5 research outputs found
Ion dynamics and coherent structure formation following laser pulse self-channeling
The propagation of a superintense laser pulse in an underdense, inhomogeneous
plasma has been studied numerically by two-dimensional particle-in-cell
simulations on a time scale extending up to several picoseconds. The effects of
the ion dynamics following the charge-displacement self-channeling of the laser
pulse have been addressed. Radial ion acceleration leads to the ``breaking'' of
the plasma channel walls, causing an inversion of the radial space-charge field
and the filamentation of the laser pulse. At later times a number of
long-lived, quasi-periodic field structures are observed and their dynamics is
characterized with high resolution. Inside the plasma channel, a pattern of
electric and magnetic fields resembling both soliton- and vortex-like
structures is observed.Comment: 10 pages, 5 figures (visit http://www.df.unipi.it/~macchi to download
a high-resolution version), to appear in Plasma Physics and Controlled Fusion
(Dec. 2007), special issue containing invited papers from the 34th EPS
Conference on Plasma Physics (Warsaw, July 2007
Radiation Pressure Acceleration by Ultraintense Laser Pulses
The future applications of the short-duration, multi-MeV ion beams produced
in the interaction of high-intensity laser pulses with solid targets will
require improvements in the conversion efficiency, peak ion energy, beam
monochromaticity, and collimation. Regimes based on Radiation Pressure
Acceleration (RPA) might be the dominant ones at ultrahigh intensities and be
most suitable for specific applications. This regime may be reached already
with present-day intensities using circularly polarized (CP) pulses thanks to
the suppression of fast electron generation, so that RPA dominates over sheath
acceleration at any intensity. We present a brief review of previous work on
RPA with CP pulses and a few recent results. Parametric studies in one
dimension were performed to identify the optimal thickness of foil targets for
RPA and to study the effect of a short-scalelength preplasma. Three-dimensional
simulations showed the importance of ``flat-top'' radial intensity profiles to
minimise the rarefaction of thin targets and to address the issue of angular
momentum conservation and absorption.Comment: 11 pages, 8 figures, accepted for publication to the special issue
"EPS 2008" of PPC
Laser acceleration of ion bunches at the front surface of overdense plasmas
SUMMARY The acceleration of ions in the interaction of high intensity laser pulses
with overdense plasmas is investigated with particle-in-cell simulations. For
circular polarization of the laser pulses, high-density ion bunches moving into
the plasma are generated at the laser-plasma interaction surface. A simple
analytical model accounts for the numerical observations and provides scaling
laws for the ion bunch energy and generation time as a function of pulse
intensity and plasma density