Efficient laser energy conversion to ions in a laser-foil interaction

Improvement of energy conversion efficiency from laser to proton beam is demonstrated by particle simulations in a laser- foil interaction. When an intense short-pulse laser illuminates the thin foil target, the foil electrons are accelerated around the target by the ponderomotive force. The hot electrons generate a strong electric field, which accelerates the foil protons, and the proton beam is generated. In this paper a multihole thin- foil target is proposed in order to increase the energy conversion efficiency from laser to protons. The multiholes transpiercing the foil target help to enhance the laser-proton energy conversion efficiency significantly. 2.5-dimensional particle-in-cell simulations present that the total laser- proton energy conversion efficiency becomes 9.3% for the multihole target, though the energy con version efficiency is 1.5% for a plain thin foil target. The maximum proton energy is lO.OMeV for the multihole target and is 3.14MeV for the plain target. The transpiercing multihole target serves a new method to increase the energy conversion efficiency from laser to ions. One of problems in the laser-ion acceleration is the energy conversion efficiency from laser to ions, and the energy conversion efficiency is low in actual experiments. The sub- wavelength fine microstructure enhances the laser energy absorption and the ion beam generation.