770 research outputs found
Low-energy radioactive beam experiments using the UM-UND solenoid RNB apparatus at the UND tandem: Past, present and future
Approximately ten years ago (1987) one of the first operational low-energy radioactive nuclear beam (RNB) facilities was put into place at the University of Notre Dame (UND) as a joint project between the University of Michigan (UM) and UND. The key elements to the success of the project were the installation of a large-bore 3.5 Tesla superconducting solenoid (supplied by UM) to collect and focus secondary radioactive beams, combined with an upgrade of the UND FN Tandem, the latter including the addition of a high-intensity sputter ion source. The resulting secondary beams (8Li,8Li, 6He,6He, 7Be,7Be, 8B,8B, 18Fm,18Fm, …) are generally produced by selective, high-cross-section direct reactions. These beams are sufficiently intense (viz. 104/s104/s to 108/s108/s) to permit measurement of many low-energy reaction cross sections of interest to nuclear astrophysics, nuclear reaction theory, and high-isospin nuclear physics. A review of past and recent RNB data obtained with this apparatus will be presented together with plans for a major upgrade using a pair of 6T solenoids (M. Y. Lee et al.−this conference). © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87532/2/369_1.pd
Structure Effects on Coulomb Dissociation of B
Coulomb Dissociation provides an alternative method for determining the
radiative capture cross sections at astrophysically relevant low relative
energies. For the breakup of B on Ni, we calculate the total Coulomb
Dissociation cross section and the angular distribution for E1, E2 and M1. Our
calculations are performed first within the standard first order semiclassical
theory of Coulomb Excitation, including the correct three body kinematics, and
later including the projectile-target nuclear interactions.Comment: 6 pages, proceedings from International Workshop on RNB, Puri, India,
January 1998 - to be published in J. Phys.
Neutron Transfer reactions induced by 8Li on 9Be
Angular distributions for the elastic scattering of 8Li on 9Be and the
neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been
measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for
8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between
the experimental differential cross section and finite-range DWBA calculations
with the code FRESCO. The spectroscopic factors obtained are compared to shell
model calculations and to other experimental values from (d,p) reactions. Using
the present values for the spectroscopic factor, cross sections for the direct
neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the
framework of a potential model.Comment: 24 pages, 8 Figures, submitted as regular article to PR
TriSol: a major upgrade of the TwinSol RNB facility
We report here on the recent upgrade of the TwinSol radioactive nuclear beam
(RNB) facility at the University of Notre Dame. The new TriSol system includes
a magnetic dipole to provide a second beamline and a third solenoid which acts
to reduce the size of the radioactive beam on target.Comment: submitted to Nuclear Instruments and Methods
Reaction and proton-removal cross sections of Li, Be, B, C, ^{12N, O and Ne on Si at 15 to 53 MeV/nucleon
Excitation functions for total reaction cross sections, , were
measured for the light, mainly proton-rich nuclei Li, Be, B,
C, N, O, and Ne incident on a Si telescope
at energies between 15 and 53 MeV/nucleon. The telescope served as target,
energy degrader and detector. Proton-removal cross sections, for
Ne and for most of the other projectiles, were also measured.
The strong absorption model reproduces the -dependence of , but
not the detailed structure. Glauber multiple scattering theory and the JLM
folding model provided improved descriptions of the measured values.
radii, extracted from the measured using the optical limit of
Glauber theory, are in good agreement with those obtained from high energy
data. One-proton removal reactions are described using an extended Glauber
model, incorporating second order noneikonal corrections, realistic single
particle densities, and spectroscopic factors from shell model calculations.Comment: 16 pages, 6 figure
Astrophysical S17(0) factor extraction from breakup of 8B on 58Ni at energies near the Coulomb barrier
We have performed continuum-discretized coupled channels (CDCC) calculations of the breakup of 8B on 58Ni and direct proton transfer for the 8B+58Ni system at laboratory energies of 20-28.4 MeV. The influence of the 7Be core-target optical potential (OP) on the breakup cross section was investigated. Elastic scattering angular distributions for the 7Be+58Ni and 8B+58Ni systems at five different energies around the Coulomb barrier were studied, and a reasonable energy-independent OP for each system was obtained. Using these OPs and two different 7Be-p relative motion wave functions, and summing breakup and direct proton transfer contributions, we were able to fit the experimental cross section at a 8B laboratory energy of 25.75 MeV. We calculated the excitation function for the 7Be emission in the 8B+58Ni reaction, where 7Be products were measured at the forward angle θlab=45° in the energy interval Elab=20-28.4 MeV. In view of the peripheral character of the B8 breakup reaction at near-barrier energies, we could extract the asymptotic normalization coefficient for the 7Be-p system, which was found to be CBe-p,p3/22=0.543±0.027 fm-1. Finally, the astrophysical S17(0) factor was found to be S17(0)=20.8±1.1 eV b.Ministerio de Ciencia e Innovación FPA2006-13807-c02-01Programa Consolider-Ingenio 2010 CSD2007-0004
Transfer/Breakup Modes in the 6He+209Bi Reaction Near and Below the Coulomb Barrier
Reaction products from the interaction of 6He with 209Bi have been measured
at energies near the Coulomb barrier. A 4He group of remarkable intensity,
which dominates the total reaction cross section, has been observed. The
angular distribution of the group suggests that it results primarily from a
direct nuclear process. It is likely that this transfer/breakup channel is the
doorway state that accounts for the previously observed large sub-barrier
fusion enhancement in this system.Comment: 4 pages; 3 figure
Approximations in Fusion and Breakup reactions induced by Radioactive Beams
Some commonly used approximations for complete fusion and breakup
transmission coefficients in collisions of weakly bound projectiles at near
barrier energies are assessed. We show that they strongly depend on the adopted
classical trajectory and can be significantly improved with proper treatment of
the incident and emergent currents in the WKB approximation.Comment: 15 pages, 7 figure
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