1,720,962 research outputs found
2-DIMENSIONAL REGIMES OF SELF-FOCUSING, WAKE-FIELD GENERATION, AND INDUCED FOCUSING OF A SHORT INTENSE LASER-PULSE IN AN UNDERDENSE PLASMA
No full textElectron vortices produced by ultraintense laser pulses
No full textParticle-in-cell simulations show that finite width and length laser pulses subject to relativistic self-focusing propagate in an underdense plasma in a ''bullet'' shape and produce a quasistatic magnetic field. This held remains behind the pulse and forms a magnetic wake associated with a row of electron fluid vortices which are described by the Hasegawa-Mima equation. The vortices propagate much more slowly than the pulse and evolve into an antisymmetric configuration which is shown to be stable when the distance between its vortices is greater than the electron skin depth
NONLINEAR EVOLUTION OF ULTRASTRONG LASER-PULSES IN A PLASMA - NEW PHENOMENA OF MAGNETIC INTERACTION BETWEEN STRONG ELECTROMAGNETIC BEAMS
No full textResults of numerical simulations and analytical description of the propagation of two-dimensional, short relativistically strong laser pulses in an underdense plasma are presented. The relativistic self-focusing and filamentation of a laser pulse are demonstrated. The influence of asymmetry of the pulse shape is studied. It is shown that the merging of self-focusing channels occurs due to attraction of the electric currents produced by fast particle motion inside the channels. It is found that external magnetic fields can bend the channels. These effects extend the range of the self-focusing phenomena because they allow the energy of several channels to accumulate in one channel. Pulses that are shorter than the plasma wave but with a transverse size larger than the wavelength of the plasma wave excite the regular wake wave whose electric field accelerates the charged particles. The specific structure of the wake plasma wave makes it possible for electromagnetic radiation to be focused by this wave
Magnetic interaction and magnetic wake of high intensity laser pulses in plasmas
No full textSuper-intense laser pulses produce quasi-static magnetic fields in plasmas. The mutual attraction of the currents inside the self-focused channels, arising from the pulse filamentation, makes them interact magnetically and coalesce into a single channel. Pulses of finite length propagate in the shape of a ''bullet'' and produce a wake consisting of a row of electron vortices
MAGNETIC INTERACTION OF SELF-FOCUSING CHANNELS AND FLUXES OF ELECTROMAGNETIC-RADIATION - THEIR COALESCENCE, THE ACCUMULATION OF ENERGY, AND THE EFFECT OF EXTERNAL MAGNETIC-FIELDS ON THEM
No full textA new effect has been observed in a numerical simulation of relativistic self-focusing and filamentation of light beams: a coalescence of channels. The reason for the interaction of the chemicals is identified: an attraction of currents which arise in the self-focusing channels. It is demonstrated that external magnetic fields affect the channels, causing them to bend. These effects cast new light on the phenomenon of self-focusing. They raise the possibility of combining the energy from several channels into one. A mechanism for the generation of ultrastrong quasistatic magnetic fields is identified. Corresponding force effects are possible for other mechanisms for generating drive currents: radiation pressure; thermoelectric and thermionic-emission currents in laser discharges, laser beams, and intense microwave fields. (C) 1994 American Institute of Physics
SHORT, RELATIVISTICALLY STRONG LASER-PULSE IN A NARROW CHANNEL
No full textWe present the results of an analytical study and of a two-dimensional particle-in-cell simulation of a relativistically strong laser pulse propagating in a narrow channel which eliminates the pulse spreading due to diffraction. In an empty channel with sharp boundaries, the main absorption mechanism is ''vacuum heating'' of the electrons expelled from the walls. These electrons fill the channel and form a charged cloud which moves at a relativistic velocity behind the pulse and produces a longitudinal electric field that can be used to accelerate charged particles. This cloud can also act as a mirror and, interacting with electromagnetic radiation, upshift its frequency. The interaction with the channel wall depends on the pulse intensity and polarization. TM-polarized pulses undergo greater losses than TE-pulses, and cause the formation of a charged cloud, of high harmonics and of a quasi-static magnetic field. In the case of a channel filled by an underdense plasma, an ultrashort pulse excites a strong wake wave with a longitudinal electric wake field which can accelerate charged particles
Transverse-wake wave breaking
No full textA finite-width laser pulse of high intensity propagating in an underdense plasma excites a transversely inhomogeneous, finite amplitude wakefield. This wake wave undergoes a transverse wave breaking due to the increase of the wake front curvature, followed by the self-intersection of electron trajectories. Transverse break occurs at much lower wave amplitudes than the conventional one-dimensional wave break. The resulting structures have generic forms that can be described by modified curves parallel to a parabola. Simulations with the particle-in-cell electromagnetic relativistic code VLPLZD show such structures appearing
Controlled wake field acceleration via laser pulse shaping
No full textWe consider the interaction of high-intensity laser pulses with underdense plasmas and address the problem of the excitation of strong and stable wake plasma waves with regular electric fields to provide effective acceleration of charged particles over appreciably long distances. It is known that a relativistically strong laser pulse longer than the wavelength of plasma waves, propagating in a plasma is subject to self-modulation. This may result in a nonstationary behavior of the produced plasma wake field/particle dephasing, and reduced net acceleration. In this paper we present the results of 1(2/2)-D and 2(1/2)-D particle in cell (PIC) simulations which demonstrate that regular wake electric fields may be obtained by a properly shaped laser pulse (sharp steepening of its leading front). These results are relevant to the design of the 100 MeV laser wake field electron acceleration experiment that uses a terawatt picosecond CO2 laser and is under construction at the Brookhaven Accelerator Test Facility
Magnetic fields from high-intensity laser pulses in plasmas
No full textIn a plasma interacting with ultra-short, high-intensity laser pulses, the magnetic part of the Lorentz force on the electrons can become as important as the electric part. In this case, we can expect the magnetic field to change the pattern of the nonlinear laser-pulse-plasma interaction drastically. The relativistic nonlinearities introduced by the magnetic interaction are of general interest in relation to the field of ultra-strong electromagnetic waves propagating in media, high-energy space plasmas and laser-plasma interaction under laboratory conditions. We present a summary of analytical and numerical results concerning the generation of quasi-static magnetic fields by high-intensity laser pulses in underdense plasmas and in thin plasma foils, and discuss the dynamical effects of these fields on the plasma motion and on the pulse propagation. This analysis indicates that phenomena such as current pinching, reconnection of magnetic-field lines and vortex propagation etc, that have been previously discussed in the case of space and laboratory plasmas, are also important for laser-plasma interactions
Magnetic interaction of ultrashort high-intensity laser pulses in plasmas
No full textA review of our theoretical studies and computer simulations with PIC codes of the interaction of ultrashort, high-intensity laser pulses with plasmas is presented. The mutual attraction of the currents inside the self-focused channels, arising from the pulse filamentation, makes them interact magnetically and coalesce into a single channel with strongly enhanced electromagnetic energy density. Pulses of finite length and width propagate in the shape of a 'bullet' and produce a wake consisting of magnetic dipoles correlated with an electron vortex row behind the pulse. The vortices evolve into an antisymmetric configuration which is shown to be stable when the distance between its vortices is greater than the electron skin depth
- …
