Theory of light sail acceleration by intense lasers: an overview

Andrea Macchi

doi:10.1017/hpl.2014.13

Abstract

AbstractA short overview of the theory of acceleration of thin foils driven by the radiation pressure of superintense lasers is presented. A simple criterion for radiation pressure dominance at intensities around $5 \times 10^{20}\ \mbox{W cm}^{-2}$ is given, and the possibility for fast energy gain in the relativistic regime is discussed.

Highlights

It has been known since the discovery of Maxwell’s equations that light, i.e., electromagnetic (EM) radiation, exerts a pressure on a reflecting object, and may accelerate it
The correct balance of electrostatic and radiation pressure shows that only a fraction F 1 − a0/ζ of the ions is accelerated coherently as a sail, even if the motion of the latter is still described the total mass of the fboyil[E16q, u17a]t.ionD(u1r)inwgitthheσ0miontciolund,inags long as the geometry is one dimensional, the electrostatic pressure on the sail depends only on the total charge behind the sail, while the radiation pressure decreases by a factor
The laser-driven light sail concept, which was first studied as a visionary approach to interstellar travel, currently represents an implementation of Veksler’s coherent acceleration paradigm and a possible route towards a laser–plasma accelerator

Summary

Introduction

It has been known since the discovery of Maxwell’s equations that light, i.e., electromagnetic (EM) radiation, exerts a pressure on a reflecting object, and may accelerate it. Marx’s paper included a relativistic analysis of the motion of a sail, i.e., a plane perfect mirror, accelerated by radiation pressure, based on the equations d(γ V ) dt. Equations (1), hereafter referred to as the light sail (LS) equations, have the same form as for the motion of the Thomson scattering particle[8], evidencing the connection with Veksler’s proposed mechanism. In 2004, using particle-in-cell (PIC) simulations of the acceleration of a thin plasma foil by a laser pulse with intensity I > 1023 W cm−2, Esirkepov et al.[9] showed that the motion of the foil was well fitted by the above-mentioned equation, giving evidence that the foil was driven from radiation pressure. A. Macchi equations to foreseeable laser and target parameters showed the possibility of reaching the relativistic velocity of the foil, corresponding to an energy per nucleon above the GeV barrier. A more comprehensive presentation of experimental and simulation results may be found in recent review papers on laser-driven ion acceleration[10,11,12,13]

One-dimensional dynamics

Radiation pressure dominance

Conclusions and perspectives