Abstract
The emission of neutrons and γ rays by fission fragments reveal important information about the properties of fragments immediately following scission. The initial fragment properties, correlations between fragments, and emission competition give rise to correlations in neutron-γ emission. Recent theoretical and experimental advances have been proposed to explain the mechanism of angular momentum generation in fission, which would result in observable signature in neutron-γ emission correlations. In this paper, we present a novel analysis method of neutrons and γ rays emitted by fission fragments that allows us to discern structure in the observed correlations. We have analyzed data collected on Cf252(sf) at the Chi-Nu array at the Los Alamos Neutron Science Center. Through our analysis of the energy-differential neutron-γ multiplicity covariance, we have observed enhanced neutron-γ correlations, corresponding to rotational band γ-ray transitions, at γ-ray energies of 0.7 and 1.2 MeV. To shed light on the origin of this structure, we compare the experimental data with the predictions of three model calculations. The origin of the observed correlation structure is understood in terms of a positive spin-energy correlation in the generation of angular momentum in fission.
| Original language | English |
|---|---|
| Article number | 024602 |
| Journal | Physical Review C |
| Volume | 104 |
| Issue number | 2 |
| DOIs | |
| State | Published - Aug 2021 |
Funding
S.M. thanks the experimental group at LANSCE-LANL and M. J. Marcath for sharing the experimental data used in this analysis. This work was in part supported by the Office of Defense Nuclear Nonproliferation Research & Development (DNN R&D), National Nuclear Security Administration, US Department of Energy. This research was funded in-part by the Consortium for Verification Technology under Department of Energy National Nuclear Security Administration Award No. DE-NA0002534. The work of V.A.P. was performed under the auspices of UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The work of P.T., A.E.L., and I.S. is carried out under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory under Contract No. 89233218CNA000001. The work of R.V. was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344. J.R. acknowledges support from the Office of Nuclear Physics in the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.