Title: Indication of anisotropic TKE and mass emission in 234U(n,f)
Citation: PHYSICS PROCEDIA vol. 31 p. 158-164
Publisher: ELSEVIER BV
Publication Year: 2012
JRC N°: JRC73933
ISSN: 1875-3892
URI: http://www.sciencedirect.com/science/article/pii/S1875389212012072
DOI: 10.1016/j.phpro.2012.04.021
Type: Articles in periodicals and books
Abstract: The neutron-induced fission of U-234 has been studied for neutron energies ranging from 200 keV to 5 MeV. Special focus was put around the prominent vibrational resonance in the sub-barrier region around 800 keV incident neutron energy. The aim was to investigate the fission fragment (FF) characteristics and search for fluctuations in energy and mass distributions. The strong angular anisotropy in the case of U-234(n,f) was verified and correlations with changes in energy and mass distributions were found. The TKE around the resonance increases contrary to earlier literature data. Furthermore, the TKE and mass distribution were found to be dependent on emission angle. At the resonance, the TKE was smallest near the 0° emission of the FF. This effect was consistent and coherent with a change in the mass distribution around the resonance. The mass distribution was observed to be less asymmetric near 0° emission. From a fitting analysis based on the Multi-Modal Random Neck-Rupture (MMRNR) model, we found the yield of the standard-1 mode increasing around the resonance. Because the TKE is increasing at larger angles and the mass distribution becomes more symmetric also at larger angles, we conclude that this behavior is due to an increase of the standard-1 mode at these larger angles. Based on the formalism of MMRNR, such difference in angular distribution may be an indication of a different outer barrier height for the standard-1 and standard-2 modes.
JRC Directorate:Health, Consumers and Reference Materials

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