Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34122 Publications

Intelligente Sensorpartikel zur Prozessdiagnose in Mischbehältern

Reinecke, S.; Kryk, H.; Hampel, U.

Der Betrieb großer Anlagen und Behälter wird von dem Problem begleitet, dass darin ablaufende verfahrens- und energietechnische Prozesse aufgrund erschwerter oder unmöglicher messtechnischer Zugänglichkeit nicht genügend beschrieben und überwacht werden können. Die Installation von lokal installierten Sonden mit Kabelverbindungen ist in großen Behältern, wie Chemie- und Bioreaktoren, Fermentern oder Schüttgutbehältern, oft nicht realisierbar oder unerwünscht. Zudem sind bildgebende Messverfahren, wie Kameras oder Tomografiesysteme, auf Grund der trüben Medien und der Behälterabmessungen von mehreren Metern meist nicht anwendbar.
Der Einsatz intelligenter Strömungsfolger und autonomer Sensortechnologien ermöglicht die messtechnische Erfassung verteilter Parameter und gewinnt deshalb zunehmend an Bedeutung für Anwendungen in der Prozessindustrie [1].
Aus diesem Grund wurde am HZDR das Konzept autonomer Sensorpartikel entwickelt, welche als auftriebsneutrale Strömungsfolger in großen Behältern, wie Biogasfermentern, eingesetzt werden können und dabei kontinuierlich Prozessparameter erfassen, speichern und diese nach Rückgewinnung der Partikel aus dem Prozess einem computergestützten Analysesystem zur Verfügung stellen [2].

  • Poster
    15. Köthener Rührer-Kolloquium, 14.06.2012, Köthen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17170
Publ.-Id: 17170


Autonome Sensorik

Reinecke, S.; Hampel, U.

Für eine effiziente Steuerung von Prozessen in verfahrenstechnischen Anlagen ist eine detaillierte räumliche und zeitliche Erfassung von Prozessparametern erforderlich, die jedoch mit herkömmlichen Messverfahren nicht realisiert werden kann. Als vollkommen neuen Lösungsansatz dazu wurde am HZDR ein autonomes Sensorpartikel entwickelt, welches als Strömungsfolger in großen Behältern, wie Biogasfermentern, eingesetzt werden könnte und somit kontinuierlich Prozessparameter erfasst, speichert und diese nach Wiedergewinnung des Partikels am Behälterauslass einem Analysesystem zur Verfügung stellt.

  • Industrielle Automation 1(2012)3, 43-43

Permalink: https://www.hzdr.de/publications/Publ-17169
Publ.-Id: 17169


Autonome Sensorik für große Prozessbehälter (AUTOSENS)

Reinecke, S.; Kryk, H.; Tschofen, M.

Für eine effiziente Steuerung von Prozessen in verfahrenstechnischen Anlagen ist eine detaillierte räumliche und zeitliche Erfassung von Prozessparametern erforderlich, die jedoch mit herkömmlichen Messverfahren nicht realisiert werden kann. Als vollkommen neuen Lösungsansatz dazu wurde am HZDR ein autonomes Sensorpartikel entwickelt, welches als Strömungsfolger in großen Behältern, wie Biogasfermentern, eingesetzt werden könnte und somit kontinuierlich Prozessparameter erfasst, speichert und diese nach Wiedergewinnung des Partikels am Behälterauslass einem Analysesystem zur Verfügung stellt.

Permalink: https://www.hzdr.de/publications/Publ-17168
Publ.-Id: 17168


Grain refinement by electromagnetic stirring and the impact on the mechanical properties of alsi-alloys

Räbiger, D.; Krößig, C.; Eckert, S.; Gerbeth, G.

This present study examines the directional solidification of AlSi7 alloys from a water cooled copper chill. A rotating magnetic field was used for melt agitation. Different magnetic field configurations were considered to demonstrate the impact of diverse flow conditions on the resulting microstructure and the mechanical properties. The solidified structure was evaluated in comparison to an unaffected solidified ingot. Measurements of the phase distribution, the grain size, the hardness and the tensile strength were performed. Our results reveal the potential of magnetic fields to control the grain size, the formation of segregation freckles and the mechanical properties. In particular, time–modulated rotating fields demonstrated their capability to homogenize both the grain size distribution and to improve the mechanical properties.

Keywords: rotating magnetic field; solidification; grain refinement; mechanical properties; AlSi alloys

  • Journal of Iron and Steel Research International 19(2012)Suppl. 1-1, 341-344
  • Poster
    7th International Conference on Electromagnetic Processing of Materials, 22.-26.10.2012, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-17167
Publ.-Id: 17167


Flow control during solidification of AlSi-alloys by means of tailored ac magnetic fields

Zhang, Y.; Räbiger, D.; Vogt, T.; Eckert, S.; Gerbeth, G.

This paper presents an experimental study which in a first stage is focused on obtaining quantitative information about the isothermal flow field exposed to various magnetic field configurations. Melt stirring has been realized by utilizing time-modulated AC magnetic fields in different variants. We consider time-modulated fields or combinations of traveling magnetic fields (TMF) and rotating magnetic fields (RMF). In a second step solidification experiments are carried out to verify the effect of a certain flow field on the solidification process. Our results demonstrate that the melt agitation using modulated magnetic fields offers a considerable potential for a well-aimed modification of casting properties by an effective control of the flow field.

Keywords: rotating magnetic field; travelling magnetic field; modulated fields; solidification; AlSi alloys

  • Journal of Iron and Steel Research International 19(2012)Suppl. 1-1, 574-577
  • Poster
    7th International Conference on Electromagnetic Processing of Materials, 22.-26.10.2012, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-17166
Publ.-Id: 17166


Inertial waves occurring in a liquid metal column due to pulsed excitation by a rotating magnetic field

Räbiger, D.; Vogt, T.; Franke, S.; Czarske, J.; Eckert, S.; Gerbeth, G.

We present an experimental study concerning the flow inside a liquid metal column exposed to a pulsed rotating magnetic field. This paper is aimed at highly resolved, quantitative velocity measurements in the eutectic GaInSn alloy. A novel ultrasound Doppler system was used two measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane. It employs an array of 25 transducer elements allowing a fast electronic traversing with concurrently high spatial and temporal resolution. The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures. The results demonstrate that the arising flow structure depends sensitively on the frequency of the RMF pulses. A maximum intensity of a periodic meridional flow can be observed, if the corresponding pulse frequency fP relates to the eigenperiod of the respective inertial mode in a developed regime. The electromagnetic stirring method that uses a modulated RMF offers considerable potential to enhance the stirring efficiency and to optimize the properties of castings by a well-aimed flow control during solidification.

Keywords: rotating magnetic field; electromagnetic stirring, inertial waves; flow control

  • Lecture (Conference)
    7th International Conference on Electromagnetic Processing of Materials, 22.-26.10.2012, Beijing, China
  • Journal of Iron and Steel Research International 19(2012)Suppl. 1-1, 82-85

Permalink: https://www.hzdr.de/publications/Publ-17165
Publ.-Id: 17165


Visualization of the flow in a mold of continuous casting by contactless inductive flow tomography and mutual inductance tomography

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

The flow structure in the mold of a continuous caster has a great influence on the quality of the produced steel. Conventional flow measurement techniques are prevented by the high temperature of the liquid steel. For a physical model of the continuous casting process using a low-melting point liquid metal, we present combined measurements of the flow in the mold by Contactless Inductive Flow Tomography (CIFT), and of the conductivity distribution in the submerged entry nozzle by Mutual Inductance Tomography (MIT). In addition, we summarize experiments with a magnetic stirrer around the submerged entry nozzle and its effects on the flow in the mold. Some new developments towards a robust implementation of CIFT at a real caster, including the use of pickup coils and gradiometric probes, are also discussed.

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

  • Lecture (Conference)
    5th International Congress on the Science and Technology of Steelmaking 2012, 01.-3.10.2012, Dresden, Germany
  • Contribution to proceedings
    5th International Congress on the Science and Technology of Steelmaking 2012, 01.-3.10.2012, Dresden, Germany
  • Steel Research International 85(2014)8, 1266-1273
    DOI: 10.1002/srin.201300075

Permalink: https://www.hzdr.de/publications/Publ-17164
Publ.-Id: 17164


Flow pattern formation in a liquid metal column by pulsed excitation of a rotating magnetic field

Räbiger, D.; Vogt, T.; Franke, S.; Czarske, J.; Eckert, S.; Gerbeth, G.

We present an experimental study concerning measurements of the flow inside a liquid metal column exposed to a pulsed rotating magnetic field. A novel ultrasound Doppler system was used to measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane. It employs an array of 25 transducer elements allowing a fast electronic traversing with concurrently high spatial and temporal resolution. The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures.

Keywords: rotating magnetic field; inertial waves; liquid metal

  • Lecture (Conference)
    The 23rd International Congress of Theoretical and Applied Mechanics, 19.-24.08.2012, Beijing, China
  • Contribution to proceedings
    The 23rd International Congress of Theoretical and Applied Mechanics, 19.-24.08.2012, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-17163
Publ.-Id: 17163


Experimental Modelling of the Impact of a DC Magnetic Field on the Melt Flow in a Continuous Casting Mould

Timmel, K.; Wondrak, T.; Röder, M.; Stefani, F.; Eckert, S.; Gerbeth, G.

This paper describes experimental investigations of flow structures and related transport processes in the continuous casting mould under the influence of an external DC magnetic field at laboratory scale. Experimental results will be presented here which have been obtained using a physical model (mini-LIMMCAST) operating with the low melting point alloy GaInSn. According to the concept of the electromagnetic brake the impact of a DC magnetic field on the outlet flow from the Submerged Entry Nozzle (SEN) has been studied up to Hartmann numbers of about 400. The Ultrasound-Doppler-Velocimetry (UDV) was applied for measurements of the flow pattern in the mould. Local conductivity anemometers were used to measure the turbulent quantities of the flow. The effect of the magnetic field on the flow structure turned out to be manifold and rather complex. The magnetic field causes a deflection of the jet, at which the respective exit angle from the nozzle ports becomes more flat. Thus, both the penetration depth of the discharging flow into the lower part of the mould and the impinging velocity of the jet onto the side wall are reduced. A significant return flow occurs in the adjacent regions of the jet. Specific vortices are formed with axes being aligned with the magnetic field direction. Such vortical structures are typical for quasi-two-dimensional magneto-hydrodynamic (MHD) flows. The flow measurements do not manifest a general braking effect which would be expected as an overall damping of the flow velocity and the related fluctuations all-over the mould volume. Variations of the wall conductivity showed a striking impact on the resulting flow structures.

Keywords: continuous casting; liquid metal model; electromagnetic brake; ultrasonic flow measurement; potential probes

  • Lecture (Conference)
    7th International Conference on Electromagnetic Processing of Materials (EPM2012), 22.-26.10.2012, Peking, China
  • Journal of Iron and Steel Research International 19(2012)Suppl. 1-2, 862-865

Permalink: https://www.hzdr.de/publications/Publ-17162
Publ.-Id: 17162


Flow determination in a model of continuous casting by combining contactless inductive flow tomography and mutual inductance tomography

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

For a physical model of a continuous caster, we present results on the simultaneous measurements of the flow in the mould by the Contactless Inductive Flow Tomography (CIFT), and of the conductivity distribution in the submerged entry nozzle (SEN) by Mutual Inductance Tomography (MIT) for a two phase flow setup. Depending on the gas flow rate, various flow regimes in the SEN and in the mould are identified, among them pressure oscillations in the gas feeding system, transitions between double and single vortex flows, and transient single port ejections.
In addition we give a summary of an experimental campaign with a magnetic stirrer around the SEN and its effects on the flow in the mould. As expected and desired, the swirling flow leads to a stronger upward fluid motion along the walls. At the same time, however, the oscillatory character of the flow becomes stronger.
The paper concludes with some new developments for CIFT towards a robust measurement of the very small induced magnetic field using pickup coils which allow the application of CIFT in environments with high DC magnetic fields and strong noise.

Keywords: liquid metal; contactless inductive flow tomography (CIFT); electromagnetic inductance tomography (MIT); continuous casting

  • Lecture (Conference)
    6th International Symposium on Process Tomography, 25.-28.3.2012, Cape Town, South Afrika
  • Contribution to proceedings
    6th International Symposium on Process Tomography, 25.-28.3.2012, Cape Town, South Afrika

Permalink: https://www.hzdr.de/publications/Publ-17161
Publ.-Id: 17161


Simulation von Diffusions-Adsorptionsprozessen in natürlichem Gesteinsmaterial mit COMSOL Multiphysics.

Schikora, J.

Viele Länder innerhalb Europas, wie zum Beispiel Frankreich, Deutschland oder die Schweiz, produzieren einen (großen) Teil ihres Energiebedarfs über Kernkraft. Zwar hat Deutschland den Ausstieg aus der Atomenergie beschlossen, sodass perspektivisch
kein neuer radioaktiver Abfall aus Kraftwerken anfällt, trotzdem besteht auch danach die Notwendigkeit der Entsorgung von radioaktiven Stoffen aus der Industrie, Forschung und Medizin. Eine Option für die Entsorgung von radioaktiven Stoffen aus diesen Branchen sowie aus dem Betrieb und der Stilllegung von Kernkraftwerken ist die geologische Tiefenlagerung. Dafür geeignetes Wirtsgestein muss als Bestandteil des Multibarrierenkonzepts bestimmte Anforderungen erfüllen. Dieses Konzept soll den Einschluss der Kontaminanten über sehr lange Zeiträume garantieren, bis die Aktivität der Abfälle auf ein unbedenkliches Maß abgefallen ist. So sollte das gewählte Wirtsgestein eine möglichst geringe hydraulische Leitfähigkeit aufweisen. Der dominante Transportmechanismus ist dann die Diffusion und die Ausbreitung von Schadstoffen findet in solchen Gesteinen verlangsamt statt. Eine weitere Eigenschaft des Gesteins sollte seine Fähigkeit sein, den Transport von Kontaminanten durch Sorption zu retardieren.

Als potentielles Wirtsgestein für radioaktiven Abfall wird in der Schweiz der Opalinuston des Zürcher Weinlandes untersucht. Er weist die oben beschriebene Eigenschaft einer (sehr) geringen hydraulischen Leitfähigkeit (1·10-14 – 1·10-13 m/s) auf (Nagra, 2002). Es ist daher zu erwarten, dass der Transport von gelösten Substanzen innerhalb des Opalinuston durch Diffusion erfolgt. Des Weiteren bedingt der hohe Anteil an Tonmineralen in diesem Wirtsgestein eine gute Retardierung von Kontaminanten. Auch in Deutschland sind Tongesteine, wie der Opalinuston, Untersuchungsgegenstand im Zusammenhang mit der Lagerung von radioaktiven Abfällen und bei der Suche nach Alternativen zu Gorleben.

Der diffusive Transport spielt somit eine wichtige Rolle in Ausbreitungsrechnungen und damit in der Risikoabschätzung entsprechender untertägiger Deponien und Endlager. Für Langzeitsicherheitsanalysen werden neben einem guten Systemverständnis auch die Parameter der Transportgleichungen benötigt. Eine mögliche Vorgehensweise bei der Bestimmung von Transportparametern ist das Durchführen von Laborexperimenten. Die zugrundeliegenden Bilanzgleichungen lassen sich jedoch nicht in jedem Fall analytisch lösen. Es ist dadurch notwenig numerische Lösungsmethoden zu nutzen, zum Beispiel in Computersimulationen.

Gegenstand der vorliegenden Arbeit ist es, den Transport chemisch-toxischer und radioaktiver Kontaminanten in geologischen Formationen durch Simulation der Diffusions-Adsorptionsprozesse in natürlichem Gesteinsmaterial zu untersuchen. Als Simulationsumgebung kommt dabei COMSOL Multiphysics zum Einsatz. Sie nutzt zur numerischen Lösung von partiellen Differentialgleichungen die Methode der finiten Elemente.
Hauptziele, die in der vorliegenden Arbeit mit Hilfe der Modellbildung und Simulation der Transportprozesse erreicht werden sollen, sind die Nachrechnung vorhandener Experimente zur Parameterschätzung sowie prognostische Rechnungen zur Optimierung von Diffusionsexperimenten. Es sollen des Weiteren die Möglichkeiten des Simulationstools COMSOL Multiphysics zur effektiven Auswertung von komplexen, dreidimensionalen und anisotropen Daten aus zeitabhängigen Transportuntersuchungen evaluiert werden. Im Einzelnen werden die folgenden Teilaufgaben gelöst:

● Einarbeitung in COMSOL Multiphysics 4.2/4.2a, das Ergänzungsmodul Chemical Reaction Engineering sowie das Optimierungsmodul auch mit dem Ziel des weiteren Ausbaus der Nutzerkompetenz am Institut für Ressourcenökologie (vormals Institut für Radiochemie).

● Auswahl geeigneter Interfaces aus dem COMSOL Basismodul und ggf. dem Chemical Engineering Module für die Nachrechnung vorhandener Datensätze.

● Es sind ausgewählte explizite Diffusions- und Diffusions-Adsorptionsexperimente zu simulieren. Die Parameterbestimmung ist durch Datenabgleich zu gewährleisten. Darüber hinaus ist eine Auswahl alternativer Modelle zu testen und zu vergleichen; beispielsweise hinsichtlich der jeweils zu Grunde liegenden Gleichungen, der Porosität oder der Raum-Zeit-Skala.

● Für ein geplantes Diffusionsexperiment ist mittels prognostischer Rechnungen eine Optimierung der variablen Parameter vorzunehmen.

  • Diploma thesis
    TU Dresden, Fakultät Maschinenwesen, Professur Verfahrensautomatisierung, 2012
    105 Seiten

Permalink: https://www.hzdr.de/publications/Publ-17160
Publ.-Id: 17160


A controlled immobilization of His-tagged estrogen receptor hERa: Comparison study between the kinetics and morphology

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

A specific immobilization of macrobiomolecules on chip arrays is essential in order to increase the efficiency of biosensors as well as for the improvement of protein single studies. A comparison between a specific immobilization, like on nickel-nitrilotriacetic acid (Ni-NTA) matrix, and a covalent immobilization, like on amino self-assembling monolayers (SAMs), was investigated by using surface plasmon resonance (SPR). Whereas the number of the covalently immobilized estrogen receptors hER is higher than those of the specifically immobilized receptors, the affinity constant KD, using β-Estradiol as an analyte, is much higher in the case of the specific immobilization. This fact has been demonstrated by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The morphology of the covalent and specific immobilization of the His-tagged binding domain of the estrogen receptor (hERa-LBD-His10) confirms the SPR kinetics study.

Keywords: Estrogen receptor; Ni-NTA; His-tagged; SPR; AFM; SEM

  • Lecture (Conference)
    E-MRS 2012 SPRING MEETING, 14.-18.05.2012, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-17159
Publ.-Id: 17159


Impact of Soft Iron impellers in the Cadarache Dynamo experiment

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

Numerical simulations of the kinematic induction equation are performed on a model configuration of the Cadarache von-Karman-Sodium dynamo experiment. The effect of a localized axisymmetric distribution of relative permeability that represents soft iron material within a flow of a conducting fluid is investigated. We observe a purely toroidal axisymmetric mode localized in the impeller disks which becomes dominant for sufficiently large permeability. In this limit, the toroidal mode is close to the onset of dynamo action with a (negative) growth-rate that is rather independent of the magnetic Reynolds number. We qualitatively explain this effect by paramagnetic pumping at the fluid/disk interface and propose a simplified analytical model that quantitatively reproduces numerical results. The crucial role of the high permeability disks for the mode selection in the Cadarache dynamo experiment cannot be inferred from computations that use idealized pseudo-vacuum boundary conditions.

Keywords: dynamo

  • Lecture (Conference)
    23rd International Congress of Theoretical and Applied Mechanics (ICTAM 2012), 19.-24.08.2012, Beijing, China
  • Contribution to proceedings
    23rd International Congress of Theoretical and Applied Mechanics (ICTAM 2012), 19.-24.08.2012, Peking, China
    Abstract Book, 978-988-16022-3-7

Permalink: https://www.hzdr.de/publications/Publ-17158
Publ.-Id: 17158


Femtosecond level electron bunch diagnostic at quasi-cw SRF accelerators: test facility ELBE

Gensch, M.; Helm, M.; Kaya, C.; Kuntzsch, M.; Lehnert, U.; Mamidala, V.; Michel, P.; Schneider, C.; Schurig, R.; Seidel, W.; Staats, G.; Al-Shemmary, A.; Schlarb, H.; Stojanovic, N.; Geloni, G. A.

Superconducting radiofrequency (SRF) accelerator technology allows to accelerate electron bunches not only in considerably longer bunch trains than is possible by normal conducting accelerator technology, but also in principle enables a mode of operation that can circumvent any macropulse scheme and provides relativistic electron bunches with real repetition rates scaling from the kHz to GHz regime [1, 2, 3, 4]. In this proceedings we discuss different approaches foreseen for online electron bunch diagnostic at the new femtosecond electron beamline of the superconducting cw RF accelerator ELBE [11]. In medium term we believe the concepts tested at the femtosecond beamline at ELBE are off great importance for various energy recovvery linac accelerators (ERL) coming online in the next few years [2, 4] as well as facilities like the European X-FEL [5] and FLASH [6] when operated in long bunchtrain mode of operation.

  • Open Access Logo Contribution to proceedings
    IPAC2012, 20.-25.05.2012, New Orleans, USA
    Proceedings of IPAC2012

Permalink: https://www.hzdr.de/publications/Publ-17157
Publ.-Id: 17157


Sorption of U(VI) and Np(V) onto diorite from Äspö HRL

Schmeide, K.; Gürtler, S.; Müller, K.; Steudtner, R.; Joseph, C.; Bok, F.; Brendler, V.

Sorption of the redox-sensitive actinides U and Np onto diorite obtained from Äspö Hard Rock Laboratory (HRL, Sweden) was studied by batch sorption experiments. The influence of various parameters, such as solid-to-liquid ratio (2 to 200 g/L), grain size (0.063 – 0.2 mm, 0.5 – 1 mm, 1 – 2 mm) and temperature (25 and 10°C), on the actinide sorption was studied under anoxic conditions (N2) applying a synthetic Äspö groundwater (pH 7.8, I = 0.178 M). The influence of grain size on actinide sorption was also investigated under aerobic conditions (pCO2 = 10−3.5 atm). Applying NaClO4 as background electrolyte, the actinide sorption onto diorite was studied as a function of ionic strength (I = 0.1 to 1 M, pH 7.8). Distribution coefficients, Kd values, were determined. Radionuclide speciation in solution was verified by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Furthermore, the sorption of U and Np onto diorite was also studied by in situ time-resolved attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy to characterize the sorbed species.

Keywords: Diorite; uranium; neptunium; sorption; speciation; TRLFS; ATR FT-IR spectroscopy

  • Lecture (Conference)
    1st Workshop of the Project "Crystalline rock retention processes" (CROCK), 22.-24.05.2012, Stockholm, Sweden
  • Poster
    1st Workshop of the Project "Crystalline rock retention processes" (CROCK), 22.-24.05.2012, Stockholm, Sweden
  • Contribution to proceedings
    1st Workshop of the Project "Crystalline rock retention processes" (CROCK), 22.-24.05.2012, Stockholm, Sweden
    1st Workshop Proceedings of the Collaborative Project “Crystalline Rock Retention Processes” (7th EC FP CP CROCK), KIT Scientific Reports 7629, Karlsruhe: KIT Scientific Publishing, 169-180 (2012)
  • Lecture (others)
    Status-Seminar 2012 "Nuclear Safety Research – From Reactors to Disposal", 11.-12.12.2012, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-17156
Publ.-Id: 17156


Laser proton accelerator for radiobiological studies

Zeil, K.; Beyreuther, E.; Karsch, L.; Kluge, T.; Laschinsky, L.; Kraft, S. D.; Oppelt, M.; Pawelke, J.; Richter, C.; Schürer, M.; Cowan, T.; Sauerbrey, R.; Schramm, U.

  • Poster
    Oncoray Retreat, 07.-08.03.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17155
Publ.-Id: 17155


Beam collimation with pulse power solenoids

Kroll, F.; Joost, M.; Burris-Mog, T.; Herrmanndörfer, T.; Kraft, S. D.; Sobiella, M.; Wustmann, B.; Zherlitsyn, S.; Cowan, T.; Schramm, U.

  • Poster
    Oncoray Retreat, 07.-08.03.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17154
Publ.-Id: 17154


Laser Proton Acceleration from Reduced Mass Targets

Zeil, K.; Metzkes, J.; Kraft, S.; Kluge, T.; Bussmann, M.; Schmidt, B.; Zier, M.; Schramm, U.; Cowan, T.; Sauerbrey, R.

We present recent studies on laser proton acceleration experiments using mass limited silicon targets. Small micro machined silicon foils with 2 µm thickness and 20x20 µm2 to 100x100µm2 size mounted on very tiny stalks were shot with ultra short laser pulses 30 fs of the new 150 TW DRACO Laser facility of the Research Centre Dresden-Rossendorf. The experiments were carried out using high contrast level 10-10. Proton spectra have been measured with magnetic spectrometers and radio chromic film stacks. The scaling of the maximum proton energy as function of the target size was investigated and strong influence of the stalk as well as the target edges was found.

  • Lecture (Conference)
    SPIE Optics and Optoelectronics, 18.-21.04.2011, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-17153
Publ.-Id: 17153


Fluid flow driven self-generation of magnetic fields in laboratory experiments

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

Cosmic magnetic fields are ubiquitous phenomena that are intrinsically coupled to most astrophysical objects like planets, stars or galaxies. The origin of these fields involves the formation of electrical currents by means of a complex flow of a conducting fluid or plasma.This process, the so called dynamo effect, is necessarily three dimensional and non-linear which makes an analytical or numerical approach difficult.

Meanwhile, fluid flow driven generation of magnetic fields has also been obtained in laboratory experiments providing a complementary tool to astronomical observations or direct numerical simulations. However, whereas astrophysical dynamo action is comparably easy because of the large dimensions of the involved flows, its experimental realization requires considerable technical efforts. So far only three experiments have been able to demonstrate fluid flow driven self-excitation of magnetic fields.

I will briefly summarize the essential outcome of the seminal experiments conducted in Riga and in Karlsruhe which have demonstrated the principal possibility of the magnetic field generation process and its saturation. I will further discuss recent results of the French Von-Karman-Sodium dynamo that are still not completely understood, e.g. the dominance of the axisymmetric field or the exclusive occurrence of dynamo action when soft iron impellers are used to drive the flow.

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

Keywords: dynamo

  • Lecture (Conference)
    Plasma Physics Symposium, 24.-25.05.2012, Bochum, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17152
Publ.-Id: 17152


Influence of the Lagrangian integral time scale estimation in the near wall region on particle deposition

Lecrivain, G.; Hampel, U.

In a high temperature pebble-bed reactor core where thousands of pebbles are amassed, the friction between the outer graphite layer of the fuel elements triggers the formation of carbonaceous dust. This dust is eventually conveyed by the cooling carrier phase and deposits in the primary circuit of the high temperature reactor. The numerical prediction of carbonaceous dust transport and deposition in turbulent flows is a key safety issue. Most particle tracking procedures make use of the Lagrangian integral time scale to reproduce the turbulent dispersion of the discrete phase. In the present Lagrangian particle tracking procedure, the effect of the Lagrangian integral time scale near the wall is thoroughly investigated. It is found that, in the linear sublayer, a value of the normalised wall normal component of the Lagrangian integral time scale lower that 4 delivers accurate particle deposition velocities. The value worked out here near the wall region is in accordance with Lagrangian integral time scales derived from recent Direct Numerical Simulations.

Keywords: particle deposition; turbulent dispersion; CFD

  • Journal of Fluids Engineering - Transactions of the ASME 134(2012)7, 074502
    DOI: 10.1115/1.4006912

Permalink: https://www.hzdr.de/publications/Publ-17150
Publ.-Id: 17150


Cm(III) and Eu(III) speciation in human body fluids and cell culture media studied by luminescence spectroscopy

Heller, A.; Barkleit, A.; Sachs, S.; Bernhard, G.

The speciation of curium and europium in urine, saliva and FaDu cell culture medium is studied with time-resolved laser-induced fluorescence spectroscopy.
The complexation study of Cm(III)/Eu(III) with inorganic and organic model substances like carbonate, phosphate, citrate and various proteins which is crucial for species identification in biofluids is presented.

Keywords: curium; europium; urine; saliva; cell culture medium; TRLFS

  • Invited lecture (Conferences)
    4th Speciation Seminar, 29.-31.05.2012, Montpellier, France

Permalink: https://www.hzdr.de/publications/Publ-17149
Publ.-Id: 17149


Autonome Sensorpartikel zur räumlichen Parametererfassung in großskaligen Behältern

Reinecke, S.; Pöpping, U.; Hampel, U.

Zur Langzeiterfassung räumlich verteilter Parameter in Prozessbehältern wurde das Konzept autonomer Sensorpartikel entwickelt und getestet. Die Sensorpartikel sind auftriebsneutral und bewegen sich frei mit der vorherrschenden Strömung im Prozess. Die integrierte Messelektronik erfasst die Signale der internen Messfühler für die Temperatur, die Eintauchtiefe und die Beschleunigung in einem autonomen und energieeffizienten Messregime. Die Validierung des Messsystems erfolgte unter realen Strömungsbedingungen in einem Versuchsfermenter. Die aufgenommenen Messdaten und die daraus extrahierten Prozesskenndaten charakterisieren den Zustand des Prozesses und die vorherrschenden Strömungsbedingungen.

  • Contribution to proceedings
    16. GMA/ITG Fachtagung Sensoren und Messsysteme 2012, 22.-23.05.2012, Nürnberg, Deutschland
    Sensoren und Messsysteme 2012 - Vorträge der 16. GMA/ITG Fachtagung, 978-3-9813484-0-8, 513-521
  • Lecture (Conference)
    16. GMA/ITG Fachtagung Sensoren und Messsysteme 2012, 22.-23.05.2012, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17148
Publ.-Id: 17148


Modeling of SFR cores with Serpent-DYN3D codes sequence

Fridman, E.; Shwageraus, E.

DYN3D reactor dynamics nodal diffusion code was originally developed for the analysis of Light Water Reactors. In this paper, we demonstrate feasibility of using DYN3D for modeling of fast spectrum reactors. Homogenized cross sections data library was generated using continuous energy Monte-Carlo code Serpent which provides significant modeling flexibility compared with traditional deterministic lattice transport codes and tolerable execution time. A representative sodium cooled fast reactor core was modeled with Serpent-DYN3D code sequence and the results were compared with those produced by ERANOS code and with 3D full core Monte Carlo solution. Very good agreement between the codes was observed for the core integral parameters and power distribution suggesting that DYN3D code with cross section library generated using Serpent can be reliably used for the analysis of fast reactors.

Keywords: Serpent; Monte Carlo; lattice physics; DYN3D; few-group cross-section generation; sodium cooled fast reactor

Permalink: https://www.hzdr.de/publications/Publ-17147
Publ.-Id: 17147


Modification of ZnO:Al properties: post-deposition millisecond thermal processing vs direct growth at elevated substrate temperature

Vinnichenko, M.; Hauschild, D.; Cornelius, S.; Krause, M.; Gago, R.; Mücklich, A.; Lissotschenko, V.; Kolitsch, A.

ZnO:Al (AZO) is a promising cost-efficient transparent conducting material for a number of applications. Thermal processing at millisecond time scale (very rapid thermal processing, vRTP) is an attractive approach of AZO film properties improvement. Present study focuses on systematic comparison of the properties of the films processed by vRTP and directly grown at various substrate temperatures. The AZO films were deposited both by reactive pulsed and non-reactive DC magnetron sputtering. The vRTP was performed using innovative low-cost high power diode laser arrays with microoptically designed line-shaped beam profiles (dwell time of 1 ms). Only the films grown without substrate heating were subjected to the vRTP. Even at air ambience, the optimized laser processing of the AZO films results in a decrease of the film electrical resistivity from (1-2)x10^-3 to less than 5x10^-4 Ohm cm. This is accompanied by a substantial, in some cases almost two-fold, increase of the free electron mobility and density, and increase of the film transmittance in the visible. According to TEM, ellipsometry, Raman spectroscopy and XANES, annealing of intra-grain oxygen-related point defects during vRTP has a main effect on the film electrical properties. Using deposition at elevated temperature, the AZO films with comparable electrical and optical properties were achieved only at Ts≥250°C.

Keywords: transparent conductive oxides; ZnO:Al; very rapid thermal processing

  • Invited lecture (Conferences)
    10th International Symposium on Ceramic Materials and Components for Energy and Environmental Applications (10th CMCEE), 21.-23.05.2012, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-17146
Publ.-Id: 17146


Plasmonic nano-Ag layers in TCO and Si nanosponge for photovoltaic applications

Vinnichenko, M.; Liedke, B.; Heinig, K.-H.; Gulseren, O.; Friedrich, D.; Mücklich, A.; Schmidt, B.; Akguc, G. B.; Aydinli, A.

Ag nanoparticles (NPs) have the potential of increasing efficiency of thin film solar cells substantially due to plasmonic effects. Here, we consider two different approaches of Ag NPs embedding into: (i) transparent conductive oxide (TCO) at the rear side of thin-film PV cells to induce plasmonic scattering of red light at high angles (in-plane direction) in order to improve the light trapping in the absorber layer; and (ii) absorber layer to increase carrier generation due to plasmonic field enhancement.
For the approach (i), a thin Ag layer is sandwiched between two ZnO:Al films with all films grown by magnetron sputter deposition. Subsequently, by a thermal treatment or using high growth temperatures this Ag film is transformed into an Ag NP layer via spinodal dewetting. The formation of Ag NPs was investigated experimentally and by atomistic simulations. The electrical and optical properties of such composites were also studied.
For the approach (ii) Ag layer can be sandwiched between SiO layers grown by PVD and then thermally treated to form novel absorber material consisting of Si nanowire network in SiO2 and Ag NPs. Large-scale atomistic simulations predict formation of Ag/Si core-shell NPs isolated by SiO2. This prevents direct electrical contact of Ag NPs with percolated Si network, thus avoiding charge carriers losses. The experimental prove of this prediction is in progress.

Keywords: Transparent conductive oxides; plasmonic effects

  • Poster
    E-MRS Spring Meeting, 14.-18.05.2012, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-17145
Publ.-Id: 17145


Mechanisms of electrical and optical properties modification of ZnO:Al films induced by very rapid thermal processing

Vinnichenko, M.; Hauschild, D.; Cornelius, S.; Krause, M.; Gago, R.; Mücklich, A.; Neidhardt, J.; Lissotschenko, V.; Kolitsch, A.

Thermal processing at millisecond range (very rapid thermal processing, vRTP) is an attractive approach of ZnO:Al film properties improvement compared to RTP or time-consuming isothermal annealing. This is of importance for development of cost-efficient transparent electrodes for thin film solar cells. The present study elucidates the effects of thermal processing on the film optical and electrical properties comparing vRTP treatment at ambient atmosphere using a laser source (~1 ms dwell time) with isothermal annealing in vacuum (1 hour, Ta≤550 °C). The films were grown by reactive pulsed magnetron sputtering (MS) at lab scale and non-reactive MS using an industrial in-line system. The optimized laser processing and the isothermal annealing of the films grown at low temperatures (RT-100 °C) result in an increase of their transmittance in the visible, decrease of electrical resistivity from (1-2)x10^-3 to less than 5x10^-4 Ohm cm, substantial increase of free electron mobility, µe, and density, Ne. Laser annealing of the films grown under optimized conditions at 350 °C does not improve their properties, while isothermal annealing leads to an increase of µe values above 50 cm2V-1s-1. According to TEM, ellipsometry, Raman spectroscopy and XANES, annealing of intra-grain oxygen-related point defects during vRTP has a main effect on the film electrical properties, while during isothermal annealing additional improvement of crystallinity needs to be taken into account.

Keywords: transparent conductive oxides; ZnO:Al; high-power diode laser annealing

  • Lecture (Conference)
    E-MRS Spring Meeting, 14.-18.05.2012, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-17144
Publ.-Id: 17144


Terahertz spectroscopy of semiconductor nanostructures with the free-electron laser

Helm, M.

Free electron lasers (FEL) can deliver high-intensity narrow-band radiation in otherwise not easily accessible spectral ranges, such as the THz range.
After briefly introducing the FEL at HZDR, I will discuss a quantum optical experiment, where we use the FEL to drive the 1s-2p intra-excitonic transition in semiconductor quantum wells and observe the so-called Autler-Townes splitting, a manifestation of electronic states dressed by the radiation field [1]. Our results indicate that we enter a regime well beyond the rotating-wave and two-level approximations. As a second example I will discuss pump-probe experiments on multilayer graphene over a wide range of photon energies (10-250 meV), hereby unveiling the relevant electronic relaxation mechanisms [2]. Remarkably we observe a sign change of the probe signal, i.e. a crossover from induced bleaching to induced absorption, which is related to the interplay between inter- and intraband absorption.

[1] M. Wagner, H. Schneider, D. Stehr, S. Winnerl, A. M. Andrews, S. Schartner, G. Strasser, M. Helm: „Observation of the intra-exciton Autler-Townes effect in GaAs/AlGaAs semiconductor quantum wells”, Phys. Rev. Lett. 105, 167401 (2010)

[2] S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W. A. de Heer, H. Schneider, M. Helm: "Carrier relaxation in epitaxial graphene photoexcited near the Dirac point", Phys. Rev. Lett. 107, 237401 (2011)

Keywords: free-electron laser; semiconductor nanostructures; terahertz; graphene

  • Invited lecture (Conferences)
    Physikkolloquium TU Chemnitz, 23.05.2012, Chemnitz, Deutschland
  • Invited lecture (Conferences)
    Physikkolloquium Universität Konstanz, 26.06.2012, Konstanz, Deutschland
  • Invited lecture (Conferences)
    Physikkolloquium Universität Paderborn, 12.07.2012, Paderborn, Deutschland
  • Lecture (others)
    Seminarvortrag Southeastern University, Nanjing, China, 18.09.2012, Nanjing, China

Permalink: https://www.hzdr.de/publications/Publ-17143
Publ.-Id: 17143


Novel 7α-alkoxy-17α-(4’-halophenylethynyl)estradiols as potential SPECT/PET imaging agents for estrogen receptor expressing tumors: synthesis and binding affinity evaluation

Neto, C.; Oliveira, M. C.; Gano Fernanda Marques, M. L.; Yasuda, T.; Thiemann, T.; Kniess, T.; Santos, I.

To develop potential radiolabelled probes for SPECT/PET imaging estrogen receptor (ER) positive tumors, we have synthesized and characterized a series of novel 7α-alkoxy-17α-(4-iodophenylethynyl)estra-1,3,5(10)-triene-3,17β-diols and 7α-alkoxy-17α-(4-fluorophenylethynyl)estra-1,3,5(10)-triene-3,17β-diols.
The fluoro-substituted compounds showed a higher ER binding affinity than the corresponding iodo-compounds, where 7α-methoxy- and 17α-(4-fluorophenylethynyl)estra-1,3,5(10)-triene-3,17β-diol showed the highest ER binding affinities (RBA=80.9 and 78.9%) among the halophenylethynyl compounds studied and should be further explored as potential PET biomarkers for imaging of ER expressing tumors.

Permalink: https://www.hzdr.de/publications/Publ-17142
Publ.-Id: 17142


A 2m x 0.5m prototype of a MRPC-based neutron detector with steel converter plates

Röder, M.; Aumann, T.; Bemmerer, D.; Boretzky, K.; Caesar, C.; Cowan, T. E.; Hehner, J.; Heil, M.; Elekes, Z.; Kempe, M.; Maroussov, V.; Reinhardt, T. P.; Simon, H.; Sobiella, M.; Stach, D.; Wagner, A.; Wüstenfeld, J.; Yakorev, D.; Zilges, A.; Zuber, K.; for the R3B Collaboration

A 2m long prototype detector for the detection of neutrons in an energy range from 200MeV to 1 GeV has been successfully realized. The working principle is based on steel converter plates followed by an MRPC structure to detect charged particles produced by hadronic interactions. In order to study time resolution and efficiency, a 2m x 0.5m large module has been built which comprises a 2 x 2 gap MRPC structure. An efficiency larger than 90% and a time resolution better than 100 ps have been measured for minimum ionizing electrons. This experiment has been done using the one-electron-per-bunch mode of the superconducting electron linear accelerator ELBE, Dresden. Another test has been done using 175MeV quasi-monochromatic neutrons at TSL in Uppsala. A test using tagged high-energy neutrons is scheduled at GSI. Extensive Monte Carlo simulations have been carried out, both for the electron-beam tests and for the final application as a neutron detector. The present approach offers a cost-effective way for the time-of-flight detection of high energy neutrons.

Keywords: Detector - MRPC; neutron beam; electron beam; minimum ionizing electrons; Monte Carlo simulations

  • Lecture (Conference)
    XI workshop on Resistive Plate Chambers and Related Detectors (RPC 2012), 05.-10.02.2012, Frascati (Rom), Italien
  • Open Access Logo Proceedings of Science RPC(2012)

Permalink: https://www.hzdr.de/publications/Publ-17141
Publ.-Id: 17141


Three natural minerals - sanidine, pyrite and columbite - as potential geologic reference materials. Characterization of chemical homogeneity at a micrometer scale

Michalak, P. P.; Renno, A. D.; Munnik, F.; Radtke, M.; Buzanich, G.; Reinholz, U.; Merchel, S.

A supply risk assessment of strategic high-technology metals requires a thorough quality assurance of their concentration in ores. Because such metals are usually unevenly distributed at a micrometer scale within natural ore-minerals matrices, spatially-resolved methods must be employed in geometallurgic investigations. Unfortunately, obtaining reliable data with non-absolute micro-analytical methods requires the use of reference materials
(RMs) that fulfill the matrix-match criterion. While using natural minerals with optimum chemical composition as reference materials seems to satisfy the matrix criterion, assuring their chemical homogeneity at the sub-µg/g sampling masses usually fails. A solution is to produce synthetic minerals, doped with high-technology metals at trace concentrations, evenly distributed in homogenous chemically-optimal matrices.
Prior to the synthesis, three natural minerals - sanidine, pyrite and columbite - have been tested for lateral chemical and structural homogeneity. The assessment involved both microscopic (optical) and spectroscopic methods. The samples have been visually examined with a reflected light microscope and electron microscope (Back Scattered Emission imaging) exhibiting no optical heterogeneities. The chemical composition has been analyzed with three methods based on X-ray detection: EPMA (Electron Probe Micro Analysis), PIXE (Particle Induced X-ray Emission) and Sy-XRF (Synchrotron radiation-induced X-ray Fluorescence). EPMA analyses were carried out at the TU Bergakademie Freiberg using a wavelength dispersive spectrometer (WDS) and an accelerating voltage of 20 keV and a beam size of 2 µm2. PIXE data were obtained using a 3 MeV proton beam of about 5x5 µm2 from a 3 MV tandem accelerator at the HZDR in Dresden. Sy-XRF measurements were performed at the hard X-ray beamline “BAMline” at the BESSY synchrotron facility in Berlin. Samples were exposed in atmosphere to monochromatic X-rays of 20 keV focused with a compound refractive lens to 3x3 µm2.
Petrographically-sensible homogeneity testing procedure has been implemented into statistical analysis of the results accounting for both random and systematic heterogeneity patterns such as nugget and island type as well as periodic wave-type heterogeneities.
Quantitative (EPMA, PIXE) and qualitative (Sy-XRF) elemental spatial distribution maps have been obtained for major, minor and trace elements for each scan. Several trace elements were detected in each of the matrices: Ga, Ge, Rb, Sr, Ba in sanidine; Ni, Cu, As in pyrite and Zr, Sc, Y, W in columbite. All of them showed irregular distribution patterns, proving that selected mineral specimens are not suitable candidates for reference materials.
The proposed sequence of testes including microscopic and spectroscopic microanalytical techniques and standardized statistical procedures turn out to be adequate in quality assurance of minerals and will be used as a template in examining our synthetic material.

Keywords: EPMA; PIXE; Sy-XRF; reference materials

  • Poster
    European Mineralogical Conference 2012, 02.-06.09.2012, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17140
Publ.-Id: 17140


Interaction between europium and calcite: macroscopic and spectroscopic studies

Sabău, A.; Marmier, N.; Jordan, N.; Lomenech, C.; Barkleit, A.; Toulhoat, N.; Pipon, Y.; Moncoffre, N.; Brendler, V.; Giffaut, E.

Interactions between cations and natural or synthetic calcite may include incorporation processes, resulting in the irreversibility of some sorption reactions. Understanding and quantification of poorly to non reversible trapping mechanisms can be considered as a significant improvement in the description of a geological barrier or a backfill material performance in the safety assessment. To investigate these irreversible processes, we have decided to work on the Eu-CO2-NaCl-CaCO3 system at pH 8.3, buffered by calcite under air and corresponding to the typical pH range of natural interstitial groundwaters. Europium was chosen as analogue for trivalent actinides and due to its fluorescence properties enabling its study by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Our study combines macroscopic batch investigations and the use of spectroscopic tools to comprehensively characterize this system.
At first, a material appropriate for sorption experiments had to be selected, based on characterization studies. From a variety of sources, we focused on a calcite from SOLVAY (SOCAL U1-R) with a particle size of 0.2 µm for TRLFS investigations, mainly due to its large BET specific surface area (18.4 m2/g). We also used a calcite from OMYA (BL 200), with a bigger particle size (56 µm) and a lower specific surface area (0.66 m2/g) for Rutherford Backscattering Spectrometry (RBS) measurements, due to the specific requirements of this technique. Purity of the calcite samples and absence of polymorphic CaCO3 compounds (i.e. vaterite and aragonite) were confirmed by XRD, DRIFT or SEM.
The second step of the work was to investigate the irreversible Eu(III) uptake mechanisms onto calcite. Batch experiments, done under atmospheric conditions (pCO2 = 10−3.5), were performed under different element concentration (10−5, 10−4 and 10−3 M) and contact time (4 hours, 1 day, 1 week and 1 month), which are assumed to be the most important parameters controlling the transition between adsorption and incorporation into the solid. In addition, this allowed to monitor the potential changes in mechanisms with time. The concentrations of Eu and Ca left in the supernatant were determined by ICP-MS and ICP-OES, respectively.
Europium species formed in solution and at the solid/solution interface were identified by TRLFS. Reference blank (Eu3+ in solution and Eu3+ precipitated) spectra were compared with the sorbed samples. When elements such as europium are sorbed onto a mineral surface by inner-sphere complexation, some of the H2O molecules in the first coordination sphere are displaced. Such changes should impact the fluorescence lifetime of Eu species.
The spectrum presented in Fig. 1 corresponds to Eu-reacted calcite after a contact time of 1 month and an initial concentration of Eu of 10-4 M. Europium was found to be completely sorbed onto calcite, whose dissolution was negligible. Two lifetimes were identified. The lower value, so far not reported in the literature, can thus not unambiguously be attributed to a specific Eu species. However, the higher second lifetime is correlated with the complete loss of the europium hydration sphere, suggesting either a surface precipitate or an incorporation.
RBS measurements (Fig. 2) were carried out using the 4 MV Van De Graaff accelerator facility of IPNL with a 4 MeV incident alpha beam. They were performed at the same Eu concentration as the TRLFS results (Fig. 1), in order to obtain a high resolution signal. RBS results confirmed those obtained by TRLFS, by showing an accumulation of europium onto the calcite surface.
It can be concluded that TRLFS and RBS are appropriate and complementary techniques to study the Eu-CO2-NaCl-CaCO3 system. The results obtained so far indicate that there is either a surface precipitate following a first sorption step or that incorporation into the bulk crystal lattice already started. Both processes may occur simultaneously, further experiments shall reveal this.

Keywords: europium; calcite; TRLFS; RBS; sorption; incorporation

  • Poster
    Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, 22.-25.10.2012, Montpellier, France

Permalink: https://www.hzdr.de/publications/Publ-17139
Publ.-Id: 17139


Magnetic shielding of implanted magnetic scaffolds and fixators

Uhlarz, M.

es hat kein Abstract vorgelegen

  • Lecture (Conference)
    MAGISTER Month 36 Review Meeting, 16.-18.01.2012, Rom, Italy

Permalink: https://www.hzdr.de/publications/Publ-17138
Publ.-Id: 17138


Magnetic characterization of magnetosome growth in mesenchymial stem cells

Uhlarz, M.

es hat kein Abstract vorgelegen

  • Lecture (Conference)
    MAGISTER Month 36 Review Meeting, 16.-18.01.2012, Rom, Italy

Permalink: https://www.hzdr.de/publications/Publ-17137
Publ.-Id: 17137


Effects of sterilizing gamma-ray irradiation on Fe-hydroxyapatite paste

Uhlarz, M.

es hat kein Abstract vorgelegen

  • Lecture (Conference)
    MAGISTER Month 36 Review Meeting, 16.-18.01.2012, Rom, Italy

Permalink: https://www.hzdr.de/publications/Publ-17136
Publ.-Id: 17136


Magnetic characterization of scaffold materials, simulators and powders

Uhlarz, M.

es hat kein Abstract vorgelegen

  • Lecture (Conference)
    MAGISTER Month 36 Review Meeting, 16.-18.01.2012, Rom, Italy

Permalink: https://www.hzdr.de/publications/Publ-17135
Publ.-Id: 17135


Thin film PV cell with Ag nanoparticle layers in TCO and Si nanosponge absorber

Liedke, B.; Heinig, K.-H.; Gulseren, O.; Akguc, G. B.; Vinnichenko, M.

The plasmonic action of Ag nanoparticles has the potential to increase the efficiency of thin film PV cells substantially. Here, two different actions will be considered: (i) Ag nanoparticles (NPs) embedded in the Transparent Conductive Oxide (TCO) at the rear side of thin-film PV cells can induce plasmonic scattering of red light, which increases the light way and therefore the absorption in the absorber layer. (ii) Ag NPs embedded in the absorber layer increases carrier generation due to plasmonic light field enhancement.
For the plasmonic action (i), a thin Ag layer is sandwiched between ZnO:Al by sputter deposition. Subsequently, by a thermal treatment this Ag layer is decomposed via spinodal dewetting into an Ag NP layer. Structural, electrical and optical properties are investigated theoretically, by atomistic simulation and FDTD and boundary element calculations, and experimentally.
For the plasmonic action (ii) it has to be avoided that Ag NPs in the absorber layer become charge carrier killer. Usually this is impossible, but in our novel absorber consisting of a Si nanowire network (nanosponge) in SiO2, the Ag NPs can be located in SiO2 without contact to the electrically percolated Si network. Based on large-scale atomistic simulations it is predicted that such a nanocomposite can be synthesized by PVD deposition of SiO with a sandwiched thin Ag layer. It will be shown that subsequent thermal treatment results in nanosponge with Ag/Si core-shell NPs in SiO2.

Keywords: TCO; AZO; plasmonics; Ag nanoparticles; ZnO; kinetic Monte-Carlo; FDTD; boundary element method; light harvesting

  • Lecture (Conference)
    E-MRS 2012 Spring Meeting, 14.-18.05.2012, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-17134
Publ.-Id: 17134


EFTEM studies of Si nanowire networks in SiO2 for thin film PV cells

Liedke, B.; Mücklich, A.; Heinig, K.-H.; Schmidt, B.; Friedrich, D.; Keles, U.; Bulutay, C.

Si based nanostructures became in the last years a promising material for the PV cells. The quantum confinement effect of Si nanostructures allows for band gap engineering by size manipulation which can be used for optimization sun light absorption.
Here, we consider SiOx layers deposited by magnetron sputtering. By subsequent rapid thermal processing, SiOx decays by spinodal decomposition into a network of Si nanowires (NWs) in SiO2.
To get images of the morphology of Si NWs in SiO2 it is not sufficient to use mass contrast or lattice plane imaging. The Si and SiO2 phases can only be distinguished by energy filtering of the transmitted electrons (EFTEM). Here, the relative energy shifts of the plasmonic valence band resonances of Si and SiO2 are used. HR-EFTEM techniques are applied to study morphology and crystallinity of the Si NW networks fabricated from different metastable SiOx. To facilitate understanding of the TEM images, details of decomposition are studied using kinetic Monte-Carlo (KMC) simulations. For the EFTEM images, density-density correlations are calculated to determine the structure size of NW network, which are then compared with the 3D morphologies provided by KMC. Combining EFTEM with KMC allows us to predict and control the average size of the NWs.
Former studies and our electronic structure calculations provide a guideline for band gap optimization of Si NW networks, thus paving the way to band gap engineering via control of the mean NW diameter.

Keywords: kinetic Monte-Carlo; TEM; EFTEM; Silicon nanowires; nanosponge; nanocrystals

  • Lecture (Conference)
    E-MRS 2012 Spring Meeting, 14.-18.05.2012, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-17133
Publ.-Id: 17133


Si-nanosponge embedded in SiO2 as a new absorber material for photovoltaics

Liedke, B.; Heinig, K.-H.; Schmidt, B.; Friedrich, D.; Mücklich, A.; Kelling, J.; Hauschild, D.

Silicon based nanostructures became within the last years most promising material for the PV market. Quantum confinement effect of nanostructured silicon allows for band gap engineering just by size manipulation to absorb the light in more efficient way.
Here, we consider SiOx layers fabricated by magnetron co-sputter deposition, which after thermal treatment decompose into a network of Si nanowires embedded in SiO2. The thermally activated spinodal decomposition is performed by rapid thermal processing within a few seconds and by very rapid thermal processing within several ms using diode laser. The morphology and crystallinity of the Si-nanosponge was measured by energy filtered TEM and Raman, respectively. The details of decomposition are studied using the atomistic kinetic Monte-Carlo (KMC) simulations at different concentrations defined by the x parameter. The spatiotemporal temperature profiles T(x, t) of the scanned laser has been calculated as a function of thickness and time by the heat transport equation. The obtained profiles are used in the KMC. The combined theoretical and experimental investigations support the band gap engineering of the Si-nanosponge absorber via a control of the quantum confinement.

Keywords: Silicon nanostructures; Nanocrystals; TEM; EFTEM; kinetic Monte-Carlo; RTP; vRTP; Raman; nanosponge

  • Lecture (Conference)
    76. Jahrestagung der DPG und DPG-Frühjahrstagung, 25.-30.03.2012, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17132
Publ.-Id: 17132


Experiences with Positron Lifetime Spectroscopy using a multi-detector setup

Butterling, M.; Anwand, W.; Hartmann, A.; Wagner, A.; Haeberle, J.; Jungmann, M.; Krause-Rehberg, R.; Krille, A.; Muchow, M.

First experiments and gained knowledge using and improving a multi-detector setup for Positron Lifetime Spectroscopy are presented.

Keywords: Positron Lifetime Spectroscopy; Positron Lifetime; Multi-Detector Setup

  • Lecture (Conference)
    Treffen deutscher Positronengruppen, 28.02.-01.03.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17131
Publ.-Id: 17131


Endlagerung radioaktiver Abfälle: Wie tief muss man graben für eine Million Jahre Sicherheit?

Müller, K.

Der Vortrag gibt eine Übersicht über die in Deutschland anfallenden radioaktiven Abfälle. Desweiteren werden die Anforderungen an die sichere Verwahrung dieser Abfälle, hinsichtlich hoher Temperaturen, Wirtsgesteinseigenschaften und die sehr langen Lagerungszeiträume beleuchtet.

  • Lecture (others)
    Tag des offenen Labors 2012, 12.05.2012, Dresden, Deutschland
  • Lecture (others)
    Lange Nacht der Wissenschaften in Dresden, 06.07.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17130
Publ.-Id: 17130


Redox behavior of Tc(VII)/Tc(IV) under various reducing conditions in 0.1 M NaCl solutions

Kobayashi, T.; Scheinost, A. C.; Fellhauer, D.; Gaona, X.; Altmaier, M.

Redox behaviour of Tc(VII)/Tc(IV) was investigated under inert Ar atmosphere in 0.1 M NaCl solutions containing different reducing agents in the pH range 2 to 13 at 22ºC. Under certain conditions, the 1•10−5 mol/dm3 (M) initial TcO4– was reduced to form a sparingly soluble Tc(IV) oxide solid phase. The results can be systematized according to Eh-pH conditions. It is found that an experimental borderline for the reduction of Tc(VII) to Tc(IV), TcO4− + 3e− + 4H+  TcO2∙xH2O(coll, hyd) + (2−x)H2O is established, which is independent of the reducing chemical system. This experimental borderline is about 100 mV lower than the equilibrium line calculated from the reported standard redox potential of TcO2∙1.6H2O(s). This behaviour can be explained by the existence of more soluble solid phase modifications like small Tc(IV) oxide particles (TcO2・xH2O(coll,hyd)). The reaction kinetics correlate to the redox potentials measured in solution. Slow reduction of Tc(VII) to Tc(IV) was observed when the redox potential in the system was near the reduction borderline. Fast reduction was observed in the systems far from the borderline or containing Fe(II) solids, suggesting a specific surface mediated effect in the reduction process. EXAFS analysis on two magnetite samples indicate reduced Tc(IV) species which do not remain adsorbed at the reactive magnetite surface, but are incorporated in its structure.

Keywords: redox; Tc; EXAFS; XANES; magnetite

Permalink: https://www.hzdr.de/publications/Publ-17129
Publ.-Id: 17129


Latest results on fs-synchronization and RF at ELBE

Kuntzsch, M.

Presentation of latest results of femtosecond Synchronization System, including commissioning of first prototype link stabilizer. Additional information on preliminary test of new ELBE master oscillator unit.

Keywords: Synchronization ELBE RF Jitter

  • Lecture (others)
    Thomas Jefferson National Accelerator Facility Free Electron Laser Colloquium, 23.04.2012, Newport News, USA

Permalink: https://www.hzdr.de/publications/Publ-17128
Publ.-Id: 17128


Nitrogen interstitial diffusion induced decomposition in AISI 304L austenitic stainless steel

Martinavicius, A.; Abrasonis, G.; Scheinost, A. C.; Danoix, R.; Danoix, F.; Stinville, J. C.; Talut, G.; Templier, C.; Liedke, M. O.; Gemming, S.; Möller, W.

The nature of the near-surface γN phase produced by low-temperature (∼400 °C) plasma-assisted nitriding of an austenitic stainless steel 304L is studied. A combination of global probes (X-ray diffraction, nuclear reaction analysis, glow discharge optical emission spectroscopy) and local probes (field ion microscopy, conversion electron Mössbauer, X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopies) is employed to reveal the morphology, phase structure, atomic ordering and chemical state of the obtained γN phase. The results consistently reveal the heterogeneous nature of the nitrided layer consisting of nanometric CrN precipitates embedded in a Fe4N-like matrix. The size of the precipitates is found to be larger at the surface than at the nitrided layer–steel interface. The precipitates have irregular, sphere-like shapes. Moreover, X-ray spectroscopic investigation revealed three different intermetallic distances and different chemical environments for Fe, Cr and Ni, accompanied by a large static disorder. These findings suggest that the presence of the interstitial N destabilizes the homogeneous element distribution in 304L even at such low temperatures. This leads to the segregation into Cr-rich zones that are coherent with the Fe4N matrix. Possible atomistic decomposition mechanisms are discussed. Based on the heterogeneous nature of the γN phase revealed in 304L, an alternative view of its remarkable combination of properties such as large hardness, induced ferromagnetism and preserved corrosion resistance is considered.

Keywords: Stainless steel; Surface alloying; Interstitial diffusion; Decomposition; Precipitation

Permalink: https://www.hzdr.de/publications/Publ-17127
Publ.-Id: 17127


Alteration of magnetic anisotropy of Pt/Co/Pt trilayers by FIB irradiation

Mazalski, P.; Dobrogowski, W.; Sveklo, I.; Maziewski, A.; Fritzsche, M.; Liedke, M. O.; Fassbender, J.; Baczewski, L. T.; Wawro, A.

Investigation of the magnetic thin film structures with the out-of-plane magnetization are important for both fundamental research and applications. In nanostructures with decreasing magnetic film thickness an out-of-plane alignment of magnetization is frequently observed due to increasing contribution of surface anisotropy. It has been shown that ion beam irradiation modifies magnetic properties of such structures [1, 2]. With increasing irradiation dose D of such films the strength of perpendicular anisotropy is suppressed, magnetization rotates towards in-plane alignment or ferromagnetic ordering is converted to the superparamagnetic state. Very recently an oscillatory behaviour of magnetic anisotropy between the in-plane and out-of-plane states driven by an increasing dose of 30 keV Ga+ ion homogenous irradiation, has been observed in the molecular beam epitaxy (MBE) deposited Pt/(Co 3.3 nm)/Pt films [3].
The aim of this work is investigation of local modifications of magnetic properties in MBE grown Mo/Pt(20nm)/(Co3.3nm)/Pt(5nm) films by a focused ion beam (FIB). In the studied as deposited structure magnetization was aligned in the film plane. Numerous spots of the sample (squares 100x100μm² or 50x50μm²) have been locally irradiated with Ga+ ions with energy of 30 keV and different doses D ranging between 2•10^12 and 1•10^16 ions/cm². FIB irradiated spots were probed using polar/longitudinal Kerr effect magnetometry (sensitive to perpendicular/longitudinal magnetization component) and atomic/magnetic force microscopy techniques. Creation of the two out-of-plane magnetization branches upon increasing FIB irradiation dose D was observed, similarly to the effect reported for homogenous irradiation [3].
Presented results seem to be promising for new method for magnetic nanostructure patterning.

[1] C. Chappert et al., Science 280, 1919 (1998).
[2] J. Fassbender et al., J. Magn. Magn. Mat. 320, 579 (2008).
[3] A. Maziewski et al., Phys. Rev. B 85, 054427 (2012).

  • Poster
    Joint European Magnetic Symposia (JEMS 2012), 09.-14.09.2012, Parma, Italien

Permalink: https://www.hzdr.de/publications/Publ-17126
Publ.-Id: 17126


Application of positron beams to the investigation of memristive materials and diluted magnetic semiconductors

Potzger, K.; Liedke, M.

After a general introduction to the field of resistive switching and spin electronics and the role of defects therein, recent investigations on the above mentioned topics including positron beams are reviewed. An ongoing project at the Helmholtz Centre Dresden-Rossendorf to further extend such investigations is briefly outlined and expected benefits are mentioned.

Keywords: Resistive switching; memristive materials; diluted magnetic semiconductors; positrons

  • Book chapter
    B.N. Ganguly, G. Brauer: Near-Surfaces Depth Profiling of Solids by Mono-Energetic Positrons, Switzerland: Trans Tech Publishers, 2012, 978-3-03785-524-9, 235-251
    DOI: 10.4028/www.scientific.net/DDF.331.235

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-17125
Publ.-Id: 17125


Experiments with strong far-infrared radiation at the free-electron laser

Schneider, H.

There is no abstract.

  • Lecture (others)
    Kolloquium FB Physik, Universität Marburg, 14.05.2012, Marburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17124
Publ.-Id: 17124


High-power laser development projects for laser particle acceleration at HZDR

Zeil, K.; Baumann, M.; Beyreuther, E.; Bock, S.; Burris-Mog, T.; Cowan, T. E.; Enghardt, W.; Helbig, U.; Karsch, L.; Kraft, S. D.; Laschinsky, L.; Loeser, M.; Metzkes, J.; Naumburger, D.; Oppelt, M.; Pawelke, J.; Richter, C.; Roeser, F.; Sauerbrey, R.; Schürer, M.; Schramm, U.; Siebold, M.

Recent developments in the field of laser particle acceleration enable potential applications as, e.g., radiotherapy with laser driven proton beams. Laser driven proton therapy, not only requires sufficiently high proton energies but also a reasonable repetition rate for appropriate control of the dose delivery. In Dresden, this ambitious vision is addressed by close collaborative work at OncoRay (represented by Technical University Dresden and Helmhotz-Zentrum Dresden-Rossendorf (HZDR)) combining expertise in laser plasma physics, accelerator physics, and medicine. A dedicated research building later housing both, a laser driven proton beam delivery system and a conventional proton therapy accelerator for direct comparison in clinical trials is presently under construction.
For the development of a medical high intensity laser prototype to be installed at OncoRay we focus on two major projects in parallel. The first project uses a commercialized Ti:Sapphire based laser concept providing ultra short pulses of tens of femtoseconds at a repetition rate of 10 Hz. With the 150 TW Draco laser the proton acceleration process was investigated in the last three years [1], and a long-term stable and reliable mode of operation was established which has enabled first in vitro cell irradiation studies [2]. The laser system is presently upgraded by an additional amplifier stage and new front end components finally providing high contrast pulses of >500 TW on target at 1 Hz pulse repetition rate. By use of the increased pulse energy and the multiple beam option the proton energy scaling will be investigated and the radiobiological program will be extended to the irradiation of tumors in animals.
Complementary to the ultra short pulse laser approach, the direct diode pumped solid state laser PENELOPE is under development. The status of this energetically more efficient technology providing longer pulse durations at comparable beam power and therefore favoring potentially higher proton acceleration performance than ultra short pulses will be presented.

[1] Zeil, K. et al. New J Phys, 12, 045015, 2010.
[2] Kraft, S. et al. New J Phys 12, 085003 (2010).

  • Invited lecture (Conferences)
    Advanced Accelerator Concepts Workshop, 13.06.2012, Austin, Texas, United States of America

Permalink: https://www.hzdr.de/publications/Publ-17123
Publ.-Id: 17123


Prompt pre-thermal laser ion sheath acceleration with ultra-short laser pulses

Zeil, K.; Bussmann, M.; Cowan, T. E.; Kluge, T.; Kraft, S.; Metzkes, J.; Schramm, U.

Recent laser-ion acceleration experiments performed at the 150 TW Draco laser in Dresden, Germany, have demonstrated the importance of a precise understanding of the electron dynamics in solids on an ultra-short time scale. For example, with ultra-short laser pulses a description based purely on the evolution of a thermal electron ensemble, as in standard TNSA models, is not sufficient anymore. Rather, non-thermal effects during the ultra-short intra-pulse phase of laser-electron interaction in solids become important for the acceleration of ions when the laser pulse duration is in the order of only a few 10s of femtoseconds. While the established maximum ion energy scaling in the TNSA regime goes with the square root of the laser intensity, for such ultra short pulse durations the maximum ion energy is found to scale linear with laser intensity [1], motivating the interest in such laser systems.
Investigating the influence of laser pulse contrast, laser polarization and laser incidence angle on the proton maximum energy and angular distribution, we present recent advances in the description of the laser interaction with solids, focusing on the implications of intra-pulse non-thermal phenomena on the ion acceleration.

  • Invited lecture (Conferences)
    Advanced Accelerator Concepts Workshop, 12.06.2012, Austin, Texas, United States of America

Permalink: https://www.hzdr.de/publications/Publ-17122
Publ.-Id: 17122


High magnetic field study of the Gd-Co exchange interactions in GdCo12B6

Isnard, O.; Skourski, Y.; Diop, L. V. B.; Arnold, Z.; Andreev, A. V.; Wosnitza, J.; Iwasa, A.; Kondo, A.; Matsuo, A.; Kindo, K.

Pulsed magnetic fields up to 68 Tesla have been used to determine the intersublattice coupling strength and its temperature dependence of GdCo12B6 compound. This compound exhibits ferrimagnetic behaviour below 163 ± 2 K. Two antiferromagnetically coupled sublattices cancel out at compensation temperature at about 48 K. They are carrying magnetization of typically 0.42 μB/Co atom and 7 μB/Gd. The intrinsic magnetic properties of the GdCo12B6 compound have been determined by combining low temperature magnetic measurements in both steady and pulsed magnetic field, as well as isofield studies in steady field. At 4.2 K, the magnetization curve of GdCo12B6 is found to reach the full saturation with sum of both sublattice magnetizations for an applied magnetic field of about 68 T. In addition a detailed study is presented in the whole ordered temperature range on the basis of magnetization curves recorded using pulsed magnetic field up to 60 T. This has enabled to investigate the intersublattice coupling strength and its temperature dependence, a value JCo-Gd/kB = −5.3 ± 0.3 K is derived from the magnetization curves whereas one gets much larger value for JCo-Co/kB = 108 K.

Permalink: https://www.hzdr.de/publications/Publ-17121
Publ.-Id: 17121


Variation of the intersublattice exchange coupling due to hydrogen absorption in Er2Fe14B: A high-field magnetization study

Tereshina, E. A.; Tereshina, I. S.; Kuzmin, M. D.; Skourski, Y.; Doerr, M.; Chistyakov, O. D.; Telegina, I. V.; Drulis, H.

Single crystals of a series of hydrides Er2Fe14BHx (x ≤ 2.5) have been produced and studied in pulsed magnetic fields up to 60 T. The magnetization curve of Er2Fe14B in the easy direction [100] features a stepwise anomaly at about 45 T, corresponding to the first-order phase transition. A similar magnetization jump is also present in the curve along [110], but at a higher field, ∼52 T. The [100] data of the parent and hydrogen-charged Er2Fe14BHx with x = 0.25, 1.5, 2.5 were used to deduce the Er-Fe molecular field Hmol as a function of hydrogen content x. After moderate initial decrease, Hmol(x) drops abruptly above x = 1.5. Hydrogenation results in a 12% reduction of the Er-Fe molecular field in Er2Fe14BH2.5 as compared to Er2Fe14B. For reference, influence of hydrogen on Hmol in an Er2Fe17-H system is also presented

Permalink: https://www.hzdr.de/publications/Publ-17120
Publ.-Id: 17120


Efficient Proton Acceleration with Ultra-short Laser Pulses

Zeil, K.; Bussmann, M.; Cowan, T.; Kluge, T.; Metzkes, J.; Schramm, U.; Kraft, S.

We present a systematic investigation of ultra-short pulse laser acceleration of protons yielding unprecedented maximum proton energies of 19 MeV using the Ti:Sa based high power laser (150 TW) Draco at the Helmholtz-Zentrum Dresden-Rossendorf. For plain few micron thick foil targets a linear scaling of the maximum proton energy with laser power is observed and attributed to the short acceleration period close to the target rear surface*. The influence of laser pulse contrast, laser polarization and laser incidence angle on the proton maximum energy and angular distribution has been investigated. The reliability of the system was improved in order to perform radiobiological studies. Additionally, an increase of laser to proton energy conversion efficiency by use of mass limited Au disks with diameters between 20 µm and 100 µm and sub-micron thickness could have been demonstrated.

  • Poster
    IPAC 2012, 23.-25.05.2012, New Orleans, LA, USA

Permalink: https://www.hzdr.de/publications/Publ-17119
Publ.-Id: 17119


Direct observation of prompt pre-thermal laser ion sheath acceleration

Zeil, K.; Metzkes, J.; Kluge, T.; Bussmann, M.; Cowan, T. E.; Kraft, S. D.; Sauerbrey, R.; Schramm, U.

High-intensity laser plasma-based ion accelerators provide unsurpassed field gradients in the megavolt-per-micrometer range. They represent promising candidates for next-generation applications such as ion beam cancer therapy in compact facilities. The weak scaling of maximum ion energies with the square-root of the laser intensity, established for large subpicosecond class laser systems, motivates the search for more efficient acceleration processes. Here we demonstrate that for ultrashort (pulse duration ~ 30 fs) highly relativistic (intensity ~ 10 21 W cm − 2 ) laser pulses, the intra-pulse phase of the proton acceleration process becomes relevant, yielding maximum energies of around 20 MeV. Prominent non-target-normal emission of energetic protons, reflecting an engineered asymmetry in the field distribution of promptly accelerated electrons, is used to identify this pre-thermal phase of the acceleration. The relevant timescale reveals the underlying physics leading to the near-linear intensity scaling observed for 100 TW class table-top laser systems.

Permalink: https://www.hzdr.de/publications/Publ-17118
Publ.-Id: 17118


Efficient proton acceleration with ultra-short laser pulses

Zeil, K.; Bussmann, M.; Cowan, T. E.; Kluge, T.; Kraft, S. D.; Metzkes, J.; Schramm, U.

We present a systematic investigation of ultra-short pulse laser acceleration of protons yielding unprecedented maximum proton energies of 19 MeV using the Ti:Sa based high power laser (150 TW) Draco at the Helmholtz-Zentrum Dresden-Rossendorf. For plain few micron thick foil targets a linear scaling of the maximum proton energy with laser power is observed and attributed to the short acceleration period close to the target rear surface [1]. The influence of laser pulse contrast, laser polarization and laser incidence angle on the proton maximum energy and angular distribution has been investigated.
Although excellent laser pulse contrast was available slight deformations of the target rear were found to lead to a predictable shift of the direction of the energetic proton emission away from target normal towards the laser direction. The change of the emission characteristics are compared to analytical modelling and 2D PIC simulations.
Additionally, an increase of laser to proton energy conversion efficiency by use of mass limited Au disks with diameters between 20 µm and 100 µm and sub-micron thickness could have been demonstrated.

  • Lecture (Conference)
    Laser and Plasma Accelerators Workshop, 22.06.2011, Shanghai, China

Permalink: https://www.hzdr.de/publications/Publ-17117
Publ.-Id: 17117


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

Viehrig, H.-W.; Houska, M.; Altstadt, E.; Valo, M.

Nuclear power plant operators must demonstrate that the structural integrity of a nuclear reactor pressure vessel (RPV) is assured during routine operations or under postulated accident conditions. The aging of the RPV steels is monitored via surveillance programs. Radiation loading, metallurgical and environmental histories, however, can differ between surveillance and RPV materials. Therefore, the investigation of RPV material from decommissioned NPPs offers the unique opportunity to evaluate the real toughness response.
The Greifswald units representing the first generation of WWER-440/V-230 reactors were shut down after 11 to 15 years of operation and the RPVs represent different material conditions as follows: Irradiated (Unit 4), irradiated and recovery annealed (Units 2 and 3), and irradiated, recovery annealed and re-irradiated (Unit1). The recovery annealing of the RPV was performed at a temperature of 475° for about 150 hours and includes a region covering ±0.70 m above and below the circumferential core weld.
Material samples of a diameter of 119 mm called trepans were extracted from the RPV walls. The working program is focused on the characterisation of the RPV steels (base and weld metal) across the thickness of the RPV wall. The paper presents an overview about test results measured on the trepans taken from the welding seam SN0.1.4. and forged base metal ring 0.3.1. located in the reactor core region of the Greifswald units 1, 2 and 4 RPV. It comprises chemical analysis, microstructure investigations (by means of metallography, electron microscopy and SANS) and mechanical testing (hardness measurements, tensile, Charpy-V), and fracture mechanics testing. The key part of the testing is focussed on the determination of the reference temperature T0 following the ASTM test standard E1921 to determine the facture toughness, and how it degrades under neutron irradiation.
Following results have been determined:
• The recovery annealing of the welding seams and base metal could be confirmed.
• KJc values of the weld metals generally follow the course of the MC though with a large scatter.
• There is a large variation in the T0 values evaluated across the thickness of the multilayered welding seams. The T0 measured on TS oriented SE(B) from different thickness locations of the welding seams strongly depends on the structure along the crack tip.
• A strong scatter of the fracture toughness KJc values of the irradiated (unit 4) and recovery annealed base (unit 1) metal of is observed with clearly more than 2% of the values below the fracture toughness curve for 2% fracture probability.
• It was demonstrated that T0 evaluated according to the SINTAP MC extension represents the brittle fraction of the data sets.
• The application of the Unified Curve concept gave T0 values comparable to the standard MC approach, but the slope of the fracture toughness temperature curve is more shallow for highly embrittled conditions.
• The embrittlement of the unit 4 base and weld metal does not follow the prediction according to the Russian code PNAE G-7-008-86.

Keywords: reactor pressure vessel steel; neutron embrittlement; fracture toughness; Master Curve; integrity assessment; prediction

  • Contribution to proceedings
    12th International Conference “Material Issues in Design, Manufacturing and Operation of Nuclear Power Plants Equipment", 04.-08.06.2012, St. Petersburg, Russia
    Proceedings of the 12th International Conference “Material Issues in Design, Manufacturing and Operation of Nuclear Power Plants Equipment", St. Petersburg: Prometey Institute St. Petersburg

Permalink: https://www.hzdr.de/publications/Publ-17116
Publ.-Id: 17116


New iron(III) nitrate hydrates: Fe(NO3)3•xH2O with x = 4, 5 and 6

Schmidt, H.; Asztalos, A.; Bok, F.; Voigt, W.

Crystals of the title compounds were grown from their hydrous melts or solutions. The crystal structure of iron(III) trinitrate hexahydrate {hexaaquairon(III) trinitrate, [Fe(H2O)6](NO3)3} is built up from [Fe(H2O)6]2+ octahedra and nitrate anions connected via hydrogen bonds. In iron(III) trinitrate pentahydrate {pentaaquanitratoiron(III) dinitrate, [Fe(NO3)(H2O)5](NO3)2}, one water molecule in the coordination octahedron of the FeIII atom is substituted by an O atom of a nitrate group. Iron(III) trinitrate tetrahydrate {triaquadinitratoiron(III) nitrate monohydrate, [Fe(NO3)2(H2O)3]NO3H2O} represents the first example of a simple iron(III) nitrate with pentagonal–bipyramidal coordination geometry, where two bidentate nitrate anions and one water molecule form a pentagonal plane.

Permalink: https://www.hzdr.de/publications/Publ-17115
Publ.-Id: 17115


Microbiological analysis of the in situ Bitumen-Nitrate-Opalinus Clay interaction

Moors, H.; Boven, P.; Geissler, A.; Selenska-Pobell, S.; Leys, N.

Clay formations like the Opalinus Clay are foreseen to serve as the host rock for geological disposal of high- and intermediate-level long-lived radioactive waste in several countries, because of their favourable properties to delay the migration of radionuclides over time. However, bituminized intermediate-level long-lived radioactive waste may physico-chemically perturb the clay barrier properties because in time it will leach substantial amounts of nitrate and organic bitumen degradation products (BDP).
To study the physico-chemical impact of intermediate-level radioactive waste containing bitumen and nitrate, an in situ experiment in the Opalinus Clay (Saint Ursanne, Switzerland) named the Bitumen-Nitrate-Clay interaction (BN) experiment, is being performed at the Mont Terri Rock Laboratory. The in situ equipment of the BN-experiment consists of three separate packed-off intervals, supplied with a filter screen. Each interval is equipped with its own stainless steel water circulation unit. Such water circulation unit contains water sampling containers, circulation pumps and flow meters. One of the circulation units is equipped with an on-line UV spectrophotometer and pH electrode intervals, allowing a continuous monitoring of nitrate, nitrite concentrations, organic carbon level and pH.
In a first series of tests, the microbial and biogeochemical effect of a nitrate and/or acetate perturbation is studied. Acetate is used as it a good representation of BDP. Hereto, nitrate was injected in interval 1 while a mixture of nitrate and acetate is injected in interval 2. As an active microbial community can have a significant impact on the physical and (geo)chemical conditions of the clay surrounding the disposal gallery, microbial analyses were performed on samples taken from the interval solutions before, during and after this first series of tests. Our microbial investigations which included Scanning Electron Microscopy, molecular biology methods, ATP-measurements, and cultivation based techniques of the initial pore water samples, proved the presence and activity of bacteria.
Analysis of the 16S rDNA sequences obtained from the initial interval solutions, i.e. artificial pore water used to fill the intervals and which have been in contact with the surrounding clay for more than six months, indicates similar bacterial communities in all three solutions of the test intervals with the dominant population being Proteobacteria (81.5 – 94.9 %) and Firmicutes (3.4 – 11.1%). Actinobacteria (1.7 and 7.4%) have only been detected in the initial pore water of two intervals.
The first results of the Ribosomal Intergenic Spacer Amplification (RISA) analysis, using universal bacterial primers for 16S rDNA968-983 and 23S rDNA115-130, demonstrate that in both injection tests, i.e. nitrate (interval 1) or nitrate and acetate (interval 2), a strong shift in bacterial communities was induced. Just before the start of these injection tests the pore waters of the two intervals were strongly predominated by different Clostridial species most of them related to Desulfosporosinus species. In addition, smaller populations of Bacteroidetes and Beta– proteobacteria were found as well. Twenty-four hours later, a rapid and strong proliferation of Bacteroidetes, in interval 1, and of Alphaproteobacteria, in intervals 1 and 2, occurred. Specific for interval 1, a stimulation of Beta– and Deltaproteobacteria and a complete masking of the Clostridial groups had occured. In contrast, in interval 2, Gammaproteobacteria were stimulated and some Clostridia continued to persist. This shift may be due to bacterial contamination of the exchanged interval solutions and/or the drastic change of carbon– and/or electron acceptor source.

Keywords: opalinus clay; microbial communities; 16S rDNA retrieval; RISA analyses

  • Poster
    Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, 22.-25.10.2012, Montpellier, France

Permalink: https://www.hzdr.de/publications/Publ-17114
Publ.-Id: 17114


Coherent THz pulses from linear SRF accelerators: Perspectives for naturally synchronized THz pump probe experiments and novel electron beam diagnostic

Gensch, M.

At the ELBE accelerator at the HZDR a new electron beamline, providing for femtosecond electron bunches with nC bunch charges and repetition rates in the 1 – 200 KHz regime is currently constructed. The 40 MeV electrons will be used in photon-electron interaction experiments with TW and PW class laser and for the generation of broad band and narrow bandwidth coherent THz pulses in the frequency range between 0.1 THz – 3 THz. Similar to previous work at the prototype THz pump probe facility at FLASH [1,2] the natural synchronization between light pulses generated by the same electron bunch shall be employed for fully synchronized experiments between narrow and broad band THz pulses. The pulse energies are expected to exceed the 100 microJ limit at scalable repetition rates between 1 and 200 KHz (cw), thereby the coherent THz facility will represent a worldwide unique facility. Besides user experiments the laboratory is also foreseen as a test bed for THz-based electron bunch diagnostics (arrival time, bunch form, …) on cw linear accelerators. The current status of the project and planned experiments are presented.
[1] M. Gensch et. al., The new THz undulator beamline at FLASH, Infrared Phys. Technol. 51 (2008), 423.
[2] U. Fruehling, M. Wieland, M. Gensch et. al., Single-shot Terahertz-field driven Streak camera, Nature Photonics 3 (2009), 523.
[3] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch et. al., Few Femtosecond Timing at 4th Generation X-ray light sources, Nature Photonics 5 (2011), 162."

  • Invited lecture (Conferences)
    Workshop on Terahertz Sources for Time Resolved Studies of Matter, 30.-31.07.2012, Chicago, USA

Permalink: https://www.hzdr.de/publications/Publ-17113
Publ.-Id: 17113


Age and Genesis of Greisen Mineralization in the Li-Sn(-W) Deposit Zinnwald, Eastern Erzgebirge, Germany

Atanasova, P.; Gutzmer, J.; Seifert, T.; Pfänder, J.

The Zinnwald greisen-type ore deposit forms part of the Altenberg-Teplice caldera in the eastern part of Saxony, Germany. Flat dipping quartz-zinnwaldite-topaz-fluorite-cassiterite greisen ore bodies and veins are hosted in the uppermost part of the “small intrusion” Zinnwald Li-F-granite stock (cf. Seifert & Kempe, 1994). The current investigation was aimed to provide new insight into the metallogenesis of the deposit and its temporal and genetic relation to the late Variscan magmatic evolution of the Altenberg-Teplice Caldera.
Greisen-type mineralization in Zinnwald is the product of high temperature post-magmatic hydrothermal alteration (i.e., greisenization), which affected and overprinted the uppermost part of the narrow Zinnwald granite stock. Pertrographic and mineral paragenetic evidence is used to illustrate that the genesis of the greisen mineralization is related to the interaction of a felsic igneous protolith with aqueous magmatic fluids, highly enriched in alkali metals, incompatible elements and volatiles, such as F. The chemical and mineralogical effects of greisenization are subdivided into three different stages, reflecting in a logical sequence the predicted physicochemical evolution of a magmatic hydrothermal fluid system.
A model is suggested that predicts upward directed fluid flow explaining the characteristic textural and geochemical alteration patterns within the granite stock, as well as high rare metal contents of the Zinnwald granite and provides a possible solution for the problem of fluid access to the solidified granite cap. This holistic metallogenetic model for the origin of the Zinnwald Li-Sn(-W) deposit integrates available field geological, geochronological, petrological and geochemical data and is largely based on the Burnham (1997) model for porphyry deposits, on the Shcherba (1970) model for greisen deposits, but augmented by peculiarities of greisen-type ore deposits of the Erzgebirge.
Zinnwaldite mica separates from the Zinnwald greisen dated in this study yield an average age of 314.1 ± 1.5 Ma. This age is significantly younger than available intrusion ages of similar A-type granitic intrusions into the Teplice Rhyolite (TR) such as 324 ± 2 Ma Re–Os molybdenite age for the Altenberg granite (Romer et al. 2007). The Ar-Ar age is thought to reflect cooling of the greisen below the closure temperature of zinnwaldite, estimated to be about 373 ± 21°C (closure temperature of biotite, Berger & York 1981). In this case, the Ar-Ar age obtained is a minimum age estimate for Li-Sn(-W) mineralization, known to have formed at temperatures above this closure temperature. Ore formation is regarded as an integral part of the development of the Altenberg-Teplice caldera and associated with the intrusion of peraluminous A-type Li-mica granites in an extensional post-orogenic environment during the later stage of the Variscan Orogeny.

Keywords: Zinnwald; Lithium; Greisen

  • Abstract in refereed journal
    Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften (2012)80, 72-72
  • Lecture (Conference)
    GeoHannover 2012, 01.-03.10.2012, Hannover, Deuschland

Permalink: https://www.hzdr.de/publications/Publ-17112
Publ.-Id: 17112


(THz based) Electron Bunch Diagnostic at Superconducting Continuous Wave Accelerators

Caglar, K.; Mamidala, V.; Lehnert, U.; Schneider, C.; Seidel, W.; Schlarb, H.; Kuntzsch, M.; Staats, G.; Al-Shemmary, A.; Stojanovic, N.; Geloni, G.; Helm, M.; Michel, M.; Gensch, M.

At the srf based prototype cw accelerator ELBE a new electron beamline, providing for femtosecond electron bunches with nC bunch charges and repetition rates in the 1 – 200 KHz regime and with pC bunch charge and repetition rates of 13 MHz is currently constructed. The 40 MeV electrons will be used in photon-electron interaction experiments with TW and PW class laser and the generation of broad band and narrow bandwidth coherent THz pulses. In this paper we outline ideas for novel online diagnostics of the electron bunch properties (e.g. arrival time and bunch form) based on the time and frequency domain analysis of the emitted coherent THz radiation but also based on direct measurements by e.g. electro-optic sampling. The suitability of ELBE as a testbed for diagnostic of future cw X-ray photon sources (e.g. energy recovery linacs) will be discussed.

  • Poster
    IPAC 2012 - International Particle Accelerator Conference 2012, 21.-25.05.2012, New Orleans, USA

Permalink: https://www.hzdr.de/publications/Publ-17111
Publ.-Id: 17111


Evaluation of tomographic data

van den Hoff, J.

kein Abstract verfügbar

  • Book chapter
    R. Salzer: Biomedical Imaging: Principles and Applications, New York: Wiley, 2012, 978-0-470-64847-6, 30-62

Permalink: https://www.hzdr.de/publications/Publ-17110
Publ.-Id: 17110


Interaction of Uranium(VI) with Bioligands Present in Human Biological Fluids: The Case Study of Urea and Uric Acid

Osman, A. A. A.; Geipel, G.; Bernhard, G.

The complexation of uranium(VI) with bioligands that found in human biological fluids, viz, urea and uric acid in aqueous solutions has been investigated using time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature, I = 0.1 M (NaClO4) and pH (3 for uric acid; 4 for urea). In both complex systems a static quench effect with increasing ligand concentration and no peaks shift upon complexation were observed. With uranium(VI) both ligands formed a fairly weak 1:1 complex with av-erage stability constants of log β110 = 4.67 ± 0.29 for uric acid and log β110 = 3.79 ± 0.15 and 2.12 ± 0.18 for relatively low and relatively high urea concentrations, re-spectively. Application of the newly generated data on the U(VI) speciation modelling in biofluids, e.g., human urine was also discussed.

Keywords: uranium(VI); urea; uric acid; complexation; stability constant; TRLFS; biofluids; speciation modelling

Permalink: https://www.hzdr.de/publications/Publ-17109
Publ.-Id: 17109


Charakterisierung von Wirt/Gast-Systemen mittels Radiotracertechnik

Stephan, H.

kein Abstract verfügbar

  • Lecture (Conference)
    Institutsseminar, Freie Universität Berlin, Institut für Chemie und Biochemie, 11.05.2012, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17108
Publ.-Id: 17108


Coherent THz Radiation from linear accelerators and 4th Generation X-ray Light sources: Status, Challenges and Diagnostic opportunities

Gensch, M.

The past fifteen years have seen a rapid development of novel techniques to generate and detect ultra-short and high power THz pulses. The availability of these pulses with electric field strength in the few 10 to 100 MV/m regime has led to a number of exciting experiments in particular in the field of non-linear THz spectroscopy and THz control experiments. One class of these THz generation techniques utilizes highly charged, ultra short electron bunches accelerated to relativistic speed in linear particle accelerators [1]. A variety of different source concepts allows to shape the THz pulses from single cycle/broad band pulses to multicycle/narrow-bandwidth pulses with polarizations ranging from radial to linear. One main attraction of accelerator-based THz originates from the fact that the THz generation process does not take place in a medium but in the ultra-high vacuum of the accelerator, so that the THz pulse energy can hence theoretically much easier up scaled than in any of the table top sources available today. Additionally it could recently be shown that coherent THz radiation can be generated residually and in parallel to the femtosecond X-ray pulses in 4th Generation X-ray Light sources such as FLASH [2,3,and 4] and LCLS [5]. This opens up the exciting opportunity to perform naturally synchronized THz pump X-ray probe experiments on few femtosecond time scales [2,3,and 5], the THz sources furthermore constitute an ideal tool for online diagnostic on the electron bunch form at superconducting linear accelerators. An overview over different THz facility projects will be presented and experimental and diagnostic opportunities as well as challenges will be discussed on the example of recent pilot experiments.

[1] G.L. Carr et. al., High power terahertz radiation from relativistic electrons, Nature 420 (2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol. 51 (2008), 423.
[3] U. Fruehling et. al., Single-Shot THz-field-driven X-ray streak camera, Nat. Photon. 3 (2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray Light sources, Nat. Photon. 5 (2011), 162.
[5] D. Daranciang et. al., Single-cycle terahertz pulses with > 0.2 V/angstrom field amplitudes via coherent transition radiation, Appl. Phys. Lett. 99 (2011), 141117.

  • Invited lecture (Conferences)
    Kolloquium des Physik Fakultät der Universität Siegen, 03.05.2012, Siegen, Germany

Permalink: https://www.hzdr.de/publications/Publ-17107
Publ.-Id: 17107


Synthesis and characterization of novel tetrahedral copper(I) complexes comprising tridentate PNP-aminodiphosphines and tetradentate PN(X)P-substituted aminodiphosphines (X = O, S)

Peruzzo, V.; Pretzsch, C.; Tisato, F.; Porchia, M.; Refosco, F.; Marzano, C.; Gandin, V.; Schiller, E.; Walther, M.; Pietzsch, H.-J.

Two series of novel tetrahedral copper(I) complexes comprising tridentate PNP-aminodiphosphines and tetradentate PN(X)P-substituted aminodiphosphines (X = O, S) have been prepared and characterized by conventional physico-chemical techniques. The first series includes ‘3 + 1’-type complexes comprising an aromatic PNP-aminodiphosphine and acetonitrile or triphenylphosphine. In the second series, the central amine function of the PNP-ligand was substituted with functionalized pendant arms containing ether, hydroxyl or thioether groups to enhance the chelation ability of the ligand. Fully coordinated neutral and cationic complexes were isolated. A preliminary study investigating both the labeling of 64Cu with the prototype PN(S)P ligand and the potential cytotoxic activity of the ‘cold’ [Cu(PN(S)P)][BF4] complex is reported.

Permalink: https://www.hzdr.de/publications/Publ-17106
Publ.-Id: 17106


Synthesis, in vitro and in vivo characterization of novel 99mTc-‘4+1’-labeled 5-nitroimidazole derivatives as potential agents for imaging hypoxia

Giglio, J.; Fernández, S.; Pietzsch, H.-J. D.; Dematteis, S.; Moreno, M.; Pacheco, J. P.; Cerecetto, H.; Rey, A.

The evaluation of oxygenation status of solid tumors is an important field of radiopharmaceutical research. With the aim to develop new potential 99mTc-radiopharmaceuticals for imaging hypoxia, we have synthesized two novel isocyanide derivatives of metronidazole, which has demonstrated high affinity for hypoxic tumors in vitro and in vivo.
Methods: Metronidazole derivatives 4-isocyano-N-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]butanamide (M1) and 1-(4-isocyanobutanoyl)-4-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]piperazine (M2) were synthesized, and labeling was performed through preparation of their corresponding 99mTc-(4+1) complexes, 99mTc-NS3M1 and 99mTc-NS3M2. The structure of the technetium complexes was corroborated by preparation and characterization of the corresponding rhenium complexes. We have studied the main physicochemical properties (stability, lipophilicity and plasma protein binding). Biological behavior in HCT-15 cells both in oxia and in hypoxia was assessed.
Biodistribution in normal mice and in animals bearing induced 3LL Lewis murine lung carcinoma was also studied.
Results: Metronidazole derivatives were successfully synthesized. Labeling with high radiochemical purity was achieved for both ligands.
99mTc complexes were stable in labeling milieu and human plasma. However, presence of the piperazine linker in M2 resulted in higher lipophilicity and protein binding. Although cell uptake in hypoxic conditions was observed for both radiotracers, 99mTc-NS3M2 biodistribution was considered unsuitable for a potential radiopharmaceutical due to high liver uptake and poor blood clearance. However, 99mTc-NS3M1 demonstrated a very favorable in vivo profile both in normal mice and in mice bearing induced tumors.
Conclusion: Selective uptake and retention in tumor together with favorable tumor/muscle ratio make 99mTc-NS3M1 a promising candidate for further evaluation as potential hypoxia imaging agent in tumors.

Permalink: https://www.hzdr.de/publications/Publ-17105
Publ.-Id: 17105


Brilliant Infrared Light Sources for Micro-Ellipsometric Studies of Organic Thin Films

Gensch, M.

Micro-ellipsometric studies in the infrared and THz spectral range are of increasing interest in particular for the determination of the optical constants of organic films and multilayers as in these cases the composition, thickness or roughness often vary on micro- and mesoscopic length scales. In cases where the aforementioned properties change across the probed spot, the degree of polarization of the reflected beam is deteriorated and sophisticated models have to be employed to derive the optical constants or other parameters from the determined ellipsometric angles. The achievable spot size in an ellipsometric set-up is now limited by the necessity to perform a specular reflectance measurement with a reasonably defined angle. In the optimal case the infrared radiation can be focused to near diffraction limited spot sizes with opening angles in the incoming beam of less than 7°. In other words such an experiment turns out to be limited by a source property that is typically called brilliance or brightness and makes the technique particularly suited for the use of accelerator based infrared sources such as 3rd generation synchrotron storage rings. The current status of such activities worldwide will be reviewed and discussed on the example of different pilot experiments and an outlook on future developments will be given.

Keywords: Brilliance; Brightness; infrared; THz; polymer brushes; degree of polarization; diffraction limit

  • Book chapter
    K. Hinrichs, K. Eichhorn: Ellipsometry of Functional Organic Surfaces and Films, Berlin: Springer, 2014, 978-3-642-40128-2, 325-336
    DOI: 10.1007/978-3-642-40128-2_16

Permalink: https://www.hzdr.de/publications/Publ-17104
Publ.-Id: 17104


Coherent THz Radiation from linear accelerators and 4th Generation X-ray Light sources: Status, Challenges and Opportunities

Gensch, M.

The past fifteen years have seen a rapid development of novel techniques to generate and detect ultra-short and high power THz pulses. The availability of these pulses with electric field strength in the few 10 to 100 MV/m regime has led to a number of exciting experiments in particular in the field of non-linear THz spectroscopy and THz control experiments. One class of these THz generation techniques utilizes highly charged, ultra short electron bunches accelerated to relativistic speed in linear particle accelerators [1]. A variety of different source concepts allows to shape the THz pulses from single cycle/broad band pulses to multicycle/narrow-bandwidth pulses with polarizations ranging from radial to linear. One main attraction of accelerator-based THz originates from the fact that the THz generation process does not take place in a medium but in the ultra-high vacuum of the accelerator, so that the THz pulse energy can hence theoretically much easier up scaled than in any of the table top sources available today. Additionally it could recently be shown that coherent THz radiation can be generated residually and in parallel to the femtosecond X-ray pulses in 4th Generation X-ray Light sources such as FLASH [2,3,and 4] and LCLS [5]. This opens up the exciting opportunity to perform naturally synchronized THz pump X-ray probe experiments on few femtosecond time scales [2,3,and 5]. An overview over different THz facility projects will be presented and experimental opportunities and challenges will be discussed on the example of recent pilot experiments.

[1] G.L. Carr et. al., High power terahertz radiation from relativistic electrons, Nature 420 (2002), 153.
[2] M. Gensch et. al., New infrared undulator beamline at FLASH, Infrared Phys. Technol. 51 (2008), 423.
[3] U. Fruehling et. al., Single-Shot THz-field-driven X-ray streak camera, Nat. Photon. 3 (2009), 523.
[4] F. Tavella, N. Stojanovic, G. Geloni, M. Gensch, Few-Femtosecond timing at Fourth-Generation X-ray Light sources, Nat. Photon. 5 (2011), 162.
[5] D. Daranciang et. al., Single-cycle terahertz pulses with > 0.2 V/angstrom field amplitudes via coherent transition radiation, Appl. Phys. Lett. 99 (2011), 141117.

  • Invited lecture (Conferences)
    Kolloquium des Fachbereichs Physik der Freien Unisversität Berlin, 27.04.2012, FU Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-17103
Publ.-Id: 17103


Design, Evaluation, and Comparison of Ghrelin Receptor Agonists and Inverse Agonists as Suitable Radiotracers for PET Imaging

Chollet, C.; Bergmann, R.; Pietzsch, J.; Beck-Sickinger, A. G.

Ghrelin agonist and inverse agonist radiotracers, suitable for positron emission tomography (PET), were developed to study the behavior of ghrelin receptor ligands in vivo and for further design of druggable peptides. The target peptides were synthesized on solid support and conjugated to the bifunctional chelator 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA), which is known to form a stable complex with Ga3+. Complexation with 68Ga could be achieved under mild conditions and led to radiotracers with high radiochemical purity and specific activity. The biological activity of the radiotracers was evaluated in vitro by an inositol phosphate turnover assay. Pharmacokinetic profile and metabolic stability of the 68Ga-NODAGA-radiotracers were investigated by small animal PET in rodent. Ghrelin derived agonists presented very high kidney accumulation, negligible tissue distribution, fast blood clearance, and poor stability in blood. Contrarily, the inverse agonist radiotracer exhibited very high stability in blood, large diffusion in tissues, reasonable kidney and liver metabolism, and slow blood clearance. This pharmacokinetic profile makes the ghrelin inverse agonist motif KwFwLL-CONH2 suitable for further development of radiotracers and a promising lead to design peptide-based therapeutics against obesity.

Permalink: https://www.hzdr.de/publications/Publ-17102
Publ.-Id: 17102


Irradiation affects cellular properties and Eph receptor expression in human melanoma cells

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

X-ray irradiation influences metastatic properties of tumor cells and, moreover, metastasis and cellular motility can be modified by members of the Eph receptor/ephrin family of receptor tyrosine kinases. We hypothesized that irradiation-induced changes in cellular properties relevant for metastasis in melanoma cells could be mediated by Eph receptor/ephrin signaling. In this pilot study, we analyzed one pre-metastatic (Mel-Juso) and three metastatic human melanoma (Mel-Juso-L3, A375, and A2058) cells lines and predominantly found anti-metastatic effects of X-ray irradiation with impaired cell growth, clonal growth, and motility. Additionally, we observed an irradiation-induced increase in adhesion paralleled by a decrease in migration in Mel-Juso and Mel-Juso-L3 cells and, in part, also in A375 cells. We further demonstrate a decrease of EphA2 both in expression and activity at 7 d after irradiation paralleled by an up-regulation of EphA3. Analyzing downstream signaling after irradiation, we detected decreased Src kinase phosphorylation, but unchanged focal adhesion kinase (FAK) phosphorylation, indicating, in part, irradiation-induced downregulation of signaling via the EphA2-Src-FAK axis in melanoma cells. However, to which extent this finding contributes to the modification of metastasis-relevant cellular properties remains to be elucidated.

Permalink: https://www.hzdr.de/publications/Publ-17101
Publ.-Id: 17101


Forming-Free Unipolar Resistive Switching in BiFe0.95Co0.05O3 Films

Xu, Q.; Wen, Z.; Shuai, Y.; Wu, D.; Zhou, S.; Schmidt, H.

We report the forming-free unipolar resistive switching effects in polycrystalline BiFe0.95Co0.05O3 films which were spin-coated on ITO/glass substrates by a chemical solution deposition method. The resistive ratio of the high resistive state (HRS) to the low resistive state (LRS) is more than 2 orders of magnitude. The conduction of the HRS is dominated by the space-charge-limited conduction mechanism, while Ohmic behavior dominates the LRS, which suggests a filamentary conduction mechanism. The oxygen vacancies are considered to play an important role in forming the conducting filaments.

Keywords: Unipolar resistive switching; Multiferroics; Chemical deposition

Permalink: https://www.hzdr.de/publications/Publ-17100
Publ.-Id: 17100


The impact of salinity on the sorption of selenate onto aged gamma-Al2O3 in the context of salt dome repositories

Franzen, C.; Hering, D.; Jordan, N.

The radioactive isotope Selenium-79 is a long-lived fission product found in nuclear waste. Due to its long half life of 3.27 ∙ 105 years, it is expected to be one of the isotopes most contributing to the potential radiation dose according to safety assessments of nuclear waste underground repositories. A detailed knowledge of the mobility and bioavailability of selenium is therefore of great importance for a safe disposal of radioactive waste.
One major process controlling selenium mobility and bioavailability is the adsorption onto mineral surfaces of both the engineered and geological barrier. In this context, it is important to understand to what extent this sorption is influenced by different parameters, which are characteristic of deep underground storage of high level and long-lived radioactive waste. These parameters include inter alia the presence of different background salts, which are important with regard to salt domes as potential repositories.
The present study focuses on the impact of ionic strengths due to NaCl, MgCl2 and CaCl2 background electrolytes on the sorption of selenate (SeO42-) onto aged γ-Al2O3. Al2O3 contributes to the formation of clays and other rock forming minerals. Thus and due to its well characterized properties it serves as a model oxide for process understanding.
A combination of macroscopic sorption experiments, electrophoretic mobility and in-situ ATR FT-IR spectroscopy measurements was used to study the interaction of selenate with aged γ-Al2O3 in the presence of NaCl, MgCl2 and CaCl2.
From In-situ ATR FT-IR spectra, a change in the symmetry of the aqueous tetrahedral selenate anion can be derived, which is an evidence for the formation of a surface complex on γ-Al2O3. From batch experiments, we observe that the sorption of selenate is dependent on the ionic strengths and electrolyte composition. Additionally, the sorption decreases with increasing pH.
The isoelectric point (pHIEP) of γ-Al2O3 is located at pH 9.6 for low NaCl background electrolyte concentration (I = 0.1 M). The increase of ionic strength (up to I = 1 M) results in a decrease of the zeta potential for both the acidic and alkaline pH range. However, in the alkaline range the decrease of the zeta potential is more pronounced. Additionally, we observe that the pHIEP is shifted to more alkaline values and finally no charge reversal is found. To what extent these differences influence the sorption of selenate in the alkaline range has to be checked in detail.

Keywords: Sorption; Selenate; Ionic Strength gamma-Al2O3

  • Lecture (Conference)
    EMC2012 - European Mineralogical Conference, 02.-06.09.2012, Frankfurt (Main), Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17099
Publ.-Id: 17099


Status of the Femtosecond Synchronization System at ELBE

Kuntzsch, M.; Buechner, A.; Gensch, M.; Lehnert, U.; Roeser, F.; Bock, M. K.; Bousonville, M.; Felber, M.; Lamb, T.; Schlarb, H.; Schulz, S.; Sydlo, C.

The superconducting electron accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf is currently upgraded to enable continuous wave operation with bunch charges of up to 1 nC and durations down to 200 fs (RMS). The new beamline will drive a THz source and an X-ray source based on Thomson scattering. In collaboration with DESY, Hamburg, an optical synchronization system based on a mode locked master laser is currently being set up to ensure timing stability on the few 10 fs level. It allows high temporal resolution pump-probe experiments and new electron beam diagnostics like bunch arrival-time monitors. The synchronization system is assembled in a dedicated laboratory to ensure stable environmental conditions. In this paper the concept of the optical synchronization system is presented and first experience on the link stabilization system, its installation and commissioning is reported.

Keywords: Synchronization ELBE

  • Lecture (Conference)
    Beam Instrumentation Workshop (BIW12), 15.-19.04.2012, Newport News, USA
  • Open Access Logo Contribution to proceedings
    Beam Instrumentation Workshop (BIW12), 15.-19.04.2012, Newport News, USA
    Status of the Femtosecond Synchronization System at ELBE

Permalink: https://www.hzdr.de/publications/Publ-17098
Publ.-Id: 17098


Electrical Evaluation of Ru-W(-N), Ru-Ta(-N) and Ru-Mn films as Cu diffusion barriers

Wojcik, H.; Kaltofen, R.; Merkel, U.; Krien, C.; Strehle, S.; Gluch, J.; Knaut, M.; Wenzel, C.; Preusse, A.; Bartha, J.; Geidel, M.; Adolphi, B.; Neumann, V.; Liske, R.; Munnik, F.

Co-sputtered Ru–Ta(N), Ru–W(N) and Ru–Mn composites are investigated in terms of their barrier properties against Cu diffusion. A wide range of stoichiometries is analyzed with regard to crystallization, barrier properties, resistivity, Cu adhesion and direct Cu plating behaviour. All films were annealed at 350 °C and 600 °C in forming gas for 1h and subsequently stressed at elevated temperatures and electrical fields (BTS, 250 °C, 2 MV/cm, 30 min). The leakage current was monitored during BTS to observe increased leakage due to Cu diffusion. The Cu ions that eventually have passed the barrier and drifted into the dielectric of the MIS test structure were detected and quantified using the triangular voltage sweep method. The addition of 10% W or Ta into a Ru film already leads to a highly improved barrier performance against Cu diffusion, comparable to TaN, as long as the temperatures involved are kept below 350 °C. Outstanding barriers were identified after 600 °C annealing and subsequent BTS, among them Ru50W50, Ru50Ta50 and Ru95Mn5. However, only Ru90Ta10 and Ru95Mn5 offer an excellent Cu adhesion and the possibility of direct Cu plating.

Permalink: https://www.hzdr.de/publications/Publ-17097
Publ.-Id: 17097


An automatic method for accurate volume delineation of heterogeneous tumors in PET

Hofheinz, F.; Langner, J.; Beuthien-Baumann, B.; Steffen, I.; Steinbach, J.; Kotzerke, J.; van den Hoff, J.

Objectives: Accurate volumetric tumor delineation is of increasing importance in radiation treatment planning. Many tumors exhibit only moderate tracer uptake heterogeneity and delineation methods using an adaptive threshold lead to robust results. These methods use a tumor reference value R (e.g. ROI maximum) and the tumor background Bg to compute the volume reproducing threshold. This threshold corresponds to an iso-contour which defines the tumor boundaries. However, the boundaries of strongly heterogeneous tumors can not be described by an iso-contour anymore and therefore conventional threshold methods are not suitable for accurate delineation. The aim of this work is the development and validation of a delineation method for heterogeneous tumors.

Methods: The new method (TV) can be considered as an extension of the adaptive threshold methods (TK), where instead of a single threshold for the whole ROI a local threshold is computed by determining for each voxel Bg and R in the close vicinity of the voxel. The absolute threshold for the considered voxel is then given by T_abs=Tx(R -Bg)+Bg, where T=0.39 was determined with phantom measurements. Validation: 10 clinical datasets (5 patients with lung cancer, 5 with head and neck cancer) were used to generate 10 realistic anthropomorphic software phantoms of strongly heterogeneous tumors with well known volume and boundaries. Volume delineation was performed with TK and TV.

Results: In contrast to TK, TV was able to reproduce the true tumor boundaries accurately. The deviation of the determined volume from the true volume was 6.9+/-6.6% for TV and 47.5+/-16.8% for TK.

Conclusions: In anthropomoric software phantoms the new method leads to promising results and a clear improvement of volume delineation in comparison to conventional background-corrected thresholding. In the next step, the suitability for clinical routine will be further investigated.

  • Poster
    SNM 2012 Annual Meeting, 09.-13.06.2012, Miami Beach, Florida, USA

Permalink: https://www.hzdr.de/publications/Publ-17096
Publ.-Id: 17096


A novel method for quantitative assessment of irregularity of FDG uptake in head-and-neck carcinoma for prediction of outcome

Apostolova, I.; Steffen, I. G.; Wedel, F.; Hofheinz, F.; Buchert, R.; Brenner, W.

Objectives: The prognostic value of SUV is unsatisfactory in head-and-neck carcinoma. The aim of the present study was to evaluate a new measure for the irregularity of the tumor`s shape in the FDG image as prognostic factor in this cancer type.

Methods: FDG PET/CT had been performed in 32 patients (61.3±10.1y) with advanced head-and-neck cancer prior to therapy. The FDG image of the primary tumor was segmented using the ROVER 3D segmentation tool based on thresholding at the volume-reproducible intensity threshold after subtraction of local background. The novel irregularity measure (IRREG) is defined as the deviation of the tumor's shape from sphere symmetry, computed as the ratio of the third power of the tumor's surface divided by the second power of its volume. Kaplan-Meier curves with respect to both overall (OAS) and progression-free survival (PFS) were separated by the best discrimination threshold according to ROC analysis and then compared by log-rank tests.

Results: Four patients died during follow-up, 11 experienced tumor progression. Median PFS was 11.3 mo. IRREG was prognostic for OAS (p=0.016), as was the glycolytic volume (GV, p=0.003). Statistical significance for the prediction of PFS was very high for both IRREG (p=0.0003) and GV (p=0.0006). Total mean glycolytic volume was also predictive for PFS, although significance was somewhat lower (p=0.029). Higher tumor irregularity was associated with a higher risk of progression and reduced survival. Pts. with IRREG >2 showed 3-year OAS rate of 58% compared to 92% in pts. with IRREG< 2. Neither SUVmax nor SUVmean was predictive for OAS or PFS.

Conclusions: The irregularity of the pretherapeutic FDG uptake pattern in the primary tumor as quantitatively characterized by the novel measure is predictive for tumor recurrence and survival in patients with head-and-neck carcinoma. The measure should be further evaluated for risk stratification in these patients.

  • Lecture (Conference)
    SNM 2012 Annual Meeting, 09.-13.06.2012, Miami Beach, Florida, USA

Permalink: https://www.hzdr.de/publications/Publ-17095
Publ.-Id: 17095


Heterogeneity and irregularity of FDG uptake as a prognostic marker for outcome in patients with Ewing sarcoma

Steffen, I.; Apostolova, I.; Schräpler, A.; Nyuyki, F.; Hofheinz, F.; Buchert, R.; Brenner, W.

Objectives: To determine the prognostic value of FDG-PET for progression-free survival (PFS) and overall survival (OAS) in patients with Ewing sarcoma, we evaluated two novel parameters for tumor heterogeneity and irregularity.

Methods: Twenty-two pts ( age 14.9±8.5) with Ewing Sarcoma (EWS) received FDG-PET for primary staging prior to treatment. Tumor segmentation was performed with ROVER using semi-automatic background detection. Shape irregularity (IRREG) was defined as the deviation of the tumor's shape from sphere symmetry, quantified by the ratio of the third power of the tumor's surface to the second power of its volume. Scale heterogeneity (HETER) was determined using a multiscale variance technique (MSVT) calculating the AUC ratio of heterogeneity-curves based on spatial scales of 8, 16 and 32 mm and varying binarization thresholds. Association of OAS and PFS with heterogeneity parameters (IRREG, HETER) as well as SUVmax was analyzed using Kaplan-Meier (KM) curves. Groups were separated by the best discrimination threshold according to ROC analysis and compared by log-rank test.

Results: Seventeen pts survived with a mean OAS of 58.5 months (min, 18.8 m; max, 97.8 m). Fifteen pts were progression free with a mean PFS of 50.1 month ranging from 2.7 to 91.0 months. KM analysis revealed a 5-year OAS rate of 92% for pts with SUVmax >7 and of 42% in pts with SUVmax ≤ 7 (p=0.012). Pts with HETER >37.5% showed a 5-year OAS rate of 38% compared with 92% in pts with HETER ≤ 37.5% (p=0.004). Higher IRREG> 2.2 was associated with higher 5-year OAS (98% vs. 56%; p=0,049). Higher SUVmax (>7.8) was also associated with higher 5-year PFS rates (91% vs. 62%; p=0.019) whereas neither IRREG nor HETER were predictive for PFS.

Conclusions: Surprisingly, in EWS higher initial SUVmax was significantly correlated with a higher OAS and PFS. Scale heterogeneity seems to be a new promising parameter for prediction of outcome based on FDG-PET in EWS.

  • Lecture (Conference)
    SNM 2012 Annual Meeting, 09.-13.06.2012, Miami Beach, Florida, USA

Permalink: https://www.hzdr.de/publications/Publ-17094
Publ.-Id: 17094


The prognostic value of a novel irregularity measure of FDG uptake in sarcomas

Apostolova, I.; Steffen, I. G.; Schräpler, A.; Hofheinz, F.; Buchert, R.; Brenner, W.

Ziel/Aim:

In sarcoma patients it is important to estimate the prognosis at the time of diagnosis, particularly to define patients at high risk. FDG PET is widely used for this purpose. Heterogeneity of FDG uptake in the tumor has been shown to be a useful characteristic for grading and prediction of outcome in patients with various sarcoma types, independent of the SUV. Here we propose and evaluate a novel measure for the irregularity of the tumor`s shape in the FDG image with respect to its predictive power in sarcoma patients.

Methodik/Methods:

The retrospective analysis included 56 sarcoma patients with different histological background: 17 patients with osteosarcoma (OS), 22 with Ewing sarcoma (EW) and 17 with various different sarcoma types (VS). Whole-body FDG-PET had been performed prior to therapy in all patients. The tumors were segmented fully automatically using the ROVER 3D segmentation tool which is based on thresholding at the volume-reproducible intensity threshold after subtraction of the local background. SUVmax, SUVmean were determined in addition to the novel measure of spatial irregularity (IRREG) of the primary tumor. IRREG is defined as the deviation of the tumor's shape from sphere symmetry, which can be computed as the third power of the tumor's surface devided by the second power of its volume. IRREG is normalized to 1 for a spherical lesion. Kaplan-Meier curves were obtained for IRREG, SUVmax and SUVmean with respect to both overall (OAS) and progression-free survival (PFS). Survival and PFS curves were separated by the best discrimination threshold according to ROC analysis and then compared by log-rank tests.

Ergebnisse/Results:

Median follow-up in all patients was 37.2 months. Sixteen patients died, 24 further patients experienced tumor progression. Median PFS was 29.5 months. SUVmax / SUVmean were higher in OS (median 12.5/4.9) than in EW (7.5/3.6, Wilcoxon p=0.002/0.096, Holm-adjusted) and VS (7.8/3.5, p=0.001/0.066). Median IRREG was smaller in OS (1.7) than in EW (2.9, p=0.002), it was intermediate in VS (2.3). Kaplan-Meier analysis revealed prognostic power of IRREG with respect to OAS in all patient groups with highest statistical significance in OS (p=0.0001, 0.049 and 0.031 in OS, EW and VS, respectively). Higher pretherapeutic IRREG was associated with shorter OAS, i.e. high risk, in OS, whereas it was associated with low risk in EW and VS. SUVmax and SUVmean were not predictive for OAS in OS and VS, but in EW only (high risk at SUVmax≤7.0, p=0.012, and SUVmean≤3.3, p=0.004). In OS, IRREG provided prognostic power also with respect to PFS (p=0.015). SUVmean was predictive for PFS in both OS (p=0.016) and EW (p=0.019), SUVmax in EW only (p=0.019).

Schlussfolgerungen/Conclusions:

The novel irregularity measure is promising for the identification of high risk sarcomas. It appears to provide better prognostic power than SUV, particularly in osteosarcomas.

  • Poster
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.04.2012, Bremen, DE
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A100

Permalink: https://www.hzdr.de/publications/Publ-17093
Publ.-Id: 17093


Radionuclide sorption studies of Co, Cs and Sr onto soils from an Australian legacy radioactive waste site

Gückel, K.; Comarmond, M. J.; Payne, T. E.; Chong, E.; Mokher-Shahin, L.

This paper discusses results of radionuclide sorption studies on a soil profile taken from a low level radioactive waste site in South Eastern Australia, known as the Little Forest Burial Ground. Low level radioactive waste was buried at this site in a series of shallow trenches in the 1960s, and the site has an on-going environmental monitoring program. This site has been the focus of a field study in recent years and an extensive core-drilling program was undertaken in 2009. Measurable amounts of Co-60, Sr-90, Cs-137 and traces of actinides have been observed at this legacy waste site in some soils, groundwater and vegetation samples taken in close proximity to the disposal area.

The sorption of Co, Cs and Sr has been studied at four depth intervals from one corehole located near the trenches using radioactive tracers and a batch sorption method to assess the key site characteristics governing contaminant release and transport. The studies were conducted on bulk samples (< 1 mm) with a mass loading of 10 g/L, ionic strength of 0.01 M (NaCl) in the presence of air. Strong sorption was observed for Cs over the entire pH range studied, whereas the sorption of Co and Sr on the soils was pH dependent with sorption edges between pH 3 and pH 6. Distribution coefficients (Kd values) for Cs sorption were similar for each soil over the entire pH range, with variations of less than one order of magnitude between samples. However, the Kd values for Sr and Co sorption varied over two and three orders of magnitude, respectively, over the pH range studied.

The four soil samples were mineralogically characterised and the BET surface areas and cation exchange capacities (CEC) determined. The bulk mineralogy of the soils was found to be similar with quartz, kaolinite and interstratified illite/smectite to be the main mineralogical phases. Most soils also contained iron oxides and anatase as minor minerals. The BET surface areas of the bulk samples varied from 27 m2/g to 47 m2/g and no strong correlation of surface area with sorption was observed. For the bulk samples, those with the higher clay fraction had the highest CEC, with CEC ranging between 10 and 24 cmol/kg. The CEC of the clay fractions were significantly higher, ranging from 21 to 34 cmol/kg and 34 to 55 cmol/kg for the < 2 µm and < 0.2 µm fractions, respectively. Further studies to elucidate the role of the various minerals with respect to sorption are in progress.

  • Lecture (Conference)
    12th South Pacific Environmental Radioactivity Association Conference, 16.-19.10.2012, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-17092
Publ.-Id: 17092


The simplified P3 approach on a trigonal geometry of the nodal reactor code DYN3D

Duerigen, S.; Fridman, E.

DYN3D is a three-dimensional nodal code for steady-state and transient analyses of Light Water Reactors applicable for square and hexagonal fuel assembly geometries. Several versions of the DYN3D code are available including a multi-group diffusion and a simplified P3 (SP3) neutron transport option. The multi-group SP3 method based on a trigonal geometry was developed recently. This method is applicable to the analysis of reactor cores with hexagonal fuel assemblies and allows flexible mesh refinement. In this paper, the theoretical background for the SP3 method is briefly described. The consistency of the implementation of the trigonal SP3 methodology in DYN3D is demonstrated by means of a simplified VVER-440 core test example. The corresponding few-group homogenized cross sections and reference solutions were produced by the Monte Carlo code Serpent. The DYN3D results are in good agreement with the reference solutions.

  • Kerntechnik 4(2012), 226-229

Permalink: https://www.hzdr.de/publications/Publ-17091
Publ.-Id: 17091


Prediction of outcome in sarcoma patients based on spatial heterogeneity of F18-FDG uptake using a multiscale variance technique

Steffen, I. G.; Apostolova, I.; Schräpler, A.; Brenner, W.; Buchert, R.; Hofheinz, F.

Ziel/Aim:

Spatial heterogeneity of tracer uptake in the tumor is a promising predictor of patient outcome in various tumor entities. Different definitions have been proposed for spatial heterogeneity of tracer uptake. However, as heterogeneity is a very complex characteristic, the most appropriate mathematical approach for quantitative description of heterogeneity has still to be determined. Here we propose the use of a multiscale variance technique (MSVT) that provides a vector of heterogeneity values at different spatial scales (distances). The technique is widely used for the characterization of geographical data (maps). The prognostic value of spatial heterogeneity based on MSVT was evaluated in sarcoma patients with F18-FDG-PET for initial staging.

Methodik/Methods:

In total 51 sarcoma patients (29 m, median age 15 y, range 2-61 y) were included retrospectively. Histological subtypes were 19 Ewing sarcomas (EWS), 16 osteosarcomas (OS) and 16 sarcomas with other subtypes (MS). The primary tumor was segmented fully automatically using the ROVER 3D segmentation tool which is based on thresholding at the volume-reproducible intensity threshold after subtraction of the local background. For the computation of heterogeneity, SUV values were first binarized at a given threshold. Then MSVT was used to compute heterogeneity at the following spatial scales: 8mm, 16mm, 32mm. For each scale, heterogeneity was plotted as function of the binarization threshold. The area under the curve (AUC) from SUVmin to SUVmax was computed. The AUC ratio of heterogeneity (HR) at 8mm to 16mm was used for the univariate analysis presented here. The best threshold for discrimination between survivors and non-survivors was determined by ROC analysis. Overall survival rates between the resulting groups were compared by Kaplan-Meier curves and log-rank tests.

Ergebnisse/Results:

36 patients (15 EWS, 14 OS, 7 MS) survived till the end of the follow-up ranging from 9.1 to 97.8 months (median 46.5 months). Overall survival of non-survivors ranged from 2.7 to 49.6 months (median 16.3 months). The highest HR was observed in the group of miscellaneous sarcomas (median 44.6, IQR 38.5-53.6) followed by osteosarcomas (median 43.6, IQR 35.3-46.0) and Ewing sarcomas (median 34.4, IQR, 31.2-39.6) (Kruskal-Wallis p<0.05). HR was significantly higher in non-survivors (median, 39.6; IQR, 14.6) than in survivors (median 36.3, IQR 31.5-44.8, Mann-Whitney p<0.05) with a threshold of 38.3 in ROC analysis (p<0.05). Kaplan-Meier-analysis revealed a higher overall 5-year-survival rate of 85.6% in patients with HR≤38.3 compared to 37.7% in patients with HR>38.3 (log-rank-test p<0.01). Significantly different distribution of survival rates was also observed in subgroups of EWS (p<0.05) and OS (p<0.05), but not in MS (p=0.23).

Schlussfolgerungen/Conclusions:

MSVT based spatial heterogeneity is promising for outcome prediction based on F18-FDG-PET in sarcoma. Studies with enlarged patient numbers using multivariate statistical models with adjustment of confounders are necessary for further evaluation of the potential of MSVT.

  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A98-A99
  • Poster
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 26.-29.04.2012, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17090
Publ.-Id: 17090


Irregularity of pretherapeutic tumor FDG uptake as prognostic factor in head and neck carcinoma

Apostolova, I.; Wedel, F.; Steffen, I. G.; Schreiter, N.; Marnitz, S.; Hofheinz, F.; Buchert, R.; Brenner, W.

Ziel/Aim:

FDG PET is widely used for diagnosis, staging, and therapy monitoring in patients with head and neck carcinoma. Quantitative analysis of FDG uptake in the tumor has the potential to complement visual reading for improvement of diagnostic accuracy. However, the prognostic value of SUV-based and some more sophisticated (semi-)quantitative measures is unsatisfactory in this cancer type. The aim of the present study was to propose and evaluate a new histogram-based measure of the irregularity of FDG uptake in the tumor as prognostic factor in head-and-neck carcinoma.

Methodik/Methods:

The retrospective analysis included 32 pts with head and neck tumor in whom whole-body FDG-PET/CT had been performed for primary staging (n=26) or recurrence diagnosis (n=6). All patients underwent therapy after PET/CT. The FDG image of the primary tumor was segmented fully automatically using the ROVER 3D segmentation tool which is based on thresholding at the volume-reproducible intensity threshold after subtraction of the local background. SUVmax, SUVmean, glycolytic volume (GV) and total mean glycolytic volume (MGV) were determined in addition to the novel measure of irregularity IRREG in the ROI. IRREG is defined as the deviation of the ROI's symmetry from a sphere symmetry, which can be computed as the third power of the ROI's surface divided by the second power of the ROI's volume. IRREG is normalized in such a way that for a spherical ROI IRREG is 1. Kaplan-Meier curves were obtained for all tested parameters with respect to both progression-free (PFS) and overall survival (OAS). Survival and PFS curves were separated by the best discrimination threshold by ROC analysis and compared by log-rank tests.

Ergebnisse/Results:

Four patients died during the follow-up, 11 further patients experienced tumor progression. Median PFS was 12.5 months. Median SUVmax/mean over the whole group was 10.9/5.9. Median glycolytic volumes were 16.0 ml and 85.6 ml for GV and MGV, respectively. Kaplan-Meier analysis revealed prognosticpower with respect to OAS for IRREG (p=0.016) and both glycolytic volumes (GV: p=0.0025, MGV: p=0.08). Statistical significance for the prediction of PFS was very high for IRREG (p=0.0003) and GV (p=0.0006), somewhat smaller for MGV (p=0.043). Higher tumor irregularity was associated with high risk with respect to both recurrence and survival. The SUV measures were not predictive, neither for OAS nor PFS.

Schlussfolgerungen/Conclusions:

The irregularity of FDG uptake of the primary tumor in the baseline FDG-PET as measured by the novel irregularity measure is predictive for tumor recurrence and survival in patients with head and neck carcinoma. Therefore, the irregularity measure is a promising marker for risk stratification in these patients. Reliable analysis of the independent contribution to risk stratification over other parameters such as the glycolytic volume requires further studies with larger patient samples.

  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A99
  • Poster
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 26.-29.04.2012, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17089
Publ.-Id: 17089


Metabolisches Volumen von Lungenkarzinomen - Vergleich mit dem Goldstandard, der Pathologie

Schäfer, A.; Kim, Y. J.; Mai, S.; Schäfers, H. J.; Bohnenberger, H.; Hofheinz, F.; Farmakis, G.; Khreish, F.; Hellwig, D.; Bohle, R. M.; Kirsch, C. M.; Grgic, A.

Ziel/Aim:

F-18-FDG-PET und -PET/CT werden zur Bestimmung des metabolisch aktiven Tumorgewebes im Staging und Follow-up des nicht-kleinzelligen Lungenkarzinoms (NSCLC) und zunehmend auch für die Bestrahlungsplanung eingesetzt. Zur Konturierung des PET-Volumens wurde ein kontrastorientierter Algorithmus vorgeschlagen, der eine optimierte Beziehung zwischen dem wahren Volumen einer Aktivitätsanreicherung in der FDG-PET und dem Schwellwert SUV beinhaltet. Der Algorithmus wurde aus Phantommessungen entwickelt und mit CT-Daten von Patienten validiert (1). Ziel der vorliegenden Arbeit ist die Validierung des Algorithmus im Vergleich zum Goldstandard, der Pathologie.

Methodik/Methods:

Die prospektive Studie umfasste 15 Patienten (65±7 Jahre, 10m) mit histologisch gesichertem NSCLC und einem Tumorvolumen > 3 ml. Für alle Patienten wurde zeitnah nach der PET die Lobektomie des betroffenen Lappens durchgeführt. Die nativen Präparate wurden in standardisierter Form lamelliert und digitale Makrofotografien jeweils sämtlicher Tumorscheiben zur Volumenermittlung erstellt. Das Volumen der nativen Tumorschnitte (TV) wurde mithilfe der Software ImageJ (Open Source) berechnet. Die Konturierung der PET-Volumina mittels kontrastorientiertem Algorithmus erfolgte mit der Software ROVER (ABX, Radeberg). Zum besseren Vergleich wurden hypothetische Kugeldurchmesser aus den Tumorvolumina berechnet. Zur Beurteilung der Unterschiede der Volumina bzw. der Durchmesser (D) wurden die Varianzanalyse (ANOVA) sowie die Bland-Altman Analyse durchgeführt. Des Weiteren wurden die Lokalisation (L) der Tumore (Ober- vs. Unterlappen), Kontakt (K) zum Mediastinum/Hilus sowie histologischer Tumortyp (H) in der Analyse berücksichtigt.

Ergebnisse/Results:

Die Volumina der Tumoren in der Pathologie betrugen zwischen 3 ml und 177 ml. Die mittels kontrastorientiertem Algorithmus konturierten PET-Volumina zeigten eine gute Übereinstimmung mit den Volumina der makropathologischen Analyse (r=0,99, p<0,001). Alle Tumorvolumina wurden in der PET überschätzt (mittlere Abweichung: 37,1%, range: 6 - 102 %). Die maximalen Abweichungen der Durchmesser der PET mit denjenigen der Pathologie betrugen im Mittel 3,1 mm (range: 0,2-7 mm). Die Abweichung vom D der Pathologie war signifikant unterschiedlich (p<0,01) zwischen den zentralen (Abweichung von 5,0 mm, n=8) und den intrapulmonalen Tumoren (Abweichung von 1,4 mm, n=7).

Schlussfolgerungen/Conclusions:

Die Konturierung von PET-Volumina mittels kontrast-orientiertem Algorithmus zeigt eine gute Übereinstimmung mit der Pathologie. Die Abhängigkeit der Ergebnisse von der Tumorlokalisation zeigt, dass eine Weiterentwicklung des Algorithmus unter Berücksichtigung von Atemgating sinnvoll ist.

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.04.2012, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A19-A20

Permalink: https://www.hzdr.de/publications/Publ-17087
Publ.-Id: 17087


Open Access - Publizieren im Helmholtz-Zentrum Dresden-Rossendorf

Reschke, E.

Im Rahmen des Frühjahrstreffen der EU-Referenten der Helmholtz-Gemeinschaft im Helmholtz-Zentrum Dresden-Rossendorf am 08.u. 09.Mai 2012 werden die HZDR-Aktivitäten zu OPen Access dargestellt.

Keywords: Open Access, Open Data, Helmholtz-Zentrum Dresden Rossendorf, HZDR, Bibliothek, HORIZON 2020, EU Open Access Pilot; Special Clause 39

  • Invited lecture (Conferences)
    Frühjahrstreffen EU Referenten der Helmholtz-Gemeinschaft, 08.05.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17086
Publ.-Id: 17086


Usefulness of voxel-wise Pearson correlation coefficient for reproducibility and repeatability measurements in PET

Haase, R.; Zöphel, K.; Andreeff, M.; Steinbach, J.; Kotzerke, J.; Abolmaali, N.

Ziel/Aim:

In the field of molecular imaging using Positron Emission Tomography (PET), a method for measuring reproducibility or repeatability of serial PET is discussed continuously. For example the limited reproducibility of [18F]fluoromisonidazole PET measurements was shown using voxel-wise Pearson correlation coefficient (PCC) (1). But the applied method may not be suitable for this purpose (2). The argumentation follows the statement of Westgard and Hunt (3): “The correlation coefficient [...] is of no practical use in the statistical analysis of comparison data.” This investigation focuses on visualizing the usefulness of the PCC method.

Methodik/Methods:

A PET phantom was used to gather 3D volumetric PET data sets. The phantom consists of a cylinder filled with [18F]fluorodeoxyglucose. It contains four wax spheres partly made of [68Ga]gallium-chloride and two glass spheres filled with a [68Ga]gallium-chloride solution. After scanning this phantom in a clinical PET/CT scanner (Biograph16, Siemens, Germany) for 10 hours several 3D data sets were reconstructed showing the phantom at different contrast levels. PCC was then measured in pairs of high- and low-contrast data sets and in several sub volumes of the phantom: a) at the centre and b) at the boundary of all spheres, c) in the cylinder, d) on the cylinder-air boundary and e) in the air.

Ergebnisse/Results:

Even though all objects appear reproducible by visual interpretation, PCC inside the glass spheres, in the cylinder and in the air (0.13<0.91) was always lower than in wax spheres showing inhomogeneous activity distribution (0.92<1). PCC at object boundaries and in the wax spheres always indicated strong correlation (0.83 < PCC < 1). PCC in all target spheres was higher in high-contrast data sets compared to low-contrast data sets.

Schlussfolgerungen/Conclusions:

The fact that PCC is higher in volumes where activity gradients are located compared to homogeneously distributed volumes indicates that this method is not applicable to measure repeatability or reproducibility of PET measurements. PCC describes a combination of image properties like presence of signal gradients, signal homogeneity, noise and other imaging related effects.

Literatur/References:

1. Nehmeh SA, Lee NY, Schröder H, et. Al. (2008) Reproducibility of intratumor distribution of (18)F-fluoromisonidazole in head and neck cancer. Int J Radiat Oncol Biol Phys. 70(1):235-42.
2. Schwartz J, Humm JL, Gonen M, et. Al. (2011) Repeatability of SUV measurements in serial PET. Med Phys. 38(5):2629-38.
3. Westgard JO, Hunt MR. (1973) Use and interpretation of common statistical tests in method-comparison studies. Clin Chem. 19(1):49-57.

  • Poster
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2012, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A92-A93

Permalink: https://www.hzdr.de/publications/Publ-17084
Publ.-Id: 17084


Motion compensated fully 3D list-mode reconstruction

Lougovski, A.; Langner, J.; Beuthien-Baumann, B.; Oehme, L.; Steinbach, J.; van den Hoff, J.

Ziel/Aim:

PET investigations of the brain, e.g. in receptor studies, typically exhibit long acquisition times making them sensitive to patient motion during the data acquisition and leading to potentially significant motion blur of the reconstructed activity distribution. This circumstance makes motion compensation one of the most pressing problems in high resolution PET scanners. We report on our work concerning integration of event-based motion compensation algorithm into a previously developed high resolution fully 3D list-mode reconstruction.

Methodik/Methods:

We integrated motion compensation into our implementation of 3D list-mode Ordered Subsets Expectation Maximization reconstruction (3D LMOSEM). The system matrix elements are computed on-the-fly and are modelled to be proportional to the intersection volume of voxels with Lines Of Response having a finite cross section (TOR: Tube Of Response). Motion information with high temporal resolution is provided by an external infra-red motion tracking system and used by the motion compensation algorithm for suitable spatial transformation of the individual TORs. Scatter correction factors (calculated using Single Scatter Simulation) are reconstructed into a scatter image, which is afterwards used in the forward projection step of the reconstruction together with an image of the delayed events. We have evaluated the new method in phantom and patient studies by comparing it with the previously developed procedure of using standard sinogram-based OSEM-reconstruction after motion pre-correction of the list mode data. The evaluation procedure has been divided into two parts: i) quantitative accuracy and spatial resolution (FWHM comparison) in phantoms and ii) visual evaluation of patient brain studies.

Ergebnisse/Results:

The new method provides a significant improvement of the reconstructed resolution (more than 25%) in comparison to the standard reconstruction of our scanner (Siemens ECAT HR+) while maintaining a high level of quantitative accuracy. Visual evaluation of five F-DOPA and five FDG brain studies showed substantially higher level of details in several brain structures as well as almost complete elimination of motion related artefacts.

Schlussfolgerungen/Conclusions:

The developed reconstruction allows almost complete elimination of motion blurring artefacts in brain studies and provides substantially better resolution than the standard reconstruction of the Siemens HR+ scanner. However, high computational complexity of the algorithm leads to substantial reconstruction times, which currently prevent its use for on-the-fly reconstruction in clinical routine. Further developments are necessary to eliminate this

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2012, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A21-A22

Permalink: https://www.hzdr.de/publications/Publ-17083
Publ.-Id: 17083


Gold diffusion into silicon during thermal annealing

Müller, A.-D.; Müller, F.; Wengel, S.; Baumgart, C.; Skorupa, S.; Reuther, H.; Mücklich, A.; Schmidt, H.

Gold was found to diffuse into silicon by a complex mechanism involving a vacancy-controlled interstitial-substitutional equilibrium. We investigated the Au diffusion into silicon using differently thick Au layers on n-Si and thermal annealing in a tube furnace at 800°C for 20 h in an argon atmosphere. After thermal treatment the lateral inhomogeneity in the Au distribution has been probed by Auger electron spectroscopy (AES) scans, Scanning electron microscopy, High resolution transmission electron microscopy (HRTEM), and by Kelvin probe force microscopy (KPFM) measurements [1]. The Au diffusion led to very complex diffusion concentration profiles which deviate from the ideal ones for Au diffusion into dislocation-free silicon. The resulting depth distribution of Au in Si has been determined by AES measurements. The KPFM contrast is independent of the surface topography and reveals different long-range chemical and local electrostatic interaction between the conducting KPFM tip and sample surface. HRTEM on cross-sections prepared from the sample with a nominal 10 and 20 nm thick Au layer reveal different phases of silicide formation.
[1] C. Baumgart, A.-D. Müller, F. Müller, H. Schmidt, phys. stat. sol. (a), 2011, 208, 777-789.

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 25.-30.03.2012, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17082
Publ.-Id: 17082


A novel method for in-vivo evaluation of quantification accuracy in PET

Langner, J.; Hofheinz, F.; Schramm, G.; Oehme, L.; Beuthien-Baumann, B.; Lukas, M.; Buchert, R.; Steinbach, J.; van den Hoff, J.

Ziel/Aim:

One of the strengths of PET is the ability to measure regional tracer concentrations, which is the basis of a quantitative evaluation of patient studies. Parameters such as the standardized uptake value (SUV) or transport constants derived from kinetic modeling are commonly used for this purpose. The quantitative accuracy strongly depends on accurate calibration of the scanner, which is commonly performed with suitable phantoms. While this calibration procedure ensures quantitatively correct results in geometrically comparable phantoms, it still leaves questions to be asked regarding its reliability for in-vivo measurements due to different scatter distribution as well as tracer distribution in phantoms compared to patient scans.
It was therefore the aim of our study to investigate the actual in-vivo accuracy of a phantom-based scanner cross-calibration against a well-counter by comparison of the tracer concentration in the patient’s urine as determined by the PET system to the concentration measured in a well-counter.

Methodik/Methods:

In 39 routinely scanned F18-FDG patients on two different PET scanners (EXACT HR+ PET: N=22; Biograph PET/CT: N=17) the bladder region was imaged as the last bed position and urine samples collected immediately after the end of the scan. 3D region-of-interests (ROI) were placed in the bladder by three different observers via a threshold-based delineation method using the ROVER software and image-based activity concentrations were determined. Activity concentration in the urine samples was determined in well-counters which were cross-calibrated against the respective scanner via routine phantom procedures.

Ergebnisse/Results:

Our first results show, that the measured activity concentrations are significantly lower in PET than in the well-counter for all patients and both investigated scanners; PET vs. well-counter ratio: 0.88±0.06 [range: 0.79-1.10] (EXACT HR+), 0.86±0.11 [range: 0.57-1.06] (Biograph).

Schlussfolgerungen/Conclusions:

The presented results suggest, that the commonly used phantom-based scanner calibration is not sufficient to guarantee high quantitative in-vivo accuracy. A possible reason for the observed deviations of up to 43% and the patient and scanner related variations of up to 49% might be an insufficient scatter correction in the manufacturer provided image reconstruction. To further investigate, we are currently acquiring more data sets from a third PET scanner (Gemini-TF PET/CT). We propose to augment standard calibration procedures by measurement of the in-vivo accuracy of the calibration using the described method. Furthermore, we believe that the proposed in-vivo method might also be of value for multi-center studies where monitoring the calibration accuracy for each scanner could be an important benefit and quality control method.

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2012, Bremen, D
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A77

Permalink: https://www.hzdr.de/publications/Publ-17081
Publ.-Id: 17081


Kelvin probe force microscopy imaging on horizontal locally doped silicon nanowires

Baumgart, C.; Habicht, S.; Feste, S.; Helm, M.; Mantl, S.; Schmidt, H.

Kelvin probe force microscopy (KPFM) [1] has been used for the electrical characterization of silicon nanowires (NWs). Arrays of horizontal Si NWs [2] with widths down to 10 nm have been prepared from a silicon-on-insulator (SOI) starting material. After transferring the NW structures into the Si top layer by conventional top-down approach, the samples have been locally implanted with B and As. Quantitative dopant profiling by means of KPFM is successfully employed to locate the junctions along the B-doped and As-doped Si NWs. In addition, the influence of local intrinsic electric fields [3] is discussed for the investigated SOI structures.
[1] C. Baumgart, M. Helm, H. Schmidt, Phys. Rev. B 80, 085305 (2009).
[2] S. F. Feste, J. Knoch, S. Habicht, D. Buca, Q.-T. Zhao, S. Mantl, Solid-State Electronics 53, 1257 (2009).
[3] C. Baumgart, A.-D. Müller, F. Müller, and H. Schmidt, Phys. Stat. Sol. A 208, 777 (2011).

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 25.-30.03.2012, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17080
Publ.-Id: 17080


FDG-PET/MR im Rahmen der Primärdiagnostik von Patienten mit Kopf-Hals-Tumoren

Beuthien-Baumann, B.; Platzek, I.; Schneider, M.; Gudziol, V.; Langner, J.; Laniado, M.; Kotzerke, J.; van den Hoff, J.

Ziel/Aim:

Ganzkörper-PET/MR-Geräte kombinieren die metabolische Information der Positronen-Emissions-Tomographie mit dem hohen Weichteilkontrast der Magnet-Resonanz-Tomographie in einem Untersuchungsablauf. Ziel dieser Untersuchung ist es, den möglichen diagnostischen Zugewinn bei der kombinierten Anwendung beider Untersuchungsmodalitäten beim Primärstaging von Patienten mit Kopf-Hals-Tumoren zu untersuchen

Methodik/Methods:

40 Patienten (32 Männer, 8 Frauen, Alter 38 -82 Jahre, mittleres Alter 64 Jahre) mit histologisch gesicherten Kopf-Hals-Tumoren wurden an einem kombinierten PET/MR-Gerät (Philips Ingenuity PET-MR (TOF-PET/ 3T-MRT)) vor geplanter kurativer Operation untersucht (Untersuchungsablauf Kopf/Hals: Schwächungs-MRT; PET:350 MBq F-18-FDG, Start ab ca. 175 min p.i, 6 min /bed.; diagn. MRT: NV16-Spule, T1/T1-KM, T2, STIR). Beurteilt wurden die Detektierbarkeit des Primärtumors und von regionalen Lymphknotenmetastasen getrennt für PET, MRT und deren Kombination im Vergleich zur histologischen Aufarbeitung des Op-Präparates. Zum Ausschluss von Fernmetastasen wurde vor der dedizierten Kopf-Hals-Untersuchung eine konventionelle PET-Untersuchung des Körperstammes 60 min nach Injektion von 350 MBq F-18-FDG (ECAT-EXAT HR+, Siemens/CTI) durchgeführt.

Ergebnisse/Results:

Der Primärtumor war bei 5 Patienten im PET (bei geringer Größe), bei 10 Patienten im MRT (geringe Größe bzw. bei Metallartefakten) nicht abgrenzbar. Bei bisher 26 Patienten konnte ein Vergleich mit der Histologie bzgl. der LK-Metastasen erfolgen. Insgesamt wurden 863 LK histologisch beurteilt, davon waren 56 LK metastatisch befallen. Die Sensitivität und Spezifität hinsichtlich der Detektion von LK-Metastasen für PET und MRT betrug jeweils 69% bzw. 98%, die kombinierte Auswertung von PET-MRT erhöhte die Sensitivität auf 83%. Bei 8 Patienten wurde in der PET-Untersuchung des Körperstammes eine weitere hypernmetabole Läsion mit V.a. Zweittumor bzw. Fernmetastase detektiert.

Schlussfolgerungen/Conclusions:

In dieser vorläufigen Datenauswertung scheint die Kombination von FDG-PET und diagnostischem MRT in einem Untersuchungsablauf die Sensitivität bezüglich der Detektion von LK-Metastasen von Kopf-Hals-Tumoren deutlich zu erhöhen. Primärtumoren können dem Nachweis bei sehr kleiner Ausdehnung sowohl im PET als auch im MRT entgehen. Die MRT-Bildgebung kann, insbesondere im Mundbereich, durch Metallartefakten deutlich beeinträchtigt werden; auch hier bringt die Kombination von PET-MRT einen diagnostischen Zugewinn. Eine PET-Untersuchung des Körperstammes zum Ausschluss von Fernmetastasen oder Zweittumoren erscheint sinnvoll.

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2012, Bremen, D
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A48

Permalink: https://www.hzdr.de/publications/Publ-17079
Publ.-Id: 17079


Kombinierte PET/MR in der Diagnostik von Skelettmetastasen mit F-18-Natriumfluorid-PET (NaF-PET) und Ganzkörper-MRT (GK-MRT): Erste Erfahrungen

Beuthien-Baumann, B.; Platzek, I.; Langner, J.; Schramm, G.; Oehme, L.; Laniado, M.; van den Hoff, J.; Kotzerke, J.

Ziel/Aim:

Die Skelettszintigraphie mit F-18-NaF-PET weist eine hohe Sensitivität für die Detektion von Skelettmetastasen auf. Voraussetzung für deren Nachweis ist jedoch, dass die Metastase die Knochenmatrix alteriert. Knochenmarkmetastasen, die noch keine Stoffwechselreaktion der Knochenmatrix verursachen, entgehen dem Nachweis der Skelettszintigraphie. Im MRT können Knochenmarkmetastasen mit hoher Sensitivität detektiert werden. Ziel dieser Untersuchung ist es, den möglichen diagnostischen Zugewinn hinsichtlich der Detektion von Knochen- bzw. auch mgl. Knochenmarkmetastasen bei der kombinierten Anwendung der F-18-NaF-PET und einem GK-MRT mit einem Ganzkörper-PET/MR-Gerät zu untersuchen.

Methodik/Methods:

Seit Inbetriebnahme des PET/MR-Gerätes (Philips Ingenuity (TOF-PET/ 3T-MRT)) im Januar 2011 wurden 345 Untersuchungen durchgeführt, davon handelte es sich bei 96 Untersuchungen um Skelettszintigraphien mit F-18-Natriumfluorid mit der Frage nach Skelettmetastasen. Bei 52 Untersuchungen konnte neben dem Schwächungs-MRT und der PET noch ein diagnostisches Ganzkörper-MRT durchgeführt werden. 28 Patientendatensätze gehen in diese vorläufige Datenauswertung ein: 19 Männer, 9 Frauen, mittleres Alter 65 Jahre, 15 Prostata-Karzinome, 5 Mamma-Karzinome, 3 Schilddrüsen-Karzinome, 2 Karzinoide, 1 Bronchial-Karzinom, 1 CUP, 1 Plasmozytom. Injektion von 250 MBq F18-Natriumfluorid, Schwächungs-MRT; Start der Ganzkörper-PET ab 60 min p.i.. MRT: GK-coronar T1 und wenn möglich sagittale STIR der Wirbelsäule.

Ergebnisse/Results:

Qualitativ ergibt die NaF-PET Skelettszintigramme von hoher Qualität. Die coronaren GK-MRT und die sagittalen MRT-Schichten der Wirbelsäule ergänzen die PET mit exzellenten morphologischen Informationen. Metastasenverdächtige Läsionen wurden bei 16/28 Patienten gefunden. Davon bei 9 Patienten ausschließlich im NaF-PET, bei 5 Patienten fanden sich metastasenverdächtige Läsionen ausschließlich im MRT. Die MRT zeigte zusätzliche metastasenverdächtige Läsionen überwiegend im Bereich der Wirbelsäule. Skelettmetastasen im Bereich des Rippenthorax entgingen der GK-MRT auf Grund der coronaren Orientierung. Zusätzliche volldiagnostische MRT-GK-Untersuchungen in Ergänzung zum GK-Skelettszintigramm sind auf Grund des zusätzlichen Zeitbedarfes oft durch den Allgemeinzustand des Patienten limitiert

Schlussfolgerungen/Conclusions:

Die NaF-PET bietet Skelettszintigramme von hoher Bildqualität. In dieser vorläufigen Datenauswertung scheint die Kombination von NaF-PET und diagnostischem GK-MRT in einem Untersuchungsablauf die Nachweiswahrscheinlichkeit kleiner Skelettmetastasen bzw. Knochenmarkmetastasen in der Wirbelsäule zu erhöhen. Eine Optimierung der Untersuchungszeit hinsichtlich der Kombination von PET-und MRT ist erstrebenswert.

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2012, Bremen, D
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A47-A48

Permalink: https://www.hzdr.de/publications/Publ-17078
Publ.-Id: 17078


Automatisierte volumetrische Abgrenzung heterogener Tumoren in der PET

Hofheinz, F.; Langner, J.; Beuthien-Baumann, B.; Oehme, L.; Steffen, I.; Apostolova, I.; Steinbach, J.; Zöphel, K.; Kotzerke, J.; van den Hoff, J.

Ziel/Aim:

Die akkurate Abgrenzung von Tumoren in der PET gewinnt zunehmend an Bedeutung für die Strahlentherapie sowohl bei der Zielvolumendefinition als auch bei der Bewertung des Therapieansprechens. Für hinreichend homogen anreichernde Tumoren liefern adaptive Schwellwertverfahren, die neben einem Tumor-Referenzwert R (z.B. dem ROI-Maximum) den Untergrund Bg in der Tumorumgebung berücksichtigen, gute Ergebnisse. Der Schwellwert entspricht hierbei einer bestimmten 3D-Isokontur, welche die Tumorabgrenzung definiert. Bei stark heterogenen Tumoren kann es mit adaptiven Schwellwertverfahren jedoch zu merklichen Fehlern bei der Abgrenzung kommen, da die Grenzfläche nicht länger durch eine Isointensitätskontur gegeben ist. Ziel dieser Arbeit war die Entwicklung einer Abgrenzungsmethode, die auch bei stark heterogenen Zielstrukturen einsetzbar ist.

Methodik/Methods:

Die neue Methode (TV) kann als eine Erweiterung der adaptiven Schwellwertverfahren (TK) betrachtet werden, wobei statt eines ortsinvarianten, konstanten Schwellwertes ein voxelabhängiger Schwellwert berechnet wird, indem separat fuer jedes Voxel Bg und R in der Voxelumgebung bestimmt werden. Der absolute Schwellwert für das aktuell betrachtete Voxel ist dann gegeben durch T_abs = T x (R - Bg) + Bg, wobei die Konstante T = 0.39 in Phantommessungen mit homogen gefüllten Kugeln bestimmt wurde.

Der zugrunde liegende Algorithmus ist iterativ und benoetigt als Startwert eine grobe initiale Abgrenzung, welche durch einen benutzerdefinierten Schwellwert erfolgt. Unabhängig für jedes Voxel innerhalb der initialen Abgrenzung werden Bg und R bestimmt. Die zur Untergrundbestimmung genutzte Umgebung des Voxels ist hierbei durch eine Kugel mit Durchmesser 3 x FWHM definiert. Bg ergibt sich als Mittelwert über alle Voxel in dieser Kugel mit einem Mindestabstand zur derzeitigen Schätzung der ROI-Grenzfläche von 1 x FWHM. R ist der Maximalwert innerhalb der Kugel. Durch Anwendung von T_abs für jedes betrachtete Voxel ergibt sich sodann eine erste Schätzung der ROI-Grenze, die Ausgangspunkt des nächsten Iterationsschrittes ist. Iteration erfolgt bis zur Konvergenz des resultierenden ROI-Volumens.

Validierung: 10 klinische Datensätze (5 Bronchial-, 5 Kopf-Hals CA) dienten zur Simulation praxisnaher Bilddaten mit 10 stark heterogenen Tumoren bekannten Volumens (Heterogenität: 35 +/- 8%). Volumenabgrenzung erfolgte mit TK und TR.

Ergebnisse/Results:

Folgende Abweichungen vom wahren Volumen wurden bestimmt: TV: (6.9 +/- 6.6)%, TK: (47.5 +/- 16.8)%. Im Gegensatz zu TK führt TV zu einer sehr guten Reproduktion der wahren Volumina.

Schlussfolgerungen/Conclusions:

In simulierten praxisnahen Datensätzen liefert das neue Verfahren eine deutlich genauere Abgrenzung bei stark heterogenen Zielstrukturen als das konventionelle Verfahren. Die Eignung der Methode für den klinischen Einsatz muss noch näher untersucht werden.

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2012, Bremen, D
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A20

Permalink: https://www.hzdr.de/publications/Publ-17077
Publ.-Id: 17077


First results of quantitative ASL perfusion measurements on a whole-body PET/MR system

Petr, J.; Bos, A.; Schramm, G.; Langner, J.; Hofheinz, F.; Beuthien-Baumann, B.; Platzek, I.; Kotzerke, J.; Steinbach, J.; van den Hoff, J.

Ziel/Aim:

In the beginning of 2011, a whole-body PET/MR system (Philips Ingenuity TF) became fully operational for patient investigations at our institute. With both imaging modalities, non-invasive quantitative perfusion measurements in the brain are possible. With PET, perfusion can be measured using [O-15]H2O which is considered as the gold standard but requires arterial blood sampling. Alternatively, perfusion values can be derived from arterial spin labeling (ASL) measurements in MR which has the advantage of being completely non-invasive and free of ionizing radiation. The combination of both imaging devices in a hybrid system allows a direct validation of ASL derived perfusion values against the PET measurements. Here, we present our first results of ASL perfusion measurements using the Ingenuity TF PET/MR.

Methodik/Methods:

We used multiphase EPISTAR ASL with Look-Locker sampling allowing a multiple inversion time image acquisition every 300 ms starting at 50 ms after the labeling. Crusher gradients were employed to remove signal from vascular blood. Two sequences with flip angles of 30° and 10° were performed to allow real flip-angle and T1 estimation. We performed two separated measurements on a healthy volunteer acquiring 4 slices in the brain with an in-plane pixel size of 3 mm by 3 mm and a slice thickness of 6 mm. The 3-parameter model proposed by Gunther et al. (1) was used to generate a parametric perfusion image and to calculate the cerebral blood flow (CBF).

Ergebnisse/Results:

The perfusion-weighted images showed reasonable signal-to-noise ratio and good contrast between gray and white matter. Gray matter structures were clearly delineated. Preliminary quantitative results are as follows: mean (slice average) CBF was 25 ml/100 g/min, gray matter CBF was 40 ml/100 g/min and white matter CBF was 12 ml/100 g/min. The deduced CBF value for gray matter fit the one given in (2) but are significantly lower than published results obtained with [O-15]H2O.

Schlussfolgerungen/Conclusions:

Our first measurements showed good image quality with the possibility of recognizing gray matter structures across the whole imaged area. The CBF quantification yielded values in partial agreement with the literature. Further work on the ASL quantification model needs to be done before validating the ASL results against [O-15]H2O PET measurements can be performed.

Literatur/References:

(1) Gunther, M., Bock, M., Schad, L. R., Magn. Reson. Med., 46:974-984, 2001.
(2) Petersen, E. T., Mouridsen, K., Golay, X., NeuroImage, 49:104-13, 2010

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2012, Bremen, D
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A10-A11

Permalink: https://www.hzdr.de/publications/Publ-17076
Publ.-Id: 17076


PT-symmetry, indefinite damping and dissipation-induced instabilities

Kirillov, O.

With perfectly balanced gain and loss, dynamical systems with indefinite damping can obey the exact PT-symmetry being marginally stable with a pure imaginary spectrum. At an exceptional point where the symmetry is spontaneously broken, the stability is lost via passing through a non-semi-simple 1: 1 resonance. In the parameter space of a general dissipative system, marginally stable PT-symmetric ones occupy singularities on the boundary of the asymptotic stability. To observe how the singular surface governs dissipation-induced destabilization of the PT-symmetric system when gain and loss are not matched, an extension of recent experiments with PT-symmetric LRC circuits is proposed

Keywords: PT-symmetry; indefinite damping; stability; dissipation-induced instabilities; modulational instability

Permalink: https://www.hzdr.de/publications/Publ-17075
Publ.-Id: 17075


Application of Ex-vessel Neutron Dosimetry Combined with In-core measurements for Correction of Neutron Source Used for RPV Fluence Calculations

Borodkin, P. G.; Borodkin, G. I.; Khrennikov, N. N.; Konheiser, J.

The paper deals with calculational and semi-analytical evaluations of VVER-1000 reactor core neutron source distributions and their influence on measurements and calculations of the integral through-vessel neutron leakage. Neutron activation measurements analyzed in the paper were carried out in ex-vessel air cavity at different NPP units with VVER-1000 during different fuel cycles. Time-integrated neutron source distributions used for DORT calculations were prepared by two different approaches based on a) calculated fuel burn-up (standard routine procedure) and b) in-core measurements by means of SPD & TC (new approach). Taking into account that fuel burn-up distributions in operating VVER may be evaluated now by analytical methods (calculations) only, it is needed to develop new approaches for testing and correction of calculational evaluations of neutron source. Results presented in this paper allow to consider a reverse task of alternative estimation of fuel burnup distributions. The approach proposed is based on adjustment (fitting) of time-integrated neutron source distributions, and hence fuel burn-up patterns in some part of reactor core, on the base of ex-core neutron leakage measurement, neutron-physical calculation and in-core SPD & TC measurement data.

Keywords: VVER-1000; DORT; TRAMO; Neutron activation measurements

Permalink: https://www.hzdr.de/publications/Publ-17074
Publ.-Id: 17074


Möglichkeiten der multimodalen Bildgebung in der Krebsdiagnostik

Stephan, H.

kein Abstract verfügbar

  • Invited lecture (Conferences)
    Universität Heidelberg, Institut für Anorganische Chemie, 16.03.2012, Heidelberg, D

Permalink: https://www.hzdr.de/publications/Publ-17072
Publ.-Id: 17072


Synthese und Charakterisierung von Cyclammonopropionsäure-Peptid-Konjugaten

Peschel, L.

kein Abstract verfügbar

  • Bachelor thesis
    FH Zittau/Görlitz, 2012
    64 Seiten

Permalink: https://www.hzdr.de/publications/Publ-17071
Publ.-Id: 17071


Synthese und Charakterisierung asymmetrischer multifunktionaler Cyclam-Liganden mittels Staudinger Ligation

Weißpflog, M.

kein Abstact verfügbar

  • Bachelor thesis
    HTW Dresden, 2012
    68 Seiten

Permalink: https://www.hzdr.de/publications/Publ-17070
Publ.-Id: 17070


Functional nanomaterials for multimodality cancer imaging

Stephan, H.

kein Abstract verfügbar

  • Lecture (others)
    OncoRay-Retreat 2012, 07.-08.03.2012, Dresden, D

Permalink: https://www.hzdr.de/publications/Publ-17069
Publ.-Id: 17069


Extraction Methods

Stephan, H.; Kubeil, M.; Gloe, K.; Gloe, K.

Molecular recognition, binding and transport of different chemical species represents an aspect of supramolecular chemistry that has relevance to a number of areas that include biochemical processes, analytical techniques, recycling and environmental processes as well as aspects of catalysis and medicine. Over the years, a large number of both efficient and selective receptors for cations, anions, salts and zwitterions based on different architectures and binding modes have been developed and studied.
Among the manifold experimental techniques employed for the application of such receptors has been the investigation of the distribution of species between two immiscible solutions, normally an aqueous and an organic phase, under the influence of the receptor in the organic phase. Such a procedure has often allowed characterization of the receptor’s complexation behavior towards individual species as well as enabling an evaluation of its suitability for species monitoring, separation and/or concentration; especially with respect to possible analytical applications as well as for use in extraction and membrane transport processes.

  • Book chapter
    C. A. Schalley (Ed.): Analytical Methods in Supramolecular Chemistry, 2nd, completely revised and enlarged edition, Weinheim: Wiley-VCH, 2012, 978-3-527-32982-3, 105-125

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-17068
Publ.-Id: 17068


Quantitative accuracy of MR based attenuation correction for PET - first experience with a whole-body PET/MR system

Schramm, G.; Langner, J.; Hofheinz, F.; Beuthien-Baumann, B.; Platzek, I.; Kotzerke, J.; Steinbach, J.; van den Hoff, J.

Ziel/Aim:

Combined whole body PET/MR systems have become commercially available recently. In 2010, one of the first of these systems (Philips Ingenuity TF PET/MR) has been installed at our institute. PET/MR is expected to offer new possibilities, in particular in the field of quantitative bimodal functional imaging (1). Quantitative PET image reconstruction requires attenuation correction (AC) which is commonly based on a direct measurement of photon attenuation using either a transmission scan with a Ge-68 radioactive source in standalone PET (TRAC) or a CT scan in PET/CT systems (CTAC). In PET/MR systems such a measurement cannot be performed. Hence, AC is performed with a software-based approach (MRAC) using dedicated tissue segmentation and tissue type identification (air, lung, soft tissue) of a MR image (2). Here, we report on a first evaluation of the accuracy of the manufacturer provided MRAC in whole body investigations with the Ingenuity TF PET/MR.

Methodik/Methods:

An evaluation of MRAC was performed by a direct comparison of the MR derived attenuation maps with transmission based attenuation maps acquired with a Siemens ECAT Exact HR+ PET system for 10 patients (8m/2f). We compared the pairs of coregistered attenuation maps in a voxel by voxel correlation analysis in the lung and the torso. In order to assess the influence of differences between the two AC methods on the resulting emission images we developed methods allowing to reconstruct PET emission data acquired at the PET/MR using the transmission based attenuation maps from the HR+ PET .

Ergebnisse/Results:

Our correlation analysis has shown that approximately 80% of the voxels in the lung and torso are in quantitative agreement. In one case, the MRAC algorithm failed to correctly detect the lung of the patient. In a further investigation, we observed metal artifacts resulting in distorted MR-derived attenuation maps.

Schlussfolgerungen/Conclusions:

The vendor-provided MRAC algorithm generally yields satisfactory results with respect to soft tissue and air segmentation. However, the algorithm relies on anatomic reference data and thus artifacts can arise if the anatomy of the patient does not fit to the reference. Additionally, metal artifacts can lead to distortion of the MR based attenuation maps.

Literatur/References:

(1) Pichler, B.J. et al., Sem. Nucl. Med., 38:199-208, 2008
(2) Martinez-Möller, A. et al., J. Nucl. Med., 50:520-526, 2009

  • Invited lecture (Conferences)
    50. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 25.-28.04.2012, Bremen, D
  • Abstract in refereed journal
    Nuklearmedizin 51(2012), A79

Permalink: https://www.hzdr.de/publications/Publ-17067
Publ.-Id: 17067


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