| 1. |
- Enders, J., et al.
(författare)
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Reactions with polarized electrons and photons at low momentum transfers at the superconducting Darmstadt electron linear accelerator S-DALINAC
- 2011
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 295:1, s. Art. no. 012152-
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Konferensbidrag (refereegranskat)abstract
- A source of polarized electrons has been installed at the superconducting Darmstadt electron linear accelerator S-DALINAC. Experiments with polarized electrons from 100 keV to about 80 MeV are expected to commence in early 2011. This contribution summarizes the status of the polarized source as well as ongoing preparations for the experimental program with polarized beams. In particular, we present results on unpolarized test experiments of the, 234,238U(γ,f) reactions and considerations for the 2D(e→,e′p) and reactions.
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| 2. |
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| 3. |
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| 4. |
- Burda, O., et al.
(författare)
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Resonance parameters of the first 1/2+ state in 9Be and astrophysical implications
- 2010
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 82:1
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Tidskriftsartikel (refereegranskat)abstract
- Spectra of the Be-9(e, e') reaction have been measured at the Superconducting Darmstadt Electron Linear Accelerator at an electron energy of E-0 = 73 MeV and scattering angles of 93 degrees and 141 degrees with high-energy resolution up to excitation energies of E-x = 8 MeV. The astrophysically relevant resonance parameters of the first excited 1/2(+) state of Be-9 have been extracted in a one-level approximation of R-matrix theory, resulting in resonance energy E-R = 1.748(6) MeV and width Gamma(R) = 274(8) keV, which are in good agreement with the latest Be-9(gamma, n) experiment but with considerably improved uncertainties. However, the reduced B(E1) transition strength deduced from an extrapolation of the (e, e') data to the photon point is smaller by a factor of two. Implications of the new results for possible production of C-12 in neutron-rich astrophysical scenarios are discussed.
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| 5. |
- Eckardt, C., et al.
(författare)
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Development of an Active 238UF6 Gas Target
- 2012
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 31, s. 141-146
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Konferensbidrag (refereegranskat)abstract
- At the superconducting 130 MeV Darmstadt electron linac S-DALINAC a new source of spin-polarized electrons using a GaAs cathode has been installed, opening the path for experiments with polarized electron and photon beams for nuclear structure studies at low momentum transfers, e.g., the search for forward-backward asymmetries originating from parity non-conservation (PNC) in the photon-induced fission process of 238U.Detailed studies of different properties, e.g., the energy dependence of fission modes, the population of fission isomers, or the search for (PNC) effects in the photon-induced fission process of 238U, depends on high quality data, therefore needing high luminosities. An active gas target containing uranium may overcome the problem that large solid target thicknesses cause poor energy and angular resolution.A single Frisch-grid ionization chamber has been built to test a mixture of standard counting gases (e.g., argon) with depleted uraniumhexafiliguoride (238UF6) using a triple alpha source, evaluating signal quality and drift velocity. For mass fractions up to 2 percent of 238U in the counting gas. The drift velocity increases with rising UF6 content, while a good signal quality and energy resolution is preserved.
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| 6. |
- Enders, J, et al.
(författare)
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Electric dipole strength below the giant dipole resonance
- 2005
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Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 36:4, s. 1077-1087
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Tidskriftsartikel (refereegranskat)abstract
- Recent experimental findings and theoretical approaches to the electric dipole (El) strength distribution below the particle emission threshold at shell closures are revisited. Results from photon scattering experiments are discussed and compared to predictions within the quasiparticle-phonon nuclear model. An analysis of the fine structure of the El strength is presented. Recent studies of the E1 response of light exotic nuclei are also discussed.
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| 7. |
- Enders, J, et al.
(författare)
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Spectral statistics and the fine structure of the electric pygmy dipole resonance in N=82 nuclei
- 2004
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Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474. ; 741, s. 3-28
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Tidskriftsartikel (refereegranskat)abstract
- We study the statistical properties of the electric pygmy dipole resonance in four different isotones with neutron number N = 82. These nuclei are Ba-138(56), Ce-140(58), Nd-142(60), (144)(62)sm. The data set comprises levels with spin and parity J(pi) = 1(-) and their ground state B(E1) transition strengths. The statistics are found to be "mixed", i.e., in between the predictions of random matrix theory for correlated and uncorrelated spectra. Moreover, we calculate spectra and transition strengths in the quasiparticle phonon model (QPM). We compare experimental and theoretical findings. The incompleteness of the data sets and its impact on the results is discussed. A consistent picture emerges which yields an improved understanding of the statistical properties of the pygmy resonance. (
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| 8. |
- Göök, A., et al.
(författare)
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Fragment characteristics from fission of U-238 and U-234 induced by 6.5-9.0 MeV bremsstrahlung
- 2011
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 851:1, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Fission of U-238 and U-234 induced by bremsstrahlung of 6.5-9.0 MeV endpoint energy has been investigated at the superconducting Darmstadt electron linear accelerator S-DALINAC. Using a twin Frisch grid ionization chamber, fission-fragment energy and mass distributions have been determined by means of the double kinetic-energy technique. Results on the fission-fragment characteristics from U-238(gamma, f) are in agreement with results from the literature. In addition fission-fragment mass and energy distributions from U-234(gamma, f) are presented for the first time in this energy region. An analysis of fission modes within the Brosa model has been performed. The relative yield of the S 1 mode was found to be (13 +/- 3)% in U-234 and (35 +/- 2)% in U-238.
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