This paper reports on an experimental demonstration of efficient proton acceleration to energies exceeding 94 MeV via a hybrid scheme of radiation pressure-sheath acceleration in an ultrathin foil irradiated by a linearly polarised laser pulse. This is complimented with a set of numerical particle-in-cell simulations using the EPOCH code. The mechanism occurs via a double-peaked electrostatic field structure, which, at an optimum foil thickness, is significantly enhanced by relativistic transparency and an associated jet of super-thermal electrons. The range of parameters over which this hybrid scenario occurs is discussed and implications for ion acceleration driven by next-generation, multi-petawatt laser facilities are explored. The analysis was originally done using MATLAB but could be performed with any code that can read in SDF outputs from EPOCH.
This work is well cited in the field of laser driven ion acceleration and provides a good study on the interaction of multiple laser driven ion acceleration mechanisms along with the impact of relativistic induced transparency.
The formation of the electron jet that influences the highest energy protons can be unstable and is dependant on local perturbations at the point of transparency. This can lead to the jet not optimally influencing the highest energy protons and can lead to slight variations in maximum proton energy but the maximum proton energy trend with target thickness should remain the same.
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