Bulletin of the American Physical Society
6th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Sunday–Friday, November 26–December 1 2023; Hawaii, the Big Island
Session 3WDA: Recent Developments in Fission IInvited Workshop
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Chair: Ramona Vogt, LLNL/UC Davis Room: Hilton Waikoloa Village Kings 2 |
Monday, November 27, 2023 9:00AM - 9:30AM |
3WDA.00001: Angular momentum generation before and after scission Invited Speaker: Jorgen Randrup During its evolution towards scission, the fission complex acquires several tens of MeV of internal excitation in the form of quasi particles which each carries some angular momentum. As scission is approached, the geometric restrictions favor population of orbitals having angular momentum perpendicular to the fission axis. The observed saw-tooth patterns of the mass dependence of the neutron multiplicity and the angular momentum emerge if the perpendicular angular momenta have thermal distributions, provided that proper account is taken of shell and pairing effects in the level densities of the distorted fragments at scission. After scission, the torque exerted by the Coulomb force on the deformed fragments may amplify their angular momenta by 1-2 units. |
Monday, November 27, 2023 9:30AM - 10:00AM |
3WDA.00002: Measuring spin-energy correlations in fission with Gammasphere Invited Speaker: Nathan P Giha We analyze an experiment performed at Argonne National Laboratory, with the intention of expanding upon a recent experimental analysis [J. Wilson et al., Nature 590, 566 (2021)] that confirmed the existence of the spin sawtooth in nuclear fission. We combined a twin Frisch-gridded ionization chamber with Gammasphere, a world-class gamma-ray spectrometer which was designed to measure high-multiplicity gamma-ray events. The chamber, loaded with a 252Cf(sf) source, provides a fission trigger, the total kinetic energy (TKE) of the fragments, and the approximate fragment masses. Gammasphere provides the total gamma-ray yield, fragment identification through the tagging of decay gamma rays, and the feeding of rotational bands in the fragments. We will determine how the spin sawtooth varies with the fragments’ TKE by correlating the fragment properties with the distribution of discrete levels that are fed. This approach allows us to explore spin-energy correlations in fission in a nearly model-independent way. |
Monday, November 27, 2023 10:00AM - 10:30AM |
3WDA.00003: Effect of neutron evaporations in fission process with dynamical model and mass distribution of fission fragments Invited Speaker: Yoshihiro Aritomo Through joint research by the Japan Atomic Energy Agency (JAEA)[1,2] and Kindai University, it has revealed that the yield distribution of fission products (fission fragments) changes significantly depending on the neutrons emitted from the compound nucleus. This multi-chance fission (MCF) effect is particularly important to treat high energy fissions [1,3]. In this work, we have introduced the neutron evaporation during fission process in the Langevin model [4] and aimed to describe the entire reaction process in a unified manner. Fission fragment mass distribution of 234−240U, 236−242Np, and 238−244Pu were calculated in the initial excitation energy range of the excitation energy E∗=15-55 MeV. The results show that the double-peak structure is maintained even at the highest excitation energies and successfully reproduced the experimental data taken at the JAEA tandem facility. |
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