Bulletin of the American Physical Society
Fall 2022 Meeting of the APS Division of Nuclear Physics
Volume 67, Number 17
Thursday–Sunday, October 27–30, 2022; Time Zone: Central Daylight Time, USA; New Orleans, Louisiana
Session PE: Nuclear Astrophysics VIII |
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Chair: Adrian Valverde, Argonne National Laboratory/University of Manitoba Room: Hyatt Regency Hotel Celestin C |
Sunday, October 30, 2022 10:30AM - 10:42AM |
PE.00001: Study of 18Ne for HCNO breakout Ashton B Morelock, Sergio J Almaraz-Calderon, Eilens Lopez Saavedra, Rajat Aggarwal Nuclear properties of the proton-rich exotic nuclei 18Ne are needed to reduce uncertainties in the reaction rate calculations for the nuclear reaction sequence 14O(α,p)17F(p,γ)18Ne, which leads to breakout from the HCNO cycle. The rates of these reactions are critical in understanding nucleosynthesis in stellar environments such as Classical Novae and Type I X-ray bursts. The level structure of 18Ne has been studied at Florida State University through the 16O(3He,n)18Ne reaction via a neutron/charged-particle coincidence measurement using the CATRiNA neutron detector array, which is composed of 32 deuterated benzene liquid scintillators, and a compact silicon detector array. Coincidences between neutrons and charged particles were used to directly obtain branching ratios above the particle decay threshold in 18Ne. Preliminary results from this experiment will be presented. |
Sunday, October 30, 2022 10:42AM - 10:54AM |
PE.00002: Measurement of 19Ne Excited States Relevant to the 18F(p,α)15O Reaction in Classical Novae Khang H Pham, Sudarsan Balakrishnan, Kevin T Macon, Jeffery C Blackmon, Catherine M Deibel, Akhil Bhardwaj, Will Braverman, Sergio Lopez-Caceres, Keilah S Davis, David He, Molly McLain, Gordon W McCann, Lagy T Baby, Ingo Wiedenhoever, Samuel Ajayi, Caleb Benetti, Chris Esparza, Kenneth G Hanselman, Ashton B Morelock, Eilens Lopez Saavedra, Vignesh Sitaraman, Eli Temanson, Catur Wibisono The most prominent gamma-ray line emission in classical novae (511 keV) is created by the annihilation of 18F decay positrons. Thus, accurate abundance calculations of 18F are needed to model explosive nucleosynthesis to compare with observations and study the underlying stars in these stellar environments. Currently, the main uncertainties in these calculations involve the main destruction pathway of 18F: the 18F(p,α)15O reaction. The reaction rate of this destruction pathway remains uncertain due to proton branching ratios of higher lying states in the compound nucleus 19Ne, and Jπ values of the sub- and near-threshold states in 19Ne. We performed a 19F(3He,t)19Ne transfer reaction using the Super Enge Split-Pole Spectrograph (SE-SPS) at the Fox Accelerator Laboratory at Florida State University in order to observe these states. Proton and alpha decays were collected by the Silicon Array for Branching Ratio Experiments (SABRE) in coincidence with the triton reaction products detected at the focal plane. I will present a preliminary data analysis of the collected coincidence data. |
Sunday, October 30, 2022 10:54AM - 11:06AM |
PE.00003: Gamma-Particle Coincidence Studies of 93Sr(d,p)94Sr via the Surrogate Reaction Method Andrea L Richard, Richard O Hughes, Daniel Yates, Gregory Hackman, Reiner Kruecken, Cameron Angus, Daryl Bishop, Roger Caballero-Folch, Laetitia Canete, Robin Coleman, Barry S Davids, Sophia Devinyak, Iris Dillmann, Adam Garnsworthy, Shaun Georges, Matt D Gott, Beau Greaves, Christopher Griffin, Heinz Asch, Jack Henderson, Kevan Hudson, D Hymers, Vasil Karayonchev, Eva M Kasanda, Guy Leckenby, Peter Machule, Matthew S Martin, Connor Natzke, Kihong Pak, Andrew Ratkiewicz, Daniel M Rhodes, Yukiya Saito, Nicholas D Scielzo, Bryerton Shaw, James Smallcombe, Carl E Svensson, Diego Torres, Rashmi Umashankar, Sriteja Upadhyayula, Paul Virally, Jonathan Williams, Matthew Williams Neutron-capture cross sections play a vital role in our understanding of heavy element nucleosynthesis, particularly in astrophysical processes such as the i-process (intermediate) and r-process (rapid). Element formation occurs in these neutron-rich environments and involves short-lived isotopes for which capture cross sections cannot be measured via direct techniques. Reactions rates in these regions instead rely on theoretical calculations that can have uncertainties up to a few orders of magnitude. Previous measurements of the β-decay of 94Rb compared the neutron-to gamma-ray-branching ratio of state decays above the neutron separation energy in 94Sr and found an enhancement in the γ-ray branch which would in turn lead to an unexpectedly large 93Sr(n,γ) cross section. Such an enhancement could have a strong impact on our understanding of nucleosynthesis processes for nuclei in this region. In order to investigate this potential enhancement of the 93Sr(n,γ) cross section, an experiment was performed at TRIUMF using an 8 MeV/u 93Sr beam impinging on a CD2 target. The (d,pγ) coincidence data were obtained using the SHARC and TIGRESS arrays. Experimental details from the measurement of 93Sr(d,p)94Sr will be presented along with preliminary gamma-particle coincidence analysis using the Surrogate Reaction Method. |
Sunday, October 30, 2022 11:06AM - 11:18AM |
PE.00004: Investigating 23Na(p,γ)24Mg sodium destruction reaction in Globular Clusters using 23Na(3He,d) spectroscopy Kaixin Song, Caleb A Marshall, Kiana Setoodehnia, Federico E Portillo Chaves, Richard Longland Current studies had a hard time explaining the Na-O anticorrelation in globular cluster stars. The reaction rates of a sodium destruction reaction 23Na(p,γ)24Mg play an important role while suffering from large uncertainties in hydrogen burning temperatures. For better understandings of such reaction, we performed a 23Na(3He,d) experiment in angular range of 5°≤θlab≤21° at E(3He)=21MeV using the Enge Split-pole Spectrograph at Triangle Universities Nuclear Laboratory. Energy states below the 23Na + p threshold in 24Mg were examined. For those states, spectroscopic factors were extracted with rigorous uncertainties using Bayesian MCMC and DWBA method, R-matrix analysis were performed, and direct capture cross sections and reaction rates were calculated. Their impacts on globular cluster nucleosynthesis were further discussed. |
Sunday, October 30, 2022 11:18AM - 11:30AM |
PE.00005: First experimentally-determined 93,94,95Sr(n,γ)94,95,96Sr cross section via the β-Oslo Method Adriana Sweet, Darren L Bleuel, Nicolas D Scielzo, Hannah C Berg, Lee A Bernstein, Aaron Chester, Jason A Clark, Dennis Mucher, Bethany L Goldblum, Magne S Guttormsen, Caley Harris, Stephanie M Lyons, Erin C Good, Adam Hartley, Jordan Owens-Fryar, Mejdi J Mogannam, Timilehin H Ogunbeku, Andrea L Richard, Eleanor Ronning, Daniel Santiago-Gonzalez, Guy Savard, Mallory K Smith, Artemis Spyrou, Artemis Tsantiri, Jasmina Vujic, Mathis Wiedeking, Ann-Cecilie Larsen, Sean Liddick Our understanding of nuetron-induced reactions on nuclei far from stability has far reaching implications for cosmogenic nucleosynthesis and fundamental nuclear phyics. Direct measurement of the radiative-capture cross section is experimentally inaccessible for these short-lived nuclei; however, indirect methods such as the β-Oslo Method enable the experimentally constraint of key nuclear properties that are inputs for reaction-theory calculations. |
Sunday, October 30, 2022 11:30AM - 11:42AM |
PE.00006: Nucleosynthesis s-Process Calculations Including the Astromer 85Kr Jaad Tannous, Bradley S Meyer, Gordon W Misch, Aaron J Couture, Christopher L Fryer, Matthew R Mumpower, Francis X Timmes The 85Kr nucleus is an astrophysical isomer (an "astromer") since its excited states can be out of equilibrium with its ground state in astrophysical environments. We have computed the nuclear properties of 85Kr as two separate ensembles of states: one tied to the ground state and one to the excited state. We have computed the rate of transitions between these two ensembles, which is the internal equilibration rate for 85Kr, and the transition rates between other species and these two ensembles, such as neutron capture into the ensembles from 84Kr and neutron capture out of each ensemble to 86Kr. We have included these rates in a nuclear reaction network and computed nucleosynthetic yields from a set of parameterized s-process trajectories. We delineate four regimes of s-process branching at 85Kr depending on the competition among neutron-capture, beta-decay, and isomerization rates and show how s-process ows vary as the system evolves through these dierent regimes. We also confirm our treatment of isomerization with a full equilibration model for 85Kr and have developed open-source codes that allow users to treat other astromers with our methods. |
Sunday, October 30, 2022 11:42AM - 11:54AM |
PE.00007: Total Cross-Section Measurement of 14O(α,p)17F with an Active Target Ionization Chamber William von Seeger, Dan W Bardayan, Drew Blankstein, Patrick O'Malley, Chevelle Boomershine, Scott R Carmichael, Jacob Allen In certain stellar environments such as Type I X-ray Bursts, proton-capture rates exceed β-decay rates which induce burning processes like the hot-CNO cycle, which ultimately may transition to the rp process. The 14O(α,p)17F reaction is thought to be a trigger reaction that may induce this transition. Understanding this reaction is thus important to understanding how the rp-process proceeds in X-ray bursts. The Active Target High Efficiency detector for Nuclear Astrophysics (ATHENA) was built and commissioned at the Notre Dame Nuclear Science Lab for the purposes of measuring astrophysically important reactions with low-intensity radioactive beams. ATHENA will be used to measure the total cross section of the 14O(α,p)17F reaction with a radioactive 14O beam produced by the new TriSol facility at Notre Dame. Preliminary results, plans, and comparisons to simulations will be discussed. |
Sunday, October 30, 2022 11:54AM - 12:06PM |
PE.00008: Determining the 95Zr(n, γ) and 93Zr(n, γ) cross sections via 96Zr(p, p’) and 94Zr(p, p’) surrogate reactions Barbara S Wang, Craig S Reingold, Jason T Harke, Richard O Hughes, Jutta E Escher, Sean P Burcher, Emanuel V Chimanski, Jessica Koros, Brenden R Longfellow, Wei Jia Ong, Michael R Savina, Danielle Z Shulaker, Aaron S Tamashiro, Reto Trappitsch, Peter K Weber, Brett H Isselhardt The surrogate-reaction method was used to obtain the (n, γ) cross section for the short-lived s-process branching point 95Zr, which constrains crucial parameters in stellar-nucleosynthesis models. Inelastic proton scattering from the stable isotope 96Zr served as the surrogate. The measurement was carried out at the Texas A&M University K150 Cyclotron. An enriched 96Zr foil was bombarded with 21-MeV protons. Scattered protons and coincident γ rays were measured with the LLNL Hyperion array, which consists of three segmented annular silicon detectors in a dE-E1-E2 configuration surrounded by an array of BGO Compton-suppressed HPGe Clover detectors. A benchmark was also performed using 94Zr(p, p’) to determine the 93Zr(n, γ) cross section, which has been previously measured via direct methods. Results of the experiment will be discussed. |
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