The 14N(n,p) reaction cross-section measurement at n TOF - CERN and its application to the design of a facility for neutron capture therapy

Resumo

Experimental nuclear data and simulations are crucial for new radiotherapies of cancer. In Boron Neutron Capture Therapy (BNCT), an accurate knowledge of neutron interaction with the elements present in body tissues is key for dosimetry. At low neutron energies, the reaction between neutrons and nitrogen, 14N(n,p), becomes a main component of the dose in most human tissues. There are several discrepancies in previous measurements of this reaction, which increase the uncertainty in dose estimations needed for treatment planning. Furthermore, Neutron Capture Therapy needs intense and clean neutron sources, suitable for therapy and with the possibility of being installed in hospital environments, getting over previous facilities at nuclear reactors. This thesis aims to contribute to these two topics. The nuclear data from a new measurement of the 14N(n,p) reaction, carried out at the n TOF Facility at CERN will be shown. The new high-accuracy data span from 8 meV to 800 keV, covering the range of interest for BNCT, including the thermal point (25.3 meV), whose cross-section value was found to be at 1.809 0.045 b. The implications of this new nuclear data to BNCT dosimetry will be explored via Monte Carlo simulations. A new Beam Shaping Assembly (BSA) will be proposed for a proton acceleratorbased neutron source, using 30 mA of 2.1 MeV protons onto a lithium target. This BSA produces a high-intensity and well-collimated neutron eld that also provides low contamination from gamma radiation and both thermal and fast neutrons. The spectrum of the beam coming out of the BSA aperture will be shown to be adequate for BNCT treatments, full lling all recommendations from the IAEA and also performing well in in-phantom dose simulations. The new nuclear data and the proposed neutron beam will be put together as input in order to develop a Treatment Planning System (TPS). The TPS processes medical images (DICOM) and runs Monte Carlo simulations of neutron transport through the model of the patient, allowing to compute dose estimations in the tumor and surrounding tissues, including organs at risk. The TPS will be used to perform a pilot test simulation with a realistic case of a Glioblastoma patient.