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1.
The ponderomotive force plays a fundamental role in the absorption of laser light on self-consistent plasma density profiles, in multiple-photon ionization, and in intense field electrodynamics. The relativistic corrections to the ponderomotive force of a transversely polarized electromagnetic wave lead to an approximately 20-percent reduction in the single particle ponderomotive force produced by a 10-?m 1016-W/cm2 laser field. Recent experimental investigations are based on using two intense laser fields to produce desired laser-matter interactions. This paper presents the first derivation of the nonlinear relativistic ponderomotive force produced by two intense laser fields. The results demonstrate that relativistic ponderomotive forces are not additive. 相似文献
2.
Coulomb explosion of a metal exposed to an intense picosecond laser pulse is numerically simulated using a plasma layer as an example. It is shown that plasma electrons leave the plasma layer under the action of the ponderomotive force opposing the laser radiation field gradient, whereas plasma ions fly away in the field of the self-space charge. 相似文献
3.
We present analytical studies of electron acceleration in the low-density preplasma of a thin solid target by an intense femtosecond laser pulse. Electrons in the preplasma are trapped and accelerated by the ponderomotive force as well as the wake field. Two-dimensional particle-in-cell simulations show that when the laser pulse is stopped by the target, electrons trapped in the laser pules can be extracted and move forward inertially. The energeticelectron bunch in the bubble is unaffected by the reflected pulse and passes through the target with small energy spread and emittance. There is an optimal preplasma density for the generation of the monoenergetic electron bunch if a laser pulse is given. The maximum electron energy is inverse proportion to the preplasma density. 相似文献
4.
A. I. Lomtev 《Technical Physics》2014,59(3):438-440
The ponderomotive force acting on a variable-charge granule in a dusty plasma from an intense ion-sound wave is considered. Allowance for oscillations of the granule charge in the field of an ion-sound wave makes it possible to reveal new components of this force that are proportional to the wave vector of the field and the cube of its amplitude. These components do not vanish in the case of a uniform field and also lead to a directed transport of the dust plasma fraction. 相似文献
5.
Pulse chirping effect on controlling the transverse cavity oscillations in nonlinear bubble regime 下载免费PDF全文
The propagation of an intense laser pulse in an under-dense plasma induces a plasma wake that is suitable for the acceleration of electrons to relativistic energies. For an ultra-intense laser pulse which has a longitudinal size shorter than the plasma wavelength, λp, instead of a periodic plasma wave, a cavity free from cold plasma electrons, called a bubble, is formed behind the laser pulse. An intense charge separation electric field inside the moving bubble can capture the electrons at the base of the bubble and accelerate them with a narrow energy spread. In the nonlinear bubble regime, due to localized depletion at the front of the pulse during its propagation through the plasma, the phase shift between carrier waves and pulse envelope plays an important role in plasma response. The carrier–envelope phase(CEP) breaks down the symmetric transverse ponderomotive force of the laser pulse that makes the bubble structure unstable. Our studies using a series of two-dimensional(2D) particle-in-cell(PIC) simulations show that the frequency-chirped laser pulses are more effective in controlling the pulse depletion rate and consequently the effect of the CEP in the bubble regime. The results indicate that the utilization of a positively chirped laser pulse leads to an increase in rate of erosion of the leading edge of the pulse that rapidly results in the formation of a steep intensity gradient at the front of the pulse. A more unstable bubble structure, the self-injections in different positions, and high dark current are the results of using a positively chirped laser pulse. For a negatively chirped laser pulse, the pulse depletion process is compensated during the propagation of the pulse in plasma in such a way that results in a more stable bubble shape and therefore, a localized electron bunch is produced during the acceleration process. As a result, by the proper choice of chirping, one can tune the number of self-injected electrons, the size of accelerated bunch and its energy spectrum to the values required for practical applications. 相似文献
6.
DiPeso G. Rognlien T.D. Vahedi V. Hewett D.W. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1995,23(4):550-557
An analysis is given of the influence of the electron ponderomotive force on the equilibrium plasma profiles of partially ionized, radio frequency discharge sources, The ponderomotive force can be written as a gradient of a potential varying with the square of the RF field in the plasma and is largest for electrons, The impact of this electron ponderomotive force on density and electrostatic potential profiles is demonstrated using a one-dimensional analytic model with supporting numerical solutions and a two dimensional fluid simulation. For nearly collisionless plasmas the ponderomotive force is valid when ωceh/ω<1 where ωce h is the electron cyclotron frequency due to the RF magnetic field and ω is the RF driving frequency, In processing plasmas with parameters that satisfy this validity criteria, the equilibrium density profiles are weakly modified, For nearly collisionless processing plasmas with parameters such that ωceh /ω>1, the ponderomotive force, is modified by other nonlinear force terms that need to be evaluated 相似文献
7.
We consider nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and electron plasma oscillations (EPOs) in a dense quantum plasma, taking into account the electron density response in the presence of the relativistic ponderomotive force and mass increase in the CPEM wave fields. The dynamics of the CPEM waves and EPOs is governed by the two coupled nonlinear Schr?dinger equations and Poisson's equation. The nonlinear equations admit the modulational instability of an intense CPEM pump wave against EPOs, leading to the formation and trapping of localized CPEM wave pipes in the electron density hole that is associated with a positive potential distribution in our dense plasma. The relevance of our investigation to the next generation intense laser-solid density plasma interaction experiments is discussed. 相似文献
8.
A. G. Khachatryan 《Journal of Experimental and Theoretical Physics》2002,94(3):516-520
The effect of a longitudinal magnetic field on the linear wake fields excited by a relativistic electron bunch in a cold homogeneous plasma is considered. The obtained results prove that the presence of an external magnetic field leads to a dependence of the wake wavelength on the transverse coordinate, to a change in the wave amplitude with increasing distance from the bunch, and to the emergence of anharmonicity. It is found that a strong magnetic field reduces the wave amplitude significantly for narrow bunches and changes the amplitude insignificantly for broad bunches. 相似文献
9.
We examine the effect of wiggler magnetic field on pulse slippage of short pulse laser-induced third harmonic generation in plasma. The process of third harmonic generation of an intense short pulse laser in plasma is resonantly enhanced by the application of a magnetic wiggler. The laser exerts a ponderomotive force at second harmonic driving density oscillations. The second harmonic oscillations coupled with electron velocity at the laser frequency, produces a non-linear current, driving the third harmonic. Third harmonic pulse generates in the fundamental pulse domain. However, the group velocity of the third harmonic wave is greater than the fundamental wave. Hence, the third harmonic pulse saturates strongly and moves forward from the fundamental pulse at shorter distance than the second harmonic pulse. 相似文献
10.
Reza Fallah Reza Khooniki Seyed Mohammad Khorashadizadeh Ali Reza Niknam 《等离子体物理论文集》2021,61(2):e202000086
The influence of relativistic-ponderomotive nonlinearities and the plasma inhomogeneity on the nonlinear interaction between a high-power laser beam and a warm underdense plasma are studied. It is clear that the relativistic ponderomotive force and the electron temperature modify the electron density distribution and consequently change the dielectric permittivity of the plasma. Therefore, by presenting the modified electron density and the nonlinear dielectric permittivity of the warm plasma, the electromagnetic wave equation for the propagation of intense laser beam through the plasma is derived. This nonlinear equation is numerically solved and the distributions of electromagnetic fields in the plasma, the variations of electron density, and plasma refractive index are investigated for two different background electron density profiles. The results show that the amplitude of the electric field and electron density oscillations gradually increase and decrease, during propagation in the inhomogeneous warm plasma with linear and exponential density profiles, respectively, and the distribution of electron density becomes extremely sharp in the presence of intense laser beam. It is also indicated that the electron temperature and initial electron density have an impact on the propagation of the laser beam in the plasma and change the plasma refractive index and the oscillations' amplitude and frequency. The obtained results indicate the importance of a proper choice of laser and plasma parameters on the electromagnetic field distributions, density steepening, and plasma refractive index variations in the interaction of an intense laser beam with an inhomogeneous warm plasma. 相似文献
11.
We present a new mechanism of energy gain of electrons accelerated by a laser pulse.It is shown thatwhen the intensity of an ultrafast intense laser pulse decreases rapidly along the direction of propagation,electrons leaving the pulse experience an action of ponderomotivc deceleration at the descending part ofa lower-intensity laser field than acceleration at the ascending part of a high-intensity field, thus gain netenergy from the pulse and move directly forward. By means of such a mechanism, a megaelectronvoltelectron beam with a bunch length shorter than 100 fs could be realized with an ultrafast(≤30 fs),intense (>10~(19)W/cm~2)laser pulse. 相似文献
12.
13.
The interaction of a relativistic classical electron with an inhomogeneous electromagnetic field is investigated. In second-order
perturbation theory the motion is separated into fast and slow motions, and the relativistic Newtonian equation is averaged
over the fast oscillations. The rate of change obtained for the slow component of the electron momentum is interpreted as
a relativistic ponderomotive force. The result is generalized to the relativistic case of the wellknown expression for the
Gaponov-Miller force acting on an electron at rest. The expressions obtained for the relativistic ponderomotive forces are
very complicated in the general case. They simplify in the limit of a stationary field (pulses of long duration) and a small
gradient. The most typical and simplest special case of an inhomogeneous field—a stationary plane-focused beam—is investigated.
The main difference between relativistic ponderomotive forces and their nonrelativistic limit is they have multiple components.
In addition to the usual force directed along the gradient of the field, the relativistic case is also characterized by force
components that do not have the form of the gradient of a potential and are parallel to the wave vector and the direction
of the field polarization. It is shown that when a relativistic electron travels in a direction close to the direction of
the wave vector of a focused laser beam, these components can greatly exceed the gradient force. A force directed along the
field polarization vector arises even when the gradient of the field in this direction is zero.
Zh. éksp. Teor. Fiz. 116, 1198–1209 (October 1999) 相似文献
14.
P. K. Shukla L. Stenflo R. Bingham H. A. Bethe J. M. Dawson J. T. Mendon a 《Physics letters. A》1997,230(5-6):353-357
The nonlinear propagation of an intense neutrino flux in an electron-positron plasma with equilibrium density and magnetic field inhomogeneities is considered. It is found that the neutrinos are nonlinearly coupled with electrostatic and electromagnetic disturbances due to weak Fermi interaction and ponderomotive forces. The process is governed by a Klein-Gordon equation for the neutrino flux and a wave equation for the plasma oscillations in the presence of the ponderomotive force of the neutrinos. This pair of equations is then used to derive a nonlinear dispersion relation which exhibits that nonthermal electrostatic and electromagnetic fluctuations are created on account of the energy density of the neutrinos. The relevance of our investigation to the anomalous absorption of neutrinos in a nonuniform magnetized medium is pointed out. 相似文献
15.
Ph. Balcou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):525-537
A scheme for an X-ray free electron laser is proposed, based on a Raman process occurring during the interaction between a
moderately relativistic bunch of free electrons, and twin intense short pulse lasers interfering to form a transverse standing
wave along the electron trajectories. In the high intensity regime of the Kapitza-Dirac effect, the laser ponderomotive potential
forces the electrons into a lateral oscillatory motion, resulting in a Raman scattering process. I show how a parametric process
is triggered, resulting in the amplification of the Stokes component of the Raman-scattered photons. Experimental operating
parameters and implementations, based both on LINAC and Laser Wakefield Acceleration techniques, are discussed. 相似文献
16.
A.G. Khachatryan M.J.H. Luttikhof F.A. van Goor K.-J. Boller 《Applied physics. B, Lasers and optics》2007,86(1):41-47
For the purpose of laser wakefield acceleration, it turns out that the injection of electron bunches longer than the plasma wavelength can also generate accelerated femtosecond bunches with a relatively low energy spread. This is of great interest because such injecting bunches can be provided, e.g., by photo cathode rf linacs. Here we show that when an e-bunch is injected into the wakefield, it is important to take into account the interaction of the injected bunch with the laser pulse in the vacuum region located in front of the plasma. We show that at low energies of the injected bunch, this leads to ponderomotive scattering of the bunch and results in a significant drop of the collection efficiency. For certain injection energies the ponderomotive scattering may result in a smaller energy spread in the accelerated bunch. It is found that the injection position in the laser wakefield plays an important role. Higher collection efficiency can be obtained for certain injection energies, when the bunch is injected in plasma at some distance from the laser pulse; the energy spread, however, is typically larger in this case. We also estimate the minimum trapping energy for the injected electrons and the length of the trapped bunch. PACS 52.38.Kd; 41.75.Jv; 41.85.Ar 相似文献
17.
在低密等离子体通道中, 横向有质动力可以有效调制电子的横向振荡过程. 一方面, 横向有质动力可以向外推动电子, 增大电子横向振荡振幅, 减小失相率, 使电子获得能量增益; 另一方面, 横向有质动力也可以通过对失相率的非线性调制来降低失相率, 在电子横向振荡振幅很小的情况下导致激光直接加速. 横向有质动力调制的大小由等离子体密度、激光强度和束宽共同决定. 三维模型结果也证实可以通过参数放大实现激光直接加速, 弥补了准二维模型的局限性. 相似文献
18.
In this paper, the growth rate, ponderomotive force and the exciting
condition for parametric instability are derived by considering the loss
reaction using a new method. On the basis of the hydrodynamic
equations, we take the production and loss reactions in plasma into account
to derive the coupling equations for the electron plasma oscillation and
ion acoustic oscillation, and obtain the growth rate for the parametric
instability, the ponderomotive force and the exciting condition. The result
shows that (a) the production reaction has no effect on the parametric
instability, and the effect of loss reaction on the parametric instability
is a damping one, (b) the more intensive the external field or pump is, the larger
the growth rate is, (c) there exist two modes of the ponderomotive force,
i.e.\ the high frequency mode and the low frequency mode,
and (d) when ponderomotive force counteracts the damping force, the
oscillations become non-damping and non-driving. The ratio of the
electron plasma oscillation to ion acoustic oscillation is independent of
the loss reaction and the external field. 相似文献
19.
《中国光学快报(英文版)》2018,(11)
We report the terahertz(THz) wave generation from a single-color scheme modulated by pre-ionized air plasma via an orthogonal pumping geometry. It is found that the amplitude of the THz signal generated by the pump beam tends to decrease gradually with the increase of the modulation power. We believe that the ponderomotive force plays an important role in the process of the interaction between the pump beam and the pre-ionization beam. The hydrostatic state of the electrostatic separation field caused by the modulation beam will directly affect the generation efficiency of the THz wave. Our results contribute to further understanding of the theoretical mechanism and expanding of the practical applications of THz wave generation and modulation. 相似文献
20.
Collective properties of a relativistic electron beam injected into a high intensity optical lattice
I. A. Andriyash Ph. Balcou V. T. Tikhonchuk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(3):533-540
Behaviour of a relativistic electron bunch, injected and trapped in a high intensity
optical lattice resulting from the interference of two laser beams is studied. The optical
lattice modifies the phase space distribution of the electron bunch due to the trapping
and compression of the electrons by a ponderomotive force. High-frequency longitudinal
beam eigenmodes of the trapped electron bunch are described in the framework of fluid and
kinetic models. Such beam oscillations are expected to play a pivotal role in a stimulated
Raman scattering of laser beams on the electrons. 相似文献