Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35836 Publications

An approach for few femtosecond timing of fourth generation X-ray lightsources and single shot electron bunch diagnostics

Gensch, M.

Fourth-generation X-ray light sources are being developed to deliver laser-like X-ray pulses at intensities and/or repetition rates that are beyond the reach of table-top devices. An important class of experiments at these new facilities comprises pump–probe experiments, which are designed to investigate chemical reactions and processes occurring on the molecular or even atomic level, and on the timescale of a few femtoseconds. Good progress has been made towards the generation of ultrashort X-ray pulses (for example, at FLASH or LCLS), but experiments suffer from the intrinsic timing jitter between the X-ray pulses and external laser sources. Here I present a new approach that provides few-femtosecond temporal resolution for pump probe experiments at FLASH. The method uses residual coherent terahertz radiation generated at the end of the X-ray undulator by the same electron bunch that emits the X-ray pulse. It can therefore be applied at any advanced light source working with ultrashort electron bunches and undulators. The employed instrumentation also has a high potential to allow analysis of the electron bunch form on a single shot basis. An outlook on how the method will be employed at the currently upgraded cw electron linac ELBE at the HZDR to aid laser-electron interaction experiments with dedicated TW and PW lasers is also given

  • Invited lecture (Conferences)
    X-FEL Seminar, 25.03.2011, Hamburg, Germany

Publ.-Id: 15741

Photondiagnostics at X-Ray FEL´s

Gensch, M.

SASE FEL´s have now truly evolved into the long anticipated so called 4th generation of accelerator based X-ray light sources. A number of piloting experiments are proof that these novel X-ray sources provide radiation with the theoretically predicted unprecedented properties such as femtosecond pulse duration or Gigawatt peak power in a photon energy range extending from the soft X-ray into the hard X-ray regime. However, the success of these facilities depends strongly on the availability of suitable photon diagnostics. To be precise, due to the stochastic nature of the SASE process, properties such as pulse energy, wavelength, pulse duration and arrival time are varying from pulse to pulse and more complex experiments will crucially depend on the determination of these properties for every individual X-ray pulse. In this talk, the state of the art of currently available photon diagnostic is discussed and novel single shot techniques for the measurement of X-ray pulse duration [1] and arrival time [2] are presented.
[1] U. Fruehling, M. Wieland, M. Gensch et. al., Single-Shot THz-field-driven X-Ray streak camera, Nature Photon. 3 (2009), 528.
[2] F. Tavella, N. Stojanovic, G.A. Geloni and M. Gensch, Few-femtosecond timing at fourth-generation X-ray light sources, accepted.

  • Invited lecture (Conferences)
    DIPAC 2011, 15.-19.05.2011, Hamburg, Germany

Publ.-Id: 15740

CFD Simulation of Counter-current Two-phase Flow in a Model of PWR Hot Leg

Deendarlianto; Höhne, T.; Lucas, D.; Vallée, C.

This paper provides a numerical study of the phenomena around the counter-current flow limitation (CCFL) of air-water and steam-water in a model of the hot leg pressurized water reactor (PWR). The calculations were conducted using the commercial CFD software, CFX 13.0 (ANSYS CFX), based on the finite volume method for an Euler-Euler model or free surface model. The simulations were carried out in fully transient manner using a gas/liquid inhomogeneous multiphase flow model coupled with a shear stress transport (SST) turbulence model. In the present numerical study, the drag coefficient was approach by using the Algebraic Interfacial Area Density (AIAD). Next, an image processing technique was also developed in order to obtain the liquid film thickness data in a model PWR hot leg from the high-speed video observations. The results indicated that quantitative agreement between calculation and experimental data was obtained for the occurrence of flooding point and water level inside the hot leg channel.

Keywords: Numerical simulation; Computational fluid dynamics; Counter-current flow limitation; PWR; Drag force

  • Lecture (Conference)
    Multiphase Flows Workshop, Simulation, Experiment and Application, 09.-10.06.2011, Dresden, Germany
  • Contribution to proceedings
    Multiphase Flows Workshop, Simulation, Experiment and Application, 09.-10.06.2011, Dresden, Germany
    Proceeding of the 9th Multiphase Flows Workshop, Simulation, Experiment and Application

Publ.-Id: 15739

A novel pilot program for homogeneity testing of natural analogs of synthetic mineral reference materials

Michalak, P. P.; Renno, A. D.; Wiedenbeck, M.; Merchel, S.; Munnik, F.

The growing demand for elements (PGE, REE and refractory metals) desired by the high-tech industry stresses the need for searching for them in non-conventional raw materials. Natural variability of distribution of such elements within the matrices of mineral carriers, frequently, at the micro- and submicrometer level requires employing high-resolution spatial microanalytical techniques as an essential step in quantitative measurements as well as quality assurance procedures (Renno et al. 2010). The necessity for providing reliable, traceable and comparable results for such measurements at the picogram sampling scale makes the use of certified reference materials to be of critical importance. The database of certified reference materials in the form of solutions, powders, pellets, glass beads etc. has been developed by several research groups as well as governmental agencies with certifying capabilities (Jochum 2010). Unfortunately, among such materials natural and synthetic minerals are scarce (Jochum 2010, Wiedenbeck 2010).
Such a lack of mineral reference materials was an incentive for creating a consortium of several German scientific and federal institutions with a common goal of providing a sufficient quantity of synthetic mineral reference materials with concentrations of economically important elements certified at the submicrometer level useful for in-situ analyses with a number of microanalytical methods.
Due to various geological processes natural minerals may develop heterogeneous elemental distribution as well as many structural features that seriously limit their suitability as reference materials. A logical assumption on superiority of synthetic minerals over natural minerals can be made as far as one is able to control chemical and structural homogeneity of the grown crystal. This can be assured by inventing robust homogeneity testing procedure employing both absolute and matrix-corrected methods.
In this study we introduce a systematic approach to homogeneity testing of reference materials using their natural analogs. Microanalytical techniques were selected and introduced on a step-by-step basis in a sequence, depending on their sensitivity and spatial resolution: light and electron microscopy, EPMA, SIMS, PIXE-PIGE, LA-ICPMS, μ-SXRF. The pilot program was launched using three minerals, each representing a different group of minerals of a specific interest to the industry: pyrite, columbite-tantalite and sanidine. All specimens were tested with reflected-light microscopy and scanning electron microscopy (BSE images) and showed no inhomogeneities apart from cracks and some minor inclusions. The results of the chemical homogeneity test will be presented in detail.
The research was supported by the Free State of Saxony, European Union and Helmholtz Association.
[1] A.D. Renno et al., 2010: A development strategy for creating a suite of reference materials for the in-situ microanalysis of non-conventional raw materials. Abstract V51C-2210 presented at 2010 Fall Meeting, AGU, San Francisco, Calif., 13-17 Dec.
[2] K.P. Jochum, 2010: Reference materials for in situ microanalysis: Successes and needs, Goldschmidt Conference Abstracts 2010, A470.
[3] M. Wiedenbeck, 2010: Challenges facing the production of RMs for geochemical microanalyses, Goldschmidt Conference Abstracts 2010, A1130.

Keywords: reference materials; spatially resolved analysis

  • Poster
    89. Jahrestagung der Deutschen Mineralogischen Gesellschaft (DMG) in Kooperation mit der Deutschen Kristallographischen Gesellschaft (DGK) und der Österreichischen Mineralogischen Gesellschaft (ÖMG), 20.-24.09.2011, Salzburg, Österreich

Publ.-Id: 15738

Fachsitzung: „CFD-Methoden für sicherheitsrelevante Fragestellungen“

Höhne, T.; Schaffrath, A.

Die Leitung der Sitzung hatte Herr Dr. Th. Höhne vom Helmholtz-Zentrum Dresden- Rossendorf, und Herr Dr. A. Schaffrath (TÜV NORD SysTec GmbH & Co. KG) inne.

Keywords: Jahrestagung Kerntechnik; CFD; Fachsitzung; nukleare Sicherheitsforschung

  • atw - International Journal for Nuclear Power 56(2011)7, 419-423

Publ.-Id: 15737

XANES and EXAFS analysis of oxidation state and local structure of plutonium reacted with iron oxides under anoxic conditions

Kirsch, R.; Fellhauer, D.; Altmaier, M.; Rossberg, A.; Fanghänel, T.; Charlet, L.; Scheinost, A. C.

Iron minerals form as corrosion products of zero-valent iron and steel in the “near field”, are present in many "far field" barriers (clay or granite) and occur widely in natural sediments. Depending on redox conditions, ground water composition and microbial activity, iron(hydr)oxides such as goethite (-FeOOH), lepidocrocite (-FeOOH), magnetite (FeIIFeIII2O4), and maghemite (-Fe2O3) have been observed as corrosion products of steel [1,2]. The solubility and complexation behavior of plutonium in aqueous systems are highly oxidation state dependent. As Iron(hydr)oxides have been shown to undergo redox reactions with plutonium [3-5] and to form plutonium surface complexes [6], they are expected to control to a large extent the migration behavior of plutonium. For example, sorption of Pu(V) to hematite, goethite and magnetite was found to be accompanied by surface mediated reduction to Pu(IV) [3-5,7]. While many previous laboratory studies have been conducted under air, the intention of our work was to investigate redox reactions of Pu with common iron oxides under well controlled and anoxic conditions to better simulate deep underground conditions. We combined in-situ oxidation state analysis on the mineral surfaces using advanced XAS techniques with wet chemical characterization of redox conditions and thermodynamic modeling. The part of the joint work focusing on aqueous Pu chemistry and thermodynamic description of Pu redox state distribution is presented at Migration’11 by Fellhauer et al..
Synthetic hematite, goethite, maghemite and magnetite were allowed to react under anoxic conditions (O2 ≤ 10 ppmv) in carbonate free 0.1 M NaCl with aqueous 242Pu(III) and 242Pu(V). Pu-LIII-edge XANES and EXAFS spectra were collected after 40 days and six months at the Rossendorf Beamline at ESRF, France, to assess in-situ oxidation states and local structures of plutonium reaction products. All measurements were carried out at 15 K using a closed-cycle He cryostat to reduce thermal disorder in the samples and avoid beam-induced changes in oxidation state.
After reaction with hematite, Pu(V) was largely reduced to Pu(IV) while Pu(III) was oxidized to Pu(IV). For example, after 6 months of reaction with hematite at pH 7.5, 30 % Pu(V) and 70 % Pu(IV) were observed for the sample with Pu(V)initial. Under similar reaction conditions, Pu(III)initial yielded 20 % Pu(V) and 80 Pu(IV). Despite these similar oxidation state distributions of Pu associated with the solid phase, [Pu] concentrations in solution differ for most of the 6 months reaction period by about two orders of magnitude. Final [Pu] concentrations are 2×10 10 M for the Pu(III)initial and 6×10 9 M for the Pu(V)initial samples. The EXAFS spectra gave no evidence for the formation of a solid PuO2 phase.
In magnetite suspensions at pH 6 and pH 8, reduction of Pu(V) to Pu(III) and formation of a Pu(III)-magnetite surface sorption complex was observed. In this surface complex, situated on (111) surfaces with octahedral termination, one Pu atom is linked via three oxygen atoms to three edge-sharing FeO6-octahedra. Due to the tridentate nature of the complex, it is likely to be very stable and play an important role in controlling Pu-magnetite reactions and Pu mobility under reducing conditions. However, at a higher plutonium loading (1 Pu atom / 29 nm2 instead of 1 Pu atom / 58 nm2) and with Pu(V)initial, only 60 % of Pu is surface complexed Pu(III)ads while about 40 % is present as solid PuO2. After 6 months, solution concentrations for Pu(III)initial or Pu(V)initial were at or below the detection limit of ~5×10 11 M (242Pu measured with liquid scintillation counting or ICP-MS).
Reaction with maghemite at pH 6 yielded very similar oxidation state distributions and solution concentrations for Pu(III)initial and Pu(V)initial samples. Changes in Pu(III) / Pu(IV) ratios in the reaction products can be attributed to differing residual Fe(II) contents (maghemite was prepared by oxidation of magnetite). After six months of reaction, Pu was present as 80% Pu(IV). As with magnetite, iron backscatterering indicates formation of an inner sphere surface complex. Formation of a solid PuO2 phase does not occur.
These data highlight the importance of plutonium surface complexation on different iron oxides in controlling environmental [Pu] concentrations. In particular, conservation of non negligible amounts of Pu(V) with hematite (20 to 30 % after 6 months) and goethite (45 % Pu(V) after 40 days) contrasts with published data [5]. In addition, our results highlight the necessity to consider trivalent Pu(III) species in addition to tetravalent Pu(IV) species and PuO2(am,hyd) for risk assessment under reducing conditions.

Keywords: plutonium redox hematite goethite maghemite magnetite XANES EXAFS

  • Contribution to proceedings
    Migration 2011 - 13th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 18.-23.09.2011, Beijing, China
    Migration 2011 - 13th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, Peking, China: Peking University

Publ.-Id: 15736

Plutonium redox reactions with iron oxides under anoxic conditions

Kirsch, R.; Fellhauer, D.; Altmaier, M.; Rossberg, A.; Fanghänel, T.; Charlet, L.; Scheinost, A. C.

The environmental fate of plutonium, the major transuranium actinide in nuclear waste, is largely impacted by its sorption onto [1] and redox reactions [2] with iron oxide minerals that form as corrosion products of steel in the "near field" and occur widely in sediments. To obtain information on oxid-ation state and local structure, we reacted 242Pu as electro-lytically prepared Pu(V) or Pu(III) (1×10-5 M) under anoxic conditions in carbonate free 0.1 M NaCl with hematite, goethite, maghemite and magnetite. Pu-LIII-edge XAFS spectra were collected after 40 d and 6 months of reaction.
Results and Discussion
After reaction of either Pu(III) or Pu(V) with hematite (α-Fe2O3), Pu associated with the solid phase ( > 99.9 % of added Pu) is mainly present as Pu(IV) and up to 30 % Pu(V). Also after reaction with goethite (γ-FeOOH) both Pu(IV) (55 %) and Pu(V) (45 %) are present. For both minerals, EXAFS spectra show no strong Fe-backscattering from the substrate and also give no evidence for the formation of a solid PuO2 phase. In contrast, EXAFS spectra of Pu reacted with maghemite (γ-Fe2O3) and magnetite (Fe3O4) are charac-terized by strong iron backscattering, indicating the formation of inner-sphere surface sorption complexes. With maghemite, oxidation state mixtures of Pu(III) and Pu(IV) or Pu(IV) and Pu(V) were found while with magnetite, Pu(III) was the predominant oxidation state [3]. However, in one case and probably due to an increased Pu / magnetite surface area ratio, formation of PuO2 after reaction of Pu(V) with magnetite was observed. These results highlight the importance of plutonium surface complexation on different iron oxides in controlling environmental [Pu] concentrations. Further, for risk assessment under reducing conditions where Fe(II)-bearing oxides such as magnetite exist, it is necessary to consider trivalent in addition to tetravalent plutonium species and PuO2(am,hyd).
[1] Novikov et al. (2006) Science 314, 638-641. [2] Powell et al. (2005) Environ. Sci. Technol. 39, 2107-2114. [3] Kirsch et al. (2011) submitted to Environ. Sci. Technol.

Keywords: plutonium redox iron oxides magnetite maghemite hematite goethite

  • Contribution to proceedings
    Goldschmidt 2011, 12.-19.08.2011, Prague, Czech Republic
    Proceedings of the Goldschmidt Conference 2011, Cambridge, UK: Cambridge Publications, 1194

Publ.-Id: 15735

Validation of a new surface drag formulation within the Morphology Detection Algorithm AIAD for improving horizontal two-phase flow simulations

Höhne, T.; Vallée, C.; Apanasevich, P.

This paper presents different CFD-simulations on flows which are relevant for nuclear reactor safety using a new modelling approach for the interfacial drag at free surfaces. The developed drag coefficient model was implemented together with the Algebraic Interfacial Area Density (AIAD) model (Höhne, 2009) into the three-dimensional (3-D) computational fluid dynamics (CFD) code ANSYS-CFX. The applications considered include the prediction of counter-current flow limitations (CCFL) in a PWR hot leg, the development of hydraulic jump during the air-water co-current flow in a horizontal channel, and pressurized thermal shock (PTS) phenomena in a PWR cold leg and downcomer. For the modelling of these tasks, an Euler–Euler approach was used. This approach allows the use of different models depending on the local morphology. In the frame of an Euler-Euler simulation, the local morphology of the phases has to be considered in the drag model.

To demonstrate the feasibility of the present approach, the computed main parameters of each case were compared with experimental data. It is shown that the CFD calculations agree well with the experimental data. This indicates that the AIAD model combined with new drag force modeling is a promising way to simulate the phenomena in frame of the Euler-Euler approach. Moreover the further validation of the model by including mass transfer effects should be carried out.

Keywords: Computational fluid dynamics (CFD); Algebraic interfacial area density (AIAD) model; Drag coefficient; Pressurized water reactor (PWR); Hot leg; Cold leg; Counter-current flow limitation (CCFL); Hydraulic jump; Slug flow; Stratified flow; Pressurized thermal shocks (PTS); Downcomer

  • Contribution to proceedings
    Multiphase Flows: Simulation, Experiment and Application, 08.-10.06.2011, Dresden, Deutschland
  • Lecture (Conference)
    Multiphase Flows: Simulation, Experiment and Application, 08.-10.06.2011, Dresden, Deutschland

Publ.-Id: 15734

41 Jahre Betrieb des Rossendorfer Zyklotrons U-120 - Eine Bildersammlung

Guratzsch, H.; (Editor)

Das Rossendorfer Zyklotron ist ein "klassisches" Zyklotron mit 120 cm Polschuhdurchmesser. Als klassisches Zyklotron verfügt es über ein rotationssymmetrisches Magnetfeld. Mit der in radialer Richtung abfallenden Magnetfeldstärke wir die "weiche" Fokussierung erreicht.
Zunächst wurde das Zyklotron für die kernphysikalische Grundlagenforschung genutzt. Später überwogen die Herstellung von Radionukliden, die Neutronenerzeugung für medizinische und radiochemische Anwendungen sowie spezielle Dünnschichtaktivierungen für die Verschleißforschung.
Die Betriebszeit des Zyklotrons erstreckte sich über einen Zeitraum von 41 Jahren, von August 1958 bis Dezember 1999.

Keywords: Zyklotron

  • Other report
    Dresden: FZ Rossendorf, 2000
    20 Seiten

Publ.-Id: 15733

Determination of muon attenuation lengths in depth profiles from in situ produced cosmogenic nuclides

Braucher, R.; Bourlès, D.; Merchel, S.; Vidal Romani, J.; Fernadez-Mosquera, D.; Marti, K.; Leanni, L.; Chauvet, F.; Arnold, M.; Aumaître, G.; Keddadouche, K.

Cosmogenic nuclides are important tools to understand and quantify the processes that control the development and evolution of landscapes during the Quaternary. Among all published studies, few are related to the accurate and precise determination of the physical parameters governing their production in the Earth's crust surface (in-situ produced cosmogenic nuclides) and its evolution as a function of depth below the Earth's surface. Currently, it is nearly impossible to advocate global parameters that could be used worldwide. Indeed, at each sampling site, not only the geometry and the mineralogy will differ but also their evolution as a function of depth. In this paper, a new approach based on the measurement of the evolution of cosmogenic nuclide concentrations along depth profiles to determine the muon attenuation lengths is proposed. In this study, the determined attenuation length will integrate the potential effect of the chemical composition of the overlying matrix and will take into account the entire energy range of the incident particles. More, when denudational steady state is reached, muon contributions can be determined. When scaled to sea level, these contributions are similar for a given nuclide whatever the site where they have been determined. The average weighted muon contribution are (0.028 ± 0.004) at/g/a for 10Be, (0.233±0.045) at/g/a for 26Al and (1.063 ± 0.329) at/g/a for 36Cl and are valid within the depth range 0 - 6500 g/cm2.

Keywords: Cosmogenic nuclides; muon; attenuation length; depth profile

Publ.-Id: 15732

Sorption and interfacial redox of Sn(II) under anoxic conditions: Magnetite vs. anatase

Dulnee, S.; Banerjee, D.; Rossberg, A.; Scheinost, A. C.

The long-lived fission product 126Sn is of substantial interest in the context of nuclear waste deposition in deep underground repositories. However, the redox state (di- or tetravalent) under the expected anoxic conditions is still a matter of debate. We therefore investigated the stability of Sn(II) in the presence of a highly redox-reactive mineral, magnetite (FeIIFeIII2O4), in comparison to a non-redox-reactive, anatase (TiO2).
Sorption experiments were performed at < 2 ppm O2, and redox state and local structure was monitored over time by X-ray absorption spectroscopy (XAS).
We found a rapid (< 30 min) oxidation of Sn(II) to Sn(IV) in the presence of magnetite. Although solubility calculation predicted the precipitation of SnO2, the local structure determined by XAS showed two Sn-Fe distances of about 3.15 and 3.60 Å in line with edge and corner sharing arrangements between octahedrally coordinated Sn(IV) and the magnetite surface, indicative of inner-sphere complexation. The structure of the complex remained largely unchanged up to an equilibration time of 1 month.
After 30 min reaction with anatase, Sn(II) was conserved. However, even with the redox-inert anatase, Sn(II) oxidized to Sn(IV) over time, forming an Sn(IV) inner-sphere complex with Sn-Ti distances at 3.24 and 3.53 Å. Therefore, our results clearly indicate that Sn(IV) is the most relevant oxidation state to be considered even under reducing conditions, and that inner-sphere complexation is a relevant retention mechanism.

Keywords: Sn; Sorption; Magnetite; Anatase; Redox; XAFS; Molecular structure

  • Poster
    Goldschmidt2011, 14.-19.08.2011, Prague, Czech Republic
  • Poster
    6th PhD Seminar HZDR, 05.-07.10.2011, Rabenberg, Germany

Publ.-Id: 15731

Countercurrent flow limitations in a pressurized water reactor

Deendarlianto; Höhne, T.; Murase, M.

In the event of hypothetical accident scenarios in a pressurized water reactor (PWR), emergency strategies have to be mapped out, in order to guarantee the reliable removal of decay heat from the reactor core. One essential passive heat removal mechanism is the reflux cooling mode. It can appear during a small break loss-of-coolant-accident (LOCA) or because of loss of residual heat removal (RHR) system during mid loop operation at plant outage. In the scenario of a loss-of-coolant-accident (LOCA) in a PWR, it is considered that the reactor will be depressurized and vaporization will take place. Should this lead to “reflux condensation”, which may be a favorable event progression, the generated steam will flow to the steam generator. This steam will condense in the steam generator and the condensate will flow back through the hot leg to the reactor, resulting in countercurrent steam/water flow.

For a given condensate flow rate, if the steam mass flow rate increases to a certain value, a portion of the condensate will exhibit a partial flow reversal by the steam in the opposite flow direction towards the steam generator. This phenomenon is known as counter-current flow limitation (CCFL). The keys to CCFL control is an improved understanding of these conditions, development of a suitable experimental data base, novel tools to characterize the practical conditions in order to produce a better physical CCFL model.

We invite investigators to contribute original research articles as well as review articles that will simulate the continuing efforts to understanding this important phenomenon. We are interested also in articles that explore the CCFL in a simple pipe configuration in order to support the physic behind the CCFL phenomena.

Potential topics include, but are not limited to:

  • New experimental investigations on the counter-current gas-liquid two-phase flow in a PWR hot leg as well as in downcomer and tie plate during blow down
  • Development of experimental database on CCFL in a simple pipe/channel construction.
  • Development of phenomenological and analytical model for the prediction of CCFL in a certain part of a PWR as well as in a simple channel construction.
  • Computational fluid dynamics (CFD) effort on CCFL and relating phenomena, such as, water hammer, steam-condensation and reflooding behavior.
  • Latest experimental techniques require to investigate CCFL and provide data for CFD validation
  • Future discussion on R&D need about CCFL issues, with a focus on fuel coolability and relating severe accidents in a nuclear reactor

Keywords: CCFL; CFD; AIAD

  • Open Access Logo Science and Technology of Nuclear Installations (2012), 608678
    Online First (2012) DOI: 10.1155/2012/608678

Publ.-Id: 15730

Magneto-optical coupling of ferromagnetic thin films investigated by vector-magneto-optical generalized ellipsometry

Mok, K. M.; Kovacs, G. J.; McCord, J.; Li, L.; Helm, M.; Schmidt, H.

We performed generalized Mueller matrix ellipsometry measurements in a magnetic field of arbitrary orientation and magnitude up to 400 mT at room temperature and probed the magneto-optical response of capped, ferromagnetic Fe, Ni20Fe80, Co, Ni80Fe20, and Ni thin films on ZnO substrates in the spectral range from 300 to 1100 nm. We determined the off-diagonal elements in the magneto-optical dielectric tensor under saturated magnetization conditions in the sample surface plane via a model analysis. The off-diagonal elements depend on the net spin polarization and the electronic band structure of the ferromagnetic thin films. For the pure ferromagnetic metals Fe, Co, and Ni, the converted off-diagonal elements agree well with the reported experimental optical conductivity data. As a result we use the extracted wavelength-dependent magneto-optical coupling constant to predict the wavelength-dependent magneto-optical response of different Ni/Fe multilayer structures.

Keywords: magneto-optics; Mueller matrix; generalized ellipsometry; ferromagnetic

Publ.-Id: 15729

Combined electromagnetic tomography for determining two-phase flow characteristics in the submerged entry nozzle and in the mould of a continuous-casting model

Wondrak, T.; Eckert, S.; Gerbeth, G.; Klotsche, K.; Stefani, F.; Timmel, K.; Peyton, A.; Terzija, N.; Yin, W.

The paper describes experiments on the combined determination of the distribution of liquid metal and argon in the submerged entry nozzle (SEN) and of the flow in the mould of a small-scale physical model of a continuous slab caster. For visualizing the metal distribution in the SEN, Mutual Inductance Tomography (MIT) is applied, while the flow in the mould is determined by Contactless Inductive Flow Tomography (CIFT). The results of the latter are validated in part by Ultrasonic Doppler Velocimetry (UDV). Accompanying measurements provide information about the levels in the tundish and in the mould, as well as on the pressure in the SEN. Depending on the gas flow rate, various flow regimes are identified, among them mould level oscillations, transitions between double and single vortex flows, and transient single port ejections.

Publ.-Id: 15728

Magnetic properties of granular CoCrPt:SiO2 recording media deposited on GaSb nanocones

Ball, D. K.; Günther, S.; Krone, P.; Fritzsche, M.; Varvaro, G.; Makarov, D.; Lenz, K.; Mücklich, A.; Facsko, S.; Fassbender, J.; Albrecht, M.

Investigation of the magnetization reversal in arrays of magnetic nanostructures is relevant for both fundamental understanding as well as application for magnetic data storage. We present a study of the magnetization reversal in granular CoCrPt:SiO2 recording media with weakly interacting magnetic grains grown onto prestructured templates fabricated by ion irradiation of GaSb. By tuning the irradiation conditions assemblies of nanocones of different size and periodicity were prepared. Columnar CoCrPt grains with their c-axis normal to the surface of the cones were formed as evidenced by HR-TEM. The spread of the c-axis of these grains results in a tilted easy magnetization axis with respect to the substrate normal. Investigation of the integral magnetic properties by vector-VSM reveals a decrease of the remanence with increasing cone size. The magnetic domain patterns observed by MFM suggest that the CoCrPt behaves as a single-domain cap structure on the cones.

  • Poster
    INTERMAG 2011 Taipei, IEEE International Magnetics Conference, 25.-29.04.2011, Taipei, Taiwan

Publ.-Id: 15727

Morphology Induced Magnetic Anisotropy of Thin Films Deposited on Nanoscale Ripple Substrates

Körner, M.; Liedke, M. O.; Lenz, K.; Ranjan, M.; Fritzsche, M.; Facsko, S.; Fassbender, J.; von Hörsten, U.; Krumme, B.; Wende, H.

The control of static and especially dynamic magnetic response of ferromagnetic thin films is one of the utmost challenges in applied magnetism. Therefore the adjustment of magnetic anisotropy and the connected resonance frequency, as well as the magnetic damping parameter are of fundamental importance to insure functionality in existing and envisioned spintronic applications.
Here we indirectly tailor the effective magnetic properties of magnetic thin films by changing the morphology of substrates with periodically modulated patterns on the nanometer scale [1]. These well ordered surface modulations (ripple) can be produced by low energy ion beam erosion and are tuneable over a wide range [2]. Thin magnetic films deposited on these ripple surfaces repeat the surface profiles of the patterns and thus an additional uniaxial magnetic anisotropy is induced. Results are shown for thin films of Fe, Co as well as the quasi-Heusler compound Fe3Si. The effective magnetic anisotropy is determined by means of angular- as well as frequency-dependent ferromagnetic resonance measurements using a vector network analyzer based setup. We find a strong uniaxial magnetic anisotropy induced by the ripple surface, which is superimposed on the cubic anisotropy in the case of single crystalline films. Influences of the rippled surface on the magnetic damping parameter will be discussed.
This work is supported by DFG grant FA 314/6-1.

[1] M. Körner et al., Phys. Rev. B 80, 214401 (2009).
[2] J. Fassbender et al., New Journal of Physics 11, 125002 (2009).

  • Poster
    IEEE Magnetics Society Summer School, 22.-28.05.2011, New Orleans, USA

Publ.-Id: 15725

Improved 36Cl Performance at the ASTER HVE 5 MV Accelerator Mass Spectrometer National Facility

Finkel, R. C.; Arnold, M.; Aumaître, G.; Benedetti, L.; Bourlès, D. L.; Keddadouche, K.; Merchel, S.

The HVE 5 MV ASTER AMS national facility at CEREGE was accepted in 2007. Since then we have continued to optimize performance for 36Cl. Cl-36 analyses use AgCl, a Cs negative ion sputter source, Ar stripping to +5 in the terminal of the Tandetron™ accelerator at 5 MV and a Si3N4 postacceleration stripper foil to enhance suppression of 36S relative to 36Cl. The major challenges to obtaining the desired performance for Earth science applications are ion source memory, mass fractionation effects, 36S isobar suppression and sensitivity. Redesign of the SO110 ion source by HVE to change the size of the aperture and the shape of cathode significantly reduced ion source memory to less than ~0.1%, a level that can be compensated for by matching standards to samples. We observe small systematic drifts in 35Cl/37Cl ratios over time, the source of which is not yet determined.
Measurement of standards indicates that this effect limits the precision of 35Cl/37Cl ratio determination to about 2%. 36S is suppressed in several ways. First, the sample chemistry has been designed to reduce S to very low levels. Second, cathodes are constructed of low-S nickel, enabling direct target loading without the use of AgBr pre-packing. Third, a post-acceleration Si3N4 stripper foil differentially absorbs energy from 36Cl and 36S. A ubsequent electrostatic deflector is then able to suppress 36S by a factor of ~5x10-3. Differential energy loss in the detector further suppresses 36S by about 10-4, for an overall suppression of 5x10-7. 36S count rates are typically equivalent to a background 36Cl/Cl of <10-15. At typical 35Cl currents of 20 μA samples with 36Cl/35Cl of 5x10-14 can be measured to ± 6% statistical uncertainty with one hour of analysis time. Typical machine blanks have 36Cl/Cl ~2x10-15.

Keywords: accelerator mass spectrometry; 36Cl capability; ASTER; ion source memory

Publ.-Id: 15724

Magnetic anisotropy engineering: single crystalline Fe films on ripple surfaces

Liedke, M. O.; Körner, M.; Lenz, K.; Strache, T.; Shalimov, A.; Ranjan, M.; Facsko, S.; Fassbender, J.; McCord, J.

Nanostructuring by means of ion erosion has proven its versatility with respect to the surface morphology control. By varying different ion irradiation parameters, e.g. ion energy, fluence, incident angle, and sample temperature, the assembly of self-organized periodically ordered arrays of nano-dots [1] and ripples [2] is possible. This has been proven for semiconductors as well as for metals [3,4]. Especially, nanopatterning of magnetic materials is intriguing due to the fact that not only the surface morphology is affected, but the overall magnetic properties are accordingly modified. For example, ion bombardment of single crystal Fe films enables the manipulation of the in-plane uniaxial magnetic anisotropy (UMA) that is associated with the ripple morphology [5].

Here we present a novel bottom-up method of magnetic film patterning, where a highly ordered periodic MgO ripple surface with a wavelength on the nanometer scale is coated by a magnetic Fe layer. The modulations can be induced along any arbitrary in-plane orientation and outstandingly, the surface stays crystalline upon ion irradiation. Thus, due to the low lattice mismatch single crystalline Fe can be grown onto such templates. Despite the intrinsic magnetic cubic anisotropy (CA) of bcc Fe additional UMA is introduced.

As a reference a model cubic system, i.e. Fe on flat MgO(100), has been grown. 15 nm of Fe (tFe) was deposited onto the MgO(100) substrate at room temperature by means of molecular beam epitaxy (MBE). In-plane magneto-optic Kerr effect (MOKE) and ferromagnetic resonance (FMR) angular measurements were performed revealing clear evidence of a four-fold symmetry (CA; K4||/M=186.3 Oe) superimposed with a very small two-fold symmetry contribution (UMA; K2||/M=2 Oe). The magnetic reversal curves (MRCs) shown in Fig. 1a (top panel) correspond to three distinguished sample orientations with respect to the angle φH of the external magnetic field. The curves represent the hard (HA), intermediate, and easy (EA) magnetization orientations of the cubic system. The MRC at φH=18° exhibits a two-jump magnetization process that is a consequence of nucleation and propagation of 90° domain walls (DWs), which is confirmed by magnetic domain observations performed by magneto-optical Kerr microscopy.

In a second step, ripple MgO substrates of a wavelength λrip≈20 nm were prepared (for the AFM micrograph refer to Fig. 1a, top panel) and coated with Fe. Several Fe thicknesses were evaporated in the range of 5-30 nm onto templates with a few distinct in-plane ripple orientations with respect to the MgO [100] direction (0°≤φrip≤60°). Thus, due to the combination of the periodic morphology and the intrinsic magnetic properties of Fe, an ensemble of two-fold and four-fold magnetic symmetry is created. This is confirmed by FMR and MOKE measurements. In general, the UMA originates from dipolar and step-edge effects. The orientation and strength of the UMA depends on the angle of ripple ridges elongation φrip with respect to the MgO [100] direction and Fe film thickness, respectively. First evidence of strong UMA emerges already from MRCs analysis as shown for a sample with φrip≈25° (Fig. 1a, bottom panel), where for in-plane orientations between HA and EA directions a three-jump magnetization process is found. From Kerr microscopy investigations, the magnetization reversal process can be described as a subsequent nucleation and propagation of 90°, 180°, and then again 90° DWs. FMR analysis, i.e. fit of the in-plane angular resonance frequency fres dependence, reveals anisotropy fields and orientations of both anisotropy contributions (Fig. 1b). E.g., for the ripple sample with tFe=15 nm the CA and UMA fields are K4||/M=306 Oe and K2||/M=20 Oe, respectively. Both values are strongly increased relative to flat Fe films. Moreover, the orientation of the UMA coincides with the elongation direction of the ripple ridges for all the samples. In addition, we find that the UMA decreases as a function of Fe thickness, whereas the CA behaves the opposite way. The origin and interaction of the magnetic anisotropy contributions will be discussed in detail. References: [1] S. Facsko et al., Science 285, 1551 (1999)
[2] E. Chason et al., Phys. Rev. Lett. 72, 3040 (1994)
[3] R. Moroni et al., Phys. Rev. Lett. 91, 167207 (2003)
[4] F. Bisio et al., Phys. Rev. Lett. 96, 057204 (2006)
[5] Q. F. Zhan et al., Phys. Rev. B 80, 094416 (2009)

  • Lecture (Conference)
    IEEE International Magnetics Conference, Intermag 2011, 25.-29.04.2011, Tapei, Taiwan

Publ.-Id: 15723

Experiments for real time in-vivo dosimetry

Fiedler, F.

no abstract available

Keywords: in-vivo dosimetry; ion therapy; prompt gamma imaging; in-beam PET; TOF PET

  • Invited lecture (Conferences)
    KVI PAC Meeting, 22.06.2011, Groningen, The Netherlands

Publ.-Id: 15722

Operating a high QE photocathode inside a SRF gun, introducing the HZDR/ELBE SRF gun, and plans for operation of GaAs cathodes at HZDR

Teichert, J.

  • Lecture (Conference)
    Workshop on photocathodes for high brightness, high average current beams, 30.-31.05.2011, Berlin, Germany

Publ.-Id: 15720

Slice-Emittance Measurements at ELBE/SRF-Injector

Teichert, J.; Rudolph, J.; Kamps, T.; Abo-Bakr, M.

The linear accelerator ELBE delivers high-brightness electron bunches to multiple user stations, including an IR-FEL. The current thermionic injector is being replaced by a superconducting rf photoinjector (SRFinjector) which promises higher beam quality. Using a transfer chicane, beam from the SRF-injector can be injected into the ELBE linac. Detailed characterization of the electron beam is achieved by measuring the vertical slice emittance of the beam. To perform this measurement a combination of rf zero-phasing, spectrometer dipole and quadrupole scan is used. The electron beam is accelerated by the first cavity of the ELBE accelerator module and send through a second cavity which is operated at zero-crossing of the rf. In doing so a linear energy-time correlation is induced to the beam. The chirped beam is send through a spectrometer dipole and the longitudinal distribution can be made visible on a scintillator screen. Performing a quadrupole scan allows the determination of the emittance for di_erent slices. This paper explains the working principle of the method and the experimental setup and shows results of performed simulations as well as first measurement results.

  • Poster
    DIPAC 2011, 16.-18.05.2011, Hamburg, Deutschland
  • Open Access Logo Contribution to proceedings
    DIPAC 2011, 16.-18.05.2011, Hamburg, Deutschland
    Proceedings of DIPAC 2011, 416-418


Publ.-Id: 15719

Pulsed Mode Operation and Longitudinal Parameter Measurement of the Rossendorf SRF Gun

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

The Rossendorf SRF gun with a 3 1/2 cell cavity has been operated since 2007. It has produced CW beam with the electron energy of 3 MeV and the average current up to 16 μA. The electron beam of the gun has successfully injected the ELBE superconducting linac since 2010. The Nb cavity has shown constant quality during the operation and for the Cs2Te photocathode life time of months could be obtained. Recently the gun started to run in the pulsed mode with higher gradient. The longitudinal parameters have been measured in this mode. The dark current arose from the high gradient is studied. The main field emission source has been found to be the half cell. Meanwhile, two modified 3+1/2 cell niobium cavities have been fabricated and tested in Jlab. In this paper the new status of the SRF gun will be presented, and the latest results of the beam experiments will be discussed.

  • Poster
    IPAC 2011, 04.-09.09.2011, San Sebastian, Spain
  • Open Access Logo Contribution to proceedings
    IPAC 2011, 04.-09.09.2011, San Sebastian, Spain
    Proceedings of IPAC2011, 262-264


Publ.-Id: 15718

Operational Experience of NC Cathodes Inside SRF Gun Cavity

Teichert, J.

  • Lecture (Conference)
    Workshop on Photocathodes for RF guns, 01.-02.03.2011, Lecce, Italy

Publ.-Id: 15717

Cryostats and Mechanics

Murcek, P.

German-Turkish Workshop on Superconducting Accelerators for FEL and Bremsstrahlung Applications

  • Lecture (Conference)
    German-Turkish Workshop on Superconducting Accelerators for FEL and Bremsstrahlung, 31.01.-03.02.2011, Antalya, Turkey

Publ.-Id: 15715

Superconducting Resonators

Arnold, A.

  • Lecture (Conference)
    German-Turkish Workshop on Superconducting Accelerators for FEL and Bremsstrahlung Applications, 31.01.-03.02.2011, Antalya, Turkey

Publ.-Id: 15714

PET imaging of central σ 1 receptors: Automated synthesis and purification of [18F]fluspidine

Maisonial, A.; Funke, U.; Fischer, S.; Hiller, A.; Wünsch, B.; Steinbach, J.; Brust, P.

Objectives: Sigma1 (σ1) receptors represent attractive targets for the development of new therapeutic drugs and diagnostic imaging agents for various cerebral diseases. Currently, there is a growing interest in the development of selective and high affinity radioligands for in vivo imaging studies of these receptors using positron emission tomography (PET). With this view, we recently developed a promising fluorinated radioligand, [18F]fluspidine, which offers great potential for neuroimaging of central σ1 receptors with PET [1,2]. Herein we report on a first reliable and high yield automatic synthesis of [18F]fluspidine.
Methods: The synthesis of [18F]fluspidine was performed in a lead-shielded hot cell using a modified TRACERlab FXFN synthesizer. The synthesis module is schematized in Figure 1. First, target water solution was passed through a preconditioned anion exchange cartridge (1). Trapped [18F]fluoride was then eluted to the reactor (2) with a potassium carbonate solution (3). A solution of K2.2.2 in acetonitrile (4) was added and the mixture was dried azeotropically according to standard procedures. The K[18F]F-K2.2.2-carbonate complex reacted with the corresponding tosylate precursor in acetonitrile (5) at 85°C for 15 minutes. After cooling, the crude reaction mixture was diluted with water (6) and directly applied to an isocratic semi-preparative RP-HPLC for purification (7), featured by three optional systems of mobile (organic solvent/H2O with no, neutral or acidic buffer) and stationary phase (nonpolar and polar encapped RP). The appropriate fraction was collected in a flask prefilled with water (8) and the whole solution was passed through a solid phase extraction cartridge (9). The trapped radiotracer was then washed with water (10) and finally eluted to the product vial (11) with absolute ethanol (12).

Results: Nucleophilic radiofluorination of the tosylate precursor was optimized regarding reaction time, temperature and concentration to reach labelling efficiencies > 87%. After purification by semi-preparative HPLC and solid phase extraction methods, [18F]fluspidine was produced within 60-75 minutes for the entire process with an overall radiochemical yield of 37.9 ± 3.9% (based on cyclotron-produced [18F]fluoride ion). The radiochemical purity exceeded 99 % in all cases and the specific activity determined at the end of the process was > 120 GBq/µmol.
Conclusions: A rapid one-pot automated procedure for the regular and consistent production of [18F]fluspidine was successfully accomplished with highly reproducible yields as well as high radiochemical purity and specific activity. The implementation of this radiosynthesis into a commercial platform will make [18F]fluspidine easier accessible for further preclinical and clinical studies.
Research Support: This work was supported by the Deutsche Forschungsgemeinschaft.
References: [1] Große Maestrup, E. et al. (2011), Bioorg. Med. Chem., 19, 393-405, [2] Fischer, S. et al. (2011), Eur. J. Nucl. Med. Mol. Imaging., 38, 540-551.

  • Poster
    ISRS2011, 28.08.-02.09.2011, Amsterdam, The Netherlands
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011)1, 420-420

Publ.-Id: 15713

Radiosynthesis, in vitro and in vivo evaluation of a 7-(2-[18F]fluoroethoxy)-6-methoxyquinazoline derivative for imaging PDE10A with PET

Funke, U.; Schwan, G.; Scheunemann, M.; Maisonial, A.; Hiller, A.; Fischer, S.; Deuther-Conrad, W.; Egerland, U.; Briel, D.; Nieber, K.; Sträter, N.; Brust, P.

Objectives: To improve some of the cognitive symptoms of schizophrenia, a 6,7-dimethoxy-4-pyrrolidinylquinazoline has been designed as a potent and selective brain penetrable inhibitor of phosphodiesterase 10A (PDE10A, Ki,PDE10A = 4 nM [1]). Based on this structure we developed a 7-[18F]fluoroethoxy-derivative [18F]I as potential PET radiotracer for imaging PDE10A in brain.
Methods: Non-radioactive reference compounds and precursors were prepared by multi-step syntheses and screened for their PDE10A inhibition as well as selectivity in enzyme activity studies. Radiolabelling of the derivative of highest PDE10A inhibition was initially performed via conversion of 1,3-bistosyloxyethane into [18F]fluoroethyltosylate using n.c.a. K[18F]F-K2.2.2-carbonate complex, and subsequently direct etherification of a deprotonated 7-hydroxy-derivative II to [18F]I (Fig. 1, left-hand). Afterwards, one-step radiosynthesis was developed by direct substitution of a 7-tosyloxy-analogue III with n.c.a. [18F]fluoride (Fig. 1, right-hand). [18F]I was purified by SPE and semi-preparative radio-HPLC. Samples were monitored by radio-TLC and -HPLC. Lipophilicity (logD7.0-7.4) was determined by shake-flask as well as HPLC methods. Further pharmacological characterisation of [18F]I included in vitro determination of PDE10A affinity (KD,PDE10A, PDE10A transfected SF21 cells), in vivo biodistribution and brain uptake studies, metabolism and ex vivo brain autoradiography in female CD-1 mice, with validation of target specificity by homologous competition (I, 5 mg/kg at 15 min before radiotracer) and pre-treatment with high PDE10A specific MP-10 (5 mg/kg at 15 min before radiotracer).

Results: Two-step radiosyntheses of [18F]I resulted in radiochemical yields (RCY) of 18-29% (3.5-4.5 h, based on [18F]F- aqueous solution) and radiochemical purities (RP) of 92-99%. Improvement was obtained by direct radiofluorination: RCY of 17-40% (3-4 h), RP ≥ 99% and specific activities of 110-1110 GBq/mol. By homologous competition assays a KD,PDE10A of 14 nM was estimated. The logD7.0-7.4 was determined with ~ 2.6. According to this a sufficiently high initial brain uptake has been observed (2.3%ID/g at 5 min p.i. in striatum). However, radioligand binding in vivo (1.14%ID/g 60 min p.i.) was not inhibited by competition with I (1.3%ID/g) as well as MP-10 (1.4%ID/g). In plasma and brain, respectively, 70% and 96% of the radioactivity detected at 30 and 60 min p.i. corresponded to native radioligand. No evidence for defluorination of the radioligand was obtained.
Conclusions: Convenient radiochemical results, a moderate lipophilicity and a high PDE10A affinity indicate [18F]I to be a suitable radiotracer. However, further structural optimization is needed to improve the in vivo properties and to make this radioligand appropriate for neuroimaging of PDE10A with PET.
Research Support: Europäischer Fond für regionale Entwicklung (EFRE).
References: [1] Chappie, T.A. et al. (2007), J. Med. Chem., 50, 182-185.

  • Poster
    ISRS2011, 28.08.-02.09.2011, Amsterdam, The Netherlands
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011)1, 268-268

Publ.-Id: 15712

Synthesis and evaluation of THIQ based indoles as potential PET radioligands for imaging the serotonin transporter

Funke, U.; Ben-Daniel, R.; Scheunemann, M.; Fischer, S.; Hiller, A.; Rühl, T.; Deuther-Conrad, W.; Patt, M.; Mishani, E.; Steinbach, J.; Sabri, O.; Brust, P.

Objectives: The serotonin transporter (SERT) is crucial for the regulation of the synaptic concentration of serotonin and is a primary target in the development of antidepressants. To provide access to new efficient ligands for the SERT binding site for PET imaging, N-substituted tetrahydroisoquinoline (THIQ) derivatives both of electron-deficient 3-cyclohexyl and 3-propylindole were selected as lead. Thus, cis-5-cyanoindole-3-yl cyclohexylamine (CFPI, Ki,hSERT = 6.2 nM) labelled with fluorine-18 [1] and the 5-fluoroindole-3-yl propylamine (FMI, Ki,hSERT = 4.1 nM) labelled with carbon-11 [2] were developed as new PET-agents. Here we report on the labelling of CFPI and FMI, and the evaluation of both radiotracers in vivo.
Methods: [18F]CFPI was synthesized via nucleophilic etherification of the corresponding tetrahydroisoquinolin-6-ol with 1-[18F]fluoro-2-tosyloxyethane ([18F]FETos) as secondary labelling agent. It was obtained by a two-step process followed by semipreparative HPLC purification with an overall RCY of 13±7% (decay corrected EOB, total synthesis time 180 min). [11C]FMI was synthesized similarly by an etherification process of the corresponding tetrahydroisoquinolin-6-ol with [11C]CH3I to yield the product with RCY 10±4% (decay corrected EOB, total synthesis time 27 min). The brain uptake kinetics and the target specicficity of [18F]CFPI was investigated in female CD-1 mice by organ distribution at 5, 30, 60, and 120 min p.i., and blocking studies at 60 min p.i. (n=4 per time point). The distribution of [11C]FMI in the brain of juvenile pig was assessed by dynamic PET imaging under baseline and consecutively blocking conditions (n=2). Pre-treatment with citalopram (5 mg/kg) as selective SERT ligand was used to asses the specificity of the binding of [11C]FMI. For comparison, [11C]DASB was investigated in an additional animal.

Results: Radiotracers were obtained in radiochemical purity of ≥99%, with specific activity of 1500 GBq/µmol for [11C]FMI and 150 GBq/µmol for [18F]CFPI. PET scans were performed after i.v. injection of 0.5 – 1 GBq [11C]FMI. In comparison to [11C]DASB with a midbrain-to-cerebellum ratio of 2 at 120 min p.i., [11C]FMI displayed no specific accumulation in SERT-relevant regions (midbrain-to-cerebellum ratio ~1 at 120 min p.i.). Furthermore, pre-tretament with citalopram did not affect the uptake of [11C]FMI in different brain regions as observed by the time activity curves. Comparable results were obtained in biodistribution studies on [18F]CFPI. After i.v. injection of ~ 300 kBq [18F]CFPI, brain-to-plasma ratios of <1 were determined at each time up to 120 min p.i. Low clearance from the brain and other organs implies a high non-specific binding. Pre-treatment with citalopram was without effect on the activity distribution or elimination route of [18F]CFPI.
Conclusions: The in vivo data obtained for [11C]FMI in pig brain and [18F]CFPI in mice indicate a high non-specific binding of the two radiolabelled N-substituted THIQ derivatives. Therefore, both [11C]FMI and [18F]CFPI are not suitable as SERT-selective PET radioligands.
Research Support: Work was supported by DFG, BMBF and Joint German-Israeli Research Program (MOST #1888).
References: [1] Funke, U. et al. (2008), Biorg. Med. Chem. Lett. 18, 4727-3047, [2] Ben-Daniel, R. et al. (2008) Biorg. Med. Chem. 16, 6364-6370.

  • Poster
    ISRS2011, 28.08.-02.09.2011, Amsterdam, The Netherlands
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011)1, 284-284

Publ.-Id: 15711

Electron Sources

Teichert, J.

  • Lecture (Conference)
    German-Turkish Workshop on Superconducting Accelerators for FEL and Bremsstrahlung Applications, 31.01.-02.03.2011, Antalya, Turkey

Publ.-Id: 15710

Ge-Si-O phase separation and Ge nanocrystals growth in Ge:SiO2/SiO2 multilayers – A new dc magnetron approach

Zschintzsch, M.; Sahle, C. J.; von Borany, J.; Sternemann, C.; Mücklich, A.; Nyrow, A.; Schwamberger, A.; Tolan, M.

Ge:SiOx /SiO2 multilayers are fabricated using a new reactive dc magnetron sputtering approach. The influence of the multilayer stoichiometry on the ternary Ge–Si–O phase separation and the subsequent size-controlled Ge nanocrystal formation is explored by means of x-ray absorption spectroscopy, x-ray diffraction, electron microscopy and Raman spectroscopy. The ternary system Ge–Si–O reveals complete Ge–O phase separation at 400°C which does not differ significantly to the binary Ge–O system. Ge nanocrystals of < 5 nm size are generated after subsequent annealing below 700°C. It is shown that Ge oxides contained in the as-deposited multilayers are reduced by a surrounding unsaturated silica matrix. A stoichiometric regime was found where almost no GeO2 is present after annealing. Thus, the Ge nanocrystals become completely embedded in a stoichiometric silica matrix favouring the use for photovoltaic applications.

Keywords: annealing; elemental semiconductors; germanium; germanium nanocrystals; nanofabrication; nanoparticles; growth; quantum confinement; quantum dots; multilayer; phase separation; sub-oxides; Raman; phonon confinement, semiconductor growth; semiconductor thin films; silicon nanocrystals; sputter deposition; superlattices; transmission electron microscopy; tunnelling; X-ray scattering

Publ.-Id: 15708

The French accelerator mass spectrometry facility ASTER after 4 years: Status and recent developments on 36Cl and 129I

Arnold, M.; Aumaître, G.; Bourlès, D. L.; Keddadouche, K.; Braucher, R.; Finkel, R. C.; Nottoli, E.; Benedetti, L.; Merchel, S.

Since the acceptance tests of the French 5 MV accelerator mass spectrometry facility ASTER in 2007, routine measurement conditions for the long-lived radionuclides 10Be and 26Al have been established. Yearly sample throughput as high as over 3300 unknowns has been reached for 10Be in 2010. Unacceptable cross-contamination for volatile elements has been largely solved by an ion source upgrade allowing 36Cl measurements at ASTER. However, recent long-term tests using 35Cl/37Cl samples with strongly varying ratios have shown that identical targets lead to different 35Cl/37Cl results at the 2-4% level when being measured after a time gap of 24 hours while the source is running other samples. Besides time dependent mass fractionation, another very likely reason for this effect might be source memory, thus, asking for sophisticated measurement strategies and improved data evaluation and eventually further ion source improvement. Finally, after establishing quality assurance by cross-calibration of secondary in-house 26Al and 41Ca standards and taking part in round-robin exercises of 10Be and 36Cl, a two-step cross-calibration of secondary in-house 129I standards has been performed. The NIST 3231 containing 129I/127I at 0.981 x 10-6 has been used for step-wise dilution with NaI to produce gram-quantities of lower-level standards for every-day use. The resulting material SM-I-9 (129I/127I: ~1 x 10-9) has been measured vs. AgI produced from the two NIST ampoules with (0.982+0.012) x 10-8 solution using minimum chemistry. In a second stage, SM-I-10 and SM-I-11 with ratios of ~1 x 10-10 and ~1 x 10-11, respectively, have been cross-calibrated against SM-I-9. Individual uncertainties of the traceable secondary standards are 1.3-1.4 % (2σ), mainly originating from the given uncertainty of the primary NIST 3231 at 10-8. The cross-contamination for iodine is in the range of 0.4-0.6% within the first 20 hours of running the source.

Keywords: accelerator mass spectrometry; terrestrial cosmogenic nuclides (TCN); calibration

Publ.-Id: 15707

Fracture mechanics characterisation of forged base metal ring of the decommissioned reactor pressure vessel of NPP Greifswald WWER-440 unit 4

Viehrig, H.-W.; Houska, M.; Altstadt, E.; Kuechler, R.

The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald NPP representing the first generation of Russian type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs represent different material conditions viz. irradiated, irradiated & annealed and irradiated, annealed and re-irradiated. The paper presents test results measured on the trepan taken from the forged base metal ring 0.3.1. located in the reactor core region of the Unit 4 RPV. This unit was shut down after 11 years of operation and represents the irradiated condition. The key part of the testing is focused on the determination of the reference temperature T0 following the ASTM test standard E1921-10. The T0 of 11 thickness locations from the inner to the outer RPV wall varies between 112°C and 130°C with a mean value of 121°C. These are very low values for WWER RPV steel irradiated with fluences between 5.4 to 1.2•1019n/cm2 (E>0.5 MeV) from the inner to the outer RPV wall.
The fracture toughness values at cleavage failure, KJc, measured on LS oriented pre-cracked and side-grooved Charpy size SE(B) specimens from defined thickness locations of the forged ring strongly scatter. More than allowed 2% of the specimen size adjusted KJc-1T values lie below the fracture toughness curve for 2% fracture probability. The application of modified MC based evaluation methods indicates the material as non-homogeneous. Because of very low KJc values the SINTAP step 3 evaluation gave a maximum T0SINTAP of -40°C. The multimodal MC evaluation of KJc values from all thickness locations gives a T0MM of -118°C and a standard deviation of 25 K. The course of the fracture toughness curves evaluated by multi modal approach also do not represent the measured KJc values since more than 2% lie below the fracture toughness curve for 2% fracture probability. The reason for the occurrence of very low KJc values is seen in intergranular planes detected on the fractured surfaces of the specimens.

Keywords: reactor pressure vessel steel; neutron irradiation; fracture toughness; Master Curve approach; non-homogeneous steel; SINTAP; multimodal approach

  • Book chapter
    T. Yamamoto: Effects of Radiation on Nuclear Materials: 25th Volume, STP 1547, USA: ASTM International, 2013, 978-0-8031-7533-4
    DOI: 10.1520/STP104056

Publ.-Id: 15706

Trehalose renders dauer larva of Caenorhabditis elegans resistant to extreme desiccation

Erkut, C.; Penkov, S.; Khesbak, H.; Vorkel, D.; Verbavatz, J. M.; Fahmy, K.; Kurzchalia, T. V.

Water is essential for life on Earth. In the absence of it, however, some organisms are able to interrupt their life cycle and enter an ametabolic state, known as anhydrobiosis [1, 2]. Upon reappearance of water, anhydrobiotes can resume life activities. How can an organism cope with depletion of water? What are the molecular principles of anhydrobiosis? It is assumed that sugars (in particular trehalose) are instrumental for survival under anhydrobiotic conditions and for the preservation of cellular structure [3, 4]. However, the role of trehalose remained obscure since the corresponding evidence was purely correlative and based mostly on in vitro studies. So far, genetic manipulations on trehalose metabolism of anhydrobiotic animals with the aim to study desiccation tolerance have not been reported. In order to study molecular mechanisms of anhydrobiosis, we decided to make use of one of the best genetic models, Caenorhabditis elegans. In this study we show that C. elegans dauer larva is a true anhydrobiote: Under defined conditions it can survive extreme desiccation and lose up to 98% of its body water. This ability is correlated with a several fold increase in the amount of trehalose. To study the role of trehalose, we produced a strain that cannot synthesize it and show that mutant larvae do not survive even mild dehydration. This strain allowed us dissecting the function of trehalose on the cellular and molecular levels. Light and electron microscopy show that one of the major functions of trehalose on the cellular level is the preservation of membrane organization. Fourier-transform infrared spectroscopy of whole worms suggests that this is achieved by preserving homogeneous and compact packing of lipid acyl chains. The damage in the absence of trehalose occurs already during desiccation and spectroscopy allows distinguishing a “dry, yet alive” larva from a “dry and dead” one.

Keywords: in vivo infrared spectroscopy; lipid order; anhydrobiosis

  • Current Biology 21(2011)15, 1331-1336

Publ.-Id: 15705

Motion compensation in emission tomography

van den Hoff, J.; Langner, J.

With the ever-improving spatial resolution available in single photon emission computed tomography (SPECT) and, especially, in positron emission tomography (PET), the unavoidable organ and subject motion is becoming one of the dominant factors limiting the practically achievable spatial resolution in the tomographic images. Moreover, uncorrected subject motion can lead to potentially severe image artifacts and compromise the quantitative integrity of the data.The latter is of special importance in PETwhere quantitative assessment of tracer concentrations is commonplace both in static investigations via so-called standardized uptake values (SUVs) and in dynamic studies aiming at tracer kinetic modeling and quantification of the corresponding transport constants. Correction of the heart cycle – related motion in cardiac applications has a long tradition and is covered extensively in the literature. Correction of breathing-related organmotion in emission tomography, however, has drawn considerable interest only in recent years in the context of oncological PET.This ismainly due to the demands of therapy responsemonitoring and radiation treatment planning. The third important area is high-precision motion correction of random head motion in brain investigations. In this chapter, we give an overview of the methods employed to minimize – and possibly eliminate – the motion influence in emission tomography.

  • Book chapter
    C. Grupen and I. Buvat: Handbook of particle detection and imaging, Berlin, Heidelberg: Springer, 2011, 978-3-642-13270-4, 1007-1043

Publ.-Id: 15704

Photoinduced Melting of Antiferromagnetic Order in La0:5Sr1:5MnO4 Measured Using Ultrafast Resonant Soft X-Ray Diffraction

Ehrke, H.; Tobey, R. I.; Wall, S.; Cavill, S. A.; Fo¨Rst, M.; Khanna, V.; Garl, T.; Stojanovic, N.; Prabhakaran, D.; Boothroyd, A. T.; Gensch, M.; Mirone, A.; Reutler, P.; Revcolevschi, A.; Dhesi, S. S.; Cavalleri, A.

We used ultrafast resonant soft x-ray diffraction to probe the picosecond dynamics of spin and orbital order in La0:5Sr1:5MnO4 after photoexcitation with a femtosecond pulse of 1.5 eV radiation. Complete melting of antiferromagnetic spin order is evidenced by the disappearance of a (0.25; 0.25; 0.5) diffraction peak. On the other hand, the (0.25; 0.25; 0) diffraction peak, reflecting orbital order, is only partially reduced. We interpret the results as evidence of destabilization in the short-range exchange pattern with no significant relaxation of the long-range Jahn-Teller distortions. Cluster calculations are used to analyze different possible magnetically ordered states in the long-lived metastable phase. Nonthermal coupling between light and magnetism emerges as a primary aspect of photoinduced phase transitions in manganites.

Publ.-Id: 15703

THz control in correlated electron solids: sources and applications

Foerst, M.; Hoffmann, M.; Dienst, A.; Kaiser, S.; Rini, M.; Tobey, R. I.; Gensch, M.; Manzoni, C.; Cavalleri, A.

Materials with strongly correlated electrons often show rich phase diagramswith dramatic differences in physical properties as doping, applied pressure, or magnetic fields are changed. Even subtle perturbations can cause colossal rearrangements in the electronic spectrum, and irradiation with light can be used to drive spectacular rearrangements in the structural, electronic, and magnetic properties.
Here, we discuss the use of THz radiation to selectively excite one single degree of freedom at a time to drive a phase change. This is in contrast to what is done in most studies, which achieve photo-induced phase transitions by non-specific excitation in the visible spectral range. This chapter will combine a summary of developments in instrumentation for strong THz fields with some selected scientific applications of THz control of correlated electron systems.

  • Book chapter
    K.-E. Peiponen et al.: Terahertz Spectroscopy and Imaging, Springer Series in Optical Sciences 171, Berlin Heidelberg: Springer-Verlag, 2012
    DOI: 10.1007/978-3-642-29564-5_23

Publ.-Id: 15702

Probing properties of nuclear matter with HADES

Pietraszko, J.; Agakishiev, G.; Balanda, A.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Huck, P.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Lang, S.; Lange, J. S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Moriniere, E.; Mousa, J.; Müntz, C.; Naumann, L.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Pechenov, V.; Pechenova, O.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wendisch, C.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

This paper presents a review of selected physics results obtained at GSI Helmholtzzentrum für Schwerionenforschung GmbH by HADES (High-Acceptance Di-Electron Spectrometer). The e+e− pair emission measured for proton and heavy-ion induced collisions is reported together with results on strangeness production. The future HADES activities at the planned FAIR facility are also discussed.

  • Open Access Logo Proceedings of Science (2011), PoS(BORMIO2011)054

Publ.-Id: 15701

Structural and functional investigation of astaxanthin binding to the catalytic domain of matrix metalloprotease MMP-13

Sayed, A.; Elsayed, M. M.; Tucker, P.; Fahmy, K.

Matrix metalloproteases (MMPs) are zinc-containing proteases involved in the remodeling and breakdown of extracellular matrix proteins. Overexpression of the MMPs has been associated with a variety of diseases ranging from periodontal disease and arthritis to tumor invasion and metastasis. The majority of the more powerful synthetic inhibitors of MMPs incorporate a hydroxamate group, but exhibit low selectivity and are toxic. In a recent modeling study, Astaxanthin (AST), a carotenoid with potent antioxidant property, has been shown to be a potential inhibitor of MMP-13 function by occupying a binding site near the active center of the enzyme (Bika´di et. al. 2006). In our ongoing project, we investigate the binding of AST to the catalytic domain of MMPs using biochemical and ultimately crystallization to validate the proposed action of AST. Along these lines, the catalytic domain of MMP-13 (cdMMP-13) was expressed in E.coli BL21(DE3) CodonPlus and refolded using a novel effective refolding method. Our results reveal that AST has a potent inhibitory effect on cdMMP-13 activity, however, determination of IC50% or Ki is difficult due to fast oxidation and structural instability of AST. Ongoing work aims at optimizing the inhibition conditions and improving the refolding yield to allow analyzing structure and function of the AST-bound MMP-13 in more detail.
Bikádi et al. (2006) Bioorg Med Chem 14:5451-8.

  • Contribution to proceedings
    8th European Biophysics Congress, 23.-27.08.2011, Budapest, Hungary
    European Biophysics Journal with Biophysics Letters 40 (2011), 58-59

Publ.-Id: 15700

Spectroscopic investigation of the structure and function of the copper ATPase CopB of Enterococcus hirae

Groß, M.; Solioz, M.; Fahmy, K.

The Cu+-ATPase CopB of Enterococcus hirae is a bacterial P-type ATPase involved in resistance to high levels of environmental copper by expelling excess copper. The membrane protein CopB was purified from an over-expressing strain and solubilized in dodecyl-maltoside. By UV circular dichroism the secondary structure is predicted to contain 40-50 % alpha-helices and 10-15% beta-sheets in agreement with estimates based on homology with the Ca ATPase SERCA1. We present CD-spectroscopic data on thermal unfolding of the protein to address the influence of the binding of the ATP analogs ATPgS and the fluorescent analog mant-ATP on the protein stability. Such analogs are used to mimic functional states of the ATPase but undergo different interactions with the binding site that are not well characterized. We propose a competition-based assay for nucleotide binding using CD-spectroscopy to deduce the occupancy of the nucleotide-binding site by non-fluorescent nucleotides. Alternatively, the change of intrinsic fluorescence of mant-ATP upon binding to the ATPase is exploited in these assays. Finally, we show how the simultaneous measurement of protein CD and nucleotide fluorescence in thermal denaturation experiments may help to determine the stability of several functional conformational states of CopB.

Keywords: circular dichroism; nucleotide binding

  • Contribution to proceedings
    8th European Biophysics Congress, 23.-27.08.2011, Budapest, Hungary
    European Biophysics Journal with Biophysics Letters 40 (2011), 168

Publ.-Id: 15699

FTIR and calorimetric investigation of the effects of trehalose and multivalent cations on lipid structure

Abu Sharkh, S.; Oertel, J.; Fahmy, K.

The structure of membrane lipids is of fundamental importance for the integrity of cell and organelle membranes in living organisms. Membrane lipids are typically hydrated and their headgroup charges counter-balanced by solvated ions. Consequently, water loss can induce severe structural changes in lipid packing (lyotropic transitions) and can lead to the damage of lipid membranes even after rehydration. This can be one out of several factors that affect the viability of organisms undergoing desiccation. Many organisms, however, are resistant to even extreme water loss. Some of them synthesize trehalose which has been shown to be associated with survival of desiccation in phylogenetically diverse organisms (yeast, nematodes, brine shrimp, insect larvae, resurrection plants, and others). Here we have studied hydration sensitive transitions in model lipids to determine the effect of trehalose and electrostatics on lipid order. Hydration pulse-induced time-resolved Fourier-transform infrared (FTIR) difference spectroscopy was used to address hydration-dependent lipid structure as a function of trehalose. In combination with differential scanning calorimetry and studies of Langmuir-Blodget films we arrive at a structural and energetically consistent picture of how trehalose can affects lipidic phase behaviour and support a native lipid structure under water loss. Experiments were performed on model lipids with different headgroups and native lipids from desiccation-tolerant organisms.

Keywords: infrared spectroscopy; anhydrobiosis

  • Contribution to proceedings
    8th European Biophysics Congress, 23.-27.08.2011, Budapest, Hungary
    European Biophysics Journal with Biophysics Letters 40 (2011), 72

Publ.-Id: 15698

Coupling of the hydration shell of B-DNA to conformational substates and peptide recognition studied by time-resolved FTIR spectroscopy

Khesbak, H.; Savchuk, O.; Tsushima, S.; Fahmy, K.

Biomolecular recognition typically proceeds in an aqueous environment, where hydration shells are a constitutive part of the interacting species. The coupling of hydration shell structure to conformation is particularly pronounced for DNA with its large surface to volume ratio. Conformational substates of the phosphodiester backbone in B-DNA contribute to DNA flexibility and are strongly dependent on hydration. We have studied by rapid scan FTIR spectroscopy the isothermal BI-BII transition on its intrinsic time scale of seconds. Correlation analysis of IR absorption changes induced by an incremental growth of the DNA hydration shell identifies water populations w1 (PO2--bound) and w2 (non-PO2--bound) exhibiting weaker and stronger H-bonds, respectively, than those in bulk water. The BII substate is stabilized by w2. The water H-bond imbalance of 3-4 kJ mol-1 is equalized at little enthalpic cost upon formation of a contiguous water network (at 12-14 H2O molecules per DNA phosphate) of reduced (OH) band width. In this state, hydration water cooperatively stabilizes the BI conformer via the entropically favored replacement of w2-DNA interactions by additional w2-water contacts, rather than binding to BI-specific hydration sites. Such water rearrangements contribute to the recognition of DNA by indolicidin, an antimicrobial 13-mer peptide from bovine neutrophils which, despite little intrinsic structure, preferentially binds to the BI conformer in a water-mediated induced fit. In combination with CD-spectral titrations, the data indicate that in the absence of a bulk aqueous phase, as in molecular crowded environments, water relocation within the DNA hydration shell allows for entropic contributions similar to those assigned to water upon DNA ligand recognition in solution.

Keywords: infrared spectroscopy; molecular recognition; DNA structure

  • Contribution to proceedings
    8th European Biophysics Congress, 23.-27.08.2011, Budapest, Hungary
    European Biophysics Journal with Biophysics Letters 40 (2011), 45

Publ.-Id: 15697

Flash II: Perspectives and challenges

Faatz, B.; Baboi, N.; Ayvazyan, V.; Balandin, V.; Decking, W.; Duesterer, S.; Eckoldt, H.; Feldhaus, J.; Golubeva, N.; Honkavaara, K.; Koerfer, M.; Laarmann, T.; Leuschner, A.; Lilje, L.; Limberg, T.; Noelle, D.; Obier, F.; Petrov, A.; Ploenjes, E.; Rehlich, K.; Schlarb, H.; Schmidt, B.; Schmitz, M.; Schreiber, S.; Schulte-Schrepping, H.; Spengler, J.; Staack, M.; Tavella, F.; Tiedtke, K.; Tischer, M.; Treusch, R.; Vogt, M.; Willner, A.; Bahrdt, J.; Follath, R.; Gensch, M.; Holldack, K.; Meseck, A.; Mitzner, R.; Drescher, M.; Miltchev, V.; Ronsch-Schulenburg, J. J.; Rossbach, J.

FLASH has been a user facility since 2005, delivering radiation in the wavelength range between 7 and 47 nm using the SASE principle. After the present upgrade, the wavelength range is extended to 4.45 nm. With the third harmonic accelerating module in place to linearize the longitudinal phase space, the stability and reproducibility of the machine is substantially improved. The user requests for beam time by far exceeds the time available. In order to increase user beam time and to improve the radiation properties delivered to users, a major extension of the user facility called FLASH II has been proposed by DESY in collaboration with the HZB. FLASH II is a seeded FEL in the parameter range of FLASH. As logical continuation, the seeding with HHG which started with sFLASH will result in direct seeding. Because in the foreseeable future there will probably not be HHG seed lasers available at high repetition rates down to wavelengths of 4 nm, a cascaded HGHG scheme is proposed to produce short wavelengths.
After a first design report, the project now enters its technical design phase. During this time, the FLASH beam parameters after the present upgrade 2009/2010 will be characterized and the present design will be re-evaluated and adjusted. In addition, start-to-end simulations will complete the simulations which have been performed so far, including a design of the extraction area.

Keywords: Free-electron laser; XUV FEL

Publ.-Id: 15696

Few-femtosecond timing at fourth-generation X-ray light sources

Tavella, F.; Stojanovic, N.; Geloni, G.; Gensch, M.

Fourth-generation X-ray light sources are being developed to deliver laser-like X-ray pulses at intensities and/or repetition rates that are beyond the reach of table-top devices. An important class of experiments at these new facilities comprises pump–probe experiments, which are designed to investigate chemical reactions and processes occurring on the molecular or even atomic level, and on the timescale of a few femtoseconds. Good progress has been made towards the generation of ultrashort X-ray pulses (for example, at FLASH1 or LCLS2),but experiments suffer from the intrinsic timing jitter between the X-ray pulses and external laser sources3. In this Letter, we present a new approach that provides few-femtosecond temporal resolution. Our method uses coherent terahertz radiation generated at the end of the X-ray undulator by the same electron bunch that emits the X-ray pulse. It can therefore be applied at any advanced light source working with ultrashort electron bunches and undulators.

Publ.-Id: 15695

The new 6 MV-AMS-facility DREAMS at Dresden

Akhmadaliev, S.; Heller, R.; Hanf, D.; Rugel, G.; Merchel, S.

A new 6 MV electrostatic tandem accelerator has been put into operation at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). It will be used for ion beam analysis as well as for material modification via high-energy ion implantation. The system is also equipped for accelerator mass spectrometry and opens a new research field at HZDR and the Helmholtz Association. The research activity at the DREsden Accelerator Mass Spectrometry facility (DREAMS) based on a 6 MV Tandetron is primarily dedicated to the long-lived radioisotopes of 10Be, 26Al, 36Cl, 41Ca, and 129I.
DREAMS background levels have been found of 4.5·10-16 for 10Be/9Be, 8·10-16 for 26Al/27Al, 3·10-15 for 36Cl/35Cl and 8·10-15 for 41Ca/40Ca, respectively. The observed background of 2·10-13 for 129I/127I originates from intrinsic 129I from AgI produced from commercial KI (MERCK).
During first experiments at the accelerator an energy calibration of the machine has been carried out. For this purpose the 1H(15N,γ α)12C nuclear reaction has been used. The charge states of the 15N ion of 1+, 2+ and 3+ corresponding to different terminal voltages of the accelerator have been chosen to obtain an absolute energy calibration.

Keywords: Accelerator Mass Spectrometry; AMS; electrostatic accelerator

  • Contribution to proceedings
    AMS-12, Twelfth International Conference on Accelerator Mass Spectrometry, 21.-25.03.2011, Wellington, New Zealand
    Accelerator Mass Spectrometry, Nucl. Instr. and Meth. B (2012), North-Holland: Elsevier

Publ.-Id: 15694

Bio-Au nanoparticles on archaeal and bacterial S-layers

Selenska-Pobell, S.; Reitz, T.; Geißler, A.; Merroun, M. L.; Herrmannsdoerfer, T.

Gold nanoparticles with substantially different properties were produced by using two alternative S-layer templates. The first one was a bacterial template, representing sheets of the S-layer of Bacillus sphaericus; the second one was in a form of empty cells (ghosts) consisting of the so-called SlaA-layer of the thermoacidophilic archaeon Sulfolobus acido-caldarius. The archaeal SlaA-layer is resistant not only to high temperatures and acidity but also to detergents, that allowed to purify the SlaA-layer-ghosts keeping the shape of the cells. The production of the Au nanoparticles was performed according to [1,2] in a two-step procedure by using DMAB as a reducing agent.
We demonstrate that the SlaA-ghosts of S. acido-caldarius serve as a very efficient template for complete reduction of Au(III) to Au(0). In the case of using S-layer sheets of B. sphaericus only 40 % of the added Au(III) was reduced to Au(0) [2]. The size of the archaeal bio-Au nanoparticles was about 2.5 nm, while those of the bacterial ones was about 4 nm. The most stricking property of the archaeal bio-Au nanoparticles is, however, that that they are paramagnetic, in contrast to the bacterial ones and also to bulk gold, which are diamagnetic. As demonstrated by SQUID magnetometry, the archaeal bio-Au possesses an unusually large magnetic moment of about 0.1 µB/Au atom. HR-TEM combined with EDX analysis revealed that the archaeal Au nanoparticles are bound to sulfur atoms. The latter originate from the thiol groups of the cystein amino acid residues which are characteristic for the SlaA-layer of S. acidocaldarius but absent in the S-layer of B. sphaericus. Surprisingly, the magnetic moment of the archaeal bio-Au nanoparticles is substantially larger than the ones observed for thiol capped, chemically produced Au nanoclusters [3]. We suggest that the unusual shape and the biochemical characteristics of the SlaA-ghosts are responsible for the observed extraordinary properties of the archaeal bio-Au.

[1] Merroun et al. (2007) Mat. Sc. Tech. 27, 188-192.
[2] Jankovski et al. (2010) Spectroscopy 24, 177-181, 2010.
[3] Crespo et al. (2004) Phys. Rev. Lett. 93, 087204.

  • Lecture (Conference)
    Goldschmidt2011, 14.-19.08.2011, Prague, Czech Republic

Publ.-Id: 15693

Combined correction of recovery effect and motion blur for SUV quantification of solitary pulmonary nodules in FDG PET/CT

Apostolova, I.; Wiemker, R.; Paulus, T.; Kabus, S.; Dreilich, T.; van den Hoff, J.; Plotkin, M.; Mester, J.; Brenner, W.; Burchert, R.; Klutmann, S.

Objective: We evaluate a fully data-driven method for the combined recovery and motion blur correction of small solitary pulmonary nodules (SPNs) in F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT).
Methods: The SPN was segmented in the low-dose CT using a variable Hounsfield threshold and morphological constraints. The combined effect of limited spatial resolution and motion blur in the SPN’s PET image was then modelled by an effective Gaussian point-spread function (psf). Both isotropic and non-isotropic psfs were used. To validate the method, PET/CT measurements of the NEMA/IEC spheres phantom were performed. The method was applied to 50 unselected SPNs ≤30 mm from routine patient care.
Results: Recovery of standardised uptake value (SUV) in the phantom image was significantly improved by combined recovery and motion blur correction compared with recoveryonly correction, particularly with the non-isotropic model (residual average error 10%). In the patient images, automated segmentation and fit of the effective psf worked properly in all cases. Volume-equivalent diameter ranged from 4.9 to 27.8 mm. Uncorrected maximum SUV ranged from 0.9 to 13.3. Compared with recoveryonly correction, combined correction with the non-isotropic model resulted in a ‘relevant’ (≥30%) SUV increase in 47 SPNs (94%).
Conclusions: Correction of both recovery and motion blur is mandatory for accurate SUV quantification of SPNs.

Keywords: Solitary pulmonary nodule; FDG; SUV; Recovery correction; Motion correction

Publ.-Id: 15692

Radiotracer studies on the mobility of radionuclides in clay matrices containing organic matter: Elementary processes and influence of heterogeneous structures

Lippold, H.; Kulenkampff, J.; Gründig, M.; Lippmann-Pipke, J.

In einem Übersichtsvortrag wurden die wesentlichen Forschungsergebnisse vorgestellt, die in der zurückliegenden Bewilligungsphase des Verbundprojektes erzielt wurden. Themenschwerpunkte des Vortrages waren (i) die Rekonstruktion ternärer Systeme (Metall / Huminstoff / Tonmineral) aus Verteilungskoeffizienten in den binären Randsystemen, (ii) Zeitabhängigkeiten im Konkurrenzeffekt von Fe(III) und Al(III) bzgl. der Huminstoff-Komplexbildung von Radionukliden, (iii) Dynamik von Huminstoff-Adsorptionsgleichgewichten, (iv) PET-Untersuchungen von Transportprozessen in intaktem Opalinuston, (v) Monte-Carlo-Simulation von Streuprozessen zur PET-Bildkorrektur.

  • Lecture (others)
    Abschlussworkshop zum Verbundvorhaben "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 17.-18.05.2011, Karlsruhe, Deutschland

Publ.-Id: 15691

An Experiment-Based Approach for Predicting Positron Emitter Distributions Produced during Therapeutic Ion Irradiation

Priegnitz, M.; Fiedler, F.; Kunath, D.; Laube, K.; Enghardt, W.

In-beam positron emission tomography (PET) is a valuable method for a beam-delivery independent dose monitoring in radiation therapy with ion beams. Up to now, its clinical feasibility has been demonstrated for patient irradiation with carbon ions. From radiobiological point of view it is highly desirable to perform tumor irradiation also with other light ions. To extend the application of in-beam PET also to these ions, extensive knowledge about positron emitter production via nuclear fragmentation reactions during ion irradiation is necessary. To model the positron emitter production correctly, cross sections for all possible nuclear reactions occurring in the tissue during irradiation and leading to positron emitters are required. Since these cross sections are available only for a few reaction channels in the required energy range, a novel approach for estimating the positron emitter production from experimental data is introduced. The prediction of positron emitter distributions is based on depth dependent thick target yields, which are derived by linear superposition of measured yields in water, graphite and polyethylene as reference materials. Results on the prediction of positron emitter distributions in polymethyl methacrylate (PMMA) as well as inhomogeneous targets induced by lithium and carbon irradiation are presented. By comparison with data deduced from experiments, it is shown that a rather accurate prediction of positron emitter distribution is feasible using this method.

Keywords: In-beam positron emission tomography; ion beam tumor therapy; positron emitter distribution; prediction method

Publ.-Id: 15690

Hydrogen mediated ferromagnetism in ZnO single crystals

Khalid, M.; Esquinazi, P.; Spemann, D.; Anwand, W.; Brauer, G.

We investigated the magnetic properties of hydrogen plasma treated ZnO single crystals by SQUID magnetometry. In agreement with the expected hydrogen penetration depth we found ferromagnetic behavior located at the first 20 nm of the H-treated surface of ZnO with magnetization at saturation up to 6 emu/g at 300 K and Curie temperature Tc > 400 K. In the ferromagnetic samples a hydrogen concentration of a few atomic percent in the first 20 nm surface layer was determined by nuclear reaction analysis. The saturation magnetization of H-treated ZnO increases with the concentration of hydrogen.

Keywords: ZnO; hydrogen plasma treatment; ferromagnetic behavior

  • Open Access Logo New Journal of Physics 13(2011), 063017

Publ.-Id: 15689

Two-region diffusion model for the improved analysis of ADS experiments

Glivici-Cotruţă, V.; Merk, B.

A fast lead core and an external neutron source create rapidly varying transients in which the spatial and time effects are important, and, in combination with a thick lead reflector, impose a constraint on an application of the traditional point reactor kinetics approximation. Thereby, for the foreseen GUINEVERE experiments a two-region space and time dependent diffusion approximation was chosen to be solved and analysed. It is necessary to represent the solution for two-region core owing to a presence of an external neutron source, sub-criticality of the system, and an increasing impact of the reflector in a small experimental reactor, as well as due to the inaccuracy of the diffusion approximation around the core reflector, core blanket interfaces, and throughout fast reactor blankets. This two-region solution without separation of space and time gives a significantly improved methodology for the analysis of the future experiments like GUINEVERE. The efficiency of the derived solution over the accurate numerical solutions (like Monte Carlo calculation, for example) lies in a comparatively short calculation time, which is of major importance for the on-line monitoring the reactivity of a subcritical reactor system.

Keywords: Yalina; experimental analysis; Green’s function; Two-region diffusion equation; GUINEVERE experiment

  • Open Access Logo Contribution to proceedings
    The 22nd International Conference on Transport Theory, 11.-15.09.2011, Portland, USA
  • Lecture (Conference)
    The 22nd International Conference on Transport Theory, 11.-15.09.2011, Portland, USA

Publ.-Id: 15688

Evaluation of the ASTM and ISO J initiation procedures by applying the unloading compliance technique to reactor pressure vessel steels

Arora, K. S.; Viehrig, H.-W.

Other than the brittle failure, the ductile behavior of the aged reactor pressure vessels (RPV) steels is also of interest for the integrity assessment and the evaluation of the irradiation response. The fracture toughness of high toughness materials like RPV steels can be characterized by a J-R curve. Since, the RPV steel material available for testing purposes, like surveillance specimens is limited the single specimen method is used for J-R curve determination. In this study, J-R curves were measured on Charpy size SE(B) and 1T-C(T) specimens of different RPV steels in the un¬irradiated and irradiated condition. It was observed that despite the available sophisticated instrumentation and strict implementation of the recommended test procedures, J-initiation value for all the different material specimens tested, could not be ascertained according to the tests standards ASTM E1820-09 und ISO 12135. For charpy size SE(B) specimens, it was found that though in irradiated condition valid JIc/J0.2BL values could be obtained but in un-irradiated condition especially for high toughness RPV steels it was not possible. The evaluation showed that the aoq fit of the ASTM standard compensates uncertainties in the initial J-Δa value resulting in reliable and more number of qualified test results. But these uncertainties strongly influence the A parameters of the ISO fit and the J0.2BL(B) value. Additionally, in ISO evaluation, the lower offset of the first exclusion line and a higher slope results in lower J0.2BL values compared to ASTM analysis. Furthermore, for the two specimen geometries the course of J-R curves up to the JQ value was similar even for high toughness material, but the lower specimen size was disqualified due to the lower prescribed Jlimit.. Similarly, the J-R curves for un-irradiated and irradiated condition had a similar course up to the J0.2BL value, even for extremely high irradiation induced embrittlement.

Keywords: fracture toughness; ductile tearing; J-R curve; single specimen approach; unloading compliance; ASTM E1820; ISO 12135; reactor pressure vessel steels

  • Journal of Testing and Evaluation 39(2011)6, 10.1520/JTE103405
    DOI: 10.1520/JTE103405

Publ.-Id: 15687

Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling

Kehr, S. C.; Liu, Y. M.; Martin, L. W.; Yu, P.; Gajek, M.; Yang, S.-Y.; Yang, C.-H.; Wenzel, M. T.; Jacob, R.; von Ribbeck, H.-G.; Helm, M.; Zhang, X.; Eng, L. M.; Ramesh, R.

A planar slab of negative-index material works as a superlens with sub-diffraction-limited resolution, as propagating waves are focused and, moreover, evanescent waves are reconstructed in the image plane. Here we demonstrate a superlens for electric evanescent fields with low losses using perovskites in the mid-infrared regime. The combination of near-field microscopy with a tunable free-electron laser allows us to address precisely the polariton modes, which are critical for super-resolution imaging. We spectrally study the lateral and vertical distributions of evanescent waves around the image plane of such a lens, and achieve imaging resolution of λ/14 at the superlensing wavelength. Interestingly, at certain distances between the probe and sample surface, we observe a maximum of these evanescent fields. Comparisons with numerical simulations indicate that this maximum originates from an enhanced coupling between probe and object, which might be applicable for multifunctional circuits, infrared spectroscopy and thermal sensors.

Keywords: Physical Sciences; Materials science; Optical physics; near-field microscopy; infrared

Publ.-Id: 15686

Temperature dependence of complexation, sorption and diffusion in the system uranium(VI)/clay organics/clay rock

Schmeide, K.; Joseph, C.; Steudtner, R.

The temperature dependence of U(VI) lactate and citrate complexation as well as the temperature dependence of the U(VI) migration in Opalinus Clay in the absence and presence of clay organics is shown.

Keywords: U(VI); complexation; sorption; diffusion; Opalinus Clay; citric acid

  • Lecture (others)
    Abschlussworkshop zum Verbundvorhaben "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 17.-18.05.2011, Karlsruhe, Deutschland

Publ.-Id: 15684

Structural modifications induced by FIB implantation in magnetic thin films

Roshchupkina, O. D.; Grenzer, J.; Strache, T.; McCord, J.; Fritzsche, M.; Muecklich, A.; Baehtz, C.; Fassbender, J.

Recently, there is a rise of interest in fabrication and investigation of nanometre sized magnetic objects. Magnetic properties can easily be manipulated by ion beam implantation. Focused-ion beam (FIB) techniques are one way to combine both nanopatterning and implantation. The main difference between standard ion implantation and FIB implantation is the beam current density, which could lead to differences in the structural and magnetic properties. The aim of this work is to compare both implantation techniques in terms of structural changes and to relate them to magnetic property changes.
For our investigation we have used 50 nm thick non-ordered nano-crystalline permalloy (Ni81Fe19) films modified by a 30 keV Ga+ ion beam. The magnetic properties were characterised via magneto-optic Kerr effect measurements at room temperature. Both types of implantation demonstrate a degradation of saturation magnetisation with increasing ion fluence. For structural investigations we have applied several techniques. We have used the advantage of non-destructive X-ray techniques to study the structural changes. Besides X-ray diffraction, providing the long-range order information, EXAFS measurements to probe the local structure were performed. Both methods are statistical ones, whereas TEM imaging provides information on a local scale.
Implantation leads to a crystallite growth from ~12 nm up to ~25 nm and further texturing of the material towards (111) direction at almost constant lattice parameter. In the case of FIB implanted samples the TEM images show crystallites growing through the entire film at high implantation fluences. The EXAFS analysis shows an almost perfect near-order coordination, corresponding to an fcc cell; only in the vicinity of the Ga atoms a small local deviation could be observed. In general FIB and standard implantation demonstrate similar behaviour with a shift in the fluence value. These results let us conclude that the simple presence of the Ga atoms is the dominating effect leading the degradation of saturation magnetisation.

Keywords: Focused-ion beam; EXAFS

  • Lecture (Conference)
    8th Autumn School on X-ray Scattering from Surfaces and Thin Layers, 04.-07.10.2011, Smolenice, Slovakia

Publ.-Id: 15683

FIB induced structural modifications in thin magnetic films

Roshchupkina, O.; Grenzer, J.; Strache, T.; Fritzsche, M.; Mücklich, A.; Fassbender, J.

Focused ion beam irradiation is a versatile tool that can be used for magnetic nanostructuring. In this work we compare both FIB irradiation and a standard implantation taking into account their distinctive irradiation features. A 50nm thick permalloy layer (Ni80Fe20) irradiated with different Ga+ ion fluences was used for the investigations. The structure was studied via XRD and EXAFS measurements carried out on the ESRF ROBL and ID01 facilities. Additionally TEM and magneto-optic Kerr effect magnetometry were performed. Both types of irradiation demonstrate a similar behaviour: increasing the ion fluence causes a further material crystallization and a decrease of the magnetic moment. However FIB irradiation leads to a stronger crystallite growth due to the high current densities used.

Keywords: Focused ion beam; EXAFS

  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM), 13.-18.03.2011, Dresden, Germany

Publ.-Id: 15682

Nonvolatile bipolar resistive switching in Au/BiFeO3/Pt

Shuai, Y.; Zhou, S.; Bürger, D.; Helm, M.; Schmidt, H.

Nonvolatile bipolar resistive switching has been observed in an Au/BiFeO3/Pt structure, where a Schottky contact and an Ohmic contact were formed at the Au/BiFeO3 and BiFeO3/Pt interface, respectively. By changing the polarity of the external voltage, the Au/BiFeO3/Pt is switched between two stable resistance states without an electroforming process. The resistance ratio is larger than two orders of magnitude. The resistive switching is understood by the electric field – induced carriers trapping and detrapping, which changes the depletion thickness.

Keywords: BiFeO3; nonvolatile; resistive switching; Schottky

  • Journal of Applied Physics 109(2011), 124117

Publ.-Id: 15681

Experimental investigation of the collection efficiency of a PTW Roos ionization chamber irradiated with pulsed beams at high pulse dose with different pulse lengths

Karsch, L.; Richter, C.; Pawelke, J.

In gas-filled ionization chambers as radiation detectors, the collection of the charge carriers is affected by the recombination effect. In dosimetry this effect must be accounted for by the saturation correction factor k(S). The physical description of the correction factor by Boag, Hochhauser and Balk for pulsed radiation is well established. However, this description is only accurate when the pulse length is short compared to the collection time of the ionization chamber. In this work experimental investigations of the saturation correction factor have been made for pulses of 4 mu s up to pulse doses of about 230 mGy, and the theory of Boag, Hochhauser and Balk was again confirmed. For longer pulses, however; the correction factor decreases and at a pulse duration of about 200 mu s reaches 75% of the value valid for short pulses. This reduced influence of the ion recombination is interpreted by the reaction kinetics of ion recombination as a second-order reaction. This effect is negligible for PTW Roos chambers at clinical linear accelerators with 4 mu s pulse duration for pulse doses up to 120 mGy.

Publ.-Id: 15680

THEREDA - Thermodynamic Reference Database. Summary of Final Report

Altmaier, M.; Brendler, V.; Bube, C.; Marquardt, C.; Moog, H. C.; Richter, A.; Scharge, T.; Voigt, W.; Wilhelm, S.

A long term safety assessment of a repository for radioactive waste requires evidence, that all relevant processes, which might have a significant positive or negative impact on its safety, are known and understood. In the case of brine intrusion into the disposal area, it has to be demonstrated, that the initiated chemical reactions don’t lead to an undue release of radionuclides into the biosphere. The starting point for this is to assess the solubility of contaminants in the solutions interacting with the waste. Solubility estimations can either be based on experimental data determined at conditions closely resembling those in the repository or on thermodynamic calculations.
A so called “thermodynamic database” created from experimental data is the basis for thermodynamic model calculations. Several research institutions in Germany are working on an improvement of the thermodynamic database. This work comprises investigations into fundamental thermodynamic data (such as vapour pressures or solubili-ties) as well as the application of sophisticated analytical or spectroscopic tools, which allow insight into aqueous speciation or structural details of surface complexes as basis for correct chemical and thermodynamic models.
Experience teaches that thermodynamic equilibrium calculations performed by different experts readily become difficult to compare and evaluate. This is only in part due to ill-defined (and -documented!) boundary conditions imposed on the calculations, but is frequently related to the use of different thermodynamic data or different conceptual models underlying them. Further difficulties arise by the fact that thermodynamic data used for a calculation actually are strongly interrelated; modification of an individual value without adapting the dependent values leads to “inconsistent” data. If applied in a calculation, this may lead to erroneous results, often unnoticed by the user.
As a result, in different institutions various databases exist that are appropriate for spe-cific tasks. However, they might lead to different results when they are applied to the same problem. This situation is unacceptable, both from a scientific point of view and considering the special public awareness for the final disposal of radioactive waste.
In 2002, a working group of five institutions was established for the creation of a com-mon thermodynamic database for nuclear waste disposal in deep geological formations (HZDR, GRS, TU BAF, KIT, AF-Consult). The common database was named THEREDA: Thermodynamic Reference Database.
It was agreed that the newly created database should be operated jointly by all members of the working group. In the mean term it is intended, that its usage becomes mandatory for geochemical model calculations for nuclear waste disposal in Germany. Furthermore, it was agreed that the new database should be developed along the guidelines long-term usability, easy access, applicability, internal consistency, comprehensiveness, documentation.
Activities within the time for which this report is valid cover a wide range of aspects. At first, a data model had to be designed from scratch which allows for the storage of thermodynamic data, at the same time facilitating export into code-specific parameter files. Creating the data model emphasis was laid upon its long term usage. Thus, a degree of abstraction was chosen which exceeds todays necessities and allows for future extensions. Technically the databank is implemented on a web server. Programs were created, which permit reading and writing access to the data. From the created webpages programs can be called that produce code specific parameter files ready for download upon specific request by the user.
THEREDA can thus be thought of as a databank in conjunction with a suite of peripheral programs, which aims at administrating, processing and extracting data. The data export is intended for the use in programs that calculate thermodynamic equilibria in aqueous solutions at temperatures which are of potential interest for hydrogeochemical systems in general and solutions containing hazardous contaminants like radionuclides or heavy metals in particular. As such, THEREDA is not designed to hold primary experimental data, neither data concerning any liquid other than aqueous solu-tion, e. g. melts or other substances which are stable under conditions beyond those where aqueous solutions may exist. Emphasis is laid on the correct calculation of ex-perimentally determined solubilities and aqueous speciation. Accompanying the above mentioned activities the working group agreed upon guide-lines which are to be followed upon selection and assessment of data. A system of quality assuring measure was set up; this comprises technical aspects relating to the databank as well as criteria determining how data are to be internally reviewed prior to release (auditing). As an external measure of quality assurance an internet forum was established to feedback questions and requirements from realistic problems into the project. A handbook was written to guide users in the handling of THEREDA (for the time being in german only).
Finally, thermodynamic data were entered. They comprise the system of oceanic salts as well as species and solid phase of a variety of radio-toxic and chemo-toxic ele-ments. This piece of work is on-going. At present, benchmark calculations are prepared. The first release of data will cover the system of oceanic salts (apart from C).

Keywords: THEREDA; thermodynamic reference database; repository; radioactive waste; equlibrium calculations; hydrogeochemical modelling

  • Other report
    Braunschweig: Gesellschaft für Anlagen- und Reaktorsicherheit, 2011
    63 Seiten

Publ.-Id: 15679

Nonvolatile resistive switching in BiFeO3 thin films

Shuai, Y.; Zhou, S.; Bürger, D.; Helm, M.; Schmidt, H.; Slesazeck, S.; Mikolajick, T.

Nonvolatile resistive switching has been observed in an Au/BiFeO3/Pt structure, where a Schottky contact and an Ohmic contact were formed at the Au/BiFeO3 and BiFeO3/Pt interface, respectively. By changing the polarity of the external voltage, the Au/BiFeO3/Pt is switched between two stable resistance states with a resistance ratio larger than two orders of magnitude. Based on a systematic investigation of its electrical properties with an emphasize on its transport characteristics, a model associated with the redistribution of oxygen vacancies and the formation of an electron hopping path is proposed, which agrees well with our experimental observations. In the present work we found that the electron hopping can be controlled and utilized to realize bipolar resistive switching, which is promising for future high density memory devices.

Keywords: BiFeO3; resistive switching; Schottky; electron hopping

  • Lecture (Conference)
    E-MRS 2011 SPRING MEETING, 08.05.2011, Nice, France
  • Lecture (Conference)
    ISPSA 2011, 05.-08.07.2011, Jeju, Republic of Korea

Publ.-Id: 15678

Reduced leakage current in BiFeO3 thin films with rectifying contacts

Shuai, Y.; Zhou, S.; Streit, S.; Reuther, H.; Bürger, D.; Slesazeck, S.; Mikolajick, T.; Helm, M.; Schmidt, H.

BiFeO3 thin films were grown on Pt/c-sapphire substrates by pulsed laser deposition with different growth rates. With increasing growth rate the leakage current is decreased and the conduction mechanism changes from bulk-limited Poole-Frenkel emission to interface-limited Schottky emission. In the present work, we show that only the growth rate of the BiFeO3 films close to the metal contacts has to be increased in order to reduce the leakage current and to observe saturated polarization-electric field hysteresis loops.

Keywords: BiFeO3; leakage current; rectifying contact

Publ.-Id: 15677

"Forschen für den Mittelstand"

Joehnk, P.; Wolf, B.

"Dresdner Industrietage" - eine Initiative des Arbeitskreises Industrierat im Bundesverband mittelständischer Wirtschaft e.V. in Kooperation mit der TU Dresden, der HTW Dresden, der Hochschule Zittau/Görlitz sowie weiteren wissenschaftlichen Einrichtungen Sachsens ... unter aktiver Mitwirkung zahlreicher sächsischer Mittelstands- und Branchenvereinigungen

  • Lecture (others)
    10. Dresdner Industrietage - Der Mittelstand lädt ein", 11.05.2011, Dresden, Deutschland

Publ.-Id: 15676

Nanoparticle Formation in Solids

Schmidt, B.; Heinig, K.-H.

Nanoparticles in solids can be formed through phase separation in mixtures of immiscible components. The relaxation of far-from-equilibrium mixtures towards equilibrium can proceed via self-organization of nanostructures. Depending on the degree of supersaturation, phase separation proceeds via nucleation and growth of nanoparticles or spinodal decomposition.
One of the main goals of materials research using chemical and physical vapour deposition (CVD and PVD) as well as ion beams is to synthesize nanostructures. A great effort is currently devoted to NC fabrication for micro- and optoelectronics by these techniques, because they are compatible with CMOS technology.
At first, the present contribution addresses the Si NC formation in the gate oxide by conventional ion beam synthesis (IBS) and by ion beam mixing of SiO2/Si interfaces, with special emphasis on well-controlled size and position tailoring. The two approaches will be compared and technological challenges will be discussed. Compared to conventional Si NC synthesis by Si+ ion implantation into the gate oxide, ion-beam-induced interface mixing takes advantage of self-alignment, i.e., the Si NCs are formed in SiO2 at a well-controlled distance of ~2 nm from the Si/SiO2 interfaces. Applications in non-volatile nanocrystal memories and in light emitting field-effect transistors (LEFET) are demonstrated.
Then, the phase separation by spinodal decomposition of Si-rich SiO2 layers grown by PVD (or CVD) into isolated Si NCs and percolated Si sponge-like nanostructures will be considered. Promising application in future thin film solar cells will be discussed.
The work is partially supported by BMBF (TUR 09/240).

Keywords: Nanoparticles; Ion beam synthesis; PVD synthesis; Si nanoparticle memory; Si nanoparticle electroluminesence; Si nanostructure PV cell

  • Invited lecture (Conferences)
    E-MRS Spring Meeting, 09.-13.05.2011, Nice, France

Publ.-Id: 15675

Herstellung und Untersuchung von (selbstorganisierten) Nanostrukturen – Das NVision 40 am HZDR

Fritzsche, M.

Es handelt sich um einen Überblicksvortrag über die am NVision untersuchten und/oder hergestellten Nanostrukturen und ihre Verwendung am HZDR.

  • Invited lecture (Conferences)
    CrossBeam® Workshop, 03.-04.05.2011, Jena, Deutschland

Publ.-Id: 15673

Swift Heavy Ion Shaping of Sub-Micron Structures

Ferhati, R.; Fritzsche, M.; Amirthapandian, S.; Guilliard, N.; Weishaar, T.; Bolse, W.

We applied swift heavy ions (SHI) for shaping of already existing submicron- and nano-scale structures by irradiation at small angles and simultaneous azimuthal rotation. The investigated samples consisted of 100nm thick films of NiO or ZnO deposited on an oxidized Si-wafer by reactive magnetron sputtering. Prestructuring into 3-dimensional sub-μm and nm-sized objects with quadratic or rectangular cross-sections was done by means of focused ion beam technique. The process produced a grid of perpendicular lines cut into the film, reaching from the surface down to the interface and having line distances varying between 5 μm and 250 nm. These samples were then irradiated with SHI in the chamber of our new in-situ scanning electron microscope (SEM) installed at the M1-beamline of the UNILAC.

  • Contribution to external collection
    K.Große: GSI Scientific Report 2010, GSI Report 2011-01, GSI Darmstadt: GSI Helmholtzzentrum f¨ur Schwerionenforschung, 2011, 391

Publ.-Id: 15672

Phase formation and separation in NiO/SiO2 and NiO/Si layer systems during swift heavy ion irradiation

Ferhati, R.; Guilliard, N.; Fritzsche, M.; Bolse, W.

We have recently investigated restructuring effects in thin oxide films (NiO, Fe2O3 and ZnO on pure Si- or oxidized Si-substrates) during swift heavy ion (SHI) irradiation. On the one hand we have observed that the films rupture upon SHI bomdardment under normal ion incidence and exhibit dewetting patterns similar to those observed for liquid polymer films on Si. On the other hand, grazing incidence irradiation of NiO-films leads to an instability against cracking perpendicular to the beam direction projected onto the surface and subsequent growth of an almost periodic lamellae pattern with lamellae thicknesses of the order of 100 nm and heights of the order of 2 µm. Subsequent irradiation under perpendicular directions at sufficiently low ion fluences results in a more or less rectangular crack pattern, i.e. the generation of spacially separated rectangular NiO-plates on top of the substrate. By further irradiation under grazing incidence and continuous azimuthal rotation of the sample, the oxide plates shrink in their lateral dimensions and grow in height. At the same time the egdes become round and finally a ”forest” of cylindrical NiO-pillars with radii of the order of 100 nm forms. However, because of the irregular cracking, the pillar are not arranged in a regular manner and exhibit a wide distribution of heigth and radius. These limitations can be overcome by replacing the initial cracking due to the ”Grinfeld instability” by artificial production of regularely ordered rectangular ”oxide plates” utilizing the focused ion beam (FIB) technique. SHI irradiation under grazing angle incidence and continuous azimuthal rotation than indeed results in the formation of regularely ordered objects of various (not only pillar-like) shapes, depending on the size of the initial plate. These phenomena can be understood in terms of the ”ion hammering effect” and ion-induced visco-elastic flow due to yield stresses and surface tensions as well as interface energies (capillary forces). However, until now it is not clear whether or not the above described phenomena are influenced also by phase formation and separation in the film and at its interfaces. Related studies require the utilization of phase- or at least element-sensitive analysis techniques with good lateral spacial or/and depth resolution. In the present report we’ll present our first EDX- (Energy Dispersive X-Ray Spectroscopy) and XPS- (Foto-Electron Spectroscopy) results on SHI irradiated coherent as well as pre-structured NiO-layers on Si and SiO2, respectively.

  • Contribution to external collection
    Prof. Dr. Peter Michler, Prof. Dr. Wolfgang Bolse: Annual Report 2010, Institut für Halbleiteroptik und funktionale Grenzflächen, Universität Stuttgart, Stuttgart: Universität Stuttgart, 2011, 50-51

Publ.-Id: 15671

In-situ investigation of swift-heavy-ion shaping of micron- and submicron structures

Ferhati, R.; Fritzsche, M.; Bolse, W.

Materials modification by swift heavy ion (SHI) irradiation has become a field of investigation in the early 80’s, when Klaumünzer and Schumacher observed that irradiation of metallic glasses with swift heavy ions of some MeV/amu results in anistropic plastic deformation (shrinking along and expansion perpendicular to the beam direction). Since such a behaviour is reminiscent of treating a metal sheet with a hammer, it is often called hammering effect”. Trinkaus has theoretically explained this phenomenon by the local rapid solid-liquid-solid phase transition, which is caused by the passage of a SHI through the material with sufficient ionisation cross-section (electronic stopping power). This transient melting and rapid resolidification (within some tens of ps) of a cylinder (ion track) of typically 10 nm in diameter along the ion trajectory creates tensile stresses along and compressive stresses perpendicular to the ion track axis. As we have shown before, these induced stresses may result in surface instabilities of thin oxide films, causing self-organised restructuring into lamellae- and pillar-like patterns on a nm-scale.
Here we will report about the continuation of our recently started exploration of the potential use of the hammering effect for shaping and modifying micron and sub-micron structures by swift heavy ion irradiation. In addition to the results on pre-structured NiO-films presented in the preceeding annual report we will now discuss the results of our recent experiment on pre-structured ZnO-films on oxidized Si-wafers and compare them with the previous study.

  • Contribution to external collection
    Prof. Dr. Peter Michler, Prof. Dr. Wolfgang Bolse: Annual Report 2010, Institut für Halbleiteroptik und funktionale Grenzflächen, Universität Stuttgart, Stuttgart: Universität Stuttgart, 2011, 48-49

Publ.-Id: 15670

Granular CoCrPt:SiO2 recording media on assemblies of GaSb nanocones

Ball, D.; Günther, S.; Fritzsche, M.; Varvaro, G.; Makarov, D.; Lenz, K.; Fassbender, J.; Albrecht, M.

Investigation of the magnetization reversal in arrays of magnetic nanostructures is relevant for both fundamental understanding as well as application for magnetic data storage.We present a study of the magnetization reversal in granular CoCrPt:SiO2 recording media with weakly interacting magnetic grains grown onto pre-structured templates fabricated by ion irradiation of GaSb. By tuning the irradiation conditions, assemblies of nanocones of dierent size and periodicity were prepared. Columnar CoCrPt grains with their c-axis normal to the surface of the cones were formed as evidenced by HR-TEM. The spread of the caxis of these grains results in a tilted easy magnetization axis with respect to the substrate normal. Investigation of the integral magnetic properties by vector-VSM reveals a decrease of the remanence with increasing cone size. The magnetic domain patterns observed by MFM suggest that the CoCrPt behaves as a single-domain cap structure on the cones. This work is supported by DFG FA 314-7.1 and AL 618-6.

  • Poster
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Publ.-Id: 15669

Swift Heavy Ion Beam Shaping Of Sub-Micron Structures

Ferhati, R.; Guilliard, N.; Weishaar, T.; Amirthapandian, S.; Fritzsche, M.; Bischoff, L.; Bolse, W.

Already in 1983 it was discovered, that swift heavy ion (SHI) irradiation of metallic glasses results in anisotropic deformation (shrinking along the beam direction expansion in perpendicular directions) [1]. We have employed this ”hammering effect” to reshape sub-micrometer structures by SHI bombardment under proper variation of the beam incidence angle. Utilizing the focused ion beam (FIB) technique, a rectangular grid with varying lateral distances of 100 to 5000 nm was cut into a 100 nm thick NiO- resp. ZnO-film from their surfaces down to the oxidized Si-substrate, in order to produce small oxide ”ashlars”. The samples were then irradiated under grazing incidence and continuous azimuthal target rotation with 1.4 GeV U- (NiO) and 0.95 GeV Au-ions (ZnO), respectively, in our new in-situ SEM at the UNILAC accelerator of GSI [2]. After certain fluence steps, the irradiation was stopped and one and the same spot was analyzed by means of SEM in order to investigate the evolution of the irradiated objects. Depending on their initial size complex structures (egg-, cone-, pillar-, forceps-, tooth-like) were formed, which can only be understood if besides the hammering effect deformation due to surface tension and yield stress are taken into account.
[1] S. Klaumünzer, G. Schumacher, Phys. Rev. Lett. 51 (1983),
[2] S. Amirthapandian, et al., Rev.Sci.Instr. 81, (2010)

  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Publ.-Id: 15668

Nanohole Pattern Formation on Ge by Focused Ion Beam and Broad Beam

Fritzsche, M.; Facsko, S.; Mücklich, A.; Lenz, K.

The morphology of surfaces strongly influences optical, electrical, and magnetic properties of thin films. Using low energy ion beam sputtering different self-organized periodic patterns can be obtained. These are ripple patterns with periodicities in the nanometre range for oblique ion incidence and hexagonal dot patterns on compound materials for normal incidence. Low energy ion beam sputtering of Ge at normal incidence using a 5 keV Ga+ focused ion beam (FIB) produces periodic nanohole patterns [1]. In this work we studied the flux dependence of nanohole formation using FIB technique and compared the results with patterns produced by broad Ga+ beam sputtering with a six orders of magnitude smaller ion flux. In both cases Ga+ ions with an energy of 5 keV at normal incidence were used. Obtaining the same results shows that nanohole formation is independent of flux over a few orders of magnitude and that rastering of the FIB does not add extra contributions.
[1] Q. Wei, X. Zhou, B. Joshi, Y. Chen, K. Li, Q. Wei, K. Sun, and L. Wang, Adv. Mater. 21, 2865 (2009).

  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Deutschland

Publ.-Id: 15667

Radiolabeled inhibitors for tyrosine kinase - a tool for monitoring the angiogenic process

Knieß, T.

kein Abstract verfügbar

  • Lecture (Conference)
    COST CM06-02 Inhibitors of Angiogenesis: design synthesis and biological exploitation (ANGIOKEM) Final Conference, 11.-14.06.2011, Smolenice, Slovakia

Publ.-Id: 15666

Investigations of structure, energetics, thermodynamics and kinetics of copper-vacancy clusters in bcc-Fe

Talati, M.; Posselt, M.; Bonny, G.; Al-Motasem, A. T.; Bergner, F.

The irradiation-enhanced formation and evolution of Cu-rich precipitates in reactor pressure vessel steels are multiscale phenomena. These processes can be effectively investigated by rate theory using thermodynamic parameters which must be obtained from atomistic simulations. The present work reports on the structure, energetics, thermodynamics and kinetics of nanoclusters consisting of vacancies and/or Cu. The most recent Fe-Cu interatomic potential by Pasianot and Malerba is used. A combination of Metropolis Monte Carlo and Molecular Dynamics simulation is applied to determine the most stable configurations the Cu-rich nanoclusters. The phonon contributions to the free formation energies of the clusters are evaluated from vibrational density of states obtained using dynamical matrix method. The absolute value of the total free binding energy decreases for vacancy clusters with increasing temperature while the increase is observed for pure Cu clusters. Mixed vacancy-Cu defect clusters show non-uniform behaviour in the absolute value of total free binding energy.

Keywords: Vibrational Density of States; Total free energy; Free binding energy; bcc-Fe; Thermodynamics; Molecular Dynamics Simulation

  • Poster
    European Nuclear Young Generation Forum (ENYGF), 17.-22.05.2011, Prague, Czech Republic

Publ.-Id: 15665

Vibrational Effects on Thermodynamics of Copper-Vacancy Clusters in bcc-Fe

Talati, M.; Posselt, M.; Bonny, G.; Al-Motasem, A. T.; Bergner, F.

The irradiation-enhanced formation and evolution of Cu-rich precipitates in reactor pressure vessel steels are multiscale phenomena. These processes can be effectively investigated by rate theory using thermodynamic parameters which must be obtained from atomistic simulations. The present work reports on the vibrational effects on the thermodynamics of nanoclusters consisting of vacancies and/or Cu. The most recent Fe-Cu interatomic potential by Pasianot and Malerba is used. The vibrational density of states obtained from dynamical matrix method is used to evaluate the phonon contributions to the free energy of formation and free binding energy of defect clusters. Pure bcc-Fe and pure fcc-Cu are used as references. The vibrational effects on total free energy of pure bcc-Fe and pure fcc-Cu are compared with available CALPHAD data and literature data obtained by first-principle calculations or other interatomic potentials. The absolute value of the total free binding energy decreases for pure vacancy clusters with increasing temperature, while the increase is observed for pure Cu clusters. Mixed vacancy-Cu defect clusters show the non-uniform behaviour in the absolute value of the total free binding energy .

Keywords: Vibrational Density of States; Total free energy; Free binding energy; bcc-Fe; Thermodynamics; Molecular Dynamics Simulation

  • Lecture (Conference)
    E-MRS 2011 Spring Meeting IUMRS ICAM 2011 & E-MRS/ MRS Bilateral Conference on Energy, 09.-13.05.2011, Nice, France

Publ.-Id: 15664

Immobilization strategies for the estrogen receptor hERα in optical biosensors using Si-based light emitters

Cherkouk, C.; Rebohle, L.; Gerlach, T.; Kunze, G.; Lenk, J.; Pietzsch, J.; Skorupa, W.

Biosensing devices based on fluorescence emission and detection become more and more increasing common in the fields of agricultural science, health science and food industry. Endocrine-disrupting compounds (EDC´s), such as estrogen, constitute a wide group of environmental pollutants, especially in drinking water. For this reason, there is an increasing demand for fast and convenient detection methods for estrogenic activity in water, but current detection methods base on laboratory facilities. Further miniaturization can be achieved by using light sources integrated on chip. In our case a metal-oxide-semiconductor based light emitting device (MOSLED) was developed, which is placed directly beneath the bioactive layer consisting of a silane coupling agent, a receptor and a dye-labeled analyte. However, the sensitivity of the biosensor crucially depends on the specific binding of estrogen to the receptor. Furthermore, the binding pocket inside the receptor has to be oriented toward the top of the chip surface.
In this work we investigate immobilization strategies for the estrogen receptor. A ligand binding domain tagged with histidine (hERa-LBD-10xHis) was synthesized and used. The surface plasmon resonance (SPR) method was applied in order to control and quantify the immobilization of the receptor. The SPR chip is based on a nickel nitrilotriacetic acid (Ni-NTA) matrix on gold substrate with high affinity to histidine, which allows a free linking of the receptor to the surface and thus the estrogen docking into the binding pocket of the receptor. Finally, concentration measurements of β-estradiol as an analyte have been done.

Keywords: Biosensing; estrogen; MOSLED; estrogen receptor hERa; immobilization; the surface plasmon resonance (SPR); Ni-NTA

  • Lecture (Conference)
    E-MRS 2011 Spring meeting, 08.-13.05.2011, Nice, France

Publ.-Id: 15663

Structure and energetics of nanoclusters in bcc-Fe containing vacancies, Cu, and Ni.

Al-Motasem, A. T.; Posselt, M.; Bergner, F.; Birkenheuer, U.

Reactor pressure vessel (RPV) steels consist of polycrystalline bcc-Fe containing Cu, Ni and other foreign atoms. The continuous irradiation by fast neutrons leads to supersaturation of vacancies and self-interstitials and enhances the diffusion of Cu and Ni which occurs via the vacancy mechanism. These processes favor the formation of nanoclusters consisting of vacancies, Cu and Ni. The interaction of dislocations with these precipitates is considered to be the main cause of hardening and embrittlement of the RPV steels. In order to model the evolution of the precipitates under irradiation by rate theory or object kinetic Monte Carlo simulations, the energetics and thermodynamics of the clusters must be known. These data are hardly obtainable by experiments, however, they can be provided by atomic-level computer simulations. In the present work a combination of on-lattice simulated annealing based on Metropolis Monte Carlo simulations and off-lattice relaxation by Molecular Dynamics calculations is employed to determine structure and energetics of the nanoclusters. In particular the influence of Ni on the formation of clusters containing Cu and/or vacancies is investigated. The atomistic simulations show that ternary clusters exhibit a shell structure with a core consisting of vacancies followed by a shell of Cu and an outer shell of Ni. Binary vacancy-Cu and Ni-Cu clusters show a similar shell structure, whereas the atomic configuration of vacancy-Ni agglomerates is completely different. For further application in rate theory and object kinetic Monte Carlo simulations compact and physically-based fit formulae are derived from the atomistic data for the total and the monomer binding energy.

Keywords: Fe-Cu-Ni; defects; Metropolis Monte Carlo and Molecular Dynamics

  • Lecture (Conference)

Publ.-Id: 15662

Concurrent annealing and irradiation of germanium to control dopant diffusion and activation

Bracht, H.; Schneider, S.; Klug, J. N.; Posselt, M.; Schmidt, B.

Germanium (Ge) as material for microelectronic applications has received renewed attention over the past decade. This is due to the advantageous electron and hole mobilities that are higher than those of silicon (Si). However, several obstacles still exist that limit the fabrication of Ge-based nanoelectronic devices. One aspect concerns the limited activation of donor atoms. The deactivation is mainly attributed to the formation of dopant-vacancy clusters whose existence is supported by density functional theory calculations. In this work we discuss experiments on the diffusion of implanted phosphorous (P) and arsenic (As) in Ge under proton irradiation. Continuum theoretical simulations of dopant profiles measured by means of secondary ion mass spectrometry reveal that diffusion under irradiation is much less affected by inactive donor-vacancy clusters than diffusion under annealing only. The suppression of donor-vacancy clusters is caused by interstitials in supersaturation and vacancy concentrations close to thermal equilibrium. Applying the approach of concurrent annealing and irradiation high active doping levels in Ge can be realized even at low processing temperatures.

Keywords: germanium; dopants; defects; diffusion; activation

  • Poster
    E-MRS ICAM IUMRS 2011 Spring Meeting, 09.-13.05.2011, Nice, France

Publ.-Id: 15661

Combining contactless inductive flow tomography and mutual inductance tomography for the flow determination in a model of continuous casting

Wondrak, T.; Stefani, F.; Gerbeth, G.; Timmel, K.; Peyton, A. J.; Yin, W.; Terzija, N.

In the continuous casting process the flow structure in the mold plays an important role for the quality of the produced steel. Open issues of this technoloqy concern the influence of a two phase flow in the submerged entry nozzle and the influence of electromagnetic stirrers.

One possible method to determine the flow structure in the mold is the contactless inductive flow tomography (CIFT) which is able to reconstruct the three-dimensional velocity field in electrically conducting melts from externally measured induced magnetic fields. Since for thin slab casting the velocity can be assumed to be mainly two-dimensional it is sufficient to apply only one external magnetic field and to measure the induced fields at the narrow faces of the mold. The actual time resolution is about 1 Hz.

We will present the results [1,2] of an experiment with a two phase flow regime and the effects of an electromagnetic stirrer around the submerged entry nozzle on the flow field in the mold.

[1] Th. Wondrak et al. (2010), Meas. Sci. Techn. 21, 045402
[2] N. Terzija et al. (2011), Meas. Sci. Techn. 22, 015501

Keywords: contactless inductive flow tomography; mutual inductance tomography; flow visualization; continuous casting

  • Contribution to proceedings
    8th International PAMIR conference on fundamental and applied MHD, 05.-9.9.2011, Borgo, France, 569-573
  • Lecture (Conference)
    8th International PAMIR conference on fundamental and applied MHD, 05.-9.9.2011, Borgo, France

Publ.-Id: 15660

Contactless inductive flow tomography at a liquid metal model of the steel casting process

Wondrak, T.; Stefani, F.; Gundrum, T.; Timmel, K.; Gerbeth, G.

The contactless inductive flow tomography (CIFT) allows the reconstruction of the full three- dimensional mean velocity field in electrically conducting melts from externally measured induced magnetic fields. One of its possible applications is the velocity reconstruction in the continuous casting process. We present CIFT measurements performed at the small-scale liquid metal facility Mini-LIMMCAST which uses the room-temperature liquid alloy GaInSn for modelling of the thin-slab casting process. It will be shown that the flow structure, in general, and the jet position and intensity, in particular, can be reliably determined from magnetic field data using only a modest number (in the order of 5) of sensors. Even the very asymmetric flow in case of artificially closing one of the two nozzle outlets is reproduced by CIFT. The CIFT measurements are partly validated by comparison with ultrasonic velocity measurements.

Keywords: contactless inductive flow tomography; flow visualization; continuous casting

  • Lecture (Conference)
    4th International Conference on Modelling and Simulation of Metallurgical Processes in Steelmaking (SteelSim), 27.06.-1.7.2011, Düsseldorf, Deutschland
  • Contribution to proceedings
    4th International Conference on Modelling and Simulation of Metallurgical Processes in Steelmaking (SteelSim), 27.06.-1.7.2011, Düsseldorf, Deutschland
    Proceedings of the 4th International Conference on Modelling and Simulation of Metallurgical Processes in Steelmaking (SteelSim)

Publ.-Id: 15659

Combination of the contactless inductive flow tomography and the mutual inductance tomography for the flow visualization in a model of continuous casting

Wondrak, T.; Gerbeth, G.; Stefani, F.; Timmel, K.; Peyton, A. J.; Terzija, N.; Yin, W.

Continuous casting is a widely used technique in the steel producing industry today. The flow structure in the mold has a great impact on the quality of the produced steel. Open issues of this technology concern the influence of a two phase flow in the submerged entry nozzle and the influence of electromagnetic stirrers.

One possible technique to visualize the flow structure in electrically conducting melts is the contactless inductive flow tomography (CIFT) which is able to reconstruct the three-dimensional velocity field by measuring induced magnetic fields outside the melt. Since for thin slab casting the velocity in the mold can be assumed to be mainly two-dimensional it is sufficient to apply only one external magnetic field and to measure the induced fields at the narrow faces of the mold. The actual time resolution is about 1 Hz.

We will present the results [1,2] of an experiment with a two phase flow regime combining CIFT and the mutual inductance tomography to measure the flow structure in the mold and the gas/liquid distribution in the submerged entry nozzle. Additionally we show the effects of an electromagnetic stirrer around the submerged entry nozzle on the flow field in the mold.

[1] Th. Wondrak et al. (2010), Meas. Sci. Techn. 21, 045402
[2] N. Terzija et al. (2011), Meas. Sci. Techn. 22, 015501

Keywords: contactless inductive flow tomography; mutual inductance tomography; flow visualization; continuous casting

  • Lecture (Conference)
    Jahrestagung der Gesellschaft für angewandte Mathematik und Mechanik (GAMM 2011), 18.-21.04.2011, Graz, Österreich

Publ.-Id: 15658

A TRLFS study of curium(III) naphthalene and hydroxyquinoline complexes in aqueous solution

Moll, H.; Bernhard, G.

The unknown complex formation of Cm(III) with two naphthalene ligands, 2,3­dihydroxynaphthalene (23NAP) and 2­naphthalene (2NAP) as well as 6­hydroxyquinoline (6HQ) was studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Aromatic molecules with hydroxyl groups have the potential to enhance the solubility and mobility of metals by forming complexes. We explored both the luminescence (lifetimes and individual emission spectra) and the excitation properties (excitation spectra) of the formed Cm(III) species. The experiments were performed at a fixed total Cm(III) concentration of 0.3 µM by varying the ligand concentrations (0.03-3.0 mM) and the pH (1.9-12.4) at an ionic strength of 0.1 M (NaClO4). The spectroscopic speciation indicates the formation of CmpLqHr species. In more detail, Cm(III) forms 1:1 and 1:2 complexes with 23NAP, a 1:2 complex with 2NAP and a 1:1 complex with 6HQ. Independent from the ligand and at pH values above 9.5 strong indications were found for ternary complexes with OH- with a 1:2:-1 stoichiometry. The Cm(III)-23NAP complexes exhibited the largest red shift of the Cm3+ emission maximum at 593.7 nm to: 598.3 nm for Cm(23NAP)H2+, 604.4 nm for Cm(23NAP)+, 608.4 nm for Cm(23NAP)2-, and 616 nm for Cm(23NAP)2OH2-. Based on the factor analysis of the emission data the stability constants were calculated to be: (a) for 23NAP log ß111 = 20.2 ± 0.8, log ß110 = 12.7 ± 0.4, log ß120 = 20.5 ± 0.4, and log ß12-1 = 9.7 ± 0.4; (b) for 2NAP log ß120 = 19.4 ± 0.2, and log ß12-1 = 10.3 ± 0.1; and (c) for 6HQ log ß110 = 8.8 ± 0.3, and log ß12-1 = 5.1 ± 0.9 at an ionic strength of 0.1 M (NaClO4). The stability constants were compared to those of natural pyoverdins.

Keywords: Cm(III); Complexation; TRLFS; 2,3-hydroxynaphthalene; 2-naphthalene; 6-hydroxyquinoline

Publ.-Id: 15657

CFD for two-phase flows - recent developments, status and further requirements -

Lucas, D.; Laurien, E.

The use of Computational Fluid Dynamics (CFD) Codes for two-phase flow problems in Nuclear Safety Research is discussed. Examples for recent developments are the qualification of MUSIG model for dispersed flows and the modelling of free surfaces. Up to now the predictive capabilities of CFD codes for two-phase flows are limited to special cases. Nevertheless a valuable contribution to understand such complex flows is obtained. The aim of the future research is to develop CFD codes towards a quantitative method to obtain reliable predictions for broad range of applications.

Keywords: CFD; two-phase flow

  • Invited lecture (Conferences)
    Annual Meeting on Nuclear Technology, Jahrestagung Kerntechnik, 17.-19.05.2011, Berlin, Germany

Publ.-Id: 15656

Characterization of plunging liquid jets: A combined experimental and numerical investigation

Qu, X. L.; Khezzar, L.; Danciu, D.; Labois, M.; Lakehal, D.

This paper presents a combined experimental and numerical study of the flow characteristics of round vertical liquid jets plunging into a cylindrical liquid bath. The main objective of the experimental work consists in determining the plunging jet flow patterns, entrained air bubble sizes and the influence of the jet velocity and variations of jet falling lengths on the jet penetration depth. The instability of the jet influenced by the jet velocity and falling length is also probed. On the numerical side, two different approaches were used, namely the mixture model approach and interface-tracking approach using the level-set technique with the standard two-equation turbulence model. The numerical results are contrasted with the experimental data. Good agreements were found between experiments and the two modelling approaches on the jet penetration depth and entraining flow characteristics, with interface tracking rendering better predictions. However, visible differences are observed as to the jet instability, free surface deformation and subsequent air bubble entrainment, where interface tracking is seen to be more accurate. The CFD results support the notion that the jet with the higher flow rate thus more susceptible to surface instabilities, entrains more bubbles, reflecting in turn a smaller penetration depth as a result of momentum diffusion due to bubble concentration and generated fluctuations. The liquid average velocity field and air concentration under tank water surface were compared to existing semianalytical correlations. Noticeable differences were revealed as to the maximum velocity at the jet centreline and associated bubble concentration. The mixture model predicts a higher velocity than the level-set and the theory at the early stage of jet penetration, due to a higher concentration of air that cannot rise to the surface and remain trapped around the jet head. The location of the maximum air content and the peak value of air holdup are also predicted differently.

Keywords: Plunging jet; Penetration; Air entrainment; Mixture model; Level-set; CFD

Publ.-Id: 15655

Comparison of two turbulence models in simulating an axisymmetric water jet evolving into a water tank

Zidouni Kendil, F.; Danciu, D.-V.; Mataoui, A.; Schmidtke, M.; Lucas, D.; Bousbia Salah, A.

Experiments and computational fluid dynamics (CFD) simulations have been carried out to predict a turbulent water jet plunging into a tank filled with the same liquid. A zero distance of the free falling water jet to the free surface of the tank is considered in order to avoid air bubble entrainment which may be caused by surface instabilities.
For both impinging region and recirculation zone, measurements are made using Particle Image Velocimetry (PIV). Instantaneous and time-averaged velocity fields are obtained over the cross-section of the tank. Numerical data is obtained on the basis of both k-ε and SSG (Speziale, Sarkar and Gatski) of Reynolds Stresses Turbulent Model (RSM) in three dimensional frame and compared to experimental results via the axial velocity and turbulent kinetic energy.
It was found that, for axial distances lower than 5 cm from the jet impact point, the axial velocity matches well the measurements, using both models. A progressive difference is noticed near the jet for higher axial distances from the jet impact point. These discrepancies are more important in the case of RSM than in the case of k-ε model. Nevertheless, it was observed that the turbulent kinetic energy agrees very well with the measurements when applying the SSG-RSM model for the lower part of the tank, whereas it is underestimated in the upper region, especially in the region near the jet exit. Inversely, the k-ε model shows better results in the upper part of the water tank and underestimates results for the lower part of the water tank. From the overall results, it can be concluded that the k-ε model describes well the average axial velocity, whereas the turbulent kinetic energy is better represented by the SSG-RSM model. The flow pattern obtained using both turbulent models and the corresponding comments of the results are detailed in the paper.

Keywords: Impinging jet; Standard k-ε Turbulent Model; Reynolds Stresses Turbulent Model

  • Contribution to proceedings
    European Turbulence Conference (ETC 13), 12.-15.09.2011, Warsaw, Poland
    Comparison of two turbulence models in simulating an axisymmetric water jet evolving into a water tank
  • Open Access Logo Journal of Physics: Conference Series 318(2011), 042035
    DOI: 10.1088/1742-6596/318/4/042035

Publ.-Id: 15654

S-Layer-basierte Materialien zur Detektion und Entfernung von Schad- und Wertstoffen

Raff, J.

Vorstellung aktueller Arbeiten zur Entwcklung S-Layer-basierter Materialien

  • Lecture (others)
    Biomatum-Seminar, 17.05.2011, Dresden, Deutschland

Publ.-Id: 15653

Image based in-vivo dosimetry: from PET to in-beam SPECT

Fiedler, F.

no abstract available

Keywords: in-beam PET; in-beam SPECT; PET; dose monitoring; in vivo dosimetry; ion therapy; proton therapy

  • Invited lecture (Conferences)
    2nd Workshop on Hadron Beam Therapy of Cancer, 20.-27.05.2011, Erice, Italy

Publ.-Id: 15652

A 200 cm × 50 cm MRPC-based prototype for the NeuLAND detector at R3B

Bemmerer, D.; Cowan, T.; Elekes, Z.; Kempe, M.; Röder, M.; Sobiella, M.; Stach, D.; Wagner, A.; Yakorev, D.; Zuber, K.

A detector for high-resolution momentum measurements of neutrons in the energy range 0.2-1.0 GeV is being developed for the R3 B experiment at FAIR. Two solutions are currently being studied: A pure scintillator concept and an approach based on a sequence of converter material (iron) to produce secondary charged particles, and Multigap Resistive Plate Chambers (MRPC’s) to detect these particles. Here, work on the latter solution is reported.

  • Contribution to external collection
    Katrin Große: GSI Annual Report 2010; GSI-Report 2011-1, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung, 2011, 182

Publ.-Id: 15651

NeuLAND - Concepts for the Detection of Fast Neutrons

Aumann, T.; Basu, P.; Bemmerer, D.; Bertini, D.; Blanco, A.; Boretzky, K.; Caesar, C.; Chakraborty, S.; Chatterjee, S.; Cherciu, M.; Datta Pramanik, U.; Elekes, Z.; Fonte, P.; Galaviz, D.; Gonzalez Diaz, D.; Haiduc, M.; Hehner, J.; Heil, M.; Ignatov, A.; Kempe, M.; Leifels, Y.; Machado, J.; Maroussov, V.; Panja, J.; Potlog, M.; Rahaman, A.; Reifarth, R.; R. ̈Oder, M.; Rossi, D.; Simon, H.; Sobiella, M.; Stach, D.; Stan, E.; Teubig, P.; Wagner, A.; Yakorev, D.; Zilges, A.; Zuber, K.

The acronym NeuLAND (new Large Area Neutron De-tector) stands for the high-efficiency time-of-flight spectrometer for high-energy neutrons (200 to 1000 MeV) within the R3B experiment being designed for FAIR. A spatial resolution of approximately sigma~1 cm and a time resolution of approximately sigma~100 ps are envisaged together with an efficiency of more than 90 % for one-neutron events, as well as a high multi-neutron recognition capability.

  • Contribution to external collection
    Katrin Große: GSI Annual Report 2010; GSI-Report 2011-1, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung, 2011, 180

Publ.-Id: 15650

Direct reactions of light exotic beams measured in complete kinematics at R3B

Adachi, T.; Aksyutina, Y.; Alcantara, J.; Altstadt, S.; Alvarez-Pol, H.; Ashwood, N.; Aumann, T.; Barr, M.; Beceiro, S.; Bemmerer, D.; Benlliure, J.; Boretzky, K.; Burgunder, G.; Caamano, M.; Caesar, C.; Casarejos, E.; Catford, W.; Chakraborty, S.; Chartier, M.; Chulkov, L.; Cortina-Gil, D.; Datta Pramanik, U.; Diaz, P.; Dillmann, I.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; Fraile, L. M.; Freer, M.; Freudenberger, M.; Galaviz Redondo, D.; Geissel, H.; Gonzalez Diaz, D.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Henriques, A.; Holl, M.; Ignatov, A.; Johansson, H.; Jonson, B.; Kalantar, N.; Knöbel, R.; Kroell, T.; Krücken, R.; Kurcewicz, J.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Machado, J.; Marganiec, J.; Movsesyan, A.; Najafi, A.; Nilsson, T.; Nociforo, C.; Panin, V.; Pietri, S.; Plag, R.; Prochazka, A.; Rahaman, A.; Rastrepina, G.; Reifarth, R.; Ribeiro, G.; Ricciardi, M. V.; Rigollet, C.; Riisager, K.; Röder, M.; Rossi, D.; Sanchez Del Rio, J.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Streicher, B.; Taylor, J.; Tengblad, O.; Terashima, S.; Thies, R.; Yasuhiro, T.; Uberseder, E.; van de Walle, J.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Wheldon, C.; Wilson, G.; Wimmer, C.; Winfield, J.; Woods, P.; Yakorev, D.; Zoric, M.; Zuber, K.

An experiment has been performed by the R3B collaboration aiming at the investigation of light neutron-rich nuclei utilizing kinematically complete measurements of reactions at relativistic energies with the R3 B-LAND reaction setup at Cave C. The physics topics to be studied comprise the measurement of astrophysical reaction rates relevant for r-process nucleosynthesis using heavy-ion induced electromagnetic excitation and quasi-free knockout reactions to study the evolution of shell and cluster structures close to and beyond the dripline.

  • Contribution to external collection
    Katrin Große: GSI Scientific Report 2010, GSI Report 2011-1, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung Gm, 2011, 166

Publ.-Id: 15649

Magnetic phase diagram of multiferroic MnWO4 probed by ultrasound,

Felea, V.; Lemmens, P.; Yasin, S.; Zherlitsyn, S.; Choi, K. Y.; Lin, C. T.; Payen, C.

The magnetic phase diagram of multiferroic MnWO4 is studied in magnetic fields up to 60 T using sound velocity and sound attenuation measurements. Anomalies are observed at temperatures TN1 = 7.6 K, TN2 = 12.6 K and TN3 = 13.6 K that separate commensurate antiferromagnetic (AF1) to helical AF2 and commensurate AF3 to paramagnetic phases, respectively. The anomalies are significantly different and shed light on the spin–phonon coupling and evolution of the various order parameters in this multiferroic material. For temperatures below TN2 pronounced field hysteresis effects are also observed in the sound velocity, indicating field-induced transformations. In the temperature dependence of the attenuation we observe anomalies distinctively different from the usual maxima related to relaxation effects. They are attributed to the combination of dispersion effects due to domain walls and the discontinuously changing sound velocity. In total, six different magnetic phases, at various temperatures and fields including a novel high-field phase, are revealed and analyzed.

Publ.-Id: 15648

Influence of Hydrophobicity on the Surface-Catalyzed Assembly of the Islet Amyloid Polypeptide

Keller, A.; Fritzsche, M.; Yu, Y.-P.; Liu, Q.; Li, Y.-M.; Dong, M.; Besenbacher, F.

The islet amyloid polypeptide (IAPP) Is a hormonal factor secreted by the beta-cells in the pancreas. Aggregation of misfolded IAPP molecules and subsequent assembly of amyloid nanofibrils are critical for the development Of type 2 diabetes mellitus. In the physiological environment, amyloid aggregation is affected by the presence of interfaces such as cell membranes. The physicochemical properties of the interface dictates the interaction of the peptide with the surface, i.e., electrostatic and hydrophobic Interactions on hydrophilic and hydrophobic surfaces, respectively. We have studied the Influence of hydrophobicity on the surface-catalyzed assembly of IAPP on ultrasmooth hydrocarbon films grown on ion-beam-modified mica surfaces by atomic force microscopy. The contact angle theta of these surfaces can be tuned continuously in the range from <= 20 degrees to similar to 90 degrees by aging the samples without Significant changes of the chemical composition or the topography of the surface. On hydrophilic surfaces with a theta of similar to 20 degrees, electrostatic interactions Induce the assembly of IAPP nanofibrils, whereas aggregation of large (similar to 2.6 nm) oligomers Is observed at hydrophobic surfaces with a theta of similar to 90 degrees. At intermediate contact angles, the interplay between electrostatic and hydrophobic substrate interactions dictates the pathway of aggregation with fibrillation getting continuously delayed when the contact angle is increased. In addition, the morphology of the formed protofibrils and mature fibrils at intermediate contact angles differs from those observed at more hydrophilic surfaces. These results might contribute to the understanding of the surface-catalyzed assembly of different amyloid aggregates and may also have implications for the technologically relevant controlled synthesis of amyloid nanofibrils of desired morphology.

Publ.-Id: 15647

Long-Acting Lipidated Analogue of Human Pancreatic Polypeptide Is Slowly Released into Circulation

Bellmann-Sickert, K.; Elling, C. E.; Madsen, A. N.; Little, P. B.; Lundgren, K.; Gerlach, L.-O.; Bergmann, R.; Holst, B.; Schwartz, T. W.; Beck-Sickinger, A. G.

The main disadvantages of;peptide pharmaceuticals are their rapid degradation and excretion, their low hydrophilicity, and low shelf lifes. These bottlenecks can be circumvented by acylation with fatty acids (lipidation) or polyethylene glycol (PEGylation). Here, we describe the Modification of a human pancreatic polypeptide analogue specific for the human (h)Y2 and hY4 receptor with PEGs of different size and palmitic acid. Receptor specificity was demonstrated by competitive binding studies. Modifications had only small influence on binding affinities and no influence on secondary structure. Both modifications improved pharmacokinetic properties of the hPP analogue in vivo and in vitro,,however, lipidation showed a greater resistance to degradation and excretion than PEGylation, Furthermore, the lipidated peptide is taken up and degraded solely by the liver but not the kidneys. Lipidation resulted in prolonged action of the hPP analogue in respect of reducing food intake in mice after subcutaneous administration. Therefore, the lipidated hPP analogue could constitute a potential new therapeutic agent against obesity.

Publ.-Id: 15646

High temperature oxidation resistance of 316 stainless steel doped with Yttrium using intense pulsed plasma beams

Barlak, M.; Piekoszewski, J.; Werner, Z.; Sartowska, B.; Waliś, L.; Starosta, W.; Kierzek, J.; Bocheńska, K.; Heller, R.; Wilhelm, R.; Kolitsch, A.; Pochrybniak, C.; Kowalska, E.

Doping stainless steels or iron chromium alloys with oxygen reactive elements like Y and rare earth elements (REE) like Ce, La, Er and others improves their oxidation resistance at high temperature.
There are numerous methods of incorporating REE into steel by surface treatment, e.g.: ion implantation, metalo-organic, chemical vapour deposition, sol-gel coating, pack cementation, screen-printing, molten-salt electrodeposition.
Recently we undertook an attempt to incorporate REE into steels using a new approach based on the use of high intensity pulsed plasma beams (HIPPB). The characteristic feature of this method rely upon the fact that the REE elements are alloyed into the near-surface region of the substrate in its transient liquid state. The preliminary results obtained on AISI 316L steel samples doped with Ce-La in this way and then oxidized in air for 80 hours at 1000°C were encouraging as regards the scales which were thinner, more compact and well adhered.
In the present work we report on the use of yttrium as an active element incorporated into 316 stainless steel using HIPPB. The surface modification of treated samples was performed using 3 pulses with their energy density of 2 Jcm-2 each. Nitrogen was used as a working gas. The yttrium doses accumulated in stainless steel range from 2.34e16 to 1.28e17 cm-2.
The samples are examined by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-ray diffraction (XRD) and crucially important Rutherford Back Scattering (RBS) measurements and subjected to oxidation in air at a temperature of 1000°C for a period of 100 h.

  • Poster
    SMMIB2011 - 17th International Conference on Surface Modification of Materials by Ion Beams, 13.-17.09.2011, Harbin, China

Publ.-Id: 15645

Scale Resolved Simulations of the OECD/NEA−Vattenfall T-Junction Benchmark

Höhne, T.

Mixing of fluids in T-junction geometries is of significant interest for nuclear safety research. The most prominent example is the thermal striping phenomena in piping T-junctions, where hot and cold streams join and turbulently mix, however not completely or not immediately at the T-junction. This results in significant temperature fluctuations near the piping wall, either at the side of the secondary pipe branch or at the opposite side of the main branch pipe. The wall temperature fluctuation can cause cyclical thermal stresses and subsequently fatigue cracking of the wall.

Thermal mixing in a T-junction has been studied for validation of CFD-calculations. A T-junction thermal mixing test was carried out at the Älvkarleby Laboratory of Vattenfall Research and Development (VRD) in Sweden. Data from this test have been reserved specifically for a OECD CFD benchmark exercise. The computational results show that RANS fail to predict a realistic mixing between the fluids. The results were significantly better with scale-resolving methods such as LES, showing fairly good predictions of the velocity field and mean temperatures. The calculation predicts also similar fluctuations and frequencies observed in the model test.

Keywords: T-junction; CFD; mixing; LES; Vattenfall; OECD

  • Contribution to proceedings
    SMiRT 21, 06.-11.11.2011, New Dehli, India
  • Lecture (Conference)
    Smirt21, 06.-11.11.2011, New Dehli, India

Publ.-Id: 15644

Monte Carlo simulations of a ClearPET: Scatter and attenuation of gamma rays in various rock formations

Zakhnini, A.; Kulenkampff, J.; Sauerzapf, S.; Lippmann-Pipke, J.; Pietrzyk, U.

Positron emission tomography (PET) is applied in geosciences for the visualization of flow and transport processes in various rock formations (GeoPET [1]). Denser rock material requires more demanding and stronger corrections of scatter and attenuation of the gamma rays than in human body tissue. Once the quantification of scatter and attenuation is acquired, correction strategies can be established and the physical limit of the spatial resolution of ~1 mm for the GeoPET method be accomplished. We suggest Monte Carlo (MC) simulations of a ClearPET camera (Raytest) as means for achieving this aim.

We report simulation results of the GeoPET using software GATE (Geant4 Application for Tomographic Emission [2]). The purpose of this investigation is to determine the scatter fraction of gamma rays in various rock formations with different gantry diameter configurations, various Isotopes and different energy windows.
The simulations show that the energy window and increasing gantry diameter are important physical parameters affecting the scatter fraction values in denser material. Reconstructed images from measurements and simulations show good qualitative agreement.
[1] Kulenkampff, J. et al. (2008) Phys. Chem. Earth 33, 937-942.
[2] Jan, S. et al. (2011) Phys. Med. Biol. (56) 881-901.

  • Poster
    2011 IEEE Nuclear Science Symposium and Medical Imaging Conference, 23.-29.10.2011, Valencia, Spain

Publ.-Id: 15643

Dampf-Experimente zur Kontaktkondensation und zum Blasenmitriss in der TOPFLOW-Anlage

Seidel, T.; Lucas, D.

Die Belastung des Reaktordruckbehälters von Druckwasserreaktoren wird in Thermoschock-Szenarien insbesondere durch Vermischungsvorgänge und von Direktkondensation bestimmt. Die zunehmend auch für Fragestellungen der Reaktorsicherheitsforschung verwendeten CFD-Modelle können diese Phänomene bislang nur mit einigen Einschränkungen abbilden. Die zur Weiterentwicklung der Modelle benötigten Experimente werden gegenwärtig im Helmholtz-Zentrum Dresden-Rossendorf vorbereitet. In einem Bassin werden verschiedene Experimente mit unterkühltem Wasser in Dampfatmosphäre durchgeführt und mit zeitlich und örtlich hoch aufgelösten Messverfahren beobachtet.

Keywords: TOPFLOW; condensation; experiments; bubble entrainment

  • Contribution to proceedings
    Jahrestagung der Kerntechnischen Gesellschaft, 17.-19.05.2011, Berlin, Deutschland
    Dampf-Experimente zur Kontaktkondensation und zum Blasenmitriss in der TOPFLOW-Anlage
  • Lecture (Conference)
    Jahrestagung der Kerntechnischen Gesellschaft, 17.-19.05.2011, Berlin, Deutschland

Publ.-Id: 15642

Wettability of carbon and silicon caramics induced by their alloying with Ti, Zr, and Cu elements using high intensity pulsed plasma beams

Barlak, M.; Piekoszewski, J.; Werner, Z.; Sartowska, B.; Waliś, L.; Starosta, W.; Kierzek, J.; Bocheńska, K.; Heller, R.; Kolitsch, A.; Pochrybniak, C.; Kowalska, E.

Ceramics materials, such as: oxides, nitrides, borides, carbides and carbon are widely used in modern constructions and devices. Their advantages are: low density, high mechanical strength and corrosion resistance at high temperature and favourable performance/weight relationship. However, an application of these materials in joints or in composites with metals is very difficult, because usually the ceramics are non-wettable by liquid metals.
In the present work, we used high intensity plasma pulses technique for the preparation of carbon and silicon carbide surface before the wetting process by liquid copper. The Ti, Zr and Cu plasma was applied to induce the wettability.
The experiments were preceded by thermodynamical considerations. The prepared samples were investigated by sessile-drop tests, SEM observations, EPMA, GXRD analysis and RBS measurements.
The results of Ti and Zr plasma modifications were beneficial and similar to each other. The measured contact angles were below 90°. The results of Cu plasma were unfavorable with contact angles close to 180°.

  • Lecture (Conference)
    NUTECH-2011, Development and Applications of Nuclear Technologies, 11.-14.09.2011, Krakow, Poland

Publ.-Id: 15641

High temperature oxidation resistance of stainless steel doped with Yttrium using ion implantation

Barlak, M.; Piekoszewski, J.; Werner, Z.; Sartowska, B.; Waliś, L.; Starosta, W.; Kierzek, J.; Bocheńska, K.; Heller, R.; Wilhelm, R.; Kolitsch, A.; Pochrybniak, C.; Kowalska, E.

The addition of some amount of oxygen reactive elements like Y and rare earth elements (REE) Ce, La, Er and others into stainless steels or iron chromium alloys improves their oxidation resistance at high temperature.
There are numerous methods of incorporation of REE into steel by surface treatment, e.g.: ion implantation, metal organic, chemical vapour deposition, sol-gel coating, pack cementation, screen-printing, molten-salt electrodeposition.
In the present work we intend to use yttrium as an active element which will be incorporated into 304, 316 and 430 stainless using conventional implantation with MEVVA type of Y ion source.
The samples will be examined by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-ray diffraction (XRD) and crucially important Rutherford Back Scattering (RBS) measurements and subjected to oxidation in air at a temperature of 1000°C for a period 100 h.
Results obtained with the use of HIPPB method and ion implantation will be compared and discussed.

  • Lecture (Conference)
    NUTECH-2011 International Conference on Development and Applications of Nuclear Technologies, 11.-14.09.2011, Krakow, Poland

Publ.-Id: 15640

Ionenimplantation und Unterstützung von PVD Prozessen mit energetischen Ionen als innovativer Technologiefortschritt

Kolitsch, A.

Die simultane Kombination verschiedener Ionenenergien mittels Plasma Immersions Ionenimplantation und reaktivem Magnetronsputtern zur Herstellung extrem glatter, superharter und haftfester tribologischer Schichten für Hochtechnologieanwendungen wird beschrieben

Keywords: PBII; PIII; TiN; cBN; PVD; super hard coatings

  • Invited lecture (Conferences)
    Oberflächenmodifikation von Werkstoffen, 13.05.2011, Zittau, Deutschland

Publ.-Id: 15639

Neon identifies two billion year old fluid component in Kaapvaal Craton

Lippmann-Pipke, J.; Sherwood Lollar, B.; Niedermann, S.; Stroncik, N. A.; Naumann, R.; van Heerden, E.; Onstott, T. C.

We analysed shallow (to ~1 km) and deep fracture waters (to > 3 km) from the Witwatersrand Basin, South Africa for their noble gas isotopic composition. Their neon signature clearly differentiates a group of typical crustal fluids from another one with a significantly enriched nucleogenic neon signal with the highest 21Ne/22Ne ratios (0.160 +/- 0.003) ever reported in groundwater [1]. Fluid inclusions in adjacent rocks yield even higher 21Ne/22Ne ratios between 0.219 and 0.515, consistent with an extrapolated 21Ne/22Ne value of 3.3 +/- 0.2 at 20Ne/22Ne = 0. We show that this enriched nucleogenic neon end-member represents a fluid component that was produced in the fluorine-depleted Archaean formations and trapped in fluid inclusions > 2 Ga ago [1]. The observation of enriched nucleogenic neon signatures in deep fracture water implies the release of this billion year old neon component from the fluid inclusions and its accumulation in exceptionally isolated fracture water systems. The observed association of this Archaean neon signature with H2-hydrocarbon-rich geogases of proposed abiogenic origin [2] dissolved in the same deep groundwater suggests that the fracture systems have also allowed for the accumulation of various products of water-rock reactions throughout geologic times. One of these fracture systems contained a chemolithotrophic, single species ecosystem surviving on radiolytically produced H2 and sulfate completely independent of the surface photosphere [3,4].

[1] Lippmann-Pipke et al. 2011 Chem. Geol. 283, 287-296
[2] Sherwood Lollar et al. 2002 Nature 416(6880) 522-524
[3] Lin L.-H. et al. 2006 Science 314(5798), 479-482
[4] Chivian, D. et al. 2008 Science 322(5899), 275-278

  • Lecture (Conference)
    Goldschmidt 2011, 14.-19.08.2011, Prague, Czech Republic

Publ.-Id: 15638

Steinalte Wässer in Südafrikas Goldminen

Lippmann-Pipke, J.

Ein internationales Forscherteam untersucht Wasserproben aus den tiefsten Bergwerken der Welt. Eine Wasserkomponente entpuppt sich als ein "urzeitliches" Signal und belegt die außerordentliche Isolation dieser tiefen, mikrobiell besiedelten Wasserreservoire.

  • Lecture (others)
    Lange Nacht der Wissenschaften, 01.07.2011, Dresden, Deutschland

Publ.-Id: 15637

Influence of a point source motion in PET images and its compensation

Laube, K.; Fiedler, F.; Schöne, S.; Bert, C.; Enghardt, W.

no abstract available

Keywords: in-beam PET; motion

  • Contribution to external collection
    in: GSI Scientific Report 2010, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung, 2011, 470

Publ.-Id: 15636

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