%0 Journal Article
%T Measurement of the U-235(n, f) cross section relative to the Li-6(n, t) and B-10(n,alpha) standards from thermal to 170 keV neutron energy range at n_TOF
%A n_TOF Collaboration (Amaducci, S. et al
%A Domingo-Pardo, C.
%A Tain, J. L.
%J European Physical Journal A
%D 2019
%V 55
%N 7
%I Springer
%@ 1434-6001
%G English
%F n_TOFCollaborationAmaducci_etal2019
%O WOS:000477050900001
%O exported from refbase (https://references.ific.uv.es/refbase/show.php?record=4083), last updated on Mon, 19 Aug 2019 07:00:41 +0000
%X .The U-235(n, f ) cross section was measured at n_TOF relative to Li-6(n, t) and B-10(n,alpha) , with high resolution ( L=183.49(2) m) and in a wide energy range (25meV-170keV) with 1.5% systematic uncertainty, making use of a stack of six samples and six silicon detectors placed in the neutron beam. This allowed us to make a direct comparison of the yields of the U-235(n, f ) and of the two reference reactions under the same experimental conditions, and taking into account the forward/backward emission asymmetry. A hint of an anomaly in the 10-30keV neutron energy range had been previously observed in other experiments, indicating a cross section systematically lower by several percent relative to major evaluations. The present results indicate that the cross section in the 9-18keV neutron energy range is indeed overestimated by almost 5% in the recently released evaluated data files ENDF/B-VIII.0 and JEFF3.3, as a consequence of a 7% overestimate in a single GMA node in the IAEA reference file. Furthermore, these new high-resolution data confirm the existence of resonance-like structures in the keV neutron energy region. The results here reported may lead to a reduction of the uncertainty in the 1-100keV neutron energy region. Finally, from the present data, a value of 249.7 +/- 1.4( stat )+/- 0.94( syst ) b<bold>eV has been extracted for the cross section integral between </bold>7.8 and 11eV, confirming the value of 247.5 +/- 3 b<bold>eV recently established as a standard</bold>.
%R 10.1140/epja/i2019-12802-7
%U https://arxiv.org/abs/1902.10631
%U https://doi.org/10.1140/epja/i2019-12802-7
%P 120-19pp