Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33412 Publications

Towards a novel THz-based monitor for sub picosecond electron bunches working at MHz repetition rates and low bunch charges

Gensch, M.; Green, B.; Kovalev, S.; Kuntzsch, M.; Golz, T.; Stojanovic, N.; Fisher, A.
The control and measurement of electron bunch properties at the femtosecond (fs) level has become an important field in modern accelerator physics, in particular since these became crucial parameters for the operation of 4th Generation X-ray Light-sources. In order to operate modern-day photon factories such as LCLS and the future European X-FEL reliably, a number of novel approaches have been developed that allow the noninvasive measurement of electron bunch form and arrival time. Some of those are based on the electro-optic detection of the coulomb field of the electron bunches in the electron beamline; some detect the super-radiant THz pulses from the electron bunch. However, none of these concepts allows for pulse-to-pulse detection on a quasi-CW accelerator operating at the MHz repetition rates planned for the next generation of X-ray free electron lasers. In this contribution we present first results from a new monitor concept, based on the single-shot electro-optic detection of super-radiant THz pulses, that has the potential to operate at MHz repetition rates.
  • Poster
    IBIC 2014 - 3rd International Beam Instrumentation Conference, 14.-18.09.2014, Monterey, USA

Permalink: https://www.hzdr.de/publications/Publ-20422
Publ.-Id: 20422


Ионный синтез нанокристаллов InSb в захороненном слое SiO2 структуры кремний-на-изоляторе
Ion-beam synthesis of InSb nanocrystals in the buried SiO2 layer of a silicon-on-insulator structure

in Russian
Tyschenko, I. E.; Voelskow, M.; Tscherkov, A. G.; Popov, V. P.
Исследован ионный синтез нанокристаллов InSb в слое захороненного SiO2 структуры кремний-на-изоляторе. Изучены профили распределения атомов индия и сурьмы после отжига при температуре Ta = 500−1100◦C. Установлено, что перераспределение имплантированных атомов имеет немонотонный характер в зависимости от температуры отжига. Формирование нанокристаллов InSb происходит при Ta ≥ 800◦C вблизи границы Si/SiO2 и на глубине средних пробегов Rp. Анализ профилей имплантированных атомов и структуры и распределения по глубине формирующихся нанокристаллов позволил сделать предположение о двухстадийном характере образования фазы InSb: на первой стадии происходит формирование преципитатов сурьмы, которые играют роль зародышей для дальнейшего стока на них атомов In и Sb.

The ion-beam synthesis of InSb nanocrystals in the buried SiO2 layer of a silicon-on-insulator structure is investigated. The distributions of In and Sb atoms after annealing at a temperature of T a = 500–1100°C are studied. It is established that the redistribution of implanted atoms is unsteadily dependent on the annealing temperature. The formation of InSb nanocrystals occurs at Ta ≥ 800°C near the Si/SiO2 interface and at a depth corresponding to the mean paths R p . Analysis of the profiles of implanted atoms and of the structure and depth distribution of nanocrystals formed allows an inference regarding the two-stage character of formation of the InSb phase. In the initial stage, antimony precipitates are formed; further the precipitates serve as nuclei for indium and antimony to flow to them.
Keywords: Ion beam Synthesis, InSb, SOI, RBS
  • Fizika i Tekhnika Poluprovodnikov 48(2014)9, 1228-1233
  • Semiconductors 48(2014)9, 1196-1201

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Permalink: https://www.hzdr.de/publications/Publ-20421
Publ.-Id: 20421


Enhanced wear resistance of high-speed steel by pulsed electron-beam melting

Ivanov, Y.; Matz, W.; Rotshtein, V.; Guenzel, V.; Shevchenko, N.
  • Contribution to proceedings
    3rd International Conference on Surface Engineering, 09.-11.03.1993, Bremen, Germany
    Contributions of surface engineering to modern manufacturing and remanufacturing, Chengdu, China: Southwest Jiaotong University Press, 7810576615, 397-402

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Permalink: https://www.hzdr.de/publications/Publ-20420
Publ.-Id: 20420


Ion beam synthesis by tungsten implantation into 6H-silicon carbide at elevated temperatures

Weishart, H.; Matz, W.; Skorupa, W.
  • Contribution to proceedings
    1995 MRS Fall Meeting & Exhibit, 27.11.-1.12.1995, Massachusetts, USA
    MRS Symposium Proceedings Series: III-Nitride, SiC, and Diamond Materials for Electronic Devices: Cambridge University Press, 9781558993266, 195-200

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Permalink: https://www.hzdr.de/publications/Publ-20419
Publ.-Id: 20419


Electron bunch form monitoring at quasi-cw SRF accelerators: Status at the ELBE accelerator

Gensch, M.; Green, B.; Hauser, J.; Kuntzsch, M.; Lehnert, U.; Michel, P.; Schurig, R.; Golz, T.; Stojanovic, N.; Mueller, A. S.; Schwarz, M.; Fisher, A. S.; Neumann, N.; Plettemeier, D.; Bauer, C.
In the past few years the quasi-cw SRF electron accelerator ELBE has been upgraded so that it now allows to compress electron bunches to the sub-picosecond regime at repetition rates of up to 13 MHz and bunch charges up to 100 pC. The actual optimization and control of the electron bunch form represents one of the largest challenges of the coming years at ELBE. In particular with respect to the midterm goal to utilize the ultra-short electron bunches for Laser-Thomson scattering experiments or high field THz experiments. Since 2012, the ELBE accelerator, together with its recently established super-radiant THz facility TELBE serves as a unique test facility for the development of novel diagnostic for quasi-cw electron beams. In this contribution different diagnostic approaches for the online determination of the electron bunch form are presented. The results of the different techniques, ranging from adapted classical laser-based and interferometer-based concepts to novel on-chip THz spectrometers are compared. The merits of the different concepts: e.g. pulse to pulse diagnostics at few 100 kHz repetition rates or a sensitivity for charges down to the few 100 femto coulomb regime are discussed based on the results of recent commissioning campaigns by a multi-institutional collaboration. A careful analysis of simultaneous measurements with the different techniques allows an educated guess for the presently shortest electron bunch duration achieved at ELBE of 1.2 ps (FWHM). It is also shown that interferometric concepts at this moderately short bunch durations systematically underestimate the bunch length due to diffraction effects at low THz frequencies.
  • Poster
    IBIC 2014 - 3rd International Beam Instrumentation Conference, 14.-18.09.2014, Monterey, USA

Permalink: https://www.hzdr.de/publications/Publ-20418
Publ.-Id: 20418


How magnetic fields can be used for controlling the electrochemical deposition of metal

Mutschke, G.; Mühlenhoff, S.; Yang, X.; Eckert, K.; Tschulik, K.; Uhlemann, M.; Fröhlich, J.; Bund, A.
The contribution attempts to give an overview of recent results regarding the influence of magnetic fields on the electrochemical deposition of metal. Magnetic fields give rise to forces on the electrolyte which, if properly applied, can be useful. Lorentz forces have been known long-since for causing convection of the electrolyte, and thus, to affect mass transfer. In case of homogeneous magnetic fields at vertical electrodes, a short detour to fluid mechanics helps to better understand the resulting changes in mass transfer and the convection pattern. Two different ways of achieving desired properties by tailored magnetic fields are discussed. For vertical electrodes, despite of the influence of buoyancy, inhomogeneous magnetic fields can be utilized for improving the uniformity of the metal deposit [1]. On the contrary, magnetic fields can also be beneficial for obtaining a desired non-uniform deposition at length scales down to the micrometer range. Here, the magnetic Kelvin force becomes important if para- or diamagnetic ions are exposed to inhomogeneous magnetic fields. In both examples, simulations and experimental results will be presented which elucidate the interplay of forces, the electrolyte flow and the effect on mass transfer [2,3].
References:
[1] Mühlenhoff, S.; Mutschke, G.; Uhlemann, M.; Yang, X.; Odenbach, S.; Fröhlich, J.; Eckert, K.; On the homogenization of the thickness of Cu deposits by means of MHD convection within small dimension cells. Electrochem. Comm. 36 (2013) 80–83.
[2] Mutschke, G.; Tschulik, K.; Uhlemann, M.; Bund, M.; Fröhlich, J.: Comment on "Magnetic Structuring of Electrodeposits". Phys. Rev. Lett. 109 (2012) 229401.
[3] Uhlemann, M.; Tschulik, K.; Gebert, A.; Mutschke, G.; Fröhlich, J.; Bund, A.; Yang, X.; Eckert, K.: Structured Electrodeposition in Magnetic Gradient Fields. Eur. Phys. J. Spec. Top. 220 (2013) 287-302.
Keywords: Electrodeposition, magnetic field, layer thickness, Lorentz force, Kelvin force, numerical simulation
  • Lecture (Conference)
    Electrochemistry 2014, 22.-24.09.2014, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20417
Publ.-Id: 20417


Magnetohydrodynamic Effects in Electrodeposition Reactions

Bund, A.; Ispas, A.; Mutschke, G.
This paper will discuss the effect of magnetic fields in electrodeposition reactions. The best studied effect is the magnetohydrodynamic effect which is due to the Lorentz force. In general Lorentz forces are generated in the electrolyte where the cross product of current density and magnetic flux density is different from zero. At places where the curl of this force density does not vanish a flow is driven. This in turn causes an increased mass transport and thus higher deposition rates in an electroplating cell. Of course the magnetically driven flow will always interact with other types of convective flows in the cell, e.g. the natural convection.
By tailoring the magnetic field (e.g. via its gradient) the uniformity of electroplated layers can be enhanced [1]. Also the structure of deposits (e.g. in the case of nickel fine-grained vs. coarse-grained) can be affected by the magnetic field [2]. Corresponding examples from the author's labs will be discussed in this paper.
In this contribution we will also show that numerical simulation is a powerful tool if one wants to harvest the full potential of magnetic flow control in electrochemical reactions.
References
[1] S. Mühlenhoff, G. Mutschke, M. Uhlemann, X. Yang, S. Odenbach, J. Fröhlich, K. Eckert. Electrochem. Commun. 36 (2013) 80.
[2] A. Ispas, H. Matsushima, A. Bund, B. Bozzini. J. Electroanal. Chem. 626 (2009) 174.
Keywords: Electrodeposition, Electrolysis, Magnetic field, Lorentz force, numerical simulation
  • Lecture (Conference)
    226th Meeting of The Electrochemical Society (ECS), 05.-10.10.2014, Cancun, Mexico

Permalink: https://www.hzdr.de/publications/Publ-20416
Publ.-Id: 20416


Modelling the Hydrogen evolution during water electrolysis

Mutschke, G.; Arndt, F.; Gerke, S.; Yang, X.; Fröhlich, J.; Eckert, K.
Hydrogen produced from wind or solar power can be used easily for storing energy, also at large scale, thus allowing to bridge the gap between offer and demand of green energy with respect to time and place. When splitting water by electrolysis, a deeper look at local phenomena near single bubbles at the electrode might be helpful to improve our understanding of the process. The presentation will first introduce a numerical model based on a phase field method to simulate growth and departure of gas bubbles from the electrode. The modelling is supported by detailed data of recent experiments on hydrogen single bubbles evolving at a platinum electrode. The numerical method is then validated by test cases. Work is still in progress at the time of writing this abstract. The simulation results will provide first insight into the local and temporal behaviour of species concentrations, current density and electrolyte velocity during growth and departure of a hydrogen bubble from the electrode.
Keywords: Water electrolysis, hydrogen evolution, bubble growth and departure, phase-field method, numerical simulation
  • Lecture (Conference)
    85th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM), 10.-14.03.2014, Erlangen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20415
Publ.-Id: 20415


How to improve the uniformity of metal deposition at vertical electrodes by electromagnetic forces

Mutschke, G.; Mühlenhoff, S.; Selent, R.; Yang, X.; Uhlemann, M.; Fröhlich, J.; Odenbach, S.; Eckert, K.
In electrochemical plating often a uniform deposition is desirable allowing to reduce both energy and material costs. Magnetic fields are well known to influence the mass transfer during electrolysis and offer easy control of the deposition process. In this paper, first, time-constant Lorentz forces are considered which, if properly designed, may considerably improve the uniformity of the deposit. Second, time-dependent Lorentz forces are investigated. It is demonstrated that pulsed deposition offers a comparable enhancement of the uniformity.
Keywords: Electrolysis, Metal deposition, magnetic field, Lorentz force, pulsed deposition
  • Contribution to proceedings
    9th PAMIR International Conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Lettland
    Proceedings of the 9th PAMIR International Conference on Fundamental and Applied MHD, Vol. 2, 164-168

Permalink: https://www.hzdr.de/publications/Publ-20414
Publ.-Id: 20414


Numerical simulation of the mass transfer of magnetic species at electrodes exposed to small-scale gradients of the magnetic field

Mutschke, G.; Tschulik, K.; Uhlemann, M.; Fröhlich, J.
The mechanisms responsible for the spatially inhomogeneous thickness of metal layers obtained by electrochemical deposition in magnetic gradient fields at small scale are controversially discussed in the literature. The paper presents the results of numerical simulations which support the reasoning that local convection at the electrode, driven by the curl of the magnetic gradient force, is responsible for the effects observed. The deposition of paramagnetic and of diamagnetic ions is discussed, and the influence of electrically inert magnetic ions present in the electrolyte is enlighted.
Keywords: Electrolysis, Magnetic field, Metal deposition, Kelvin force, Numerical simulation
  • Contribution to proceedings
    9th PAMIR International Conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Lettland
    Proceedings of the 9th PAMIR International Conference on Fundamental and Applied MHD, Vol. 2, 169-171
  • Magnetohydrodynamics 51(2015)2, 369-374

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Permalink: https://www.hzdr.de/publications/Publ-20413
Publ.-Id: 20413


MaterialVis: Material visualization tool using direct volume and surface rendering techniques

Okuyan, E.; Güdükbay, U.; Bulutay, C.; Heinig, K.-H.
Visualization of the materials is an indispensable part of their structural analysis. We developed a visualization tool for amorphous as well as crystalline structures, called MaterialVis. Unlike the existing tools, MaterialVis represents material structures as a volume and a surface manifold, in addition to plain atomic coordinates. Both amorphous and crystalline structures exhibit topological features as well as various defects. MaterialVis provides a wide range of functionality to visualize such topological structures and crystal defects interactively. Direct volume Rendering techniques are used to visualize the volumetric features of materials, such as crystal defects, which are responsible for the distinct fingerprints of a specific sample. In addition, the tool provides surface visualization to extract hidden topological features within the material. Together with the rich set of parameters and options to control the visualization, MaterialVis allows users to visualize various aspects of materials very efficiently as generated by modern analytical techniques such as the Atom Probe Tomography.
Keywords: Material visualisation, Embedded nanostructure visualisation, Direct volume rendering, Unstructured tetrahedral meshes, Crystal defects

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Permalink: https://www.hzdr.de/publications/Publ-20412
Publ.-Id: 20412


High-field electron spin resonance spectroscopy of singlet-triplet transitions in the spin-dimer systems Sr3Cr2O8 and Ba3Cr2O8

Wang, Z.; Kamenskyi, D.; Cépas, O.; Schmidt, M.; Quintero-Castro, D. L.; Islam, A. T. M. N.; Lake, B.; Aczel, A. A.; Dabkowska, A. B.; Dabkowski, A. B.; Luke, G. M.; Wan, Y.; Loidl, A.; Ozerov, M.; Wosnitza, J.; Zvyagin, S. A.; Deisenhofer, J.
Magnetic excitations in the isostructural spin-dimer systems Sr3Cr2O8 and Ba3Cr2O8 are probed by means of high-field electron spin resonance at subterahertz frequencies. Three types of magnetic modes were observed. One mode is gapless and corresponds to transitions within excited states, while two other sets of modes are gapped and correspond to transitions from the ground to the first excited states. The selection rules of the gapped modes are analyzed in terms of a dynamical Dzyaloshinskii-Moriya interaction, suggesting the presence of phonon-assisted effects in the low-temperature spin dynamics of Sr3Cr2O8 and Ba3Cr2O8.

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Permalink: https://www.hzdr.de/publications/Publ-20411
Publ.-Id: 20411


Spontaneous and field-induced phase transitions inTbFe5Al7

Gorbunov, D. I.; Yasin, S.; Andreev, A. V.; Mushnikov, N. V.; Skourski, Y.; Zherlitsyn, S.; Wosnitza, J.
Magnetization and ultrasound measurements have been performed on a TbFe5Al7 single crystal (tetragonal crystal structure) in the temperature range from 2 to 260 K in steady magnetic fields up to 18 T and in pulsed magnetic fields up to 60 T. The compound is a ferrimagnet (TC = 242 K) having an easy-plane anisotropy. Strong anisotropy is also present within the basal plane. At 2K, the easy magnetization direction is the [100] axis. In the vicinity of the compensation temperature, Tcomp = 84 K, TbFe5Al7 displays a spin-reorientation transition from [100] to the [110] axis accompanied by pronounced anomalies in the relative sound-velocity change and sound attenuation. Further, field-induced magnetic transitions have been observed in TbFe5Al7 by magnetization and acoustic measurements. Step-wise rotationof the magnetic moments with a wide hysteresis occurs for fields applied along the [100] axis at T < Tcomp and along the [110] axis at T > Tcomp. The relative sound-velocity change displays sharp minima and the sound attenuation sharp maxima at the transitions. The critical field of the transitions tends to zero near the compensation point and grows sharply away from it reaching 19 and 33 T for fields applied along the [100] and [110] directions, respectively. The Tb–Fe inter-sublattice exchange constant has been determined directly from the high-field data and using molecular-field theory.

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Permalink: https://www.hzdr.de/publications/Publ-20410
Publ.-Id: 20410


Radiolabelling of nanoparticles and its use for transport studies

Franke, K.; Schymura, S.; Hildebrand, H.; Kulenkampff, J.; Lippmann-Pipke, J.
Hundreds of products containing nanoparticles (NP) are already in use. Nanotechnological innovation is identified in many sectors, including public health, employment and occupational health and safety, information society, industry, environmental protection, fuel and energy generation, transportation, security and space exploration. But the new materials may also pose risks to the environment and raise health and safety concerns. These risks have been addressed in several ongoing research projects. The overall conclusion so far is that, even though NP are not per se dangerous, there still is scientific uncertainty about the safety of NP in many aspects and therefore the safety assessment of the substances must be done on a case-by-case basis.
A key factor for the fate of NP in the environment and their introduction into the food chain is the bioavailability and thereby the mobility of the NP. Multiple factors control the migration behaviour of the NP in water and water saturated/unsaturated soils. Reversible and irreversible physical and chemical interactions cause a complex scenario with a great variety of boundary conditions. The transport of NP through soil, water and sediments is influenced by advection, diffusion, retardation due to sedimentation, filtration, staining, size exclusion effects, aging due to chemical corrosion, sorption and aggregation.
The experimental access to transport studies requires the observation of NP in complex environmental media at naturally relevant concentrations. This is a major challenge in laboratory work which can be overcome by the use of radiotracers.
In this work we present different techniques for the introduction of the radiotracers into the NP (Ag0, TiO2, MWCNT) including activation of NP, radiosynthesis of NP, radiolabelling of NP, self-diffusion of radioisotopes into NP and recoil labeling. The radiolabelled NP were used for 1D and 4D (time resolved Positron Emission Tomography (PET)) transport studies. The first results of the transport studies (BTC- break through curves and PET images) will be given as prove of principle.
Keywords: nanoparticle, radiolabelling, transport studies
  • Poster
    4th International Nuclear Chemistry Congress (INCC), 14.-19.09.2014, Maresias, Brasil

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Permalink: https://www.hzdr.de/publications/Publ-20409
Publ.-Id: 20409


Transport system for solid targets of the COSTIS-system mounted at the BTL of the Cyclone 18/9

Franke, K.
The COSTIS system is a commercially available target station for the irradiation of solid targets. Up to 3 targets can be provided for irradiation by a slot system. In standard setup the target can be ejected via a pneumatically driven piston system. The target is then allowed to drop down into an open lead container, which can be closed remotely afterwards. The described procedure is well established and reliable. But the concept is limited to low dose targets and environments. The required entering of the cyclotron vault for manual pick up of the container at the cyclotron and the light 18 mm Pb lead shielding of the container itself cause exposure risk for the per-sonnel after long term irradiations with highly activated cyclotron parts and target. The purpose of this work was the design of an alternative for the pickup and the transport of irradiated targets to minimize the radiation dosage of the personnel during manual handling of the COSTIS-lead container.
Keywords: transport system, solid target, cyclotron
  • Poster
    15th International Workshop on Targetry and Target Chemistry (WTTC15), 18.-21.08.2014, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-20408
Publ.-Id: 20408


Metamagnetic transitions in U2Ni2Sn probed by high-field magnetization and acoustic measurements

Yasin, S.; Andreev, A. V.; Skourski, Y.; Zherlitsyn, S.; Wosnitza, J.
  • Poster
    DPG Frühjahrstagung, 31.03.-04.04.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20407
Publ.-Id: 20407


Magneto-acoustic quantum oscillations in YNi2B2C

Nössler, J.; Yasin, S.; Erfanifam, S.; Seerig, R.; Behr, G.; Zherlitsyn, S.; Wosnitza, J.
  • Poster
    DPG Frühjahrstagung, 31.03.-04.04.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20406
Publ.-Id: 20406


Modification of the COSTIS-system mounted at the Cyclone 18/9

Franke, K.
A widely distributed commercially available target station for the irradiation of solid targets is the COSTIS system. The system is specified for beams up to 500 W and is equipped with a front side He-cooling and water cooling on the back side. The target itself has a coin shape with a diameter of 24 mm and thickness of 2 mm. This recommends the system for irradiation of thin targets like foils but it is also useable for irradiation of metal and oxide powders. However the irradiation of powders and granulates is limited due to the dimension of the target cap-sule. A setup of a capped closed target is hardly achievable. The purpose of this work was the modification of the COSTIS target station for the use of thicker target capsules. This shall enable the more easy and safe handling and irradiation of powdery targets and the use of lockable target capsules.
Keywords: solid tagert, COSTIS, cyclotron
  • Poster
    15th International Workshop on Targetry and Target Chemistry (WTTC15), 18.-21.08.2014, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-20405
Publ.-Id: 20405


Superconductivity and ferromagnetism in nanostructured Bi3Ni

Schönemann, R.; Herrmannsdörfer, T.; Naumann, M.; Skrotzki, R.; Kaiser, M.; Heise, M.; Ruck, M.; Kummer, K.; Graf, D.; Wosnitza, J.
es hat kein Abstract vorgelegen
  • Poster
    DPG Frühjahrstagung, 31.03.-04.04.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20404
Publ.-Id: 20404


Magnetic-field-dependent reentrant superconductivity in Ga-implanted Si

Skrotzki, R.; Herrmannsdörfer, T.; Schönemann, R.; Heera, V.; Fiedler, J.; Kampert, E.; Wolff-Fabris, F.; Förster, T.; Völskow, A.; Mücklich, A.; Schmidt, B.; Skorupa, W.; Helm, M.; Wosnitza, J.
  • Poster
    DPG Frühjahrstagung, 30.03.-04.04.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20403
Publ.-Id: 20403


Magneto-elastic effects in Tb3Ga5O12

Löw, U.; Zherlitsyn, S.; Araki, K.; Akatsu, M.; Nemoto, Y.; Goto, T.; Zeitler, U.; Lüthi, B.
We report new results for the elastic constants studied in Faraday and Cotton-Mouton geometry in Tb3Ga5O12 (TGG), a frustrated magnetic substance with strong spin-phonon interaction and remarkable crystal-electric-field (CEF) effects. We analyze the data in the framework of CEF theory taking into account the individual surroundings of the six inequivalent Tb3+-ion positions. This theory describes both, elastic constants in the magnetic field and as a function of temperature. Moreover we present sound-attenuation data for the acoustic Cotton-Mouton effect in TGG.

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Permalink: https://www.hzdr.de/publications/Publ-20402
Publ.-Id: 20402


Ultra high hole mobilities in a pure strained Ge quantum well

Mironov, O. A.; Hassan, A. H. A.; Morris, R. J. H.; Dobbie, A.; Uhlarz, M.; Chrastina, D.; Hague, J. P.; Kiatgamolchai, S.; Beanland, R.; Gabani, S.; Berkutov, I. B.; Helm, M.; Drachenko, O.; Myronov, M.; Leadley, D. R.
Hole mobilities at low and room temperature (RT) have been studied for a strained sGe/SiGe heterostructure using standard Van der Pauw resistivity and Hall effect measurements. The range of magnetic field and temperatures used were - 14 T < B < + 14 T and 1.5 K < T < 300 K respectively. Using maximum entropy-mobility spectrum analysis (ME-MSA) and Bryan's algorithm mobility spectrum (BAMS) analysis, a RT two dimensional hole gas drift mobility of (3.9 ± 0.4) × 103 cm2/V s was determined for a sheet density (ps) 9.8 × 1010 cm− 2 (by ME-MSA) and (3.9 ± 0.2) × 103 cm2/V s for a sheet density (ps) 5.9 × 1010 cm− 2 (by BAMS).

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Permalink: https://www.hzdr.de/publications/Publ-20401
Publ.-Id: 20401


Crystal structure and magnetic properties of FeSeO3F - Alternating antiferromagnetic S = 5/2 chains

Hu, S.; Johnsson, M.; Law, J. M.; Bettis, J. L.; Whangbo, M.-H.; Kremer, R. K.
The new oxofluoride FeSeO3F, which is isostructural with FeTeO3F and GaTeO3F, was prepared by hydrothermal synthesis, and its structure was determined by X-ray diffraction. The magnetic properties of FeSeO3F were characterized by magnetic susceptibility and specific heat measurements, by evaluating its spin exchanges on the basis of density functional theory (DFT) calculations, and by performing a quantum Monte Carlo simulation of the magnetic susceptibility. FeSeO3F crystallizes in the monoclinic space group P21/n and has one unique Se4+ ion and one unique Fe3+ ion. The building blocks of FeSeO3F are [SeO3] trigonal pyramids and cis-[FeO 4F2] distorted octahedra. The cis-[FeO4F2] octahedra are condensed by sharing the O-O and F-F edges alternatingly to form [FeO3F]∞ chains, which are interconnected via the [SeO3] pyramids by corner-sharing. The magnetic susceptibility of FeSeO3F is characterized by a broad maximum at 75(2) K and a long-range antiferromagnetic order below ∼45 K. The latter is observed by magnetic susceptibility and specific heat measurements. DFT calculations show that the Fe-F-Fe spin exchange is stronger than the Fe-O-Fe exchange, so each [FeO3F]∞ chain is a Heisenberg antiferromagnetic chain with alternating antiferromagnetic spin exchanges. The temperature dependence of the magnetic susceptibility is well-reproduced by a quantum-Monte Carlo simulation.

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Permalink: https://www.hzdr.de/publications/Publ-20400
Publ.-Id: 20400


Direct measurements of the magnetocaloric affect in the Heusler alloy Ni50Mn35In15 in pulsed magnetic fields

Ghorbani Zavareh, M.; Salazar Mejia, C.; Nayak, A.; Nicklas, M.; Skourski, Y.; Felser, C.; Wosnitza, J.
  • Poster
    Intermag 2014, 04.-08.05.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20399
Publ.-Id: 20399


Magnetic, thermal, and transport properties of single crystalline U3Cu4Ge4

Skourski, Y.; Andreev, A. V.; Gorbunov, D. I.; Henriques, M. S.; Havela, L.; Wosnitza, J.; Goncalves, A. P.
  • Poster
    Intermag 2014, 04.-08.05.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20398
Publ.-Id: 20398


Precision measurement of Timing RPC gas mixtures with laser-beam induced electrons

Naumann, L.; Siebold, M.; Kaspar, M.; Kämpfer, B.; Kotte, R.; Laso Garcia, A.; Loeser, M.; Schramm, U.; Wüstenfeld, J.
The main goals of a new test facility at Helmholtz-Zentrum Dresden-Rossendorf are precision measurements of the electron drift velocity and the Townsend coefficient of gases at atmospheric pressure in the strongest ever used homogenous electrical fields and the search for new RPC gas mixtures to substitute the climate harmful Freon. Picosecond UV laser pulses in the UV were focused into a sub-millimeter gas gap to initialize a defined tiny charge. These gaps are formed by electrodes of low-resistive ceramics or high-resistive float glass. The charge multiplication occurs in a strong homogeneous electric field of up to 100\,kV/cm. Electron-ion pairs were generated in a cylindrical micro-volume by multi-photon ionization. The laser-pulse repetition rate ranges from 1\,Hz to a few kHz. The RPC time resolution has been measured for different gases. First results of the Townsend coefficient at 100\,kV/cm show a strong disagreement between the present measurement and Magboltz simulations for the typical Timing RPC gas mixture C2F4H2/SF6/i-C4H{10}, while the measured electron drift velocities are in a good agreement with the model predictions.

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Permalink: https://www.hzdr.de/publications/Publ-20397
Publ.-Id: 20397


Phylogenetic diversity of archaea and the archaeal ammonia monooxygenase gene in uranium mining-impacted locations in Bulgaria

Radeva, G.; Kenarova, A.; Bachvarova, V.; Flemming, K.; Popov, I.; Vassilev, D.; Selenska-Pobell, S.
Uranium mining and milling activities adversely affect the microbial populations of impacted sites. The negative effects of uranium on soil bacteria and fungi are well studied, but little is known about the effects of radionuclides and heavy metals on archaea. The composition and diversity of archaeal communities inhabiting the waste pile of the Sliven uranium mine and the soil of the Buhovo uranium mine were investigated using 16S rRNA gene retrieval. A total of 355 archaeal clones were selected, and their 16S rDNA inserts were analysed by restriction fragment length polymorphism (RFLP) discriminating 14 different RFLP types. All evaluated archaeal 16S rRNA gene sequences belong to the 1.1b/Nitrososphaera cluster of Crenarchaeota. The composition of the archaeal community is distinct for each site of interest and dependent on environmental characteristics, including pollution levels. Since the members of 1.1b/Nitrososphaera cluster have been implicated in the nitrogen cycle, the archaeal communities from these sites were probed for the presence of the ammonia monooxygenase gene (amoA). Our data indicate that amoA gene sequences are distributed in a similar manner as in Crenarchaeota, suggesting that archaeal nitrification processes in uranium mining-impacted locations are under the control of the same key factors controlling archaeal diversity.

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Publ.-Id: 20396


EGF receptor-targeting peptide conjugate incorporating a near-IR fluorescent dye and a novel 1,4,7-triazacyclononane-based 64Cu(II) chelator assembled via click chemistry

Viehweger, K.; Barbaro, L.; Pombo García, K.; Joshi, T.; Geipel, G.; Steinbach, J.; Stephan, H.; Spiccia, L.; Graham, B.
A new Boc-protected 1,4,7-triazacyclononane (TACN)-based pro-chelator compound featuring a “clickable” azidomethylpyridine pendant has been developed as a building block for the construction of multimodal imaging agents. Conjugation to a model alkyne (propargyl alcohol), followed by deprotection, generates a pentadentate ligand, as confirmed by X-ray crystallographic analysis of the corresponding distorted square-pyramidal Cu(II) complex. The ligand exhibits rapid 64Cu2+-binding kinetics (> 95% radiochemical yield in < 1 min) and a high resistance to demetallation. It may thus prove suitable for use in 64Cu-based in vivo positron emission tomography (PET). The new chelating building block has been applied to the construction of a bimodal (PET/fluorescence) peptide-based imaging probe targeting the epidermal growth factor (EGF) receptor, which is highly over-expressed on the surface of several types of cancer cells. The probe consists of a hexapeptide sequence, Leu-Ala-Arg-Leu-Leu-Thr (designated “D4”), coupled to a β-homopropargylglycine residue with the TACN-based chelator “clicked” to its side chain, followed by a Cys-β-Ala-β-Ala spacer. A sulfonated near-infrared (NIR) fluorescent cyanine dye (sulfo-Cy5) was introduced at the N-terminus to study the EGF receptor-binding ability of the probe by laser-fluorescence spectroscopy. Binding was also confirmed by co-immunoprecipitation methods, and an apparent dissociation constant (Kd) of ca. 10 nM was determined from radioactivity-based measurements of probe binding to two EGF receptor-expressing cell lines (FaDu and A431). The probe is shown to be a biased or partial allosteric agonist of the EGF receptor, inducing phosphorylation of Thr669 and Tyr992, but not the Tyr845, Tyr998, Tyr1045, Tyr1068 or Tyr1148 residues of the receptor, in the absence of the orthosteric EGF ligand. Additionally, the probe was found to suppress the EGF-stimulated autophosphorylation of these latter residues, indicating that it is also a non-competitive antagonist.

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Permalink: https://www.hzdr.de/publications/Publ-20395
Publ.-Id: 20395


Diagnostic nanoparticle targeting of the EGF-receptor in complex biological conditions using single-domain antibodies

Zarschler, K.; Prapainop, K.; Mahon, E.; Rocks, L.; Bramini, M.; Kelly, P.; Stephan, H.; Dawson, K. A.
For effective localization of functionalized nanoparticles at diseased tissues such as solid tumours or metastases through biorecognition, appropriate targeting vectors directed against selected tumour biomarkers are a key prerequisite. The diversity of such vector molecules ranges from proteins, including antibodies and fragments thereof, through aptamers and glycans to short peptides and small molecules. Here, we analyse the specific nanoparticle targeting capabilities of two previously suggested peptides (D4 and GE11) and a small camelid single-domain antibody (sdAb), representing potential recognition agents for the epidermal growth factor receptor (EGFR). We investigate specificity by way of receptor RNA silencing techniques and look at increasing complexity in vitro by introducing increasing concentrations of human or bovine serum. Peptides D4 and GE11 proved problematic to employ and conjugation resulted in non-receptor specific uptake into cells. Our results show that sdAb functionalised particles can effectively target the EGFR, even in more complex bovine and human serum conditions where targeting specificity is largely conserved for increasing serum concentration. In human serum however, an inhibition of overall nanoparticle uptake is observed with increasing protein concentration. For highly affine targeting ligands such as sdAbs, targeting a receptor such as EGFR with low serum competitor abundance, receptor recognition function can still be partially realised in complex conditions. Here, we stress the value of evaluating the targeting efficiency of nanoparticle constructs in realistic biological milieu, prior to more extensive in vivo studies.

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Publ.-Id: 20394


What next?

Baumann, M.; Overgaard, J.

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Permalink: https://www.hzdr.de/publications/Publ-20393
Publ.-Id: 20393


A new drag correlation from fully resolved simulations of flow past monodisperse static arrays of spheres

Tang, Y.; Kriebitzsch, S.; Peters, E. A. J. F.; van der Hoef, M. A.; Kuipers, J. A. M.
We performed fully resolved simulations of flows past fixed assemblies of monodisperse spheres using an iterative Immersed Boundary (IB) Method, for both face-centered-cubic (FCC) array and random configurations. For the latter, a methodology has been applied such that the computed gas-solid force is almost independent of the grid resolution. Simulations in this work extend the previously similar studies to a wider range of solids volume fraction (φ ∈ [0.1, 0.6]) and Reynolds number (Re ∈ [50, 1000]). We propose a new drag correlation combining the existed drag correlations for low-Re flows and single-sphere flows, which fits the entire data set with an average relative deviation of 4%. This correlation is so-far the best possible expression for the drag force in monodisperse static arrays of spheres, and is the most accurate basis to introduce the particle mobility for dynamic gas-solid systems, such as in fluidized beds.
Keywords: Immersed Boundary Method, fully resolved simulations, drag correlation

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Permalink: https://www.hzdr.de/publications/Publ-20392
Publ.-Id: 20392


Early increase of cannabinoid receptor density after experimental traumatic brain injury in the newborn piglet

Donat, C. K.; Fischer, F.; Walter, B.; Deuther-Conrad, W.; Brodhun, M.; Bauer, R.; Brust, P.
Paediatric traumatic brain injury (TBI) is a leading cause of death and disability. Previous studies showed neuroprotection after TBI by (endo)cannabinoid mechanisms, suggesting involvement of cannabinoid receptors (CBR). We therefore determined CBR densities and expression of the translocator protein 18 kDA(TSPO) in newborn piglets after experimental TBI. Newborn female piglets were subjected to sham operation (n=6) or fluid-percussion (FP)injury (n=7) under controlled physiological conditions. After six hours, brains were frozen, sagittally cut and incubated with radioligands for CBR ([3H]CP-55,940, [3H]SR141716A) and TSPO ([3H]PK11195), an indicator of gliosis/brain injury. Early after injury, FP-TBI elicited a significant ICP increase at a temporary reduced cerebral perfusion pressure; however, CBF and CMRO2 remained within physiological range.
At 6 hours post injury, we found a statistically significant increase in binding of the non-selective agonist [3H]CP-55,940 in 15 of the 24 investigated brain regions of injured animals. By contrast, no significant changes in binding of the CB1R-selective antagonist [3H]SR141716A were observed. A non-significant trend towards increased binding of [3H]PK11195 was observed, suggesting an incipient microglial activation. We therefore conclude that in this model and time span after injury, the increase in [3H]CP-55,940 binding reflects changes in CB2R density, while CB1R density is not affected. The results may provide explanation for the neuroprotective properties of cannabinoid ligands and future therapeutic strategies of TBI.
Keywords: traumatic brain injury, autoradiography, cannabinoid receptors, neuroprotection
  • Open Access Logo Acta Neurobiologiae Experimentalis 74(2014), 197-210

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Permalink: https://www.hzdr.de/publications/Publ-20391
Publ.-Id: 20391


Sputtered Si-containing low-friction carbon coatings for elevated temperatures

Jantschner, O.; Field, S. K.; Music, D.; Terziyska, V. L.; Schneider, J. M.; Munnik, F.; Zorn, K.; Mitterer, C.
This work presents a tribological study on three sputtered amorphous carbon-based coatings containing Si and Cr (a-C, a-C:Cr and a-C:Si). Molecular dynamics simulations predict tetrahedral bonds between C and Si in the a-C matrix. Ball-on-disk-tests against Al2O3 carried out at room temperature revealed a coefficient of friction of 0.08–0.1 for all films. Between 250 and 325 °C, Si decreases the COF and wear rate to <0.05 and <5×10-17m3/N×laps, respectively. The a-C reference shows a COF of 0.15±0.05 and a wear rate of 1×10-16m3/N×laps, whereas the a-C:Cr film failed. The improved tribological performance of a-C:Si expands its application temperature to 450 °C and is most probably related to formation of Si-compounds on the film surface, as evidenced by X-ray photoelectron spectroscopy.
Keywords: Amorphous carbon; Elevated temperatures; Thermal stability; Temperature induced lubrication

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Publ.-Id: 20390


Mapping Hydrophobicity combining AFM and Raman Spectroscopy

Rudolph, M.; Peuker, U. A.
A new concept to evaluate the floatability of individual minerals in an ore specimen is presented. The method is based on the combination of colloidal probe atomic force microscopy to determine hydrophobic interactions responsible for the flotation of fine mineral particles and Raman spectroscopy to identify the mineral phase at the same location. Both methods show a high spatial resolution and allow investigating even small individual minerals. The ore sample of this study is a syenite rock from south Sweden containing the valuable rare earth mineral eudialyte and gangue minerals mainly comprising feldspars, nepheline, aegirine and zeolites. Using the poor selective collector sodium oleate we demonstrate how hydrophobic interactions become apparent conducting force distance measurements in the aqueous environment. We discuss different parameters of the force spectroscopy in static and dynamic mode to be used to define a measure for floatability. In contrast to other studies on the hydrophobic interactions in flotation we propose to draw Information from the detachment of the hydrophobic probe particle of the atomic force microscope from the mineral surface in contrast to the approach force distance spectroscopy. All the hydrophobic interactions identified can be contributed to the appearance of gas layers on the surfaces leading to capillary interactions.
Keywords: Floatability; Flotation; Nanobubbles; Eudialyte; Rare Earth Elements

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Permalink: https://www.hzdr.de/publications/Publ-20389
Publ.-Id: 20389


Magnetic films tailored by ion irradiation

Fassbender, J.ORC
In recent years the tailoring of magnetic properties by means of ion irradiation and implantation techniques has become fashionable. Early investigations relied on the fact that the perpendicular magnetic anisotropy of Co/Pt multilayers depend sensitively on the interface sharpness [1]. Subsequently also the ion induced modification of exchange bias phenomena as well as interlayer exchange coupling has been investigated [2]. For single magnetic films ion implantation has been used to reduce the Curie temperature and hence the saturation magnetization [3]. Nowadays also the reverse process, i.e. the creation of nanomagnets within special binary alloys is employed [4,5]. In combination with lithography a pure magnetic patterning becomes possible [6] leading to hybrid magnetic materials [7] with properties different from both, the ion irradiated as well as the untreated material. Even ion induced chemical reduction can be employed to create a nanomagnetic pattern [8,9].

In an alternative route to design magnetic properties periodically modulated substrates are used. Low energy ion erosion provides an easy technology to create modulated surfaces with periods ranging from 20 to 200 nm. Due to the broken translational invariance new anisotropy contributions appear [10] and additional relaxation channels are opened [11].

An overview of the present status in this research field will be given.


References:
1. C. Chappert et al., Science 280, 1919 (1998).
2. J. Fassbender, D. Ravelosona, Y. Samson, J. Phys. D 37, R179 (2004).
3. J. Fassbender, J. McCord, Appl. Phys. Lett. 88, 252501 (2006).
4. E. Menendez et al., Small 5, 229 (2009).
5. R. Bali et al., Nano Lett. in press.(2014).
6. J. Fassbender and J. McCord, J. Magn. Magn. Mater. 320, 579 (2008).
7. J. McCord, L. Schultz, J. Fassbender, Adv. Mater. 20, 2090 (2008).
8. S. Kim et al., Nature Nanotechnology 7, 567 (2012).
9. J. Fassbender, Nature Nanotechnology 7, 554 (2012).
10. M. O. Liedke, et al., Phys. Rev. B 75, 220407(R) (2007).
11. M. Körner et al., Phys. Rev. B 88, 054405 (2013).
Keywords: magnetism, ion irradiation, patterning
  • Invited lecture (Conferences)
    Physics of Surfaces and Interfaces, 24.-28.02.2014, Puri, Indien

Permalink: https://www.hzdr.de/publications/Publ-20388
Publ.-Id: 20388


Form follows function - neue Funktionalitäten durch Nanostrukturierung

Fassbender, J.ORC
Festvortrag anlässlich des 10-jährigen Jubiläums des Nano Structuring Center Kaiserslautern
Keywords: nano, patterning, ion irradiation, magnetism
  • Invited lecture (Conferences)
    10 Jahre Nano Structuring Centre Kaiserslautern, 08.07.2014, Kaiserslautern, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20387
Publ.-Id: 20387


Biosorption and Biomineralization of U(VI) by the Marine Bacterium Idiomarina loihiensis MAH1: Effect of Background Electrolyte and pH

Morcillo, F.; Gonzalez-Munoz, M. T.; Reitz, T.; Romero-Gonzalez, M. E.; Arias, J. M.; Merroun, M. L.
The main goal of this study is to compare the effects of pH, uranium concentration, and background electrolyte (seawater and NaClO4 solution) on the speciation of uranium(VI) associated with the marine bacterium Idiomarina loihiensis MAH1. This was done at the molecular level using a multidisciplinary approach combining X-ray Absorption Spectroscopy (XAS), Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS), and High Resolution Transmission Electron Microscopy (HRTEM). We showed that the U(VI)/bacterium interaction mechanism is highly dependent upon pH but also the nature of the used background electrolyte played a role.
At neutral conditions and a U concentration ranging from 5-10(-4) to 10(-5) M (environmentally relevant concentrations), XAS analysis revealed that uranyl phosphate mineral phases, structurally resembling meta-autunite [Ca(UO2)(2)(PO4)(2) 2-6H(2)O] are precipitated at the cell surfaces of the strain MAH1. The formation of this mineral phase is independent of the background solution but U(VI) luminescence lifetime analyses demonstrated that the U(VI) speciation in seawater samples is more intricate, i. e., different complexes were formed under natural conditions. At acidic conditions, pH 2, 3 and 4.3 ([U] = 5 . 10(-4) M, background electrolyte = 0.1 M NaClO4), the removal of U from solution was due to biosorption to Extracellular Polysaccharides (EPS) and cell wall components as evident from TEM analysis. The LIII-edge XAS and TRLFS studies showed that the biosorption process observed is dependent of pH. The bacterial cell forms a complex with U through organic phosphate groups at pH 2 and via phosphate and carboxyl groups at pH 3 and 4.3, respectively. The differences in the complexes formed between uranium and bacteria on seawater compared to NaClO4 solution demonstrates that the actinide/microbe interactions are influenced by the three studied factors, i.e., the pH, the uranium concentration and the chemical composition of the solution.

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Publ.-Id: 20386


Realization of a spin-wave multiplexer

Vogt, K.; Fradin, F. Y.; Pearson, J. E.; Sebastian, T.; Bader, S. D.; Hillebrands, B.; Hoffmann, A.; Schultheiss, H.
Recent developments in the field of spin dynamics—like the interaction of charge and heat currents with magnons, the quasi-particles of spin waves—opens the perspective for novel information processing concepts and potential applications purely based on magnons without the need of charge transport. The challenges related to the realization of advanced concepts are the spin-wave transport in two-dimensional structures and the transfer of existing demonstrators to the micro- or even nanoscale. Here we present the experimental realization of a microstructured spin-wave multiplexer as a fundamental building block of a magnon-based logic. Our concept relies on the generation of local Oersted fields to control the magnetization configuration as well as the spin-wave dispersion relation to steer the spin-wave propagation in a Y-shaped structure. Thus, the present work illustrates unique features of magnonic transport as well as their possible utilization for potential technical applications.
Keywords: Magnonics, Spintronics, Spin Waves, Brillouin Light Scattering Microscopy
  • Nature Communications 5(2014), 3727
    DOI: 10.1038/ncomms4727
  • Invited lecture (Conferences)
    Magnetism and Magnetic Materials, 7.11.2014, Honolulu, Hawaii, USA

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Publ.-Id: 20385


Ultrafast detection from 0.6 THz to 33 THz employing graphene flakes

Mittendorff, M.; Winnerl, S.; Kamann, J.; Eroms, J.; Weiss, D.; Drexler, C.; Ganichev, S.; Schneider, H.; Helm, M.
Graphene can serve as an excellent active material for the development of ultrafast electro-optic devices. With the vanishing bandgap, photons can be absorbed via interband processes over an extremely wide spectral range (from ultraviolet to far-infrared). However, in the regime of non-zero Fermi energy and very low photon energies, interband absorption can be prohibited. In this case intraband absorption is an efficient process. T. Müller et al. [1] presented an ultrafast detector for the near-infrared range. Their device was operated at room temperature and reached frequencies of up to 16 GHz. Field-effect transistors made of graphene flakes have been employed for the detection of THz radiation. Vicarelli et al. [2] developed a very sensitive detector for cw radiation at room temperature, while Yan et al. [3] presented an ultrafast bolometer which was cooled to 4 K.
We present a detector based on a graphene flake for a very broad spectral range from 0.6 THz to 33 THz, corresponding to wavelengths of 500 µm to 9 µm, respectively. To couple the far-infrared radiation efficiently to the flake, which is orders of magnitude smaller than the largest wavelengths, a logarithmic periodic antenna [5] is patterned on top of the substrate. The antenna is connected to the graphene flake by an interdigitated structure (see fig. 1). A coaxial cable, bonded to the outer part of the two antenna arms, serves as signal line. The signal is amplified by a high-frequency amplifier and recorded with a fast sampling oscilloscope with a bandwidth of 30 GHz.
The free-electron laser (FEL) FELBE at the Dresden lab served as radiation source for the characterizing the detectors at wavelengths of up to 220 µm. Additional data were obtained using a THz gas laser at the University of Regensburg providing radiation pulses with wavelengths of up to 500 µm. The response time of the devices is about 50 ps, which highlights the potential of this detector for timing measurements of intense THz pulses. The signal of two FEL pulses with a temporal delay of 500 ps is shown in fig. 2. The pulse energy of each of the pulses was about 40 nJ, which lead to a signal amplitude of 30 mV. Despite a low responsivity of about 5 nA/W, pulses with energies down to 1 nJ can be resolved. For high pulse energies, the signal amplitude saturates strongly. While this saturation limits the dynamic range for linear detection, it can be exploited in autocorrelation measurements [6]. In this regime the response time is not limited by the RC time constant but by the intrinsic response time of the graphene flake (< 10 ps).
Furthermore we demonstrate the important role of the substrate for these devices. Our first devices were produced on SiO2 on Si [7]. When a low-resistivity substrate is used, the high-speed performance of the device is strongly deteriorated. The antenna forms a capacitor with the conductive substrate material and therefore increases the RC time constant of the detector. Devices on high-resistive Si could resolve fast signals only for wavelengths above 20 µm. This can be attributed to phonon-related absorption in the Si substrate resulting in higher substrate conductivity due to thermally activated carriers. To overcome this restriction, a new set of detectors has been fabricated on semi-insulating SiC. As graphene is nearly invisible on top of SiC, graphene grown by chemical vapor deposition on copper was transferred to the new substrate and located by Raman mapping. With these new devices FEL pulses can be measured down to a wavelength of 9 µm.

References

[1] T. Müller et al., Nature Photon. 4, 297 (2010).
[3] L. Vicarelli et al., Nature Mat. 11, 865 (2012).
[4] J. Yan et al., Nature Nanotechnol. 7, 472 (2012).
[5] R. Mendis et al., IEEE Antennas and Propag. Lett. 4, 85 (2005).
[6] S. Winnerl et al., Appl. Phys. Lett. 73, 2983 (1998).
[7] M. Mittendorff et al. Appl. Phys. Lett. 103, 021113 (2013).
  • Lecture (Conference)
    Graphene 2014, 06.-09.05.2014, Toulouse, France

Permalink: https://www.hzdr.de/publications/Publ-20384
Publ.-Id: 20384


Positron annihilation in flight: experiment with slow and fast positrons

Cizek, J.; Vlcek, M.; Lukac, F.; Melikhova, O.; Prochazka, I.; Anwand, W.; Wagner, A.; Butterling, M.; Krause-Rehberg, R.
A novel digital coincidence Doppler broadening (D-CDB) spectrometer was employed for energy resolved investigations of two-quantum annihilation-in-flight (TQAF). The TQAF phenomenon was studied using monoenergetic positrons produced in a slow positron beam and also using fast positrons. Because of a low background the measurements on the slow positron beam could be performed in a close geometry and the TQAF contribution in the two-dimensional gamma ray energy spectra fills a ‘bowl-like’ area delimited by a hyperbolic curve and a kinematical cut-off determined by the kinetic energy of positrons. With decreasing positron energy the area of TQAF contribution becomes smaller and disappears completely for slow positrons with energies below ~ 100 eV. The measurements with fast positrons were restricted to a limited range of angles between the annihilation gamma rays and the TQAF events contribute to a hyperbolic band in gamma ray energy spectrum.
Keywords: positron annihilation in flight, fast and slow positrons

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Publ.-Id: 20383


Optical ridge waveguides in 4H-SiC single crystal produced by combination of carbon ion irradiation and femtosecond laser ablation

Luan, Q.; Jia, Y.; Wang, Y.; Akhmadaliev, S.; Zhou, S.; de Aldana, J.; Tan, Y.; Chen, F.
Optical ridge waveguides were fabricated in 4H-SiC single crystal by combination of 15 MeV C5+ ion irradiation and femtosecond laser ablation. The near-field modal intensity distributions exhibit the well-confined light propagation in the waveguides. A propagation loss as low as 5.1 dB/cm has been achieved at 632.8 nm for the ridge waveguide. The investigation of confocal micro-Raman spectra suggests partial transition of 4H-SiC to 6H-SiC in the irradiated region.
Keywords: Waveguides, SiC, Ion irradiation

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Publ.-Id: 20382


Commissioning of a compact laser-based proton beam line for high intensity bunches around 10 MeV

Busold, S.; Schumacher, D.; Deppert, O.; Brabetz, C.; Kroll, F.; Blažević, A.; Bagnoud, V.; Roth, M.
We report on the first results of experiments with a new laser-based proton beam line at the GSI accelerator facility in Darmstadt. It delivers high current bunches at proton energies around 9.6 MeV, containing more than 10^9 particles in less than 10 ns and with tunable energy spread down to 2.7% (ΔE/E0 at FWHM). A target normal sheath acceleration stage serves as a proton source and a pulsed solenoid provides for beam collimation and energy selection. Finally a synchronous radio frequency (rf) field is applied via a rf cavity for energy compression at a synchronous phase of −90 deg. The proton bunch is characterized at the end of the very compact beam line, only 3 m behind the laser matter interaction point, which defines the particle source.

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Permalink: https://www.hzdr.de/publications/Publ-20381
Publ.-Id: 20381


Effect of Waveform of ac Voltage on the Morphology and Crystallinity of Electrochemically Assembled Platinum Nanowires

Nerowski, A.; Pötschke, M.; Wiesenhütter, U.; Nicolai, J.; Cikalova, U.; Dianat, A.; Erbe, A.; Opitz, J.; Bobeth, M.; Baraban, L.; Cuniberi, G.
Here we present electrochemically grown ultrathin platinum nanowires and demonstrate that their morphology and crystalline structure can be tuned by the waveform of the alternating voltage applied to the microelectrodes. The structure of the nanowires was analyzed by scanning and transmission electron microscopy. The voltage signal, applied to grow the nanowires, consisted of several Fourier components of a square-shaped wave. We observed that, depending on the number of Fourier components, the morphology of the nanowires changed from branched dendritic-like patterns to straight wires and the wire crystallinity changed from polycrystalline to highly oriented growth with the [111] direction of platinum crystallites along the nanowire axis. We propose a simple model to explain this intriguing observation.
Keywords: directed electrochemical nanowire growth, dielectrophoresis

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Permalink: https://www.hzdr.de/publications/Publ-20380
Publ.-Id: 20380


Defects Studies of ZnO Single Crystals Prepared by Various Techniques

Lukac, F.; Cizek, J.; Prochazka, I.; Melikhova, O.; Anwand, W.; Brauer, G.
The aim of the present work was a comparison of defects in ZnO crystals grown by various techniques available nowadays, namely hydrothermal growth, pressurized melt, Bridgman method growth and vapor phase growth. Positron annihilation spectroscopy was employed as a principal tool for characterization of defects in ZnO crystals grown by above mentioned various techniques. ZnO crystals can be divided into two groups: (i) hydrothermal grown crystals, which exhibit positron lifetime of 179-182 ps and (ii) ZnO crystals grown by the other techniques (pressurized melt, Bridgman method, vapor phase growth) which are characterized by the lower lifetimes falling in the range of 160-173 ps. Comparison of experimental data with ab initio theoretical calculations revealed that HT grown ZnO crystals contains Zn vacancies associated with hydrogen atom in a bond-centered site. On the other hand, ZnO crystals prepared by other techniques contain most probably stacking faults created by stresses induced by temperature gradients in the melt.
Keywords: Crystal defects, Positron annihilation spectroscopy; Ab initio theoretical calculations, Hydrogen, Hydrothermal growth, Vapor phase growth; Zn vacancies; ZnO single crystals

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Publ.-Id: 20379


Uranium redox processes and uptake by plant cells

Geipel, G.; Viehweger, K.
Recently we have shown that uranium can be taken up by plant cells. Fractionation studies showed that the uranium was present in nearly all cell compartments. Nevertheless, luminescence measurements showed that the speciation of the uranium in the several cell compartments differs from each other.
One of the major remaining questions concerns to the ways of uranium uptake. Recently published work /1,2/ proposed that the uranium uptake is influenced by the iron uptake. As it is known that the iron uptake occurs via reduction of the iron(III) into iron(II), we conclude that uranium uptake should also by accompanied by a redox process. First measurements by laser-induced photo-acoustic spectroscopy gave evidence for the presence of uranium(IV) inside the cells.
The formation of uranium(IV) from uranium(VI) is a more complicated redox process, as the oxo-cation uranium(VI) has to be transformed into an oxo-hydrate form. Electrochemically this process is irreversibly. In systems existing at nearly neutral pH additionally hydrolysis or complex formation of the uranium ions occur.
On the other hand the formed uranium(IV) can also be formed by a disproportionation step from uranium(V).

2UO2+ + 4H2O  UO2(OH)2 + U(OH)4 + 2H+

From electrochemical point of view the formation of uranium(V) is a reversible process and the redox potential uranium(VI)/uranium(V) is of the same order as the redox potential iron(III)/iron(II) (values for acidic solution).

UO22+ + e-  UO2+ E0 = - 0.16 V
Fe3+ + e-  Fe2+ E0 = - 0.77 V

However, these values are strongly influenced by pH and complex formation. Uranium(VI) as well as uranium(IV) was detected in cells of Brassica napus.
Therefore we tried to prove the oxidation state uranium(V) by electrochemical and spectroscopic methods.
Keywords: Uranium, Plant cells, redox chemistry
  • Contribution to proceedings
    Biometals 2014, 13.-18.07.2014, Durham, USA
    Proceedings of Biometals 2014

Permalink: https://www.hzdr.de/publications/Publ-20378
Publ.-Id: 20378


Cross-section measurements at astrophysically relevant energies: The LUNA experiment

Formicola, A.; Bruno, C. G.; Caciolli, A.; Cavanna, F.; Depalo, R.; Di Leva, A.; Scott, D. A.; Trezzi, D.; Aliotta, M.; Anders, M.; Bemmerer, D.; Broggini, C.; Corvisiero, P.; Elekes, Z.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Menegazzo, R.; Prati, P.; Somorjai, E.; Straniero, O.; Strieder, F.; Szücs, T.
Accurate knowledge of thermonuclear reaction rates is important in understanding the generation of energy, the luminosity of neutrinos, and the synthesis of elements in stars. Cross-section measurements for quiescent stellar H-burning are mainly hampered by extremely low counting rate and cosmic background. The LUNA Collaboration has shown that, by going underground and by using the typical techniques of low background physics, it is possible to measure nuclear cross-sections down to the energy of the nucleosynthesis inside stars. This paper reports an overview of the experimental techniques adopted in underground nuclear astrophysics through a summary of the main recent results and achievements. The future developments of the LUNA experiment are also given.
Keywords: Nuclear astrophysics LUNA Underground accelerator Solar fusion Big Bang nucleosynthesis

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Permalink: https://www.hzdr.de/publications/Publ-20377
Publ.-Id: 20377


First-principles study of the free energy of point defects and their clusters in bcc-Fe

Devaraj, M.; Posselt, M.; Schiwarth, M.
No abstract available. For informations please contact the authors.
Keywords: DFT calculations, point defects, foreign atoms, embedded clusters, bcc-Fe
  • Lecture (Conference)
    n-FAME Workshop, 06.-07.05.2014, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-20376
Publ.-Id: 20376


Ain films obtained by a broad energy Nitrogen ion Implantation and rapid thermal anealing process

Grigorov, K. G.; Nedkov, I.; Beshkov, G.; Angelov, C.; Maciel, H. S.; Matz, W.; Groetzchel, R.; Velchev, N.
The paper describes structural, morphological and electrical investigations of thin AlN films. The films were obtained by broad energy range ion bombardment (BERIB) of aluminium, with doses ranging from 1.5 × 1017 cm-2 to 6 × 1017 cm-2. This technique, to our knowledge, has not been described previously in the literature. The ion implantation was carried out with two species - nitrogen atoms with energies from 50, 30, and 20 keV and nitrogen ions with energies of 50 and 30 keV. These energy values were chosen in order to ensure a continuous and wide nitride layer, at least of 150 nm thick.
Keywords: Aluminium nitrides, RTA, PECVD, Ion implantation and characterization
  • Journal of Optoelectronics and Advanced Materials 7(2005)1, 381-384

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Publ.-Id: 20375


Summary of the investigations on the decommissioned WWER-440 reactor pressure vessel of the NPP Greifswald

Viehrig, H.-W.; Houska, M.; Altstadt, E.; Valo, M.
The Greifswald WWER-440/V-230 nuclear reactors represent the first generation of this reactor type. The four units of the Greifswald NPP were eternity shut down in 1990 after 11 –15 years of operation and represent different material conditions as follows:
• Irradiated (Unit 4),
• irradiated and recovery annealed (Units 2 and 3), and
• irradiated, recovery annealed and re-irradiated (Unit1).
The recovery annealing of the RPV was performed at a temperature of 475° for about 152 hours and included a region covering ±0.70 m above and below the core beltline welding seam.
Material samples of a diameter of 119 mm called trepans were extracted from the RPV walls. The research program is focused on the characterisation of the RPV steels (base and weld metal) across the thickness of the RPV wall.
This paper presents test results measured on the trepans of the beltline welding seam and base metal of the Units 1, 2 and 4 RPV. The key part of the testing is focussed on the determination of the reference temperature T0 following the ASTM standard E1921 to determine the facture toughness, and how it degrades under neutron irradiation and is recovered by thermal annealing. Other than that the mentioned test results include Charpy-V and tensile test results. Following results have been determined:
• The results represent the material conditions within the multilayer beltline welding seams and base metals aged under real operating conditions.
• The fracture toughness values at cleavage failure, KJc, of the weld metals generally follow the course of the MC though with a large scatter. A strong scatter of the KJc values of the irradiated and recovery annealed base metal of Unit 1 and Unit 4 RPV, respectively, is observed with clearly more than 2% of the values below the fracture toughness curve for 2% fracture probability.
• There is a large variation in the T0 values evaluated across the thickness of the multilayered welding seams from the investigated RPV’s.
• For the beltline welding seam of the Unit 4 RPV it is demonstrated that the ductile-to-brittle transition temperature (TT) shift predicted by the Russian code [PNAE G-7-008-86] for the present content of deleterious elements P and Cu and the accumulated neutron fluences lies within the scatter of the measured T0 values. The expected shift of T0 is not visible because of the strong variation of toughness caused by the intrinsic weld bead structure and the different filling materials used for weld root and the main weld within the multilayer welding seam. Hence, the position of the crack tip of the specimen in the multilayer welding seam is crucial and defines the cleavage fracture toughness.
• The mitigation of the neutron embrittlement of the weld and base metal by recovery annealing could be confirmed.
• For both weld and base metal the highest value of ductile-to-brittle transition temperatures (MC T0 and and Charpy-V TT47J) were not measured directly at the inner surface of the RPV. This points to the fact that the fracture toughness values measured on specimens machined from the “templates” taken directly at the inner RPV wall may not represent the conservative condition.
• The orientation of the specimens from a multilayer RPV welding seam is of essence for the fracture toughness testing according to ASTM E1921. For TS oriented specimens, the crack propagation across the thickness of the welding seam results in a uniform structure along the crack front, whereas for the T-L specimens with crack propagation in the circumferential direction, the structure along the crack front varies. This influences the KJc values and their scatter as also the MC reference temperature T0. Strictly speaking T-L specimens of weld metal do not fulfil the essential pre-assumption of the MC approach, because of the macroscopically non homogenous structure along the crack front length.
Keywords: nuclear reactor pressure vessel, irradiation behaviour, thermal annealing, fracture toughness, Master Curve, integrity assessment
  • Contribution to proceedings
    Material Issues in Design, Manufacturing and Operation of Nuclear Power Plants Equipment The Thirteenth International Conference, 02.-06.06.2014, St. Petersburg, Russia
    Proceedings of the Thirteenth International Conference on "Material Issues in Design, Manufacturing and Operation of Nuclear Power Plants Equipment", St. Petersburg: Prometey Institute

Permalink: https://www.hzdr.de/publications/Publ-20374
Publ.-Id: 20374


Effects of high-temperature treatment on the hydrogen distribution in silicon oxynitride/silicon nitride stacks for crystalline silicon surface passivation

Schwab, C.; Hofmann, M.; Heller, R.; Seiffe, J.; Rentsch, J.; Preu, R.
This work investigates a double layer stack system that can be used for surface passivation of crystalline silicon. The stack consists of amorphous silicon-rich silicon oxynitride and amorphous silicon nitride on top. Both layers are fabricated by means of plasma-enhanced chemical vapour deposition. We investigate the stack in terms of changes in the hydrogen content and distribution within the different stack layers due to a high temperature treatment. For that purpose the stack is studied by Fourier-transformed infrared spectroscopy and nuclear reaction analysis before and after fast firing at 850 degrees C. Our results determine the bottom silicon oxynitride layer as very hydrogen-rich.
Furthermore, we identify the silicon nitride capping layer as diffusion barrier to atomic hydrogen but still allowing an effusion of molecular hydrogen. We present a qualitative model that explains our findings and distinguishes between atomic and molecular hydrogen.
Keywords: Nuclear reaction analysis, Hydrogen depth profiling, silicon oxynitride, surface passivation

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Publ.-Id: 20373


Radiation and annealing response of WWER 440 beltline welding seams

Viehrig, H.-W.; Houska, M.; Altstadt, E.
The focus of this paper is on the irradiation response and the effect of thermal annealing in weld materials extracted from decommissioned WWER 440 reactor pressure vessels of the nuclear power plant Greifswald. The characterisation is based on the measurement of the hardness, the yield stress, the Master Curve reference temperature, T0, and the Charpy-V transition temperature through the thickness of multi-layer beltline welding seams in the irradiated and the thermally annealed condition. Additionally, irradiation-induced defect/solute clusters were measured by small angle neutron scattering.
We observed a large variation in the through thickness T0 values in the irradiated as well as in thermally annealed condition. The T0 values measured with the T-S-oriented Charpy size SE(B) specimens cut from different thickness locations of the multilayer welding seams strongly depend on the intrinsic weld bead structure along the crack tip. The Master Curve, T0, and Charpy-V, TT47J, based ductile-to-brittle transition temperature progressions through the thickness of the multi-layer welding seam do not correspond to the forecast according to the Russian code.
Thermal annealing at 475°C for 152 h results in the expected decrease of the tensile strength and the shift of Master Curve and Charpy-V based ductile-to-brittle transition temperatures to lower temperatures.
Keywords: reactor pressure vessel, multi-layer welding seam, neutron irradiation, fracture toughness, Master Curve approach, Charpy-V

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Publ.-Id: 20372


Absence of spin dependence in the final state interaction of the d(pol) p --> 3He eta reaction

Papenbrock, M.; Barsov, S.; Burmeister, I.; Chiladze, D.; Dymov, S.; Fritzsch, C.; Gebel, R.; Goslawski, P.; Hartmann, M.; Kacharava, A.; Keshelashvili, I.; Khoukaz, A.; Kulessa, P.; Kulikov, A.; Lorentz, B.; Mchedlishvili, D.; Mersmann, T.; Merzliakov, S.; Mielke, M.; Mikirtychiants, S.; Ohm, H.; Prasuhn, D.; Rathmann, F.; Rausmann, T.; Serdyuk, V.; Ströher, H.; Täschner, A.; Trusov, S.; Valdau, Y.; Wilkin, C.
The deuteron tensor analysing power t_{20} of the d(pol) p --> 3He eta reaction has been measured at the COSY-ANKE facility in small steps in excess energy Q up to Q = 11 MeV. Despite the square of the production amplitude varying by over a factor of five through this range, t_{20} shows little or no energy dependence. This is evidence that the final state interaction causing the energy variation is not influenced by the spin configuration in the entrance channel. The weak angular dependence observed for t_{20} provides useful insight into the amplitude structure near threshold.

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Publ.-Id: 20371


Functional lipid–protein interactions at the single amino acid level in experiment and simulation

Eichler, S.; Sandoval-Perez, A.; Böckmann, R.; Reeves, P.; Fahmy, K.
Membrane proteins such as receptors and channels fulfil vital functions in cellular signalling and ion exchange across cell membranes. Their function involves structural transitions of transmembrane and extramembraneous protein domains. The latter experience aqueous and hydrophobic solvation forces, respectively. We have used time-resolved FTIR spectroscopy coupled to static fluorescence measurements to study how this solvation balance at the membrane water interface affects membrane protein structure. Transmembrane peptides derived from rhodopsin, a prototypical G protein-coupled receptor (GPCRs), exhibit solvent-accessible stretches which couple protonation and hydration to local helical structure: protonation of a conserved cytosolic site in helix 3 (Glu-134) causes side chain partitioning at the water lipid interface [1]. Vice versa, the side chain charge affects structural transitions that are induced by transients (seconds) of interfacial water potential. These local processes depend on the hydrophobic context of the amino acid sequence. Opsin mutants containing amino acid replacements of the same carboxyl side chain also exhibit altered responses of their structure to water potential. The data indicate that the conserved carboxyl in helix 3 of GPCRs is a protonation-controlled hydration site that regulates the partial entry of water at the protein lipid interface, thereby contributing to the free enthalpy difference between active and inactive structures of the receptor. MD simulations agree with the experimental evidence that side chain partitioning can be a driving force for local proton-induced structural changes in membrane proteins.
Keywords: g protein-coupled receptor rhodopsin infrared fluorescence
  • Poster
    Physics of Biological Systems, 24.-27.06.2014, Gif-sur-Yvette, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-20370
Publ.-Id: 20370


"Bumble Bee Jasper" - Jaspis oder nicht?

Götze, J.; Mavris, C.; Möckel, R.
„Bumble Bee Jasper" ist ein attraktiver Schmuckstein, welcher seit einigen Jahren auf dem Markt ist und vor allem durch seine intensive Farbgebung besticht. Dabei handelt es sich jedoch nicht um Jaspis; die Matrix wird durch Calcit aufgebaut. Die gelb-orange Farbe der Bänderung wird durch Realgar hervorgerufen. Zudem wurde in den dunkleren Bereichen Pyrit nachgewiesen, der z.T. in Form von Framboiden vorliegt.
Keywords: Bumble Bee Jasper
  • Mineralien-Welt 25(2014)3

Permalink: https://www.hzdr.de/publications/Publ-20369
Publ.-Id: 20369


Identifying and fixing methodical weaknesses by participating the Reynolds Cup competition in quantitative mineral analysis

Kleeberg, R.; Möckel, R.; Kempe, U.
The Reynolds Cup does not only pose a scientific challenge for mineralogists but offers also an independent sight on the weaknesses of the techniques applied in an individual laboratory. Some of the errors seem to be related to well known problems, but nevertheless these mistakes are common in routine as well as in intensive competitive analytical work. The aim of this talk is to highlight problems of mineral analysis using the data of the 7th Reynolds Cup competition. Some exemplary conclusions will be drawn and ideas for methodic improvements will be drafted.
Qualitative identification of minor non-clay minerals in complex mixtures by X-ray powder diffraction techniques is known to be limited due to low peak intensity and peak overlap. Successful strategies are (i) applying mineral enrichment or even single grain separation for XRD and SEM, (ii) performing low-noise measurements, (iii) applying peak identification from difference plots of preliminary Rietveld refinements, and (iv), more unconventional, running measurements on just coarsely powdered samples to enhance peak intensities. Such techniques were successfully applied to identify of < 1 wt% of tourmaline in samples 1 and 3 as well as for the identification of amphibole and its compositional constraint. On the other hand, SEM-EDX analysis can give valuable information for the presence of phases which could not be identified in any XRD pattern, as demonstrated for apatite and nahcolite.
The correct identification of clay minerals from basal reflections measured on oriented samples seems to be straightforward, but practical limitations arise from the limited amount of sample, complicating the application of standard particle size separation techniques. Nevertheless, it is important to apply standard procedures commonly used in clay mineralogy like controlling the interlayer cation occupation, as demonstrated by the improved detection limit for I/S in sample 2.
In fact all quantification procedures successful in the RC competition are based on XRPD patterns but suffer from profile overlap. Especially, the differentiation of disordered 2:1 minerals needs for improved modeling of the diffraction profiles, including the basal reflections in randomly oriented samples. Some minerals call for the application of other techniques than XRD.
Keywords: Reynolds Cup, X-ray diffraction, analytics
  • Lecture (Conference)
    7th Mid-European Clay Conference, 16.-19.09.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20368
Publ.-Id: 20368


Low mass dielectrons radiated off cold nuclear matter measured with HADES

Lorenz, M.; Agakishiev, G.; Behnke, C.; Belver, D.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Blume, C.; Böhmer, M.; Cabanelas, P.; Chernenko, S.; Dritsa, C.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; González-Díaz, D.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Höhne, C.; Holzmann, R.; Huck, P.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Krizek, F.; Kuc, H.; Kugler, A.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Lopes, L.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.
The High Acceptance DiElectron Spectrometer HADES [1] is installed at the Helmholtzzentrum für Schwerionenforschung (GSI) accelerator facility in Darmstadt. It investigates dielectron emission and strangeness production in the 1-3 AGeV regime. A recent experiment series focusses on medium-modifications of light vector mesons in cold nuclear matter. In two runs, p+p and p+Nb reactions were investigated at 3.5 GeV beam energy; about 9 109 events have been registered. In contrast to other experiments the high acceptance of the HADES allows for a detailed analysis of electron pairs with
low momenta relative to nuclear matter, where modifications of the spectral functions of vector mesons are predicted to be most prominent. Comparing these low momentum electron pairs to the reference measurement in the elementary p+p reaction, we find in fact a strong modification of the spectral distribution in the whole vector meson region.

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Publ.-Id: 20367


In-medium hadron properties measured with HADES

Pietraszko, J.; Agakishiev, G.; Behnke, C.; Belver, D.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Blume, C.; Böhmer, M.; Cabanelas, P.; Chernenko, S.; Dritsa, C.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; González-Díaz, D.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Höhne, C.; Holzmann, R.; Huck, P.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Krizek, F.; Kuc, H.; Kugler, A.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Przygoda, W.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.
Many QCD based and phenomenological models predict changes of hadron properties in a strongly interacting environment. The results of these models differ significantly and the experimental determination of hadron properties in nuclear matter is essential. In this paper we present a review of selected physics results obtained at GSI Helmholtzzentrum für Schwerionenforschung GmbH by HADES (High-Acceptance Di-Electron Spectrometer). The e+e− pair emission measured for proton and heavy-ion induced collisions is reported together with results on strangeness production. The future HADES activities at the planned FAIR facility are also discussed.

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Publ.-Id: 20366


A spherical couette experiment to observe inductionless MHD instabilities at medium Reynolds numbers

Kaplan, E.; Gohl, B.; Seilmayer, M.; Stefani, F.
A liquid metal (GaInSn) spherical Couette flow is being carried out at the Helmholtz-Zentrum in Dresden-Rossendorf to explore a region of Reynolds-Hartmann space in which numerical simulations [1, 2] show hydrodynamically unstable and magnetohydrodynamically unstable regions separated by an isthmus of stability. The region is of further interest because these (inductionless) instabilities have similar signatures to the instabilities found in a larger scale, less thoroughly diagnosed experiment, that were reported as the (induction dependent) Magnetorotational instabiliity (MRI) [3].

[1] Hollerbach, R. (2009). Non-axisymmetric instabilities in magnetic spherical Couette flow. Proc. R. Soc. London A, 465:2003–2013.
[2] Travnikov, V.; Eckert, K.; and Odenbach, S.: (2011). Influence of an axial magnetic field on the stability of spherical Couette flows with different gap widths. Acta Mech, 219:255–268.
[3] Sisan, D. R.; Mujica, N.; Tillotson, W. A.; Huang, Y.-M.; Dorland, W.; Hassam, A. B.; Antonsen, T. M.; and Lathrop, D. P.: (2004). Experimental Observation and Characterization of the Magnetorotational Instability. Phys. Rev. Lett., 93(11):114502.
Keywords: Spherical Couette MHD Instabilities
  • Contribution to proceedings
    9th Pamir International Conference: Fundamental and Applied MHD, 16.-20.6.2014, Riga, Latvia
    Proceedings of the 9th Pamir International Conference, 215

Permalink: https://www.hzdr.de/publications/Publ-20365
Publ.-Id: 20365


Saturation of nonaxisymmetric instabilites of magnetized spherical Couette flow

Kaplan, E. J.
We numerically investigate the saturation of the hydromagnetic instabilities of a magnetized spherical Couette flow. Previous simulations [Hollerbach, 2009] demonstrated region where the axisymmetric flow, calculated from a 2-D simulation, was linearly unstable to nonaxisymmetric perturbations. Full, nonlinear, 3d simulations [Hollerbach 2009, Travnikov 2011] showed that the saturated state would consist only of harmonics of one azimuthal wave number, though there were bifurcations and transitions as nondimensional parameters (Re, Ha) were varied. Here, the energy transfer between different aziumthal modes is formulated as a network. This demonstrates a mechanism or the saturation of one mode and for the suppression of other unstable modes. A given mode grows by extracting energy from the axisymmetric flow, and then saturates as the energy transfer to its second harmonic equals this inflow. At the same time, this mode suppresses other unstable modes by facilitating an energy transfer to linearly stable modes.
Keywords: Spherical Couette Spectral methods in Fluid Mechanics Fluid equation (plasma simulation)

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Permalink: https://www.hzdr.de/publications/Publ-20364
Publ.-Id: 20364


The status of the DRESDYN project

Stefani, F.; Albrecht, T.; Galindo, V.; Gerbeth, G.; Giesecke, A.; Gundrum, T.; Kaplan, E.; Kirillov, O.; Seilmayer, M.; Weber, N.; Weier, T.
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.
  • Open Access Logo Abstract in refereed journal
    Geophysical Research Abstracts 16(2014), EGU2014-10886
  • Lecture (Conference)
    General Assembly of the European Geosciences Union 2014, 27.04.-02.05.2014, Vienna, Austria

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Publ.-Id: 20363


Refined reconstruction of liquid-gas interface structures for oil-gas stratified two-phase flow using wire-mesh sensor

Schleicher, E.; Hampel, U.; Aydin, T. B.; Torres, C. F.; Pereyra, E.; Sarica, C.
Wire-Mesh sensors (WMS), developed at HZDR [1], are potential tools to measure phase fraction distributions quantitatively and visualize two-phase pipe flow phenomena with a very high temporal resolution. They have been extensively applied to a wide range of two-phase gas-liquid flow situations with conducting and non-conducting liquids. However, for very low liquid loadings the state of the art data evaluation algorithms for WMS data suffer under the comparable low spatial resolution and under boundary effects, caused by the flange rings - especially in case of capacitance type WMS. Recently, a pair of capacitance WMS with 32x32 wires has been applied to study interfacial wave characteristics in stratified-wavy configuration for air-oil two-phase flow at Tulsa University Fluid Flow Projects (TUFFP) in a 6-inch ID low pressure flow loop. The superficial liquid and gas velocities for these experiments vary between 9.2 m/s ≤ νSG ≤ 15 m/s and 0.01 m/s ≤ νSL ≤ 0.02 m/s, respectively [2]. To understand the flow phenomena of the stratified wavy structure an accurate reconstruction of the liquid-gas interface is essential. Due to the comparable low spatial resolution of app. 5 mm, the liquid-gas interface recognition has always an unknown uncertainty level since a specific threshold level for the ISO-surface has to be applied. In this work a new algorithm for refined liquid-gas interface reconstruction is introduced, using a-priory information in case of completely stratified flow situations.
Keywords: Keywords Wire-mesh sensor, oil-gas stratified flow, liquid-gas interphase recognition
  • Contribution to proceedings
    5th International Workshop on Process Tomography (IWPT-5), 16.-18.09.2014, Jeju, South Korea
    Proceedings of IWPT-5

Permalink: https://www.hzdr.de/publications/Publ-20362
Publ.-Id: 20362


Experimental results on the azimuthal magnetorotational instability

Seilmayer, M.; Galindo, V.; Gerbeth, G.; Gundrum, T.; Stefani, F.; Gellert, M.; Rüdiger, G.; Schultz, M.; Hollerbach, R.
Hydrodynamically stable rotating flows can be destabilized by an azimuthal magnetic field. The arising non-axisymmetric, or azimuthal magnetorotational instability (AMRI) is important for explaining the angular momentum transport in accretion disks, and plays a central role in the concept of the MRI dynamo. We report the observation of AMRI in a magnetized liquid metal Taylor-Couette experiment, and discuss the surprisingly strong effects of a slight symmetry breaking of the applied magnetic field.
  • Contribution to proceedings
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia
    Proceedings of the 9th PAMIR conference on Fundamental and Applied MHD, Riga, Latvia: University of Latvia, 240-244
  • Lecture (Conference)
    9th PAMIR conference on Fundamental and Applied MHD,, 16.-20.06.2014, Riga, Latvia

Permalink: https://www.hzdr.de/publications/Publ-20361
Publ.-Id: 20361


Experimental Study of Vertical Gas-Liquid Pipe Flow for Annular and Liquid Loading Conditions using Dual Wire-Mesh Sensors

Vieira, R. E.; Parsi, M.; Torres, C. F.; Shirazi, S. A.; Mclaury, B. S.; Schleicher, E.; Hampel, U.
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 co-current annular flow to partially co-current 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 liquid and gas superficial 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, two-phase flow, flow visualization, void fraction, annular flow, liquid loading
  • Contribution to proceedings
    ASME 2014 - 4th Joint US-European Fluids Engineering Summer Meeting, 03.-07.08.2014, Chicago, Illinois, USA
    Proceedings of FEDSM2014: ASME

Permalink: https://www.hzdr.de/publications/Publ-20360
Publ.-Id: 20360


Inductionless magnetorotational instability beyond the Liu limit

Kirillov, O.; Stefani, F.; Fukumoto, Y.
Employing the short wavelength approximation, we develop a unified framework for the investigation of the standard, the helical, and the azimuthal version of the magnetorotational instability (MRI) as well as of the current-driven Tayler instability. We show that the inductionless types of MRI that were previously thought to be restricted to comparably steep rotation profiles extend well to the Keplerian case if only the azimuthal field deviates slightly from its field-free profile.
  • Contribution to proceedings
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia
    Proceedings of the 9th PAMIR conference on Fundamental and Applied MHD, Riga, Latvia: University of Latvia, 273-277
  • Lecture (Conference)
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia

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Permalink: https://www.hzdr.de/publications/Publ-20359
Publ.-Id: 20359


Towards a precession driven dynamo experiment

Stefani, F.; Albrecht, T.; Gerbeth, G.; Giesecke, A.; Gundrum, T.; Steglich, C.; Nore, C.
The most ambitious project within the DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN) is the construction of a precession-driven dynamo experiment. After discussing the scientific background and some results of water pre-experiments and numerical predictions, we focus on the numerous structural and design problems of the machine. We also delineate the progress of the building construction, and the status of some other experiments that are planned in the framework of DRESDYN.
  • Invited lecture (Conferences)
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia
  • Contribution to proceedings
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia
    Proceedings of the 9th PAMIR conference on Fundamental and Applied MHD, Riga, Latvia: University of Latvia, 147-151
  • Magnetohydrodynamics 51(2015)2, 275-284

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Permalink: https://www.hzdr.de/publications/Publ-20358
Publ.-Id: 20358


Characterizing Slug/Churn Flow using Wire-Mesh Sensor

Parsi, M.; Vieira, R. E.; Torres, C. F.; Kesana, N. R.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.
A wire mesh sensor (WMS) is an intrusive device used to investigate multi-phase flows. The WMS measures the instantaneous local electrical conductivity of multiphase flows at different measuring points. There is a significant difference in the electrical conductivity of the employed fluids (in this work air and water, conductivity of water is much higher than that of air). Using the difference in the electrical conductivity, the WMS provides the local void fraction. The WMS utilized in this work includes two identical planes of parallel 16×16 grid of wires. The separation distance between these two planes is 32 mm. The WMS was installed in a 76.2 mm (3-inch) diameter vertical pipe to extract information such as void fraction distribution, structure velocity, and slug/churn flow structure. The superficial gas (air) velocity (VSG) ranged from 10 to 38.4 m/s. Liquid (water) superficial velocities (VSL) of 0.30, 0.46, 0.61 and 0.76 m/s were employed. To study the effects of viscosity on the slug/churn flow structure, Carboxyl Methyl Cellulose (CMC) was added to water to increase the liquid viscosity without altering its density. Each experiment was performed for 60 seconds. An operation frequency for the WMS of 10 kHz (totally 600,000 frames per experiment) was used for all experiments.
Keywords: Wire-Mesh Sensor, muliphase flow, slug flow, churn flow
  • Contribution to proceedings
    ASME 2014 4th Joint US-European Fluids Engineering Summer Meeting, 03.-07.08.2014, Chicago, Illinois, USA
    Proceedings of FEDSM2014

Permalink: https://www.hzdr.de/publications/Publ-20357
Publ.-Id: 20357


Ultrasound Doppler velocimetry for liquid metal batteries

Starace, M.; Weber, N.; Seilmayer, M.; Weier, T.; Stefani, F.; Eckert, S.
The Tayler instability (TI) due to current flow through a liquid GaInSn column is under consideration here. It is a consequence of electric current surpassing a critical value in the order of a few kA and manifests itself as a stack of vortices. Two ultrasound transducers encased in a copper electrode on top of the column were used to measure the vertical component of the liquid metal flow caused by the TI, which is of the order of several mm/s. UDV measurements were only possible after noise suppression mechanisms were added to the experimental setup. The results of the UDV retrievals will be discussed here.
Keywords: Doppler velocimetry, liquid metal batteries, magnetohydrodynamics, Tayler Instability
  • Open Access Logo Contribution to proceedings
    9th PAMIR International Conference Fundamental and Applied MHD, 16.-20.06.2014, Rīga, Latvija
    9th International Conference on Fundamental and applied MHD, Thermo acoustic and Space technologies, 263-267
  • Poster
    9th PAMIR International Conference Fundamental and Applied MHD, 19.06.2014, Rīga, Latvija

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Permalink: https://www.hzdr.de/publications/Publ-20356
Publ.-Id: 20356


Measurement in a downscaled water mockup and numerical simulation for the DRESDYN large scale precession experiment

Gundrum, T.; Steglich, C.; Stefani, F.; Gerbeth, G.; Albrecht, T.; Giesecke, A.
Precession has long been discussed as a complementary energy source of homogeneous dynamo action. In the framework of DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) a precession driven dynamo experiment is under construction. For proper dimensioning of the sodium experiment, measurements at the 1:6 down scaled water mockup are compared to numerical simulations. We present pressure, velocity, and motor power measurements for the water mockup. Furthermore we provide an insight into mechanical engineering aspects of the real sodium experiment.
  • Contribution to proceedings
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia
    Proceedings of the 9th PAMIR conference on Fundamental and Applied MHD, Riga, Latvia: University of Latvia, 152-155
  • Poster
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia

Permalink: https://www.hzdr.de/publications/Publ-20355
Publ.-Id: 20355


Channel flow profile measurements at hot liquid metal loops by the Ultrasound Doppler method

Franke, S.; Eckert, S.; Gundrum, T.; Gerbeth, G.
The successful application of the ultrasound Doppler method at hot channel flows by means of commercial high temperature probes is presented. To obtain sufficient Doppler signals, different problems have to be solved: the transmission of the ultrasonic beam through the channel wall made of stainless steel, the acoustic coupling between the transducer and the channel wall, and the wetting of the inner surface of the wall by the liquid metal, respectively. An integrated sensor concept and method are figured out to meet these requirements. The feasibility of this sensor concept is demonstrated in experiments in metallic melts at temperatures up to 230°C. Measurements are performed at a circular channel flow at the LIMMCAST facility at HZDR applying an eutectic bismuth-tin alloy. In addition, a lead-bismuth flow in a rectangular channel profile measured at the METAL:LIC loop at the Institute of Physics Riga (IPUL) is presented in this report.
Keywords: Flow measurements, ultrasound Doppler method, liquid metal, channel flow, high temperature measurements
  • Open Access Logo Contribution to proceedings
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering (ISUD), 27.-29.08.2014, Strasbourg, Frankreich
    Proceedings of the 9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, Strasbourg: Ubertone, 153-156
  • Lecture (Conference)
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering (ISUD), 27.-29.08.2014, Strasbourg, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-20354
Publ.-Id: 20354


Grain refinement in Al-Si alloys caused by electric current pulses and the role of melt convection

Räbiger, D.; Zhang, Y.; Franke, S.; Galindo, V.; Eckert, S.
The application of the so-called Electric Current Pulse technique (ECP) unlocks a remarkable potential to influence the solidified macrostructure of metals during the solidification process. Many studies have shown that beneficial effects like a distinct grain refinement or the promotion of the transition from a columnar to an equiaxed dendritic growth (CET) can be achieved (see for instance [1-3]). However, the physical mechanism of the grain refinement effect caused by ECP has not been understood so far. Various effects are under discussion, such as the fragmentation of dendrite induced by the electric current [1], the reduction of the nucleation activation energy [2], or the break out and the transport of little grains from the boundary by the periodic Lorentz force [3]. However, the previous studies did not consider the possibility that intense Lorentz forces resulting from the interaction between the strong electrical current and the self-induced magnetic field can create significant melt flows.
This paper presents an experimental study which focuses on the effect of forced melt flow during solidification under the influence of a strong electric current. A first set of experiments was conducted to obtain quantitative information about the isothermal flow field exposed to various electrical parameters like the frequency and amplitude of the current as well as the pulse length. Flow measurements were carried out by the ultrasound Doppler method. In a second step solidification experiments were carried out using a binary Al-Si alloy to verify the effect of certain current parameters on the solidified structure. In our experimental setup the electrical current was supplied through two parallel electrodes at the free surface. The results demonstrate that the grain refining effect observed in our experiments can be ascribed to the forced melt flow driven by the Lorentz force.
Keywords: Electric Current Pulse technique (ECP), grain refinement, flow measurements, ultrasound Doppler method
  • Lecture (Conference)
    4th International Conference on Advances in Solidification Processes, 08.-11.07.2014, Old Windsor, UK

Permalink: https://www.hzdr.de/publications/Publ-20353
Publ.-Id: 20353


Electric current pulse driven liquid metal flow studied by the multi-dimensional Ultrasound Doppler array technique

Franke, S.; Räbiger, D.; Zhang, Y.; Eckert, S.
The electric current pulse (ECP) technique is an effective method of applied MHD to be used for promoting grain refinement in the macrostructure of metal alloys during the solidification process. However, the physical mechanism of the ECP grain refinement technique has not been fully understood until now because of a shortage of knowledge of the forced flow induced by current pulses. In a comprehensive study, experimental investigations were performed considering the configuration of two parallel electrodes immersed through the free surface into a liquid metal column of GaInSn. A melt flow is driven by the Lorentz force resulting from an interaction of the electric current between the electrodes and its induced magnetic field. By means of the ultrasonic Doppler array technique the time-dependent flow field structure induced by DC and pulsed currents under various conditions and parameters was investigated. The measuring results of the study will be presented and discussed.
Keywords: electric current pulse, ultrasound Doppler method, ultrasonic array sensors, liquid metal flow, magnetohydrodynamics
  • Open Access Logo Contribution to proceedings
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering (ISUD), 27.-29.08.2014, Strasbourg, Frankreich
    Proceedings of the 9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, Strasbourg: Ubertone, 65-68
  • Lecture (Conference)
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering (ISUD), 27.-29.08.2014, Strasbourg, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-20352
Publ.-Id: 20352


Investigation of metal sorption behavior of Slp1 from Lysinibacillus sphaericus JG-B53 – A combined study using QCM-D, ICP-MS and AFM

Suhr, M.; Unger, N.; Viacava, K. E.; Günther, T. J.; Raff, J.; Pollmann, K.
Surface layer proteins (S-layer) of Lysinibacillus sphaericus JG-B53 are biological compounds with several bio-based technical applications such as biosorptive materials for heavy and noble metals removal or rare metals recovery from the environment. Despite their well-described applications, a deeper understanding of their metal sorption behavior still remains challenging. The metal sorption stability of gold, palladium, platinum and europium was investigated by ICP-MS, AFM and QCM-D which enables the detection of the sorption in real-time during the in-situ experiments. The results indicate a high binding of Pd, followed by Au, Eu and Pt to the proteins. The comparison between the different methods allowed a deeper understanding of the metal sorption of the isolated S-layer proteins either frees in liquid, adsorbed forming a protein layer or as the bacteria surface.
Keywords: Biosorption, noble metals, bacteria, cells, cell wall components, S-layer, proteins, coatings, polyelectrolytes, QCM-D, ICP-MS, AFM

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Permalink: https://www.hzdr.de/publications/Publ-20351
Publ.-Id: 20351


Quality control in hadrontherapy

Nuclear Physics European Collaboration Committee; Enghardt, W.; Fiedler, F.; Priegnitz, M.
No abstract available
  • Open Access Logo Contribution to external collection
    F. Azaiez, A. Bracco, J. Dobeš, A. Jokinen, G.-E. Körner, A. Maj, A. Murphy, P. Van Duppen: Nuclear Physics for Medicine, Europe: NuPECC, 2014, 978-2-36873-008-9, 84-87

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Permalink: https://www.hzdr.de/publications/Publ-20350
Publ.-Id: 20350


Overview of studies on ultra-short relativistic laser-solid material interactions in HZDR

Huang, L.; Bussmann, M.; Kluge, T.; Metzkes, J.; Zeil, K.; Schramm, U.; Cowan, T. E.
Control of ultra-short relativistic laser-solid material interactions requires modelling of transient, non-equilibrium processes on the atomic scale. We present recent results on ultrafast plasma dynamics for ion heating in buried layer targets [1], ionization dynamics, instabilities and filamentation [2]. In order to connect the plasma dynamics seen in simulations with experiments we will discuss the role of in-situ synthetic diagnostics that mimic experimental diagnostics. As one key example we propose to use X-Ray Free Electron Lasers for probing laser-driven solid-density plasmas by small angle X-ray scattering [3] which allows for femtosecond resolution of transient plasma processes. With these techniques, probing fundamental plasma properties will allow for direct comparison to simulations, challenging state of the art theoretical modeling of collisions, ionization, radiation transport and atomic processes. Increasing the predictive capability of codes will require highly-scalable simulations [4] in order to estimate the influence of these models on the systematic error.

[1] L. G. Huang et al., Phys. Plasmas 20, 093109 (2013)
[2] J. Metzkes et al., New J. Phys. 16, 023008 (2014)
[3] T. Kluge et al., arXiv, 1306.0420 (2013)
[4] M. Bussmann et al., Proceedings of SC’13, 5-1 (2013)
Keywords: laser-solid material interactions,heating,ionization,instabilities and filamentation,XFELs,PIConGPU
  • Invited lecture (Conferences)
    The 8th International West Lake Symposium – Laser Plasma Interactions, 21.-25.04.2014, Hangzhou, China

Permalink: https://www.hzdr.de/publications/Publ-20349
Publ.-Id: 20349


Study of the effects of plasma immersion ion implantation on austenitic stainless steel using E × B fields

Pillaca, E. J. D. M.; Ueda, M.; Reuther, H.; Lepienski, C. M.
The effect of magnetic field enhanced plasma immersion ion implantation (PIII) on SS304 austenitic stainless steel samples has been investigated. Application of magnetic field in PIII process leads to the formation of the crossed E × B field configuration, promoting the increase of the plasma density by electron-neutrals collision. As a result, a high nitrogen ion flux on SS304 sample was achieved. In this experiment, a moderate temperature of about 350 °C was measured after two hour of treatment, discarding the possibility of the formation of chromium nitride. Measurements performed by Auger electron spectroscopy (AES) showed the formation of a nitrogen implanted layer which wasmuch greater than the one obtained by standard PIII (at the same pulsing conditions). Due to that, new peaks in the characteristic profile of X-ray diffraction were observed as consequence of the formation of a new phase (γN phase). It has caused as twice as high improvement in the surface hardness compared to the conventional PIII. Consequently, a substantial reduction in the wear rate was obtained.

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Permalink: https://www.hzdr.de/publications/Publ-20348
Publ.-Id: 20348


P1222 - Vorrichtung und Verfahren zum Schalten hoher Ströme bei der elektromagnetischen Pulsumformung

Dittrich, S.
Gegenstand der Erfindung ist die Verwendung einer Crowbardiode, die zugleich als Zuleitung zwischen Kondensator und Umformspule dient. Diese Vorrichtung ermöglicht die Verwendung verschleißfreier Schalter zur elektromagnetischen Pulsumformung, wobei die sonst nötigen Thyristorparallelschaltungen entfallen können.
  • Patent
    DE102012109413 - Offenlegung 17.04.2014

Permalink: https://www.hzdr.de/publications/Publ-20347
Publ.-Id: 20347


Disposal of nuclear waste in host rock formations featuring high-saline solutions – Implementation of a thermodynamic reference database (THEREDA)

Moog, H. C.; Bok, F.; Marquardt, C. M.; Brendler, V.
Research on the solubility of hazardous substances in saturated salt solutions is an ongoing task in Germany. Several institutions deliver contributions in line with their respective expertise. Scientific studies ultimately yield thermodynamic data which are used for thermodynamic equilibrium modelling. In order to join forces and render thermodynamic equilibrium calculations comparable it was decided to set up a common thermodynamic reference database (THEREDA) from which ready-to-use parameter files for commonly used geochemical codes should be created.

It is the objective of this paper to explain how THEREDA is designed from a data management point-of-view, both conceptionally and technically. Data tables and mutual dependencies are described that allow managing administration of data for aqueous solution, solids, solid solutions, and surfaces. Moreover, quality assurance, traceability, consistency, and efficient, long-term maintenance are major topics shaping the database structure. Finally, robust and flexible human interfaces (to editors as well as end-users) are implemented. This paper is not aimed at giving an account of the model definitions, system selections, evaluation schemes, and thermodynamic data themselves stored in THEREDA, which represent the actual scientific work done by many more scientists within the project. However, this methodological guide to THEREDA has its own merits as it helps to bring thermodynamic data to work. Its specific implementation may serve as a useful example for similar projects going far beyond waste disposal.
Keywords: THEREDA, Thermodynamic Reference Database, Pitzer

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Permalink: https://www.hzdr.de/publications/Publ-20346
Publ.-Id: 20346


SRF Gun – A Candidate for Future CW Linear Accelerators?

Arnold, A.
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.
Keywords: SRF gun, superconducting radio frequency photo electron source, ELBE
  • Invited lecture (Conferences)
    ARD Lunch Seminar, 25.04.2014, Hamburg, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-20345
Publ.-Id: 20345


P1216 - Einrichtung zur Bestimmung der Dosisdeposition von Teilchenstrahlung zur Tumorbehandlung in Gewebe

Schöne, S.; Dersch, U.; Rahm, J.; Komoll, T.
Die Erfindung betrifft Einrichtungen zur Bestimmung und Kontrolle der Dosisdeposition von Teilchenstrahlung zur Tumorbehandlung in Gewebe. Die Einrichtungen zeichnen sich insbesondere dadurch aus, dass die Dosisdeposition während der Tumorbehandlung mit Teilchenstrahlen kontrolliert werden kann. Dazu sind im Strahlengang mindestens ein durch die Dosisdeposition hervorgerufenen prompten Gammastrahlung der die Compton-Streuung verursachender Körper und ein Absorber angeordnet. Der Absorber als Absorberdetektor besteht aus wenigstens einem Szintillator in Form wenigstens eines ersten Kristalls oder in einer Matrix angeordneten ersten Kristallen und Vetodetektoren zum Nachweis der im Körper inkohärent gestreuten Photonen. Der Szintillator ist weiterhin von wenigstens einem zweiten Szintillatorkristall als Vetodetektor umgeben oder umschlossen oder wenigstens bereichsweise begrenzt. Im Strahlengang hinter dem ersten Kristall oder den ersten Kristallen ist mindestens ein weiterer Szintillatorkristall als weiterer Vetodetektor angeordnet. Halbleiterbasierte Photodetektoren sind zum Auslesen an den Szintillator und die Vetodetektoren gekoppelt und mit einem Datenverarbeitungssystem verbunden.
  • Patent
    DE102013212983 - Offenlegung 09.01.2014

Permalink: https://www.hzdr.de/publications/Publ-20344
Publ.-Id: 20344


P1013-2 - Anordnung zur Erzeugung hochenergetischer Protonenstrahlen und deren Verwendung

Herrmannsdörfer, T.; Cowan, T.; Sauerbrey, R.
Die Anmeldung beschreibt eine Anordnung zur Erzeugung hochenergetischer Protonenstrahlen unter Verwendung gepulster Hochfeld-Magnetspulen, die u. a. in der lasergetriebenen Protonenstrahltherapie angewendet werden kann. Wesentlicher Vorteil bei der Bestrahlung mit Protonen gegenüber der Bestrahlung mittels hochenergetischer Photonen ist, dass der Tumor aufgrund des Energieeintrages der Protonen effektiver ausgeschaltet und das den Tumor umgebende gesunde Gewebe effizienter geschützt werden kann. Ein weiterer Vorteil der beschriebenen Anordnung durch den Einsatz hoher gepulster Magnetfelder ist, dass sich Protonenstrahlvorrichtungen unter anderem für medizinische Anwendungen räumlich sehr kompakt als „Tabletop-Geräte”, d. h. unter erheblich reduzierten Investitionsmitteln, produziert werden können. Der benötigte Energieverbrauch zur Erzeugung eines Magnetpulses beträgt lediglich 10 bis 100 kJ. Bei einem Strompreis von ~ 0,1 EUR/kWh fallen dabei pro Puls Kosten in Höhe von 0,0003 bis 0,003 EUR an. Ein weiterer Vorteil der erfindungsgemäßen Anordnung ist die vereinfachte Dosierung der Strahlungsintensität und die genauere Fokussierung des zu bestrahlenden Gebiets. Dadurch werden diese Geräte einfacher bedienbar.
  • Patent
    DE102011052269 - Offenlegung 22.03.2012, Nachanmeldung: WO

Permalink: https://www.hzdr.de/publications/Publ-20343
Publ.-Id: 20343


P1312 - Funktionalisierung von Edelmetallnanopartikeln mit Monomeren und Oligomeren bakterieller Hüllproteine für biosensorische Anwendungen

Raff, J.; Lakatos, M.; Matys, S.; Katzschner, B.; Pompe, W.
Die vorliegende Erfindung betrifft ein Biosensorsystem, basierend auf der Nutzung von Monomeren und Oligomeren bakterieller Hüllproteine für die Beschichtung von Edelmetallnanopartikeln zum Nachweis von Ionenkomplexen in wässrigen Lösungen. Erfindungsgemäß wird ein Verfahren zur Detektion von Ionen und/oder Ionenkomplexen vorgeschlagen, umfassend folgende Schritte: a. Bereitstellung einer Lösung enthaltend Nanopartikel, b. Bereitstellung einer Lösung enthaltend vereinzelte bakterielle Hüllproteine, c. Mischung der beiden Lösungen im Teilchenverhältnis Nanopartikel zu Oligomere 1:1 bis 1:1000, wobei die Nanopartikel mit den bakteriellen Hüllproteinen ummantelt und funktionalisiert werden, d. Inkontaktbringen dieser Mischung mit den zu detektierenden Ionen und/oder Ionenkomplexen, e. Detektion einer Änderung der optischen Eigenschaften dieser Analytlösung. Gegenstand der Erfindung sind auch eine Lösung zur Detektion von Ionen und/oder Ionenkomplexen enthaltend Nanopartikel und vereinzelte bakterielle Hüllproteine, hergestellt aus einer Nanopartikellösung und einer Lösung, enthaltend bakterielle Hüllproteine, nach dem erfindungsgemäßen Verfahren, sowie die Verwendung dieser Lösung zur Detektion von Ionen und/oder Ionenkomplexen.
  • Patent
    DE102013204543 - Erteilung 13.02.2014

Permalink: https://www.hzdr.de/publications/Publ-20342
Publ.-Id: 20342


P1213 - Verfahren und Anlage zur Erzeugung eines monoenergetischen Einzelelektronen-Sekundärstrahles (pro Puls) gleichzeitig zu einem Hochstromstrahl

Michel, P.
Die Erfindung beschreibt eine Anordnung und ein Verfahren zur Erzeugung eines monoenergetischen Einzelelektronen-Sekundärstrahles (pro Puls) gleichzeitig zu einem Hochstromstrahl aus einem Hochstrom-Primärstrahl, wobei der Hochstromstrahl derart geteilt wird, dass ca. 1% als Sekundärstrahl abgespaltet wird. Dazu wird ein Wolframdraht in den Primärstrahl eingebracht. Durch die Abteilung eines Strahls mit geringem mittlerem Strahlstrom wird der gleichzeitige Betrieb beiden Elektronenstrahlen, also ein Parallelbetrieb, ermöglicht.
  • Patent
    DE102012109453 - Offenlegung 10.04.2014

Permalink: https://www.hzdr.de/publications/Publ-20341
Publ.-Id: 20341


P1210 - Metallmembran

Kolitsch, A.; Rogozin, A.; Brinke-Seiferth, S.
Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung einer porösen Metallmembran, eine solche Metallmembran, die Verwendung der Metallmembran wie auch entsprechende Filtermodule. Die Aufgabe besteht in der Herstellung einer sehr dünnen, flexiblen und beständigen Membran mit einer hohen Festigkeit. Dabei soll auf aufwändige Produktionsschritte mit Opferung von Stützschichten oder durch nachträgliches Ablösen einer Ursprungsmembran verzichtet werden. Aufgabe ist zudem, eine Porenstruktur auch zwischen 10 nm und 1 µm zu erreichen und diese je nach Wunsch einfach konfigurieren zu können. Die Porosität soll dabei so hoch sein, dass sie dem Ionenspurverfahren deutlich überlegen ist. Weiterhin soll auf den Einsatz von Chemikalien möglichst verzichtet werden. Zur Lösung der Aufgabe wird ein Verfahren genutzt, was in Grundzügen und abgewandelt aus der Behandlung von Metalloberflächen bekannt ist. Erfindungsgemäß wird das Plasma Immersions Ionen Implantation Verfahren derart genutzt, dass eine sehr dünne Folie aus Metall mit durch eine erste Beschleunigungsspannung beschleunigten Edelgasionen, insbesondere von beiden Seiten, beschossen wird. Dabei wird der Ionenstrom so gewählt, dass es zu einer Übersättigung in der Metallfolie kommt. Dann bilden sich nach Übersättigung durch Bläschen-Segregation Poren, insbesondere unter der Metalloberfläche. Die Öffnung der unter der Metalloberfläche durch Ionenimplantation entstandenen Poren erfolgt durch ein Zerstäuben der Oberfläche mittels Beschuss durch Edelgasionen mit einer zweiten Beschleunigungsspannung, die niedriger ist als die erste Beschleunigungsspannung.
  • Patent
    DE102012105770 - Offenlegung 02.01.2014, Nachanmeldung: WO, CN, EP, US

Permalink: https://www.hzdr.de/publications/Publ-20340
Publ.-Id: 20340


P1208 - Nadelsonde zur Untersuchung von Mehrphasenströmungen und deren Verwendung

Schleicher, E.; Kayser, S.
Die erfindungsgemäße Nadelsonde ermöglicht eine sichere Unterscheidung von mehrphasigen Stoffgemischen, wovon beispielsweise eine Phase gasförmig und zwei Phasen flüssig sind und gasförmige und flüssige Phasen bestimmt werden sollen. Die Nadelsonde umfasst einen metallisierenden Mantel 6 der sich im Untersuchungsmedium befindet, einen im Inneren angeordeten Lichtwellenleiter 1, einer um den Lichtwellenleiter 1 und gegen diesen mittels eines Isolators 4 elektrisch isolierter angeordneten hohlzylinderförmigen Schirmelektrode 2 angeordneten und einer um die Schirmelektrode 2 und gegen diese mittels eines Isolators elektrisch isoliert angeordneten hohlzylinderförmigen Bezugselektrode 3 und einer an die Nadelsonde angeschlossenen Messschaltung, wobei die Messschaltung sowohl die optischen Brechindexeigenschaften im Medium als auch die Leitfähigkeit des Mediums auswertet. Mit Hilfe eines Prototyps wird die Funktionsweise praktisch gezeigt.
  • Patent
    DE102012102870 - Offenlegung 02.10.2013, Erteilung 24.12.2013, Nachanmeldung: CA, EP, US

Permalink: https://www.hzdr.de/publications/Publ-20339
Publ.-Id: 20339


P1207 - Sputterverfahren

Abrasonis, G.; Neidhardt, J.
Die Erfindung betrifft ein Verfahren zur Beschichtung eines Substrats, das einer Abtragsoberfläche 2 eines Targets 1 gegenüber angeordnet und das Beschichtungsmaterial mittels Sputtern unter inertem oder Reaktivgas enthaltendem Prozessgas zerstäubt und auf dem Substrat abgeschieden wird. Um die Sputterraten mit geringerem technischen Aufwand, als aus dem Stand der Technik bekannt, und ohne Verlust in der Einstellbarkeit der Schichteigenschaften erhöhen zu können, erfolgt die Beschichtung von einem Mischtarget 1 mit zumindest einer Targetkomponente A und einer Targetkomponente B, wobei zu Beginn des Sputterverfahrens die Verteilung der Targetkomponenten A und B in einer oberflächlichen Targetschicht 3 der Abtragsoberfläche 2 mittels Hochenergieimpuls-Magnetronsputtern, nachfolgend als HiPIMS bezeichnet, modifiziert wird.
  • Patent
    DE102012209293 - Erteilung 20.06.2013

Permalink: https://www.hzdr.de/publications/Publ-20338
Publ.-Id: 20338


P1206 - Herstellung transparenter leitfähiger Titanoxidschichten, diese selbst und ihre Verwendung

Neubert, M.; Vinnichenko, M.; Kolitsch, A.; Skorupa, W.
Die Anmeldung beschreibt die Herstellung von dotierten Titandioxidschichten als transparentes leitfähiges Oxid (n > 2) und mögliche Einsatzgebiete des transparenten leitfähigen Oxids. Die Vorteile des erfindungsgemäßen Verfahrens sind: die Einsatzmöglichkeit zur Temperung dünner Schichten auf hoch-temperatursensiblen Substraten, der im Vergleich zum Stand der Technik für transparente leitfähige Oxide sehr hohe Brechungsindex von n ≈ 2,4 hergestellt werden können, der Resistenz gegenüber Umwelteinflüssen und der sehr viel kostengünstigeren Herstellung gegenüber zum Beispiel Indiumzinnoxid Durch die Verwendung der Blitzlampenausheilung kann die Herstellung des TCO von einigen Minuten bis Stunden auf wenige Millisekunden reduziert werden. Für die Kristallisation der amorphen Titandioxid-Schichten sind keine Vakuumanlagen notwendig, weil der Kristallisierungsprozess auch unter Normalbedingungen an Luft durchgeführt werden kann. Die kürzere Prozesszeit und der geringere Anlagenbedarf vermindern erheblich die Kosten des Herstellungsprozesses.
  • Patent
    DE102012104374 - Offenlegung 21.11.2013, Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-20337
Publ.-Id: 20337


P1205 - Integrierbare Elektrode mit nichtflüchtig positionierbarer, statisch geladener Grenzschicht, Aufbau und Verwendung

Schmidt, H.; Shuai, Y.; Zhou, S.; Skorupa, I.; Luo, W.; Du, N.
Die Erfindung beschreibt den Aufbau einer in einem Halbleiterbauelement integrierbaren Elektrode mit nichtflüchtig positionierbarer, statisch geladener Grenzschicht. Weiterhin wird die Verwendung der integrierbaren Elektrode in Photobauelementen, Teilchendetektoren, in kapazitiven Energiespeichern und in Logikbauelementen beschrieben.
  • Patent
    DE102012104425 - Offenlegung 12.12.2013, Erteilung 06.03.2014

Permalink: https://www.hzdr.de/publications/Publ-20336
Publ.-Id: 20336


P1204 - Integrierter nichtflüchtiger Analogspeicher

Schmidt, H.; Shuai, Y.; Ou, X.; Zhou, S.; Skorupa, I.; Mayr, C.
Die Erfindung beschreibt den Aufbau eines integrierten nichtflüchtigen Analogspeichers, umfassend eine piezo- oder ferrroelektrische Schicht zwischen mindestens einem Oberflächenkontakt oder einem zugehörigen Gegenkontakt, wobei die Leitfähigkeit der piezo- oder ferroelektrischen Schicht zwischen den Kontakten und/oder unter dem Oberflächenkontakt und/oder unter dem zugehörigen Gegenkontakt modifiziert ist, so dass eine an gegenüberliegenden Kontakten von außen angelegte Spannung nicht gleichmäßig in der piezo- oder ferroelektrischen Schicht abfällt und das elektrische Feld lokal groß/klein ist und ein großes Feld eine Phasenumwandlung der piezo- oder ferroelektrischen Schicht induzieren kann. Weiterhin wird die Integration und Verwendung des nichtflüchtigen Analogspeichers beispielsweise in einer Arraystruktur für neuromorphe Anwendungen oder als Kalibrierelement beschrieben.
  • Patent
    DE102012102326 - Offenlegung 26.09.2013

Permalink: https://www.hzdr.de/publications/Publ-20335
Publ.-Id: 20335


Strong electroluminescence from SiO2-Tb2O3-Al2O3 mixed layers fabricated by atomic layer deposition

Rebohle, L.; Braun, M.; Wutzler, R.; Liu, B.; Sun, J. M.; Helm, M.; Skorupa, W.
We report on the bright green electroluminescence (EL) with power efficiencies up to 0.15% of SiO2-Tb2O3-mixed layers fabricated by atomic layer deposition and partly co-doped with Al2O3. The electrical, EL and breakdown behavior is investigated as a function of the Tb and the Al concentration. Special attention has been paid to the beneficial role of Al2O3 co-doping which improves important device parameters. In detail, it increases the maximum EL power efficiency and EL decay time, it nearly doubles the fraction of excitable Tb3+ ions, it shifts the region of high EL power efficiencies to higher injection currents, and it reduces the EL quenching over the device lifetime by an approximate factor of two. It is assumed that the presence of Al2O3 interferes the formation of Tb clusters and related defects. Therefore, the system SiO2-Tb2O3- Al2O3 represents a promising alternative for integrated, Si-based light emitters.
Keywords: electroluminescence, atomic layer deposition, terbium, MOS structure, decay time

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Permalink: https://www.hzdr.de/publications/Publ-20334
Publ.-Id: 20334


P1121 - Strukturierbares Trägermaterial zur kontrollierten Adsorption und Desorption von Polyelektrolytmaterialien, dessen Herstellung und Verwendung

Schmidt, H.; Baumgart, C.; Müller, M.; Skorupa, I.
Die Erfindung betrifft hinsichtlich der oberflächennahen elektrostatischen Kräfte kontrolliert einstellbare und strukturierbare Trägermaterialen (Carrier) für Polyelektrolytmaterialien, wobei Träger- und Polyelektrolytmaterialien kompatibel zu Materialien sind, die in der Mikroelektronik verwendet werden. Mit dem Trägermaterial kann die Anordnung von Polyelektrolytmaterialien und gegebenenfalls daran adsorbierter Biomoleküle, Biomaterialien, biologische Funktionseinheiten oder Zellen gezielt beeinflusst werden.
  • Patent
    DE102011055115 - Offenlegung 28.02.2013

Permalink: https://www.hzdr.de/publications/Publ-20333
Publ.-Id: 20333


P1120 - Einrichtung und Verfahren zur Erzeugung beschleunigter Teilchen aus Targets zur Strahlentherapie

Karsch, L.; Schürer, M.; Pawelke, J.; Zeil, K.
Die Erfindung betrifft Einrichtungen und Verfahren zur Erzeugung beschleunigter Teilchen aus Targets zur Strahlentherapie. Diese zeichnen sich insbesondere dadurch aus, dass durch Umwandlung eines Targets Teilchen weitestgehend gleicher Energie zur Strahlentherapie erzeugt werden. Dazu ist eine Kammer mit wenigstens einer Vorrichtung zur Zuführung - zum Einen von festen Körpern aus bei Normalbedingungen flüssigen oder gasförmigen Stoffen oder - zum Anderen von in der Kammer in die feste Phase zu überführenden flüssigen oder gasförmigen Stoffen ausgestattet, so dass in der Kammer mindestens ein fester Körper des Stoffes vorhanden ist. Weiterhin weist die Einrichtung mindestens einen Laser - zum Schneiden eines freien Targets aus dem Körper sowie - zum Erzeugen und Beschleunigen von Teilchen aus dem unmittelbar nach dem Schneiden vorhandenen freien Target durch Bestrahlung des freien Targets auf. Unmittelbar nach dem Schneiden entsteht somit ein frei schwebendes oder fallendes Target aus dem Körper, welches die Eigenschaften des Teilchenstrahls wesentlich bestimmt.
  • Patent
    WO2013107860 - Offenlegung 25.07.2013, Nachanmeldung: DE

Permalink: https://www.hzdr.de/publications/Publ-20332
Publ.-Id: 20332


P1115 - Funktionalisierte Festkörperoberflächen von Materialien, Halbleitern und Isolatoren mit Nanostrukturen

Schmidt, H.; Bürger, D.; Skorupa, I.
Die Erfindung betrifft die kontrolliert einstellbare Umverteilung von Fremdatomen während der thermischen Behandlung von Metallen, Halbleitern und/oder Oxiden und die Herstellung von Festkörpern mit einer definierten laterale und vertikalen Verteilung von Fremdatomen für neuartige Materialien, die in der Halbleitertechnologie und in der Transparenten Elektronik verwendet werden. Die funktionalisierten Festkörperoberflächen können gegebenenfalls durch die Umverteilung der Fremdatome völlig neuartige magnetische, optische und Transporteigenschaften als die entsprechenden Festkörperoberflächen ohne Fremdatome aufweisen.
  • Patent
    DE102011055604 - Offenlegung 23.05.2013, Nachanmeldung WO

Permalink: https://www.hzdr.de/publications/Publ-20331
Publ.-Id: 20331


P1112 - Trägermaterial zur Sortierung und Manipulation von Biomaterialien und dessen Herstellung und Verwendung

Schmidt, H.; Baumgart, C.; Skorupa, I.; Helm, M.; Schmidt, O. G.; Müller, M.
Die Erfindung betrifft Trägermaterialen (Carrier) für Biomaterialien, wobei das Material kompatibel zu Materialien ist, die in der Mikroelektronik verwendet werden. Mit dem Trägermaterial kann die Anordnung der Biomaterialien bzw. Biomoleküle gezielt beeinflusst werden
  • Patent
    WO2013029609 - Offenlegung 07.03.2013, Nachanmeldungen: EP, US

Permalink: https://www.hzdr.de/publications/Publ-20330
Publ.-Id: 20330


P1003-Anordnung und Verfahren zur Speicherung elektrischer Energie in elektrochemischen Zellen mit großem Durchmesser und hoher Speicherkapazität

Stefani, F.; Weier, T.; Gerbeth, G.
Die vorliegende Erfindung betrifft eine Anordnung und ein Verfahren zur elektrochemischen Energiespeicherung in elektrochemischen Zellen mit großem Durchmesser und hoher Speicherkapazität. Ein bevorzugtes Einsatzgebiet der Erfindung ist die Nutzung zur Stabilisierung elektrischer Versorgungssysteme. Die Anordnung zur Speicherung elektrischer Energie in einer elektrochemischen Zelle besteht aus der Schichtung eines die Kathode bildenden flüssigen Metalls, eines flüssigen Elektrolyten und eines die Anode bildenden flüssigem Metalls oder Halbmetalls, wobei ein entlang der vertikalen Achse der Anordnung elektrisch isolierendes Innenrohr angebracht ist, dessen Vorhandensein das Auftreten der Tayler-Instabilität oder anderer durch den Stromfluss bedingter Instabilitäten in den Flüssigkeiten und damit deren gegenseitige Durchmischung verhindert. Eine weitere sehr effiziente Möglichkeit zur Erhöhung des maximalen Stroms der Zelle besteht darin, dass ein Strom geeigneter Richtung und Stärke durch das Innere des als hohl angenommenen Innenrohrs geleitet wird.
  • Patent
    DE102010002931 - Offenlegung - 22.09.2011; Nachanmeldung: EP, WO, JP, US

Permalink: https://www.hzdr.de/publications/Publ-20329
Publ.-Id: 20329


P1002-Vorrichtung zur Stromverstärkung für die elektromagnetische Pulsumformung und Verwendung

Dittrich, S.; Herrmannsdörfer, T.
Gegenstand der Erfindung ist die Verwendung einer sättigbaren Induktivität, die zugleich als Zuleitung zwischen Kondensator und Umformspule dient. Diese Vorrichting ermöglicht die Verwendung verschleissfreier Schalter zur elektromagnetischen Pulsumformung. Ein weiterer Vorteil ist die Vermeidung der voluminöse Parallelschaltung von vielen Kabeln.
  • Patent
    DE102010001934: Offenlegung-18.08.2011; Erteilung-22.10.2014; Nachanmeldung EP (validiert in DE, FR)

Permalink: https://www.hzdr.de/publications/Publ-20328
Publ.-Id: 20328


Investigating the selective separation of very fine magnetite and quartz particles using two-liquid flotation

Leistner, T.; Rudolph, M.; Peuker, U. A.
One of the research key aspects of the Helmholtz-Institute Freiberg (HIF), founded in 2011, lies in the further development of efficient beneficiation concepts for disseminated mineral resources, and thus, in processing (ultra)fine particles effectively. In this paper we present results of a fundamental study regarding the selective separation of very fine particles by two-liquid flotation, a flotation-related process using oil droplets instead of air bubbles. Experimental tests use iso-octane and water as the two immiscible liquid phases and fine, below 10 micron respectively, magnetite and quartz particles as the chosen academic solid mixture. The selective accumulation of the solids at the oil/water interface or the transfer into the oil phase, respectively, was investigated depending on several process parameters including pH and surfactant concentration. Furthermore, the selective transfer of magnetite particles from the aqueous with a high yield into the oil phase is demonstrated by means of a modified laboratory-scale flotation column.
  • Poster
    Flotation '13, 18.-21.11.2013, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-20327
Publ.-Id: 20327


Application of a Particle Extraction Process at the Interface of Two Liquids in a Drop Column—Consideration of the Process Behavior and Kinetic Approach

Erler, J. V.; Leistner, T.; Peuker, U. A.
The focus of this research is a new type of particle extraction process for the transfer of magnetite nanoparticles from an aqueous to an immiscible organic phase, directly through the liquid-liquid phase boundary in a drop column. The particle extraction process comprises several advantages such as a minimum amount of stabilizing surfactant, no exposure of the particles to a gas atmosphere and with it the avoidance of sintering by capillary forces and a high particle concentration in the receiving phase as well. The study presents experimental results of the characterization of the process environment and the transfer behavior in a drop column. The solution of surfactant in the continuous phase has been investigated during a particle-free phase transfer experiment including the measurements of the total organic carbon (TOC) content and analysis of the size of the stabilized droplets using the laser diffraction spectroscopy. The determination of the transfer fluxes, the mass flows as well as the yield of transferred magnetite by ICP-OES measurements provide information on the impact of interaction of the elementary processes at the phase boundary. Furthermore, the transfer kinetics of the process is described and compared with calculated theoretical values resulting from a kinetic approach.
Keywords: Magnetite, Nanoparticles, Particle Extraction, Drop Column, Ricinoleic Acid, Oleic Acid

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Permalink: https://www.hzdr.de/publications/Publ-20326
Publ.-Id: 20326


P1110-Thermochromes Einzel- und Mehrkomponentensystem, dessen Herstellung und Verwendung

Kovacs, G.; Schmidt, H.; Skorupa, I.; Bürger, D.; Varun, J.; Slesazeck, S.; Helm, M.
Die Anmeldung beschreibt ein elektrisches Element das Einzel- oder Mehrkomponentensysteme umfasst, wobei die Komponenten des Einzel- und Mehrkomponentensystems teilweise oder vollständig aus thermochromem Material mit anisotropen oder isotropen Dielektrizitätseigenschaften bestehen und in sich strukturiert ausgeführt sein können. Diese Elemente können zum lokalen Heizen, als elektronische oder optische Schalter oder zur Magnetfelderzeugung genutzt werden.
  • Patent
    DE102011056951 - Offenlegung - 27.06.2013; Nachanmeldung: WO

Permalink: https://www.hzdr.de/publications/Publ-20325
Publ.-Id: 20325


P1109-Magnetisierbare Einzel- und Mehrschichtstrukturen, deren Herstellung und Verwendung

Schmidt, H.; Mok, K. M.; Scarlat, C.; Weber, I.
Die Erfindung beschreibt die Auslegung einer Anordnung eines magnetooptischen Systems, bei dem für eine vorgegebene Wellenlänge der einfallenden elektromagnetischen Welle eine bestimmte Polarisation der reflektierten oder transmittierten Welle erreicht wird. Die erfindungsgemäße Anordnung und das Verwendungsverfahren ermöglicht den Einsatz zur Optimierung der Auslegung eines magnetooptischen Systems um die "Ziel"-Polarisation der reflektierten oder transmittierten Welle zu erreichen oder eines magnetooptischen Speichers oder eines Magnetfeldsensors. Weiterhin werden mit der Erfindung der Aufbau eines magnetooptischen Modulators oder eines Multiplexers mit magnetooptischen Komponente ermöglicht.
  • Patent
    DE102011052217 - Offenlegung - 31.01.2013

Permalink: https://www.hzdr.de/publications/Publ-20324
Publ.-Id: 20324


Resonant coherent X-ray diractive imaging in ultra intense laser interaction with matter

Kluge, T.; Gutt, C.; Huang, L. G.; Zacharias, M.; Cowan, T.; Schramm, U.; Bussmann, M.
We describe a novel proposed experimental method for X-ray diagnostics of terawatt class laser - solid interaction. Here resonant bound-bound electron transitions in ions give rise to a diraction pattern that can be used to derive the distribution of ions. The transition energy of a specic transition (e.g. K alpha) is sensible to the degree of ionization, so that an intense mono energetic X-ray beam (XFEL) can be used to select a given in species. The feasibility is studied using quantitative simulations and the great potentials and unique possibilities of this method are highlighted.
Keywords: Laser Ionization Filamentation RCXD resonant coherent XFEL
  • Lecture (Conference)
    DPG-Frühjahrstagung, 30.03.-05.04.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20323
Publ.-Id: 20323


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