708 research outputs found
Vlasov simulation of laser-driven shock acceleration and ion turbulence
We present a Vlasov, i.e. a kinetic Eulerian simulation study of nonlinear
collisionless ion-acoustic shocks and solitons excited by an intense laser
interacting with an overdense plasma. The use of the Vlasov code avoids
problems with low particle statistics and allows a validation of
particle-in-cell results. A simple original correction to the splitting method
for the numerical integration of the Vlasov equation has been implemented in
order to ensure the charge conservation in the relativistic regime. We show
that the ion distribution is affected by the development of a turbulence driven
by the relativistic "fast" electron bunches generated at the laser-plasma
interaction surface. This leads to the onset of ion reflection at the shock
front in an initially cold plasma where only soliton solutions without ion
reflection are expected to propagate. We give a simple analytic model to
describe the onset of the turbulence as a nonlinear coupling of the ion density
with the fast electron currents, taking the pulsed nature of the relativistic
electron bunches into account
Few-cycle Surface Plasmon Polariton Generation by Rotating Wavefront Pulses
A concept for the efficient generation of surface plasmon polaritons (SPPs)
with a duration of very few cycles is presented. The scheme is based on grating
coupling and laser pulses with wavefront rotation (WFR), so that the resonance
condition for SPP excitation is satisfied only for a time window shorter than
the driving pulse. The feasibility and robustness of the technique is
investigated by means of simulations with realistic parameters. In optimal
conditions, we find that a ~fs pulse with ~nm wavelength can excite
a ~fs SPP ( laser cycles) with a peak field amplitude
times the peak value for the laser pulse
Laser-Driven Rayleigh-Taylor Instability: Plasmonics Effects and Three-Dimensional Structures
The acceleration of dense targets driven by the radiation pressure of
high-intensity lasers leads to a Rayleigh-Taylor instability (RTI) with
rippling of the interaction surface. Using a simple model it is shown that the
self-consistent modulation of the radiation pressure caused by a sinusoidal
rippling affects substantially the wavevector spectrum of the RTI depending on
the laser polarization. The plasmonic enhancement of the local field when the
rippling period is close to a laser wavelength sets the dominant RTI scale. The
nonlinear evolution is investigated by three dimensional simulations, which
show the formation of stable structures with "wallpaper" symmetry.Comment: 5 pages, 5 figures. New version includes 2D and 3D simulations. More
details in the analytical calculation are given in the previous versio
Two-Surface Wave Decay
Using an analytical model we discuss the parametric excitation of pairs of
electron surface waves (ESW) in the interaction of an ultrashort, intense laser
pulse with an overdense plasma which has a step-like density profile. The ESWs
can be excited either by the electric or by the magnetic part of the Lorentz
force exerted by the laser and, correspondingly, have frequencies around
or , where is the laser frequency.Comment: 4 EPS figures, Revte
Solitary versus Shock Wave Acceleration in Laser-Plasma Interactions
The excitation of nonlinear electrostatic waves, such as shock and solitons,
by ultraintense laser interaction with overdense plasmas and related ion
acceleration are investigated by numerical simulations. Stability of solitons
and formation of shock waves is strongly dependent on the velocity distribution
of ions. Monoenergetic components in ion spectra are produced by "pulsed"
reflection from solitary waves. Possible relevance to recent experiments on
"shock acceleration" is discussed.Comment: 4 pages, 4 figure
Ion acceleration by radiation pressure in thin and thick targets
Abstract Radiation Pressure Acceleration (RPA) by circularly polarized laser pulses is emerging as a promising way to obtain efficient acceleration of ions. We briefly review theoretical work on the topic, aiming at characterizing suitable experimental scenarios. We discuss the two reference cases of RPA, namely the thick target ("Hole Boring") and the (ultra)thin target ("Light Sail") regimes. The different scaling laws of the two regimes, the related experimental challenges and their suitability for foreseen applications are discussed
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