16 research outputs found

    A high efficiency, low background detector for measuring pair-decay branches in nuclear decay

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    We describe a high efficiency detector for measuring electron-positron pair transitions in nuclei. The device was built to be insensitive to gamma rays and to accommodate high overall event rates. The design was optimized for total pair kinetic energies up to about 7 MeV.Comment: Accepted for publication by Nucl. Inst. & Meth. in Phys. Res. A (NIM A

    High-resolution spectroscopy of decay pathways in the 12C(12C,γ) reaction

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    The decay branchings of a resonance in the 12C(12C,γ)24Mg reaction at Ec.m. = 8.0 MeV have been studied with high resolution using the Gammasphere array. Radiative capture residues were discriminated from scattered beam and the dominant evaporation channels using the fragment mass analyzer coupled to a multistage Parallel Grid Avalanche Counter (PGAC)/ion chamber system. The clean selection of residues has allowed the population of excited states up to 10 MeV in 24Mg to be examined in detail. Strong feeding of an excited Kπ=0- band is observed. A Jπ = 4+ assignment to the resonance is strongly favored

    High-resolution spectroscopy of decay pathways in the C-12(C-12,gamma) reaction

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    The decay branchings of a resonance in the 12C(12C,γ)24Mg reaction at Ec.m. = 8.0 MeV have been studied with high resolution using the Gammasphere array. Radiative capture residues were discriminated from scattered beam and the dominant evaporation channels using the fragment mass analyzer coupled to a multistage Parallel Grid Avalanche Counter (PGAC)/ion chamber system. The clean selection of residues has allowed the population of excited states up to 10 MeV in 24Mg to be examined in detail. Strong feeding of an excited Kπ=0− band is observed. A Jπ = 4+assignment to the resonance is strongly favored

    Neutron single-particle strength outside the N=50 core

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    The single-neutron properties of N = 51 nuclei have been studied with the (d,p) and (α,3He) reactions, at beam energies of 15 and 50 MeV respectively, on 88Sr, 90Zr, and 92Mo targets. The light reaction products were momentum analyzed using a conventional magnetic spectrometer. Additionally, the 2H(86Kr,p) reaction was measured at a beam energy of 10 MeV/u, where outgoing light ions were analyzed using a helical-orbit spectrometer. Absolute cross sections and angular distributions corresponding to the population of different final states in the heavy product were obtained for each reaction. Spectroscopic factors were extracted and centroids of the single-particle strength were deduced. The observations appear consistent with calculations based on an evolution of single-particle structure driven by the nucleon-nucleon forces acting between valence protons and neutrons

    HELIOS - Progress and possibilities

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    The helical orbit spectrometer, HELIOS, at Argonne National Laboratory has been developed to measure transfer reactions in inverse kinematics with good Q-value resolution. The technique is discussed alongside examples of measurements with medium-mass beams, the first exploration of reactions in the the forward hemisphere, and a future outlook. © Published under licence by IOP Publishing Ltd
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