共查询到20条相似文献,搜索用时 31 毫秒
1.
Yu. V. Bobylev M. V. Kuzelev A. A. Rukhadze 《Journal of Experimental and Theoretical Physics》2000,91(1):93-105
Analytic and numerical methods are used to study the nonlinear dynamics of the resonant interaction between a dense nonrelativistic electron beam and a plasma in a spatially bounded system. Regimes such as collective (Raman) and single-particle (Thomson) Cherenkov effects are considered. It is shown that in the first case, the motion of both the beam and plasma electrons exhibits significant nonlinearities. However, because of the weak coupling between the beam and the plasma, the nonlinear dynamics of the instability can be studied analytically and it can be strictly shown that saturation of instability is caused by a nonlinear shift of the radiation frequency and loss of resonance. In the second case, the nonlinear instability dynamics can only be studied numerically. In this regime, at low beam densities significant nonlinearity is only observed in the motion of the beam electrons while the plasma remains linear and saturation of the instability is caused by trapping of beam electrons in the field of the beam-excited plasma wave. 相似文献
2.
The dynamic stability of a vertically standing cantilevered beam simultaneously excited in both horizontal and vertical directions at its base is studied theoretically. The beam is assumed to be an inextensible Euler–Bernoulli beam. The governing equation of motion is derived using Hamilton's principle and has a nonlinear elastic term and a nonlinear inertia term. A forced horizontal external term is added to the parametrically excited system. Applying Galerkin's method for the first bending mode, the forced Mathieu–Duffing equation is derived. The frequency response is obtained by the harmonic balance method, and its stability is investigated using the phase plane method. Excitation frequencies in the horizontal and vertical directions are taken as 1:2, from which we can investigate the influence of the forced response under horizontal excitation on the parametric instability region under vertical excitation. Three criteria for the instability boundary are proposed. The influences of nonlinearities and damping of the beam on the frequency response and parametric instability region are also investigated. The present analytical results for instability boundaries are compared with those of experiments carried out by one of the authors. 相似文献
3.
The modulational instability of ion-acoustic wave in a collisionless, unmagnetized plasma consisting ofwarm ions, hot isothermal electrons, and relativistic electron beam is studied. A modified nonlinear Schrodinger equationincluding one additional term that comes from the effect of relativistic electron beam is derived. It is found that theinclusion of a relativistic electron beam would modify the modulational instability of the wave packet and could notadmit any stationary soliton waves. 相似文献
4.
In this paper, we use a thin filament two dimensional Gaussian beam to model the self-trapping filament. The instability of
the propagation of a Gaussian beam through a nonlinear refractive index media is investigated, theoretically and numerically.
Specifically, the small scale instability of the beam is examined. The numerical results show that the propagation of the
two dimensional Gaussian beam presents one or more nonlinear focal points.
相似文献
5.
M. V. Kuzelev O. V. Lazutchenko A. A. Rukhadze 《Radiophysics and Quantum Electronics》1999,42(10):841-858
We study the nonlinear evolution of an arbitrary initial disturbance due to the development of Čerenkov beam instability in
a magnetized plasma-beam system of finite transverse size. Singleparticle, collective, and aperiodic regimes of this instability
are considered. We calculate the nonlinear spatial spectra of the waves excited at different development stages of the beam
instability in a plasma for the cases of quasi-monochromatic, pulsed, and noise initial disturbances. We analyze the formation
and decay of regular structures in the beam and plasma at the developed nonlinear stage of the process. We find that plasma
nonlinearity leads to the transfer of disturbance energy to the short-wave region of the spectrum. We show that, due to the
development of beam instability, noise initial disturbance tends to become more monochromatic, whereas the shape of a pulsed
one tends to remain unchanged. Transformation of monochromatic spatial disturbances into quasi-monochromatic plasma waves
due to the instability development is analyzed.
Institute of General Physics of the Russian Academy of Sciences, Moscow, Russia. Translated from Izvestiya Vysshikh Uchebnykh
Zavedenii, Radiofizika, Vol. 42, No. 10, pp. 958–976, October 1999. 相似文献
6.
《Physics letters. A》2019,383(27):125855
The nonlinear beam-core evolution equation approach is proposed as a powerful tool to estimate the acceptable beam current in a given circular accelerator. The approach is justified by the macroparticle simulation over a wide beam current parameter region. Space-charge effects on the beam-core evolution are discussed by Poincaré mapping on the beam-core phase space (σ, dσ/ds). The instability seen in the beam-core evolution is rigorously analyzed as an eigenvalue problem in the coupled linear system derived from the linearized beam-core evolution equations. A threshold current resulting in the instability is given by both the nonlinear beam-core evolution equation approach and the coupled linear system approach. As an example, a fast cycling induction synchrotron is evaluated in which the space-charge effects are significant because it is injector-free. 相似文献
7.
We study theoretically wideband modulation instability at combination frequencies in media having cubic nonlinearity of self-focusing
type along with the higher-order defocusing nonlinearity. It is assumed that in a medium with a purely cubic nonlinearity,
the medium dispersion does not permit modulation instability. In this case, a collapse of the wave field exists if the beam
power is higher than the critical power of self-focusing. The higher-order nonlinearity limits the field at the nonlinear
focus, and the instability at combination frequencies becomes possible. It turns out that the field at the nonlinear focus
increases with increasing excess of the beam power over the critical power of self-focusing. The obtained values of the nonlinear
dielectric permittivity are used for determination of the growth rates of instability at combination frequencies. These growth
rates ensure an increase in the combination fields from noise levels up to values comparable with the field of the high-power
beam. Such an increase takes place if the beam power is severalfold higher than the critical one. The developed theory can
be used for explanation of spectrum superbroadening during self-focusing of sufficiently short laser pulses and high-harmonic
generation.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 6, pp. 522–532, June 2007. 相似文献
8.
The nonlinear stage in the development of a resistive hose instability of a highcurrent relativistic electron beam in a finite-conductivity plasma has been studied in the rigid-beam model. The attenuation of the force of the interaction of the beam with the magnetic field of the total current for large beam displacements is shown to result in the stabilization of the instability. The stabilization time and the amplitudes of the oscillations in the saturation regime are determined as functions of the parameters of the beam in the plasma.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fiz., No. 10, pp. 78–81, October, 1987. 相似文献
9.
Huang Z De Luca A Atherton TJ Bird M Rosenblatt C Carlès P 《Physical review letters》2007,99(20):204502
In a Rayleigh-Taylor instability a dense fluid sits metastably atop a less dense fluid, a configuration that can be stabilized using a magnetic field gradient when one fluid is highly paramagnetic. On switching off the magnetic field, the instability occurs as the dense fluid falls under gravity. By affixing appropriately shaped magnetically permeable wires to the outside of the cell, one may impose arbitrarily chosen and well-controlled initial perturbations on the interface. This technique is used to examine both the linear and nonlinear growth regimes for which the perturbation amplitudes, growth rates, and nonlinear growth coefficients are obtained. 相似文献
10.
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12.
We investigate the spatial modulation instability in colloidal suspension based on the nonlinear Schrödinger equation. By a standard linear stability analysis, we obtain the expression for instability gain and identified the relationship between the measurable instability characteristic parameters and the particle radius, the optical beam width. It is shown that the modulation growth rate, the maximum growth rate, cut-off frequency and the fastest growth frequency increase as the particle radius decreases and (or) the beam width increases if the optical intensity is constant. Moreover, the ultimate values of the cut-off frequency and the fastest growth frequency are proportional to the beam width, while are independent of the sphere radius. The results provide a new approach to measure the sphere radius and to control the characteristic parameters of modulation instability through the beam width. 相似文献
13.
14.
The theoretical framework predicting the long-term evolution, structure, and coalescence energetics of current filaments during the Weibel instability of an electron beam in a collisionless plasma is developed. We emphasize the nonlinear stage of the instability, during which the beam density of filaments increases to the background ion density, and the ambient plasma electrons are fully expelled from the filaments. Our analytic and numerical results demonstrate that the beam filaments can carry super-Alfvénic currents and develop hollow-current density profiles. This explains why the initially increasing magnetic field energy eventually decreases during the late stage of the instability. 相似文献
15.
A. Kendl 《Physics letters. A》2011,375(35):3138-3141
A semi-classical nonlinear collisional drift wave model for dense magnetized plasmas is developed and solved numerically. The effects of fluid electron density fluctuations associated with quantum statistical pressure and quantum Bohm force are included, and their influences on the collisional drift wave instability and the resulting fully developed nanoscale drift wave turbulence are discussed. It is found that the quantum effects increase the growth rate of the collisional drift wave instability, and introduce a finite de Broglie length screening on the drift wave turbulent density perturbations. The relevance to nanoscale turbulence in nonuniform dense magnetoplasmas is discussed. 相似文献
16.
The force of interaction between a relativistic electron beam deflected by resistive hose instability and the eddy current induced in a tubular plasma channel of finite conductivity is computed. Dependences of the force on channel ohmic conductivity and current rise time in a beam pulse are studied. For a beam propagating through a perfectly conducting waveguide under the ion-focused regime, the interaction of the beam with the ion-channel electrostatic image on the waveguide wall is studied for the case when the beam and the channel are deflected from the waveguide axis as a result of ion hose instability. The dependence of the force on both deflection amplitudes is ascertained for the nonlinear phase of instability. It is demonstrated that the force under study may become comparable to the beam-channel interaction force if the deflections are large. 相似文献
17.
M. V. Kuzelev 《Bulletin of the Lebedev Physics Institute》2009,36(8):225-229
The quantum theory of induced Cherenkov radiation by an electron beam of longitudinal waves in isotropic plasma is presented.
Nonrelativistic quantum nonlinear equations of Cherenkov beam-plasma instability are obtained. A quantum dispersion relation
is derived in the linear approximation and instability development increments are determined. 相似文献
18.
19.
Modulation instability of an intense right-hand elliptically polarized laser beam propagating through an electron-positron plasma is investigated by a new method. The nonlinear dispersion relation, in which the relativistic and ponderomotive nonlinearities are taken into account, is obtained for the laser radiation in electron-positron plasma by the Lorentz transformation. The Karpman equation is generalized to the case of three dimensions with three field components. When the nonlinear frequency shift of the electromagnetic field in plasma is involved, the nonlinear evolution equation for the slowly varying envelope of the laser field is obtained. Thus, modulation instability of the intense laser beam in electron-positron plasma is studied and the temporal growth rate of the instability is derived. The analysis shows that the growth rate of modulation instability is increased significantly near the critical surface in a laser-plasma. 相似文献
20.
采用洛伦兹变换推导出左旋椭圆偏振强激光在磁化等离子体中的非线性色散关系,根据Karpman方法推导出激光场包络的非线性控制方程,分析了在磁化等离子体中左旋椭圆偏振激光的调制不稳定性,得到了调制不稳定的时间增长率。分析结果表明,磁化等离子体中自调制不稳定的极大增长率较非磁化情况明显减小,且在激光等离子体临界面附近处调制不稳定性的时间增长率显著增大。 相似文献