Structure in the Event-by-Event Energy-Dependent Neutron-Gamma Multiplicity Correlations in ${}^{252}\text{Cf}$(sf)

Abstract

The emission of neutrons and gamma 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-gamma emission. Neutron-gamma correlations are important in nonproliferation applications because the characterization of fissionable samples relies on the identification of signatures in the measured radiation. Furthermore, recent theoretical and experimental advances have proposed to explain the mechanism of angular momentum generation in fission. In this paper, we present a novel analysis method of neutrons and gamma rays emitted by fission fragments that allows us to discern structure in the observed correlations. We have analyzed data collected on \ce{^{252}Cf}(sf) at the Chi-Nu array at the Los Alamos Neutron Science Center. Through our analysis of the energy-differential neutron-gamma multiplicity covariance, we have observed enhanced neutron-gamma correlations, corresponding to rotational band gamma-ray transitions, at gamma-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.

arXiv comment21 pages, 4 figures, 1 table

References in corpus (11)

• Calculation of fission observables through event-by-event simulation
• Fission Fragment Decay Simulations with the CGMF Code
• Generation of fragment angular momentum in fission
• Correlated Prompt Fission Data in Transport Simulations
• Final excitation energy of fission fragments
• Study of angular momentum effects in fission
• Benchmarking Nuclear Fission Theory
• Correlations of neutron multiplicity and gamma multiplicity with fragment mass and total kinetic energy in spontaneous fission of 252Cf
• A New Measurement of the 6Li(n,α)t Cross Section at MeV Energies Using a Fission Chamber and 6Li Scintillators
• High resolution measurement of tagged two-neutron energy and angle correlations in Cf-252(sf)
• Event-by-Event Multiplicity Correlations in ${}^{252}$Cf(sf)

Cited by in corpus (2)

• Directional-dependence of the event-by-event neutron-$\gamma$ multiplicity correlations in ${}^{252}$Cf(sf)
• Instrumentation for correlated prompt $n$-$\gamma$ emission studies in coincidence with fission fragments