Laser-plasma ion acceleration is a new field of Physics rapidly evolving thanks to the continuing development of high power laser systems, thus allowing to investigate the interaction of ultrahigh laser intensities with the matter. As a result of such interaction, extremely high electric and magnetic fields are generated. Such tremendous fields, which can be supported only in plasmas, allow accelerating particles at relativistic energies by very compact approaches (in sub-mm distances). High repetition rate operation (0.1 - 10 Hz) would be beneficial for high-power laser experiments in order to have better statistics (shot-to-shot variations introduce large uncertainties), to investigate complex effects such as plasma instabilities, to build up signal for X-ray diagnostics and for the production of laser-driven radiation and particle sources.
Fast target refreshing, positioning and alignment are the main issues related to high repetition rate operation.
To address these issues we are working on research and design of liquid and solid cryogenic target system using cryogenic gases (H, D, He). The generation of pure hydrogen plasma has advantages from the experimental point of view in terms of the plasma itself and its characterization (single ion species), as well as for future multidisciplinary applications of laser-accelerated proton beams. Additionally, this type of target is debris-free and is convenient media for theoretical modelling or numerical simulations.