Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session MD: Light Elements in Nuclear Astrophysics |
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Chair: Carl Brune, Ohio University Room: Hilton Kohala 3 |
Saturday, October 27, 2018 2:00PM - 2:15PM |
MD.00001: Abstract Withdrawn
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Saturday, October 27, 2018 2:15PM - 2:30PM |
MD.00002: Big Bang Nucleosynthesis with an Inhomogeneous Primordial Magnetic Field Strength Yudong Luo, Toshitaka Kajino, Motohiko Kusakabe, Grant James Mathews Big Bang Nucleosynthesis (BBN) agrees well with the observational abundances of light elements 2H, 3He and 4He except for 7Li. We find that the abundances of these elements can be affected strongly by a stochastic primordial magnetic field (PMF) whose strength is spatially inhomogeneous. We assume an uniform total energy density with a large-scale stochastic PMF and a gaussian distribution of field strength. We show that in such case, the effective distribution function of particle velocities averaged over domains of different temperature is deviates from the Maxwell-Boltzmann (MB) distribution. We perform BBN network calculations taking account the PMF strength distribution and find that the fluctuation of the PMF reduces the 7Be production and enhances 2H production. Finally, we constrain the parameters ρBc and σ for our fluctuating PMF model from observed abundances of 4He and 2H. In this model, the 7Li abundance is significantly reduced. We also discuss the possibility that the baryon-to-photon ratio decreased after the BBN epoch. In this case, we find that for η larger than the present-day value, all light elements can be consistent with observational data. |
Saturday, October 27, 2018 2:30PM - 2:45PM |
MD.00003: Newly measured 7Be+n reaction cross sections and resonance study for the BBN Seiya Hayakawa, Keijiro Abe, Marco La Cognata, Livio Lamia, Hideki Shimizu, Lei Yang, Hidetoshi Yamaguchi, for the CRIB-THM collaboration The cosmological 7Li problem is still an open question although several solutions have been proposed for years. Since the primordial 7Li abundance strongly depends on the 7Be production and destruction rate during the Big-Bang nucleosynthesis (BBN), those of the main destruction processes 7Be(n,p)7Li and 7Be(n,α)4He need to be determined. In spite of several recent experimental efforts, there are still some uncertainties at the most relevant energies. We have performed indirect measurements of both of these reactions by the Trojan Horse Method (THM). The experiments were performed both at the EXOTIC, INFN-LNL, and at the Center-for-Nuclear-Study Radioactive Ion Beam (CRIB) separator in collaboration. We will present the results of the latter experiment. We observed both the 7Be(d,7Lip)1H and 7Be(d,αα)1H reactions in inverse kinematics by a single measurement, approaching the 7Be(n,p)7Li and 7Be(n,α)4He reactions in quasi-free kinematics, respectively. The (n,p1) yields were successfully extracted for the first time in the relevant energy region. We will discuss the normalization of the present THM cross sections for the (n,p0), (n,p1) and (n,α) by multichannel R-matrix analysis, and possible astrophysical implications. |
Saturday, October 27, 2018 2:45PM - 3:00PM |
MD.00004: Spectroscopy of Resonances in 9B with the FSU-LSU Split-Pole Spectrograph Ingo Wiedenhoever, Nabin Rijal, Gordon McCann, Catherine M Deibel, Jeffery C Blackmon, Maria Anastasiou, Lagy T Baby, Powell E. Barber, Erin Good, Paul D. Cottle, Kenneth Hanselmann, Peter A Hoeflich, Ashley A Hood, Jon Lighthall, Khang Pham The cross sections of nuclear reactions between the radioactive isotope 7Be and deuterium, a possible path of reducing the production of mass-7 nuclides in Big-Bang nucleosynthesis, have recently been measured with the ANASEN active-target detector system at the RESOLUT facility of Florida State University [1]. In order to further reduce the uncertainties in the reaction rates of Big-Bang nucleosynthesis, we performed an indirect experiment with the 10B(3He,alpha) reaction with the newly commissioned large-acceptance Enge Split-Pole Spectrograph. The implications for the synthesis of 7Li will be discussed. |
Saturday, October 27, 2018 3:00PM - 3:15PM |
MD.00005: Study of the contribution of the 7Be(d, p) reaction to the 7Li problem in the Big-Bang Nucleosynthesis Azusa Inoue, Atsushi Tamii, Satoshi Adachi, Masato Asai, Agnieszka Czeszumska, Mitsunori Fukuda, Seiya Hayakawa, Nobuyuki Kobayashi, Hiroyuki Makii, Kensaku Matsuta, Mototsugu Mihara, Shoken Nakamura, Tatsushi Shima, Hideki Shimizu, Dinh Trong Tran, Hidetoshi Yamaguchi, Lei Yang Our research purpose is to measure the 7Be(d, p) reaction to shed light on the 7Li problem in the Big-Bang Nucleosynthesis. We are developing an unstable 7Be target for a high-resolution measurement of the 7Be(d, p)8Be reaction. We plan to compare two methods to produce the 7Be target: (1) Activation method, and (2) Implantation method. We performed an activation method experiment at the Van de Graaff at Osaka University, and obtained the cross-section data in December 2015. We continue the development of the activation target method to obtain more accurate data at the Tandem Electrostatic Accelerator, Kobe University. The first trial of the target production experiment at Kobe was in March 2018, and we could produce 3×1012 7Be target in 7 mm2. The (d, p) reaction measurement is scheduled in August 2018. We have also made a 7Be target with the implantation method at CRIB, Center for Nuclear Study, University of Tokyo in 2016. We could produce 1012 7Be target in 7 mm2 after a development for the high intensity 7Be beam at CRIB in 2017. We had the target implantation experiment in April 2018. An experiment to measure the (d, p) reaction with the implanted target was done in June 2018 at Japan Atomic Energy Agency, tandem facility. The result will be reported and discussed. |
Saturday, October 27, 2018 3:15PM - 3:30PM |
MD.00006: Cross-section measurement of 7Be+d and its implications in the Big Bang Nucleosynthesis. Nabin Rijal, Ingo Wiedenhover, Lagy T Baby, Jeffery C Blackmon, Peter A Hoeflich The cross sections of nuclear reaction 7Be+d, which is a possible path of destruction of mass-7 nuclides in Big-Bang nucleosynthesis, were measured at center-of-mass energies between 0.2 MeV and 1.5 MeV. The experiment was performed with the ANASEN active-target detector system at the RESOLUT facility of Florida State University. We measured cross sections consistent with prior measurements at higher energies but significantly higher at lower energy, especially in the Gamow window. The implications of these cross-sections in the primordial lithium abundance will be discussed. |
Saturday, October 27, 2018 3:30PM - 3:45PM |
MD.00007: High energy density plasma experiments to study the T+T and 3He+3He six-nucleon systems at OMEGA and the NIF Maria Gatu Johnson, Alex Zylstra, Andrew Bacher, Carl Richard Brune, Daniel Casey, Chad Forrest, Matthias Hohenberger, Daniel Sayre, Steve Craxton, Johan Frenje, Warren Garbett, Emma Garcia, Vladimir Glebov, Gerald M Hale, Martin Hoppe, Brandon J Lahmann, Dennis Paul McNabb, Mark W Paris, Richard Petrasso, Jesse Pino, Bruce Remington, Michael Schoff, Hong Sio, Christian Stoeckl, Heather Whitley Thermonuclear reaction rates and nuclear processes are explored traditionally in accelerator experiments, which are difficult to execute at conditions relevant to Stellar and Big Bang Nucleosynthesis. High-Energy-Density (HED) plasmas mimic astrophysical environments and can complement accelerator experiments. We describe HED experiments1,2 to study the T+T reaction at the OMEGA laser, and the 3He+3He reaction at the National Ignition Facility (NIF). Neutron spectra from the T+T reaction at ion temperatures from 4 to 18 keV, corresponding to center-of-mass (c-m) energies from 16 to 50 keV, show the 5He ground state resonant peak at 8.6 MeV being stronger at the higher than at the lower energy.3 This indicates a reaction mechanism that must involve resonances and/or higher angular momenta than L=0. Preliminary 3He+3He reaction data at c-m energies from 60-120 keV also indicate that the underlying physics changes with c-m energy. [1] M. Gatu Johnson et al., Phys. Plasmas 24, 041407 (2017). [2] M. Gatu Johnson et al., Phys. Plasmas 25, 056303 (2018). [3] M. Gatu Johnson et al., submitted to Phys. Rev. Lett. (2018). |
Saturday, October 27, 2018 3:45PM - 4:00PM |
MD.00008: Proton spectra from $^3$He+T and $^3$He+$^3$He fusion at low center-of-mass energy Alex Zylstra, Johan Frenje, Maria Gatu Johnson, Gerald M Hale, Carl Richard Brune, Andrew Bacher, Dan Casey, Chikang Li, Dennis Paul McNabb, Mark W Paris, Richard Petrasso, Thomas C Sangster, Dan Sayre, Fredrick Seguin Proton spectra from the $^3$He+$^3$He and T+$^3$He have been studied at the OMEGA laser facility using inertially-confined plasmas. These high-temperature plasmas are created using shock-driven `exploding pusher' implosions. The advantage of using these plasmas is that they better mimic astrophysical systems than cold-target accelerator experiments, and are suited to unique low-energy measurements. The measured proton spectra disagree substantially with R-matrix predictions made using data from the mirror T+T reaction. R-matrix fits to the spectra suggest significant uncertainty in the proton energy distribution [A.B. Zylstra et al., Phys. Rev. Lett. 119, 222701 (2017)]. This reaction is directly relevant to the solar proton-proton chain, and these low-energy spectra may aid interpretation of low-statistics cross section measurements in accelerator experiments. |
Saturday, October 27, 2018 4:00PM - 4:15PM |
MD.00009: Cross Section Measurements of $^{10}$B(p,$\alpha$)$^7$Be Bryant Vande Kolk, Kevin T Macon, Richard J DeBoer, Axel Boeltzig, Patrick D O'Malley, Khachatur Manukyan, Alexander Voinov, Thomas Massey, Carl Richard Brune, Michael C F Wiescher The $^{10}$B(p,$\alpha$)$^7$Be reaction is a potential temperature diagnostic for laser-driven plasmas. While this technique would be implemented at sub-MeV energies, higher energy resonances may interfere with those that lie within the plasma environment energies. Additionally, there are significant uncertainties and inconsistencies in the reaction cross section data at higher energy. A measurement of $^{10}$B(p,$\alpha$)$^7$Be over a broader range of energies and angles will better determine the resonance interferences and constrain the R-matrix parametrization for the lower energies. This cross section was measured at the University of Notre Dame and at Ohio University with charged particle Si detectors in the energy range E$_{p}$ = 800 - 2000 keV for $^{10}$B(p,$\alpha_{0,1}$)$^7$Be and at multiple angles for complete angular distributions. Data overlap with previous comprehensive lower energy cross section measurements now provides constraints on the interference effects of higher energy resonances. This data better informs the R-matrix analysis of this reaction and helps to confirm the reaction as a potential temperature diagnostic for NIF plasma analysis. |
Saturday, October 27, 2018 4:15PM - 4:30PM |
MD.00010: Generating near solid density reacting ion distributions using intense short pulse lasers Gary Grim, Andreas Kemp, Edward P Hartouni, Scott Wilks, Shaun Kerr Simulations and recent experimental results of a new platform for generating near solid density reacting ion distributions using intense short pulse lasers will be presented. The platform consists of a thin unstructured CH or CD foam with O(100) nm scale pores and ligaments mounted on a thin solid density CH support. The solid CH is illuminated by an intense, ~5 x 1019 W/cm2, short pulse, ~40 fs, laser having an ASE component less than 10-8 of the main pulse. The recirculating hot electrons generated at the pre-plasma critical surface induce electric fields within the foam structure causing TNSA acceleration of the foam ions into the voids. This resuls in a near solid density charged ion distribution with kinetic energies approaching 200 keV. These energies and densities are sufficient to produce measurable quantities of charged particle reactions, such as, 12C(p,γ)13N, allowing for the study of cross sections with astrophysical relevance, as well as for direct studies of screening effects in charged particle reactions occurring in hot plasma like conditions. |
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