained in an inhomogeneous magnetized plasma with a use of an electrostatic kinetic theory. The spatial numerical results are indicated mainly below the electron plasma and cyclotron frequencies. Reflections of the mode in the plasma density lower than the electron plasma frequency are made clear numerically.     

Two-Dimensional MHD Simulations of Magnetic Field Penetration in the Plasma Opening Switch

Three mechanisms for anomalous magnetic field penetration have been investigated in computer simulations of Sandia's plasma opening switch (POS). The POS simulations have been performed using the two-dimensional (2-D) two-temperature single-fluid magnetohydrodynamic (MHD) code HAM [1], [2]. The three penetration mechanisms considered are 1) the Chodura model based on the ion-acoustic instability where the saturated value of the anomalous collision frequency is approximated by the ion plasma frequency; 2) a model based on the lower hybrid instability in which the anomalous collision frequency is proportional to both the ion plasma frequency and the electron drift velocity; and 3) a model that limits the ion drift velocity to the plasma influx velocity. Two-dimensional MHD calculations of the POS will be presented which show these models to be qualitatively similar for densities above a few 1013 cm-3, though at lower densities they can be quite different. The calculations are compared to experiments, and some agreement is seen with the lower hybrid model. The other models compare only marginally to experimental results.     

Reflection and Transmission of Extraordinary Waves in an Inhomogeneous Magnetized Plasma I. Infinite Plasma

By retaining higher order terms in analysis, a more accurate expression for the reflection and transmission coefficients of an extraordinary wave propagating perpendicular to a static magnetic field through an infinite warm plasma is obtained. The result is compared with previous analytical and numerical results, the latter obtained by an integral equation method. In addition to occurring at resonances, the total reflection of the extraordinary wave is shown to also occur at anti-resonances with a standing wave of larger amplitude.     

Attenuation of Electromagnetic Waves by a Plasma Layer at Atmospheric Pressure

Plasma layers at atmospheric pressure, are good broad band absorbers of electromagnetic radiation. However, to get substantial attenuations, two parameters have to be optimized. These are the plasma number density, and the thickness of the plasma layer. It is found that in order to be an effective attenuator of microwave radiation, a plasma layer has to have a number density in the 10¹³ cm^–3 range, and a thickness equal or larger than the wavelength of the incident wave. However, as the frequency increases, the amount of attenuation tends to reach a limiting value directly proportional to the number density.     

Lattice Waves in Two-Dimensional Hexagonal Quantum Plasma Crystals

Lattice waves including a longitudinal wave and a transverse wave in two-dimensional hexagonal quantum plasma crystals are investigated by using the modified Debye-Hückel screening potential. It is shown that there exists an unstable region of lattice parameters, where the system will melt. The general dispersion relations are derived, and the waves propagating parallel to a primitive translation vector are discussed. We find that both the longitudinal and transverse waves are acoustic-like, and the longitudinal wave has a greater sound speed than that of the transverse wave in the long wavelength limit region.     

超短强激光脉冲驱动等离子体波加速电子方案

随着超短脉冲激光技术的发展, 人们可以在台面尺度获得光强超过10¹⁸W/cm²、脉宽小于100fs的超短脉冲激光.超短脉冲激光很容易把静止的电子加速到兆电子伏的能量. 而更重要的是超短激光脉冲可以通过其有质动力激发大振幅的等离子体波(称为激光尾波场), 后者可以在毫米空间尺度把电子加速到上百兆电子伏的能量.文章将介绍激光尾波场加速电子的物理机制和方案、这个领域的最新进展、以及目前存在的问题.