When high-intensity laser pulses interact with matter, the atoms subjected to the electromagnetic pulse are ionized by the light field, so that the actual laser pulse interacts with a completely, or at least partially, ionized plasma. When so-called supercritical targets are used (e.g. thin metal foils, but also spherical, few-µm-diameter targets that form a supercritical plasma when interacting with the intense laser field), the laser radiation can not penetrate the target, however, a significant portion of its energy is converted to kinetic energy of relativistic electrons. These electrons are in turn capable of generating electric fields (on the order of 1 TV/m) which accelerate ions to energies of several 10 MeV, over distances of but a few µm. To optimize the parameters of the generated ion pulses, various acceleration mechanisms are investigated using the different laser systems at HI-Jena.