Bulletin of the American Physical Society
2016 Fall Meeting of the APS Division of Nuclear Physics
Volume 61, Number 13
Thursday–Sunday, October 13–16, 2016; Vancouver, BC, Canada
Session CH: Nuclear Astro I |
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Chair: Kelly Chipps, Oak Ridge National Laboratory Room: Pavilion Ballroom C |
Friday, October 14, 2016 8:30AM - 8:42AM |
CH.00001: Enhancement of the triple alpha process in hot, dense environments Mary Beard, Sam M. Austin, Richard Cyburt The triple alpha process plays a particularly important role in nuclear astrophysics, bridging the A$=$5 and A$=$8 stability gaps, producing $^{12}$C . The reaction itself proceeds via the 0$+$ (Hoyle) resonance at 7.65 MeV in $^{12}$C, at a rate proportional to the radiative width of the state. For sufficiently hot and dense environments, the rate of the triple alpha reaction is significantly enhanced by hadronic inelastic scattering that de-excites the Hoyle state. We present theoretical calculations for the enhancement of the triple alpha rate based on inelastic n, p and alpha cross sections. For comparable densities, neutrons play the largest role. [Preview Abstract] |
Friday, October 14, 2016 8:42AM - 8:54AM |
CH.00002: $^{\mathrm{10}}$B($\alpha $,$n )^{\mathrm{13}}$N cross section measurement$^1$ Qian Liu, Michael FEBBRARO, RICHARD DEBOER, MICHAEL WIESCHER The reactoin $^{\mathrm{10}}$B($\alpha $,$n )^{\mathrm{13}}$N has been identified as a possible background source for underground experiments at low energy[1]. Previously the differential cross section data has only been available at energies above $E_\alpha $ = 1.0 MeV [2]. An improved measurement of this reaction has been performed extensively down to 0.57 MeV. It has been measured 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 [3], and has been used to do angular distribution measurements. In addition, the ($\alpha ,\alpha_1 \gamma$) and $(\alpha,p_3\gamma)$ channels have been monitored independently by observation of the 718 keV $\gamma$ transition in $^{10}$B and 3853 keV $\gamma$ transition in $^{13}$C. Preliminary data analysis indicates the discovery of a new resonance in low energy region. Future measurements will be carried out at CASPAR using the same detectors.[1] D.-M.Mei, C.zhang, A.hime, NIMA \textbf{606}, 651 (2009). [2] L. [2] L. Van Der Zwan and K.W. Geiger, NPA \textbf{216}, 188 (1973). [3] F.D Becchetti \textit{et al.} NIMA \textbf{820}, 112 (2016). [Preview Abstract] |
Friday, October 14, 2016 8:54AM - 9:06AM |
CH.00003: Measurements Of Stellar And Big-Bang Nucleosynthesis Reactions Using Inertially-Confined Plasmas Alex Zylstra, Hans Herrmann, Maria Gatu Johnson, Yongho Kim, Johan Frenje, Gerry Hale, Chikang Li, Mike Rubery, Mark Paris, Andy Bacher, Carl Brune, Chad Forrest, Vladimir Glebov, Roger Janezic, Dennis McNabb, Abbas Nikroo, Jesse Pino, Craig Sangster, Fredrick Seguin, Hong Sio, Christian Stoeckl, Richard Petrasso The $^3$He+$^3$He, T+$^3$He, and p+D reactions directly relevant to either Stellar or Big-Bang Nucleosynthesis (BBN) have been studied at the OMEGA laser facility using inertially-confined plasmas, created using shock-driven `exploding pusher' implosions. These plasmas better mimic astrophysical systems than cold-target accelerator experiments. A new measured S-factor for the T($^3$He,$\gamma$)$^6$Li reaction rules out an anomalously-high $^6$Li production during the Big Bang as an explanation to the high observed values in metal poor first generation stars. Our value is also inconsistent with values used in previous BBN calculations. Proton spectra from the $^3$He+$^3$He and T+$^3$He reactions are used to constrain nuclear R-matrix modeling, and recent experiments have probed the p+D reaction for the first time in a plasma. [Preview Abstract] |
Friday, October 14, 2016 9:06AM - 9:18AM |
CH.00004: A Measurement of the Interaction of Neutrons With $^{\mathrm{7}}$Be at Cosmological Energies E.E. Kading, M. Gai, T. Palchan, M. Paul, M. Tessler, A. Weiss, D. Berkovits, Sh. Halfon, D. Kijel, A. Kreisel, A. Shor, I. Silverman, L. Weissman, R. Dressler, S. Heinitz, E.A. Maugeri, D. Schumann, M. Hass, I. Mukul, Y. Shachar, Ch, Seiffert, Th. Stora, D. Ticehurst, C.R. Howell, N. Kivel We exposed the 4.4 GBq electroplated $^{\mathrm{7}}$Be target prepared at the Paul Scherrer Institute in Switzerland to the high neutrons flux of 5x10$^{\mathrm{10}}$ /sec/cm$^{\mathrm{2}}$ generated by the LiLiT at the Soreq Applied Research Accelerator Facility (SARAF) in Israel. The so produced quasi-Maxwelian neutron spectrum with an equivalent kT $=$ 49.2 keV simulate directly BBN conditions with T$=$ 700 - 500 MK (kT $=$ 60 - 43 keV), allowing the first measurement at Big Bang energies. The measured alpha-particles emanating from all possible $^{\mathrm{8}}$Be states populated in the $^{\mathrm{7}}$Be(n,$\alpha )$ and $^{\mathrm{7}}$Be(n,$\gamma \alpha )$ reaction, detected with a CR39 plastic track detectors, will be shown and discussed. [Preview Abstract] |
Friday, October 14, 2016 9:18AM - 9:30AM |
CH.00005: Interference solutions in the $^{\mathrm{12}}$C($\alpha $,$\gamma )^{\mathrm{16}}$O reaction Richard deBoer, R.E. Azuma, A. Best, C.R. Brune, J. Görres, S. Jones, M. Pignatari, D. Sayre, K. Smith, E. Uberseder, M. Wiescher The reaction rate of $^{\mathrm{12}}$C($\alpha $,$\gamma )^{\mathrm{16}}$O is critical in modeling the evolution of stars throughout the many stages of their lifecycles [1]. Yet despite its importance, a precise determination of the cross section remains elusive. This is largely because the cross section at stellar energies is over an off-resonance region, where it is determined by the delicate interference between several broad resonances. Complicating the situation, are the high energy tails of subthreshold levels whose properties are difficult to determine directly. These resonances can interfere in a complicated way that is often difficult to determine. In this presentation the different interference solutions for the $E$1 ground state [2], 6.05 MeV, and 6.13 MeV transitions [3,4] will be discussed by way of a phenomenological $R$-matrix analysis, addressing several questions raised in the literature. It will be shown how the data of [3] are in good agreement with both the asymptotic normalization coefficients determined by [4] and the data of [5], if systematic uncertainties are taken into consideration. [1] W.A. Fowler, Science, \textbf{226}, 4677 (1984) [2] M. Gai, ArXiv:1506.04501 (2015) [3] Matei et al. PRL \textbf{97}, 242503 (2006) [4] Avila \textit{et al.} PRL \textbf{114}, 071101 (2015) [5] Sch\"{u}rmann \textit{et al.} PLB \textbf{703}, 557 (2011) [Preview Abstract] |
Friday, October 14, 2016 9:30AM - 9:42AM |
CH.00006: Mass-7 destruction through $^7Be+d$ and $^7Li+d$ reactions, studied with ANASEN. Nabin Rijal, Ingo Wiedenhover, L.T. Baby, M. Anastasiou, J.J. Parker, J.C. Blackmon, K.T. Macon, D.S. Gonzalez, E. Koshchiy, G. Rogachev, J. Belarge, A. Kuchera The astrophysically observed amount of $^7Li$ is only 25$\%$-33$\%$ of the one predicted by current models of Standard Big Bang Nucleosynthesis(SBBN). However, nuclear reactions between $^7Be+d$ are not well constrained experimentally and can destroy a good fraction of mass-7 nuclei under the conditions of SBBN. At the FSU accelerator laboratory, we performed a measurement of reactions between a beam of the radioactive isotope $^{7}$Be and the pure deuterium gas target located inside ANASEN (Array for Nuclear Astrophysics Studies with Exotic Nuclei). ANASEN is an active target detector system which tracks the charged particles between a position-sensitive proportional counter and 28 position-sensitive Silicon detectors, all backed up by CsI scintillation detectors. The experiment measures a continuous excitation function by slowing down the beam in the target gas, with a high detection efficiency for all relevant reaction channels, using single beam energy. We also performed an experiment for the mirror nuclear reaction $^7Li+d$ with ANASEN in active gas target mode. The preliminary results of these experiments along with details of ANASEN will be presented. [Preview Abstract] |
Friday, October 14, 2016 9:42AM - 9:54AM |
CH.00007: Measuring the Nuclear Levels in $^{\mathrm{19}}$Ne using GODDESS Matthew Hall A direct way to test nova explosion models is to observe gamma rays created in the decay of radioactive isotopes produced in the nova. One such isotope, $^{\mathrm{18}}$F, is believed to be the main source of observable 511-keV gamma rays. The main destruction mechanism of $^{\mathrm{18}}$F is thought to be the $^{\mathrm{18}}$F(p,$\alpha )^{\mathrm{15}}$O reaction, and the uncertainty in the reaction rate is attributed to uncertainties in the energies, spins, and parities of the nuclear levels in $^{\mathrm{19}}$Ne above the proton threshold. A $^{\mathrm{3}}$He beam was used at Argonne National Lab in an effort to understand the levels in $^{\mathrm{19}}$Ne via the $^{\mathrm{19}}$F($^{\mathrm{3}}$He,t)$^{\mathrm{19}}$Ne reaction. Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies (GODDESS) was used to measure gamma rays from the decay of $^{\mathrm{19}}$Ne in coincidence with the reaction tritons. Preliminary data from the experiment will be presented. This research was supported by the National Science Foundation, the US DOE Office of Nuclear Physics and the National Nuclear Security Administration. [Preview Abstract] |
Friday, October 14, 2016 9:54AM - 10:06AM |
CH.00008: Spectroscopic strengths of low-lying levels in $^{\mathrm{18}}$Ne Patrick OMalley, J. M. Allen, D.W. Bardayan, F.D. Becchetti, J. A. Cizewski, M. Febbraro, R. Gryzwacz, M. Hall, K. L. Jones, J.J. Kolata, S.V. Paulauskas, K. Smith, C. Thornsberry Much effort has been made to understand the origins of $^{\mathrm{18}}$F in novae. Due to its relatively long half-life (\textasciitilde 2 hours), $^{\mathrm{18}}$F can survive until the nova envelope is transparent, and therefore it can provide a sensitive diagnostic of nova nucleosynthesis. It is likely produced through the beta decay of $^{\mathrm{18}}$Ne, which is itself produced (primarily) through the $^{\mathrm{17}}$F(p,$\gamma )$ reaction. Understanding the direct capture contribution to the $^{\mathrm{17}}$F(p,$\gamma )$ reaction is important to accurately model it. As such, the spectroscopic strengths of low-lying states 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 with TwinSol Low energy radioactive beam facility. The neutrons were detected using a combination of VANDLE and UoM deuterated scintillator arrays. Data will be shown and preliminary results discussed. Research sponsored by the National Science Foundation, the US DOE Office of Nuclear Physics, and the National Nuclear Security Administration. [Preview Abstract] |
Friday, October 14, 2016 10:06AM - 10:18AM |
CH.00009: Status of The Facility for Experiments of Nuclear Reactions in Stars Richard Longland, John Kelley, Caleb Marshall, Federico Portillo, Kiana Setoodehnia, Daniel Underwood To make connections between observations of stellar atmospheres and the processes occurring deep inside stars, me must rely on accurate nuclear cross sections. Often, the Coulomb barrier makes these cross sections immeasurably small in the laboratory. Particle transfer reactions are one tool in our inventory that can be used to infer the necessary properties of nuclear reactions, thus opening an avenue to calculate their cross sections. Enge split-pole magnetic spectrographs are one tool in our inventory that have been used successfully to perform these experiments. However, after a rash of closures, there were no operational spectrographs of this kind in North America to provide these valuable capabilities. Over the last few years, we have revived the Enge split-pole spectrograph at TUNL. We have also upgraded much of the equipment, ranging from the data acquisition system to the control system and detector package. These upgrades have enabled a powerful, flexible, and modern facility - the Facility for Experiments of Nuclear Reactions in Stars (FENRIS). In this talk, I will present a status upgrade of FENRIS, highlighting our upgrades, capabilities, and first science results. I will also highlight future upgrade plans for the facility. [Preview Abstract] |
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