Dynamics of binary dissipative collisions at GANIL energies

Dynamical aspects associated with the binary dissipative collisions induced by heavy ions at intermediate energies are reviewed. A particular attention is paid to the mid-rapidity emission which is proved to enlight the reaction mechanism. Recent experimental data obtained by the INDRA and DEMON Collaborations as well as new Landau-Vlasov calculations are presented. Consequences on the energy dissipation, on the excitation energy sharing between the partners and on the temperature of the equilibrated fragments are discussed.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Contribution à la chimie des neiges antarctiques. Estimation du taux de déposition de matière extra-terrestre

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Contribution à la chimie des neiges antarctiques. Estimation du taux de déposition de matière extra-terrestre

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

GEOL-F-103: Problème actuels de la gestion de l’énergie

info:eu-repo/semantics/publishe

Le 180mhf dans l'analyse par activation du hafnium

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Fission of medium and heavy nuclei induced by 40Ar from 160 to 300 MeV: Cross sections

Cross sections have been measured for argon-induced fission following full momentum transfer. Two incident energies (between 200 and 300 MeV) have been used for 238U, 209Bi, 165Ho and natMo targets. For a natSb target, the fission excitation function has been measured from 160 to 300 MeV. The experimental method was an improved version of the angular correlation method, which takes into account kinetic energies and time-of-flight correlations. This allowed us to eliminate fission events following transfer reactions and also random events. Assuming that the angular distribution is that characteristic of fission fragments issued from a compound nucleus (close to 1/sinθ) the fission cross sections range from 10 ± 1 mb for Ar + Mo at 200 MeV to 1030 ± 120 mb for Ar + U at 300 MeV. When necessary, these cross sections have been added to the cross sections for the formation of evaporation-residue nuclei measured by other authors in order to obtain complete-fusion cross sections. The deduced critical angular momentum for formation of a complete-fusion nucleus are found to be an increasing function of the mass and energy of the incoming particle. These results are used to test the concept of a critical distance of approach which would govern fusion between two complex nuclei. The threshold of the excitation function measured for Ar + Sb is compared with calculations based on the statistical model for the competition between fission and evaporation. These calculations include the effects of multiple-chance fission and of angular momentum on fission widths. © 1975.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Dynamical effects on the way to fusion of very heavy nuclei

The central collision of 40Ar and 208Pb is studied considering the ellipsoidal deformations and isovector dipole mode of motion in the approaching phase. The collective energy dissipation is suggested to originate from the Fermi surface deformation which is treated as a kinematically independent mode of motion within the canonical Lagrange-Rayleigh dynamics. The possible extensions of the approach are discussed. The potential energy surface, calculated using the generalized (folded) surface potential, is studied. The saddle point in the potential energy surface lying at the border of strongly deformed compact configurations is located. The potential energy at this point is about 10MeV smaller than that of the ions touching each other in the spherical shape. The examination of trajectories followed by the system in its evolution shows that the inertia forces strongly hinder the motion of ions along the potential energy valley. The collective energy dissipated during the approach is found to be smaller than the difference in the potential energies at saddle point and at the touching configuration of unpolarized ions.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

The French-Belgian neutron multidetector facility: The DEMON project

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Chimie des neiges antarctiques et taux de deposition de matiere extraterrestre - deuxieme article

Sodium, magnesium, potassium, calcium, iron, manganese and nickel were measured in firn samples from Base Roi Baudouin (BRB, 70°S, 24°E), Amundsen-Scott Station (ASS, 90°S) and Plateau Station (PLA, 79°S, 40°E). The rates of snow accumulation at the three stations are respectively, in g.cm-2.yr-1 :40, 6 and 2.8. The analyses were carried out by neutron activation, atomic absorption and isotope dilution. In most cases, Fe, Mn, Ni were measured simultaneously by two or three methods on aliquots of the same sample. The corrections for contamination never exceeded 10%. Average concentrations found at BRB (5 samples, 14 kg total) and at PLA (4 samples, 32 kg) respectively are as follows, in p.p.b. Na 250-30; Mg 29-5; K 29-5; Ca 17-8; Mn 0.1-0.35; Fe 6-7; Ni 0.36-0.08. At AAS (2 samples, 3 kg) :Na 9; Mn 0.2; Ni 0.1. On account of the everpresent possibility of contamination, these values must be considered as upper limits. The following conclusions are drawn from the results: 1. 1)SCOPUS: ar.jinfo:eu-repo/semantics/publishe