Laser Accelerated Ions from a Shock Compressed Gas Foil
  We present results of energetic laser-ion acceleration from a tailored, near solid density gas target. Colliding hydrodynamic shocks compress a pure hydrogen gas jet into a 70 {\mu}m thick target prior to the arrival of the ultra-intense laser pulse. A density scan reveals the transition from a regime characterized by a wide angle, low energy beam to one of a more focused beam with a high energy halo. In the latter case, three dimensional simulations show the formation of a Z-pinch driven by the axial current resulting from laser wakefield accelerated electrons. Ions at the rear of the target are then accelerated by a combination of space charge fields from accelerated electrons and Coulombic repulsion as the pinch dissipates. 
M. H. Helle, D. F. Gordon, D. Kaganovich, Y. Chen, J. P. Palastro, and   A. Ting
physics.plasm-ph