Proton acceleration from high-contrast short pulse lasers interacting with sub-micron thin foils.

A theoretical study complemented with published experimental data of proton acceleration from sub-micron (thickness < 1 µm) foils irradiated by ultra-high contrast (>1010) short pulse lasers is presented. The underlying physics issues pertinent to proton acceleration are addressed using two-dimensional particle-in-cell simulations. For laser energy ε ≤ 4 J (intensity I ≤ 5 x 1020 W/cm²), simulation predictions agree with experimental data, both exhibiting scaling superior to Target Normal Sheath Acceleration's model. Anomalous behavior was observed for ε > 4 J (I > 5 x 1020 W/cm²), for which the measured maximum proton energies were much lower than predicted by scaling and these simulations. This unexpected behavior could not be explained within the frame of the model, and we conjecture that pre-pulses preceding the main pulse by picoseconds may be responsible. If technological issues can be resolved, energetic proton beams could be generated for a wide range of applications such as nuclear physics, radiography, and medical science. [ABSTRACT FROM AUTHOR]