| 1. |
- Rodriguez-Tajes, C., et al.
(författare)
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Isotopic distributions of fission fragments from transfer-induced fission
- 2013
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 47, s. 125-130
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Konferensbidrag (refereegranskat)abstract
- Fissioning systems from U to Cm as well as 250Cf were produced by 238U+12C transfer and fusion reactions. The detection of the target-like transfer partner made the characterization of the fissioning systems in (Z, A) and excitation energy possible. The isotopic identification of the fission fragments was achieved by using the VAMOS spectrometer combined to with reactions in inverse kinematics. Results regarding the populated transfer channels and excitation of the target-like transfer partner are presented, as well as the 240Pu fission probability. Isotopic yields of the fission-fragments for 240,*241Pu and 250Cf, having excitation energies of about 10 and 45 MeV, respectively, are discussed.
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| 2. |
- Farget, F., et al.
(författare)
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Transfer-induced fission in inverse kinematics: Impact on experimental and evaluated nuclear data bases
- 2015
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 51:12, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Inverse kinematics is a new tool to study nuclear fission. Its main advantage is the possibility to measure with an unmatched resolution the atomic number of fission fragments, leading to new observables in the properties of fission-fragment distributions. In addition to the resolution improvement, the study of fission based on nuclear collisions in inverse kinematics beneficiates from a larger view with respect to the neutron-induced fission, as in a single experiment the number of fissioning systems and the excitation energy range are widden. With the use of spectrometers, mass and kinetic-energy distributions may now be investigated as a function of the proton and neutron number sharing. The production of fissioning nuclei in transfer reactions allows studying the isotopic yields of fission fragments as a function of the excitation energy. The higher excitation energy resulting in the fusion reaction leading to the compound nucleus Cf-250 at an excitation energy of 45MeV is also presented. With the use of inverse kinematics, the charge polarisation of fragments at scission is now revealed with high precision, and it is shown that it cannot be neglected, even at higher excitation energies. In addition, the kinematical properties of the fragments inform on the deformation configuration at scission.
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| 3. |
- Hagen, T. W., et al.
(författare)
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Evolution of nuclear shapes in odd-mass yttrium and niobium isotopes from lifetime measurements following fission reactions
- 2017
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Ingår i: Physical Review C: covering nuclear physics. - 2469-9985. ; 95:3
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Tidskriftsartikel (refereegranskat)abstract
- Lifetimes of excited states in Y99,Y101,Nb101,Nb103, and Nb105 were measured in an experiment using the recoil distance Doppler shift method at GANIL (Grand Accélérateur National d'Ions Lourds). The neutron-rich nuclei were produced in fission reactions between a U238 beam and a Be9 target. Prompt γ rays were measured with the EXOGAM array and correlated with fission fragments that were identified in mass and atomic number with the VAMOS++ spectrometer. The measured lifetimes, together with branching ratios, provide B(M1) and B(E2) values for the strongly coupled rotational bands built on the [422]5/2+ ground state in the Y and Nb nuclei with neutron number N≥60. The comparison of the experimental results with triaxial particle-rotor calculations provides information about the evolution of the nuclear shape in this mass region.
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| 4. |
- Ramos, D., et al.
(författare)
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Dependence of Fission-Fragment Properties On Excitation Energy For Neutron-Rich Actinides
- 2016
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. - 9782759819706 ; 111
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Konferensbidrag (refereegranskat)abstract
- Experimental access to full isotopic fragment distributions is very important to determine the features of the fission process. However, the isotopic identification of fission fragments has been, in the past, partial and scarce. A solution based on the use of inverse kinematics to study transfer-induced fission of exotic actinides was carried out at GANIL, resulting in the first experiment accessing the full identification of a collection of fissioning systems and their corresponding fission fragment distribution. In these experiments, a U-238 beam at 6.14 AMeV impinged on a carbon target to produce fissioning systems from U to Am by transfer reactions, and Cf by fusion reactions. Isotopic fission yields of Cf-250, Cm-244, Pu-240, Np-239 and U-238 are presented in this work. With this information, the average number of neutrons as a function of the atomic number of the fragments is calculated, which reflects the impact of nuclear structure around Z=50, N=80 on the production of fission fragments. The characteristics of the Super Long, Standard I, Standard II, and Standard III fission channels were extracted from fits of the fragment yields for different ranges of excitation energy. The position and contribution of the fission channels as function of excitation energy are presented.
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| 5. |
- Ramos, D., et al.
(författare)
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Experimental evidence of the effect of nuclear shells on fission dissipation and time
- 2023
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 107:2
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Tidskriftsartikel (refereegranskat)abstract
- Nuclear fission is still one of the most complex physical processes we can observe in nature due to the interplay of macroscopic and microscopic nuclear properties that decide the result. An example of this coupling is the presence of nuclear dissipation as an important ingredient that contributes to drive the dynamics and has a clear impact on the time of the process. However, different theoretical interpretations, and scarce experimental data make it poorly understood. In this Letter, we present the first experimental determination of the dissipation energy in fission as a function of the fragment split, for three different fissioning systems. The amount of dissipation was obtained through the measurement of the relative production of fragments with even and odd atomic numbers with respect to different initial fission energies. The results reveal a clear effect of particular nuclear shells on the dissipation and fission dynamics. In addition, the relative production of fragments with even and odd atomic numbers appears as a potential contributor to the long-standing problem of the time scale in fission.
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| 6. |
- Ramos, D., et al.
(författare)
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Fission Yields of Minor Actinides at Low Energy Through Multi-nucleon Transfer Reactions of 238U on 12C
- 2015
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Ingår i: Acta Physica Polonica, Series B.. - 1509-5770 .- 0587-4254. ; 46:3, s. 443-446
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Tidskriftsartikel (refereegranskat)abstract
- First preliminary results of fragments distribution as a function of the excitation energy for different fissioning systems from U to Cm and Cf-250 are presented. A new method based on inverse kinematics to study transfer-induced fission of minor actinides was carried out in GANIL in 2008, and again in 2011. In these experiments, a U-238 beam at 6.1 A MeV impinged on a carbon target to produce fissioning systems by multi-nucleon transfer reactions, resulting in the first experiments accessing the full identification of a collection of fissioning systems and their corresponding fission fragments distribution. The excitation energy is deduced from the detection of the recoil nucleus in an angular DE-E stripped silicon telescope, and the identification of the fragments is made possible by the VAMOS spectrometer.
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| 7. |
- Ramos, D., et al.
(författare)
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Insight into excitation energy and structure effects in fission from isotopic information in fission yields
- 2019
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 99:2
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Tidskriftsartikel (refereegranskat)abstract
- The use of the inverse kinematics technique and a magnetic spectrometer permits the simultaneous measurement of proton and neutron content of full fission fragment distributions. This paper reports new measurements of five fissioning systems - U238,Np239,Pu240,Cm244, and Cf250 - produced in inelastic scattering, transfer, and fusion reactions at different excitation energies. As a result, isotopic, elemental, and isotonic fission yields are presented. The contribution of the different fission modes and the proton even-odd effect are studied. Structure effects are investigated by means of the neutron excess and the total neutron multiplicity as a function of the fragment atomic number.
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| 8. |
- Ramos, D., et al.
(författare)
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Isotopic fission-fragment distributions of U-238, Np-239, Pu-240, Cm-244, and Cf-250 produced through inelastic scattering, transfer, and fusion reactions in inverse kinematics
- 2018
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 97:5
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Tidskriftsartikel (refereegranskat)abstract
- Transfer- and fusion-induced fission in inverse kinematics has proved to be a powerful tool to investigate nuclear fission, widening information on the fission fragments and access to unstable fissioning systems with respect to other experimental approaches. An experimental campaign is being carried out at GANIL with this technique since 2008. In these experiments, a beam of U-238, accelerated to 6.1 MeV/u, impinges on a C-12 target. Fissioning systems from U to Cf are populated through inelastic scattering, transfer, and fusion reactions, with excitation energies that range from a few MeV up to 46 MeV. The use of inverse kinematics, the SPIDER telescope, and the VAMOS spectrometer allow the characterization of the fissioning system in terms of mass, nuclear charge, and excitation energy, and the isotopic identification of the full fragment distribution. This work reports on new data from the second experiment of the campaign on fission-fragment yields of the heavy actinides U-238, Np-239, Pu-240, Cm-244, and Cf-250, which are of interest from both fundamental and application points of view.
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| 9. |
- Rodriguez-Tajes, C., et al.
(författare)
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Transfer reactions in inverse kinematics: An experimental approach for fission investigations
- 2014
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 89:2
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Tidskriftsartikel (refereegranskat)abstract
- Inelastic and multinucleon transfer reactions between a U-238 beam, accelerated at 6.14 MeV/u, and a C-12 target were used for the production of neutron-rich, fissioning systems from U to Cm. A Si telescope, devoted to the detection of the targetlike nuclei, provided a characterization of the fissioning systems in atomic and mass numbers, as well as in excitation energy. Cross sections and angular and excitation-energy distributions were measured for the inelastic and transfer channels. Possible excitations of the targetlike nuclei were experimentally investigated for the first time, by means of gamma-ray measurements. The decays from the first excited states of 12C, B-11, and Be-10 were observed with probabilities of 0.12-0.14, while no evidence for the population of higher-lying states was found. Moreover, the fission probabilities of U-238, Np-239 and Pu-240,Pu-241,Pu-242 and Cm-244 were determined as a function of the excitation energy.
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