Surface plasmon (SP) excitation in intense laser interaction with solid target can be exploited for enhancing secondary emissions, in particular efficient acceleration of high charge electron bunches. Previous studies have mostly used grating coupling to allow SP excitation, which requires stringent laser contrast conditions to preserve the structural integrity of the target. Here we show via simulations that efficient SP electron acceleration for currently available short pulse lasers can occur in a flat foil irradiated at parallel or grazing incidence (∼ 50 with the target surface) without a surface modulation. In turn, the accelerated electrons can be effective for generating proton beams with narrow spectra peaked at >100 MeV energies for currently available laser drivers.
The use of nano-structured targets has the ability to enhance the energy and quality of accelerated electron and ion beams in comparison to conventional flat foil targets. Ion acceleration from plastic foil target of sub-micron thickness embedded with rods of nano-meter length using ultra-short intense laser pulse of intensity ≥ 1021 W/cm2 is investigated using PIC simulation. The laser and target parameters are tuned to achieve better performance with nano-structured targets compared to flat foil. Several new features of the ion acceleration process are revealed in the present study. A hybrid RPA-TNSA mechanism using a linearly polarised laser is found to play a key role in accelerating protons to ∽ 300 MeV of energy. The effect of multiple ion species on the acceleration of protons has been studied and a narrow peak in the proton energy spectrum around ∽ 100 MeV is observed which is attributed to the presence of heavier ions in the target.
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