Shock-Wave Acceleration of Protons on OMEGA EP

Recent experimental results using shock-wave acceleration (SWA) driven by a CO$_{2}$ laser in a H$_{2}$ gas-jet plasma have shown the possibility of producing proton beams with energy spreads \textless 10{\%} and with energies of up to 20 MeV using a modest peak laser power of 4 TW.\footnote{D. Haberberger \textit{et al.}, Nature Phys., \textbf{8}, 95 (2012).} Here we propose the investigation of the scaling of the SWA mechanism to higher laser powers using the 1-$\mu $m OMEGA EP Laser System at the Laboratory for Laser Energetics. The required tailored plasma profile is created by expanding a CH target using the thermal x-ray emission from a UV ablated material. The desired characteristics optimal for SWA are met: (a) peak plasma density is overcritical for the 1-$\mu $m main pulse and (b) the plasma profile exponentially decays over a long scale length on the rear side. Results will be shown using a 4$\omega $ probe to experimentally characterize the plasma density profile. Scaling from simulations of the SWA mechanism\footnote{F. Fiuza \textit{et al}., Phys. Rev. Lett. \textbf{109}, 215001 (2012).} shows that ion energies in the range of 100 MeV/amu are achievable with a focused $a_{0}$ of 5 from the OMEGA~EP Laser System. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.