Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session KG: Nuclear Reactions: Heavy-Ions/Rare Isotope Beams II |
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Chair: Sean Kuvin, LANL Room: Copley & Kenmore |
Wednesday, October 13, 2021 11:30AM - 11:42AM |
KG.00001: Using Bayesian analysis to constrain the momentum-dependence of the nuclear equation of state. Kyle W Brown Nucleons in dense nuclear matter appear to have reduced inertial masses due to momentum-dependent interactions they experience with other nucleons. This reduction of their masses is often referred to as their effective mass, and at saturation density the effective masses are about 70% of their vacuum mass. In asymmetric matter the effective masses of neutrons and protons can be different, leading to an effective-mass splitting. The sign and magnitude of this splitting is poorly constrained at densities away from saturation density. |
Wednesday, October 13, 2021 11:42AM - 11:54AM |
KG.00002: Measurement of the Tm168(n,n’) and Tm168(n,2n) cross section using surrogate reactions Jason T Burke, Barbara Wang, Richard O Hughes, Craig S Reingold, Robert Casperson, Antti Saastamoinen The direct reaction Tm169(a,a’)Tm169 was used as a surrogate reaction for Tm169(n,n’) and Tm169(n,2n). A 55 MeV alpha beam was used to induce reactions on Tm169, C12 and a mylar target. The (a,a’xn) reactions on these targets were measured using the LLNL NeutronSTARS array located at the Texas A&M Cyclotron Institute. Particle singles events were measured for each target over an angle range of approximately 32 to 60 degrees with respect to the beam direction. Neutrons were detected in coincidence with the scattered particles using a 2.2-ton Gd doped liquid scintillator detector that surrounded the main reaction chamber. The surrogate cross sections of the Tm168(n,xn) reactions will be compared to the known Gd155(n,xn) cross sections. Progress on the surrogate Tm168(n,xn) cross sections and the measurement technique will be presented. |
Wednesday, October 13, 2021 11:54AM - 12:06PM |
KG.00003: Neutron-Induced Reaction Cross Section Measurements on Pt Cathleen E Fry, Aaron J Couture, Ingrid Knapova, Kelly Knickerbocker, Shea Mosby, Christopher J Prokop, John L Ullmann For many stable isotopes, neutron capture has been studied in detail. However, the stable platinum isotopes have only been investigated in a few measurements, all of which provide no information below 1 keV, and no resolved resonance information. Photon strength functions in Pt isotopes have exhibited surprising behavior, and neutron capture data across the Pt isotopic chain will allow more detailed study of these effects. To address this at LANSCE, DANCE has been used to measure neutron-capture reaction cross sections on 192,194,195,196,198Pt, all stable isotopes of Pt with abundance >0.1% at the Lujan Center. DANCE is a highly segmented BaF2 detector array with approximately 3.6π solid angle coverage for calorimetric measurements of prompt γ-ray emission following neutron capture. Experimental determination of the capture cross sections and resonance properties on Pt isotopes will reduce uncertainties in existing nuclear data evaluations and improve confidence in simulations using these evaluations. This will provide improved nuclear data to validate models in this mass region. |
Wednesday, October 13, 2021 12:06PM - 12:18PM |
KG.00004: Level scheme of 96Mo from the (d,pγ) reaction measurement with 95Mo beams and GODDESS Heather I Garland, Jolie A Cizewski, Steven D Pain, Andrew Ratkiewicz, Harrison E Sims, Gwenaelle Seymour, Alexandre A Lepailleur The Surrogate Reactions Method (SRM) has validated the (d,pγ) reaction as a surrogate for (n,γ) in normal kinematics. [1] To extend the validity of the SRM to inverse kinematics and prepare for studies with rare isotope beams, the (d,pγ) reaction with 95Mo beams was measured with GODDESS (Gammasphere ORRUBA: Dual Detectors for Experimental Structure Studies) where ORRUBA (Oak Ridge Rutgers University Barrel Array) is an array of position-sensitive silicon strip detectors. A SRM analysis of the 95Mo(d,pγ) reaction requires intricate knowledge of the 96Mo level scheme – which can be extended by this first inverse kinematics measurement of the 95Mo(d,pγ) reaction with GODDESS. Preliminary results for the 96Mo level scheme deduced through analysis of the (d,pγ) reaction will be presented. |
Wednesday, October 13, 2021 12:18PM - 12:30PM |
KG.00005: Abstract Withdrawn
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Wednesday, October 13, 2021 12:30PM - 12:42PM |
KG.00006: Evidence for the asymmetry dependence of the nuclear caloric curve seen in fusion reactions Alan B McIntosh, Kris Hagel, Lauren McIntosh, Sherry J Yennello The nuclear equation of state emerges from the microscopic nucleon-nucleon interaction. The leading uncertainty in the EoS is in regards to the energy due to neutron-excess. We study here in particular one facet of the EoS: the caloric curve. Reactions of 78,86Kr + 12C @ 15, 25, 35 MeV/u were conducted. The mean excitation energy of the compound nucleus is varied via the beam energy, and the mean neutron excess of the compound nucleus is varied by changing the projectile isotope. Light charged particles were measured with good energy and good position resolution with the FAUST (Forward Array Using Silicon Technology). The velocity of heavy residues were measured by time of flight. Temperatures are extracted using both kinetic and population approaches. Mean excitation energies are calculated from the measured residue velocities. The caloric curves thus constructed show a dependence on the neutron excess, with systematically higher temperatures for the more neutron-rich system. |
Wednesday, October 13, 2021 12:42PM - 12:54PM |
KG.00007: Constrain neutron star properties with SpiRIT experiment Chun Tsang, Manyee B Tsang, William G Lynch, Justin B Estee, Jonathan E Barney, Jin-Hee Chang Both Neutron star (NS) and the core of nucleus are made up of nuclear matter. If the bulk properties of nuclear matter are understood, this knowledge can be extrapolated to predict neutron star properties. A particularly important parameter is the density dependence of the symmetry energy of neutron-rich nuclear matter. A way to constrain nuclear symmetry energy is through the measurement of π+/π- ratio in heavy-ion collision. Since pion are only generated in the high density region, it serves as a proxy to probe the amount of high density interactions inside the core. This goal is achieved with the SpiRIT experiment yielding a symmetry energy values of 52+13 MeV at 1.5 times the saturation energy (rho_0). By combining with the symmetry energy values obtained at low density, I will present studies on the neutron star properties applying the experimental symmetry energy functional to the Tolman–Oppenheimer–Volkoff (TOV) equation. |
Wednesday, October 13, 2021 12:54PM - 1:06PM |
KG.00008: Point-cloud machine learning methods for analysis of TPC data Michelle P Kuchera, Yassid Ayyad, Daniel Bazin, Anela Davis, Sidney Knowles, Niya Ma, Wolfgang Mittig, Erika Navarro, Raghu Ramanujan, Mike Remezo, Andrew Rice, Annabel Winters-McCabe Machine learning techniques that operate directly on point cloud data were investigated for events in the Active-Target Time Projection Chamber at the Facility for Rare Isotope Beams at Michigan State University. PointNet++ was used for event classification and track identification in the 22Mg +4He experiment that ran at NSCL1 and on simulated data for the upcoming 10Be + 4He experiment at NSCL. Accuracy as high as $98\%$ was achieved for the event classification method. Point-wise convolutions were also examined for both data cleaning and simulating detector response tasks. Results are compared with other machine learning methods such as Convolutional Neural Networks and traditional analysis methods. |
Wednesday, October 13, 2021 1:06PM - 1:18PM Not Participating |
KG.00009: Surrogate Measurement of the 88Zr(n,γ)89Zr Cross Section Craig S Reingold, Jason T Harke, Barbara S Wang, Jutta E Escher, Robert J Casperson, Nicholas D Scielzo, Richard O Hughes, Jennifer J Ressler, Scott Fisher, Roby A Austin, Shuya Ota, Antti Saastamoinen, Hyo I Park There exist many radiative neutron-capture cross sections of interest to nuclear astrophysics, nonproliferation, and other applications that cannot currently be measured using direct measurement techniques. One alternative is to use the surrogate-reaction method. This method uses a more feasible reaction relative to neutron capture to probe the same compound nucleus, studying the behavior of the system above and below the neutron-separation energy to gain insight into the competition between neutron evaporation and γ-decay. In this work, the surrogate method has been utilized to constrain the 88Zr(n,γ)89Zr cross section. Particle-γcoincidence measurements were conducted on a 90Zr target using the STARLiTeR detector array. Coincidence data from the (p,d) reaction channel have been used to extract γ-decay probabilities that can be used in tandem with a calculated formation probability to constrain the neutron-capture cross section. Progress toward constraining the capture cross section will be presented. |
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