33 research outputs found
Comparative Study of Multifragmentation of Gold Nuclei Induced by Relativistic Protons, He, and C
Multiple emission of intermediate-mass fragments has been studied for the
collisions of p, He and C on Au with the setup FASA. The mean
IMF multiplicities (for the events with at least one IMF) are saturating at the
value of for the incident energies above 6 GeV. The observed IMF
multiplicities cannot be described in a two-stage scenario, a fast cascade
followed by a statistical multifragmentation. Agreement with the measured IMF
multiplicities is obtained by introducing an intermediate phase and modifying
empirically the excitation energies and masses of the remnants.
The angular distributions and energy spectra from the p-induced collisions
are in agreement with the scenario of ``thermal'' multifragmentation of a hot
and diluted target spectator. In the case of C+Au(22.4 GeV) and
He(14.6 GeV)+Au collisions, deviations from a pure thermal break-up are
seen in the energy spectra of the emitted fragments, which are harder than
those both from model calculations and from the measured ones for p-induced
collisions. This difference is attributed to a collective flow.Comment: 33 pages 15 figures, accepted in Nucl. Phys.
Nuclear Skins and Halos in the Mean-Field Theory
Nuclei with large neutron-to-proton ratios have neutron skins, which manifest
themselves in an excess of neutrons at distances greater than the radius of the
proton distribution. In addition, some drip-line nuclei develop very extended
halo structures. The neutron halo is a threshold effect; it appears when the
valence neutrons occupy weakly bound orbits. In this study, nuclear skins and
halos are analyzed within the self-consistent Skyrme-Hartree-Fock-Bogoliubov
and relativistic Hartree-Bogoliubov theories for spherical shapes. It is
demonstrated that skins, halos, and surface thickness can be analyzed in a
model-independent way in terms of nucleonic density form factors. Such an
analysis allows for defining a quantitative measure of the halo size. The
systematic behavior of skins, halos, and surface thickness in even-even nuclei
is discussed.Comment: 22 RevTeX pages, 22 EPS figures included, submitted to Physical
Review
Monitoring fissile and matrix materials in closed containers by means of pulsed neutron sources
Computational and experimental studies of the possibility of determining the fissile and matrix materials by means of differential neutron attenuation are presented. The time response of 235U fission under the action of 14 MeV neutrons from an ING-07T pulsed neutron generator, fabricated by VNIIA, on a 70-liter steel container holding uranium in graphite, iron and polyethylene matrices is analyzed. It is shown that milligram quantities of 235U can be detected and the matrix type and density as well as the location of fissile material inside a container can be determined.\ua92013 Springer Science+Business Media New York
Seismogeological analysis of the pre-Jurassic sediment complexes of the South Kara syneclise in connection with the tectonic zoning of the sedimentary cover
Total charge-changing cross sections for neutron-rich light nuclei
Total charge-charging cross sections at relativistic energies on a carbon target have been measured for the light stable and neutron-rich radioactive nuclei "1"4Be, "1"0"-"1"9B, "1"2"-"2"0C, "1"4"-"2"3N, "1"6"-"2"4O, and "1"8"-"2"7F. A combined analysis of interaction and total charge-changing cross sections allows to draw definite conclusions concerning the thickness of the neutron skins or the size of the neutron halos for very neutron-rich isotopes. The obtained cross sections are also important in astrophysical applications to describe the propagation of galactic cosmic rays through the interstellar medium. A simple parameterization can reproduce the total charge-changing cross section within an accuracy of 5% for light nuclei from the valley of #beta#-stability up to the drip line. These systematics improve the predictive capability of the formulae used to describe the unknown cross sections. (orig.)Available from TIB Hannover: RO 801(2000-07) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman