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 FD: Nuclear Astrophysics III |
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Chair: Steven Pain, ORNL Room: The Loft |
Tuesday, October 12, 2021 2:00PM - 2:12PM |
FD.00001: High precision mass measurement of 24Si and a final determination of the rp-process at the A=22 waiting point Daniel J Puentes, Zachary P Meisel, Georg Bollen, Alec S Hamaker, Christoph Langer, Erich Leistenschneider, Catherine R Nicoloff, Wei Jia Ong, Matthew Redshaw, Ryan J Ringle, Chandana S Sumithrarachchi, Jason Surbrook, Adrian A Valverde, Isaac T Yandow Type I X-ray bursts occur at astrophysical sites where a neutron star accretes H/He-rich matter from a companion star, leading to nuclear burning on the neutron star surface. The only observable is the X-ray burst light curve, which is used as a unique diagnostic of the outer layers of accreting neutron stars such the accretion rate and fuel composition. In addition to the astrophysical conditions, the main determinant of the shape of the light curve is the nuclear physics involved. Variations within the uncertainty of the 23Al(p,γ)24Si reaction rate lead to significant shifts in simulated X-ray light curves, where the ground state mass of 24Si is currently the dominant source of the reaction rate uncertainty (19 keV). A beam of 24Si was produced at the National Superconducting Cyclotron Laboratory and delivered to the LEBIT facility, where Penning trap mass spectrometry was used to improve the mass uncertainty by a factor of 5 (3.7 keV). The impact of this new mass value on the reaction rate and the onset of the (α,p)-process at the 22Mg waiting point will be presented, settling the rp-process at the A=22 mass region. |
Tuesday, October 12, 2021 2:12PM - 2:24PM |
FD.00002: Study of low-lying resonances in 26Si relevant for understanding the nucleosynthesis of Galactic 26Al Jesus F Perello, Sergio J Almaraz-Calderon, Benjamin W Asher, Lagy T Baby, Ingo L Wiedenhoever, Vandana Tripathi, Eilens Lopez Saavedra, Gordon W McCann, Sudarsan Balakrishnan, Caleb B Benetti, Ashton B Morelock The 25Al (p,γ) 26Si proton-capture reaction is critical in understanding the nucleosynthesis of the radioactive isotope 26Al throughout the Galaxy. This reaction plays a key role re-directing the flux of nuclear material away from the ground state (26Alg), in favor of its short-lived isomeric state (26Alm), which bypasses the gamma-ray emission but is observed in, for example, isotopic abundances of 26Mg in meteorites. Uncertainties in the 25Al(p,γ)26Si reaction are dominated by the nuclear properties of low-lying proton-unbound states in 26Si. |
Tuesday, October 12, 2021 2:24PM - 2:36PM |
FD.00003: Measurement of low-lying proton resonances in 26Si using the 25Al(d,n)26Si proton transfer reaction. Eli S Temanson, Kenneth G Hanselman, Sean A Kuvin, Jane Case, Ingo Wiedenhover, Gordon W McCann, Juan C Esparza, Vignesh Sitaraman, Lagy T Baby The synthesis of galactic 26Al is an interesting subject that spans from nuclear astrophysics to observational astronomy. This isotope is observed through γ-ray astronomy and is a probe into the ongoing nucleosynthesis in the galaxy as well as the frequency of Core-Collapse Supernovae. One of the reactions of interest for the 26Al yield is 25Al(p,γ)26Si, which bypasses the population of the 26Al ground state. An experiment using the proton transfer reaction 25Al(d,n)26Si was performed with the RESOLUT radioactive beam facility at Florida State University to study proton resonances just above the separation energy. As a result, the proton resonance spectrum and cross sections were obtained with better precision than in previous measurements. Further results and astrophysical implications will be discussed. |
Tuesday, October 12, 2021 2:36PM - 2:48PM |
FD.00004: Active Target Measurement of the 25,26Mg(α,n)28,29Si Total Cross Section Drew Blankstein, Jacob Allen, Thomas L Bailey, Chevelle Boomershine, Daniel P Burdette, Dan W Bardayan, Lauren K Callahan, Scott R Carmichael, Adam M Clark, Alexander C Dombos, Orlando J Olivas-Gomez, Sydney Coil, Samuel L Henderson, Kevin Lee, Luis A Morales, Austin D Nelson, Patrick D O'Malley, Graham L O'Donnell, John Wilkinson
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Tuesday, October 12, 2021 2:48PM - 3:00PM |
FD.00005: Commissioning of HECTOR at CASPAR: 27Al(p, γ)28Si resonance strength measurements 4,850 feet underground Orlando J Olivas-Gomez, Anna Simon, Daniel Robertson, Alexander C Dombos, Frank Streider, Thomas Kadlecek, Mark Hanhardt, Rebeka Kelmar, Manoel Couder, Joachim Goerres, Edward J Stech, Michael C F Wiescher The High EffiCiency TOtal absorption spectrometeR (HECTOR) is a 4π γ-summing detector designed to measure radiative-capture cross sections. Here, we present the commissioning of HECTOR at the Compact Accelerator System for Performing Astrophysical Research (CASPAR) laboratory, which is located at the Sandford Underground Research Facility 4,850 feet underground. With the underground environment drastically improving the signal-to-noise ratio of the detector, it is estimated HECTOR will be able push cross-section measurements down to the order of picobarns. Details of the experimental setup will be discussed along with the analysis of several resonance strengths measured for the 27Al(p,γ)28Si reaction between the lab energies 0.2-1 MeV. The measurements are in excellent agreement with those found in the literature. |
Tuesday, October 12, 2021 3:00PM - 3:12PM |
FD.00006: Measurement of near-threshold proton branching ratios in $^{31}$S using $^{28}$Si($^6$Li,t)$^{31}$S(p)$^{30}$P Sudarsan Balakrishnan, Kevin T Macon, Jeff C Blackmon, Catherine M Deibel, Keilah S Davis, William D Braverman, Erin C Good, David He, Sergio Lopez, Rachel Malecek, Khang H Pham, Zachary M Purcell, Gordon W McCann, Kenneth G Hanselman, Lagy T Baby, Ingo L Wiedenhoever, Samuel O Ajayi, Benjamin W Asher, Caleb Bennetti, Alex C Conley, Juan C Esparza, Bryan Kelly, Ashton B Morelock, Jesus F Perello, Gary C Ragsdale, Eilens L Saavedra, Eli S Temanson, Catur Wibisono The $^{30}$P(p,$\gamma$) reaction is a key step in the nucleosynthesis of elements up to A=40 in models of ONe nova explosions. Prior studies involving particle and/or gamma-ray detection have constrained branching ratios and resonance strengths of a few states in $^{31}$S close to the proton threshold. However, similar information is lacking for a few other states with center-of-mass energy less than 600keV, which is important to determine the reaction rate. In this study, we used the reaction $^{28}$Si($^6$Li,t) to probe a few resonances in this region using the Super-Enge Split-Pole Spectrograph (SE-SPS) at the FSU . Proton decays from $^{31}$S states were detected in coincidence with tritons using the Silicon Array For Branching Ratio Experiments(SABRE). The experimental setup, preliminary results, and astrophysical implications will be discussed. |
Tuesday, October 12, 2021 3:12PM - 3:24PM |
FD.00007: Constraining the 30P(p,γ)31S reaction rate via 31Cl β-delayed proton decay and its effect on ONe nova nucleosynthesis Tamas A Budner, Moshe Friedman, Christopher L Wrede, B. A Brown, Jordi Jose, David Perez-Loureiro, Lijie Sun, Jason Surbrook, Yassid Ayyad, Dan W Bardayan, Kyungyuk Chae, Alan Chen, Kelly A Chipps, Marco Cortesi, Brent E Glassman, Matthew Hall, Molly A Janasik, Johnson Liang, Patrick D O'Malley, Emanuel Pollacco, Athanasios * Psaltis, Jordan Stomps, Tyler Wheeler The 30P(p,γ)31S reaction rate plays a crucial role in understanding the nucleosynthesis of oxygen-neon (ONe) novae. This thermonuclear rate influences the isotopic and chemical abundances of nova ejecta, and constraing this reaction rate could help identify candidate presolar nova grains as well as provide more accurate calibrations for nova thermometers. The reaction proceeds primarily via proton capture into narrow, isolated resonance states lying just above the proton-separation energy in 31S. By determining the strength of a recently observed low-energy, Jπ = 3/2+ resonance, we can substantially reduce the nuclear uncertainties associated with modeling explosive nucleosynthesis in novae. Here we report the results of a 31Cl β-delayed proton decay experiment in which we meausred the very weak proton decay branch of this potentially dominant resonance. This represents the weakest β+-delayed particle emission ever measured for resonances below 400 keV. Using our experimentally determined proton branching ratio as well as available information in literature, we calculated the new total thermonuclear rate for 30P(p,γ)31S and interpret its astrophysical impact with fully hydrodynamic 1D nova simulations. |
Tuesday, October 12, 2021 3:24PM - 3:36PM |
FD.00008: 30P(p,γ)31S reaction rate in novae: lifetimes of 31S states Lijie Sun, Cathleen E Fry, Martin Alcorta, Soumendu S Bhattacharjee, Michael D Bowry, Tamas A Budner, Roger Caballero-Folch, Barry S Davids, Nicholas Esker, Lee Evitts, Moshe Friedman, Adam Garnsworthy, Brent E Glassman, Gregory Hackman, Jack Henderson, Oliver Kirsebom, Alexander Kurkjian, Peter Machule, James Measures, Mohamad Moukaddam, Joochun Park, Chris Pearson, David Perez-Loureiro, Chris Ruiz, Panu Ruotsalainen, James Smallcombe, Jenna Smith, Daniel Southall, Jason Surbrook, Matthew Williams, Christopher L Wrede In classical novae, the 30P(p,γ)31S reaction acts as a nucleosynthesis bottleneck in the flow of material to heavier masses. The thermonuclear rate of the 30P(p,γ)31S reaction is dominated by proton capture into narrow resonances just above the proton-emission threshold in 31S. To constrain the resonance strengths, we carried out lifetime measurements of the 31S resonances using the Doppler Shift Attenuation Method. The experiment was performed using the Doppler Shift Lifetimes (DSL) facility at the TRIUMF-ISAC-II facility. The 31S states were populated by the 3He(32S,α)31S reaction. The deexcitation γ rays were detected by Clover detectors in coincidence with the α particles detected by a Si telescope. We applied a Bayesian parameter estimation method and obtained the lifetimes for the two lowest 31S excited states. The upper limits of the lifetimes for five higher-lying states were obtained for the first time. The γ rays originating from a key 3/2+ resonance were observed but with limited statistics. To further improve the sensitivity, an upgrade of the DSL facility is currently underway. |
Tuesday, October 12, 2021 3:36PM - 3:48PM |
FD.00009: Constraining the 30P(p,γ)31S reaction using 30P(d,pγ)31P with GODDESS Rajesh Ghimire, Kate L Jones, Steven D Pain, Andrew Ratkiewicz, Jolie A Cizewski, Harrison E Sims, Joshua Hooker, Gwenaelle Seymour, Gemma L Wilson, Chad C Ummel In classical nova nucleosynthesis, the 30P(p,γ)31S reaction rate critically affects the mass flow into the A=30-40 range, impacting the abundances of isotopes of phosphorus, sulfur, and silicon. Direct measurement of the (p,γ) reaction is not currently possible due to insufficient beam intensities. The rate of this reaction depends on undetermined spectroscopic strengths of low-lying resonances in 31S, located between 6 and 7 MeV in excitation energy. Due to experimental challenges to measure the proton spectroscopic factors on unstable nuclei, we performed a 30P(d,pγ)31P neutron transfer reaction measurement using the newly commissioned GODDESS (GRETINA-ORRUBA: Dual Detectors for Experimental Structure Studies) detection system—with an 8 MeV/u 30P beam, from RAISOR at ATLAS, in order to provide constraints on the spectroscopic strengths for 31S levels via mirror symmetry. Details of the experiment and progress in data analysis, including excitation energy spectrums, proton-gamma matrices, and angular distributions, will be presented. |
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