Generation of collimated quasi-monoenergetic target surface electron beams in laser solid interaction

Abstract

Collimated quasi-monoenergetic target surface electron beams with divergence angle as small as 2° and energy peaked at 3-4 MeV were first generated in 200 TW sub-picoseconds laser interacted with solid target. We found that the laser contrast plays an important role in generating such kind of target surface electron beams. Resonant absorption might be the main heating regime through Back Scattering spectra analyses. Fine structures of shadow imaging of probe beam and plasma self-emission illustrate that over dense pre-plasma were generated. Such pre-plasma acts as a plasma reflective mirror which confines the main pulse propagating in the channel between pre-plasma and target surface and eventually guiding the electron beams along target surface. Such kind of electron beams might be used as an igniter in inertial confinement fusion, especially in the fast ignition concept.