Simple model of the slingshot effect

TL;DR

This paper provides a detailed quantitative model of the slingshot effect, where intense laser pulses expel electrons from plasma, offering insights into a potential new electron acceleration mechanism.

Contribution

It introduces a simple, yet powerful 3D correction to a plane MHD model to predict the conditions and features of the slingshot effect for experimental validation.

Findings

Conditions for electron expulsion identified

Predicted energy spectrum and collimation of expelled electrons

Potential for a new electron acceleration method

Abstract

We present a detailed quantitative description of the recently proposed "slingshot effect" [Fiore, Fedele, De angelis 2014]. Namely, we determine a broad range of conditions under which the impact of a very short and intense laser pulse normally onto a low-density plasma (or matter to be locally completely ionized into a plasma by the pulse) causes the expulsion of a bunch of surface electrons in the direction opposite to the one of propagation of the pulse, and the detailed, ready-for-experiments features of the expelled electrons (energy spectrum, collimation, etc). The effect is due to the combined actions of the ponderomotive force and the huge longitudinal field arising from charge separation. Our predictions are based on estimating 3D corrections to a simple, yet powerful plane magnetohydrodynamic (MHD) model where the equations to be solved are reduced to a system of Hamilton equations in one dimension (or a collection of) which become autonomous after the pulse has overcome the electrons. Experimental tests seem to be at hand. If confirmed by the latter, the effect would provide a new extraction and acceleration mechanism for electrons, alternative to traditional radio-frequency-based or Laser-Wake-Field ones.