The Research Program 3 (RP3) will also focus on the demonstration of proof-of-principle experiments aimed at envisioning future societal applications in various areas with special attention paid to biomedical ones. Thus, the optimization of particle beam quality and reproducibility (spatial profile, pointing, divergence and energy stability) will be a crucial issue. In order to realize such a challenging and wide range of envisioned activities, two scientific groups are currently working on the implementation of two different target areas, the ELIMAIA ion acceleration beamline and the HELL electron acceleration platform, with the main goal being to fulfill the expectations of the scientific user community, which are summarized in the ELI-White Book .

Laser-driven particle acceleration is a new field of physics that is rapidly evolving thanks to the continuing development of high power laser systems, thus allowing researchers to investigate the interaction of ultrahigh laser intensities (> 1019 W/cm2) with 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 for the acceleration of particles at relativistic energies by way of very compact approaches. In particular, spectacular progress in the acceleration of electrons and protons has been achieved. On the one hand, electrons are currently being accelerated to very high energies (several GeV) from gas targets, which are transformed in plasma by high intensity laser pulses [ Leemans et al ]. On the other hand, 100-MeV-class protons are presently being accelerated in thin solid targets through the energy transfer of high energy electrons [ Macchi et al ].

Ion Acceleration

According to the state of the art in laser-driven ion acceleration, maximum proton energies of several tens of MeV have been experimentally achieved with a relatively high yield (1010-1012 protons/pulse). However, laser-accelerated ion beams are still not mature for several applications in which additional features, such as low divergence, monoenergeticity, spatial profile uniformity, or shot-to-shot stability, are essential. Nevertheless, new laser technologies that will soon be available, e.g. ELI Beamlines, will allow the scientific community to investigate new regimes that are very promising in terms of future use of laser-driven ion beams for various applications.

Electron Acceleration

Electron acceleration driven by high peak power femtosecond lasers was theoretically predicted in 1979 by Tajima and Dawson [5]. The brilliant idea to use laser-driven plasma-waves was experimentally demonstrated more than a decade ago, and presently this technique is used on a daily basis in many laboratories worldwide.