Towards optical polarization control of laser-driven proton acceleration in foils undergoing relativistic transparency

Gonzalez-Izquierdo, Bruno and King, Martin and Gray, Ross J. and Wilson, Robbie and Dance, Rachel J. and Powell, Haydn and MacLellan, David A. and McCreadie, John and Butler, Nicholas M.H. and Hawkes, Steve and Green, James S. and Murphy, Chris D. and Stockhausen, Luca C. and Carroll, David C. and Booth, Nicola and Scott, Graeme G. and Borghesi, Marco and Neely, David and McKenna, Paul (2016) Towards optical polarization control of laser-driven proton acceleration in foils undergoing relativistic transparency. Nature Communications, 7. ISSN 2041-1723

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Abstract

Control of the collective response of plasma particles to intense laser light is intrinsic to relativistic optics, the development of compact laser-driven particle and radiation sources, as well as investigations of some laboratory astrophysics phenomena. We recently demonstrated that a relativistic plasma aperture produced in an ultra-thin foil at the focus of intense laser radiation can induce diffraction, enabling polarization-based control of the collective motion of plasma electrons. Here we show that under these conditions the electron dynamics are mapped into the beam of protons accelerated via strong charge-separation-induced electrostatic fields. It is demonstrated experimentally and numerically via 3D particle-in-cell simulations that the degree of ellipticity of the laser polarization strongly influences the spatial-intensity distribution of the beam of multi-MeV protons. The influence on both sheath accelerated and radiation pressure accelerated protons is investigated. This approach opens up new routes to control laser-driven ion sources.