Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33397 Publications

P0604 - Verfahren und Anordnung zur kontaktlosen Messung des Durchflusses elektrisch leitfähiger Medien

Priede, J.; Buchenau, D.; Gerbeth, G.; Eckert, S.
Die Aufgabe der vorliegenden Erfindung besteht darin, eine Durchflussmessung zu ermöglichen, die ohne mechanischen oder elektrischen Kontakt zum fließenden Medium auskommt, keine Vielzahl von Magnetfeldmessstellen erfordert, eine Durchflussmessung hoher zeitlicher Auflösung liefert, gegenüber äußeren Einflüssen möglichst unempfindlich ist und nicht die lageempfindlichen Amplituden in Empfängerspulen bei Wechselstromerregung benutzt. Die Erfindung geht aus von einem magnetischen Wechselfeld außerhalb des elektrisch leitfähigen Mediums und beinhaltet, dass der Einfluss des strömenden Mediums auf das angelegte Magnetfeld zu einer Phasenverschiebung in den Magnetfeldsignalen an zwei verschiedenen Messorten führt, die als direktes Maß für die mittlere Durchflussgeschwindigkeit des Mediums verwendet wird. Die Phasenverschiebung kann auch mittels zweier Empfängerspulen entlang des Strömungskanals gemessen werden.
  • Patent
    EP 1847813B1 - 21.03.2012
  • Patent
    EP 1847813A2 - 24.10.2007
  • Patent
    DE102006018623A1 - 25.10.2007
  • Patent
    DE102006018623B4 - 15.05.2008

Permalink: https://www.hzdr.de/publications/Publ-18418
Publ.-Id: 18418


P1012 - Supraleitende Strukturen auf Schaltungen oder Schaltungselementen, Herstellung dieser Strukturen und deren Verwendung

Skrotzki, R.; Heera, V.; Hermannsdörfer, T.; Fiedler, J.; Schmidt, B.; Helm, M.
Die Erfindung beschreibt die Herstellung integrierter supraleitender Strukturen in Schaltungen und Schaltungselementen auf der Basis von Silizium- bzw. Germanium-Wafern durch Implementieren von Ausscheidungen, neuen chemischen Verbindungen oder einer Dotierung via Ionenimplantation und anschließender Kurzzeitausheilung. Vorteil dieser Strukturen ist die kostengünstige Produktion, und der höheren Leistungsdichte dieser Schaltungen bezüglich Transistorschaltungen. Diese Strukturen ermöglichen die Steuerung quantenmechanischer Interferenzerscheinungen mit Hilfe eines äußeren Magnetfeldes oder auf dem Chip erzeugten Magnetfeldes. Eine weitere Einsatzmöglichkeit bieten Logikschaltungen für das Quantum Computing.
  • Patent
    WO 2012037936A1 - 29.03.2012
  • Patent
    DE102010039911A1 - Offenlegung - 01.03.2012, Zurückweisung - 22.01.2013; Nachanmeldung WO

Permalink: https://www.hzdr.de/publications/Publ-18416
Publ.-Id: 18416


Gas bubble detection in liquid metals by means of the ultrasound transit-time-technique

Andruszkiewicz, A.; Eckert, K.; Eckert, S.; Odenbach, S.
In this work the ultrasound-transit time technique is introduced as a versatile method to analyze the bubble dynamics in liquid metal-gas flows. After discussing the principle of operation and the implementation of the technique, the methods used to extract the positions of the bubbles, their velocities, or their diameters are explained. Finally, the performance of the method is demonstrated for a liquid metal-gas flow with and without a magnetic field.
Keywords: liquid metal, two-phase flow, bubbly flow, bubble detection, ultrasound transit-time technique

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Permalink: https://www.hzdr.de/publications/Publ-18415
Publ.-Id: 18415


P1019 - Verfahren zur hochgenauen Messung der Strahlungsschwächung von veränderlichen Materialverteilungen mit Photonen- oder Teilchenstrahlung

Hampel, U.
Verfahren zur hochgenauen Messung der Strahlungsschwächung von veränderlichen Materialverteilungen mit Photonen- oder Teilchenstrahlung, verwendend eine Anordnung umfassend eine kollimierte Strahlungsquelle 1, mindestens einen Detektor 2 und einer dem Detektor 2 nachgeordneten Datenerfassungs- und Verarbeitungseinheit 3, dadurch gekennzeichnet, dass a) die Photonen- oder Teilchenstrahlung ausgehend von der Strahlungsquelle 1 das zu untersuchende Material 4 durchdringt und anschließend auf den Detektor 2 fällt, wobei der Detektor 2 die eintreffenden Photonen bzw. Teilchen zählt; b) die Datenerfassungs- und -verarbeitungseinheit 3 aufeinander folgend eine Anzahl von Zählwerten K des Detektors 2 für hinreichend kurze Zeitintervalle &Dgr;Tkurz erfasst, in denen die Materialverteilung in ausreichender Näherung als unveränderlich angesehen werden kann; c) die Datenerfassungs- und -verarbeitungseinheit 3 die aufeinander folgend aufgenommenen Zählwerte als Häufigkeitsverteilung in einem Datenfeld F abspeichert; d) die Datenerfassungs- und -verarbeitungseinheit 3 durch nacheinander folgende Berechnung des algebraischen Gleichungssystems Q = P+ F und den mittleren Schwächungswert A...
  • Patent
    DE 102010061440A1 - 21.06.2012

Permalink: https://www.hzdr.de/publications/Publ-18414
Publ.-Id: 18414


Flow measurements in liquid metals by means of the ultrasonic Doppler method and local potential probes

Cramer, A.; Eckert, S.; Gerbeth, G.
Substantial research activities have been carried out at HZDR during the last 15 years on the development and qualification of various methods to measure the velocity field in liquid metal flows. In this paper we report on two complementary methods for measuring the local velocity. The potential difference probe is a local sensor which is immersed into the liquid. Such sensors are very effective for investigations of the turbulent fluctuations at a local point. However, the installation of the probe in the bulk of the liquid might disturb the flow to be measured. Ultrasonic techniques are non-invasive, but need a continuous path from the ultrasonic transducer to the liquid under investigation. The ultrasound Doppler method delivers instantaneous profiles of the local velocity. Experimental applications of these measuring techniques in diverse liquid metal flows under the influence of magnetic fields will be presented here showing the capabilities and limitations of both methods.
Keywords: liquid metal, flow measurements, ultrasound Doppler velocimetry, potential difference probe

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Permalink: https://www.hzdr.de/publications/Publ-18413
Publ.-Id: 18413


Experimental demonstration of gas entrainment into liquid metals

Eckert, S.; Vogt, T.; Boden, S.; Shevchenko, N.; Gerbeth, G.
Entrainment of cover gas into the liquid metal coolant is one of the essential safety issues in the design of innovative liquid metal-cooled fast reactors. We present experimental studies of this phenomenon in low-melting metals. Ultrasonic and X-ray were considered as diagnostic tools for a visualization of gas entrainment at the free surface of the melt. Laboratory experiments were conducted using the eutectic alloy GaInSn which is liquid at room temperature. The vortex activated entrainment of air at the free surface of a rotating flow was disclosed by means of ultrasonic techniques. The X-ray radioscopy was used to visualize the behaviour of Argon bubbles inside a slit geometry. The measurements reveal distinct differences between water and GaInSn especially with respect to the process of bubble formation, the coalescence and the breakup of bubbles. Our results emphasize the importance of liquid metal experiments which are able to provide a suitable data base for numerical code validation.
Keywords: liquid metal fast reactor, gas entrainment, two-phase flow, ultrasound Doppler method, X-ray radioscopy
  • Lecture (Conference)
    International Conference on Fast Reactors and Related Fuel Cycles: Safe Technologies and Sustainable Scenarios (FR13), 04.-07.03.2013, Paris, France
  • Contribution to proceedings
    International Conference on Fast Reactors and Related Fuel Cycles: Safe Technologies and Sustainable Scenarios (FR13), 04.-07.03.2013, Paris, France
    IAEA-CN-199/289

Permalink: https://www.hzdr.de/publications/Publ-18412
Publ.-Id: 18412


P1108 - Integriertes nichtflüchtiges Speicherbauelement, Herstellung und Verwendung

Schmidt, H.; Shuai, Y.; Skorupa, I.; Zhou, S.
Die Erfindung beschreibt die Herstellung, den Aufbau eines integrierten Speicherbauelementes, umfassend mindestens einen gleichrichtenden Bottom-Kontakt oder einen Top-Kontakt und eine ferrroelektrische Schicht als leitfähigen Kanal zwischen den Kontakten. Weiterhin wird die Verwendung des integrierten Speicherbauelementes in einem integrierten Feldeffekttransistor beschrieben.
  • Patent
    DE 102011051767A1 - Offenlegung - 17.01.2013; Nachanmeldung WO, US

Permalink: https://www.hzdr.de/publications/Publ-18411
Publ.-Id: 18411


P1015 - Anordnung und Verfahren zur Erfassung des räumlichen Geschwindigkeitsprofils

Hampel, U.; Reinecke, S.
Die Erfindung beschreibt eine Anordnung zur Bestimmung des dreidimensionalen räumlichen Geschwindigkeitsprofils rheologischer Medien, wobei die Anordnung in einem Prozessbehälter untergebracht ist und aus im Prozessbehälter drehbar und beweglich angeordneten Messlanzen mit mindestens einer Detektoreinheit besteht. In das Prozessmedium eingebrachte Tracer werden von den Detektoren erfasst und die gemessenen Signale zur Bestimmung des räumlichen Geschwindigkeitsprofiles herangezogen. Die für die Geschwindigkeitsprofilmessung benutzten Tracer können im Anschluss für die Bestimmung des Verweilzeitspektrums des Prozessgemischs im Prozessbehälter verwendet werden.
  • Patent
    DE 102010060131A1 - 26.04.2012

Permalink: https://www.hzdr.de/publications/Publ-18410
Publ.-Id: 18410


P1101 - Sensoranordnung und Verfahren zur berührungslosen Bestimmung des wirksamen Drehmomentes in einer Welle

Buchenau, D.; Schmidt, G.; Wustmann, B.
Die Erfindung betrifft ein auf der Grundlage des magnetoelastischen Effektes basierendes, berührungsloses Messprinzip zur Bestimmung des Drehmomentes, welches auf ein magnetisierbares, rotationssymmetrisches Bauteil wirkt. Der Vorteil der erfindungsgemäßen Anordnung und des erfindungsgemäßen Messverfahrens ist die Überwindung der bisher ungelösten Problematik von materialspezifischen, eigenspannungsbedingten Hystereseeffekten, sowie der Begrenzung von Drift- und Störeinflüssen im dynamischen Betrieb. Lösung Die erfindungsgemäße Anordnung besteht aus einer Senderspule die mit symmetrisch oder asymmetrisch zur Senderspule angeordneten Empfängerspulen zusammenwirkt, wobei die Spulenlängsachsen der verwendeten Sender- und Empfängerspulen senkrecht zur Wellenlängsachse angeordnet sind. Erfindungsgemäß stehen sich Senderspule und Empfängerspulen bezogen auf das Messobjekt (Welle) diametral gegenüber, wobei speziell eine der Empfängerspulen auf der gleichen Längsachse zur Senderspule diametral gegenübersteht. Die verbleibenden beiden weiteren (äußeren) Empfängerspulen sind in der symmetrischen Anordnung in äquidistanten Abständen zur mittleren Empfängerspule angeordnet.
  • Patent
    EP2549255A2 - Offenlegung - 23.01.2013

Permalink: https://www.hzdr.de/publications/Publ-18409
Publ.-Id: 18409


P1009 - Magnetisierbare Einzel- und Mehrschichtstrukturen, deren Herstellung und Verwendung

Schmidt, H.; Mok, K. M.; Scarlat, C.; Weber, I.
Die Erfindung beschreibt die Auslegung einer Anordnung eines magnetooptischen Systems, bei dem für eine vorgegebene Wellenlänge der einfallenden elektromagnetischen Welle eine bestimmte Polarisation der reflektierten oder transmittierten Welle erreicht wird. Die erfindungsgemäße Anordnung und das Verwendungsverfahren ermöglicht den Einsatz zur Optimierung der Auslegung eines magnetooptischen Systems um die „Ziel“-Polarisation der reflektierten oder transmittierten Welle zu erreichen oder eines magnetooptischen Speichers oder eines Magnetfeldsensors. Weiterhin werden mit der Erfindung der Aufbau eines magnetooptischen Modulators oder eines Multiplexers mit magnetooptischen Komponente ermöglicht.
  • Patent
    Anmeldung: DE102011052217A1 31.01.2013
  • Patent
    Anmeldung WO2013013674A1 - 31.01.2013

Permalink: https://www.hzdr.de/publications/Publ-18408
Publ.-Id: 18408


Setting-up a Super-SIMS at DREAMS

Rugel, G.; Akhmadaliev, S.; Merchel, S.; Pavetich, S.; Renno, A.; Ziegenrücker, R.
At the Helmholtz-Zentrum Dresden-Rossendorf a new AMS (accelerator mass spectrometry) facility, DREsden AMS (DREAMS), with a 6-MV tandem accelerator has been successfully installed [1]. The range of applications will be broaden by setting up a Super-SIMS (SIMS = Secondary ion mass spectrometry) as an ultrasensitive analytical method for the determination of stable elements and isotopes. A commercial SIMS (from CAMECA) is connected to the accelerator and the high-energy setup of DREAMS, which will be additionally equipped with a time-of-flight detector system. The spatial resolution (x,y: ∼ 3μm; z: ∼ 5nm) of the SIMS will be kept as the SIMS is utilized as the negative ion source for the accelerator-based mass spectrometry. By the complete destruction of molecules detection limits some orders of magnitude better than for traditional dynamic SIMS are expected, i.e. ∼10-9-10-12, see e.g. [2]. The focus of applications will be geological samples in the framework of resource technology research.
Ref.: [1] S.\ Akhmadaliev et al., NIMB 294 (2013) 5. [2] C. Maden, Dissertation. ETH Zürich 2003.
Keywords: AMS, SIMS, sensitive analytical method
  • Poster
    DPG-Frühjahrstagung der Sektion AMOP (SAMOP), 18.-22.03.2013, Hannover, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18407
Publ.-Id: 18407


Amorphous Li-Al-based compounds: Novel approach for designing high performance electrode materials for Li-ion batteries

Thoss, F.; Thomas, J.; Oswald, S.; Potzger, K.; Reuther, H.; Ehrenberg, H.; Eckert, J.; Giebeler, L.
A new amorphous compound with the atomic composition Al43Li43Y6Ni8 applied as electrode material for Li-ion batteries is investigated. Unlike other amorphous compounds so-far investigated as anode materials it already contains Li as a base element in the uncycled state. The amorphous compound powder is prepared by high energy ball milling of a master alloy. It shows a strongly enhanced specific capacity in contrast to amorphous alloys without Li in the initial state and furthermore to conventional graphite anodes. According to the charge rate (C-rate) the specific capacity is reversible over 20 cycles at minimum in contrast to conventional crystalline intermetallic phases failing by volume changes. The delithiation process occurs quasi-continuously over a voltage range of nearly 4 V, while the lithiation is mainly observed between 0.1 V and 1.5 V. That way, the electrode is applicable for different potential needs. We suggest the application as anode. The electrode stays amorphous during cycling, thus avoiding volume changes. The cycling performance is further enhanced by a significant amount of Fe introduced as wear debris from the milling tools, which acts as a promoting element.
Keywords: high energy ball milling; pre-lithiation; anode; intermetallic phase

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Permalink: https://www.hzdr.de/publications/Publ-18406
Publ.-Id: 18406


P1114 - Extraktion von Edelmetall(ionen) mittels ionischer Flüssigkeiten

Straßner, T.; Schulz, T.; Bernhard, G.; Raff, J.; Lehmann, F.
Die vorliegende Erfindung betrifft ein Verfahren zur Extraktion von Metallen aus einer wässrigen Phase mit Hilfe spezifischer ionischer Flüssigkeiten.
  • Patent
    DE102011080230 - Offenlegung 07.02.2013, Nachanmeldungen: WO, EP, US

Permalink: https://www.hzdr.de/publications/Publ-18405
Publ.-Id: 18405


P1117 - Präkursorverbindungen für die Radiosynthese von [18F]Norchlor-fluor-homoepibatidin

Brust, P.; Deuther-Conrad, W.; Fischer, S.; Hiller, A.; Hoepping, A.; Patt, J. T.; Patt, M.; Sabri, O.; Smits, R.; Steinbach, J.
Die Erfindung betrifft eine Verbindung der Formel Ia oder Ibworin R1-CO2R3, -COR4 oder -R5 darstellt, worin R3 unsubstituiertes oder substituiertes C1-C6-Alkyl darstellt, R4 Wasserstoff, unsubstituiertes oder substituiertes C1-C6-Alkyl darstellt und R5 Wasserstoff, unsubstituiertes oder substituiertes C1-C6-Alkyl darstellt, R2-N+(R6)(R7)(R8)X– oder eine Nitrogruppe darstellt, worin R6, R7, R8 unabhängig von einander unsubstituiertes oder substituiertes C1-C6-Alkyl oder unsubstituiertes oder substituiertes -(CH)n- mit n = 1 bis 12 darstellen mit der Maßgabe, dass zumindest zwei der Substituenten R6, R7 und R8 C1-C6-Alkyl sind, und X– ein Halogenid, Sulfonat, unsubstituiertes oder substituiertes Acetat, Sulfat, Hydrogensulfat, Nitrat, Perchlorat oder Oxalat darstellt.
  • Patent
    DE102011052348 - Erteilung 07.02.2013, Nachanmeldung: WO, AU, BR, CA, CN, EP, JP, KR, US

Permalink: https://www.hzdr.de/publications/Publ-18404
Publ.-Id: 18404


Feasibility study of in vivo MRI based dosimetric verification of proton end-of-range for liver cancer patients

Yuan, Y.; Andronesi, O. C.; Bortfeld, T. R.; Richter, C.; Wolf, R.; Guimaraes, A. R.; Hong, T. S.; Seco, J.
Purpose: To investigate the feasibility of using MRI to verify proton beam distal range for liver tumor treatment in a retrospective study.
Methods and Materials: Because the follow-up hepatocyte-specific functional MR imaging can detect the radiobiological change of liver tissue after radiation, we firstly registered the contrast-enhanced MR images to the planning CT images from 5 liver patients, then overlaid the prescribed dose distribution on the MR images. Since dose calculation is most accurate at the penumbra dose region, we correlated the MR signal intensity (SI) to the radiation dose at the superior/inferior penumbra region. This dose-SI correlation was finally employed on registered MR images to estimate the proton end-of-range.
Results: Statistically significant correlations between radiation dose and MR SI were observed in superior/inferior penumbrae regions, with correlation coefficient ranging from 0.93 to 0.99. By applying the dose-SI correlation to the distal region of each proton beam, the mean difference between MR-estimated and the planned dose range was -2.18±4.89 mm for anterior-posterior beams and -3.90±5.87 mm for lateral beams.
Conclusions: This feasibility study proved the principle that proton dose range can be verified in vivo by follow-up MR images after proton liver treatment.
Keywords: Proton therapy, liver tumor, radiation effects on liver, magnetic resonance imaging, in vivo dosimetry, distal proton range verification

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Permalink: https://www.hzdr.de/publications/Publ-18403
Publ.-Id: 18403


EXAFS and X-ray scattering as complementary techniques to determine metal coordination in solutions

Hennig, C.
The determination of stability constants of metal complexes in aqueous solutions requires at least an estimate of the complex stoichiometry or better the determination of the complex structure. The structure analyses of metal complexes in solution is restricted to near-order sensitive techniques like X-ray scattering and X-ray absorption spectroscopy. X-ray scattering provide important structure information, but summarizes scattering contributions from all scattering pairs whose separation becomes difficult in real space with increasing number of involved elements. EXAFS is an element selective technique und provides structural information from the direct neighborhood of the absorbing atom. A statistical analysis of a sample series of solutions with pH variation provides furthermore direct access to the species distribution function. The advantages of both techniques will be discussed and typical applications will be demonstated.
Keywords: X-ray absorption, X-ray scattering, EXAFS, HEXS, XRD, structure analysis, aqueous solutions, actinides
  • Lecture (Conference)
    School and Conference on Analysis of Diffraction Data in Real Space, 18.-22.03.2013, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-18402
Publ.-Id: 18402


Fabrication of nanopores in 1 nm thick carbon nanomembranes with slow highly charged ions

Ritter, R.; Wilhelm, R. A.; Stöger-Pollach, M.; Heller, R.; Mücklich, A.; Werner, U.; Vieker, H.; Beyer, A.; Facsko, S.; Gölzhäuser, A.; Aumayr, F.
We describe the use of slow highly charged ions as a simple tool for the fabrication of nanopores with well-defined diameters typically between 10 and 20 nm in freestanding, 1 nm thick carbon nanomembranes (CNMs). When CNMs are exposed to a flux of highly charged ions, for example Xe40+, each individual ion creates a circular nanopore, the size of which depends on the kinetic and potential energy of the impinging ion. The controlled fabrication of nanopores with a
uniform size opens a path for the application of CNM based filters in nanobiotechnology.

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Permalink: https://www.hzdr.de/publications/Publ-18401
Publ.-Id: 18401


Investigations to the Eu(III)-B(OH)3-Organic System at increased salt concentrations

Schott, J.; Acker, M.; Kretzschmar, J.; Barkleit, A.; Taut, S.; Brendler, V.; Bernhard, G.
Boric acid (B(OH)3) and (poly)borates are of great interest regarding the mobilization of trivalent actinides in nuclear waste repositories, particularly in salt deposits.
This work describes the influence of boric acid on the Eu salicylate complexation due to the formation of a borate ester of salicylate, which could be the key to determine the stability constants of Eu-borate complexes.
Furthermore, at pH 6 the formation of a solid Eu borate species in presence of polyborates is observed. The formation progress of the solid Eu borate species depends on the polyborate concentration and salt concentration. The solid formation could be an interesting possibility for the immobilization of trivalent actinides in a nuclear waste repository.
Keywords: lanthanides, actinides, europium, boric acid, borates, polyborates
  • Contribution to proceedings
    Actinide and Brine Chemistry in a Salt Repository Workshop (III), ABC-Salt(III), 15.-17.04.2013, Santa Fe, New Mexico, USA
  • Lecture (Conference)
    Actinide and Brine Chemistry in a Salt Repository Workshop (III), ABC Salt III, 15.-17.04.2013, Santa Fe, New Mexico, USA

Permalink: https://www.hzdr.de/publications/Publ-18400
Publ.-Id: 18400


Spinwaves in Nanostructures: The Transition from Periodical Perturbations to Magnonic Crystals

Lenz, K.; Gallardo, R. A.; Bali, R.; Neudert, A.; Banholzer, A.; Wagner, K.; Langer, M.; Körner, M.; Grebing, J.; Lindner, J.; Landeros, P.; Fassbender, J.ORC
Two-magnon scattering is a well-known effect e.g. in ferromagnetic resonance (FMR) experiments leading to a linewidth broadening. Available theory so far was based on random defects acting as scattering centers for spin waves. Recently it was shown by Landeros and Mills [1] that this theory can be extended to handle two-magnon scattering in periodically perturbed films, which can be easily created by lithographical patterning processes. We present, that the uniform resonance mode splits into several modes and we compare the experimental results with analytical theory and simulations.
The periodically perturbed films are the intermediate step in the transition from a planar film towards full magnonic crystals. Small magnetic perturbations can be achieved by magnetic patterning using ion beam implantation [2]. A lithographically defined mask (stripes, dots, squares, …) covers part of the sample. Thus, these areas are protected from the ion beam changing the magnetic properties in the surface region of the sample creating magnetic defects. Another method we apply is to use ion etching to mill the pattern into the magnetic film to create geometric defects. Both techniques allow for precise control of the defect depth. With the latter approach the defect depth can be increased reaching the substrate, such that the structures are finally separated resembling a 1D or 2D magnonic crystal.
The evolution of spinwave modes and magnon bands in this transition from just a perturbation to a magnonic crystal has not been investigated so far.The extended model allows for analytically calculating the response function of 1D and 2D periodically perturbed ferromagnetic films in almost perfect agreement to FMR experiments as it will be shown. A striking feature e.g. is the level splitting due to the two-magnon scattering, which even leads to magnonic band gaps in full magnonics crystals. Exactly this splitting can be tailored by the geometric and magnetic sample parameters as described above.

This work was supported by the DFG grants FA 314/6-1 and FA314/3-2, as well as by CONICYT and MECESUP FSM0806.
Keywords: spin waves, ferromagnetic resonance, magnonic crystals, nanostructures, damping, relaxation, dispersion relation
  • Poster
    Yamada Conference LXVII -The 8th International Symposium on Metallic Multilayers (MML2013), 19.-24.05.2013, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-18399
Publ.-Id: 18399


Splitting of spin-wave modes in thin films with Arrays of periodic perturbations: theory and experiment

Gallardo, R. A.; Lenz, K.; Banholzer, A.; Körner, M.; Lindner, J.; Fassbender, J.ORC; Landeros, P.
We present an analytical theory focused on the description of the ferromagnetic resonance (FMR) response of thin lms in the case that periodic surface perturbations are introduced. These perturbations can be any kind of one- or two-dimensional rectangular arrays of defects patterned onto one surface of the magnetic lm. Our theory allows us to describe their influence in such a way that the periodic defect structure can have any given shape. We calculate the response functions that are the components of the dynamic susceptibility tensor of the lm exposed to the FMR microwave excitation. These allow us to obtain the resonant response of the system, trough relevant quantities as the microwave absorption, the FMR linewidth, and resonance eld. We show examples where the periodic defects have the shape of stripes, dots, and rectangles. In our framework the perturbations may be considered either as bumps or pits. Finally, we compare our results with recent experimental FMR results, which manifest a very good agreement with the theory.
Keywords: spin relaxation, ferromagnetic resonance, two-magnon scattering, periodic perturbations, magnonic crystals

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Permalink: https://www.hzdr.de/publications/Publ-18398
Publ.-Id: 18398


Linear and non-linear stability of melt flows in magnetic fields

Grants, I.; Galindo, V.; Gerbeth, G.
This review considers the stability of melt motion in two simplified models of semiconductor crystal growth by either vertical gradient freeze (VGF) or Czochralski (Cz) processes under the influence of various magnetic fields. In VGF the crystal is grown at the bottom of the crucible, resulting in a stable thermal stratification of the melt. The presence of a stabilizing temperature gradient surprisingly decreases the stability of the flow driven by a rotating magnetic field (RMF). The instability of the travelling magnetic field (TMF)-driven flow, in contrast, is significantly delayed by thermal stratification in VGF. The TMF may, thus, be used in VGF to control the shape of the solidification interface or the radial dopant distribution without causing undesirable flow oscillations. The crystal is pulled out from the melt in the Cz process, producing an unstable temperature gradient below the crystal. The RMF is able to force the resulting unstable buoyant flow into a state of small-scale, high-frequency turbulence that may be regarded as stable for practical purposes. This effect is experimentally observed over a wide range of Grashof numbers, up to 10^9, characteristic for a large Cz system.
Keywords: crystall grwoth, vertical gradient freeze, Czochralski, Linear and non-linear stability, liquid metal flows, magnetic fields

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Permalink: https://www.hzdr.de/publications/Publ-18397
Publ.-Id: 18397


The Use of Magnetic Fields in vertical Bridgman/Gradient Freeze-type Crystal Growth

Pätzold, O.; Niemietz, K.; Lantzsch, R.; Galindo, V.; Grants, I.; Bellmann, M.; Gerbeth, G.
This paper outlines advanced vertical Bridgman/Gradient Freeze techniques with flow control using magnetic fields developed for the growth of semiconductor crystals. Low-temperature flow modelling, as well as laboratory-scaled crystal growth under the influence of rotating, travelling, and static magnetic fields are presented. Experimental and numerical flow modelling demonstrate the potential of the magnetic fields to establish a well-dened flow for tailoring heat and mass transfer in the melt during growth. The results of the growth experiments are discussed with a focus on the influence of a rotating field on the segregation of dopants, the influence of a travelling field on the temperature field and thermal stresses, and the potential of rotating and static fields for a stabilization of the melt flow.
Keywords: crystal growth, vertical Bridgman technique, Gradient Freeze technique, magnetic fields

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Permalink: https://www.hzdr.de/publications/Publ-18396
Publ.-Id: 18396


Advances in Principal Balances for Compositional Data

Martin-Fernandez, J. A.; Pawlowsky-Glahn, V.; Egozcue, J. J.; Tolosana-Delgado, R.
A prior reduction of dimension is often a necessary step when dealing with largedimensional data sets (geochemical surveys, microarray data, genetic Compositional data analysis requires selecting an orthonormal basis with which to work on coordinates. In most cases this selection is based on a data driven criterion. Principal component analysis provides bases that are, in general, functions of all the original parts, each with a different weight hindering their interpretation. For interpretative purposes, it would be better to have each basis component as a ratio or balance of the geometric means of two groups of parts, leaving irrelevant parts with a zero weight. This is the role of principal balances, defined as a sequence of orthonormal balances which successively maximize the explained variance in a data set. The new algorithm to compute principal balances requires an exhaustive search along all the possible sets of orthonormal balances. To reduce computational time, the sets of possible partitions for up to 15 parts are stored. Two other suboptimal, but feasible, algorithms are also introduced: (i) a new search for balances following a constrained principal component approach and (ii) the hierarchical cluster analysis of variables. The latter is a new approach based on the relation between the variation matrix and the Aitchison distance. The properties and performance of these three algorithms are illustrated using a typical data set of geochemical compositions and a simulation exercise.
Keywords: Aitchison norm; Cluster analysis; Compositions; Isometric logratio coordinates; Principal component analysis; Simplex

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Publ.-Id: 18394


CFD Modeling of Bubble-induced Turbulence

Rzehak, R.; Krepper, E.
Modeling of bubble-induced turbulence in dispersed gas-liquid multiphase flow is an important but still unresolved issue. Aside from its intrinsic interest, turbulence in this type of flow has a strong impact on other important processes like turbulent dispersion of the bubbles and bubble-coalescence and -breakup and thus is a central part of the overall model. Especially the latter require as input values of turbulent kinetic energy and dissipation, which as shown subsequently are not readily obtained from the most common approach to add a bubble-induced contribution to the effective viscosity. This may be overcome by including source terms in the single phase two-equation turbulence models that describe the bubble effects on the liquid turbulence. However, no consensus on the precise form of these terms has been reached yet. We here report a comparison of different models of this type. Special care has been given to the selection of a rather comprehensive set of reference data allowing to qualify the validity of the different models. Conclusions towards best practice guidelines for modeling bubbly turbulence are drawn and needs for further research identified.

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Room temperature ferromagnetism in Ti Dioxide DMS

Smekhova, A.; Orlov, A. F.; Balagurov, L. A.; Perov, N. S.; Ganshina, E. A.; Semisalova, A. S.; Novikov, A.; Potzger, K.; Butterling, M.; Cornelius, S.; Yildirim, O.
Abstract: A detailed study of a room-temperature ferromagnetism in diluted magnetic semiconductors on the basis of Titanium dioxide thin films with incorporated Co and V atoms has been performed. The relations between the structure, magnetization, transport and magneto-optical properties as well as evolution of defects and some peculiarities of preliminary element-specific XANES spectra are presented.
A continues interest to diluted magnetic semiconductors (DMS) during the last decade caused by an ambitious idea to get spin-polarized carriers in transparent semiconductor materials.1 A new physics exhibited by such materials could be exploited in fast developed information processing, storage and other diverse spintronic technologies. Up to now lot of systems have been already studied 2,3,4,5,6; and among them a particular interest to the DMS on the basis of Titanium Dioxide with incorporated 3d impurities (Co, V and Mn) have been ascertained.
The main goal of our present research is the study of the influence of structural properties such as point defects or defect complexes linked to oxygen deficiency on the magnetic, magneto-optical and magneto-transport properties of V (Mn) doped TiO2 anatase thin films. According to preliminary basic researches, magnetism in doped oxides is strongly influenced by defects and represents so far not-understood kind of magnetic phenomenon.
The TiO2 anatase thin films (200÷500 nm) with several percents (3 and 8%) of 3d transition metals with unpaired electrons (Co and V) have been prepared by rf magnetron deposition technique as well as ion-beam implantation (for samples with Vanadium). The presence of room temperature ferromagnetism in the samples has been initially checked by VSM and SQUID magnetometry measurements. The further magneto-optical (Transversal Kerr Effect) and transport (Hall Effect) measurements have been performed to obtain a more detailed picture of magnetism and concentration of carries. The special attention has been applied to verify an absence of any additional phases and magnetic impurities as metallic clusters insight the samples: in addition to a standard XRD analysis the element-specific XANES measurements at the Ti and 3d transition metal K- absorption edges have been done. The positron annihilation spectroscopy (PAS) has been used in order to investigate open volume defects on a very local scale and the first preliminary results will be presented.
The relationship of observed hysteresis loop in the sample magnetization, carrier concentration and characteristic features of magneto-optical spectra depending on film thicknesses, preparation route and structural defects is discussed. The difference in magnetic behaviour of TiO2:V and previously studied TiO2:Co is established.
This work is supported by the Initiative and Networking Fund of the German Helmholtz Association, Helmholtz-Russia Joint Research Group HRJRG-314 and RFBR #12-02-91321-SIG_а
References
1. Y. Matsumoto et al., Science 291, pp. 854 - 856 (2001).
2. H. Ohno et al., Appl. Phys. Lett. 69, 363 - 365 (1996).
3. H. Akai, Phys. Rev. Lett. 81, pp. 3002 - 3005 (1998).
4. S. Sonada et al., J. Cryst. Growth 237–239, 1358 (2002).
5. S.Q. Zhou et al., Appl. Phys. Lett. 93, pp. 232507 (2008).
6. A. F. Orlov et al., Phys. Solid State 53, pp. 482 - 484 (2011).
Keywords: diluted magnetic semiconductors
  • Lecture (Conference)
    ETOPIM (Electrical, Transport and Optical Properties of Inhomogeneous Media), 02.-07.09.2012, Marseille, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-18392
Publ.-Id: 18392


Experimental Investigation of Horizontal Gas-Liquid Stratified and Annular Flow using Wire Mesh Sensor

Vieira, R. E.; Kesana, N. R.; Torres, C. F.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.
Stratified and annular gas-liquid flow patterns are commonly encountered in oil and gas transportation pipelines. The measurement and visualization of two-phase flow characteristics is of great importance as two-phase flows persist in many fluids engineering applications. A Wire Mesh Sensor technique based on conductance measurements was applied to investigate two-phase horizontal pipe flow. The horizontal flow test section consisting of a 76 mm ID pipe, 18 m long was employed to generate stratified and annular flow conditions. A 16×16 wire configuration sensor, installed at 17 m from the inlet test section, is used to determine the void fraction within the cross-section of the pipe. Physical flow parameters were extracted based on processed raw measured data obtained by the sensors using signal processing techniques. In this work, the principle of wire mesh sensors and the methodology of flow parameter extraction are described. From the obtained raw data time series of void fraction, mean void fraction and characteristic liquid film velocities are determined for different liquid and gas superficial velocities that ranged from 0.03m/s to 0.2 m/s and from 9 m/s to 34 m/s, respectively. The effects of liquid viscosity on the measured parameters are also investigated using three different viscosities.
Keywords: Wire Mesh Sensor, two-phase flow, flow visualization, void fraction.
  • Contribution to proceedings
    ASME 2013 Fluids Engineering Division Summer Meeting (FEDSM 2013), 07.-11.07.2013, Incline Village, Nevada, United States
    ASME 2013 Fluids Engineering Division Summer Meeting Volume 1C: ASME, 978-0-7918-5556-0, V01CT17A0
  • Journal of Fluids Engineering - Transactions of the ASME 136(2014)12, 121301
    DOI: 10.1115/1.4027799

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Publ.-Id: 18391


Simulation of instabilities in liquid metal batteries

Weber, N.; Galindo, V.; Weier, T.; Stefani, F.; Wondrak, T.
Liquid metal batteries, i.e. batteries in which both electrodes as well as the electrolyte are in the liquid state are usable for grid-scale energy storage and have received considerable attention recently. However, in completely liquid systems, fluid dynamic instabilities have to be considered. We focus here on the current driven Tayler instability and present results of a numerical study using a finite volume code for the calculation of the fluid flow coupled to a Biot-Savart integration to obtain the magnetic field. Growth rates of the instability as well as the magnetic field structure of the saturated instability fit very well to the experimental findings.
Keywords: Liquid metal battery, Tayler instability, finite volume method
  • Lecture (Conference)
    ERCOFTAC WORKSHOP Direct and Large-Eddy Simulation 9 (DLES 9), 03.-05.04.2013, Dresden, Deutschland
  • Contribution to proceedings
    ERCOFTAC WORKSHOP Direct and Large-Eddy Simulation 9 (DLES 9), 03.-05.04.2013, Dresden, Deutschland
    ERCOFTAC Series Volume 20: Springer, 978-3-319-14447-4, 585-594
    DOI: 10.1007/978-3-319-14448-1_74

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Publ.-Id: 18390


Interaction of Selected Actinides (U, Cm) with Bacteria Relevant to Nuclear Waste Disposal

Lütke, L.
To assess the safety of a site destined for storage of nuclear waste enhanced research effort is demanded to investigate the complex interactions of released radionuclides with parts of the environment that includes indigenous microorganisms.
As part of a BMWi-funded project this work aimed at assessing the interactions of two bacterial strains with the actinides uranium and curium with a focus on thermodynamics to provide stability constants of the actinide bacteria species formed usable for modelling the distribution of these actinides in the environment. The influences of Pseudomonas fluorescens (CCUG 32456A) isolated from the granitic aquifers at Äspö (Sweden) and a novel isolate from Mont Terri Opalinus clay (Switzerland), Paenibacillus sp. MT-2.2, were investigated. A combined approach using microbiological and spectroscopic techniques as well as potentiometry was employed to characterize the U(VI) and Cm(III) binding onto the cell surface functional groups structurally and thermodynamically. Further, due to its similar ionic radius to Cm(III) also Eu(III) was studied as non-radioactive analog.
The results evidenced that U(VI) and Cm(III) binding onto the cells is strongly pH-dependent. Both strains displayed high U(VI) binding capacities. In view of the versatile possible interaction mechanisms between microbes and actinides, it was found that both investigated strains display besides direct also indirect interaction in the form of a pronounced pH-dependent phosphatase activity and concomitant phosphate release which was drastically decreased in presence of U(VI). A moderate to strong interaction of U(VI) and Cm(III) (Eu(III)) with carboxylic and phosphoryl sites of the bacterial surfaces could be proven. Based on the determined stability constants of the different U(VI) phosphoryl and the U(VI) carboxyl surface complexes it could be shown that U(VI) is bound thermodynamically more stable to phosphoryl sites than to carboxylic ones. U(VI) speciation calculations indicated a dominant binding of U(VI) to the bacterial surface functional groups up to pH 7. For Eu(III) interaction with the bacterial surfaces the complexes R-O-PO3H-Eu2+ and R-COO-Eu2+ were identified and characterized thermodynamically. Spectroscopic results on Cm(III) binding onto Paenibacillus sp. cells indicated that binding occurred to H-phosphoryl surface sites over a wide pH range while sorption was found to be fully reversible. The identified complex R­-O-­PO3H-­Cm2+ was characterized spectroscopically and thermodynamically.
The stability constants calculated in the present work are valuable for modelling the U(VI), Cm(III) and Eu(III) speciation and distribution in the environment.
Keywords: U(VI), Cm(III), Eu(III), Pseudomonas fluorescens, Paenibacillus sp., Äspö, Mont Terri, Opalinus clay, potentiometry, TRLFS, EXAFS
  • Doctoral thesis
    TU Dresden, 2013
    133 Seiten

Permalink: https://www.hzdr.de/publications/Publ-18389
Publ.-Id: 18389


The U(VI) Speciation Influenced by Novel Bacterial Isolates from Mont Terri Opalinus Clay

Lütke, L.; Moll, H.; Bachvarova, V.; Geißler, A.; Selenska-Pobell, S.; Bernhard, G.
High-level nuclear waste is supposed to be stored in deep geological formations. An example is the Opalinus clay formation located in the North-Western part of Switzerland (Mont Terri, Canton Jura) which is currently studied in terms of its suitability as host rock for future nuclear waste storage. Bacteria are ubiquitous in nature and together with archaea represent the only form of life which can inhabit and even thrive in the hostile environment of a nuclear waste repository. It is well known that bacteria can affect the actinide speciation through versatile mechanisms and therefore the migration behaviour. The presented work is embedded in the project “Microbial Diversity in Claystone (Opalinus Clay) and Interaction of Dominant Microbial Strains with Actinides” funded by the Federal Ministry of Economics and Technology (BMWi). The project is integrated in the German-Swiss cooperation within the Mont Terri Project.
The talk deals with the U(VI) interactions of two bacterial strains isolated from Mont Terri Opalinus clay, namely Paenibacillus sp. and Sporomusa sp.. The morphology/ surfaces functional groups of the strains have been characterized using microbiological techniques combined with potentiometry. Further, potentiometry and TRLFS results about the U(VI) species formed at the bacterial cell surfaces are presented. Emphasize of this work was to characterize the formed U(VI) species thermodynamically.
Keywords: Mont Terri, Opalinus Clay, Uranium(VI), Paenibacillus sp., Sporomusa sp., potentiometry, TRLFS
  • Lecture (Conference)
    TD-227 Joint HT, MA, BN, GD, PC-C Meeting, 11.-12.02.2013, St. Ursanne, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-18388
Publ.-Id: 18388


Structure, Function and Dynamics of G-Protein coupled Receptors

Eichler, S.
Understanding the function of membrane proteins is crucial to elucidate the molecular mechanisms by which physiological processes are regulated by transmembrane signaling based on the interaction of extracellular ligands with membrane-bound receptors. In this work, synthetic transmembrane segments derived from the visual photoreceptor rhodopsin, the full length system rhodopsin and mutants of opsin are used to study physical processes that underlie the function of this prototypical class-A G protein-coupled receptor. The dependency of membrane protein hydration and protein-lipid interactions on side chain charge neutralization is addressed by uorescence spectroscopy on synthetic transmembrane segments in detergent and lipidic environment constituting transmembrane segments of rhodopsin in the membrane. Results from spectroscopic
studies allow us to construct a structural and thermodynamical model of coupled protonation of the conserved ERY motif in transmembrane helix 3 of rhodopsin and of helix restructuring in the micro-domain formed at the protein/lipid water phase boundary. Furthermore, synthesized peptides and full length systems were studied by time resolved FTIR-Fluorescence Cross Correlation Hydration Modulation, a technique specically developed for the purpose of this study, to achieve a full prospect of time-resolved hydration eects on lipidic and proteinogenic groups, as well as their interactions. Multi-spectral experiments and time-dependent analyses based on 2D correlation where established to analyze large data sets obtained from time-resolved FTIR dierence spectra and simultaneous static fluorescence recordings. The data reveal a sequential process where water H-bond formation to the lipid carbonyl precedes transmembrane protein conformational changes which are eventually followed by the intrusion of water into the protein interior as monitored by the fluorescence of hydrophobic buried tryptophan. Our results support the assumption of the critical role of the lipid/water interface in membrane protein function and they prove in particular the important influence of electrostatics, i.e., side chain charges at the phase boundary, and hydration on that function.
Keywords: GPCR FTIR Lipid protein interactions Fluorescence membrane receptor
  • Doctoral thesis
    TU Dresden, 2011
    122 Seiten

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Publ.-Id: 18387


Mapping the Local Elastic Properties of Nanostructured Germanium Surfaces: from Nanoporous Sponges to Self-Organized Nanodots

Böttger, R.; Keller, A.; Bischoff, L.; Facsko, S.
Due to their reduced dimensions, the mechanical properties of nanostructures may differ substantially from those of bulk materials. Quantifying and understanding the nanomechanical properties of individual nanostructures is thus of tremendous importance both from a fundamental and a technological point of view. Here we employ a recently introduced atomic force microscopy (AFM) mode, i.e., peak-force quantitative nanomechanical imaging, to map the local elastic properties of nanostructured germanium surfaces. This imaging mode allows for the quantitative determination of the Young’s modulus with nanometer resolution. Heavy-ion irradiation was used to fabricate different self-organized nanostructures on germanium surfaces. Depending on the sample temperature during irradiation, nanoporous sponge-like structures and hexagonally ordered nanodots are obtained. The sponge-like germanium surface is found to exhibit a surprisingly low Young’s modulus well below 10 GPa which furthermore depends on the ion energy. For the nanodot patterns, local variations in the Young’s modulus are observed: at moderate sample temperatures, the dot crests have a lower modulus than the dot valley whereas this situation is reversed at high temperatures. These observations are explained by vacancy dynamics in the amorphous germanium matrix during irradiation. Our results furthermore offer the possibility to tune the local elastic properties of nanostructured germanium surfaces by adjusting the ion energy and sample temperature.
Keywords: atomic force microscopy, Young’s modulus, nanopatterning, ion irradiation, vacancy dynamics

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Publ.-Id: 18385


Bewertung der Werkstoffzähigkeit im duktil-spröden Übergangsbereich

Viehrig, H.-W.
The presentation summarizes the fracture behaviour of ferritic steels in the ductile-to-brittle region. In the ductile region the material fails by microvoid coalescence, wherein the crack grows as the load is increased. Unlike to the brittle region where the material suddenly fails by cleavage failure. In the ductile-to-brittle region both micromechanisms of fracture can occur in the same specimen or structure. The Master Curve concept models the probability for failure of a specimen within the ductile-to-brittle transition range using a three-parameter Weibull model. It allows to quantify the variation of fracture toughness with the temperature throughout the ductile-to-brittle transition region. Limit curves of fracture tough¬ness for defined failure probabilities and a reference temperatures can be determined using this method. Thus, fracture mechanical values can be supplied for an integrity assessment of structural components.
Keywords: fracture toughness, ductile-to-brittle transition region, Master Curve, integrity assessment
  • Lecture (others)
    DVM Fortbildungsseminar für Anwender der Bruchmechanik: Bruchmechanische Bewertung rissbehafteter Strukturen, 18.02.2013, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18384
Publ.-Id: 18384


Bestimmung der J-Risswiderstandskurve an einem zähen Reaktordruckbehälterstahl - Ergebnisse eines Round Robin Tests

Viehrig, H.-W.; Houska, M.; Mottitschka, T.; Grundmann, N.; Trupitz, P.; Bär, W.; Gerwien, P.; Lucon, E.
The fracture toughness of high toughness materials like reactor pressure vessel (RPV) steels can be characterized by a crack resistance curve (JR) measured by single and multi-specimen methods according to the test standards ISO 12135 and ASTM E1820. Four institutions measured JR curves with 1T-C(T) specimens of RPV steel by using the single specimen unloading compliance (UC) technique. The applicability of the UC method and the problems occurred in determining engineering J initiation fracture toughness values according to the tests standards ASTM E1820 and ISO 12135 are discussed. In addition the JR data determined with the UC method are compared with the multiple-specimen method as a reference.
Keywords: ductile tearing, J integral, unloading compliance, fracture toughness
  • Contribution to proceedings
    45. Tagung DVM-Arbeitskreis Bruchvorgänge, Bruchmechanische Werkstoff- und Bauteilbewertung: Beanspruchungsanalyse, Prüfmethoden und Anwendungen, 19.-20.02.2013, Berlin, Deutschland
    Tagungsband: 45. Tagung DVM-Arbeitskreis Bruchvorgänge, Berlin: DVM
  • Lecture (Conference)
    45. Tagung DVM-Arbeitskreis Bruchvorgänge, Bruchmechanische Werkstoff- und Bauteilbewertung: Beanspruchungsanalyse, Prüfmethoden und Anwendungen, 19.-20.02.2013, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18383
Publ.-Id: 18383


Herstellung und Reinigung von 56Co, 64Cu und 85Sr am Leipziger Zyklotron Cyclone 18/9.

Mansel, A.; Poetsch, M.; Franke, K.
Die Abteilung „Reaktiver Transport“ der Forschungsstelle Leipzig beschäftigt sich mit dem Migrations-/Sorptionsverhalten von (Schad)stoffen in geologischen Formationen. In aktuellen Projekten werden zur Zeit toxische Schwermetalle sowie langlebige Radionuklide untersucht. Für unsere Studien werden kurzlebige Radionuklide eingesetzt (64Cu, 85Sr, 56Co). Diese werden am Leipziger Zyklotron durch Protonenbeschuss von isotopenangereichertem 64Ni und 85Rb und natFe hergestellt. Die chemische Aufarbeitung erfolgt durch Flüssig-flüssig-Extraktion und Ionenchromatographie. Die Radionuklide werden mit einer chemischen Ausbeute von ca. 95 % erhalten. Das wertvolle Targetmaterial (isotopenangereichert bis zu 95 %) wird mit ~ 90 % Ausbeute wiedergewonnen. Die Targets werden entweder durch Verpressen ihrer Chloride oder durch elektrolytische Abscheidung auf Goldfolien hergestellt. Die Bestrahlung erfolgt bei einem Protonenstrom von 27 µA bei Strahlzeiten von bis zu 4 Stunden und einer Projektilenergie von ca. 12 MeV. Die produzierten Radionuklide wurden erfolgreich in Verteilungsstudien an Geomaterialien sowie in der Calixarenkomplexierung eingesetzt.
  • Poster
    Anakon2013, 04.-07.03.2013, Essen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18382
Publ.-Id: 18382


Bruchmechanische Bewertung von Reaktordruckbehälter Mehrlagenschweißnähten

Viehrig, H.-W.; Houska, M.; Kalkhof, D.; Schindler, H.-J.
The Master Curve (MC) approach as standardised in the ASTM Standard Test Meth-od E 1921-05 was applied on the multilayer beltline welding seam of the not commissioned Biblis C reactor pressure vessel (RPV). The main focus in is on the investigation of the influence of the specimen orientation (crack extension directions circumferential and through the thickness) and -type on the MC reference temperature T0. Furthermore RPV integrity assessment concepts based on the MC approach are applied on the test results. The non-homogeneous weld structure results in a strong variation of the fracture toughness values at cleavage failure of the specimens. The range of the T0 values measured with specimens from individual thickness locations of the multilayer welding seam amounts 40 K.
Keywords: fracture toughness, Master Curve, structure, reference temperature, integrity
  • Contribution to proceedings
    45. Tagung DVM-Arbeitskreis Bruchvorgänge, Bruchmechanische Werkstoff- und Bauteilbewertung: Beanspruchungsanalyse, Prüfmethoden und Anwendungen, 19.-20.02.2013, Berlin, Deutschland
    Tagungsband: 45. Tagung DVM-Arbeitskreis Bruchvorgänge, Berlin: DVM
  • Lecture (Conference)
    45. Tagung DVM-Arbeitskreis Bruchvorgänge, Bruchmechanische Werkstoff- und Bauteilbewertung: Beanspruchungsanalyse, Prüfmethoden und Anwendungen, 19.-20.02.2013, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18381
Publ.-Id: 18381


Entwicklung von PET-Radioliganden für den Alpha7-Subtyp des nikotinischen Acetylcholinrezeptors

Rötering, S.
  • Lecture (others)
    Doktorandenkolloquium des Biotechnologisch-Biomedizinischen Zentrums der Universität Leipzig, 06.02.2013, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18380
Publ.-Id: 18380


Synthesis of Short and Versatile Heterobifunctional Linkers for Conjugation Purposes of Bioactive Molecules with (Radio-)Labels

Heldt, J.-M.; Kerzendörfer, O.; Mamat, C.; Starke, F.; Pietzsch, H.-J.; Steinbach, J.
The preparation of a series of short and versatile (eleven and twelve atom length) hydrophilic heterobifunctional linkers from low-cost chemicals using simple experimental setups is described.
The approach can be used to connect high molecular weight bioactive molecules with azamacrocycles to enable radiolabeling with radiometals. The ring opening reaction of three cyclic anhydrides with 2-(2-aminoethoxy)ethanol afforded precursors 4a–c, which were subsequently converted into various heterobifunctional linkers for radiofluorination, Huisgen–Click approaches, or Staudinger ligation and for solid-phase peptide synthesis. As examples for successful building block ligation using the strain-promoted Huisgen cycloaddition on the one hand and the traceless Staudinger approach on the other hand, the Cetuximab antibody was modified by using 13a in a convenient two-step procedure.

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Permalink: https://www.hzdr.de/publications/Publ-18379
Publ.-Id: 18379


NMR Spectroscopy in Nuclear Safety Research

Kretzschmar, J.; Barkleit, A.; Brendler, V.; Brunner, E.
Radioactive elements can be emitted to the environment for several reasons. There are natural uranium and thorium compounds (and their decay products) in rock formations, which can be released by geologic alteration or mining processes. As a consequence of energy production in nuclear power plants over the last decades, huge amounts of nuclear waste were produced. If this waste is not stored adequately, radionuclides can enter the geo- or biosphere. Studying the transport behaviour of these radioactive elements and their fission products is the key aspect of our research. Here, rocks and natural mineral phases as well as organic molecules as potential binding sites are objects of investigation.
Both, NMR spectroscopic structure elucidation of environmentally relevant complexes of lanthanides, actinides and selenium as well as the verification of results obtained by other techniques in former studies, are the aims of this work.
The study of large biomolecules such as proteins or humic acids is rather complicated. Therefore, compounds which are themselves potential complexing agents or at least possess structural similarities to larger molecules, are used as model substances, for instance glutathione (a tripeptide) or citrate.
Different one- and two-dimensional solution and solid state NMR methods will be applied to dedicated systems, supplied by TRLFS, ATR FT-IR and EXAFS. Where possible, the radionuclides are supposed to be replaced by inactive analogues or isotopes. In the case of selenium*, the spin-½ nucleus of Se-77 is well suited to be directly observed by NMR spectroscopy.

* in cooperation with E. Brendler, Institut für Analytische Chemie, Technische Universität Bergakademie Freiberg
Keywords: NMR spectroscopy, nuclear safety research, lanthanides, actinides, selenium, boric acid
  • Poster
    15th JCF Frühjahrssymposium, 06.-09.03.2013, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18378
Publ.-Id: 18378


Formation of surface nano-structures by plasma expansion induced by highly charged ions

Moslem, W.; El-Said, A. S.
Slow highly charged ions (HCIs) create surface nano-structures (nano-hillocks) on the quartz surface. The formation of hillocks was only possible by surpassing a potential energy threshold. By using the plasma expansion approach with suitable hydrodynamic equations, the creation mechanism of the nano-hillocks induced by HCIs is explained. Numerical analysis reveal that within the nanoscale created plasma region, the increase of the temperature causes an increase of the self-similar solution validity domain, and consequently the surface nano-hillocks become taller. Furthermore, the presence of the negative (positive) nano-dust particles would lead to increase (decrease) the nano-hillocks height.

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Permalink: https://www.hzdr.de/publications/Publ-18377
Publ.-Id: 18377


Experimental Study of a Simplified 3 x 3 Rod Bundle using DPTV

Dominguez-Ontiveros, E. E.; Hassan, Y. A.; Franz, R.; Barthel, F.; Hampel, U.
Computational Fluid Dynamics (CFD) has evolved in the last years as an important tool for the simulation and prediction of rod bundles in plant components under various scenarios, contributing to the continuing improve of performance and safety of nuclear power plants. However, these tools must be validated and verified in order to assure with enough confidence the reliability and quality of CFD predictions. The present work focuses in the basic study and a benchmark case of rod bundles using a top-bench experimental set up. The setup consist of a 3 x 3 rod bundle with a rod diameter of d= 10 mm, length L=1078 mm, and pitch to diameter ratio P/d = 1.28. The rods are kept in fixed distance from each other by three in-house designed simple grids with no mixing devices. The experimental set-up provides complete optical access to the test section by using a matching refractive index between the liquid flow, rods and flow envelope. Dynamic Particle Tracking Velocimetry (DPTV) was used to measure the time resolved velocity fields in the rod bundle. Experimental turbulence parameters and main flow characteristics are presented in this work. The interaction between sub-channels due to cross flow will be presented under Re number ranging from 5000- 20,000. This study seeks to provide a basic yet enough comprehensive benchmark case for CFD under single phase conditions. The geometry associated with the bundle problem has been simplified in order to provide high quality data with temporal and spatial resolution able to compare directly with CFD results. The measurement uncertainties in these experiments are discussed and evaluated yielding a 6% uncertainty in the axial and lateral velocity components and up-to 11% in the normal component of the measured velocity vectors. This work is a collaborative effort between Texas A&M University and the HZR institute in Germany.
Keywords: 3 x 3 rod bundle, Dynamic Particle Tracking Velocimetry, Channel geometry, single phase flow, refractive index matching fluid
  • Lecture (Conference)
    The Experimental Validation and Application of CFD and CMFD Codes in Nuclear Reactor Technology / CFD4NRS-4, 10.-12.09.2012, Daejeon, Korea

Permalink: https://www.hzdr.de/publications/Publ-18376
Publ.-Id: 18376


Radiation therapy of Cancer with laser-accelerated Ions - a Vision (Strahlentherapie von Krebs mit laserbeschleunigten Ionen – eine Vision)

Sauerbrey, R.
Experimente und klinische Studien, die seit den 70er Jahren durchgeführt werden, zeigen die Überlegenheit von Ionen bei der Strahlentherapie von bestimmten Krebsarten. Das Potential von Ionen für die Strahlentherapie insgesamt ist noch nicht voll‐ständig bekannt und derzeit Gegenstand der klinischen Forschung.
Für die Ionenbehandlung werden Protonen von etwa 200 MeV Energie bzw. Ionen mit einer Energie von 400 MeV/Nukleon und Strahlendosen von einigen 10 Gray benötigt.
Konventionelle Beschleuniger können diese Parameter zur Verfügung stellen. Für ein Behandlungssystem mit Ionen ist jedoch eine sehr aufwändige Apparatur zur Ionenbeschleunigung und Ionenstrahlführung erforderlich, die hohe Investitionskosten verursacht. Am Helmholtz‐Zentrum Dresden‐Rossendorf (HZDR) wird eine neue Methode zur Beschleunigung von Ionen mit Hochintensitätslasern verfolgt sowie alternative Technologien zur Ionenstrahlführung untersucht, um kompaktere und preisgünstigere Ionenbestrahlungsplätze zu realisieren. Die gemeinsame Plattform OncoRay der Technischen Universität Dresden, des Uniklinikums Dresden und des HZDR bietet die Möglichkeit der translationalen Krebsforschung auf diesem Zukunftsgebiet.
  • Biomedical Engineering / Biomedizinische Technik 57(2012)1, 959

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Publ.-Id: 18375


A Neural Network Approach for Acoustic Leak Monitoring in the VVER-440 Pressure Vessel Head

Hessel, G.; Schmitt, W.; van der Vorst, K.; Weiss, F. P.
A neural network approach has been developed for localizing leakages and estimating the leak rate in the VVER-440 pressure vessel head. Results are presented from experiments with simulated leaks. Threelayer perceptron networks were found to be best suited for leak localization and for the estimation of leak rates. However, the estimation of leak rates required an additional neural network because a different normalization procedure was necessare for extracting features from RMS values of the acoustic emission sensors. Perceptron networks with continuously valued outputs corresponding to the coordinates of the leak positions were useful for identifiying even leak positions which had not been offered during training
Keywords: Leak, monitoring, neural networks, pressurized water reactors, VVER reactors
  • Progress in Nuclear Energy 34(1999)3, 173-183

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Publ.-Id: 18374


ms-Temperung von HL & Dielektrika more Moore & more than Moore & Nothing more...

Skorupa, W.
It is obvious that we approach the limits of Moore’s law and have to think about moving on, or, move different route, or, may be, move not anymore? Having spent more than 35 years with microelectronics and chip technology the answer to this question is not simple for me… In this talk I will try to discuss some aspects of that kind of “cultural doubting”, but will not miss to present also a review of our recent results regarding advanced processing for silicon and germanium nanostructures based on ion beam processing and/or short time annealing in the millisecond range: a) III-V nanocrystals heteroepitaxially arranged on silicon nanowires (S. Prucnal et al., NanoLett. 11, 2814 (2011)) b) Superconductivity from Ga-rich nanoscale layers at Si/Ge-SiO2 interfaces (J. Fiedler et al., Phys.Rev. B 85, 134530 (2012)) c) Horizontal silicon nanowires on insulator by ion beam erosion (X. Ou et al., AIP Advances 1, 042174 (2011))
Keywords: short time annealing, Moore’s law, ion beam processing
  • Invited lecture (Conferences)
    EFDS-Workshop "Struktur und Eigenschaften dielektrischer Schichten für die Optik", 07.11.2012, Jena, Germany

Permalink: https://www.hzdr.de/publications/Publ-18373
Publ.-Id: 18373


More Moore or More-than-Moore or Nothing more? A nanoView on silicon & germanium...

Skorupa, W.
It is obvious that we approach the limits of Moore’s law and have to think about moving on, or, move different route, or, may be, move not anymore? Having spent more than 35 years with microelectronics and chip technology the answer to this question is not simple for me… In this talk I will try to discuss some aspects of that kind of “cultural doubting”, but will not miss to present also a review of our recent results regarding advanced processing for silicon and germanium nanostructures based on ion beam processing and/or short time annealing in the millisecond range: a) III-V nanocrystals heteroepitaxially arranged on silicon nanowires (S. Prucnal et al., NanoLett. 11, 2814 (2011)) b) Superconductivity from Ga-rich nanoscale layers at Si/Ge-SiO2 interfaces (J. Fiedler et al., Phys.Rev. B 85, 134530 (2012)) c) Horizontal silicon nanowires on insulator by ion beam erosion (X. Ou et al., AIP Advances 1, 042174 (2011))
Keywords: short time annealing, Moore’s law, ion beam processing
  • Invited lecture (Conferences)
    E-MRS 2012 FALL MEETING, 17.-21.09.2012, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-18372
Publ.-Id: 18372


Dot and Ripple Nanopatterns on Ge Surfaces by Normal and Tilted Bombardment with Bi2 and Bi3 Ions

Bischoff, L.; Heinig, K.-H.; Schmidt, B.; Facsko, S.; Pilz, W.
The self-organisation of surface pattern on (001)Ge was investigated after bombardment with different heavy bismuth species of monomers Bi+, Bi++ and clusters Bi2+, Bi3+, Bi4+, and Bi3++, obtained from a Bi-liquid metal ion source [1] in a mass separating 30 kV focused ion beam system. The surface patterns, depending on the angle of ion cluster incidence at ion irradiation differ drastically from the well-known porous or sponge-like nanostructures formed on Ge at monomer ion irradiation so far: the surface remains crystalline as proven by Raman measurements, and the dots and ripples heights were in the order of their wavelengths in contrast to monomer irradiation where an porous surface layer was obtained. The structure formation was investigated in the fluence range from1015 to 1017 ions/cm2 as a function of angle of incidence and energy per atom of the different projectile ions. The high mass of the cluster ions leads to a patterning mechanism different from the Bradley-Harper model, which becomes strikingly apparent by the crystalline Ge surface. An identified threshold of this new patterning mode could help to understand the mechanism: The ion-impact-induced deposition of energy per volume (as estimated by SRIM) must exceed a value which coincides with the energy needed for melting. Thus, Bi segregation during melt pool re-solidification and the 5% volume difference between molten and solid Ge can cause the observed Bi separation and Ge patterning, respectively. A consistent, qualitative model will be discussed. [1] L. Bischoff, W. Pilz, P. Mazarov, and A.D. Wieck, Appl. Phys. A 99 (2010) 145.
Keywords: ion-solid-interaction, heavy polyatomic ions, germanium, surface patters, modeling
  • Poster
    MRS 2011 Spring Meeting, 26.-29.04.2011, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-18371
Publ.-Id: 18371


Anticorrosion studies for pipe organ-related materials using plasma processing

Skorupa, W.; Cherkouk, C.; Henke, D.; Prucnal, S.; Reuther, H.; Werner, H.; Pfeifer, D.; Eule, A.-C.
There is no doubt that lead (and its alloys with tin) and brass materials do not really belong to the stuff of primary interest for advanced materials studies. Also, lead gets more and more removed from the technology of soldering in electronics etc., and brass is, at least, a material of doubtful character if treated in vacuum. On the other hand these metals are of primary interest for the construction of pipe organs, and that already for millenia! Corrosion of lead and brass are a serious obstacle in old and even new pipe organs if the microclimate inside of the organ, the church, the concert hall etc. is containing special residuals or impurities leading to the growth of corrosive layers. Finally, even holes can be “drilled” into metal pipes making them voiceless!
For this end we have started to fight with this problem by using nanotechnology to cover metallic sheets of lead and brass with thin layers of anticorrosive material. Plasma immersion ion implantation of nitrogen was used to keep the technology simple and to have certain intermixed interface layers between the surface and the substrate. AES and XPS demonstrated surface layers with a thickness in the range below 50 nm. The exact composition and mechanism is a matter of discussion yet. Laboratory-based corrosion studies were developed and applied to the plasma-treated surfaces. First results were quite promising and showed strong corrosion resistance, especially for lead. Field studies at historical organs in Saxony and Mecklenburg are ongoing.
Keywords: pipe organ, plasma immersion, corrosion protection, lead, brass
  • Lecture (Conference)
    13th International Conference on Plasma Surface Engineering, 10.-14.09.2012, Garmisch-Partenkirchen, Germany

Permalink: https://www.hzdr.de/publications/Publ-18370
Publ.-Id: 18370


Shaping of Au and Ge Nanoparticles by Irradiation with Swift Heavy Ions

Heinig, K.-H.; Schmidt, B.; Muecklich, A.; Akhmadaliev, C.
The driving forces of nanomaterials processing by swift heavy ions as identified by our studies are (i) the materials dependent electronic stopping power, (ii) the volume change upon melting as well as (iii) far-from-equilibrium steady-state solubilities and strongly anisotropic diffusion coefficients. Size distributions, shapes and anisotropies of nanoparticles can be tailored by appropriate tuning of these driving forces. The evolution of Au and Ge nanospheres under swift heavy ion irradiation was studied experimentally and by atomistic computer simulations. Au nanospheres of 15 nm di-ameter elongate to rods, whereas Ge nanospheres become flat. Surprisingly, this shaping as well as the quantitative dependence on experimental conditions can be described completely with classical thermodynamics, which will be demonstrated by our atomistic computer simulation studies: For instance, the ratio (rod length)/(initial sphere diameter) increases with the square root of the ion fluence, and the speed of the elongation follows the law of Hagen-Poiseuille. Of special interest is the nanostructure evolution when en-ergy deposition into the nanoparticle suffice melting only for central tracks. This rare event for broad size distributions can be seen, e.g., in Phys.Rev. B78(2008)054102. Us-ing unimodal size distributions and changing the ion direction during irradiation, tailor-ing of very exotic nanoparticle shapes become feasible.
Keywords: ion-solid-interaction, swift heavy ions, nanoparticles, shaping, electron microscopy, modeling, computer simulations
  • Lecture (Conference)
    MRS 2011 Spring Meeting, 26.-29.04.2011, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-18369
Publ.-Id: 18369


Response of bacteria in pore water of opalinus clay to addition of nitrate and acetate

Selenska-Pobell, S.; Geissler, A.; Moors, H.; Leys, N.
The in situ BN experiment performed at the international underground rock laboratory Mont Terry in Switzerland estimates the risks of release of nitrate and organic molecules into the opalinus clay due to the weathering of the bitumen containers, foreseen for disposal of long-living radioactive waste. The changes induced by the bitumen degradation products in the opalinus clay have many different bio-geo-chemical aspects which may facilitate migration of radionuclides. For this reason the BN experiment exploits a set of interdisciplinary (chemical, technical, and biological) approaches [1]. Response of bacteria present in the pore water of the interval 2 of the BN experiment to addition of nitrate, nitrite, and acetate is reported here.
Bacterial diversity in three samples collected from interval 2 of the BN experiment was studied by using ribosomal intergenic spacer amplification (RISA), cloning and sequencing of the 16S rRNA-gene of the RISA amplicons as described in [2]. The first sample was collected before the supplementation, the second sample - one day after the addition of 70 mg/L NO3-, 35 mg/L NO2- and 46 mg/L acetate, and the third sample - five days after the treatment.
The chemical analyses of the samples monitored by Bleyen at al. [1] demonstrated that three days after the supplementation the added nitrate was fully reduced to nitrite. Between the third and the fifth days from the beginning of the experiment fast reduction of nitrite occurred. After the fifth day - complete consumption of acetate was monitored and a process of slow nitrite reduction started which finished with complete removal of the latter two weeks after the supplementation.
The RISA molecular analyses performed in this work demonstrated strong shifting in bacterial community of the interval 2 only 24 hours after the addition of nitrate, nitrite and acetate. The strongly predominant in the untreated sample Firmicutes were almost completely overgrown by Alphaproteobacteria and by one particular population of Pseudomonas stutzeri (Gammaproteobacteria). The latter not identified in the non-supplemented samples. As P. stutzeri can use acetate as electron donor for nitrate reduction our results clearly demonstrate that this species is involved in the above reported [1] rapid reduction of nitrate to nitrite during the first 3 days after the treatment. The RISA analyses demonstrated that P. stutzeri was even more predominant in the sample collected five days after the treatment. On the basis of this result we suggested that this species plays also the major role in the fast reduction of nitrite. Our suggestion is in agreement with the published capability of P. stutzeri to perform fast reduction of nitrite to molecular nitrogen with acetate under conditions similar to ours [3]. The role (if any) of the rest of the bacterial community in the fast nitrate and nitrite reduction has to be cleared.
Analyses of additional samples collected between the 5th and the 14th days after the supplementation is needed in order to clear the role of the other members of the bacterial community of interval 2 in the slow nitrite reduction occurring after the 5th day of the treatment when acetate was completely utilized.

REFERENCES
[1] Bleyen et al. (2012) Clays in natural and engineered barriers for radioactive waste confinement. Montpellier, 22-25.10.2012, p.755.
[2] Selenska-Pobell et al (2001) Ant. Van Leeuvenhoek.79., 149-161.
[3] Strohm et al. (2007) Appl. Environ. Microbiol. 73, 1420-1424.
Keywords: Deposition of nuclear waste, bacterial diversity in opalinus clay
  • Lecture (Conference)
    Mont Terri Project: Joint HT-MA-BN-GD-PCC Meeting, 11.-12.02.2013, St- Ursanne, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-18368
Publ.-Id: 18368


Millisecond annealing and beyond

Skorupa, W.
This talk reviews the advances that subsecond thermal processing using flash lamps and lasers brings to the processing of the most advanced semiconductor materials, thus enabling the fabrication of novel electronic structures and materials. It will be demonstrated how such developments can translate into important practical applications leading to a wide range of technological benefits. Recently we could demonstrate that germanium and silicon exhibit superconductivity at ambient pressure. Techniques of the state-of-the-art semiconductor processing as ion implantation and FLA were used to fabricate such material based on a highly doped Ga-rich layer at the surface. Moreover we demonstrated that carrier-mediated ferromagnetism can be reached in manganese-implanted and Laser-annealed Ge. Regarding photovoltaic applications, we dealt with two aspects: (i) the thermal processing of so-called dirty silicon demonstrating a distinct improvement of the metal diffusion suppression compared to RTP and furnace treatments, and (ii), for the annealing of CIGS layers millisecond annealing leads to better optical output and lower degradation Whereas all these examples base on solid phase processing the more sophisticated approach of subsecond thermal processing regards on working with the liquid phase at the surface of solid substrates. A very recent example is the controlled formation of III-V nanocrystals (InAs, GaAs) in silicon after ion beam synthesis (Nano Lett. 11 (2011) 2814).
Keywords: flash lamp annealing
  • Lecture (others)
    Eingeladener Seminarvortrag, 12.10.2012, Oslo, Norway

Permalink: https://www.hzdr.de/publications/Publ-18367
Publ.-Id: 18367


Si Nanosponge Embedded in Silica - A More Efficient Thin-film PV Cell Semiconductor?

Heinig, K.-H.; Schmidt, B.; Stegemann, K.-H.; Muecklich, A.; Liedke, B.; Friedrich, D.
Nanostructured thin-film PV materials are expected to become more and more important due to their high competitiveness in cost reduction. Assemblies composed of quantum dots and/or wires have been reported in which quantum confinement is used as a design parameter. However, there are still problems related to the low-cost fabrication of such structures, and, in case of quantum dots embedded in a dielectric matrix, to charge carrier separation. Here, we present Si nanosponge embedded in silica as a new nanostructured active PV cell material which could overcome such problems. The Si nanosponge has typical feature sizes of 2…4 nm. This is much smaller than the ~100nm of electrochemically etched porous Si, which was studied intensively several years ago. Thus, the nanosponge shows a band gap widening by quantum confinement which allows band gap engineering for optimum adjustment to the solar spectrum. Furthermore, the Si sponge/SiO2 matrix interface is electrically passive which lowers losses. And, the Si sponge is electrically percolated, resulting in an efficient charge carrier separation. Si nanosponge is expected to replace easily a-Si in thin-film PV cell production lines. The PECVD equipment will be used to deposit SiOx instead of a-Si. The Si nanosponge is formed by thermally activated spinodal decomposition of SiOx. The large glass panels of thin-film PV cells allow a low thermal budget only, therefore scanned laser processing with ms dwell times has to be used. EFTEM images of Si nanosponge formed by co-sputtering of SiOx followed by rapid thermal processing are in full agreement with atomistic simulations of the spinodal decomposition process. Electrical and optical properties measured so far are in agreement with the expectations. Studies on the morphology of sponges form by very rapid thermal processing are under way.
Keywords: nanocomposite, silicon, silica, embedded sponge, sputter deposition, spinodal phase separation, computer simulations
  • Poster
    MRS 2011 Spring Meeting, 26.-29.04.2011, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-18366
Publ.-Id: 18366


Self-organization of Nanopatterns under Ion Irradiation: Atomistic 3D Simulations including Collision Cascades and Thermally Activated Kinetics

Heinig, K.-H.; Liedke, B.; Moeller, W.
The dominating driving force for self-organisation of surface nanopattern during low-energy ion irradiation is still under discussion. Thus, so far continuum models cannot include 3D non-local processes of ion-solid interactions. On the other hand, till now atomistic simulations could not describe pattern dynamics on the spatiotemporal scale of experiments.
Combining collision cascades of ion impacts with continuum equations [1] is one approach to achieve a better understanding of mechanisms, like surface smoothing by an effective ‘downhill’ mass current which are neglected so far [2][3].
Here we present a novel program package, which unifies atomistic 3D simulations of the col-lision cascades with 3D kinetic Monte-Carlo simulations. Atom relocations were calculated with the Binary Collision Approximation (BCA), whereas the thermally activated relaxation of ener-getic atomic configurations as well as diffusive processes were simulated by a very efficient bit-coded kinetic lattice Monte Carlo program. Effects like ballistic mass drift or dependence of lo-cal morphology on sputtering yield are automatically included by this approach.
The mechanism of ripple formation induced by local surface currents is studied. The quantita-tive description of current vectors for different environmental parameters, and initial surface condition of sinusoidal structure, can be analized in time and space, following the local atomic drift. Different mechanisms can be distinguished. Without ion irradiation the mass current vec-tors parallel to the surface cause always surface smoothing by Mullins-Herring diffusion. Surface defects created by collsion cascades may inverse the surface mass currents, resulting in self-organization of nanopatterns.
Sputtering violates mass conservation of processes mentioned till now. The majority of pub-lished papers assume that sputtering is the dominating driving force for pattern formation. Here it will be shown that ripple patterns perpendicular to oblique ion impacts originate not from the sputtering process but from defect kinetics. Sputtering dominates only formation of ripple pat-terns parallel to the ion beam at grazing incidence.
[1] S. A. Norris and M. P. Brenner and M. J. Aziz J. Phys. Condens. Matter 21 (2009) 224017.
[2] G. Carter and V. Vishnyakov PRB 54 (1996) 17647.
[3] M. Moseler and P. Gumbsch and C. Casiraghi and A. C. Ferrari and J. Robertson Science 309 (2005) 1545.
Keywords: Computer simulations, kinetic Monte Carlo, TRIM, new algorithmen, nanopatterns, self-organization
  • Invited lecture (Conferences)
    MRS 2011 Spring Meeting, 25.-29.04.2011, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-18365
Publ.-Id: 18365


Nanoclusters and interfaces under ion irradiation: Inverse Ostwald ripening and pattern formation

Heinig, K.-H.
Ion irradiation of solids can change well-known processes of structure evolution dramatically. For instance, the thermally activated corsening of nanocluster ensembles embedded in a matrix (i.e. Ostwald ripening) can change to inverse Ostwald ripening under ion irradiation if ion-beam-induced atomic displacements dominate the kinetics. Inverse ripening means that the nanocluster sizes no longer coarsens with time, but all nanocluster reach asymtodically the same size. On the other hand, intense ion-beam-induced displacements can result in self-organization of ordered surface pattern. Here, the competion between thermally activated smoothening and the ion-beam-induced roughening are the driving forces for surface patterning.
Keywords: ion-solid-interaction, inverse Ostwald ripening, self-organization, surface pattern, modeling, computer simulations
  • Lecture (others)
    Seminar, 16.12.2011, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-18364
Publ.-Id: 18364


Ion Beam Induced Self-Organization and Modification of Nanostructures

Heinig, K.-H.
This presentation consists of three parts:
(i) The self-organization of regular morphologies on elemental semiconductor surfaces under ion
irradiation will be discussed. At least for low-energy ions the driving force is not sputtering, as it was
claimed in most published papers so far, but ion impact induced mass drift.
(ii) Our progress on shaping of metal and semiconductor nanospheres using swift heavy ions will be
reported. Metal spheres can be shaped into rods and quadruples, whereas germanium nanospheres have been shaped into disks. A quantitative model will be presented.
(iii) Nanowires have been synthesized by FIB implantation. By subsequent thermal treatment, nanocluster chains have been formed by a controlled decay of these wires. Atomistic simulations show that rather complex nanostructures can be fabricated.
Keywords: ion-solid-interaction, surface patterning, self-organization, nanoparticle shaping, nanowire synthesis, modeling, computer simulations
  • Invited lecture (Conferences)
    21st MRS-Japan Academic Symposium, 19.-21.12.2011, Yokohama, Japan

Permalink: https://www.hzdr.de/publications/Publ-18363
Publ.-Id: 18363


Möglichkeiten und Anwendungen der Laserfluoreszenzmikroskopie bei extrem tiefen Temperaturen

Großmann, K.; Tondera, C.; Mosch, B.; Wimmer, C.; Arnold, T.; Pietzsch, J.
kein Abstract, geladener Vortrag (Institutsseminar)
  • Lecture (others)
    Institutskolloquium, 15.01.2013, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18362
Publ.-Id: 18362


Nanoporous Si in Silica – an Efficient Absorber for Thin Film PV Cells ?

Heinig, K.-H.; Schmidt, B.; Stegemann, K.-H.; Mücklich, A.; Liedke, B.; Friedrich, D.
Nanostructured thin-film PV materials are expected to become more and more important due to their high competitiveness in cost reduction. Assemblies composed of quantum dots and/or wires have been reported in which quantum confinement is used as a design parameter. However, there are still problems related to the low-cost fabrication of such structures, and, in case of quantum dots embedded in a dielectric matrix, to charge carrier separation. Here, we present Si nanosponge embedded in silica as a new nanostructured active PV cell material which could overcome such problems. The Si nanosponge has typical feature sizes of 2…4 nm. This is much smaller than the ~100nm of electrochemically etched porous Si, which was studied intensively several years ago. Thus, the nanosponge shows a band gap widening by quantum confinement which allows band gap engineering for optimum adjustment to the solar spectrum. Furthermore, the Si sponge/SiO2 matrix interface is electrically passive which lowers losses. And, the Si sponge is electrically percolated, resulting in an efficient charge carrier separation. Si nanosponge is expected to replace easily a-Si in thin-film PV cell production lines. The PECVD equipment will be used to deposit SiOx instead of a-Si. The Si nanosponge is formed by thermally activated spinodal decomposition of SiOx. The large glass panels of thin-film PV cells allow a low thermal budget only, therefore scanned laser processing with ms dwell times has to be used. EFTEM images of Si nanosponge formed by co-sputtering of SiOx followed by rapid thermal processing are in full agreement with atomistic simulations of the spinodal decomposition process. Electrical and optical properties measured so far are in agreement with the expectations. Studies on the morphology of sponges form by very rapid thermal processing are under way.
Keywords: nanocomposite, silicon, silica, spinodal phase separation, embedded Si sponge, solar cell
  • Lecture (Conference)
    XX. International Materials Research Congress - IMRC XX, 14.-19.08.2011, Cancun, Mexico

Permalink: https://www.hzdr.de/publications/Publ-18361
Publ.-Id: 18361


Novel Nanopattern on Ge after Heavy Bi Cluster Bombardment

Heinig, K.-H.; Bischoff, L.; Schmidt, B.
Ge surfaces have been irradiated with 30 keV Bi+ and 60 keV Bi++ monomers, 30 keV Bi2+ dimers, 60 keV Bi3++ trimers as well as 30 keV Bi4+. The ions are obtained from a Bi-liquid metal ion source in a mass separating 30 kV focused ion beam system. The surface pattern found after dimer and trimer irradiation differ drastically from the well-known porous or sponge-like nanostructures formed on Ge by ion irradiation with monomers: The surface remains crystalline as proven by Raman measurements, and the dots and ripples heights were in the order of their wavelengths. Under monomer irradiation a porous surface layer was obtained. The structure formation was investigated in the fluence range from1015 to 1017 ions/cm2 in dependence on the angle of incidence and the energy per atom of the different projectile ions. The high mass of the cluster ions leads to a patterning mechanism different from the Bradley-Harper mechanism, which becomes strikingly apparent by the crystalline Ge surface. An identified threshold of this new patterning helped to understand the mechanism: The ion-impact-induced deposition of energy per volume (as estimated by SRIM) must exceed a value which coincides with the energy needed for melting. Thus, Bi segregation during melt pool re-solidification and the 5% volume difference between molten and solid Ge can cause the observed Bi separation and Ge patterning, respectively. A consistent, qualitative model will be discussed.
Keywords: ion-solid-interaction, polyatomic ions, germanium, surface patterns, focussed ion beam, modeling, computer simulations
  • Lecture (Conference)
    XX. International Materials Research Congress - IMRC XX, 14.-19.08.2011, Cancun, Mexico

Permalink: https://www.hzdr.de/publications/Publ-18360
Publ.-Id: 18360


Surface Nanopatterning and Nanocluster Shaping using Ion Beams

Heinig, K.-H.; Schmidt, B.; Bischoff, L.; Röntzsch, L.; Numazawa, S.; Liedke, B.
Ion irradiation of solids can result in self-organization of very regular surface morphologies and in shaping of particles embedded in a solid matrix. Regular chains of nanoparticles can be formed by the decay of nanowires which were synthesized using focused ion beams. This presentation consists of three parts: (i) The self-organization of pattern on elemental semiconductor surfaces under irradiation with ions of 100 eV to a few tens of keV will be reported. It will be proven by comparisons of atomistic computer simulations with experiments that the driving force for this pattern formation is not sputtering, as it was claimed in most published papers so far, but ion impact induced mass drift. Only a minority of former studies came to the same conclusion (see, e.g. [1, 2]), whereas very recently this understanding is more and more convincingly proven [3,4]. (ii) Our progress of shaping of metal and semiconductor nanospheres embedded in silica using swift heavy ions will be reported. Metal spheres can be shaped into rods and quadruples, whereas germanium nanospheres have been shaped into disks. It will be proven that electronic stopping power melts the nanoparticles, and that the volume change upon melting causes the shaping. (iii) Nanowires have been synthesized by FIB implantation, e.g. CoSi2 wires in silicon. By subsequent thermal treatment, nanocluster chains have been formed by a controlled decay of these wires. Computer experiments will show that rather complex nanostructures can be fabricated by this technique.
[1] G. Carter, V. Vishnyakov PRB 54 (1996) 17647.
[2] M. Moseler et al., Science 309 (2005)
[3] S.A. Norris et al., Nature Comm., 2011, Apr12, DOI: 10.1038/ncomms1280
[4] C.S. Madi et al., PRL 106, 066101 (2011)
Keywords: ion-solid-interaction, surface patterning, nanoparticle deformation, theory, computer simulations
  • Invited lecture (Conferences)
    XX. International Materials Research Congress - IMRC2011, 14.-18.08.2011, Cancun, Mexico

Permalink: https://www.hzdr.de/publications/Publ-18359
Publ.-Id: 18359


Computer experiments on ion-induced pattern formation vs. continuum equations

Heinig, K.-H.; Liedke, B.; Numazawa, S.; Facsko, S.
Ripple pattern and hexagonally ordered dot pattern are frequently found after ion irradiation under off-normal incidence and under normal or close to normal ion incidence, respectively [1]. A first consistent analytical model for the evolution of these patterns was given by Bradley and Harper [2]. They showed that a surface curvature dependent ion erosion rate can result in a surface instability, whereas a surface smoothing process by surface-curvature-driven diffusion (Mullins-Herring diffusion) competes with that instability. By this competition regular surface patterns may evolve. Lateron, this simple model was extended to more sophisticated partial differential equations like the Kuramoto-Sivashinsly equation in order to improve the agreement with experimental findings. However, it remains difficult to describe details of the pattern evolution and dynamics by continuum equations.
Here we present atomistic 3D computer simulations on ion irradiation of surfaces which unify both, the collision cascades caused by the incident ions (including sputtering, mass drift, ion beam mixing) and the thermally excited relaxation processes (including surface and bulk diffusion of defects and impurities, phase separation, Mullins-Herring diffusion,…). For that aim, the collision cascade simulations in the BCA approximation are carried out for atom densities on the 3D lattice of the kinetic Monte Carlo (kMC) simulation which contains the full history of defects, surface undulations etc. Each ion impact is followed immediately by some kMC steps. The computer experiments show that, with the exception of grazing incidence, in silicon the Ar+ ion induced patterns are dominated by defect kinetics rather than sputtering. The results are in nice agreement with recent experiments of Madi [3]. Secondly, we show how this computer experiments can be directly related to continuum equations. In the computer all atomic jumps and the time evolution of the surface heights as well as of its slopes, curvatures etc can be registered. Thus, it might be possible to find out which term(s) of the partial differential equations should dominate the pattern formation.
[1] W. L. Chan and E. Chason, Making waves: Kinetic processes controlling surface evolution during low energy ion sputtering, J. Appl. Phys. 101, 121301 (2007).
[2] R. M. Bradley and J. M. E. Harper, Theory of Ripple Topography Induced by Ion-Bombardment, J. Vac. Sci. Technol. A 6, 2390 (1988).
[3] C.S. Madi, H.B. George and M.J. Aziz, Linear stability and instability patterns in ion-sputtered silicon, J. Phys.: Cond. Mat. 21, 224010 (2009).
Keywords: Ion-solid-interaction, surface pattern, self-organisation, theory, computer simulations
  • Invited lecture (Conferences)
    International Conference on Ion-Beam Induced Nanopatterning of Materials (IINM-2011), 06.-10.02.2011, Bhubaneswar, India

Permalink: https://www.hzdr.de/publications/Publ-18358
Publ.-Id: 18358


Nanostructure Formation and Modification with Ion Beams

Heinig, K.-H.
This presentation consists of three parts:
(i) The self-organization of regular morphologies on elemental semiconductor surfaces under irradiation with ions will be discussed. It will be proven that at least for low-energy ions the driving force for this pattern formation is not sputtering, as it was claimed in most published papers so far, but ion impact induced mass drift.
(ii) Our progress on shaping of metal and semiconductor nanospheres embedded in silica using swift heavy ions will be reported. Metal spheres can be shaped into rods and quadruples, whereas germanium nanospheres have been shaped into disks. It will be shown that electronic stopping power melts the nanoparticles, and that the volume change upon melting is the driving force for shaping.
(iii) Nanowires have been synthesized by FIB implantation, e.g. CoSi2 wires in silicon. By subsequent thermal treatment, nanocluster chains have been formed by a controlled decay of these wires. Computer experiments will show that rather complex nanostructures can be fabricated by this technique.
Keywords: Nanostructures, Ion-solid-interaction, self-organisation, nanowires, computer experiments
  • Lecture (others)
    Physics Department Seminar, 05.10.2011, Ankara, Turkey

Permalink: https://www.hzdr.de/publications/Publ-18357
Publ.-Id: 18357


Berechnungen bezüglich des Strahlenschutzes für die Errichtung der Protonentherapieanlage in Dresden

Kunath, D.; Enghardt, W.
  • Poster
    43. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 26.-29.09.2012, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18356
Publ.-Id: 18356


Uranium(VI) Complexation with Carbonate studied by Cryo-TRLFS and PARAFAC

Steudtner, R.; Drobot, B.; Raff, J.; Scheinost, A.; Brendler, V.
Cryogenic techniques in laser spectroscopy are currently used in scanning tunneling microscopy (STM) and single molecule spectroscopy. Recently such cryogenic devices have also been adapted to time-resolved laser-induced fluorescence spectroscopy (TRLFS) applied to uranium. We used TRLFS at low temperatures (cryo-TRLFS) to investigate the uranium(VI) complexation with carbonate. The luminescence spectra were analyzed with parallel factor analysis (PARAFAC). The PARAFAC modeling provided the luminescence spectra, decay lifetimes, and relative intensity profiles of four U(VI) species in presence of carbonate. The U(VI) species distribution calculated from the known stability constants of relevant U(VI) hydrolysis and carbonate species,compared well with the pH-depending U(VI) speciation derived from PARAFAC-analyzed TRLFS spectra. In the acidic pH range below pH 4.5 the U(VI) speciation is dominated by the free UO22+ and one UO22+/OH- species. With increasing pH we observed the formation of two different U(VI) carbonate species. Our results suggest that PARAFAC is a promising data analysis tool for TRLFS in the context of speciation studies of fluorescent metal ions.
Keywords: U(VI), Luminescence, Low temperature, Analysis
  • Poster
    ANAKON 2013, 04.-07.03.2013, Essen, Deutschland
  • Poster
    ThUL summer school 2014, 02.-06.06.2014, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-18355
Publ.-Id: 18355


U(VI) removal kinetics in presence of synthetic magnetite nanoparticles

Huber, F.; Schild, D.; Vitova, T.; Rothe, J.; Kirsch, R.; Schaefer, T.
The interaction of hexavalent U with a freshly synthesized nanoparticulate magnetite ((FeFe2O4)-Fe-II-O-III) (stochiometric ratio x(Fe(II)/Fe-TOT) = 0.25-0.33), a partly oxidized synthetic nanoparticulate magnetite (x = 0.11-0.27) and maghemite nanoparticles (x = 0-1) under anoxic conditions and exclusion of CO2 as function of pH, contact time and total U concentration (3 x 10(-5) M and 1 x 10(-7) M) has been examined. Short term kinetic batch experiments (contact time of 90 d) for four different pH values have been conducted. Moreover, classical batch pH sorption edges have been prepared for two different uranium concentrations for a contact time of 550 d. Spectroscopic techniques (XPS, XAS) were applied to probe for the presence and amount of reduced U on the magnetite surface. Batch kinetic studies revealed a fast initial U removal from aqueous solution with >90% magnetite associated U after 24 h within the pH range 5-11. Long-term contact time batch experiments (550 d) showed neither a U removal below pH < 3 nor a decrease in the magnetite associated U at pH >= 9. Redox speciation by XPS verifies the presence of reduced U (both U(IV) and U(V) were resolved if the satellite structures were used in the fitting procedure) at the near surface of magnetite up to a contact time of 550 d and a clear correlation of the amount of available Fe(II) on the magnetite surface and the amount of reduced U is observed. XANES investigation supports presence of U(V)/U(VI) uranate and U(IV). Interpretation of the EXAFS for one sample is consistent with incorporation of U into an Fe oxide phase, after long reaction times. Thermodynamic calculations based on the experimentally determined redox potentials corroborate the spectroscopic findings of U oxidation states. Overall, the results reflect the importance of structurally bound Fe(II) as redox partner for uranyl reduction.
Keywords: uranyl magnetite XAS ROBL

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Permalink: https://www.hzdr.de/publications/Publ-18354
Publ.-Id: 18354


The Fulde-Ferrell-Larkin-Ovchinnikov state in BEDT-TTF-based organic superconductors

Wosnitza, J.
  • Invited lecture (Conferences)
    International Symposium on Materials Science Opened by Molecular Degrees of Freedom (MDF2012), 01.-04.12.2012, Miyazaki, Japan

Permalink: https://www.hzdr.de/publications/Publ-18353
Publ.-Id: 18353


The Fulde-Ferrell-Larkin-Ovchinnikov state in quasi-two-dimensional organic superconductors

Wosnitza, J.
  • Lecture (Conference)
    Conference on Materials and Mechanisms of Superconductivity, 29.07.-03.08.2012, Washington DC, USA

Permalink: https://www.hzdr.de/publications/Publ-18352
Publ.-Id: 18352


Evidence for Fulde-Ferrell-Larkin-Ovchinnikov states in layered organic superconductors

Wosnitza, J.
  • Invited lecture (Conferences)
    12th Japanese-German Symposium Emergent Phenomena in Novel Quantum Phases of Condensed Matter, 14.-17.07.2012, Izu, Japan

Permalink: https://www.hzdr.de/publications/Publ-18351
Publ.-Id: 18351


Tracking ore mineral characteristics from mine to concentrate: The fate of electrum at the Cavanacaw gold deposit, Northern Ireland

Birtel, S.; Wunderlich, I.; Gutzmer, J.
A systematic geometallurgical assessment was carried out to follow changes of mineral composition and microfabric following the ore extracted from two ore blocks at the Cavanacaw Au Mine through the beneficiation process. SEM-based image analysis was used to carry out the investigation on the finely disseminated Au ores. A general assessment quickly reveals that the beneficiation plant suffers only little loss to the tailings. Despite this positive assesment results illustrate that there are some losses that appear to be systemic: Large electrum grains (>16 µm ecd) are abundant in the original uncrushed material only make a minor contribution to the final concentrate. Due to the ductile behaviour of electrum, fracturing of larger electrum grains into smaller grain sizes appears unlikely – it is thus concluded that these particles may be captured in the plant during processing.
Our results reveal that sulphide-rich veins are typically higher in grade than the final concentrate. This results from processing a mixture of high-grade ore and low-grade wall rock. To reduce processing costs it might be considered to introduce an early stage of optical sorting
Keywords: gold, MLA, mineral processing, geometallurgy
  • Open Access Logo Contribution to proceedings
    12th SGA Biennial Meeting, 12.-15.08.2013, Uppsala, Sweden
    Mineral deposit Research for a high-tech world Proceedings, Volume 1, Sweden: Elanders Sverige AB, 978-91-7403-207-9, 306-309
  • Lecture (Conference)
    12th SGA Biennial Meeting, 12.08.-15.11.2013, Uppsala, Sweden
  • Lecture (Conference)
    Workshop on Advanced Analysis Techniques in Process Mineralogy, 03.02.2014, Lulea, Sweden

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Permalink: https://www.hzdr.de/publications/Publ-18350
Publ.-Id: 18350


Competing exchange interactions in Co-doped ZnO: Departure from the superexchange picture

D'Ambrosio, S.; Pashchenko, V.; Mignot, J.; Ignatchik, O.; Kuzian, R.; Savoyant, A.; Golacki, Z.; Grasza, K.; Stepanov, A.
We report the results of a comprehensive study of the exchange interactions in Co-doped ZnO using inelastic neutron scattering, electron paramagnetic resonance, and magnetic property measurements. In particular, we observe an unprecedentedly strong spatial anisotropy of the two nearest-neighbor exchanges, J((1)) = -25.6 +/- 0.3 K and J((2)) = -8.5 +/- 0.4 K, along with the distant-neighbor J values of ferromagnetic sign. We argue that the superexchange mechanism alone cannot account for the obtained data and we suggest that an additional mechanism leading to a strong ferromagnetic spin coupling is responsible for these findings. We also discuss the origin of this ferromagnetic mechanism.

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Permalink: https://www.hzdr.de/publications/Publ-18349
Publ.-Id: 18349


Spin dynamics of S = 1/2 Heisenberg chains with a staggered transverse field: electron spin resonance studies

Zvyagin, S. A.
This article is a review of the recent achievements in experimental studies of magnetic excitations in the copper pyrimidine dinitrate [PM-Cu(NO3)(2)(H2O)(2)](n) (PM = pyrimidine), an S = 1/2 antiferromagnetic chain material with an alternating g-tensor and the Dzyaloshinskii-Moriya interaction, by means of high-field electron spin resonance (ESR). Due to this alternation, in the 1D critical regime this material exhibits a field-induced gap. The excitation spectrum is formed by solitons and their bound states, breathers, and can be effectively described using the sine-Gordon model. With increasing temperature, the soliton-breather regime can be suppressed, resulting in a substantial evolution of ESR parameters. These changes can be described using a new theoretical concept recently proposed for S = 1/2 AF chains with a staggered transverse field. High magnetic field induces a transition into the spin-polarized state with the excitation spectrum formed by magnons. Nonmonotonous behavior of the field-induced gap is observed in vicinity of the saturation field. Experimental data are compared with results of existing theoretical approaches, revealing excellent agreement with predictions.

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Permalink: https://www.hzdr.de/publications/Publ-18348
Publ.-Id: 18348


Magnetic excitations in the spin-1 anisotropic antiferromagnet NiCl2-4SC(NH2)2

Psaroudaki, C.; Zvyagin, S. A.; Krzystek, J.; Paduan-Filho, A.; Zotos, X.; Papanicolaou, N.
The spin-1 anisotropic antiferromagnet NiCl2-4SC(NH2)2 exhibits a field-induced quantum phase transition that is formally analogous to Bose-Einstein condensation. Here we present results of systematic high-field electron spin resonance (ESR) experimental and theoretical studies of this compound with a special emphasis on single-ion two-magnon bound states. In order to clarify some remaining discrepancies between theory and experiment, the frequency-field dependence of magnetic excitations in this material is reanalyzed. In particular, a more comprehensive interpretation of the experimental signature of single-ion two-magnon bound states is shown to be fully consistent with theoretical results. We also clarify the structure of the ESR spectrum in the so-called intermediate phase.

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Permalink: https://www.hzdr.de/publications/Publ-18347
Publ.-Id: 18347


Soliton-magnon crossover in spin-1/2 Heisenberg chains

Zvyagin, S.
Copper pyrimidine dinitrate ([PM-Cu(NO3)2(H2O)2]n, PM = pyrimidine) is a spin-1/2 antiferromagnetic chain material with alternating g-tensor and Dzyaloshinskii-Moriya interactions, whose spin dynamics can be described using the effective sine-Gordon model. Due to the presense of alternating staggered magnetization, this material exhibits a field-induced spin gap, formed by first breather. Here, we report on electron spin resonance (ESR) studies of this material in magnetic fields up to 64 T. In particular, a minimum of the gap in the vicinity of the saturation field Hsat = 48.5 T associated with a transition from the quantum disordered sine-Gordon (with soliton-breather elementary excitations in the magnetic excitation spectrum) to a spin-polarized state (with excitation spectrum formed by magnons) has been observed. This interpretation is fully confirmed by the quantitative agreement over the entire field range of the experimental data with the DMRG calculations for spin-1/2 Heisenberg chain with a staggered transverse field [1]. Such a behavior appears to be a general feature of the high-field excitation spectrum of quantum spin-1/2 chain systems with alternating g-tensor and/or Dzyaloshonskii-Moriya interactions
  • Invited lecture (Conferences)
    JEMS 2012 - Joint European Magnetic Symposia, 13.09.2012, Parma, Italy

Permalink: https://www.hzdr.de/publications/Publ-18345
Publ.-Id: 18345


High density plasma instabilities in intense laser irradiation

Kluge, T.; Cowan, T.; Huang, L.; Metzkes, J.; Schramm, U.; Gutt, C.; Schlenvoigt, H.-P.; Bussmann, M.
High energy electron channel formation in solid targets is discussed on two exemplary PIC simulations. The feasibility of SAXS diagnostics in laser accelerated plasma physics is discussed on the basis of scattering at high density plasma waves.
  • Lecture (Conference)
    33rd International Workshop on Physics of High Energy Density in Matter, 13.-18.01.2013, Hirschegg, Österreich
  • Lecture (Conference)
    77. Jahrestagung der DPG und DPG-Frühjahrstagung, 04.-08.03.2013, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18344
Publ.-Id: 18344


Coexistence of ferromagnetism and superconductivity in single-nanostructures

Herrmannsdörfer, T.
  • Invited lecture (Conferences)
    PNI in-house workshop on "Magnetism and highly correlated electron systems", 11.06.2012, Freising, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18343
Publ.-Id: 18343


Electron Spin Resonance in High Magnetic Fields

Zvyagin, S.
  • Invited lecture (Conferences)
    Dynamics and Transport in Quantum Magnets LOTHERM, Summer School 2012, 05.06.2012, Ljubljana, Slovenia

Permalink: https://www.hzdr.de/publications/Publ-18340
Publ.-Id: 18340


The Rossendorf Beamline at ESRF: A Pooled Facility of ACTINET-I3

Scheinost, A. C.
Overview on experimental possibilities and Joint Research Projects performed at The Rossendorf Beamline during ACTINET-I3
Keywords: XAS
  • Invited lecture (Conferences)
    2nd ACTINET-I3 Plenary Meeting, 23.-24.01.2013, Avignon, France

Permalink: https://www.hzdr.de/publications/Publ-18339
Publ.-Id: 18339


AcXAS: Actinide Reference X-ray Absorption Spectroscopy Database

Scheinost, A. C.; Schmeisser, N.; Banerjee, D.; Rossberg, A.; Denecke, M.; Dardenne, K.; Rothe, J.; Daehn, R.
Why do we need an Actinide Reference X-Ray Absorption Spectroscopy Database?
The team
The concept
The work status
Keywords: XAS actinides
  • Invited lecture (Conferences)
    2nd ACTINET Plenary Meeting, 23.-24.01.2013, Avignon, France

Permalink: https://www.hzdr.de/publications/Publ-18338
Publ.-Id: 18338


Nanostructures by mass-separated FIB

Bischoff, L.; Böttger, R.; Philipp, P.; Schmidt, B.
The introduction of mass-separated systems in the field of focused ion beams significantly increases the area of application in nanotechnology due to the availability of a broad spectrum of ions with the same advantages compared to classical Ga instruments. A short description of the configuration of a mass-separated FIB tool is given as well as the fundamentals of alloy liquid metal ion sources. Examples of application include patterned tailoring of functional surfaces and ion-induced phase transformation in thin layers, in particular the Si nanowire fabrication by FIB implantation and subsequent wet-chemical, anisotropic etching and the FIB lithography of thin ta-C films. Furthermore, the ion beam synthesis of CoSi2 nanostructures by Co-FIB writing and annealing, and the modification of surface morphology by various mono- and polyatomic projectiles in a broad energy- and temperature range in different materials are described and discussed.
Keywords: mass-separated focused ion beam, alloy liquid metal ion source, ExB filter, Si nanowire, ion beam synthesis, CoSi2 nanostructures, ta-C films, self-organized surface morphology, polyatomic ions
  • Book chapter
    Zhiming Wang: “FIB Nanostructures” Springer Series in Materials Science Lecture Notes on Nanoscale Science and Technology, Peking, Berlin: Springer, 2013, 978-3-319-02874-3

Permalink: https://www.hzdr.de/publications/Publ-18337
Publ.-Id: 18337


Scanning Tunnelling Spectroscopy of FIB-induced Local Phase Changes in Tetrahedral Amorphous-Carbon

Klein, F.; Philipp, P.; Bischoff, L.; Mühl, T.
Ion irradiation of tetrahedral amorphous-carbon leads to both an ion implantation and a local phase change of the carbon. The latter is equivalent to an increase of the carbon sp2/sp3 bond ratio. It is caused by the deposition of the ion energy and leads to an increased electrical conductivity. We perform spatially resolved scanning tunneling spectroscopy in order to investigate the impact of different ion species (Ga, Si, Ge, Au). A direct contribution of the implanted metal will be carefully considered.
Keywords: tetrahedral amorphous-carbon, ion implantation, spatially resolved STM
  • Poster
    DPG Frühjahrstagung der Sektion Kondensierte Materie, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18336
Publ.-Id: 18336


Watching the quantum race of electrons

Schütte, B.; Bauch, S.; Frühling, U.; Wieland, M.; Gensch, M.; Ploenjes, E.; Gaumnitz, T.; Azima, A.; Bonitz, M.; Drescher, M.
When a photon of sufficient high energy hits an atom it may kick out an electron. Quantum mechanics predicts that the electron behaves like a wave that runs away from the atom. If the photon energy was chosen right then a second electron (Auger electron) may be liberated from the atom, racing behind the first one. We were able to detect how this second electron overtakes the first one within only a few femtoseconds (1 fs = 10-15 seconds) and observe the dynamic exchange of energy between the two electrons when they are passing each other.
Keywords: THz, X-ray, pump probe, femtosecond, super-radiant THz sources
  • Open Access Logo Contribution to external collection
    in: DESY - Photon Science 2012: Highlights, Hamburg: DESY, 2013, 48-49

Permalink: https://www.hzdr.de/publications/Publ-18335
Publ.-Id: 18335


Interaction of energetic ultraheavy ions with surfaces

Bischoff, L.; Böttger, R.; Heinig, K.-H.; Facsko, S.
Energetic ultraheavy polyatomic ions like Bi3++ and Bi2+ produce very dense collision cascades in surface layers. Compared to monatomic ion impacts, which do not overlap in space and time within the heat relaxation time, the simultaneous impact of a few atoms in the same point can cause very different effects. Here, we report on FIB irradiation with fluences up to 1017 cm−2 using a liquid metal ion source. Using ultraheavy ions, a significantly increased sputter yield of Ge has been found, which can be attributed to thermal processes. Another, more striking feature is the dramatic difference in the surface morphologies caused by monatomic and ultraheavy ion irradiation. For instance, the well-known spongy surface layer forms on Ge upon 20 keV Bi+ irradiation, whereas normal incidence Bi3++ irradiation with the same energy per atom results in hexagonally ordered dot pattern having an aspect ratio of about one. Similar pattern have been found on Si by ultraheavy ion irradiation, but only under substantial substrate heating. And, in hot Ge substrates, normal incidence monatomic Bi+ ions produce no longer Ge sponge but also dot pattern. A crude thermal analysis of the experiments shows that the considered dot pattern formation is associated with a critical energy density deposited by an ion close to the surface. A more comprehensive model on this pattern formation will be presented in a subsequent talk by K.-H. Heinig.
R. Böttger, L. Bischoff, K.-H. Heinig, et al. JVST B30 (2012)06FF12
Keywords: ultraheavy polyatomic ions, bismuth, liquid metal ion source, germanium, sponge, dot pattern
  • Invited lecture (Conferences)
    DPG Frühjahrstagung der Sektion Kondensierte Materie, 10.-15.03.2013, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-18334
Publ.-Id: 18334


Account of the intratrack radiolytic processes for interpretation of the AMOC spectrum of liquid water

Zvezhinskiy, D.; Butterling, M.; Stepanov, S.; Krause-Rehberg, R.; Wagner, A.
Recent development of the Gamma-induced Positron Spectroscopy (GiPS) setup significantly extends applicability of the Age-Momentum Correlation technique (AMOC) for studies of the bulk samples. It also provides many advantages comparing with conventional positron annihilation experiments in liquids, such as extremely low annihilation fraction in vessel walls, absence of a positron source and e+ annihilations in it. We have developed new approach for processing and interpretation of the AMOC-GiPS data based on the diffusion recombination model of the intratrack radiolytic processes. This approach is verified in case of liquid water, which is considered as a reference medium in the positron and positronium chemistry.
Keywords: Gamma-induced Positron Spectroscopy, Age-Momentum Correlation, Positronium Chemistry
  • Lecture (Conference)
    16th International Conference on Positron Annihilation (ICPA-16), 19.-24.08.2012, Bristol, Great Britain
  • Open Access Logo Journal of Physics: Conference Series 443(2013), 012057
    DOI: 10.1088/1742-6596/443/1/012057

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Permalink: https://www.hzdr.de/publications/Publ-18333
Publ.-Id: 18333


Optimization of growth parameters of TiO2 thin films using a slow positron beam

Butterling, M.; Anwand, W.; Cornelius, S.; Potzger, K.; Smekhova, A.; Vinnichenko, M.; Wagner, A.
TiO2 thin films grown on fused silica were investigated using positron Doppler broadening spectroscopy at the slow-positron-beam SPONSOR at the Helmholtz-Zentrum Dresden-Rossendorf.
Effects of changes in different parameters like temperature or oxygen flow during film deposition on positron sensitive parameters have been investigated and first results will be presented.
Keywords: Slow Positron, Doppler Broadening Spectroscopy, Thin Films
  • Open Access Logo Journal of Physics: Conference Series 443(2013), 012073
    DOI: 10.1088/1742-6596/443/1/012073
  • Poster
    16th International Conference on Positron Annihilation (ICPA-16), 19.-24.08.2012, Bristol, Great Britain

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Permalink: https://www.hzdr.de/publications/Publ-18332
Publ.-Id: 18332


Si nanowire networks for 3rd generation solar cells

Heinig, K.-H.; Schmidt, B.; Mücklich, A.; Liedke, B.; Kelling, J.; Friedrich, D.; Hauschild, D.; Stegemann, K.-H.; Bulutay, C.; Keles, U.; Aydinli, A.
Large-scale self-structuring by spinodal decomposition of metastable SiO is a very promising synthesis process of novel nanostructured Si absorbers for 3rd generation solar cells [1]. The SiO layers have been produced by different techniques, sputtering, CVD and e-beam evaporation. Spinodal decomposition has been activated by Rapid Thermal Processing (RTP) and laser annealing. When the volume fraction of Si exceeds ~30% after the phase separation SiOx-->0.5SiO2+(1-0.5x)Si, then Si forms a nanowire network. Energy-Filtered Transmission Electron Microscopy (EFTEM) studies show that nanowires have diameters of a few nanometers with a narrow distribution. This is in excellent agreement with large-scale simulations based on bit-coded kinetic Monte-Carlo accelerated by Massive Parallel Programming on NVIDIA graphic cards using a CUDA code. There is a considerable Si band gap widening due to quantum confinement in the nanowire network. As the wire diameter coarsens with time of heat treatment like d~t0.33, the band gap of the Si nanosponge can be optimized for solar cell application. Using an atomistic pseudopotential method, the band gaps of sponge have been studied. Finally it will be shown that up-scaling of the nanotechnology described above to large-scale PV cell production is under way by industrial partners.
Keywords: nanocomposite, silicon, silica, sponge, sputter deposition, solar cell, band gap, atomistic simulations
  • Invited lecture (Conferences)
    4th International Conference on Nanostructure Selfassembly (NANOSEA2012), 25.-29.06.2012, Margherita di Pula, Sardinia/Italy

Permalink: https://www.hzdr.de/publications/Publ-18331
Publ.-Id: 18331


Networks of Si nanowires in SiO2 for solar cells

Heinig, K.-H.; Schmidt, B.; Mücklich, A.; Liedke, B.; Kelling, J.; Friedrich, D.; Hauschild, D.; Stegemann, K.-H.; Keles, U.; Bulutay, C.; Aydinli, A.
In Si-based thin film solar cells the a-Si:H or nanocrystalline absorber layer can be replaced by a network of Si nanowires (Si nanosponge) embedded in SiO2[1]. The Si nanosponge is formed by spinodal decomposition of metastable SiO layers which have been deposited by different techniques, sputtering, CVD and e-beam evaporation. The spinodal decomposition has been activated by Rapid Thermal Processing and laser annealing. When the volume fraction of Si exceeds ~30% after the phase separation SiOx-->0.5SiO2+(1-0.5x) Si, then Si forms a nanowire network. Energy-Filtered Transmission Electron Microscopy (EFTEM) studies show that nanowires have diameters of a few nanometers with a narrow distribution. This is in excellent agreement with large-scale simulations based on bit-coded kinetic Monte-Carlo. There is a considerable Si band gap widening due to quantum confinement in the nanowire network. As the wire diameter coarsens with time of heat treatment like d~t0.33, the band gap of the Si nanosponge can be optimized for solar cell application. Using an atomistic pseudopotential method, the band gap of sponges have been studied. Finally it will be shown that up-scaling of the nanotechnology described above to large-scale PV cell production is under way by industrial partners. [1] BMBF-TÜBITAK project “RainbowEnergy”, coordinators K.-H. Heinig and A. Aydinli
Keywords: nanocomposite, silicon, silica, sponge, solar cell, sputter deposition, laser annealing, band gap, atomistic simulations
  • Lecture (Conference)
    E-MRS Spring Meeting 2012, Symp. A, 14.-18.05.2012, Strasbourg, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-18330
Publ.-Id: 18330


Morphology of Ge surfaces after Bi, Bi2 and Bi3 ion impacts: holes, dots and sponge

Heinig, K.-H.; Böttger, R.; Bischoff, L.; Liedke, B.; Urbassek, H.; Anders, C.
Outline: (1) Motivation; (2) Patterns after normal Bi_n^+ and Bi_n^++ impacts; (3) Patterns after normal Bi_1^+ and Bi_1^++ impacts; (4) Different regions in the T-E_i phase diagram --> driving forces; (5) MD simulations; (6) kMC simulations; (7) Predictions of damped KS equation; (8) Conclusions
Keywords: polyatomic ions, ion-solid interaction, surface morphology, self-organization
  • Lecture (Conference)
    Workshop Ionenstrahlphysik, 10.-11.07.2012, Augsburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-18329
Publ.-Id: 18329


Surface Patterning of Ge and Si by Heavy Ion and Cluster Impacts: Experiments, Atomistic Simulations and Theory

Heinig, K.-H.; Böttger, R.; Liedke, B.; Bischoff, L.; Anders, C.; Urbassek, H.
The driving forces for pattern formation on surfaces by ion irradiation have been under discussion for many years. Bradley and Harper published a straightforward derivation of a partial differential equation based on the surface curvature dependent sputtering, which describes some features. Later on, ion impact induced viscous flow and a mass drift in the amorphous surfaces layer caused by the impinging ions where discussed. Only a few years ago it became obvious that on semiconductor surfaces the formation of many of the beautiful patterns are dominated by contaminations with metals. Thus, a discussion started, whether the pattern formation is induced by preferential sputtering of one of the components or by driving forces like phase separation. Additionally, the kinetics of the collision-induced defects in a sub-surfaces layer can produce instabilities resulting in surface pattern. In order to identify the dominating driving forces at least for Ge and Si surface patterning by heavy ion (Bi) and cluster (Bi3) impacts of a few to a few tens of keV, experimental Focussed Ion Beam (FIB) and broad-beam studies were combined with computer experiments (MD and kinetic Monte Carlo simulations) and theoretical studies, e.g. of the damped Kuramoto-Sivashinsky equation. A detailed comparison between experiments, simulations and PDE solutions of the surfaces evolution of specificmorphologies is a powerful approach for a deeper understanding of this kind of self-organization of structures. In this abstract for each approach, experiment, simulation and theory, an example is presented. Experiments cover a wide range of ion energies and fluences. The atomistic simulations study the influence of the ion collision cascades on the pattern formation via defect kinetics. And finally, relations of this defect kinetics to parameters of the damped Kuramoto-Sivashinsky equation are studied.
Keywords: ion-solid interaction, self-organization, surface pattern, theory, kinetic Monte Carlo simulation
  • Lecture (Conference)
    19th International Workshop on Inelastic Ion-Surface Collisions (IISC-19), 16.-21.09.2012, Frauenchiemsee, Germany

Permalink: https://www.hzdr.de/publications/Publ-18328
Publ.-Id: 18328


Near-surface depth profiling of solids by mono-energetic positrons

Ganguly, B. N.; Brauer, G.; (Editors)
This work reflects the wide and fascinating range of fields to which positrons have made important contributions. This covers, in particular, the development of low-energy (eV-keV) beams of essentially mono-energetic positrons, in the late 1960s, which opened the door to an even wider range of fundamental and technological studies: from surface physics to polymer films. The volume offers some background knowledge on the extent to which positrons have influenced and contributed to work in numerous fields.
Keywords: mono-energetic positrons, near-surface depth profiling, advances in techniques
  • Book (Authorship)
    Durnten-Zurich: Trans Tech Publications Ltd, 2012
    296 Seiten

Permalink: https://www.hzdr.de/publications/Publ-18327
Publ.-Id: 18327


Cerebral blood flow quantification in the rat: a direct comparison of arterial spin labeling MRI with radioactive microsphere PET

Bos, A.; Bergmann, R.; Strobel, K.; Hofheinz, F.; Steinbach, J.; van den Hoff, J.
Background
Arterial spin labeling magnetic resonance imaging (ASL-MRI) has been recognised as a valuable method for non-invasive assessment of cerebral blood flow but validation studies regarding quantification accuracy by comparison against an accepted gold standard are scarce, especially in small animals. We have conducted the present study with the aim of comparing ASL flow-sensitive alternating inversion recovery (FAIR)-derived unidirectional water uptake (K1) and 68Ga=64Cu microsphere (MS)-derived blood flow (f ) in the rat brain.
Methods
In 15 animals, K1 and f were determined successively in dedicated small animal positron emission tomography and MR scanners. The Renkin-Crone model modified by a scaling factor was used for the quantification of f and K1.
Results
Below about 1 mL/min/mL, we obtain an approximately linear relationship between f and K1. At higher flow values, the limited permeability of water at the blood brain barrier becomes apparent. Within the accessed dynamic flow range (0.2 to 1.9 mL/min/mL), the data are adequately described by the Renkin-Crone model yielding a permeability surface area product of .1.53 ± 0.46/ mL/min/mL.
Conclusion
The ASL-FAIR technique is suitable for absolute blood flow quantification in the rat brain when using a one-compartment model including a suitable extraction correction for data evaluation.

Trial registration
24-9168.21-4/2004-1 (registered in Freistadt Sachsen, Landesdirektion Dresden)
Keywords: Arterial spin labeling; Cerebral blood flow; Positron emission tomography; Kinetic modeling; Blood brain barrier.

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Permalink: https://www.hzdr.de/publications/Publ-18326
Publ.-Id: 18326


Velocity Measurement Using ROFEX Ultrafast Dual Plane X-ray CT Imaging

Barthel, F.; Hoppe, D.; Hampel, U.
Ultrafast electron beam X-ray computed tomography was developed at HZDR as a powerful imaging tool to observe two phase flows in several industrial applications, such as pipe flow that cannot be accessed by optical techniques. The ROssendorf Fast Electron beam X-ray Tomograph (ROFEX) combines advantages of non-invasive conventional CT systems, with a very high temporal and spatial resolution. This CT system is specially designed for investigations at a vertical test section at TOPFLOW (Transient two phase flow test facility) at HZDR. As a step forward recently ultrafast dual plane X-ray CT imaging was implemented, using new fast double ring X-ray detector electronics and a dual source path target in the ROFEX scanner. For the first time measurements of velocities in gas/water and steam/water flow are possible without any influence to the flow itself. The system provides pairs of slice images with an axial distance of 11mm at frame rates of up to 8000 kHz in time multiplex mode on both CT imaging planes. Thus one can assess the velocity of the interfacial area in the flow using cross correlation algorithm in two corresponding slice images. Beside parameters like phase fraction distribution, bubble sizes and interfacial areas, measurement of gas fraction velocity is possible for the first time non-invasively. From these data one can estimate slip between gas and liquid phase and calculate volumetric gas fraction. Furthermore CFD (Computational Fluid Dynamics) models can be enhanced providing parameters for calculations of bubble forces such as drag force or lift force, which influence shape and flow of bubbles. In chemical engineering applications like catalytic packaging or monolith ceramics it is possible to assess the residence time as well.
Keywords: velocity measurements, electron beam X-ray CT, dual plane CT
  • Lecture (Conference)
    6th International Symposium on Process Tomography, 26.-28.03.2012, Cape Town, South Africa
  • Contribution to proceedings
    6th International Symposium on Process Tomography, 26.-28.03.2012, Cape Town, South Africa
    Proceedings of 6th International Symposium on Process Tomography

Permalink: https://www.hzdr.de/publications/Publ-18325
Publ.-Id: 18325


Si Nanocrystal Networks by Si/SiO2 Phase Separation in SiOx Thin Films for Third Generation Solar Cells

Gündoğdu, S.; Özen, E. S.; İlday, S.; Heinig, K.-H.; Turan, R.; Aydinli, A.
Si/SiO2 phase separation in Silicon rich oxides is a very promising synthesis process of novel nanocrystaline Si (nc-Si) structures for 3rd generation thin-film solar cells. The incorporation of larger band gap nanocrystaline silicon into the solar cell structure can be utilized to improve the single band gap silicon solar cells efficiency by allowing a better use of the solar spectrum. We present cw laser annealing of Si-rich oxide thin films with varying Si content to obtain nc-Si embedded in silica. Silicon nanocrystals in the form of a nanocrystaline network (sponge-like) are particularly interesting for their percolated structure. Calculations show that considerable Si band gap widening due to quantum confinement in the nanocrystals network is expected. Beside this wide band gap, sponge-like Si has another potential advantage of suppressing the carrier recombination loss mechanism by electrically percolated nanostructures. SiOx thin films with x<2 were obtained by plasma enhanced chemical vapour deposition (PECVD). Hydrogen or nitrogen diluted silane (SiH4) gas was used as the Si source and two different precursor gasses, N2O and CO2, were used for oxygen incorporation. Fine tuning the Si excess in SiOx and optimizing the annealing conditions is pursued to control the inter-nanocrystal distance to generate a network of Si nanocrystals. The network formation depends critically on the precise control of composition during deposition. In the case of SiOx films, it is expected that the network is formed upon phase separation when the stoichiometry parameter of the initial SiOx film is x ~ 1 [1]. Nevertheless, in the case of PECVD grown Si-rich oxides, different elements such as nitrogen, carbon and especially hydrogen can be present in the films. A detailed elemental study has been performed to determine the precise composition of the films using ion beam techniques as elastic recoil detection analysis (ERDA) and Rutherford back scattering (RBS), as well as X-Ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and ellipsometry. The presence of hydrogen in PECVD grown samples makes ERDA an essential technique for compositional analysis although it is an expensive and hard to reach method. We have compared the ERDA data of different sets of samples with XPS, FTIR and ellipsometry analysis within the scope of listing a number of correlations between them and, further to be able to obtain the compositional information with these more accessible techniques. After the characterisation of the as-grown samples, the role of the composition in phase separation, as well as the laser irradiation parameters have been investigated and hydrogen has been identified as a key parameter for the Si/SiO2 phase separation. This research is supported by BMBF-TÜBITAK project "RainbowEnergy". [1] T. Muller et al, Applied Physics Letters, 85, 2373 (2004).
Keywords: Phase separation, SiOx, nuclear analysis, layer deposition
  • Lecture (Conference)
    Solar Electricity Conference & Exhibition (SOLARTR-2), 07.-09.11.2012, Antalya, Turkey

Permalink: https://www.hzdr.de/publications/Publ-18324
Publ.-Id: 18324


The recovery procedure of pin-by-pin fields of power distribution in the core of VVER type reactor for the program BIPR-8. Verification calculations

Gordienko, P.; Kotsarev, A.; Lisorkin, M.; Kozmenkov, Y.; Kliem, S.
Reconstruction of power distribution gives a means to check the compliance with design limits in steady-state calculations and to take account of power distribution deformation from one fuel element to another in transient calculations with use of spatial kinetics model. In calculation of reactivity accidents, its application makes it possible to avoid the additional conservatism derived from nodal calculation of power distributions. The resulting description of distribution behavior is expected to be used in thermal and mechanical calculation of fuel assemblies in transients.
The reconstructed power distributions will be used to calculate power densities in all fuel elements in the reactor core with use of BIPR-8 calculation code [1]. Verification calculations have been carried out by comparing the data of element-by-element power distribution in one cassette calculated with use of PERMAK [2] and BIPR-8 codes to test the method used and a new nodule of BIPR-8 where the method is implemented.
  • Contribution to proceedings
    22nd Symposium of Atomic Energy Research (AER) on VVER Reactor Physics and Reactor Safety, 01.-05.10.2012, Pruhonice, Czech Republic
    Proceedings of the 22nd AER Symposium, Budapest: MTA Energoatom, 9789635086276, 177-191

Permalink: https://www.hzdr.de/publications/Publ-18323
Publ.-Id: 18323


The first comparison of the seventh AER Dynamic Benchmark problem results obtained by RELAP5-3D and DYN3D/ATHLET computing codes

Bencik, M.; Hadek, J.; Kozmenkov, Y.; Kliem, S.
The paper gives the first comparison of the 7th three-dimensional AER dynamic benchmark calculation results received with the codes RELAP5-3D (ÚJV) and DYN3D/ATHLET (HZDR). This benchmark was defined by A. Kotsarev, M. Lizorkin and R. Petrin at the 20th AER Symposium in Hanassari (Finland). It is focused on investigation of transient behavior in a VVER-440 nuclear power plant. Its initiating event is the opening of the main isolation valve and re-connection of the loop with its main circulation pump in operation. A water slug with lower temperature of 100 K enters the core which leads to a reactor power excursion. The activation of the reactor scram is caused by the corresponding power level signal. As a result of the scram, the turbines are turned-off by closure of the turbine isolation valves. All main circulation pumps remain in operation. Each participant had to use its own developed input plant data deck and parameterized library of macroscopic cross sections. The VVER-440/213 plant is at the end of the first fuel cycle and in hot full power conditions. The initial reactor power tuning and burnup calculations were performed with the code DYN3D by both participants. The first part of paper contains a brief description of RELAP5-3D and DYN3D/ATHLET system codes, their NPP input decks and reactor core models. The second part shows the comparison of important global and local time dependent parameters. The trends of main calculated parameters are very close. The calculated nuclear and thermal-hydraulic phenomena like reactor power, cold leg mass flow rates, cold and hot leg coolant temperatures, upper plenum pressure, pressurizer water level and steam generator powers agree quite well.
  • Contribution to proceedings
    22nd Symposium of Atomic Energy Research (AER) on VVER Reactor Physics and Reactor Safety, 01.-05.10.2012, Pruhonice, Czech Republic
    Proceedings of the 22nd AER Symposium, Budapest: MTA Energoatom, 9789635086276, 653-675

Permalink: https://www.hzdr.de/publications/Publ-18322
Publ.-Id: 18322


Spectroscopic Ellipsometry Studies of nc-Si/a-Si and nc-Si/SiOx Systems: Optical Characterization of Crystallization

Nogay, G.; İlday, S.; Turan, R.; Heinig, K.-H.; Friedrich, D.
Third generation solar cells are expected to utilize the quantum size effect occurring in the semiconductor quantum dots fabricated in an appropriate matrix. A promising and well-studied material system is the Si nanocrystals fabricated in an oxide matrix such as SiO2. In spite of extensive research efforts on this material system, a successful device realization has not been possible due to the difficulties in the device fabrication and the electronic transport in the dielectric matrix that forms an insulating medium for the charge transport. In order to overcome the problems related to the electronic transport while not losing the quantum size effect, the use of a sponge-like nanostructure has recently been proposed. Si nanosponge is composed of tiny interconnected Si nanostructures embedded in an oxide matrix. These nanostructures form an interconnected quantum structure where the charge transport does not require the tunneling current which needs well positioned quantum dots. The band gap of the material can still be engineered by process parameters for tandem solar cell fabrication. Sinanosponge is then a promising candidate for the fabrication of third generation photovoltaic (PV) solar cells. In this work, Si-nanosponge structures were fabricated successfully in a SiOx matrix in a wide range of x values (0 Keywords: phase separation, SiO, silicon, Raman, Ellipsometry, PV cell
  • Lecture (Conference)
    Solar Electricity Conference & Exhibition (SOLARTR-2), 07.-09.11.2012, Antalya, Turkey

Permalink: https://www.hzdr.de/publications/Publ-18321
Publ.-Id: 18321


Overcoming challenges to the formation of high-quality polycrystalline TiO2:Ta transparent conducting films by magnetron sputtering

Neubert, M.; Cornelius, S.; Fiedler, J.; Gebel, T.; Liepack, H.; Kolitsch, A.; Vinnichenko, M.
The work is focused on understanding the physical processes responsible for the modification of the structure, electrical and optical properties of polycrystalline TiO2:Ta films formed by annealing of initially amorphous films grown by DC magnetron sputtering of electrically conductive ceramic targets. It is shown that fine tuning of the oxygen content during deposition of amorphous TiO2:Ta films is critical to achieving low resistivity and high optical transmittance after annealing. Increasing the total pressure during magnetron sputter deposition is shown to decrease the sensitivity of the annealed films to the oxygen flow variation during deposition of the initially amorphous layers. Polycrystalline anatase TiO2:Ta films of low electrical resistivity (ρH=1.5×10-3 Ω cm), high free electron mobility (µH=8cm²/Vs) and low extinction (k550nm=0.006) are obtained in this way at a total pressure of 2 Pa. The dependence of the polycrystalline film electrical properties on the oxygen content is discussed in terms of Ta dopant electrical activation/deactivation taking into account the formation of compensating defects at different oxygen pressures. The temperature-dependent transport of the polycrystalline anatase TiO2:Ta films is investigated showing the dominant role of the optical phonon scattering in the case of films with an optimum Ti/O ratio.
Keywords: TCO, transparent, conductive, oxide, TiO2, titania, tantalum, polycrystalline, sputter, annealing

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Permalink: https://www.hzdr.de/publications/Publ-18320
Publ.-Id: 18320


The German-Turkish project RainbowEnergy: A Si-based nanocomposite absorber for thin film PV cells

Heinig, K.-H.; Aydinli, A.; Turan, R.; Hauschild, D.
Si-based thin film PV cells suffer from a rather low efficiency. This leads to a relative small market share, although their module prices are comparably low. RainbowEnergy aims at a novel nanostructured Si-based thin film PV cell absorber, which increases the efficiency substantially without increasing the module costs. Large-scale patterning by spontaneous self-structuring during spinodal decomposition of metastable SiO is a
promising synthesis process of nanostructured Si absorbers for 3rd generation thin-film solar cells. The SiO layers have been produced by different techniques, sputtering, CVD and e-beam evaporation. Spinodal decomposition has been activated by Rapid Thermal Processing (RTP, several seconds), very Rapid Thermal Processing (vRTP, dwell time tens of msec), and laser annealing. If after phase separation SiOx --> 0.5SiO2 + (1-0.5x)Si the volume fraction of Si exceeds ~30%, then Si forms a percolated nanowire network. Energy-Filtered Transmission Electron Microscopy (EFTEM) studies show that nanowires have diameters of a few nanometers with a narrow distribution. This is in excellent agreement with large-scale simulations based on kinetic Monte-Carlo. As the wire diameters coarsens with time of heat treatment like d~t1/3, and because the Si bandgap opens for nmstructures by quantum confinement, a band gap engineering for PV cell optimization becomes feasible. It will be shown that up-scaling of the nanotechnology described above to large-scale PV cell production is under way with industrial partners
Keywords: solar cells, nanocomposite, silicon, thin film, laser annealing, kinetic Monte Carlo simulations
  • Invited lecture (Conferences)
    Solar Electricity Conference & Exhibition (SOLARTR-2), 07.-09.11.2012, Antalya, Turkey

Permalink: https://www.hzdr.de/publications/Publ-18319
Publ.-Id: 18319


Development of recombinant receptor tyrosine kinase ligands for diagnostics and therapy of tumors based on radionuclides

Pietzsch, D.; Mosch, B.; Pietzsch, J.
Introduction
Several receptor tyrosine kinases, like the epidermal growth factor receptor (EGFR) play a critical role in tumors and, therefore, are promising targets for tumor imaging and tumor therapy. The present work aims at development of novel recombinant EGF analogs as potential radioligands or receptor-targeted components for functionalization of nanoparticles. This approach uses selective alteration of protein structure by unnatural amino acids, which amenables the protein for both radiolabeling and functionalization by the Click-chemistry.

Material and methods
The structural alteration of the recombinant protein is possible by supplementation based incorporation, because E. coli tRNA can not differ between methionine and azidohomoalanine. So these two amino acids can be exchanged during protein biosynthesis. Therefore, azidohomolalanine was added into methionine-free medium during cultivation of transformed bacteria. Vectors with both GST-tag and His-tag and corresponding methods for purification were tested and first experiments for the Click reaction of the structurally modified protein with biotinylated alkynes, fluorescence dye-labeled and 18F labeled alkynes were realised.

Results and conclusion
The purification of the GST fusion protein only resulted in the unmodified protein, but not in the azido-functionalised protein. Subsequently, native purification of a His-tagged EGF was established and the incorporation of azides into the target protein could be demonstrated by Click reaction with an alkyne. Ongoing work focuses on optimization of this approach. Afterwards, the purified and labeled proteins will be tested concerning their pharmacological properties as potential radioligands or targeted components of functionalized nanoparticles.
  • Lecture (Conference)
    Sixth Berder meeting "Nanomedicine in Oncology", 26.-29.09.2012, Berder Island, France
  • Contribution to proceedings
    Sixth Berder meeting "Nanomedicine in Oncology", 26.-29.09.2012, Berder Island, France
    Proceedings of Sixth Berder meeting "Nanomedicine in Oncology", Paris, 12-13

Permalink: https://www.hzdr.de/publications/Publ-18318
Publ.-Id: 18318


Experimental hypoxia does not influence gene expression and protein synthesis of Eph receptors and ephrin ligands in human melanoma cells in vitro.

Reissenweber, B.; Mosch, B.; Pietzsch, J.
Eph receptor tyrosine kinases and their ephrin ligands are supposed to play important roles in melanoma progression and metastasis. Moreover, hypoxia is known to contribute to melanoma metastasis. In this study, the influence of experimental hypoxia on expression and synthesis of EphA2 and EphB4, and their corresponding ligands ephrinA1, ephrinA5, and ephrinB2 was systematically studied in four human melanoma cell lines in vitro. Melanoma cell monolayer and spheroid cultures were used as both extrinsic and intrinsic hypoxia models. Hypoxic conditions were confirmed by analyzing HIF-1α/-2α expression, VEGF expression, and cellular uptake of [18F]fluoromisonidazol. In normoxia, EphA2, EphB4, ephrinA1, ephrinA5, and ephrinB2 expression was detectable in all cell lines with varying extent. Considerable protein synthesis of EphA2 was detected in all cell lines. However, no effect of experimental hypoxia on both Eph/ephrin expression and protein synthesis was observed. This contributes critically to debating the hypothesis that hypoxia regulates the Eph/ephrin system in melanoma.

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Permalink: https://www.hzdr.de/publications/Publ-18317
Publ.-Id: 18317


Si nanowire networks embedded in SiO2 formed by spinodal decomposition of SiO – a novel absorber material for 3rd generation solar cells

Heinig, K.-H.; Schmidt, B.; Mücklich, A.; Liedke, B.; Kelling, J.; Friedrich, D.; Hauschild, D.; Stegemann, K.-H.; Keles, U.; Bulutay, C.; Aydinli, A.
Large-scale patterning by spontaneous self-structuring during spinodal decomposition of metastable SiO is a very promising synthesis process of novel nanostructured Si absorbers for 3rd generation thin-film solar cells [1]. The SiO layers have been produced by different techniques, sputtering, CVD and e-beam evaporation. Spinodal decomposition has been activated by Rapid Thermal Processing (RTP, several seconds) and very Rapid Thermal Processing (vRTP, dwell time tens of msec). When the volume fraction of Si exceeds ~30% after the phase separation SiOx-->0.5SiO2+(1-0.5x)Si, then Si forms a nanowire network. Energy-Filtered Transmission Electron Microscopy (EFTEM) studies show that nanowires have diameters of a few nanometers with a narrow distribution. This is in excellent agreement with large-scale simulations based on bit-coded kinetic Monte-Carlo. There is a considerable Si band gap widening due to quantum confinement in the nanowire network. As the wire diameter coarsens with time of heat treatment like d~t0.33, the band gap of the Si nanosponge can be optimized for solar cell application. Using an atomistic pseudopotential method, the band gap of sponges have been studied. Finally it will be shown that up-scaling of the nanotechnology described above to large-scale PV cell production is under way by industrial partners.
Keywords: solar cells, nanocomposite, silicon, nanowire, band gap, laser annealing, sputter deposition, kinetic Monte Carlo simulations
  • Invited lecture (Conferences)
    E-MRS Spring Meeting 2012, Symp. Y, 14.-18.05.2012, Srasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-18316
Publ.-Id: 18316


Ion-beam synthesis of magnetic semiconductors

Potzger, K.
This review focuses on current research on the topic of ion beam based approaches for the fabrication of magnetic semiconductors. Among them, classic semiconductors such as Si, Ge, GaAs as well as solid–gas compounds such as ZnO or GaN doped with transition metals are currently in the focus of research. Those are considered to be basic materials for future spintronics devices. In the review also possible pitfalls leading to misinterpretation of the data obtained will be discussed.
Keywords: Ion implantation, Diluted magnetic semiconductors

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Permalink: https://www.hzdr.de/publications/Publ-18315
Publ.-Id: 18315


Kinetic Monte Carlo Simulations at Spatiotemporal Scales of Experiments

Heinig, K.-H.
In comparison with MD, the kinetic Monte Carlo (kMC) method allows the treatment of much larger systems for much longer time periods on the atomistic level. Implementing the kMC method as a stochastic probabilistic cellular automaton according to the definition of Steven Wolfram, the simulations can be performed with many-body potentials projected onto a lattice, and a bit-coding makes the calculations extremely fast. Additionally, by Massively Parallel Programming (MPP) using NVIDIA graphic cards with CUDA programming, we accelerated kMC simulations by almost two orders of magnitude. Other than for finite element and MD codes, MPP cannot be straightforward implemented for the stochastic probabilistic Markov chain of kMC. We have extended the recently by Tobias Preis developed MPP method (Ising model with spin-flip kinetics) to much more complex conservative cellular automata with Kawasaki exchanges. Based on these methodological developments, we present large-scale simulations on the self-organization of surface nanopatterns under ion irradiation and on the scaling behavior of nanosponge formation.
Keywords: kinetic Monte Carlo simulations, program code development, massive parallel programming, CUDA, scaling phenomena
  • Invited lecture (Conferences)
    International Workshop on "Beyond Molecular Dynamics: Long Time Atomic-Scale Simulations", 26.03.2012, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-18314
Publ.-Id: 18314


Inactivation of HNSCC Cells by 90Y-Labeled Cetuximab Strictly Depends on the Number of Induced DNA Double-Strand Breaks

Saker, J.; Kriegs, M.; Zenker, M.; Heldt, J.-M.; Eke, I.; Pietzsch, H.-J.; Grénman, R.; Cordes, N.; Petersen, C.; Baumann, M.; Steinbach, J.; Dikomey, E.; Kasten-Pisula, U.
Radioimmunotherapy is considered to have great potential for efficient and highly specific treatment of tumors. The aim of this study was to determine the efficacy of radioimmunotherapy when using 90Y-labeled cetuximab and to determine to what degree induction and repair of DNA double-strand breaks (DSBs) are decisive for this approach.
Methods: This study was performed with 9 cell lines of squamous cell carcinoma of the head and neck (HNSCC) differing strongly in epidermal growth factor receptor (EGFR) expression. The radionuclide 90Y was coupled by the chelator trans-cyclohexyl-diethylene-triaminepentaacetic acid (CHX-A"-DTPA)/linker construct to the EGFR-directed antibody cetuximab to yield 90Y-Y-CHX-A"-DTPA-cetuximab with a specific activity of approximately 1.2 GBq/mg. EGFR expression was determined by immunofluorescence and Western blotting, cetuximab binding by fluorescence-activated cell sorter analysis, the number of DSBs by immunofluorescence staining Gamma-H2AX/53BP1-positive repair foci, and cell survival by colony formation.
Results: For the 9 HNSCC cell lines, cetuximab binding correlated with the amount of EGFR present in the cell membrane (r2 = 0.967, P < 0.001). When cells were exposed to 90Y-Y-CHX-A"-DTPA-cetuximab, the number of induced DSBs increased linearly with time (r2 = 0.968, P 5 0.016). This number was found to correlate with the amount of membranous EGFR (r2 = 0.877, P = 0.006). Most DSBs were repaired during incubation at 37C, but the small number of remaining DSBs still correlated with the amount of membranous EGFR (24 h: r2 = 0.977, P < 0.001; 48 h: r2 = 0.947, P < 0.001). Exposure to 90Y-Y-CHX-A"-DTPA-cetuximab also resulted in efficient cell killing, whereby the extent of cell killing correlated strongly with the respective number of remaining DSBs (r2 = 0.989, P < 0.001) and with the amount of membranous EGFR (r2 = 0.967, P < 0.001). No cell killing was observed for UTSCC15 cells with low EGFR expression, in contrast to the strong reduction of 86% measured for UTSCC14 cells showing a strong overexpression of EGFR.
Conclusion: 90Y-YCHX-A"-DTPA-cetuximab affected cell survival through the induction of DSBs. This treatment was especially efficient for HNSCC cells strongly overexpressing EGFR, whereas no effect was seen for cells with low levels of EGFR expression. Therefore, EGFR-directed radioimmunotherapy using 90Y-YCHX-A"-DTPA-cetuximab appears to be a powerful tool that can be used to inactivate tumors with strong EGFR overexpression, which are often characterized by a pronounced radioresistance.
Keywords: targeted radioimmunotherapy; EGFR; 90Y-Y-CHXA"-DTPA-cetuximab; double-strand breaks; cell inactivation

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Permalink: https://www.hzdr.de/publications/Publ-18313
Publ.-Id: 18313


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