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 A1: Nuclear Astrophysics I |
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Chair: Daniel Bardayan, University of Notre Dame Room: Hesburgh Library Carey Auditorium |
Friday, November 20, 2015 9:00AM - 9:36AM |
A1.00001: Accelerator Mass Spectrometry at the Nuclear Science Laboratory: Applications to Nuclear Astrophysics Invited Speaker: Philippe Collon The Accelerator Mass Spectrometry (AMS) program at the Nuclear Science Laboratory (NSL) of the University of Notre Dame is focused on measurements related to galactic radioactivity and to nucleosynthesis of main stellar burning as well as the production of so called Short-Lived Radionuclides (SLRs) in the Early Solar System (ESS). The research program is based around the 11MV FN tandem accelerator and the use of the gas-filled magnet technique for isobar separation. Using a technique that evolved from radiocarbon dating, this talk will give an overview of the ongoing research at the NSL and then focus on a number of research programs that rely on the use of an 11MV tandem accelerator at the center of the AMS program. [Preview Abstract] |
Friday, November 20, 2015 9:36AM - 9:48AM |
A1.00002: Nuclear Physics of the Outer Crust of Accreting Neutron Stars Zach Meisel The thermal structure of the outer layers of neutron stars that have accreted material from a binary companion impacts a number of astronomical observables, such as the x-ray burst and superburst ignition frequencies and the cooling of transiently accreting neutron stars after accretion turn-off. The thermal and compositional structure of accreted neutron star crusts is determined by the host of nuclear processes occurring on and near the neutron star surface. The thermal structure of the outer crust is primarily determined by the strength of heating and cooling resulting from electron-capture reactions. This talk will discuss the recently discovered shallow Urca cooling process occurring in the neutron star outer crust, with an emphasis on the impact recent nuclear physics results have on the strength of the cooling inferred for the A$=$56 electron-capture chain. The impact of these results on astronomical observations, as well as future directions for shallow Urca cooling research will briefly be discussed. [Preview Abstract] |
Friday, November 20, 2015 9:48AM - 10:00AM |
A1.00003: Measurement campaign for astrophysically relevant $^{\mathrm{36}}$Cl production cross sections Tyler Anderson, Matt Bowers, Michael Skulski, Wenting Lu, Karen Ostdiek, Will Bauder, Philippe Collon, Mary Beard The short-lived radionuclide $^{\mathrm{36}}$Cl (t$_{\mathrm{1/2}}^{\mathrm{\thinspace }}=$ 0.301 Ma) is known to have existed in the Early Solar System (ESS), and evaluating its production sources can lead to better understanding of the processes taking place in ESS formation and their timescales. The x-wind production model is used to explain $^{\mathrm{36}}$Cl production via solar energetic particles from the young Sun, but is lacking empirical data for many relevant reactions. Bowers et al. (2013) measured the cross section of $^{\mathrm{33}}$S($\alpha $,p)$^{\mathrm{36}}$Cl at various energies in the range of 0.70-2.42 MeV/A, and found them to be systematically under predicted by statistical Hauser-Feshbach model codes TALYS and NON-SMOKER, highlighting the need for more empirical data for these cross sections. A recent paper by Mohr (2013) called these results in to question, prompting the re-measurement of the cross section for $^{\mathrm{33}}$S($\alpha $,p)$^{\mathrm{36}}$Cl at new energies in the same energy range as Bowers et al. This talk will also discuss two further planned measurements of cross sections suggested by Bowers et al. to be the next most significant in $^{\mathrm{36}}$Cl production. [Preview Abstract] |
Friday, November 20, 2015 10:00AM - 10:12AM |
A1.00004: Commissioning of the St. George Recoil Separator Christopher Seymour Measurement of alphacapture reactions at energies of astrophysical interest is hindered by low cross sections and relatively high gammabackgrounds. The precision of these measurements, using traditional techniques, is limited by the ability to reduce this gammabackground. Using a recoil separator enables the direct detection of the heavy reaction products. These recoils are separated from the primary beam using a Wienfilter and a series of magnetic dipoles, and then identified using a total energy loss plus time- offlight detection system. A series of commissioning experiments to measure the energy acceptance of the St. George recoil separator are currently underway at Notre Dame. The progress of these measurements will presented, along with plans for upcoming angular acceptance measurements. [Preview Abstract] |
Friday, November 20, 2015 10:12AM - 10:24AM |
A1.00005: A Measurement of 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] |
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