Enhanced ion acceleration with extremely thin foils
Laser Physics and Nonlinear Optics Group, Faculty of Science and Technology, MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
2 Groupe de Physique à Haute Intensité, CEA Saclay-DSM/IRAMIS/SPAM, 91191 Gif-sur-Yvette, France
3 also FOM Institute for Plasma Physics, Rijnhuizen, 3439 MN Nieuwegein, The Netherlands
Enhanced backward-acceleration of ions is experimentally observed when ultra-short, high-intensity and ultra-high-contrast laser pulses interact with thin foils having thicknesses in the order of the penetration depth of the laser light. Below the experimentally observed optimum foil thickness for the maximum ion energy versus thickness, there arises a second peak. 1D simulations on foils with an initial plasma density gradient show a similar trend as the experiment. It appears that in this regime of extremely thin foils it is important to take into account the limited expansion of the plasma that is formed by ultra-high-contrast pulses.
© EDP Sciences, Springer-Verlag, 2009