Measurement of the $^{243}$Am capture cross section at the n_TOF facility

This thesis presents the analysis of the neutron capture measurement of $^{243}$Am carried out at the n_TOF facility at CERN, in the energy range from 0.7 eV to 2.5 keV. The importance of this measurement is related to the design of new nuclear reactors, especially in relation to the transmutation of radioactive waste. This is the first time that $^{243}$Am neutron capture data below 250 eV, excluding the thermal point, has been published. This results suggest that this cross section is underestimated up to 25% in the neutron energy range between 50 eV and a few keV in the present evaluated data libraries.