A. Matic

Nuclear deformation and neutron excess as competing effects for dipole strength in the pygmy region.

The electromagnetic dipole strength below the neutron-separation energy has been studied for the xenon isotopes with mass numbers A=124, 128, 132, and 134 in nuclear resonance fluorescence experiments using the γELBE bremsstrahlung facility at Helmholtz-Zentrum Dresden-Rossendorf and the HIγS facility at Triangle Universities Nuclear Laboratory Durham. The systematic study gained new information about the influence of the neutron excess as well as of nuclear deformation on the strength in the region of the pygmy dipole resonance. The results are compared with those obtained for the chain of molybdenum isotopes and with predictions of a random-phase approximation in a deformed basis. It turned out that the effect of nuclear deformation plays a minor role compared with the one caused by neutron excess. A global parametrization of the strength in terms of neutron and proton numbers allowed us to derive a formula capable of predicting the summed E1 strengths in the pygmy region for a wide mass range of nuclides.

Neutron total cross section measurements of gold and tantalum at the nELBE photoneutron source

Neutron total cross sections of 197Au and natTa have been measured at the nELBE photoneutron source in the energy range 0.1–10MeV with a statistical uncertainty of up to 2% and a total systematic uncertainty of 1%. This facility is optimized for the fast neutron energy range and combines an excellent time structure of the neutron pulses (electron bunch width 5ps) with a short flight path of 7m. Because of the low instantaneous neutron flux transmission measurements of neutron total cross sections are possible, that exhibit very different beam and background conditions than found at other neutron sources.

Measurement of the photodissociation of the deuteron at energies relevant to Big Bang nucleosynthesis

The photodissociation of the deuteron is a key reaction in Big Bang nucleosynthesis, but is only sparsely measured in the relevant energy range. To determine the cross section of the d(γ,n)p reaction we used pulsed bremsstrahlung and measured the time-of-flight of the neutrons. In this article, we describe how the efficiency of the neutron detectors was experimentally determined and how the modification of the neutron spectrum by parts of the experimental setup was simulated and corrected.

EXPERIMENTS WITH NEUTRONS AND PHOTONS AT ELBE

We describe the photo-neutron source at the superconducting electron accelerator ELBE of the Helmholtz-Zentrum Dresden-Rossendorf and present first experiments to determine cross sections of inelastic scattering of neutrons in the MeV range. We discuss analysis and results of photon-scattering experiments using the bremsstrahlung facility at ELBE. A consistent determination of the dipole strength function from the combination of photon scattering and radiative neutron capture is presented.

Fast neutrons for transmutation research within the EFNUDAT project

As a Network for research on waste transmutation and on Generation IV nuclear systems within the 6th EU framework program funds are available for EFNUDAT: European effort to exploit up‐to‐date neutron beam technology for novel research on the transmutation of radioactive waste. They cover joint research activities on n‐beams, targets, data collection and quality assurance as well as transnational access to 10 neutron research facilities. We intend to arouse interest in European research groups to approach the EFNUDAT consortium in case of interest in transmutation related research. As an example we give a brief overview of the new neutron beam of the Strahlungsquelle ELBE at Dresden‐Rossendorf.

Proton-recoil detectors for time-of-flight measurements of neutrons with kinetic energies from some tens of keV to a few MeV

At the nELBE time-of-flight facility at Forschungszentrum Dresden-Rossendorf fast neutrons are produced by the electron beam from the superconducting accelerator ELBE impinging on a liquid lead circuit as a radiator. The short beam pulses of about 10 ps provide the basis for an excellent time resolution for neutron time-of-flight experiments. An energy resolution below 1 % at 1 MeV with a short flight path of ca. 6 m can be reached with a time-of-flight resolution of 1 ns.