Generation of quasi-monochromatic beams of accelerated electrons during interaction of weak-contrast intense femtosecond laser radiation with a metal-foil edge

The formation of monoenergetic beams of accelerated electrons by focusing femtosecond laser radiation with an intensity of 2 × 10¹⁷ W cm^-2 onto an edge of aluminium foil has been experimentally demonstrated. The electrons had energy distributions peaking in the range from 0.2 to 0.8 MeV and an energy spread less than 20 %. The acceleration mechanism related to the generation of a plasma wave as a result of self-modulation instability of the laser pulse in the subcritical plasma formed the prepulse of the laser system (arriving 10 ns before the main pulse) is considered. Onedimensional PIC simulation of the interaction between the laser radiation and plasma with a concentration of 5 × 10¹⁹ cm^-3 showed that effective excitation of a plasma wave, as well as the trapping and acceleration of the electron beam with an energy on the order of 1 MeV, may occur in the presence of inhomogeneities in the density at the plasma boundary and in the temporal shape of the beam.