Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34122 Publications

Dinuclear complexes of tetravalent cerium in an aqueous perchloric acid solution

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

Primary aquo species of tetravalent cerium (Ce(IV)) in perchloric acid has been identified as a single oxo-bridging dinuclear complex, not a mononuclear one, by extended X-ray absorption fine structure (EXAFS) spectroscopy combined with density functional theory (DFT) calculations.

Keywords: Tetravalent cerium; Dimer; XAS; EXAFS; DFT calculations

Permalink: https://www.hzdr.de/publications/Publ-16630
Publ.-Id: 16630


Field-induced gap in a quantum spin-1/2 chain in strong magnetic fields

Zvyagin, S.

Magnetic excitations in copper pyrimidine dinitrate, a spin-1/2 antiferromagnetic chain with alternating g-tensor and Dzyaloshinskii-Moriya interactions that exhibits a field-induced spin gap, are probed by means of high-frequency electron spin resonance spectroscopy in pulsed magnetic fields up to 64 T. In particular, we report on a minimum of the gap in the vicinity of the saturation field Hsat = 48.5 T associated with a transition from the sine-Gordon region (with soliton-breather elementary excitations in the magnetic excitation spectrum) to a spin-polarized state with magnon excitations (Fig. 1). This interpretation is fully confirmed by the quantitative agreement over the entire field range of the experimental data with the DMRG calculations for spin-1/2 Heisenberg chain with a staggered transverse field [1]. Such a behavior appears to be a general feature of the high-field excitation spectrum of quantum spin-1/2 chain systems with alternating g-tensor and/or Dzyaloshonskii-Moriya interactions. In addition, the development of the high-field Electron Spin Resonance facilities at the Dresden High Magnetic Field Laboratory is reported.
This work was partly supported by DFG and EuroMagNET II.

  • Invited lecture (Conferences)
    International Workshop "Advanced ESR Studies for New Frontiers in Biofunctional Spin Science and Technology" (AEBST 2011), 13.-14.11.2011, Kobe, Japan

Permalink: https://www.hzdr.de/publications/Publ-16629
Publ.-Id: 16629


Biotechnologie zur Gewinnung von Ressourcen

Pollmann, K.; Kutschke, S.; Raff, J.

Vorstellung der Forschungsvorhaben Ressourcengewinnung

  • Lecture (others)
    Vorstellung beim Städtebund Silberberg, 27.01.2012, Aue, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16628
Publ.-Id: 16628


EduGATE - basic examples for educative purpose using the GATE simulation platform

Pietrzyk, U.; Zakhnini, A.; Axer, M.; Sauerzapf, S.; Benoit, D.; Gaens, M.

EduGATE is a collection of basic examples to introduce students to the fundamental physical aspects of medical imaging devices. It is based on the GATE platform, which has received a wide acceptance in the field of simulating medical imaging devices including SPECT, PET, CT and also applications in radiation therapy.
GATE can be configured by commands, which are, for the sake of simplicity, listed in a collection of one or more macro files to set up phantoms, multiple types of sources, detection device, and acquisition parameters. The aim of the EduGATE is to use all these helpful features of GATE to provide insights into the physics of medical imaging by means of a collection of very basic and simple GATE macros in connection with analysis programs based on ROOT. A graphical user interface to define a configuration is also included.

Keywords: Monte Carlo Simulation; GATE; PET; SPECT; Education; Imaging

Permalink: https://www.hzdr.de/publications/Publ-16627
Publ.-Id: 16627


Numerical simulations of CCFL experiments using a morphology detection algorithm

Höhne, T.; Darlianto, D.; Lucas, D.

In order to improve the understanding of counter-current two-phase flows and to validate new physical models, CFD simulations of 1/3rd scale model of the hot leg of a German Konvoi PWR with rectangular cross section was performed. Selected counter-current flow limitation (CCFL) experiments at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) were calculated with ANSYS CFX 12.1 using the multi-fluid Euler-Euler modeling approach. The transient calculations were carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a SST turbulence model for each phase. In the simulation, the surface drag was approached by a new correlation inside the Algebraic Interfacial Area Density (AIAD) model. The AIAD model 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 using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows a good qualitative agreement. The results indicated that quantitative agreement of the CCFL characteristics between calculation and experimental data was obtained. The goal is to provide an easy usable AIAD framework for all ANSYS CFX users, with the possibility of the implementation of their own correlations.

Keywords: Numerical simulation; CFD; CCFL; AIAD model; reflux condensation; PWR hot leg; air-water experiment

Permalink: https://www.hzdr.de/publications/Publ-16626
Publ.-Id: 16626


Image-Processing-Based Study of the Interfacial Behavior of the Countercurrent Gas-Liquid Two-Phase Flow in a Hot Leg of a PWR

Montoya, G.; Deendarlianto; Lucas, D.; Höhne, T.; Vallee, C.

The interfacial behavior during counter-current two-phase flow of air-water and steam-water in a model of a PWR hot leg was studied quantitatively using digital image processing of a subsequent recorded video images of the experimental series obtained from the TOPFLOW facility, Helmholtz-Zentrum Dresden-Rossendorf e.V. (HZDR), Dresden, Germany. The developed image processing technique provides the transient data of water level inside the hot leg channel up to flooding condition. In this technique, the filters such as median and Gaussian were used to eliminate the drops and the bubbles from the interface and the wall of the test section. A Statistical treatment (average, standard deviation, and probability distribution function (PDF)) of the obtained water level data was carried-out also to identify the flow behaviors.

The obtained data are characterized by a high resolution in space and time, which makes them suitable for the development and validation of CFD-grade closure models, e.g. for two-fluid model. This information is essential also for the development of mechanistic modeling on the relating phenomenon. It was clarified that the local water level at the crest of the hydraulic jump is strongly affected by the liquid properties.

Keywords: CFD; Hot Leg

  • Open Access Logo Science and Technology of Nuclear Installations 2012(2012), ID 209542
    DOI: 10.1155/2012/209542

Permalink: https://www.hzdr.de/publications/Publ-16625
Publ.-Id: 16625


Counter-current Flow Limitation of Gas-Liquid Two phase Flow in Nearly Horizontal Pipe

Prayitno, S.; Santoso, R.; Darlianto, D.; Höhne, T.; Lucas, D.

Experimental on the work counter current two phase flow of air and gas in nearly horizontal flows have been performed. The experiments are conducted with 50 mm inner diameter pipe, in two inclination angle setting (20° and 10° from horizontal) and smooth liquid and air inlet i.e. a porous liquid inlet and a nozzle connected with calm section for gas inlet. The effect of liquid properties are examined by using five different working fluids (Water, two different concentration of butanol and glycerin aqua solutions). As results, (1) CCFL causes a drastic change in the delivered liquid to the lower plenum. (2) The effect of inclination angle is significantly observed. The flooding gas superficial velocity needed decreases with inclination angle. (3) The liquid viscosity affects the flooding phenomena.

Keywords: counter-current flow limitation; flooding; inclined pipe; liquid properties

Permalink: https://www.hzdr.de/publications/Publ-16624
Publ.-Id: 16624


CFD studies of the insulation material transport inside the reactor pressure vessel under LOCA conditions

Höhne, T.; Grahn, A.; Kliem, S.

In 1992, strainers on the suction side of the ECCS pumps in Barsebäck NPP Unit 2 became partially clogged with mineral wool because after a safety valve opened the steam impinged on thermally-insulated equipment and released mineral wool. This event pointed out that strainer clogging is an issue in the course of a loss-of-coolant accident (LOCA). In the LOCA event inside the containment, energetic pressure waves and fluid jets would impinge upon components in the vicinity of the break and could release thermal insulation and dust. In addition, debris can be created by chemical reactions between reactive ECC solutions and the materials in the containment. These reactions may result in additional debris such as disbanded coatings and chemical precipitates being generated [1].Through transport mechanisms such as entrainment in steam/water discharge from the break and wash down due to condensate flow in the containment, a fraction of the generated debris and other material in the containment would be transported to the containment sump. Subsequently, if the ECCS is operating in the sump recirculation mode, the debris suspended in the containment sump would begin to accumulate on the sump strainers. A small part could penetrate trough the strainers and could be transported towards the core. The accumulation of this suspended debris on the sump strainers can create an almost uniform covering on the strainer, which would tend to increase the head loss across the strainer. On account of this phenomenon, modifications of the insulation material, the strainer size and the mesh size at the strainers were carried out in most of the German NPPs to assure the emergency core cooling during the sump recirculation mode. Moreover, differential pressure measurements and back flushing procedures were implemented to remove the mineral wool from the strainers, before the differential pressure exceeds a certain level. Nevertheless, it cannot be completely ruled out, that small fractions of the insulation material are transported into the RPV. During hot leg ECC injection, the fibres enter the upper plenum and can accumulate at the fuel element spacer grids, preferably at the uppermost grid level. This effect might cause a reduction of the ECC flow into the core and degradation of core cooling.
It was the aim of the numerical simulations to study where and how many mineral wool fibres are deposited at the upper spacer grid. The 3D, time dependent, multi-phase flow problem was modelled applying the CFD code ANSYS CFX. Best practice guidelines were used to specify the grid size, turbulence model and the multiphase model. The spacer grids were modelled as a strainer, which completely retains all the insulation material reaching the uppermost spacer level. In this model, which was validated against experiments at HTWS Zittau, the accumulation of the insulation material gives rise to the formation of a compressible fibrous cake, the permeability of which to the coolant flow is calculated in terms of the local amount of deposited material and the local value of the superficial liquid velocity. The CFD simulations have shown that after starting the sump mode, the ECC water injected through the hot legs flows down into the core at so-called “breakthrough channels” at the outer regions of the core, which were first recognized in UPTF experiments. In contradiction the hotter, lighter coolant rises in the centre of the core. As a consequence, the insulation material is preferably deposited at the uppermost spacer grids positioned in the breakthrough zones. This means that the fibres are not uniformly deposited over the core cross section.
Further investigations are necessary to determine the accumulation of insulation material for a longer period of time. Also steam production in the core or re-suspension of the insulation material during back flow should be considered.

Keywords: CFD; UPTF; ECC; RPV

  • Lecture (Conference)
    CFD4NRS-4, The Experimental Validation and Application of CFD and CMFD Codes in Nuclear Reactor Technology, 10.-12.09.2012, Daejeon, Korea
  • Contribution to proceedings
    CFD4NRS-4, The Experimental Validation and Application of CFD and CMFD Codes in Nuclear Reactor Technology, 10.-12.09.2012, Daejeon, Korea
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-16623
Publ.-Id: 16623


CFD-modelling of CCFL phenomena in a PWR hot leg model

Höhne, T.; Darlianto, D.; Lucas, D.

The detailed three-dimensional (3-D) information on the transient flow behaviour under countercurrent flow limitation (CCFL) in a pressurized water reactor (PWR) hot leg is an important issue in the reactor safety analysis. It relates to a hypothetical scenario of small break Loss of Coolant Accident (LOCA) in a PWR, and leads to the reflux-condensing mode. During this scenario, a part of the condensate flows back towards the reactor pressure vessel (RPV) in counter current to the steam. In this mode, a CCFL could occur, affecting the core cooling. Deendarlianto et al. (2011a) has already reviewed different applications of CFD codes to simulate the phenomena around the CCFL in a PWR hot leg. They indicated that there is still a lack of knowledge regarding suitable closure models for this application. In some cases empirical correlations originally obtained for one-dimensional codes were used for this multidimensional problem.

Keywords: LOCA; PWR; AIAD; CFD

  • Lecture (Conference)
    Jahrestagung Kerntechnik 2012, 22.-24.05.2012, Stuttgart, Deutschland
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2012, 22.-24.05.2012, Stuttgart, Deutschland
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-16622
Publ.-Id: 16622


Multiphase Flows in Industrial Applications – Theory, Experiments and CFD Validation

Höhne, T.

Strong increase of usage of three-dimensional Computational Fluid Dynamics (CFD) in industrial applications because for instance
slugging,
pressurized thermal shocks,
coolant mixing,
thermal striping
cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution.

Keywords: CFD; slugging; pressurized thermal shocks; coolant mixing; thermal striping

  • Invited lecture (Conferences)
    International Seminar Series 2012, Universitas Gadjah Mada, Faculty of Engineering, 30.01.2012, Yogyakarta, Indonesia

Permalink: https://www.hzdr.de/publications/Publ-16621
Publ.-Id: 16621


CFD in Safety of Nuclear Industry

Höhne, T.

Strong increase of usage of three-dimensional Computational Fluid Dynamics (CFD) in industrial applications because for instance
slugging,
pressurized thermal shocks,
coolant mixing,
thermal striping
cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution.

Keywords: CFD; slugging; pressurized thermal shocks; coolant mixing; thermal striping

  • Invited lecture (Conferences)
    International Conference on Computational Modeling Validation, 14.-15.01.2012, Sydney, Australien
  • Open Access Logo Contribution to proceedings
    International Conference on Computational Modeling Validation, 14.-15.01.2012, Sydney, Australien
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-16620
Publ.-Id: 16620


Recent Developments in CFD Modeling of Multiphase Flows

Höhne, T.

CFD (Computational Fluid Dynamics) is the simulation of fluids engineering systems using modeling (mathematical physical problem formulation) and numerical methods (discretization methods, solvers, numerical parameters, and grid generations, etc.)
CFD made possible by the advent of digital computer and advancing with improvements of computer resources (500 Floating Point Operations per Second (flops), 1947 10 Petaflops, 2011)

Keywords: CFD; AIAD; Multiphase flow

  • Invited lecture (Conferences)
    INTERNATIONAL CONFERENCE ON COMPUTATIONAL MODELING VALIDATION, 14.-15.01.2012, Sydney, Australien
  • Open Access Logo Contribution to proceedings
    INTERNATIONAL CONFERENCE ON COMPUTATIONAL MODELING VALIDATION, 14.-15.01.2012, Sydney, Australien
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-16619
Publ.-Id: 16619


Modelling and Simulation of 4D GeoPET Measurements with COMSOL Multiphysics 4.2a

Schikora, J.; Kulenkampff, J.; Gründig, M.; Lippmann-Pipke, J.

Our GeoPET-method allows the 4D monitoring of (reactive) transport processes in geological material on laboratory scale (Gründig et al., 2007; Kulenkampff et al., 2008; Richter et al., 2005) by quantitative imaging of tracer concentrations. Recently we have conducted a long-term 22Na+ in-diffusion experiment in an Opalinus clay drill core over aperiod of 7 months. We modelled this experiment with COMSOL Multiphysics ® 4.2a (3D convection-diffusion equation, PDE mode, PARDISO solver) for reproducing the observed spatiotemporal concentration distribution data with the following underlying equation for this anisotropie diffusion and adsorption:
8Ci ( ) 8q
cßt = \l Dc . \lCi P8t
-c [-] porosity, ci[moVm3] 22Na+concentration, D e [m2/s] tensor of the effective diffusion constant for 22Na+ in Opalinus clay, P [kg/m3 ] bulk density and 8q/8t sink term for considering the sorption. By importing GeoPET images from various time steps and applying the Optirnization Module (least square fit applying the LevenbcrgMarquardt algorithrn) to these images we efficiently deterrnined hest fit values e.g. of the diffusion tensor. Cornbined with the parameter sweep operation the sensitivity analysis is performed in parallel and covers the range of literature values for porosity and Kd values for 22Na+sorption on Opalinus cIay.
The experimental data could be reproduced quite weIl, but the obtained parameter values for diffusion parallel and normal to the bedding are slightly larger than reported in Gimmi and Kosakowski (2011). This is coherent with our observations of an emerging gas bubble in the central borehole tracer reservoir: Soil moisture tension in the partly unsaturated clay must have significantly influenccd thc transport regime by an additional advective component.
We suggest COMSOL Multiphysics ® is a powerful tool for the inverse modelling of timedependent, multidimensional experimental data as obtained by GeoPET.
References.
Gründig, M. et a1., 2007. Tomographie radiotraeer studies ofthe spatial distribution ofheterogeneous geoehemieal transport proeesses. Appl. Geochem., 22: 2334-2343.
Kulenkampff, J. et al., 2008. Evaluation ofpositron emission tomography for visualisation ofmigration proeesses in geomaterials. Phys. Chern. Earth, 33: 937-942.
Richter, M. et al., 2005. Positron Emission Tomography for modelling of geochmical transport processes in clay. Radiochirn. Acta, 93: 643-651.
Gimmi, T. & Kosakowski, G. 2011. How mobile are sorbed eations in clay and clay rocks? Environ. Sei. Techn., 45:1443-1449

  • Poster
    EGU General Assembly 2012, 22.-27.04.2012, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-16618
Publ.-Id: 16618


Influence of Temperature on the Sorption of Selenate onto Anatase

Franzen, C.; Jordan, N.; Mueller, K.

The radioactive isotope Selenium-79 is a long-lived fission product found in nuclear waste. Due to its long half life of 3.27 ∙ 105 years, it is expected to be one of the isotopes most contributing to the potential radiation dose according to safety assessments of nuclear waste underground repositories. A detailed knowledge of the mobility and bioavailability of selenium is therefore of great importance for a safe disposal of radioactive waste.
One major process controlling selenium mobility and bioavailability is the adsorption onto mineral surfaces of both the geological and engineered barrier. High level and long-lived radioactive waste increase the temperature in the vicinity of the waste disposal site. Thus, it is important to understand to what extent this temperature increase influences the sorption of selenium.
The present study focuses on the impact of temperature on the sorption of selenate (SeO42-) onto anatase (TiO2). Because of its abundance in rocks and its well-known crystal structure, anatase represents an ideal model system for the study of sorption behaviour of Se onto transition metal oxide phases. The sorption of selenate onto anatase at different temperatures (25 °C – 60 °C) was investigated both with batch experiments and ATR FT-IR spectroscopy. In order to explain possible differences in sorption at higher temperatures, the surface of the anatase was investigated.
The sorption of Se(VI) onto anatase as a function of pH was similar at 25 °C and 60 °C, i.e. sorption decreased with increasing pH. However, the sorption capacity of anatase towards Se(VI) was lowered at a higher temperature. Furthermore, the pH value above which no Se(VI) sorption occurs was shifted to lower pH values (from pH 6.5 at 25 °C to pH 5.5 at 60 °C).
The isoelectric point of anatase (pHIEP) was located at pH 6.3 at 25 °C. At higher temperatures, the pHIEP was shifted towards lower pH with a value of 5.5 at 60 °C. In addition, the absolute values of the zeta potential were lowered at higher temperatures. Both findings were in good agreement with the batch experiments.
The observed decrease in selenate sorption at higher temperatures could be assigned to a change in the surface properties of anatase.

Keywords: Selenium; selenate; sorption; anatase; temperature

  • Lecture (Conference)
    Experimental Mineralogy Petrology and Geochemistry, 04.-07.03.2012, Kiel, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16617
Publ.-Id: 16617


THEREDA - One Database for thermodynamic and sorption data

Bok, F.; Brendler, V.; Richter, A.

For geochemical modeling of scenarios for the disposal of radioactive and (chemo)toxic waste, comprehensive and internally consistent thermodynamic data are required as well as sorption data for the surrounding host rocks. The use of different databases renders it difficult to compare results of geochemical modeling, due to incompleteness, inconsistencies, resticted ranges of variation (temperature, density, pressure), limitations in solution composition (ionic strength) and last but not least missing sorption data.
THEREDA (THErmodynamic REference DAtabase, www.thereda.de) is a project adressing these issues through high quality standards: full documentation and thus transparency of all data, internal consistency, quality assurance measures, different interaction models, comprehensiveness. It shall imporve geochemical modelling for various environmental applications, namely radiochemical waste disposal assessment.
THEREDA contains data for the three ion-ion interaction models: extendend Debye-Hückel, Specific Ion Interaction Theory, and Pitzer model. Tailored parameter files for various geochemical modeling codes are provided (PhreeqC, ChemApp, EQ3/6, Geochemist‘s Workbench). Documented benchmark calculations allow comparisons with other databases as well as between the different geochemical codes. All data, documentation and references are freely accessible via the projects homepage. Additionally, a user forum allows direct contact with the THEREDA members.
A holistic view of geochemical processes in the context of a safety analysis requires the inclusion of sorption calculations. A thermodynamically consistent treatment of these processes is only possible with surface complexation modelling (SCM). Existing SCM data from the RES³T (Rossendorf expert system for surface and sorption thermodynamics, www.hzdr.de/res3t) database is currently subjected to critical evaluation and will be included in THEREDA.

Keywords: THEREDA; RES³T; RES3T; database; thermodynamic; sorption

  • Poster
    Experimental Mineralogy Petrology and Geochemistry 2012, 04.-07.03.2012, Kiel, Deutschland
  • Contribution to proceedings
    Experimental Mineralogy Petrology and Geochemistry 2012, 04.-07.03.2012, Kiel, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16616
Publ.-Id: 16616


Different types of outer-sphere complexes of selenate ions on mineral surfaces

Jordan, N.; Ritter, A.; Heim, K.; Foerstendorf, H.

  • Lecture (others)
    Helmholtz-Koordinierungstreffen, 23.-24.01.2012, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16615
Publ.-Id: 16615


Manuskriptband für die Berliner Recycling- und Rohstoffkonferenz 2012

Dürkoop, A.; Gutzmer, J.; Faulstich, M.; Klossek, A.

Auf Basis der Rohstoffstrategie und der High-Tech Strategie 2020 der Bundesregierung (2010a, 2010b) sollen mit der vom Bundesministerium für Bildung und Forschung (BMBF) geförderten Maßnahme „r3 – Innovative Technologien für Ressourceneffizienz – Strategische Metalle und Mineralien“ konkrete Vorschläge für die Erhöhung der Versorgungssicherheit strategisch bedeutender Ressourcen in Deutschland erarbeitet werden. Unter diesen strategisch bedeutenden Ressourcen sind seltene Metalle und Industriemineralien zu verstehen, die mehr und mehr in der High-Tech-Industrie zum Einsatz kommen. Im Rahmen der Fördermaßnahme r³ wird neben zahlreichen Verbundprojekten ein übergeordnetes Begleitforschungsprojekt „INTRA r³+“ angestrebt, welches die Fördermaßnahme koordiniert, entstandenes Wissen bündelt und die Forschungspartner miteinander vernetzt. Ein zentrales Anliegen von INTRA r3+ ist die Aufbereitung und Kommunikation des entstandenen Wissens sowie die Entwicklung von gezielten Transfermaßnahmen für Akteure und Interessengruppen inner- und außerhalb des Forschungsnetzwerkes. Durch diese Maßnahmen soll der Weg zur Übertragung und wirtschaftlichen Nutzung der Projektergebnisse erleichtert werden.
Das Begleitforschungsprojekt startete im November 2011 und wird bis Januar 2016 als Serviceprogramm für r3 die Forschungsaktivitäten zur Optimierung der gesamten Wertschöpfungskette der Bereitstellung von strategischen Metallen und Industriemineralien begleiten. Koordinator des INTRA r3+ ist das Helmholtz-Institut Freiberg für Ressourcentechnologie (HIF), (siehe Punkt V). Die geförderten Verbundprojekte innerhalb des r3-Rahmenprogramms werden ab Mitte 2012 mit ihren Forschungsarbeiten für innovative Technologien zur Ressourceneffizienz beginnen.
Durch die Bündelung, Analyse und Bewertung neuer Erkenntnisse sollen im Begleitforschungsprojekt INTRA r3+ Impulse erzeugt werden, die einerseits auf eine erfolgreiche Durchführung der Verbundprojekte abzielen, anderseits die Kooperation und Vernetzung der Verbundprojekte untereinander fördern sollen. Die Verbundprojekte werden dafür in verschiedene Forschungscluster unterteilt, die wiederum von Clusterbetreuern gesteuert werden. Im Rahmen von INTRA r³+ steht den technischen Verbundprojekten auch ein Analyseservice im Gerätepool des Koordinators HIF zur Verfügung.

Keywords: Resource efficieny; rare earth elements; industrial minerals; recycling; substitution; urban-mining

  • Invited lecture (Conferences)
    Berliner Recycling- und Rohstoffkonferenz 2012, 26.-27.03.2012, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16614
Publ.-Id: 16614


Specific targeting of hypoxic tumor tissue with nitroimidazole-peptide conjugates

Splith, K.; Bergmann, R.; Pietzsch, J.; Neundorf, I.

Nitroimidazole–peptide conjugates: Attachment of a nitroimidazole unit to a cell-penetrating peptide was used to create conjugates able to target hypoxic tumor tissue. In vivo studies have demonstrated the successful delivery of these conjugates to even less well-perfused hypoxic regions in solid tumors. This approach provides a targeted delivery system with the option to use it as an imaging agent or to conjugate it with therapeutics.

Keywords: antitumor agents; cell-penetrating peptides; drug delivery; hypoxia; tumor targeting

Permalink: https://www.hzdr.de/publications/Publ-16613
Publ.-Id: 16613


The impact of atmospheric carbonate on the sorption of actinyl (V/VI) ions onto gibbsite studied by in situ ATR FT-IR and EXAFS spectroscopy

Gückel, K.; Foerstendorf, H.; Rossberg, A.

The talk shows a first comparative insight into the course of the surface complex formation of U(VI) and Np(V) onto gibbsite on a molecular level studied by ATR FT-IR and EXAFS spectroscopy.

  • Lecture (others)
    HELMHOLTZ-KOORDINIERUNGSTREFFEN 2012, 23.-24.01.2012, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16612
Publ.-Id: 16612


Determination of potential landscapes using video microscopy

Kreuter, C.; Leiderer, P.; Erbe, A.

Video microscopy can be used for the detection of surface potentials, when colloidal particles are present and act as tracer particles for then surface corrugation. Here we present measurements on colloidal particles, which are confined in narrow channels on a substrate and interact with a barrier, which impedes the motion along the channel. The motion of the particles then contains information on the gravitational potential as well as on the potential defined by the presence of the barrier. Statistical analysis is performed in order to extract the potential shapes which arise from the two interactions. We use brownian dynamics simulations in order to complement the experiments with tests of a large range of scenarios, which cannot be accessed in experiments.

Keywords: video microscopy; colloidal model systems; soft matter

Permalink: https://www.hzdr.de/publications/Publ-16611
Publ.-Id: 16611


Influence of the residual oxygen in the plasma immersion ion implantation (PI3) processing of materials

Ueda, M.; Silva Jr., A. R.; Mello, C. B.; Silva, G.; Reuther, H.; Oliveira, V. S.

In this work, we investigated the effects of the contaminants present in the vacuum chamber of the PI3 system, in particular, the residual oxygen, which results in the formation of the oxide compounds on the surface and hence is responsible for the high implantation energies required to achieve reasonably thick treated layers. We used a mass spectrometer (RGA) with a quadruple filter to verify the composition of the residual vacuum and pressure of the elements present in the chamber. Initially we found a high proportion of residual oxygen in a vacuum with a pressure of 1 × 10−3 Pa. Minimizing the residual oxygen percentage in about 80%, by efficient cleaning of the chamber walls and by improving the gas feeding process, we mitigated the formation of oxides during the PI3 process. Therefore we achieved a highly efficient PI3 processing obtaining implanted layers reaching about 50 nm, even in cases such as an aluminum alloy, where is very difficult to nitrogen implant at low energies. We performed nitrogen PI3 treatment of SS304 and Al7075 using pulses of only 3 kV and 15 × 10−6 s at 1 kHz with an operating pressure of 1 Pa.

Permalink: https://www.hzdr.de/publications/Publ-16610
Publ.-Id: 16610


Ion Beam Modification of Magnetic Materials

Fassbender, J.

Overview of current research on ion beam modification of magnetic materials

Keywords: magentism; ion irradiation; ion implantation

  • Invited lecture (Conferences)
    IMW-Seminar des IFW Dresden, 19.01.2012, Dresden, Deutschland
  • Invited lecture (Conferences)
    Colloquium CIC Nanogune San Sebastian, 16.02.2016, San Sebastian, Spanien
  • Invited lecture (Conferences)
    International Conference on 'Accelerators in Materials and Medical Sciences' 2017, 05.-07.10.2017, Dubai, United Arabic Emirates

Permalink: https://www.hzdr.de/publications/Publ-16609
Publ.-Id: 16609


Interaction of U(VI) with Bacterial Isolates from Äspö and Mont Terri

Lütke, L.; Moll, H.; Bachvarova, V.; Geißler, A.; Selenska-Pobell, S.; Bernhard, G.

Microorganisms are ubiquitous in nature, having a significant impact on the sorption and hence the migration behavior of actinides. Thus it is necessity to characterize the actinide-bacteria species formed and to elucidate the involved interaction mechanisms. This talk deals with the interaction of two microbial strains isolated from destined host rocks for future nuclear waste deposition, namely Pseudomonas fluorescens from Äspö, Sweden, and a novel strain of the genus Paenibacillus from Mont Terri, Switzerland. Potentiometric titration, TRLFS and EXAFS results on the U(VI) interaction with these strains are presented. The talk involves a special focus on the effect of the cell wall constitution (Gram-negative vs. Gram-positive) and the oxygen availability on the U(VI) speciation.

Keywords: Uranium; Pseudomonas fluorescens; Paenibacillus sp; Speciation; Potentiometric Titration; TRLFS; EXAFS

  • Lecture (others)
    Helmholtz-Koordinierungstreffen 2012, 23.-24.01.2012, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16608
Publ.-Id: 16608


Biological characterization of [18F]-radiolabeled anilinopyrimidine: a potential radiotracer for EphB4 receptor imaging

Neuber, C.; Mosch, B.; Mamat, C.; Bergmann, R.; Pietzsch, J.

Background:
The receptor tyrosine kinase EphB4 and its ligand ephrinB2 play a critical role in tumor angiogenesis. Therefore, EphB4/ephrinB2 system is a potential target for tumor diagnosis and therapy, and different approaches including tyrosine kinase inhibitors are under investigation. Our study aimed the development and biological characterization of a novel radiotracer targeted to EphB4.
Material and Methods:
Based on a known EphB4 kinase inhibitor (lead compound 1) containing a bis anilinopyrimidine motif a methylsulfonyl residue was replaced by 3 fluoropropylsulfonyl moiety (2) followed by 18F-radiolabeling ([18F]2). Human melanoma cells A375 transfected with human EphB4 full length protein (A375 EphB4) or mock plasmid (A375 pIRES) were analyzed for cell viability and EphB4 tyrosine phosphorylation after incubation with compounds 1 and 2. Cellular uptake of [18F]2 was investigated using specific inhibitors. [18F]2 was analyzed in biodistribution experiments and dynamic positron emission tomography (PET) studies using nude mice bearing A375 EphB4 or A375 pIRES tumors.
Results:
Overexpression of EphB4 in A375 EphB4 cells was confirmed by mRNA and protein expression. Both compound 1 and 2 reduced EphB4 tyrosine phosphorylation and influenced cell morphology and viability. [18F]2 showed internalization by A375 and transfected A375 cells. Partial inhibitory effects of different specific inhibitors provided information on possible uptake mechanisms, which further have to be characterized. Biodistribution and PET studies revealed high stability of [18F]2 in vivo with fast hepatobiliary excretion. No differences between A375 EphB4 and A375 pIRES tumors could be observed in uptake of [18F]2.
Conclusion:
The novel compound 2 substantially inhibited EphB4 tyrosine phosphorylation, when radiolabelded with 18F represents a potential PET tracer. Since [18F]2 was internalized by A375 melanoma cells in vitro the use of [18F]2 for imaging of EphB4 in vivo by PET is supported. However, further studies will deal with optimization of its pharmacokinetic properties.

  • Lecture (Conference)
    5th European Workshop on "Apoptosis, Angiogenesis & Hypoxia in Tumor Microenvironment: Biological aspects and Imaging", 05.-08.10.2011, Berder Island, France
  • Contribution to proceedings
    5th Berder Meeting on Apoptosis, Angiogenesis and Hypoxia in Tumor Microenvironment: Biological Aspects and Imaging, 05.-08.10.2011, Berder Island, France
    Proceedings of the 5th Berder Meeting on Apoptosis, Angiogenesis and Hypoxia in Tumor Microenvironment: Biological Aspects and Imaging, 33-34

Permalink: https://www.hzdr.de/publications/Publ-16607
Publ.-Id: 16607


Influence of external radiation on cellular properties and Eph receptor/ephrin expression in human melanoma cells

Mosch, B.; Pietzsch, D.; Pietzsch, J.

There is first experimental evidence that progression and metastasis of melanoma is associated with receptor tyrosine kinases (RTK) of the Eph receptor family. However, RTK can be regulated by different factors, but the influence of radiation on Eph receptors and their ligands and, furthermore, on melanoma metastasis is unclear. In this study, we radiated one pre-metastatic and three metastatic human melanoma cells lines, including one self-generated metastatic cell line with X-rays (5 and 10 Gy vs. sham). At day 1 and day 7 post radiation we analyzed cellular viability, proliferation, colony formation, migration, adhesion, and motility. Additionally, selected Eph receptors and ephrin ligands were analyzed regarding radiation-dependent changes in mRNA and protein.
In all cell lines a dose dependent decrease in viability and cell growth for up to 1 week after radiation was demonstrated. Colony formation was unaffected in pre-metastatic and only marginally influenced in metastatic cell lines. Migration and adhesion increased 1 day after radiation, while motility of all cells decreased. In contrast, 7 days after radiation, migration decreased while adhesion remained increased in treated cells. Furthermore, an increase in motility was observed in pre-metastatic cells. For EphA2 we detected an increase in mRNA in 2 of 3 metastatic cell lines, with simultaneously decreased protein level. EphA3 was found to be up-regulated in mRNA and protein in 3 of 4 cell lines. Expression of ephrinA1 and A5 was generally low and seemed unaffected by radiation, with the exception of an increase in ephrinA1 mRNA in 3 of 4 cell lines.
In conclusion, we showed that X-ray radiation strongly decreased viability and proliferation of human melanoma cells. Concerning metastatic properties, it remained ambiguous if X-ray acts pro- or anti-metastatic to melanoma cells, probably depending on cell line and time after radiation. Regarding the present data an involvement of A-type Eph receptors in radiation-mediated effects in melanoma can be hypothesized. Ongoing studies will clarify whether and how over-expression and inhibition of Eph influences metastatic properties of human melanoma cells.

  • Poster
    Keystone Symposium “Stem cells, Cancer and Metastasis”, 06.-11.03.2011, Keystone, Colorado, USA

Permalink: https://www.hzdr.de/publications/Publ-16606
Publ.-Id: 16606


Development of [90Y]Y-CHX-A´´-DTPA-Cetuximab for combination of radioimmunotherapy and external radiotherapy: Radiochemistry and first in vivo results

Heldt, J.-M.; Koi, L.; Zenker, M.; Brüchner, K.; Dittfeld, C.; Bergmann, R.; Mosch, B.; Pietzsch, H.-J.; Pietzsch, J.; Zips, D.; Kunz-Schughart, L. A.; Baumann, M.; Steinbach, J.

Objectives:
Radiochemical development, characterisation and preparation of [90Y]Y-CHX-A´´-DTPA-Cetuximab ([90Y]C225). Preclinical evaluation of [90Y]C225 by combination of radioimmunotherapy and external radiotherapy.
Methods:
CHX-A´´-DTPA was conjugated to C225 via thiourea bond formation in HEPES-buffer at pH 7.2 by reacting 20 equivalents of chelator with C225 for 24 h. Purification of the conjugate was done by ultrafiltration. Chelator to C225 ratio was determined by MALDI-TOF MS and the conjugate’s affinity determined by flow cytometric analysis. Radiolabeling was performed in MES buffer at pH 6.1 at 30°C for 30 min using [90Y]YCl3. Free DTPA chelator (0.1 μg/μL) was added to the reaction mixture for quenching the labeling reaction and fixing unreacted radionuclide. Ex vivo autoradiography ([90Y]C225) was performed, in vivo kinetics were measured with PET using 86Y as radiolabel and biodistribution studies were performed. FaDu tumour bearing nude mice were treated with [90Y]C225 (2.8 MBq 13 g C225 / mouse, i.v.) and external beam irradiation (X-rays, single dose, 1.1 Gy/min). Experimental endpoints are the tumour growth delay and the local tumour control. Some animals are still in follow-up and not all cohorts are completed. The data are preliminary (figure 1B).
Results:
MALDI-TOF MS analysis of the purified conjugate showed that approximately 5 CHX-A´´-DTPA moieties have been conjugated to C225. The conjugate has not lost affinity to EGFR on cell surfaces when compared to the unconjugated C225 at 0.33 nM (flow cytometry). CHX-A´´-DTPA-C225 was labelled with [90Y]YCl3 with radiolabelling yields >95% and a reproducible specific activity of 1.2 GBq/mg was achieved. Autoradiography studies revealed high tumour accumulation 48 h p.i., also PET showed an increasing antibody accumulation in the tumour, which was abundant after 24 h p.i. These data validate the conjugate to be suitable for therapeutical studies: The combined treatment (internal and external irradiation) was well tolerated by all mice and no histological alterations in organs could be found. The preliminary data in Figure 1B clearly show a dose-effect of the external irradiation. A significant improvement of the local tumour control after external irradiation with 26 Gy was achieved after application of 13 g of radiolabelled C225 compared to unlabelled C225 or to the treatment by external irradiation solely.
Conclusions:
[90Y]C225 has been successfully prepared, characterized and it can be produced in routine with high avidity and specific activity as prerequisite for long-term preclinical therapeutic studies. Our in-vivo preliminary data support the concept that multimodal cancer treatment results in a potentially relevant improvement of local tumour control in an experimental tumour model.
Research Support:
The Bundesministerium für Bildung und Forschung (grant 02NUK006, framework “Kompetenzverbund Strahlenforschung” (KVSF)) is gratefully acknowledged for the financial support.

  • Poster
    19th International Symposium on Radiopharmaceutical Sciences (ISRS), 28.08.-02.09.2011, Amsterdam, Niederlande
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), S568

Permalink: https://www.hzdr.de/publications/Publ-16605
Publ.-Id: 16605


Radiosynthesis of 3-[18F]fluoropropanesulfonamides derived from aliphatic and aromatic amines

Löser, R.; Hiller, A.; Fischer, S.; Funke, U.; Maisonial, A.; Brust, P.; Steinbach, J.

Objectives:
Facing the ample palette of prosthetic groups available for the introduction of radiofluorine into pharmacologically relevant molecules, the careful selection of the appropriate labelling agent often reveals critical for tracer development as it can influence target binding and/or stability in vivo. Labelling based on the formation of carboxylic acid amides often results in metabolic instability due to hydrolytic cleavage. As an alternative to acyl-based prosthetic groups the 3-[18F]fluoropropanesulfonyl group introduced by Li et al. attracted our interest [1]. Therefore, we established and optimised the preparation of 3-[18F]fluoropropanesulfonyl chloride in our lab and studied its reaction with various aliphatic and aromatic amines.
Methods:
To obtain 3-[18F]fluoropropanesulfonyl chloride ([18F]4) we followed the route described in [1] that includes conversion of intermediary 3-[18F]fluoropropyl thiocyanate ([18F]3) with chlorine leading to the desired sulfonyl chloride (Figure 1). As the preparation of [18F]3 from the corresponding tosyl precursor 1 proceeded with only moderate labelling yields, the nosylate 2 was synthesised by two different pathways both starting from 3-bromopropanol. The syntheses of the non-radioactive sulfonamides as reference compounds resembled those of the radiotracers with the oxidation of 3 to 4 as the key step. This was realised by employing a solution of chlorine in water using acetic acid as organic co-solvent. The resulting sulfonyl chloride 4 was reacted with various aliphatic and aromatic amines. Due to the fact that 3 and 4 show an almost identical chromatographic behaviour on silica gel
as observed by TLC, a radio-HPLC method had to be developed that allowed to prove the identity of [18F]4 but prevented its hydrolysis on the column. The synthesis of the final radioactive sulfonamides was done by reacting
[18F]4 with different primary and secondary aliphatic amines as well as various aniline derivatives in dichloromethane at room temperature both in the absence and presence of triethylamine (TEA) and/or 4-
dimethylaminopyridine (DMAP) as reaction enhancing mediators. The results were evaluated by radio-TLC and radio-HPLC.
Results:
The nosyl precursor 2 accounted for high labelling yields of 78-85% (n=11) in the first step of the radiosynthesis. A concentration of 2.5 to 3.0 mg/mL and a reaction time of 10 min in acetonitrile (approx. 0.4 mL) at reflux were found to be optimal for the radiofluorination of 2. For the conversion of [18F]3 into the corresponding sulfonyl chloride the repetitive treatment of this intermediate adsorbed at a C18 matrix with an aqueous solution of chlorine and subsequent desorption with dichloromethane led to [18F]4 of high radiochemical purity ranging from 85 to 95%. The reaction of [18F]4 with primary amines always resulted in high yields of radioactive sulfonamides (75 to 85%) that did not improve upon addition of TEA or DMAP. In contrast, the conversion of [18F]4 with various anilines was low (<10%) but could be significantly increased in the presence of TEA or DMAP resulting in yields of 55 to 65%.
Conclusions:
The structural optimisation of the sulfonate precursor together with optimised reaction conditions for the radiosynthesis of 3-[18F]fluoropropanesulfonyl chloride ([18F]4) enabled the preparation of 3-[18F]fluoropropanesulfonamides derived from various aliphatic and aromatic amines. This will allow the preparation of 18F-labelled sulfonamides of pharmacologically interesting amino-functionalised compounds.
References:
[1] Li et al. (2008) J. Label. Compd. Radiopharm. 51, 23-27

  • Poster
    19th International Symposium on Radiopharmaceutical Sciences (ISRS), 28.08.-02.09.2011, Amsterdam, Niederlande
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), S477

Permalink: https://www.hzdr.de/publications/Publ-16604
Publ.-Id: 16604


Design and synthesis of novel radiolabelled peptide-based Eph receptor inhibitors for PET

Pretze, M.; Mamat, C.; Steinbach, J.

Objectives:
Eph receptors and their ephrin ligands belong to the largest receptor tyrosine kinase family of transmembrane proteins. Since Eph receptors are found to be dysregulated in certain tumour species [1, 2] many efforts have been made to inhibit such receptors in order to stop tumourigenesis and tumour growth [3]. To date, several promising candidates of small molecules exist [4, 5], which inhibit Eph receptors at the intracellular domain. Furthermore, peptides with the key amino acid sequence SNEW show the highest affinity for the EphB2 receptor and, in this regard, block the extracellular receptor domain [6]. In this case, the development of a labelling strategy for the radiofluorination of SNEW peptides to design new PET-tracers is promising for specific tumour diagnosis.
Methods:
Several novel SNEW peptides were synthesized via an automated Fmoc-protecting group strategy. The key sequence at the N-terminus has to be unmodified in order to sustain the affinity to EphB2-receptor. The C-terminus was modified with cysteine, lysine and azidoproline for a radiofluorination with [18F]FBAM, [18F]SFB [7] and by use of bioorthogonal reactions like the Staudinger ligation or the Huisgen cycloaddition.
Results:
Since the key sequence of SNEW peptides is essential for the affinity to the EphB2-receptor, the SNEW peptides were modified at the C-terminus for the bioorthogonal labelling. In order to compare the new bioorthogonal reactions with established labelling methods, the cysteine modified SNEW peptide was reacted with [18F]FBAM (60 °C, 60 min, Sørensen-buffer (pH = 7.2)/acetonitrile (vv = 1:1)). Additionally, [18F]BFP as new and
versatile labelling building block for the copper-catalyzed Huisgen-cycloaddition was developed. Therefore, the azidoproline modified SNEW peptide was labelled with this click building block under milder conditions (r.t., 30 min, Sørensen-buffer (pH = 7.2)/ethanol (vv = 1:1)).
Conclusions:
New labelling building blocks were synthesized for the bioorthogonal radiofluorination of novel azide-functionalized peptides with a SNEW sequence and compared to standard labelling methods like [18F]FBAM. The SNEW peptides show a high affinity to the EphB2 receptor and represent promising radiotracers for a specific tumour diagnosis.
References:
[1] Surawska, H.; Ma, P. C.; Salgia, R., (2004), Cytokine Growth Factor Rev., 15, 419-433,
[2] Mosch, B.; Reissenweber, B.; Neuber, C.; Pietzsch, J., (2010), J. Oncol., DOI: 10.1155/2010/135285,
[3] Choi, Y.; Syeda, F.; Walker, J. R.; Finerty Jr., P. J.; Cuerrier, D.; Wojciechowski, A.; Liu, Q.; Dhe-Paganon, S.; Gray, N. S., (2009), Bioorg. Med. Chem. Lett., 19, 4467-4470,
[4] Miyazaki, Y.; Nakano, M.; Sato, H.; Truesdale, A. T.; Stuart, J. D.; Nartey, E. N.; Hightower, K. E.; Kane-Carson, L., (2007), Bioorg. Med. Chem. Lett., 17, 250-254,
[5] Caligiuri, M.; Molz, L.; Liu, Q.; Kaplan, F.; Xu, J. P.; Majeti, J. Z.; Ramos-Kelsey, R.; Murthi, K.; Lievens, S.; Tavernier, J.; Kley, N., (2006), Chem. Biol., 13, 711-722.
[6] Chrencik, J. E.; Brooun, A.; Recht, M. I.; Nicola, G.; Davis, L. K.; Abagyan, R.; Widmer, W.; Pasquale, E. B.; Kuhn, P., (2007), J. Biol. Chem., 282, 36505-36513.
[7] Wuest, F.; Köhler, L.; Berndt, M.; Pietzsch, J., (2009), Amino Acids, 36, 283-295

  • Poster
    19th International Symposium on Radiopharmaceutical Sciences (ISRS), 28.08.-02.09.2011, Amsterdam, Niederlande
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), S460

Permalink: https://www.hzdr.de/publications/Publ-16603
Publ.-Id: 16603


Site-selective labelling of peptides with fluorine-18 in solution and on solid phase using succinimidyl 4-[18F]fluorobenzoate ([18F]SFB) – a comparative study

Kuchar, M.; Pretze, M.; Mamat, C.; Knieß, T.; Steinbach, J.; Löser, R.

Objectives:
The growing interest in peptides as probes for the molecular imaging of physiological and pathological processes by positron emissions tomography (PET) is accompanied with the increasing need for generally applicable methods that allow a selective labelling of these biomolecules [1]. The site-selective introduction of the well-established 4-[18F]fluorobenzoyl prosthetic group into peptides containing multiple amino acids with nucleophilic entities located in the side chains is very often challenging. This is especially valid for lysine-containing peptides. Sometimes, a selective labelling can be achieved by taking advantage of the slight difference between the pKa values of the N-terminus and the ε-amino group of lysine [2]. However, the success of this strategy is moderate. Therefore, the potential to label various lysine containing peptides with [18F]SFB at defined sites by solid-phase synthesis was evaluated in this study in comparison to 18F-fluorobenzoylation in solution.
Methods:
Four different peptides were chosen to comparatively evaluate the solid phase approach and labelling in solution (Figure 1). The selection included the N-terminal telopeptide of collagen α1(I) 1 [3] and its derivative 2 [4] both containing a lysine residue important for collagen crosslinking, the k7 sequence of a cell-penetrating peptide 3 [5] and a derivative of a so-called SNEW peptide 4. The latter is a ligand for the EphB2 receptor whose binding affinity is critically dependent on a free N-terminus [6]. The aim was to label 1-3 at their N-terminus whereas 4 was to be labelled selectively at its C-terminal lysine residue. The precursors as well as the corresponding non-radioactive fluorobenzoylated peptides were synthesised by microwave-assisted solid-phase peptide synthesis employing the Fmoc/tBu strategy. For labelling in solution the fully deprotected peptides were reacted with [18F]SFB at pH 7 and 9. Labelling on solid phase was carried out by suspending the preswollen peptide-loaded resin in a mixture of DMF and phosphate buffer containing [18F]SFB followed by a washing step and final acidic deprotection and cleavage from the resin. For every labelling experiment the labelling yields were determined by radio-HPLC. In addition, peptides 1 and 2 were labelled in solution by using derivatives with Alloc/All-protected side chains followed by Pd-catalysed deprotection and solid phase extraction.

1 *H-Leu-Ser-Tyr-Gly-Tyr-Asp-Glu-Lys-Ser-Thr-Gly-Ile-Ser-Val-Pro-NH2
2 *H-Gly-Gly-Gly-Asp-Pro-Lys-Gly-Gly-Gly-Gly-Gly-NH2
3 *H-Lys-Lys-Arg-Lys-Ala-Pro-Lys-Lys-Lys-Arg-Lys-Phe-Ala-NH2
4 H-Ser-Asn-Glu-Trp-Ile-Leu-Pro-Arg-Leu-Pro-Gln-His-Val-*Lys-NH2

Figure 1. Sequences of the peptides studied in the labelling experiments. The desired labelling position is indicated by an asterisk.

Results:
Labelling in solution always resulted in product mixtures independent of the pH that were often difficult to purify. In contrast, labelling on solid-phases yielded 18F-fluorobenzoylated peptides in radiochemical purities of 95-99%. The optimised procedure allowed to prepare the labelled peptides in activities ranging from 30-100 MBq (8-15%, d.c.) with a specific activity of 10-12 GBq/μmol and a reaction time of 135-140 min (without [18F]SFB production). The labelling of the Alloc/All-protected peptides in solution was less successful due to the presence of unreacted [18F]SFB during the deprotection step.
Conclusions:
The selective labelling [18F]SFB on solid phase is a useful tool in the development of radiotracers based on peptides, especially if the lysine side chain or the N-terminus is functionally important for target binding.
References:
[1] Tolmachev & Stone-Elander (2010) Biochim. Biophys. Acta 1800, 487-510,
[2] Wester et al. (1995) J. Label. Compd. Radiopharm. 37, S513-S515,
[3] Helseth et al. (1979) Biopolymers 18, 3005-3014,
[4] Nagan & Kagan (1994) J. Biol. Chem. 269, 22366-22371,
[5] Rennert et al. (2008) ChemMedChem 3, 241-253
[6] Chrencik et al. (2007) J. Biol. Chem. 282, 36505-36513

  • Poster
    19th International Symposium on Radiopharmaceutical Sciences (ISRS), 28.08.-02.09.2011, Amsterdam, Niederlande
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), S449

Permalink: https://www.hzdr.de/publications/Publ-16602
Publ.-Id: 16602


Fluorinated cyclobutyl group for increased metabolic stability using a tyrosine model system

Franck, D.; Kniess, T.; Steinbach, J.; Zitzmann-Kolbe, S.; Friebe, M.; Dinkelborg, L.; Graham, K.

Objectives: [18F]Fluoroalkyl chains are known to be potential sites for metabolic instability and can result in suboptimal PET image quality [1]. The aim of this work was to develop the [18F]fluorocyclobutyl substituent as a novel 18F-labeled prosthetic group that should have an increased metabolic stability whilst maintaining its efficacy. The well-characterized tyrosine LAT transporter system was used as a model test system.
Methods:
The precursors (cis-cyclobutane-1,3-diol ditosylate and tert-butyl N-(tert-butoxycarbonyl)-O-[trans-3-(tosyloxy)cyclobutyl]-L-tyrosinate) and the reference compound, 3-(cis-fluorocyclobutyl)-tyrosine, for the indirect and direct radiosyntheses of 3-(cis-[18F]fluorocyclobutyl)tyrosine (3-[18F]FCBT) were synthesized. The radiosynthesis of the 3-[18F]FCBT via indirect and direct methods were successfully established as outlined in Scheme 1. In vitro studies were performed in A549 cells after incubation with 3-[18F]FCBT at 37°C for up to 60 min with/without inhibitors FET and non-radioactive 3-FCBT. In vivo PET imaging studies were performed on mice bearing human lung cancer xenografts (A549 carcinoma).
Results:
3-[18F]FCBT was synthesized via the direct method from precursor 3 in good yield (27-37% d.c.) and excellent radiochemical purity (>99%) in 57-73 minutes. In comparison, the indirect method from the precursor 1 and tyrosine gave only moderate yields (6-12% d.c.) and required longer synthesis times (140-158 minutes). The cell uptake studies showed an increase of 3-[18F]FCBT over time reaching a plateau of 5.87% at 30 min . In animal PET imaging the A549 lung carcinoma xenografts in mice were clearly visualized by the injection of 6 MBq 3-[18F]FCBT. The compound showed fast clearance from the blood and renal as well as hepatobiliary excretion. Preliminary in vitro stability investigations using 3-FCBT indicate excellent stability.
Conclusions:
The radiosynthesis of 3-[18F]FCBT via indirect and direct methods were established The introduction of fluorinated cyclobutyl group into the LAT-targeting tyrosine was shown to be tolerated and actively transported in the in vitro and in vivo setting using A549 cells and their xenografts. The principle of this fluorinated cyclobutyl group as stabilizing moiety will be further investigated.
References:
[1] Treble, (1962) Biochemistry, 82, 129-134

  • Poster
    19th International Symposium on Radiopharmaceutical Sciences (ISRS), 28.08.-02.09.2011, Amsterdam, Niederlande
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), S447

Permalink: https://www.hzdr.de/publications/Publ-16601
Publ.-Id: 16601


Automated radiosynthesis and purification of the thiol-reactive labeling agent [18F]FBAM

Kniess, T.; Kuchar, M.; Steinbach, J.; Pietzsch, J.

Objectives: The interest on 18F-radiolabeled peptides and proteins has increased over the last decade. Consequently, prosthetic groups as N-succinimidyl 4-[18Ffluorobenzoate ([18F]SFB) have been designed for labeling peptides at the amino functionality. Due to in some cases unsatisfactory or inconsistent radiolabeling results with [18F]SFB a strategy directed to a single functionality would circumvent these drawbacks. Therefore, prosthetic groups reacting exclusively with thiol groups were designed1, one of them N-[6-(4-[18F]fluorobenzylidene)aminooxyhexyl] maleimide [18F]FBAM2 (Figure 1). To make [18F]FBAM more applicable for routine use we developed an automated radiosynthesis of this labeling agent including a solid phase purification3.
Methods:
The labeling precursor 4-N,N,N-trimethylaminobenzaldehyde triflate, the FBAM precursor N-(6-aminooxyhexyl)maleimide hydrochloride and the non-radioactive FBAM were synthesized according to the literature2. [18F]Fluoride was produced on a CYCLONE 18/9 Cyclotron (IBA) via the 18O(p,n)18F reaction. A commercially available synthesis module TRACERlab FXFDG (GE) was adapted in terms of program and hardware. Results: For the 18F-labeling 10 mg of 4-N,N,N-trimethylaminobenzaldehyde triflate were reacted with the [18F]KF-Kryptofix222 complex in 1.0 mL of acetonitrile for 10 min at 90°C in reactor 1. After addition of 12 mL of water the solution was passed over a Strata C18U cartridge (Phenomenex) to trap the 4-[18F]fluorobenzaldehyde. The cartridge was eluted with 3.5 mL of methanol into reactor 2 and 7 mg of the aminooxy-precursor was added dissolved in 0.5 mL of methanol. The Schiff-base reaction was performed for 6 min at 40°C, 10 mL of water were added and the content of reactor 2 was passed over a LiChrolut RP18 cartridge (Merck). After washing with 6 mL of acetonitrile/water=1:1 the [18F]FBAM was finally eluted with 2mL of acetonitrile into a product vial. A typical radiosynthesis started with 3.1 GBq [18F]fluoride and yielded about 580 MBq [18F]FBAM (29% yield d.c.) within a total synthesis time of 40 min, the radiochemical purity was 94-98% .
Conclusions:
An automated procedure for the routine radiosynthesis of [18F]FBAM will help to make the thiolreactive prosthetic group more broadly available for selective 18F radiolabeling of peptides and proteins as
molecular imaging probes.
Research Support:
References:
[1] Toyokuni et al., (2003), Bioconjug. Chem., 14, 1253-159, [2] Berndt et al., (2007), Nucl. Med. Biol., 34, 5-15[3] Kniess et al., (2011), Appl. Radiat. Isot., submitted

  • Poster
    19 International Symposium on Radiopharmaceutical Sciences (ISRS), 28.08.-02.09.2011, Amsterdam, Niederlande
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), S413

Permalink: https://www.hzdr.de/publications/Publ-16600
Publ.-Id: 16600


Magnetic solitons in quantum spin chains

Zvyagin, S.

The first documentary observation of solitons was done in 1834 by John Scott Russell on Union Canal in Scot-land, UK, who found that a heap of water in a canal propagates undistorted over several kilometers. Nowadays, a large number of soliton manifestations is known, including for instance solitons in fiber-optics communication systems, solitons in conducting polymers, low-frequency collective motion in proteins and DNA, etc. Many types of solitons can be described using the famous sine-Gordon equation... The sine-Gordon equation can be solved exactly, with solitons and their bound states, breathers, as solution. In this presentation I will talk about magnetic solitary waves in quantum spin chains, probed in copper pyrimidine dinitrate (Cu-PM, which is a spin-1/2 antiferromagnetic chain with alternating g-tensor and Dzyaloshinskii-Moriya interactions) by means of high-frequency and high-field Electron Spin Resonance (ESR) spectroscopy. Signa-tures of three breather branches and a soliton were identified, as predicted by the sine-Gordon quantum-field theory. Having a fully quantum-mechanical nature, the solitary waves in quantum spin chains can be destroyed by thermal fluctuations. This can be nicely illustrated by analyzing the parameters of ESR spectra using a new theoretical concept by Oshikawa and Affleck. Finally, I will show the crucial effect of high magnetic fields sup-pressing the solitary-wave behavior and transforming the soliton-breather excitation spectrum into magnons. These studies were done employing ESR technique in pulsed magnetic fields up to 64 T. Excellent agreement between the theory and experiment in all cases was obtained. In addition, the development of the high-field Elec-tron Spin Resonance facilities at the Dresden High Magnetic Field Laboratory will be presented.

  • Invited lecture (Conferences)
    Seminar University of Kyoto, 30.11.2011, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-16599
Publ.-Id: 16599


ESR studies of the quasi-2D frustrated Cs2CuBr4

Zvagin, S. A.; Kamenskyi, D.; Wosnitza, J.; Ikeda, M.; Fujita, T.; Hagiwara, M.; Kyokuen, N. N.; Starykh, O. A.; Hu, R.; Ryu, H.; Petrovic, C.

We report low-temperature electron spin resonance (ESR) studies of single-crystalline samples of Cs2CuBr4, a spin-1/2 antiferromagnet with a triangular spin-lattice structure. A remarkable angular dependence of the resonance field, including the splitting of the ESR line for some orientations of the magnetic field, and the presence of a gap in the ESR excitation spectrum at temperatures above TN ~1.3 K have been revealed. Our observations suggest that uniform Dzyaloshinskii-Moriya interaction affects the low-energy excitation spectrum in this frustrated compound. The results are compared with that obtained recently for the isostructural material Cs2CuCl4 [Povarov et al., Phys. Rev. Lett. 107, 037204 (2011)]

  • Lecture (Conference)
    APS March Meeting, 27.02.-02.03.2011, Boston, USA
  • Lecture (Conference)
    Frühjahrstagung der DPG, 25.-30.03.2012, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16598
Publ.-Id: 16598


The Attempt of Using GaN(Cs) Cathodes for Photo Injectors

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

There are a lot of opportunities to improve the electron source quality. Especially for the high average power gun producing up to mA level of average current, the searching for the better photo cathodes is a principal challenge. Gallium nitride (GaN) is a novel III-V semiconductor with the wide band gap close to the Cs2Te. As photo emitter material, GaN has a number of interesting characteristics. It has high QE and the negative electron affinity (NEA) on its surface can be achieved only with cesium; GaN (Cs) is more robust against contamination than GaAs and multi-alkali photocathodes. Thus GaN(Cs) has the chance to be a candidate for a high average current source. In this paper, the result of the first activation experiment in HZDR and the next plan will be presented.

Keywords: Photo Cathode; Electron Source; GaN; Gallium Nitride; NEA; Quantum Efficiency

  • Poster
    ERL 2011, The 50th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 16.-21.10.2011, Tsukuba, Japan

Permalink: https://www.hzdr.de/publications/Publ-16597
Publ.-Id: 16597


NMR signal averaging in 62 T pulsed fields

Meier, B.; Greiser, S.; Haase, J.; Herrmannsdörfer, T.; Wolff-Fabris, F.; Wosnitza, J.

es hat kein Abstract vorgelegen.

  • Lecture (Conference)
    Gordon Research Seminar Magnetic Resonance, 11.06.2011, Biddeford, USA
  • Poster
    Gordon Research Conference Magnetic Resonance, 12.06.2011, Biddeford, USA

Permalink: https://www.hzdr.de/publications/Publ-16596
Publ.-Id: 16596


Ultrasound Investigations of Magnetic Monopole in Spin Ice

Erfanifam, S.

  • Poster
    6th PhD Seminar, 05.-07.10.2011, Rabenberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16595
Publ.-Id: 16595


Gallium-induced thin-film superconductivity in Ge and Si and its possible applications

Skrotzki, R.; Herrmannsdörfer, T.; Heera, V.; Fiedler, J.; Voelskow, M.; Mücklich, A.; Schmidt, B.; Skorupa, W.; Helm, M.; Wosnitza, J.

We present two unconventional routes of embedding superconducting nanolayers in a semiconducting environment. On the one hand, ion implantation and subsequent annealing have been used to prepare intrinsic superconducting thin-films of Ga-doped germanium (Ge:Ga) with Tc of 0.5 to 1.2 K. On the other hand, the same technique has been applied to fabricate thin amorphous Ga-rich layers in silicon (Si:Ga) revealing a Tc of about 7 K. Extended structural investigations by means of XTEM, EDX, RBS/C, and SIMS have been performed in addition to low-temperature electrical transport and magnetization measurements. A narrow window of preparation parameters turns out to be necessary to obtain best sample properties in a reproducible way. While Ge:Ga films scale 60 - 100 nm and reveal a small critical current density Jc ≈ 3 A/cm2, Si:Ga layers exhibit Jc > 1 kA/cm2 and a thickness of 15 nm. Relative high and anisotropic critical fields have been found for both nanostructures proving their quasi-two-dimensionality. The implementation of prospective microstructuring may offer an on-chip combination of super- and semiconducting circuits that could be integrated in novel heterostructured devices.

  • Lecture (Conference)
    EUCAS 2011, 18.-23.09.2011, Den Haag, The Netherlands
  • Poster
    6th PhD Seminar, 05.-07.10.2011, Rabenberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16594
Publ.-Id: 16594


Coexistence of ferromagnetism and superconductivity in single-phase Bi3Ni nanostructures

Herrmannsdörfer, T.; Skrotzki, R.; Schönemann, R.; Wosnitza, J.; Köhler, D.; Boldt, R.; Ruck, M.

  • Invited lecture (Conferences)
    Seminar an der TU Chemnitz, 08.11.2011, Chemnitz, Deutschland
  • Poster
    26th International Conference on Low Temperature Physics (LT26), 10.-17.08.2011, Beijing, China
  • Invited lecture (Conferences)
    Workshop on “Magnetic Materials under Extreme Conditions" und ESRF Users´Meeting, 06.-08.02.2012, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-16593
Publ.-Id: 16593


Fermi-Surface Topology of Ce1-xYbxCoIn5

Ignatchik, O.; Polyakov, A.; Wosnitza, J.; Bianchi, A. D.; Prevost, B.; Blackburn, S.; Coté, M.; Capan, C.; Hurt, D.; Fisk, Z.

  • Poster
    Moscow International Symposium on Magnetism (MISM) 2011, 20.-25.08.2011, Moscow, Russia

Permalink: https://www.hzdr.de/publications/Publ-16592
Publ.-Id: 16592


Magneto-acoustic study of UCuGe

Zherlitsyn, S.; Andreev, A. V.; Yasin, S.; Skourski, Y.; Wosnitza, J.; Zvyagin, A. A.

We present results of a magneto-acoustic study of single crystalline UCu0.95Ge in static (up to 18 T) and pulsed (up to 60 T) magnetic fields. This intermetallic compound exhibits antiferromagnetic (AF) ordering at TN = 48 K. The magnetic structure of UCuGe, characterized by the AF arrangement of the magnetic moments in the basal plane of the hexagonal lattice is determined by competing intra- and inter-layer exchange interactions. In magnetic fields applied along the c direction this material shows a phase transition at 38 T to a spin-polarized state with an U magnetic moment of 1.3µB. This phase transition is seen as a jump in the magnetization, accompanied by a hysteresis. The sound velocity and sound attenuation demonstrate pronounced anomalies in the vicinity of both the antiferromagnetic ordering and the field-induced phase transition proving the important role of magneto-elastic interactions in the physics of this actinide compound. We discuss our results in frame of a phenomenological model, which describes qualitatively the main experimental observations. In addition to the features accompanying the magnetic phase transitions, a broad and frequency-dependent step-like change of the sound velocity together with a broad maximum of the sound attenuation have been observed for the ultrasound wave propagating along the c axis at temperatures above TN. We discuss these anomalies in relation to vacancy dynamics in the nonstoichiometric UCu0.95Ge.

  • Poster
    SCES 2011, 29.08.-03.09.2011, Cambridge, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-16591
Publ.-Id: 16591


Abschlussbericht Reaktorsicherheitsforschung - Vorhaben-Nr.: 150 1331 Wissenschaftlich-technische Zusammenarbeit mit Russland: Untersuchungen zu Mechanismen der Strahlenversprödung und des Ausheilverfahrens sowie Fluenzberechnungen für Reaktordruckbehälter von WWER-Reaktoren

Viehrig, H.-W.; Houska, M.; Ulbricht, A.; Konheiser, J.; Altstadt, E.; Noack, K.

The project was performed in the framework of the scientific technical cooperation in the scope of nuclear safety research between Germany and Russia. Objects of the investiga-tions are the decommissioned reactor pressure vessels (RPV) of the Greifswald nuclear power plant. The Greifswald WWER-440/V-230 nuclear reactors represent the first genera-tion of this reactor type. The investigation of these RPV’s enable the assessment of the aging and the effect of an industrial thermal annealing of serial RPVs for the first time. The main focus of the investigations was not on the application of mechanical-technological test methods on which the Russian technical regulation is based, but on the application of ad-vanced fracture mechanics test methods. This enables a fracture mechanics RPV integrity assessment which is based on direct measured fracture toughness values. With the investi-gations it is shown that real neutron induce embrittlement of the beltline welding seam and the forged base metal ring cannot be predicted by the Russian technical regulation. The direct measured KJC values and the resulting Master Curve T0 values, which characterise the ductile-to-brittle transition, differ fundamentally of those which were determined on mechani-cal technological values.
A further topic is the investigation of irradiation induced microstructural defects which origi-nates the embrittlement and their mitigation by the thermal annealing. Within separate sub-projects neutron fluence calculations were performed for the investigated WWER-440/V-230 RPVs and their support constructions.

Keywords: nuclear reactors; Russian WWER type; reactor pressure vessel; reactor pressure vessel steels; base metal; welding seam; fracture toughness; microstructure; integrity assessment; neutron fluence

  • Other report
    Dresden: Abschlussbericht HZDR\FWS\2011\06, 2011
    161 Seiten

Permalink: https://www.hzdr.de/publications/Publ-16590
Publ.-Id: 16590


Ion-assisted bottom-up nanostructuring of carbon-transition metal nanocomposite films: a GISAXS study

Abrasonis, G.; Krause, M.; Buljan, M.; Wintz, S.; Zschornak, M.; Grenzer, J.

Nanocomposite materials become of ever increasing importance in numerous fields of science and technology such as tribology, plasmonics, spintronics, sensing, catalysis, including the strategic quest for renewable energies regarding photovoltaics, solar collectors or thermoelectrics. The macroscale properties of nanocomposite materials are strongly influenced by their nanoscale morphology. Therefore a control of this nanoscale morphology is of major importance.

Here we present a GISAXS study of C:Ni nanocomposite thin films grown by ion beam assisted deposition (IBAD). IBAD combines Ar+ ion beam co-sputtering of a C-Ni target to produce film forming species with a simultaneous irradiation of the growing film with low energy (50-140 eV) Ar+ ions. Depending on the ion energy and metal content this leads to different 3D morphologies such as dispersed nanoparticles, tilted nanocolumns or spatially ordered compositional nanopatterns. These structures show their characteristic fingerprints in GISAXS patterns. A theoretical approach to reproduce such patterns will be presented. The results show that low energy ions provide a powerful means to induce the self-organizion leading to the formation of 3D compositional nanopatterns.

  • Poster
    GISAXS 2011, 10.-12.10.2011, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-16589
Publ.-Id: 16589


Spin transfer oscillators with different geometries

Fowley, C.; Sluka, V.; Bernert, K.; Deac, A.

For applications one requires high power, narrow line-width oscillators which can operate ideally at zero field. Spin transfer torque can induce precession in GMR and TMR spin valves.
There are recent demonstrations of out of plane precession in both in-plane and perpendicular magnetic free layers. Here, we calculate the outputs by solving the LLGS equations for these two geometries. We find that the system with perpendicular free layer is advantageous for two reasons: a further reference layer is not required as the polarising layer itself acts as a reference layer for the GMR effect; precession is independent of the initial magnetisation state, that is various magnetisation directions can be excited into precession at specific fields and currents.

Keywords: spin-transfer torque; spin-torque oscillators; giant magnetoresistance; perpendicular anisotropy

  • Poster
    Spin Master Voice, 13.-16.12.2011, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-16588
Publ.-Id: 16588


Commissioning Results of the SRF Gun with Lead Cathode

Barday, R.; Anders, W.; Jankowiak, A.; Kamps, T.; Knobloch, J.; Kugeler, O.; Matveenko, A.; Neumann, A.; Quast, T.; Rudolph, J.; Schenk, M.; Völker, J.; Sekutowicz, J.; Smedley, J.; Kneisel, P.; Nietubyc, R.; Teichert, J.

A superconducting radio-frequency (SRF) gun with a superconducting Pb photocathode was build up for the first stage of the BERLinPro gun. We report on the activities on the gun and measurements of the beam parameters like beam energy and beam current. Improvement of the quantum efficiency after the laser cleaning treatments is discussed.

Keywords: Superconducting Radio Frequency; Photo Injector; Electron Source; Photo Cathode; Pb Cathode; Quantum Efficiency; Laser Cleaning

  • Open Access Logo Contribution to proceedings
    PSTP 2011, XIV International Workshop on Polarized Sources, Targets and Polarimetry, 12.-16.09.2011, St. Petersburg, Russia
    Proceedings of the PSTP 2011

Permalink: https://www.hzdr.de/publications/Publ-16587
Publ.-Id: 16587


Incorporation of N in TiO2 films grown by DC-reactive magnetron sputtering

Sério, S.; Melo Jorge, M. E.; Nunes, Y.; Barradas, N. P.; Alves, E.; Munnik, F.

Photocatalytic properties of TiO2 are expected to play an important role on emerging technologies based on OH radicals to destroy harmful nonbiodegradable organic and inorganic contaminants in water. The drawback is the wide band gap of TiO2 (3.2 eV) limiting its use to the UV part of electromagnetic spectrum under sunlight. Therefore, modifications of TiO2 are needed to tune the gap in order to allow an efficient use of the entire solar spectrum. One possibility is N-doping of TiO2 to make the photocatalytic activity possible under visible light and more suitable for water treatment.
In our study nitrogen-doped TiO2 (TiO2-xNx) films were deposited by DC-reactive magnetron sputtering using a dual-magnetron co-deposition apparatus on unheated glass and silicon substrates using a pure titanium target. The depth profile of nitrogen was measured with heavy ion elastic recoil detection analysis combined with Rutherford backscattering spectrometry (RBS) and correlated with the optical and structural properties obtained by UV–VIS spectroscopy and X-ray diffraction (XRD).

Keywords: N-doping TiO2; Band gap tuning; Sputtering; Ion beam analysis

Permalink: https://www.hzdr.de/publications/Publ-16586
Publ.-Id: 16586


Modified SRF photoinjector for the ELBE at HZDR

Murcek, P.; Arnold, A.; Büttig, H.; Michel, P.; Teichert, J.; Xiang, R.; Kneisel, P.

The superconducting radio frequency photoinjector (SRF photoinjector) with Cs2Te cathode has been successfully
operated under the collaboration of HZB, DESY, HZDR, and MBI. In order to improve the gradient of the gun cavity and the beam quality, a new modified SRF gun (SRF-gun 2008) has been designed. The main updates of the new cavity design for the new photoinjector were published before (SRF09 Conference Berlin). This cavity is being fabricated in Jefferson Lab.
In this paper the new ideas of the further parts of the SRF-gun 2008 will be presented. The most important issue is the special design of half-cell and choke filter. The cathode cooler is also slightly changed, which simplifies the installation of the cathode cooler in the cavity. The next update is the separation of input and output of the liquid nitrogen supply, for the purpose of the stability of the nitrogen pressure as well as the better possibility of temperature measurement. Another key point is the implementation of the superconducting solenoid inside the cryomodule. The position of the solenoid can be accurately adjusted with two step motors, which are thermally isolated to the solenoid itself.

Keywords: Superconducting Radio Frequency; Photo Injector; Electron Source; Superconducting Cavity; Superconducting Solenoid; Cryomodule

  • Poster
    SRF 2011, 15th International Conference on RF Superconductivity, 25.-29.07.2011, Chicago, USA
  • Open Access Logo Contribution to proceedings
    SRF 2011, 15th International Conference on RF Superconductivity, 25.-29.07.2011, Chicago, USA
    SRF2011 Proceedings: JACoW

Permalink: https://www.hzdr.de/publications/Publ-16585
Publ.-Id: 16585


Ion beam analysis of as-received, H-implanted and post implanted annealed fusion steels

Gonzalez-Arrabal, R.; Munnik, F.; González, M.; Romero, P.; Heller, R.; Leardini, F.; Perlado, J. M.

The elemental distribution for as-received (AR), H implanted (AI) and post-implanted annealed (A) Eurofer and ODS-Eurofer steels has been characterized by means of micro Particle Induced X-ray Emission (µ-PIXE), micro Elastic Recoil Detection (µ-ERD) and Secondary Ion Mass Spectrometry (SIMS). The temperature and time-induced H diffusion has been analyzed by Resonance Nuclear Reaction Analysis (RNRA), Thermal Desorption Spectroscopy (TDS), ERDA and SIMS techniques. µ-PIXE measurements point out the presence of inhomogeneities in the Y distribution for ODS-Eurofer samples. RNRA and SIMS experiments evidence that hydrogen easily outdiffuses in these steels even at room temperature. ERD data show that annealing at temperatures as low as 300 °C strongly accelerates the hydrogen diffusion process, driving out up to the 90% of the initial hydrogen.

Keywords: Fusion reactor steels; ODS-Eurofer; Hydrogen depletion; Elemental composition; Ion beam analysis; Nuclear microprobe

Permalink: https://www.hzdr.de/publications/Publ-16584
Publ.-Id: 16584


Beam Loss Monitoring and Machine Protection at the ELBE CW Accelerator

Teichert, J.; Büchner; A.; Justus, M.; Lehnert, U.; Michel, P.; Schurig, R.

The superconducting CW linac of the ELBE facility produces an electron beam up to 40 MeV and 1 mA average current. The beam is used to drive two IR FELs and target stations for production of bremsstrahlung, neutrons, and positrons. An upgrade of the ELBE facility is ongoing which includes an increase of beam current as well as new experimental opportunities such as the production of broadband THz radiation and the interaction of electrons with high power laser beams. The high beam power requires a fast and safe machine protection system. It was found that a continuous beam loss of about 10 µA or a total beam loss for longer than 2 ms produce damage. The beam loss at ELBE is monitored by two systems: beam loss monitors measuring the radiation in cable-like ionization chambers along the beamline, and beam current difference measurement system based on stripe line beam position monitors.

Keywords: Superconducting Linac; Beam Loss; Machine Protection; Ionization Chamber; Beam Position Monitor

  • Lecture (Conference)
    ERL 2011, The 50th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 16.-21.10.2011, Tsukuba, Japan

Permalink: https://www.hzdr.de/publications/Publ-16583
Publ.-Id: 16583


Structure and Formation of hexanuclear Actinide(IV) complexes

Hennig, C.

The structure and the formation of Actinide(IV) complexes in aq. solution and related crystal structures will be discussed.

Keywords: EXAFS; XRD; Actinide(IV)

  • Invited lecture (Conferences)
    Johannes Gutenberg Universität Mainz, Institut für Kernchemie, 23.1.2012, Mainz, Germany

Permalink: https://www.hzdr.de/publications/Publ-16582
Publ.-Id: 16582


ERL2011 Summary of Working Group 1: Progress with RF injectors

Rao, T.; Arnold, A.; Belomestnykh, S.; Nguyen, D.

This paper summarizes the progress made in the past two years, with RF injectors as electron sources for high average power Energy Recovery Linac-based light sources (ERL) and Free Electron Lasers (FEL).

Keywords: RF injectors

  • Open Access Logo Contribution to proceedings
    The 50th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 16.-21.10.2011, Tsukuba, Ibaraki, Japan: Joint Accelerator Conferences Web Site (JACoW), 10-29

Permalink: https://www.hzdr.de/publications/Publ-16581
Publ.-Id: 16581


Interactions of U(VI) with archaea: what is different than with bacteria?

Selenska-Pobell, S.; Reitz, T.; Merroun, M.

Archaea, in contrast to the diverse and dense bacterial populations, occur in uranium mining wastes in low numbers and belong mostly to particular crenarchaeal groups, some of them not yet cultured [1,2].
On the example of the termoacidophilic crenarchaeon Sulfolobus acidocaldarius, indigenous for many uranium contaminated wastes [3,4], we demonstrate that archaea tolerate substantially lower concentrations of U(VI) than bacteria and that they interact with this radionuclide in a significantly different way. One of the reasons for this behaviour is the unusual cell wall structure of the representatives of Crenarchaeota which is restricted to a single proteinaceous surface layer (S-layer), that is in contrary to the complex, rather thick, and rich on metal-binding ligands cell wall structure of bacteria. Due to the extreme acidic and mechanic stability of the S. acidocaldarius S-layer, it was possible to produce empty cells (ghosts) consisting only of the outermost S-layer membrane and to study their interactions with U(VI) at highly acidic (pH 1.5 and 3.0) and at moderate acidic (pH 4.5 and 6.0) conditions. Applying a set of modern spectroscopic techniques such as Time-Resolved Laser-induced Fluorescence (TRLF), X-ray Absorption, and Fourier-Transformed Infrared (FT-IR) we were able to clearly demonstrate that at highly acidic conditions the S. acidocaldarius S-layer does not play any protective role against the toxic U(VI). At these conditions low amounts of uranium are bound mainly by the phosphate groups of the cytoplasma membrane [5]. This finding is in distinction to the results obtained with S-layers of the bacterial isolates recovered from uranium mining wastes. The S-layers of the latter bind significant amounts of U(VI) and strongly contribute to the remarkable uranium resistance of their hosts [6]. The high capability of the mentioned bacterial S-layers to bind U(VI) was contributed to the fact that they are phosphorylated [6]. This feature is unusual for both bacterial and archaeal S-layers and is not the case for the S-layer of S. acidocaldarius [6, 7]. At moderate acidic conditions (pH 4.5), typical for most uranium mining wastes, the studied archaeal S-layer ghosts, again in contrast to the bacterial ones, bind insufficient amounts of U(VI) exclusively via the carboxylic groups of their carboxylated amino acid residues [7]. At pH 6.0, which is substantially above the growth optimum of S. acidocaldarius, the permeability of its cells is increased due to the pH stress and possibly also to the presence of U(VI). As a result uncontrolled uptake of U(VI) as well as release of phosphorylated biomolecules and also of orthophosphate occurs. These processes result initially in formation and precipitation of mixed uranyl phosphate phases. With the time the most part of U(VI) is bio-mineralized in inorganic mineral phases. The efficacy of these biomineralization processes is, however, much lower then those published for bacteria, possibly due to the lower amount of polyphosphatic granules in the studied archaeon [8].
We suggest that the limited presence of archaea in uranium wastes is related to their lower resistance to U(VI) which is determined by their cell wall structure and possibly also by some particular physiological and biochemical characteristics.

[1] Rastogi (2009) Microbial Ecology 58, 129-139. [2] Reitz (2007) FZR-Report 459, 42. [3] Marsh (1983] FEMS Microb. Lett., 17, 311-315. [4] Groudev (1993) FEMS Microb. Rev., 11, 260-268. [5] Reitz (2010) Radiochim Acta 98, 249-257. [6] Merroun (2005) Appl. Environ. Microbiol. 71, 5532-5543. [7] Reitz (2011] Radiochim Acta 99, 543-553. [8] Remonselez (2006) Microbiology, 152, 59-66.

Keywords: U(VI) binding; archaea; S-layers; biomineralization

  • Lecture (Conference)
    Goldschmidt 2012, 24.-29.06.2012, Montreal, Canada
  • Abstract in refereed journal
    Mineralogical Magazine 76(2012), 2352

Permalink: https://www.hzdr.de/publications/Publ-16580
Publ.-Id: 16580


Dipole strength in 78 Se below the neutron separation energy from a combined analysis of 77 Se(n, γ) and 78 Se(γ , γ') experiments

Schramm, G.; Massarczyk, R.; Junghans, A. R.; Belgya, T.; Beyer, R.; Birgersson, E.; Grosse, E.; Kempe, M.; Kis, Z.; Kosev, K.; Krticka, M.; Matic, A.; Schilling, K. D.; Schwengner, R.; Szentmiklosi, L.; Wagner, A.; Weil, J. L.

The dipole strength function and the nuclear level density of the compound nucleus 78Se were studied in a combined analysis of a cold neutron capture experiment on 77Se performed at the research reactor in Budapest and a photon-scattering experiment on 78Se performed at the electron linear accelerator ELBE with bremsstrahlung produced at a kinetic electron energy of 11.5 MeV. In the combined analysis we developed the extreme statistical code γ DEX for the simulation of radiative cascade deexcitations occurring in neutron capture and photon scattering. Comparisons of experimental and simulated neutron capture spectra allow us to estimate a temperature of T = 900 keV for the level density according to the constant-temperature model for 78Se. Using γ DEX, we were also able to estimate ground-state branching ratios and intensities of inelastic transitions for states in 78Se excited via photon scattering. In this way, we derived the photoabsorption cross section from 4 MeV up to the neutron separation energy from the measured photon-scattering data. The results obtained match the photoabsorption cross section derived from (γ , n) measurements and show an enhancement of dipole strength around 9 MeV.

Keywords: Nuclear level density; Strength functions; Statistical model

Permalink: https://www.hzdr.de/publications/Publ-16578
Publ.-Id: 16578


The Superconducting RF Photoinjector at ELBE

Arnold, A.

A superconducting RF photo-injector (SRF gun) has been installed at the ELBE linac. It is the first SRF gun which is in operation at an accelerator up to now. The SRF gun consists of a 3½ cell, 1.3 GHz superconducting cavity with normal conducting photocathode in it. At present, the gun delivers electron bunches with kinetic energies of 3 MeV in CW mode and up to 4 MeV in pulsed mode operation. The Cs2Te photo cathodes used in the gun exhibit a very long life time, e.g. a cathode was in use for more than one year and delivers a charge of 35 C. A degradation of the cavity performance due the normal conducting photo cathode was no found. The electron beam delivered to ELBE was used for beam transport optimization, longitudinal parameter and slice emittance measurements. The performance of the gun is mainly limited by the low gradient of the present cavity. For that reason two new and slightly modified cavities have been fabricated and tested at Jlab. The results of the vertical tests are very promising.

Keywords: superconducting RF photo-injector; SRF-Gun; ELBE

  • Invited lecture (Conferences)
    The 50th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 16.-21.10.2011, Tsukuba, Ibaraki, Japan

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-16577
Publ.-Id: 16577


Formation and structure of hexanuclear Actinide(IV) carboxylates

Hennig, C.

Recent insights into formation and structure of hexanuclear Actinide(IV) carboxylates will be discussed

Keywords: EXAFS; XRD; Uranium; Thorium; Neptunium

  • Invited lecture (Conferences)
    University of Grenoble I, Institute of Earth Science, 17.01.2012, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-16576
Publ.-Id: 16576


Contactless flowrate sensors for Na, PbBi and Pb flows

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

Accurate and reliable flow rate measurements are required for various liquid metal systems such as the Na or Lead-flows in fast reactors, the PbBi-flows in transmutation systems, or the flows in liquid metal targets. Commercial flow meters are typically based on the flow-induced electrical voltage, which is measured by electrodes in direct contact to the melt, in a steady magnetic field. For liquid metal flows, a contactless measurement is preferable. We report on the recent development of two types of such flow meters. The former operates by detecting the flow-induced disturbance in the phase distribution of an externally applied AC magnetic field. Such a phase-shift flow meter was developed with an emitting coil at one side of the duct and two sensing coils at the opposite side. The second approach uses a rotatable single cylindrical permanent magnet, which is placed close to the liquid metal duct. The rotation rate of this magnet is proportional to the flow rate. The signal of this sensor is independent on the electrical conductivity of the flowing melt, thus independent on temperature. Both flow rate sensors have been tested at several liquid metal loops: a Na- and a Lead-loop at HZDR, and a PbBi-loop at SCK-CEN Mol (Belgium). In all cases, both sensors show a very good linearity of their signal with the true flow rate in the pipe. For the sodium flow at the NATAN facility of HZDR, the measured flow rates were also compared with measurements of the local velocity profile in the duct performed by ultrasonic Doppler velocimetry.

Keywords: Contactless flowrate measurement; Phase-shift sensor; Rotating magnet; Ultrasonic Doppler Velocimetry; Na; Pb; PbBi

  • Contribution to proceedings
    The 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14 , 25.-30.09.2011, Toronto, Canada
    Proceedings of the 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics (NURETH-14)
  • Lecture (Conference)
    The 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14 , 25.-30.09.2011, Toronto, Canada

Permalink: https://www.hzdr.de/publications/Publ-16575
Publ.-Id: 16575


Quo vadis, Partikeltherapie?

Enghardt, W.; Hodapp, N.; Schreiber, L.; Zink, K.

Permalink: https://www.hzdr.de/publications/Publ-16574
Publ.-Id: 16574


Selected research topics on nuclear reactor thermal hydraulics

Lucas, D.; Schäfer, F.; Tusheva, P.

In the presentation some aspects of nuclear reactor thermal hydraulics are discussed. It focusses on accident analyses for loss of coolant accidents (LOCA) and demonstrates the capabilities of system codes. In a second part recent research on the qualification of CFD codes for nuclear reactor safety issues is presented. Special attention is paid to experimental work done at HZDR to obtain CFD-grade experimental data. The TOPFLOW facility is combined with innovative measuring techniques to obtain such data.

Keywords: nuclear reactor thermal hydraulics; LOCA; CFD; experiment

  • Invited lecture (Conferences)
    International Seminar Series of the Universitas Gadjah Mada, Faculty of Engineering, 30.01.-03.02.2012, Yogyakarta, Indonesia

Permalink: https://www.hzdr.de/publications/Publ-16573
Publ.-Id: 16573


Innovative Pressure Tube Light Water Reactor with Variable Moderator Control

Rachamin, R.; Galperin, A.; Fridman, E.

The features of a reactor based on multiple pressure tubes, rather than a single pressure vessel, provide the reactor with considerable flexibility for continuous design improvements and developments. This paper presents the development of innovative pressure tube light water reactor, which has the ability to advance the current pressure tubes reactors. The proposed design is aimed to simplify the pressure tubes reactors by:
• replacing heavy water by a light water as a coolant and moderator,
• adopting batch refueling instead of on-line refueling.
Furthermore, the design is based on proven technologies, existing fuel and structure materials. Therefore, it is reasonable to expect significant capital cost savings, short licensing and introduction period of the proposed concept into the power production grid.
The basic novelty of the proposed design is based on an idea of variable moderator content in the core and “breed & burn” mode of operation. In order to achieve a practical reactor design build on proven technology, several features of the advanced CANDU reactor (ACR-1000) were adopted. It should be stressed however, that while some of the ACR-1000 mechanical design features are adopted, the core design basics of the reactor proposed here are completely different. First, the inter fuel channels spacing, surrounded by the calandria tank, contains a low pressure gas instead of heavy water moderator. Second, the fuel channel design features an additional/external tube (designated as moderator tube) connected to a separate moderator management system. The proposed design is basically pressure tube light water reactor with variable moderator Control (PTVM LWR).
This paper presents a detailed description of the PTVM core design and demonstrates the reactivity control and the “breed & burn” mode of operation, which are implemented by the variation of the moderator in the core, from a neutronics point of view.

Keywords: pressure tube reactor; moderator variation; “breed & burn”; reactivity control

  • Lecture (Conference)
    The 26th Conference of the Nuclear Societies in Israel, 21.-23.02.2012, Dead Sea, Israel
  • Contribution to proceedings
    The 26th Conference of the Nuclear Societies in Israel, 21.-23.02.2012, Dead Sea, Israel

Permalink: https://www.hzdr.de/publications/Publ-16572
Publ.-Id: 16572


Loss of Coolant Accident Analysis for IRR 1

Rachamin, R.; Elias, E.; Galperin, A.

Detailed LOCA analysis has been performed for the 5MWth swimming pool type IRR-1, which utilizing highly enriched uranium fuel. The analysis was aimed to assess the possibility of passively cooling the exposed reactor core by natural convection of air and thermal radiation. The core uncover time was estimated by assuming that the LOCA was induced by a guillotine break of a 10 inch water pipe at the bottom of the pool, causing the core to uncover about 20 min after reactor SCRAM.
The effect of the reflector on the core cooling was studied by comparing the total heat transfer from the core with and without considering the thermal contact between the core and the graphite reflector elements. It has been shown that for uncover time of 20 min the core may reach melting point if thermal contact with the graphite is neglected. On the other hand, considering perfect thermal contact between the core and the graphite reflector, the core temperature is predicted to remain below the clad melting point.

Keywords: Loss of Coolant Accident (LOCA); Decay heat; Natural convection; Thermal radiation; IRR-1

  • Lecture (Conference)
    The 26th Conference of the Nuclear Societies in Israel, 21.-23.02.2012, Dead Sea, Israel
  • Open Access Logo Contribution to proceedings
    The 26th Conference of the Nuclear Societies in Israel, 21.-23.02.2012, Dead Sea, Israel

Permalink: https://www.hzdr.de/publications/Publ-16571
Publ.-Id: 16571


Entwicklung und Validierung von CFD-Modellen für polydisperse Blasenströmungen auf der Basis von TOPFLOW-Experimenten

Lucas, D.; Krepper, E.; Beyer, M.

In Rahmen der Qualifizierung von CFD-Methoden für Fragestellungen der nuklearen Sicherheitsforschung werden am Helmholtz-Zentrum Dresden-Rossendorf (HZDR) CFD-Modellkonzepte und Schließungsmodelle entwickelt. Für die Modellentwicklung und deren Validierung werden experimentelle Daten in hoher Orts- und Zeitauflösung benötigt. Die TOPFLOW-Anlage des HZDR verbindet Experimente bei anwendungsnahen Parametern mit innovativer Messtechnik, die solche Daten in der erforderlichen Qualität liefert. Am Beispiel der Modellentwicklung für polydisperse Blasenströmungen werden entsprechende Experimente an der TOPFLOW-Anlage vorgestellt und die Verwendung der Resultate für die CFD-Code-Entwicklung und Validierung demonstriert.

Keywords: bubbly flow; experiment; CFD; measuring technique

  • Invited lecture (Conferences)
    Garchinger Seminare, 19.01.2012, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16570
Publ.-Id: 16570


Conceptual Design of a Pressure Tube Light Water Reactor with Variable Moderator Control

Rachamin, R.; Galperin, A.; Fridman, E.

This paper presents the development of innovative pressure tube light water reactor with variable moderator control. The core layout is derived from a CANDU line of reactors in general, and advanced ACR-1000 design in particular. It should be stressed however, that while some of the ACR-1000 mechanical design features are adopted, the core design basics of the reactor proposed here are completely different. First, the inter fuel channels spacing, surrounded by the calandria tank, contains a low pressure gas instead of heavy water moderator. Second, the fuel channel design features an additional/external tube (designated as moderator tube) connected to a separate moderator management system. The moderator management system is design to vary the moderator tube content from “dry” (gas) to “flooded” (light water filled). The dynamic variation of the moderator is a unique and very important feature of the proposed design. The moderator variation allows an implementation of the “breed & burn” mode of operation. The “breed & burn” mode of operation is implemented by keeping the moderator tube empty (“dry” filled with gas) during the breed part of the fuel depletion and subsequently introducing the moderator by “flooding” the moderator tube for the “burn” part. This paper assesses the conceptual feasibility of the proposed concept from a neutronics point of view. The variation of the moderator in the fuel channels has been modeled and shown to have a potential to increase the discharged burnup and improve the reactivity control.

Keywords: pressure tube reactor; moderator variation; “breed & burn”; reactivity control

  • Lecture (Conference)
    PHYSOR 2012 - Advances in Reactor Physics, 15.-20.04.2012, Knoxville, Tennessee, USA
  • Open Access Logo Contribution to proceedings
    PHYSOR 2012 – Advances in Reactor Physics, 15.-20.04.2012, Knoxville, Tennessee, USA

Permalink: https://www.hzdr.de/publications/Publ-16569
Publ.-Id: 16569


Demonstration of the Serpent Monte-Carlo code applicability to Few-group Constants Generation for Existing and Advanced Reactor concepts

Fridman, E.; Shwageraus, E.

Serpent is a continuous-energy Monte Carlo (MC) reactor physics code recently developed at VTT Technical Research Centre of Finland. Serpent can be used for 2D fuel lattice calculations as well as for 3D full core simulations. Due to its built-in decay and burnup routine Serpent can perform depletion and decay analysis to provide time-dependent isotopic compositions and spent fuel characteristics including radioactivity and decay heat. Serpent uses matrix exponential method to solve the Bateman decay and depletion equations while the solution of the matrix exponential relies on the Chebyshev Rational Approximation Method (CRAM). Serpent runs significantly faster than other MC codes due to the two main reasons: 1) the use of the Woodcock delta-tracking in a combination with a typical surface-to-surface ray-tracing in a geometry routine, and 2) the use of the unionized energy grid for all point-wise reaction cross sections. The later, however, considerably increases the memory requirements and can be a bottleneck in simulations with a large number of involved nuclides.
Serpent is especially designed to generate homogenized constants for deterministic 3D core analysis. For any region of interest the code automatically calculates homogenized few-group cross sections, group-to-group scattering matrices, diffusion coefficients, assembly discontinuity factors, kinetics parameters, etc. More details can be found in Serpent User's Manual. Recently some new calculation methods related to the production of homogenized few-group constants were implemented in the Serpent code including homogenization in leakage-corrected criticality spectrum, group constant generation in reflectors and other non-fissile regions, and improved treatment of neutron-multiplying scattering reactions.
The capability to generate homogenized few-group constants can be considered as one of the most attractive features of Serpent. Being a MC code, Serpent is capable of handling complex geometries without any major approximations and can be used for producing cross section data for virtually any fuel or reactor type. The demonstration of the Serpent capability to generate few-group cross sections for different reactor systems is the main topic of this paper.

  • Lecture (Conference)
    26th Conference of the Nuclear Societies in Israel, 21.-23.02.2012, Dead Sea, Israel
  • Contribution to proceedings
    26th Conference of the Nuclear Societies in Israel, 21.-23.02.2012, Dead Sea, Israel

Permalink: https://www.hzdr.de/publications/Publ-16568
Publ.-Id: 16568


Liquid metal experiments on the creation and action of cosmic magnetic fields

Stefani, F.; Gerbeth, G.; Giesecke, A.; Gundrum, T.; Seilmayer, M.; Gailitis, A.; Gellert, M.; Rüdiger, G.

The success of the large-scale dynamo experiments in Riga and Karlsruhe at the end of 1999 has boosted a strong worldwide activity to simulate the creation and action of cosmic magnetic fields in the liquid metal laboratory. With some focus on our own projects, we review the recent efforts to study hydromagnetic dynamo action and related magnetic instabilities, such as the magnetorotational instability (MRI) and the Tayler instability (TI). We sketch our plans to set-up the new liquid sodium facility DRESDYN that will include a dynamo experiment based on precession, and a Taylor-Couette experiment for the combined investigation of MRI and TI.

  • Invited lecture (Conferences)
    DPG-Frühjahrstagung der Sektion AMOP (SAMOP), 12.-16.03.2012, Stuttgart, Germany

Permalink: https://www.hzdr.de/publications/Publ-16567
Publ.-Id: 16567


Kosmische Magnetfelder im Experiment

Stefani, F.

Seit langem schon ist bekannt, dass die Magnetfelder von Planeten, Sternen und Galaxien durch den sogenannten Dynamoeffekt, also durch Selbsterregung in strömenden elektrisch leitfähigen Fluiden erzeugt werden. Weniger bekannt ist hingegen, dass Magnetfelder eine ganz entscheidende Rolle in der kosmischen Strukturbildung spielen. So ist das beobachtete schnelle Wachstum von Sternen und Schwarzen Löchern nur erklärbar, wenn die Akkretionsscheiben, aus denen sie gefüttert werden, turbulent sind und damit Drehimpuls effektiv nach außen transportieren können. Die Ursache dieser Turbulenz liegt in der destabilisierenden Wirkung von Magnetfeldern auf rotierende Strömungen, welche als Magneto-Rotationsinstabilität bezeichnet wird.
Der Vortrag gibt zunächst eine leicht verständliche Einführung in die Theorien zur Entstehung und Wirkung kosmischer Magnetfelder. Im Mittelpunkt stehen dann die Flüssigmetall-Experimente der letzten Jahre, in denen sowohl der Dynamoeffekt als auch die Magneto-Rotationsinstabiliät untersucht worden sind. Im Detail werden insbesondere das Rigaer Dynamo-Experiment und das PROMISE-Experiment am Helmholtz-Zentrum Dresden-Rossendorf (HZDR) besprochen.
Zum Schluss werden die Pläne für ein neues großes Dynamoexperiment am HZDR vorgestellt, in dem Selbsterregung in einer nur durch Präzession getriebenen Strömung von flüssigem Natrium nachgewiesen werden soll.

  • Invited lecture (Conferences)
    Hauptvorträge der Olbers-Gesellschaft Bremen, 10.01.2012, Bremen, Germany
  • Invited lecture (Conferences)
    Hauptvorträge der Sternfreunde Nordenham, 11.01.2012, Nordenham, Germany

Permalink: https://www.hzdr.de/publications/Publ-16566
Publ.-Id: 16566


Physical properties and valence state of cerium in the filled skutterudite CePt4Ge12

Gumeniuk, R.; Kvashnina, K. O.; Schnelle, W.; Nicklas, M.; Borrmann, H.; Rosner, H.; Skourski, Y.; Tsirlin, A. A.; Leithe-Jasper, A.; Grin, Y.

Electronic, magnetic, and transport properties of the filled platinum-germanium skutterudite CePt4Ge12 are investigated. High resolution x-ray absorption spectroscopy measurements at the cerium L(III) edge demonstrate that Ce in this compound has a temperature-independent valence close to three. However, magnetic susceptibility, thermopower, Hall effect, and electronic specific heat reveal a broad maximum at Tmax = 65-80 K, suggesting the presence of valence fluctuations. The Sommerfeld coefficient gamma = 105 mJmol-1K-2, deduced from specific heat, indicates moderately enhanced band masses for CePt4Ge12. We discuss these findings and conclude that CePt4Ge12 represents a system at the border between intermediate valence (IV) and Kondo lattice behavior. In addition, the lattice specific heat and the thermal conductivity are discussed with respect to the vibrational dynamics of Ce in the [Pt4Ge12] framework.

Permalink: https://www.hzdr.de/publications/Publ-16565
Publ.-Id: 16565


Recent and future liquid metal experiments on homogeneous dynamo action and magnetic instabilities

Stefani, F.; Gerbeth, G.; Giesecke, A.; Gundrum, T.; Kirillov, O.; Seilmayer, M.; Gailitis, A.; Gellert, M.; Rüdiger, G.

The present status of the Riga dynamo experiment is summarized and the prospects for its future exploitation are evaluated. We further discuss the plans for a large-scale precession driven dynamo experiment to be set-up in the framework of the new installation DRESDYN (DREsden Sodium facility for dynamo and thermohydraulic studies) at Helmholtz-Zentrum Dresden-Rossendorf. We report recent investigations of the magnetorotational instability and the Tayler instability and sketch the plans for another large-scale liquid sodium facility devoted to the combined study of both effects.

  • Invited lecture (Conferences)
    53rd Annual Meeting of the APS Division of Plasma Physics, 14.-18.11.2011, Salt Lake City, USA
  • Open Access Logo Abstract in refereed journal
    Bulletin of the American Physical Society 56(2011)12, 275-275

Permalink: https://www.hzdr.de/publications/Publ-16564
Publ.-Id: 16564


High-Field Magnetization Study of R2Fe17H3 (R = Tb, Dy, Ho and Er) Single-Crystalline Hydrides

Tereshina, I. S.; Doerr, M.; Skourski, Y.; Tereshina, E. A.; Watanabe, K.; Telegina, I. V.; Drulis, H.

The high-field magnetization process in the hydrogen-charged R2Fe17H3 (R = Tb, Dy, Ho and Er) single crystals is studied along principal crystallographic directions at T = 4.2 K and compared with that of the known parent R2Fe17 compounds. Substantial changes of the magnetic anisotropy behavior induced by hydrogenation are found. Depending on the rare earth atom, the R2Fe17H3 compounds possess the "easy-axes", "easy-cone" and "easy-plane" types of magnetocrystalline anisotropy (MCA), whereas the precursors R2Fe17 have the easy-plane type of MCA only. The various observed types of the field-induced phase transitions in R2Fe17H3 are discussed and information on the effect of hydrogen on the strength of R-Fe coupling is obtained.

Permalink: https://www.hzdr.de/publications/Publ-16563
Publ.-Id: 16563


Magnetoconductance of carbon nanotubes probed in parallel magnetic fields up to 60 T

Jhang, S. H.; Marganska, M.; Del Valle, M.; Skourski, Y.; Grifoni, M.; Wosnitza, J.; Strunk, C.

Magnetoconductance of carbon nanotubes (CNTs) is investigated. We clearly show that a semiconducting CNT can be converted into a metallic one, or vice versa, with the application of a large magnetic field parallel to the tube axis, providing a consistent confirmation of the Aharonov–Bohm (AB) effect on the band structure of CNTs. We also demonstrate that magnetic-field values where the semiconductor-to-metal transition occurs can be tuned by mechanical strain. Combined control of both the strain and the AB effect may open up new possibilities for CNT devices. In addition, we propose an idea to manipulate spin-split subbands of CNTs, resulting from spin–orbit interaction (SOI), by using the magnetic field to generate sizeable spin-polarized currents.

Permalink: https://www.hzdr.de/publications/Publ-16562
Publ.-Id: 16562


Intrinsic and extrinsic nonstationary field-driven processes in the spin-ice compound Dy2Ti2O7

Erfanifam, S.; Zherlitsyn, S.; Wosnitza, J.; Moessner, R.; Petrenko, O. A.; Balakrishnan, G.; Zvyagin, A. A.

Nonequilibrium processes are probed by ultrasound waves in the spin-ice material Dy2Ti2O7 at low temperatures. The sound velocity and the sound attenuation exhibit a number of anomalies versus applied magnetic field for temperatures below the “freezing” temperature of ∼500 mK. These robust anomalies can be seen for longitudinal and transverse acoustic modes for different field directions. The anomalies show a broad hysteresis.Most notable are peaks in the sound velocity,which exhibit two distinct regimes: an intrinsic (extrinsic) one in which the data collapse for different sweep rates when plotted as function of field strength (time). We discuss our observations in context of the emergent quasiparticles which govern the low-temperature dynamics of the spin ice.

Permalink: https://www.hzdr.de/publications/Publ-16561
Publ.-Id: 16561


DRESDYN - A new liquid sodium facility for experimental studies of dynamo action and related instabilities

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

The DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN) will comprise large scale liquid sodium experiments related to geo- and astrophysics as well as experiments for safety and thermohydraulic studies related to sodium fast reactors and liquid metal batteries. The most ambitious parts of DRESDYN are a homogeneous dynamo driven solely by precession, and a large Tayler-Couette type experiment for the combined investigation of the magnetorotational instability and the Tayler instability. After a short summary of our previous achievements we delineate the next steps for the realization of DRESDYN.

  • Invited lecture (Conferences)
    Dyanamo iGDR Meeting, 12.-17.09.2011, Cargese, France

Permalink: https://www.hzdr.de/publications/Publ-16560
Publ.-Id: 16560


Integral equations in MHD: theory and application

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

The induction equation of kinematic magnetohydrodynamics is mathematically equivalent to a system of integral equations for the magnetic field in the bulk of the fluid and for the electric potential at its boundary. We summarize the recent developments concerning the numerical implementation of this scheme and its applications to various forward and inverse problems in dynamo theory and applied MHD.

Permalink: https://www.hzdr.de/publications/Publ-16559
Publ.-Id: 16559


DRESDYN - A new platform for sodium related thermohydraulic studies and measurement developments

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

The safe and reliable operation of liquid metal systems in innovative reactor concepts like sodium cooled fast breeder reactors or lead-bismuth targets in transmutation systems requires appropriate measuring systems and control units, both for the liquid metal single-phase flow as well as for gas bubble liquid metal two-phase flows. We report on the liquid sodium facility DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies), presently under construction, that will comprise experiments with geo- and astrophysical background as well as experiments for thermohydraulic studies and for the development and the test of measurement techniques for sodium flows.

  • Lecture (Conference)
    The 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14, 25.09.-30.11.2011, Toronto, Canada
  • Contribution to proceedings
    The 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14, 25.-30.09.2011, Toronto, Canada
    Proceedinngs of the 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14, 223

Permalink: https://www.hzdr.de/publications/Publ-16558
Publ.-Id: 16558


Development of an ion source for volatile elements at DREAMS

Pavetich, S.; Akhmadaliev, S.; Merchel, S.; Rugel, G.

After successful measurements of 10Be, 26Al and 41Ca [1] at DREAMS (DResden Accelerator Mass Spectrometry), extensive test measurements of 36Cl started. Besides the challenge of separating the stable isobar 36S, which at DREAMS is accomplished by post-stripping and a split-anode-ionization-chamber, the problem of ion source memory must be solved [2]. To characterize this effect we use 35Cl/37Cl samples of natural composition and 35Cl-enriched samples with a 35Cl/37Cl-ratio > 100. Similar measurements at the French AMS facility ASTER [3] showed differences of 2-4% in the 35Cl/37Cl ratios of the highly enriched samples after 24 h of sputtering samples with natural isotopic ratios [3]. To minimize the long-term-memory effect, two modified designs of the original source (HVEE) were constructed at DREAMS. A more open geometry was used to improve the vacuum level, and parts of the target loading system were modified to allow the exchange of the individual cathode aperture with each target.
[1] G. Rugel, these proceedings.
[2] K.M. Wilcken et al. NIM B, 268 (2010) 748-751
[3] M. Arnold et al. The French accelerator mass spectrometry facility ASTER after 4 years: Status and recent developments on 36Cl and 129I, article submitted NIM B

Keywords: AMS; DREAMS; 36Cl; long-term-memory-effect; ion source

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion AMOP (SAMOP), 12.-16.03.2012, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16557
Publ.-Id: 16557


Self-assembling of Ge quantum dots in an alumina matrix

Buljan, M.; Pinto, S. R. C.; Rolo, A. G.; Martin-Sanchez, J.; Gomes, M. J. M.; Grenzer, J.; Mücklich, A.; Bernstorff, S.; Holy, V.

In this work we report on a self-assembled growth of a Ge quantum dot lattice in a single 600-nm-thick Ge+Al(2)O(3) layer during magnetron sputtering deposition of a Ge+Al(2)O(3) mixture at an elevated substrate temperature. The self-assembly results in the formation of a well-ordered three-dimensional body-centered tetragonal quantum dot lattice within the whole deposited volume. The quantum dots formed are very small in size (less than 4.0 nm), have a narrow size distribution and a large packing density. The parameters of the quantum dot lattice can be tuned by changing the deposition parameters. The self-ordering of the quantum dots is explained by diffusion-mediated nucleation and surface-morphology effects and simulated by a kinetic Monte Carlo model.

Keywords: NANOCRYSTALS; NANOSTRUCTURES; SILICON; E(1)

Permalink: https://www.hzdr.de/publications/Publ-16556
Publ.-Id: 16556


Ion-Irradiated Laterally Graded Ni/C Multilayers: A Combined X-ray Standing Wave and X-ray Reflectivity Analysis

Dev, B. N.; Roy, S.; Bera, S.; Tawara, Y.; Schell, N.; Grenzer, J.; von Borany, J.; Grötzschel, R.

An X-ray standing wave (XSW) experimental facility was set up at the Rossendorf Beam Line (ROBL) at the European Synchrotron Radiation Facility (ESRF). Using this facility, the microstructures and ion-beam induced microstructural modifications of a nanoscale laterally graded Ni/C multilayer systems have been studied by the combined X-ray reflectivity (XRR) and XSW technique. The multilayer stack with 15 Ni/C layer pairs was fabricated on a glass substrate by ion beam sputtering. A 2MeV Cu(2+) ion beam was rastered on the samples to obtain uniformly irradiated strips with fluences from 1 x 10(14) to 7 x 10(14) ions/cm(2). We have observed that X-ray reflectivity at the first order Bragg peak gradually increases due to increase in multilayer period in the virgin samples. The multilayer period has expanded and interfaces broadened due to ion irradiation. Xray standing wave analysis indicates that, during deposition, a significant amount of Ni diffuses into C layers. Up to a certain fluence, we have observed that more and more Ni atoms are incorporated into C layers. At higher fluences, Ni is progressively segregated from the C layers. These mixing and demixing phenomena of Ni in C layers as a function of ion fluence have been explained in terms of two competitive processes including ballistic mixing and chemically guided atomic movements. (C) 2011 The Japan Society of Applied Physics

Keywords: CO/PT MULTILAYERS; GIANT MAGNETORESISTANCE; BEAM IRRADIATION; CO/CU NANOSTRUCTURES; GALLIUM IRRADIATION; MAGNETIC-PROPERTIES; FILMS; EVOLUTION; MEDIA

Permalink: https://www.hzdr.de/publications/Publ-16555
Publ.-Id: 16555


Phenomenology of iron-assisted ion beam pattern formation on Si(001)

Macko, S.; Frost, F.; Engler, M.; Hirsch, D.; Hoche, T.; Grenzer, J.; Michely, T.

Pattern formation on Si(001) through 2 keV Kr(+) ion beam erosion of Si(001) at an incident angle of v = 30 degrees and in the presence of sputter co-deposition or co-evaporation of Fe is investigated by using in situ scanning tunneling microscopy, ex situ atomic force microscopy and electron microscopy. The phenomenology of pattern formation is presented, and experiments are conducted to rule out or determine the processes of relevance in ion beam pattern formation on Si(001) with impurities. Special attention is given to the determination of morphological phase boundaries and their origin. Height fluctuations, local flux variations, induced chemical inhomogeneities, silicide formation and ensuing composition-dependent sputtering are found to be of relevance for pattern formation.

Keywords: SI; BOMBARDMENT; TOPOGRAPHY; SURFACES; SILICON; SYSTEMS

Permalink: https://www.hzdr.de/publications/Publ-16554
Publ.-Id: 16554


Acclerator Mass Spectrometry

Rugel, G.

Accelerator Mass Spectrometry (AMS) is presently one of the most sensitive techniques for the detection of long-lived radioisotopes at very low abundances. In recent years more isotopes can be measured via AMS and many isotopes ratios can be determined relatively precise. The main fields of applications are climate history and environmental processes where radioisotopes act as natural tracers. In earth sciences and archaeology AMS provides valuable dating tools. Radioisotopes commonly measured are 10Be, 14C, and 26Al. Accelerators with intermediate energies of 3–6 MeV also allow sensitive detection of 36Cl and 41Ca. More exotic isotopes like 44Ti, 53Mn, 55Fe, 59Ni, 60Fe, 63Ni, 79Se have been measured for astrophysical reasons.
An overview on recent AMS measurements with a focus on nuclear astrophysics will be given.
The technique of AMS at different laboratories will be shown. The new facility DREAMS at the Helmholtz–Zentrum Dresden–Rossendorf with an 6 MV tandem accelererator and the unique facility at Munich of the Technische Universit¨at M¨unchen and the Ludwig Maximilians Universit¨at M¨unchen will be described in more detail.

  • Invited lecture (Conferences)
    496. Wilhelm und Else Heraeus-Seminar - Astrophysics with modern small-scale accelerators, 06.-10.02.2012, Bad Honnef, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16553
Publ.-Id: 16553


Determining the C60 molecular arrangement in thin films by means of X-ray diffraction

Elschner, C.; Levin, A. A.; Wilde, L.; Grenzer, J.; Schroer, C.; Leo, K.; Riede, M.

The electrical and optical properties of molecular thin films are widely used, for instance in organic electronics, and depend strongly on the molecular arrangement of the organic layers. It is shown here how atomic structural information can be obtained from molecular films without further knowledge of the single-crystal structure. C60 fullerene was chosen as a representative test material. A 250 nm C60 film was investigated by grazing-incidence X-ray diffraction and the data compared with a Bragg-Brentano X-ray diffraction measurement of the corresponding C60 powder. The diffraction patterns of both powder and film were used to calculate the pair distribution function (PDF), which allowed an investigation of the short-range order of the structures. With the help of the PDF, a structure model for the C60 molecular arrangement was determined for both C60 powder and thin film. The results agree very well with a classical whole-pattern fitting approach for the C60 diffraction patterns.

Keywords: PAIR DISTRIBUTION FUNCTION; LIGHT-EMITTING-DIODES; REVERSE MONTE-CARLO; POWDER DIFFRACTION; STRUCTURAL REFINEMENT; ROOM-TEMPERATURE; C-60 POLYMER; EFFICIENCY; FULLERENE; PHASE

Permalink: https://www.hzdr.de/publications/Publ-16552
Publ.-Id: 16552


Complex formation of Np(V) with fulvic acid at tracer metal concentration

Mueller, K.; Sasaki, T.

Apparent formation constants of pentavalent Np with fulvic acid were determined in 0.1 M NaClO4, at 25 °C using a solvent extraction technique with thenoyltrifluoroacetone and phenanthroline in an isoamyl alcohol solution. The metal concentration was set constant to a tracer level of 10-15 M Np(V), relevant for the far field safety assessment of a nuclear waste disposal site. The impact of several solution conditions, namely pH, ionic strength, the initial fulvic acid concentration and the presence of Ca2+, on the complex formation were studied. Similar to the sodium system, the divalent calcium ion effectively prevents complexation of the neptunyl ion with humic substance. Furthermore, the derived apparent formation constants were comparatively discussed with literature values obtained at very similar solution conditions.

Keywords: humic substances; apparent formation constant; pentavalent neptunium; solvent extraction; TTA

Permalink: https://www.hzdr.de/publications/Publ-16551
Publ.-Id: 16551


Evaluation of radiation damage using nonlinear ultrasound

Matlak, K.; Wall, J.; Kim, J.-Y.; Qu, J.; Jacobs, L. J.; Viehrig, H.-W.

Nonlinear ultrasound was used to monitor radiation damage in two reactor pressure vessel (RPV) steels. The microstructural changes associated with radiation damage include an increase in dislocation density and the formation of precipitates, and nonlinear ultrasonic waves are known to be sensitive to such changes. Six samples each of two different types of RPV steel were previously irradiated in the Rheinsberg power reactor to two fluence levels, up to 1020 n/cm2. Longitudinal waves were used to measure the acoustic nonlinearity in these samples, and the results show a clear increase in the measured acoustic nonlinearity from the unirradiated state to the medium dose, and then a decrease from medium dose to high dose.

Keywords: reactor pressure vessel steel; neutron irradiation; embrittlement; nonlinear ultrasound; microstructural changes

Permalink: https://www.hzdr.de/publications/Publ-16550
Publ.-Id: 16550


PT brachistochrone and state discrimination

Günther, U.

In recent work by Bender, Brody, Caldeira and Meister it was shown that the brachistochrone solution of PT Quantum Mechanics (PTQM) can be used to orthogonalize a set of two originally non-orthogonal quantum states. The still remaining draw-back of the proposed technique is in its use of a non-Hermitian PT-symmetric Hamiltonian to achieve the PTQM brachistochrone evolution --- a Hamiltonian which up to now for quantum systems is beyond experimental reach.

We demonstrate that the Bender-Brody-Caldeira-Meister approach can be naturally extended into a higher-dimensional Hilbert space. This allows to interpret the PTQM setup as a very special subsystem of a larger Hermitian system. Moreover we show that this extension can be connected with the standard text-book scheme of unambiguous quantum state discrimination. Technical details of the extension procedure are discussed and ways toward a time-optimal unambiguous state discrimination scheme are indicated.

Keywords: PT quantum mechanics; unambiguous state discrimination; time-optimal state discrimination; PT brachistochrone; extension scheme

  • Invited lecture (Conferences)
    PTQM 2011 symposium, 25.-28.09.2011, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16549
Publ.-Id: 16549


Mineral dusts - a valuable resource or only dust in the wind?

Renno, A. D.

Rock dust from quarries and from mining operations is a potential valuable resource. Well known and unconventional ways of using are shown. The base for a sustainable use is a very precise chemical and mineralogical characterization of the different dust types.

Keywords: rock dust; sustainable usage of resources; quarry; tailing; mieral dust

  • Invited lecture (Conferences)
    Workshop Internacional Encuentro Alumni DAAD 2012 Geociencias y Energía Desarrollo y Perspectivas de la Cooperación Chileno-Alemana, 18.-21.01.2012, Concepcion, Chile

Permalink: https://www.hzdr.de/publications/Publ-16548
Publ.-Id: 16548


On the use of fine distributed moderating material to enhance feedback coefficients in fast reactors

Merk, B.; Weiß, F.-P.

Recently, the use of moderating materials in fuel assemblies for Sodium cooled fast reactors has been investigated and published in several papers (Annals of Nuclear Energy 38, 5, Annals of Nuclear Energy 38, 11 (2011)). Especially the fine distribution of the moderating material in a layer inside the fuel rod or inside the wire spacer has shown very promising results for the enhancement of the feedback coefficients. The validity of the HELIOS results has been demonstrated in a comparison with MCNP and the transferability of the effect to full core calculations has been shown. The fine distribution of the moderating material is very attractive since it causes only a very limited influence on the safety relevant fuel assembly structure and on the operational parameters like power distribution and end of life burnup distribution. In extension to this published work the influence of the use of moderating materials on systems containing fuels for Minor Actinide transmutation (3% Am, 5% Am, and 2% Np – 2% Am) is examined on the basis of detailed lattice calculations based on 112 energy groups and an unstructured mesh geometry modeling of all fuel assembly details. The influence of the insertion of the Minor Actinides on the fuel temperature and the coolant coefficient is investigated for a reference case and the possibilities of enhancing the feedback coefficients by the insertion of ZrH moderating material are analyzed. The changes in the power and burnup distribution due to the use of the moderating material ZrH will be discussed. Further on, the transmutation potential is compared for the cases with and without moderating material. Neptunium and Americium is slightly more reduced during burnup of the fuel with moderating material only the Curium production rises slightly. A detailed analysis demonstrates that the increase of Cm breeding due to the use of moderating material is lower than the additional amount of destroyed Np and Am. Thus, the results demonstrate that even more Am is burnt with the investigated fuel assembly containing moderating material inside the wire wrapper.
Additionally, a first test of the effect of the use of fine distributed moderating material in a lead cooled fast reactor will be shown. The test is based on preliminary data of the fuel assembly in the GUINEVERE facility. The effect of the moderating material on the neutron spectrum, on the kinf, and on the fuel temperature feedback of the zero power facility is shown and discussed.
Over all, the use of fine distributed moderating material has the potential to open the stage for designable feedback coefficients in fast reactors without creating a major influence on the operational parameters and core coolability.

Keywords: Sodium void effect; SFR; Fast reactor; Zirconium hydride; designable feedback coefficient; transmutation; GUINEVERE; LFR

  • Contribution to proceedings
    Innovative Fast Reactor Designs with Enhanced Negative Reactivity Feedback Features, 27.-29.02.2012, Wien, Österreich
  • Lecture (Conference)
    Innovative Fast Reactor Designs with Enhanced Negative Reactivity Feedback Features, 27.-29.02.2012, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-16547
Publ.-Id: 16547


On the use of moderating material to enhance the feedback coefficients in SFR cores with high minor actinide content

Merk, B.; Weiß, F.-P.

The use of fine distributed moderating material to enhance the feedback effects and to reduce the sodium void effect is described. The consequences of the introduction of fine distributed moderating material into fuel assemblies with fuel configurations foreseen for minor actinide transmutation is analyzed. The degradation of the feedback effects due to the insertion of minor actinides and the compensation by the use of moderating materials is discussed.

Keywords: Sodium void effect; SFR; Fast reactor; Zirconium hydride; designable feedback coefficient; transmutation

  • Contribution to proceedings
    International Congress on Advances in Nuclear Power Plants (ICAPP'12), 24.-28.06.2012, Chicago, USA
  • Lecture (Conference)
    International Congress on Advances in Nuclear Power Plants (ICAPP'12), 24.-28.06.2012, Chicago, USA

Permalink: https://www.hzdr.de/publications/Publ-16546
Publ.-Id: 16546


Solutions without space-time separation for ADS experiments: Overview on Developments and Applications

Merk, B.; Glivici-Cotruţă, V.

The different analytical solutions without space-time separation foreseen for the analysis of ADS experiments are described. The SC3A experiment in the YALINA-Booster facility is described and investigated. For this investigation the very special configuration of YALINA-Booster is analyzed based on HELIOS calculations. The results for the time dependent diffusion and the time dependent P1 equation are compared with the experimental results for the SC3A configuration. A comparison is given for the deviation between the analytical solution and the experimental results versus the different transport approximations. To improve the representation to the special configuration of YALINA- Booster, a new analytical solution for two energy groups with two sources (central external and boundary source) has been developed starting form the Green’s function solution. Very good agreement has been found for these improved analytical solutions.

Keywords: Yalina; experimental analysis; Green’s function; Two group diffusion equation

Permalink: https://www.hzdr.de/publications/Publ-16545
Publ.-Id: 16545


An analytical solution for the consideration of the effect of adjacent fuel assemblies; extension to hexagonal VVER-440 type fuel assemblies

Merk, B.; Rohde, U.

A new analytical method is described to deal with the Leakage Environmental Effect. The method is based on the one dimensional analytical solution of the two-group diffusion equation for two adjacent fuel assemblies. The quality of the results for this highly efficient method is demonstrated for quadratic fuel assemblies. In additional tests the transferability of the concept to hexagonal VVER-440 type fuel assemblies is shown.

Keywords: VVER; Analytical Solution; Homogenization; Cross Section Preparation; Leakage Assembly Environmental Effect

  • Kerntechnik 4(2012), 230-239

Permalink: https://www.hzdr.de/publications/Publ-16544
Publ.-Id: 16544


Overview of major HZDR developments for fast reactor analysis

Merk, B.; Glivici-Cotruţă, V.; Duerigen, S.; Rohde, U.; Kliem, S.

The upgrading of the DYN3D code for the application for fast reactors is described. After validation, a diverse code with the possibility for steady state and transient core analysis on the basis of coupled thermal hydraulics/neutronics calculations is available. The work on the use of fine distributed moderating material in SFR cores is discussed with the target on enhancing the feedback coefficients in SFR cores without influencing the operational. Newly developed analytical solutions without separation of space and time for the analysis of ADS experiments are shown with good agreement for the YALINA experiment. The analytical solutions are a very promising tool for the development of a new method for the analysis of ADS experiments.

Keywords: DYN3D; coupled thermalhydraulics/neutronics calculations; Sodium void effect; designable feedback coefficient; analytical solutions; ADS experiments

Permalink: https://www.hzdr.de/publications/Publ-16543
Publ.-Id: 16543


Curium(III) and europium(III) speciation studies with Mont Terri Opalinus clay isolates

Moll, H.; Bachvarova, V.; Lütke, L.; Geissler, A.; Selenska-Pobell, S.; Bernhard, G.

Microorganisms are ubiquitous also in host rocks of potential nuclear waste disposal sites. In this talk, some results will be presented from the current project about the microbial diversity in Opalinus clay and the interactions of dominant microorganisms with actinides. Especially the interactions of a Sporomusa sp. clay isolate with curium(III) and europium(III) will be shown and discussed.

Keywords: Curium; Europium; Bacteria; TRLFS; Speciation

  • Lecture (others)
    Mont Terri Project: Joint HT-MA-BN-GD-PCC Meeting, 06.-07.02.2012, St. Ursanne, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-16542
Publ.-Id: 16542


DRESDYN: A large scale liquid sodium facility for experiments on dynamo action and related magnetic instabilities

Giesecke, A.; Gerbeth, G.; Gundrum, T.; Kirillov, O.; Seilmayer, M.; Stefani, F.

The DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN), which is presently in the design phase, will comprise a number of large scale liquid sodium experiments devoted to problems of geo- and astrophysical magnetohydrodynamics. A homogeneous dynamo, driven exclusively by precession, will represent the most ambitious compound of DRESDYN.
Another experiment, a sodium filled Taylor-Couette cell, will allow the combined investigation of various versions of the magnetorotational instability and of the Tayler instability. For both experiments, recent results of preparatory studies are presented, and the scientific prospects for the final set-ups are delineated.

Keywords: DRESDYN; Dynamo; MHD-Instabilities; Magnetohydrodynamics; Precession; Magnetorotational Instability

  • Poster
    European Geosciences Union General Assembly 2012, 23.-27.04.2012, Wien, Austria
  • Open Access Logo Abstract in refereed journal
    Geophysical Research Abstracts 14(2012), EGU2012-2824

Permalink: https://www.hzdr.de/publications/Publ-16541
Publ.-Id: 16541


Shallow-underground accelerator sites for nuclear astrophysics: Is the background low enough?

Szücs, T.; Bemmerer, D.; Cowan, T.; Degering, D.; Elekes, Z.; Fülöp, Z.; Gyürky, G.; Junghans, A.; Köhler, M.; Marta, M.; Schwengner, R.; Wagner, A.; Zuber, K.

In order to reliably estimate the rate of a charged particle induced nuclear reaction in a non-explosive astrophysical scenario, its cross section must be measured far below the Coulomb barrier. However, at the corresponding energies the cross section values are very low, so that the experimental counting rate is dominated by cosmic-ray induced background, even if a suitable anticoincidence shield is applied. This problem can be overcome by performing an accelerator-based experiment in a deep underground site, as has been done with great success at the LUNA 0.4 MV accelerator in Gran Sasso, Italy. Several underground accelerators with higher beam energy are in the planning phase worldwide. All of them are shielded by over 1000 m of rock, a depth at which cosmic-ray effects are negligible for the purposes of nuclear astrophysics experiments. It is shown here that a combined approach, using a shallow underground laboratory below 47 m of rock and an active shield to veto surviving muons in simple detectors, results in a background level that is not far from that of deep underground sites. Data have been obtained using two ”traveling” gamma-detectors. They have been transported both shallow underground, to the Dresden Felsenkeller in Germany, and deep underground, to the Gran Sasso laboratory in Italy. As shallow-underground facilities are more easily accessible than deep-underground ones, the present finding holds the promise of greatly accelerated progress in the field of cross section measurements for nuclear astrophysics.

Permalink: https://www.hzdr.de/publications/Publ-16539
Publ.-Id: 16539


Dose rate dependence for different dosimeters and detectors: TLD, OSL, EBT films, and diamond detectors

Karsch, L.; Beyreuther, E.; Burris-Mog, T.; Kraft, S.; Richter, C.; Zeil, K.; Pawelke, J.

Purpose: The use of laser accelerators in radiation therapy can perhaps increase the low number of proton and ion therapy facilities in some years due to the low investment costs and small size. The laser-based acceleration technology leads to a very high peak dose rate of about 1011 Gy/s. A first dosimetric task is the evaluation of dose rate dependence of clinical dosimeters and other detectors.
Methods: The measurements were done at ELBE, a superconductive linear electron accelerator which generates electron pulses with 5 ps length at 20 MeV. The different dose rates are reached by adjusting the number of electrons in one beam pulse. Three clinical dosimeters (TLD, OSL and EBT radiochromic films) were irradiated with four different dose rates and nearly the same dose. A faraday cup, an integrating current transformer and an ionization chamber were used to control the particle flux on the dosimeters. Furthermore two diamond detectors were testet.
Results: The dosimeters are dose rate independent up to 4•109 Gy/s within 2 % (OSL and TLD) and up to 15•109 Gy/s within 5 % (EBT films). The diamond detectors show strong dose rate dependence.
Conlusion: TLD, OSL dosimeters and EBT films are suitable for pulsed beams with a very high pulse dose rate like laser accelerated particle beams.

Permalink: https://www.hzdr.de/publications/Publ-16538
Publ.-Id: 16538


A Tapered Undulator Experiment At The ELBE Far Infrared Hybrid-Resonator Oscillator Free Electron Laser

Lehnert, U.; Michel, P.; Asgekar, V.

A tapered undulator experiment was carried out at the Helmholtz Forschungszentrum Dresden-Rossendorf (ELBE) far-infrared FEL. The oscillator FEL makes use of a hybrid optical resonator. The main motivation was to see whether the presence of a dispersive medium in the form of a waveguide in the resonator has any effect on the outcome. The FEL saturated power and the wavelength shifts have been measured as a function of both positive as well as negative undulator field amplitude tapering. In contrast to the typical high-gain FELs where positive tapering proves beneficial for the output power we observe an improvement of performance at negative taper. During the same experiments we studied the characteristics of the detuning curves. The width of the curves indicate a maximum small-signal gain for zero taper while the output peak power is highest for negative taper. Whereas the saturated power output and the detuning curve characteristics agree with the known theoretical predictions, the wavelength shifts showed deviations from the expected values. Details of the experiment are presented.

Keywords: undulator; hybrid optical resonator; waveguide effect on the outcome; saturated power; positive and negative undulator field; detuning curves

Permalink: https://www.hzdr.de/publications/Publ-16537
Publ.-Id: 16537


Studies on Boiling Water Reactor design with reduced moderation and analysis of reactivity accidents using the code DYN3D-MG

Rohde, U.; Pivovarov, V. A.; Matveev, Y. A.

The multi-group version of the DYN3D reactor dynamics code was used for calculations for a new concept of a boiling water reactor with tight lattice of fuel rods and reduced neutron moderation. For that purpose, a 5-group cross section library was prepared and connected to the DYN3D code. Comparison calculations with the steady-state finite-difference code ACADEM showed a very good agreement.
The capability of the DYN3D multi-group code in modeling transients in boiling water reactors with tight fuel element lattices was demonstrated by the analysis of two reactivity accidents initiated by the ejection of one control rod and unauthorized withdrawal of a control rod bank from the reactor core. The corresponding analyses were performed for begin of cycle conditions, when the considered control rods are at their maximum insertion depth.

Keywords: high conversion reactor; boiling water reactor; tight fuel lattice; core design; reactor dynamics; reactivity-initiated accidents

  • Kerntechnik 77(2012)4, 240-248

Permalink: https://www.hzdr.de/publications/Publ-16536
Publ.-Id: 16536


XAS/XMCD studies of Ga+ irradiation driven magnetization reorientation in Pt/Co/Pt nanostructures

Mazalski, P.; Maziewski, A.; Liedke, M. O.; Fassbender, J.; Ferré, J.; Mougin, A.; Baczewski, L. T.; Wawro, A.; Rogalev, A.; Wilhelm, F.

The magnetic properties of ultrathin films are usually tuned by the varying film thickness, chemical composition or structure (see e.g. [1,2]). It has been demonstrated that the magnetic properties of thin films with perpendicular magnetic anisotropy of interfacial origin may be also tuned by ions irradiation [3]. A Pt/Co/Pt trilayer irradiated by different ions exhibits an out-of-plane to in-plane magnetization reorientation phase transition. Moreover, an ion irradiation-driven intermixing and disordering at the Co–Pt interfaces was shown to lead to a reduction of the anisotropy, coercivity, and Curie temperature.
In our recent paper [4] we presented new effect - remarkable oscillation of the magnetic anisotropy in the Pt/Co(2.6 nm)/Pt (deposited by sputtering technique) induced by an uniform low fluence Ga+ ion irradiation at 30 keV. Increasing fluence F magnetization rotates from in-plane to out-of-plane state and then back to in-plane state. Similar effect, driven by Ga+ ion irradiation, has been recently observed in Pt/Co/Pt deposited by molecular beam epitaxy.
The key question is the origin of observed out-of-plane magnetization state induced by ions irradiation. Ion irradiation driven creation of strongly anisotropic Co-Pt L10 phase is proposed. This hypothesis is supported by measurement of K-edge X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD) on the ID12 ERSF beamline. The study was done on: Pt/Co/Pt samples both as deposited film and irradiated one with fluence creating out-of-plane magnetization state, reference sample - L10 Co0.5Pt0.5 thin film. The XMCD spectrum of the irradiated sample is interpreted as the superposition of pure Co and L10 CoPt alloy contributions. TRIDYN [5] simulations, for different Ga ion fluence, were performed for results discussion.
This work was supported by the following projects: SPINLAB - EU programme Innovative Economy, Priority 2.2, SPIRIT European Community - contract no. 227012, ESRF/73/2006.
References
[1] - M. Kisielewski et al., Phys. Rev. Lett. 89, 87203 (2002)
[2] - A. Stupakiewicz et al., Phys. Rev. Lett. 101, 217202 (2008)
[3] - C. Chappert et al., SCIENCE 280, 1919 (1998)
[4] - J. Jaworowicz et al., Appl. Phys. Lett. 95, 022502 (2009)
[5] - W. Möller et al., Comp. Phys. Commun. 51, 355 (1988).

Keywords: XAS/XMCD studies of Ga+ irradiation driven magnetization reorientation in Pt/Co/Pt nanostructures

  • Lecture (Conference)
    ESRF Users' Meeting 2012, 06.-09.02.2012, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-16535
Publ.-Id: 16535


Interaction of dislocationswith Cu-Ni-vacancy clusters in Fe

Terentyev, D.; Malerba, L.; Bonny, G.; Al-Motasem, A. T.; Posselt, M.

not available, please contact authors

Keywords: dislocations; iron; Cu-Ni-vacancy clusters; Monte Carlo simulations; molecular dynamics

  • Lecture (Conference)
    16th Meeting of International Group on Radiation Damage Mechanisms in Pressure Vessel Steels (IGRDM-16), 04.-09.12.2011, Santa Barbara, USA

Permalink: https://www.hzdr.de/publications/Publ-16534
Publ.-Id: 16534


X-ray investigations on CoSi2 nano wires manufactured by focused ion beam synthesis

Grenzer, J.; Roshchupkina, O.; Fritzsche, M.; Mücklich, A.; Bischoff, L.

Nanowires and chains of nanoparticles are of emerging interest in nanoelectronics, nano-optics and plasmonics as well as for their monolithic integration into microelectronic devices. Epitaxial buried or surface CoSi2 layers in silicon can be formed by implanting Co in stoichiometric concentration and subsequent annealing. Ion beam synthesis allows the fabrication of submicron pattern, which can be formed either directly by a mass separated writing Co focused ion beam (FIB) or indirectly by a Ga FIB in combination with a thin Co film on the rear side of the Si wafer, providing the Co for the nanowire formation by diffusion.

We have studied the strain of the Si host lattice around a single nanostructure depending on their crystallographic orientation using high-resolution x-ray diffraction and TEM. The X-ray experiment was carried out using a highly focused beam (~0.5µm) at the beam line ID01 at ESRF. Surrounding a wire a peak was found indicating a tensile strain of approx. -1.4%.

The CoSi2 peak intensity is strongly modulated by moving from one wire to another. Moreover the diffuse scattered intensity around the Si bulk reflection is increased and is getting even more enhanced between the wires. A possible mechanism lying behind the CoSi2 structure formation is the lattice relaxation by stable dislocation loops. A zigzag like defect structure, characteristic for the formation of 311 defects, was identified by TEM at the grain boundary between the CoSi2 nanowires and the Si bulk.

  • Poster
    E-MRS 2011 SPRING MEETING, 09.-13.05.2011, Nice, France

Permalink: https://www.hzdr.de/publications/Publ-16533
Publ.-Id: 16533


Material science towards the fs range: What we can do?

Grenzer, J.

Material science towards the fs range:
What we can do?

  • Lecture (others)
    Workshop on Petawatt-Lasers at Hard X-Ray Light Sources, 05.-09.09.2011, Helmholtz-Zentrum Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16532
Publ.-Id: 16532


The ROBL Upgrade: in-situ investigations for material science

Grenzer, J.; Baehtz, C.; von Borany, J.

Werkstoffcharakterisierung mit Strahllinien

  • Lecture (others)
    DGM Fachausschusssitzung, BAM Berlin, 27.05.2011, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16531
Publ.-Id: 16531


Material science towards the fs range: Experimental challanges using an XFEL

Grenzer, J.

Seminar Series:
"Understanding advanced materials and processes on the atomic level:
Materials research with ultrashort, intense and coherent X-ray pulses and high-power lasers"

  • Lecture (others)
    Seminar Serie - HZDR, 04.11.2011, Helmholtz-Zentrum Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-16530
Publ.-Id: 16530


High-Electron-Mobility InN Layers Grown by Boundary-Temperature-Controlled Epitaxy

Wang, X.; Liu, S.; Ma, N.; Feng, L.; Chen, G.; Xu, F.; Tang, N.; Huang, S.; Chen, K. J.; Zhou, S.; Shen, B.

A boundary-temperature-controlled epitaxy, where the growth temperature of InN is controlled at its maximum, is used to obtain high-electron-mobility InN layers on sapphire substrates by molecular beam epitaxy. The Hall-effect measurement shows a recorded electron mobility of 3280 cm^2 V^-1 s^-1 and a residual electron concentration of 1.47×10^17 cm^-3 at room temperature. The enhanced electron mobility and reduced residual electron concentration are mainly due to the reduction of threading dislocation density. The obtained Hall mobilities are in good agreement with the theoretical modelling by the ensemble Monte Carlo simulation.

  • Applied Physics Express 5(2012), 015502
    DOI: 10.1143/APEX.5.015502
  • Communication & Media Relations
    News release at Semiconductor Today 30.01.2012

Permalink: https://www.hzdr.de/publications/Publ-16529
Publ.-Id: 16529


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