Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session ME: Nuclear Reactions/Rare Isotope Beams III |
Hide Abstracts |
Chair: David Morrissey, Michigan State University Room: 103AB |
Saturday, October 29, 2011 8:30AM - 8:42AM |
ME.00001: Interaction and reaction cross sections calculations in the Glauber theory framework Ivan Novikov, Yuli Shabelski The parameters of nuclear densities can be extracted from the comparison between experimentally measured interaction cross sections and reaction or interaction cross sections calculated in optical approximation or using exact expressions of the Glauber theory. The difference between reaction and interaction cross sections between stable isotopes with atomic weight $A<40$ was calculated in various approximations as well as using exact expressions. In addition, the cross sections of the processes with excitation or disintegration of one or both nuclei were calculated in the same approximations. Lastly, we will discuss the accuracy of the obtained results. [Preview Abstract] |
Saturday, October 29, 2011 8:42AM - 8:54AM |
ME.00002: Exploration of the possible new island of inversion with the production of neutron rich nuclei T. Baumann, O.B. Tarasov, A.M. Amthor, L. Bandura, D. Bazin, J.S. Berryman, A. Gade, T.N. Ginter, M. Hausmann, D.J. Morrissey, A. Nettleton, J. Pereira, M. Portillo, B.M. Sherrill, A. Stolz, C. Sumithrarachchi, M. Thoennessen, D. Weisshaar, N. Fukuda, N. Inabe, T. Kubo, G. Chubarian Recent experiments at the NSCL have demonstrated that fragmentation coupled with two-stage separation technique can be used to explore the properties of very neutron-rich nuclei. Production cross sections for a large number of neutron-rich nuclei produced from the fragmentation of a 76Ge beam at 132 MeV/u with beryllium and tungsten targets were measured, including 15 new isotopes of the elements 17 $\le $ Z $\le $ 25. The higher cross sections of several new nuclei relative to a simple thermal evaporation framework, previously shown to describe similar production cross sections, indicate that nuclei in the region around 62Ti might be more stable than predicted by current mass models. This could indicate the existence of a new island of inversion. This year, a newly-developed primary beam of 82Se at 140 MeV/u has been used to extend these measurements of production cross sections to even more neutron-rich isotopes for elements from calcium to cobalt. [Preview Abstract] |
Saturday, October 29, 2011 8:54AM - 9:06AM |
ME.00003: Evolution of fragmentation momentum distributions with mass K. Meierbachtol, D.J. Morrissey, M. Mosby, D. Bazin Parallel momentum distributions of fragmentation products as a function of fragment mass have been used extensively to understand the fragmentation mechanism. Mass dependencies of the perpendicular momentum distributions, however, are much less well-understood. Complete momentum distributions of projectile-like fragments produced in $^{76}$Ge+$^{9}$Be and $^{76}$Ge+$^{197}$Au reactions have been measured using a 130 MeV/nucleon beam. Parallel distributions of all fragments follow established mass systematics, regardless of target species. However, the perpendicular distributions of fragments produced with the $^{197}$Au target that are near the projectile mass contain a clear peak near the grazing momentum that diminishes in significance as fragment mass decreases, a deviation from predictions. In addition, proton-pickup fragments were also observed to peak away from zero degrees. The origin of this peak and its systematic variation will be discussed in the context of fragmentation reaction mechanisms. [Preview Abstract] |
Saturday, October 29, 2011 9:06AM - 9:18AM |
ME.00004: Measurement of Excitation Energy of Neon Prefragments M. Mosby, D.J. Morrissey, M. Thoennessen Projectile fragmentation forms the basis for beam production at radioactive beam facilities such as the National Superconducting Cyclotron Laboratory (NSCL), yet uncertainties remain about the specifics of the production mechanism. For example, very little is known about the excitation energy of the precursors of the observed final fragments. In the present work, neon isotopes produced in the fragmentation of a $^{32}$Mg beam at 86 MeV/nucleon on a Beryllium target, ranging in mass loss from $\Delta$A = 3-10, were observed and the coincident neutrons were detected using the Modular Neutron Array (MoNA). A strong correlation between the neutron multiplicities and fragmentation mass loss was observed, and the variation compares well to that from a statistical evaporation model. [Preview Abstract] |
Saturday, October 29, 2011 9:18AM - 9:30AM |
ME.00005: A feasibility study on the production of $^{235m}$U by nuclear excitation by electronic transition Perry Chodash, Eric Norman, Erik Swanberg, Jason Burke, Mau Chen, Mark Foord Nuclear excitation by electronic transition (NEET) is predicted to occur in nuclei where a nuclear transition closely matches the energy and multipolarity of an electronic transition. NEET is considered to be the inverse of bound internal conversion. This rare form of excitation is predicted to occur in many nuclei. In $^{235}$U, the 1/2+ isomeric state decays to the 7/2- ground state with a transition energy of 77 eV and a half life of 26 minutes. This decay proceeds by internal conversion emitting a low energy electron. In order for NEET to occur in uranium, it must be partially ionized to create an electronic configuration that has a transition that matches the nuclear transition. Numerous experiments have been performed to search for this excitation mechanism in $^{235}$U by creating a plasma using either a laser or an electron beam. The difficulty in finding this excitation is due to the low excitation rates, 10$^{-9 }$s$^{-1 }$to 1 s$^{-1}$, as well as the ability to detect the low energy internal conversion electrons. The results of previous experiments as well as the current experimental plan will be discussed. [Preview Abstract] |
Saturday, October 29, 2011 9:30AM - 9:42AM |
ME.00006: Search for the inverse fission of uranium W. Loveland, R. Yanez, J. Beckerman, M. Leonard, G. Pettersson, C.J. Gross, D. Shapira, J.F. Liang, Z. Kohley, R.L. Varner A search for the ``inverse fission'' of uranium has been made. Two ``inverse fission'' reactions were studied, the reaction of $^{124}$Sn + $^{100}$Mo and the reaction of $^{132}$Sn + $^{100}$Mo. In the former case, evaporation residues were searched for using (a) in-beam $\alpha $-spectroscopy, (b) post-irradiation $\alpha $-spectroscopy and (c) in-beam detection of recoiling evaporation residues while in the latter case, the evaporation residue, $^{230}$U was searched for using post irradiation radio-analytical techniques. Data acquisition and analysis is on-going with expected upper limits or production cross sections of $<$ 1 microbarn. The implications of these results for determining the fusion probability, P$_{CN}$, in the collisions of massive nuclei are discussed. [Preview Abstract] |
Saturday, October 29, 2011 9:42AM - 9:54AM |
ME.00007: The ratio technique: a new way to study exotic nuclei Pierre Capel, Ron Johnson, Filomena Nunes The study of exotic nuclear structures, like halo nuclei, is usually performed through indirect techniques, such as reactions. Unfortunately, the complexity of the reaction mechanism renders the analysis of measurements more difficult than initially thought. Here, we present a new way to extract information about the structure of halo nuclei through reactions. The basic idea of this new technique is to perform the ratio of angular distributions for breakup and scattering. The recoil excitation and breakup (REB) model [1] predicts this observable to be independent of the projectile-target interaction, and hence to reveal detailed information on the structure of these nuclei. We have checked the validity of this approach within the dynamical eikonal approximation [2]. Our calculations show this ratio to be fairly independent of the reaction mechanism and thus to provide a unique way to measure halo wave functions.\\[4pt] [1] R. Johnson, J. Al-Khalili, and J. Tostevin, Phys. Rev. Lett. 79, 2771 (1997)\\[0pt] [2] D. Baye, P. Capel, and G. Goldstein, Phys. Rev. Lett. 95, 082502 (2005) [Preview Abstract] |
Saturday, October 29, 2011 9:54AM - 10:06AM |
ME.00008: Investigation of the Affect of a Coulomb Force on Velocity Distributions in Multifragmentation L. Heilborn, G. Souliotis, S. Soisson, P. Cammarata, P. Marini, L.W. May, A. McIntosh, A. Raphelt, B. Stein, S. Yennello The relationship between the N/Z of the fragmenting source and the nature of its subsequent fragmentation was studied in the reaction of $^{32}$S with $^{112}$Sn at 45 MeV/nucleon. Isotopically resolved Light Charged Particles (LCPs) Intermediate Mass Fragments (IMFs) were measured with the FAUST Array. The velocity distribution of $^7$Li was observed to be asymmetric and backward peaked in the frame of the moving quasiprojectile (QP). We observed a clear shift in the peak of the velocity distributions of the emitted towards the quasitarget (QT) as the particles of a given Z become more neutron-rich. In order to investigate the velocity distributions of the emitted fragments, a theoretical simulation consisting of Deep Inelastic Transfer followed by Statistical Multifragmentation for the system was run for different distances between the QP and the QT at the time of breakup. The proximity of the QP to the QT at the time of breakup in SMM does affect the distribution of fragments in the QP frame. However, the effect is diminished when an experimental filter is applied. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700