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 CC: Nuclear Astrophysics I |
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Chair: Zachary Meisel, Ohio University Room: Salon 3 |
Thursday, October 26, 2017 8:30AM - 8:42AM |
CC.00001: Measurement of the $^7$Li($\gamma$,t)$^4$He reaction between 4 and 11 MeV Steven Pain, Catalin Matei, Michael Munch, Carl Brune, Michael Febbraro, Hugon Karwowski, David Walter The discrepancy in the primordial $^7$Li abundance, as derived from stellar observations and nucleosynthesis calculations at WMAP baryonic density, is sensitive to alpha capture rates on $^3$He and $^3$H. The $^3$He($\alpha$,$\gamma$)$^7$Be reaction has been well studied over a wide range of energies, but for $^3$H($\alpha$,$\gamma$)$^7$Li discrepancies exist in measurements below $E_{CM}=1$ MeV, and limited data above 1.2 MeV do not sufficiently constrain the contribution from higher-lying resonances at astrophysical energies. To contribute to the understanding of this process we have measured cross sections and angular distributions for the time-reversed $^7$Li($\gamma$,$\alpha$)$^3$H reaction. The measurement was performed at the HIGS facility at the Triangle Universities Nuclear Laboratory (TUNL) using quasi-monoenergetic ($\sim$3$\%$ resolution) photon energies between 4 and 11 MeV. Tritons and alpha particles were detected in silicon detectors of SIDAR surrounding the $^7$Li target, and the beam intensity was monitored using multiple techniques. Details of the measurement, including the challenges of charged-particle measurements with gamma-ray beams, and preliminary results will be presented. [Preview Abstract] |
Thursday, October 26, 2017 8:42AM - 8:54AM |
CC.00002: Cross-section measurement of $^7Be + d$ and $^7Li + d$ with ANASEN* and its implication in the Big Bang Nucleosynthesis. Nabin Rijal, Ingo Wiedenhover, L. T. Baby, J. C. Blackmon, G. Rogachev Astrophysically observed $^7Li$ is $3 - 4$ times less than predicted amount by current models of Standard Big Bang Nucleosynthesis (SBBN). The nuclear reaction $^7Be + d $ at energies relevant to SBBN, has been discussed as a possible means to destroy mass-7 nuclei. We investigated the $^7Be + d$ and it's mirror nuclear reaction $^7Li + d$ at SBBN energies using a radioactive $^7Be$ and stable $^7Li$ beam both in deuterium gas target inside ANASEN at Florida State University. ANASEN is an active target detector system which tracks the charged particles using a position sensitive proportional counter and 24-SX3 and 4-QQQ position sensitive Silicon detectors, all backed up by CsI detectors. ANASEN has wide angular coverage. The experiment measures a continuous excitation function by slowing down the beam in the target gas down to zero energy by using a single beam energy. Our set-up provides a high detection efficiency for all relevant reaction channels including $(d,p), (d,\alpha)$ and/or direct breakup that can destroy mass-7 nuclei in contrast to previous measurements. The preliminary results of these experiments along with details of ANASEN detector will be presented. *ANASEN: Array for Nuclear Astrophysics and Structure with Exotic Nuclei. [Preview Abstract] |
Thursday, October 26, 2017 8:54AM - 9:06AM |
CC.00003: Abstract Withdrawn
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Thursday, October 26, 2017 9:06AM - 9:18AM |
CC.00004: Reaction rate studies of 7Li(a,g)11B at nu-process energies Gwenaelle Gilardy, Joachim Gorres, Richard DeBoer, Kevin Howard, Edward Lamere, Kevin Macon, Christopher Seymour, Michael Skulski, Michael Wiescher, Manoel Couder At the end of its life, a massive star collapses into a neutron star leading to a supernovae explosion. The neutrino flux released during the collapse is so significant that the probability of a neutrino interacting with a nucleus can actually influence the nucleosynthesis [1]. The origins of light element, especially 11B, is not fully understood and the $\nu $-process has been proposed as a candidate for its production [2]. Neutrino triggered reaction lead to the production of 11B via the reaction 7Li(a,g)11B. The cross section of 7Li(a,g)11B is then critical to estimate the contribution of the nu-process to 11B abundance. This reaction was recently studied at Notre Dame in the range of energy relevant to the nu-process and the result of this experiment will be presented. [1] S.E. Woosley et \textit{al}\textbf{\textit{, }}Astro. Journal, \textbf{356}:272-301(1990) \newline [2] K. Nakamura et \textit{al}, Astro. Journal Letters, \textbf{718}:L137-L140(2010) [Preview Abstract] |
Thursday, October 26, 2017 9:18AM - 9:30AM |
CC.00005: $^{\mathrm{10,11}}$B($\alpha $,$n )^{\mathrm{13,14}}$N cross section measurements$^1$ Qian Liu, Febbraro Michael, Richard Deboer, Wiescher Michael $^{\mathrm{10,11}}$B($\alpha $,$n )^{\mathrm{13,14}}$N have been identified as possible background sources for underground experiments at low $E_{\alpha}$ energy [1]. These reactions have been studied at University of Notre Dame's Nuclear Science Laboratory using Santa Anna 5 MV accelerator. $^{\mathrm{11}}$B($\alpha $,$n )^{\mathrm{14}}$N was measured with a $^{3}$He counter, and a good R-matrix fit was obtained, which shows our data in agreement with other published data. Measurement of $^{\mathrm{10}}$B($\alpha $,$n )^{\mathrm{13}}$N was performed down to $E_{\alpha}=0.57$MeV, with two deuterated liquid scintillators, EJ315 and EJ301D, and with the help of unfolding technique, neutron energy information can be extracted. EJ301D is a newly-developed neutron detector, with better pulse shape discrimination [2], and has been used to do angular distribution measurements. Additionally, the ($\alpha ,\alpha_1 \gamma$) and ($n,p\gamma$) channels have been monitored independently by observation of 718keV $\gamma$ transition in $^{10}$B and 3853keV $\gamma$ transition in $^{13}$C. Preliminary analysis indicates the discovery of a new resonance in low energy region. [1] D.-M.Mei \textit{et al.} NIMA \textbf{606}, 651(2009). [2] F.D Becchetti \textit{et al.} NIMA \textbf{820}, 112(2016). [Preview Abstract] |
Thursday, October 26, 2017 9:30AM - 9:42AM |
CC.00006: ABSTRACT WITHDRAWN |
Thursday, October 26, 2017 9:42AM - 9:54AM |
CC.00007: Spectroscopic Factors of low-lying levels in $^{\mathrm{18}}$Ne Patrick O'Malley, Jacob Allen, Dan Bardayan, Fred Becchetti, Jolie Cizewski, Michael Febbraro, Matthew Hall, Kate Jones, Robert Grzywacz, Stan Paulauaskas, Karl Smith, Cory Thornsberry Much effort has been made to understand the origins of 18F in novae. Due to its relatively long half-life, $^{\mathrm{18}}$F can survive until nova envelope is transparent, and therefore can provide a sensitive diagnostic of nova nucleosynthesis. It is likely produced through the beta decay of $^{\mathrm{18}}$Ne, which is itself primarily produced through the $^{\mathrm{17}}$F(p,gamma) reaction. Understanding the direct capture to the $^{\mathrm{17}}$F(p,gamma) reaction is important to accurately model it. As such, the spectroscopic strengths of low-lying levels in $^{\mathrm{18}}$Ne are needed. At the University of Notre Dame a measurement of the $^{\mathrm{17}}$F(d,n) reaction has been performed using a beam produced by the TwinSol low energy radioactive ion beam facility. The neutrons were 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 discussed. Research supported by U.S. DOE and NSF. [Preview Abstract] |
Thursday, October 26, 2017 9:54AM - 10:06AM |
CC.00008: Establishing the Acceptance of St. George Christopher Seymour, George Berg, Manoel Couder, William Feltman, Gwenaelle Gilardy, Zachary Meisel, Luis Morales, Michael Moran, Shane Moylan, Daniel Robertson, Edward Stech, Michael Wiescher The St George recoil separator will be used to measure alpha capture reaction cross sections in order to enhance our understanding of the astrophysical sites and processes in which the reactions occur. Measurements will be carried out in the Nuclear Science Laboratory of Notre Dame at relatively low energies and over a broad energy range. Performing measurements over a large energy range, and at as low an energy as possible, will help improve the S-factor extrapolations necessary to calculate the reaction rate at actual stellar energies; where the reaction cross section is too low to measure directly in the lab. However, before cross section measurements can be carried out, the separator must be commissioned. The objective of commissioning St George is to establish angular and energy acceptance characteristics while simultaneously optimizing the ion optics of the system. A summary of recent angular and energy acceptance results along with the techniques used to achieve them will be presented. [Preview Abstract] |
Thursday, October 26, 2017 10:06AM - 10:18AM |
CC.00009: Position sensitivty with the St. George time of flight vs energy detection system Luis Morales, Sunil Kalkal, Hyo Soon Jung, J Laurence, Zachary Meisel, William Feltman, A Hanner, E-Lexis Thornton, B.B. Wiggins, Romualdo deSouza, Jerry Hinnefeld, Manoel Couder, Michael Wiescher At the University of Notre Dame the St. George recoil mass separator will be used to study $(\alpha,\gamma)$ reactions of astrophysical interest. The particle identification system developed for the St. George recoil mass separator at the University of Notre Dame, in collaboration with Indiana University South Bend, utilizes time-of-flight and energy to separate reaction products from residual unreacted beam particles. The detection system uses two microchannel plate (MCP) detectors for time-of-flight, and a silicon strip detector to measure the particles kinetic energy. A position sensitive anode was designed in collaboration with Indiana University Bloomington to enhance particle identification (PID). The performance of the PID system will be presented. [Preview Abstract] |
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