Efficient Ion Acceleration by Continuous Fields in Target Transparency Regime*

Ion beams driven by short-pulse lasers have been an increasingly active area of research as the beams have potential applications where maximizing energy and yield of ions would be beneficial. Here, we present a new feasible scheme of short-pulse laser-driven ion acceleration with multi-ps pulses and ultra-thin targets in which the synergetic effects of laser-induced target transparency and continuous field acceleration efficiently enhance the flux and peak cutoff energy of accelerated ions. Recent experiment conducted on the OMEGA EP lasers demonstrated the new approach showing the maximum proton energy of higher than 70MeV from the moderate-intensity, ~10^19 W/cm^2 with sub-micron thick targets, and significantly higher yield of protons than expected from a typical TNSA mechanism. The computational study indicates the enhanced temperature of electrons from laser interaction with expanding plasma drives a strong electric field for further ion acceleration. Detailed experimental results including various measurements and systematic simulations will be presented.