651 research outputs found

    2000 BUSINESS ANALYSIS SUMMARY FOR GENERAL CROPS FARMS

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    Crop Production/Industries,

    One-neutron knockout from 57^{57}Ni

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    The single-particle structure of 57^{57}Ni and level structure of 56^{56}Ni were investigated with the \mbox{9^{9}Be (57^{57} Ni,56^{56}Ni+γ\gamma)X\it{X}} reaction at 73 MeV/nucleon. An inclusive cross section of 41.4(12) mb was obtained for the reaction, compared to a theoretical prediction of 85.4 mb, hence only 48(2)% of the theoretical cross section is exhausted. This reduction in the observed spectroscopic strength is consistent with that found for lighter well-bound nuclei. One-neutron removal spectroscopic factors of 0.58(11) to the ground state and 3.7(2) to all excited states of 56^{56}Ni were deduced.Comment: Phys. Rev. C, accepte

    Development of superconducting YBa2Cu3O(x) wires with low resistance electrical contacts

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    Materials exhibiting superconductivity above liquid nitrogen temperatures (77 K) will enable new applications of this phenomena. One of the first commercial applications of this technology will be superconducting magnets for medical imaging. However, a large number of aerospace applications of the high temperature superconducting materials have also been identified. These include magnetic suspension and balance of models in wind tunnels and resistanceless leads to anemometers. The development of superconducting wires fabricated from the ceramic materials is critical for these applications. The progress in application of a patented fiber process developed by Clemson University for the fabrication of superconducting wires is reviewed. The effect of particle size and heat treatment on the quality of materials is discussed. Recent advances made at Christopher Newport College in the development of micro-ohm resistance electrical contacts which are capable of carrying the highest reported direct current to this material is presented

    Nuclear Theory and Science of the Facility for Rare Isotope Beams

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    The Facility for Rare Isotope Beams (FRIB) will be a world-leading laboratory for the study of nuclear structure, reactions and astrophysics. Experiments with intense beams of rare isotopes produced at FRIB will guide us toward a comprehensive description of nuclei, elucidate the origin of the elements in the cosmos, help provide an understanding of matter in neutron stars, and establish the scientific foundation for innovative applications of nuclear science to society. FRIB will be essential for gaining access to key regions of the nuclear chart, where the measured nuclear properties will challenge established concepts, and highlight shortcomings and needed modifications to current theory. Conversely, nuclear theory will play a critical role in providing the intellectual framework for the science at FRIB, and will provide invaluable guidance to FRIB's experimental programs. This article overviews the broad scope of the FRIB theory effort, which reaches beyond the traditional fields of nuclear structure and reactions, and nuclear astrophysics, to explore exciting interdisciplinary boundaries with other areas. \keywords{Nuclear Structure and Reactions. Nuclear Astrophysics. Fundamental Interactions. High Performance Computing. Rare Isotopes. Radioactive Beams.Comment: 20 pages, 7 figure

    S17(0) Determined from the Coulomb Breakup of 83 MeV/nucleon 8B

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    A kinematically complete measurement was made of the Coulomb dissociation of 8B nuclei on a Pb target at 83 MeV/nucleon. The cross section was measured at low relative energies in order to infer the astrophysical S factor for the 7Be(p,gamma)8B reaction. A first-order perturbation theory analysis of the reaction dynamics including E1, E2, and M1 transitions was employed to extract the E1 strength relevant to neutrino-producing reactions in the solar interior. By fitting the measured cross section from Erel = 130 keV to 400 keV, we find S17(0) = 17.8 (+1.4, -1.2) eV b

    Isotopic distribution of fission fragments in collisions between 238U beam and 9Be and 12C targets at 24 MeV/u

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    Inverse kinematics coupled to a high-resolution spectrometer is used to investigate the isotopic yields of fission fragments produced in reactions between a 238U beam at 24 MeV/u and 9Be and 12C targets. Mass, atomic number and isotopic distributions are reported for the two reactions. These informations give access to the neutron excess and the isotopic distribution widths, which together with the atomic-number and mass distributions are used to investigate the fusion-fission dynamics.Comment: Submitted to PR

    Production cross sections from 82Se fragmentation as indications of shell effects in neutron-rich isotopes close to the drip-line

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    Production cross sections for neutron-rich nuclei from the fragmentation of a 82Se beam at 139 MeV/u were measured. The longitudinal momentum distributions of 126 neutron-rich isotopes of elements 11 <= Z <= 32 were scanned using an experimental approach of varying the target thickness. Production cross sections with beryllium and tungsten targets were determined for a large number of nuclei including several isotopes first observed in this work. These are the most neutron-rich nuclides of the elements 22 <= Z <= 25 (64Ti, 67V, 69Cr, 72Mn). One event was registered consistent with 70Cr, and another one with 75Fe. The production cross sections are correlated with Qg systematics to reveal trends in the data. The results presented here confirm our previous result from a similar measurement using a 76Ge beam, and can be explained with a shell model that predicts a subshell closure at N = 34 around Z = 20. This is demonstrated by systematic trends and calculations with the Abrasion-Ablation model that are sensitive to separation energies.Comment: 13 pages, 11 figures, accepted to Phys.Rev.

    Production cross sections of neutron rich isotopes from a 82Se beam

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    Production cross sections for neutron-rich nuclei from the fragmentation of a 82Se beam at 139 MeV/u were measured. The longitudinal momentum distributions of 122 neutron-rich isotopes of elements 11Z3211 \le Z \le 32 were determined by varying the target thickness. Production cross sections with beryllium and tungsten targets were determined for a large number of nuclei including several isotopes first observed in this work. These are the most neutron-rich nuclides of the elements 22Z2522 \le Z \le 25 (64Ti, 67V, 69Cr, 72Mn). One event was registered consistent with 70Cr, and another one with 75Fe. A one-body Qg systematics is used to describe the production cross sections based on thermal evaporation from excited prefragments. The current results confirm those of our previous experiment with a 76Ge beam: enhanced production cross sections for neutron-rich fragments near Z=20.Comment: Talk given at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS

    Measurement of the Gamow-Teller Strength Distribution in 58Co via the 58Ni(t,3He) reaction at 115 MeV/nucleon

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    Electron capture and beta decay play important roles in the evolution of pre-supernovae stars and their eventual core collapse. These rates are normally predicted through shell-model calculations. Experimentally determined strength distributions from charge-exchange reactions are needed to test modern shell-model calculations. We report on the measurement of the Gamow-Teller strength distribution in 58Co from the 58Ni(t,3He) reaction with a secondary triton beam of an intensity of ~10^6 pps at 115 MeV/nucleon and a resolution of \~250 keV. Previous measurements with the 58Ni(n,p) and the 58Ni(d,2He) reactions were inconsistent with each other. Our results support the latter. We also compare the results to predictions of large-scale shell model calculations using the KB3G and GXPF1 interactions and investigate the impact of differences between the various experiments and theories in terms of the weak rates in the stellar environment. Finally, the systematic uncertainties in the normalization of the strength distribution extracted from 58Ni(3He,t) are described and turn out to be non-negligible due to large interferences between the dL=0, dS=1 Gamow-Teller amplitude and the dL=2, dS=1 amplitude.Comment: 14 pages, 8 figure
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