Bulletin of the American Physical Society
2012 Fall Meeting of the APS Division of Nuclear Physics
Volume 57, Number 9
Wednesday–Saturday, October 24–27, 2012; Newport Beach, California
Session NE: Nuclear Reactions: Heavy Ions/Rare Isotope Beams |
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Chair: Artemis Spyrou, Michigan State University Room: Garden II |
Saturday, October 27, 2012 8:30AM - 8:42AM |
NE.00001: Asymmetry Dependence of Nuclear Temperatures and Densities Alan McIntosh, A. Bonasera, Z. Kohley, S. Galanopoulos, K. Hagel, L.W. May, P. Marini, D.V. Shetty, W.B. Smith, S.N. Soisson, G.A. Souliotis, B.C. Stein, R. Tripathi, S. Wuenschel, S.J. Yennello Quasi-projectile sources produced in collisions of 70Zn+70Zn, 64Zn+64Zn and 64Ni+64Ni at E/A=35MeV have been reconstructed using the charged particles and free neutrons measured in the NIMROD-ISiS 4-pi detector. Equilibrated sources were selected which have a mass A=48-52 and which are on average spherical. Caloric curves for these quasi-projectiles have been extracted with the quadrupole momentum fluctuation thermometer (QMFT) and the Albergo thermometer. The classical QMFT and the Albergo thermometer exhibit a clear dependence on the composition, (N-Z)/A, of the source. For a given excitation (E*/A), the neutron-poor sources exhibit higher temperatures. The quantum QMFT exhibits a somewhat different dependence on the composition. Since the density and temperature are correlated in the quantum QMFT, this difference may be due to a dependence of the nuclear density on the composition. [Preview Abstract] |
Saturday, October 27, 2012 8:42AM - 8:54AM |
NE.00002: Bulk Nuclear Properties from Pion Yields Jun Hong, Pawel Danielewicz Intermediate energy (100 MeV/A $\sim$ 2 GeV/A) heavy ion collisions have been a powerful tool to extract information on bulk properties of nuclear matter. We find that net pion yields in central collisions are strongly sensitive to the momentum dependence of isoscalar nuclear mean field. We have reexamined the momentum dependence assumed in the Boltzmann equation model for the collisions and have optimized that dependence to describe FOPI pion yield measurements in the Au + Au collisions at different beam energies. The optimized dependence yields values of baryonic elliptic flow that compare favorably with measurements as well. On the other hand, ratios of charged pions from central collisions are believed to provide information about symmetry energy at supranormal densities. While our results differ in detail from some in the literature, we have optimized the observables exploiting differences between the charged pions, to provide the best guidance on the symmetry energy at supranormal densities, in central collision experiments. [Preview Abstract] |
Saturday, October 27, 2012 8:54AM - 9:06AM |
NE.00003: Measurement of the $^{12}$C+$^{12}$C Fusion Reaction with MUSIC P.F.F. Carnelli, S. Almaraz-Calderon, D. Henderson, K.E. Rehm, M. Albers, M. Alcorta, P.F. Bertone, H. Esbensen, J.O. Fernandez-Niello, C.L. Jiang, J.C. Lighthall, S.T. Marley, T. Palchan-Hazan, R.C. Pardo, M. Paul The fusion of the $^{12}$C+$^{12}$C system is of great interest in nuclear structure and nuclear astrophysics. Above the Coulomb barrier, the excitation function of this system exhibits oscillations, which are not well understood. There is also a significant discrepancy between the experimental fusion cross-section and recent coupled-channel calculations that is not present in other carbon systems. To address these issues, we have re-measured the fusion excitation function for $^{12,13}$C+$^{12}$C in the energy range of 10 MeV $<$ E$_{cm}$ $<$ 20 MeV using a Multi-Sampling Ionization Chamber (MUSIC) detector. The gas of the ionization chamber (CH$_{4}$) served as both the target material and the counter gas. One of the main advantages of this method is that the excitation function is measured over a large range of energies using only one beam energy. This method has been proven to be successful and it will be used to measure fusion reactions in other light systems. The experimental results will be presented and compared to previous experimental data and theoretical models. [Preview Abstract] |
Saturday, October 27, 2012 9:06AM - 9:18AM |
NE.00004: Feasibility of using $^{2}$H as a probe in studying iso-scalar giant monopole resonance (ISGMR) in unstable nuclei using inverse kinematics D. Patel, U. Garg, M. Fujiwara, H. Akimune, G.P.A. Berg, M. Itoh, C. Iwamoto, T. Kawabata, K. Kawase, T. Murakami, A. Okamoto, T. Sako, K. Schlax, F. Takahashi, M. White, M. Yosoi Nuclear incompressibility is studied using ISGMR, a collective excitation mode of the nucleus. With the advent of the radioactive ion beam facilities, it would be very interesting to measure the ISGMR strength distributions in nuclei far from the stability line. However, these experiments would have to be done in inverse kinematics and the most appropriate targets would be $^{2}$H and $^{4}$He. However, little is known about ISGMR excitation with $^{2}$H. With this in mind, ISGMR measurements have been made using a $^{2}$H probe at 100 MeV/A at RCNP, Osaka university, Japan. Small-angle inelastic scattering data were obtained for $^{58}$Ni, $^{90}$Zr, and $^{208}$Pb. The results of the ISGMR strengths extracted from the multipole decomposition analysis will be presented. [Preview Abstract] |
Saturday, October 27, 2012 9:18AM - 9:30AM |
NE.00005: The fusion of $^{11}$Li with $^{208}$Pb Walter Loveland, A.M. Vinodkumar, R. Yanez, M. Leonard, L. Yao, P. Bricault, M. Dombsky, P. Kunz, J. Lassen, A.C. Morton, D. Ottewell, D. Preddy, M. Trinczek We studied the fusion of $^{11}$Li with $^{208}$Pb at TRIUMF. The intensity of the $^{11}$Li beam (chopped) was 1000 p/s and the beam on-target time was 114 hours. The stacked foil technique was used to step the beam energies from 40 to 29 MeV (E$_{c.m.}$ = 27-38 MeV) throughout the array. The $\alpha$-decay of the stopped EVRs was detected in a $\alpha$-detector array at each beam energy in the beam-off period. The geometrical efficiency of detection of the decay $\alpha$-particles has been calculated to be 0.4. To verify this, we measured the evaporation residue yield for the well-known $^{7}$Li + $^{209}$Bi reaction. We have previously measured the evaporation residue cross sections when $^{9}$Li, the $^{11}$Li core, fuses with $^{208}$Pb. We also have done HIVAP calculations of what we might expect for evaporation residue cross sections if $^{11}$Li were to fuse with $^{208}$Pb rather than breakup. The At isotope patterns observed on-line are not those observed for the $^{9}$Li + $^{208}$Pb reaction but are consistent for expectations of complete fusion. [Preview Abstract] |
Saturday, October 27, 2012 9:30AM - 9:42AM |
NE.00006: Searching for nuclear excitation by electronic transition in U-235 P. Chodash, E.B. Norman, E. Swanberg, J.T. Burke, R.J. Casperson, S. Wilks Nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that is predicted to occur in numerous isotopes, including U-235. NEET can occur when a nuclear transition closely matches the energy and multipolarity of an electronic transition. U-235 has a 1/2+ isomeric state that decays to the 7/2- ground state with a transition energy of 77 eV and a half life of 26 minutes. Theory predicts that electronic transitions exist within a partially ionized uranium plasma that would allow NEET to occur. The NEET process would excite U-235 into its isomeric state and then it will subsequently decay to the ground state via internal conversion. It is currently not known if this excitation occurs in U-235 and at what rate. In order to generate the uranium plasma with the correct conditions, a high power Q-switched Nd:YAG laser will irradiate a sample of highly enriched uranium. The resulting plasma will be collected on a catcher foil and counted using a microchannel plate detector. Current progress on the experiment will be presented. [Preview Abstract] |
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