Cross-section measurement of 237Np (n, γ) from 10 meV to 1 keV at Japan Proton Accelerator Research Complex

The cross-section of the Np-237 (n, gamma) reaction has been measured in the energy range from 10 meV to 1 keV using the ANNRI-NaI(Tl) spectrometer at the Japan Proton Accelerator Research Complex (J-PARC). The cross-section was obtained relative to that of the B-10 (n, alpha(1)) reaction. The absolute value of the cross-section was deduced by normalizing the relative cross-section to the evaluated value of JENDL-4.0 at the first resonance. The thermal cross-section was obtained to be (176.7 +/- 0.5(sta) +/- 4.7(sys)) b. The Maxwellian-averaged cross-section for kT - 25.3 meV was derived as (174.6 +/- 0.6(sta) +/- 5.1(sys)) b by referring the cross-section below 10 meV from JENDL-4.0. These results lead to the Westcott's g-factor of 0.988 +/- 0.004(sta) +/- 0.009(sys).