209 research outputs found

    Microcanonical studies concerning the recent experimental evaluations of the nuclear caloric curve

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    The microcanonical multifragmentation model from [Al. H. Raduta and Ad. R. Raduta, Phys. Rev. C 55, 1344 (1997); 56, 2059 (1997); 59, 323 (1999)] is refined and improved by taking into account the experimental discrete levels for fragments with A≤6A \le 6 and by including the stage of sequential decay of the primary excited fragments. The caloric curve is reevaluated and the heat capacity at constant volume curve is represented as a function of excitation energy and temperature. The sequence of equilibrated sources formed in the reactions studied by the ALADIN group (197^{197}Au+197^{197}Au at 600, 800 and 1000 MeV/nucleon bombarding energy) is deduced by fitting simultaneously the model predicted mean multiplicity of intermediate mass fragments (MIMFM_{IMF}) and charge asymmetry of the two largest fragments (a12a_{12}) versus bound charge (ZboundZ_{bound}) on the corresponding experimental data. Calculated HeLi isotopic temperature curves as a function of the bound charge are compared with the experimentally deduced ones.Comment: 13 pages, 4 figure

    Spallation reactions. A successful interplay between modeling and applications

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    The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200 MeV deuterons and 400 MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. The same year R. Serber describes the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a worskhop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie

    The GALLEX Project

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    AbstractThe GALLEX collaboration aims at the detection of solar neutrinos in a radiochemical experiment employing 30 tons of Gallium in form of concentrated aqueous Gallium-chloride solution. The detector is primarily sensitive to the otherwise inaccessible pp-neutrinos. Details of the experiment have been repeatedly described before [1-7]. Here we report the present status of implementation in the Laboratori Nazionali del Gran Sasso (Italy). So far, 12.2 tons of Gallium are at hand. The present status of development allows to start the first full scale run at the time when 30 tons of Gallium become available. This date is expected to be January, 1990

    TRANSFER REACTIONS BETWEEN 18O IONS AND LIGHT NUCLEI

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    Les sections efficaces expérimentales des réactions de transfert de deux neutrons18O(18O, 20O)16O et 14C(18O, 20O)12C sont comparées aux sections efficaces des réactions de transfert d'un neutron correspondantes. Aux énergies incidentes proches de la barrière coulombienne, on observe des sections efficaces considérablement plus grandes pour les réactions de transfert de deux neutrons. Les fonctions d'excitation et les distributions angulaires expérimentales de la réaction de transfert de deux neutrons 26Mg(18O, 16O)28Mg sont comparées à des calculs faits dans le cadre de l'approximation de Born avec ondes déformées et du modèle diffractionnel.The experimental 18O(18O, 20O)16O and 14C(18O, 20O)12C 2-neutron transfer reaction cross sections are compared with the corresponding single-neutron transfer reactions. The 2-neutron transfer reactions are found to have a considerably larger cross section at bombarding energies near the Coulomb barrier. The experimental excitation function and angular distribution of the 26Mg(18O, 16O)28Mg 2-neutron transfer reaction are compared to calculations based on the DWBA method and the diffraction model
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