Microscopic calculations of double and triple Giant Resonance excitation in heavy ion collisions

We perform microscopic calculations of the inelastic cross sections for the double and triple excitation of giant resonances induced by heavy ion probes within a semicalssical coupled channels formalism. The channels are defined as eigenstates of a bosonic quartic Hamiltonian constructed in terms of collective RPA phonons. Therefore, they are superpositions of several multiphonon states, also with different numbers of phonons and the spectrum is anharmonic. The inclusion of (n+1) phonon configurations affects the states whose main component is a n-phonon one and leads to an appreacible lowering of their energies. We check the effects of such further anharmonicities on the previous published results for the cross section for the double excitation of Giant Resonances. We find that the only effect is a shift of the peaks towards lower energies, the double GR cross section being not modified by the explicity inclusion of the three-phonon channels in the dynamical calculations. The latters give an important contribution to the cross section in the triple GR energy region which however is still smaller than the experimental available data. The inclusion of four phonon configurations in the structure calculations does not modify the results.Comment: Revtex4, to be published in PR

New antineutrino energy spectra predictions from the summation of beta decay branches of the fission products

In this paper, we study the impact of the inclusion of the recently measured beta decay properties of the $^{102;104;105;106;107}$Tc, $^{105}$Mo, and $^{101}$Nb nuclei in an updated calculation of the antineutrino energy spectra of the four fissible isotopes $^{235, 238}$U, and $^{239,241}$Pu. These actinides are the main contributors to the fission processes in Pressurized Water Reactors. The beta feeding probabilities of the above-mentioned Tc, Mo and Nb isotopes have been found to play a major role in the $\gamma$ component of the decay heat of $^{239}$Pu, solving a large part of the $\gamma$ discrepancy in the 4 to 3000\,s range. They have been measured using the Total Absorption Technique (TAS), avoiding the Pandemonium effect. The calculations are performed using the information available nowadays in the nuclear databases, summing all the contributions of the beta decay branches of the fission products. Our results provide a new prediction of the antineutrino energy spectra of $^{235}$U, $^{239,241}$Pu and in particular of $^{238}$U for which no measurement has been published yet. We conclude that new TAS measurements are mandatory to improve the reliability of the predicted spectra.Comment: 10 pages, 2 figure

Antineutrino emission and gamma background characteristics from a thermal research reactor

The detailed understanding of the antineutrino emission from research reactors is mandatory for any high sensitivity experiments either for fundamental or applied neutrino physics, as well as a good control of the gamma and neutron backgrounds induced by the reactor operation. In this article, the antineutrino emission associated to a thermal research reactor: the OSIRIS reactor located in Saclay, France, is computed in a first part. The calculation is performed with the summation method, which sums all the contributions of the beta decay branches of the fission products, coupled for the first time with a complete core model of the OSIRIS reactor core. The MCNP Utility for Reactor Evolution code was used, allowing to take into account the contributions of all beta decayers in-core. This calculation is representative of the isotopic contributions to the antineutrino flux which can be found at research reactors with a standard 19.75\% enrichment in $^{235}$U. In addition, the required off-equilibrium corrections to be applied to converted antineutrino energy spectra of uranium and plutonium isotopes are provided. In a second part, the gamma energy spectrum emitted at the core level is provided and could be used as an input in the simulation of any reactor antineutrino detector installed at such research facilities. Furthermore, a simulation of the core surrounded by the pool and the concrete shielding of the reactor has been developed in order to propagate the emitted gamma rays and neutrons from the core. The origin of these gamma rays and neutrons is discussed and the associated energy spectrum of the photons transported after the concrete walls is displayed.Comment: 14 pages, 11 figures, Data in Appendix A and B (13 pages

Anharmonic vibrations in nuclei

In this letter, we show that the non-linearitites of large amplitude motions in atomic nuclei induce giant quadrupole and monopole vibrations. As a consequence, the main source of anharmonicity is the coupling with configurations including one of these two giant resonances on top of any state. Two-phonon energies are often lowered by one or two MeV because of the large matrix elements with such three phonon configurations. These effects are studied in two nuclei, 40Ca and 208Pb

Reactor monitoring and safeguards using antineutrino detectors

Nuclear reactors have served as the antineutrino source for many fundamental physics experiments. The techniques developed by these experiments make it possible to use these very weakly interacting particles for a practical purpose. The large flux of antineutrinos that leaves a reactor carries information about two quantities of interest for safeguards: the reactor power and fissile inventory. Measurements made with antineutrino detectors could therefore offer an alternative means for verifying the power history and fissile inventory of a reactors, as part of International Atomic Energy Agency (IAEA) and other reactor safeguards regimes. Several efforts to develop this monitoring technique are underway across the globe.Comment: 6 pages, 4 figures, Proceedings of XXIII International Conference on Neutrino Physics and Astrophysics (Neutrino 2008); v2: minor additions to reference

First measurements with a new β\beta-electron detector for spectral shape studies

The shape of the spectrum corresponding to the electrons emitted in $\beta$ decay carries a wealth of information about nuclear structure and fundamental physics. In spite of that, few dedicated measurements have been made of $\beta$-spectrum shapes. In this work we present a newly developed detector for $\beta$ electrons based on a telescope concept. A thick plastic scintillator is employed in coincidence with a thin silicon detector. First measurements employing this detector have been carried out with mono-energetic electrons from the high-energy resolution electron-beam spectrometer at Bordeaux. Here we report on the good reproduction of the experimental spectra of mono-energetic electrons using Monte Carlo simulations. This is a crucial step for future experiments, where a detailed Monte Carlo characterization of the detector is needed to determine the shape of the $\beta$-electron spectra by deconvolution of the measured spectra with the response function of the detector. A chamber to contain two telescope assemblies has been designed for future $\beta$-decay experiments at the Ion Guide Isotope Separator On-Line facility in Jyv\"askyl\"a, aimed at improving our understanding of reactor antineutrino spectra

A non-perturbative approach to halo breakup

The theory of weakly bound cluster breakup, like halo nucleus breakup, needs an accurate treatment of the transitions from bound to continuum states induced by the nuclear and Coulomb potentials. When the transition probability is not very small, a non-perturbative framework might be necessary. Nuclear excitation dominates at small impact parameters whereas the Coulomb potential being long range acts over a larger impact parameter interval. In this article, we propose an effective breakup amplitude which meets a number of requirements necessary for an accurate quantitative description of the breakup reaction mechanism. Furthermore our treatment gives some insight on the interplay between time dependent perturbation theory and sudden approximation and it allows to include the nuclear and Coulomb potentials to all orders within an eikonal-like framework.Comment: 22 Latex pages, 1 table, 8 eps figures. Accepted for publication on Nucl. Phys.

Anharmonic vibrations in nuclei

We show that the non-linearities of large amplitude motions in atomic nuclei induce giant quadrupole and monopole vibrations. As a consequence, the main source of anharmonicity is the coupling with configurations including one of these two giant resonances on top of any state. Two-phonon energies are often lowered by one or two MeV because of the large matrix elements with such three phonon configurations. These effects are studied in two nuclei, 40Ca and 208Pb

Les Jessour dans le Sud-Est tunisien : un système hydro-agricole ancestral dans un milieu aride

Malgré un bilan hydrique largement déficitaire dans le Sud-Est tunisien à climat aride, l'Homme a pu pratiquer l'agriculture en développant la technique des Jessour. Cette technique est confrontée aujourd'hui au risque d'abandon suite aux changements socio-économiques qu'a connus cette région au cours des cinq dernières décennies. Cet article fait le point de l'intérêt hydro-agricole des Jessour et présente les grandes lignes d'une recherche visant à évaluer le bilan hydrique de parcelles utilisant cette technique. Le but est de participer à la conservation de ce savoir-faire ancestral et d'optimiser son utilisation

Emergence of Biofuel Production Chain in Mali and Madagascar: Governance and Risk Management

La biomasse a suscité, ces dernières années, un intérêt renouvelé pour la production d’énergie. L’attention s’est focalisée, entre autres, sur les agrocarburants et sur les pays du Sud pour la production de biomasse. En Afrique, la majorité des filières agrocarburants sont à l’heure actuelle dans une phase d’émergence. Au Mali et à Madagascar, ces dernières visent principalement la valorisation des graines de jatropha, pour l’électrification rurale ou le transport (biodiesel pour le marché national, ou huile végétale pure pour l’export). Dans la littérature en économie des filières, la plupart des analyses s’intéressent au mode de gouvernance et aux stratégies de gestion du risque dans des filières d’ores et déjà établies. L’exemple des agro carburants produits à partir du Jatropha offre l’opportunité de s’interroger sur les processus de construction des filières. Il permet d’analyser les stratégies de gestion de risque dans un contexte de nombreuses incertitudes, liées non seulement à la nécessaire coordination d’activités de production agricoles et de distribution d’énergie, mais aussi au caractère méconnu de la culture, à la mise au point de procédés de conversion énergétique adaptés aux contextes africains et à l’adoption de nouvelles pratiques par les distributeurs d’énergie ou les consommateurs finaux. Sur la base de l’analyse des dynamiques en cours au Mali et à Madagascar, l’objectif de l’article est double. Il vise tout d’abord à identifier les opérateurs qui jouent un rôle moteur dans le développement des filières Jatropha et à analyser leurs outils de gouvernance. Il étudie ensuite la façon dont ces opérateurs « moteurs » mobilisent ces outils de gouvernance pour gérer les risques de production, de transformation et de mise en marché