Bulletin of the American Physical Society
2019 Fall Meeting of the APS Division of Nuclear Physics
Volume 64, Number 12
Monday–Thursday, October 14–17, 2019; Crystal City, Virginia
Session KG: Nuclear Astrophysics: Classical Novae and X-ray Bursts |
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Chair: Dan Bardayan, University of Notre Dame Room: Salon A |
Wednesday, October 16, 2019 8:30AM - 8:42AM |
KG.00001: Constraining the $^{30}$P(p,$\gamma$)$^{31}$S reaction using $^{30}$P(d,p$\gamma$)$^{31}$P with GODDESS Rajesh Ghimire, Steven Pain, Kate Jones, Andrew Ratkiewicz, Jolie Cizewski, Chad Ummel, Harrison Sims, Gwenaelle Seymour In classical nova nucleosynthesis, the $^{30}$P(p,$\gamma$)$^{31}$S reaction rate critically affects the mass flow into the A=30-40 range, impacting the abundances of isotopes of phosphorus, sulfur and silicon. However, currently available $^{30}$P beam intensities are insufficient to measure the (p,$\gamma$) reaction directly. The rate of this reaction depends on undetermined spectroscopic strengths of low-lying resonances in $^{31}$S, located between 6 and 7 MeV in excitation. However, it is experimentally difficult to measure proton spectroscopic factors on unstable nuclei. We performed a $^{30}$P(d,p$\gamma$)$^{31}$P neutron transfer reaction measurement using the newly commissioned GODDESS (Gretina-ORRUBA: Dual Detectors for Experimental Structure Studies) system with an 8 MeV/u $^{30}$P beam, from RAISOR at ATLAS, in order to provide constraints on the spectroscopic strengths for $^{31}$S levels via mirror symmetry. Details of the experiment and initial data analysis will be presented. [Preview Abstract] |
Wednesday, October 16, 2019 8:42AM - 8:54AM |
KG.00002: GADGET: a Gaseous Detector with Germanium Tagging Christopher Wrede, Moshe Friedman, David PĂ©rez-Loureiro, Tamas Budner, Emanuel Pollacco, Marco Cortesi, Cathleen Fry, Brent Glassman, Madison Harris, Joe Heideman, Molly Janasik, Brian Roeder, Michael Roosa, Antti Saastamoinen, Jordan Stomps, Jason Surbrook, Pranjal Tiwari, John Yurkon Nucleosynthesis and energy generation in classical novae and type I x-ray bursts depend on the thermonuclear rates of radiative proton capture reactions. Many of these rates are dominated by contributions from narrow isolated resonances. Each resonance strength can be constructed from the proton branching ratio and lifetime. A new detection system, the Gaseous Detector with Germanium Tagging (GADGET), has been designed and constructed at the National Superconducting Cyclotron Laboratory (NSCL) to measure proton branching ratios. GADGET consists of a gaseous proportional counter to measure the spectrum of low-energy beta-delayed protons and the Segmented Germanium Array (SeGA) of high-purity germanium detectors to measure beta-delayed gamma rays. GADGET has been commissioned at NSCL using a rare-isotope beam of $^{\mathrm{25}}$Si. [Preview Abstract] |
Wednesday, October 16, 2019 8:54AM - 9:06AM |
KG.00003: Proton Capture on 34S in the Astrophysical Energy Regime Matthew Lovely, Devin Connolly, Jonathan Karpesky, Stephen Gillespie, Patrick O'Malley, Alen Chen, Barry Davids, Annika Lennarz, Alison Laird, Chris Ruiz, Dave Hutcheon, Uwe Greife Novae are explosive astrophysical events which provide a unique environment for nucleosynthesis. Oxygen-Neon(O-Ne) novae caused by the thermonuclear runaway of accreted material on the white dwarf of a close binary system can reach peak temperatures of 0.1-0.4 GK. These novae are particularly important for the production of higher mass nuclides through complex reaction networks. Many of the resonance strengths in these networks have been theoretically calculated and lead to a large degree of uncertainty in the final production of the nova. One reaction of particular importance for these processes is the proton capture on 34S at energies relevant to nova nucleosynthesis. Previously, this reaction has been measured above Ecm=495 keV but here we will discuss the recent direct measurement conducted at DRAGON in inverse kinematics from Ecm=272 keV to 495 keV. [Preview Abstract] |
Wednesday, October 16, 2019 9:06AM - 9:18AM |
KG.00004: Studying the Energy Levels of $^{39}$Ca for the $^{38}$K($p$,$\gamma$)$^{39}$Ca Reaction Rate Matthew Hall, Daniel Bardayan, Travis Baugher, Alex Lepailleur, Steven Pain, Andrew Ratkiewicz It has been established that nuclei up to $A=40$ are produced in nova explosions, but there exist discrepancies between theory and observation regarding their abundances. The $^{38}$K($p$,$\gamma$)$^{39}$Ca reaction rate has been identified as a large source of uncertainty at the endpoint of nova nucleosynthesis and could be key in understanding this discrepancy. To reduce its uncertainty, the $^{40}$Ca($^{3}$He,$\alpha$) $^{39}$Ca reaction was measured at Argonne National Laboratory using GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies) to study the energy levels in $^{39}$Ca. $\gamma$ rays from the decay of excited states in $^{39}$Ca were measured in coincidence with alpha particles from the reaction. In total, 23 new $\gamma$-ray transitions were found in $^{39}$Ca, including new $\gamma$-decay information for three $J^\pi=5/2^+$ excited states that are important in the calculation of the reaction rate. These decay results, as well as how these results affect the reaction rate, will be presented. [Preview Abstract] |
Wednesday, October 16, 2019 9:18AM - 9:30AM |
KG.00005: Toward Understanding the $^{15}$O($\alpha,\gamma$)$^{19}$Ne Reaction Rate: $\alpha$-Transfer Reactions on $^{15}$N Catherine Deibel, Gemma Wilson, Erin Good, Amber Lauer, Alan Chen, Birger Back, Calem Hoffman, Ben Kay, Richard Pardo, Daniel Santiago-Gonzalez, Tsz Leung Tang, Alan Wuosmaa The $^{15}$O($\alpha,\gamma$)$^{19}$Ne reaction is well known to be an important breakout from the hot CNO cycle into the thermonuclear runaway that drives Type I X-Ray Bursts. This reaction rate is dominated by resonant $\alpha$ capture into a state at $E_x=4.033$ MeV in $^{19}$Ne. While there have been a variety of experimental studies aimed at determining this reaction rate, the $\alpha$ width of this resonance remains the dominant uncertainty. Currently, $^{15}$O beams of sufficient intensity to study this reaction directly are not available and indirect techniques must be used in order to study the 4.033-MeV state in $^{19}$Ne. Measurements of the ($^6$Li,$d$) and ($^7$Li,$t$) $\alpha$-particle transfer reactions on beams of $^{15}$N have been performed at the Argonne Tandem LINAC Accelerator System facility at Argonne National Laboratory using the HELIcal Orbit Spectrometer (HELIOS) in order to study the mirror to the 4.033-MeV state, located at 3.908 MeV in $^{19}$F. Preliminary results will be shown and implications for the $^{15}$O($\alpha,\gamma$)$^{19}$Ne reaction rate discussed. [Preview Abstract] |
Wednesday, October 16, 2019 9:30AM - 9:42AM |
KG.00006: Study of proton-resonances in the $^{19}$Ne(d,n)$^{20}$Na reaction using RESONEUT detector system Meenu Thakur, L.T. Baby, I. Wiedenh\"{o}ver$^1$, E Temanson, K Hanselman, G McCann, J Blackmon Studies of nucleosynthesis in stellar explosions reveal that obtaining relevant information on the lowest lying resonances is crucial step to determine reaction rates in the astrophysical rp-process. In previous experiments at the RESOLUT facility, (d,n) reaction in inverse kinematics has been used to populate these resonances of astrophysical interest [1]. For such measurements, a compact neutron detector array RESONEUT has been developed which can efficiently detect low energy neutrons from (d,n) reaction [1]. In the present paper, results from our recently performed radioactive-beam experiment studying $^{19}$Ne(d,n)$^{20}$Na reaction using RESONEUT will be presented. This reaction is comparable to direct proton capture $^{19}$Ne(p,$\gamma$)$^{20}$Na, which is of astrophysical significance. Results from previous studies indicate the contradictions in spin and parity assignment of the first proton resonance in $^{20}$Na. So, we study the population of the lowest lying proton resonances in $^{20}$Na using neutron time of flight spectroscopy in an attempt to resolve these contradictions and determine accurate information of reaction rate. [1]S. Kuvin et al, PRC 96, 045812 (2017) [Preview Abstract] |
Wednesday, October 16, 2019 9:42AM - 9:54AM |
KG.00007: Measurement of the $^{18}$Ne($\alpha$,p)$^{21}$Na reaction with ANASEN between 2 and 4 MeV in the center of mass Maria Anastasiou, Ingo Wiedenhoever, Lagy T Baby, Nabin Rijal, John J Parker IV, Jeffery C Blackmon, Catherine M Deibel, Ashley A Hood, Jon C Lighthall, Kevin T Macon, Daniel Santiago-Gonzalez, Yevgen Koshchiy, Grigory V Rogachev The $^{18}$Ne($\alpha$,p)$^{21}$Na reaction is one of the reactions providing a pathway for breakout from the hot CNO cycles to the rp-process in Type I X-ray bursts. The actual conditions under which the breakout occurs depend critically on the thermonuclear reaction rate. This rate has not yet been sufficiently determined under X-ray burst conditions. We study the direct $^{18}$Ne($\alpha$,p)$^{21}$Na reaction with the Array for Nuclear Astrophysics and Structure with Exotic Nuclei (ANASEN), using a helium gas target and an $^{18}$Ne radioactive beam from RESOLUT facility at the FSU accelerator lab. The results are consistent with the time-reverse measurements [1] and provide a total cross section between 2 and 4 MeV in the center of mass. [1] Salter et al., \textit{Measurement of the $^{18}\text{Ne}(\alpha,\text{p}_0)^{21}\text{Na}$ Reaction Cross Section in the Burning Energy Region for X-Ray Bursts}, Phys.Rev.Lett. 108 (242701), 2012 [Preview Abstract] |
Wednesday, October 16, 2019 9:54AM - 10:06AM |
KG.00008: Cross section measurements and R-Matrix analyses of the $^{24}$Mg($\alpha,p\gamma$)$^{27}$Al and $^{27}$Al($p,\alpha\gamma$)$^{24}$Mg reactions with HAGRiD S. Aguilar, T. Ahn, A. Boeltzig, C. R. Brune, R. J. DeBoer, K. L. Jones, K. T. Macon Alpha-induced reactions have been identified as playing an important role in various astrophysical phenomena. Sensitivity studies have indicated the $^{24}$Mg($\alpha,p$)$^{27}$Al reaction is important in understanding the energy generation in Type Ia X-ray bursts; therefore precise cross section measurements are needed. The $^{24}$Mg($\alpha,p$)$^{27}$Al cross section has not been measured directly, and no data is available for the inelastic channels which may contribute to its reaction rate. Present $^{24}$Mg($\alpha,p$)$^{27}$Al reaction rates rely exclusively on the inverse $^{27}$Al$(p,\alpha)^{24}$Mg cross section. The direct $(\alpha,p)$ and inverse $(p,\alpha)$ reactions have been performed at the University of Notre Dame's Nuclear Science Laboratory using the 5U Sta. ANA accelerator to produce a high-intensity beam with high energy resolution, providing new precision cross section measurements. The LaBr$_3$ Hybrid Array of Gamma Ray Detectors (HAGRiD) was utilized to span seven unique angles to detect the secondary $\gamma$ rays in the inelastic channels. R-Matrix analyses of the cross sections using secondary $\gamma$ rays and the inelastic channels effect on reaction rates will be presented. [Preview Abstract] |
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