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Sökning: WFRF:(Azaiez F.)

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1.
  • Akkoyun, S., et al. (författare)
  • AGATA - Advanced GAmma Tracking Array
  • 2012
  • Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002 .- 0167-5087 .- 1872-9576. ; 668, s. 26-58
  • Tidskriftsartikel (refereegranskat)abstract
    • The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation γ-ray spectrometer. AGATA is based on the technique of γ-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a γ ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of γ-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector- response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer. © 2011 Elsevier B.V. All rights reserved.
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2.
  • Caceres, L., et al. (författare)
  • Nuclear structure studies of F-24
  • 2015
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 92:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of the F-24 nucleus has been studied at GANIL using the beta decay of O-24 and the in-beam.-ray spectroscopy from the fragmentation of Na-27,Na-28, Ne-25,Ne-26, and Mg-29,Mg-30 nuclei. Combining these complementary experimental techniques, the level scheme of F-24 has been constructed up to 3.6 MeV by means of particle-gamma and particle-gamma gamma coincidence relations. Experimental results are compared to shell-model calculations using the standard USDA and USDB interactions as well as ab initio valence-space Hamiltonians calculated from the in-medium similarity renormalization group based on chiral two- and three-nucleon forces. Both methods reproduce the measured level spacings well, and this close agreement allows unidentified spins and parities to be consistently assigned.
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3.
  • Hadynska-Klek, K., et al. (författare)
  • Quadrupole collectivity in Ca-42 from low-energy Coulomb excitation with AGATA
  • 2018
  • Ingår i: Physical Review C. - : AMER PHYSICAL SOC. - 2469-9985 .- 2469-9993. ; 97:2
  • Tidskriftsartikel (refereegranskat)abstract
    • ACoulomb-excitation experiment to study electromagnetic properties of Ca-42 was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. gamma rays from excited states in Ca-42 were measured with the AGATA spectrometer. The magnitudes and relative signs of ten E2 matrix elements coupling six low-lying states in Ca-42, including the diagonal E2 matrix elements of 2(1)(+) and 2(2)(+) states, were determined using the least-squares code GOSIA. The obtained set of reduced E2 matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for 0(1),(+)(2) and 2(1,2)(+) states, as well as triaxiality for 0(1,2)(+) states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in Ca-42. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in Ca-42.
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4.
  • Hadynska-Klek, K., et al. (författare)
  • Superdeformed and Triaxial States in Ca-42
  • 2016
  • Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 117:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Shape parameters of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in Ca-42 were determined from E2 matrix elements measured in the first low-energy Coulomb excitation experiment performed with AGATA. The picture of two coexisting structures is well reproduced by new state-of-the-art large-scale shell model and beyond-mean-field calculations. Experimental evidence for superdeformation of the band built on 0(2)(+) has been obtained and the role of triaxiality in the A similar to 40 mass region is discussed. Furthermore, the potential of Coulomb excitation as a tool to study superdeformation has been demonstrated for the first time.
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5.
  • Hadynska-Klek, K., et al. (författare)
  • Towards The Determination Of Superdeformation In Ca-42
  • 2013
  • Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 44:3, s. 617-625
  • Tidskriftsartikel (refereegranskat)abstract
    • The Coulomb excitation experiment to study electromagnetic structure of low-lying states in Ca-42 with a focus on a possible superdeformation in this nucleus was performed at the Laboratori Nazionali di Legnaro in Italy. Preliminary values of the determined quadrupole deformation parameters for both the ground state band and the presumed superdeformed band are presented.
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6.
  • Stanoiu, M., et al. (författare)
  • Study of neutron rich carbon and oxygen nuclei up to drip line
  • 2004
  • Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 746, s. 135C-139C
  • Tidskriftsartikel (refereegranskat)abstract
    • In-beam gamma-spectroscopy using fragmentation reactions of radioactive beams have been performed in order to study the structure of excited states in neutron rich oxygen and carbon isotopes. For the produced fragments, gamma-ray energies, intensities and gamma-gamma coincidences have been measured. The experiment was performed at GANIL. New gamma-lines have been identified and placed in level schemes for C17-20. The non observation of any gamma-ray in O-23,O-24 suggests that their first excited states lie above the neutron threshold. These results are discussed in the framework of shell model calculations.
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7.
  • Mason, P, et al. (författare)
  • Octupole signatures in Ba-124,Ba-125
  • 2005
  • Ingår i: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 31:10, s. S1729-S1733
  • Tidskriftsartikel (refereegranskat)abstract
    • The gamma decay of the nuclei Ba-121,Ba-125 has been investigated with the EUROBALL array, using the reaction Ni-64+Ni-64 at E-beam = 255 and 261 MeV. Six new E1 transitions have been found in the nucleus Ba-125, suggesting a significant role of octupole correlations in the origin of its parity doublets. The J(pi) = 3(-) level of the nucleus Ba-124 has been identified for the first time. Its excitation energy is in very good agreement with a prediction based on a microscopic model including octupole interactions.
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8.
  • Stanoiu, M., et al. (författare)
  • Study of drip line nuclei through two-step fragmentation
  • 2004
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 20:1, s. 95-96
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied the structure of light neutron-rich nuclei around N = 16 by employing the in-beam gamma-ray spectroscopy technique using the fragmentation of secondary beams of Ne-25,Ne-26, Na-27,Na-28 and Mg-29,Mg-30 isotopes. This secondary-beam cocktail was obtained by the fragmentation of a 36 S beam at 77.5 MeV.A by the SISSI/GANIL facility. By a second-step fragmentation, we have measured gamma-ray-residue coincidences in C17-20 and O-23,O-24 and described the obtained levels in the framework of the shell model.
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9.
  • Wilson, A. N., et al. (författare)
  • Magnetic dipole bands in 190Hg : First evidence of excitations across the Z = 82 sub-shell in Hg nuclei
  • 2001
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 505:1-4, s. 6-14
  • Tidskriftsartikel (refereegranskat)abstract
    • An experiment aimed at studying high-spin states in 190Hg was performed with the Eurogam II array. The data have revealed the presence of cascades of magnetic dipole transitions with some unexpected properties. Unlike the MI bands previously observed in the heavier Hg isotopes, these structures have extremely large B(M1)/B(E2) ratios, The observation of a third dipole band with much lower B(M1)/B(E2) values in the same spin/excitation energy regime suggests that the bands may represent configurations occurring in different minima in the potential energy surface. Configuration-dependent Cranked Nilsson-Strutinsky calculations predict the presence of a minimum in the nuclear potential energy surface at a deformation of ε ≅ 0.2, γ ≅ -90°, occurring when a proton is excited across the Z = 82 shell-gap into an h9/2 orbital. It is suggested that the bands exhibiting anomalously large B(M1)/B(E2) ratios may be associated with this minimum.
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10.
  • Brownstein, Catherine A., et al. (författare)
  • An international effort towards developing standards for best practices in analysis, interpretation and reporting of clinical genome sequencing results in the CLARITY Challenge
  • 2014
  • Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 15:3, s. R53-
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: There is tremendous potential for genome sequencing to improve clinical diagnosis and care once it becomes routinely accessible, but this will require formalizing research methods into clinical best practices in the areas of sequence data generation, analysis, interpretation and reporting. The CLARITY Challenge was designed to spur convergence in methods for diagnosing genetic disease starting from clinical case history and genome sequencing data. DNA samples were obtained from three families with heritable genetic disorders and genomic sequence data were donated by sequencing platform vendors. The challenge was to analyze and interpret these data with the goals of identifying disease-causing variants and reporting the findings in a clinically useful format. Participating contestant groups were solicited broadly, and an independent panel of judges evaluated their performance. Results: A total of 30 international groups were engaged. The entries reveal a general convergence of practices on most elements of the analysis and interpretation process. However, even given this commonality of approach, only two groups identified the consensus candidate variants in all disease cases, demonstrating a need for consistent fine-tuning of the generally accepted methods. There was greater diversity of the final clinical report content and in the patient consenting process, demonstrating that these areas require additional exploration and standardization. Conclusions: The CLARITY Challenge provides a comprehensive assessment of current practices for using genome sequencing to diagnose and report genetic diseases. There is remarkable convergence in bioinformatic techniques, but medical interpretation and reporting are areas that require further development by many groups.
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11.
  • Clark, R M, et al. (författare)
  • Superdeformation in bismuth
  • 1996
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 53:1, s. 117-123
  • Tidskriftsartikel (refereegranskat)abstract
    • High angular momentum states in Bi-195-197 are populated in two reactions: W-183(F-19,xn)Bi-202-x and Ta-181(Ne-20,xn)Bi-201-x at beam energies of 108 and 123 MeV, respectively. Gamma rays were detected using the Gammasphere array. Three weakly populated rotational sequences have been found. They each have properties characteristic of other superdeformed bands in this mass region. On the basis of cross-bombardment information we believe that one band belongs to each of Bi-195, Bi-196, and Bi-197. The properties of the bands in the odd-Bi nuclei are best reproduced if the odd proton occupies the favored signature of the [651]1/2 orbital, while the band in Bi-196 has this same proton configuration coupled to an additional N=7 (j(15/2)) neutron. The relative behavior of the J((2)) moments of inertia can be qualitatively understood in terms of Pauli-blocking effects.
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12.
  • Stanoiu, M., et al. (författare)
  • Disappearance of the N=14 shell gap in the carbon isotopic chain
  • 2008
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 78:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of C-17-20(6) nuclei was investigated by means of the in-beam gamma-ray spectroscopy technique using fragmentation reactions of radioactive beams. Based on particle-gamma and particle-gamma gamma coincidence data, level schemes are constructed for the neutron-rich C17-20 nuclei. The systematics of the first excited 2(+) states in the carbon isotopes is extended for the first time to A = 20 showing that in contrast to the case of the oxygen isotopes, the N = 14 subshell closure disappears. Experimental results are compared with shell-model calculations. Agreement between them is found only if a reduced neutron-neutron effective interaction is used. Implications of this reduced interaction in some properties of weakly bound neutron-rich Carbon are discussed.
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13.
  • Stanoiu, M., et al. (författare)
  • Spectroscopy of (26)F
  • 2012
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 85:1, s. 017303-
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of the weakly bound (26)(9)F(17) odd-odd nucleus, produced from (27,28)Na nuclei, has been investigated at GANIL by means of the in-beam gamma-ray spectroscopy technique. A single gamma-line is observed at 657(7) keV in (26)(9)F which has been ascribed to the decay of the excited J = 2(+) state to the J = 1(+) ground state. The possible presence of intruder negative parity states in (26)F is also discussed.
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14.
  • Vajta, Zs., et al. (författare)
  • Excited states in the neutron-rich nucleus F-25
  • 2014
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 89:5, s. 054323-
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of the nucleus F-25(9) was investigated through in-beam. gamma-ray spectroscopy of the fragmentation of Ne-26 and Na-27,Na-28 ion beams. Based on the particle-gamma and particle-gamma gamma coincidence data, a level scheme was constructed and compared with shell model and coupled-cluster calculations. Some of the observed states were interpreted as quasi-single-particle states built on top of the closed-shell nucleus O-24, while the others were described as states arising from coupling of a single proton to the 2(broken vertical bar) core excitation of O-24.
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15.
  • Grawe, H, et al. (författare)
  • Experimental approach towards shell structure at Sn-100 and Ni-78
  • 2002
  • Ingår i: Nuclear Physics, Section A. - 0375-9474. ; 704, s. 211-222
  • Tidskriftsartikel (refereegranskat)abstract
    • The status of experimental approach to Sn-100 and Ni-78 is reviewed. Revised single particle energies for neutrons are deduced for the N=Z=50 shell closure and evidence for low lying I-pi=2(+) and 3(-) states is presented. Moderate E2 polarization charges of 0.1 e and 0.6 e are found to reproduce the experimental data when core excitation of Sn-100 is properly accounted for in the shell model. For the neutron rich Ni region no conclusive evidence for an N=40 subshell is found, whereas firm evidence for the persistence of the N=50 shell at Ni-78 is inferred from the existence of seniority isomers. The disappearance of this isomerism in the mid nug(9/2) shell is discussed.
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16.
  • Cederwall, Bo, et al. (författare)
  • NEW OBLATE BAND IN HG-196 WITH QUENCHED M1 STRENGTH
  • 1993
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 47:6, s. R2443-R2446
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in the nucleUs Hg-196 were populated in the reaction (Os(Be,5n))-Os-192 at a beam energy of 65 MeV. A regular rotational-like DELTAI = 1 band has been observed up to an excitation energy of E* almost-equal-to 8.7 MeV and spin I almost-equal-to 30hBAR. This is the second observation of a band of this character in a mercury isotope. The experimental results are compared with mean field calculations and semiclassical estimates based on the Donau-Frauendorf formalism. The mercury bands show significantly lower B(M1)/B(E2) branching ratios as compared with similar bands in light lead nuclei. This difference may be more readily explained by a difference in single-particle structure rather than by large differences in deformation between the lead and mercury configurations.
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17.
  • CLARK, RM, et al. (författare)
  • SUPERDEFORMATION IN THE BISMUTH NUCLEI
  • 1995
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 51:3, s. R1052-R1056
  • Tidskriftsartikel (refereegranskat)
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18.
  • Franchoo, S., et al. (författare)
  • RECENT RESULTS FROM GANIL
  • 2009
  • Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 40:3, s. 419-425
  • Tidskriftsartikel (refereegranskat)abstract
    • The shell structure of the nucleus implies the existence of magic numbers. Since several years many indications have been accumulated, theoretically as well as through experiments at various laboratories around the world, that if one moves away from stability, the location of the magic numbers shifts as an inescapable consequence of the evolving nature of the nuclear force itself. In this respect, it is the balance between the tensor and spin-orbit components that seems particularly instrumental. Illustrative examples from recent experiments at Ganil, at the neutron-rich and proton-rich side of the nuclear chart for N or Z equal 20 or 28, will be presented here.
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19.
  • Lagergren, K, et al. (författare)
  • Coexistence of superdeformed shapes in Er-154
  • 2001
  • Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 8702:2
  • Tidskriftsartikel (refereegranskat)abstract
    • A new superdeformed rotational band has been observed in Er-154 using the Euroball Ge detector array. The new band and the one previously observed can be understood as based on coexisting superdeformed structures at prolate and triaxial shapes, respectively. The observation resolves long-standing difficulties in the theoretical interpretation of superdeformed states in Er-154.
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20.
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21.
  • Podolyak, Z., et al. (författare)
  • gamma-ray spectroscopy with a He-8 beam
  • 2003
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 511:3, s. 354-359
  • Tidskriftsartikel (refereegranskat)abstract
    • The He-8 + Pb-208 reaction was studied in the first experiment with the EXOGAM germanium detector array using beam delivered by the SPIRAL facility. gamma-rays from direct and fusion-evaporation reactions were observed with high resolution. gamma-gamma coincidence data were obtained at a beam intensity level of 105 8He particles per second. Specially designed absorbers and beam detectors could further reduce the background radiation by orders of magnitude.
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22.
  • Podolyak, Zs., P.M.Walker, H.Mach, G.de France, G.Sletten, F.Azaiez, J.M.Casandjian, B.Cederwall, D.M.Cullen, Zs.Dombradi, G.D.Dracoulis, L.M.Fraile, S.Franchoo, H.Fynbo, M.Gorska, Y.Kopatch, G.J.Lane, S.Mandal, L.Milechina, J.Molnar, C.O'Leary, W.Plocien (författare)
  • g-ray spectroscopy with a 8He beam
  • 2003
  • Ingår i: Nucl.Instrum.Methods Phys.Res. A. ; 511, s. 354-
  • Tidskriftsartikel (refereegranskat)
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