Helmholtz-Gemeinschaft
DRESDEN-concept

Mobile version: On

Publication database - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

< Seite 1 von 195 >   Gesamtzahl lt. Auswahl: 19427 Title records (100 Title records je Seite)
23896 Publications
Sponge-like Si-SiO2 nanocomposite as photovoltaic absorber: Synthesis by solid vs. liquid state decomposition of SiOx
Schumann, E.; Heinig, K.-H.; Hübner, R.; Carcelen, V.; Krause, M.; Gemming, S.
Abstract: Absorber layers consisting of nanostructured Si are candidates to improve the efficiency of thin film Si solar cells. Si-SiO2 nanocomposites with sponge-like Si embedded in SiO2 are promising materials due to a widened band gap and a maintained electrical interconnectivity. These structures can be formed upon isothermal or rapid thermal annealing of SiOx films (x<1), which leads to phase separation into a percolated network of Si nanowires embedded in SiO2, tentatively accompanied by crystallization of the Si. SiOx layers have been grown by ion beam sputter deposition as well as by reactive magnetron sputtering. Phase separation into Si-SiO2 nanocomposites has been achieved by classical thermal oven treatment, which has been compared to a very rapid thermal processing by scanning a diode laser line source. Compositional and structural characterization has been performed by Rutherford backscattering spectroscopy, energy filtered transmission electron
microscopy, and Raman spectroscopy. The two sputter techniques of SiOx lead to distinct nanostructures during the classical thermal treatment throughout a phase separation in the solid state. In contrast, the decomposition with laser treatment occurs in the liquid state.

Keywords: sponge-like, nanostructure, nanocomposite, silicon, siliconoxide, photovoltaic
  • Poster
    79. DPG-Jahrestagung und DPG-Frühjahrstagung der Sektion Kondensierte Materie, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21820

Structural and electrical characterization of Ar+ irradiated TiO2 thin films
Blaschke, D.; Agnieszka, B.; Huebner, R.; Munnik, F.; Heller, R.; Scholz, A.; Nierobisch, F.; Rana, V.; Zahn, P.; Gemming, S.
Abstract: Transition metal oxide thin films, like TiO2, which show a redox-based switching process between two or more resistance levels, are promising candidates for future memory storage devices.
They are extensively studied to get a better understanding of the role of mobile oxygen ions and/or oxygen vacancies for structural changes and electronic transport inside the films.
A defective, nonstoichiometric TiO2-x layer can act as a reservoir for oxygen vacancies and improves the switching characteristics. Such a layer was introduced into the virgin TiO2 film by low energy Ar+ irradiation with different energies and fluencies to modulate the depths and level of the defective region. The impact of the irradiation to the surface morphology and crystal structure was monitored by AFM and TEM measurements and was found to be surface smoothing and amorphization. The role of the preferential sputtering of oxygen to the stoichiometry of the film was investigated with TRIDYN simulations. Electrical properties of the irradiated films were characterized by I-V and C-V measurements and are related to the structural changes caused by the Ar+ irradiation.

The project is funded by the Initiative and Networking Fund of the Helmholtz Association (Virtual Institute Memriox, VH-VI-422).

Keywords: TiO2, resistive switching, Ar irradiation
  • Poster
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21818

Simultaneous measurement of AMR and observation of magnetic domains with dual Kerr microscopy
Osten, J.; Lenz, K.; Lindner, J.; Fassbender, J.
Abstract: Anisotropic magneto resistance (AMR) sensors are widely used in daily life. But the influence of magnetic domains on the AMR is still not fully understood. AMR depends on the direction of the magnetization. For the understanding of the AMR it is therefore important to know about the domain structure. Dual Kerr microscopy is used for the observation of the magnetic domains while at the same time the AMR is measured. Dual Kerr microscopy means that it is possible to measure two magnetization directions at the same time. These two sensitivity directions make it possible to calculate quantitative Kerr images for a complete loop. The investigated samples were magnetic stripe patterned permalloy. The patterning was archived with Cr-Implantation. In addition to the measured resistance the AMR is calculated from the quantitative Kerr images. We also compare the field dependence of the AMR by variation of the magnetic field angle.Our measurements show a clear dependence of the AMR on the magnetic domain types. This work is supported by DFG grant FA316/3-2.
Keywords: Kerr microscopy, AMR
  • Lecture (Conference)
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21817

Evidence of U(VI) sorption on Acidovorax facilis by TRLFS and EF-TEM/EELS
Krawczyk-Bärsch, E.; Gerber, U.; Steudtner, R.; Lünsdorf, H.; Arnold, T.
Abstract: Acidovorax facilis, an aerobic Gram-negative Betaproteobacteria which is commonly found in soil, was used for U(VI) sorption experiments. Experiments were performed in batch cultures under aerobic conditions at 25 °C using nutrient broth. For U(VI) sorption experiments UO2(NO3)2 was added to the culture to achieve an initial U concentration of 0.05 and 0.1 M, respectively, at a neutral pH range. The duration of the sorption experiments were limited to 8 h and 48 h, respectively. By time-resolved laser fluorescence spectroscopy (TRLFS) the measured emission spectrum of the cells is characterized by four emission bands with peak maxima at 497.8, 519.5, 544.1 and 568.6 nm ± 0.5 nm. In addition, the spectra of the Uranyl-lipopolysaccharide-complexes R-O-PO3-UO2 and [R-O-PO3]2-UO22-, reported by Barkleit et al. (2008), were used for comparison. They show only a small deviation from those observed in our studies. Hence, it can be concluded that phosphoryl groups are the main binding sites for uranyl, located in the lipopolysaccharide (LPS) unit in the outer membrane by Gram-negative Acidovorax facilis cells. After the U(VI) biosorption experiments, Acidovorax facilis cells were prepared for Energy-filtered transmission electron microscopy (EF-TEM) and electron energy-loss spectroscopy (EELS). The results provide microscopically and spectroscopically evidence of U(VI) sorbed at the outer membrane of Acidovorax facilis cells by showing high electron density and U ionization intensity peaks.
Keywords: Acidovorax facilis, uranium, sorption, TRLFS, EF-TEM
  • Lecture (Conference)
    Goldschmidt Conference, 16.-21.03.2015, Prague, Czech
Registration No. 21813

Evolution of Spin Wave Modes in Periodically Perturbed Thin Films
Langer, M.; Gallardo, R.; Banholzer, A.; Schneider, T.; Wagner, K.; Landeros, P.; Lenz, K.; Lindner, J.; Fassbender, J.
Abstract: The transition from a continuous thin film to a magnonic crystal is studied by ferromagnetic resonance (FMR). Ion irradiation as well as reactive ion beam etching were used to realize a periodic modulation of the sample surface after patterning by electron beam lithography. Mode-splitting in the FMR spectra has been investigated dependent on the size of the perturbations and compared to available analytical perturbation theory. Numerical simulations have been carried out to identify the spin waves corresponding to the mode spectra as well as to understand deviations between measurement and analytical theory for large perturbations. This work is supported by DFG grant LE2443/5-1.
  • Lecture (Conference)
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21807

Determination of the Exchange Stiffness Constant in Ultrathin Magnetic Films by Ferromagnetic Resonance
Langer, M.; Wagner, K.; Sebastian, T.; Schultheiss, H.; Lenz, K.; Lindner, J.; Fassbender, J.
Abstract: In ultrathin magnetic films of 10 — 20 nm thickness, it is hardly possible to determine the exchange constant A using conventional techniques, such as Brillouin light scattering. In this work, a method is presented allowing for analytical determination of the exchange constant A in ultrathin magnetic films. Periodical surface modulations are introduced by electron beam lithography with subsequent sub-nanometer etching. The periodical stray field induces two-magnon scattering leading to a coupling of the uniform excitation with higher in-plane spin waves. An analytical model is presented, that can be used to precisely calculate the exchange constant A under usage of the measured ferromagnetic
resonance spectra (frequency versus field dependence). This work is supported by DFG grant LE2443/5-1.
  • Poster
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21804

Pulsed magnetic field spectroscopy up to 70 T on the dilute nitride GaAsN
Eßer, F.; Schneider, H.; Winnerl, S.; Drachenko, O.; Patanè, A.; Helm, M.
Abstract: Magnetic fields above 45 T offer great opportunities as a tool for materials research but can only be realized in the pulsed regime. We use pulsed magnetic fields up to 70 T for spectroscopic investigations of the dilute nitride GaAsN. This material is a promising candidate for optical applications because of the possibility for tuning its band gap by the nitrogen content. Our studies focus on the exploration of the band structure and in particular on the determination of the effective mass. Cyclotron-resonance spectroscopy indicates that the effective mass is not strongly affected by nitrogen in comparison to previous publications. Our magneto-photoluminescence investigations reveal the formation of localized and delocalized states as a result of the nitrogen incorporation. Delocalized states undergo transitions to localized ones in very high magnetic fields. This result is in good agreement with a pressure dependent study [1].

[1] J. Endicott, A. Patanè, D. Maude, L. Eaves, M. Hopkinson, and G. Hill, Phys. Rev. B 72, 041306(R) (2005)

Keywords: GaAsN, dilute nitride, effective mass, cyclotron-resonance, pulsed magnetic field
  • Lecture (Conference)
    79. DPG-Jahrestagung und DPG-Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21802

THz spectroscopy of solids using a free-electron laser
Helm, M.
Abstract: I will start describing the Dresden free-electron laser FELBE as an intense, tunable, pulsed and narrowband source of infrared and THz radiation and the unique opportunities it offers for the spectroscopy of low-energy excitations in solids. In particular, the FEL can be used for nonlinear optical experiments, for time-resolved pump-probe studies, and also for near-field microscopy. I will present some recent results and will conclude with an outlook on further developments, including the superradiant THz radiation source TELBE.
Keywords: free electron laser, pump probe, spectroscopy
  • Lecture (others)
    Vortrag am Shanghai Institute for Applied Physics (SINAP), 10.03.2015, Shanghai, China
Registration No. 21801

Topological Spin Textures in Magnetic Multilayers
Wintz, S.
Abstract: Topological spin textures, such as vortices or skyrmions, are attracting significant attention because of their intriguing fundamental properties as well as their promising applicability in memory devices or spin torque oscillators. A particular topological texture that was theoretically predicted is the two-dimensional hedgehog state, also known as ’spin meron’. It had been unclear, however, whether this kind of highly divergent magnetization structure may occur in real systems. Only recently, evidence for the existence of meron-like pair states was reported for the case of trilayer elements consisting of two ferromagnetic layers and a non-ferromagnetic interlayer [1]. On this background, a direct proof for the existence of meron-like states in trilayer elements via direct magnetic imaging will be presented. It will also be shown that in the presence of biquadratic interlayer exchange coupling, such meron-like pair states may even represent the magnetic ground state of the system. Interestingly, the highly divergent magnetization distribution induces an additional, three-dimensional torus vortex that in-turn causes a symmetry break for the possible topological pair configurations [2]. In addition the dynamic properties of vertically coupled topological spin textures will be addressed, where the focus will be set on spin wave emission processes in such systems.
References: [1] C. Phatak et al., Phys. Rev. Lett. 108, 067205 (2012). [2] S. Wintz et al., Phys. Rev. Lett. 110, 177201 (2013).

Keywords: vortex multilayer
  • Invited lecture (Conferences)
    DPG Frühjahrstagung der Sektion kondensierte Materie, 15.-20.03.2015, Berlin, Deutschland
Registration No. 21800

Magnetic interactions in BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices
Xu, Q.; Sheng, Y.; Khalid, M.; Cao, Y.; Wang, Y.; Qiu, X.; Zhang, W.; He, M.; Wang, S.; Zhou, S.; Li, Q.; Wu, D.; Zhai, Y.; Liu, W.; Wang, P.; Xu, Y.; Du, J.
Abstract: The clear understanding of exchange interactions between magnetic ions in substituted BiFeO3 is the prerequisite for the comprehensive studies on magnetic properties. BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices have been fabricated by pulsed laser deposition on (001) SrTiO3 substrates. Using piezoresponse force microscopy (PFM), the ferroelectricity at room temperature has been inferred from the observation of PFM hysteresis loops and electrical writing of ferroelectric domains for both samples. Spin glass behavior has been observed in both samples by temperature dependent magnetization curves and decay of thermo-remnant magnetization with time. The magnetic ordering has been studied by X-ray magnetic circular dichroism measurements, and Fe-O-Mn interaction has been confirmed to be antiferromagnetic (AF). The observed spin glass in BiFe0.5Mn0.5O3 films has been attributed to cluster spin glass due to Mn-rich ferromagnetic (FM) clusters in AF matrix, while spin glass in BiFeO3/BiMnO3 superlattices is due to competition between AF Fe-O-Fe, AF Fe-O-Mn and FM Mn-O-Mn interactions in the well ordered square lattice with two Fe ions in BiFeO3 layer and two Mn ions in BiMnO3 layer at interfaces.

Downloads:

Registration No. 21799

Leaching of copper from Kupferschiefer by glutamic acid and heterotrophic bacteria
Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.; Gutzmer, J.
Abstract: Polymetallic Cu–Ag ores of the Central European Kupferschiefer deposits are one of the most important sources of copper in Europe. Because the ores are typically complex and often exceptionally fine-grained the development of efficient alternatives to conventional beneficiation strategies are an important target of current research. Biomining – the use of biological components for metal extraction – may offer solutions that are both efficient and environmentally benign. As conventional bioleaching with acidophilic microorganisms is impeded by the high carbonate content of the Kupferschiefer ores, heterotrophic microorganisms and glutamic acid are investigated as a possible alternative in the present study. The focus of this investigation is solely on the recovery of copper from the Kupferschiefer sensu strictu. Bioleaching experiments were carried out using such material from the Polkowice Mine in Poland. This material is marked by high grade (3.8 wt.% Cu), complex ore mineralogy (chalcocite, bornite, chalcopyrite and covellite in significant quantity) and a gangue mineralogy that is rich in carbonate, organic carbon and clay minerals that together form a very fine-grained matrix. (Bio)leaching experiments yield best results when glutamic acid alone is used – reaching copper recoveries up to 44%. Recoveries are consistently lower in experiments in which glutamic acid and microbiological metabolites are both present. The leaching of chalcocite renders the greatest contribution to the copper recovered to the leach solution in all experiments. It can be concluded that glutamic acid solubilises copper efficiently from Kupferschiefer, mainly from chalcocite.
Keywords: sulphide ores, bacteria, bioleaching, liberation analysis, ore mineralogy Registration No. 21795

Morphology and Microstructure of Si-SiO2 Nanocomposite Layers
Hübner, R.
  • Invited lecture (Conferences)
    EFDS-Workshop "Morphologie und Mikrostruktur dünner Schichten und deren Beeinflussung", 12.03.2015, Dresden, Deutschland
Registration No. 21790

Experimental Characterization of Vertical Gas-Liquid Pipe Flow For Annular and Liquid Loading Conditions Using Dual Wire-Mesh Sensor
Vieira, R. E.; Parsi, M.; Torres, C. F.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.
Abstract: In gas well production, liquid is produced in two forms, droplets entrained in the gas core and liquid film flowing on the tubing wall. For most of the gas well life cycle, the predominant flow pattern is annular flow. As gas wells mature, the produced gas flow rate reduces decreasing the liquid carrying capability initiating the condition where the liquid film is unstable and flow pattern changes from fully cocurrent annular flow to partially cocurrent annular flow. The measurement and visualization of annular flow and liquid loading characteristics is of great importance from a technical point of view for process control or from a theoretical point of view for the improvement and validation of current modeling approaches. In this experimental investigation, a Wire-Mesh technique based on conductance measurements was applied to enhance the understanding of the air-water flow in vertical pipes. The flow test section consisting of a 76 mm ID pipe, 18 m long was employed to generate annular flow and liquid loading at low pressure conditions. A 16×16 wire configuration sensor is used to determine the void fraction within the cross-section of the pipe. Data sets were collected with a sampling frequency of 10,000 Hz. Physical flow parameters were extracted based on processed raw measured data obtained by the sensors using signal processing. In this work, the principle of Wire-Mesh Sensors and the methodology of flow parameter extraction are described. From the obtained raw data, time series of void fraction, mean local void fraction distribution, characteristic frequencies and structure velocities are determined for different superficial liquid and gas velocities that ranged from 0.005 to 0.1 m/s and from 10 to 40 m/s, respectively. In order to investigate dependence of liquid loading phenomenon on viscosity, three different liquid viscosities were used. Results from the Wire-Mesh Sensors are compared with results obtained from previous experimental work using Quick Closing Valves and existing modeling approaches available in the literature.
Keywords: Wire-mesh sensor; gas-liquid flow; void fraction; phase distribution; flow visualization Registration No. 21775

The effect of magnetic annealing on crystallographic texture and magnetic properties of Fe-2.6%Si
Salih, M. Z.; Uhlarz, M.; Pyczak, F.; Brokmeier, H.-G.; Weidenfeller, B.; Al-Hamdany, N.; Gan, W. M.; Zhong, Z. Y.; Schell, N.
Abstract: The effect of magnetic annealing on crystallographic texture ,microstructure, defects density and magnetic properties of a Fe-2.6%Si steel has been analyzed. After two stage cold rolling (75% and 60% cold rolled) with intermediate annealing process at (600 °C/1 h) the sample annealed at 600 °C for one hour during which different magnetic field of 0,7 and 14 T were applied has been investigated. The effect of defects density after cold rolling process on the recrystallization texture and magnetic properties was characterized. Heat treatments under a high external field of14 T show a drastic improvement of the magnetic properties such as significantly increased permeability. Neutron diffraction measurements were preferred for measurement of the bulk sample texture so that sufficient grain statistics were obtained. Because of its small wavelength (0.05–0.2 Å) synchrotron diffraction with high photon energy was used to evaluate the defects density by a modified Williamson–Hall plot. Registration No. 21772

Investigating Spinodal Decomposition and Coarsening using Massively Parallel Kinetic Metropolis Lattice Monte-Carlo Simulations
Kelling, J.; Heinig, K. H.; Gemming, S.
Abstract: Nano-structured materials are important for many applications, including energy technologies. The desired structures can be created using bottom-up processes, which utilize self-assembling. By way of spinodal decomposition of a metastable phase, like SiOx into Si and SiO2, sponge-like networks of nanowires can be obtained. Understanding the coarsening kinetics of spinodal structures is crucial not only for bottom-up production, but also helps to increase the life-time of components like porous matrices in fuel cells, where suppression of coarsening has a huge economic impact.

Two theories on coarsening of spinodal structures exist: one assuming diffusion through the bulk [1], the other along interfaces [2]. Since orders of magnitude in both space and time have to be covered by simulations, numerical studies are quite demanding. Nevertheless, simulations are essential in studying systems containing size-inhomogeneities in initial nano-structures, where strongly accelerated coarsening is observed.

Here, a multi-GPU Kinetic Metropolis Lattice Monte-Carlo implementation, capable of atomistic simulations of phase-separation and coarsening at spatio-temporal experimental scales (billions of particles over millions of time-steps) is presented while laying focus on the above-mentioned applications.

[1] A. Chakrabarti, R. Toral, J.D. Gunton, Phys. Rev. B 39(7) 4386 (1989) suggesting a modified Lifschitz-Slyozov law: I.M. Lifshitz, V.V. Slyozov, J. Phys. Chem. Solids 19(1-2), 35-50 (1961)
[2] W.W. Mullins, J. Appl. Phys. 28(3), 333-339 (1957)

Keywords: Nano Structures, GPGPU, Supercomputing, Statistical Physics,
  • Lecture (Conference)
    Conference of the Middle European Cooperation in Statistical Physics, 23.-25.03.2015, Esztergom, Hungary
Registration No. 21768

Simulation of Surface Growth and Lattices Gases Using GPUs
Schulz, H.; Kelling, J.; Ódor, G.; Ódor, G.; Ferenc Nagy, M.
Abstract: Restricted solid on solid surface growth models can be mapped onto binary lattice gases. We show that efficient simulation algorithms can be realized on GPUs either by CUDA or by OpenCL programming. We consider a deposition/evaporation model following Kardar–Parisi–Zhang growth in d+1 dimensions, related to the Asymmetric Simple Exclusion Process. Up to 100 - 400 x speedup can be achieved with respect to the serial code running on a I5 core. This permits studying disorder and aging behavior in these system.
Keywords: Computational Physics, Supercomputing
  • Poster
    GPU Technology Conference, 17.-20.03.2015, San Jose, CA, USA
  • Poster
    Conference of the Middle European Cooperation in Statistical Physics, 23.-25.03.2015, Esztergom, Hungary
Registration No. 21767

Annual Report 2014 - Institute of Resource Ecology
Stumpf, T.; Foerstendorf, H.; Bok, F.; Richter, A. (Editors)
Abstract: The Institute of Resource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden – Rossendorf (HZDR).
The research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”.
Additionally, various activities have been started investigating chemical and environmental aspects of processing and recycling of strategic metals, namely rare earth elements. These activities are located in the HGF program “Energy Efficiency, Materials and Resources (EMR)”. Both programs, and therefore all work which is done at IRE, belong to the research sector “Energy” of the HGF.
The research objectives are the protection of humans and the environment from hazards caused by pollutants resulting from technical processes that produce energy and raw materials. Treating technology and ecology as a unity is the major scientific challenge in assuring the safety of technical processes and gaining their public acceptance. We investigate the ecological risks exerted by radioactive and nonradioactive metals in the context of nuclear waste disposal, the production of energy in nuclear power plants, and in processes along the value chain of metalliferous raw materials. A common goal is to generate better understanding about the dominating processes essential for metal mobilization and immobilization on the molecular level by using advanced spectroscopic methods. This in turn enables us to assess the macroscopic phenomena, including models, codes, and data for predictive calculations, which determine the transport and distribution of contaminants in the environment.
  • Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-059 2015

Downloads:

Registration No. 21762

Carrier relaxation dynamics in graphene
Mittendorff, M.
Abstract: Graphene, the two-dimensional lattice of sp2-hybridized carbon atoms, has a great potential for future electronics, in particular for opto-electronic devices. The carrier relaxation dynamics, which is of key importance for such applications, is in the main focus of this thesis. Besides a short introduction into the most prominent material properties of graphene and the experimental techniques, this thesis is divided into three main parts.
The investigation of the carrier relaxation dynamics in the absence of a magnetic field is presented in Chapter 3. In the first experiment, the anisotropy of the carrier excitation and relaxation in momentum space was investigated by pump-probe measurements in the near-infrared range. While this anisotropy was not considered in all previous experiments, our measurements with a temporal resolution of less than 50 fs revealed the polarization dependence of the carrier excitation and the subsequent relaxation. About 150 fs after the electrons are excited, the carrier distribution in momentum space gets isotropic, caused by electron-phonon scattering. In a second set of two-color pump-probe experiments, the temperature of the hot carrier distribution, which was obtained within the duration of the pump pulse (about 200 fs), could be estimated. Furthermore, a change in sign of the pump-probe signal can be used as an indicator for the Fermi energy of different graphene layers. Pump-probe experiments in the far-infrared range in reflection and transmission geometry were performed at high pump power. A strong saturation of the pump-induced transmission was found in previous experiments, which was attributed to the pump-induced change in absorption. Our investigation shows the strong influence of pump-induced reflection at long wavelengths, as well as a lot smaller influence of the saturation of the pump-induced change in absorption. At a high pump power, the increase of the reflection exceeds the change in absorption strongly, which leads to negative pump-probe signals in transmission geometry.
In Chapter 4, investigations of the carrier dynamics of graphene in magnetic fields of up to 7T are presented. Even though the optical properties of Landau-quantized graphene are very interesting, the carrier dynamics were nearly unexplored. A low photon energy of 14meV allows the investigation of the intraband Landau-level (LL) transitions. These experiments revealed two main findings: Firstly, the Landau quantization strongly suppresses the carrier relaxation via optical-phonon scattering, resulting in an increased relaxation time. Secondly, a change in sign of the pumpprobe signal can be observed when the magnetic field is varied. This change in sign indicates a hot carrier distribution shortly after the pump pulse, which means that carrier-carrier scattering remains very strong in magnetic fields. In a second set of pump-probe measurements, carried out at a photon energy of 75meV, the relaxation dynamics of interband LL transitions was investigated. In particular, experiments on the two energetically degenerate LL transitions LL−1 ) LL0 and LL0 ) LL1 showed the influence of extremely strong Auger processes.
An ultrafast and extremely broadband terahertz detector, based on a graphene flake, is presented in the last chapter of this thesis. To couple the radiation efficiently to the small flake, the inner part of a logarithmic periodic antenna is connected to it. With a rise time of about 50 ps in a wavelength range of 9 μm to 500 μm, this detector is very interesting to obtain the temporal overlap in two-color pump-probe experiments with the free-electron laser FELBE. Furthermore, the importance of the substrate material, in particular for the high-speed performance, is discussed.
  • Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-057 2015

Downloads:

Registration No. 21760

Magnetic, thermal and transport properties of Tb3Ru4Al12 with a distorted kagome lattice
Gorbunov, D. I.; Henriques, M. S.; Andreev, A. V.; Skourski, Y.; Dusek, M.
Abstract: The Tb3Ru4Al12 compound (hexagonal crystal structure) having a distorted kagome net of the Tb atoms is studied on a single crystal by measurements of magnetization, specific heat and electrical resistivity. The system is an antiferromagnet with the Néel temperature TN = 22 K. A substantial magnetic anisotropy is observed that persists at least up to 60 T. Tb3Ru4Al12 displays field-induced magnetic phase transitions: one along [100] and [120] and two along the [001] axis. The transitions are accompanied by sharp peaks in magnetoresistance and subsequently lead to a large negative effect in it, −20% in the longitudinal and −40% in the transverse geometry. The peaks are explained by changes in conduction electron spectra at the transitions due to the interaction between the conduction electrons and localized magnetic moments. The large negative effect suggests field-induced magnetic phases with a reduced period as compared to zero field. Registration No. 21759

Fast-neutron Induced Reactions at the nELBE Time-of-flight Facility
Junghans, A. R.; Beyer, R.; Elekes, Z.; Grosse, E.; Hannaske, R.; Koegler, T.; Massarczyk, R.; Schwengner, R.; Wagner, A.
Abstract: The compact neutron-time-of-flight facility nELBE at the superconducting electron accelerator ELBE of Helmholtz-Zentrum Dresden-Rossendorf is being rebuilt and extended with a low-background experimental hall. The neutron radiator consists of a liquid lead circuit without additional neutron moderators. The useful neutron spectrum extends from some tens of keV to about 10 MeV. nELBE is intended to deliver cross section data of fast-neutron nuclear interactions e.g. for the transmutation of nuclear waste and improvement of neutron physical simulations of innovative nuclear systems. Before the extension of the facility, the photon production cross section of 56 Fe was measured with an HPGe detector and the inelastic neutron scattering cross section to the first few excited states in Fe-56 was determined. The neutron total cross sections of Au and Ta were determined in the energy from 200 keV to 7 MeV in a transmission experiment.
Keywords: neutron time-of-flight, neutron induced reactions Registration No. 21758

A simple method for deadtime corrections in microbeam measurements.
Munnik, F.
Abstract: In microbeam measurements on inhomogeneous samples large variations in count-rate can occur. These variations result in variations in deadtime that have to be used to correct elemental distribution maps. However, the deadtime is usually not available on a pixel by pixel basis. In this work, a simple model is proposed to calculate the deadtime for each pixel. Measurements to determine the deadtime per event, needed in the model, are presented and the deadtime corrections are presented for real samples.
Keywords: dead time, PIXE
  • Poster
    14th International Conference on Particle Induced X-ray Emission (PIXE 2015), 26.02.-03.03.2015, Somerset West, South Africa
Registration No. 21756

Eliashberg analysis of the optical conductivity in superconducting Pr2CuOx with x similar or equal to 4
Schachinger, E.; Chanda, G.; Lobo, R. P. S. M.; Naito, M.; Pronin, A. V.
Abstract: Superconducting Pr2CuOx, x similar or equal to 4 films with T' structure and a Tc of 27 K have been investigated by millimeter-wave transmission and broadband (infrared-to-ultraviolet) reflectivity measurements in the normal and superconducting state. The results obtained by both experimental methods show a consistent picture of the superconducting condensate formation below Tc. An Eliashberg analysis of the data proves d-wave superconductivity and unitary-limit impurity scattering of the charge carriers below Tc. The derived electron-exchange boson interaction spectral function I2chi(omega) shows only marginal changes at the superconducting transition with the mass enhancement factor lambda, the first inverse moment of I2chi(omega), being equal to 4.16 at 30 K and to 4.25 at 4 K. Registration No. 21755

Comparability and accuracy of nitrogen depth profiling in nitride austenitic stainless steel
Manova, D.; Díaz, C.; Pichon, L.; Abrasonis, G.; Mändl, S.
Abstract: A comparative study of nitrogen depth profiles in low energy ion implantation nitrided austenitic stainless steel 1.4301 by glow discharge optical emission spectroscopy (GDOES), secondary ion mass spectrometry (SIMS) and nuclear reaction analysis (NRA) is presented. All methods require calibration either from reference samples or known scattering or reaction cross sections for the nitrogen concentration, while the methods producing a sputter crater – SIMS and GDOES – need additional conversion from sputter time to depth. NRA requires an assumption of material density for a correct conversion from the ‘natural’ units inherent to all ion beam analysis methods into ‘conventional’ depth units. It is shown that a reasonable agreement of the absolute concentrations and very good agreement of the layer thickness is obtained. The observed differences in broadening between the nitrogen distribution near the surface and the deeper region of the nitrided layer–steel interface are discussed on the basis of surface contaminations, surface roughening and energy straggling effects.
Keywords: GDOES SIMS NRA Austenitic stainless steel Expanded austenite Registration No. 21754

Towards Atomic Physics in PIConGPU
Huebl, A.; Garten, M.; Widera, R.; Huang, L.; Kluge, T.; Bussmann, M.
Abstract: Particle-in-Cell (PIC) codes are a ubiquitous tool to study laser-plasma physics in a fully relativistic environment. Theoretical models for plasma based accelerators and corresponding experiments, as planned by the HIBEF collaboration (XFEL), depend dramatically on the ability to precisely predict the complex processes inside of targets.

Unfortunately, basic atomic processes like the ionization dynamics of solid foil target in ultra-high fields of modern short-pulse laser systems in the PW class are not covered by the basic PIC algorithm. This talk shows ways to introduce the microscopic ionization dynamics inside the targets in a self-consistent and rigorous way. Combined with modern compute hardware such as GPUs and manycore systems in general, this paves the road to a new quality of multi-physics simulations with ab-initio modeling of atomic processes in strong laser fields.

Keywords: PIC, GPU, Ionization, CUDA, PIConGPU, HPC, HIBEF
  • Lecture (Conference)
    DPG-Frühjahrstagung: FV Kurzzeitphysik und Plasmaphysik, 02.-05.03.2015, Bochum, Deutschland
Registration No. 21753

Heating and Ionization Dynamics in Solid Density Plasmas Driven by Ultra-short Relativistic Lasers
Huang, L. G.; Kluge, T.; Bussmann, M.; Cowan, T. E.
Abstract: The dynamics of heating and ionization, which determines the crucial plasma parameters such as temperature, free electron density and so on, is one of the fundamental issues in the realm of ultra-short relativistic laser-solid target interactions. We present our work on investigation of heating and ionization dynamics in solid copper target irradiated by ultra-short intense laser using two dimensional particle-in-cell simulations. The simulation results show that the bulk electron temperature is very sensitive to the initial preplasma scale length. By varying the preplasma scale length from 0 to 0.1 λ_0, the bulk electron temperatures in the interest of region increase from ~26 eV to ~109 eV, which agrees very well with the theory based on Ohmic heating mechanism by treating the return current correctly. The bulk electron heating is finally translated into bulk ionization, which leads to the average Cu ion charge state increasing from ~4.3 to ~10.7.
Keywords: Heating,Ionization,Return Current
  • Lecture (Conference)
    DPG-Frühjahrstagung, 02.-05.03.2015, Bochum, Deutschland
Registration No. 21752

Kompromissbereite Supraleitung
Zwicknagl, G.; Wosnitza, J.
Abstract: Hohe Magnetfelder und Supraleitung vertragen sich üblicherweise nicht: Das Magnetfeld favorisiert parallel ausgerichtete Elektronenspins, während die Supraleitung Cooper-Paare mit antiparallelen Spins voraussetzt. Daher sollte bei ausreichend großen Feldern die Supraleitung zusammenbrechen. Wie Fulde und Ferrell sowie Larkin und Ovchinnikov bereits 1964 vorhergesagt haben, können räumlich getrennte supraleitende sowie magnetisch geordnete Bereiche aber auch bei noch höheren Magnetfeldern koexistieren.
  • Physik Journal 14(2015)3, 31-36
Registration No. 21748

Novel phase transition and metastable regions in the frustrated magnet CdCr2O4
Zherlitsyn, S.; Tsurkan, V.; Zvyagin, A. A.; Yasin, S.; Erfanifam, S.; Beyer, R.; Naumann, M.; Green, E.; Wosnitza, J.; Loidl, A.
Abstract: A new magnetic phase transition, which we assign to the separation of two different spiral phases, has been observed by ultrasound studies below the Néel temperature (TN = 7.8 K) in the frustrated antiferromagnet CdCr2O4. This transition renormalizes the velocity and amplitude of the transverse acoustic mode cT whereas the longitudinal mode cL is not affected. The specific heat does not show any significant change in the entropy at this transition. Furthermore, in an applied magnetic field, the mode cT exhibits extended metastable magnetostructural states neighboring the one-half magnetization plateau in CdCr2O4. By applying an exchange-striction model we can quantitatively describe the field dependence of the sound velocity below and above the one-half magnetization plateau. Registration No. 21747

Direct measurements of the magnetocaloric effect in pulsed magnetic fields: The example of the Heusler alloy Ni50Mn35In15
Ghorbani Zavareh, M.; Salazar Mejia, C.; Najak, A. K.; Skourski, Y.; Wosnitza, J.; Felser, C.; Nicklas, M.
Abstract: We have studied the magnetocaloric effect (MCE) in the shape-memory Heusler alloy Ni50Mn35In15 by direct measurements in pulsed magnetic fields up to 6 and 20 T. The results in 6 T are compared with data obtained from heat-capacity experiments. We find a saturation of the inverse MCE, related to the first-order martensitic transition, with a maximum adiabatic temperature change of ΔTad= - 7 at 250 K and a conventional field-dependent MCE near the second-order ferromagnetic transition in the austenitic phase. The pulsed magnetic field data allow for an analysis of the temperature response of the sample to the magnetic field on a time scale of 10 to 100 ms, which is on the order of typical operation frequencies (10–100 Hz) of magnetocaloric cooling devices. Our results disclose that in shape-memory alloys, the different contributions to the MCE and Hysteresis effects around the martensitic transition have to be carefully considered for future cooling applications. Registration No. 21746

Ultrasmall Nanomaterials for Multimodal Imaging
Stephan, H.
Abstract: kein Abstract verfügbar
  • Lecture (Conference)
    Gründungsveranstaltung der Deutschen Plattform NanoBioMedizin, DECHEMA, 04.03.2015, Frankfurt/Main, Deutschland
Registration No. 21745

Radiolabelling of colloids for highly sensitive detection in complex systems
Hildebrand, H.; Schymura, S.; Barthen, R.; Bellido, E.; Ojea-Jiménez, I.; Cydzik-Giacchin, I.; Kozempel, J.; Dalmiglio, M.; Bulgheroni, A.; Cotogno, G.; Simonelli, F.; Gründig, M.; Kulenkampff, J.; Holzwarth, U.; Gibson, N.; Lippmann-Pipke, J. K. Franke1
Abstract: Colloids and nanoparticulate matter play an important role in the environment since they can act as carriers for (toxic) compounds and thereby enhance migration of substances that might normally be immobile under the given environmental conditions. The carrier properties of colloidal clay particles, humic substances and silica actinide colloids may play an important role in nuclear waste repositories. However, monitoring of these colloids in complex systems such as geological formations or groundwater is nearly impossible using conventional methods, especially at environmentally relevant concentrations and the high background load of other colloids or dissolved species of the same element. This obstacle can be overcome by the use of radiolabelling, which may be of crucial value in enabling such research.
We have developed various methods of introducing radiotracers into natural organic colloids such as humic or fulvic acids [1] and some of the most common technical nanoparticles, such as Ag0 [2], carbon and TiO2 nanoparticles [3]. Current studies are dealing with radiolabelling of CeO2 and quantum dots.
Five different approaches can be pursued in the radiolabelling of colloids or nanoparticles:
(1) Radiosynthesis – the synthesis of a compound using radioactive material
(2) Radiochemistry – the binding of a radioactive tracer to an existing compound
(3) In-diffusion – the in-diffusion of radioisotopes into existing particles
(4) Direct Activation – the activation of existing particles by proton irradiation
(5) Recoil labelling – the implantation of radionuclides into an existing particles using the recoil of a nuclear reaction

Radiosynthesis can be used to produce custom-made radiolabelled nanoparticles provided a suitable radiotracer is available. If the labelling is isotopic no difference in properties compared to non-radioactive particles are expected. We used this method to produce radiolabelled [105/110mAg]Ag nanoparticles.
Binding a radiotracer to a compound is a way of radiolabelling existing commercial or natural materials by a suitable radiochemical protocol. Carbon nanotubes and humic acids were successfully labelled with radioactive Iodine following the one-pot Iodogen method to yield [124/125/131I]CNTs and [125I]humic acid. No significant change in properties was detected compared to the original compounds.
Commercial TiO2 and Ag0 nanoparticles were labelled by the in-diffusion of isotopic radionuclides into surface defects and lattice structure at elevated temperatures. The resulting [110mAg]Ag0 and [44/45Ti]TiO2 nanoparticles showed no change in properties and the radiolabel proved to be stable under various conditions.
If a cyclotron is available, nanoparticles can be radiolabelled by activation via proton irradiation. The proton irradiation causes a nuclear reaction in the nanopowder producing the radiolabel inside the particles. Commercial TiO2 particles were labelled with 48V via a 48Ti(p,n)48V reaction.
If no suitable radiotracers/nuclear reactions are available for the above described methods, nanoparticles can be labelled utilising the recoil of a nuclear reaction to implant a radiotracer. Typically a mixture of a lithium compound and the to-be-labelled particles is irradiated with protons. The nuclear reaction 7Li(p,n)7Be produces 7Be which is implanted in the nanoparticles due to the recoil of the nuclear reaction. [7Be]MWCNT were produced successfully.
Table 1 shows the results for radiolabelling of particles. The described methods are adaptable for a wide range of other nanoparticles or colloids. The so-labelled nanoparticles can be detected at minimal concentrations well in the ng/L range even with a background of the same element and without complicated sample preparations necessary. In the research area of radioactive waste repositories the radiolabelling of humic substances, clay colloids and actinide silica colloids may be of particular interest.

Table 1: Comparison of the radiolabelling procedures and the resulting radiolabelled NP analysis.
Radiolabeling procedure Resulting NP Half-life of the radionuclide Activity concentration [MBq/mg] Detection limit [ng/L]
Radiosynthesis [110mAg]Ag0 250 d 1.5 33
[105Ag]Ag0 41.3 d 0.65 77

Radiochemistry [124I]CNT 4.2 d 8.0 6
[125I]CNT 59.4 d 19.9 2
[131I]CNT 8.0 d 3.7 14

In-Diffusion [110mAg]Ag 250 d 1 50
[44Ti]TiO2 60.4 a 0.01 5000
[45Ti]TiO2 3.08 h 135 0.5

Direct Activation [48V]TiO2 15.97 d 3.7 14
[7Be]MWCNT 53.29 d 0.041 1000

Recoil Labelling [7Be]TiO2 0.3 170
[7Be]SiO2 [4] 53.29 d 1.4 36
[7Be]MWCNT 0.055 1000
References:
[1] Franke, K., Patt, J.T., Kupsch, H., Warwick, P.: Radioiodination of Humic Substances via Azocoupling with 3-[125I]Iodoaniline. Environ Sci Technol 42(11) (2008) 4083 - 4087.
[2] Hildebrand, H., Franke, K.: A new radiolabeling method for commercial Ag0 nanopowder with 110mAg for sensitive nanoparticle detection in complex media. J Nanopart Res 14 (2012) 1142.
[3] Hildebrand, H., Schymura, S., Holzwarth, U., Gibson, N., Dalmiglio, M., Franke, K.: Strategies for radiolabeling of commercial TiO2 nanopowder as a tool for sensitive nanoparticle detection. J Nanopart Res, submitted.
[4] Holzwarth, U., Bellido, E., Dalmiglio, M., Kozempel, J., Cotogno, G., Gibson, N.: 7Be-recoil radiolabelling of industrially manufactured silica nanoparticles. J Nanopart Res 16 (2014) 2574.
  • Poster
    3nd BELBaR Annual Meeting, 05.-06.03.2015, Madrid, Spain
Registration No. 21743

Performance of timing resistive plate chambers with relativistic neutrons from 300 to 1500MeV
Blanco, A.; Adamczewski-Musch, J.; Boretzky, K.; Cabanelas, P.; Cartegni, L.; Ferreira Marques, R.; Fonte, P.; Fruehauf, J.; Galaviz, D.; Heil, M.; Henriques, A.; Ickert, G.; Körper, D.; Lopes, L.; Palka, M.; Pereira, A.; Rossi, D.; Simon, H.; Teubig, P.; Traxler, M.; Velho, P.; Altstadt, S.; Atar, L.; Aumann, T.; Bemmerer, D.; Caesar, C.; Charpy, A.; Elekes, Z.; Fiori, E.; Gasparic, I.; Gerbig, J.; Göbel, K.; Heftrich, T.; Heine, M.; Heinz, A.; Holl, M.; Ignatov, A.; Isaak, J.; Johansson, H.; Kelic-Heil, A.; Lederer, C.; Lindberg, S.; Löher, B.; Machado, J.; Marganiec, J.; Martensson, M.; Nilsson, T.; Panin, V.; Paschalis, S.; Petri, M.; Plag, R.; Pohl, M.; Rastrepina, G.; Reifarth, R.; Reinhardt, T. P.; Röder, M.; Savran, D.; Scheit, H.; Schrock, P.; Silva, J.; Stach, D.; Strannerdahl, F.; Thies, R.; Wagner, A.; Weigand, F. Wamers M.
Abstract: A prototype composed of four resistive plate chamber layers has been exposed to quasi-monoenergetic neutrons produced from a deuteron beam of varying energy (300 to 1500 AMeV) in experiment S406 at GSI, Darmstad, Germany. Each layer, with an active area of about 2000 × 500 mm2, is made of modules containing the active gaps, all in multigap construction. Each gap is defined by 0.3 mm nylon mono-filaments positioned between 2.85 mm thick float glass electrodes. The modules are operated in avalanche mode with a non-flammable gas mixture composed of 90% C2H2F4 and 10% SF6. The signals are readout by a pick-up electrode formed by 15 copper strips (per layer), spaced at a pitch of 30 mm, connected at both sides to timing front end electronics. Measurements of the time of flight jitter of neutrons, in the mentioned energy range, point to a contribution of the resistive plate chamber in the order of 150 ps, independent of the neutron energy.
Keywords: Instrumentation and methods for time-of-flight (TOF) spectroscopy Resistive-plate chambers Particle detectors Neutron detectors (cold, thermal, fast neutrons) Registration No. 21738

Performance of timing Resistive Plate Chambers with protons from 200 to 800 MeV
Machado, J.; Adamczewski-Musch, J.; Blanco, A.; Boretzky, K.; Cabanelas, P.; Cartegni, L.; Ferreira Marques, R.; Fonte, P.; Fruehauf, J.; Galaviz, D.; Heil, M.; Henriques, A.; Ickert, G.; Körper, D.; Lopes, L.; Palka, M.; Pereira, A.; Rossi, D.; Simon, H.; Teubig, P.; Traxler, M.; Velho, P.; Altstadt, S.; Atar, L.; Aumann, T.; Bemmerer, D.; Caesar, C.; Charpy, A.; Elekes, Z.; Fiori, E.; Gasparic, I.; Gerbig, J.; Göbel, K.; Heftrich, T.; Heine, M.; Heinz, A.; Holl, M.; Ignatov, A.; Isaak, J.; Johansson, H.; Kelic-Heil, A.; Lederer, C.; Lindberg, S.; Löher, B.; Marganiec, J.; Martensson, M.; Nilsson, T.; Panin, V.; Paschalis, S.; Petri, M.; Plag, R.; Pohl, M.; Rastrepina, G.; Reifarth, R.; Reinhardt, T. P.; Röder, M.; Savran, D.; Scheit, H.; Schrock, P.; Silva, J.; Stach, D.; Strannerdahl, F.; Thies, R.; Wagner, A.; Wamers, F.; Weigand, M.
Abstract: A prototype composed of four resistive plate chamber layers has been exposed to quasi-monoenergetic protons produced from a deuteron beam of varying energy (200 to 800 AMeV) in experiment S406 at GSI, Darmstadt, Germany. The aim of the experiment is to characterize the response of the prototype to protons in this energy range, which deposit from 1.75 to 6 times more energy than minimum ionizing particles. Each layer, with an active area of about 2000 × 500 mm2, is made of modules containing the active gaps, all in multigap construction. Each gap is defined by 0.3 mm nylon mono-filaments positioned between 2.85 mm thick float glass electrodes. The modules are operated in avalanche mode with a non-flammable gas mixture composed of 90% C2H2F4 and 10% SF6. The signals are readout by a pick-up electrode formed by 15 copper strips (per layer), spaced at a pitch of 30 mm, connected at both sides to timing front end electronics. Results show an uniform efficiency close to 100% along with a timing resolution of around 60 ps on the entire 2000 × 500 mm2 area. Registration No. 21736

In situ spectroscopic identification of neptunium(V) inner-sphere complexes on the hematite-water interface
Müller, K.; Gröschel, A.; Rossberg, A.; Bok, F.; Franzen, C.; Brendler, V.; Foerstendorf, H.
Abstract: Hematite plays a decisive role in regulating the mobility of contaminants in rocks and soils. The Np(V) reactions at the hematite−water interface were comprehensively investigated by a combined approach of in situ vibrational spectroscopy, X-ray absorption spectroscopy and surface complexation modeling. A variety of sorption parameters such as Np(V) concentration, pH, ionic strength, and the presence of bicarbonate was considered. Time-resolved IR spectroscopic sorption experiments at the iron oxide−water interface evidenced the formation of a single monomer Np(V) inner-sphere sorption complex. EXAFS provided complementary information on bidentate edge-sharing coordination. In the presence of atmospherically derived bicarbonate the formation of the bis-carbonato inner-sphere complex was confirmed supporting previous EXAFS findings.1 The obtained molecular structure allows more reliable surface complexation modeling of recent and future macroscopic data. Such confident modeling is mandatory for evaluating water contamination and for predicting the fate and migration of radioactive contaminants in the subsurface environment as it might occur in the vicinity of a radioactive waste repository or a reprocessing plant.
Keywords: iron oxides, Fe2O3, neptunyl, actinides, ATR FT-IR spectroscopy, x-ray absorption, EXAFS, surface complexation Registration No. 21722

Tregs activated by bispecific antibodies: Killers or suppressors?
Koristka, S.; Cartellieri, M.; Arndt, C.; Feldmann, A.; Seliger, B.; Ehninger, G.; Bachmann, Michael P.
Abstract: In recent years, bispecific antibodies (bsAb) have emerged as promising tools for a target-specific redirection of T cells in order to eliminate malignant cells. However, CD3-engaging constructs might also activate T regulatory cells (Tregs) present in the tumor microenvironment. Whether this has detrimental or beneficial effects for tumor therapy is still controversially discussed.
Keywords: cytotoxicity, immunotherapy, immunsuppression, single-chain bispecific antibodies, T cell retargeting, T regulatory cells Registration No. 21715

Electromagnetic Dipole Strength in 124,128,134Xe
Massarczyk, R.; Schwengner, R.; Junghans, A. R.
Abstract: The electromagnetic dipole strength in several even nuclei in the chain of Xenon isotopes has been investigated at the bremsstrahlung facility of the ELBE accelerator in Dresden, Germany and at the HIγS facility in Durham, USA. The goal of these measurements is to extend the knowledge about the general behavior of the dipole strength in the energy region below the neutron separation energy under the aspect of neutron excess and nuclear deformation. Registration No. 21709

Charged defects and defect-induced processes in nitrogen films
Savchenko, E.; Khyzhniy, I.; Uyutnov, S.; Barabashov, A.; Gumenchuk, G.; Ponomaryov, A.; Bondybey, V.
Abstract: Radiation effects in solid nitrogen irradiated with an electron beam were studied with emphasis on the role of charged centers in radiation-induced phenomena. The experiments were performed employing luminescence method and activation spectroscopy techniques - spectrally resolved thermally stimulated luminescence TSL and thermally stimulated exoelectron emission. Samples were probed in depth by varying electron energy, thus discriminating radiation-induced processes in the bulk and at the surface. Spectroscopic evidence of the excited N2 * (C3Πu) molecule desorption was obtained for the first time and mechanism of the phenomenon based on recombination of electron with intrinsic charged center N4 + was proposed. The key role of N3 + center dissociative recombination in generation of N radicals is suggested. Registration No. 21701

Low-dimensional compounds containing cyanido groups. XXVIII. Crystal structure, spectroscopic and magnetic properties of two copper(II) tetracyanidoplatinate complexes with 1,2-diaminopropane
Vavra, M.; Potočňák, I.; Dušek, M.; Čižmár, E.; Ozerov, M.; Zvyagin, S. A.
Abstract: Violet crystals of {[Cu(pn)2]2[Pt(CN)4]}[Pt(CN)4]·2H2O (1, pn=1,2-diaminopropane) and blue crystals of [Cu(pn)Pt(CN)4]n·nH2O (2) were prepared under hydrothermal conditions and characterized using elemental analysis, IR and UV–vis spectroscopy and by X-ray crystal structure analysis. Different number of ν(C≡N) absorption bands of these two compounds reflects their different structures. An X-ray crystal structure analysis has shown that complex 1 is of ionic character and is formed from trinuclear [Cu(pn)2–Pt(CN)4–Cu(pn)2]2+ complex cation and discrete [Pt(CN)4]2– anion together with two molecules of crystal water. On the other hand, complex 2 is of polymeric character and is formed by 2D networks of [Cu(pn)Pt(CN)4]n composition and completed by n molecules of crystal water. Magnetic measurements show the presence of a weak antiferromagnetic exchange interaction in complex 1 (Θ = –0.2 K), while the magnetic susceptibility of complex 2 is well described by the model of uniform S = 1/2 spin chain with exchange interaction J/kB = –1.64 K. Registration No. 21696

Laser Fluoride Nanoceramic And Method For Production Thereof / Lasertechnische, fluoridische Nanokeramika und Methode zur Herstellung
in Russian
Siebold, M.; Schramm, U.; Garibin, E. A.; Gusev, P. E.; Krutov, M. A.; Mironov, I. A.; Osiko, V. V.; Smirnov, A. N.; Tchernova, Y. V.; Hein, J.; Nietzold, D.; Pohl, H.-J.
Abstract: (EN) FIELD: chemistry. SUBSTANCE: fluoride nanoceramic is obtained by thermomechanical treatment of the starting crystalline material made from CaF2-YbF3, at plastic deformation temperature to obtain a workpiece in form of a polycrystalline microstructured substance, which is characterised by crystal grain size of 3-100 mcm and a nanostructure inside the grains, by annealing on air at temperature of not less than 0.5 of the melting point with compaction of the obtained workpiece in a vacuum at pressure of 1-3 tf/cm2 until the end of the deformation process, followed by annealing in an active medium of carbon tetrafluoride at pressure of 800-1200 mmHg. The starting crystalline material used can be a fine powder which has been subjected to heat treatment in carbon tetrafluoride, or a moulded workpiece of crystalline material made from the powder and heat treated in carbon tetrafluoride. EFFECT: invention enables to obtain a fluoride nanoceramic with high degree of purity and high uniformity of the structure of said optical material. 4 cl, 3 ex

(RU) Изобретение относится к технологии получения оптических поликристаллических материалов, а именно фторидной керамики, имеющей наноразмерную структуру и усовершенствованные оптические, лазерные и генерационные характеристики. Фторидную нанокерамику получают термомеханической обработкой исходного кристаллического материала, выполненного из CaF2-YbF3, при температуре пластической деформации до получения заготовки в виде поликристаллического микроструктурированного вещества, характеризующегося размером зерен кристаллов 3-100 мкм и наноструктурой внутри зерен, путем отжига на воздухе при температуре не менее 0,5 от температуры плавления с уплотнением полученной заготовки в вакууме при давлении 1-3 тс/см2 до окончания процесса деформации, после чего отжигают в активной среде тетрафторида углерода при давлении 800-1200 мм рт.ст. В качестве исходного кристаллического материала могут быть использованы мелкодисперсный порошок, прошедший термообработку в тетрафториде углерода, или отформованная заготовку кристаллического материала, полученная из порошка и термообработанная в тетрафториде углерода. Изобретение позволяет получать фторидную нанокерамику высокой степени чистоты с повышенной однородностью структуры данного оптического материала. 2 н. и 2 з.п. ф-лы, 3 пр., 1 табл.
  • Patent
    RU2484187 - Erteilung 08.12.2013
Registration No. 21695

Partikeltherapie-PET – Optimierung der Datenverarbeitung für die klinische Anwendung
Helmbrecht, S.
Abstract: Die Strahlentherapie ist einer der drei Partner im interdisziplinären Feld der Onkologie. In Europa, Asien und den USA besteht zunehmend die Möglichkeit einer Therapie mit Strahlen aus geladenen Ionen anstelle von Photonen. Eine Anlage in Dresden befindet sich in der Kommissionierungsphase.
Die Ionenstrahltherapie bietet den Vorteil einer sehr konformalen Behandlung des Tumorvolumens durch die endliche Reichweite der Strahlen und ein ausgeprägtes Dosismaximum kurz vor dem Ende des Strahlpfades. Da eine Therapie in der Regel über bis zu 30 Sitzungen an verschiedenen Tagen durchgeführt wird und der Strahlweg stark von dem durchdrungenen Gewebe beeinflusst wird, sind Verfahren für eine in vivo Verifikation der Strahlapplikation wünschenswert. Eine dieser Methoden ist die Partikeltherapie–Positronen-Emissions-Tomografie (PT-PET). Sie beruht auf der Messung der vom Therapiestrahl erzeugten β+-Aktivitätsverteilung. Da eine direkte Berechnung der Dosis aus der Aktivität in lebendem Gewebe nicht möglich ist, wird die gemessene Aktivitätsverteilung mit einer berechneten Vorhersage verglichen und anschließend entschieden, ob die nächste Therapiesitzung wie geplant erfolgen kann oder Anpassungen notwendig sind. Die vorliegende Arbeit beschäftigt sich mit drei Themen aus dem Bereich der Datenverarbeitung für die PT-PET.
Im ersten Teil wird ein Algorithmus zur Bestimmung von Reichweitendifferenzen aus zwei β+- Aktivitätsverteilungen adaptiert und evaluiert. Dies geschieht zunächst anhand einer Simulationsstudie mit realen Patientendaten. Ein Ansatz für eine automatisierte Analyse der Daten lieferte keine zufriedenstellenden Ergebnisse. Daher wird ein Software-Prototyp für eine semiautomatische, assistierte Datenanalyse entwickelt. Die Evaluierung erfolgt durch Experimente mit Phantomen am 12C-Strahl.
Die erzeugte Aktivitätsverteilung wird von physiologischen Prozessen im Organismus beeinflusst.
Dies führt zu einer Entfernung von Emittern vom Ort ihrer Erzeugung und damit zu einer Verringerung der diagnostischen Wertigkeit der erfassten Verteilung. Zur Quantifizierung dieses als Washout bezeichneten Effektes existiert ein am Tierexperiment gewonnenes Modell. Dieses Modell wird im zweiten Teil der Arbeit auf reale Patientendaten angewendet. Es konnte gezeigt werden, dass das Modell grundsätzlich anwendbar ist und für die betrachtete Tumorlokalisation Schädelbasis ein Washout mit einer Halbwertszeit von (155,7±4,6) s existiert.
Die Berechnung der Vorhersage der β+-Aktivitätsverteilung kann durch übliche Monte-Carlo-Verfahren erfolgen. Dabei werden die Wechselwirkungsquerschnitte zahlreicher Reaktionskanäle benötigt. Als alternatives Verfahren wurde die Verwendung gemessener Ausbeuten (Yields) radioaktiver Nuklide in verschiedenen Referenzmaterialien vorgeschlagen. Auf Basis einer vorhandenen Datenbank dieser Yields und einer existierenden Condensed-History-Monte-Carlo-Simulation wird ein Programm zur Berechnung von Aktivitätsverteilungen auf Yieldbasis entwickelt. Mit der Methode kann die β+-Aktivitätsverteilung in Phantomen und Patienten zufriedenstellend vorhergesagt werden.
Die entwickelten Verfahren sollen einen Einsatz der PT-PET im klinischen Umfeld erleichtern und damit einen breiten Einsatz ermöglichen, um das volle Potential der Ionenstrahltherapie nutzbar zu machen.
  • Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-058 2015

Downloads:

Registration No. 21693

Improving material properties and performance of nuclear targets for transmutation-relevant experiments
Vascon, A.; Wiehl, N.; Runke, J.; Drebert, J.; Reich, T.; Trautmann, N.; Cremer, B.; Kögler, T.; Beyer, R.; Junghans, A. R.; Eberhardt, K.; Düllmann, Ch. E.
Abstract: To improve the properties and performance of thin layers produced by molecular plating as targets for nuclear experiments investigations with lanthanide elements (i.e., natural Nd and 147Sm-enriched Sm) were carried out. Plating parameters like roughness of the deposition substrate, plating solvent, electrolyte concentration, and applied current density were varied. The influence of each parameter on the properties of the layers was studied by characterizing the deposits. The characterizations showed that nuclear targets perform differently depending on their layer properties. The results obtained from the investigations were applied for the quantitative preparation of homogeneous large-area (i.e., 42 cm2) 242Pu targets to be used for transmutation-relevant experiments.
Keywords: Molecular plating Improved layer properties α-Particle spectroscopy 242Pu Transmutation Registration No. 21691

Magnetfelder für die Forschung
Wosnitza, J.
Abstract: Magnetfelder wirken auf bewegliche Ladungsträger und die magnetischen Freiheitsgrade eines Materials. Sie können somit das Verhalten von Materialien ebenso vielfältig beeinflussen wie z. B. Temperatur und Druck. Hohe Magnetfelder erlauben deshalb in der Physik und vielen anderen Forschungsdisziplinen grundlegende Untersuchungen der elektronischen und magnetischen Eigenschaften der Materie. So sind mehr als 15 Nobelpreise in Physik, Chemie und Medizin eng mit der Forschung in Magnetfeldern verknüpft. Nicht nur deshalb wächst die wissenschaftliche Nachfrage nach Forschungsanlagen, in denen Experimente in hohen Magnetfeldern möglich sind. Registration No. 21690

Iron and phosphorus speciation in Fe-conditioned membrane bioreactor activated sludge
Wu, H.; Ikeda-Ohno, A.; Wang, Y.; Waite, T. D.
Abstract: Iron dosing of membrane bioreactors (MBRs) is widely used as a means of meeting effluent phosphorus targets but there is limited understanding of the nature of iron and phosphorus-containing solids that are formed within the bioreactor (an important issue in view of the increasing interest in recovering phosphorus from wastewaters). In this study, bench scale MBRs were dosed with either ferrous or ferric salts and the Fe and P-containing mineral distributions in the Fe-conditioned sludges determined using X-ray absorption spectroscopy (XAS). Regardless of whether iron was dosed to the anoxic or aerobic chambers and regardless of whether ferrous (Fe(II)) or ferric (Fe(III)) iron was dosed, iron present in the minerals in the conditioned sludges was consistently in the +III oxidation state. Significant proportions of an Fe(III) mineral exhibiting very similar EXAFS spectra to strengite were present in all cases with the remaining fraction dominated by lepidocrocite in the Fe(II)-dosed case and ferrihydrite in the Fe(III)-dosed case. Approximately half the phosphorus in the activated sludge samples was present as a distinct Fe-PO4 mineral (such as strengite or an amorphous ferric hydroxyl phosphate analog) and half as phosphorus adsorbed to an iron oxyhydroxide mineral phase indicating that both co-precipitation and adsorption of phosphorus with iron contribute to removal of phosphorus from the MBR supernatant.
Keywords: Iron / Phosphor / Sulfur / Waste water treatment / Membrane Bioreactors / XAS / Speciation Registration No. 21687

Positron studies of interaction between yttrium atoms and vacancies in bcc iron with relevance for ODS nanoparticles formation
He, C. W.; Barthe, M. F.; Desgardin, P.; Akhmadaliev, S.; Behar, M.; Jomard, F.
Abstract: The very high calculated binding energy of vacancy (V)-Y-sub (1.45 eV) in Fe makes it be one possible earliest formation stage of (Y, Ti, O) nanoclusters in ODS alloy. Our direct slow positrons annihilation observations are used to valid the interaction between V and Y. The pure bcc iron samples have been implanted by 1.2 MeV Y ions at three fluences from 1 x 10(14) to 3 x 10(15) cm(-2). Vacancy clusters are observed for all these three fluences. Their size and concentration decrease with Y concentration measured by using SIMS. Two hypotheses are proposed to explain the results, including the formation of complexes V-m-Y-n, and/or of precipitates Y-m-X-n (X = Y, O, etc.). In addition, vacancy clusters are detected deeper than predicted by SRIM calculation due to, at least for a part, channelling which is confirmed by Marlowe calculation and SIMS measurements.
Keywords: Nanostructured ferritic alloys, Dispersion, Metals, FE Registration No. 21686

New RP-CVD grown ultra-high performance selectively B-doped pure-Ge 20 nm QWs on (100)Si as basis material for post-Si CMOS technology
Mironov, O. A.; Hassan, A. H. A.; Uhlarz, M.; Kiatgamolchai, S.; Dobbie, A.; Morris, R. J. H.; Halpin, J. E.; Rhead, S. D.; Allred, P.; Myronov, M.; Gabani, S.; Berkutov, I. B.; Leadley, D. R.
Abstract: Magnetotransport studies at low and room temperature are presented for two-dimensional hole gases (2DHG) formed in fully strained germanium (sGe) quantum wells (QW). Two designs of modulation doped heterostructure grown by reduced pressure chemical vapour deposition (RP-CVD) were used and included a normal structure (doping above the Ge channel and inverted structure (doping beneath the Ge channel). The mobility (μH) for the normal structure was measured to be 1.34×106 cm2/Vs with a sheet density (ps) of 2.9×1011 cm-2 at 1.5 K, and μH = 3970 cm2/Vs and ps ~1×1011 cm-2 for room temperature, determined from simulation using the Maximum Entropy- Mobility Spectrum Analysis (ME-MSA) method.
For the inverted structure a μH of 4.96×105 cm2/Vs and ps of 5.25×1011 cm-2 was measured at 90 mK. From the temperature dependent amplitude of Shubnikov de Haas oscillations, the normal structure was found to have a very low effective mass (m*) value of 0.063 m0 and a ratio of transport to quantum lifetime (α) of ~78. This extremely high α is indicative of the carrier transport being dominated by small angle scattering from remote impurities i.e. a sample having an extremely low background impurity level and very smooth hetero-interfaces. The inverted structure had an m* of 0.069 m0 and α ~29, which also indicates exceedingly high quality material.

Keywords: pure strained Ge channel, ultra-high mobility, SdH oscillation, impurity scattering Registration No. 21685

Bi2Se3Q-switched Nd:YAG ceramic waveguide laser
Tan, Y.; Zhang, H.; Zhao, C.; Akhmadaliev, Sh.; Zhou, S.; Chen, F.
Abstract: Using a topological insulator (TI) Bi2Se3 as a saturable absorber, highly stable Q-switched laser pulses were realized in an Nd:YAG ceramic waveguide fabricated by carbon ion irradiation. The laser operation was at a wavelength of 1064 nm, with a repetition rate ranging from 2.7 to 4.7 MHz. The minimum pulsed duration was 46 ns. The maximum output power was up to 168.6 mW corresponding to the pulse energy of 31.3 nJ. This work opens up a practical way for implementation of TI modulated pulsed laser devices in dielectric waveguide platforms.
Keywords: Integrated optics, Lasers, Q-switched, Waveguides, Ion irradiation Registration No. 21684

SRF Gun – A Candidate for Future CW Linear Accelerators
Arnold, A.
Abstract: The success future continuous wave (CW) linear accelerators (LINAC) depend strongly on the development of appropriate sources. Thus, high brightness electron injectors for CW operation with megahertz pulse repetition rates and high bunch charges up to 1 nC are a hot topic of contemporary accelerator research and development. Present state-of-the-art CW photo electron sources are limited to a medium acceleration field; DC guns because of high-voltage discharge and normal conducting RF (NCRF) guns because of the dissipated power that scales with the square of the surface magnetic field (P~H²). Thus, in both cases the beam quality as well as the maximum extractable bunch charge is limited.
To get rid of these limitations the SRF gun concept is merging the well-established NCRF gun technology with the superconductivity. The resulting saving on dissipated power allows comparable high acceleration fields in continuous wave operation and thus high brightness and high average current at the same time. The talk will concentrate on the most advance electron source of this kind, the ELBE 3.5 cell SRF gun of Helmholtz-Zentrum Dresden-Rossendorf. Beside a historical classification and an overview on different design concepts, recent results as well as future challenges are discussed.
  • Lecture (others)
    Beschleunigerseminar am Institut für Kernphysik, 28.01.2015, Mainz, Deutschland
Registration No. 21678

Felsenkeller shallow-underground accelerator laboratory for nuclear astrophysics
Bemmerer, D.; Akhmadaliev, S.; Cowan, T. E.; Gohl, St.; Grieger, M.; Ilgner, C.; Junghans, A. R.; Müller, S. E.; Reinhardt, T. P.; Rimarzig, B.; Reinicke, S.; Röder, M.; Schmidt, K.; Schwengner, R.; Stöckel, K.; Szücs, T.; Takács, M. P.; Wagner, A.; Wagner, L.; Zuber, K.
Abstract: Underground, low-background accelerator-based experiments are an important tool to study nu- clear reactions directly at energies relevant for astrophysical processes. This technique has been developed and proven at the 0.4 MV LUNA accelerator in the Gran Sasso laboratory in Italy, shielded from cosmic rays by 1400 m of rock. However, the nuclear reactions of helium and car- bon burning and the neutron source reactions for the astrophysical s-process require higher beam energies. The same is true for the study of solar fusion reactions. Therefore, the NuPECC long range plan for nuclear physics in Europe strongly recommends the installation of one or more higher-energy underground accelerators.
Detailed background studies have shown that the Felsenkeller shallow-underground laboratory in Dresden, with a rock overburden of 45 m, has very low background in γ -ray detectors typical for nuclear astrophysics experiments when an additional active shield is used to veto the remaining muon flux.
A used 5 MV pelletron tandem with 250 μ A upcharge current and external sputter ion source is currently being refurbished for installation in Felsenkeller. Work on an additional radio-frequency ion source on the high voltage terminal is underway. The project is fully funded, and the installa- tion of the accelerator in the Felsenkeller laboratory is expected for the near future.

Keywords: Felsenkeller Nuclear Astrophysics Low-background techniques Solar fusion
  • Contribution to proceedings
    Nuclei in the Cosmos XIII, 07.-11.07.2014, Debrecen, Ungarn
    Proceedings of Science 044

Downloads:

Registration No. 21674

Development and application of computational fluid dynamics approaches within the European project THINS for the simulation of next generation nuclear power systems
Papukchiev, A.; Roelofs, F.; Shams, A.; Lecrivain, G.; Ambrosini, W.
Abstract: Today computational fluid dynamics (CFD) is widely used in industrial companies, research institutes and technical safety organizations to supplement the design and analysis of diverse technical components and large systems. Such numerical programs are applied to better understand complex fluid flow and heat transfer phenomena. In the last decades there is an increasing interest in the nuclear community to utilize such advanced programs for the evaluation of different nuclear reactor safety issues, where traditional analysis tools show deficiencies. Within the FP7 European project THINS (Thermal Hydraulics of Innovative Nuclear Systems), CFD and coupled 1D-3D thermal–hydraulic simulations are being carried out. These are dedicated to the analysis of the thermal–hydraulics of gas, liquid metal and supercritical water cooled reactors. Such concepts utilize innovative fluids, which have different properties from the ones used in the current nuclear reactors. In order to improve the thermal–hydraulic predictions of their behavior, CFD development, application and validation activities are performed within THINS. This overview paper highlights some of the CFD related work within the European project. Registration No. 21673

Non-Thermal Induction of Conforamtional Rearrangment in Proteins by Far-Infrared Excitation
Lörincz, I. Z.; Schay, G.; Rauscher, A. A.; Kellermayer, M. S. Z.; Gensch, M.; Malnasi-Csizmadia, A.
Abstract: How does a protein respond to infrared excitation? Our aim was to induce a specific non-thermal conformational change of a protein by infrared laser excitation. The fluorescence intensity of an intrinsically fluorescent protein, LSS-mOrange was monitored upon irradiation with a free electron laser at two of its IR absorption peaks (11.36/9.56 microns) and at a wavelength (9.06 microns) where the protein has no absorption. The irradiation at the absorption peaks caused a reversible fluorescence intensity increase on the sec-min timescale. Registration No. 21666

Bruchmechanische Prüfung von “Alten“ Konstruktionsstählen
Viehrig, H.-W.; Houska, M.; Stroetmann, R.; Sieber, L.; Vetter, B.; Schubert, V.
Abstract: In the framework of a research project concerning the brittle fracture resistance of “old” civil steel structures, mechanical and fracture mechanics parameters are determined on specimens from such structural steels. The specimens were sampled from steel structures erected between the years 1904 and 1930. The main focus was on fracture toughness testing according to the Master Curve (MC) approach according to the test standard ASTM E1921. Except one steel all fracture toughness values followed the Master Curve description and gave valid T0 values. The dataset was characterised as inhomogeneous and the MC based evaluation approaches of the SINTAP procedure characterising the brittle fraction of a dataset had to be applied.
Keywords: brittle fracture, impact energy, fracture toughness, Master Curve
  • Contribution to proceedings
    47. Tagung DVM Arbeitskreis Bruchvorgänge und Bauteilsicherheit: Bruchmechanische Werkstoff- und Bauteilbewertung: Beanspruchungsanalyse, Prüfmethoden und Anwendungen, 10.-11.02.2015, Freiberg, Deutschland
    Proceedings der 47. Tagung DVM Arbeitskreis Bruchvorgänge und Bauteilsicherheit: Bruchmechanische Werkstoff- und Bauteilbewertung: Beanspruchungsanalyse, Prüfmethoden und Anwendungen, Berlin: DVM
Registration No. 21665

Geometallurgy of iron ores
Gutzmer, J.
Abstract: Geometallurgy is an emerging field of research that has the aim to quantify compositional variability of ores contained in a deposit. Relevant parameter spaces to be considered include geochemistry, mineralogy, metal deportment and microfabric. These quantitative parameters need to be integrated with macroscopic geological and technical characteristics to define so-called geometallurgical domains, i.e., portions of an ore body that will exhibit similar beneficiation characteristics. This knowledge may then be used to optimize mining schedules and beneficiation routes, to optimize resource and energy efficiency, to maximize product quality and to minimize environmental impact. The value of developing a geometallurgical model is obvious for ore bodies that are either complex and/or of low grade. Important examples include PGE and Au deposits as well polymetallic base metal deposits. In accordance there are a number of case studies for such ore deposit types readily available in literature.

Iron ore deposits are, at least at first sight, not at all complex. In the last four decades very few deposit types have dominated the global supply of iron ore. High-grade iron ore deposits hosted by Precambrian iron formations clearly dominate, as these are often able to produce a direct shipping lump ore (DSO with > 60 wt%) Fe by simple crushing, screening and desliming. In fact, these deposits form the world’s largest virtually monomineralic ore bodies, not uncommonly reaching billions of tons of ore in size. Other deposit types that contribute significantly to the worlds iron ore supply are metamorphosed iron formation deposits (often referred to as taconites), Kiruna-type magnetite-apatite deposits and Robe River-type deposits. Magnetite deposits hosted by mafic/ultramafic intrusive complexes are increasingly gaining economic significance. Common to these deposit types are high concentrations of iron (≥ 50 wt.% Fe, but note that taconite only contains about 35 wt. % Fe) and uniform ore mineralogy, with only hematite, magnetite, and goethite of any significance.

The question thus arises what value geometallurgy may add to the utilization of iron ore deposits. In fact, a number of tangible benefits are being realized by taking this approach. Ore bodies that do not produce DSO require grinding followed by magnetic separation and/or flotation. Pellets need to be produced from the concentrate in order to have a saleable product. To assure that stringent quality requirements by the customer steel mills are being met consistently requires detailed knowledge of ore and gangue mineralogy – and its spatial variability across the ore body. Variations in gangue mineralogy, in particular, will determine concentrations of deleterious elements (Si, Ti, Al, P, S and alkali elments), whereas ore mineralogy will determine the suitability of beneficiation unit operations. Even if mineral assemblages remain uniform, relative proportions and microfabric relations (e.g., mineral grain sizes, intergrowth) will determine comminution and liberation characteristics, thus determining comminution energy requirements.

Keywords: geometallurgy, iron ores
  • Contribution to proceedings
    The Arctic Conference Days 2014, 02.-06.06.2014, Tromso, Norway
    Abstracts and Proceedings of the Geological Survey of Norway, Trondheim: Norsk Geologisk Forening, 72-73
Registration No. 21663

Optical imaging of COX-2: Studies on an autofluorescent 2,3-diaryl-substituted indole-based cyclooxygenase-2 inhibitor.
Tondera, C.; Ullm, S.; Laube, M.; Meister, S.; Neuber, C.; Mosch, B.; Kniess, T.; Pietzsch, J.
Abstract: This study aimed at in vivo visualization of cyclooxygenase-2 (COX-2) by optical imaging using a representative compound of a class of autofluorescent 2,3-diaryl-substituted indole-based selective COX-2 inhibitors (2,3-diaryl-indole coxibs). COX-2 was successfully visualized in mice models with phorbol myristate ester (TPA)-induced inflammation or bearing xenografted human melanoma cells by 2-[4-(aminosulfonyl)phenyl]-3-(4-methoxyphenyl)-1H-indole (C1). COX-2 protein expression in both TPA-induced inflammatory sites and human melanoma xenografts was confirmed by immunoblotting. Control experiments using surrogate markers, sham injections, and non-COX-2 expressing melanoma cells further confirmed specificity of tissue association of C1. The merging of therapeutic and diagnostic properties of 2,3-diaryl-indole coxibs may widen the range of applications of COX-2-targeted treatment, e.g., for in situ-guided surgery and ex vivo diagnostics.
Keywords: Fluorescence; Luminescence; Melanoma-associated inflammation; Phorbol myristate ester-induced COX-2 expression; Rodent melanoma xenograft model Registration No. 21656

Absolute value determination of vacancy concentration in silicon crystals using low-temperature ultrasonic measurements
Yamada-Kaneta, H.; Okabe, K.; Akatsu, M.; Baba, S.; Mitsumoto, K.; Nemoto, Y.; Goto, T.; Saito, H.; Kashima, K.; Saito, Y.
Abstract: For the samples taken from the void region of the CZ silicon crystal grown with the same solidification condition and different thermal histories after the solidification, we measure the magnitude S of the elastic softening which is proportional to the concentration of the single vacancies [V], For these samples, we also measure the size distribution of the void density by using the infrared lightscattering tomography, to evaluate the concentration [Vc] of the vacancies consumed for the void formation. From these two experiments, we find a sum rale [Vc] + a S= C, where C depends only on the solidification condition and is independent of the thermal history after the solidification. This enables us to find the conservation rale of the vacancies [Vc] + [V] = C. The value of the proportionality constant a in the relation [V] = a S is determined. Demonstration of determining the absolute values of [V] from the measured S is given. An estimate is made for the value of the quadrupole-strain coupling constant.
Keywords: Coupling constants; Different thermal history; Elastic softening; Light-scattering tomography; Low temperatures; Single vacancies; Solidification condition; Vacancy concentration Registration No. 21653

Production and Diagnostics of Dense Matter
Brambrink, E.; Amadou, N.; Benuzzi-Mounaix, A.; Geissel, M.; Harmand, M.; Pelka, A.; Vinci, T.; Koenig, M.
Abstract: High energy lasers are a unique tool to create high pressure states above 10 Mbar at ns time scales, which allow to study material properties under these extreme conditions. These conditions are, for example, comparable with planetary cores, where material properties play an important role for the properties and evolution of a planet. The rapid compression allows also to study dynamic effects of phase transitions as compression times are comparable to relaxation times. We will present recent results of laser compression of iron reaching conditions of so called “super-Earth” cores. A description of the compression schemes as well as present and future diagnostics is presented. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Keywords: Warm dense matter;high energy density physics;ramp compression Registration No. 21652

Evaluation of the cone-shaped pickup performance for low charge sub-10 fs arrival-time measurements at free electron laser facilities
Angelovski, A.; Kuntzsch, M.; Czwalinna, M. K.; Penirschke, A.; Hansli, M.; Sydlo, C.; Arsov, V.; Hunziker, S.; Schlarb, H.; Gensch, M.; Schlott, V.; Weiland, T.; Jakoby, R.
Abstract: An evaluation of the cone-shaped pickup performance as a part of the high bandwidth bunch arrival-time monitors (BAMs) for a low charge sub-10 fs arrival-time measurements is presented. Three sets of pickups are installed at the free electron laser FLASH at Deutsches Elektronen-Synchrotron, the quasi-cw SRF accelerator ELBE at the Helmholtz-Zentrum Dresden-Rossendorf and the SwissFEL injector test facility at Paul Scherrer Institute. Measurements and simulations are in good agreement and the pickups fulfill the design specifications. Utilizing the high bandwidth BAM with the cone-shaped pickups, an improvement of the signal slope by a factor of 10 is demonstrated at ELBE compared to the BAM with a low bandwidth.
Keywords: BAM ELBE FLASH Arrival-Time Diagnostic Registration No. 21651

Synthetic Scattering Images from Laser-Plasma Interaction - Heating and Ionization
Huang, L. G.; Bussmann, M.; Chung, H. K.; Zacharias, M.; Cowan, T. E.; Kluge, T.
Abstract: We present the dynamics of bulk electron heating and ionization in ultra-short relativistic laser plasmas interactions. In order to connect the plasma dynamics seen in simulations with experiments we also discuss the role of in-situ synthetic Scattering Images that mimic experimental diagnostics.
Keywords: Heating,Ionization,Laser-Plasma interaction,Synthetic Scattering
  • Poster
    European XFEL Users' Meeting 2015, DESY Photon Science Users' Meeting 2015, 28.-30.01.2015, Hamburg, Germany
Registration No. 21650

Photophysical Property of Catena-Bis(thiocyanato)aurate(I) Complexes in Ionic Liquids
Aoyagi, N.; Shinha, Y.; Ikeda-Ohno, A.; Haga, Y.; Shimojo, K.; Brooks, N. R.; Izuoka, A.; Naganawa, H.; Kimura, T.; Binnemans, K.
Abstract: The photochemistry of a gold(I) thiocyanate complex has been investigated to determine the coordination structure in both the solid and liquid states. The coordination geometries of the supramolecular [Au(SCN)2]n complex and the concomitant exciplex have mainly been analyzed by crystallographic analysis and X-ray absorption spectroscopy. The Au-S bond distance and Au···Au separation of the compound in the S0 ground state and in the T1 phosphorescent excited state (λex = 340 nm) were compared. Upon irradiation with UV light, the excimeric interactions were enhanced, resulting in a contraction of the AuI···AuI aurophilic distance by 0.0113(4) Å. A broad luminescence spectrum was observed for the one-dimensional chain suprastructure. The time-resolved luminescence spectra indicated the entity of several oligomeric species in the crude liquid without neutral solvent molecules. In addition, EXAFS spectroscopy exhibited a slight change in the nearest Au-S distance due to the photo-switched transformation. The deformation of the (Au---Au)* exciplexes was not apparently promoted in the liquid state with the asymmetrical imidazoium cations having a non-local charge distribution in the present observation.
Keywords: Gold, Au(I), thiocyanate, aurophilic interaction, ionic liquids, exciplex, XAS, TRLFS, polymers Registration No. 21649

Coordination chemistry for separation of nuclear-related metals
Ikeda, A.
Abstract: In order to understand the separation mechanism of metals in chemical processes, the chemical species formed in the processes should be characterised particularly on a molecular level. Structural characterisation is of particular importance to understand the interaction between the metal of interest and separating reagents (i.e. ligands), which would be also beneficial to further improve the efficiency of separation processes and/or to develop new separation ligands. This talk will cover the application of X-ray-based characterisation techniques (single-crystal X-ray diffraction (SC-XRD) and X-ray absorption spectroscopy (XAS)) to the separation chemistry of nuclear-related elements, such as actinides (An) or strontium (Sr).
Keywords: actinides, lanthanides, f-elements, nuclear-related elements, X-ray technique, synchrotron, XAS, XRD, coordination chemistry, separation
  • Invited lecture (Conferences)
    LEPMI-CNRS internal seminar, 13.02.2015, Grenoble, France
Registration No. 21648

Floating-zone single crystal growth of intermetallic compounds using a two-phase RF inductor
Hermann, R.; Priede, J.; Gerbeth, G.
Abstract: In this chapter the favorable applicability of the crucible-free floating zone method will be shown for the growth of single crystal intermetallic compounds
  • Book chapter
    P. Rudolph: Handbook of Crystal Growth, Vol. 2A, Amsterdam: Elsevier, 2014, 9780444633033, 313-329
Registration No. 21647

Carbide formation and optical properties in carbon:transition metal nanocomposite films
Heras, I.; Guillén, E.; Abrasonis, G.; Krause, M.; Pardo, A.; Endrino, J. L.
Abstract: The physical vapour deposition of transition metals with carbon leads to the formation of metal nano-clusters or nanocrystalline metallic carbides embedded in a carbon matrix. Interstitial carbides are very stable at high temperature, have high melting points and possess a high reflectivity. In contrast, carbon: transition metal nanocomposites can show optical selective properties such as good absorptance in the visible with high reflectance in the infrared. These properties make them very attractive for applications were high temperature resistant materials with selective optical properties are required.
In this study, Carbon: transition metal nanocomposites were grown using a physical vapour deposition system incorporating two pulsed filtered cathodic arc sources, one provided with a graphite cathode and the other with a metal cathode (Zr, V and Mo). The metal content in the composite was controlled by adjusting the ICarbon/IMetal pulse ration between the two sources, and determined by Rutherford backscattering spectroscopy (RBS) and nuclear reaction analysis (NRA). Comprehensive structure characterization was carried out using a combination of X-ray diffraction (XRD), Raman spectroscopy and high resolution transmission electron microscopy (HRTEM). Optical characterization has been done using both with ellipsometry and spectrophotometer measurements in order to obtain the optical constants and the reflectance spectra of the samples.
Together with experimental characterization, the computer program CODE is used to simulate the reflectance spectra of different carbon: transition metal films. Bruggeman effective medium theory was used to average the dielectric functions of the two components which compose the film. According to our simulations, the resulting reflectance of the nanocomposite films is strongly affected by the same metal content, independently if it results in metallic nano-clusters or nanocrystalline metallic carbides. Simulated spectra were compared with the measured reflectance of the deposited films obtaining good agreement between simulations and experimental results.
  • Lecture (Conference)
    International Conference on Nanotechnology, Nanomaterials & Thin Films for Energy Applications (Nanoenergy), 19.-21.02.2014, London, Großbritannien
Registration No. 21646

Comprehensive environmental testing of optical properties in thin films
Heras, I.; Guillén, E.; Krause, M.; Wenisch, R.; Escobar-Galindoa, R.; Endrino, J. L.
Abstract: Environmental characterization of optical and structural properties of thin films continues to be a challenging task. To understand the failure mechanism in high temperature thin film applications, it is crucial to understand how material properties change with temperature. An accurate knowledge of the variation of the dielectric function of thin films and its relation to compositional and microstructural changes could help to prevent failures. This article presents an environmental in-situ characterization methodology that combines the study of the optical constants in an environmental chamber by spectroscopic ellipsometry, with compositional depth profile analysis using ion beam analysis techniques and a structure analysis by Raman spectroscopy. The main novelty of this methodology is that all analytical techniques are carried out sequentially in a multi-chamber cluster tool without sample exposure to undefined atmospheres. Carbon-titanium metal thin film had been studied following the described characterization methodology.
Keywords: Thin films; optical constants; cluster tool; high temperature applications; thermal degradation; real time spectroscopic ellipsometry; ion beam analysis; Raman spectroscopy
  • Contribution to proceedings
    3rd International Conference on Through-life Engineering Services, 04.-05.11.2014, Cranfield, Großbritannien
    Procedia CIRP 22 ( 2014 ), 271-276
  • Lecture (Conference)
    3rd International through – life engineering services conference, 04.11.2014, Cranfield, United Kingdom
Registration No. 21645

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.
Abstract: 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
Registration No. 21644

Crystallization of quasiantiferromagnetic colloids
Steinbach, G.; Gemming, S.; Erbe, A.
Abstract: 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
Registration No. 21643

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.
Abstract: 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
Registration No. 21642

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.
Abstract: 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. Registration No. 21640

AIDA - Apparatus for In-situ Defect Analysis: Investigations on Fe60Al40
Trinh, T.; Wagner, A.; Liedke, M. O.; Anwand, W.; Butterling, M.; Potzger, K.
Abstract: 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
Registration No. 21638

Apparatus for In-situ Defect Analysis (AIDA)
Liedke, M. O.; Anwand, W.; Butterling, M.; Potzger, K.; Heidarian, A.; Bali, R.; Wagner, A.
Abstract: 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
Registration No. 21637

Apparatus for In-situ Defect Analysis (AIDA)
Liedke, M. O.; Anwand, W.; Potzger, K.; Wagner, A.
Abstract: 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
Registration No. 21636

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.
Abstract: 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
Registration No. 21632

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.
Abstract: 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
Registration No. 21630

Energy-Angle Characteristic of an ICS source
Jochmann, A.
Abstract: 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
Registration No. 21628

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.
Abstract: 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
Registration No. 21627

Experimental modelling using liquid metals
Gerbeth, G.; Eckert, S.
Abstract: 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
Registration No. 21626

Recent results on flow measurements and magnetic control
Gerbeth, G.; Eckert, S.
Abstract: 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
Registration No. 21625

Towards laser wakefield acceleration with external injection at HZDR
Irman, A.
Abstract: 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
Registration No. 21624

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.
Abstract: 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
Registration No. 21623

Fluid dynamics research at HZDR Dresden
Gerbeth, G.
Abstract: 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
Registration No. 21622

Laser-plasma based electron acceleration
Irman, A.
Abstract: 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
Registration No. 21621

Research on crystal growth problems at Institute of Fluid Dynamics of HZDR
Gerbeth, G.
Abstract: 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
Registration No. 21620

Tornado-like flows driven by magnetic body forces
Gerbeth, G.; Grants, I.; Vogt, T.; Eckert, S.
Abstract: 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
  • Abstract in refereed journal
    Bulletin of the American Physical Society 59(2014), 20
Registration No. 21619

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, Th.; Seipt, D.; Thorn, D. B.; Ledingham, K. D.; Cowan, T.; Sauerbrey, R.; Schramm, U.
Abstract: 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
Registration No. 21618

LIMTECH A5: Liquid metal two-phase flows
Strumpf, E.; Eckert, S.; Richter, T.; Gerbeth, G.
Abstract: 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
Registration No. 21617

Approaches to the Simulation of Compositional Data: A Nickel-Laterite comparative case study
Mueller, U.; Tolosana-Delgado, R.; van den Boogaart, K. G.
Abstract: 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
Registration No. 21615

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.
Abstract: 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 Registration No. 21614

The Tayler instability at low magnetic Prandtl numbers
Stefani, F.; Barry, L.; Gundrum, T.; Kirillov, O.; Seilmayer, M.; Weber, N.; Gellert, M.; Rüdiger, G.
Abstract: 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
Registration No. 21613

The present status of the DRESDYN project
Stefani, F.
Abstract: 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
Registration No. 21612

The present status of the DRESDYN project
Stefani, F.
Abstract: 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
Registration No. 21611

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, Alan M. M.; Young, Lloyd M.; Lehnert, U.; Michel, P.; Seidel, W.; Wünsch, R.; Gottschalk, S. C.
Abstract: 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
Registration No. 21610

The new ELBE Center for High Power Radiation Sources at HZDR: Status and Opportunities
Seidel, W.
Abstract: 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
Registration No. 21609

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.
Abstract: 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 Registration No. 21607

Wissens- und Innovationsgemeinschaften (KIC) am Beispiel des KIC Rohstoffe - nachhaltige Erkundung, Gewinnung, Verarbeitung, Verwertung und Substitution
Dirlich, S.; Klossek, A.
Abstract: 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
Registration No. 21606

Attachment of solid elongated particles on the surface of a stationary gas bubble
Lecrivain, G.; Petrucci, G.; Rudolph, M.; Hampel, U.; Yamamoto, R.
Abstract: 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 Registration No. 21605

NeuLAND time of flight detector for 200-1000 MeV neutrons read out by fast photosensors
Bemmerer, D.
Abstract: 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
Registration No. 21604

Experimental investigations of a magnetically driven Tornado-like vortex by means of Ultrasound-Doppler Velocimetry
Vogt, T.; Grants, I.; Eckert, S.; Gerbeth, G.
Abstract: 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
  • Contribution 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
Registration No. 21603

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.
Abstract: 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
Registration No. 21602

The 22Ne(p,gamma)23Na reaction studied at LUNA: results from the germanium detector based part of the experiment
Bemmerer, D.
Abstract: 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
Registration No. 21601

Separation of ultrafine particles by two-liquid flotation: Selectivity and process behavior analysis
Rudolph, M.; Peuker, Urs A.
Abstract: 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
  • Lecture (Conference)
    XXVII International Mineral Processing Congress, 20.-24.10.2014, Santiago de Chile, Chile
Registration No. 21600

Mineralization derived from felsic magma? A case study on Zr-Nb-REE deposits in Western Mongolia
Kempe, U.; Möckel, R.
Abstract: 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
Registration No. 21598

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.
Abstract: 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
Registration No. 21597

Determination of level widths in 15N using nuclear resonance fluorescence
Szücs, T.; Bemmerer, D.; Caciolli, A.; Fülöp, Zs.; Massarczyk, R.; Michelagnoli, C.; Reinhardt, T. P.; Schwengner, R.; Takács, M. P.; Ur, C. A.; Wagner, A.; Wagner, L.
Abstract: 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
Registration No. 21596
Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195]