377 research outputs found
Théories de l'accueil, puisque tous les chemins y mènent
No full textSource : Amphore du Berry. « Nous n'avons pas toujours le regard adéquat pour appréhender les phénomènes émergents. Nous tendons à les approcher avec des grilles de lectures anciennes et nous concluons alors que rien n'a changé ». Jacques Lévy, « Vers la société-monde ? », in M.-F. Durand, J. Lévy et D. Retaillé, Le Monde, espaces et systèmes, Dalloz-Sirey, 1992. La Ville Accueillante ((HANAPPE Cyrille et al., 2018 : La ville accueillante – Accueillir à Grande-Synthe. Question théoriques et p..
Bimodal fission of Hs*
No full textMass and energy distributions of fission fragments obtained in the reactions 22Ne + 249Cf, 26Mg + 248Cm, and 22Ne + 238U have been measured. A special attention will be paid on the properties of mass-energy distribution of fission fragments obtained in the reaction 26Mg + 248Cm at an excitation energy of 35 MeV. At this energy shell effects should become more effective in fission, the TKE distribution of symmetric fragments obtained in the reaction 26Mg + 248Cm differs strongly from a Gaussian shape. Besides a low-energy component, a high-energy component, not foreseen in the LDM, arises. This is attributed to the fact that both fission fragments are close to the spherical neutron shell N 82. It means that for the compound nucleus 274Hs*, formed in the reaction 26Mg + 248Cm, the phenomenon of bimodal fission was observed for the first time. For the compound nucleus 260No* formed in the reaction 22Ne + 238U at the initial excitation energy of 41 MeV the bimodal fission as well as superasymmetric fission were observed. © Published under licence by IOP Publishing Ltd.SCOPUS: cp.jinfo:eu-repo/semantics/publishe
The fusion-fission process in the reaction 34S+186W near the interaction barrier
No full textThe reaction S-34 + W-186 at E-lab=160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The coupling of the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fission process and gives information regarding production of neutron-rich heavy nuclei. The FF-gamma coincidence method is of better use then the gamma - gamma coincidence method when dealing with low statistic measurements and also offers the opportunity to precisely correct the Dopler shift for in-flight emitted gamma rays.
Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting a specific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented
Fission Dynamics in the Proton Induced Fission of Actinide Nuclei at Intermediate Energies
No full textA multi-parameter correlation study of the reactions 232Th(p,f), 238U(p,f) and 242Pu(p,f) at E_{p}=13, 20, 40 and 55 MeV has been conducted. The fission fragment mass, total kinetic energy distributions, double differential neutron spectra and \gamma-ray spectra have been measured. The three humped shape of mass distributions has been observed up to higher proton energy. Pre-equilibrium, pre-scission and post-scission neutron and \gamma-ray multiplicities measured in coincidence with primary fission fragments provided access to fission dynamics. Shell structure effects were observed in fission fragment mass distributions even at high excitation energy. Manifestation of the nuclear shell Z = 28 near fragment mass A_{fr} = 78 has been detected
DEMON : a thermometer and a clock for fusion-fission dynamics studies: an introduction
No full textThe DEMON program on the study of the fusion-fission dynamics is presented. After a brief review of the present status in this field, the motivations are discussed and the main characteristics of the detector are described.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Dynamics of binary collisions in Kr + Ho at 60 MeV/u with DEMON
No full textResults of the E236 experiment performed at GANIL in 1994 concerning the 86Kr+165Ho binary dissipative collisions at 60 MeV / u are presented. A continuation to this experiment, the E236a experiment planned in 1998, is also presented.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
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