| 1. |
- Chatillon, A., et al.
(författare)
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Accurate measurements of fission-fragment yields in U-234,U-235,U-236,U-238(gamma,f) with the SOFIA set-up
- 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
- SOFIA (Studies On Fission with Aladin) is a new experimental set-up dedicated to accurate measurement of fission-fragments isotopic yields. It is located at GSI, the only place to use inverse kinematics at relativistic energies in order to study the (gamma,f) electromagnetic-induced fission. The SOFIA set-up is a large-acceptance magnetic spectrometer, which allows to fully identify both fission fragments in coincidence on the whole fission-fragment range. This paper will report on fission yields obtained in U-234,U-235,U-236,U-238(gamma,f) reactions.
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| 2. |
- Elter, Zsolt, 1987, et al.
(författare)
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Energy Correlation of Prompt Fission Neutrons
- 2016
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. - 9782759819706 ; 111, s. Art no 05003-
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Konferensbidrag (refereegranskat)abstract
- In all cases where neutron fluctuations in a branching process (such as in multiplicity measurements) are treated in an energy dependent description, the energy correlations of the branching itself (energy correlations of the fission neutrons) need to be known. To date, these are not known from experiments. Such correlations can be theoretically and numerically derived by modelling the details of the fission process. It was suggested earlier that the fact that the prompt neutrons are emitted from the moving fission targets, will influence their energy and angular distributions in the lab system, which possibly induces correlations. In this paper the influence of the neutron emission process from the moving targets on the energy correlations is investigated analytically and via numerical simulations. It is shown that the correlations are generated by the random energy and direction distributions of the fission fragments. Analytical formulas are derived for the two-point energy distributions, and quantitative results are obtained by Monte-Carlo simulations. The results lend insight into the character of the two-point distributions, and give quantitative estimates of the energy correlations, which are generally small.
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| 3. |
- 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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| 4. |
- Alberdi, Antxon, et al.
(författare)
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The jet of the Low Luminosity AGN of M81. Evidence of Precession
- 2013
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 61
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Konferensbidrag (refereegranskat)abstract
- In this contribution, we summarize our main results of a big campaign of global VLBI observations of the AGN in M81 (M81*) phase-referenced to the radio supernova SN 1993J. Thanks to the precise multi-epoch and multi-frequency astrometry, we have determined the normalized core-shift of the relativistic jet of M81* and estimated both the magnetic field and the particle density at the jet base. We have also found evidence of jet precession in M81* coming from the systematic time evolution of the jet orientation correlated with changes in the overall flux density.
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| 5. |
- Audouin, L., et al.
(författare)
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High-precision measurement of isotopic fission yields of 236 U
- 2018
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 193
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Konferensbidrag (refereegranskat)abstract
- We report on the second SOFIA experiment, dedicated to the fission yields of 236U∗, analog to 235U(n,f). The measurement is based on the inverse kinematics method, using a relativistic, secondary beam of 236U. Both fission fragments are identified in mass and charge in the SOFIA recoil spectrometer. The obtained isotopic yields are compared with existing spectroscopy measurements and the elemental yields are used to discuss the treatment of the even-odd effect with energy in nuclear data libraries.
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| 6. |
- Babaahmadi, Arezou, 1985, et al.
(författare)
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Electrochemical migration technique to accelerate ageing of cementitious materials
- 2013
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. - 9782759810468 ; 56
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Konferensbidrag (refereegranskat)abstract
- Durability assessment of concrete structures for constructions in nuclear waste repositories requires long term service life predictions. As deposition of low and intermediate level radioactive waste (LILW) takes up to 100 000 years, it is necessary to analyze the service life of cementitious materials in this time perspective. Using acceleration methods producing aged specimens would decrease the need of extrapolating short term data sets. Laboratory methods are therefore, needed for accelerating the ageing process without making any influencing distortion in the properties of the materials. This paper presents an electro-chemical migration method to increase the rate of calcium leaching from cementitious specimens. This method is developed based on the fact that major long term deterioration process of hardened cement paste in concrete structures for deposition of LILW is due to slow diffusion of calcium ions. In this method the cementitious specimen is placed in an electrochemical cell as a porous path way through which ions can migrate at a rate far higher than diffusion process. The electrical field is applied to the cell in a way to accelerate the ion migration without making destructions in the specimen's micro and macroscopic properties. The anolyte and catholyte solutions are designed favoring dissolution of calcium hydroxide and compensating for the leached calcium ions with another ion like lithium.
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| 7. |
- Bensby, Thomas, et al.
(författare)
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Chemical constraints on the formation of the Galactic thick disk
- 2012
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Ingår i: Assembling the Puzzle of the Milky Way. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 19
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Konferensbidrag (refereegranskat)abstract
- We highlight some results from our detailed abundance analysis study of 703 kinematically selected F and G dwarf stars in the solar neighbourhood. The analysis is based on spectra of high-resolution (R = 45 000 to 110 000) and high signal-to-noise (S/N approximate to 150 to 300). The main findings include: (1) at a given metallicity, the thick disk abundance trends are more alpha-enhanced than those of the thin disk; (2) the metal-rich limit of the thick disk reaches at least solar metallicities; (3) the metal-poor limit of the thin disk is around [Fe/H] approximate to -0.8; (4) the thick disk shows an age-metallicity gradient; (5) the thin disk does not show an age-metallicity gradient; (6) the most metal-rich thick disk stars at [Fe/H] approximate to 0 are significantly older than the most metal-poor thin disk stars at [Fe/H] approximate to -0.7; (7) based on our elemental abundances we find that kinematical criteria produce thin and thick disk stellar samples that are biased in the sense that stars from the low-velocity tail of the thick disk are classified as thin disk stars, and stars from the high-velocity tail of the thin disk are classified as thick disk stars; (8) age criteria appears to produce thin and thick disk stellar samples with less contamination.
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| 8. |
- Bijnens, Johan
(författare)
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ChPT loops for the lattice : Pion mass and decay constant, HVP at finite volume and nn̄ -oscillations
- 2018
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 175
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Tidskriftsartikel (refereegranskat)abstract
- I present higher loop order results for several calculations in Chiral perturbation Theory. 1) Two-loop results at finite volume for hadronic vacuum polarization. 2) A three-loop calculation of the pion mass and decay constant in two-flavour ChPT. For the pion mass all needed auxiliary parameters can be determined from lattice calculations of ππ-scattering. 3) Chiral corrections to neutron-anti-neutron oscillations.
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| 9. |
- Bijnens, Johan
(författare)
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On the Hadronic light-by-light contribution to the muon g-2
- 2018
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 179
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Tidskriftsartikel (refereegranskat)abstract
- This talk is about the hadronic light-by-light contribution to the muon anomalous magnetic moment, mainly our old work but including some newer results as well. It concentrates on the model calculations. Most attention is paid to pseudo-scalar exchange and the pion loop contribution. Scalar, a1-exchange and other contributions are shortly discussed as well. For the π0-exchange a possible large cancellation between connected and disconnected diagrams is expected.
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| 10. |
- Bijnens, Johan, et al.
(författare)
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The hadronic light-by-light contribution to the muon anomalous magnetic moment and renormalization group for EFT
- 2012
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 37
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Tidskriftsartikel (refereegranskat)abstract
- We give a short overview of the theory of the muon anomalous magnetic moment with emphasis on the hadronic light-by-light and the pion loop contribution. We explain the difference between the hidden local symmetry and full VMD pion loop and discuss leading logarithms in the anomalous sector of 2-flavour chiral perturbation theory.
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