Integrated double-plasma-mirror targets for contrast enhancement in laser ion acceleration

We introduce a target concept for laser-driven ion acceleration with ultrashort, highly intense laser pulses that includes an integrated double plasma mirror for contrast enhancement. It comprises three nanometer thin plastic foils, embedded in a small metal structure, which ensures precise mounting. The geometry allows to apply a double plasma mirror directly in front of a target foil within the converging beam, enabling moderate-energy (∼1 J) laser systems to reach the required fluence of several hundred J/cm² on the plasma mirrors. During an experimental campaign, performed at the Laboratory for Extreme Photonics in Munich, we observed proton energies increased by a factor of three using this new target, which is attributed to an enhanced laser contrast after the integrated double plasma mirrors.