Cross-section measurement of $^{235}$U(n, f) at n_TOF from thermal energy to 170 keV

In the scenario of neutron data standards needed to measure neutron fluences and cross-sections of several kinds of reactions, the $^{235}$U(n,f) reaction plays a key role. Motivated by significant inconsistencies found in measurements in the 10–30 keV energy range, we measured the energy-dependent cross-section of $^{235}$U(n,f) at the n TOF facility from thermal energy to 170 keV, with high energy resolution and uncertainty below 2%. This measurement, based on the two reference reactions $^6$Li(n,t) and $^{10}$B(n,$\alpha$), allowed to ascertain that the origin of the discrepancies is an overestimation in average of 5% of the cross-section between 9 and 18 keV in major nuclear data libraries.