| A microstructure layer on the laser-irradiated side of a thin foil is used here in order to increase the absorption efficiency of high-contrast laser pulses. Due to the boosted total fast electron energy, the maximum proton energy and the total energy of the proton beam generated via TNSA mechanism are enhanced. We have proposed this mechanism via numerical simulations and we have developed targets with a monolayer of nanospheres on the foil front size. Experiments were carried out at the 100 TW laser installation in APRI GIST, Korea. The experiments confirmed the existence of the optimum nanoshere diameter. The maximum proton energy and the total proton beam energy were increased up to 50% and up to 3 times, respectively. The results of our 2D3V particle-in-cell simulations are presented for various microstructure shapes and various nanosphere diameters. Our simulations carried out for the experimental conditions compare favorably with the experimental results. The existing differences are discussed in detail and tentative explanations are suggested. (co-aurhors: O. Klimo, J. Psikal, J. Proska, F. Novotny, D. Margarone, J. Prokupek, T.M. Jeong, I.J. Kim, H.T. Kim) |
|