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 $^{[1]}$. Using fission product yields (FPYs) as a sensitive probe, we have performed novel high-precision test 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 $^{[2]}$ and quasimonenergetic photon beams from the High Intensity Gamma-ray Source (HIGS) facility. A comparison of the FPYs from $^{239}$Pu(n,f) at E$_\text{n}$=1.5 and 4.6 MeV with those from $^{240}$Pu(γ,f) at E$_{γ}$=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.
$^{[1]}$ N. Bohr and J. A. Wheeler, “The Mechanism of Nuclear Fission.” Physical Review 56, 426 (1939).
$^{[2]}$ 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).