Bulletin of the American Physical Society
2015 Annual Fall Meeting of the APS Prairie Section
Thursday–Saturday, November 19–21, 2015; South Bend, Indiana
Session F1: Nuclear Physics II |
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Chair: Anna Simon, University of Notre Dame Room: Nieuwland Science 127 |
Saturday, November 21, 2015 10:30AM - 10:42AM |
F1.00001: Alpha Cluster States in $^{12}$C and $^{16}$O Bryce Frentz, Armen Gyurjinyan, Ethan Sauer, Wanpeng Tan, Anthony Battaglia, Andrew Nystrom, Clark Casarella, Mallory Smith, Patrick O'Malley, Scott Marley, Sabrina Strauss, Andre Bermundez-Perez, Benjamin Guerin, Patrick Fasano, Ani Aprahamian, Michael Febbraro, Ram\'{o}n Torres-Isea, Frederick Becchetti, Martin Freer, Gvirol Goldring The reaction $^{13}$C($\alpha$, n)$^{16}$O and the subsequent breakup of $^{16}$O was measured the University of Notre Dame Nuclear Science Laboratory in order to explore the $\alpha$-cluster states above the $4\alpha$ decay threshold in $^{16}$O. The charged particles were detected using four double-side strip detectors with 256 total channels and 12 deuterated liquid scintillators were used to detect neutrons. Locating and understanding these states is crucial in understanding the stellar evolution and the CNO cycle. Details of the experimental setup, data analysis, and preliminary results will be presented. [Preview Abstract] |
Saturday, November 21, 2015 10:42AM - 10:54AM |
F1.00002: Search for novel $\alpha$-cluster structure in light unstable nuclei Tan Ahn, J. Allen, D. W. Bardayan, B. Becker, W. Boeschenstein, K. Cushman, M. Hall, O. Hall, J. Hu, J. Koci, L. Jensen, J. J. Kolata, P. O'Malley, Y. Ayyad, D. Bazin, S. Beceiro-Novo, J. Bradt, L. Carpenter, W. Mittig, F. D. Becchetti The formation of $\alpha$-cluster structure in nuclei is an example of an emergent ordering that appears under certain conditions. It is still an open question of what the exact conditions are for $\alpha$ cluster-formation. In order understand these conditions, we have a program to search for $\alpha$-cluster states in light unstable nuclei. To access these unstable nuclei we use in-flight radioactive beams that are produced with TwinSol, a pair of superconducting solenoids. The Prototype Active-Target Time-Projection Chamber was used to measure differential cross sections with high precision. Recent experiments for confirming a novel type of cluster structure, the linear-chain structure, in $^{14}$C and the search for cluster structure in $^{14}$O will be presented. The presence or absence of cluster structures in $^{14}$C and $^{14}$O will help elucidate the role of extra nucleons on the formation of cluster structures. [Preview Abstract] |
Saturday, November 21, 2015 10:54AM - 11:06AM |
F1.00003: Precision half-life measurement of 17F Catherine Nicoloff Precision measurements in low energy nuclear physics have led to considerable advances in the topic of fundamental symmetry. Efforts to improve the precision and accuracy of branching ratios, half-lives, and Q-values of superallowed $0^+ \rightarrow 0^+$ pure Fermi $\beta$-decays have led to what is now the most stringent test of the unitarity of the CKM matrix and the standard model of electroweak interactions. One of the critical elements in this unitarity test is $V_{ud}$, which currently comes from 14 corrected $\mathscr{F}$t-values of superallowed $0^+ \rightarrow 0^+$ pure Fermi $\beta$-decays. Despite the great precision achieved from pure Fermi transitions, measurements in other systems, such as superallowed $0^+ \rightarrow 0^+$ mixed Fermi decays, remain important. Among the mirror transitions, an excellent candidate for measurement is $^{17}$F. This transition proceeds from the ground state directly to the ground state of the daughter nucleus, eliminating the need to measure the branching ratios. Since its measured lifetime is currently less precise than its measured Q-value, we performed a precision half-life measurement of $^{17}$F at the Nuclear Science Laboratory of the University of Notre Dame. [Preview Abstract] |
Saturday, November 21, 2015 11:06AM - 11:18AM |
F1.00004: Simulations of the University of Notre Dame Multi-Reflection Time-of-Flight Spectrograph James Kelly A multi-reflection time-of-flight mass spectrograph (MR-ToF) is currently being designed to provide isobarically pure ion bunches to experiments for the future N = 126 factory at ANL. To characterize and optimize the MR-ToF, and to guide the design, we performed the series of simulations that will be presented. [Preview Abstract] |
Saturday, November 21, 2015 11:18AM - 11:30AM |
F1.00005: CONSTRUCTION OF A MULTI-REFLECTION TIME-OF-FLIGHT MASS SPECTROGRAPH FOR ISOBARIC PURIFICATION AT THE UNIVERSITY OF NOTRE DAME Brad Schultz One of the most significant problems in the production of rare isotopes is the simultaneous production of isobaric contaminants. Thus, a high-resolution beam purification method is required to isolate the desired radionuclide, which must be compatible with both short half-lives and low yields. A multi-reflection time-of-flight mass spectrograph (MR-TOF-MS) meets all these criteria, in addition to boasting a smaller footprint relative to traditional separator dipole magnets. Such a device has been designed and constructed at the University of Notre Dame and will be installed in the upcoming cyclotron facility. The motivation, conceptual design and status report will be presented. [Preview Abstract] |
Saturday, November 21, 2015 11:30AM - 11:42AM |
F1.00006: Systematic measurements of proton-induced reactions on enriched molybdenum Edward Lamere, Gwenaelle Gilardy, Zach Meisel, Michael Moran, Michael Skulski, Antonio Simonetti, Manoel Couder Between 2008 and 2010, shortages in the world-wide supply of $^{\mathrm{99}}$Mo highlighted weaknesses in the current fission-based production method of $^{\mathrm{99m}}$Tc, a critical medical isotope. This crisis sparked interest in developing alternative production methods, including the direct production of $^{\mathrm{99m}}$Tc from proton-induced reactions on enriched $^{\mathrm{100}}$Mo targets. One complication with this method is that $^{\mathrm{99m}}$Tc must be chemically extracted from the irradiated target. Therefore radiopharmaceuticals will contain a mixture of all Tc-species produced from the proton bombardment, affecting radiochemical purity, specific activity and total production yield of $^{\mathrm{99m}}$Tc---factors critical for the feasibility of this production method. Reactions on trace impurities in the enriched targets have been shown to impact these factors dramatically. Precise cross-section measurements for all Mo $+$ p reactions that lead to Tc or Mo species are required for proper assessment of this production technique. Cross-section measurements for the main reaction of interest, $^{\mathrm{99m}}$Tc(p,2n), have been performed in recent years, however, other reactions producing Tc have been mostly neglected. We will introduce a systematic study of proton-induced reactions on 92, 94-98, 100 Mo currently being performed at Notre Dame. First results on $^{\mathrm{96}}$Mo $+$ p reactions will be presented. [Preview Abstract] |
Saturday, November 21, 2015 11:42AM - 11:54AM |
F1.00007: Excited state lifetimes for A=109 nuclei via electronic timing with LaBr3(Ce) detectors M. K. Smith, A. Aprahamian, H. Mach, B. Bucher, L. M. Fraile, B. Olaizola The neutron-rich region near A=100 exhibits markedly different behaviours. The Mo, Zr nuclei show rapid onset of deformation, while the Pd, and Ru isotopes show a slower transition from spherical to gamma-soft and triaxial. Much of the evidence for this is based on level energies, particularly away from stability. Lifetimes of excited states provide one of the best tools to understand nuclear structure, but this information is scarce for the shorter lived neutron rich nuclei. We have measured level lifetimes of the A=109 isobars produced from the fission of natural uranium using the Advanced Time-Delay Technique. This technique exploits the fast timing response of LaBr3(Ce) detectors in coincidence with Ge detectors to measure level lifetimes. Details of this technique will be presented along with new results. [Preview Abstract] |
Saturday, November 21, 2015 11:54AM - 12:06PM |
F1.00008: Including higher energy data in the R-matrix extrapolation of $^{12}$C$(\alpha,\gamma)^{16}$O R.J. deBoer, E. Uberseder, R.E. Azuma, A. Best, C. Brune, J. Goerres, D. Sayre, K. Smith, Michael Wiescher The phenomenological $R$-matrix technique has proved to be very successful in describing the cross sections of interest to nuclear astrophysics. One of the key reactions is $^{12}$C$(\alpha,\gamma)^{16}$O, which has frequently been analyzed using $R$-matrix but usually over a limited energy range. This talk will present an analysis that, for the first time, extends above the proton and $\alpha_1$ separation energies taking advantage of a large amount of additional data. The analysis uses the new publicly released JINA $R$-matrix code AZURE2. The traditional reaction channels of $^{12}$C$(\alpha,\gamma)^{16}$O, $^{12}$C$(\alpha,\alpha_0)^{12}$, and $^{16}$N$(\beta\alpha)^{12}$C are included but are now accompanied by the higher energy reactions. By explicitly including higher energy levels, the uncertainty in the extrapolation of the cross section is significantly reduced. This is accomplished by more stringent constraints on interference combination and background poles by the additional higher energy data and by considering new information about subthresold states from transfer reactions. The result is the most comprehensive $R$-matrix analysis of the $^{12}$C$(\alpha,\gamma)^{16}$O reaction to date. [Preview Abstract] |
Saturday, November 21, 2015 12:06PM - 12:18PM |
F1.00009: O-18(p,g)F-19 and Na-23(p,g)Mg-24 at LUNA Andreas Best, Axel Boeltzig, Francesca Pantaleo The Laboratory for Underground Nuclear Astrophysics at the Gran Sasso National Laboratories in Italy has for over 20 been measuring cross sections of interest for stellar nucleosynthesis. We will present a short overview of the facility and showcase two measurements that are part of the current experimental campaign, the reactions O-18(p,g)F-19 and Na-23(p,g)Mg-24. [Preview Abstract] |
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