arXiv subjects

Andrea Macchi

Publications and source records attributed to Andrea Macchi.

24 records · Page 2Linked to original sources

arXiv2009

"Light Sail" Acceleration Revisited

The dynamics of the acceleration of ultrathin foil targets by the radiation pressure of superintense, circularly polarized laser pulses is investigated by analytical modeling and particle-in-cell simulations. By addressing self-induced transparency and charge separation effects, it is shown that for "optimal" values of the foil thickness only a thin layer at the rear side is accelerated by radiation pressure. The simple "Light Sail" model gives a good estimate of the energy per nucleon, but overestimates the conversion efficiency of laser energy into monoenergetic ions.

physics.plasm-ph↗

arXiv2008

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.

physics.plasm-ph↗

arXiv2007

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.

physics.plasm-ph↗

arXiv2005

Laser acceleration of ion bunches at the front surface of overdense plasmas

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.

physics.plasm-ph↗

arXiv2002

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 $ω/2$ or $ω$, where $ω$ is the laser frequency.

physics.plasm-ph↗

arXiv1998

Collective Absorption Dynamics and Enhancement in Deformed Targets

The interaction of intense fs laser pulses with thin foils that have an imposed deformation is compared with thick targets that develop bow shocks. Both target types yield good absorption. Up to 80% absorption is obtained for a $0.2μm$ thick, 15 times over-dense foil at $4 \cdot 10^{18} W/cm^2$. A value of 50% is obtained for a $4 μm$ thick, 2 times over-dense thick target at $10^{18} W/cm^2$. For comparable extension and curvature of the laser-plasma interfaces absorption levels in both targets become similar. In both absorption scales weakly with intensity and density. Energy transport in thin foils and thick targets, however, is different.

physics.plasm-ph↗