Measurement of the N 14 (n,p) C 14 cross section at the CERN n_TOF facility from subthermal energy to 800 keV

Background: The 14 N(n, p) 14 C reaction is of interest in neutron capture therapy, where nitrogen-related doseis the main component due to low-energy neutrons, and in astrophysics, where 14 N acts as a neutron poison inthe s process. Several discrepancies remain between the existing data obtained in partial energy ranges: thermalenergy, keV region, and resonance region.Purpose: We aim to measure the 14 N(n, p) 14 C cross section from thermal to the resonance region in a singlemeasurement for the first time, including characterization of the first resonances, and provide calculations ofMaxwellian averaged cross sections (MACS).Method: We apply the time-of-flight technique at Experimental Area 2 (EAR-2) of the neutron time-of-flight(n_TOF) facility at CERN. 10 B(n, ?) 7 Li and 235 U(n, f ) reactions are used as references. Two detection systemsare run simultaneously, one on beam and another off beam. Resonances are described with the R-matrix codeSAMMY.Results: The cross section was measured from subthermal energy to 800 keV, resolving the first two resonances(at 492.7 and 644 keV). A thermal cross section was obtained (1.809 ± 0.045 b) that is lower than the two mostrecent measurements by slightly more than one standard deviation, but in line with the ENDF/B-VIII.0 andJEFF-3.3 evaluations. A 1/v energy dependence of the cross section was confirmed up to tens of keV neutronenergy. The low energy tail of the first resonance at 492.7 keV is lower than suggested by evaluated values, whilethe overall resonance strength agrees with evaluations.Conclusions: Our measurement has allowed determination of the 14 N(n, p) cross section over a wide energyrange for the first time. We have obtained cross sections with high accuracy (2.5%) from subthermal energy to800 keV and used these data to calculate the MACS for kT = 5 to kT = 100 keV.