Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31745 Publications
Modeling and regrowth mechanisms of flash lamp processing of SiC-on-silicon heterostructures
Smith, M.; Mcmahon, R.; Voelskow, M.; Skorupa, W.;
This paper describes the development of a thermal model for flash lamp processing of 3C-SiC on silicon substrates in the millisecond regime, the FLASiC process. The model is a numerical solution of the enthalpy equation, using a modified implicit Crank-Nicholson scheme to combine accurate prediction of melt depths with reasonable computation times. The model has been calibrated against experiments and then used to compute the temperature distribution in the wafer during annealing. The results show the time and extent of melting as a function of layer thickness, wafer preheat temperature, and pulse intensity and duration. The kinetics of melting and regrowth have also been considered.
Keywords: flash lamp, SiC, annealing, implantation

Publ.-Id: 6932 - Permalink


Hochfrequenz-Elektronenquelle
Janssen, D.;
Der Erfindung liegt die Aufgabe zugrunde, die Erzeugung eines Elektronenstrahls mit einer extrem großen mittlerer Leistung und einer kleinen Emittanz mit einem einfachen HF-Koppler und geringen Kosten bei koaxialer Einkopplung und variabler externer Güte sowie geringer thermischer Belastung des supraleitenden Resonators zu erreichen.
  • Patent
    Patentanmeldung DE 10 2004 055 256.8

Publ.-Id: 6931 - Permalink


Kohärente Terahertz-Strahlungsquelle
Dekorsy, T.; Dreyhaupt, A.; Winnerl, S.; Helm, M.;
Die Strahlungsquelle kann im Frequenzbereich von 10 GHz bis 50 THz arbeiten und spezielle Parameter erfüllen.
  • Patent
    Patentanmeldung DE 10 2004 046 123.6

Publ.-Id: 6929 - Permalink


Insulinresistenz (IR) und Lipoprotein (Lp)-subfraktionen (Sf) bei verschiedenen Graden der Glukosetoleranz (GT)
Weck, A.; Julius, U.; Pietzsch, J.;
  • Poster
    39. Jahrestagung der Deutschen Diabetes-Gesellschaft, Hannover, 19.-22.05.2004
  • Abstract in refereed journal
    Diabetes und Stoffwechsel 13(2004), 117

Publ.-Id: 6928 - Permalink


Rheumatoid arthritis synovial fluid LDL induce monocyte chemotaxis and adhesion
Pietzsch, J.; Bergmann, R.; Kopprasch, S.;
  • Poster
    74th European Atherosclerosis Society Congress, Seville, 17.-20.04.2004
  • Abstract in refereed journal
    Atherosclerosis 5(2004)Suppl. 1, 16

Publ.-Id: 6927 - Permalink


Anlage zur gesteuerten Erstarrung von Schmelzen elektrisch leitender Medien
Eckert, S.; Nikrityuk, P.; Grundmann, R.; Eckert, K.;
Es werden Instabilitäten gedämpft und das Kornwachstum während der Erstarrung von Legierungen gesteuert.
  • Patent
    Patentanmeldung DE 10 2004 044 637.7

Publ.-Id: 6926 - Permalink


Analysis of specific markers of protein oxidation in rheumatoid arthritis plasma and synovial fluid LDL
Pietzsch, J.; Bergmann, R.; Kopprasch, S.;
  • Poster
    74th European Atherosclerosis Society Congress, Seville, Spain, 17.-20.04.2004
  • Abstract in refereed journal
    Atherosclerosis 5(2004)Suppl. 1, 16

Publ.-Id: 6925 - Permalink


Integration nuklearmedizinischer Bilder in die Bestrahlungsplanung des nichtkleinzelligen Bronchialkarzinoms
Oehme, L.; Hoinkis, C.; Appold, S.; Beuthien-Baumann, B.; Pötzsch, C.; Baumann, M.; Kotzerke, J.;
  • Poster
    42. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-24.04.2004, Rostock

Publ.-Id: 6924 - Permalink


P0408-Faseroptischer Sensor zur Bestimmung von Stoff- und Phasenverteilungen
Hampel, U.; Schleicher, E.;
Es ist ein Sensor dargestellt, der in der Lage ist, die Stoffzusammensetzung mittels faseroptischer Refrakometrie an einer Vielzahl räumlicher Punkte eines Untersuchungsvolumens gleichzeitig zu messen, ohne eine Vielzahl von Anordnungen zu verwenden.
  • Patent
    Patentanmeldung DE 10 2004 037 883.5

Publ.-Id: 6923 - Permalink


Increased LDL apolipoprotein B-100 oxidation in IGT and overt Type 2 diabetes
Julius, U.; Pietzsch, J.;
  • Poster
    64th Scientific Sessions of the American Diabetes Association (ADA), Orlando, USA, 04.-08.06.2004
  • Abstract in refereed journal
    Diabetes 53(2004), A231

Publ.-Id: 6922 - Permalink


Vorrichtung zur Vermeidung von Druckstößen in Rohrleitungssystemen
Prasser, H.; Dudlik, A.; Apostolidis, A.; Schlüter, S.; Wickl, G.;
Es wird eine kostengünstig zu realisierende und zuverlässig arbeitende Armatur in Rohrleitungssystemen angegeben.
  • Patent
    Patentanmeldung DE 10 2004 025 983.6
  • Patent
    DE 10 2004 025 983 B4 - 06. Sept. 2007

Publ.-Id: 6921 - Permalink


Metallkomplexe auf der Basis von Tetrathiol-Liganden und deren Anwendung in der nuklearmedizinischen Diagnostik und Endoradionuklidtherapie sowie Verfahren zur Herstellung der Metallkomplexe
Heinrich, T.; Johannsen, B.; Pietzsch, H.; Seifert, S.; Spies, H.;
Es werden radiolytisch und metabolisch stabile Metallkomplexe vorgeschlagen, die zur Konjugation mit Biomolekülen geeignet sind sowie ein Verfahren zu ihrer Herstellung.
  • Patent
    DE 10 2004 022 461 A1

Publ.-Id: 6920 - Permalink


Effect of low density lipoproteins (LDL) isolated from subjects with normal and impaired glucose tolerance on the gene expression of CD36, SR-BI, and PPARγ
Graessler, J.; Westendorf, T.; Kopprasch, S.; Pietzsch, J.; Schroeder, H.;
  • Poster
    74th European Atherosclerosis Society Congress, Seville, 17.-20.04.2004
  • Abstract in refereed journal
    Atherosclerosis 5(2004)Suppl. 1, 83

Publ.-Id: 6918 - Permalink


Lipoprotein kinetics as measured with stable isotopes in familial combined hyperlipidemia and impaired glucose tolerance
Julius, U.; Pietzsch, J.;
  • Poster
    15th International Symposium on Drugs Affecting Lipid Metabolism (DALM), Venedig , 24.-27.10.2004

Publ.-Id: 6917 - Permalink


LDL isolated from subjects with impaired glucose tolerance increase the expression of CD36 and PPARg in macrophages.
Westendorf, T.; Kopprasch, S.; Pietzsch, J.; Graessler, J.;
  • Poster
    15th International Symposium on Drugs Affecting Lipid Metabolism (DALM), Venedig, 24.-27.10.2004

Publ.-Id: 6916 - Permalink


Design and biological evaluation of Tc-99m ligands derived from WAY 100635 for serotonin 5-HT1A receptor binding
Drews, A.; Heimbold, I.; Pietzsch, H.-J.; Johannsen, B.;
  • Contribution to external collection
    Development of Tc-99m Agents for Imaging Central Neural System Receptors, IAEA Technical Reports Series no. 426(2004), Wien, Austria

Publ.-Id: 6915 - Permalink


Transition metal-mediated C-C and C-N bond forming reactions with the short-lived positron emitters 11C and 18F
Wüst, F.;
  • Invited lecture (Conferences)
    Washington University, School of Medicine St. Louis, 12.10.2004, Washington, USA

Publ.-Id: 6914 - Permalink


Radiopharmaceutical Chemistry at the PET Center Rossendorf
Wüst, F.;
  • Invited lecture (Conferences)
    Washington University, School of Medicine St. Louis, 08.10.2004, Washington, USA

Publ.-Id: 6913 - Permalink


Positronen-Emissions-Tomographie (PET): Wie radioaktive Substanzen den Körper biochemisch transparent machen
Wüst, F.;
  • Lecture (others)
    Tag der offenen Tür, Forschungszentrum Rossendorf, 18.09.2004, Dresden, Germany

Publ.-Id: 6912 - Permalink


PET Radiochemistry and the Potential of PET in Drug Development and Evaluation
Wüst, F.;
  • Invited lecture (Conferences)
    Boehringer Ingelheim, 07.04.2004, Germany

Publ.-Id: 6911 - Permalink


Aspekte der PET-Radiochemie in der Lebensmittelchemie
Wüst, F.;
  • Lecture (others)
    1. Workshop Positronen-Emissions-Tomographie in der Lebensmittelforschung, 17.05.2004, Dresden, Germany

Publ.-Id: 6910 - Permalink


In vino sanitas. Den Geheimnissen des Weines auf der Spur
Pietzsch, J.;
  • Lecture (others)
    Vortrag zur „Langen Nacht der Wissenschaften“, 25.06.2004, Dresden, Germany

Publ.-Id: 6909 - Permalink


Metabolismus oxidierter Proteine in vivo: Einblicke mit Kleintier-PET-Untersuchungen
Pietzsch, J.;
  • Lecture (others)
    1. Workshop „Positronen-Emissions-Tomographie in der Lebensmittelforschung“, 17.05.2004, Dresden, Germany

Publ.-Id: 6908 - Permalink


Radiomarkierung von Polyphenolen und Flavonoiden mit PET-Radionukliden
Gester, S.;
  • Lecture (others)
    1. Workshop Positronen-Emissions-Tomographie in der Lebensmittelforschung, 17.05.2004, Dresden, Germany

Publ.-Id: 6907 - Permalink


PET in clinical oncology and research
Beuthien-Baumann, B.;
  • Lecture (others)
    European Master Course in Radiobiology, University College London and Gray Laboratory, 30.01.2004, London, UK

Publ.-Id: 6906 - Permalink


Früh- und Differentialdiagnose von Parkinsonsyndromen: Teilgebiet Nuklearmedizinische Diagnostik
Beuthien-Baumann, B.;
  • Lecture (others)
    Klinische Visite Parkinson, 03.09.2004, Universitätsklinikum Carl Gustav Carus, Dresden, Germany

Publ.-Id: 6905 - Permalink


Low level CRP increases adhesion of leukocytes to endothelial cells and decreases phagocyte respiratory burst activities
Kopprasch, S.; Graessler, J.; Pietzsch, J.; Schröder, H.;
  • Lecture (Conference)
    15th International Symposium on Drugs Affecting Lipid Metabolism (DALM), 24.-27.10.2004, Venedig, Italy

Publ.-Id: 6904 - Permalink


Listmode Based Movement Correction in PET
van den Hoff, J.;
  • Invited lecture (Conferences)
    Workshop on Physical and Chemical Aspects of PET Radiopharmaceuticals, 19.-22.09.2004, Bratislava, Slovakia

Publ.-Id: 6903 - Permalink


Brain Trauma Elicits Increased AADC Acticity in Newborn Piglets
Brust, P.; Walter, B.; Hinz, R.; Müller, M.; Kuwabara, H.; Füchtner, F.; Bauer, R.; Steinbach, J.;
  • Lecture (Conference)
    Neuroreceptor Mapping 2004 Meeting, 15.-18.07.2004, Vancouver, Canada
  • Abstract in refereed journal
    NeuroImage 22(2004)2, T140

Publ.-Id: 6902 - Permalink


Early Alzheimer’s Disease with apathy or depression: Differences in regional brain metabolism
Spirling, S.; Lüdecke, S.; Kalbe, E.; Beuthien-Baumann, B.; Lenz, O.; Zündorf, G.; Herholz, K.; Holthoff, V. A.;
  • Abstract in refereed journal
    American Psychological Association 2004 New Research Program NR 663

Publ.-Id: 6901 - Permalink


Quanten-Kaskaden-Laser-Struktur
Georgiev, N.; Dekorsy, T.; Helm, M.; Semtsiv, M.; Dreßler, S.; Ziegler, M.; Masselink, W.;
Es wird eine Quanten-Kaskaden-Laser-Struktur zur Verfügung gestellt, welche die Herstellung von Quanten-Kaskaden-Lasern, die bei Zimmertemperatur emittieren können, ermöglicht.
  • Patent
    DE 10 2004 009 531 A1
  • Patent
    DE 102004009531B4

Publ.-Id: 6900 - Permalink


Synthesis and biological characterization of fluorinated N-benzoylpolyamines as substrates for tissue transglutaminase
Pietzsch, J.; Knop, K.; Rode, K.; Wüst, F.; Bergmann, R.; van den Hoff, J.;
  • Lecture (Conference)
    42. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-24.04.2004, Rostock, Germany
  • Abstract in refereed journal
    Nuklearmedizin 43(2004), A78

Publ.-Id: 6899 - Permalink


P0403 - Verfahren zur Korrektur der beim Monitoring der strahlentherapeutischen Behandlung mittels in-beam Positronen-Emissions-Tomographie erhaltenen Messwerte
Enghardt, W.; Pawelke, J.; Parodi, K.; Crespo, P.;
Es wird die Fehlerquote bei der in-beam PET weiter gesenkt, in dem ihre statistische Sicherheit erhöht wird.
  • Patent
    DE 10 2004 009 784 A1
  • Patent
    DE 10 2004 009 784 B4 - 10. Dez. 2009

Publ.-Id: 6898 - Permalink


Verfahren zur Verbesserung der Strahleigenschaften einer supraleitenden Hochfrequenz-Fotoelektronenquelle
Janssen, D.;
Mit der Erfindung soll die Effektivität der supraleitenden HF-Fotoelektrode und die Strahleigenschaft, insbesondere die transversale Emittanz, für mittlere und hohe Leistungen verbessert werden.
  • Patent
    DE 10 2004 005 612 A1

Publ.-Id: 6897 - Permalink


Hydromechanische Maschine
Hoppe, D.; Kernchen, R.;
Mit der Erfindung wird erreicht, dass die sprunghafte Veränderung des übertragenen Drehmnoments nicht mehr oder in sehr abeschwächter Form geschieht und die Drehmomentveränderung über dem Drehzahlverhältnis zwischen Pumpen- und Turbinenrad weitgehend kontinuierlich erfolgt.
  • Patent
    DE 10 2004 001 047.1-12
  • Patent
    DE 10 2004 001 047 A1

Publ.-Id: 6896 - Permalink


Assessment of metabolism of native and oxidized low density lipoprotein in vivo: insights from high resolution animal positron emission tomography studies
Pietzsch, J.; Bergmann, R.; Wuest, F.; Pawelke, B.; van den Hoff, J.;
  • Lecture (Conference)
    42. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-24.04.2004, Rostock, Germany
  • Abstract in refereed journal
    Nuklearmedizin 43(2004), A77

Publ.-Id: 6895 - Permalink


Intercomparison of sampling and measurement of Be-7 in air at four high-altitude locations in Europe
Tositti, L.; Hübener, S.; Kanter, H.-J.; Ringer, W.; Sandrini, S.; Tobler, L.;
For several years Be-7 measurements have been conducted at high-altitude stations in Austria (Sonnblick, 3106 m), Switzerland (Jungfraujoch, 3580 m), Germany (Zugspitze, 2962 m), and Italy (Mt. Cimone 2165 m) with the aim to support a study on vertical ozone transport in the Alps (VOTALP project).
Aerosol samples, collected on filtering media with high volume samplers, are analysed for Be-7 by high-resolution gamma-spectrometry.
Prior to evalution of the Be-7 time series of the four stations, both sampling and measurement procedures were cheked for comparibility. The results of an intercomparison exercise performed within the mentioned project are reported.
Keywords: Be-7, Gamma-spectrometry, Aerosol, Intercomparison

Publ.-Id: 6894 - Permalink


Forschung für Mensch und Umwelt 2001/2002
Ottow, S.; (Editor)
  • Open Access LogoWissenschaftlich-Technische Berichte FZR-349 Januar 2003

Downloads:

Publ.-Id: 6893 - Permalink


Far-IR spectroscopy of the nonlinear susceptibility of GaAs with an FEL
Dekorsy, T.; Helm, M.; Yakovlev, V.; Seidel, W.; Keilmann, F.;
The non-linear optical properties of solid state materials in the THz frequency region are to a large extent unexplored due to missing high-intensity coherent light sources in this frequency range. Although recent advances in table-top laser based THz systems have been enormous, free-electron lasers (FEL) are at present still the only tunable lasers which provide high peak intensities and a sufficient narrow spectral width to perform nonlinear spectroscopy at THz frequencies. Recently we investigated the dispersion of the second order nonlinear susceptibility (c(2)) in thin GaAs crystals below the optical phonon resonance via second harmonic generation (SHG) experiments with an FEL [1]. These experiments provide insight into the relative contributions of higher-order cohesive lattice forces to c(2). The nonlinear optical susceptibility in polar semiconductors in the THz frequency range is strongly influenced by the presence of optical phonons and should exhibit several peculiarities: A strong resonant enhancement of the SHG at half the frequency of the TO phonon (8.0 THz in GaAs) and at the TO phonon itself as well as a zero-crossing for frequencies between 4.0 THz and the TO phonon resonance due to the cancellation of higher order ionic and electronic contributions was predicted [2]. The experiments are performed with the THz FEL FELIX (Nieuwegein, Netherlands), which delivers picosecond pulses with µJ energy. We could observe both the resonance and the zero-crossing of c(2) below the Reststrahlen-band for the first time. From the value obtained for the zero-crossing of the nonlinear susceptibility we conclude that the contribution of the phonon interaction through the second-order lattice dipole moment has to be significantly smaller and the contribution from the third-order lattice potential anharmonicity has to be larger than determined previously [3]. Besides the relevance for the THz nonlinear susceptibility these terms are also important for two-phonon sidebands in the infrared absorption, phonon decay [3] and for a quantitative description of Raman spectra [4]. We propose that SHG below the optical phonon resonance is an elegant method to quantitatively determine the higher-order potential contributions to the nonlinear susceptibility.

[1] T. Dekorsy et al., Phys. Rev. Lett. 90, 055508 (2003).
[2] A. Mayer and F. Keilmann, Phys. Rev B 33, 6954 (1986).
[3] C. Flytzanis, Phys. Rev. B 6, 1264 (1972); Phys. Rev. Lett. 29, 772 (1972).
[4] S. Go, H. Bilz, and M. Cardona, Phys. Rev. Lett. 34, 580 (1975).

Keywords: FEL, nonlinear, THz, phonon-polariton, GaAs, resonance
  • Lecture (Conference)
    International Conference on Low Energy Electrodynamics in Solids, LEES 04, Kloster Banz, Germany, 19.7.-23.7.2004

Publ.-Id: 6890 - Permalink


N-Arylation of indoles with 4-[18F]fluoroiodobenzene: synthesis of 18F-labelled σ2 receptor ligands for positron emission tomography (PET)
Wüst, F.; Knieß, T.;
Summary: The palladium-mediated N-arylation of indoles with 4-[18F]fluoroiodobenzene as a novel radiolabelling method has been developed. Optimized reaction conditions were elaborated by variation of different catalyst systems (CuI/1,2-diamines and Pd2(dba)3/phosphine ligands), based and solvents in the reaction of indole with 4-[18F]fluoroiodobenzene. Optimized reaction conditions (Pd2(dba)3/(2-(dicyclohexyl-phosphino)-2´-(N,N-dimethylamino)-biphenyl, NaOBut, toluene, 100 °C for 20 min) were applied for the synthesis of 18F-labelled σ2 receptor ligands [18F]-11 and [18F]-13 which were obtained in 91 and 84 % radiochemical yields, respectively.
Keywords: N-arylation; 4-[18F]fluoroiodobenzene; σ2 ligands
  • Journal of Labelled Compounds and Radiopharmaceuticals 48(2005), 31-43
    DOI: 10.1002/jlcr.893

Publ.-Id: 6887 - Permalink


Recursively Coupled FEM-Analysis Of Pressure Vessel Creep Failure Experiments
Willschütz, H.-G.; Altstadt, E.; Weiss, F.-P.;
The hypothetical scenario of a severe accident with core meltdown and formation of a melt pool in the lower plenum of a Light Water Reactor Pressure Vessel (RPV) can result in the failure of the RPV and the discharging of the melt to the containment. One accident management strategy could be to stabilize the in-vessel debris or melt pool configuration in the RPV as one major barrier against uncontrolled release of heat and radionuclides into the containment of the plant.
To obtain an improved understanding and knowledge of the melt pool convection, the vessel creep, possible failure processes and modes occurring during the late phase of a core melt down accident the FOREVER-experiments have been performed at the Division of Nuclear Power Safety of the Royal Institute of Technology, Stockholm. These experiments were simulating the behavior of the lower head of the RPV under the thermal loads of a convecting melt pool with decay heating.
An axisymmetric Finite Element (FE) model was developed to simulate these experiments. First the temperature field within the melt pool and within the vessel wall was calculated with a CFD-Model. But due to the lack of a turbulence model for very high internal Rayleigh numbers of up to 1017 in the prototypic case and due to the very time consuming CFD-solution, the Effective Conductivity Convectivity Model (ECCM) as proposed by Bui has been implemented. Once the temperature field in the vessel wall is evaluated, the transient structural mechanical calculations are then performed applying a creep model which takes into account the large temperature, stress and strain variations. The creep model includes the primary, secondary and tertiary creep stages.
In the prior work only a one-way coupling between the thermal and the mechanical model was applied: first the transient temperature field was calculated and then the transient mechanical calculation was performed applying the appropriate temperature field at each time step. To take into account the melt level drop by thermal expansion the initial level was lowered “by hand”. The feedback from the viscoplastic deformation to the temperature field was not correctly considered in the one-way coupling. On the other hand the earlier investigations showed that slight temperature shifts of only 10 K at an overall temperature level clearly above 1000 K had significant effects concerning the failure time of the vessel.
To overcome the disadvantages of the single coupling model a new recursively coupled model is developed. This paper deals with the new results and so far the results show that a recursively coupled thermal and mechanical solution is closer to reality than a single coupled model where the mechanical deformations have no impact to the thermal model. Due to the scaling effect it is expected, that the fully coupled model is necessary to be able to perform reliable best estimate calculations for prototypic light water reactor scenarios.

Keywords: LWR core melt down scenario, creep failure experiments, recursively coupled FEM-analysis
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 2005, 10.-12.05.2005, Nürnberg, Germany, Proceedings on CD-ROM, Paper 311, pp. 202-208

Publ.-Id: 6884 - Permalink


Assessment of metabolism of native and oxidized low density lipoprotein in vivo: insights from animal positron emission tomography (PET) studies.
Pietzsch, J.; Bergmann, R.; Wuest, F.; Pawelke, B.; van den Hoff, J.;
  • Lecture (Conference)
    74th European Atherosclerosis Society Congress, 17.-20.04.2004, Seville, Spain
  • Abstract in refereed journal
    Atherosclerosis 5(2004)Suppl. 1, 143-144

Publ.-Id: 6883 - Permalink


Integration nuklearmedizinischer Bilder in die Bestrahlungsplanung des nichtkleinzelligen Bronchialkarzinoms.
Oehme, L.; Hoinkis, C.; Appold, S.; Beuthien-Baumann, B.; Pötzsch, C.; Baumann, M.; Kotzerke, J.;
  • Lecture (Conference)
    42. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-24.04.2004, Rostock, Germany
  • Abstract in refereed journal
    Nuklearmedizin 43(2004), A130

Publ.-Id: 6882 - Permalink


Nutzung von Mehrprozessorsystemen für den routinefähigen Einsatz listmode-basierter Bewegungskorrektur in der PET
Langner, J.; Bühler, P.; Pötzsch, C.; van den Hoff, J.;
  • Lecture (Conference)
    42. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-24.04.2004, Rostock, Germany
  • Abstract in refereed journal
    Nuklearmedizin 43(2004)V189, 10

Publ.-Id: 6881 - Permalink


Konventionelles Staging und Staging mit FDG-PET bei Patienten mit Morbus Hodgkin unter Berücksichtigung der Therapieentscheidung
Kühnel, G.; von Ruthendorf-Przewoski, J.; Naumann, R.; Beuthien-Baumann, B.; Reiß, A.; Kotzerke, J.; Laniado, M.;
  • Lecture (Conference)
    Deutscher Röntgenkongress, 20.-22.05.2004, Wiesbaden, Germany
  • Abstract in refereed journal
    RöFo : Fortschritte auf dem Gebiete der Röntgenstrahlen und der Nuklearmedizin 176(2004), S249

Publ.-Id: 6880 - Permalink


Atemtriggerung zur Verbesserung der Darstellung und Abgrenzbarkeit von intrathorakalen Raumforderungen in der PET
Just, U.; Pötzsch, C.; Bühler, P.; Beuthien-Baumann, B.; van den Hoff, J.;
  • Lecture (Conference)
    42. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-24.04.2004, Rostock, Germany
  • Abstract in refereed journal
    Nuklearmedizin 43(2004), V192

Publ.-Id: 6879 - Permalink


Mikro-PET-Untersuchungen zu Bioverteilung und Metabolismus von F-18-fluorbenzoylierten Aminosäuren und Dipeptiden in den Nieren
Hultsch, C.; Wüst, F.; Pawelke, B.; Bergmann, R.;
  • Abstract in refereed journal
    Nuklearmedizin 43(2004), P40

Publ.-Id: 6878 - Permalink


Depression and regional cerebral glucose metabolism in early dementia
Holthoff, V. A.; Herholz, K.; Perani, D.; Sorbi, S.; Beuthien-Baumann, B.; Kalbe, E.;
  • Abstract in refereed journal
    European Journal of Neurology (2004)Suppl. 172

Publ.-Id: 6877 - Permalink


Synthese eines Fluor-18 markierten COX-2
Höhne, A.; Bergmann, R.; Wüst, F.;
  • Abstract in refereed journal
    Nuklearmedizin 43(2004), V173
  • Lecture (Conference)
    42. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-24.04.2004, Rostock, Deutschland

Publ.-Id: 6876 - Permalink


Depressive Symptoms and regional cerebral glucose metabolism in patients with MSA and PSP
Herting, B.; Holthoff, V. A.; Triemer, A.; Poetrich, K.; Herholz, K.; Beuthien-Baumann, B.; Reichmann, H.;
  • Abstract in refereed journal
    J Neurol Sciences, Abstraktband 2004

Publ.-Id: 6875 - Permalink


Schweres Schädel-Hirn-Trauma löst im unreifen Gehirn eine Erhöhung der dopaminergen Aktivität aus
Brust, P.; Walter, B.; Füchtner, F.; Müller, M.; Hinz, R.; Kuwabara, H.; Steinbach, J.; Bauer, R.;
  • Lecture (Conference)
    42. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-24.04.2004, Rostock, Germany
  • Abstract in refereed journal
    Nuklearmedizin 43(2004) A97

Publ.-Id: 6874 - Permalink


High-intensity THz radiation pulses from a scalable photoconductive device
Winnerl, S.; Dreyhaupt, A.; Krenz, M.; Stehr, D.; Dekorsy, T.; Helm, M.;
Photoconductive emitters are an attractive way for impulsive generation of THz radiation. There are two main categories, namely large-aperture emitters and interdigitated electrodes coupled to antennas. Large-aperture emitters have the advantage of a high active volume, while interdigitated structures provide high electric fields for efficient acceleration of photogenerated carriers. We present a large-aperture emitter consisting of a interdigitated metal-semiconductor-metal (MSM) structure, which combines both advantages. A second metallization layer, which is electrically insulated from the first one, blocks the optical excitation in every second period of the MSM structure, resulting in an unidirectional acceleration of carriers in the device. Focussing fs optical pulses with an average power of 100 mW from a Ti:sapphire oscillator on the emitter lead to THz field amplitudes of up to 85 V/cm (Ubias = 65 V). Excitation with unfocussed radiation from a 1 kHz repetition rate Ti:sapphire amplifier system (average power 10 mW) provided THz field amplitudes of 6 kV/cm (Ubias = 23 V). In case of the excitation with the Ti:sapphire amplifier system a pronounced nonlinear behavior of the THz field amplitude with respect to both the excitation density and the bias electric field was observed.
Keywords: THz emitter, photoconductive device, ultrafast processes in semiconductors
  • Lecture (Conference)
    DPG Frühjahrstagung, Fachverband Halbleiterphysik, 4.-9.3.2005, Berlin, Deutschland

Publ.-Id: 6873 - Permalink


Einfluss von klinischen Charakteristika auf den regionalen cerebralen Glukosestoffwechsel bei der unipolaren Depression
Beuthien-Baumann, B.; Zündorf, G.; Lüdecke, S.; Triemer, A.; Schierz, K.; Herholz, K.; Holthoff, V.;
  • Lecture (Conference)
    42. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-24.04.2004, Rostock, Germany
  • Abstract in refereed journal
    Nuklearmedizin 43(2004), A82

Publ.-Id: 6872 - Permalink


Can [F18]FDG Positron emission tomography replace bone marrow biopsy in staging of patients with malignant lymphoma?
Naumann, R.; Beuthien-Baumann, B.;
  • Clinical Lymphoma 5(2004), 127

Publ.-Id: 6871 - Permalink


Regional cerebral metabolism in early Alzheimer’s disease with clinically significant apathy or depression
Holthoff, V.; Beuthien-Baumann, B.; Kalbe, E.; Lüdecke, S.; Lenz, O.; Zündorf, G.; Spirling, S.; Schierz, K.; Winiecki, P.; Herholz, K.;
BACKGROUND: Alzheimer's disease (AD) is clinically characterized by cognitive impairment and behavioral disturbances. The aim of the study was to identify regional alterations in brain function associated with neuropsychiatric symptoms in early AD. METHODS: Patients underwent measures of cerebral glucose metabolism applying positron emission tomography (PET) and (18)F-fluorodeoxyglucose. Neuropsychiatric symptoms were assessed using the Neuropsychiatric Inventory (NPI). Positron emission tomography images of patients suffering a neuropsychiatric symptom of clinical significance (NPI subscore for a specific item >/=4 points) were compared with the images of patients without the specific symptom under study (NPI subscore for a specific item = 0 points). RESULTS: A total of 53 patients with AD (Mini-Mental State Examination [MMSE] 22.5 +/- 2.94 points) entered the study. Of all symptoms, apathy and depression were most frequently encountered. The patient group with apathy (n = 17) revealed significant decreases in left orbitofrontal regions when compared with patients free of apathy. Depression of clinical significance (n = 10) was associated with hypometabolism in dorsolateral prefrontal regions. CONCLUSIONS: These findings support the notion that different functional circuits underlie apathy and depression in early AD.
  • Biological Psychiatry 57(2005) 412-421

Publ.-Id: 6870 - Permalink


Functional imaging of vegetative state applying Single Photon Emission Tomography and Positron Emission Tomography
Beuthien-Baumann, B.; Holthoff, V. A.; Rudolf, J.;
Nuclear medicine techniques, such as single photon emission tomography (SPECT) and positron emission tomography (PET) have been applied in patients in a vegetative state to investigate brain function in a non invasive manner. Parameters investigated include glucose metabolism, perfusion at rest, variations of regional perfusion after stimulation, and benzodiazepine receptor reduction of glucose metabolism and perfusion. While patients post-anoxia exhibit a rather homogenous cortical reduction of glucose metabolism, patients after head trauma often show severe cortical and sub-cortical reductions at the site of primary trauma. To distinguish reduced glucose metabolism due to neuronal inactivation from neuronal loss, flumazenil-PET, and indicator of benzodiazepine receptor density, could add valuable information on the extent of brain damage. Activation studies focus on the evaluation of residual brain network, looking for processing in secondary projection fields. So far the predictive strength concerning possible recovery for the individual patient is limited, and PET und SPECT are not routine procedures in the assessment of patients in a vegetative state.
  • Neuropsychological Rehabilitation 15(2005)3/4, 276-282

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Publ.-Id: 6869 - Permalink


Electro-vortex flows in a square layer of liquid metal
Kolesnichenko, I.; Khripchenko, S.; Buchenau, D.; Gerbeth, G.;
We study electro-vortex flows generated by electro-magnetic forces in a shallow square layer of liquid metal. The force driving the flow is produced by the interaction between the electric current flowing through the layer and its own magnetic field. Rotational parts of that force are particularly caused by ferromagnetic yokes placed around the layer. Depending of the position and type of those yokes flows of one-, two- or four-eddies are initiated. The basic flow structure and the related velocity oscillations have been investigated both by experimental techniques using the ultrasound Doppler velocimetry and by numerical calculations. Compared to the single vortex flow the double vortex flow shows a much higher level of large-scale velocity oscillations. The theoretical model turned out to be in good agreement with the experimental data.
  • Magnetohydrodynamics 41(2005)1, 39-51

Publ.-Id: 6868 - Permalink


High-Intensity THz Radiation Pulses from a Scalable Large-Aperture Emitter
Winnerl, S.; Krenz, M.; Dreyhaupt, A.; Stehr, D.; Dekorsy, T.; Helm, M.;
Using a novel metal-semiconductor-metal (MSM) structure, we combine a large-active-emitter volume with strong electric fields for carrier acceleration. We obtain THz field amplitudes of 6 kV/cm using excitation pulse energies of 10 µJ.

Keywords: Terahertz emitter, photoconductive materials, ultrafast processes in semiconductors
  • Lecture (Conference)
    Conference on Lasers and Opto-Electronics 2005, Baltimore, USA
  • Abstract in refereed journal
    CLEO/QELS & PhAST Technical Digest CD-ROM, Berlin 2005: "Physik seit Einstein" (2005)

Publ.-Id: 6866 - Permalink


On the feasibility of dose quantification with in-beam PET data in radiotherapy with 12C and proton beams
Parodi, K.;
This thesis has contributed to the achievement of in-beam PET as a promising clinical monitoring technique. In response to a pressing medical demand, this work has provided a tool for quantification of local dose deviations in case of observed discrepancies between the measured and expected PET images. The implemented interactive approach described in chapter 3 is in clinical use since 2001. It provides the radio-oncologist with a valuable feedback which may allow a prompt reaction in the strategy of the therapy prior to the delivery of the successive treatment fraction in case of significant deviations between planned and actually applied dose. ...

Keywords: PET, ion therapy
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-415, November 2004

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Publ.-Id: 6865 - Permalink


Darstellung und Charakterisierung von Glycoclustern auf der Basis von PAMAM-Dendrimeren mit Cyclam-Core
Röhrich, A.; Stephan, H.;
  • Lecture (others)
    Institutsseminar, Universität Bonn, 01.12.2004, Bonn, Germany

Publ.-Id: 6864 - Permalink


The Surface Layer Protein of the Bacillus sphaericus Isolate JG A-12 from a Uranium Waste Pile
Raff, J.; Kirsch, R.; Kutschke, S.; Mertig, M.; Selenska-Pobell, S.; Bernhard, G.; Pompe, W.;
Many bacteria possess a crystalline protein or glycoprotein surface layer (S-layer) as the outermost component of their cell wall. The interest in bacterial S-layers increased in the last time. This protein might be applied as biomolecular template for making nanostructures, e.g. for the development of biosensors. The surface layer of a natural Bacillus sphaericus isolate JG A-12, recovered from a uranium waste pile, was analyzed and compared to the surface layer
of a reference strain (Bacillus sphaericus NCTC 9602). The molecular weights of the S-layer proteins of both, the reference strain NCTC 9602 and the strain JG A-12, were examined with a denaturating polyacrylamid gel electrophoresis and were estimated to be approximately 135 kDa. In addition to that, the first 20 amino acids at the N-termini of the 135 kDa proteins of the strains 9602 and JG A-12 were identical. However, no similarity to the S-layer proteins of
the Bacillus sphaericus strains 2362 and P-1 was found. Interestingly, in the case of the uranium waste isolate, in addition to the S-layer protein a second, smaller protein with a size of 30 kDa was copurified. The amino acid sequence of the N-terminus of the 30 kDa protein was significantly different from those of the S-layer proteins. This small protein possesses a similarity to many flagellins of different bacteria. The S-layer of the reference strain Bacillus
sphaericus NCTC 9602 and of the uranium waste isolate JG A-12 were also characterized using transmission electron microscopy after negative staining. Both S-layers have a p4 symmetry with lattice constants of 12,9 nm (S-layer of Bacillus sphaericus NCTC 9602) and 12,5 nm (S-layer of JG A-12). It seems, that the reference strain Bacillus sphaericus NCTC 9602 and the isolate JG A-12 possess the S-layer protein with same structure.
  • Poster
    99TH General Meeting of the American Society for Microbiology (ASM), May 30 - June 3, 1999, Chicago, Illinois, USA

Publ.-Id: 6863 - Permalink


Biosorption of Heavy Metals by Sol-Gel Immobilized Bacillus sphaericus Cells, Spores and S-Layers
Soltmann, U.; Raff, J.; Selenska-Pobell, S.; Matys, S.; Pompe, W.; Böttcher, H.;
Different types of biocers were prepared by dispersing vegetative cells, spores and surface layer proteins (S-layers) of Bacillus sphaericus JG-A12 in aqueous silica nanosols, gelling or coating on glass, and drying. The enzymatic activity of embedded B. sphaericus cells depends noticeably on the water content of the biocer. The cells are destroyed by drying and shrinkage of the silica network whereas embedded spores retain their ability for germination. The biosorption
of uranium and copper of these biocomposites was investigated. Biocers with cells possess the highest metal binding capacity compared to matrices with spores or S-layers. An additional increasement of the metal binding capacity is achieved by using penetration reagents like sorbitol. For renewed use biosorpted uranium and copper can be completely removed from the biocers by using aqueous citric acid. The use of spores as biocomponent offers new interesting possibilities for the preparation of storage-stable bioactive biocers.
  • Journal of Sol-Gel Science and Technology, 26: 1209-1212 (2003)

Publ.-Id: 6862 - Permalink


Impact of FDG Positron Emission Tomography in addition to conventional staging procedures in patients with Hodgkin´s lymphoma
Naumann, R.; Beuthien-Baumann, B.; Reiss, A.; Kühnel, G.; Schulze, J.; Haenel, A.; Bredow, J.; Kropp, J.; Haenel, M.; Laniado, M.; Ehninger, G.;
  • Poster
    45th Meeting of the American Society of Haematology; San Diego, 06.-09.12.2003

Publ.-Id: 6861 - Permalink


Novel Re and 99mTc ‘3+1’ oxocomplexes with high affinity for the 5-HT1A receptor.
Fernandes, C.; Bergmann, R.; Correia, J. D. G.; Gano, L.; Santos, I.; Spies, H.; Seifert, S.;
  • Poster
    7th FIGIPS Meeting in Inorganic Chemistry, Lisbon, Portugal, 11.-15.06.2003

Publ.-Id: 6860 - Permalink


Síntese, Caracterizaçăo e Avaliaçăo Biológica de Complexos Lipofílicos de 99mTc
Fernandes, C.; Kniess, T.; Seifert, S.; Spies, H.; Gano, L.; Santos, I.;
  • Poster
    Contendo Grupos Siloxo Hidrolisáveis, 1ş Congresso da Sociedade Portuguesa de Cięncias Farmacęuticas, Lisbon, Portugal, 04.-16.04.2003

Publ.-Id: 6859 - Permalink


Positron Emission Tomography (PET): Fundamentals and the potential role in drug research and development
Wüst, F.;
  • Invited lecture (Conferences)
    PET-Tagung der BAYER AG; Wuppertal, 16.06.2003

Publ.-Id: 6858 - Permalink


Linearisations in compartment modelling
van den Hoff, J.;
  • Invited lecture (Conferences)
    XV Annual PET Pharmacokinetic Course; Montreal, 25.-30.06.2003

Publ.-Id: 6857 - Permalink


Untersuchungen zum in vivo-Metabolismus nativer und oxidierter Lipoproteine am Tiermodell mittels PET
Pietzsch, J.;
  • Lecture (Conference)
    11. Jahrestagung der AG Radiochemie/Radiopharmazie; Leipzig-Brehna, 18.09.2003

Publ.-Id: 6856 - Permalink


Synthetische Arbeiten in der medizinischen Chemie und der Re/Tc-Chemie
Heinrich, T.;
  • Lecture (others)
    Dies Academicus 2003; Zittau, 04.06.2003

Publ.-Id: 6855 - Permalink


Erfahrungen bei der Verwendung von kommerziellen Ausrüstungen für die PET-Radiopharmakaherstellung
Füchtner, F.;
  • Lecture (Conference)
    11. Jahrestagung der AG Radiochemie/Radiopharmazie; Leipzig-Brehna, 18.09.2003

Publ.-Id: 6854 - Permalink


Status and perspectives in neurotensin receptor PET imaging
Bergmann, R.;
  • Lecture (Conference)
    International Workshop “Radiolabelled peptides in tumour research”; Leipzig, 26.05.2003

Publ.-Id: 6853 - Permalink


Experience with neurotensin and bombesin labelled with fluorine-18
Bergmann, R.;
  • Lecture (Conference)
    European Association of Nuclear Medicine Annual Congress 2003; Amsterdam, 23.-27.08.2003

Publ.-Id: 6852 - Permalink


[N-methyl(11)C]meta-Hydroxyephedrine positron emission tomography in Parkinson's disease and multiple system atrophy
Berding, G.; Schrader, C. H.; Peschel, T.; van den Hoff, J.; Kolbe, H.; Meyer, G. J.; Dengler, R.; Knapp, W. H.;

Publ.-Id: 6851 - Permalink


Spektroskopische Untersuchungen zur Wechselwirkung von Actiniden mit Huminsäuren unter Einsatz von spezifischen Huminsäure-Modellverbindungen
Sachs, S.; Keywords: Huminsäuren, Komplexierung, Actinide, Neptunium, Uran, Huminsäure-Modellverbindungen, EXAFS, NIR, LIPAS
  • Invited lecture (Conferences)
    4. Mainzer Symposium über Spurenanalytik, Johannes Gutenberg-Universität Mainz, 26.11.2004, Mainz, Germany

Publ.-Id: 6850 - Permalink


Enzymatischer Test potentieller Substrate der Herpes Simplex Virus 1 Thymidinkinase zum Monitoring der Genexpression
Grote, M.; Noll, B.; Noll, S.; Knieß, T.; Johannsen, B.;
  • Poster
    GDCh Jahrestagung in Würzburg, 23.09.-29.09.2001

Publ.-Id: 6848 - Permalink


Study of the Redox Stability of Uranium(VI) in Presence of Humic Substances
Sachs, S.; Geipel, G.; Bernhard, G.;
We studied the stability of the oxidation state of U(VI) in the presence of natural humic acid from Aldrich and synthetic acids Hyd-Glu and Cat-Gly representing humic acid model substances with pronounced redox functionalities. Using laser-induced photoacoustic spectroscopy we obtained the first spectroscopic proof for the reduction of U(VI) to U(IV) by the applied synthetic humic acids. In contrast to that, no spectroscopic indications for an Aldrich humic acid-mediated reduction of U(VI) were found. From that we concluded that both humic acid-like products show higher U(VI) redox capacities than Aldrich humic acid.
Keywords: Uranium, U(VI), U(IV), Humic Acids, Synthetic Humic Acids, Redox Processes, LIPAS
  • Contribution to external collection
    Humic Substances in Performance Assessment of Nuclear Waste Disposal: Actinide and Iodine Migration in the Far-Field. Third Technical Progress Report (G. Buckau, ed.), Forschungszentrum Karlsruhe, Wissenschaftliche Berichte, FZKA 7070, Karlsruhe 2005, 9-18.

Publ.-Id: 6847 - Permalink


Magnetic domain structure of micro-patterned PtMn/NiFe exchange bias bilayers
Potzger, K.; Bischoff, L.; Liedke, M. O.; Hillebrands, B.; Rickart, M.; Freitas, P.; McCord, J.; Fassbender, J.ORC
The local modification of magnetic properties by means of ion irradiation has been demonstrated for perpendicularly magnetized Co/Pt [1], for amorphous soft magnetic alloys [2] and for exchange-bias systems [3-5]. In all cases the magnetic features are not determined by the patterning itself, but by the micromagnetic feature sizes. Therefore, if the pattern sizes are close to the intrinsic length scales of the system under investigation a change in the overall magnetic behaviour is expected. For an exchange bias system this intrinsic length scale is in the range between 100 – 1000 nm [5].
The aim of the present study is to investigate the domain structure of a micro-patterned exchange bias system during magnetization reversal. Special attention is paid to the interaction between adjacent features changing the overall magnetic behaviour of the system. As a test system we chose a bottom pinned exchange bias bilayer consisting of 20 nm PtMn and 6 nm NiFe, capped with 5 nm of Ta, prepared by ion beam and physical vapour deposition. PtMn is chosen as the antiferromagnetic material due to its technological relevance and due to the chemically ordered L10-phase which is required in order to obtain a large exchange bias field. This phase can easily be disordered by means of ion irradiation leading to a very low ion fluence required to suppress the exchange bias effectively [6]. Thus sputtering effects are minimized. Using a 25 keV Ga+ focused ion beam (FIB) a stripe array consisting of 1 µm wide lines exposed to a fluence 21014 Ga/cm2 separated by 1 µm spacing is created. The long axes of the lines are oriented parallel to the exchange bias direction.
The global magnetic properties of the stripe array were analyzed by means of magneto-optic Kerr effect magnetometry (MOKE) and Kerr microscopy. It was found, that the overall loop shift in the patterned region is reduced to ~30 Oe compared to an exchange bias field of 180 Oe in the unpatterned area. After saturation in an applied field of +800 Oe there is no domain pattern observed in remanence by Kerr microscopy. With increasing negative field first the magnetization in the irradiated stripes reverse. This leads to an alignment of the soft magnetic (irradiated) stripes parallel to the applied field direction while the magnetization of the non-irradiated stripes remains antiparallel. After saturation at -500 Oe and increase of the applied field a hysteretic behaviour was observed that is consistent with the MOKE-measurements leading to a remaining domain contrast in remanence.
At an applied field between -12 Oe and -80 Oe a sharp contrast originating from Néel walls between irradiated and non-irradiated regions is observed by magnetic force microscopy. Moreover, a successive increase of the domain width in the irradiated areas at the expense of those in the non-irradiated areas is observed. At an applied magnetic field of about -100 Oe the magnetization in the non-irradiated area is nearly completely reversed due to the influence of the adjacent soft magnetic areas which are reversed at lower field values already. A magnetization ripple as a remainder of the non-irradiated stripes persists up to large negative field values consistent with the large exchange bias field in the completely unpatterned region.

References
[1]J. Lohau, A. Moser, C. T. Rettner, M. E. Best, B. D. Terris, Appl. Phys. Lett. 78, 990 (2001).
[2]J. McCord, J. Fassbender, M. Frommberger, M.O. Liedke, E. Quandt, L. Schultz, Appl. Phys. Lett., submitted.
[3]A. Mougin, S. Poppe, J. Fassbender, B. Hillebrands, G. Faini, U. Ebels, M. Jung, D. Engel, A. Ehresmann, H. Schmoranzer, J. Appl. Phys. 89, 6606 (2001).
[4]J. McCord, R. Schäfer, K. Theis-Bröhl, H. Zabel, J. Schmalhorst, V. Höink, H. Brückl, T. Weis, D. Engel, A. Ehresmann, J. Appl. Phys. accepted.
[5]S. Blomeier, D. McGrouther, S. McVitie, R. O’Neill, J. N. Chapman, M. C. Weber, B. Hillebrands, J. Fassbender, J. Magn. Magn. Mater. accepted.
...
Keywords: magnetism, exchange-bias, magnetic patterning, MFM, ion irradiation, Kerr microscopy, patterning
  • Poster
    Intermag 2005, Nagoya

Publ.-Id: 6846 - Permalink


Spectroscopic Characterization of Synthetic Becquerelite, Ca[(UO2)6O4(OH)6]•8H2O, AND SWARTZITE, CaMg[UO2(CO3)3]•12H2O
Amayri, S.; Arnold, T.; Foerstendorf, H.; Geipel, G.; Bernhard, G.;
Becquerelite, Ca[(UO2)6O4(OH)6]•8H2O, and swartzite, CaMg[UO2(CO3)3]•12H2O, have been synthesized and identified by X-ray powder diffraction (XRD). Chemical compositions were verified by ICP–MS and AAS. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) and Fourier-transformed infrared spectroscopy (FTIR) were used for the first time to characterize these phases. In becquerelite, there are four fluorescence emission bands, at 518.9, 535.6, 553.4, and 578.9 nm, and a characteristic fluorescence lifetime of 3.1 ± 0.2 s. Swartzite shows six characteristic fluorescence emission bands, at 472.3, 488.9, 509.0, 531.1, 554.7, and 578.9 nm, and a fluorescence lifetime of 59.4 ± 0.1 s. The FTIR spectra of becquerelite are characterized by an intense asymmetric stretching vibration (v3 UO22+ mode) band at 946 cm-1, with shoulders at approximately 925 and 902 cm-1. Swartzite shows its characteristic v3 UO22+ mode of the uranyl cation at 898 cm-1. As natural U6+-bearing samples commonly form thin coatings on rock or mineral surfaces or as a component mixed with other solids, it is generally difficult to identify small quantities of these secondary phases. Spectroscopic methods like TRLFS and FTIR spectroscopy are found to be promising methods to identify such secondary phases.
Keywords: uranium, synthesis, TRLFS spectroscopy, FTIR, spectroscopy.
  • The Canadian Mineralogist 42(2004)4, 953 – 962

Publ.-Id: 6845 - Permalink


Target mass number dependence of subthreshold antiproton production in proton-, deuteron- and alpha-particle-induced reactions
Müller, H.; Komarov, V. I.;
Data from KEK on subthreshold antiproton as well as on π± and K± production in proton-, deuteron- and alpha-particle-induced reactions at energies between 2.0 and 12.0 AGeV for C, Cu and Pb targets are described within a unified approach. We use a model which considers a nuclear reaction as an incoherent sum over collisions of varying numbers of projectile and target nucleons. It samples complete events and thus allows for the simultaneous consideration of all final particles including the decay products of the nuclear residues. The enormous enhancement of the antiproton cross section, as well as the moderate increase of meson production in deuteron and alpha induced compared to proton-induced reactions, is well reproduced. In our approach, the observed enhancement near the production threshold is mainly due to the contributions from the interactions of few-nucleon groups.
  • Journal of Physics G: Nuclear and Particle Physics 31 (2005) 285-293

Publ.-Id: 6844 - Permalink


Increased magnetic damping of permalloy upon Cr implantation
Fassbender, J.ORC; McCord, J.; Weisheit, M.; Mattheis, R.
The understanding and the modification of the magnetic damping processes in thin ferromagnetic films has gained considerable interest in recent years. In addition to applied research on ultrafast magnetization reversal [1-3] also studies concerning the basic damping phenomena [4,5] and their modification by means of adjacent non-magnetic layers [6] or alloying [7] have been reported. Also the use of ion implantation to modify magnetic properties on a local scale has been addressed [8].

Here we report on investigations of the static and dynamic magnetic properties of 20 nm thick permalloy films as prepared and after 30 keV Cr implantation with different Cr fluences. Due to the doping the Curie temperature of the permalloy film decreases with the implantation fluence. At an averaged Cr concentration of about 7% (≈ 1.4·10^16 Cr/cm^2) the Curie temperature drops below room temperature. The uniaxial anisotropy, induced by a magnetic field during deposition, decreases but persists with increasing Cr fluence as indicated by the 2-fold symmetry of the magnetic remanence as a function of in-plane angle measured by magneto-optic Kerr effect magnetometry.

In order to investigate the magnetization damping pulsed inductive microwave magnetometry (PIMM) has been performed for various applied magnetic fields. In Fig. 3 the magnetization traces for the as-deposited permalloy film as well as the Cr-implanted samples are shown for an applied field of 10 Oe. Upon Cr implantation the PIMM amplitude is decreased consistent with a decrease in the uniaxial anisotropy AND a reduction in saturation magnetization. This results in a decrease of the precession frequency which is easily observed. However, the magnetic damping, i. e. the relaxation of the precession, is also altered by the Cr implantation. A detailed analysis of the damping parameter leads to 7-fold increase of the damping for only 4% of Cr doping. In order to clarify the basic mechanism for the enhancement the chemical and structural contributions to the magnetic damping parameter are separated.

References
[1] T. Gerrits, H. A. M. van den Berg, J. Hohlfeld, O. Gielkens, L. Bär, Th. Rasing, Nature 418, 509 (2002).
[2] S. Kaka, S. Russek, Appl. Phys. Lett. 80, 1958 (2002).
[3] H. W. Schumacher, C. Chappert, P. Crozat, R. C. Sousa, P. P. Freitas, J. Miltat, J. Fassbender, B. Hillebrands, Phys. Rev. Lett. 90, 017201 (2003).
[4] D. L. Mills, S. M. Rezende, Topics in Applied Physics 87, 27 (2003).
[5] B. Heinrich, in Ultrathin Magnetic Structures III, IV, edited by B. Heinrich and J. A. C. Bland (Springer-Verlag, Berlin, 2003).
[6] S. Mizukami, Y. Ando, T. Miyazaki, Jap. J. Appl. Phys. 40, 580 (2001).
[7] S. G. Reidy, L. Cheng, W. E. Bailey, Appl. Phys. Lett. 82, 1254 (2003).
[8] L. Folks, R. E. Fontana, B. A. Gurney, J. R. Childress, S. Maat, J. A. Katine, J. E. E. Baglin, A. J. Kellock, J. Phys. D: Appl. Phys. 36, 2601 (2003).

Keywords: magnetism, ion implantation, doping, magnetic damping, Curie temperature, PIMM, magnetization dynamics
  • Lecture (Conference)
    Intermag 2005, Nagoya, Japan

Publ.-Id: 6843 - Permalink


Structural phase transformation of FePt nanoparticles by ion irradiation
Rellinghaus, B.; Dmitrieva, O.; Liedke, M. O.; Fassbender, J.ORC
Owing to its large magneto-crystalline anisotropy energy, L10 ordered tetragonal FePt is among the most intensively discussed materials when it comes to pushing the superparamagnetic limit towards minimum particle sizes for future ultra-high density magnetic data storage media [1]. Depending on the preparation technique, however, the formation of the L10 thermodynamic equilibrium phase is often impeded by either a lack of thermodynamic driving forces or a lack of diffusivity.
Recently it has been shown [2,3] that gas phase prepared FePt nanoparticles can exhibit a very narrow size distribution with a mean diameter of roughly 6 nm. Together with a packing density of 2.8 × 10^12 particles /cm^2 a potential data storage density of 18 Tbit/inch^2 could be achieved. Unfortunately these particles are superparamagnetic at room temperature due to their multiply twinned icosahedral structure. Therefore it is of essential importance to transform these nanoparticles into the favourable L10 phase in a post-deposition treatment. Since annealing usually results in sintering of adjacent particles, a possible alternative is the use of ion irradiation techniques to create vacancies within the particles and thereby enhance the bulk diffusion of the constituents which has been successfully demonstrated to promote the L10 ordering in the case of FePd films [4].
In the present study, post-deposition 5 keV He irradiation has been performed on such gas phase prepared FePt nanoparticles. Structural characterization of the samples was carried out by means of High Resolution Transmission Electron Microscopy (HRTEM). Fig. 1 shows the HRTEM micrographs of two typical Fe42Pt58 particles with a mean diameterof dP = 6.2 nm. The power spectra as obtained by Fourier transform of the original images (see insets in Fig 1) clearly evidence that the particles are multiply twinned and of icosahedral structure. In Fig. 2, two typical HRTEM micrographs of particles are presented which had been subjected to irradiation with 5 keV He ions at a fluence of f = 3×10^17 ions/cm2. The particles are no longer multiply twinned but rather single crystal fcc, and their mean diameter is reduced to dP_irr = 5.2 nm. This size reduction is ascribed to irradiation induced sputtering of the particles. Although the defect concentration apparently increases the atomic diffusivity temporarily to an extent that allows for structural transformations in the FePt nanoparticles at RT, no L10 ordered particles have been observed. This observation is in contrast to the bulk phase diagram [5], theoretical calculations [6], and thermodynamic investigations in thin films [7], based on which the L10 phase is expected to be energetically favoured over the fcc phase by some 0.1 eV/atom.
There are two possible origins for the experimental findings. Either the particles investigated are already smaller than a critical particle size below which the L10 phase is no longer the thermodynamic equilibrium phase in FePt, or kinetic aspects may be of increasing importance at these length scales. Since the sputtering process that comes along with the ion irradiation is element specific and tends to remove more iron than platinum atoms, the He ion irradiation results in a shift of the elemental composition of the FePt nanoparticles towards a more Pt-rich concentration. As a consequence, the remaining alloy approaches the borderline of the L10
stability region in the phase diagram. Concurrently, the thermodynamic ordering temperature is reduced and the chemical driving force for the L10 ordering will be significantly reduced.

References
[1] D. Weller, A. Moser, L. Folks, M.E. Best, W. Lee, M.F. Toney, M. Schwickert, J.-U. Thiele, and M.F. Doerner, IEEE Trans. Mag. 36, 10 (2000).
[2] S. Stappert, B. Rellinghaus, M. Acet, and E.F. Wassermann, J. Cryst. Growth 252, 440 (2003).
[3] B. Rellinghaus, S. Stappert, M. Acet, and E.F. Wassermann, J. Magn. Magn. Mater. 266, 142 (2003).
[4] H. Bernas, J.-Ph. ...
Keywords: magnetism, structure, phase transformation, nanoparticles, L10-structure, HRTEM, binary alloys
  • Lecture (Conference)
    Intermag 2005, Nagoya, Japan

Publ.-Id: 6842 - Permalink


Small and large angle precession in exchange biased bilayers
Weber, M.; Nembach, H.; Hillebrands, B.; Fassbender, J.ORC
Small and large angle excitations in exchange bias systems have been investigated in real time by means of all-optical pump-probe experiments. Time resolved magneto-optics has been employed as a probe of the transient magnetic phenomena upon laser excitation. Due to an increased spin temperature upon photoexcitation, an unpinning of the interfacial exchange coupling takes place resulting in a collapse of the unidirectional anisotropy. An effective internal anisotropy pulse field with a rise time of the order of the pump laser pulse duration (τ =8.3 ps) is launched which governs the time evolution of the effective field acting on the magnetization of the ferromagnetic layer of the bilayer system. The time evolution of the exchange bias shift field and the zero-field susceptibility reveal a fingerprint of the internal field pulse and can be understood taking ultrafast thermal activation into account [1]. The excess energy of the spin system - upon a sudden increase of the interfacial spin temperature – can lead to the excitation of a high frequency precessional response of the magnetization of the ferromagnetic layer for both the easy and the hard axis geometry [2,3]. Even, the initial deflection direction of the magnetization of the ferromagnet away from the initial equilibrium orientation can be controlled on the picosecond timescale in the hard axis geometry. The magnitude of the internal pulse field, and thus the torque acting on the magnetization of the ferromagnetic layer, can be controlled by the absorbed photons [3]. Hence, the precessional motion depending on the magnitude of the anisotropy pulse field, i.e., the precession angle can
be investigated. Moreover, by comparing the measured real time precessional motion with solutions of the Landau-Lifshitz and Gilbert equation the dependence of the effective Gilbert parameter α on the precession angle can be studied. The extracted Gilbert parameter depends not or only rather weakly on the magnitude of the internal pulse field. There are no non-linear effects present for this material system. Both small and large angle precession of the ferromagnetic layer upon photoexcitation can be modeled with reasonable values of the Gilbert parameter within the Landau-Lifshitz and Gilbert framework.
Employing the known antiferromagnetic thickness dependence of the exchange bias field Heb, the exchange bias field dependence of the Gilbert parameter α was investigated. For this purpose a wedge shaped exchange bias bilayer with a fixed thickness of the ferromagnetic layer and a varying thickness of the antiferromagnetic layer along the sample was prepared and measured.
The extracted Gilbert parameter from the time-resolved Kerr traces and thus, the dissipation rate increases linearly with the exchange bias field magnitude. Local fluctuations of the interfacial exchange coupling, due to interface roughness, can increase the two-magnon relaxation probability, which in terms of an additional dissipation channel finally leads to an increased Gilbert damping parameter [4,5].
The work is supported by the Graduiertenkolleg 792 of the Deutsche Forschungsgemeinschaft and the European Communities Human Potential programs HPRN-CT-2002-00318
ULTRASWITCH and HPRN-CT-2002-00296 NEXBIAS.

References
[1] M.C. Weber, H. Nembach, and J. Fassbender, J. Appl. Phys. 95, 6613 (2004).
[2] G. Ju, A. V. Nurmikko, R.F.C. Farrow, R.F. Marks, M.J. Carey, and B.A. Gurney, Phys. Rev. Lett. 82, 3705 (1999).
[3] M.C. Weber, H. Nembach, B. Hillebrands, and J. Fassbender, Phys. Rev. B, submitted for publication.
[4] S.M. Rezende, A. Azevedo, M.A. Lucena, and F.M. de Aguiar, Phys. Rev. B 63, 214418 (2001).
[5] M.C. Weber, H. Nembach, B. Hillebrands, and J. Fassbender, J. Appl. Phys, in press.
  • Lecture (Conference)
    Intermag 2005,4.-8.4.2005, Nagoya, Japan

Publ.-Id: 6841 - Permalink


Magnetic anisotropy patterning of amorphous films by He-ion irradiation
McCord, J.; Gemming, T.; Schultz, L.; Fassbender, J.ORC; Liedke, M. O.; Frommberger, M.; Quandt, E.
The magnetic anisotropy in amorphous soft magnetic CoFeSiB films is modified by He-ion irradiation. A rotation of uniaxial anisotropy depending on the applied field direction in the irradiated areas is observed by magnetometry and complementary domain observation by Kerr microscopy. No significant degradation in magnetic properties relative to the as-deposited state is found from the magnetization loops on non-patterned films. Using irradiation together with photolithography the films were treated locally, resulting in ‘anisotropy patterned’ structures. Complicated periodic domain patterns form due to the locally varying anisotropy distribution. Overall magnetic properties and domain patterns can be adjusted.
Keywords: magnetism, ion irradiation, magnetic anisotropy, patterning, amorphous alloys, Kerr microscopy, magnetic domains
  • Applied Physics Letters 86(2005), 162502

Publ.-Id: 6840 - Permalink


Spectroscopic Characterization of Pd Nanoclusters Formed by S-Layer of B. sphaericus JG-A12 and Biocers
Merroun, M.;
  • Lecture (others)
    BIO-CAT Project Meeting, 05.11.2004, Paris, France

Publ.-Id: 6838 - Permalink


Damping in thin ferromagnetic films
Nembach, H.; Martin-Pimentell, P.; Weber, M.; Fassbender, J.ORC; Hillebrands, B.
The understanding of the damping processes of the magnetization dynamics is an important issue. Several different damping channels are proposed. Here the importance of magnon-magnon processes for the damping is investigated with a magneto-optical method. This method allows to determine the length of the magnetization vector and therefore gives an indication for magnon-magnon processes. Higher order magneto-optic effects are also taken into account, which allows the determination of the quadratic magneto-optic constant.
This work was supported by the DFG-Graduiertenkolleg 792 and the EU-RTN ULTRASWITCH network (HPRN-CT-2002-00318).
Keywords: magnetism, magnetic damping, damping processes, time-resolved techniques
  • Lecture (Conference)
    DPG Frühjahrstagung 2005, Berlin

Publ.-Id: 6835 - Permalink


The modelling of positron emitter production and PET imaging during carbon ion therapy
Pönisch, F.; Parodi, K.; Hasch, B. G.; Enghardt, W.;
At the carbon ion therapy facility of GSI Darmstadt in-beam positron emission tomography (PET) is used for imaging the ß+-activity distributions which are produced via nuclear fragmentation reactions between the carbon ions and the atomic nuclei of the irradiated tissue. On the basis of these PET images the quality of the irradiation, i.e. the position of the field, the particle range in vivo and even local deviations between the planned and the applied dose distribution, can be evaluated. However, for such an evaluation the measured ß+-activity distributions have to be compared with those predicted from the treatment plan. The predictions are calculated as follows: a Monte Carlo event generator produces list mode data files of the same format as the PET scanner in order to be processed like the measured ones for tomographic reconstruction. The event generator models the whole chain from the interaction of the projectiles with the target, i.e. their stopping and nuclear reactions, the production and the decay of positron emitters, the motion of the positrons as well as the propagation and the detection of the annihilation photons. The steps of the modelling, the experimental validation and clinical implementation are presented.

Publ.-Id: 6834 - Permalink


Hydrophile 99mTc/188Re-Komplexe zur Kopplung an Biomoleküle
Schiller, E.; Pietzsch, H.-J.; Seifert, S.; Bergmann, R.; Kraus, W.; Spies, H.;
  • Lecture (Conference)
    11. Jahrestagung der AG Radiochemie/Radiopharmazie, Leipzig, 18.-20.09.2003
  • Poster
    GDCh-Jahrestagung 2003, München 07.-10.10.2003

Publ.-Id: 6833 - Permalink


CoSi2 nanowires synthesized by FIB
Bischoff, L.; Schmidt, B.; Akhmadaliev, C.;
Nanowires and chains of nanoparticles are of emerging interest in nanoelectronics, nano-optics and plasmonics as well as for their monolithic integration into microelectronic devices. CoSi2 is a promising material due to its CMOS-compatibility microelectronics technology. Two fabrication methods of CoSi2 -nanowires by using ion beam synthesis (IBS) with Focused Ion Beams (FIB) technique are presented. In a first approach, an oxide layer, structured by sputtering with a focused Ga+ ion beam, have been used as an implantation mask for large area homogeneous Co+ implantation. Alternatively, a mass separated FIB of cobalt ions, emitted from a Co36Nd64 alloy liquid metal ion source, is applied for a direct writing IBS process. Implantation into Si with doubly charged Co+ ions emitted from the Co source allows ion energies up to 60 keV, which result in CoSi2 nanostructures buried in silicon. The processes of damaging and annealing of the substrate due to extremely high current density of the FIB were investigated. The fabrication of nanowires down to 30 nm diameter has been demonstrated.
Keywords: nano-wire, Focused Ion Beam, cobaltdisilicide
  • Poster
    Tagung der Deutschen Physikalischen Gesellschaft 03. - 09. 03. 2005 Berlin

Publ.-Id: 6832 - Permalink


Modifikation der strukturellen und magnetischen Eigenschaften von Permalloy-Schichten bei Cr-Implantation
Fassbender, J.ORC; von Borany, J.; Potzger, K.; Grötzschel, R.; Mücklich, A.
Die magnetischen und strukturellen Eigenschaften von Permalloy-Schichten lassen sich gezielt durch Cr-Implantation modifizieren. Dazu
wurde ein 20 nm Permalloy/5 nm Tantal/SiOx/Si Schichtsystem mit 30 keV Cr-Ionen im Dosisbereich zwischen 2×10^15 und 2×10^16 Ionen/cm^2
implantiert. Daraus resultiert ein Implantationsprofil mit einer mittleren Konzentration an Cr innerhalb der Permalloy-Schicht von 1 bis 10
%. Die Änderungen in der Schichtstruktur wurden mit Röntgenbeugung, Auger-Tiefenprofilanalyse, Rutherford-Backscattering und Querschnitts-
Transmissions-Elektronenmikroskopie untersucht. Neben der eigentlichen Implantation wird schon bei relativ kleinen Ionendosen eine Durchmischung
der Grenzfläche zwischen Permalloy und Tantal beobachtet. Mit steigender Ionendosis diffundiert Tantal zunehmend an die Oberfläche des Schichtstapels. Diese experimentellen Ergebnisse werden gut durch TRIDYN-Simulationen beschrieben [1].
[1] Transport and Range of Ions (Dynamic): W. Möller, W. Eckstein, Nucl. Instr. and Meth. B 2, 814 (1984).
Keywords: magnetism, permalloy, ion implantation, TRIDYN, XRD, RBS, TEM
  • Poster
    DPG-Frühjahrstagung 2005, Berlin, 4.-9.3.2005

Publ.-Id: 6831 - Permalink


Magnetic domain structure of micro-patterned PtMn/NiFe exchange bias bilayers
Potzger, K.; Bischoff, L.; Liedke, M. O.; Hillebrands, B.; Rickart, M.; Freitas, P.; McCord, J.; Fassbender, J.ORC
A bottom pinned exchange bias bilayer system consisting of 20 nm PtMn and 6 nm NiFe (produced using ion beam deposition (IBD) and physical vapour deposition (PVD, magnetron sputtering)) was laterally magnetic patterned by means of focused ion beam irradiation (FIB) on a micrometer scale. 25 keV ion irradiation with a fluence of
2×1014Ga+·cm−2 leads to a disordering of the as prepared chemically ordered PtMn-phase with only minor changes in sample topography. Thus the exchange bias field as well as the coercive field was reduced to a large extent on a local scale. The magnetic properties of FIB written 1µm wide stripes and their interaction with the non-irradiated spacing were analyzed by means of magneto-optic Kerr effect, magnetic force microscopy, and Kerr microscopy. The application of a magnetic field between -12
Oe and -80 Oe with respect to the exchange bias field direction leads to an antiparallel alignment of irradiated and non-irradiated stripes forming pronounced domain walls. A parallel alignment was found below -100 Oe and in the positive field region.
Keywords: magnetism, exchange bias, chemically ordered alloys, MFM, patterning
  • Poster
    DPG-Frühjahrstagung 2005, Berlin, 4.-9.3.2005

Publ.-Id: 6830 - Permalink


Modifikation der magnetischen Dämpfung in Permalloy-Schichten durch Cr-Implantation
Fassbender, J.ORC; McCord, J.; Weisheit, M.; Mattheis, R.
Das magnetische Dämpfungsverhalten, die Curie-Temperatur und die uniaxiale magnetische Anisotropie von 20 nm dicken Permalloy-Schichten wurde mittels Cr-Implantation modifiziert. Die Implantation wurde bei 30 keV Beschleunigungsspannung im Dosisbereich zwischen 2×10^15 und 2 × 10^16 Ionen/cm2 durchgeführt. Daraus resultiert ein Implantationsprofil mit einer mittleren Konzentration an Cr innerhalb der Permalloy-Schicht von 1 bis 10 %. Bei einer mittleren Konzentration von ca. 7% wird die Curie- Temperatur der Permalloy-Schicht auf Raumtemperatur abgesenkt. Damit einher geht eine leichte Verringerung der uniaxialen magnetischen Anisotropie. PIMM-Messungen (”pulsed inductive microwave magnetometry”) zeigen jedoch eine starke Vergrösserung des magnetischen Dämpfungsverhaltens durch die Cr-Implantation. Die möglichen Ursachen dieser Erhöhung werden diskutiert.
Keywords: magnetism, magnetization dynamics, ion implantation, magnetic damping, magnetic anisotropy, permalloy
  • Lecture (Conference)
    DPG Frühjahrstagung 2005, 4.-9.3.2005, Berlin, Deutschland

Publ.-Id: 6829 - Permalink


Anisotropy patterning of amorphous CoFeSiB films by Heion irradiation
McCord, J.; Fassbender, J.ORC; Frommberger, M.; Liedke, M. O.; Quandt, E.; Schultz, L.
The alteration of magnetic properties in magnetic thin films by ion radiation has gained increasing attention in recent years. Here, we present data on the local alteration of the magnetic anisotropy axis in amorphous soft magnetic FeCoBSi films by He-ion irradiation in an applied magnetic in-plane field. Sputtered CoFeSiB (thickness 30 nm) were irradiated with 5 keV He-ions. A magnetic field of 600 Oe was applied during irradiation aligned orthogonal to the initial easy axis of anisotropy. Above a critical fluence an alignment of anisotropy in the applied field direction is observed by MOKE magnetometry and complementary domain observation by Kerr microscopy. Using irradiation together with photolithography the films were irradiated locally, thus resulting in anisotropypatterned structures. Domain patterns in different elements with varying angles of anisotropy and edge orientation, separating regions of different anisotropy alignment, are shown. The influence of the patterning on the (still) full film reversal is discussed in detail.
Keywords: magnetism, amorphous films, magnetic anisotropy, He ion irradiation, patterning
  • Lecture (Conference)
    DPG Frühjahrstagung 2005, 4.-9.3.2005, Berlin, Deutschland

Publ.-Id: 6828 - Permalink


Real-time evolution of the ITO film properties and structure during annealing in vacuum
Rogozin, A.; Shevchenko, N.; Vinnichenko, M.; Prokert, F.; Cantelli, V.; Kolitsch, A.; Möller, W.; Keywords: Indium Tin Oxide, annealing, structure, in-situ studies
  • Other report
    ESRF Highlights 2004

Publ.-Id: 6827 - Permalink


X-ray and Neutron Scattering studies of NiMn-CoFe exchange bias systems
Solina, D.; Lott, D.; Kaltofen, R.; Schumann, J.; Fassbender, J.ORC; Tietze, U.; Schreyer, A.
Preliminary results are presented on the structural and magnetic properties of epitaxial antiferromganetic NiMn and their correlation to the Exchange Bias Effect. Included are x-ray diffraction, reflection and rocking curves of pertinent diffraction peaks. The rocking curves have a FWHM of less than 3 indicating good epitaxial growth of the film. Polarized neutron reflectivity and high angle scattering measurements have been made in order to assess the magnetic properties of the system.
Keywords: magnetism, exchange bias, XRD, neutron diffraction
  • Poster
    DPG Frühjahrstagung 2005, Berlin, 4.-9.3.2005

Publ.-Id: 6826 - Permalink


Magnetic domain structure of micro-patterned PtMn/CoFe exchange bias bilayers
Liedke, M. O.; Potzger, K.; Hillebrands, B.; Rickart, M.; Freitas, P.; Fassbender, J.ORC
Using magnetron sputtering deposition a number of high exchange bias field samples were prepared for magnetic pattering investigations. The system prepared is as follow: glass/Ta 70 °A/PtMn 200 °A/ tCoFe = 20 - 60 °A/Ta 40 °A. One of such bottom pinned samples with 40 °A of CoFe was used for optical lithography. Several patterns have been etched physically with decreasing lateral sizes of either the edges or the spacing between the elements. The largest square is 50 × 50 µm and the smallest only 1 µm2. The separating lines are ranging from 10 µm to 2 µm width. The magnetic characterization of the samples have been done by VSM and MOKE. All samples exhibit well defined exchange bias field. A series of MFM images were taken from the structures. All images show a monodomain magnetization state in zero magnetic field. The shape
of the structure itself dose not influence stray field direction. The shape anisotropy contribution is thus smaller than the unidirectional anisotropy
given by the exchange bias. MFM investigation in an applied magnetic field have been done to get a deeper understanding of the domain pattern.
Keywords: magnetism, magnetic patterning, exchange bias, MFM
  • Poster
    DPG-Frühjahrstagung 2005, Berlin, 4.-9.3.2005

Publ.-Id: 6825 - Permalink


Ionenstrahlinduzierte StrukturÄanderungen in FePt Nanopartikeln
Rellinghaus, B.; Dmitrieva, O.; Liedke, M. O.; Schultz, L.; Fassbender, J.ORC
Monodisperse, vielfach verzwillingte FePt Nanopartikel mit ikosaedrischer Struktur und Konzentrationen im Bereich der stÄochiometrischen Zusammensetzung wurden durch DC-Sputtern in der Gasphase hergestellt. Die ikosaedrische Struktur der Partikel hat sich dabei als Äau¼erst stabil erwiesen, und weder thermisches Anlassen im Fluge noch nach der Deposition fÄuhrt zur Einstellung der magnetisch hochanisotropen, chemisch geordneten tetragonalen L10-Gleichgewichtsstruktur [1]. Eine Bestrahlung dieser Teilchen durch 5 keV He-Ionen bei Fluenzen von f > 10^17 Ionen/cm2 hingegen fÄuhrt zur Umwandlung in die kfz Struktur. Obwohl die Ionenbestrahlung die Versinterung benachbart liegender Partikel initiiert und somit eine erhÄohte Di®usion aufgrund einer temporär erhöhten Defektkonzentration belegt, wird die Einstellung der L10-Phase nicht beobachtet. Die Ergebnisse werden durch kinetisch bedingte Modifikationen der thermodynamischen Gleichgewichtsphasen erklärt.
[1] S. Stappert, B. Rellinghaus, M. Acet, and E.F. Wassermann, Proc. Mat. Res. Soc. Vol. 704, 73 (2002); S. Stappert, B. Rellinghaus, M. Acet, and E.F. Wassermann, J. Cryst. Growth 252, 440 (2003).
Gefördert durch die DFG im Rahmen des SFB 445.
Keywords: magnetism, magnetic particles, clusters, FePt, L10-phase, hard magnetic, ion irradiation, phase transformation
  • Lecture (Conference)
    DPG-Frühjahrstagung 2005, 4.-9.3.2005, Berlin, Deutschland

Publ.-Id: 6824 - Permalink


All-optical probe of magnetization dynamics in exchange bias systems
Weber, M.; Nembach, H.; Schultheiss, H.; Bayer, C.; Blomeier, S.; Kaltofen, R.; Schumann, J.; Carey, M.; Hillebrands, B.; Fassbender, J.ORC
The picosecond optical control of the exchange bias anisotropy was investigated in real time for different exchange bias bilayers (NiFe/FeMn, CoFe/NiMn, CoFe/IrMn) using time-resolved magneto-optics. Upon photoexcitation the spin temperature is increased leading to a collapse of the interfacial exchange coupling. Both the shift fields and the easy axis coercivities are reduced within the first 10 ps. The unpinning is followed by a slower spin-lattice relaxation process. The deduced relaxation times turn out to be quite comparable (< 205 ps) for all bilayers. The thermal decoupling of the bilayers can lead to a high frequency precession of the magnetization of the ferromagnetic layers. The precessional response of the CoFe/IrMn system reveals a Kittel type field dependence of the precession frequency. Brillouin light scattering measurements of the field dependence of the FMR frequency are in good agreement with the real time measurements, further supporting the homogeneous mode character of the optically excited precession.
Keywords: magnetism, magnetization dynamics, pump-probe techniques, time-resolved, damping, exchange-bias
  • Poster
    DPG-Frühjahrstagung 2005, Berlin, 4.-9.3.2005

Publ.-Id: 6823 - Permalink


Small and large angle precession in exchange biased bilayers
Weber, M.; Nembach, H.; Hillebrands, B.; Fassbender, J.ORC
Small and large angle excitations in exchange bias systems have beeninvestigated in real time by means of all-optical pump-probe experiments. Due to an increased spin temperature upon photoexcitation, an unpinning of the interfacial exchange coupling takes place resulting in a collapse of the unidirectional anisotropy. In terms of an internal pulse field the excess energy of the spin system leads to the excitation of a high frequency precessional response. The magnitude of the internal pulse field can be controlled by the absorbed photons [1]. Hence, the precessional motion depending on the precession angle can be investigated. The extracted Gilbert parameter does not depend on the magnitude of the internal pulse field. Both small and large angle precession can be modeled within the Landau-Lifshitz-Gilbert framework. Employing the antiferromagnetic thickness dependence of the exchange bias field, the exchange bias field dependence of the Gilbert parameter was investigated. The dissipation
rate increases linearly with the exchange bias field magnitude which can be understood taking local fluctuations of the interfacial exchange coupling as an additional dissipation mechanism into account [2].
[1] M. C. Weber et al., Phys. Rev. B, submitted. [2] M.C. Weber et al., J. Appl. Phys., in press.
Keywords: magnetism, magnetization dynamics, pump-probe techniques, time-resolved damping
  • Lecture (Conference)
    DPG-Frühjahrstagung 2005, 4.-9.3.2005, Berlin, Deutschland

Publ.-Id: 6822 - Permalink


Boundary-integral method for calculating poloidal axisymmetric AC magnetic fields
Priede, J.; Gerbeth, G.;
This paper presents a novel boundary-integral equation (BIE) method for the calculation of poloidal axisymmetric magnetic fields applicable in a wide range of AC frequencies. The method is based on the vector potential formulation and it uses the Green's functions of Laplace and Helmholtz equations for the exterior and interior of conductors, respectively. In such a way, a coupled system of two complex surface-boundary equations is obtained that reduces the problem of finding the field distribution in the whole space to the determination of the vector potential and its normal derivative on the surface only. This reduction comes at the price of an increased complexity of the Green's function for the axisymmetric Helmholtz equation whose calculation is discussed in detail. The method is verified by comparing with the analytical solution for a sphere in a uniform external AC field. Application of the method is demonstrated for a simple model inductor.
  • IEEE Transactions on Magnetics 42(2006)2,Part 2, 301-308

Publ.-Id: 6821 - Permalink


Post mortem investigations of Greifswald VVER 440 reactor pressure vessel: Recent progress in dosimetry and material investigations
Konheiser, J.; Rindelhardt, U.; Viehrig, H.-W.;
Pressure vessel integrity assessment after long-term service irradiation is commonly based on surveillance program results. Radiation loading, metallurgical and environmental histories, however, can differ between surveillance and RPV materials. Therefore, the investigation of RPV material from decommissioned NPPs offers the unique opportunity to evaluate the real toughness response. A chance is given now through the investigation of material from the decommissioned Greifswald NPP (VVER-440/230) to evaluate the state of a standard RPV design and to assess the quality of prediction rules and assessment tools.

Some years ago first fluence calculations were done for the four Greifswald units in the frame of a TACIS project [1]. Neutron fluence integrals E>0.5MeV, E>1MeV and dpa-values at the inner and outer pressure vessel walls were obtained with the help of a Green’s functions method. New improved results will be presented based on new calculations of pin-wise time dependent neutron sources and an updated nuclear data base. The Monte Carlo calculations of neutron and gamma fluence spectra for different time intervals were done at all positions throughout the RPV wall, where the material specimens will be taken. The statistical error was estimated to be smaller than 1%. A comparison between the calculated fluences and experimental values (12th cycle of unit 1) shows a good agreement, the differences were smaller than 5 %.

The fluence at the inner wall of the RPV for E > 0.5 MeV for the critical weld was 4.64* 10^18 n/cm2. The maximum fluence at the RPV is larger by a factor 1.5. In addition, it could be shown that the fluence at the designated reference positions can be neglected (3 orders of magnitude smaller).

Because of changes in the dismantling procedure a new technology was developed to extract trepans from the interesting RPV positions. A special drilling machine is under development, which will be positioned at the ring water tank near the main coolant loops. The RPV will be moved by crane in the wanted positions (height and azimuth). The remotely controlled trepanning will start in 2005 at unit 1.

The testing and investigation program is focussed on the characterization of the material state as received. It comprises chemical analysis, microstructure investigations (by means of metallography, electron microscopy and SANS), and mechanical testing (hardness measurements, tensile, Charpy-V and fracture mechanics testing). The key part of the testing will be focussed on the determination of the reference temperature T0 following the ASTM test standard E1921-03. Trepans from 4 height positions (welds 3 and 4, base material from the maximum load position and from reference position) will be investigated..

[1] TACIS-Project NUCRUS 96601, Final Report, Brussels 2000

Keywords: reactor pressure vessel, neutron dosimetry, neutron embrittlement, VVER-440
  • Lecture (Conference)
    4th International Conference on: Safety assurance of nuclear power plants with WWER, 23.-25.05.2005, Podolsk, Russia
  • Contribution to proceedings
    4th International Conference on Safety Assurance of Nuclear Power Plants with WWER, 23.-25.05.2005, Podolsk, Russia
    CD-ROM, Podolsk

Publ.-Id: 6820 - Permalink


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