Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35174 Publications

Synthesis and size control of Si nanocrystals by SiO/SiO2 superlattices and Er doping

Heitmann, J.; Kovalev, D.; Schmidt, M.; Yi, L. X.; Scholz, R.; Eichhorn, F.; Zacharias, M.

  • Contribution to external collection
    Mat. Res. Soc. Symp. Proc. 737 (2003) 271

Publ.-Id: 6225

Characteristics of erbium-producing liquid metal ion sources

Ganetsos, T.; Mair, G. L. R.; Aidinis, C. J.; Bischoff, L.

  • Physica B 340-342 (2003) 1166

Publ.-Id: 6224

14.5% normal-incidence reflectance of Cr/Sc X-ray multilayer mirrors for the water window

Eriksson, F.; Johansson, G. A.; Hertz, H. M.; Gullikson, E. M.; Kreissig, U.; Birch, J.

  • Optics Letters 28 (2003) 2494

Publ.-Id: 6223

Modification of growth mode of Ge on Si by pulsed low-energy ion-beam irradiation

Dvurechenskii, A. V.; Smagina, J. V.; Zinovyev, V. A.; Grötzschel, R.; Teys, S. A.; Gutakovskii, A. K.

  • Contribution to external collection
    Proc. of 11th Int. Symp. "Nanostructures: Physics and Technology", St. Petersburg, Russia, June 23-28, 2003, p. 305

Publ.-Id: 6222

Research of coatings containing zirkonium properties on metallic substrate

Deshkovskaya, A. A.; Lynkov, L. M.; Nagibarov, A. V.; Pham, M. T.; Richter, E.

  • Doklady BGUNP 1 (2003) 57

Publ.-Id: 6221

Gluon Emission of Heavy Quarks: Dead Cone Effect

Thomas, R.; Kämpfer, B.; Soff, G.

The lowest-order induced soft gluon radiation processes of heavy quarks are considered with the aim to quantify the dead cone effect. The dead cone effect is expected to suppress significantly the energy loss of charm quarks passing an amorphous colour-neutral deconfined medium, as anticipated in recent experiments at RHIC.

Keywords: Induced gluon radiation; energy loss; dead cone

  • Contribution to external collection
    Acta Physica Hungarica A 22(2005), 83

Publ.-Id: 6220

Uran-Aufnahme in Pflanzen - Transferfaktoren und chemische Speziation

Günther, A.

  • Lecture (others)
    Friedrich-Schiller-Universität Jena, Biologisch-Pharmazeutische Fakultät 18.05.2004, Jena, Germany

Publ.-Id: 6219

Relaxation kinetics in amorphous carbon films: An insight from atomic scale simulation

Belov, A. Y.; Jäger, H. U.

Using molecular-dynamics (MD) techniques and a hydrocarbon potential of Brenner with an increased C-C interaction range, we investigate kinetics of relaxation processes in tetrahedral amorphous carbon films (ta-C) with high sp3 fractions. The structural models for as-grown non-equilibrium ta-C networks were generated using MD film deposition simulation with ion energy of 80 eV. The results of MD simulations of low temperature annealing show that both film stress and energy behave with annealing time t as a+bexp(-t/t1 ). This exponential dependency is interpreted in terms of structural transformations in the amorphous carbon networks. It is also shown that the relaxation times for the energy and stress do not coincide, indicating that some atomic rearrangements in the networks may reduce their energy without changing the stress. At the annealing temperature of 1000 K, the relaxation constant t1 for energy was found to be in the range of 0.5-0.7 ns, depending on the simulation parameters. It considerably exceeds an estimate of 10 ps for the thermalization stage of the subplantation model for ta-C film formation from energetic C ions. A decrease in the ta-C energy during the first 10 ps of the simulated annealing is much larger than that predicted by the exponential law with the relaxation constant t1 .

Keywords: Tetrahedral amorphous carbon; Intrinsic Stress; Structural relaxation; Molecular Dynamics

  • Thin Solid Films 482(2005)74-78

Publ.-Id: 6218

Bacteria from extreme environments: basis for new technical applications

Raff, J.; Selenska-Pobell, S.

The Molecular Microbiological Group at the Institute of Radiochemistry, Research Centre Rossendorf nearby Dresden, performs as part of an institute from the Wissenschaftsgemein-schaft Gottfried Wilhelm Leibniz e.V. basic and applied research. Main interests are

  • bacterial diversity of soil and water
samples highly contaminated with radionuclides and heavy-metals
  • investigation and characterization of
metal-microbe interactions
  • development of novel bacteria-based bioremediation strategies for cleaning contaminated wastewater
  • use of bacteria or bacterial components as biotemplates for the formation of nanoclusters for biotechnological applications

Bacteria consist of only one single cell, but apart from their simple organisation and their small size they are an unbelievable complex and highly efficient group of creatures. Some bacteria are able to thrive at the most forbidding, uninviting places on Earth: they live in hot springs, in extremely alkaline or acid waters, in muds of marshes or even at the bottom of the ocean. For production of energy they can use different kinds of organic and inorganic matter or sun light. Against this background, investigation of bacteria recovered from extreme environments shows a great promise to discover novel and yet unknown properties of this interesting group of organisms.

  • BioMeT-Magazin (2004), 18

Publ.-Id: 6217

Comparison of TiN and Ti1-xAlxN coatings deposited on Al using plasma immersion ion implantation assisted deposition

Mukherjee, S.; Prokert, F.; Richter, E.; Möller, W.

TiN and Ti1-xAlxN coatings were deposited on Al substrates using the plasma immersion ion implantation and deposition technique, employing a filtered Ti and Ti0.5Al0.5 cathodic arc in a nitrogen atmosphere. Negative pulsed bias voltages between 0 to –4.0 kV were applied with varying duty cycles, at a constant time-averaged bias. Stress measurements using X-ray diffraction reveal an increase and then a decrease in the intrinsic compressive stress at increasing on-time bias, more pronounced for Ti1-xAlxN coatings. A bias dependent preferred orientation is observed for both the coatings, with [200] being the preferred orientation at higher bias. The hardness always reduces for TiN coatings with increase in bias, whereas for Ti1-xAlxN it shows a reverse trend. The results are qualitatively explained by the role played by Al in Ti1-xAlxN. The results indicate that the peak bias plays a more dominant role than time averaged bias.

Keywords: Plasma immersion ion implantation assisted deposition; titanium nitride; preferred orientation; stress

  • Surface and Coatings Technology 200 (2005)7 2459-2464

Publ.-Id: 6216

Structures and energetics of defects: a comparative study of 3C- and 4H-SiC

Gao, F.; Posselt, M.; Belko, V.; Zhang, Y.; Weber, W. J.

The structures, formation energies and stable configurations of elementary defects (vacancies, antisite defects and self-interstitials) in 3C- and 4H-SiC are studied using classical molecular dynamics simulation with a recently developed interatomic potential. The defect structures in 3C-SiC are relatively simple, but those in 4H-SiC are more complex. The interstitials between hexagonal and trigonal rings are characteristic for 4H-SiC and other hexagonal polytypes, but not for 3C-SiC. The number of non-equivalent defects in 4H-SiC is much higher than that in 3C-SiC, and a considerable difference is found for some complex and anisotropic defects, in particular for the dumbbells D1Si+Si, D1Si+C and D2Si+C. The lattice deformation beyond the first nearest neighbor shell, which depends strongly on the polytype structure, plays an important role on these effects. However, the polytypism does not have a significant influence on the structure and energetics of the more compact and isotropic defects, such as vacancies and antisite defects. Despite the complexity of defect configurations, the tetrahedral interstitials have very similar properties in 3C- and 4H-SiC because their first, second and third nearest neighbor shells are identical.

Keywords: Defects and defect properties; Computer simulations; 3C- and 4H-SiC

Publ.-Id: 6215

Ultrafast X-ray Computed Tomography with a Linearly Scanned Electron Beam Source

Hampel, U.; Speck, M.; Koch, D.; Menz, H.-J.; Mayer, H.-G.; Fietz, J.; Hoppe, D.; Schleicher, E.; Zippe, C.; Prasser, H.-M.

We devised and tested a novel computed tomography approach that utilises a scanned electron beam X-ray source to produce fast sequences of tomographic images of transient density distributions. In contrary to classical electron beam tomography we used a linear deflection pattern for the electron beam and a non-annular detector arc to record transmission data of an object from different projection angles. This approach gives the highest achievable axial resolution and is comparatively moderate in effort and costs. For the inverse problem we applied iterative image reconstruction techniques to reconstruct the density distribution from a limited data set. The method has been experimentally tested on static and dynamic phantoms with a frame rate of 1000 images per second and a spatial resolution of approximately 1 mm in plane and axial.

Keywords: high-speed X-ray computed tomography; limited angle reconstruction

  • Flow Measurement and Instrumentation 16 (2005), 65-72

Publ.-Id: 6213

Magnetic field controlled FZ single crystal growth of intermetallic compounds

Hermann, R.; Behr, G.; Gerbeth, G.; Priede, J.; Uhlemann, H.-J.; Fischer, F.; Schultz, L.

Intermetallic Rare-Earth-Transition-Metall compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of massive single crystals is very often unsuccessful due to an unfavourable solid-liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds. This control is provided by a tailored design of the electromagnetic field and the resulting electromagnetically driven convection. Numerical simulations for the determination of the electromagnetic field configuration induced by the RF heater coil and the solution of the coupled heat and hydrodynamic equations were done for the model substance Ni with and without additional magnetic field. As a result, an innovative magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards/outwards flows to flows almost at rest. The selection of parameters necessary for the desired fluid flow is determined from numerical simulation. The basis for the calculations are the process-related fluid flow conditions which are determined by the mode of heating, heat radiation at the free surface and material parameters. This treatment of the problem leads to the customised magnetic field for the special intermetallic compound. The application of the new magnetic system leads to a distinct improvement of the solid-liquid interface validated on experiments with the model substance Nickel.

  • Journal of Crystal Growth 275(2005), e1533-e1538

Publ.-Id: 6211

Magnetic field controlled FZ single crystal growth of intermetallic compounds

Hermann, R.; Behr, G.; Gerbeth, G.; Priede, J.; Uhlemann, H.-J.; Fischer, F.; Schultz, L.

Intermetallic Rare-Earth-Transition-Metall compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of massive single crystals is very often unsuccessful due to an unfavourable solid-liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds. This control is provided by a tailored design of the electromagnetic field and the resulting electromagnetically driven convection. Numerical simulations for the determination of the electromagnetic field configuration induced by the RF heater coil and the solution of the coupled heat and hydrodynamic equations were done for the model substance Ni with and without additional magnetic field. As a result, an innovative magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards/outwards flows to flows almost at rest. The selection of parameters necessary for the desired fluid flow is determined from numerical simulation. The basis for the calculations are the process-related fluid flow conditions which are determined by the mode of heating, heat radiation at the free surface and material parameters. This treatment of the problem leads to the customised magnetic field for the special intermetallic compound. The application of the new magnetic system leads to a distinct improvement of the solid-liquid interface validated on experiments with the model substance Nickel.

  • Lecture (Conference)
    14th "International Conference on Crystal Growth", 09.-13.08.2004, Grenoble, France

Publ.-Id: 6210

Experimental Evidence of Si Nanocluster delta-Layer Formation in Buried and Thin SiO2 Films Induced by Ion Irradiation

Röntzsch, L.; Heinig, K. H.; Schmidt, B.

Self-aligned Si nanocluster (NC) formation in thin MOSFET gate oxides by means of ion beam mixing and post-irradiation annealing of SiO2-Si interfaces is proven for the first time by cross-section TEM. This study proves a recent prediction based on kinetic Monte Carlo (KLMC) simulations that a delta-layer of tiny Si NCs in SiO2, located 2…3nm apart from the SiO2-Si interface, can be fabricated by ion irradiation [1]. Such a self-aligned NC delta-layer configuration meets the requirements of non-volatile multi-dot floating-gate memory transistors [2], on which immense research effort has been spent in recent years.
By conventional TEM techniques the delta-layer of Si NCs in SiO2 can not be observed due to the low mass contrast between Si and SiO2 and the tininess of the Si NCs which have a mean diameter of 1.5nm. Here we present a method of mass contrast enhancement of such tiny Si NCs by alloying them with Ge. For this purpose, a thin Ge layer was embedded into the oxide far above the SiO2-Si interface, i.e. outside the mixing range of the SiO2-Si interface in order not to interfere with the original Si NC formation process. During post-irradiation annealing, diffusing Ge atoms are captured by the Si NCs due to the strong Si-Ge bond.

Keywords: ion-beam-mixing; SiO2-Si interface; ion irradiation; self-alignment; Si nanocluster; Ge decoration; multi-dot; non-volatile memory

  • Contribution to external collection
    Materials Science in Semiconductor Processing 7(2004), 357-362
    DOI: 10.1016/j.mssp.2004.09.098
  • Lecture (Conference)
    EMRS Spring Meeting, 26.05.2004, Strasbourg, France

Publ.-Id: 6208

Limitations on ultra-thin multilayers: pulsed cathodic arc and computer simulation

Chun, S. Y.; Chayahara, A.; Posselt, M.

Nanoscale metallic multilayers have been deposited by a pulsed double-cathodic arc deposition with varying thicknesses of each layer from a few to tens of angstroms and examined by cross-sectional transmission electron microscopy (XTEM). TRIDYN computer simulations are performed to get a better understanding of the nanoscale deposition of multilayers during the cathodic arc deposition process. Their results are compared with the experimental data. For the higher ion fluence ( > 1.e16 ions/cm**2 ) and larger bilayer thickness ( > 2 nm), the periodicity of multilayers was good. However, the results of the simulations for the lower ion flux and smaller bilayer thickness reveal that the individual layers are intermixed and diffused. The experimental results are in good agreement with those of simulations that the limit of bilayer period of the ultra-thin multilayers is approximately 2 nm in the present case.

Keywords: Pulsed cathodic arc; Multilayers and computer simulation

Publ.-Id: 6207

Developmental changes in the activity of aromatic amino acid decarboxylase and catechol-O-methyl transferase in pigs: a positron emission tomography study

Brust, P.; Walter, B.; Hinz, R.; Füchtner, F.; Müller, M.; Steinbach, J.; Bauer, R.

Newborn (7-10 days old) and young (6-8 weeks old) pigs were used to study the metabolism of 6-[F-18]fluoro-L-DOPA (FDOPA) in various brain regions with positron emission tomography (PET). Compartmental modeling of PET data was used to calculate the rate constants for the decarboxylation of FDOPA (k(3)) and for the metabolism of the resulting [F-18]fluoro-dopamine (k(cl)). Whereas general physiological parameters such as cerebral blood flow, cerebral oxygen uptake, arterial blood gases and glucose concentration remained unchanged in young pigs as compared to newborns, a 50-200% increase of k(3) in frontal cortex, striatum and mesencephalon was found. Also a 60% enhancement of k(cl) in the frontal cortex was measured, which is related to changes of the catechol-O-methyl-transferase (COMT) activity and implies a special function of this enzyme in the development of this brain region. In addition, measurement of plasma metabolites of FDOPA with HPLC was performed. The metabolism of FDOPA in young pigs was significantly faster than in newborns. Calculation of the rate constant for O-methylation of FDOPA by COMT revealed a significant elevation of this enzyme activity in young pigs compared to newborns. The increase of AADC and COMT activity with brain development is considered to be associated with special stages of neuronal maturation and tissue differentiation.

Keywords: aromatic amino acid decarboxylase; cerebral blood flow; catechol-0-methyl transferase; development; dopamine; pig; positron emission tomography

  • Neuroscience Letters, 364(2004)3, 159-163

Publ.-Id: 6206

Age-dependent effects of severe traumatic brain injury on cerebral dopaminergic activity in newborn and juvenile pigs

Walter, B.; Brust, P.; Füchtner, F.; Müller, M.; Hinz, R.; Kuwabara, H.; Fritz, H.; Zwiener, U.; Bauer, R.

There is evidence that the dopaminergic system is sensitive to traumatic brain injury (TBI). However, the age-dependency of this sensitivity has not been studied together with brain oxidative metabolism. We postulate that the acute effects of severe TBI on brain dopamine turnover are age-dependent. Therefore F-18-labelled 6-fuoro-L-3,4-dihydroxyphenylalanine (FDOPA) together with Positron-Emission-Tomography (PET) was used to estimate the activity of the aromatic amino acid decarboxylase (AADC) in the brain of Ill newborn piglets (7-10 days old) and nine juvenile pigs (6-7 weeks old). Six newborn and five juvenile animals were subjected to a severe fluid-percussion (FP) induced TBI. The remaining animals were used as sham operated untreated control groups. Simultaneously, the regional cerebral blood flow (CBF) was measured with colored microspheres and the cerebral metabolic rates of oxygen and glucose were determined. At 1 h after FP-TBI, [F-18]FDOPA was infused and PET sca! nning was performed for 2 h. At 2 h after FP-TBI administration, a second series of measurements of physiological values including CBF and brain oxidative metabolism data had been obtained. Severe FP-TBI elicited a marked increase in the rate constant for fluorodopamine production (k(3)(FDOPA)) in all brain regions of newborn piglets studied by between 97% (mesencephalon) and 143% (frontal cortex) (p < 0.05). In contrast, brain hemodynamics and cerebral oxidative metabolism remained unaltered after TBI. Furthermore, the permeability-surface area product of FDOPA (PSFDOPA) was unchanged. In addition, regional blood flow differences between corresponding ipsi- and contralateral brain regions did not occur after TBI. Thus, it is suggested that severe FP-TBI induces an upregulation off AADC activity of newborn piglets that is not related to alterations in brain oxidative metabolism.

  • Journal of Neurotrauma 21(2004)8, 1076-1089

Publ.-Id: 6205

Messung von Phasen- und Konzentrationsverteilungen in Blasensäulen mit Positronen-Emissions-Tomographie

Zippe, C.; Hoppe, D.; Fietz, J.; Hampel, U.; Hensel, F.; Mäding, P.; Prasser, H.-M.; Zippe, W.

Schaumbildung in Chemiereaktoren ist eine oft unerwünschte Begleiterscheinung bei mehrphasigen Prozessen und Anlagenstörfällen. Die hier vorgestellte Experimentiertechnik gestattet die berührungslose Messung von Phasen- und Konzentrationsverteilungen mittels PET und wurde für Grundlagenuntersuchungen zum Verhalten von Tensiden bei Schaumbildungs- und Zerfallsprozessen in rohrförmigen Reaktionsgefäßen entwickelt und erprobt.

Keywords: PET; Phasenverteilung; Konzentrationsverteilung; Blasensäule; Chemiereaktor; Anlagenstörfall; Tensidanreicherung

Publ.-Id: 6204

Two-proton small-angle correlations in central heavy-ion collisions: a beam-energy- and system-size-dependent study

Kotte, R.; Alard, J. P.; Andronic, A.; Barret, V.; Basrak, Z.; Bastid, N.; Benabderrahmane, M. L.; Caplar, R.; Cordier, E.; Crochet, P.; Dupieux, P.; Dzelalija, M.; Fodor, Z.; Gasparic, I.; Gobbi, A.; Grishkin, Y.; Hartmann, O. N.; Herrmann, N.; Hildenbrand, K. D.; Hong, B.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Koczon, P.; Korolija, M.; Kress, T.; Lebedev, A.; Leifels, Y.; Lopez, X.; Merschmeyer, M.; Mösner, J.; Neubert, W.; Pelte, D.; Petrovici, M.; Rami, F.; Reisdorf, W.; de Schauenburg, B.; Schüttauf, A.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynska, K.; Stoicea, G.; Tyminski, Z.; Wagner, P.; Wisniewski, K.; Wohlfarth, D.; Xiao, Z. G.; Yushmanov, Y.; Zhilin, A.

Small-angle correlations of pairs of protons emitted in central collisions of Ca + Ca, Ru + Ru and Au + Au at beam energies from 400 to 1500 MeV per nucleon are investigated with the FOPI detector system at SIS/GSI Darmstadt. Dependences on system size and beam energy are presented which extend the experimental data basis of pp correlations in the SIS energy range substantially. The size of the proton-emitting source is estimated by comparing the experimental data with the output of a final-state interaction model which is processing either static Gaussian sources or the one-body phase-space distribution of protons provided by the BUU transport approach. The trends in the experimental data, i.e. system-size and beam energy dependences, are well reproduced by this hybrid model. However, the pp correlation function is found rather insensitive to the stiffness of the equation of state entering the transport model calculations.

Keywords: PACS. 25.70.Pq; 25.75.Gz

  • European Physical Journal A 23(2005), 271
    DOI: 10.1140/epja/i2004-10075-y
  • Lecture (Conference)
    FOPI Collaboration Meeting, 02.04.2004, Darmstadt, Germany

Publ.-Id: 6203

From QCD lattice calculations to the equation of state of quark matter

Peshier, A.; Kaempfer, B.; Soff, G.

We describe two-flavor QCD lattice data for the pressure at a nonzero temperature and vanishing chemical potential within a quasiparticle model. Relying only on thermodynamic consistency, the model is extended to nonzero chemical potential. The results agree with lattice calculations in the region of a small chemical potential.

Publ.-Id: 6202

Neutral oxorhenium(V) and oxotechnetium(V) complexes with novel amide thioether dithiolate ligands derived from cysteine

Noll, B.; Hilger, C. S.; Leibnitz, P.; Spies, H.

Summary. Bifunctional ligands able to form neutral complexes with radioactive technetium and rhenium and to couple to biological relevant anchor groups play an important role in the design of new radiopharmaceuticals for diagnosis and therapy. A novel tetradentate amide thioether dithiolate ligand HS-CH2CH2-S-CH2CONH-CH(COOR)CH2SH(H3SNSS) with R = CH3, C10H21 was synthesized that forms stable complexes with technetium and rhenium in oxidation state V. The molecular structures of the rhenium and technetium complexes MO(SNSS) were determined by X-ray structural analysis and show that the metal coordination number is five and the coordination polyhedron is between square-pyramidal and trigonal-bipyramidal. The pendent ester group allows coupling of the chelate unit at biologically relevant anchor groups. As a relevant representative the X-ray structural analysis of the rhenium decylester complex was carried out. The complex formation with Tc at teh n.c.a. level and 186Re at 10-10M level is described.

  • Radiochimica Acta 92(2004)4-6, 271-276

Publ.-Id: 6200

Labelling of biomolecules using 99mTc(III) and 188Re(III) mixed-ligand complexes

Seifert, S.; Künstler, J.-U.; Schiller, E.; Pietzsch, H.-J.; Pawelke, B.; Bergmann, R.; Spies, H.

The trigonal-bipyramidal Re(III) and Tc(III) mixed-ligand complexes of the general formula [MIII(Ln)(Lm)] (M = Tc, Re; Ln = 2,2‘,2“-nitrilotris-(ethanethiol) NS3 or NS3-COOH; Lm = isocyanide or phosphine) are stable against ligand exchange with cysteine or glutathione and in vitro in incubations with plasma as well as whole blood of rats and represent therefore an alternative to the more unstable ‘3+1‘ Re(V) or Tc(V) complexes concerning the possibilities of designing biologically interesting 99mTc or 188Re labelled compounds1. Improved methods for their preparation are presented. To avoid the unrequested formation of reduced-hydrolysed species of both metals the preparation of complexes is performed in a two-step procedure.
At first the Tc(III)- or Re(III)-EDTA complex is formed which reacts in a second step with the tripodal ligand NS3 or its carboxyl derivative NS3-COOH and the monodentate phosphine or isocyanide ligands to the so-called ‘4+1’ complexes. Copper(I) isocyanide complexes are used for preparing the ‘4+1’ complexes. That facilitates storage stability and allows kit formulations. Moreover, using that stabilized form of isocyanides enables the formation of 188Re complexes in acidic solution. Only micromolar amounts of the monodentate ligand are needed and that results in high specific activity labelling of interesting molecules. The stability of the 99mTc and 188Re preparations is discussed. The introduction of a carboxyl group into the tetradentate ligand and/or the monodentate ligands enables the conjugation of biomolecules and controlling of lipophilicity.

  • Poster
    ISBOMC’04, Second International Symposium on Bioorganometallic Chemistry; Zürich, 14.-17.07.2004

Publ.-Id: 6199

99mTc and 188Re mixed-ligand complexes at lower oxidation state

Seifert, S.; Künstler, J.-U.; Schiller, E.; Pietzsch, H.-J.; Pawelke, B.; Bergmann, R.; Spies, H.

Technetium and rhenium mixed-ligand complexes represent an important approach to the development of radiotracers for diagnostic and therapeutic application because of the many possibilities to vary their biobehaviour. The trigonal-bipyramidal Re(III) and Tc(III) complexes of the general formula [MIII(Ln)(Lm)] (M = Tc, Re; Ln = 2,2‘,2“-nitrilotris-(ethanethiol) NS3 or NS3-COOH; Lm = isocyanide or phosphine) are stable against ligand exchange with cysteine or glutathione and in vitro in incubations with plasma as well as whole blood of rats and represent therefore an alternative to the more unstable ‘3+1‘ Re(V) or Tc(V) complexes concerning the possibilities of designing biologically interesting 99mTc or 188Re labelled compounds. Improved methods for their preparation are presented. To avoid the unrequested formation of reduced-hydrolyzed species of both metals the preparation of complexes is performed in a two-step procedure. At first the Tc(III)- or Re(III)-EDTA complex is formed which reacts in a second step with the tripodal ligand NS3 or its carboxyl derivative NS3-COOH and the monodentate phosphine or isocyanide ligands to the so-called ‘4+1’ complexes. Copper(I) isocyanide complexes are used for preparing the ‘4+1’ complexes. That facilitates storage stability and allows kit formulations. Moreover, using that stabilized form of isocyanides enables the formation of 188Re complexes in acidic solution. Only micromolar amounts of the monodentate ligand are needed and that results in high specific activity labeling of interesting molecules. The stability of the 99mTc and 188Re preparations is discussed. The introduction of a carboxyl group into the tetradentate ligand and/or the monodentate ligands enables the conjugation of biomolecules and controlling of lipophilicity.

  • Invited lecture (Conferences)
    19th KAIF/KNS Annual Conference, 25.-27.04.2004, Seoul, Korea
  • Invited lecture (Conferences)
    Institutskolloquium, The Korea Atomic Energy Research Institute, Hanaro Application Research, 24.04.2004, Daejeon, Republic of Korea,

Publ.-Id: 6198

Structural studies of epitaxial Au nanocrystals in rutile

Eichhorn, F.; Fromknecht, R.

Besides promising applications for electronic nanostructures or nonlinear optical devices nanocrystalline Au may be used as efficient catalysis material (e.g. chemisorption of CO or hydrocarbons). The catalytic reaction is often very sensitive to the structure and size of the metal crystallites and their crystallographic orientation Both conditions may be controlled by growing the nanocrystals in a single crystalline non-metallic matrix.
Here, Au nanocrystals were generated inside rutile TiO2 by implantation of 260 keV Au ions. The growth in a matrix allows to stabilize the precipitates structurally. Furthermore, no impurities were introduced because of mass separation during the process. However, the host crystal is damaged by the ion impact processes. This damage may be reduced by in situ or post-implantation annealing.
Various x-ray scattering techniques were used for the structural characterization of the material: specular reflection for surface and near-surface studies, diffraction for determination of strain and crystal size, pole figure measurements to reveal the orientation relationship.
In the as-implanted state randomly oriented crystals with a size of 5 … 7 nm as well as crystals oriented in a fibre texture with axis parallel to the rutile surface normal have been obtained. Annealing at 1000 K let the nanocrystals grow to 15 nm; simultaneously the amount of epitaxially oriented Au crystals increases. The orientation relationship is controlled by the crystallographic axis of the rutile matrix surface so that the ensemble of the Au nanocrystals fits to the crystal symmetry of the matrix:

  • the surface normal is the two-fold rutile [100] direction:
surface normal - Au < 2 1 1 > || TiO2 < 1 0 0 >
in the surface - Au < 1 1 0 > || TiO2 < 0 0 1 > and Au < 1 1 1 > || TiO2 < 0 1 0 >.
In order to fulfil the two-fold matrix symmetry there are two groups of Au crystallites rotated by 180° each to other around the surface normal.
  • the surface normal is the four-fold rutile [001] direction:
surface normal - Au <110> || TiO2 <001>
In order to fulfil the four-fold matrix symmetry there are two groups of Au crystallites rotated by 90° each to other around the surface normal. Each of them is split into two sub-groups rotated by +9.7° and –9.7° around the surface normal from the “ideal” orientation: Au <110> + 9.7° and –9.7° || TiO2 <110 > and Au <100 > + 9.7° and –9.7° || TiO2 <110>.

Keywords: nanocrystals; Au; Rutile; x-ray diffraction; structure

  • Lecture (Conference)
    7th Biennial Conference on High Resolution X-Ray Diffraction and Imaging - XTOP 2004, Prague, Czech Republic, September 7-10, 2004

Publ.-Id: 6197

Herstellung von Nanometer-Strukturen mittels feinfokussiertem Ionenstrahl (FIB)

Mucke, S.

Feinfokussierte Ionenstrahlen dienen in den Gebieten der Halbleiterindustrie und Materialforschung der Mikro- und Nanostrukturierung. Die vorliegende Arbeit beschäftigt sich mit den beiden Hauptanwendungen von fokussierten Ionenstrahlen, dem Materialabtrag und der ionenstrahlinduzierten Materialabscheidung. Dabei wird die hochauflösende Ionensäule CANION 31Z der Firma Orsay Physics mit Stromdichten von bis zu 10 A/cm2 und mit integriertem Gassystem eingesetzt. Es wird ausführlich auf Anwendungsbeispiele von Fokussierten Ionenstrahlsystemen im Bereich der Industrie und Forschung eingegangen.
Schwerpunktmäßig wird die Abscheidung von Wolfram aus dem Precursorgas W(CO)6 (Wolframhexacarbonyl) auf Si und SiO2 als Substrat untersucht, mit dem Ziel, gut leitfähige Drähte (hier im Sinne von Leiterbahnen) mit minimalem Querschnitt herzustellen. Die Optimierung der Ionenstrahl-Parameter dieser Feinfokussierten Ionenstrahlanlage bezüglich der Abscheidung steht im Vordergrund. Dabei wird ein kurzer Einblick in die Theorie der Schichtentstehung beim Abscheidevorgang gegeben. Untersuchungen der erzeugten Strukturen entsprechend der Schichtqualität und der Strukturabmessungen werden erläutert und die Ergebnisse diskutiert. Es konnten Wolframdrähte mit einer Länge von 20 ... 100 µm, einer Breite von minimal 150 nm und einer Höhe von maximal 600 nm angefertigt werden. Die Zusammensetzung der Drähte in Abhängigkeit der Prozessparameter wurde mittels AES bestimmt. Im optimalen Fall wurden die Schichtanteile zu 80% W, 5% O, 6% C und 9% Ga ermittelt (Angaben in Atomprozent). Der spezifische Widerstand der Wolframdrähte ist im Bereich 150 ... 320 µWcm gemessen worden.

Keywords: Fokussierter Ionenstrahl; MOCVD; Wolfram Nanodrähte; Sputtern

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZR-402 2004
    ISSN: 1437-322X


Publ.-Id: 6196

Stability of melt flow due to traveling magnetic field in a closed ampoule

Grants, I.; Gerbeth, G.

The linear three-dimensional instability of the flow due to a low frequency traveling magnetic field in a regular cylinder is studied numerically for height-to-diameter ratios in the range [0.5:2.5]. The first instability has the form of a non-rotating azimuthal wave with wave numbers between 1 and 6 depending on the aspect ratio. It is shown that the flow is stable if the Reynolds number is below 290. Even stronger stationary flows may be obtained in a flattened cylinder.

  • Journal of Crystal Growth 269(2004), 630-638

Publ.-Id: 6195

Classical MD study on the the mobility of di- and tri-interstitials

Posselt, M.

In a recent work [1], a combined simulation method was applied to investigate ion-beam-induced defect formation in silicon. BCA simulations were used to treat the ballistic processes, whereas the subsequent fast relaxation and the first stage of thermally activated processes were described by classical MD calculations. It was found that the metastable defect structure formed immediately after ion impact consists not only of isolated vacancies and self-interstitials but also of complex defects. A more detailed analysis of the results shows, that at elevated implantation temperatures or during the annealing of the defect structures obtained at room temperature, di- and tri-interstitials are formed. In some cases a high mobility of these defects is observed. In agreement with former studies [2,3], the di-interstital is found to move relatively fast. The present contribution deals with systematic investigations on the migration of di- and tri-interstitials. The classical MD simulations allow direct investigations of the motion of defects and its atomic mechanisms. Particular attention is paid to the role of transformations between different modifications of di- or tri-interstitials. These transformations may lead to an substantial increase or decrease of the defect mobility. The present results are compared with the few literature data obtained by tight-binding and density-functional methods which employ mainly static potential energy calculations.
[1] M. Posselt, Mat. Res. Soc. Symp. Proc. 647 (2001) O2.1.1.
[2] G. H. Gilmer, T. Diaz de la Rubia, D. M. Stock, M. Jaraiz, Nucl. Instr. Meth. Phys. Res. B 102 (1995) 247.
[3] M. Hane, T. Ikezawa, G. H. Gilmer, Proc. SISPAD 2000, IEEE Catalog Number 00TH8502, p. 119 , IEEE, Piscataway, 2000.

Keywords: defect diffusion; silicon; simulation; molecular dynamics

  • Lecture (Conference)
    MRS 2004 Spring Meeting, April 12 - 16, 2004, San Francisco, USA

Publ.-Id: 6194

Multiple implantations - experiments and computer simulations

Posselt, M.; Mäder, M.; Lebedev, A.; Grötzschel, R.

Advanced technologies use successive implantations of p- and/or n-dopants without any intermediate annealing steps. A characteristic example is the engineering of the regions of source, drain, extension and halo. The sequence of the implantations may influence the final distribution of dopants and radiation damage. In particular it affects the as-implanted distribution of dopants if in one or more implantation steps the direction of ion incidence is close to a major crystallographic axis of the silicon substrate. For example, extension implantations are often performed perpendicularly to the wafer surface, i.e. nearly parallel to the [100] axis. The defect production in previous implantations influences the shape of dopant and damage profiles in a subsequent channeling implantation step, since these defects may lead to increased dechanneling. Furthermore, the amorphization dose in a certain implantation step may be affected by the level of radiation damage formed during the previous steps. The present work deals with the simple example of two consecutive implantations in order to demonstrate the effects mentioned above. Two implantation sequences are investigated: (i) 35 keV B followed by 50 keV As into the [100] channel direction, (ii) 50 keV As followed by 35 keV B [100] channeling implantation. The depth profiles of B and As are measured by SIMS. The as-implanted damage is determined by RBS/C. The experimental data can be reproduced by atomistic computer simulations using the Crystal-TRIM code with an improved phenomenological model for damage buildup during multiple implantations. The present results contribute to a better understanding of ion-beam-induced defect formation and to progress in TCAD.

Keywords: ion implantation; silicon; process simulation

  • Lecture (Conference)
    MRS 2004 Spring Meeting, April 12 - 16, 2004, San Francisco, USA

Publ.-Id: 6193

Crack initiation determination for Charpy size 3-point bend specimens by ICFPD method

Dzugan, J.; Viehrig, H.-W.

The paper deals with the problematic of determination of the crack initiation for three point bend specimens during fracture toughness testing of materials in the upper transition and upper shelf region. In the presented study was developed Induced Current Focussed Potential Drop method for the fracture mechanics tests of Single Edge Notched Bend specimens of Charpy size. The performance of the newly developed technique is shown here. Obtained crack initiation integrals are compared with Stretch Zone Width based crack initiation integrals.

  • Lecture (Conference)
    Fatigue and Fracture Mechanics, 20.-22.04.2004, Zinkovy, Czechia

Publ.-Id: 6192

Dose quantification from in-beam positron emission tomography

Enghardt, W.; Parodi, K.; Crespo, P.; Fiedler, F.; Pawelke, J.; Pönisch, F.

Positron emission tomography (PET) imaging of the radioactivity distributions induced by therapeutic irradiation is at present the only feasible method for an in-situ and non-invasive monitoring of radiooncology treatments with ion-beams. The clinical implementation of this imaging technlogy at the experimental carbon ion therapy facility at the Gesellschaft für Schwerionenforschung (GSI) at Darmstadt, Germany is outlined and an interactive approach for a PET guided quantification of local dose deviations with respect to the treatment plan is presented.

Keywords: Positron emission tomography; Charged hadron therapy; Ion therapy

  • Radiotherapy and Oncology 73(2004)Suppl. 2, S96-Sp98

Publ.-Id: 6190

Betriebserfahrungen beim Online-Monitoring exothermer chemischer Prozesse mit adaptiven Stoff- und Wärmebilanzen

Schmitt, W.; Hessel, G.; Kryk, H.

Es wird ein entwickeltes Überwachungssystem vorgestellt, das zum Online-Monitoring sicherheitstechnisch schwieriger chemischer Reaktionen in Rührkesselreaktoren entwickelt wurde. Die Industrieerprobung erfolgte an einer Mehrzweckanlage der Degussa AG.
Betriebserfahrungen und der praktische Nutzen werden am Beispiel des Semibatch-Betriebes eines heterogenen exothermen Hydrierprozesses aufgezeigt und diskutiert.

  • Contribution to external collection
    Fortschritte in Wissenschaft und industrieller Herstellung von Backhefe, Berlin: Versuchsanstalt der Hefeindustrie e.V., 2004, 87-96

Publ.-Id: 6189

Separation control by stationary and time periodic Lorentz forces

Weier, T.; Gerbeth, G.; Mutschke, G.

Stationary and time periodic wall parallel Lorentz forces in streamwise direction have been used to control the suction side flow
of NACA 0015 and PTL IV hydrofoils. Experimental results, consisting of flow visualizations and force measurements in the low Reynolds number range $Re=0.5 \dots 1.5 \times 10^5$ will be presented.
A stationary Lorentz force may increase lift by two mechanisms: 1) reattaching the separated flow and therefore increasing the critical angle and 2) introducing circulation due to acceleration of the attached suction side flow. Periodic excitation by oscillatory Lorentz forces near the leading edge is able to reattach the separated flow with much less momentum input then required for stationary forcing. However, to increase the maximum lift gain requires a comparable expenditure for both methods. The action of a wall parallel Lorentz force compares well to that of momentum input by blowing.

Keywords: Lorentz force; separation control; periodic addition of momentum

  • Lecture (Conference)
    XXI International Congress of Theoretical and Applied Mechanics, 15 - 21 August 2004, Warsaw, Poland

Publ.-Id: 6186

Electromagnetic control of flow separation by stationary and time periodic forces

Weier, T.; Mutschke, G.; Gerbeth, G.

Electromagnetic flow control is a viable option, if the fluid in question is electrically conducting. In the case of liquid metals or
semiconductor melts, this control method is being used on an industrial scale. The application of Lorentz forces to fluids of low
electrical conductivity like seawater and other electrolytes is less common, although first efforts date back to the 1950s [1]. The present talk gives a short overview on separation control with steady wall parallel Lorentz forces [2], while the main part reports on recent activities on time periodic forces. The latter topic reveals certain parallels to current aerodynamic research on separation control by oscillatory blowing. The main motivation to investigate time periodic Lorentz forces is that periodic input of momentum has proven to be around two orders of magnitude more efficient than steady blowing [3].

An electromagnetic body force F results from the vector product of current density j and magnetic induction B. For fluids of low
electrical conductivity (10 S/m) as seawater and other electrolytes, the currents due to the induced voltages are generally very low for magnetic fields of moderate strength (1 T). Consequently, the Lorentz force due to these currents is negligible. In order to obtain current densities large enough for flow control purposes it is therefore necessary to additionally apply an electric field.

There are several distinct features, that make the Lorentz force an attractive actuator: momentum is directly generated in the fluid
without associated mass flux; its frequency response is practically unlimited; virtually any excitation wave form might be realized by
feeding the electrodes with appropriate current. On the other hand, efficiency of momentum generation by weak magnetic and strong electric fields is generally small, since Joule losses dominate in electrically low conducting fluids.

For the experiments described in the following, an arrangement of flush mounted electrodes and permanent magnets producing a streamwise wall parallel Lorentz force has been used. The Lorentz force decays exponentially with the wall distance. The characteristic parameter to describe the Lorentz force action on the suction side flow is the effective momentum coefficient cµ. It relates the rms­value of the momentum injected by the Lorentz force to the freestream dynamic pressure multiplied by the foil area. Since the mechanism of periodic forcing is supposed to be connected to shear layer excitation (see [3]), the actuator should be placed near the separation line. A sketch of the NACA 0015 equipped with permanent magnets and electrodes is given in Fig. 1. Flow visualizations on an inclined flat plate (Fig. 2) show, that the otherwise fully separated flow can be reattached in an averaged sense by a time periodic Lorentz force acting near the leading edge. A characteristic feature of the flow are the vortices moving along the plate. F+ is the excitation frequency nondimensionalized by chord length and freestream velocity. Direct force measurements on the stalled NACA 0015 reveal that the maximum lift gain occurs around F+ 1, the forcing effect decays relatively
rapidly for higher frequencies. A specific lift increase at a constant angle of attack and relativ to the value for the separated flow can be obtained by oscillatory forcing with fractions of the momentum input necessary for steady Lorentz forces. In contrast, an equal increase of the maximum lift gain requires a similar expenditure of momentum for both control methods.

Direct numerical simulations (DNS) at lower Reynolds numbers have been performed by using an well-established spectral element method [4]. The results obtained confirm the experimental findings in a qualitative sense. Figure 3 shows a snapshot of velocity contours (gray) and streamtraces of the controlled flow around an hydrofoil of 30o angle of attack at Re = 500, cµ = ...

Keywords: Lorentzf force; separation control; periodic addition of momentum

  • Lecture (Conference)
    13th European Drag Reduction Meeting,17.06.2004, Aussois, France

Publ.-Id: 6185

Seawater Flow Transition and Separation Control

Weier, T.; Albrecht, T.; Mutschke, G.; Gerbeth, G.

First efforts on using Lorentz forces to control the flow of electrically low conducting fluids date back to the 1950s [1]. The
present talk reports on recent activities to delay transition in flat plate boundary layers and to control separation at hydrofoils by means of streamwise, wall parallel Lorentz forces. The actuator consists of a strip­like arrangement of permanent magnets and electrodes as proposed by [2].

Direct Numerical Simulations (DNS) by means of a spectral element method investigate the stability of a flat plate boundary layer under the influence of the Lorentz force. The evolution of Tollmien­Schlichting waves and proper 3­D disturbances is reported. A
stabilizing effect of the mean profile modification due to the Lorentz forces applied was found, verifying the assumption of [2].

Separation control at hydrofoils is undertaken by means of steady [3] as well as time periodic Lorentz forces. The latter topic reveals certain parallels to current aerodynamic research on separation control by oscillatory blowing. The main motivation for applying time periodic momentum input is that efficiency can be around two orders of magnitude higher than in case of steady blowing [4]. Since the mechanism of periodic forcing is supposed to be connected to shear layer excitation (see [4]), the Lorentz force actuator is placed in the nose region of the NACA 0015 investigated here. Direct force measurements on the stalled NACA 0015 reveal that the maximum lift gain occurs around a nondimensionalized excitation frequency of F+ 1, decaying rapidly for larger frequencies. For stalled hydrofoils, the same lift increase can be obtained by oscillatory forcing with only fractions of the momentum input necessary for steady forcing. In contrast, an equal increase of the maximum lift gain requires a similar expenditure of momentum for both control methods. DNS at lower Reynolds numbers confirm the experimental findings in a qualitative sense.

[1] Resler, E.L., Sears, W.: The prospects for
magneto­aerodynamics. J. Aero. Sci. 25, 235­245, 1958.

[2] Gailitis, A., Lielausis, O.: On a possibility to reduce the
hydrodynamic resistance of a plate in an electrolyte. Applied
Magnetohydrodynamics. Reports of the Physics Institute, 12, 143­146,
1961 (in Russian).

[3] Weier, T., Gerbeth, G., Mutschke, G., Lielausis, O., Lammers, G.:
Control of Flow Separation Using Electromagnetic Forces. Flow,
Turbulence and Combustion, 71, 5-17, 2003.

[4] Greenblatt, D., Wygnanski, I.J.: The control of flow separation by
periodic excitation. Prog. Aero. Sci., 36, 487­545, 2000.

Keywords: Lorentz force; flow control; transition delay; separation control

  • Lecture (Conference)
    International Workshop on "Flow Control by Tailored Magnetic Fields (FLOWCOMAG)", 01.-02.04.2004, Dresden, Germany

Publ.-Id: 6184

Advanced Thermal Processing of Semiconductor Materials by Flash Lamp Annealing

Skorupa, W.; Panknin, D.; Voelskow, M.; Anwand, W.; Gebel, T.; Yankov, R. A.; Paul, S.; Lerch, W.

The use of flash lamp annealing for processing semiconductor materials is outlined. Specific applications include ultra-shallow junction formation and heteroepitaxial growth of improved quality thin films of cubic silicon carbide. It is demonstrated that flash lamp annealing holds great promise as a technique for fabricating novel devices.

Keywords: flash lamp annealing; ultra shallow junctios; silicon carbide-silicon heteroepitaxy; ion implantation

  • Lecture (Conference)
    Materials Research Society Spring Meeting, Symp.C: Silicon Front-End Junction Formation—Physics and Technology, 12.-16.04.2004, San Francisco, USA
  • Contribution to proceedings
    Materials Research Society Spring Meeting, Symp.C: Silicon Front-End Junction Formation - Physics and Technology, 12.-16.04.2004, San Franzisco, USA
    Proceeding 810(2004), C4.16, C4.16

Publ.-Id: 6183

Contactless inductive flow tomography: theory and experiment

Stefani, F.; Gerbeth, G.; Gundrum, T.

When a moving electrically conducting fluid is exposed to an applied magnetic field, electrical currents are induced that give rise to an additional magnetic field. The ratio of the induced field to the applied field is determined by the magnetic Reynolds number Rm. If Rm is not too small, the induced field can be measured in the exteriour of the fluid. Applying the imposed magnetic fields in different directions and measuring the respective induced fields one can gather sufficient information to reconstruct, at least approximatively, the velocity structure of the fluid. The theory of such a contactless inductive flow tomography (CIFT) is delineated, and its practical feasibility is demonstrated in a liquid metal experiment. Qualitative as well as quantitative changes of the flow field were resolved by the CIFT method in a reasonable and reproducible way.

  • Lecture (Conference)
    XXI International Congress of Theoretical and Applied Mechanics, 15-21 August 2004, Warsaw, Poland

Publ.-Id: 6182

Inferring flows from magnetic field constraints

Stefani, F.; Gerbeth, G.; Gundrum, T.; Xu, M.

Examplified by three case studies, we address the problem on how flow structures can be inferred from various magnetic field constraints. At first, we present the contactless inductive flow tomography in which we reconstruct the three-dimensional velocity field from externally measured induced magnetic fields. At second, we reconsider the optimization problem for the sodium flow in the Riga dynamo experiment. The third example concerns the special inverse spectral dynamo problem on how a spherically symmetric alpha^2 dynamo can become oscillatory.

  • Lecture (Conference)
    International Workshop on "Flow Control by Tailored Magnetic Fields (FLOWCOMAG)", 01.-02.04.2004, Dresden, Germany

Publ.-Id: 6181

Nonlinear transition of a flow driven by a rotating magnetic field

Grants, I.; Gerbeth, G.

Non-normal nonlinear transition of a linearly stable liquid metal flow driven by a rotating magnetic field is simulated numerically. Three dimensional Navier-Stokes equations are solved by a highly accurate spectral methods. Response of the flow to noise is simulated introducing a random body force. We observe four flow regimes. At a low control parameter the flow response does not differ from the response of a fluid at rest. In the second regime the amplitude of response is considerably higher though it scales linearly with the noise amplitude. Nonlinear intermittent outbursts are observed in the third regime. Duration of outbursts increases with noise amplitude until they merge in a continuous series in the fourth regime. We demonstrate that direct numerical simulation of the flow response to random forcing can uncover mechanisms which lead to transition in linearly stable flows.

  • Lecture (Conference)
    XXI International Congress of Theoretical and Applied Mechanics, 15.–21.08.2004, Warsaw, Poland

Publ.-Id: 6180

Investigation of the Fluid Flow Driven by an Alternating Magnetic Field with Ultrasonic Doppler Velocimetry

Cramer, A.; Varshney, K.; Gerbeth, G.

We report on an experimental study of the influence of technical frequency pulsating magnetic field on a liquid metal volume. Such single-phase a.c. fields are widely used in metallurgy. Ultrasonic Doppler Velocimetry (UDV) has been used to determine the topology of the flow in a liquid metal column contained in a cylindrical vessel. Profile-scan-rates exceeding 25 Hz permit to acquire sequential time series for different radial co-ordinates which in turn allow to map the statistical properties of the flow. Concerning the sensitivity of UDV it was possible to measure values of the velocity down to a few mm/s. Even the flow is no more laminar in this regime almost any industrial situations are more turbulent. Limited by the maximum current which can be supplied to our magnet a range nearly spanning one order of magnitude of the driving magnetic field strength could be investigated. By that scaling laws derived analytically can be checked over a wide parameter range of industrial interest. The characteristic velocity was estimated from the time averaged mean profile in the centre of the container. Here the maximum absolute values of the vertical velocity component are found throughout the whole vessel in the up-stream in the upper half and the downstream in the lower half. Both local maxima scale nearly perfectly linear with the applied magnetic induction. This characteristic is similar to that of classical turbulent shear flows, even here the skin depth is not large compared to the dimension of the bath.

Keywords: MHD; fluid flow; alternating magnetic field; flow measurement techniques; ultrasonic Doppler velocimetry

  • Lecture (Conference)
    International Symposium HES-04 Heating by Electromagnetic Sources, 23.-25.06.2004, Padua, Italy
  • Contribution to proceedings
    International Symposium on Heating by Electromagnetic Sources (ISBN 88-86281-92-7), 23.-25.06.2004, Padua, Italy, 413-420

Publ.-Id: 6179

New possibilities for velocity measurements and model experiments in liquid metal processing

Cramer, A.; Varshney, K.; Gerbeth, G.

Potential difference probes and ultrasound have been employed to investigate liquid metal flows in cylindrical containers.
The fluid motion was driven by either a rotating or a pulsating magnetic field. Experimental results containing flow mapping and scaling of mean velocities for very small driving forces will be presented. We report on our new MULTIMAG facility which allows for almost any combination of rotating, traveling, pulsating and d.c. magnetic fields in extended geometries for industrially relevant regimes.

  • Lecture (Conference)
    XXI International congress of theoretical and applied mechanics (ICTAM), 15.-21.08.2004, Warsaw, Poland

Publ.-Id: 6178

Directional solidification of Pb-Sn alloys affected by a rotating magnetic field

Eckert, S.; Willers, B.; Michel, U.; Zouhar, G.; Nikritjuk, P. A.; Eckert, K.

An experimental and numerical study with respect to the influence of a rotating magnetic field (RMF) on the directional solidification of a Pb-Sn alloys is reported. A cylindrical crucible with a diameter of 50 mm was positioned on a water cooled copper chill thus inducing an axial heat transfer from the mold. The electromagnetically driven convection shows a distinct effect on the solidification parameters such as the cooling rate, the temperature gradient or the growth velocity of the liquidus isotherm resulting in significant modifications of the observed macro- and microstructures. The fluid flow promotes the heat transfer rate and decreases the temperature gradients in the melt. Analyzing the columnar-equiaxed transition (CET) a dependence of the CET position and shape on the applied Taylor number was demonstrated. The experiments also revealed that the permanent modification of the fluid volume due to the movement of the solidification front prevents the development of stationary flow pattern as known for the isothermal case.

Keywords: solidification; forced convection; rotating magnetic field; CET; macrosegregation

  • Lecture (Conference)
    XXI International Conference of Theoretical and Applied Mechanics (ICTAM), 15.-21.08.2004, Warsaw, Poland

Publ.-Id: 6177

The post-ionisation of Pb ions from a molten Sn host field-ion emitter

Bischoff, L.; Mair, G. L. R.; Akhmadaliev, C.; Mair, A. W. R.; Ganetsos, T.

A tin liquid metal ion source contaminated with led has been studied. From a detailed analysis of the source mass spectra as a function of emission current it is established that while Sn+, Sn++ and Pb+are directly field-evaporated from the liquid surface, Pb++ forms by the post-ionisation of Pb+. Moreover, our results for, the Pb++/Pb+ ratio are in excellent agreement with those of Komuro (1983), obtained with a pure led LMIS.

Keywords: SnPb liquid metal ion source; post-ionisation; mass-spectra

Publ.-Id: 6176

Level structure of 69Se

Stefanescu, I.; Eberth, J.; de Angelis, G.; Warr, N.; Gersch, G.; Steinhardt, T.; Thelen, O.; Weisshaar, D.; Martinez, T.; Jungclaus, A.; Schwengner, R.; Lieb, K. P.; Stefanova, E. A.; Curien, D.; Gelberg, A.

Excited levels in 69Se have been studied using the 40Ca(32S,2pn)69Se reaction at 95- and 105-MeV beam energy. γ-rays have been detected with the EUROBALL spectrometer operated in conjunction with the wall and the charged-particle detector array EUCLIDES. New level sequences with positive and negative parities have been identified from n-γγ and n-γγγ coincidences. Spins have been assigned to many of the levels on the basis of angular distribution and directional correlation measurements. Excitation energies of the positive-parity yrast band and the branching ratios of its decay are compared with the predictions of the rigid triaxial rotor plus particle model.

Publ.-Id: 6175

Substantial impact of FDG PET imaging on the therapy decision in patients with early-stage Hodgkin´s lymphoma

Naumann, R.; Beuthien-Baumann, B.; Reiß, A.; Schulze, J.; Hänel, A.; Bredow, J.; Kühnel, G.; Kropp, J.; Hänel, M.; Laniado, M.; Kotzerke, J.; Ehninger, G.

This prospective study assessed the impact of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) on the staging an d possible consequential changes of treatment regimen in patients with Hodgkin´s lymphoma (HL). A total of 88 consecutive patients with histologically verified Hodgkin´s lymphoma underwent a PET scan in addition to conventional staging procedures. Treatment was based on the conventional staging only, and the results of the FDG-PET did not affect the treatment strategy. The evaluation focused on the suggested change in clinical stage according to the Ann Arbor classification and on the suggested change in treatment strategy rather than on a lesion-by-lesion analysis. Using all the methods performed as the standard of reference, 18F-FDG-PET staging was concordant with conventional staging in 70 out of 88 patients (80 %). 18F-fluorodeoxyglucose positron emission tomography suggested a change to a different clinical stage in 18 patients (20 %). Management would have been changed in 16 patients (18 %): intensification of treatment in nine patients (10 %) and minimisation of treatment in seven patients (8 %). In the 44 patients with early disease (stage IA - IIB), treatment would have benn intensified in nine out of 44 patients (20 %). 18F-fluorodeoxyglucose postitron emission tomography is a relevant noninvasive method that supplements conventional staging procedures and should therefore be used routinely to stage Hodgkin´s lymphoma, particularly in patients with an early stage.

Keywords: Hodgkin´s lymphoma; 18F-fluorodeoxyglucose (FDG) prositron emission tomography (PET); staging; lymphoma

  • British Journal of Cancer 90(2004), 620-625

Publ.-Id: 6174

The Temperature Dependence of Energy Spread and Mass Spectra of an Au73Ge27 Liquid Metal Alloy Ion Source

Pilz, W.; Bischoff, L.; Mair, G. L. R.; Akhmadaliev, C.; Ganetsos, T.

Focused ion beams from liquid metal ion sources (LMISs) have become of increasing interest in recent years. A promising source is one of Ge ions, important in the semiconductor technology; e.g., local doping of SixGe1-x structures. The beam energy spread, ΔE½, of the source - which, through the chromatic aberrations of the system determines the final spot size at the target - and the peak energy deficit (PED), as well as the mass spectra of a Au73Ge27 eutectic liquid metal alloy ion source were investigated. Source temperature was the main experimental parameter. The melting point of the eutectic was determined as 366oC. ΔE½, measured with a retarding field analyser, is expressed as the full width of the distribution at half its maximum height (FWHM). Doubly-charged ions attain twice the energy of singly-charged ions, for a given voltage drop, and this has to be taken into account when determining the value of ΔE½ and the PED. Ge was found to be much more abundant in the doubly-charged state, in accordance with Brandon`s criterion [1]. From PED measurements we conclude that Ge++ as well as Au+ and Ge+ are directly field-evaporated, whereas Au++ is post-ionized from the singly-charged state. As expected for liquid metals that display a linear decrease of their surface tension coefficient with temperature, the liquid metal ion source under investigation shows an increase in emission current with increasing temperature. This is in contrast to Si containing metallic glass alloys, e.g., AuSi or AuGeSi, that have an anomalous surface tension coefficient [2]. The mass spectra, where obtained with an ExB filter. Alongside the main monomer species, cluster ions, the result of droplet disintegration, were identified. The conclusions drawn from a study of the ratio of the abundance of doubly to singly-charged monomer ions, support our deductions from PED measurements, as far as the mechanisms of creation of the monomer ions are concerned.
[1] D.G. Brandon, Surf. Sci. 3 (1964) 1.
[2] L. Bischoff and G.L.R. Mair, Recent Res. Devel. Appl. Phys. 6 (2003) 123.

Keywords: AuGe alloy liquid metal ion source; mass spectra; energy spread

  • Lecture (Conference)
    49th International Field Emission Symposium (IFES 04)July 12 - 15, 2004, Seggau Castle, Graz, Austria
  • Contribution to proceedings
    49th International Field Emmissions Symposium IFES 04, 12.-15.07.2004, Seggau, Österreich

Publ.-Id: 6173

Numerical Simulation of Coolant Mixing at the ROCOM Test Facility with CFX-4 and CFX-5 based on Complex Meshes

Höhne, T.

Die Kühlmittelvermischung im Primärkreislauf von Druckwasserreaktoren (DWR) ist für zwei Klassen von hypothetischen Störfällen relevant: Borverdünnungsstörfälle und Kaltwassertransienten. Ausgehend von den Vermischungsphänomenen, die für diese Szenarien bedeutsam sind, wurde die Versuchsanlage ROCOM (Rossendorf Coolant Mixing Facility) konzipiert und aufgebaut. Die Untersuchung der Vermischung erfolgt anhand eines Tracers (verdünnte Salzlösung) und der Messung der Leitfähigkeit des Fluids. Die experimentellen Ergebnisse wurden auf Grundlage eines blockstrukturierten Gitters mit CFX-4 (450000 Nodes) bzw. eines unstrukturierten, tetraederbasierten Gitters mit CFX-5 (5 Mio. Tetraeder) unter Zuhilfenahme des k,e Turbulenzmodells nachgerechnet. Dabei mussten Einbauten im strukturierten Gitter mit Hilfe des Modells des porösen Körpers und Einführung von richtungsabhängigen Körperkräften modelliert werden, während im unstrukturierten Gitter die Geometrie komplett abgebildet werden konnte. Die Rechnungen wurden auf einem LINUX-Cluster im Parallelmode durchgeführt. Die Experimente an der ROCOM-Anlage zur stationären Kühlmittelzirkulation bei Betrieb aller Schleifen zeigen übereinstimmend mit den numerischen Berechnungen eine Beschränkung der Verteilung des eingespeisten Tracers am Kerneintritt überwiegend auf den Quadranten der mit dem Tracer beaufschlagten Schleife. Für turbulente Strömungen konnten die Berechnungscodes somit anhand von Experimenten validiert werden und steht für weitere Untersuchungen in der Reaktorsicherheitsforschung zur Verfügung. Die Ergebnisse der Experimente und CFD-Rechnungen fließen in ein Modul ein, welches in Computercodes für Störfallanalysen integriert wird. Über eine verbesserte Beschreibung der Vermischung wird dadurch eine realistische Störfallsimulation erreicht.

Keywords: Boron Dilution; CFD; Pressurized Water Reactor; Coolant Mixing

  • Lecture (Conference)
    NAFEMS Seminar: „Simulation of Complex Flows (CFD) – Application and Trends“, May 3 - 4, 2004, Niedernhausen/Wiesbaden, Germany
  • Contribution to proceedings
    NAFEMS Seminar: „Simulation of Complex Flows (CFD) – Application and Trends“, 03.-04.05.2004, Niedernhausen/Wiesbaden, Germany, Proceedings, S. 24

Publ.-Id: 6172

Experimental investigation of coolant mixing in the RPV of a PWR during natural circulation conditions

Kliem, S.; Höhne, T.; Prasser, H.-M.; Rohde, U.; Weiß, F.-P.

Partial depletion of the primary circuit during a hypothetical small break loss of coolant accident can lead to interruption of one-phase flow natural circulation. In this case, the decay heat is removed from the core in the reflux-condenser mode. Thermal hydraulics analyses using the system code ATHLET showed for the scenario of hot leg side leak and hot leg safety injection, that weakly borated condensate can accumulate in particular in the pump loop seal of those two loops, which do not receive safety injection. According to these ATHLET-calculations, one-phase flow is maintained in the remaining two loops at high residual heat conditions because of the entrainment of safety injection coolant into the steam generators. After refilling of the primary circuit, the natural circulation in the two stagnant loops simultaneously re-establishes and the de-borated slugs are shifted towards the reactor pressure vessel (RPV). Mixing in the downcomer and the lower plenum is an important phenomenon mitigating the reactivity insertion into the core in this postulated scenario.
Therefore, the mixing of the de-borated slugs with the ambient coolant in the RPV was investigated at the four loop 1:5 scaled Mixing Test Facility ROCOM.
Based on the ATHLET-calculations, a volume flow rate of 5 % of the nominal rate was set in the loops running in one-phase flow. The volume flow rate in the two restarting loops increases from zero to 6 %. In these two loops, de-borated slugs of 7.2 m3 were assumed corresponding to the volume of the whole loop seal. An experimental parameter study was carried out with different duration of the flow ramp and variation of the density difference between de-borated slug and ambient coolant due to differences in boron concentration and temperature.
The variation of the density difference significantly changes the mixing behavior. With no density differences, the weakly borated coolant almost perpendicularly flows down in the downcomer and a maximum of 64 % of the initial perturbation is detected in the core entry section below the loops where the slugs were formed. Increasing the density difference, a stratification is observed in the downcomer. The less dense slugs flow around the core barrel at the top of the downcomer. At the opposite side the lower borated coolant is entrained by the colder safety injection water and transported to the core. This entrainment effect leads to the admixture of boron from the safety injection to the under-borated slugs. Consequently, the maximum of under-boration at the core entry is lower. For the maximum density difference of 2 % investigated in the frame of this work, a value of 31 % only of the initial perturbation was measured.

  • Lecture (Conference)
    12th International Conference on Nuclear Engineering ICONE-12, 25.-29.05.2004, Washington D.C., United States
  • Contribution to proceedings
    12th International Conference on Nuclear Engineering ICONE-12, 25.-29.05.2004, Washington D.C., United States, Proc. CD-ROM paper 49424

Publ.-Id: 6171

Structural studies on ion implanted semiconductors using x-ray synchrotron radiation: strain evolution and growth of nanocrystals

Eichhorn, F.; Gaca, J.; Heera, V.; Schell, N.; Turos, A.; Weishart, H.; Wojcik, M.

Modification of semiconductor materials by ion implantation is a well-established technological process. It can modify semiconductor material by producing crystal lattice defects as well as by alloying the substrate with the implant. The first introduces stress/strain into material or mixing of the constituents. The second effect leads to semiconductor doping or creation of new phases. Precise control of structural properties are crucial for technological applications. We present here, how various methods of x﷓ray scattering can be used for structural studies on such materials for optimization of the ion beam treatment of semiconductors. In some cases also complementary techniques like RBS/c were used.
As+ ions with an energy of 1.2 MeV were implanted into InP single crystals and epitaxial layers. Due to the ion induced strain, interplanar spacing in the growth direction decreases with increasing ion dose. Important recovery of radiation damage was observed upon prolonged storage at RT. Furthermore, patterned ion implantation is used for modification of lateral regions. XRD revealed that the presence of a masked region produces strain variations across the sample. RBS/c analysis showed that such an edge effect is independent on implantation conditions.
Silicon carbide and diamond are semiconductor materials for high temperature, high frequency and high power applications. However, a heavy p-type doping of SiC is difficult and a sufficient n-type doping of diamond was not yet realized. Therefore, the fabrication of diamond-SiC heterostructures by ion beam synthesis (IBS) is a new approach to novel devices. It was found that the synthesized nanocrystals grow in the surrounding single crystalline matrix highly oriented. The crystal size and shape, their strain and strain fluctuation vary in dependence on the implantation parameters like dose, dose rate and substrate temperature. The lattice damage of the matrix may be minimized by high temperature treatment.

Keywords: ion implantation; InP; SiC; diamond

  • Lecture (Conference)
    Vth International Conference on “Ion Implantation and Other Applications of Ions and Electrons“ – ION2004, Kazimierz Dolny, Poland, June 14 - 17, 2004

Publ.-Id: 6169

Rhenium- and technetium-complexes with steroids as ligands for the estrogen receptor, progesterone receptor and androgen receptor

Wüst, F.

This review covers a part of the current general directions in radiopharmaceutical research and development, being the design of 99mTc-containing steroids capable of binding and imaging the estrogen receptor, progesterone receptor or androgen receptor. The non-physiological metal technetium has to be adapted to the biological environmental by means of coordination chemistry. As a d-block transition metal, technetium must be incorporated into small-molecule receptor ligands like steriods by some chelation system, which may involve multiple heteroatom coordination of the formation of stable organometallic species. The review will also address examples of rhenium-containing steroids as non-radioactive models for the radiopharmaceutically relevant 99mTc compounds.

  • Current Topics in Steroid Research 4(2004), 197-205

Publ.-Id: 6168

Ein Online-Zustandserkennungssystem für Batch-Reaktoren in der chemischen Industrie

Kryk, H.

Aus Gründen der Anlagensicherheit und der Sicherung einer hohen Ausbeute und Produktqualität ist die frühzeitige Erkennung von unerwünschten Prozessabweichungen bei Batch- und Semibatchprozessen von besonderer Bedeutung. Aufgrund der instationären Prozessführung sind diese oft nicht aus den Prozesssignalverläufen eindeutig erkennbar. Ziel war deshalb die Entwicklung eines Online-Monitoring-Systems, das dem Operator Informationen über die Konzentrationsverläufe und den Prozessfortschritt zur Verfügung stellt.
Die Bewertung des Prozesszustandes erfolgte bisher in der Regel auf Grundlage der Prozessdatenverläufe (z.B. Temperaturen und Drücke) unter Einbeziehung von Erfahrungswissen, wobei Konzentrationsmessungen erst nach dem Prozessende im Rahmen von Qualitätskontrollen oder während des Prozesses stichprobenartig offline durchgeführt wurden. Der Aufwand bezüglich Probenahme und Handling ist hierbei erheblich. Alternativ ist die Nutzung einer Online-Analytik möglich, die jedoch sehr hohe Investitions- und Betriebskosten verursacht.
Das Online-Monitoring-System MoSys ist ein auf adaptiven Stoff- und Energiebilanzen basierendes Softwaresystem, das dem Operator Informationen über den Prozessfortschritt, das voraussichtliche Reaktionsende und die Konzentrationen der Reaktionsmedien zur Verfügung stellt. Die Berechnungen erfolgen online auf Grundlage von Prozessmessdaten und Zusatzinformationen über den Prozess. Der Einsatz einer Online-Analytik ist nicht erforderlich. Die Ergebnisse sind an den Terminals des Prozessleitsystems abrufbar.
Die Entwicklung richtet sich in erster Linie an Anlagenbetreiber der Feinchemie und der pharmazeutischen Industrie. Ein derartiges Online-System ist bei allen ausreichend exothermen Batch- und Semibatch-Prozessen einsetzbar, wenn die Nutzinformationen in den Wärme- und Stoffbilanzen enthalten sind. Neben einer Erhöhung der Anlagen- und Umweltsicherheit wird durch den Einsatz des Systems weiterführendes Prozesswissen generiert, das als Grundlage für eine Prozessoptimierung genutzt werden kann.

  • Contribution to external collection
    P&A Kompendium 20045, München: Publish-Industry Verlag GmbH, 2004

Publ.-Id: 6167

Scaling effects in vertical bubbly pipe flow

Lucas, D.; Prasser, H.-M.

On the basis of detailed experimental data obtained for stationary bubbly flow in vertical pipes with an inner diameter of 51.2 mm and 194.1 mm, analytical investigations on scaling effects were made. Because of the interaction between the phases the scaling behavior is very complex in case of two phase flow. Similarity can only be achieved regarding selected parameters. Thus the modeling of scaling effects has to be based on local models for the phase interaction. A simplified model, introduced earlier, is used for the validation of such models by consideration of scaling effects. Because of the strong influence of the bubble size distribution on the flow, the model considers a number of bubble classes. Models for the non-drag forces acting on bubbles were validated for the small pipe and afterwards used for the prediction of radial gas volume profiles in the large pipe. The comparison with measured profiles shows that there is a generality of these models. Even more complex is the situation regarding the development of the flow along the pipe. Here bubble coalescence and break-up are important. There is still a need for an improvement of these models.

Keywords: bubble flow; scaling; pipe flow; modeling

  • Lecture (Conference)
    5th International Conference on Multiphase Flow, ICMF’04, 30.05.-04.06.2004, Yokohama, Japan
  • Contribution to proceedings
    5th International Conference on Multiphase Flow, ICMF’04, 30.05.-04.06.2004, Yokohama, Japan, paper 187

Publ.-Id: 6166

X-ray study of in-plane layer stress and orientation degree in Fe/Cr multilayers grown by MBE on R-plane sapphire

Prokert, F.; Kravtsov, E.; Milyaev, M.; Romashev, L.; Ustinov, V.

Annealing or increasing growth temperature enhance interface fluctuations, causing drastic influence on GMR and interlayer coupling. The present X-ray measurements were aimed to study the influence of the sapphire substrate temperature during MBE on the in-plane layer stress and the degree of orientation in the Fe/Cr multilayers (MLs). A series of five samples was investigated, grown in the range 60-240°C on the oriented substrate, having a Cr buffer layer in the assembly Al2O3/Cr(8nm)/[Fe(3nm)/Cr(1.2nm)]x8. The data were received with Cu radiation using a standard goniometer setup. At the sapphire R-plane the Fe/Cr multilayers grow in [100] direction. The orientation distribution in the layers was analyzed by rocking curves of the (200) reflection. The layer stress could be determined from the (200) reflection, measured in ML normal direction, and the perpendicularly measured reflections (020) and (002). The studies reveal that the sharpness of the (200) Fe/Cr orientation is proceedingly reduced with increasing substrate temperature. This is accompanied by a drastic relaxation of the tensile in-plane layer stress.

Keywords: Fe/Cr Multilayer; MBE; In-plane stress

  • Poster
    Zeitschrift für Kristallographie, Supplement Issue No. 21, S. 142; Referate, Gemeinsame Jahrestagung der DGK und der DGKK vom 15. bis 19. März 2004 in Jena.
  • Contribution to proceedings
    Gemeinsame Jahrestagung der DGK und der DGKK vom 15. bis 19. März 2004 in Jena. Zeitschrift für Kristallographie, 21(2004)Suppl., 142; Referate

Publ.-Id: 6165

Bacterial diversity in water samples from two uranium mill tailings as revealed by 16S rDNA retrieval

Selenska-Pobell, S.; Radeva, G.

Bacterial diversity was assessed in water samples collected from two uranium mill tailings, one in Germany and one in the USA, by using the 16S rDNA retrieval. Mainly individual RFLP types were found in the 16S rDNA library constructed for the samples of the German tailings, Gittersee/Coschütz, that indicated a high bacterial diversity. Several small groups of Proteobacteria and of Cytophagales were identified in those samples as well. Significantly lower bacterial diversity was demonstrated in the samples collected from the Shiprock tailings in the USA, which were predominated by a few large populations of gamma-Proteobacteria.
Key words: bacterial diversity, 16S rDNA, uranium mill tailings
Introduction: Bacteria significantly influence the migration and the toxicity of heavy metals and radionuclides in nature due to their ability to biotransform and accumulate them [1,2]. Uranium mining wastes are contaminated with radionuclides and other toxic metals [2]. The toxicity of uranium is primarily attributed to its chemical properties rather than to its radioactivity [3]. As in other extreme environments, most parts of the indigenous bacterial populations in the uranium mining wastes are not yet cultured due to the limited knowledge of their life necessities. The problems of culturability in the analysis of bacterial diversity were overcome during the last decade by the application of direct molecular methods for analysis, such as the 16S rDNA retrieval [4]. This molecular method was successfully used for compositional analysis of the natural microbial communities in many different environments [5,6,7]. The aim of the present work was to assess bacterial diversity in water samples collected from two uranium wastes by using the 16S rDNA retrieval.
Materials and methods. Samples collection. Samples were collected from two uranium mill tailings: Gittersee/Coschütz, a former uranium-coal mine, near the town of Dresden in Germany and Shiprock, New Mexico, in the USA, located in north western New Mexico,

  • Comptes rendus de l´Academie bulgare des Sciences 57(2004)6, 85-90

Publ.-Id: 6164

Comparative Microbial Diversity in Uraniuim Wastes in Germany and in the USA

Selenska-Pobell, S.; Geißler, A.; Radeva, G.; Merroun, M.; Flemming, K.; Satchanska, G.; Tzvetkova, T.

Structures of the natural bacterial and archaeal communities in soil and water samples from three U wastes in Germany and from two in the USA were compared by using the 16S rDNA and the RISA retrievals. We found that the composition of the bacterial communities is very diverse and site-specific. However, several particular groups of bacteria including also novel lineages were identified in the samples of all habitats. Some of the retrieved 16S rDNAs were related to sequences already found in other heavy metal contaminated environments and it seems that they represent not yet cultured bacterial populations characteristic for the latter.
A quantitative analysis of the Geobacter sp. populations demonstrated that they are present in low but site-specific number at the studied environments.
The archaeal populations in the studied environments were, in contrast to the bacterial, not very dense and they were limited to only two lineages of not yet cultured groups of Crenarchaeotae. Only in one of the samples studied representatives of methanogenic Euryarchaeotae were identified.
Chemolithoautotrophic strains involved in U mobilization and also heterotrophic U reducing and immobilizing strains were cultured from the samples from the U wastes. In addition, several ultramicrobacterial isolates were cultured on oligotrophic media. These isolates were characterized morphologically and physiologically. Their interactions with U and several other metals were studied by using ICP-MS, EXAFS, and IR spectroscopy.

  • Lecture (Conference)
    ISME 10, 22.-27.08.2004, Cancum, Mexico
  • Contribution to proceedings
    ISME 10, 22.-27.08.2004, Cancun, Mexico

Publ.-Id: 6163

Bacterial and Archaeal Diversity in Ground Waters of the Siberian Deep--Well Radioactive DisposaI Site Tomsk-7

Selenska-Pobell, S.; Nedelkova, M.

Microbial diversity was studied in water samples collected from depths of 290 to 324 m near the radioactive waste injection site Tomsk-7 in Siberia, Russia. The biomass from the samples was concentrated via consequent filtration on filters with pore sizes of 1.2, 0.45 and 0.22 µm. 16S rDNA clone libraries were constructed for total DNA recovered simultaneously from the three filters and also for the DNA extracted individually from 0.45 and 0.22 µm filters in parallel. The analysis of the 16S rDNA libraries demonstrated that the estimation of microbial diversity strongly depends on the way of collecting the biomass.
About 65% of the clones retrieved in the total DNA were affiliated to the Rhodocyclus group. The rest of the clones represented very diverse bacterial groups. Euryarchaeota and Grenarchaeota were also identified in this total DNA.
No archaeal sequences were amplified in the 0.45 and 0.22 µm filter DNA. This indicates that the archaea were associated (possibly with some bacteria) with the larger aquatic particles.
In the 0.45 mm library the representatives of the Rhodocyclus group represented 30% of the total number of clones. Another 20% of the clones were affiliated with a low identity to a novel cyanobacteria related lineage.
Sequences representing the same "cyanobacteria-like" lineage were also found in the 0.22 µm library. However, populations of possibly oligotrophic Cytophagales were the most predominant in the latter library and represented about 55% of the clones. Microdiverse ultramicrobacterial isolates were cultured from one 0.22 µm filter and characterized morphologically and physiologically.

  • Lecture (Conference)
    ISME 10, 22.-27.08.2004, Cancun, Mexico
  • Contribution to proceedings
    ISME 10, 22.-27.08.2004, Cancun, Mexico

Publ.-Id: 6162

Möglichkeiten und Grenzen des Mikrostrahles für Channeling-Messungen

Grambole, D.

RBS - Channeling - Messungen werden routinemäßig zur Untersuchung von Kristallqualität und -defekten genutzt, wobei die Größe des Ionenstrahls üblicherweise im mm-Bereich liegt. Durch eine Verkleinerung des Strahldurchmessers in den µm-Bereich erschließen sich Möglichkeiten der Untersuchung von Mikrokristallen. Damit verbunden ist jedoch eine starke Erhöhung der notwendigen Fluenz des Ionenstrahles, die zu einer verstärkten Kristallschädigung während der Analyse führt.
Im Vortrag werden nach der Vorstellung der Rossendorfer Mikrochanneling-Apparatur die durch den Mikrostrahl erzeugten Kristallschädigungen diskutiert und daraus Grenzen für die Anwendung abgeleitet. Ein erstes Untersuchungsbeispiel soll die Möglichkeiten von Channeling-Messungen mit dem Mikrostrahl verdeutlichen.

  • Lecture (others)
    Ruhr-Universität Bochum, Angewandte Festkörperphysik, Nov. 13, 2003

Publ.-Id: 6161

Wavelet analysis of extended x-ray absorption fine structure data

Funke, H.; Scheinost, A.; Chukalina, M.

Fourier transform (FT) is a fundamental step for the data reduction and interpretation of extended x-ray absorption fine structure (EXAFS) spectra. The FT separates backscattering atoms by their radial distance from the absorbing atom (so-called shells). We suggest to routinely complement the FT by a wavelet transform (WT), which provides not only radial distance resolution, but resolves in k space. This information eases the discrimination of atoms by their elemental nature, especially if these atoms are at the same distance. We present an in-depth analysis of the Morlet wavelet, which has specific advantages for EXAFS analysis, including the possibility to estimate Morlet parameter values optimized either for elemental or for spatial resolution. Using an experimental spectrum of Zn-Al layered double hydroxide, we demonstrate the discrimination of Al and Zn at a similar crystallographic position, in spite of destructive interference substantially reducing signal information. Finally, the extension to multiple scattering paths leads to a deeper understanding of the resolution properties of the WT.

  • Physical Review B 71(2005)9, 4110-4110

Publ.-Id: 6160

The Physics Program of the HADES Experiment at GSI

Holzmann, R.; Hades Collaboration

The high-acceptance dielectron spectrometer HADES has become operational at GSI. Its physics program is reviewed with special emphasis on the planned studies of hadron properties in proton- and pion-induced reactions. The relevance of these data for the interpretation of dilepton data from heavy-ion reactions is stressed as well.

  • Contribution to proceedings
    XLII International Winter Meeting on Nuclear Physics, 25.01.-01.02.2004, Bormio, Italy
    Ricerca Scientifica ed Educazione Permanente Supplemento, 161-170

Publ.-Id: 6159

The Favre Averaged Drag Model for Turbulent Dispersion in Eulerian Multi-Phase Flows

Burns, A. D.; Frank, T.; Hamill, I.; Shi, J.-M.

A general framework is presented for the modeling of turbulent dispersion in Eulerian Multi-Phase Flows. The approach is based on a double averaging procedure of the local instant equations. We start with the ensemble averaged equations of Eulerian multi-phase flow. We perform a second time average of these, in order to form equations which may be used to model turbulent multi-phase flows. These are conveniently expressed in terms of Favre or Mass averaged variables. Turbulent dispersion is modeled by performing a time average of the interphase drag term in its modeled form, and expressing it in terms of Favre averaged variables. The resulting double averaged momentum equations contain additional terms which account for a turbulent dispersion force. We call the resulting model the Favre Averaged Drag (FAD) model for turbulent dispersion. It is first presented in a general form which may be used in conjunction with any Reynolds averaged turbulence model, and for an arbitrary number of phases with arbitrary morphologies. For the purposes of this study, we make two further specializations, to poly-dispersed multiphase flows, and to turbulence models which employ the eddy diffusivity hypothesis. The resulting model is compared to several other models that have appeared in the literature, We show that all are special cases of the FAD model, within certain physical and mathematical limitations. Hence the FAD model encompasses all of these models, but has a potentially wider range of universality. The FAD model has been implemented in the commercial CFD package, CFX-5, and tested against a range of dispersed multiphase flows, including bubbly flows in vertical pipes, and liquid-solid flows in mixing vessels. The FAD model is shown to yield superior predictions in all cases.

Keywords: Multi-fluid model; turbulent dispersion model; drag force; Favre average; double average

  • Contribution to proceedings
    5th International Conference on Multiphase Flow, ICMF 04, 30.05.-04.06.04, Yokohama, Japan
    ICMF2004 Proceedings CD-ROM, paper No. 392, 1-17

Publ.-Id: 6158

Hadron production in C+C at 2 A GeV measured by the HADES spectrometer

Tlusty, P.; Agakichiev, G.; Agodi, C.; Alvarez-Pol, H.; Atkin, E.; Balanda, A.; Bellia, G.; Belver, D.; Bielcik, J.; Böhmer, M.; Bokemeyer, H.; Boyard, J.; Braun-Munzinger, P.; Chepurnov, V.; Chernenko, S.; Christ, T.; Coniglione, R.; Daues, H.; Diaz, J.; Djeridi, R.; Dohrmann, F.; Duran, I.; Eberl, T.; Emeljanov, V.; Fabbietti, L.; Fateev, O.; Fernandez, C.; Finocchiaro, P.; Friese, J.; Fröhlich, I.; Fuentes, B.; Garzon, J.; Gernhäuser, R.; Golubeva, M.; Gonzalez, D.; Grosse, E.; Guber, F.; Hehner, J.; Heinz, T.; Hennino, T.; Hlaváè, S.; Hoffmann, J.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Jaskula, M.; Jurkoviè, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B.; Kopf, U.; Kotte, R.; Kotuliè-Bunta, J.; Krücken, R.; Kugler, A.; Kühn, W.; Kulessa, R.; Kurepin, A.; Kurtukian-Nieto, T.; Lang, S.; Lehnert, J.; Maiolino, C.; Marín, J.; Markert, J.; Mishin, Y.; Montes, N.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotný, J.; Ott, W.; Otwinowski, J.; Pachmayer, Y.; Panebratsev, Y.; Pechenov, V.; Perez, T.; Pietraszko, J.; Pleskaè, R.; PospíšIl, V.; Przygoda, W.; Rabin, N.; Ramstein, B.; Reshetin, A.; Ritman, J.; Rodriguez Prieto, G.; Roy-Stephan, M.; Rustamov, A.; Sabin Fernandez, J.; Sadovsky, A.; Sailer, B.; Salabura, P.; Sanchez, M.; Sapienza, P.; Schmah, A.; Schroeder, C.; Schwab, E.; Senger, P.; Simon, R.; Smolyankin, V.; Smykov, L.; Spataro, S.; Stelzer, H.; Stroebele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Titov, A.; Toia, A.; Traxler, M.; Tsertos, H.; Vazquez, A.; Volkov, Y.; Wagner, V.; Walus, W.; Wang, Y.; Winkler, S.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Zanevsky, Y.; ŽOvinec, D.; Zumbruch, P.

The C+C reaction at 2 A GeV has been recently studied using the HADES spectrometer installed at GSI Darmstadt,with the main aim to reconstruct the dielectron signal from the decay of low mass vector mesons.We have analyzed the data with respect to emission of charged hadrons,in order to study production of ð mesons from excited nuclear matter with high temperature and high energy density.
Efficient hadron identification is also important for dielectron analysis.The main source of electron pairs at this energy is the neutral ð meson Dalitz decay,so normalization of its yield to charged ð mesons is a natural way for data presentation.Analysis of produced hadrons also allows event characterization,and check of the detector performance. The particle identification method (PID),based on a likelihood technique to select the most probable particle type,is described.In case of hadrons,the particle momentum,velocity and energy loss are used for the PID decision.The performance of the method is evaluated in detailed simulations.
Preliminary results of analysis of charged hadron production are presented.The particle yields and transverse mass distributions are shown and interpreted in terms of the thermal model.Results are compared with existing data from previous experiments.

  • Lecture (Conference)
    XLII International Winter Meeting on Nuclear Physics, 25.01.-01.02.2004, Bromio, Italy
  • Contribution to external collection
    XLII International Winter Meeting on Nuclear Physics Bormio, Riceria Scientifica ed Educazione Permanente Supplemento (2004), 171-179

Publ.-Id: 6157

Dynamische Investitionsrechnungen als Instrument zur Priorisierung von Investitionsentscheidungen in öffentlich-finanzierten Einrichtungen am Beispiel des Forschungszentrums Rossendorf

Prauser, M.

Keywords: Investitionsentscheidungen; öffentliche Einrichtungen

  • Other report
    Diplomarbeit, eingereicht bei HTW Dresden am 09.09.2003

Publ.-Id: 6151

Direct Nanopatterning of Metal Surfaces Using Self-Assembled Molecular Films

Azzaroni, O.; Fonticelli, M. H.; Benítez, G.; Schilardi, P. L.; Gago, R.; Caretti, I.; Vázquez, L.; Salvarezza, R. C.

This work shows that self-assembled molecular (SAM) films of silanes and alkanethiolates can be used as surface active agents for direct 50 nm pattern transfer from a metallic or semiconductor master to metallic surfaces. The patterned metallic surfaces can be modified again by alkanethiolate SAMs to be used as a further mold for master replication. It is also demonstrated that the patterned metallic surfaces are excellent templates to produce nanopatterned metal-semiconductor hybrid surfaces by controlled chemical reactions.

Keywords: Nanopatterning; Self-assembled monolayers

  • Advanced Materials 16(2004)5, 405-409

Publ.-Id: 6150

Surface plasmon interaction with single grooves in thin silver films

Bischoff, L.; Seidel, J.; Grafström, S.; Eng, L. M.

The propagation of surface plasmons in thin silver films and their interaction with defined surface grooves are presented. Of interest to photonic structures are both the optical transmission across barriers and other structures, but also the coupling to free-space electromagnetic waves. We present results on plasmon transmission and reflection at grooves written with a focused ion beam (FIB) into a thin silver film. In order to monitor the optical properties of travelling plasmons excited in attenuated total eflection (ATR), we apply near-field optical microscopy using a dielectric fiber tip. Our results agree well with former theoretical redictions.
Furthermore, we report on optical observation of plasmons propagating at the silver-glass interface rather than the silver-air interface as usually monitored. This manifests itself in a very exciting beating phenomenon between plasmon modes running at the silver-air and silver-glass interface.

Keywords: surface plasmons; propagation; silver film; focused ion beam structuring

  • Lecture (Conference)
    E-MRS 2004 Spring Meeting, Symposium A2, Strasbourg,France, May 24 - 28, 2004

Publ.-Id: 6149

Coupling between surface plasmon modes on metal films

Seidel, J.; Baida, F. I.; Bischoff, L.; Guizal, B.; Grafström, S.; van Labeke, D.; Eng, L. M.

Using scanning near-field optical microscopy for probing surface plasmon fields, we show that energy can be transferred from the plasmon propagating on one interface to the mode bound to the other interface of a thin metal film. This coupling is mediated by a narrow groove interrupting the silver film. Excitation of the second plasmon mode is detected by mapping the spatial intensity modulation induced by the interfering fields of the two plasmons. A quantitative analysis provides detailed knowledge about the degree of coupling. Our inter-pretation of the experimental results is confirmed by a numerical simulation of the field distribution.

Keywords: surface plasmon modes; thin metal film; numerical simulation; SNOM

Publ.-Id: 6148

The effect of electrode geometry on the stability of a liquid metal ion emitter

Mair, G. L. R.; Akhmadaliev, C.; Bischoff, L.; Ganetsos, T.; Aidinis, C. J.; Anagnostakis, E. A.

The e ffect on source stability of removing the extractor electrode from a liquid metal ion source system has been investigated.The noise of the current and the corresponding frequency spectra were carefully studied. The findings in
the two cases,i.e.with and without an extractor electrode,were found to be very different.The explanation for this is given in terms of different droplet emission mechanisms being operative in the two cases.The liquid emitter used was a AuGeSi alloy.Focused Ge and Si ion beams are important for icroelectronics applications.Thus,an understanding of the mechanisms that lead to source instability is essential.

Keywords: liqid metal ion emitter; current fluctuations; instabilities; geometry

Publ.-Id: 6147

Alloy liquid metal ion sources and their application in mass separated focused ion beams

Bischoff, L.

During the last decades, the focused ion beam (FIB) became a very useful and versatile tool in the microelectronics industry, as well as in the field of research and development. For special purposes like writing ion implantation or ion mixing in the µm- or sub-µm range ion species other than gallium are needed. Therefore alloy liquid metal ion sources (LMIS) were developed. The energy distribution of the ions from an alloy LMIS is one of the determining factors for the performance of an FIB column. Different source materials like Au73Ge27, Au82Si18, Au77Ge14Si9, Co36Nd64, Er69Ni31, and Er70Fe22Ni5Cr3 were investigated with respect to the energy spread of the different ion species as a function of emission current I, ion mass m and emitter temperature T. For singly charged ions a predicted dependence of the energy spread, DE µ I2/3 m1/3 T1/2 found for Ga could be reasonable confirmed. The alloy LMIS`s discussed above have been used in the Rossendorf FIB system IMSA-100 as well as in recent time in the new IMSA-OrsayPysics FIB especially for writing implantation to fabricate sub-µm pattern without any lithographic steps. A Co-FIB obtained from a Co36Nd64 alloy LMIS was applied for the ion beam synthesis of CoSi2 micro-structures down to 60 nm. Additionally, the possibility of varying the current density of the FIB by changing the pixel dwell-time was used for investigations of radiation induced damage and its dynamic annealing in Si and SiC at elevated implantation temperatures. Furthermore, a broad spectrum of ions was employed to study the sputtering process depending on temperature, angle of incidence and ion mass on a couple of target materials using the volume loss method. Especially this direct patterning 3D technique was used for the fabrication of various kinds of micro-tools.
Running and future activities will be discussed which are focused to the preparation and investigation of plasmonic structures, like nano-wires and nano-chains in the sub-micron scale down to a few ten nanometers.
All these examples underline the importance of FIBs in modern research and the new possibilities opened up by a mass separated system applying a broad spectrum of ion species.

Keywords: Focused Ion Beam; alloy Liqid Metal Ion Source; Nanotechnology

  • Lecture (others)
    Ruhr-Universität BochumGraduiertenkolleg 384April 22, 2004
  • Ultramicroscopy 103(2005)1, 59-66
  • Lecture (others)
    Seminar Elektronen- und Ionenoptik, Institut für Angewandte Physik der, 01.12.2004, Tübingen, Germany

Publ.-Id: 6146

Principles of quantitative positron emission tomography in the lung

van den Hoff, J.

  • Contribution to external collection
    IV. Postgraduate Course on Respiratory Intensive Care Medicine (2003) 10-12.

Publ.-Id: 6145

Brain perfusion and cerebral glucose metabolism in patients in persistent vegetative state

Beuthien-Baumann, B.; Handrick, W.; Schmidt, T.; Burchert, W.; Oehme, L.; Schackert, G.; Schuewer, U.; Kropp, J.; Franke, W. G.

  • Nucl. Med. Commun. 24 (2003) 643-650

Publ.-Id: 6144

What is evidence for positron emission tomography in the management of patients with indolent non-Hodgkin's lymphoma?

Naumann, R.; Beuthien-Baumann, B.

  • Clinical Lymphoma 4 (2003) 50-51

Publ.-Id: 6143

Annual Report 2003 - Institute of Bioinorganic and Radiopharmaceutical chemistry

Spies, H.; Seifert, S.; (Editors)

The report gives an overview on the activities of the Institute ofBioinorganic and Radiopharmaceutical Chemistry in 2003.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-394 2004
    ISSN: 1437-322X


Publ.-Id: 6140

Separation of Uranium(VI) from Aqueous Solution by Textile Bound Calix[6]arenes

Schmeide, K.; Bernhard, G.; Keil, D.; Buschmann, H.-J.; Praschak, D.

The remediation of former uranium mining and milling sites of Saxony and Thuringia requires, amongst others, the purification of uranium contaminated seepage and mine waters. For this, predominantly conventional water treatment methods (precipitation, flocculation) are applied.
We developed an alternative method for the separation of uranium(VI) from aqueous solution. For this, a uranophile calix[6]arene (p-tert-butyl-calix[6]arene hexacarboxylic acid) is permanently immobilized onto textile material (polyethylene terephthalate fabric) via spacer groups [1]. Calixarenes are macrocyclic molecules formed by 4, 6 or 8 para-substituted phenolic units linked by methylene bridges ortho-positioned to the OH functions. Thus, molecules of various ring sizes are formed. The substitution of calix[6]arenes on the hydroxyl group by carboxylic and hydroxamic groups, respectively, leads to ligands that are able to bind uranium(VI) selectively.
In the present work, the uranium(VI) binding onto the calixarene modified textile is studied as a function of pH value and initial uranium concentration in the absence and presence of competing ions by means of batch experiments. Furthermore, the kinetics of the uranium binding is studied as well as the possibility for remobilization of the bound uranium.
The results have shown, that the calixarene modified textile is suitable for the separation of uranium(VI) from aqueous solution at pH values higher than 4. Maximal 7.6x10-7 mol uranium per 1 g of the calixarene modified textile is bound at pH 5. The influence of competing ions (sodium, potassium, calcium, magnesium, carbonate and sulfate) on the uranium separation at pH 5 is very small. At pH 7 in carbonate rich waters calcium ions have a competing effect. Under environmentally relevant pH conditions (near-neutral pH range) the uranium is strongly bound to the calixarene modified textile and cannot be mobilized. Under acidic conditions an almost complete regeneration of the calixarene modified textile is feasible. The regenerated textile filter material can be utilized for further uranium separation cycles.
In dependence on the specific requirements on-site the textile filter material can be used in batch or column operation. Especially for smaller remediation objects and for objects with lower contamination levels ([UO22+] = 1×10-6 M) this method provides a lower cost alternative to conventional water treatment methods. The applicability of this separation principle to further actinides is expected.

[1]Schmeide, K., Heise, K.H., Bernhard, G., Keil, D., Jansen, K., Praschak, D.: Uranium(VI) separation from aqueous solution by calix[6]arene modified textiles. J. Radioanal. Nucl. Chem. 261 (1), 61-67 (2004).

Keywords: Uranium; Calixarene; Water Purification; Complexation

  • Lecture (Conference)
    55. Berg- und Hüttenmännischer Tag, Treatment Technologies for Mining Impacted Water, 18.06.2004, Freiberg, Germany
  • Contribution to external collection
    B. Merkel et al.: Wissenschaftliche Mitteilungen 25, GIS – Geoscience Applications and Developments / Treatment Technologies for Mining Impacted Water, Freiberg: Technische Universität Bergakademie Freiberg, 2004, 133-139

Publ.-Id: 6139

Spatial profiles of fusion product flux in the gas dynamic trap with deuterium neutral beam injection

Maximov, V. V.; Anikeev, A. V.; Bagryansky, P. A.; Ivanov, A. A.; Lizunov, A. A.; Murakhtin, S. V.; Noack, K.; Prikhodko, V. V.

Recently, a plasma with energetic deuterons has been produced in the Gas Dynamic Trap (GDT) experiment under skew injection of 4 MW, 15-17 keV deuterium neutral beams. The GDT is a long, axially symmetric magnetic mirror device with a high mirror ratio. The deuterium neutral beams have been injected at the midplane of the device under 45o to the axis. High anisotropy of the fast ion angular distribution results in a strong peaking of the fast ion density at the turning points near the end mirrors. The axial profile of DD fusion product fluxes has been measured and found to be strongly peaked in the same regions. The characteristics of the profiles are consistent with the classical mechanism of fast ion relaxation caused by two-body Coulomb collisions with plasma particles. This observation validates an approach used in a GDT based neutron source, in which the regions of high neutron flux would be surrounded by the testing zones for fusion material irradiations.

Keywords: fusion; neutron source; gas dynamic trap; neutral beam injection; deuterium-deuterium fusion reaction; neutron flux; proton flux

  • Nuclear Fusion 44(2004)4, 542-547

Publ.-Id: 6134

Liquid metal model experiments on casting and solidification processes

Cramer, A.; Eckert, S.; Galindo, V.; Gerbeth, G.; Willers, B.; Witke, W.

This paper is concerned with laboratory studies using liquid metals with Tmelt £ 300°C to model realistic processes. Considering three selected examples the main features of such cold models are described. In the first instance we examine an aluminium alloy investment casting process. The request to reduce the high flow velocities was served by the installation of a d.c. magnetic field. Local velocity measurements as well as integrated flow rate determination have been carried out utilizing eutectic InGaSn (Tmelt = 10°C). As a second example, model experiments on the electromagnetic stirring of liquid metals have been performed in a cylindrical cavity. We applied a rotating (RMF) and a travelling magnetic field, and recorded flow maps by means of the ultrasonic Doppler velocimetry. With the goal of an efficient 3D-mixing first measurements with promising results were done for the combination of both field types. Third, we report on systematic studies of the impact exerted by a RMF on the solidification of a PbSn alloy. Directional solidification experiments demonstrate the influence of the electromagnetically driven convection on the resulting microstructure.

  • Journal of Materials Science 39(2004), 7285-7294

Publ.-Id: 6133

Applications of AC and DC magnetic fields in metallurgical or crystal growth processes

Cramer, A.; Eckert, S.; Galindo, V.; Gerbeth, G.

Magnetic fields provide an attractive possibility of a tailored flow control for metallurgical and crystal growth processes. The following examples will be presented:
-the application of a specially shaped steady magnetic field in the melt extraction process of thin metallic fibers,
-the control of the flow filling process in the investment casting of aluminum alloys,
-the stabilization of electromagnetically levitated droplets,
-the magnetic field control of the Czochralski growth of single crystals of silicon.
The role of model experiments and the development of velocity measuring techniques for metallic melts will be stressed.

  • Contribution to proceedings
    International Workshop on Materials Analysis and Processing in Magnetic Fields, National High Magnetic Field Laboratory, 17.-19.03.2004, Tallahassee, FL, United States, Proceedings (2005), 157-168
  • Invited lecture (Conferences)
    International Workshop on Materials Analysis and Processing in Magnetic Fields, 17.-19.03.2004, Tallahassee, FL, United States

Publ.-Id: 6132

Stabilization effect of a rotating magnetic field on the flow of a conducting liquid in a cylindrical container

Priede, J.; Gerbeth, G.

This study presents a numerical stability analysis of a flow of electrically conducting liquid driven by a rotating magnetic field in a cylindrical container. The aim of the work is to investigate the previously often neglected effect of the strength of the rotating magnetic field on the stability of the flow driven by the field. Linear hydrodynamic stability analysis has been carried out by Chebyshev-tau and Galerkin spectral numerical methods. We find that the strength of the rotating magnetic field has a stabilizing effect on the flow. The obtained results may be of practical relevance for certain semiconductor growth technologies from the melt.

  • Lecture (Conference)
    International. Conference on Computational & Experimental Engineering and Sciences, 26.-29.07.2004, Madeira, Portugal
  • Contribution to proceedings
    International. Conference on Computational & Experimental Engineering and Sciences, 26.-29.07.2004, Madeira, Portugal, Proceedings

Publ.-Id: 6131

A review on velocity measurements in liquid metals

Gerbeth, G.; Eckert, S.; Cramer, A.; Stefani, F.

For an MRI experiment with some liquid metal the possibilities for velocity measurements should be taken into account from the beginning. We present a summary of such measuring techniques, mainly focussing on local potential probes and the ultrasonic Doppler velocimetry. The latter is especially attractive as it provides a full velocity profile along the ultrasonic beam. The possibility of a full 3D velocity tomography, recently shown in a demo experiment, will also be discussed.

  • Lecture (Conference)
    Workshop: MHD Couette Flows: Experiments and simulations, 29.02.-02.03.2004, Catania, Italy,

Publ.-Id: 6130

Magnetic Field Control of the Mould Filling Process of Aluminum Investment Casting

Galindo, V.; Gerbeth, G.; Eckert, S.; Witke, W.; Gerke-Cantow, H.; Nicolai, H.; Steinrücken, U.

The mould filling process of aluminum investment casting consists basically of the flow in a U-bend showing a high pouring velocity at the beginning and decreasing velocity values during the course of the process. The high velocities during the starting phase are supposed to cause distinct problems like bubble or inclusion entrapment. Several types of filters are already in use for the purpose of inclusion filtering but velocity reduction, too.
We present results on the design and application of a DC magnetic field to control the pouring velocity. Numerical calculations were performed to simulate the filling process and the effect of the magnetic field. The free surface problem which occurs in the riser of the casting unit was taken into account by a Volume-of-Fluids Method. 3d transient calculations using the commercial finite- element code FIDAP (FLUENT Inc.) were carried out for a simplified model system as well as for the real aluminum casting unit. The term for the electromagnetic force was implemented into the code via a user defined subroutine, and an additional equation for the electrical potential was solved. End effects due to the limited size of the magnet poles were taken into account. In that way, results from three-dimensional transient simulations of the filling process were obtained.
Parallel to the simulations model experiments have been performed using the low melting eutectic InGaSn. The casting unit was modelled by a plexiglas model [1]. The ultrasonic Doppler velocimetry was applied to carry out detailed velocity measurements in the model [2]. Such measurements delivered the basis to validate the numerical calculations. A comparison between numerical and experimental results showed an excellent agreement, allowing scaling up the simulations to the realistic aluminium casting process.
Real tests have been performed at an industrial investment caster with molten aluminium. The primary action of the magnetic field, i.e. the reduction of the velocity peaks at the beginning of the process, was clearly shown. In a second set of experiments the amplitude of the DC field was tuned during the process. At the beginning the maximum braking force was applied, whereas the field strength was reduced with increasing fluid level in the casting unit. In this regime, a clear reduction of the peak velocities is obtained without a significant prolongation of the overall filling time.


[1] S. Eckert, G. Gerbeth, A. Cramer, B. Willers, W. Witke, V. Galindo, Liquid metal model experiments on casting and solidification processes, Proc. Int. Symposium on liquid metal processing and casting, Eds.: P.D. Lee, A. Mitchell, J.-P. Bellot, A. Jardy, (2003), 333-343.
[2] S. Eckert, G. Gerbeth, T. Gundrum, F. Stefani, W. Witke, New approaches to determine the velocity field in metallic melts, EPM 2003, Lyon, Proceedings PL13 (2003).

  • Contribution to proceedings
    Computational Mechanics, WCCM VI in conjunction with APCOM`04, 05.-10.09.2004, Beijing, China, paper No. 677
  • Invited lecture (Conferences)
    6th World Congress on Computational Mechanics, 05.-10.09.2004, Beijing, China

Publ.-Id: 6129

Emittance Compensation of a Superconducting RF Photoelectron Gun by a Magnetic RF Field

Janssen, D.; Volkov, V.

For compensation of transverse emittance in normal conducting RF photoelectron guns a static magnetic field is applied. In superconducting RF guns the application of a static magnetic field is impossible. Therefore we put instead of a static field a magnetic RF field (TE-mode) together with the corresponding accelerating mode into the superconducting cavity of the RF gun. For a 3-cell cavity of the superconducting gun with frequencies f = 1.3 GHz for the accelerating mode and f = 3.9 GHz for the magnetic mode an a bunch charge of 1 nC a transversal emittance of 0.5 mm mrad has been obtained. In this case the maximal field strength on the axis were Ez = 50 MV/m for the accelerating mode and Bz = 0.34 T for the magnetic mode (this corresponds to Bs(max) = 0.22 T on the surface of the cavity). Possibilities for the technical realization (input of RF power for the TE mode, tuning of two frequencies in one cavity, phase stability) are discussed.

Publ.-Id: 6128

A Superconducting Photo-Injector with 31/2-Cell Cavity for the ELBE Linac

Teichert, J.; Büttig, H.; Evthushenko, P.; Janssen, D.; Lehnert, U.; Michel, P.; Schneider, C.; Stephan, J.; Volkov, V.; Will, I.; Möller, K.; Lehmann, W.-D.

After sucessful tests of an SRF gun with a superconducting half-cell cavity (*), a new SRF photo-injector for CW operation at the ELBE linac has been designed. In this report the design layout of the SRF photo-injector, the parameters of the superconducting cavity and the expected electron beam parameters are presented. The SRF gun has a 3 1/2-cell niobium cavity working at 1.3 MHz and will be operated at 2 K. The three full cells have TESLA-like shapes. In the half cell the photocathode is situated which will be cooled by liquid nitrogen.

  • Poster
    J. Teichert et al., EPAC 2004 Contributions to the Proceedings, 9th European Particle Accelerator Conference EPAC 2004, 333-335, 05.07. – 09.07.2004, Lucerne, Switzerland
  • Contribution to proceedings
    9th European Particle Accelerator Conference, EPAC 2004, 05.-09.07.2004, Lucerne, Switzerland
    ISBN 92-9083-231-2 (Web version), ISBN 92-9083-323-0 (CD-ROM), 333-335
  • Contribution to WWW
    EPAC 2004 Contributions to the Proceedings, 9th European Particle Accelerator Conference EPAC 2004, 333-335, MOPKF015, 05.07. – 09.07.2004, Lucerne, Switzerland, ISBN 92-9083-231-2 (Web version):

Publ.-Id: 6127

Neutron-kinetic code validation against measurements in the Moscow V-1000 zero-power facility

Mittag, S.; Grundmann, U.; Weiß, F.-P.; Petkov, P. T.; Kaloinen, E.; Keresztúri, A.; Panka, I.; Kuchin, A.; Ionov, V.; Powney, D.

Measurements carried out in an original-size VVER-1000 mock-up (V-1000 facility, Kurchatov Institute Moscow) were used for the validation of three-dimensional neutron-kinetic codes, designed for VVER safety calculations. The significant neutron flux tilt measured in the V-1000 core, which is caused only by radial-reflector asymmetries, was successfully modeled. A good agreement between calculated and measured steady-state powers has been achieved, for relative assembly powers and inner-assembly pin power distributions. Calculated effective multiplication factors exceed unity in all cases. The time behaviour of local powers, measured during two transients that were initiated by control rod moving in a slightly super-critical core, has been well simulated by the neutron-kinetic codes.

  • Nuclear Engineering and Design 235(2005), 485-506

Publ.-Id: 6125

Synthesis of carbon nitride thin films by low-energy ion beam assisted evaporation: on the mechanisms for fullerene-like microstructure formation

Gago, R.; Neidhardt, J.; Vinnichenko, M.; Kreissig, U.; Czigány, Z.; Hultman, L.; Kolitsch, A.; Moeller, W.

Carbon nitride (CNx) thin films were grown at different substrate temperatures by low-energy (<100 eV) ion beam assistance deposition (LE-IBAD) in order to discern possible formation mechanisms of a fullerene-like (FL) microstructure. The samples were characterized by elastic recoil detection analysis, Raman spectroscopy, spectroscopic ellipsometry, and high-resolution transmission electron microscopy. The results are compared to those of well-structured FL-CNx films synthesized by reactive magnetron sputtering (MS). The comparison yields similar trends for both techniques, such as limitation of the nitrogen content at 20-25 at. %, dominance of sp2 hybrids, as well as thermally activated chemical desorption of CxNy species from the substrate during growth. However, CNx films produced by LE-IBAD are amorphous and, thus, lack FL features. This result correlates with a lower sp2 clustering, attributed to the promotion of nitrile groups. Therefore, low-energy ion bombardment is shown not to be a sufficient condition for the FL microstructure formation. An important difference in the film-forming fluxes between both techniques is the contribution of pre-formed CxNy species from the sputtering target in MS. These species may play a determinant role, serving as precursors for the introduction of FL arrangements during growth.

  • Thin Solid Films 483(2005)1-29, 89-94

Publ.-Id: 6124

Small angle neutron scattering study on the effect of hydrogen in irradiated reactor pressure vessel steels

Ulbricht, A.; Böhmert, J.; Uhlemann, M.; Müller, G.

Hydrogen uptake can potentially enhances the neutron embrittlement of reactor pressure vessel (RPV) steels. This suggests that irradiation defects act as hydrogen traps. The evidence of hydrogen trapping was investigated using the small angle neutron scattering (SANS) method on four RPV steels. The samples were examined in the unirradiated and irradiated state and both in the as-received condition and after hydrogen precharging. Despite the low bulk content of hydrogen achieved after precharging with low current densities, an enrichment of hydrogen in small microstructural defects could be identified. Preferential traps were the microstructural defects in the size range of approx. > 10 nm in the unirradiated as well as in the irradiated samples. However, the results do not show any evidence for hydrogen trapping in irradiation defects.

  • Journal of Nuclear Materials 336(2005), 90-96

Publ.-Id: 6123

Droplet formation in expanding nuclear matter: a system-size dependent study

Reisdorf, W.; Rami, F.; de Schauenburg, B.; Leifels, Y.; Alard, J. P.; Andronic, A.; Barret, V.; Basrak, Z.; Bastid, N.; Benabderrahmane, M. L.; Caplar, R.; Crochet, P.; Dupieux, P.; Dzelalija, M.; Fodor, Z.; Gobbi, A.; Grishkin, Y.; Hartmann, O. N.; Herrmann, N.; Hildenbrand, K. D.; Hong, B.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Koczon, P.; Korolija, M.; Kotte, R.; Kress, T.; Lebedev, A.; Lopez, X.; Merschmeyer, M.; Mösner, J.; Neubert, W.; Pelte, D.; Petrovici, M.; Schüttauf, A.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynska, K.; Smolyankin, V.; Stockmeier, M. R.; Stoicea, G.; Tyminski, Z.; Wagner, P.; Wisniewski, K.; Wohlfarth, D.; Xiao, Z. G.; Yushmanov, I.; Zhilin, A.

Cluster production is investigated in central collisions of Ca+Ca, Ni+Ni, 96Zr+96Zr, 96Ru+96Ru, Xe+CsI and Au+Au reactions at 0.4 AGeV incident energy. We find that the multiplicity of clusters with charge Z >= 3 grows quadratically with the system's total charge and is associated with a mid-rapidity source with increasing transverse velocity fluctuations. When reduced to the same number of available charges, an increase of cluster production by about a factor of 5.5 is observed in the mid-rapidity region between the lightest system (Ca+Ca) and the heaviest one (Au+Au). The results, as well as simulations using Quantum Molecular Dynamics, suggest a collision process where droplets, i.e. nucleon clusters, are created in an expanding, gradually cooling, nucleon gas. Within this picture, expansion dynamics, collective radial flow and cluster formation are closely linked as a result of the combined action of nucleon-nucleon scatterings and the mean fields.

Publ.-Id: 6122

Finite-Elemente-Modellierung des Risswachstums an 3-Punktbiegeproben

Werner, M.; Altstadt, E.

Das Verhalten einer 3-Punkt-Biegeprobe mit Anriss unter Belastung kann mittels eines Finite-Element-Modells nachgebildet werden. Das Modell ermöglicht die Berücksichtigung von elastisch-plastischem Materialverhalten entsprechend der jeweiligen materialspezifischen Spannungs-Dehnungs-Kurve, welche mit dem Ansatz der multilinearen kinematischen Verfestigung (MKIN) umgesetzt wird. Weiterhin gestattet das Modell die Einbeziehung der realen Rollenkinematik beim Biegevorgang. Für die Beschreibung des Bruchkriteriums wird ein spezielles Damage-Modell verwendet, mit dem man in der Lage ist, das Risswachstums in geeigneter Weise wiederzugeben.
Mit diesem Modell lässt sich auch das Teilentlastungs-Compliance-Verfahren nachbilden. Diese Simulation ermöglicht die Einschätzung von Korrekturansätzen zur experimentellen Risslängenbestimmung über die Compliance-Methode.

Keywords: Finite-Elemente-Methode; Charpy-Probe; Risswachstum

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-397 2004
    ISSN: 1437-322X


Publ.-Id: 6121

Crack initiation determination for thee-point-bend specimens

Dzugan, J.; Viehrig, H.-W.

The paper deals with the problematic of determination of the crack initiation for three point bend specimens during fracture toughness test of materials in the upper transition and upper shelf region. In the presented study various published methods as Double Clip Gauge Method, Strain Near to Crack Tip Measurement method, Double Displacement Method, Compliance Changing Rate Method, Stretch Width Zone measurement were applied together with the methods using the crack extension vs. crack mouth opening displacement and force vs. displacement for the crack initiation determination. Blunting line based evaluations were also performed and all results were compared. The investigation was carried out on five different steels.

  • Journal of Testing and Evaluation, 35(2007)3, 245-253

Publ.-Id: 6120

The effect of garlic on arteriosclerotic nanoplaque formation and size

Siegel, G.; Malmsten, M.; Pietzsch, J.; Schmidt, A.; Buddecke, E.; Michel, F.; Ploch, M.; Schneider, W.

Objective: In an in vitro biosensor model (PCT/ET 97/05212), the interplay between different lipoproteins in arteriosclerotic nanoplaque formation, as well as aqueous garlic extract (0.2-5.0 g/l from LI 111 powder) as a possible candidate drug against arterio/atherosclerosis were tested within the frame of a high throughput screening. Methods: The processes described below were studied by ellipsometric techniques quantifying the adsorbed amount (nanoplaque formation) and layer thickness (nanoplaque size). A thorough description of the experimental setup has been given previously. Results: Proteoheparan sulfate (HS-PG) absorption to hydrophobic silica was monoexponential and after approximately 30 min constant. The addition of 2.52 mmol/l Ca2+ led to a further increase in HS-PG adsorption because Ca2+ was bound to the polyanionic glycosaminoglycan (GAG) chains thus screening their negative fixed charges and turning the whole molecule more hydrophobic. Incubation with 0.2 g/l aqueous garlic extract (GE) for 30 min did not change the adsorption of HS-PG. However, the following addition of Ca2+ ions reduced the increase in adsorption by 50.8 % within 40 min. The adsorption of a second Ca2+ step to 10.08 mmol/l was reduced by even 82.1 % within the next 40 min. Having detected this inhibition of receptor calcification, it could be expected that the build-up of the ternary nanoplaque complex is also affected by garlic. The LDL plasma fraction (100 mg/dl) from a healthy probationer showed beginning arteriosclerotic nanoplaque formation already at a normal blood Ca2+ concentration, with a strong increase at higher Ca2+ concentration. GE, preferably in a concentration of 1 g/l, applied acutely in the experiment, markedly slowed down this process of ternary aggregational nanoplaque complexation at all Ca2+ concentrations used. In a normal blood Ca2+ concentration of 2.52 mmol/l, the garlic induced reduction of nanoplaque formation and molecular size amounted to 14.8 % and 3.9 %, respectively, as compared to the controls. Furthermore, after ternary complex build-up. GE similar to HLD, was able to reduce nanoplaque formation and size. The incubation time for HDL and garlic was only 30 min each in these experiments. Nevertheless, after this short time the deposition of the ternary complex decreased by 6.2 % resp. 16.5 %, i.e. the complex aggregates were basically resolvable. Conclusions: These experiments clearly proved that garlic extract strongly inhibits Ca2+ binding to HS-PG. In consequence, the formation of the ternary HS-PG/LDL/Ca2+ complex, initially responsible for the nanoplaque´composition and ultimately for the arteriosclerotic plaque generation, is decisively blunted.

Keywords: Arteriosclerosis model; calcification; ellipsometry; aqueous garlic extract; lipoproteins; proteoglycan receptor

  • Phytomedicine 11(2004), 24-35

Publ.-Id: 6118

Kolloidgetragene Schwermetalle im Entwässerungsstollen einer stillgelegten Zn-Pb-Ag Grube

Hüttig, G.; Zänker, H.

Colloid-borne Heavy Metals in the Drainage Gallery of an Abandoned Zn-Pb-Ag Mine (in German). The colloid inventories and the colloid-borne heavy metals in the Rothschönberger Stolln adit, the main drainage gallery of the Freiberg, Germany, mining district, were investigated. This adit runs from Freiberg to the village of Rothschönberg, where it flows into the river Triebisch, a tributary of the river Elbe. The water of the adit is a typical mine water from a flooded ore mine. The main reason for choosing the Rothschönberger Stolln adit for colloid investigations was that ample knowledge concerning the origin of the water and the geology of its catchment area exists. The aim was to characterize the colloids at the mouth of the adit and to elucidate if important contaminants occur in a colloid-borne form. A colloid concentration of about 1 mg/L was found. The particles have a size of 50 to 150 nm. They primarily consist of iron and aluminum oxyhydroxide and carry trace elements such as Pb, As, Cu, Y, La. The contaminants Pb and As are almost entirely colloid-borne. Colloids can have both a retarding and a stimulating influence on the transport of contaminants. The existence of colloids should be taken into account if mine waters flow to the biosphere or if mine waters are to be purified by permeable reactive barriers.

Keywords: Mine drainage; Colloids; Arsenic; Lead; Copper; Adsorption

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-403 2004
    ISSN: 1437-322X


Publ.-Id: 6117

Thermal and Mechanical Analysis of a PWR core baffle considering creep

Altstadt, E.; Fischer, E.; Kumpf, H.; Nagel, G.; Sgarz, G.; Weiss, F.-P.

The core baffle of a PWR is loaded by the pressure difference between bypass and core and by temperature profiles originating from gamma and neutron heating and heat transfer into the coolant. Strain, deformation and gaps between the core baffle sheets resulting from this load are determined considering the effect of neutron irradiation induced creep of the core baffle bolts. The finite element code ANSYS® is applied for the thermal and mechanical analyses. The FE-model comprises a complete 45° sector of the core baffle structure including the core barrel, the formers, the core baffle sheets and about 230 bolt connections with non-linear contact between the single components and the effect of friction. The complete analysis requires three major steps:
· Evaluation of the three dimensional distribution of neutron flux and gamma induced internal heating
· Calculation of the temperature distribution in the core baffle
· Calculation of time dependent deformation, stresses and strains
The results show the equalizing effect of redistribution of bolt loads from high flux to lower flux exposure locations in a self controlled process, keeping the mechanical and geometrical stability of the core baffle structure and leaving the gaps between sheet edges unaffected.

  • ATW - International Journal for Nuclear Power 49(2004)5, 333-336

Publ.-Id: 6115

Implementation and Validation of Non-Drag Interfacial Forces in CFX-5.6

Shi, J.-M.; Frank, T.; Krepper, E.; Lucas, D.; Rohde, U.; Prasser, H.-M.

In Eulerian-Eulerian modeling of multiphase flow, closure models are needed for interfacial forces. The present work was concentrated on the non-drag forces, namely the lift, virtual mass, turbulent dispersion and wall lubrication force. They are reported to be mainly responsible for the gas volume fraction distribution in a vertical bubbly flow. Different models were proposed in the literature for each of these forces. In this work, we implemented a number of non-drag force models in the Eulerian multiphase flow package of the commercial code CFX-5.6 in order to enhance its application range. Extensive numerical experiments were carried out in order to examine their numerical properties (convergence characteristics, grid dependence of the results) and to
evaluate their validity. The evaluation was based on the experimental database for upward air-water flows in a vertical pipe established at Forschungszentrum Rossendorf (FZR) using the fast wiremesh sensor measurement technique. In all simulations a zero-equation model was used for the dispersed phase whereas two different turbulence models, namely the $k$-$\varepsilon$ and SST model, were investigated for the liquid phase. The bubble induced turbulence was taken into account by the Sato model. Fairly good agreements were observed between the numerical solutions and measurements for all test cases when the SST model was chosen together with the Tomiyama correlations for the lift and wall lubrication force and the {Favr\'e}-Averaged Drag (FAD) model for the turbulent dispersion force due to Burns (2001). The results clearly show the advantage of the FAD model over the widely applied model by Lopez de Bertodano et al.(1994). In addition, the investigation also indicates that further efforts in multiphase phase flow turbulence modeling and in near-wall treatment are very necessary.

Keywords: Multiphase flow; Non-drag force; CFD; Turbulence model; Bubble

  • Contribution to proceedings
    5th International Conference on Multiphase Flow, ICMF04, 30.05.-04.06.2004, Yokohama, Japan
    Proceedings CD-ROM, paper 400, 1-14
  • Lecture (Conference)
    5th International Conference on Multiphase Flow, ICMF04,, 30.05.-04.06.2004, Yokohama, Japan

Publ.-Id: 6113

Formation and evolution of sp2 clusters in amorphous carbon networks as predicted by molecular dynamics annealing simulations

Belov, A. Y.; Jäger, H. U.

A comparative study of clustering of sp2 -bonded atoms in the as-deposited and annealed diamond-like amorphous carbon (DLC) films is presented. The as-deposited DLC with a grown-in compressive stress of ~10 GPa is modelled using amorphous networks generated by ion-beam film deposition simulations with a modified hydrocarbon potential of Brenner. The DLC networks were annealed in the temperature range of 600-2000 K, using molecular-dynamics with the same interatomic potential. The size and type of the sp2 clusters were analysed as a function of the annealing temperature and simulation parameters. An essential finding of this study is that at the density less than 3.0 g/cm3 the structure of DLC can become unstable with respect to formation of large sp2 clusters. In particular, molecular-dynamics simulations show how the small sp2 clusters coalesce, forming the large ones. The influence of the sp2 clustering on the mechanical properties of DLC is also discussed.

Keywords: diamond-like carbon; molecular-dynamics; sp2 clustering; mechanical properties

  • Poster
    15th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides & Silicon Carbide, 12-17 Sept. 2004, Riva Del Garda, Trentino, Italy

Publ.-Id: 6112

Insights from the FOREVER-Programme and the Accompanying Finite Element Calculations

Willschütz, H.-G.; Altstadt, E.; Weiss, F.-P.; Sehgal, B. R.

The hypothetical scenario of a severe accident with core meltdown and formation of a melt pool in the lower plenum of a light water Reactor Pressure Vessel (RPV) can result in the failure of the RPV and the discharging of the melt to the containment. To obtain an improved understanding and knowledge of the melt pool convection thermal loads, the vessel creep, and vessel failure modes occurring during the late phase of a core melt down accident the FOREVER-experiments have been performed at the Royal Institute of Technology, Stockholm. These experiments simulated the behaviour of the lower head of the RPV under the thermal loads of a convecting melt pool with decay heating, and under the pressure loads that the vessel experiences in a depressurised vessel scenario.
Due to the multi-axial creep deformation of the vessel with prototypic non-uniform temperature field these experiments are on the one hand an excellent source of data to validate numerical creep models that are developed on the basis of uniaxial creep tests and on the other hand they provide reasonably accurate insights into the course of a prototypic accident in which vessel failure may occur.
A Finite Element model was developed simulating melt pool convection and calculating the temperature field within the melt pool and within the vessel wall. The transient structural mechanical calculations are then performed applying a creep model, which takes into account the large temperature, stress and strain variations.
After performing successful pre- and post-test calculations, a discussion about the lessons learned from the experiments and the analyses led to the idea of providing a vessel support and an external water-flooding device.

Keywords: Finite Element Calculations; In-Vessel-Retention; FOREVER-Experiments

  • atw - International Journal for Nuclear Power 49(2004)5, 345-349

Publ.-Id: 6111

Evolution of sp2 networks with substrate temperate in amorphous carbon films: theory and experiment

Jäger, H. U.; Belov, A. Y.; Gago, R.; Vinnichenko, M.; Jiménez, I.; Huang, N.; Leng, Y. X.; Sun, H.; Maitz, M. F.

Amorphous carbon (a-C) film deposition was studied theoretically by molecular-dynamics simulations in the temperature range of 100-873 K. For each temperature the simulations yield a mixture of sp2 and sp3 hybrids, which allows for the sp2 and sp3 fractions, and size and type of the sp2 clusters to be calculated. In parallel, the bonding structure of a-C thin films prepared by filtered cathodic vacuum arc (FCVA) at different substrate temperatures was analysed by x-ray absorption near edge spectroscopy (XANES) and Raman techniques. In addition, the optical properties of these films were determined from spectroscopic ellipsometry (SE).

Both, theory and experiment, show a transition from diamond-like to graphite-like films as the substrate temperature exceeds a certain threshold, in agreement with previous observations. The evolution of the sp2 clusters, as defined by the number of consecutive sp2 atoms, and of sp2 sites rings with substrate temperature was computed from the simulated films. The results indicate an increase of sp2 clustering with temperature and a pronounced promotion of six to ten membered rings for substrate temperatures above the transition threshold. The further formation of these rings above the transition temperature does not correlate with the sp2 content and suggests an in-situ sp2 rearrangement process during deposition. The evolution of the sp2 networks predicted by the simulations will be contrasted with the data from the XANES and Raman investigations. Finally, the correlation of sp2 arrangement and of observed optical properties will be discussed.

Keywords: amorphous carbon; molecular-dynamics; sp2 clustering; optical properties

  • Lecture (Conference)
    15th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides & Silicon Carbide, 12-17 Sept. 2004, Riva Del Garda, Trentino, Italy

Publ.-Id: 6110

Overview REDOS Work-Package 3 - Comparisons of REDOS Participants Calculation Results and C/E Comparisons for the VVER-1000 Mockup at the LR-0 Reactor

Böhmer, B.

Neutron and gamma fluence calculation results of participants of the REDOS project for the VVER-1000 mock-up at the LR0-reactor in Rez had been compared between themselves and with measured data. 11 fluence spectrum integrals and neutron and gamma DPA-values obtained independently by 6 participants from 4 countries were included into the comparison. For fast neutrons mostly excellent agreement between participants results and with experimental data was reached. For thermal neutrons and photons the agreement was much worse.

Keywords: reactor pressure vessel dosimetry; neutron and gamma fluence spectra

  • Lecture (others)
    REDOS Progress Meeting, September 3-6, 2003, Elena, Bulgaria

Publ.-Id: 6109

Isoscaling in low-energy binary fission

Andronenko, M. N.; Andronenko, L. N.; Neubert, W.

no abstract

  • Preprint St. Petersburg Nuclear Physics Institute, Nr. 2541, Gatchina 2003

Publ.-Id: 6108

Isoscaling of spallation products from p(1 GeV)+A interactions

Andronenko, M. N.; Andronenko, L. N.; Neubert, W.; Seliverstov, D. M.

An analysis of experimental data consisting of isotopically resolved spallation products from 1 GeV proton-necleus interactions with targets from Fe to Cd is presented. It was found that the yield ratios of isotopes classified by the difference of the neutron numbers are compatible with relations derived in the grand canonical approach. The independence of isotopic temperatures on the target mass was demonstrated for spallation products. An 'unified' isoscaling is proposed which takes into account different nucleonic compositions of the emitting sources. Modified isoscaling parameters are proposed and their physical meaning is discussed.

  • Other report
    Gatchina: Preprint St. Petersburg Nuclear Physics Institute, PN PI - 2540, 2003
    24 Seiten

Publ.-Id: 6107

Isospin diffusion in heavy ion reactions

Tsang, M.; Liu, T. X.; Shi, L.; Danielewicz, P.; Gelbke, C. K.; Liu, X. D.; Lynch, W. G.; Tan, W. P.; Verde, G.; Wagner, A.; Xu, H. S.; Friedman, W. A.; Beaulieu, L.; Davin, B.; de Souza, R. T.; Larochelle, Y.; Lefort, T.; Yanez, R.; Viola Jr., V. E.; Charity, R. J.; Sobotka, L. G.

Using symmetric 112Sn + 112Sn, 124Sn + 124Sn collision as references, we probe isospin diffusion in peripheral asymmetric 112Sn + 124Sn, 124Sn + 112Sn systems at incident energy of E/A = 50 MeV. Isoscalic analyses imply that the quasi-projectile and quasi-target in these collisions do not achieve isospin equilibrum, permitting an assesment of the isospin transport rates. We find that comparisons between isospin sensitive experimental and theoretical obstacles, using suitably chosen scaled ratios, permit investigation of the density dependence of the asymmetry term of the nuclear equation of state.

  • Michigan State University MSUCL -1273 October 2003

Publ.-Id: 6106

Laboratory astrophysics as examplified by the Riga dynamo experiment

Stefani, F.; Gerbeth, G.; Gailitis, A.; Lielausis, O.; Platacis, E.

It has been proposed to investigate the magnetorotational instability at a large scale liquid sodium facility. This sort of laboratory astrophysics is encouraged by the recent successful dynamo experiments. We report on our experiences with the Riga dynamo experiment where magnetic field self-exciation is achieved in a cylindrical vessel filled with approximately 2 qm of liquid sodium which can reach flow velocities up to 20 m/s. The main experimental results on the kinematic and the saturation regime are compared with numerical modelling. Some focus is also laid on the technical design of the facility and the measurement instrumentation.

  • Lecture (Conference)
    Workshop: MHD Couette flows: experiments and models, 29.02.-02.03.2004, Acitrezza, Catania, Italy

Publ.-Id: 6105

Magnetorotational Instability in Taylor-Dean Flows

Stefani, F.; Gerbeth, G.

The experimental demonstration of MRI in a liquid sodium Taylor-Couette experiment might be hampered by sealing problems at the two end plates whose sophisticated design could be crucial to avoid non-linear instabilities. Thus motivated, we consider alternative flow configurations with respect to their suitability to show MRI. First results for flows that are driven by azimuthal pressure gradients (Dean flows) and for combinations with Couette flows (Taylor-Dean flows) are presented. The influence of an axial magnetic field on the stability of Dean and Taylor-Dean flows with arbitrary gap spacing between the cylinders is considered. For Dean flows with magnetic Prandtl number equal to one it is found that, similar to the result for the Taylor-Couette flow, a significant decrease of the critical Reynolds number occurs for intermediate Hartmann numbers. This MRI is more pronounced for small values of the ratio of the radii of the inner and outer cylinder. For Taylor-Dean flows the onset of the instability in dependence on the ratio of azimuthal pressure gradient and cylinder rotation is investigated.

  • Lecture (Conference)
    Workshop: MHD Couette flows: experiments and models, 29.02.-02.03.2004, Acitrezza, Catania, Italy

Publ.-Id: 6104

Transition strengths between particle hole excitations in 95Ru

Galindo, E.; Hausmann, M.; Jungclaus, A.; Lieb, K. P.; Yordanov, O.; Johnstone, I. P.; Schwengner, R.; Dewald, A.; Fitzler, A.; Möller, O.; de Angelis, G.; Gadea, A.; Martinez, T.; Napoli, D. R.; Ur, C. A.

High-spin states of 95Ru have been populated using the 35Cl+ 64Zn reaction at a beam energy of 135 MeV. In a recoil-distance Doppler-shift experiment, the lifetimes or lifetime limits of 26 high-spin states have been measured, giving information on a total of 49 reduced transition strengths. The results are compared with shell-model calculations with different model spaces and residual interactions. Several families of states with defined proton and neutron seniorities are proposed. The M1 strengths in the negative-parity yrast sequence show a pronounced staggering which is reproduced by the shell-model calculations.

  • Physical Review C 69(2004), 024304

Publ.-Id: 6103

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