TOF-based diagnostics system development and Geant4 simulation of the ELIMED transport and dosimetry beam line for high energy laser-driven ion beam applications @ ELI Beamlines

The acceleration processes based on the coherent interaction of high-power laser with matter is by now one of the most interesting topics in the field of particle acceleration, becoming a real alternative to conventional approaches. Some of the peculiarities of laser accelerated ion beams, if well controlled, are very promising for fundamental research as well as for multidisciplinary applications, including the medical field. In this framework, a complete transport and dosimetry beam line, named ELIMED, has been realized at INFN-LNS and will be installed at ELI-Beamlines by the end of 2017. It will be a section of the user-oriented ELIMAIA (ELI Multidisciplinary Applications of laser-Ion Acceleration) beam line at ELI-Beamlines, dedicated to the high-energy ion acceleration as well as high-intense X-rays generation and their possible multidisciplinary applications. The present thesis describes the Monte Carlo Geant4-based application, simulating the complete ELIMED beam line, in terms of geometry as well as magnetic and electric fields. Realistic top-to-bottom simulations have been performed to predict beam parameters and optimize dose distributions at the irradiation point in terms of homogeneity and dose delivered per shot in view of medical applications. In particular, the simulation performed clearly indicates the possibility to obtain a Spread Out Bragg Peak (SOBP) of clinical relevance with the selected proton beams. A specific on-line diagnostics system based on the Time Of Flight (TOF) technique coupled with diamond and/or silicon carbide detectors, has been developed and will be used for shot-to-shot energy distribution and flux measurement. Considering the high-energy laser-driven ion beams that will be delivered at ELIMAIA, a new analysis procedure, optimized for high-energy laser-driven proton beams, to extract the energy distribution for a given in species from the TOF signal has been developed and validated. The experiments carried out in the multi-TW laser facilities, Rutherford Appleton Laboratory (RAL, UK), Ludwig Maximilians University Munchen (LMU, GE) and the Prague Asterix Laser System (PALS,CZ), will be described in details together with the results achieved using the TOF method for beam diagnostics. The results confirmed the reliability of the TOF technique and of the procedure developed for high-energy laser-driven ion beams, pointing out that TOF technique can be particularly suitable for the on-line diagnosis of the high-energy ion beam characteristics, giving real time information useful to optimize transport as well as to investigate specific nuclear reactions occuring in the laser-target interaction.