Results of beam parameter measurement of the ELBE electron accelerator after commissioning

Teichert, J.; Büchner, A.; Evtushenko, P.; Gabriel, Frank; Lehnert, U.; Michel, P.; Voigtländer, J.

doi:10.1016/s0168-9002(03)00918-5

Cited by 35 publications

(18 citation statements)

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“…The low-N stable Mo isotopes are p-process nuclides with a surprisingly high cosmic abundance thus making accurate information on the response of Mo isotopes to dipole radiation especially desirable. The photon scattering experiment at the new radiation source ELBE with its superconducting electron linac [26] was set up similar to previous nrfstudies [13,14,15,27]. One of its special features is, that the bremsstrahlung emerges from a thin Nb-foil (approx.…”

Section: Photon Scattering Experiments On Mo Isotopesmentioning

confidence: 99%

Pygmy dipole strength close to particle-separation energies --The case of the Mo isotopes

et al. 2006

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Abstract. The distribution of electromagnetic dipole strength in 92, 98, 100 Mo has been investigated by photon scattering using bremsstrahlung from the new ELBE facility. The experimental data for wellseparated nuclear resonances indicate a transition from a regular to a chaotic behaviour above 4 MeV of excitation energy. As the strength distributions follow a Porter-Thomas distribution much of the dipole strength is found in weak and in unresolved resonances appearing as fluctuating cross section. An analysis of this quasi-continuum -here applied to nuclear resonance fluorescence in a novel way-delivers dipole strength functions, which are combining smoothly to those obtained from (γ, n) data. Enhancements at 6.5 MeV and at ∼ 9 MeV are linked to the pygmy dipole resonances postulated to occur in heavy nuclei.PACS. 21.10.Pc Single-particle levels and strength functions -24.10.Lx Monte Carlo simulations (including hadron and parton cascades and string breaking models) -25.20.Dc Photon absorption and scattering -26.50.+x Nuclear physics aspects of novae, supernovae, and other explosive environments Dipole strength in heavy nucleiThe response of nuclei to dipole radiation is of special importance for the synthesis of the chemical elements in the cosmos: particle thresholds may be crossed in hot or explosive scenarios leading to the production of new nuclides from previously formed heavier ones by dissociation in the thermal photon bath. This is likely to be the main path for the generation of the approximately 30-40 neutrondeficient nuclides which cannot be produced in neutron capture reactions [1]. For the understanding and modelling of this so-called p-process the dipole strength function up to and near the particle thresholds has to be known accurately [2]. As shown previously [3], details of the dipole strength (now in n-rich nuclei) may as well have large consequences for the r-process path and also s-process branchings are influenced by nuclear excitations [4] induced by thermal photons.The experimental knowledge [5] on dipole strength is reasonably well established for many heavy and medium mass nuclei in the region of the giant dipole resonance (GDR) by (γ, xn) studies, which often also cover the region directly above the neutron threshold S n . At lower energies three features have been discussed to be of importance for processes in high-temperature cosmic environments: a) the fall-off [6,7,8,9] of the E1-strength on the lowenergy slope of the GDR; a e-mail: e.grosse@fz-rossendorf.de b) the E1-strength between the ground-state (gs) and low energy excitations and its proper extension [10,11,12] into the regime a); c) the occurrence of additional pygmy-resonances, [3,13,14,15], which are assumed to be not as broad as the GDR, but wider as compared to the average level distance D -thus forming an intermediate structure enclosing many levels. Their low energy may well enhance their contribution to photo-dissociation processes in spite of their relatively low strength as compared to the GDR.In principle, also...

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Section: Photon Scattering Experiments On Mo Isotopesmentioning

confidence: 99%

Pygmy dipole strength close to particle-separation energies --The case of the Mo isotopes

et al. 2006

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“…To address the need for precise experimental data we started studying the reaction d(γ,n)p at the radiation source ELBE (acronym for Electron Linac for beams with high Brilliance and low Emittance) at Forschungszentrum Dresden-Rossendorf [6]. At ELBE, an electron beam with energies up to 40 MeV, with a bunch charge of 77 pC and with a bunch length of less than 10 ps is delivered by a superconducting continous-wave linear accelerator with variable frequencies of 26 MHz / 2 n (0 ≤ n ≤ 8).…”

Section: Methodsmentioning

confidence: 99%

Precision measurement of the photodissociation of the deuteron at energies relevant to Big Bang nucleosynthesis

Hannaske¹,

Bemmerer²,

Beyer³

et al. 2011

Proceedings of 11th Symposium on Nuclei in the Cosmos — PoS(NIC XI)

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Experimental data for the reaction p(n,γ)d are scarce at energies relevant to Big Bang nucleosynthesis. In network calculations, the reaction rate used relies on theoretical models constrained by nucleon-nucleon scattering data, the capture cross section for thermal neutrons and experimental data of the inverse reaction d(γ,n)p. The latter reaction -the photodissociation of the deuteronis also sparsely investigated at Big-Bang energies. A comparison of measurements with precise calculations is difficult due to large experimental uncertainties.To address the need for precise experimental data we started to measure the cross section of the reaction d(γ,n)p. We use high-intensity bremsstrahlung with an endpoint energy of 5.0 MeV generated at the superconducting electron accelerator ELBE at Forschungszentrum DresdenRossendorf. The incoming photon flux is determined by photon scattering at 27 Al by measuring the well known transitions at 2.2 and 3.0 MeV with high-purity germanium detectors. With a pulse length of a few ps and an adjustable repetition rate, ELBE offers ideal conditions for precise time-of-flight experiments. For neutron detection we use plastic scintillators read out on two sides by high-gain photomultipliers. With this setup we can measure neutrons between 20 keV and 1.4 MeV with an energy resolution of about 4 %. The statistical uncertainty reached so far is about 5 %, the analysis of systematic effects is ongoing. 11th Symposium on Nuclei in the Cosmos

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“…At nELBE an electron beam of about 30 MeV kinetic energy is focused onto a liquid lead target to produce bremsstrahlung that subsequently produces neutrons via photo-nuclear reactions on the lead nuclei. The short (5 ps) micropulse length and variable repetition rate (typically 25-400 kHz) of the electron beam of the ELBE accelerator [12,13] together with a very compact neutron producing target (thickness 11 mm) [14] allows us to use a short flight path (5 to 11 m) and a correspondingly high neutron intensity. With such a neutron producing target the energy resolution in the fast neutron range is dominated by the achievable ToF resolution of the detectors used.…”

Section: The Nelbe Neutron Time-of-flight Facilitymentioning

confidence: 99%

Inelastic scattering of fast neutrons from⁵⁶Fe

et al. 2017

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Abstract. The inelastic scattering of fast neutrons on 56 Fe was investigated in different manners at the neutron time-of-flight facility nELBE. The scattering cross section was determined via the measurement of the γ -ray production and by means of a kinematically complete double time-of-flight method. In a further measurement the γ -ray angular distribution was determined to correct the measured cross sections for anisotropy. The resulting inelastic scattering cross section determined from the photo production cross sections is in very good agreement with evaluations and previous measurements. In contrast, the result of the double time-offlight measurement is about 10% lower than these data, giving a hint to neutron-γ -ray angular correlations in the process of inelastic neutron scattering.

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Results of beam parameter measurement of the ELBE electron accelerator after commissioning

Cited by 35 publications

References 1 publication

Pygmy dipole strength close to particle-separation energies --The case of the Mo isotopes

Pygmy dipole strength close to particle-separation energies --The case of the Mo isotopes

Precision measurement of the photodissociation of the deuteron at energies relevant to Big Bang nucleosynthesis

Inelastic scattering of fast neutrons from⁵⁶Fe

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Results of beam parameter measurement of the ELBE electron accelerator after commissioning

Cited by 35 publications

References 1 publication

Pygmy dipole strength close to particle-separation energies --The case of the Mo isotopes

Pygmy dipole strength close to particle-separation energies --The case of the Mo isotopes

Precision measurement of the photodissociation of the deuteron at energies relevant to Big Bang nucleosynthesis

Inelastic scattering of fast neutrons from56Fe

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Inelastic scattering of fast neutrons from⁵⁶Fe