Conversion Efficiency Enhancement for Laser Generated Protons in Reduced Mass Targets

We demonstrate experimentally that minimizing the area and maximizing the isolation of proton beam sources, can increase the efficiency with which they convert energy into protons. The experiment was performed on the Tcubed laser facility at the University of Michigan. The hybrid Ti:Sapphire/ Nd-glass laser delivers up to 5 J on target in 400 fs, with a peak intensity of 2x10$^{19}$ W/cm$^{2}$. Micro machined Cu foils, 10 $\mu $m thick, were used as reduced mass targets. These 150 $\mu $m x 150 $\mu $m Cu targets, were connected to the supporting mount foil by identical legs at their corners, of the same thickness and 3 varying widths: 21$\mu $m, 42 $\mu $m and 84 $\mu $m. Detailed experimental data and simulations will be presented. The work was performed under the auspices of the U.S. Department of Energy under contract DE-SC0001265.