4,675 research outputs found
Nuclear structure and reaction studies at SPIRAL
The SPIRAL facility at GANIL, operational since 2001, is described briefly.
The diverse physics program using the re-accelerated (1.2 to 25 MeV/u) beams
ranging from He to Kr and the instrumentation specially developed for their
exploitation are presented. Results of these studies, using both direct and
compound processes, addressing various questions related to the existence of
exotic states of nuclear matter, evolution of new "magic numbers", tunnelling
of exotic nuclei, neutron correlations, exotic pathways in astrophysical sites
and characterization of the continuum are discussed. The future prospects for
the facility and the path towards SPIRAL2, a next generation ISOL facility, are
also briefly presented.Comment: 48 pages, 27 figures. Accepted for publication in Journal of Physics
Fusion11 Conference Summary
A summary account of the conference "Fusion11", held in Saint Malo, France,
May 2-6, 2011.Comment: 10 pages, 13 figure
Cooper pair transfer in nuclei
The second order DWBA implementation of two-particle transfer direct
reactions which includes simultaneous and successive transfer, properly
corrected by non-orthogonality effects is tested with the help of controlled
nuclear structure and reaction inputs against data spanning the whole mass
table, and showed to constitute a quantitative probe of nuclear pairing
correlations
Strong coupling effects in near-barrier heavy-ion elastic scattering
Accurate elastic scattering angular distribution data measured at bombarding
energies just above the Coulomb barrier have shapes that can markedly differ
from or be the same as the expected classical Fresnel scattering pattern
depending on the structure of the projectile, the target or both. Examples are
given such as 18O + 184W and 16O + 148,152Sm where the expected rise above
Rutherford scattering due to Coulomb-nuclear interference is damped by coupling
to the target excited states, and the extreme case of 11Li scattering, where
coupling to the 9Li + n + n continuum leads to an elastic scattering shape that
cannot be reproduced by any standard optical model parameter set. The recent
availability of high quality 6He, 11Li and 11Be data provides further examples
of the influence that coupling effects can have on elastic scattering.
Conditions for strong projectile-target coupling effects are presented with
special emphasis on the importance of the beam-target charge combination being
large enough to bring about the strong coupling effects. Several measurements
are proposed that can lead to further understanding of strong coupling effects
by both inelastic excitation and nucleon transfer on near-barrier elastic
scattering. A final note on the anomalous nature of 8B elastic scattering is
presented as it possesses a more or less normal Fresnel scattering shape
whereas one would a priori not expect this due to the very low breakup
threshold of 8B. The special nature of 11Li is presented as it is predicted
that no matter how far above the Coulomb barrier the elastic scattering is
measured, its shape will not appear as Fresnel like whereas the elastic
scattering of all other loosely bound nuclei studied to date should eventually
do so as the incident energy is increased, making both 8B and 11Li truly
"exotic".Comment: Review articl
Barrier Distributions as a Tool to Investigate Fusion and Fission
The recent availability of precisely measured fusion cross-sections has
enabled the extraction of a representation of the distribution of barriers
encountered during fusion. These representations, obtained from a variety of
reactions, provide a direct observation of how the structure of the fusing
nuclei changes the inter-nuclear potential landscape, thus affecting the fusion
probability. Recent experiments showing the effects of static quadrupole and
hexadecapole deformation, single-- and double-phonon states, transfer of
nucleons between two nuclei, and high lying excited states are reviewed. The
application of these concepts to the explanation of the anomalous
fission-fragment anisotropies observed following reactions with actinides is
discussed.Comment: 12 pages, To be published in the Proceedings of the NN 97 Conference,
Gatlinburg, Tennessee, June 1997 (Nucl. Phys. A
Mechanisms for Direct Breakup Reactions
We review some simple mechanisms of breakup in nuclear reactions. We mention
the spectator breakup, which is described in the post-form DWBA. The relation
to other formulations is also indicated. An especially important mechanism is
Coulomb dissociation. It is a distinct advantage that the perturbation due to
the electric field of the nucleus is exactly known. Therefore firm conclusions
can be drawn from such measurements. Some new applications of Coulomb
dissociation for nuclear astrophysics are discussed.Comment: 17 pages, 5 figures, to appear in the proceedings of the RCNP-TMU
Symposium on Spins in Nuclear and Hadronic Reactions, October 16-18 199
Astrophysical S factor for the radiative capture 12N(p,gamma)13O determined from the 14N(12N,13O)13C proton transfer reaction
The cross section of the radiative proton capture reaction on the drip line
nucleus 12N was investigated using the Asymptotic Normalization Coefficient
(ANC) method. We have used the 14N(12N,13O)13C proton transfer reaction at 12
MeV/nucleon to extract the ANC for 13O -> 12N + p and calculate from it the
direct component of the astrophysical S factor of the 12N(p,gamma)13O reaction.
The optical potentials used and the DWBA analysis of the proton transfer
reaction are discussed. For the entrance channel, the optical potential was
inferred from an elastic scattering measurement carried out at the same time
with the transfer measurement. From the transfer, we determined the square of
the ANC, C^2(13Og.s.) = 2.53 +/- 0.30 fm-1, and hence a value of 0.33(4) keVb
was obtained for the direct astrophysical S factor at zero energy. Constructive
interference at low energies between the direct and resonant captures leads to
an enhancement of Stotal(0) = 0.42(5) keVb. The 12N(p,gamma)13O reaction was
investigated in relation to the evolution of hydrogen-rich massive Population
III stars, for the role that it may play in the hot pp-chain nuclear burning
processes, possibly occurring in such objects.Comment: 15 pages, 10 figures, 3 tables submitted to Phys. Rev.
Spectroscopy of Na: Bridging the two-proton radioactivity of Mg
The unbound nucleus Na, the intermediate nucleus in the two-proton
radioactivity of Mg, was studied by the measurement of the resonant
elastic scattering reaction Ne(p,Ne)p performed at 4 A.MeV.
Spectroscopic properties of the low-lying states were obtained in a R-matrix
analysis of the excitation function. Using these new results, we show that the
lifetime of the Mg radioactivity can be understood assuming a sequential
emission of two protons via low energy tails of Na resonances
- âŠ