Density effect on proton acceleration from carbon-containing high-density thin foils irradiated by high-intensity laser pulses

The acceleration of protons in dense plastic foils irradiated by ultrahigh intensity laser pulses is simulated using a two-dimensional hybrid particle-in-cell scheme. For the chosen parameters of the overdense foils of densities rho=0.2, 1, and 3 g/cm(3) and of an ultrahigh intensity (2x10(20) W/cm(2)) laser pulse, our simulations illustrate that a high-density target is favorable to high collimation of the target-normal-sheath acceleration protons but less energy for a short acceleration time (< 100 fs). In particular, the difference of strong local heating of the carbon ion for different plasma densities is clearly observed at both the front and rear surfaces of thin solid targets, suggesting that the effect of the density and composition of the targets are also important for correctly simulating energetic ion generation in ultraintense laser-solid interactions. (c) 2007 American Institute of Physics.