相对论电子束在离子通道中的聚焦与输运

 基于单粒子理论,描述了相对论电子束在离子通道中的聚焦输运过程,讨论了离子-电子密度比、相对论因子、束加速电压和入射电流等系统参数对电子束的聚焦半径、纵向聚焦位置的影响。研究表明,离子通道对电子束具有强烈的聚焦效应,束流在离子通道内的传输是类周期波动传输,随传输距离增加,聚焦点处的半径逐渐增加,束流的波动幅度逐渐减小。选择适当的系统参数,可调节束聚焦点位置和聚焦点半径的大小,实现电子束的长距传输并且减少电子束的耗散。     

Propagation of electron cyclotron waves in a weakly relativistic plasma with steep density and temperature profiles

Summary A detailed analysis is made of the deduction of systems of differential equations describing the propagation of both ordinary and extraordinary waves in the electron cyclotron frequency range in a stratified plasma, perpendicularly to the magnetic field and across the electroncyclotron fundamental resonance layer. The equations are derived under conditions of not too large electron temperature (the so-called weakly relativistic condition) and of very weak nonuniformities of the confining magnetic field. The effects of the nonhomogeneities of the equilibrium plasma density and temperature are carefully examined. It is shown that the propagation equations derived previously in the literature can be extended with only a moderately larger effort in computations to take account also of very strong density and temperature gradients.     

On the envelope solitons in a relativistic ion-acoustic plasma

Summary Nonlinear Schr?dinger equation describing the envelope solitons is deduced in the case of ion-acoustic relativistic plasma, without taking recourse to the usual reductive perturbation theory. The methodology is that of Friedet al. (1973), which in some sense can be considered to be an extension of the effective (pseudo) potential theory. Amplitude and velocity of the solitary wave are obtained in terms of the physical parameters of plasma.

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Riassunto Si deriva l'equazione di Schr?dinger non lineare che descrive i solitoni dell'involucro nel caso del plasma relativistico a onde ioniche, senza fare ricorso all'usuale teoria di perturbazione riduttiva. La metodologia è quella di Friedet al. (1973) che si può considerare in qualche modo come un'estensione della teoria efficace di (pseudo) potenziale. Si ottengono l'ampiezza e la velocità dell'onda solitaria nei termini dei parametri fisici del plasma.

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Резюме Выводится нелинейное уравнение Шредингера, описывающее огибающие солитоны в случае релятивистской плазмы, без использования обычной теории возмущений. Методология аналогична методологии фрейда и др. (1973), которая в некотором смысле представляет обобщение теории эффективного (псевдо) потенциала. Получается вмплитуда и скорости одиночной волны в терминах физических параметров плазмы.

     

Surface waves on the relativistic quantum plasma half-space

We present a theoretical investigation on the propagation of surface waves on the relativistic quantum plasma half-space. The dispersion relations of surface plasmon polaritons (SPPs) and electrostatic surface waves containing relativistic quantum corrected terms are derived. Results show that the frequency of SPPs has a blue-shift, and surface Langmuir oscillations can propagate on the cold plasma half-space due to quantum effects. Numerical evaluation indicates that quantum effects to SPPs and electrostatic surface waves are significant and observable.     

A standing-wave approach for discussing electron transport in relativistic quantum conductors

Electron transport through a generic one-dimensional relativistic quantum conductor is discussed by calculating the quantized electron velocity as well as the quantized energy for sufficiently large values of the involved quantum number in the framework of a standing-wave approach. Fermi velocity and Fermi energy are discussed near the classical limit.     

相对论返波管注-波作用不稳定区的研究

 以环形电子注驱动的、正弦型周期慢波结构的相对论返波管（RBWO）为模型,理论推导出RBWO慢波结构的色散方程,画出了不包括和包括电子注的色散曲线,然后采用在复平面上绘制等高线图进行逼近的方法对注-波作用不稳定区工作频率的实部和虚部进行了求解,绘出了完整的包括电子注的慢波结构色散关系曲线,并估算了微波的时间增长率和能量转换效率。研究得出：当a（电子注电流参数）较大时,电磁波与慢电荷波的相互作用是不稳定的;而在a较小时,注-波相互作用具有明显的三波作用的特点;微波增长是通过注-波不稳定作用引起的;随着a的增大,微波时间增长率先增大后减小,在a为0.02时有最大值1.37,此时的能量转换效率为19%;增大电子注半径或慢波结构的波纹深度都可以增强注-波不稳定作用。     

Propagation and interaction of ion-acoustic solitary waves in a quantum electron-positron-ion plasma

This paper discusses the existence of ion-acoustic solitary waves and their interaction in a dense quantum electron-positron-ion plasma by using the quantum hydrodynamic equations.The extended Poincar’e-Lighthill-Kuo perturbation method is used to derive the Korteweg-de Vries equations for quantum ion-acoustic solitary waves in this plasma.The effects of the ratio of positrons to ions unperturbation number density p and the quantum diffraction parameter H e (H p) on the newly formed wave during interaction,and the phase shift of the colliding solitary waves are studied.It is found that the interaction between two solitary waves fits linear superposition principle and these plasma parameters have significantly influence on the newly formed wave and phase shift of the colliding solitary waves.The investigations should be useful for understanding the propagation and interaction of ion-acoustic solitary waves in dense astrophysical plasmas (such as white dwarfs) as well as in intense laser-solid matter interaction experiments.     

Rotating relativistic electron beam-plasma interaction and formation of a field-reversed configuration

Experimental results on interaction of a rotating relativistic electron beam with plasma and neutral gas are presented. The rotating relativistic electron beam has been propagated up to a distance of 150 cm in a plasma. The response of the plasma to the rotating electron beam is found to be of magnetic diffusion type over a plasma density range 10¹¹–10¹³ cm⁻³. Excitation of the axial and azimuthal return currents by the rotating beam and subsequent trapping of the azimuthal return current layer by the magnetic mirror field are observed. A field-reversed configuration has been formed by the rotating relativistic electron beam when injected into neutral hydrogen gas. We have observed field reversal up to three times the initial field in an axial length of 100 cm.     

Propagation of ion-acoustic waves in a dusty plasma with non-isothermal electrons

For an unmagnetised collisionless plasma consisting of warm ions, nonisothermal electrons and cold, massive and charged dust grains, the Sagdeev potential equation, considering both ion dynamics and dust dynamics has been derived. It has been observed that the Sagdeev potential V(ϕ) exists only for ϕ > 0 up to an upper limit (ϕ ≃ 1.2). This implies the possibility of existence of compressive solitary wave in the plasma. Exhaustive numerics done for both the large-amplitude and small-amplitude ion-acoustic waves have revealed that various parameters, namely, ion temperature, non-isothermality of electrons, Mach numbers etc. have considerable impact on the amplitude as well as the width of the solitary waves. Dependence of soliton profiles on the ion temperature and the Mach number has also been graphically displayed. Moreover, incorporating dust-charge fluctuation and non-isothermality of electrons, a non-linear equation relating the grain surface potential to the electrostatic potential has been derived. It has been solved numerically and interdependence of the two potentials for various ion temperatures and orders of non-isothermality has been shown graphically.      

Generation of whistler mode in a relativistic plasma

This paper contains the plasma maser interaction between high frequency nonresonant whistler R-mode and low frequency resonant ion acoustic mode in a relativistic plasma. It shows that the whistler R-mode grows through the plasma maser interaction between the relativistic electrons and the ion acoustic fluctuation.      

Equilibrium distribution function of a relativistic dilute perfect gas

An alternative to the Jüttner distribution has been recently proposed by several authors. The literature on the topic is reviewed critically. It is found that the Jüttner distribution is correct and that the alternative distribution contradicts quantum field theory, statistical physics and continuum mechanics.     

Linear and nonlinear fluctuations of electron-temperature-gradient driven mode and electron acoustic mode in a two-electron temperature nonthermal magnetized plasma

Nonlinear vortical structures and soliton formation are investigated for electron temperature gradient instability in a two-electron temperature non-Maxwellian magnetoplasma. The inhomogeneity in magnetic field is also considered. A new set of nonlinear equations, using transport equations of Braginskii”s model, are formulated to study the nonlinear structures. A modified linear dispersion relation of coupled electron temperature gradient (ETG) mode and electron acoustic wave is derived. The ETG instability is found to increase with increase in η_ec value that increases with sharp density gradients. The results are applied to auroral region of earth's magnetosphere and the calculated values of the nonlinear electric field of fast solitary waves are found to be in agreement with the Viking satellite observations.     

Orbital angular momentum of channeling radiation from relativistic electrons in thin Si crystal

We propose to use channeling radiation (CR) from relativistic electrons as a source of high energy twisted photons in the MeV range. We calculate numerically the orbital angular momentum (OAM) of radiation produced by electrons with the energies $155÷2500$ MeV for the axial and planar channeling in the thin Si crystal. We obtain that the average OAM of CR in this case is approximately $1÷6?$ per photon with the photon energies about $1÷2$ MeV.     

Refractive index and material dispersion in relativistic electron optics

The refractive index and material dispersion associated with relativistic motion of electrons are calculated. Moreover, the wavelength dependence of refractive index is compared with the Sellmeier model for the index of refraction of lightwaves.     

Stimulated Raman scattering of gaussian laser beam in relativistic plasma

This paper presents an investigation of Stimulated Raman Scattering of gaussian laser beam in relativistic Plasma. The pump beam interacts with a pre-excited electron plasma wave and thereby generate a back-scattered wave. Due to intense laser beam, electron oscillatory velocity becomes comparable to the velocity of light, which modifies the background plasma density profile in a direction transverse to pump beam axis. The relativistic non-linearity due to increase in mass of the electrons effects the incident laser beam, electron plasma wave and back-scattered beam. We have set up the non-linear differential equations for the beam width parameters of the main beam, electron plasma wave, back-scattered wave and derived SRS back-reflectivity by taking full non-linear part of the dielectric constant of relativistic plasma with the help of moment theory approach. It is observed from the analysis that self-focusing of the pump beam greatly affects the SRS reflectivity, which plays a significant role in laser induced fusion.     

相对论电子束在离子通道中的聚焦与输运

基于单粒子理论,描述了相对论电子束在离子通道中的聚焦输运过程,讨论了离子-电子密度比、相对论因子、束加速电压和入射电流等系统参数对电子束的聚焦半径、纵向聚焦位置的影响。研究表明,离子通道对电子束具有强烈的聚焦效应,束流在离子通道内的传输是类周期波动传输,随传输距离增加,聚焦点处的半径逐渐增加,束流的波动幅度逐渐减小。选择适当的系统参数,可调节束聚焦点位置和聚焦点半径的大小,实现电子束的长距传输并且减少电子束的耗散。