Laser-driven ultraintense proton beams for high energy-density physics

The results of studies of high-intensity proton beam generation from thin (1~--~3$\mu $m) solid targets irradiated by 0.35-ps laser pulse of energy up to 15J and intensity up to 2$\times $10$^{19}$ W/cm$^{2}$ are reported. It is shown that the proton beams of multi-TW power and intensity above 10$^{18~}$W/cm$^{2}$ at the source can be produced when the laser-target interaction conditions approach the Skin-Layer Ponderomotive Acceleration requirements. The laser-protons energy conversion efficiency and proton beam parameters remarkably depend on the target structure. In particular, using a double-layer Au/PS target (plastic covered by 0.1~-- 0.2$\mu $m Au front layer) results in two-fold higher conversion efficiency and proton beam intensity than in the case of a plastic target. The values of proton beam intensities attained in our experiment are the highest among the ones measured so far.