Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34752 Publications

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

A 3D microstructural model of freckle initiation from pre-existing imperfections

Karagadde, S.; Yuan, L.; Shevchenko, N.; Eckert, S.; Lee, P. D.

The quality and lifing of high performance turbine blades are severely hampered by presence of freckles, which are initiated by presence of enriched solute plumes during solidification [1]. Nickel based turbine blades can be cast as equiaxed, directionally solidified or single crystals. Several types of perturbations may occur during these casting techniques, which can eventually lead to freckles.
In this work, a 3D microstructural numerical model of freckle formation is presented [2]. A typical simulation of stabilized solute plume formation leading to a freckle channel is shown in Fig. 1. The model is validated with in situ x-ray radiographic measurements [3], comparing solute partitioning, convection and freckle channel width. This model was then used to investigate freckle formation under a range of solidification conditions. Using the dendrite tip growth and solute profiles, freckle onset was observed to occur in two distinct stages. The influence of imperfections that occur in primary arm spacing and grain boundary was investigated from the proposed model. It was found that the freckles initiate from these irregularities, with a higher propensity for converging grain boundaries. In addition, the effect of dendrite orientation angle on freckle formation is studied.

Keywords: 3D microstructural model; freckle; x-ray radiography; model validation; dendrite tip growth

  • Lecture (Conference)
    4th International Conference on Advances in Solidification Processes, 08.-11.07.2014, Old Windsor, United Kingdom

Publ.-Id: 20841

Melt flow and temperature gradient effects on freckle formation

Shevchenko, N.; Roshchupkina, O.; Eckert, S.

A visualization of the segregation freckle formation and the main convection pattern in solidifying Ga - In alloys was obtained by using the X-ray imaging technique [1, 2]. A Ga - In alloy was used because its density variation and thermo-physical properties are similar to many commercial alloys. Furthermore, it has a very good X-ray contrast and shows a melting point near room temperature. Recently, formation of stable chimney at several solidification conditions and captured the solute distribution and flow velocities were reported [2]. Variations of the vertical and lateral temperature gradients induce modifications of the melt flow pattern, which lead to different segregation structures.
In the case of solidification at higher vertical temperature gradients (up to 2 K/mm), we identified a converging flow ahead of the mushy zone coming from the side walls. Such flow patterns are driven by the lateral temperature gradient and the convex shape of the solidification front. This leads to a continuous accumulation of solute in the central part of the solidification cell followed by a remelting of the solid fraction and the occurrence of a sustaining chimney. This mechanism of chimney formation is different as compared to the case where the evolution of the segregation channel is related to any initial growth defect.
Variations of the lateral temperature gradient by additional side cooling lead to a collapse of the double-vortex convection over entire cell volume. A more complicated flow pattern occurs consisting of multiple convection rolls along the solid - liquid interface. At such solidification conditions a sustainable development of stable chimneys was rarely observed.

Keywords: Visualization; X-ray radioscopy; freckle formation; solid liquid interface; flow patterns; temperature gradient

  • Lecture (Conference)
    4th International Conference on Advances in Solidification Processes, 08.-11.07.2014, Old Windsor, United Kingdom

Publ.-Id: 20840

In situ X-ray radiography study on the impact of forced melt convection on solidification processes

Shevchenko, N.; Roshchupkina, O.; Eckert, S.

In this paper, we present experimental investigations focusing on the question how natural and forced convection influence the microstructure formation in solidifying alloys.
In situ visualization of the solidification of Ga–25wt%In alloys was carried out by means of X-ray radioscopy. An electromagnetically driven flow was produced inside the solidifying liquid by a rotating wheel with two parallel disks containing at their inner sides a set of permanent NdFeB magnets with alternating polarisation [1, 2]. Rotation speeds of the magnetic wheel were chosen in the range of 10 – 80 revolutions per minute resulting in local flow velocities between 0.5 and 1.5 mm/s in the area just ahead of the solidification front. The melt flow is almost perpendicular with respect to the growth direction of the dendrites.
The forced convection induces a redistribution of solute concentration, re-orientation of the dendritic structure, changes of primary and secondary branching, and leads to a formation of segregation channels. Flow patterns, dendrite morphologies and tip velocities were quantified by image analysis and related to the experimental conditions. In principle, the forced flow is an external operational parameter that can be used to control the final microstructure. However, the optimization of the microstructure by electromagnetic flow control is a complex task which requires a deep understanding of the complex interplay between melt flow and solidification process.

Keywords: X-ray radiography; Solidification; Ga-In alloy; Forced convection; Dendritic structure; Tip velocity

  • Lecture (Conference)
    4th International Conference on Advances in Solidification Processes, 08.-11.07.2014, Old Windsor, United Kingdom

Publ.-Id: 20839

Dependence of all-optical magnetic switching on the sublattice magnetization orientation in Tb-Fe thin films

Hassdenteufel, A.; Schubert, C.; Schmidt, J.; Richter, P.; Zahn, D. R. T.; Salvan, G.; Helm, M.; Bratschitsch, R.; Albrecht, M.

We demonstrate that the direction of all-optical switching (AOS) in rare-earth transition-metal (RE-TM) alloy Tb-Fe thin films depends on the orientation of the sublattice magnetization and not on the direction of the resulting net magnetization. For this purpose, we investigated the AOS ability for a sample dominated by the Fe sublattice magnetization (Tb24Fe76) and another dominated by the Tb sublattice (Tb30Fe70). This finding of the sublattice dependence of AOS contributes to the understanding of switching in RE-TM multilayered thin films and heterostructures.

Keywords: all-optical magnetic switching; AOS; sublattice magnetization; rare earth metal alloy

Publ.-Id: 20838

Why Do Strategic Alliances Persist? A Behavioral Decision Model

Klossek, A.; Meyer, K. E.; Nippa, M.

Strategic alliances are considered a flexible form of organizing, yet they are often long-lived. Even when systematic benefit–cost analysis suggests that their organizational form should be changed or terminated, some alliances still persist. Drawing on behavioral decision theory, we propose a theoretical model that explains this phenomenon. Decision makers are subject to a variety of biases that can lead to the overvaluation of the net benefits of an alliance and, hence, inhibit the change or discontinuation of underperforming alliances. Our model illustrates how decision-making biases at the individual, interpersonal, organizational, and interorganizational levels are moderated by the design of an alliance and the tools employed in the decision-making process. This behavioral decision perspective advances our theoretical understanding of the longevity of strategic alliances and their embeddedness in complex decision-making contexts.

Publ.-Id: 20837

Visualization of liquid metal two-phase flows in a physical model of the continuous casting process of steel

Timmel, K.; Shevchenko, N.; Röder, M.; Anderhuber, M.; Gardin, P.; Eckert, S.; Gerbeth, G.

We present an experimental study concerned with investigations of the two-phase flow in a mockup of the continuous casting process of steel. A specific experimental facility was designed and constructed at HZDR for visualizing liquid metal two-phase flows in the mold and the submerged entry nozzle (SEN) by means of X-ray radioscopy. This setup operates with the low melting, eutectic alloy GaInSn as model liquid. The argon gas is injected through the tip of the stopper rod into the liquid metal flow. The system operates continuously under isothermal conditions. First results will be presented here revealing complex flow structures in the SEN widely differing from a homogeneously dispersed bubbly flow. The patterns are mainly dominated by large bubbles and large-area detachments of the liquid metal flow from the inner nozzle wall. Various flow regimes can be distinguished depending on the ratio between the liquid and the gas flow rate. Smaller gas bubbles are produced by strong shear flows near the nozzle ports. The small bubbles are entrained by the submerged jet and mainly entrapped by the lower circulation roll in the mold. Larger bubbles develop by coalescence and ascend towards the free surface.

Keywords: continuous casting; liquid metal model; two-phase flow; x-ray imaging

Publ.-Id: 20836

Decision-making criteria in rare earths exploration projects: An interview study

Klossek, P.; van den Boogaart, K. G.

When the rare earth prices skyrocketed in 2011, over 400 exploration projects appeared in the rest of the world. Before any of these exploration projects comes into production, it has to pass various stages of the project development and face multiple challenges at each of these stages. According to the Cooper’s stage-gate system, a decision about whether to move on to the next project stage should be based on the evaluation of certain criteria. The case of rare earth elements, however, differs from other metals in terms of mineralogy, market, technology, environmental issues, strategic importance etc. Therefore, the decision criteria might also partly differ. To find these criteria for the case of rare earths, interviews with decision- makers from several rare earths projects at different stages of development were conducted. In the paper, obtained criteria are listed, explained, and analysed for each stage/gate. Suggestions about their application to project management are made.

Keywords: exploration; mining; project development process; project management; project evaluation; decision-making; stage-gate system; decision-making criteria; rare earth elements; interview study; project realisability; project economics; project externalities; project uncertainty

Publ.-Id: 20835

High-magnetic-field properties of frustrated magnets

Wosnitza, J.

es hat kein Abstract vorgelegen

  • Invited lecture (Conferences)
    13th Japanese-German Symposium “Interplay of Spin- and Orbital Degrees of Freedom in Strongly Correlated Electron Systems”, 13.-16.07.2014, Rottach-Egern, Deutschland

Publ.-Id: 20834

Emerging evidence for FFLO states in layered organic superconductors

Wosnitza, J.

es hat kein Abstract vorgelegen

  • Invited lecture (Conferences)
    2nd International Symposium of the SFB/TR 49 on “Novel states in correlated condensed matter – from model systems to real materials”, 08.-10.04.2014, Königstein, Deutschland
  • Invited lecture (Conferences)
    The 11th International Conference on Materials & Mechanisms of Superconductivity, 23.-28.08.2015, Geneva, Switzerland
  • Invited lecture (Conferences)
    Workshop on "Interference of Magnetism and Superconductivity", 18.07.-02.09.2016, Natal, Brasilien
  • Invited lecture (Conferences)
    Gordon Research Conference on Conductivity & Magnetism in Molecular Materials, 14.-19.08.2016, South Hadley, USA
  • Invited lecture (Conferences)
    3rd International Workshop GRK 1621, 26.-27.05.2016, Meissen, Deutschland
  • Invited lecture (Conferences)
    10th Workshop "Control of Quantum Correlations in Tailored Matter", 03.-06.04.2017, Loveno di Menaggio, Italien

Publ.-Id: 20833

The Fulde-Ferrell-Larkin-Ovchinnikov state in layered organic superconductors

Wosnitza, J.

es hat kein Abstract vorgelegen

  • Invited lecture (Conferences)
    International Workshop on Topological quantum matter and two-dimensional superconductors, 11.-14.01.2014, Kuming, China

Publ.-Id: 20832

Observation of the hyperfine transition in lithium-like bismuth Bi20980+ : Towards a test of QED in strong magnetic fields

Lochmann, M.; Jöhren, R.; Geppert, C.; Andelkovic, Z.; Anielski, D.; Botermann, B.; Bussmann, M.; Dax, A.; Frömmgen, N.; Hammen, M.; Hannen, V.; Kühl, T.; Litvinov, Y. A.; López-Coto, R.; Stöhlker, T.; Thompson, R. C.; Vollbrecht, J.; Volotka, A.; Weinheimer, C.; Wen, W.; Will, E.; Winters, D.; Sánchez, R.; Nörtershäuser, W.

We performed a laser spectroscopic determination of the 2s hyperfine splitting (HFS) of Li-like 209Bi80+ and repeated the measurement of the 1s HFS of H-like 209Bi82+. Both ion species were subsequently stored in the Experimental Storage Ring at the GSI Helmholtzzentrum für Schwerionenforschung Darmstadt and cooled with an electron cooler at a velocity of ≈0.71c. Pulsed laser excitation of the M1 hyperfine transition was performed in anticollinear and collinear geometry for Bi82+ and Bi80+, respectively, and observed by fluorescence detection. We obtain ΔE(1s)=5086.3(11)meV for Bi82+, different from the literature value, and ΔE(2s)=797.50(18)meV for Bi80+. These values provide experimental evidence that a specific difference between the two splitting energies can be used to test QED calculations in the strongest static magnetic fields available in the laboratory independent of nuclear structure effects. The experimental result is in excellent agreement with the theoretical prediction and confirms the sum of the Dirac term and the relativistic interelectronic-interaction correction at a level of 0.5%, confirming the importance of accounting for the Breit interaction.

Keywords: laser spectroscopy; qed; storage ring; esr; bismuth; li-like

Publ.-Id: 20831

Synthesis and evaluation of a 18F-labeled spirocyclic piperidine derivative as promising σ1 receptor imaging agent

Chen, Y.-Y.; Wang, X.; Zhang, J.-M.; Deuther-Conrad, W.; Zhang, X.-J.; Huang, Y.; Li, Y.; Ye, J.-J.; Cui, M.-C.; Steinbach, J.; Brust, P.; Liu, B.-L.

Several spirocyclic piperidine derivatives were designed and synthesized as σ1 receptor ligands. In vitro competition binding assays showed that the fluoroalkoxy analogues with small substituents possessed high affinity towards σ1 receptors and subtype selectivity. Particularly for ligand 1'-((6-(2-fluoro-ethoxy)pyridin-3-yl)methyl)-3H-spiro[2-benzofuran-1,4'-piperidine] (2), high σ1 receptor affinity (Ki = 2.30 nM) and high σ12 subtype selectivity (142-fold) as well as high σ1/VAChT selectivity (234-fold) were observed. [18F]2 was synthesized using an efficient one-pot, two-step reaction method in a home-made automated synthesis module, with an overall isolated radiochemical yield of 8-10%, a radiochemical purity of higher than 99%, and specific activity of 56-78 GBq/µmol. Biodistribution studies of [18F]2 in ICR mice indicated high initial brain uptake and a relatively fast washout. Administration of haloperidol, compound 1 and different concentrations of SA4503 (3, 5, or 10 µmol/kg) 5 min prior to injection of [18F]2 significantly decreased the accumulation of radiotracer in organs known to contain σ1 receptors. Ex vivo autoradiography in Sprague-Dawley rats demonstrated high accumulation of radiotracer in brain areas with high expression of σ1 receptors. These encouraging results prove that [18F]2 is a suitable candidate for σ1 receptor imaging with PET in humans.

Keywords: PET; 18F; Sigma-1 receptors; Imaging agent; Spirocyclic piperidine derivatives

Publ.-Id: 20830

Adsorption of zinc by biogenic elemental selenium nanoparticles

Jain, R.; Jordan, N.; Schild, D.; van Hullebusch, E. D.; Weiss, S.; Franzen, C.; Farges, F.; Hübner, R.; Lens, P. N. L.

The adsorption of Zn2+ ions onto biogenic elemental selenium nanoparticles (BioSeNPs) was investigated. BioSeNPs were produced by reduction of selenite (SeO32−) in the presence of anaerobic granules from a full scale upflow anaerobic sludge blanket (UASB) reactor treating paper mill wastewater. The BioSeNPs have an iso-electric point at pH 3.8 at 5 mM background electrolyte concentration. X-ray photoelectron spectroscopy showed the presence of a layer of extracellular polymeric substances on the surface of BioSeNPs providing colloidal stability. Batch adsorption experiments showed that the uptake of Zn2+ ions by BioSeNPs was fast and occurred at a pH as low as 3.9. The maximum adsorption capacity observed was 60 mg of zinc adsorbed per g of BioSeNPs. The Zn2+ ions adsorption on the BioSeNPs was largely unaffected by the presence of Na+ and Mg2+, but was impacted by the presence of Ca2+ and Fe2+ ions. The colloidal stability of BioSeNPs decreased with the increasing Zn2+ ions loading on BioSeNPs (increase in mg of zinc adsorbed per g of BioSeNPs), corresponding to the neutralization of the negative surface charge of the BioSeNPs, suggesting gravity settling as a technique for solid-liquid separation after adsorption. This study proposes a novel technology for removal of divalent cationic heavy metals by their adsorption on the BioSeNPs present in the effluent of an UASB reactor treating selenium oxyanions containing wastewaters.

Keywords: adsorption; selenium nanoparticles; zinc removal; XPS analysis; ζ-potential; colloidal stability

Publ.-Id: 20829

Spin-lattice effects in selected magnetic materials

Zherlitsyn, S.

  • Invited lecture (Conferences)
    V International Conference of Young Scientists LOW TEMPERATURE PHYSICS (ICYS–LTP–2014), 02.-06.06.2014, Kharkov, Ukraine

Publ.-Id: 20828

Direct determination of exchange parameters in spin-1/2 Heisenberg triangular-lattice antiferromagnets: high-field ESR studies

Zvyagin, S.

Spin-1/2 Heisenberg antiferromagnets Cs2CuCl4 and Cs2CuBr4 with distorted triangular-lattice structures are studied by means of electron spin resonance spectroscopy in magnetic fields up to the saturation field and above. In the magnetically saturated spin polarized phase, quantum fluctuations are fully suppressed, and the spin dynamics is defined by ordinary magnons. This allows us to accurately describe the magnetic excitation spectra in both materials and, using the harmonic spin-wave theory, to determine their exchange parameters. The proposed approach has a broader impact and can be potentially used for any quantum magnet with reduced (e.g., by the staggered DM interaction) translational symmetry, resulting, as predicted, in emergence of a new exchange mode in the magnetically saturated phase.

  • Invited lecture (Conferences)
    International Conference Magnetic Resonance: fundamental research and pioneering applications (MR 70), 23.-27.06.2014, Kazan, Russia

Publ.-Id: 20827

Magnetic fields in Europe

Wosnitza, J.

  • Invited lecture (Conferences)
    Farewell Symposium of Jan Kees Maan, 23.05.2014, Nijmegen, The Netherlands

Publ.-Id: 20826

Measurement of the quasi free np -> npπ+π- and np ->ppπ-π0 reactions at 1.25 GeV with HADES

Kurilkin, A.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; González-Díaz, D.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, K.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Krizek, F.; Kuc, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

We present the results of two-pion production in tagged quasi-free np collisions at a proton incident beam energy of 1.25 GeV measured with the High-Acceptance Di-Electron Spectrometer (HADES) installed at GSI. The specific acceptance of HADES allowed for the first time to obtain high-precision data on π+π- and π-π0 production in np collisions in a region corresponding to large transverse momenta of the secondary particles. The obtained differential cross section data provide strong constraints on the production mechanisms and on the various baryon resonance contributions (, N(1440), N(1520), Δ(1600)). The invariant mass and angular distributions from the np->npπ+π- and np->ppπ-π0 reactions are compared with dierent theoretical model predictions.

Publ.-Id: 20825

Application of computational fluid dynamics in nuclear reactor safety analysis

Höhne, T.

The last decade has seen an increasing use of three-dimensional CFD codes to predict steady state and transient flows in nuclear reactors because a number of important phenomena such as pressurized thermal shocks, coolant mixing, and thermal striping cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution. CFD codes contain models for simulating turbulence, heat transfer, multi-phase flows, and chemical reactions. Such models must be validated before they can be used with sufficient confidence in NRS applications.

Numerical investigations on single phase coolant mixing in Pressurized Water Reactors (PWR) have been performed at the HZDR for more than a decade. The work is aimed at describing the mixing phenomena relevant for both safety analysis, particularly in steam line break and boron dilution scenarios, and mixing phenomena of interest for economical operation and the structural integrity.

On the other hand slug flow as a multiphase flow regime can occur in the cold legs of pressurized water reactors, for instance after a small break Loss of Coolant Accident (SB-LOCA). Slug flow is potentially hazardous to the structure of the system due to the strong oscillating pressure levels formed behind the liquid slugs. For the experimental investigation of horizontal two phase flows, different non pressurized channels and the TOPFLOW Hot Leg model in a pressure chamber was build and simulated with ANSYS CFX.

The behavior of insulation material released by a LOCA into the containment and the reactor core might compromise the long term emergency cooling systems. Subsequently, if the ECCS is operating in the sump recirculation mode, the debris suspended in the containment sump would begin to accumulate on the sump strainers. A small part could penetrate through the strainers and could be transported towards the reactor core. It was the aim of the numerical simulations to study where and how many mineral wool fibres are deposited at the upper spacer grid of a core.


  • Contribution to proceedings
    24th SYMPOSIUM of AER on VVER Reactor Physics and Reactor Safety, 14.-18.10.2014, Sotschi, Russland
  • Lecture (Conference)
    24th SYMPOSIUM of AER on VVER Reactor Physics and Reactor Safety, 14.-18.10.2014, Sotschi, Russland

Publ.-Id: 20824

Validation of closure models for interfacial drag and turbulence of horizontal segregated flows

Höhne, T.

In the last decade, applications of Computational Fluid Dynamic (CFD) methods for nuclear applications received more and more attention, as they proved to be a valuable complementary tool for design and safety. The main interest towards CFD consists in fact in the possibility of obtaining detailed 3D complete flow-field information on relevant physical phenomena at lower cost than experiments. Typically free surfaces manifest as stratified and wavy flows in horizontal flow domain where gas and liquid are separated by gravity. Stratified two-phase flows are relevant in many nuclear applications, e.g. pipelines, main coolant lines, horizontal heat exchangers and storage tanks.

CFD simulations for free surface flows require the modeling of the non-resolved scales. For modeling of interfacial transfers it is necessary to select the adequate interfacial transfer models and to determine the interfacial area. The numerical solution can resolve the statistically averaged motion of the free surface (including waves) which may not be too small relatively to the channel height and to the characteristic length of the spatial discretization. However, the detailed structure of interacting boundary layers of the separated continuous phases and surface ripples cannot be resolved. Instead, its influence on the average flow must be modeled.

The development of a general model closer to physics and including less empiricism is a long-term objective of the activities of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) research programs. Such models are an essential precondition for the application of CFD codes to the modeling of flow related phenomena in nuclear facilities. Here local geometry independent models for mass, momentum, heat transfer, and scalar transport are developed and validated. The new formulation for the drag force at the free surface within the algebraic interfacial area density model (the FSD model inside AIAD) is one result of these activities.

A further step of improvement of modeling the turbulence is the consideration of sub-grid wave turbulence (SWT) that means waves created by Kelvin-Helmholtz instabilities that are smaller than the grid size. So fare in the present code versions they are neglected. However, the influence on the turbulence kinetic energy of the liquid side can be significantly large. A region of marginal breaking is defined according Brocchini and Peregrine (2001). In addition turbulence damping functions should cover all the free surface flow regimes, from weak to strong turbulence.

CFD validation of the new approach was done using experiments of the HZDR HAWAC channel. A discussion of the general requirements of such CFD grade experiments was performed. The CFD calculations were done using the Best Practice Guidelines for two-phase flow modeling. One result of the simulations was that the sub-grid wave turbulence which exists in the area of the free surface follows the slug formations. At the wavy front and back of the slugs the value of the sub-grid wave turbulence is the highest in the channel. The slug frequency analysis was done using fast Fourier transform (FFT). The characteristic slug frequency of the simulation was around 2.0 Hz, which corresponds roughly to the experimental value of approximately 2.4 Hz. The model improves the physics of the existing two fluid approaches and is already applicable for a wide range of industrial two phase flows.

More verification and validation of the approach is still necessary – more CFD grade experimental data are required for the validation.

Keywords: CFD; AIAD; HZDR; two-phase flow

  • Contribution to proceedings
    CFD4NRS-5, Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, Joint OECD/NEA & IAEA Workshop, 09.-11.09.2014, Zürich, Schweiz
  • Lecture (Conference)
    CFD4NRS-5, Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, Joint OECD/NEA & IAEA Workshop, 09.-11.09.2014, Zürich, Schweiz

Publ.-Id: 20823

Uranium retention by montmorillonite at high ionic strengths

Fritsch, K.; Schmeide, K.

Clay and clay minerals are viewed as potential host rock as well as backfill material for nuclear waste disposal in deep geological formations. While South German clay deposits have pore waters with ionic strengths below 0.5 mol l-1, North German clay deposits exhibit high ionic strengths up to 4 mol l-1 in the depth relevant for repositories.[1] Such high ionic strength conditions are rarely investigated and are thus in the focus of the present work. Montmorillonite is used as model clay for uranium sorption experiments in sodium and calcium chloride. Additionally, a mixed electrolyte was prepared that resembles the groundwater composition at the Konrad site, which serves as a reference site. Surface complexation modelling is employed to gain thermodynamic data from the sorption experiments.

Sorption experiments were conducted with Na montmorillonite SWy-2, which was purified according to Poinssot et al. [2] and Bradbury et al. [3]. Sorption edges were determined with an initial U(VI) concentration of 1.10-6 mol kg-1 and a solid-liquid ratio of 4 g kg-1 in a pH range of 4 to 10 with electrolyte concentrations from 0.1 to 3 mol kg-1. The U(VI) concentration for sorption isotherms ranged from 1.10-8 to 1.10-5 mol kg-1. The mixed electrolyte was composed of cNaCl = 2.52 mol kg-1, cCaCl2 = 0.12 mol kg-1 and cMgCl2 = 0.048 mol kg-1 (overall I = 3.02 mol kg-1).

The classic ionic strength effect describes the decrease of sorption with increasing ionic strength and is generally only observed in the acidic pH range, where cation exchange is the predominant sorption mechanism. Natural groundwaters at the Konrad site have pH values above 5.5, where cation exchange is not the dominant sorption mechanism anymore, which in turn causes a smaller influence of ionic strength on sorption. The sorption maxima in the different salt systems usually lie just below the neutral point and well within the pH range of groundwaters at the reference site. The sorption edge in NaCl is observed at pH 4.1. In the mixed electrolyte, sorption is increased in the alkaline pH range when compared to pure electrolytes. This is due to the magnesium content in this electrolyte, which forms hydroxide precipitates that influence uranium retention by co-precipitation.

Surface complexation modelling with the 2 site protolysis non-electrostatic surface complexation and cation exchange model (2SPNE SC/CE)[4] in conjunction with spectroscopic investigation of the sorption phenomena can be used to identify the surface species involved. The results show that ≡SOUO2 + is the dominant surface complex below pH 6 Uranium hydroxide complexes become the dominant surface complexes above pH 7 in absence of CO2. In presence of CO2, sorption above pH 7 is decreased due to aqueous uranium carbonate complexes.

In general, there is no influence of ionic strength on U(VI) retention by montmorillonite at environmentally relevant pH values. The classic ionic strength effect can only be observed in the acidic pH range, and only up to a sodium concentration of 2 mol kg-1. However, in the presence of calcium or magnesium, uranium retention is promoted by secondary phase formation which leads to partial irreversibility of immobilisation at high ionic strengths in the alkaline pH range.

[1] Brewitz, W. et al. Eignungsprüfung der Schachtanlage Konrad für die Endlagerung radioaktiver Abfälle. GSF-T 136; 1982.
[2] Poinssot, C. et al. Experimental studies of Cs, Sr, Ni, and Eu sorption on Na-illite and the modelling of Cs sorption. NTB 99-04; 1999.
[3] Bradbury, M.; Baeyens, B. Geochim Cosmochim Acta 2009, 73, 990–1003.
[4] Bradbury, M.; Baeyens, B. J Contam Hydrol 1997, 27, 223–248.

Keywords: uranium sorption; argillaceous rock; clay; uranium; montmorillonite; high ionic strength; surface complexation modelling

  • Contribution to proceedings
    Clays in natural and engineered barriers for radioactive waste confinement, 23.-26.03.2015, Brussels, Belgium
    Proceedings of Clays in natural and engineered barriers for radioactive waste confinement
  • Poster
    Clays in natural and engineered barriers for radioactive waste confinement, 23.-26.03.2015, Brussels, Belgium

Publ.-Id: 20822

Parameter Estimation of anisotropic diffusion in Clay with COMSOL Multiphysics

Gerasch, R.; Kulenkampff, J.; Lippmann-Pipke, J.

Our GeoPET camera is explicitly dedicated for and well capable of 4D monitoring of solute transport in dense geological material, c = c(x,y,z,t) (Richter et al., 2005; Gründig et al., 2007; Kulenkampff et al., 2008; Zakhnini et al., 2013). We apply COMSOL Multiphysics for reproducing our experiments and extracting parameter sets for our 4D problems (Lippmann-Pipke et al., 2011; Schikora, 2012). By aligning simulated results of anisotropic diffusion in clay to our observations we are able to clearly differentiate and evaluate likely explicit sample features and transport processes.

Use of COMSOL Multiphysics: A quarter section of a cylinder (3D geometry) is representing our clay core. The bedding of the clay is about vertical. A central bore allows for the application of a labelled pore water solution to diffuse into the material. Isotropic diffusion is assigned to the fluid in the bore hole, while anisotropic diffusion is assigned to the porous media (both with cdeq). From our non-invasive, spatio-temporal PET observations of the diffusion process in a real clay sample two 2D sets ci(x,z) and ci(y,z), are extracted and provided to the Optimization Module for the parameter estimation for Dxx=Dyy and Dzz. A sensitivity analysis quantifies the effects on uncertainties regarding porosity n, initial concentration c0 and spatial resolution.

The 4D simulation results quantitatively nicely match with our 4D experimental results obtained in GeoPET experiments.

  • Lecture (Conference)
    COMSOL Conference 2014, 17.-19.09.2014, Cambridge, UK

Publ.-Id: 20821

FP7 Project LONGLIFE: Overview of Results and Implications

Altstadt, E.; Keim, E.; Hein, H.; Serrano, M.; Bergner, F.; Viehrig, H.-W.; Ballesteros, A.; Chaouadi, R.; Wilford, K.

LONGLIFE (“Treatment of long term irradiation embrittlement effects in RPV safety assessment”) was a collaborative project of the 7th Framework Programme of EURATOM under the umbrella of NULIFE/NUGENIA, aiming at an improved understanding of irradiation effects in reactor pressure vessel steels under conditions representative of long term operation. The LONGLIFE project was completed by end of January 2014. The paper gives an overview of the main project results and their implications for future research, as discussed at the final project workshop. The microstructural database for neutron-irradiated RPV steels was extended considerably and existing gaps on mechanical property data were closed. Indications of late blooming effects (LBE) were found in some cases, but clear criteria for the occurrence/exclusion in terms of irradiation conditions and chemical composition have still to be developed. The commonly accepted trend, that low flux and low irradiation temperature promotes LBE, is supported. A significant flux effect on the size of defect clusters was observed in two high Cu weld materials, while the changes of mechanical properties are not affected by the neutron flux. The database requires completion in particular for low-Cu RPV steels. The shift of reference temperature T0 over the thickness location of a VVER-440 welding seam does not follow the prediction Russian code, because of the strong variation of the intrinsic weld bead structure. Therefore, the effect of the initial microstructure and of the heterogeneity on the radiation behaviour has to be addressed in future works. Existing embrittlement trend curves models were applied to the LONGLIFE data base. None of the trend curves could predict the behaviour of the entirety of the LONGLIFE materials sufficiently. A guideline for monitoring radiation embrittlement during life extension periods was developed.

Keywords: Reactor pressure vessel steel; radiation induced defects; embrittlement; hardening; flux effect; late blooming; trend curves

Publ.-Id: 20818

Novel Cyclopentadienyl Tricarbonyl 99mTc Complexes Containing 1‑Piperonylpiperazine Moiety: Potential Imaging Probes for Sigma‑1 Receptors

Wang, X.; Li, D.; Deuther-Conrad, W.; Lu, J.; Xie, Y.; Jia, B.; Cui, M.; Steinbach, J.; Brust, P.; Liu, B.; Jia, H.

We report the design, synthesis, and evaluation of a series of novel cyclopentadienyl tricarbonyl 99mTc complexes as potent σ1 receptor radioligands. Rhenium compounds 3-(4-(1,3-benzodioxol-5-ylmethyl)piperazin-1-yl)-propylcarbonylcyclopentadienyl tricarbonyl rhenium (10a) and 4-(4-(1,3-benzodioxol-5-ylmethyl)piperazin-1-yl)-butylcarbonylcyclopentadienyl tricarbonyl rhenium (10b) possessed high in vitro affinity for σ1 receptors and moderate to high selectivity for σ2 receptors and the vesicular acetylcholine transporter. Biodistribution studies in mice demonstrated high initial brain uptake for corresponding 99mTc derivatives [99mTc] 23 and [99mTc]24 of 2.94 and 2.13% injected dose (ID)/g, respectively, at 2 min postinjection. Pretreatment of haloperidol significantly reduced the radiotracer accumulation of [99mTc]23 or [99mTc]24 in the brain. Studies of the cellular uptake of [99mTc]23 in C6 and DU145 tumor cells demonstrated a reduction of accumulation by incubation with haloperidol, 1-(3,4-dimethoxyphenethyl)-4-(3-phenylpropyl)piperazine (SA4503), or 1,3-di-otolyl-guanidine (DTG). Furthermore, blocking studies in C6 glioma-bearing mice confirmed the specific binding of [99mTc]23 to σ1 receptors in the tumor.

Publ.-Id: 20817

Cyclotron based production of high specific activity [197(m)Hg]HgCl2

Walther, M.; Preusche, S.; Pietzsch, H.-J.; Bergmann, R.; Steinbach, J.

197mHg (T1/2 = 23.8 h, Eγ 133.98 keV, 33.5%) and 197Hg (T1/2 = 64.14 h, Eγ 77.4 keV, 18.7%) are gamma-emitting radionuclides suitable for SPECT imaging and of additional interest because of the potential therapeutic us of their Auger- and conversion electron emission. The unique chemical and physical properties as metal which forms water-stable carbon-metal bonds and the easy volatility awakened interest on mercury decades ago. The medical use of mercury was virtually complete after the scientific determination of the high toxicity and long biological half life of mercury compounds in vivo. From this follows that the condition precedent to develop new radiopharmaceuticals based on mercury radionuclides is their high specific activity. The production of nca 197Hg radionuclide together with the short lived 197mHg isomer is possible by proton or deuteron irradiation of natural gold using a cyclotron. The 197Au(p,n)197Hg reaction was applied until now only for small scale tracer production, beam monitoring or stacked foil measurements. The main goal of the research project is the evaluation of the cyclotron-based radionuclides 197Hg/197mHg regarding their suitability for diagnostics and therapy of tumors. First results of investigations concerning nca 197Hg/197mHg production and the development of bifunctional mercury chelate complexes stable in vivo will be reported.

  • Abstract in refereed journal
    Nuclear Medicine and Biology 41(2014)7, 646
    DOI: 10.1016/j.nucmedbio.2014.05.018
  • Lecture (Conference)
    2nd International Symposium on TECHNETIUM and other RADIOMETALS in CHEMISTRY and MEDICINE (Terachem 2014), 10.-13.09.2014, Bressanone, Italy

Publ.-Id: 20816

Pharmacological characterization of α-MSH-derivatives

Sihver, W.; Gao, F.; Jurischka, C.; Haase-Kohn, C.; Steinbach, J.; Carta, D.; Bolzati, C.; Calderan, A.; Pietzsch, J.; Pietzsch, H.-J.

The melanocortin-1 receptor is known to be overexpressed in melanoma. Thus, it is a potential target for novel α-MSH peptide derivatives aiming at diagnosis and therapy of melanoma. In this study, NOTA-NCS was conjugated with two peptides: NAP-NS1, a linear peptide with 9 amino acids (Ahx-βAla-Nle-Asp-His-D-Phe-Arg-Trp-Gly-NH2) and NAP-NS2, a lactam bridge-cyclized peptide with 12 amino acids (ε-Ahx-β-Ala-cyclo(Lys-Glu-His-D-Phe-Arg-Trp-Glu)-Arg-Pro-Val-NH2) each with the sequence His-Phe-Arg-Trp for biological activity. Four α-MSH derivatives were investigated in competition assays in murine B16-F10 and human MeWo melanoma cells. (S)-p-NH2-Bn-NOTA (NOTA-NAP-NS1) labeled with 64Cu and 68Ga, showing no transchelation in the cysteine and histidine challenge, was applied in saturation assays. Determination of octanol/water partition coefficients suggested that [64Cu]Cu-NOTA-NAP-NS1 had high hydrophilicity, and in buffer and serum it was stable after 1 h and 24 h. NAP-NS1 and NOTA-NAP-NS1 showed higher affinity than the cyclic derivatives. Linking the chelate unit at the peptide was accompanied by some loss of affinity. Saturation studies with the labeled peptide resulted in Kd values in the lower nanomolar range for [64Cu]Cu-NOTA-NAP-NS1 and [68Ga]Ga-NOTA-NAP-NS1, respectively. Thus, both radiolabeled peptides appear to be promising for further investigations in animal melanoma models.

This research was supported by MIUR (PRIN 2008F5A3AF_002).

  • Abstract in refereed journal
    Nuclear Medicine and Biology 41(2014)7, 637-638
    DOI: 10.1016/j.nucmedbio.2014.05.038
  • Lecture (Conference)
    2nd International Symposium on TECHNETIUM and other RADIOMETALS in CHEMISTRY and MEDICINE (Terachem 2014), 10.-13.09.2014, Bressanone, Italy

Publ.-Id: 20815

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