Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31745 Publications
Experimental investigation on bubble turbulent diffusion in a vertical large-diameter pipe by wire-mesh sensors and correlation techniques
Manera, A.; Lucas, D.; Prasser, H.-M.;
Experiments with air-water flows have been carried out in a vertical pipe of ~194-mm diameter and 9-m length, and a wide range of superficial liquid and gas velocities has been covered. At a distance of 7.6 m from the air injection, two wire-mesh sensors are installed, located at a distance of 63.3 mm from each other. The wire-mesh sensors measure sequences of instantaneous two-dimensional gas-fraction distributions in the cross section in which they are mounted, with a spatial resolution of 3 mm and a frequency of 2500 Hz. The spatial cross-correlations of the gas-fraction signals have been evaluated, and on their basis turbulent diffusion coefficients have been estimated.
It is found that for a given liquid superficial velocity, a sudden increase of the diffusion coefficient takes place when the superficial gas velocity is increased above a certain value. The abrupt increase of the diffusion coefficient occurs in correspondence of the transition from mono- to bimodal bubble size distributions.
The experimental diffusion coefficients are compared with the prediction of the Sato model (experimental gas-fraction profiles and bubble size distributions are given as input). Even though this model has been developed for bubbly flow, the general trends are well captured also in the churn-turbulent regime.
Keywords: Two-phase flow, eddy diffusivity, cross-correlation, bubble-induced turbulence
  • Nuclear Technology 158 (2007) 275-290

Publ.-Id: 6819 - Permalink


Three-dimensional flow pattern visualization and bubble size distributions in stationary and transient upward flashing flow
Manera, A.; Prasser, H.-M.; Lucas, D.; van der Hagen, T. H. J. J.;
An experimental three-dimensional reconstruction and visualization of stationary and transient flashing flow in a vertical pipe (47 mm diameter) is presented. The measurements have been performed by means of wire-mesh sensors. This type of sensor delivers two-dimensional void fraction distributions in the pipe cross-section where it is mounted with a maximum sampling rate of 10,000 frames per second. A sampling rate of 1200 frames per second has been used in this work. Steam bubbles have been identified from the wire-mesh data and their complete three-dimensional reconstruction has been performed by taking into account the steam bubble velocity. For the estimation of the bubble velocity, two wire-mesh sensors positioned at a small axial distance from each other have been used. The velocity has been determined by cross-correlation of the two wire-mesh signals, by direct identification of the traveling time of the steam bubbles between the two sensors and by means of a drift-flux model. A comparison between the three methods of bubbles velocity measurement is reported. Stationary and time-dependent bubble size distributions have been derived. The stationary radial void-fraction profiles have been decomposed according to bubble size classes and compared with the results obtained with an equilibrium model.
Keywords: Flashing, two-phase flow, three-dimensional visualization, bubble size
  • International Journal of Multiphase Flow 32(2006), 996-1016

Publ.-Id: 6818 - Permalink


Bubble size distributions and three dimensional flow pattern visualization in stationary and transient upward flashing flow
Manera, A.; Prasser, H.-M.; Lucas, D.; van der Hagen, T. H. J. J.;
An experimental three-dimensional reconstruction and visualization of stationary and transient flashing flow in a vertical pipe (47 mm diameter) is presented. The measurements have been performed by means of wire-mesh sensors. This type of sensor delivers two-dimensional void fraction distributions in the pipe cross-section where it is mounted with a maximum sampling rate of 10,000 frames per second. A sampling rate of 1200 frames per second has been used in this work. Steam bubbles have been identified from the wire-mesh data and their complete three-dimensional reconstruction has been performed by taking into account the steam bubble velocity. For the estimation of the bubble velocity, two wire-mesh sensors positioned at a small axial distance from each other have been used. The velocity has been determined by cross-correlation of the two wire-mesh signals and by direct identification of the travelling time of the steam bubbles between the two sensors. A comparison between the two methods of bubbles velocity measurement is reported. Stationary and time-dependent bubble size distributions have been derived. The stationary radial void-fraction profiles have been decomposed according to bubble size classes and compared with the results obtained with an equilibrium model.
  • Contribution to proceedings
    3rd International Symposium on Two-phase Flow Modelling and Experimentation, 22.-24.09.2004, Pisa, Italy, Proceedings on CD-ROM, paper CVG10.

Publ.-Id: 6817 - Permalink


Modeling of flashing-induced instabilities in the start-up phase of natural-circulation BWRs using the code FLOCAL
Manera, A.; Rohde, U.; Prasser, H.-M.; van der Hagen, T. H. J. J.;
This paper reports on the modeling and simulation of flashing-induced instabilities in natural circulation systems, with special emphasis on natural circulation Boiling Water Reactors (BWRs). For the modeling the 4-equation two-phase model FLOCAL (Rohde, 1986), developed at the Forschungszentrum Rossendorf (FZR, Germany), has been used. The model allows for the liquid and vapor to be in thermal non-equilibrium and, via drift-flux models, to have different velocities.
The phenomenology of the instability has been studied and the dominating physical effects have been determined. The results of the simulations have been compared qualitatively and quantitatively with experiments (Manera and van der Hagen, 2002) that have been carried out within the framework of a European project (NACUSP) on the CIRCUS facility. The facility, built at the Delft University of Technology in The Netherlands, is a water/steam 1:1 height-scaled loop of a typical natural-circulation-cooled BWR.
Keywords: Flashing, instabilities, experimental, numerical
  • Nuclear Engineering and Design 235(2005)14, 1517-1535

Publ.-Id: 6816 - Permalink


Evidence for a structurally-driven insulator-to-metal transition in VO2: A view from the ultrafast timescale
Cavalleri, A.; Dekorsy, T.; Chon, H. H. W.; Kiefer, J. C.; Schoenlein, R. W.;
We apply ultrafast spectroscopy to establish a time-domain hierarchy between structural and electronic effects in a strongly correlated electron system. We discuss the case of the model system VO2, a prototypical nonmagnetic compound that exhibits cell doubling, charge localization, and a metal-insulator transition below 340 K. We initiate the formation of the metallic phase by prompt hole photo-doping into the valence band of the low-T insulator. The insulator-to-metal transition is, however, delayed with respect to hole injection, exhibiting a bottleneck time scale, associated with the phonon connecting the two crystallographic phases. This structural bottleneck is observed despite faster depletion of the d bands and is indicative of important bandlike character for this controversial insulator.
Keywords: femtosecond, ultrafast, phase transition, Mott-insulator transition, vanadiumdioxide, coherent phonons, bottleneck

Publ.-Id: 6814 - Permalink


Well-width dependence of coupled Bloch-phonon oscillations in biased InGaAs/InAlAs superlattices
Först, M.; Kurz, H.; Dekorsy, T.; Leavitt, R.;
The coupling between Bloch oscillations and longitudinal optical (LO) phonons is investigated in ternary In0.53Ga0.47As / In0.52Al0.48As superlattices of different well widths. In femtosecond time-resolved studies, a strong increase of the coherent LO phonon amplitudes is observed when the Bloch oscillations are subsequently tuned into resonance with the different optical phonon modes of the ternary semiconductor materials. In a narrow-well superlattice where electronic minibands are energetically shifted close to the confining barrier potential, the phonon amplitudes are asymmetrically enhanced on the high-frequen cy edge
of the resonance. Here, at high electric fields, field induced tunneling into above-barrier continuum states leads to a rapid dephasing of Bloch oscillations. The associated polarization change provides an additional excitation process for coherent LO phonons.
Keywords: Bloch oscillations, quantum coherence, ultrafast, femtosecond, superlattice, coherent phonons, minibands, field dynamics, optoelectronic

Publ.-Id: 6813 - Permalink


Grazing-Incidence Diffraction Strain Analysis of a Laterally patterned Si wafer treated by Focused Ge and Au Ion Beam Implantation
Grenzer, J.; Bischoff, L.; Pietsch, U.;
Strain analysis of a laterally patterned Si-wafer was carried out utilizing X-ray grazing-incidence diffraction performed at the ID10B at the ESRF. The lateral patterning was done by focused ion beam implantation using a AuGeSi alloy liquid metal ion source. Samples were prepared by either a 35 keV Au+ ion beam (dose: 0.3, 2 ·10E14cm−2) or by a 70 keV Ge++ ion beam (dose: 8 · 10E14cm−2). It was shown that a periodical defect structure consisting of both implanted and not implanted stripes is created due to ion beam implantation. The induced strain distribution induced, however, shows no periodicity. This can be only explained by an overlap of the strain fields created in each implanted stripe. We found a maximum strain for the Au implanted samples in a depth of about 20 nm (da/a = −1,−3 · 10E−4 for the Au samples); for the Ge sample in a depth of 100nm (da/a = −1.2 · 10E−4). At depths 500nm below the sample surface the strain of the Ge sample becomes smaller than the detection limit (da/a < 2 · 10E−5). Using this technique we were able to create a buried Ge layer with a thickness of about 200 nm and an averaged Ge content of about 1%.
Keywords: Ion beam implantation, Grazing incidence diffraction
  • Lecture (Conference)
    DPG Frühjahrstagung 2005, 04.03. bis 09.03.2005, Berlin, Deutschland
  • Physica Status Solidi (A) 202(2005)6, 1009-1016
    DOI: 10.1002/pssa.200420005

Publ.-Id: 6812 - Permalink


Actinide, lanthanide, fission product speciation and electrochemistry
Bhatt, A.; Kinoshita, H.; Koster, A. L.; May, I.; Sharrad, C. A.; Volkovich, V. A.; Vox, O. D.; Jones, C. J.; Lewin, B. G.; Charnock, J. M.; Hennig, C.;
There is currently a great deal of research interest in the development of molten salt technology, both classical high temperature melts and low temperature ionic liquids, for the electrochemical separation of the actinides from spent nuclear fuel. We are interested in gaining a better understanding of actinide and key fission product speciation and electrochemical properties in a range of melts. Our studies in high temperature alkali metal melts (including LiCl and LiCl-KCl and CsCl-NaCl eutectics) have focussed on in-situ species of U, Th, Tc & Ru using X-ray absorption spectroscopy (XAS, both EXAFS and XANES) electronic absorption spectroscopy (EAS) and Raman spectroscopy. We report unusual actinide speciation in high temperature melts and an evaluation of the likelihood of Ru or Tc volatilisation during plant operation. Our studies in lower temperature melts (ionic liquids) have focussed on salts containing tertiary alkyl group 15 cations and the bis(trifluormethyl)sulfonyl)limide anion, melts which we have shown to have exceptionally wide electrochemical windows. We report Ln, Th, U, Np and Pu speciation (XAS, EAS and vibrational spectroscopy) and electrochemistry in these melts and relate the solution studies to crystallographic characterised benchmark species.
  • Invited lecture (Conferences)
    227th ACS National Meeting, 31.03.2004, Anaheim, CA, United States

Publ.-Id: 6811 - Permalink


Speciation of U4+ in high concentrated [Cl-] solutions with a spectro-electrochemical cell
Hennig, C.;
The coordination of the U(IV) and U(VI) ions as a function of the chloride concentration in aqueous solution has been studied by U LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The oxidation state of uranium was changed in situ using a gas-tight spectro-electrochemical cell, specifically designed for the safe use with radioactive solutions. For U(IV) the complexes U(H2O)8Cl3+, U(H2O)6-7Cl22+ and U(H2O)5Cl+.
  • Invited lecture (Conferences)
    ACTINET Coordination Meeting "Electrochemistry of Ionic Liquids" 8.11.2004, Strasbourg, France

Publ.-Id: 6810 - Permalink


Comparative EXAFS investigation of Uranium(VI) and -(IV) aquo chloro complexes in solution using a newly developed spectroelectrochemical cell
Hennig, C.; Tutschku, J.; Rossberg, A.; Bernhard, G.; Scheinost, A.;
The coordination of the U(IV) and U(VI) ions as a function of the chloride concentration in aqueous solution has been studied by U LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The oxidation state of uranium was changed in situ using a gas-tight spectro-electrochemical cell, specifically designed for the safe use with radioactive solutions. For U(VI) we observed the complexes UO2(H2O)4Cl+, UO2(H2O)3Cl20 and UO2(H2O)2Cl3 with [Cl] increasing from 3 to 9 M, and for U(IV) the complexes U(H2O)8Cl3+, U(H2O)6-7Cl22+ and U(H2O)5Cl3+. In the uranium coordination sphere U-O distances are 2.41-0.02 Å and U-Cl distances are 2.71-0.02 Å, independent of oxidation state and chloride concentration.
  • Inorganic Chemistry 44(2005), 6655-6661

Publ.-Id: 6809 - Permalink


Beitrag zur Modellierung der Schmelzerückhaltung im RDB nach Verlagerung von Corium in das untere Plenum: Berechnung des Temperaturfeldes und der viskoplastischen Verformung der Behälterwand
Altstadt, E.; Willschütz, H.-G.;
Bezüglich eines hypothetischen Kernschmelzeszenarios in einem Leichtwasserreak-tor (LWR) ist es notwendig, mögliche Versagensformen des Reaktordruckbehälters sowie Versagenszeiträume zu untersuchen, um die Belastung für das Containment bestimmen zu können. Es wurden bereits eine Reihe von Experimenten durchge-führt, welche Erkenntnisse hierüber liefern sollen.
Vom Institut für Sicherheitsforschung des FZR wurde ein Finite-Elemente-Modell er-stellt, das sowohl die Temperaturfeldberechnung für die Wand als auch die elasto-plastische Mechanik der Behälterwand beschreibt. Dabei wurde ein fortgeschrittenes Modell für das Kriechen und für die Materialschädigung entwickelt und an Hand von experimentellen Daten validiert. Die thermischen und mechanischen Berechnungen sind rekursiv und sequentiell gekoppelt. Das Modell ist in der Lage, Versagenszeit und Versagensposition eines Behälters mit beheiztem Schmelzepool zu berechnen.
Das Modell wurde für Voraus- und Nachrechnungen der FOREVER-Experimente, die den RDB eines LWR im Maßstab 1:10 nachbilden, angewendet. Diese Experimente wurden an der KTH Stockholm durchgeführt. Die Ergebnisse der Berechnungen sind qualitativ und quantitativ sehr zufriedenstellend.
Erste Rechnungen für eine LWR-Geometrie wurden durchgeführt, um Unterschiede und Gemeinsamkeiten zwischen prototypischen Szenarien und skalierten Experi-menten herauszuarbeiten.

Keywords: Schmelzerückhaltung, Finite-Elemente-Modell, Kriechen, Schädigung, Schmelzepool, Leichtwasserreaktor
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-412 2005

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Publ.-Id: 6808 - Permalink


Suppression of Random Coincidences during In-Beam PET Measurements at Ion Beam Radiotherapy Facilities
Crespo, P.; Barthel, T.; Frais-Koelbl, H.; Griesmayer, E.; Heidel, K.; Parodi, K.; Pawelke, J.; Enghardt, W.;
In-beam positron emission tomography (PET) is currently the only method for an in-situ monitoring of charged hadron therapy.
However, in-beam PET data, measured at beams with a sub-microsecond-microstructure due to the accelerator radiofrequency (RF), are highly corrupted by random coincidences arising from prompt gamma-rays following nuclear reactions as the projectiles penetrate the tissue. Since random-correction techniques from conventional PET cannot be applied, the clinical in-beam PET at the therapy facility at the Gesellschaft fuer Schwerionenforschung (GSI) Darmstadt merely reconstructs events registered in the
pauses (~ 2 - 4 s) between the beam macropulses (< 2 s). We have successfully tested at GSI two methods for suppressing
the micropulse-induced random coincidences during beam extraction. Image statistics increased by about 90 %. Both methods rely on the synchronization of the gamma-gamma-coincidences measured by the positron camera with the time microstructure of the beam, either by using the RF-signal from the accelerator or the signal of a thin diamond detector placed in the beam path in front of the target. Energy and triple-coincidence time correlated spectra first-measured during beam extraction, combined with the corresponding tomographic images of the beta+ activity induced by the beam in a plastic phantom, clearly confirm the feasibility of the proposed random suppression methods. These methods provide the solution for applying in-beam PET at synchrotron and cyclotron radiotherapy facilities with optimal utilization of the annihilation photon flux.
Keywords: PET, charged hadron therapy, LSO, APD
  • IEEE Transactions on Nuclear Science, 52(2005)4, 980-987

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Publ.-Id: 6806 - Permalink


Electron Beam Diagnostic at the ELBE Free Electron Laser
Evtushenko, P.;
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-413 2004

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Publ.-Id: 6805 - Permalink


High brightness electron guns for next-generation light sources and accelerators
Bluem, H. P.; Todd, A. M. M.; Cole, M. D.; Rathke, J.; Schultheiss, T.; Lewellen, J.; Phillips, L.; Preble, J.; Ben-Zvi, I.; Srinivasan-Rao, T.; Neil, G. R.; Colestock, P.; Nguyen, D. C.; Wood, R. L.; Young, L.; Janssen, D.;
Next-generation light sources and accelerators are being proposed that set unique requirements for the electron source parameters. No single source is suitable for the diverse applications, which have operating characteristics ranging from high-average-current, quasi-CW, to high-peak-current, single-pulse electron beams. Advanced Energy Systems, in collaboration with our various partners, is developing a variety of electron gun concepts for these important applications.
  • Contribution to proceedings
    9th European Particle Accelerator Conference EPAC 2004, 05.-09.07.2004, Lucerne, Switzerland
    Contributions to the Proceedings, 9th European Particle Accelerator Conference EPAC 2004, 92-9083-232-0, 899-901
  • Contribution to WWW
    EPAC 2004 Contributions to the Proceedings, 9th European Particle Accelerator Conference EPAC 2004, 899-901, MOPLT156, 05.07. – 09.07.2004, Lucerne, Switzerland ISBN 92-9083-231-2 (Web version), ISBN 92-9083-232-0 (CD-ROM): http://epaper.kek.jp/e04/PAPERS/MOPLT156.PDF

Publ.-Id: 6804 - Permalink


The influence of the main coupler field on the traverse emittance of a superconducting RF gun
Janssen, D.; Dohlus, M.;
The field disturbance in the RF coupler plane increases the transverse emittance of RF electron guns. This effect has been calculated for the Rossendorf superconducting RF gun. For 10 kW beam power the increasing is smaller than 5 %.
  • Contribution to proceedings
    9th European Particle Accelerator Conference EPAC 2004, 05.-09.07.2004, Lucerne, Switzerland
    EPAC 2004 Contributions to the Proceedings, 9th European Particle Accelerator Conference EPAC 2004, 92-9083-232-0, 327-329
  • Contribution to WWW
    EPAC 2004 Contributions to the Proceedings, 9th European Particle Accelerator Conference EPAC 2004, 327-329, MOPKF013, 05.07. – 09.07.2004, Lucerne, Switzerland, ISBN 92-9083-231-2 (Web version): http://epaper.kek.jp/e04/PAPERS/MOPKF013.PDF
  • Poster
    9th European Particle Accelerator Conference EPAC 2004, 05.-09.07.2004, Lucerne, Switzerland

Publ.-Id: 6802 - Permalink


Tc and Re labelling of biomolecules according to the "4+1" mixed-ligand approach: Switching from Diagnostic to Therapeutic Radiopharmaceuticals
Pietzsch, H.-J.; Schiller, E.; Seifert, S.; Künstler, J.-U.; Spies, H.;
  • Invited lecture (Conferences)
    2nd Research Co-ordination Meeting of the International Atomic Energy Agency's Co-ordinated Research Project on "Development of 99mTc based Small Bio Molecules Using Novel 99mTc Cores", 5.-13.02.2004, Wien, Austria

Publ.-Id: 6801 - Permalink


Spectator detection for the measurement of proton-neutron interactions at ANKE
Lehmann, I.; Barsov, S.; Schleichert, R.; Wilkin, C.; Drochner, M.; Hartmann, M.; Hejny, V.; Merzliakov, S.; Mikirtychiante, S.; Mussgiller, M.; Protic, D.; Stroher, H.; Trusov, S.; Wustner, P.;
A telescope of three silicon detectors has been installed close to the internal target position of the ANKE spectrometer, which is situated inside the ultra-high vacuum of the COSYJulich light-ion storage ring. The detection and identification of slow protons and deuterons emerging from a deuterium cluster-jet target thus becomes feasible. A good measurement of the energy and angle of such a spectator proton (p(sp)) allows one to identify a reaction as having taken place on the neutron in the target and then to determine the kinematical variables of the ion-neutron system on an event-by-event basis over a range of c.m. energies.The system has been successfully tested under laboratory conditions. By measuring the spectator proton in the pd-->p(sp)dpi(0) reaction in coincidence with a fast deuteron in the ANKE Forward Detector, values of the pn-->dpi(0) total cross-section have been deduced. Further applications of the telescope include the determination of the luminosity and ! beam polarisation which are required for several experiments.
  • Nuclear Instruments and Methods in Physics Research A 530(2004)3, 275-285

Publ.-Id: 6798 - Permalink


ρ-ω splitting and mixing in nuclear matter
Zschocke, S.; Kämpfer, B.;
We investigate the splitting and mixing of ρ and ω mesons in nuclear matter. The calculations were performed on the basis of QCD sum rules and include all operators up to mass dimension-6 twist-4 and up to first order in the coupling constants. Special attention is devoted to the impact of the scalar four-quark condensates on both effects. In nuclear matter the Landau damping governs the ρ-ω mass splitting while the scalar four-quark condensates govern the strength of individual mass shifts. A strong in-medium mass splitting causes the disappearance of the ρ-ω mixing.
  • Physical Review C 70(2004), 035207

Publ.-Id: 6797 - Permalink


Quadrupole moments and g factors for high-spin neutron isomers in Pb-193
Ionescu-Bujor, M.; Iordachescu, A.; Balabanski, D. L.; Chmel, S.; Neyens, G.; Baldsiefen, G.; Bazzacco, D.; Brandolini, F.; Bucurescu, D.; Danchev, M.; de Poli, M.; Georgiev, G.; Grogen, A.; Haas, H.; Hubel, H.; Ilie, G.; Marginean, N.; Menegazzo, R.; Pavan, P.; Rainovski, G.; Ribas, R. V.; Alvarez, C. R.; Ur, C. A.; Vyvey, K.; Frauendorf, S.;
The g factors and quadrupole moments of the 21/2(-) and 33/2(+) isomers in Pb-193 have been measured by the time-differential perturbed gamma-ray angular distribution method as g(21/2(-))=-0.059(11), \Q(21/2(-))\=0.22(2) eb and g(33/2(+))=-0.171(9), parallel toQ(33/2(+))\=0.45(4) eb. The results support the three-neutron configurations (1i(13/2))(12)(+2)x3p(3/2) and (1i(13/2))(3) for the 21/2(-) and 33/2(+) states, respectively. The quadrupole moment of the 12(+) isomer in Pb-194 described by the two-neutron (1i(13/2))(2) configuration has been remeasured as \Q(12(+))\=0.48(3) eb in perfect agreement with the previous data. The experimental results are discussed within a microscopic Bardeen-Cooper-Schrieffer approach in a number-projected one- and three-quasiparticle neutron space, and in the frame of the pairing plus quadrupole tilted-axis cranking model.
  • Physical Review C 7003(2004), 4305

Publ.-Id: 6796 - Permalink


Simulationsrechnungen zur Validierung des Monte Carlo Codes FLUKA für de Vorhersage der bei Tumorbestrahlungen mit Ionen erzeugten β+-Aktivität
Sommerer, F.; Enghardt, W.; Parodi, K.; Poljanc, K.; Aiginger, H.;
Contribution to 54. Jahrestagung der Österreichischen Physikalischen Gesellschaft
  • Contribution to proceedings
    Contribution to 54. Jahrestagung der Österreichischen Physikalischen Gesellschaft, Linz, Austria, 28-30

Publ.-Id: 6795 - Permalink


Positronenemissionstomographie in der Therapie mit Kohlenstoffionen und Validierung des FLUKA Monte Carlo Codes für die Vorhersage der bei Tumorbestrahlungen mit Ionen erzeugten β+-Aktivität
Poljanc, K.; Sommerer, F.; Parodi, K.; Aiginger, H.; Enghardt, W.;
  • Contribution to proceedings
    ÖGMP Annual Meeting, Wiener Neustadt, 04.-05.06.2004, Wiener Neustadt, Austria
    Abstract of the ÖGMP Annual Meeting

Publ.-Id: 6794 - Permalink


The FLUKA code: new developments and application to 1 GeV/n Iron beams
Aiginger, H.; Andersen, V.; Ballarini, F.; Battistoni, G.; Campanella, M.; Carboni, M.; Cerutti, F.; Empl, A.; Enghardt, W.; Fassò, A.; Ferrari, A. C.; Gadioli, E.; Garzelli, M. V.; Lee, K. S.; Ottolenghi, A.; Parodi, K.; Pelliccioni, M.; Pinsky, L.; Ranft, J.; Roesler, S.; Sala, P. R.; Sacannicchio, D.; Smirnov, G.; Sommerer, F.; Wilson, T.; Zapp, N.;
The modelling of ion transport and interactions in matter is a subject of growing interest, driven by the multiplication of applicaton fields. These include hadron therapy, dosimetry, and space missions, but there are also several fundamental research, accelerator physics, and cosmic ray physics issues where a reliable description of heavy ion induced cascades is important. In the present work, the capabilities of the FLUKA code for ion beams will be briefly recalled and some recent developments presented. Applications of the code to the simulation of therapeutic carbon, nitrogen and oxygen ion beams, and of iron beams, which are of direct interest for space mission related experiments, will be also presented, together with interesting consideration about the evaluation of dosimetric quantities. Both applications involve ion beams in the AGeV range.
  • Advances in Space Research 35(2005)2, 214-222

Publ.-Id: 6793 - Permalink


Investigation of acoustic waves generated in an elastic solid by a pulsed ion beam and their application in a FIB based scanning ion acoustic microscope
Akhmadaliev, C.;
The rapid growth of the microelectronics industry in the last decades made it possible to produce structures in the sub-micrometer scale on silicon chips and to reach an integration scale under 100 nm. Decreasing the size and increasing the complexity of these structures make a control of quality and defects investigation more difficult. During a long time ultrasound devices are being used for nondestructive investigation of materials, like ultrasound microscopes, scanning photo-acoustic microscopes or scanning electron-acoustic microscopes, where acoustic waves are generated by acoustic transducers, focused laser or electron beams, respectively.
The aim of this work is to investigate more precisely the acoustic wave generation by pulsed and periodically modulated ion beams in different solid materials depending on the beam parameters and to demonstrate the possibility to apply an intensity modulated focused ion beam (FIB) for acoustic emission and for nondestructive investigation of the internal structure of materials on a microscopic scale. The combination of a FIB and an ultrasound microscope in one device can provide the opportunity of nondestructive investigation, production and modification of micro- and nanostructures simultaneously. The FIB spot size in modern systems is comparable with that of a focused electron beam and the penetration depth of ions with energy of 20-60 keV is lower than 100 nm. This makes it possible to reach a sub-micrometer resolution of a scanning ion acoustic microscope. On the other hand side a FIB with energy of 20-60 keV is a good tool which can be used for the fabrication of nanostructures using ion milling, implantation or ion beam assisted deposition techniques.
The bulk ultrasound emission in a solid was investigated using a pulsed high energy ion beam focused on aluminum, copper, iron and silicon samples. Oxygen, silicon and gold ion beams were applied in charge states from 1+ to 4+ with the pulse duration of 0.5 - 4 µs and an energy of 1.5 - 10 MeV. Intensity of the detected acoustic waves shows a linear dependence on the energy of the incident ions, on the ion flux as well as on the pulse duration. No influence of the ion charge and ion mass to the emission of acoustic waves was observed.
The ion acoustic effect was applied for a nondestructive material inspection using intensity modulated FIB providing by the IMSA-100 FIB system with an accelerating potential of 30-35 kV. The achieved lateral resolution of this scanning ion acoustic microscope is in the micrometer range depending on the sample material and the beam modulation frequency. The resolution can be improved by increasing the frequency. The maximal modulation frequency which was obtained at IMSA-100 is about 2 MHz corresponding to lateral resolution of 4-5 µm on silicon. Using this microscope, some images of integrated microstructures on a silicon chip were obtained using the lock-in technique for filtering of the signal from the noise and increasing of the total imaging time. The possibility to visualize near sub-surface structure was demonstrated. Due to the strong sputtering effect and the long time of irradiation the imaged structures were significantly damaged. Si2+, Ge2+, Ga+ and Au+ ions were used. All these ions are quite heavy and have high sputtering coefficients. Long-time imaging improves the quality of acoustic images, i. e. the signal-to-noise ratio is reduced with the square root from the pixel time, but leads to significant erosion of the imaged structure.


Keywords: acoustic microscopy, nondestructive investigation, scanning ion acoustic microscope, focused ion beam, ion acoustic effect in solids
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-416 2004

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Publ.-Id: 6791 - Permalink


Gold and Palladium Nanoclusters Formed by Cells and S-Layer of Bacillus Spaericus JG-A12 Spectroscopic Studies
Merroun, M.;
  • Lecture (others)
    SMWK Projekttreffen an der Technischen Universität Dresden, 21.10.2004, Dresden, Germany

Publ.-Id: 6788 - Permalink


Abtrennung von Uran aus wässriger Lösung durch Calix[6]arene mittels Flüssig-Flüssig-Extraktion sowie Festphasen-Extraktion
Schmeide, K.; Geipel, G.; Bernhard, G.;
Die Uranspeziation in ausgewählten Sicker- und Grubenwässern des ehemaligen Uranbergbaus wurde mittels spektroskopischer Methoden (TRLFS, LIPAS) untersucht. Deren Kenntnis in Abhängigkeit vom pH-Wert ermöglicht die Optimierung der Uranabtrennung mittels uranophiler Calixarene. Mittels Flüssig-Flüssig-Extraktion wurde gezeigt, dass COOH-derivatisierte Calix[6]arene als effektive Extraktionsmittel für die selektive Uranylabtrennung aus umweltrelevanten Wässern bei pH-Werten größer 4 geeignet sind und für Praxisanwendungen eingesetzt werden können. Extraktionskonstanten wurden bestimmt. Die durch Fixierung dieser Calixarenderivate auf Polyester dargestellten calixarenmodifizierten Vliese sind in der Lage Uranylionen aus synthetischen Grubenwässern in Anwesenheit von Konkurrenzionen abzutrennen. Die Untersuchungen zur Reversibilität der Uranbindung an calixarenausgerüsteten Polyestervliesen haben gezeigt, dass eine fast vollständige Regenerierung der calixarenmodifizierten Vliese mittels verdünnter Mineralsäuren möglich ist. Die regenerierten textilen Filtermaterialien können für weitere Uranabtrennungszyklen eingesetzt werden. Nach Auswahl geeigneter Calixarenderivate ist eine Übertragung des entwickelten Abtrennungsprinzipes auf weitere Actinide (z.B. Np, Pu) bzw. Schwermetall-Kontaminanten (z.B. As, Cd, Pb) möglich.
Keywords: Uran, Calixarene, Extraktion, Textile Filter, Komplexierung, Sanierung, Abwasser
  • Open Access LogoWissenschaftlich-Technische Berichte, Forschungszentrum Rossendorf, FZR-414 2004

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Publ.-Id: 6786 - Permalink


Level scheme of Mo-94 at high angular momentum
Zhang, Y. H.; Liu, M. L.; de Angelis, G.; Podolyàk, Z.; Guo, W. T.; Gadea, A.; Ur, C.; Marginean, N.; Rusu, C.; Schwengner, R.; Napoli, D. R.; Menegazzo, R.; Lunardi, S.; Bazzacco, D.; Martinez, T.; Axiotis, M.; Gargano, A.; Lenzi, S.; Brandolini, F.; von Oertzen, W.;
High-spin level structure of Mo-94 has been re-investigated using the modem multidetector array of GASP via the O-16(Se-82, 4ngamma)Mo-94 reaction at E(Se-82) = 459 MeV. The previously reported level scheme has been largely modified up to similar to 10 MeV in excitation energy due to identifications of some important linking transitions. The level structure of Mo-94 has been compared with the shell model calculations. It is suggested that the valence neutron excitation within d(5/2), g(7/2), and h(11/2) orbitals should be taken into account in order to adequately describe the high-spin level structure of Mo-94 above I-pi = 14(+).
  • High Energy Physics and Nuclear Physics - Chinese Edition 28(2004)9, 941-946

Publ.-Id: 6784 - Permalink


Experimental Study on the Feasibility of In-Beam PET for Accurate Monitoring of Proton Therapy
Parodi, K.; Pönisch, F.; Enghardt, W.;
Positron emission tomography is currently the only feasible method for in-situ and non-invasive 3D monitoring of the precision of the treatment in highly conformal ion therapy. Its positive clinical impact has been proven for fractionated carbon ion therapy of head and neck tumours at the experimental facility at the Gesellschaft f"ur Schwerionenforschung Darmstadt, Germany. Following previous promising experiments, the possible extension of the method to the monitoring of proton therapy has been investigated further in extensive in-beam measurements at GSI. Millimetre accuracy for verification of the lateral field position and for the most challenging issue of range monitoring has been demonstrated in mono-energetic and spread-out Bragg-peak proton irradiation of PMMA targets. The irradiation of an inhomogeneous phantom with tissue equivalent inserts in combination with further dynamic analysis has supported the extension of such millimetre precision to real clinical cases, at least in regions of interest for low perfused tissues. All the experimental investigations have been reproduced by the developed modeling rather well. This indicates the possible extraction of valuable clinical information as particle range in-vivo, irradiation field position and even local deviations from the dose prescription on the basis of the comparison between measured and predicted activity distributions. Hence, the clinical feasibility of in-beam PET for proton therapy monitoring is strongly supported.
  • IEEE Transactions on Nuclear Science 52(2005)3, 778-786

Publ.-Id: 6783 - Permalink


The QCD equation of state near T_0 within a quasi-particle model
Bluhm, M.; Kampfer, B.; Soff, G.;
We present a description of the equation of state of strongly interacting matter within a quasi-particle model.
The model is adjusted to lattice QCD data near T0 at non-vanishing baryon density. We compare in detail the excess pressure and its expansion coefficients available from two-flavor lattice QCD calculations and outline prospects of the extrapolation to large baryon density.
Keywords: Equation of state, Strongly interacting matter, Lattice QCD
  • Physics Letters B 620(2005),131-136

Publ.-Id: 6782 - Permalink


Berührungslose Messung von Phasen- und Konzentrationsverteilungen in Blasensäulen mit positronenemittierenden Radionukliden
Zippe, C.; Hoppe, D.; Fietz, J.; Hampel, U.; Hensel, F.; Mäding, P.; Prasser, H.-M.; Zippe, W.;
Die Positronen-Emissions-Tomographie (PET) ist eine etablierte Untersuchungsmethode in der Medizin. Das vorgestellte Projekt beschäftigt sich mit einer nichtmedizinischen Anwendung dieses bildgebenden Verfahrens – dem Aufbau und der Anwendung eines PET-Tomographen zur Untersuchung des Verhaltens von Schaum in Blasensäulen. Am Beispiel von Natriumcapronat als schwaches Tensid, das einen feuchten, instabiler Schaum erzeugt, wird gezeigt, dass sich die Anreicherung eines Tensids in einer Schaumschicht mit der Positronen-Emissions-Tomographie nachweisen lässt.
Keywords: PET, Positronen-Emissions-Tomographie, Blasensäule, Schaum, Chemiereaktor, Tensid, Anreicherung
  • Poster
    2. DECHEMA/GVC VDI-Symposium "Schäume - Grundlagen und Anwendungen", 16.-17.11.2004, Baden-Baden

Publ.-Id: 6781 - Permalink


High-fluence Si-implanted diamond: optimum implantation temperature for SiC formation
Weishart, H.; Eichhorn, F.; Heera, V.; Pécz, B.; Barna, Á.; Skorupa, W.;
In this paper we investigate the effect of implantation temperature on the structural properties of diamond implanted with high fluences of Si between 5.3 ´ 1017 Si cm-2 and 1 ´ 1018 Si cm-2. In order to reduce radiation-induced damage and to enhance SiC formation the implantations were performed at elevated temperatures in the range from 900 °C to 1200 °C. Subsequently, all samples were annealed for 10 minutes at 1500 °C in an rf-heated furnace. X-ray diffraction revealed the formation of cubic SiC nanocrystallites in a buried layer inside the implanted diamond. The implantation-induced damage was assessed by analyzing graphitization of the surface-near layer using Raman spectroscopy. With increasing Si fluence the implantation-induced damage rises and the nearly perfect alignment of the formed SiC crystallites within the host diamond lattice deteriorates. However, rising the implantation temperature from 900 °C to 1000 °C reduces the damage in the diamond and increases amount, size and epitaxial alignment of the crystalline SiC precipitates. Further increase of the implantation temperature gives no improvement in the quality of the SiC rich layer. Instead, the damaged diamond converts into graphite and the formation of SiC crystallites is obstructed.
Keywords: Ion implantation, thin films, Heterostructures, structure and nonelectronic properties, Ion radiation effects
  • Journal of Applied Physics 98(2005), 043503.

Publ.-Id: 6780 - Permalink


Positronen Emissions Tomographie zur in vivo Charakterisierung neuer Substanzen
Bergmann, R.;
  • Lecture (others)
    Institutskolloquium, Max-Bergmann- Zentrum, 22.10.2004, Dresden, Germany

Publ.-Id: 6779 - Permalink


In vivo Biochemie mit PET
Bergmann, R.;
  • Lecture (others)
    Institutsseminar, Technische Universität Dresden, 26.10.2004, Dresden, Germany

Publ.-Id: 6778 - Permalink


Angular distribution and azimuthal asymmetry for pentaquark production in proton-proton collisions
Barz, H.-W.; Zetenyi, M.;
Angular distributions for production of the Theta+ pentaquark are calculated for the collisions of polarized protons with polarized target protons. We compare calculations based on different assumptions concerning spin and parity (J=1/2+/-,3/2+/-) of the Theta+ state.
For a wide class of interactions the spin correlation parameters describing the asymmetric angular distributions are calculated up to 250 MeV above production threshold. The deviations from the near threshold behavior are investigated.
  • Physical Review C 71(2005), 065207

Publ.-Id: 6777 - Permalink


High-spin states and band terminations in 69As
Stefanescu, I.; Eberth, J.; Gersch, G.; Steinhardt, T.; Thelen, O.; Warr, N.; Weisshaar, D.; Carlsson, B. G.; Ragnarsson, I.; de Angelis, G.; Martinez, T.; Jungclaus, A.; Schwengner, R.; Lieb, K. P.; Stefanova, E.; Curien, D.;
Excited levels in 69As were studied using the 40Ca(32S, 3p)69 As reaction at 95 and 105 MeV beam energy. Gamma rays were detected with the EUROBALL spectrometer operated in conjunction with the Neutron Wall and the charged-particle detector array EUCLIDES. New level sequences with positive and negative paity were identified from 3p-γγ and γγγ coincidences. Spins were assigned to many of the levels on the basis of directional correlations of oriented states measurements. The previously observed positive-parity band was extended to spin 45/2+ and it was found to exhibit a crossing with another configuration identified up to spin 53/2+. Three negative-parity bands were observed for the first time up to spins (43/2-), 39/2-, and (41/2-). The previously known band was extended to spin (49/2-). No evidence for superdeformation was found, despite very high counting statistics. Configurations were assigned to each of the observed bands through comparisons to the cranked Nilsson-Strutunsky calculations.

Publ.-Id: 6775 - Permalink


Phase composition and properties of iron nanocrystals and clusters embedded in MgO matrix
Schneeweiss, O.; Pizurova, N.; Jiraskova, Y.; Zak, T.; Bezdicka, P.; Reuther, H.;
Phase composition of the Mg-Fe powder prepared by spark erosion is investigated using Mossbauer spectroscopy and X-ray diffraction. The results are compared with the phase analysis of MgO single crystal wafer implanted by Fe-57.
  • Hyperfine Interactions 156(2004), 81-87

Publ.-Id: 6774 - Permalink


Mixed-Ligand Rhenium-188 Complexes with Tetradentate/Monodentate NS3/P (‘4+1’) Coordination: Relation of structure with antioxidation stability
Schiller, E.; Seifert, S.; Tisato, F.; Refosco, F.; Bolzati, C.; Kraus, W.; Spies, H.; Pietzsch, H.-J.;
Development of new radiopharmaceuticals based on rhenium-188 depends on finding appropriate ligands able to give complexes with high in vivo stability. Rhenium(III) mixed-ligand complexes with tetradentate/monodentate (‘4 + 1’) coordination of the general formula [Re(NS3)(PRR’R’’)] (NS3 = tris-(2-mercaptoethyl)amine and derivatives thereof, PRR’R’’ = phosphorus(III) ligands) appear to be among the promising tools to achieve this goal. According to this approach, we synthesized and characterized series of rhenium model complexes. In vitro stabilities of the corresponding rhenium-188 complexes were determined by incubating 2-3 MBq or alternatively 37 MBq of the complexes in phosphate buffer, human plasma and rat plasma, respectively, at 22 °C or 37 °C, followed by checking the amount of 188ReO4- formed after 1 h , 24 h and 48 h by thin-layer chromatography. The rate of perrhenate formation varied over a wide range, depending primarily on the nature of the phosphorus(III) ligand. Physicochemical parameters of the corresponding nonradioactive rhenium complexes were analyzed in detail to find out the factors influencing their different stability and furthermore to design new substitution-inert ‘4 + 1’ complexes. Tolman’s cone angle of phosphorus(III) ligands and the lipophilic character of the inner coordination sphere were found to be crucial factors to build up stable rhenium ‘4 + 1’ complexes. Additional information useful to describe electronic and steric properties of these compounds were selected from electronic spectra (wavelength of the Re→S charge-transfer band), cyclovoltammetric measurements (E° of the ReIII/ReIV couple), and NMR investigations (31P chemical shift of coordinated P(III) ligands).
  • Bioconjugate Chemistry 16(2005), 634-643

Publ.-Id: 6773 - Permalink


Design and performance of a high-resolution gamma tomography device
Bieberle, A.; Hampel, U.; Schleicher, E.; Hoppe, D.; Prasser, H.-M.; Sühnel, T.; Zippe, C.;
We introduce and discuss the design and performance of a new high-resolution gamma ray tomography device that has been built for the measurement and visualisation of quasi-stationary flow structures in hydrodynamic machines and of gas fraction distributions in thermohydraulic facilities. The gamma tomography system can be operated either with a Cs-137 or a Co-60 source, which allows measurements in radiologically dense enclosures, such as pressure vessels, chemical reactors, or hydrodynamic machines. The detector arc is made of 320 small scintillation detector elements comprising LYSO scintillation crystals with an active area of 2 mm x 8 mm and large area avalanche photodiodes coupled to the crystals. For the photodiode read-out we developed a special charge sensitive pre-amplifier electronics based on a monolithic IC amplifier. This preamplifier stage is followed by pulse shaping and energy discrimination electronics. Data is acquired by fully parallel pulse counting with energy discrimination. For tomographic image reconstruction we implemented a set of analytic and iterative image reconstruction algorithms including filtered backprojection, ART, MART, and SIRT. In the presentation we will especially discuss the performance of the system with regard to density resolution and spatial resolution.
Keywords: high-resolution gamma ray tomography device measurement scintillator avalanche photodiode visualisation of quasi-stationary flow structures tomographic sensor design
  • Contribution to proceedings
    4th World Congress on Industrial Process Tomography, 05.09.-08.09.2005, Aizu, Japan

Publ.-Id: 6772 - Permalink


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.;
X-ray synchrotron radiation is a very powerful tool in structural analysis of solids. Due to its extremely high intensity and low angular divergence synchrotron radiation allows the study of structures that otherwise are impossible. Here the typical studies on different semiconductor materials using various methods of synchrotron x-ray scattering are presented.
Ion implantation in compound semiconductors is a quite complicated process leading to some usually detrimental effects like buildup of damage and strain. In the case of InP produced strain is rather low and is hardly accessible by the conventional x-ray analysis. InP single crystals implanted with different doses of 1.2 MeV As+ ions were studied. It was found that implanted layers are under tensile stress, which relaxes upon prolonged storage at RT.
Another important issue is the analysis of nanocrystals. Diamond-SiC heterostructures produced by ion beam synthesis are considered as a promising technique for production of novel devices for high power applications. Synthesized by ion bombardment nanocrystals that grow in the single crystalline matrix are highly oriented. As revealed by x-ray scattering size and shape of nanocrystals, as well as incorporated strain depend on the ion implantation parameters.

Keywords: ion bombardment, compound semiconductors, diamond, HRXRD, RBS, ion beam synthesis
  • Proceedings of the Vth International Conference "Ion Implantation and Other Applications of Ions and Electrons" - ION2004, June 14 - 17, 2004, Kazimierz Dolny, Poland, Vacuum 78(2005), 303-309

Publ.-Id: 6771 - Permalink


Two-phase flow simulations in the FZ Rossendorf using CFX-5
Krepper, E.; Lucas, D.; Prasser, H.-M.; Shi, J.-M.; Rohde, U.;
To qualify CFD codes for gas-liquid two-phase flows, they have to be equipped with constitutive models standing for the interaction between the gaseous and the liquid phases. In case of bubbly flow this particularly concerns the forces acting on the bubbles as well as bubble coalescence and break-up. Besides the drag forces describing the momentum exchange in flow direction, the non drag forces acting perpendicular to the flow direction play an important role for the development of the flow structure. The presentation describes the two phase flow test facilities in the Forschungszentrum Rossendorf, the applied measurement technique and the modelling efforts simulating the momentum exchange between the phases by means of a two-fluid model. The simulation of a rectangular bubble column and a hot channel in a nuclear reactor fuel assembly are presented as application examples.
Keywords: two-phase flow measurements, two-phase flow CFD calculations, Euler/Euler two fluid approach, momentum exchange non drag forces, wall boiling
  • Contribution to proceedings
    22nd CAD-FEM User's Meeting 2004 and ANSYS CFX & ICEM CFD Conference, 10.-12.11.2004, Dresden, Germany
  • Lecture (Conference)
    22nd CAD-FEM User's Meeting 2004 and ANSYS CFX & ICEM CFD Conference, 10.-12.11.2004, Dresden, Germany

Publ.-Id: 6766 - Permalink


Two-Phase Boundary Layer Prediction In Upward Boiling Flow
Končar, B.; Mavko, B.; Krepper, E.; Hassan, Y. A.;
In the present work, the numerical modelling of the two-phase turbulent boundary layer in upward boiling flow was investigated. First, non-dimensional liquid velocity and temperature profiles in the two-phase boundary layer were validated on the one-dimensional section of a pipe with prescribed radial void fraction profiles. Simulations were performed on a fine grid with a commercial code CFX-5 using the k-w turbulence model. A significant deviation of results from the analytical single-phase and two-phase wall functions from the literature was observed. Second, a wall boiling model in a vertical heated pipe was simulated (CFX-5) on the coarse grid. Here the prediction of the two-phase thermal boudary layer was compared to the experimental data, k-w calculation on the fine grid and against the single-phase analytical wall function. Again a major deviation against single-phase temperature wall function was obtained. Presented analyses suggest that the existing analytical velocity and temperature wall functions cannot be valid for the boiling boundary layer with the high void fraction on the wall.
Keywords: Computatioal fluid dynamics, two-phase flow, subcooled boiling, boundary layer
  • Contribution to proceedings
    International Conference "Nuclear Energy for New Europe 2004", 06.-09.09.2004, Portorož, Slovenia

Publ.-Id: 6763 - Permalink


A limited-angle CT approach for a fast scanned electron-beam X-ray tomography with application to multi-phase flow measurements
Speck, M.; Hampel, U.; Koch, D.; Mayer, H.-G.; Menz, H.-J.; Prasser, H.-M.; Schleicher, E.;
We devised and tested a computed tomography approach that utilises a scanned electron beam X-ray source to produce multiple projections of an object at scan rates of 1000 frames per second and at an in-plane resolution of 1 mm. The measurement setup consists of an electron beam unit, a cylindrical tungsten target, and a detector line array which are operated inside a vacuum enclosure. By means of fast periodic electron beam deflection we produce a linearly moving focal X-ray spot on the tungsten target. The X-ray detector is read out in synchronisation with the beam deflection signal such that a set of consecutive tomographic projections from an object that is placed between target and detector can be obtained. This approach has some attractive features: it gives the highest achievable axial resolution, which is necessary to image fast moving flow structures and it is comparatively moderate in effort and costs. However, these advantages are compromised by the fact, that the projection data is incomplete with regard to the projection angle. The arising limited-angle problem may be solved by iterative image reconstruction algorithms. We will show, that this approach is suitable for a certain class of flow problems which are characterised by less complex object distributions and a high degree of available a-priori information, such as two-phase flows and particle tracking problems. In the presentation we will give an overview on the method, present first experimental results and discuss the image reconstruction process in some more detail.
Keywords: limited-angle tomography, high-speed tomography, algebraic reconstruction
  • Contribution to proceedings
    Proceedings of the 4th World Congress on Industrial Process Tomography, 05.-08.09.2005, Aizu, Japan
  • Lecture (Conference)
    4th World Congress on Industrial Process Tomography, 05.-08.09.2005, Aizu, Japan

Publ.-Id: 6762 - Permalink


Gamma tomography with application to two-phase flow imaging in hydrodynamic machines
Hampel, U.; Baldauf, D.; Christen, M.; Diele, K.-H.; Fietz, J.; Höller, H.; Hoppe, D.; Kernchen, R.; Prasser, H.-M.; Will, G.; Zippe, C.; Zschau, J.; (Editors)
We discuss the application of gamma tomography to the fully three-dimensional measurement of gas and fluid distributions inside rotating hydrodynamic machines. For such investigations we use a gamma tomography setup that currently employs a Cs-137 source of 180 GBq activity and approximately 5 mm focal spot together with a detector arc made of 64 scintillation crystals (BGO) with photomultiplier read-out. The detector is operated in pulse counting mode with energy discrimination. In the presentation we will introduce the principle of phase-correlated projection acquisition. Thus, projection data of a rotating object is acquired by a fast detector read-out and subsequent integration of the data for a set of equal angular intervals which are recorded by an angle sensor at the rotating object. As a first example we demonstrate the measurement of gas fractions in an axial pump that is in two-phase flow operation. In this study we were able to visualise the gas profiles at 10% gas fraction within the impeller of the pump at different axial measurement planes. The results directly provided an understanding of the interrelation between the hydraulic conveyance characteristics of the pump in two-phase flow operation and the flow structure in the impeller. In a second example we introduce the measurement of fluid distributions in a hydrodynamic coupling. In this study we successfully applied gamma tomography to visualise flow patterns inside the coupling for varying filling levels and slips. These results now find application in the optimisation of coupling designs and in the validation of computational fluid dynamics simulations for such devices.
Keywords: gamma tomography, two-Phase flow imaging
  • Contribution to proceedings
    Proceedings of the 4th World Congress on Process Tomography, 05.-08.09.2005, Aizu, Japan

Publ.-Id: 6761 - Permalink


Characterization of Er : LiNbO3 and APE : Er : LiNbO3 by RBS-channeling and XRD techniques
Mackova, A.; Groetzschel, R.; Eichhorn, F.; Nekvindova, P.; Spirkova, J.;
The samples of erbium-doped lithium niobate (Er:LiNbO3) were prepared by the standard Czochralski method and treated by the annealed proton exchange (APE) procedure to create a planar waveguide for further optical application. The positions of Er atoms in the crystal lattice of pristine and APE treated Er:LiNbO3 samples were studied by the Rutherford backscattering spectrometry (RBS)-channeling method. The Er3+ ion positions in the pristine and the APE treated Er:LiNbO3 samples are compared. X-ray diffraction (XRD) was used to determine the damage to the crystal structure caused by the APE treatment. It was found that the APE treatment leads to significant crystal structure damage and to shifts of the Er3+ ions from their positions in the pristine crystal.
Keywords: Er:LiNbO3; RBS-channeling;APE treatment;optical waveguides
  • Surface and Interface Analysis 36(2004)8, 949-951

Publ.-Id: 6759 - Permalink


Optical and electronic properties of CrOxNy films, deposited by reactive DC magnetron sputtering in Ar/N2/O2(N2O) atmospheres
Mientus, R.; Grötzschel, R.; Ellmer, K.;
Chromium oxynitride films CrOxNy were prepared by reactive magnetron sputtering from a chromium target in Ar/O-2(N2O)/N-2 gas mixtures. The argon-to-nitrogen partial pressure ratio and the DC discharge power were kept constant in the experiments. By changing the gas composition the film stoichiometry can be continuously varied from CrN to Cr2O3. The film composition has been determined by Rutherford backscattering (RBS) and by elastic recoil detection analysis (ERDA). From an XRD analysis it was concluded that the films consist of CrN nanocrystals in an amorphous oxide matrix. Depending on the oxygen content [O], the electronic behaviour of the films changes, accompanied by the evolution of an optical band gap, which was determined by spectral transmission and reflection measurements. The (negative) temperature coefficient at approximate to 300 K of the resistivity of the films is in the range of 0.5 (CrN) to 2% K-1 (CrO0.5N0.7). This film property can be used for temperature-dependent resistors, for instance in thermal radiation detectors.
Keywords: chromium oxid,chromium nitride,reactive magnetron sputtering, ion beam analysis electronic properties
  • Surface & Coatings Technology 200(2005)(1-4), 341-345

Publ.-Id: 6758 - Permalink


A study of the dechanneling of protons in SiC polytype crystals in the energy range E-p=400-650 keV
Kokkoris, M.; Perdikakis, G.; Kossionides, S.; Petrovic, S.; Vlastou, R.; Grötzschel, R.;
In the present work, the energy spectra of protons channeled along the (0 0 0 1) axis of SiC polytype crystals (namely 4H and 6H) in the energy range E-P = 400-650 keV, in the backscattering geometry, were taken and analyzed. Computer simulations are in very good agreement with the measured spectra. The accurate reproduction of the experimental channeling spectra in the backscattering geometry is strongly based on the investigation of the correct dechanneling function and a, the ratio of the stopping powers in the aligned and random mode. In the present work, the applicability of a Gompertz type sigmoidal dechanneling function, with two parameters, k and x(c), which represent characteristic dechanneling rate and range, respectively, is examined, and the results are compared to the ones obtained in the past, concerning the same polytype structures, based on the assumption that the dechanneling of protons follows an exponential law, for the energy range E-P = 1.7-2.4 MeV.

Publ.-Id: 6757 - Permalink


The Influx of Neutral Amino Acids into the Porcine Brain During Development: A Positron Emission Tomography Study
Brust, P.; Vorwieger, G.; Walter, B.; Füchtner, F.; Stark, H.; Kuwabara, H.; Steinbach, J.; Bauer, R.;
Pigs of three different age groups (newborns, 1 week old, 6 weeks old) were used to study the transport of the large neutral amino acids 6-[F-18]fluoro-L-DOPA ([F-18]FDOPA) and 3-O-methyl-6-[F-18]fluoro-L-DOPA ([F-18]OMFD) across the blood-brain barrier (BBB) with positron emission tomography (PET). Compartmental modeling of PET data was used to calculate the blood-brain clearance (K-1) and the rate constant for the brain-blood transfer (k(2)) of [F-18]FDOPA and [F-18]OMFD after i.v. injection. A 40-70% decrease of K-1(OMFD), K-1(FDOPA) and k(2)(OMFD) from newborns to juvenile pigs was found whereas k(2)(FDOPA) did not change. Generally, K-1(OMFD) and k(2)(OMFD) are lower than K-1(FDOPA) and k(2)(FDOPA) in all regions and age groups. The changes cannot be explained by differences in brain perfusion because the measured regional cerebral blood flow did not show major changes during the first 6 weeks after birth. In addition, alterations in plasma amino acids cannot account for the described transport changes. In newborn and juvenile pigs, HPLC measurements were performed. Despite significant changes of single amino acids (decrease: Met, Val, Leu; increase: Tyr), the sum of large neutral amino acids transported by LAT1 remained unchanged. Furthermore, treatment with a selective inhibitor of the LAT1 transporter (BCH) reduced the blood-brain transport of [F-18]FDOPA and [F-18]OMFD by 35% and 32%, respectively. Additional in-vitro studies using human LAT1 reveal a much lower affinity of FDOPA compared to OMFD or L-DOPA. The data indicate that the transport system(s) for neutral amino acids underlie(s) developmental changes after birth causing a decrease of the blood-brain barrier permeability for those amino acids during brain development. It is suggested that there is no tight coupling between brain amino acid supply and the demands of protein synthesis in the brain tissue. (C) 2004 Elsevier B.V. All rights reserved.
  • Developmental Brain Research 152(2004), 241-253

Publ.-Id: 6756 - Permalink


Hydromagnetic dynamo experiments
Stefani, F.;
Planetary, stellar, and galactic magnetic fields are caused by the hydromagnetic dynamo action in moving electrically conducting fluids. While theory and numerics of hydromagnetic dynamos have flourished during the last decades, an experimental validation of the effect was missing until recently. Therefore, it was a nice coincidence that, after years of preparations, the large-scale liquid sodium dynamo facilities in Riga and Karlsruhe became operative nearly simultaneously at the end of 1999. Since those pioneering times, a number of runs have been carried out in either place, yielding reproducible data on the kinematic as well as on the saturation regime. With the main focus on the Riga experiment, I give a summary of what has been achieved so far and what is left for future dynamo experiments.
  • Lecture (others)
    Seminarvortrag, Technische Universiteit Delft, 20.10.2004, Delft, Netherlands

Publ.-Id: 6755 - Permalink


Depth profiling of light elements in PAMBE-grown GaN and helium-implanted titanium with heavy ion time-of-flight elastic recoil detection
Markwitz, A.; Kennedy, V. J.; Durbin, S. M.; Johnson, P. B.; Mücklich, A.; Dytlewski, N.;
The heavy ion time-of-flight elastic recoil detection analysis (HI-ERDA) technique was used to investigate the possibility of measuring near-surface elemental depth profiles of light and mid-Z elements in thin films of plasma-assisted molecular beam epitaxy (PAMBE)-grown GaN and helium-implanted titanium. The great advantage of HI-ERDA is the ability to measure mass-separated elemental depth profiles simultaneously. However for some materials it is not certain whether HI-ERDA can be used successfully because significant sputtering or other beam-induced damage may occur. The damage to the surfaces by a 77 MeV iodine beam was assessed using RBS, AFM and profilometry. The results show that for thin PAMBE-grown polycrystalline GaN films and for titanium that has been heavely implanted with helium a significant modification of the near-surface region is caused by the probing heavy ion beam. For the PAMBE-grown GaN films the most significant loss trend is observed for nitrogen. Surprisingly this was not accompanied by a change in surface topology. In contrast, an almost complete removal of the heavily helium-implanted surface layer was measured for the titanium specimens. The investigation shows that reference measurements with additional techniques such as RBS, AFM and profilometry have to be performed to ascertain sample integrity before HI-ERDA data can be used.
Keywords: HI-ERDA, GaN, He-implanted Ti, nanoporous surfaces, sputtering, depth profiling

Publ.-Id: 6754 - Permalink


Investigation of the Formation and Phase Transition of Ge and Co Nanoparticles in a SiO2 matrix
Cantelli, V.; von Borany, J.; Mücklich, A.; Schell, N.;
The evolution of ion beam synthesized Co and Ge nanoclusters in a SiO2 matrix during annealing processes has been investigated by in-situ X-ray diffraction and ex-situ transmission electron microscopy. Remarkable differences has been found for Ge and Co clusters. For Ge implanted SiO2 films a clear influence of near-surface Ge oxidation and nanocluster melting has been established. Annealing at temperatures at around 1000°C leads to the formation of an ensemble of small (d~5 nm) nanocrystals. The cluster growth is mainly thermodynamically driven by classical diffusion limited Ostwald ripening. Contrary, for Co-implanted SiO2 films a drastic transition in nanoclusters evolution has been established. Within a relatively small temperature range at around 800°C an ensemble of small (d~4nm) amorphous Co clusters is transformed into a bimodal cluster distribution with large Co nanocrystals of 20-40 nm diameter near the surface. The influence of oxidation or nanocluster melting can be neglected.
Keywords: Nanoclusters, Cobalt, Germanium, Microstructure, XRD, TEM
  • Poster
    4th Int. Conference on Synchrotron Radiation in Materials Science (SRMS-4), August 23-25, 2004, Grenoble, France

Publ.-Id: 6753 - Permalink


Recent developments in the field of nuclear safety research
Rindelhardt, U.; Weiss, F.-P.;
Some recent developments in the field of nuclear safety research will be presented. The contribution starts from the general aim of safety research – to contribute to the sustainability of nuclear energy compared with other energy resources.
The first two examples refers to the safety of operating NPPs. Possible boron dilution transients can lead to reactivity accidents at certain conditions. Comprehensive experimental and numerical studies were carried out to identify the critical conditions of such transients. Another topic – which belongs to the severe accident research - is the investigation of the reactor pressure vessel behaviour during core melt and corium in the lower plenum. Pre- and post-test calculations of the Swedish FOREVER-experiments will be presented.
The third topic deals with the transmutation of long-lived radionuclides. Up to now the radioactive waste has safely to be isolated for millions of years. Implementing new concepts a drastic reduction of waste and isolation time can be expected. As example accelerator driven systems (ADS) are discussed.

Keywords: Nuclear safety research, Boron dilution, severe accidents, partitioning and transmutation, ADS
  • Invited lecture (Conferences)
    CO-MAT-TECH 2004, 12th International Scientific Conference, 14.-15.10.2004, Trnava, Slovakia

Publ.-Id: 6752 - Permalink


In-situ x-ray diffraction during sputter deposition of Ti1-xAlxN thin films
Beckers, M.; Schell, N.; Martins, R. M. S.; Möller, W.; (Editors)
Due to improved hardness and oxidation resistance, Ti1-xAlxN coatings are constantly displacing TiN in tooling and microelectronic industry. Since the coating’s performance can be further increased by tailoring preferred orientation, an understanding of how deposition parameters influence thin film texture is crucial. The approach used here is in situ x-ray diffraction both in-plane and off-plane during film growth. For this purpose a growth chamber has been installed into the goniometer of the Rossendorf synchrotron BeamLine (ROBL) at the ESRF. Ti1-xAlxN films were deposited by reactive co-sputtering from metallic Ti and Al targets, varying substrate temperature, bias voltage and aluminum concentration. In-situ experiments with x~0.1 revealed competitive growth between low surface free energy (002) grains and low strain energy (111) grains parallel to the surface with (002) orientation dominating at higher substrate temperature in accordance with models found in literature. Contrary to pure TiN, here no sub-surface recrystallisation as a driving factor for texture crossover has been observed. Halving the deposition rate led to almost pure (002) fiber texture independent of film thickness pointing towards kinetic restrictions during film growth. Data of current experiments on nano-composite structured Ti1-xAlxN with x~0.5 will also be presented at the conference.
  • Poster
    Plasma surface Engineering (PSE) 2004, Garmisch-Partenkirchen
  • Lecture (Conference)
    9th Int. Conf. on Plasma Surface Enginneering, 13.-17.09.2004, Garmisch-Partenkirchen, Germany

Publ.-Id: 6751 - Permalink


The crucial role of the diphosphine heteroatom X in the stereochemistry and stabilization of the substitution-inert [M(N)(PXP)]2+ metal fragments (M = Tc, Re; PXP = diphosphine ligand)
Tisato, F.; Refosco, F.; Porchia, M.; Bolzati, C.; Bandoli, G.; Dolmella, A.; Duatti, A.; Boschi, A.; Jung, C. M.; Pietzsch, H.-J.; Kraus, W.;
The nature of the heteroatom X incorporated in the five-member PXP-diphosphine spacer was found to play a primary unit role both in the stereochemical arrangement and overall stability of nitrido containing [M(N)(PXP)]2+ metal fragments (M = Tc, Re). Thus, by mixing PXP ligands with labile [Re(N)Cl4]- and [Tc(N)Cl2(PPh3)2] nitrido precursors in CH2Cl2/MeOH mixtures, a series of neutral [M(N)Cl2(PXP)] complexes (M = Tc, 1-5; M = Re, 8-9) was collected. In the resulting distorted octahedrons PXP adopted facial or meridional coordination, and combination with halide co-ligands produced three different stereochemical arrangements, i.e. fac,cis mer,cis and mer,trans, depending primarily on the nature of the diphosphine heteroatom X. When X = NH, mer,cis-[Tc(N)Cl2(PNP1)] 1 was the only isomer formed. Alternatively, when a tertiary amine nitrogen (X = NR; R = CH3, CH2CH2OCH3) was introduced in the spacer, fac,cis-[M(N)Cl2(PN(R)P)] complexes (M = Tc, 2, 3; M = Re, 8f) were obtained. Isomerization into the the mer,cis-[Re(N)Cl2(PN(R)P)], 8m, species was observed only in the case of rhenium when the tertiary amine group carried the less encumbering methyl substituent. Fac,cis-[Tc(N)Cl2(PSP)], 4f, was isolated in the solid state when X = S, but mixture of fac,cis-[Tc(N)Cl2(PSP)] and mer,trans-[Tc(N)Cl2(PSP)], 4m, isomers was found in equilibrium in the solution state. A similar equilibrium between fac,cis-[M(N)Cl2(POP)] (M = Tc, 5f; M = Re, 9f) and mer,trans-[M(N)Cl2(POP)] (M = Tc, 5m; M = Re, 9m) species was detected in POP containing complexes. The molecular structure of all of these complexes were assessed by means of conventional physico-chemical techniques including multinuclear NMR spectroscopy and X-ray diffraction analysis of representative mer,cis-[Tc(N)Cl2(PN(H)P)] 1, fac,cis-[Tc(N)Cl2(PSP)] 4f, and mer,cis-[Re(N)Cl2(PN(Me)P)] 8m compounds.
  • Inorganic Chemistry 43(2004), 8617-8625

Publ.-Id: 6750 - Permalink


In-situ Charakterisierung während der Hochenergie - Sauerstoffionen - Implantation in Übergangsmetalle
Bohne, Y.; Shevchenko, N.; Prokert, F.; von Borany, J.; Rauschenbach, B.; Möller, W.; Keywords: In-situ, Implantation, Übergangsmetalle, Oxid
  • Poster
    DPG - spring meeting, Regensburg, March 8-12, 2004

Publ.-Id: 6749 - Permalink


Surface processes and properties of ion implanted NiTi alloy
Shevchenko, N.; Pham, M.-T.; Richter, E.; Maitz, M. F.; Keywords: NiTi, ion implantation, surface, biocompatibility
  • Poster
    9th International conference on plasma surface engineering, Garmisch-Partenkirchen, Germany, September 13 - 17, 2004

Publ.-Id: 6748 - Permalink


3-O-Methyl-6-18F-Fluoro-L-Dopa, a New Tumor Imaging Agent: Investigation of Transport Mechanism In Vitro
Bergmann, R.; Pietzsch, J.; Füchtner, F.; Pawelke, B.; Beuthien-Baumann, B.; Johannsen, B.; Kotzerke, J.;
18F-Labeled amino acids represent a promising class of imaging agents in tumors, particularly brain tumors. However, the determination of their potential to image peripheral tumors, possibly depending on individual transport characteristics, still remains an area of investigation. The present study investigated the transport mechanism for 3-O-methyl-618F-fluoro-L-dopa (OMFD), a novel 18F-labeled phenylalanine derivative, into tumor cells. Methods: OMFD has routinely and reliably been prepared for clinical use in 20 % - 25 % radiochemical yield (decay corrected, related to 18F-F2) using 6-18F-fluoro-L-3,4-dihydroxyphenylalanine preparation devices with minor modifications. In vitro uptake assays with HT-29 (human colon adenocarcinoma) cells, FaDu (squamous cell carcinoma) cells, and RBE4 (immortalized rat brain endothelial) cells were performed with OMFD under physiologic amino acid concentrations without and with the competitive transport inhibitors 2-aminobicyclo[2,2,1]-heptane-2-carboxylic acid and α-(methylamino)isobutyric acid plus serine and without or with Na+. Results: Transport inhibition experiments using specific competitive inhibitors demonstrated that uptake of OMFD in all cell lines tested was mediated mainly by the sodium-independent high-capacity amino acid transport systems. The highest OMFD uptake was in FaDu cells. Conclusion: OMFD seems to be a promising PET tracer for imaging of amino acid transport in tumors.
Keywords: amino acid transport; 18F; PET; radiotracer
  • Journal of Nuclear Medicine 45(2004), 2116-2122

Publ.-Id: 6747 - Permalink


Fluid-dynamic instabilities during mass transfer across the interface between to immiscible liquids
Grahn, A.; Prasser, H.-M.;
Experiments and simulations were conducted in a vertically oriented Hele-Shaw cell. Buoyancy driven convection, in particular plumes and double diffusive fingering as well as surface tension driven convection in the form of roll cells have been found in the experiments and reproduced numerically. The calculations reveal the mechanism of the enhancement of mass transfer rates in the presence of the instabilities. The model can be used to predict the mass transfer for the simple geometry of a flat surface.
Keywords: double diffusive instability, Marangoni effect, mass transfer, chemical reaction
  • Contribution to proceedings
    6th world conference on experimental heat transfer, fluid mechanics and thermodynamics, 17.-21.04.2005, Miyagi, Japan

Publ.-Id: 6746 - Permalink


Improvements of tribological properties of CrNiMo and CrCoMo alloys by nitrogen plasma immersion ion implantation
Ueda, M.; Berni, L. A.; Castro, R. M.; Reuther, H.; Lepienski, C. M.; Soares Jr., P. C.;
Improvements of tribological properties of CrNiMo and CrCoMo alloys by nitrogen plasma immersion ion implantation
  • Lecture (Conference)
    9th International Conference on Plasma Surface Engineering, September 13 - 17, 2004, Garmisch-Partenkirchen

Publ.-Id: 6744 - Permalink


Chromium enrichment of AISI 304 stainless steel surface after nitrogen ion recoil bombardment of chromium film
Gomes, G. F.; Ueda, M.; Beloto, A. F.; Reuther, H.; Richter, E.;
Chromium enrichment of AISI 304 stainless steel surface after nitrogen ion recoil bombardment of chromium film
  • Lecture (Conference)
    8th European Conference on Accelerators in Applied Research and Technology September 20-24, 2004 Paris

Publ.-Id: 6743 - Permalink


Comparison of nitrogen ion beam and plasma immersion implantation in Al5052 alloy
Ueda, M.; Reuther, H.; Lepienski, C. M.;
Comparison of nitrogen ion beam and plasma immersion implantation in Al5052 alloy
  • Lecture (Conference)
    8th European Conference on Accelerators in Applied Research and Technology September 20-24, 2004, Paris, France

Publ.-Id: 6742 - Permalink


Plasma immersion ion implantation of nitrogen into H13 steel under moderate temperatures
Ueda, M.; Leandro, C.; Reuther, H.; Lepienski, C. M.;
Plasma immersion ion implantation of nitrogen into H13 steel under moderate temperatures
  • Lecture (Conference)
    8th European Conference on Accelerators in Applied Research and Technology September 20-24, 2004, Paris, France

Publ.-Id: 6741 - Permalink


Sn4+ charge density variation in In2O3
Reuther, H.; Menzel, M.; Vinnichenko, M.; Kolitsch, A.;
Thin tin-doped indium oxide films have a low resistivity (10-3-10-4 W·cm) and a high luminous transmittance (>80%) [1]. Therefore they find an application as electrodes in flat panel displays, solar cells, etc.
The lowest resistivities (in the order of 1·10-4 W·cm) are reported for ITO films prepared by sputtering of ceramic targets which are expensive and mechanically fragile. The stable process with metallic targets can be much more favorable for industrial application, because of low cost and high deposition rates. The production of ITO films with low resistivity by reactive sputtering usually requires postdeposition annealing step or deposition on heated substrates [1].
A number of publications were devoted to investigate ITO powders with different Sn content [2] and ITO films subjected to oxidizing and reducing annealing [3]. These films were prepared from ceramic targets. Mössbauer spectroscopy in combination with X-ray diffraction and Hall measurements have been applied in these studies on ITO to investigate the chemical state of Sn atoms.
Similar investigations on the ITO films prepared by reactive magnetron sputtering at elevated substrate temperatures are missing up to now. Therefore indium-tin oxides (ITO) films were deposited by reactive middle frequency dual magnetron sputtering at heated substrates.
The doping of Sn in In2O3 was investigated using the surface sensitive 119mSn Conversion-Electron Mössbauer Spectroscopy (CEMS) to investigate the chemical state of tin.

  • Poster
    International Symposium on the Industrial Applications of the Mössbauer Effect, 4-9 October, 2004. Madrid

Publ.-Id: 6740 - Permalink


Einfluss unvermeidbarer Patientenbewegungen auf PET-Hirnuntersuchungen
Bühler, P.; Langner, J.; Kotzerke, J.; van den Hoff, J.;
  • Abstract in refereed journal
    Nuklearmedizin 43(2004), V196
  • Lecture (Conference)
    42. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-24.04.2004, Rostock, Germany

Publ.-Id: 6739 - Permalink


Scanning capacitance microscopy and spectroscopy on SiO2 films with embedded Ge and Si nanoclusters
Beyer, R.; Beyreuther, E.; von Borany, J.; Weber, J.;
Scanning capacitance microscopy (SCM) and -spectroscopy (SCS) were applied to study the charge trapping and the charge retention in silicondioxide layers with embedded Ge- or Si-nanoclusters. The nanoclusters were formed by ion beam synthesis. Applying a dc bias to the conductive nano-tip charge injection into the dielectric was achieved. While SCM images visualize the localized trapped charge in the oxide, the locally recorded dC/dV versus V curves allow to quantify the trap density. The evaluation of dCldV shifts was used to compare the electronic properties of different oxide layers in dependence on the implantation parameters. In addition it is demonstrated, that combined SCM/SCS measurements are a suitable tool for the examination of the charge decay as well as of the reliability and degradation of oxide layers on a nanoscale.
Keywords: Interface states, Charge, Junctions, Dynamics, Layer
  • Microelectronic Engineering 72(2004), 207-212

Publ.-Id: 6738 - Permalink


Luminescence center transformation in wet and dry SiO2
Fitting, H.-J.; Ziems, T.; von Czarnowski, A.; Schmidt, B.;
The main luminescent centers in SiO2 films are the red luminescence R (1.85 eV) of the nonbridging oxygen hole center (NBOHC) and the oxygen deficient center (ODC) with a blue B (2.7 eV) and a UV (4.4 eV). By means of a new "track-stop" technique we have investigated especially the initial luminescence behaviour at the beginning of irradiation. Thus the blue-emitting center is produced under irradiation , but from existing precursers. Contrary to that, the dose behaviour of the red (R) luminescence in wet and dry oxide is quite different, decreasing in wet oxide from a high initial level and increasing in dry oxide from almost zero. We propose a model of luminescence center transformation based on radiolytic dissociation and the reactions of mobile oxygen and hydrogen.
Keywords: Cathodoluminescence, irradiation dose, center transformation, precursers
  • Radiation Measurements 38(2004), 649-753

Publ.-Id: 6737 - Permalink


Ion-beam Synthesis of Nanocrystals for Multidot Memory Structures
Beyer, V.; von Borany, J.;
not available
  • Contribution to external collection
    E.Zschech, C.Whelan, T.Mikolajick: Materials for Information Technology - Devices, Interconnects and Packaging; Series: Engineering Materials and Processes, Berlin: Springer-Verlag, 2005, 1-85233-941-1

Publ.-Id: 6736 - Permalink


Dendrimers for Separation Processes
Gloe, K.; Antonioli, B.; Gloe, K.; Stephan, H.;
kein Abstract verfügbar
  • Contribution to external collection
    C. A. M. Afonso, J. G. Crespo: Green Separation Processes, Weinheim: Wiley-VCH, 2005, 3-527-30985-3, 304-322

Publ.-Id: 6728 - Permalink


Untersuchungen zur Kühlmittelvermischung: Ergebnisse numerischer Simulationen mit CFX-5 im Vergleich mit experimentellen Ergebnissen an der Vermischungsanlage ROCOM
Höhne, T.;
The coolant mixing in the downcomer and the lower plenum of pressurized water reactors (PWR) is significant for safety assessment of boron dilution and cold water transients.

The research project FLOMIX-R within the 5th Framework Programme of EC had the objective to obtain experimental data on the relevant coolant mixing phenomena using improved measurement techniques with enhanced resolution in space and time for CFD validation.

Recent experiments at the Rossendorf test facility ROCOM were integrated into this research project. ROCOM is a 1:5 scaled Plexiglas model of a German PWR allowing conductivity measurements by wire mesh sensors for analyzing the mixing pattern at selected positions in the reactor pressure vessel and velocity measurements by LDA technique.

A few benchmark problems based on selected experiments were used to study the effect of different turbulent mixing models under various flow conditions, to investigate the influence of the geometry, the boundary conditions, the grid and the time step in the CFD analyses. In doing the calculations the Best Practice Guidelines for nuclear reactor safety calculations have been followed. Results of this numerical mixing studies will be discussed.
Keywords: Boron Dilution, CFD, Kühlmittelvermischung, Borverdünnung
  • Invited lecture (Conferences)
    Forschungzentrum Karlsruhe, Insitut für Reaktorsicherheit, Seminarreihe 2004/2005, 13.01.2005, Karlsruhe, Germany

Publ.-Id: 6727 - Permalink


Transient effects in fission from new experimental signatures
Jurado, B.; Schmitt, C.; Schmidt, K.-H.; Benlliure, J.; Enqvist, T.; Junghans, A. R.; Kelic, A.; Rejmund, F.;
A new experimental approach is introduced to investigate the relaxation of the nuclear deformation degrees of freedom. Highly excited fissioning systems with compact shapes and low angular momenta are produced in peripheral relativistic heavy-ion collisions. Both fission fragments are identified in atomic number. Fission cross sections and fission-fragment element distributions are determined as a function of the fissioning element. From the comparison of these new observables with a nuclear-reaction code a value for the transient time is deduced.

Publ.-Id: 6726 - Permalink


Electroproduction of Strangeness on 3,4λH bound states on Helium
Dohrmann, F.; Ahmidouch, A.; Armstrong, C. S.; Arrington, J.; Asaturyan, R.; Avery, S.; Bailey, K.; Baker, O. K.; Bitao, H.; Breuer, H.; Brown, D. S.; Carlini, R.; Cha, J.; Chant, N.; Christy, E.; Cochran, A.; Cole, L.; Crowder, J.; Danagoulian, S.; Elaasar, M.; Ent, R.; Fenker, H.; Fujii, Y.; Gan, L.; Garrow, K.; Geesaman, D. F.; Gueye, P.; Hafidi, K.; Hinton, W.; Juengst, H.; Keppel, C.; Liang, Y.; Liu, J. H.; Lung, A.; Mack, D.; Markowitz, P.; Mitchell, J.; Miyoshi, T.; Mkrtchyan, H.; Mtingwa, S. K.; Mueller, B.; Niculescu, G.; Niculescu, I.; Potterveld, D. H.; Raue, B. A.; Reimer, P. E.; Reinhold, J.; Roche, J.; Sarsour, M.; Sato, Y.; Segel, R. E.; Semenov, A. Y.; Stepanyan, S.; Tadevosian, V.; Tajima, S.; Tang, L.; Uzzle, A.; Wood, S.; Yamaguchi, H.; Yan, C.; Yuan, L.; Zeier, M.; Zeidman, B.; Zihlmann, B.;
The A(e,e'K+)X reaction has been investigated at Jefferson Laboratory. Data were taken for Q2 approx 0.35\,\rm GeV2 at a beam energy of 3.245 GeV for 1H,3He and 4He targets.
Evidence for Lambda-hypernuclear bound states is seen for 3,4He targets. This is the first time that the electroproduction of these hypernuclei has been observed.
Keywords: Electroproduction of Strangeness, Hyperons, Hypernuclear Physics
  • Contribution to proceedings
    AIP Conference Proceedings 768(2005), 294, Proceedings of the 19th European Conference on Few-Body Problems in Physics

Publ.-Id: 6725 - Permalink


Application of ultra-high energy boron implantation for superjunction power (CoolMOS) devices
von Borany, J.; Friedrich, M.; Rüb, M.; Deboy, G.; Butschke, J.; Letzkus, F.;
Superjunction devices (SJDs) are a novel class of power devices which break the physical limit of silicon with respect to the area specific turn-on-resistance. SJDs consist of a modified vertical MOSFET structure which is characterized by additional deep pillar-like p-type regions formed inside the n(-) epi-layer below the transistor gate. In the present investigation ultra-high energy boron ion implantation of 2-25 MeV were applied for forming the deep p-type regions laterally structured using Si stencilmasks. For energies above 12 MeV the incident ions exceed the Coulomb barrier for Si which leads (i) to a significant gamma and neutron emission during implantation and, (ii) an activation of the wafer and the mask material. Fortunately, the most relevant reaction (11B+28Si >n,alpha>34mCl> 34S+beta) has a half-life time of only 32 min so that the radiation level of the wafers drops below the critical radiation protection limit within the processing time. Based on the described technology Infineon Technologies successfully prepared a set of prototype wafers with fully functional high-voltage transistors. Typical blocking capability was in the range of 560 V with an on-state resistance of about 185 mOhm.
Keywords: Power devices, Si doping, Ultra-high energy ion implantation, nuclear reactions
  • Lecture (Conference)
    15th Intern. Conference on Ion Implantation Technology 2004, 24.-29.10.2004, Taipeh, PR China (Taiwan)
  • Nuclear Instruments and Methods in Physics Research B 237(2005), 62-67

Publ.-Id: 6724 - Permalink


In-situ X-ray diffraction investigations during high-energy oxygen ion iplantation in transition metals
Bohne, Y.; Shevchenko, N.; Prokert, F.; von Borany, J.; Rauschenbach, B.; Moeller, W.;
An in-situ X-ray diffraction study was performed to characterize aspects of the kinetics of struc-tural phase formations in transition metals during oxygen implantation. A special designed high-temperature vacuum chamber for X-ray measurements was installed at the high-energy implantation beamline of the 3 MV-Tandetron accelerator. Titanium and molybdenum sheets were implanted with oxygen ions with an energy of 1.5 MeV up to a fluence of 1.6 × 1018 O+-ions/cm2 without sample cooling. During implantation, the phase formation was continually investigated by in-situ and real-time X-ray diffraction (XRD) with a position sensitive proportional counter system. The phase formation was studied during annealing treatments by in-situ XRD. The obtained results were com-pared with ex-situ XRD measurements performed by different techniques at a standard diffractometer. The analysis of XRD patterns indicates the formation of a buried MoO2 layer in molybdenum. In the Ti-samples no buried oxide is formed due to significant oxygen diffusion.
Keywords: In-situ XRD, Ion implantation, Transition metals, Phase formation
  • Contribution to proceedings
    13th International School on Vacuum, Electron and Ion Technologies, 15 – 19 September, 2003, Varna, Bulgaria
  • Vacuum 76(2004)2-3, 281-285

Publ.-Id: 6723 - Permalink


86Y-Markierung von Neurotensin(8-13)-Derivaten
Schlesinger, J.; Bergmann, R.; Seifert, S.; Wüst, F.;
  • Lecture (others)
    12. Jahrestagung der AG Radiochemie/Radiopharmazie, 23.-25.09.2004, Walberberg, Germany

Publ.-Id: 6722 - Permalink


Rhenium-188-Gemischtligandkomplexe mit Phoshinliganden: Stabilitätsbetrachtungen
Schiller, E.;
  • Lecture (others)
    12. Jahrestagung der AG Radiochemie/Radiopharmazie, 23.-25.09.2004, Walberberg, Germany

Publ.-Id: 6721 - Permalink


Untersuchungen zur Bioverteilung und Elimination des Isopeptides N-ε-(γ-Glutamyl)-lysin mittels Positronen-Emissions-Tomographie
Hultsch, C.; Bergmann, R.; Pawelke, B.; Pietzsch, J.; Wüst, F.; Johannsen, B.; Henle, T.;
  • Lecture (Conference)
    14. Arbeitstagung der Lebensmittelchemischen Gesellschaft – Fachgruppe in der Gesellschaft Deutsche Chemiker Regionalverband Süd-Ost, 01.-02.04.2004, Halle, Germany
  • Lecture (Conference)
    11. Jahrestagung der AG Radiochemie/Radiopharmazie, Leipzig-Brehna, 18.09.2003

Publ.-Id: 6720 - Permalink


Neuartige Re-188-Komplexe abgeleitet von Dimercaptobernsteinsäure
Heinrich, T.;
  • Lecture (others)
    12. Jahrestagung der AG Radiochemie/Radiopharmazie, 23.-25.09.2004, Walberberg, Germany

Publ.-Id: 6719 - Permalink


Ultrafast carrier dynamics in nitrogen containing GaAs
Dekorsy, T.; Sinning, S.; Helm, M.; Mussler, G.; Daweritz, L.; Ploog, K. H.;
Poster of experimental results of time resolved carrier relaxation of nitrogen containing GaAs
Keywords: GaNAs, MBE, Implantation, carrier relaxation, nitrogen, III-V, ultrafast
  • Poster
    presented at the 27th International Conference on the Physics of Semiconductors (ICPS) ,July 25-30, 2004 in Flagstaff, Arizona, USA.
  • Contribution to proceedings
    27th Int. Conf. on the Physics of Semiconductors, 26.-30.07.2004, Flagstaff, AZ, USA
    American Institute of Physics Conference Proceedings 772(2005), 235-236

Publ.-Id: 6718 - Permalink


Rhenium-188: Chemie eines therapeutischen interessanten Radionuklides
Heinrich, T.;
  • Invited lecture (Conferences)
    Bundesanstalt für Materialforschung und –prüfung, 19.03.2004, Berlin, Germany

Publ.-Id: 6717 - Permalink


Synthese und radiopharmakologische Untersuchung eines 18F-markierten Resveratrolderivates
Gester, S.; Pietzsch, J.; Wüst, F.;
  • Lecture (others)
    12. Jahrestagung der AG Radiochemie/Radiopharmazie, 23.-25.09.2004, Walberberg, Germany

Publ.-Id: 6716 - Permalink


Ultrafast carrier dynamics in nitrogen implanted GaAs
Sinning, S.; Dekorsy, T.; Helm, M.;
We report on the comparative analysis of the ultrafast carrier dynamics of pure GaAs and ion-implanted GaNAs. Different nitrogen concentrations (up to 4%) are implanted and subsequently annealed by rapid thermal annealing (RTA). Damage analysis by channeling Rutherford backscattering (RBS) reveals that the annealing step improves the crystal quality but does not restore the original quality. From photoreflectance measurements we conclude that the highest achieved active nitrogen content in the implanted samples is 0.5% for an equivalent implantation dose of 1%. Carrier dynamics are investigated by one-colour pump-probe measurements covering an excitation wavelength range from 730nm to 860nm (1.7eV to 1.44eV) with femtosecond time resolution. Comparison with non-implanted GaAs indicates that the carrier relaxation in the implanted samples is dominated by traps associated with implantation damage.
Keywords: GaNAS, Implantation, Nitrogen, ultrafast, carrier dynamics, carrier relaxation

Publ.-Id: 6715 - Permalink


Ladungsträger-Dynamik in Stickstoff-implantiertem GaAs
Sinning, S.; Dekorsy, T.; Helm, M.;
III-V-Halbleitern mit geringen Stickstoffkonzentrationen gelten sowohl als Materialsystem als auch für Anwendungen seit einiger Zeit gr¨oßeres Interesse. Neben epitaktischen Methoden bietet die Ionen-Implantation einen effektiven Weg zur Einbringung des Stickstoffs in das Substrat. Nachteil dieses Verfahrens ist der dem Gitter durch die Ionen-Implantation zugefügte Schaden.
Wir untersuchen die Effektivität des Einbaus von aktivem Stickstoff nach Implantation und thermischer Ausheilung (RTA). Bei RTA-Bedingungen von 650°C/30s ist der Einbau des Stickstoffs in die Matrix optimal. Eine Verbesserung der Gitterqualität kann durch Implantation bei erhöhten Temperaturen (T > 200°C) erreicht werden. Die Ladungsträger-Dynamik im sub-Pikosekunden-Bereich für Implantationen bei Raumtemperatur und bei erhöhten Temperaturen wird mit der von nicht-implantiertem GaAs verglichen. Es werden signifikante Unterschiede beobachtet, die auf eine starke Modifizierung der Bandstruktur des stickstoffhaltigen GaAs zurückzuführen sind.
Keywords: GaNAs, Stickstoff, III-V, RTA, Implantation, Dynamik, ultrafast
  • Lecture (Conference)
    DPG-Tagung, Frühjahrs-Tagung des Arbeitskreises Festkörperphysik, 08.-12.03. 2004, Regensburg, Deutschland

Publ.-Id: 6714 - Permalink


Ultrafast carrier dynamics in nitrogen containing GaAs
Sinning, S.; Dekorsy, T.; Helm, M.; Mussler, G.; Daweritz, L.; Ploog, K. H.;
Poster of experimental results of time resolved carrier dynamics of nitrogen containing GaAs.
Keywords: GaNAs, Nitrogen, III-V, ultrafast, carrier dynamics
  • Poster
    presented at the EMRS 2004, Strasbourg, France, May 24-28, 2004

Publ.-Id: 6713 - Permalink


Magnetic field controlled solidification of Nd-Fe-B melts
Hermann, R.; Filip, O.; Gerbeth, G.; Priede, J.; Shatrov, V.;
The reduction of the a-Fe volume fraction and the a-Fe grain size represents a known objective for the improvement of this magnet material. It is attained here by a controlled influence on the melt flow via tailored magnetic fields. The reduction of the internal melt motion results in a significant decrease of the a-Fe volume fraction in the solidified Nd-Fe-B material.

  • Poster
    Konferenz "High performance magnets and their applications", Annecy (France), 29.8.-2.9.2004

Publ.-Id: 6712 - Permalink


Multiplicity correlations of intermediate-mass fragments with pions and fast protons in C-12+Au-197
Turzo, K.; Auger, G.; Begemann-Blaich, M.; Et Al.;
Low-energy pi(+) (E-pi less than or similar to 35 MeV) from C-12 + Au-197 collisions at incident energies from 300 to 1800 MeV per nucleon were detected with the Si-Si(Li)-CsI(Tl) calibration telescopes of the INDRA multidetector. The inclusive angular distributions are approximately isotropic, consistent with multiple rescattering in the target spectator. The multiplicity correlations of the low-energy pions and of energetic protons (E-p greater than or similar to 150 MeV) with intermediate-mass fragments were determined from the measured coincidence data. The deduced correlation functions 1 + R approximate to 1.3 for inclusive event samples reflect the strong correlations evident from the common impact parameter dependence of the considered multiplicities. For narrow impact parameter bins (based on charged-particle multiplicity), the correlation functions are close to unity and do not indicate strong additional correlations. Only for pions at high particle multiplicities (! central collisions) a weak anticorrelation is observed, probably due to a limited competition between these emissions. Overall, the results are consistent with the equilibrium assumption made in statistical multifragmentation scenarios. Predictions obtained with intranuclear-cascade models coupled to the Statistical Multifragmentation Model are in good agreement with the experimental data.

Publ.-Id: 6711 - Permalink


Dendritic Carriers and Cage Compounds for Radionuclides
Stephan, H.;
  • Invited lecture (Conferences)
    Kolloquium, Department of Materials Science, JAERI, Tokai-mura (Japan), 26.11.2003

Publ.-Id: 6709 - Permalink


Solvent Extraction As a Helpful Tool for the Characterisation of Supramolecular Receptors
Stephan, H.;
  • Invited lecture (Conferences)
    Kolloquium, Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, Tokyo (Japan), 25.11.2003

Publ.-Id: 6708 - Permalink


Novel Approaches for Binding Therapeutically Relevant Copper and Rhenium Radionuclides
Stephan, H.;
  • Invited lecture (Conferences)
    Kolloquium, Department of Chemistry, Tohoku University, Sendai (Japan), 19.11.2003

Publ.-Id: 6707 - Permalink


Development of Rhenium Complexes and Metal Clusters for Therapy
Stephan, H.;
  • Invited lecture (Conferences)
    Kolloquium, Department of Applied Chemistry, Saga University, Saga (Japan), 14.11.2003
  • Invited lecture (Conferences)
    Kolloquium, Department och Chemical Processes and Environments, University Kitakyushu, Kitakyushu, Japan, 11.11.2003

Publ.-Id: 6706 - Permalink


Development of Highly Stable Rhenium Complexes
Stephan, H.;
  • Invited lecture (Conferences)
    Kolloquium, Department of Chemical Processes and Environments, University Kitakyushu, Kitakyushu (Japan), 11.11.2003

Publ.-Id: 6705 - Permalink


Design of a Travelling Magnetic Field for Vertical Gradient Freeze - Crystal Growth
Lantzsch, R.; Galindo, V.; Gerbeth, G.; Cröll, A.;
The melt flow in the vertical Gradient Freeze growth of GaAs can efficiently be controlled by an external travelling magnetic field. The latter directly provides for a poloidal flow in the molten part. Controlling this flow offers the possibility to influence the interface shape, to increase the growth rate or to improve the homogeneity of the crystal. We report on the design of the magnetic field system and preliminary flow measurements with it.

  • Lecture (Conference)
    Workshop „Angewandte Simulation in der Kristallzüchtung“, 05.-06.02.2004, Volkach, Germany

Publ.-Id: 6704 - Permalink


Calorimetric and Potentiometric Study of PAMAM Dendrimers: Protonation and Interactions with Human Serum Albumin
Kirchner, R.; Seidel, J.; Gloe, K.; Stephan, H.;
  • Poster
    3rd International Dendrimer Symposium, Berlin, 17.–20.09.2003

Publ.-Id: 6703 - Permalink


Development of Dendrons for Binding Rhenium Radionuclides
Appelhans, D.; Clausnitzer, C.; Gloe, K.; Johannsen, B.; Spies, H.; Stephan, H.; Stute, S.; Voit, B.;
  • Poster
    3rd International Dendrimer Symposium, Berlin, 17.–20.09.2003

Publ.-Id: 6702 - Permalink


Dendritic Receptors for Binding Therapeutically Relevant Copper and Rhenium Radionuclides
Stephan, H.;
  • Lecture (Conference)
    10th International Conference “Separation of Ionic Solutes”, Podbanske (Slovakia), 06.–11.09.2003

Publ.-Id: 6701 - Permalink


Preparation and Characterisation of Polyoxotungstates
Stephan, H.; Sawatzki, A.-K.;
  • Lecture (others)
    Institutskolloquium, Institute of Chemical Technology Prag, 20.08.2003

Publ.-Id: 6700 - Permalink


Neue Rhenium- und Kupfer-Koordinationsverbindungen für die Radiotherapie
Stephan, H.;
  • Invited lecture (Conferences)
    Institutskolloquium, Universität Heidelberg, Institut für Anorganische Chemie, 30.06.2003

Publ.-Id: 6699 - Permalink


Oxathiaaza-Makrocyclen: Potentielle Extraktionsmittel für Metallionen und Metallsalze
Antonioli, B.; Gloe, K.; Goretzki, G.; Glenny, M. W.; Schröder, M.; Herrmann, E.; Stephan, H.;
  • Lecture (others)
    DECHEMA-Sitzung „Das Neue geschieht an den Grenzflächen“, Würzburg, 05.-07.03.2003

Publ.-Id: 6698 - Permalink


Supramolecular Systems in the Design of Radiopharmaceuticals
Stephan, H.; Johannsen, B.;
  • Lecture (others)
    Workshop FWB Rossendorf/Schering AG, Hinterhermsdorf, 4. – 5. April 2002

Publ.-Id: 6697 - Permalink


Synergistic Solvent Extraction of Cu(II), Zn(II), and Ni(II) Based on Supramolecular Assemblies
Gasperov, V.; Gloe, K.; Leong, A. J.; Lindoy, L. F.; Mahinay, M. S.; Stephan, H.; Tasker, P. A.; Wichmann, K.;
  • Lecture (Conference)
    Int. Solvent Extraction Conference 2002, Cape Town (South Africa), 17 – 21 März 2002

Publ.-Id: 6696 - Permalink


Binding and in vitro transport behaviour of polyoxotungstates in the presence of aminosaccharides
Stephan, H.; Bergmann, R.; Rode, K.; Röllich, A.; Sawatzki, A.-K.; Inoue, K.; Jelínek, L.; Parschová, H.; Matejka, Z.;
  • Lecture (Conference)
    International Conference on Supramolecular Science & Technology , 05.-09.09.2004, Prag, Czech Republic
  • Contribution to proceedings
    Chemické Listy 98(2004), s35-36

Publ.-Id: 6695 - Permalink


Octahedral Rhenium Cluster Complexes with Organic Ligands as New Preparations for Medical Applications
Fedorov, V.; Mironov, Y.; Shestopalov, M.; Brylev, K.; Yarovoi, S.; Spies, H.; Pietzsch, H.-J.; Stephan, H.; Kraus, W.;
  • Lecture (Conference)
    Topical Meeting of the European Ceramic Society “Nanostuctures & Nanocomposites”, 05.-07.07.2004, St. Petersburg, Russia

Publ.-Id: 6694 - Permalink


Interaction of Polyoxotungstates with Aminosaccharide Based Sorbents: Sorption Kinetics, Complex Stability and Implications for the Therapeutic Application of Polyoxotungstates
Jelínek, L.; Krotká, P.; Burda, R.; Parschová, H.; Matejka, Z.; Sawatzki, A.-K.; Röllich, A.; Stephan, H.;
  • Lecture (Conference)
    XVIVth International Symposium “Ars Separatoria 2004”, 10.-13.06.2004, Potok, Poland
  • Contribution to proceedings
    Proceedings of the XIXth International Symposium “Ars Separatoria 2004”, 86-88

Publ.-Id: 6693 - Permalink


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