Low-Divergent, Energetic Electron Beams from Ultra-Thin Foils

In this work we report on a recent experiment where an energetic, well-collimated electron beam has been observed in the laser direction following the short pulse (600 fs) high-intensity laser interaction with ultra-thin solid foils. These results are in contrast to the typical low-energy divergent electrons accompanying ions in the target normal direction usually seen in solid targets. We observe the foils being preheated and expanded by ASE prior to the main pulse which makes them transparent for the laser. The experimental evidence as well as 2D particle-in-cell simulations suggest the excitation of a wakefield that can accelerate electrons to energies of tens of MeV.