35 research outputs found
Fusion Hindrance in the Heavy Ion Reactions -- Border Between the Normal and Hindered Fusions
The fusion hindrance in heavy ion collisions is studied in the framework of
the two-center liquid drop model. It appears that the neck and the radial
degrees of freedom might both be hampered by an inner potential barrier on
their path between the contact configuration to the compound nucleus. Heavy ion
reactions with and without the two kinds of fusion hindrance are classified
through systematic calculations. It is found that the number of reactions
without radial fusion hindrance is much smaller than that without neck fusion
hindrance, and for both kinds of fusion hindrance the number of reactions
without fusion hindrance at small mass-asymmetry parameter is smaller
than that at large . In the formation of a given compound nucleus, if a
reaction with is not hindered, then other reactions with are also not hindered as it is well known experimentally.Comment: 14 pages, 7 figure
On the predictions of the models for the Super-Heavy Elements
Nuclear structure calculations predict the existence of super-heavy elements (SHE) that are tentatively synthesized through heavy-ion collisions. A complete description of the reaction to synthesize Super-Heavy Elements is necessary to bridge these predictions with the experimental results on the fission time and residue cross sections. In this contibution, we will present the constraints that can be given on the shell correction energy from experimental data and the developments that are needed for the dynamical models
Diffusion over a saddle with a Langevin equation
The diffusion problem over a saddle is studied using a multi-dimensional
Langevin equation. An analytical solution is derived for a quadratic potential
and the probability to pass over the barrier deduced. A very simple solution is
given for the one dimension problem and a general scheme is shown for higher
dimensions.Comment: 13 pages, use revTeX, to appear in Phys. Rev. E6
Analysis of the Fusion Hindrance in Mass-symmetric Heavy Ion Reactions
The fusion hindrance, which is also denominated by the term extra-push, is
studied on mass-symmetric systems by the use of the liquid drop model with the
two-center parameterization. Following the idea that the fusion hindrance
exists only if the liquid drop barrier (saddle point) is located at the inner
side of the contact point after overcoming the outer Coulomb barrier, the
reactions in which two barriers are overlapped with each other are determined.
It is shown that there are many systems where the fusion hindrance does not
exist for the atomic number of projectile or target nucleus , while
for , all of the mass-symmetric reactions are fusion-hindered.Comment: 6 pages, 4 figures. to be published in Sci. in China
KEWPIE: a dynamical cascade code for decaying exited compound nuclei
A new dynamical cascade code for decaying hot nuclei is proposed and
specially adapted to the synthesis of super-heavy nuclei. For such a case, the
interesting channel is the tiny fraction that will decay through particles
emission, thus the code avoids classical Monte-Carlo methods and proposes a new
numerical scheme. The time dependence is explicitely taken into account in
order to cope with the fact that fission decay rate might not be constant. The
code allows to evaluate both statistical and dynamical observables. Results are
successfully compared to experimental data.Comment: 15 pages, 3 Figures, Submitted to Comp. Phys. Co
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Sunny windy Sundays
Rapid expansion of wind and solar capacity in Great Britain presents challenges for managing electricity systems. One concern is the reduction in system inertia during periods where renewables provide a high proportion of demand which has led to some networks imposing system nonsynchronous penetration limits. However, given the lack of operational data, the relationship between
renewable generation and demand for the full range of meteorological conditions experienced in Great
Britain is poorly understood. This study uses reanalysis datasets to determine the proportion of
demand from renewable generation on an hourly resolution for a 36-year period.
The days with highest penetration of renewables tend to be sunny, windy weekend days between May
and September, when there is a significant contribution of both wind and solar generation and demand
is suppressed due to human behaviour. Based on the current distribution of wind and solar capacity,
there is very little curtailment for all system non-synchronous penetration limits considered. However,
as installed capacity of renewables grows the volume of generation curtailed also increases with a
disproportionate volume occurring at weekends. The total volume of curtailment is highly dependent
on ratio of wind and solar capacity, with the current blend close to the optimum level
Radioactivité dans l’environnement : le rôle des associations de contrôle
Depuis la catastrophe de Tchernobyl, l’opinion publique s’est mobilisée pour demander plus de transparence dans l’établissement de l’impact des accidents nucléaires sur les populations et l’environnement. Dans ce cadre, plusieurs associations participent au contrôle de l’exploitation des centrales nucléaires, en particulier par des mesures de radioactivité, aussi bien en France qu’à l’étranger
Non-Markovian diffusion over a saddle with a Generalized Langevin equation
Pour publication dans "Journal of Statistical Physics"The diffusion over a simple parabolic barrier is exactly solved with a non-Markovian Generalized Langevin Equation. For a short relaxation time, the problem is shown to be similar to a Markovian one, with a smaller effective friction. But for longer relaxation time, the average trajectory starts to oscillate and the system can have a very fast first passage over the barrier. For very long relaxation times, the solution tends to a zero-friction limi
Nouveau programme de Terminale : évaluation numérique des incertitudes de mesures Partie 1 : Concepts et méthodes
International audienceLes incertitudes de mesure, désormais introduites progressivement dès la Seconde, occupent une place importante dans les nouveaux programmes de lycée, qui comportent aussi des capacités numériques. Une d'elles consiste à « simuler, à l'aide d'un langage de programmation, un processus aléatoire illustrant la détermination de la valeur d'une grandeur avec incertitudes-types composées. ». Le but de cet article est d'introduire les concepts liés à l'évaluation des incertitudes et de proposer des méthodes numériques applicables au lycée. Des exemples pour aborder progressivement les notions associées à ces nouvelles capacités seront publiés dans un autre article