Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34122 Publications

Analytische HPLC synthetischer Sparteinabkömmlinge

Fähnemann, S.; Matterna, M.

kein Abstract verfügbar

  • Lecture (others)
    2. Workshop "Möglichkeiten und Grenzen der HPLC in den Lebenswissenschaften", 20.02.2009, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12442
Publ.-Id: 12442


From experiment to clinical application: particle therapy PET solution

Shakirin, G.

A knowledge transfer of particle therapy PET applications to industry is discussed

Keywords: PET; particle therpay

  • Invited lecture (Conferences)
    4th Meeting of the Scientific Advisory Board of OncoRay, 26.02.2009, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12441
Publ.-Id: 12441


Spectroscopic identification of ternary carbonate complexes upon U(VI) sorption onto ferrihydrite

Foerstendorf, H.; Heim, K.

The sorption processes of uranium(VI) onto ferrihydrite (Fh) were investigated by in situ Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR) spectroscopy. This technique provides structural information of the molecular complexes occurring during the sorption processes of actinide ions on mineral phases in aqueous solution [1].
The influence of the presence of atmospheric carbon dioxide during the sorption processes of the actinide ions was studied by sorption experiments which were carried out under inert gas conditions and in an ambient atmosphere.
The spectra demonstrate that the uranyl ion recovers in a similar molecular environment irrespective to the prevailing atmospheric conditions. However, the carbonate ions sorbed to the mineral phase in ambient atmosphere undergo significant structural changes upon the sorption of the actinide ions. While carbonate binds monodentately to the pristine Fh-surface, it forms bidendate surface complexes upon the sorption of U(VI). Moreover, the formation of ternary inner-sphere complexes can be derived from spectra recorded during the sorption processes of atmospheric carbonate onto a Fh-film which was preloaded with U(VI) under inert gas conditions. With respect to the absorption frequency of the uranyl ion sorbed onto Fh under different conditions, we suggest the formation of [Fh•••UO2•••O2CO] complexes. Surface complexes with carbonate serving as a bridging ligand between Fh and UO22+ ions were not found in our experiments. These findings are in good agreement with recent EXAFS results [2].
Furthermore, we investigated the sorption processes at acidic (5.5) and at ambient (7.8) pH values. No significant differences were observed in the spectra. However, the sorption processes obviously occur with reduced velocity at higher pH values which might be due to the dominating aqueous U(VI) species at different pH values [3].

[1] Lefèvre (2004) Adv. Colloid Interface Sci. 107, 109-123. [2] Rossberg et al. (2009) Environ. Sci. Technol. (in press). [3] Müller et al. (2008) Inorg. Chem. 47, 10127-10134.

  • Poster
    Goldschmidt™2009 - "Challenges to Our Volatile Planet", 21.-26.06.2009, Davos, Switzerland
  • Geochimica et Cosmochimica Acta 73(2009)13, A386-A386

Permalink: https://www.hzdr.de/publications/Publ-12440
Publ.-Id: 12440


Investigation of fuel assembly design options for high conversion thorium fuel cycle in PWRs

Fridman, E.; Shwageraus, E.; Volaski, D.

This study explores the basic possibility of achieving a self-sustainable Th-U233 fuel cycle that can be adopted in the current generation of Pressurized Water Reactors. This study outlines some fuel design strategies to achieve (or to approach as closely as possible) a sustainable fuel cycle. Major design tradeoffs in the core design are discussed. Preliminary neutronic analysis performed on the fuel assembly level with BOXER computer code suggests that net breeding of U233 is feasible in principle within a typical PWR operating envelope. However, some reduction in the core power density and/or shorter than typical fuel cycle length would most likely be required in order to achieve such performance.

Keywords: thorium fuel cycle; high conversion reactor

  • Contribution to proceedings
    Advances in Nuclear Fuel Management IV, 12.-15.04.2009, Hilton Head Island, South Carolina, USA

Permalink: https://www.hzdr.de/publications/Publ-12439
Publ.-Id: 12439


Growth Aspects of Iron-Filled Carbon Nanotubes Obtained by Catalytic Chemical Vapor Deposition of Ferrocene

Müller, C.; Leonhardt, A.; Kutz, M. C.; Büchner, B.; Reuther, H.

The thermal decomposition of ferrocene combined with an Fe-catalyst nanostructuring on an oxidized Si
substrate is investigated in the temperature range of 1015-1200 K. The optimal growth conditions for aligned
and homogeneous Fe-filled carbon nanotubes are found at 1100 K. From the nanostructures the corresponding
growth rates are determined, and the activation energy of carbon diffusion is calculated to be ∼0.4-0.5
eV/atom. Further, the Fe particle size on the substrate after pretreatment in different gas atmospheres is studied
and compared with the nanotube dimensions. With these data the diffusion coefficient of carbon in the catalyst
particle amounts to 0.5-1.5 × 10-9 m2/s. Such values prove the formation of liquid catalyst particles during
the nanotube growth. Mo¨ssbauer spectroscopy was utilized to analyze and quantify the different Fe phases.
In conclusion we propose a simple base-growth model from the experimental results.

  • Journal of Physical Chemistry C 113(2009)7, 2736-2740

Permalink: https://www.hzdr.de/publications/Publ-12438
Publ.-Id: 12438


Experimental Conditions in Underground Measurements

Bemmerer, D.

I will summarize technical aspects relevant to the measurement of extremely small cross sections at accelerator facilities deep underground, with a focus on the laboratory background observed in gamma-ray detectors.

Keywords: underground nuclear astrophysics

  • Invited lecture (Conferences)
    Nuclear Astrophysics Opportunities at the Underground Laboratory in Canfranc, 19.-20.02.2009, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-12437
Publ.-Id: 12437


Study of high temperature and high density plasmoids in axially symmetrical magnetic fields

Anikeev, A. V.; Bagryansky, P. A.; Prikhodko, V. V.; Soldatkina, E. I.; Tsidulko, Y. A.; Kolesnikov, E. Y.; Lizunov, A. A.; Noack, K.; Konheiser, J.; Berger, T.

Within the framework of an Institutional Partnership of the Alexander von Humboldt Foundation, the Budker Institute of Nuclear Physics Novisibirsk (BINP) and Forschungszentrum Dresden-Rossendorf worked together in a joint project devoted to the research at the coupled GDT-SHIP facility of the BINP with the focus on the study of plasma phenomena within the SHIP mirror section. The project began at July 1st, 2005 and ended on August 30th, 2008. It included work packages of significant theoretical, computational and analyzing investigations.
The focus of this final report is on the presentation of results achieved whereas the work that was done is described briefly only. Chapter 2 illustrates the GDT-SHIP facility and describes shortly the planned topics of the SHIP plasma research. Chapter 3 explains the main extensions and modifications of the Integrated Transport Code System (ITCS) which were necessary for the calculations of the fast ion and neutral gas particle fields in SHIP, describes briefly the scheme of computations and presents significant results of pre-calculations from which conclusions were drawn regarding the experimental program of SHIP. In chapter 4, the theoretical and computational investigations of self-organizing processes in two-component plasmas of the GDT-SHIP device are explained and the results hitherto achieved are presented. In chapter 5, significant results of several experiments with moderate and with enhanced plasma parameters are presented and compared with computational results obtained with the ITCS. Preparing neutron measurements which are planned for neutron producing experiments with deuterium injection, Monte Carlo neutron transport calculations with the MCNP code were also carried out. The results are presented. Finally, from the results obtained within the joint research project important conclusions are drawn in chapter 6.

Keywords: fusion neutron source; gas dynamic trap; synthesized hot ion plasmoid

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZD-513 2009
    ISSN: 1437-322X

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-12436
Publ.-Id: 12436


Aktivitäten des FZD für die (Dünnschicht) Photovoltaik

von Borany, J.

Kurze Übersicht der PV-Aktivitäten im FZD.

Keywords: Photovoltaik; Ionentechniken; dünne Schichten; Magnetohydrodynamik

  • Lecture (others)
    EFDS Fachausschuss "Großflächenbeschichtung für solar- und lichttechnische Anwendungen", 10.07.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12435
Publ.-Id: 12435


In-situ study of film growth by synchrotron radiation scattering

Martins, R.M.S; Schell, N.; von Borany, J.; Bähtz, C.

The possibilities of in-situ X-ray investigations at ROBL for the study of thin films growth are summarized.

Keywords: ROBL; X-ray studies; thin films; microstructure

  • Poster
    2008 International Conference for Shape Memory and Superelatic Technologies (R&D Exhibition Event), 21.-25.09.2008, Stresa, Italy

Permalink: https://www.hzdr.de/publications/Publ-12434
Publ.-Id: 12434


Texture development and phase transformation behaviour of sputtered Ni-Ti films

Martins, R. M. S.; Schell, N.; Silva, R.; Pereira, L.; Mahesh, K. K.; Braz Fernandes, F. M.

The technological importance of thin films has led to an unabated interest in the detailed characterization of their structure, morphology, and their interfaces. A real understanding of the underlying growth mechanisms and their microstructural development requires sophisticated in situ techniques. X-ray diffraction with high-brilliance beams is such a powerful technique, as it is demonstrated here for the study of Ni-Ti films.
Numerous examples of investigations on Ni-Ti films can be found in the literature but it has been reported that the deposition of Ni-Ti films with definite stoichiometry and high purity remains a challenge, and important issues like formation of film texture and its control are still unresolved.
It is essential to identify and control their preferential orientation since it is a crucial factor in determining the shape memory behaviour. Widening the scope of our previous experiments concerning the influence of the deposition parameters on the structure of the Ni-Ti films, the incorporation of a TiN buffer layer has been tested.
Here, it is established a clear relationship between the TiN substrates and Ni-Ti texture development (B2 phase) and it is shown that the distinct crystallographic orientations of the Ni-Ti films influence their phase transformation behaviour. The influence of a substrate bias voltage on the preferential orientation of the B2 phase and transformation temperatures is as well revealed. A lower biaxial stress state and lower phase transformation temperatures have been observed for the films deposited with bias (-45 and -90V). Therefore, the control of the energy of the bombarding ions could be used as a tool for the manipulation of the transformation temperatures.

Keywords: NiTi; shape memory alloys; texture; X-ray diffraction

  • Lecture (Conference)
    2008 International Conference for Shape Memory and Superelastic Technologies, 21.-25.09.2008, Stresa, Italy
  • Journal of Materials Engineering and Performance 18(2009), 543-547

Permalink: https://www.hzdr.de/publications/Publ-12433
Publ.-Id: 12433


Texture development and phase transformation behaviour of sputtered Shape Memory Alloy Ni-Ti films

Martins, R. M. S.; Schell, N.; Silva, R.; Pereira, L.; Mahesh, K. K.; Braz Fernandes, F. M.

Ni-Ti SMA films are attractive materials for microfabrication and integration in micro-miniature systems composed of mechanical elements, actuators, sensors and electronics made on one chip. However, there are still important issues unresolved like formation of film texture and its control as well as substrate effects. It is essential to identify and control their preferential orientation since it is a crucial factor in determining the shape memory behaviour. Widening the scope of previous experiments concerning the influence of the deposition parameters on the Ni-Ti films structure, the incorporation of a TiN intermediate layer was tested.
Here, it is established a clear relationship between the TiN substrates and Ni-Ti texture development (B2 phase) and it is shown that the distinct crystallographic orientations of the Ni-Ti films influence their phase transformation behaviour. The influence of a substrate bias voltage on the preferential orientation of the B2 phase and transformation temperatures is as well revealed.

Keywords: NiTi; shape memory alloys; texture; x-ray diffraction

  • Poster
    ESRF User Meeting 2008, 05.-07.02.2008, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-12432
Publ.-Id: 12432


Speciation and Structural Study of U(IV) and -(VI) in Perchloric and Nitric Acid Solutions

Ikeda-Ohno, A.; Hennig, C.; Tsushima, S.; Scheinost, A. C.; Bernhard, G.; Yaita, T.

In order to elucidate the uranium solution chemistry at the high HNO3 concentrations typically employed for the reprocessing of spent nuclear fuels, speciation and complex structures of UIV and UVI are studied in aqueous HNO3 solutions, as well as in HClO4 solutions, by means of UV-visible-near-infrared and X-ray absorption spectroscopies and density functional theory calculations. In 1.0 M HClO4, UIV exists as a spherical cation of U4+, which is surrounded by 9-10 water molecules in the primary coordination sphere, while it forms a colloidal hydrous oxide, UIVO2 nH2O, at a lower acidic concentration of 0.1 M HClO4. UVI exists as a transdioxo uranyl cation, UO22+, and forms a 5-fold pure hydrate complex of [UVIO2(H2O)5]2+ in 1.0M HClO4. With increasing HNO3concentration, the water molecules of the UIV and UVI hydrate complexes are successively replaced by planar bidentate coordinating nitrate ions (NO3-), forming dominant species of [UIV(H2O)x(NO3)5]- in 9.0 M HNO3 and [UVIO2(NO3)3]- in 14.5 M HNO3, respectively. The present multitechnique approach also suggests the formation of two intermediate UVI species, a 5-fold mononitrato complex ([UVIO2(H2O)32-NO3)]+) and a 6-fold dinitrato complex ([UVIO2(H2O)22-NO3)2]0), involving an increase in the total coordination number on the uranyl(VI) equatorial plane from 5 to 6 with increasing HNO3 concentration. The presence of unidentate coordinate nitrato complexes or tetranitrato UVI complexes is less probable in the present HNO3 system.

Permalink: https://www.hzdr.de/publications/Publ-12431
Publ.-Id: 12431


Persistent decoupling of valence neutrons toward the dripline: Study of C-20 by gamma-spectroscopy

Elekes, Z.; Dombrádi, Z.; Aiba, T.; Aoi, N.; Baba, H.; Bemmerer, D.; Brown, B. A.; Furumoto, T.; Fülöp, Z.; Iwasa, N.; Kiss, Á.; Kobayashi, T.; Kondo, Y.; Motobayashi, T.; Nakabayashi, T.; Nannichi, T.; Sakuragi, Y.; Sakurai, H.; Sohler, D.; Takashina, M.; Takeuchi, S.; Tanaka, K.; Togano, Y.; Yamada, K.; Yamaguchi, M.; Yoneda, K.

he very neutron-rich nucleus 20C has been investigated by inelastic scattering on 208Pb and liquid hydrogen targets. Through distorted wave analysis, the reduced electric quadrupole transition probability B(E2;02)<18.4 (stat) e2 fm4 and the neutron transition probability M=292±52 (stat) fm4 have been derived. A simple shell model calculation has shown a need for a factor of about 0.4 decrease of the normal polarization charges to elucidate the results. This is interpreted as a decoupling of the valence neutrons from the nuclear core in carbon isotopes heavier than 14C.

Permalink: https://www.hzdr.de/publications/Publ-12430
Publ.-Id: 12430


The sulfate coordination of Np(IV), Np(V) and Np(VI) in aqueous solution

Hennig, C.; Ikeda-Ohno, A.; Tsushima, S.; Scheinost, A.

Coordination and redox behavior of Np(IV), Np(V) and Np(VI) sulfate in aqueous solution has been investigated by Np L3-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, cyclic voltammetry and density functional theory (DFT) calculations. The sulfate coordination mode, i.e. monodentate or bidentate, has been determined from neptunium-sulfur distances RNp-S and coordination numbers NS obtained by EXAFS. Np(VI) is coordinated by sulfate in bidentate (RNp-S = 3.12  0.02 Å) and monodentate (RNp-S = 3.61  0.02 Å) modes at a low sulfate concentration of [SO42-]/[NpO22+] = 1. At higher [SO42-]/[NpO22+] ratios bidentate coordination prevails. Approximately two bidentate sulfate groups are coordinated to Np(VI) at 2.0 M SO42- and pH 1.1. Np(V) is coordinated by sulfate in bidentate (RNp-S = 3.16  0.02) and monodentate (RNp-S = 3.67  0.02 Å) modes. However, sulfate coordination is less pronounced here and does not exceed in total one SO42- ligand in a solution of 2.0 M SO42-. The redox couple Np(VI)/Np(V) is reversible at low [SO42-]/[NpO22+] ratio and becomes irreversible at high sulfate concentration due to structural rearrangement of the sulfate ligands. Finally, Np(IV) also shows bidentate (RNp-S = 3.06  0.02 Å) and monodentate (RNp-S = 3.78  0.02 Å) coordination modes. The sulfate coordination increases with increasing [SO42-]/[Np4+] ratio. A comparison of other tetravalent actinides reveals that the monodentate sulfate coordination decreases whereas the bidentate coordination increases along the series Th(IV) - U(IV) - Np(IV). This trend was studied by DFT calculations and is discussed in terms of solvation energy and covalency of the molecular bonds.

Keywords: EXAFS; DFT; Neptunium; Sulfat

Permalink: https://www.hzdr.de/publications/Publ-12429
Publ.-Id: 12429


Electroluminescence (at 316 nm) and electrical stability of a MOS light-emitting device operated at different temperatures

Prucnal, S.; Rebohle, L.; Skorupa, W.

The influence of the operating temperature on the electrical and optical stability of the Metal-Oxide-Silicon-based light-emitting device (MOSLED) with Gd and Gd plus K implanted SiO2 layers was investigated. An increase of the temperature from room temperature up to 423 K reduces the gate voltage by about 8 V due to the Auger de-excitation mainly. It increases the rate of the EL quenching process and the degradation of the MOSLED structure by a factor of three. On the other hand, the MOSLED structure containing Gd and K atoms shows that an increase of the operating temperature leads to a threefold decrease of the decay time what was not observed in the gadolinium-implanted sample. The decrease of the operating temperature down to 70 K leads to an increase of the EL intensity and the operating time in both cases.

Keywords: electroluminescence; gadolinium; MOS device; K codoping; operation temperature dependence

Permalink: https://www.hzdr.de/publications/Publ-12428
Publ.-Id: 12428


U(VI) sorption on granite: prediction and experiments

Nebelung, C.; Brendler, V.

The sorption characteristics of U(VI) on granite was investigated in batch experiments for understanding the far-field behaviour in granitic geological nuclear repositories. The granite (from Eibenstock, Germany) was a mixture of quartz (40.9%) albite (26.7%), orthoclase (14.0%), biotite (2.0%), rubicline (0.7%), muscovite (14.7%), and hematite (1.0%) according to the ICP-MS after digestion. Except hematite and rubicline all components were found by XRD. The surface area (N2-BET) of the granite was 0.35 m2/g. The sorption conditions were ambient atmosphere, 0.1M NaClO4, sorption time 5 d for pH dependence (pH 3-11, at U(VI) 10-6 M), and U(VI) concentration dependence (10-9-10-3 M, at pH 5).

A scientifically founded description of sorption processes at the mineral-liquid surface is possible with the surface complexation models (SCM), the ion adsorption on surface sites as complexation reaction. The approach to real systems is the component additivity, the superposition of simultaneous sorption and competition reactions based on mineralogical composition. We used the diffuse double layer model (DDL) to predict the sorption with the code MINTEQA2 (Version 4.03, US EPA May 2006), thermodynamic data of aqueous and solid species from the NEA-TDB [1], and the respective protolysis data and surface complex constants for all mineralogical components of granite.

The prediction of U(VI) sorption on granite vs. pH was very good. Even the increased retention at pH 11 can be explained as precipitation of uranophane by calculation with the measured CO2 (lower than the equilibrium CO2). The modelling of the sorption on granite vs. U(VI) concentration shows a good agreement of measured and predicted values. At high concentrations the precipitation of well crystallized schoepite was predicted. Such a well crystallized mineral is unlikely after only 5 days sorption time. Excluding schoepite, the precipitation of metaschoepite was predicted for concentrations >10-4 mol/L U(VI).

[1] Guillaumont, R. et al. (2003) "Update on the chemical thermodynamics of U, Np, Pu, Am, Tc. Chemical Thermodynamics", Vol. 5 (OECD Nuclear Energy Agency, ed.), Elsevier, Amsterdam.

Acknowledgement
Funding by the BMBF and BMWA (02C1144) is gratefully acknowledged.

Keywords: sorption; sorption prediction; surface complex model; granite

  • Lecture (Conference)
    Migration '09 12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 20.-25.09.2009, Kennewick, Washington,, USA
  • Radiochimica Acta 98(2010)9-11, 621-625

Permalink: https://www.hzdr.de/publications/Publ-12427
Publ.-Id: 12427


Validation of DYN3D pin-power calculation against experimental VVER-full-core benchmark

Hádek, J.; Mittag, S.

The EU NURESIM V1000-VALCO-STAT benchmark is focused on three-dimensional VVER-1000 steady-states with assembly-averaged and fine-mesh power distributions. Calculation results are compared with measurements from the Moscow zero-power critical facility V-1000, which was used as a full-scale mock-up of the Russian VVER-1000 reactor core. A very low moderator temperature and radial-reflector asymmetries were significant for this core. The calculations are performed with the reactor dynamic nodal code DYN3D. The usual node-averaged approach is applied in the first step. Then, an intra-nodal pin-wise power reconstruction method and its combination with the pin-powers from the lattice code HELIOS zero-net-current fuel-assembly calculations are applied. The power distributions calculated by pin-wise reconstruction show better agreement with the measurement than the node-averaged values, which is particularly obvious for fuel assemblies with inserted control clusters.

Keywords: benchmark; NURESIM; VVER; DYN3D; pin-power reconstruction

  • Lecture (Conference)
    International Conference on Mathematics, Computational Methods & Reactor Physics (M&C 2009), 03.-07.05.2009, Saratoga Springs, New York, USA
  • Contribution to proceedings
    International Conference on Mathematics, Computational Methods & Reactor Physics (M&C 2009), 03.-07.05.2009, Saratoga Springs, New York, USA
    Proceedings on CDROM: paper 200483, La Grange Park, USA: ANS

Permalink: https://www.hzdr.de/publications/Publ-12426
Publ.-Id: 12426


Hydrogen-vacancy complexes in electron-irradiated niobium

Cizek, J.; Procházka, I.; Daniš, S.; Brauer, G.; Anwand, W.; Gemma, R.; Nikitin, E.; Kirchheim, R.; Pundt, A.; Islamgaliev, R. K.

The aim of the present work was to investigate the microstructure of bulk niobium irradiated by 10 MeV electrons. Positron-annihilation spectroscopy was employed as a principal technique for the characterization of irradiation-induced defects. Experimental results were compared to first-principles theoretical calculations of positron characteristics. In addition to extended positron-annihilation studies, the specimens were characterized also by x-ray diffraction. It was found that irradiation-induced vacancies are surrounded by hydrogen. Complexes consisting of a Nb vacancy surrounded by one and two H atoms were identified in the irradiated specimens. The concentration of these vacancy-hydrogen complexes was estimated to be (18–24)x10^−5 at. %. Vacancy-2H complexes are found to represent the dominating type of defects. Hydrogen atoms surrounding a Nb vacancy cause a shortening of the lifetime of trapped positrons. Moreover, it was demonstrated that hydrogen attached to Nb vacancy can be identified by coincidence Doppler broadening technique. The effect of a thin Pd (or Cr) overlayer on the irradiation-induced defects was investigated also. It was found that the relative fraction of vacancy-2H complexes is higher in the specimens irradiated with such an overlayer.

  • Physical Review B 79(2009), 054108

Permalink: https://www.hzdr.de/publications/Publ-12425
Publ.-Id: 12425


Spezialsensorik für die Prozessindustrie - Technologietransfer aus der Sicherheitsforschung

Da Silva, M. J.; Thiele, S.; Schleicher, E.; Hauptmann, T.; Schmid, R.; Hampel, U.

Der Vortrag gibt einen Überblick über bedeutende Sensorkonzepte aus dem Bereich der Abteilung "Experimentelle Thermofluiddynamik". Die Zielgruppe des Vortrages sind potentielle Interessenten aus der Industrie, welche im Rahmen des FORMAT-Projektes kontaktiert wurden.

Keywords: sensor concepts; process industry; FORMAT

  • Lecture (others)
    Informationsveranstaltung bei CHOREN Fuel Freiberg GmbH & Co. KG, 06.02.2009, Freiberg, Deutschland
  • Lecture (others)
    Informationsveranstaltung bei EBZ GmbH, 27.01.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung für Sick Engineering GmbH, 04.02.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung bei der GlaxoSmithKline GmbH & Co. KG, 16.02.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung für die Umwelt- und Ingenieurtechnik GmbH Dresden, 17.02.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung für Roxar ASA, 23.02.2009, Bergen, Norwegen
  • Lecture (others)
    Informationsveranstaltung für Statoil Hydro, 24.02.09, Porsgrunn, Norwegen
  • Lecture (others)
    Informationsveranstaltung für die Lechler GmbH, 10.03.2009, Metzingen (Württ), Deutschland
  • Lecture (others)
    Informationsveranstaltung für die Riesaer Brennstoffzellentechnik GmbH, 18.02.2009, Riesa, Deutschland
  • Lecture (others)
    Informationsveranstaltung für LyondellBasell Industries, 11.03.2009, Ferrara, Italien
  • Lecture (others)
    Informationsveranstaltung für Bayer Technology Services GmbH, 13.03.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung für die Evonik Oxeno GmbH, 30.03.2009, Marl, Deutschland
  • Lecture (others)
    Informationsveranstaltung für das Institut für Leichtbau und Kunststofftechnik (ILK) der TU-Dresden, 26.02.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung bei Endress + Hauser - Conducta Gesellschaft für Mess- und Regeltechnik mbH u. Co.KG, 30.03.2009, Waldheim, Deutschland
  • Lecture (others)
    Informationsveranstaltung bei der Dow Olefinverbund GmbH, 31.03.2009, Schkopau, Deutschland
  • Lecture (others)
    Informationsveranstaltung für das "Institute of Nuclear Safety System" (INSS), 26.05.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung für die Firma DuPont (USA), 18.04.2009, Tokyo, USA

Permalink: https://www.hzdr.de/publications/Publ-12424
Publ.-Id: 12424


Atomic layer deposition of MgF2 thin films using TaF5 as a novel fluorine source

Pilvi, T.; Puukilainen, E.; Kreissig, U.; Leskela, M.; Ritala, M.

Magnesium fluoride is one of the most important optical thin film materials due to the good light transparency down to the vacuum ultraviolet (UV) range. A novel atomic layer deposition (ALD) process was developed for depositing MgF2 thin films. Instead of the previously used fluorine sources, namely HF or TiF4, we used TaF5 as the fluorine precursor for the first time in ALD. The films were grown in a temperature range of 225-400 degrees C. The films were characterized by X-ray diffraction, X-ray reflection, atomic force microscopy, scanning electron microscopy, spectrophotometer, and elastic recoil detection analysis. Optical and electrical properties of the films were also studied. The films grew in columnar fashion onto silicon and all the films were polycrystalline. The film densities were close to bulk MgF2. Films with a good stoichiometry and low impurity levels were achieved. The refractive indices were between 1.36 and 1.38 at lambda = 580 nm. The permittivity of a film grown at 300 degrees C was 5.0. The transmittance of a film deposited at 350 degrees C was good even in the deep UV range. This type of novel ALD process using the new fluorine precursor TaF5 is a convenient method also for depositing other metal fluoride thin films.

Keywords: CHEMICAL-VAPOR-DEPOSITION; OPTICAL COATINGS; ASSISTED DEPOSITION; LASER INTERACTION; ALD PROCESS; PRECURSOR; MICROSCOPY; EPITAXY; SI2H6; TIF4

  • Chemistry of Materials 20(2008)15, 5023-5028

Permalink: https://www.hzdr.de/publications/Publ-12423
Publ.-Id: 12423


Modelling of stratified two phase flows using an interfacial area density model

Höhne, T.; Vallee, C.

Stratified two-phase flow regimes can occur in chemical plants, nuclear reactors and oil pipelines. A relevant problem is the development of wavy stratified flows which can lead to slug generation. The slug flow regime is characterized by an acceleration of the gaseous phase and by the transition of fast liquid slugs, which carry a significant amount of liquid with high kinetic energy. It is potentially hazardous to the structure of the system due to the strong oscillating pressure levels formed behind the liquid slugs as well as the mechanical momentum of the slugs. Because these flow conditions cannot be predicted with the required accuracy and spatial resolution by the one-dimensional system codes, the stratified flows are increasingly modelled with computational fluid dynamics (CFD) codes. In CFD, closure models are required that must be validated. The recent improvements of the multiphase flow modelling in the ANSYS CFX code make it now possible to simulate these mechanisms in detail. In order to validate existing multiphase flow models and to further develop these, measurement data with a high-resolution in time and also in space are needed. For the experimental investigation of co-current air/water flows, the HAWAC (Horizontal Air/Water Channel) was built. The channel allows in particular the study of air/water slug flow under atmospheric pressure. Parallel to the experiments, CFD calculations were carried out. The two-fluid model was applied with a special turbulence damping procedure at the free surface. An Algebraic Interfacial Area Density (AIAD) model on the basis of the implemented mixture model was introduced, which allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface. The behaviour of slug generation and propagation at the experimental setup was qualitatively reproduced by the simulation, while local deviations require a continuation of the work. The creation of small instabilities due to pressure surge or an increase of interfacial momentum should be analysed in the future. Furthermore, experiments with pressure and velocity measurements are planned and will allow quantitative comparisons, also at other superficial velocities.

Keywords: CFD; stratified flow; slug flow; HAWAC

  • Contribution to proceedings
    Fifth International Conference on Computational and Experimental Methods in Multiphase and Complex Flow, 15.-17.06.2009, New Forest, Großbritannien
    CD-ROM
  • Lecture (Conference)
    Fifth International Conference on Computational and Experimental Methods in Multiphase and Complex Flow, 15.-17.06.2009, New Forest, Großbritannien
  • WIT Transactions on Engineering Sciences Volume 63(2009), 123-135

Permalink: https://www.hzdr.de/publications/Publ-12422
Publ.-Id: 12422


Spectroscopic comparison of aqueous Np(VI) and U(VI) species

Müller, K.; Foerstendorf, H.; Tsushima, S.; Brendler, V.; Bernhard, G.

The distribution of aqueous species of actinide(VI) ions primarily defines their geochemical reactions and, thus, influences their migration behaviour in the environment. In aqueous solution, uranium and neptunium exist as actinyl ions AnO22+ (An = U, Np). They form different complexed species depending on their concentration level, pH range and the presence of potential ligands, such as carbonate. In recent years, the aqueous U(VI) system has been investigated intensively, in contrast to Np(VI). However, the thermodynamic data often arise from non-spectroscopic experiments mostly performed in the millimolar concentration range. [1] Up to now, a verification of the data of the different actinyl species by spectroscopic techniques providing direct molecular structural information is still incomplete. In particular, actinide solutions at lower concentrations and at neutral pH values, reasonably in an environmental context, were addressed seldom. [2]
In this study, the Np(VI) speciation at a submillimolar concentration range was investigated applying ATR FT-IR and NIR absorption spectroscopy, and computed modeling of updated NEA thermodynamic data. The findings are comparatively discussed with results obtained from U(VI) under identical conditions.
At ambient atmosphere, the formation of similar actinyl(VI) species can be derived from IR spectroscopic results at pH ≤ 4, namely the fully hydrated AnO22+ (An = U, Np) and monomeric hydrolysis products. At higher pH, the spectra evidence structurally different species contributing to the speciation of both actinides. At pH 5, the formation of (NpO2)2CO3(OH)3− probably occurs which is supported by modeling NEA data and results from NIR spectroscopy. For uranium, the presence of additional hydroxo complexes is assumed in this pH range.
1. Guillaumont, R. et al. Update on the Chemical Thermodynamics of U, Np, Pu, Am and Tc. Elsevier: Amsterdam, 2003; p 970.
2. Müller, K. et al. Inorganic Chemistry 2008, 47, (21), 10127-10134.

  • Lecture (Conference)
    Goldschmidt 2009 - "Challenges to Our Volatile Planet", 21.-26.06.2009, Davos, Schweiz
  • Geochimica et Cosmochimica Acta 73(2009)13S, A914

Permalink: https://www.hzdr.de/publications/Publ-12421
Publ.-Id: 12421


Blasenmitriss durch Impinging Jets

Schmidtke, M.; Danciu, D.

Der Gaseintrag durch impinging jets wird mittels Experimenten und CFD-Simulationen untersucht. In den Experimenten wird die Düsenhöhe über dem Waserbecken und die Wassergeschwindigkeit in der Düse variiert. Der Blasenmitriss durch den Wasserstrahl wird mittels einer Hochgeschwindigkeits-Video-Kamera beobachtet. Quantitative Daten zu Blasengrößen so wie Geometrien der Blasenfahne werden durch Bildverarbeitung aus den Videofilmen gewonnen. Zusätzlich wird die Entwicklung zweiphasiger Jets unter Wasser mittels CFD untersucht, unter Verwendung des Euler-Euler Ansatzes. Es wird ein Kriterium für die Eindringtiefe definert, und die simulierten Blasenfahnen werden mit den experimentell beobachteten hinsichtlich der Eindringtiefe verglichen.

The gas entrainment by impinging water jets is studied by the means of experiments and CFD simulations. In the experiments, the nozzle height above the water pool and the water velocity inside the nozzle is varied and the bubble entrainment below the jet is observed with a video camera. Quantitative data for bubble sizes and the geometry of the bubble plume are obtained by image processing. The development of two phase jets under water is also studied with CFD, using the Euler-Eulerian approach. Defining a criterion for an average penetration depth, the simulated plumes are compared with those observed in the experiments.

Keywords: impinging jets; bubble entrainment; gas carryunder; multiphase; penetration depth; plunging

  • Lecture (Conference)
    Jahrestreffen der Fachausschüsse Mehrphasenströmungen und Wärme- und Stoffübertragung, 03.-05.03.2009, Bad Dürkheim, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12420
Publ.-Id: 12420


Air entrainment by impinging jets. Experimental identification of the key phenomena and approaches for their modelling.

Schmidtke, M.; Danciu, D.; Lucas, D.

The gas entrainment by impinging water jets is studied by the means of experiments and CFD simulations. In the experiments, the nozzle height above the water pool and the water velocity inside the nozzle is varied and the bubble entrainment below the jet is observed with a video camera. Quantitative data for bubble sizes and the geometry of the bubble plume are obtained by image processing. The development of two phase jets under water is also studied with CFD, using the Euler-Eulerian approach. Defining a criterion for an average penetration depth, the simulated plumes are compared with those observed in the experiments

Keywords: impinging jets; plunging; gas entrainment; bubble; carryunder; plume; multiphase; CFD

  • Contribution to proceedings
    17th International Conference on Nuclear Engineering ICONE 17, 12.-16.7.2009, Brussels, Belgium
  • Lecture (Conference)
    17th International Conference on Nuclear Engineering ICONE 17, 12.-16.07.2009, Brussels, Belgium

Permalink: https://www.hzdr.de/publications/Publ-12419
Publ.-Id: 12419


Studies on oxygen concentrations in uranium contaminated biofilms: Comparing electrochemical and fiber-optic sensors

Krawczyk-Bärsch, E.

Within the framework of ReCosy first comparative investigations of electrochemical and fiber-optic sensors were performed in collaboration with the University Potsdam (UPPC). Fiber-optic sensor measurements in biofilms have some advantages compared to those made by electro-chemical microelectrodes. As described in Beyenal et al. (2000) fiber-optic sensors are immune to environmental changes in pH, salinity, and ionic strength and immune to interference from moisture, carbon dioxide, methane, and other substances. A range of fiber-optic sensor studies were carried out to measure in situ geochemical gradients in biofilms. To our knowledge optical sensors applied to biofilm samples exposed to heavy metals are so far not reported in the literature. In our first collaboration with the UPPC we compared the oxygen concentration profiles obtained by electrochemical and optical microsensors, respectively. Oxygen concentration profiles were measured in the biofilms by electrochemical microsensors of the Clark design (Unisense, Denmark). These Clark-type oxygen microsensors are generally used for microbial ecology studies and contain a guard electrode. They have a tip diameter of 10 µm, a stirring sensitivity of <1–2%, and a response time of <1 s. The used multispecies biofilms (microbial diversity described in Krawczyk-Bärsch et al., 2008) were cultivated in the laboratory under non-sterile conditions in different biofilm reactors. One biofilm reactor was adjusted to a uranium concentration of (1x10-6 M), which is typical for uranium contaminated sites. The data achieved from both sensor methods are directly comparable. Fiber-optic sensor measurements showed high concentrations of oxygen over the total thickness of the biofilms, which were not in contact with uranium. In contrast, biofilms exposed to uranium revealed a much lower oxygen concentration in the bottom parts of the biofilm as described before in Krawczyk-Bärsch et al. (2008). Already at a depth of approximately 400 µm no oxygen was detectable. The comparative studies revealed that depending on the existing environmental conditions during the measurements a decision for the appropriate method is possible. However, further developments, e.g. miniaturization of the sensor equipments, are needed and aimed for within ReCosy.

References:
Beyenal, H. et al. (2000) Appl Opt 39, 3408.
Krawczyk-Bärsch, E. et al. (2008) Geochimica et Cosmochimica Acta 72, 5251–5265

  • Lecture (Conference)
    1st Annual Workshop of the Recosy Project, 10.-12.02.2009, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-12418
Publ.-Id: 12418


The influence of charge-transfer complexes on the copolymerization behavior of cyclic maleic acid derivatives with donor monomers

Schmidt-Naake, G.; Drache, M.; Leonhardt, K.

- wird nachgereicht

  • Macromolecular Chemistry and Physics 199(1998)3, 353-361

Permalink: https://www.hzdr.de/publications/Publ-12417
Publ.-Id: 12417


First reporting of the scientific-technical outcome of WP 4.2: Chemical and redox behavior of the investigated radionuclides in the different systems through microbial mediated processes

Krawczyk-Bärsch, E.

Within the framework of ReCosy redox processes in biofilms, grown in-situ in radionuclide contaminated environments, will be studied by oxygen and redox potential microsensors. First in-situ measurement activities have already taken place in a former uranium mine in Saxony (Germany). Since the mining activities had stopped in 1990, the uranium mine has been partially flooded for remediation. This resulted in encroaching release of heavy metals and radionuclides as contaminants in acid, sulphate-rich waters. Huge biofilms with a thickness of more than 10 centimeters are currently growing in drainage channels (so far not flooded) under acid conditions and in the presence of uranium concentrations of approximately 1x10-4 M. Concentration profiles of oxygen were measured in these biofilms in-situ by means of electrochemical microsensors of the Clark design (Unisense, Denmark) with a tip diameter of 10 µm. The sensors were connected to a picoammeter and fixed in a holder on a motor-driven micromanipulator stage, connected with a motor controller, for a precise small-scale positioning and for automated measurements in 50 µm steps in Z-axis. Due to the hetero-geneities of the biofilm, numerous microprofiles were measured at different points of the biofilm. The results revealed a fast decrease of the oxygen concentration in the biofilm profiles. Already at a depth of approximately 2 mm no oxygen was detectable. It can be assumed that the microorganisms of the biofilm battle the toxic effects of aqueous uranium in a similar way as the biofilms described in Krawczyk-Bärsch et al. (2008). The biofilm community is reacting to the exposition of uranium in environmentally relevant concen-trations with an increase of the respiratory activity of the microorganisms. The increased metabolic activity of the microorganisms, as a result of an activation of heavy metal resistance mechanisms, will lead to larger anoxic zones (reducing zones) within the biofilms, which may induce redox processes. In these zones uranium (VI) can be reduced to highly insoluble uranium (IV) through abiotic processes. The precipitations of uranium (IV) solids will result in an increased removal of uranium and immobilisation of uranium from the solution.

References:
Krawczyk-Bärsch, E. et al. (2008) Geochimica et Cosmochimica Acta 72, 5251–5265

  • Lecture (Conference)
    1st Annual Workshop of the Recosy Project, 10.-12.02.2009, Barcelona, Spain
  • Contribution to proceedings
    1st Annual Workshop of the Recosy Project, 10.-12.02.2009, Barcelona, Spain
    Collaborative Project "Redox Phenomena Controlling Systems", Karlsruhe: Forschungszentrum Karlsruhe GmbH, KIT Report FZKA 7466 Dezember 2009, 43-46

Permalink: https://www.hzdr.de/publications/Publ-12416
Publ.-Id: 12416


Zur Anwendung von Schwerionen und Protonen in der Strahlentherapie

Enghardt, W.

no abstract available

  • Lecture (others)
    34. Seminar für Mitarbeiter von Landesbehörden, Landesanstalt für Personendosimetrie und Strahlenschutzausbildung Mecklenburg-Vorpommern, 13.11.2008, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12415
Publ.-Id: 12415


Cell response to laser-accelerated electron beams.

Pawelke, J.

wird nachgereicht

  • Invited lecture (Conferences)
    N4 Workshop on Radiation Protection Issues, 14.-17.12.2008, Chamonix, France

Permalink: https://www.hzdr.de/publications/Publ-12414
Publ.-Id: 12414


Neue Entwicklungen im Strahlenschutz in der Forschung.

Pawelke, J.

wird nachgereicht

  • Invited lecture (Conferences)
    2. Strahlenschutzseminar für Lehrer im Freistaat Sachsen, 18.11.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12413
Publ.-Id: 12413


Mensch und Strahlung – Wie verstehen wir die Wirkung der zur Krebstherapie eingesetzten Strahlen auf menschliche Zellen?

Pawelke, J.

wird nachgereicht

  • Lecture (others)
    Lange Nacht der Wissenschaften, 04.07.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12412
Publ.-Id: 12412


Laser Radiooncology.

Pawelke, J.

wird nachgereicht

  • Lecture (others)
    3rd Meeting of the Scientific Advisory Board of OncoRay, 28.02.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12411
Publ.-Id: 12411


Ultra fast electron beam x-ray computed tomography for two-phase flow measurement

Fischer, F.; Hampel, U.

Electron beam X-ray CT is a new technique for a fast measurement of multiphase flows with frame rates of 1000 images per second and more. It gives, in principle, quantitatively accurate images of the flow at high spatial resolution and it is non-intrusive since moderately radiation absorbing vessel walls can be penetrated by X-rays. However, on the road to a technical realisation of such a technique within a computed tomography system many problems have to be solved. As a first prototype for scientific flow measurement studies we devised and built a fast scanned electron beam X-ray tomography scanner. The scanner consists of an electron beam unit that can be operated at up to 150 kV acceleration voltage and up to 65 mA electron beam current, with the required electron optics for beam adjustment, beam focussing and beam deflection unit and a fast circular CZT detector comprising 240 elements of 1.5 mm × 1.5 mm × 1.5 mm active pixel area. X-ray radiation is produced on a circular water cooled tungsten target. The CT system achieves up to 7000 frames per second with a spatial resolution of 1 millimetre. First two-phase flow experiments have been carried out on gas-water flows in bubble columns. Further, a vertical test section made of titanium alloy has been installed at the TOPFLOW facility and will be used in the future to study the evolution of two-phase gas-water pipe flow at high pressures and temperatures.

Keywords: Two-phase flow; electron beam tomography; CFD code validation

Permalink: https://www.hzdr.de/publications/Publ-12410
Publ.-Id: 12410


Implications of three dimensional velocity distributions on the generation of magnetic fields in the Von-K\'arm\'an-Sodium dynamo experiment.

Giesecke, A.; Stefani, F.; Gerbeth, G.

Numerical simulations of the kinematic induction equation have been carried out in a cylindrical domain that resembles the configuration of the VKS dynamo experiment. Primary objective are investigations of non-axisymmetric source terms and their impact on the critical Reynolds number as well as onthe structure of the field geometry.

In case of an axisymmetric velocity distribution the resulting magnetic field is always determined by an azimuthal m=1-mode which is in contradiction to the experimental realization that is dominated by an axisymmetric field.

A simple non-axisymmetric contribution can be parameterized by a localized $\alpha$-effect which arises from the induction action of radially oriented helical outflow between the impeller blades that drive the flow. However, it turns out, that the amplitude of $\alpha$ which is necessary to obtain an axisymmetric field is far above realistic values.

Further potential contributions involve a time dependent non-axisymmetric velocity component in form of azimuthal drifting equatorial vortices as they have been found in water experiments. These structures provide a coupling between different field modes, but the m=1 mode still remains dominant. Resonance effects provide a strong increment of the field growthrate if the vortex drift motion proceeds phase synchronous with a drift of the magnetic field caused by equatorial symmetry braking of the velocity distribution. Presumably this phenomenon is not relevant in the experiment, as the drift of the eigenfield is very small so that resonance would require a much slower vortex drift velocity than it is observed.

So far, non-axisymmetric source terms in the induction equation are not able to explain the dominance of the m=0 mode, however it remains still possible that a quite exotic dynamo mechanism is operating which is essentially based on induction terms generated by the azimuthal variation of the permeability introduced by the ferrous impellers.

Keywords: dynamo; alpha-effect; induction; kinematic simulations

  • Lecture (Conference)
    Frontiers in Dynamo Theory, 16.-20.03.2009, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-12409
Publ.-Id: 12409


Mensch und Strahlung – Forschung an ELBE.

Pawelke, J.

wird nachgereicht

  • Lecture (others)
    Lehrerfortbildung 2007/2008 im FZD: „Moderne Beschleunigerkonzepte und ihre Anwendung in der Medizin“, 15.02.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12408
Publ.-Id: 12408


Weltweit erste Zellbestrahlungsexperimente mit laserbeschleunigten Teilchenstrahlen.

Pawelke, J.

wird nachgereicht

  • Invited lecture (Conferences)
    Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität, 21.01.2008, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12407
Publ.-Id: 12407


Therapie von Tumorerkrankungen mit laserbeschleunigten Teilchenstrahlen.

Pawelke, J.

wird nachgereicht

  • Invited lecture (Conferences)
    OncoRay, Strategie-Meeting, 08.-09.01.2008, Gröditz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12406
Publ.-Id: 12406


Präzisions-Strahlentherapie mit Laser-Ionenbeschleunigern.

Karsch, L.; Messner, L.; Pawelke, J.; Richter, C.; Schüttig, R.

wird nachgereicht

  • Poster
    Tag der Gesundheitsforschung, 17.02.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12405
Publ.-Id: 12405


Auf dem Weg zu einer neuen Strahlentherapie mit laserbeschleunigten Teilchen – Erste Experimente mit Elektronen.

Karsch, L.; Hümmerich, J.; Beyreuther, E.; Lessmann, E.; Pawelke, J.; Nicolai, M.; Schlenvoigt, H.

wird nachgereicht

  • Poster
    OncoRay, Strategie-Meeting, 08.-09.01.2008, Gröditz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12404
Publ.-Id: 12404


Mit laserbeschleunigten Teilchen gegen Tumore – Erste in vitro Experimente an laserbeschleunigten Elektronenstrahlen.

Naumburger, D.; Beyreuther, E.; Enghardt, W.; Karsch, L.; Lessmann, E.; Messner, L.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.; Baumann, M.

wird nachgereicht

  • Lecture (Conference)
    11. Jahrestagung der Gesellschaft für Biologische Strahlenforschung (GBS), 06.-08.10.2008, Tübingen, Deutschland
  • Contribution to proceedings
    11. Jahrestagung der Gesellschaft für Biologische Strahlenforschung (GBS), 06.-08.10.2008, Tübingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12403
Publ.-Id: 12403


Implementation of a High Level Hands-on-Training at an Experimental PET Scanner.

Würschig, T.; Kluge, T.; Enghardt, W.

The remarkable increase of medical imaging within the last decade demands the implementation of teaching programs for experts and students. Such courses must achieve both the realization of theoretical basics and an understanding of its implementation within real systems. This accounts for positron emission tomography (PET) as well. PET is, among other techniques like computer tomography (CT) or magnetic resonance imaging (MRI), one of the key technologies for biological and medical imaging. To teach and demonstrate the fundamentals of CT and the physical background of PET as well as to illustrate the signal processing of a coincidence measurement and the data processing of multi-parameter, list-mode data sets, the experimental PET scanner PET-TW05 has been developed. It is a simplified but still fully functional scanner consisting of two commercial BGO block-detectors. They are fixed in opposite to each other and can be moved along a linear axis and rotated around the field of view (FOV). The hardware layout and the software performance of the PET-TW05 scanner support the demonstration of important process steps of PET imaging like (i) system calibration, (ii) detector efficiency measurements, (iii) determination of time and spatial resolution of a PET scanner, (iv) list-mode data acquisition, (v) tomographic reconstruction by means of filtered backprojection, (vi) the effect of different filter kernels as well as of time and energy windows on the image quality, (vii) the influence of scatter on the image quality. Furthermore, the principle of time-of-flight PET can be experimentally demonstrated.

Keywords: PET; education; filtered backprojection; BGO block detector; list-mode data acquisition

  • Poster
    IEEE NSS-MIC Nuclear Science Symposium Conference Record M06-147, 19.-25.10.2008, Dresden, Deutschland
  • Contribution to proceedings
    IEEE NSS-MIC Nuclear Science Symposium Conference Record M06-147, 19.-25.10.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12402
Publ.-Id: 12402


Considerations on the Biological Effect of Laser Induced Radiation with High Dose Rates.

Khaless, A.; Karsch, L.; Enghardt, W.

wird nachgereicht

  • Lecture (Conference)
    IEEE NSS-MIC Nuclear Science Symposium Conference Record N51-5, 19.-25.10.2008, Dresden, Deutschland
  • Contribution to proceedings
    IEEE NSS-MIC Nuclear Science Symposium Conference Record N51-5, 19.-25.10.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12401
Publ.-Id: 12401


Dosimetric comparison between gated and steady photon and electron beams delivered by the Siemens ONCOR linear accelerator.

Wieczorkowski, L.; Hoinkis, C.; Lehmann, D.; Enghardt, W.

Objective: The gated irradiation technique is a sophisticated tool for focusing the prescribed dose to periodically moving target volumes while sparing the surrounding healthy tissue. Thus, gated irradiation is predominantly applied to organ motion caused by breathing. The tumour is irradiated in a specific phase of its motion. This requires to switch on and off the beam periodically. The beam-on time may change in a certain range depending on the individual breathing curve, site specific conceptions and the tumour dose conformity required. The latter will be increased for a short beam-on time, however, causing an increase in the number of irradiation cycles for reaching the prescribed dose. Prior to the therapeutic application of gated irradiation, the dose distributions delivered for photons and electrons in steady and gated mode in static phantoms were measured.

Materials: Photon and electron beams were delivered by a Siemens ONCOR Impression linear accelerator. The gating signal was provided by a commercial respiratory gating system based onto a pressure belt feedback mechanism in combination with a respiratory phantom (AZ-733, Anzai Medical). For measurements in stationary phantom linear diode array BMS 96 (Schuster Medizinische Systeme GmbH) was used to measure beam profiles and a solid water phantom (RW3, PTW) with ionization chamber (0.6 cm3 Farmer, PTW) were used to measure the depth dose at different depths. Respiratory frequency were set to 10 and 15 min-1 and beam-on time to 1, 2 and 3 s. Different field sizes (5 × 5, 10 × 10 and 20 × 20 cm2) for 6 and 15 MV photons and 10 × 10 cm2 for 9 and 12 MeV electrons were used.

Results: Depth doses maximum deviation for gated photon and electron beams is up to 0.8 % in comparison to non-gated beams. The maximum deviation between gated and non-gated dose profiles has been found to be less than 3 % and is located in the penumbra region. Deviations are randomized and do not depend on the photon and electron energy. Minor dependence of field size was observed but in most cases, the results for the 10 × 10 cm2 field were more accurate. None respiratory frequency dependence was noticed as well.

Conclusion: To evaluate more realistic cases with respect to therapy the dosimetric and geometric verification using a moving phantom will also been done.

  • Poster
    39. Jahrestagung Deutsche Gesellschaft für Medizinische Physik e.V. Oldenburg, 10.-13.09.2008, Oldenburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12400
Publ.-Id: 12400


Entwicklung eines bildgeführten Bestrahlungsgerätes für die präzise Tumorbestrahlung an Kleintieren.

Khaless, A.; Thute, P.; Hietschold, V.; Enghardt, W.

In den letzen Jahren erzielte man große Fortschritte bei der Bildgebung von Kleintieren. Mittlerweile gibt es für fast alle Modalitäten, die für die Bildgebung am Menschen eingesetzt werden, auch Varianten für Nagetiere (microCT, microMRI, microPET). In der Krebsforschung werden diese bildgebenden Verfahren bis jetzt überwiegend bei Tierexperimenten genutzt, die sich mit der Untersuchung von pharmazeutischen Substanzen beschäftigen. Obwohl in der Strahlentherapie am Menschen schon seit einiger Zeit bildgebende Verfahren eingesetzt werden und diese eine immer größere Rolle spielen, um die Therapie präziser und effizienter zu machen, werden diese Entwicklungen nicht am Tiermodell nachvollzogen. Diese Tatsache liegt darin begründet, dass sich die Bestrahlungstechnik für Kleintiere in der experimentellen Strahlentherapie verglichen mit der bei der Humantherapie auf dem Niveau der 1950er Jahre befindet. Während Tumoren beim Menschen mittlerweile hochkonformal, intensitätsmoduliert und stereotaktisch bestrahlt werden, positioniert man Versuchtiere noch unter Stehfeldern mit grober Standardkollimierung. Will man die heutige Präzisionsstrahlentherapie in Tierexperimenten untersuchen, ist es unbedingt erforderlich, mit einem geeigneten Kleintierbestrahlungsgerät die technischen Voraussetzungen dafür zu schaffen.

  • Poster
    39. Jahrestagung Der DGMP, 10.-13.09.2008, Oldenburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12399
Publ.-Id: 12399


Uranium(IV) colloid in near-neutral solutions: Influences on particle size

Dreissig, I.; Weiss, S.; Zaenker, H.; Bernhard, G.

Uranium(IV) is only sparingly soluble in near-neutral solutions [1]. As a consequence, uranium is expected to be immobile (deposited) under reducing conditions. However, we found out that under certain conditions U(IV) formes stable colloids which leads to a mobilization of the uranium. The colloids were generated by galvanostatic reduction of a 20 mM UO2(ClO4)2 solution in 1 M NaHCO3. The stock solutions were diluted to 1 mM uranium using solutions of dissolved silicic acid (2 – 5 mM). Then they were neutralized with perchloric acid. Measurement of the scattered light intensity (SLI), photon correlation spectroscopy (PCS) and ultracentrifugation (UC) were carried out.
Typically, the colloids produced did not reach their final particle size immediately but showed a certain growth phase of about one week. This could be seen from both PCS and simple SLI measurements.
It turned out that the highest SLIs occurred in the solutions of the lowest silicate content and vice versa. All samples exhibited an increase in SLI with decreasing pH. Obviously, very small colloidal particles are generated at high pH and/or high silicate concentration and larger ones at low pH and/or low silicate concentration. At the highest initial silicate concentration applied, the colloids were still stable at pH values below 7.
This silicate and pH dependency of U(IV) colloid particle size was also confirmed by our UC results. The smaller the colloids, the longer the time they needed for separation at the given centrifugal acceleration of 170000 x g. After 1 h of UC the supernatants of samples with higher silicate content still contained significantly higher U concentrations than samples with low silicate content. After 5 h UC time the uranium was almost completely removed from all samples, indicating that truly dissolved uranium did not play a significant part in the system, i.e. almost all the U was colloidal.

Keywords: uranium(IV) colloids; photon correlation spectroscopy; light scattering; silicic acid; ultracentrifugation; ultrafiltration

  • Poster
    Goldschmidt2009 - "Challenges to Our Volatile Planet", 21.-26.06.2009, Davos, Switzerland
  • Geochimica et Cosmochimica Acta 73(2009)13, A304 Suppl

Permalink: https://www.hzdr.de/publications/Publ-12398
Publ.-Id: 12398


Dosimetric comparison between gated and stationary photon and electron beams delivered by the Siemens ONCOR Avant-Garde linear accelerator.

Wieczorkowski, L.; Hoinkis, C.; Lehmann, D.; Enghardt, W.

Objective: The gated irradiation technique is a sophisticated tool for focusing the prescribed dose to periodically moving target volumes whilst sparing the surrounding healthy tissue. Thus, gated irradiation is predominantly applied to organ motion caused by breathing. The tumour is irradiated in a specific phase of its motion. This requires to switch on and off the beam periodically. The duty cycle may vary in a certain range (about 17 to 75%). It depends on the individual and site specific time dependent elongation and the tumour dose conformity required. Obviously the latter will be increased at a low duty cycle, which, however, increases the number of irradiation cycles for reaching the prescribed dose. Transient effects during switching on and off the beam may influence the dose and its homogeneity. Prior to the therapeutic application of gated irradiation of bronchial carcinoma the dose distributions delivered for photons and electrons in steady and gated mode have been measured.

Methods: Photon and electron beams were delivered by an ONCOR AvantGarde linear accelerator (Siemens). The gating signal was provided by a commercial respiratory gating system based on a pressure belt feedback mechanism (AZ-733, Anzai Medical, Tokyo, Japan) in combination with a respiratory phantom. Lateral profiles of dose were measured by means of a linear diode array BMS 96 (Schuster Medizinische Systeme GmbH, Forchheim, Germany). Depth distributions within a solid water phantom (Piacryl RW3, PTW Freiburg, Germany) and output factors were determined using a Farmer ionization chamber (0.6 cm3) of PTW, Freiburg, Germany. Respiratory frequency values were set to 10 and 15 min-1 (i.e. 6 and 4 s, respectively) and beam-on time values of 1, 2 and 3 s were chosen. Different field sizes (5 × 5, 10 × 10 and 20 × 20 cm2) were used for 6 and 15 MV photons and 10 × 10 cm2 for 9 and 12 MeV electrons. The dose values and output factors of the gated beam delivery have been evaluated relative to those of the constant mode at 50, 100 and 200 MU for photons and 100 and 200 MU for electrons.

Results: Output factors and depth doses maximum deviations for gated photon and electron beams are up to 0.8 % in comparison to non-gated beams. The difference in symmetry and flatness of the dose profiles is less than 3 %. Deviations increase with decreasing beam-on time, decrease with increasing depth, are randomized and do not depend on the photon and electron energy. Minor dependence on the field size was observed but in most cases the results for the 10 × 10 cm2 field were more accurate. None respiratory frequency dependence (i.e. 15 min-1 or 10 min-1) was noticed as well.

Conclusion: All this measurements were performed in a stationary phantom and they are acceptable for clinical applications. To evaluate more realistic cases with respect to therapy the geometric and dosimetric verification in moving phantoms will be done.

  • Poster
    14. Jahreskongress der Deutschen Gesellschaft für Radioonkologie 25. Jahrestagung der Österreichischen Gesellschaft für Radioonkologie, Radiobiologie und Medizinische Strahlenphysik „Der Wiener Kongress“ Radioonkologie-Medizin.Physik-Strahlenbiologie, 01.-04.05.2008, Wien, Österreich
  • Contribution to proceedings
    14. Jahreskongress der Deutschen Gesellschaft für Radioonkologie 25. Jahrestagung der Österreichischen Gesellschaft für Radioonkologie, Radiobiologie und Medizinische Strahlenphysik „Der Wiener Kongress“, 01.-04.05.2008, Wien, Österreich
    Strahlentherapie und Onkologie 2008;184 (Sondernr 1): 1–165 DOI 10.1007/s00066-008-1001-9, München: Verlag Urban & Vogel, 124

Permalink: https://www.hzdr.de/publications/Publ-12397
Publ.-Id: 12397


Der supraleitende Fotoelektronen-Injektor an ELBE (SRF-Gun)

Arnold, A.; Teichert, J.; Murcek, P.; Xiang, R.

no abstract available

  • Lecture (others)
    FZD-Seminar, Institut für Strahlenphysik, 17.12.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12395
Publ.-Id: 12395


A high-brightness superconducting photo-electron injector

Arnold, A.

  • Lecture (others)
    Abteilungsseminar der Universität Rostock am Institut für allgemeine Elektrotechnik/Theoretische Elektrotechnik, 09.04.2008, Rostock, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12393
Publ.-Id: 12393


A high-brightniess superconducting photo-electorn injector for future FEL's

Arnold, A.; Büttig, H.; Teichert, J.; Janssen, D.; Lehnert, U.; Michel, P.; Moeller, K.; Murcek, P.; Schneider, C.; Xiang, R.

Most of the proposed electron accelerator projects for future FELs, ERLs, or 4th generation light sources require electron beams with an unprecedented combination of high-brightness, low emittance and high average current. While the concepts of DC- and NC-guns are well proofed, the SRF gun development still possesses a high risk. Challenges are the design of the superconducting cavity, the choice of the right photocathode type, its life time and possible cavity contamination. But in combination with SRF linacs, the SRF guns will be the best solution for high average currents and continuous wave operation.
The contribution will give an overview on the technical concept, the proposed performance, and the current status of the leading superconducting rf gun project developed in Dresden-Rossendorf. At the moment the cryomodule and a diagnostic beamline are installed next to the ELBE superconducting linear accelerator. During the first commissioning and test period the gun is operated in parallel to the existing dc thermionic gun, but at the end of 2008 it will be used to improve the beam quality of the ELBE accelerator significantly.
The first beam, using a copper cathode, was imaged on the screens on 12th November 2007. The UV-laser with an output power of 400mW at 100kHz rep. rate produced a beam current of 40nA and a corresponding bunch charge of 0.5pC. At next the commissioning of the diagnostic beamline, to measure all important beam parameters, will be finished and first high current tests using a Cs2Te-Cathode will be done.

  • Lecture (Conference)
    DPG Frühjahrstagung, 03.-07.03.2008, Freiburg, Deutschland

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-12391
Publ.-Id: 12391


Rossendorf SRF-Gun Cavity Characteristics

Arnold, A.; Teichert, J.; Buettig, H.; Janssen, D.; Justus, M.; Lehnert, U.; Michel, P.; Murcek, P.; Schamlott, A.; Schneider, C.; Schurig, R.; Staufenbiel, F.; Wiang, R.; Kamps, T.; Rudolph, J.; Schenk, M.; Klemz, G.; Will, I.

At the Forschungszentrum Rossendorf the development and the setup of the 2nd superconducting radio frequency photo electron injector (SRF-Photo-Gun) is finished. This new injector is placed next to the existing thermionic gun of the superconducting linear accelerator called ELBE. In the next shutdown a connection between this accelerator and the SRF-Gun will provide the improved beam parameters for the users. At the moment the commissioning is fully under way.
The contribution will present important results concerning cavity commissioning like measurements of: Q vs. E, microphonics, Lorentz detuning, tuner parameters, spectra HOM excitation spectra and the field distribution calculated from measured fundamental mode passband. The results will be used to improve the existing cavity design.

  • Poster
    Workshop on Sources of Polarized Electrons and High Brightness Electron Beams, 01.-03.10.2008, Newport News, USA
  • Contribution to proceedings
    SPIN PHYSICS: 18th International Spin Physics Symposium, 06.-11.11.2008, Charlottesville, Virginia, USA
    AIP Conference Proceedings, Volume 1149,, Melville/NY, 978-0-7354-0686-5, 1125-1132
  • Poster
    First DITANET School on Beam Diagnostics, 30.03.-03.04.2009, London, UK

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-12390
Publ.-Id: 12390


Experiences on NC Cathodes and Choke Filters

Arnold, A.; Teichert, J.; Buettig, H.; Janssen, D.; Justus, M.; Lehnert, U.; Michel, P.; Murcek, P.; Schamlott, A.; Schneider, C.; Schurig, R.; Staufenbiel, F.; Xiang, R.; Kamps, T.; Rudolph, J.; Schenk, M.; Klemz, G.; Will, I.

  • Invited lecture (Conferences)
    CW Source Workshop at BESSY, 08.-10.09.2008, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12389
Publ.-Id: 12389


Verbessert die IMRT die Möglichkeit einer Dosiseskalation bis 78 Gy für Patienten mit einem nichtkleinzelligen Bronchialkarzinom (NSCLC)?

Appold, S.; Evers, C.; Gillham, C.; Pönisch, F.; Enghardt, W.; Abolmaali, N.; Zöphel, K.; Hölscher, T.; Kotzerke, J.; Herrmann, T.; Baumann, M.; Zips, D.

Hintergrund: In einer früheren Planungsstudie an Patienten mit NSCLC wurde untersucht, ob mittels einer FDG-PET/CT während einer fraktionierten Strahlentherapie eine Verkleinerung des Zielvolumens und damit eine Dosiseskalation der Dosis über 66 Gy möglich ist. Es zeigte sich, dass die Tumorvolumina während der Therapie abnahmen. Doch bei 6/10 Patienten war eine Therapie mit einer Dosis von 78 Gy selbst dann nicht möglich, wenn das Bestrahlungsvolumen nach 66 Gy auf die Tumorausdehnung des PET/CT 5-6 Wochen nach Beginn der RT (PET/CT w5-6) reduziert wurde (Radiother Oncol, in press). In der vorliegenden Untersuchung soll geprüft werden, ob eine optimierte inverse Therapieplanung für eine intensitätsmodulierte Strahlentherapie (IMRT) zu einer Reduktion der Normalgewebsbelastung führt und in diesen Fällen eine Dosiseskalation bis 78 Gy ermöglicht.

Patienten und Methodik: 10 Patienten mit einem NSCLC im Stadium III wurden in Bestrahlungsposition vor und während einer fraktionierten Strahlentherapie (66 Gy in 33 Fraktionen) mittels FDG-PET/CT (Biograph 16) untersucht. Die Konturierung des GTV in PET und CT erfolgte durch den Strahlentherapeuten (GC) und wurde durch einen Radiologen (NA) bzw. Nuklearmediziner (KZ) überprüft. Das PTV ergab sich durch einen Sicherheitsabstand von 1,5 cm um das GTV-PET/CT ohne prophylaktische Bestrahlung des Mediastinums. Die Strahlentherapie wurde mit einer Zieldosis von 78 Gy (Bestrahlung auf das Ausgangsvolumen oder Feldverkleinerung ab 66 Gy auf PTV-PET/CT w5-6) geplant (Pinnacle, Phillips). Die Vorgaben für die Normalgewebsbelastung waren:
Myelon max. 45 Gy , mittlere Lungendosis (MLD) £20 Gy, Lungenvolumen 20 Gy (V20) £37%, Ösophagusvolumen 60 Gy (V60) £30 %, Herzbelastung 1/3 £60 Gy, 2/3 £50 Gy und 3/3 £40 Gy. Für 6/10 Patienten, bei denen diese Vorgaben mit 3D-konformaler Planung nicht eingehalten werden konnten (5/10 Pat. V60 >30%; 3/10 Pat. V20>37% bzw. MLD>20 Gy), wurde eine IMRT geplant. Hierbei sollten die Minima im CTV (GTV+7 mm) ³95% sein, eine geringe Unterdosierung im PTV wurde akzeptiert.

Ergebnisse: Eine Reduktion der Belastung kritischer Organe (Lunge, Ösophagus) konnte bei 5 der 6 Patienten durch eine IMRT-Planung erreicht werden. Allerdings führte nur in 2 Fällen die IMRT zu einer Unterschreitung der vorgegebenen Dosisgrenzen und ermöglichte damit eine Dosiseskalation bis 78 Gy. Eine Reduktion des Bestrahlungsvolumens nach 66 Gy brachte dabei keinen entscheidenden Vorteil. Bei einem Patienten war eine inverse Planung mit einer akzeptablen Dosisverteilung nicht möglich. In 5/6 Fällen führte die IMRT-Planung zu einer inhomogeneren Erfassung des PTV und CTV mit geringen Minima im PTV.
Schlussfolgerung: In ausgewählten Fällen kann für Patienten mit NSCLC, für die mittels konventioneller Planung das Risiko der Normalgewebstoxizität zu hoch ist, durch eine IMRT-Planung eine Dosiseskalation bis 78 Gy möglich werden. Gefördert durch das BMBF (03ZIK042)

  • Poster
    14. Jahreskongress der Deutschen Gesellschaft für Radioonkologie 25. Jahrestagung der Österreichischen Gesellschaft für Radioonkologie, Radiobiologie und Medizinische Strahlenphysik „Der Wiener Kongress“, 01.-04.05.2008, Wien, Österreich
  • Contribution to proceedings
    14. Jahreskongress der Deutschen Gesellschaft für Radioonkologie 25. Jahrestagung der Österreichischen Gesellschaft für Radioonkologie, Radiobiologie und Medizinische Strahlenphysik „Der Wiener Kongress“, 01.-04.05.2008, Wien, Österreich
    Strahlentheraphie und Onkolologie 2008;184 (Sondernr 1): 1–165, München: Verlag Urban & Vogel

Permalink: https://www.hzdr.de/publications/Publ-12388
Publ.-Id: 12388


Overview on the most advanced SRF-Gun Projects in the world

Arnold, A.; Teichert, J.; Buettig, H.; Janssen, D.; Justus, M.; Lehnert, U.; Michel, P.; Murcek, P.; Schamlott, A.; Schneider, C.; Schurig, R.; Staufenbiel, F.; Xiang, R.; Kamps, T.; Rudolph, J.; Schenk, M.; Klemz, G.; Will, I.

  • Invited lecture (Conferences)
    CW Source Workshop at BESSY, 08.-10.09.2008, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12387
Publ.-Id: 12387


Commissioning results of the superconducting photoinjector for ELBE at FZ Dresden-Rossendorf

Teichert, J.; Arnold, A.; Büttig, H.; Janssen, D.; Justus, M.; Lehnert, U.; Michel, P.; Murcek, P.; Schamlott, A.; Schneider, C.

  • Invited lecture (Conferences)
    CARE 2008 Annual Meeting, 02.-05.12.2008, Geneva, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-12386
Publ.-Id: 12386


Attenuation correction of four dimensional (4D) PET using phase-correlated 4D-computed tomography.

Pönisch, F.; Richter, C.; Just, U.; Enghardt, W.

The image quality in a conventional positron emission tomography (PET)/computed tomography (CT) scanner is degraded by respiratory motion because of erroneous attenuation correction when three-dimensional image acquisition is used. To overcome this problem, time-resolved data acquisition (4D) is required. For this, a Siemens Biograph 16 PET/CT scanner has been modified and its normal capability has been extended to a true 4D-PET/4D-CT imaging device including phase-correlated attenuation correction. To verify the correct functionality of this device, experiments on a respiratory motion phantom that allowed movement in two dimensions have been performed. The measurements showed good spatial correlation as well as good time synchronization between the PET and CT data. Furthermore, the motion pattern of the phantom and the shape of the activity distribution have been examined, and the volume of the reconstructed PET images has been analyzed. The results demonstrate the feasibility of such a procedure, and we therefore recommend that 4D-PET data should be reconstructed using 4D-CT data, which can be acquired on the same machine.

Permalink: https://www.hzdr.de/publications/Publ-12384
Publ.-Id: 12384


First Test of a Turnkey 1.3 Ghz 30 kW IOT - Based Power Amplifier at ELBE

Büttig, H.; Erber, J.; Justus, M.; Lehnert, U.; Michel, P.; Schurig, R.; Staats, G.; Bedau, J.; Dupire, P.; Gonella, O.

Bruker BioSpin has developed a turnkey IOT-based RF-power amplifier in cooperation with CPI within a very short time of six months.
In the framework of a co-operation between Bruker, CPI and FZD (ELBE) first successfully tests were carried out to study the behaviour of the new amplifier at the superconducting linac ELBE. The results obtained and presented are used to optimize the design.

Keywords: turnkey IOT-based RF-power amplifier

  • Poster
    24. Linear Acc. Conference, 29.09.-03.10.2008, Victoria, Canada

Permalink: https://www.hzdr.de/publications/Publ-12382
Publ.-Id: 12382


Gain Deterioration at particular wavelengths in a partially waveguided FEL

Lehnert, U.; Staats, G.; Wünsch, R.

abstract available

  • Poster
    30th annual International Conference on Free Electron Laser, 24.-29.8.2008, Gyeongju, Republic of Korea
  • Contribution to proceedings
    30th annual International Conference on Free Electron Laser, 24.-29.8.2008, Gyeongju, Republic of Korea

Permalink: https://www.hzdr.de/publications/Publ-12381
Publ.-Id: 12381


Design of the Nijmegen High-Resolution FIR-FEL

Lehnert, U.; Jongma, R.; Dunkel, K.; Piel, C.; van der Meer, A.; Michel, P.; Wuensch, R.; van der Zande, W.; van der Geer, K.; van der Slot, P.

abstract available

  • Contribution to proceedings
    30th International (FEL) Conference on Free Electron Laser, 24.-29.8.2008, Gyeongju, Republic of Korea

Permalink: https://www.hzdr.de/publications/Publ-12380
Publ.-Id: 12380


The New Superconducting RF Photoinjector – a High-Average Current & High-Brightness Gun

Teichert, J.

The paper reports on the first operation results of the Rossendorf superconducting RF photo electron gun (SRF gun). Developed in a collaboration with BESSY, DESY, and MBI and within the frame of European CARE project, the SRF gun is now installed at the superconducting electron accelerator ELBE. In November 2007 the first beam was produced. In 2008 the gun was operated with Cs2Te photo cathodes and RF and electron beam parameter measurements were carried out.

Keywords: RF photo electron gun; electron accelerator ELBE

  • Lecture (Conference)
    The Second Workshop on High Average Power & High Brightness Beams, 14.-16.1.2009, Los Angeles, USA

Permalink: https://www.hzdr.de/publications/Publ-12379
Publ.-Id: 12379


Die supraleitenden Fotoelektronen-Injektor an ELBE (SRF-Gun)

Xiang, R.; Murcek, P.; Arnold, A.; Teichert, J.

  • Lecture (others)
    FWKE Seminar, 17.12.2008, Dresden, Deutschlnad

Permalink: https://www.hzdr.de/publications/Publ-12378
Publ.-Id: 12378


Status Report on the Report on the Radiation Source ELBE User Facility and the NEw Superconducting Photoelectron Injector

Teichert, J.

  • Lecture (others)
    SFB Seminar, 12.12.2008, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12377
Publ.-Id: 12377


The Superconducting RF Photoinjector at ELBE - First Operational Experience

Teichert, J.; Arnold, A.; Büttig, H.; Michel, P.; Justus, M.; Lehnert, U.; Schamlott, A.; Xiang, R.; Schneider, C.; Schurig, R.

A RF photo injector with a superconducting cavity (SRF gun) for installation at the Radiation Source ELBE was developed within a collaboration of BESSY, DESY, FZD, and MBI. This new and promising injector type allows CW operation and has the potential for the production of high-brightness electron beams. The gun cryostat, the electron diagnostic beamline, and the driver laser with optical beamline were installed. In November 2007 the first beam was produced. Results of the beam parameter measurements with Cs2Te photo cathodes are presented.

Keywords: RF photo injector; high brightness electron beams

  • Lecture (Conference)
    The Superconducting RF Photoinjector at ELBE – First Operational Experience, 01.-03.10.2008, Newport News, USA

Permalink: https://www.hzdr.de/publications/Publ-12375
Publ.-Id: 12375


Commissioning Results of the Superconducting Photo-Injector at ELBE

Teichert, J.; Büttig, H.; Janssen, D.; Justus, M.; Lehnert, U.; Michel, P.; Murcek, P.; Arnold, A.; Schurig, R.; Staats, G.; Büchner, A.; Staufenbiel, F.; Xiang, R.; Will, I.; Kamps, T.; Klemz, G.; Matheisen, A.

  • Contribution to proceedings
    11th biennial European Particle Accelerator Conference EPAC'08,, 23.-27.6.2008, Genoa, Italy, Proceeding 2755

Permalink: https://www.hzdr.de/publications/Publ-12374
Publ.-Id: 12374


Current-voltage characteristics of metal-oxide-semiconductor devices containing Ge or Si nanocrystals in thin gate oxides

Beyer, V.; von Borany, J.; Klimenkov, M.; Müller, T.

Current-voltage characteristics were measured, electrically modeled, and calculated for gate oxides, which contain nanocrystals (NCs) in different distributions, sizes, and densities. Ge and Si NCs were synthesized embedded in separate thin SiO2 layers by ion implantation at different fluences and subsequent annealing. It was found that the currents through the NC containing thin gate oxides are strongly related to the NCs’ location and are not driven by ion implantation induced oxide defects. Charging of the NCs determines the internal electrical fields, which is confirmed by simultaneous current and capacitance measurements. Depending on the implanted fluence the Ge NCs were mainly detected in the oxide center or close to the Si/SiO2 interface. The Si NCs were fabricated in the oxide center sandwiched between two oxide regions denuded of NCs. The processes of Si NC formation, growth and dissolution are discussed by means of kinetic lattice Monte Carlo simulations.

Keywords: nanocrystal; Si; Ge; ion implantation; leakage current; kinetic lattice Monte Carlo simulation; memory device

  • Journal of Applied Physics 106(2009), 064505

Permalink: https://www.hzdr.de/publications/Publ-12373
Publ.-Id: 12373


High-field splitting of the cyclotron resonance absorption in strained p-InGaAs/GaAs quantum wells

Drachenko, O.; Kozlov, D. V.; Aleshkin, V.; Gavrilenko, V. I.; Maremyanin, K. V.; Ikonnikov, A. V.; Zvonkov, B. N.; Goiran, M.; Leotin, J.; Fasching, G.; Winnerl, S.; Schneider, H.; Wosnitza, J.; Helm, M.

We report a systematic study of the cyclotron resonance (CR) absorption of two-dimensional holes in strained InGaAs/GaAs quantum wells (QWs) in the quantum limit. The energies of the CR transitions are traced as a function of magnetic field up to 55 T. A remarkable CR line splitting was evidenced when the resonant field exceeds 20 T. We analyze our data with a 4x4 Luttinger Hamiltonian including strain and QW potentials using two different methods to calculate Luttinger parameters for ternary alloys. We found excellent agreement with the experiment when linear interpolation of the Luttinger parameters is used.

Keywords: Cyclotron resonance; high magnetic field; p-type; strain; InGaAs; GaAs; free electron laser; FEL; effective mass; Luttinger parameter; splitting

Permalink: https://www.hzdr.de/publications/Publ-12372
Publ.-Id: 12372


Field-controlled magnetic order in the quantum spin-ladder system (Hpip)2CuBr4

Thielemann, B.; Rüegg, C.; Kiefer, K.; Rønnow, H. M.; Normand, B.; Bouillot, P.; Kollath, C.; Orignac, E.; Citro, R.; Giamarchi, T.; Läuchli, A. M.; Biner, D.; Krämer, K. W.; Wolff-Fabris, F.; Zapf, V. S.; Jaime, M.; Stahn, J.; Christensen, N. B.; Grenier, B.; Mcmorrow, D. F.; Mesot, J.

Neutron diffraction is used to investigate the field-induced, antiferromagnetically ordered state in the two-leg spin-ladder material (Hpip)2CuBr4. This “classical” phase, a consequence of weak interladder coupling, is nevertheless highly unconventional: its properties are influenced strongly by the spin Luttinger-liquid state of the ladder subunits. We determine directly the order parameter (transverse magnetization), the ordering temperature, the spin structure, and the critical exponents around the transition. We introduce a minimal microscopic model for the interladder coupling and calculate the quantum fluctuation corrections to the mean-field interaction.

  • Physical Review B 79(2009), 020408(R)

Permalink: https://www.hzdr.de/publications/Publ-12371
Publ.-Id: 12371


Medizinische Strahlenphysik in Dresden

Kunath, D.

Vortrag über die Struktur und Forschungs-Schwerpunkte von OncoRay

  • Lecture (Conference)
    Seminar "Netzwerke für die Medizinische Physik in der Strahlentherapie", 13.-14.02.2009, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12370
Publ.-Id: 12370


Die Jagd nach dem Feldrekord - Forschung in hohen Magnetfeldern

Wosnitza, J.

Was sind Magnetfelder? Wo findet man sie? Wie erzeugt man sie und zu was sind sie nutze? Antworten auf diese Fragen sollen in dem Vortrag durch Vorstellung der weltweiten Bestrebungen, immer höhere Magnetfelder zu erreichen, gegeben werden. Ähnlich wie z. B. Druck und Temperatur haben magnetische Felder einen tief greifenden Einfluss auf den Zustand und Zustandsänderungen der Materie. Untersuchungen von Materialien in hohen Magnetfeldern sind daher mittlerweile Standard und eine Vielzahl von Anwendungen in unserem täglichen Leben sind ohne Magnetfeldeffekte undenkbar. In der Forschung wird der stetig wachsende Bedarf an möglichst großen Magnetfeldstärken durch Hochfeldlaboratorien abgedeckt. In dem neu aufgebauten Hochfeld-Magnetlabor Dresden sollen demnächst gepulste Magnetfelder bis zu 100 Tesla erzeugt werden. Erste Hochfeldmagnete sind in Betrieb und seit 2007 hat neben der Eigenforschung der Nutzerbetrieb begonnen. Der momentane Status des Labors, die Schwierigkeiten, die zur Erzeugung so hoher Magnetfelder überwunden werden müssen, und exemplarische wissenschaftliche Ergebnisse aus Hochfeldstudien sollen vorgestellt werden.

  • Invited lecture (Conferences)
    Universität Ulm, 09.02.2009, Ulm, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12369
Publ.-Id: 12369


Die Jagd nach dem Feldrekord - Forschung in hohen Magnetfeldern

Wosnitza, J.

hat nicht vorgelegen

  • Lecture (others)
    Eröffnungsvortrag zum Tag des offenen Labors des Forschungszentrum Dresden-Rossendorf, 24.05.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12368
Publ.-Id: 12368


Window Coupler Test Stand at ELBE

Staats, G.; Buechner, A.; Büttig, H.; Michel, P.; Schurig, R.; Teichert, J.; Winter, A.

abstract available

  • Lecture (Conference)
    TTC 2008, 14.-17.1.2008, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12366
Publ.-Id: 12366


Tunable-frequency ESR as a tool to study magnetic excitations in highly-correlated electron systems

Zvyagin, S.

In this presentation I will talk about recent development of the high-field Electron Spin Resonance program at the Dresden High Magnetic Field Laboratory (HLD) in Rossendorf. A unique feature of the facility is a combination of an extraordinary broad frequency range, 9 GHz - 100 THz (quasi-continuously covered by a number of tunable-frequency radiation sources, including THz-range free-electron laser FELBE) and high magnetic fields (up to 60 T). The talk will be illustrated by tunable-frequency ESR results obtained in sine-Gordon chain material Cu-PM and BEC candidate NiCl2-4SC(NH22 (known as DTN).

  • Invited lecture (Conferences)
    Invited talk at the University of Florida, 18.11.2008, Gainesville, Florida, USA

Permalink: https://www.hzdr.de/publications/Publ-12365
Publ.-Id: 12365


Die Jagd nach dem Feldrekord - Forschung in hohen Magnetfeldern

Wosnitza, J.

hat nicht vorgelegen

  • Lecture (others)
    Vorlesung in der Reihe "Physik am Samstag" der Fachrichtung Physik der TU Dresden, 13.12.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12364
Publ.-Id: 12364


Die Jagd nach dem Feldrekord - Forschung in hohen Magnetfeldern

Wosnitza, J.

hat nicht vorgelegen

  • Lecture (others)
    Helmholtzabend am Forschungszentrum Dresden-Rossendorf, 05.09.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12363
Publ.-Id: 12363


Force-free and contactless sensor for electromagnetic flowrate measurements

Priede, J.; Buchenau, D.; Gerbeth, G.

We present a novel design of a contactless flowmeter using a single cylindrical permanent magnet magnetised perpendicularly to its axis, about which it can freely rotate, and placed close to a duct with a liquid metal flow. The electromagnetic torque on the magnet caused by the liquid metal flow sets the magnet into rotation. The equilibrium rotation rate, which is attained at a vanishing net electromagnetic torque on the magnet, depends only on the flowrate and the geometry of the system while it is independent of the electromagnetic torque itself. A laboratory model of such a flowmeter has been built and tested at a liquid metal flow.

  • Magnetohydrodynamics 45(2009)3, 451-458

Permalink: https://www.hzdr.de/publications/Publ-12361
Publ.-Id: 12361


Design, Synthese und Anwendungsmöglichkeiten radiomarkierter Verbindungen

Stephan, H.

kein Abstract verfügbar

  • Invited lecture (Conferences)
    Universität Duisburg-Essen, Institut für Organische Chemie, 05.02.2009, Essen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12360
Publ.-Id: 12360


Role of D(E)RY motif in switching mechanism of G protein-coupled receptors studied by ITC

Eichler, S.; Fahmy, K.

Membrane proteins, especially GPCRs (G-protein coupled receptors), play a fundamental role in many physiological processes. Their function is based on the ability to switch between different structures. Due to the low dielectricity of the lipidic environment, side chain charges contribute to the energetics of such transitions much more than in purely aqueous environment.
Our aim is to understand the functional implication of charged amino acids in the conformational control of membrane-spanning protein domains.
We used Isothermal Titration Calorimetry (ITC) to study proton uptake from the buffer by the class-defining and highly conserved D(E)RY motif in a synthetic peptide derived from rhodopsin transmembrane (TM) helix 3. By adding a negatively charged molecule (SDS) the pKA of the peptide is expected to be shifted and proton uptake from the buffer by glutamic acid in the D(E)RY motif is assumed to occur depending on pH. Thus the heat of buffer ionization depending on pH and buffer ionization enthalpy is measured according to Baker and Murphy. First experiments in phosphate buffer at pH 4.8 showed promising results, i.e. a titration curve with stoichiometry around 1:1 (SDS:peptide) and ∆H in good agreement to buffer ionization heat of phosphate buffer. However the buffer ionization heat of phosphate buffer is comparatively low and so are other buffers at that pH. Thus these results were not sufficiently reproducible and following experiments were performed at pH 6 and 8 with Imidazole buffer, PIPES and TRIS. These results were good reproducible but no buffer ionization could be shown. A pKA shift in our model peptide introduced by an additional charge (SDS) could not be proved by means of ITC. Thus, there is no evidence for breakage of the internal Glu-Arg salt bridge by competition with an Arg-sulfate interaction.

Keywords: GPCR; D(E)RY motif; Isothermal Titration Calorimetry

  • Poster
    18. Ulm-Freiberger Kalorimetrietage, 18.-20.03.2009, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12359
Publ.-Id: 12359


Instability of the melt flow in VGF growth with a traveling magnetic field

Grants, I.; Klyukin, A.; Gerbeth, G.

The linear instability of a thermally stratified melt flow in the VGF configuration driven by a traveling magnetic field (TMF) is considered numerically and experimentally. The dependency of the instability threshold on the governing parameters is found for several cuts through the parameter space covering a wide range of possible applications. In a first approximation the linear instability occurs when the dimensionless TMF forcing parameter reaches the magnitude of the Grashof number. This is particularly true in a medium-sized crucible where the first instability is axisymmetric and sub-critical. As the Grashof number increases the flow develops self-similar boundary layers and the instability becomes three-dimensional. The instability originates in the bottom boundary layer where the convection tends to suppress the imposed temperature gradient in the central part of the melt zone. It is shown that the TMF may serve as a tool to control the phase interface shape without causing flow instationarity when the crucible diameter exceeds a certain value. This value is estimated to be around 5-6 cm for GaAs. The flow stays stable if the TMF is used for a reversal of the meridional flow with the aim to remove a possible dopant concentration peak on the axis.

  • Journal of Crystal Growth 311(2009)17, 4255-4264

Permalink: https://www.hzdr.de/publications/Publ-12358
Publ.-Id: 12358


Growth and Electrical Properties of the (Si/Ge)-on-Insulator Structures Formed by Ion Implantation and Subsequent Hydrogen-Assisted Transfer

Tyschenko, I. E.; Voelskow, M.; Cherkov, A. G.; Popov, V. P.

Systematic features of endotaxial growth of intermediate germanium layers at the bonding interface
in the silicon-on-insulator structure consisting of buried SiO2 layer implanted with Ge+ ions are studied in relation to the annealing temperature. On the basis of the results for high-resolution electron microscopy and thermodynamic analysis of the Si/Ge/SiO2 system it is assumed that the endotaxial growth of the Ge layer occurs via formation of a melt due to enhanced segregation and accumulation of Ge at the Si/SiO
interface. Effect of germanium at the bonding interface on the Hall mobility of holes in silicon layers with nanometer-scale thickness is studied. It is found that the structures including the top silicon layer with the thickness 3–20 nm and incorporating germanium feature the hole mobility that exceeds by a factor of 2–3 the hole mobility in corresponding Ge-free silicon-on-insulator structures.

Keywords: Si/Ge; Electrical Properties; Ion Implantation; Hydrogen Transfer

  • Semiconductors 43(2009)1, 52-56
  • Fizika i Tekhnika Poluprovodnikov 43(2009)1, 58-63

Permalink: https://www.hzdr.de/publications/Publ-12357
Publ.-Id: 12357


Evidence for an FFLO state in layered organic superconductors

Wosnitza, J.

In the so-called FFLO state, named after Fulde, Ferrell, Larkin, and Ovchinnikov, the superconducting state can survive even at high magnetic fields above the Pauli paramagnetic limit. The quasi-two-dimensional (2D) organic superconductors have been suggested as good candidates for exhibiting the FFLO state. When applying the magnetic field exactly parallel to the conducting layers the orbital pair breaking is greatly suppressed and the Pauli limit is reached. We performed high-resolution specific-heat and torque-magnetization experiments in magnetic fields up to 28 T for different 2D organic superconductors. In a very narrow region close to parallel orientation we observe additional anomalies below the upper critical field signalling the existence of an additional superconducting phase. The specific-heat data for kappa-(BEDT-TTF)2Cu(NCS)2 with Tc = 9.1 K show that the superconducting transition becomes first order for fields above 21 T indicating that the Pauli limit is reached. Below about 3 K, the upper critical field increases sharply and a second first-order transition appears within the superconducting phase. Our results give strong evidence for the realization of the FFLO state in organic superconductors.

  • Invited lecture (Conferences)
    10th German-Japanese Symposium "Collective Quantum Phenomena in Correlated Condensed Matter Systems", 28.09.-01.10.2008, Ringberg Castle, Rottach-Egern, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12356
Publ.-Id: 12356


Magnetic quantum oscillations in strongly correlated metals - experimental data meet theoretical predicitons

Wosnitza, J.

hat nicht vorgelegen

  • Invited lecture (Conferences)
    DFT Meets Experiment & 7th Tutorial Hand-on-FPLO, Workshop at the IFW Dresden, 25.-28.08.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12355
Publ.-Id: 12355


Calorimetric Evidence for an FFLO superconducting state in the layered organic superconductor κ-(BEDT-TTF)2Cu(NCS)2

Wosnitza, J.

hat nicht vorgelegen

  • Invited lecture (Conferences)
    The 63rd Calorimetry Conference, 02.-06.07.2008, Jersey City, New Jersey, USA

Permalink: https://www.hzdr.de/publications/Publ-12354
Publ.-Id: 12354


Amorphous clusters in Co implanted ZnO induced by boron pre-implantation

Potzger, K.; Shalimov, A.; Zhou, S.; Schmidt, H.; Mücklich, A.; Helm, M.; Fassbender, J.; Arenholz, M.; Liberati, E.

We demonstrate the formation of superparamagnetic/ferromagnetic regions within ZnO(0001) single crystals sequentially implanted with B and Co. While the pre-implantation with B plays a minor role for the electrical transport properties, its presence leads to the formation of amorphous phases. Moreover, B acts strongly reducing on the implanted Co. Thus, the origin of the ferromagnetic ordering in local clusters with large Co concentration are itinerant d-electrons as in the case of metallic Co. The amorphous Co-based phases are non-detectable by common X-ray diffraction.

Keywords: ZnO; DMS; Ion implantation

  • Journal of Applied Physics 105(2009)12, 123917

Permalink: https://www.hzdr.de/publications/Publ-12353
Publ.-Id: 12353


Static and dynamic magnetization processes in magnetic property patterned thin films

McCord, J.; Hamann, C.; Martin, N.; Mönch, I.; Kaltofen, R.; Schultz, L.; Strache, T.; Fassbender, J.; Mattheis, R.

The control of the effective magnetic anisotropy, saturation magnetization as well as the dynamic magnetic properties in ferromagnetic thin films is of significant importance for most applications in spin electronics. Usually, the magnetic anisotropy, e.g. uniaxial anisotropy or unidirectional anisotropy (exchange bias), in ferromagnetic single or multi-layers is initialized by applying a magnetic field during film deposition or by a magnetic field anneal, which results in an anisotropy aligned along the applied field direction. The saturation magnetization is mainly determined by the film's composition. Whereas anisotropy and saturation magnetization together determine the precessional frequency of the films, the magnetic damping parameter cannot easily be varied in a controlled way.

We demonstrate different ways to pattern soft magnetic magnetic films in terms of laterally varying magnetic properties [1]. In distinction from conventionally patterned systems, the magnetic behavior of these hybrid property films is strongly influenced by the direct exchange interaction across the (now) magnetic property element's borders. Therefore, the effects are directly correlated with the magnetic feature size. Below a critical magnetic feature size, a transition from a magnetic two-phase material to an effective magnetic meta material occurs. This makes them in some sense comparable to magnetic multilayer structures. However, the lateral 'layers' permit access to spatially resolved characterization methods.

Different samples of anisotropy [1,2], exchange bias [1,3], and saturation magnetization [4] modulated thin films are prepared by local oxidation, introducing local stress variation [5], or local ion irradiation. The magnetization reversal processes in the two-phase materials exhibit unique features, some of them so far only known from magnetic multilayer samples. The main emphasis is on the role of magnetic domain formation and domain wall effects in stripe-like magnetic hybrid structures on the overall magnetization properties. Quasi-cubic anisotropies and bi-directional anisotropies, as well as lateral exchange spring behavior are derived from hysteresis loop measurements and magnetic domain imaging. Effects from the introduced quasi-domains, which are related to the domain wall structure and the corresponding wall interaction, will be discussed. In addition, data regarding the influence of pattern density on precessional frequency and effective damping parameter will be shown.

The presented paths of film preparation provide additional degrees of freedom for the tailoring of magnetic properties and functionality of soft-magnetic thin films. Some of the presented methods allow for a local setting of magnetic properties without irreversible structural and magnetic alterations.

Financial support from the Deutsche Forschungsgemeinschaft DFG is highly acknowledged.

References:
[1] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320, 579 (2008)
[2] J. McCord, I. Mönch et al., J. Phys. D: Appl. Phys., accepted (2009)
[3] C. Hamann, I. Mönch et al., J. Appl. Phys. 104, 13926 (2008)
[4] J. McCord, L. Schultz et al., Adv. Mat. 20, 2009 (2008)
[5] N. Martin, J. McCord et al., Appl. Phys. Lett., accepted (2009)

Keywords: magnetism; ion irradiation; ion implantation; magnetic domains; magnetization processes; property patterning

  • Invited lecture (Conferences)
    International Magnetics Conference, 04.-08.05.2009, Sacramento, USA

Permalink: https://www.hzdr.de/publications/Publ-12352
Publ.-Id: 12352


Engineering surfaces, interfaces and structural phases to tailor magnetic properties

Fassbender, J.

Surfaces and interfaces play an important role in order to determine the overall properties of ultrathin magnetic films and multilayers. In particular, the morphology and roughness of the surface and the sharpness of mutual interfaces between magnetic and non-magnetic thin films are crucial. All these parameters are easily accessible by means of ion irradiation [1,2], ion implantation [2,3] and ion erosion approaches [4]. Also structural phase transitions can be accompanied by magnetic ones [5] which allow the creation of nanomagnets in the sub-100 nm regime [6]. In this talk I am going to present a survey of ion beam modifications of magnetic materials with special emphasis on the basic phenomena including some technological applications. Supported by DFG FA 314/3-1, FA 314/6-1 and FA 314/7-1.

[1] J. Fassbender, D. Ravelosona, Y. Samson, J. Phys. D 37, R179 (2004).
[2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320, 579 (2008).
[3] J. McCord, L. Schultz, J. Fassbender, Adv. Mater. 20, 2090 (2008).
[4] M. O. Liedke et al., Phys. Rev. B 75, 220407(R) (2007).
[5] J. Fassbender et al., Phys. Rev. B 77, 174413 (2008).
[6] E. Menendez et al., Small, in press.

Keywords: magnetism; ion irradiation; ion implantation; interface; phase transition

  • Invited lecture (Conferences)
    Gaede-Preis-Vortrag auf der Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 22.-27.03.2009, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12351
Publ.-Id: 12351


Atembewegungskorrektur von listmode-basierten Ganzkörperuntersuchungen mit dem PET-Scanner ECAT Exact HR+

Mölle, H.; Langner, J.; Beuthien-Baumann, B.; Hofheinz, F.; Will, E.; van den Hoff, J.

Ziel/Aim:
Die Messzeit bei Ganzkörperuntersuchungen (GKU) am PET-Scanner ECAT Exact HR+ beträgt 6-8 Minuten pro Bettposition. Atembewegungen des Patienten sind während einer solchen Aufnahme unvermeidbar, woraus unter anderem eine lageabhängige Beeinträchtigung der Tumorabbildung resultiert. Hieraus ergibt sich insbesondere eine Verfälschung quantitativer Parameter wie des SUV und des scheinbaren Tumorvolumens, die unter anderen im Rahmen der Therapieresponse und Follow-up Untersuchungen von Bedeutung sind. Daher ist es wünschenswert die atmungsbedingte Unschärfe bei GKU in der klinischen Routine zu korrigieren.

Methodik/Methods:
Es wurden Methoden für die Durchführung listmode-basierter GKU implementiert (Akquisition der Listmodedaten für jede Bettposition, Steuerung des Bettvorschubs, Eintrag der Datensätze in die ECAT-Datenbank). Das Verfahren wurde bisher bei 32 klinischen Untersuchungen eingesetzt. Gleichzeitig erfassten Infrarot-Tracking-Kameras die Brustkorbbewegung der Patienten. Anhand der Bewegungsamplitude erfolgte die Einteilung der Listmodedaten in einzelne Atemphasen (Gates). Mit Hilfe eines Atembewegungsmodells, das die Atembewegung im inneren des Körpers vereinfacht modelliert, wurden alle Atemphasen auf eine einzige Atemphase abgebildet.

Ergebnisse/Results:
Erstmals konnten listmode-basierte GKU (6-8 Bettpositionen) mit gleichzeitiger Atembewegungserfassung am PET-Scanner ECAT Exact HR+ in der klinischen Routine durchgeführt werden. Dadurch wird eine Atembewegungskorrektur bei GKU ermöglicht. Um die Größe der Korrektur zu prüfen, wurde die Organbewegung der Patienten bestimmt. Vorläufige Ergebnisse zeigen eine mittlere transaxiale Bewegung der Niere von 0.93 ± 0.43 cm. Die Bewegung war so groß, dass bei den meisten Patienten eine Korrektur sowohl im Bereich des Thorax als auch im Abdomen notwendig ist. Die bewegungskorrigierten GKU enthalten nur noch minimale Bewegungen, wodurch eine bessere Quantifizierung des Tumorvolumens und des SUV im Tumor möglich ist.

Schlussfolgerungen/Conclusions:
Die hier vorgestellte Methode der Atembewegungskorrektur bei GKU mit dem PETScanner ECAT Exact HR+ führt zu einer deutlichen Verbesserung der Bildqualität. Die Bewegungskorrektur erfolgt weitestgehend automatisch, wodurch ein Einsatz in der klinischen Routine problemlos möglich ist.

  • Lecture (Conference)
    47. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 22.-25.04.2009, Leipzig, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 48(2009)2, A21

Permalink: https://www.hzdr.de/publications/Publ-12350
Publ.-Id: 12350


Atomistic simulation of amorphous germanium and its solid phase epitaxial recrystallization

Posselt, M.; Gabriel, A.

Amorphous Ge and its recrystallization are investigated by molecular dynamics simulations using a Stillinger-Weber-type interatomic potential. Unlike previously used parametrizations of this potential the parameter set employed in this work yields a reasonable description of all condensed phases of Ge. The preparation of amorphous Ge is performed by cooling from the molten state. Structural and thermal properties of the amorphous phase such as the pair correlation function, the atomic density as well as the melting temperature are calculated and a good agreement with experimental data is found. In order to obtain the initial atomic configuration for the simulation of recrystallization of amorphous Ge, a simulation cell that contains an amorphous and a crystalline layer is carefully prepared by melting a part of a primarily crystalline simulation cell and by cooling the liquid in a similar manner as in the preparation of bulk amorphous Ge. The recrystallization is simulated in the temperature range between 600 and 950 K. The simulation cell is built in such a manner that the main regrowth direction is parallel to [100]. Using an efficient characterization method the configuration of the current amorphous-crystalline interface, its average position with respect to the [100] direction and its roughness given by the rms deviation of this position are determined throughout the simulations. Consistently with former models for Si it is found that recrystallization of amorphous Ge occurs mainly at small {111} facets and is characterized by a sequential local rearrangement of atomic bonds and positions. In very good agreement with experiments the dependence of the velocity of solid phase epitaxial recrystallization on temperature can be approximated by a straight line in an Arrhenius plot. However, the absolute value of the velocity is too high compared to the experimental data. The main reason for this discrepancy may be the overestimation of the flexibility of atomic bonds by the present interatomic potential which leads to an underestimation of the activation energy. Similar to the state of the art in atomistic simulations of solid phase epitaxial regrowth in Si, there is not yet a suitable interatomic potential which allows a consistent quantitative modeling of both the condensed phases and the solid phase epitaxial recrystallization.

Keywords: solid phase epitaxy; atomistic simulation; germanium

  • Physical Review B 80(2009), 045202

Permalink: https://www.hzdr.de/publications/Publ-12349
Publ.-Id: 12349


Boron activation and diffusion in silicon and strained silicon-on-insulator by rapid thermal and flash lamp annealing

Lanzerath, F.; Buca, D.; Trinkaus, H.; Goryll, M.; Mantl, S.; Knoch, J.; Breuer, U.; Skorupa, W.; Ghyselen, B.

We present experimental results on the activation and diffusion behaviors of boron in silicon-on-insulator and strained silicon-on-insulator using standard rapid thermal processing treatments as well as flash lamp annealing. After boron implantation at different doses and at a low energy of 1 keV, samples were annealed to activate the dopants, and secondary ion mass spectrometry and Hall measurements were carried out to determine boron diffusion and the amount of activated dopants, respectively. In contrast to rapid thermal annealing, flash lamp annealing enables the activation without significant diffusion of dopants. In addition, we investigated the effect of coating the samples with antireflection layers to increase the absorbed energy during flash annealing. As a result, the activation was increased significantly to values comparable with the activation obtained with standard annealing. Furthermore, the relation between the observed boron diffusion and activation as a function of the implantation and annealing parameters is discussed in terms of the kinetics of the defects involved in these processes.

Keywords: silicon-on-insulator; strained silicon-on-insulator; flash lamp annealing; rapid thermal annealing; Boron implantation; electrical activation

  • Journal of Applied Physics 104(2008), 044908-1-044908-7

Permalink: https://www.hzdr.de/publications/Publ-12348
Publ.-Id: 12348


Ion beam analysis (IBA) and accelerator mass spectrometry (AMS) with the new 6 MV accelerator at FZ Dresden-Rossendorf

Neelmeijer, C.; Grambole, D.; Grötzschel, R.; Merchel, S.; Munnik, F.

Since more than 30 years IBA is performed at the Forschungszentrum Dresden-Rossendorf (FZD) for the determination of element distributions. Due to continuous upgrades of the different experimental set-ups, we are able to routinely perform:
• Rutherford Backscattering Spectrometry (RBS) & Channeling (C-RBS)
• Nuclear Reaction Analysis (NRA)
• Elastic Recoil Detection Analysis (ERDA)
• Particle-Induced X-Ray (PIXE) and Gamma-Emission (PIGE)
Most of our applications lie within material sciences. We are able to measure non-destructively “all natural” elements, i.e. H to U; most elements with lateral, some in 3-D resolution with the following typical parameters (matrix- and analyte-depending):
• depth resolution: 0.5-30 nm
• depth range: nm-µm
• lateral resolution: few µm
• usual mapping area: 2x2 mm2
• maximum sample size: 3x10 cm2 (vacuum) & “unlimited” (external beam)
• detection limits: ~10 µg/g (H); 500 µg/g – 1% (He-F); 10-100 µg/g (Na-U)
In summer 2009, our 5 MV van-de-Graaff accelerator will be replaced by a 6 MV Tandetron model [1], which is even more sophisticated than the lately installed 5 MV one in France [2]. The new accelerator will need less maintenance allowing more beam time. It might be also possible to expand from two to three 8-hour-shifts a day with the new fully automatic system. The main scientific advantages are an increased depth range by a factor of two for ERDA and improved detection limits for NRA. The high energy resolution also provides the ion optical requirements for a MeV-ion nanoprobe for selective in vivo-irradiation of cell nuclei at the nanometre-scale.
In addition, the machine will have special equipment for AMS [3]. There is a main advantage of using a high-energy accelerator for mass spectrometry: The background and interfering signals, resulting from molecular ions and ions with similar masses (e.g. isobars), are nearly completely eliminated. Thus, AMS provides much lower detection limits compared to conventional mass spectrometry (isotope ratios: 10-10-10-15).
In contrast to common low-energy AMS facilities, which have mainly specialized in radiocarbon analyses, the FZD-AMS is the first modern-type facility in the EU that will run at a terminal voltage of 6 MV. Especially in environmental and geosciences, the determination of long-lived (t1/2 > 0.3 Ma) cosmogenic radionuclides like 10Be, 26Al, and 36Cl became more and more important within the last decades [4]. Using these nuclides dating of e.g. volcanic eruptions, rock avalanches, earth quakes, and glacier movements is possible.
References: [1] A. Gottdang et al., Nucl. Instr. and Meth. B 2002, 190, 177. [2] M.G. Klein et al., Nucl. Instr. and Meth. B 2008, 266, 1828. [3] http://www.fzd.de/ams. [4] J.C. Gosse and F.M. Phillips, Quat. Sci. Rev. 2001, 20, 1475.

Keywords: ion beam analysis; accelerator mass spectrometry

  • Poster
    GDCh-Wissenschaftsforum Chemie 2009, 30.08.-02.09.2009, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12347
Publ.-Id: 12347


Radio-induced alteration in cordierite – Implications for petrology, gemmology and materials science

Krickl, R.; Nasdala, L.; Grambole, D.; Kaindl, R.

Cordierite is a common metamorphic and magmatic mineral, which is used as petrologic tool for reconstructing the history of its host rock. Further applications include cordierite gemstones and the use of synthetic analogs in ceramics. Cordierite is stable over a wide temperature and pressure range and relatively resistant to chemical alteration; however, its properties can be significantly changed upon the impact of external irradiation.
In the course of a comprehensive study, natural radiohaloes in cordierite (a widespread feature caused by the impact of alpha-particles originating from radioactive inclusions) as well as artificial analogs produced by implantation of 8.8 MeV He2+ ions were investigated using modern micro-techniques. Additional irradiation experiments were performed using O6+ ions, electrons and gamma-rays.
Ion irradiation causes yellow colouration that is strongly pleochroic, and fades at higher doses. The possibility of radiation-treatment for enhancing the quality of gem-cordierite is discussed. While samples remain crystalline up to doses of 1016 He2+ /cm², the same material is fully amorphised when irradiated with the same dose of 30 MeV O6+ ions. These different observations may help to estimate the performance assessment of cordierite-ceramics in radiated environments.
A most important result concerning the petrological use of cordierite is the radio-induced transformation of channel constituents: Inside the irradiated areas the vibrational bands of CO2 decrease in intensity, whereas two new bands appear at 2135 cm-1 (both IR and Raman; cf. Nasdala et al., 2006) and 1550 cm-1 (Raman only). They are assigned to stretching vibrations of carbon monoxide and molecular oxygen, respectively, thus indicating a radio-chemical transformation 2CO2 → 2CO + O2 in alpha-irradiated cordierite. This study yields the first spectroscopic evidence for the irradiation-induced formation of molecular oxygen in cordierite. Polarised vibrational spectra of oriented samples give evidence that not only CO2 but also CO and O2 are preferentially oriented parallel [100], most probably being located at the Ch0 position in the large channel cavities. Carbon monoxide and O2 molecules seem to coexist in artificially irradiated cordierite without any sign of back reaction. Investigations on natural CO2 -bearing cordierite from different localities show that the 2CO2 → 2CO + O2 transformation is ubiquitous in radiohaloes.
Up to date, the detection of CO in cordierite has solely been ascribed to a reducing environment during crystal formation (Khomeko & Langer, 2005). In contrast, this present study shows that CO can also be produced by the action of radioactivity. This, as well as the production of radiogenic O2 , has to be taken into account in reconstructing palaeofluid compositions from molecules trapped in the structural channels of cordierite.

Khomenko VM, Langer K (2005): Carbon oxides in cordierite channels: Determination of CO2 isotopic species and CO by single crystal IR spectroscopy. Am Mineral 90: 1913-1917
Nasdala L, Wildner M, Wirth R, Groschopf N, Pal DC, Möller A (2006): Alpha particle haloes in chlorite and cordierite. Mineral Petrol 86: 1-27

  • Poster
    General Assembly 2009 of the European Geosciences Union (EGU), 19.-24.04.2009, Vienna, Austria
  • Open Access Logo Abstract in refereed journal
    Geophysical Research Abstracts 11(2009), EGU2009-2657-2

Permalink: https://www.hzdr.de/publications/Publ-12346
Publ.-Id: 12346


Binding Form of Uranium in Environmental Relevant Compartments

Bernhard, G.; Geipel, G.

wird nachgereicht

  • Invited lecture (Conferences)
    School cum Workshop on Trace Element Speciation (SEISS-08), 21.-29.11.2008, Kolkata, India

Permalink: https://www.hzdr.de/publications/Publ-12345
Publ.-Id: 12345


Chemistry of Actinides

Bernhard, G.; Geipel, G.

wird nachgereicht

  • Invited lecture (Conferences)
    School cum Workshop on Trace Element Speciation (SElS-08), 24.-28.11.2008, Kolkata, India

Permalink: https://www.hzdr.de/publications/Publ-12344
Publ.-Id: 12344


Subsecond melt processing for achieving SiGe surface layers

Voelskow, M.; Kanjilal, A.; Skorupa, W.

High dose germanium (Ge) ion implantation in silicon (Si) substrate in combination with flash lamp irradiation was used to produce a thin SiGe surface layer. Due to the reduced melting temperature of the SiGe alloys, the possibility to form an undesirable facetted liquid/solid interface, well known for pulse melting in the millisecond time regime, was found to decrease significantly using ion beam implantation technique. The formation of a dislocation network in the surface SiGe layer and strain were evidenced by transmission electron microscopy and -Raman spectroscopy measurements, respectively.

Keywords: SiGe; FLA; RBS; Raman spectroscopy

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-12343
Publ.-Id: 12343


Planned experiment on 40Ca(alpha,gamma)44Ti in Dresden

Bemmerer, D.

The 40Ca(alpha,gamma)44Ti nuclear reaction is important for the production of 44Ti in the alpha-rich freezeout in supernovae. The decay of 44Ti has been observed in several staellite-based gamma observatories for the Cas A supernova remnant, but surprisingly not in other cases. A new 40Ca(alpha,gamma)44Ti cross section measurement planned in Dresden is briefly described in the talk. The irradiations are to be performed at the FZD 3 MV Tandetron. Besides in-beam gamma-spectrometry and accelerator mass spectrometry, the main detection method will be an activation measurement. The weak activated 44Ti samples will be counted in the Felsenkeller underground low-level counting facility.

  • Invited lecture (Conferences)
    Research Day "44Ti" of the Excellence cluster "Origin and structure of the universe", 15.01.2009, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12342
Publ.-Id: 12342


Comparison of two dedicated 'in beam' PET systems via simultaneous imaging of 12C-induced β+-activity

Attanasi, F.; Belcari, N.; Del Guerra, A.; Enghardt, W.; Moehrs, S.; Parodi, K.; Rosso, V.; Vecchio, S.

The selective energy deposition of hadrontherapy has led to a growing interest in quality assurance techniques such as ‘in-beam’ PET. Due to the current lack of commercial solutions, dedicated detectors need to be developed. In this paper, we compare the performances of two different ‘in-beam’ PET systems which were simultaneously operated during and after lowenergy carbon ion irradiation of PMMA phantoms at GSI Darmstadt. The results highlight advantages and drawbacks of a novel in-beam PET prototype against a long-term clinically operated tomograph for ion therapy monitoring.

  • Physics in Medicine and Biology 54(2008), n29-n35

Permalink: https://www.hzdr.de/publications/Publ-12341
Publ.-Id: 12341


Direct measurement of the 15N(p,gamma)16O total cross section at novae energies

Bemmerer, D.; Caciolli, A.; Bonetti, R.; Broggini, C.; Confortola, F.; Corvisiero, P.; Costantini, H.; Elekes, Z.; Formicola, A.; Fulop, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyurky, G.; Junker, M.; Limata, B.; Marta, M.; Menegazzo, R.; Prati, P.; Roca, V.; Rolfs, C.; Alvarez, C. R.; Somorjai, E.; Straniero, O.

The 15N(p,gamma)16O reaction controls the passage of nucleosynthetic material from the first to the second carbon-nitrogen-oxygen (CNO) cycle. A direct measurement of the total 15N(p,gamma)16O cross section at energies corresponding to hydrogen burning in novae is presented here. Data have been taken at 90-230 keV center-of-mass energy using a windowless gas target filled with nitrogen of natural isotopic composition and a bismuth germanate summing detector. The cross section is found to be a factor two lower than previously believed.

Keywords: Nuclear astrophysics; Nova burning, CNO cycle; gas target; BGO detector; LUNA

Permalink: https://www.hzdr.de/publications/Publ-12340
Publ.-Id: 12340


First 4D in-beam PET measurement for beam tracking of a moving phantom with a scanned carbon ion beam

Parodi, K.; Saito, N.; Richter, C.; Chaudhri, N.; Enghardt, W.; Rietzel, E.; Bert, C.

More than 10 years of clinical operation of in-beam PET at GSI Darmstadt have proven its positive impact on quality assurance of carbon ion therapy, mostly for head-and-neck sites. Due to the promise of ion beam therapy for indications such as lung and liver tumors which are influenced by respiratory motion we started to investigate the potential of time-resolved, 4D in-beam PET. 4D in-beam PET is expected to facilitate in-vivo assessment of tumor miss or unwanted involvement of nearby critical structures in the presence of organ motion. In a first experiment performed at GSI, in-beam PET was used in combination with beam tracking. A homogeneous PMMA phantom was placed in the center of the field of view of the PET camera and moved parallel to the two detector heads (left-right in beam's eye view, amplitude: 3 cm peak-to-peak, period: ~ 3 s). Dose was delivered by beam tracking as a two-dimensionally spread-out Bragg-peak of 5 x 5 cm2 extension, centered at a depth of 10 cm in the central plane of the phantom. The dynamic PET acquisition was performed during the 6 min of beam delivery and for 25 min after irradiation. The data stream was synchronized with the time course of the dynamic beam application and with the phantom motion. Additional 18 min of decay were acquired with the activated phantom kept steady, for comparison with a separate measurement of the same treatment field without motion. Reconstruction of the data taken with a steady phantom yielded comparable activation patterns for beam tracking and stationary irradiation. 4D PET reconstruction is currently in progress. Motion phase sorted data as well as results for imaging performance in dependence on the amount of reconstructed events will be presented. First conclusions on the feasibility of in-beam PET for monitoring ion treatment of moving targets will be discussed.

  • Lecture (Conference)
    IEEE MIC 2008, 19.-25.10.2008, Dresden, Deutschland
  • Contribution to proceedings
    IEEE Dresden 2008, 19.-25.10.2008, Dresden, Deutschland
    IEEE Conference Report

Permalink: https://www.hzdr.de/publications/Publ-12339
Publ.-Id: 12339


Phasenkorrelierte Schwächungskorrektur von 4D-PET mit Hilfe von 4D-CT

Richter, C.; Just, U.; Pönisch, F.; Enghardt, W.

kein Abstract vorhanden

  • Poster
    OncoRay Retreat 2008, 08.-09.01.2008, Gröditz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12338
Publ.-Id: 12338


Phase-Correlated Attenuation Correction (PC-AC) for 4D-PET/4D-CT

Richter, C.

  • Lecture (others)
    3rd Meeting of the Scientific Advisory Board of OncoRay, 28.02.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12337
Publ.-Id: 12337


On the multivariate nature of brain metabolic impairment in Alzheimer's disease

Salmon, E.; Kerrouche, N.; Perani, D.; Lekeu, F.; Holthoff, V.; Beuthien-Baumann, B.; Sorbi, S.; Lemaire, C.; Herholz, K.

We used principal component analysis to decompose functional images of patients with AD in orthogonal ensembles of brain regions with maximal metabolic covariance. Three principal components explained 38% of the total variance in a large sample of FDG-PET images obtained in 225 AD patients. One functional ensemble (PC2) included limbic structures from Papez's circuit (medial temporal regions, posterior and anterior cingulate cortex, thalamus); its disruption in AD patients was related to episodic memory impairment. Another principal component (PC1) illustrated major metabolic variance in posterior cerebral cortices, and patients’ scores were correlated to instrumental functions (language and visuospatial abilities). PC3 comprised frontal, parietal, temporal and posteromedial (posterior cingulate and precuneus) cortices, and patients’ scores were related to executive dysfunction and global cognitive impairment. The three main metabolic covariance networks converged in the posterior cingulate area that showed complex relationships with medial temporal structures within each PC. Individual AD scores were distributed as a continuum along PC axes: an individual combination of scores would determine specific clinical symptoms in each patient.

Keywords: Alzheimer; Dementia; PET; Brain imaging; Multivariate; PCA

Permalink: https://www.hzdr.de/publications/Publ-12336
Publ.-Id: 12336


Magnetic Structure of RuSr2GdCu2O8 Determined by Resonant X-Ray Diffraction

Bohnenbuck, B.; Zegkinoglou, I.; Strempfer, J.; Nelson, C. S.; Wu, H.-H.; Schüßler-Langeheine, C.; Reehuis, M.; Schierle, E.; Leininger, P.; Herrmannsdörfer, T.; Lang, J. C.; Srajer, G.; Lin, C. T.; Keimer, B.

X-ray diffraction with photon energies near the Ru L2-absorption edge was used to detect resonant
reflections characteristic of a G-type superstructure in RuSr2GdCu2O8 single crystals. A polarization
analysis confirms that these reflections are due to magnetic order of Ru moments, and the azimuthal-angle
dependence of the scattering amplitude reveals that the moments lie along a low-symmetry axis with
substantial components parallel and perpendicular to the RuO2 layers. Complemented by susceptibility
data and a symmetry analysis of the magnetic structure, these results reconcile many of the apparently
contradictory findings reported in the literature

  • Physical Review Letters 102(2009), 037205

Permalink: https://www.hzdr.de/publications/Publ-12335
Publ.-Id: 12335


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