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• High Power Laser Science and Engineering
• Vol. 4, Issue 3, 03000e33 (2016)
Bruno Gonzalez-Izquierdo1, Ross J. Gray1, Martin King1, Robbie Wilson1, Rachel J. Dance1, Haydn Powell1, David A. MacLellan1, John McCreadie1, Nicholas M. H. Butler1, Steve Hawkes1、2, James S. Green2, Chris D. Murphy3, Luca C. Stockhausen4, David C. Carroll2, Nicola Booth5, Graeme G. Scott1、2, Marco Borghesi2, David Neely1、2, and Paul McKenna1
Author Affiliations
• 1SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK
• 2Central Laser Facility, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, UK
• 3Department of Physics, University of York, Heslington, York YO10 5DD, UK
• 4Centro de L′aseres Pulsados (CLPU), M5 Parque Cient′?fico, 37185 Salamanca, Spain
• 5Centre for Plasma Physics, Queens University Belfast, Belfast BT7 1NN, UK
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Abstract

The collective response of electrons in an ultrathin foil target irradiated by an ultraintense (6  1020 W cm??2) laser pulse is investigated experimentally and via 3D particle-in-cell simulations. It is shown that if the target is sufficiently thin that the laser induces significant radiation pressure, but not thin enough to become relativistically transparent to the laser light, the resulting relativistic electron beam is elliptical, with the major axis of the ellipse directed along the laser polarization axis. When the target thickness is decreased such that it becomes relativistically transparent early in the interaction with the laser pulse, diffraction of the transmitted laser light occurs through a so called ‘relativistic plasma aperture’, inducing structure in the spatial-intensity profile of the beam of energetic electrons. It is shown that the electron beam profile can be modified by variation of the target thickness and degree of ellipticity in the laser polarization.

1 Introduction

The interaction of ultraintense laser pulses (${>}10^{18}~\text{W}~\text{cm}^{-2}$) with thin foil targets (nanometre–micrometre scale thickness) results in the generation of high energy ion beams[1, 2], bright x-ray sources[3, 4] or in the production of high harmonics[5]. The basis of the underlying physics of all these laser–plasma sources is the collective response of the plasma electrons to the intense laser light. The electrons are directly accelerated by the laser electric and magnetic fields, which in turn exhibit distinct characteristics depending on the polarization. Therefore, the role of polarization in the collective dynamics of electrons in ultraintense laser pulse interactions with thin foil targets is both of fundamental interest and potentially important for controlling the production of secondary particles and radiation.

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Bruno Gonzalez-Izquierdo, Ross J. Gray, Martin King, Robbie Wilson, Rachel J. Dance, Haydn Powell, David A. MacLellan, John McCreadie, Nicholas M. H. Butler, Steve Hawkes, James S. Green, Chris D. Murphy, Luca C. Stockhausen, David C. Carroll, Nicola Booth, Graeme G. Scott, Marco Borghesi, David Neely, Paul McKenna. Influence of laser polarization on collective electron dynamics in ultraintense laser–foil interactions[J]. High Power Laser Science and Engineering, 2016, 4(3): 03000e33