Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31745 Publications
On sampling bias in multiphase flows: Particle image velocimetry in bubbly flows
Ziegenhein, T.; Lucas, D.;
Measuring the liquid velocity and turbulence parameters in multiphase flows is a challenging task. In general, measurements based on optical methods are hindered by the presence of the gas phase. In the present work, it is shown that this leads to a sampling bias. Here, particle image velocimetry (PIV) is used to measure the liquid velocity and turbulence in a bubble column for different gas volume flow rates. As a result, passing bubbles lead to a significant sampling bias, which is evaluated by the mean liquid velocity and Reynolds stress tensor components. To overcome the sampling bias a window averaging procedure that waits a time depending on the locally distributed velocity information (hold processor) is derived. The procedure is demonstrated for an analytical test function. The PIV results obtained with the hold processor are reasonable for all values. By using the new procedure, reliable liquid velocity measurements in bubbly flows, which are vitally needed for CFD validation and modeling, are possible. In addition, the findings are general and can be applied to other flow situations and measuring techniques.
Keywords: velocity measurement, sampling bias, multiphase flow, bubbly flow, particle image velocimetry, turbulence measurement

Publ.-Id: 22056 - Permalink


Dilute ferromagnetic semiconductors prepared by the combination of ion implantation with pulse laser melting
Zhou, S.;
Combining semiconducting and ferromagnetic properties, dilute ferromagnetic semiconductors (DFS) have been under intensive investigation for more than two decades. Mn doped III–V compound semiconductors have been regarded as the prototype of DFS from both experimental and theoretic investigations. The magnetic properties of III–V:Mn can be controlled by manipulating free carriers via electrical gating, as for controlling the electrical properties in conventional semiconductors. However, the preparation of DFS presents a big challenge due to the low solubility of Mn in semiconductors. Ion implantation followed by pulsed laser melting (II-PLM) provides an alternative to the widely used low-temperature molecular beam epitaxy (LT-MBE) approach. Both ion implantation and pulsed-laser melting occur far enough from thermodynamic equilibrium conditions. Ion implantation introduces enough dopants and the subsequent laser pulse deposit energy in the near-surface region to drive a rapid liquid-phase epitaxial growth. Here, we review the experimental study on preparation of III–V:Mn using II-PLM. We start with a brief description about the development of DFS and the physics behind II-PLM. Then we show that ferromagnetic GaMnAs and InMnAs films can be prepared by II-PLM and they show the same characteristics of LT-MBE grown samples. Going beyond LT-MBE, II-PLM is successful to bring two new members, GaMnP and InMnP, into the family of III–V:Mn DFS. Both GaMnP and InMnP films show the signature of DFS and an insulating behavior. At the end, we summarize the work done for Ge:Mn and Si:Mn using II-PLM and present suggestions for future investigations. The remarkable advantage of II-PLM approach is its versatility. In general, II-PLM can be utilized to prepare supersaturated alloys with mismatched components.
Keywords: Magnetic semiconductors; Ion implantation

Publ.-Id: 22055 - Permalink


Bildgebende Messverfahren für thermohydraulische Experimente in der Reaktorsicherheitsforschung
Hampel, U.;
Thermohydraulische Phänomene im Kühlkreislauf von Kernkraftwerken sind ein wichtiges Teilgebiet der Reaktorsicherheitsforschung. Relevante Fragestellungen umfassen die Strömung und Wärmeübertragung von den Brennstäben im Reaktorkern bis zum Dampferzeuger im Reaktornormalbetrieb, Probleme der Vermischung, Strömung und Wärmeabfuhr bei Auslegungsstörfällen und schweren Störfällen bis hin zur sicheren Funktion passiver Nachzerfallswärmeabfuhrmechanismen. Während heute die zugrundeliegenden Strömungs- und Wärmetransportprozesse oft mit Systemcodes berechnet werden, geht ein Trend hin zur Anwendung geometrieunabhängiger, dreidimensional auflösender CFD-Verfahren. Besondere Schwierigkeiten bereiten hierbei die Maßstabübertragung vom Laborexperiment an Einzelkomponenten hin zur Gesamtanlage sowie die Komplexität von Zweiphasenströmungen, die insbesondere im Störfall vorherrschend sind. Die Entwicklung von Strömungsberechnungsverfahren ebenso wie das grundlegende Verständnis von Strömungsphänomenen erfordern Experimente mit hohem Detaillierungsgrad, die aber gleichzeitig wegen der Übertragbarkeit bei anlagenrelevanten Prozessparametern und Stoffwerten führen sind. Insbesondere Experimente zu Zweiphasenströmungen erfordern darüber hinaus eine Instrumentierung, die Strömungsstrukturen mit möglichst hoher räumlicher und zeitlicher Auflösung wiedergibt. Hierzu eignen sich insbesondere bildgebende Messverfahren. Der Vortrag gibt eine Einführung in wichtige, in diesem Bereich verwendete Mess- und Bildgebungsverfahren und demonstriert deren Anwendung im Kontext der Reaktorsicherheitsforschung.
Keywords: Bildgebende Messverfahren, Reaktorsicherheitsforschung, Thermohydraulik
  • Invited lecture (Conferences)
    Aachener Kerntechnisches Kolloquium, 02.06.2015, Aachen, Deutschland

Publ.-Id: 22054 - Permalink


Flow Phenomena in Liquid Metal Batteries
Weier, T.; Galindo, V.; Stefani, F.; Weber, N.;
Liquid metal batteries (LMBs) are high temperature systems consisting of liquid metal electrodes and a molten salt ionic conductor. The densities are chosen in such a way that a stable density stratification of the inmiscible layers results. LMBs were considered mainly as part of energy conversion systems in the 1960s \ and have only recently received renewed interest for economic large-scale storage. Our work concentrates on the fluid dynamic aspects of this cell type with a special focus on the effects and properties of the Tayler instability (TI).
Due to the completely liquid interior of LMBs, fluid flow is an important aspect of their operation. It can be beneficial, when enhancing mass transfer in the cathode, or it might have harmful consequences, if the integrity of the electrolyte layer is disrupted.
The latter case can result form the action of the current-driven TI. We therefore studied the characteristics of the TI depending on the cell's aspect ratio using an integro-differential approach implemented in the open source library OpenFOAM. The TI occurs if a critical value of a dimensionless parameter Ha is exceeded. Ha, the Hartmann number, is in our case solely determined by the total current I and the material properties density, kinematic viscosity, and electrical conductivity. The critical Ha is lowest for an infinitely high cuboid and corresponds to a total current of approx. 1 kA in the case of Na. Decreasing the aspect ratio increases Hacrit since the wavelength selection for the TI becomes more and more restricted.
Current densities in LMBs are typically very high. A current density of 10 kA/m2 is a characteristic value for a Na|NI-NaCl-NaF|Bi-system and results in an approximately 10 mm thick sodium layer transferred per hour from the anodic to the cathodic compartment. Depending on the design capacity and cell area, aspect ratios of the anodic compartment up to one seem imaginable.
Keywords: liquid metal batteries, Tayler instability
  • Lecture (Conference)
    Energy, Science and Technology Conference 2015 (EST 2015), 20.-22.05.2015, Karlsruhe, Deutschland

Publ.-Id: 22053 - Permalink


"Energie-Allianz Energieeffiziente Chemische Mehrphasenprozesse": Forschung für effiziente chemische Prozesse
Hampel, U.;
Energieeffizienz ist ein wesentlicher Baustein nachhaltigen Wirtschaftens und unabdingbare Voraussetzung zur Erreichung aktueller klimapolitischer Ziele. Die von der Helmholtz-Gemeinschaft Deutscher Forschungszentren geförderte Energie-Allianz „Energieeffiziente chemische Mehrphasenprozesse“ bündelt Kompetenzen und Forschungsaktivitäten im Bereich der chemischen Verfahrenstechnik mit dem Ziel der Weiterentwicklung von Entwurfs- und Auslegungsmethoden, numerischen und experimentellen Techniken sowie neuer Messeverfahren zur Effizienzsteigerung chemischer Mehrphasenprozesse. Der Vortrag führt in wesentliche Zielstellungen, Methoden und Ergebnisse der von sechs deutschen Forschungseinrichtungen getragenen Allianz ein. Insbesondere werden die Themen Systemanalysen für chemische Prozesse, neue Prozessfenster und Katalysatoren, Wärmeintegration, optimale Prozessführungskonzepte, strukturierte Reaktoren, Hydroydynamik mehrphasiger Reaktionen, fortgeschrittene CFD-Modellierung reaktiver Mehrphasenprozesse und innovative Mehrphasen und Prozessanalyse-Messtechniken für behandelt.
Keywords: Chemische Industrie, Prozesseffizienz, Energieeffizienz, Prozessintensivierung, Mehrphasen-Prozesstechnik
  • Invited lecture (Conferences)
    ACHEMA, 15.-19.06.2015, Frankfurt, Deutschland

Publ.-Id: 22052 - Permalink


Efficient multiphase chemical processes – from advanced modelling, simulation and measurement to novel reactor concepts and technologies
Hampel, U.; Kryk, H.; Schubert, M.; Lucas, D.; Dittmeyer, R.; Patyk, A.; Dietrich, B.; Wörner, M.; Lange, R.; Freund, H.; Schwieger, W.; Grünewald, M.; Schlüter, M.; Petasch, U.;
The chemical and process industry is one of the major industrial consumers of primary energy resources worldwide. Hence, this industry is especially concerned with rising energy prices and demands for reduction of greenhouse gas emissions [1]. In recent years, many advances in energy efficiency have been made especially in the production of bulk chemicals. Efficient heat recovery, efficient plant and production structures as well as improved synthesis routes and catalysts are examples for that. A further increase of efficiency is hardly achievable by simple improvements and game-changing technologies will most possibly only punctually come up. Gradual improvement of processes and equipment still has the highest potential to achieve a broader impact, particularly if a methodological base for optimal process designs is developed that can be applied to many of the different processes and process classes in chemical production.
Keywords: Process Efficiency, Energy Efficiency, Chemical Industry, Process Intensification
  • Lecture (Conference)
    Energy Science Technology 2015, 20.-22.05.2015, Karlsruhe, Deutschland

Publ.-Id: 22051 - Permalink


Synthesis and Molecular Structure of 2-(Diphenylphosphano) phenyl Benzoate Borane Adduct
Mamat, C.; Köckerling, M.;
The crystal and molecular structure of 2-(diphenylphosphano) phenyl benzoate borane adduct are reported. The title compound crystallizes from a petroleum ether/ethyl acetate mixture in the triclinic space group P (1) over bar with two molecules in the unit cell. The unit cell parameters are: a = 8.67(1) angstrom, b = 9.202(1) angstrom, c = 14.224(2) angstrom; a = 72.600(7)degrees, beta = 73.577(7)degrees, gamma = 84.349(7)degrees and V = 1039.5(2) angstrom(3). Bond lengths and angles are typical for this phosphane borane adduct.

Publ.-Id: 22050 - Permalink


DAP12-Based Activating Chimeric Antigen Receptor for NK Cell Tumor Immunotherapy
Toepfer, K.; Cartellieri, M.; Michen, S.; Wiedemuth, R.; Mueller, N.; Lindemann, D.; Bachmann, M.; Fuessel, M.; Schackert, G.; Temme, A.;
NK cells are emerging as new effectors for immunotherapy of cancer. In particular, the genetic engraftment of chimeric Ag receptors (CARs) in NK cells is a promising strategy to redirect NK cells to otherwise NK cell-resistant tumor cells. On the basis of DNAX-activation protein 12 (DAP12), a signaling adaptor molecule involved in signal transduction of activating NK cell receptors, we generated a new type of CAR targeting the prostate stem cell Ag (PSCA). We demonstrate in this article that this CAR, designated anti-PSCA-DAP12, consisting of DAP12 fused to the anti-PSCA single-chain Ab fragment scFv(AM1) confers improved cytotoxicity to the NK cell line YTS against PSCA-positive tumor cells when compared with a CAR containing the CD3ζ signaling chain. Further analyses revealed phosphorylation of the DAP12-associated ZAP-70 kinase and IFN-γ release of CAR-engineered cells after contact with PSCA-positive target cells. YTS cells modified with DAP12 alone or with a CAR bearing a phosphorylation-defective ITAM were not activated. Notably, infused YTS cells armed with anti-PSCA-DAP12 caused delayed tumor xenograft growth and resulted in complete tumor eradication in a significant fraction of treated mice. The feasibility of the DAP12-based CAR was further tested in human primary NK cells and confers specific cytotoxicity against KIR/HLA-matched PSCA-positive tumor cells, which was further enhanced by KIR-HLA mismatches. We conclude that NK cells engineered with DAP12-based CARs are a promising tool for adoptive tumor immunotherapy.

Publ.-Id: 22049 - Permalink


A promising PET tracer for imaging of α7 nicotinic acetylcholine receptors in the brain: Design, synthesis, and in vivo evaluation of a dibenzothiophene-based radioligand
Teodoro, R.; Scheunemann, M.; Deuther-Conrad, W.; Wenzel, B.; Colombo, S.; Gotti, C.; Kranz, M.; Donat, C.; Patt, M.; Hillmer, A.; Zheng, M.; Peters, D.; Steinbach, J.; Sabri, O.; Huang, Y.; Brust, P.;
Changes in the expression of α7 nicotinic acetylcholine receptors (α7 nAChRs) in the human brain are widely assumed to be associated with neurological and neurooncologial processes. Investigation of these receptors in vivo depends on the availability of imaging agents such as radioactively labelled ligands applicable in positron emission tomography (PET).
We report on a series of new ligands for α7 nAChRs designed by combination of dibenzothiophene-dioxide as novel hydrogen bond acceptor functionality with diazabicyclononane as an established cationic center. To assess the structure-activity relationship (SAR) of this new basic structure, we further modified the cationic center systematically by introduction of three different piperazine-based scaffolds. Based on in vitro binding affinity and selectivity, assessed by radioligand displacement studies at different nAChR subtypes, we selected compound 10a (7-(1,4-diazabicyclo[3.2.2]nonan-4-yl)-2-fluorodibenzo[b,d]thiophene 5,5-dioxide) for radiolabeling and further evaluation in vivo. Radiosynthesis of [18F]10a was optimized manually and then transferred to an automated module. Dynamic PET imaging studies with [18F]10a in piglets and a monkey demonstrated robust uptake of radioactivity in the brain, followed by washout and target-region specific accumulation by the radioligand under baseline conditions. Kinetic analysis of [18F]10a in pig was performed using a two-tissue compartment model with arterial-derived input function and non-displaceable binding potential (BPND) values were estimated in various brain regions. Our initial evaluation revealed that the dibenzothiophene-based PET radioligand [18F]10a has high potential to provide clinically relevant information about the expression and availability of α7 nAChR in the brain.

Publ.-Id: 22048 - Permalink


Re–Os geochronology on sulfides from the Tudun Cu–Ni sulfide deposit, Eastern Tianshan, and its geological significance
Gutzmer, J.; Wang, M.; Wang, W.; Liu, K.; Li, C.; Przemyslaw, P. M.; Xia, Q.; Guo, X.;
The Tudun deposit is a medium-sized Cu–Ni sulfide deposit, located at the westernmost edge of the Huangshan–Jing’erquan Belt in the northern part of Eastern Tianshan, NW China. Sulfide separates including pentlandite, pyrrhotite and chalcopyrite from the Tudun deposit, contain Re, common Os and 187Os ranging from 40.46 to 201.2, 0.8048 to 6.246 and 0.1709 to 0.9977 ppb, respectively. They have very low 187Os/188Os ratios of 1.224–2.352. The sulfides yield a Re–Os isochron age of 270.0 ± 7.5 Ma (MSWD = 1.3), consistent within uncertainty with the SHRIMP zircon U–Pb age for the Tudun mafic intrusion (gabbro) of 280.0 ± 3.0 Ma. The calculated initial 187Os/188Os ratio is 0.533 ± 0.022, and γOs values range from 283 to 307, with a mean of 297, indicating significant crustal contamination of the parent melt prior to sulfide saturation. The Tudun deposit shares the same age and Re–Os isotopic compositions with other orthomagmatic Cu–Ni sulfide deposits in Huangshan–Jing’erquan Belt, suggesting that they have formed in Early Permian.
Keywords: Tudun Cu–Ni deposit, Re–Os, geochronology, Early Permian, Eastern Tianshan

Publ.-Id: 22047 - Permalink


Sputter yield of curved surfaces
Urbassek, H. M.; Bradley, R. M.; Nietiadi, M. L.; Möller, W.;
The mean sputter yield produced by the impact of a single ion depends on the radii of curvature of the target surface at the point of impact. Using the Sigmund model of ion sputtering, we develop analytical formulas for this dependence for the case in which the radii of curvature are large compared to the size of the ion-induced collision cascade; both locally perpendicular and oblique ion impact are considered. The sputter yield is increased for impact on convex surfaces. The influence of surface curvature along the incident-ion azimuth and perpendicular to it are discussed separately. Our analytical results are in good agreement with Monte Carlo simulations for the specific case of 20 keV Ar ion impact on a cylindrical nanowire consisting of amorphous silicon. We also extend the results for this case to small radii of curvature using both Monte Carlo and molecular dynamics simulations.
Keywords: MOLECULAR-DYNAMICS; COMPUTER-SIMULATION; NANOPARTICLES; IONS; BOMBARDMENT; CLUSTERS; SILICON; PROGRAM; SOLIDS; REGION

Publ.-Id: 22046 - Permalink


CuII-selective bispidine–dye conjugates
Bronx, D.; Comba, P.; Herten, D.-P.; Kimmle, E.; Morgen, M.; Rühl, C. L.; Rybina, A.; Stephan, H.; Storch, G.; Wadepohl, H.;
The substitution of tetradentate bispidine ligands with rhodamine and cyanine dye molecules, coupled to an amine donor, forming an amide as potential fifth donor, is described. Bispidines are known to lead to very stable CuII complexes, and the coordination to CuII was expected toefficiently quench the fluorescence of dyemolecules. However, at physiological pH the amide is not coordinated, as shown by titration experiments and crystallographic structural data of three possible isomers of these complexes. This may be due to the specific cavity shape of bispidines and the Jahn–Teller lability of the CuII center. While CuII coordination in aqueous solution leads to efficient fluorescence quenching, experiments show that the complex stabilities are not large enough for CuII sensing in biological media, and possibilities are discussed, how this may be achieved by optimized bispidine–dye conjugates.

Publ.-Id: 22045 - Permalink


Investigation of the flow driven by an alternating magnetic field
Cramer, A.; Galindo, V.; Zennaro, M.; Eckert, S.;
The flow induced by a single-phase alternating magnetic field is studied numerically and in a physical model. It is shown that the flow structure depends drastically on the frequency of the field, owing to a changeover of the rotor of the Lorentz force in the corners from a single local maximum to a pair of local maxima, one in close vicinity of another, with different signs of vorticity.
Keywords: Alternating magnetic field, ultrasonic flow measurements, convective pattern, vorticity
  • Contribution to proceedings
    8th International Conference on Electromagnetic Processing of Materials, 12.-16.10.2015, Cannes sur Mer, France
    Proceedings of the 8th International Conference on Electromagnetic Processing of Materials, 978-2-9553861-0-1, 291-294
  • Lecture (Conference)
    8th Internatinal Conference on Electromagnetic Processing of Materials, 12.-16.10.2015, Cannes sur Mer, France

Publ.-Id: 22044 - Permalink


Phenol degradation by environmental bacteria entrapped in cryogels
Satchanska, G.; Topalova, Y.; Dimkov, R.; Groudeva, V.; Petrov, P.; Tsvetanov, C.; Selenska-Pobell, S.; Golovinsky, E.;
The aim of this study was to assess the capability of bacterial isolates immobilized on poly(ethylene oxide) (PEO) cryogels to degrade and utilize phenol as a sole source of carbon and energy. Two xenobiotic-degrading bacteria were isolated from industrial areas polluted with heavy metals and aromatics. Sequencing of their 16S rDNA classified them as Pseudomonas rhodesiae (denoted as KCM R-5) and Bacillus subtilis (denoted as KCM RG(5)). The following operation parameters were used: sequencing batch process, 24 h cycle of feeding, increasing phenol concentrations from 300 to 1000 mg center dot L-1, volume of inflow - 250 mL, volume of outflow - from 212 to 7 mL and temperature of 28 degrees C. The PEO-KCM R-5 biofilter was found to remove phenol at a concentration of 1000 mg center dot L-1, while the PEO-KCM RG(5) system was unable to degrade phenol at a concentration of about 600 mg center dot L-1. After four weeks of biodegradation, the PEO biofilms remained compact, porous and elastic, while containing compact microbial biofilm as shown by scanning electron microscopy analysis of the cryogels. Taken together, our results demonstrate that our novel bacterial entrapment system in PEO cryogels is highly effective and sustainable for phenol degradation and can be relevant for application in the detoxification technologies of industrially polluted waters.
Keywords: polluted environment; bacteria; 16S rDNA gene; phenol biodegradation; immobilization; cryogel

Publ.-Id: 22043 - Permalink


Synthesis and optical characterization of Gd-neso-borate single crystals
Reuther, C.; Möckel, R.; Götze, J.; Hengst, M.; Heide, G.;
Single crystals of Ca4GdO[BO3]3 and Sr3Gd2[BO3]4 were synthesized using the Czochralski method, both in different crystallographic directions. Best result were obtained for View the MathML source010 orientated seeds and growth rates of 1 mmh−1. The morphology of the as-grown crystals reflects the symmetry and for Ca4GdO[BO3]3-crystals a typical rhombohedral and for Sr3Gd2[BO3]4-crystals almost circular cross section are formed. UV–VIS and IR measurements show a wide range of transmission of light. Between 350–1100 and 1600–2500 nm no absorption was observed. Below 350 nm the crystals show distinct absorption peaks caused by electron transitions of Gd. In the IR region most vibration modes can be assigned to [BO3]3−-groups and Gd/Ca-O or Gd/Sr-O-polyhedra.
Keywords: Crystal growth; Sr3Gd2[BO3]4; Ca4GdO[BO3]3; Spectroscopy; Optics; SGB; GdCOB; Borate

Publ.-Id: 22042 - Permalink


The interaction of Eu(III) with organoborates – a further approach to understand the complexation in the An/Ln(III)–borate system
Schott, J.; Kretzschmar, J.; Tsushima, S.; Drobot, B.; Acker, M.; Barkleit, A.; Taut, S.; Brendler, V.; Stumpf, T.;
The formation equilibria of salicylatoborate, lactatoborate and 3-hydroxybutyratoborate were studied by means of 11B NMR spectroscopy. The smaller the pKa of the respective organic acid, the higher is the formation constant of the organoborate. The complexation of Eu(III) with salicylatoborate and lactatoborate was investigated by means of TRLFS (time-resolved laser-induced fluorescence spectroscopy) and 11B NMR spectroscopy, yielding complexation constants lg β0(11) = 2.6–3.2. A Eu(III)–3-hydroxybutyrate complex was characterized by TRLFS and 1H NMR spectroscopy (lg β0(11) = 2.89). DFT calculations of the investigated Eu(III)–organoborates and inorganic Eu(III)–(poly)borates provided information about the Eu(III) coordination (most likely chelate). They support the hypothesis that the complexation of Eu(III) with organic as well as inorganic borate structures containing the binding site “B(OR)4−” (R = H, threefold coordinated boron center(s), organic moiety) is comparable.

Publ.-Id: 22041 - Permalink


Smart Kd-values, their uncertainties and sensitivities - Applying a new approach for realistic distribution coefficients in geochemical modeling of complex systems
Stockmann, M.; Schikora, J.; Becker, D.-A.; Flügge, J.; Noseck, U.; Brendler, V.;
One natural retardation process to be considered in risk assessment for contaminants in the environment is sorption on mineral surfaces. A realistic geochemical modeling is of high relevance in many application areas such as groundwater protection, environmental remediation, or disposal of hazardous waste. Most often concepts with constant distribution coefficients (Kd-values) are applied in geochemical modeling with the advantage to be simple and computationally fast, but not reflecting changes in geochemical conditions.
In this paper, we describe an innovative and efficient method, where the smart Kd-concept, a mechanistic approach mainly based on surface complexation modeling, is used (and modified for complex geochemical models) to calculate and apply realistic distribution coefficients. Using the geochemical speciation code PHREEQC, multidimensional smart Kd-matrices are computed as a function of varying (or uncertain) environmental conditions. On the one hand, sensitivity and uncertainty statements for the distribution coefficients can be derived. On the other hand, smart Kd-matrices can be used in reactive transport (or migration) codes (not shown here). This strategy has various benefits: (1) rapid computation of Kd-values for large numbers of environmental parameter combinations; (2) variable geochemistry is taken into account more realistically; (3) efficiency in computing time is ensured, and (4) uncertainty and sensitivity analysis are accessible.
Results are presented exemplarily for the sorption of uranium(VI) onto a natural sandy aquifer material and are compared to results based on the conventional Kd-concept. In general, the sorption behavior of U(VI) in dependence of changing geochemical conditions is described quite well.
Keywords: Distribution coefficient; Risk assessment; Sensitivity; Smart Kd-concept; Uranium

Publ.-Id: 22040 - Permalink


Contactless inductive bubble detection in a liquid metal column
Gundrum, T.; Büttern, P.; Peyton, A.; Dekdouk, B.; Wondrak, T.; Eckert, S.;
The detection of bubbles in liquid metal is important for many technical applications. The opaqueness and the high temperature of liquid metals set high demands on the measurement system. The electrical conductivity of the liquid metal is relatively high, which can be exploited with contactless methods based on electromagnetic induction. We will present a measurement system which consists of one transmitting coil and a planar gradiometer on opposite sides of the pipe. With this sensor we were able to detect bubbles in a sodium flow inside a stainless steel pipe.
Keywords: bubble detection, two phase flow, liquid metal, inductive contactless measurement, void fraction
  • Contribution to proceedings
    8th International Conference on Electromagnetic Processing of Materials, 12.-16.10.2015, Cannes, Frankreich
    sciencesconf.org:epm2015:53627
  • Poster
    8th International Conference on Electromagnetic Processing of Materials, 12.-16.10.2015, Cannes, Frankreich

Publ.-Id: 22039 - Permalink


Contactless inductive bubble detection in a liquid metal column
Gundrum, T.; Büttern, P.; Dekdouk, B.; Peyton, A. J.; Wondrak, T.; Galindo, V.; Eckert, S.;
The detection of bubbles in liquid metals is important for many technical applications like for continuous casting and for liquid metal cooled reactors. The opaqueness and the high temperature of liquid metals set high demands on the measurement system. Exploiting the high electrical conductivity contactless electromagnetic methods can be used. For instance, Mutual Inductance Tomography is able to visualize the distribution of gas and liquid metal in one cross section of a pipe using a sensor array of 8 induction coils.
Keywords: bubble detection, two phase flow, liquid metal, inductive contactless measurement, void fraction
  • Lecture (Conference)
    3rd International Workshop on Measuring Techniques for Liquid Metal Flows (MTLM2015), 15.-17.04.2015, Dresden, Deutschland

Publ.-Id: 22038 - Permalink


Electrically driven flows and instabilities in liquid metal batteries
Weier, T.; Galindo, V.; Kasprzyk, C.; Stefani, F.; Weber, N.;
Liquid metal batteries are currently discussed as a means to economic large scale energy storage. They consist of three fluid layers in stable density stratification. This fully liquid arrangement relies on the stable stratification to remain intact in order to function properly. Fluid motion has the potential to disrupt the molten salt layer sandwiched in-between the upper and lower metal electrodes. A situation like this would result in an internal short-circuit and thus in a malfunction of the cell. We consider here two electromagnetic flow driving mechanisms: the Tayler instability and rotational Lorentz force distributions leading to electro-vortex flows. In a simplified setting, the stabilization of the electrolyte layer can be described fairly well by the ratio of potential to kinetic energy, i.e., the Richardson number.
Keywords: liquid metal batteries, electro-vortex flows, Richardson number, Tayler instability
  • Lecture (Conference)
    8th International Conference on Electromagnetic Processing of Materials, 12.-16.10.2015, Cannes, Frankreich
  • Contribution to proceedings
    8th International Conference on Electromagnetic Processing of Materials, 12.-16.10.2015, Cannes, Frankreich
    Proc. 8th Int. Conf. on Electromagnetic Processing of Materials EPM2015, 978-2-9553861-0-1, 163-166

Publ.-Id: 22037 - Permalink


Design of Radioligands for PET Imaging of Neuropsychiatric Diseases
Brust, P.;
Es ist kein Abstract vorhanden.
  • Invited lecture (Conferences)
    Kolloquium an der Universität Mannheim, Central Institute of Mental Health, 29.09.2015, Mannheim, Deutschland

Publ.-Id: 22036 - Permalink


Experimentally constrained (p,γ)89Y and (n,γ)89Y reaction rates relevant to the p-process nucleosynthesis
Larsen, A. C.; Guttormsen, M.; Schwengner, R.; Bleuel, D. L.; Goriely, S.; Harissopulos, S.; Bello Garrote, F. L.; Bernstein, L. A.; Byun, Y.; Eriksen, T. K.; Giacoppo, F.; Görgen, A.; Hagen, T. W.; Klintefjord, M.; Nyhus, H. T.; Renstrøm, T.; Rose, S. J.; Sahin, E.; Siem, S.; Tornyi, T. G.; Tveten, G. M.; Voinov, A. V.; Wiedeking, M.;
Nuclear level densities and γ-ray strength functions have been extracted for 89,90Y, using the Oslo Method on data sets from the 89Y(p,p')89Y and 89Y(d,p)90Y reactions. The γ-ray strength functions display a low-energy enhancement consistent with previous observations in this mass region (93-98Mo). Shell-model calculations give support that the observed enhancement is due to strong, low-energy M1 transitions at high excitation energies. The data were further used as input for calculations of the 88 Sr(p,γ)89Y, 88Y(n,γ)89Y, and 89Y(n,γ)90Y cross sections with the TALYS reaction code. Comparison with cross-section data, when available, shows a satisfying agreement, as well as with values from the BRUSLIB library.
Keywords: Electromagnetic strength functions, level densities, nuclear reactions, shell model, statistical model.

Publ.-Id: 22035 - Permalink


Hyperspectral remote sensing exploration of carbonatite – an example from Epembe, Kunene region, Namibia
Zimmermann, R.; Brandmeier, M.; Andreani, L.; Gloaguen, R.;
Remote sensing data can provide valuable information about ore deposits and their alteration zones at surface level. High spectral and spatial resolution of the data is essential for detailed mapping of mineral abundances and related structures.

Carbonatites are well known for hosting economic enrichments in REE, Ta, Nb and P (Jones et al. 2013). These make them a preferential target for exploration for those critical elements. In this study we show how combining geomorphic, textural and spectral data improves classification result. We selected a site with a well-known occurrence in northern Namibia: the Epembe dyke. For analysis LANDSAT 8, SRTM and airborne hyperspectral (HyMap) data were chosen. The overlapping data allows a multi-scale and multi-resolution approach. Results from data analysis were validated during fieldwork in 2014.

Data was corrected for atmospherical and geometrical effects. Image classification, mineral mapping and tectonic geomorphology allow a refinement of the geological map by lithological mapping in a second step. Detailed mineral abundance maps were computed using spectral unmixing techniques. These techniques are well suited to map abundances of carbonate minerals, but not to discriminate the carbonatite itself from surrounding rocks with similar spectral signatures. Thus, geometric indices were calculated using tectonic geomorphology and textures. For this purpose the TecDEM-toolbox (SHAHZAD & GLOAGUEN 2011) was applied to the SRTM-data for geomorphic analysis. Textural indices (e.g. uniformity, entropy, angular second moment) were derived from HyMap and SRTM by a grey-level co-occurrence matrix (CLAUSI 2002). The carbonatite in the study area is ridge-forming and shows a narrow linear feature in the textural bands.

Spectral and geometric information were combined using kohonen Self-Organizing Maps (SOM) for unsupervised clustering. The resulting class spectra were visually compared and interpreted. Classes with similar signatures were merged according to geological context.

The major conclusions are:
1. Carbonate minerals can be mapped using spectral unmixing techniques.
2. Carbonatites are associated with specific geometric pattern
3. The combination of spectral and geometric information improves classification result and reduces misclassification.

References
Clausi, D. A. (2002): An analysis of co-occurrence texture statistics as a function of grey-level quantization. - Canadian Journal of Remote Sensing, 28 (1), 45-62
Jones, A. P., Genge, M. and Carmody, L (2013): Carbonate Melts and Carbonatites. - Reviews in Mineralogy & Geochemistry, 75, 289–322
Shahzad, F. & Gloaguen, R. (2011): TecDEM: A MATLAB based toolbox for tectonic geomorphology, Part 2: Surface dynamics and basin analysis. - Computers & Geosciences, 37 (2), 261-271
  • Poster
    EGU General Assembly 2015, 14.04.2015, Wien, Österreich

Publ.-Id: 22034 - Permalink


Ultra-fast data processing and image reconstruction using parallel processing architectures
Bieberle, A.; Vogt, S.; Wagner, M.; Bieberle, M.; Barthel, F.; Hampel, U.;
An ultra-fast electron beam X-ray tomography measuring system (Fischer et al., 2008) was developed at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) that is prior applied to fundamental multiphase flow investigations, e.g. in various technical devices, and for validation of enhanced flow simulation models, e.g. developed for computational fluid dynamic codes (CFD). The ultra-fast computed tomography (CT) system delivers contactless cross-sectional material distributions with a spatial resolution of approximately 1 mm and a temporal resolution of max. 8 kHz. Currently, both measuring data transfer as well as data processing has been identified as the most time consuming processes that have to be tackled to ensure an optimal use of that worldwide unique CT technique. As a first step, the data reconstruction algorithm is transferred to many-core graphics processing units (GPUs) using the so called ultra-fast X-ray imaging UFO framework (in this case: the filtered back projection algorithm). Subsequently, most of the data processing algorithms, originally implemented as sequentially executed code on single-core central processing units (CPUs), are adapted for both multi-core CPUs and, eventually, many-core GPUs application. To increase the performance improvements once more, an advanced performance PC (AP-PC) with two parallel operated high performance graphics processing units (Tesla K20c, NVIDIA®), a six-core processor (Xeon E5-1650 v3, Intel®) and a high data bus speed and memory and transfer volume (DDR4, 2133 MHz, 128 GByte) is assembled. Thus, data processing performance could be improved again using the specifically assembled hardware configurations. The timing results show that an optimized multi-core CPU-based code increases the data processing performance by a factor of 40. Moreover, the applied many-core GPU-optimized code, including the AP-PC hardware configuration adaptions, led to a data processing performance improvement factor of 138.
Keywords: computed tomography, many-core graphics processing units, multi-core central processing units, massive parallel data processing
  • Contribution to proceedings
    7th International Symposium on Process Tomography, 01.-03.09.2015, Dresden, Deutschland
    Proceedings of the 7th International Symposium on Process Tomography
  • Poster
    7th International Symposium on Process Tomography, 01.-03.09.2015, Dresden, Deutschland

Publ.-Id: 22033 - Permalink


Simulation und Parameterschätzung von 22Na-Diffusion in einem Opalinuston-Bohrkern mittels COMSOL Multiphysics und GeoPET-Datenabgleich
Gerasch, R.;
Es ist kein Abstract vorhanden.
  • Master thesis
    BTU-Cottbus-Senftenberg, 2015
    Mentor: Prof. Dr. Peer Schmidt (BTU) , Dr. J. Lippmann-Pipke (HZDR)
    89 Seiten

Publ.-Id: 22032 - Permalink


Application of the ultrasound Doppler velocimetry in model experiments for casting and solidification
Räbiger, D.; Vogt, T.; Timmel, K.; Franke, S.; Willers, B.; Gerbeth, G.; Eckert, S.;
The optimisation of methods and facilities for material processing technologies such as melting, refining or casting of metals or alloys has to be considered as an enduring challenge. Key issues are an improvement of the final product quality, an enhancement of the process efficiency and an economical consumption of resources and energy. Further advancement often requires a better knowledge with respect to the details of the flow structure, the heat and mass transfer properties of the flow especially during phase transitions like melting or solidification. Experimental studies on industrial scale with hot metallic melts (T > 600°C) may require formidable effort and expense. Cost-saving model experiments using low melting point metallic melts permit detailed investigations of the flow structure and related problems with a high grade of flexibility. Experiments at room temperature are possible using the ternary alloy GaInSn. The ultrasound Doppler velocimetry (UDV) became an accepted method for flow investigations in various liquid metals. In this presentation various applications of UDV in liquid metal flows will be shown to demonstrate the capabilities and current restrictions of this technique. For instance, we consider single- and multi-transducer arrangements for flow mapping or present velocity measurements obtained during the solidification of a metallic melt. Besides the determination of velocity profiles in the liquid phase the UDV data allow for an assessment of the current position of the solidification front, too. Specific problems arising in the context of UDV measurements in liquid metal experiments will be discussed. The following examples have been selected to demonstrate the benefit of using UDV for flow measurements in cold model experiments, namely the electromagnetic stirring of a metallic melt in a pool, the directional solidification of Pb-Sn alloys under the influence of an electromagnetically driven flow and the
behaviour of the mould flow in continuous casting under the effect of a DC magnetic field.
  • Lecture (Conference)
    3rd International Workshop on Measuring Techniques for Liquid Metal Flows (MTLM2015), 15.-17.04.2015, Dresden, Deutschland

Publ.-Id: 22031 - Permalink


Modular Ultrasound Array Doppler Velocimeter with FPGA-based Signal Processing for Flow Mapping in Liquid Metals
Nauber, R.; Thieme, N.; Beyer, H.; Büttner, L.; Räbiger, D.; Franke, S.; Eckert, S.; Czarske, J.;
Investigating the complex interaction of conductive fluids and magnetic fields is relevant for a variety of applications from basic research in magnetohydrodynamics (MHD) to modeling industrial processes involving metal melts, such as the crystal growth process in the photovoltaic industry. This enables targeted optimizations of the melt flow and allows to significantly increase the yield and energy efficiency of an industrial process. However, experimental studies in this field are often limited by the performance of flow instrumentation for opaque liquids. We present an ultrasound array Doppler velocimeter (UADV) for flow mapping in opaque liquids at room temperature. It is modular and flexible regarding its measurement configuration, for instance it allows capturing two velocity components in two planes (2d-2c). It uses up to 9 linear arrays with a total element count of 225, driven in a parallelized time division multiplex (TDM) scheme. A FPGA-based signal pre-processing allows to handle the massive data bandwidth of typ. 1.2 GB/s and enables a continuous and near-realtime operation of the measurement system. Combining the velocity information of multiple arrays necessitates precise knowledge of their relative geometric position. We present a novel method for spatial self-calibration by a mutual time of flight measurement that significantly reduces the alignment errors.
The capabilities of the UADV system are demonstrated in an experiment for basic MHD research. A cubic plexiglas container (67mm3) is filled with a metal melt (GaInSn, melting point 10°C). The flow induced by time-varying rotating magnetic fields is captured with a temporal resolution of 250ms and an uncertainty of approx. 1% for the horizontal and vertical central cross-section of the cube (2d- 2c).
Keywords: Flow-Mapping, Ultrasound Doppler Velocimetry, Liquid Metals, Magnetohydrodynamics, Flow Control, Spatial Self-Calibration, FPGA
  • Lecture (Conference)
    3rd International Workshop on Measuring Techniques for Liquid Metal Flows (MTLM2015), 15.-17.04.2015, Dresden, Deutschland

Publ.-Id: 22030 - Permalink


Anwendung von AC-Magnetfelder zum Rühren einer metallischen Schmelze im Rundstrangmodell und während der Erstarrung einer Al-Si-Legierung
Räbiger, D.; Willers, B.; Eckert, S.;
Der Einsatz elektromagnetischer Felder zum Rühren metallischer Schmelzen stellt eine elegante Möglichkeit einer völlig kontaktlosen Strömungskontrolle in erstarrenden Metalllegierungen dar, wobei die Strömungsintensität über die elektrischen Regelgrößen Strom und Frequenz gesteuert werden kann.
Trotz der nachweislichen Verbesserung der Gefügeeigenschaften, wie Kornfeinung und Vergrößerung des equiaxialen Erstarrungsbereiches, sowie der Verbesserung der Oberflächenqualität, ist der Einsatz des elektromagnetischen Rührens auch problembehaftet. Negative Auswirkungen wie strömungsinduzierte Porosität oder Gefügeinhomogenitäten (z.B. weiße Bänder beim Stahlguss) erschweren eine industrielle Anwendung des Verfahrens im Strangguss.
Der Einsatz maßgeschneiderter Magnetfelder bietet die Perspektive, die oben genannten, nachteiligen Effekte zu vermeiden. Mit dem Konzept der maßgeschneiderten Magnetfelder können Strömungsregime erzeugt werden, welche die für die Herausbildung vorteilhafter Gefüge notwendigen Temperatur- und Konzentrationsfelder in der erstarrenden Schmelze liefern. Dies erfordert jedoch ein genaues Verständnis der Wechselwirkung von Magnetfeld, induzierter Strömung und Erstarrungsvorgang.
In diesem Vortrag wird die Wirkung des elektromagnetischen Rührens der Schmelze mittels Magnetfelder in einem Continuous Casting - Rundstrang Modellexperiment untersucht. Des Weiteren wird die Auswirkung einer erzwungenen Konvektion auf das Gefüge am Beispiel einer gerichtet erstarrten, binären Al-Si-Legierung gezeigt. Für eine optimale Gefügebeeinflussung dieses Verfahrens sind geeignete Kombinationen der Magnetfeldparameter zu ermitteln. Zu diesem Zweck wurden Strömungsmessungen in einer isothermen Modellschmelze unter dem Einfluss modulierter Magnetfelder durchgeführt. Die Erstarrungsversuche demonstrieren, dass es möglich ist, mit Hilfe zeitmodulierter magnetischer Felder korngefeinte, equiaxiale Gefüge unter Vermeidung der Herausbildung makroskopischer Gefügeinhomogenitäten herzustellen.
Die Ergebnisse veranschaulichen das große Potenzial des elektromagnetischen Rührens zur Verbesserung der Materialeigenschaften der erstarrten Struktur und einer Optimierung der Prozesskontrolle.
  • Lecture (Conference)
    Werkstoffwoche 2015, 14.-17.09.2015, Dresden, Deutschland

Publ.-Id: 22029 - Permalink


Experimental study on directional solidification of Al-Si alloys under the influence of electric currents
Räbiger, D.; Zhang, Y.; Galindo, V.; Franke, S.; Willers, B.; Eckert, S.;
The application of electric currents during solidification can cause grain refinement in metallic alloys. However, the knowledge about the mechanisms underlying the decrease in grain size remains fragmentary. This study considers the solidification of Al-Si alloys under the influence of electric currents for the configuration of two parallel electrodes at the free surface. Solidification experiments were performed under the influence of both direct currents (DC) and rectangular electric current pulses (ECP). The interaction between the applied current and its own induced magnetic field causes a Lorentz force which produces an electro-vortex flow. Numerical simulations were conducted to calculate the Lorentz force, the Joule heating and the induced melt flow. The numerical predictions were confirmed by isothermal flow measurements in eutectic GaInSn. The results demonstrate that the grain refining effect observed in our experiments can be ascribed solely to the forced melt flow driven by the Lorentz force.
  • Lecture (Conference)
    Liquid Metal Processing & Casting Conference 2015, 20.-24.09.2015, Leoben, Österreich
  • Contribution to proceedings
    Liquid Metal Processing & Casting Conference 2015, 20.-24.09.2015, Leoben, Österreich
    LMPC - Proceedings of the International Symposium on Liquid Metal Processing and Casting, 978-3-901384-63-9, 327-333
  • Open Access LogoIOP Conference Series: Materials Science and Engineering 143(2016)1, 012021
    DOI: 10.1088/1757-899X/143/1/012021

Publ.-Id: 22028 - Permalink


Grain refinement in Al-Si alloys induced by applying electric currents during solidification
Zhang, Y.; Räbiger, D.; Galindo, V.; Franke, S.; Willers, B.; Eckert, S.;
The solidification of Al - 7 wt. % Si alloys under the influence of electric current pulses (ECP) through two parallel electrodes at the melt surface is investigated. An effective grain refinement was found if the ECP is applied during the initial solidification period (nucleation and recalescence). The grain size can be gradually reduced, which is likely due to the remelting process of high-order dendrite arms in the mushy zone driven by solute fluctuation and promoted by thermal fluctuation. This fragmentation process is mainly driven by electromagnetically forced convection. The grain refinement does not require the formation of nuclei from a solidified shell near the electrodes, which would result in a grain rain inside the sample.
Keywords: Grain refinement, Al-Si alloys, electric current, electrovortex flows
  • Lecture (Conference)
    Electromagnetic Processing of Materials (EPM), 12.-16.10.2015, Cannes, Frankreich
  • Contribution to proceedings
    Electromagnetic Processing of Materials (EPM), 12.-16.10.2015, Cannes, Frankreich
    EPM2015, 978-2-9553861-0-1, 29-32

Publ.-Id: 22027 - Permalink


Qualification of CFD for multiphase flows in industrial applications
Lucas, D.;
Multiphase flows are frequently applied in industrial processes as e.g. in chemical engineering, oil industries or power plants. Reliable predictions of the flow characteristics such as local concentration of species, interfacial area density or heat transfer in gas-liquid flows can contribute to an optimization of the design of corresponding apparatuses and processes. Computational Fluid Dynamics (CFD) in principle allows the simulation of such flows and provides local flow characteristics. While it is frequently used for industrial problems in case of single phase flows it is not yet mature for two-phase flows. The reason is the complex gas-liquid interface. For medium and large scale flow domains it is not feasible to resolve all details of this interface. Averaging procedures have to be applied and in most cases the so-called two- or multi-fluid approach is used. It assumes interpenetrating phases and the information on the interface gets lost by these averaging procedures. This information has to be added to the basic balance equations by so-called closure models. The development and validation of such models is done at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) to obtain tools for reliable predictions of multiphase flow characteristics in medium and large industrial scales.
One difficulty for the model development and validation results from the fact that we still have a lack of knowledge on local phenomena which determine the two-phase flow characteristics and which should be considered in the closure models. Experimental data with high resolution in space and time are required. To get such information on the gas-liquid interface new innovative measuring techniques as wire-mesh sensors and ultrafast X-ray tomography were developed at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) and extensively used to establish comprehensive databases. The corresponding experiments were conducted at the TOPFLOW-facility of HZDR. It can be operated for air-water and steam-water flows with a pressure up to 7 MPa and the corresponding saturation temperature of 286 °C. An electrical steam generator with a power of 4 MW is able provide up to 1.5 kg steam per second.
In this keynote lecture the strategy of the CFD-model development and validation for multiphase flows is presented. This includes the corresponding experimental work and development of innovative measuring techniques.
Keywords: CFD, multiphase flows, experiments
  • Contribution to proceedings
    IFOST 2015 : The 10th International Forum on Strategic Technology 2015, 03.-05.06.2015, Denpasar, Indonesien
  • Invited lecture (Conferences)
    IFOST 2015 : The 10th International Forum on Strategic Technology 2015, 03.-05.06.2015, Denpasar, Indonesien

Publ.-Id: 22026 - Permalink


Status and challenges of CFD-modelling for poly-disperse bubbly flows
Lucas, D.; Krepper, E.; Rzehak, R.; Liao, Y.; Ma, T.; Ziegenhein, T.;
A clear progress was achieved during the last 20 years in the qualification of CFD-codes for problems of the nuclear safety research. Especially two-phase flows are important, e.g. for LOCA scenarios, but up to now the predictive capabilities of CFD-methods for such flows are limited. Two-phase flows are determined by complex interactions between the phases. Some of them are not yet well understood at the local scale and, therefore, CFD models are limited. This paper discusses such local phenomena and their reflection in presently available CFD-models. It turns out that most of the assumptions in the formulation of closure models for the multi-fluid approach reflect the real phenomena only in a coarse way. Possible uncertainties are listed. Nevertheless, the simulation results obtained by the HZDR baseline model for poly-disperse flows in which all models including model parameter are fixed show in general a rather good agreement with experimental data. One sensitive issue seems to be how to handle the bubble size. In case of poly-disperse flows the sub-division of the gas phase with respect to the bubble size is important and the exact choice of the limits for this division sensitively influences the simulation results.
Keywords: bubbly flow, CFD, multi-fluid model, closure models
  • Lecture (Conference)
    The 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16), 30.08.-04.09.2015, Chicago, USA
  • Contribution to proceedings
    The 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16), Paper 13018, 30.08.-04.09.2015, Chicago, USA

Publ.-Id: 22025 - Permalink


Qualification of CFD-models for multiphase flows
Lucas, D.;
In this talk an overview on the CFD activities at HZDR is given. The general strategy to qualify CFD for multiphase flows is presented. Examples for specific topics related to nuclear safety research are discussed.
Keywords: CFD, multiphase flow
  • Invited lecture (Conferences)
    1st Sino-German Symposium on Fundamentals of Advanced Nuclear Safety Technology, 08.-12.03.2015, Shanghai, China

Publ.-Id: 22024 - Permalink


Ion beam induced modifications of Pt/Co/Pt magnetic films for control of perpendicular magnetic anisotropy
Jakubowski, M.; Kurant, Z.; Böttger, R.; von Borany, J.; Fassbender, J.ORC; Wawro, A.; Maziewski, A.
Modifications of magnetic and magnetooptical properties of Pt/Co/Pt tri-layers upon irradiation with ion beam are investigated in this work. They are studied in detail as a function of the Co layer thickness, dCo (up to 5 nm), ion species (Ne+, Ar+, Ga+) the energy of ions, E (up to 30 keV) and ion fluence, F (range from 1013 to 3∙1016 ions/cm2). Modified magnetic properties are correlated with structural features of irradiated samples. Numerical simulations of in-depth atomic concentration profile and surface etching carried out by TRIDYN software complements explanation of the observed effects.
MBE grown Pt/Co/Pt tri-layers display a spin reorientation transition (SRT) at a well-defined Co thickness, dSRT from out-of-plane to in-plane magnetization alignment as dCo increases. Upon ion irradiation various processes undergo: degradation of chemically sharp interfaces, formation of Co-Pt alloys and lattice strain development [1, 2]. Spread interfaces reduce perpendicular anisotropy whereas formation of the ordered alloy may strength this property. Therefore a resulting magnetic state of the sample is a product of interplay of these two opposing trends in anisotropy evolution and the sample surface etching, particularly effective for highest fluences. It is very sensitive to dCo, ion species, their energy and the ion fluence.
Discussion is focused on results obtained with Ar+ ions irradiation, which is commonly used for technological processes especially for nanostructures sputtering. Set of (dCo, log F) diagrams of remanence, mr (Figure. 1), (normalized magnetization perpendicular component) measured by means of magnetooptical Kerr effect magnetometry in polar configuration (PMOKE) upon irradiation with Ar+ ions with different energies. Irradiation of the samples modifies magnetic properties in various manners depending on dCo, F and ion energy. The suppression of the dSRT with F in the range from 1013 to 1014 ions/cm2 and formation of branch(es) corresponding to strong perpendicular anisotropy (higher value of mr) are the most distinguished differences depending on the ion energy. As the ion energy increases a single branch with high mr (for 1.2 keV) begins to split into two parts for 5.0 keV, which are clearly separated for 30.0 keV. Qualitatively this evolution resembles that one already reported for Ga ions [1]. However, the mr modifications strength are weaker due to the lower mass of Ar atoms. Nevertheless, up to 5 transitions between various magnetic states are observed with F increase, e. g. for dCo = 1.6 nm and E = 30 keV. It is worth to notice that even the lowest applied energy of Ar+ ions induces visible modifications of magnetic properties. In the case of the lightest studied Ne ions modification of magnetic anisotropy is weaker than for Ar+ ions and the branches in a similar diagram are non-continuous.
TRIDYN software determined in-depth chemical profile (Figure 2) is helpful in identification of possible alloy composition being responsible for enhanced perpendicular magnetic anisotropy. Also the surface etching extent allows to estimate an amount of sputtered (also magnetic) material that may result in superparamagnetic state observed for the highest ion doses.
Structural properties of the irradiated samples are investigated by Rutherford backscattering (RBS). Evolution of the acquired chemical profiles is correlated with that simulated with TRIDYN software. Moreover, the etching efficiency is estimated from topography step profile between irradiated and non-irradiated areas of the sample investigated by means of profilometer and atomic force microscopy.
Discussed above abundance of magnetic investigated states in combination with controlled structural features developing upon ion irradiation enable a precise tuning of desired magnetic properties. In particular, such approach, exploiting a focused ion beam, might be of great importance in fabrication of magnonic crystals – a new type of metamaterial with reprogrammable band structure.
  • Lecture (Conference)
    22nd International Colloquium on Magnetic Films and Surfaces, 12.-17.07.2015, Cracow, Poland

Publ.-Id: 22023 - Permalink


A strategy for the CFD-qualification for two-phase flows
Lucas, D.; Krepper, E.; Ziegenhein, T.; Rzehak, R.; Liao, Y.; Apanasevich, P.;
In this presentation the requirement to consolidate the CFD modelling for two-phase flows in frame of the Euler-Euler approach is discussed. To do that a baseline model strategy is proposed and illustrated by the HZDR baseline model for poly-dispersed bubbly flows.
Keywords: CFD, closure models, poly-dsiperse bubbly flows
  • Lecture (Conference)
    26th Meeting of the German CFD Network of Competence, 04.-05.03.2015, Otterfing, Deutschland

Publ.-Id: 22022 - Permalink


A comparison of SIMS and RBS for the depth profiling of silica glasses implanted by metal ions
Lorincik, J.; Vytykacova, B.; Svecova, B.; Nekvindoca, P.; Mackova, A.; Miksova, R.; Böttger, R.;
Ion implantation of metal ions followed by annealing can be used for the formation of buried layers of metal nanoparticles in glasses with optical properties for perspective photonic materials. Results are presented from three samples of silica glasses implanted with Cu+, Ag+ or Au+ ions under the same conditions (energy 330 keV and fluence 1×10^16 ions/cm2) and three silica glass samples implanted with the same metals and conditions but coimplanted subsequently by oxygen into the same depth. All the implanted glasses were annealed at 600°C, which lead to forming of metal nanoparticles. The depth profiles measured by RBS and SIMS indicated that the sequential implantation of oxygen followed by post-annealing caused the shift of Cu, Ag and Au aggregated into nanoparticles deeper into the glass substrate. Both RBS and SIMS are shown to be valuable complementary techniques.
Keywords: SIMS; RBS; ion Implantation, metal nanoparticles
  • Poster
    20th International Conference on Secondary Ion Mass Spectrometry, 13.-18.09.2015, Seattle, USA

Publ.-Id: 22021 - Permalink


Code intercomparison and benchmark for muon fluence and absorbed dose induced by an 18 GeV electron beam after massive iron shielding
Fass`O, A.; Ferrari, A.; Mokhov, N. V.; Müller, S. E.; Nelson, W. R.; Roesler, S.; Sanami, T.; Striganov, S. I.; Versaci, R.;
In 1974, Nelson, Kase, and Svenson published an experimental investigation on muon shielding using the SLAC high energy LINAC. They measured muon fluence and absorbed dose induced by a 18 GeV electron beam hitting a copper/water beamdump and attenuated in a thick steel shielding. In their paper, they compared the results with the theoretical models available at the time. In order to compare their experimental results with present model calculations, we use the modern transport Monte Carlo codes to model the experimental setup and run simulations. The results will then be compared between the codes, and with the SLAC data.
  • Lecture (Conference)
    FLUKA collaboration meeting, 15.-16.12.2014, Pavia, Italy

Publ.-Id: 22020 - Permalink


Background studies in the 148 m deep Reiche Zeche mine in Freiberg and in the 45 m deep Felsenkeller in Dresden
Szücs, T.; Agramunt, J.; Bemmerer, D.; Degering, D.; Dillmann, I.; Fraile, L. M.; Grieger, M.; Marta, M.; Reinhardt, T. P.; Schmidt, K.; Tain, J. L.; Takács, M. P.; Wagner, L.;
A very low background level is a key requirement for underground nuclear astrophysics experiments.
A detailed gamma-background study with two escape-suppressed HPGe detectors has been performed at a medium deep underground site, namely the Reiche Zeche mine (148m) in Freiberg, Germany [1]. The new data complement a data set with the same detector at other underground sites [2,3].
Now, detailed background data are available at the Earth’s surface and at underground sites with depths of 45m, 148m, 1400m from one and the same escape-suppressed HPGe detector. This allows to investigate the effect of the active and passive shielding on the high energy (E_g > 3 MeV) laboratory background.
A detailed interpretation of the behaviour of different background components as a function of the underground depth will be presented.

In addition to this work with gamma-ray detectors, the neutron background has been studied by 3He counters from the BELEN neutron detector, equipped with polyethylene moderators of various thicknesses in the Felsenkeller laboratory (45m). By mean of the varied moderation, spectral information of the neutron flux is derived. The same detectors and same method were used previously deep underground in Canfranc/Spain (850m) to measure the neutron flux and spectrum [4]. This allows a direct comparison of the two sites.

- Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (HGF VH-VI-417), and via the Helmholtz Young Investigators Group LISA (VH-NG 627).

[1] T. Szücs et al., Eur. Phys. J. A 51, (2015) 33
[2] T. Szücs et al., Eur. Phys. J. A 44, (2010) 513
[3] T. Szücs et al., Eur. Phys. J. A 48, (2012) 8
[4] D. Jordan et al., Astropart. Phys. 42, (2013) 1
Keywords: Underground, gamma background, neutron background, HPGe, 3He counter
  • Poster
    Nuclear Physics in Astrophysics Conference (NPA VII), 18.-22.05.2015, York, United Kingdom

Publ.-Id: 22019 - Permalink


Code intercomparison and benchmark for muon fluence and absorbed dose induced by an 18 GeV electron beam after massive iron shielding
Müller, S. E.;
In 1974, Nelson, Kase, and Svenson published an experimental investigation on muon shielding using the SLAC high energy LINAC. They measured muon fluence and absorbed dose induced by a 18 GeV electron beam hitting a copper/water beamdump and attenuated in a thick steel shielding. In their paper, they compared the results with the theoretical models available at the time. In order to compare their experimental results with present model calculations, we use the modern transport Monte Carlo codes to model the experimental setup and run simulations. The results will then be compared between the codes, and with the SLAC data.
  • Lecture (Conference)
    FLUKA Advanced Course and Workshop, 01.-05.12.2014, Frascati, Italy

Publ.-Id: 22018 - Permalink


Status of the Task 11.1 from HZDR: Part 1
Ferrari, A.; Konheiser, J.; Müller, S. E.;
Results on activation calculation for the CHANDA project are presented.
  • Lecture (Conference)
    CHANDA Work Package 11 Meeting, 20.02.2015, Dresden, Germany

Publ.-Id: 22017 - Permalink


He+ ions damage on optical coatings for solar missions
Bacco, D.; Corso, A. J.; Zuppella, P.; Gerlin, F.; Böttger, R.; Napolitani, E.; Tessarolo, E.; Nardello, M.; Zuccon, S.; Pelizzo, M. G.;
Single layer thin films have been exposed to low energy alpha particles (4keV). Implanted doses are equivalent to those accumulated in 1, 2, 4 and 6 years of ESA Solar Orbiter mission operation. Two ions fluences have been considered. In order to change the total dose accumulated, for each ion flux the time of exposure was varied. Reflectance in the visible spectral range has been measured prior and after implantation. Results show no significant change in performances in gold and palladium, while a small decrease in performances is observed in iridium. The implantation rate does not seem to affect the experiment.
Keywords: Optical coatings; Ions; Iridium; Gold; Palladium; Particles; Reflectivity; Thin films

Publ.-Id: 22016 - Permalink


Velocimetry in fluidized beds by ultrafast X-ray CT
Bieberle, M.; Barthel, F.; Hampel, U.;
Ultrafast X-ray electron beam computed tomography (CT) is an imaging technique, which has been developed for measuring phase distributions in multiphase flows. For example, two- and multiphase flow experiments in vertical pipes, conventional and slurry bubble columns, fluidized beds, monolithic structures and bundle geometries could be evaluated by this technique. With extending the measurement system towards dual-plane imaging, the option of velocity measurement has been created and applied for instance in two-phase vertical pipe flow.
In this study, we focus on measuring velocities in particulate systems. Some methods for velocity evaluation can be adapted from gas-liquid flows, such as the cross-correlation technique for determining the velocity of gas bubbles. Now, we present a technique, which allows velocity evaluation of the solid particles. This is achieved by adding marker particles with higher X-ray absorption to the particle phase and determining their velocities representatively.
In this paper, two different velocity evaluation techniques are described and selected results achieved by conducting experiments on a spout fluidized bed are presented. This combination of spouting and fluidized bed is a rather new type of particulate system, which combines the advantages of both, but whose dynamics is yet not fully understood. The capability of ultrafast X-ray CT to recover phase distributions as well as velocity information from particulate systems in order to better understand the dynamics of particulate systems is demonstrated with this exemplary experiment.
Keywords: ultrafast, X-ray CT, spout fluidized bed, velocity measurement
  • Contribution to proceedings
    7th International Symposium on Process Tomography (ISPT7), 01.-03.09.2015, Dresden, Deutschland
    Proceeding of the 7th International Symposium on Process Tomography
  • Lecture (Conference)
    7th International Symposium on Process Tomography (ISPT7), 01.-03.09.2015, Dresden, Deutschland

Publ.-Id: 22015 - Permalink


Defect-induced ferromagnetism in silicon
Liu, Y.; Zhang, X.; Yuan, Q.; Han, J.; Helm, M.; Zhou, S.; Song, B.;
I. INTRODUCTION
Defect-induced ferromagnetism provides an alternative for organic and semiconductor spintronics. Though it is weak, it can be stable above room temperature. Till now it has been confirmed at least in oxides [1, 2] and carbon based materials [3, 4]. Interestingly, the relation between magnetism and defects in Silicon was demonstrated decades ago [5]. Since then, some progresses were made [6-9] and push forward the research of magnetic Mn doped Si a lot but it is drawn little attention itself. Here, with the latest growth purifying technique and sensitive measurements, we investigated the magnetism in Silicon after neutron irradiation and try to correlate the observed magnetism to particular defects in Si.

II. RESULTS
Commercially available p-type Si wafer (Hefei Ke Jing) is cut into pieces for performing neutron irradiations. The magnetic impurities are ruled out as they can not be detected by secondary ion mass spectroscopy. The concentration of the main impurity Boron is around 4 × 1014 cm-3. Pieces are irradiated for varying durations, corresponding doses in the ranges of 1.91 × 1017 - 2.29 × 1018 n/cm2. Each piece is irradiated only once and pristine pieces are kept for the purpose of comparison.
Raman spectra show the patterns of Si crystals irradiated similar to that of the pristine one. The relative intensity variation confirms the slight damage induced by irradiation. Positron annihilation lifetime spectroscopy is performed to investigate the defect types. All the measured spectra are fit into an exponential function of three components. The lifetime τ2, usually corresponding to defects, takes value of 375 ps, independent of irradiation dose. This positron trapping center is assigned to a kind of stable vacancy clusters of hexagonal rings (V6) [10]. The fraction of the longer lifetime (τ2) component I2 is closely correlated with irradiation dose, which means the concentration of V6 is enhanced by increasing neutron doses.
After irradiation, the samples still show strong diamagnetism. Only weak paramagnetism can be found in zero-field-cooled / field-cooled magnetization. The ferromagnetic signal in Silicon after irradiation enhances and then weakens with increasing irradiation doses as shown in Fig. 1. The saturation magnetization can reach 6 × 10-5 emu/g at 5 K. At room temperature it still remains as much as 5 × 10-5 emu/g. In such a transition metal free system, the ferromagnetism in neutron irradiated Si is closely associated with V6 defects. A Silicon 2 × 2 × 2 supercell with a defect of V6 is built to understand the magnetism in neutron irradiated Silicon. Unfortunately, the V6 shows no spin-polarized state. The change of charge state or Boron doping can not make it spin-polarized, either. At this end, more efforts are needed to comprehend this phenomenon.


REFERENCES
1) M. Venkatesan, C. B. Fitzgerald, and J. M. D. Coey, "Thin films: unexpected magnetism in a dielectric oxide", Nature, 430 630 (2004).
2) J. B. Yi, C. C. Lim, G. Z. Xing, H. M. Fan, L. H. Van, S. L. Huang, K. S. Yang, X. L. Huang, X. B. Qin, B. Y. Wang, T. Wu, L. Wang, H. T. Zhang, X. Y. Gao, T. Liu, A. T. S. Wee, Y. P. Feng, and J. Ding, "Ferromagnetism in dilute magnetic semiconductors through defect engineering: Li-doped ZnO", Phys. Rev. Lett., 104 137201 (2010).
3) P. Esquinazi, D. Spemann, R. Höhne, A. Setzer, K. H. Han, and T. Butz, "Induced magnetic ordering by proton irradiation in graphite", Phys. Rev. Lett., 91 227201 (2003).
4) Y. Liu, G. Wang, S. C. Wang, J. H. Yang, L. Chen, X. B. Qin, B. Song, B. Y. Wang, and X. L. Chen, "Defect-induced magnetism in neutron irradiated 6H-SiC single crystals", Phys. Rev. Lett., 106 087205 (2011).
5) A. F. Khokhlov and P. V. Pavlov, "Ferromagnetism induced in silicon by radiation defects", JETP Lett., 24(4) 211–213 (1976).
6) R. Laiho, E. Lähderanta, L. Vlasenko, M. Viasenko, and M. Afanasiev, "Magnetic properties of light-emitting porous silicon", J. Lumin., 57 197–200 (1993).
7) T. Dubroca, J. Hack, R. E. Hummel, and A. Angerhofer, "Quasiferromagnetism in semiconductors", Appl. Phys. Lett., 88 182504 (2006).
8) S. V. Adashkevich, N. M. Lapchuk, V. F. Stel’makh, G. G. Fedoruk, and E. N. Shumskaya, "Local magnetic order in silicon implanted with high-energy ions", JETP Lett., 84(10) 547–550 (2006).
9) L. Chow, J. C. Gonzalez-Pons, E. del Barco, R. Vanfleet, A. Misiuk, A. Barcz, E. S. Choi, and G. Chai, "Structures and magnetization of defect-associated sites in Silicon", AIP Conf. Proc., 1003 248 (2008).
10) T. E. M. Staab, A. Sieck, M. Haugk, M. J. Puska, Th. Frauenheim, and H. S. Leipner, "Stability of large vacancy clusters in silicon", Phys. Rev. B, 65 115210 (2002).
Keywords: defect-induced ferromagnetism, silicon, neutron irradiation, semiconductors
  • Lecture (Conference)
    INTERMAG 2015, 11.-15.05.2015, Beijing, China

Publ.-Id: 22014 - Permalink


Construction and Test of a Large NeuLAND Prototype Array
Boretzky, K.; Agrawal, B.; Alkhazov, G. D.; Altstadt, S.; Alvarez Pol, H.; Andreev, V. A.; Atar, L.; Aumann, T.; Basu, P.; Bemmerer, D.; Bendel, M.; Bertini, D.; Bhattacharya, P.; Bhattacharya, S.; Blanco, A.; Bonilla, J.; Caesar, C.; Cartegni, L.; Chakraborty, S.; Charpy, A.; Chatterjee, S.; Cherciu, M.; Chulkov, L.; Ciobanu, M.; Cowan, T.; Datta Pramanik, U.; Elekes, Z.; Endres, J.; Fetisov, A. A.; Fiori, E.; Fonte, P.; Galaviz, D.; Gasparic, I.; Gerbig, J.; Gernhäuser, R.; Göbel, K.; Golotsov, V. L.; Haiduc, M.; Heftrich, T.; Hehner, J.; Heil, M.; Heine, M.; Heinz, A.; Hennig, A.; Henriques, A.; Holl, M.; Ignatov, A.; Ickert, G.; Isaak, J.; Ivanov, E. A.; Jährling, S.; Johansen, J.; Johansson, H.; Kelic-Heil, A.; Kiselev, O.; Körper, D.; Kresan, D.; Krivshich, A. G.; Kumar Das, P.; Lebleis, T.; Lederer, C.; Leifels, Y.; Lindberg, S.; Lopes, L.; Löher, B.; Machado, J.; Marganiec, J.; Netterdon, L.; Nilsson, T.; Panin, V.; Panja, J.; Paschalis, S.; Perea, A.; Pietras, B.; Plag, R.; Pohl, M.; Potlog, M.; Rahaman, A.; Rastrepina, G.; Ray, A.; Reifarth, R.; Reinhardt, T.; Ribeiro, G.; Röder, M.; Rossi, D.; Sanchez Del Rio, J.; Sauerwein, A.; Savran, D.; Scheit, H.; Schmidt, S.; Schrock, P.; Silva, J.; Simon, H.; Sinha, T.; Sobiella, M.; Sonnabend, K.; Stach, D.; Stan, E.; Tengblad, O.; Teubig, P.; Thies, R.; Uvarov, L. N.; Velho, P.; Vikhrov, V. V.; Volkov, S. S.; Volkov, V.; Wagner, A.; Wamers, F.; Weigand, M.; Winkel, M.; Wüstenfeld, J.; Yakorev, D.; Zhdanov, A. A.; Zilges, A.; Zuber, K.;
NeuLAND (new Large-Area Neutron Detector) is the next-generation neutron detector integrated into the R3B experiment, and is a key instrument for a major part of the physics program. NeuLAND features a high detection effciency, a high resolution, and a large multi-neutronhit resolving power, achieved by a highly granular design with a total of 3000 plastic scintillator bars [1]. In January 2013 the Technical Design Report [2] has been approved by FAIR, following the recommendation by the Expert Committee Experiments (ECE) at its first meeting in November 2012.
Here we report about the progress of the NeuLAND project, which was dominated in 2012 by the transition from prototypes to mass production. During the previous year 200 NeuLAND modules and their readout were purchased and brought into operation.
  • Open Access LogoContribution to external collection
    Katrin Große: GSI Scientific Report 2012, GSI Report 2013-1, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung, 2013

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Publ.-Id: 22013 - Permalink


Decomposition of Silicon rich oxide films by Diode Laser processing to fabricate Sponge-like Si-SiO2 nanocomposites for photovoltaics
Schumann, E.; Heinig, K.-H.; Hübner, R.; Carcelen, V.; Krause, M.;
Absorber layers consisting of nanostructured Si are candidates for next generation thin film Si solar cells. For this aim, Si-SiO2 nanocomposites with crystalline sponge-like Si are promising materials since their band gap is increased by quantum confinement and since they provide electrical interconnectivity. Such nanosilicon has recently been fabricated by annealing of non-reactively sputter deposited SiOx films (x< 1). It is formed by solid state phase separation into a percolated network of Si nanowires. The phase separation is usually accompanied by crystallization of Si. Here, SiOx layers have been grown by ion beam sputter (IBS) as well as by reactive magnetron sputter (RMS) deposition. Phase separation into Si-SiO2 nanocomposites has been achieved by scanning a diode laser line source with dwell times in the ms range and compared to a furnace treatment lasting ~106 times longer. Furnace annealing of IBS and RMS deposited layers result in sponge-like and filament-like silicon nanostructures, respectively. Laser processing of IBS layers leads to morphologies self-similar to furnace annealed samples, but scaled up by a factor of ~10. This indicates that the faster phase separation mechanism occurs in the liquid state. It is expected that laser processing of RMS layers will result in sponge-like morphologies too, and not filament like ones due to the liquid state phase separation.
Keywords: silicon nanostructure, sponge-like Si-SiO2, nanocomposite, silicon, silicon oxide, photovoltaic, Energy Filtered TEM
  • Poster
    2015 E-MRS Spring Meeting, 11.-15.05.2015, Lille, France

Publ.-Id: 22012 - Permalink


Diode laser array used for decomposition of SiOx into sponge-like Si-SiO2 nanocomposites
Schumann, E.; Heinig, K.-H.; Hübner, R.; Carcelen, V.; Hauschild, D.; Krause, M.;
Line-shaped light beams from diode laser arrays permit homogeneous and long-term stable processing of surface layers. Here we report on thermally activated decomposition of SiOx using a commercial diode laser of the LIMO GmbH, with cw-operation at a wavelength of 808nm, a maximum power density of 30 kW/cm², a minimum line focus < 100 µm, and a variable scan speed. Dwell times from < 1ms to 100ms can be realized by adjusting the scan speed and focus width, which allows very Rapid Thermal Processing (vRTP) of surfaces layers. SiOx layers of < 1µm thickness have been grown on quartz by sputter deposition. Two different modes of thermal treatment have been used: Furnace annealing at 950°C for 90 minutes and vRTP with 17ms dwell time. Energy-Filtered Transmission Electron Microscopy (EFTEM) reveals that in both cases the homogeneous SiOx has been transformed into a sponge-like Si-SiO2 nanocomposite. Raman spectroscopy shows that the crystallinity of spongy Si is higher for the laser treated sample. Whereas the characteristic structure size of the spongy Si of the furnace annealed sample amounts to a few nm only, it is a few tens of nm for vRTP. It will be shown that in the furnace the phase separation proceeds in the solid state, whereas the more complete phase separation by laser treatment can only be understood by liquid state processes. The laser-synthesized Si nanosponge can be applied as new material in next generation solar cells.
Keywords: silicon nanostructure, sponge-like Si-SiO2, nanocomposite, silicon, silicon oxide, photovoltaic, Energy Filtered TEM , diode laser annealing
  • Lecture (Conference)
    2015 E-MRS Spring Meeting, 11.-15.05.2015, Lille, France

Publ.-Id: 22011 - Permalink


R&D for NeuLAND development for R3B, FAIR at SINP, Kolkata
Datta Pramanik, U.; Aumann, T.; Boretzky, K.; Basu, P.; Basu, J.; Bhattachaya, S.; Bemmerer, D.; Chakraborty, S.; Chatterjee, S.; Das, P. K.; Elekes, Z.; Gonzalez-Diaz, D.; Kempe, M.; Panja, J.; Rahaman, A.; Ray, J.; Simon, H.; Sobiella, M.; Stach, D.; Wagner, A.; Yakorev, D.;
In the upcoming R3B-FAIR facility, to achieve the design goal for high resolution neutron time-of-flight [1,2], various types of prototypes have been explored at several places [3,4,5,6]. The possible candidates for active material of such a spectrometer can be either Multigap Resistive Plate Chamber (MRPC) or conventional plastic scintillators. At initial stage of NeuLAND development, at Saha Institute of Nuclear Physics, Kolkata, MRPC design feasibility was studied extensively[3,5].
  • Open Access LogoContribution to external collection
    Katrin Große: GSI Scientific Report 2012, GSI Report 2013-1, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung, 2013

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Publ.-Id: 22010 - Permalink


Shielding and activation analysis status for the MYRRHA research reactor
Ferrari, A.; Konheiser, J.; Müller, S. E.;
Shielding and activation analysis status of the MYRRHA research reactor is presented.
  • Lecture (Conference)
    MAXSIMA Work Package 2 - Technical Meeting, 20.04.2015, Mol, Belgien

Publ.-Id: 22009 - Permalink


Tests of Silicon Photomultipliers for NeuLAND
Reinhardt, T.; Bemmerer, D.; Cowan, T.; Heidel, K.; Kempe, M.; Röder, M.; Stach, D.; Wagner, A.; Zuber, K.;
NeuLAND, the successor of the LAND time-of-flight neutron spectrometer is planned to be constructed of 5 × 5 × 250 cm3 scintillator bars of RP-408 [1] or equivalent. Light readout will be performed by 1" photomultiplier tubes (PMTs). A demonstration prototype of the detector concept was recently tested at GSI [2]. During the operation of the complete detector with 6,000 channels a significant number of photomultiplier tubes may have to be replaced each year. Recent developments in the field of semiconductor based photon readout systems [2, e.g.] raise the possibility of using Silicon Photomultipliers (SiPMs) for this task.
  • Open Access LogoContribution to external collection
    Katrin Große: GSI Scientific Report 2012, GSI Report 2013-1, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung, 2013

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Publ.-Id: 22008 - Permalink


Sponge-like Si-SiO2 nanocomposite as photovoltaic absorber –phase separation in the liquid and the solid state
Schumann, E.; Heinig, K.-H.; Hübner, R.; Carcelen, V.; Krause, M.;
Absorber layers consisting of nanostructured Si are candidates for next generation thin film Si solar cells. For this aim, Si-SiO2 nanocomposites with crystalline sponge-like Si are promising materials since their band gap is increased by quantum confinement and since they provide electrical interconnectivity. Such nanosilicon has recently been fabricated by annealing of non-reactively sputter deposited SiOx films (x< 1). It is formed by solid state phase separation into a percolated network of Si nanowires. The phase separation is usually accompanied by crystallization of Si. Here, SiOx layers have been grown by ion beam sputter (IBS) as well as by reactive magnetron sputter (RMS) deposition. Formation of sponge-like Si-SiO2 nanocomposites has been achieved for the IBS deposited layers by scanning with a diode laser line source (LIMO GmbH) and furnace treatment. Laser processing leads to morphologies self-similar to furnace annealed samples, but scaled up by a factor of ~10. Moreover, the laser process proceeds approximately 106 times faster. The larger mean structure size for the shorter process is explained by a phase separation in the liquid state in contrast to a solid state process which has been observed for furnace annealing. Furthermore, filament-like morphologies produced by RMS deposition and furnace annealing are compared to those of the IBS deposited layers.
Keywords: silicon nanostructure, sponge-like Si-SiO2, nanocomposite, silicon, silicon oxide, photovoltaic, Energy Filtered TEM
  • Lecture (Conference)
    2015 E-MRS Spring Meeting, 11.-15.05.2015, Lille, France

Publ.-Id: 22007 - Permalink


Tests of timing silicon photomultipliers for NeuLAND
Gohl, S.; Reinhardt, T.; Bemmerer, D.; Cowan, T. E.; Heidel, K.; Röder, M.; Stach, D.; Wagner, A.; Weinberger, D.; Wüstenfeld, J.; Zuber, K.;
It is investigated whether NeuLAND may be reinstrumented with semiconductor based photosensors. Tests with an 11cm long slab of RP-408 plastic scintillator and a PiLas 45 ps laser diode system show time resolutions of σ = 100 ps.
The NeuLAND time-of flight detector for 1GeV neutrons will consist in its final configuration of 30 double planes of 100 scintillator bars (RP-408) each. Each bar of 270×5×5cm3 must be read out at each end. Thus altogether 6000 timing photomultipliers of 1” diameter are needed [1]. In order to limit their cost impact, it is being investigated whether parts of NeuLAND may be (re-)instrumented with semiconductor-based photosensors, socalled Silicon Photomultipliers (SiPMs). Previous experiments using the one-electron-per-bunch mode of the superconducting electron accelerator ELBE have shown that nearly full efficiency can be reached even when instrumenting one NeuLAND bar with just one 3×3mm2 SiPM [2]. However, in those first tests the charge resolution did not allow to separate single photons, and the time resolution did not fulfill the required σ ≤ 150 ps.
  • Open Access LogoContribution to external collection
    Katrin Große: GSI Scientific Report 2013, GSI Report 2014-1, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung, 2014

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Publ.-Id: 22006 - Permalink


Low-aspect ratio nanopatterns on bioinert alumina influence the response and morphology of osteoblast-like cells
Wittenbrink, I.; Hausmann, A.; Schickle, K.; Lauria, I.; Davtalab, R.; Foss, M.; Keller, A.; Fischer, H.;
Topographical features on the nanometer scale are known to influence cellular behavior. The response of specific cell types to various types of surface structures is currently still being investigated. Alumina ceramics play an important role as biomaterials, e.g., in medical and dental applications. In this study, we investigated the influence of nanoscale surface features with low aspect ratio (< 0.1) on the response of osteoblast-like MG-63 cells. To this end, low-energy ion irradiation was employed to produce shallow nanoscale ripple patterns on Al2O3(0001) surfaces with lateral periodicities of 24 nm and 179 nm and heights of only 0.7 and 11.5 nm, respectively. The nanopatterning was found to increase the proliferation of MG-63 cells and may lead to pseudopodia alignment along the ripples. Furthermore, focal adhesion behavior and cell morphology were analyzed. We found that MG-63 cells are able to recognize surface nanopatterns with extremely low vertical variations of less than 1 nm. In conclusion, it is shown that surface topography in the sub-nm range significantly influences the response of osteoblast-like cells.
Keywords: Alumina, Nanotopography, Ion beam, Osteoblast

Publ.-Id: 22005 - Permalink


Hyperdoping silicon with chalcogen: solid vs. liquid phase epitaxy
Liu, F.; Prucnal, S.; Gao, K.; Khalid, M.; Skorupa, W.; Helm, M.; Zhou, S.;
Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ≈ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability.
Keywords: Ion implantation, flash lamp annealing
  • Lecture (Conference)
    E-MRS 2015 Spring meeting, 11.-15.05.2015, Lille, France

Publ.-Id: 22004 - Permalink


NeuLAND - from prototypes to double-planes
Boretzky, K.; Agrawal, B.; Alkhazov, G. D.; Altstadt, S.; Alvarez Pol, H.; Andreev, V. A.; Atar, L.; Aumann, T.; Babic, V.; Basu, P.; Bemmerer, D.; Bendel, M.; Bertini, D.; Bhattacharya, P.; Bhattacharya, S.; Blanco, A.; Bonilla, J.; Caesar, C.; Cartegni, L.; Chakraborty, S.; Charpy, A.; Chatterjee, S.; Cherciu, M.; Chulkov, L.; Ciobanu, M.; Cowan, T.; Datta Pramanik, U.; Dentinger, G.; Elekes, Z.; Fetisov, A. A.; Fiori, E.; Fonte, P.; Galaviz, D.; Gasparic, I.; Gerbig, J.; Gernhäuser, R.; Göbel, K.; Golotsov, V. L.; Haiduc, M.; Heftrich, T.; Hehner, J.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Holl, M.; Ignatov, A.; Ickert, G.; Isaak, J.; Ivanov, E. A.; Jährling, S.; Johansen, J.; Johansson, H.; Kahlbow, J.; Kelic-Heil, A.; Kiselev, O.; Kissel, R.; Kobayashi, K.; Körper, D.; Kresan, D.; Krivshich, A. G.; Kumar Das, P.; Lebleis, T.; Lederer, C.; Leifels, Y.; Lindberg, S.; Lopes, L.; Löher, B.; Machado, J.; Marganiec, J.; Netterdon, L.; Nilsson, T.; Panin, V.; Panja, J.; Paschalis, S.; Perea, A.; Pickstone, S. G.; Pietras, B.; Plag, R.; Pohl, M.; Potlog, M.; Rahaman, A.; Rastrepina, G.; Ray, A.; Reifarth, R.; Reinhardt, T.; Ribeiro, G.; Röder, M.; Rossi, D.; Sanchez Del Rio, J.; Sauerwein, A.; Savran, D.; Scheit, H.; Schindler, F.; Schmidt, S.; Schrock, P.; Silva, J.; Simon, H.; Sinha, T.; Sobiella, M.; Sonnabend, K.; Stach, D.; Stan, E.; Tengblad, O.; Teubig, P.; Thies, R.; Uvarov, L. N.; Velho, P.; Vikhrov, V. V.; Volkov, S. S.; Volkov, V.; Wagner, A.; Wamers, F.; Weigand, M.; Winkel, M.; Wüstenfeld, J.; Yakorev, D.; Zhdanov, A. A.; Zilges, A.; Zuber, K.;
During 2013 the NeuLAND (new Large-Area Neutron Detector) project passed the important step from prototype tests to series production. Being one of the key instruments of the R3B experiment [1] the NeuLAND demonstrator will be utilized in the 2014 beam times together with demonstrators of other major R3B components. NeuLAND is a highly granular detector composed of 3000 scintillator bars with a total volume of 250x250x300 cm3. It enables the detection of fast neutrons with high efficiency, high time and spatial resolution and a high resolving power for multi-neutron events [2]. Despite the compact cubical arrangement of the NeuLAND components, the detector is built up from individual subgroups with an independent functionality, the so-called NeuLAND double-planes. This modular design facilitates maintenance and it allows upon experimental needs to split the detector in subdetectors being located at different positions with respect to the target area.
  • Open Access LogoContribution to external collection
    Katrin Große: GSI Scientific Report 2013, GSI Report 2014-1, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung, 2014

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Publ.-Id: 22003 - Permalink


Bispidines as versatile bifunctional chelators for 64Cu PET imaging
Stephan, H.;
Objectives: Ligands based on 3,7-diazabicyclo[3.3.1]nonane (bispidine) form very stable coordination compounds, particularly with CuII. Due to the formation of thermodynamically and kinetically very stable 64CuII complexes, pentadentate I, hexadentate II and macrocyclic bispidines III are well suited for in vivo application. The bispidine scaffold has a number of options for derivatization that permit the introduction of additional functions such as biological vectors and fluorescent molecules. This allows the adjustment of defined features of solubility and of selective binding properties for in vivo applications with controllable targeting.

Methods: Bispidine ligands I and II were synthesized by two consecutive Mannich reactions. The bispidine dioxotetraaza macrocycle III was synthesized by cyclization of 5,7-dimethyl-1,3-diazabicyclononane with the bis(α-chloroacetamide) of o-phenylendiamine. 64Cu was produced following an established protocol with high specific activities of 150-250 GBq/µmol. 64Cu-labeling of bispidine ligands and peptide conjugates were performed using [64Cu]CuCl2 dissolved in 0.05 M 2-[N-morpholino]ethansulfonic acid (MES)-NaOH buffer (pH 5.5, 6.0, and 6.5). The stability of the 64CuII-labeled bispidine ligands I – III was studied in the presence of an excess of human superoxide dismutase (SOD) and human serum using standard gel electrophoresis techniques. Biodistribution and PET studies were conducted in male Wistar rats. Small animal PET studies were performed in tumor (PC3, MPC#) bearing mice.

Results: Bispidine ligands I and II form highly stable metal complexes with 64CuII under mild conditions (ambient temperature, aqueous solution). 64Cu-labeling of bispidine dioxotetraaza macrocycles III shows relatively rapid complex formation at 50°C. Challenge experiments with SOD and human serum indicate a high in vitro stability of 64CuII complexes with bispidine ligands I – III. Biodistribution studies, showing rapid blood and tissue clearance, support the high complex stability in vivo. 64Cu-labeled bispidine bioconjugates, incorporating specific vector molecules, such as bombesin and TATE peptides, permit clear tumor visualization with high target-to-background ratio.
Conclusions: Bifunctional bispidine ligands I - III represent a versatile platform for the development of new copper radiopharmaceuticals. The bispidine scaffold holds promising potential to tune the charge and lipophilicity of the radiocopper complexes and consequently to influence the biodistribution and pharmacokinetic properties. Moreover, bispidine ligands can be readily modified with appropriate vector molecules and fluorescence tags.
Acknowledgements: Financial support by the Helmholtz Virtual Institute NanoTracking (Agreement Number VH-VI-421) is gratefully acknowledged.
References:
[1] Comba, P., et al. (2007) Progr. Inorg. Chem. 46, 458-464.
[2] Juran S., et al. (2009) Bioconjugate Chem. 20, 347-359.
[3] Comba P., et al. (2013) Inorg. Chem. 52, 8131-8143.
[4] Comba, P., et al. (2014) Inorg. Chem. 53, 6698-6707.
[5] Stephan, H., et al. (2014) Chem. Eur. J. 20, 17011-17018.
[6] Zarschler K., et al. (2013), RSC Adv. 4, 10157-10164.
[7] Thieme S., et al. (2012) Appl. Radiat. Isot. 70, 602-608.
  • Lecture (Conference)
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S64
    DOI: 10.1002/jlcr.3302_1

Publ.-Id: 22002 - Permalink


1,4,7-triazacyclononane ligands as versatile platform for radiocopper-labeled agents
Pant, K.; Stephan, H.; Bergmann, R.; Pietzsch, J.; Steinbach, J.; Graham, B.; Spiccia, L.;
Objectives: Pyridine containing bifunctional chelating agents (BFCA) based on 1, 4, 7 – triazacyclononane backbones (DMPTACN) are suitable platforms for copper (II) complexes. These ligands rapidly form highly stable, inert square pyramidal complexes that are resistant to metal leaching.1 The ligand structure enables convenient introduction of additional conjugatable functional groups like -COOH end groups to allow a regioselective coupling to various biomolecules for e.g. bombesin.2 Since Cu-64 is a highly useful PET (positron emission tomography) radioisotope because of its intermediate half-life (64Cu, t1/2 -12.7 h) and a high resolution image, these conjugatable DMPTACN chelators can be coupled with various vectors for e.g., proteins, dendritic polymers in order to understand their detailed in vivo pharmacokinetic properties with respect to their ADME behavior. The current objective of the work was to synthesize new maleimide and -SCN derivatives of DMPTACN ligands which could be employed to be conjugated to anti-inflammatory dendritic polyglcerol sulfate (dPGS) & neutral dPG derivatives under mild conditions in order to study the metabolic fate of these potentially therapeutic polymers using positron emission tomography.
Methods: DMPTACN was synthesized by a 10-step process using an established protocol.1 Two coupling groups such as maleimide (1) or isothiocyanate (2) have been attached for further conjugation. These ligands were then conjugated to the thiolated dPGS via Michael addition of 1 and also via direct labeling of 2 to dPGS amine to yield highly stable conjugates. 64Cu was produced following an already established protocol with high specific activities of 150-250 GBq/µmol.3 64Cu-labeling of the conjugates were performed using [64Cu]CuCl2 at ambient temperature in aqueous buffer solution (0.1 M MES/NaOH) and resulted in a radiochemical purity of ≥99% within a few minutes. Challenge experiments were conducted in presence of EDTA or copper seeking superoxide dismutase (SOD) for evaluation of in vitro stability.4 Biodistribution and PET studies were conducted in male Wistar rats.
Results: DMPTACN-dPG/S conjugates form highly stable metal complexes with 64Cu under mild conditions (ambient temperature, aqueous solution) showing resistance to demetalation in vitro and high in vivo stability. Biodistribution data and PET experiments show a charge dependant excretion of the dPGS and dPG macromolecules.
Conclusions: DMPTACN ligands are a versatile platform which can be applied for labeling small molecules, proteins as well as polymers for detailed insight on their biodistribution profiles using 64Cu that allows studying relatively long biochemical processes and thus, prove to be an attractive candidate for PET imaging.
Acknowledgements: This study is part of a research initiative “Technologie und Medizin – Multimodale Bildgebung zur Aufklärung des in-vivo Verhaltens von polymeren Biomaterialien” of the Helmholtz-Portfoliothema.
References:
[1] Gasser G., et al. (2008) Bioconjugate Chem. 19, 719-730.
[2] Bergmann R., et al. (2013) Eur. J. Med. Chem. 70, 434-446.
[3] Thieme S., et al. (2012) Appl. Radiat. Isot. 70, 602-608.
[4] Zarschler K., et al. (2013) RSC Adv. 4, 10157-10164.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S92
    DOI: 10.1002/jlcr.3302_2
  • Lecture (Conference)
    GDCh-Wissenschaftsforum 2015, 30.08.-02.09.2015, Dresden, Deutschland

Publ.-Id: 22001 - Permalink


Spin dynamics in the triangular-lattice antiferromagnet Cs2CuBr4
Zvyagin, S.;
kein Abstract vorhanden
  • Invited lecture (Conferences)
    International Symposium Spin Waves 2015, 08.-10.06.2015, St. Petersburg, Russia

Publ.-Id: 22000 - Permalink


Exposure and terrestrial age of the Twannberg meteorite based on cosmogenic noble gases and radionuclides
Smith, T.; Leya, I.; Hofmann, B.; Merchel, S.; Rugel, G.; Pavetich, S.;
Introduction: The 15.9 kg main mass of the Twannberg meteorite has been found in 1984 in the Canton of Bern, Switzerland. Five additional masses were found until 2007 [1]. Since then, nearly 100 new finds brought the known mass to ~37 kg. The Twannberg meteorite belongs to the small IIG group (6 members), which is characterized by a low concentration of nickel and large inclusions of schreibersite.
Here we study the cosmic ray exposure (CRE) history of 17 individuals of Twannberg using cosmogenic radionuclides and noble gases. We are especially interested in the terrestrial age of Twannberg to better understand its relation with the associated glacial sediments.
Experimental Methods: Noble gas isotopes (He, Ne, and Ar) are analyzed by noble gas mass spectrometry at the University of Bern following procedure described earlier [2,3]. Analyses of the cosmogenic radionuclides (10Be, 26Al, 36Cl, and 41Ca) are performed at the DREsden Accelerator Mass Spectrometry facility (DREAMS, [4]) adapted from procedures described in [5].
Results: So far, 17 samples have been analyzed for the noble gas; 6 of them have also been investigated for their cosmogenic radionuclide contents. We observed a wide range of noble gas and radionuclide concentrations (more than one order of magnitude). The noble gas and radionuclide concentration correlate, indicating the reliability of the analysis despite low concentrations. Combining the data with model calculations indicate a preatmospheric radius in range of 1 to 10 meters. Considering an average density of about 8 g/cm3 and assuming a spherical object, the Twannberg preatmospheric mass was greater than at least 33 tons.
The CRE age has been determined using the 36Cl-36Ar method [6]. The average CRE age is 243±64 Ma, which is in the range of typical CRE ages for iron meteorites [7] and which is in good agreement with the adopted age of 230±50 Ma found previously [1]. The average terrestrial age based on the 36Cl/10Be-10Be systematics is 88±38 ka, indicating that the meteorite fell during the last glaciation, the Würm event (~110-15 ka), but before the maximum glaciation at 24 ka. We expect 41Ca measurements soon, which will help to further pin down the terrestrial age of the Twannberg meteorite and bring the fall into context of glacial events, as suggested by geological indicators [1].
References: [1] Hofmann B. et al. 2009. Meteoritics and Planetary Science 44:187-199. [2] Ammon K. et al. 2008. Meteoritics and Planetary Science 43:685-699. [3] Ammon K. et al. 2011. Meteoritics and Planetary Science 46:785-792. [4] Akhmadaliev S. et al. 2013. Nuclear Instruments and Methods in Physic B 294:5-10. [5] Merchel S. and Herpers U. 1999. Radiochimica Acta 84:215-219. [6] Lavielle B. et al. 1999. Earth and Planetary Science Letters 170:93-104. [7] Eugster O. 2003. Chemie der Erde-Geochemistry 63:3-30.
Acknowledgments: This work is supported by the Swiss National Science Foundation. We thank all the ion beam center members in Dresden for their precious help. This study is heavily based on a close cooperation with enthusiastic meteorite hunters.
Keywords: accelerator mass spectrometry, cosmogenic nuclide, meteorite
  • Lecture (Conference)
    78th Annual Meeting of the Meteoritical Society, 27.07.2015, Berkeley, California, USA
  • Abstract in refereed journal
    Meteoritics & Planetary Science 50 Suppl.(2015), 5201

Downloads:

Publ.-Id: 21999 - Permalink


A novel cyclopentadienyl tricarbonyl 99mTc complex containing 5,6-dimethoxyisoindoline motif - synthesis and evaluation of a radiotracer for imaging of sigma-2 receptors in cancer
Chen, Y.; Deuther-Conrad, W.; Steinbach, J.; Brust, P.; Liu, B.; Jia, H.;
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences - ISRS2015, 26.-31.05.2015, Columbia, Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015)1, 098-098

Publ.-Id: 21997 - Permalink


Evaluation of the novel radiotracer 18F-DBT-10 for imaging the α7 nicotinic acetylcholine receptor in non-human primates
Zheng, M.-Q.; Hillmer, A.; Scheunemann, M.; Holden, D.; Li, S.; Lin, S.; Labaree, D.; Deuther-Conrad, W.; Teodoro, R.; Carson, R. E.; Brust, P.; Huang, H.;
Objectives: The α7nAChR is involved in cognition and a potential drug target for treatment of Alzheimer’s disease and schizophrenia. 18F-DBT-10 is a candidate radioligand for α7nAChR imaging (Kranz et al. J Nucl Med 2014; 55 (Suppl. 1):1143). We performed PET experiments in rhesus monkeys to assess its kinetic and imaging characteristics.

Methods: 18F-DBT-10 was prepared from its nitrophenyl precursor by nucleophilic substitution. The affinity of DBT-10 on human nAChRs was determined by radioligand binding studies. Dynamic PET imaging of two monkeys (each control and blockade) was performed using a Focus-220 scanner. Brain and plasma metabolites were analysed by HPLC. Regional volumes of distribution (VT) were estimated from brain and plasma time-activity data.

Results: DBT-10 has high binding affinity to α7nAChR (Ki = 0.60 nM) and excellent selectivity over other nicotinic receptor subtypes. 18F-DBT-10 was prepared in 14.5±4.6% radiochemical yield and >99% radiochemical purity (n=5). Free plasma fraction of 18F-DBT-10 was 18±2 % (n=4). Plasma metabolism varied considerable between the two animals. Brain uptake was high and tissue kinetics fairly fast, with peak uptake at 10-50 min (Figure 1). No radioactive metabolites were found in brain tissue (thalamus, frontal cortex, hippocampus, and cerebellum) taken from one monkey at 120 min p.i. Time-activity curves were fitted well with the 2-tissue kinetic model. Mean VT values were 58.0, 57.5, 54.9, 54.5, 52.0, 48.4, 39.9, and 34.8 cm3/mL, respectively, for the thalamus, insular, frontal and cingulate cortices, striatum, temporal cortex, hippocampus, occipital cortex, and cerebellum (n=2). Pre-treatment with the selective α7 ligand ASEM (0.69 & 1.24 mg/kg) dose-dependently reduced binding of 18F-DBT-10 in all regions by 30% and 64%, respectively.

Conclusions: 18F-DBT-10 is a novel PET radiotracer with high affinity and selectivity for the α7nAChR. In rhesus monkeys it displays high uptake, appropriate kinetics and high specific binding in brain and thus is a promising agent for PET imaging of α7nAChR in humans.


Figure 1. MR and PET VT images (left) and tissue TACs (right) from a baseline scan with 18F-DBT-10.

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  • Poster
    ISRS2015, 26.-31.05.2015, Columbia, Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015)1, 226-226
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 21996 - Permalink


C++11/14 features relevant in GPGPU APIs
Kelling, J.;
  • Invited lecture (Conferences)
    GPU Day 2015 - The Future of Many-Core Computing in Science, 20.05.2015, Budapest, Hungary

Publ.-Id: 21995 - Permalink


Laser-to-hot-electron conversion limitations in relativistic laser matter interactions due to multi-picosecond dynamics
Schollmeier, M.; Geissel, M.; Arefiev, A. V.; Flippo, K. A.; Gaillard, S. A.; Johnson, R. P.; Kimmel, M. W.; Offermann, D. T.; Rambo, P. K.; Schwarz, J.; Shimada, T.; Sevkov, A. B.;
High-energy short-pulse lasers are pushing the limits of plasma-based particle acceleration, x-ray generation, and high-harmonic generation by creating strong electromagnetic fields at the laser focus where electrons are being accelerated to relativistic velocities. Understanding the relativistic electron dynamics is key for an accurate interpretation of measurements. We present a unified and self-consistent modeling approach in quantitative agreement with measurements and differing trends across multiple target types acquired from two separate laser systems, which differ only in their nano-second to picosecond-scale rising edge. Insights from high-fidelity modeling of laser-plasma interaction demonstrate that the ps-scale, orders of magnitude weaker rising edge of the main pulse measurably alters target evolution and relativistic electron generation compared to idealized pulse shapes. This can lead for instance to the experimentally observed difference between 45MeV and 75MeV maximum energy protons for two nominally identical laser shots, due to ps-scale prepulse variations. Our results show that the realistic inclusion of temporal laser pulse profiles in modeling efforts is required if predictive capability and extrapolation are sought for future target and laser designs or for other relativistic laser ion acceleration schemes.
Keywords: Laser plasma acceleration

Publ.-Id: 21994 - Permalink


Spatially resolved measurement of gas phase temperature and velocity in the subchannels of a fuel element during dry-out
Arlit, M.; Partmann, C.; Schleicher, E.; Hampel, U.;
After the Fukushima accident the spent fuel pool has got a stronger focus in nuclear safety research. The objective of the German national joint project SINABEL (Safety of wet storage facilities for spent fuel) is the experimental investigation and modelling of the thermal hydraulics of fuel elements (10 fuel rods in square, D = 10 mm, P/D = 1.24) in the pool dry-out phase. Key parameters for validation of the models are the steam temperatures and velocities in the subchannels. Due to the complex geometry and the thermal insulation of the test facility there is a strong limitation in the optical and mechanical accessibility for measurements. As a result there is a need of novel measurement techniques to provide spatially resolved gas phase temperatures and velocities.
Our approach is a modified wire-mesh sensor that is usually used for phase discrimination in two-phase flows via the measurement of conductivity or capacity in the crossing points of the wires. In the new sensor concept we integrate special miniaturized converters, which are resistance thermometers for the temperature and velocity measurement. The advantage of this technique is the possibility to overheat the sensor by increasing the current through the sensor. By controlling the sensor temperature the use of the thermal anemometry principle becomes possible.
The challenges in the development of this combining measurement system are the boundary conditions. The range of the steam velocity is down to 0.01 m/s. The temperature range is from the water boiling temperature of 100 °C up to 500 °C overheated steam. As a result of this there are high requirements in temperature compensation and the mechanical resistivity of the measurement setup.
In the contribution we will describe both the new sensor technology as well as its application in thermal hydraulic experiments for advanced analysis of safety issues for the spent fuel pool.
Keywords: Thermal anemometry, Wire-mesh sensor, temperature grid sensor, velocity grid sensor
  • Contribution to proceedings
    NURETH-16 - 16th International Topical Meeting on Nuclear Reactor Thermalhydraulics, 30.08.-04.09.2015, Chicago, USA
  • Poster
    NURETH-16 - 16th International Topical Meeting on Nuclear Reactor Thermalhydraulics, 30.08.-04.09.2015, Chicago, USA

Publ.-Id: 21993 - Permalink


Evaluation of measurement techniques for gas flow characterization in the subchannels of a rodbundle during dry-out
Arlit, M.; Schleicher, E.; Hampel, U.;
For quantification of the thermal hydraulics in a heated rod bundle assembly the gas phase temperature and velocity in the subchannels has to be measured. The accessibility for sensors is strongly restricted due to the test facility design. In this paper the selection process for a suitable measurement device is presented. The approach is the modification of a wire-mesh sensor by implementation of special converters into the crossing points of the grid. Using a sensor material with a high thermal coefficient of resistance, both the resistance thermometer principle and the thermal anemometry principle, can be applicate by modulation of the sensor current.
  • Lecture (Conference)
    46th Annual Meeting on Nuclear Technology, 05.-07.05.2015, Berlin, Deutschland
  • Contribution to proceedings
    46th Annual Meeting on Nuclear Technology, 05.-07.05.2015, Berlin, Deutschland

Publ.-Id: 21992 - Permalink


Blue shift in absorption edge and widening of band gap of ZnO by Al doping and Al–N co-doping
You, Q.; Cai, H.; Hu, Z.; Liang, P.; Prucnal, S.; Zhou, S.; Sun, J.; Xu, N.; Wu, J.;
Al doped ZnO (ZnO:Al) and Al–N co-doped ZnO (ZnO:Al–N) films were synthesized based on plasma assisted reactive deposition of ZnO matrix and in-situ doping of Al or co-doping of Al and N. Similar with undoped ZnO, the synthesized ZnO:Al and ZnO:Al–N films are hexagonal wurtzite in structure and exhibit high optical transparency in a wide spectral region. Al doping and Al–N co-doping in ZnO result in a significant variation of the optical properties in the ultraviolet (UV) region and an UV extension of the transparent range. Compared with undoped ZnO, the doped films show blue-shifted absorption edge of 320 nm and widened band gap of 3.69 eV after annealing in H2/N2 mixed gas because of the incorporation of dopants and the improvement in the crystal structure. The ZnO:Al film exhibits declined transparency in the near infrared (IR) region, while the ZnO film co-doped with Al and N preserves high transparency from near UV to medium IR in addition to the UV extension of the transparent range. The annealed ZnO:Al and ZnO:Al–N films show better electrical properties than those of the undoped ZnO film and the as-deposited doped ZnO films.
Keywords: Absorption edge; Band gap; Al doped ZnO; Al–N co-doped ZnO; In-situ doping

Publ.-Id: 21991 - Permalink


Interactions of natural occurring eukaryotic microorganisms with uranium(VI)
Gerber, U.; Krawczyk-Bärsch, E.; Arnold, T.; Merroun, M. L.;
Despite high uranium concentrations (up to 14 mg L-1) and low pH (2.5 - 3.0) a high biodiversity was detected by culture independent methods in the flooding water of the former uranium mine Königstein (Saxony, Germany). In this study culture dependent methods were used for the isolation of eukaryotic microorganisms from the flooding water. It was possible to isolate different eukaryotic fungi with a glucose riche medium. The results of uranium immobilization tests showed high immobilization rates of about 120 to 160 mg uranium per 1 g dry mass. Flow cytometry experiments with KS5 and DSM 10134 were performed in liquid medium to quantitatively determine the uranium tolerance. In comparison, the isolate KS5 showed a higher uranium tolerance than the reference culture of DSM 10134 on solid as well as in liquid medium. In conclusion, this study indicates that eukaryotic microorganisms within a uranium-contaminated environment could potentially play an important role in the bioremediation of uranium.
Keywords: Bioremediation, Uranium, Königstein, Immobilization
  • Poster
    Petrus PhD Conference 2015, 22.-26.06.2015, Nancy, Frankreich

Publ.-Id: 21990 - Permalink


In situ visualisation of dendritic growth in solidifying Ga – In alloys
Shevchenko, N.; Roshchupkina, O.; Grenzer, J.; Baehtz, C.; Eckert, S.;
X-ray absorption contrast techniques are an effective tool for investigating solidification processes in opaque metallic alloys. This work is devoted to the in situ visualization of the dendritic growth during the bottom-up solidification of a Ga-25wt%In alloy under natural and forced convections. Many effects of melt flow on the mushy zone structure were observed by standard X-ray radiography with a spatial resolution of 5-10 microns [1, 2]. The flow-induced variations of the local solute concentration result in an unsteady development of the primary dendrites and trigger or inhibit the development of secondary and tertiary arms. Variations of the vertical and lateral temperature gradients induce modifications of the melt flow pattern, which lead to different segregation structures and dendrite morphology.
A more detailed analysis of the particular processes (a detachment of side branches and growth of a dendrite tip) were carried out using synchrotron X-ray radiography with a spatial resolution of less than 1 µm. The synchrotron experiments were performed at the ROBL beam line (BM20, European Synchrotron Radiation Facility, Grenoble) at an energy of 28.5 keV. The combination of synchrotron X-ray radiography and synchrotron X-ray diffraction shows a big potential for orientation analysis of the growing grains and a lattice parameter determination of the solid phase.
Keywords: Directional solidification, melt flows, X-ray radiography, Ga–In alloys
  • Lecture (Conference)
    European Crystallographic Meeting, 23.-28.08.2015, Rovinj, Croatia
  • Abstract in refereed journal
    Acta Crystallographica Section A 71(2015), s156
    DOI: 10.1107/S2053273315097727

Publ.-Id: 21989 - Permalink


Detection of melt flow in solidifying metal alloys by X-ray radioscopy
Shevchenko, N.; Roshchupkina, O.; Eckert, S.;
X-ray radioscopic methods enable the in-situ real-time observation of solidification processes in metal alloys with a spatial resolution of a few microns. Visualization of bottom up directional solidification of a Ga-25wt%In binary metal alloy contained in a capillary slit container was conducted. The solidification is obviously affected by natural thermo-solutal melt flow patterns. Externally forced melt convection was superimposed by means of a magnetic stirrer in form of a rotating wheel equipped with permanent magnets. The electromagnetic flow provokes a considerable redistribution of the solutal boundary layers around the solidifying dendrites, and influences therewith the formation of the microstructure.
The X-ray radioscopy delivers a two-dimensional projection of the local density in the slit container corresponding to the distribution of the relative brightness P in the acquired images. The relative brightness P allows for an assessment of the local constitution inside the liquid phase. Our analysis of the flow field in the present article follows the Optical Flow approach proposed by Horn and Schunck. [1] The applied algorithm to determine the optical flow from the X-ray images delivers reliable information concerning the velocity field in regions where sufficiently large brightness gradients occurs. The solidification process creates differences of the local composition within the melt leading to characteristic pattern of transmitted light intensity. The analysis of the flow field relies on the monitoring of the temporal variations of characteristic brightness patterns in the liquid phase.
Our results show that melt flow induces various effects on the grain morphology primarily caused by the convective transport of solute. Our observations show a facilitation of the growth of primary trunks or lateral branches, suppression of side branching, dendrite remelting and fragmentation. The manifestation of all phenomena depends on the dendrite orientation, local direction and intensity of the flow. The forced flow eliminates the solutal plumes and damps the local fluctuations of solute concentration. It provokes a preferential growth of the secondary arms at the upstream side of the primary dendrite arms, whereas the high solute concentration at the downstream side of the dendrites can inhibit the formation of secondary branches completely. Moreover, the flow changes the inclination angle of the dendrites and the angle between primary trunks and secondary arms.
  • Lecture (Conference)
    3rd International Workshop on Measuring Techniques for Liquid Metal Flows, 15.-17.04.2015, Dresden, Germany

Publ.-Id: 21988 - Permalink


Mobility Investigations on Strained 30-nm High-k Metal Gate MOSFETs by Geometrical Magnetoresistance Effect
Beister, J.; Wachowiak, A.; Boschke, R.; Herrmann, T.; Uhlarz, M.; Mikolajick, T.;
In this paper, we present mobility investigations of strained nMOS and pMOS short-channel transistors with dimensions down to 30-nm gate length. Using the geometrical magnetoresistance (MR) effect, carrier mobility of electrons and holes in the inversion channel of a recent state-of-the-art CMOS technology is presented from linear to saturation operation conditions. The MR effect allows for a more direct access to the carrier mobility compared with the conventional current/voltage and capacitance/voltage mobility derivation methods, in which series resistance, inversion charge density, and effective channel length are necessary to extract the mobility values of the short-channel devices. In another way, the MR effect can help to disentangle the performance gain of the strained state-of-the art devices to changes in channel mobility or device connection, e.g., series resistance effects.

Publ.-Id: 21987 - Permalink


Observation of dendritic growth under the influence of forced convection
Roshchupkina, O.; Shevchenko, N.; Eckert, S.;
The directional solidification of Ga–25wt%In alloys within a Hele-Shaw cell was visualized by X-ray radioscopy. The investigations are focused on the impact of melt convection on the dendritic growth. Natural convection occurs during a bottom up solidification because lighter solute is rejected during crystallization. Forced convection was produced by a specific electromagnetic pump. The direction of forced melt flow is almost horizontal at the solidification front. Melt flow induces various effects on grain morphology primarily caused by convective transport of solute, such as a facilitation of the growth of primary trunks or lateral branches, dendrite remelting, fragmentation or freckle formation depending on the dendrite orientation, the flow direction and intensity. Forced flow eliminates solutal plumes and damps local fluctuations of solute. A preferential growth of the secondary arms occurs at the upstream side of the dendrites, whereas high solute concentration at the downstream side inhibits the formation of secondary branches.
Keywords: X-ray radioscopy, in situ studies, melt convection, forced convection, dendritic growth
  • Open Access LogoContribution to proceedings
    Modeling of Casting, Welding and Advanced Solidification Processes, 21.-26.06.2015, Awaji Yumebutai, Japan
    IOP Conference Series: Materials Science and Engineering 84(2015)1, 012080
    DOI: 10.1088/1757-899X/84/1/012080
  • Lecture (Conference)
    Modeling of Casting, Welding and Advanced Solidification Processes, 21.-26.06.2015, Awaji Yumebutai, Japan

Publ.-Id: 21986 - Permalink


Visualization of liquid metal bubbly flows using the X-ray radioscopy
Roshchupkina, O.; Shevchenko, N.; Strumpf, E.; Timmel, K.; Eckert, S.;
The quality of continuous cast steel is significantly affected by the flow pattern in the mould and submerged entry nozzle (SEN). The flow in continuous casting machines is often a two-phase one because argon is injected to avoid clogging inside the casting nozzle. Moreover, the argon bubbles are supposed to drag alumina particles and transport them towards the slag layer at the free surface. On the other hand, the gas injection leads to highly turbulent and complex two-phase flows, which are difficult to predict by numerical simulations. The injected bubbles have a distinct influence on the flow pattern and may trigger instabilities in the mold, for instance, observations made on real casters showed correlations between gas pressure variations in the SEN and mould meniscus perturbations.

Despite of the considerable number of previous studies mainly performed as numerical simulations and water models the understanding of liquid metal two phase flows remains fragmentary. Many open questions require further investigations, as concerns the formation process of gas bubbles, their distribution and flow regime in the SEN, the size of bubbles entering the mould, the flotation of the gas in the mould, the gas entrapment in the solidifying strand, etc. This situation motivated us to construct a specific model experiment where liquid metal two-phase flows can be investigated under flow conditions which are similar to those in the real continuous casting process.

We present an experimental study in a mockup of the continuous casting process. The two-phase flows in the mould and the SEN were visualized by means of X-ray radioscopy. The argon gas is injected through the tip of the stopper rod into the liquid metal flow. The system operates continuously with the low melting, eutectic alloy GaInSn under isothermal conditions. Experimental results will be presented and discussed accompanied by statistical analysis.
Keywords: X-ray radioscopy, two-phase flows, continuous casting
  • Lecture (Conference)
    3rd International Workshop on Measuring Techniques for Liquid Metal Flows, 15.-17.04.2015, Dresden, Deutschland

Publ.-Id: 21985 - Permalink


Thin Sample Alloy Solidification in Electromagnetic Driven Convection
Kao, A.; Shevchenko, N.; Roshchupinka, O.; Eckert, S.; Pericleous, K.;
During the directional solidification of Ga-In25%wt., density variations in the liquid cause plumes of solute to be ejected from the interface through natural convection. This can lead to the formation of chimneys during solidification and ultimately freckles. The application of external magnetic fields can be used to suppress these plumes. Two magnetic systems are considered. The first is a rotating magnetic wheel, which provides conditions analogous to forced convection at the solidification interface. The forced convection causes preferential growth of secondary branches and the plumes to be transported downstream and back into the bulk. The second is the application of a static magnetic field, which interacts with inherent thermoelectric currents, generating a Lorentz force that drives fluid flow within the inter-dendritic region. However, in the bulk, where there are no thermoelectric currents electromagnetic damping dominates and plumes are stunted.

Using a fully coupled transient numerical model a quantitative analysis of each of these systems has been investigated. Figure 1 shows numerical results of the velocity profiles and dendritic morphology for each of these cases. Comparisons to experiments are given for the cases of natural and forced convection. The experimental setup uses a Hele-Shaw cell with an electric heater and Peltier cooler allowing for control over the thermal gradient and cooling rate.
  • Lecture (Conference)
    8th International Congress on Electromagnetic Processing of Materials (EPM2015), 12.-16.10.2015, Cannes, France
  • Contribution to proceedings
    8th International Congress on Electromagnetic Processing of Materials (EPM2015), 12.-16.10.2015, Cannes, France

Publ.-Id: 21984 - Permalink


Multi Group Geometrical Correction for Coupled Monte Carlo Codes: Multi-Regional Thermal System
Kotlyar, D.; Shwageraus, E.; Fridman, E.;
This paper focuses on generating accurate 1-g cross section values that are necessary for evaluation of nuclide densities as a function of burnup for coupled Monte Carlo codes. The proposed method is an alternative to the conventional direct reaction rate tally approach, which requires extensive computational efforts. The method presented here is based on the multi-group (MG) approach, in which pre-generated MG sets are collapsed with MC calculated flux. In our previous studies we showed that generating accurate 1-g cross sections requires their tabulation against the background cross-section (σ0) to account for the self-shielding effect. However, in previous studies, the model that was used to calculate σ0 was simplified by fixing Bell and Dancoff factors. This work demonstrates that 1-g values calculated under the previous simplified model may not agree with the tallied values. Therefore, the original background cross section model was extended by implicitly accounting for the Dancoff and Bell factors. The method developed here reconstructs the correct value of σ0 by utilizing statistical data generated within the MC transport calculation by default. The method does not carry any additional computational burden and it is universally applicable to the analysis of thermal as well as fast reactor systems.
Keywords: Monte Carlo; BGCore; Multi group; one-group cross sections
  • Contribution to proceedings
    Joint International Conference on Mathematics and Computation, Supercomputing in Nuclear Applications and the Monte Carlo Method 2015, 19.-23.04.2015, Nashville, TN, USA
    Multi Group Geometrical Correction for Coupled Monte Carlo Codes: Multi-Regional Thermal System
  • Lecture (Conference)
    Joint International Conference on Mathematics and Computation, Supercomputing in Nuclear Applications and the Monte Carlo Method 2015, 19.-23.04.2015, Nashville, TN, USA

Publ.-Id: 21983 - Permalink


The effects of natural, forced and thermoelectric magnetohydrodynamic convection during the solidification of thin sample alloys
Kao, A.; Shevchenko, N.; Roshchupinka, O.; Eckert, S.; Pericleous, K.;
Using a fully coupled transient 3-dimensional numerical model, the effects of convection on the microstructural evolution of a thin sample of Ga-In25%wt. was predicted. The effects of natural convection, forced convection and thermoelectric magnetohydrodynamics were investigated numerically. A comparison of the numerical results is made to experimental results for natural convection and forced convection. In the case of natural convection, density variations within the liquid cause plumes of solute to be ejected into the bulk. When forced convection is applied observed effects include the suppression of solute plumes, preferential secondary arm growth and an increase in primary arm spacing. These effects were observed both numerically and experimentally. By applying an external magnetic field inter-dendritic flow is generated by thermoelectrically induced Lorentz forces, while bulk flow experiences an electromagnetic damping force. The former causes preferential secondary growth, while the latter slows the formation of solute plumes. This work highlights that the application of external forces can be a valuable tool for tailoring the microstructure and ultimately the macroscopic material properties.
  • Lecture (Conference)
    Modelling of Casting, Welding and Advanced Solidification Processes, 21.-26.06.2015, Awaji island, Hygo, Japan
  • Open Access LogoContribution to proceedings
    Modelling of Casting, Welding and Advanced Solidification Processes, 21.-26.06.2015, Awaji island, Hygo, Japan
    IOP Conference Series: Materials Science and Engineering 84(2015)1, 012018
    DOI: 10.1088/1757-899X/84/1/012018

Publ.-Id: 21982 - Permalink


In situ analysis of dendritic growth and fragmentation in solidifying Ga – In alloys
Shevchenko, N.; Roshchupkina, O.; Eckert, S.;
Simultaneous study of solidification phenomena on different length scales (e.g. µm-sized dendrite morphology and mm-sized flow structures) raises a serious problem. Since several years X-ray radioscopy has been proposed and successfully used as an effective tool for in situ real time observations of the dendrite growth, concentration field and flow patterns. The upward directional solidification of Ga-25wt%In alloy within a Hele-Shaw cell was studied by in situ X-ray radioscopy. This work is focused on the investigation of the influence of natural convection on the concentration profiles, dendrite morphology, growth velocities, freckle formation and fragmentation. Additionally, we use the Optical Flow approach proposed by Boden et al. [1] for the estimation of the melt flow ahead of the solidification front.
The ascending plumes and the downward flow of In-rich melt lead to an inhomogeneous horizontal concentration profile along the solidification front. Variations of the vertical and lateral temperature gradients induce modifications of the melt flow pattern, which lead to different segregation structures and dendrite morphology. The dendrite growth velocity is mainly determined by the dynamics of the solute plumes which cause significant fluctuations of solute concentration. Our in situ experiments provide quantitative data on concentration, flow fields, tip velocity, etc. for the verification of actual models of freckle formation [2].
The second part of the study is devoted to the visualization of the fragmentation process in the mushy zone. Numerous events of detachment of secondary arms from the primary trunks occur in the deeper mushy zone. These fragments remain within the inter-dendritic regions. Fragments originating in the upper mushy zone can ascend by convective transport in the plumes and arrive in undercooled regions ahead of the dendritic front. Future work is in progress in order to classify our experimental data with respect to the known fragmentation mechanisms.
  • Poster
    Modelling of Casting, Welding and Advanced Solidification Processes, 21.-26.06.2015, Awaji island, Hygo, Japan

Publ.-Id: 21981 - Permalink


X-ray observations showing the effect of fluid flow on dendritic solidification in Ga-In alloys
Shevchenko, N.; Roshchupkina, O.; Eckert, S.;
The directional solidification of Ga–25wt%In alloys within a Hele-Shaw cell has been studied by X-ray radioscopy. The investigations have focused on the influence of melt convection on the dendritic growth. Natural convection occurs during a bottom up solidification because a lighter solute is rejected during crystallization. Forced convection has been produced by a specific electromagnetic pump. The direction of forced melt flow is almost horizontal at the solidification front. Melt flow induces various effects on grain morphology caused primarily by convective transport of solute, such as facilitation of the growth of primary trunks or lateral branches, dendrite remelting, fragmentation or freckle formation depending on the dendrite orientation, the flow direction and intensity. Forced flow eliminates solutal plumes and damps local fluctuations of solute. A preferential growth of the secondary arms occurs at the upstream side of the dendrites, whereas high solute concentration at the downstream side inhibits the formation of secondary branches.
Keywords: Fluid flow, solidification, convection, X-ray radiography, in situ observation
  • Invited lecture (Conferences)
    Advances in the Science and Engineering of Casting Solidification: An MPMD Symposium Honoring Doru Michael Stefanescu; 2015 TMS Annual Meeting & Exhibition, 15.-19.03.2015, Orlando, Florida, USA
  • Contribution to proceedings
    Advances in the Science and Engineering of Casting Solidification: An MPMD Symposium Honoring Doru Michael Stefanescu; 2015 TMS Annual Meeting & Exhibition, 15.-19.03.2015, Orlando, Florida, USA

Publ.-Id: 21980 - Permalink


Modular Ultrasound Array Doppler Velocimeter with FPGA-based Signal Processing for Real-time Flow Mapping in Liquid Metal
Nauber, R.; Thieme, N.; Beyer, H.; Büttner, L.; Räbiger, D.; Eckert, S.; Czarske, J.;
Investigating the complex interaction of conductive fluids and magnetic fields is relevant for a variety of applications from basic research in magnetohydrodynamics (MHD) to modeling industrial processes involving metal melts, such as the crystal growth process in the photovoltaic industry. This enables targeted optimizations of the melt flow and allows to significantly increase the yield and energy effciency of industrial processes. However, experimental studies in this field are often limited by the performance of flow instrumentation for opaque liquids. We present an ultrasound array Doppler velocimeter (UADV) for flow mapping in opaque liquids at room temperature. It is modular and flexible regarding its measurement configuration, for instance it allows capturing two velocity components in two planes (2d - 2c). It uses up to 9 linear arrays with a total element count of 225, driven in a parallelized time division multiplex (TDM) scheme. A FPGA-based signal pre-processing allows to handle the massive data bandwidth of typ. 1.2 GB/s and enables a continuous and near-realtime operation of the measurement system. The capabilities of the UADV system are demonstrated in a basic MHD research experiment with a metal melt (GaInSn) in a cubic container of (67 mm)³. The flow induced by a rotating magnetic field is captured with a temporal resolution of 250 ms for the horizontal and vertical central cross-section of the cube.
Keywords: Flow-Mapping, Ultrasound Doppler Velocimetry, Liquid Metals, Magnetohydrodynamics, Flow Control, FPGA
  • Lecture (Conference)
    International Congress on Ultrasonic, 10.-14.05.2015, Metz, Frankreich
  • Open Access LogoPhysics Procedia 70(2015), 537-540
    DOI: 10.1016/j.phpro.2015.08.011

Publ.-Id: 21979 - Permalink


Realizing Optical Free-Electron Lasers with Traveling-Wave Thomson-Scattering
Steiniger, K.; Bussmann, M.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Röser, F.; Schramm, U.; Sauerbrey, R.;
Optical free-electron lasers (OFELs) from the EUV to X-ray range can be realized in Traveling-Wave Thomson-Scattering (TWTS)[1,2] by utilizing pulse-front tilted high-power laser pulses as optical undulators.
The interaction distances required to induce microbunching to the electron beam for coherent radiation emission are realized in TWTS with a combination of side-scattering and a tilt of the laser pulse-front, as depicted in fig. 1. In the side-scattering geometry the electron beam and laser pulse directions of motion enclose the interaction angle. The tilt of the laser pulse-front by half of the interaction angle then ensures continuous overlap of electrons and laser while both are propagating in different directions. In this way, the interaction distances realized in TWTS are only limited by the transverse size of the laser and thus by the available laser power and size of available optics.
Our fully analytic theory of TWTS OFELs provides scaling laws for the electron and laser pulse quality requirements for OFEL operation. We show that TWTS OFELs can be realized with state-of-the-art technology in electron accelerators and laser systems if the presented scheme for dispersion control is applied. Thereby the variability of TWTS with respect to the interaction angle is used to control the electron and laser beam quality requirements. Especially the sub-μm transv. emittance beams from laser wakefield accelerators with energy spreads in the percent level can be used for the realization of all-optical FELs with acceleration and interaction distances in the centimeter range. An outlook on 3D simulations of TWTS OFELs using the particle in cell code PIConGPU is given.
Keywords: Thomson-scattering, X-ray, FEL, PIConGPU
  • Invited lecture (Conferences)
    Laser Plasma Acceleration Workshop 2015, 11.-15.05.2015, Guadeloupe, France

Publ.-Id: 21978 - Permalink


Realizing all optical free-electron lasers with Traveling-Wave Thomson-Scattering
Steiniger, K.; Bussmann, M.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Roeser, F.; Schramm, U.;
Optical free-electron lasers (OFELs) from the ultra violet to x-ray range can be realized with Traveling-Wave Thomson-Scattering (TWTS). This becomes possible in TWTS by increasing the photon scattering efficiency of standard Thomson scattering geometries more than one order of magnitude by changing the interaction geometry. In TWTS a side-scattering geometry is used where the laser and electron propagation directions enclose the interaction angle $\phi$. Together with a tilt of the laser pulse front the interaction distance is increased in TWTS beyond the limits of head-on Thomson scattering. TWTS implements dispersion control of the laser pulse to compensate for variations of the optical undulator period originating from the pulse-front tilt. Altogether, the combination of side-scattering, pulse-front tilt and dispersion control in TWTS allows for meter-scale interaction distances in which the electron beam becomes microbunched and OFEL operation is achieved. These TWTS OFELs provide transverse coherence as well as brilliances an order of magnitude enhanced over standard head-on Thomson scattering geometries.
We present the scaling laws of TWTS OFELs derived from a fully analytic theory of the electron laser interaction in TWTS scattering geometries. TWTS OFELs can be realized in an all-optical setup with a meter-scale footprint using laser wakefield accelerated electrons featuring both ultralow transverse emittances and large energy spreads.
Keywords: Traveling-Wave, Thomson scattering, X-ray, FEL
  • Poster
    Novel Light Sources from Laser-Plasma Interactions, 20.-24.04.2015, Dresden, Deutschland

Publ.-Id: 21977 - Permalink


Realizable Optical Free-Electron Lasers with Traveling-Wave Thomson-Scattering
Steiniger, K.; Bussmann, M.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Röser, F.; Schramm, U.; Sauerbrey, R.;
In Traveling-Wave Thomson-Scattering (TWTS) a high-power laser pulse is scattered off a relativistic electron pulse to realize optical free-electron lasers (OFELs) with a wavelength range from ultraviolet to Angstrom. TWTS employs a side-scattering geometry where laser and electron beam propagation direction enclose an interaction angle to become independent of the Rayleigh length limit for the maximum interaction distance inherent to standard head-on Thomson scattering geometries. For optimum spatial overlap between electrons and laser pulse in TWTS geometries the laser pulse features a pulse-front tilt. In this way, the electrons interact with all parts of the laser pulse and the brilliance of a TWTS light source become by orders of magnitude larger than in standard head-on geometries where spatial overlap between electrons and laser pulse is lost due to defocusing of the laser pulse. OFELs can be operated with TWTS using multi-hundred to petawatt class laser systems with beam diameters in the centimeter range since the interaction distance in TWTS can be controlled with the laser beam diameter in the interaction plane.
We show that interaction distances achieved in TWTS are long enough for microbunching of the electron beam and coherent amplification of the radiation from our 1.5D FEL theory for the interaction of electrons with laser fields in side-scattering geometries.
We give the scaling laws for the design of TWTS OFELs derived from this 1.5D theory and present possible experimental setups for TWTS OFELs using electrons from conventional and laser wakefield accelerators. We put emphasize on how the ultra-low emittance of a laser wakefield accelerator can be exploited to compensate for the one percent level energy spread and how laser pulse dispersion introduced with the pulse-front tilt in TWTS setups can be compensated with an additional pair of gratings in the laser pulse path before the interaction.
Keywords: Traveling-Wave, Thomson scattering, X-ray, FEL
  • Invited lecture (Conferences)
    SPIE Optics + Optoelectronics 2015, 13.-16.04.2015, Prague, Czech Republic

Publ.-Id: 21976 - Permalink


Experimental design of optical free-electron lasers in the Traveling-Wave Thomson-Scattering geometry
Steiniger, K.; Bussmann, M.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Röser, F.; Schramm, U.; Sauerbrey, R.;
Traveling-Wave Thomson-Scattering (TWTS) realizes optical free-electron lasers (OFEL) from the extreme ultraviolet to the X-ray range with existing electron accelerators and high-power laser systems. In TWTS ultrashort laser pulses and relativistic electron bunches are utilized in a side-scattering geometry where laser pulse and electron bunch direction of motion enclose an interaction angle. The laser electric field thereby is the undulator field in which the electrons oscillate and emit radiation during the interaction. When the electrons traverse the laser beam cross-section, TWTS provides continuous overlap of electron bunch and laser pulse by employing a laser pulse-front tilt which compensates the spatial separation of electrons and laser at the beginning and end of the interaction originating from their different propagation directions. The combination of laser pulse-front tilt and side-scattering in TWTS enables interaction lengths long enough to induce microbunching of the electron beam leading to coherent amplification of the emitted radiation and the realization of TWTS OFELs.
We present the scaling laws for the electron beam and laser pulse requirements to operate TWTS OFELs and show with example scenarios that TWTS OFELs can be realized with existing radio-frequency accelerated electrons such as ELBE at HZDR as well as laser-wakefield accelerated electrons. We detail the necessary equipment in a TWTS OFEL experiment and discuss how current experimental limitations affect the design of TWTS OFEL setups.
Keywords: Traveling-wave, Thomson scattering, X-ray, FEL
  • Lecture (Conference)
    DPG Frühjahrstagung Wuppertal 2015, 09.-13.03.2015, Wuppertal, Deutschland

Publ.-Id: 21975 - Permalink


From Optical Undulators to Optical FELs with Traveling-Wave Thomson-Scattering
Steiniger, K.; Bussmann, M.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Röser, F.; Schramm, U.; Sauerbrey, R.;
No abstract needed
Keywords: Traveling-Wave, Thomson scattering, X-ray, FEL
  • Invited lecture (Conferences)
    Materie und Technologie Kick-Off Meeting, 24.-26.02.2015, Hamburg, Deutschland

Publ.-Id: 21974 - Permalink


Defect induced magnetism in SiC
Zhou, S.; Wang, Y.; Liu, Y.; Gemming, S.; Helm, M.;
Defect-induced magnetism is attracting intensive research interest. It not only challenges the traditional opinions about magnetism, but also has some potential applications in spin-electronics. SiC is a new candidate for the investigation of defect-induced ferromagnetism after graphitic materials and oxides due to its high material purity and crystalline quality [1, 2]. In this contribution, we made a comprehensive investigation on the structural and magnetic properties of ion implanted and neutron irradiated SiC sample. In combination with X-ray absorption spectroscopy and first-principles calculations, we try to understand the mechanism in a microscopic picture.
For neon or xenon ion implanted SiC, we identify a multi-magnetic-phase nature [3]. The magnetization of SiC can be decomposed into paramagnetic, superparamagnetic and ferromagnetic contributions. The ferromagnetic contribution persists well above room temperature and exhibits a pronounced magnetic anisotropy. By combining X-ray magnetic circular dichroism and first-principles calculations, we clarify that p-electrons of the nearest-neighbor carbon atoms around divacancies are mainly responsible for the long-range ferromagnetic coupling [4]. Thus, we provide a correlation between the collective magnetic phenomena and the specific electrons/orbitals.
With the aim to verify if a sample containing defects through its bulk volume can persist ferromagnetic coupling, we applied neutron irradiation to introduce defects into SiC [5]. Besides a weak ferromagnetic contribution, we observe a strong paramagnetism, scaling up with the neutron fluence. The ferromagnetic contribution only occurs in a narrow fluence window or after annealing. We speculate that defect-induced ferromagnetism rather locally appears in particular regions, like surface/interface/grain boundaries.
[1] L. Li, et al., Appl. Phys. Lett. 98, 222508 (2011). [2] Y. Wang, et al., Phys. Rev. B 90, 214435 (2014). [3] Y. Wang,et al., Phys. Rev. B 89, 014417 (2014). [4] Y. Wang, et al., Sci. Reports 5, 8999 (2015). [5] Y. Wang, et al., Phys. Rev. B, submitted (2015).
  • Lecture (Conference)
    20th International Conference on Mangetism, 05.-10.07.2015, Barcelona, Spain
  • Lecture (Conference)
    EMRS2016Fall, 19.-22.09.2016, Warsaw, Poland
  • Lecture (Conference)
    DPG-Frühjahrstagung 2016, 06.-11.03.2016, Regensburg, Germany

Publ.-Id: 21973 - Permalink


Magnetization and X-ray absorption spectroscopy of Mn implanted Ge after flashlamp annealing
Zhou, S.; Wang, Y.; Prucnal, S.; Jiang, Z.; Zhang, W.; Wu, C.; Weschke, E.; Skorupa, W.; Helm, M.;
Ge-based diluted magnetic semiconductors have drawn extensive attention over the past decades due to their potential to be applied in spintronic devices and to be integrated with the mainstream Si microelectronics as well. The hole-mediated effect in diluted magnetic semiconductors provides the possibility to realize the control of magnetic properties by the electrical control of free carriers. In this contribution, we will present the magnetic properties and X-ray absorption spectroscopy of Mn implanted Ge annealed by flashlamp.
Keywords: Magnetic thin films and nanostructures
  • Lecture (Conference)
    IEEE International Conference on Magnetics 2015, 11.-15.05.2015, Beijing, China

Publ.-Id: 21972 - Permalink


Composition and bandgap control of AlxGa1−xN films synthesized by plasma-assisted pulsed laser deposition
Cai, H.; Liang, P.; Hübner, R.; Zhou, S.; Li, Y.; Sun, J.; Xu, N.; Wu, J.;
Ternary AlxGa1−xN films with different Al compositions were synthesized on sapphire and Si substrates by pulsed laser co-ablation of a polycrystalline GaAs target and a metallic Al target in nitrogen plasma generated by electron cyclotron resonance discharge of N2 gas. Spectroscopy was used to characterize the synthesis process for the mechanisms responsible for AlxGa1−xN synthesis and film deposition. The synthesized AlxGa1−xN films were evaluated using field emission scanning electron microscopy, atomic force microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman scattering spectroscopy, transmission electron microscopy and optical transmission measurements. The AlxGa1−xN films have hexagonal wurtzite structure, which degenerates as the Al composition increases, and show high optical transparency with the absorption edge blue shifted and the bandgap widened with the increasing Al composition. A comparison of the synthesized AlxGa1−xN films with the binary GaN and AlN films synthesized by a similar method reveals their similarity in the structure and the optical properties.
Keywords: AlGaN, PLD

Publ.-Id: 21971 - Permalink


lll-V nanocrystal formation in ion-implanted Ge and Si via liquid phase epitaxy during short-time flash lamp annealing
Wutzler, R.; Rebohle, L.; Prucnal, S.; Böttger, R.; Hübner, R.; Facsko, S.; Helm, M.; Skorupa, W.;
The integration of III-V compound semiconductors into existing semiconductor technology is a milestone in future development of micro- and opto-electronics. III-V compound semiconductor nanocrystals (NCs) were fabricated in Ge and Si substrates by high-fluence ion implantation and short-time flash lamp annealing (FLA). The III-V NC formation takes place after amorphization due to implantation, followed by recrystallization via millisecond liquid phase epitaxy. Using this approach, GaAs and InAs NCs were fabricated. Whereas this formation process was recently investigated for Si, the case of Ge has not been reported yet but shows remarkable differences. In order to get III-V/Ge and III-V/Si heterojunctions in the form of free-standing III-V NCs on Ge and Si nanocolumns an additional selective etching of Ge and Si was performed using H2O2 and KOH solution, respectively.
Raman spectroscopy measurements confirmed the formation of III-V NCs within the particular, recrystallized matrices. The microstructural properties of the III-V NCs and the distribution of implanted species were investigated by scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (TEM), and Auger electron spectroscopy (AES). SEM and TEM images show distinct, crystalline NCs. Conductive atomic force microscopy (c-AFM) was performed to investigate the electrical behavior of the fabricated heterojunctions.
Keywords: Ion implantation, Flash lamp annealing, III-V integration, Liquid phase epitaxy, Silicon, Germanium
  • Lecture (Conference)
    E-MRS Spring Meeting 2015, 11.-15.05.2015, Lille, France

Publ.-Id: 21970 - Permalink


Wechselwirkung von Actiniden/Lanthaniden mit Ton, Tonorganika und Mikroorganismen
Schmeide, K.; Fritsch, K.; Lippold, H.; Poetsch, M.; Kulenkampff, J.; Jordan, N.; Moll, H.; Cherkouk, A.;
In the talk, the most important results obtained in the project for the system radionuclide/clay organics/clay rock are presented. The influence of salinity and temperature on complexation, sorption as well as diffusion/transport of radionuclides is discussed.
Keywords: Uranium, plutonium, europium, terbium, fulvic acid, propionic acid, microorganisms, montmorillonite, Opalinus Clay, PET
  • Lecture (others)
    Abschlussworkshop des Verbundprojekts "Rückhaltung endlagerrelevanter Radionuklide im natürlichen Tongestein und in salinaren Systemen", 12.-13.05.2015, Mainz, Deutschland

Publ.-Id: 21969 - Permalink


Sustainable solutions for restoration & conservation of pipe organs by using Plasma Ion based surface engineering vs. EMA copolymer surface treatment techniques.
Pelic, B.; Skorupa, W.;
Pipe organs with their unique sound and beautiful housing are important objects of the cultural heritage. The instrument consists of a number of pipes (flute and reed), which are prone to heavy corrosion attack, resulting in a loss of voice. The atmospheric corrosion of reed (CuZn alloys) and flute pipes (PbSn alloys) is strongly enhanced by traces of volatile organic compounds (VOCs) and the alloy’s instability.
Experiments have been undertaken to explore the improvement of an aqueous corrosion with the high acetic acid concentration (2–5 v/v%) of CuZn and PbSn alloys, by deposition of protective films (Al2O3 and Al) in nano scale using Pulsed laser deposition and Magnetron sputtering. Afterwards, the samples were implanted with N+ ions using plasma immersion ion implantation. Such coating is then able to withstand stresses and vibrations due to sound generation in organ pipes, and it produces a barrier to VOCs and water vapor. Furthermore, for the treatments of new or slightly corroded flute pipes, solution of 4% Paraloid B-72 in toluene has been applied as corrosion inhibitor. The complete and overall application of the PB-72 improved significantly the corrosion resistance of flute pipes. The laboratory corrosion tests were combined with field studies at affected church organs.
Keywords: Plasma immersion ion implantation (PI3), Pulsed laser deposition (PLD), Magnetron sputtering (MS), EMA copolymer (Paraloid B-72), corrosion of organ pipes
  • Lecture (Conference)
    E-MRS Spring Meeting 2015, 11.-15.05.2015, Lille, France

Publ.-Id: 21968 - Permalink


Measurement of α-particle quenching in LAB based scintillator in independent small-scale experiments
von Krosigk, B.; Chen, M.; Hans, S.; Junghans, A. R.; Kögler, T.; Kraus, C.; Kuckert, L.; Liu, X.; Nolte, R.; O’Keeffe, H. M.; Wan Chan Tseung, H.; Wilson, J. R.; Wright, A.; Yeh, M.; Zuber, K.;
The alpha–particle light response of liquid scintillators based on linear alkylbenzene (LAB) has been measured with three different experimental approaches. In the first approach, alpha–particles were produced in the scintillator via 12C(n,alpha)9Be reactions. In the second approach, the scintillator was loaded with 2% of natSm providing an alpha–emitter, 147Sm, as an internal source. In the third approach, a scintillator flask was deployed into the water–filled SNO+ detector and the radioactive contaminants 222Rn, 218Po and 214Po provided the alpha–particle signal. The behavior of the observed alpha–particle light outputs are in agreement with each case successfully described by Birks’ law. The resulting Birks parameter kB ranges from (0.0066 +- 0.0014) cm/MeV to (0.0076+-0.0003) cm/MeV. In the first approach, the alpha–particle light response was measured simultaneously with the light response of recoil protons produced via neutron–proton elastic scattering. This enabled a first time a direct comparison of kB describing the proton and the alpha–particle response of LAB based scintillator. The observed kB values describing the two light response functions deviate by more than 5 sigma. The presented results are valuable for all current and future detectors, using LAB based scintillator as target, since they depend on an accurate knowledge of the scintillator
response to different particles.
Keywords: Liquid Scintillatiors, Linear Alcyl Benzene

Publ.-Id: 21967 - Permalink


Tuning physical properties by introducing defects: Applications in magnetic data storage and sustainable energy materials
Potzger, K.;
Structural or chemical defects in materials can have a tremendeous effect on their functunality, e.g. in magnetic data storage or sustainable energy materials. Ion beam techniques are ideal methods for a controlled induction of defects, e.g. in thin films since the defect production rate can be controlled by the ion flux whereas the depth of generated defects can be controlled by means of the ion energy. The analysis of the defects generated, on the other hand, can be performed by means of positron annihaltion spectroscopy, where the positrons are implanted either from a radioactive source or from a free electron laser induced nuclear reaction.
In this tutorial, basic concepts of ion implantation as well as positron annihilation spectroscopy at HZDR will be presented. In addition, the effect of ion irradiation, i.e. defect generation, on the magnetic properties of metal alloys will be explained. We will focus on the potential of ion beams for writing magnetic nano- and microstructures. Moreover, magnetic , defect and structural properties of materials for hydrogen processing will be presented.
Keywords: Ion Irradiation, magnetism, sustainable energy materials
  • Invited lecture (Conferences)
    50. Zakopane School of Physics Breaking Frontiers: Submicron Structures in Physics and Biology, 18.-23.05.2015, Zakopane, Polen

Publ.-Id: 21966 - Permalink


Comparison of LSO and BGO block detectors for prompt gamma imaging in ion beam therapy
Hueso González, F.; Biegun, A. K.; Dendooven, P.; Enghardt, W.; Fiedler, F.; Golnik, C.; Heidel, K.; Kormoll, T.; Petzoldt, J.; Römer, K. E.; Schwengner, R.; Wagner, A.; Pausch, G.;
A major weakness of ion beam therapy is the absence of applicable tools for verifying the particle range in clinical routine. The application of the Compton camera concept for the imaging of prompt gamma rays, a by-product of the irradiation correlated to the dose distribution, is a promising approach for range assessment and even two-dimensional in vivo dosimetry. Multiple position sensitive gamma ray detectors arranged in scatter and absorber planes, together with an imaging algorithm, are required to reconstruct the prompt gamma emission density map. Conventional block detectors deployed in Positron Emission Tomography (PET), which are based on Lu2SiO5:Ce (LSO) and Bi4Ge3O12 (BGO) scintillators, are suitable candidates for the Absorber of a Compton camera due to their high density and absorption efficiency even for the prompt Gamma energy range (several MeV). We compare experimentally LSO and BGO block detectors in clinical-like radiation fields in Terms of energy, spatial and time resolution. The high energy range compensates for the low light yield of the BGO material and boosts significantly its performance compared to the PET scenario. Notwithstanding the overall superiority of LSO, BGO catches up in the field of prompt gamma Imaging and can be considered as a competitive alternative to LSO for the absorber plane due to its lower price and the lack of intrinsic radioactivity.
Keywords: Instrumentation for hadron therapy; Detector modelling and simulations; Compton imaging; block detector; prompt gamma; in vivo dosimetry

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Publ.-Id: 21965 - Permalink


SEM-based automated mineralogy: A fast and effective method for in-situ particle analysis
Osbahr, I.; Heinig, T.; Krause, J.;
Scanning electron microscope-based automated mineralogy such as the Mineral Liberation Analyser (MLA) allows several automated procedures based on backscattered electron (BSE) image acquisition and the collection of energy-dispersive X-ray spectra of particles with a specified contrast in the BSE image. The collected spectra are classified with a standard mineral spectra list which has been collected and specified for the samples. Samples should be solid with a polished surface. Different measurement modes are available on the MLA which can deliver extensive sets of information as modal mineralogy, particle- and grain size/shape distribution, liberation, mineral association or intergrowth. SEM-based automated mineralogy is a well-established tool in applied mineralogy and mineral- and metallurgic processing. The features of this method can also be applied in wide areas of research fields including material sciences, geology or environmental sciences.
Keywords: SEM, MLA, automated mineralogy
  • Lecture (Conference)
    ANAKON 2015, 23.-26.03.2015, Graz, Österreich

Publ.-Id: 21963 - Permalink


Liquid drainage in inclined packed beds – Accelerating liquid draining time via column tilt
Assima, G. P.; Hamitouche, A.; Schubert, M.; Larachi, F.;
The dynamics of liquid drainage in inclined packed beds was studied experimentally using electrical capacitance tomography. The evolution of textural flow regimes and liquid saturation profiles were monitored as a function of bed tilt angle and bed height. Film and droplet textural regimes were discriminated during bed drainage tests. They consisted of a rapid step discharging, virtually at constant flow rate, ca. 80% of the poral dynamic liquid followed by a slower step of partially-saturated pores discharging the remaining 20%. The drainage time was markedly reduced upon tilting the column resulting ultimately in virtually bed-length independent drainage times. Bed inclination reduced the droplet paths to the vessel wall, stimulating migration and coalescence of liquid droplets towards the lowermost area of the column cross-section. This ensured sufficient hydraulic pressure nearby the high-porosity wall area to maintain enhanced liquid outflows. As a prospective process intensification artifice, inclining packed beds way exhibit superior advantage in stimulating drainage of tall vessels especially if emergency circumstances arise.
Keywords: Liquid drainage; static inclined packed bed; electrical capacitance tomography; liquid saturation; film and droplet texture

Publ.-Id: 21962 - Permalink


Critical evaluation of the small punch test as a screening procedure for mechanical properties
Altstadt, E.; Ge, H. E.; Kuksenko, V.; Serrano, M.; Houska, M.; Lasan, M.; Bruchhausen, M.; Lapetite, J.-M.; Dai, Y.;
For quick screening of material properties, it is important to provide simple experimental test techniques to address specific aspects of material properties. Within work package 2 of the Euratom FP7-MATTER project, a small punch test collective exercise was conducted to critically evaluate the potential of this technique for the characterisation of irradiation hardening and embrittlement. The ferritic-martensitic 9%Cr-steel T91 was used. Several data sets were produced for two major specimen geometries by different European laboratories. The reproducibility and scatter of results expressed by coefficient of variation for the total and plastic energy, the elastic-plastic transition load, the maximum load and the displacement at maximum load was analysed. The largest scatter was observed for the elastic-plastic transition load and for the plastic energy. Correlations for the estimation of tensile properties were shown to be device dependent.The estimations of the ductile-to-brittle transition temperatures are in a good agreement in cases of identical main geometrical parameters. The SP tests of neutron irradiated T91 (dose between 2.3 and 4 dpa) showed that the equivalent Charpy transition temperature shifts obtained from SP tests are in very good agreement with KLST based values. Thus the small punch test is an appropriate tool for the screening of the neutron irradiation induced embrittlement. We also observed a significant effect of irradiation on the recalculated yield stress and ultimate tensile strength. In comparison with tensile data, the irradiation induced hardening was underestimated. The small punch test is less appropriate for the screening of hardening (yield stress increase) than it is for embrittlement.
Keywords: Small punch test, ferritic-martensitic steel, ductile-brittle transition temperature, yield stress, neutron irradiation

Publ.-Id: 21960 - Permalink


Towards safe long-term operation of reactor pressure vessels
Rouden, J.; Hein, H.; May, J.; Planman, T.; Todeschini, P.; Brumovsky, M.; Ballesteros, A.; Gillemot, F.; Chaouadi, R.; Efsing, P.; Altstadt, E.;
This paper summarizes long-term operation conditions in European nuclear power plants. Recommendations for monitoring the radiation embrittlement of reactor pressure vessels during life extension periods (to 60 or 80 years) are presented. The guidelines were developed in the EURATOM FP7 project LONGLIFE. The work performed responds to the need for guidance to treat long term irradiation effects within the ageing management of NPPs, since the standard RPV surveillance programmes were designed for a time period of 40 years. In particular the following issues are addressed: re-use of tested surveillance speciems, transferability of material test reactor results to reactor operation conditions, extension of reactor pressure vessel surveillance programmes, withdrawal schemes for lon-term operation surveillance programmes.
Keywords: Reactor pressure vessel, irradiation embrittlement
  • atw - International Journal for Nuclear Power 60(2015)5, 287-293

Publ.-Id: 21959 - Permalink


He stripping for AMS of 236U and other actinides using a 3 MV tandem accelerator
Winkler, S. R.; Steier, P.; Buchriegler, J.; Lachner, J.; Pitters, J.; Priller, A.; Golser, R.;
Interest in the long-lived radioisotope 236U (t1/2 = 23.4 million years) has significantly increased recently, due to the emergence of environmental and earth science applications. Presently, only a few (AMS) accelerator mass spectrometry instruments are suited for this measurement. One major limitation is the relatively low total detection efficiency (on the order of 10^4), which is partly caused by a low stripping yield of the positive ion charge state selected after the tandem accelerator. It has been shown that high yield can be achieved using helium as stripper gas for uranium ion energies below 0.35 MeV. Here we investigate the potential of He stripping of U at the 3-MV tandem accelerator VERA. Phenomenological charge state distributions for U and Th are presented for terminal voltages from 1.0 to 1.7 MV. These terminal voltages provide better background rejection than possible below 1 MeV, and are suited to the widely used 1–3 MV workhorses of many accelerator mass spectrometry laboratories. The methods can be applied to other actinides also.
Keywords: Uranium-236, Accelerator mass spectrometry, Actinides, Gas stripping, Time-of-Flight

Publ.-Id: 21958 - Permalink


Meißener Deckelvase mit späterer Ergänzung - Protonenstrahl-Analyse beweist die Unterschiede
Neelmeijer, C.; Roscher, R.;
Skepsis und die daraus resultierende Frage, ob ein Kunstobjekt vielleicht ergänzt, restauriert oder gar gefälscht ist, sind berechtigt und stellen sich nicht nur dem Kunsthistoriker aus Museen, Sammlern oder interessierten Laien. Die Protonenstrahl-Analyse unterstützt bei der Suche nach der richtigen Antwort. Im Visier: eine Meißener Vase und ihr Deckel. Sowohl die chemischen Zusammensetzungen von Porzellanmassen und Glasuren als auch die Analysen von Pigmenten der Dekore auf Vasenkörper und Deckel beweisen, dass der Deckel nicht original, sondern eine spätere Ergänzung ist.
Keywords: Porzellan/Porcelain, Original/Original, Nachbildung/Replica, Materialanalyse/Material analysis, PIXE, PIGE
  • Restauro 4(2015)

Publ.-Id: 21957 - Permalink


Mineralogical and chemical analysis of secondary raw materials – challenges and pitfalls
Dreßler, S.; Bachmann, K.; Renno, A. D.; Scharf, O.; Schaefer, J.;
Secondary raw materials (SRM) are becoming increasingly more important in ensuring the stability of critical metal supply. Like for natural raw materials, processing and metallurgical treatment demands a detailed and meticulous geometallurgical characterisation. Unlike municipal solid waste and Waste Electrical and Electronic Equipment (WEEE), ashes, slags, dusts and other industrial residues are "produced" centrally in large quantities. In light of these circumstances, the logistics of supply is simpler. This makes these types of SRM ideal candidates for the extraction of critical metals.
Precise and accurate chemical and mineralogical data, knowledge of distribution of valuable and deleterious elements in the single phases as well as information about homogeneity and grain size distribution of the minerals are crucial for the development of new extraction technologies. Gaining these essential information can be achieved by using SEM-based automated mineralogical analysis. However, the large particle size range, the dominance of very small grain sizes (< 5 µm) and the diversity of phases are challenging for the analysis. Furthermore, in contrast to natural materials the analysis of secondary materials faces the challenge of developing new methods for non-natural extreme combinations of elements and phases. To overcome these challenges we used complementary analytical methods, like XRD and optical microscopy. Two of them, High-Speed PIXE and the “MEGA” instrument are still in the stage of development. Both instruments deliver additional information about trace element distribution.
Nevertheless, in contrast to natural materials the analysis of secondary materials faces the challenge of developing new methods for non-natural extreme combinations of elements and phases. We present initial results of ash and slag samples, like residues of pyrometallurgical recycling of spent lead batteries.
Keywords: Secondary raw materials, SEM-based automated mineralogical analysis
  • Poster
    Geoanalysis 2015, 09.-14.08.2015, Leoben, Österreich

Publ.-Id: 21956 - Permalink


Fit-for-purpose analytics for resource technology?
Dreßler, S.; Gurlit, S.; Merchel, S.; Michalak, P. P.; Renno, A. D.; Sazonov, A. M.; Schenk, F.; Sterba, J. H.;
Along the value chain (exploration, mining, processing, recycling) generally solid samples of complex matrix and non-stoichiometric composition need to be analysed. Besides spatially-resolved analytics applied to technology development, bulk analytics is mainly used for characterisation of value components.
In the search of the best-suited method, there are important questions to answer at first:
1. What is already known about the sample (matrix, stability, solubility, interferences)?
2. What data are needed (quantitative, semi-quantitative or qualitative)?
3. Are the concentrations of the elements of interest at a major, minor or trace level?
4. How urgently are the data needed and what are the financial restraints?
Here, two different projects are selected to demonstrate a typical search for fit-for-purpose analytics spanning from commonly available Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to more rarely applied Instrumental Neutron Activation Analysis (INAA). These are two examples of primary and secondary raw materials (intermediate goods and waste), which would open possibilities for side products of critical metals, e.g. REE, PGE, Re, Ga.
The first project deals with a natural mineral sample of molybdenite (MoS2) taken from an open pit mine in Kačaran (Armenia) in use for Mo and by-product Re mining. Rhenium is important for catalytic and petrochemical industry, metallurgy, and aviation, e.g. it is used for steel reinforcement in turbine blades for aircrafts [1,2].
The second project focus on secondary raw materials from the non-bauxitic production of aluminium and alumina in Siberia. The analysed materials were taken from different stages of the production process: The final product alumina (Al2O3), waste products like red mud (mainly calcium carbonate and SiO2), sodium salts (e.g. Na2SO4) and anode slag (carbon, Cu-Al alloy, Al) and by-products like wollastonite ceramics (CaSiO3) and soda-potash (K2CO3/Na2CO3).
Of course, there are pros and cons of every analytical method (Total Reflection X-ray Fluorescence (TXRF), ICP-MS, INAA) for different samples yielding to clear conclusions about the best-suited method for future analytical tasks. For example in the case of Re, INAA is identified as method of choice for such kind of analysis due to high sample throughput, an easy and quick sample preparation and a low detection limit (0.26 μg/g).

References:
[1] A. Brumby, M. Verhelst, D. Cheret, Catalysis today. 2005, 106, 166-169.
[2] C. Zhan-Fang, Z. Hong, Q. Zhao-hui, Hydrometallurgy. 2009, 97, 153-157.
Keywords: Resource Technology, raw materials, INAA, Re, aluminium production
  • Poster
    GDCh-Wissenschaftsforum Chemie 2015, 30.08.-02.09.2015, Dresden, Deutschland

Publ.-Id: 21955 - Permalink


Herstellung und Reinigung von n.c.a. 88Y am Leipziger Zyklotron Cyclone® 18/9
Mansel, A.; Franke, K.;
Die Abteilung „Reaktiver Transport“ der Forschungsstelle Leipzig beschäftigt sich mit dem Migrations-/Sorptionsverhalten von (Schad)stoffen in geologischen Formationen. In aktuellen Projekten werden partikuläre, kolloidale, gelöste und komplexierte, toxische und radiotoxische Stoffe in Batch- und Säulenstudien sowie Extraktionsverfahren für seltene Metalle untersucht. Bei der eingesetzten Radiotracertechnik kommen kurzlebige, nicht kommerziell erhältliche Radionuklide zum Einsatz. Am Leipziger Zyklotron Cyclone® 18/9 neu implementiert ist die 88Y-Herstellung (T1/2 = 106,6 d) durch Protonenbeschuss von Strontium mit natürlicher Isotopenzusammensetzung via 88Sr(p,n)88Y[1-3]. Das Target wird durch Verpressen von ca. 30 mg Strontiumcarbonat in eine Aluminiumhalterung hergestellt. Die Bestrahlung erfolgt bei einem Protonenstrom von 3 µA, einer Strahlzeit von 2 Stunden und einer Projektilenergie von ca. 12 MeV. Die chemische Aufarbeitung des bestrahlten Strontiumcarbonats erfolgte erstmals durch Ionenchromatographie mit LN-Resin-A (TrisKem Int.) aus salpetersaurer Lösung[4-5]. N.c.a. (no-carrier-added) 88Y wird mit einer radiochemischen Ausbeute von 95 % ± 4 % erhalten. Der entwickelte Trennungsgang dient zur Vorbereitung für die Produktion und Aufarbeitung des kurzlebigen Radionuklids 86Y (T1/2 = 14,7 h; Iβ+ = 31,9 %) für die Positronen-Emissions-Tomographie (PET) durch Bestrahlung von isotopenangereichertem 86Sr.

Literatur:
[1] S. A. Kandil, B. Scholten, K. F. Hassan, H. A. Hanafi, S. M. Qaim, J. Radioanal. Nucl. Chem. 2009, 279, 823. [2] K. Kettern, K.-H. Linse, S. Spellerberg, H. H. Coenen, S. M. Qaim, Radiochim. Acta 2002, 90, 845. [3] N. P. van der Meulen, T. N. van der Walt, G. F. Steyn, F. Szelecsenyi, Z. Kovacs, C. M. Perrang, H. M. Raubenheimer, Appl. Radiat. Isot. 2009, 67, 1320. [4] E. P. Horwitz, C. A. A. Bloomquist, J. Inorg. Nucl. Chem. 1975, 37, 425. [5] C. Pin, J. F. S. Zalduegui, Anal. Chim. Acta 1997, 339, 79.
  • Poster
    GDCh Jahrestagung 2015, Fachgruppe Nuklearchemie, 30.08.-02.09.2015, Dresden, Deutschland

Publ.-Id: 21952 - Permalink


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