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[en] The fragmentation of heavy beams at intermediate energy and the opportunities offered by this in the exploration of heavy nuclei near the drip lines will be discussed. First, a study of ¹⁹⁷Au projectile fragmentation at 30 MeV/nucleon will be presented in which an appreciable number of new p-rich nuclei were observed. Perspectives of proton radioactivity studies using the fragmentation approach will be discussed. Second, a study of the fission of ²³⁸U projectiles at 20 MeV/nucleon will be presented, where a number of new neutron rich nuclei were identified. Production rates of extremely n-rich nuclides from a typical projectile-fragmentation facility are given. A large number of nuclei along the astrophysical reprocess path can be investigated and approach of the neutron dripline in the region Z = 45-50 may be possible. The ability to produce and study these either p-rich or n-rich nuclei at intermediate (and possibly lower) energy facilities may open a variety of possibilities for experimental studies of exotic heavy nuclei. (author)

[en] We measured the capture-fission excitation functions for the ³²S+¹⁸¹Ta reaction and the ³⁸S+¹⁸¹Ta reaction. (The radioactive ³⁸S beam was produced by projectile fragmentation.) In the ³²S-induced reaction, an incomplete fusion component was observed at high energies, with an average linear momentum transfer corresponding to the escape of an α particle. The deduced interaction barrier heights were 130.7±0.3 and 124.8±0.3 MeV for the ³²S- and ³⁸S-induced reactions, respectively. No differences between the two reactions were observed beyond a simple shift in the interaction barrier height

[en] The symmetry energy is an important quantity in the equation of state of isospin asymmetric nuclear matter. This currently unknown quantity is key to understanding the structure of systems as diverse as the neutron-rich nuclei and neutron stars. At TAMU, we have carried out studies, aimed at understanding the symmetry energy, in a variety of reactions such as, the multifragmentation of 40Ar, 40Ca + 58Fe, 58Ni and 58Ni, 58Fe + 58Ni, 58Fe reactions at 25 - 53 AMeV, and deep-inelastic reactions of 86Kr + 124,112Sn, 64,58Ni (25 AMeV), 64Ni + 64,58Ni, 112,124Sn, 232Th, 208Pb (25 AMeV) and 136Xe + 64,58Ni, 112,124Sn, 232Th, 197Au (20 AMeV). Here we present an overview of some of the results obtained from these studies. The results are analyzed within the framework of statistical and dynamical models, and have important implications for future experiments using beams of neutron-rich nuclei

[en] The density dependence of the symmetry energy in the equation of state of isospin asymmetric nuclear matter is of significant importance for studying the structure of systems as diverse as the neutron-rich nuclei and the neutron stars. A number of reactions using the dynamical and the statistical models of multifragmentation, and the experimental isoscaling observable, are studied to extract information on the density dependence of the symmetry energy. It is observed that the dynamical and the statistical model calculations give consistent results assuming the sequential decay effect in dynamical model to be small. A comparison with several other independent studies is also made to obtain important constraints on the form of the density dependence of the symmetry energy. The comparison rules out an extremely 'stiff' and 'soft' forms of the density dependence of the symmetry energy with important implications for astrophysical and nuclear physics studies

[en] The density dependence of the symmetry energy in the equation of state of isospin asymmetric nuclear matter is studied using the isoscaling of the fragment yields and the antisymmetrized molecular dynamic calculation. It is observed that the experimental data at low densities are consistent with the form of symmetry energy, E_sym≅31.6(ρ/ρ_circle)^0.69, in close agreement with those predicted by the results of variational many-body calculation. A comparison of the present result with those reported recently using the NSCL-MSU data suggests that the heavy ion studies favor a dependence of the form, E_sym≅31.6(ρ/ρ_circle)^γ, where γ=0.6-1.05. This constrains the form of the density dependence of the symmetry energy at higher densities, ruling out an extremely 'stiff' and 'soft' dependences

[en] This paper deals with heavy-ion peripheral reactions in the Fermi energy region for the production of neutron-rich isotopes. Experimental data of projectile fragments from the reactions of an ⁴⁰Ar beam at 15 MeV/nucleon with ⁶⁴Ni and ⁵⁸Ni targets, collected with the MARS spectrometer at the Cyclotron Institute of Texas A&M University, are considered. Momentum distributions, which provide valuable information on the reaction mechanisms, are extracted and compared with two types of calculations: These are, the Deep Inelastic Transfer (DIT) model and the microscopic Constrained Molecular Dynamics model (CoMD). For the latter, the parameters of the original code were systematically varied in order to achieve an overall satisfactory description of the experimental data. Our results will be discussed.

[en] The evolution of the symmetry energy coefficient of the binding energy of hot fragments with increasing excitation is explored in multifragmentation processes following heavy-ion collisions below the Fermi energy. In this work, high-resolution mass spectrometric data on isotopic distributions of projectile-like fragments are systematically compared to calculations involving the statistical multifragmentation model (SMM). Within the SMM picture, the present study suggests a gradual decrease of the symmetry energy coefficient of the hot primary fragments from 25 MeV at the compound nucleus regime towards 15 MeV in the multifragmentation regime. The isotopic distributions of the hot primary fragments are found to be very wide and extend towards the neutron drip line. These findings are expected to have important implications in the modeling of the composition and the evolution of hot and dense astrophysical environments, such as those of core-collapse supernova

[en] Several methods have been used to determine the temperatures of systems formed in multifragmentation reactions. From these temperatures, caloric curves can be constructed and possible nuclear phase transitions can be explored. This work presents a previously observed, low temperature phase transition predicted by a theoretical simulation, and an experimental proposal to observe this transition. The proposed experiment will explore what types of reactions produce fragments near the phase transition temperature, and expand the range of fragments that can be detected in this low temperature region.

[en] Current advances in technology have enabled dramatic improvements to the performance of multi-detector arrays within the last 10 years. FAUST is a forward array of 68 Si-CsI(Tl) detector telescopes that has been in use since 1996. To take full advantage of current technology, FAUST has undergone an overhaul installing new preamplifiers from Zepto Systems and modifications to allow for Dual-Axis Dual-Lateral position sensitive detectors to be installed. A new calibration software package has also been developed utilizing a novel linearization algorithm. The combination of these upgrades has led to isotopic identification for elements in the Z = 1-13 range and has greatly increased the angular resolution of the array.