First demonstration of multi-MeV proton acceleration from a cryogenic hydrogen ribbon target.

We show efficient laser driven proton acceleration up to 14MeV from a 50 $\mu$m thick cryogenic hydrogen ribbon. Pulses of the short pulse laser ELFIE at LULI with a pulse length of $\approx$ 350 fs at an energy of 8 J per pulse are directed onto the target. The results are compared to proton spectra from metal and plastic foils with different thicknesses and show a similar good performance both in maximum energy as well as in proton number. Thus, this target type is a promising candidate for experiments with high repetition rate laser systems.