Bulletin of the American Physical Society
2017 Fall Meeting of the APS Division of Nuclear Physics
Volume 62, Number 11
Wednesday–Saturday, October 25–28, 2017; Pittsburgh, Pennsylvania
Session DC: Nuclear Astrophysics II |
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Chair: Patrick O'Malley, Notre Dame Room: Salon 3 |
Thursday, October 26, 2017 10:30AM - 10:42AM |
DC.00001: Constraining the astrophysical $^{23}$Mg(p,$\gamma$)$^{24}$Al reaction rate using the $^{23}$Na(d,p)$^{24}$Na reaction E. A. Bennett, W. N. Catford, G. Christian, S. Dede, S. Hallam, G. Lotay, S. Ota, A. Saastamoinen, R. Wilkinson The $^{23}$Mg(p,$\gamma$)$^{24}$Al 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 $\sim$475 keV is thought to be dominant. The strength of this resonance has been directly measured using a radioactive $^{23}$Mg beam impinging on a windowless H$_2$ gas target; however, recent high-precision $^{24}$Al mass measurements have called this result into question. Here we make an indirect measurement using the $^{23}$Na(d,p)$^{24}$Na reaction in inverse kinematics to study the mirror state of the $\sim$475 keV resonance in $^{24}$Na. The experiment, performed at the Texas A\&M Cyclotron Institute, utilized the TIARA silicon array, four HPGe detectors, and the MDM spectrometer to measure the excited states of the $^{24}$Na nucleus. Preliminary results from the experiment will be presented along with progress from the ongoing analysis. [Preview Abstract] |
Thursday, October 26, 2017 10:42AM - 10:54AM |
DC.00002: Cross Section Measurements of the Reaction ${}^{23}$Na(p,$\gamma$)${}^{24}$Mg Axel Boeltzig, Richard James deBoer, Kevin Macon, Michael Wiescher, Andreas Best, Gianluca Imbriani, Gy\"orgy Gy\"urky, Frank Strieder The reaction ${}^{23}$Na(p,$\gamma$)${}^{24}$Mg can provide a link from the NeNa to the MgAl cycle in stellar burning and is therefore of interest in nuclear astrophysics. To determine the reaction rates at stellar temperatures, new cross section measurements at low proton energies have been performed recently [1], and further experiments are underway [2]. The current cross section data implies that the reaction rate up to temperatures of 1\,GK is determined by a few narrow resonances and direct capture. Complementary to these experimental efforts at low proton energies, cross section measurements at higher energies can help to constrain the direct capture and broad resonance contributions to the cross section and reduce the uncertainty of the extrapolation towards stellar energies. In this paper we report an experiment to measure the ${}^{23}$Na(p,$\gamma$)${}^{24}$Mg cross section with a solid target setup at the St.\ ANA 5U accelerator at the University of Notre Dame. The experiment and the current status of data analysis will be described. \newline [1] Cesaratto et al., Phys. Rev. C 88, 065806 (2013) \newline [2] Boeltzig et al., JPS Conf. Proc. 14, 020409 (2017) [Preview Abstract] |
Thursday, October 26, 2017 10:54AM - 11:06AM |
DC.00003: Study of astrophysical $\alpha + \quad^{\mathrm{22}}$Ne reaction using alpha transfer with TIARA and MDM spectrometer Shuya Ota, Gregory A. Christian, Eames B. Bennett, Heshani Jayatissa, Joshua Hooker, Curtis Hunt, Cordero Magana, Grigory Rogachev, Antti Saastamoinen, Sriteja Upadhyayula, Wilton N. Catford, Sam Hallam, Gavin Lotay, Mohamad Mouhkaddam, Ryan Wilkinson In core He burning and C-shell burning of massive stars, the $^{\mathrm{22}}$Ne($\alpha $,n)$^{\mathrm{25}}$Mg reaction is considered to be a main neutron source driving the synthesis of nuclides in the A$=$60-90 mass range during the $s$ process. While a variety of attempts to experimentally determine the rate for this reaction at the Gamow window corresponding to $s$ process temperatures have been made either through direct $^{\mathrm{22}}$Ne($\alpha $,n)$^{\mathrm{25}}$Mg measurements or indirect measurements, uncertainties of some resonance parameters in $^{\mathrm{26}}$Mg has remained a longstanding problem. To address this problem, we performed an experiment using the $^{\mathrm{6}}$Li($^{\mathrm{22}}$Ne,$^{\mathrm{26}}$Mg)$d \quad \alpha $-transfer reaction at K150 cyclotron of Texas A{\&}M University. A $^{\mathrm{6}}$LiF target was bombarded with a 7 MeV/u $^{\mathrm{22}}$Ne beam. Deuterons, gamma-rays, and recoil Mg ions were detected in coincidence using a large Si detector array, TIARA, HPGe clover detectors, and an MDM spectrometer backed by an ionization chamber, respectively. Preliminary data from the experiment will be presented. [Preview Abstract] |
Thursday, October 26, 2017 11:06AM - 11:18AM |
DC.00004: Abstract Withdrawn
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Thursday, October 26, 2017 11:18AM - 11:30AM |
DC.00005: Development of the focal plane system for the SEparator for CApture Reactions A. A. D. Hood, J. C. Blackmon, R. Cottingham, C. M. Deibel, E. Good, K. Joerres, A. Laminack, A. Garrity The SEparator for CApture Reactions (SECAR) is currently under construction for the National Superconducting Cyclotron Laboratory and future Facility for Rare Isotope Beams. SECAR is designed to conduct sensitive measurements of capture reactions critical to understanding stellar explosions. We have developed a versatile focal plane system that will differentiate reaction recoils from unreacted scattered beam particles in measurements covering a large range of energies and masses. The elements of the focal plane system include two metal-foil, micro-channel plate (MCP) detectors, a variety of diagnostics, and two alternative recoil stopping detectors. The MCP detectors will measure the time-of-flight (and therefore velocity) as well as the position of the recoils. Our primary heavy ion recoil detector is a gas ionization chamber that measures position, total energy and relative energy loss and provides good atomic number discrimination at energies greater than about 0.5 $MeV/u$. For some cases, this gas counter will be replaced by silicon strip detectors to provide superior energy resolution. We will describe the overall design and report on construction and testing of the detector systems. [Preview Abstract] |
Thursday, October 26, 2017 11:30AM - 11:42AM |
DC.00006: Proton capture studies for the nucleosynthesis p-process using HECTOR Anna Simon, C.S. Reingold, O. Gomez, F. Naqvi, J. Arroyo, M. Chamberlain The p-process is a nucleosynthesis scenario that occurs during an explosion of a supernova and produces the proton-rich isotopes of elements between Se and Hg. The p-process involves series of ($\gamma$,n), ($\gamma$,p) and ($\gamma$,$\alpha$) reactions on pre-existing s-process seed nuclei. The reactions relevant for the p-process are studied in the lab via the inverse ones: capture reactions. The High EffiCiency TOtal Absorption SpectrometeR (HECTOR) was built for this purpose. HECTOR is a NaI(Tl) summing detector at the University of Notre Dame is comprised of 16 separate NaI(Tl) crystals and 32 photomultiplier tubes read by a digital data acquisition system. The array is designed for precision cross section measurements for (p,$\gamma$) and ($\alpha$,$\gamma$) reactions across the p-process Gamow window. The efficiency of HECTOR is about 52.7 (2.0)\% for the $^{60}$Co source. The first measurements of the proton-capture reactions on Pd and Cd proton-rich isotopes will be presented in this talk. The results will be compared to the cross sections obtained with other techniques, when available, and to the Hauser-Feshbach model calculations using the Talys code. [Preview Abstract] |
Thursday, October 26, 2017 11:42AM - 11:54AM |
DC.00007: Constraints on Bygone Neutron Star Nucleosynthesis Using Urca Coolers in the Crust Zach Meisel, Alex Deibel Nuclear burning near the surface of an accreting neutron star produces ashes that, when compressed deeper by further accretion, alter the star's thermal and compositional structure. Bygone nucleosynthesis can be constrained by the impact of compressed ashes on the thermal relaxation of quiescent neutron star transients. In particular, Urca cooling nuclei pairs in nuclear burning ashes, which cool the neutron star crust via neutrino emission from $e^{-}$/$\beta$-decay cycles, provide signatures of prior nuclear burning over the $\sim$century timescales it takes to accrete to the $e^{-}$-capture depth of the strongest cooling pairs. This talk will present crust cooling models of the accreting neutron star transient MAXI J0556-332 used to show that this source likely lacked Type I X-ray bursts and superbursts $\geq$120 years ago. We also identify the key nuclear physics uncertainties in rp-process reaction rates and $e^{-}$-capture weak-transition strengths for low-lying transitions whose reduction will improve nucleosynthesis constraints using this technique. [Preview Abstract] |
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