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The changes of delayed neutron yields (vd) of Actinides have been analyzed for incident energy up to 20MeV using realized data of precursor after prompt neutron emission, from semi-empirical model, and delayed neutron emission probability data (Pn) to carry out a summation method. The evaluated nuclear data of the delayed neutron yields of actinide nuclides are still uncertain at the present and the cause of the energy dependence has not been fully understood. In this study, the fission yields of precursor were calculated considering the change of the fission fragment mass yield based on the superposition of fives Gaussian distribution; and the change of the prompt neutrons number associated with the incident energy dependence. Thus, the incident energy dependent behavior of delayed neutron was analyzed. The total number of delayed neutron is expressed as vd=ΣYi.Pni in the summation method, where Yi is the mass yields of precursor i and Pni is the delayed neutron emission probability of precursor i. The value of Yi is derived from calculation of post neutron emission mass distribution using 5 Gaussian equations with the consideration of large distribution of the fission fragments. The prompt neutron emission vp increases at higher incident-energy but there are two different models; one model says that the fission fragment mass dependence that prompt neutron emission increases uniformly regardless of the fission fragments mass; and the other says that the major increases occur at heavy fission fragments area. In this study, the changes of delayed neutron yields by the two models have been investigated. [ABSTRACT FROM AUTHOR]

Fragment mass distributions from neutron-induced fission of 232Th and 238U have been measured at quasi-monoenergetic neutron beam of the Louvain-la-Neuve cyclotron facility CYCLONE. The measurements have been carried out making use of a multi-section Frisch-gridded ionization chamber. The measurement technique as well as the data processing is described. Preliminary data on primary fragment mass yields are given for an incident neutron energy of 32.8 MeV. [ABSTRACT FROM AUTHOR]

Neutron capture cross section data on Am isotopes were measured using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory. The neutron capture cross section was determined for 241Am for neutron energies between thermal and 320 keV. Preliminary results were also obtained for 243Am for neutron energies between 10 eV and 250 keV. The results on concurrent neutron-induced fission and neutron-capture measurements on 242mAm will be presented where the fission events were actively triggered during the experiments. In these experiments, a Parallel-Plate Avalanche Counter (PPAC) detector that surrounds the target located in the center of the DANCE array was used as a fission-tagging detector to separate (n,γ) events from (n,f) events. The first direct observation of neutron capture on 242mAm in the resonance region in between 2 and 9 eV of the neutron energy was obtained. [ABSTRACT FROM AUTHOR]

The Detector for Advanced Neutron Capture Experiments (DANCE) is a 4π BaF2 array consisting of 160 active detector elements. The primary purpose of the array is to perform neutron capture cross section measurements on small (>=100 μg) and/or radioactive (<=100 mCi) species. The measurements made possible with this array will be useful in answering outstanding questions in the areas of national security, threat reduction, nuclear astrophysics, advanced reactor design and accelerator transmutation of waste. Since the commissioning of DANCE we have performed neutron capture cross section measurements on a wide array of medium to heavy mass nuclides. Measurements to date include neutron capture cross sections on 241,243Am, neutron capture and neutron-induced fission cross sections and capture-to-fission ratio (α = σγ/σf) for 235U using a new fission-tagging detector as well as neutron capture cross sections for several astrophysics branch-point nuclei. Results from several of these measurements will be presented along with a discussion of additional physics information that can be extracted from the DANCE data. [ABSTRACT FROM AUTHOR]

Prompt fission neutrons and gamma-rays emitted by excited primary fission fragments are indirect probes to the nuclear configurations present near the scission point. By studying detailed characteristics of these quantities, it is shown that one can discriminate between various assumptions regarding the sharing of the free energy at scission among the two fragments. The case of low-energy neutron-induced fission on 235U is studied and interpreted in terms of fission modes. [ABSTRACT FROM AUTHOR]

The Surrogate nuclear reactions method, an indirect approach for determining cross sections for compound-nuclear reactions involving difficult-to-produce targets, is reviewed. The underlying formalism is outlined, the challenges involved in carrying out a complete Surrogate treatment are detailed, and the present status of the theory is summarized. The approximations employed in the analyses of Surrogate experiments are discussed and their validity is examined. [ABSTRACT FROM AUTHOR]

The mass and kinetic energy distribution of nuclear fragments from thermal neutron-induced fission of 235U(nth,f) have been studied using a Monte-Carlo simulation. Besides reproducing the pronounced broadening in the standard deviation of the kinetic energy at the final fragment mass number around m = 109, our simulation also produces a second broadening around m = 125. These results are in good agreement with the experimental data obtained by Belhafaf et al. and other results on yield of mass. We conclude that the obtained results are a consequence of the characteristics of the neutron emission, the sharp variation in the primary fragment kinetic energy and mass yield curves. We show that because neutron emission is hazardous to make any conclusion on primary quantities distribution of fragments from experimental results on final quantities distributions. [ABSTRACT FROM AUTHOR]

High-spin states of 84Se, produced as a fission fragment in the fusion-fission reaction 18O+208Pb and studied with the EUROBALL IV array, have been identified for the first time. Their interpretation gives new insights about the evolution of the N=50 shell gap at the vicinity of 78Ni. To characterize this evolution, it would be worth using a new device devoted to the high-spin studies of neutron-rich nuclei produced by asymetric fission modes. Such dedicated studies are reported in a second part. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Based on the recently measured cross-section values for the neutron-induced fission of 231Pa and our experience gained with other isotopes, new self consistent neutron cross section calculations for n+231Pa have been performed up to 30 MeV. The results are quite different to the existing evaluations, especially above the first chance fission threshold. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The cross-section for the neutron-induced fission of 231Pa has recently been measured from the threshold to En = 3.5 MeV. The experimental results are described in terms of extended statistical model calculations. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Intense radioactive ion beams of the neutron-rich zinc isotopes 69–81Zn have been produced at the isotope separation on-line facility ISOLDE at CERN. The combined use of spallation-neutron induced fission of 238UCx targets and resonant laser ionization provided sufficient suppression of disturbing isobars (mainly gallium and rubidium) to perform decay spectroscopy up to 81Zn. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The future plans of the GANIL/SPIRAL facility related to the SPIRAL∼2 project are presented. In the frame of this project a new superconducting linear driver (LINAG) will deliver a high intensity, 40 MeV deuteron beam as well as a variety of heavy-ion beams with mass over charge ratio equals to 3 and energy up to 14.5 AMeV. Using a carbon converter and the 5 mA deuteron beam, a neutron-induced fission rate is expected be up to 1014 fissions/s for high-density UCx target. In the contribution different schemes of production of intense beams of fission-fragments as: low and high neutron-induced fission, photo-fission and charge-particle-induced fission proposed by several Radioactive Nuclear Beams projects are shortly compared. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The recoil mass spectrometer LOHENGRIN of the Laue-Langevin Institute, Grenoble has been used to measure the light fission-fragment mass yield and kinetic energy distributions from neutron-induced 252Cf*, using 251Cf as target material. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]