Event-by-event neutron–photon multiplicity correlations in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e386" altimg="si1.svg"><mml:msup><mml:mrow/><mml:mrow><mml:mn>252</mml:mn></mml:mrow></mml:msup></mml:math>Cf(sf)

Marin, Stefano; Protopopescu, V.; Vogt, R.; Marcath, Matthew J.; Okar, M. Stephan; Hua, Michael Y.; Talou, P.; Schuster, P.; Clarke, Shaun D.; Pozzi, Sara A.

doi:10.1016/j.nima.2020.163907

Cited by 9 publications

(3 citation statements)

References 33 publications

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“…In addition to the neutron and γ-ray multiplicities, it is also important to understand particle energies and angular distributions. Our recent papers [13,14,15] have shown that organic scintillator arrays provide insight into the Email addresses: stmarin@umich.edu (S. Marin), itolstukhin@anl.gov (I. A. Tolstukhin) fission process, revealing several features of the fragments' angular momenta, including their magnitudes, directions, and correlations between them.…”

Section: Introductionmentioning

confidence: 99%

Instrumentation for correlated prompt $n$-$γ$ emission studies in coincidence with fission fragments

Marin¹,

Tolstukhin²,

Oberling³

et al. 2022

Preprint

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Recent theoretical and experimental results have brought renewed interest and focus on the topic of fission fragment angular momentum. Measurements of neutrons and γ rays in coincidence with fission fragments remain the most valuable tool in the exploration of fission physics. To achieve these scientific goals, we have developed a system that combines a state-of-the-art fission fragment detector and n-γ radiation detectors. A new twin Frisch-gridded ionization chamber has been designed and constructed for use with a spontaneous fission source and an array of forty trans-stilbene organic scintillators (FS-3) at Argonne National Laboratory. The new ionization chamber design we present in this work aims at minimizing particle attenuation in the chamber walls, and provides a compact apparatus that can be fit inside existing experimental systems. The ionization chamber is capable of measuring fission fragment masses and kinetic energies, whereas the FS-3 provides neutron and gamma-ray multiplicities and spectra. The details of both detector assembly are presented along with the first experimental results of this setup. Planned eventby-event analysis and future experiments are briefly discussed.

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Section: Introductionmentioning

confidence: 99%

Instrumentation for correlated prompt $n$-$γ$ emission studies in coincidence with fission fragments

Marin¹,

Tolstukhin²,

Oberling³

et al. 2022

Preprint

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“…In this work, we continue our analysis of the event-by-event neutron-γ multiplicity correlations presented in Refs. [18,19]. In Ref.…”

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confidence: 99%

“…In Ref. [18], we determined that neutron and γ-ray emissions are slightly negatively correlated, as a result of energy and angular momentum conservation. The more recent analysis of Ref.…”

mentioning

confidence: 99%

Directional-dependence of the event-by-event neutron-$γ$ multiplicity correlations in $^{252}$Cf(sf)

Marin,

Sansevero,

Okar

et al. 2022

Preprint

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We differentiate the event-by-event n-γ multiplicity data from 252 Cf(sf) with respect to the energies of the emitted particles as well as their relative angles of emission. We determine that neutron emission enhances γ-ray emission around 0.7 and 1.2 MeV, but the only directional alignment was observed for E γ ≤ 0.7 MeV and tended to be parallel and antiparallel to neutrons emitted in the same event. The emission of γ rays at other energies was determined to be nearly isotropic. The presence of the emission and alignment enhancements is explained by positive correlations between neutron emission and quadrupole γ-ray emission along rotational bands in the de-exciting fragments. This observation corroborates the hypothesis of positive correlations between the angular momentum of a fragment and its intrinsic excitation energy. The results of this work are especially relevant in view of the recent theoretical and experimental interest in the generation of angular momentum in fission. Specifically, we have determined an alignment of the fragments angular momenta in a direction perpendicular to the direction of motion. We interpret the lack of n-γ angular correlations for fission fragments near closed shells as a weakening of the alignment process for spherical nuclei. Lastly, we have observed that statistical γ rays are emitted isotropically, indicating tha the average angular momentum removed by this radiation is small. These results, and the analysis tools presented in this work, representing a stepping stone for future analysis of n-γ emission correlations and their connection to angular momentum properties. I. INTRODUCTIONNeutrons and γ rays emitted from fission fragments reveal important features of the nuclear fission process and the state of the fragments immediately following fission. Among several open questions in fission, the n-γ angular correlations are particularly interesting because of their intimate relation to the fission fragment angular momenta. The angular momentum of a fragments plays a pivotal role in the emission of γ rays and the n-γ angular distribution. The characterization of the fragment angular momenta is one of the most important open questions in fission physics.

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