Speaker
Description
The Bohr Hypothesis, one of the most fundamental assumptions in nuclear fission theory, states that the decay of a compound nucleus with a given excitation energy, spin and parity is independent of its formation. Using fission product yields (FPYs) as a sensitive probe, we have performed novel high-precision tests of the combined effects of the entrance channel, spin, and parity on the fission process. Two different reactions were used in a self-consistent manner to produce a compound $^{240}Pu$ nucleus with the same excitation energy: neutron-induced fission of $^{239}Pu$ and photon-induced fission of $^{240}Pu$. The FPYs from these two reactions were measured using quasimonoenergetic neutron beams from the Triangle Universities Nuclear Laboratory’s (TUNL’s) FN tandem Van de Graaff accelerator [1] and quasimonenergetic photon beams from the High Intensity Gamma-ray Source (HI$\gamma$S) facility. An updated comparison of the FPYs from $^{239}Pu\left(n,f\right)$ at En=1.5 and 4.6 MeV with those from $^{240}Pu\left(\gamma,f\right)$ at $E_\gamma=8$ and 11.2 MeV will be presented.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.
[1] M.E. Gooden et al., “Energy Dependence of Fission Product Yields from $^{235}$U, $^{238}$U and $^{239}$Pu for Incident Neutron Energies Between 0.5 and 14.8 MeV.” Nuclear Data Sheets 131, 319 (2016).
