Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32083 Publications
Bioflotation with Siderophores
Schrader, S.ORC
Siderophores are small organic molecules with a high affinity for binding Fe(III) and the ability to form strong complexes. They are produced by microorganisms to equalize the low bioavailability of iron in their environment.
There already is wide knowledge about siderophores, their different structures and the microorganisms (aerobic bacteria and fungi), that produce them.
The aim of the study is to test for the first time, whether it is possible to use siderophores for flotation processes.
Molecules with similar functional groups from the chemical industry have been applied successfully in flotation processes. The main advantage of using biotechnology for the production of siderophores is the wide natural diversity of the structures.
Keywords: siderophore, flotation, hydroxamates
  • Lecture (others)
    Microbiology Meeting HZDR - TU Bergakademie Freiberg, 07.11.2016, Freiberg, Deutschland

Publ.-Id: 24725 - Permalink


Production of 2-hydroxyisobutyric acid from methanol by Methylobacterium extorquens AM1 expressing (R)-3-hydroxybutyryl-CoA isomerizing enzymes
Rohde, M.-T.ORC; Tischer, S.ORC; Harms, H.ORC; Rohwerder, T.
The biotechnological production of the methyl methacrylate precursor 2-hydroxyisobutyric acid (2-HIBA) via bacterial poly-3-hydroxybutyrate (PHB) overflow metabolism requires suitable (R)-3-hydroxybutyryl-CoA specific coenzyme B12-dependent mutases (RCM). Here, we characterized a predicted mutase from Bacillus massiliosenegalensis JC6 as a mesophilic RCM, closely related to the thermophilic enzyme previously identified in Kyrpidia tusciae DSM 2912 (M.-T. Weichler, N. Kurteva-Yaneva, D. Przybylski, J. Schuster, R. H. Müller, H. Harms, and T. Rohwerder, Appl Environ Microbiol 81:4564-4572, 2015, http://dx.doi.org/10.1128/AEM.00716-15). Using both RCM variants, 2-HIBA production from methanol was studied in fed-batch bioreactor experiments with recombinant Methylobacterium extorquens AM1. After complete nitrogen consumption, concomitant formation of PHB and 2-HIBA was achieved, indicating that both sets of RCM genes were successfully expressed. However, although identical vector systems and incubation conditions were chosen, metabolic activity of the variant bearing the RCM genes from strain DSM 2912 was severely inhibited, likely due to negative effects caused by the heterologous expression. In contrast, biomass yield of the variant expressing the JC6 genes was close to wild-type performance and 2-HIBA titers of 2.1 g L-1 could be demonstrated. In this case, up to 24% of the substrate channeled into overflow metabolism was converted to the mutase product and maximal combined 2-HIBA plus PHB yields from methanol of 0.11 g g-1 were achieved. Reverse transcription-quantitative PCR analysis revealed that metabolic genes, such as methanol dehydrogenase and acetoacetyl-CoA reductase genes, are strongly down-regulated after exponential growth which currently prevents a prolonged overflow phase and, thus, higher product yields with strain AM1.
Keywords: bulk chemicals, fed-batch bioreactor, overflow metabolism, polyhydroxybutyrate, acyl-CoA mutase

Publ.-Id: 24723 - Permalink


Constrained indicator data resampling — A parameter constrained irregular resampling method for scattered point data
Menzel, P.;
Resampling of high-resolution data sets is often required for real-time applications in geosciences, e.g., interactive modeling and 3D visualization. To support interactivity and real-time computations, it is often necessary to resample the data sets to a resolution adequate to the application. Conventional resampling approaches create uniformly distributed results, which are not always the best possible solution for particular applications. I have developed a new resampling method called constrained indicator data resampling (CIDRe). This method results in irregular point distributions that are adapted to local parameter signal wavelengths of the given data. The algorithm identifies wavelength variations by analyzing gradients in the given parameter distribution. A higher point density is ensured in areas with larger gradients than in areas with smaller gradients, and thus the resulting data set shows an irregular point distribution. A synthetic data test showed that CIDRe is able to represent a data set better than conventional resampling algorithms. In a second application, CIDRe was used to reduce the number of gravity stations for interactive 3D density modeling, in which the resulting point distribution still allows accurate interactive modeling with a minimum number of data points.
Keywords: resampling, potential field modelling, data reduction

Publ.-Id: 24722 - Permalink


Bioflotation mit Siderophoren
Schrader, S.ORC; Kutschke, S.ORC; Pollmann, K.; Rudolph, M.ORC
Siderophoren stellen organische Verbindungen niedrigen Molekulargewichts dar, die eine hohe Affinität zur selektiven Komplexierung von Eisen(III)-Ionen aufweisen. Mikroorganismen, wie aerobe Bakterien oder Pilze, bilden diese Moleküle, um die geringe Bioverfügbarkeit des in der Natur vorkommenden Eisens zu kompensieren.
Mit Hilfe der biotechnologischen Herstellung von Siderophoren besteht die Möglichkeit, diese in unterschiedlichen Anwendungsgebieten zu nutzen. Neben dem medizinischen Einsatz zur Behandlung übermäßiger Eisenaufnahme und Schwermetallvergiftungen, liegt eine weitere Applikation in der (Rück)-Gewinnung des Rohstoffes Eisen, sowie anderer Metalle, die gleichermaßen durch Siderophoren gebunden werden können. Ein weiteres potenzielles Anwendungsgebiet ist ihr Einsatz in Flotationsprozessen. Der Vorteil in der Verwendung biotechnologisch hergestellter Siderophoren liegt in der strukturellen Vielfalt, die diese aufweisen. So sind u.a. Hydroxamate als chelatisierende Gruppen weit verbreitet und finden umgekehrt als Kollektoren in zahlreichen Flotationsprozessen Anwendung. Siderophoren sollten daher ebenfalls als Kollektoren wirken können. Vor allem die Klasse der amphiphilen Siderophoren, die sowohl einen hydrophoben, als auch hydrophilen Bereich besitzen, ist von großem Interesse. Die damit verbundene natürliche Hydrophobie der Moleküle könnte den häufig notwendigen und zusätzlichen Schritt der Hydrophobierung der Mineralpartikel in Flotationsprozessen unnötig machen.
Da bereits eine Vielzahl von Mikroorganismen und den von ihnen produzierten Siderophoren identifiziert und auch strukturell analysiert wurden, existiert ein großes Potenzial möglicher Liganden, welche im Prozess der Flotation Anwendung finden könnten. Neben dem Nachweis der prinzipiellen Eignung von Siderophoren als Flotationsreagenz, besteht allerdings noch die Notwendigkeit der Optimierung sowohl der biotechnologischen Produktion, als auch des Flotationsprozesses, sowie der genaueren Untersuchung und Charakterisierung der Bindungseigenschaften innerhalb dieses Verfahrens.
Keywords: Siderophoren, Hydroxamate, Flotation
  • Poster
    Tagung 2016 „Aufbereitung und Recycling“, 09.-10.11.2016, Freiberg, Deutschland

Publ.-Id: 24721 - Permalink


Experimentelle Untersuchung der Chemisorption von CO2 in NaOH und Kopplung zur Hydrodynamik von Blasenströmungen
Gustke, M.;
Die vorliegende Arbeit beschäftigt sich mit der Ermittlung lokaler Informationen zum Vermischungsverhalten in einer reaktiven Blasensäule. Die Gittersensortechnik dient dabei als Messtechnik zur Quantifizierung des Reaktionsfortschrittes bei der Chemisorption von CO2 in NaOH-Lösung. Der im Vordergrund stehende Verbrauch der Hydroxid-Ionen wird, in Abhängigkeit des CO2-Durchsatzes und der NaOH-Startkonzentration, untersucht. Durch den Einsatz mehrerer querschnittsauflösender Gittersensoren können zahlreiche radiale und axiale Abhängigkeiten des Hydroxid-Ionen-Verbrauchs festgestellt werden. Die experimentell gewonnenen Erkenntnisse können mithilfe von mathematischen Modellen, auf Basis von Zellenmodell und axialem Dispersionsmodell, verglichen werden.
  • Diploma thesis
    TU Dresden, 2016
    Mentor: Ragna Kipping
    83 Seiten

Publ.-Id: 24720 - Permalink


Application of wire-mesh sensor for the study of chemical species conversion in a bubble column during chemical absorption of carbon dioxide in sodium hydroxide
Kipping, R.; Kryk, H.; Schleicher, E.; Gustke, M.; Hampel, U.;
In this paper we report for the first time on the utilization of the wire-mesh sensor for the measurement of chemical species conversion during the chemical absorption of carbon dioxide in sodium hydroxide solution. The wire mesh-sensor obtains cross-sectional images of the liquid phase conductivity which changes with the conversion of hydroxides during the reaction. A theoretical model has been applied to verify the use of conductivity as indicator for the reaction progress. Demonstration experiments have been carried out in a lab-scale bubble column reactor using two wire-mesh sensors in different reactor heights. Results obtained from reactor model and experimental data show a very good agreement. The results demonstrate the potential of this imaging instrument to follow the course of a chemical reaction via ionic species concentration even in a dense bubbly flow. This way, a better understanding of the coupling of hydrodynamics, mass transfer and reaction in bubble columns and other reaction devices can be gained.
Keywords: chemical absorption, reactive two-phase flow, species concentration measurement, wire-mesh sensor

Publ.-Id: 24719 - Permalink


Simulation of Condensation in a slightly inclined tube at COSMEA facility with ATHLET code
Zhang, Y.; Hampel, U.ORC; Geißler, T.; Leyer, S.
Safety is an essential topic in the development process of nuclear power plant. Several Generation III reactor designs contain passive safety system to control accident without the need for external power supply. An example for such passive systems is the Emergency Condenser (EC) of the KERENA reactor design. The system removes heat from the Reactor Pressure Vessel in the case of design basis accidents. The experimental facility COSMEA at Helmhotz Zentrum Dresden Rossendorf (HZDR) was set up to investigate the flow morphology and heat transfer structure of condensation processes. The test rig consists of a 3 m long condenser pipe whichpipe that is 0.76° inclined with inner diameter 43.3 mm. On the shell side active cooling is performed using the TOPFLOW facility infrastructure. According to the Emergency Condenser Reference design, the experiments of COSMEA are conducted in different pressure levels (5, 15, 25, 45 and 65 bar) with steam mass flow rates up to 1 kg/s. An inlet mixing system was developed to operate the experiment in a stepwise method due to the scale of the test rig. Condensation rates, pressure, temperature and flow rate for different steam fraction are measured. In addition, an x-ray tomography is installed to study the details of the resulting stratified flow structures. Extra heat flux probes are assembled to detect the azimuthal distribution of the heat flux. In this work, COSMEA was simulated with the thermal hydraulic system codes ATHLET. The performance of the ATHLET heat transfer models wereas identified. Primarily, the steady-state model was developed and the simulation results were compared to the experiment. The thermal coupling which considers the heat exchange between outside and inside of the pipe during the condensation was analyzed. Posteriorly the case of modeling transient condensation process was simulated. The influence on thermal coupling parameters, particularly heat transfer coefficient due to pressure drop inside the pipe was predicted and the feasibility and limitation of the system codes were evaluated.
Keywords: COSMEA, TOPFLOW, condensation, high pressure, ATHLET
  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-8.9.17, Xi'an, Shaanxi, China
    Proceedings of NURETH-17

Publ.-Id: 24718 - Permalink


Suppressed Fat Appetite after Roux-en-Y Gastric Bypass Surgery Associates with Reduced Brain µ-opioid Receptor Availability in Diet-Induced Obese Male Rats
Hankir, M.; Patt, M.; Patt, J.; Becker, G.; Rullmann, M.; Kranz, M.; Deuther-Conrad, W.; Schichke, K.; Seyfried, F.; Brust, P.; Hesse, S.; Sabri, O.; Krügel, U.; Fenske, W.;
Brain µ-opioid receptors (MORs) stimulate high-fat (HF) feeding and have been implicated in the distinct long term outcomes on body weight of bariatric surgery and dieting. Whether alterations in fat appetite specifically following these disparate weight loss interventions relate to changes in brain MOR signaling is unknown. To address this issue, diet-induced obese male rats underwent either Roux-en-Y gastric bypass (RYGB) or sham surgeries. Postoperatively, animals were placed on a two-choice diet consisting of low-fat (LF) and HF food and sham-operated rats were further split into ad libitum fed (Sham-LF/HF) and body weight-matched (Sham-BWM) to RYGB groups.
An additional set of sham-operated rats always only on a LF diet (Sham-LF) served as lean controls, making four experimental groups in total. Corresponding to a stage of weight loss maintenance for RYGB rats, two-bottle fat preference tests in conjunction with small-animal positron emission tomography (PET) imaging studies with the selective MOR radioligand [11 C]carfentanil were performed. Brains were subsequently collected and MOR protein levels in the hypothalamus, striatum, prefrontal cortex and orbitofrontal cortex were analyzed by Western Blot. We found that only the RYGB group presented with intervention-specific changes: having markedly suppressed intake and preference for high concentration fat emulsions, a widespread reduction in [11 C]carfentanil binding potential (reflecting MOR availability) in various brain regions, and a downregulation of striatal and prefrontal MOR protein levels compared to the remaining groups. These findings suggest that the suppressed fat appetite caused by RYGB surgery is due to reduced brain MOR signaling, which may contribute to sustained weight loss unlike the case for dieting.
Keywords: bariatric surgery, caloric-restriction, fat appetite, Brain µ-opioid receptors, positron emission Q13, tomography imaging

Publ.-Id: 24717 - Permalink


Structures of Plutonium(IV) and Uranium(VI) with N,N‑Dialkyl Amides from Crystallography, X‑ray Absorption Spectra, and Theoretical Calculations
Acher, E.; Cherkaski, Y. H.; Dumas, T.; Tamin, C.; Guillaumont, D.; Boubals, N.; Javierre, G.; Hennig, C.; Solari, P. L.; Charbonnel, M.-C.;
The structures of plutonium(IV) and uranium(VI) ions with a series of N,N-dialkyl amides ligands with linear and branched alkyl chains were elucidated from single-crystal X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and theoretical calculations. In the field of nuclear fuel reprocessing, N,N-dialkyl amides are alternative organic ligands to achieve the separation of uranium(VI) and plutonium(IV) from highly concentrated nitric acid solution. EXAFS analysis combined with XRD shows that the coordination structure of U(VI) is identical in the solution and in the solid state and is independent of the alkyl chain: two amide ligands and four bidentate nitrate ions coordinate the uranyl ion. With linear alkyl chain amides, Pu(IV) also adopt identical structures in the solid state and in solution with two amides and four bidentate nitrate ions. With branched alkyl chain amides, the coordination structure of Pu(IV) was more difficult to establish unambiguously from EXAFS. Density functional theory (DFT) calculations were consequently performed on a series of structures with different coordination modes. Structural parameters and Debye−Waller factors derived from the DFT calculations were used to compute EXAFS spectra without using fitting parameters. By using this methodology, it was possible to show that the branched alkyl chain amides form partly outer-sphere complexes with protonated ligands hydrogen bonded to nitrate ions.
Keywords: Pu(IV), U(VI), XRD, EXAFS, DFT

Publ.-Id: 24716 - Permalink


3D potential field modelling and 3D prints of complex geological structures
Götze, H.-J.; Schmidt, S.; Menzel, P.;
The new techniques used here are user-friendly because they are highly interactive, ideally real-time and topology conserving and can be used for both flat and spherical models in 3D. These are important requirements for joint inversion not only for gravity and magnetic modelling of fields and derivatives, constrained by seismic and structural input from independent data sources, but also essential toward a true integration of Full Waveform Inversion. A borehole tool for magnetic and gravity modelling will also be introduced. We are close to the demand of treating several geophysical methods in a single model for the subsurface and aim for fulfilling most of the constraints: measurements and geological plausibility.
For 3D modelling, polyhedrons built by triangles are used. All elements of the gravity and magnetic tensors can be included. In the modelling interface, after geometry changes the effect of the model can quickly be updated because only the changed triangles have to be recalculated. Because of the triangular model structure our approach can handle complex structures very well (e.g. overhangs of salt domes). For regional models the use of spherical geometries and calculations can be necessary and is provided. 3D visualization is performed with a 3D-printer (Ultimaker 2) and provides new insights in even rather complicate Earth subsurface structures.
Inversion can either be run over the whole model, but typically it is used in smaller parts of the model, helping to solve local problems and/or proving/disproving local hypotheses. Instead of optimizing the position of model vertices, interactive inversion uses a different parameterization of the model. The inner points of a lattice are used to define a distortion of space. The user can monitor model updates live on screen and stop the process at any time. The base principles behind this interactive approach are highly performance optimized algorithms (CMA-ES: Covariance-matrix-adoption-evolution-strategy). The efficiency of the algorithm is very good in terms of stable convergence due to topological model validity.
Potential field modelling is always influenced by the area outside the core area of investigation, causing edge effects. To avoid these effects a simple but very robust method has been developed: Derive a density/susceptibility-depth function by taking the mean value of the borders of depth slices through the model. The focus of the poster presentation is set on practical examples from the international KTB – Project, Germany´s deep continental borehole.
Keywords: geophysics, interactive 3D potential field modeling, 3D visualization
  • Poster
    77. Jahrestagung der Deutschen Geophysikalischen Gesellschaft e.V., Potsdam, 27.-30.03.2017, Potsdam, Deutschland
  • Lecture (Conference)
    DGMK/ÖEGW Frühjahrstagung 2017, 05.-06.04.2017, Celle, Deutschland

Publ.-Id: 24715 - Permalink


Local Lorentz force flowmeter at a continuous caster model using a new generation multicomponent force and torque sensor
Hernandez, D.; Schleichert, J.; Karcher, C.; Fröhlich, T.; Wondrak, T.; Timmel, K.;
Lorentz force velocimetry is a non-invasive velocity measurement technique for electrical conductive liquids like molten steel. In this technique, the metal flow interacts with a static magnetic field generating eddy currents which, in turn, produce flow-braking Lorentz forces within the fluid. These forces are proportional to the electrical conductivity and to the velocity of the melt. Due to Newton’s third law, a counter force of the same magnitude acts on the source of the applied static magnetic field which is in our case a permanent magnet. In this paper we will present a new multicomponent sensor for the local Lorentz force flowmeter (L2F2) which is able to measure simultaneously all three components of the force as well as all three components of the torque. Therefore, this new sensor is capable of accessing all three velocity components at the same time in the region near the wall. In order to demonstrate the potential of this new sensor, it is used to identify the 3-dimensional velocity field near the wide face of the mold of a continuous caster model available at the Helmholtz-Zentrum Dresden-Rossendorf. As model melt, the eutectic alloy GaInSn is used.
Keywords: liquid metals, magnetohydrodynamics, Lorentz force, flow measurement

Publ.-Id: 24714 - Permalink


Sustainable high magnetic field Research in Europe - EMFL AISBL
Wosnitza, J.;
es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    Workshop on the sustainability of Laserlab-Europe, 11.10.2016, Amsterdam, The Netherlands

Publ.-Id: 24713 - Permalink


The FFLO state in quasi-two-dimensional organic superconductors
Wosnitza, J.;
es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    14th Bilateral Japanese-German Symposium "Effects of Parity Mixing in Correlated Electron Systems", 26.-29.09.2016, Sapporo, Japan

Publ.-Id: 24712 - Permalink


Magnetic quantum oscillations - From simple metals to Weyl semimetals
Wosnitza, J.;
es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    Summer School of SFB 1143, 19.-20.09.2016, Kloster Nimbschen, Deutschland

Publ.-Id: 24711 - Permalink


The ternary sorption system U(VI)/ phosphate/SiO2: a consistent surface speciation derived from a multimethodological approach
Foerstendorf, H.ORC; Comarmond, M. J.; Heim, K.; Steudtner, R.; Stockmann, M.; Payne, T. E.
The surface speciation of the ternary system containing aqueous U(VI), phosphate and the model mineral phase SiO2 was comprehensively investigated at a low micromolar concentration level by batch experiments, in situ Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR), luminescence spectroscopy, and Surface Complexation Modeling (SCM). In the absence of phosphate, two predominant U(VI) surface species were independently identified by luminescence and in situ IR spectroscopy. The concordance of the two species is corroborated by the shifts of the signals which were found to be of same extent in terms of energy units in the spectra of both spectroscopic techniques.
In the presence of phosphate, batch sorption studies indicate an increase in U(VI) uptake, consistent with previously reported studies. In situ IR spectroscopic sorption experiments strongly suggest the formation of a solid U(VI) phosphate phase as a surface precipitate on the silica phase, evidenced by characteristic bands observed in spectra after prolonged sorption and following sequential sorption of U(VI) then phosphate. Again, the results obtained from luminescence spectroscopy support these findings.
SCM provides excellent fitting results only when exclusively considering two binary uranyl surface species and formation of a solid uranyl phosphate phase as suggested from spectroscopic results. The results of this study indicate that the sorption of U(VI) on SiO2 in the presence of inorganic phosphate initially involves binary surface-sorption species and then evolves towards surface precipitation.
  • Lecture (Conference)
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Publ.-Id: 24710 - Permalink


Atomic force microscopy – A variable tool to characterize processes in the field of particle technology
Fritzsche, J.ORC; Peuker, U. A.ORC; Babel, B.; Rudolph, M.ORC
The paper aims at giving an overview on strategies and methods applying atomic force microscopy (AFM) in various particle based processes. AFM has a wide range of applications in the field of particle technology. The typical application of the AFM is the characterization of the surface topography in the submicron range. Using the AFM in combination with the colloidal probe technique allows furthermore the direct measurement of forces acting on a particle down to atomic interactions. This enables the study of several fundamental effects on these forces.
When a liquid cell is used, the direct measurement of forces between particles surrounded by a liquid can be studied. This allows the investigation of electrostatic as well as hydrophobic and hydrophilic interactions which superimpose the van der Waals forces in liquid media. It is also possible to determine the forces acting on particles at fluid interfaces (liquid/liquid or liquid/gas) which is quite important for research e.g. in flotation or particle extraction applications.
Especially in hydrophobic systems capillary bridges due to nano-bubbles (generally gas layers) on the surfaces can occur. This bridging can be seen as an additional strong adhesive interaction mechanism leading to forces which can be orders of magnitude higher than for pure van der Waals or classic hydrophobic interactions.
The detection of nano-bubbles is possible using a combination of topography and phasecontrast scans in non-contact mode. This allows the distinction between gas and solid phases during the surface scanning. On smooth surfaces, phase contrast AFM also allows a distinction between two different solid phases, e.g. in a nano-composite material. Furthermore the combination of AFM with Raman spectroscopy superimposes the measurements of mechanical forces, topographies and detailed chemical spectral characterization. With this method local surface modification can be identified. A proper choice of tip material of the AFM (noble metal nanostructures) can even lead to the so called tip enhanced Raman spectroscopy (TERS) enabling detection of vibrational signals from a small number of molecules on a solid surface, e.g. collector molecules on mineral surfaces for flotation applications.
  • Lecture (Conference)
    Partec 2016 - International Congress on Particle Technology, 19.-21.04.2016, Nürnberg, Deutschland

Publ.-Id: 24709 - Permalink


Surface Energy Heterogeneities and Hydrophobic Interactions - New Insights to understand Flotation
Rudolph, M.ORC
Flotation is a heterocoagulation separation process first described in 1877 by a patent issued in Dresden, Germany. Since then it has become to be the most important and most variable separation process in the beneficiation of minerals. Especially the modern fine grained and polymetallic deposits call for a continuation in process development and even more so in better understanding the flotation process which is based on the selective hydrophobization/hydrophilization of minerals. This paper will present novel insights on the hydrophobization of various mineral particles, i.e. silicates, semi-soluble salt type minerals, metal oxides and sulfides with different collector molecules, which are the surfactants used to selectively hydrophobize minerals in flotation. We investigate the effect of the collectors on the surface energy distribution which is determined with inverse gas chromatography. With this method it is possible to assess the wettability of particles without the difficulties encountered with the conventional sessile drop and penetration methods. By applying inverse gas chromatography we can show that it is due to the collector adsorption the reduction of the highly energetic moieties which only make up less than ten percent of the particle surface. Furthermore we can present the effect of collector adsorption on the different surface energy components, i.e. disperse and specific interactions. By calculating the free energy of interaction between a particle and a bubble immersed in water using the complex surface energy information we can find a good correlation to the flotation response, i.e. recovery determined with classic microflotation experiments in the Hallimond tube. Further insight into the surface heterogeneity regarding the wettability is presented with respect to investigations on planarized mineral samples using the colloidal probe technique in atomic force microscopy in the liquid environment. By assessing force distance spectra on various surface sites with and without the adsorption of collectors we find the well described but so far not well understood long range attractive hydrophobic interactions. Based on the results presented we will critically discuss the different concepts of long range hydrophobic interactions in the context of a fundamental model which describes the floatability of minerals. The minerals used are: quartz, apatite, magnetite and pyrite. The collectors assessed are cationic and different anionic surfactants.
  • Lecture (Conference)
    Partec 2016 - International Congress on Particle Technology, 19.-21.04.2016, Nürnberg, Deutschland

Publ.-Id: 24708 - Permalink


Floatability of synthetic light and heavy rare earth element carbonates and selectivity towards calcite
Rudolph, M.ORC; Kratzsch, R.
The fourteen lanthanoid elements, also commonly referred to as rare earth elements (REE) or rare earth metals (REM) and often including lanthanum as well as both Yttrium and Scandium, can be referred to as the vitamins of the periodic systems table. They are used for green and high tech applications such as powerful magnets, batteries, glasses and triband dyes. Commonly they can be found and mined as carbonate minerals, e.g. bastnäsite, synchisite and ankylite or as phosphate minerals, e.g. monazite and xenotim. Usually they all occur as mixed REM carbonates with different proportions of light and heavy rare earth elements. The light rare earth elements LREE (lanthanum through samarium) are less scarce and thus economically becoming less critical (EU list of critical elements from 2014). The heavy rare earths HREE (europium through lutetium plus yttrium) are indeed rare, scarce and thus considered critical elements. The ratio of LREE and HREE depends very much on the deposits. When beneficiating rare earth carbonate minerals flotation is often an important unit process operation especially to reduce content of silicates, calcite and barite. As flotation reagents in principle simple carboxylic acid type collectors are used in combination with silicate and calcite depressants. It has been reported (Nature (2013), 12, 315) that the surface wettability of REE oxides very much is influenced by high ionic radius of the REE cations. The ionic radius is indeed one of the distinguishable properties of the REE amongst one another. Therefore the question is how different synthetic unmixed individual LREE and HREE carbonates behave in terms of floatability.
Results are presented for the REE carbonates of yttrium, lanthanum, cer, neodymium, dysprosium and ytterbium with sodium oleate at different pH values. Lignin sulfonate is investigated as the selective depressant for calcite and barium carbonate and not the REE carbonates.
Keywords: Light Rare Earth Elements, Heavy Rare Earth Elements, Microflotation, Lignin Sulfonate
  • Poster
    IMPC 2016 - XXVIII International Mineral Processing Congress, 11.-15.09.2016, Quebec, Canada

Publ.-Id: 24707 - Permalink


Surface Energy Heterogeneities - New Insights to the Microprocesses of Flotation Separation of Minerals
Rudolph, M.ORC; Hartmann, R.
Especially the modern fine grained and polymetallic deposits call for a continuation in process development and even more so in better understanding the flotation process which is based on the selective hydrophobization/hydrophilization of minerals. This poster will present novel insights on the hydrophobization of various mineral particles, i.e. silicates, semi-soluble salt type minerals and metal oxides with different collector molecules. We investigate the effect of the collectors on the surface energy distribution which is determined with inverse gas chromatography. With this method it is possible to assess the wettability of particles without the difficulties encountered with the conventional sessile drop and penetration methods. By applying inverse gas chromatography we can show that it is due to the collector adsorption the reduction of the highly energetic moieties which only make up less than 10 percent of the particle surface. Furthermore we can present the effect of collector adsorption on the different surface energy components, i.e. disperse and specific interactions. By calculating the free energy of interaction between a particle and a bubble immersed in water using the complex surface energy information we can find a good correlation to the flotation response, i.e. recovery determined with classic microflotation experiments in the Hallimond tube. The minerals used are: quartz, apatite and magnetite. The collectors assessed are cationic and different anionic surfactants at various pH and collector concentration.
Keywords: Surface Free Energy, Wettability, Heterogeneity, Flotation, Particle Bubble Interactions
  • Poster
    IMPC 2016 - XXVIII International Mineral Processing Congress, 11.-15.09.2016, Quebec, Canada

Publ.-Id: 24706 - Permalink


Investigation on the fine particle flotation of a carbonate-rich apatite ore from Vietnam
Hoang, D. H.; Rudolph, M.ORC; Schubert, H.
The phosphate beneficiation process is facing a lot of challenges, especially in case of flotation of an apatite ore which is rich in carbonate and sedimentary finely disseminated phosphate minerals. The effect of mineral fineness combined with the presence of carbonate minerals which have mineralogical similarities with phosphate minerals is the reason for reduced selectivity of separation and low recoveries in froth flotation. The fine intergrowths in complex phosphate ores require very fine grinding for liberation in flotation. However, high fineness strongly effects the bubble-particle collisions and the attachment processes, a negative effect on the rheological properties of the slurry, a decrease of the flotation kinetics, and an increase of the entrainment of fine gangue particles.In order to find out the suitable flotation process for the separation of carbonates from the finely disseminated sedimentary phosphate ores, two process complexes are distinguished: the reagent regime and the hydrodynamics of the three-phase system. Especially the turbulent conditions are key to get high collision and attachment between particles and bubbles. The hydrodynamics of the three-phase system relate directly to many sub-processes of the flotation, such as air dispersion, mixing of the slurry and particle-bubble collision and attachment in the high-turbulent rotor stream. In flotation research and practice the control of the hydrodynamics has been a neglected field for a long time, above all for the flotation of fine and finest particles.
In this study, the effects of some important hydrodynamics parameters such as solid content, impeller speed, and air flow rate on the flotation performance were investigated and evlauated.
The flotation rate constant is measured experimentally and compared to the flotation rate kinetic models. Bubble size and energy distribution rate are measured for calculation based on the flotation kinetic model to understand the influence of these factors on flotation behaviour.
  • Lecture (Conference)
    Tagung 2016 "Aufbereitung und Recycling", 09.-10.11.2016, Freiberg, Deutschland

Publ.-Id: 24705 - Permalink


Untersuchung von dynamischen Schaumeigenschaften der Flotation – Stabilität, Struktur und Wassergehalt
Rudolph, M.ORC; Klöpfel, K.; Michaux, B.
Die Eigenschaften der Schaumphase in der Schaumflotation sind entscheidend für den Erfolg der Trennung und Anreicherung von Partikeln im Gesamtprozess der Flotation. Einige Autoren betrachten gar die Schaumphase als eigene Trennzone. Neben der Schaumhöhe und der mittleren Verweilzeit von Blasen spielen die Blasengrößenverteilung und der Wassergehalt, beide als Funktion der Höhe, eine wichtige Rolle. In der Masterarbeit von Frau Karin Klöpfel wurden Schaumeigenschaften von flotationsrelevanten Systemen das erste Mal mit dem dynamischen Schaumanalysator DFA 100 der Firma Krüss untersucht. Es wurden drei unterschiedliche Messprinzipien kombiniert, nämlich die zeitabhängige Auswertung der Schaumhöhe (Lokalität der Grenzflächen Trübe-Schaum und Schaum-Luft) sowie die zeit- und höhenabhängigen Bestimmungen von Blasengrößenverteilungen und Wassergehalten. Im Rahmen der Studie wurde die Komplexität des Systems sukzessive erhöht. Zu Beginn werden unterschiedliche Schäumermoleküle ohne Partikel verglichen. Es folgt eine Diskussion von spezifischen Ioneneffekten auf die Schäumerwirkung. Nachfolgend werden den Schäumersystemen entweder hydrophile oder hydrophobe sphärische Glaspartikel zugefügt. Zum Abschluss der Untersuchungen wird eine akademische binäre Mischung von Mineralen unterschiedlicher selektiver Hydrophobierung und Größenklassen betrachtet.
  • Poster
    Tagung 2016 "Aufbereitung und Recycling", 09.-10.11.2016, Freiberg, Deutschland

Publ.-Id: 24704 - Permalink


Zusammenfassung der Beiträge eines Sonderheftes im International Journal of Mineral Processing zum 90. Geburtstag von Prof. Heinrich Schubert
Rudolph, M.ORC; Peuker, U. A.ORC
Zu Beginn des Jahres feierte Prof. Heinrich Schubert seinen 90. Geburtstag. Ihm zu Ehren wurde in der renommierten Fachzeitschrift International Journal of Mineral Processing ein Sonderheft zusammengestellt mit Beiträgen aus aller Welt und mit Bezug zu Prof. Schuberts Wirken. Ein besonderes Augenmerk liegt auf neuesten Beiträgen im Bereich der turbulenten hydrodynamischen Betrachtung des Flotationsprozesses, einer Entwicklung in der Forschung, die von Prof. Schuberts Beiträgen inspiriert wurden und immer mehr Beachtung finden. Der Vortrag fasst die Beiträge zusammen und gibt somit einen Überblick über das nachhaltige Wirken von innovativen Ideen und Ansätzen der „Freiberger Schule“ um Prof. Schubert.

Sonderheft:
International Journal of Mineral Processing, Heft 156, 2016
ISSN 0301-7516
  • Invited lecture (Conferences)
    Tagung 2016 "Aufbereitung und Recycling", 09.-10.11.2016, Freiberg, Deutschland

Publ.-Id: 24703 - Permalink


Design and performance of an ionisation chamber for the measurement of low alpha-activities
Hartmann, A.; Hutsch, J.; Krüger, F.; Sobiella, M.; Wilsenach, H.; Zuber, K.;
A new ionisation chamber for alpha-spectroscopy has been built from radio-pure materials for the purpose of investigating long lived alpha-decays. The measurement makes use of pulse shape analysis to discriminate between signal and background events. The design and performance of the chamber is described in this paper. A background rate of View the MathML source(10.9±0.6)countsperday in the energy region of 1–9 MeV was achieved with a run period of 30.8 days. The background is dominantly produced by radon daughters.
Keywords: Frisch grid; Ionisation chamber; Alpha-decay

Publ.-Id: 24702 - Permalink


Highly Mismatched GaAs1-xNx and Ge1-xSnx Alloys Prepared by Ion Implantation and Ultrashort Annealing
Zhou, S.ORC
Doping allows us to modify semiconductor materials for desired properties such as conductivity, bandgap, and/or lattice parameter. A small portion replacement of the highly mismatched isoelectronic dopants with the host atoms of a semiconductor can result in drastic variation of its structural, optical, and/or electronic properties. Here, the term 'mismatch' describes the properties of atom size, ionicity, and/or electronegativity. In this talk, we present the fabrication of two kinds of highly mismatched semiconductor alloys, i.e., Ge1-xSnx [1] and GaAs1-xNx [2]. The results suggest an efficient above-solubility doping induced by non-equilibrium methods of ion implantation and ultrashort annealing. Pulsed laser melting promotes the regrowth of monocrystalline Ge1-xSnx, whereas flash lamp annealing brings about the formation of high quality GaAs1-xNx with room temperature photoluminescence. The bandgap modification of Ge1-xSnx and GaAs1-xNx has been verified by optical measurements of spectroscopic ellipsometry and photoluminescence, respectively. In addition, effective defect engineering in GaAs has been achieved by flash lamp annealing, by which a quasi-temperature-stable photoluminescence at 1.3 um has been obtained [3, 4]. [1] K. Gao, et al., APL 105, 042107 (2014); [2] K. Gao, et al., APL 105, 012107 (2014); [3] K. Gao, et al., JAP 114, 093511 (2013); [4] S. Prucnal, et al., Opt. Express, 20, 26075 (2012).
  • Lecture (Conference)
    DPG-Frühjahrstagung 2016, 06.-11.03.2016, Regensburg, Germany

Publ.-Id: 24701 - Permalink


Following our DREAMS (DREsden Accelerator Mass Spectrometry)
Merchel, S.; DREAMS-Team; DREAMS-Users; DREAMS-Friends;
Since 2011 the DREAMS (DREsden Accelerator Mass Spectrometry) facility [1] produces data of several long-lived radionuclides (Tab. 1).

Table 1: Radionuclides measured at DREAMS. Updated from [1]. 44Ti and actinides are under development.
Nuclide(s) t1/2 [Ma] AMS material Blank level [10-16] Sample ratios [10-12]
10Be (/9Be) 1.387 BeO 5 0.01-300
26Al (/27Al) 0.705 Al2O3 6 0.001-60
36Cl (/35Cl) 0.301 AgCl 4 0.007-700
41Ca (/40Ca) 0.104 CaF2 20 0.006-9000
129I (/127I) 15.7 AgI 200 0.5-200

AMS reduces background and interfering signals resulting from molecular ions and isobars enormously. Thus, AMS provides much lower detection limits compared to conventional MS or decay counting. DREAMS offers excellent measurement capabilities also for external users (see www.hzdr.de/ibc for beam time application).
Long-lived radionuclides have thousands of exciting applications, especially within environmental and geosciences. In nature, the so-called cosmogenic nuclides (CNs) are products of nuclear reactions induced by primary and secondary cosmic rays. Hence, they can be found in extraterrestrial material such as meteorites - originating from the asteroid belt, the Moon or Mars - and lunar samples in higher concentrations (e.g. ~1010 10Be atoms/g or < 0.5 mBq/g). A combination of several CNs is used to reconstruct the exposure history of this unique material while in space (irradiation age) and on Earth (terrestrial age).
Though, in terrestrial material the concentrations are typically only on the order of 104-109 atoms/g (i.e. μBq/g - nBq/g) for 10Be produced in the Earth’s atmosphere, then transported to the surface and further absorbed and incorporated at and in e.g. sediments or ice. Some of the lowest 10Be concentrations (~103 atoms/g), produced in-situ by neutron- and muon-induced nuclear reactions from e.g. oxygen and silicon in quartz, can be found in samples taken from the Earth’s surface. The concentrations of atmospheric or in-situ produced CNs record information that is used to reconstruct sudden geomorphological events such as volcanic eruptions, rock avalanches, tsunamis, meteor impacts, earthquakes [e.g. 2] and glacier movements. These movements and data from ice cores give also hints for the reconstruction of historic climate changes and provide information for the validation of climate model predicting future changes. Slower processes such as sedimentation, river incision and erosion rates can also be investigated and indirect dating of bones as old as several Ma’s is possible. Finally, remnants of supernova-produced nuclides can also be found in deep-sea archives (sediment, crust, nodule) [e.g. 3].
Anthropogenic production e.g. by release from nuclear reprocessing, accidents and weapon tests led to increased radionuclide levels in surface water, ice and soil (36Cl, 129I,…). Hence, some nuclides can be used as tracers to follow pathways in oceanography, to date and identify sources of groundwater, to perform retrospective dosimetry and to study aspects in radioecology and pharmacology. Obviously, also nuclear installation materials are radioactive (41Ca,…).

Radiochemistry

Typical measurement times are on the order of one hour per sample. However, radiochemical separation of the nuclides of interest is absolutely essential and may take from several days for simple matrices (ice, water) to several weeks for more complicated ones (rock, sediments,…).
DREAMS offers external users to perform this sample preparation of AMS targets in two dedicated chemistry labs at Dresden since 2009. Up to several hundreds of samples from interdisciplinary research topics such as astronomy, climate, cosmochemistry and geology could be transformed into AMS material (Tab. 1) showing reasonable to excellent performance. Besides our constant approach to become a little better every day, sometimes very new challenges can arise due to the low availability of the sample material, low radionuclide concentration or a possible contamination of the sample with disturbing elements and nuclides.

Two examples of challenges

Ice samples are always in our focus. As we were facing problems with 10Be contamination in "dirty" ground ice, instead, we measured 36Cl and natCl by isotope dilution in permafrost ice wedge samples as heavy as 1.6 kg. The chemical yield of AgCl was only 20-35% (and is a function of total natCl), which might be improved by preceding preconcentration steps.
The determination of in-situ or atmospherically produced 26Al in marine and terrestrial sediments suffered sometimes from very low chemical yields. This seems to be mainly caused by redissolving Al(OH)3 in the very last washings. We hope to overcome the problem by longer waiting times, i.e. increased altering of the hydroxides making them less-soluble.

Acknowledgments: Thanks to J. Feige, A. Gärtner, S. Gurlit, P. Ludwig, D. Rodrigues, T. Opel, T. Smith and several students for providing/processing samples and/or ICP-MS.

[1] G. Rugel et al., Nucl. Instr. Meth. Phys. Res. B. 2016, 370, 94-100.
[2] W. Schwanghart et al., Science 2016, 351, 147-150.
[3] A. Wallner et al., Nature 2016, 532, 69-72.
Keywords: accelerator mass spectrometry, radionuclide, radiochemistry
  • Poster
    26. Seminar Aktivierungsanalyse und Gammaspektroskopie (SAAGAS 26), 20.-22.02.2017, Wien, Österreich

Publ.-Id: 24700 - Permalink


Application of Ion Beams to Fabricate and Tune Properties of Dilute Ferromagnetic Semiconductors
Zhou, S.ORC
Combining semiconducting and ferromagnetic properties, dilute ferromagnetic semiconductors (DFS) have been under intensive investigation for more than two decades. Mn doped III-V compound semiconductors have been regarded as the prototype of the type. In this contribution, we will show how the implantation technique, a standard method for doping Si in microelectronic industry, can be utilized in fabricating and deeper understanding of DFS. First, ion implantation followed by pulsed laser melting (II-PLM) provides an alternative to the widely used low-temperature molecular beam epitaxy (LTMBE) approach in the preparation of diverse DFS. The prepared DFS materials exhibit pronounced magnetic anisotropy, large X-ray magnetic circular dichroism as well as anomalous Hall effect and magnetoresistance [1-9]. Going beyond LT-MBE, II-PLM is successful to bring two new members, GaMnP and InMnP, into the family of III-Mn-V. Both GaMnP and InMnP films show clear signatures of ferromagnetic coupling and an insulating behavior. Second, helium ions can be used to precisely compensate the holes while keeping the Mn concentration constant [10-12]. We monitor the change of Curie temperature (TC) and conductivity. For a broad range of samples including (Ga,Mn)As and (Ga,Mn)(As,P) with various Mn and P concentrations, we observe a smooth decrease of TC over a wide temperature range with carrier compensation while the conduction is changed from metallic to insulating. In the low compensation regime, we can tune the uniaxial magnetic easy axis of (Ga,Mn)(As,P) from out-of-plane to in-plane with an isotropic-like intermediate state. These materials synthesized or tailored by ion beams provide an alternative avenue to understand how carrier-mediated ferromagnetism is influenced by localization.

[1] M. Scarpula, et al., Phys. Rev. Lett. 95, 207204 (2005).
[2] D. Bürger, S. Zhou, et al., Phys. Rev. B 81, 115202 (2010).
[3] S. Zhou, et al., Appl. Phys. Express 5, 093007 (2012).
[4] M. Khalid, …, S. Zhou, Phys. Rev. B 89, 121301(R) (2014).
[5] Y. Yuan, … S. Zhou, IEEE Trans. Magn. 50, 2401304 (2014).
[6] M. Khalid, …, S. Zhou, J. Appl. Phys. 117, 043906 (2015).
[7] Y. Yuan, …, S. Zhou, J. Phys. D: Appl. Phys. 48, 235002 (2015).
[8] S. Zhou, J. Phys. D: Appl. Phys. 48, 263001 (2015).
[9] Y. Yuan, …, S. Zhou, ACS Appl. Mater. Interfaces, 8, 3912 (2016).
[10] L. Li, S. Yao, S. Zhou, et al., J. Phys. D: Appl. Phys. 44 099501 (2011).
[11] L. Li, …, Shengqiang Zhou, Nucl. Instr. Meth. B 269, 2469-2473 (2011).
[12] S. Zhou, et al., Phys. Rev. B 95, 075205 (2016).
  • Lecture (Conference)
    45th International School & Conference on the Physics of Semiconductors, 19.-24.06.2016, Szczyrk, Poland
  • Invited lecture (Conferences)
    24th Conference on Application of Accelerators in Research and Industry, 30.10.-04.11.2016, Fort Worth, USA
  • Lecture (Conference)
    DPG-Frühjahrstagung 2016, 06.-11.03.2016, Regensburg, Germany
  • Poster
    MML2016 Workshop at DESY, 14.-16.12.2016, Hamburg, Germany
  • Invited lecture (Conferences)
    Invited lecture at Shanghai University, 07.07.2016, Shanghai, China

Publ.-Id: 24699 - Permalink


Precisely doping semiconductors by ion implantation
Zhou, S.ORC
Precisely doping semiconductors by ion implantation, an invited lecture at University of Warsaw
  • Lecture (others)
    Invited seminar at University of Warsaw, 22.09.2016, Warsaw, Poland

Publ.-Id: 24698 - Permalink


Ion implantation + sub-second annealing: a route towards hyperdoped semiconductors
Zhou, S.ORC
Doping allows us to modify semiconductor materials for desired electrical, optical and magnetic properties. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Hyperdoping refers to doping a semiconductor much beyond the corresponding solid solubility limit and often results in exotic properties. For example, Ga hyperdoped Ge reveals superconductivity and Mn hyperdoped GaAs represents a typical ferromagnetic semiconductor. Ion implantation followed by annealing is a well-established method to dope Si and Ge. This approach has been maturely integrated with the IC industry production line. However, being applied to hyperdoping, the annealing duration has to be shortened to millisecond or even nanosecond. The intrinsic physical parameters related to dopants and semiconductors (e.g. Solubility, diffusivity, melting point and thermal conductivity) have to be considered to choose the right annealing time regime. In this talk, we propose that ion implantation combined with flash lamp annealing in millisecond and pulsed laser melting in nanosecond can be a versatile approach to fabricate hyperdoped semiconductors. The examples include magnetic semiconductors [1-4], highly mismatched semiconductor alloys (Ge1-xSnx [5] and GaAs1-xNx [6]), n++ Ge [7] and chalcogen doped Si [8, 9].

[1] M. Khalid, et al., Phys. Rev. B, 89, 121301(R) (2014).
[2] S. Zhou, J. Phys. D: Appl. Phys,. 48, 263001 (2015).
[3] S. Prucnal, et al., Phys. Rev. B, 92, 222407 (2015).
[4] Y. Yuan, et al., ACS Appl. Mater. Interfaces, 8, 3912 (2016).
[5] K. Gao, et al., Appl. Phys. Lett., 105, 042107 (2014).
[6] K. Gao, et al., Appl. Phys. Lett.., 105, 012107 (2014) .
[7] S. Prucnal, et al., Sci. Reports, 6, 27643 (2016).
[8] S. Zhou, et al., Sci. Reports, 5, 8329 (2015).
[9] Y. Berencén, et al., ACS Photonics, submitted (2016).
  • Invited lecture (Conferences)
    The 26th annual meeting of MRS-J, 19.-22.12.2016, Yokohama, Japan
  • Invited lecture (Conferences)
    Invited lecture at Shanghai Institute of Microsystem And Information Technology, 05.07.2016, Shanghai, China
  • Invited lecture (Conferences)
    Invited lecture at University of Electronic Science and Technology of China, 18.07.2016, Chengdu, China

Publ.-Id: 24697 - Permalink


Defect induced magnetism in SiC
Zhou, S.ORC; Wang, Y.; Liu, Y.; Hübner, R.; Gemming, S.; Helm, M.
Defect induced magnetism, which can be controllably generated by ion or neutron irradiation, is attracting intensive research interest. It not only challenges the traditional opinions about magnetism, but also has some potential applications in spin-electronics. SiC is a new candidate for the investigation of defect-induced ferromagnetism after graphitic materials and oxides due to its high material purity and crystalline quality [1, 2]. In this contribution, we made a comprehensive investigation on the structural and magnetic properties of ion implanted and neutron irradiated SiC samples. In combination with X-ray absorption spectroscopy, high-resolution transmission electron microscopy and first-principles calculations, we try to understand the mechanism in a microscopic picture.
For neon or xenon ion implanted SiC, we identify a multi-magnetic-phase nature [3]. The magnetization of SiC can be decomposed into paramagnetic, superparamagnetic and ferromagnetic contributions. The ferromagnetic contribution persists well above room temperature and exhibits a pronounced magnetic anisotropy. By combining X-ray magnetic circular dichroism and first-principles calculations, we clarify that p-electrons of the nearest-neighbor carbon atoms around divacancies are mainly responsible for the long-range ferromagnetic coupling [4]. Thus, we provide a correlation between the collective magnetic phenomena and the specific electrons/orbitals.
With the aim to verify if a sample containing defects through its bulk volume can persist ferromagnetic coupling, we applied neutron irradiation to introduce defects into SiC [5]. Besides a weak ferromagnetic contribution, we observe a strong paramagnetism, scaling up with the neutron fluence. The ferromagnetic contribution only occurs in a narrow fluence window or after annealing. First-principles calculations hint towards a mutually exclusive role of the concentration of defects: Defects favor spin polarization at the expense of magnetic interaction. Although both Raman scattering and X-ray diffraction reveal essential structure damage to SiC due to irradiation, high-resolution transmission electron microscopy does not detect significant structural variation even upon the largest neutron fluence.

[1] L. Li, et al., Appl. Phys. Lett. 98, 222508 (2011).
[2] Y. Wang, et al., Phys. Rev. B 90, 214435 (2014).
[3] Y. Wang, et al., Phys. Rev. B 89, 014417 (2014).
[4] Y. Wang, et al., Scientific Reports, 5, 8999 (2015).
[5] Y. Wang, et al., Phys. Rev. B 92, 174409 (2015).
  • Lecture (Conference)
    Atomic structure of nanosystems from first-principles simulations and microscopy experiments, AS-SIMEX 2016, 31.05.-02.06.2016, Helsinki, Stockholm, Finland, Sweden

Publ.-Id: 24696 - Permalink


Stabilitätsuntersuchungen an biomimetischen Schichten
Matys, S.; Vogel, M.; Weinert, U.; Suhr, M.; Günther, T.; Pollmann, K.; Raff, J.;
Die Quarzmikrowaage als hochsensibler Massendetektor wird derzeit für eine zunehmende Anzahl unterschiedlicher Fragestellungen in verschiedenen wissenschaftlichen Bereichen eingesetzt und auf ihre Tauglichkeit getestet. Die Schichtbildung von Polyelektrolyten mittels Layer-by-Layer-Technik sowie die nachfolgende Abscheidung von S-layer-Proteinen und die Bildung von metallischen Nanopartikeln auf modifizierten Schwingquarzen wurde anhand von Frequenzänderung und Dissipation gemessen und die stattfindenden Wechselwirkungen auf der Quarzoberfläche diskutiert.
Keywords: biomimetische Schichten, Quarzmikrowaage, Frequenzänderung, Dissipation, S-Layer, Polyelektrolyte
  • Lecture (others)
    QCM Workshop, 07.07.2016, Darmstadt, Deutschland

Publ.-Id: 24695 - Permalink


Combined hyperspectral and lithogeochemical estimation of alteration intensities in a volcanogenic massive sulfide deposit hydrothermal systems: A Case study from northern Canada
Laakso, K.; Peter, J.; Rivard, B.; Gloaguen, R.;
The most intense hydrothermally altered rocks in volcanogenic massive sulfide (VMS) deposit systems occur in the stratigraphically underlying feeder zone. This alteration zone is typically much larger than the mineralization itself, and hence the ability to detect such alteration by optical remote sensing can be invaluable for mineral exploration. Our investigation focuses on assessing the applicability of hyperspectral data to determine trends in hydrothermal alteration intensity in and around the Izok Lake VMS deposit in northern Canada. To this end, we linked hydrothermal alteration intensity information based on two indices, the Ishikawa (AI) and chlorite-carbonate-pyrite (CCPI), to hyperspectral field and laboratory data in three dimensions. Our results suggest that chlorite group minerals display variable chemical composition across the study area that broadly correlates with hydrothermal alteration intensity.
Keywords: Hyperspectral, VMS, hydrothermal, alteration index, mineral exploration
  • Contribution to proceedings
    WHISPERS 2016 - 8th Workshop on Hyperspectral Image and Signal Processing : Evolution in Remote Sensing, 21.-24.08.2016, Los Angeles, USA

Publ.-Id: 24694 - Permalink


Distribution of REE minerals in Fluorite Flotation at the Vergenoeg Mine, South Africa
Minz, F. E.; Kern, M.; Birtel, S.; Höfig, T. W.; Krause, J.; Gutzmer, J.;
The ore of the Vergenoeg fluorite mine, South Africa, contains rare earth elements in concentrations that may be of commercial interest. To assess the distribution of the rare earth minerals in the industrial flotation process currently used to produce fluorite concentrates, one mining block, that was carefully chemically, mineralogically and petrographically characterised, was fed to the flotation plant and subsequently the plant was systematically sampled. Mineral liberation analysis was conducted on the feed and the flotation products. Monazite and xenotime are the two main rare earth minerals. They are microcrystalline and occur mostly in association with each other and with iron oxide minerals in the ground flotation feed. A Particle Tracking technique was used to process the mineral liberation analysis and to assess the flotation behaviour of monazite and xenotime. Based on the study, different flotation behaviour was proposed for liberated and locked monazite and xenotime. The highest grade of monazite and xenotime was found in the tailing sample from the second cleaner unit of the flotation plant. Monazite and xenotime show high degree of liberation in this product. The tailings, especially of the second cleaner unit, were recommended for further beneficiation of rare earth elements.
  • Lecture (Conference)
    Process Mineralogy’17, 20.-22.03.2017, Cape Town, South Africa

Publ.-Id: 24693 - Permalink


Magnetic Force Microscopy studies of synthetic perpendicular anisotropy antiferromagnets modified by ion beam irradiation
Samad, F.; Böhm, B.; Koch, L.; Ganss, F.; Arekapudi, S. S. P. K.; Lenz, M.; Stienen, S.; Hellwig, O.;
By using ion beam irradiation of different energy and flux we modify and tune the magnetic reversal and microstructure in synthetic perpendicular anisotropy antiferromagnets consisting of [(Co/Pt)Co/Ru] multilayer systems. The magnetic energy balance between antiferromagnetic interlayer exchange and dipolar fields in the initial state of the samples has been tuned to have two local energy minima, one for laterally correlated and vertically anti-correlated magnetic structure (single domain antiferromagnet) and the other for laterally anti-correlated and vertically correlated magnetic structure (ferromagnetic stripe domains) [1]. Ion beam irradiation is then subsequently used to locally alter the magnetic microstructure from one state to the other to create laterally co-existing phases and study their reversal behavior in external magnetic fields using Magnetic Force Microscopy.
  • Poster
    Frühjahrestagung der Deutschen Physikalischen Gesellschaft, 19.-24.03.2017, Dresden, Deutschland

Publ.-Id: 24692 - Permalink


Impact of ion irradiation on magneto-resistance properties of synthetic antiferromagnets based on [(Co/Pt)X-1Co/Ru]N multilayers
Böhm, B.; Samad, F.; Koch, L.; Arekapudi, S. S. P. K.; Ganss, F.; Lenz, M.; Stienen, S.; Hellwig, O.;
The tuning of the magnetic properties of antiferromagnetically (AF) coupled multilayer films by ion beam irradiation has been investigated. Stacks of Co/Pd respectively Co/Pt multilayers, AF-coupled by Ru or Ir interlayers, have been useful for studying the energy contribution of interlayer exchange, perpendicular anisotropy and long range dipole interactions. The system shows a complex mixture of magnetic phases that can be tuned by the number of repeats of the multilayers (X). A lateral homogeneous AF remanent structure occurs for small X due to the dominance of the AF-coupling. For large X the demagnetisation energy prevails and ferromagnetic stripe domains evolve. With ion irradiation the balance of the energy contributions can be locally manipulated, thus a lateral heterogeneous structure of magnetic phases may be realised. Initial irradiation studies will be discussed.
  • Poster
    Frühjahrestagung der Deutschen Physikalischen Gesellschaft, 19.-24.03.2017, Dresden, Deutschland

Publ.-Id: 24691 - Permalink


Manipulation of AF-Coupled Thin Film Systems by Ion Beam Irradiation
Koch, L.; Samad, F.; Böhm, B.; Ganss, F.; Arekapudi, S. S. P. K.; Lenz, M.; Stienen, S.; Hellwig, O.;
The tuning of the magnetic properties of antiferromagnetically (AF) coupled multilayer films by ion beam irradiation has been investigated. Stacks of Co/Pd respectively Co/Pt multilayers, AF-coupled by Ru or Ir interlayers, have been useful for studying the energy contribution of interlayer exchange, perpendicular anisotropy and long range dipole interactions. The system shows a complex mixture of magnetic phases that can be tuned by the number of repeats of the multilayers (X). A lateral homogeneous AF remanent structure occurs for small X due to the dominance of the AF-coupling. For large X the demagnetisation energy prevails and ferromagnetic stripe domains evolve. With ion irradiation the balance of the energy contributions can be locally manipulated, thus a lateral heterogeneous structure of magnetic phases may be realised. Initial irradiation studies will be discussed.
  • Poster
    Frühjahrstagung der Deutschen Physikalische Gesellschaft, 19.-24.03.2017, Dresden, Deutschland

Publ.-Id: 24690 - Permalink


Multiscale Self-Assembly of Quantum Dots into an Anisotropic Three-Dimensional Random Network
Ilday, S.; Ilday, F.; Hübner, R.; Prosa, T.; Martin, I.; Nogay, G.; Kabacelik, I.; Mics, Z.; Turchinovich, D.; Ustunel, H.; Toffoli, D.; Friedrich, D.; Schmidt, B.; Heinig, K.-H.; Turan, R.;
One of the well-known challenges in design of nanomaterials is to simultaneously achieve material properties pertaining to few-atom scale and bulk properties through which the material connects to other materials or interacts with devices. This is difficult because properties arising from physics at different scales are often mutually exclusive. An important example is the 30 year-old problem of realizing a connected-but-confined Si nanostructure embedded in a dielectric matrix (e.g., SiO2) that simultaneously brings together quantum-dot (QD)-like optical properties and good electrical conduction. Here, we solve this problem through creation of a hierarchically self-assembled anisotropic random network of Si QDs: At the atomic scale, QDs are formed, which sparsely interconnect without inflating their diameters to form an isotropic random network, and larger scales, this network becomes anisotropic, preferentially growing in the vertical direction to form nanowire-like structures. We report simultaneous achievement of good electrical conductivity (~0.1 S/cm) and a bandgap tuneable over the visible light range (from 1.8 to 2.7 eV).
In order to determine how to self-assemble such a topology without using advanced control over dynamical details of the system, we developed a toy model of the stochastic deposition process, from which we related the intended topology to parameters governing stochastic growth and determined the experimental conditions that can give rise to it. Monte Carlo and Molecular Dynamics simulations are performed to guide our methodology and fabrication was done using magnetron sputter deposition. The two leverages that we used for multiscale self-assembly were as follows: (i) We keep the substrate “cold” and adjust how “hot” the deposited particles are. This way, we create spatio-temporal temperature gradients on the surface and thereby, we control surface diffusion and promote vertical growth in the microscale resembling nanowires. (ii) We fine-tune the thin-film stoichiometry in order to control the phase-separation. This way, we control the nominally unstable medium that QDs are embedded in and limit further inflation of their diameters in the atomic scale. This way we show that self-assembly under nonequilibrium conditions and nonlinear dynamics sweeps aside a large number of factors that influence the details of thin-film growth, but provides a couple of simple “rules” (with clearly identifiable corresponding experimental conditions) to determine the final morphology. The generality and material-independence of this methodology is strongly suggestive of possibility to apply it to solve a variety of other nanomaterial problems, which also pertain to multiple scales.
  • Poster
    2016 MRS Spring Meeting & Exhibit, 28.03.-01.04.2016, Phoenix, AZ, USA

Publ.-Id: 24689 - Permalink


Ion Implantation and Annealing Based Synthesizing of AIII-BV Nanostructures in SiO2/Si Matrix
Kopycinski, P.; Prucnal, S.; Pyszniak, K.; Grudzinski, W.; Zuk, J.;
Most of modern electronics manufacturing is based on silicon. But because of its indirect energy band gap silicon cannot be used as an efficient light source. Therefore from economical and technological points of view it is important to find light sources than can be integrated into Si technology. One of the possible solutions is to integrate AIII-BV semiconductor nanocrystals inside Si-based matrices. For synthesis of such structures sequential ion implantation and annealing techniques can be used.In this work As+ + In+and As+ + Ga+ions were implanted into SiO2(100nm)/Si. Flash Lamp Annealing (FLA) in the ms range with preheating was employed within a wide range of annealing parameters such as temperature and time. In that way different sizes of InAs and GaAs nanocrystals were obtained.
To investigate optical properties of InAs and GaAs structures we used lowtemperature photoluminescence (PL) and micro-Raman spectroscopic techniques including 2D mapping. PL spectra were obtained in a temperature range from 10K up to RT. Raman spectroscopy was performed at room temperature. The Raman spectra confirms very good quality of InAs and GaAs crystals, and deconvoluted PL spectra give interesting information about expected quantum size effect - related blue shift and nanocrystals sizes.
Keywords: Flash lamp annealing, Si, GaAs, ion implantation
  • Poster
    45th International School & Conference on the Physics of Semiconductors SZCZYRK, POLAND June 18th – 24th, 2016, 18.-24.06.2016, Szczyrk, Poland

Publ.-Id: 24688 - Permalink


Band gap engineering in Ge via non-equilibrium thermal processing and Sn doping
Prucnal, S.; Berencen, Y.; Skorupa, W.; Zhou, S.;
The incorporation of different functional optoelectronic elements on a single chip enables performance progress which can overcome the downsizing limit in silicon technology. For example, the use of Ge instead of silicon as a basic material in nanoelectronics would enable faster chips containing smaller transistors. As was shown recently, Ge can be used not only for fast electronics but also for optical devices e.g. LEDs and detectors. In order to fully exploit and boost further its unique properties, the alloying of Ge with Sn and ultra-doping with P for n-type conductivity have to be explored. To this day, both Sn and P impurity are introduced into Ge mainly in-situ during the growth process (e.g. using molecular beam epitaxy (MBE) or chemical vapour deposition (CVD)).
In this work, we report on the band gap modification of Ge by Sn alloying and P co-doping.
The doping of Ge was be performed using ion beam implantation of P and Sn with a concentration far exceeding the solid solubility limit of Sn in Ge (>> 0.2%). The implanted Sn was alloyed with Ge using rear-side flash lamp annealing. According to both XRD and HRTEM fabricated layer is single crystalline for the Sn doping up to 6 %. After P-implantation and annealing fabricated GeSn layers are n-type with active carrier concentration above 5×10^19cm-3. The GeSn alloy made by presented method enable the integration of innovative Ge-based devices in the mainstream of Si CMOS technology which can be used for the fabrication of three-dimensional (3D) large-scaleintegration devices with modulated optoelectronic properties.
Keywords: GeSn, flash lamp annealing, n-type doping
  • Poster
    45th International School & Conference on the Physics of Semiconductors, 18.-24.06.2016, Szczyrk, Poland

Publ.-Id: 24687 - Permalink


Ultra-doped Ge: old material with new functionalities
Prucnal, S.; Berencen, Y.; Skorupa, W.; Zhou, S.;
One of the main obstacles towards wide application of Ge in nanoelectronics is the lack of an efficient doping method for the fabrication of heavily doped Ge layers with well controlled junction depth. In fact, n-type doping of Ge is a key bottleneck in the realization of advanced negative-channel metal-oxide-semiconductor (NMOS) devices. Here we use ion implantation followed by flash-lamp (FLA) annealing for the fabrication of heavily doped Ge with comparably high mobility. In contrast to conventional annealing procedures, rear-side FLA leads to full recrystallization of Ge and dopant activation independently of pre-treatment. The maximum carrier concentration is well above 1020 cm-3 for n-type and above 1021 for p-type doping. The recrystallization mechanism and the dopant distribution during rear-side FLA are discussed in detail.
In this work, we report on the strong mid-IR plasmon absorption from heavily P-doped Ge thin films and superconductivity in Ga implanted Ge obtained by non-equilibrium thermal processing.
Ultra-doped Ge layers were fabricated by ion implantation of P or Ga ions followed by rear-side flash lamp annealing in the millisecond range. This approach, in contrast to conventional annealing procedures, leads to full recrystallization of Ge films and high dopant activation. In this way single crystalline Ge thin films free of defects were obtained. The mid-IR plasmon spectral response at room temperature from those samples was characterized by means of Fourier transform infrared spectroscopy. It is proven that the position of the plasmonic resonance frequency signal can be
tuned as a function of the P concentration.
Keywords: Ge, ion implantation, ultra-doping, n-type
  • Poster
    45th International School & Conference on the Physics of Semiconductors, 18.-24.06.2016, Szczyrk, Poland

Publ.-Id: 24686 - Permalink


Mid-infrared plasmonic absorption from heavily doped Ge thin films
Berencén, Y.; Liu, F.; Lang, D.; Voelskow, M.; Skorupa, I.; Kehr, S.; Rebohle, L.; Helm, M.; Skorupa, W.; Zhou, S.; Prucnal, S.;
Exploiting plasmonics for mid-IR sensing purposes has become an increasing area of research. The reason is that many molecules present molecular vibrational resonances, which provide spectral fingerprints in the near- and mid-IR region [1, 2]. Of particular interest is the gas detection, diagnostic and medical care. To this day, strong plasmon resonances in the visible and near-IR spectral range have been identified in nanostructured metals such as silver, aluminum and gold [3]. In principle, heavily doped semiconducting materials like Si or Ge could be an interesting alternative to replace metals due to their compatibility with CMOS technology. Indeed, the possibility to control the plasmon resonance frequency in semiconductors via the carrier density opens new route for near- and mid-IR detectors.
In this work, we report on the strong mid-IR plasmon absorption from heavily P-doped Ge thin films obtained by non-equilibrium thermal processing. Ultra-doped Ge layers were fabricated by ion implantation of P ions followed by rear-side flash lamp annealing in the millisecond range. This approach, in contrast to conventional annealing procedures, leads to full recrystallization of Ge films and high P activation irrespective of pre-treatment. In this way, single crystalline Ge thin films free of defects with carrier concentration much above 1×1020 cm-3 and carrier mobility above 260 cm2/(V·s) were obtained. The mid-IR plasmon spectral response at room temperature from those samples was characterized by means of Fourier transform infrared spectroscopy. It is proven that the position of the signal from the plasmon resonance frequency can be tuned as a function of the P concentration.
Keywords: plasmonics, heavily doped n-type Ge, flash-lamp annealing.
[1] A. G. Brolo, Nat. Photonics 6, 709 (2012).
[2] N. Liu, M. Mesch, T. Weiss, M. Hentschel, and H. Giessen, Nano Lett. 10, 2342 (2010).
[3] G. Konstantatos and E. H. Sargent, Nat. Nanotechnology 5, 391 (2010).
Keywords: Ultra-doped Ge, Plasmonics, FLA, Ion implantation
  • Lecture (Conference)
    E-MRS 2016 Spring Meeting (European-Materials Research Society), 02.-06.05.2016, Lille, France

Publ.-Id: 24685 - Permalink


Room-temperature extended IR photoresponse from hyperdoped Si p-n photodiodes
Berencén, Y.; Prucnal, S.; Liu, F.; Wang, M.; Zhou, S.; Lang, D.; Skorupa, I.; Helm, M.; Rebohle, L.; Skorupa, W.;
The development of room-temperature Si infrared photodetectors, whose range of detection lies on the traditional telecommunication wavelengths around 1300 nm and 1550 nm, is of paramount importance for optical communications, integrated photonics, sensing and medical imaging applications [1]. The typical peak photoresponse of conventional Si photodetectors is between 700 and 900 nm, which is primarily limited by the 1.12 eV-Si band gap. However, such intrinsic material limitation can be overcome by introducing transition metals or chalcogens into the Si band gap at concentrations far above those obtained at equilibrium conditions [1, 2]. This new class of hyperdoped materials with a donor impurity band has been postulated as a viable route to extend the Si photoresponse at the infrared spectral region [3].
In this work, we report on the significant room-temperature photoresponse and performance at the two primary telecommunication wavelengths as exhibited by hyperdoped Si p-n photodiodes fabricated by Se implantation followed by millisecond flash lamp annealing (FLA). The FLA approach in the millisecond range allows for a solid-phase epitaxy that has been reported to be superior to liquid-phase epitaxy induced during pulsed laser annealing [2]. The success of our devices is primarily based on the high quality of the developed n-type hyperdoped material, which is single-phase single crystal with high electrical activation, without surface segregation of Se atoms and with an optically flat surface.
[1] J. P. Mailoa, A. J. Akey, C. B. Simmons, D. Hutchinson, J. Mathews, J. T. Sullivan, D. Recht, M. T. Winkler, J. S. Williams, J. M. Warrender, P. D. Persans, M. J. Aziz, and T. Buonassisi, Nat. Commun. 5, 3011 (2014).
[2] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015).
[3] I. Umezu, J. M. Warrender, S. Charnvanichborikarn, A. Kohno, J. S. Williams, M. Tabbal, D. G. Papazoglou, X. C.Zhang, and M. J. Aziz, J. Appl. Phys. 113, 213501 (2013).
Keywords: Se, Si, hyperdoping, FLA, Ion implantation, Si-based IR photodetectors
  • Lecture (Conference)
    E-MRS 2016 Spring Meeting (European-Materials Research Society), 02.-06.05.2016, Lille, France

Publ.-Id: 24684 - Permalink


Structural impact of Cr doping in titanium oxide thin films grown by co-sputtering and flash-lamp annealed
Gago-Fernandez, R.; Prucnal, S.; Pérez-Casero, R.; Caretti, I.; Lungwitz, F.; Cornelius, S.;
Titanium dioxide (TiO2) is used in many applications as a photocatalyst. However, TiO2 activity is mostly limited to the UV spectral region due to its wide band-gap (~3eV). For this reason, many efforts1 have been focused on band-gap narrowing to achieve visible-light (VISL) response in TiO2, mostly by doping. Metal (cation) doping increases VISL absorption significantly but, unfortunately, it introduces structural distortions in the host matrix that result in a large number of defects acting as carrier recombination centers.1 Post-processing thermal treatments are normally employed here to improve the structural order.2 In this work, we study the impact of rapid non-contact thermal processes as flash-lamp annealing (FLA) on the electronic structure of Cr-doped TiO2. For this purpose, (amorphous) thin films with different Cr contents were produced at room temperature by magnetron co-sputtering. The dopant concentration was quantified by Rutherford backscattering spectrometry (RBS) whereas the resulting structural phases after FLA were assessed by Raman and X-ray diffraction (XRD). Due to the disordered nature of the samples, the structural characterization has been complemented with local-order information around host and dopant sites from the X-ray near-edge structure (XANES). Finally, the optical properties have been studied by spectroscopic ellipsometry (SE). It is found that FLA can selectively tune the anatase/rutile phase formation in pure TiO2. In addition, films
with low doping (Cr < 6 at.%) display a rutile structure. For higher doping level, the formation of high-valence Cr sites is observed, which seems to be detrimental for the structural promotion. Nonetheless, these sites are thermally unstable and annihilated upon FLA. REFs: 1Asahi et al. SCI 293, 269 (2001); 2W. Zhu et al. PRL 103, 226401 (2009).
Keywords: TiO2, Cr, FLA, XRD, PL
  • Poster
    15th International Conference on Plasma Surface Engineering, 12.-16.09.2016, Garmisch-Partenkirchen, Germany

Publ.-Id: 24683 - Permalink


Non-equilibrium thermal processing for hyperdoping Si
Berencén, Y.; Prucnal, S.; Liu, F.; Wang, M.; Zhou, S.; Helm, M.; Rebohle, L.; Skorupa, W.;
Hyperdoping has recently emerged as a potential powerful technique to explore new functionalities of semiconductor materials with unique electrical and optical properties [1-3]. Hyperdoping facilitates to introduce dopants into a semiconductor material at concentrations far above those obtained at equilibrium conditions, viz. doping far beyond the solubility limit. Hyperdoped Si with chalcogens or transition metals like Au or Ti has been postulated to be a promising material for many applications, especially for Si-based infrared photodetectors and intermediate band solar cells [2, 3].
In this work, we report on a groundbreaking approach, for hyperdoping Si with Se, consisting of ion implantation followed by millisecond-range flash lamp annealing. This method allows for a solid-phase epitaxy that has been reported to be superior to liquid-phase epitaxy induced during conventional pulsed laser annealing [1]. The resulting Se-hyperdoped Si material is single-phase single crystal with high electrical activation, without surface segregation of Se atoms and with an optically flat surface. We also present a significant room-temperature sub-band gap photoresponse exhibited by Se-hyperdoped Si p-n photodiodes that have been fabricated by this novel approach.
[1] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015).
[2] M. J. Sher & E. Mazur, App. Phys. Lett. 105, 032103 (2014).
[3] E. Ertekin, M. T. Winkler, D. Recht, A. J. Said, M. J. Aziz, T. Buonassisi, and J. C. Grossman, Phys. Rev. Lett. 108, 026401 (2012).
Keywords: Hyperdoping, Si, , Se, FLA, ion implantation
  • Invited lecture (Conferences)
    ION 2016 - International Conference of ion implantation and other applications of ions and electrons, 13.-16.06.2016, Kazimierz Dolny, Poland

Publ.-Id: 24682 - Permalink


The role of flash lamp annealing for the recrystallization of ion implanted ZnO
Prucnal, S.; Braun, M.; Wang, M.; Liu, F.; Snigurenko, D.; Berencen, Y.; Guziewicz, E.; Rebohle, L.; Zhou, S.; Skorupa, W.;
A highly doped n-type ZnO thin layer is an attractive candidate to replace the much more expensive indium-tin-oxide layer in photovoltaics and low cost electronics. The optoelectronic properties of ZnO are determined by the type of doping and carrier concentration. The n-type conductivity of ZnO is easily achieved by substitution of Zn through the group III elements (Al, Ga, In), or by doping with halogen elements (F, Cl or I) substituting into the oxygen lattice site. However, the effective p-type doping of ZnO remains challenging. The most promising p-type dopants in ZnO are group V elements. In this paper, we have investigated the influence of millisecond range flash lamp annealing (FLA) on the recrystallization mechanism and optoelectronic properties of ion implanted ZnO thin films. The 120 nm thick ZnO films were grown on Si substrates by atomic layer deposition and implanted with P and Sb ions. After ion implantation FLA was used to anneal defects created during the ion implantation process and to activate finally the dopants. Samples were annealed for 3 or 20 ms using oxygen-poor (N2 or Ar) and pure oxygen atmosphere. The influence of the annealing conditions (atmosphere, annealing time and flash energy) on the optical and electrical properties of implanted ZnO was investigated using temperature dependent photoluminescence, Raman spectroscopy and Hall Effect measurements. The microstructural properties of fabricated ZnO films were studied using cross-section TEM and X-ray diffraction spectroscopy. It will be demonstrated that via millisecond range FLA treatment not only the implanted ions can be efficiently incorporated into the lattice of ZnO but also defect engineering is possible. By a proper selection of the implanted species and annealing atmosphere the main optical emission observed from doped ZnO can be easily changed from the UV to the red. This allows the fabrication of spectrally-clean blue, green and red emitters. According to Hall Effect and PL measurements the annealing atmosphere during FLA is crucial for the realization of p-type ZnO layers. The oxygen-poor atmosphere promotes the Zn-interstitial formation enhancing the n-type conductivity of ZnO. Annealing in oxygen suppresses the formation of n-type defects and stabilizes the p-type conductivity of ZnO films. This work has been partially supported by the EU 7th Framework Programme (EAgLE) (REGPOT-CT-2013-316014).
Keywords: ZnO, doping, flash lamp annealing, photoluminescence
  • Poster
    E-MRS 2016 Fall Meeting, 19.-22.09.2016, Warsaw, Poland

Publ.-Id: 24681 - Permalink


Complex electronic structure of Zni and Oi defects in ZnO
Prucnal, S.; Wang, M.; Liu, F.; Wu, J.; Cai, H.; Zhou, S.; Skorupa, W.;
To these days ZnO is one of the most widely investigated types of transparent conductive oxides except ITO. The electronic structure of most of the native defects in ZnO was studied both theoretically and experimentally using various methods. Based on simulation and experimental results, A. Sokol, et al., , have proposed a complex model for the electronic structure of different point defects in doped and undoped ZnO [Faraday Discuss., 134, 267-282 (2007)]. There is agreement that the zinc interstitial (Zni) is a shallow donor and is mainly responsible for the n-type conductivity of intrinsic ZnO. The oxygen interstitial (Oi) is neutral in ZnO, has the energy level located about 2.8 eV below the bottom of the conduction band, and is mainly responsible for the blue-green emission at 2.5 – 2.3 eV. But the energy levels of exited Zni* and Oi are controversial. Using density functional theory calculations, Yong-Sung Kim and C. H. Park have shown that Zni* should have an energy level above the conduction band but to this day it has not been proven experimentally and the exact energy position is unknown [Phys. Rev. Lett. 102, 086403 (2009)]. In order to verify their theory we have performed detailed optical and electrical investigations of ZnO films deposited on insulating Si wafers by reactive pulsed laser deposition. The defect engineering in ZnO was performed using non-equilibrium flash lamp annealing operated in the millisecond range with different annealing ambient. Temperature dependent photoluminescence (PL) emission and excitation (PLE) were utilised to determine the radiative transitions and excitation levels in ZnO, respectively. In order to determine the carrier concentration and conductivity type of processed ZnO films, Hall Effect measurements were performed in the temperature range from 3 to 300K. According to PLE the first excited levels of Zni* and Oi are located at 0.83 eV and 0.70 eV above the conduction band, respectively. The concentration of Zni* and Oi is determined by the annealing atmosphere. The oxygen-poor atmosphere promotes the Zn-interstitial formation while annealing in oxygen suppresses the n-type defects and increases the Oi concentration. Comparison of temperature dependent PL and Hall Effect data confirms that the Zni is a main intrinsic source of n-type conduction in ZnO.
Keywords: ZnO, defect engineering, flash lamp annealing, photoluminescence
  • Poster
    E-MRS 2016 Fall Meeting, 19.-22.09.2016, Warsaw, Poland

Publ.-Id: 24680 - Permalink


Atomic layer deposition of nitrogen-doped titanium dioxide films
Luka, G.; Wierzbicka, A.; Guziewicz, E.; Prucnal, S.; Skorupa, W.;
Layers and nanostructures of titanium dioxide (TiO2) have found several practical applications for paints, sunscreens, protecting layers, photocatalysis, water splitting or photovoltaics. The applicability of this material depends on its crystalline phase. Among the three possible crystal structures of TiO2, anatase is commonly used for photocatalysis. TiO2 with anatase structure, however, can undergo transition to the rutile phase, which is accelerated by the heat treatment at temperatures between 450 and 1200 °C. In our work, we obtained undoped and nitrogen-doped titanium dioxide (TiO2:N) films, grown by atomic layer deposition, with a stable anatase structure. The as-grown amorphous films were deposited at 120 °C on single crystalline Si substrates. After deposition samples were annealed by flash lamp annealing for 20 ms in nitrogen ambient. Annealed films show anatase structure which is stable up to anneal temperatures close to the melting point of Si (< 1400 °C). This was confirmed by ?-Raman and x-ray diffraction studies. We analyze the anatase crystal structure of the annealed TiO2:N films as a function of the annealing energy density and the N concentration. The investigations are complemented by temperature-dependent photoluminescence measurements. The work was partially supported by the EU 7th Framework Programme project REGPOT-CT-2013-316014 (EAgLE).
Keywords: TiO2, photoluminescence, flash lamp annealing
  • Lecture (Conference)
    E-MRS 2016 Fall Meeting, 19.-22.09.2016, Warsaw, Poland

Publ.-Id: 24679 - Permalink


RBS/c and PL studies of ZnO implanted with Pr ions
Ratajczak, R.; Prucnal, S.; Mieszczynski, C.; Guziewicz, E.; Stachowicz, M.; Snigurenko, D.; Kopalko, K.; Witkowski, B. S.; Krajewski, T. A.; Turos, A.;
High-quality ZnO epitaxial layers deposited by Atomic Layer Deposition were implanted at room temperature with 150 keV Pr3+ions to fluence of 1x1015 and 2x1015. Two different types of annealing on as implanted samples were performed: rapid thermal annealing (RTA) and flash lamp annealing (FLA). Crystalline quality, damage recovery and Yb lattice site location were evaluated by the Channeling Rutherford Backscattering Spectrometry (RBS/c). The optical properties were studied by photoluminescence (PL). Upon annealing defects recovery has been observed. After RTA the return of Zn atoms to their substitutional sites produces displacement RE atoms into interstitial positions. The increase of RTA temperature and time leads to enhanced out-diffusion of RE atoms. Consequently, better recovery of the crystal structure is accompanied by lower photoluminescence (PL) efficiency. The FLA precludes the RE-atom surface segregation. The substitutional fraction of Pr ions is higher than after RTA with the same structure recovery, but PL intensity from Pr3+ is lower. This suggests that the substitutional RE atoms are preferentially in the 2+ state. Acknowledgments: The work was supported by the NCBiR (Poland) project PBS2/A5/34/2013 and by the EU 7th FP project REGPOT-CT-2013-316014 (EAgLE), by the Polish Ministry of Science and Higher Education (3418/SPIRIT/2015/0) and by the Helmholtz Zentrum Dresden-Rossendorf (HZDR) in a frame of the program Access to Infrastructure (15100222-ST and 16000696-ST).
Keywords: ZnO, Rare Earths, ion implantation, flash lamp annealing, photoluminescence
  • Poster
    E-MRS 2016 Fall Meeting, 19.-22.09.2016, Warsaw, Poland

Publ.-Id: 24678 - Permalink


Fabrication and studies of short period ZnO/MgO superlattices
Kozanecki, A.; Pietrzyk, M.; Stachowicz, M.; Prucnal, S.; Skorupa, W.; Dyczewski, J.; Dluzewski, P.;
In this work we present the optical and structural characteristics of ZnO/MgO short period superlattices grown on c-plane ZnO. The structures were composed on 80 pairs of ZnO/MgO thin layers. Rutherford backscattering allowed to estimate the real thickness of the structures and compare them with the intended one. The thicknesses differed from growth to growth and they were on the order of 1 nm ZnO to 1-1.5 nm MgO. The thickness of MgO layers was crucial for the growth mode and resulting quality of the structures. Channeling measurement revealed that in the case of the thinnest MgO layers the growth of superlattices was coherent, as χmin of the backscattering yield for the superlattice is the same as for ZnO substrate. This very good crystalline quality was also reflected in photoluminescence (PL) measurements, which revealed PL typical of superlattice. However, the PL of some structures showed that ZnMgO alloy was formed instead of the superlattice. PL excitation spectra allowed to determine the band gap values of the ZnO/MgO structures by observation of the PL from the ZnO substrate. Reasons for it are discussed. Transmission Electron Microscope imaging allows to compare both types of structures. Acknowledgements. The work was supported by the NCN project DEC-2014/15/B/ST3/04105 and by the EU 7th FP project REGPOT-CT-2013-316014 (EAgLE).
Keywords: ZnO, ZnO/MgO, photoluminescence, superlattice
  • Poster
    E-MRS 2016 Fall Meeting, 19.-22.09.2016, Warsaw, Poland

Publ.-Id: 24677 - Permalink


Hot electron engineering for boosting electroluminescence efficiencies of silicon-rich nitride light emitting devices
Berencén, Y.; Mundet, B.; Rodríguez, J. A.; Montserrat, J.; Domínguez, C.; Garrido, B.;
The combination of a SiO2 electron accelerator layer with a silicon-rich nitride layer forming a bilayer embedded in a metal-oxide-semiconductor structure has proved to enhance the integrated visible-infrared EL intensity by more than two orders of magnitude in comparison to the single-layer electroluminescent device approach. The origin of such an improvement is attributed to the massive ionization of defects in the silicon-rich nitride layer by direct impact of injected hot electrons coming from the SiO2 conduction band. Our premises are further corroborated by performing a thorough study of the charge transport in the bilayer structure. This study displays a main electrical mechanism at steady state that combines hot-electron tunneling injection from the SiO2 accelerator layer and space charge-limited current enhanced by Poole-Frenkel conduction from the silicon-rich nitride electroluminescent layer. The proposed electrical mechanism is validated by numerical simulations that provide good agreement with the experimental behavior. These results point out the feasibility of boosting electroluminescence efficiency of Si-based light emitting devices by performing an adequate gate stack engineering that maximizes the hot-electron injection into the electroluminescent layer.
Keywords: Hot electron engineering; Silicon-rich nitride; Electrical transport; Electroluminescent devices

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  • Secondary publication expected

Publ.-Id: 24676 - Permalink


Non equilibrium thermal processing of highly implanted ZnO:Yb
Stachowicz, M.; Ratajczak, R.; Prucnal, S.; Skorupa, W.; Krajewski, T. A.; Witkowski, B. S.; Snigurenko, D.; Turos, A.; Guziewicz, E.;
ZnO epitaxial layers deposited by Atomic Layer Deposition were implanted with Yb ions to a fluence of 1x1016 at./cm2 at energy of 150 keV. Different types of annealing (in oxygen or ambient atmosphere) of ZnO:Yb samples have been performed: millisecond range flash lamp annealing (FLA), rapid thermal annealing (RTA) up to 30 min. and tube furnace annealing (TFA) up to 1 h at 800oC. It was found that the optical properties of ZnO:Yb films are strongly affected by the annealing time. According to Rutherford Backscattering and channeling (RBS/c) the annealing of implanted films leads to a partial recovery of the crystal lattice. The photoluminescence (PL) spectra in combination with RBS/c reveal that the worse reconstruction of lattice and reduction of the fraction of substitutional Yb ions results in more intense emission around 0.98 µm in case of RTA and TFA annealing. Surprisingly, the FLA annealing has shown very good result in terms of PL intensity at RT as a thermal quenching effect is much weaker in this case. The RBS/c and PL results lead to a conclusion that RTA and FTA annealing promotes cluster formation and outdiffusion of Yb while FLA suppresses it. Acknowledgements. The work was supported by the NCBiR (Poland) through the project PBS2/A5/34/2013 and by the EU 7th FP project REGPOT-CT-2013-316014 (EAgLE). It was also co-financed by Helmholtz Zentrum Dresden-Rossendorf (HZDR) in the frame of the program Access to Infrastructure (15100222-ST).
Keywords: ZnO, Yb, ion implantation, photoluminescence
  • Poster
    E-MRS 2016 Fall Meeting, 19.-22.09.2016, Warsaw, Poland

Publ.-Id: 24675 - Permalink


Ge comeback - new properties of an old material
Prucnal, S.;
One of the main obstacles towards wide application of Ge in nanoelectronics is the lack of an efficient doping method for the fabrication of heavily doped Ge layers with well controlled junction depth. In fact, n-type doping of Ge is a key bottleneck in the realization of advanced negative-channel metal-oxide-semiconductor (NMOS) devices. Here we use ion implantation followed by flash-lamp (FLA) annealing for the fabrication of heavily doped Ge with comparably high mobility. In contrast to conventional annealing procedures, rear-side FLA leads to full recrystallization of Ge and dopant activation independently of pre-treatment. The maximum carrier concentration is well above 1020 cm-3 for n-type and above 1021 for p-type doping. The recrystallization mechanism and the dopant distribution during rear-side FLA are discussed in detail.
In this work, we report on the strong mid-IR plasmon absorption from heavily P-doped Ge thin films and superconductivity in Ga implanted Ge obtained by non-equilibrium thermal processing. Ultra-doped Ge layers were fabricated by ion implantation of P or Ga ions followed by rear-side flash lamp annealing in the millisecond range. This approach, in contrast to conventional annealing procedures, leads to full recrystallization of Ge films and high dopant activation. In this way single crystalline Ge thin films free of defects were obtained. The mid-IR plasmon spectral response at room temperature from those samples was characterized by means of Fourier transform infrared spectroscopy. It is proven that the position of the plasmonic resonance frequency signal can be tuned as a function of the P concentration.
Keywords: Ge, n-type doping, plasmonics, FLA
  • Invited lecture (Conferences)
    International Conference Ion Implantation and other Applications of Ions and Electrons, 13.-16.06.2016, Kazimierz Dolny, Poland

Publ.-Id: 24674 - Permalink


Room-temperature sub-band gap photoresponse from Se-hyperdoped Si p-n photodiodes
Berencén, Y.; Liu, F.; Wang, M.; Zhou, S.; Rebohle, L.; Helm, M.; Skorupa, W.; Prucnal, S.;
The development of room-temperature short-wavelength infrared Si photodetectors is of paramount importance for optical communications, integrated photonics, sensing and medical imaging applications [1]. The typical peak photoresponse of conventional Si photodetectors is between 700 and 900 nm, which is mainly limited by the 1.12 eV-Si indirect band gap. Nevertheless, such intrinsic material limitation can be circumvented by introducing transition metals or chalcogens into the Si band gap at concentrations far above those obtained at equilibrium conditions [1, 2]. This new class of hyperdoped materials with a donor impurity band has been postulated as a viable route to extend the Si photoresponse at the short-wavelength infrared spectral region [3]. In this work, we report on the significant room-temperature photoresponse and performance at wavelengths as long as 3100 nm as exhibited by hyperdoped Si p-n photodiodes fabricated by Se implantation followed by flash lamp annealing (FLA). The FLA approach in the millisecond range allows for a solid-phase epitaxy that has been reported to be superior to liquid-phase epitaxy induced during pulsed laser annealing [2]. The success of our devices is primarily based on the high quality of the developed n-type hyperdoped material, which is single-phase single crystal with high electrical activation, without surface segregation of Se atoms and with an optically flat surface. [1] J. P. Mailoa, A. J. Akey, C. B. Simmons, D. Hutchinson, J. Mathews, J. T. Sullivan, D. Recht, M. T. Winkler, J. S. Williams, J. M. Warrender, P. D. Persans, M. J. Aziz, and T. Buonassisi, Nat. Commun. 5, 3011 (2014). [2] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015). [3] I. Umezu, J. M. Warrender, S. Charnvanichborikarn, A. Kohno, J. S. Williams, M. Tabbal, D. G. Papazoglou, X. C.Zhang, and M. J. Aziz, J. Appl. Phys. 113, 213501 (2013)
Keywords: Si, hyperdoping, FLA, Se, ion implantation
  • Lecture (Conference)
    E-MRS 2016 Fall Meeting, 19.-22.09.2016, Warsaw, Poland

Publ.-Id: 24673 - Permalink


Optoelectronic properties of ultra-doped Ge fabricated by ion implantation and flash lamp annealing
Prucnal, S.; Berencén, Y.; Heera, V.; Voelskow, M.; Yuan, Y.; Wang, M.; Poddar, V.; Mazur, G. P.; Grzybowski, M.; Zgirski, M.; Sawicki, M.; Hübner, R.; Zhou, S.; Skorupa, W.;
Independent of the type of doping, it is challenging to achieve in semiconductors an effective carrier concentration much above 10^20 /cm3. On the other hand, the successful realization of defect free n-type and p-type ultra-doped Ge layers will enable a range of devices from sensors to quantum computers. In the case of conventional doping techniques (using equilibrium processing) the maximum carrier concentration is limited by the out-diffusion of dopants, a relatively low solid solubility limit, clustering and self-compensation processes. To overcome such limitations we have utilised strong nonequilibrium process consisting of an ion beam implantation to introduce dopants into Ge and rear-side millisecond range flash lamp annealing (FLA) for recrystallization of implanted layer and dopant activation. In contrast to conventional annealing procedures, rear-side FLA leads to full recrystallization of Ge and dopant activation independent of the pre-treatment. The maximum carrier concentration is well above 10^20 /cm3 for n-type and above 10^21 /cm3 for p-type dopants. The so-fabricated n-type Ge can be used in the field of mid-infrared plasmonics which has not been accessible by group-IV semiconductors. Single crystalline n-type Ge with carrier concentrations as high as 2.2×10^20 /cm3 displays a room-temperature plasma frequency above 1850 /cm1 (?=5.4 ?m), which is the highest value ever reported for n-type Ge. In the case of Ga implanted Ge the maximum effective carrier concentration measured at 3K is 1.1×10^21 /cm3 which is two times higher than the solid solubility limit of Ga in Ge. Our p-type Ge is defect and cluster free and shows the superconductivity at Tc = 0.95 K. These results base on the successful combination of ion beam implantation followed by the novel approach consisting of millisecond range rear-FLA. This work has been partially supported by the EU 7th Framework Programme "EAgLE" (REGPOT-CT-2013-316014).
Keywords: Ge, n-type, ion implantation, FLA
  • Lecture (Conference)
    E-MRS 2016 Fall Meeting, 19.-22.09.2016, Warsaw, Poland

Publ.-Id: 24672 - Permalink


In Situ Study of Metal Induced Crystallization Processes for Low-Dimensional Materials Synthesis
Wenisch, R.; Janke, D.; Heras, I.; Heller, R.; Hanf, D.; Hübner, R.; Munnik, F.; Gemming, S.; Krause, M.;
Metal induced crystallization (MIC) is a promising technique for low-temperature thin film transistor fabrication and graphene synthesis. In MIC, a transition metal catalyzes the crystallization of the amorphous phase of a group IV element by bond screening near the interface and facilitation of nucleation. So far, in situ studies have been performed using X-ray diffraction, which is sensitive to the degree of crystallinity. In situ Rutherford backscattering spectrometry has the advantage of elemental depth resolution and time resolved tracking of diffusion and layer exchange processes. Graphene formation through MIC has been demonstrated with an a-C/Ni layer stack [1].
As a model system for MIC, the Si/Ag bilayer system is studied here. The Si/Ag layer stacks are annealed at temperatures of 380 to 700 °C. Depth profiles of the elements are investigated by in situ RBS. Their analysis reveals the diffusion kinetics of the elements. The changes in the phase structure are explored by in situ Raman spectroscopy. Both the quick initial nucleation and ensuing growth processes are investigated.
[1] Weatherup et al., Nano Letters 13, pp. 4624 (2013)
Keywords: Metal induced crystallization In situ Raman In situ RBS
  • Poster
    International Winterschool on Electronic Properties of Novel Materials 2016, 13.-20.02.2016, Kirchberg in Tirol, Österreich

Publ.-Id: 24671 - Permalink


Effect of microstructure on the magnetic properties of transition metal implanted TiO2 films
Yildirim, O.; Cornelius, S.; Butterling, M.; Anwand, W.; Wagner, A.; Smekhova, A.; Huebner, R.; Boettger, R.; Fiedler, J.; Baehtz, C.; Potzger, K.;
The origin of the ferromagnetic order in TM:TiO2 (TM: transition metal) systems is studied by investigating the interplay between structural order, defects and incorporation of implanted TM ions within the host lattice. The defect properties of the host TiO2 films are altered by preparing different microstructures of TiO2 (e.g. amorphous, polycrystalline anatase and epitaxial anatase). The difference in microstructure is also found to influence the incorporation of the implanted ions into the host lattice. The crystallographic incorporation of the implanted TM atom is found only in crystalline films. Moreover, it is observed that the suppression of the dopant related secondary phases can also be achieved by changing the microstructure. Based on this discussion we propose an ideal microstructural candidate for a dilute magnetic oxide material based on our results.
  • Poster
    80. DPG-Jahrestagung und DPG-Frühjahrstagung der Sektion Kondensierte Materie, 06.-11.03.2016, Regensburg, Germany

Publ.-Id: 24670 - Permalink


Long-range focal series reconstruction in the TEM
Lubk, A.; Vogel, K.; Wolf, D.; Röder, F.; Clark, L.; Verbeeck, J.;
Focal series wave reconstruction in the Transmission Electron Microscope (TEM) is a well established holographic technique employed in both the medium and atomic resolution regime to study electric, magnetic and strain fields in solids as well as atomic configurations at crystal defects or grain boundaries. Focal series reconstruction does not require an undisturbed reference wave as off-axis holography and may be conducted under relaxed partial coherence provided that the latter is well-behaved and well-known in advance [1]. Moreover, focal series holography may be considered as an instance of the more general quantum state tomography (see Fig. 1) that is successfully employed to study mixed (i.e., incoherent) quantum states of matter (e.g., atoms) and light [2].
These advantages are opposed by ambiguities in the reconstructed wave function, e.g., due to inconsistent and incomplete focal series data. In reality every focal series is inconsistent, e.g., due to the presence of partial coherence, shot and detector noise, as well as geometric and chromatic aberrations depending on the defocus. Similarly, every focal series is incomplete because of a limited number of foci, typically limited to the near field regime, and the restriction to isotropic foci, where astigmatic foci are necessary to provide a dataset allowing for an unabiguous reconstruction of an underlying wave function [3]. For instance, the problematic reconstruction of low spatial frequencies can be traced back to missing focal series data in the far field.
Here, we elaborate on focal series reconstruction from the perspective of quantum state tomography and use the obtained results to increase the scope of the technique in terms of convergence and uniqueness in particular for low spatial frequencies. Moreover, we explain a number of previous results by exploiting the above analogy, and open pathways to further improvements.
We particularly report on the recording, preprocessing, calibration and reconstruction of a long range focal series ranging from the near to the far field in a TEM. We calibrate the focal series, including the effective defocus and magnification, by a careful calibration of the proportionality between squared current and reziprocal focal length in a magnetic lens. We derive non-linear focal sampling schemes from the phase space analogy. Subsequently, we adapt a modified Gerchberg-Saxton algorithm to the long range focal series by exploiting the link to randomized Kaczmarz (ART) algorithm used in tomography [4]. We use different numerical propagation regimes in the near and far field to take into account the scaling of the wave function and overcome convergence problems by replacing the Kaczmarz iteration with the Landweber (SIRT) iteration as proposed by Allen et al.. [5]. To overcome remaining ambiguities in the reconstruction (e.g, pertaining to a different starting guess in the Gerchberg-Saxton algorithm) resulting from inconsistencies in combination with the non-convex nature of the set of wave functions possessing the same modulus, we discuss several additional constraints such imposed by the topology of the starting guess [6].
To illustrate the above reconstruction principles, we perform a case study on a higher-order vortex beam with topological charge (winding number) 3 truncated by a square aperture (Fig. 2). The beam possesses a non-trivial topology by design, which is nicely suited to discuss the impact of (implicit) topology constraints, rotation alignment as well as other issues.

[1] Koch, C. T., Micron, 2014, 63, 69-75
[2] Schleich, W. P., Quantum Optics in Phase Space, Wiley VCH, 2001
[3] Lubk, A. & Röder, F., Phys. Rev. A, 2015, 92, 033844
[4] Natterer, F., Wübbeling, F., Mathematical Methods in Image Reconstruction,SIAM, 2001
[5] Allen, L. J.; McBride, W.; O’Leary, N. L.,Oxley, M. P., Ultramicroscopy, 2004, 100, 91-104
[6] Martin, A. & Allen, L., Optics Communications, 2007, 277, 288-294
[7] Financial support by the DIP programme of the DFG is greatly acknowledged.
  • Lecture (Conference)
    16th European Microscopy Congress, EMC 2016, 28.08.-02.09.2016, Lyon, Lyon

Publ.-Id: 24669 - Permalink


Electron interferometry techniques for strain analysis using a multibiprism microscope
Denneulin, T.; Röder, F.; Houdellier, F.; Gatel, C.; Snoeck, E.; Hÿtch, M. J.;
Electron interferometric techniques have progressed in the last years thanks to the development of multiple biprisms microscopes. Here, we will discuss some recent developments in the field of strain measurement carried out with the I2TEM microscope (In-situ Interferometry Transmission Electron Microscope) installed in Toulouse in 2012. The I2TEM is a Hitachi HF-3300 equipped with one pre-specimen electrostatic biprism, three post-specimen biprisms, an image corrector (CEOS B-COR for correcting off-axial aberrations) and two stages (objective stage and Lorentz stage above the objective lens). In the dark-field off-axis scheme [1], electron beams diffracted by an epitaxially grown region are interfered with beams diffracted by the substrate thanks to a post-specimen biprism (Fig. 1(a)). Fig. 1(b-d) is an example obtained on a p-MOSFET like transistor with SiGe source/drain. The deformation is recorded as a frequency modulation (FM) in the hologram (Fig. 1(c)) and it can be calculated from the gradient of the reconstructed phase image (Fig 1(d)). In a recently proposed variant called differential phase contrast dark-field holography (DPCDFEH) [2], a pre-specimen biprism is used to create two overlapping waves on the sample (Fig. 1(e)). The interference of beams diffracted by slightly distant regions is acquired in a defocused plane. The deformation is recorded as a phase modulation (PM) in the hologram (Fig. 1(f)) and the DPC phase is directly proportional to the deformation (Fig. 1(g)). Another option is the 4-wave dark-field setup where two biprisms oriented perpendicularly are used to interfere three reference waves and one object wave (Fig. 1(h-j)). The holographic fringes are modulated in amplitude (AM) and each amplitude contour corresponds to a given displacement of the lattice planes. It can provide live information if a sufficient fringe contrast is achieved. In any case, strain measurement requires a reference wave diffracted by a region of known lattice parameter (usually the substrate). One solution is the “tilted reference wave” (TRW) where a pre-specimen biprism and the condenser system are used to create an object-independent reference wave with an adjustable tilt angle [3]. Fig 2(a,b) is an example acquired in the vacuum and Fig. 2(c,d) shows the dark-field configuration for strain measurement. Finally, a pre-specimen biprism can also be useful for electron diffraction techniques. For instance, one can create two parallel half cones on a specimen (SCBED) with a controllable distance (Fig. 3(a)) [4]. Each spot in the diffraction pattern contains two lobes related to the regions crossed by the two probes. Fig. 1(b) shows an example of SCBED pattern series where the left and right lobes are related to unstrained and increasingly strained regions respectively.

[1] MJ Hÿtch et al, Nature 453 (2008), 1086–1089.
[2] T Denneulin et al, Ultramicroscopy 160 (2016), 98–109.
[3] F Röder et al, Ultramicroscopy 161 (2016), 23–40.
[4] F Houdellier et al, Ultramicroscopy 159, Part 1 (2015), 59–66.

Acknowledgments
This work was funded through the European Metrology Research Programme (EMRP) Project
IND54 Nanostrain. The EMRP is jointly funded by the EMRP participating countries within
EURAMET and the European Union. The authors acknowledge the European Union under the
Seventh Framework Programme under a contract for an Integrated Infrastructure Initiative
Reference 312483-ESTEEM2.
  • Lecture (Conference)
    16th European Microscopy Congress, EMC 2016, 28.08.-02.09.2016, Lyon, France

Publ.-Id: 24668 - Permalink


Electron holography by means of tilted reference waves
Röder, F.; Lubk, A.; Houdellier, F.; Denneulin, T.; Snoeck, E.; Hÿtch, M.;
Off-Axis Electron Holography permits the direct reconstruction of amplitude and phase of electron waves elastically scattered by an object (see, e.g., [1]). The technique employs the Möllenstedt biprism to mutually incline an object modulated wave and a plane reference wave to form an interference pattern at the detector plane. Limited coherence of the electron beam in presence of aberrations attenuates high spatial frequencies of the object exit wave spectrum, which is illustrated by the sideband envelope function for a non-corrected TEM in Fig. 1a. In this work, we explore an extension of the conventional setup given by deliberately tilting the reference wave independent from the object wave. This allows the transfer of spatial frequencies beyond the conventional sideband information limit in Fig. 1a as predicted by a generalized transfer theory for Off-Axis Electron Holography [2]. This is because a reference wave tilted by q0 compensates the berration impact on the spatial frequency q0 of the object wave spectrum. The resulting transfer envelope for a tilt of q0x = -10/nm perpendicular to the post-specimen biprism is shown in Fig. 1b, where the contrast maximum of the total envelope (TCC) is located at q0x. Thus, an off-axis hologram series with varying reference wave tilt allows in principle a linear synthesis of an effective coherent aperture with a radius reaching out beyond the conventional information limit. Furthermore, an object-independent measurement of aberrations as well as dark-field electron holography can be realized using this setup. The experimental realization of an arbitrarily tilted reference wave is challenging and could be realized for the first time at the Hitachi HF3300C I2TEM at CEMES Toulouse for one direction [3]. We used an additional biprism placed in the illumination system. Three condenser lenses were adjusted to provide a demagnified image of the condenser biprism at the sample plane under parallel illumination (Fig. 2). The pre-specimen deflectors were adapted to maintain the incident wave vector of the object wave and to realize a tilt of the reference wave as a function of the condenser biprism voltage. Optimal condenser lens settings were found by means of paraxial ray tracing (Fig. 3) finally producing a mutual tilt of up to 20/nm at the object plane. We verified the kink-like phase modulation of the incident beam by means of holographic measurements. Contrast transfer theory including condenser aberrations and biprism instabilities was applied to explain detailed fringe contrast measurements. Finally, we have experimentally shown that dark-field holography [4] can be conducted with an object-independent reference.

[1] H Lichte et al, Rep. Prog. Phys. 71 (2008) 016102
[2] F Röder et al, Ultramic. 152 (2015) 63-74
[3] F Röder et al, Ultramic. 161 (2016) 23–40
[4] MJ Hÿtch et al, Nature 453 (2008), 1086–1089

Acknowledgments
We thank the Graduate Academy of the TU Dresden for the financial support. The research leading to these
results has received funding from the European Union Seventh Framework Programme under Grant Agreement
312483-ESTEEM2 (Integrated Infrastructure Initiative-I3).
  • Lecture (Conference)
    16th European Microscopy Congress, EMC 2016, 28.08.-02.09.2016, Lyon, Fracne

Publ.-Id: 24667 - Permalink


Direct holographic depth- and lateral- imaging of nanoscale magnets generated by ion impact
Röder, F.; Hlawacek, G.; Wintz, S.; Hübner, R.; Bischoff, L.; Lichte, H.; Potzger, K.; Lindner, J.; Fassbender, J.ORC; Bali, R.
The alloy Fe60Al40 is described by a paramagnetic B2 structure in its ordered phase, which transforms into a ferromagnetic A2 structure by chemical disordering that can be induced locally by ion irradiation [1,2]. This mechanism allows writing arbitrary magnetic nanostructures on paramagnetic thin films e.g. by means of a focused ion beam available in novel scanning ion microscopes. However, reproducible fabrication of nanoscale magnets requires knowledge about the depth and lateral distribution of the induced magnetization in dependence on irradiation parameters. Off-Axis Electron Holography provides suitable insights by revealing the local distribution of the projected magnetic flux density with nanometer resolution [3]. By means of the coherent superposition of an electron wave passing through the object with one passing through vacuum, interference fringes can be formed at the detector plane encoding the amplitude and phase of the electron wave. The phase of an electron wave shifted by electric and magnetic fields of the object permits direct field mapping at the nanometer scale. In cross-sectional samples of irradiated thin films, we studied the effect of the kinetic ion energy ranging from 5-30 keV on the depth distribution of the induced magnetization [4]. In agreement with irradiation damage simulations [2], we found a magnetized film adjacent to the ion entrance surface growing in depth with increasing kinetic ion energy. We conclude that a homogeneous magnetization depth distribution in a 40 nm thick film requires a kinetic Ne+ ion energy of at least 20 keV. The resolution of the ion beam nano-pattering is mainly limited by the effect of lateral ion scattering blurring the magnetization distribution at the pattern edges. To study this effect, we fabricated 500 nm wide magnetized stripes separated by non-ferromagnetic (i.e. non-irradiated) spacers (Fig. 1) using a focused Ne+ ion beam (2 nm probe size) at 25 keV in a helium ion microscope [5]. The flux distribution at the stripe facets is an indicator for the effect of lateral scattering but is difficult to directly interpret in terms of magnetization because of the superposition with stray fields. Therefore, we applied a magneto-static model for the field distribution around the nanoscale magnet as a function of the magnetization blurring, which returns a width of lateral scattering of about 20 nm fitting best to experimental results [4].

[1] J Fassbender et al, Phys. Rev. B 77 (2008) 174430.
[2] R Bali et al, Nanoletters 14 (2014) 435-441.
[3] H Lichte et al, Rep. Prog. Phys. 71 (2008) 016102.
[4] F Röder et al, Sci. Rep. 5 (2015) 16786.
[5] G Hlawacek et al, J. Vac. Sci. Technol. B 32 (2014) 020801.

Acknowledgments
We thank the Ion Beam Center at Helmholtz-Zentrum Dresden-Rossendorf for providing the necessary facilities.
The research leading to these results has received funding from the European Union Seventh Framework
Programme under Grant Agreement 312483 - ESTEEM2 (Integrated Infrastructure Initiative- I3).
  • Poster
    16th European Microscopy Congress, EMC 2016, 28.08.-02.09.2016, Lyon, France

Publ.-Id: 24666 - Permalink


Inducing confined magnetic regions in B2 materials using a nanofocussed light-ion beam
Bali, R.; Röder, F.; Hlawacek, G.; Wintz, S.; Heidarian, A.; Semisalova, A.; Hübner, R.; Bischoff, L.; Potzger, K.; Lichte, H.; Lindner, J.; Fassbender, J.ORC
The use of focussed beams of ions to induce strong saturation magnetization (Ms) can lead to unprecedented flexibility in rapidly producing modulated magnetic materials of desired geometry. True flexibility is achieved if the process is non-destructive i.e., Ms is activated at the point of ion impact. Furthermore, the ion is ideally chemically inert and of low mass, such that it escapes the lattice after undergoing the collision process with host atoms and coming to rest. Here we describe the possibility of using a nano-focussed beam of Ne+ ions to generate ferromagnetic phases within initially non-ferromagnetic B2 materials such as Fe60Al40 and Fe50Rh50. The transition occurs as the penetrating ions displace atoms, and the subsequent vacancy creation and recombination leading to the formation of the chemically disordered A2 structure, which is ferromagnetic. The beam has a diameter of ≈ 2 nm and the transformed region is confined to the interaction volume of the ions with the host atoms, with a diameter < 50 nm. Such an ion-beam is readily available in a He+-ion microscope (where Ne+ can also be loaded). The locally formed ferromagnetic nanostructures are embedded within the electrically conducting B2 precursor material. In the case of Fe60Al40 ferromagnetic regions of Ms = 780 kAm-1 [1] are embedded within a non-ferromagnetic matrix. For Fe50Rh50, ferromagnetic regions of Ms = 1000 kAm-1 [2] can be embedded within an antiferromagnetic matrix. The ion-induced B2 → A2 phase transition is the most viable route to achieving well-defined ferromagnetic nanostructures of desired geometry within non-ferromagnetic metallic matrices. We describe our recent direct nanoscale imaging of ion-induced magnetic regions [3] and our attempts to demonstrate possible applications in spin-transport and magnonic devices.
References:
[1] R. Bali, S. Wintz, F. Meutzner, R. Hübner, R Boucher, A. A. Ünal, S Valencia, A. Neudert, K. Potzger,
J. Bauch, F. Kronast, S. Facsko, J. Lindner, and J. Fassbender, Nano Letters 14, 2, 435 (2014).
[2] Alireza Heidarian, Rantej Bali, Jörg Grenzer, Richard A. Wilhelm, Rene Heller, Oguz Yildirim, Jürgen Lindner and
Kay Potzger, Nucl. Instrum. Methods Phys. Res. B 358, 251-254 (2015).
[3] Falk Röder, Gregor Hlawacek, Sebastian Wintz, René Hübner, Lothar Bischoff, Hannes Lichte, Kay Potzger,
Jürgen Lindner, Jürgen Fassbender, and Rantej Bali, under review, Scientific Reports (2015).
Keywords: Phase transitions, Chemical disorder, Ion beams.
  • Lecture (Conference)
    13th Joint MMM-Intermag Conference, 11.-15.01.2016, San Diego, USA

Publ.-Id: 24665 - Permalink


PRONTOX - proton therapy to reduce acute normal tissue toxicity in locally advanced non-small-cell lung carcinomas (NSCLC): study protocol for a randomised controlled trial
Zschaeck, S.; Simon, M.; Löck, S.; Troost, E. G. C.; Stützer, K.; Wohlfahrt, P.; Appold, S.; Makocki, S.; Bütof, R.; Richter, C.; Baumann, M.; Krause, M.;
BACKGROUND:
Primary radiochemotherapy with photons is the standard treatment for locally advanced-stage non-small cell lung cancer (NSCLC) patients. Acute radiation-induced side effects such as oesophagitis and radiation pneumonitis limit patients' quality of life, and the latter can be potentially life-threatening. Due to its distinct physical characteristics, proton therapy enables better sparing of normal tissues, which is supposed to translate into a reduction of radiation-induced side effects.
METHODS/DESIGN:
This is a single-centre, prospective, randomised controlled, phase II clinical trial to compare photon to proton radiotherapy up to 66 Gy (RBE) with concomitant standard chemotherapy in patients with locally advanced-stage NSCLC. Patients will be allocated in a 1:1 ratio to photon or proton therapy, and treatment will be delivered slightly accelerated with six fractions of 2 Gy (RBE) per week.
DISCUSSION:
The overall aim of the study is to show a decrease of early and intermediate radiation-induced toxicity using proton therapy. For the primary endpoint of the study we postulate a decrease of radiation-induced side effects (oesophagitis and pneumonitis grade II or higher) from 39 to 12%. Secondary endpoints are locoregional and distant failure, overall survival and late side effects.
TRIAL REGISTRATION:
Registered at ClinicalTrials.gov with Identifier NCT02731001 on 1 April 2016.
Keywords: Locally advanced; Non-small-cell lung cancer (NSCLC); Phase II trial; Photon radiotherapy; Proton radiotherapy; Randomised clinical trial; Toxicity

Publ.-Id: 24664 - Permalink


Self Assembly of Magnetic Nanoclusters in Diamond-Like Carbon: A Diffusion Enhanced Process Activated by Collision Cascades
Markwitz, A.; Williams, G.; Osipowicz, T.; Hübner, R.; Saumitra, V.; Gupta, P.;
Improvements in device performance are limited by our capabilities in fabrication techniques. To overcome the current barriers, we need a method to atomically position and configure impurities in sub-micron scale devices. Our recent investigations show that this may be possible. By using hydrogen as atomic “lubricants” during ion implantation, we were able to engineer the position of dopants/impurities in near surface region of semiconducting materials in nanometre level precision. We are currently studying cobalt implantation into diamond-like carbon (DLC) system. The implantation profile of cobalt ions matched theoretical prediction when DLC was lacking of hydrogen. However, when hydrogen was introduced into the base material, the implantation profile was found to be strikingly different. On closer examination it was found that that the impurity atoms track the profile of hydrogen within the material. This brings us to an interesting hypothesis: the physical and chemical interaction between the impurities and the hydrogen atoms allows rearrangement of the impurities by increasing their mobility. The remarkable aspect of this result is that the dopants were manipulated using a room temperature process. This ability will have wide implications for many industries such as: engineering dopant profiles in semiconductor devices, positioning magnetic nanoparticles in magnetic sensors and data storage devices, increasing the capacity of hydrogen storage for fuel cell applications.
  • Invited lecture (Conferences)
    International Union of Materials Research Societies – International Conference on Electronic Materials, IUMRS-ICEM 2016, 04.-08.07.2016, Singapore, Singapore

Publ.-Id: 24663 - Permalink


Self-ordered Ge-based core/shell quantum dots in glass matrix
Buljan, M.; Nekic, N.; Sancho Paramon, J.; Jercinovic, M.; Bogdanovic-Radovic, I.; Grenzer, J.; Hübner, R.; Bernstorff, S.;
Simple fabrication processes of Ge-based nanostructures in glasses are very interesting due to the highly tuneable electronic structure and many relevant applications. We address the recent advances in the production of regularly ordered Ge/Si and Ge/metal core/shell nanostructures formed by magnetron sputtering deposition in glass alumina matrix [1]. The regular ordering of these nanostructures is achieved by the self-ordering growth regime that occurs under specific deposition conditions [2]. We have developed the theory and software for the analysis of such materials by small grazing incidence angle x ray scattering (GISAXS) [3].
The light absorption properties of these films are significantly different compared to films that form quantum dot lattices of the pure Ge, Si, metal or a solid solution of the constituents. The Ge/Si core/shell quantum dots show a strong narrow absorption peak that characterizes a type II confinement in accordance with the theoretical predictions. In addition, we show that the peak position and width depend strongly on the size of Ge core and Si shell [4]. These materials are very interesting for the application in quantum dot solar cells.
[1] M. Buljan, et al., Nanotechnology 26 065602 (2015).
[2] M. Buljan, et al., J. Appl. Cryst. 46, 1490-1500 (2013).
[3] M. Buljan, et al., Acta Cryst. A, 68, 124 (2012); http://homer.zpr.fer.hr/gisaxstudio/doku.php
[4] N. Nekic, et al., (in preparation)
  • Invited lecture (Conferences)
    20th International Vacuum Congress (IVC-20), 21.-26.08.2016, Busan, Korea

Publ.-Id: 24662 - Permalink


Comment on „Dosimetric comparison of stopping power calibration with dual-energy CT and single-energy CT in proton therapy treatment planning“ [Med. Phys. 43(6), 2845-2854 (2016)]
Wohlfahrt, P.ORC; Möhler, C.ORC; Greilich, S.; Richter, C.
A dosimetric comparison of proton treatment planning based on single-energy CT (SECT) and dual-energy CT (DECT) was recently published by Zhu and Penfold in Medical Physics. In this study, the polymer phantom Catphan Module 404 (The Phantom Laboratory, Salem, NY, USA) of known material composition was used to demonstrate an improved accuracy of dose calculation using DECT instead of SECT. To confirm this result in a more realistic human case, the authors show for a single axial CT slice the dose difference of a SECT- and DECT-based treatment plan using the anthropomorphic phantom Rando (Radiological Support Devices, Inc., CA, USA) of unknown composition.
Keywords: dual-energy CT, proton therapy, range uncertainty, absolute range verification

Downloads:

  • Secondary publication expected

Publ.-Id: 24660 - Permalink


What is needed to demonstrate the benefit of dual-energy CT for particle treatment planning?
Möhler, C.ORC; Wohlfahrt, P.ORC; Richter, C.; Greilich, S.
Purpose/Objective:
To thoroughly understand and quantify the benefit of dual-energy CT (DECT) for the reduction of range uncertainty in particle treatment planning.

Material/methods:
In a multi-step procedure, DECT-based direct prediction of stopping-power ratios (SPRs) was improved in accuracy, robustness and clinical applicability by optimizing CT scan protocols, as well as post-reconstruction voxelwise SPR calculation algorithms. Subsequently, it was verified by three independent, yet complementary, studies in comparison to the current clinical standard (single-energy CT, SECT): (A) a relative comparison in patient cases; two absolute comparisons in (B) a controlled experimental setting measuring photon and ion absorption in animal tissues and tissue base components; and in (C) an inhomogeneous head phantom providing a well-established ground truth (Figure 1).

Results:
For a large collective of proton therapy patients (A), substantial intra- and inter-patient variability in CT-number-to-SPR-conversion as well as relative range differences of about 1.5-2.5% between SECT- and DECT-based treatment plans were observed. Both reveal the relevance of accurate CT-based SPR prediction and the potential for improvement. While naturally missing in patient studies, a reliable ground truth was provided in (B) and (C) to allow for absolute evaluations of SPR accuracy. The DECT method hereby proved capable to correctly predict SPR of homogenized animal tissues, tissue base components and the tissue substitutes in the anthropomorphic head phantom within measurement uncertainty.

Conclusion:
Only with the all-encompassing combination of theoretical considerations, lab experiments and the analysis of patient data, we are able to demonstrate clinically relevant reduction of range uncertainty with DECT-based treatment planning.

All authors contributed equally.
Keywords: dual-energy CT, proton therapy, particle therapy, range uncertainty
  • Lecture (Conference)
    56th Annual Conference of the Particle Therapy Co-operative Group (PTCOG), 08.-13.05.2017, Kanagawa, Japan

Publ.-Id: 24659 - Permalink


A novel metal flow imaging using electrical capacitance tomography
Wondrak, T.; Soleimani, M.;
The measurement of gas-liquid metal two phase flow is a challenging task due to the opaqueness and the high temperatures. For instance, during continuous casting of steel the distribution of argon gas and liquid steel in the submerged entry nozzle is of high interest, since it influences the quality of the produced steel. In this paper we present the results of a feasibility study for applying the electrical capacitance tomography (ECT) to detect the outer surface of a liquid metal stream. The results of this study are the basis for the development of a new contactless sensor which should be able to detect the outer shape of a liquid metal using ECT and the bubbles inside the jet at the same time using mutual inductance tomography.
Keywords: electrical capacitance tomography, liquid metal, surface detection

Publ.-Id: 24658 - Permalink


Improved Efficiency by Adaptive Processing
van den Boogaart, K. G.; Gutzmer, J.; Reuter, M. A.; Tolosana Delgado, R.;
- Get more value out of the ground
- Pick-and-choose your required tools based on NPV established criteria
- Understand how the realized value depends on you as a manager and investor
Keywords: NPV, Adaptive Processing, Optimisation
  • Lecture (others)
    Mines & Technology, 29.11.-01.12.2016, London, Great Britain

Publ.-Id: 24657 - Permalink


What CEOs and Investors should know about process optimization
van den Boogaart, K. G.; Gutzmer, J.; Reuter, M. A.; Tolosana Delgado, R.;
Geometallurgy, long term mine planing, automated scheduling and other instances of software assisted process control and optimization rapidly gain importance in the mining sector. Decisions are taken based on big data and predictive models. Comparisons show substantial - but not always positive - effects on NPV, reliability, efficiency and recovery. Automated optimization is however not a technology like every other. It changes how we approach decision making and can easily gain or lose big money. CEOs and investors need to be aware of the chances, the pitfalls and the fundamental mechanisms of this industrial transformation. The presentation will demonstrate some of the relevant effects and principles on worked examples and extract the important implications for leading engineers, CEOs and investors. It shows how in this context disregarding uncertainty ruins your company, how classical KPIs and company structures cut the NPV, and why investors need to ask new questions. But it also shows how a rigorous and integrated approach to decisions making can help to increase net profit substantially. Leading the mining business into the 4th industrial revolution requires a deep understanding of these effects. Let's get started.
Keywords: Adaptive Processing, Geometallurgy, NPV
  • Lecture (others)
    PDAC, Prospectors and Developers Conference, 05.-08.03.2017, Toronto, Canada

Publ.-Id: 24656 - Permalink


Ionospheric tomography by gradient-enhanced kriging with STEC measurements and ionosonde characteristics
Minkwitz, D.; van den Boogaart, K. G.; Gerzen, T.; Hoque, M.; Hernandez-Pajares, M.;
The estimation of the ionospheric electron density by kriging is based on the optimization of a parametric measurement covariance model. First, the extension of kriging with slant total electron content (STEC) measurements based on a spatial covariance to kriging with a spatial-temporal covariance model, assimilating STEC data of a sliding window, is presented. Secondly, a novel tomography approach by gradient enhanced kriging (GEK) is developed. Beyond the ingestion of 5 STEC measurements, GEK assimilates ionosonde characteristics providing peak electron density measurements as well as gradient information. Both approaches deploy the 3D electron density model NeQuick as a priori information and estimate the covariance parameter vector within a maximum likelihood estimation for the dedicated tomography time stamp. The methods are validated in the European region for two periods covering quiet and active ionospheric conditions. The kriging with spatial and spatial-temporal covariance model is analysed regarding its capability to reproduce STEC, differential STEC and foF2. 10 Therefore the estimates are compared to the NeQuick model results, the 2D TEC maps of the International GNSS Service and the DLR’s Ionospheric Monitoring and Prediction Center, and in case of foF2 to two independent ionosonde stations. Moreover, simulated STEC and ionosonde measurements are used to investigate the electron density profiles estimated by the GEK in comparison to a kriging with STEC only. The results indicate a crucial improvement of the initial guess by the developed methods and point out the potential compensation of a bias in the peak height hmF2 by means of GEK.
Keywords: STEC, VTEC, Geostatistics, Kriging of functionals

Publ.-Id: 24655 - Permalink


Measurements pf the diameter of rising gas bubbles by means of the ultrasound transit time technique
Richter, T.; Wondrak, T.; Eckert, K.;
This study presents ultrasound transit time technique (UTTT) measurements of single Ar bubbles rising in Galinstan under an applied magnetic field. Two setups were used to analyze the bubble rise, which led to different bubble trajectories. UTTT was able to visualize the bubble trajectory and to measure the bubble diameters. Due to the straightening of the bubble trajectories with increasing magnetic field, variation of the apparent bubble diameter were detected.
  • Poster
    10th PAMIR International Conference -- Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italia
  • Contribution to proceedings
    10th PAMIR International Conference -- Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italia, 978-88-90551-93-2, 542-546

Publ.-Id: 24654 - Permalink


Contactless inductive flow tomography for a simplified model of Czochralski crystal growth
Wondrak, T.; Pal, J.; Stefani, F.; Eckert, S.;
In the Czochralski crystal growth the poloidal flow structure in the melt just below the meniscus plays a key role for the quality of the crystal. In order to investigate the applicability of the contactless inductive flow tomography to such a configuration, we equipped a modified Rayleigh-Benard setup with an axial excitation magnetic field and 20 magnetic field sensors. In this paper we present measurements of the flow induced magnetic field perturbations for several temperature gradients between the cooled top and the heated bottom. Typical features of the thermally driven turbulent flow could be detected in the magnetic field measured around the fluid vessel. Additionally, we will show first reconstructions of the flow.
  • Poster
    10th PAMIR International Conference -- Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italia
  • Contribution to proceedings
    10th PAMIR International Conference -- Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italia, 978-88-90551-93-2, 346-350

Publ.-Id: 24653 - Permalink


Dry calibration of a new generation local Lorentz force flowmeter
Hernandez, D.; Karcher, C.; Wondrak, T.;
Local Lorentz force velocimetry (LFV) is a local velocity measurement technique for liquid metals. Due to the interaction between an electrically moving liquid and an applied magnetic field, eddy currents and flow-braking Lorentz forces are induced within the fluid. Due to Newtons’s third law, a force of the same magnitude acts on the source of the applied magnetic field which is in our case a permanent magnet. The magnet is connected to a new generation L2F2 that has been especially developed to record all these three force and three torque components. This sensor has already been tested at a continuous casting model with a 15 mm cubic magnet providing an insight of the 3-D velocity distribution of GaInSn near the wide face of the mold. For a better understanding of these results, especially regarding torque sensing, we propose dry experiments which consist on replacing the flowing liquid by a moving solid. In this kinematic approach, where the velocity field is already given, we are able to decrease considerably the variability and the noise of the measurements providing an accurate calibration of the system. In this paper we present the numerical results using a rotating disc made of aluminum and two different magnet systems that move across the plane of its axis of rotation.
  • Poster
    10th PAMIR International Conference -- Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italia
  • Contribution to proceedings
    10th PAMIR International Conference -- Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italia, 978-88-90551-93-2, 198-202

Publ.-Id: 24652 - Permalink


Visualization of the global flow structure in a modified Rayleigh-Bénard setup using the contactless inductive flow tomography
Wondrak, T.; Pal, J.; Stefani, F.; Galindo, V.; Eckert, S.;
Rayleigh-Bénard (RB) convection is not only a classical problem in fluid dynamics, but also plays an important role in many metallurgical applications, like Czochralski crystal growth. The measurement of the flow field and of the dynamics of the emerging large-scale circulation (LSC) in liquid metals is a challenging task due to the opaqueness and the high temperature of the melt. The contactless inductive flow tomography (CIFT) is able to visualize the mean three dimensional flow structure in liquid metals by measuring the flow induced magnetic field perturbations under the influence of one, or several, applied magnetic fields. In this paper, the first measurements of the flow induced magnetic field in a RB setup, which can be used to investigate the dynamics of the LSC, will be presented. Additionally, the quality of the reconstruction of the three dimensional flow field, for such a configuration, will be investigated numerically.
Keywords: Contactless inductive flow tomography, flow measurement, liquid metal
  • Contribution to proceedings
    WCIPT8 - 8th World Congress on Industrial Process Tomography, 26.-29.09.2016, Foz do Iguacu, Brasilia
  • Lecture (Conference)
    WCIPT8 - 8th World Congress on Industrial Process Tomography, 26.-29.09.2016, Foz do Iguacu, Brasilia

Publ.-Id: 24651 - Permalink


Detection of the shape of liquid metals using electrical capacitance tomography
Wondrak, T.; Zhang, M.; Soleimani, M.;
In metallurgical processes gas-liquid metal two-phase flows play an important role. The monitoring of single bubbles in a free liquid metal jet is quite challenging due to the high temperature and the opaqueness of the melt. In this paper we investigate the applicability of the electrical capacitance tomography (ECT) for imaging the outer surface of a liquid metal strand. The results of this feasibility study are the basis for the development of a new sensor combining ECT for the detection of the outer shape of the jet and mutual induction tomography (MIT) for the detection of bubbles inside the jet at the same time. In order to show the principal applicability, we will present a first static measurement of the level of the eutectic alloy GaInSn in a pipe. An ECT sensor with 12 electrodes was mounted on the outer surface of an acrylic glass pipe with inner diameter of 70 mm. For different levels of liquid metal in the cross section of the sensor, the capacitance was measured and the image was reconstructed. Additionally, we will shorty discuss the challenges of the application of ECT in this setup, such as the wettability of the material of the pipe with liquid metal.
Keywords: electrical capacitance tomography, liquid metal, surface detection
  • Contribution to proceedings
    WCIPT8 - 8th World Congress on Industrial Process Tomography, 26.-29.09.2016, Foz do Iguacu, Brasilia
  • Lecture (Conference)
    WCIPT8 - 8th World Congress on Industrial Process Tomography, 26.-29.09.2016, Foz do Iguacu, Brasilia

Publ.-Id: 24650 - Permalink


Experimental setup for first in-phantom measurements of magnetic field effects on dose distributions of proton pencil beams
Hoffmann, A.; Schellhammer, S.; Gantz, S.; Zeil, K.; Lühr, A.;
Purpose: To present an experimental measurement setup for MR-integrated proton therapy (MRiPT) dosimetry studies of magnetic field-induced dose distortion effects on slowing down proton pencil beams in a tissue-equivalent phantom.

Methods: A 0.95 T NeFeB permanent dipole magnet was utilized to generate a transverse magnetic field over a 4x20x15 cm3 air gap. A PMMA slab phantom with Gafchromic EBT3 film was placed inside the air gap to measure planar dose distributions of 80-180 MeV proton pencil beams. Integrated depth-dose curves, beam trajectories, range and deflection of the Bragg peak were extracted from the films. A 3D finite-element model -- developed to generate magnetic vector field data -- was experimentally validated by Hall probe magnetometry. Repeated measurements of the magnetic field strength were performed to assess its stability during irradiation experiments.

Results: The modelled magnetic vector field data differed less than 2% from the measured data. Magnetic field-induced beam deflection was clearly observed from the planar dose distributions (Fig. 1). Integrated depth-dose curves showed a similar form in comparison to measurements without magnetic field. Lateral displacement of the Bragg peak increased with energy from 1 to 10 mm for 80 and 180 MeV, respectively (Fig. 2). Spot measurements of the magnetic field strength showed high reproducibility (sigma=3 mT) and no effects of radiation-induced degradation.

Conclusion: For the first time, a measurement setup to study magnetic field-induced proton beam dose effects in a film phantom has been realized. The method is instrumental for building and validating Monte Carlo beam models for future MRiPT concepts.
Keywords: Proton therapy, magnetic field, film dosimetry
  • Open Access LogoAbstract in refereed journal
    International Journal of Particle Therapy 4(2017)1, 58-58

Publ.-Id: 24649 - Permalink


Recent developments on contactless inductive flow tomography for continuous casting
Wondrak, T.; Ratajczak, M.; Stefani, F.; Timmel, K.; Eckert, S.;
In continuous casting the flow of the liquid steel in the mold has great impact on the quality of the produced steel. During casting even a rough knowledge of the flow field would be highly desirable in order to control process parameters or electromagnetic actuators. The high temperature of the liquid steel recommends a contactless measurement technique.
The contactless inductive flow tomography (CIFT) is able to reconstruct the dominating two-dimensional flow structure in a slab casting mold by measuring the perturbation of an applied magnetic field outside the mold and solving a linear inverse problem. In this paper we will give an overview of the application of CIFT to two models of continuous casting available at the Helmholtz-Zentrum Dresden – Rossendorf. For a physical model of a mold with a cross section of 140 mm × 35 mm we present the new measurement system using induction coils and show preliminary measurements of the flow field in the mold in the presence of a magnetic brake. In addition, we show first reconstructions of the flow field in a mold with the cross section of 400 mm × 100 mm demonstrating the upward scalability of CIFT. We will conclude with recent developments towards an implementation in industry.
  • Lecture (Conference)
    SCANMET V - 5th International Conference on Process Development in Iron and Steelmaking, 12.-16.06.2016, Lulea, Schweden
  • Contribution to proceedings
    SCANMET V - 5th International Conference on Process Development in Iron and Steelmaking, 12.-16.06.2016, Lulea, Schweden
    Book of abstracts, 978-91-639-1232-7, 131

Publ.-Id: 24648 - Permalink


Contactless inductive flow tomography: inverse problem and applications
Wondrak, T.; Ratajczak, M.; Stefani, F.;
In many industrial applications dealing with liquid metals even a rough knowledge of the flow field of the melt would be of high value. For instance, in continuous casting of steel the flow of the melt in the upper region of the mold is very important for the quality of the produced steel, regarding surface defects or the number of inclusions. The high temperatures and the chemical aggressiveness of liquid melts recommend contactless measuring techniques. Well-established optical methods like particle image velocimetry are not applicable, because of the opaqueness of the melt.
Due to the high electrical conductivity of liquid metals, inductive methods can be used. One of them is the Contactless Inductive Flow Tomography (CIFT) which allows the reconstruction of the mean three-dimensional flow structure of conducting liquids. CIFT works by applying one or more magnetic fields to the melt and measuring the flow induced perturbation of those fields outside the fluid volume. From these measurements the mean three dimensional velocity field can be reconstructed by solving a linear inverse problem similar to magnetoencephalography. In order to handle the non-uniqueness, Tikhonov regularization in combination with the L-curve method is used.
In this paper we will give an overview about the mathematical foundation of CIFT and delineate the linear inverse problem. In order to illustrate the numerical model and the regularization, we will show numerical and physical results of a model of a continuous caster and of a Rayleigh-B ́enard convection setup. Complementary Ultrasound Doppler Velocimetry measurements will be shown to be in good agreement with the reconstructed flow using CIFT. We will conclude with a short overview of the challenges to measure the flow induced magnetic field perturbations, which are usually about 3 to 4 magnitudes smaller than the applied magnetic field.
  • Lecture (Conference)
    22nd Inverse Days 2016, 13.-15.12.2016, Kuopio, Finnland

Publ.-Id: 24647 - Permalink


First experimental results of applying the contactless inductive flow tomography to a thermally driven convection problem motivated by Czochralski crystal growth
Wondrak, T.; Pal, J.; Stefani, F.; Eckert, S.;
In Czochralski crystal growth (CZ) the flow structure of the liquid silicon in the crucible and especially below the meniscus plays an important role for the quality of the grown crystal, because it controls the mass flow and the temperature gradient. A direct measurement of the flow would be highly desirable. However, the melt temperature of more than 1420°C, its corrosive impact on most materials, and the high demands on its purity, makes the flow measurement a complicated task. The contactless inductive flow tomography (CIFT) is able to reconstruct the approximate flow structure in conducting liquids [1]. Exposing the liquid to one or multiple applied magnetic fields and measuring the flow induced magnetic field around the fluid volume, it is possible to infer the velocity field by solving a linear inverse problem with appropriate regularization techniques. Great challenges for applying CIFT to the Cz process are, first, the small poloidal melt velocities in the order of a few cm/s and, second, the large distance between the liquid silicon and the magnetic field sensors which are located outside the puller. After having carried out successfully some preliminary magnetic field measurements at a real industrial Cz puller, we are presently evaluating the applicability of CIFT for small velocities.
A modified Rayleigh-Bénard (RB) setup has been chosen, which was already used to model and control temperature fluctuations in a Cz setup [2]. The growing crystal rod is simulated by a “cold finger” placed on the top of the cylindrical geometry. The diameter of the cold finger is about one third smaller than the heated bottom part. As working fluid GaInSn was used. Large efforts were made to adapt CIFT to the experimental setup in order to compensate thermal expansion during the measurement.
We will present preliminary results which demonstrate the applicability of CIFT on thermally driven convection systems. Typical features of the thermally driven turbulent flow were detected in the magnetic field measurements and were also verified by simultaneous temperature measurements recorded by small thermocouples placed in the vicinity of the rim of the cold finger.

References
1. F. Stefani, G. Gerbeth, T. Gundrum, Physical Review E, 70 (2004), 056306
2. A. Cramer, M. Röder, J. Pal, G. Gerbeth, Magnetohydrodynamics, 46 (2010), 353-361
  • Poster
    1st German Czechoslovak Conference on Crystal Growth - GCCCG-1, 16.-18.03.2016, Dresden, Deutschland

Publ.-Id: 24646 - Permalink


3D Druck – ein anschauliches Präsentationsmittel für geophysikalische Inhalte
Menzel, P.; Götze, H.-J.; Schmidt, S.; Steinberg, A.;
Für die öffentliche Kommunikation geophysikalischer Arbeiten spielt eine anschauliche Präsentation der Sachverhalte eine entscheidende Rolle. Seit in den 1980er Jahren erste Ansätze für Rapid Prototyping vorgestellt wurden, hat sich die Technologie von 3D Druckern stetig weiterentwickelt und wird inzwischen regelmäßig in verschiedenen wissenschaftlichen Disziplinen von den Ingenieurswissenschaften bis hin zu Medizin und Chemie eingesetzt, um Vorserien-Prototypen, Bau- und Ersatzteile sowie Anschauungsmodelle günstig und schnell produzieren zu können. In den Geowissenschaften und speziell in der Geophysik wurden diese Verfahren bisher sehr selten, zur Anfertigung von Ersatz- und Zusatzteilen für verschiedene Messinstrumente, verwendet. Im Rahmen des DGMK-Projektes TiPot3D wurde in der Arbeitsgruppe Geophysik und Geoinformation der Christian-Albrechts-Universität zu Kiel ein 3D Drucker Ultimaker² angeschafft und steht dort seit 2013 für spezielle geophysikalische Anwendungen bei der Interpretation und für die Visualisierung von 3D Modellen der Erdkruste zur Verfügung. Für die Präsentation von Daten nach einem 3D Druck ist kein zusätzliches Equipment notwendig. Diese neue Visualisierungsmöglichkeit bietet sich somit vor allem dann als Kommunikationsmedium an, wenn die Präsentation z.B. mittels 3D Computergrafik nicht angemessen ist oder technisch nicht in Frage kommt. Um Daten und Modelle mit Hilfe des 3D Drucks zu repräsentieren, müssen die Eingabedaten als digitale triangulierte Geometriemodelle vorliegen oder aber in diese überführt werden. Es wird anhand mehrerer unterschiedlicher Beispiele (z.B. 3D Untergrundmodelle aus Seismik und Gravimetrie, sowie Erdbebendeformationskarten) gezeigt, in welcher Weise geophysikalische Daten und Ergebnisse unterschiedlicher Komplexität für den 3D Druck aufbereitet und repräsentiert werden. Generell lassen sich die meisten geophysikalischen Datensätze mittels 3D Druck repräsentieren. Der zu betreibende Aufwand hängt dabei sowohl von der Komplexität der Eingabedaten, als auch vom kommunikativen Zweck und der beabsichtigten Größe des zu druckenden Datensatzes ab. Die gezeigten Ergebnisse haben sich vor allem für fachfremdes Publikum als ein eindrucksvolles Präsentationsmittel erwiesen.
Keywords: Geophysik, Visualisierung, 3D Druck
  • Poster
    77. Jahrestagung der Deutschen Geophysikalischen Gesellschaft, 27.-30.03.2017, Potsdam, Deutschland

Publ.-Id: 24645 - Permalink


Contactless inductive flow tomography for industrially relevant applications
Wondrak, T.; Ratajczak, M.; Stefani, F.; Pal, J.; Timmel, K.; Eckert, S.;
The contactless inductive flow tomography (CIFT) allows reconstructing the mean 3-dimensional flow structure of liquid melts by measuring the flow induced perturbations of one or more applied magnetic fields. These measurements are utilized to infer the flow field by solving a linear inverse problem using an appropriate regularization. We will give an overview of the application of CIFT to two models of continuous casting available at the Helmholtz-Zentrum Dresden-Rossendorf and report recent developments towards an implementation in industry. Additionally, we present preliminary results of CIFT applied to a thermally driven flow with some similarity to Czochralski silicon crystal growth. Due to the low velocities in the order of 1 cm/s, the dynamic range of the measurement system has to be enhanced by about one order of magnitude in comparison with the continuous casting application.
  • Lecture (Conference)
    2016 TMS Annual Meeting & Exhibition, 14.-18.02.2016, Nashville (Tennessee), USA

Publ.-Id: 24644 - Permalink


First experimental insights into the transition from AMRI to HMRI
Seilmayer, M.ORC
In the last years the magnetorotational instability (MRI) was focused intensively by theory and experiments. It turns out that investigating the standard MRI (SMRI), with its magnetic field pointing perpendicular to the rotation direction, is very hard. It is only possible to get this type of instability in rather large (1 m-scale) or fast rotating (f > 10 Hz) cylinders. Beside that two other types of MRI were discovered[1, 2]. The helical and azimuthal MRI, which where successfully investigated in the laboratory with the PROMISE2 facility. This setup consists of two concentric cylinders, a current carrying rod on the axis producing Bϕ and a cylindrical coil providing Bz to the fluid. In the past, experiments proved the theory of each individual instability [3, 4].
With the improved magnetic field system the PROMISE3 setup gains advantage of a more homogeneous magnetic field. So it becomes possible now to observe the transition between these two instabilities. First we like to give a prove of function and show how the velocity distribution and other properties changed with the improved magnetic field. Next to that we like to present very first results on the mode transition form the AMRI unstable m = 1 regime to the HMRI unstable m = 0 case. Here we start in a AMRI unstable parameter set (Re = 1500, Ha = 100 and µ = Ωout /Ωin = 0.26). By increasing the axial magnetic field Bz the AMRI m = 1 mode is disturbed successively until it is completely damped. At a certain field strength the other m = 0 mode emerges which also disappears at higher fields.
Finally we can conclude that AMRI and HMRI still work in the modified experiment according to the theory. There is a possible transition region between these two instabilities. One open question is why the flow structure changes so significant for AMRI in comparison to the PROMISE2 campaign [3]. And would it be better to improve the field further?

References
[1] G. Rüdiger et al., AN, 328(10):1158-1161, 2007.
[2] G. Rüdiger et al., AN, 329(7):659-666, 2008.
[3] M. Seilmayer et al., PRL, 113(2):024505, 2014.
[4] F. Stefani et al., NJP, 9(8):295, 2007.
Keywords: AMRI, magnetic field, magnetohydrodynamic, experiment
  • Lecture (Conference)
    17th MHD Days, 30.11.-02.12.2016, Göttingen, Deutschland

Publ.-Id: 24643 - Permalink


Modeling Traveling-wave Thomson scattering using PIConGPU
Debus, A.; Steiniger, K.; Pausch, R.; Huebl, A.; Schramm, U.; Cowan, T.; Bussmann, M.;
Traveling-wave Thomson scattering (TWTS) laser pulses are pulse-front tilted and dispersion corrected beams that enable all-optical free-electron lasers (OFELs) up to the hard X-ray range. Electrons in such a side-scattering geometry experience the TWTS laser field as a continuous plane wave over centimeter to meter interaction lengths.
After briefly discussing which OFEL scenarios are currently numerically accessible, we detail implementation and tests of TWTS beams within PIConGPU (3D-PIC code) and show how numerical dispersion and boundary effects are kept under control.
Keywords: TWTS, FEL, free-electron laser, particle-in-cell code, PIC
  • Lecture (Conference)
    DPG Frühjahrstagung Darmstadt 2016, 14.-18.3.2016, Darmstadt, Deutschland

Publ.-Id: 24642 - Permalink


Scaling EUV and X-ray Thomson Sources to Optical Free-Electron Laser Operation with Traveling-Wave Thomson Scattering
Debus, A.; Steiniger, K.; Albach, D.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.;
Abstract
Traveling-Wave Thomson-Scattering (TWTS) provides optical undulators with hundreds to thousands of undulator periods from high-power, pulse-front tilted lasers pulses. These allow to realize optical free-electron lasers (OFELs) with state-of-the-art technology in electron accelerators and laser systems in TWTS. The talk focuses on experimental realization and the combination of TWTS and laser-wakefield acceleration allowing for ultra-compact, inherently synchronized and highly brilliant light sources.

Summary
Traveling-Wave Thomson-Scattering (TWTS) employs a side-scattering geometry where 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 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 over the whole laser pulse width while the electrons cross the laser beam path. TWTS thus allows to control the interaction length 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 photon yield of TWTS sources can therefore be orders of magnitude higher than that of 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.

Two key features of TWTS allow for the realization of optical free-electron lasers (OFELs). First, it provides optical undulators with lengths required for microbunching and thus coherent radiation amplification. Second, the variability in interaction angle allows to control the electron beam quality requirements for a target radiation wavelength. This is used to reduce the electron beam quality requirements to a level technically feasible today. 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. 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: TWTS, FEL, free-electron laser, EUV, xray
  • Lecture (Conference)
    17th Advanced Accelerator Concepts Workshop, 31.07.-5.8.2016, National Harbor, MD, USA

Publ.-Id: 24641 - Permalink


Recent advances in PIConGPU methods for modeling lasers, ionization and radiation
Debus, A.; Pausch, R.; Garten, M.; Burau, H.; Huebl, A.; Widera, R.; Irman, A.; Schramm, U.; Bussmann, M.;
Abstract
We present recent simulations of laser wakefield acceleration (LWFA) and nonlinear Thomson scattering performed with the fully relativistic 3D3V particle-in-cell code PIConGPU. These cover both experimental setups currently carried out at HZDR and setups beyond state-of-the-art experiments. We discuss the recent advances in our code that allowed performing these simulations and examine their physical implications in detail.

Summary
The simulations presented require a variety of algorithmic extensions to the standard particle-in-cell cycle. These include a laser implementation which allows more freedom in modifying the simulated laser to describe the experimentally available laser to a high degree of accuracy, including setups ranging from simple chirping to TWTS-type laser pulses. These extensions also encompass a variety of ionization schemes, including BSI and ADK, for which we will discuss the physical foundation and the performance implications. Our code also provides algorithms for both classical radiation reaction effects, based on Landau and Lifshitz, and QED recoil to include radiation losses, as they occur for example during betatron oscillation. Furthermore, PIConGPU also provides in-situ synthetic radiation diagnostics: a classical radiation diagnostic, based on Liénard-Wiechert potentials, that allows predicting coherent and incoherent radiation spectra simultaneously for hundreds of observation directions and thousands of frequencies and a just recently implemented extension to include QED based photon generation and electron recoil beyond the classical scope. Encompassing these new algorithms and still being able to reach performances that allow large scale parameter scans is crucial and was only possible by strictly following an in-situ approach and efficiently using the GPU hardware, which will be discussed in detail.

The simulation presented will cover the emission expected during nonlinear Thomson scattering as experimentally performed with the DRACO laser and the ELBE accelerator at HZDR. We will further discuss the simulated plasma dynamic, electron acceleration and resulting X-ray signatures from laser wakefield acceleration for various He/N gas mixture and compare these to experiments. Furthermore we will present a radiation sky map of LWFA containing various spectral signatures to diagnose the plasma dynamic and new accelerator schemes.
Keywords: PIC, PIConGPU
  • Poster
    17th Advanced Accelerator Concepts Workshop, 31.07.-5.8.2016, National Harbor, MD, USA

Publ.-Id: 24640 - Permalink


Monte Carlo simulations of magnetic field effects on proton dose distributions in a 1T measurement setup
Schellhammer, S. M.ORC; Oborn, B.; Lühr, A.; Gantz, S.; Bussmann, M.; Hoffmann, A. L.
For an integration of proton therapy and magnetic resonance Imaging (MRI), mutual effects of these two modalities need to be assessed. We studied the magnetic field-induced proton beam deflection as well as the radiation-induced activation and demagnetization of the magnet material by simulating irradiation experiments with a realistic magnet.

Geant4 Monte Carlo simulations were performed for 80-180 MeV proton pencil beams traversing the 0.95 T transverse magnetic field of a dipole magnet. A PMMA slab phantom containing a radiochromic EBT3 film was placed between the magnetic poles, such that the incident beams were stopped in the film plane (Fig. 1). The magnetic field was modelled using 3D finite-elements and validated by magnetometry. Beam trajectories were analyzed from the film’s planar dose distributions. Upper bounds for radioactivation were deduced by analyzing the most common mother nuclides, and demagnetization was assessed by relating the simulated magnet dose to previously published data.

Considerable magnetic field-induced dose distortions can be observed from the planar dose distributions, as depicted for a 140 MeV beam in Fig 2. Lateral displacement of the Bragg peak ranged from 1-11 mm for 80-180 MeV beams. Initial activation of the magnet material was less than 25 kBq, and the mean dose to the magnet poles was ~20 μGy when delivering a dose of 2Gy at the Bragg peak to the film.
These results indicate that the Lorentz force-induced dose distortions are substantial, and measurable with the presented setup. Radiation-induced activation and demagnetization effects are small but should be monitored during the irradiation experiments.
  • Poster
    PTCOG56 - 56th Annual Conference of the Particle Therapy Co-Operative Group, 11.-13.05.2017, Yokohama, Japan

Publ.-Id: 24639 - Permalink


Animal PET/MR - a modern tool for radiotracer development and molecular imaging
Brust, P.;
Es ist kein Abstract vorhanden.
  • Invited lecture (Conferences)
    Kolloquien Thammasat University, Mahidol University, Chiang Mai University, 22.-31.10.2016, Bangkok, Thailand

Publ.-Id: 24638 - Permalink


Use of animal PET/MR for radiotracer development and molecular imaging
Brust, P.;
Es ist kein Abstract vorhanden.
  • Invited lecture (Conferences)
    TransportDementia2, 02.-06.09.2016, Oslo, Norway

Publ.-Id: 24637 - Permalink


Effiziente Nutzung mineralischer und metallhaltiger Rohstoffe
Reuter, M. A.;
Ziel dieses Workshops ist es, programmübergreifende Schnittstellen in der Materialforschung zu stärken und Synergien zu nutzen.
  • Invited lecture (Conferences)
    Materialien und Modelierung - Workshop, 08.-09.11.2016, Berlin, Deutschland

Publ.-Id: 24636 - Permalink


Challenges in the analysis of mineral surfaces in flotation technology
Firkala, T.; Lederer, F.; Pollmann, K.; Rudolph, M.;
Flotation is one of the most traditional and widely used technologies in industrial mineral processing. This methodology is based on changing the hydrophobic behaviour of the mineral surfaces using organic flotation collector molecules. The mineral – collector interactions in the flotation interface are very important for the detailed understanding of the technology, but presently they are practically unexplored. We present our concepts to study the flotation interface applying some ultrasensitive nanospectroscopic facilities of Helmholtz Institute Freiberg for Resource Technology and Helmholtz-Zentrum Dresden-Rossendorf.
  • Lecture (others)
    University of Applied Sciences Wildau, Department Seminar, 12.12.2016, Wildau, Deutschland

Publ.-Id: 24635 - Permalink


Experimental study on rise velocities of single bubbles in liquid metal under the influence of strong horizontal magnetic fields in a flat vessel
Strumpf, E.;
The ascent of single argon bubbles with equivalent diameters (deq) between 3.43 and 6.28 mm is investigated at room temperature in a flat, cubic vessel by means of Ultrasound Doppler Velocimetry (UDV). GaInSn is used as a working liquid and magnetic flux intensities up to B ≈ 0.918 T are applied. A decelerating effect on the rise velocity is observed at lower, an accelerating effect at medium and a reduction at higher field strengths. Maximum velocities are achieved when N/CD ≈ 1, bubble paths are substantially rectilinear at N/CD > 2. The mean ascent velocities are compared with literature and data of this work as well of other publications is provided in tables.
Keywords: bubble, rise velocity, liquid metal, magnetic field, ultrasound

Downloads:

Publ.-Id: 24634 - Permalink


Alpaka - One Programming Model for Parallel Kernel Acceleration of Heterogeneous Systems
Matthes, A.; Zenker, E.; Worpitz, B.; Widera, R.; Huebl, A.; Juckeland, G.; Knüpfer, A.; Nagel, W.; Bussmann, M.;
Alpaka provides a uniform, abstract C++ interface to a range of parallel programming models. It can express multiple levels of parallelism and allows for generic programming of kernels either for a single accelerator device or a single address space with multiple CPU cores. The Alpaka abstraction of parallelization is influenced by and based on the groundbreaking CUDA abstraction of a multidimensional grid of blocks of threads. The four main execution hierarchies introduced by Alpaka are called grid, block, thread, and element level. The element level denotes an amount of work a thread needs to process sequentially. These levels describe an index space which is called work division.

Alpaka does not dictate any memory containers nor memory iterators, instead it is based on a simple pointer based memory model, allowing to allocate memory buffers device-wise and copy them between devices. This model provides full power over data structures and their data access and is totally data structure agnostic.

Separating parallelization abstraction from specific hardware capabilities allows for an explicit mapping of these levels to hardware. The current implementation includes mappings to programming models, called back-ends, such as OpenMP, CUDA, C++ threads, and boost fibers. Nevertheless, mapping implementations are not limited to these choices and can be extended or adapted for application-specific optimizations. Which back-end and work division to utilize is parameterized per kernel within the user code.

We have demonstrated platform and performance portability for the DGEMM benchmark, which provides consistently 20% of the theoretical peak performance on AMD, Intel, IBM, and NVIDIA hardware, being on par with the respective native implementations. Moreover, performance measurements of a real world application (PIConGPU, HASEonGPU, ISAAC) translated to Alpaka unanimously demonstrated that Alpaka can be used to write performance portable code.
Keywords: Heterogeneous computing, HPC, C++, CUDA, OpenMP, platform portability, performance portability
  • Lecture (others)
    GPU Technology Conference Europe, 28.-29.09.2016, Amsterdam, Niederlande

Publ.-Id: 24633 - Permalink


Quasiparticle Excitations in the Superconducting State of FeSe Probed by Thermal Hall Conductivity in the Vicinity of the BCS–BEC Crossover
Watashige, T.; Arsenijevic, S.; Yamashita, T.; Terazawa, D.; Onishi, T.; Opherden, L.; Kasahara, S.; Tokiwa, Y.; Kasahara, Y.; Shibauchi, T.; von Löhneysen, H.; Wosnitza, J.; Matsuda, Y.;
There is growing evidence that the superconducting semimetal FeSe (Tc ∼ 8 K) is in the crossover regime between weak-coupling Bardeen–Cooper–Schrieffer (BCS) and strong-coupling Bose–Einstein-condensate (BEC) limits. We report on longitudinal and transverse thermal conductivities, κxx and κxy, respectively, in magnetic fields up to 20 T. The field dependences of κxx and κxy imply that a highly anisotropic small superconducting gap forms at the electron Fermi-surface pocket whereas a more isotropic and larger gap forms at the hole pocket. Below ∼1.0 K, both κxx and κxy exhibit distinct anomalies (kinks) at the upper critical field Hc2 and at a field H* slightly below Hc2. The analysis of the thermal Hall angle (κxyxx) indicates a change of the quasiparticle scattering rate at H*. These results provide strong support to the previous suggestion that above H* a distinct field-induced superconducting phase emerges with an unprecedented large spin imbalance.

Publ.-Id: 24631 - Permalink


Ultrafast electronic response of graphene to a strong and localized electric field
Gruber, E.; Wilhelm, R. A.ORC; Petuya, R.; Smejkal, V.; Kozubek, R.; Hierzenberger, A.; Bayer, B. C.; Aldazabal, I.; Kazansky, A. K.; Libisch, F.; Krasheninnikov, A. V.; Schleberger, M.; Facsko, S.; Borisov, A. G.; Arnau, A.; Aumayr, F.
The way conduction electrons respond to ultrafast external perturbations in low dimensional materials is at the core of the design of future devices for (opto)electronics, photodetection and spintronics. Highly charged ions provide a tool for probing the electronic response of solids to extremely strong electric fields localized down to nanometre-sized areas. With ion transmission times in the order of femtoseconds, we can directly probe the local electronic dynamics of an ultrathin foil on this timescale. Here we report on the ability of freestanding single layer graphene to provide tens of electrons for charge neutralization of a slow highly charged ion within a few femtoseconds. With values higher than 1012 A cm 2, the resulting local current density in graphene exceeds previously measured breakdown currents by three orders of magnitude. Surprisingly, the passing ion does not tear nanometre-sized holes into the single layer graphene. We use time-dependent density functional theory to gain insight into the multielectron dynamics.
  • Open Access LogoNature Communications 7(2016), 13948
    DOI: 10.1038/ncomms13948
  • Lecture (Conference)
    Ionenstrahltreffen, 13.-15.02.2017, Göttingen, Deutschland
  • Lecture (Conference)
    Frühjahrestagung der Deutschen Physikalischen Gesellschaft, Sektion Kondensierte Materie, 20.-24.03.2017, Dresden, Deutschland
  • Invited lecture (Conferences)
    Optical NanoSpectroscopy IV, 28.-31.03.2017, Lissabon, Portugal

Publ.-Id: 24630 - Permalink


Electronic structure of UN based on specific heat and field-induced transitions up to 65 T
Troc, R.; Samsel-Czekala, M.; Pikul, A.; Andreev, A. V.; Gorbunov, D. I.; Skourski, Y.; Sznajd, J.;
The 5f electrons of uranium in the uranium mononitride (UN) compound are described in the literature as either localized or fully itinerant. Motivated by these contradictory statements, we studied low-temperature specific heat and high-field magnetization of single-crystalline UN in magnetic fields up to 9 and 65 T, respectively. Our detailed analysis of the magnetic contribution to the specific heat of UN revealed that its real ground state is complex and the 5f electrons seem to have a dual nature; i.e., they possess simultaneously local and itinerant characters in two substates. High-field experiments allowed us to construct a tentative magnetic phase diagram of UN with a metamagnetic transition from antiferromagnetism to ferrimagnetism at a magnetic field as high as 58 T at 2 K. Such a field only enables a reversal of 1 of the 12 antiferromagnetically coupled ferromagnetic layers in the direction of the magnetic field. Any further steplike transitions require application of ever higher magnetic fields, which is beyond the experimental possibilities. We show that the magnetic phase diagram can be successfully reproduced considering a layer model of the Ising spins. That model allows rough estimation of a phase transition into fully induced ferromagnetism at a field as high as about 258 T. It gives rise to a giant coupling between ferromagnetically ordered layers in UN. The obtained characteristics are presented, together with the results of recent x-ray photoemission spectroscopy and transport property measurements. They are analyzed and compared with a number of earlier experiments and band structure calculations that were performed for this compound and are widely described in the literature. We show that different experiments probe different substates of the uranium 5f electrons in UN (itinerant or localized), which supports our hypothesis on their dual nature.

Publ.-Id: 24629 - Permalink


Ultrasonic flow measurements in a 1:6 downscaled water mockup of the DRESDYN dynamo experiment
Gundrum, T.; Vogt, T.; Giesecke, A.; Herault, J.; Stefani, F.;
The project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) conducted at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) provides a platform for a variety of liquid sodium experiments. Most ambitious experiment will be a precession driven dynamo experiment which consists of a large cylindrical cavity filled with liquid sodium that will simultaneously rotate around two axis. The experiment is motivated by the idea of a precession-driven flow as a complementary energy source for the geodynamo or the ancient lunar dynamo. The detailed knowledge of the flow structure in the precessing cylindrical vessel is of key importance for the prediction of the dynamo action. My presentation addresses experimental examinations with ultrasonic Doppler velocimetry in the low Reynolds region to validate numerical simulations.
Keywords: DRESDYN, sodium experiments, precession driven dynamo, ultrasonic Doppler velocimetry
  • Lecture (Conference)
    17th MHD Days, 30.11.-02.12.2016, Göttingen, Deutschland

Publ.-Id: 24628 - Permalink


Comparison of single-field and robust multi-field IMPT plans for oropharynx carcinoma by an enhanced method of robustness analysis
Stützer, K.; Lin, A.; Kirk, M.; Lin, L.;
Purpose:
Presentation of an enhanced robustness analysis and its application on single-field (SFO) and robust multi-field optimized (rMFO) plans for intensity modulated proton therapy (IMPT).

Material/Methods:
rMFO IMPT plans were optimized (Eclipse v13.7, Varian, Palo Alto, CA) for 11 oropharynx carcinoma patients, which had been treated post-surgery with SFO IMPT with simultaneous integrated boost prescription. Expected mean dose per voxel is calculated for minimal, 0% and maximal range uncertainty (RU), considering 19 setup error (SE) scenarios and their likelihood of occurrence. Voxel-wise boundary dose distributions are created from all 57 scenarios including systematic RU and random SE while also taking into account the averaging effect of fractionation to approximate realistic worst cases for the total treatment course. Dose error distributions for under- and overdosage with according ROI-specific metrics are derived from these boundary doses.

Results:
Nominal rMFO plans show improved CTV coverage and homogeneity while simultaneously reducing the average mean dose to the constrictor muscles, larynx and ipsilateral middle ear by 5.6Gy(RBE), 2.0Gy(RBE) and 3.9Gy(RBE), respectively. The comparison of SFO and rMFO boundary doses reveals slightly larger differences for these organs, and significantly lower brainstem maximum and ipsilateral parotid mean dose in rMFO plans. Many dose error metrics are significantly superior for rMFO plans.

Conclusions:
The nominal benefit of better CTV coverage and OAR dose sparing by rMFO compared to SFO plans is preserved under considerations of SE and RU. DVH bands and dose metrics from the boundary dose distributions will help to judge plan robustness in clinical routine.
  • Lecture (Conference)
    56th Annual Conference of the Particle Therapy Co-Operative Group, 08.-13.05.2017, Chiba, Yokohama, Nihon

Publ.-Id: 24627 - Permalink


Recycling 4.0 A metallurgical perspective
Reuter, M. A.;
Der Umgang mit Rohstoffen und Energie spielt für die industrielle Entwicklung Europas eine entscheidende Rolle. Darüber hinaus beeinflussen Entwicklungstrends wie Industrie 4.0, Energiewende, E-Mobility, Wasserstofftechnologie usw. die Nichteisenmetallurgie im Bereich der Prozesstechnik und Produkte. Dies wird in den nächsten Jahren neben einer rascheren Veränderung auf Verfahrensebene ebenfalls zu einer verstärkten Vernetzung von Disziplinen, wie der Rohstofftechnik, der Metallurgie sowie den Werkstoffwissenschaften führen, sodass auf dem Gebiet des Recyclings von komplexen Reststoffen und Produkten zukünftig ein entscheidender Schritt hinsichtlich höherer Ressourcen- und Energieeffizienz gelingen könnte. Daneben ist es besonders wichtig, dass Lehre und Forschung als Einheit weiterhin bestehen bleiben, um den Anforderungen in den erwähnten Bereichen hinsichtlich einer hochqualitativen Ausbildung gerecht zu werden.
  • Invited lecture (Conferences)
    Treffen der Nichteisenmetallurgie, 26.11.2015, Leoben, Österreich

Publ.-Id: 24626 - Permalink


Platinum-group mineral distribution of LG6 and LG6a chromitites of the western Bushveld Complex, South Africa
Bachmann, K.; Osbahr, I.; Gutzmer, J.;
The Bushveld Complex (BVC) in South Africa hosts the majority of global resources of chromium and platinum group elements (PGE). A correlation between chromitite seams and PGE is exceptionally well expressed as all chromitite layers carry elevated levels of PGE. Furthermore, the Bushveld chromitite seams show a progressive and massive increase in PPGE (Pt, Pd, Rh) contents up sequence, whereas the IPGE (Os, Ir, Ru) values remain broadly constant or rise only slightly. This trend coincides with decreasing Cr/Fe of the chromitites resulting in a focus of mining the upper seams, namely the upper group (UG)-2 for PGE and the middle groups (MG)/ lower groups (LG) for chromite. In recent years, companies already commenced extracting PGE from the MGs and LGs as a by-product during and/or after chromite production. However, only few mineralogical studies about the siting of the PGE (in silicates, sulfides or discrete platinum-group minerals (PGM)) in the LGs and MGs are available. Furthermore, information about parameters such as variation of the proportions of PGM within the chromitite seams, PGM association and grain sizes are scarce. From a geometallurgical perspective, these fundamental parameters about modal mineralogy and microfabric of the PGM in the chromite ores are crucial.
The purpose of this study is to fill this knowledge gap for the western limb of the BVC by investigating drill cores of the LG6 and LG6a seams from the Thaba mine near Thabazimbi. The study follows systematic studies of Voordouw et al.. More than 30 polished thin sections from three drill cores were analyzed by mineral liberation analysis to determine both, the modal mineralogy and the contained PGM (>100 grains per section in average) as well as base metal sulfides in-situ. This work was complemented by detailed analysis of the silicates by electron probe microanalyzer. The PPGE-bearing minerals include various Pt-Pd-Rh sulfides and -alloys as well as a significant amount of PPGE arsenides, bismuthides, and antimonides. IPGE are bound in laurite as well as sulfarsenides with various composition. The PGM are associated with sulfides as well as chromite and minor silicates. Grain-sizes are typically small (below 10 µm, usually c. 5 µm and smaller).
Keywords: -
  • Lecture (Conference)
    1st GOOD meeting, 15.-18.03.2016, Freiberg, Deutschland

Publ.-Id: 24625 - Permalink


Platinum-group mineral composition and mineralogy of LG6 and LG6a chromitites of the western Bushveld Complex, South Africa
Bachmann, K.; Osbahr, I.; Krause, J.; Gutzmer, J.;
The Bushveld Complex (BVC) in South Africa hosts the majority of global resources of chromium and platinum group elements (PGE). A correlation between chromitite seams and PGE is exceptionally well expressed as all chromitite layers carry elevated levels of PGE. Furthermore, the Bushveld chromitite seams show a progressive and massive increase in PPGE (Pt, Pd, Rh) contents up sequence, whereas the IPGE (Os, Ir, Ru) values remain broadly constant or rise only slightly. This trend coincides with decreasing Cr/Fe of the chromitites resulting in a focus of mining the upper seams, namely the upper group (UG)-2 for PGE and the middle groups (MG)/ lower groups (LG) for chromite. In recent years, companies already commenced extracting PGE from the MGs and LGs as a by-product during and/or after chromite production. However, only few mineralogical studies about the siting of the PGE (in silicates, sulfides or discrete platinum-group minerals (PGM)) in the LGs and MGs are available. Furthermore, information about parameters such as variation of the proportions of PGM within the chromitite seams, PGM association and grain sizes are scarce. From a geometallurgical perspective, these fundamental parameters about modal mineralogy and microfabric of the PGM in the chromite ores are crucial.


The purpose of this study is to fill this knowledge gap for the western limb of the BVC by investigating drill cores of the LG6 and LG6a seam from the Thaba mine near Thabazimbi. Currently, the deposit is mined for chromite by CRONIMET Chrome SA (Pty.) Ltd. The study follows systematic studies of Voordouw et al. More than 60 polished thin sections from three drill cores were analyzed by mineral liberation analysis to determine both, the modal mineralogy and the contained PGM (>100 grains per section in average) as well as base metal sulfides in-situ. This work was complemented by detailed analysis of the PGM, base metal sulfides (pentlandite, pyrite, pyrrhotite) and silicates by electron probe microanalyzer. The PPGE-bearing minerals include various Pt-Pd-Rh sulfides and -alloys as well as a significant amount of PPGE arsenides, bismuthides, and antimonides. IPGE are bound in laurite as well as sulfarsenides with various composition. The PGM are associated with sulfides as well as chromite and minor silicates. Grain-sizes are typically small (below 10 µm, usually c. 5 µm and smaller). Furthermore, feed, concentrate and tailings from the Thaba mine processing plant were investigated to estimate the mineralogical controls on the distribution of the PGM during chromite processing.
Keywords: -
  • Lecture (Conference)
    35th INTERNATIONAL GEOLOGICAL CONGRESS, 27.08.-04.09.2016, Kapstadt, Südafrika

Publ.-Id: 24624 - Permalink


Advanced discrimination of In-bearing minerals by automated mineralogy
Bachmann, K.; Frenzel, M.; Krause, J.; Gutzmer, J.;
The identification and accurate characterization of discrete Indium minerals is usually a very cumbersome procedure due to their small grain size (typically below 10 μm) and complex mineral assemblage in massive sulfide mineralizations. A novel strategy for finding discrete In minerals and quantifying their composition was developed by using a mineral liberation analyzer (MLA) and an electron microprobe analysis (EPMA). The method was successfully applied to polymetallic massive sulfide ores with an incompletely known mineralogical composition from the Neves-Corvo deposit in Portugal. The occurrence of roquesite and sakuraiite could be systematically detected, their concentration quantified by MLA measurements, and their identity later confirmed by EPMA analyses. Based on the results obtained, an almost complete deportment of In was obtained for the six samples studied. This supports the approach taken, combining automated mineralogical data with electron microprobe analysis. A similar approach can be easily applied to other common minor and trace elements in complex base-metal sulfide ores, e.g. Se, Ge, Sb, or Ag, thus permitting targeted development of resource technologies suitable for by-product recovery.
Keywords: MLA, automated mineralogy, Indium, Neves Corvo, roquesite, sakuraiite

Publ.-Id: 24623 - Permalink


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