Efficient energy conversion from laser to proton beam in a laser-foil interaction

Demonstrated is a remarkable improvement on the energy conversion efficiency from laser to protons in a laser-foil interaction by particle simulations. The total laser-proton energy conversion efficiency becomes 16.7%, although a conventional plane foil target serves a rather low efficiency. In our previous study we found that Al multihole thin-foil target was efficient for the energy conversion from laser to protons [Y. Nodera and S. Kawata, Phys. Rev. E 78, 046401 (2008)], and the energy conversion efficiency was 9.3%. In our 2.5-dimensional particle-in-cell simulations the Al multihole structure is also employed, and the parameters of the Al multihole wing width and length are optimized in the paper. The present results clarify the roles of the target Al hole width and depth in the laser-proton energy conversion. The main physical reason for the enhancement of the conversion efficiency is a reduction of the laser reflection at the target surface area. The optimized multihole foil target provides a rema...