Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35175 Publications

Rapid Data Processing for Ultrafast X-Ray Computed Tomography Using Scalable and Modular CUDA based Pipelines

Frust, T.; Wagner, M.; Stephan, J.; Juckeland, G.; Bieberle, A.

Ultrafast X-ray tomography is an advanced imaging technique for the study of dynamic processes basing on the principles of electron beam scanning. A typical application case for this technique is e.g. the study of multiphase flows, that is, flows of mixtures of substances such as gas-liquid flows in pipelines or chemical reactors. At Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a number of such tomography scanners are operated. Currently, there are two main points limiting their application in some fields. First, after each CT scan sequence the data of the radiation detector must be downloaded from the scanner to a data processing machine. Second, the current data processing is comparably time-consuming compared to the CT scan sequence interval. To enable online observations or use this technique to control actuators in real-time, a modular and scalable data processing tool has been developed, consisting of user-definable stages working independently together in a so called data processing pipeline, that keeps up with the CT scanner's maximal frame rate of up to 8 kHz. The data processing stages are arbitrarily programmable and combinable. In order to achieve the highest processing performance all relevant data processing steps, which are required for a standard slice image reconstruction, were individually implemented in separate stages using Graphics Processing Units (GPUs) and NVIDIA's CUDA programming language. Data processing performance tests on different high-end GPUs (Tesla K20c, GeForce GTX 1080) and external computer clusters (Tesla P100) showed excellent performance.

Keywords: Computed tomography; Image reconstruction; Multithreading; Parallel algorithms; Pipeline processing; Real-time systems


Publ.-Id: 24546

Hydrogen treatment of Fe60Al40 thin films

Ehrler, J.; Bali, R.; Otalora, C.; Anwand, W.; Trinh, T. T.; Liedke, M. O.; Böttger, R.; Yuan, Y.; Grenzer, J.; Cornelius, S.; Potzger, K.

The effect of hydrogen treatment on the magnetic properties and the defect concentration of Fe60Al40 films, possessing A2 and B2 structure respectively, have been investigated. The H treatment was realized by proton irradiation as well as by reactor loading. Ferromagnetic A2-Fe60Al40 films of 250 nm thickness were irradiated with protons at an energy of 17 keV and fluences of up to 1.46 E18 ions cm-2. Magneto-optical Kerr effect showed a variation of coercivity and an increase of saturation magnetization (MS) as a function of ion fluence. Positron annihilation Spectroscopy (PAS) indicates an increase of the open volume defect concentration.
Superparamagnetic B2-Fe60Al40 films were capped with 10 nm Pd and annealed at 423 K in 30 bar H atmosphere. PAS shows that the H-annealing process led to a decrease in the open volume defect concentration. H-treatment caused a small increase in MS from 0.013 to 0.017 μb/Fe atom, as well as a shift in the superparamagnetic blocking temperature from 85 to 115 K respectively. While H treatment significantly modifies the magnetic properties of Fe60Al40, elastic recoil detection suggests that the hydrogen is not retained in the vacancies present in the film, suggesting that the variations in magnetic properties may be mostly due to structural changes.

  • Poster
    IEEE Magnetics Society Summer School 2016, 10.-16.07.2016, Tohoku University, Sendai, Japan

Publ.-Id: 24545

Sloshing instability and electrolyte layer rupture in liquid metal batteries

Weber, N.; Beckstein, P.; Herreman, W.; Horstmann, G. M.; Nore, C.; Stefani, F.; Weier, T.

Liquid metal batteries (LMBs) are discussed today as a cheap grid scale energy storage, as required for the deployment of fluctuating renewable energies. Built as a stable density stratification of two liquid metals separated by a thin molten salt layer, LMBs are susceptible to short-circuit by fluid flows. Using direct numerical simulation, we study a sloshing long wave interface instability in cylindrical cells, which is already known from aluminium reduction cells. After characterising the instability mechanism, we investigate the influence of cell current, layer thickness, density, viscosity, conductivity and magnetic background field. Finally we study the shape of the interface and give a dimensionless parameter for the onset of sloshing as well as for the short-circuit.


Publ.-Id: 24544

Hydrogen treatment of Fe60Al40 thin films

Ehrler, J.; Bali, R.; Otalora, C.; Yildirim, O.; Anwand, W.; Trinh, T. T.; Liedke, M. O.; Böttger, R.; Heller, R.; Cornelius, S.; Yuan, Y.; Grenzer, J.; Potzger, K.

The effect of H treatment on the magnetic properties and the defect concentration of Fe60Al40 films, possessing A2 and B2 structure respectively, have been investigated. The treatment was realized by H+ irradiation as well as by reactor loading. Ferromagnetic A2-Fe60Al40 films of 250 nm thickness were irradiated with protons at an energy of 17 keV and fluences of up to 1.46 E18 ions cm−2. Magneto-optical Kerr effect showed a variation of coercivity and an increase of saturation magnetization (MS) as a function of ion fluence. Positron annihilation spectroscopy (PAS) indicates an increase of the open volume defect concentration. Superparamagnetic B2-Fe60Al40 films were annealed at 423 K in 30 bar H atmosphere. PAS shows that the H-annealing process led to a decrease in the open volume defect concentration. H-treatment caused a small increase in MS from 0.013 to 0.017 µb/Fe atom, as well as a shift in the blocking temperature from 85 to 115 K respectively. While H treatment significantly modifies the magnetic properties of Fe60Al40, elastic recoil detection suggests that the hydrogen is not retained in the vacancies present in the film, suggesting that the variations may be mostly due to structural changes.

  • Poster
    80. Jahrestagung der DPG und DPG-Frühjahrstagung, 06.-11.03.2016, Regensburg, Germany

Publ.-Id: 24543

Thermal Rayleigh-Marangoni convection in a three-layer liquid-metal-battery model

Köllner, T.; Boeck, T.; Schumacher, J.

The combined effects of buoyancy-driven Rayleigh-B\'{e}nard convection (RC) and surface tension-driven Marangoni convection (MC) are studied in a triple-layer configuration which serves as a simplified model for a liquid metal battery (LMB). The three-layer model consists of a liquid metal alloy cathode, a molten salt separation layer, and a liquid metal anode at the top. Convection is triggered by the temperature gradient between the hot electrolyte and the colder electrodes, which is a consequence of the release of resistive heat during operation. We present a linear stability analysis of the state of pure thermal conduction in combination with three-dimensional direct numerical simulations of the nonlinear turbulent evolution on the basis of a pseudospectral method. Five different modes of convection are identified in the configuration, which are partly coupled to each other: RC in the upper electrode, RC with internal heating in the molten salt layer, MC at both interfaces between molten salt and electrode as well as anti-convection in the lower electrode. The linear stability analysis confirms that the additional Marangoni effect in the present setup increases the growth rates of the linearly unstable modes, i.e. Marangoni and Rayleigh-B\'{e}nard instability act together in the molten salt layer.
The critical Grashof and Marangoni numbers decrease with increasing middle layer thickness. The calculated thresholds for the onset of convection are found for realistic current densities of laboratory-sized LMBs. The global turbulent heat transfer follows scaling predictions for internally heated RC. The global turbulent momentum transfer is comparable with turbulent convection in the classical Rayleigh-B\'{e}nard case. In summary, our studies show that incorporating Marangoni effects generates smaller flow structures, alters the velocity magnitudes, and enhances the turbulent heat transfer across the triple-layer configuration.

Keywords: Marangoni convection; Free convection; Interfacial flows; Turbulent convection


Publ.-Id: 24542

Evaluating Moisture and Geometry Effects on L-Band SAR Classification Performance over a Tropical Rain Forest Environment

Liesenberg, V.; Souza Filho, C. R.; Gloaguen, R.

Multitemporal single (HH) and dual-polarization (i.e., HH, HV) L-band spaceborne synthetic aperture radar (SAR) scenes were evaluated under different moisture conditions caused by precipitation prior to data acquisition at varying incidence angles. The changes affecting backscattering intensity, polarimetric decomposition, backscattering mechanism, and land use/land cover classification performance were evaluated. The study area is a shifting-cultivation environment in the eastern Amazon (Brazil). Several data input scenarios were proposed in the classification scheme (i.e., backscattering intensity alone and combined with alpha/entropy decomposition parameters, band ratios, and textural parameters) using a random forest classifier framework. Integration with optical data was also examined. The classification accuracy scores were then compared with accumulated precipitation data. The results showed that the variation in both the vegetation moisture and incidence angle increases the backscattering intensity for pasture, riparian forest and young regenerated forest by at least 1 dB compared with old successional forest stages due to its more uniform vertical structure and the landscape's increased dielectric constant. The overall classification accuracy proved low for each SAR acquisition date compared with the performance of the Landsat data. Based on SAR data, misclassification occurs for the young successional forest stages and increases in scenes with higher moisture conditions. The classification performance benefits from data integration only for one SAR scene acquired in the dry season. The results highlight the importance of selecting proper temporal intervals for the different SAR polarization modes of the forthcoming SAR missions. Further investigations should address both multitemporal at a single frequency as well as multifrequency SAR approaches.

Keywords: secondary forest; Advanced land observing satellite (ALOS)-phased-arrayed L-band synthetic aperture radar (PALSAR); eastern Amazon; L-band; polarization modes; random forest

  • IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 9(2016)12, 5357-5368
    DOI: 10.1109/JSTARS.2016.2617120

Publ.-Id: 24541

Cenozoic intracontinental deformation and exhumation at the northwestern tip of the India-Asia collision—southwestern Tian Shan, Tajikistan, and Kyrgyzstan

Käßner, A.; Ratschbacher, L.; Jonckheere, R.; Enkelmann, E.; Khan, J.; Sonntag, B.-L.; Gloaguen, R.; Gadoev, M.; Oimahmadov, I.

Along the Ghissar-Alai Range of the southwestern Tian Shan (southwestern Kyrgyzstan, northern Tajikistan), the deformation front of the India-Asia collision—the Pamir-Tibet orogen—is interacting with the intracontinental Tian Shan orogen without the intervening Tarim Craton. Apatite fission track (n = 33, ~3.3–145.6 Ma, 27% <10 Ma) and (U-Th)/He (n = 32, ~1.9–26.1 Ma, 56% <10 Ma) thermochronologic ages suggest approximate isothermal holding (very slow cooling to weak reheating) during relative tectonic quiescence between ~150 and 15 Ma. Accelerated exhumation (~0.2–1.0 km/Myr, median ~0.5 km/Myr) and cooling (11–16°C/Myr) occurred over the last ~10 Myr. Geomorphologic parameters—incision, river steepness, and concavity—confirm the youth of the southwestern Tian Shan's mountain building. High exhumation/cooling rates are correlated with pronounced local relief, produced by Cenozoic faults reactivating inherited (Late Paleozoic) structures. Regions with similarly young exhumation are centered along rims of rigid crustal blocks in the central and eastern Tian Shan. Structurally, the Ghissar-Alai Range is a broad, east trending zone of dextral transpression that includes the northern Tajik Basin (Illiak Fault Zone) and the Pamir Thrust System of the frontal northern Pamir. It is the particular deformation field at the northwestern tip of the India-Asia collision—the interaction of the westward gravitational collapse of the Pamir Plateau into the Tajik Basin with the bulk northward motion of the Pamir—that transformed the southwestern Tian Shan into a dextral transpression belt. The dextral transpression in the southwestern Tian Shan contrasts with sinistral strike-slip shear localized along inherited fault zones, accommodating dominant north-south shortening, in the central and eastern Tian Shan. The deformation field influenced by the Pamir and the associated young exhumation make the Ghissar-Alai Range a unique feature in the Tian Shan orogen.


Publ.-Id: 24540

10Be Surface-Exposure Age Dating of the Last Glacial Maximum in the Northern Pamir (Tajikistan)

Grin, E.; Ehlers, T. A.; Schaller, M.; Sulaymonova, V.; Ratschbacher, L.; Gloaguen, R.

Knowledge of the spatial and temporal variations in Alpine glaciations is essential for reconstructing the regional and global timing of ice ages. This study investigates glacial deposits at the mouth of the Muksu catchment in the northern Pamir using 10Be surface-exposure age dating. We sampled boulders from the furthest downstream recessional moraine (20 samples) and five lateral moraines (41 samples) near the former terminus of the Fedchenko Glacier, the longest (∼72 km) present-day Alpine glacier of the Pamir. After the identification of outliers, the boulder population of the recessional moraine yielded a mean exposure age of 17.5 ± 1.9 ka. The maximum exposure age of the lateral moraines, collected ∼5 km up-valley of the recessional moraine, is 18.2 ± 1.7 ka. The boulder ages reflect glacial deposition during the Last Glacial Maximum (Marine Isotope Stage 2) in the region; they are in accordance with published glacial deposition ages in the western Tian Shan.

Keywords: Moraine; Cosmogenic radionuclides; Exposure-age dating; Last glacial maximum; Pamir; Fedchenko Glacier

Publ.-Id: 24539

Evaluation of a deformable registration algorithm for subsequent lung computed tomography imaging during radiochemotherapy

Stützer, K.; Haase, R.; Lohaus, F.; Barczyk, S.; Exner, F.; Löck, S.; Rühaak, J.; Lassen-Schmidt, B.; Corr, D.; Richter, C.


Rating both a lung segmentation algorithm and a deformable image registration (DIR) algorithm for subsequent lung computed tomography (CT) images by different evaluation techniques. Furthermore, investigating the relative performance and the correlation of the different evaluation techniques to address their potential value in a clinical setting.

Two to seven subsequent CT images (69 in total) of 15 lung cancer patients were acquired prior, during, and after radiochemotherapy. Automated lung segmentations were compared to manually adapted contours. DIR between the first and all following CT images was performed with a fast algorithm specialized for lung tissue registration, requiring the lung segmentation as input. DIR results were evaluated based on landmark distances, lung contour metrics, and vector field inconsistencies in different subvolumes defined by eroding the lung contour. Correlations between the results from the three methods were evaluated.

Automated lung contour segmentation was satisfactory in 18 cases (26%), failed in 6 cases (9%), and required manual correction in 45 cases (66%). Initial and corrected contours had large overlap but showed strong local deviations. Landmark-based DIR evaluation revealed high accuracy compared to CT resolution with an average error of 2.9 mm. Contour metrics of deformed contours were largely satisfactory. The median vector length of inconsistency vector fields was 0.9 mm in the lung volume and slightly smaller for the eroded volumes. There was no clear correlation between the three evaluation approaches.

Automatic lung segmentation remains challenging but can assist the manual delineation process. Proven by three techniques, the inspected DIR algorithm delivers reliable results for the lung CT data sets acquired at different time points. Clinical application of DIR demands a fast DIR evaluation to identify unacceptable results, for instance, by combining different automated DIR evaluation methods.

Keywords: lung segmentation; deformable lung registration; landmarks; inconsistency vector field


Publ.-Id: 24538

Structural control on drainage network and catchment area geomorphology in the Dead Sea area: an evaluation using remote sensing and geographic information systems in the Wadi Zerka Ma’in catchment area (Jordan)

Odeh, T.; Gloaguen, R.; Mohammada, S. H.; Schirmer, M.

The geology of Jordan is characterized by fault systems with three major trends: (1) NW–SE, the oldest, (2) WNW–ESE, and (3) NNW–SSE, the youngest. The drainage network of the Wadi Zerka Ma’in catchment area, located in the middle of the Dead Sea rift, parallels these structural orientations. A regional transtensive fault, with embedded normal faults, bounds the lower and middle part of the catchment area. The topographic profile of the Zerka Ma’in River exhibits two major knickpoints where it crosses two major embedded normal faults. The second major knickpoint developed as a result of the dramatic lowering of the Lisan Lake water level, a lake that pre-dates the Dead Sea. The decreased water level triggered river incision into the clastic sandstone units of Wadi Zerka Ma’in. We performed a morphotectonic analysis study to investigate how the rock structures control the drainage network and the catchment area geomorphology. According to the transverse topographic symmetry factor (T), the catchment area is highly asymmetric. The major basin asymmetry trend is SE-oriented, parallel to the oldest set of fault systems. The catchment area displays a convex hypsometric curve indicating a very recent stage in the geomorphologic cycle. Our study indicates that the Lisan Lake catchment area shrinkage and structures growth controlled and shaped the Wadi Zerka Ma’in catchment area geomorphology. The combined use of a geographic information system (GIS) and remote sensing was shown to be very efficient in unraveling the evolution of the drainage network and catchment area geomorphology.

Publ.-Id: 24537

Recent progress in pulsed laser deposition of iron based superconductors

Haindl, S.; Molatta, S.; Hiramatsu, H.; Hosono, H.

Pulsed laser deposition (PLD) is the most commonly used deposition technique for Fe-based superconductor thin films today. The number of grown compounds using PLD is still quite limited to so-called 11 compounds (FeTexSy, FeSe1−xTex) and 122 compounds (primarily Co-and P-substituted BaFe2As2). Especially in the growth of Fe-chalcogenides, PLD is challenged by the strong volatility of the elements and their non-negligible vapour pressure. In addition, in situ PLD of the high-temperature superconducting F-doped iron oxypnictides seemed to be feasible only under reactive deposition and stayed disregarded for some time. Here, we summarise the progress that was recently made in the growth of Fe-based superconducting thin films towards an improved control of thin film stoichiometry and the in situ growth of F-doped iron oxypnictides. The presented new ideas deviate from the standard approach of an adjustment of target composition. We first focus on the growth of FeSe1−xTex films, where the introduction of a buffer layer of same composition decreased surface roughness and allowed epitaxial film growth at reduced deposition temperatures with enhanced reproducibility. Second, we illustrate how F-doping in iron oxypnictide thin films can be obtained during in situ PLD using a diffusive reaction between substrate and the growing film.

Publ.-Id: 24536

Reply to the comment of Mitchell et al. on “Geomorpho-tectonic evolution of the Jamaican restraining bend” by L. Domínguez-González, L. Andreani, K.P. Stanek and R. Gloaguen [Geomorphology, 228 (2015) 320–334]

Domínguez-González, L.; Andreani, L.; Stanek, K. P.; Gloaguen, R.

We reply to the comments of Mitchell et al. on our paper entitled “Geomorpho-tectonic evolution of the Jamaican restraining bend”. The comments contain statements about the methods that need to be balanced. We agree that the interpretation of the modeled drainage network in some karstified parts of the Jamaican island is difficult, but this does not affect the validity of our analysis elsewhere. We consider that our geomorphic analyses (which also include topographic profiles and morphometric maps) are still valid. The view expressed by Mitchell et al. that we used serially developed landscapes to ‘date’ progressive uplift is an oversimplification of our discussion. We highlighted the differences between the geomorpho-tectonic provinces of Jamaica, and we proposed to explain these differences by a model which involves (1) a westward propagation of the restraining bend and (2) a difference in tectonic styles between the different provinces of Jamaica. Our interpretation does not contradict existing models based on seismotectonic data, provenance analysis or on the origin of Jamaican bauxite. There is a disagreement between James-Williamson et al. (2014), which suggested that central Jamaica was already being uplifted by the end of the Late Miocene, and Domínguez-González et al. (2015), which proposed a Pliocene to present onset of the NE-trending compression toward the SW. However, the timing of the deformation in central and western Jamaica is still poorly constrained and, at this time, any interpretation of the uplift history of central Jamaica should be considered as hypothetical.

Keywords: Landscape models; GIS; Digital elevation models

Publ.-Id: 24535

Geomorphic analysis of transient landscapes in the Sierra Madre de Chiapas and Maya Mountains (northern Central America): implications for the North American–Caribbean–Cocos plate boundary

Andreani, L.; Gloaguen, R.

We use a geomorphic approach in order to unravel the recent evolution of the diffuse triple junction between the North American, Caribbean, and Cocos plates in northern Central America. We intend to characterize and understand the complex tectonic setting that produced an intricate pattern of landscapes using tectonic geomorphology, as well as available geological and geophysical data. We classify regions with specific relief characteristics and highlight uplifted relict landscapes in northern Central America. We also analyze the drainage network from the Sierra Madre de Chiapas and Maya Mountains in order to extract information about potential vertical displacements.

Our results suggest that most of the landscapes of the Sierra Madre de Chiapas and Maya Mountains are in a transient stage. Topographic profiles and morphometric maps highlight elevated relict surfaces that are characterized by a low-amplitude relief. The river longitudinal profiles display upper reaches witnessing these relict landscapes. Lower reaches adjust to new base-level conditions and are characterized by multiple knickpoints.

These results backed by published GPS and seismotectonic data allow us to refine and extend existing geodynamic models of the triple junction. Relict landscapes are delimited by faults and thus result from a tectonic control. The topography of the Sierra Madre de Chiapas evolved as the result of (1) the inland migration of deformation related to the coupling between the Chiapas Massif and the Cocos forearc sliver and (2) the compression along the northern tip of the Central American volcanic arc. Although most of the shortening between the Cocos forearc sliver and the North American Plate is accommodated within the Sierra de Chiapas and Sierra de Los Cuchumatanes, a small part may be still transmitted to the Maya Mountains and the Belize margin through a "rigid" Petén Basin.


Publ.-Id: 24534

Room-temperature tetragonal non-collinear Heusler antiferromagnet Pt2MnGa

Singh, S.; D'Souza, S. W.; Nayak, J.; Suard, E.; Chapon, L.; Senyshyn, A.; Petricek, V.; Skourski, Y.; Nicklas, M.; Felser, C.; Chadov, S.

Antiferromagnetic spintronics is a rapidly growing field, which actively introduces new principles of magnetic storage. Despite that, most applications have been suggested for collinear antiferromagnets. In this study, we consider an alternative mechanism based on long-range helical order, which allows for direct manipulation of the helicity vector. As the helicity of long-range homogeneous spirals is typically fixed by the Dzyaloshinskii–Moriya interactions, bi-stable spirals (left- and right-handed) are rare. Here, we report a non-collinear room-temperature antiferromagnet in the tetragonal Heusler group. Neutron diffraction reveals a long-period helix propagating along its tetragonal axis. Ab-initio analysis suggests its pure exchange origin and explains its helical character resulting from a large basal plane magnetocrystalline anisotropy. The actual energy barrier between the left- and right-handed spirals is relatively small and might be easily overcome by magnetic pulse, suggesting Pt2MnGa as a potential candidate for non-volatile magnetic memory.

Publ.-Id: 24533

Implementing a Thomson parabola spectrometer for laser driven ions

Brack, F.-E.; Kraft, S.; Kroll, F.; Metzkes, J.; Obst, L.; Schlenvoigt, H.-P.; Zeil, K.; Schramm, U.

Durch die Fokussierung eines ultrakurzen und hochintensiven Laserpulses auf ein Festkörpertarget können Pulse von Protonen und anderen positiv geladenen Ionen erzeugt werden. Auf Basis des etablierten TNSA (target-normal sheath acceleration) Prozesses konnten am Helmholtz-Zentrum Dresden-Rossendorf mit dem 150 TW Ultrakurzpulslaser DRACO Protonenpulse mit Energien bis zu 20 MeV erzeugt und charakterisiert werden. Die Charakterisierung dieser Teilchenstrahlung erfordert die Identifizierung der Ionenspezies und die Bestimmung ihrer spektralen Verteilung möglichst nach jedem Puls, wofür standardmäßig Thomsonspektrometer verwendet werden.
In den letzten Jahren wurde das DRACO-Lasersystem bis zu einer Pulsleistung über 500 TW erweitert. Aufbauend auf dem bisherigen Spektrometerdesign wurde in dieser Arbeit ein kompaktes Spektrometer für einen höheren Energiebereich bis über 150 MeV entworfen und in Betrieb genommen. Zusätzlich wurde für die Identifizierung möglicher das Messergebnis verfälschender Sekundärstrahlungsquellen Monte-Carlo Simulationen durchgeführt.

  • Lecture (others)
    Annual Meeting of the LIGHT collaboration, 26.-27.09.2016, GSI Darmstadt, Deutschland

Publ.-Id: 24532

Preparation of Animal Irradiation Experiments with Laser-Accelerated Protons and Pulsed High-Field Magnets

Kroll, F.; Beyreuther, E.; Brack, F.; Karsch, L.; Kraft, S.; Pawelke, J.; Schlenvoigt, H.-P.; Schürer, M.; Zeil, K.; Schramm, U.

Particle therapy with energetic proton or heavy ion beams is considered as beneficial for a multitude of radiotherapy patients. The facility and operation costs as well as size and construction demands are considerably higher than for in-room radiotherapy systems based on generation of bremsstrahlung from an electron beam. Laser-acceleration has been considered a potential alternative for conventional accelerators like cyclotrons or synchrotrons and thus could provide a more compact and cost-efficient particle therapy solution in the future. The beam properties of laser accelerated beams strongly differ from the quasi-continuous beams generated by conventional accelerators. Laser accelerated beams exhibit fs to ps bunch length, carry up to 1013 particles with broad energy spectrum and are highly divergent. Furthermore, fluctuations of the said beam parameters on a shot-to-shot basis are inherent to the acceleration mechanism. Thus, special measures are required to make use of the novel particle source, especially considering the goal of a future medical application.

Pulsed high-field magnets, as also facilitated within the LIGHT collaboration, are a versatile and efficient way of shaping laser-accelerated beams both spatially and spectrally for application. Nevertheless, the bunches remain short and therefore intense, leading to high dose rates when stopped in matter. These dose rates make special demands for dosimetry and are a core aspect for radiobiological studies.

We performed experiments with the PW beam of the Draco laser to investigate the feasibility of worldwide first controlled volumetric tumour irradiations with laser-accelerated protons. Therefore, a setup of up to two solenoid magnets was used to efficiently capture and shape the beam, which was then analysed by means of spectrometer, electronic dosimeter and radiochromic film.

The talk will focus on reliable generation of homogeneous dose distributions lateral and in depth. Practical issues, like magnet repetition rate and stability, mean dose rate and future radiobiological challenges will be critically discussed. We will close with an outlook on the volumetric tumour irradiation study with specifically developed tumour model of LN229 cells, grown on the ears of nude mice. The radiobiological endpoint that will be investigated is the radiation induced tumour growth delay.

  • Lecture (others)
    Annual Meeting of the LIGHT collaboration, 26.-27.09.2016, GSI Darmstadt, Deutschland

Publ.-Id: 24531

Boat based mapping of geological features using 3D-Photogrammetry and hyperspectral imaging system (Case study: Greenland)

Salehi, S.; Jakob, S.; Vest Sørensen, E.

Artic environments provide a challenging ground for geological mapping and mineral exploration. Inaccessibility and harsh conditions complicate ground surveys and a dense cover of ice, vegetation, and lichens hinders supportive remote sensing surveys. Steep coastal cliffs are often the only accessible major outcrops, but are mostly not observable by air- or space-borne remote sensing data due to their off-nadir viewing angle. Former studies of those cliff sections focused on the manual interpretation of ground- or boat-based RGB images. However, detailed spectral and morphological data is missing, which is essential for common semi-automatic remote sensing data processing and interpretation of mineralogy and structures.
This contribution introduces an approach for photogrammetry and hyperspectral remote sensing of near-vertical cliff sections of geological outcrops in central west Greenland. A 3D image-based surface reconstruction technique is developed to enable a more automated outcrop evaluation. The focus lies hereby on the integration of digital photogrammetry with boat-based hyperspectral imaging to complement Digital Outcrop Models (DOM) with quantitative information about mineral variations in the outcrop. The project focuses on: 1) integration of hyperspectral images with the photogrammetry derived DOM´s, 2) geometric distortion correction of boat-based hyperspectral images, 3) extraction and mapping of geological features from close range hyperspectral images. The extreme off-nadir (nearly horizontal) scanning view and the resulting scan geometry need to be taken into account during processing. This contribution also highlights future possibilities for rapid semi-automatic interpretation of the data and advances in technology.
Our approach provides a promising workflow for off-nadir remote sensing campaigns in coastal artic environments including photogrammetry and hyperspectral imagery even in remote regions, which are only accessible by boat and can hardly be observed by classic geological mapping.

Keywords: Hyperspectral Remote Sensing; 3D-Digital Photogrammetry; Spectral Mapping

  • Lecture (Conference)
    GRSG 27th Annual Conference - Future of Geological Remote Sensing: Innovation and Challenges, 07.-09.12.2016, London, United Kingdom

Publ.-Id: 24530

Direct numerical simulation-based Reynolds-averaged closure for bubble-induced turbulence

Ma, T.; Santarelli, C.; Ziegenhein, T.; Lucas, D.; Fröhlich, J.

Budgets of the turbulent kinetic energy from direct numerical simulations (DNS) of disperse bubbly channel flows are used to develop a new model for bubble-induced turbulence in the Euler-Euler Reynolds-averaged framework.

Publ.-Id: 24529

Processing of Drone-Borne Hyperspectral Data for Geological Applications

Jakob, S.; Zimmermann, R.; Gloaguen, R.

Unmanned Aerial Systems (UAS) are used increasingly to close the gap between space- or airborne and field spectral data. They are able to provide high-resolution hyperspectral images within a short time. However, complex geometric and radiometric corrections are required. These correction steps are crucial, especially when the data should be used in geological applications such as detection of raw materials. Thus, in the following paper we present a new toolbox for processing drone-borne hyperspectral data. Processing steps comprise automatic co-registration, mosaicking and geo- referencing as well as topographic and illumination correction. For the first time we show the applicability of drone-borne hyperspectral data for geological surveys.

Keywords: hyperspectral data; Unmanned Aerial Systems; drone-borne remote sensing; processing toolbox; Acidic Mine Drainage

  • Lecture (Conference)
    8th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 21.-24.08.2016, Los Angeles, United States of America
  • Contribution to proceedings
    8th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 21.-24.08.2016, Los Angeles, United States of America
    DOI: 10.1109/WHISPERS.2016.8071689

Publ.-Id: 24528

Modelling of turbulence modulation in bubbly flows with the aid of DNS data

Ma, T.; Santarelli, C.; Ziegenhein, T.; Lucas, D.; Fröhlich, J.

Budgets of the turbulent kinetic energy from direct numerical simulations of disperse bubbly channel flows are used to develop a new model for bubble-induced turbulence in the Euler-Euler framework. Appropriate scales for the bubble-induced turbulence are determined and the corresponding source terms in the Shear Stress Transport Model are derived from the data. This yields a closure which can be readily used in many existing methods. The model is validated by dedicated Euler-Euler simulations.

  • Poster
    14th Multiphase Flow Conference and Short Course, 08.-10.11.2016, Dresden, Deuschland

Publ.-Id: 24527

Turbulence modelling in bubbly flows

Ma, T.

Different turbulence modelling approaches in bubbly flows is introduced.

  • Invited lecture (Conferences)
    The 25th annual meeting of GCPD, 01.-02.10.2016, Aachen, Deuschland

Publ.-Id: 24526

The twofold nature of Coulomb scattering in graphene

König-Otto, J. C.; Mittendorff, M.; Winzer, T.; Kadi, F.; Malic, E.; Knorr, A.; Berger, C.; de Heer, W. A.; Pashkin, A.; Schneider, H.; Helm, M.; Winnerl, S.

The ultrafast dynamics in graphene, which is of great interest from both a fundamental as well as an application oriented point of view, has been studied intensively during the last years and ascinating effects such as carrier multiplication have been found. Here we focus on the Coulomb scattering dynamics in the energetic vicinity of the Dirac point. Utilizing an optical anisotropy, we reveal the twofold nature of Coulomb scattering in graphene by polarization resolved pump-probe experiments. Coulomb scattering is the main mechanism that transforms an optical excited non-equilibrium carrier distribution into a thermalized one and dominates the initial carrier dynamics. Many publications report extremely fast Coulomb scattering rates and thermalization times in the order of tens of fs often only estimated because of limited time resolution in experiments. This is comprehensible as the linear band structure of graphene allows carriers to scatter along a line easily since this inherently fulfils energy and momentum conservation. However, in case of excitation with linearly polarized light, the initial carrier distribution is anisotropic in k space. This means thermalization needs also a redistribution in momentum direction additionally to the equilibration in energy. When scattering with optical phonons is suppressed by photo excitation at low energy, noncollinear Coulomb scattering is limiting the thermalization time to surprisingly long times (several ps) [1]. This contrasting behaviour, namely a fast equilibration in energy but a slow one in momentum space, is what we refer to as the twofold nature of Coulomb scattering in graphene.

[1] J. C. König-Otto, M. Mittendorff, T. Winzer, F. Kadi, E. Malic, A. Knorr, C. Berger, W. A. de Heer, A. Pashkin, H. Schneider, M. Helm, and S. Winnerl, Phys. Rev. Lett. 117, 087401 (2016).

Keywords: graphene; ultrafast dynamics; anisotropy; Coulomb scattering

  • Poster
    Workshop on Science of “From Matter to Materials and Life”, 14.-16.12.2016, Hamburg, Deutschland

Publ.-Id: 24525

Circular Economy Engineering - Metallurgy & its infrastructure are key enablers of a CE - Recycling towards Recycling 4.0

Reuter, M. A.

  • Circular Economy - SIMP
– System integrated metal production – SIMP
– Rigorous quantification of Resource Efficiency (RE)
  • Digitalization - Recycling 4.0
– Internet-of-Metallurgical-Things
– Link all stakeholders in material cycle
  • Circular Economy Engineering - CEE
– Metallurgical infrastructure & deep knowledge key
– Inform society in an understandable manner
  • Invited lecture (Conferences)
    Steel in Circular Economy / 3rd European Scientific Steel Panel, 29.04.2016, Düsseldorf, Deutschland

Publ.-Id: 24524

Four-Wave Mixing in Landau-Quantized Graphene

König-Otto, J. C.; Wang, Y.; Belyanin, A.; Berger, C.; de Heer, W. A.; Orlita, M.; Pashkin, A.; Schneider, H.; Helm, M.; Winnerl, S.

For Landau-quantized graphene, featuring an energy spectrum consisting of a series of nonequidistant Landau levels, theory predicts a giant resonantly-enhanced optical nonlinearity. We verify the nonlinearity in a time-integrated degenerate four-wave mixing (FWM) experiment in the mid-infrared spectral range, involving the Landau LL_{-1}, LL_{0} and LL_{1}. A rapid dephasing of the optically induced microscopic polarization on a timescale shorter than the pulse duration (~4 ps) is observed, while a complementary pump-probe experiment under the same experimental conditions reveals a much longer lifetime of the induced population. The FWM signal shows the expected field dependence with respect to lowest order perturbation theory for low fields. Saturation sets in for fields above ~6 kV/cm. Furthermore, the resonant behavior and the order of magnitude of the third-order susceptibility are in agreement with our theoretical calculations.

Keywords: Graphene; Landau-quantized graphene; THz; Spectroscopy; Dynamics; nonlinear Dynamics


Publ.-Id: 24523

Electronic transport in helium-ion-beam etched encapsulated graphene nanoribbons

Nanda, G.; Hlawacek, G.; Goswami, S.; Watanabe, K.; Taniguchi, T.; Alkemade, P. F. A.

We report the etching and electronic transport in nanoribbons of graphene sandwiched between atomically flat hexagonal boron nitride (h-BN). The etching of ribbons of varying width was achieved with a focused beam of 30 keV He+ ions. Using in-situ electrical measurements, we established a critical dose of 7000 ions nm−2 for creating a 10 nm wide insulating barrier between a nanoribbon and the rest of the encapsulated graphene. Subsequently, we measured the transport properties of the ion-beam etched graphene nanoribbons. Conductance measurements at 4 K show an energy gap, that increases with decreasing ribbon width. The narrowest ribbons show a weak dependence of the conductance on the Fermi energy. Furthermore, we observed power-law scaling in the measured current-voltage (I-V) curves, indicating that the conductance in the helium-ion-beam etched encapsulated graphene nanoribbons is governed by Coulomb blockade.

Keywords: Helium Ion Microsope; Graphene; h-BN; Bandgap; Graphene Nanoribbons; Electronic Transport

  • Open Access Logo Carbon 119(2017), 419-425
    DOI: 10.1016/j.carbon.2017.04.062
  • Invited lecture (Conferences)
    User Meeting Kleindiek, 25.-26.04.2017, Reutlingen, Deutschland
  • Lecture (Conference)
    FOR3NANO, 25.-30.06.2017, Helsinki, Finland

Publ.-Id: 24522

Evaluation of GENTOP concept for the buoyancy-driven motion of a single bubble

Schlegel, F.; Gauß, F.; Krepper, E.; Lucas, D.

Different approaches for numerical simulations of multiphase flows have been developed, e.g., Volume-of-Fluid methods (VoF) for free surface flows and Euler-Euler (EE) methods for disperse flows. Nevertheless, most industrial applications involve interfacial structures, which have different morphologies. Therefore, hybrid approaches combining resolved interfaces between the gaseous and liquid phases with EE methods would be desirable. A recent development with promising results is the GENTOP concept (Hänsch et al., 2012), which is based on the multi-fluid concept and statistically resolved interfaces that are formed by a separate liquid and gas phase. The present contribution investigates the differences between VoF methods and the GENTOP framework using the example of a buoyancy-driven motion of a single bubble. Different CFD solvers are compared as well as different density ratios, Eötvös numbers, Morton numbers and grid resolutions. Finally, all results are checked against experiments and data obtained by more advanced methods, e.g., level-set methods. For instance is known from one-fluid approaches (e.g. VoF) that at least 20 – 30 cells per bubble diameter are required to reflect the bubble motion sufficiently. Despite a much coarser grid resolution, GENTOP shows a good agreement with experimental results.

  • Lecture (Conference)
    ICMF 2016 International Conference on Multiphase Flow, 22.-27.05.2016, Florenz, Italien

Publ.-Id: 24521

Programmability of Co-antidot lattices of optimized geometry

Schneider, T.; Langer, M.; Alekhina, J.; Kowalska, E.; Oelschlägel, A.; Semisalova, A.; Neudert, A.; Lenz, K.; Potzger, K.; Kostylev, M. P.; Fassbender, J.; Adeyeye, A. O.; Lindner, J.; Bali, R.

Programmability of stable magnetization configurations in a magnetic device is a highly desirable feature for a variety of applications, such as in magneto-transport and spin-wave logic. Periodic systems such as antidot lattices may exhibit programmability; however, to achieve multiple stable magnetization configurations the lattice geometry must be optimized. We consider the magnetization states in Co-antidot lattices of ≈ 50 nm thickness and ≈ 150 nm inter-antidot distance. Micromagnetic simulations were applied to investigate the magnetization states around individual antidots during the reversal process. The reversal processes predicted by micromagnetics were confirmed by experimental observations. Magnetization reversal in these antidots occurs via field driven transition between 3 elementary magnetization states – termed G, C and Q. These magnetization states can be described by vectors, and the reversal process proceeds via step-wise linear operations on these vector states. Rules governing the co-existence of the three magnetization states were empirically observed. It is shown that in an n × n antidot lattice, a variety of field switchable combinations of G, C and Q can occur, indicating programmability of the antidot lattices.

Keywords: Magnetic devices; Periodic systems; Antidot lattices; Magnetization reversal

Publ.-Id: 24519

Laser-driven formation of transient local ferromagnetism in FeRh thin films

Ünal, A. A.; Parabas, A.; Arora, A.; Ehrler, J.; Barton, C.; Valencia, S.; Bali, R.; Thomson, T.; Yildiz, F.; Kronast, F.

The magnetic phase transition from antiferromagnetic to ferromagnetic order in FeRh can be induced globally by heating the material above its phase transition temperature, applying mechanical strain or magnetic fields. To induce this phase transition locally requires a confined source of energy such as a focused laser beam. Here we combine optical excitation with X-ray magnetic imaging to determine the effect of laser heating on the magnetization of FeRh using time-resolved photoelectron emission microscopy. Excitation by a 100 fs laser pulse generates a ferromagnetic state within 0.6 ns which recovers its initial antiferromagnetic state within a further 2 ns. The form of magnetic domains during the growth and disappearance of magnetization suggests an intrinsic speed limit for magnetic and structural changes.


Publ.-Id: 24518

Positive magnetic patterning using ion beams – principles and device applications

Bali, R.; Hlawacek, G.; Liersch, V.; Röder, F.; Wintz, S.; Semisalova, A.; Fassbender, J.

Magnetic data-storage, spintronic and magnonic devices have driven the need for producing well-defined nanoscale magnets of complex geometries. We show how ion-beams can be used to generate nanomagnets in thin films of certain alloys such as B2 ordered Fe60Al40 and Fe50Rh50.[1,2] In these materials a large increase of the saturation magnetization is achieved by inducing subtle atomic displacements caused by collision cascades of penetrating light ions. The ions knock atoms from their ordered sites, generating antisite defects and causing an increase of the Fe-Fe nearest-neighbour interactions which are linked to the increasing magnetization. For instance, a weak magnetization of 0.04 μB per Fe-atom in B2-Fe60Al40 can be increased to 1.67 μB per Fe-atom by the irradiation of light noble gas ions such as He+ or Ne+.
The above ion-induced increase of magnetization can be manifested at the local scale and is termed positive magnetic patterning. Patterning can be performed either by irradiation through lithographed masks,[1] or by a direct writing process using the highly focused ion-beam of a Gas Field Ion-Source.[3] Lateral magneto-resistive devices and magnetic arrays produced by ion-irradiation will be described. The application of ion-assisted magnetic writing opens vast opportunities not only in the field of nanomagnetism and devices, but also in the study of disorder-induced magnetic phase transitions at the nanoscale.
[1] R. Bali et al., Nano Letters (2014) 14 435.
[2] A. Heidarian et al., Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms (2015) 358 251.
[3] F. Röder et al., Scientific Reports (2015) 5 16786.

  • Lecture (Conference)
    20th International Conference on Ion Beam Modification Of Materials, 30.10.-04.11.2016, Wellington, New Zealand
  • Invited lecture (Conferences)
    603. WE-Heraeus-Seminar: Magnonics – Spin Waves Connecting Charges, Spins and Photons, 06.-08.01.2016, Bad Honnef, Germany

Publ.-Id: 24517

Digitalizing the Circular Economy-System-Integrated-Material-Production

Reuter, M. A.

Metals have always been a pillar of society. Presently more so than ever, as they are key to enabling our sustainability aspirations. The complex Web of Metals (WoM) is the crucial basis for enabling a sustainable Circular Economy (CE) society. Digitalization and quantification of the WoM (or Internet-of-Metallurgical-Things (IoMT)) are keys to driving CE innovation. Examples of specialized technology and flow sheet needs are presented with consideration given to a “whole of chain” or Systems-Integrated-Metal-Production (SIMP) approach. Examples enabling SIMP include: system, metallurgical process and reactor simulation (e.g. CFD, thermodynamics, flowsheeting, LCA), big data analysis (AI, black box techniques), process control, Design for Recycling/Sustainability, etc. Also outlined are the challenges facing legislators who need to consider the balance between providing our societal sustainability needs with key baseline technology infrastructure requirements for economically viable valuable metals extraction from resources flowing within society. Digitalization enables the IoMT of a CE.

  • Invited lecture (Conferences)
    Distinguished Lecturer Award, 16.02.2016, Nashville, USA

Publ.-Id: 24516

Simulation of Boil-off Scenarios in Spent Fuel Pools

Oertel, R.; Hanisch, T.; Krepper, E.; Lucas, D.; Rüdiger, F.

The thermo-hydraulic analysis of Spent Fuel Pool accident scenarios is predominantly carried out using one-dimensional codes, based on simplified assumptions for the flow paths around the storage racks and inside the reactor building. Here, CFD is employed to investigate these convective phenomena in order to study their relevance for the cooling of the individual fuel assemblies. A partial exposure of the fuel assemblies is anticipated.

  • Invited lecture (Conferences)
    Fachtagung der KTG-Fachgruppen, 17.-18.11.2016, Eggenstein-Leopoldshafen, Deutschland

Publ.-Id: 24515

Mountain rivers may need centuries to adjust to earthquake-triggered sediment pulses, Pokhara, Nepal

Stolle, A.; Korup, O.; Schwanghart, W.; Bernhardt, A.; Adhikari, B. R.; Andermann, C.; Wittmann-Oelze, H.; Merchel, S.

Mountain rivers respond to strong earthquakes by not only adjusting to changes in local base level, but also by rapidly aggrading to accommodate excess sediment delivered by co- and post-seismic landslides. A growing number of detailed sediment budgets suggests that it takes rivers several years to decades to recover from such seismic disturbances, depending on how recovery is defined. We test this notion and study how rivers adjusted to catastrophic sedimentation triggered by at least three medieval earthquakes in the central Nepal Himalaya. In the vicinity of Pokhara, the nation’s second largest city, rapid aggradation formed a large fan covering 150 km2 of mountainous terrain over a length of some 70 km. The fan prograded into several tributary valleys, rapidly infilling their lower reaches with several tens of meters of sediment from a major point source tens of kilometers away. A robust radiocarbon chronology of these valley fills provides an ideal framework for gauging average rates of fluvial incision and adjustment. We use high-resolution digital elevation data, geodetic field surveys, aerial photos documenting historic channel changes, and several re-exhumed tree trunks in growth position to define dated geomorphic marker surfaces. We compare various methods of computing the volumes lost from these surfaces to arrive at net sediment yields averaged over decades to centuries. We find that contemporary rates of river incision into the medieval earthquake debris are between 160 and 220 mm yr–1, with corresponding sediment yields of 103 to 105 t km–2 yr–1, several hundred years after the last traceable seismic disturbance. These rates greatly exceed the density-adjusted background rates of catchment-wide denudation inferred from concentrations of cosmogenic 10Be in river sands sampled in different tributaries. The lithological composition of active channel-bed load differs largely from local bedrock and confirms that rivers are still busy with excavating medieval valley fills. Pronounced knickpoints and epigenetic gorges at tributary junctions add to the picture of a drawn-out fluvial response, while the re-exhumed tree trunks indicate that some distal portions of the earthquake-derived sediment wedge have been incised to near their base. Our results challenge the notion that mountain rivers recover within years or even decades following earthquake disturbance. We caution against generalizing the spectrum of fluvial response in this context, as the valley fills around Pokhara document the possibility of a more protracted fluvial response that may have been ongoing for as long as 900 years despite the high and aggressive erosion that characterizes Himalayan rivers. Beyond the scientific community, our results may motivate some rethinking of post-seismic hazard appraisals and infrastructural planning during the rehabilitation phase in earthquake-struck regions.

Keywords: AMS; landslides; earthquake; Nepal; Himalalya

  • Poster
    European Geosciences Union (EGU) General Assembly, 23.-28.04.2017, Vienna, Austria

Publ.-Id: 24514

CFD Simulation of Spent Fuel Pool Accidents resulting in partially uncovered Fuel Assemblies

Oertel, R.; Krepper, E.; Lucas, D.

The thermal-hydraulic analysis of Spent Fuel Pool accident scenarios is predominantly carried out using one-dimensional system or severe accident codes. Within these codes, very simplified assumptions are made for the flow paths around the storage racks and inside the reactor building. This work presents CFD simulations which deliver a more detailed insight into these convective phenomena, given the scenario of partially uncovered fuel assemblies. It is shown that the spatial distribution of the fuel assemblies in the pool with respect to their decay heat production plays a subordinate role in the development of the large scale flow paths in the pool atmosphere.

  • Contribution to proceedings
    47th Annual Meeting on Nuclear Technology (AMNT 2016), 10.-12.05.2016, Hamburg, Deutschland
  • Invited lecture (Conferences)
    47th Annual Meeting on Nuclear Technology (AMNT 2016), 10.-12.05.2016, Hamburg, Deutschland

Publ.-Id: 24513

Digitalizing the Circular Economy - The role of process metallurgical systems

Reuter, M. A.

Metallurgy is a key enabler of a Circular Economy (CE), its digitalization the metallurgical Internet-of-Things (m-IoT). In short: Metallurgy is at the heart of a CE as metals all have strong intrinsic recycling potentials.Process metallurgy as a key enabler for a CE will help much to deliver its goals. The first principles models of process engineering help quantify the Resource Efficiency (RE) of the CE system, connecting all stakeholders via digitalization. This provides well-argued and first principles environmental information to empower tax paying consumer society, policy, legislators and environmentalists. It provides the details to detail Capital and Operational Expenditure (CAPEX & OPEX) estimates. Through this path the opportunities and limits of a CE, recycling and its technology can be estimated. The true boundaries of sustainability can be determined in addition to the techno-economic evaluation of RE.The digital integration of metallurgical reactor technology and systems, not only on one site but linking different sites globally via hardware, is the basis for describing CE systems as dynamic feedback control loops i.e. the metallurgical Internet of Things (m-IoT). It is the linkage of the global carrier metallurgical processing system infrastructure, that maximizes the recovery of all minor and technology elements in its associated refining metallurgical infrastructure. This will be illustrated through:

System optimization models for multi-metal metallurgical processing. These map large scale m-IoT systems, which link to Computer Aided Design (CAD) tools of the Original Equipment Manufacturers (OEMs), and then establish a recycling index (RI) through the quantification of RE.
Reactor optimization and industrial system solutions to realize the “CE (within a) Corporation - CEC”; realizing the CE of society.
Real-time measurement of ore and scrap properties in intelligent plant structures, linked to the modelling, simulation and optimization of industrial extractive process metallurgical reactors and plants for both primary and secondary materials processing.
Big-data analysis and process control of industrial metallurgical systems, processes and reactors by the application of among others artificial intelligence (AI) techniques and computer aided engineering (CAE).
Minerals processing and process metallurgical theory, technology, simulation and analytical tools, which are all key enablers of the CE.
Visualizing the results of all the tools used for estimating the RE of the CE system in a form that the consumer and general public can understand.
The smart integration of tools and methods that quantify RE and deliver sustainable solutions, named in this paper Circular Economy Engineering (CEE).

  • Invited lecture (Conferences)
    Fostering a synergistic environment in engineering simulation, 17.-18.10.2016, Parma, Italien

Publ.-Id: 24512

A multi-field two-fluid concept for the simulation of two-phase flow regime transitions

Oertel, R.; Schlegel, F.; Ziegenhein, T.; Lucas, D.

Multiphase flows feature a range of regimes, which can roughly be categorized into disperse and segregated flows. The past research in the simulation of multiphase flows mainly focused on establishing methods that are appropriate within a well-defined regime. This work aims at the development of a framework for the simulation of multiphase flows with largely varying interfacial length scales, allowing the simulation of flow regime transitions. The basis forms the Euler-Euler concept, which is widely accepted for the simulation of disperse flows and allows for coarse computational meshes. It is also capable to handle complete phase inversion as in stratified flows. In vertical two-phase pipe flow, small disperse elements may exist alongside larger gas structures. The goal of this work is to formulate a hybrid solution procedure which allows treating the former in terms of a probability density and the latter in an interface-resolving manner. The development of the method is conducted using the open source CFD toolbox OpenFOAM.

  • Lecture (others)
    Vortrag im Rahmen eines Gastaufenthaltes am Paul-Scherrer-Institutes, 02.12.2016, Villigen, Schweiz

Publ.-Id: 24511

Developing Rapid and Advanced Visualisation of Magnetic Structures Using 2-D Pixelated STEM Detectors

Nord, M.; Krajnak, M.; Bali, R.; Hlawacek, G.; Liersch, V.; Fassbender, J.; Mcvitie, S.; Paterson, G. W.; Maclaren, I.; Mcgrouther, D.

In Transmission Electron Microscopy (TEM) electron diffraction patterns, imaged from the back focal plane of the objective lens, reveal rich information about the structure of materials. The sharpest patterns are obtained using a parallel (semi-convergence angle < 1 mrad) electron beam which typically illuminate an area with a diameter of 100 nm. In Scanning Transmission Electron Microscopy (STEM) the electron beam is focused to form a fine probe, potentially with sub-Ångström diameter, where image signals are collected by detectors which integrate single intensity values for each scan position from two-dimensional scattering in the back focal plane. A key aspect to obtaining high resolution information is that the performance of scanning and detection should be performed rapidly in order to provide live imaging for the user but to also to mitigate for instabilities and specimen drifts.

Recently, advances in fast direct electron counting systems have enabled the development of 2-D pixelated detectors that can operate at fast acquisition speeds. Applying these to the STEM technique enables imaging of the contents of the back focal plane at high frame rates, i.e. the full diffraction pattern can be acquired for every scan position in a STEM dataset. This yields a 4 dimensional dataset: two spatial probe position dimensions, and two reciprocal detector positions. While this opens up many new and exciting research avenues, there are still many challenges in how to use the 4-D datasets optimally. In this work we focus on solutions for performing live or near-live magnetic imaging using a fast pixelated STEM detector. The experimental work was performed on a probe corrected Jeol ARM200cF equipped with a Medipix3 fast pixelated detector capable of acquiring at 1100 frames per second. To image magnetic induction in the materials the STEM was operated in Lorentz mode[1], which involves turning off the objective lenses so that the sample resides in a near field free environment. A custom aberration corrector mode was utilised to enable probe semi-convergence angles from 0.4-3.0 mrad with corresponding probe diameters from < 1 nm to 6 nm[1]. For magnetic samples, the Lorentz interaction with the beam results in electron wave phase changes and beam deflections proportional to the magnetic induced phase gradients across the sample. Using a pixelated detector the direction and strength of the integrated magnetic induction for the sample can be quantitatively measured by tracking the angular deflection of the bright field disc. This presentation will focus on solutions for live imaging of magnetic structures in FeAl thin films patterned with Ne + ions, shown in Fig. 1. An example of magnetic contrast is shown in (c-h), where the areas within the circle (seen in Fig 1a) are ferromagnetic, while the area outside is paramagnetic. The light and dark magnetic contrast is due to deflection of the electron beam, and the figures show two different methods for extracting this deflection. In (c-f), only a single pixel at the edge of the STEM disk is used from each diffraction pattern, with the different figures having the pixel at different places on the disk (marked by the points in (b)). For (g-h), a more advanced edge detection is performed. Here, cross correlation is used to determine the position of the disk. As seen in Fig. 1(g-h), the edge detection techniques clearly produce increased level of magnetic contrast and better signal to noise, but is much more computationally demanding. Thus for live imaging, the more simple method is more suited.

We will also show how offloading the data processing to central and graphical processing units allows for rapid processing with different methods. This includes the single pixel and edge detection methods explained above, as well as centre of mass methods. Lastly, the output data is transferred into Digital Micrograph using open and standard network components, which enables both control of the detector system and live imaging to be performed on a single machine. The presentation will also touch on file formats chosen for data storage and ways of visualising the 4-D datasets.

[1] S. McVitie, et al, “Aberration corrected Lorentz scanning transmission electron microscopy”, Ultramicroscopy, Volume 152, May 2015, Pages 57-62

  • Lecture (Conference)
    Microscopy & Microanalysis 2016 Meeting, 24.-28.07.2016, Columbus, Ohio, USA
  • Open Access Logo Microscopy and Microanalysis 22(2016)S3, 530-531
    DOI: 10.1017/S1431927616003500


Publ.-Id: 24510

Evolution of the local environment and magnetism in Fe60Al40 films under Ne+ irradiation

Smekhova, A.; La Torre, E.; Eggert, B.; Cöster, B.; Szyjka, T.; Walecki, D.; Salamon, S.; Ollefs, K.; Bali, R.; Lindner, J.; Rogalev, A.; Weschke, E.; Banerjee, R.; Sanyal, B.; Schmitz-Antoniak, C.; Wende, H.

X-ray absorption spectroscopy has been applied to study the consequential changes of the local environment around Fe and its magnetic moments in Fe60Al40 thin films of 40 nm thickness along the order-disorder (B2 → A2) phase transition initiated by 20 keV Ne+ ion-irradiation with fluences of (0.75-6)×1014 ions*cm−2. The analysis of EXAFS spectra measured at the Fe K-edge at room temperature revealed an increased number of Fe-Fe nearest-neighbors from 3.47(7) to 5.0(1) and ∼ 1% of volume expansion through the transition. The visualization of the Fe and Al nearest-neighbours rearrangement in the first coordination shell of Fe absorbers was done by wavelet transformations. The observed structural changes will we related to the magnetic properties of the studied samples. The results of self-consistent DFT calculations using VASP and SPR-KKR program packages on relaxed Fe60Al40 structures are consistent with the experimental findings for the ordered (B2) and the disordered (A2) phases.

  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Germany
  • Lecture (Conference)
    DPG-Tagungen 2018, 12.-16.03.2018, Berlin, Deutschland
  • Lecture (Conference)
    9th Joint European Magnetic Symposia (JEMS) Conference 2018, 03.-07.09.2018, Mainz, Deutschland
  • Contribution to proceedings
    2018 IEEE International Magnetic Conference (INTERMAG), 23.-27.04.2018, Singapore, Singapore
    Proceedings of the 2018 IEEE International Magnetic Conference (INTERMAG): IEEE
    DOI: 10.1109/INTMAG.2018.8508108

Publ.-Id: 24509

A generalized multi-field two-fluid concept for the numerical simulation of two-phase flows

Oertel, R.; Schlegel, F.; Ziegenhein, T.; Lucas, D.

Multiphase flows occur in a variety of industrial applications, e.g. in chemical engineering or in nuclear safety research. An important feature of these flows is the formation of different flow patterns depending on the relative flow rates of the phases. These patterns are not explicitly defined by the conduit and have different characteristics. Past research on the simulation of multiphase flows mainly focused on establishing methods that are appropriate within a well-defined flow regime. The present contribution aims at the development of a generalized framework in OpenFOAM for the simulation of industrial scale multiphase flows with largely varying interfacial length scales, which has the capability to reproduce the mechanisms of flow pattern transitions. For the simulation of disperse flows, the two-fluid approach, where each phase is represented by its own phase-averaged velocity field, is widely accepted.
This concept serves as a basis and is extended to allow interface-resolving simulations for large gas structures, while disperse phase elements are still represented in terms of a number density function.

The present contribution focuses on two parts. Firstly, one feature of multiphase flow pattern transitions is the inherent polydispersity of the occurring gas structures. The difference in diameter between the smallest and the largest elements spans over at least one order of magnitude. In general, this aspect is taken into account by population balance modeling. A successful and stable method for this purpose is the method of classes which will be utilized here, following the ideas of the GENTOP-approach of Hänsch et al. (2012). Since lift-force induced separation of bubbles according to their size is considered as an important mechanism for the transition from bubbly to slug flow, particular emphasis is put on employing a class method which also takes different velocity fields for the disperse phase into account.

The second part focuses on the handling of interface-resolving gas structures within the two-fluid model. Beside the aspect of interface sharpening to counteract the numerical diffusion, the momentum exchange between the separate velocity fields is important. In reality, the phases share a single velocity field and a no-slip condition is present at the interface. This condition can also be met in a two-fluid model by forcing the velocity of the two phases to be equal at interface. However, as such a method requires a high grid resolution, we introduce a direction depended model for the momentum exchange at the interface, that accounts separately for pressure and friction induced drag. Finally, the presented framework allows the simulation of multiphase flow problems close to an industrial scale and gives realistic predictions, even on a coarse grid.

Haensch, S.; Lucas, D.; Krepper, E. & Hoehne, T. A multi-field two-fluid concept for transitions between different scales of interfacial structures, International Journal of Multiphase Flow, 2012, 47, 171-182

  • Invited lecture (Conferences)
    4th Annual OpenFOAM User Conference 2016, 11.-13.10.2016, Köln, Deutschland

Publ.-Id: 24508

An elementspecific investigation of the disorder induced phase transition in Fe60Al40 thin films driven by ion irradiation

Eggert, B.; La Torre, E.; Szyjka, T.; Smekhova, A.; Bali, R.; Ollefs, K.; Salamon, S.; Wilhelm, F.; Bannerjee, R.; Rogalev, A.; Weschke, E.; Lindner, J.; Sanyal, B.; Schmitz-Antoniak, C.; Wende, H.

Chemically ordered Fe60Al40 in the B2 structure presents a paramagnetic ordering, while the chemical disordered phase with the A2 structure exhibits a ferromagnetic state. This phase transition leads to a change of the effective number of nearest Fe neighbors [1] and of the lattice constant [2]. This phase transition can be driven by ion irradiation [3]. In this work we investigate Fe60Al40 thin films before and after 20 keV Ne+ irradiation by means of x-ray magnetic circular dichroism (XMCD) at the Fe L2,3- and K-edge to analyze the microscopic magnetic structure. For a comparison macroscopic magnetometry was used concerning the depth-profile of the induced magnetism [1]. These results are correlated to the modified structural properties.

  • Poster
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Germany

Publ.-Id: 24507

Ein Eckstein der Industrie 4.0

Reuter, M. A.

Seit vielen Jahrhunderten ist Freiberg weltweit führend in den Bereichen Bergbau, Aufbereitung und Metallurgie. Heute spielt die Stadt außerdem eine wichtige, innovative Rolle in der nachhaltigen Rohstoffnutzung. Ein maßgeblicher Schlüssel für eine nachhaltige Nutzung der Rohstoffe wird unter dem Begriff „Industrie 4.0“ zusammengefasst, zu deren Kernbausteinen die Prozessmetallurgie sowie ihre Digitalisierung gehören.

Der Vortrag beschreibt die Rolle Freibergs in der Gestaltung einer nachhaltigen Kreislaufwirtschaft mit dem Ziel, Energie- und Ressourceneffizienz miteinander in Einklang zu bringen.

  • Lecture (Conference)
    19th-krueger-colloquium, 09.06.2016, Freiberg, Deutschland

Publ.-Id: 24506

Ferromagnetism of Fe60Al40 thin films under a magnifying glass of hard X-rays

Smekhova, A.; Eggert, B.; Cöster, B.; La Torre, E.; Szyjka, T.; Ollefs, K.; Bali, R.; Potzger, K.; Cornelius, S.; Liedke, M. O.; Lindner, J.; Salamon, S.; Rogalev, A.; Wende, H.

Формирование дальнего ферромагнитного порядка в сплавах FeAl, наведенного химическим разупорядочением кристаллической решетки, интенсивно исследуется в течение более 40 лет [1]. В настоящее время это явление успешно используется для создания магнитных структур на основе тонких пленок Fe60Al40 с контролируемыми магнитными свойствами [2], приготовленных при помощи технологии ионного облучения. Однако до сих пор вопрос о наиболее существенной причине возникновения этого эффекта –локального окружения атомов железа [3] и/или изменений параметров решетки [4] – остается открытым.
В нашей работе методами элементно-селективной спектроскопии поглощения EXAFS и XMCD в жесткой рентгеновской области исследовались тонкие пленки Fe60Al40 (40 нм)/SiO2/Si, приготовленные при помощи магнетронного напыления с последующим отжигом и облучением ионами Ne+ с энергией 20 кэВ как предложено в [2]. Предварительные XRD, MOKE и VSM магнетометрия показали, что облучение ионами разрушает химическое упорядочение в системе при сохранении структурной целостности, и что химически разупорядоченная А2 фаза обладает дальним ферромагнитным порядком, в то время как упорядоченная B2 фаза является парамагнитной.
Анализ EXAFS и XMCD спектров, измеренных на К крае поглощения Fe при комнатной температуре, показал, что увеличение химического беспорядка, обусловленного дозой облучения, ведет к кардинальному изменению ближайшего локального окружения атомов железа с преимущественным расположением атомов Fe в качестве ближайших соседей и к увеличению степени магнитной поляризации 4p состояний железа, определяющей его ор- битальный момент. Вопрос о природе поляризации 4р состояний обсуждается.
Измерения на ESRF были проведены в рамках проекта НС-1811 на линии ID12
1. G. P. Huffman et al., J.Appl. Phys. 38, 735 (1967).
2. R. Bali et al., Nano Lett. 14, 435 (2014).
3. L. Zamora et al., Phys. Rev. B 79, 094418 (2009).
4. J. Nogués et. al., Phys. Rev. B 74, 024407 (2006).

  • Invited lecture (Conferences)
    50th School PNPI condensed matter physics, 14.-19.03.2016, St. Petersberg, Russian Federation

Publ.-Id: 24505

Magnetism and structural changes in Fe60Al40 films under Ne+ irradiation

Smekhova, A.; Szyjka, T.; Eggert, B.; Cöster, B.; La Torre, E.; Walecki, D.; Salamon, S.; Ollefs, K.; Bali, R.; Lindner, J.; Rogalev, A.; Weschke, E.; Banerjee, R.; Sanyal, B.; Schmitz-Antoniak, C.; Wende, H.

XANES, EXAFS and XMCD techniques have been applied to probe substantial changes in Fe magnetic moments and the local environment in Fe60Al40 films along the order-disorder phase transition caused by Ne+ irradiation of different fluence and energies. An increased magnetic polarization, drastic changes of coercivity, a rearrangement in the expanded unit cell and structural distortions were observed.

  • Poster
    Eighth Joint BER II and BESSY II User Meeting, 07.-09.12.2016, Berlin, Germany

Publ.-Id: 24504

Driving properties of magnetic nanostructures

Mazalski, P.; Kisielewski, J.; Jakubowski, M.; Kurant, Z.; Tahir, N.; Bali, R.; Wojciechowski, T.; Sveklo, I.; Fassbender, J.; Wawro, A.; Spiridis, N.; Maziewski, A.

No abstract available.

  • Poster
    European XFEL Users' Meeting 2016, 27.-29.12.2016, Hamburg, Germany

Publ.-Id: 24503

Life Cycle Assessment of Metallurgical Processes Based on Physical Flowsheet Models

Scheidema, M.; Reuter, M. A.; Roine, A.

Simulation combined with Life Cycle Assessment (LCA) can be used to quantify the environmental impact of metals production processes. The results for different processing options, as well as the effect of having the same plant at different locations can be evaluated and compared. HSC SIM 8, which is linked with GaBi, or other LCA software can be used to carry out this work. The material flows are calculated using HSC SIM, and they are then converted to environmental indicators. The refining of silver using the High Current Density (HCD) electrorefining process is used as an example in this paper in order to show the link between simulation software and LCA.

Keywords: Process Modeling; Environmental Footprints; LCA; Recycling

  • Book chapter
    Apelian, D., Blanpain, B., Howarter, J., Kvithyld, A., Meskers, C., Mishra, B., Olivetti, E., Spange: REWAS 2016, Schweiz: Springer International Publishing, 2016, 978-3-319-48768-7, 179-185
    DOI: 10.1007/978-3-319-48768-7_26

Publ.-Id: 24502

Eco-efficiency indicator framework implemented in the metallurgical industry: part 1 - a comprehensive view and benchmark

Rönnlund, I.; Reuter, M. A.; Horn, S.; Aho, J.; Päällysaho, M.; Ylimäki, L.; Pursula, T.

The purpose of this work was to develop an indicator framework for the environmental sustainability benchmarking of products produced by the metallurgical industry. Sustainability differentiation has become an important issue for companies throughout the value chain. Differentiation is sometimes not attainable, due to the use of average data, lack of comparative data, certain issues being overshadowed by others, and a very narrow palette of indicators dominating the current sustainability assessments. There is a need for detailed and credible analyses, which show the current status and point out where improvements can be made. The indicator framework is developed to give a comprehensive picture of eco-efficiency, to provide methods that enable relevant comparisons as well as the tools for communicating the results. In this way, the methodology presented in this study aims to make differentiation easier and thus aid companies in driving the development toward more sustainable solutions.

The framework is based on the existing indicator framework Gaia Biorefiner, which is primarily intended for bio-based products. In this work, the framework was further developed for application in the metallurgical industry. The indicator framework is built by first looking at the issues, which are critical to the environment and global challenges seen today and which the activities of the metallurgical industry may have an impact on. Based on these issues, suitable indicators are chosen if they exist and built if they do not. The idea is that all indicators in a group form a whole, showing areas of innovation while refraining from aggregating and weighting, which often compromise a comprehensive and objective view. Both qualitative and quantitative indicators are included. The indicators are constructed following the criteria set by the EU and OECD for building indicators. Each indicator further has a benchmark. The rules for building the benchmark are connected to the indicators. Suitable data sources and criteria for the benchmark and the indicators are gathered from literature, publicly available databases, and commercial LCA software. The use of simulation tools for attaining more reliable data is also studied.
Results and discussion

The result is a visual framework consisting of ten indicator groups with one to five indicators each, totaling up to 31 indicators. These are visualized in a sustainability indicator “flower.” The flower can be further opened up to study each indicator and the reasons behind the results. The sustainability benchmark follows a methodology that is based on utilization of baseline data and sustainability criteria or limits. A simulation approach was included in the methodology to address the problem with data scarcity and data reliability. The status of the environment, current production technologies, location-specific issues, and process-specific issues all affect the result, and the aim of finding relevant comparisons that will support sustainability differentiation is answered by a scalable scoping system.

A new framework and its concise visualization has been built for assessing the eco-efficiency of products from the metallurgical industry, in a way that aims to answer the needs of the industry. Since there is a baseline, against which each indicator can be benchmarked, a sustainability indicator “flower” can be derived, one of the key innovations of this methodology. This approach goes beyond the usual quantification, as it is also scalable and linked to technology and its fundamental parameters. In part 2, a case study “A case study from the copper industry” tests and illustrates the methodology.

Keywords: Benchmarking; Circular economy; Indicator; Metallurgy; Process and system simulation; Product environmental footprint; Resource efficiency; Sustainability

Publ.-Id: 24500

Linking dissipation-induced instabilities with nonmodal growth: The case of helical magnetorotational instability

Mamatsashvili, G.; Stefani, F.

The helical magnetorotational instability is known to work for resistive rotational flows with comparably steep negative or extremely steep positive shear. The corresponding lower and upper Liu limits of the shear are continuously connected when some axial electrical current is allowed to flow through the rotating fluid. Using a local approximation we demonstrate that the magnetohydrodynamic behavior of this dissipation-induced instability is intimately connected with the nonmodal growth and the pseudospectrum of the underlying purely hydrodynamic problem.


Publ.-Id: 24499

Phased Array Ultrasound System for Planar Flow Mapping in Liquid Metals

Mäder, K.; Nauber, R.; Galindo, V.; Beyer, H.; Büttner, L.; Eckert, S.; Czarske, J.

Research in magnetohydrodynamics (MHD) aims at a better understanding of the interaction of conductive fluids and time-varying magnetic fields. Controllable magnetic fields can be used to optimize flows in technical and industrial processes involving liquid metals in order to improve quality and yield. However, necessary experimental studies for the investigations on physical models at room temperature are often limited by the performance of flow instrumentation for opaque liquids. With the phased array ultrasound Doppler velocimeter (PAUDV) we present a modular research platform for flow mapping in liquid metals. It consists of a modular electronics unit capable to interface ultrasound arrays with up to 256 channels. Each channel can be individually configured regarding the excitation pattern (three-level quantization, 64 samples) and the delay (1.6 ns resolution). With the individual addressing of channels the phased array technique to dynamically focus the ultrasound beam can be employed. This allows to resolve smaller flow structures in planar measurements compared to fixed-beam sensors. In addition, it enables the use of receive beamforming and plane wave transmission, which allows to significantly increase the time resolution and to perform 2d flow mapping with only one acoustical access via the cross beam technique. Fast electrical traversing of the measurement volume allows to obtain and visualize turbulence statistics. The capabilities of this research platform are demonstrated on measurements in the alloy gallium-indium-tin at room temperature. 2d velocity measurements of a flow in a cubic vessel influenced by a rotating magnetic field (RMF) are shown and compared to results of a semi-analytical simulation. Furthermore, two-point correlation functions of the velocity field for different magnitudes of the RMF are presented and discussed.

Keywords: Ultrasound Velocimeter; Liquid Metals; Rotating Magnetic Fields


Publ.-Id: 24498

Scattering-type scanning near-field infrared microscopy at low temperatures

Lang, D.; Döring, J.; Kuschewski, F.; Kehr, S. C.; Eng, L. M.; Winnerl, S.; Schneider, H.; Helm, M.

We present a combination of a versatile low-temperature scattering-type near-field infrared microscope (LT-s-SNIM ) with a tunable infrared free-electron laser (FEL). Our s-SNIM operates over a broad temperature range from 15 - 300 K and is unique in being tunable over a broad frequency range, thanks to the FEL. The over-all LT-s-SNIM functionality down to lowest temperature was tested on both standard gold and structured silicon dioxide samples, revealing net near-field contrasts and no topography cross-talk. Secondly, we investigated several ferroelectric phase transitions in barium titanate single crystals at 273 K and 193 K, allowing to associate clear near-field resonances to every phase and each ferroelectric domain; here, the clear benefit of our LT-s- SNOM pays off, being able to record s-SNOM, PFM, KPFM and topographic data with one and the same tip from every sample surface spot. Thirdly, we used the Jahn-Teller-Transition in the piezoelectric material GVS to quantify the local temperature increase under the AFM tip upon IR irradiation.

Keywords: infrared; spectroscopy; low-temperature; s-SNOM; FEL; near-field; microscopy; phase transition

  • Poster
    Smaller and Faster: Infrared and Terahertz Spectral-Imaging at the Nanoscale with Synchrotron Radiation and Free Electron Laser Sources, 01.-02.12.2016, Trieste, Italia

Publ.-Id: 24497

Product-Centric Simulation-based design for recycling: case of LED lamp recycling

Reuter, M. A.; van Schaik, A.

This paper will illustrate how a product-centric simulation approach to recycling is core to Design for Recycling (DfR) & Design for Resource Efficiency. This approach is underpinned by rigorous recycling rate calculations, building on the extensive expertise, knowhow and tools of classical minerals, and metallurgical processing. Process simulation and design tools such as the commercial HSC Sim software are applied to quantify critical DfR rules for a particular product as well as to quantify the recycling rates of all materials and elements in a product. The ten DfR rules we have developed for Waste Electric and Electronic Waste recycling in a study performed for NVMP/Wecycle (the Netherlands) are applied to light emitting diode (LED) lamps. The results produced include recycling and recovery rates, as well as recyclate qualities and quantities, and losses and emissions of materials during recycling for various LED lamp redesigns. Metallurgical processing is also briefly discussed, showing that, in many cases, element recoveries are reduced to zero due to product complexity and ppm levels in the products. Simulation models are linked to life cycle assessment (LCA) and exergy, demonstrating how the applied simulation basis provides the detail to innovate the system. In addition, rigorous environmental assessment is a further outcome of the approach, while at the same time revealing the development that has to occur in LCA databases to improve their value for Ecodesign.

Keywords: Product-centric design for recycling; WEEE system design; Greenprinting; Metallurgy; LED lamp; Ecodesign; Simulation

Publ.-Id: 24495

Simulation-based design for resource efficiency of metal production and recycling systems: Cases - copper production and recycling, e-waste (LED lamps) and nickel pig iron

Reuter, M. A.; Gediga, J.; van Schaik, A.

This paper illustrates how a product-centric approach to recycling, building on the extensive expertise, knowhow and tools of the mineral-centric classical minerals and metallurgical processing, should be core to Design for Resource Efficiency (DfRE).

Process simulation (HSC Sim 1974-2014, Outotec's design tool) and environmental software (GaBi 2014) are applied to quantify resource efficiency (RE) in a rigorous manner. These digitalisation tools are linked and will be used to show how the environmental performance of copper primary production, the processing of residues and the recycling of e-waste, e.g. light emitting diode (LED) lamps as well as the production of nickel pig iron can be evaluated. The paper also shows how technologies can be compared relative to a precise thermodynamic and techno-economic baseline.

The results include simulation-based environmental indicators, exergy, recycling and recovery rates, as well as the qualities and quantities of the recyclates, losses and emissions of materials during production recycling. The complete mass and energy balance simulation provides the mineralogical detail of all streams (both mineral and recyclate as well as offgas and dust) to define and improve environmental assessment, while at the same time revealing the aspects of LCA databases and their results that require improvement. Furthermore, this paper presents an approach for industry to implement life-cycle methods in practice. It shows that the DfRE is all about predicting stream grades and thus is equivalent to Design for Recyclate grade and quality (as this determines whether a recyclate or product stream has economic value and can be treated or processed further). DfRE also reveals especially the grade, composition, minerals etc. of the leakage streams, i.e. diffuse emissions, thus permitting a more precise evaluation of environmental impact.

The prediction of recyclate and stream compositions and grade makes the environmental analysis of systems more precise and will help to expand the detail that defines these flows on environmental databases. This is especially valuable for DfR, where the methodological rigour suggested in this paper is a very necessary addition and requirement for estimating the true environmental impact of product redesigns and the resource efficiency of processing technology and complete recycling systems. The methodology produces mass- and energy-consistent, economically viable best available technique (BAT) process blocks, the inclusion of which on environmental databases will be invaluable in benchmarking technology and systems in terms of estimating the achievable resource efficiency baseline.

Keywords: Copper production and scrap recycling; Design for Resource Efficiency; E-waste and WEEE; Greenprinting; LED lamp recycling; Nickel pig iron (NPI) production; Process metallurgy; Product-centric Design for Recycling (DfR); System design; Ecodesign; LCA

Publ.-Id: 24494

Arbeiten am und für den Grenzbereich

Joehnk, P.

Der experimentelle Nachweis von Hypothesen der Grundlagenphysik ist oftmals nur mit einem gigantischen technologischen Aufwand zu erreichen; CERN in der Schweiz mit seinem Large Hadron Collider ist ein beredtes Beispiel dafür. Die Errichtung und der (sichere) Betrieb solcher Anlagen stellen Forschungszentren und beteiligte Unternehmen vor völlig neue Anforderungen hinsichtlich des Entwurfs wie auch des Betriebs solcher großen Forschungsgeräte. Wenn nicht bereits bei der Planung der sichere Alltagsbetrieb berücksichtigt wurde, bleibt es offen, ob solche Anlagen in der Praxis noch beherrschbar sind bzw. was man tun muss, damit die Risiken für die Betreiber überschaubar bleiben.

Keywords: Wissenschaftliche Großanlagen; Beherrschbarkeit von Technik sicherer Betrieb von Anlagen

  • Book chapter
    in: BeHerrscht die Technik!? Band 3, Reihe: Arbeit und Technik im Wandel, Aachen: Shaker Verlag, 2016, 978-3-8440-4781-3, 55-64

Publ.-Id: 24493

Instabilities and spin-up behaviour of a rotating magnetic field driven flow in a rectangular cavity

Galindo, V.; Nauber, R.; Räbiger, D.; Franke, S.; Beyer, H.; Büttner, L.; Czarske, J.; Eckert, S.

This study presents numerical simulations and experiments considering the flow of an electrically conducting fluid inside a cube driven by a rotating magnetic field (RMF). The investigations are focused on the spin-up, where a liquid metal (GaInSn) is suddenly exposed to an azimuthal body force generated by the RMF, and the subsequent flow development. The numerical simulations rely on a semi-analytical expression for the induced electromagnetic force density in an electrically conducting medium. Velocity distributions in two perpendicular planes are measured using a novel dual-plane, two-component ultrasound array Doppler velocimeter (UADV) with continuous data streaming, enabling long term measurements for investigating transient flows. This approach allows to identify the main emerging flow modes during the spontaneous transition from a stable flow to unstable flow regimes with exponentially growing velocity oscillations using the Proper Orthogonal Decomposition (POD) method.
Characteristic frequencies in the oscillating flow regimes are determined in the super critical range above the critical magnet Taylor number Ta_c=1.3x10^5 , where the transition from the steady double vortex structure of the secondary flow to an unstable regime with exponentially growing oscillations is detected.
The mean flow structures and the temporal evolution of the flow predicted by the numerical simulations and observed in experiments are in very good agreement.

Keywords: Rotating magnetic field; spin-up; flow instabilities; square container


Publ.-Id: 24492

Hyperdoping by Ion Implantation for Extended Infrared Si p-n Photodiodes

Berencen, Y.; Prucnal, S.; Liu, F.; Wang, M.; Rebohle, L.; Zhou, S.; Helm, M.; Skorupa, W.

The development of room-temperature extended infrared Si photodetectors is of great interest for integrated photonics, optical communications, sensing and medical imaging applications [1]. The typical peak photoresponse of traditional Si photodetectors is between 700 and 900 nm, which is mostly limited by the 1.12 eV-Si indirect band gap. Nevertheless, such intrinsic material limitation can be circumvented by introducing transition metals or chalcogens into the Si band gap at concentrations far above those obtained at equilibrium conditions [1, 2]. Ion implantation and short-time annealing have been the adopted methods in those approaches. This new class of hyperdoped materials with a donor impurity band has been postulated as a promising route to extend the Si photoresponse at the short-wavelength infrared spectral region [3].
In this work, we report steady-state room-temperature extended infrared p-n photodiodes at the two primary telecommunication wavelengths from single-crystalline Si hyperdoped with Se concentrations as high as 9×1020 cm-3, which are introduced by a robust and reliable non-equilibrium processing consisting of ion implantation followed by millisecond-range flash lamp annealing (FLA). The FLA approach in the millisecond range allows for a solid-phase epitaxy that has been reported to be superior to liquid-phase eExtended infrared photodetektorpitaxy induced during pulsed laser annealing [2]. The success of our devices is primarily based on the high quality of the developed n-type hyperdoped material, which is single-phase single crystal with high electrical activation, without surface segregation of Se atoms and with an optically flat surface. A detailed description of the working principle and performance of the photodiodes as well as the main features in the studied wavelength region is provided.
[1] J. P. Mailoa, A. J. Akey, C. B. Simmons, D. Hutchinson, J. Mathews, J. T. Sullivan, D. Recht, M. T. Winkler, J. S. Williams, J. M. Warrender, P. D. Persans, M. J. Aziz, and T. Buonassisi, Nat. Commun. 5, 3011 (2014).
[2] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015).
[3] I. Umezu, J. M. Warrender, S. Charnvanichborikarn, A. Kohno, J. S. Williams, M. Tabbal, D. G. Papazoglou, X. C.Zhang, and M. J. Aziz, J. Appl. Phys. 113, 213501 (2013).

Keywords: extended infrared Si photodetector; flash lamp annealing; pulsed laser annealing selenium; doping; ion implantation; solid phase epitaxy; liquid phase epitaxy

  • Lecture (Conference)
    Ion Beam-Enabled Nanoscale Fabrication and Advanced Materials Synthesis, Symposium PM1 at MRS Fall Mtg. 2016, 28.11.-02.12.2016, Boston MA, USA

Publ.-Id: 24491

Corrosion phenomena at and nanoscale anticorrosion treatments of pipe organ metallic materials using ion beam based methods

Pelic, B.; Skorupa, W.; Eule, D.

Historical pipe organs with their unique sound and beautiful housing are important objects of the European cultural heritage dating back to the 15th century for the oldest ones being playable yet. But new instruments are built permanently up to the present time. The instruments contain mostly a considerable number of metallic pipes (flute and reed types), which are sometimes prone to heavy corrosion attack, resulting finally in a loss of their voice. Under certain conditions, the atmospheric corrosion of reed pipe tongues as well as flute pipe foots consisting of Cu-Zn alloys (brass) and PbSn-based alloys, respectively, is strongly enhanced by traces of volatile organic compounds (especially acetic acid vapor) and other corrosive gases.
Experiments have been undertaken to explore the corrosion resistance of CuZn and PbSn-based alloys against vapour from an aqueous solution containing high acetic acid concentration (2 – 5 v/v%), by deposition of protective films of either Al2O3 or Al on the nanoscale using pulsed laser deposition (PLD) and magnetron sputtering (MS). Afterwards, in order to improve the adhesion between the deposited layer and the substrate as well as to perform a kind of nitridation of the coatings, the samples were implanted with nitrogen ions using the plasma immersion ion implantation (PI3) process.
Such a nanoscale coating (~50 nm) is then able to withstand stresses and vibrations due to sound generation in organ pipes. Moreover it produces a barrier to volatile organic acids and water vapour. The laboratory corrosion test of the applied protective treatment for lead-tin and brass samples were combined with the field work studies to approach the best conditions for the samples research in real environment. Some of the samples were exposed for 15 months in a small North-German church with a harmful (corrosive) indoor environment.
Modifying the surface of metals and thin film properties on the nanoscale using fundamental phenomena based on ion-solid interactions as well as standard conventional methods can create new technological applications in restoration and conservation to preserve our historical and modern cultural heritage.

Keywords: Ion implantation; Plasma immersion implantation; Brass; Pb-Sn-alloys; Nanotechnology

  • Lecture (Conference)
    Materials Issues in Art and Archaeology, Symposium TC3 at MRS Fall Mtg. 2016, 28.11.-02.12.2016, Boston MA, USA

Publ.-Id: 24490

The effect of melt flow on dendritic solidification in Ga–In alloys

Shevchenko, N.; Keplinger, O.; Hoppe, D.; Eckert, S.

Simultaneous study of solidification phenomena on different length scales (dendrite networks - microscale and flow structure - mesoscale) is a main advantage of a conventional X-ray radiography. This work is focused on new benchmark experiments with different modes of melt convection and their effect on the dendritic growth in metallic alloys. The directional solidification of Ga-In alloy within a Hele-Shaw cell was investigated in situ. The visualization experiments with sufficient spatial resolution (5-10 µm) deliver simultaneous information of both the dendrite structure and the flow patterns especially in the mushy zone and ahead of the solidification front. Our results show that convection alters the solutal field near the solidification front, leading to different microstructures or even the formation of freckle defects. Flow patterns, solute concentration, the mushy zone morphology and permeability, dendrite growth velocities were quantified by image analysis. Particular attention was paid to the temporal dynamics of equiaxed grain growth, which plays an important role in grain structure formation in solidifying alloys. Small equiaxed grains frequently appeared in the undercooled melt near a continuous strong plume. Two mechanisms are under discussion: (i) crystal fragments transported by the ascending flow from the mushy zone; (ii) the equiaxed dendrites nucleated in the vicinity of the ascending plume due to modification of the the temperature/ solutal fields. We explored experimentally the size, the velocity and the conditions of formation of these equiaxed dendrites.

Keywords: X-ray radiography; melt convection; directional solidification; equiaxed grains

  • Lecture (Conference)
    6th Decennial Conference on Solidification Processing (SP17), 25.-28.07.2017, Old Windsor, UK

Publ.-Id: 24489

Hydrodynamics in cellular grid packed bubble columns disclosed with ultrafast X-ray tomography

Wagner, M.; Möller, C.-O.; Hessenkemper, H.; Bieberle, M.; Hampel, U.; Schlüter, M.

The chemical industry is one of the largest consumers of energy and resources. Therefore, process intensification is a field of high interest. Although the chemical reactor is only part of a highly integrated process, its design can significantly affect the overall process efficiency. A very common reactor type is the bubble column in which a liquid and a gas phase react with each other. The mass transfer across the liquid-gas interface is a crucial parameter regarding the process efficiency and should be as high as possible. It can be increased by higher interfacial area and better mixing of the phases. In the past, various internals like static mixers and structured packings were tested in order to control the bubble hydrodynamics in the column. Recent investigations of the authors showed that periodic open cellular structures (POCS) tend to increase the mass transfer significantly. These internals are three-dimensional regular grids with various geometries.
At the Helmholtz-Zentrum Dresden – Rossendorf the ultrafast X-ray computed tomography (CT) system is used to provide insights into the hydrodynamics of such bubble column internals. This imaging technique produces up to 8,000 cross-sectional images per second and provides a spatial resolution of about 1 mm for gas-water contrast. Two simultaneously scanned measurement planes allow determining vertical velocities and with that the extraction of quasi three-dimensional data sets from the original cross-sectional image data. For varying POCS geometries and gas flow rates, the axial bubble velocities, time-averaged gas hold-ups and the Sauter mean diameter are quantified and compared to measurements of unpacked bubble columns.

Keywords: packed bubble column; ultrafast X-ray CT

  • Contribution to proceedings
    8th WORLD CONGRESS ON INDUSTRIAL PROCESS TOMOGRAPHY, 26.-29.09.2016, Foz do Iguaçu, Brasil
  • Lecture (Conference)
    Hydrodynamics in cellular grid packed bubble columns disclosed with ultrafast X-ray tomography, 27.09.2016, Foz do Iguaçu, Brasil

Publ.-Id: 24488

Combining in-situ synchrotron X-ray techniques to study the dendrite morphology in solidifying Ga–In alloys

Shevchenko, N.; Grenzer, J.; Keplinger, O.; Rack, A.; Hoppe, D.; Eckert, S.

The processes involved in the formation of different dendrite morphologies are rather complex and still far from being fully understood. To verify existing micro-structural models in situ, in high resolution, in time and space, X-ray techniques are needed. In this work, in situ synchrotron X-ray radiography and diffraction methods have been combined to study the evolution of dendritic microstructures during the solidification of Ga - In alloys. The in situ directional solidification experiments were performed at the ID19 beamline (ESRF, France) at a high spatial resolution of < 1 µm. The dendritic growth and essential dynamics of the sidearm development were quantified. Melt flow induces various effects on the dendrite and grain morphology primarily caused by the convective transport of the solute. Usually, the morphologies of these dendrites differ from those developing under purely diffusive condition. Our observations show a facilitation of the growth of primary trunks or lateral branches, a suppression of side branching, dendrite remelting and fragmentation. The dendrite morphologies with their random character are difficult to analyse by means of the 2D radiographic projections. The flow-induced variations of the local solute concentration may result in the changes of dendrite crystal orientations. The coupling of in situ X-ray imaging with X-ray diffraction provides additionally information of the crystallographic orientation of the growing dendrites. These measurements show that the Indium dendrites grow along the <110> orientation, typically observed in body-centered metals. The analysis of the diffraction patterns with its complex morphology show that further improvements towards a 3D imaging experiment are needed. These first results demonstrate that the combination of different X-ray techniques can provide new data about the solidification process and help to validate different solidification models.

Keywords: dendritic microstructure; crystallographic orientation; synchrotron X-ray radiography; X-ray diffraction

  • Poster
    6th Decennial Conference on Solidification Processing (SP17), 25.-28.07.2017, Old Windsor, United Kingdom

Publ.-Id: 24487

X-ray radiography studies of melt convection effects on dendritic evolution in Ga – In alloy

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

X-ray radiography technique is a powerful tool for investigating solidification processes in metallic alloys. In particular, in-situ X-ray visualization enables a general, intuitive understanding of flow phenomena and dendrite formation in opaque systems. Our work is devoted to the in situ investigation of the dendritic growth during a bottom-up solidification of a Ga-25wt%In alloy under natural and forced convections. Natural convection occurs during the bottom-up solidification because a lighter solute is rejected during crystallization. Forced convection has been produced by a specific electromagnetic pump. The direction of forced melt flow is almost horizontal at the solidification front.
Melt flow induces various effects on the dendrite morphology primarily caused by the convective transport of solute. Our investigations show a facilitation of the growth of primary trunks or lateral branches, suppression of side branching, dendrite remelting, fragmentation or freckle formation. Typical radiographs of stabilized segregation freckles are shown in Fig. 1. We demonstrate that the actual manifestation of all phenomena depends sensitively on the dendrite orientation, the local direction and intensity of the flow. Forced flow eliminates solutal plumes and damps local fluctuations of solute. A preferential growth of the secondary arms occurs at the upstream side of the dendrites, whereas high solute concentration at the downstream side inhibits the formation of secondary branches. Flow patterns and local solute concentration were quantified by image analysis and related to the experimental conditions. These in situ experiments provide benchmark data that can be used to validate simulations of dendritic growth or channel segregations.

Keywords: X-ray radiography; solidification; dendrites; segregation; convection; electromagnetic stirring

  • Invited lecture (Conferences)
    The 4th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR2016), 11.-15.05.2016, Xi’an, China

Publ.-Id: 24486

Morphology and orientation of growing dendrites in GaIn alloy characterized by synchrotron X-ray techniques

Shevchenko, N.; Grenzer, J.; Roshchupkina, O.; Baehtz, C.; Eckert, S.

The dendrite growth kinetics and morphology have been of great interest in the solidification science and casting industry. A detailed analysis of the particular solidification phenomena requires techniques with a better spatial and temporal resolution. High resolution experimental data are also very important for verification of the existing microstructural models. We demonstrate an advantage of the synchrotron X-ray sources, which allows the unique combination of in situ synchrotron X-ray radiography with a spatial resolution of less than 0.5 µm and synchrotron X-ray diffraction. The directional solidification experiments of Ga–25wt%In alloys were performed at the ROBL beam line (BM20, European Synchrotron Radiation Facility, Grenoble) at an energy of 28.5 keV. The study is especially focused on the sidearm evolution, refraction and detachment, dendrite morphology and orientation. Typical radiographs of sidearm evolution of an indium dendrite are shown in Fig. 1. The development of sidearms is quantified by an image analysis in a manner appropriated for comparison to simulations. Furthermore, we report on first attempt of reconstruction of crystallographic orientation of growing dendrites by using the CaRIne crystallography software.

Keywords: synchrotron X-ray radiography; GaIn alloys; directional solidification; X-ray diffraction; sidearm evolution

  • Poster
    The 4th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR2016), 11.-15.05.2016, Xi’an, China

Publ.-Id: 24485

Metalle: Aktivatoren von Kreislaufwirtschaft und Recycling 4.0

Reuter, M. A.

Aktuell stammen etwa 70 % der weltweiten Zinkproduktion aus primärem Bergbau und der Rest aus Recycling und sekundärem Zink (Zn). Der Recyclinganteil steigt von Jahr zu Jahr gemeinsam mit der Technologie von Zn-Produktion und -recycling (Reuter et al. 2015a). Mehr als 50 % des Zinks wird heute aus Produkten am Ende ihrer Lebensdauer (EoL) zurückgewonnen. Beim Pb-Recycling werden etwa 60 % der gesamten Produktionsmenge erreicht (Reuter et al. 2015a). Vom Element Gold (Au) wurde im Zeitfenster von 1995 bis 2014 rund ein Drittel der gesamten Umsatzmenge rezykliert (Hewitt et al. 2015).

Keywords: Recycling; Zink

  • Book chapter
    Kausch, P., Matschullat, J., Bertau, M., Mischo, H.: Rohstoffwirtschaft und gesellschaftliche Entwicklung, Berlin: Springer Berlin Heidelberg, 2016, 978-3-662-48854-6, 73-98
    DOI: 10.1007/978-3-662-48855-3

Publ.-Id: 24484

Thermodynamics of Palladium (Pd) and Tantalum (Ta) Relevant to Secondary Copper Smelting

Shuva, M. A. H.; Rhamdhani, M. A.; Brooks, G. A.; Masood, S. H.; Reuter, M. A.

The slag-to-metal distribution ratios of palladium (Pd), Ls/mPd, in the range of oxygen partial pressure (pO2) from 10−10 to 10−7 atm at 1473 K to 1623 K (1200 °C to 1350 °C); distribution ratios of tantalum (Ta), Ls/mTa, in the range of pO2 from 10−16 to 10−12 atm at 1673 K and 1873 K (1400 °C and 1600 °C), have been determined in this study. The Ls/mPd in FeOx-CaO-SiO2-MgO and copper at 1573 K (1300 °C) and pO2 = 10−8 atm is dependant strongly on basicity of slag, i.e. (CaO + MgO)/SiO2 or optical basicity. The current results suggest that Pd presents in the FeOx-CaO-SiO2-MgO slag predominantly as Pd2+. The activity coefficient of PdO in the slag at 1573 K (1300 °C) and pO2 = 10−8 atm was calculated to be in the range of 3.89 × 10−3 to 2.63 × 10−2. The Ls/mPd was also found to increase with increasing of pO2 and with decreasing of temperature. It was observed that Ta mostly partition to slag phase and very small amount of Ta was found in liquid copper at the high temperature and reduced condition studied. It can be suggested that to promote recovery of palladium from Pd-containing e-waste, a slag with lower silica content and basic flux based, high temperature with reducing atmosphere, is highly desired particularly in secondary copper smelting.

Publ.-Id: 24483

Mining of critical and strategic metals in socially and environmentally sensitive areas in Namibia

Tesh, D.; Barakos, G.; Musiyarira, H.; Mischo, H.

Namibia has a rapidly growing minerals industry and is a primary source for numerous valuable commodities, among which are many strategic metals; rare earth elements, tantalum and niobium. The insatiable global demand for such critical and strategic elements can therefore give Namibia an opportunity to become a major player in the market. The country has adopted a mining friendly policy that can attract investments and encourage the development of mining projects. Alongside this, some areas in Namibia are sensitive in terms of cultural heritage both socially and environmentally, whilst tourism grows as part of the competitive industry sectors. Thus, the potential exploitation of rare earths and respective metals may raise issues due to the presence of radioactivity, the use of hazardous chemical compounds and the treatment of their tailings. Under such controversial circumstances, future mining plans require thorough assessments and closer considerations with respect to the special boundary conditions that govern this specific sector of the mining industry. This paper investigates the mineability of three different deposits that are located in respective sensitive areas in Namibia with the use of evaluation indicators. Furthermore, suggestions are made in order to ensure the sustainability of the mining projects while fully satisfying the competing industries and preserving the environmental and cultural balance.

Keywords: Rare earth elements; niobium; strategic metals; environmental sustainability; mining in Namibia

  • Open Access Logo Contribution to proceedings
    24th World Mining Congress - Mining in a World of Innovation, 18.-21.10.2016, Rio de Janeiro, Brasil
    Proceedings of the 24th World Mining Congress, Rio de Janeiro: IBRAM

Publ.-Id: 24482

Electron microprobe petrochronology ofzite-bearing garnet micaschists in the Oetztal-Stubai Complex (Alpeiner Valley, Stubai)

Schulz, B.; Krause, J.; Zimmermann, R.

Monazite dating in metapelites is an emerging method to investigate polymetamorphic areas A protocol for Th–U–Pb dating of monazite by electron microprobe was adopted for a JEOL JXA-8530F. It was applied to the Variscan and Early- Alpine metamorphic Austroalpine Oetztal-Stubai Complex (OSC). In the Alpeiner Valley in the Stubai region, the Schrankogel complex is the eastern succession of the Central Metabasite Zone. In this part, metabasites are alternating with metapelites. In 4 samples from micaschist lenses, dominantly Carboniferous monazite isochrone ages at 335 ± 4 Ma, 320 ± 4 Ma; 319 ± 4 Ma and 319 ± 4 Ma were obtained. The micaschist samples with diverse modal compositions and variable bulk rock Ca contents of calculated assay, display distinct monazite microstructures, as quantified by automated SEM-MLA (mineral liberation analysis) routines. Clusters of small monazite could indicate new crystallization and yielded isochrones at 313 and 304 Ma. In contrast, corona structures of apatite and allanite around large monazites with isochrones between 350 and 315 Ma suggest a decomposition during decreasing temperature. Garnets in metapelitic assemblages display growth zonations with low pyrope contents in the cores and pyrope-rich rims. A prograde metamorphism with high pressure amphibolite-facies peak conditions at * 12 kbar and * 680 °C, and a post Pmax path with decompression to 4 kbar and 640–600 °C was estimated from the micaschists and from zoned Ca-amphiboles in retrogressed amphibolitized eclogites. The P–T path entered the monazite stability field during the decompression. This signals a Carboniferous age of the metamorphism. A minor population in one sample is composed of sporadic Permian single monazite ages. A Creta- ceous monazite population is lacking. In the wide parts of the Austroalpine basement with Carboniferous-to-Cretaceous mica mixing ages, monazite age populations allow to discriminate a distinct Permian metamorphic event.

Keywords: Th–U–Pb-monazite dating; Geothermobarometry; Automated SEM mineral liberation analysis; Variscan; Austroalpine basement; Eastern Alps


Publ.-Id: 24481

Tracing the Gouy phase shift of focused, radially polarized THz pulses

Kaltenecker, K. J.; König-Otto, J. C.; Mittendorff, M.; Winnerl, S.; Schneider, H.; Helm, M.; Helm, H.; Walther, M.; Fischer, B. M.

THz microscopic imaging is used to extract the Gouy phase shift of the transverse and longitudinal field components of a tightly focused, radially polarized beam. We demonstrate that the applied THz time domain approach allows to observe directly the evolution of the geometric phase as the wave propagates through the focus. Our method yields a Gouy phase shift of 2π for the transverse component and of π for the longitudinal component. In addition, we apply our method to the well-known case of a focused, linearly polarized beam and pinpoint a fundamental connection between the field components of tightly focused, radially and linearly polarized light. The applied procedure is universal and may even allow to determine the geometric phase of arbitrary shaped and polarized propagating waves.

Keywords: Terahertz; Gouy phase

  • Invited lecture (Conferences)
    41st International Conference on Infrared, Millimeter and Terahertz Waves, 25.-30.09.2016, Kopenhagen, Denmark
  • Contribution to proceedings
    41st International Conference on Infrared, Millimeter and Terahertz Waves, 25.-30.09.2016, Kopenhagen, Denmark, 1-3
    DOI: 10.1109/IRMMW-THz.2016.7758577

Publ.-Id: 24480

On the experimental investigation of gas-liquid flow in bubble columns using ultrafast X-ray tomography and radioactive particle tracking

Azizi, S.; Yadav, A.; Lau, Y. M.; Hampel, U.; Roy, S.; Schubert, M.

Several techniques have been developed in the past to measure gas and liquid phase dynamics; however, reported data were mostly gathered individually for either liquid velocity, or volume fraction (phase holdup), but never when both are measured in the same system. In this work, arguably for the first time, bubble column hydrodynamics have been investigated using two complementary advanced non-invasive measurement techniques, namely Ultrafast X-ray Computed Tomography (UXCT) and Radioactive Particle Tracking (RPT). The UXCT experimental data in terms of gas phase structure is used in a supportive way to explain the liquid velocity profiles of the RPT data. Results of both experimental techniques are verified in a complementary manner using the mass conservation calculation. The results show good agreement. It is envisioned that the presented data would be helpful in the development and validation of numerical models for better predicting the flow profiles in bubble columns.

Keywords: Gas-liquid flow; Bubble column; Radioactive particle tracking; Ultrafast X-ray computed tomography

  • Lecture (Conference)
    ICMF 2016 International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy
  • Chemical Engineering Science 170(2017), 320-331
    DOI: 10.1016/j.ces.2017.02.015

Publ.-Id: 24479

Relation between Bubble Dispersion and Liquid Flow Field in Bubble Columns: A Complementary Study using Ultrafast X-Ray Tomography and Radioactive Particle Tracking

Azizi, S.; Yadav, A.; Yuk Man, L.; Roy, S.; Schubert, M.

Bubble column reactors are widely used in chemical and petrochemical industries due to their simple design and beneficial mass and heat transfer rates. The design of bubble columns requires thoughtful information about the complex gas-liquid hydrodynamics. The bubble size distribution, which results from bubble-liquid interactions, has a crucial impact on the reactor performance. Furthermore, reliable modeling of bubble columns requires validated hydrodynamic information.
In the present work, Radioactive Particle Tracking (RPT) and Ultrafast X-Ray Tomography (XRT) were applied for the first time at one bubble column setup to study the liquid velocity field and the corresponding bubble size distributions at different axial positions. In particular, the relation between the bubble dispersion, i.e. size and velocity, and the liquid flow field will be discussed. The velocity distribution of the liquid phase influences the bubble breakup and coalescence rates and accordingly the bubble size. In turn, turbulence and recirculation of the liquid phase depend on the bubble sizes. This mutual interaction will be revealed based on experiments with different distributer designs.

Keywords: RPT; XRT; Experiment; Bubble column

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Agglomerations- und Schüttguttechnik, Mehrphasenströmungen und Computational Fluid Dynamics, 29.02.-02.03.2016, Bingen, Germany

Publ.-Id: 24478

Multiphase CFD activities at HZDR

Lucas, D.

The poster gives an overview on the main working fields of the CFD department of HZDR.

Keywords: CFD; multiphase; multi-fluid

  • Poster
    14th Multiphase Flow Conference & Short Course, 08.-10.11.2016, Dresden, Deutschland
  • Poster
    16th Multiphase Flow Conference and Short Course, 13.-16.11.2018, Dresden, Germany

Publ.-Id: 24477

Validation of the baseline model for poly-disperse bubbly flows

Lucas, D.; Krepper, E.; Rzehak, R.

During the last years a modelling framework for CFD-simulations of poly-disperse bubbly flows using the Euler-Euler approach was formulated at Helmholtz-Zentrum Dresden – Rossendorf (HZDR). The main idea behind is to achieve a consolidation of multiphase CFD by having a fixed set of closures applicable for a range of expected local flow conditions (Lucas et al., 2016). The corresponding closures concern the momentum transfer between liquid and gaseous phases, the influence of gas on the liquid phase turbulence and models for bubble breakup and coalescence (Rzehak et al., 2015, Liao et. al 2015). This baseline model was applied to a large variety of bubbly flows as round and rectangular bubble columns, bubble plumes, airlift reactors and upwards vertical pipe flow with different pipe diameter without any modification or tuning. In the results a good or at least acceptable agreement was found for most of the cases, but for some other cases also clear deviations were observed. Such deficiencies have to be investigated more in detail to improve the models step by step.
In this work the model is applied to co-current upward, counter-current and co-current downward vertical pipe flows recently measured at the HZDR TOPFLOW facility using ultrafast X-ray tomography. The results are discussed in detail.

Keywords: CFD; bubbly flow; downward; counter-current; baseline model; poly-disperse

  • Contribution to proceedings
    Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation (CFD4NRS-6), 13.-15.09.2016, Cambridge, USA
  • Lecture (Conference)
    Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, 13.-15.09.2016, Cambridge, USA

Publ.-Id: 24476

Nuclear Laboratories and Experiments: Overview and HZDR

Bemmerer, D.

I provide an overview of experimental nuclear astrophysics research in Germany. In addition, I review related recent progress at HZDR Dresden.

Keywords: Experimental Nuclear Astrophysics

  • Invited lecture (Conferences)
    Nuclear Astrophysics in Germany - A Community Meeting in Darmstadt, 15.-16.11.2016, Darmstadt, Deutschland

Publ.-Id: 24475

Nuclear Astrophysics in Germany

Bemmerer, D.

I review the status of nuclear astrophysics in Germany, with a focus on recent experimental progress

Keywords: Nuclear Astrophysics; Origin of the Elements

  • Invited lecture (Conferences)
    Astroteilchenphysik in Deutschland, Strategietreffen, 24.-25.11.2016, Bad Honnef, Deutschland

Publ.-Id: 24474

Nuclear Astrophysics at HZDR Dresden

Bemmerer, D.

I review recent nuclear astrophysics work at HZDR Dresden, both related to the LUNA underground accelerator in Italy and independently from it.

Keywords: Experimental Nuclear Astrophysics; Felsenkeller; ELBE

  • Invited lecture (Conferences)
    Silver Moon, 01.-02.12.2016, Assergi, Italien

Publ.-Id: 24473

Overview of the results from HZDR/IRE in the EcoMetals Project

Barthen, R.; Karimzadeh, L.; Gründig, M.; Schymura, S.; Kulenkampff, J.; Mansel, A.; Lippold, H.; Grenzer, J.; Lippmann-Pipke, J.

This talk gives an overview of the results obtained by Institute of Resource Ecology of the HZDR in the German-French Project EcoMetals

  • Lecture (others)
    EcoMetals General Meeting 6, 07.-09.12.2016, Hannover, Deutschland

Publ.-Id: 24472

Formation of InxGa1-xAs nanocrystals in thin Si layers by ion implantation and flash lamp annealing

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

The integration of high-mobility III-V compound semiconductors emerges as a promising route for Si device technologies to overcome the limits of further down-scaling. In this paper, a non-conventional approach of the combination of ion beam implantation with short-time flash lamp annealing is employed to fabricate InxGa1-xAs nanocrystals and to study their crystallization process in thin Si layers. The implantation fluence ratio of Ga and In ions has been varied to tailor the final nanocrystal composition. Raman spectroscopy and X-ray diffraction analyses verify the formation of ternary III-V nanocrystals within the Si layer. Transmission electron microscopy reveals single-crystalline precipitates with a low number of defects. A liquid epitaxy mechanism is used to describe the formation process of III-V nanocrystals after melting of the implanted thin Si layer by flash lamp annealing. The fabricated InxGa1-xAs nanocrystals are mainly Ga-rich with respect to the implanted Ga/In ratio.

Keywords: ion implantation; flash lamp annealing; III-V integration into silicon; nanostructure; InGaAs; liquid phase epitaxy

Publ.-Id: 24471

Electron sources and polarization

Xiang, R.; Teichert, J.

In this presentation the present electron sources and the relevant issues will be discussed. For the electron positron colliders and accelerator based light sources, the electron gun and injector design, are arguably the most critical part. There are a variety of electron source designs: DC guns, normal-conducting RF guns, superconducting RF gun and hybrid guns. All variants have their own ad-vantages and difficulties. We will overview the typical sources around the world, and compare their advantages and main challenges. The polarization production will also be discussed.

Keywords: injector; electron gun

  • Invited lecture (Conferences)
    58th ICFA Advanced Beam Dynamics Workshop on High Luminosity Circular e+e- Colliders, 24.-27.10.2016, Cockcroft Institute at Daresbury Laboratory, UK
  • Open Access Logo Contribution to proceedings
    the 58th ICFA Advanced Beam Dynamics Workshop on High Luminosity Circular e+e– Colliders, 24.-27.10.2016, Daresbury, UK
    Proceedings of the 58th ICFA Advanced Beam Dynamics Workshop on High Luminosity Circular e+e– Colliders

Publ.-Id: 24470

SAXS: From data to pictures. Key aspects of iterative reconstruction algorithms.

Zacharias, M.; Knespel, M.; Kluge, T.; Bussmann, M.; Debus, A.; Widera, R.

We present an overview of iterative reconstruction schemes for Small Angle X-Ray Scattering (SAXS) and also Positron Emission Tomography (PET) that we implemented. Aspects of such algorithms and details about their implementation that we think will be crucial for making visible the electron dynamics in laser-driven plasma experiments are highlighted.

Keywords: SAXS; PET; reconstruction

  • Poster
    EUCALL Annual Meeting, 31.08.-02.09.2016, Helmholtz-Zentrum Dresden - Rossendorf, Deutschland

Publ.-Id: 24469

Gold – a Key Enabler of a Circular Economy: Recycling of WEEE

Reuter, M. A.; van Schaik, A.

Gold Ore Processing: Project Development and Operations, Second Edition, brings together all the technical aspects relevant to modern gold ore processing, offering a practical perspective that is vital to the successful and responsible development, operation, and closure of any gold ore processing operation. This completely updated edition features coverage of established, newly implemented, and emerging technologies; updated case studies; and additional topics, including automated mineralogy and geometallurgy, cyanide code compliance, recovery of gold from e-waste, handling of gaseous emissions, mercury and arsenic, emerging non-cyanide leaching systems, hydro re-mining, water management, solid–liquid separation, and treatment of challenging ores such as double refractory carbonaceous sulfides. Outlining best practices in gold processing from a variety of perspectives, Gold Ore Processing: Project Development and Operations is a must-have reference for anyone working in the gold industry, including metallurgists, geologists, chemists, mining engineers, and many others.

  • Book chapter
    M. Adams: Gold Ore Processing, Project Development and Operations, Amsterdam: Elsevier, 2016, 9780444636584, 937-956

Publ.-Id: 24468

Recycling processes

Hack, K.; Reuter, M. A.; Petersen, S.; Arnout, S.

In the context of integrated computational materials engineering (ICME) recycling covers processes at the end of the lifetime (EoL) of mechanical, electronic, or other components of machines and devices. Depending on the state in which they exist as EoL material they can either be used directly for new material production. This chapter provides a short overview of materials that are being recycled today and the methods applied. It focuses on computational methods applied in the field of recycling, the foremost being methods of computational thermochemistry since mutual solubilities, phase transformations, and reactions as well as heat balances play the most important part in recycling just as they do in standard production. The chapter discusses materials-centric recycling, product-centric recycling, physical separation methods and chemical separation methods. It shows various aspects and phenomena that affect the final recovery of all elements from a product, including the residence time of materials in the market, and subsequent metallurgical processing.

Keywords: chemical separation methods; computational thermochemistry; heat balances; integrated computational materials engineering; material production; materials-centric recycling; metallurgical processing; phase transformations; physical separation methods; product-centric recycling

  • Book chapter
    Eds. Georg J. Schmitz, Ulrich Prahl: Handbook of Software Solutions for ICME, Berlin: Wiley, 2016, 978-3-527-33902-0, 247-268

Publ.-Id: 24467

Spin wave propagation in ion-induced FeAl conduits

Osten, J.; Hula, T.; Bali, R.; Potzger, K.; Schultheiss, H.

Spin waves, the eigen-excitations of ferromagnets, are promising candidates for spin transport in lateral devices. Fe60Al40 films in the B2 phase is paramagnetic. Starting from a FeAl film in the paramagnetic state the incident ions randomize the site occupancies and, thereby, transform it to the chemically disordered, ferromagnetic A2 phase. The aim is to investigate spin wave propagation in this ferromagnetic material in free standing structure as well as in structure within a paramagnetic matrix. By using Helium-Ion microscopy it is possible to create well defined disordered FeAl conduits with resolution down to nm range. Two di↵erent ferromagnetic stripes were implanted in a microstructure paramagnetic FeAl. A free-standing 2 μm width stripe. And a stripe of the same width with was additionally embedded in the paramagnetic FeAl. For the excitation of spin waves we processed a microwave antenna on top of these stripes. To observe Spin wave behavior Billouin light scattering microscopy was applied. We show that the spin wave behaviour is influenced by the surrounding paramagnetic material due to a di↵erent internal field distribution. In addition the normalized transversal mode widths of spin waves in the embedded systems are wider than in the free standing stripes.

  • Lecture (Conference)
    Deutsche Physikerinnentagung, 03.-06.11.2016, Hamburg, Deutschland

Publ.-Id: 24466

The Why and How of Amino Acid Analytics in Cancer Diagnostics and Therapy

Manig, F.; Kuhne, K.; von Neubeck, C.; Schwarzenbolz, U.; Yu, Z.; Kessler, B. M.; Pietzsch, J.; Kunz-Schughart, L. A.

Pathological alterations in cell functions are frequently accompanied by metabolic reprogramming including modifications in amino acid metabolism. Amino acid detection is thus integral to the diagnosis of many hereditary metabolic diseases. The development of malignant diseases as metabolic disorders comes along with a complex dysregulation of genetic and epigenetic factors affecting metabolic enzymes. Cancer cells might transiently or permanently become auxotrophic for non-essential or semi-essential amino acids such as asparagine or arginine. Also, transformed cells are often more susceptible to local shortage of essential amino acids such as methionine than normal tissues. This offers new points of attacking unique metabolic features in cancer cells. To better understand these processes, highly sensitive methods for amino acid detection and quantification are required. Our review summarizes the main methodologies for amino acid detection with a particular focus on applications in biomedicine and cancer, provides a historical overview of the methodological pre-requisites in amino acid analytics. We compare classical and modern approaches such as the combination of gas chromatography and liquid chromatography with mass spectrometry (GC-MS/LC-MS). The latter is increasingly applied in clinical routine. We therefore illustrate an LC-MS workflow for analyzing arginine and methionine as well as their precursors and analogs in biological material. Pitfalls during protocol development are discussed, but LC-MS emerges as a reliable and sensitive tool for the detection of amino acids in biological matrices. Quantification is challenging, but of particular interest in cancer research as targeting arginine and methionine turnover in cancer cells represent novel treatment strategies.


Publ.-Id: 24465

Gender Differences in Neural Networks for Color Processing in Mice: A PET/MR Study

Njemanze, P. C.; Kranz, M.; Amend, M.; Wehrl, H.; Brust, P.

Color processing is a central component of mammalian vision. Gender-related differences of color processing revealed by non-invasive functional transcranial Doppler ultrasound suggested right hemisphere pattern for Blue/Yellow chromatic opponency by men, and a left hemisphere pattern by women. The present study measured the blood-flow related accumulation of [18F]fluorodeoxyglucose ([18F]FDG) in mouse brain using small animal positron emission tomography and magnetic resonance imaging (PET/MRI) with statistical parametric mapping during light stimulation with Blue and Yellow filters compared to darkness condition.
PET revealed a reverse pattern compared to previous human studies: Male mice presented with left visual cortex dominance for blueON-channels through the right eye, while female mice presented with right visual cortex dominance for blueON-channel through the left eye. We applied statistical parametric mapping (SPM) to examine gender differences in activated architectonic areas within the orbital and medial prefrontal cortex and their cortico-cortical connections and sub-cortical networks that lead to the striatum, medial thalamus and other brain areas. The connectivity evoked by Blue stimulation spread through a wide range of brain structures implicated in viscerosensory and visceromotor systems in the left intra-hemispheric regions in male mice, but in the right-to-left inter-hemispheric regions in female mice. Spatial and chromatic opponency was maintained using a yellowON-OFF push-pull interaction in male mice, but a blueON-ON push-forward interaction in female mice. Color functional ocular dominance plasticity was noted in the right eye in male mice but in the left eye in female mice. This animal model could be used in the study of color processing mechanisms and gender complementarity in normal and pathological brain conditions.

Publ.-Id: 24464

Comparison between the transition velocities in both core and annulus of bubble columns based on a modified Shannon entropy

Nedeltchev, S.; Schubert, M.

Bubble columns (BC) are frequently used in chemical, petroleum and biochemical industries due to their simple construction, ease of temperature control and good heat and mass transfer characteristics. Their hydrodynamics depend on the prevailing flow patterns (regimes) which in turn depend mainly on the superficial gas velocity Ug, the gas distributor design and column diameter. At low Ug values the bubbly flow (homogeneous) regime prevails, which is characterized with relatively small and uniform bubbles and a gentle agitation of the gas-liquid dispersion. The bubble size distribution (BSD) is very narrow and it is only influenced by the gas distributor. A relatively uniform gas holdup profile and a rather flat liquid velocity profile are observed. When the gas distributor is not effective, a gas maldistribution instead of the bubbly flow is observed. The transition regime is characterized by large eddies and a widened BSD due to bubble coalescence. It has been found that the occurrence and the persistence of the transition regime depend largely on the quality of the aeration. The transition from the homogeneous to the heterogeneous (churn-turbulent flow) regime is a gradual process.
In the churn-turbulent flow regime large bubbles start to form whose wakes cause gross circulation patterns. This flow regime is characterized by a wide BSD, vigorous mixing and by the existence of a radial gas holdup profile, which causes liquid circulation, as well. Both bubble coalescence and break-up occur. The gas sparger has little effect on the hydrodynamics.
In particular, the circulation zones give rise to the assumption that regime transitions in different regions occur at different operating conditions. Thus, the primary objective of this work is to compare the main transition velocities Utrans in both the core and annulus of two different BCs based on the modified Shannon entropy (SE). The ratio of the minimum-to-maximum SE in a time-dependent signal can be used successfully for position-dependent flow regime identification in BCs.
The modified SE algorithm has been applied to gas holdup time series data obtained by means of a conductivity wire-mesh sensor (fs=2000 Hz, sensor’s axial position: 1.3 m). Two different BCs operated with an air-deionized water (clear liquid height: 2.0 m) system were used. Both facilities were equipped with perforated plate distributors having the same opening diameter (Ø 4.0×10-3 m). The gas sparger in the small BC (0.15 m in ID) consisted of 14 holes, while the one in the large BC (0.4 m in ID) consisted of 101 holes. In both cases the open area was 1 %.
The SE quantifies the degree of uncertainty involved in predicting the output of a probabilistic event. In the case of fully predictable outcome of an event, the SE will be zero. The definition of the probability in the SE algorithm (Zhong et al., 2009) was modified. Then, the total number of points (60,000) in the signal was divided into six segments (each consisting of 10,000 points) and the modified SE in each of them was calculated. It was found that the ratio of the minimum-to-maximum (SEmin/SEmax) modified SE in every time series at various Ug values can be used for the flow regime identification.
It was found that the dimensionless SEmin/SEmax ratio in the annulus (r/R=0.88) of the small BC (0.15 m in ID) was characterized with two local minima, which corresponded to the two main Utrans values (0.045 and 0.089 m/s). These two boundaries delineated the ranges of the three main hydrodynamic regimes: gas maldistribution (Ug≤0.045 m/s), transition (0.0450.089 m/s). The existence of the gas maldistribution regime in both BCs has been visualized by Nedeltchev et al. (2015).
The SEmin/SEmax in the core (r/R=0) of the small BC (0.15 m in ID) was also capable of identifying the two main Utrans values. At Ug=0.034 m/s the onset of the transition flow regime was identified, whereas at Ug=0.089 m/s the second minimum in the SE ratio distinguished the formation of the churn-turbulent flow regime. The same Utrans values for the whole cross-section of the small BC have been reported by Nedeltchev et al. (2015). It is noteworthy that the minima in the core are much deeper and very well pronounced.
The results in Figure 2 exhibit further that the gas maldistribution ends at lower Ug value in the core of the small BC. The second Utrans value is independent of the radial position. A similar comparison between the Utrans values in both zones of the large BC will be presented. The effect of the radial position on the Utrans values will be studied since it will give an information about the BSD.

Keywords: Bubble columns; Gas holdup time series; Modified Shannon entropy; Flow regime identification; Core; Annulus

  • Poster
    13th International Conference on Gas–Liquid and Gas–Liquid–Solid Reactor Engineering (GLS-13), 20.-23.08.2017, Bruxelles, Belgium

Publ.-Id: 24462

Extraction of both information and reconstruction entropies from ultrafast x-ray tomography data in a bubble column

Nedeltchev, S.; Hampel, U.; Schubert, M.

Due to the complex hydrodynamics of bubble columns, there are no reliable methods for identification of both main transition velocities. In addition, it is not clear which type of signal is most suitable for flow regime identification. In this work, both the information entropies (IE) and reconstruction entropies (RE) have been extracted for the first time from tomographic raw images obtained by means of ultrafast X-ray tomography. The time series have been recorded with a sampling frequency of 1000 Hz in a bubble column (0.1 m in ID) operated with an air-deionized water system under ambient conditions. The main transition velocities Utrans in two semi-rings from the cross-section of the bubble column have been identified based on both the IE and RE values calculated from 5 signal reconstructions. In each semi-ring the RE algorithm has been applied to two different cases for signal’s processing. In the centrally located smaller semi-ring the two main Utrans values were successfully identified at 0.04 and 0.1 m/s. In the surrounding larger semi-ring the onsets of the transition and heterogeneous regimes occurred at 0.03 and 0.09 m/s. The results imply that following the above-described approaches the main transition velocities can be extracted from any part of the column’s cross-section.
In summary, this work demonstrates that the ultrafast X-ray tomography data can be used for flow regime identification in a bubble column provided that the hidden information in the time series is quantified by both the IE and RE algorithms.

Keywords: Bubble columns; Information entropies; Reconstruction entropies; Ultrafast X-ray tomography; Hydrodynamic regimes; Transition velocities

  • Lecture (Conference)
    13th International Conference on Gas–Liquid and Gas–Liquid–Solid Reactor Engineering (GLS-13), 20.-23.08.2017, Bruxelles, Belgium
  • Chemical Engineering Science 170(2017), 225-233
    DOI: 10.1016/j.ces.2017.03.020

Publ.-Id: 24461

Simulations for the precession experiment at HZDR

Giesecke, A.; Gundrum, T.; Vogt, T.; Stefani, F.; Herault, J.

The project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) conducted at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) provides a new platform for a variety of liquid sodium experiments devoted to problems of geo- and astrophyscal magnetohydrodynamics.
Most ambitious experiment will be a precession driven dynamo experiment which consists of a large cylindrical cavity lled with liquid sodium that will simultaneously rotate around two axis.
The experiment is motivated by the idea of a precession-driven ow as a complementary energy source for the geodynamo or the ancient lunar dynamo. My presentation addresses corresponding numerical examinations aimed at an optimization of the precession driven ow with regard to improve the dynamo process in the planned experiment.

Keywords: Dynamo; DRESDYN

  • Lecture (Conference)
    MHDDAYS 2016, 30.11.-02.12.2016, Goettingen, Germany

Publ.-Id: 24460

Determination of the entropy radial minimum and the various transition velocities in an air-water bubble column

Nedeltchev, S.; Schubert, M.

The bubble column hydrodynamics are complex and the macroscopic flow structure is different in the column core and annulus due to both the bubble coalescence and breakup phenomena as well as the gross liquid circulation. In this work, for the first time the local Kolmogorov entropy (KE) minima at different superficial gas velocities Ug were identified. It was found that there is an agreement between the local KE minima (occurring around r/R=0.63) and the inversion point (dimensionless radius=0.7) for the axial liquid velocity reported by both Chen et al. (1994) and Wu and Al-Dahhan (2001).
The KE radial profiles were also used to confirm the chaotic similarities between the flow patterns in the bubble bed at three different Ug values (0.089, 0.134 and 0.146 m/s) belonging to the heterogeneous regime. This implies that the flow patterns and the degrees of turbulence at these Ug values are also identical. The same similarity was also found between the KE profiles at Ug = 0.056 and 0.067 m/s, which belong to the transition flow regime. These results imply that the flow patterns in the bubble bed repeat (especially at different Ug values falling into the same flow regime).
Based on the KE profiles as a function of Ug , the effect of the dimensionless radial position on the various transition velocities was studied. It was found that the end of the gas maldistribution regime is shifted to slightly higher Ug value in the column core and annulus. In most of the cases, the onset of the churn-turbulent regime occurs at Ug = 0.101 m/s.

Keywords: Bubble columns; Kolmogorov entropy; Entropy radial minimum; Transition velocities identification; Flow pattern similarities

  • Lecture (Conference)
    13th International Conference on Gas–Liquid and Gas–Liquid–Solid Reactor Engineering (GLS-13), 20.-23.08.2017, Bruxelles, Belgium
  • Chemical Engineering Science 170(2017), 234-240
    DOI: 10.1016/j.ces.2017.03.031

Publ.-Id: 24459

New method for flow regime identification in a bubble column based on ultrafast x-ray tomography data

Nedeltchev, S.; Hampel, U.; Schubert, M.

Bubble columns (used for absorption, oxidation, chlorination, hydrogenation, waste water treatment, etc.), operate in different hydrodynamic regimes (homogeneous, transition and heterogeneous). It is essential to identify the boundaries between these flow regimes since most of the correlations for prediction of the main design parameters (gas holdup, interfacial area, mass transfer coefficients, etc.) are valid only within a certain flow regime. In the past three decades different methods of data analysis (statistical, spectral, fractal, chaotic, wavelet, etc.) have been developed for flow regime identification. However, they can identify successfully only the first transition velocity (from homogeneous to transition regime). The bubble column hydrodynamics are very complex and usually more than two regime transitions occur. They could be detected by means of some new and more powerful method of data analysis. In this work, we introduce a new dimensionless parameter based on the division of the X-ray tomography data into many state vectors. Some routines from nonlinear chaos analysis (Schouten et al., 1994) are used.
The bubble column had an inner diameter of 0.1 m and was equipped with a perforated plate distributor (55 holes, ø 0.5×10-3 m). The gas-liquid system consisted of air and deionized water. The clear liquid height Ho was set at 0.66 m. Superficial gas velocities Ug ranging from 0.01 up to 0.10 m/s were employed. The data used for the new method were recorded by means of ultrafast X-ray tomography (scan level=0.5 m). The time series consisted of 29,000 points and were sampled with a frequency of 1000 Hz.
Every reconstructed image was divided into the same semi-rings. In this work the pixel values in a specific semi-ring (inner radius=10×10-3 m ; outer radius=15×10-3 m) were used for further analysis. The data were divided into state vectors consisting of 50 elements and then the distance between pre-selected vector pairs was estimated. For this purpose, the maximum norm (Schouten et al., 1994) was used, i.e. the vector distance was equal to the maximum absolute difference between two elements from the vector pair. The number of vector pairs with distance smaller than some pre-selected criterion (three times the average absolute deviation (AAD)) was used as a basis for the new method for flow regime identification in a bubble column.
It was found that the ratio of the number of vector pairs (with a distance smaller than 3AAD) found in the second part of the signal divided by the one in the first part of the signal can be used for identifying three transition velocities Utrans. They correspond to three well-pronounced local minima. At Ug=0.02 m/s the gas maldistribution regime transforms itself into homogeneous (bubbly) regime. This flow regime is stable up to Ug=0.04 m/s. Beyond this critical gas velocity begins the transition flow regime. The onset of the heterogeneous (churn-turbulent) regime occurs at Ug=0.06 m/s.
When the reconstruction entropies (RE) (Nedeltchev, 2015) are extracted from the vector pairs (meeting the criterion about the vector distance) in both the first and second parts of the signal and the ratio between them is calculated, the same three Utrans values are identified. It was illustrated that the three local minima occur at Ug=0.02, 0.04 and 0.06 m/s, respectively.
In the full-length contribution, based on the above-mentioned new approach, the transition velocities Utrans in many different parts from the column’s cross-section will be identified. A comparison between the transition velocities in the column core and annulus will also be shown.

Keywords: Bubble column; Air-water system; Transition velocities; Ultrafast X-ray tomography; State vectors; Reconstruction entropy

  • Poster
    Third International Symposium on Multiscale Multiphase Process Engineering, 08.-11.05.2017, Toyama City, Japan

Publ.-Id: 24458

Effect of heat exchanger internals on the main transition velocities in a bubble column

Nedeltchev, S.; Möller, F.; Hampel, U.; Schubert, M.

The application of bubble columns to industrial processes, such as Fischer-Tropsch synthesis and liquid-phase methanol synthesis, often involves a large amount of heat generation. That is why, heat exchangers are installed to remove the generated heat. However, the bubble dynamics in bubble columns with dense internals is still not well understood.
In this work, for the first time a flow regime identification in a bubble column with internals (dense vertical heat exchanger tubes) was performed. The bubble column had an inner diameter of 0.1 m and was equipped with a perforated plate distributor (55 holes, ø 0.5×10-3 m). The gas-liquid system consisted of air and deionized water. The clear liquid height Ho was set at 1.1 m. Superficial gas velocities Ug ranging from 0.01 up to 0.15 m/s were employed. The bubble column was equipped with 37 heat exchanger tubes having a square pitch with a diameter of 8×10-3 m and a clearance of 3×10-3 m. Gas holdup fluctuations were recorded by means of a conductivity wire-mesh sensor installed at an axial position of 0.715 m. The time series (60,000 points, sampling frequency (fs)=2000 Hz) were further treated based on the non-linear chaos theory (Schouten et al., 1994; Nedeltchev et al., 2014).
For comparison, the two main transition velocities Utrans in the empty bubble column (Ho=0.66 m) counterpart were also identified. The information entropies were extracted from X-ray data (29,000 points, fs=1000 Hz) recorded by the ultrafast tomographic facility. It was shown that in a bubble column with internals two main transition velocities Utrans can be identified by means of the Kolmogorov entropy (KE) profile. The flow regime boundaries are identifiable on the basis of the sudden change in the decreasing KE rate. It is interesting to note that well-pronounced local KE minima (Nedeltchev et al., 2014), known from empty bubble columns, are not observed in a bubble column with internals.
At Ug=0.05 m/s the bubbly flow (homogeneous) regime transforms itself into the transition regime. The rate of the KE decrease in both flow regimes is different. At Ug=0.11 m/s the heterogeneous regime (mixture of churn-turbulent and slug flow regimes) is formed. It is characterized with constant KE values. The existence of the slug flow regime in the column core is explainable with the relatively small diameter of the column at which, according to Wilkinson et al. (1992), the effect of the column wall is still present.
In an empty bubble column, two well-pronounced local minima of the information entropy values denote the two main Utrans values. The first transition velocity occurs earlier at Ug=0.04 m/s as compared to the column with internals, which means that the presence of internals stabilizes the bubbly flow regime. The second transition velocity (the onset of the heterogeneous flow regime) is unaffected by the internals.
In the full-length contribution, the time-dependent nature of the main transition velocities as well as the effect of the axial height on the Utrans values in bubble columns with and without internals will also be discussed in a comparable manner. A comparison between the transition velocities in the column core and annulus will also be shown.

Keywords: Bubble column with internals; Transition velocities; Kolmogorov entropy; Gas holdup fluctuations; Wire-mesh sensor; Ultrafast X-ray tomography

  • Lecture (Conference)
    Third International Symposium on Multiscale Multiphase Process Engineering, 08.-11.05.2017, Toyama City, Japan

Publ.-Id: 24457

Comparison Between the Boundaries of the Main Flow Regimes Identified by Ultrafast X-Ray Tomography in Different Parts from the Cross-Section of a Bubble Column

Nedeltchev, S.; Schubert, M.

Bubble columns are characterized by an effective phase contact, high heat and mass transfer coefficients, low maintenance and operating costs due to the absence of moving parts and low column pressure drop. Due to their numerous advantages bubble columns are used extensively in many applications (oxidation, chlorination, waste water treatment, etc.). Therefore, it is essential to have detailed knowledge about the hydrodynamic behavior of these gas-liquid contactors. The identification of the boundaries of the main hydrodynamic regimes is important for improvement of the design, operation and control of bubble columns. The main objective of our work is to apply a new identification method (based on the modified Shannon entropy) to x-ray tomography data for accurate determination of the boundaries of the main hydrodynamic regimes (homogeneous, transition and heterogeneous).
The time series (extracted from reconstructed raw images) were measured by means of ultrafast x-ray tomography (sampling frequency=1000 Hz) in a bubble column (0.1 m in ID) and they were subsequently treated by the modified Shannon entropy algorithm developed by Nedeltchev et al. (2016). The raw time series give very good information about the x-ray attenuation and they are measure for the density distribution and the fraction of gas phase in different regions from the column’s cross-section. The column was equipped with a perforated plate distributor (55 holes, Ø 0.5×10-3 m) and operated with an air-deionized water system at ambient conditions. The tomographic scans were performed at an axial height of 0.5 m.
The data were organized in groups of 100 points and their sums were calculated. These sums were needed for the calculation of the probabilities of appearance of a particular value in the time series and the local Shannon entropies. It was found that the maximum sum can be used as a flow regime identifier. It was shown that two well-pronounced minima can be distinguished in the maximum sum values extracted at different superficial gas velocities Ug in the central part of the column’s cross-section. The first local minimum occurs at Ug=0.03 m/s and identifies the end of the homogeneous regime. The onset of the heterogeneous regime occurs at Ug=0.07 m/s. It was illustrated that the information entropy extracted from the data in the entire cross-section is capable of identifying the two main transition velocities at 0.025 m/s and 0.085 m/s. So, it was concluded that the heterogeneous regime starts somewhat earlier in the center of the cross-section. The homogeneous regime in the center and the entire cross-section ends at practically the same Ug value (0.025-0.03 m/s). It is noteworthy that for air-water system the theoretical prediction (0.029 m/s) by the correlation of Reilly et al. (1994) is very close to our experimental results.
Such a comparison has been performed at 20 different segments of the column’s cross section. The approach enables the preparation of a radial profile of the transition velocities. Flow regime identification results based on the maximum sums, information amounts and Shannon entropies are compared and discussed.

Keywords: Bubble column; x-ray tomography; Shannon entropy; flow Regime identification

  • Lecture (Conference)
    ASME 2016 Heat Transfer, Fluids Engineering & Nanochannels, Microchannels and Minichannels Conference, 10.-14.07.2016, Washington DC, USA

Publ.-Id: 24456

LC-MS supported studies on the metabolism of the sigma-1 receptor ligand (–)-(S)-[18F]fluspidine

Ludwig, F.-A.; Fischer, S.; Houska, R.; Hoepping, A.; Patt, M.; Wünsch, B.; Sabri, O.; Steinbach, J.; Brust, P.

Objectives: In an ongoing clinical study (–)-(S)-[18F]fluspidine (1, 2) is being investigated for imaging of sigma-1 receptors in patients with major depression by PET. Beside estimation of the fraction of unchanged radiotracer in plasma and urine, radiometabolites formed should be detected and their structures elucidated.
Methods: (–)-(S)-[18F]Fluspidine or unlabelled reference were incubated with human liver microsomes (HLM) in presence of NADPH and/or activated glucuronic acid (UDPGA) at 37°C. Metabolites were detected by radio-HPLC or LC-MS and characterized by aid of reference compounds or structural elucidation using different MS methods (EPI, MS3). Plasma (10, 20, 30 min p.i) and urine (90 min p.i.) samples of human subjects receiving 268 (245-290) MBq (–)-(S)-[18F]fluspidine i.v. were investigated and compared to results from HLM incubations.
Results: By incubation with HLM mainly 3 hydroxylation products and one debenzylation product were formed. The product hydroxylated at the alkyl side chain was glucuronidated subsequently. Plasma samples (10, 20, 30 min p.i.) obtained from human showed 97.7%, 93.8%, and 88.6% (SD=2.6-7.9, n=6-8) of unchanged tracer. In urine (90 min p.i.) the fraction of tracer was 0–7.8% (average of 2.3%, n=10) and up to 3 main radiometabolites were detected (Figure 1). The one with the highest intensity, also found in plasma, matched the glucuronide formed in vitro. Debenzylation of the parent tracer was detected with a small proportion.
Conclusions: The results demonstrate an appropriate metabolic stability of (–)-(S)-[18F]fluspidine for the application as PET ligand. The structure of the major radiometabolite found in plasma and urine could be assigned by means of in vitro studies. Routes of metabolism are currently investigated in more detail. 302
[1] German Clinical Trial Register, DRKS-ID: DRKS00008321
[2] Fischer et al. Eur. J. Nucl. Med. Mol. Imaging 2011, 38, 540–551

  • Poster
    International Symposium On Radiopharmaceutical Sciences (ISRS), 14.-19.05.2017, Dresden, Deutschland
  • Open Access Logo Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)1, 385
    DOI: 10.1002/jlcr.3508

Publ.-Id: 24455

Non-linear quantum dynamics in strong and short electromagnetic fields

Titov, A. I.; Kämpfer, B.; Hosaka, A.; Takabe, H.

In our contribution we give a brief overview of two widely discussed quantum processes: electron-positron pairs production off a probe photon propagating through a polarized short-pulsed electromagnetic (e.m.) (e.g.\ laser) wave field or generalized Breit-Wheeler process and a single a photon emission off an electron interacting with the laser pules, so-called non-linear Compton scattering. We show that at small and moderate laser field intensities the shape and duration of the pulse are very important for the probability of considered processes. However, at high intensities the multi-photon interactions of the fermions with laser field are decisive and completely determined all aspects of subthreshold electron-positron pairs and photon production

Publ.-Id: 24452

The impact of the revised 17O(p,α)14N reaction rate on 17O stellar abundances and yields

Straniero, O.; Bruno, C. G.; Aliotta, M.; Best, A.; Boeltzig, A.; Bemmerer, D.; Broggini, C.; Caciolli, A.; Cavanna, F.; Ciani, G. F.; Corvisiero, P.; Cristallo, S.; Davinson, T.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Piatti, D.; Piersanti, L.; Prati, P.; Samorjai, E.; Strieder, F.; Szucs, T.; Takács, M. P.; Trezzi, D.

Context. Material processed by the CNO cycle in stellar interiors is enriched in 17O. When mixing processes from the stellar surface reach these layers, as occurs when stars become red giants and undergo the first dredge up, the abundance of 17O increases. Such an occurrence explains the drop of the 16O/17O observed in RGB stars with mass larger than 1.5 M_\solar. As a consequence, the interstellar medium is continuously polluted by the wind of evolved stars enriched in 17O . Aims. Recently, the Laboratory for Underground Nuclear Astrophysics (LUNA) collaboration released an improved rate of the 17O(p,alpha)14N reaction. In this paper we discuss the impact that the revised rate has on the 16O/17O ratio at the stellar surface and on 17O stellar yields. Methods. We computed stellar models of initial mass between 1 and 20 M_\solar and compared the results obtained by adopting the revised rate of the 17O(p,alpha)14N to those obtained using previous rates. Results. The post-first dredge up 16O/17O ratios are about 20% larger than previously obtained. Negligible variations are found in the case of the second and the third dredge up. In spite of the larger 17O(p,alpha)14N rate, we confirm previous claims that an extra-mixing process on the red giant branch, commonly invoked to explain the low carbon isotopic ratio observed in bright low-mass giant stars, marginally affects the 16O/17O ratio. Possible effects on AGB extra-mixing episodes are also discussed. As a whole, a substantial reduction of 17O stellar yields is found. In particular, the net yield of stars with mass ranging between 2 and 20 M_\solar is 15 to 40% smaller than previously estimated. Conclusions. The revision of the 17O(p,alpha)14N rate has a major impact on the interpretation of the 16O/17O observed in evolved giants, in stardust grains and on the 17O stellar yields.

Keywords: Nuclear Astrophysics


Publ.-Id: 24451

Active and passive electronics for smart implants

Makarov, D.

The portable consumer electronics necessitates functional elements to be lightweight, flexible, and wearable [1-4]. The unique possibility to adjust the shape of the devices offered by this alternative formulation of the electronics provides vast advantages over the conventional rigid devices particularly in medicine and consumer electronics. There is already a remarkable number of available flexible devices starting from interconnects, sensing elements towards complex platforms consisting of communication and diagnostic components.
We developed shapeable magnetoelectronics [5] – namely, flexible [6-8], printable [9,10], stretchable [11,12] and even imperceptible [13] magnetosensitive large area elements, which were completely missing in the family of flexible electronics, e.g. for smart skin applications. On the other hand, we realized self-assembled compact tubular microchannels based on strain engineering [14] with integrated passive sensory elements [15-17] and communication antenna devices [18] for on-chip and bio-medical applications, e.g. smart implants [19,20].
Combining these two research directions carried out at different length scales into a single truly interdisciplinary topic opens up the novel field of smart biomimetics [20]. In this respect, we demonstrated mechanically and electrically active compact biomimetic microelectronics, which can serve as a base for realization of novel regenerative neuronal cuff implants with unmatched functionalities. The biomimetic microelectronics can mechanically adapt to and impact the environment possessing the possibility to assess, adopt and communicate the environmental changes and even stimulate the environment electrically.
In my talk, these recent developments will be covered.

[1] M. G. Lagally, MRS Bull. 32, 57 (2007).
[2] J. A. Rogers et al., Nature 477, 45 (2011).
[3] S. Bauer et al., Adv. Mater. 26, 149 (2014).
[4] M. Kaltenbrunner et al., Nature 499, 458 (2013).
[5] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
[6] G. Lin, D. Makarov et al., Lab Chip 14, 4050 (2014).
[7] M. Melzer, D. Makarov et al., Adv. Mater. 27, 1274 (2015).
[8] N. Münzenrieder, D. Makarov et al., Adv. Electron. Mater. (2016), 10.1002/aelm.201600188.
[9] D. Karnaushenko, D. Makarov et al., Adv. Mater. 27, 880 (2015).
[10] D. Karnaushenko, D. Makarov et al., Adv. Mater. 24, 4518 (2012).
[11] M. Melzer, D. Makarov et al., Adv. Mater. 27, 1333 (2015).
[12] M. Melzer, D. Makarov et al., Nano Lett. 11, 2522 (2011).
[13] M. Melzer, D. Makarov et al., Nat. Commun. 6, 6080 (2015).
[14] O. G. Schmidt et al., Nature 410, 168 (2001).
[15] I. Mönch, D. Makarov et al., ACS Nano 5, 7436 (2011).
[16] C. Müller, D. Makarov et al., Appl. Phys. Lett. 100, 022409 (2012).
[17] E. J. Smith, D. Makarov et al., Lab Chip 12, 1917 (2012).
[18] D. D. Karnaushenko, D. Makarov et al., NPG Asia Materials 7, e188 (2015).
[19] D. Karnaushenko, D. Makarov et al., Adv. Mater. 27, 6582 (2015).
[20] D. Karnaushenko, D. Makarov et al., Adv. Mater. 27, 6797 (2015).

Keywords: shapeable magnetoelectronics; magnetic field sensors

  • Invited lecture (Conferences)
    MRS Fall Meeting 2016, 27.11.-02.12.2016, Boston, USA

Publ.-Id: 24450

Observations on surface magnetic order in FeGe and FeSi

Makarov, D.; Streubel, R.; Perez Rodriguez, N.; Pierce, D. T.; Unguris, J.; Pofahl, S.; Schäfer, R.; Schmidt, M.; Baenitz, M.; Kronast, F.; Wilhelm, H.; Rößler, U. K.

The twisted magnetization textures in chiral magnets are inherently frustrated, similarly to the mesophases in chiral liquid-crystals. The twisted basic texture can become dramatically altered by the penetration of secondary twists over larger lengths and the formation of defects. Hence, a well-ordered and smooth texture like a simple spiral may be twisted or defected. In chiral liquid-crystal systems, the frustration results in the formation of defects like the disclination networks of blue phases or twisted-grain-boundary phases. Such states can easily be shaped and transformed under the influence of competing anisotropies, e.g., by applied fields in the bulk and by anchoring the molecules of a liquid crystal at surfaces.
We investigated surfaces of FeGe single crystals with the cubic B20 structure using various magnetic imaging techniques and found a ferromagnetic order above the magnetic ordering transition in the bulk. This ferromagnetic order is seen by magnetic optical Kerr effect (MOKE) microscopy as a simple ferromagnetic domain structure of an Ising-like magnet at room-temperature. Scanning electron microcopy with polarization analysis (SEMPA) and X-ray photoemission electron microscopy (XPEEM) allowed us to follow the evolution of a fine-structure in this ferromagnetic surface upon lowering the temperature, when the bulk of the FeGe crystal orders into the spiral ground-state.
We discover a static defect-ordered state with a network of line-defects emerges near the surface under the influence of a particular surface-magnetic ordering transition. These defects of the helical magnetic order are topologically necessary lines where the magnetic order becomes singular or passes through zero at elevated temperatures. This ferromagnetic skin has a strong uniaxial anisotropy and frustrates the helimagnetic texture by anchoring it to the surface. In the spiral below the Neel temperature at 279 K, conical modulations in the ferromagnetic surface layer are observed that prove the formation of a network of dislocations because the propagation direction of the surface-modulation deviates from the propagation direction in the bulk. Near magnetic ordering temperature a coexistence of bubble-like circular domains and stripes is observed in the surface layer. This illustrates the appearance of complex three-dimensional textures with defects, double-twists and spiral-like kinks near the surface and related to the particular surface-magnetic ordering. Hence, at the first-order transition between the precursor state and spiral order in zero magnetic field of FeGe, a co-existence of helical and skyrmionic textures is revealed. Ab initio calculations have been used to motivate the existence of enhanced spin-moments at the surfaces of FeGe and an increased effect of spin-orbit coupling. This explains the experimental observations of a surface-magnetic ordering in FeGe, which acts like a strongly uniaxial ferromagnetic film with an Ising-like character on the underlying spiral bulk state.
Similar experiments using MOKE and XPEEM on the isostructural compound FeSi give evidence of a fragile magnetic ordering at the surface of this anomalous paramagnetic semiconductor, too. This may mean that the FeSi surfaces may behave like strongly anisotropic ultrathin magnetic films, while no magnetic long-range ordering takes place in the bulk.

Keywords: FeGe; FeSi; skyrmions

  • Invited lecture (Conferences)
    MRS Fall meeting 2016, 27.11.-02.12.2016, Boston, USA

Publ.-Id: 24449

Argonne: Curved magnetic nanomembranes

Makarov, D.

While conventionally magnetic films and structures are fabricated on flat surfaces, the topology of curved surfaces has only recently started to be explored and leads to new fundamental physics as well as applied device ideas [1]. In particular, novel effects occur when the magnetization is modulated by curvature providing a new degree of freedom that leads to new magnetization configurations (see for instance [2,3]) and is predicted to have major implications on the spin dynamics due to topological constraints for instance in circular tubes and rolls [4].
Advances in this novel field solely rely on the understanding of the fundamentals behind the modifications of magnetic responses of 3D-curved magnetic thin films. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and Dzyaloshinskii-Moriya interaction are characteristic of curved surfaces [5-7], leading to curvature-driven magnetochiral effects [8-10] and topologically induced magnetization patterning [7, 11], including unlimited domain wall velocities in hollow tubes [4], chirality symmetry breaking [7-10] and Cherenkov-like effects for magnons [12]. In addition to these rich physics, the application potential of 3D-shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications [13], spin-wave filters [14], magneto-encephalography devices [15] and high-speed racetrack memory devices [4]. To this end, the initially fundamental topic of the magnetism in curved geometries strongly benefited from the input of the application-oriented community, which among others explores the shapeability aspect of the curved magnetic thin films. These activities resulted in the development of the family of shapeable magnetoelectronics [16], which already includes flexible [17], printable [18], stretchable [19] and even imperceptible [20] magnetic field sensorics.
These recent developments starting from the theoretical predictions to the fabrication and characterization of 3D-curved magnetic thin films and their application potential are in the focus of this talk.
[1] R. Streubel, DM et al., J. Phys. D: Appl. Phys. vol. 49, pp. 363001, 2016.
[4] M. Yan et al., Phys. Rev. Lett. vol. 104, pp. 057201, 2010.
[5] Y. Gaididei et al., Phys. Rev. Lett. vol. 112, pp. 257203, 2014.
[6] O. V. Pylypovskyi, DM et al., Phys. Rev. Lett. vol. 114, pp. 197204, 2015.
[7] O. V. Pylypovskyi, DM et al., Sci. Rep. vol. 6, pp. 23316, 2016.
[8] R. Hertel, SPIN vol. 03, pp. 1340009, 2013.
[9] M. Yan et al., Appl. Phys. Lett. vol. 100, pp. 252401, 2012.
[10] J. A. Otalora et al., Appl. Phys. Lett. vol. 100, pp. 072407, 2012.
[11] V. P. Kravchuk, DM et al., Phys. Rev. B vol. 85, pp. 144433, 2012.
[12] M. Yan et al., Phys. Rev. B vol. 88, pp. 220412, 2013.
[13] I. Mönch, DM et al., ACS Nano vol. 5, pp. 7436, 2011.
[14] F. Balhorn et al., Phys. Rev. Lett. vol. 104, pp. 037205, 2010.
[15] D. Karnaushenko, DM et al., Adv. Mater. vol. 27, pp. 6582, 2015.
[16] D. Makarov et al., Appl. Phys. Rev. vol. 3, pp. 011101, 2016.
[17] M. Melzer, DM et al., Adv. Mater. vol. 27, pp. 1274, 2015.
[18] D. Karnaushenko, DM et al., Adv. Mater. vol. 27, pp. 880, 2015.
[19] M. Melzer, DM et al., Nano Lett. vol. 11, pp. 2522, 2011.
[20] M. Melzer, DM et al., Nature Commun. vol. 6, pp. 6080, 2015.

Keywords: curved magnetic thin films; chiral interactions

  • Invited lecture (Conferences)
    Seminar at Argonne National Lab, 28.11.2016, Lemont, USA

Publ.-Id: 24448

New data for cosmogenic 53Mn and 60Fe in iron meteorites

Smith, T.; Leya, I.; Merchel, S.; Rugel, G.; Pavetich, S.; Fröhlich, M.; Wallner, A.; Fifield, K.; Tims, S.; Korschinek, G.; Faestermann, T.

Cosmogenic nuclides in meteorites can provide information on cosmic ray exposure (CRE) histories. In space, meteoroids are irradiated by galactic cosmic ray particles, inducing the production of cosmogenic nuclides (10Be, 26Al, 36Cl, 41Ca, 53Mn, 60Fe). Meteorites are routinely measured for 10Be, 26Al, and 36Cl. However the database for 53Mn and 60Fe is scarce due to the low availability of high-MV accelerators and the debate over the half-lives of 53Mn and 60Fe. We Report new 53Mn and 60Fe data for iron meteorites measured at Canberra (53Mn, 60Fe) and Munich (60Fe). Among these radionuclides, 53Mn has the longest half-life, thus is least influenced by terrestrial ages. The advantage of 53Mn and 60Fe isotopes is that only two (Fe, Ni) and one (Fe) target element(s), respectively, dominate production, overcoming the problem of inhomogeneous S and P distribution. Our new 60Fe data almost doubles that present in the literature. We measured 53Mn in seven subsamples of the iron meteorite Twannberg. The new 53Mn and 60Fe data, with 10Be, 26Al, 36Cl, 41Ca and the noble gases, will better constrain the CRE histories of meteorites and will also serve as benchmarks to validate and improve Monte-Carlo model calculations.

Keywords: AMS; meteorite; cosmogenic; exposure age; accelerator mass spectrometry

  • Lecture (Conference)
    DPG Frühjahrstagung des Arbeitskreises Atome, Moleküle, Quantenoptik und Plasmen (AMOP), 06.-10.03.2017, Mainz, Deutschland

Publ.-Id: 24447

Spin torque switching in nanopillars with antiferromagnetic reference layer

Arora, M.; Fowley, C.; Mckinnon, T.; Kowalska, E.; Sluka, V.; Deac, A. M.; Heinrich, B.; Girt, E.

Spin-transfer-torque induced switching is investigated in 200 nm diameter circularly shaped, perpendicular magnetized nanopillars. A synthetic antiferromagnet, consisting of two Co/Ni multilayers coupled anti-ferromagnetically across a Ru layer, is used as a reference layer to minimize the dipolar field on the free layer. The free layer is a single 4x[Co/Ni] multilayer. The use of Pt and Pd was avoided to lower the spin-orbit scattering in magnetic layers and intrinsic damping in the free layer, and therefore, reduce the critical current required for spin-transfer-torque switching. The intrinsic Gilbert damping of a continuous 4[Co/Ni] multilayer film was measured by ferromagnetic resonance to be alpha = 0.022, which is significantly lower than in Pt or Pd based magnetic multilayers. In zero magnetic field the critical current required to switch the free layer from the parallel to antiparallel alignment is 5.2 mA, and from antiparallel to parallel alignment is 4.9 mA. Given the volume of the free layer, V_FL = 1.011022 m3, the switching efficiency, I_c=(V_FL/µ0H_c), is 5.281020 A/Tm^3, twice as efficient as any previously reported device with a similar structure

Keywords: Spin transfer switching; perpendicular magnetic anisotropy; MRAM


Publ.-Id: 24446

Mass spectrometry and the evolution of the western Namibian drainage systems

Gärtner, A.; Linnemann, U.; Merchel, S.; Niedermann, S.; Gerdes, A.; Rugel, G.; Scharf, A.; Le Bras, L.; Hofmann, M.; Zieger, J.

Our multi-method MS study (AMS, noble gas MS, LA-(MC)-ICP-MS) aims to constrain the evolution of the western Namibian drainages since the last ca. 40 Ma. Therefore, fluvial sediments of several rivers and their precursors were sampled. In order to obtain precise Surface exposure ages of the various terrace levels, the routinely used cosmogenic nuclides 10Be, 21Ne, 26Al (quartz), and 36Cl (calcite) were applied either on surface samples or on depth-profiles consisting of 3 to 5 samples each. U-Pb small scale isochrone (SSI) ages of calcareous matrices were also used for terrace dating. Sedimentary provenances were revealed by detrital zircon (ZrSiO4) geochronology using U-Th-Pb and Lu-Hf isotope systematics. They indicate varying detrital zircon patterns through time. Our approach facilitates the recognition of changes in the fluvial sediment provenance at certain points in time. Such combined studies have a huge potential for revealing the palaeohydrological history, and to estimate amplitudes and processing Speeds of past events or changing sizes of catchment areas, which is of particular interest for modelling the palaeoclimate and palaeogeography.

Keywords: AMS; accelerator mass spectrometry; palaeoclimate; LA-ICP-MS

  • Lecture (Conference)
    DPG Frühjahrstagung des Arbeitskreises Atome, Moleküle, Quantenoptik und Plasmen (AMOP), 06.-10.03.2017, Mainz, Deutschland

Publ.-Id: 24445

Generic zinc corrosion studies at PWR LOCA conditions

Harm, U.; Kryk, H.; Wiezorek, M.; Hampel, U.

During the sump recirculation phase after loss-of-coolant accidents (LOCA) in pressurized water reactors (PWR), coolant spilling out of the leak in the primary cooling circuit is collected in the reactor sump and recirculated to the reactor core by residual-heat removal pumps. The long-term contact of the boric acid containing coolant with hot-dip galvanized containment internals (e.g. grating treads, supporting grids of sump strainers) may cause corrosion of the corresponding materials influencing the cooling water chemistry.
Generic investigations regarding such zinc corrosion processes, changes of the coolant chemistry and possible resulting in-core effects are subject of joint research projects of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), TU Dresden (TUD) and Zittau/Görlitz University of Applied Sciences (HSZG). Lab-scale experiments at HZDR and TUD were focused on elucidation of physico-chemical corrosion and precipitation processes as well as resulting clogging effects [1-2].
Recent results of generic experiments in a lab-scale corrosion test facility led to further information regarding the main parameters determining the zinc corrosion rates and the whole corrosion process in such scenarios.
Main influences on the zinc corrosion rates were identified as the impact of the coolant jet onto the corroding surface and the particular flow conditions around submerged zinc surfaces.
In contrast, variations of the coolant temperature in the range between 25 °C and 70 °C as well as small changes in the boric acid concentration have no significant influence on the corrosion rates during the first stage of the corrosion process.
Further lab-scale experiments at realistic time-dependent LOCA parameters like calculated temperature courses in the sump and inside the reactor core are planned to evaluate, if zinc corrosion processes with subsequent zinc borate precipitations could lead to considerable clogging effects inside the reactor core.
The results obtained at lab-scale were complemented by corresponding experiments in semi-technical test facilities of the project partner HSZG.

[1] Seeliger, A.; Alt, S.; Kästner, W.; Renger, S.; Kryk, H., Harm, U. : Zinc corrosion after loss-of-coolant accidents in pressurized water reactors - thermo- and fluid-dynamic effects. Nuclear Engineering and Design, 2016, 305, 489-502
[2] Hoffmann, W.; Kryk, H.; Seeliger, A.; Kästner, W.; Alt, S. & Renger, S.: Zinc corrosion after loss-of-coolant accidents in pressurized water reactors - physicochemical effects. Nuclear Engineering and Design, 2014, 280, 570-578

  • Contribution to proceedings
    48. Jahrestagung Kerntechnik (Annual Meeting on Nuclear Technology / AMNT 2017), 16.-17.05.2017, Berlin, Deutschland
    Generic Zinc Corrosion Studies At PWR LOCA Conditions, Berlin: INFORUM Verlags- und Verwaltungsgenossenschaft mbH, 978-3-926956-96-5
  • Lecture (Conference)
    48. Jahrestagung Kerntechnik (Annual Meeting on Nuclear Technology / AMNT 2017), 16.-17.05.2017, Berlin, Deutschland

Publ.-Id: 24444

Entwicklung und Überprüfung eines Photonenmodells für die Abstrahlung durch hochenergetische Elektronen

Burau, H.

This diploma thesis extends the open source particle-in-cell code PIConGPU by two new physics modules which incorporate effects of radiation emission and back reaction of highly relativistic electrons in strong electromagnetic background fields into the simulation. The first module involves the treatment of nonlinear Thomson- and Compton-scattering using the synchrotron approximation. It allows for the generation of X-ray and gamma photons in the classical regime as well as in the QED regime including self consistent radiation back reaction. Through simulations of collisions between laser pulses and electron bunches the impact of QED effects on experimental spectra is investigated. The second module covers the scattering of electrons on atomic nuclei including electron deflection and generation of Bremsstrahlung-photons. In a numerical case study it is shown that the analysis of Bremstrahlung can be used as experimental diagnostic for electron dynamics in overdense plasmas.

Keywords: PIConGPU; QED radiation reaction; nonlinear Comptonscattering; Bremsstrahlung

  • Diploma thesis
    TU Dresden, 2016
    Mentor: Prof. Ulrich Schramm, Prof. Tom Cowan, Dr. Michael Bussmann

Publ.-Id: 24443

Erste Tests für 44Ti-AMS an DREAMS

Scharf, A.; Bemmerer, D.; Ditrói, T.; Khojasteh, N.; Merchel, S.; Rugel, G.; Zuber, K.

Das Radionuklid 44Ti (T1/2 = 58,9 a) wird vor allem während Supernovaexplosionen gebildet und spielt eine wichtige Rolle für deren theoretische Modelle und die Nukleosynthese schwerer Elemente. In Supernovaüberresten kann 44Ti mittels &gamma-Astronomie nachgewiesen werden, allerdings befinden sich die Beobachtungen nicht im Einklang mit den theoretischen Modellen. Problematisch dabei ist, dass der Wirkungsquerschnitt der Reaktion 40Ca(&alpha,&gamma)44Ti bisher nur unzureichend bekannt ist [1].
Während bislang nur 44Ti-AMS-Messungen an großen Beschleunigern (ab 10 MV Terminalspannung) durchgeführt wurden [2], sollte es prinzipiell auch möglich sein, an 6-MV-Anlagen dieses Radionuklid zuverlässig zu messen. Wir präsentieren erste Tests an der AMS-Anlage DREAMS des HZDR, die zeigen, dass mithilfe einer Degrader-Folie eine zuverlässige Abtrennung des stabilen Isobars 44Ca und Messung des Radionuklids 44Ti auch bei Beschleunigungsspannungen von 6 MV möglich ist.
Diese ersten Tests dienen dazu, die Machbarkeit von AMS-basierten Messungen des Wirkungsquerschnitts der Reaktion 40Ca(&alpha,&gamma)44Ti an DREAMS auszuloten.
Das Projekt wurde unterstützt vom DAAD.

Ref.: [1] Schmidt et al., Phys. Rev. C 88, 025803 (2013)
[2] Nassar et al., Phys. Rev. Let. 96, 041102 (2006)

Keywords: AMS; DREAMS; 44Ti; Supernova; Nukleosynthese

  • Lecture (Conference)
    DPG Frühjahrstagung des Arbeitskreises Atome, Moleküle, Quantenoptik und Plasmen (AMOP), 06.-10.03.2017, Mainz, Deutschland, 06.-10.03.2017, Mainz, Deutschland

Publ.-Id: 24442

Experimental investigation on the influence of surfactant concentration on the bubble shape and mass transfer in a small channel

Haghnegahdar, M.; Boden, S.; Hampel, U.

In the work presented in this paper, the shape and absorption rate of an individual elongated Taylor bubble of CO2 through contaminated water was measured in millimeter-size channel. The influence of concentration of surfactant on dissolution rate of an individual elongated Taylor bubble of carbon dioxide in water was investigated using high resolution X-ray radiography technique in vertical channels. The bubbles were held stationary in the down-flowing liquid and the liquid-side mass transfer coefficient was determined from microfocus X-ray images.
The experiments cover a range of initial bubble equivalent diameter (deq: sphere-volume equivalent bubble diameter) varying from 6 to 10 mm. The pipe is a glass pipe with 6 mm inside diameter (D). The bubble is unceasingly monitored by holding the bubble stationary using downward flow of liquid. The X-ray method was chosen since it is not dependent on the refractive index; therefore it is the most accurate method in comparison with other conventional optical techniques. This technique was qualified to disclose the three-dimensional shape of Taylor bubbles in capillary and enabled the acquisition of a series of high-resolution radiographic images of nearly stationary Taylor bubbles (Haghnegahdar et al., 2015). The processed images which give volume (and also the interfacial area) of the bubble with high accuracy as a function of time, are used to evaluate the liquid side mass transfer coefficient between bubble and liquid using the mass conservation equation. The liquid phase is milli-pore water contaminated by conventional surfactants and the gas phase is CO2.
The results confirmed the accumulation of surfactants on the tail of the bubbles. Furthermore, applying different concentrations of surfactant reveals that in our case, where surface coverage ratio of surfactant on the bubbles is high, increase of contamination does not have a noticeable influence on the mass transfer coefficient of bubbles.

Keywords: Surfactant concentration; Taylor bubble; Mass transfer coefficient

  • Poster
    14th Multiphase Flow Conference and Short Course:Simulation, Experiment and Application, 08.-10.11.2016, HZDR, Dresden, Germany

Publ.-Id: 24441

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