Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session FB: Mini-Symposium: The Properties of rp-Process Nuclei II |
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Chair: Ingo Wiedenhoever, Florida State University Room: Hilton Kohala 1 |
Friday, October 26, 2018 9:00AM - 9:15AM |
FB.00001: New Evidence for Near-Threshold 3/2+ States in 19Ne and Constraints on the 18F(p,α)15O Reaction Rate Matthew Hall, Daniel W Bardayan, Sunghoon Ahn, Jacob Allen, Travis Ray Baugher, Jeffery C Blackmon, Sean P Burcher, Michael P Carpenter, Kelly A. Chipps, Jolie Antonia Cizewski, Michael T Febbraro, Oscar B Hall, Cheng Lie Jiang, Kate L Jones, Alexandre A Lepailleur, Patrick D O'Malley, Shuya Ota, Steven D. Pain, B. C. Rasco, Andrew Ratkiewicz, Dariusz Seweryniak, Harrison E Sims, Karl Smith, Wanpeng Tan, David G Walter Energy levels above the 18F+p threshold in 19Ne are significant for nova nucleosynthesis and the prospect of γ ray detection from novae because they are resonances in the 18F(p,α)15O reaction. In an effort to better understand the astrophysically important levels in 19Ne, the 19F(3He,t)19Ne reaction was studied. Particle-γ-γ coincidences were measured using GODDESS (Gammasphere ORRUBA: Dual Detectors for Experimental Structure Studies), which allows for nuclear structure studies with high angular coverage and resolution, in addition to good energy resolution. Reaction tritons were detected in the Oak Ridge Rutgers University Barrel Array (ORRUBA), an array of position-sensitive silicon strip detectors, in coincidence with γ rays from the de-excitation of 19Ne. Preliminary results from the experiment will be presented. |
Friday, October 26, 2018 9:15AM - 9:30AM |
FB.00002: Spectroscopic strengths of low-lying levels in 18Ne Patrick O'Malley, Daniel W Bardayan, Jacob Allen, Frederick D Becchetti, Jolie Antonia Cizewski, Michael T Febbraro, Robert Gryzwacz, Matthew Hall, Kate L Jones, Stan V Paulauskas, Karl Smith, Cory R Thornsberry, James J Kolata Much effort has been made to understand the origins of 18F in novae. Due to its relatively long half-life (~2 hours), 18F can survive until the nova envelope is transparent, and therefore can provide a sensitive diagnostic of nova nucleosynthesis. It is likely produced through the beta decay of 18Ne, which is itself produced (primarily) through the 17F(p,γ) reaction. Understanding the direct capture contribution to the 17F(p,γ) reaction is important to accurately model it. As such, the spectroscopic strengths of low-lying states in 18Ne are needed. At the University of Notre Dame a measurement of the 17F(d,n) reaction has been performed using a beam produced by the TwinSol Low energy radioactive beam facility. The neutrons were detected using a combination of Versatile Array of Neutron Detectors (VANDLE) and UoM Deuterated Scintillator Array (UMDSA). Data will be shown and results will be discussed. |
Friday, October 26, 2018 9:30AM - 9:45AM |
FB.00003: Measuring the astrophysical 20Ne(p, γ)21Na rate at DRAGON Jonathan Karpesky, Devin Connolly, Matthew Lovely, Charlie Akers, Gregory Christian, Barry S Davids, Jennifer P Fallis, Uwe Greife, Ulrike Hager, Dave Hutcheon, Alex Rojas, Chris Ruiz Understanding the abundance levels of isotopes produced in oxygen-neon (ONe) novae within our galaxy requires accurate measurements of nuclear reaction rates within their associated reaction network. During these cataclysmic events, the produced radioisotope 22Na is ejected into the interstellar medium and β-decays predominately to the first excited state in 22Ne leading to a characteristic 1.275 MeV γ-ray. To date, there has been no astronomical observation of this characteristic γ-ray that can be a potential probe into the physics occuring within novae. The production of 22Na in classical novae is limited by the 20Ne(p, γ)21Na nuclear reaction that sets the focus of this experiment. Using the DRAGON recoil separator, new measurements of the 20Ne(p, γ)21Na reaction are performed at lower energies closer to astrophysically relevant energy ranges. The aim is to reduce experimental uncertainties in the 20Ne(p, γ)21Na reaction rate in order to more accurately predict the production yield of 22Na in ONe novae and to measure the direct capture to the ground state in order to constrain the astrophysical S-factor. Experimental methods and preliminary results to be discussed. |
Friday, October 26, 2018 9:45AM - 10:00AM |
FB.00004: Remeasuring the resonance strength of the 21Ne(p,γ)22Na reaction at DRAGON Matthew Lovely, Jonathan Karpesky, Devin S Connolly, Charlie Akers, Greg Christian, Barry S Davids, Jennifer Fallis, Uwe Greife, Chris Ruiz, Ulrike Hager, Dave Hutcheon, Alex Rojas Novae are explosive astrophysical events which provide a unique environment for nucleosynthesis. Oxygen-Neon(O-Ne) novae, which are caused by the thermonuclear runaway of accreted material on the surface of a white dwarf in a close binary system, can reach peak temperatures of 0.1-0.4 GK. These novae are particularly important for the production of intermediate mass nuclides through cycles such as the Ne-Na cycle. The 21Ne(p,γ)22Na reaction of the Ne-Na cycle is of great interest in studying these events due to the beta decay and subsequent release of a characteristic gamma ray at 1.275 MeV and the relatively long half-life of 2.6 years. To date, no gammas from the 22Na decay have been detected and this remains a problem in understanding novae nucleosynthesis. The 21Ne(p,γ)22Na reaction was measured at Ecm =258.6 keV in inverse kinematics at the DRAGON recoil separator as a part of the commissioning measurements and yielded a resonance strength over twice the literature value previously measured by Görres et al.. The resonance strength was then remeasured in order to resolve this discrepancy. Preliminary results and analysis of the remeasurement will be discussed. |
Friday, October 26, 2018 10:00AM - 10:15AM |
FB.00005: Constraining the astrophysical 23Mg(p,γ)24Al reaction rate using direct and indirect measurement Eames Alexander Bennett, Gregory Christian, Shuya Ota The 23Mg(p,γ)24Al reaction provides an escape from the Ne-Na cycle in classical novae and is therefore important in understanding nova nucleosynthesis in the A > 20 mass range. Although several resonances may contribute to the overall rate at novae temperatures, the resonance at ∼475 keV is thought to be dominant. The strength of this resonance has been directly measured using a radioactive 23Mg beam impinging on a windowless H2 gas target; however, recent high-precision 24Al mass measurements have called this result into question. Here we make an indirect measurement using the 23Na(d,p)24Na reaction in inverse kinematics to study the mirror state of the ∼475 keV resonance in 24Na. Preliminary cross sections for the relevant resonance will be shown. Additionally, plans for a direct measurement of the 23Mg(p,γ)24Al reaction at the DRAGON facility utilizing their recently upgraded Lanthanum Bromide array will be discussed. |
Friday, October 26, 2018 10:15AM - 10:30AM |
FB.00006: Constraining the 30P(p,γ)31S Reaction Rate with a Measurement of the 32S(p,d)31S* Reaction Sean Burcher, Kelly A. Chipps, Richard O Hughes, Kate L Jones, Sunghoon Ahn, James M. Allmond, Jason T Burke, Henry Clark, Jolie Antonia Cizewski, Nathan M Cooper, Joshua Hooker, Heshani D Jayatissa, Shuya Ota, Steven D. Pain, Craig S Reingold, Antti Saastamoinen, Konrad Schmidt, Anna Simon, Sriteja Upadhyayula The 30P(p,γ)31S reaction rate is the largest source of uncertainty in the abundances of intermediate-mass nuclei produced in classical novae involving ONe white dwarfs. While it is currently not feasible to directly measure the 30P(p,γ)31S reaction, it is possible to use indirect methods, such as the 32S(p,d)31S* reaction, to obtain the relevant information about the important resonant states in 31S. In particular, resonance energies, spin, and proton and γ partial widths are required to calculate the reaction rate. A measurement of the 32S(p,d)31S* reaction has been performed at the Texas A&M Cyclotron Institute using the charged-particle and γ-ray detector array, Hyperion. The goal of the experiment was to populate states above the proton threshold in 31S, which the 30P(p,γ)31S reaction proceeds through, and observe the subsequent proton and γ-ray decays. Preliminary results including proton decay and particle-γ coincidence spectra will be presented. |
Friday, October 26, 2018 10:30AM - 10:45AM |
FB.00007: Benchmarking the (d,p) reaction for obtaining (p,γ) rates for N=Z nuclei Steven D. Pain, ORRUBA Collaboration, GODDESS Collaboration Radiative capture rates via low-lying proton resonances are of astrophysical interest in both stellar and explosive burning scenarios, but are difficult to measure directly due to the small proton widths. The (d,p) reaction can be used to determine energies, Jπ assignments, and spectroscopic factors of the mirror neutron states in the conjugate nucleus. Guided by Shell Model Embedded in the Continuum calculations, (p,γ) rates can be calculated. This technique is especially applicable to capture on self-conjugate (N=Z) nuclei, as the ground state of the "target" nucleus is common to both systems; several such nuclei are of particular astrophysical interest, including 26Al, 30P, 34Cl and 38K. We have benchmarked resonance strengths extracted from 26Al(d,p) against direct 26Al(p,γ) measurements for several resonances, guided by analysis of almost 30 bound states and elastic scattering differential cross sections. The results, and its implications for upcoming measurements on other N=Z nuclei at the ATLAS facility at ANL and the ReA3 facility at the NSCL, will be presented. |
Friday, October 26, 2018 10:45AM - 11:00AM |
FB.00008: Spectroscopic study on \textsuperscript{39}Ca for classical nova endpoint nucleosynthesis Johnson Liang, Alan Chen, Marius Anger, Shawn Bishop, Thomas Faestermann, Cathleen E Fry, Ralf Hertenberger, Athanasios Psaltis, Dominik Seiler, Pranjal Tiwari, Hans-Friedrich Wirth, Christopher Lars Henrik Wrede
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