Neutron capture cross sections of 69Ga and 71Ga at 25 keV and e peak = 90 keV

This project was supported by EFNUDAT, ERINDA, the EuroGENESIS project MASCHE, HIC for FAIR and BMBF (05P15RFFN1).We measured the neutron capture cross sections of 69Ga and 71Ga for a quasi-stellar spectrum at kBT = 25 keV and a spectrum with a peak energy at 90 keV by the activation technique at the Joint Research Centre (JRC) in Geel, Belgium. Protons were provided by an electrostatic Van de Graaff accelerator to produce neutrons via the reaction 7Li(p,n). The produced activity was measured via the γ emission of the product nuclei by high-purity germanium detectors. We present preliminary results.publishersversionpublishe

How Euphydryas maturna survived extinction in the Czech Republic : status of a relic population after intensive conservation management

In the Czech Republic, the scarce fritillary (Euphydryas maturna) had been considered extinct until the rediscovery of an extant population in Domanovicky les, Central Bohemia. Subsequent efforts to protect the locality were thwarted by disputes between landowners and researchers. In 2010, when the population size was reaching critically low levels, appropriate management was finally established at the locality. To evaluate the current status of the population, an intensive mark-release-recapture study was conducted in the area in 2016 and 2017, comprising several hundreds captured individuals. The total population size was estimated at 764 butterflies for 2016 and 518 butterflies for 2017. In comparison with the pilot study performed in 2002, the population size was slightly higher, but the dispersal rates were lower. These results indicate that Euphydryas maturna in the Czech Republic has managed to bounce back from a critical population size. On the other hand, the risk of extinction has not been averted due to continued habitat loss and stochastic environmental effects. Management efforts should aim to expand the habitats used by the breeding populations, at present predominantly confined to temporary forest clearings and to open canopy forest with low tree density. Moreover, assisted reintroductions of this only surviving population to the surrounding areas should be considered

Neutron capture cross sections of 69Ga and 71Ga at 25 keV and Epeak = 90 keV

We measured the neutron capture cross sections of 69Ga and 71Ga for a quasi-stellar spectrum at kBT = 25 keV and a spectrum with a peak energy at 90 keV by the activation technique at the Joint Research Centre (JRC) in Geel, Belgium. Protons were provided by an electrostatic Van de Graaff accelerator to produce neutrons via the reaction 7Li(p,n). The produced activity was measured via the γ emission of the product nuclei by high-purity germanium detectors. We present preliminary results

Monte Carlo MSM correction factors for control rod worth estimates in subcritical and near-critical fast neutron reactors

The GUINEVERE project was launched in 2006, within the 6th Euratom Framework Program IP-EUROTRANS, in order to study the feasibility of transmutation in Accelerator Driven subcritical Systems (ADS). This zero-power facility hosted at the SCK·CEN site in Mol (Belgium) couples the fast subcritical lead reactor VENUS-F with an external neutron source provided by interaction of deuterons delivered by the GENEPI-3C accelerator and a tritiated target located at the reactor core center. In order to test on-line subcriticality monitoring techniques, the reactivity of all the VENUS-F configurations used must be known beforehand to serve as benchmark values. That is why the Modified Source Multiplication Method (MSM) is under consideration to estimate the reactivity worth of the control rods when the reactor is largely subcritical as well as near-critical. The MSM method appears to be a technique well adapted to measure control rod worth over a large range of subcriticality levels. The MSM factors which are required to account for spatial effects in the reactor can be successfully calculated using a Monte Carlo neutron transport code

Neutron activation of Ga 69 and Ga 71 at kBT≈25 keV

Funding Information: This project was supported by EFNUDAT, ERINDA, the EuroGENESIS project MASCHE, HIC for FAIR, BMBF (05P15RFFN1) and DFG (RE 3461/4-1).Background: About 50% of heavy elements are produced by the slow neutron capture process (s process) in stars. The element gallium is mostly produced during the weak s process in massive stars. Purpose: Our activation at kBT≈25 keV is the first experiment in a series of activation and time-of-flight measurements on Ga69 and Ga71 relevant for astrophysics. Methods: We activated Ga69 and Ga71 with a neutron distribution that corresponds to a quasistellar distribution with kBT=25keV at the Joint Research Centre (JRC), Geel, Belgium. Protons were provided by an electrostatic Van de Graaff accelerator to produce neutrons via the reaction Li7(p,n). The produced activity was measured via the γ emission by the decaying product nuclei by high-purity germanium detectors. Results: We provide spectrum-averaged cross sections (SACS) and ratios of the cross sections σGa/σAu for the neutron spectrum of the activation. We obtain values of σ69Ga,SACS=(186±12)mb and σ71Ga,SACS=(112±7)mb, and cross-section ratios of σ69Ga/σAu=0.29±0.02 and σ71Ga/σAu=0.17±0.01. Conclusions: Our data disagree with the available evaluated data provided by KADoNiS v0.3, our cross-section ratio is about 20% higher for Ga69 and about 20% lower for Ga71.publishersversionpublishe

Resonance production in p+p, p+A and A+A collisions measured with HADES

The knowledge of baryonic resonance properties and production cross sections plays an important role for the extraction and understanding of medium modifications of mesons in hot and/or dense nuclear matter. We present and discuss systematics on dielectron and strangeness production obtained with HADES on p+p, p+A and A+A collisions in the few GeV energy regime with respect to these resonances

Measurement of the quasi free np → npπ+π− and np → ppπ−π0 reactions at 1.25 GeV with HADES

We present the results of two-pion production in tagged quasi-free np collisions at a deutron incident beam energy of 1.25 GeV/c measured with the High-Acceptance Di-Electron Spectrometer (HADES) installed at GSI. The specific acceptance of HADES allowed for the first time to obtain high-precision data on π+π− and π−π0 production in np collisions in a region corresponding to large transverse momenta of the secondary particles. The obtained differential cross section data provide strong constraints on the production mechanisms and on the various baryon resonance contributions (∆∆, N(1440), N(1520), ∆(1600)). The invariant mass and angular distributions from the np → npπ+π −and np → ppπ−π0 reactions are compared with different theoretical model predictions

Low mass dielectrons radiated off cold nuclear matter measured with HADES

The High Acceptance DiElectron Spectrometer HADES [1] is installed at the Helmholtzzentrum für Schwerionenforschung (GSI) accelerator facility in Darmstadt. It investigates dielectron emission and strangeness production in the 1-3 AGeV regime. A recent experiment series focusses on medium-modifications of light vector mesons in cold nuclear matter. In two runs, p+p and p+Nb reactions were investigated at 3.5 GeV beam energy; about 9·109 events have been registered. In contrast to other experiments the high acceptance of the HADES allows for a detailed analysis of electron pairs with low momenta relative to nuclear matter, where modifications of the spectral functions of vector mesons are predicted to be most prominent. Comparing these low momentum electron pairs to the reference measurement in the elementary p+p reaction, we find in fact a strong modification of the spectral distribution in the whole vector meson region

The dp-elastic cross section measurement at the deuteron kinetic energy of 2.5 GeV

New results on the differential cross section in deuteron-proton elastic scattering are obtained at the deuteron kinetic energy of 2.5 GeV with the HADES spectrometer. The angular range of 69° – 125° in the center of mass system is covered. The obtained results are compared with the relativistic multiple scattering model calculation using the CD-Bonn deuteron wave function. The data at fixed scattering angles in the c.m. are in qualitative agreement with the constituent counting rules prediction

In-medium hadron properties measured with HADES

Many QCD based and phenomenological models predict changes of hadron properties in a strongly interacting environment. The results of these models differ significantly and the experimental determination of hadron properties in nuclear matter is essential. In this paper we present a review of selected physics results obtained at GSI Helmholtzzentrum für Schwerionenforschung GmbH by HADES (High-Acceptance Di-Electron Spectrometer). The e+e− pair emission measured for proton and heavy-ion induced collisions is reported together with results on strangeness production. The future HADES activities at the planned FAIR facility are also discussed