Advanced polymer targets for TNSA regime producing 6 MeV protons at 1016 W/cm2 laser intensity

Abstract

High intensity laser pulses, at an intensity of the order of 1016 W/cm2, are employed to irradiate in vacuum polyethylene terephthalate thin foils in the target normal sheath acceleration (TNSA) regime. The plasma obtained in the forward emission is investigated using ion collectors and semiconductor detectors connected in a time-of-flight configuration, Thomson parabola spectrometer, and X-ray streak camera. The results indicate that the foil thickness of 1 micron is optimal to accelerate protons of up to 6.5 MeV. The high ion acceleration can be due to different effects such as the high absorption in the advanced semicrystalline polymer containing spherulite centers, the high resonant absorption in gold nanoparticles embedded in the polymer, the optimal thickness of the used polymer to enhance the electron density in the forward plasma, and the self-focusing effect induced by preplasma created in front of the irradiated target.