Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

33403 Publications

Surface deformation and magnetocapacitance of superconductors

Morawetz, K.; Lipavsky, P.; Kolacek, J.; Brandt, E. H.
Electrostatic potentials have been measured at surfaces of superconductors in order to access directly the gap and material parameters. The reason why no thermodynamic corrections are measured as predicted by the theory, e.g. by Rickayzen, has remained a puzzle for almost 30 years. The solution is found in the Budd-Vannimenus theorem due to the surface dipoles. To access thermodynamic corrections one has to look deeper in the bulk like in an experiment by Kumagai et al measuring the quadrupole shift of the NMR in YBCO. The found large magnitude and unexpected sign is explained by the charge transfer between Cu chains and planes. To this end we develop the theory of electrostatic potentials above the Abrikosov vortex lattice within Bardeen's extension of the Ginzburg-Landau theory to low temperatures including the surface dipole.
As applications it is proposed:
(i) The deformation of the crystal due to the presence of vortices is calculated and the corresponding effective mass of vortices is suggested to be measured.
(ii) We found a jump of the magnetocapacitance at the surface critical magnetic field which should be experimentally accessible.

The experimentally confirmed Bernoulli potential is a consequence of the correla ted density which follows from the concept of nonlocal kinetic theory. Therefore we see this Bernoulli potential as a justification of our kinetic equation of nonlocal and non-instantaneous character which has unified the achievements of transport in dense gases with the quantum transport of dense Fermi systems.
  • Invited lecture (Conferences)
    1st Bilateral Estonian-German Workshop, 30.04.-02.05.2008, Tartu, Estland

Permalink: https://www.hzdr.de/publications/Publ-11284
Publ.-Id: 11284


Phase diagram for interacting Bose systems

Maennel, M.; Morawetz, K.; Schreiber, M.
no abstract available
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11283
Publ.-Id: 11283


The chemical potential for the inhomogeneous electron liquid in terms of its kinetic and potential parts with special consideration of the surface po tential step and BCS-BEC crossover

Morawetz, K.; March, N. H.; Squire, R. H.
The chemical potential $\mu$ of a many-body system is valuable since it carries fingerprints of phase changes. Here, we summarize results for $\mu$ for a three-dimensional electron liquid in terms of average kinetic and potential energies per particle. The difference between $\mu$ and the energy per particle is found to be exactly the electrostatic potential step at the surface. We also present calculations for an integrable one-dimensional many-body system with delta function interactions, exhibiting a BCS-BEC crossover. It is shown that in the BCS regime the chemical potential can be expressed solely in terms of the ground-state energy per particle. A brief discussion is also included of the strong coupling BEC limit.
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11282
Publ.-Id: 11282


Dominant motion vs. localization in quasiperiodic chains

Morawetz, K.; Schreiber, M.
Chains of coupled clusters arranged in a quasiperiodic sequence are analyzed with respect to the dynamics of wave packets. The recurrence probability is shown to show characteristic plateaus described by an interplay of localization and dominant motion. A three-mode model is developed which allows to understand the features of the recurrence probability as well as of the time-dependent width of the wave packets. The relation to waiting probabilities and anomalous diffusion is worked out. The consequences for the transmission coefficient realizable in experiments by sequences of quasiperiodic chains are discussed and the generalizations towards two-dimensional tilings are presented.
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11281
Publ.-Id: 11281


Surface superconductivity and capacitance of superconductors under electric and magnetic fields

Morawetz, K.; Lipavsky, P.; Kolacek, J.; Brandt, E. H.; Schreiber, M.
A superconducting layer exposed to a perpendicular electric and parallel magnetic field is considered within the Ginzburg-Landau (GL) approach. The GL equation is solved near the surface and the surface energy is calculated. The nucleation critical field is shown to be changed in dependence on the magnetic and electric field. Special consideration is payed to the induced magnetic-field effect caused by diamagnetic surface currents. The latter effect constitutes the main contribution to the effective inverse capacitance which determines the effective penetration depth.
The surface energy becomes strongly dependent on the width of the sample.
An experimental realization is suggested for determining the change in the effective capacitance of the layer.
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-11280
Publ.-Id: 11280


VVER-1000 main steam line break analysis using the coupled code system DYN3D/ATHLET

Kliem, S.; Kozmenkov, Y.; Höhne, T.; Rohde, U.; Weiß, F.-P.
Calculations using the coupled code system DYN3D/ATHLET were performed in the frame of the OECD/NEA MSLB benchmark for a VVER-1000 reactor. The coolant mixing inside the reactor pressure vessel was treated using a validated empirical mixing model implemented into the DYN3D/ATHLET code.
Using very conservative boundary conditions (reduced scram worth, two stuck rods, running MCP throughout the whole transient) a return-to-power was predicted.
For the assessment of the empirical mixing model a time dependent calculation using the computational fluid dynamics code CFX-10 was performed. For that analysis, a detailed model of the reactor pressure vessel consisting of the inlets nozzles, downcomer, lower plenum and a part of the core and having 4.67 million unstructured tetra cell elements was used. For the considered case with running main coolant pumps, this calculation shows a sector formation at the core inlet with a certain amount of mixing at the edges of the sector.
A core calculation using these CFX results as boundary conditions predicted also a return-to-power with a maximum value being about 200 MW lower than in the coupled code calculation. This variation calculation confirms the applicability of the empirical mixing model. The comparison shows also, that in this way results with a reasonable degree of conservatism can be obtained.
  • Contribution to proceedings
    International Conference on the Physics of Reactors (PHYSOR'08), 14.-19.09.2008, Interlaken, Switzerland
    Proceeedings of the International Conference on the Physics of Reactors 2008, CDROM paper 311, Villigen: Paul Scherrer Institut, 978-3952140956
  • Lecture (Conference)
    International Conference on the Physics of Reactors (PHYSOR'08), 14.-19.09.2008, Interlaken, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-11279
Publ.-Id: 11279


Nanocluster in implantierten Lichtemitter-Bauelementen durch ms-Temperung

Skorupa, W.; Rebohle, L.; Prucnal, S.; Kanjilal, A.; Sun, J. M.; Cherkouk, C.; Helm, M.; Nazarov, A.; Behar, M.
Die effiziente Erzeugung silizium-basierter Elektrolumineszenz ist eine Schlüsselproblematik, die für den avisierten Übergang von der Nanoelektronik zur Nanophotonik von entscheidender Bedeutung ist. Im Vortrag wird über die Korrelation von Temperzeit, der Größe von Seltenerde-Nanoclustern und deren Einfluß auf die Elektrolumineszenz-Ausbeute in Lichtemitter-Bauelementen berichtet, die auf implantierten, thermisch gewachsenen SiO2-Schichten auf Si-Wafern basieren.
Keywords: nanocluster, rare earth, ion implantation, electroluminescence, silicon-based light emitting devices
  • Lecture (Conference)
    Workshop Ionenstrahlphysik und Nanotechnologie, 11.-12.04.2008, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-11278
Publ.-Id: 11278


Assembly, structure, and performance of an ultra-thin film organic field-effect transistor (OFET) based on substituted oligothiophenes

Haubner, K.; Jaehne, E.; Adler, H.-J.; Koehler, D.; Loppacher, C.; Eng, L. M.; Grenzer, J.; Herasimovich, A.; Scheinert, S.
We report on the improved assembly and characterization of a small molecule organic field-effect transistor (OFET). Novel alpha-omega-dicyano substituted beta-beta'-dibutylquaterthiophene molecules (DCNDBQT) were synthesized and characterized by UV–Vis spectroscopy, differential scanning calorimetry, thermal gravimetric analysis and cyclic voltammetry. The ultra-thin organic film formation on TiO2 templates was effectively promoted through the specifically designed bifunctional self assembly molecules (SAM) 5-cyano-2-(butyl-4- phosphonic acid)-3-butylthiophene (CNBTPA). Excellent structural properties were found for up to 9 DCNDBQT molecule thick films prepared through UHV vacuum sublimation as investigated with UHV non-contact atomic force microscopy (nc-AFM) and X-ray diffraction. Both X-ray and nc-AFM data indicate that the DCNDBQT molecules form a well-ordered terraced structure exhibiting step heights of 1.5 nm to 2.0 nm layers. Hence, the DCNDBQTmolecules are linked to the functional SAM interface layer by H-bond interactions (see structure model) standing quasi perpendicular to the TiO2 template, and thus providing optimal orbital overlap neigh-bouring thiophene rings. The vacuum sublimated DCNDBQT molecules form a closed packed and dense molecular layer that was used to construct and operate a nanoscopic OFET-structure. The resulting field mobilities of 10^–5 cm^2 /V /s reflect a high current density in our ultrathin but highly ordered structure.
Keywords: organic field-effect transistor (OFET)

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11277
Publ.-Id: 11277


Flow structure and concentration distribution in seemingly parallel magnetic and electric fields

Weier, T.; Cierpka, C.; Eckert, K.; Uhlemann, M.; Bund, A.
We aim to show that flow field and concentration measurements are a valuable aid in understanding magnetoelectrochemical phenomena. Two examples, the flow field in a cylindrical cell and the concentration distribution near a circular millielectrode, will be discussed. Both cases have in common that at first sight electric and magnetic fields seem to be parallel. However, in reality, Lorentz forces are generated at locations, where the assumption of parallelism is locally violated, inducing convection phenomena of surprising complexity.
  • Lecture (Conference)
    7th PAMIR International Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France
  • Contribution to proceedings
    7th International pamir Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France, 333-337

Permalink: https://www.hzdr.de/publications/Publ-11276
Publ.-Id: 11276


Biodiversität im Filter: Wie Forscher helfen, Uran-Altlasten zu beseitigen

Raff, J.; Pollmann, K.
Mikrobiologen im Forschungszentrum Dresden-Rossendorf entwickeln intelligente Filtersysteme zur Entfernung oder Rückgewinnung von Metallen aus Wässern, indem sie den Überlebensmechanismus von Bakterien nutzen. Vor wenigen Jahren fanden sie Bakterien mit verblüffenden Eigenschaften auf einer Uran-Abfallhalde im sächsischen Johanngeorgenstadt. Wie am Beispiel des Isolates Lysinibacillus sphaericus JG-A12 gezeigt werden konnte, haben die Bakterien im Laufe der Evolution eine spezielle Schutzschicht entwickelt, um sich vor dem toxischen Schwermetall Uran zu schützen. Die Schicht besteht aus besonderen Hüllproteinen, die auf der Zelloberfläche nanoskalige Gitter ausbilden und dazu dienen, giftige Metalle am Eindringen in die Zelle zu hindern, für das Überleben des Bakteriums wichtige Substanzen jedoch passieren zu lassen.
Die Forscher kopieren für ihre neuartigen Filtersysteme diese genialen Vorbilder aus der Natur. Sie stellen Bioverbundmaterialien aus Hüllproteinen auf der Grundlage von konventionellen Immobilisierungsverfahren her bzw. beschichten herkömmliche Filtermaterialien mit den Hüllproteinen. Im Ergebnis erhalten sie Filter, die nur die Metalle aus dem Wasser holen, die entfernt oder gewonnen werden sollen, und das selbst bei niedrigsten Konzentrationen. Durch die Verwendung unterschiedlicher Proteine sollen zukünftig Filtermaterialien für verschiedene Metalle hergestellt werden und derartig miteinander kombinierbar sein, dass schließlich eine individuelle Wasserbehandlung möglich wird. Bis zur großtechnischen Anwendung dieser Verfahren werden jedoch noch einige Jahre vergehen.
  • Poster
    Parlamentarischer Abend der Leibniz-Gemeinschaft, 06.05.2008, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11275
Publ.-Id: 11275


Simulation von ATWS-Transienten in Druckwasserreaktoren

Kliem, S.; Mittag, S.; Rohde, U.; Grundmann, U.; Weiß, F.-P.
Im Rahmen von Sicherheitsanalysen für KKW werden auch Transienten mit unterstelltem Ausfall der Reaktorschnellabschaltung (RESA) betrachtet. Bei diesen ATWS-Transienten (Anticipated Transients Without Scram) wird angenommen, dass das mechanische Einfahren der Regel- und Abschaltstäbe vollständig versagt, wenn es infolge eines bestimmten Ereignisses angefordert wird. Bei einem derartigen Versagen der RESA wird die Leistungsentwicklung im Reaktorkern ausschließlich durch die neutronenkinetische Rückkopplung über Brennstofftemperatur, Moderatortemperatur und –dichte sowie Borkonzentration bestimmt.
Die ATWS-Transiente „Ausfall der Hauptspeisewasserversorgung mit Nichtabschalten der Hauptkühlmittelpumpen“ wurde mit dem gekoppelten neutronenkinetisch/thermohydraulischen Programmkomplex DYN3D/ATHLET analysiert. Dabei wurde der Einfluss systemtechnischer und neutronenkinetischer Randbedingungen auf die Rechenergebnisse untersucht. Bei den durchgeführten Rechnungen handelt es sich um methodische Untersuchungen und nicht um Nachweisführungen.
Die Reduktion der Abblasemenge aus dem Primärkreislauf, welche die Unsicherheiten beim zweiphasigen kritischen Ausströmen abdecken soll, hat unter den ausgewählten Variationen den größten Einfluss auf den Druckverlauf im Primärkreislauf, der bei der betrachteten Transiente der wichtigste Sicherheitsparameter ist.
Die Veränderung der Kernbeladung (Variation der Anzahl der MOX-Brennelemente) hat einen großen Einfluss auf die Reaktivitätskoeffizienten der Brennstofftemperatur und der Moderatordichte. Über diese zwei Koeffizienten wird der Primärdruck stark beeinflusst. Wesentliches Ergebnis ist, dass das berechnete Druckmaximum mit Erhöhung der Anzahl der MOX-Brennelemente deutlich niedriger ausfällt.
Mit einer statistischen Variation der globalen Rückkopplungsparameter wurden für eine konkrete Kernbeladung die Auswirkungen von Unsicherheiten, die sich bei der Erstellung der Zweigruppen-Wirkungsquerschnittsdaten ergeben können, auf den Verlauf der betrachteten Transiente analysiert. Die Bereiche für die statistische Variation der Daten wurden auf Grund von Erfahrungswerten vorgegeben. Die Variation des Reaktivitätskoeffizienten der Moderatordichte bewegt sich dabei in einem ähnlichen Bereich, wie er sich bei der Variation der Anzahl der MOX-Brennelemente er-gab, der Variationsbereich des entsprechenden Koeffizienten der Brennstofftemperatur ist ungefähr doppelt so groß. Im Ergebnis ergibt sich eine größere Streuung des berechneten Maximaldrucks. Eine Streuung der Koeffizienten um ± 20 % ergibt eine Streubreite im Maximalwert des Drucks im Primärkreislauf von 2.17 MPa, die entsprechenden berechneten Toleranzgrenzen sind 18.26 und 20.43 MPa. Eine Sensitivitätsanalyse ergab, dass der Primärdruck in größerem Maß vom Dichtekoeffizienten abhängt, der Koeffizient der Brennstofftemperatur beeinflusst das Druckmaximum bei gleicher relativer Variation nur halb so stark.
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
    Tagungsband der Jahrestagung Kerntechnik 2008, CDROM, Berlin: INFORUM GmbH
  • Invited lecture (Conferences)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
  • atw - International Journal for Nuclear Power 54(2009)2, 100-110

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11274
Publ.-Id: 11274


Study of the L-shell ionisation of gold by 3.0-18.2 MeV nitrogen-ion bombardment

Palinkas, J.; Sarkadi, L.; Schlenk, B.; Török, I.; Kalman, G.; Bauer, C.; Brankoff, K.; Grambole, D.; Heiser, C.; Rudolph, W.; Thomas, H. J.
The angular distributions of the L x-ray line intensities of gold have been measured by nitrogen-ion bombardment in the 3.0-18.2 MeV energy region. From the measured data absolute subshell ionisation cross sections and the anisotropy parameter of the Ll x-ray line have been deduced. Comparing the experimental data with the first-order perturbation theories significant deviations have been found, especially for the L2-subshell ionisation cross section and for the anisotropy parameter of the Ll x-ray line.
  • Journal of Physics B 17(1983), 131-145

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11273
Publ.-Id: 11273


CO2 laser nitriding of titanium

Raaif, M.; El-Hossary, F. M.; Negm, N. Z.; Khalil, S. M.; Kolitsch, A.; Möller, W.; Höche, D.; Kaspar, J.; Schaaf, P.; Mändl, S.
Samples of pure titanium were laser nitrided by continuous wave CO2 laser irradiation in mixtures of nitrogen and argon gas with different ratios. In all cases, TiN formed in the surface. The properties and the characteristics of the processed samples were evaluated using nanoindentation technique, optical microscopy, surface roughness measurements, X-ray diffraction and wear resistance measurements. It was found that the nitrogen content in the gas atmosphere has a massive effect on the microstructure and the mechanical properties of the laser nitrided samples. For all treated samples, the mechanical properties are improving with the nitrogen content in the gas atmosphere. Moreover, the thickest TiN layers with high values of the microhardness and good wear resistance were obtained for the titanium sample that was treated in 80% N2 and 20% Ar. In addition, the strain and the grain size of the coatings formed at the surface of the laser nitrided titanium samples were determined from X-ray data.
Keywords: laser nitriding, TiN
  • Journal of Physics D: Applied Physics 41(2008), 085208

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11272
Publ.-Id: 11272


Ion implantation followed by laser/pulsed plasma/ion beam annealing: a new approach to fabrication of superconducting MgB2 thin films

Piekoszewski, J.; Werner, Z.; Barlak, M.; Kolitsch, A.; Szymczyk, W.
The paper presents a new approach to formation of superconducting MgB2 thin films: ion implantation followed by annealing in an unconventional second step treatment using pulsed laser, plasma, or ion beams. Merits and drawbacks of individual approaches are discussed.
Keywords: superconductivity
  • Nukleonika 53(2008)1, 7-10

Permalink: https://www.hzdr.de/publications/Publ-11271
Publ.-Id: 11271


Infrared spectroscopic identification of aqueous neptunium species

Müller, K.; Foerstendorf, H.; Brendler, V.
In the safety assesment of underground disposal of radioactive waste neptunium (Np) is one of the most relevant radionuclides. Due to its long half-life, its hazardous to human health and its mobility under aerobic conditions Np-237 is considered as a possible long-term pollutant of the ecosystem from the safety point of view. The distribution of aqueous neptunium species, as there are the free neptunyl ions of Np(V) and Np(VI) and various complexes arising from hydrolysis or carbonate complexation, primarily defines its geochemical reactions and migration behavior in the environment.

Current knowledge about Np speciation is mainly based on data obtained by non-structural experiments such as potentiometric titration [1]. A spectroscopic verification of these Np species is still incomplete. There are only few EXAFS and Raman spectroscopic studies [2-4], using very high Np concentrations. Attenuated Total Reflectance Fourier-transform Infrared (ATR-FTIR) spectroscopy is a useful technique for the identification of different molecular species and it allows the direct measurement of liquid samples to obtain important spectral information even at low neptunyl concentrations relevant to environmental conditions.

In this study we investigate the Np speciation in aqueous solution using ATR-FTIR spectroscopy focusing on micromolar neptunyl concentrations. We work with varied experimental conditions, i.e. Np oxidation state (Np(V) and Np(VI)), wide pH range (pH 2 – 10), inert gas atmosphere, ionic strength. We present the first IR spectra of aqueous Np solutions and compare our results critically to thermodynamic calculations.

[1] R. Guillaumont et al. (OECD-NEA TDB), Update on the Chemical Thermodynamics of Uranium, Neptunium, Plutonium, Americium and Technetium, Elsevier, 2003.
[2] Gregoire-Kappenstein, A. C. et al., Radiochim. Acta 91, 665 (2003).
[3] Jones, L. H. et al., J. Chem. Phys. 21, 542 (1953).
[4] Madic, C. et al., Inorg. Chem. 22, 1494 (1983).
  • Lecture (Conference)
    V Ibero-American Congress of Environmental Physics and Chemistry, 14.-18.04.2008, Mar del Plata, Argentina
  • Contribution to proceedings
    V Ibero-American Congress of Environmental Physics and Chemistry, 14.-18.04.2008, Mar del Plata, Argentina
    Las Fronteras de la Física y Química Ambiental en Ibero América: libro de actas del V congreso iberoamericano de física y química ambiental, Buenos Aires, Argentina: Universidad Nacional de San Martin, 978-987-1435-05-0, 39

Permalink: https://www.hzdr.de/publications/Publ-11270
Publ.-Id: 11270


Enhanced electric dipole strength below particle-threshold as a consequence of nuclear deformation

Rusev, G.; Schwengner, R.; Beyer, R.; Erhard, M.; Grosse, E.; Junghans, A. R.; Kosev, K.; Nair, C.; Schilling, K. D.; Wagner, A.; Dönau, F.; Frauendorf, S.
Photoabsorption cross sections up to the neutron-separation energy were measured for the stable even-mass isotopes 92-100Mo in photon-scattering experiments. The photon-scattering data were analyzed in a novel way by taking into account the intensity of unresolved levels at high excitation energy and high level density. Simulations of gamma-ray cascades were performed to estimate the intensity distribution of inelastic transitions to low-lying levels and, hence, to deduce intensities and branching ratios of the ground-state transitions needed for the determination of the absorption cross section. The present (gamma,gamma') data can be combined for the first time with (gamma,n) data which allows us to obtain the absorption cross section in the energy range from about 4 MeV up to the giant dipole resonance for a series of isotopes. The absorption cross section below the neutron-separation energy increase with the number of neutrons above the neutron shell closure at N = 50. Calculations using a quasiparticle-random-phase approximation in a deformed Woods-Saxon potential describe this effect as a consequence of the increasing nuclear deformation.
Keywords: photon scattering, photoabsorption cross section, dipole strength function, nuclear deformation, random phase approximation

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11269
Publ.-Id: 11269


Sorption von U(VI) in Abwesenheit und Gegenwart von Huminsäure an Kaolinit und Opalinuston

Joseph, C.
Die Sorption von Uran(VI) an Kaolinit in Abhängigkeit der Ionenstärke und des Salzsystems (NaClO4, Opalinustonwasser) wurde untersucht. Zusätzliche Uran(VI)-Sorptionsversuche fanden in Abwesenheit oder Gegenwart von C-14-markierter Huminsäure statt. Die Huminsäuresorption an Kaolinit wurde zusätzlich untersucht. Erste Ergebnisse zur Uran(VI)-Sorption an Opalinuston (optimales S/L-Verhältnis) konnten vorgestellt werden.
Keywords: uranium(VI), humic acid, kaolinit, opalinus clay, sorption
  • Lecture (others)
    Workshop zum Forschungsvorhaben "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 01.-02.04.2008, München, Germany

Permalink: https://www.hzdr.de/publications/Publ-11268
Publ.-Id: 11268


Komplexierung von U(VI) durch stickstoffhaltige Modellliganden

Raditzky, B.
Im Vortrag werden Ergebnisse zur spektroskopischen Bestimmung von Stabilitätskonstanten für die U(VI)-Komplexierung durch organische Modellliganden vorgestellt. Insbesondere werden die stickstoffhaltigen Liganden Anthranilsäure und Nicotinsäure betrachtet.
Keywords: Uran, hexavalent, Benzolsulfonsäure, 4-Phenolsulfonsäure, Anthranilsäure, Nicotinsäure, TRLFS
  • Lecture (others)
    Workshop zum Forschungsvorhaben "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 01.-02.04.2008, München, Germany

Permalink: https://www.hzdr.de/publications/Publ-11267
Publ.-Id: 11267


Current without external bias and diode effect in shuttling transport of nanoshafts

Morawetz, K.; Gemming, S.; Luschtinetz, R.; Eng, L. M.; Seifert, G.; Kenfack, A.
A row of parallely ordered and coupled molecular nanoshafts is shown to develop a shuttling transport of charges at finite temperature. The appearance of a current without applying an external bias voltage is reported as well as a natural diode effect allowing unidirectional charge transport along one field direction while blocking the opposite direction. The zero-bias voltage current appears above a threshold of initial thermal and/or dislocation energy.
Keywords: Current without bias, ratchets, OFET, nanotubes, shuttling transport
  • Open Access Logo New Journal of Physics 10(2008)103014, 1-8

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11266
Publ.-Id: 11266


International Co-operation in Research - a German View onto the Challenges of Management

Joehnk, P.; Gilge, B.
Actually there is a worldwide competition for the best ideas and for the best outcome. By now large-scale equipment for research is so expensive, that it’s nearly impossible to buy and run it single nations going it alone. A way out are international co-operation. Thereby appear a lot of new questions that concern particularly the management of such co-operation. The author gives a review about the requirements of research co-operation, some examples from a German institution and the management of programmes and projects. Also the author points out the importance of co-operation for evaluation.
Keywords: International co-operation Reqiurements of research co-operation Role of the State Management of programmes Management of projects Evaluation Management
  • Contribution to proceedings
    Technical Universities: Integration with European and World Education Systems, 22.-24.04.2008, Izhevsk, Russia, 978-5-7526-0353-2, 12-19

Permalink: https://www.hzdr.de/publications/Publ-11265
Publ.-Id: 11265


A new database on the evolution of two-phase flows in a large vertical pipe

Lucas, D.; Beyer, M.; Szalinski, L.; Schütz, P.
A comprehensive database with high quality was obtained for stationary upward air-water flows in a vertical pipe with an inner diameter of 195.3 mm using the wire-mesh sensor technology. During the experiments the sensor was always mounted on the top of the test section while the distance between gas injection and measuring plane was varied to up to 18 different L/D by using gas injection chambers at different vertical positions. The gas was injected via holes in the pipe wall. The pressure was kept at 0.25 MPa (absolute) at the location of the active gas injection while the temperature was constant at 30°C 1K. This procedure exactly represents the evolution of the flow along the pipe, as it would be observed for an injection at a constant height position and a shifting of the measurement plane. The experiments were done for 48 combinations of air and water superficial velocities varying from 0.04 m/s to 1.6 m/s for water and 0.0025 m/s to 3.2 m/s for air. From the raw data time averaged data as: radial gas volume fraction profiles, bubble size distributions, radial volume fraction profiles decomposed according to the bubble size and the radial profiles of the gas velocity were calculated. Due to the combination of the new experimental procedure with the high spatial and temporal resolution of the wire-mesh sensor technology the data are have new quality especially regarding their consistency in the evolution with increasing L/D. This closes a gap for data suitable for the development and validation of closure models for two-phase flows and especially for models on bubble coalescence and break up.
Keywords: multiphase flow, bubbly flow, churn turbulent flow, annular flow, bubble size, pipe flow
  • International Journal of Thermal Sciences 49(2010), 664-674

Permalink: https://www.hzdr.de/publications/Publ-11264
Publ.-Id: 11264


Reduction of antimony by nanoparticulate magnetite and mackinawite

Kirsch, R.; Scheinost, A. C.; Rossberg, A.; Banerjee, D.; Charlet, L.
Speciation of Sb is strongly influenced by its oxidation state (V, III, 0, -III). Redox processes under anerobic groundwater conditions may therefore greatly alter the environmental behavior of Sb. Employing X-ray absorption and photon spectroscopy, we show here that Sb(V) is reduced to Sb(III) by magnetite and mackinawite, two ubiquitous Fe(II)-containing minerals, while Sb(III) is not further reduced. At the surface of magnetite, Sb(III) forms a highly symmetrical sorption complex at the position else occupied by tetrahedral Fe(III). The Sb(V) reduction increases with pH, at values above pH 6.5 Sb(V) is completely reduced to Sb(III) within 30 days. In contrast, Sb(V) is completely reduced at the mackinawite surface across a wide pH range and within 15 days. Sb(V) reduction proceeds solely by oxidation of surface Fe(II), while the oxidation state of sulfide is conserved. Independent of whether Sb(V) or Sb(III) was added, an amorphous or nanoparticulate SbS3-like solid forms.
Keywords: antimony, reduction, Fe(II), magnetite, mackinawite
  • Mineralogical Magazine 72(2008)1, 185-189
  • Contribution to proceedings
    Geochemistry of the Earth's Surface 8 (GES8), 18.-22.08.2008, London, UK
    abstracts published in "Mineralogical Magazine"
  • Poster
    Geochemistry of the Earth's Surface 8 (GES8), 18.08.2008, London, UK

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11262
Publ.-Id: 11262


Reduction of antimony by nanoparticulate Fe3O4 and FeS

Kirsch, R.; Scheinost, A. C.; Rossberg, A.; Banerjee, D.; Charlet, L.
Antimony finds a wide range of industrial applications, e.g. in flame retardants, brake pads and as a lead-alloy in storage batteries and ammunition and is widely distributed in the environment. Sb may occur in several oxidations states (-III, 0, III, V). Under oxic conditions, Sb0 oxidizes prevalently to SbV, forming the anionic species Sb(OH)6- which is strongly sorbed by Fe oxides[1]. In contrast, SbIII forms an uncharged complex Sb(OH)3(aq), which is more mobile. Under anoxic conditions, SbV and SbIII may be reduced by FeII-bearing minerals. Magnetite (FeIIFeIII2O4) and mackinawite (FeS) have been shown to reduce e.g. Se[2], As[3], and Pu[4]). We therefore investigated the reaction of SbIII and SbV with these two minerals at <1ppm O2 (v/v) using Sb-K XAS.
When SbIII was reacted with magnetite at pH 4.7 to 7.6 during 1 h to 67 d, the oxidation state was stable and only one Sb species was identified by EXAFS. SbIII is coordinated with 4 to 5 iron atoms at a distance of 3.6 Å. FEFF Monte Carlo simulations revealed formation of a highly ordered surface complex on the {111} faces of magnetite. The trigonal pyramidal SbO3 units occupy positions of FeIII tetrahedra, that would be ideally coordinated to six Fe06 octahedra via corner-sharing. The experimental Fe coordination numbers below six suggest that Sb occupies positions near edges of the {111} faces. When SbV was reacted with magnetite, reduction to SbIII increased linearly between pH 4.5 and 6.5, with little influence of reaction time. The SbIII produced by the surface reaction formed the same surface complex as after direct addition of SbIII.
In the presence of mackinawite, SbV was completely reduced to SbIII within 30 d and in the pH range 4.3 - 8.4. The local structure shows SbIII surrounded by three sulfur atoms at a distance of 2.5 Å as in Sb2S3. The lack of more distant atomic shells suggests a highly dissordered structure. Again the resulting surface complex is the same as after direct addition of SbIII. Cryo-XPS measurements of shock-frozen samples show that the S 2p spectra remain unchanged before and after SbV reduction, while a FeIII-shoulder emerged in the Fe 2p spectra after reduction, indicating that SbV was reduced by FeII and not by S. In no case, reduction to an oxidation state below III was observed.

[1] Scheinost et al., Geochim. Cosmochim. Acta 70 (2006) 3299-3312. [2] Scheinost & Charlet, Environ. Sci. Technol. (2008) online. [3] Gallegos et al., Environ. Sci. Technol. 41 (2007) 7781-7786. [4] Powell et al., Environ. Sci. Technol. 38 (2004) 6016-6024.
Keywords: antimony, reduction, mackinawite, magnetite
  • Abstract in refereed journal
    Geochimica et Cosmochimica Acta 72(2008)12, A476

Permalink: https://www.hzdr.de/publications/Publ-11261
Publ.-Id: 11261


Electronic transport in magnetically ordered Mn5Si3Cx films

Gopalakrishnan, B.; Sürgers, C.; Montbrun, R.; Singh, A.; Uhlarz, M.; von Löhneysen, H.
Mn5Si3Cx films exhibit antiferromagnetic or ferromagnetic behavior depending on the carbon doping level x. We report a detailed electronic-transport study of films prepared with different x. All films exhibit metallic behavior of the temperature-dependent resistivity ρ(T) with a logarithmic increase towards low temperatures attributed to the structural disorder and the accompanied scattering of conduction electrons by two-level systems. Below 1 K, the Kondo-type behavior ρ(T)~−ln T shows a crossover to Fermi-liquid behavior ρ−T2 independent of the type of magnetic order. The magnetoelectronic properties such as Hall effect and magnetoresistance show clear differences characteristic for the different magnetically ordered phases, i.e., antiferromagnetic vs ferromagnetic.
  • Physical Review B 77(2008), 104414

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11260
Publ.-Id: 11260


The Atomic Layer Deposition of HfO2 and ZrO2 using advanced metallocene precursors and H2O as an oxidant

Dezelah, C. L.; Niinistö, J.; Kukli, K.; Munnik, F.; Lu, J.; Ritala, M.; Leskelä, M.; Niinistö, L.
The atomic layer deposition of HfO2 and ZrO2 thin films was investigated using (CH3C5H4)2Hf(CH3)2, (CH3C5H4)2Hf(OCH3)(CH3), (CH3C5H4)2Zr(CH3)2, and (CH3C5H4)2Zr(OCH3)(CH3) precursors at deposition temperatures between 300 and 500 °C using water vapor as the oxidant. A surface-limited growth mechanism was confirmed at 350 °C for all metal precursors examined. The processes provided nearly stoichiometric HfO2 and ZrO2 films with carbon and hydrogen concentrations below 0.5 and 1.0%, respectively, for representative samples. All films were polycrystalline as deposited and possessed a thin interfacial SiO2 layer. The capacitance-voltage and current density-voltage behavior is reported and discussed for capacitor structures containing films from this study.
Keywords: ALD, hafnium oxide, zirconium oxide, cyclopentadienyl (Cp) complexes, high-k dielectric

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11259
Publ.-Id: 11259


Prozessautomatisierung des Versuchsstandes TOPFLOW des Forschungszentrums Dresden Rossendorf

Lenk, S.; Carl, H.; Beyer, M.
Der Vortrag beschreibt das Steuerungs- und Messdatenerfassungssystem der Versuchsanlage TOPFLOW. Beginnend bei der ursprünglichen Konfiguration des Automatisierungssystems werden die bis heute ausgeführten Erweiterungen und Optimierungen ausführlich erläutert. Des Weiteren beinhaltet der Vortrag Erklärungen zu den an TOPFLOW eingesetzten Hardware- und Softwarelösungen. Außerdem werden die Systemdokumentation und Maßnahmen zur Qualitätssicherung erklärt. Ausgewählte Beispiele zur Anlageninstrumentierung und Erläuterungen zur online Berechnung wichtiger thermo-physikalischer Stoffdaten schließen den Beitrag ab.
Keywords: process automation, OPC interface, ethernet communication, interbus
  • Lecture (others)
    Frühjahrstagung der Studiengruppe für Elektronische Instrumentierung, 07.-09.04.2008, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11258
Publ.-Id: 11258


Speciation and coordination of U(VI) and U(IV) sulfate in aqueous solution

Hennig, C.
The abandoned uranium mine Königstein near Dresden/Germany, where uranium ore has been leached by sulfuric acid, is even nowadays concerned from the problem of heavy metal mobility affecting adjacent aquifers used for recovering drinking water. A rising interest can be observed worldwide to use such in situ leaching techniques to obtain uranium from ore mines. At the other hand, the thermodynamics of uranium in presence of high sulfate concentration is actually not well understood, especially under reduced conditions. The extended Debye-Hückel formalism, commonly used to estimate the species distribution and to correct activity coefficients, is above the validity limit in case of high ionic strength originated by the sulfuric acid. The specific ion interaction theory (SIT) and the Pitzer model are useful at higher ionic strengths but partly not to the extent in the directly concerned rock areas. In this study were combined therefore EXAFS, HEXS, XRD, TRLFS and UV-vis spectroscopy to extract the species distribution and the coordination of U(VI) and U(IV) sulfate complexes from model systems with low pH values and high sulfate concentrations [1-3]. For that purpose a spectro-electrochemical cell has been constructed that allowed the investigation of the solutions under controlled redox conditions. The study revealed that in contrast to neutral pH conditions, where U(VI) is highly soluble but U(IV) is nearly insoluble, even U(IV) becomes highly soluble at low pH by forming stable complexes resulting in an enlarged migration capacity.

[1] C. Hennig, K. Schmeide, V. Brendler et al.: EXAFS investigation of U(VI), U(IV), and Th(IV) sulfato complexes in aqueous solution. Inorg. Chem. 46, 5882 (2007).
[2] C. Hennig, W. Kraus, F. Emmerling et al.: The coordination of a U(IV) sulfate monomer in aqueous solution and in solid state, Inorg. Chem. 47, 1634, (2008)
[3] C. Hennig, A. Ikeda, K. Schmeide et al.: The relationship of monodentate and bidentate coordinated uranium(VI) sulfate in aqueous solution. Radiochim. Acta, submitted.
Keywords: Uranium, Sulfat, U(IV), U(VI), EXAFS, HEXS, XRD, TRLFS,UV-vis
  • Lecture (Conference)
    Uranium Mining and Hydrogeology V, 14.-18.09.2008, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-11257
Publ.-Id: 11257


Coordinatiom of actinides in aqueous sulfate solution

Hennig, C.; Ikeda, A.; Tsushima, S.; Le Naour, C.; Den Auwer, C.; Wilson, R.
Structural information on the sulfate coordination of actinides in aqueous solution is actually rather scarce. At the other hand there is often a high sulfuric acid concentration in the environment mines containing pyrite, because pyrite, exposed to aerobic conditions, undergoes a weathering followed by sulfuric acid release. An artificial source of sulfate in natural environment is in situ leaching, so-called solution mining, where sulfuric acid is injected into the ore deposit, as has been used especially for uranium mining in sandstone formations. Due to the lack of information on the coordination of sulfate with actinides in aqueous solution, we investigated Th(IV), Pa(V), U(IV), U(VI), Np(IV), Np(V) and Np(VI) complexes in aqueous sulfate solution by L3-edge EXAFS, high energy x-ray scattering (HEXS), and UV-Vis spectroscopy using samples of 10-50 mM of actinide and total sulfate concentrations, 0.05 ≤ [SO42-] ≤ 10 M. In contrast to the coordination of actinides with carbonate where bidentate coordination always prevails, the coordination with sulfate comprises monodentate and bidentate linkage with a wide variety of combinations. In general, with increasing [SO42-]/[Ann+] ratio the bidentate coordination becomes dominant in solution. As example, at low [SO42-]/[UO22+] ratio, where the UO2SO4(aq) species prevails, the sulfate coordinates in a monodentate and only to a less extend in bidentate fashion. At high [SO42-]/[UO22+] ratio, where UO2(SO4)22- species prevails, bidentate sulfate coordination with the species [UO2(SO4)2bid]2- becomes dominant [1]. In oxidation state IV, up to five coordinating sulfate groups have been observed, mostly with predominant bidentate coordination as for example in the high-charged complex [U(SO4bid)3(SO4mon)2]6- [2]. Pa(V) shows in high excess of sulfate a coordination of monodentate and bidentate sulfate, e.g. the complex [PaO(SO4bid)2(SO4mon)3]7- [3]. Np(IV) and Np(VI) follows the tendency of U(IV) and U(VI), whereas Np(V) is weakly coordinated by sulfate, in accordance with its low formation constant. The attempt to preserve solution species in crystal structures led in most of the cases to a rearrangement of bidentate sulfate groups in solution to monodentate–bridging coordination in solid state. The coordination of the solution complexes was optimized by DFT calculation and the results were compared with the experimental observations.


[1] C. Hennig, K. Schmeide, V. Brendler, H. Moll, S. Tsushima, A.C. Scheinost, Inorg. Chem. 46, 5882, 2007.
[2] C. Hennig, W. Kraus, F. Emmerling, A. Ikeda, A.C. Scheinost, 47, 2987, 2008
[3] C. Le Naour, D. Trubert, M.V. Di Giandomenico, C. Fillaux, C. Den Auwer, P. Moisy,C. Hennig, Inorganic Chemistry 44, 9542, 2005
Keywords: Th, Pa, U, Np, sulfate, EXAFS, HEXS, UV-vis, XRD
  • Lecture (Conference)
    Plutonium Futures "The Science" 2008, 07.-11.7.2008, Dijon, France

Permalink: https://www.hzdr.de/publications/Publ-11256
Publ.-Id: 11256


Infrared absorption strengths of ion-implanted hydrogenated amorphous silicon

Danesh, P.; Pantchev, B.; Schmidt, B.
Silicon and hydrogen ion implantations have been used to affect the absorption of the infrared stretching modes in hydrogenated amorphous silicon (a-Si:H). Hydrogen ions have been implanted with ion energy of 16 keV and the doses in the range of 2.2 x 1014 -7.2 x 1016 cm-2. Silicon ion implantation has been carried out with the energy of 160 keV and the doses in the range of 9.5 x 1012 cm-2 -1.7 x 1015 cm-2. The a-Si:H films have been prepared by plasma-enhanced chemical vapor deposition. Nuclear reaction analysis has been used for the determination of the hydrogen concentration in the as-deposited and ion-implanted samples. It has been established that the values of the absorption strengths of stretching modes of the isolated monohydrides, A(2000), and clustered hydrogen forms, A(2100), are not equal and remain constant for all ion implantation doses. A(2100) has been considered as a weighted average of the absorption strengths of polyhydrides and clustered monohydrides, A(2100,SiHx) and A(2100,(SiH)n). It has been established that the ion implantation does not induce any change in the ratio between polyhydrides and clustered monohydrides. It has been suggested that the absorption strengths do not vary when a post-deposition treatment of samples is associated with the introduction of structural defects in the amorphous silicon network.
Keywords: hydrogenated amorphous silicon, ion implantation, infrared absorption spectroscopy, nuclear reaction analysis
  • Thin Solid Films 516(2008)10, 3383-3386

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11255
Publ.-Id: 11255


Bacteria –Actinide Interactions: an Environmental Perspective

Merroun, M.; Selenska-Pobell, S.
Soils, sediments, and waters heavily polluted with radionuclides and other toxic metals, are a reservoir of unusual bacteria well adapted to these toxic environments. These bacteria possess fascinating mechanisms for interaction with and bio-transformation of radionuclides and other heavy metals, thus regulating the mobility of the metals in the environment. Microorganisms can mobilize radionuclides and metals through autotrophic and heterotrophic leaching, chelation by microbial metabolites and siderophores, and methylation, which can result in volatilization. Conversely, immobilization can result from sorption to cell components or exopolymers, intracellular sequestration, or precipitation as insoluble organic and inorganic compounds, e.g. oxalates, sulfides, or phosphates. The present work is intended to give a brief overview of the key processes implicated in the interaction of uranium with bacterial strains isolated from different extreme environments including uranium mining waste piles as well as groundwater of a radioactive repository. For this purpose, a combination of spectroscopic (EXAFS, XANES, TRLFS), microscopic (TEM), microbiological and wet chemistry techniques is used. Elucidating the interaction mechanisms microbe/metals is helpful for understanding the role which bacteria play in the transport and mobility of toxic metals in the environment as well as their biotechnological application in the bioremediation of heavy metal contaminated waters.
  • Lecture (Conference)
    38èmes Journées des Actinides 2008, 12.-15.04.2008, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-11254
Publ.-Id: 11254


Search for exotics in γD => φnp reactions near threshold

Titov, A. I.; Kämpfer, B.
We discuss coherent and incoherent -meson photoproduction off the deuteron at low energy and small momentum transfer with the aim to check whether the recent experimental data need for their interpretation an inclusion of exotic channels. Our analysis of the differential cross-section and spin-density matrix elements shows that new data on the D → X reaction at Eγ ∼ 2GeV may be understood on the basis of conventional dynamics.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11253
Publ.-Id: 11253


Untersuchung von lateralen und vertikalen Elementverteilungen mittels Kernmikrosonde

Grambole, D.; Herrmann, F.; Klabes, R.; Böhmert, J.; Klemm, W.; Plier, F.
Die Kernmikrosonde, die am 5 MV Tandembeschleuniger des Zentralinstituts für Kernforschung Rossendorf installiert ist und über eine laterale Auflösung von ca. 4 µm für 3 MeV Protonen verfügt, wurde zur Mikrobereichsanalytik in der Medizin, Werkstofforschung und Geologie eingesetzt. Tiefenprofile von F im menschlichen Zahnschmelz und von O in Zr-Legierungen wurden bestimmt. Mikroeinschlüsse fester und flüssiger Phasen im Quarz wurden ebenfalls analysiert.

Investigation of lateral and vertical element distributions by means of nuclear microprobe:
The nuclear microprobe at the5 MV tandem accelerator of the Central Institute for Nuclear Research Rossendorf with a lateral resolution of about 4 µm for 3 MeV protons was used for microanalysis in medicine, material science, and geology. Depth profiles of F in human tooth enamels and of O in Zr alloys were determined. Microinclusions of solid and fluid phases in quartz were also investigated.
  • Beiträge zur elektronenmikroskopischen Direktabbildung und Analyse von Oberflächen 23(1990), 263-266

Permalink: https://www.hzdr.de/publications/Publ-11252
Publ.-Id: 11252


Protonenmikrosonde am Rossendorfer Tandemgenerator

Gersch, H.-U.; Grambole, D.; Herrmann, F.; Thomas, H.-J.
Der Aufbau einer Protonenmikrosonde am Rossendorfer Tandemgenerator wird beschrieben. Testmessungen bei einer Energie von 3 MeV ergaben eine Auflösung von etwa 4 µm bei einem Strahlstrom von etwa 200 pA.

The development of a protonen microprobe at the Rossendorf tandem generator is described. A resolution of about 4 µm with a beam current of 200 pA was reached during first measurements at an energy of 3 MeV.
  • Experimentelle Technik der Physik 30(1982)3, 227-234

Permalink: https://www.hzdr.de/publications/Publ-11251
Publ.-Id: 11251


Hydrogen determination by means of the 1H(19F,α y) 16O and 1H(15N,α y) 12C resonance reactions

Rudolph, W.; Bauer, C.; Gippner, P.; Grambole, D.; Heiser, C.; Herrmann, F.; Thomas, H.-J.
Hydrogen surface contamination and depth profiles can be measured by the resonant nuclear reactions 1H(19F,α y) 16O and 1H(15N,α y) 12C. The method was applied to study hydrogen-implanted silicon, amorphous silicon layers and silicon oxide films produced by anodic oxidation.
  • Journal of Radioanalytical and Nuclear Chemistry 83(1984)1, 99-105

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11250
Publ.-Id: 11250


Phase diagram and binding energy of interacting Bose gases

Männel, M.; Morawetz, K.; Schreiber, M.; Lipavský, P.
From the many-body T-matrix the condition for a medium-dependent bound state and its binding energy is derived for a homogeneous interacting Bose gas. This condition provides the critical line in the phase diagram in terms of the medium-dependent scattering length. Separating the Bose pole from the distribution function the influence of a Bose condensate is discussed and a thermal minimum of the critical scattering length is found.
Keywords: BEC, phase diagramm, interacting Bose gases, bound states
  • Physical Review B 78(2008), 054508-1-054508-5

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11247
Publ.-Id: 11247


Fluorine determination in the near-surface region of solids using the 19F(p,p'y)19F resonance reaction

Grambole, D.; Bauer, C.; Gippner, P.; Heiser, C.; Rudolph, W.; Thomas, H.-J.
Fluorine surface contamination and depth profiles were studied using the 19F(p,p'y)19F resonance reaction. Fluorine implanted silicon samples as well as ZrNb plates and Cr-Al layers after a HF-treatment have been examined. The resonance strengths of the narrow 1088 keV resonance were estimated.
  • Journal of Radioanalytical and Nuclear Chemistry 83(1984)1, 107-115

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11246
Publ.-Id: 11246


PECVD Si nitride and Si oxide layers - hydrogen analysis and etching after ion implantation

Neelmeijer, C.; Schmidt, B.; Rudolph, W.; Münzer, H.; Grambole, D.; Heiser, C.; Herrmann, F.
Ion-implantation-induced selective etching of dielectric materials is considerably diminished with increasing hydrogen content.
Making use of the 1H(15N,αy)12C resonance reaction, low-temperature PECVD Si oxide and Si nitride layers were observed to
contain 12 and 23 at.% H, respectively. For different reagents etch rates were measured regarding the virgin and ion-implanted - He+, Ne+ at 60, 100 keV - PECVD films.
  • Nuclear Instruments and Methods in Physics Research B 50(1990), 439-443

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11245
Publ.-Id: 11245


Favorable Conditions of Θ+ Formation in γD Reaction

Titov, A.; Kämpfer, B.; Daté, S.; Ohashi, Y.
We show that a Θ+ signal may appear in the [γD, pK−] missing mass distribution in inclusive γD → pK−X reaction when the pK− pair is knocked out in the forward direction and its invariant mass is close to the mass of Λ(1520). We show that the conditions of the recent CLAS experiment reduce the Θ+ formation probability making it difficult to extract a Θ+ peak from the data.
  • Open Access Logo Progress of Theoretical Physics 168(2007), 86-89

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11244
Publ.-Id: 11244


Dynamo action and magnetorotational instability: cosmic magnetism in the liquid metal lab

Stefani, F.
It is widely known that cosmic magnetic fields are produced by the hydromagnetic dynamo effect. Yet it is less well known that cosmic magnetic fields play an active role in cosmic structure formation by means of the magnetorotational instability (MRI). The last ten years have seen tremendous efforts in studying both effects in the laboratory. In 1999, magnetic field self-excitation was observed nearly simultaneously in the liquid sodium facilities in Riga and Karlsruhe. Recently, self-excitation was also obtained in the French "von Karman sodium" (VKS) experiment, although with the help of iron propellers. The helical MRI was recently studied in the ''Potsdam Rossendorf Magnetic Instability Experiment'' (PROMISE), and an improved version of this experiment (PROMISE 2) has provided sharper transitions between stable and unstable regimes. In the talk, the history of dynamo and MRI experiments is delineated, and some interesting directions of future work are discussed.
  • Invited lecture (Conferences)
    MHD fundamentals, from liquid-metals to astrophysics, 14.-16.04.2008, Bruxelles, Belgium

Permalink: https://www.hzdr.de/publications/Publ-11243
Publ.-Id: 11243


Plastic foils as primary hydrogen standards for nuclear reaction analysis

Rudolph, W.; Bauer, C.; Brankoff, K.; Grambole, D.; Grotzschel, R.; Heiser, C.; Herrmann, F.
Plastic materials like polypropylene, polyester (Mylar) and polycarbonate (Lexan or Makrofol E) contain large amounts of hydrogen and their compositions are well known. However, these materials are not stable during ion bombardment. Using the 1H(15N,αγ)12C and 1H(19F, αγ)16O nuclear resonance reaction at energies EN = 6.50 MeV and EF = 6.83 MeV, respectively, we have investigated the behaviour of plastic foils during 15N and 19F ion bombardment. By means of a rotating sample holder low current densities of 1–2 nA/cm² and large irradiated foil areas of up to 10 cm² were realized. Under these measuring conditions the γ-ray yields change only slightly and the initial yields, which correspond to the known compositions of the foils, can be determined with good accuracy. In this way the plastic foils can be used as primary standards for hydrogen content calibration. The method was employed to calibrate an a-Si(H) reference target.
  • Nuclear Instruments and Methods in Physics Research B 15(1986), 508-511

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11242
Publ.-Id: 11242


Void measurement in boiling water reactor rod bundles using high resolution gamma ray tomography

Bieberle, A.; Hoppe, D.; Zippe, C.; Schleicher, E.; Tschofen, M.; Suehnel, T.; Zimmermann, W.; Hampel, U.
We present a high resolution gamma ray computed tomography (CT) system for the measurement of the void distribution in sub-channels in an electrically heated fuel rod bundle at the thermal hydraulic test loop KATHY (AREVA NP GmbH, Germany). This measurement system generates cross-sectional void fraction profiles through the pressure vessel for true-to-scale fuel rod bundles operating under typical nuclear reaction conditions and in steady state. Measurements are non-invasive, thus the two-phase flow in the bundle is not influenced. The gamma ray computed tomography system consists of a collimated 137Cs isotopic source, a gamma radiation detector arc including 320 single elements and a pulse processing unit. The average spatial resolution of the CT system is about 3 mm in plane and 8 mm axial. The thermal design of the detector arc is optimised to keep the temperature of internal components constant under changing environmental conditions. A specially developed gantry was constructed to realise vertical positioning and continuous rotation of the CT system. To determine the void fraction distribution a two-point calibration method is used. Here, data sets at zero and one hundred percent void fraction are required. The non-superposed slice image is generated using the filtered back projection reconstruction algorithm.
Keywords: high resolution gamma ray tomography, void fraction determination
  • Contribution to proceedings
    XCFD4NRS - Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.08, Grenoble, France
    PaperNo BOI-06
  • Lecture (Conference)
    XCFD4NRS - Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.08, Grenoble, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-11241
Publ.-Id: 11241


Eta-prime meson production in nucleon-nucleon collisions near the threshold

Kaptari, L. P.; Kämpfer, B.
The production of eta' mesons in the reactions pp to ppeta' and pn to pn eta' at threshold-near energies is analyzed within a covariant effective meson-nucleon theory. The description of cross section and angular distributions of the available data in this kinematical region in the pp channel is accomplished by including meson currents and nucleon currents with the resonances S_{11}(1650), P_{11}(1710) and P_{13}(1720). Predictions for the pn channel are given. The di-electron production from subsequent eta' Dalitz decay eta' to gamma gamma^* to gamma e^+e^- is also calculated and numerical results are presented for intermediate energy and kinematics of possible experiments with HADES, CLAS and KEK-PS.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11240
Publ.-Id: 11240


Investigating the ESBWR stability with experimental and numerical tools: a comparative study

Rohde, M.; Marcel, C. P.; Manera, A.; van der Hagen, T. H. J. J.; Shiralkar, B.
In this work, the stability of the Economic Simplified Boiling Water Reactor (ESBWR) has been studied by using a Freon-134a based experimental facility (GENESIS) and two system codes, being ATHLET 2.0a and (to a lesser extent) TRACG. During setting up the GENESIS facility and the numerical calculations, a great effort has been made to approximate the ESBWR system as accurate as possible.
In general, it was found that a sufficient margin to instability exists regarding the ESBWRs nominal point. In addition, a comparison was made between the numerical and experimental results for both the thermal-hydraulic system and the reactor system. Deviations were found between the numerical and experimental results, in spite of the close similarity between the GENESIS facility and the definition of the ESBWR system in the system code. This result shows that predictions regarding real nuclear reactors, based on modeled systems, should be taken with care.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11239
Publ.-Id: 11239


Quantum well infrared photodetector array development and applications

Schneider, H.
Quantum well infrared photodetector (QWIP) technology has opened up new opportunities to realize focal plane arrays (FPA) for high-performance thermal imaging [1]. High thermal and spatial resolution, low 1/f noise, low fixed-pattern noise, and high pixel operability makes QWIP FPAs appropriate for many applications. Due to their narrow absorption bands with relative spectral widths of the order of 10%, QWIPs are particularly suitable for thermal imaging applications involving several atmospheric transmission bands or several colors within the same band. In this talk, I will report on the development of QWIP structures optimized for thermal imaging applications and on the performance of QWIP cameras which were jointly realized by the Fraunhofer-Institute for Applied Solid State Physics (Freiburg, Germany) and AIM Infrarot-Module GmbH (Heilbronn, Germany). Besides imagers for the 8 – 12 micron long-wavelength infrared (LWIR) and 3 – 5 micron mid-wavelength infrared (MWIR) regimes, a LWIR/MWIR dual-band QWIP FPA will also be discussed.
[1] H. Schneider and H. C. Liu, Quantum Well Infrared Photodetectors: Physics and Applications, ISBN 3540363238, Springer Series in Optical Sciences Vol. 126, 2007.
Keywords: quantum well infrared photodetector, QWIP
  • Lecture (others)
    Seminarvortrag, Shanghai Institute of Technical Physics, Chinese Academy of Science, 24.03.2008, Shanghai, China
  • Lecture (others)
    Seminarvortrag, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Science, 27.03.2008, Suzhou, China
  • Lecture (others)
    Seminarvortrag, Institute of Semiconductors, Chinese Academy of Science, 02.04.2008, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-11238
Publ.-Id: 11238


TEM, SANS and PAS applied to neutron-irradiated pure Fe

Hernández Mayoral, M.; Bergner, F.; Almazouzi, A.; Lambrecht, M.
Irradiation-induced microstructural features in pure Fe were investigated by a triple of methods: TEM, SANS and PAS. In the talk it will be analyzed, if and how the features detected by the individual techniques reflect themselves in the output of each other method. This information is used in order to derive a coherent picture of irradiation damage in pure Fe.
  • Lecture (Conference)
    14th Meeting of the International Group on Radiation Damage Mechanisms (IGRDM-14), 20.-25.04.2008, Pittsburgh, United States

Permalink: https://www.hzdr.de/publications/Publ-11237
Publ.-Id: 11237


Flux dependence of cluster formation in neutron irradiated weld material

Bergner, F.; Ulbricht, A.; Hein, H.
SANS results for an RPV weld material irradiated at two different neutron fluxes up to the same neutron fluence will be presented. We have observed a remarkable effect of flux on the size of irradiation-induced clusters. A rate theory model is applied in order to give a tentative explanation for the findings. Interestingly, the mechanical properties do not show a corresponding flux effect. The results will be faced with observations for another RPV steel exhibiting a different behaviour.
  • Lecture (Conference)
    14th Meeting of the International Group on Radiation Damage Mechanisms (IGRDM-14), 20.-25.04.2008, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-11236
Publ.-Id: 11236


Double photoexcitation involving 2p and 4f electrons in L3-edge x-ray absorption spectra of protactinium

Hennig, C.; Le Naour, C.; Den Auwer, C.
The L3-edge x-ray absorption spectrum of Pa(V) fluoride in aqueous solution show clear evidence for the double photoexcitation involving 2p and 4f electrons. A comparison with the [2p4f] double-electron excitations observed in the L3-edge x-ray absorption spectra of other actinides (thorium, uranium, neptunium, plutonium and americium) indicates a monotonic increase of the excitation energy. The sharp edge-like structure of the multielectron excitation reveals the origin of a shake-up channel.
Keywords: [2p4f] double-electron excitation, protactinium

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11235
Publ.-Id: 11235


Experiments on slug mixing under natural circulation conditions at the ROCOM test facility using high resolution measurement technique and numerical modeling

Kliem, S.; Höhne, T.; Rohde, U.; Weiß, F.-P.
ROCOM is a four-loop test facility for the investigation of coolant mixing in the primary circuit of pressurized water reactors. Recently, a new sensor was developed for an improved visualisation and quantification of the coolant mixing in the downcomer. This new sensor spans a dense measuring grid and covers nearly the whole downcomer. In the presented work, special emphasis was given to the comparison of the data of this sensor with the results of calculations using the CFD code ANSYS CFX. A coolant mixing experiment during natural circulation conditions has been conducted. The underlying scenario of this experiment is based on a boron dilution scenario following a SBLOCA event. The corresponding CFD code solution has been obtained using the Best Practice Guidelines. All main effects observed in the measurement are described by the calculation. The detailed comparison reveals that the calculation underestimates the coolant mixing inside the reactor pressure vessel.
The measurement data, boundary conditions of the experiment and facility geometry can be made available to other CFD code users for benchmarking.
  • Lecture (Conference)
    XCFD4NRS - Experiments and CFD Codes Application to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France
  • Contribution to proceedings
    XCFD4NRS - Experiments and CFD Codes Application to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, Frankreich
    Proceedings of the XCFD4NRS - Experiments and CFD Codes Application to Nuclear Reactor Safety, CDROM
  • Nuclear Engineering and Design 240(2010)9, 2271-2280
    DOI: doi:10.1016/j.nucengdes.2009.11.015

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11234
Publ.-Id: 11234


Advanced two-phase flow measurement techniques at Research Centre Dresden-Rossendorf - sensors, systems and applications

Hampel, U.
Understanding and modelling of two-phase flow is a key issue in nuclear engineering and in many other engineering fields. The Research Centre Dresden-Rossendorf is, amongst others, engaged in safety research for nuclear light water reactors and performs combined experimental and theoretical work on two-phase flow phenomena. In the frame of this work considerable effort has been spent in the past to develop innovative two-phase flow measuring techniques. Special focus has been given to imaging techniques which are able to resolve phase distributions at high temporal and spatial resolution. The presentation introduces the most advanced of these techniques, including different types of wire-mesh sensors, gamma ray tomography and ultra fast electron beam tomography and discusses application of such techniques and systems in basic research as well as industrial applications.
Keywords: Two-phase flow, flow measurement
  • Invited lecture (Conferences)
    Meeting der Industrial Tomography Systems Ltd., 01.04.2008, Manchester, UK
  • Invited lecture (Conferences)
    Frontier Seminar at Institute of Particle Science and Engineering, Leeds University, 2.4.2008, Leeds, UK
  • Invited lecture (Conferences)
    Research Seminar, School of Chemical, Environmental and Mining Engineering, Nottinhgam University, 3.4.2008, Nottingham, UK
  • Invited lecture (Conferences)
    Research Seminar, Nuclear Physics Group, Positron Imaging Centre, Birmingham University, 4.3.2008, Birmingham, UK

Permalink: https://www.hzdr.de/publications/Publ-11233
Publ.-Id: 11233


Recent progress in ultra fast electron beam X-ray computed tomography

Hampel, U.; Fischer, F.; Bieberle, M.; Schleicher, E.
A new ultra fast electron beam X-ray CT scanner has been developed, implemented and tested in different applications. It consists, amongst other components, of an electron beam unit with 10 kHz scanning capability and 1 mm focal spot size and a 240 element circular CZT detector arc. The system is capable to produce slice images at up to 7 kHz frame rate of moderately absorbing objects with maximum 120 mm diameter. The paper introduces the scanner and first results for two-phase flow measurements in a bubble column and a fluidized bed.
Keywords: ultra fast electron beam ray tomography, two-phase flow
  • Contribution to proceedings
    5th International Symposium on Process Tomography, 25.-26.08.2008, Zakopane, Poland
    Proceedings of the 5th International Symposium on Process Tomography, Paper No. PT08_cr11
  • Lecture (Conference)
    5th International Symposium on Process Tomography, 25.-26.08.2008, Zakopane, Poland

Permalink: https://www.hzdr.de/publications/Publ-11232
Publ.-Id: 11232


Wire-mesh and X-ray microtomography studies of flow patterns in the mixing chamber of an effervescent atomizer

Otahal, J.; Boden, S.; Schleicher, E.; Beyer, M.; Jícha, M.; Hampel, U.
We performed wire-mesh and X-ray micro¬tomography studies of the two-phase flow in the mixing chamber of an effervescent atomizer. Flow patterns in the mixing chamber can be revealed by the miniature wire mesh sensor with a temporal resolution of 10 kHz whereas microtomography provides accurate and high-resolution axial-radial gas fraction profiles. The paper describes both measurement techniques and first results of experimental investigation.
Keywords: Two-phase flow, wire mesh sensor, X-ray microtomography
  • Contribution to proceedings
    5th International Symposium on Process Tomography, 25.-26.08.2008, Zakopane, Poland
    Proceedings of the 5th International Symposium on Process Tomography, Paper No. PT08_cr8
  • Lecture (Conference)
    5th International Symposium on Process Tomography, 25.-26.08.2008, Zakopane, Poland

Permalink: https://www.hzdr.de/publications/Publ-11231
Publ.-Id: 11231


Ultra fast scanned electron beam X-ray CT for two-phase flow measurement

Hampel, U.; Fischer, F.; Schleicher, E.; Hoppe, D.
We developed an ultra fast X-ray CT scanner based on scanned electron beam technology. The new device enables ultra fast two-dimensional phase fraction imaging in flow cross-sections at frame rates up to 7 kHz. As an example flow measurement in a 60 mm diameter bubble column is presented.
Keywords: Electron beam CT, X-ray CT, multiphase flow imaging
  • Contribution to proceedings
    CT2008: TOMOGRAPHY CONFLUENCE - An International Conference on the Applications of Computerized Tomography, 15.-17.02.2008, Kanpur, India
    AIP Conference Proceedings 1050: American Institute of Physics, 978-0-7354-0578-3, 144-150
  • Invited lecture (Conferences)
    CT2008: TOMOGRAPHY CONFLUENCE - An International Conference on the Applications of Computerized Tomography, 15.-17.02.2008, Kanpur, India

Permalink: https://www.hzdr.de/publications/Publ-11230
Publ.-Id: 11230


High resolution gamma ray tomography and its application to multiphase flow measurement

Hampel, U.; Bieberle, A.; Schleicher, E.; Hoppe, D.; Zippe, C.
Gamma ray tomography is a valuable tool for multiphase flow analysis in different areas of process, nuclear and mechanical engineering. Here, we introduce the design of a high resolution gamma ray tomography scanner and discuss two application examples from different technical fields.
Keywords: gamma ray tomography, multiphase flow imaging
  • Contribution to proceedings
    CT2008: TOMOGRAPHY CONFLUENCE - An International Conference on the Applications of Computerized Tomography, 15.-17.02.2008, Kanpur, India
    AIP Conference Proceedings 1050: American Institute of Physics, 978-0-7354-0578-3, 138-143
  • Invited lecture (Conferences)
    CT2008: TOMOGRAPHY CONFLUENCE - An International Conference on the Applications of Computerized Tomography, 15.-17.02.2008, Kanpur, India

Permalink: https://www.hzdr.de/publications/Publ-11229
Publ.-Id: 11229


Solidification of metal alloys under the influence of pulse-modulated magnetic fields

Nikrityuk, P. A.; Räbiger, D.; Eckert, K.; Eckert, S.; Gerbeth, G.
Alternating current (AC) magnetic fields are commonly used in industrial practice for melt stirring. The requirements arising from the particular metallurgical or casting operation can be manifold. For instance, the electromagnetic stirring is applied to provide an efficient mixing of metallic melts, to control the flow at the mold region in the continuous casting process or to achieve a purposeful alteration of the microstructure of casting ingots.
In the present study we introduce a novel type of electromagnetic stirring using a pulse-modulated rotating magnetic field (RMF). Capabilities of this approach are exemplarily demonstrated for controlling the melt flow during the unidirectional solidification of an Al-7wt%Si alloy. Two variants have been examined. Firstly, we use a succession of pulses that always have the same rotational direction (RMF-PSCD). Secondly, we use an RMF pulse sequence of alternating direction (RMF-PSAD). The latter method is related to a periodic inversion of the sense of rotation between two consecutive pulses. The characteristic period of the inversion for RMF-PSAD and of the pulses for RMF-PSCD is derivable from the spin-up dynamics of a continuously applied RMF.
Numerical and experimental investigations of different configurations applying an RMF either continuously or in form of RMF-PSAD and RMF-PSCD reveal the development of different flow pattern. It was found that the application the time-modulated RMF with suitable modulation frequencies delivers a homogeneous, equiaxed microstructure. Typical segregation pattern or flow-induced gas porosity usually arising from a continuous RMF application can be avoided with the new stirring methods. Essential features of the interplay between the electromagnetically-driven melt flow and solidification parameters such as temperature and mixture mass concentration of Si are discussed. Our results demonstrate that the success of the presented RMF-PSAD technique requires a precise tuning of the magnetic field parameter with respect to the material properties of the alloy, the geometry of the casting or process parameters like the cooling rate.
Keywords: solidification, Al alloys, electromagnetic stirring, pulse-modulated magnetic fields, macrosegregation
  • Poster
    7th PAMIR International Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France
  • Contribution to proceedings
    7th PAMIR International Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France, 879-884

Permalink: https://www.hzdr.de/publications/Publ-11228
Publ.-Id: 11228


Bubble-driven liquid metal flows influenced by miscellaneous magnetic fields

Zhang, C.; Eckert, S.; Gerbeth, G.
Bubble driven flows have found wide applications in industrial technologies. In metallurgical processes gas bubbles are injected into a bulk liquid metal to drive the liquid into motion, to homogenize the physical and chemical properties of the melt or to refine the melt. For such gas-liquid metal two-phase flows, external magnetic fields provide a possibility to control the bubble motion in a contactless way.
Compared to the numerous experimental studies on the movement of bubbles in transparent liquids, especially in water, the number of publications dealing with gas bubbles rising in liquid metals is comparatively small. The shortage of suitable measuring techniques can be considered as one reason for the slow progress in the investigations of gas-liquid metal flows. We applied the Ultrasound Doppler Velocimetry (UDV) for measurements of the velocity structure in liquid metal bubbly flows. Because of the ability to work non-invasively in opaque fluids and to deliver complete velocity profiles in real time it is very attractive for liquid metal applications. In the range of small or moderate void fractions the UDV technique delivers both the bubble and the liquid velocity.
Keywords: bubble plume, magnetic fields, velocity measurements, Ultrasound Doppler method
  • Lecture (Conference)
    7th PAMIR International Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France
  • Contribution to proceedings
    7th PAMIR International Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France, 363-368

Permalink: https://www.hzdr.de/publications/Publ-11227
Publ.-Id: 11227


Benchmark database on the evolution of two-phase flows in a vertical pipe

Lucas, D.; Beyer, M.; Kussin, J.; Schütz, P.
Basing on many years of experience a new extensive high quality database was obtained for stationary upward air-water flows in a vertical pipe with an inner diameter of 195.3 mm using the wire-mesh sensor technology. During the experiments the sensor was always mounted on the top of the test section while the distance between gas injection and measuring plane was varied to up to 18 different L/D by using gas injection chambers at different vertical positions. The gas was injected via holes in the pipe wall. In this new test series the pressure was kept at 0.25 MPa (absolute) at the location of the active gas injection while the temperature was constant at 30°C +- 1K. The experiments were done for 48 combinations of air and water superficial velocities varying from 0.04 m/s to 1.6 m/s for water and 0.0025 m/s to 3.2 m/s for air. From the raw data time averaged data as: radial gas volume fraction profiles, bubble size distributions, radial volume fraction profiles decomposed according to the bubble size and the radial profiles of the gas velocity were calculated. All data were checked regarding their consistency. They are characterized by a high resolution in space what makes them suitable for the development and validation of CFD-grade closure models, e.g. for bubble forces and coalescence and break-up. It is also an ideal base to validate CFD approaches for poly-dispersed flow. For this reason it is proposed to use the database as a benchmark for modelling poly-dispersed flows.
Keywords: multiphase flow, bubbly flow, churn turbulent flow, annular flow, bubble size, pipe flow
  • Contribution to proceedings
    XCFD4NRS, Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France, BOI-001
  • Lecture (Conference)
    XCFD4NRS, Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France
  • Nuclear Engineering and Design 240(2010), 2338-2346
    DOI: 10.1016/j.nucengdes.2009.11.010

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11226
Publ.-Id: 11226


A hybrid finite volume - boundary element method (FV-BEM) for the numerical solution of the kinematic induction equation

Giesecke, A.; Stefani, F.; Gerbeth, G.
The experimental realization of dynamo excitation has demonstrated the relevance of boundary conditions and material properties for a self-sustaining dynamo. The consideration of conductivity or permeability inhomogeneities requires a flexible numerical method that utilizes a local discretization scheme. A fast and accurate approach is provided by the constraint transport (CT) approach, a well known realization of a finite volume (FV) method that intrinsically maintains the solenoidal character of the magnetic field. The
problem of laboratory boundary conditions is treated by the boundary element method (BEM) which in combination with the FV scheme offers the flexibility of a local discretization with a stringent treatment of insulating magnetic boundary conditions.

Test simulations reproduce key results of the induction effects of a von-Karman-like flow and demonstrate the applicability and reliability of the approach.

Current examinations investigate the dynamo process presented by Busse & Wicht (1992, GaFD, 64, 135-144) who showed that a constant flow over a conducting material that exhibits a sinusoidal variation of the conductivity is already sufficient to generate a dynamo.
  • Lecture (Conference)
    MHD fundamentals, from liquid-metals to astrophysics, 14.-16.04.2008, Brussels, Belgium

Permalink: https://www.hzdr.de/publications/Publ-11225
Publ.-Id: 11225


Coexistence of localized and delocalized f-electrons in α-YbPdSn from thermodynamic and transport measurements

Görlach, T.; Putselyk, S.; Hamann, A.; Tomanic, T.; Uhlarz, M.; Schappacher, F. M.; Pöttgen, R.; von Löhneysen, H.
We report the specific heat, magnetic susceptibility, and magnetization as well as resistivity of hexagonal α-YbPdSn polycrystals down to temperatures T of 50 mK and fields up to 12 T. In the susceptibility χ(T), several different temperature regimes can be distinguished. For 300 K>T>170 K, a Curie-Weiss-like behavior is obtained with the effective moments close to that of Yb>sup>3+. The large Weiss temperature ΘH≈150 K and the leveling off of χ toward low T are indicative of valence fluctuations. Around 30 K, crystal-field excitations manifest themselves in features of χ(T) and the resistivity ρ(T). For 5 K>T>0.2 K, a Curie-Weiss behavior with µeff=1.27µB/Yb atom and ΘL=0.41 K is found, signaling the occupation of the lowest crystal-field doublet. A sharp maximum in χ(T) and in the specific heat C(T) indicates antiferromagnetic ordering at 250 mK. The specific-heat peak develops into a broadened Schottky anomaly in moderate magnetic fields. The sizable linear specific-heat coefficient γ=68 mJ/mole K2 is attributed to valence fluctuations. Likewise, the magnetization at 10 and 2.3 K measured up to 12 T can be decomposed into a contribution of delocalized electrons and localized magnetic moments. The data can be consistently interpreted in terms of a two-fluid model with ~6% localized and ~94% delocalized moments derived from (nearly) trivalent Yb.
  • Physical Review B 76(2007), 205112

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11224
Publ.-Id: 11224


Spin dynamics of NiCl2-4SC(NH2)2 in the field-induced ordered phase

Zvyagin, S.; Wosnitza, J.; Kolezhuk, A. K.; Zapf, V. S.; Jaime, M.; Paduan-Filho, A.; Glazkov, V. N.; Sosin, S. S.; Smirnov, A. I.
NiCl2-4SC(NH2)2 (known as DTN) is a spin-1 material with a strong single-ion anisotropy that is regarded as a new candidate for Bose-Einstein condensation (BEC) of spin degrees of freedom. We present a systematic study of the low-energy excitation spectrum of DTN in the field-induced magnetically ordered phase by means of high-field electron spin resonance measurements at temperatures down to 0.45 K. We argue that two gapped modes observed in the experiment can be consistently interpreted within a four-sublattice antiferromagnet model with a finite interaction between two tetragonal subsystems and unbroken axial symmetry. The latter is crucial for the interpretation of the field-induced ordering in DTN in terms of BEC.
  • Physical Review B 77(2008), 092413

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11223
Publ.-Id: 11223


An easy mechanical way to create ferromagnetic defective ZnO

Potzger, K.; Zhou, S.; Grenzer, J.; Helm, M.; Fassbender, J.ORC
We present an experiment for the creation of unconventional ferromagnetism in pure ZnO powder by application of mechanical force. The ferromagnetism is related to flake like structures in planar compressed pieces of the powder with easy axis in the plane. It is associated with defect creation and disappears upon annealing in oxygen. Besides cluster formation, such defects might be one of the non-intrinsic origins of ferromagnetism in transition metal doped ZnO.
Keywords: ZnO, Intendation, diluted magnetic semiconductors
  • Applied Physics Letters 92(2008), 182504

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11222
Publ.-Id: 11222


Large carbon-isotope shift of Tc in boron-doped diamond

Dubrovinskaia, N.; Dubrovinsky, L.; Papageorgiou, T.; Bosak, A.; Krisch, M.; Braun, H. F.; Wosnitza, J.
We report the carbon-isotope effect for boron-doped diamond (BDD). Resistive as well as specific-heat measurements reveal a 0.2 K shift in the superconducting transition temperature Tc between BDDs containing 13C and 12C. This is more than two times larger than could be expected from the mass difference by the use of the simple BCS formula in case the phenomenon is related to electron-phonon mediated superconductivity in BDD.
  • Applied Physics Letters 92(2008), 132506

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11221
Publ.-Id: 11221


Uranium(VI) Complexation with Pyoverdins and Related Model Compounds Studied by EXAFS

Moll, H.; Glorius, M.; Roßberg, A.; Bernhard, G.
Synchrotron-based EXAFS spectroscopy is a powerful technique to obtain structural information on radionuclide bioligand species in solution. As an example pyoverdin-type siderophores are a unique class of bioligands, with a high potential to dissolve, bind, and thus transport uranium in the environment. Pyoverdins are secreted from fluorescent Pseudomonas species which are ubiquitous soil bacteria. The functional groups of the pyoverdin molecule, LH4, participating in metal binding are the catechol group of the chromophore and two ligand sites in the peptide chain, i.e., one or two hydroxamate groups and one or two -hydroxy acid moieties [1]. The formation of complexes of UO22+ with pyoverdins released by the groundwater bacterium Pseudomonas fluorescens (CCUG 32456) isolated at a depth of 70 m in the Äspö Hard Rock Laboratory, Sweden, was investigated in our previous study [2]. Two UO22+-P. fluorescens pyoverdin species, UO2LH2 and UO2LH-, could be distinguished on the basis of UV-vis spectroscopy and fs-TRLFS.

Little structural information is available regarding the U(VI) pyoverdin species formed in aqueous solutions. We therefore performed U LIII-edge EXAFS measurements of test solutions containing 5x10-4 or 0.001 M UO22+ and pyoverdins or related model compounds at an ionic strength of 0.1 M NaClO4. The pH was varied between 2 and 8 depending on the bioligand. EXAFS measurements were carried out on the Rossendorf Beamline (ROBL) BM20 at the ESRF [3]. The samples were measured at room temperature using a water-cooled Si(111) double-crystal monochromator in channel cut mode (5-35 keV). The spectra were collected either in fluorescence mode using a 13-element Ge solid-state detector or in transmission mode using Ar filled ionization chambers. The model compounds simulate the hydroxamate function (simple hydroxamate and a trihydroxamate compound) and the chromophore of the pyoverdin molecule. The obtained structural information for the axial and equatorial oxygen atoms surrounding the uranium atom will be presented. Estimations of the near order surrounding of uranyl in pyoverdin complexes are based on the comparison with those found in uranium(VI) model ligand species.
Keywords: Uranyl, pyoverdins, bioligands, EXAFS
  • Contribution to proceedings
    Actinide XAS 2008, 15.-17.07.2008, Saint-Aubin, France
  • Lecture (Conference)
    Actinide XAS 2008, 15.-17.07.2008, Saint-Aubin, France

Permalink: https://www.hzdr.de/publications/Publ-11220
Publ.-Id: 11220


Annual Report 2007 - Institute of Ion Beam Physics and Materials Research

von Borany, J.; Heera, V.; Helm, M.; Möller, W.; (Editors)
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-493 2008

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-11219
Publ.-Id: 11219


CFD-modeling and Experiments of insulation debris transport phenomena in water flow

Krepper, E.; Cartland-Glover, G.; Grahn, A.; Weiss, F.-P.; Alt, S.; Hampel, R.; Kästner, W.; Seeliger, A.
The investigation of insulation debris generation, transport and sedimentation becomes important with regard to reactor safety research for PWR and BWR, when considering the long-term behavior of emergency core cooling systems during all types of loss of coolant accidents (LOCA). The insulation debris released near the break during a LOCA incident consists of a mixture of disparate particle population that varies with size, shape, consistency and other properties. Some fractions of the released insulation debris can be transported into the reactor sump, where it may perturb/impinge on the emergency core cooling systems.
Open questions of generic interest are the sedimentation of the insulation debris in a water pool, its possible re-suspension and transport in the sump water flow and the particle load on strainers and corresponding pressure drop. A joint research project on such questions is being performed in cooperation between the University of Applied Sciences Zittau/Görlitz and the Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow and the development of CFD models for its description. While the experiments are performed at the University at Zittau/Görlitz, the theoretical modeling efforts are concentrated at Forschungszentrum Dresden-Rossendorf.
In the current paper the basic concepts for CFD modeling are described and feasibility studies including the conceptual design of the experiments are presented.
Keywords: CFD, two-fluid approach, fiber flows, experiments
  • Contribution to proceedings
    XCFD4RS Experiments and CFD Codes Application to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France
  • Lecture (Conference)
    XCFD4RS Experiments and CFD Codes Application to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11218
Publ.-Id: 11218


Heat and charge transport in YNi2B2C and HoNi2B2C single crystals

Schneider, M.; Gladun, A.; Kreyssig, A.; Wosnitza, J.; Petzold, V.; Rosner, H.; Behr, G.; Souptel, D.; Müller, K.-H.; Drechsler, S.-L.; Fuchs, G.
For a systematic investigation of the heat- and charge-transport properties of YNi2B2C and HoNi2B2C, single-crystal measurements of the electrical resistivity, the thermal conductivity, and the thermoelectric power were performed on the same samples. For HoNi2B2C, a local maximum of the Lorenz number at 20 K is evidently connected with the occurrence of magnetic fluctuations well above the ordering temperature. For the in-plane thermal conductivity, a kink near the superconducting transition was observed, consistent with an anisotropic gap or a multiband description. For both investigated borocarbides, the electrical resistance is isotropic. In contrast, the thermal conductivity shows a pronounced anisotropy. The thermoelectric power exhibits a minor anisotropy and can be well described by electron-diffusion and phonon-drag contributions over a wide temperature range. Based on an analysis of full-potential local-orbital calculations, a strong influence of the boron z position on the thermoelectric power has been
revealed.
  • Journal of Physics: Condensed Matter 20(2008), 175221

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11217
Publ.-Id: 11217


Radiosynthesis of novel 18F-labelled derivatives of indiplon as potential GABAA receptor imaging tracers for PET

Fischer, S.; Hiller, A.; Scheunemann, M.; Deuther-Conrad, W.; Hoepping, A.; Diekers, M.; Wegner, F.; Brust, P.; Steinbach, J.
The involvement of gamma amino butyric acid (GABA) receptors in a variety of neurological and psychiatric diseases has promoted the development and use of radiolabelled benzodiazepines (BZ) for brain imaging by PET. However, these radioligands are unable to distinguish between the various subtypes of GABAA receptors. Novel non-BZ such as the pyrazolo-pyrimidine indiplon proved to be selective for the alpha1-subunit of the GABAA receptor. Here, we describe the syntheses of four novel 18F-labelled indiplon derivatives. Radiosyntheses were performed via n.c.a. 18F-nucleophilic substitution starting from the tosyl, bromo, and 4-nitrobenzoyl precursors to obtain fluorine substituted N-alkylamide side chain derivatives of indiplon, followed by multistep purification using semi-preparative high-performance liquid chromatography and solid phase extraction. Tosyl and bromo precursors were converted into 18F-labelled indiplon derivatives with good and reproducible radiochemical yield (RCY) (35–70%, decay corrected), high radiochemical purity (>/= 98.5%), and high specific activity ( > 150 GBq/lmol). By contrast, a low RCY (5–10%) and specific activity (10–15 GBq/lmol) were achieved for the 4-nitrobenzoyl precursor.
Keywords: GABAA receptor; 18F-labelled indiplon derivatives; PET
  • Journal of Labelled Compounds and Radiopharmaceuticals 51(2008), 123-131
    DOI: 10.1002/jlcr.1473

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11216
Publ.-Id: 11216


New chelating agents for copper(II): emerging opportunities for the application in nuclear medicine

Stephan, H.
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Institutskolloquium, Ruhr Universität Bochum, Lehrstuhl für Anorganische Chemie, 11.04.2008, Bochum, Germany

Permalink: https://www.hzdr.de/publications/Publ-11215
Publ.-Id: 11215


Design und Synthese mehrfunktionaler Liganden zur Entwicklung von radioaktiven Kupferkomplexen für Diagnostik und Therapie

Stephan, H.
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Institutskolloquium, Universität Bonn, Institut für Organische Chemie und Biochemie, 10.04.2008, Bonn, Germany

Permalink: https://www.hzdr.de/publications/Publ-11214
Publ.-Id: 11214


Uranium Speciation - from mineral to water

Geipel, G.; Bernhard, G.
Following the possible transport of uranium under environmental conditions we may start with the weathering of uranium compounds in the soil or in a mining waste rock pile. The seepage water contains about 2 mg/L uranium and the speciation is mainly influenced be the formation of the dicalcium-uranyl-tricarbonate species. The input of these seepage water leads to a dilution of the uranium by about three orders of magnitude. Using the cryogenic technique in TRLFS we could also determine the uranium speciation in the river water nearby the former uranium mining area. The uranium concentration was about 2 µg/L uranium and in the river water mainly uranyl-tricarbonate species are formed.
Despite this uranium can migrate down to the groundwater. In this case uranium may come back to the food chain by the production of mineral waters. We have studied the uranium speciation in several German mineral waters with uranium concentrations between 50 ng/L and 5 µg/L. In agreement with speciation calculations the sparkling and the calcium poor waters contain uranium as uranyl-tricarbonate species, whereas the non-sparkling waters if they are rich in calcium show clearly the formation of the dicalcium-uranyl-tricarbonate species. Using cryogenic TRLFS the detection limit for uranium species was estimated to be about 50 ng/L. Additionally a Hungarian medicinical water shows a uranium concentration of 150 µg/L. Due to the high mineralisation of this water also the dicalcium-uranyl-tricarbonate species was determined.
Summarizing it can be concluded that the most natural waters contain uranium as tri-carbonate species. According to investigations of these uranium species are less hazardous than phosphate and citrate species.
Keywords: Uranium, Speciation, Depleted
  • Invited lecture (Conferences)
    Institutsseminar, 28.05.2008, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-11213
Publ.-Id: 11213


Uranium Speciation - from mineral phases to mineral waters

Geipel, G.; Bernhard, G.
Uranium in the environment is ubiquitous. Nevertheless human activities as uranium mining and milling, use of uranium in nuclear power production and as penetrating ammunitions as well as the distribution of uranium with fertilizers lead to an increase of the uranium content in the environment.
Especially the uranium ammunition can generate locally high concentrations of uranium in the environment.
Weathering processes of the uranium metal lead in a first step to the formation of uranium minerals1. Depending on the composition of the soil the formation of several types of minerals can be estimated. Especially the content of phosphate from fertilizers and the aluminium from soil components are involved in the mineral formation.
By use of time-resolved laser-induced fluorescence spectroscopy (TRLFS) the mineral type can be determined without any destruction. A large database of luminescence spectra, obtained from uranium minerals of the collection of the Technical University Mining Academy Freiberg, enables us to identify the formed uranium mineral2. In the experiment, described in (1) we found that mainly the mineral sabugalite was formed. Other experiments with pure calcium and phosphate containing solution lead to the formation of the mineral meta-autunite3.
In a second step the formed minerals than undergo further weathering processes, forming dissolved uranium species.
In the former uranium mining areas of eastern Germany we could discover a new dissolved uranium carbonate species4,5. However, the uranium concentration of about 2 mg/L in these mining related waters is relatively high. Nevertheless the carbonate and calcium concentration are high enough to form a very stable dicalcium-uranyl-tricarbonate species. This species is of great importance, as its existence explains the uranium migration at the Hanford site6.
In addition to the calcium species it can be stated that also the other alkaline earth elements form this type of alkaline earth uranyl carbonate species7,8,910.
Following the uranium migration in the soil we could detect in the experiments that mainly carbonate species are formed. The pure carbonate species do not show any luminescence properties at room temperature. Therefore the samples have to be frozen to temperatures below 220 K11, in order to minimize the dynamic quench effect of the carbonate anion. This increases also the luminescence intensity and the luminescence lifetime of all carbonate containing species.
Nevertheless, in one case of the soil experiment also hydroxo species were found. This may be connected to a non-equilibrium with atmospheric CO2 in this column.
Following the possible transport of uranium under environmental conditions we may start with the weathering of uranium compounds in the soil or in a mining waste rock pile. The seepage water contains about 2 mg/L uranium and the speciation is mainly influenced be the formation of the dicalcium-uranyl-tricarbonate species. The input of these seepage water leads to a dilution of the uranium by about three orders of magnitude. Using the cryogenic technique in TRLFS12 we could also determine the uranium speciation in the river water nearby the former uranium mining area. The uranium concentration was about 2 µg/L uranium and in the river water mainly uranyl-tricarbonate species are formed.
Keywords: Uranium, Speciation
  • Contribution to proceedings
    2nd International Nuclear Chemistry Congress, 13.-18.04.2008, Cancun, Mexico
  • Lecture (Conference)
    2nd International Nuclear Chemistry Congress, 13.-18.04.2008, Cancun, Mexico
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 599-601
  • Lecture (Conference)
    5th International Conference Uranium Mining and Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11212
Publ.-Id: 11212


High cluster formation tendency in Co implanted ZnO

Potzger, K.; Kuepper, K.; Xu, Q.; Zhou, S.; Schmidt, H.; Helm, M.; Fassbender, J.ORC
ZnO(0001) single crystals have been implant-doped with maximum 5 atomic % of Co at low temperatures. While as-implanted crystals do not show ferromagnetic properties, post implantation annealing leads to the transformation of the implanted Co ions into small metallic clusters giving rise to a pronounced hysteresis upon magnetization reversal. The dispersed Co ions are in 2+ oxidation state. Positive magneto-resistance could be observed at low temperatures.
Keywords: zno, ion implantation, diluted magnetic semiconductors
  • Journal of Applied Physics 104(2008)2, 23510

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11211
Publ.-Id: 11211


Resonant Ring Test Bench for Warm Window and Coupler Tests at ELBE.

Staats, G.; Buechner, A.; Buettig, H.; Michel, P.; Schurig, R.; Teichert, J.; Winter, A.
A new coupler test bench based on a resonant ring has been built at ELBE in Dresden-Rossendorf to run warm window as well as coupler tests with RF power up to 190 kW (warm window tests up to 250kW) in CW operation. The ring is driven by a 10 kW klystron. This test bench also includes liquid nitrogen cooling of the ceramic cold window of the RF-coupler which allows testing under almost real conditions. A special waveguide to coupler transition was designed to match couplers with different antenna tips. At the beginning with the test bench it was possible to test the warm windows used at ELBE. It has been shown that the used warm windows are usable up to 70kW of CW-RF power with additional air cooling, much more than the 10kW CW used at ELBE. After this test the coupler used at the ELBE cryomodules was tested, in CW operation a power level of about 20kW was reached. More tests are in program and in near future some improvements are planned.
  • Lecture (Conference)
    Fifth CW and High Average Power RF Workshop, 25.-28.03.2008, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-11210
Publ.-Id: 11210


Summary of the OECD VVER-1000 MSLB benchmark results

Kolev, N.; Donov, J.; Spasov, I.; Royer, E.; Höhne, T.
Recent coupled code benchmarks have identified coolant mixing in the reactor vessel as an unresolved issue in the analysis of complex plant transients with reactivity insertion. This issue was one of the main topics in Phase 2 of the recently completed OECD VVER-1000 Coolant Transient Benchmark (V1000CT-2). Exercise 1 of this benchmark is a VVER-1000 V320 vessel mixing problem based on a steam generator isolation experiment at Kozloduy-6 in Bulgaria. Plant data are available for code validation. The validated codes can be used to calculate asymmetric MSLB transients involving similar mixing patterns. A variety of mixing models were tested including multi-1D with cross flow, coarse 3D and fine CFD.
This presentation summarizes a comparison of six submitted CFD results for the V1000CT-2 Exercise 1. The results were obtained with a specified CAD model of the real vessel geometry. Five participants used a solution region from vessel inlet to the core inlet. FZK solved the benchmark for the whole pressure vessel. The comparison is code-to-code and code to experiment. The results show good overall agreement with the experiment and between the codes as well as specific features depending on the turbulence model.
  • Lecture (Conference)
    Annual Meeting of the AER Working Group D, 31.03.-01.04.2008, Garching, Germany

Permalink: https://www.hzdr.de/publications/Publ-11209
Publ.-Id: 11209


A PWR boron dilution benchmark

Kliem, S.
The presentation describes the outline, assumptions and preliminary results of a boron dilution benchmark for pressurized water reactors. In this benchmark the neutron kinetic code DYN3D in combination with three different thermal hydraulic models has been used. Besides the own thermal hydraulic model of DYN3D, models based on the ATHLET and the RELAP5 code were created. The calculations were carried out for a generic PWR core for the subcritical hot zero power state at beginning of an equilibrium cycle. All control rods except the most effective one are inserted into the core. The deboration scenario is based on the start-up of the first main coolant pump with a slug of deborated coolant in the loop. Time dependent core inlet distribution of the boron concentration used as boundary condition for the calculations is based on corresponding experiments at the coolant mixing test facility ROCOM.
Stationary core calculations for the initial state show an excellent agreement between the three calculations. The influence of the different thermal hydraulic models reveals after the return to power. The deboration front causes in all three cases a super-prompt overcriticality jump. The time and the height of the first power peak depend on the ability of the codes to suppress the numerical diffusion of the deboration front. DYN3D and DYN3D/RELAP5 shows with about 30000 MW a considerably lower value than the 53000 MW of DYN3D/ATHLET. This difference has also an influence on the maximum cladding temperature. DYN3D/ATHLET shows with nearly 300 °C the highest value, what is still far from safety relevant conditions.
  • Lecture (Conference)
    Annual Meeting of the AER Working Group D, 31.03.-01.04.2008, Garching, Germany

Permalink: https://www.hzdr.de/publications/Publ-11208
Publ.-Id: 11208


Second dynamic AER benchmark – new results

Kliem, S.
The presentation describes the new results obtained for the asymmetric control rod ejection benchmark defined in the frame of the co-operation inside the AER.
  • Lecture (Conference)
    Annual Meeting of the AER Working Group D, 31.03.-01.04.2008, Garching, Germany

Permalink: https://www.hzdr.de/publications/Publ-11207
Publ.-Id: 11207


CW Operation of the Superconducting LINAC "ELBE"

Buettig, H.; Arnold, A.; Buechner, A.; Gabriel, F.; Justus, M.; Lehnert, U.; Michel, P.; Schneider, C.; Schurig, R.; Staats, G.; Teichert, J.
The superconducting CW-LINAC of the Radiation Source ELBE, based on 1.3 GHz-TESLA cavities, has been operational since 2001. An overview of the ELBE facility and of the RF-system of the superconducting CW-LINAC are presented. It is reported on different improvements on RF components to ensure stable operation of this user facility and on experience gathered during 7 years of CW- operation.
  • Lecture (Conference)
    Fifth CW and High Average Power RF Workshop 2008, 25.-28.03.2008, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-11206
Publ.-Id: 11206


The impact of turbulent flow on the solidification of metal alloys driven by a rotating magnetic field

Nikrityuk, P. A.; Eckert, K.; Eckert, S.
The paper presents a study concerning the impact of a turbulent, rotating melt flow on the macrosegregation and the shape of the mushy zone during unidirectional solidification of an Al-7wt%Si alloy. The flow is generated by applying a rotating magnetic field (RMF). Direct numerical simulations (DNS) were performed to study the weakly turbulent flow. The transient heat and mass transfer were simulated using a standard mixture model (Bennon and Incropera, 1987). The treatment of the fluid flow in the mushy zone requires the use of permeability and mixture viscosity models, which also allow for consideration of both columnar and equiaxed solidification. Our results demonstrate that in the case of columnar solidification the Ekman pumping effect causes the development of a Si-enriched liquid channel along the rotational axis . The Taylor-Goertler vortices, which appear randomly along the side wall of the cylinder, amplify the solute transport from the wall to the axis intermittently in the upper part of the mushy zone. This effect leads to a wavy shape of the mushy zone and segregation in the form of a fir tree with a distinct accumulation of silicon along the axis of the cylinder. Moreover, we propose strategies to avoid macrosegregation by using a pulse-modulated rotating magnetic field.
Keywords: solidification, rotating magnetic field, turbulent flow, macrosegregation
  • Lecture (Conference)
    2nd International Conference on Advances in Solidification Processes, 17.-22.06.2008, Leoben, Austria
  • International Journal of Cast Metals Research 22(2009)No 1-4, 236-239

Permalink: https://www.hzdr.de/publications/Publ-11205
Publ.-Id: 11205


CFD approaches for modeling bubble entrainment by an impinging jet

Schmidtke, M.; Lucas, D.
This contribution presents different approaches for the modeling of air entrainment under water by a plunging jet. Since the generation of bubbles happens on a scale which is smaller than the bubbles, this process cannot be resolved in meso-scale simulations, which include the full length of the jet and its environment. This is why the air entrainment has to be modeled in meso-scale simulations.
In the frame of an Euler-Euler simulation, the local morphology of the phases has to be considered in the drag model. For example the air is a continuous phase above the water level but bubbly below the water level. Various drag models are tested and their influence on the gas void fraction below the water level is discussed.
As a first approach the air is modelled as dispersed phase everywhere in the domain. This causes an air entrainment which is obviously determined by numerical effects. Thus, this approach is not suitable for the implementation of a physical model for gas entrainment. The algebraic interface area density (AIAD) model applies a drag coefficient for bubbles and a different drag coefficient for the free surface. If the AIAD model is used for the simulation of impinging jets, the gas entrainment depends on the free parameters included in this model. The calculated gas entrainment can be adapted via these parameters. Therefore, an advanced AIAD approach could be used in future for the implementation of models (e.g. correlations) for the gas entrainment.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11204
Publ.-Id: 11204


Multi-Vendor Enterprise Storage-Lösungen erfolgreich integrieren

Konrad, U.
Eingeladener Vortrag der Computerwoche Fachkonferenz: Data Center up-to-date 08 - virtualisieren, konsolidieren, outsourcen
Es wird ein Anwendervortrag gehalten, der Fokus liegt auf folgenden Schwerpunkten:
- IT-Profil des Forschungszentrums Dresden-Rossendorf
- Enterprise Storagelösungen
- Virtualisierung im Speichernetzwerk
- Einsatz von Filesystemen
- Lebenszyklus eines Storagesystems
Ein wesentlicher Punkt des Vortrages ist die Beschreibung der am FZD geschaffenen Lösung mit in-band Virtualisierung des Speichers im Netzwerk über spezielle Appliances sowie die Auswertung der Erfahrungen dazu.
Keywords: information technology, data center, enterprise storage solutions, in-band virtualization, SAN, file systems, computerwoche
  • Invited lecture (Conferences)
    Data Center up-to-date 08 - virtualisieren, konsolidieren, outsourcen, 10.04.2008, Frankfurt am Main, Germany

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11203
Publ.-Id: 11203


Velocity measurements in liquid metal flows using the Ultrasonic Doppler Method: examples and perspectives

Eckert, S.; Gerbeth, G.
The Ultrasound Doppler Velocimetry (UDV) is a non-intrusive technique to measure velocities of liquid flows. Because of the ability to work in opaque fluids and to deliver complete velocity profiles in real time it becomes very attractive for liquid metal applications. But, in case of hot metallic melts the user is confronted with a number of specific problems: First of all the application of the ultrasonic transducers is usually restricted to maximum temperatures of about 150°C. The transmission of a sufficient amount of ultrasonic energy from the transducer to the fluid has to be guaranteed. Here, the acoustic coupling and the wetting conditions have to be considered as important issues. Moreover, the flow has to be seeded with reflecting particles to obtain Doppler signals from the fluid.
In this presentation various applications of UDV in liquid metal flows will be shown to demonstrate the capabilities and current restrictions of this technique. For instance, we consider single- and multi-transducer arrangements for flow mapping or present velocity measurements obtained during the solidification of a metallic melt. Besides the determination of velocity profiles in the liquid phase the UDV data allow for an assessment of the current position of the solidification front, too. Specific problems arising in the context of UDV measurements in liquid metal experiments will be discussed.
Keywords: Ultrasonic Doppler velocimetry, velocity measurements, liquid metals, electromagnetic stirring
  • Invited lecture (Conferences)
    6th. International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 09.-11.09.2008, Praha, Czech Republic
  • Contribution to proceedings
    6th. International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 09.-11.09.2008, Praha, Czech Republic, 1-6

Permalink: https://www.hzdr.de/publications/Publ-11202
Publ.-Id: 11202


Application of the Ultrasound Doppler method for velocity measurements in an electromagnetically-stirred liquid metal

Räbiger, D.; Eckert, S.; Gerbeth, G.
Alternating current (AC) magnetic fields are commonly used in industrial practice for melt stirring. The requirements arising from the particular metallurgical or casting operation can be manifold. For instance, the electromagnetic stirring is applied to provide an efficient mixing of metallic melts, to control the flow at the mold region in the continuous casting process or to achieve a purposeful alteration of the microstructure of casting ingots. However, a purposeful practice of melt stirring requires suitable flow measurements which deliver a detailed knowledge of the magnetic field impact on the flow pattern.
This experimental study considers the transient liquid metal flow which is generated inside a cylindrical container by discontinuously applying a rotating magnetic field (RMF). The focus is on the fluid motion arising from the impulsive spin-up from the resting state, a single pulse or a sequence of RMF pulses. The ultrasonic Doppler velocimetry (UDV) has been used to determine profiles of the fluid velocity in the ternary alloy GaInSn. The azimuthal and vertical velocity components have been measured allowing for an analysis of both the primary, swirling flow and the secondary flow in the radial-meridional plane. The experimental results show an excellent agreement with recently published numerical results. The investigations reveal that the recirculating flow in the radial- meridional plane undergoes characteristic oscillations. Periodic reversals of the meridional flow direction can be observed for a specific length of the RMF pulses.
Our results demonstrate that the utilisation of a time-modulated rotating magnetic field (RMF) offers a considerable potential to provide optimal flow pattern for an efficient melt mixing. For instance, such tailored methods of electromagnetic stirring can be applied during the solidification of metal alloys, where a well-aimed modification of casting properties is achieved by controlling the melt flow in the bulk and adjacent to the solidification front.
Keywords: Ultrasonic Doppler velocimetry, velocity measurements, liquid metal, modulated magnetic fields
  • Lecture (Conference)
    6th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 09.-11.09.2008, Praha, Czech Republic
  • Contribution to proceedings
    6th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 09.-11.09.2008, Praha, Czech Republic, 143-146

Permalink: https://www.hzdr.de/publications/Publ-11201
Publ.-Id: 11201


Thermophysical properties of Al-Cu liquid alloys

Plevachuk, Y.; Sklyarchuk, V.; Yakymovych, A.; Eckert, S.; Willers, B.
Considerable effort is permanently directed to optimise methods and facilities for material processing technologies like melting, refining or casting of metallic alloys. The main goals are an improvement of the final product quality, an enhancement of the process efficiency and an economical consumption of resources and energy. Nowadays it is impossible to imagine such optimisation without performing numerical simulations and a corresponding physical modelling. However, the accuracy of the predictions depends sensitively on the availability of precise and trustworthy data concerning the thermophysical properties of the alloys under consideration. The development of new workable aluminium-based light alloys is a key issue in current materials science. Al-Cu alloys, for instance AlCu4TiMg (A356), are the most utilized casting alloys in the aluminium industry. The distinctive characteristics of these alloys are low density, high melting temperature, good thermal conductivity and excellent oxidation resistance.
In this work, thermophysical properties (density, viscosity and electrical conductivity) of liquid Al96Cu4, Al80Cu20, Al70Cu30, and AlCu4TiMg (wt.%) alloys have been measured in a wide temperature range from the melting point up to 1200 K. Corresponding fit relations have been derived for the density, the dynamic viscosity and the electrical conductivity. All properties are compared to available literature data. An increase of a copper content raises gradually the density and the dynamic viscosity of aluminium suggesting a short-range order in the liquid state. According to the density and viscosity data, no substantial structure rearrangement takes place with admixtures. At the same time, the electrical conductivity results demonstrate that small additions of copper slightly raise the conductivity of liquid Al, while further increase of a copper content decreases predictably the conductivity values.
Keywords: aluminium alloys, density, viscosity, electrical conductivity
  • Poster
    11th International Conference on Aluminium Alloys, 22.-26.09.2008, Aachen, Germany
  • Contribution to proceedings
    11th International Conference on Aluminium Alloys, 22.-26.09.2008, Aachen, Germany, 1359-1360

Permalink: https://www.hzdr.de/publications/Publ-11200
Publ.-Id: 11200


Solidification of aluminium alloys under the influence of modulated magnetic fields

Eckert, S.; Willers, B.; Räbiger, D.; Dong, J.; Nikrityuk, P. A.; Eckert, K.
AC magnetic fields are used in industrial practice for melt stirring. The requirements are manifold for miscellaneous metallurgical operations or casting technologies, mainly the magnetic field application should provide an efficient mixing of the melt in order to achieve homogeneous distributions of solute and/or temperature. The rotary stirring during solidification has been proved to be a striking method to achieve a purposeful alteration of the microstructure of casting ingots, such as a distinct grain refining or the promotion of a transition from a columnar to an equiaxed dendritic growth (CET). Solidification experiments as well as numerical simulations were carried out considering the directional solidification of Al-Si alloys from a water cooled copper chill. A modulated rotating magnetic field (RMF) was applied for melt agitation. Thermocouples were used to measure the temperature field during solidification. The velocity field in the liquid phase was determined by means of Ultrasound Doppler velocimetry (UDV). The comparison between numerical simulations and solidification experiments delivered a good agreement. Our results demonstrate that the modulated magnetic field enables an effective control of the flow field and the structure of the solidified samples.
Keywords: solidification, aluminium alloys, electromagnetic stirring, modulated magnetic fields, macrosegregation
  • Lecture (Conference)
    11th International Conference on Aluminium Alloys, 22.-26.09.2008, Aachen, Germany
  • Contribution to proceedings
    11th International Conference on Aluminium Alloys, 22.-26.09.2008, Aachen, Germany, 497-502

Permalink: https://www.hzdr.de/publications/Publ-11199
Publ.-Id: 11199


Use of time-modulated AC magnetic fields for melt flow control during unidirectional solidification

Eckert, S.; Räbiger, D.; Willers, B.; Nikrityuk, P. A.; Eckert, K.
The rotary stirring during solidification has been proved to be a striking method for achieving a purposeful alteration of the microstructure of casting ingots, such as grain refinement or the promotion of a transition from a columnar to an equiaxed dendritic growth (CET). However, the imposition of a rotating magnetic field (RMF) also causes problems like the occurrence of typical segregation pattern or a deflection of the upper free surface leading to surface defects or the entrainment of gas. A permanent radial inward flow along the solidification front is responsible for the transport of solute to the axis of the ingot resulting in typical freckle segregation pattern in form of vertical channels filled with alloy of eutectic composition. We present a new innovative method of electromagnetic stirring using a modulated RMF which offers a considerable potential for a well-aimed modification of casting properties. This paper considers the directional solidification of Al-Si alloys from a water cooled copper chill. Modulated AC magnetic fields were applied for melt agitation. The comparison between numerical simulations and solidification experiments delivered a good agreement. Our results demonstrate that the modulated magnetic field enables an effective control of the flow field and the structure of the solidified samples.
Keywords: solidification, electromagnetic stirring, rotating magnetic field, modulated AC magnetic fields, macrosegregation
  • Lecture (Conference)
    Second International Conference on Advances in Solidification Processes, 17.-20.06.2008, Leoben, Austria
  • International Journal of Cast Metals Research 22(2009), 78-81

Permalink: https://www.hzdr.de/publications/Publ-11198
Publ.-Id: 11198


Observation of melt flow effects on dendritic growth of Ga-In alloys by X-ray radioscopy

Boden, S.; Eckert, S.; Willers, B.; Gerbeth, G.
Capabilities of the X-ray attenuation contrast radioscopy were utilized to provide a real-time diagnostic technique for observations of dendritic growth and the melt flow during solidification of a Ga-30wt%In alloy. The solidification process was visualised using a microfocus X-ray tube. The X-ray facility provided shadow radiographs at spatial resolutions of about 10 µm and frame repetition rates up to 25 Hz. We used the optical flow approach to derive information about the velocity field ahead of the solidification front and in the mushy zone from the observed displacement of the brightness patterns appearing during the X-ray image sequence. Experiments have been carried out to solidify the Ga-In alloy unidirectionally either starting from the bottom or the top of the specimen. The first case is significantly affected by solutal convection. Buoyancy-driven flow patterns were found at length scales being larger than the length scales of the solidifying microstructure. A strong coupling between convection and dendritic growth became apparent via flow-induced modifications of the concentration profile in the liquid. Dendritic fragmentation can be observed during the solidification in the reverse top-down direction. Variations of the applied cooling rate evoked a transition from a columnar to an equiaxed dendritic growth (CET).
Keywords: solidification, X-ray radioscopy, dendritic growth, dendrite fragmentation
  • Lecture (Conference)
    Second International Conference on Advances in Solidification Processes, 17.-20.06.2008, Leoben, Austria

Permalink: https://www.hzdr.de/publications/Publ-11197
Publ.-Id: 11197


Shear flow compositions on the Galerkin piano: A unified theory for instabilities, strange attractors, statistical mechanics and attractor control

Noack, B. R.; Schlegel, M.; Pastoor, M.; Luchtenburg, M.; Mutschke, G.; Morzynski, M.; Comte, P.; Tadmor, G.; Ahlborn, B.
A well-tuned Galerkin melody about fluid flows requires a piano with the right keys (called modes, e.g. POD), musical notes (physics resolution), an audience (observer), and a composer (control law) in case the music shall be changed. Here, we briefly review new key enablers for these tasks. Then, a finite-time thermodynamics is proposed bridging fluid mechanics disciplines and theoretical physics treasures. This formalism opens the path to fully nonlinear attractor control, as required for turbulence manipulation in experimental demonstrators. Presented studies include shear flows with simple to complex dynamics.
Keywords: Galerkin method, POD, control, shear flow, instabilities, finite-time thermodynamics
  • Invited lecture (Conferences)
    Workshop Industrial applications of low-order models based on proper orthogonal decomposition, 31.03.-02.04.2008, Bordeaux, France

Permalink: https://www.hzdr.de/publications/Publ-11196
Publ.-Id: 11196


Ion irradiation induced sub-100nm ferromagnetic patterns

Liedke, M. O.; Strache, T.; Fassbender, J.ORC; Möller, W.; Menéndez, E.; Sort, J.; Gemming, T.; Weber, A.; Heyderman, L. J.; Rao, K. V.; Deevi, S. C.; Nogués, J.
Focus ion beam (FIB) patterning of Fe60Al40 provides the potential to create arrays of microscopic ferromagnetic regions embedded in a paramagnetic matrix. As the consequence of low fluence irradiation such a method does not affect the surface roughness. Due to the ion damage distribution the phase transition from the chemically ordered B2-phase to the chemically disordered, ferromagnetic A2-phase is setup. The magnetic phase transformation is studied as a function of noble gases mass and is directly related to the number of displacements per atom (dpa) during ion irradiation. In case of heavy ions (Ar+, Kr+ or Xe+) the phase transformation originates purely from ballistic nature of the disordering process. For light ions (He+, Ne+) the disordering conditions deviates from the former case. The bulk vacancy diffusion from dilute collision cascades, that leads to a partial recovery of the thermodynamically favored B2-phase, plays a major role. Furthermore, by means of moderately high temperature annealing (about 900 K) the paramagnetic phase is completely recovered due to the annealing-induced atomic reordering. Therefore, local ion irradiation may lead to a novel type of patterned recording media free from tribological and exchange coupling effects.
Keywords: focus ion beam, irradiation, phase transition, defects, magnetic pattering
  • Lecture (Conference)
    The European Conference PHYSICS OF MAGNETISM 2008, 24.-27.06.2008, Poznan, Poland

Permalink: https://www.hzdr.de/publications/Publ-11195
Publ.-Id: 11195


Spectroscopic THz near-field microscope

von Ribbeck, H.-G.; Brehm, M.; van der Weide, D. W.; Winnerl, S.; Drachenko, O.; Helm, M.; Keilmann, F.
We demonstrate a scattering-type scanning near-field optical microscope (s-SNOM) with broadband THz illumination. A cantilevered W tip is used in tapping AFM mode. The direct scattering spectrum is obtained and optimized by asynchronous optical sampling (ASOPS), while near-field scattering is observed by using a space-domain delay stage and harmonic demodulation of the detector signal. True near-field interaction is determined from the approach behavior of the tip to Au samples. Scattering spectra of differently doped Si are presented.
Keywords: terahertz, SNOM
  • Open Access Logo Optics Express 16(2008), 3430-3438

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11194
Publ.-Id: 11194


BACOPP-D - An etoposide-free dose-escalated polychemotherapy regimen in advanced Hodgkin Lymphoma

Naumann, R.; Wetzko, K.; Haenel, A.; Friedrichsen, K.; Zschuppe, E.; Schmidt, H.; Dawel, M.; Beuthien-Baumann, B.; Scbwanebeck, U.; Ehninger, G.; Haenel, M.
Introduction:
The development of the escalated BEACOPP regimen let to an improved outcome in patients with advanced Hodgkin Lymphoma (HD9 study of the GHSG). However, the application of high dose etoposide (cumulative 4,8 g/m2 per 8 cycles) seems to be associated with an increased incidence of secondary MDS and AML, respectively. Therefore, the aim of our multicenter pilot study was to evaluate the efficacy and toxicity of the etoposide free as well as dose intensified BACOPP-D protocol.

Methods:
Since May 2000 a total of 115 patients with Hodgkin Lymphoma (HL) stage IIB, III, and IV were treated with BACOPP-D which included cyclophosphamide 1250 mg/m2 (d1), adriamycin 25 mg/m2 (d1+2), dacarbazine 250 mg/m2 (d1-3), procarbazine 100 mg/m2 (d1-7), prednisolone 40 mg/m2 (d1-14), bleomycin 10 mg/m2 (d8) and vincristine 1,4 mg/m2 (maximum 2 mg, d8) at three-weekly intervals with granulocyte colony-stimulating factor (G-CSF). A consolidating involved field radiation (30 Gy) was performed only in patients who achieved less than CR following chemotherapy. Post-treatment follow-up included PET imaging.

Results:
Until now 97 patients (median age 35 years, range 17-65; 61 male, 36 female) are assessable for toxicity and treatment outcome. We analyzed the acute toxicity for 728 cycles of BACOPP-D. CTC/WHO grade III/IV haematological toxicities per patient were observed as follows: leukopenia 93%, anemia 39%, and thrombocytopenia 33%. CTC grade III/IV non-haematological side effects included documented infection (4%) and lung toxicity (one patient). A total of 85 patients (88%) achieved complete remission, 9 patients (9%) achieved partial remission, three patients (3%) had progressive disease. At a median observation time of 39 months (0,9-77 months), five patients have relapsed, and nine deaths were documented (4 HL-specific and 3 treatment related deaths, 1 death due to ruptured Meckel diverticulum with peritonitis, one 65 year-old woman died in CR following myocardial infarction). One patient developed a second neoplasia (hypopharyngeal carcinoma in an alcoholic). The overall survival and freedom from treatment failure rates at 39 months were 91% and 85%, respectively. FDG-PET scans after BACOPP-D chemotherapy were performed in 68 of 97 patients. PET scans revealed no increased FDG uptake in 48/68 patients (71%), in 20 patients (29%) increased FDG uptake was detected. In the group of patients with increased FDG uptake, one patient developed progressive disease and four patients relapsed. In the group with PET-negative findings no patient relapsed.

Diskussion:
BACOPP-D regimen appears as a feasible and effective treatment which induced a complete morphologic and metabolic remission in a high proportion of patients with advanced HL. The treatment was associated with moderate acute toxicity. No secondary AML or MDS occurred until now.

Footnotes

Disclosure: No relevant conflicts of interest to declare.
  • Poster
    ASH 49th Annual Meeting, 08.-11.12.2007, Atlanta/Georgia, USA
  • Abstract in refereed journal
    BLOOD 110(2007)11, 685A

Permalink: https://www.hzdr.de/publications/Publ-11193
Publ.-Id: 11193


Das neue Urheberrecht seit 1.1.2008, Dokumentenbereitstellung, SUBITO, EZB - Erfahrungen aus der Praxis

Reschke, E.
Die Umsetzung des neuen Urheberechts für den Bereich der Dokumentenbereitstellung durch Bibliotheken ist äußerst problematisch. Die Einschränkungen der Verfügbarkeit elektronischer Lieferungen bedingen umfangreiche Schulungen des Bibliothekspersonals, Informationen der Bibliotheksbenutzer, zusätzlichen Bearbeitungsaufwand der Bestellungen und Bestelleingangs- und Rechnungsverwaltung und wesentlichen finanziellen Mehraufwand. Im Vortrag wird am Beispiel des Subito-Rahmenvertrages auf die aktuellen Probleme eingegangen.
  • Lecture (others)
    Treffen des Arbeitskreises Spezialbibliotheken Dresden, 02.04.2008, Dresden, Germany

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11192
Publ.-Id: 11192


Wire mesh sensor studies in a vertical pipe

Azzopardi, B.; Hernandez Perez, V.; Kaji, R.; Da Silva, M. J.; Beyer, M.; Hampel, U.
A Wire Mesh Sensor system has been employed on a vertical 67 mm diameter pipe up which air and water mixtures flow. This enables an examination of the flow to be carried out at several levels of complexity. The measuring system provides time and cross-sectionally resolved information about the spatial distribution of the phases. The information can be used to obtain space and time averaged void fractions, radial profiles of time averaged void fraction and cross-sectional averaged time series of void fraction. This last yields Probability Density Function information as well as other statistical information. It also yields data of the frequency of periodic structures within the flow. More powerfully, the fully resolved data can give deep insights into the structure of the gas/liquid interface. A hitherto unreported structure has been seen in churn flow which could be linked to the wisps in wispy-annular flow.
Keywords: wire-mesh sensor, pipe flow, wispy-annular flow
  • Contribution to proceedings
    Fifth International Conference on Transport Phenomena In Multiphase Systems, HEAT 2008, 30.06.-03.07.2008, Bialystok, Poland
    Proceedings of the 5th International Conference on Transport Phenomena in Multiphase Systems, HEAT 2008, 405-412
  • Lecture (Conference)
    Fifth International Conference on Transport Phenomena In Multiphase Systems, HEAT 2008, 30.06.-03.07.2008, Bialystok, Poland

Permalink: https://www.hzdr.de/publications/Publ-11191
Publ.-Id: 11191


Spectral shaping of laser generated proton beams

Pfotenhauer, S. M.; Jäckel, O.; Sachtleben, A.; Polz, J.; Ziegler, W.; Schlenvoigt, H.-P.; Amthor, K.-U.; Kaluza, M. C.; Ledingham, K. W. D.; Sauerbrey, R.; Gibbon, P.; Robinson, A. P. L.; Schwoerer, H.
The rapid progress in the field of laser particle acceleration has stimulated a debate about the promising perspectives of laser based ion beam sources. For a long time, the beams produced exhibited quasi-thermal spectra. Recent proof-of-principle experiments demonstrated that ion beams with narrow energy distribution can be generated from special target geometries. However, the achieved spectra were strongly limited in terms of monochromacity and reproducibility. We show that microstructured targets can be used to reliably produce protons with monoenergetic spectra above 2 MeV with less than 10% energy spread. Detailed investigations of the effects of laser ablation on the target resulted in a significant improvement of the reproducibility. Based on statistical analysis, we derive a scaling law between proton peak position and laser energy, underlining the suitability of this method for future applications. Both the quality of the spectra and the scaling law are well reproduced by numerical simulations.
Keywords: perspectives of laser; proof-of-principle experiments; ion beams with narrow energy distribution can be generated from special target geometries microstructured targets can be used to reliably produce protons with monoenergetic spectra above 2 MeV with less than 10% energy spread; derive a scaling law between proton peak position and laser energy
  • Open Access Logo New Journal of Physics 10(2008), 033034

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11190
Publ.-Id: 11190


Shielding and Fuel Storage Calculations for GUINEVERE

Noack, K.; Rindelhardt, U.; Rogov, A.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-490 2008

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-11189
Publ.-Id: 11189


Annual Report 2007 - Institute of Radiochemistry

Bernhard, G.; Foerstendorf, H.; Richter, A.; Viehweger, K.; (Editors)
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-489 2008

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-11188
Publ.-Id: 11188


Defect studies of ZnO single crystals electrochemically doped with hydrogen

Cizek, J.; Zaludova, N.; Vlach, M.; Danis, S.; Kuriplach, J.; Prochazka, I.; Brauer, G.; Anwand, W.; Grambole, D.; Skorupa, W.; Gemma, R.; Kirchheim, R.; Pundt, A.
Various defect studies of hydrothermally grown (0001) oriented ZnO crystals electrochemically doped with hydrogen are presented. The hydrogen content in the crystals is determined by nuclear reaction analysis and it is found that already 0.3 at. % H exists in chemically bound form in the virgin ZnO crystals. A single positron lifetime of 182 ps is detected in the virgin crystals and attributed to saturated positron trapping at Zn vacancies surrounded by hydrogen atoms. It is demonstrated that a very high amount of hydrogen (up to similar to 30 at. %) can be introduced into the crystals by electrochemical doping. More than half of this amount is chemically bound, i.e., incorporated into the ZnO crystal lattice. This drastic increase of the hydrogen concentration is of marginal impact on the measured positron lifetime, whereas a contribution of positrons annihilated by electrons belonging to O-H bonds formed in the hydrogen doped crystal is found in coincidence Doppler broaden!
ing spectra. The formation of hexagonal shape pyramids on the surface of the hydrogen doped crystals by optical microscopy is observed and discussed.
  • Journal of Applied Physics 103(2008)5, 053508

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11187
Publ.-Id: 11187


In-beam PET measurement of 7Li3+ irradiation induced beta+-activity

Priegnitz, M.; Möckel, D.; Parodi, K.; Sommerer, F.; Fiedler, F.; Enghardt, W.
At present positron emission tomography (PET) is the only feasible method of an in situ and non-invasive monitoring of patient irradiation with ions. At the experimental carbon ion treatment facility of the Gesellschaft für Schwerionenforschung (GSI) Darmstadt an in-beam PET scanner has been integrated into the treatment site and lead to a considerable quality improvement of the therapy. Thus, it is highly desirable to extend in-beam PET also to other therapeutic relevant ions which requires an extensive knowledge on the spatial distribution of generated positron emitters. Therefore, by means of the in-beam PET scanner at GSI the beta+-activity induced by 7Li3+ ions has been investigated for the first time. Targets of PMMA, water, graphite and polyethylene were irradiated with monoenergetic, pencil-like beams of 7Li3+ with energies between 129.1 AMeV and 205.3 AMeV and intensities ranging from 3.0 e7 to 1.9 e8 ions s-1. This paper presents the measured beta+-activity profiles as well as depth dependent thick target yields which have been deduced from the experimental data. The beta+-activity induced by 7Li ions was found to be a factor of 1.9 higher than the one induced by 12C ions at the same physical dose and particle range.
  • Physics in Medicine and Biology 53(2008), 4443-4453

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11184
Publ.-Id: 11184


Implementation of temperature control into a high resolution gamma ray detector for tomography applications

Bieberle, A.; Bärtling, Y.; Fleischer, A.; Sühnel, T.; Zimmermann, W.; Schleicher, E.; Hampel, U.
In this paper the development of a new thermal design for a high resolution gamma ray computed tomography detector is presented. The new design has become necessary due to stringent requirements on count rate accuracy under varying thermal conditions at thermal hydraulic test loops. The components of the existing tomography detector have been analysed with respect to their thermal response and a new arrangement has been devised that is optimized with respect to efficient heat conduction from internal as well as external heat sources to a cooling circuit.
Keywords: gamma ray tomography, temperature control
  • Contribution to proceedings
    5th International Symposium on Process Tomography, 25.-26.08.08, Zakopane, Poland
    PaperNo PT08_cr12
  • Poster
    5th International Symposium on Process Tomography, 25.-26.08.08, Zakopane, Polen

Permalink: https://www.hzdr.de/publications/Publ-11183
Publ.-Id: 11183


Simulation of buble coalescence in bubble column using the least-squares method

Zhu, Z.; Patruno, L. E.; Dorao, C. A.; Lucas, D.; Jakobsen, H. A.
The population balance equation (PBE) has been combined with a steady-state gas phase momentum equation to model the operation of an air-water bubble column. Instead of solving a bubble number density constitutive equation, a population balance equation with coalescence term has been solved. The system of equations has been linearized by successive iteration and solved by the least-squares method with high accuracy and fast convergence. The bubble size distribution along the column axis has been investigated and compared to the corresponding experimental data, showing good agreement.
Keywords: bubble, coalescence, population balance
  • Contribution to proceedings
    11th International Conference on Multiphase Flow in Industrial Plant (MFIP'08), 07.-10.09.2008, Palermo, Italy, 643-650

Permalink: https://www.hzdr.de/publications/Publ-11182
Publ.-Id: 11182


Kinematic simulation of dynamo action with a hybrid boundary-element/finite-volume method.

Giesecke, A.; Stefani, F.; Gerbeth, G.
The experimental realization of dynamo excitation as well as theoretical and numerical examinations of the induction equation have shown the relevance of boundary conditions for a self-sustaining dynamo. Within the interior of a field producing domain geometric constraints or varying material properties (e.g. electrical conductivity of the container walls or localized high-permeability material) might also play a role. Combining a grid based finite volume approach with the boundary element method in a hybrid FV-BEM scheme offers the flexibility of a local discretization with a stringent treatment of insulating magnetic boundary conditions in almost arbitrary geometries at comparatively low costs. Kinematic simulations of dynamo action generated by a well known prescribed mean flow demonstrate the reliability of the approach.


Future examinations are intended to understand the behavior of the VKS-dynamo experiment where the field producing flow is driven by ferrous propell lers and the induction effects of conductivity/permeability inhomogeneities might provide the required conditions for the measured dynamo characteristics.
Keywords: kinematic dynamo, boundary element method, numerical simulations, induction equation
  • Magnetohydrodynamics 44(2008)3, 237-252

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-11181
Publ.-Id: 11181


Contactless inductive flow tomography: theory, experiments, perspectives

Wondrak, T.; Gundrum, T.; Stefani, F.; Gerbeth, G.
The velocity field of a propeller-driven liquid metal flow is reconstructed by a contactless inductive flow tomography (CIFT). A robust reconstruction of large scale velocity fields is already achieved by applying the external magnetic field in two orthogonal directions. The results of this technique are shown to be in satisfactory agreement with ultrasonic measurements.
Keywords: Inverse Problems, Industrial tomography, Liquid metal flow measurement
  • Contribution to proceedings
    The 10th Workshop on Optimization and Inverse Problems in Electromagnetism (OIPE 2008), 14.-17.09.2008, Ilmenau, Germany, 75-76
  • Lecture (Conference)
    The 10th Workshop on Optimization and Inverse Problems in Electromagnetism (OIPE 2008), 14.-17.09.2008, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11180
Publ.-Id: 11180


Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208] [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247] [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258] [259] [260] [261] [262] [263] [264] [265] [266] [267] [268] [269] [270] [271] [272] [273] [274] [275] [276] [277]