Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32216 Publications
Magnetic characterization of curved thin [Co/Pd]-multilayers and Py films
Steinbach, G.; Göhler, F.; Wolf, D.; Sluka, V.; Lindner, J.; Gemming, S.; Albrecht, M.; Erbe, A.;
In the last decades thin film technology has led to a vast increase in the variety of fabricated magnetic nano- and microstructures with desired shape, size and properties. Usually flat substrates are used to grow structures. Recently, a study on magnetic thin films with perpendicular anisotropy on curved substrates, for instance on silica spheres [1], has shown that the film curvature enormously influences the magnetic properties. In contrast to structures on flat substrates those so-called magnetic caps exhibit a spatial change of the magnetic easy axis and a film thickness variation across the cap. These features extend the possibilities in tailoring the magnetic specifications such as the magnetic anisotropy [2,3] and coercivity [1,4] or magnetization reversal process [1,2,5]. This complex structure geometry, however, leads to difficulties in characterizing the magnetic properties of the caps using standard techniques: In the case of micrometer-sized structures magnetic imaging methods suffer, for example, from beam deflection or the huge structure height due to the surface curvature.
We will present our results on 4.5µm and 0.33µm sized magnetic caps consisting of [Co(0.28nm)/Pd(0.9nm)]x8-multilayers with perpendicular magnetic anisotropy. First, we concentrate on the interior materials’ properties by studying the magnetic switching process of the cap in external fields and the spin dynamics. Second, the stray field is investigated, which determines the cap’s interaction with the environment.
The magnetization reversal in micron-sized caps has been studied by both, superconducting quantum interference device and magnetic force microscopy, for two distinct directions of an externally applied magnetic field: normal and parallel to the substrate surface. We observe clear deviations from curves measured for the flat film: The caps also show a hysteretic behavior with a very small coercivity of 150Oe in the field parallel to the substrate surface. In the normal field there is no abrupt switching as known from the flat film, but a continuous, two-step like reversal. The origin of the switching features is investigated with in-field and remanent MFM. We will present the magnetic reversal as a multi-step process across the different regions of the cap. In the parallel field two different nucleation processes during the magnetization switching have been observed: a ring nucleation, which is also mentioned in [2], and isolated domain nucleation.
The dynamic properties of the [Co/Pd]-caps have been investigated with ferromagnetic resonance. Due to the small particle size the use of conventional FMR setups does not allow single particle detection. Therefore we prepared micron sized resonators using electron beam lithography [6]. The angular dependence of the FMR modes is investigated. The results are compared with FMR measurements on geometrically similar permalloy caps with in-plane magnetic anisotropy.
The curvature-induced spatial modulation of the magnetic anisotropy further leads to a complicated stray field around the cap. So far, micromagnetic simulations [2] have been carried out to calculate the spin distribution giving rise to the stray field. Here we experimentally visualize the magnetic stray field of 0.33 µm particles by off-axis electron holography (figure 2, left). This technique provides access to the projected in-plane component of the magnetic induction by reconstructing the phase shift of the electron wave when passing through the magnetic stray field of the sample [7]. The projected stray field can be obtained by the gradual rotation of the cap. In contrast to standard measurements on flat samples, for magnetic caps the interpretation of the electron holograms is not straightforward since the stray field is not constant along the electron path. Therefore, we compare the experimentally obtained results with the outcome of micromagnetic simulations performed with the finite element based simulation software SpinFlow 3D (figure 2, right). The qualitative agreement proves the reliability of the simulation.
  • Poster
    IEEE International Magnetics Conference, INTERMAG Europe 2014, 05.05.2014, Dresden, Deutschland

Publ.-Id: 21644 - Permalink


Crystallization of quasiantiferromagnetic colloids
Steinbach, G.; Gemming, S.; Erbe, A.;
The microscopic interactions between atomic magnetic moments determine the macroscopic magnetic properties of matter. For strongly correlated magnetic systems the local spin configuration plays a key role. High relaxation times, however, make direct investigations of dynamic processes such as crystallization very difficult. Here, we present an artificial spin system of magnetic colloids, which are often discussed as potential mesoscopic model systems for condensed matter. The very low relaxation rates of interacting colloids enable the visualization of phase transitions or crystallization processes by video microscopy. The used colloids have a predened net magnetic moment, as analogue to the atomic spin. These micromagnets show a quasiantiferromagnetic interaction. They form two-dimensional hexagonal clusters with a spin configuration similar to the 120° antiferromagnetic Neel state in the cluster center and strong deviations along the edges. The cluster size emerged as critical parameter for the occurrence of spin defects. Dur-ing the cluster growth the total magnetization of the system increased in discrete steps. Further we obtained a linear increase of the inverse spin pair correlation for particles in the center. The influence of an external constant or uctuating magnetic field is investigated as control tool for cluster growth and defect formation.
  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 30.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 21643 - Permalink


Cluster-Tool zur In situ Modifizierung und Analyse von Werkstoffen unter extremen Bedingungen am 6 MV Ionenbeschleuniger des HZDR
Wenisch, R.; Schumann, E.; Lungwitz, F.; Hanf, D.; Heller, R.; Gemming, S.; Krause, M.;
Moderne Werkstoffe sind bei vielen Anwendungen extremenUmgebungsbedingungen ausgesetzt. Dazu zählen hohe und tiefe Temperaturen bzw. große Temperaturschwankungen, die teilweise in Verbindung mit korrosiven oder reaktiven Atmosphären oder hohen mechanischen Belastungen auftreten. Sie stellen hohe Anforderungen an die Beständigkeit und Stabilität der verwendeten Werkstoffe. Als Beispiele seien solarselektive Absorber, Komponenten des Antriebsstranges von Verbrennungsmotoren und Rotoren von Turboladern und Turbinen genannt. Die Gewährleistung der Werkstofffunktionalität über die gesamte Lebensdauer erfordert neue Konzepte der Analyse und Prüfung. Dazu wurde am 6MV Ionenbeschleuniger des HZDR mit Fördermitteln des Impuls- und Vernetzungsfonds des Präsidenten der HGF sowie des KFSI ein Cluster-Tool zur in situ Modifizierung und Analyse von Werkstoffen bei Temperaturen von bis zu 1000°C, unter korrosiven Atmosphären und mechanischem Verschleiß aufgebaut.
Kernbestandteil des Cluster-Tools ist eine zentrale Hochvakuum (HV)-Probenaufnahme- und Transferkammer. Diese ist mit weiteren HV-Kammern verbunden, in denen die sequentielle Probensynthese und -modifizierung, die Element- und Strukturanalytik und die optische Charakterisierung erfolgt, ohne das Vakuum zu brechen und die Werkstoffe undefinierten Umgebungsbedingungen auszusetzen. In allen Kammern besteht die Möglichkeit, in situ Heizexperimente bei Temperaturen von bis zu 1000°C durchzuführen. Die mit dem 6MV Tandem-Ionenbeschleuniger verbundene Kammer zur Ionenstrahlanalytik ermöglicht die Untersuchung der Elementzusammensetzung durch Rutherford Rückstreuung und Nuklearer Reaktionsanalyse. Die Schichtzusammensetzung kann bis in eine Tiefe von ca. 1μm auf bis zu 10 nm genau bestimmt werden. Bei Hochtemperaturuntersuchungen reduziert sich die Tiefenauflösung auf etwa 25 nm. Zur strukturellen Charakterisierung der Proben dient ein fasergekoppeltes Ramanspektrometer an der Analysenkammer des Cluster-Tools, dessen Probenkopf über eine Kamera auch die visuelle Beurteilung der Proben ermöglicht. Die Untersuchung der optischen Eigenschaften und deren Abhängigkeit von Temperatur und Atmosphäre erfolgt durch spektroskopische Ellipsometrie in einer Umweltkammer, in der korrosive Umgebungen simuliert werden können. Für 2015 ist die Installation eines in situ Tribometers in Vorbereitung, mit dem das Reib- und Verschleißverhalten von Werkstoffen unter definierten Atmosphären untersucht werden kann.
Zusammengefasst entsteht mit dem Cluster-Tool am 6 MV Ionenbeschleuniger des HZDR ein Messplatz zur umfassenden in situ Modifizierung und Analyse von Werkstoffen, mit Hilfe dessen komplexe Probenbehandlungsprotokolle unter extremen Umgebungsbedingungen bearbeitet werden können.
  • Poster
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten 2014, 21.-23.09.2014, Bonn, Deutschland

Publ.-Id: 21642 - Permalink


Optical nanoscopy of transient states in condensed matter
Kuschewski, F.; Kehr, S. C.; Green, B.; Bauer, C.; Gensch, M.; Eng, L. M.;
Recently, the fundamental and nanoscale understanding of complex phenomena in both, materials research and the life sciences, has witnessed considerable progress. However, elucidating the underlying complex mechanisms, often governed by disentangled degrees of freedom such as lattice, spin, orbit, charge for solids or conformation, electric potentials and ligands for proteins, has remained an experimental challenge. . Techniques that allow for distinguishing between different contributions to these processes by their spectral and/or temporal responses and/or by their characteristic lenght scales are hence urgently required.
In this paper we demonstrate the application of scattering-type scanning near-field optical microscopy (s-SNOM) as a novel nano-probe for tracking transient states of matter. We introduce a sideband-demodulation technique that allows for probing exclusively the stimuli-induced change of near-field optical properties. We exemplify this development by probing the transient decay of an electron-hole plasma generated in SiGe thin films through near-infrared laser pulses. This method can universally be applied to optically track ultrafast/-slow transient processes over the whole spectral range from UV to THz frequencies.
Keywords: THz, near-field microscopy, phase transitions, accelerator-based THz sources

Publ.-Id: 21641 - Permalink


Nanostructuring CaF2 surfaces with slow highly charged ions
El-Said, A. S.; Wilhelm, R. A.; Heller, R.; Ritter, R.; Wachter, G.; Facsko, S.; Lemell, C.; Burgdörfer, J.; Aumayr, F.;
In recent years the potential of slow highly charged ions (HCI) as tools for nanostructuring purposes has received considerable attention and a wide range of material classes, from insulating ionic crystals, polymers and ultrathin films, to semiconducting and conducting substrates have been investigated regarding their response to individual HCI impact. For the majority of investigated materials, however, consistent theoretical modeling to supplement with experimental evidence and to satisfactorily explain the complete physical process from ion approach and impact to the formation of an individual nanostructure is still lacking. CaF2, from both an experimental and theoretical point of view, might be considered the most thoroughly investigated material. Combining results from numerous studies has allowed for the generation of a "phase diagram" for nanostructuring of CaF2 in dependence of ion beam parameters. This paves the way for a first unified picture, as implications from this phase diagram should be applicable to similar materials as well.

Publ.-Id: 21640 - Permalink


Terahertz field control of in-plane orbital order in La0.5Sr1.5MnO4
Miller, T. A.; Chhaajlany, R. W.; Tagliacozzo, L.; Green, B.; Kovalev, S.; Prabhakaran, D.; Lewenstein, M.; Gensch, M.; Wall, S.;
In-plane anisotropic ground states are ubiquitous in correlated solids such as pnictides1, cuprates2 and manganites3. They arise naturally from doping Mott insulators4 and compete with phases such as superconductivity5. However, strong coupling between lattice, charge, orbital and spin degrees of freedom results in simultaneous ordering of multiple parameters, masking the mechanism that drives the anisotropy6. We demonstrate that orbital domains in a manganite can be oriented by the polarization of an external pulsed THz light field. The THz control field non-resonantly couples to electrons, indicating that Coulomb interactions are the primary driving factor for the orbital order. Field control is explained by a simple Hubbard model that shows the force on the domain originates from the Coulomb interaction. Our results demonstrate the key role played by charge localization in driving orbital order in manganites and show how THz can be utilized in new ways to understand and manipulate anisotropic phases in a broad range of correlated materials.
Keywords: THz, Domains, correlated solids, ultra-fast

Publ.-Id: 21639 - Permalink


AIDA - Apparatus for In-situ Defect Analysis: Investigations on Fe60Al40
Trinh, T.; Wagner, A.; Liedke, M. O.; Anwand, W.; Butterling, M.; Potzger, K.;
We performed in-situ annealing investigations of 250 nm Fe60Al40 thin films. The magnetic properties of disorderd Fe60Al40 thin films change from the ferromagnetic to paramagnetic state du to annealing. No conclusive discussion of that phase transtion as a function of the open volume defects exists in the literature. First results on the Fe60Al40 annealing driven magnetic phase transition between the ferromagnetic A1 phase and the paramagnetic B2 phase as a function of the open volume defects will be shown. The magnetization of the film after each annealing step indicates its progress reflecting chemical ordering of the alloy and dinishing of ferromagnetism [1]. Fig. 1 shows the temperature dependence of the positron annihilation spectorscopy (PAS) S-parameter indicating the open volume defects evolution during annealing. The defects are very stable with respect to annealing and do not directly relate to the change of magnetic properties. Our results indicate that Fe60Al40 could be a promising candidate for Hydrogen storage due to a large amount of stable defects. Through hybridisation the electronic structure can be modified, combined with a local lattice distortion. Hydrogen can therefore be viewed as a tool to modify the electronic structure, allowing tuning of the magnetic properties as a consequence.
For the in-situ annealing we have utilized a unique high vacuum system combining material evaporation and ion beam modification with positron annihilation spectroscopy. The system has been developed and installed in the Helmholtz-Zentrum Dresden-Rossendorf. The system is capable to perform Doppler broadening spectroscopy as well as resistometry and provides a monoenergetic positron beam pre-accelerated in the range of 80 eV to 35 keV thus enabling sample depth profiling.
Keywords: Positron anihilation, In-situ, Apparatus, Defects, Spectroscopy
  • Poster
    14th International Symposium Metal Hydride Systems, 20.-25.07.2014, Manchester, United Kingdom

Publ.-Id: 21638 - Permalink


Apparatus for In-situ Defect Analysis (AIDA)
Liedke, M. O.; Anwand, W.; Butterling, M.; Potzger, K.; Heidarian, A.; Bali, R.; Wagner, A.;
A unique high vacuum system combining material evaporation and ion beam modication with positron annihilation spectroscopy (PAS) has been developed and installed in the Helmholtz-Zentrum Dresden-Rossendorf. The in-situ system is capable to perform Doppler broadening spectroscopy as well as resistometry (4 point probe). It is an end station of the Slow-Positron System of Rossendorf (SPONSOR) that provides a mono-energetic positron beam pre-accelerated in the range of 80 eV to 35 keV thus enabling sample depth proling. The main focus of studies is the in-situ modication (during growth, ion irradiation, cooling/annealing) and the analysis of open volume defects and the chemical environment in thin lms of, e.g., memristive oxides or metal alloys. First results on the FeAl ion irradiation/annealing driven magnetic phase transition between the paramagnetic and ferromagnetic state as a function of the open volume defects will be shown. The project is nanced by the Impuls- und Vernetzungsfonds of the Helmholtz Association (code VH-VI-442).
Keywords: MBE, ion irradiation, evaporation, annealing, FeAl, transition metals, sheet resistance
  • Lecture (Conference)
    DPG-Frühjahrstagung (DPG Spring Meeting) 2014, 30.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 21637 - Permalink


Apparatus for In-situ Defect Analysis (AIDA)
Liedke, M. O.; Anwand, W.; Potzger, K.; Wagner, A.;
A unique high vacuum system combining material evaporation and ion beam modication with positron annihilation spectroscopy (PAS) has been developed and installed in the Helmholtz-Zentrum Dresden-Rossendorf. The in-situ system is capable to perform Doppler broadening spectroscopy as well as resistometry (4 point probe). It is an end station of the Slow-Positron System of Rossendorf (SPONSOR) that provides a mono-energetic positron beam pre-accelerated in the range of 80 eV to 35 keV thus enabling sample depth proling. The main focus of studies is the in-situ modication (during growth, ion irradiation, cooling/annealing) and the analysis of open volume defects and the chemical environment in thin lms of, e.g., memristive oxides or metal alloys. First results on the FeAl ion irradiation/annealing driven magnetic phase transition between the paramagnetic and ferromagnetic state as a function of the open volume defects will be shown. The project is nanced by the Impuls- und Vernetzungsfonds of the Helmholtz Association (code VH-VI-442).
Keywords: MBE, ion irradiation, evaporation, annealing, FeAl, transition metals
  • Lecture (Conference)
    Treffen Deutscher Positronengruppen Kiel 2014, 25.-27.02.2014, Kiel, Deutschland

Publ.-Id: 21636 - Permalink


Capacitance wire mesh imaging of bubbly flows for offshore treatment applications
Assima, G. P.; Larachi, F.; Schleicher, E.; Schubert, M.;
The impact of ship motion bubbly flow was emulated using as well simulator to expose flow structure changes emerging in bubble columns relevant to offshore floating applications. Roll, roll+pitch, yaw, heave and sway were implemented at various frequencies and changes in bubbly flow resulting from the imposed motions were monitored for the first time by means of a dual capacitance wire mesh sensor to measure local gas holdup and velocity. Visualizations of the two-phase flow revealed that roll, roll+pitch, and high-frequency sway were the most impactful in terms of bubble zigzag and swirl, and bubble-clustering and segregation due to vessel dynamic inclinations. As a consequence of the se motions, lateral migration of bubbles and their clustering enhanced liquid recirculation and local streamwise gas velocity. Compared to static vertical bubble column, bubbly flow pattern was barely altered by yaw and low-frequency sway except the heave displacements which tended to slow down the bubble rise.
Keywords: bubble column, wire mesh capacitance sensor, gas holdup, gas interstitial velocity, swell simulator, marine applications

Publ.-Id: 21635 - Permalink


Highly charged ion induced nanostructures at surfaces by strong electronic excitations
Wilhelm, R. A.; El-Said, A. S.; Krok, F.; Heller, R.; Gruber, E.; Aumayr, F.; Facsko, S.;
Nanostructure formation by single impacts of slow highly charged ions can be associated with high density of electronic excitations at the impact points of the ions. Experimental results show that depending on the target material these electronic excitations may lead to very large desorption yields in the order of a few 1000 atoms per ion or the formation of nanohillocks at the impact site. Even in ultra-thin insulating membranes the formation of nanometer sized pores are observed after ion impact. In this paper we show recent results on nanostructure formation by highly charged ions and compare these to structures and single defects observed after intense electron and light ion irradiation on ionic crystals and Graphene. Additional data on energy loss, charge exchange and secondary electron emission of highly charged ions clearly show that the ion's charge state dominate the defect formation at the surface.
Keywords: slow highly charged ion, HCI, ion charge state, nanostructure, electronic excitation, color centers

Publ.-Id: 21633 - Permalink


Development of a Laser wakefield acceleration source as a secondary radiation driver
Couperus, J. P.; Jochmann, A.; Köhler, A.; Messmer, M.; Zarini, O.; Debus, A.; Hübl, A.; Widera, R.; Bussmann, M.; Sauerbrey, R.; Cowan, T.; Schramm, U.; Irman, A.;
In laser wakefield electron acceleration a high intensity ultrashort laser pulse drives plasma density waves, inducing a high accelerating field gradient (~GV/m) which can accelerate electrons to high energies within a very short distance.
For the development of secondary radiation sources, the maximization of the bunch charge is important. For this reason we investigate the beam-loading effect at the self-injected highly nonlinear regime. Beam-loading deteriorates the accelerating field structure and limits the maximum bunch charge.
Supported by intensive Particle-in-Cell code simulations run on a GPU-cluster (using the PIConGPU code), we aim on developing a stable high peak current (hundreds of kA) electron source.
Keywords: laser wakefield electron acceleration LWFA plasma PIConGPU
  • Poster
    Advanced School on Laser Applications at Accelerator, 29.09.-03.10.2014, Salamanca, Spain

Publ.-Id: 21632 - Permalink


Effects of the Background Electrolyte on Th(IV) Sorption to Muscovite Mica
Schmidt, M.; Hellebrandt, S.; Knope, K. E.; Lee, S. S.; Stubbs, J. E.; Eng, P. J.; Soderholm, L.; Fenter, P.;
The adsorption of tetravalent thorium on the muscovite mica (001) basal plane was studied by resonant anomalous X-ray reflectivity (RAXR), crystal truncation rods (CTR) and alpha spectrometry in the presence of perchlorate background electrolytes LiClO4, NaClO4, and KClO4 ([Th(IV)] = 0.1mM, I = 0.1 M or 0.01 M, pH = 3.3 ± 0.3). RAXR data show strong influence of the background electrolyte on the sorption behavior of the actinide. No significant Th adsorption was observed in 0.1 M NaClO4, i.e., the Th coverage θ(Th), the number of Th per unit cell area of the muscovite surface (AUC = 46.72 Ų), was ≤0.01 Th/AUC, whereas limited uptake (θ(Th) ~ 0.04 Th/AUC) was detected at a lower ionic strength (I = 0.01 M). These results are in stark contrast to the behavior of Th in 0.1 M NaCl which showed a coverage of 0.4 Th/AUC (Schmidt et al., 2012a). Th uptake was also influenced by the electrolyte cation. Weak adsorption was observed in 0.1M KClO4 (θ(Th) ~ 0.07 Th/AUC) similar to the results in NaClO4 at lower ionic strength. In contrast, strong adsorption was found in 0.1 M LiClO4 , with θ(Th) = 4.9 Th/AUC, a ~10-fold increase compared with that previously reported in NaCl. These differences are confirmed independently by alpha spectrometry, which shows no measurable coverage of Th in 0.1 M NaClO4 background in contrast to a large coverage of 1.6 Th/AUC in 0.1 M LiClO4. Alpha spectrometry cannot be obtained in situ, but sample preparation requires several washing steps that may affect Th(IV) sorption, RAXR, however, is considered to reflect the in situ sorption structure. The CTR/RAXR analyses show the sorption structure consisting of two types of broadly distributed Th species centered at 4.1 Å and 29 Å distance from the interface. Neither the very large distribution height of the second species nor the high coverage can be explained with (hydrated) ionic adsorption, suggesting that the enhanced uptake is presumably due to the formation and sorption of Th nanoparticles.
Keywords: thorium, sorption, RAXR, CTR, nanoparticles, surface diffraction

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Publ.-Id: 21631 - Permalink


Investigation of the beam loading effect in laser wakefield acceleration
Couperus, J. P.; Jochmann, A.; Köhler, A.; Messmer, M.; Zarini, O.; Debus, A.; Hübl, A.; Widera, R.; Bussmann, M.; Sauerbrey, R.; Cowan, T.; Schramm, U.; Irman, A.;
In laser wakefield electron acceleration a high intensity ultrashort laser pulse drives plasma density waves, inducing a high accelerating field gradient (~GV/m) which can accelerate electrons to high energies within a very short distance.
For the development of secondary radiation sources, the maximization of the bunch charge is important. For this reason we investigate the beam-loading effect at the self-injected highly nonlinear regime. Beam-loading deteriorates the accelerating field structure and limits the maximum bunch charge.
Keywords: laser plasma electron acceleration LWFA wakefield gas-jet PIConGPU
  • Poster
    International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Deutschland

Publ.-Id: 21630 - Permalink


Boron dilution transient simulation analyses in a PWR with neutronics/thermal-hydraulics coupled codes in the NURISP project
Jimenez, G.; Herrero, J.; Gommlich, A.; Kliem, S.; Cuervo, D.; Jimenez, J.;
The detailed 3D calculation of a boron slug transient with neutronics/thermal hydraulics coupled systems has been a highly demanding and difficult exercise because of the trouble coupling with boron transport models. Within subproject 3 of the FP7 European Project NURISP, two neutron kinetics codes, COBAYA3 and DYN3D, coupled with the thermal hydraulics code FLICA4 in the NURESIM platform were employed to simulate boron dilution transients.
Three transients were defined in the project, involving increasing volumes of diluted water entering the core inlet, to test the adequacy of the coupling between the codes. This paper contains the results obtained with COBAYA3/FLICA4 and DYN3D/FLICA4 couplings for the PWR boron dilution benchmark defined. Additionally, results from the coupled codes DYN3D/FLOCAL are applied for further verification in some cases.
A thorough sensitivity study of the solutions accuracy to the time step and the axial mesh size was performed, and optimal options applicable to all three boron slugs were obtained. The results verify the applicability of the implemented couplings to this type of problems accurately, where peak powers reached can be very high during short periods after which the reactor stabilizes at a few per cent of the nominal power.

Publ.-Id: 21629 - Permalink


Energy-Angle Characteristic of an ICS source
Jochmann, A.;
A tunable source of intense ultra-short hard X ray pulses represents a novel tool for the structural analysis of complex systems with unprecedented temporal and spatial resolution. At Helmholtz-Zentrum Dresden-Rossendorf (HZDR) we demonstrated the principle of such a light source (PHOENIX – Photon Electron collider for Narrow bandwidth Intense X-Rays) by colliding picosecond electron bunches from the ELBE linear accelerator with counter-propagating femtosecond laser pulses from the 150 TW Draco Ti:Sapphire laser system. The generated narrowband X rays are highly collimated and can be reliably adjusted by tuning the electron energy. A complete spectral characterization of this source is performed with high angular and energy resolution. These intensive studies provide predictive capability for the future high brightness hard X ray source PHOENIX and potential gamma-ray sources suited to an application.
Keywords: Laser Compton Scattering X-ray pulsed source femtosecond intense backscattering inverse
  • Lecture (Conference)
    LA3NET 3rd Topical Workshop on Novel Acceleration Techniques, 28.04.2014, Dresden, Deutschland

Publ.-Id: 21628 - Permalink


Effect of a superimposed DC magnetic field on an AC induction semi-levitated molten copper droplet
Bojarevics, A.; Beinerts, T.; Grants, I.; Kaldre, I.; Sivars, A.; Gerbeth, G.; Gelfgats, J.;
While a piece of pure Copper on a ceramic substrate was inductively melted by 9 to 18 kHz AC magnetic field with axial magnetic DC field superimposed, the liquid metal stably semi-levitated in the expected “conical” free surface shape. The diameter of the liquid metal at the basis was 30 mm, the volume – more than 20 cm3. Replacing the ceramic substrate with a Glassy Carbon, which was not wetted by the molten Copper, caused instability of the semi-levitated Copper droplet. In the absence of the DC field severe chaotic instabilities of the liquid metal shape occurred, causing splashes and uncontrolled contact with crucible walls. When axial DC magnetic field with induction 0.35 T was superimposed the liquid metal droplet exhibited harmonic azimuthal wave deformation of the free surface. Higher frequencies lead to smaller characteristic wavelength. Transverse DC magnetic field direction suppressed the travelling wave deformations of the droplet shape. Stabilizing effect of the DC magnetic field during induction melting has been shown for axial, transverse and 45 degree direction magnetic field. These results experimentally demonstrate the possibilities to improve the stability of levitated metal volumes by superimposed DC magnetic field.
Keywords: -
  • Lecture (Conference)
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Lettland
  • Contribution to proceedings
    9th PAMIR conference on Fundamental and Applied MHD,, 16.-20.06.2014, Riga, Lettland
    Proceedings of the 9th PAMIR conference on Fundamental and Applied MHD, Vol 2, 125-129

Publ.-Id: 21627 - Permalink


Experimental modelling using liquid metals
Gerbeth, G.; Eckert, S.;
An overview on liquid metal modelling experiments is presented for the steel casting process. Particular attention is given to the recent developments on measuring techniques for liquid metal flows, including the perspectives for measurements in real steel melts.
Keywords: -
  • Invited lecture (Conferences)
    VDEh Steel Academy Workshop „Computational Fluid Dynamics in Metallurgy“, 01.-03.12.2014, Mönchengladbach, Deutschland

Publ.-Id: 21626 - Permalink


Recent results on flow measurements and magnetic control
Gerbeth, G.; Eckert, S.;
A brief summary is given on measurements in metal melts developed at HZDR. Melt velocities can be measured by local electromagnetic probes, ultrasonic Doppler velocimetry and by the Contactless Inductive Flow Tomography (CIFT). The latter is fully contactless and offers a possibility for an online monitoring of the melt flow. We report on first test measurements with CIFT at Czochralski facilities for Si growth. Regarding the details of solidification and the occurrence of inclusions, we present results on X-ray visualizations of alloy solidification. They allowed to demonstrate for metal alloys the formation of freckles driven by the mesoscopic melt convection ahead of the solidification front. For the magnetic melt control we present results of model experiments on the reduction of buoyant temperature oscillations using a rotating magnetic field. Related studies were performed for cylindrical melt volumes and a Cz-like configuration. The melt flow in the float-zone process can be efficiently influenced by a so-called magnetic two-phase stirrer. Its principle and related growth results for intermetallic compounds will be presented.
Keywords: -
  • Lecture (others)
    DGKK-Tagung, 12.-13.03.2014, Halle, Deutschland

Publ.-Id: 21625 - Permalink


Towards laser wakefield acceleration with external injection at HZDR
Irman, A.;
Progress towards laser wakefield acceleration with external injection is presented.
  • Invited lecture (Conferences)
    Novel acceleration techniques ANAC2/EUCARD2 JRA meeting, 30.04.2014, HZDR, Germany

Publ.-Id: 21624 - Permalink


High Resolution Energy-angle Correlation Measurement of Hard X rays from Laser Thomson Backscattering
Irman, A.; Bussmann, M. H.; Couperus, J. P.; Debus, A. D.; Jochmann, A.; Pausch, R. G.; Schlenvoigt, H. P.; Schramm, U.; Steiniger, K.; Cowan, T. E.; Kuntzsch, M.; Lehnert, U.; Sauerbrey, R.; Seipt, D.; Wagner, A.; Ledingham, K.; Stöhlker, T.; Thorn, D. B.; Trotsenko, S.;
A tunable source of intense ultra-short hard X ray pulses represents a novel tool for the structural analysis of complex systems with unprecedented temporal and spatial resolution. At Helmholtz-Zentrum Dresden-Rossendorf (HZDR) we demonstrated the principle of such a light source (PHOENIX – Photon Electron collider for Narrow bandwidth Intense X-Rays) by colliding picosecond electron bunches from the ELBE linear accelerator with counter-propagating femtosecond laser pulses from the 150 TW Draco Ti:Sapphire laser system. The generated narrowband X rays are highly collimated and can be reliably adjusted by tuning the electron energy. A complete spectral characterization of this source is performed with high angular and energy resolution. These intensive studies provide predictive capability for the future high brightness hard X ray source PHOENIX and potential gamma-ray sources suited to an application.
Keywords: Laser Compton Scattering X-ray pulsed source femtosecond intense backscattering inverse
  • Poster
    IPAC’14 - 5th International Particle Accelerator Conference, 18.06.2014, Dresden, Deutschland

Publ.-Id: 21623 - Permalink


Fluid dynamics research at HZDR Dresden
Gerbeth, G.;
An overview on fluid dynamics research activities is given, including multiphase and magnetohydrodynamic flows and the related computational fluid dynamics.
Keywords: -
  • Invited lecture (Conferences)
    Shandong Universität, 11.05.2014, Jinan, China

Publ.-Id: 21622 - Permalink


Laser-plasma based electron acceleration
Irman, A.;
The concept of laser-driven plasma-based electron acceleration is reviewed. This lecture will be started by description of plasmas and its characteristics then follows with electron injection and acceleration. In the end, recent progress in the field will be highlighted.
Keywords: laser wakefield acceleration
  • Invited lecture (Conferences)
    LA3NET Advanced School on Laser Applications at Accelerators, 28.09.-03.10.2014, Salamanca, Spain

Publ.-Id: 21621 - Permalink


Research on crystal growth problems at Institute of Fluid Dynamics of HZDR
Gerbeth, G.;
Research activities at HZDR on the measurement and magnetic field control of melt flows in crystal growth processes are summarized. Examples are given for the tailored control by magnetic fields of Czochralski, Vertical-Gradient-Freeze as well as Float-Zone growth processes.
Keywords: -
  • Invited lecture (Conferences)
    SICC Science & Technology, Ltd., 12.05.2014, Jinan, China

Publ.-Id: 21620 - Permalink


Tornado-like flows driven by magnetic body forces
Gerbeth, G.; Grants, I.; Vogt, T.; Eckert, S.;
Alternating magnetic fields produce well-defined flow-independent body forces in electrically conducting media. This property is used to construct a laboratory analogue of the Fiedler chamber with a room-temperature liquid metal as working fluid. A continuously applied rotating magnetic field (RMF) provides the source of the angular momentum. A pulse of a much stronger travelling magnetic field drives a converging flow at the metal surface, which focuses this angular momentum towards the axis of the container. The resulting vortex is studied experimentally and numerically. In a certain range of the ratio of both driving actions the axial velocity changes its direction in the vortex core, resembling the subsidence in an eye of a tropical cyclone or a large tornado. During the initial deterministic spin-up stage (T. Vogt et al., JFM 736, 2013, pp. 641) the vortex is well described by axisymmetric direct numerical simulation. Being strong enough the flow develops a funnel-shaped surface depression that enables visual observation of the vortex structure. As the RMF strength is increased the eyewall diameter grows until it breaks down to multiple vortices. A number of further observed similarities to tornado-like vortices will be discussed.
Keywords: -
  • Invited lecture (Conferences)
    APS-DFD 2014 meeting, 23.-25.11.2014, San Francisco, USA
  • Open Access LogoAbstract in refereed journal
    Bulletin of the American Physical Society 59(2014), 20

Publ.-Id: 21619 - Permalink


Correlation of electron and laser beam parameters to the spectral shape and bandwidth of laser-Thomson backscattering x-ray beams
Irman, A.; Jochmann, A.; Debus, A.; Couperus, J. P.; Trotsenko, S.; Kuntzsch, M.; Lehnert, U.; Wagner, A.; Schlenvoigt, H.-P.; Bussmann, M.; Sthöhlker, T.; Seipt, D.; Thorn, D. B.; Ledingham, K. D.; Cowan, T.; Sauerbrey, R.; Schramm, U.;
Development of advanced x-ray sources based on laser-Thomson scattering mechanism is becoming important pushed by a strong demand for ultrashort hard x-ray pulses, which can serve as a novel tool for structural analysis of complex systems with unprecendented temporal and spatial resolution. The spectral shape and bandwidth of this x-ray beam is the result from the interplay between interacting electron and laser beam parameters. We present high resolution angle and energy resolved measurements on the x-ray photon distribution generated by colliding picosecond electron bunches from the ELBE linear accelerator with counter-propagating laser pulses from the 150 TW DRACO Ti:Sapphire laser system. The measured data and an ab-initio comparison with the 3D radiation code CLARA enable us to reveal parameter influences and correlation of both interacting beams. We conclude that in the low laser intensity interaction regime the electron angular distribution and the laser bandwidth, as in the case of ultrashort laser pulses, give a strong influence to the x-ray spectral shape and bandwidth. We also show the x-ray spectral broadening as the laser intensity increases indicating nonlinear interaction on the scattering process. Controlling these parameters is necessary for designing future Thomson x-ray sources with a specific bandwidth suited to an application.
Keywords: laser-Thomson backscattering x-ray, ELBE electron beam, ultrashort x-ray, high power laser
  • Invited lecture (Conferences)
    16th Advanced Accelerator Concepts Workshop (AAC 2014), 13.-18.07.2014, San Jose, United States

Publ.-Id: 21618 - Permalink


LIMTECH A5: Liquid metal two-phase flows
Strumpf, E.; Eckert, S.; Richter, T.; Gerbeth, G.;
Measurements for rising single bubbles were performed in a cuboid benchmark experiment filled with the liquid metal GaInSn. Data was acquired by two different ultrasound techniques simultaneously, which are Ultrasound Doppler Velocimetry (UDV) and Ultrasound Transit Time Technique (UTTT). The focus was on the influence of a horizontal magnetic field on the bubble behavior.
Keywords: liquid metal, two-phase, single bubble, horizontal magnetic field, UDV, UTTT
  • Poster
    LIMTECH annual meeting 2014, 10.-11.11.2014, Ilmenau, Deutschland

Publ.-Id: 21617 - Permalink


Highlights of Resonance Measurements Obtained With HADES
Epple, E.; Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dybczak, A.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, K.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc3, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.;
This contribution aims to give a basic overview over the latest results regarding the production of resonances in dierent collision systems. The results were extracted with help of the HADES experiment which is a multipurpose detector located at the GSI Helmholtzzentrum, Darmstadt. The main points discussed here are: the properties of the strange resonances Λ(1405) and Σ(1385), the role of Δ’s as a source of pions in the final state, production dynamics reflected in form of differential cross sections, and the role of the Φ meson as a source for K- particles.

Publ.-Id: 21616 - Permalink


Approaches to the Simulation of Compositional Data: A Nickel-Laterite comparative case study
Mueller, U.; Tolosana-Delgado, R.; van den Boogaart, K. G.;
An accurate prediction of benefit for some types of ore may require not just the ore grade, but a whole compositional characterization of the estimates, that is, its full mineral composition, including waste composition and nuisance elements. An example is Nickel laterite ores, where Ni/Co content must be complemented by estimates of many other elements, as these might have a notable impact on ore processing.
Estimates are often obtained with (co)kriging or co-simulation. However, geostatistics applied to compositional data may yield spurious and inconsistent results because of the constant sum constraint. The log-ratio approach avoids such problems. Like anamorphosis, it proposes a three-step procedure: (1) data are mapped to a set of log ratios of components, for example the additive log-ratio transformation (alr); (2) transformed scores are modelled with an appropriate fully multivariate geostatistical toolbox (e.g. direct/cross-variograms and cokriging or co-simulation); and (3) results are back-transformed to the original units. Some practical aspects may make the application of this technique difficult: the assumption of Gaussianity and the high dimensionality of the compositions combined with the need for using multivariate methods. This contribution compares several ways of treating compositional data (combining anamorphosisnormal score transformation, logratio transformations, and minimum maximummax autocorrelation decomposition) with respect to their ability to generate sensible simulations. The various approaches considered are illustrated with a Nickel laterite data set for which 10 variables are available. Both theoretical considerations and illustration results suggest that the best combination is (log)ratio-anamorphosisnormal score transform-MAF, in this order. The factors so obtained are closer to Gaussian, approximately spatially decorrelated and can be simulated independently. Simulations can later be recombined to alr-simulations, which in turn may be converted back to point compositions. The resulting simulated compositions are compared with a full Gaussian co-simulation of the raw data. The logratio methodsy show a reasonable to good reproduction of mean values and distribution of the data set and by construction honour the total sum constraint, in contrast to the simulations based on the raw data for which the total sums fluctuate strongly.
  • Contribution to proceedings
    SMP 2014, Ore body Modelling and Strategic Mine Planning Symposium 2014, 24.-26.11.2014, Perth, Australia
    Orebody Modelling and Strategic Mine Planning, SMP 2014, Integrated mineral investment and supply chain optimisation, Cartlon Victoria, Australia: Australasian Institute of Mining and Metallurgy, 987-1-925100-19-8, 61-72

Publ.-Id: 21615 - Permalink


A comprehensive study of the magnetic, structural, and transport properties of the III-V ferromagnetic semiconductor InMnP
Khalid, M.; Gao, K.; Weschke, E.; Hübner, R.; Baehtz, C.; Gordan, O.; Salvan, G.; Zahn, D. R. T.; Skorupa, W.; Helm, M.; Zhou, S.;
The manganese induced magnetic, electrical, and structural modification in InMnP epilayers, prepared by Mn ion implantation and pulsed laser annealing, are investigated in the following work. All samples exhibit clear hysteresis loops and strong spin polarization at the Fermi level. The degree of magnetization, the Curie temperature, and the spin polarization depend on the Mn concentration. The bright-field transmission electron micrographs show that InP samples become almost amorphous after Mn implantation but recrystallize after pulsed laser annealing. We did not observe an insulator-metal transition in InMnP up to a Mn concentration of 5 at. %. Instead all InMnP samples show insulating characteristics up to the lowest measured temperature. Magnetoresistance results obtained at low temperatures support the hopping conduction mechanism in InMnP. We find that the Mn impurity band remains detached from the valence band in InMnP up to 5 at. % Mn doping. Our findings indicate that the local environment of Mn ions in InP is similar to GaMnAs, GaMnP, and InMnAs; however, the electrical properties of these Mn implanted III-V compounds are different. This is one of the consequences of the different Mn binding energy in these compounds.
Keywords: III-V magnetic semiconductors

Publ.-Id: 21614 - Permalink


The Tayler instability at low magnetic Prandtl numbers
Stefani, F.; Barry, L.; Gundrum, T.; Kirillov, O.; Seilmayer, M.; Weber, N.; Gellert, M.; Rüdiger, G.;
The Tayler instability is a kink type instability which appears when an axial current in a cylinder crosses a certain critical value. It has been discussed as a main ingredient of the Tayler-Spruit stellar dynamo model, but may also play a role as a size-limiting factor in large-scale liquid metal batteries. We discuss several theoretical aspects and the first experimental evidence of the Tayler instability in liquid metals.
  • Lecture (Conference)
    European GdR Dynamo Meeting, 01.-04.09.2014, Cambridge, England

Publ.-Id: 21613 - Permalink


The present status of the DRESDYN project
Stefani, F.;
The DRESDYN project at Helmholtz-Zentrum Dresden-Rossendorf is intended as a platform for large-scale liquid sodium experiments on dynamo action and magnetically triggered flow instabilities. We report on the progress of the building construction, and on the design status of the precession driven dynamo experiment. Special focus is laid on new theoretical and experimental results on the magnetorotational and Tayler instability, and on the consequences for the planned liquid sodium experiment for the combined study of those instabilities. Some very recent results of a small-scale spherical Couette experiment with an applied axial magnetic field are also discussed.
  • Invited lecture (Conferences)
    Grands séminaires ISTerre, 13.11.2014, Grenoble, France

Publ.-Id: 21612 - Permalink


The present status of the DRESDYN project
Stefani, F.;
The DRESDYN project is new platform for a variety of liquid sodium experiments, comprising a large-scale precession driven dynamo experiment and a combined set-up for investigating different versions of the magnetorotational instability and the Tayler instability. We sketch the history of previous liquid metal experiments on cosmic magnetic field, and outline the status of preparations for the various facilities planned in the framework of DRESDYN.
  • Invited lecture (Conferences)
    MHD-Days 2014, 02.-03.12.2014, Potsdam, Germany

Publ.-Id: 21611 - Permalink


The new IR FEL Facility at the Fritz-Haber-Institut in Berlin
Schöllkopf, W.; Gewinner, S.; Erlebach, W.; Junkes, H.; Liedke, A.; Meijer, G.; Paarmann, A.; von Helden, G.; Bluem, H.; Dowell, D.; Lange, R.; Rathke, J.; Todd, A. M. M.; Young, L. M.; Lehnert, U.; Michel, P.; Seidel, W.; Wünsch, R.; Gottschalk, S. C.;
A mid-infrared oscillator FEL has been commissioned at the Fritz-Haber-Institut. The accelerator consists of a thermionic gridded gun, a subharmonic buncher and two S-band standing-wave copper structures. It provides a final electron energy adjustable from 15 to 50 MeV, low longitudinal (<50 keV-ps) and transverse emittance (<20 PI mm-mrad), at more than 200 pC bunch charge with a micro-pulse repetition rate of 1 GHz and a macro-pulse length of up to 15 µs. Pulsed radiation with up to 50 mJ macro-pulse energy at about 0.5% FWHM bandwidth is routinely produced in the wavelength range from 4 to 48 µm. Regular user operation started in Nov. 2013 with 6 user stations. These include, for instance, spectroscopy of bio-molecules (peptides and small proteins), which are conformer selected or embedded in superfluid helium nano-droplets at 0.4 K, as well as vibrational spectroscopy of mass-selected metal-oxide clusters and protonated water clusters in the gas phase.
  • Poster
    36th International Free Electron Laser Conference 2014, 25.-29.08.2014, Basel, Schweiz
  • Open Access LogoContribution to proceedings
    36th International Free Electron Laser Conference 2014, 25.-29.08.2014, Basel, Schweiz
    Proceedings of 36th International Free-Electron Laser Conference, CERN: JACoW

Publ.-Id: 21610 - Permalink


The new ELBE Center for High Power Radiation Sources at HZDR: Status and Opportunities
Seidel, W.;
The ELBE user facility located at the Helmhotz-Zentrum Dresden-Rossendorf operates a superconducting electron linear accelerator , which provides short (picosecond) electron bunches with energies up to 35 MeV at a 13 MHz repetition rate. Here we discuss the basic parameters of the ELBE Center and the experimental opportunities at the facility.
  • Invited lecture (Conferences)
    Turkish-German Workshop on Particle Accelerators and Light Sources, 09.-10.07.2014, Istanbul, Turkey

Publ.-Id: 21609 - Permalink


Strategies for radiolabeling of commercial TiO2 nanopowder as a tool for sensitive nanoparticle detection in complex matrices
Hildebrand, H.; Schymura, S.; Holzwarth, U.; Gibson, N.; Dalmiglio, M.; Franke, K.;
Detection and quantification of engineered nanoparticles (NPs) in complex environmental or biological media is a major challenge since NP concentrations are generally expected to be low compared to elemental background levels. This study presents three different options for radiolabeling of commercial titania NP (TiO2-NP, AEROXIDE® P25, Evonik Industries, mean diameter 21 nm) for particle detection, localization and tracing under various experimental conditions. The radiolabeling procedures ensure stability and consistency of important particle properties such as size and morphology. For the first time, detection (and quantification) limits for TiO2-NPs in concentrations as low as 0.5 ng/L can be realized.

Publ.-Id: 21608 - Permalink


Theranostic mercury: 197(m)Hg with high specific activity for imaging and therapy
Walther, M.; Preusche, S.; Bartel, S.; Wunderlich, G.; Freudenberg, R.; Steinbach, J.; Pietzsch, H.-J.;
The no carrier added (NCA) radionuclide 197(m)Hg is accessible through proton induced nuclear reactions on gold.The decay properties of both simultaneous produced nuclea risomers 197mHg and 197Hg like convenient half life, low energy gamma radiations for imaging, Auger and conversion electrons for therapy are combined with unique chemical and physical properties of mercury and its compounds. Gold as a monoisotopic element has a natural abundance of 100% 197Au superseding expensive enrichment for the target material. Additionally, the high thermal conductivity of gold enables high beam current irradiations. For separation of target material a liquid–liquid extraction method was applied.
Keywords: 197Hg; Theranostics; Dosimetry; 177Lu; Auger and conversion electrons

Publ.-Id: 21607 - Permalink


Wissens- und Innovationsgemeinschaften (KIC) am Beispiel des KIC Rohstoffe - nachhaltige Erkundung, Gewinnung, Verarbeitung, Verwertung und Substitution
Dirlich, S.; Klossek, A.;
Der Vortrag erläutert anhand von drei Leitfragen (Ziele von KIC, Synergien zur nationalen Forschung und aktuelle Entwicklungen) Wissens- und Innovationsgemeinschaften im Allgemeinen und geht im Besondere auf das geplante KIC Rohstoffe ein. Mit dem KIC Rohstoffe sollen die Ziele "vom Labor in den Markt", "vom Studenten zum Unternehmer" und "von der Idee zum Produkt" auf den Rohstoffsektor übertragen werden. Dabei wird die gesamte Kette von der Erkundung bis zum Recycling berücksichtigt. Für deutsche Wissenschaftler gibt es zahlreiche Synergiemöglichkeiten angesichts eines europäischen Netzwerks aus fast 120 Partnern aus den Bereichen Forschung, Bildung und Industrie. Das KIC beschäftigt sich insbesondere mit der Rohstoffverfügbarkeit in Europa, der Substitution kritischer Rohstoffe und der Nachhaltigkeit in der gesamten Kette der Rohstoffindustrie.
Keywords: raw materials, resources supply, innovation, knowledge, KIC
  • Invited lecture (Conferences)
    11. Fona-Forum, 29.09.2014, Berlin, Deutschland

Publ.-Id: 21606 - Permalink


Attachment of solid elongated particles on the surface of a stationary gas bubble
Lecrivain, G.; Petrucci, G.; Rudolph, M.; Hampel, U.; Yamamoto, R.;
Froth flotation is a separation process which plays a major role in the mining industry. It is essentially employed to recover a vast array of different valuable commodities such as rare earth minerals essential to the manufacture of high-tech products. Owing to its simplicity, the process is also widely used for the de-inking of recycled paper fibres and for the removal of pollutants from waste water. The flotation process essentially relies on the attachment of solid particles on the surface of gas bubbles immersed in water. The present study seeks to investigate the effect of the particle shape on the attachment mechanism. Using an in-house optical micro-bubble sensor the approach, the sliding and the adhesion of micron milled glass fibres on the surface of a stationary air bubble immersed in stagnant water is thoroughly investigated. The translational and rotational velocities were measured for fibres of various aspect ratios. The results are compared with a theoretical model and with experimental data obtained with spherical glass beads. It is found that the fibre orientation during the sliding motion largely depends on the collision area. Upon collision near the upstream pole of the gas bubble the major axis of the fibre aligns with the local bubble surface (tangential fibre alignment). If collision occurs at least 30° further downstream only head of the fibre is in contact with the gas–liquid interface (radial fibre alignment).
Keywords: Froth flotation; Three-phase system; Solid elongated particles; Particle attachment; Gas-liquid interface

Publ.-Id: 21605 - Permalink


NeuLAND time of flight detector for 200-1000 MeV neutrons read out by fast photosensors
Bemmerer, D.;
A new setup for kinematically complete reaction experiments for beams of radioactive nuclei far from the valley of stability is under construction at FAIR Darmstadt, Germany. NeuLAND, a highly efficient (>90%) neutron time of flight detector made of fast plastic scintillators is included in the setup. In order to reach proper resolution in the reconstructed energy spectrum, a time resolution of sigma < 150 ps is required. Using the ELBE picosecond electron beam as a time reference, it is currently being studied whether semiconductor-based photosensors (SiPMs) can be used for the readout of the NeuLAND scintillator bars.
  • Lecture (Conference)
    WINS 2014 Workshop on Elastic and Inelastic Neutron Scattering, 03.-05.12.2014, Dresden, Deutschland

Publ.-Id: 21604 - Permalink


Experimental investigations of a magnetically driven Tornado-like vortex by means of Ultrasound-Doppler Velocimetry
Vogt, T.; Grants, I.; Eckert, S.; Gerbeth, G.;
The spin-up of a concentrated vortex in a liquid metal cylinder with a free surface is considered experimentally. The vortex is driven by two flow independent magnetic body forces. A continuously applied rotating magnetic field provides the source of the angular momentum. A pulse of about one order of magnitude stronger travelling magnetic field drives a converging flow that temporarily focuses this angular momentum towards the axis of the container. A highly concentrated vortex forms that produces a funnel-shaped surface depression. In this study we have used some modified settings for the UDV device in order to detect the vertical position of the free surface along the beam line. The main modification was a reduction of the echo detection sensitivity. In this way the echo from microscopic particles was blinded out. Instead, only the position of the strong echo from the free surface was detected and recorded. We explore experimentally the duration, the depth and the conditions of formation of this funnel.
Keywords: gas entrainment, bubble detection
  • Lecture (Conference)
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 26.-29.08.2014, Strasbourg, Frankreich
  • Open Access LogoContribution to proceedings
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 26.-29.08.2014, Strasbourg, Frankreich
    Proceedings of the 9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering

Publ.-Id: 21603 - Permalink


Using XFELs to probe the interaction dynamics of ultra-intense lasers with solid-density matter
Cowan, T. E.; Kluge, T.; Huang, L.; Gutt, C.; Pelka, A.; Bussmann, M.;
The advent of intense coherent hard x-ray sources based on free electron lasers have opened a new era of ultrafast science. Facilities such as FLASH, LCLS, SACLA, and the under-construction European XFEL, will enable time and spatially resolved probing of atomic, molecular, chemical, biological and plasma dynamics, on the scale of fs and nm. Here we present theoretical concepts to make use of coherent x-ray scattering to probe ultra-intense laser-driven plasmas. In addition, status of the HIBEF User Consortium at the European XFEL will be presented.
Keywords: X-rays, XFEL, ultrafast science, relativistic plasmas
  • Invited lecture (Conferences)
    Graduate School of Engineering Seminar, Osaka University, 07.01.2014, Osaka, Japan

Publ.-Id: 21602 - Permalink


The 22Ne(p,gamma)23Na reaction studied at LUNA: results from the germanium detector based part of the experiment
Bemmerer, D.;
The 22Ne(p,γ)23Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle is active in asymptotic giant branch stars as well as in novae and contributes to the nucleosythesis of neon and sodium isotopes. In order to reduce the uncertainties in the predicted nucleosynthesis yields, new experimental efforts to measure the 22Ne(p,γ)23Na cross section directly at the astrophysically relevant energies are needed.
The seminar talk will report on the recently concluded first phase of the 22Ne(p,γ)23Na experiment at LUNA. Using a windowless, isotopically enriched 22Ne gas target and two high-purity germanium detectors, selected, previously unobserved low-energy resonances were studied. The preliminary results will be summarized, and an outlook on the second phase of the experiment with a 4pi summing detector will be given.
  • Invited lecture (Conferences)
    INFN Laboratori Nazionali del Gran Sasso Seminar, 10.12.2014, Assergi, Italien

Publ.-Id: 21601 - Permalink


Separation of ultrafine particles by two-liquid flotation: Selectivity and process behavior analysis
Rudolph, M.; Peuker, U. A.; Leistner, T.;
It is well known, that for conventional froth flotation techniques the processing of ultrafine mineral particles is generally inefficient and results in rather low-grade concentrates and relatively high losses of valuable minerals. Therefore, the investigation of other possible methods, which can selectively separate such fine particle systems effectively, is of considerable interest.
In this study, the application of two-liquid flotation, a flotation-related process using oil droplets instead of air bubbles, is investigated as a possible processing strategy for the separation of ultrafine particle systems. The investigation involves the testing of the two-liquid flotation technique as simple laboratory-scale batch trials and moreover, the up-scaling to a semi-continuous process by using a modified lab scale flotation column. Magnetite and quartz particles, with particle sizes below 10 μm respectively, as academic mineral mixture and iso-octane and water as the two immiscible liquid phases are chosen for the experiments. To manipulate the wettability of the magnetite particles as well as the interfacial tension of the oil/water interfaces, surface active reagents of fatty acid basis are introduced in the system. The selectivity of the process is characterized by determining the removal of magnetite particles from the aqueous suspension through selective accumulation at the oil/water interface or extraction into the oil phase, respectively. Operational parameters including pH of the aqueous suspension, additional electrolyte addition and surfactant type as well as dosage are varied in order to maximize the efficiency and stability of the process.
Keywords: ultra fine particle prossessing, flotation methods, two-liquid flotation
  • Contribution to proceedings
    XXVII International Mineral Processing Congress, 20.-24.10.2014, Santiago de Chile, Chile
    Proceedings of the XXVII International Mineral Processing Congress

Publ.-Id: 21600 - Permalink


Mineralization derived from felsic magma? A case study on Zr-Nb-REE deposits in Western Mongolia
Kempe, U.; Möckel, R.;
The genesis of unconvential Zr-Nb-REE deposits is still under discussion. The mineralization of the Khalzan Buregte and surrounding massifs in western Mongolia is introduced as a case study. We present data showing that the enrichment of valuable elements is mainly due to multistage metasomatic alteration, although the primary contents are quite high as well. The theory of secondary enrichment is also widened on other deposits in the Erzgebirge mountains, Saxony/Germany for comparison.
Keywords: rare earth elements REE, Khalzan Buregte, Mongolia
  • Invited lecture (Conferences)
    13th Freiberg Short Course in Economic Geology - Rare earth element deposits, 08.-12.12.2014, Freiberg, Deutschland

Publ.-Id: 21598 - Permalink


Background intercomparison with an active shielded HPGe detector extended to Freiberg mine in Germany
Szücs, T.; Bemmerer, D.; Reinhardt, T. P.; Schmidt, K.; Takács, M. P.; Wagner, L.;
A key requirement for underground nuclear astrophysics experiments is the very low background level in germanium detectors. The reference for these purposes is the world’s so far only underground accelerator laboratory for nuclear astrophysics, LUNA. LUNA is located deep underground in the Gran Sasso laboratory in Italy, shielded from cosmic rays by 1400m of rock. The background at LUNA was studied in detail using an escape-suppressed Clover-type HPGe detector [1]. Exactly the same detector was subsequently transported to the Felsenkeller underground laboratory in Dresden, shielded by 45m of rock, and the background was shown to be only a factor of three higher than at LUNA when comparing the escape-suppressed spectra, with interesting consequences for underground nuclear astrophysics [2]. As the next step of a systematic study of the effects of a combination of active and passive shielding on the cosmic ray induced background, this detector has recently been brought to the "Reiche Zeche" mine in Freiberg, Germany, shielded by 150m of rock.
The data available with one and the same actively shielded HPGe detector at the Earth's surface and below 45, 150, and 1400m of rock allow getting a general understanding of the effects of active shielding with depth.
– Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (HGF VH-VI-417).

[1] T. Szücs et al., Eur. Phys. J. A 44, 513 (2010).
[2] T. Szücs et al., Eur. Phys. J. A 48, 8 (2012).
Keywords: underground, nuclear astropysics, gamma background
  • Poster
    13th international symposium on Nuclei in the Cosmos (NIC-XIII), 07.-11.07.2014, Debrecen, Hungary

Publ.-Id: 21597 - Permalink


Determination of level widths in 15N using nuclear resonance fluorescence
Szücs, T.; Bemmerer, D.; Caciolli, A.; Fülöp, Z.; Massarczyk, R.; Michelagnoli, C.; Reinhardt, T. P.; Schwengner, R.; Takács, M. P.; Ur, C. A.; Wagner, A.; Wagner, L.;
The stable nucleus 15N is the mirror of the astrophysically important 15O, the product of the slowest reaction in the hydrogen burning CNO cycle, which therefore determine the production rate of the cycle.
Most of the 15N level widths below the nucleon emission thresholds are known from just one nuclear resonance fluorescence (NRF) measurement published more than 30 years ago, with limited precision in some cases [1]. A recent experiment with the AGATA demonstrator array aimed to determine level widths using the Doppler Shift Attenuation Method (DSAM) in 15O and 15N populated in the 14N + 2H reaction. In order to set a benchmark value for the upcoming AGATA demonstrator data, the widths of several 15N levels have been studied with high precision using the bremsstrahlung facility gELBE [2] at the electron accelerator of Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The precision of our new dataset are on a 10% level for the weak transitions, which have 60% and 100% error bars in the old dataset. The preliminary data seem to confirm the earlier NRF data.
- Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (HGF VH-VI-417).

[1] R. Moreh et al., Phys. Rev. C 23, 988 (1981).
[2] R. Schwengner et al., Nucl. Inst. Meth. A 555, 211 (2005).
Keywords: Level widths, nuclear astrophysics, bremsstrahlung
  • Poster
    13th international symposium on Nuclei in the Cosmos (NIC-XIII), 07.-11.07.2014, Debrecen, Hungary
  • Poster
    Fifteenth International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS15), 25.-29.08.2014, Dresden, Germany
  • Open Access LogoContribution to proceedings
    Fifteenth International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS15), 25.-29.08.2014, Technische Universität Dresden, Germany
    Capture Gamma-Ray Spectroscopy and Related Topics Proceedings of the Fifteenth International Symposium: EPJ Web of Conferences, 978-2-7598-1794-8, 03013
    DOI: 10.1051/epjconf/20159303013

Publ.-Id: 21596 - Permalink


Background intercomparison with escape-suppressed germanium detectors in underground mines
Szücs, T.; Bemmerer, D.;
A key requirement for underground nuclear astrophysics experiments is the very low background level in germanium detectors underground. The reference for these purposes is the world’s so far only underground accelerator laboratory for nuclear astrophysics, LUNA. LUNA is located deep underground in the Gran Sasso laboratory in Italy, shielded from cosmic rays by 1400 m of rock. The background at LUNA was studied in detail using an escape-suppressed Clover-type HPGe detector [1]. Exactly the same detector was subsequently transported to the Felsenkeller underground laboratory in Dresden, shielded by 45 m of rock, and the background was shown to be only a factor of three higher than at LUNA when comparing the escape-suppressed spectra, with interesting consequences for underground nuclear astrophysics [2]. As the next step of a systematic study of the effects of a combination of active and passive shielding on the cosmic ray induced background, this detector is now being brought to the "Reiche Zeche" mine in Freiberg/Sachsen, shielded by 150 m of rock. The data from the Freiberg measurement will be shown and discussed. – Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (HGF VH-VI-417).

[1] T. Szücs et al., Eur. Phys. J. A 44, 513 (2010)
[2] T. Szücs et al., Eur. Phys. J. A 48, 8 (2012)
Keywords: Underground, nuclear astrophysics, low background
  • Lecture (Conference)
    DPG Frühjahrstagung, Fachgruppe Hadronen und Kerne, 21.03.2014, Frankfurt, Germany

Publ.-Id: 21595 - Permalink


Gamma-ray width measurements in 15N at the ELBE nuclear resonance fluorescence setup
Szücs, T.; Bemmerer, D.; Massarczyk, R.; Schwengner, R.; Takács, M.; Wagner, L.;
The stable nucleus 15N is the mirror of the astrophysically important 15O, compound nucleus of the leading reaction of the Bethe-Weizsäcker cycle of hydrogen burning. Most of the 15N level widths below the neutron and proton emission thresholds are known from just one nuclear resonance fluorescence (NRF) measurement published more than 30 years ago, with unsatisfactory precision on some cases [1]. A recent experiment with the AGATA demonstrator array aimed to determine level widths with the Doppler Shift Attenuation Method (DSAM) in 15O and 15N populated in 14N + 2H reaction. In order to set a benchmark value for the upcoming AGATA demonstrator data, the widths of several 15N levels are being studied using the bremsstrahlung facility γELBE at the electron accelerator of Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The γELBE experiment and its preliminary results will be presented. – Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (HGF VH-VI-417).

[1] R. Moreh et al., Physical Review C 23, 988 (1981)
Keywords: Nuclear astrophysiscs, level widths, gamma scattering, bremsstrahlung
  • Lecture (Conference)
    DPG Frühjahrstagung, Fachgruppe Hadronen und Kerne, 20.03.2014, Frankfurt, Germany

Publ.-Id: 21594 - Permalink


Underground nuclear astrophysics (Dubna lecture)
Szücs, T.;
The very low background level is a key requirement for underground nuclear astrophysics experiments. The reference for these purposes is the world’s so far only underground accelerator laboratory for nuclear astrophysics, LUNA. LUNA is located deep underground in the Gran Sasso laboratory in Italy, shielded from cosmic rays by 1400m of rock.
This talk presents the need and the advantages of an underground setting. It covers also new findings, regarding active shielding at underground settings, leading to have the possibility to perform nuclear astrophysics experiments with sufficient precision also at shallow underground.
Finally the recent nuclear astrophysics related experiments performed at the surface, at LUNA, and at different underground depths will be presented.
Keywords: Underground, Nuclear Astropysics, low background
  • Invited lecture (Conferences)
    Helmholtz International Summer School "NUCLEAR THEORY AND ASTROPHYSICAL APPLICATIONS", 29.07.2014, Dubna, Russia

Publ.-Id: 21593 - Permalink


Advanced multi-physics simulation for reactor safety in the framework of the NURESAFE project
Chanaron, B.; Ahnert, C.; Crouzet, N.; Sanchez, V.; Kolev, N.; Marchand, O.; Kliem, S.; Papukchiev, A.;
Since some years, there is a worldwide trend to move towards “higher-fidelity” simulation techniques in reactor analysis. One of the main objectives of the research in this area is to enhance the prediction capability of the computations used for safety demonstration of the current LWR nuclear power plants through the dynamic 3D coupling of the codes simulating the different physics of the problem into a common multi-physic simulation scheme.
In this context, the NURESAFE European project aims at delivering to the European stakeholders an advanced and reliable software capacity usable for safety analysis needs of present and future LWR reactors and developing a high level of expertise in Europe in the proper use of the most recent simulation tools including uncertainty assessment to quantify the margins toward feared phenomena occurring during an accident. This software capacity is based on the NURESIM European simulation platform created during FP6 NURESIM project which includes advanced core physics, two-phase thermal-hydraulics, fuel modeling and multi-scale and multi-physics features together with sensitivity and uncertainty tools. These physics are fully integrated into the platform in order to provide a standardized state-of-the-art code system to support safety analysis of current and evolving LWRs.
Keywords: NURESIM, SALOME, NURESAFE, Multi-physics, Multi-scale, reactor safety, simulation platform

Publ.-Id: 21592 - Permalink


Nanopatterning of Magnetic CrNi Prussian Blue Nanoparticles Using a Bacterial S-layer as Biotemplate
Valero, E.; Martín, M.; Gálvez, N.; Sánchez, P.; Raff, J.; Merroun, M. L.; Dominguez-Vera, J. M.;
We have developed a simple process to fabricate on a bioplatform patterns of nanoparticles of a molecule-based magnet. Nanoparticles of the ferromagnetic Prussian blue derivative CsxNi[Cr(CN)6] were orderly deposited onto S-layers of Lysinibacillus sphaericus, forming a dense carpet of nanoparticles following the square lattice (p4) pattern of the biotemplate. These results are encouraging to extend this approach by focusing on molecule-based magnets patterned into domains with controlled shapes and positions on a biosurface.
Keywords: Prussian blue nanoparticles, S-layer, molecular magnet, nanopatterning

Publ.-Id: 21591 - Permalink


High-field High-Repetition-rate sources for the Coherent THz Control of Matter
Green, B.; Kovalev, S.; Asgekar, V.; Geloni, G.; Lehnert, U.; Golz, T.; Kuntzsch, M.; Bauer, C.; Hauser, J.; Voigtlaender, J.; Wustmann, B.; Koesterke, I.; Schwarz, M.; Freitag, M.; Arnold, A.; Teichert, J.; Justus, M.; Seidel, W.; Ilgner, C.; Awari, N.; Nicoletti, D.; Kaiser, S.; Laplace, Y.; Rajasekaran, S.; Zhang, L.; Winnerl, S.; Schneider, H.; Schay, G.; Lorenzc, I.; Rauscher, A.; Radu, I.; Mährlein, S.; Kampfrath, T.; Wall, S.; Heberle, J.; Malnasi, A.; Cavalleri, A.; Steiger, A.; Müller, A. S.; Helm, M.; Schramm, U.; Cowan, T.; Michel, P.; Fisher, A. S.; Stojanovic, N.; Gensch, M.;
Ultra-short flashes of THz light with low quantum energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic ultra-short electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented repetition rates up to the MHz regime. We demonstrate parameters that already exceed state of the art laser-based sources by more than 2 orders of magnitude. The parameters are scalable and once operational at their design parameters this type of sources will provide 1 MV/cm electric fields and magnetic fields in the few 100 mT regime at repetition rates of few 100 kHz.
Keywords: superradiance, coherent control, THz, High-field

Publ.-Id: 21590 - Permalink


Using nature´s genius for the functionalization of surfaces
Raff, J.; Günther, T.; Weinert, U.; Vogel, M.; Suhr, M.; Matys, S.; Drobot, B.; Pollmann, K.;
Many useful physical and chemical methods have been developed to modify and functionalize surfaces of different materials. These techniques allow a broad variety of surface modifications ranging from nanostructuring, implanting ions over hydrophilization and hydrophobization to immobilization of functional molecules. Nevertheless, for some applications also biology offers interesting alternatives. Examples therefore are so called surface layer (S-layer) proteins. These self-assembling proteins form nanostructured lattices with different symmetries, provide regular arranged pores with defined size and possess different kinds of regular arranged functional groups. One of their intrinsic properties is to provide a physiological environment and to stabilize coupled biofunctional molecules. Additionally, S-layers from isolates recovered from heavy metal contaminated environments have outstanding metal binding properties and are highly stable. By combining S-layers with a layer-by-layer technique different materials can be furnished with such coatings.
The produced biohybrid materials can be directly used as selective metal filter material or can be further modified. The S-layer coatings are perfect templates for the production and immobilization of regular arranged precious metal nanoparticles (e.g. Pd, Pt, Au) with defined sizes and for the immobilization of commercially available nanoparticles. Thusly immobilized TiO2 nanoparticles (P25) show a higher catalytic activity compared to same amounts of suspended TiO2 nanoparticles. Incidentally, formed reactive oxygen species do not affect the S-layer support. As S-layers in nature act as immobilization matrix for exoenzymes, these biohybrid materials can also be modified with dyes and biofunctional molecules. Combining these last two, a new generation of biosensors can be developed.
These four examples demonstrate the S-layer technology platform possess a high potential for materials science and industrial application.
Keywords: S-layer, nanoparticle, biofilter, biosensor
  • Lecture (Conference)
    Euro BioMAT 2015, 21.-22.04.2015, Weimar, Deutschland

Publ.-Id: 21589 - Permalink


Strategische Metalle und Mineralien - die BMBF Fördermaßnahme r³
Dürkoop, A.; Gräbe, G.;
Übersicht zur r³ Fördermaßnahme (Präsentation auf PIUS Länderkonferenz)
  • Invited lecture (Conferences)
    PIUS Länderkonferenz 2014, 02.07.2014, Frankfurt am Main, Deutschland

Publ.-Id: 21588 - Permalink


European Benchmark on the ASTRID-like Low-void-effect Core Characterization: Neutronic Parameters and Safety Coefficients
Bortot, S.; Alvarez-Velarde, F.; Fridman, E.; Cruzado, I. G.; Herranz, N. G.; Mikityuk, K.; Panadero, A.-L.; Pelloni, S.; Ponomarev, A.; Sciora, P.; Seubert, A.; Tsige-Tamirat, H.; Vasile, A.;
A benchmark analysis was launched within the Work Package on Core Safety of the EU FP7 cross-cutting project supporting the European Sustainable Industrial Initiative (ESNII), named ESNII+, aimed at providing a quantitative estimation of the uncertainties affecting the calculation of both core static neutronic parameters and safety coefficients of a Sodium-cooled Fast Reactor (SFR) low-void-effect core similar to the one considered for the Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID). Established deterministic and stochastic neutronic codes, as well as different nuclear data libraries, were employed by eight European organizations to perform a complete core characterization, with the ultimate goal to achieve consensus on computational methods and associated databases to be employed for advanced-design SFRs safety analyses. The comparison of the results obtained by the participating institutions provided quantitative information about capabilities and limitations of the different approaches, and about library effects, by highlighting the sensitivity of safety parameters to both computational techniques and nuclear data. Selected results of the first phase of the benchmark are presented and analyzed, along with a discussion of the planned R&D activities needed to improve the present benchmark status.
  • Contribution to proceedings
    2015 International Congress on Advances in Nuclear Power Plants (ICAPP '15), 03.-06.05.2015, Nice, France

Publ.-Id: 21587 - Permalink


Applications of Atomic Force Microscopy in Particle Technology
Fritzsche, J.; Rudolph, M.; Peuker, U. A.;
Atomic force microscopy (AFM) and the colloidal probe mode allow for the first time the direct measurement of particle interactions. Thus, it is the direct way to evaluate the adhesion of particles to surfaces or to each other. With the direct measurement it is significantly easier to quantify the effect of changing surface properties on the interaction forces. Several surface properties influence the interaction forces like surface roughness, local chemical composition (e.g. adsorbed surfactants), electrostatic charge and surface energies.
Phase contrast AFM
The non-contact mode of AFM also allows characterizing the composition of a heterogeneous surface like that of a nano-composite material, with a high resolution, which is comparable to TEM. For this method, it is not necessary to prepare translucent samples, but only to minimize the surface roughness, e.g. by polishing to avoid a secondary signal.
Colloidal Probe AFM (dry)
The colloidal probe provides the real adhesion effects taking into account both the roughness of the substrate as well as that of the particle.
Colloidal Probe AFM (wet - liquid cell)
The colloidal probe measurements in the liquid phase allow quantifying the surface modification due to adsorption from the aqueous phase to the substrate, or to the particle at the cantilever itself. This adsorption of surfactants like modifiers or flotation collectors becomes visible as well as an interaction of the surface with one component of a water-alcohol mixture. The detection of nano-bubbles, which are one source of strong hydrophobic interactions, is also possible.
Keywords: AFM, particle technology, CP-AFM, Phase contrast, contact mode, non-contact mode, tapping mode
  • Invited lecture (Conferences)
    International Powder and Nanotechnology Forum, Achema 2015, 15.-19.06.2015, Frankfurt am Main, Germany

Publ.-Id: 21586 - Permalink


Inverse Gas Chromatografie und Mikroflotation an Mineralen belegt mit physi- und chemisorbierenden Sammlermolekülen
Rudolph, M.;
Der Heterokoagulationsprozess Flotation ist eines der bedeutendsten Verfahren in der Aufbereitungstechnik und ein Schwerpunkt der Forschung am Helmholtz-Institut Freiberg für Ressourcentechnologie. Die Trennung basiert auf den unterschiedlichen Benetzbarkeiten von suspendierten (Mineral)partikeln, die zumeist durch selektiv adsorbierende amphiphile Moleküle beeinflusst werden. Häufig wurden in der Flotationsforschung für die Benetzungsbeschreibung die Kontaktwinkel zu Wasser herangezogen und mit dem Flotationsausbringen korreliert. Eine fundamentalere Charakterisierung der Mineraloberfläche basiert auf der Bestimmung der spezifischen freien Oberflächenenergien, die zusammen mit den spezifischen freien Oberflächenenergien von Wasser die Benetzung über die Young-Gleichung beschreiben. Die Inverse Gas Chromatographie (iGC) ist eine geeignete Methode die spezifischen freien Oberflächenenergieanteile und deren Verteilung an Partikelsystemen zu bestimmen. Jedoch erfolgt diese Messung an trockenen Pulverschüttungen und nicht an suspendierten Partikeln. Um den Einfluss von oberflächenaktiven Flotationsreagenzien auf die Flotierbarkeit und damit korrelierend auf die Oberflächenenergien zu bestimmen ist es daher notwendig die Art und Weise der Probenpräparation für die iGC nach Konditionierung mit Flotationsreagenzien in Wasser zu untersuchen.
In dieser Arbeit werden die Minerale Quartz (SiO2), Apatit (Ca5[F,(PO4)3]) und Magnetit (Fe3O4) auf ihre Flotierbarkeit und Oberflächenenergie für unterschiedliche Probenpräparationen untersucht sowie der Einfluss der ionischen Sammler Natriumoleat (kationisch) und Dodecyl Ammonium Acetat (anionisch), welche chemi- bzw. physisorbieren aufgezeigt. Es wird diskutiert, welcher Parameter der spezifischen freien OberIflächenenergien (und deren Verteilung) am ehesten die Hydrophobizität beschreibt und somit einen wichtigen Einfluss auf die Flotierbarkeit eines Mineralpartikels beinhaltet, also mit dem Flotationsausbringen der Mikroflotation korreliert.
Keywords: Flotation, inverse gas chromatography, collector, adsorption, hydrophobicity, surface free energy, wettability
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Agglomerations- und Schüttguttechnik, Lebensmittelverfahrenstechnik mit Lebensmittelbiotechnologie, Grenzflächenbestimmte Systeme und Prozesse, 16.-18.03.2015, Magdeburg, Germany

Publ.-Id: 21585 - Permalink


Trace elements - small concentrations, great importance!
Frenzel, M.;
A lecture was given to school students (~ ages 16 - 18) about the industrial importance of certain trace elements occurring in different raw materials, and the methods used to study their behaviour in the related geological systems.
Keywords: Trace elements, geology, analytics
  • Lecture (others)
    Akademische Woche 2014, 13.02.2014, Meißen, Germany

Publ.-Id: 21584 - Permalink


Partikelsonden-Rasterkraftmikroskopie für die Untersuchung hydrophober Wechselwirkungen in der Flotation von Mineralen
Rudolph, M.;
Spätestens seit dem Patent der Gebrüder Bessel aus Dresden von 1877 nutzt man die Anhaftung hydrophober Partikel an Gasblasen in der Flotation, einer Heterokoagulationstrennung, technologisch aus, um Partikelgemische auf Basis ihrer chemisch veränderlichen Benetzungseigenschaften voneinander zu trennen. Ein wesentlicher Mikroprozess ist hierbei der Anlagerungsvorgang, bestimmt durch das Wechselwirkungspotential zwischen einem Partikel und einer Gasblase. Die klassische DLVO Wechselwirkungstheorie beinhaltet für diese Partner nur repulsive Terme, d.h. abstoßende Doppelschichtwechselwirkungen und abstoßende van der Waals Wechselwirkungen durch eine negative Hamaker-Konstante. Über die Physik der zwingend notwendigen, weil prozessbestimmenden, weit reichenden, anziehenden Wechselwirkungskomponente ist man sich in der Literatur noch nicht einig. Viele Wissenschaftler sehen feinste Gasdomänen auf hydrophoben Oberflächen, oft als Nanobubbles oder Micropancakes bezeichnet, als Vermittler von weit reichenden kapillaren Anziehungskräften. Andere sehen eine weit reichende Wasserstrukturstörung an hydrophoben Oberflächen als Ursache für eine somit entropisch begründete Anziehung.
Am Helmholtz-Institut Freiberg für Ressourcentechnologie werden atomare Gesamtwechselwirkungen zwischen unterschiedlich benetzenden Oberflächen (z.B. Mineralen) und hydrophoben Modellpartikeln in Lösung mit Hilfe der Partikelsonden Rasterkraftmikroskopie analysiert. Mit diesen Untersuchungen soll es später möglich werden, die Flotierbarkeit von Mineralen in Erzschliffen als Funktion der physikalisch chemischen Variablen direkt zu untersuchen. Zudem wird ein Beitrag geleistet um die noch stark diskutierten Mechanismen der Anhaftung hydrophober Partikel an Gasblasen letztlich zu klären. Am Poster wird der aktuelle Forschungsstand kurz reflektiert, die Methode der Partikelsonden Rasterkraftmikroskopie vorgestellt und experimentell verifiziert an den Mineralen Magnetit und Quarz unter Einwirkung unterschiedlicher ionaktiver Sammler im Vergleich zu Mikroflotationsuntersuchungen an der Hallimond-Röhre.
Keywords: AFM, hydrophobic interactions, Flotation, DLVO, nanobubbles
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppen Agglomerations- und Schüttguttechnik, Lebensmittelverfahrenstechnik mit Lebensmittelbiotechnologie, Grenzflächenbestimmte Systeme und Prozesse, 16.-18.03.2015, Magdeburg, Germany

Publ.-Id: 21583 - Permalink


Trace elements - small concentrations, great importance
Frenzel, M.;
A presentation was given to school students (~ ages 16 - 18) on some aspects of trace elements occurring in different kinds of raw materials, their industrial importance, the uncertainties about their geological behaviour, and the methods used to study their occurrence and distribution in geological systems.
Keywords: Trace elements, Analytical techniques
  • Lecture (others)
    Akademische Woche, 13.02.2014, Meißen, Germany

Publ.-Id: 21582 - Permalink


Selektive Trennung feinstdisperser Partikelsysteme mit Hilfe von Flotationstechniken
Schützenmeister, L.;
Deutschland ist eine der am höchsten technologisierten Industrienationen der Welt und liegt mit einem Rohstoffverbrauch von 200 kg pro Kopf und Tag ebenfalls mit an der Spitze [1]. Das Umweltbundesamt hat jedoch aus diesem Grund im Jahr 2012 nicht nur auf die damit verbundenen Umweltschäden hingewiesen sondern nachdrücklich fest-gestellt, dass Deutschland in der Zukunft sparsamer mit seinen Ressourcen umgehen muss. Anderenfalls wird es in der Zukunft aufgrund wachsender Rohstoffpreise seine weltweite Führungsrolle verlieren [1]. Die modernen High-Tech-Produkte wie Smart-phones, Tablet-PCs und LEDs aber insbesondere auch „grüne“ Technologien wie So-larzellen, Elektromotoren und Windkraftanlagen sind alle eng mit dem Verbrauch selte-ner Metalle wie Gallium, Germanium und Indium sowie den sogenannten seltenen Er-den verknüpft [2,3]. Im Zuge des wirtschaftlichen Aufschwungs der Schwellenländer nimmt jedoch der Rohstoffbedarf weltweit rasant zu. Eine herausragende Rolle spielt dabei China, da sich dort über 97 % der weltweiten Förderstätten für seltene Erden befinden [1]. Aufgrund des wachsenden Eigenbedarfs hat China jedoch den Export seltener Erden bereits zwischen 2009 und 2012 um 38 % reduziert, Tendenz steigend [seltene Erden]. Gleichzeitig wird prognostiziert, dass sich der weltweite Bedarf bspw. an Neodym und Dysprosium in den nächsten 25 Jahren um ca. 700 und 2600 % stei-gern wird [4]. Dabei ist der Preis für eine Tonne Neodym, wie sie bspw. für die Herstel-lung des Elektromagneten eines leistungsstarken, getriebelosen Offshore-Windrades benötigt wird, zwischen 2005 und 2012 bereits von 25.000 auf rund 700.000 US-Dollar gestiegen [3]. Zwar werden auch heute noch neue, reichhaltige Lagerstätten entdeckt, wie zum Beispiel durch japanische Forscher im Pazifik im Jahre 2013, jedoch ist die Gewinnung speziell in großen Tiefen auf offenem Meer mit großen Problemen verbun-den [3].
Diese Faktoren haben in den letzten Jahren zu einem Umdenken in der Ressourcen-politik geführt. So wurde von der Bundesregierung im Jahre 2011 das Helmholtz-Institut für Ressourcentechnologie in Freiberg gegründet, mit dem Ziel neue Technolo-gien zu entwickeln, welche eine effizientere Bereitstellung und Nutzung mineralischer und metallischer Rohstoffe ermöglichen [2]. Das Hauptziel der Forschung liegt sowohl in der Nutzbarmachung komplexer Erze, wie sie auch in Deutschland lagern, deren Aufbereitung mit bisherigen Technologien jedoch nicht wirtschaftlich ist, als auch in der Entwicklung effizienter Recyclingmethoden für verbrauchte Rohstoffe [2]. Eine bedeu-tende Rolle nimmt dabei die Weiterentwicklung von Flotationstechniken, speziell auch der Kolonnenflotation, ein.
Seit Beginn der achtziger Jahre wurden insbesondere zur Nachanreicherung zuneh-mend Flotationskolonnen anstelle von Flotationszellen eingesetzt [5]. Diese zeichnen sich durch ein verbessertes Wertstoffausbringen und Anreicherungsvermögen, niedri-gere Anschaffungs- und Betriebskosten, geringeren Verschleiß und geminderten Platzbedarf aus [6].
Die heute geforderten Aufbereitungsziele erfordern in der Regel eine Zerkleinerung des Materials in den Feinstkornbereich. Klassische Schaumflotation versagt jedoch ab Korngrößen von x < 20 zunehmend [7]. Eine Lösung dieses Problems kann in der Anwendung der sogenannten Flüssig-Flüssig-Flotation in Flotationskolonnen liegen. Dabei wird anstelle von Luft eine organische Phase zur Flotation eingesetzt.
Die vorliegende Arbeit befasst sich daher mit der Konzeptionierung, dem Bau und dem Einfahren einer Versuchsanlage für Schaum- und Flüssig-Flüssig-Flotation. Weiterhin werden Grundlagenuntersuchungen, welche für einführende Flotationstests an der neuen Kolonne benötigt wurden, beschrieben.
Keywords: Flotation, extraction, particles, disperse systems
  • Bachelor thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Tom Leistner, Dr. Martin Rudolph
    77 Seiten

Publ.-Id: 21581 - Permalink


Transmutation of all German Transuranium under Nuclear Phase Out Conditions – Is this Feasible from Neutronic Point of View?
Merk, B.; Litskevich, D.;
The German government has decided for the nuclear phase out, but a decision on a strategy for the management of the highly radioactive waste is not defined yet. Partitioning and Transmutation (P&T) could be considered as a technological option for the management of highly radioactive waste, therefore a wide study has been conducted. In this group objectives for P&T and the boundary conditions of the phase out have been discussed. The fulfillment of the given objectives is analyzed using simulations of molten salt reactors with fast neutron spectrum. It is shown that the efficient transmutation of all existing transuranium isotopes would be possible in a time frame of about 60 years using three reactors and a twofold life cycle consisting of a transmuter operation and a deep burn phase. A basic insight for the optimization of the time duration of the deep burn phase is given. Further on a detailed balance of different isotopic inventories is given to allow a deeper understanding of the processes during transmutation and the effect of modelling and simulation is investigated based on three different modelling strategies and two different code versions.
Keywords: transmutation; Germany; nuclear; nuclear reactor; waste management; nuclear waste; molten salt; molten salt reactor; HELIOS; plutonium; minor actinides; transuranium

Publ.-Id: 21580 - Permalink


Flüssig-Flüssig Flotation in einer Tropfensäule – Tropfendispersitätsanalyse und Selektivität im System Magnetit-Quarz
Müller, M.;
Die selektive Extraktion von hydrophobisierten Partikeln in einer Tropfensäule ist eine Heterokoagulationstrennung, wie die Flotation. Dieser neuartige Prozess soll als Erweiterung der Flotation, insbesondere für Partikel kleiner 10 µm dienen.
In dieser Masterarbeit ist die bestehende Tropfensäule am Institut für Mechanische Verfahrenstechnik und Aufbereitungstechnik der TU Bergakademie Freiberg zu erweitern, sodass die Tropfen mit einer kamerabasierten Methode im einfachen und doppelten Kreislauf als Funktion der Zeit und unter Berücksichtigung von grenzflächenaktiven Substanzen quantifiziert werden können. Hierfür wird ein Messfenster konzipiert und in die bestehende Anlage integriert. Es soll gezeigt werden, wie die Prozessregime die Tropfendispersität über der Zeit beeinflussen.
Des Weiteren wird die selektive Trennung von Magnetit und Quarz als akademisches Stoffsystem im Scheidetrichter untersucht. Hierfür sind die natürlichen Minerale auf eine mittlere Partikelgröße von 10 µm zu konfektionieren. Als Ergebnis der Trennung im Scheidetrichter unter Variation der hydrophobisierenden Substanzen (Fettsäuren für Magnetit, bzw. Amine für Quarz), sowie von Reglern (pH Wert ändernd) wird das erfolgreichste Reagenzregime auf erste Versuche für Trennungen in der Tropfensäule zum Ende der Arbeit übernommen und untersucht. Zudem wird das natürliche Magnetit in separaten Versuchen ersetzt mit synthetischen gefällten Magnetit Nanopartikeln.
Die Untersuchungen erfolgen am Institut MVTAT in Kooperation mit dem Helmholtz-Institut Freiberg für Ressourcentechnologie des Helmholtz-Zentrums Dresden-Rossendorf.
Keywords: flotation, extraction, drop formation, magnetite, quartz
  • Master thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Tom Leistner, Dr. Martin Rudolph
    86 Seiten

Publ.-Id: 21579 - Permalink


Flotation eines Seltene-Erden-Erzes mit dem Wertmineral Eudialyt
Ludwig, K.;
Bei der Herstellung moderner elektronischer Produkte sind Erze mit Seltenen Erden unverzichtbar. Ein Beispiel hierfür ist eudialythaltiges Erz, welches das chemische Element Yttrium beinhaltet. Yttrium wird z.B bei der Produktion von Leuchtstoffen, Laserkristallen, Keramiken für Zündkerzen und Lambda-Sonden verwendet. Daneben wird es zur Steigerung der Festigkeit in einigen Legierungen genutzt. Der Anteil an Yttrium im Eudialyt-Mineral ist sehr gering. Eudialyt selbst ist außerdem stark in anderen silikatischen Mineralen verwachsen. Zudem ähneln diese silikatischen Minerale aufgrund ihrer chemischen Struktur dem Eudialyt. Die Gewinnung und Anreicherung dieses Wertstoffes aus dem Erz ist daher eine Herausforderung für die Aufbereitungsindustrie. Eine Dichtesortierung ist aufgrund der ähnlichen Dichten der einzelnen Minerale nicht möglich. Zurzeit untersucht man zwei Trennverfahren hinsichtlich ihrer Brauchbarkeit: Magnetscheidung und Flotation. Bei der Flotation spielen die Wechselwirkungen zwischen den einzelnen Mineralen und den zugesetzten Reagenzien eine entscheidende Rolle. Letztere bieten Ansatzmöglichkeiten für eine Steuerung der Flotation. Daher werden auch gegenwärtig immer wieder neue Reagenzien entwickelt und damit neue flotative Verfahren geschaffen. Im Rahmen dieser Arbeit ist die Aufbereitung eines eudialythaltigen Erzes aus Norra Kärr in Schweden mit Hilfe der Flotation zu untersuchen. Dabei wird der Einfluss von verschiedenen Reagenzien, der sogenannten Sammler und Drücker, auf die Anreicherung der einzelnen Bestandteile des Aufgabegutes analysiert.Weiterhin werden die Flotationsergebnisse von entschlammten und nicht entschlammten Proben verglichen. Die Versuche finden sowohl in saurem als auch in basischem Milieu statt. Die Zusammensetzung des Aufgabegutes und der Konzentrate wird mit Hilfe der Röntgendiffraktometrie ermittelt.
Keywords: eudialyte, rare earth elements, Flotation, aegirine, collector, hydroxamate, oleate
  • Bachelor thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Dr. Martin Rudolph
    84 Seiten

Publ.-Id: 21578 - Permalink


Charakterisierung partikelhaltiger Öl/Wasser-Emulsionen - Phasenzusammensetzung und Stabilitätsbetrachtung
Landgraf, K.;
Seit Jahrzehnten steigt die Nachfrage nach Rohstoffen und die Anforderung aus diesen einen Wertstoff möglichst rein anzureichern. Durch die zunehmende Rohstoffknappheit werden längst sekundäre Rohstoffquellen genutzt, aber auch primäre Quellen, in welchen der Wertstoff nur zu geringen Anteilen und in sehr hohen Verwachsungsgraden vorkommt. Für den Aufbereitungsprozess ist es von Nöten den Rohstoff so weit aufzuschließen, dass der Wertstoff getrennt von dem Bergematerial vorliegt. Bei einem stark verwachsenen Material entsteht dadurch ein hoher Anteil an Feingut, welches in nachgeschalteten Sortierprozessen Probleme bereitet.
Etabliert zur Feinstgutaufbereitung sind die Verfahren der Heterokoagulationstrennung, in denen Berge- und Wertstoffmaterial auf Grund verschiedener physikalischer Eigenschaften sortiert werden [1], [2], [3].
Die Schaumflotation ist der am häufigsten angewandte Prozess, wobei Partikel mit einem Durchmesser zwischen 5 und 5000 mm flotiert werden können [4]. Am effizientesten werden Partikel im Größenbereich zwischen 10 mm und 100 mm [5], [6], [7] erfasst. Damit kann in diesem Größenbereich eine hohe Produktqualität erzielt werden.
Partikel, die kleiner als 10 mm sind, bereiten im Flotationsprozess Probleme und wurden darum meist vor der Flotation abgetrennt. Der darin enthaltene Wertstoff kann somit nicht gewonnen werden.
Um auch die im Feinstanteil vorkommenden Rohstoffe nutzbar zu machen, wurde für einige Anwendungen der Schaumflotationsprozess modifiziert.
Beispielsweise wurde die Flüssig-Flüssig-Flotation entwickelt, bei der die feinen Feststoffpartikel anstatt mit Luftblasen, mit einer zweiten fluiden, mit Wasser nicht mischbare Phase koagulieren. Dies kann den Trennerfolg im Aufbereitungsprozess verbessern.
Noch setzten sich diese Prozesse in der großtechnischen Aufbereitung nicht durch, unter anderem da sie kostenintensiv sind und der Einsatz von Öl umweltproblematisch ist. Des Weiteren entsteht im Verlauf der Flüssig-Flüssig-Flotation eine Emulsion, die durch die feinen Partikel stabilisiert wird. Ein Sortierprozess ist erfolgreich, wenn es gelingt die Feststoffpartikel selektiv auszutragen und die entstehende Emulsion zu brechen. Erst dann liegen die Wertstoffpartikel getrennt von den fluiden Phasen und dem Bergematerial vor.
Um weiterhin den Rohstoffbedarf decken zu können, sollten sich Bemühungen darauf richten, diese Verfahren zu optimieren, um sie in der Aufbereitung hoch aufgeschlossener Rohstoffe einsetzen zu können.
Diese Arbeit handelt von partikelstabilisierten Emulsionen, die in einem Flüssig-Flüssig-Flotationsprozess entstehen. Mineralisches Magnetit und Quarz mit einer Partikelgröße dP,80 < 10 mm [8] werden eingesetzt und lagern sich im Versuchsverlauf an Öltropfen, die in Wasser dispergiert sind und stabilisieren diese. Die so entstehenden Emulsionen werden von der wässrigen Phase getrennt und Untersuchungen zu Phasenzusammensetzung sowie Stabilität der Emulsionen durchgeführt.
Dies soll dazu beitragen, Erkenntnisse zu deren Handhabung und Destabilisierung zu erhalten und somit auf lange Sicht die Anwendbarkeit der ölbasierten Flotationsprozesse zu ermöglichen [2], [3], [6], [8], [9].
Keywords: Flotation, extraction, Emulsion, colloidal stability
  • Bachelor thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Tom Leistner, Dr. Martin Rudolph
    119 Seiten

Publ.-Id: 21577 - Permalink


Oberflächenladungseigenschaften von synthetischen Selten-Erden Karbonaten und Selten-Erden Phosphaten und Wirkung von Sammlern und Drückern
Kratzsch, R.;
Das Helmholtz-Institut Freiberg für Ressourcentechnologie wurde im August 2011 als Institut des Helmholtz-Zentrum Dresden-Rossendorf gegründet um sich ressourcentechnologischen Fragestellungen für primäre und sekundäre Rohstoffe mit strategischen Metallen zu widmen. Die Abteilung Aufbereitung befasst sich insbesondere mit der Trennung von feinen Partikeln basierend auf unterschiedlichen Benetzungseigenschaften der Oberflächen, wie dem Prozess der Flotation. Im Fokus bzgl. Wertstoffen liegen insbesondere die Metalle der Seltenen-Erden, welche wichtig sind für High-Tech Anwendungen und somit essentiell für die deutsche Industrie.
In dieser studentischen Arbeit sollen die Oberflächenladungseigenschaften von synthetischen Selten-Erden Karbonaten (SEE-CO3) und Selten-Erden Phosphaten (SEE-PO4) im Vergleich zu Calciumcarbonat und Bariumcarbonat systematisch untersucht werden. Die physikochemischen Eigenschaften sind über den pH-Wert zu variieren. Die Wirkung von Fettsäuren als Sammler, sowie von Ligninsulfonat als Drücker sind zu untersuchen. Die Partikel sind granulometrisch zu beschreiben.
Die Untersuchungsmethoden umfassen hierbei:
- Mikroflotationsuntersuchungen in einer Hallimondröhre
- Zeta-Potential Bestimmung mit Zetasizer Nano ZS
- Partikelgrößenmessung mit Laserbeugung
- Bestimmung der spezifischen Oberfläche mit der BET-Methode
- Dichtebestimmung mit Pyknometer
- Schwingungsspektroskopie mit ATR-FTIR
- Adsorptionsuntersuchungen unter Verwendung von UV/VIS
Die Arbeit umfasst zudem eine begleitende Literaturrecherche unter Berücksichtigung aktuellster wissenschaftlicher Erkenntnisse zum Thema.
Keywords: Flotation, rare earth elements, collector, depressant, zeta potential
  • Bachelor thesis
    TU Bergakademie Freiberg, 2013
    Mentor: Dr. Martin Rudolph
    53 Seiten

Publ.-Id: 21576 - Permalink


Vergleich von Carbonsäuren, Alkylhydroxamaten und Sarkosinaten als Sammler für die Apatitflotation
Klöpfel, K.;
Am Helmholtz-Institut Freiberg für Ressourcentechnologie werden Technologien entwickelt, um die Verfügbarkeit wirtschaftskritischer mineralischer Rohstoffe für die deutsche und europäische Industrie zu sichern. Ein wichtiges Wertmineral ist Apatit, aus dem Phosphor, sowie in Spuren Seltene Erden Metalle gewonnen werden kann. Die Flotation spielt hierbei eine wichtige Rolle, um Silikate und Carbonate als Gangminerale abzutrennen. Üblicherweise kommen Carbonsäuresalze als Sammler für die direkte Flotation zum Einsatz, wobei deren Selektivität besonders gegenüber den Carbonaten gering ist. Es existieren mit den Sarkosinaten und Hydroxamaten molekular ähnliche Substanzen, die in dieser Arbeit bzgl. Ihres Flotierbarkeitsverhalten zu Apatit untersucht werden sollen. Die Wirkung der zu vergleichenden Sammler wird in dieser Arbeit mit Hilfe von Oberflächenspannungsmessungen, Zeta-Potential-Bestimmungen sowie Mikroflotationsuntersuchungen an der reinen Mineralphase des Fluor-Apatits untersucht.
Es ist zudem die aktuelle Literatur zum Thema zu recherchieren und zusammenzutragen.
Keywords: flotation, apatite, collector, sodium oleate, sodium sarcosinate, potassium octyl hydroxamate, zeta potential
  • Bachelor thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Dr. Martin Rudolph
    72 Seiten

Publ.-Id: 21575 - Permalink


Partikelsonden Rasterkraftmikroskopie - Untersuchung der hydrophoben Eigenschaften von Mineraloberflächen im Kontext der Flotation
Kaminsky, P.;
Das Helmholtz-Institut Freiberg für Ressourcentechnologie führt Grundlagenforschungen zur flotativen Aufbereitung von Erzen durch. Ein wichtiger Aspekt der Flotation ist die selektive Hydrophobisierung von Mineralen des Erzes. Der attraktive hydrophobe Effekt ist hierbei verantwortlich für die Anhaftung von selektiven Mineralen an Gasblasen und somit der Abtrennung dieser Mineralphasen aus einer gemahlenen Erzsuspension. Es wird eine Messmethode entwickelt, die es erlauben soll auf Mineralschliffen eines Erzes hydrophobe Eigenschaften ortsaufgelöst zu bestimmen. Grundbestandteil ist dabei die Partikelsonden-Rasterkraftmikroskopie (CP-AFM).
Diese Masterarbeit soll die CP-AFM Methode an grobkristallinen Magnetit- und Quarzproben unter Verwendung selektiver Sammler untersuchen. Die Ergebnisse dieser Hydrophobizitätsmessung sollen im Kontext gesetzt werden zu Mikroflotationsuntersuchungen der Stoffsysteme. Es soll die CP-AFM Methode kritisch analysiert werden. Neben den genannten Methoden sind die Stoffsysteme bzgl. der Sammlerwechselwirkung und der Benetzung näher zu untersuchen. Der aktuelle Stand der Forschung soll ebenfalls in einer Literaturrecherche erfasst und zusammengefasst werden.
Keywords: AFM, hydrophic interactions, Magnetite, quartz, Flotation, zeta potential, collector
  • Master thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Dr. Martin Rudolph
    120 Seiten

Publ.-Id: 21574 - Permalink


Structural changes in amorphous GexSiOy on the way to nanocrystal formation
Nyrow, A.; Sternemann, C.; Sahle, C. J.; Hohl, A.; Zschintzsch-Dias, M.; Schwamberger, A.; Mende, K.; Brinkmann, I.; Sala, M. M.; Wagner, R.; Meier, A.; Voelklein, F.; Tolan, M.;
Temperature induced changes of the local chemical structure of bulk amorphous GexSiOy are studied by Ge K-edge x-ray absorption near-edge spectroscopy and Si L-2/3-edge x-ray Raman scattering spectroscopy. Different processes are revealed which lead to formation of Ge regions embedded in a Si oxide matrix due to different initial structures of as-prepared samples, depending on their Ge/Si/O ratio and temperature treatment, eventually resulting in the occurrence of nanocrystals. Here, disproportionation of GeOx and SiOx regions and/or reduction of Ge oxides by pure Si or by a surrounding Si sub-oxide matrix can be employed to tune the size of Ge nanocrystals along with the chemical composition of the embedding matrix. This is important for the optimization of the electronic and luminescent properties of the material.
Keywords: KeyWords Plus:VISIBLE PHOTOLUMINESCENCE; GE NANOCRYSTALS; ALLOY-FILMS; SILICON NANOCRYSTALS; THIN-FILMS; MICROCRYSTALS; MEMORY; LUMINESCENCE; EXCITATIONS; DEFECTS

Publ.-Id: 21573 - Permalink


Investigation of the surface free energy of several minerals by iGC (inverse gas chromatography) and correlation with floatability
Hartmann, R.;
It is well known that the flotation process separates particles with different wettability dispersed in water. The fundamental physical-chemical property therefore is the specific surface free energy of the mineral surface which together with the specific surface free energy of water causes wettability phenomena besides the surface morphology (e.g. roughness). Inverse Gas Chromatography is a tool which enables determination of the specific surface free energy of powders. There are a few reports on the correlation of flotation response and surface free energy, however the crucial problem is that the flotability is determined in water and the surface free energy is evaluated in the dried powder phase. To determine the effect flotation chemicals have on the specific surface free energy of minerals it is important to investigate the preparation of the dried powder after conditioning with the chemicals in water.
In this Master thesis different minerals (quartz, apatite and magnetite) and ionic collectors (sodium oleate and dodecyl ammonium acetate) with crucially different surfactant adsorption mechanisms will be used to determine floatability and specific surface free energy with different steps of preparation, i.e. washing with mother liquid only or further with solvents with another polarity. The flotation response and the specific surface free energy shall be put in context. It is important to find the proper presentation of the surface free energy components and define a quantitative description of hydrophobicity. It should finally, based on the results, be described in which way flotation samples should be treated for iGC measurements.
The literature is to be researched and summarized for the latest information on the topic.
Keywords: inverse gas chromatography, flotation, surface free energy, wettability, hydrophobicity
  • Master thesis
    TU Bergakademie Freiberg, 2014
    Mentor: Dr. Martin Rudolph
    113 Seiten

Publ.-Id: 21572 - Permalink


Specific surface free energy distributions and floatabilities of minerals with physi- and chemisorbing collectors
Rudolph, M.; Chehreh Chelgani, S.; Hartmann, R.;
Flotation separates particles with different wettability dispersed in water. The fundamental physical-chemical property therefore is the specific surface free energy of the mineral surface which together with the specific surface free energy of water causes wettability phenomena besides the surface morphology (e.g. roughness). Inverse Gas Chromatography (iGC) is a tool which enables determination of the specific surface free energy of powders. There are a few reports on the correlation of flotation response and surface free energy, however the crucial problem is that the floatability is determined in water and the surface free energy is evaluated in the dried powder phase. To determine the effect flotation chemicals have on the specific surface free energy of minerals it is important to investigate the preparation of the dried powder after conditioning with the chemicals in water.
In this paper different minerals (quartz, apatite and magnetite) and ionic collectors (anionic sodium oleate and cationic dodecyl ammonium acetate) with crucially different surfactant adsorption mechanisms are used to determine floatability (microflotation) and specific surface free energy distributions (iGC) with different steps of preparation, i.e. washing with mother liquid only or further with solvents with another polarity. The flotation response and the specific surface free energy are put in context and discussed. A proper presentation of the surface free energy components is presented giving a quantitative description of hydrophobicity. There will also be a short introduction to and discussion of the method of inverse Gas Chromatography as it is rather new in the field of mineral processing.
Keywords: inverse gas chromatography, flotation, surface free energy, wettability, hydrophobicity, particle-bubble intreractions, apatite, magnetite, quartz, collector, adsorption
  • Lecture (Conference)
    Conference in Minerals Engineering, 03.-04.02.2015, Lulea, Sweden

Publ.-Id: 21571 - Permalink


A review of rare earth minerals flotation: Monazite and Xenotime
Chehreh Chelgani, S.; Rudolph, M.; Leistner, T.; Gutzmer, J.; Peuker, U. A.;
This paper reviews rare earth minerals (monazite and xenotime) separation by flotation. A wide range of monazite and xenotime flotation test results are reviewed including: reasons of variation in the point of zero charges on these minerals, the effects of various flotation conditions on zeta potential and the point of zero charges on the surface of monazite and xenotime, interactions of collectors and depressants on the surface of these mineral phases during flotation separation, relationship between surface chemistry of the minerals and different types of collector adsorptions, effects of the conditioning temperature on flotation of rare earth minerals. This review summarizes various approaches for selective separation of monazite and xenotime by flotation for further research in future.
Keywords: Flotation, Rare earth, Monazite, Xenotime, IEP, Hydroxamate, Sodium oleate

Publ.-Id: 21570 - Permalink


Charge trapping of Ge-nanocrystals embedded in TaZrOx dielectric films
Lehninger, D.; Seidel, P.; Geyer, M.; Schneider, F.; Klemm, V.; Rafaja, D.; von Borany, J.; Heitmann, J.;
Ge-nanocrystals (NCs) were synthesized in amorphous TaZrOx by thermal annealing of co-sputtered Ge-TaZrOx layers. Formation of spherical shaped Ge-NCs with small variation of size, areal density, and depth distribution was confirmed by high-resolution transmission electron microscopy. The charge storage characteristics of the Ge-NCs were investigated by capacitance-voltage and constant-capacity measurements using metal-insulator-semiconductor structures. Samples with Ge-NCs exhibit a maximum memory window of 5 V by sweeping the bias voltage from −7 V to 7 V and back. Below this maximum, the width of the memory window can be controlled by the bias voltage. The fitted slope of the memory window versus bias voltage characteristics is very close to 1 for samples with one layer Ge-NCs. A second layer Ge-NCs does not result in a second flat stair in the memory window characteristics. Constant-capacity measurements indicate charge storage in trapping centers at the interfaces between the Ge-NCs and the surrounding materials (amorphous matrix/tunneling oxide). Charge loss occurs by thermal detrapping and subsequent band-to-band tunneling. Reference samples without Ge-NCs do not show any memory window

Publ.-Id: 21569 - Permalink


Towards a novel THz-based monitor for sub picosecond electron bunches working at MHz repetition rates and low bunch charges
Kovalev, S.; Green, B.; Golz, T.; Kuntzsch, M.; Fisher, A.; Stojanovic, N.; Gensch, M.;
Femtosecond level diagnostic and control of sub-picosecond electron bunches is an important topic in modern accelerator research. At the same time new quasi-cw linear electron accelerators are the drivers of many future 4th Generation lightsources such as X-ray free electron lasers. A high duty cycle, high stability and online pulse to pulse diagnostic of these new accelerators are crucial ingredients to the success of these large scale facilities. A novel THz based online monitor concept is presented that has the potential to give access to pulse to pulse information on bunch form, arrival time and energy at high repetition rate and down to sub pC charges. It has been shown experimentally that pulse to pulse arrival time measurements can be used to perform high temporal resolution and dynamic range experiments, removing the influence of synchronization problems between the accelerator and external laser systems.
  • Poster
    4th workshop on longitudinal instrumentation for future accelerators, 15.-16.01.2015, Villigen, Switzerland

Publ.-Id: 21567 - Permalink


Re-Green Indicator System
Dirlich, S.;
The presentation deals with the development of an indicator system for the sustainability assessment of green policies dedicated to retrofitting of buildings, urban districts, and entire cities.
Based on existing building sustainability assessment schemes a specific indicator system is developed meeting the requirements of the Re-Green project.
The flexible and modular structure of the system allows an adaptation of the sustainability assessment to the particular circumstances and conditions of the region/city to be evaluated.
Keywords: sustainability assessment; green building; retrofit
  • Invited lecture (Conferences)
    FutureBuild 2014, 05.-06.11.2014, Sheffield, Großbritannien

Publ.-Id: 21566 - Permalink


Automated mineralogical analysis of secondary raw materials – challenges and pitfalls
Dressler, S.; Renno, A. D.; Bachmann, K.; Schaefer, J.;
Secondary raw materials are becoming increasingly more important in ensuring the stability of critical metal supply. Ashes, slags, dusts and other industrial residues are produced in large quantities.
Precise and accurate chemical and mineralogical data, knowledge of distribution of valuable and deleterious elements in the single phases as well as information about homogeneity and grain size distribution of the minerals are crucial for the development of new extraction technologies.
Gaining these essential information can be achieved by using SEM-based automated mineralogical analysis. However, the large particle size range, the dominance of very small grain sizes (< 5 µm) and the diversity of phases are challenging for the analysis. Furthermore, in contrast to natural materials the analysis of secondary materials faces the challenge of developing new methods for non-natural extreme combinations of elements and phases. Initial results of ash and slag samples will be presented and evaluated.
  • Poster
    ANAKON, 23.-26.03.2015, Graz, Österreich

Publ.-Id: 21565 - Permalink


Role of electric and magnetic dipole strength functions in the 114Cd(gamma,gamma') and 113Cd(n, gamma) reactions
Massarczyk, R.; Schramm, G.; Belgya, T.; Schwengner, R.; Beyer, R.; Bemmerer, D.; Elekes, Z.; Grosse, E.; Hannaske, R.; Junghans, A. R.; Kis, Z.; Kögler, T.; Lorenz, C.; Schmidt, K.; Szentmiklosi, L.; Wagner, A.; Weil, J. L.;
The distribution of the electromagnetic dipole strength below the neutron separation energy and its influence on the photon distribution after neutron capture was investigated in a twin experiment for the compound nucleus 114Cd. The experimentally deduced spectra after photon scattering on 114Cd and the neutron capture in 113Cd were analyzed in matters of electro magnetic strength function and nuclear level density. By measuring the photoabsorption cross section at the bremsstrahlung facility gammaELBE at the Helmholtz-Zentrum Dresden-Rossendorf it was possible to deduce information about the distribution of dipole strength below the neutron separation energy. The deexcitation spectrum after cold-neutron capture in 113 Cd was calculated and different magnetic dipole strength function models were tested with the help of the statistical code gammaDEX.
Keywords: Photon scattering, nuclear resonance fluorescence, strength functions, cross sections

Publ.-Id: 21564 - Permalink


High magnetic field study of the Dy2Fe17Hx compounds with x = 0-3.8
Isnard, O.; Andreev, A. V.; Heczko, O.; Skourski, Y.;
The Dy2Fe17Hx compounds crystallizing in a hexagonal Th2Ni17-like structure are studied on aligned powder by magnetization measurements carried out in steady (up to 5 T) and pulsed (60 T) magnetic fields at 4.2-300 K. Dy2Fe17 is a ferrimagnet with TC = 375 K and a spontaneous moment of 16.5 μB/f.u. Magnetization curves recorded for two different crystal orientations for Dy2Fe17Hx polycrystalline oriented samples show that the insertion of hydrogen in the Dy2Fe17 crystal lattice significantly modifies the magnetization, Curie temperature and intersublattice exchange interactions of the Dy2Fe17 phase. The high-field behavior of Dy2Fe17 is compared with that of its hydrides derivatives. Despite different types of magnetic anisotropy, the high-field behavior of the hydrides and the parent compound is qualitatively similar. Depending upon the composition, they can exhibit easy plane or else conical type anisotropy as for x = 0 and 3, respectively. The low temperature spontaneous magnetization exhibits a moderate composition dependence, it first decreases continuously upon increasing the hydrogen composition up to x = 3 then slightly increases for x = 3.8 reflecting the Fe sublattice evolution. A mean Fe moment of about 2.1 μB is derived for Dy2Fe17H3.8 composition, this magnetization value is close to that of the original Dy2Fe17 compound. It is found that the intersublattice coupling between the Fe and Dy sublattices is reduced as illustrated by the decrease of the nDy-T coefficient from about 3.3 down to 2.82 T f.u./μB for Dy2Fe17 and Dy2Fe17H3.8, respectively.

Publ.-Id: 21563 - Permalink


PIConGPU - The World’s Fastest Particle-in-Cell Plasma Simulation
Pausch, R.; Burau, H.; Bussmann, M.; Debus, A.; Eckert, C.; Garten, M.; Huebl, A.; Juckeland, G.; Kluge, T.; Knespel, M.; Schmitt, F.; Schumann, C.; Steiniger, K.; Widera, R.; Worpitz, B.;
PIConGPU is currently the fastest particle-in-cell code available. This talk explains how using GPUs increased the performance of this simulation code making parameter scans of previously hard to compute plasma setups possible. Additionally newly developed techniques are discussed and an outlook on simulations of foil targets and high harmonic generation are presented.
Keywords: PIConGPU, particle-in-cell code, GPU, high harmonic generation
  • Invited lecture (Conferences)
    Workshop on PIConGPU and high harmonic generation, 12.-16.01.2015, Jena, Deutschland

Publ.-Id: 21562 - Permalink


Highly transparent and conductive Al-doped ZnO films synthesized by pulsed laser co-ablation of Zn and Al targets assisted by oxygen plasma
You, Q.; Cai, H.; Gao, K.; Hu, Z.; Guo, S.; Liang, P.; Sun, J.; Xu, N.; Wu, J.;
Highly optically transparent and electrically conductive Al-doped ZnO (AZO) thin films were deposited by pulsed laser co-ablation of a Zn target and an Al target in an oxygen plasma. Zn ablation resulted in the reactive deposition of ZnO films assisted by the plasma, while Al ablation provided the growing ZnO films with Al dopants. The morphology, composition and structure as well as the optical and electrical properties were characterized and the effects of Al doping and annealing treatment were investigated. The deposited AZO films have a hexagonal wurtzite structure with deteriorated crystal quality which can be improved by annealing. The AZO films are highly transparent from ultraviolet up to 1450 nm and present an obvious blue shift in absorption edge and a widening of band gap compared with undoped ZnO. The electrical properties were also improved after annealing with the resistivity decreasing by over two orders of magnitude because of the increase of free carrier concentration. The variation in the carrier concentration also affects the absorption edge and the band gap of the films as well as the transparency in the infrared region. Meanwhile, this method offers an approach for in-situ doping preparation of other doped compound films with different dopant concentrations.
Keywords: Al-doped ZnO; Co-ablation deposition; Electrical properties; In-situ doping; Optical properties; Thin films

Publ.-Id: 21561 - Permalink


Study of the p\vec{d}→n{pp}s charge-exchange reaction using a polarised deuterium target
Gou, B.; Mchedlishvili, D.; Bagdasarian, Z.; Barsov, S.; Garbonell, J.; Chiladze, D.; Dymov, S.; Engels, R.; Gaisser, M.; Gebel, R.; Grigoryev, K.; Hartmann, M.; Kacharava, A.; Khoukaz, A.; Kulessa, P.; Kulikov, A.; Lehrach, A.; Li, Z.; Lomidze, N.; Lorentz, B.; Macharashvili, G.; Merzliakov, S.; Mielke, M.; Mikirtychyants, M.; Mikirtychyants, S.; Nioradze, M.; Ohm, H.; Prasuhn, D.; Rathmann, F.; Serdyuk, V.; Shmakova, V.; Ströher, H.; Tabidze, M.; Trusov, S.; Tsirkov, D.; Uzikov, Y.; Valdau, Y.; Wang, T.; Weidemann, C.; Wilkin, C.; Yuan, X.;
The vector and tensor analysing powers, Ayand Ayy, of the p d→n{pp}scharge-exchange reaction have been measured at a beam energy of 600MeV at the COSY-ANKE facility by using an unpolarised proton beam incident on an internal storage cell target filled with polarised deuterium gas. The low energy recoiling protons were measured in a pair of silicon tracking telescopes placed on either side of the target. Putting a cut of 3MeV on the diproton excitation energy ensured that the two protons were dominantly in the 1S0state, here denoted by {pp}s. The polarisation of the deuterium gas was established through measurements in parallel of proton–deuteron elastic scattering. By analysing events where both protons entered the same telescope, the charge-exchange reaction was measured for momentum transfers q ≥160MeV/c. These data provide a good continuation of the earlier results at q ≤140MeV/cobtained with a polarised deuteron beam. They are also consistent with impulse approximation predictions with little sign evident for any modifications due to multiple scatterings. These successful results confirm that the ANKE deuteron charge-exchange programme can be extended to much higher energies with a polarised deuterium target than can be achieved with a polarised deuteron beam.

Publ.-Id: 21560 - Permalink


High-resolution Positron-Emission-Tomography for ultrasensitive spatio-temporal monitoring of tracer transport in porous media
Kulenkampff, J.; Gründig, M.; Lippmann-Pipke, J.;
Positron-Emission-Tomography (PET) has favourable characteristics for monitoring the propagation of tracers in opaque media on the drill core scale. PET directly yields quantitative tracer concentrations, without retroaction on the process, with ultimate sensitivity (less than 109 atoms per voxel) and selectivity, with negligible matrix effect, and with expedient spatial resolution. It only requires radiolabelling of the observed substance with a positron-emitting isotope and therefore allows investigating processes in fluids without physical or compositional contrasts.
PET is a widely applied nuclear medical technique for 3D functional imaging. Since 1988 [1], some exemplary applications for the visualization of flow processes in various rock formations and other non-medical applications were conducted with clinical PET scanners with low spatial resolution and with short living radionuclides (e.g. 18F, T1/2=109.77 min).
In contrast, we take advantage of a high-resolution PET-scanner, originally dedicated for biomedical research on small animals, with a resolution at the physical limit of 1 mm [2]. Also, we are able to conduct long-time experiments in our laboratory, applying radionuclides with longer lifetimes (e.g. 22Na, T1/2=2.602 a).
Our applications cover conservative and reactive flow of solutes and particles in soils and rocks, as well as diffusion processes in clays [3]. We strive to characterize heterogeneous transport effects on the basis of our visualisations of the propagation of the tracer. Frequently, we observe the evolution of strongly localized pathways, which depict the reduced effective volume, coming along with a reduced efficiency of the internal surface area for sorption processes. Our data can be used also for experimental calibration and verification of computer simulations of transport processes.
REFERENCES
[1] van den Bergen, E.A., Jonkers, G., Strijckmans, K., Goethals, P., 1989. Industrial Applications of Positron Emission Computed Tomography. Nuclear Geophysics 3, pp. 407-418.
[2] Zakhnini, A., Kulenkampff, J., Sauerzapf, S., Pietrzyk, U. and Lippmann-Pipke, J., 2013. Monte Carlo simulations of GeoPET experiments: 3D images of tracer distributions (18F, 124I and 58Co) in Opalinus Clay, anhydrite and quartz. Computers & Geosciences, 57: 183-196.
[3] Kulenkampff, J.; Gründig, M.; Korn, N.; Zakhnini, A.; Barth, T.; Lippmann-Pipke, J., 2013. Application of high-resolution positron-emission-tomography for quantitative spatiotemporal process monitoring in dense material. 7. World Congress on Industrial Process Tomography, Krakow, Poland, free available on http://www.isipt.org/world-congress/7/902.html
  • Poster
    Interpore Conference, 18.-21.05.2015, Padova, Italy

Publ.-Id: 21559 - Permalink


Examples of XRF and PIXE imaging with few microns Resolution using SLcam® – a Color X-Ray Camera
Nowak, S. H.; Bjeoumikhov, A.; von Borany, J.; Buchriegler, J.; Munnik, F.; Petric, A.; Renno, A. D.; Radtke, A.; Reinholz, U.; Scharf, O.; Strüder, L.; Wedell, R.; Ziegenrücker, R.;
The Color X-ray Camera, type SLcam®, can detect X-ray radiation with spatial and energy resolution. The device is used as an X-ray detector in applications at synchrotrons and on PIXE beamlines. The unique properties of SLcam®, a combination of a single photon counting CCD with a polycapillary optics objective, allows a fast overview over a large detection area with first results visible almost immediately.
The maximal field of view exceeds 1 cm² and the spatial resolution can Approach several microns when using a sub-pixel algorithm.
Keywords: SLcam, HSPIXE, High-Speed PIXE, PIXE, Proton, X-Ray

Publ.-Id: 21558 - Permalink


Defect-induced magnetism in SiC: Interplay between ferromagnetism and paramagnetism
Wang, Y.; Liu, Y.; Wendler, E.; Hübner, R.; Anwand, W.; Wang, G.; Chen, X.; Tong, W.; Yang, Z.; Munnik, F.; Bukalis, G.; Chen, X.; Gemming, S.; Helm, M.; Zhou, S.;
Defect-induced ferromagnetism has triggered a lot of investigations and controversies. The major issue is that the induced ferromagnetic signal is so weak that it can be sufficiently accounted for by trace contamination. To resolve this issue, we studied the variation of the magnetic properties of SiC after neutron irradiation with fluence covering four orders of magnitude. A large paramagnetic component has been induced and scales up with defect concentration, which can be well accounted for by uncoupled divacancies. However, the ferromagnetic contribution is still weak and only appears in the low fluence range of neutrons or after annealing treatments. First-principles calculations hint towards a mutually exclusive role of the concentration of defects: A higher defect concentration favors a larger magnetic interaction at the expense of spin polarization. Combining both experimental and first-principles calculation results, the defect-induced ferromagnetism can probably be understood as a local effect which cannot be scaled up with the volume.
Keywords: SiC, Defect-induced magnetism, Neutron irradiation

Publ.-Id: 21557 - Permalink


Subthreshold Xi- Production in Collisions of p(3.5 GeV)+Nb
Agakishiev, G.; Arnold, O.; Balanda, A.; Belver, D.; Belyaev, A. V.; Berger-Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Chernenko, S.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O. V.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Göbel, K.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kornakov, G.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, V.; Wagner, T.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y. V.;
Results on the production of the double strange cascade hyperon Xi(-) are reported for collisions of p(3.5 GeV) + Nb, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18 at GSI Helmholtzzentrum for Heavy-Ion Research, Darmstadt. For the first time, subthreshold Xi(-) production is observed in proton-nucleus interactions. Assuming a Xi(-) phase-space distribution similar to that of. hyperons, the production probability amounts to P Xi- = [2.0 +/-0.4(stat) +/- 0.3(norm) +/- 0.6(syst)] x 10(-4) resulting in a Xi(-)/d(Lambda + Sigma(0)) ratio of P Xi-/P Lambda+Sigma 0 = [1.2 +/-0.3(stat) +/- 0.4(syst)] x 10(-2). Available model predictions are significantly lower than the measured Xi(-) yield.

Publ.-Id: 21556 - Permalink


Biosorption of uranium on the cells of the halophilic archaea Halobacterium noricense DSM 15987 under highly saline conditions
Bader, M.; Drobot, B.; Müller, K.; Stumpf, T.; Cherkouk, A.;
For the long-term storage of radioactive waste in salt rock formations it is important to know how microorganisms can affect the performance of a repository. It is possible that in salt rock indigenous microbes are able to influence the oxidation state, the speciation and hence the solubility of actinides. So the migration of actinides can be reduced or enhanced by different processes as for example by biosorption with cellular ligands [1].
The biosorption capacity of the archaea Halobacterium noricense DSM 15987, which was used as a reference strain due to its worldwide occurrence in salt rock, was investigated. The strain was isolated from an Austrian salt mine [2] and similar species were also found in the WIPP (Waste Isolation Pilot Plant, Carlsbad, New Mexico, USA) [3]. This rod shaped microorganism is a halophilic one which requires at least 2.1 M NaCl whereat the optimum is 3.0 M NaCl [2].
Independent of the uranium concentration (10 – 120 µM) Halobacterium noricense DSM 15987 shows good sorption capabilities at room temperature (RT). Constantly, 90 % of added uranium was bound on the cells. Looking at the time dependence of biosorption with a constant uranium concentration (100 µM) an asymptotic sorption curve was obtained. This accumulation kinetic indicates a two stage process.
Directly after the addition of uranium it is rapidly sorbed by the cells. After 3 h 35 % of uranium was accumulated. The second slower step is reached after 42 h, where 90 % of added uranium was bound to the cells. Under these conditions this corresponds to 37.5 ± 0.7 mg U(VI) per 1 g dry biomass. A slightly faster sorption can be seen at higher temperatures especially at 50 °C. There the maximal sorption of 90 % is already reached after 24 h.
Interestingly, with increasing incubation time, uranium concentration and also temperature an agglomeration of the cells occurred. Live/Dead staining showed that agglomerated cells were mostly alive but nearly all single cells were dead. So we conclude that this agglomeration process is a kind of stress response to protect the cells themselves for environmental challenges.
Furthermore, the supernatant and the washed cell suspension were analysed with TRLFS to characterize the binding of uranium to the cells. Despite the high quenching effect of chloride to uranium fluorescence a luminescence signal could be detected. The reason is the high quantum yield of some formed complexes. With parallel factor analysis (Parafac) we could assume that two uranium-cell-complexes were formed. Species 1 is difficult to interpret due to the unspecific form of the spectrum. Further investigations with reference substances have to be done. But comparing with literature we assign species 2 to a carboxylic cell-uranyl-complex [4]. These results were confirmed by IR spectroscopy where as well carboxylic vibrations could be detected.
The archaeum Halobacterium noricense DSM 15987 shows good uranium sorption efficiencies. Independent of the occurring agglomeration always 90 % of the added uranium was bound to the cells. The binding of uranium to carboxylic groups on the cell wall was proven with TRLFS and IR spectroscopy. A binding of uranium to phosphate groups is still under investigation.
Thanks to Sabrina Gurlit for analysing the samples with ICP-MS and Karsten Heim for recording the IR-spectra.

REFERENCES
1. Morris, K. et al., “Biogeochemical cycles and remobilisation of the actinide elements” Interactions of microorganisms with radionuclides, Volume 2, Page 101-141 (2002).
2. Gruber, C. et al., “Halobacterium noricense sp. nov., an archaeal isolate from a bore core of an alpine Permian salt deposit, classification of Halobacterium sp. NRC-1 as a strain of H. salinarum and emended description of H. salinarum” Extremophiles, 8, Page 431-439 (2004).
3. Swanson, J. S. et al., “Status Report on the Microbial Characterization of Halite and Groundwater Samples from the WIPP” Status report Los Alamos National Laboratory, Page 1ff. (2012).
4. Vogel, M. et al., “Biosorption of U(VI) by the green algae Chlorella vulgaris in dependence of pH value and cell activity” Science of the Total Environment , Page 384-395. (2010).
  • Lecture (Conference)
    ABC-Salt IV Workshop 2015, 14.-15.04.2015, Heidelberg, Deutschland

Publ.-Id: 21555 - Permalink


Carbon p Electron Ferromagnetism in Silicon Carbide
Wang, Y.; Liu, Y.; Wang, G.; Anwand, W.; Jenkins, C.; Arenholz, E.; Munnik, F.; Gordan, O.; Salvan, G.; Zahn, D. R. T.; Chen, X.; Gemming, S.; Helm, M.; Zhou, S.;
Ferromagnetism can occur in wide-band gap semiconductors as well as in carbon-based materials, when specific defects are introduced. It is thus desirable to establish a direct relation between the defects and the resulting ferromagnetism. Here, we contribute to revealing the origin of defect-induced ferromagnetism using SiC as a prototypical example. We show that the long-range ferromagnetic coupling can be attributed to the p electrons of the nearest-neighbor carbon atoms around VSiVC divacancies. Thus, the ferromagnetism is traced down to its microscopic, electronic origin.
Keywords: SiC, Defect induced magnetism, XMCD

Publ.-Id: 21554 - Permalink


(V,Nb):TiO2 - a transparent conductor and ferromagnetic semiconductor !?
Cornelius, S.;
Both the property combinations a) transparent conductivity and b) diluted magnetic semiconductivity are based on the concept of dispersed substitutional doping of a suitable semiconductor with dopants that provide free electrons and/or carry a magnetic moment. The implications of current point defect theory with respect to defect formation enthalpies in anatase TiO2 are discussed in context with experimental results on electrical, optical and magnetic properties of V and Nb doped TiO2 thin films prepared by reactive magnetron sputtering. While transparent conductivity could be achieved via Nb doping, V doped films remain paramagnetic (in contrast to theoretical predictions).
Keywords: anatase, titanium oxide, magnetron sputtering, transparent conductive oxide, doping, magnetic semiconductor
  • Lecture (Conference)
    Deti.2 project meeting, 22.10.2014, Dresden, Deutschland

Publ.-Id: 21553 - Permalink


Dopant activation and charge transport limits in transparent conductive (Al,Ga):ZnO and Nb:TiO2
Cornelius, S.;
Transparent conductive oxides (TCOs) are a class of wide bandgap metal oxides in which high densities of free charge carriers can be induced in such a way, that a unique combination of high optical transmittance in the visible spectral range and metal-like electrical conductivity is achieved. The influence of the oxygen partial pressure, substrate temperature, dopant concentration and substrate type on the properties (Al,Ga) doped ZnO and Nb doped TiO2 thin films has been studied systematically. The correlations between electrical, structural and optical properties as well as the elemental composition of the films have been characterized by a combination of Hall-effect, XRD, spectroscopic ellipsometry, spectral photometry, RBS and PIXE techniques including complementary XANES and TEM studies. The results are discussed with a focus on understanding the dopant incorporation into the ZnO and TiO2 host materials as well as finding physical limits for the resistivity based on charge transport models for degenerate polar semiconductors.
Keywords: transparent conductive oxide, zinc oxide, doping, titanium oxide, anatase, electron mobility, reactive sputtering, magnetron sputtering
  • Invited lecture (Conferences)
    Institutsseminar, Institut für experimentelle Physik II, Universität Leipzig, 26.11.2014, Leipzig, Deutschland

Publ.-Id: 21552 - Permalink


Formation and propagation of laser-driven plasma jets in an ambient medium studied with X-ray radiography and optical diagnostics
Diziere, A.; Pelka, A.; Ravasio, A.; Loupias, B.; Falize, E.; Kuramitsu, Y.; Sakawa, Y.; Morita, T.; Pikuz, S.; Yurchak, R.; Koenig, M.;
In this paper, we present experimental results obtained on the LULI2000 laser facility regarding structure and dynamics of astrophysical jets propagating in interstellar medium. The jets, generated by using a cone-shaped target, propagate in a nitrogen gas that mimics the interstellar medium. X-ray radiography as well as optical diagnostics were used to probe both high and low density regions. In this paper, we show how collimation of the jets evolves with the gas density.

Publ.-Id: 21551 - Permalink


Bacterial diversity in bentonites, engineered barrier for deep geological disposal of radioactive wastes
Lopez-Fernandez, M.; Cherkouk, A.; Vílchez-Vargas, R.; Sandoval, R.; Pieper, D.; Boon, N.; Sánchez-Castro, I.; Merroun, M.;
The long-term disposal of radioactive wastes in a deep geological repository is the accepted international solution for the treatment and management of these special residues. The microbial community of the selected host rocks and engineered barriers for the deep geological repository may affect the performance and the safety of the radioactive waste repository. In this work the bacterial community of bentonite formations of Almeria (Spain), selected as reference material for bentonite engineered barriers in the disposal of radioactive wastes, was studied. 16S rRNA gene-based approaches were used to study the bacterial community of the bentonite samples by traditional clone libraries and Illumina-sequencing. A high bacterial diversity was found by both techniques, with phylotypes belonging to 13 different bacterial phyla: Acidobacteria, Actinobacteria, Armatimonadetes, Bacteroidetes, Choloroflexi, Cyanobacteria, Deinococcus-Thermus, Firmicutes, Gemmatimonadetes, Planctomycetes, Proteobacteria, Nitrospirae and Verrucomicrobia. The dominant groups of the community were mainly represented by Proteobacteria and Bacteroidetes.
Some of the identified genera were previously described for their capacity to interact with iron and different heavy metals as well as radionuclides, as for example, Acidovorax, Ralstonia, Variovorax and Sphingomonas. The results obtained in this work demonstrate the high bacterial diversity of these Spanish bentonite formations, and their possible negative effect on the structure of the clay minerals as well as interactions with different radionuclides, which may affect the safety of the deep geological repository of radioactive wastes.
Keywords: Spanish bentonite, bacterial diversity, Illumina sequencing, Cloning and sequencing

Publ.-Id: 21550 - Permalink


Investigation of ionoluminescence of semiconductor materials using helium ion microscopy
Veligura, V.; Hlawacek, G.; van Gastel, R.; Zandvliet, H. J. W.; Poelsema, B.;
Helium ion microscopy has been employed to investigate the ionoluminescence of various semiconduc- tors. We have verified the possibility of application of this technique for high-resolution ionolumines- cence analysis of this kind of materials. In this work the ionoluminescence signal was induced by a sub- nanometer Heþ beam with an energy of 35 keV. Several types of semiconductor samples were investigated: bulk materials, nanowires and quantum dots. All samples were found to exhibit ionoluminescence. However, the ionoluminescence signal rapidly degrades under the ion irradiation. The signal degradation was found to depend not only on the sample's composition, but also on its size. The ionoluminescence emission spectra were recorded and emission peaks identified.
Keywords: Ionoluminescence Helium ion microscopy Semiconductors Nanowires Quatum dots

Downloads:

Publ.-Id: 21549 - Permalink


Experimental studies of contact angle hysteresis phenomena on polymer surfaces — Toward the understanding and control of wettability for different applications
Grundke, K.; Pöschel, K.; Synytska, A.; Frenzel, R.; Drechsler, A.; Nitschke, M.; Cordeiro, A. L.; Uhlmann, P.; Welzel, P. B.;
Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis — Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid–base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements.
Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core–shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions.
The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications.
Keywords: Contact angle hysteresis Polymer surfaces Morphological and chemical heterogeneity Swelling and reorientation at the solid/liquid interface Different solutes in the liquid

Publ.-Id: 21548 - Permalink


Flow measurements in continuous casting models by means of contactless inductive flow tomography under the influence of electromagnetic brakes
Ratajczak, M.; Wondrak, T.; Stefani, F.; Timmel, K.; Eckert, S.;
Most of the steel in the world is produced by continuous casting, where liquid metal flows from a tundish through a submerged entry nozzle into a copper mould. The mould is cooled by water, so a solid shell starts to form at the mould walls. The resulting steel strand is pulled out of the mould continuously and solidifies completely.
In industry it is well-known that an unstable flow in the mould has negative effects on the resulting steel’s quality. Electromagnetic brakes (EMBr) are expected to dampen instabilities, although their impact on the flow can hardly be examined directly in liquid steel. In spite of the casting method’s economical and industrial importance, only a few simple measurement techniques are available to investigate the actual flow patterns in the mould. A more sophisticated technique for liquid metal flow measurements could help to resolve the open issues in the mould flow.
The contactless inductive flow tomography (CIFT) is a technique that measures the mean global flow of an electrically conducting melt by exposing it to a magnetic excitation field and measuring the flow induced perturbations of that field outside the melt. The velocity profile can then be calculated by solving an inverse problem, using adequate regularization techniques to deal with the non-uniqueness.
We present preliminary results for a physical model of a mould with a rectangular cross-section of 140 × 35 mm 2 in the presence of an EMBr. Additionally we show flow reconstructions for a 400 × 100 mm 2 mould, demonstrating the upward scalability of CIFT.
  • Lecture (Conference)
    3rd International Workshop on Measuring Techniques for Liquid Metal Flows (MTLM2015), 15.-17.04.2015, Dresden, Deutschland

Publ.-Id: 21547 - Permalink


Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy
Zhou, S.; Liu, F.; Prucnal, S.; Gao, K.; Khalid, M.; Baehtz, C.; Posselt, M.; Skorupa, W.; Helm, M.;
Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ≈ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability.
Keywords: Ion implantation, Solid phase epitaxy, Deep level impurity, Si

Publ.-Id: 21546 - Permalink


Ion irradiation and nanoindentation as a screening test for irradiation effects on neutron-irradiated ferritic/martensitic high-Cr steels
Heintze, C.; Akhmadaliev, S.; Altstadt, E.; Bergner, F.;
A combined approach based on ion irradiation and nanoindentation as a screening test procedure for the irradiation response of structural materials foreseen for components exposed to heavy neutron irradiation has been selected and specified in detail. Important constituents of the approach are:
• Design of the ion irradiation experiments using the MD code SRIM and taking into account recommendations according to [1], detailed documentation of the irradiation experiments and the SRIM calculations,
• Nanoindentation testing over a large range of indentation depths (from about 5% to 100% of the thickness of the ion-irradiated layer) to gain information on the indentation size effect and the substrate effect, analysis according to the Oliver-Pharr method [2,3],
• Elimination of the indentation size effect (ISE) based on an unirradiated reference sample of the same material using a suitable model (e.g. [4]), elimination of the substrate effect.

A version of the approach specified above was applied to unirradiated, ion-irradiated and neutron-irradiated 9%Cr F/M steel T91 (MATTER reference material). The findings indicate that the approach based on ion irradiation and nanoindentation is suitable as a screening test for F/M steels exposed to neutron irradiation.

References
[1] R. E. Stoller, M. B. Toloczko, G. S. Was, A. G. Certain, S. Dwaraknath, F. A. Garner, Nucl. Instrum. Methods Phys. Res. B 310 (2013) 75–80.
[2] W. C. Oliver, G. M. Pharr, J. Mater. Res., 7 (1992) 1564–1583.
[3] W. C. Oliver, G. M. Pharr, J. Mater. Res., 19 (2004) 3–20.
[4] W. D. Nix, H. Gao, J. Mech. Phys. Solids, 46 (1998) 411–425.
Keywords: ion irradiation, neutron irradiation, nanoindentation, irradiation hardening, ferritic/martensitic steels, T91
  • Lecture (Conference)
    MATTER - “MATerials TEsting and Rules“ Project Final Workshop, 20.-22.10.2014, Rom, Italy

Publ.-Id: 21544 - Permalink


The Zn-vacancy related green luminescence and donor-acceptor pair emission in ZnO grown by pulsed laser deposition
Wang, Z.; Su, S. C.; Younas, M.; Ling, F. C. C.; Anwand, W.; Wagner, A.;
Low temperature (10 K) photoluminescence study shows that green luminescence (GL) peaked at 2.47 eV and near band edge (NBE) emission at 3.23 eV are introduced in undopd ZnO grown by pulsed laser deposition (PLD) after the 900°C annealing. The NBE emission exhibiting blue shift with increasing temperature is assigned to the transitions of donor-acceptor-pair (DAP)/free-electron-to-acceptor (FA). Positron annihilation spectroscopy (PAS) study shows that the introduction of the GL is correlated with the formation of the Zn vacancy-related defect (VZn). Comparing the transition energies of VZn obtained by the previous first principle calculation [Janotti and Van de Walle, Phys. Rev. B 76, 165202 (2007)], the GL is associated with the transition from the conduction band to the ε(-/2-) state of VZn and the DAP/FA emission involves the acceptor level ε(0/-) of VZn.
Keywords: ZnO, green luminescence, Zn vacancy

Publ.-Id: 21543 - Permalink


Influence of the discharge regime on Ti thin films growth and properties in dc, single pulsed and chopped high power impulse magnetron sputtering
Meško, M.; Heller, R.; Hübner, R.; Krause, M.;
High power impulse magnetron sputtering (HiPIMS) has been becoming an appealing deposition process for synthesis of high quality coatings over the last decade. It utilizes average power similar to the dc magnetron sputtering (DCMS) applied on magnetron target, which is however concentrated in short pulses. This ensures generation of dense plasmas with high fraction of ionized film forming species. Control over the energy and trajectory of ionized sputtered species can lead to the formation of coatings with improved properties. Despite of certain advantages the HiPIMS process has often a lower deposition rate compared to DCMS. This is one reason which hinders the HiPIMS process from further exploration in industrial applications. However more recently it has been shown that deposition rates of Ti thin films can be significantly increased by so called chopped-HiPIMS (c-HiPIMS) technique [1]. In this case a single HiPIMS pulse is decomposed into several individual pulses with microsecond pulse off-times. C-HiPIMS can be especially effective in suppression of thermal spikes on the target. The effect of thermal spikes is most pronounced during long single HiPIMS pulses. It negatively influences mobility of arriving ad-atoms leading to the formation of larger grains and rougher surface of Ti thin films [2]. In present work we compare the density, crystallinity, roughness, and microstructure of Ti thin films prepared by dc, single pulsed, and c-HiPIMS. Much attention has been paid on role of microsecond pulse off-times on Ti thin films properties. Plasma parameters have been measured to supplement our investigations.
References:
[1] P. M. Barker, E. Lewin, and J. Patscheider “Modified high power impulse magnetron sputtering process for increased deposition rate of titanium” J. Vac. Sci. Technol. A 31 (2013) 0606041
[2] F. J. Jing, T. L. Yin, K. Yukimura, H. Sun, Y. X. Leng, and N. Huang “Titanium film deposition by high-power impulse magnetron sputtering: Influence of pulse duration” Vacuum 86 (2012) 2114
Keywords: HiPIMS, Ti thin film, microstructure, plasma parameters
  • Poster
    14th International Conference on Plasma Surface Engineering, 15.-19.09.2014, Garmisch-Partenkirchen, Deutschland

Publ.-Id: 21542 - Permalink


The effect of He on irradiation hardening of Fe-9Cr-based non-ODS and ODS alloys at 300°C
Heintze, C.; Kögler, R.; Bergner, F.; Hernández Mayoral, M.;
The influence of helium on the irradiation hardening and embrittlement of reduced-activation ferritic/martensitic Cr-steels and their oxide dispersion strengthened variants under fusion-relevant irradiation conditions is still a concern. While the fact that He can influence the mechanical properties is well established [1,2], the underlying mechanisms are not fully understood [1,2]. In this work the effect of He and displacements per atom (dpa) on the irradiation-induced hardening of an Fe-9at%Cr alloy, Eurofer97 and an oxide dispersion strengthened variant of Eurofer (ODS-Eurofer) at 300°C was studied. Self-ion irradiation was applied to simulate the neutron-irradiation-induced damage. To separate the effect of helium different irradiation modes were applied. Apart from single-beam irradiations with He or self-ions, only, Helium was implanted prior to (pre-implantation), simultaneously (dual-beam irradiation) or following the (post-implantation) self-ion irradiation. The ion irradiated layer was characterized by means of nanoindentation. We conclude, that:
• there is a significant interaction between dpa and He
• pre-implantation of He followed by self-ion irradiation is not suitable to replace simultaneous irradiations or to simulate neutron irradiation induced damage
• nano-oxides in ODS-Eurofer mitigate the effect of helium on irradiation hardening

[1] H. Trinkaus, B.N. Singh, J. Nucl. Mater. 323 (2003) 229
[2] R. Schäublin, Y.L. Chiu, J. Nucl. Mater. 362 (2007) 152
Keywords: irradiation hardening, ODS, dual-beam, ion irradiation, nanoindentation
  • Poster
    2nd International Workshop on ODS Materials, 26.-27.06.2014, Dresden, Deutschland

Publ.-Id: 21541 - Permalink


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