Guiding of high-energy electrons in high-intensity-laser interactions with wire targets through surface wave excitation

Experiments investigating the interaction of an ultra-short pulse laser (intensity of up to 2x10$^{19}$ W/cm$^{2})$ with thin metal wires of different diameter, length and conductivity at different angles of incidence were performed. The generation of a highly collimated electron beam with a charge of several nC, electron energies in the range of 1-7 MeV and efficiency of few percents were demonstrated. The beam was confined and guided along a thinnest wire of 15 microns to a distance of 130 cm. The spatial structure for different components of the spectrum demonstrated a better confinement of the lower energy electrons. The experimental results were interpreted through the generation of a strong Sommerfeld surface wave propagating along the wire with phase velocity close to $c$, which is produced due to electron expulsion from the focal region and generation of magnetic fields near the surface of the wire during the laser-plasma interaction. 2D PIC simulation combined with test particle simulations shows that Sommerfeld surface wave provides the crucial conditions for collimating and confining the laser-produced electron beams along the wire.