Measurement of 14N(n,p)14C cross section for kT = 25.3 keV Maxwellian neutrons using gridded ionization chamber

We measured the 14N(n,p)14C reaction cross section for neutrons with a quasi-Maxwellian distribution of kT = 25.3 keV which is one of the key parameters for the s-process nucleosynthesis in astrophysics. Protons were detected with high efficiency using a gridded ionization chamber. We employed a thick Li target and a 1.912 MeV proton beam for neutron production, and a vacuum-evaporated melamine (C3H6N6) film as a 14N sample. The absolute cross section was determined relatively to the 6Li(n,t)α cross section by measuring the triton yield from a 6LiF film in place of melamine. Our result (1.70 ± 0.08 mb) is approximately a factor 2 larger than the value reported in an earlier direct measurement for the same Maxwellian neutron spectrum; it is consistent with results deduced from monoenergetic neutrons or inverse reaction.