64 research outputs found

    High-resolution measurements of the exited states (n,pn), (n,dn) C-12 cross sections

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    Measurements of C12 cross sections for the excited states (n,p 0 ) up to (n,p 4 ) and (n,d 0 ), (n,d 1 ) have been carried out. The Van de Graaff neutron generator of the EC-JRC-IRMM laboratory has been used for these measurements. A very thin tritiated target (263 őľg/cm 2 ) was employed with deuteron beams energies impinging on the target in the range 2.5‚Äď4.0‚ÄČMeV. Neutrons in the range 18.9‚Äď20.7‚ÄČMeV were produced with an intrinsic energy spread of 0.2‚Äď0.25% FWHM. With such narrow neutron energy spread, using a high energy resolution device such as a single crystal diamond detector, several peaks from the outgoing charged particles produced by the (n,p n ), (n,d n ) and also (n,őĪ 0 ) reactions appear in the pulse height spectrum. The peaks can be identified using the reaction Q-values. The diamond detector used for these measurements has shown an intrinsic energy resolution lower than 0.9% FWHM. The analysis of the peaks has permitted to derive the partial carbon reaction cross sections for several excited states. The results are presented in this paper with the associated uncertainties and they are compared with different versions of TENDL compilation when these data are available (e.g. versions 2009, 2010, 2011 and 2015) and also with experimental results available in the EXFOR database

    Viscosity and fission time scale of^{156}Dy

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    In the fusion-fission reaction Ar-40+Cd-116-->Dy-156-->fission, performed at beam energies E(b) = 216 MeV and 238 MeV, gamma rays were measured in coincidence with fission fragments. The gamma-ray spectra are interpreted using a modified version of the statistical-model code CASCADE. From a comparison of the experimental and calculated spectra it is deduced that the nuclear viscosity is in the range 0.01 <gamma <4. The extracted fission time scale is of the order of 10(-19) s

    Lack of evidence for a superdeformed band in^{192}Pb

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    An experiment was performed to measure the lifetimes of the states in the superdeformed band reported in Pb192. No evidence for such a band was found, despite the fact that the experimental conditions were nearly identical to those of an earlier measurement where this band was proposed. The problems and questions encountered in the analysis are described. The arguments presented here indicate that further measurements are needed to establish the existence of a superdeformed band in this nucleus unambiguously

    Fast-neutron induced pre-equilibrium reactions on 55Mn and 63,65Cu at energies up to 40 MeV

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    Excitation functions were measured for the 55^{55}Mn(n,2n)54^{54}Mn, 55^{55}Mn(n,őĪ\alpha)52^{52}V, 63^{63}Cu(n,őĪ\alpha)60^{60}Co, 65^{65}Cu(n,2n)64^{64}Cu, and 65^{65}Cu(n,p)65^{65}Ni reactions from 13.47 to 14.83 MeV. The experimental cross sections are compared with the results of calculations including all activation channels for the stable isotopes of Mn and Cu, for neutron incident energies up to 50 MeV. Within the energy range up to 20 MeV the model calculations are most sensitive to the parameters related to nuclei in the early stages of the reaction, while the model assumptions are better established by analysis of the data in the energy range 20-40 MeV. While the present analysis has taken advantage of both a new set of accurate measured cross sections around 14 MeV and the larger data basis fortunately available between 20 and 40 MeV for the Mn and Cu isotopes, the need of additional measurements below as well as above 40 MeV is pointed out. Keywords: 55Mn, 63,65Cu, E‚ȧ\leq40 MeV, Neutron activation cross section measurements, Nuclear reactions, Model calculations, Manganese, CopperComment: 39 pages, 12 figure

    Preparation and characterization of ¬≥¬≥S samples for ¬≥¬≥S(n,őĪ)¬≥‚ĀįSi cross-section measurements at the n_TOF facility at CERN

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    Thin 33S samples for the study of the 33S(n,őĪ)30Si cross-section at the n_TOF facility at CERN were made by thermal evaporation of 33S powder onto a dedicated substrate made of kapton covered with thin layers of copper, chromium and titanium. This method has provided for the first time bare sulfur samples a few centimeters in diameter. The samples have shown an excellent adherence with no mass loss after few years and no sublimation in vacuum at room temperature. The determination of the mass thickness of 33S has been performed by means of Rutherford backscattering spectrometry. The samples have been successfully tested under neutron irradiation
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