共查询到20条相似文献,搜索用时 218 毫秒
1.
《Waves in Random and Complex Media》2013,23(3):472-490
The theoretical investigation of terahertz waves and their excitation by electron beam injection in a cylindrical metallic plasma waveguide is investigated. This metallic waveguide includes a cold collisionless unmagnetized annular degenerate plasma and a dielectric rod. The dispersion characteristics of these waves, the frequency spectra of fast and slow E-modes waves (transverse magnetic field), are studied. Also, the effects of the dielectric permittivity, the radius of the dielectric rod and the radius of the plasma on the frequency spectra and the time growth rate of waves are simulated. In addition, the electric field profiles in this waveguide are plotted. 相似文献
2.
《Waves in Random and Complex Media》2013,23(2):259-267
A perfectly conducting elliptical cylinder filled with a warm plasma and immersed in an infinite axial magnetic field is considered. Using Maxwell’s equations and dielectric tensor, a Mathieu differential equation for axial component of electric field is obtained. Considering the boundary conditions, dispersion relation for waves in a plasma of warm electrons and immobile ions, which fills an elliptical waveguide and it is under the action of infinite axial magnetic field are calculated. Furthermore, dispersion relation and scalar potential in the quasi-static approximation in a cold magnetized plasma elliptical waveguide is calculated. The obtained results are graphically presented. 相似文献
3.
N. I. Karbushev 《Radiophysics and Quantum Electronics》1991,34(7):672-679
It is shown when the cross-section of a waveguide is partially filled by magnetized plasma, slow and fast E-waves can exist simultaneously at the same frequency, which is lower than the plasma frequency. In the case of spatially periodic corrugation of the waveguide wall, the waves can be coupled, forming new waves with hybrid properties in a certain frequency range. The interaction of an electron beam with the hybrid waves differs from the interaction with a slow plasma wave in a waveguide with smooth walls or with the wave in an evacuated corrugated waveguide. For example, when two waves traveling in the same direction are coupled, the increments of the hybrid waves have values on the order of but somewhat smaller than those of the increment of a slow plasma wave in a smooth waveguide.Moscow Radio-Engineering Institute, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 7, pp. 825–836, July, 1991. 相似文献
4.
The damping decrement of Landau damping and the effect of thermal velocity on the frequency spectrum of a propagating wave in a bounded plasma column are investigated.The magnetized plasma column partially filling a cylindrical metallic tube is considered to be collisionless and non-degenerate.The Landau damping is due to the thermal motion of charge carriers and appears whenever the phase velocity of the plasma waves exceeds the thermal velocity of carriers.The analysis is based on a self-consistent kinetic theory and the solutions of the wave equation in a cylindrical plasma waveguide are presented using Vlasov and Maxwell equations.The hybrid mode dispersion equation for the cylindrical plasma waveguide is obtained through the application of appropriate boundary conditions to the plasma-vacuum interface.The dependence of Landau damping on plasma parameters and the effects of the metallic tube boundary on the dispersion characteristics of plasma and waveguide modes are investigated in detail through numerical calculations. 相似文献
5.
In this work we investigate the effect of a relativistic homogeneous electron beam on the field stability and minimizing the energy losses in waveguide filled homogeneously with plasma. Analytical calculations are performed to find the plasma dielectric tensor by applying the boundary conditions at the plasma‐conductor interface. We derive the dispersion equations which describe the propagated E‐ and H‐waves and their damping rate. The necessary condition for the field stability in the waveguide and the amplification coefficient for the E‐wave are obtained. The effects of plasma warmness and an external static magnetic field are taken into consideration. Relativistic electron beam is found to play a crucial role in controlling the field attenuation in waveguide. 相似文献
6.
The dispersion of nonsymmetrical electromagnetic waves in waveguide, partially filled with plasma, is studied numerically and experimentally. An external d.c. coaxial magnetic field is applied to the waveguide. The dispersion equation of these waves is obtained, and it is solved numerically for the experimental conditions. Results are obtained, which show coupling of the waveguide HEl1-modes with the family of the high-frequency plasma HEln-modes. The numerical dispersion curves are experimentally examined, and the influence of the magnetic field and the plasma density is studied. 相似文献
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Godfrey Brendan B. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1978,6(4):380-383
We investigate the dispersion relation for long wavelength slow Langmuir waves in a relativistic particle beam propagating along a strong magnetic guide field in an evacuated metallic waveguide. For a large class of beam radial profiles, wave phase velocity drops to zero with infinite slope as beam current approaches the space-charge limit. This result is of importance to certain collective ion acceleration proposals. 相似文献
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等离子体中非线性朗谬尔波的哈密顿描述 总被引:1,自引:1,他引:0
研究了在双离子(H^ ,O^ )成份等离子体中的非线性朗谬尔波的特性,从流体方程出发,考虑低频离子运动的完全非线性和双极势的色散,得到了描述高频电场缓变振幅与低频势扰动的耦合方程组。利用哈密顿方法,在小振幅情况下,对方程组解耦合,利用Sagdeev势方法,对孤立波的性状进行了讨论,结果表明,双离子成份等离子体中双极势的孤立子的幅度相对电子,离子等离子体的双极势孤立子的幅度要大,而相应的高频电场强度的幅度相对要小,相应的孤立子的速度传播区也较小。 相似文献
11.
《等离子体物理论文集》2017,57(5):196-208
This paper studies the propagation and spatial attenuation of high‐frequency eigen‐symmetric and dipolar electromagnetic waves along a coaxial plasma–metal waveguiding structure that contains a slightly axial and strong radial non‐uniform cylindrical plasma slab in an external azimuthal non‐uniform magnetic field. The influence of such parameters as the effective electron collision frequency, the direct current value producing the external azimuthal magnetic field, parameters that characterize plasma density radial profile, and waveguide geometric parameters on the dispersion, spatial attenuation, and radial field structure of the waves is considered. The regions of waveguiding structure parameters where the electromagnetic wave properties can be effectively controlled are studied and analyzed. 相似文献
12.
M. V. Kuzelev 《Journal of Experimental and Theoretical Physics》2010,110(4):710-721
Nonlinear quantum-mechanical equations are derived for Langmuir waves in an isotropic electron collisionless plasma. A general
analysis of dispersion relations is carried out for complex spectra of Langmuir waves and van Kampen waves in a quantum plasma
with an arbitrary electron momentum distribution. Quantum nonlinear collisionless Landau damping in Maxwellian and degenerate
plasmas is studied. It is shown that collisionless damping of Langmuir waves (including zero sound) occurs in collisionless
plasmas due to quantum correction in the Cherenkov absorption condition, which is a purely quantum effect. Solutions to the
quantum dispersion equation are obtained for a degenerate plasma. 相似文献
13.
We study the field structure and dispersion properties of a hybrid eigenmode guided by a nonuniform magnetized plasma waveguide.
It is shown that the rotational and quasi-potential waves contribute to the formation of such a mode in the whistler frequency
range. Depending on the plasma density, the rotational component of the hybrid mode is determined by either waves with complex
transverse wave numbers or whistler waves, or by true surface waves. In the presence of an axial nonuniformity of the plasma
in a channel, the transverse field structure of the propagating mode changes, which is stipulated by changes in both the values
of transverse wave numbers and their dependence on the radial coordinate. It is found that the spectrum of axial wave numbers
of eigenmodes of a plasma waveguide undergoes a pronounced condensation when smoothing the waveguide walls. The damping of
the hybrid mode of a nonuniform waveguide due to electron collisions is found and it is shown that collisional losses determine
the damping of waves trapped in the waveguide in the experiments on ionization self-channeling of whistler waves. We have
found the effect of “displacing” the strong field from the inner core to the background outer region of the waveguide with
increasing plasma density on its axis and broadening background region.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 7, pp. 607–617, July 2006. 相似文献
14.
Parametrical excitation of surface type X-modes (STXM) at the second harmonic of electron cyclotron frequency by nonmonochromatic external alternating electric field is under consideration. STXM are the eigenmodes of a planar magnetoactive plasma waveguide structure consisting of a metal wall with dielectric coating and uniform plasma filling. An external steady magnetic field is applied along the plasma interface, so it is perpendicular to the group velocity of the considered extraordinarily polarized waves. Influence of the plasma waveguide parameters on the parametrical instability of the STXM is studied. External alternating electric field is assumed to consist of two fields with different amplitudes and frequencies. A theoretical investigation is carried out using kinetic equation for plasma particles under the conditions of weak plasma spatial dispersion and small amplitudes of external electric fields. The obtained results can be useful for research in branch of edge plasma physics. 相似文献
15.
A study is made of the spectrum of surface waves in a semibounded plasma flow. The frequency spectra and damping rates of the waves propagating along the flow are analyzed both in the high-frequency range (in which the spatial dispersion is weak and the wave damping is governed primarily by electron collisions) and the low-frequency range (in which the spatial-dispersion effects dominate), with focus on the effect of the flow velocity on the propagation of ion-acoustic waves. Special attention is paid to the penetration of a static field into a plasma flowing at a supersonic velocity. 相似文献
16.
We study the features of the dispersion curves and field structures of the fundamental axisymmetric mode of nonuniform layered
plasma waveguides in a longitudinal magnetic field. It is shown that the presence of sharp boundaries between layers leads
to the appearance of additional branches of the dispersion curves in the frequency range ω Be < ω < ωUH(0), where ωBe is the electron gyrofrequency and ωUH(0) is the upper-hybrid resonance frequency for the near-axis region of a nonuniform waveguide. The fields of eigenmodes corresponding
to these branches comprise resonance structures near the sharp plasma-density variation at which the upper-hybrid resonance
conditions are satisfied and plasma waves are excited. The frequency interval of such a branch is limited by the resonant
frequencies of the neighboring uniform layers. It turns out that in the case of a strong magnetic field ({ie392-01}, where
ωp is the plasma frequency having the value {ie392-02} in the near-axis region of a nonuniform waveguide), the fundamental-mode
field is localized in the near-axis region of a nonuniform waveguide, whereas in the opposite case {ie392-03}, the maximum
wave fields are localized in either the upper-hybrid resonance region or the outer (near-boundary) layer of the waveguide
if there is no resonance region. It is found that the whistler (helicon) contribution to the field structure of the fundamental
axisymmetric mode is very small for narrow nonuniform waveguides (b < λ0, where b is the waveguide radius and λ0 is the wavelength in free space) if the plasma density on the axis is high compared with the cutoff density {ie392-04}. We
present one of the possible explanations for the effect of narrowing of the plasma channel of a high-frequency whistler-range
discharge with distance from a source in the increasing magnetic field.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 5, pp. 434–446, May 2008. 相似文献
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Qiang-Lin Hu Xiao-Bin Luo Gui-Lan Xiao Wen Hu Ji-Chang Peng Shen-Lin Zhou 《理论物理通讯》2018,70(5):609-612
The linear Langmuir and electromagnetic (EM) waves in relativistic hot plasmas are discussed, and the dispersion relations are obtained based on the covariant Maxwell's and fluid equations. When kBT/mc2>1, the effective mass of electrons will be increased obviously. As the results, many other influences are induced, such as the decrease of the plasmas frequency and the critical frequency, the reduction of the electron sound velocity and the electrons' oscillation velocity, and so on. Numerical results show that these influences can affect the dispersion relations of Langmuir and EM waves seriously even in linear regime. 相似文献
20.
Freely propagating electrostatic waves (free modes) are observed to be produced by intense, localized field structures in laboratory measurements performed in an unmagnetized plasma in a state of strong Langmuir turbulence. The freely traveling waves conform to the Langmuir dispersion relation and have an average frequency which is approximately 11% higher than the average frequency of the localized field structures. The observations are consistent with the predictions of strong Langmuir turbulence theory. 相似文献