Measurement of the 235U(n, f) cross section relative to the 6Li(n, t) and 10B(n, a) standards from thermal to 170 keV neutron energy range at n_TOF
The 235U(n, f ) cross section was measured at n_TOF relative to 6Li(n, t) and 10B(n,a) , 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 a...
| Authors: | , , , , , , |
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| Format: | article |
| Publication Date: | 2019 |
| Country: | España |
| Institution: | Universitat Politècnica de Catalunya (UPC) |
| Repository: | UPCommons. Portal del coneixement obert de la UPC |
| Language: | English |
| OAI Identifier: | oai:upcommons.upc.edu:2117/174567 |
| Online Access: | https://hdl.handle.net/2117/174567 https://dx.doi.org/10.1140/epja/i2019-12802-7 |
| Access Level: | Open access |
| Keyword: | Neutrons Nuclear physics Neutron n_TOF CERN Nuclear reaction Cross section Física nuclear Àrees temàtiques de la UPC::Física Àrees temàtiques de la UPC::Energies::Energia nuclear |
| Summary: | The 235U(n, f ) cross section was measured at n_TOF relative to 6Li(n, t) and 10B(n,a) , 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 235U(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·eV has been extracted for the cross section integral between 7.8 and 11eV, confirming the value of 247.5±3 b·eV recently established as a standard. |
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