  Intense laser acceleration of ions is inherently difficult due to the
velocity mismatch between laser pulses moving at the speed of light and slowly
moving massive ions. Instead of directly accelerating the ions, current
approaches rely on TV/m laser fields to ionize and drive out electrons. The
ions are then accelerated by the resulting electrostatic fields from charge
separation. Here we report experimental and numerical acceleration of ions by
means of laser driven Z-pinch exiting a sharp plasma interface. This is
achieved by first driving a plasma wakefield in the self-modulated bubble
regime. Cold return currents are generated to maintain quasi-neutrality of the
plasma. The opposite current repel and form an axial fast current and a
cylindrical-shell cold return current with a large (100 MG) azithmuthal field
in between. These conditions produce a Z-pinch that compresses the fast
electrons and ions on axis. If this process is terminated at a sharp plasma
interface, a beam of ions are then accelerated in the forward direction as the
Z-pinch collapses. These results provide a new route towards laser-accelerated
ions as well as potential laboratory scale modeling of z-pinches in
astrophysical events.
