493 research outputs found
Giga-Gauss scale quasistatic magnetic field generation in an 'escargot' target
A simple setup for the generation of ultra-intense quasistatic magnetic
fields, based on the generation of electron currents with a predefined geometry
in a curved 'escargot' target, is proposed and analysed. Particle-In-Cell
simulations and qualitative estimates show that giga-Gauss scale magnetic
fields may be achieved with existent laser facilities. The described mechanism
of the strong magnetic field generation may be useful in a wide range of
applications, from laboratory astrophysics to magnetized ICF schemes.Comment: Submitted to PRL. arXiv admin note: text overlap with arXiv:1409.524
A plasma solenoid driven by an Orbital Angular Momentum laser beam
A tens of Tesla quasi-static axial magnetic field can be produced in the
interaction of a short intense laser beam carrying an Orbital Angular Momentum
with an underdense plasma. Three-dimensional "Particle In Cell" simulations and
analytical model demonstrate that orbital angular momentum is transfered from a
tightly focused radially polarized laser beam to electrons without any
dissipative effect. A theoretical model describing the balistic interaction of
electrons with laser shows that particles gain angular velocity during their
radial and longitudinal drift in the laser field. The agreement between PIC
simulations and the simplified model identifies routes to increase the
intensity of the solenoidal magnetic field by controlling the orbital angular
momentum and/or the energy of the laser beam
Dynamics and stability of radiation-driven double ablation front structures.
The dynamics of double ablation front (DAF) structures is studied for planar targets with moderate atomic number ablators. These structures are obtained in hydrodynamic simulations for various materials and laser intensities and are qualitatively characterized during the acceleration stage of the target. The importance of the radiative transport for the DAF dynamics is then demonstrated. Simulated hydrodynamic profiles are compared with a theoretical model, showing the consistency of the model and the relevant parameters for the dynamics description. The stability of DAF structures with respect to two-dimensional perturbations is studied using two different approaches: one considers the assumptions of the theoretical model and the other one a more complete physics. The numerical simulations performed with both approaches demonstrate good agreement of dispersion curve
Coherent forward stimulated Brillouin scattering of a spatially incoherent laser beam in a plasma and its effect on beam spray
A statistical model for forward stimulated Brillouin scattering (FSBS) is
developed for a spatially incoherent, monochromatic, laser beam propagating in
a plasma. A threshold for the average power in a speckle is found, well below
the self-focusing one, above which the laser beam spatial incoherence can not
prevent the coherent growth of FSBS. Three-dimensional simulations confirm its
existence and reveal the onset of beam spray above it. From these results, we
propose a new figure of merit for the control of the propagation through a
plasma of a spatially incoherent laser beam.Comment: submitted to PR
Effect of electron heating on self-induced transparency in relativistic intensity laser-plasma interaction
The effective increase of the critical density associated with the
interaction of relativistically intense laser pulses with overcritical plasmas,
known as self-induced transparency, is revisited for the case of circular
polarization. A comparison of particle-in-cell simulations to the predictions
of a relativistic cold-fluid model for the transparency threshold demonstrates
that kinetic effects, such as electron heating, can lead to a substantial
increase of the effective critical density compared to cold-fluid theory. These
results are interpreted by a study of separatrices in the single-electron phase
space corresponding to dynamics in the stationary fields predicted by the
cold-fluid model. It is shown that perturbations due to electron heating
exceeding a certain finite threshold can force electrons to escape into the
vacuum, leading to laser pulse propagation. The modification of the
transparency threshold is linked to the temporal pulse profile, through its
effect on electron heating.Comment: 13 pages, 12 figures; fixed some typos and improved discussion of
review materia
Electron kinetic effects in the nonlinear evolution of a driven ion-acoustic wave
The electron kinetic effects are shown to play an important role in the nonlinear evolution of a driven ion-acoustic wave. The numerical simulation results obtained (i) with a hybrid code, in which the electrons behave as a fluid and the ions are described along the particle-in-cell (PIC) method, are compared with those obtained (ii) with a full-PIC code, in which the kinetic effects on both species are retained. The electron kinetic effects interplay with the usual fluid-type nonlinearity to give rise to a broadband spectrum of ion-acoustic waves saturated at a low level, even in the case of a strong excitation. This low asymptotic level might solve the long-standing problem of the small stimulated Brillouin scattering reflectivity observed in laser-plasma interaction experiments
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