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由色散方程和流体方程推导得到了横等离激元和对等离子体相互作用的非线性控制方程,利用场论的方法构建非线性控制方程的拉格朗日密度函数并求得相互作用过程中守恒的等离激元数和总能量。通过标度变换发现横等离激元由于调制不稳定性将坍塌形成小尺度的局域结构。在坍塌过程中横等离激元产生的有质动力随场强的增强而增强。由于有质动力对粒子的排斥,对等离子体中将产生小尺度的密度空穴。     

Electron acceleration considering pondermotive force effect in a plasma-filled rectangular waveguide by microwave radiation

The electron acceleration inside the plasma-filled rectangular waveguide is numerically investigated for the externally injected single-electron model considering the effects of density modification under a balance between the ponderomotive force and the pressure gradient force. Using Maxwell’s equations, we evaluate the field components of the fundamental mode in the plasma-filled rectangular waveguide, where the obtained equations are solved numerically using the fourth-order Runge–Kutta method for the electric field amplitude of the microwave. Besides, by solving the relativistic momentum and energy equations using the fourth-order Runge–Kutta method, the deflection angle and the total energy of the electron in the waveguide are obtained. Furthermore, it is shown that the electron energy gain can be controlled using superposing microwave fundamental modes. Effects of various parameters on the results are graphically presented.     

Nonlinear interaction of an intense laser beam with millimeter sized underdense plasmas

Experimental results are reported on the nonlinear interaction of a 0.5 μm laser light with long scalelength preformed plasmas. Spectra from stimulated Brillouin and Raman scattering, as well as measurements of the transmitted laser light clearly indicate the occurence of strong nonlinearities driven by filamentation of the laser beam.     

孤子和辐射场的非线性相互作用

利用穿衣服的方法推导出了在纯辐射场情况下Jost函数对的显式,由此得到了孤子与辐射场相互作用的解析表达式,发现脉冲在传输过程中,由于受到辐射场的作用,其振幅的演化在传播方向上是按照幂指数的负的平方根的规律衰减,并且将最终演化成一个类孤子的形式,且阐明了因子γ对光脉冲输出的光谱特性将会产生重要影响;并对辐射场的存在对类孤子演化的动力学行为作了分析. 关键词： 穿衣服方法 类孤子 孤子 辐射场     

Study of boron and molybdenum plasmas on multipulse interaction of femtosecond radiation with a target

Laser plasmas generated by femtosecond radiation on the surface of boron and molybdenum targets are investigated by the shadowgraph method. The modes of single-pulse and multipulse interaction of laser radiation with a target are compared. The occurrence of plasma bullets is discussed, which were observed on both single-pulse and multipulse interaction with the same area of a target. The wavefront velocities of expanding boron and molybdenum plasmas were measured to be 5 × 10⁴ and 6 × 10³ m s^?1, respectively. The electron density measured by interferometry using a time delay of 800 ps in a boron plasma excited by 795-nm radiation with an intensity of 10¹⁶ W cm^?2 amounted to 8 × 10¹⁹ cm^?3. The correlation between some specific features of the plasma and the generation of the 3/2 harmonic, observed on multipulse interaction of femtosecond radiation with a boron target, is discussed.     

Nonlinear interaction of a two-level atom with counterpropagating radiation beams of different frequencies

The theoretical and numerical results on the nonlinear dynamics of an atom in the fields of two counterpropagating radiation beams of different frequencies are presented. Both resonant and nonresonant interaction regimes are investigated. The atom center-of-mass energy dependence on the field amplitudes exhibits the nonlinear threshold effect of reflection of an atom in the interference field. This phenomenon leads to the atom acceleration or deceleration depending on its initial state. This acceleration or deceleration is base of a shock character because of the impact with the moving potential barrier; it occurs at ultrashort distances on the order of radiation field wavelengths. Furthermore, the role of initial conditions is discussed and analyzed numerically. The text was submitted by the authors in English.     

Nonlinear interaction of linearly polarized laser radiation with condensed media and overcoming the diffraction limit

We have analyzed known experimental results on the formation of periodic structures in condensed media under the action of a series of femtosecond linearly polarized laser pulses. The found examples of the formation of spatial periods of structures with a scale smaller than the diffraction optical limit in the condensed medium have been interpreted in terms of a nonlinear mathematical model, a one-dimensional unimodal logistic mapping that describes how a change in the period that is multiple of two depends on the changing control parameter.     

Nonlinear dynamics associated with rotating magnetized electron-positron-ion plasmas

By using the hydrodynamic equations of electrons and positrons and Poisson equation with stationary ions, a three-dimensional extended Zakharov-Kuznetsov (EZK) equation is derived for small but finite amplitude nonlinear Langmuir structures (solitary and shock pulses) The EZK equation is solved analytically and the features of the nonlinear excitations are investigated numerically. Furthermore, the propagation condition for the nonlinear structures is examined.     

Nonlinear wave modulations in plasmas

A review of the generic features as well as the exact analytical solutions of coupled scalar field equations governing nonlinear wave modulations in plasmas is presented. Coupled sets of equations like the Zakharov system, the Schrödinger-Boussinesq system and the Schrödinger-KDV system are considered. For stationary solutions, the latter two systems yield a generic system of a pair of coupled, ordinary differential equations with many free parameters. Different classes of exact analytical solutions of the generic system which are valid in different regions of the parameter space are obtained. The generic system is shown to generalize the Hénon-Heiles equations in the field of nonlinear dynamics to include a case when the kinetic energy in the corresponding Hamiltonian is not positive definite. The relevance of the generic system to other equations like the self-dual Yang-Mills equations, the complex KDV equation and the complexified classical dynamical equations is also pointed out.     

Plastic plasma interaction with plasmas with growing atomic number

This paper describes the investigation of the influence of target material atomic number (Z) on the laser-produced plasma pressure. For this reason, several target materials representing a wide range of atomic numbers (Z = 3.5 - 73), i.e. plastic (CH), Al, Cu, Ag, and Ta, were used. The results presented show that the plasma pressure decreases with growing atomic number but in a limited range of Z only. For higher Z, starting approximately from Z = 47 (Ag), the plasma pressure becomes constant, as confirmed by interferometric measurements and x-ray plasma imaging.     

Nonlinear interaction of ultraintense laser pulse with relativistic thin plasma foil in the radiation pressure-dominant regime

We present a study of the effect of laser pulse temporal profile on the energy /momentum acquired by the ions as a result of the ultraintense laser pulse focussed on a thin plasma layer in the radiation pressure-dominant (RPD) regime. In the RPD regime, the plasma foil is pushed by ultraintense laser pulse when the radiation cannot propagate through the foil, while the electron and ion layers move together. The nonlinear character of laser–matter interaction is exhibited in the relativistic frequency shift, and also change in the wave amplitude as the EM wave gets reflected by the relativistically moving thin dense plasma layer. Relativistic effects in a high-energy plasma provide matching conditions that make it possible to exchange very effectively ordered kinetic energy and momentum between the EM fields and the plasma. When matter moves at relativistic velocities, the efficiency of the energy transfer from the radiation to thin plasma foil is more than 30% and in ultrarelativistic case it approaches one. The momentum /energy transfer to the ions is found to depend on the temporal profile of the laser pulse. Our numerical results show that for the same laser and plasma parameters, a Lorentzian pulse can accelerate ions upto 0.2 GeV within 10 fs which is 1.5 times larger than that a Gaussian pulse can.     

Theory of the interaction of high-power short laser pulses with plasmas

A theory of the interaction of short laser pulses with plasmas is constructed based on the previously developed kinetic theory of a tenuous plasma. The generation of fast electrons by a relativistically strong femtosecond laser pulse in a plasma with a nearly critical density is investigated. The results obtained agree with the results from particle-in-cell simulations and with the experimental data.     

Simulation of THz emission from laser interaction with plasmas

One-dimensional particle-in-cell (PIC) program is used to simulate the generation of high power terahertz (THz) emission from the interaction of an ultrashort intense laser pulse with underdense plasma. The spectra of THz radiation are discussed under different laser intensity, pulse width, incident angle and density scale length. High-amplitude electron plasma wave driven by a laser wakefield can produce powerful THz emission through linear mode conversion under certain conditions. With incident laser intensity of 10¹⁸ W/cm², the generated emission is computed to be of the order of several MV/cm field and tens of MW level power. The corresponding energy conversion efficiency is several ten thousandths, which is higher then the efficiency of other THz source and suitable for the studies of THz nonlinear physics.     

Near QED regime of laser interaction with overdense plasmas

Interaction of laser plulses with intensities up to 10²⁵?W/cm² with overdense plasma targets is investigated via three-dimensional particle-in-cell simulations. At these intensities, radiation of electrons in the laser field becomes important. Electrons transfer a significant fraction of their energy to γ-photons and obtain strong feedbacks due to radiation reaction (RR) force. The RR effect on the distribution of laser energies among three main species: electrons, ions and photons is studied. The RR and electron-positron pair creation are implemented by a QED model. As the laser intensity inreases, the ratio of laser energy coupled to electrons drops while the one for γ-photons reaches up to 35%. Two distinctive plasma density regimes of the high-density carbon target and low-density solid hydrogen target are identified from the laser energy partitions and angular distributions of photons. The power-laws of absorption efficiency versus laser intensity and the transition of photon divergence are revealed. These show enhanced generation of γ-photon beams with improved collimation in the relativistically transparent regime. A new effect of transverse trapping of electrons inside the laser field caused by the RR force is observed: electrons can be unexpectedly confined by the intense laser field when the RR force is comparable to the Lorentz force. Finally, the RR effect and different regions of photon emission in laser-foil interactions are clarified.     

Nonlinear electromagnetic modes in plasmas with variable dust charges

Fluctuations in the charges of dust grains, due to capture or liberation of electrons and protons, induce density and momentum losses or gains in dusty plasmas. This mechanism gives rise to wave damping or growth. We address an interesting intermediate regime, where the linear electromagnetic waves are not affected, but the dust charging influences the slower nonlinear development, leading to a derivative nonlinear Schrödinger equation with a source term. As a rule no stable solitary waves are possible, and the damping mechanism still is active.     

Nonlinear interaction of CO2 laser radiation with aluminum and polyethylene targets

The characteristics of A1 and (CH₂)_n plasmas produced by a high-power CO₂ laser are investigated over the flux range 10¹⁰-5 × 10¹¹W/cm² where absorption processes other than simple inverse Bremsstrahlung are active. The threshold dependent behavior of the measured plasma parameters indicates the presence of the parmetric decay instability.     

Nonlinear scattering with nonlocal interaction

We consider the scattering problem for the Hartree type equation in ⁿ withn2: