Comparative study of amplified spontaneous emission and short pre-pulse impacts onto fast electron generation at sub-relativistic femtosecond laser-plasma interaction

This paper describes the study of hot electron generation under the action of intense (∼1018 W/cm2) femtosecond pulses onto the surface of a solid target, in the presence of a long pre-plasma, which varied with different spatial extents and densities. The corona was formed by pre-pulses with varied intensities and temporal profiles (amplified spontaneous emission (ASE) and short pre-pulses). The most efficient fast electron acceleration, to energies well beyond the ponderomotive potential, was observed if the ASE was able to form to the extent of ∼100 μm a slightly undercritical plasma. Energy of accelerated electrons underwent further growth if the laser pulse duration increased from ∼45 to ∼350 fs at constant energy fluence. The experimental results were supported by numerical simulations using 3D3V Mandor PIC code.