## 2 Overview of the ELIMAIA Beam Line  
As already pointed out, the ELIMED main goal is the realization of a beam transport line (from the laser-target interaction chamber to the final sample irradiation point) and a number of dosimetric endpoints that will enable the users to apply laser-driven ion beams (protons, alpha-particles and carbon/lithium ions) in multidisciplinary fields. The technical solution proposed for the realization of the ELIMED beam line is based on a modular system, which allows adapting and combining the devices depending on the different phases of the project and the different user's requirements. Three different sections of the ion beam line have been identified for its implementation: the Ion Beam Collection and Diagnostics; the In-Vacuum Ion Beam Selection, Transport and Diagnostics and the Dosimetry and sample Irradiation systems. Laser-driven ion beams are characterized by high intensities, several species with multiple charge states, broad energy spectra and energy-dependent angular distributions. Therefore, in order to make these beams suitable for multidisciplinary purposes, the main task of the beam transport line will be to control the particle energy and angular distributions as well as the flexibility and reproducibility of the delivered beam spot size and dose distribution. The requirements needed to perform accurate dosimetric measurements and radiobiological irradiations for pre-clinical studies imply that the transported beam must fulfill specific characteristics. Indeed, these preparatory pre-clinical studies, which are based on _in vivo_ irradiations on mice, have to be done with a level of accuracy on delivered dose close to the one characterizing human tumor treatments. The specific characteristics of the transported beams are mainly related to the beam flatness and symmetry at the irradiation point, which have to be within 3%. In particular, the purpose of the collecting and focusing section is to reduce the initial angular divergence of the particle beam accelerated from the target improving the transmission and the selection efficiency of the entire transport system. The focusing element will consist of a set of permanent magnet quadrupoles (PMQs) [15, 16, 17] based on a hybrid Halbach array in order to maximize the magnetic field strength, quality and uniformity by keeping the system as compact as possible. A quadrupole set is necessary to obtain a focusing effect on both transversal planes, as well as for a suitable matching with selection system acceptance. The PMQs system will be placed few cm downstream the target. Since the field strength is fixed for each magnet, the PMQs system will be provided with mechanical stages allowing modifying the relative distance of each quadrupole along the beam direction (_i.e._ the longitudinal axis) and, thus, the focal point position as a function of the beam energy. The moving system will be provided with a remote control. The energy selection system is the critical element of the whole beam line. The beam accelerated by the laser-target interaction, after the collecting and focusing section, might still show a broad energy spectrum. Therefore, it is important to realize a system able to select ion beams with controlled energy spread and kinetic energy. The energy selector system (ESS) proposed will be placed along the beam transport line, downstream from the PMQs system. The ESS will consist of tunable resistive conductors allowing varying the performances depending on the ion species to be selected. It will be based on a resistive coil system with alternating field gradient. A set of resistive quadrupoles placed downstream from the ESS will allow recovering both vertical and radial focusing of the beam after the selection. Two steering magnets (in both vertical and horizontal directions) will allow for control of the beam direction after the selection and correcting of any possible beam misalignments.