Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34106 Publications

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

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.


[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

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

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

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.

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

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

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

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

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

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

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

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

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

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.

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

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

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

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.

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.

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

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)

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

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: 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

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

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

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

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

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

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


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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

Publ.-Id: 20323

Impact of the cation distribution homogeneity on the americium oxidation state in the (U0.54Pu0.45Am0.01)O2-x mixed oxide

Vauchy, R.; Robisson, A.-C.; Martin, P. M.; Belin, R. C.; Aufore, L.; Scheinost, A. C.; Hodaj, F.

The impact of the cation distribution homogeneity of the U0.54Pu0.45Am0.01O2−x mixed oxide on the americium oxidation state was studied by coupling X-ray diffraction (XRD), electron probe micro analysis (EPMA) and X-ray absorption spectroscopy (XAS). Oxygen-hypostoichiometric Am-bearing uranium–plutonium mixed oxide pellets were fabricated by two different co-milling based processes in order to obtain different cation distribution homogeneities. The americium was generated from β− decay of 241Pu. The XRD analysis of the obtained compounds did not reveal any structural difference between the samples. EPMA, however, revealed a high homogeneity in the cation distribution for one sample, and substantial heterogeneity of the U–Pu (so Am) distribution for the other. The difference in cation distribution was linked to a difference in Am chemistry as investigated by XAS, with Am being present at mixed +III/+IV oxidation state in the heterogeneous compound, whereas only Am(IV) was observed in the homogeneous compound. Previously reported discrepancies on Am oxidation states can hence be explained by cation distribution homogeneity effects.

Keywords: EXAFS; XANES; nuclear materials; XRD; EPMA

  • Journal of Nuclear Materials 456(2015), 115-119
    DOI: 10.1016/j.jnucmat.2014.09.014
  • Lecture (Conference)
    Plutonium Futures - The Science 2014, 07.-12.09.2014, Las Vegas Nevada, USA

Publ.-Id: 20322

Electromagnetic flow control in the Ribbon Growth on Substrate (RGS) process

Beckstein, P.; Galindo, V.; Gerbeth, G.

The Ribbon Growth on Substrate (RGS) technology promises a very efficient approach for future photovoltaic (PV) silicon wafer production compared to the majority of commonly accepted processes. Although, for an eventual break-through of this RGS technology a number of remaining problems need to be addressed to increase process stability. We have therefore performed numerical investigations in order to study the influence of the involved AC magnetic fields on the silicon melt during the RGS process.

Keywords: Ribbon Growth on Substrate; Crystal Growth; Numerical Simulation; Magnetic Fields; Fluid Dynamics; ALE

  • Contribution to proceedings
    9th International PAMIR Conference on Fundamental and Applied Magnetohydrodynamics, 16.-20.06.2014, Riga, Latvia
    Proceedings of the 9th International PAMIR Conference on Fundamental and Applied MHD, Volume 2, 196-201
  • Open Access Logo Magnetohydrodynamics 51(2015)2, 385-396
  • Lecture (Conference)
    9th International PAMIR Conference on Fundamental and Applied Magnetohydrodynamics, 16.-20.06.2014, Riga, Latvia


Publ.-Id: 20320

Es war einmal im Weltall: Meteoritengeschichten erzählt von kosmogenen Nukliden

Merchel, S.; Smith, T.; Ott, U.; Beyersdorf-Kuis, U.; Herrmann, S.; Leya, I.; Akhmadaliev, S.; Rugel, G.; Pavetich, S.; Ziegenrücker, R.; Wallner, A.; Fifield, L. K.; Tims, S.; Fimiani, L.; Korschinek, G.

Meteorite sind während ihres Fluges durch das Weltall der kosmischen Strahlung ausgesetzt. Diese induziert Kernreaktionen, deren Produkte die sog. kosmogenen Nuklide (KN) sind. Landet ein Meteorit auf der Erde, stoppt deren Produktion mehrheitlich, während die Radionuklide weiterhin zerfallen. Somit speichern stabile und radioaktive KNs Informationen über Expositionszeit und terrestrische Aufenthaltsdauer von Meteoriten. Wird eine große Zahl von Meteoriten betrachtet, können zudem Rückschlüsse auf die Konstanz der kosmischen Strahlung selbst gezogen werden [1].

An der Beschleunigermassenspektrometrie-Anlage DREAMS (DREsden Accelerator Mass Spectrometry) werden kosmogene Radionuklide wie 10Be, 26Al, 36Cl und 41Ca (t½=0.1-1.4 Ma) bestimmt [2]. Ergänzende Daten von schweren Radionukliden wie 53Mn (t½=3.7 Ma) und 60Fe (t½=2.6 Ma), welche an größeren Tandembeschleunigern in Canberra und München gemessen werden, und stabile Edelgasisotopendaten aus Mainz und Bern, ermöglichen die vollständige Rekonstruktion der Geschichte der Meteorite.

Beispielhaft sind Untersuchungen des Eisenmeteoriten Gebel Kamil, der einen ~45 m großen Krater in Südägypten verursachte. Der Vergleich von KN-Konzentrationen mit Monte-Carlo-Rechnungen zeigt, dass Gebel Kamil als Körper mit einem Radius von 115-120 cm (~50-60 t) für (366 ± 18) Ma der kosmischen Strahlung ausgesetzt war [3].

Ref.: [1] Smith et al., 13th Int. Conf. on AMS. [2] Akhmadaliev et al., NIMB 294 (2013) 5. [3] Ott et al., MAPS, subm.

Keywords: accelerator mass spectrometry; cosmogenic radionuclide; cosmic radiation; meteorite

  • Poster
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten 2014 (SNI2014), 21.-23.09.2014, Bonn, Deutschland

Publ.-Id: 20318

Underground nuclear astrophysics in Europe: a status update

Bemmerer, D.

The cross sections of nuclear reactions taking place in stars and in the Big Bang are generally so low that they can only be measured in the low-background environment of an underground accelerator. The talk will report about progress achieved in the past year at the world’s only such machine, the LUNA 0.4 MV accelerator in Gran Sasso/Italy. The 2H(α,γ)6Li cross section has been measured for the first time directly in the Big Bang energy region, pinning down the amount of primor- dial 6Li. Measurements of the 17O(p,α)14N and 22Ne(p,γ)23Na cross sections important for nucleosynthesis in an astrophysical nova are underway at LUNA, and preliminary data at unprecedented low en- ergies are already available. An activation study of the 40Ca(α,γ)44Ti reaction using offline counting in the Felsenkeller underground labora- tory in Dresden has yielded new and more precise resonance strengths. In order to apply the method of underground nuclear astrophysics to topics such as helium and carbon burning and the neutron sources for the astrophysical s-process, it is necessary to install a higher-energy accelerator underground. The status of the relevant new accelerator projects at Gran Sasso and at Felsenkeller will be reported.

Keywords: Underground nuclear astrophysics; LUNA; Felsenkeller; Hydrogen burning; Astrophysical nova; Big-Bang nucleosynthesis

  • Lecture (Conference)
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 17.-21.03.2014, Frankfurt am Main, Deutschland

Publ.-Id: 20317

S-factor measurement of the 2H(α,γ)6Li reaction at energies relevant for Big-Bang nucleosynthesis

Anders, M.

For about 20 years now, observations of 6Li in several old metal-poor stars inside the halo of our galaxy have been reported, which are largely independent of the stars’ metallicity, and which point to a possible primordial origin. The observations exceed the predictions of the Standard Big-Bang Nucleosynthesis model by a factor of 500. In the relevant energy range, no directly measured S-factors were available yet for the main production reaction 2H(α,γ)6Li, while different theoretical estimations have an uncertainty of up to two orders of magnitude. The very small cross section in the picobarn range has been measured with a deuterium gas target at the LUNA acceler- ator (Laboratory for Underground Nuclear Astrophysics), located deep underground inside Laboratori Nazionali del Gran Sasso in Italy. A beam-induced, neutron-caused background in the γ-detector occurred which had to be analyzed carefully and sub- tracted in an appropriate way, to finally infer the weak signal of the reaction. For this purpose, a method to parameterize the Compton background has been developed. The results are a contribution to the discussion about the accuracy of the recent 6Li observations, and to the question if it is necessary to include new physics into the Standard Big-Bang Nucleosynthesis model.

Keywords: Experimental nuclear astrophysics; Big-Bang nucleosynthesis; Underground accelerator; LUNA; in-beam gamma-ray spectrometry; neutron background

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-042 2013
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 20316

Analyse leichter Elemente mittels Kernreaktionsanalyse an der Ionenstrahlmikrosonde

Freiherr, C.; Eder, F.; Grimm, A.; Merchel, S.; Munnik, F.; Neelmeijer, C.; Renno, A. D.

Die Entwicklung von neuen Analysemethoden ist eine Kernaufgabe des Helmholtz-Institutes Freiberg für Ressourcentechnologie (HIF). Die Methoden dienen der Bewertung und Verbesserung von Technologien zur Erkundung, Gewinnung, Nutzung und Recycling von Rohstoffen entlang der Wertschöpfungskette. Ein etabliertes Verfahren der chemischen Analyse mittels Ionenstrahlen ist die simultane Anwendung verschiedener Methoden wie Rutherford-Rückstreu-Spektrometrie (RBS = Rutherford Backscattering Spectrometry), teilchen-induzierte Röntgen- und Gamma-Emission (PIXE = Particle-Induced X-ray Emission & PIGE = Particle-Induced Gamma Emission) und Kernreaktionsanalyse (NRA = Nuclear Reaction Analysis). Das HIF - in Zusammenarbeit mit dem Ionenstrahlzentrum des Helmholtz-Zentrums Dresden-Rossendorf – führt derartige Messungen mit einem fokussierten Ionenmikrostrahl mit einer lateralen Auflösung von bis zu 3 x 3 µm² durch. Derzeitiger Schwerpunkt dieser Arbeiten ist die quantitative Analyse von Lithium, Bor und Fluor in Mineralen und Erzen. Die isotopensensitive Messung solch leichter Elemente gelingt durch PIGE und NRA. Hierbei werden durch die beschleunigten Projektilionen Kernreaktionen mit den Atomen der Probe induziert und deren Reaktionsprodukte (Photonen bzw. massive Teilchen) detektiert. Ergebnisse der Analyse geeigneter Kernreaktionen gestatten die Darstellung der Elementverteilung in Aufbereitungsprodukten des Lithiumbergbaus, aber auch in hochsensiblen Kunst- und Kulturgutproben.

Keywords: accelerator; PIGE; NRA; ion beam analysis; resources

  • Poster
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten 2014 (SNI2014), 21.-23.09.2014, Bonn, Deutschland

Publ.-Id: 20315

THEREDA - added value to contaminant speciation in brines

Bok, F.; Richter, A.; Brendler, V.

The cooperative project THEREDA establishes a consistent and quality assured database for elements, temperature and pressure ranges relevant for (nuclear) waste disposal. Its focus is on repositories in salt host rocks, thus utilizing the Pitzer model for ion-ion-interactions. Data access is possible via including ready-to-use databases for four common geochemical codes (ChemApp, EQ3/6, Geochemist’s Workbench, PHREEQC). A first data release was issued in 2011; the newest release covers tetra- and hexavalent uranium data for the system of oceanic salts containing Na, K, Mg, Ca, Cl, S, C, and Si.
The NEA Thermodynamic Database (TDB) [1,2] is the major source for thermodynamic data of the aqueous and solid uranium species. Additionally, recently published papers and partially unpublished works from KIT-INE are considered, also addressing Pitzer parameters [3]. Moreover, the THEREDA data release included thermodynamic data of secondary mineral phases formed in the waste material, which were excluded by [1,2] as a result of very stringent quality demands.
The main focus of the THEREDA database is the provision of data for the correct calculation of the solubility of radiotoxic elements in highly saline solutions. Thus, predictive test calculations for the solubility of uranium minerals for both main redox states of uranium (+IV and +VI) were carried out including other Pitzer databases. Modeling results were compared to experimental solubility data from literature references [4–6] and indicate the high quality of the THEREDA data base itself.

Keywords: THEREDA; Thermodynamic Reference Database; Pitzer; uranium

  • Poster
    International Symposium on Solubility Phenomena and Related Equilibrium Processes (ISSP), 21.-25.07.2014, Karlsruhe, Deutschland

Publ.-Id: 20314

High-Speed PIXE – schnelle Multielementanalyse mit Ionenstrahlen

Ziegenrücker, R.; Buchriegler, J.; Hanf, D.; Gutzmer, J.; Merchel, S.; Munnik, F.; Nowak, S. H.; Renno, A. D.; Rugel, G.; Scharf, O.; von Borany, J.

Das Helmholtz-Institut Freiberg für Ressourcentechnologie entwickelt innovative Analysemethoden, um Technologien zur Erkundung, Gewinnung, Nutzung und Recycling von Rohstoffen entlang der Wertschöpfungskette zu bewerten und zu verbessern. Eines dieser neuen Verfahren ist die unikale High-Speed PIXE, eine schnelle ortsaufgelöste teilchen-induzierte Röntgenemission (PIXE = Particle-Induced X-ray Emission). Via High-Speed PIXE wird die chemische Zusammensetzung großflächiger Proben in kurzer Zeit (min-h) bestimmt.

Die elementspezifische Röntgenstrahlung wird mit 3 MeV Protonen aus einem Tandembeschleuniger [1] angeregt. Der ca. 3 mm große Strahl wird mittels eines elektrostatischen Scanningsystems aufgeweitet und regt simultan alle Atome über einer Probenfläche von bis zu 12 x 12 mm² an. Für die ortsaufgelöste Detektion wird eine sog. Röntgenfarbkamera SLcam® [2] verwendet, bestehend aus einer speziellen Röntgenkapillaroptik in Verbindung mit einer pnCCD. Der Detektorchip dieser Kamera ist aus 69696 48x48 µm² großen Pixeln aufgebaut, die alle ein energieaufgelöstes, elementspezifisches und quantifizierbares Röntgenspektrum messen. Es sind somit Elementverteilungsbilder mit einer lateralen Auflösung von 50 µm (in Zukunft mit 6:1-Optik ~10 µm) möglich. Derzeit können alle Elemente von Magnesium bis Uran und zukünftig ab Bor mit Nachweisgrenzen bis in den µg/g-Bereich detektiert werden.

Ref.: [1] Akhmadaliev et al., NIMB 294 (2013) 5. [2] Scharf et al., Anal. Chem. 83 (2011) 2532.

Keywords: accelerator; PIXE; ion beam analysis; X-rays; resources

  • Poster
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten 2014 (SNI2014), 21.-23.09.2014, Bonn, Deutschland

Publ.-Id: 20313

New Insight into the Photochemical Reaction Mechanism of Uranyl Citrate by NMR and DFT

Kretzschmar, J.; Steudtner, R.; Tsushima, S.

A sound understanding of the major reaction mechanisms is crucial to handle uranium containing waste appropriately. This means both the synthesis of unique compounds and the treatment of uranium occurring in or released into the environment. In an environmental context, uranium occurs in two main redox states: mobile U(VI) and immobile U(IV).
Due to both its model character in U(VI) complexation by chelating polycarboxylates and the citrate being a ubiquitous occurring ligand, particularly being important in the citric acid cycle in vivo, the uranyl citrate system itself [1–4] and also its photoreaction [5, 6 and refs. cited therein] is already repeatedly investigated, but still not fully understood.
This investigation provides not only further insight into the U(VI)-citrate complexation, but also a better understanding of the (photo-)redox chemistry of uranium in general.
Here we want to present the reaction pathway of the U(VI) citrate complex photooxidation to its degradation products ketoglutaric acid, acetoacetic acid and acetone with concomitant CO2 formation by several decarboxylation steps and the formation of U(IV). The oxidation state of the latter is indicated by NMR showing 1H chemical shifts > 50 ppm and proven by UV-vis. Moreover, the yielded U(IV) appears as soluble complexes of citrate and its degradation products. The identity of the formed compounds was experimentally proven by one- and twodimensional NMR methods and confirmed by DFT calculations.
The photoreaction starts by irradiating the sample with light from a simple light source such as the sun or a commercial mercury lamp. Interestingly, the initial chemical alteration starts by a single electron transfer from a citrate molecule, being hydrogen bonded to the fifth remaining coordination site not occupied by U(VI)–coordinating citrate. Most likely the intermediate, i.e., not observable U(V) disproportionates fast to U(VI) and the aforementioned U(IV).

[1] R. Bramley, W. F. Reynolds, I. Feldman, J. Am. Chem. Soc. 1965, 87, 3329–3332.
[2] E. Ohyoshi, J. Oda, A. Ohyoshi, Bull. Chem. Soc. Jap. 1975, 48, 227–229.
[3] S. P. Pasilis and J. E. Pemberton, Inorg. Chem. 2003, 42, 6793–6800.
[4] A. Günther, R. Steudtner, K. Schmeide, G. Bernhard, Radiochim. Acta 2011, 99, 535–541.
[5] H. D. Burrows and T. J. Kemp, Chem. Soc. Rev. 1974, 3, 139–165.
[6] A. J. Francis and C. J. Dodge, DAE-BRNS Biennial Symposium on Emerging Trends in Separation Science and Technology (SESTEC) 2008 (BNL-80322-2008-CP).

Keywords: uranium; citrate; photoreaction; reaction mechanism; NMR spectroscopy; DFT calculation

  • Poster
    Advancing the Chemistry of the f-elements: Dalton Discussion 14, 28.-30.07.2014, Edinburgh, United Kingdom

Publ.-Id: 20312

Nuclear Magnetic Resonance Spectroscopy in Rare Earth and Actinide Research

Kretzschmar, J.; Schott, J.; Barkleit, A.; Paasch, S.; Brunner, E.; Scholz, G.; Brendler, V.

Lanthanide complexes have become a useful tool in nuclear magnetic resonance (NMR) spectroscopy within the last 40 years as lanthanide shift reagents (LSR) [1,2]. Since signal separation by LSR has been overcome by elaborate pulse sequences and high-field spectrometers, lanthanides have advanced from auxiliaries to real objects of interest, also as inactive analogues for trivalent actinides in consequence of their similar chemistry.
Here we want to report on interactions and structures of the Ln(III) (La3+, Eu3+ and, where applicable, Y3+) with selected systems, i.e., O-phospho-L-serine, L-lactate [3] and (poly)borates [4]. Both organics are important as model molecules and potential complexing agents found throughout the biosphere and in vivo. Borates occur in remarkable amounts in geological (salt) formations for nuclear waste repositories, but also in boron containing cooling water or borosilicate glass coquilles for spent nuclear fuel.
Among several possible structures, infrared (IR) and NMR measurements, supported by density functional theory (DFT) calculation, revealed that lactate forms Ln(III) (and Am3+) complexes with both the carboxyl and hydroxyl group involved. The phosphorylated amino acid phosphoserine, able to act as a bifunctional ligand, shows Ln(III) complexation by both the phosphate and the carboxylate group as studied by solution and solid state NMR methods. Upon complexation, even at low pH, the respective protons are abstracted, followed by aggregation and precipitation, possibly forming coordination polyhedra rather than 1:1 (chelate) complexes. Polyborates, i.e., triborate and pentaborate form soluble weak aqueous Ln(III) complexes prior to precipitation as white solids, whereas condensation to higher polyborates can be excluded. Two signals in both the 89Y and the 11B NMR spectra probably arise from two coordination sites, which may reflect the polyborate species found in the supernatant solution.

[1] C. C. Hinckley, J. Am. Chem. Soc. 1969, 91, 5160–5162.
[2] O. A. Gansow, M. R. Willcott, R. E. Lenkinski, J. Am. Chem. Soc. 1971, 93, 4295–4297.
[3] A. Barkleit, J. Kretzschmar, S. Tsushima, M. Acker, Dalton Trans. 2014, submitted.
[4] J. Schott, J. Kretzschmar, M. Acker, S. Eidner, M. U. Kumke, B. Drobot, A. Barkleit, S. Taut, V. Brendler, T. Stumpf, Dalton Trans. 2014, accepted.

Keywords: lanthanides; lanthanum; europium; yttrium; phosphorylated amino acid; boric acid; polyborate; NMR spectroscopy

  • Lecture (Conference)
    Rare Earth Research Conference (RERC) 2014, 22.-26.06.2014, Squaw Valley, Lake Tahoe, California, USA

Publ.-Id: 20311

High-fluence Ga-implanted silicon – the effect of annealing and cover layers

Fiedler, J.; Heera, V.; Hübner, R.; Voelskow, M.; Germer, S.; Schmidt, B.; Skorupa, W.

The influence of SiO2 and SiNx cover layers on the dopant distribution as well as microstructure of high fluence Ga implanted Si after thermal processing is investigated. Rapid thermal annealing at temperatures up to 750°C leads to a polycrystalline layer structure containing amorphous Ga-rich precipitates. Already after a short 20 ms flash lamp annealing a Ga-rich interface layer is observed for implantation through the cover layers. This effect can partly be suppressed by annealing temperatures of at least 900°C. However, in this case Ga accumulates in larger, cone-like precipitates without disturbing the surrounding Si lattice parameters. Such a Ga-rich crystalline Si phase does not exist in the equilibrium phase diagram according to which the Ga solubility in Si is less than 0.1 at%. The Ga-rich areas are capped with SiOx grown during annealing which only can be avoided by the usage of SiNx cover layers.

Publ.-Id: 20310

Noise reduction of UDV measurements in liquid metal experiments with high magnetic fields

Seilmayer, M.; Stefani, F.; Gundrum, T.

The last decades have seen a number of liquid metal experiments on the interaction of magnetic fields and the flow of electrically conducting fluids. The opaqueness of liquid metals requires non-optical methods for inferring the velocity structure of the flow. Quite often, such experiments are carried out with very high electrical currents to generate the necessary magnetic fields. Depending on the specific purpose, these currents can reach several kA. The utilized switching mode power supply can then influence seriously the UDV measurements by electromagnetic interference. As an example, a recent experiment on the azimuthal magnetorotational instability (AMRI) has shown that a hydrodynamically stable Taylor-Couette flow becomes unstable under the influence of a high azimuthal magnetic field. An electrical current on the axis of the experiment with up to 20 kA generates the necessary field to destabilize the flow. We will present experimental results on this AMRI experiment carried out at the PROMISE facility with an enhanced power supply. For this system, we discuss the elaborate measures that were needed to obtain a reasonable signal-to-noise ratio of the ultrasonic measurement system. In dependence on various parameter variations, some typical features of the observed instability, such as the energy content, the wavelength, and the frequency are analyzed and compared with theoretical predictions.

Keywords: Taylor-Couette flow; magnetic fields; noise reduction; UDV

  • Contribution to proceedings
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 27.-29.08.2014, Strasbourg, France
    Proceedings of the 9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering

Publ.-Id: 20309

Cytotoxic properties of radionuclide-conjugated Cetuximab without and in combination with external irradiation in head and neck cancer cells in vitro

Eke, I.; Ingargiola, M.; Förster, C.; Kunz-Schughart, L.; Baumann, M.; Runge, R.; Freudenberg, R.; Kotzerke, J.; Heldt, J.; Pietzsch, H.; Steinbach, J.; Cordes, N.

Purpose: Epidermal growth factor receptor (EGFR) is critically involved in progression and therapy resistance of squamous cell carcinoma (SCC). Albeit EGFR targeting could improve the effect of radiotherapy on patients' outcome, the clinical results failed to meet expectations from preclinical studies. In this work, we evaluated the potential of the radionuclide Yttrium-90 (90Y) bound to Cetuximab (90Y-Cetuximab) as novel targeting approach for SCC cells in vitro. Materials and methods: FaDu and A431 cell lines were used. EGFR subcellular localization, clonogenic survival, radiation-induced γH2AX foci and EGFR signaling were examined. Cells were treated with DTPA, DTPA-Cetuximab, 90Y and 90Y-Cetuximab alone or in combination with external X-ray irradiation. Results: Dose- and cell line-dependently, 90Y-Cetuximab mediated a significant reduction in clonogenicity relative to unbound 90Y. Combined 2-Gy external radiation plus 2-Gy equivalent dose of 90Y-Cetuximab was more effective than equivalent doses of 90Y and X-ray radiation. Analogous effects were observed in the number of residual radiation-induced foci. Additionally, EGFR, ERK1/2 and AKT phosphorylation showed alterations upon different treatments. Conclusions: Our findings show that Cetuximab-conjugated 90Y has a significant potential to eradicate human SCC cells. A combination of radioimmunotherapeutic compounds and external radiotherapy might be a promising treatment strategy for clinical application.

Keywords: Targeted radioimmunotherapy; radionuclide; EGFR; Cetuximab

Publ.-Id: 20308

Synthesis and characterization of MnAs and MnP nanoclusters embedded in III–V semiconductors

Khalid, M.; Prucnal, S.; Liedke, M. O.; Gao, K.; Facsko, S.; Skorupa, W.; Helm, M.; Zhou, S.

We report on a systematic study of the synthesis and magnetism of hybrid ferromagnetic semiconductors comprised of MnAs and MnP nanoclusters embedded in GaAs and InP matrices, respectively. Samples were prepared by Mn-ion implantation followed by millisecond-range flash lamp annealing. X-ray diffraction and Auger electron spectroscopy results confirm the formation of MnAs nanoclusters of sizes 150 ± 50 nm. Ferromagnetic properties of MnAs: GaAs (MnP:InP) hybrid systems are studied by magnetic force microscopy and superconducting quantum interference device magnetometry. We show that the magnetization at saturation and the ferromagnetic transition temperature Tc, of MnAs:GaAs depend on the Mn-concentration and on the annealing energy density. While in the case of MnP:InP they are independent of the annealing energy density used. Ferromagnetism in such hybrid systems (ferromagnet–semiconductor) above 300 K makes them very attractive for applications in spintronic devices.

Keywords: magnetic semiconductor; flash lamp annealing; nanoclusters

Publ.-Id: 20305

XRF and PIXE Imaging with few microns Resolution using SLcam® - a Color X-Ray Camera

Nowak, S. H.; Scharf, O.; Bjeoumikhov, A.; von Borany, J.; Buchriegler, J.; Munnik, F.; Renno, A. D.; Ziegenrücker, R.; Soltau, H.; Strüder, L.; Wedell, R.

SLcam® – a full-field energy dispersive portable X-ray camera [1,2], is a combination of a single photon counting CCD with a poly capillary optics objective. The standard CCD matrix consist of 48×48 μm2 pixels sensitive for photons from 3 to 18 keV and has an energy resolution of 156 eV (@Mn Kα). The polycapillary optics is used to achieve the spatial resolution guiding the fluorescence photons from the point of origin to the detection pixel. The device allows fast overview over a large detection area with first results visible almost immediately. A dedicated software enables steering the camera and online visualization of the hyper spectral data cube (x,y,E) by displaying regional spectra, element/line maps and overlay images.
With the use of a sub-pixel resolution algorithm the SLcam® spatial resolution becomes limited by the end diameter of a single capillary channel. A one to one optics, with a field of view of 12 × 12 mm2, can reach a resolution of 20 μm. This optics has an unlimited depth of sharpness and is ideal to visualize uneven objects. With the use of a conical shaped optics allowing 8 times magnification and a field of view of 1.5 × 1.5 mm2 a resolution approaching 1 μm is possible also with laboratory X-ray sources.
We will present recent developments for the SLcam® concerning the sub-pixel resolution, optics aperture, image processing software, and connection to new High-Speed PIXE beamline at Helmholtz-Zentrum Dresden-Rossendorf (HZDR).

[1] O. Scharf, et al., Analytical Chemistry, 83 (7), 2011, 2532-2538.
[2] I. Ordavo, et al., NIM A, 654 (1), 2012, 250-257.

Keywords: SLcam; HSPIXE; High-Speed PIXE; PIXE; Proton; X-Ray; Röntgenstrahlung

  • Lecture (Conference)
    European Conference on X-Ray Spectrometry, 15.-20.06.2014, Bologna, Italien

Publ.-Id: 20304

Numerical simulation of the non-axisymmetric magneto-rotational instability in a dominantly azimuthal magnetic field

Galindo, V.; Stefani, F.; Seilmayer, M.

In a Taylor-Couette experiment on the non-axisymmetric version of the magnetorotational instability, performed by Seilmayer et al. [1], a dominantly azimuthal magnetic field was created by a central vertical copper rod connected to the power source by two horizontal rods at a height of approximately 0.8 m below and above the cylindrical volume. The liquid metal flow in the cylindrical gap between the cylinders was simulated using the OpenFoam library including a Poisson equation for the determination of the induced electric potential. The slight deviation from a purely axisymmetric azimuthal imposed magnetic field turns out to have a surprisingly strong effect on both the critical Hartmann number and the flow structure of the instability.

Keywords: magnetorotational instability; Taylor-Couette

  • Contribution to proceedings
    9th International PAMIR Conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia
    Proceedings of the 9th PAMIR International Conference on Fundamental and Applied Magnetohydrodynamics, Volume I, 200-204
  • Poster
    9th International PAMIR Conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia

Publ.-Id: 20303

novel induction coil sensor system for contactless inductive flow tomography

Ratajczak, M.; Wondrak, T.; Timmel, K.; Stefani, F.; Eckert, S.

We present preliminary results of flow measurements for two different models of continuous casters using the contactless inductive flow tomography. In the first experiment we used a rectangular slab caster with a dominating two-dimensional flow structure under the influence of an electromagnetic brake. For the second experiment a round caster was used in which a magnetic stirrer around the submerged entry nozzle should create an unstable three-dimensional swirling flow.

  • Contribution to proceedings
    9th International PAMIR Conference on Fundamental and Applied MHD, Thermo Acoustic and Space Technologies, 16.-20.06.2014, Riga, Lettland
  • Lecture (Conference)
    9th International PAMIR Conference on Fundamental and Applied MHD, Thermo Acoustic and Space Technologies, 16.-20.06.2014, Riga, Lettland

Publ.-Id: 20302

Simulation of positron energy distribution generated by photons from channeled relativistic electrons on different crystallographic planes and axes of Si, C, Ge and W crystals with Mathematica and Geant 4

Azadegan, B.; Mahdipour, A.; Dabagov, S. B.; Wagner, W.

A non-conventional positron source using the channeling radiation of relativistic electrons on different planes and axes of Si, C, Ge and W crystals which materialize into e+e- pairs in a tungsten amorphous converter is described. In this work we have calculated channeling radiation spectra from different planes and axes of Si, C, Ge and W crystals using the Doyle-Turner approximation for the continuum potentials of crystallographic planes and axes. The dependence of channeling radiation on the incidence angle of electrons are also investigated. The channeling radiation is then impinging on an amorphous tungsten target producing positrons by e+e- pair creation. The simulations are made with our developed Mathematica codes which realy calculate the photon energy spectrum of channeled electrons in the crystal target and Geant4 Monte Carlo code which calculates the the materialization of photons into e+e- pairs in an amorphous W target.

Keywords: channeling radiation; pair creation; positron source

  • Open Access Logo Contribution to proceedings
    5th International Conference on Charged & Neutral Particles Channeling Phenomena (Channeling 2012), 23.-28.09.2012, Alghero, Sardinia, Italy
    Proceedings, 5th International Conference on Charged & Neutral Particles Channeling Phenomena (Channeling 2012), Moscow, Russia: Publishing Office NRNU MEPhI, 978-5-7262-1864-9, 123-136

Publ.-Id: 20301

Multiphase Flow System with Suspended Particles

Yeoh, G. H.; Lucas, D.; Cheung, S. C. P.; Tu, J.

Industrial system that comprises flow of suspended particles in fluid generally requires an understanding of the multiscale physics occurring from micro/nanoscale to mesoscale and eventually to the macroscale phenomena. Because of the inherent complexities that are prevalent in such flow, investigations are certainly at the crossroads of intense research and development in the environment of significant advancements in experimentation as well as in computing power and performance. Much concerted development is nonetheless still needed to gain a better understanding of the complicated physics through the advancement of experimental techniques and computational methodologies and models and to specifically meet the increasing demand of improving efficiency of industrial multiphase flow system. The advances of experimental and modelling investigation of multiphase flow system are presented in this special issue.

Keywords: multiphase; particle; bubble

Publ.-Id: 20300

Tunnel magnetoresistance in double barrier magnetic tunnel junctions with different free layer deposition conditions

Fowley, C.; Feng, W.; Gan, H.; Hübner, R.; Kunz, A.; Lindner, J.; Fassbender, J.; Coey, J.; Deac, A. M.

Double barrier magnetic tunnel junctions (DB-MTJs) allow for operation at higher bias voltages than their single barrier counterparts, but their total tunnelling magnetoresistance (TMR) ratio is still less than in the single barrier case.[1] Here, we prepare CoFeB/MgO-based DB-MTJs with differing free layer deposition conditions. The deposition conditions for the outer CoFeB electrodes and the MgO barriers were kept the same. The middle CoFeB layer was deposited at differing sputtering power densities (from 1.3 to 4.4 W/cm2) to vary the B concentration.[2] Contributions of the upper and lower junction to the total TMR were compared as a function of sputtering power density and annealing temperature. As the sputtering power density of the free layer is increased the TMR response of the upper and lower junctions is opposite, indicating that the growth of both MgO on CoFeB as well as CoFeB on MgO is sensitive to B content. This is attributed to the suppression of B diffusion which is confirmed by transmission electron microscopy analysis. [1] T. Nozaki et al., Appl. Phys. Lett., 86, 082501 (2005). [2] H.D. Gan et al., IEEE Trans. Magn. 47, 1567 (2011).

Keywords: magnetic tunnel junctions; boron diffusion; CoFeB; tunneling magnetoresistance; sputtering power density

  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft, 31.03.-04.04.2014, Dresden, Germany

Publ.-Id: 20299

Numerical modeling of horizontal annular pipe flow using a droplet entrainment model

Höhne, T.

Annular flow occurs in many industrial processes, and is characterized by high gas flow at the center of the pipe and liquid film flow around the pipe wall. Due to the high gas velocity, large shear velocities are induced that result in high interfacial shear stress causing continuous entrainment of liquid droplets into the gas core from the liquid film. When the liquid fraction is small in horizontal annular flow, it is possible to cause an extremely important problem that relates to the damage of heat exchanger tubes, because the drainage of liquid due to gravity, as well as the evaporation, leads to the dry-out of thin liquid film near the top of the tube. Therefore, it is important to accurately predict the circumferential distribution of film thickness in horizontal annular flow. Furthermore the thin water film at the cold wall plays a major role for the heat transfer resistance of the condensation process. For better understanding of condensation heat transfer the film formation mechanism and the film distribution need to be known.
One limitation in current simulating horizontal annular flows is the lack of treatment of droplet formation mechanisms. For self-generating annular flows in horizontal pipes, the interfacial momentum exchange and the turbulence parameters have to be modelled correctly. Furthermore the understanding of the mechanism of droplet entrainment in annular flow regimes for heat and mass transfer processes is of great importance in the chemical and nuclear industry.
The development of general computational fluid dynamics (CFD) models closer to physics and including less empiricism is a long-term objective of the activities of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) research programs. Such models are an essential precondition for the application of CFD codes to the modelling of flow related phenomena in industrial scales. The algebraic interfacial area density model (AIAD), which is one result of these HZDR activities, allows the use of different physical models depending on the local morphology inside a macro-scale multi-fluid framework.
A further step of improvement of modelling interfaces is the consideration of droplet entrainment mechanisms. The proposed entrainment model assumes that due to liquid turbulence the interface gets rough and wavy and forms droplets. The new approach is validated with HZDR annular flow experiments. Important phenomena like the pressure drop, the wave pumping effect, the droplet entrainment rate, the liquid film formation and the transient flow behavior could be calculated, analyzed and compared with the measurement. Verification and Validation is going on – more experimental data are required for the validation.

Keywords: AIAD; HZDR; droplet entrainment

  • Lecture (Conference)
    The 52nd European Two-Phase Flow Group Meeting (ETPFGM2014), 07.-09.05.2014, Dresden, Deutschland

Publ.-Id: 20298

Surface Reaction of SnII on Goethite (α-FeOOH): Surface Complexation, Redox Reaction, Reductive Dissolution, Phase Transformation

Dulnee, S.; Scheinost, A. C.

To elucidate the potential risk of 126Sn migration from nuclear waste repositories, we investigated the surface reactions of SnII on goethite as a function of pH and SnII loading under anoxic condition with O2 level < 2 ppmv. Tin redox state and surface structure were investigated by Sn-K edge X-ray absorption spectroscopy (XAS), goethite phase transformations were investigated by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The results demonstrate the rapid and complete oxidation of SnII by goethite and formation of SnIV 1E and 2C surface complexes. The contribution of 2C complexes increasesd with Sn loading. The SnII oxidation leads to a quantitative release of FeII from goethite at low pH, and to the precipitation of magnetite at higher pH. Based on the XAS data, we developed a surface complexation model using the CD-MUSIC approach, with log K values of 15.5 ±1.4 for the 1E complex and 19.2 ±0.6 for the 2C complex. This model predicts Sn sorption across pH 2 to 12 and at two different Sn loadings (12.5 and 62.5 μmol/g).

Keywords: tin; EXAFS; goethite; sorption; redox; surface complexation; CD-MUSIC

Publ.-Id: 20297

Filament formation by metabolic enzymes is a specific adaptation to an advanced state of cellular starvation

Petrovska, I.; Nüske, E.; Munder, M. C.; Kulasegaran, G.; Malinovska, L.; Kroschwald, S.; Richter, D.; Fahmy, K.; Gibson, K.; Verbavatz, J.-M.; Alberti, S.

One of the key questions in biology is how the metabolism of a cell responds to changes in the environment. In budding yeast, starvation causes a drop in intracellular pH, but the functional role of this pH change is not well understood. Here, we show that the enzyme glutamine synthetase (Gln1) forms filaments at low pH and that filament formation leads to enzyme inactivation. Filament formation by Gln1 is a highly cooperative process, strongly dependent on macromolecular crowding, and involves back-to-back stacking of cylindrical homo-decamers into filaments that associate laterally to form higher order fibrils. Other metabolic enzymes also assemble into filaments at low pH. Hence, we propose that filament formation is a general mechanism to inactivate and store key metabolic enzymes during a state of advanced cellular starvation. These findings have broad implications for understanding the interplay between nutritional stress, the metabolism and the physical organization of a cell.

Keywords: enzyme deactivation; circular dichroism; fluorescence microscopy

Publ.-Id: 20296

Interaction of plutonium and neptunium with magnetite under anoxic conditions: Reduction, surface complexation, and structural incorporation

Scheinost, A. C.; Dumas, T.; Steudtner, R.; Fellhauer, D.; Gaona, X.; Altmaier, M.

For the redox-reactive fission products and actinides Se, Tc, U, and Np, it is assumed that the strongly reducing conditions in deep underground, anoxic nuclear waste repositories will reduce their mobility, since their lower-oxidation states commonly form solids of very low solubility. This is not necessarily the case for Pu, where the hexa- and pentavalent aquo-complexes prevalent at higher pe are replaced at lower pe by a tetravalent solid of low solubility, PuO2, but also by a trivalent aquocomplex at lower pH. FeII-bearing mineral phases, especially those with low bandgap, play an important role in this process, since they are able to catalyse redox reactions at their surface. Magnetite, FeIII2FeIIO4, is an important mineral in this context, since it forms by steel corrosion under anoxic conditions and is also prevalent as geogenic mineral. Therefore, we investigated the reaction of PuV, and in comparison also of NpV, with magnetite in sorption and coprecipiation experiments with X-ray absorption spectroscopy. We found that PuV is indeed reduced to the trivalent oxidation state in the presence of magnetite. The PuIII aquo-complexes are, however, strongly sorbed by forming tridentate surface complexes [1]. PuIII can also be partly incorporated by the structure of magnetite by rapid coprecipitation. During aging, however, it is expelled from the structure and readsorbed at the magnetite surface. This behaviour of Pu is then compared to that of Np.
[1] Kirsch, R., Fellhauer, D., Altmaier, M., Neck, V., Rossberg, A., Fanghänel, T., Charlet, L., and Scheinost, A. C. (2011). Oxidation state and local structure of plutonium reacted with magnetite, mackinawite and chukanovite. Environmental Science & Technology 45, 7267–7274.

Keywords: XAS; EXAFS; XANES; ROBL; Pu; Np; magnetite

  • Invited lecture (Conferences)
    Actinide XAS 2014, 20.-22.05.2014, Schloss Boettstein, Switzerland

Publ.-Id: 20295

FDG PET/MR for lymph node staging in head and neck cancer

Platzek, I.; Beuthien-Baumann, B.; Schneider, M.; Gudziol, V.; Kitzler, H. H.; Maus, J.; Schramm, G.; Popp, M.; Laniado, M.; Kotzerke, J.; van den Hoff, J.

To assess the diagnostic value of PET/MR (positron emission tomography/magnetic resonance imaging) with FDG (18F-fluorodeoxyglucose) for lymph node staging in head and neck cancer.

Materials and Methods
This prospective study was approved by the local ethics committee; all patients signed informed consent. Thirty-eight patients with squamous cell carcinoma of the head and neck region underwent a PET scan on a conventional scanner and a subsequent PET/MR on a whole-body hybrid system after a single intravenous injection of FDG. The accuracy of PET, MR and PET/MR for lymph node metastases were compared using receiver operating characteristic (ROC) analysis. Histology served as the reference standard.

Metastatic disease was confirmed in 16 (42.1%) of 38 patients and 38 (9.7%) of 391 dissected lymph node levels. There were no significant differences between PET/MR, MR and PET and MR (p > 0.05) regarding accuracy for cervical metastatic disease. Based on lymph node levels, sensitivity and specificity for metastatic involvement were 65.8% and 97.2% for MR, 86.8% and 97.0% for PET and 89.5% and 95.2% for PET/MR.

In head and neck cancer, FDG PET/MR does not significantly improve accuracy for cervical lymph node metastases in comparison to MR or PET.

Keywords: PET/MR; head and neck cancer; lymph node metastasis; staging

Publ.-Id: 20294

Self-assembled growth of Ni nanoparticles in amorphous alumina matrix

Jercinovic, M.; Radic, N.; Buljan, M.; Grenzer, J.; Delac-Marion, I.; Kralj, M.; Bogdanovic-Radovic, I.; Hübner, R.; Dubcek, P.; Salamon, K.; Bernstorff, S.

We present the formation of an ordered three-dimensional lattice of Ni nanocrystals in an amorphous alumina matrix by a self-assembly process. The self-assembled growth achieved by single-step magnetron sputtering deposition of a Ni/Al2O3 multilayer is driven by surface morphology effects. The influence of the Ni layer thickness on the Ni particle size, separation, and quality of ordering is examined. The quality of Ni nanoparticles ordering in alumina is compared to their ordering in a silica matrix. The obtained results are important for the understanding of the self-assembly process of metallic particles in amorphous matrices and the applications of such materials.

Keywords: Ni nanoparticles; GISAXS; Self-assembly; Al2O3; Nanocomposites

Publ.-Id: 20293

Compositional Regression: An Overview

Tolosana-Delgado, R.; van den Boogaart, K. G.; Filzmoser, P.; Templ, M.; Hron, K.

A general common statistical task in geosciences is to relate a compositional data set with a set of covariables, a task often dealt with a linear model. Within the Euclidean framework of the Aitchison geometry on the simplex, the sample space of compositional data, such models are easy to construct, fit, visualize, test and use for prediction. This contribution presents in a systematic way the three cases of compositional regression, namely: (1) regression and analysis of the variance with compositional response (composition as Y); (2) regression with compositional explanatory variables (composition as X); and (3) composition-to-composition regression (compositions as both X and Y). The construction of these models is based on common tools of linear algebra: (1) the linear vector operations of the simplex, perturbation and powering; (2) the Aitchison scalar product; and (3) the concept of a linear operator between vector spaces. Fitting and usage for prediction is straightforward to obtain in logratio coordinates of the compositional objects, using classical multivariate regression (cases 1,2 and 3). Visualization of the output is based on matrices of scatterplots or boxplots, the principle of parallel plotting and the usage of all possible pairwise logratios (1 and 2). Visualization of case 3 models is possible through biplots, based on ideas from correspondence analysis. Finally, testing should target hypotheses of subcompositional independence (i.e. that the linear dependence is limited to a given subcomposition), which requires joint testing techniques. Existing multivariate tests can be adapted to the cases 1 and 2, but case 3 is only possible with asymptotic likelihood ratio tests. These concepts are illustrated with data from GEMAS, a soil survey campaign covering whole Europe.

Keywords: compositional regression; robustness; multivariate regression

  • Lecture (Conference)
    IAMG 2014, 16th conference of the international association for mathematical geosciences, 17.-20.10.2014, New Delhi, India

Publ.-Id: 20292

Compositionally compliant contact analysis

Tolosana-Delgado, R.; Mueller, U.; van den Boogaart, K. G.

Contact analysis provides an assessment of the evolution of the average value along boreholes of a given variable at increasing distances from the contact between two facies or domains. The concept is long established in the geostatistical literature and software, albeit for studying the behavior of a single variable. This contribution explores practical ways for studying this transient behavior of a set of variables forming a composition, in such a way that spurious correlation effects are avoided. The main idea is to complement a classical contact analysis of raw percentages with similar diagrams for each possible pairwise logratio of two components, as well as with a contact analysis of the centered-logratio transformed components. This approach is particularly promising when the set of components considered account for a considerable amount of the total mass, or dilution effects are suspected to have affected only a subset of the components. In these scenarios, the classical approach would show an apparent parallel absolute enrichment of the unaffected components, although in reality, the relations between them would have not changed. Thus, a classical assessment would lead the analyst to consider all contacts as “hard”, while in nature a subset of parts would actually be virtually unchanged near the contact. This might be unimportant for simple tonnage or grade calculations (where the raw percentage of value metal present is relevant), but it becomes critical where the relations between several value and/or deleterious elements are necessary, like in complex polymetallic deposits and in geometallurgical studies. These concepts are illustrated with toy examples and data from Murrin Murrin, WA, a Ni-Co laterite deposit where intensive remobilitzation of both value and deleterious components is known to have occurred.

  • Lecture (Conference)
    IAMG 2014, 16th conference of the international association for mathematical geosciences, 17.-20.10.2014, New Delhi, India
  • Contribution to proceedings
    IAMG 2014, 16th conference of the international association for mathematical geosciences, 17.-20.10.2014, New Delhi, India
    Geostatistical and Geospatial Approaches for the Characterization of Natural Resources in the Environment: Challenges,Processes and Strategies Geostatistical, New Dehli: Capital Publishing Company, 978-93-81891-25-4, 6-8

Publ.-Id: 20291

Joint geostatistical simulation of categorical and continuous variables

van den Boogaart, K. G.; Tolosana-Delgado, R.; Lehmann, M.; Mueller, U.

Various geostatistical techniques have been developed for several data scales, like: sequential Gaussian simulation or cumulants for continuous variables, SNESIM and extensions for binary and categorical variables, or lognormal geostatistics for positive variables. However, the same material can often be described at the same time by multiple aspects, like its facies, its composition or its grade in a certain value element. Typically, these different regionalized variables are stochastically mutually dependent, and often observed at different locations. It would thus be interesting to have a joint conditional simulation methodology of all random fields integrating all observations regardless of its scale. We have developed a multipoint-based conditional simulation technique, which allows to simulate dependent random fields of more than one scale. It fits generalized linear models to training images in order to predict the conditional distribution of prediction points to the observed or already simulated data. It then follows an iterative scheme to fill in more points until a complete simulation is obtained. For well-chosen combinations of generalized linear models for all scales we get a simulation system preserving the observations and various properties of the joint distribution in the training image. Training images need to have a separate layer for each of the regionalized variables and typically must be quite large to ensure enough variation of conditioning variables. Training images are sampled with space-filling sequences rather than systematically in order to get reasonable performance. The generalized linear modes are stabilized to avoid specific artifacts generated by complex dependence.

Keywords: multiple point statistics; geostatistics; scales

  • Lecture (Conference)
    IAMG 2014, 16th conference of the international association for mathematical geosciences, 17.-20.10.2014, New Delhi, India
  • Open Access Logo Contribution to proceedings
    Orebody Modelling and Strategic Mine Planning (SMP 2014), 24.-26.11.2014, Perth, Australien
    On the joint multi point simulation of discrete and continuous geometallurgical parameters, Melbourne: AusIMM, 9781925100198, 379-388

Publ.-Id: 20290

Electrical Characterization of a Switchable Molecular Wire via Mechanically Controllable Break Junctions

Sendler, T.; Wieser, M.; Wolf, J.; Huhn, T.; Scheer, E.; Moresco, F.; Grebing, J.; Gemming, S.; Erbe, A.

Molecular electronics has been a eld of big interest for the last years. Using the technique of mechanically controllable break junctions we characterize the Switchable Molecular Wire Oligo(phenylene ethynylene)-embedded Difurylperuorocyclopentenes (SMW) in liquid environment. Via light irradiation the SMW can be switched between two well-defined conductance states. Conductance and hysteresis measurements allow us to identify the two states providing the basis for a comprehensive study of the in situ switching process. Based on the analysis with the transport model assuming transport through a single molecular level, we confirm that a reliable contact of the molecules to the gold contacts is formed and extract the energy of the molecular levels and the coupling constants between molecule and electrodes.

Keywords: Molecular Electronics; MCBJ; Switchable Molecular Wire

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 30.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 20289

Nonlinear spin-wave scattering in a micro-structured magnonic crystal

Obry, B.; Meyer, T.; Pirro, P.; Brächer, T.; Osten, J.; Chumak, A. V.; Serga, A. A.; Fassbender, J.; Hillebrands, B.

We study the nonlinear multi-magnon processes in a micro-structured magnonic crystal consisting of a Ni81Fe19 waveguide, which has been periodically modulated in its saturation magnetization by localized ion implantation. A significant modification of the nonlinear magnon spectrum compared to a reference waveguide is determined, exhibiting a predominant scattering into modes with a frequency at the magnonic band gaps and an enhancement of the nonlinearities for some excitation frequencies. The results prove the feasibility to utilize nonlinear multi-magnon scattering for magnon spintronic applications on the micrometer scale.

Keywords: magnonic crystal; permalloy; magnon process; spintronic

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 30.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 20287

Subnanosecond relaxation of free carriers in compensated n- and p-type germanium

Deßmann, N.; Pavlov, S.; Shastin, V.; Zhukavin, R.; Tsyplenkov, V.; Winnerl, S.; Mittendorff, M.; Abrosimov, N.; Riemann, H.; Hübers, H.-W.

The relaxation of free holes and electrons in highly compensated germanium doped with gallium (p-Ge:Ga:Sb) and antimony (n-Ge:Sb:Ga) has been studied by a pump-probe experiment with the free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf. The relaxation times vary between 20 ps and 300 ps and depend on the incident THz intensity and compensation level. The relaxation times are about five times shorter than previously obtained for uncompensated n-Ge:Sb and p-Ge:Ga. The results support the development of fast photoconductive detectors in the THz frequency range.

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 31.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 20286

Polarization dependence of optical carrier excitation in graphene

Mittendorff, M.; Winzer, T.; Malic, E.; Knorr, A.; Schneider, H.; Helm, M.; Winnerl, S.

We present near-infrared pump-probe measurements to investigate the polarization dependence of optical carrier excitation in graphene. Excitation with linearly polarized radiation leads to an anisotropic distribution of the nonequilibrium carriers in momentum space. This anisotropy can be revealed by the comparison of pump-probe signals for different polarization configurations. In parallel configuration the probe beam has the same polarization with respect to the pump beam, for the perpendicular configuration the polarization of the probe beam is rotated by 90°. The signal amplitude of the parallel configuration is about twice as large as compared to the perpendicular configuration. The initial relaxation process is faster for the parallel polarized probe beam, which leads to identical signals about 150 fs after excitation. At this time delay an isotropic carrier distribution is reached by electron-phonon scattering. These findings are confirmed by microscopic calculations.

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 31.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 20285

Carrier dynamics in graphene under Landau quantization

Wendler, F.; Mittendorff, M.; Winnerl, S.; Helm, M.; Knorr, A.; Malic, E.

We investigate the ultrafast dynamics of low-energetic Dirac electrons in graphene under Landau quantization [1]. In a joint experiment-theory study, we provide calculations based on the density matrix formalism [2] as well as measurements of the relaxation dynamics via differential transmission spectroscopy.

As a consequence of the linear dispersion at the Dirac points, graphene exhibits a non-equidistant Landau level spectrum which allows to address specific transitions by optical pumping. Exploiting this to selectively excite the energetically lowest Landau levels, we employ pump-probe spectroscopy to explore the carrier dynamics in this regime. A surprising sign reversal in differential transmission spectra is observed both in experiment and theory and provides evidence for strong Auger scattering on a picosecond timescale. Our calculations even predict the occurrence of a substantial carrier multiplication in Landau quantized graphene [3].

[1] M. Mittendorff et al., (in preparation).

[2] E. Malic, A. Knorr, Graphene and Carbon Nanotubes: Ultrafast Optics and Relaxation Dynamics, (Wiley-VCH, Berlin, 2013).

[3] F. Wendler, A. Knorr, and E. Malic, (submitted).

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 31.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 20284

A strategy for the qualification of multi-fluid approaches for nuclear reactor safety

Lucas, D.

CFD-simulations for two-phase flows applying the multi-fluid approach are not yet qualified to provide reliable predictions for unknown flows. Among others, one important reason is the missing agreement within the community on closure models to be used. Considering specific phenomena or not, using different models and adjustable constants, most papers presenting a model validation end up with a good agreement with experimental data. However a case by case selection of models and constants does not help to improve the predictive capabilities of such models. For this reason the definition of baseline models considering all known phenomena that could be important is proposed. In such baseline models all parameter have to be defined, i.e. there are no tuning parameters by definition. Such baseline models have to be applied to many experiments with different complexity. Shortcomings of the models and our physical understanding of the complex flow phenomena have to be identified by detailed analyses on the deviations between experimental data and simulation results. A modification of the baseline model will only be done if it bases on physical considerations and improves the overall performance of the model. This requires a huge effort, but seems to be the only way to improve the situation. More complete experimental data are required. Joint activities on the development of such baseline models are desirable. The paper illustrates this strategy by a baseline model for polydisperse bubbly flows which is presently developed at HZDR.

Keywords: CFD; two-phase flow; multi-fluid; bubbly flow; validation

  • Contribution to proceedings
    CFD4NRS-5, Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, 09.-11.09.2014, Zurich, Switzerland
  • Invited lecture (Conferences)
    CFD4NRS-5, Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, 09.-11.09.2014, Zurich, Switzerland

Publ.-Id: 20283

Numerical Simulation for Countercurrent Flows in a Pressurizer Surge Line Model

Murase, M.; Utanohara, Y.; Kusunoki, T.; Lucas, D.; Tomiyama, A.

Numerical simulation was carried out for air-water countercurrent flows in a 1/10-scale model of the pressurizer surge line and
the simulated countercurrent flow limitation (CCFL) values agreed well with the experimental CCFL data.

Keywords: pressurizer surge line; countercurrent flow; numerical simulation; CCFL

  • Contribution to proceedings
    2014 Fall Meeting of Atomic Energy Society of Japan, 08.-10.09.2014, Kyoto, Japan

Publ.-Id: 20282

Terahertz Stimulated Emission from Silicon Doped by Hydrogenlike Acceptors

Pavlov, S. G.; Deßmann, N.; Shastin, V. N.; Zhukavin, R. K.; Redlich, B.; van der Meer, A. F. G.; Mittendorff, M.; Winnerl, S.; Abrosimov, N. V.; Riemann, H.; Hübers, H.-W.

Stimulated emission in the terahertz frequency range has been realized from boron acceptor centers in silicon. Population inversion is achieved at resonant optical excitation on the 1Γ+8 → 1Γ−7, 1Γ−6, 4Γ−8 intracenter transitions with a midinfrared free-electron laser. Lasing occurs on two intracenter transitions around 1.75 THz. The upper laser levels are the 1Γ−7, 1Γ−6, and 4Γ−8 states, and the lower laser level for both emission lines is the 2Γ+8 state. In contrast to n-type intracenter silicon lasers, boron-doped silicon lasers do not involve the excited states with the longest lifetimes. Instead, the absorption cross section for the pump radiation is the dominating factor. The four-level lasing scheme implies that the deepest even-parity boron state is the 2Γ+8 state and not the 1Γ+7 split-off ground state, as indicated by other experiments. This is confirmed by infrared absorption spectroscopy of Si:B.

Publ.-Id: 20281

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