Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34133 Publications

Alteration in the area of the Kristineberg VHMS deposit, Skellefte district, Sweden.

Bachmann, K.; Gutzmer, J.; Persson, M.; Jansson, N.

The Skellefte district in north-central Sweden is one of the most important mining districts in northern Europe. It contains over 85 pyritic Zn-Cu-Au-Ag massive sulphide deposits of which 21 deposits have been mined since 1924 and 4 are still in operation by Boliden Mineral AB. The most productive deposit, the Kristineberg mine, has been operated by Boliden since 1940 with a current annual production of 670,000 t of polymetallic ore containing 3.0 wt.-% Zn, 0.7 wt.-% Cu, 0.4 wt.-% Pb, 1.9 g/t Au and 47 g/t Ag. Alteration of the volcanic rocks around the Kristineberg deposit is very intense. The main aim of this study has been to describe the alteration intensity and to define alteration trends around the Kristineberg deposit. The success of this approach provides a new exploration tool for future exploration in the Skellefte District where alteration renders the recognition of primary volcanic facies difficult.

Keywords: Kristineberg; Skellefte district; VHMS; alteration

  • Poster
    12th Biennial SGA Meeting: Mineral deposit research for a high-tech world, 12.-15.08.2013, Uppsala, Sweden

Publ.-Id: 20946

Raman spectroscopy – casting (laser) light on microbe – mineral interactions

Kostudis, S.; Kutschke, S.; Pollmann, K.

Highly efficient and sustainable mining strategies gain importance due to the fact that available resources of base metals like copper but strategic elements such as gallium and molybdenum as well face a steadily decreasing grade. This issue is enhanced by the increased demand and production amounts of those metal compounds. Biohydrometallurgy – the use of microorganisms or related substances in metal extraction - provides the potential of processing low grade ores efficiently. Thus it is applied yet in some gold and uranium mining.
Also due to strategic reasons mining of regional resources such as the European Kupferschiefer come to the fore. Its complex composition including sulphide rich ores, carbonates and organic compounds challenges biotechnological approaches. Nevertheless promising approaches have been reported. We examine heterotrophic bioleaching of copper from Kupferschiefer ores. To investigate the interactions between mineral surface and microorganisms Raman spectroscopy offers a versatile applicability: Identification of minerals and differentiation of microorganisms is nicely provided and is accompanied by imaging opportunities in a two or even three dimensional manner. Thus biofilms, for example, can be analysed with respect to microbial diversity or preferences of minerals during the attaching process.

  • Poster
    Microbiology and Infection, 05.-08.10.2014, Dresden, Deutschland

Publ.-Id: 20945

Evaluation of mineral processing by assessment of liberation and upgrading.

Leißner, T.; Mütze, T.; Bachmann, K.; Rode, S.; Gutzmer, J.; Peuker, U.

A model is presented to evaluate mineral processing on basis of gangue recovery and valuables recovery. It combines mineralogical limiting curves with upgrading curves in the Fuerstenau diagram. These curves are used to assess mineral liberation and mineral beneficiation compared with the ideal result. Two new parameters (ratio of separation and ratio of liberation) are calculated based on a comparison of areas enclosed by the mineralogical limiting curve, the upgrading curve, the curve representing a total liberation of valuables, and the curve representing a perfect mixture of valuables and gangue.
An assessment of the success of mineral processing is possible using these parameters. The assessment shows whether the quality of a separation product is influenced by the separation process itself or by the achieved liberation of the feed.
A series of experiments on the magnetic separation of a greisen-type ore proves the applicability of this model to mineral processing. SEM-based image analysis and ICP-OES measurements have been used to obtain the necessary data.

Keywords: liberation; upgrading; separation; mineral liberation analysis

Publ.-Id: 20944

Discrimination of hematite and magnetite in finely intergrown natural iron ores by automated mineralogy.

Bachmann, K.; Bartzsch, A.; Gutzmer, J.

Providing a fast, quantitative characterization of iron ores in terms of liberation, grain sizes and shapes as well as mineral association remains a big challenge. Whilst quantitative mineralogical data are easily attained by QXRD, an automated SEM-EDS based approach is needed for the quantification of relevant microfabric attributes. Two different iron ores were investigated for this study, to illustrate the capabilities and limitations of the latter approach. The first example is a banded-iron formation (BIF) ore from Thabazimbi/RSA, the second ore type studied is a magnetite iron ore from Svappavaaragruvan, c. 50 km east of Kiruna/N-Sweden. The greatest difficulty in the characterization of iron ores is certainly the discrimination between different relevant iron oxides (magnetite, hematite, goethite) that are all of very similar elemental composition – and thus have both very similar backscattered electron (BSE) brightness, as well as almost identical EDS spectra. A principle approach was suggested by Figueroa et al. (2011) by using the Mineral Liberation Analyzer (MLA). The suitability of this method was illustrated on synthetic mixtures. The approach of the present study utilizes the method on thin sections of natural iron ores, which show a fine intergrowth of hematite and magnetite with an unknown composition. For calibration, an in-house magnetite and hematite standard was prepared to further optimize the set-up of the method. A new feature in the MLA suite v.3.1.4 is the capability to define the exact working distance for every single sample separately. Slight variations in the working distance between the different samples and the standard were equalized. The MLA results were compared to bulk chemical data as well as traditional point counting-data by reflected light-microscopy. The results are within a relative error of 5 %. It can be concluded that the method was successfully applied and can be applied to iron ores with complex oxide mineral associations.

  • Poster
    EMAS 2014 - 11th EMAS Regional Workshop on Electron Probe Microanalysis of Materials Today - Practical Aspects, 22.-24.09.2014, Leoben, Austria

Publ.-Id: 20943

Li isotopes and geochemistry of Li–F–Sn greisen from the Zinnwald deposit.

Bachmann, K.; Seifert, T.; Magna, T.; Neßler, J.

The Sn–W greisen deposits, located in the eastern part of the Variscan metallogenic Erzgebirge province (zinnwaldite Ar–Ar ages between 313 and 315 Ma), are emplaced in highly metamorphosed and/or igneous rocks and typically are associated with post-collisional Li–F-enriched small granitic intrusions. This metallogenic province traditionally belonged to the major source of economic Sn, Ag, U, W, Co and fluorite–barite deposits for central Europe. The Zinnwald/Cínovec Li–Sn greisen deposit is associated with a unique zinnwaldite–quartz–topaz mineralization hosted by an albitized stock-granite.
Li contents and isotope compositions were measured in host albite granites (n=2), greisens (n=3), and a sample from a flat-dipping vein in the Zinnwald deposit, paralleled by individual mineral phases. All investigated bulk rocks have extreme Li contents reaching from 1,600–2,200 ppm in albite-granite, to 3,400–6,200 ppm in greisen-type rocks and to ~8,000 ppm in a vein-type sample, most likely carried by zinnwaldite (15,000–19,200 ppm) and muscovite (9,500–15,700 ppm) whereas albite and quartz, in particular, have significantly lower Li abundances (560–660 and 33–330 ppm, respectively). The high bulk Li contents are very unusual even for chemically evolved granitic systems with the exception of Li-rich pegmatites. Bulk 7Li values are restricted (–1.0 to 0.3 ‰), consistent with late orogenic granites from a larger area of the Erzgebirge Mts.. Zinnwaldite and muscovite carry isotopically heavy Li relative to the corresponding bulk rocks and, at the same time, muscovite always is slightly heavier than zinnwaldite. 7Li values of quartz become progressively heavier from granites through greisens to a vein sample. Zinnwaldite may represent a late-stage ingress of Li-rich fluids/melts rather than indigenous phase of these lithologies because from mass balance considerations and mineral modes, bulk [Li] and 7Li values cannot easily be reconstructed for either sample of the suite.

  • Poster
    Goldschmidt2014, 08.-14.06.2014, Sacramento, USA

Publ.-Id: 20942

Method for evaluation of upgrading by liberation and separation.

Leißner, T.; Mütze, T.; Anatasova, P.; Bachmann, K.; Peuker, U.

A method is presented for the evaluation of mineral processing by liberation and upgrading. The method bases on the plot of recovery of valuables versus the recovery of gangue (Fuerstenau upgrading curve). The locking curve of a feed material was plotted together with the upgrading curve in a Fuerstenau diagram. The assessment of liberation and upgrading is done by a comparison of surfaces formed by the curves and some characteristic lines of the diagram. This plot allows the calculation of two new quantitative measures for liberation and upgrading.
Both parameters can be combined to a third parameter describing the quality of the whole technical setup for mineral processing by subtracting the upgrading parameter from the liberation parameter. The third parameter shows a positive value in cases of upgrading determined processes, a negative value in cases of liberation affected processes and about zero for processes affected equally by liberation and upgrading. Thus it is easily possible to distinguish between poor results in the mineral processing caused by insufficient liberation or poor results caused by insufficient upgrading.
Preliminary results from two case studies, performed on two completely different ore types, are very promising illustrating the practical use of such an approach.

  • Lecture (Conference)
    International Mineral Processing Congress, 20.-24.10.2014, Santiago, Chile

Publ.-Id: 20941

WASA-BOSS: ATHLET-CD model for severe accident analysis for a generic KONVOI reactor

Tusheva, P.; Schäfer, F.; Kozmenkov, Y.; Kliem, S.; Hollands, T.; Trometer, A.; Buck, M.

The work described in this paper is a part of the ongoing joint research project WASA-BOSS, Weiterentwicklung und Anwendung von Severe Accident Codes – Bewertung und Optimierung von Störfallmaßnahmen, aiming at investigation of severe accident scenarios and severe accident management measures in boiling water reactors (BWR) and pressurized water reactors (PWR) [1]. The GRS, IKE and HZDR cooperation is focused on the development of an ATHLET-CD (Analysis of THermal-hydraulics of LEaks and Transients – Core Degradation) code model for a generic PWR of type KONVOI, including investigations of core degradation scenarios and possible accident management. This paper discusses the possible accident management measures (AMM), the ATHLET-CD model as well as the first preliminary simulations for a station blackout (SBO) scenario without and with application of countermeasures.

Keywords: severe accidents; AMM; ATHLET-CD

  • Contribution to proceedings
    Jahrestagung Kerntechnik/Annual Meeting on Nuclear Technology, 05.-07.05.2015, Berlin, Germany
  • Lecture (Conference)
    Jahrestagung Kerntechnik/Annual Meeting on Nuclear Technology, 05.-07.05.2015, Berlin, Germany
  • atw - International Journal for Nuclear Power 60(2015)7, 442

Publ.-Id: 20940

Multifunctional S-layer proteins as building blocks for hybrid materials

Weinert, U.; Günther, T.; Lehmann, F.; Vogel, M.; Suhr, M.; Matys, S.; Bobeth, C.; Kutschke, S.; Pollmann, K.; Raff, J.

Nanostructured bio-inorganic hybrid materials are very attractive for technical applications, e.g. nanocatalysts, photocatalytic materials, sensors and filter systems. Self-assembling biomolecules like Surface layer (S-layer) proteins represent a promising tool as hybrid material due to their ability to self-assembly in aqueous solutions and on surfaces. In nature S-layer proteins coat the bacterial and archaeal cells with a highly ordered nanostructure and defined symmetry and fulfill various functions, e.g. protection, binding matrix for exoenzymes and molecular sieves. Isolates, which were taken from a uranium mining waste pile in Saxony, produce S layer proteins to protect themselves from heavy metals and radionuclides. If the S layer proteins are saturated with heavy metals or radio nucleotides, the protein will be rejected and a new one will be produced.

We take advantage of the high affinity to heavy metals to produce hybrid filter materials from micro sieves and S-layers. The so called “S-sieves” will be able to bind heavy and noble metals from aqueous solutions even in low concentration ranges economically.

Another aspect will be the synthesis of Pd, Pt and Au nanoparticles on S-layer proteins. Pd and Au nanoparticles were built in the pores of S-layer proteins. Due to that a surface of nanoparticles of a defined size and regularly arrangement can be constructed. Those surfaces will work as nanocatalysts for many technical applications, e.g. the production of CNTs which has already been demonstrated.

Further work deals with the design of a hybrid materials which will work as photocatalysators for drinking water purification. Especially pharmaceuticals can be disintegrated by radicals. The radicals are formed in sunlight and in presence of the catalytic active ZnO- or TiO2-nanoparticles which are coupled and regularly arranged on S-layer protein interface.

These three examples emphasize the use of S-layer proteins their potential in nanotechnology and will give new prospective in the mentioned techniques.

Keywords: hybrid material; s-layer; nanaoparticles; filter material; nanocatalysts

  • Lecture (Conference)
    Multifunctional S-layer proteins as building blocks for hybrid materials, 23.-25.09.2014, Darmstadt, Deutschland

Publ.-Id: 20939

Bioinspired hybrid nanomaterials based on self-assembling proteins

Weinert, U.; Lederer, F.; Günther, T.; Lehmann, F.; Drobot, B.; Vogel, M.; Pollmann, K.; Raff, J.

Many microorganisms like bacteria developed during evolution highly effective mechanisms and structures to survive at the most forbidding, uninviting places on Earth. One example is the binding of heavy metals and actinides by cell surface proteins of uranium mining waste pile isolates. The so called surface layer (S-layer) proteins (Fig. 1a) bind toxic metals and metalloids and thusly protect the cells from being damaged by these elements. On other cells, S-layers may act for example as immobilization matrix for exoenzymes, as molecular sieve or as ion and molecule trap.
These properties and their ability to self-assemble in suspension, on surfaces and at interfaces qualify S-layers as interesting building blocks for the construction of new bioinspired nanomaterials for different technical applications. Using the two-dimensional protein arrays, different kinds of surfaces can be nanostructured and novel bio-inorganic hybrid materials with multiple functions can be produced.
Currently three materials are in the focus: metal filters, catalysts and sensors (Fig. 1b). Biocomposites made of microsieves and S-layers are under development to selectively recover strategic metals from aqueous solutions. S-layer proteins with immobilized and regularly arranged metals or metal oxides are useful for diverse catalytic applications. Furthermore, S-layer coatings combining highly specific receptors like aptamers and stable fluorescence dyes are very promising for the construction of new biosensors for organics or pharmaceuticals.
Basis for those materials and their industrial application is an effective production of S-layer proteins. The latter is possible by the extraction of the S-layers from growing cells or by heterologous expression of the proteins. In bacteria or yeasts expressed S-layers can be genetically engineered with molecular modifications to further combine the outstanding S layer protein characteristics with additional expedient features. Native as well as engineered S-layer proteins have an application potential going far beyond above mentioned applications ranging from the chemical industry, water and environmental technologies to medicine.

Keywords: nanoparticles; filter material; S-layer; biosensors; nanocatalysts

  • Lecture (Conference)
    Biomaterials - Made in Bioreactors, 26.-28.05.2014, Radebeul, Deutschland

Publ.-Id: 20938

Correct averaging in transmission radiography: analysis of the inverse problem

Wagner, M.; Hampel, U.; Bieberle, M.

Transmission radiometry is frequently used in industrial measurement processes as a mean to assess the thickness or composition of a material. A common problem encountered in such applications is the so-called dynamic bias error, which results from averaging beam intensities over time while the material distribution changes. We recently reported on a method to overcome the associated measurement error by solving an inverse problem, which in principle restores the exact average attenuation by considering the Poisson statistics of the underlying particle or photon emission process. In this paper we present a detailed analysis of the inverse problem and its optimal regularized numerical solution. As a result we derive an optimal parameter configuration for the inverse problem.

Publ.-Id: 20937

Quantum structure THz photonics and spectroscopy at HZDR

Schneider, H.

Es gibt kein Abstract.

  • Lecture (others)
    Seminarvortrag, Centre Suisse d'Electronique et Microtechnique SA (CSEM), 19.09.2014, Neuchâtel, Schweiz

Publ.-Id: 20936

Photoinduzierte Dynamik in der ps Zeit- und THz Frequenz-Domäne

Schneider, H.; Schmidt, J.; Teich, M.; Stephan, D.; Fehrenbacher, M.; Franke, C.; Winnerl, S.; Gensch, M.; Seidel, W.; Helm, M.

Dieser Vortrag stellt die im Rahmen des BmBF-Verbundprojekts PIDID geschaffenen erweiterten Messmöglichkeiten für den Nutzerbetrieb am Freie-Elektronenlaser (FEL) FELBE vor und beschreibt einige exemplarische Experimente. FELBE erlaubt als einziger FEL in Europa einen quasikontinuierlichen Pulsbetrieb, der bei vielen Experimenten zu erheblichen Vorteilen führt im Hinblick auf die Stabilität sowie das Signal-zu-Rauschverhältnis. Aufgrund der Resonatorlänge beträgt die FEL-Pulsrate hierbei 13 MHz (77 ns Pulsabstand). Innerhalb des PIDID-Vorhabens wurden reduzierte Pulsraten (1 kHz bzw. 100 kHz) realisiert, wie sie zur Untersuchung physikalischer Prozesse mit längeren Zeitkonstanten im Bereich µs bis ms benötigt werden. Hierzu wurde ein optischer Schalter aufgebaut, der auf der hohen Reflektivität eines Elektron-Loch-Plasmas beruht, das mittels synchroner optischer Pulse in einem Germaniumkristall angeregt wurde. Des Weiteren wurden ein Fourier-Spektrometer sowie ein Tieftemperatur-Nahfeldmikroskop aufgebaut, die vorwiegend in Teilprojekten der Projektpartner eingesetzt wurden. Im zweiten Teil des Vortrags werden die wichtigsten Messmöglichkeiten an FELBE anhand einiger ausgewählter Experimente dargelegt.

  • Lecture (Conference)
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten 2014 (SNI 2014), 21.-23.09.2014, Bonn, Deutschland

Publ.-Id: 20935

Formation of neptunium(IV)-silica colloids at near-neutral and slightly alkaline pH

Husar, R.; Weiss, S.; Hennig, C.; Hübner, R.; Ikeda-Ohno, A.; Zänker, H.

The reducing conditions in a nuclear waste repository render neptunium tetravalent. Thus, Np is often assumed to be immobile in the subsurface. However, tetravalent actinides can also become mobile if they occur as colloidal precipitation products. We show that Np(IV) is able to form silica-rich colloids in solutions containing silicic acid at concentrations of both the regions above and below the “mononuclear wall” of silicic acid at 2∙10-3 M (where silicic acid is expected to start polymerization). These Np(IV)-silica colloids have a size of only very few nanometers and can reach significantly higher concentrations than Np(IV) oxyhydroxide colloids. They can be stable in the waterborne form over longer spans of time. In the Np(IV)-silica colloids the actinide-oxygen-actinide bonds are increasingly replaced by actinide-oxygen-silicon bonds due to structural incorporation of Si. Possible implications of the formation of such colloids for environmental scenarios are discussed.

Keywords: Neptunium; Np(IV)-silica colloids; nanoparticles; EXAFS

Publ.-Id: 20934

Low-energy behavior of E2 strength functions

Schwengner, R.

Electric quadrupole strength functions have been deduced from averages of a large number of E2 transition strengths calculated within the shell model for the nuclides 94Mo and 95Mo. These strength functions are compared with phenomenological approximations as provided by the Reference Input Parameter Library (RIPL) for calculations of reaction rates on the basis of the statistical model. The low-energy behavior of the calculated strength functions differs from the one of the phenomenological E2 strength functions and may be used to improve the input for calculations of reaction rates.

Keywords: Photonuclear reactions; photon strength functions; shell model; transition strengths

Publ.-Id: 20933

Monte-Carlo Simulationen zur Untersuchung der Auswirkungen von Quelländerung im Reaktorkern auf die Excore-Instrumentierung

Konheiser, J.

Verschiedene Auswirkungen von möglichen Variationen der Kerngeometrie auf die Signalwerte der Excore-Instrumentierung eines Druckwasserreaktors (DWR) werden in dieser Arbeit gezeigt. Zu diesem Zweck werden Neutronenflüsse für mögliche Brennelementanordnungen mit Hilfe stationären Monte Carlo-Berechnungen außerhalb des Reaktors bestimmt. Typische Daten eines deutschen PWR wurden für die Untersuchungen verwendet.
Unterschiede in den Neutronenflüssen der Excore-Instrumentierung von bis zu 4 % wurden bei Änderungen der Abstände von 1 mm zwischen bestimmten Brennelementen, die im Randbereich des Kerns liegen, berechnet.
Der Grund ist eine verbesserte Moderation von Neutronen, die zu einem höheren Leistung bzw. Neutronenfluss im Randbereich des Kerns führt. Die Folge ist ein höherer Neutronenstrom in Richtung der Excore-Instrumentierung. Dieser Effekt ist Abhängigkeit von Zykluszeitpunkt.
Mögliche Wassertemperaturschwankungen von 1K im Ringspalt, die zu Veränderungen der Wasserdichte und somit des Absorptionsvermögens führen, haben dagegen kaum Auswirkungen auf den Neutronenfluss an der Excore-Instrumentierung.

Effects of possible variations of the core geometry on the signal values of excore instrumentation of a pressure water reactor (PWR) are shown in this work. For this purpose, neutron fluxes outside of the reactor are determined for possible arrangements of fuel assemblies by means of stationary Monte Carlo calculations. Typical data of a German PWR were used for the investigations. Differences in the neutron flux of the excore instrumentation of up to 4% were calculated with changes of the pitch from 1 mm between certain fuel assemblies, which lie in the boundary area of the core. The reason is an improved moderation of neutrons, which results in a higher power and neutron flux in the periphery of the core. The result is a higher neutron flux in the direction of excore instrumentation. This effect is a function of cycle time. Possible water temperature fluctuations of 1 K in the downcomer, which leads to changes in water density and thus in the absorbance, have marginal effect on the neutron flux at the excore instrumentation.

Keywords: excore instrumentation; Monte Carlo calculation; pressure water reactor; neutron flux

  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2014
    56 Seiten
    ISSN: 2191-8708, eISSN: 2191-8716

Publ.-Id: 20932

Terahertz spectroscopy of zero- and two-dimensional semiconductor nanostructures with the free-electron laser FELBE

Schneider, H.; Teich, M.; Bhattacharyya, J.; Zybell, S.; Jacob, R.; Winnerl, S.; Helm, M.

The free-electron laser facility FELBE in Dresden, a unique source of intense, quasi-cw, nearly transform-limited ps pulses in the mid-infrared and terahertz (THz) regimes, provides unique research opportunities. In high-quality semiconductor quantum wells, we investigate the dynamics of excitons, i.e. two-dimensional, hydrogen-like electron-hole quasi-atoms. Tuning FELBE in resonance with the transition between the excitonic 2s and 2p states (at ca. 2 THz) allows us to study the dynamics of intra-excitonic population transfer. Moreover, strong terahertz pumping results in a characteristic Rabi splitting of the 1s exciton state, which is a manifestation of the intra-excitonic Autler-Townes effect. In semiconductor quantum dots, resonant THz excitation between different sublevels is shown to produce an absorption contrast in aperture-less scattering scanning near-field optical microscopy (s-SNOM). This effect allows us to obtain functional s-SNOM images with deep sub-wavelength resolution, where the contrast originates from far-infrared absorption by single electrons. Quantum dots are also known to have very long electronic relaxation times caused by a reduced phase space for optical phonon scattering. We will report on THz four-wave mixing experiments demonstrating that the associated electronic coherence times approximately equal the population relaxation time at low temperatures. This property makes quantum dots promising for quantum optical applications at THz frequencies.

Keywords: free-electrpn laser

  • Lecture (Conference)
    Science@FELs 2014, 15.-17.09.2014, Villigen, Schweiz

Publ.-Id: 20931

QWIP-Based “Ultrafast” Detectors for QCL Research

Schneider, H.

In this talk, I will summarize two approaches for “ultrafast” QWIP-based detection of mid-infrared signals and cover a few examples for practical applications.

  • Invited lecture (Conferences)
    International Quantum Cascade Laser School and Workshop 2014 (IQCLSW2014), 07.-12.09.2014, Policoro (Matera), Italien

Publ.-Id: 20930

Intrinsic formation of nanocrystalline neptunium dioxide under neutral aqueous conditions relevant to deep geological repositories

Husar, R.; Hübner, R.; Hennig, C.; Martin, P. M.; Chollet, M.; Weiss, S.; Zänker, H.; Stumpf, T.; Ikeda-Ohno, A.

Nano-sized crystals of neptunium dioxide (NpO2) were prepared successfully based on novel synthetic approach to neutralise a basic Np(IV) carbonate solution. The formation of nanocrystalline NpO2 was monitored by UV/visible absorption and X-ray absorption spectroscopies, and the resultant NpO2 crystals were further characterised by transmission electron microscopy.

Keywords: actinides; neptunium; NpO2; nanocrystals; colloids; formation; UV/visible absorption spectroscopy; X-ray absorption spectroscopy; transmission electron microscopy

Publ.-Id: 20928

Selektive Trennung sehr feiner Partikelsysteme mittels Flüssig/Flüssig-Flotation

Leistner, T.; Müller, M.; Erler, J. V.; Rudolph, M.; Peuker, U. A.

Die Vergrößerung des effizienten Anwendungsbereiches von Sortierprozessen in den Bereich feinster Partikelsysteme (0,1 – 10 μm) stellt eine erhebliche Herausforderung für die Forschung dar. Ein möglicher Prozessansatz zur Verbesserung des Sortierergebnisses ist die Flüssig/Flüssig-Flotation. In dieser Studie werden Aussagen bezüglich Anwendbarkeit und Prozessverhalten dieses Ansatzes in Abhängigkeit von ausgewählten Prozessparametern an verschiedenen Modellpartikelsystemen präsentiert.

Keywords: Particle-oil-water emulsions; Phase transfer; Surfactant; Two-liquid flotation; Ultrafine particle separation

Publ.-Id: 20927

Efficient and accurate identification of platinum group minerals by a combination of mineral liberation and electron microprobe analysis

Osbahr, I.; Krause, J.; Bachmann, K.; Gutzmer, J.

Identification and accurate characterization of platinum group minerals (PGM) is a very cumbersome procedure due to grain sizes that are mostly below 10 µm and inconspicuous appearance. A novel strategy on finding and quantifying PGM was applied by combining Mineral Liberation Analyzer (MLA) 650F, point logger (JEOL) and a field emission electron probe micro-analyzer (FE-EPMA, JEOL JXA-8530F). Thin sections from a layered intrusion (UG2) in the Bushveld Complex and from two Uralian-Alaskan-type complexes in the Ural Mountains, Russia, were investigated as case studies.
As a first step the PGM are identified, using the Mineral Liberation Analyzer (MLA). The SPL (Sparse Phase Liberation) mode is the best way to find and identify the PGM with high spatial resolution and great accuracy. For this purpose, a series of back-scattered electron images is collected. Within these images, mineral grains are selected that match or exceed a set grey-scale value. These grains are characterized by collecting EDS spectra. Grains identified as PGMs are then marked and coordinates recorded in a format suitable for the EPMA at the point logger. With these coordinates recorded, the sample can be transferred to the microprobe. Despite their small grain sizes the PGM can be retrieved without any difficulties (deviation from the position logged with the point logger is only a few µm). Case studies illustrate that the combination of MLA, point logger and EPMA results in the identification of 4-5 times more PGMs than by careful reflected light microscopy. This is mainly due to the facts that (a) PGM with grain sizes < 5µm are reliably identified and (b) PGM and closely associated base metal sulfides and sulfosalts are well differentiated with the MLA. Furthermore, identification of PGMs remains unaffected by human error and is efficient with respect to the time spent by the mineralogist on a particular sample.
Despite the efficient identification of PGM grains using MLA, the combination with FE-EPMA bears at least one significant advantage. FE-EPMA allows for the accurate determination of mineral chemical composition by WDS, whereas MLA permits only for EDS spot analyses. WDS analyses of PGM by FE-EPMA requires considerable caution, though, due to overlaps of X-rays on both peak and background of almost all PGE and associated elements (e.g. OsMβ on IrMα and AuMβ on HgMα). It is thus necessary to look carefully at every element and to set peak and backgrounds individually for every element. X-ray lines suitable for quantitative analyses (e.g. Mβ instead of Mα) need to be carefully selected. As peak overlaps cannot be avoided completely, an offline overlap correction has been developed in order to correct the interferences afterwards. Results obtained in this study attain acceptable totals and atomic proportions, suggesting that the applied corrections are appropriate.

Keywords: Mineral Liberation Analyser; Electron Microprobe; Pointlogger; Platinum Group Minerals; Overlap corrections

  • Contribution to proceedings
    EMAS 2014 - 11th EMAS Regional Workshop on Electron Probe Microanalysis of Materials Today, Practical Aspects, 21.-24.09.2014, Leoben, Österreich
    EMAS Regional Workshop on Electron Probe Microanalysis of Materials Today, Antwerp-Wilrijk, Belgien: European Microbeam Analysis Society eV EMAS, 9789082276909, 303-303
  • Poster
    EMAS 2014 - 11th EMAS Regional Workshop on Electron Probe Microanalysis of Materials Today, 21.-24.09.2014, Leoben, Österreich

Publ.-Id: 20926

Abschlussbericht "WTZ Russland - Fluenzberechnungen für Voreilproben beim WWER-440"

Konheiser, J.; Grahn, A.

Reactor pressure vessels (RPV) are non-restorable equipment and their lifetime may restrict the nuclear power plant-life as a whole. Surveillance specimen programs for RPV materials are among the most important measures of in-service inspection pro-grams that are necessary for realistic and reliable assessment of the RPV residual lifetime. In addition to the chemical composition of the RPV steel, the radiation pa-rameters (neutron and gamma fluences and spectra) have the most important impact on the RPV embrittlement characteristics.
In this work, different geometric positions which have influence on the radiation conditions of the samples are investigated. Thus, the uncertainties can be determined in the fluence values of surveillance specimens. The fluence calculations were carried out by the codes TRAMO and DORT. This study was accompanied by ex-vessel neutron dosimetry experiments at Kola NPP, Unit 3 (VVER-440/213), which provide the basis for validation of calculated neutron fluences. The main neutron-activation monitoring reactions were 54Fe(n,p)54Mn and 58Ni(n,p)58Co. The activity measurements were carried out by “Scientific and Engineering Centre for Nuclear and Radiation Safety (SEC NRS).
Good agreement between the deterministic and stochastic calculation results as well as between the calculations and the ex-vessel measurements was found. The aver-age difference between measured and calculated values is 5%. The influence of the channels for surveillance specimens and the shielding effect of a baffle rib on the monitors and on the Monte-Carlo calculated results was studied.
For the surveillance specimens in the maximum of the flux, an average flux of around 2.45 * 1012 neutrons/cm2 was calculated for the neutron flux E> 0.5 MeV. The differences in the surveillance specimens could be up to 20% depending on the direction to the core. Discrepancies up to 10% can be caused by the change of the position of the capsules in the irradiation channel. Based on these calculations the lead factor of specimens was determined. The maximum fluence of RPV may be achieved after two cycles.
The calculated maximum gamma flux is around 3.4 * 1012 g/cm2s for E> 1.0 MeV and around 8.4 * 1012 g/cm2s for E> 0.5 MeV, with the largest part of the flux (around 97%) from the neutron reactions. The gamma fluxes in the surveillance specimens are two to three times bigger than the neutron fluxes. Nevertheless, the material damage by the gamma radiation is very small, because the dpa (displacement per atom) cross sections of gamma rays are about two to three orders of magnitude smaller.
In order to exclude the possibility of healing effects of the samples due to excessive temperatures, the heat release in the surveillance specimens was determined based on the calculated gamma fluences. The analytic treatment of the heat conduction equation and simplified SS geometries were adopted to calculate the range of tem-peratures to be expected. The temperature increase of 20 K above the inlet coolant temperature was estimated using a conservative approach. Under comparatively re-alistic conditions, the heating was reduced to less than 5 K.

Keywords: Reactor pressure vessels; Surveillance specimen; fluence calculation; neutron-activation monitors

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-053 2014
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 20925

Tomographic imaging of gas holdup distribution in pressurized bubble columns

Bieberle, A.; Schubert, M.; Rollbusch, P.; Becker, M.; Schleicher, E.; Hampel, U.

The averaged and radial gas holdup as well as gas phase dynamics and approximate bubble size distribution were studied in a high-pressure bubble column reactor of 4000 mm height and 330 mm diameter. Novel imaging measurement techniques, namely high-resolution gamma-ray computed tomography and wire-mesh sensor, were developed and adapted to the industrial reactor system. The gas phase was nitrogen. Deionized water and cumene were applied as liquid phases. The effect of the superficial gas velocity was studied over a range of 0 to 0.05 m/s at low liquid superficial velocities of 0.008 and 0.018 m/s for operating temperatures and pressures up to 75°C and 18.5 bar, respectively.

Keywords: Bubble column; gas holdup; flow structure; gamma tomography; wire-mesh sensor

  • Contribution to proceedings
    2nd International Symposium on Multiscale Multiphase Process Engineering, 24.-27.09.2014, Hamburg, Deutschland
    Book of Full-Length Manuscripts, 262-267
  • Poster
    2nd International Symposium on Multiscale Multiphase Process Engineering, 24.-27.09.2014, Hamburg, Deutschland
  • Lecture (Conference)
    2nd International Symposium on Multiscale Multiphase Process Engineering, 24.-27.09.2014, Hamburg, Deutschland

Publ.-Id: 20924

INTRA r³+ Integration und Transfer der r³ Ergebnisse

Dürkoop, A.

Das Poster präsentiert die Arbeiten im Begleitforschungsprojekt INTRA r³+ zur r³ Fördermaßnahme "Innovative Technologien für Ressourceneffizienz.

  • Poster
    Urban Mining Kongress und r³ Statusseminar 2014, 11.-12.06.2014, Essen, Deutschland

Publ.-Id: 20923

Simultaneous measurement of anisotropic magnetoresistance and observation of magnetic domains by Kerr microscopy

Osten, J.; Lenz, K.; Henschke, A.; Lindner, J.; Fassbender, J.

We report a new instrument, which consists of a Kerr microscope combined with resistance measurements. This setup allows for recording magnetic domains while measuring the anisotropic magnetoresistance (AMR). For this purpose the development of a special sample holder and the extension of the measurement software was needed. The sample holder is equipped with electrical contacts in such a way to apply a current, measure the voltage, and use it in the Kerr microscope. The extension of the measurement software enables one to record resistance and Kerrimages at the same time. This Kerr microscopy combined with the simultaneous measurement of the AMR leads to a better understanding of the AMR behavior.

Keywords: anisotropic magnetoresistance; AMR; magnetic domains; Kerrmicroscope

Publ.-Id: 20922

Working with hierarchical databases in R to model geometallurgical data

Matos Camacho, S.; van den Boogaart, K. G.

For the demands of geometallurgy a vast amount of data in multifaceted shape is needed. There are high resolution images from the MLA, data tables with information on the chemistry of some mineral phases, statistics on the distribution of the grain size, and so on. This data needs to be stored in a database, which reflects the often hierarchical structure of it and is flexible enough to be extended with almost any potential occurring information. We provide a MySQL template for such a database. Finding the desired data there can be a tough task, since queries might be highly complex and confusing. Therefore, we developed an easy accessible R interface for accessing this database.

Keywords: R; geometallurgy; MySQL

  • Lecture (Conference)
    16th Annual Conference of the International Association for Mathematical Geosciences, 17.-20.10.2014, New Delhi, India
  • Contribution to proceedings
    16th Annual Conference of the International Association for Mathematical Geosciences, 17.-20.10.2014, New Delhi, India
    Geostatistical and Geospatial Approaches for the Characterization of Natural Resources in the Environment: Challenges,Processes and Strategies Geostatistical, New Delhi: Capital Publishing Company, 978-93-81891-25-4, 341-343

Publ.-Id: 20921

Evidence for Deposition of Interstellar Material on the Lunar Surface

Fimiani, L.; Cook, D. L.; Faestermann, T.; Gómez Guzmán, J. M.; Hain, K.; Herzog, G. F.; Knie, K.; Korschinek, G.; Ligon, B.; Ludwig, P.; Park, J.; Reedy, R. C.; Rugel, G.

Astronomical observations indicate that one or more supernovae (SN) ocurred in the vicinity of our solar system in the recent past (~10Myr) [1,2]. One possible indication of the arrival of SN (or perhaps AGB) debris locally was the detection of 60Fe/Fe (T1/2 = 2.62 Myr [3]) excesses in a ferroman-ganese crust from the Pacific Ocean [4,5]. Another indication came from the Moon. In a previous study [6] we reported a 60Fe/Fe depth profile constructed with 2 samples of the Apollo 12 core 12025, 4 samples of the Apollo 15 core 15008, 2 samples known as ‘skim’, ‘scoop’ and ‘under boulder’ soil collected near the shade of a small boulder in Station 9 during the Apollo 16 mission (shaded samples), and 5 samples of the deep drill core 60007/6, sampled during the same mission. We complete the previous work by reporting new measurements of 53Mn (T1/2 = 3.7 Myr [7]) in the same samples, including deeper samples of the 12025 core, and by using those measurements for a critical assessment of the 60Fe results. We also determined the activities of 60Fe and 53Mn of 7 samples from 4 iron meteorites; these activities were used to establish reference levels for local production due to galactic cosmic rays.

Keywords: supernova; Fe-60; Mn-53

  • Poster
    45th Lunar and Planetary Science Conference, 17.-21.03.2014, Houston, USA

Publ.-Id: 20920

Development of a micro reactor for the isobutane oxidation as a multiphase process

Willms, T.; Kryk, H.; Wiezorek, M.; Hampel, U.

The partial oxidation of liquid isobutane to tertiary butyl hydroperoxide (TBHP) is currently conducted on an industrial scale with bubble columns at a selectivity of 60% and a maximum conversion of 25%. In this process, liquid isobutane is converted with oxygen at high temperatures (130 to 140°C) and pressures (25 to 37 Bar) at high residence times of 10 to 12 hours. In the frame of the Helmholtz-Energy-Alliance project “Energy efficient chemical multiphase processes“ a micro reactor has been built and used to investigate this reaction for the first time as a continuous two-phase process in a broad range of flow rates, temperatures (120 to 150°C) and pressures (25 to 100 bar). For the improvement of the selectivity of the industrial process the influence of the residence time, hydrodynamics, initiator, additives and pressure on the reaction is studied. To realize a large range of residence times, flow rates in the range of 15 µl/min to 188 µl/min for isobutane and in the range of 0.1 up to 1.5 ml/min for oxygen were realized, using different capillary lengths which lie between 20 and 100 m. To charac¬terize the isobutane flow, preliminary measurements of the system isobutane – nitrogen were performed in a glass capillary. As the target product and initiator TBHP is sensitive to most metals, the micro reactor and further parts of the lab facility have been coated. To assure reasonable results of the hydrodynamic and kinetic studies, it was also important to realize a flow without pulsation by large pressure fluctuations. Therefore, the pressure is controlled by a gas pressure valve after a gas-liquid separation. The oxidation is followed by taking samples and analysis of the liquid reaction mixture by means of a GC-MS-System. In the frame of the presentation the challenges of the reactor construction and their solutions are discussed.

Keywords: Micro reactor; process intensification; isobutane oxidation

  • Lecture (Conference)
    4th European Conference on Microfluidics, 10.-12.12.2014, Limerick, Ireland

Publ.-Id: 20919

Towards Laser Driven Particle Therapy: from in vitro studies to human tumor irradiation on mice

Beyreuther, E.; Baumann, M.; Brüchner, K.; Hartmann, J.; Kaluza, M.; Karsch, L.; Krause, M.; Laschinsky, L.; Leßmann, E.; Nicolai, M.; Oppelt, M.; Reuter, M.; Richter, C.; Sävert, A.; Schürer, M.; Schnell, M.; Woithe, J.; Pawelke, J.

The novel technology of particle acceleration by high intensity lasers promises more compact and cost effective ion sources as well as electron beams of very high energy for radiotherapeutic application. However, compared to conventional beams, laser-driven acceleration results in different beam properties like ultra-short and very intensive pulses, inherent pulse-to-pulse fluctuations, low pulse repetition rate, large beam divergence and broad energy distribution. In consequence, the future medical application of these particle beams requires not only a high power laser system but also new technical solutions for dose delivery and quality assurance as well as comprehensive research on the radiobiological consequences of ultra-short radiation pulses with high pulse dose.
During the last years the laser-driven technology was developed at such a rate that cell samples and small animals can be irradiated. Within the joint research project “onCOOPtics” extensive in vitro dose response studies were already performed comparing the radiobiological effects of laser driven electron and proton beams to their conventional equivalents. As overall result, the obtained dose-effect relationships for human tumor and human normal tissue cells reveal no difference between conventional and laser-driven beams. In a second translational step, in vivo experiments were recently established at the laser system JETI. Although the experiments were motivated by future proton trials, first attempts were performed with laser accelerated electrons, since the homogeneous delivery of prescribed doses to a 3D target volume is easier for electrons than for protons. Tumor irradiation was realized for the murine sarcoma KHT and the human squamous cell carcinoma FaDu grown on nude mice ear. Doses of up to 14 Gy were applied and the radiation induced tumor growth delay was investigated and later on compared to those obtained after similar treatment at a conventional electron Linac. Moreover, the successful performance of such an experiment campaign over a period of several weeks underlines the stability and reproducibility of all implemented methods and setup components. Further experiments with laser accelerated protons are in progress.
The work was supported by the German Federal Ministry of Education and Research
(BMBF), grant nos. 03ZIK445 and 03Z1N511.

  • Lecture (Conference)
    41st Annual Meeting of the European Radiation Research Society, 14.-19.09.2014, Kallithea/Rhodos, Greece
  • Poster
    Space Radiation and Heavy Ions in Therapy Symposium 2015, incl. 15th Workshop on Ion Beams in Biology and Medicine (IBIBAM), 22.-24.05.2015, Osaka, Japan

Publ.-Id: 20918

Ultrafast Terahertz-induced Magnetization Dynamics Studied on a Nanometer Length Scale by Coherent XUV Free-electron Laser Radiation.

Berntsen, M. H.; Müller, L.; Schleitzer, S.; Steinke, I.; Lehmkühler, F.; Schroer, M. A.; Ricci, A.; Al-Shemmary, A.; Stojanovic, N.; Golz, T.; Fischer, B.; Bagschik, K.; Bach, J.; Beyersdorff, B.; Winkler, G.; Frömter, R.; Gensch, M.; Oepen, H. P.; Gutt, C.; Grübel, G.

Free-electron lasers (FELs), with their high photon flux, short pulse lengths, and coherent radiation, are ideal tools for studying complex materials, simultaneously on sub-picosecond time and on nanometer length scales. In particular, by exploiting the magneto-dichroic transitions at the L or M edges of Fe, Co, Ni or Gd, temporal and spatial studies of magnetic systems can be performed.
Infrared-pump–XUV-probe experiments performed at a FEL have revealed that the optically induced demagnetization in magnetic maze-domain structured Co/Pt samples is also accompanied by a spatial response. In this, and other studies using optical (IR) pumping, the magnetization is manipulated by heating of the spin system, i.e. through ultrafast electronic excitations.
Using terahertz (THz) radiation for pumping gives a unique possibility to investigate the influence of ultra-short pulses of strong magnetic fields on the magnetization dynamics since the THz photons do not generate direct electronic heating and because the THz phase can couple directly to the magnetic moments. Hence, the use of THz radiation could bring one a step closer to being able to control magnetism on ultrafast time scales.

  • Poster
    Science at FEL´s, 15.-17.09.2014, Villigen, Schweiz

Publ.-Id: 20917

Geometallurgy of REE deposits - state of the art

Renno, A. D.; Gutzmer, J.; Birtel, S.; Atanasova, P.; Bachmann, K.; Matos Camacho, S.; Schulz, B.; Kern, M.; Krause, J.; Munnik, F.

Review of the most recent activities of the Helmholtz-Institute Freiberg for Resource Technology in the field of geometallurgy of REE deposits

Keywords: geometallurgy; REE

  • Invited lecture (Conferences)
    Geology to Metallurgy of Critical Rare Earths, 24.-25.03.2014, Penryn, UK

Publ.-Id: 20916

Terahertz Radiation driven Dynamics of Magnetic Domain Structures probed by coherent Free-Electron Laser Light

Müller, L.; Gutt, C.; Gruebel, G.; Golz, T.; Stojanovic, N.; Gensch, M.

The new free-electron laser (FEL) sources provide radiation with unprecedented parameters in terms of ultrashort pulse length, high photon flux, and coherence. These properties make FELs ideal tools for studying ultrafast dynamics in matter on a previously inaccessible level.
Tuning the FEL photon energy resonantly to the magneto-dichroic transition of cobalt at 59.6 eV (equivalent to a wavelength of 20.8 nm) yields magnetic scattering contrast from a thin cobalt/platinum multilayer sample via the X-ray magnetic dichroism effect. Due to their magnetic anisotropy, these samples show domains magnetized in the out-of-plane direction with a typical domain width of 80 nm. For our transmission small-angle X-ray scattering (SAXS) geometry the magnetic scattering signal, therefore, originates from circular dichroism only.
After magnetic scattering of resonantly tuned XUV radiation from magnetic domains systems was proven feasible at FELs, ultrafast demagnetization, discovered initially by Beaurepaire in 1996, was for the first time measured in a mesoscopic magnetic domain systems at FLASH in Hamburg in an IR pump – FEL probe type of experiment. An ultrafast spatial response was found to accompany the demagnetization process.
In a later experimental approach, magnetic domain systems were pumped using THz radiation and probed by SAXS using XUV radiation from the FEL source. The 10-cycle THz pulse is produced by an additional electromagnetic undulator available at FLASH and therefore allows for measurements with minimal time jitter. In our experimental configuration, the THz magnetic field in the sample plane was ~ 20 mT. For samples in their close-to-equilibrium maze-domain configuration no change in form or strength of the scattering pattern was observed. However, when putting the sample in a static magnetic field of a few 10 mT, the magnetic domains are partially aligned along the magnetic field resulting in an anisotropic scattering pattern. We find that, in dependence of the pump-probe delay time, this anisotropy changes on time scales of a few picoseconds (Fig. 2). This experiment shows that THz radiation can affect magnetic domain systems directly which can be of great interest for future FEL experiments concentrating on THz control of magnetism.

  • Poster
    Intermag 2014, 04.-08.05.2014, Dresden, Germany

Publ.-Id: 20915

High-Speed PIXE – a new tool for Automated Mineralogy using a Color X-Ray Camera

Renno, A. D.; Buchriegler, J.; Dressler, S.; Hanf, D.; Merchel, S.; Munnik, F.; Nowak, S.; Scharf, O.; Ziegenrücker, R.

Methods of automated mineralogy form the analytical backbone of geometallurgy. Most of them exploit the combined imaging and analytical capabilities of optical and scanning electron microscopes. Typical results are „phase maps“ either derived from the distribution of major elements or determined directly. The effective application of such methods for strategic metals which are won as by-products from other metal ores or secondary raw materials is handicapped by the restricted possibilities to determine the spatial distribution of such trace elements like In, Ga, Ge or the rare earth elements (REE). The recently commissioned High-Speed PIXE (Particle Induced X-Ray Emission) setup at the Helmholtz-Institute Freiberg for Resource Technologies will overcome these limitations by using the advantages of PIXE over traditional electron beam based methods like the better peak-background ratio. We use the SLcam® Colour X-ray Camera - a novel pnCCD pixel detector (264×264=69696 pixel) combined with a polycapillary X-ray optics (Scharf et al., 2011) as detector for element specific X-ray radiation. This design allows us the simultaneous determination of trace element distributions on a 12 × 12 mm2 area with a lateral resolution better than 100 μm. First results of geometallurgical applications of this method are presented.

Keywords: PIXE; High-Speed PIXE

  • Lecture (Conference)
    92nd Annual Meeting Deutsche Mineralogische Gesellschaft (DMG) 2014, 21.-24.09.2014, Jena, Deutschland

Publ.-Id: 20914

High field THz sources operating at 100 kHz Repetition rates: Challenges and Opportunities

Gensch, M.

Picosecond long transients of electric and magnetic fields in combination with repetition rates in the few 100 kHz to even MHz regime is crucial to understand several recently observed fascinating nonequilibrium phenomena driven by THz excitations. A new class of compact accelerator based THz sources based on super-radiant amplification of radiation from ultra-short electron bunches allows to generate high field THz pulses at unprecedented repetition rates. First measurements at a prototype facility proof the feasibility of the approach and demonstrate already parameters which exceeds laser-based sources by more than 2 orders of magnitude. Results from first pilot experiments aiming at investigating THz driven magnetization dynamics in MnGa, NiO and YIG are discussed and an outlook into the opportunities for High-field THz science at the future TELBE user facility is given.

  • Invited lecture (Conferences)
    Seminar of the Stanford Institute for Materials and Energy Sciences, 12.09.2014, Stanford / SLAC, USA

Publ.-Id: 20913

High-Speed PIXE: Automated Mineralogy using a Color X-Ray Camera

Renno, A. D.; Buchriegler, J.; Hanf, D.; Munnik, F.; Nowak, S.; Scharf, O.; Ziegenrücker, R.

Methods of automated mineralogy form the analytical backbone of geometallurgy. Most of them exploit the combined imaging and analytical capabilities of optical and scanning electron microscopes. Typical results are „phase maps“ either derived from the distribution of major elements or determined directly. The effective application of such methods for strategic metals which are won as by-products from other metal ores is handicapped by the restricted possibilities to determine the spatial distribution of such trace elements like In, Ga, Ge or the rare earth elements (REE). The recently comissioned High-Speed PIXE (Particle Induced X-Ray Emission) setup at the Helmholtz-Institute Freiberg for Resource Technologies will overcome these limitations.
We use the SLcam® X-ray Color Camera - a novel pnCCD Pixel detector (264 x 264 = 69696 Pixel) combined with a polycapillary X-ray optic (Scharf et al., 2011) as the detector for the element specific X-ray radiation. This design allows us the simultaneous determination of the trace element distribution on a 12 * 12 mm2 area with a lateral
resolution of about 50 μm. First results of geometallurgical applications of this method are presented.

Keywords: PIXE; High-Speed PIXE

  • Lecture (Conference)
    21st General Meeting of the International Mineralogical Association, 01.-05.09.2014, Sandton, South Africa

Publ.-Id: 20912

Electron Microprobe Analysis of REE in Eudialyte Group Minerals: Challenges and Solutions

Atanasova, P.; Krause, J.; Möckel, R.; Osbahr, I.; Gutzmer, J.

Alkaline complexes containing eudialyte group minerals (EGM) comprise one of the most promising sources for future rare earth element (REE) supply. Complex mineral chemistry and crystal structure of EGM pose particular challenges for resource analytics and ore characterisation. A combination of qualitative scanning electron microscope (SEM)-based image analysis and quantitative analytical methods like electron microprobe (EPMA) is required. For this purpose polished thick sections are first mapped by the mineral liberation analyzer (MLA) to effectively identify the ore-bearing minerals and mineral associations. Backscattered electron images (BSE images) indicate varying BSE contrast within the EGM crystals. In order to determine the assumed elemental variations, element distribution maps of main (e.g., Zr, Si, Al) and minor (e.g., Ce, Y) elements are obtained by EPMA. These maps illustrate variable and complex zonation patterns within the EGM crystals. Based on the element distribution maps, quantitative analyses are then performed with a field emission electron microprobe JEOL JXA 8530F.
The accurate quantification of the chemical composition of EGM is complicated by both mineralogical and X-ray-specific challenges. These include: 1) structural and chemical variability of EGM composition (e.g., [1-3]); 2) mutual interferences of X-ray lines from major and trace elements, in particular REE elements [4]; 3) the diffusive volatility of light anions as F and Cl and cations such as K and Na; 4) particular instability of EGM under the electron beam.
A novel analytical approach has been developed to account for the above mentioned analytical challenges. Additionally, loss on ignition und differential scanning calorimetry data has been applied to constrain the content and composition of volatiles in the EGM structure. All correction for the overlapping of X-ray lines is processed offline. Preliminary results demonstrate that the parameters mentioned above need to be considered and carefully optimized to perform accurate quantitative analyses on the chemical composition of EGM with the electron microprobe.

Keywords: Electron Mikroprobe; EPMA; rare earth elements; eudialyte

  • Poster
    EMAS 2014 - 11th EMAS Regional Workshop on Electron Probe Microanalysis of Materials Today - Practical Aspects, 22.-24.09.2014, Leoben, Austria

Publ.-Id: 20910

Regression with compositional response having unobserved components or below detection limit values

van den Boogaart, K. G.; Tolosana-Delgado, R.; Templ, M.

The typical way to deal with zeros and missing values in compositional data sets is to impute them with a reasonable value, and then the desired statistical model is estimated with the imputed data set, e.g., a regression model. This contribution aims at presenting alternative approaches to this problem within the framework of Bayesian regression with a compositional response. In the first step, a compositional data set with missing data is considered to follow a normal distribution on the simplex, which mean value is given as an Aitchison affine linear combination of some fully observed explanatory variables. Both the coefficients of this linear combination and the missing values can be estimated with standard Gibbs sampling techniques. In the second step, a normally distributed additive error is considered superimposed on the compositional response, and values are taken as ‘below the detection limit’ (BDL) if they are ‘too small’ in comparison with the additive standard deviation of each variable. Within this framework, the regression parameters and all missing values (including BDL) can be estimated with a Metropolis-Hastings algorithm. Both methods estimate the regression coefficients without need of any preliminary imputation step, and adequately propagate the uncertainty derived from the fact that the missing values and BDL are not actually observed, something imputation methods cannot achieve.

Keywords: Bayesian regression; compositional regression; missing values; nondetects; MCMC

Publ.-Id: 20909

Commissioning Results of the 2nd 3.5 cell SRF Gun for ELBE

Arnold, A.; Freitag, M.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Kneisel, P.; Ciovati, G.; Turlington, L.

As in 2007 the first 3.5 cell superconducting radio frequency (SRF) gun was taken into operation, it turned out that the specified performance has not been achieved. However, to demonstrate the full potential of this new type of electron source, a second and slightly modified SRF gun II was built in collaboration with Thomas Jefferson National Accelerator Facility (TJNAF). We will report on commissioning and first results of the new gun, which includes in particular the characterization of the most important RF properties as well as their comparison with previous vertical test results.

Keywords: superconducting; radio frequency; electron; injector; SRF gun

  • Open Access Logo Contribution to proceedings
    27th Linear Accelerator Conference, LINAC14, 31.08.-05.09.2014, Genf, Schweiz
  • Poster
    27th Linear Accelerator Conference, LINAC14, 31.08.-05.09.2014, Genf, Schweitz

Publ.-Id: 20908

Uranium(VI) Binding Forms in Selected Human Body Fluids: Thermodynamic Calculations versus Spectroscopic Measurements

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

Human exposure to uranium increasingly becomes a subject of interest in many scientific disciplines such as environmental medicine, toxicology, and radiation protection. Knowledge about uranium chemical binding forms (speciation) in natural body fluids can be of great importance not only to understand its biokinetics, but also relevant for risk assessment and for designing decorporation therapy in the case of accidental overexposure. In this study, thermodynamic calculations of uranium speciation in relevant simulated and original body fluids were compared with spectroscopic data after ex-situ uranium addition. For the first time, experimental data on U(VI) speciation in natural body fluids (saliva, sweat, urine) was obtained by means of cryogenic time-resolved laser-induced fluorescence spectroscopy (cryo-TRLFS) at 153 K. By using the time dependency of fluorescence decay and the band positions of the emission spectra, various uranyl complexes were demonstrated in the studied samples. The variations of the body fluids in terms of chemical composition, pH, and ionic strength resulted in different binding forms of U(VI). The speciation of U(VI) in saliva and in urine was affected by the presence of bioorganic ligands, whereas in sweat, the distribution depends mainly on inorganic ligands. We also elucidated the role of biological buffers, i.e., phosphate (H2PO4-/HPO42-) on U(VI) distribution, and the system Ca2+/UO22+/PO43- was discussed in detail in both saliva and urine. The theoretical speciation calculations of the main U(VI) species in the investigated body fluids were significantly consistent with the spectroscopic data. Laser fluorescence spectroscopy showed success and reliability for direct determination of U(VI) in such biological matrices with the possibility for further improvement.

Keywords: uranium; speciation; saliva; sweat; urine

Publ.-Id: 20907

Simulation Studies for Prompt Gamma Imaging and Prompt Gamma Timing

Rohling, H.; Golnik, C.; Müller, A.; Pausch, G.; Schöne, S.; Kormoll, T.; Enghardt, W.; Fiedler, F.

kein Abstract verfügbar.

  • Poster
    Workshop on Range Assessment and Dose Verification in Particle Therapy, 29.09.2014, Dresden, Deutschland
  • Poster
    Workshop: "Precision, Speed und Flexibility: New radiation detection methods for ion beam radiotherapy", 23.-25.09.2014, Heidelberg, Deutschland

Publ.-Id: 20906

Migrating ignimbrite flare-ups in the Central Andes - Implications for crustal evolution based on chemical, geochronological and GIS-based volumetric data

Brandmeier, M.; Wörner, G.

Temporal and compositional patterns of Neogene ignimbrite magmatism in the Central Andes were analyzed using GIS and geostatistical modeling. We compiled a comprehensive ignimbrite data base and digitized 203 individual ignimbrite sheets, for which geochemical, isotopic (partly), and geochronological data are available from the literature and own data. Composition, timing, volumes and sources of erupted ignimbrite deposits are constrained and magma volumes through space and time are calculated for five segments of the Central Andes.
The total erupted ignimbrite magma volume of 31,000 km3 for the past 30 Ma is distributed as follows: 2,400 km3 for Southern Peru, 2,700 km3 for Southernmost Peru, 8,400 km3 for the Altiplano, 14,200 km3 for the Northern Puna and 3,100 km3 for the Southern Puna segments. Average magmatic addition per Ma and km arc for ignimbrites range between 20 to 30 km3. This is similar to the basaltic “base”-flux for arc magmatism and suggests that ignimbrite flare-ups do not represent orders of magnitude increased magma production rates but are rather punctuated, short-lived well events separated in space and time. There is a clear N-S “younging” of eruption ages and ignimbrite pulses. Major pulses occurred at 19-24 Ma (e.g. Oxaya, Nazca Group), 13-14 Ma (e.g. Huaylillas ignimbrites), 6-10 Ma (Altiplano and Puna ignimbrites, e.g. Vilama ignimbrite) and 3-6 Ma (e.g. Atana, Los Frailes, Toconao). Small and younger ignimbrites (0-3 Ma, e.g. Lauca-Perez, Purico) do not follow this pattern. We propose that large-volume ignimbrite eruptions occurred in the wake of subduction of the Juan-Fernandez ridge on the Nazca Plate that passed below the Central Andes from N to S during the past 25 Ma. Low angle subduction caused compression and fluid release is followed by massive inflow and melting of asthenospheric mantle when the slab steepened again after the passing of the ridge. This in turn caused massive melting within the crust aided by advective heat transport. Differences in chemcial and isotopic composition of the large-volume ignimbrites are related to changes in crustal thickness, and different “preconditioning” during the Anden orogeny. Isotope data and whole rock compositional data suggest a higher degree of crustal assimilation for the younger Altiplano ignimbrites in the S compared to the older (22-19 Ma) ignimbrites in the North. REE compositions for large-volume ignimbrites reflect changes in crustal thickness with a "transition" at ca. 13-9 Ma that can be related to accelerated crustal shortening at that time (Oncken et al., 2006).
Total volumes for the northern segments and the Northern Puna are similar. However, calderas and intra-caldera ignimbrite volumes in the north are less well constrained due to the lower level of study, higher ages and higher degrees of incision and erosion. In any case, there is no “single” ignimbrite flare up in the Central Andes with one regionally and temporally restricted event of high-magma flux and bath-olith construction (de Silva and Gosnold, 2007). Instead, we suggest a more dynamic scenario, with “flare ups” moving from N to S across the Central Andes during the past 25 Ma. Our database aids to better constrain numerical models of Andean geodynamic processes.
deSilva, S., Gosnold, W.D. (2007) Episodic construction of batholiths: Insights from the spatiotemporal development of an ignimbrite flare-up. J. Volcanol. Geotherm. Res. 167: 320-335
Oncken, O. et al. (2006), Deformation of the Central Andean Upper Plate System-Facts, Fiction, and Constraints for Plateau Models, in Oncken, O. et. al., eds., The Andes: Frontiers in Earth Sciences, Springer Berlin Heidelberg: 3-27.

  • Contribution to proceedings
    GeoFrankfurt 2014, 21.-24.09.2014, Frankfurt, Germany

Publ.-Id: 20905

Assessments of boundary conditions and requirements for Rare Earth Underground Mining due to presence of NORMs

Barakos, G.; Mischo, H.; Gutzmer, J.

Rare earths contain NORMs, such as uranium, thorium and their progeny, like radium and radon. The varying concentrations of NORMs are quite often significant enough to result in occupational and environmental radiation exposures during the mining, milling and processing procedures of rare earths and compounds. Ventilation is the primary technique of controlling ambient concentrations of radon. Fresh air volume flow rates, the distribution of airflow within the mine and the radon emanation rate are primary factors affecting such concentrations. In this paper, it is attempted to determine the factors that may result in radiation risks and evaluate the boundary conditions that will contribute to the restriction or even elimination of radon progeny, with a goal to use the evaluations in order to build an overall assessment tool.

Keywords: Rare Earth Elements; NORMs; Radon; Thoron; Underground Mining; Occupational Safety

  • Open Access Logo Contribution to proceedings
    ERES 2014 - 1st International Conference on European Rare Earth Resources, 04.-07.09.2014, Milos Island, Greece
    ERES 2014 - 1st International Conference on European Rare Earth Resources, Imerovigli, Santorini GR‐84700: Heliotopos Conferences Ltd., 978‐960‐6746‐15‐4

Publ.-Id: 20904

Simulation of aerosol particle deposition and resuspension in high temperature reactors

Lecrivain, G.; Hampel, U.

In a high temperature pebble-bed reactor core where thousands of pebbles are amassed, the friction between the outer graphite layer of the fuel elements triggers the formation of carbonaceous dust. This dust is eventually conveyed by the cooling carrier phase in the primary circuit of the high temperature reactor. Depending on the gas velocity, the solid aerosol particles can either attach to the wall surfaces or be re-entrained in the turbulent flow. Two numerical models developed for the prediction of particle attachment and detachment are presented.

  • Invited lecture (Conferences)
    Seminar / Commissariat à l’énergie atomique / Invited lecture, 20.06.2014, Saclay, France

Publ.-Id: 20903

Simulation of aerosol particle deposition in a high temperature reactor

Lecrivain, G.; Hampel, U.; Hurtado, A.

In a high temperature pebble-bed reactor core where thousands of pebbles are amassed, the friction between the outer graphite layer of the fuel elements triggers the formation of carbonaceous dust. This dust is eventually conveyed by the cooling carrier phase in the primary circuit of the high temperature reactor. Depending on the gas velocity, the solid aerosol particles can either attach to the wall surfaces or be re-entrained in the turbulent flow. Two numerical models developed for the prediction of particle attachment and detachment are presented.

  • Contribution to proceedings
    Workshop des CFD-Kompetenzverbunds / German CFD Network, 19.-20.03.2014, Garching, Germany
    Proceedings of the German CFD Network

Publ.-Id: 20902

Zinc corrosion after loss-of-coolant accidents in pressurized water reactors - physicochemical effects

Kryk, H.; Hoffmann, W.; Kästner, W.; Alt, S.; Seeliger, A.; Renger, S.

Within the framework of the reactor safety research, generic experimental investigations were carried out aiming at the physicochemical background of possible zinc corrosion product formation, which may occur inside the reactor pressure vessel during the sump circulation operation after loss-of-coolant accidents in pressurized water reactors. The contact of the boric acid containing coolant with hot-dip galvanized steel containment internals causes corrosion of the corresponding materials resulting in dissolution of the zinc coat. A retrograde solubility of zinc corrosion products with increasing temperature was observed during batch experiments of zinc corrosion in boric acid containing coolants. Thus, the formation and deposition of solid corrosion products cannot be ruled out if the coolant containing dissolved zinc is heated up during its recirculation into hot regions within the emergency cooling circuit (e.g. hot-spots in the core). Corrosion experiments at a lab-scale test facility, which included formation of corrosion products at a single heated cladding tube, proved that dissolved zinc, formed at low temperatures in boric acid solution by zinc corrosion, turns into solid deposits of zinc borates when contacting heated zircaloy surfaces during the heating of the coolant. Moreover, the temperature of formation influences the chemical composition of the zinc borates and thus the deposition and mobilization behavior of the products.

Keywords: pressurized water reactor; loss-of-coolant accident; corrosion; zinc; boric acid; in-vessel effects

Publ.-Id: 20901

Surface and Material Analytics based on Dresden-EBIS Platform Technology

Schmidt, M.; König, J.; Bischoff, L.; Pilz, W.; Zschornack, G.

Nowadays widely used mass spectrometry systems utilize energetic ions hitting a sample and sputter material from the surface of a specimen. The generated secondary ions are separated and detected with high mass resolution to determine the target materials constitution. Based on this principle, we present an alternative approach implementing a compact Electron Beam Ion Source (EBIS) in combination with a Liquid Metal Ion Source (LMIS).
An LMIS can deliver heavy elements which generate high sputter yields on a target surface. More than 90% of this sputtered material consists of mono- and polyatomic neutrals. These particles are able to penetrate the magnetic field of an EBIS and they will be ionized within the electron beam.
A broad spectrum of singly up to highly charged ions can be extracted depending on the operation conditions. Polyatomic ions will decay during the charge-up process. A standard bending magnet or a Wien filter is used to separate the different ion species due to their mass-to-charge ratio. Using different charge states of ions as it is common with EBIS it is also possible to resolve interferring charge-to-mass ratios of only singly charged ions.
Different setups for the realization of feeding the electron beam with sputtered atoms of solids will be presented and discussed. As an example the analysis of a copper surface is used to show high-resolution spectra with low background noise. Individual copper isotopes and clusters with different isotope compositions can be resolved at equal atomic numbers.
These results are a first step for the development of a new compact low-cost and high-resolution mass spectrometry system. In a more general context, the described technique demonstrates an efficient method for feeding an EBIS with atoms of nearly all solid elements from various solid target materials. The new straightforward design of the presented setup should be of high interest for a broad range of applications in materials research as well as for applications connected to analyzing the biosphere, hydrosphere, lithosphere, cosmosphere and technosphere.

Keywords: Electron Beam Ion Source; LMIS; Sputter yield; Mass Spectra

  • Lecture (Conference)
    International Symposium Electron Beam Ion Sources and Traps, EBIST 2014, 18.-21.05.2014, East Lansing, Michigan, USA
  • Contribution to proceedings
    12th International Symposium on Electron Beam Ion Sources and Traps (EBIST'14), 18.-21.05.2014, East Lansing, Michigan, USA
    AIP Conference Proceedings 88(2015), 1640: AIP, 88-93
    DOI: 10.1063/1.4905403

Publ.-Id: 20900

Development and characterization of new liquid metal ion sources

Bischoff, L.; Pilz, W.; Tajmar, M.

In the last decades liquid metal ion sources (LMIS) working in focused ion beam (FIB) systems became an irrecoverable instrument in research and industry [1]. Sample preparation, local ion implantation and ion analysis are the main application topics. Most of the systems are equipped with a gallium LMIS. But, modern trends in nanotechnology require more extended properties like variable ion species for local doping, non-contaminating milling at higher rates or the application of focused cluster beams for surface modifications [2]. LMIS are also used for space propulsion as precision thrusters to provide ultrastable attitude and orbit control for satellites called Field-Emission- Electric-Propulsion [3].
In this contribution the basics of LMIS operation, the measurement of the main parameters and so the characterization of this type of ion sources will be presented. Moreover, the application of new source concepts including prototypes will be shown. At present about half of the periodic table can be provided as single or double charged ions as well as heavy cluster ions up to five atoms per ion by alloy LMIS. This provokes the interest to apply such sources not only in focused ion beam systems but also in high energy single-end ion accelerators. A first concept for an injector module to adapt a high current LMIS with integrated mass separation to a high energy ion beam system will be presented and discussed.

The authors would like to thank BMBF for financial support under Projekt 05K130DC: "Verbundprojekt 05K2013 – Ioneninduzierte Materialanalyse/-modifizierung: Modifizierung und in-situ Analyse von Materialien durch mittelenergetische Ionenbestrahlung. TP 1: Ultraschwere Ionen und deren Nutzung an HZDR-Beschleunigern."

[1] L. Bischoff, R. Böttger, P. Philipp and B. Schmidt, Nanostructures by mass-separated FIB, Book chapter in “FIB Nanostructures” in “Lecture Notes in Nanoscale Science and Technology” ed. Z. Wang, Peking, Berlin: Springer, 2013, Vol. 20, 465.
[2] L. Bischoff, K.-H. Heinig, B. Schmidt, S. Facsko and W. Pilz, Nucl. Instr. and Meth. B 2012, 272 198.
[3] M. Tajmar, I. Vasiljevich and W. Grienauer, Ultramicroscopy 2010, 111, 1.

Keywords: Liquid metal ion source; cluster; single-end ion accelerators

  • Lecture (Conference)
    Workshop Ionenstrahlen & Nanostrukturen, 20.-22.07.2014, Paderborn, Deutschland

Publ.-Id: 20899

A new algorithm for segmentation of ultrafast X-ray tomographed gas-liquid flows

Banowski, M.; Lucas, D.; Szalinski, L.

The ultrafast electron beam X-ray computed tomography was developed during the last years to obtain detailed data on two-phase flows. In a recent study we investigated different gas-liquid flow regimes in a vertical pipe at the Transient Two-phase Flow test facility (TOPFLOW). The study includes experiments on gas-liquid flows with varied superficial velocities for both phases and different flow directions. The obtained data is required for understanding fundamental physics of two-phase flow phenomena and for the development and validation of CFD- codes.
To extract quantitative data from the reconstructed three-dimensional data array, a new segmentation algorithm was developed, due the results of existing segmentation algorithms aren’t satisfyingly. The originality of this new algorithm bases on a stepwise creation of new bubbles using pixel agglomeration in shrinking steps without defining markers or starting points. The results were compared with threshold and gradient methods using two different bubble phantoms and real two-phase flow measurements. The new algorithm shows the best qualitative and quantitative results.

Keywords: X-ray; computed tomography; gas-liquid flow; bubbles; segmentation

Publ.-Id: 20898

Efficient corrosion protection of organ pipes and turbine blades by Plasma immersion ion implantation.

Pelic, B.; Skorupa, W.; Yankov, R.

Experiments have been undertaken to explore the improvement of the high temperature oxidation and aqueous corrosion of Ti-Al and Cu-Zn, respectively, by applying plasma based ion implantation (PBII).
The atmospheric corrosion of the tongues within the reed pipes which consist of a Cu-20Zn alloy (namely brass) is strongly enhanced by traces of acid vapors (from wooden parts and glue) and also the alloy’s instability caused by dezincification. A significant improvement in corrosion resistance has been achieved by applying a 30 nm aluminum oxide film using pulsed laser deposition (PLD) and implanting nitrogen ions into the near surface and the interface regions. In the case of Γ-TiAl alloys which exhibit poor oxidation resistance, despite their good mechanical properties at elevated temperatures, this limits their replacement of the nowadays used heavy components made of Ni-alloys. A significant improvement in high temperature oxidation resistance of TiAl alloys (up to 900 °C) has been achieved by implanting fluorine ions (1017 cm-2) at 30 keV into the alloy’s subsurface using PBII process. A TiAl alloy modified in this way has been shown to acquire a stable, adherent and highly protective alumina scale (Al2O3) under high temperature oxidation in air. The influence of the implanted N+ into CuZn and F+ into TiAl samples on the corrosion process has been investigated. For the sample evaluation, different characterization methods including scanning electron microscope with energy dispersive X-ray spectroscopy (SEM / EDX), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), Elastic recoil detection analysis (ERDA), and Dektak stylus profiling have been applied to determine the chemical composition, the elemental depth profiles, roughness and defect formation of the samples before and after exposure.

Keywords: Plasma based ion implantation (PBII); Pulsed laser deposition (PLD); oxidation protection; Ti-Al alloys; corrosion of reed organ pipes; Cu-Zn alloys

  • Poster
    IBMM 2014 - 19th International Conference on Ion Beam Modification of Materials, 14.-19.09.2014, Leuven, Belgium

Publ.-Id: 20897

Ultraschwere Ionen und deren Nutzung an HZDR-Beschleunigern.

Tajmar, M.; Pilz, W.; Bischoff, L.

Die Modifizierung von Festkörperoberflächen durch energiereiche polyatomare Ionen („Cluster­ionen“) ist ein neues For­schungsgebiet von hohem Interesse. Diese Projektile (mehrere100 atomare Masseeinheiten) deponieren eine extrem hohe Energie­dichte, da zur glei­chen Zeit am gleichen Ort mehrere Atome mit der Fest­körperoberfläche wechselwirken. Dadurch können z.B. Oberflächenmodifikationen durch nano­skaliges Oberflächenschmelzen erreicht aber auch Io­nen­erosion durch thermisch aktiviertes Sputtern untersucht werden. Bisherige aussichtsreiche Untersuchungen wurden an Fokussierten Ionenstrahlsystemen (FIB) mit Flüssigmetall-Ionenquellen (LMIS) durchgeführt, die auf Grund der kleinen Ionenströme nur Strukturen im µm- Bereich zuließen. Um diese Erfahrungen für großflächige Untersuchungen nutzbar zu machen, sind Clusterinjektionssysteme erforderlich, die etwa den 1000fachen Ionenstrom liefern und so für Ionenbeschleuniger mittlerer Energie interessant werden.
Dafür werden nun Flüssigmetallionenquellen, die mit neuartigen porö­sen Emittern arbeiten, eingesetzt (Spin-Off aus der Weltraumforschung zu Ionenantrieben), die unterschiedlichste Metall-Clusterionen (z.B. Bi3 mit über 600 atomaren Masseneinheiten) emittieren können und lange Lebensdauern garantieren. Diese Quellen werden mit einer speziell entwickelten Ionenoptik kombiniert, um einen maximalen Ionenstrom fokussiert bereitzustellen.
Derartige Clusterionen-Injektoren werdend zuerst am 500 kV Ionenbeschleuniger des Ionenstrahlzentrums des HZDR (IBC) in Betrieb genom­men, sind aber nachfolgend auch für andere Singletron-Maschinen oder als Ter­mi­nal­quelle an einem Tandem-Beschleuniger nutzbar.

Keywords: Cluster ions; surface modification; implanter source

  • Lecture (Conference)
    SNI 2014 Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten, 21.-23.09.2014, Bonn, Deutschland

Publ.-Id: 20896

Sputter yield of heavy monatomic and polyatomic ions: dependence on impact angle and substrate temperature

Bischoff, L.; Böttger, R.; Facsko, S.; Heinig, K.-H.; Pilz, W.

Focussed ion beam irradiation can be used to pattern surfaces at a scale of tens of nm by direct writing as well as by self-organization. Both patterning modes are controlled by ion beam erosion, where the sputter yield depends on the ion species, i.e. their mass, energy and angle of incidence. It depends also on the composition, temperature and surface roughness of the substrate.
Here, peculiarities of sputtering with heavy monatomic and very heavy polyatomic ions will be presented. Ion erosion of Si, SiO2, Ge and GaAs with Au_n and Bi_n ions from a liquid metal ion source has been investigated for different irradiation conditions.
The sputter yield per incoming atom is, compared with monatomic ions, considerably higher for polyatomic ions, even if the kinetic energy per atom is chosen to be equal. A newly developed sample holder allows irradiation at substrates temperatures up to 500°C and angles of ion incidence in the range from 0° to almost 90°, which will be used to elaborate sputter yield data of polyatomic ions in a range not yet explored so far. Due to the extremely high energy density deposition into the collision cascade volume by a very heavy polyatomic ion impact, an almost classical but tiny, transient melt pool can form, which adds to the collisional sputtering a loss of atoms by evaporation [1]. The latter contribution can be increased by substrate heating. Besides of the increased sputter yield, the repeated melting and resolidification of tiny pools leads to well-ordered surface pattern [2], which in turn influence the sputter yield.
[1] C. Anders, K.-H. Heinig and H. Urbassek, Phys. Rev. B 87 (2012) 198.
[2] L. Bischoff, K.-H. Heinig, B. Schmidt, S. Facsko and W. Pilz, Nucl. Instr. Meth. Phys. Res.
B 272 (2012) 198.

Keywords: Sputtering; heavy ions; impact angle; temperature

  • Lecture (Conference)
    19th International Conference on Ion Beam Modification of Materials (IBMM 2014), 14.-19.09.2014, Leuven, Belgien

Publ.-Id: 20895

Mikrobielle Laugung von Seltenen Erden aus Leuchtpulver

Mey, S.; Kutschke, S.; Pollmann, K.

Seltene Erden (SE) werden in fast allen neuen Technologien eingesetzt. Zudem hat China mit 94% Marktanteil (2011) [1] praktisch ein Monopol in der Produktion. Dennoch gibt es bis heute kein umweltfreundliches Recycling-Verfahren. Folglich steigt die Nachfrage nach neuen Recycling-Strategien um die Versorgung mit SE sicher zu stellen.
Jährlich fallen beim Recycling von Energiesparlampen und Leuchtstoffröhren in Deutschland rund 175 Tonnen Leuchtpulver als eigenständige Fraktion an [2, 3] Bei vollständigem Recycling können daraus bis zu 17,5 Tonnen SE-Oxide gewonnen werden, die direkt für den Herstellungsprozess neuer Lampen eingesetzt werden können [4]. Pro Leuchtkörper werden 2 bis 4g Leuchtpulver benötigt [5], sodass ca. 60 Millionen neue Lampen mit Recycling-SE hergestellt werden könnten.
In dieser Arbeit wurde deshalb die Rückgewinnung von SE aus Leuchtpulver mithilfe von biohydro¬metallurgischen Techniken untersucht. Aufgrund der elektrochemischen Rand¬bedingungen, erscheint die Laugung mit organischen Säuren und metallbindenden Proteinen erfolgversprechender, als Oxidations- oder Reduktions¬reaktionen [6, 7]. Auf Grundlage dessen wurden verschiedene hetero- und autotrophe aerobe Mikroorganismen als Rein- und Mischkultur ausgewählt. Darunter befinden sich sowohl die „klassischen“ Laugungs-Mikroorganismen Acidithiobacillus ferrooxidans und A. thiooxidans, als auch die organische Säuren bildendenden Corynebacterium collunae (Glutaminsäure) und die Hefe Yarrowia lipolytica (Zitronen¬säure), sowie der „Teepilz“ Kombucha. Alle Untersuchungen bezüglich der Eignung der Mikro-organismen SE aus Recycling-Leuchtpulver zu laugen wurden als Fed-Batch-Experimente durchgeführt.
Es konnte gezeigt werden, dass die Komplexierung der Seltenen Erden durch mikrobielle Metaboliten zu wesentlich höheren SE-Konzentrationen im Überstand führte als in den jeweiligen Kontrollen. Demzufolge ist es möglich mikrobielle Prozesse für die Rückgewinnung von SE zu nutzen. Sie stellen somit eine potentielle umwelt¬freundliche Alternative zu den derzeit angewendeten Methoden dar.

1. Roskill, Rare Earths & Yttrium: Market Outlook to 2015. 14th Edition. 2011, London.
2. Gallenkemper, B. and J. Breer, Analyse der Datenerhebung nach ElektroG über die Berichtsjahre 2009 und 2010 zur Vorbereitung der EU-Berichtspflicht 2012, in Fachgebiet III 1.6 (Produktverantwortung), D. Hörig (Editor) 2012, Umweltbundesamt: Dessau-Rosslau, Ahlen.
3. Lightcycle, Verwertbare Bestandteile von Altlampen, 2014, Riemann, Stephan.
4. Haucke, E., T. Huckenbeck, and R. Otto, Verfahren zur Rückgewinnung seltener Erden aus Leuchtstofflampen, Osram AG, Editor 2011: Germany.
5. Wojtalewicz-Kasprzak, A., Erzeugung von synthetischen Selten-Erd-Konzentratenaus Leuchtstoffabfällen. Technische Universität Clausthal, Fakultät für Energie- und Wirtschaftswissenschaften. 2007
6. Evans, C.H., Biochemistry of the Lanthanides. Biochemistry of the Elements, ed. E. Frieden. Vol. 1. 1990, New York, London: Plenum Press.
7. Morss, L.R., Yttrium, Lanthanum, and the Lanthanide Elements, in Standard Potentials in Aqueous Solution, A.J. Bard, R. Parsons, and J. Jordan, Editors. 1985, Marcel Dekker, Ink.: New York, Basel. p. 587-629.

Keywords: bioleaching; fluorescent phosphor; recycling; kombucha

  • Lecture (Conference)
    Aufbereitung und Recycling, 12.-13.11.2014, Freiberg, Deutschland

Publ.-Id: 20894

Microbial leaching of rare earth elements from fluorescent phosphor

Mey, S.; Kutschke, S.; Pollmann, K.

Rare Earth Elements (REE) are used in mostly all new technologies and until now, there is no environmentally friendly recycling-process for fluorescent phosphor. Furthermore, China has with a worldwide market share of 94 % (2011) [1] a virtual monopoly in the production of REE. Therefore, there is increasing demand for novel recycling technologies to secure the supply of REE. During recycling of energy-saving bulbs fluorescent phosphor containing rare earth elements (REE) is collected as a distinct fraction. In this study hydrometallurgical techniques were investigated to recycle REE from spent technological products. Due to electrochemical restrictions, leaching with organic acids and metal binding molecules is more promising, than oxidation or reduction reactions [2, 3]. On this basis, different hetero- and autotroph aerobe microorganism pure and mixed cultures are selected. Among them are “classical” leaching organisms like Acidithiobacillus ferrooxidans and A. thiooxidans, as well as the organic acid producing Corynebacterium collunae (glutamic acid), the yeast Yarrowia lipolytica (citric acid) and the tea fungus kombucha. The investigations regarding their ability to leach the REE from fluorescent phosphor, originating from recycling processes, were performed in fed-batch experiments.
It could be shown that complexation of the REE by organic acids produced by the microorganisms lead to considerable higher concentrations of REE in the supernatant than in the control. These results show that the usage of microbial processes for the recovery of REE is possible and could be an eco-friendly alternative to the currently employed methods.

1. Roskill, Rare Earths & Yttrium: Market Outlook to 2015. 14th Edition ed. 2011, London. 534.
2. Evans, C.H., Biochemistry of the Lanthanides. Biochemistry of the Elements, ed. E. Frieden. Vol. 1. 1990, New York, London: Plenum Press. 444.
3. Morss, L.R., Yttrium, Lanthanum, and the Lanthanide Elements, in Standard Potentials in Aqueous Solution, A.J. Bard, R. Parsons, and J. Jordan, Editors. 1985, Marcel Dekker, Ink.: New York, Basel. p. 587-629.

Keywords: Bioleaching; Fluorescent Phosphor; Recycling; Kombucha

  • Lecture (Conference)
    Microbiology and Infection 2014 4. Gemeinsamer Kongress von DGHM und VAAM, 05.-08.10.2014, Dresden, Deutschland

Publ.-Id: 20893

Microbial Leaching of Rare Earth Elements from fluorescent phosphor

Mey, S.; Kutschke, S.; Möckel, R.; Pollmann, K.

kein Abstract (war für die Summer School nicht erforderlich)

Keywords: Bioleaching; Fluorescent Phosphor; Recycling; Kombucha

  • Poster
    EREAN Summer School on Rare Earth Technology, 18.-21.08.2014, Leuven, Belgien

Publ.-Id: 20892

Paramagnetic moments in YBa2Cu3O7-δ nanocomposite films

Dias, F. T.; Vieira, V. N.; Silva, D. L.; Albino Aguiar, J.; Valadao, D. R. B.; Obradors, X.; Puig, T.; Wolff-Fabris, F.; Kampert, E.

We report on magnetization studies in YBa2Cu3O7-δ thin films with dispersed Ba2YTaO6 nanoparticles. The magnetization measurements were made using a superconducting quantum interference device (SQUID) and a vibrating sample magnetometer (VSM). Magnetic moments were measured as functions temperature using zero-field cooling (ZFC) and field-cooled (FC) prescriptions for magnetic fields up to 10 T applied parallel and perpendicular to the ab planes. A paramagnetic response related to the superconducting state was observed during the FC experiments. This effect, known as paramagnetic Meissner effect (PME), apparently increases when the magnetic field is increased. We discuss our PME results in terms of the strong pinning scenario modulated by Ba2YTaO6 nanoparticles dispersed into the superconducting matrix.

Publ.-Id: 20891

Commissioning of an improved superconducting RF photo injector at ELBE

Teichert, J.; Arnold, A.; Freitag, M.; Lu, P.; Michel, P.; Murcek, P.; Vennekate, H.; Xiang, R.; Kneisel, P.; Will, I.

In order to produce high-brightness electron beams in a superconducting RF photo injector, the most important point is to reach a high acceleration field in the cavity. For this reason two new 3.5-cell niobium cavities were fabricated, chemically treated and cleaned in collaboration with Jlab. The first of these two cavities was shipped to HZDR and assembled in new cryomodule. This new gun (SRF Gun II) was installed in the ELBE accelerator hall in May 2014 and replaces the previous SRF Gun I which was in operation since 2007. Beside the new cavity the ELBE SRF gun II differs from the previous gun by the integration of a superconducting solenoid in the cryomodule. After a first test run with a Cu cathode the gun will be operated with normal-conducting Cs2Te photo cathodes.

Keywords: superconducting RF photo enjector; electron source; SRf gun; photo cathode; niobium cavity

  • Poster
    36th International Free Electron Laser Conference FEL 2014, 25.-29.08.2014, Basel, Schweiz
  • Open Access Logo Contribution to proceedings
    36th International Free Electron Laser Conference FEL 2014, 25.-29.08.2014, Basel, Schweiz
    Proceedings of the 36th International Free Electron Laser Conference FEL 2014, Genf: Jacow

Publ.-Id: 20890

Inbetriebnahme der SRF-Gun II am ELBE-Beschleuniger

Teichert, J.; Arnold, A.; Lu, P.; Murcek, P.; Vennekate, H.; Xiang, R.; Kamps, T.; Will, I.; Kneisel, P.

Hochfrequenz-Photoelektronenquellen mit supraleitenden Resonatoren (SRF-Gun) besitzen das Potential Elektronenstrahlen exzellenter Qualität und mit hohem Strahlstrom zu liefern, die für zukünftige Lichtquellen benötigt werden. An der Strahlungsquelle ELBE ist eine solche Quelle seit 2007 in Betrieb. In den vergangen Jahren wurde eine verbesserte Version (ELBE SRF-Gun II) entwickelt. Im Mai 2014 wurde die SRF-Gun II am Beschleuniger installiert. Das Poster stellt diese Elektronenquelle vor und berichtet über die Inbetriebnahme.

Keywords: electron injector; SRF; superconducting RF accelerator; photo cathode

  • Poster
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten 2014, 21.-23.09.2014, Bonn, Germany

Publ.-Id: 20889

Monazite geochronology and geothermobarometry in polymetamorphic host rocks of volcanic-hosted massive sulphide mineralizations in the Mesoproterozoic Areachap Terrane, South Africa

Bachmann, K.; Schulz, B.; Bailie, R. H.; Gutzmer, J.

The Areachap Terrane represents the medium- to high-grade metamorphic and deformed remnants of a Mesoproterozoic (ca. 1.24–1.30 Ga) volcanic arc bound to the margin of the Archean Kaapvaal Craton in the east, and the polydeformed and metamorphosed Proterozoic Namaqua Province in the west. There has been protracted debate as to the exact nature, origin, age and tectonic evolution of this terrane, adjacent to an important Mesoproterozoic crustal suture between the Archean Kaapvaal Craton and the Namaqua Province, which developed during the ~1200-1000 Ma Namaquan Orogeny. The Areachap Terrane comprises highly deformed bimodal volcanic and volcano sedimentary successions that host a number of massive sulphide base metal orebodies. Samples from three of these orebodies at different locations were analysed to determine the age and P-T conditions of metamorphism along the Areachap Terrane. Metamorphic ages were determined by electron microprobe chemical dating of monazite. Garnet- and amphibole-bearing mineral assemblages were used for geothermobarometry. At the Areachap Mine, located in the northern sector of the Areachap Terrane, monazite geochronology yields evidence for two populations of Th-U-Pb-ages at 1432±30 Ma – a possible protolith age – and a metamorphic age of 1153±21 Ma. Kantienpan and Copperton, representing the central and southern sector of the Areachap Terrane respectively, yield monazite ages for a younger metamorphic event with U-Th-Pb-ages of 1108±19 Ma and 1104±17 Ma, respectively. Geothermobarometric data give a differentiated view on the metamorphic evolution of the Areachap Terrane. An arc consistent clockwise P-T evolution path and upper amphibolite-facies peak metamorphic conditions are consistent at the three locations. The Areachap site shows a short prograde development with 9.0 kbar maximum pressure at circa 700°C maximum temperature and a subsequent retrograde metamorphism. At Kantienpan, on the other hand, maximum metamorphic conditions of 6.5 kbar at 600 - 650°C are obtained, whereas at Copperton retrograde metamorphism is most distinct with maximum pressures around 8 kbar at circa 650°C. These locally differentiated metamorphic and geochronological evolution paths in the Areachap Terrane are closely related to the Mesoproterozoic events in the adjacent Namaqua Province.

Keywords: garnet gneiss; monazite; amphibolites; polymetamorphism; Areachap Terrane; Namaquan Orogeny

Publ.-Id: 20888

Deutsche Forschungskompetenz im europäischen Rahmen im Rohstoffbereich

Köpf, H.; Gutzmer, J.; Klossek, A.

Eine der Grundbedingungen für den wirtschaftlichen Erfolg des produzierenden Sektors der Industrie ist die Verfügbarkeit von mineralischen und metallischen Rohstoffen.
Rohstoffe müssen nach den Erfordernissen der Industrie in adäquaten Mengen und zu wirtschaftlich vertretbaren Preisen verfügbar sein. Dies wurde in den letzten Jahren durch Verwerfungen und Preisvolatilitäten auf den globalen Rohstoffmärkten – gefolgt von zum Teil sehr heftigen Reaktionen aus der betroffenen Industrie – eindringlich unterstrichen. Die Versorgung der Industrie mit mineralischen und metallischen Rohstoffen ist vollständig globalisiert, vielstufig und in vielen Fällen für den Endverbraucher intransparent. Dies gilt insbesondere für die Märkte der so genannten Hochtechnologiemetalle, die in der Regel ein sehr geringes globales Volumen erreichen, aber zeitgleich hochspezialisiert und vielgliedrig sind.
Als dicht bevölkerter und hochindustrialisierter Kontinent ist Europa weitgehend abhängig von Rohstoffimporten. Diese Situation wird sich auch in absehbarer Zukunft nicht wesentlich verändern. Insbesondere gilt dies für die Bundesrepublik Deutschland. Als größte europäische Volkswirtschaft hat die Bundesrepublik Deutschland eine stark ausgeprägte industrielle Basis. Dies zieht einen hohen Rohstoffbedarf nach sich, welcher im Falle von Deutschland zusammentrifft mit einer weitgehend erodierten heimischen Metallerzbergbau- und Hüttenindustrie, sowie einer fast vollständig fehlenden Beteiligung deutscher Firmen an der globalen Rohstoffindustrie. Tatsächlich geriet die Forschung und Entwicklung zur Rohstoffversorgung, d.h. der Exploration, der Gewinnung und der Aufbereitung von Rohstoffen, seit Ende der 1980er Jahre zunehmend aus dem wirtschafts- wissenschaftspolitischen Fokus. Dies führte dazu, dass die Forschung und Entwicklung im akademischen Bereich und das Engagement von deutschen Industrieunternehmen in den relevanten Forschungsfeldern nahezu zum Erliegen kam [4].
Auf der anderen Seite hat die Bundesrepublik Deutschland den Anspruch, ein weltweit führender Hochtechnologiestandort zu sein – und verfolgt das Ziel, diese Position zu halten bzw. auszubauen. In der Tat gibt es eine erhebliche Anzahl deutscher Firmen, die in ihren Marktnischen im Anbietermarkt für Technologien zur Rohstoffgewinnung und -verarbeitung (Bergbau, Aufbereitung, Metallurgie, Recycling) Marktführer sind. Dies gilt insbesondere für den Maschinen- und Anlagenbau. Weiterhin gibt es eine kleine Anzahl von Universitäten und außeruniversitären Einrichtungen in Deutschland, die einen signifikanten Beitrag zu Ausbildung und Innovation für die globale Rohstoffindustrie leisten. Nur durch eine geeignete enge Verzahnung der relevanten Kompetenzen in Industrie und Forschung erscheint es möglich, den Beitrag Deutschlands zur effizienten und umweltgerechten Produktion mineralischer und metallischer Rohstoffe rasch signifikant zu erhöhen. Gleichzeitig wird auch eine engere Vernetzung auf europäischer Ebene angestrebt, wobei Deutschland mit seiner hohen Abhängigkeit von Rohstoffimporten auch hier besondere Verantwortung übernehmen muss.

  • Contribution to proceedings
    Berliner Recycling- und Rohstoffkonferenz, 24.-25.03.2014, Berlin, Germany
    Recycling und Rohstoffe, Berlin: TK Verlag

Publ.-Id: 20887

Brilliant and efficient optical free-electron lasers with Traveling-Wave Thomson-Scattering

Steiniger, K.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Schramm, U.; Bussmann, M.

We demonstrate that optical free-electron lasers (OFELs) realized with Traveling-Wave Thomson-Scattering (TWTS) are by orders of magnitude more efficient and brilliant than corresponding OFELs utilizing head-on Thomson scattering geometries. In addition, we emphasize that TWTS OFELs as opposed to standard head-on Thomson scattering geometries scale favorably with regard to space-charge effects degrading emittance, energy losses through photon recoil and transverse coherence of the resulting FEL beam. The presented TWTS OFELs scenarios are assumed to be driven either by conventional, rf-accelerated electrons or by currently available laser wakefield-accelerated electrons featuring energy spreads at the one percent level.

Keywords: Traveling Wave; Thomson scattering; optical FEL; LWFA; EUV; X-ray

  • Open Access Logo Contribution to proceedings
    16th Advanced Accelerator Concepts Workshop (AAC 2014), 13.07.-18.09.2014, San Jose, CA, USA
    AAC 2014 Proceedings: AIP Publishing, 978-0-7354-1439-6
    DOI: 10.1063/1.4965673

Publ.-Id: 20886

Optical Free-Electron Lasers with Traveling-Wave Thomson-Scattering

Steiniger, K.; Bussmann, M.; Pausch, R.; Cowan, T.; Irman, A.; Jochmann, A.; Sauerbrey, R.; Schramm, U.; Debus, A.

We present a fully analytic model of an all-optical free electron laser (OFEL) undulator based on the Traveling-Wave Thomson-Scattering (TWTS) scheme. The TWTS undulator provides for sub-mm undulator wavelengths, does not require any material or plasma to generate or contain the undulator field and allows for sub-meter saturation lengths.
Starting from a fully analytic description of the three-dimensional TWTS field we derive the OFEL pendulum equation for electrons in the TWTS field and discuss the constraints on laser and electron pulse parameters that have to be fulfilled for OFEL operation. We conclude in applying the TWTS OFEL to the realization of compact free electron laser sources at 13.5 nm and 0.2 nm using laser and electron sources in reach of present day technologies.

Keywords: FEL; laser undulator; X-ray; EUV; Traveling-Wave; Thomson scattering; LWFA

Publ.-Id: 20885

All-optical free-electron lasers with Traveling-Wave Thomson-Scattering

Steiniger, K.; Debus, A.; Irman, A.; Jochmann, A.; Pausch, R.; Schramm, U.; Cowan, T.; Bussmann, M.

In Travelling-Wave Thomson Scattering (TWTS) the pulse front of a high-power, short-pulse laser is tilted and the dispersion of the pulse is controlled in such a way that electrons can interact over a long distance with a quasi-monochromatic electromagnetic wave. We present a complete three dimensional analytic time-dependent description of the TWTS field and use this description to derive an analytic FEL equation that shows that TWTS indeed provides for an all-optical FEL. We further derive conditions for optimum operation of the TWTS FEL, showing that EUV and XUV FEL sources are in reach using Petawatt lasers and conventional few-hundred MeV electron sources. Future laser-wakefield accelerators could potentially drive all-optical TWTS-FELs in the X-ray and beyond. TWTS itself is optimum to provide full flexibility in terms of the wavelength and bandwidth of the scattered radiation, allowing for application-optimized, highly-brilliant Thomson Scattering sources for a broad range of wavelengths from the EUV to the gamma ray spectral region.

Keywords: Traveling-Wave; Thomson-Scattering; FEL; LWFA; X-ray

  • Poster
    5th International Particle Accelerator Conference IPAC’14, 15.06.-20.09.2014, Dresden, Germany
  • Open Access Logo Contribution to proceedings
    Proceedings of the 5th International Particle Accelerator Conference IPAC14, 15.06.-20.09.2014, Dresden, Germany
    IPAC2014 - Proceedings, 978-3-95450-132-8


Publ.-Id: 20884

Morphology analysis of sponge-like Si-SiO2 nanocomposites using energy-filtered electron tomography and electron holographic tomography

Hübner, R.; Wolf, D.; Friedrich, D.; Liedke, B.; Schmidt, B.; Heinig, K.-H.

Due to the possibility of band-gap engineering by quantum confinement, Si nanosponge structures embedded in SiO2 formed by spinodal decomposition of metastable silicon-rich silicon oxide are promising absorbers for 3rd generation solar cells. High-temperature annealing of thermodynamically metastable, silicon-rich oxide SiOx with x < 2 leads to phase separation of elemental Si from stoichiometric SiO2. While this phase separation results in disconnected Si nanoclusters for 1.2 ≤ x < 2, percolated Si nanostructures with a sponge-like morphology are observed for x < 1.2 [1].
To visualize the sponge-like morphology in SiOx films for x around 1 after thermal treatment, energy-filtered transmission electron microscopy (EFTEM) imaging, EFTEM tomography, and electron holographic tomography (EHT) [2] were carried out. To this end, 200 nm thick SiOx layers were prepared on p type (100) Si wafers by magnetron sputtering in Ar plasma from two simultaneously operating Si and SiO2 targets. During subsequent annealing, samples were heated up to 1150 °C. Sponge-like nanostructures were investigated by EFTEM imaging using an image-corrected FEI Titan 80-300 microscope equipped with a GIF 863. For EFTEM tomography, a tilt series between ±70° was acquired in a Philips CM200 FEG microscope with a GIF 678, and for EHT, a tilt series from -74° to +79° was recorded in an image-corrected FEI Tecnai TF20 microscope. Tomographic reconstruction of the Si 3D morphology was performed with the Weighted Simultaneous Iterative Reconstruction Technique [3].
Valence-band plasmon energy-loss imaging is an appropriate approach to visualize the Si morphology in phase-separated Si-SiO2 nanocomposites [4]. As an example, Figure 1 shows the Si plasmon EFTEM images (Eloss = 17 eV) of a SiOx≈1 layer decomposed into Si and SiO2 after thermal treatment at 1100 °C for 3 min (left) and 3 h (right). As indicated by the selected area electron diffraction patterns, coarsening of the Si nanostructure is accompanied by Si crystallite growth. Although Si plasmon EFTEM imaging can show the Si phase distribution in a planar projection, it does not provide 3D information. Therefore, EFTEM tomography was applied, revealing that a spinodal sponge-like morphology of Si is only partially visible in a volume of ca. (30 nm)³ (Figure 2). However, in a larger volume of ca. (140 nm)³ - as demonstrated by applying EHT on a needle-shaped specimen prepared by FIB - both isolated nanoparticles and percolated Si nanostructures with a sponge-like morphology are observed (Figure 3).

[1] T. Müller et al., Appl Phys Lett 85 (2004) 12.
[2] D. Wolf et al., Curr Opin Solid St M 17 (2013) 126.
[3] D. Wolf et al., Ultramicroscopy 136 (2014) 15.
[4] D. Friedrich et al., Appl Phys Lett 103 (2013) 131911.

The authors kindly acknowledge TEM sample preparation by Annette Kunz and Martina Missbach.

Keywords: silicon-rich silicon oxide; EFTEM imaging; EFTEM tomography; electron holographic tomography

  • Poster
    18th International Microscopy Congress, 07.-12.09.2014, Prague, Czech Republic
  • Contribution to proceedings
    18th International Microscopy Congress, 07.-12.09.2014, Prague, Czech Republic

Publ.-Id: 20883

Contributions of Cu-rich clusters, dislocation loops and nanovoids to the irradiation-induced hardening of Cu-bearing low-Ni reactor pressure vessel steels

Bergner, F.; Gillemot, F.; Hernández-Mayoral, M.; Serrano, M.; Török, G.; Ulbricht, A.; Altstadt, E.

Dislocation loops, nanovoids and Cu-rich clusters (CRPs) are known to represent obstacles for dislocation glide in neutron-irradiated reactor pressure vessel (RPV) steels, but a consistent experimental determination of the respective obstacle strengths is still missing. A set of Cu-bearing low-Ni RPV steels and model alloys was characterized by means of SANS and TEM in order to specify mean size and number density of loops, nanovoids and CRPs. The obstacle strengths of these families were estimated by solving an over-determined set of linear equations. We have found that nanovoids are stronger than loops and loops are stronger than CRPs. Nevertheless, CRPs contribute most to irradiation hardening because of their high number density. Nanovoids were only observed for neutron fluences beyond typical end-of-life conditions of RPVs. The estimates of the obstacle strength are critically compared with reported literature data.

Keywords: pressure vessel steels; electron microscopy; neutron scattering; hardening; precipitation; dislocations

Publ.-Id: 20882

Biologische Bausteine für Materialien der Zukunft

Kostudis, S.; Weinert, U.; Raff, J.

Der Vortrag stellt das Helmholtz-Zentrum Dresden-Rossendorf sowie das Helmholtz-Institut Freiberg für Ressourcentechnologie vor und gibt Einblick in Arbeiten der Arbeitsgruppe Biotechnologie. Mithilfe mikrobiologischer Organismen, Bausteine und Prozesse können neue umweltfreundliche und nachhaltige industrielle Anwendungen wie Filter und Sensoren entwickelt werden.

  • Lecture (others)
    Vortragsreihe "Werte-Wege-Welt", 13.12.2013, Bautzen, Deutschland

Publ.-Id: 20880

Spectral and geochemical characterization of onshore hydrocarbon seep-induced alteration in the Dezful Embayment, SW Iran

Salati, S.; van Ruitenbeek, F.; de Smeth, B.; van der Meer, F.

The presence of hydrocarbon seeps at the surface is indirect evidence of the presence of mature source rocks within a geologi- cal system at depth. Chemical changes in the environment of sur- face rocks caused by hydrocarbon seeps cause mineralogical alterations. To determine the nature of the alterations and the influences of lithology and type of seep, rock samples were col- lected from altered and unaltered evaporite and marly limestone formations in the Dezful embayment, southwest Iran. Reflectance spectroscopy, bulk rock/wet chemical analyses, and sulfur, carbon, and oxygen isotopic analyses were used to delin- eate surficial alterations and relate alterations to hydrocarbons seeping from underlying reservoirs. In addition, the boosted regression trees (BRT) method was used to predict the presence of alterations from spectral indices. Comparisons of geochemical data and spectral data of altered evaporites and altered marly lime- stones showed that the minerals within alteration facies have dis- tinctive spectral, chemical, and isotopic signatures. Gas-induced alterations were characterized by the formation of gypsum and native sulfur and depletion in 34S. The released H2S in natural gas reacted with gypsum in the evaporite sediments and calcite in the marly limestone formations, which led to precipitation of secondary gypsum and native sulfur. Oil-induced alterations were characterized by formation of secondary calcite and depletion in 13C. The oxidation of seeping oil and reactions between this oil and host rocks caused precipitation of secondary calcite within both formations. The combination of fieldwork data and spectral-geochemical data showed a connection exists between surficial alterations and underlying petroleum reservoirs, which can be used in exploration campaigns.

Keywords: Hydrocarbon seeps; Alterations; Spectroscopy; Geochemistry; Isotopic analysis; Boosted Regression Trees (BRT)

Publ.-Id: 20879

Detection of Alteration Induced by Onshore Gas Seeps from ASTER and WorldView-2 Data

Salati, S.; van Ruitenbeek, F.; van der Meer, F.; Naimi, B.

Hydrocarbon seeps cause chemical and mineralogical changes at the surface, which can be detected by remote sensing. This paper aims at the detection of mineral alteration induced by gas seeps in a marly limestone formation, SW Iran. For this purpose, the multispectral Advance Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the high spatial resolution WorldView-2 (WV-2) data were utilized for mapping surficial rock alteration. In addition, the potential of Visible Near Infrared (VNIR) bands of the WV-2 and its high spatial resolution for mapping alterations was determined. Band ratioing, principal component analysis (PCA), data fusion and the boosted regression trees (BRT) were applied to enhance and classify the altered and unaltered marly limestone formation. The alteration zones were identified and mapped by remote sensing analyses. Integrating the WV-2 into the ASTER data improved the spatial accuracy of the BRT classifications. The results showed that the BRT classification of the multiple band imagery (created from ASTER and WV-2) using regions of interest (ROIs) around field data provides the best discrimination between altered and unaltered areas. It is suggested that the WV-2 dataset can provide a potential tool along higher spectral resolution data for mapping alteration minerals related to hydrocarbon seeps in arid and semi-arid areas.

Keywords: hydrocarbon seep; alteration mineral; ASTER; WorldView-2; boosted regression trees (BRT) classification

Publ.-Id: 20878

Near surface silicide formation after off-normal Fe-implantation of Si(001) surfaces

Khanbabaee, B.; Lützenkirchen-Hecht, D.; Hübner, R.; Grenzer, J.; Facsko, S.; Pietsch, U.

We report on formation of non-crystalline Fe-silicides of various stoichiometries below the amorphized surface of crystalline Si(001) after irradiation with 5 keV Fe+ ions under off-normal incidence. We examined samples prepared with ion fluences of 0.1 × 1017 and 5 × 1017 ions cm−2 exhibiting a flat and patterned surface morphology, respectively. Whereas the iron silicides are found across the whole surface of the flat sample, they are concentrated at the top of ridges at the rippled surface. A depth resolved analysis of the chemical states of Si and Fe atoms in the near surface region was performed by combining X-ray photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) using synchrotron radiation. The chemical shift and the line shape of the Si 2p core levels and valence bands were measured and associated with the formation of silicide bonds of different stoichiometric composition changing from an Fe-rich silicides (Fe3Si) close to the surface into a Si-rich silicide (FeSi2) towards the inner interface to the Si(001) substrate. This finding is supported by XAS analysis at the Fe K-edge which shows changes of the chemical environment and the near order atomic coordination of the Fe atoms in the region close to surface. Because a similar Fe depth profile has been found for samples co-sputtered with Fe during Kr+ ion irradiation, our results suggest the importance of chemically bonded Fe in the surface region for the process of ripple formation.

Publ.-Id: 20877

Biologische Bausteine für Materialien der Zukunft

Kostudis, S.; Weinert, U.; Raff, J.

Der Vortrag stellt das Helmholtz-Zentrum Dresden-Rossendorf sowie das Helmholtz-Institut Freiberg für Ressourcentechnologie vor und gibt Einblick in Arbeiten der Arbeitsgruppe Biotechnologie. Mithilfe mikrobiologischer Organismen, Bausteine und Prozesse können neue umweltfreundliche und nachhaltige industrielle Anwendungen wie Filter und Sensoren entwickelt werden.

  • Lecture (others)
    Tag der Wissenschaften 2013, 13.06.2013, Radebeul, Deutschland

Publ.-Id: 20876

Bioleaching of copper from Kupferschiefer by organic acid and heterotrophic bacteria

Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.

Increasing prices of metals and strategic issues such as independent resource access force reconsideration of European Kupferschiefer deposits in Germany. For the mode of exploitation is cost-intensive and the copper content does hardly exceed four percent the processing has to be all the more efficient. This advantage of efficiency as well as ecological friendliness is brought along by biomining – the usage of biological components for metal extraction. For Kupferschiefer (Polkowice, Poland) bears carbonates up to 10 % commonly used bioleaching with acidophilic microorganisms is an issue. Therefore heterotrophic microbes and their metabolites were investigated. Results show copper yields up to nearly 48 % in undirected proof-of-principle batches.

Keywords: sulphide ores; bacteria; bioleaching; liberation analysis; environmental

  • Lecture (Conference)
    Biohydrometallurgy '14, 09.-11.06.2014, Falmouth, United Kingdom

Publ.-Id: 20875

Visualization and quantitative analysis of dispersive mixing by a helical static mixer in upward co-current gas-liquid flow

Rabha, S.; Schubert, M.; Grugel, F.; Banowski, M.; Hampel, U.

Growing interest towards process intensification in chemical industries over the last decade promotes static mixers as an attractive contactor alternative to the bubble column and mechanically stirred vessels. In the present work, the dispersion provided by a helical static mixer in a vertical pipe at turbulent gas-liquid flow conditions was studied using ultrafast electron beam X-ray tomography. Dispersive mixing was quantified upstream and downstream of three, six and nine helical static mixer elements in terms of bubble size distribution and gas holdup. Bubble breakup within the mixer elements was visualized and quantified via bubble size distribution and interfacial area density. Moreover, the power dissipation per unit mass of liquid was calculated for different number of static mixer elements and slip. The results provide a new insight into the development of the gas phase distribution within helical static mixers and a sound basis for design improvement, optimization of flow conditions and CFD validation.

Keywords: Helical static mixer; Ultrafast electron beam X-ray tomography; Gas-liquid flows; Specific interfacial area

Publ.-Id: 20874

PGE geochemistry of the Fengshan porphyry–skarn Cu–Mo deposit, Hubei Province, Eastern China

Wang, M.; Gutzmer, J.; Michalak, P. P.; Guo, X.; Xiao, F.; Wang, W.; Liu, K.

The Fengshan Cu–Mo deposit is located in the western part of the Jiurui Cu–Au–Mo district in the Late Mesozoic Middle–Lower Yangtze River Metallogenic Belt (YRMB), Eastern China. The mineralization is spatially associated with the Fengshan granodiorite porphyry stock (149–138 Ma), where two types of ore bodies (porphyry, skarn) occur. The Fengshan deposit is located on the Yangtze Craton, i.e., in an intracontinental extensional environment, a geological setting not considered by previous studies of PGE abundance and distribution in porphyry systems. For the present investigation the PGE geochemistry of fourteen samples of the granodiorite, ore and flotation concentrates were determined by ICP-MS, after preconcentration by the Lead Fire Assay technique from large (30 g) samples. A maximum of 32 ppb Pd and 81.2 ppb Pt is reported for the molybdenum flotation concentrate. Cu, Au, Pt, Pd contents from flotation concentrate samples are almost 1 to 2 orders of magnitude higher than those reported for ore samples; this is especially true for the Pt content. Covariant diagrams of Cu and Mo with noble metals (Au, Ag, Pt and Pd) reveal weak correlation between Cu vs. Au, Ag, and Mo vs. Pt. Also, Au shows a slightly positive relationship with Pt and Pd.

It is apparent that Pd and Pt contents of flotation concentrate from the Fengshan deposit are considerably lower than those reported for porphyry deposits in an island arc setting. However, Au and Ag appear to be elevated in the Fengshan deposit. The intrusion derived from an enriched mantle source, high oxygen fugacity (fO2), and liberation of mantle sulfates during partial melting, are the first steps for PGE enrichment in porphyry Cu deposits. However, the Fengshan granodiorite was most likely generated by partial melting of enriched mantle that was previously metasomatized by slab melts related to an ancient subduction system. Au, Pt, and Pd in potassic alteration zones and/or endocontact zones are transported as an aqueous chloride complex in high temperature, hypersaline fluid. In contrast, Au, Pt and Pd would be transported by bisulfide complex in low temperature, intermediate salinity fluid in phyllic alteration zones and/or exocontact marble. That is distinctly different from the porphyry Cu deposits in an island arc environment, where intrusion derived directly from slab melting and Pd and Pt are transported only as chloride complexes.

Keywords: Platinum group elements; Porphyry–skarn Cu–Mo deposit; Fengshan; Eastern China

Publ.-Id: 20873

New lithogeochemical and mineralogical exploration of Li-Sn greisen mineralisation in old mining adits of the Zinnwald deposit, Germany

Neßler, J.; Seifert, T.; Gutzmer, J.; Müller, A.; Henker, J.; Kühn, K.

The polymetallic Zinnwald-Cínovec deposit is represented by greisen-type mineralisation hosted within the apical portion of a small granite intrusion. Similar to other granitic stocks with Sn-W mineralisation in the Erzgebirge, the Zinnwald granite intruded during the post-collisional stage of the late-Variscan (Permo-Carboniferous) magmatic evolution. These intrusions are characterised by the prominent enrichment of incompatible elements (F, Li, Rb, Cs, Sn, Nb and Ta) and the depletion of P2O5. The deposit is located in the eastern part of the Erzgebirge region, Germany and straddles the border between Germany and the Czech Republic. It is characterised by flat dipping, sheet-like greisen ore bodies (up to 40 m in thickness) and veins (up to 1 m in thickness) located in the apical part and along the quaquaversal dipping edges of the granite stock. The greisen bodies predominantly consist of quartz, Li-Rb-Cs-bearing mica (named zinnwaldite), topaz, fluorite and accessory kaolinite and cassiterite. Historically mined for its cassiterite and wolframite ores since the 16th and 19th century, respectively, the deposit still provides access to a wide spread system of drifts and adits. Selected parts of the underground mine are now presented by the visitor's mine "Vereinigt Zwitterfeld zu Zinnwald". These local conditions are favourable for the re-examination of the exhibited greisen mineralisation. Within the framework of the ongoing Li and Sn exploration project of the SolarWorld Solicium GmbH in the German part of the deposit, an underground sampling campaign has been conducted, incorporating a series of 88 channel samples gained at two different levels (Tiefer Bünau adit = 750 m a.s.l.; Tiefe Hilfe Gottes adit = 720 m a.s.l.). Equally spaced channels of 2 m intervals and approximate dimensions of 180 x 5 x 2.5 cm have been created on pre-selected and detailed mapped walls of two different adits within the mine. The sample material has been gained for mineralogical and geochemical investigation using optical light microscopy and ICP-MS. The herein presented work aims to provide information about the horizontal distribution of selected elements (Li, Rb, Cs, Sn, W, Sc, Nb, Ta and Zn) and to assess historic data on mineralogy and geochemistry. Furthermore, the question of a sufficient sampling distance is tried to answer with the help of statistical exclusion principles. Investigations on the chemical composition of the greisen ore yielded homogeneous concentration of elements contained in micas (Li, Rb, Cs, Zn and Sc!) with Li concentration of about 0.3 wt. %, whereas concentrations of Sn and W (but also Nb and Ta) are more heterogenic distributed with some high-grade values connected to local mica-nests, veins and/or joint planes. Moreover, results of investigated elements from this campaign are in good agreement with the overall geochemical pattern obtained by past investigations. Compared with geochemical whole rock data from drill core samples of surrounding drill holes, the mean Li grades of channel samples are consistent for different areas within the mine. In case of Li, the application of statistical exclusion principles can provide a good estimation of the sufficient maximum sampling distance (about 5 m).

  • Open Access Logo Contribution to proceedings
    EGU General Assembly, 27.04.-02.05.2014, Vienna, Austria
    Geophysical Research Abstracts 16(2014), Vienna: Copernicus

Publ.-Id: 20872

Provenance of the Neoproterozoic rocks of the Gifberg Group (Western South Africa)

van Staden, A.; Zimmermann, U.; Gutzmer, J.; Germs, G. J. B.

New petrographic and lithogeochemical data are presented for siliciclastic units of the Gifberg Group (western South Africa), a succession rarely studied in the past. The main detrital source for the oldest succession of the Gifberg Group, the Karoetjes Kop Formation, has been identified as sourced by local metamorphic rocks with a felsic geochemical composition. Nearly unweathered detritus (Chemical index of alteration: 50 to 60; K/Cs >>5000) occurs in the metadiamictite of this formation and is interpreted as palaeovalley infill, deposited only a short distance from its sources. The provenance signature of the overlying Aties Formation indicates significant mafic and/or intermediate sources. Possible sources are rocks of the Bushmanland Group and an unknown unmetamorphosed mafic to intermediate rock succession, which might have been exposed during the deposition of the Aties Formation. The overlying Bloupoort Formation is characterised by a geochemically homogenous metadiamictite (Swartleikrans Bed) with only slightly weathered detritus (K/Cs >10000) and overlying mature silica-rich metarenites and metaconglomerates. It is proposed that the Gifberg basin formed as a small-scale rift basin and then widened through time with subsequent longer sedimentary transport of the detritus which have caused the higher compositional maturity. The predominance of detrital input from local sources in the Karoetjes Kop Formation hinders correlation based on its mineralogical and geochemical content alone. A glacial origin for the Swartleikrans Bed was proposed previously based on the occurrence of possible dropstones. Certain criteria for a glacial depositional environment as outlined by Arnaud and Etienne (2011) were met in our study and include poor sorting, rapid lateral facies changes, crude stratification, variable thicknesses, compositional immaturity, and a gradational contact plus a chaotic texture with large boulders. While these observations point to a ‘rainout’ deposit, there is still a lack of evidence for glacial transport on grain surfaces or in the form of faceted clasts and pebbles.

Publ.-Id: 20871

P1309 - Magnetooptik mit strukturierten unmagnetischen Metallen

Schmidt, H.; Kaspar, T.; Schmidt, O. G.; Brunner, R.

Die Erfindung beschreibt die Auslegung einer Anordnung eines regelmäßig strukturierten unmagnetischen Einzel- oder Mehrschichtsystems mit mehreren Basiselementen in der Einheitszellen, bei dem für eine vorgegebene Wellenlänge der einfallenden elektromagnetischen Welle eine bestimmte Polarisation der reflektierten oder transmittierten Welle in Abhängigkeit von einem von außen angelegten Magnetfeld erreicht wird.

  • Patent
    DE102013203761 - Offenlegung 11.09.2014, Nachanmeldung: WO, DE

Publ.-Id: 20870

Magnetic Characterization and Electrical Field-Induced Switching of Magnetite Thin Films Synthesized by Atomic Layer Deposition and Subsequent Thermal Reduction

Zierold, R.; Le Lam, C.; Dendooven, J.; Gooth, J.; Böhnert, T.; Sergelius, P.; Munnik, F.; Montero Moreno, J. M.; Görlitz, D.; Detavernier, C.; Nielsch, K.

Magnetite (Fe3O4) of high quality was prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. The reduction process in hydrogen atmosphere was investigated by in situ X-ray diffraction studies as a function of temperature. A complete reduction to Fe3O4 was confirmed within a narrow temperature window during the thermal treatment. Magnetic characterization of magnetite thin films as a function of temperature, applied magnetic field, and magnetic field orientation were performed. The highly stoichiometry- and impurity-sensitive Verwey transition was observed in magnetic and electrical measurements. Moreover, the isotropic point at which the magnetocrystalline anisotropy of magnetite vanishes was unveiled. Both findings prove, first, the formation of the magnetite phase against the undesired maghemite and, second, the quality of the ALD thin films to be comparable with samples grown by molecular beam epitaxy. The magnetic easy- and hard-axis could be found to be in-plane and out-of-plane, respectively. Consistent with angular-dependent studies of the coercive field, additionally performed first-order reversal curve measurements revealed a complex micromagnetic structure with different magnetization reversal path for both configurations. Finally, electric field-induced resistive switching was studied in detail being in perfect agreement with results of single-crystalline samples. The presented data and its analysis support the assumption of previous works of the magnetization reversal in magnetite nanotubes, suggest improvement for future magnetization studies of nanostructures by exploiting the isotropic point, and might open new paths for low-cost resistive switching devices.

Publ.-Id: 20869

Kupferlaugung aus Kupferschiefer mit organischer Säure

Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.; Gutzmer, J.

Die steigende Nachfrage an Basismetallen wie Kupfer, aber auch strategischen Elementen wie Gallium oder Molybdän, steht einer verringerten Qualität und erhöhter Komplexität vorhandener Erzressourcen gegenüber. Biotechnologische Ansätze wie die Biolaugung können auch mit diesem Ausgangsmaterial effiziente Abbauprozesse liefern. So konnten mithilfe von Schimmelpilzen und organischen Säuren vielversprechende Ergebnisse in der Kupferlaugung aus Kupferschiefer (Polkovice/Lubin, Polen) erzielt werden. Der europäische Kupferschiefer ist eine potente lokale Ressource und zeichnet sich durch hohe Anteile organischer Verbindungen und Carbonate, eine komplexe Matrix und maximalen Kupferkonzentrationen von ca. 5 % aus. Insbesondere der hohe Carbonatgehalt von ca. 18 % bringt die herkömmlichen Biolaugungsverfahren mit säureliebenden Bakterien an ihre Grenzen.
Der Beitrag zeigt die Auswirkungen der Säureeinwirkung auf die Mineralogie des Kupferschiefers. Vornehmlich wird Chalkosin gelaugt, aber auch Kupfereisensulfide wie Bornit und Chalkopyrit. Die Gesamtkupferausbeute liegt bei durchschnittlich 44 % in einfachen Ansätzen in Schüttelkolben.

  • Lecture (Conference)
    Aufbereitung und Recycling 2014, 12.-13.11.2014, Freiberg, Deutschland

Publ.-Id: 20868

Interfacial Reaction of SnII on Mackinawite (FeS)

Dulnee, S.; Scheinost, A. C.

The interaction of SnII with metastable, highly reactive mackinawite is a complex process due to transient changes of the mackinawite surface in the sorption process. In this work, we show that tin redox state and local structure as investigated by Sn-K X-ray absorption spectroscopy (XAS) change with pH. We observe at pH <7 that SnII forms two short (2.38 Å) Sn-S bonds, the S atoms being part of the S-terminated surface of mackinawite. Two longer Sn-S bonds of 2.59 Å point most likely towards the solution phase, completing the tetragonal SnS4 innersphere sorption complex, while precipitation of SnS or formation of a solid solution with mackinawite could be excluded. At pH > 9, SnII is completely oxidized by an FeII/FeIII (hydr)oxide, most likely green rust, forming on the surface of mackinawite. Six O atoms at 2.04 Å and 6 Fe atoms at 3.29 Å demonstrate a structural incorporation by green rust, where SnIV substitutes for Fe in the crystal structure. The transition between SnII and SnIV and between sulfur and oxygen coordination takes place between pH 7 and 8, in accordance with the transition from the mackinawite stability field to more oxidized Fe-bearing minerals. The uptake processes of SnII by mackinawite are largely in line with the uptake processes of divalent cations of other soft Lewis-acid metals like Cd, Hg and Pb.

Keywords: mackinawite; nuclear waste; Sn; EXAFS; redox

Publ.-Id: 20867

Raman spectroscopy - casting (laser) light on microbe - mineral interactions

Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.

Highly efficient and sustainable mining strategies gain importance due to the fact that available resources of base metals like copper but strategic elements such as gallium and molybdenum as well face a steadily decreasing grade. This issue is enhanced by the increased demand and production amounts of those metal compounds. Biohydrometallurgy – the use of microorganisms or related substances in metal extraction - provides the potential of processing low grade ores efficiently. Thus it is applied yet in some gold and uranium mining.
Also due to strategic reasons mining of regional resources such as the European Kupferschiefer come to the fore. Its complex composition including sulphide rich ores, carbonates and organic compounds challenges biotechnological approaches. Nevertheless promising approaches have been reported. We examine heterotrophic bioleaching of copper from Kupferschiefer ores. To investigate the interactions between mineral surface and microorganisms Raman spectroscopy offers a versatile applicability: Identification of minerals and differentiation of microorganisms is nicely provided and is accompanied by imaging opportunities in a two or even three dimensional manner. Thus biofilms, for example, can be analysed with respect to microbial diversity or preferences of minerals during the attaching process.

  • Poster
    Microbiology and Infection 2014, 05.-08.10.2014, Dresden, Deutschland

Publ.-Id: 20866

Dynamo action driven by a periodically perturbed Beltrami-flow.

Giesecke, A.; Stefani, F.

We apply kinematic simulations of the induction equations in order to examine the ability of a Beltrami flow (with curl(V) ~V) generating dynamo action. In the basic state we find a surprisingly complex behavior of the leading azimuthal modes that have a wavenumber up to m=3. Depending on the relation of poloidal to toroidal flow the eigenmodes show slow amplitude modulations and a azimuthal drift of the field pattern.

In a more complex model we add a non-axisymmetric time-dependent flow perturbation. In extension of a previous study we change the (azimuthal) pattern and amplitude of the perturbation flow. Consequently, the magnetic field growth rates are enhanced when the frequency of the perturbation is in the appropriate regime. We find small windows of perturbation frequencies with strong enhancement of the growth rates as well as broader regimes for rather fast drifting perturbations when the perturbation amplitude is sufficient to alter structure of the basic axisymmetric flow.

The effect may be relevant for forthcoming dynamo experiments conducted in Madison or in the precession dynamo experiment at HZDR, where, however, the basic flow will look quite different.

Keywords: Dynamo

  • Lecture (Conference)
    IGDR Annual Meeting Cambridge, 01.-04.09.2014, Cambridge, Great Britain

Publ.-Id: 20865

How to identify groundwater-caused thermal anomalies in lakes based on multi-temporal satellite data in semi-arid regions

Mallast, U.; Gloaguen, R.; Friesen, J.; Roediger, T.; Geyer, S.; Merz, R.; Siebert, C.

The deduction by conventional means of qualitative and quantitative information about groundwater discharge into lakes is complicated.
Nevertheless, at least for semi-arid regions with limited surface water availability, this information is crucial to ensure future water availability for drinking and irrigation purposes.
Overcoming this lack of discharge information, we present a satellite-based multi-temporal sea-surface-temperature (SST) approach.
It exploits the occurrence of thermal anomalies to outline groundwater discharge locations using the example of the Dead Sea. Based on a set of 19 Landsat Enhanced Thematic Mapper (ETM+) images 6.2 (high gain), recorded between 2000 and 2002, we developed a novel approach which includes (i) an objective exclusion of surface-runoff-influenced data which would otherwise lead to erroneous results and (ii) a temporal SST variability analysis based on six statistical measures amplifying thermal anomalies caused by groundwater.
After excluding data influenced by surface runoff, we concluded that spatial anomaly patterns of the standard deviation and range of the SST data series spatially fit best to in situ observed discharge locations and, hence, are most suitable for detecting groundwater discharge sites.

Publ.-Id: 20864

Sulfur sources of sedimentary "buckshot" pyrite in the Auriferous Conglomerates of the Mesoarchean Witwatersrand and Ventersdorp Supergroups, Kaapvaal Craton, South Africa

Guy, B. M.; Ono, S.; Gutzmer, J.; Lin, Y.; Beukes, N. J.

Large rounded pyrite grains (> 1 mm), commonly referred to as "buckshot" pyrite grains, are a characteristic feature of the auriferous conglomerates (reefs) in the Witwatersrand and Ventersdorp supergroups, Kaapvaal Craton, South Africa. Detailed petrographic analyses of the reefs indicated that the vast majority of the buckshot pyrite grains are of reworked sedimentary origin, i.e., that the pyrite grains originally formed in the sedimentary environment during sedimentation and diagenesis. Forty-one of these reworked sedimentary pyrite grains from the Main, Vaal, Basal, Kalkoenkrans, Beatrix, and Ventersdorp Contact reefs were analyzed for their multiple sulfur isotope compositions (delta S-34, Delta S-33, and Delta S-36) to determine the source of the pyrite sulfur. In addition, five epigenetic pyrite samples (pyrite formed after sedimentation and lithification) from the Middelvlei and the Ventersdorp Contact reefs were measured for comparison. The delta S-34, Delta S-33, and Delta S-36 values of all 41 reworked sedimentary pyrite grains indicate clear signatures of mass-dependent and mass-independent fractionation and range from -6.8 to +13.8 aEuro degrees, -1.7 to +1.7 aEuro degrees, and -3.9 to +0.9 aEuro degrees, respectively. In contrast, the five epigenetic pyrite samples display a very limited range of delta S-34, Delta S-33, and Delta S-36 values (+0.7 to +4.0 aEuro degrees, -0.3 to +0.0 aEuro degrees. and -0.3 to +0.1 aEuro degrees, respectively). Despite the clear signatures of mass-independent sulfur isotope fractionation, very few data points plot along the primary Archean photochemical array suggesting a weak photolytic control over the data set. Instead, other factors command a greater degree of influence such as pyrite paragenesis, the prevailing depositional environment, and non-photolytic sulfur sources. In relation to pyrite paragenesis, reworked syngenetic sedimentary pyrite grains (pyrite originally precipitated along the sediment-water interface) are characterized by negative delta S-34 and Delta S-33 values, suggesting open system conditions with respect to sulfate supply and the presence of microbial sulfate reducers. On the contrary, most reworked diagenetic sedimentary pyrite grains (pyrite originally precipitated below the sediment-water interface) show positive delta S-34 and negative Delta S-33 values, suggesting closed system conditions. Negligible Delta S-33 anomalies from epigenetic pyrite suggest that the sulfur was sourced from a mass-dependent or isotopically homogenous metamorphic/hydrothermal fluid. Contrasting sulfur isotope compositions were also observed from different depositional environments, namely fluvial conglomerates and marine-modified fluvial conglomerates. The bulk of the pyrite grains from fluvial conglomerates are characterized by a wide range of delta S-34 values (-6.2 to +4.8 aEuro degrees) and small Delta S-33 values (+/- 0.3 aEuro degrees). This signature likely represents a crustal sulfate reservoir derived from either volcanic degassing or from weathering of sulfide minerals in the hinterland.
Reworked sedimentary pyrite grains from marine-modified fluvial conglomerates share similar isotope compositions, but also produce a positive Delta S-33/delta S-34 array that overlaps with the composition of Archean barite, suggesting the introduction of marine sulfur.
These results demonstrate the presence of multiple sources of sulfur, which include atmospheric, crustal, and marine reservoirs. The prevalence of the mass-dependent crustal sulfur isotope signature in fluvial conglomerates suggests that sulfate concentrations were probably much higher in terrestrial settings in comparison to marine environments, which were sulfate-deficient. However, the optimum conditions for forming terrestrial sedimentary pyrite were probably not during fluvial progradation but rather during the early phases of flooding of low angle unconformities, i.e., during retrogradational fluvial deposition, coupled in some cases with marine transgressions, immediately following inflection points of maximum rate of relative sea level fall.

Publ.-Id: 20863

P1308 - Anordnung zur Bestimmung der Phasenverteilung in mehrphasigen Medien mit mindestens einer hochleitfähigen Phase

Schleicher, E.; Löschau, M.; van Campen, L.

Die Erfindung betrifft einen Gittersensor zur Messung der Phasenverteilung eines mehrphasigen Stoffgemisches mit gasförmigen und flüssigen Komponenten unter Vorhandensein einer hochleitfähigen Phase (wie Salzwasser oder Flüssigmetall). Anwendungsgebiete sind die Bestimmung der Flüssigkeitsverteilung und des Füllstands in Gefäßen sowie die Untersuchung von Gas-Flüssigkeits-Mehrphasenströmungen, insbesondere in Rohrleitungen z. B. in der Erdölproduktion und -verarbeitung.

  • Patent
    DE102013203437 - Offenlegung 28.08.2014, Erteilung 28.05.2015, Nachanmeldung: WO, BR, CA, EP, RU, US

Publ.-Id: 20862

Redirection of CD4+ and CD8+ T lymphocytes via a novel antibody-based modular targeting system triggers efficient killing of PSCA+ prostate tumor cells

Arndt, C.; Feldmann, A.; Töpfer, K.; Koristka, S.; Cartellieri, M.; Temme, A.; Ehninger, A.; Ehninger, G.; Bachmann, M.

There is still a need for new therapeutic options against prostate cancer. Conventional single-chain bispecific antibodies (bsAbs), that directly cross-link T cells and tumor cells, hold great potential for efficient tumor treatment. However, rapid development of novel bsAbs is hampered by laborious optimization to improve their efficacy and reduce potential side effects. To accelerate the development of a novel antibody tool for the redirection of T cells to different tumor-associated antigens, we recently introduced a modular targeting system.
We here describe a novel modular system for treatment of prostate cancer by retargeting of T cells to the prostate stem cell antigen (PSCA). Functionality of the novel PSCA-specific modular system was investigated in vitro by T cell activation and chromium release assays as well as in immunodeficient mice.
Similar to a conventional bsAb CD3-PSCA, the novel PSCA-specific modular system induces activation of both CD4+ and CD8+ T cells leading to secretion of pro-inflammatory cytokines and highly efficient target-specific tumor cell lysis. The novel TM was ready-to-use from the time point of construction and functional at low E:T ratios and picomolar concentrations without further optimization. In addition, the PSCA-specific modular system delays outgrowth of s.c. tumors in mice comparable to bsAb CD3-PSCA.
We have developed a novel PSCA-specific modular system which triggers an efficient T cell-mediated killing of PSCA+ tumor cells in vitro and in vivo. The new Ab-based targeting strategy can functionally replace conventional bsAbs and allows a flexible redirection of T cells to different tumor-associated antigens.

Publ.-Id: 20861

Ion-surface interaction in plasma processing

Möller, W.

Whereas the studies of ion-surface interaction have been a significant issue in nuclear fusion research through about four decades, corresponding knowledge in the area of low-pressure plasma processing can still be considered as marginal. Qualitatively, it is well accepted that energetic ion bombardment is essential for several processes of plasma surface treatment or plasma-assisted deposition of thin films. For the latter, it plays an important role in determining the growing thin film structure and stoichiometry. However, more quantitative models are only available for a few selected processes and for specific materials.
The lecture will briefly review the state of knowledge. It will particularly focus on the process physics of non-reactive and reactive sputtering. Open questions will be addressed in connection with recent experimental findings and computer simulation results, such as describing self-organized topographical and stoichiometric pattern formation under ion bombardment, and the characteristics of sputtering from such modified surfaces.

Keywords: Ion-surface interaction; Hard coatings; Magnetron sputtering; Plasma processing

  • Invited lecture (Conferences)
    PSE 2014 - International Conference on Plasma Surface Engineering, 15.-20.09.2014, Garmisch-Partenkirchen, Deutschland

Publ.-Id: 20860

Sputtering of nanospheres - a computer simulation study

Möller, W.; Nietiadi, M. L.; Urbassek, H. M.; Sandoval, L.

The sputtering of spherical objects – such as clusters, nanoparticles or aerosol particles – being exposed to energetic ion irradiation has been studied using both Monte Carlo simulation in the binary collisions approximation (MC) and molecular dynamics simulation (MD). 20 keV Ar impact on a-Si has been chosen as a typical example. With a denoting the mean depth of energy deposition in a planar target, inverse scaled cluster radii a/R ranging from 0 to 20 have been investigated, both addressing the impact parameter dependence and the average sputtering yield. For large radii (a/R < 0.2) sphere sputtering follows closely the sputtering of planar targets, if the variation of the incidence angle on the sphere surface is taken into account. For smaller radii, the yield increases due to the influence of sphere curvature. For a/R > 1, pronounced forward sputtering leads to a maximum in the sputter yield. In the limit of small radii, sputter emission becomes largely isotropic, but decreases in yield since the projectile energy is only partly deposited in the sphere and the surface area shrinks. However, for all spheres studied, the average sputter yield is larger than for the planar surface. Within the uncertainties of the modelling, there is an excellent agreement between the planar surface sputtering yields as obtained by MC and MD. For small spheres, however, the MD yields are significantly larger which is attributed to the influence of collisional spikes.

Keywords: Sputtering; Nanostructures; Computer Simulation

  • Lecture (Conference)
    IBMM 2014 - International Conference on Ion Beam Modification of Materials, 15.-19.09.2014, Leuven, Belgien

Publ.-Id: 20859

Ion beam synthesis of InAs, InGaAs and GaAs nanocrystals in Silicon

Rebohle, L.; Wutzler, R.; Prucnal, S.; Hübner, R.; Grenzer, J.; Helm, M.; Skorupa, W.

InAs, InGaAs and GaAs nanocrystals (NCs) were fabricated by sequential ion implantation and flash lamp annealing. In detail, silicon-SiO2-silicon structures were provided with a SiO2 capping layer followed by the sequential implantation of In, Ga and As ions with fluences in the range of a few 1016 at./cm2. In the following step of flash lamp annealing the NCs will be formed in the Si device layer by liquid phase epitaxy. The resulting III-V NCs are mostly single-crystalline with sizes in the range of a few to a few tens of nm. Depending on the specific segregation coefficients and melting temperatures, elemental In clusters can be also formed. The proposed qualitative model for the NC formation is based on Transmission electron microscopy (TEM), Raman spectroscopy, and X-ray diffraction (XRD) measurements.

Keywords: InAs; InGaAs and GaAs nanocrystals; ion implantation; flash lamp annealing; III-V integration into silicon

  • Poster
    EMRS Fall Meeting 2014, 15.-18.09.2014, Warschau, Polen

Publ.-Id: 20858

Sputtering of Si nanospheres

Nietiadi, M. L.; Sandoval, L.; Urbassek, H. M.; Möller, W.

Spherical objects, such as clusters, nanoparticles, or aerosol particles, are sputtered when exposed to energetic irradiation.We use Monte Carlo (MC) and molecular dynamics (MD) computer simulation to study this process, with 20 keV Ar impact on a-Si clusters as a prototypical example. The sputter yield is quantified as being influenced by oblique incidence and target curvature. Cluster radii R are scaled to the energy deposition depth, a. For large R (R/a > 5) sphere sputtering follows closely the sputtering of planar targets, if the variation of the incidence angle on the sphere surface is taken into account. For smaller radii, the yield increases due to the influence of curvature. For radii R/a 1 pronounced forward sputtering leads to a maximum in the sputter yield. For smaller R, sputter emission becomes isotropic, but decreases in magnitude since not all the projectile energy is deposited in the sphere. However, for all spheres studied (R > 0.05a) the average sputter yield is larger than for infinitely large spheres (R→∞). A simple model based on linear collision cascade theory and assuming that the energy deposition profile is independent of the sphere size predicts sputtering for large spheres well, but fails for small spheres where it strongly underestimates sputtering. The MC data for the smaller spheres are supplemented by MD calculations, which indicate a significant additional contribution caused by spike sputtering.

Keywords: Sputtering; Nanostructures; Computer Simulation; Binary Collision Approximation; Molecular Dynamics

Publ.-Id: 20857

The electroluminescence mechanism of Er3+ in different silicon oxide and silicon nitride environments

Rebohle, L.; Berencén, Y.; Wutzler, R.; Braun, M.; Hiller, D.; Ramírez, J. M.; Garrido, B.; Skorupa, W.; Helm, M.

Rare earth doped metal-oxide-semiconductor (MOS) structures are of great interest for Si-based light emission. However, several physical limitations make it difficult to achieve the performance of light emitters based on compound semiconductors. To address this point, in this work the electroluminescence (EL) excitation and quenching mechanism of Er-implanted MOS structures with different designs of the dielectric stack are investigated. The devices usually consist of an injection layer made of SiO2 and an Er-implanted layer made of SiO2, Si-rich SiO2, silicon nitride or Si-rich silicon nitride. All structures implanted with Er show intense EL around 1540 nm with EL power efficiencies in the order of 2×10-3 (for SiO2:Er) or 2×10-4 (all other matrices) for lower current densities. The EL is excited by the impact of hot electrons with an excitation cross section in the range of 0.5-1.5×10-15 cm-2. Whereas the fraction of potentially excitable Er ions in SiO2 can reach values up to 50%, five times lower values were observed for other matrices. The decrease of the EL decay time for devices with Si-rich SiO2 or Si nitride compared to SiO2 as host matrix implies an increase of the number of defects adding additional non-radiative de-excitation paths for Er3+. For all investigated devices EL quenching cross sections in the 10-20 cm2 range and charge-to-breakdown values in the range of 1-10 Ccm-2 were measured. For the present design with a SiO2 acceleration layer, thickness reduction and the use of different host matrices did not improve the EL power efficiency or the operation lifetime, but strongly lowered the operation voltage needed to achieve intense EL.

Keywords: electroluminescence; ion implantation; erbium; MOS structure; decay time

Publ.-Id: 20856

Electromagnetic fields of a vertical magnetic dipole above and within a horizontal stratified earth in due consideration of the electrical permittivity

Scheunert, M.; Börner, R.-U.; Siemon, B.

Our poster is motivated by the helicopter electromagnetic forward and inversion problem. In this context, we use the secondary field approach to evaluate the total electromagnetic fields of a vertical magnetic dipole (VMD) by a numerical discretization scheme. This approach requires the calculation of an analytic solution of the primary field at every receiver position, located within the air half-space. Furthermore, in order to calculate the Jacobian matrix using the sensitivity equation approach, these primary fields have to be calculated at every degree of freedom within the stratified media. The primary fields are the solution of the Helmholtz equation for a 1-D conductivity distribution.
We show the complete derivation of the electromagnetic fields of a VMD for the magnetic vector potential based on the spatial Hankel transformation. To avoid inaccuracies at high frequencies, varying electrical permittivities are incorporated. We furthermore explain the recursion algorithm that is used to find general expressions at arbitrary depths and which allows us to easily derive the different electromagnetic field components. The calculations start with the simple two layer case and are subsequently expanded to the more general N-layer case. Special attention is payed to a singularity problem arising at the derivation of the horizontal electrical and vertical magnetic fields in the air layer which is resolved by an integration by parts approach.

Keywords: fields of a VMD; stratified earth; HEM; vector potential; Fourier transform

  • Poster
    22nd EM Induction Workshop, 24.-30.08.2014, Weimar, Deutschland

Publ.-Id: 20855

A Concept for 3-D Inversion of Helicopter Electromagnetic Data Using a Tensor-based Problem Formulation

Scheunert, M.; Afanasjew, M.; Börner, R.-U.; Eiermann, M.; Ernst, O. G.; Spitzer, K.

Helicopter electromagnetic (HEM) measurements allow to manage huge surveys in a very short time. Due to the enormous data and model sizes, laterally constrained 1-D inversion schemes for the entire survey are still state of the art, even for those parts of the survey where 3-D conductivity anomalies are expected.

We introduce a new strategy that is based on the precedent localization of the entire HEM survey to parts which are actually affected by an expected local 3-D anomalies. A full 3-D inversion scheme capable of revealing those anomalous conductivity structures is presented that directly benefits from a-priori information, resulting from the localization procedure. We therefore reformulate the discrete forward problem in terms of the secondary electric field, employing either finite difference or finite element methods. For solving the inverse problem, we apply a straightforward Gauss-Newton method and a Tikhonov-type regularization scheme. The concept allows us to additionally restrict the domain where the inverse problem is solved, acting as an implicit regularization. The derived linear least squares problem is solved with Krylov subspace methods, such as LSQR, that are able to deal with the inherent ill-conditioning. The resulting systems of linear equations subsequently yield expressions for the gradient and approximate Hessian of the minimization problem. Resulting from the unique transmitter-receiver relation of the HEM problem, an explicit representation of the Jacobian matrix is used. We further introduce a tensor-based problem formulation that provides a fast update of the linear system of the forward problem and an effective handling of the sensitivity related algebraic quantities, respectively.

Keywords: HEM; 3-D inversion; cut-&-paste strategy; field data; explicit Jacobian

  • Poster
    74. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (DGG), 10.-13.03.2014, Karlsruhe, Deutschland

Publ.-Id: 20854

EM fields of a VMD calculated at arbitrary points within a layered half-space

Scheunert, M.; Börner, R.-U.; Siemon, B.

In this paper, we derive expressions for all electromagnetic (EM) field components which can be observed, when a vertical magnetic dipole (VMD) is located at z = −h, h > 0 over a stratified earth, i.e., when the electrical conductivity is a piecewise constant function of depth z. We further allow a non-vanishing but small electrical conductivity in the air layer, and let the electrical permittivity vary from its vacuum value. Apart from traditional approaches, we use a non-vanishing air conductivity to be consistent with our 3-D discretizations which would otherwise yield singular mass matrices. The basic ideas of the derivation within the following paragraphs emanate from Ward and Hohmann (1988) and Zhdanov (2009). While the first sections of this paper concern the two-layer (i.e., the nearly non-conductive air and the conductive homogeneous half-space) case we expand the concept to the general N-layer case in the last section. This work has been motivated by the one-dimensional forward and inverse problem of helicopter electromagnetics (HEM). To evaluate the observed total fields by a numerical discretization scheme, the secondary field approach requires the calculation of the analytical solution of the EM fields at the receiver positions within the air half-space. Furthermore, in order to calculate the Jacobian matrix, these fields are required at arbitrary points within the conductive layered half-space.

Keywords: electromagnetic fields; vertical magnetic dipole; stratified earth; magnetic vector potential; Fourier transform

  • Open Access Logo Contribution to proceedings
    25. Schmucker-Weidelt-Kolloquium für Elektromagnetische Tiefenforschung, 23.-27.09.2013, Kirchhundem-Rahrbach, Deutschland
    Protokoll über das 25. Schmucker-Weidelt-Kolloquium für Elektromagnetische Tiefenforschung : Kirchhundem-Rahrbach 23.-27. September 2013, Potsdam: Deutsche Geophysikalische Gesellschaft e. V., 5-20


Publ.-Id: 20853

Investigation of the effects of a variation of fuel assembly position on the ex-core neutron flux detection in a PWR

Konheiser, J.; Brachem, C.; Seidl, M.

This work shows the impact of potential displacements of the fuel assembly positions in the reactor core on the signal values of the ex-core instrumentation of a KWU – type pressurized water reactor in order to understand in detail the impact on the calibration factor of excore detectors. This was done with a range of Monte Carlo calculations which simulated the detailed geometrical effect by stepwise changing the positions of fuel assemblies for selected, conservative scenarios. First, criticality calculations were carried out for the chosen core configurations and corresponding surface sources on the core barrel were determined. In these calculations, the distances were varied between the fuel assemblies which were in the line of sight of the ex-core instrumentation. A maximal change of the fluxes on the surface of the core barrel of 4%/mm could be calculated under conservative assumptions for the combination of displaced fuel assemblies. In addition, a dependence of this effect as a function of cycle burnup was analyzed. In a second step transport calculations for the ionization chambers were performed using the surface sources. An increase of the reaction rate at the chambers of up to 3%/mm has been calculated.

Keywords: PWR type reactor; Ex-core instrumentation; Monte Carlo calculation

Publ.-Id: 20852

Hyperspectral remote sensing of carbonatite hosted REE deposits in Namibia

Zimmermann, R.; Salati, S.; Andreani, L.; Brandmeier, M.; Gloaguen, R.

High spectral and spatial resolution of hyperspectral images allow mapping and determination of minerals on the earth surface. It also provide valuable information about ore deposits and their alteration zoning.
Carbonatites are well known for hosting economic concentrations of REE-bearing minerals like bastnäsite, monazite and apatite among others (WINTER 2001). They show signifcant spectral characteristics, even REE-absorption bands (ROWAN et al. 1986).
The aim of our study is to apply recent advances in hyperspectral imaging and to develop new tools in order to map these rocks. A refnement of the geological map by lithological mapping, image classifcation, mineral mapping and tectonic geomorphology is also done.
Our research mainly focuses on carbonatites from Namibia. We selected two sites with well known occurrences in Northern Namibia: the Epembe and the Lofdal dykes. Both yield signifcant REE- concentrations and being under exploration. In these areas LANDSAT 8, SRTM, EO-1 Hyperion and airborne hyperspectral (HyMap) data overlap giving an excellent coverage.
The data had been processed for atmospherical and geometric corrections frst. For the EO-1 Hyperion data a more carefully pre-processing had to be applied due to streaking and smiling effects. Results of LANDSAT 8 classifcation had been used for validation and classifcation purposes. Detailed spectral signatures and mineral maps are extracted by hyperspectral imaging. The results confrm former observations by BEDINI (2009) on the Sarfartoq carbonatite complex in West Greenland. Secondly the structural controls of emplacement of the selected carbonatite dykes had been carried out using tectonic geomorphology and feld observation. For this purpose the TecDEM-toolbox (SHAHZAD & GLOAGUEN 2011) was applied to the SRTM-data for drainage- network and stream-profle analysis.
Combining all these information with geological knowledge of carbonatites and their occurrences, it is possible to explore new, unknown deposits by remote sensing applications.

  • Poster
    GeoFrankfurt 2014, 22.-24.09.2014, Frankfurt/Main, Deutschland

Publ.-Id: 20851

Cockade breccia: Product of mineralisation along dilational faults

Frenzel, M.; Woodcock, N. H.

Cockade breccias are fault fills in which individual clasts are completely surrounded by concentric layers of cement. They occur particularly in low-temperature near-surface hydrothermal veins. At least six mechanisms have been proposed for the formation of cockade breccia-like textures, but only two – repeated rotation-accretion, and partial metasomatic replacement of clast minerals – have been supported by detailed evidence. A typical example of cockade breccia from the Gower Peninsula (South Wales) shows clear evidence for the rotation-accretion mechanism: in particular, overgrown breakage points in cement layers – where cockades were previously touching each other – and rotated geopetal infills of haematitic sediment. Based on the available evidence, it is proposed that cockade textures result from low rates of cement growth compared to high rates of dilational fault slip. Seven criteria are given for the correct identification of cockade breccias.

Keywords: cockade ore; ring ore; syntectonic mineralisation; dilational faulting; epithermal veins

  • Journal of Structural Geology 68(2014), 194-206
    DOI: 10.1016/j.jsg.2014.09.001
  • Lecture (Conference)
    UK Tectonic Studies Group Annual Meeting, 06.-08.01.2015, Edinburgh, United Kingdom

Publ.-Id: 20850

Strongly Non-Reciprocal Dipole-Exchange Spin Wave Mode in Antiferromagnetically Coupled Magnetic Bilayers

Tyberkevych, V.; Slavin, A.; Wintz, S.; Slobodianiuk, D.; Melkov, G.

  • Lecture (Conference)
    59th Annual Magnetism & Magnetic Materials Conference, 03.-07.11.2014, Honolulu, USA

Publ.-Id: 20849

Laser pulse-shape dependence of Compton scattering

Titov, A.; Kämpfer, B.; Shibata, T.; Hosaka, A.; Takabe, H.

Compton scattering of short and ultra short (sub-cycle) laser pulses off mildly relativistic electrons is considered within a QED framework. The temporal shape of the pulse is essential for the differential cross section as a function of the energy of the scattered photon at fixed observation angle. The partly integrated cross section is sensitive to the non-linear dynamics resulting in a large enhancement of the cross section for short and, in particular, for ultra-short flat-top pulse envelopes which can reach several orders of magnitude, as compared with the case of a long pulse. Such effects can be studied experimentally and must be taken into account in Monte-Carlo/transport simulations of %e+e− pair production in the interaction of electrons and photons in a strong laser field.

Publ.-Id: 20847

Defining medium-specific condensates in QCD sum rules for D and B mesons

Buchheim, T.; Hilger, T.; Kämpfer, B.

QCD sum rules for D and B mesons in a strongly interacting environment require the decomposition of Gibbs averaged operators related to tensor structures. We present a procedure to decompose these operators into vacuum and medium-specific parts, thus defining plain medium-specific condensates with coefficients vanishing in vacuum. Our decomposition allows for an identification of potential elements of order parameters for chiral restoration, in particular for higher mass-dimension quark-condensates which would be masked otherwise if operators with uncontracted Lorentz indices would be linked to DIS amplitudes.

Publ.-Id: 20846

Recent results from the high magnetic field laboratory Dresden: Probing the 1D or 2D nature of M2+Ta2O6 (M2+=Ni,Co)

Law, J. M.

es hat kein Abstract vorgelegen

  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism MISM-2014, 29.06.-03.07.2014, Moscow, Russia

Publ.-Id: 20844

ESR Studies of the Spin-1/2 Heisenberg Antiferromagnet Copper Pyrazine Dinitrate

Ozerov, M.

Copper pyrazine dinitrate, Cu(C4H4N2)(NO3), is one of the best known model spin-1/2 Heisenberg antiferromagnet chain system. Here, we present electron spin resonance (ESR) studies of this material. Angular, temperature and field dependences of ESR parameters are studied. We evidence the inequivalence of Cu sites belonging to adjacent spin chains in the ac planes. It is revealed that the dominating interchain interaction in this compound is of zig-zag-type. This interaction gives rise to geometrical frustration strongly affecting the character of antiferromagnetic ordering. Combining our experimental findings with the results of a quasiclassical approach we predict that at low temperatures the system orders in an incommensurate spiral state.

  • Poster
    International Conference on Strongly Correlated Electron Systems, 07.-11.07.2014, Grenoble, France

Publ.-Id: 20843

Simulation of Channel Segregation During Directional Solidification of In—75 wt pct Ga. Qualitative Comparison with In Situ Observations

Saad, A.; Gandin, C.-A.; Bellet, M.; Shevchenko, N.; Eckert, S.

Freckles are common defects in industrial casting. They result from thermosolutal convection due to buoyancy forces generated from density variations in the liquid. The present paper proposes a numerical analysis for the formation of freckles using the three dimensional (3D) cellular automaton (CA) - finite element (FE) model [1]. The model integrates kinetics laws for the nucleation and growth of a microstructure to the solution of the conservation equations for the casting, while introducing an intermediate modeling scale for a direct representation of the envelope of the dendritic grains. Directional solidification of a cuboid cell is studied. Its geometry, the alloy chosen as well as the process parameters are inspired from experimental observations recently reported in the literature [2]. Snapshots of the convective pattern, the solute distribution and the morphology of the growth front are qualitatively compared. Similitudes are found when considering the coupled 3D CAFE simulations. Limitations of the model to reach direct simulation of the experiments are discussed.

Keywords: Solidification; Natural convection; Segregation; Freckle; Dendritic growth; Grain structure

Publ.-Id: 20842

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