Measurement of ¹⁹¹Ir(n,2n)¹⁹⁰Ir cross section near 14 MeV

Abstract

Natural iridium acts as a high-quality activated detector for probing the energy components of a neutron fluence. Measurements of ¹⁹¹Ir(n,2n)¹⁹⁰Ir cross sections are carried out near 14 MeV by the activation method based on ⁹³Nb(n,2n)^92mNb reaction cross section standard by PD-300 neutron generator DT neutron source. The (n,2n) products are measured by using a calibrated high pure Ge detector. The cross sections of ¹⁹¹Ir(n,2n)¹⁹⁰Ir, <i>σ</i>_m2 and <i>σ</i>_g+m1, are measured carefully. The ¹⁹¹Ir(n,2n)¹⁹⁰Ir cross sections: <i>σ</i>_m2, <i>σ</i>_g+m1, <i>σ</i>_g+m1+m2 and cross section ratio of <i>σ</i>_m2/<i>σ</i>_g+m1 are obtained in an energy range of 13.40–14.86 MeV. Experimental uncertainties are in a range of 3.4%–3.5%. The measured cross sections for the reaction of ¹⁹¹Ir(n,2n)¹⁹⁰Ir at 14 MeV are <i>σ</i>_m2 = (136.05 ± 4.93) mb, <i>σ</i>_g+m1 = (1972.35 ± 67.06) mb, <i>σ</i>_g+m1+m2 = (2108.40 ± 71.99) mb, and <i>σ</i>_m2/<i>σ</i>_g+m1 = 0.0690 ± 0.0024. The present data are compared with the previous experimental data and the ENDF/B-VIII.0 and JEFF3.0/A evaluated data, showing that the experimental data from the literature are in good agreement with the present data for <i>σ</i>_g+m1, the evaluated data from JEFF3.0/A are underestimated by 5%–20% in comparison with the present data for <i>σ</i>_m2, the evaluated data from ENDF/B-VIII.0 are underestimated by 10% in comparison with the present data for <i>σ</i>_m2, and the ENDF/B-VIII.0 data are consistent with the present data for <i>σ</i>_g+m1+m2. The discrepancies between the data from the literature and the present data are analyzed and clarified. The present data show significant improvement in accuracy in comparison with data from the literature, these results provide more reliable nuclear data for improving the future evaluation.