Title: Neutron Angular Distribution in Plutonium-240 Spontaneous Fission
Authors: MARCATH M. J.SHIN TonyCLARKE Shaun D.PEERANI PaoloPOZZI Sara
Citation: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT vol. 830 p. 163-169
Publisher: ELSEVIER SCIENCE BV
Publication Year: 2016
JRC N°: JRC100799
ISSN: 0168-9002
URI: http://dx.doi.org/10.1016/j.nima.2016.05.064
http://publications.jrc.ec.europa.eu/repository/handle/JRC100799
DOI: 10.1016/j.nima.2016.05.064
Type: Articles in periodicals and books
Abstract: Nuclear safeguards applications require accurate fission models that exhibit prompt neutron anisotropy. In the laboratory reference frame, an anisotropic neutron angular distribution is observed because prompt fission neutrons carry momentum from fully accelerated fission fragments. A liquid organic scintillation detector array was used with pulse shape discrimination techniques to produce neutron-neutron cross-correlation time distributions and angular distributions from spontaneous fission in a 252Cf, a 0.84 g 240Pueff metal, and a 1.63 g 240Pueff metal sample. The effect of cross-talk, estimated with MCNPX-PoliMi simulations, is removed from neutron-neutron coincidences as a function of the angle between detector pairs. Fewer coincidences were observed at detector angles near 90°, relative to higher and lower detector angles. As light output threshold increases, the observed anisotropy increases due to spectral effects arising from fission fragment momentum transfer to emitted neutrons. Stronger anisotropy was observed in Cf-252 spontaneous fission prompt neutrons than in Pu-240 neutrons.
JRC Directorate:Nuclear Safety and Security

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