Publication database - Helmholtz-Zentrum Dresden-Rossendorf

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Only approved publications

26699 Publications
Product-Centric Simulation-based design for recycling: case of LED lamp recycling
Reuter, M. A.; van Schaik, A.
Abstract: 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 Registration No. 24495 - Permalink

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.
Abstract: Purpose
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).

Methods
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.

Results
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.

Conclusions
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 Registration No. 24494 - Permalink

Arbeiten am und für den Grenzbereich
Joehnk, P.
Abstract: Der experimentelle Nachweis von Hypothesen der Grundlagenphysik ist oftmals nur mit einem gigantischen technologischen Aufwand zu erreichen; SERN 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
Registration No. 24493 - Permalink

Corrosion phenomena at and nanoscale anticorrosion treatments of pipe organ metallic materials using ion beam based methods
Pelic, B.; Skorupa, W.; Eule, D.
Abstract: 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
Registration No. 24490 - Permalink

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.
Abstract: 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
Registration No. 24488 - Permalink

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.
Abstract: 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-Link: http://dx.doi.org/10.1109/IRMMW-THz.2016.7758577
Registration No. 24480 - Permalink

Gas and Liquid Dynamics in Bubble Columns: Advanced Flow Imaging with Ultrafast X-Ray and Radioactive Particle Tracking
Azizi, S.; Yadav, A.; Lau, Y. M.; Roy, S.; Schubert, M.
Abstract: The performance of bubble columns depends strongly on the gas and liquid phase flow dynamics. Interactions between the two phases result in certain bubble size distributions and turbulence spectra defining the transfer rates as well as the mixing behavior. Models and experiments, which treat these systems linearly, tend to over-simplify their behavior by resorting to only time and spatially averaged descriptions. Although the employed experimental techniques are rather powerful, todays’ literature commonly reports hydrodynamic data for gas or liquid phases separately, often for different dimensions, operating conditions, etc. In this work, a body of experimental data is consolidated for a laboratory bubble column using both the complementary techniques of ultrafast X-ray tomography (UXT) and radioactive particle tracking (RPT). Sizes and velocities of the dispersed gas bubbles are measured with UXT, while RPT provides velocity distribution and turbulent kinetic energy of the liquid phase. The results of both techniques have a high spatiotemporal resolution and provide a unique benchmark of experimental validation data of bubble column reactors for CFD models. In particular, the effects of gas flow rate and sparger configuration determining the inlet bubble sizes will be discussed.
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
Registration No. 24479 - Permalink

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, Ashutosh; Yuk Man, L.; Roy, S.; Schubert, M.
Abstract: 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
Registration No. 24478 - Permalink

Multiphase CFD activities at HZDR
Lucas, D.
Abstract: 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, 08.-10.11.2016, Dresden, Deutschland
Registration No. 24477 - Permalink

Validation of the baseline model for poly-disperse bubbly flows
Lucas, D.; Krepper, E.; Rzehak, R.
Abstract: 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
Registration No. 24476 - Permalink

Nuclear Laboratories and Experiments: Overview and HZDR
Bemmerer, D.
Abstract: 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
Registration No. 24475 - Permalink

Nuclear Astrophysics in Germany
Bemmerer, D.
Abstract: 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
Registration No. 24474 - Permalink

Nuclear Astrophysics at HZDR Dresden
Bemmerer, D.
Abstract: 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
Registration No. 24473 - Permalink

Electron sources and polarization
Xiang, R.; Teichert, J.
Abstract: 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
Registration No. 24470 - Permalink

Gold – a Key Enabler of a Circular Economy: Recycling of WEEE
Reuter, M. A.; van Schaik, A.
Abstract: 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
Registration No. 24468 - Permalink

Recycling processes
Hack, K.; Reuter, M. A.; Petersen, S.; Arnout, S.
Abstract: 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
Registration No. 24467 - Permalink

Spin wave propagation in ion-induced FeAl conduits
Osten, J.; Hula, T.; Bali, R.; Potzger, K.; Schultheiss, H.
Abstract: 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
Registration No. 24466 - Permalink

Simulations for the precession experiment at HZDR
Giesecke, A.; Gundrum, T.; Vogt, T.; Stefani, F.; Herault, J.
Abstract: 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
Registration No. 24460 - Permalink

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.
Abstract: 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
Registration No. 24456 - Permalink

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.
Abstract: 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 Registration No. 24451 - Permalink

Active and passive electronics for smart implants
Makarov, D.
Abstract: 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
Registration No. 24450 - Permalink

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.
Abstract: 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
Registration No. 24449 - Permalink

Argonne: Curved magnetic nanomembranes
Makarov, D.
Abstract: 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.
References
[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
Registration No. 24448 - Permalink

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.
Abstract: 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 Registration No. 24446 - Permalink

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.
Abstract: 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
Registration No. 24441 - Permalink

X-ray tomography studies of Taylor bubbles with mass transfer in small channels
Haghnegahdar, M.; Boden, S.; Hampel, U.
Abstract: For milli- and micro-reactors the bubble shape and relative velocity between two phases are mainly governed by the cross-sectional shape of the channel. For channels with circular cross section (pipes) enormous attention has been paid in the last decades and many studies on hydrodynamics and mass transfer to be found in literature. However other channel cross sections such as square channels were a subject of only a few studies [1]. Concerning the role and importance of square channels in various existing and potential industrial applications such as micro-electromechanical systems, monolith froth reactors, there exist still some gaps particularly in related aspects of transport phenomena in these channels and there needs to be further experimental work to provide detailed heat and mass transfer data for model validation.
In the work presented in this paper, the dissolution rate of a single Taylor bubble of carbon dioxide in water was investigated using high resolution X-ray radiography and tomography technique in vertical channels. The liquid side mass transfer coefficient was calculated by measuring the changes in the size of the bubble at constant pressure. The experiments cover a large range of initial Taylor bubble length varying from 4 to 26 mm. The pipe is a glass pipe with 6 mm inside diameter and square cross section. The bubbles were held stationary using the technique of Schulze and Schluender [2]. The method which is used to measure the variation of the bubble size is X-ray tomography. 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. Furthermore this technique allows tomography for square channels, while full 3D shape determination by optical techniques is difficult in square channels. The processed images which give volume (and also the interfacial area) of the bubble 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 results for the long term dissolution of single CO2 bubbles show that the dissolution curves for bubbles with different initial size follow the same trend and have relatively constant slope. In addition, it is shown that the measured mass transfer coefficient increases as the equivalent diameter of the bubble (diameter of the sphere having the same volume) decreases. The trend for the change of liquid-side mass transfer coefficient as a function of bubble size is in accordance with the data predictivd by the penetration theory.

Keywords: Mass transfer coefficient, Taylor flow, CO2, small channel
  • Lecture (Conference)
    DFG Priority Programme SPP 1506: Transport Processes at Fluidic Interfaces Abschlusskolloquium, 09.-10.05.2016, RWTH Aachen, Germany
Registration No. 24439 - Permalink

Enzymatic Decolorization of Dye-polluted Water Using Natural Cellular Carriers
Mohammed, I.; Schubert, M.; Hampel, U.
Abstract: In the current years increasing efforts have been done to develop sustainable processes with smaller ecological footprint, which is. to decrease the industrial pollution and the environmental impact.
One serious pollutant that results from the textile industry etc. is the increasing usage of dyes. The treatment of dye-polluted water is still challenging since today's methods, such as absorption and membrane filtration, have their limitations.
The application of biocatalysts represents a sustainable solution as it results in nontoxic products at comparable eco-friendly treatment costs. In particular, oxidation enzymes, such as laccase, which can oxidize dye are in the scope. However, direct application of laccase enzyme is not favorable because it requires processes to recover the enzyme, while enzymes, immobilized on a carrier can be re-used as long as the activity is sufficiently high.
Loofa is a natural-grown material of the cucumber family, which provides attractive morphological properties. Moreover, loofa carrier can be decomposed after the process without additional treatment and is inexpensive.
In the contribution, the developed laccase immobilization methodology and the optimization of the immobilization using the Response Surface Methodology (RMS) will be discussed. Furthermore, the capability to degrade dye-polluted water will be evaluated and a novel bioreactor for the water treatment will be suggested

Keywords: Laccase, Enzymatic decolorization, Loofa sponge, Immobilization, Response surface methodology
  • Lecture (Conference)
    66th Canadian Chemical Engineering Conference(CSCh2016), 16.-19.10.2016, Quebec city, Quebec, Canada
Registration No. 24438 - Permalink

Enzymatic Decolorization of Dye-polluted Water Using Natural Cellular Carriers 66th Canadian Chemical Engineering Conference/2016
Mohammed, I.; Schubert, M.; Hampel, U.
Abstract: In the current years increasing efforts have been done to develop sustainable processes with smaller ecological footprint, which is. to decrease the industrial pollution and the environmental impact.
One serious pollutant that results from the textile industry etc. is the increasing usage of dyes. The treatment of dye-polluted water is still challenging since today's methods, such as absorption and membrane filtration, have their limitations.
The application of biocatalysts represents a sustainable solution as it results in nontoxic products at comparable eco-friendly treatment costs. In particular, oxidation enzymes, such as laccase, which can oxidize dye are in the scope. However, direct application of laccase enzyme is not favorable because it requires processes to recover the enzyme, while enzymes, immobilized on the carrier can be re-used as long as the activity is sufficiently high.
Loofa is a natural-grown material of the cucumber family, which provides attractive morphological properties. Moreover, loofa carrier can be decomposed after the process without additional treatment and is inexpensive.
In the contribution, the developed laccase immobilization methodology and the optimization of the immobilization using the Response Surface Methodology (RMS) will be discussed. Furthermore, the capability to degrade dye-polluted water will be evaluated and a novel bioreactor for the water treatment will be suggested

Keywords: Laccase, Enzymatic decolorization, Loofa sponge, Immobilization, Response surface methodology
  • Lecture (Conference)
    66th Canadian Chemical Engineering Conference, 16.-19.10.2016, Québec city, Quebec, Canada
Registration No. 24435 - Permalink

Multiphase flow measurement
Hampel, U.
Abstract: The lecture introduces and discusses principles of multiphase flow measurement. In detail it addresses fundamental issues of multiphase fluid dynamics, measureable parameters, hardware and software aspects of measurement techniques, as well as its relation to multiphase flow modelling and CFD code development.
Keywords: multiphase flow, flow measurement, local probes, PIV, tomography
  • Invited lecture (Conferences)
    Iraqi-German Partnership on Multiphase Flow Research and Training (IGP-Multiflow), Summer School, 03.-07.10.2016, Dresden, Germany
Registration No. 24432 - Permalink

Curvature-Induced Asymmetric Spin-Wave Dispersion
Otálora, A. S.; Yan, M.; Schultheiss, H.; Hertel, R.; Kákay, A.
Abstract: In magnonics, spin waves are conceived of as electron-charge-free information carriers. Their wave behavior has established them as the key elements to achieve low power consumption, fast operative rates, and good packaging in magnon-based computational technologies. Hence, knowing alternative ways that reveal certain properties of their undulatory motion is an important task. Here, we show using micromagnetic simulations and analytical calculations that spin-wave propagation in ferromagnetic nanotubes is fundamentally different than in thin films. The dispersion relation is asymmetric regarding the sign of the wave vector. It is a purely curvature-induced effect and its fundamental origin is identified to be the classical dipole-dipole interaction. The analytical expression of the dispersion relation has the same mathematical form as in thin films with the Dzyalonshiinsky-Moriya interaction. Therefore, this curvatureinduced effect can be seen as a “dipole-induced Dzyalonshiinsky-Moriya-like” effect.
Keywords: nanotubes, spin-wave dispersion, non-reciprocal Registration No. 24431 - Permalink

Comparing field ionization models in simulations of laser-matter interaction
Garten, M.
Abstract: Field ionization plays an important role in modeling the interaction of high-power, ultra-short lasers pulses with matter. Many field ionization models exist that have predictive capability at non-relativistic laser intensities and for laser pulse durations that much longer than the atomic time scales. Most existing models take a quasi-static approach to the laser field on atomic dimensions and time scales. Yet, with pulses as short as a few ~10 to ~100 as and intensities of 10 21 W/cm 2 the feasibility of these approximations becomes questionable. Still the exploration of plasma effects in relativistic laser matter interaction requires to test the boundaries of validity for these models. This thesis will take a step to point out the difficulties to be considered when existing ionization models are applied to such extreme cases.
Keywords: ionization, atomic physics, high-power, ultra-short, lasers
  • Bachelor thesis
    TU Dresden, 2013
    Mentor: Thomas Cowan, Ulrich Schramm
    0071 Seiten

Downloads:

Registration No. 24429 - Permalink

Modelling Field Ionization in PIConGPU
Garten, M.; Huebl, A.; Widera, R.; Pausch, R.; Debus, A.; Burau, H.; Kluge, T.; Huang, L.; Bussmann, M.
Abstract: It is vital to treat field ionization adequately and validate the different existing models critically in order to obtain trustworthy results from plasma simulations. This poster presents numerical methods for modelling field ionization in laser-plasma interactions. Based on results obtained in earlier Monte-Carlo simulations on CPU and later application to the fully-relativistic particle-in-cell code PIConGPU it is pointed out that different ionization models and the details of modelling field ionization can have a major influence on plasma dynamics.
Keywords: ionization, particle-in-cell, PIConGPU
  • Poster
    Summer School: Atoms and Plasmas in Super-Intense Laser Fields, 12.-22.07.2015, Erice, Italia
Registration No. 24428 - Permalink

Ultra-fast thermal processing of TCO and other thin films
Rebohle, L.; Schumann, T.; Prucnal, S.; Skorupa, W.
Abstract: Thermal processing in the ms range comprises modern, non-equilibrium annealing techniques which allow various material modifications at the surface without affecting the bulk. Flash lamp annealing (FLA) is one of the most diverse methods of short time annealing with applications ranging from the classical field of semiconductor doping to the treatment of polymers and flexible substrates. The presentation focuses on the FLA of transparent conducting oxides.
Keywords: flash lamp annealing, thin film applications, transparent conducting oxide
  • Invited lecture (Conferences)
    6. Workshop Transparente leitfähige Materialien, 22.-23.11.2016, Erfurt, Deutschland
Registration No. 24426 - Permalink

Practical demonstration of Eulerian & Lagrangian MPF simulation
Esch, T.; Krepper, E.
Abstract: The lesson 6 of the "Short Course on Multiphase Flow Modelling" deals with the simulation of a rectangular bubble colum and of a spray. Modeling advices and datasets are given.
Keywords: Bubble column, ANSYS-CFX, ANSYS-FLUENT
  • Lecture (Conference)
    14th Multiphase Flow Conference and Short Course: Simulation, Experiment and Application, 08.-10.11.2016, Dresden, Germany
Registration No. 24425 - Permalink

Towards a fully atomistic modelling of laser-plasma interaction in PIConGPU.
Garten, M.; Huebl, A.; Burau, H.; Grund, A.; Widera, R.; Zacharias, M.; Kluge, T.; Bussmann, M.
Abstract: In laser-generated plasmas the free electron density is a crucial parameter for plasma dynamics. Therefore, to model its spatial and temporal evolution the adequate treatment of ionization is vital. This poster presents the work in progress on numerical field ionization methods implemented in the world's fastest 3D3V electromagnetic particle-in-cell code PIConGPU. Thus, computing a value for the systematic error via repeating simulations with varying ionization schemes is in reach. With high performance computing we can give a range of validity for predictions of pump-probe experiments with high power lasers and X-ray free electron lasers.
Keywords: ionization, particle-in-cell, PIConGPU, XFEL
  • Poster
    Annual HZDR PhD Seminar 2016, 17.-19.10.2016, Ahorn Hotel Oberwiesenthal, Deutschland
Registration No. 24422 - Permalink

Enhancing field ionization modeling in PIConGPU towards a fully atomistic description of laser-matter interaction
Garten, M.; Huebl, A.; Burau, H.; Grund, A.; Widera, R.; Zacharias, M.; Kluge, T.; Bussmann, M.
Abstract: In laser-generated plasmas the free electron density is a crucial parameter for plasma dynamics. Therefore, to model its spatial and temporal evolution the adequate treatment of ionization is vital. This poster presents the work in progress on numerical field ionization methods implemented in the world's fastest 3D3V electromagnetic particle-in-cell code PIConGPU. Thus, computing a value for the systematic error via repeating simulations with varying ionization schemes is in reach. With high performance computing we can give a range of validity for predictions of pump-probe experiments with high power lasers and X-ray free electron lasers.
Keywords: ionization, particle-in-cell, PIConGPU, XFEL
  • Poster
    EUCALL Annual Workshop 2016, 31.08.2016, HZDR, Deutschland
Registration No. 24420 - Permalink

Analysis and applications of a multi-field approach for plunging jet configurations
Krepper, E.; Lucas, D.; Zidouni, F.
Abstract: A generalized approach developed for the simulation of two-phase flow problems with multi-scale interfacial structures is applied for the simulation of a plunging jet. The GEneralized TwO Phase flow (GENTOP) modeling approach considers different scales in term of interfacial structure. The explicit statistical simulation of the interface between continuous gas and fluid is combined with the Euler/Euler simulation of dispersed gas. For the dispersed gas the Multiple Size Group (MUSIG) approach simulates different bubble sizes. The mass transfer between the bubble sizes is considered by bubble breakup and coalescence models. The gas entrainment during the plunging jet is described by the transition between continuous gas and dispersed gas. Therefor a special sub grid model is applied.
This set of models is applied for the simulation of plunging jet experiments performed by Chanson et al. (2004). In the tests different geometric scales of plunging jet were investigated and here analyzed. The paper shows the capabilities of this approach and identifies weak points which need further development.

Keywords: CFD, two phase flow, Euler/Euler approach, interfacial area, plunging jet
  • Lecture (Conference)
    Analysis and applications of a multi-field approach for plunging jet configurations, 13.-15.09.2016, Cambridge, USA
Registration No. 24419 - Permalink

Gamma-ray computed tomography for investigations on centrifugal pumps under gas entrainment conditions
Schäfer, T.
Abstract: The lecture gives an introduction to high-resolution gamma-ray computed tomography and its application for quantitative measurements and visualization of two-phase flow in industrial and scientific applications. Exemplarily, recent results from investigations on an industrial centrifugal pump under several gas entrainment conditions will be presented.
Keywords: gamma-ray computed tomography, two-phase flow, centrifugal pump
  • Lecture (others)
    Iraqi-German Partnership on Multiphase Flow Research and Training (IGP-Multiflow), Summer School 2016, 02.-09.10.2016, Dresden, Deutschland
Registration No. 24417 - Permalink

Methoden der Zustandsüberwachung von Transport- und Lagerbehältern für abgebrannte Brennelemente und wärmeentwickelnde hochradioaktive Abfälle bei verlängerter Zwischenlagerung
Hampel, U.
Abstract: Der Vortrag stellt das vom BMWi geförderte gleichnamige Vorhaben vor. In diesem werden nichtinvasive Prüf- und Überwachunsgmethoden zur Erkennung von Veränderungen des Inventars von Transport- und Lagerbehältern (Typ CASTOR) auf ihre Machbarkeit untersucht. Hintergund ist die in Deutschland absehbare verlängerte Zwischenlagerung abgebrannter Brennelemente in Trockenlägern an den heutigen Kernkraftwerksstandorten. Für Zwischenlagerungszeiträume von mehreren Jahrzehnten ist heue keine verlässliche Aussage über etwaige Zustandsveränderungen an den Brennelementen möglich. Daher kommt nichtinvasiven Monitoringverfahren für den Behälterinhalt ein große Bedeutung zu. Untersucht werden Verfahren auf Basis von Gamma-, Neutronen- und Myonenstrahlung, akustische und schwingungsspektroskopische Verfahren sowie Thermographieverfahren.
Keywords: Nukleare Sicherheit, verlängerte Zwischenlagerung, Brennelemente, Trockenlager, Transport- und Lagerbehälter, CASTOR, Monitoring
  • Invited lecture (Conferences)
    12. Projektstatusgespräch zu BMWi-geförderten FuE-Projekten zur Entsorgung radioaktiver Abfälle, 09.-10.11.2016, Karslruhe, BRD
Registration No. 24412 - Permalink

Multiphase flow measurement via tomography : fundamentals, challenges and needs
Hampel, U.
Abstract: The invited lecture discussed and demonstrates the application of tomographic imaging in multiphase flow measurement. Thereby the discussion is guided along prototypical application examples in the fields of oil and gas production, chemical engineering and nuclear engineering. Emphasize is given to open quesions and future needs to improve applicability and significance of tomographic imaging techniques in fundmental and engineering research.
Keywords: multiphase flow, flow measurement, tomograpy, chemical engineering, nuclear engineering, oil and gas production
  • Invited lecture (Conferences)
    8th World Congress On Industrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brasilien
Registration No. 24411 - Permalink

Analysis of self-assembled monolayer coating and the influence on dropwise condensation
Unger, S.; Sarker, D.; Hampel, U.
Abstract: Das Phänomen der Tropfenkondensation, sowie der damit verbundene hohe Wärmeübertragungskoeffizient, haben ein großes Potential für die Optimierung industrieller Kondensationsprozesse. Ein wesentlicher Parameter der Kondensationsoberfläche bei der Tropfenkondensation ist der Kontaktwinkel eines Flüssigkeitstropfens auf einer Oberfläche. Insbesondere bei Arbeitsmedien mit geringen Oberflächenspannungen, sind niedrige Oberflächenenergien notwendig, um Tropfenkondensation zu realisieren. Selbst-aggregierende Monoschichten (SAM) auf der Basis von Phosphonsäure stellen eine Möglichkeit zur Herstellung von hydrophoben Oberflächen dar, welche auch bei Instandhaltung nachträglich aufgebracht oder erneuert werden können. Der Einfluss derartiger Beschichtungen auf das Verhalten von Kondensationssystemen wird untersucht.
Ein hoher Kontaktwinkel kennzeichnet die hydrophobe Eigenschaft einer Oberfläche, welche mit Hilfe von SAM durch ein auf Phosphonsäure basierendes nass¬chemisches Verfahren erzeugt wurde. Durch eine Kombination von künstlich eingestellter Rauigkeit und SAM-Beschichtung ist es möglich Kontaktwinkel in einem weiten Spektrum gezielt einzustellen. Dies eröffnet die Möglichkeit, individuell auf den Kondensationsprozess und Dampfgehalt angepasste Funktionsflächen zu fertigen.
Besonders hohe Kontaktwinkel wurden auf Proben mit hoher Rauigkeit und bei SAM mit langen Kohlenstoffketten gemessen. Aufgrund des nasschemischen Beschichtungsverfahrens können beliebige Geometrien, wie beispielsweise innen-berippte Rohre und Hohlstrukturen, behandelt werden. Dies ermöglicht die gezielte Beeinflussung der Wärmeübertragungseigenschaften und des Kondensat-Ablaufes in einer Struktur. In einem integralen Versuchsstand wird der Einsatz dieser neuartigen Wärmeübertragerflächen mit hoher Auflösung untersucht.

Keywords: dropwise condensation, condensation, heat transfer
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppe Wärme- und Stoffübertragung, 01.-02.03.2016, Kassel, Deutschland
Registration No. 24410 - Permalink

Structure of interfaces in GaN/AlN and Ge/Si multilayered heterosystems by XAFS spectroscopy
Erenburg, S. B.; Trubina, S. V.; Zhuravlev, K. S.; Malin, T. V.; Zinovyev, V. A.; Dvurechenskii, A. V.; Kuchinskaya, P. A.; Kvashnina, K. O.
Abstract: III-nitride heterostructures in the form of multilayered quantum wells (MQWs) or quantum dots (QDs) and interacting Ge QDs (“quantum molecules”) are promising candidates for high-speed intersubband (ISB) optical devices relying on the quantum confinement of electrons. Microstructural parameters (interatomic distances, coordination numbers, and Debye–Waller factors) were determined by means of EXAFS spectroscopy based on the Synchrotron Radiation, and the relationship between the variations in these parameters and the morphology of superlattices and symmetric assembles of QDs were established. The EXAFS technique has been used to study the local structure of thin hexagonal GaN/AlN MQWs grown by ammonia MBE at different temperatures. It is shown that the heterointerface intermixing leads to a decrease in the Ga-Al interatomic distance and the Ga–Ga coordination number in MQWs. The degree of intermixing in the boundary layers rises from 30% to 40% with increase of the growth temperature from 795 to 895◦ C. It was found that in the first phase of quantum molecules growth Ge atoms concentration is 25%. With further growth (deposition of the base layers) Ge concentration increases up to 35–45%, depending on the temperature (from 610 to 550◦C) of deposition
  • Contribution to proceedings
    XXXI International Conference on Equations of State for Matter (ELBRUS2016), 01.03.-06.11.2016, Elbrus, Kabardino-Balkaria, Russia
    Journal of Physics: Conference Series 774(2016), 012128
    DOI-Link: http://dx.doi.org/10.1088/1742-6596/774/1/012128

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Registration No. 24407 - Permalink

Interatomic potential to study the formation of NiCr clusters in high Cr ferritic steels
Bonny, G.; Bakaev, A.; Olsson, P.; Domain, C.; Zhurkin, E. E.; Posselt, M.
Abstract: Under irradiation NiSiPCr clusters are formed in high-Cr ferritic martensitic steels as well as in FeCr model alloys. In the literature little is known about the origin and contribution to the hardening of these clusters. In this work we performed density functional theory (DFT) calculations to study the stability of small substitutional NiCr-vacancy clusters and interstitial configurations in bcc Fe. Based on DFT data and experimental considerations a ternary potential for the ferritic FeNiCr system was developed. The potential was applied to study the thermodynamic stability of NiCr clusters by means of Metropolis Monte Carlo (MMC) simulations. The results of our simulations show that Cr and Ni precipitate as separate fractions and suggest only a limited synergetic effect between Ni and Cr. Therefore our results suggest that the NiCrSiP clusters observed in experiments must be the result of other mechanisms than the synergy of Cr and Ni at thermal equilibrium.
Keywords: interatomic potential, Fe-Cr-Ni alloys, precipitates, clusters Registration No. 24405 - Permalink

Terahertz free-electron laser spectroscopy of excitons in III-V semiconductor quantum wells and single quantum dots
Schneider, H.; Stephan, D.; Zybell, S.; Winnerl, S.; Bhattacharyya, J.; Eßer, F.; Helm, M.
Abstract: Using intense, spectrally narrow terahertz pulses from the free-electron laser facility FELBE in Dresden, Germany, we have investigated exciton population dynamics in III-V QWs and single quantum dots. To this end, carriers are optically injected by picosecond near-infrared pulses to populate the lowest excitonic level. Using narrowband terahertz pulses, excitons are resonantly excited into higher levels. Time-dependent photoluminescence measurements based on a streak camera system and on time-correlated photon counting, respectively, then allow us to study the transient population of dipole-allowed higher exciton levels and to access the relaxation dynamics.
Keywords: excitons, GaAs, quantum well, quantum dot, terahertz, free-electron laser, time-resolved photoluminescence
  • Invited lecture (Conferences)
    SPIE Photonics Asia, Symposium on "Infrared, Millimeter Wave, and Terahertz Technologies", 12.-14.10.2016, Beijing, China
Registration No. 24404 - Permalink

Terahertz free-electron laser spectroscopy of semiconductor nanostructures
Schneider, H.
Abstract: This talk reviews recent spectroscopic studies on semiconductor nanostructures using the THz free-electron laser FELBE. Its intense, quasi-continuous, nearly transform-limited ps pulses provide unique research opportunities to advance THz science.
Keywords: spectroscopy, terahertz, free-electron laser
  • Invited lecture (Conferences)
    The 8th International Symposium on Ultrafast Phenomena and Terahertz Waves (ISUPTW 2016), 10.-12.10.2016, Chongqing, China
Registration No. 24403 - Permalink

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR
Ablyazimov, T.; Abuhoza, A.; Adak, R. P.; Adamczyk, M.; Agarwal, K.; Aggarwal, M. M.; Ahammed, Z.; Ahmad, F.; Ahmad, N.; Ahmad, S.; Akindinov, A.; Akishin, P.; Akishina, E.; Akishina, T.; Akishina, V.; Akram, A.; Al-Turany, M.; Alekseev, I.; Alexandrov, E.; Alexandrov, I.; Amar-Youcef, S.; Anđelić, M.; Andreeva, O.; Andrei, C.; Andronic, A.; Anisimov, Y.; Appelshäuser, H.; Argintaru, D.; Atkin, E.; Avdeev, S.; Averbeck, R.; Azmi, M. D.; Baban, V.; Bach, M.; Badura, E.; Bähr, S.; Balog, T.; Balzer, M.; Bao, E.; Baranova, N.; Barczyk, T.; Bartoş, D.; Bashir, S.; Baszczyk, M.; Batenkov, O.; Baublis, V.; Baznat, M.; Becker, J.; Becker, K.-H.; Belogurov, S.; Belyakov, D.; Bendarouach, J.; Berceanu, I.; Bercuci, A.; Berdnikov, A.; Berdnikov, Y.; Berendes, R.; Berezin, G.; Bergmann, C.; Bertini, D.; Bertini, O.; Beşliu, C.; Bezshyyko, O.; Bhaduri, P. P.; Bhasin, A.; Bhati, A. K.; Bhattacharjee, B.; Bhattacharyya, A.; Bhattacharyya, T. K.; Biswas, S.; Blank, T.; Blau, D.; Blinov, V.; Blume, C.; Bocharov, Y.; Book, J.; Breitner, T.; Brüning, U.; Brzychczyk, J.; Bubak, A.; Büsching, H.; Bus, T.; Butuzov, V.; Bychkov, A.; Byszuk, A.; Cai, X.; Cálin, M.; Cao, P.; Caragheorgheopol, G.; Carević, I.; Cătănescu, V.; Chakrabarti, A.; Chattopadhyay, S.; Chaus, A.; Chen, H.; Chen, L.; Chen, J.; Chepurnov, V.; Cherif, H.; Chernogorov, A.; Ciobanu, M. I.; Claus, G.; Constantin, F.; Csanád, M.; D'Ascenzo, N.; Das, S.; Das, S.; de Cuveland, J.; Debnath, B.; Dementiev, D.; Deng, W.; Deng, C.; Deppe, H.; Deppner, I.; Derenovskaya, O.; Deveaux, C. A.; Deveaux, M.; Dey, K.; Dey, M.; Dillenseger, P.; Dobyrn, V.; Doering, D.; Dong, S.; Dorokhov, A.; Dreschmann, M.; Drozd, A.; Dubey, A. K.; Dubnichka, S.; Dubnichkova, Z.; Dürr, M.; Dutka, L.; Dželalija, M.; Elsha, V. V.; Emschermann, D.; Engel, H.; Eremin, V.; Eşanu, T.; Eschke, J.; Eschweiler, D.; Fan, H.; Fan, X.; Farooq, M.; Fateev, O.; Feng, S.; Figuli, S. P. D.; Filozova, I.; Finogeev, D.; Fischer, P.; Flemming, H.; Förtsch, J.; Franken... (alle 585 Autoren)
Abstract: Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.

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Registration No. 24400 - Permalink

Terahertz spectroscopy of semiconductor nanostructures with a free-electron laser
Schneider, H.
Abstract: In this talk I will present recent experimental investigations on carrier dynamics in graphene studied via pump-probe spectroscopy, on time-resolved photoluminescence dynamics of single InAs/GaAs quantum dots under pulsed inter-sublevel excitation, and on sub-diffraction limited terahertz imaging by a GaAs-based superlens studied by scattering near-field optical microscopy. The experiments have been carried out using the mid-infrared/terahertz free-electron laser facility FELBE in Dresden, Germany.
Keywords: free-electron laser, terahertz, semiconductor nanostructures
  • Lecture (others)
    Seminar, Ecole Normale Superieure, Laboratoire Pierre Aigrain, 23.09.2016, Paris, France
  • Lecture (others)
    Seminar, Chinese Academy of Engineering Physics, 18.10.2016, Chengdu, China
Registration No. 24398 - Permalink

Terahertz-induced inter-sublevel dynamics of single InAs/GaAs quantum dots studied by micro-photoluminescence
Stephan, D.; Bhattacharyya, J.; Huo, Y. H.; Schmidt, O. G.; Rastelli, A.; Helm, M.; Schneider, H.
Abstract: We explore the transient response of single self-assembled InAs/GaAs quantum dots (QD) to narrow-band terahertz (THz) pulses produced by the free-electron laser FELBE at HZDR. The THz excitation is tuned to the electron inter-sublevel s-to-p transition. For the QDs under study, this transition occurs in the range 13-20 meV because of in-situ intermixing. The THz pulse is applied at a time delay of about 0.7 ns after interband excitation. The dynamics of electron excitation and relaxation between QD sublevels is revealed by time-resolved micro-photoluminescence (PL) measurements performed on individual QDs.
Keywords: quantum dot, photoluminescence, terahertz, free-electron laser
  • Lecture (Conference)
    33rd International Conference on the Physics of Semiconductors (ICPS 2016), 31.07.-05.08.2016, Beijing, China
Registration No. 24397 - Permalink

Terahertz pump-terahertz probe system at Novosibirsk free electron laser: commissioning and results of first experiments
Choporova, Y. Y.; Gerasimov, V. V.; Hübers, H.-W.; Knyazev, B. A.; Kulipanov, G. N.; Ovchar, V. K.; Pavelyev, V. S.; Zhukavin, R. K.; Schneider, H.; Vinokurov, N. A.; Volodkin, B. O.; Shastin, V. N.
Abstract: A single-color pump-probe system has been commissioned at the Novosibirsk free electron laser facility. Monochromatic laser radiation with a bandwidth of about 1% can be tuned within the spectral ranges of 90 - 240 and 30 - 90 μm. The laser emits radiation as a continuous stream of 100-ps pulses with a repetition rate of 5.6 MHz. The average radiation power can reach 100 W. The temperature of samples located in a helium cryostat can be varied from 2 up to 325 K. The results of pump-probe measurements of non-equilibrium dynamics of hot electrons in a germanium crystal will be presented.
Keywords: free-electron laser, pump-probe
  • Lecture (Conference)
    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, 1-2
    DOI-Link: http://dx.doi.org/10.1109/IRMMW-THz.2016.7758465
Registration No. 24396 - Permalink

First terahertz-range experiments on pump-probe setup at Novosibirsk free electron laser
Choporova, Y. Y.; Gerasimov, V. V.; Knyazev, B. A.; Sergeev, S. M.; Shevchenko, O. A.; Zhukavin, R. K.; Abrosimov, N. V.; Kovalevsky, K. A.; Ovchar, V. K.; Hübers, H.-W.; Kulipanov, G. N.; Shastin, V. N.; Schneider, H.; Vinokurov, N. A.
Abstract: A single-color pump-probe system has been commissioned at the Novosibirsk free electron laser. The laser emits a tunable monochromatic terahertz radiation. To prove the proper system operation, we investigated the time-resolved absorption of a sample of n-type germanium doped with antimony, which was previously investigated at the FELBE facility, in the temperature range from 5 to 50 K. The measured relaxation time amounted to about 1.7 ns, which agreed with the results obtained at FELBE. The results of pump-probe measurements of non-equilibrium dynamics of hot electrons in a germanium crystal at cryogenic temperatures are presented for wavelengths of 105, 146 and 150 μm.
Keywords: free-electron laser, pump-probe
  • Lecture (Conference)
    2016 International Conference "Synchrotron and Free electron laser Radiation: generation and application" (SFR-2016), 04.-07.07.2016, Novosibirsk, Russia
Registration No. 24395 - Permalink

Modelling free-surface dynamics in the Ribbon Growth on Substrate process (RGS)
Beckstein, P.; Galindo, V.ORC; Gerbeth, G.
Abstract: The Ribbon Growth on Substrate (RGS) technology is a promising technology that allows the controlled, high crystallization rate production of silicon wafers and advanced metal-silicide alloys. In order to optimize this process, insights from modelling the
liquid metal flow are very desirable. The RGS process is dominated by a time-dependent, three-dimensional free-surface flow of the processed melt under the influence of electromagnetic forces. Thereby, main flow structures and possible instabilities strongly depend
on the melt shape. We have developed a new numerical multiphysics-software within the OpenFOAM (extensions) framework, which allows us to efficiently simulate hydrodynamic and electrodynamic effects and their interaction.

Keywords: RGS, Multiphysics, Free-surface, Eddy-currents, OpenFOAM
  • Contribution to proceedings
    10th PAMIR International Conference - Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italy
    Proceedings of the 10th PAMIR International Conference Fundamental and Applied MHD, Cagliari: Arti Grafiche Pisano, 978-88-90551-93-2, 257-261
  • Lecture (Conference)
    10th PAMIR International Conference - Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italy, 20.-24.06.2016, Cagliari, Italy
Registration No. 24386 - Permalink

Airlift Reactor – Experiment and CFD Simulation
Ziegenhein, T.
Abstract: It is more and more possible to design bubbly flow reactors with methods of the computational fluid dynamics (CFD). Measurements that can be used for model validation, however, are often missing, especially for complex setups like airlift reactors. Such measurements include locally resolved information about the dispersed and continuous phase, particularly the information about the flow field and interface structures are important. In the present work Reynolds stresses, liquid velocity and gas void fraction profiles as well as bubble size distributions are provided at several positions in the riser and the downcomer in a rectangular airlift reactor for this purpose. In addition, the hydrodynamics inside this airlift reactor are described in detail by the measured values.
Keywords: dispersed gas-liquid multiphase flow, airlift reactor, model validation, particle tracking velocimetry, turbulence, videography
  • Poster
    14th Multiphase Flow Conference & Short Course, 08.-10.11.2016, Dresden, Deutschland
Registration No. 24383 - Permalink

Lattice vibrations and electrical transport in (Bi1-xInx)2Se3 films
Zhu, J.; Liu, F.; Zhou, S.; Franke, C.; Wimmer, S.; Volobuev, V. V.; Springholz, G.; Pashkin, A.; Schneider, H.; Helm, M.
Abstract: We present Raman, terahertz transmission, and transport measurements on (BiIn)2Se3 films to study the evolution of phonon modes and resistivity with an increasing indium content across the metal-insulator phase transition. The frequencies of two Raman-active modes E2g and A21g as well as an infrared-active mode Eu increase with an increasing indium content due to the smaller atomic weight of indium compared to bismuth. Terahertz data are fitted by a Drude Lorentz model. Drude scattering rates increase from 47 to 75 cm -1 with an increasing indium content from 0% to 16% due to stronger impurity scattering. The carrier concentration drops significantly for x=24%. The temperature dependence of the resistivity switches from metallic at x=16% to insulating at x =24%, indicating a metal-insulator transition in between.
Keywords: lattice vibrations, Raman spectra, topological insulators, electrical transport, Bi2Se3 Registration No. 24382 - Permalink

Experimental investigations on the lift force for turbulent flows with low Morton number
Ziegenhein, T.; Lucas, D.
Abstract: The lateral lift force has an important influence on the gas distribution in bubbly flows. For this reason reliable closure models reflecting this force are required for CFD-simulations of bubbly flows. In Direct Numerical Simulations as well in experimental investigation it was shown that the lift force strongly depends on the bubble size and even changes its sign depending on the bubble size. Tomiyama et al. (2002) obtained a correlation from experiments with single bubbles in a linear laminar shear flow for high Morton number systems, which is frequently used in CFD-simulations. In this work the lift force is determined experimentally in low Morton number systems with a turbulent background flow. Single bubbles move through a linear shear field generated in a flat column by asymmetric aerating. An averaged bubble trajectory is obtained from a long-term averaged gas volume fraction field along which the force balance including buoyancy, drag, virtual mass and lift is solved to determine the lift force coefficient. The additional parameters required, as relative velocity are obtained from the experiments. The dependency of the lift force coefficient on the horizontal bubble diameter is in good agreement with the data obtained by Tomiyama et al., however the Wellek correlation for the aspect ratio seems to be not valid for the pure system considered.
Keywords: Lift Force, Bubbly flows, Turbulence
  • Lecture (Conference)
    ICMF 2016 International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy
Registration No. 24381 - Permalink

Computational Fluid-Dynamic modeling of the pseudo-homogeneous flow regime in large-scale bubble columns
Besagni, G.; Inzolia, F.; Ziegenhein, T.ORC; Lucas, D.
Abstract: An understanding of the fluid dynamics and the transport phenomena in bubble columns (in the homogeneous and heterogeneous flow regimes) is of fundamental importance to support the design and scale-up methods. In this respect, multiphase Computational Fluid-Dynamics (CFD) simulations in the Eulerian multi-fluid framework are particularly useful to study the fluid dynamics in large-scale reactors; in particular, this study concerns the modeling of the fluid dynamics in bubble columns within the boundaries of the homogeneous flow regime. Reliable predictions of the homogeneous flow regime with this approach are, however, limited up to now. One important drawback is that usually the needed closure models for the interphase forces, turbulence and coalescence and break-up are selected case-by-case, which hinder improvement of the predictive value. A set of closure relations has been collected at the Helmholtz-Zentrum Dresden-Rossendorf that represents the best available knowledge and may serve as a baseline model for further investigations. In this paper, the validation of this set of closure relations has been extended to the pseudo-homogeneous flow regime—characterized by a wide spectrum of bubble sizes and typically associated with the large sparger openings used in industrial applications—in large-scale bubble columns, thus establishing a first step towards the simulation of industrial-scale reactors. To this end, the benchmark considered is a comprehensive dataset obtained for a large-scale bubble column, which has been built accordingly with the well-known scale up criteria (large-diameter, high aspect ratio and large sparger openings). The numerical approach has been tested in its fixed-poly-dispersed formulation (considering the two- and four-classes approaches to represent the dispersed phase) and considering the coalescence and break-up closures. The results suggest that the correct simulation of the fluid dynamics in the bubble column requires the definition of coalescence and break-up closures. The results have been critically analyzed and the reasons for the discrepancies between the numerical results and the experimental data have been identified and may serve as basis for future studies.
Keywords: CFD; Bubble column; Large-scale; Bubble size distribution; Coalescence and break-up; Validation Registration No. 24380 - Permalink

Sorption competition of trivalent metals on corundum (α-Al2O3) studied on the macro- and microscopic scale
Virtanen, S.; Eibl, M.; Meriläinen, S.; Rossberg, A.; Lehto, J.; Rabung, T.; Huittinen, N.
Abstract: Sorption of trivalent actinides and lanthanides onto the surface of geological materials relevant for nuclear waste disposal is a topic that has been widely studied in recent years. However, the sorption properties of metals are often investigated by studying the sorption behaviour of a single metal at a time, thus, these experiments do not account for potential effects of sorption competition in the presence of multiple dissolved elements or compounds. Bradbury and Baeyens (2005) performed extensive investigations of the sorption competition between various metal cations on the clay mineral montmorillonite. By investigating the competition of metals with similar and dissimilar chemical behaviour (e.g. tendency to hydrolysis and valence state), the authors concluded that metal cations with dissimilar chemical properties do not affect the uptake of one another by the clay mineral, whereas metals with similar chemistries do. Thus, if the data obtained in single metal sorption experiments are used in the safety assessment of nuclear disposal, careful considerations of the chemical environment in the near- or far-field of nuclear waste repository is needed to avoid the possible overestimation of radionuclide sorption.
In this study, we have combined batch sorption and spectroscopic experiments that were performed with Eu(III), Cm(III) and Am(III) in in the absence and presence of Y(III) as competing cation. The objective was to investigate how the sorption behaviour of trivalent actinides and lanthanides is affected by the presence of another trivalent metal. Following the findings of Bradbury and Baeyens (2005) our hypothesis is that the addition of higher concentrations of trivalent Y(III) together with a chemically similar trivalent metal, Eu(III), Cm(III) or Am(III), would affect the sorption behaviour of that metal.
Batch sorption experiments were performed with Eu(III) at different pH (pH-edges) and concentrations (isotherms). The competing metal Y(III) was added before Eu(III) to the mineral suspension in concentrations ranging from 1×10-6 M to 1×10-4 M. In the Eu(III) pH-edge experiments, the sorption of 1×10-5 M Eu(III) was investigated on 0.5 g/l corundum at varying pH, with and without Y(III). In the Eu(III) isotherm experiments, the initial Eu(III) concentration was varied between 1×10-9 M – 1×10-4 M and Y(III) was used in the competing isotherm samples at a constant pH of 7. Batch experiments showed that the addition of Y(III) did decrease the sorption of Eu(III) (Figure 1) on a macroscopic scale. However, as the main emphasis of this study was the possible changes happening at the molecular level as a results of sorption competition, spectroscopic methods were also employed. Time-resolved laser fluorescence spectroscopy (TRLFS) enables the investigations of Cm(III) sorption speciation directly on the mineral surface. We investigated the changes in the speciation of 1×10-7 M Cm(III) in 0.5 g/l corundum suspensions at varying pH under non-competing and competing conditions using 1×10-4 M Y(III). The results indicate changes in the Cm(III) sorption species distribution, thus, confirming our findings in the batch sorption experiments showing that 1×10-4 M Y(III) suppresses Cm sorption complex formation on the mineral surface depending on the solution pH (Figure 2). Cm(III) luminescence spectra of only Cm(III) and of Cm(III) together with Y(III), show that the fraction of aqueous Cm species is substantially greater with high concentrations of Y(III) present. Only when the pH is increased above 7, the first Cm sorption species appears, resulting in a shift of the observed emission peak maximum. X-ray absorption spectroscopy (XAS) was applied to identify the formed trivalent actinide sorption complexes. We investigated the sorption of 6×10-6 M or 2×10-5 M Am(III) on the corundum surface at pH 8.5 in the absence and presence of 2×10-5 or 2×10-4 M Y(III). The treatment of the XAS-data is still ongoing and results will be discussed more closely in the conference presentation.
  • Lecture (Conference)
    Ninth international conference on nuclear and radiochemistry (NRC9), 29.08.-02.09.2016, Helsinki, Finland
Registration No. 24377 - Permalink

Molecular interactions of two fungi with uranium and europium
Wollenberg, A.; Günther, A.; Merroun, M. L.; Raff, J.; Stumpf, T.
Abstract: If radionuclides are released in the environment their mobility and behavior is influenced by interactions with abiotic and biotic matter. As fungi are ubiquitous in nature they have to be taken into consideration in particular. For example, fungi can bind radionuclides in different ways, with the result that the radionuclides are immobilized and preventing further migration through the soil. The aim of this study was to investigate the binding of uranium and europium, the latter as surrogate for trivalent actinides, by fungi Schizophyllum commune and Leucoagaricus naucinus.
First batch experiments showed the binding of U(VI) and Eu(III) by fungi depends on the initial conditions. Both fungi showed increasing sorption capacities with higher initial metal concentrations and lower initial biomass. In contrast, the fungi showed different metal binding behavior in dependence on pH. Scanning transmission electron microscopy in combination with high angle annular dark-field analysis (HAADF-STEM) revealed location of U(VI) on the surface and inside of cells of Schizophyllum commune.
Furthermore the U(VI)-binding of the fungi was investigate with time-resolved laser-induced fluorescence spectroscopy (TRLFS) depending on metal concentration. The results showed the speciation of U(VI) is changed in the initial solution during binding process. In addition, it was demonstrated that mainly phosphate groups are responsible for the binding on the surface of the biomass.

Keywords: fungi, uranium, europium
  • Poster
    15. Symposium on Remediation, 13.-14.10.2016, Jena, BRD
Registration No. 24376 - Permalink

Studies of activation monitors at the HZDR medical cyclotron: Simulation and Experiment
Konheiser, J.; Müller, S. E.
Abstract: The neutron source terms for a proton beam hitting an O-18 enriched water target were calculated with MCNP6 and FLUKA. First comparisons of simulation and experiments for activation studies at the IBA CYCLONE 18/9 cyclotron.
  • Lecture (others)
    16. AAA Workshop, 05.12.2016, Garching, Germany
Registration No. 24375 - Permalink

22Ne and 23Na ejecta from intermediate-mass stars: The impact of the new LUNA rate for 22Ne(p,γ)23Na
Slemer, A.; Marigo, P.; Piatti, D.; Aliotta, M.; Bemmerer, D.; Best, A.; Boeltzig, A.; Bressan, A.; Broggini, C.; Bruno, C.; Caciolli, A.; Cavanna, F.; Ciani, G. F.; Corvisiero, P.; 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.; Prati, P.; Straniero, O.; Szücs, T.; Takács, M. P.; Trezzi, D.
Abstract: We investigate the impact of the new LUNA rate for the nuclear reaction 22Ne(p,γ)23Na on the chemical ejecta of intermediate-mass stars, with particular focus on the thermally- pulsing asymptotic giant branch (TP-AGB) stars that experience hot-bottom burning. To this aim we use the PARSEC and COLIBRI codes to compute the complete evolution, from the pre- main sequence up to the termination of the TP-AGB phase, for a few sets of stellar models with initial masses in the range 3.0 M⊙ − 6.0 M⊙ and three values of metallicity, Zi = 0.0005, Zi = 0.006, and Zi = 0.014. We compare the results of the Ne-Na nucleosynthesis obtained with the new LUNA rate and others available in the literature. We find that the improvement in the astrophysical S-factor obtained with LUNA has remarkably reduced the corresponding nuclear uncertainties in the 22Ne and 23Na AGB yields, which drop from factors of ≃ 10 to just a few for the lowest metallicity models. The uncertainties that still affect the 22Ne and 23Na AGB ejecta are mainly dominated by evolutionary aspects (efficiency of mass-loss, dredge-up events, convection). With the new LUNA data AGB stars with hot-bottom burning produce amounts of 23Na that are in between those predicted with NACRE and Iliadis et al. rates. Finally, we discuss how the LUNA results impact on the hypothesis that invokes primordial massive AGB and super-AGB stars as the main agents of the observed O-Na anticorrelation in Galactic globular clusters. In this context, we derive quantitative constraints on the efficiencies that should characterize other key physical processes (mass loss, third dredge-up, sodium destruction) in order to simultaneously reproduce both the Na-rich, O-poor extreme of the anticorrelation and the observational constraints on the CNO abundance. While best-fitting AGB models can be actually singled out, yet they cannot be taken as a theoretical piece in full support to the AGB hypothesis, as various issues still remain.
Keywords: stars: evolution – stars: AGB and post-AGB – stars: carbon – stars: abundances – stars: mass loss – Physical Data and Processes: nuclear reactions, nucleosynthesis, abundances Registration No. 24374 - Permalink

FENABIUM: Research at HZDR
März, J.; Schöne, S.; Radoske, T.; Kaden, P.
Abstract: Vortrag zum Kick-off Meeting des FENABIUM Verbundprojekts (BMBF) mit der TU Dresden und Universität Leipzig.
Die Ergebnisse zeigen die Synthese und Charakterisierung vierwertiger Actinidkomplexe mit Amidinen und Schiffschen Basen unter Schutzgasbedingungen, die in der Gruppe "Chemie der f-Elemente" des Instituts für Ressourcenökologie durchgeführt wurden.

Keywords: Actinide complex Chemistry of the f-elements
  • Lecture (Conference)
    FENABIUM Kick-off Meeting, 14.11.2016, Dresden, Deutschland
Registration No. 24373 - Permalink

The upper critical field and its anisotropy in (Li1−xFex)OHFe1−ySe
Wang, Z.; Yuan, J.; Wosnitza, J.; Zhou, H.; Huang, Y.; Jin, K.; Zhou, F.; Dong, X.; Zhao, Z.
Abstract: The temperature dependence of the upper critical field (Hc2) in a (Li1−xFex)OHFe1−ySe single crystal (Tc ≈ 40 K) has been determined by means of magnetotransport measurements down to 1.4 K both for inter-plane (H‖c, H‖cc2) and in-plane (H‖ab, H‖abc2) field directions in static magnetic fields up to 14 T and pulsed magnetic fields up to 70 T. H‖cc2 exhibits a quasilinear increase with decreasing temperature below the superconducting transition and can be described well by an effective two-band model with unbalanced diffusivity, while H‖abc2 shows a flattening below 35 K and follows the Werthamer–Helfand–Hohenberg (WHH) model incorporating orbital pair-breaking and spin-paramagnetic effects, yielding zero-temperature critical fields of H‖cc2(0) ≈ 67 T and H‖abc2(0) ≈ 98 T. The anisotropy of the upper critical fields, γ(T)= H‖abc2/ H‖cc2 monotonically decreases with decreasing temperature from about 7 near Tc to 1.5 at 0 K. This reduced anisotropy, observed in most Fe-based superconductors, is caused by the Pauli limitation of H‖abc2. Registration No. 24371 - Permalink

Study of magnetic, structural and magnetocaloric properties of La0.6Pr0.4Mn2Si2 under high pressures and magnetic field
Kastil, J.; Arnold, Z.; Isnard, O.; Skourski, Y.; Kamarad, J.; Itié, J. P.
Abstract: The structural, magnetic and magnetocaloric properties of La0.6Pr0.4Mn2Si2 compound were measured in wide range of temperature, magnetic field and hydrostatic pressure. The structural study up to 10 GPa confirmed the existence of critical Mn-Mn distance 0.2883 nm for the ferromagnetic to antiferromagnetic transition at room temperature. The results demonstrated the crucial role of the volume in the suppression of the ferromagnetic phase above the transition temperature T1 = 168 K under pressure. The huge pressure shift of the transition temperature T1, dT1 /dp = 230 K/GPa, was observed. Based on our magnetization measurement the low temperature transition at T2 = 30 K is connected with reorientation of Mn moment and the rare-earth sublattice is not ordered in this case. The direct magnetocaloric measurement showed moderate values of the adiabatic temperature change connected with the magnetic transition at Tc and T1 and confirmed the first order character of the transition at T1 and second order character of the transition at Tc. Registration No. 24368 - Permalink

Uranium(VI) retention by Ca-bentonite under (hyper)alkaline conditions
Philipp, T.; Schmeide, K.
Abstract: The presentation summerizes the results of batch experiments on the uranium(VI) sorption on Ca-bentonite under (hyper)alkaline conditions combined with Time-resolved laser-induced fluorescence spectroscopy (TRLFS).
Keywords: sorption, clay, Ca-bentonite, uranium(VI), hyperalkaline, high ionic strengths, TRLFS
  • Lecture (others)
    3. Workshop des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“, Heidelberg, 25.-26.10.2016, Heidelberg, Deutschland
Registration No. 24367 - Permalink

New possibilities of plasma immersion ion implantation (PIII) and deposition (PIII&D) in industrial components using metal tube fixtures
Ueda, M.; Silva, A. R.; Pillaca, E. J. D. M.; Mariano, S. F. M.; Rossi, J. O.; Oliveira, R. M.; Pichon, L.; Reuther, H.
Abstract: New possibilities of Plasma Immersion Ion Implantation (PIII) and deposition (PIII&D) for treating industrial components in the batch mode have been explored. A metal tubular fixture is used to allocate the components inside around and along the tube, exposing to the plasma only the parts of each component that will be implanted. Hollow cathode- like plasma is generated only inside the tube filled with the desired gas, by applying high negative voltage pulses to the hollow cylindrical metal fixture which is insulated from the vacuum chamber walls. The metal tube (Me-tube) loaded with workpieces can be set-up inside the vacuum chamber in the standing-up, upside down or lying down arrangements. PIII tests were also run with and without metal sheet lids on the tube as well as with and without the components. Sputtering deposition and carbonitriding are also possible in this scheme by placing carbon tapes inside the tube and running the process with nitrogen PIII. Relatively clean DLC (Diamond Like Carbon) PIII&D deposition is possible by this method also since the plasma occupies mainly the Me-tube interior and not the whole chamber. Furthermore, operating high density PIII and PIII&D systems without additional plasma source, using only the high voltage pulser, is now possible to treat three dimensional parts. These methods are very convenient for batch processing of industrial parts by ion implantation and by ion implantation and deposition, in which a large number of small to medium size components can be treated by PIII and PIII&D, very quickly, efficiently and also at low cost. Registration No. 24366 - Permalink

New insights into the pretargeting approach to image and treat tumours
Patra, M.; Zarschler, K.; Pietzsch, H.-J.; Stephan, H.; Gasser, G.
Corresponding author: Zarschler, Kristof Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research
Corresponding author: Pietzsch, Hans-Jürgen Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research
Corresponding author: Stephan, Holger Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research
Abstract: Tumour pretargeting is a promising strategy for cancer diagnosis and therapy allowing for the rational use of long circulating, highly specific monoclonal antibodies (mAbs) for both non-invasive cancer radioimmunodetection (RID) and radioimmunotherapy (RIT). In contrast to conventional RID/RIT where the radionuclides and oncotropic vector molecules are delivered as presynthesised radioimmunoconjugates, the pretargeting approach is a multistep procedure that temporarily separates targeting of certain tumour-associated antigens from delivery of diagnostic or therapeutic radionuclides. In principle, unlabelled, highly tumour antigen specific mAb conjugates are, in a first step, administered into a patient. After injection, sufficient time is allowed for blood circulation, accumulation at the tumour site and subsequent elimination of excess mAb conjugates from the body. The small fast-clearing radiolabelled effector molecules with a complementary functionality directed to the prelocalised mAb conjugates are then administered in a second step. Due to its fast pharmacokinetics, the small effector molecules reach the malignant tissue quickly and bind the local mAb conjugates. Thereby, corresponding radioimmunoconjugates are formed in vivo and, consequently, radiation doses are deposited mainly locally. This procedure results in a much higher tumour/non-tumour (T/NT) ratio and is favourable for cancer diagnosis and therapy as it substantially minimises the radiation damage to non-tumour cells of healthy tissues. The pretargeting approach utilises specific noncovalent interactions (e.g. strept(avidin)/biotin) or covalent bond formations (e.g. inverse electron demand Diels–Alder reaction) between the tumour bound antibody and radiolabelled small molecules. This tutorial review descriptively presents this complex strategy, addresses the historical as well as recent preclinical and clinical advances and discusses the advantages and disadvantages of different available variations. Registration No. 24362 - Permalink

Erste Untersuchungen zur Uranrückhaltung an C-S-H-Phasen und Ca-Bentonit
Philipp, T.; Wolter, J.-M.
Abstract: Im Rahmen des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“ wird unter Anderem die Radionuklidrückhaltung an Tongestein und Tonmineralen unter hyperalkalinen Bedingungen und bei hohen Ionenstärken untersucht. Der Vortrag fasst die ersten Ergebnisse zur Sorption von Uran(VI) an Ca-Bentonit unter Variation verschiedener Umgebungsparameter (S/L-Verhältnis, U(VI)-Konzentration, pH, An-/Abwesenheit von CO2) zusammen.
Keywords: Ca-Bentonit, Ton, Montmorillonit, Uran(VI), Sorption, hyperalkalin, hohe Ionenstärke
  • Lecture (others)
    2. Workshop des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“, 22.03.-23.11.2016, München, Deutschland
Registration No. 24361 - Permalink

Leaching of uranium(VI) doped CSH phases in high saline water
Wolter, J.-M.
Abstract: Leaching experiments of uranium(VI) doped calcium-silicate-hydrate (CSH) phases were carried out in a 2.5 M sodium chloride solution and different additions like sodium bicarbonate or sodium sulfate to determine the CSH stability in high saline water. The results were backed up with several spectroscopic techniques like time resolved laser fluorescence spectroscopy (TRLFS), infrared spectroscopy (IR) and powder x-ray diffraction (PXRD) to structural changes of the CSH phases through the leaching.
Keywords: Uranium, CSH, TRLFS, IR, PXRD, sodium chloride, sodium sulfate, sodium carbonate
  • Lecture (others)
    3. Workshop des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“, 24.10.2016, Heidelberg, Deutschland
Registration No. 24360 - Permalink

A laser-based hadrontherapy facility: current status at HZDR
Kraft, S.
Abstract: Laser based ion acceleration has the potential to serve as a more flexible solution as compared to conventional ion beam therapies. In order to explore these potentials, several groups from physics, biology and medicine have joint forces in Dresden.
This talk will give an overview over the activities focusing especially on the proton source and the beam transport. The Ti:Sapph laser system was upgraded to 500TW in order to produce higher energies and starts operation this summer. Additionally, new target types such as solid hydrogen and liquid crystals where tested. For beam transport novel techniques with pulsed power magnets producing field of up to 20 Tesla are implemented.
  • Invited lecture (Conferences)
    3rd ELImed workshop, 07.-09.09.2016, Catania, Italien
Registration No. 24358 - Permalink

The prospect of laser plasma accelerators for ion beam therapy of cancer
Schramm, U.
Abstract: Talk and podium discussion on prospect of laser accelerated ions for therapy applications
Keywords: ion beam cancer therapy
  • Invited lecture (Conferences)
    International Symposium on Ultrafast Intene Laser Science ISUILS, 02.-05.10.2016, Cassis, Frankreich
Registration No. 24356 - Permalink

ELI related activities, potential partners and status in Germany
Schramm, U.ORC; Schramm, B.; Sauerbrey, R.
Abstract: Presentation of the German position to ELI DC and ELI ERIC
Keywords: ELI
  • Invited lecture (Conferences)
    ELI DC 2nd partners meeting, 16.-17.11.2016, Bukarest, Rumänien
Registration No. 24355 - Permalink

Spatial variability of source composition and petrogenesis in rift and rift flank alkaline lavas from the Eger Rift, Central Europe
Haase, K. M.; Beier, C.; Regelous, M.; Rapprich, V.; Renno, A. D.ORC
Abstract: Geochemical data on Oligocene melilititic and nephelinitic rocks from the northern Eger Rift flank in Central Europe reveal significant differences to nephelinites and basanites of volcanic complexes in the rift axis. The mafic rift flank lavas are more enriched in TiO2, P2O5 and CaO but have lower SiO2 compared to the alkaline volcanic rocks in the Eger Rift. The differences inmajor element compositions imply (1) lower degrees of partial melting beneath the rift flank than beneath the rift axis evident fromlower SiO2 and higher (Ce/Yb)N ratios in the off-axis basalts and (2) different assemblages of fractional crystallization. The mafic rift flankmagmas experienced crystal fractionation of olivine followed by clinopyroxene fractionation in contrast to early simultaneous olivine and clinopyroxene fractionation in the magmas below the rift basin. In addition, assimilation of continental crustal rocks is associated with crystal fractionation and changes the composition of the lavas. The rift axis lavas are enriched in Nb and Ba relative to La and have higher Sr and lower Nd isotope ratios than the rift flank magmas indicating differentmantle sources. The melting zones beneath the rift axis and the rift flank region are separated although they are only some 20 km apart and no melt exchange between the magma systems is observed. All magmas probably experienced mixing between a deep carbonatitic and a shallower low-degree silicate melt.
Keywords: Continental rifting Intraplate volcanism Magma formation Fractional crystallization Crustal assimilation Registration No. 24352 - Permalink

Magnetism of Rare Earth Tetraborides
Mat'As, S.; Siemensmeyer, K.; Wheeler, E.; Wulf, E.; Beyer, R.; Herrmannsdörfer, T.; Ignatchik, O.; Uhlarz, M.; Flachbart, K.; Gabani, S.; Priputen, P.; Efdokimova, A.; Shitsevalova, N.
Abstract: The rare earth tetraborides REB4 with RE = Ho, Er, Tm, crystallize in a tetragonal lattice where the positions of the RE ions can be mapped to a Shastry-Sutherland lattice. We have investigated the magnetic properties by means of magnetisation and specific heat experiments in a magnetic field. All compounds are anisotropic, with RE = Er, Tm they are strong Ising magnets, for RE = Ho we find xy anisotropy. In magnetic field we find complex behaviour with a number of different phases as a function of applied field, field direction and temperature. Remarkable is the observation of fractional magnetisation plateaux for magnetic field || (001) in HoB4 and TmB4. Registration No. 24344 - Permalink

Bimetallic MOFs (H3O)x[Cu(MF6)(pyrazine)2] (4-x)H2O (M = V4+, x = 0; M = Ga3+, x = 1): co-existence of ordered and disordered quantum spins in the V4+ system
Manson, J. L.; Schlueter, J. A.; Garrett, K. E.; Goddard, P. A.; Lancaster, T.; Möller, J. S.; Blundell, S. J.; Steele, A. J.; Franke, I.; Pratt, F. L.; Singleton, J.; Bendix, J.; Lapidus, S. H.; Uhlarz, M.; Ayala-Valenzuela, O.; Mcdonald, R. D.; Gurak, M.; Baines, C.
Abstract: The title compounds are bimetallic MOFs containing [Cu(pyz)2]2+ square lattices linked by MF6n- octahedra. In each, only the Cu2+ spins exhibit long-range magnetic order below 3.5 K (M = V4+) and 2.6 K (M = Ga3+). The V4+ spins remain disordered down to 0.5 K. Registration No. 24343 - Permalink

PENELOPE – a high energy 150 fs diode-pumped laser system
Albach, D.; Loeser, M.; Röser, F.; Siebold, M.; Schramm, U.
Abstract: The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is currently constructing a fully diode-pumped Petawatt laser ‒ PEnELOPE (Petawatt, Energy-Efficient Laser for Optical Plasma Experiments). A five stage amplifier system relying on Yb:CaF2 as gain medium designed for pulse energies of 150 J and a pulse duration of 150 fs operating at a repetition rate of 1 Hz...
  • Invited lecture (Conferences)
    7th International Conference on Ultrahigh Intensity Lasers (ICUIL), 11.-16.09.2016, Montebello, Canada
Registration No. 24342 - Permalink

Magnetotransport and de Haas–van Alphen measurements in the type-II Weyl semimetal TaIrTe4
Khim, S.; Koepernik, K.; Efremov, D. V.; Klotz, J.; Förster, T.; Wosnitza, J.; Sturza, M. I.; Wurmehl, S.; Hess, C.; van den Brink, J.; Büchner, B.
Abstract: The layered ternary compound TaIrTe4 has been predicted to be a type-II Weyl semimetal with only four Weyl points just above the Fermi energy. Performing magnetotransport measurements on this material we find that the resistivity does not saturate for fields up to 70 T and follows a ρ ∼ B1.5 dependence. Angular-dependent de Haas–van Alphen measurements reveal four distinct frequencies. Analyzing these magnetic quantum oscillations by use of density functional theory calculations we establish that in TaIrTe4 the Weyl points are located merely ∼40–50 meV above the chemical potential. Registration No. 24341 - Permalink

Identification of mineral-binding peptides that discriminate between chalcopyrite and enargite.
Curtis, S.; Lederer, F. L.; Dunbar, S. W.; Macgillivray, R. T. A.
Abstract: Innovative approaches to the separation of minerals and subsequent extraction of metals are imperative owing to the increasing mineralogical complexity of ore deposits that are difficult or even impossible to separate into slurries or solutions containing only the minerals or metals of interest. Low recovery of metal is typical for these complex deposits leading to significant losses to tailings. In addition, the minerals often contain impurities, some toxic, which are difficult and costly to control or manage during the processing of a concentrate or other mineral product. One example of this complex situation is the significant economic and environmental costs associated with diluting and processing copper concentrates containing arsenic (in the form of the mineral enargite, Cu3AsS4) in the production of pure copper. To overcome these separation problems, we have utilized phage display to identify peptides that demonstrate selective recognition of enargite and the arsenic-free copper sulfide, chalcopyrite. Screening of two random peptide phage display libraries resulted in the identification of an enargite-selective peptide with the sequence MHKPTVHIKGPT and a chalcopyrite-selective peptide with the sequence RKKKCKGNCCYTPQ. Mineral-binding selectivity was demonstrated by binding studies, zeta potential determination and immunochemistry. Peptides that have the ability to discriminate between enargite and chalcopyrite provide a greener option for the separation of arsenic containing contaminants from copper concentrates. This represents the first step towards a major advance in the replacement or reduction of toxic collectors as well as reducing the level of arsenic-bearing minerals in the early stages of mineral processing.
Keywords: Phage display, mineral binding peptides, enargite, chalcopyrite Registration No. 24340 - Permalink

Neue Wege zum Recycling von Seltenen Erden
Lederer, F. L.; Curtis, S.; Dunbar, S. W.; Macgillivray, R. T. A.
Abstract: Geeignete Methoden zur wirtschaftlichen Aufbereitung der Seltenen Erden im Leuchtpulver von Kompaktleuchtstofflampen (KLL) sind aufgrund fehlender Spezifität Mangelware. Phage Surface Display spielte bisher vor allem in der Medizin eine wichtige Rolle. Forscher der Universität von British Columbia in Kanada setzen es allerdings schon seit einigen Jahren erfolgreich ein, um Antikörper gegen anorganisches Material zu identifizieren. In der kanadischen Forschergruppe erlernte Methoden verhalfen zur Identifizierung von Peptiden mit einer hohen Spezifität für LaPO4:Ce,Tb, dem grünen Leuchtstoff der KLL. Gefundene Bakteriophagen mit Peptiden, die höchste Spezifität für ein Zielmaterial zeigen, sollen in Flotationsexperimenten auf ihre Bindungseigenschaften bei der Separation von Zielmaterial aus einem Materialgemisch untersucht werden. Bakteriophagen oder die Peptide selbst sollen zukünftig dabei helfen, Seltene Erden aus Elektroschrott gewinnbringend zu trennen.

This project has received funding by a Marie Curie International Outgoing Fellowship from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 623744.

Keywords: Seltene Erden, Kompaktleuchtstofflampen, Phage Surface Display
  • Lecture (Conference)
    ProcessNet-Jahrestagung und 32. DECHEMA-Jahrestagung der Biotechnologen 2016, 12.-15.09.2016, Aachen, Deutschland
Registration No. 24339 - Permalink

Enhancement of carrier mobility in thin Ge layer by Sn co-doping
Prucnal, S.; Liu, F.; Berencén, Y.; Vines, L.; Bischoff, L.; Grenzer, J.; Andric, S.; Tiagulskyi, S.; Pyszniak, K.; Turek, M.; Drozdziel, A.; Helm, M.; Zhou, S.; Skorupa, W.
Abstract: We present the development, optimization and fabrication of high carrier mobility materials based on GeOI wafers co-doped with Sn and P. The Ge thin films were fabricated using plasmaenhanced chemical vapour deposition followed by ion implantation and explosive solid phase epitaxy, which is induced by millisecond flash lamp annealing. The influence of the recrystallization mechanism and co-doping of Sn on the carrier distribution and carrier mobility both in n-type and p-type GeOI wafers is discussed in detail. This finding significantly contributes to the state-of-the-art of high carrier mobility-GeOI wafers since the results are comparable with GeOI commercial wafers fabricated by epitaxial layer transfer or SmartCut technology.
Keywords: GeOI, flash lamp annealing, ion implantation, explosive recrystallization
  • Semiconductor Science and Technology 31(2016)105012
    Button zum Volltext
Registration No. 24338 - Permalink

PEnELOPE - a high energy 150 fs hybrid thin disk and gas-cooled multi-slab laser system
Siebold, M.; Albach, D.; Loeser, M.; Schramm, U.
Abstract: The Helmholtz-Centre Dresden-Rossendorf (HZDR) is currently launching the fully diode-pumped Petawatt laser PEnELOPE (Petawatt, Energy-Efficient Laser for Optical Plasma Experiments). A five stage amplifier system using Yb:CaF2 as gain medium...
  • Lecture (Conference)
    Stuttgarter Lasertage, 31.05.-01.06.2016, Stuttgart, Germany
Registration No. 24336 - Permalink

Highly doped zinc oxide films produced by advanced thermal processing in the millisecond range
Rebohle, L.; Braun, M.; Prucnal, S.; Skorupa, W.; Guziewicz, E.; Snigurenko, D.
Abstract: Zinc oxide (ZnO) is an attractive candidate to replace indium tin oxide in microelectronic and photovoltaic applications. Furthermore, ZnO nanostructures hold great promise for sensor applications. Whereas n-type doping can be easily achieved, p-type doping is a more challenging issue as most defects like Zn interstitials act as n-type dopants.
In this work 100 nm thick ZnO layers were grown by atomic layer deposition on a thermal SiO2 layer on top of a Si wafer. Subsequently, the layers were implanted by phosphorus or antimony, followed by flash lamp annealing (FLA). The ZnO layers were investigated by means of Raman, photoluminescence, sheet resistance and Hall measurements. Depending on the FLA conditions, the doping type shifts from n-type dominated by defects to p-type caused by the implanted group V elements.

Keywords: flash lamp annealing, ion implantation, zinc oxide
  • Lecture (Conference)
    Material Science and Engineering, 27.-29.09.2016, Darmstadt, Deutschland
Registration No. 24330 - Permalink

Flow Structures Analysis Downstream Gas Spargers of Different Orifice Pattern in Bubble Columns
Möller, F.; Bieberle, A.; Barthel, F.; Schubert, M.; Hampel, U.; Weber, M.; Weber, M.
Abstract: Bubble column reactors are widely employed for gas-liquid reactions due to their superior mass and heat transfer accompanied by being geometrically simple and free from any moving part. However, the gas sparger is a crucial device, which directly determines the process performance. The bubbles released from the orifices of the gas sparger start rising up and buoyancy and drag forces etc., in turn, depending on bubble size, control the traveling velocity of the bubbles, and eventually the overall hydrodynamic behavior, such as mixing and gas holdup. Hence, to get an insight into the impact of orifice patterns and holes’ diameter of a gas sparger on the axially evolving gas-liquid dispersion, an ultrafast X-ray tomography study is performed in a 2 m height bubble column of 100 mm diameter. Two different perforated plate-type spargers are used, namely a single orifice sparger with a 2.9 mm center hole and a plate with 13 orifices arranged in a triangular pitch with a hole diameter of 0.8 mm, respectively. The experiments were performed in a non-coalescing system for superficial gas velocities up to 2.5 cm/s. From the X-ray measurements, the evolving gas structures, the bubble size distributions as well as the cross-sectional gas holdup distributions are extracted along the column height and the benefit of a fine initial distribution is evaluated.
  • Lecture (Conference)
    International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy
Registration No. 24328 - Permalink

Liquid Circulation and Swarm Dynamics in Bubble Columns with Internals
Möller, F.; Hampel, U.; Schubert, M.
Abstract: Bubble column reactors are apparatuses of choice for many gas-liquid and gas-liquid-solid reactions due to their superior mixing, heat and mass transfer behavior as well as their simple design without any moving part. In particular, they are often used for exothermic reaction processes such as methanol synthesis, Fischer-Tropsch synthesis etc. Hence, the heat has to be removed out of the system in order to guarantee safe operation at optimal reaction conditions. For this purpose a variety of heat exchangers e.g. internal heat exchanging tube bundles, which can also be used to generate steam, are applied. However, the effects of heat exchanger installation in bubble columns on the gas-liquid flow are still fragmentary.
This contribution focusses on the effect of internals on liquid circulation and swarm dynamics. Internal longitudinal flow heat exchanging bundles with various tube pattern configurations (triangular, and square pitch) and tube diameters between 8 and 13 mm while covering a cross sectional area of ~25% are subject to hydrodynamic and mixing studies in a column of 100 mm diameter.
Wire-mesh sensors with measurement points suitably distributed in the cross-section between the internals’ tubes were installed at different axial positions to study liquid mixing and dispersion in the bubble column as well as lateral fluid exchange between sub-channels. Tracer studies were performed and suitable transfer functions were applied for the determination of the liquid dispersion coefficient. It was found that bubble columns with tube bundle internals show similar behavior as airlift reactors. In addition, ultrafast X-ray tomography is applied to study the effect of the internal configurations on the axial bubble size distribution and gas fraction evolution as well as on the prevailing flow regimes.
  • Poster
    Jahrestreffen Bingen 2016 - Fachgruppen Agglomerations- und Schüttguttechnik, Mehrphasenströmungen und Computational Fluid Dynamics (AGG, MPH, CFD), 29.02.-02.03.2016, Bingen, Deutschland
Registration No. 24327 - Permalink

Mechanical properties and plasticity size effect of Fe-6%Cr irradiated by Fe ions and by neutrons
Hardie, C. D.; Odette, G. R.; Wu, Y.; Akhmadaliev, S.; Roberts, S. G.
Abstract: The mechanical behaviour of Fe6%Cr in the un-irradiated, self-ion irradiated and neutron irradiated conditions was measured and compared. Irradiations were performed to the same dose and at the same temperature but to very different damage rates for both methods. The materials were tested using nanoindentation and micromechanical testing, and compared with microstructural observations from Transmission Electron Microscopy (TEM) and Atom Probe Tomography (APT) reported elsewhere. Irradiated and un-irradiated micro-cantilevers with a wide range of dimensions were used to study the interrelationships between irradiation hardening and size effects in small-scale plasticity. TEM and APT results identified that the dislocation loop densities were ~2.9 E22 m-3 for the neutron irradiated material and only 1.4E22 m-3 for the ion irradiated material. Cr segregation to loops was only found for the neutron-irradiated material. The nanoindentation hardness increase due to neutron irradiation was 3 GPa and that due to ion irradiation 1 GPa. The differences between the effects of the two irradiation types are discussed, taking into account inconsistencies in damage calculations, and the differences in PKA spectra, dose rate and transmutation products for the two irradiation types. Registration No. 24322 - Permalink

Ion-beam induced atomic mixing in isotopically controlled silicon multilayers
Radek, M.; Bracht, M.; Liedke, B.; Böttger, R.; Posselt, M.
Abstract: Implantation of germanium (Ge), gallium (Ga), and arsenic (As) into crystalline and preamorphized isotopically controlled silicon (Si) multilayer structures at temperatures between 153 K and 973K was performed to study the mechanisms mediating ion-beam induced atomic mixing. Secondary-ion-mass-spectrometry (SIMS) was applied to determine concentration-depth profiles of the stable isotopes before and after ion implantation. The intermixing is analytically described by a depth-dependent displacement function. The maximum displacement is found to depend not only on temperature and microstructure but also on the doping type of the implanted ion. Molecular dynamics
calculations evaluate the contribution of cascade mixing, i.e., thermal-spike mixing, to the overall observed atomic mixing. Calculated and experimental results on the temperature dependence of ion-beam mixing in the amorphous and crystalline structures provide strong evidence for ion-beam induced enhanced crystallization (IBIEC) and enhanced self-diffusion (IBIESD), respectively. Whereas the former process is confirmed by channeling Rutherford backscattering analyses of the amorphous layer thickness remaining after implantation, the latter process is consistently attributed to the formation of highly mobile Si di-interstitials formed under irradiation and in the course of damage annealing. The observed ion-beam mixing in Si is compared to recent results on ion-beam mixing of Ge isotope multilayers that, in contrast to Si, are fully described by thermal-spike mixing only.

Keywords: ion beam mixing, silicon isotope multilayers Registration No. 24321 - Permalink

Selektive Phasengeschwindigkeitsmessung in Blasenströmungen durch den kombinierten Einsatz einer Heißfilmsonde und der ultraschnellen Röntgentomographie
Kipping, R.; Kryk, H.; Hampel, U.
Abstract: Blasensäulenreaktoren bieten aufgrund ihrer einfachen Bauweise und ihres ausgezeichneten Wärme- und Stofftransportverhaltens einen häufig genutzten Reaktortyp in der chemischen Industrie. Besonders die Beschreibung der Hydrodynamik und der Geschwindigkeitsprofile der unterschiedlichen Phasen, sowie deren radiale Verteilung haben einen erheblichen Einfluss auf den Stofftransport und chemische Reaktion. In diesem Beitrag sollen die Ergebnisse der Untersuchung zur Flüssigphasengeschwindigkeit in Blasenströmungen vorgestellt werden. Die Anwendbarkeit von Heißfilmsonden ist bei Vorliegen einer Mehrphasenströmung stark begrenzt. In Blasensäulen beinhaltet das gemessene Geschwindigkeitssignal Anteile der Gas- und Flüssigphase. Zur Untersuchung der Umströmung von Blasen und zur Bestimmung von Turbulenzparametern ist es notwendig diese Anteile voneinander zu trennen. Ausschließlich bei geringen Gasgehalten bietet der charakteristische Signalverlauf bei der Interaktion von Blase und Sonde eine Möglichkeit dazu. In dieser Arbeit kann mit Hilfe der Zwei-Ebenen Tomographie, die genaue Position der Heißfilmsonde und die vorliegende Phase an dieser Stelle in der Blasensäule bestimmt werden. Weiterhin können neben der Flüssigphasengeschwindigkeit auch Parameter der Hydrodynamik der Gasphase, wie Blasenform, Blasengröße bestimmt werden und in Abhängigkeit zur Flüssigphasengeschwindigkeit gestellt werden.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Agglomerations-und Schüttguttechnik, Computational Fluid Dynamics und Mehrphasenströmungen, 29.02.-02.03.2016, Bingen, Deutschland
Registration No. 24320 - Permalink

Experimental investigation of mass transfer of CO2 bubbles with ultrafast electron beam X-rax tomography
Kipping, R.; Kryk, H.; Hampel, U.
Abstract: Bubble columns are a favored reactor type for the operation of gas-liquid reactions (e.g. oxidation and hydrogenation processes) in chemical industries. The improved design and operation of bubble column reactors requires a detailed understanding of the flow phenomena as well as mass transfer processes within these reactors. This study presents the experimental investigation the gas liquid mass transfer in a bubble column on the basis of the chemical absorption of CO2. This contribution presents ultrafast X-ray CT measurements within a bubble column. The mass transfer has been determined by the analysis of the decrease of gas the gas phase, especially the shrinkage of the CO2 bubbles.
Keywords: reactive two-phase flow, ultrafast X-ray tomography, chemical absorption, mass transfer
  • Lecture (Conference)
    FERMaT-SPP1740-Symposium, 06.-08.06.2016, Toulouse, Frankreich
Registration No. 24319 - Permalink

Characterization of a chemical reaction in a bubble column using Wire-Mesh Sensor and ultrafast X-ray CT
Kipping, R.; Kryk, H.; Schleicher, E.; Hampel, U.
Abstract: Design and operation of bubble columns are of main importance, since they strongly influence yield and selectivity of chemical reactions. In order to improve the process efficiency, a fundamental understanding of flow phenomena in bubble columns is necessary. A lot of research has been carried out for the investigation of hydrodynamics of bubble columns. Nonetheless, hydrodynamics is changing in the presence of a chemical reaction (e.g. shrinkage of bubbles due to mass-transfer processes). Hence, there is a strong interaction of hydrodynamics, mass-transfer and chemical reaction within bubble columns, which has been investigated in the past, amongst others, using the reaction of sodium hydroxide and carbon dioxide. However, most works are restricted to low gas holdups or provide only single point information due to the use of local probes (e.g. pH measurement). This contribution comprises the experimental investigation of the reaction of sodium hydroxide and carbon dioxide, applying Wire-Mesh Sensors for determining the locally occurring reaction steps at different operating conditions (e.g. gas flow rate of carbon dioxide, initial concentrations of sodium hydroxide). In turn, experimental results are compared with concentration profiles derived from known reaction kinetics. The application of Wire-Mesh Sensors for this purpose allows the visualization of the concentration distribution within the cross-section of the bubble column. Additionally, ultrafast X-ray computer tomography is used simultaneously to study the change of hydrodynamics during the reaction.
Keywords: Wire-Mesh Sensor, ultrafast X-ray tomography, two-phase flow, chemical reaction
  • Lecture (Conference)
    WCIPT8 - 8th World Congress on Insutrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brasilien
Registration No. 24317 - Permalink

Targetting microglia activation in schizophrenia by minocycline treatment
Mattei, D.; Ivanov, A.; Ferrai, G.; Jordan, P.; Guneykaya, D.; Schaafsma, W.; Przanowski, P.; Deuther-Conrad, W.; Brust, P.; Hesse, S.; Eggen, B.; Bodekke, E.; Kaminska, B.; Pombo, A.; Kettenmann, H.; Wolf, S. A.
Abstract: The importance of the brain's phagocyte – the microglia – came recently into focus as a novel therapeutic target in psychiatric disorders. Dysregulations of microglia have been reported in post mortem tissue and also in vivo by increased radio ligand binding to the (phagocyte-specific) TSPO receptor in brains of schizophrenic patients. The tetracycline minocycline that partially acts on microglia has been shown to improve mainly negative symptoms in a few clinical studies. We here use an animal model of maternal immune activation to test its validity for clinical translation and investigate the pathways that are targeted by minocycline specific in microglia. Pregnant dams were injected intraperitoneally with the viral mimic PolyI:C or saline at gestational day 15 and the offspring was tested for behavioral deficits at postnatal day 60. Indeed, the offspring showed behavioral correlates of schizophrenia like decreased pre-pulse inhibition, sociability and cognitive performance along with an increased binding potential to the TSPO shown by autoradiography using [18F]GE-180 on hippocampal slices. This was accompanied by a profoundly altered transcriptome signature in hippocampal microglia and decreased phagocytic activity. Thereafter, mice were treated for five weeks with minocycline (3 mg/kg/day). This treatment normalized the behavioral deficits, TSPO binding and phagocytic activity and restored the transcriptome signature towards control levels. Our findings indicate that minocycline is a potent drug to affect specific microglial functions and thereby attenuate symptoms of schizophrenia in an animal model.
Keywords: Neuroimmunology Schizophrenia: basic Glia
  • Lecture (Conference)
    29th ECNP CONGRESS, 17.-20.09.2016, Vienna, Österreich
Registration No. 24315 - Permalink

Euler-Euler Simulation und Modellvalidierung für Blasenströmungen
Guo, J.
Abstract: Die Anwendung von Methoden der CFD („Computational fluid dynamics“) für Scale-up und Intensivierung verfahrenstechnischer Prozesse bietet die Möglichkeit, energie- und ressourceneffiziente Lösungen zu identifizieren, deren Untersuchung mit konventionellen halb-empirischen Methoden kostspielig und langwierig wäre.
Eine solche Simulation im großtechnischen Maßstab ist im Rahmen der Euler-Euler Beschreibung möglich, in der Prozesse auf der Skala einzelner Blasen modelliert werden. Ein solches Schließungsmodell für Hydrodynamik und Stofftransport in Blasenströmungen wird am HZDR entwickelt. Ziel dieser Entwicklung ist, ein vorhersagetaugliches Modell zu etablieren, das für einen breiten Bereich von Anwendungsbedingungen validiert ist.
Zu diesem Zweck werden Simulationsrechnungen mit experimentellen Daten verglichen, die zunehmend komplexere Geometrien und Effekte einbeziehen. Auf Basis der jeweils erzielten Übereinstimmung werden Modellerweiterungen und -verbesserungen vorgenommen. Im Rahmen der Diplomarbeit sollen hierzu Strömungen in Blasensäulen und Blasenströmungen in Rohren untersucht werden.

Keywords: Blasenströmung, Euler-Euler zwei-Fluid-Modell, CFD-Simulation
  • Diploma thesis
    TU Dresden, 2016
    Mentor: Dr. Roland Rzehak (HZDR), Prof. Rüdiger Lange (TU-Dresden)
    57 Seiten
Registration No. 24313 - Permalink

Analysis of SAM Coatings for Dropwise Condensation in Passive Safety Systems
Unger, S.; Sarker, D.; Harm, U.; Hampel, U.
Abstract: Passive safety systems of spent fuel pools are one key technology for further improvement of the reliability of nuclear power plants. These systems transfer high amount of heat, while using air as a heat sink. For that reason the overall temperature differences are small. Since the heat transfer is based on natural convection and gravitational force, the heat transfer resistance of the heat exchangers are high compare to active systems. A Self-Assembled Monolayer (SAM) coating can address both challenges by enable a high compact condensation heat exchanger and by reducing the heat transfer resistance during condensation. Therefore different coating chemicals and surface roughness were analysed, to create the most beneficial heat transfer surface.
Keywords: Passive safety, dropwise condensation, condensation, heat transfer
  • Lecture (Conference)
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Deutschland
Registration No. 24312 - Permalink

Surprising effects of electron-electron scattering in graphene
Helm, M.; König-Otto, J.; Mittendorff, M.; Pashkin, A.; Schneider, H.; Wendler, F.; Winzer, T.; Malic, E.; Knorr, A.; Winnerl, S.
Abstract: Two surprising effects related to electron-electron scattering in graphene are demonstrated: One is a long-lived anisotropic carrier distribution after THz excitation, and the other one is an unexpected sign reversal of the pump-probe signal in a magnetic field. The latter reflects an Auger scattering so strong that it overcomes the effect of optical pumping.
Keywords: graphene, pump-probe, terahertz, free-electron laser
  • Invited lecture (Conferences)
    5th Russia-Japan-USA-Europe Symposium on Fundamental & Applied Problems of Terahertz Devices & Technologies (RJUSE TeraTech-2016), 31.10.-04.11.2016, Sendai, Japan
Registration No. 24311 - Permalink

Simulation of Liquid Metal Batteries by Continuum Mechanics
Weber, N.; Beckstein, P.; Galindo, V.; Landgraf, S.; Stefani, F.; Weier, T.
Abstract: Liquid metal batteries (LMB) are built as a stable density stratification of two liquid metals, separated by a likewise liquid salt. If the materials are correctly chosen, all three phases self-assemble (figure 1). During discharge, the anode metal will donate electrons, the ion will diffuse through the electrolyte layer and alloy there with the cathode metal.
The main advantage of LMBs is the very low price: low-cost raw materials together with a simple set-up and scalability make such cells an ideal stationary storage, which is highly needed for buffering fluctuating renewable energies. The liquid-liquid interfaces allow for optimal kinetics, i.e. for a fast response time and current densities up to 10 A/cm2. Furthermore, they avoid micro-degradation - as known from solid cells - and allow for potentially very high life-times.
Safety will play a major role in the construction of such cells – especially due to the high amount of liquid and reactive metals. In that context, a short circuit of the thin electrolyte layer should be avoided. In large liquid metal batteries with diameters in the order of several decimetres, even the discharging current itself may lead to a fluid flow, able to short-circuit the battery.

We will present numerical simulations of the fluid flow in LMBs and estimate their relevance for real cells. The numerical solvers combining heat transfer, fluid- and electrodynamics with the volume of fluid method are implemented in the open source library OpenFOAM. Reviewed phenomena include thermal convection, electro-vortex flow, the Tayler-instability as well as metal pad rolling, which is well known from aluminium reduction cells.

Keywords: OpenFOAM, liquid metal battery
  • Lecture (Conference)
    Helmholtz-Workshop "Multiscale Modeling of Energy Storage Materials", 10.-11.11.2016, Berlin, Deutschland
Registration No. 24308 - Permalink

Particles as concentrated sources related to uptake and radiological dose in mammals
Johansen, M. P.; Caffrey, E.; Child, D. P.; Collins, R.; Hotchkis, M. A. C.; Howell, N. A.; Payne, T. E.; Mokhber-Shahin, L.; Ikeda-Ohno, A.
Abstract: The radiological residues at the former weapons testing sites at Maralinga, Emu and the Monte Bello Islands often occur in particulate form (so called hot particles). Large numbers of these particles were emitted from nuclear and non-nuclear tests. For example each square meter in a plume which extends for tens of kilometres at the Taranaki site (Maralinga) can contain more than 3000 readily identifiable particles. The physical and chemical characteristics of these particles affect their mobility and availability for uptake into living organisms. When they contain long-lived radionuclides (e.g. 239Pu) these particles may slowly weather, and thus provide a persistent source of ionic forms, or smaller particles, for many thousands of years.
From these Australian sites, we have gathered a series of particles that have weathered and interacted with the environment for 50+ years since their initial formation and release events. The particles are being evaluated using a range of methods including gamma spectrometry, autoradiography, high sensitivity Accelerator Mass Spectrometry analysis (AMS), leaching studies, and synchrotron X-ray fluorescence microscopy.
Significant findings include the clustering of Cs on the exterior of a glassy fission fragment, with Sr occurring in the nearby interior, suggesting the 137Cs may be more available for weathering processes, and the beta emissions from the 90Sr may be largely self-shielded within the particle. In contrast, a different particle from a nearby site lacked any fission products, but contained Pu(IV) oxyhydroxides consistent with weathering in a semi-arid environment. Although the 239Pu is very active, detailed dose modelling suggests most of the alpha emissions from particles > 5µm are shelf-shielded within the particles themselves, and therefore impart lower dose than the equivalent Pu dissolved and distributed throughout an organ. However, when Pu exists on exterior surfaces, a hot particle that has been internalised (e.g. lodged in a mammalian lung) may produce relatively highly concentrated dose rates to adjacent tissues.

Keywords: Plutonium / actinides / particulates / update / nuclear tests / dose / mammals / radio ecology
  • Lecture (Conference)
    2nd International Conference on Radioecological concentration processes (50 years later), 09.11.2016, Seville, Spain
Registration No. 24307 - Permalink

Scaling EUV and X-ray Thomson Sources to Optical Free-Electron Laser Operation with Traveling-Wave Thomson-Scattering
Steiniger, K.; Albach, D.; Debus, A.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.
Abstract: Traveling-Wave Thomson-Scattering (TWTS) allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources by providing optical undulators with hundreds to thousands of undulator periods from high-power, pulse-front tilted lasers pulses.

With TWTS the realization of optical free-electron lasers (OFELs) as well as incoherent radiation sources with orders of magnitude higher photon yields than classic head-on Thomson sources becomes possible with state-of-the-art technology in electron accelerators and laser systems.

TWTS employs a side-scattering geometry where laser and electron propagation direction of motion enclose an angle. Tilting the laser pulse front with respect to the wave front by half of this interaction angle optimizes electron and laser pulse overlap by compensating the spatial offset between electrons and the laser pulse-front at the beginning of the interaction when the electrons are far from the laser pulse axis. The laser pulse-front tilt ensures continuous overlap between electrons and laser pulse while the electrons cross the laser pulse cross-sectional area. Thus the interaction distance can be controlled in TWTS by the laser pulse width rather than laser pulse duration. Utilizing wide, petawatt class laser pulses allows to realize thousands of optical undulator periods.

The talk will show that TWTS OFELs emitting ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. Especially the ultra-low emittance of laser wakefield accelerated electron beams can be exploited to compensate for their one percent level energy spreads. We discuss an experimental setup to generate the tilted TWTS laser pulses. The method presented provides dispersion compensation, required due to angular dispersion, and is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups.

Keywords: Traveling-Wave, Thomson scattering, FEL, X-ray, Laser dispersion compensation
  • Lecture (others)
    Invited Seminar talk at Helmholtz Institut Jena, 30.09.2016, Jena, Deutschland
Registration No. 24305 - Permalink

Scaling EUV and X-ray Thomson Sources to Optical Free-Electron Laser Operation with Traveling-Wave Thomson-Scattering
Steiniger, K.; Albach, D.; Debus, A.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.
Abstract: Traveling-Wave Thomson-Scattering (TWTS) is a novel Thomson scattering geometry which allows for orders of magnitude higher photon yields than classic head-on Thomson sources. TWTS thereby remains compact and provides narrowband and ultra-short ultraviolet to γ-ray radiation pulses just as classic Thomson sources. Even the realization of optical free-electron lasers is possible with the TWTS geometry since it provides both optical undulators with thousands of periods needed to microbunch the electron beam and a reduction of electron beam quality requirements compared to classic Thomson scattering to a level technically feasible today.
TWTS employs a side-scattering geometry depicted in fig. 1. Laser and electron propagation direction of motion enclose the interaction angle ϕ. Tilting the laser pulse front with respect to the wave front by half the interaction angle ensures continuous overlap of electrons and laser pulse over the whole laser pulse width while the laser pulse crosses the electron beam trajectory. In this way the interaction length becomes controllable by the laser pulse width and independent of the laser pulse duration. Utilizing wide, petawatt class laser pulses for TWTS allows to realize thousands of optical undulator periods.
The variability of TWTS with respect to the interaction angle can be used to control the radiation wavelength even for electron sources with fixed energy. For a fixed target wavelength on the other hand, the free choice of interaction angle enables control over electron beam quality requirements. Small interaction angle scenarios (ϕ∼10°) typically yield the best trade-off between requirements on electron beam quality, laser power and laser intensity stability.
In the talk we will show that TWTS OFELs emitting extreme ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. We detail an experimental setup to generate the tilted TWTS laser pulses which aims at compactness and provides focusing of these high-power pulses and compensation of dispersion accompanying pulse-front tilts. The method presented for dispersion compensation is especially relevant when building high yield X- and γ-ray sources in large interaction angle setups of TWTS.

Keywords: Traveling-Wave, Thomson scattering, FEL, X-ray, Laser dispersion compensation
  • Poster
    The 15th International Conference on X-Ray Lasers, 22.-27.05.2016, Nara, Japan
Registration No. 24304 - Permalink

Inclusive Λ production in proton-proton collisions at 3.5 GeV
Adamczewski-Musch, J.; Agakishiev, G.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Maurus, S.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataroe, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.
Abstract: The inclusive production of {\Lambda} hyperons in proton-proton collisions at s√ = 3.18 GeV was measured with HADES at the GSI Helmholtzzentrum f\"ur Schwerionenforschung in Darmstadt. The experimental data are compared to a data-based model for individual exclusive {\Lambda} production channels in the same reaction. The contributions of intermediate resonances such as {\Sigma}(1385), {\Delta}++ or N* are considered in detail. In particular, the result of a partial wave analysis is accounted for the abundant pK+{\Lambda} final state. Model and data show a reasonable agreement at mid rapidities, while a difference is found for larger rapidities. A total {\Lambda} production cross section in p+p collisions at s√ = 3.18 GeV of {\sigma}(pp → {\Lambda} + X) = 207.3 ± 1.3 +6.0 -7.3 (stat.) ± 8.4 (syst.) +0.4 -0.5 (model) {\mu}b is found. Registration No. 24303 - Permalink

Forschung und Lehre innerhalb des Kompetenzzentrums Ost für Kerntechnik auf den Gebieten Endlagerung, Reaktorsicherheit und Strahlenschutz
Kliem, S.ORC; Hampel, U.; Hurtado, A.; Kästner, W.; Kratzsch, A.; Sahre, P.; Jansen, S.
Abstract: Das Kompetenzzentrum Ost für Kerntechnik ist ein regionaler Zusammenschluss der kerntechnischen Einrichtungen mit dem Ziel, die kerntechnische, strahlentechnische und radiochemische Ausbildung an den sächsischen Ausbildungseinrichtungen wie bspw. der TU Dresden und der Hochschule Zittau/Görlitz zu erhalten und möglichst weiter zu entwickeln. Damit einhergehend werden für Lehre und Forschung Versuchseinrichtungen und andere Forschungsinfrastrukturen der Partner gemeinsam genutzt.
Das Kompetenzzentrum Ost für Kerntechnik hat sich die Sicherung des akademisch gebildeten Fachkräftenachwuchses in Universitäten, Hochschulen, Instituten, bei Kernkraftwerksbetreibern und -herstellern sowie in Behörden und Gutachtern zum obersten Ziel gemacht. Dazu werden die einschlägigen Anstrengungen der Mitgliedsorganisationen durch die Vertreter der einzelnen Unternehmen des Kompetenzzentrums koordiniert, um für effizienten Wissenstransfer und Kompetenzerhalt Sorge zu tragen.
Durch den politischen Beschluss bezüglich des Umbaus des Energieversorgungssystems in Deutschland und den damit verbundenen Entscheidungen zur Beendigung der Stromerzeugung aus Kernenergie bis Ende 2022 hat auch für die Mitglieder des Kompetenzzentrums Ost eine Zäsur im Bereich Lehre und Forschung zur Folge. Neben einer deutlichen Reduzierung der Forschungsförderung seitens der Industrie schlägt sich das auch in sinkenden Studenten- und Doktorandenzahlen nieder.
Im Vortrag werden die aktuellen Lehr- und Forschungsaktivitäten der Mitglieder des Kompetenzzentrums Ost mit besonderem Augenmerk auf die gemeinsam bearbeiteten Projekte vorgestellt und Perspektiven zukünftigen Wirkens aufgezeigt.
  • Lecture (Conference)
    48. Kraftwerkstechnisches Kolloquium, 18.-19.10.2016, Dresden, Deutschland
  • Contribution to proceedings
    48. Kraftwerkstechnisches Kolloquium, 18.-19.10.2016, Dresden, Deutschland
    Kraftwerkstechnik 2016, Freiberg: SAXONIA, 9783934409699, 725-733
Registration No. 24301 - Permalink

AER Working Group D on VVER Safety Analysis – Report of the 2016 Meeting
Kliem, S.ORC
Abstract: The AER Working Group D on VVER reactor safety analysis held its 25th meeting in Villigen, Switzerland, during the period 30-31 May, 2016. The meeting was hosted by PSI Villigen and was held in conjunction with the 10th workshop on the OECD Benchmark for Uncertainty Analysis in Best-Estimate Modelling (UAM) for Design, Operation and Safety Analysis of LWRs. Altogether 19 participants attended the meeting of the working group D, 9 from AER member organizations and 5 guests from non-member organization. The co-ordinator of the working group, Mr. S. Kliem, served as chairman of the meeting.

The meeting started with a general information exchange about the recent activities in the participating organizations.

The given presentations and the discussions can be attributed to the following topics:

• Safety analyses methods and results
• Code development and benchmarking
• Thermal hydraulic analyses of passive safety systems
• Future activities

A list of the participants and a list of the handouts distributed at the meeting are attached to the report. The corresponding PDF-files of the handouts can be obtained from the chairman.
  • Lecture (Conference)
    26th Symposium of AER on VVER Reactor Physics and Reactor Safety, 10.-14.10.2016, Helsinki, Finland
Registration No. 24299 - Permalink

Self-organized Ge & Si nanostructures by heavy-ion irradiation
Böttger, R.
Abstract: Heavy ions like Bi or Au of a few tens of keV deposit a high energy density into the collision cascade volume of due to (i) their high mass and (ii) their low projected range. At higher energies, this density becomes diluted as the cascade volume increases super-linearly with ion energy. Compared to monatomic ions, heavy polyatomic ions deposit an even higher energy density. This is sufficient to form a pool of a localized, almost classical melt in a semiconductor surface lasting up to half of a nanosecond.
Local melting and re-solidification by single polyatomic ion impacts is proven by molecular dynamics calculations. Well-ordered, self-organized dot patterns on Si and Ge surfaces have been found after heavy polyatomic ion irradiation, which can be attributed to impact-induced local transient melting. Similar patterns were found with monoatomic ions at elevated substrate temperatures, where the energy per substrate atom exceeds a critical value within a larger volume.
The kinetics of localized melt pools leads to a generic, Kuramoto-Sivashinsky-type (KS) partial differential equation for the surface evolution. Whereas so far the mechanisms of ion-induced surface pattern evolution are assumed to be surface-curvature-dependent ion erosion or ion-momentum-induced mass drift of surface atoms, for heavy polyatomic ions we have identified a completely different mechanism.
The local melting and quenching process is so far from equilibrium that particularities of phase diagrams like the Bi state in Si or Ge are frozen into the nanostructure of the re-solidified volume. This opens the possibility to study extremely fast solid-liquid phase transitions.
The authors thank the German Research Foundation for financial support.

Keywords: Silicon, Germanium, nanostructures, self-organization, ion irradiation
  • Invited lecture (Conferences)
    24th International Conference on the Application of Accelerators in Research and Industry, 30.10.-04.11.2016, Texas, USA
Registration No. 24298 - Permalink

Fluid dynamics of bubbly flows
Ziegenhein, T.ORC
Abstract: Bubbly flows can be found in many applications in chemical, biological and power engineering. Reliable simulation tools of such flows that allow the design of new processes and optimization of existing one are therefore highly desirable. CFD-simulations applying the multi-fluid approach are very promising to provide such a design tool for complete facilities. In the multi-fluid approach, however, closure models have to be formulated to model the interaction between the continuous and dispersed phase. Due to the complex nature of bubbly flows, different phenomena have to be taken into account and for every phenomenon different closure models exist. Therefore, reliable predictions of unknown bubbly flows are not yet possible with the multi-fluid approach.
A strategy to overcome this problem is to define a baseline model in which the closure models including the model constants are fixed so that the limitations of the modeling can be evaluated by validating it on different experiments. Afterwards, the shortcomings are identified so that the baseline model can be stepwise improved without losing the validity for the already validated cases. This development of a baseline model is done in the present work by validating the baseline model developed at the Helmholtz-Zentrum Dresden-Rossendorf mainly basing on experimental data for bubbly pipe flows to bubble columns, bubble plumes and airlift reactors that are relevant in chemical and biological engineering applications.
In the present work, a large variety of such setups is used for validation. The buoyancy driven bubbly flows showed thereby a transient behavior on the scale of the facility. Since such large scales are characterized by the geometry of the facility, turbulence models cannot describe them. Therefore, the transient simulation of bubbly flows with two equation models based on the unsteady Reynolds-averaged Navier–Stokes equations is investigated. In combination with the before mentioned baseline model these transient simulations can reproduce many experimental setups without fitting any model. Nevertheless, shortcomings are identified that need to be further investigated to improve the baseline model.
For a validation of models, experiments that describe as far as possible all relevant phenomena of bubbly flows are needed. Since such data are rare in the literature, CFD-grade experiments in an airlift reactor were conducted in the present work. Concepts to measure the bubble size distribution and liquid velocities are developed for this purpose. In particular, the liquid velocity measurements are difficult; a sampling bias that was not yet described in the literature is identified. To overcome this error, a hold processor is developed.
The closure models are usually formulated based on single bubble experiments in simplified conditions. In particular, the lift force was not yet measured in low Morton number systems under turbulent conditions. A new experimental method is developed in the present work to determine the lift force coefficient in such flow conditions without the aid of moving parts so that the lift force can be measured in any chemical system easily.

Keywords: Bubbly flows, Fluid Dynamics, CFD, PTV, PIV, Lift-force, Bubble column
  • Doctoral thesis
    TU Berlin, 2016
Registration No. 24297 - Permalink

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