TOF-Wall and Calorimeter detector analysis in the FOOT experiment with Helium beams at the Heidelberg Ion Beam Therapy Center

Charged particle therapy (CPT) is a technique that has shown substantial physical and biological advantages with respect to conventional photon radiotherapy for cancer treatment. Indeed, unlike photons, which deliver a high entrance dose, charged particles release most of their energy at the Bragg Peak (BP). This, along with an improved biological effectiveness regarding the damage induced to the target cells, represents a major benefit of CPT compared to conventional radiotherapy. Despite this fact, the advantages of CPT cannot yet be fully exploited. Among the reasons for this is the uncertainty of the biological effectiveness of the charged particle beams introduced by fragmentation, caused by nuclear processes: target fragments can release their energy in the entrance channel of the medium while projectile fragments (in the case of heavy ion beams) can release their energy beyond the BP, thus delivering dose to non-target organs. As of today, the limited amount of available experimental data regarding fragmentation differential cross sections poses a significant challenge to the improvement of biological models, that are also important for treatment planning. In this context, the FOOT (FragmentatiOn Of Target) experiment aims to fill the lack of experimental data regarding nuclear fragmentation processes relevant to CPT. This is intended to be accomplished by measuring differential and double differential cross sections of the fragments produced by the nuclei that are most representative of the human tissue composition. Crucial for the cross section measurements are the TOF-Wall (TW), composed of two layers of 20 plastic scintillator bars each, and the Calorimeter detectors, which provide the measurement of mass, charge and energy of the produced fragments. In this thesis, the two detectors, part of the setup employed in the 2022 data taking campaign at the Heidelberg Ion Therapy (HIT) center, have been analyzed, with the focus on helium beams of energies 100, 140, 180, 200 and 220 MeV/u. The TW detector has been calibrated by analyzing its response in terms of deposited energy and Time-Of-Flight TOF, and by comparing it to Monte Carlo simulations. The calibrated energy and TOF values were then used to assess the TW performances. An energy resolution ranging from 5% at 100 MeV/u to 8% at 220 MeV/u beam energy and a TOF resolution ranging from 116 ps at 100 MeV/u to 157 ps at 220 MeV/u beam energy were calculated. Using the calibrations, it was possible to reconstruct the Z of the fragments through the Bethe-Bloch formula. Regarding the Calorimeter, which was present in a partial layout, a preliminary calibration strategy has been developed, that can be considered as a testing ground for the full experimental setup.