Many-Body Nuclear Dynamics Group: Research

The focus of our research is heavy-ion reaction dynamics spanning the range from the Coulomb barrier to intermediate energies (upto 200A MeV). Our research emphases are:

  • near and sub-barrier fusion of neutron-rich light-ions (relevant to the crust of neutron stars and X-ray superbursts), as shown here.
  • possible suppression of the fusion probability in the deep sub-barrier regime.
  • probing the nuclear equation of state (EOS), in particular how the density dependence of the symmetry energy affects the properties of nuclear matter; and the interplay between the statistical and dynamical break-up of nuclei under extreme conditions of density, temperature, shape, and isospin (neutron-proton asymmetry).
  • fission barriers of neutron-deficient sub-actinides.

    Our experimental research program requires the continual development of sophisticated detectors and associated electronics. We have played a leading role in developing segmented arrays using silicon strip technology (LASSA, HiRA) which provide isotopically resolved identification of reaction products  formed in nuclear reactions (IMFs and LCPs). Our recent development of an advanced multi-channel signal processing system (MASE) also is a major enhancement in our ability to detect these products with good angular resolution using highly segmented detector arrays. Since 2008 we have been engaged in developing sub-nanosecond timing with highly segmented silicon detectors (SiEFUS). Coupled to novel microchannel plate detectors this is an efficient approach for the investigation of near barrier fusion with radioactive beams of neutron-rich light-ions.


  • Calulations performed with a microscopic model, namely Density Constrainted Time Dependent Hartree Fock (DC-TDHF), show the story of a collision of a 20O nucleus with a 12C nucleus for Ecm = 9.5 MeV and b = 2.5 fm. The only parameter in the model is the effective nucleon-nucleon interaction. While the collision leads to complete fusion, neck formation, surface vibrations and density fluctuations can be observed. Credits to V. Oberacker and S. Umar from Vanderbilt University for the calculations.

     

    By examining the dE-E of a charged particle as it passes through a telescope stack of Si-Si-CsI(Tl), we can determine both the atomic number (Z) and mass number (A), as well as the energy (E) of the incident particle. Shown at the right is a two-dimensional plot of the dE-E from a Si-CsI portion of a LASSA telescope. The discrete bands correspond to nuclei of different Z and A. Bands corresponding to 11,12,13,14C are clearly visible. More detailed analysis reveals low yields for neutron deficient 10C and neutron-rich 16C.

     

    The two dimensional correlation between energy and time-of-flight for 20O beam traversing an MCP detector and then implanting in an S2 silicon detector is shown on the right. The MCP, with a 12C foil, was used in an active target mode. Beam scattering of the 12C target as well as of the MCP grids are clearly observed.

     

    The SAND array (Silicon Array at Notre Dame) consists of six wedge shaped strip detectors and two annular double-sided strip detectors as shown to the left. This array provides the possibility of covering a large fraction of the solid angle while providing good energy and time resolution (FWHM <50 keV and <2ns respectively). This array is flexible and the detectors can be re-organzied to meet specific experiment needs.
    Also shown to the right is the vacuum chamber built in the Machine Shop at IU-Chemistry to host the SAND array. This chamber was designed to reach pressure in the low 10-8 torrs.

     

    Upcoming Experiments

    MSU Expt. 15214: Exploring fusion of neutron-rich mid-mass nuclei as a trigger for an X-ray superburst

    Recent Experiments

    GANIL Expt. E575S: Near and sub-barrier fusion of neutron-rich light-ions
    GANIL Expt. E432: Probing the nuclear equation of state
    TAMU, 64Zn + 64Zn, 209Bi, 27Al at E/A = 45 MeV: Decay properties of nuclei under extreme conditions
    MSU, HiRA experiments: Transfer reaction, probing the nuclear equation of state
    LBL, Fission experiments in the Pb region



    E-mail us: Romualdo T. deSouza