Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32227 Publications
Recycling von Gallium mit Dialyseverfahren
Zeidler, O.;
Der Vortrag geht auf die Probleme des Ga-Recyclings aus Rückständen der GaAs-Wafererzeugung ein. Daraufhin werden ein gesamtheitliches Konzept für die Zusammenlegung der Abwässer sowie ein neu entwickeltes Dialyseverfahren zur weiteren Behandlung dieser vorgestellt. Aktuelle Ergebnisse zur dialytischen Trennung des Galliums von der Hauptverunreinigung Arsen werden ausführlich diskutiert und ein Ausblick auf weitere Untersuchungen gegeben.
  • Invited lecture (Conferences)
    Fachausschusses Sondermetalle der GDMB, 23.-24.10.2013, Reutte, Österreich

Publ.-Id: 19434 - Permalink


Current-driven flow instabilities in large-scale liquid metal batteries, and how to tame them
Weber, N.; Galindo, V.; Stefani, F.; Weier, T.;
The use of liquid metal batteries is considered as one promising option for electric grid stabilisation. While large versions of such batteries are preferred in view of the economies of scale, they are susceptible to various magnetohydrodynamic instabilities which imply a risk of short-circuiting the battery due to the triggered fluid flow. Here we focus on the current driven Tayler instability and give critical electrical currents for its onset as well as numerical estimates for the appearing flow structures and speeds. Scaling laws for different materials, battery sizes and geometries are found. We further discuss and compare various means for preventing the instability.
Keywords: Tayler instability, liquid metal battery, simulation, OpenFOAM

Publ.-Id: 19433 - Permalink


Neogene to Quaternary ash deposits in the Coastal Cordillera in northern Chile: Distal ashes from supereruptions in the Central Andes
Breitkreuz, C.; de Silva, S. L.; Wilke, H. G.; Pfänder, J. A.; Renno, A. D.;
Silicic volcanic ash deposits investigated at 14 localities between 22° and 25°S in the Chilean Coastal Cordillera are found to be the distal ash fall from supereruptions in the Central Andean cordillera several hundreds of kilometers to the east. Depositional textures, modal composition and granulometry of the ashes and tuffs (the latter lithified by halite and gypsum under ultra-arid conditions) allow for a distinction between primary fallout/aeolian deposits (mean 4 - 5 Φ, sorting 1.5 - 2Φ) and secondary deposits that formed by down wash from hill slopes during local rain fall. Primary volcanic components comprise two types of glass shards (with small stretched vesicles and coarse-walled with rounded to elliptic vesicles), and biotite. Previously published studies on ash deposits in the north Chilean Coastal Cordillera reported 14 40Ar/39Ar and K/Ar ages on biotite or sanidine ranging between 6.66 ± 0.13 and 0.6 ± 0.4 Ma. In this project, three 40Ar/39Ar ages on biotite have been determined for samples from the Cuenca del Tiburón, the northern margin of Salar de Navidad and from the Quebrada de la Chimba (3.9 ± 0.1 Ma, 4.1 ± 0.1 Ma, 6.0 ± 0.1 Ma, respectively). The range of the 17 ages coincides with the Late Miocene to Quaternary ages of the major ignimbrite-forming eruptions of the high Andes to the east such as the Altiplano Puna Volcanic Complex (APVC). Electron microprobe data of glass and biotite of the Coastal Cordillera ashes have been compared with data from major ignimbrites of the APVC, of other major Central Andean volcanic fields, and of marine ashes (ODP Leg 201). Additional new biotite microprobe data from three APVC ignimbrites (Pastos Grandes, Pujsa and Guacha) have been included in the present study. Biotite composition of the investigated Coastal Cordillera ashes is similar to those of ignimbrites from the APVC. In particular, based in Fe, Mg, Mn and Ti, distal equivalents of the 3.96 ± 0.08 Ma Atana and/or 4.09 ± 0.02 Ma Puripicar and of the 5.6 ± 0.2 Ma Pujsa and/or the 5.56 ± 0.01 Ma Guacha eruptions can be identified. In addition, based only on age relations, distal ash units of the Pastos Grandes, Tatio and Purico eruptions may be present in the Coastal Cordillera. Composition of glass is comparable to APVC ignimbrite matrix glass and to marine glass, however, significant alkali depletion and SiO2 enrichment is attributed to in situ alteration. The identification of these ashes demonstrates for the first time that the supereruptions in the southern Central Andes gave rise to voluminous ash clouds, most likely co-ignimbrite. The present outcrops represent ash dispersed by easterly winds, consistent with atmospheric models that show favorable westward-directed winds existing in the upper troposphere/stratosphere during the southern summer in the southern Central Andes. This requires that current volume estimates for the major eruptions to be considered minima with a significant augmentation likely.
Keywords: Supereruptions, Central Andes, co-ignimbrite ash clouds, 40Ar/39Ar ages, biotite composition, granulometry

Publ.-Id: 19432 - Permalink


Permanent magnet electron beam ion source/trap systems with bakeable magnets for improved operation conditions
Schmidt, M.; Zschornack, G.; Kentsch, U.; Ritter, E.;
EBIS/T systems provide ions of intermediate up to the highest ion charge states via electron impact ionization by a dense electron beam. In order to produce highly charged ions in an EBIS/T high electron beam densities of several hundred A/cm2 are necessary to realize high ionization factors and compensate for charge destructive processes such as charge exchange etc. The required electron beam compression is realized via an axial magnetic field. Two different EBIS/T magnet design approaches have been established over the past decades: Superconducting magnets with high magnetic fields of several Tesla (significant initial and maintenance costs), Compact permanent magnets with magnetic fields of Sub-Tesla (low initial and maintenance costs). Comparing both solutions shows that the produced ion species and current output of the permanent magnet EBIS/T suits most of the user requirements.
  • Poster
    International Conference on Ion Sources 2013, 09.09.2013, Chiba, Japan
  • Review of Scientific Instruments 85(2014)2, 02B704
    DOI: 10.1063/1.4828723

Publ.-Id: 19430 - Permalink


A Compact, Versatile Low-Energy Electron Beam Ion Source
König, G.; Thorn, M.; Zschornack, J.; Schmidt, A.;
Electron Beam Ion Sources (EBIS) were originally developed to produce highly charged ions (HCI) [1]. For this purpose, high density electron beams at electron beam energies higher than the ionization potential of the desired ion species are required leading to the development of high energy and high current devices working with superconducting magnet coils.
For applications with focus on low and intermediate charge states EBIS/T with high-energy density rare-earth permanent magnets are an economic and compact alternative [2-5]. EBIS/T setups for electron beam energies of 2 keV and below have become more interesting recently. They can be used as sources of electromagnetic radiation in the UV, EUV, and visible light region for calibration purposes, as reference source for emission and absorption spectroscopy with ions of intermediate charge states in astrophysical experiments, as ion sources for research in radiation biology and medicine, and for the diagnostics of plasmas in fusion devices in the low energy range.
  • Poster
    International Conference on Ion Sources 2013, 09.09.2013, Chiba, Japan
  • Review of Scientific Instruments 85(2014)2, 02B703
    DOI: 10.1063/1.4826687

Publ.-Id: 19429 - Permalink


Electron beam ion sources for use in second generation synchrotrons for medical particle therapy
Zschornack, G.; Ritter, E.; Schmidt, M.; Schwan, A.;
Cyclotrons and first generation synchrotrons are the commonly applied accelerators in medical particle therapy nowadays. Next generation accelerators such as Rapid Cycling Medical Synchrotrons (RCMS), direct drive accelerators, or dielectric wall accelerators have the potential to improve the existing accelerator techniques in this field. Innovative accelerator concepts for medical particle therapy can benefit from ion sources which meet their special requirements. In the present paper we report on measurements with a superconducting Electron Beam Ion Source, the Dresden EBIS-SC, under the aspect of application in combination with RCMS as a well proven technology. The measurements indicate that this ion source can offer significant advantages for medical particle therapy. We show that a superconducting EBIS can deliver ion pulses of medically relevant ions such as protons, C4 + and C6 + ions with intensities and frequencies required for RCMS [S. Peggs and T. Satogata, “A survey of Hadron therapy accelerator technology,” in Proceedings of PAC07, BNL-79826- 2008-CP, Albuquerque, New Mexico, USA, 2007; A. Garonna, U. Amaldi et al., “Cyclinac medical accelerators using pulsed C6 +/ H+2 ion sources,” in Proceedings of EBIST 2010, Stockholm, Sweden, July 2010]. Ion extraction spectra as well as individual ion pulses have been measured. For example, we report on the generation of proton pulses with up to 3 × 109 protons per pulse and with frequencies of up to 1000 Hz at electron beam currents of 600 mA.
  • Poster
    International Conference on Ion Sources 2013, 09.09.2013, Chiba, Japan
  • Review of Scientific Instruments 85(2014)2, 02B702
    DOI: 10.1063/1.4827306

Publ.-Id: 19428 - Permalink


Charge Exchange and Energy Loss of Slow Highly Charged Ions in 1 nm Thick Carbon Nanomembranes
Wilhelm, R. A.; Gruber, E.; Ritter, R.; Heller, R.; Facsko, S.; Aumayr, F.;
Experimental charge exchange and energy loss data for the transmission of slow highly charged Xe ions through ultra thin polymeric carbon membranes are presented. Surprisingly, two distinct exit charge state distributions accompanied by charge exchange dependent kinetic energy losses are observed. The energy loss for ions exhibiting large charge loss shows a quadratic dependency on the incident charge state, indicating that equilibrium stopping force values do not apply in this case. Additional angle resolved transmission measurements and reduction of the layer thickness due to a structural phase transition of the membrane lead to the conclusion that a charge state enhanced elastic scattering potential is the main reason for the increase in energy loss rather than charge state enhanced inelastic losses. Thus, the presented results connect scattering experiments of ions on gaseous and on solid targets.
Keywords: slow highly charged ion, HCI, carbon nanomembranes, CNM, stopping power, ion charge state, charge exchange

Publ.-Id: 19427 - Permalink


Bubbly flows with fixed polydispersity: validation of a baseline closure model
Rzehak, R.; Krepper, E.;
For practical applications the Euler-Euler two-fluid model relies on suitable closure relations describing interfacial exchange processes. In dispersed gas-liquid multiphase flow, closures are needed for bubble forces, bubble-induced turbulence, as well as bubble-coalescence and -breakup. The quest for models with a broad range of applicability allowing predictive simulations is an ongoing venture. Reasonable success has been achieved so far for flows that are amenable to a monodisperse approximation for the bubble size which limits the latter to no more than a few mm.
In the present work we extend the validation to flow in which bubbles with a broad distribution of sizes up to ~10mm are present, but the shape of the distribution remains unchanged during the flow development. The existence of such conditions which we term “fixed polydispersity” is deduced from the experimental data. For this kind of situation the complexity of the closure problem is reduced since a balance between bubble-coalescence and -breakup prevails that allows to neglect these processes and simply impose a fixed bubble size distribution. Conclusions towards best practice guidelines for modeling bubbly flows are drawn and needs for further research identified.
Keywords: dispersed gas liquid multiphase flow, Euler Euler two fluid model, fixed polydispersity, closure relations, CFD simulation, model validation

Publ.-Id: 19425 - Permalink


Surface-Mediated Formation of Pu(IV) nanoparticles at the Muscovite-Electrolyte Interface
Schmidt, M.; Lee, S. S.; Wilson, R. E.; Knope, K. E.; Bellucci, F.; Eng, P. J.; Stubbs, J.; Soderholm, L.; Fenter, P.;
The formation of Pu(IV)-oxo-nanoparticles from Pu(III) solutions by a surface- enhanced redox/polymerization reaction at the muscovite (001) basal plane is reported, with a continuous increase in plutonium coverage observed in situ over several hours. The sorbed Pu extends > 70 Å from the surface with a maximum concentration at 10.5 Å and a total coverage of >9 Pu atoms per unit cell area of muscovite (0.77 µg Pu/cm²) (determined independently by in situ resonant anomalous x-ray reflectivity and by ex situ alpha-spectrometry). The presence of discrete nanoparticles is confirmed by high resolution atomic force microscopy. We propose that the formation of these Pu(IV) nanoparticles from an otherwise stable Pu(III) solution can be explained by the combination of a highly concentrated interfacial Pu-ion species, the Pu(III) – Pu(IV) redox equilibrium, and the strong proclivity of tetravalent Pu to hydrolyze and form polymeric species. These results are the first direct observation of such behavior of plutonium on a naturally occurring mineral, providing insights into understanding the environmental transport of plutonium and other contaminants capable of similar redox/polymerization reactions.
Keywords: plutonium – colloids – nanoparticles – X-ray scattering – sorption – crystal truncation rods – resonant anomalous x-ray reflectivity

Publ.-Id: 19424 - Permalink


Die Versorgung mit wirtschaftskritischen Rohstoffen – Eine Ursachensuche und -analyse
Gutzmer, J.; Klossek, A.;
Mineralische sowie insbesondere metallhaltige Rohstoffe sind für die Wertschöpfung aller hochentwickelten Volkswirtschaften von elementarer Bedeutung. Gleichzeitig entstammen diese Rohstoffe letztlich alle der Erdkruste – und damit einem Reservoir von endlicher Größe. Auch wenn die gesamte Größe dieses Reservoirs, auch Geopotenzial genannt, für keinen mineralischen oder metallhaltigen Rohstoff bisher ausgeschöpft wird, so werden die zur Verfügung stehenden Rohstoffkörper (Lagerstätten) zunehmend minderwertiger und teurer in ihrer Erschließung, ihrem Abbau und ihrer Verarbeitung.
Durch den technischen Fortschritt wird sich die Rohstoffabhängigkeit noch weiter verschärfen, wobei insbesondere der Bedarf an bislang technologisch wenig genutzten Metallen dramatisch steigen wird. Wurden in den 1980er-Jahren für die Herstellung eines Computerchips noch zwölf verschiedene Rohstoffe benötigt, sind es heute bis zu sechzig. Prognosen zufolge lassen technischer Wandel und Innovationen den Bedarf an Technologiemetallen wie Gallium (Ga), Neodym (Nd), Indium (In), Germanium (Ge), Scandium (Sc), Platin (Pt) oder Tantal (Ta) bis 2030 auf ein Vielfaches der heutigen Weltproduktionsmenge steigen (Angerer et al. 2009).
Nicht nur technischer Wandel und Innovationen katapultieren den internationalen Rohstoffbedarf nach oben. Auch die steigende Weltbevölkerung gerade in Entwicklungs- und Schwellenländern wie China und Indien oder die Wachstumssprünge in der Wirtschaftsleistung vieler dieser Länder beeinflussen den weltweiten Bedarf nach metallhaltigen Rohstoffen dramatisch. So ist schon jetzt klar, dass die Wirtschaftsmacht China ihren eigenen immens ansteigenden Rohstoffbedarf nicht nur aus eigenen, teilweise bereits heute schon nach außen hin reglementierten Rohstoffvorkommen decken kann, sondern bei weiter steigendem volkswirtschaftlichem Wachstum alle Kategorien mineralischer und metallischer Rohstoffe in zunehmendem Maße auch von außen zukaufen muss.
In letzter Instanz führen diese globalen Entwicklungen zu Lieferrestriktionen, sich verteuernden Rohstoffen und zu Rohstoffknappheit. Rohstoffe, deren Verfügbarkeit für Zukunftstechnologien gesichert werden muss, die eine große Hebelwirkung für die Wirtschaft haben und von denen bereits ein relativ geringer Mengeneinsatz damit zu einer hohen zusätzlichen Wertschöpfung in Hochtechnologiebereichen beiträgt, werden als „wirtschaftsstrategische“ Rohstoffe bezeichnet (BMBF 2012). Rohstoffe, deren Versorgungslage sich für die Wirtschaft mittel- bis langfristig als kritisch erweisen könnte, sind als „kritisch“ zu bezeichnen (ebd.), sodass die vorliegende Studie in Anlehnung an beide Definitionen von „wirtschaftskritischen Rohstoffen“ spricht. Was genau macht jedoch einige der bereits genannten Rohstoffe wirtschaftskritischer als andere, und wie kann auf unterschiedlichen gesellschaftlichen Ebenen mit dieser Rohstoffkritikalität umgegangen werden? Dieser Frage widmet sich die vorliegende Studie.
Keywords: criticality of mineral raw materials
  • Book chapter
    Kausch, P., Bertau, M., Gutzmer, J., Matschullat, J.: Strategische Rohstoffe — Risikovorsorge, Heidelberg: Springer Spektrum, 2014, 978-3-642-39704-2, 59-74

Publ.-Id: 19423 - Permalink


Sensitivity study on Xe depletion in the high burn-up structure of UO2
Holt, L.; Schubert, A.; van Uffelen, P.; Walker, C. T.; Fridman, E.; Sonoda, T.;
Experimental results for the Xe depletion in high burn-up fuel are presented from the High Burnup Rim Project (HBRP). In this project a number of UO2 fuel discs with 235U enrichment of 25.8 wt% were irradiated. The Xe content of the fuel discs was analysed by means of electron probe microanalysis (EPMA) with respect to burn-up and temperature. The influence of the burn-up and temperature on Xe concentration was investigated using a multi-physics approach involving various simulation tools. The temperature influence was modelled by the means of the temperature dependent effective burn-up. Good agreement was found between the modelled temperature threshold of the effective burn-up and the experimental temperature threshold between un- and restructured fuel in the HBRP. However, a systematic difference is observed between the onset burn-up derived from the Xe measurements in highly enriched discs such as those of HBRP and the corresponding values derived from irradiated Light Water Reactor (LWR) fuel rods and reported in the open literature. A sensitivity study identified the neutron flux spectrum and the fission product yields as main reasons for the observed differences.

Publ.-Id: 19422 - Permalink


Calculation of effective point kinetics parameters in the Serpent 2 Monte Carlo code
Leppanen, J.; Aufiero, M.; Fridman, E.; Rachamin, R.; van der Marck, S.;
This paper presents the methodology developed for the Serpent 2 Monte Carlo code for the calculation of adjoint-weighted reactor point kinetics parameters: effective generation time and delayed neutron fractions. The calculation routines were implemented at the Politecnico di Milano, and they are based on the iterated fission probability (IFP) method. The developed methodology is mainly intended for the modeling of small research reactor cores, and the results are validated by comparison to experimental data and MCNP5 calculations in 31 critical configurations.
Keywords: Serpent, Monte Carlo, adjoint-weighted time constants, effective generation time, effective delayed neutron fraction

Publ.-Id: 19421 - Permalink


Surface patterning of GaAs under irradiation with very heavy polyatomic Au ions
Bischoff, L.; Böttger, R.; Heinig, K.-H.; Facsko, S.; Pilz, W.;
Self-organization of surface patterns on GaAs under irradiation with very heavy polyatomic Au ions has been found. The patterns depend on the ion mass, the substrate temperature as well as the incidence angle of the ions. At room temperature, under normal incidence the surface remains flat, whereas above 200 °C nanodroplets of Ga appear after irradiation with monatomic, biatomic as well as triatomic Au ions of kinetic energies in the range of 10 to 30 keV per atom. In the intermediate temperature range of 100 to 200 °C meander- and dot-like patterns form, which are not related to Ga excess. Under oblique ion incidence up to 45° from the surface normal, at room temperature the surface remains flat for mon- and polyatomic Au ions. For bi- and triatomic ions, in the range 60° ≤ a ≤ 70° ripple patterns have been found, which become shingle-like for a ≥ 80°, whereas the surface remains flat for monatomic ions.
Keywords: surface morphology, ripples, nanodots, FIB, polyatomic ions, GaAs, Au

Publ.-Id: 19420 - Permalink


Modelling of Nuclear Fuel under Accident Conditions by means of TRANSURANUS
van Uffelen, P.; van de Laar, J.; Schubert, A.; Di Marcello, V.; Vlahovic, L.; Holt, L.;
The TRANSURANUS fuel performance code, which is developed at the JRC-ITU and in collaboration with many partner institutes since more than three decades, has been adapted in order to be able to simulate design basis accident (DBA) conditions.

In a first step, the developments and associated validation work will be summarised for LOCA conditions. This part includes modifications in the model for large strains, for the crystallographic phase transition in zircaloy, and for burst release and large cladding deformations.

In a second step, the ongoing work for simulations of RIA conditions will be outlined that include the model for the plenum temperature, along with the separate effect studies and detailed model developments made in parallel by means of multi-scale and multi-physics tools for the high burnup structure.

Finally, the perspectives of model developments and needs for further verification and validation in the frame of international benchmark exercises dedicated to DBA simulations and the first phase of a sever accident, i.e. when the cylindrical fuel rod geometry is preserved, will be presented for discussion.
  • Contribution to proceedings
    Technical meeting on modelling of water-cooled fuel including design basis and severe accidents, 28.10.-01.11.2013, Chengdu, China
    Proceedings of the technical meeting on modelling of water-cooled fuel including design basis and severe accidents
  • Lecture (Conference)
    Technical meeting on modelling of water-cooled fuel including design basis and severe accidents, 28.10.-01.11.2013, Chengdu, China

Publ.-Id: 19419 - Permalink


Inclined rotating fixed bed reactors as a new reactor concept for process intensification
Härting, H.-U.; Schubert, M.;
After a short introduction about the research activities of the Experimental Thermal Fluid Dynamics Department the new reactor concept "inclined rotating fixed bed reactor" is presented.
The idea and the benefits as well as selected aspects of the design are explained in detail.
Selected results from hydrodynamic experiments coupled with tomographic imaging are presented.
Furthermore, the evaluation of the new reactor concept by gas-liquid mass transfer studies is presented.
Keywords: process intensification, fixed bed reactor, inclination, rotation, tomographic imgaging
  • Invited lecture (Conferences)
    Autumn Session PINNL 2013, 13.11.2013, Amersfoort, Nederland

Publ.-Id: 19418 - Permalink


Lambda hyperon production and polarization in collisions of p (3.5 GeV) + Nb
Agakishiev, G.; Arnold, O.; Balanda, A.; Belver, D.; Belyaev, A. V.; Berger-Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Chernenko, S.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O. V.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Göbe, K.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kornakov, G.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y. V.;
Results on Lambda hyperon production are reported for collisions of p (3.5~GeV) + Nb, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18 at GSI Helmholtzzentrum for Heavy-Ion Research, Darmstadt. The transverse mass distributions in rapidity bins are well described by Boltzmann shapes with a maximum inverse slope parameter of about 90\,MeV at a rapidity of y=1.0, i.e. slightly below the center-of-mass rapidity for nucleon-nucleon collisions, y_{cm}=1.12. The rapidity density decreases monotonically with increasing rapidity within a rapidity window ranging from 0.3 to 1.3. The Lambda phase-space distribution is compared with results of other experiments and with predictions of two transport approaches which are available publicly. None of present versions of the employed models is able to fully reproduce the experimental distributions, i.e. in absolute yield and in shape. The present high-statistics data allow for a genuine two-dimensional investigation as a function of phase space of the self-analyzing Lambda polarization in the weak decay Lambda\rightarrow p pi^-. Finite negative values of the polarization in the order of 5-20 % are observed over the entire phase space studied. The magnitude of the polarization increases almost linearly with increasing transverse momentum, {\cal P}(p_t) = (-0.19 \pm 0.02)~(GeV/c)^{-1}p_t, and increases with decreasing rapidity for y < 0.8.

Publ.-Id: 19417 - Permalink


Laser cooling of stored relativistic C3+ ions at the ESR
Winters, D.; Clark, C.; Dimopoulou, C.; Giacomini, T.; Kozhuharov, C.; Kühl, T.; Litvinov, Y.; Lochmann, M.; Nörtershäuser, W.; Nolden, F.; Sanchez, R.; Sanjari, S.; Steck, M.; Stöhlker, T.; Ullmann, J.; Beck, T.; Birkl, G.; Rein, B.; Tichelmann, S.; Walther, T.; Ma, X.; Wen, W.; Yang, J.; Zhang, D.; Schramm, U.; Seltmann, M.; Siebold, M.; Bussmann, M.;
After several years of planning, development, and tests, in August 2012 a new laser cooling experiment (E089) has been performed at the ESR. One essential goal of this beamtime was to demonstrate that the initially ‘hot’ ions can be collected inside the rf-bucket using just the laser, i.e. without changing the bucket frequency and without electron cooling. This scheme can namely be used to cool relativistic ion beams in future storage rings and synchrotrons, such as the HESR and SIS-100 at FAIR.
Keywords: laser cooling, esr, storage ring, ion beam, bunching, relativistic
  • Open Access LogoContribution to external collection
    Katrin Große: GSI Scientific Report 2012 - GSI Report 2013-1, Darmstadt: GSI Helmholtzzentrum für Schwerionenforschung GmbH, 2013, 313

Publ.-Id: 19416 - Permalink


Vacuum birefringence – a feasibility study
Schlenvoigt, H.-P.; Cowan, T. E.; Heinzl, T.; Sauerbrey, R.; Schramm, U.; Schroer, C.; Uschmann, I.;
We consider an experiment to test nonlinear QED by light-by-light-scattering: An intense optical laser pulse generates in a perfect vacuum a field which induces birefringence of the vacuum. That birefringence is measured with an XFEL beam and state-of-the-art X-ray polarimetry. We calculate for planned facilitites the phase shift, ellipticity and photon numbers per shot. In addition, we consider shot-to-shot fluctuations and beam-arrival-jitter, and derive required integration times.
  • Poster
    User workshop on High-Power Lasers, 01.-02.10.2013, Menlo Park, California, USA

Publ.-Id: 19415 - Permalink


Development of a PET-Tracer for Phoshodiesterase 10A
Wagner, S.; Scheunemann, M.; Brust, P.;
Phosphodiesterases (PDEs) are a class of enzymes heavily involved in cellular signaling by inactivating the second messenger cAMP and cGMP. So far, 11 different PDE families are known, of which one, the dual substrate enzyme PDE10A is abundantly expressed in the striatum. Since this brain region is thought to be involved in the pathomechanism of schizophrenia, PDE10A inhibition represents an approach in the treatment of this disease. In-vivo imaging via positron emission tomography (PET) of PDE10A would allow investigating the enzyme and its expression in neuropathological processes. Therefore our group is focused on the development of a F18-labeled PET tracer for PDE10A. Recently reported 1-arylimidazoquinoxaline inhibitors have been chosen as lead structure.
Based on this scaffold we synthesized a series of new fluorinated compounds as possible PET tracer candidates for PDE10A. To enable an easy F-18 incorporation, fluorine was chosen to be in the 2-position of the pyridine ring. The key step to introduce these different 2-fluoropyridines is the Pd-catalyzed Suzuki-coupling. 2-Fluoropyridines can be localized in two different positions of the arylimidazoquinoxaline scaffold leading to three different types of inhibitors (type A, type B, type C). The inhibitory potency of these compounds was tested towards human, recombinant PDE10A and other PDE-families. All synthesized compounds showed a high inhibitory potency. The most selective inhibitor was chosen to be further developed as PET tracer for PDE10A.
  • Poster
    12th Leipzig Research Festival for Life Sciences 2013, 19.12.2013, Leipzig, Deutschland
  • Contribution to proceedings
    12th Leipzig Research Festival for Life Sciences 2013, 19.12.2013, Leipzig, Deutschland
    Leipzig Research Festival for Life Sciences 2013, Leipzig: Universität Leipzig, 978-3-9810760-9-7

Publ.-Id: 19414 - Permalink


Inelastic scattering of fast neutrons from excited states in 56Fe
Beyer, R.; Schwengner, R.; Hannaske, R.; Junghans, A.; Massarczyk, R.; Anders, M.; Bemmerer, D.; Ferrari, A.; Kögler, T.; Röder, M.; Schmidt, K.; Wagner, A.;
We have studied the inelastic scattering of neutrons from 56Fe in the energy range from about 0.5 to 10 MeV at the photoneutron source nELBE. The neutron energies were determined on the basis of a time-of-flight measurement. Gamma-ray spectra were measured with an HPGe detector defining the energy resolution to about 10 ns. We deduced scattering cross sections for the 2+, 4+ and 6+ yrast states in 56Fe by applying feeding corrections. The gross features of the total scattering cross section can be described within the statistical code Talys, whereas the scattering cross sections of individual states represent new information that may be used to improve the description within statistical models.
Keywords: Inelastic neutron scattering, scattering cross sections, photoneutron source, gamma-ray spectra, HPGe detector, statistical models.

Publ.-Id: 19413 - Permalink


Magnetization and spin dynamics of the spin S = ½ hourglass nanomagnet Cu5(OH)2(NIPA)4·10H2O
Nath, R.; Tsirlin, A. A.; Khuntia, P.; Janson, O.; Förster, T.; Padmanabhan, M.; Li, J.; Skourski, Y.; Baenitz, M.; Rosner, H.; Rousochatzakis, I.;
We report a combined experimental and theoretical study of the spin S = ½ nanomagnet Cu5(OH)2(NIPA)4·10H2O (Cu5-NIPA). Using thermodynamic, electron spin resonance, and 1H nuclear magnetic resonance measurements on one hand, and ab initio density-functional band-structure calculations, exact diagonalizations, and a strong-coupling theory on the other, we derive amicroscopicmagnetic model of Cu5-NIPA and characterize the spin dynamics of this system. The elementary fivefold Cu2+ unit features an hourglass structure of two corner-sharing scalene triangles related by inversion symmetry. Our microscopic Heisenberg model comprises one ferromagnetic and two antiferromagnetic exchange couplings in each triangle, stabilizing a single spin S = ½ doublet ground state (GS), with an exactly vanishing zero-field splitting (by Kramers’ theorem), and a very large excitation gap of ∆ ≈ 68 K. Thus, Cu5-NIPA is a good candidate for achieving long electronic spin relaxation (T1) and coherence (T2) times at low temperatures, in analogy to other nanomagnets with low-spin GS’s. Of particular interest is the strongly inhomogeneous distribution of the GS magnetic moment over the five Cu2+ spins. This is a purely quantum-mechanical effect since, despite the nonfrustrated nature of the magnetic couplings, the GS is far from the classical collinear ferrimagnetic configuration. Finally, Cu5-NIPA is a rare example of a S = ½ nanomagnet showing an enhancement in the nuclear spin-lattice relaxation rate 1/T1 at intermediate temperatures.

Publ.-Id: 19412 - Permalink


Metamagnetic transition of martensitic type in electron-doped manganites Ca1-ΧCeΧMnO3 (Χ= 0.10, 0.12)
Loshkareva, N. N.; Gorbunov, D. I.; Andreev, A. V.; Mushnikov, N. V.; Skourski, Y.; Wolff-Fabris, F.;
Magnetic and electrical properties of electron-doped manganites Ca0.88Ce0.12MnO3 and Ca0.90Ce0.10MnO3 were studied in pulsed magnetic fields up to 60 T in the temperature range T = 1.5–260 K. Metamagnetic transition caused by the melting of the charge/orbital ordering and martensitic structural transition in a magnetic field was revealed. The transition is accompanied by a change in electrical resistivity of the sample by three orders. A magnetic phase diagram in the plane of the H–T was constructed. Higher values of the critical transition fields for the system Ca1-ΧCeΧMnO3, compared to the known system Ca1-ΧSmΧMnO3 are explained by a narrower range of phase separation and a bigger difference between the Néel temperatures of the C and G-type antiferromagnetic phases, which originated from the difference between the valence of the Ce4+ and Sm3+ ions.

Publ.-Id: 19411 - Permalink


Localisation and temporal variability of groundwater discharge into the Dead Sea using thermal satellite data
Mallast, U.; Siebert, C.; Wagner, B.; Sauter, M.; Gloaguen, R.; Geyer, S.; Merz, R.;
The semi-arid region of the Dead Sea heavily relies on groundwater resources. This dependence is exacerbated by both population growth and agricultural activities and demands a sustainable groundwater management. Yet, information on groundwater discharge as one main component for a sustainable management varies significantly in this area. Moreover, discharge locations, volume and temporal variability are still only partly known. A multi-temporal thermal satellite approach is applied to localise and semi-quantitatively assess groundwater discharge along the entire coastline. The authors use 100 Landsat ETM + band 6.2 data, spanning the years between 2000 and 2011. In the first instance, raw data are transformed to sea surface temperature (SST). To account for groundwater intermittency and to provide a seasonally independent data set ∆T (maximum SST range) per-pixel within biennial periods is calculated subsequently. Groundwater affected areas (GAA) are characterised by ∆T < 8.5 °C. Unaffected areas exhibit values >10 °C. This allows the exact identification of 37 discharge locations (clusters) along the entire Dead Sea coast, which spatially correspond to available in situ discharge observations. Tracking the GAA extents as a direct indicator of groundwater discharge volume over time reveals (1) a temporal variability correspondence between GAA extents and recharge amounts, (2) the reported rigid ratios of discharge volumes between different spring areas not to be valid for all years considering the total discharge, (3) a certain variability in discharge locations as a consequence of the Dead Sea level drop, and finally (4) the assumed flushing effect of old Dead Sea brines from the sedimentary body to have occurred at least during the two series of 2000–2001 and 2010–2011.
Keywords: Landsat ETM+ Sea surface temperature Submarine groundwater discharge Groundwater resource

Publ.-Id: 19410 - Permalink


Onset of Magnetic Order in U2(Ni1−xFex)2Sn-H
Mašková, S.; Havela, L.; Kolomiets, A.; Miliyanchuk, K.; Andreev, A. V.; Nakotte, H.; Peterson, J.; Skourski, Y.; Yasin, S.; Zherlitsyn, S.; Wosnitza, J.;
We present specific heat and magnetic studies as a function of temperature and magnetic field for U2(Ni1−xFex)2Sn alloys (x = 0.0, 0.05, 0.1, 0.15, 0.2, 0.4, 0.6 and 0.8) and their hydrides (absorption of ≈ 2 H/f.u.). For the parent alloys, antiferromagnetic order is rapidly suppressed with increasing Fe concentration and non-Fermi-liquid behavior was found for x = 0.2. Hydrogenation of the parent alloys causes a substantial increase of TN in Fe-low hydrides (x < 0.2), while Fe-rich hydrides show an unexpected appearance of ferromagnetism in the range 0.4 ≤ x ≤ 0.8. Some of the findings are compared with similar studies in U2Co2Sn and U2Co2InH1.9.

Publ.-Id: 19409 - Permalink


Upgrade of the Machine Interlock System for the ELBE Accelerator Facility
Justus, M.; Freitag, M.; Lange, B.; Michel, P.; Sorge, W.; Steinbrück, R.; Tietze, H.;
The ELBE facility with its 40 MeV C.W. LINAC has recently received an upgrade in terms of new secondary radiation sources and beam lines, while advancing the accelerator infrastructure towards 1.6 mA C.W. operation (1.0 mA before). Therefore, the machine interlock system (MIS) was in parts redesigned to meet the new timing requirements resulting from the increased overall beam power. It comprises fast beam loss detection and a PLC based equipment protection system (EPS), tripping the key components of the electron sources. The former tripping system using PLC interrupts was replaced by an in-house developed staggered CPLD based system with optical transmission and a PROFINET IO interface for control system integration. The EPS is distributed on several PLCs and has been improved in terms of M2M communication. Further, the vacuum inrush protection was completely renewed using brought-in equipment.
This contribution depicts the technical features and performance of the MIS subsystems, as well as the challenges posed by the project track of the ELBE upgrade during implementation.
Keywords: ELBE, MIS, Conrol System
  • Poster
    IPAC 2014 - 5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Deutschland
  • Open Access LogoContribution to proceedings
    IPAC 2014 - 5th International Particle Accelerator Conference, 14.-20.06.2014, Dresden, Deutschland
    IPAC2014: Proceedings of the 5th International Particle Accelerator Conference, Geneva, Switzerland: JACoW, 978-3-95450-132-8, 469-471

Publ.-Id: 19408 - Permalink


Determining the Stability Domain of Perturbed Four-Dimensional Systems in 1:1 Resonance
Hoveijn, I.; Kirillov, O.;
For a parametric family of four-dimensional linear dynamical systems determined by a matrix A(m) with A(0) in 1 : 1 semi-simple resonance, we have established that the central singularity on the stability boundary has codimension 8, ie the centralizer unfolding of the family needs 8 parameters. By recognizing equivalence classes in the centralizer unfolding we reduced the codimension to 5 and finally by using the homogeneity properties to 3. This allowed us to find explicitly the boundary of the stability domain and list all its singularities including six self-intersections and four ’Whitney umbrellas’. We have proposed an algorithm of approximation of the stability boundary near singularities and applied the results to the study of enhancement of the modulation instability with dissipation as well as to the study of stability of a nonconservative system of rotor dynamics.
Keywords: semi-simple resonance, dynamical systems, stability theory, modulational instability, differential equations, versal deformation
  • Book chapter
    Oleg N. Kirillov, Dmitry E. Pelinovsky: Nonlinear Physical Systems: Spectral Analysis, Stability and Bifurcations, London: Wiley-ISTE, 2013, 9781848214200, 155-175

Publ.-Id: 19407 - Permalink


Nonlinear Physical Systems: Spectral Analysis, Stability and Bifurcations
Kirillov, O.; Pelinovsky, D.; (Editors)
Bringing together 18 chapters written by leading experts in dynamical systems, operator theory, partial differential equations, and solid- and fluid mechanics, this book presents state-of-the-art approaches to a wide spectrum of new and challenging stability problems.

Nonlinear Physical Systems: Spectral Analysis, Stability & Bifurcations focuses on problems of spectral analysis, stability and bifurcations arising in the nonlinear partial differential equations of modern physics. Bifurcations and stability of solitary waves, geometrical optics stability analysis in hydro- and magnetohydrodynamics, and dissipation-induced instabilities are treated with the use of the theory of Krein and Pontryagin space, index theory, the theory of multi-parameter eigenvalue problems and modern asymptotic and perturbative approaches.

Each chapter contains mechanical and physical examples, and the combination of advanced material and more tutorial elements make this book attractive for both experts and non-specialists keen to expand their knowledge on modern methods and trends in stability theory.

List of authors

Anatoly Anikin, Davide Bigoni, Jean-Francois Bony, Radomir Bosak, Richard Cushman, Olivier Doare, Sergey Dobrokhotov, Nir Dror, Setsuro Fujiie, Yasuhide Fukumoto, George Hagstrom, Makoto Hirota, Igor Hoveijn, Oleg Kirillov, Richard Kollar, Paolo Luzzatto-Fegiz, Boris Malomed, Sherwin Maslowe, Philip Morrison, Youichi Mie, Diego Misseroni, Francis Nier, Giovanni Noselli, Michael Overton, Dmitry Pelinovsky, Thierry Ramond, Jonathan Robbins, Dmitrii Sadovskii, Emanuele Tassi, Cesare Tronci, Charles Williamson, Zensho Yoshida, Daniele Zaccaria, Mather Zerzeri
Keywords: Nonlinear dynamics, Stability theory, WKB approximation, solitary waves, vortex dynamics, material stability, index theorems, absolute and convective instabilities, dissipation-induced instabilities, Krein space, singularity theory, Hopf bifurcation, Hamiltonian system, Energy-Casimir method, root radius and abscissa, eigenvalue optimization, pseudospectra
  • Book (Editorship)
    London: Wiley-ISTE, 2013
    448 Seiten
    ISBN: 9781848214200

Downloads:

Publ.-Id: 19406 - Permalink


Automation of the radiosynthesis and purification procedures for [18F]Fluspidine preparation, a new radiotracer for clinical investigations in PET imaging of σ1 receptors in brain.
Maisonial-Besset, A.; Funke, U.; Wenzel, B.; Fischer, S.; Holl, K.; Wünsch, B.; Steinbach, J.; Brust, P.;
The radiosynthesis of [18F]Fluspidine, a potent σ1 receptor imaging probe for preclinical/clinical studies, was implemented on a TRACERlabTM FX F-N synthesizer. [18F]2 was synthesized in 15 min at 85 °C starting from its tosylate precursor. Purification via semipreparative RP-HPLC was investigated using different columns and eluent compositions and was most successful on a polar RP phase with acetonitrile/water buffered with NH4OAc.
After solid phase extraction, [18F]Fluspidine was formulated and produced within 59 ± 4 min with an overall radiochemical yield of 37 ± 8%, a radiochemical purity of 99.3 ± 0.5% and high specific activity (176.6 ± 52.0 GBq/μmol).1 receptor imaging probe for preclinical/clinical studies, was implemented on a TRACERlabTM FX F-N synthesizer. [18F]2 was synthesized in 15 min at 85 °C starting from its tosylate precursor. Purification via semipreparative RP-HPLC was investigated using different columns and eluent compositions and was most successful on a polar RP phase with acetonitrile/water buffered with NH4OAc.
After solid phase extraction, [18F]Fluspidine was formulated and produced within 59 ± 4 min with an overall radiochemical yield of 37 ± 8%, a radiochemical purity of 99.3 ± 0.5% and high specific activity (176.6 ± 52.0 GBq/μmol).
Keywords: [18F]Fluspidine; one-step automated radiosynthesis; positron emission tomography; σ1 receptors.

Publ.-Id: 19405 - Permalink


Dialyseverfahren zum Recycling von Gallium
Zeidler, O.;
Der Aufsatz beleuchtet die Anwendung von Dialyseverfahren am Beispiel eines Projektes zur Trennung von Gallium und Arsen aus verbrauchten Beizlösungen der GaAs-Waferproduktion. Der Einsatz von Diffusions- und Elektrodialyse kann durch geringere Chemikalienverbräuche sowie einen einfacheren Aufbau deutliche Vorteile gegenüber Fällungs- und Extraktionsverfahren besitzen und auf diese Weise bisher nicht ökonomisch schließbare Stoffstromketten schließen.
Während Dialyseverfahren zur Laugenregeneration, Metallrückgewinnung oder Säurerückgewinnung in der Galvanotechnik bereits seit Jahren etabliert sind und sich ständig weiter entwickeln [1], sind aus der Halbleiterindustrie kaum Anwendungsfälle bekannt. In Folge der Verknappung von Seltenen Metallen und der Debatte zur Ressourceneffizienz besteht hier ein Forschungs- und Handlungsbedarf.
  • Open Access LogoContribution to proceedings
    46. Metallurgisches Seminar der GDMB: Herstellung und Recycling von Technologiemetallen, 10.-12.12.2013, Joachimsthal, Deutschland
  • World of Metallurgy - Erzmetall 67(2014)2, 5

Publ.-Id: 19404 - Permalink


Abtrennung von Zinn beim Recycling von Bleiakkumulatoren
Beimel, B.; Stelter, M.; Morgenstern, G.; Zeidler, O.;
Der gegenwärtig anfallende Akkumulatorenschrott besitzt höhere Zinngehalte als die Bleilegierungen moderner Akkumulatoren. Dadurch fallen bei der Aufarbeitung des Akkuschrotts blei/zinnhaltige Raffinationsprodukte an, die nicht in den Wertstoffkreislauf zurückgeführt werden können. Es wird eine Möglichkeit zur Trennung dieser Produkte beschrieben. Damit hat der Recycler die Möglichkeit, die Wertstoffe Zinn und Blei der Wirtschaft wieder getrennt zur Verfügung zu stellen.
Keywords: Battery recycling, Lead, Separation of lead and tin, Tin

Publ.-Id: 19403 - Permalink


The Revival of Rare Metal Research in Freiberg/Germany - Continuation of a Success Story
in Russian
Zeidler, O.;
The mining and smelting region of Freiberg is well-known for its Pb-Zn-Ag lodes. These have been mined for their high silver contents since 1180. From the 18th century on, Pb, Zn, Sn and Ni became increasingly important as by-products. But the hydrothermally formed deposit also contains rare metals as In and Ge at unusually high concentrations.
Although metal prices decreased at the end of the 19th century and the operation of mines and smelters was more and more dependent of federal subsidization, parts of the research and industrial landscape were preserved. With semiconductor industry, a second economic pillar was established. The recent rise of metal prices may give a further momentum for economic growth.
  • Open Access LogoContribution to proceedings
    5th International Congress and Exhibition "Non-Ferrous Metals 2013", 04.-06.09.2013, Krasnoyarsk, Rossijskaja Federazija
    Proceedings of the 5th International Congress and Exhibition "Non-Ferrous Metals 2013", Krasnoyarsk: Legkie Metallie, 978-5-85981-344-5, 175-178
  • Invited lecture (Conferences)
    5th International Congress and Exhibition "Non-Ferrous Metals 2013", 04.-06.09.2013, Krasnoyarsk, Rossijskaja Federazija

Publ.-Id: 19402 - Permalink


Recycling von Gallium aus Prozessrückständen
Stelter, M.; Zeidler, O.;
Bemühungen zur Rückgewinnung von seltenen Metallen beschränken sich derzeit meist auf die Verwertung von End-of-life Produkten. In Produktionsprozessen dagegen gehen oft erhebliche Mengen dieser Wertstoffe verloren, die aus technologischen oder wirtschaftlichen Gründen nicht zurück gewonnen werden. In dem vorliegenden Beitrag werden die Möglichkeiten der Rückgewinnung von Gallium, über den bisherigen Stand der Technik hinaus, in der Halbleiterindustrie dargestellt. Als Beispiel dient das Recycling von Gallium aus Ätzlösungen der GaAs-Wafer und -Chipproduktion. Die Galliumverluste über Abwasserbehandlung und Reststoffrecycling der Waferproduktion belaufen sich auf etwa 150 g Gallium pro kg im produzierten Wafer. Ein wesentlicher Grund sind die hohen Kosten für eine umfassende selektive Rückgewinnung des Galliums aus dem Abwasser. Die TU Bergakademie Freiberg, das Helmholtz-Institut Freiberg und die Freiberger Compound Materials GmbH forschen an einem neuartigen und kostengünstigen Abwasserbehandlungsverfahren mit geringem Chemikalienverbrauch, um die Recyclingrate für Gallium wesentlich zu erhöhen und dabei die Qualität des Abwassers weiter zu verbessern. Zum Einsatz kommen sollen dabei Membranverfahren wie Dialyse und Elektrodialyse.
  • Open Access LogoContribution to proceedings
    Berliner Recycling- und Rohstoffkonferenz, 04.-05.03.2013, Berlin, Deutschland
    Recycling und Rohstoffe, Band 6, Neuruppin: TK Verlag Karl Thomé-Kozmiensky, 978-3-935317-97-9, 471-480
  • Lecture (Conference)
    Berliner Recycling- und Rohstoffkonferenz, 04.-05.03.2013, Berlin, Deutschland

Publ.-Id: 19401 - Permalink


On the acceleration of the microstructure evolution detected by SANS in low-Cu RPV steels
Wagner, A.; Chaouadi, R.; Bergner, F.; Viehrig, H.-W.;
Previous work on low-Cu RPV steels JPB and JPC irradiated at 255 °C indicated an acceleration of the increase of both yield stress and total SANS intensity as functions of neutron fluence. A new algorithm was used to analyze the original SANS data as well as SANS data obtained for new BR2-irradiations at 290 °C of the same materials. Both data sets are compared with one another and correlated with the respective mechanical test results. Additional evidence is provided on the basis of SANS experiments performed for the RPV steels irradiated at 255 °C and post-irradiation annealed at 290 °C.
  • Lecture (Conference)
    17th Meeting of the IGRDM, 19.-24.05.2013, Les Embiez, France

Publ.-Id: 19399 - Permalink


Cycloisomerization of 2-alkynylanilines to indoles catalyzed by carbon-supported gold nanoparticles and subsequent homocoupling to 3,3′-biindoles
Perea-Buceta, J. E.; Wirtanen, T.; Laukkanen, O.-V.; Mäkelä, M. K.; Nieger, M.; Melchionna, M.; Huittinen, N.; Lopez-Sanchez, J. A.; Helaja, J.;
Elevated by the support: 2-Alkynyl aniline cycloisomerization to indole is catalyzed by cationic Au NPs on a carbon support. Electroneutral and rich 2-aryl indoles are further converted into 3,3′-biindoles by oxidative homocoupling that is readily catalyzed by the Au NPs on carbon, and exclusively but also somewhat sluggishly by the carbon support.
Keywords: biindoles, carbon supports, gold, heterogeneous catalysis, homocoupling

Publ.-Id: 19398 - Permalink


Supraleitende Schichten in Ga-implantiertem Si und Ge
Fiedler, J.;
  • Lecture (Conference)
    34. Treffen der Nutzergruppe Heißprozesse und RTP, 06.11.2013, Frankfurt (Oder), Deutschland

Publ.-Id: 19397 - Permalink


Visualizing the Radiation of the Kelvin-Helmholtz Instability
Huebl, A.; Pugmire, D.; Schmitt, F.; Pausch, R.; Bussmann, M.;
Emerging new technologies in plasma simulations allow tracking billions of particles while computing their radiative spectra. We present a visualization of the relativistic Kelvin-Helmholtz Instability from a simulation performed with the fully relativistic particle-in-cell code PIConGPU powered by 18,000 GPUs on the USA’s fastest supercomputer Titan.
Keywords: Plasma stability, Simulation, Parallel machines, Particle tracking, Electromagnetic radiation, Visualization

Publ.-Id: 19396 - Permalink


Molecular Imaging of σ1 Receptors In Vivo: Current Status and Perspectives
Brust, P.; Deuther-Conrad, W.; Lehmkuhl, K.; Jia, H.; Wünsch, B.;
Abstract: It is widely accepted that sigma (σ) receptors represent a new and different avenue in the possible pharmacological treatment of cancer and several brain-related disorders. Of the two different σ receptor types the σ11 receptors are assumed to be of major impact for brain diseases. Molecular imaging of brain σ1 receptors with positron emission tomography (PET) or single photon emission computed tomography (SPECT) may provide a significant contribution to the understanding of the cross-talk between σ1 receptors and inter- and intracellular signalling systems. New insights into These functional interrelationships will allow a better diagnosis of brain and cancerous diseases and direct a rational development of new therapeutic concepts.
Keywords: brain, chaperone, cancer, disease, fluspidine, molecular imaging, positron emission tomography, sigma receptor, signalling, single photon emission computed tomography, therapy

Publ.-Id: 19395 - Permalink


Geochemische Untersuchungen an Moränen des Inylchek-Gletschers im Tien Shan
Hahne, K.; Naumann, R.; Niedermann, S.; Wetzel, H.-U.; Merchel, S.; Rugel, G.;
In this study, we present results of the chemical composition of the moraine cover from the Inylchek Glacier in Kyrgyzstan using observations from three field campaigns between 2010 and 2012. The sample locations were selected based on high-resolution remote sensing data. Sampling included the main profile from Lake Merzbacher to Station “Hochgebirgsobservatorium Gottfried Merzbacher”, which is about 8 km in length trending in N-S-direction. Chemical analyses of more than 60 elements, including Rare Earth Elements (an important tool for the discrimination and localisation of source areas of sediments, boulders and outcropping rocks) were carried out.
Based on these data different geochemical material streams have been identified. Generally, two chemical groups of sediments, the North Type/Lake Merzbacher and the South Type/Southern Inylchek can be distinguished. The Lake Merzbacher Type sediments are characterised by a uniform chemical composition, whereas the South Inylchek Type is geochemically more heterogeneous. Toxic elements in the sediments, such as Ni, As, Cd, Tl and U, are moderately enriched. The low sulphur concentration suggests that the main water transport is caused by suspended matter.
One erratic granite block was analysed for in situ cosmogenic 10Be for exposure age dating. The age of 330 ± 90 a is conform to a glacier high stand during the “Maunder“ minimum of the solar activity.
Keywords: AMS, cosmogenic exposure dating, moraine

Publ.-Id: 19394 - Permalink


Interaction of U(VI) with Schizophyllum commune studied by microscopic and spectroscopic methods
Günther, A.; Raff, J.; Merroun, M. L.; Roßberg, A.; Kothe, E.; Bernhard, G.;
Biosorption of actinides like uranium by fungal cells can play an important role in the mobilization or immobilization of these elements in nature. Sorption experiments of U(VI) with Schizophyllum commune at different initial uranium concentrations and varying metal speciation showed high uranium sorption capacities in the pH range of 4 to 7. A combination of High Angle Annular Dark-Field (HAADF) and Scanning Transmission Electron Microscopy (STEM) analysis showed that living mycelium cells accumulate uranium at the cell wall and intracellular. For the first time the fluorescence properties of uranium accumulates were investigated by means of time-resolved laser-induced fluorescence spectroscopy (TRLFS) beside the determination of corresponding structural parameters using X-ray absorption fine structure spectroscopy (EXAFS). While the oxidation state of uranium remained unchanged during sorption, uranium speciation changed significantly. Extra and intracellular phosphate groups are mainly responsible for uranium binding. TRLFS spectra clearly show differences between the emission properties of dissolved species in the initial mineral medium and of uranium species on fungi. The latter were proved to be organic and inorganic uranyl phosphates formed depending on the uranyl initial concentration and in some cases on pH.
Keywords: Fungi, Uranium, HAADF/STEM, TRLFS, EXAFS

Publ.-Id: 19393 - Permalink


Size-dependent magnetism and exchange bias effect in Sm0.27Ca0.73MnO3nanoparticles
Markovich, V.; Puzniak, R.; Fita, I.; Mogilyansky, D.; Wisniewski, A.; Skourski, Y.; Jung, G.; Gorodetsky, G.;
Magnetic properties of compacted Sm0.27Ca0.73MnO3 nanoparticles with average particle size ranging from 20 to 80 nm have been investigated in wide temperature and magnetic field range. It has been found that charge ordering transition gradually shifts to lower temperatures with decreasing particle size and almost disappears for 20 nm particles. At the same time, the relative volume of the ferromagnetic phase increases monotonously. Field-induced transition from antiferromagnetic to ferromagnetic state in 80 nmparticles appears at the same magnetic field as in the bulk. In small 20 nm particles, the transition is strongly suppressed by increasing surface spins disorder. Magnetic hysteresis loops show size-dependent exchange bias effect with exchange field, remanence asymmetry, and magnetic coercivity that depend on cooling magnetic field and temperature. Magnetic training effect has been observed in 20 nm particles and analyzed using a spin relaxation model. The thermoremanence and isothermoremanence curves have provided fingerprints of irreversible magnetization originating from the glassy component. Analysis of remanence curves has showed that the inner core of small 20 nm particles behaves as a two-dimensional diluted antiferromagnet.

Publ.-Id: 19392 - Permalink


Strong room-temperature easy-axis anisotropy in Tb2Fe17H3: An exception among R2Fe17 hydrides
Tereshina, E. A.; Drulis, H.; Skourski, Y.; Tereshina, I. S.;
The iron-rich intermetallics R2Fe17 (where R is a rare-earth element) proved unamenable to anisotropy control via interstitial doping. There is only one precedent, Sm2Fe17N3−δ (Sm2Fe17C3−δ ), where interstitial modification has stabilized an easy-axis anisotropy at all temperatures up to TC. All previous attempts to prepare a usable easy-axisR2Fe17 hydride have failed. Now we have succeeded in preparing a high-quality single-phase Tb2Fe17H3 single crystal,which has the required easy-axis anisotropy between 0 K and TC =560 K. At T =300 K, Tb2Fe17H3 has the spontaneous magnetic moment Ms of 22.5 μB per formula unit and anisotropy field μ0Ha of 2.5 T. The main mechanism stabilizing the easy-axis anisotropy in hydrides is the same as in other similar compounds by way of boosting the leading crystal field parameter A20. Terbium is rather special in having the Stevens factors such that αJ < 0 and βJ > 0, which is why the easy-axis anisotropy in Tb2Fe17 hydrides is also assisted by the fourth-order parameter A40. This proves a decisive advantage over the compounds with R = Pr, Nd, Dy, or Ho where βJ < 0 and A40 is a hindrance.

Publ.-Id: 19391 - Permalink


Magnetic and magnetoelastic properties of UCo2Si2 as studied by high-field magnetization and ultrasound measurements
Andreev, A. V.; Yasin, S.; Skourski, Y.; Zvyagin, A. A.; Zherlitsyn, S.; Wosnitza, J.;
We investigated an antiferromagnet UCo2Si2 by use of magnetization and ultrasound measurements in pulsed magnetic fields up to 60 T. It is found that the crystal UCo2Si2, which has the antiferromagnet type-I magnetic structure in zero field below TN = 83 K, undergoes the metamagnetic phase transition to ferrimagnetic structure ++− type similarly to the UNi2Si2 with substitution of 10%–15% Ni by Pd or UPd2Si2. Therefore, similar phase transitions take place in the compounds with expected essentially different strength of the 5 f -d electron hybridization. In UCo2Si2, the transition occurs when the magnetic field is applied along the c axis at 45 T (at 1.5 K). The transition is extremely sharp and exhibits a small but non-negligible hysteresis. With increasing temperature, it becomes broader and vanishes at TN. In our ultrasound measurements, the metamagnetic transition appears as anomalies in the sound velocity and attenuation. Our analysis suggests that the low-temperature changes in the sound velocity and attenuation predominantly are determined by an exchange renormalization caused by the sound waves.

Publ.-Id: 19390 - Permalink


Role of Hyperfine Coupling in Magnetic and Quadrupolar Ordering of Pr3Pd20Si6
Steinke, L.; Mitsumoto, K.; Miclea, C. F.; Weickert, F.; Dönni, A.; Akatsu, M.; Nemoto, Y.; Goto, T.; Kitazawa, H.; Thalmeier, P.; Brando, M.;
We study the ternary clathrate Pr3Pd20Si6 in specific heat and ac susceptibility measurements on a highquality single crystal, distinguishing antiferromagnetic and antiferroquadrupolar ordering, as well as a hitherto unknown magnetic low-temperature transition. The specific heat shows the direct involvement of nuclear spin degrees of freedom in the antiferromagnetic ordering, which is well supported by our calculation of the hyperfine level scheme without adjustable parameters. Pr3Pd20Si6 is, therefore, one of the rare materials where the nuclear moments are involved in the formation of the magnetic ground state.

Publ.-Id: 19389 - Permalink


Magnetic, thermal, and transport properties of single-crystalline U3Fe4Ge4
Henriques, M. S.; Gorbunov, D. I.; Waerenborgh, J. C.; Havela, L.; Andreev, A. V.; Skourski, Y.; Gonçalves, A. P.;
Magnetic, thermal, and transport properties of a U3Fe4Ge4 single crystal have been studied. The compound crystallizes in the orthorhombic Gd3Cu4Ge4 structure type. U3Fe4Ge4 displays ferromagnetic order below the Curie temperature TC = 18 K. The magnetism originates from the uranium sublattice, as iron atoms have no ordered magnetic moments. U3Fe4Ge4 exhibits a pronounced easy-axis anisotropy with the anisotropy field exceeding 60 T. The spontaneous magnetic moment is Ms = 1.2 µB/f.u. at T = 2 K. Magnetic contribution to specific heat shows a gap excitation behavior with D = 4 meV, which can be related to the magnon gap due to the anisotropy. The Sommerfeld coefficient of the electronic specific heat is \gamma = 57 mJ/(mol-U K2) in the ordered state, whereas it is much higher (145 mJ/(mol-U K2) if derived from the paramagnetic state. Electrical resistivity has very high values on the mΩ cm range.

Publ.-Id: 19388 - Permalink


High-field magnetization of a DyFe5Al7 single crystal
Gorbunov, D. I.; Andreev, A. V.; Skourski, Y.; Kuz’Min, M. D.;
The magnetization of a DyFe5Al7 single crystal with the tetragonal ThMn12-type structure was measured in pulsed fields up to 60 T along the principal axes. The compound orders ferrimagnetically at TC = 231 K and exhibits a compensation of the Dy and Fe sublattices at Tcomp = 93 K. DyFe5Al7 displays a high magnetic anisotropy of the easy-plane type, the [100] axis is the easy magnetization direction with the spontaneous magnetic moment Ms = 2.1 µB/f.u. at T = 2 K. In a field applied along the easy axis, two field-induced hysteretic transitions are observed at 30 and 53 T at T = 2 K. The critical field H of the first transition depends strongly on temperature, whereas Hcr2 is practically temperature-independent. Above the transitions the magnetization continues to grow as a function of field, as the sublattice moments continue to rotate. To reach the full saturation (forced ferromagnetic state), fields of several Tesla higher than 60 T are required. The field dependence of magnetization along the easy [100] axis was analyzed within a model for a ferrimagnet with an anisotropic dominant sublattice. The model correctly reproduces the behavior of magnetization in a magnetic field. The intersublattice molecular field on Dy and the basal-plane anisotropy constant of the Dy sublattice have been determined.

Publ.-Id: 19387 - Permalink


Ionenstrahlverfahren für die Element- und Spurenanalytik in Festkörpern
von Borany, J.; Munnik, F.; Neelmeijer, C.; Renno, A.; Merchel, S.;
Im Rahmen eines Workshops zur "Analyse von Spurenverunreinigungen auf Oberflächen und in Gasen" werden in einer Übersicht die ionenanalytischen Verfahren vorgestellt.
Keywords: Analytik, Spurenelemente, Ionen
  • Lecture (Conference)
    Workshop " Analyse von Spurenverunreinigungen auf Oberflächen und in Gasen", 03.12.2013, Dresden, Deutschland

Publ.-Id: 19386 - Permalink


Field-induced magnetic ordering and single-ion anisotropy in the quasi-one-dimensional Haldane chain compound SrNi2V2O8: A single-crystal investigation
Bera, A. K.; Lake, B.; Islam, A. T. M. N.; Klemke, B.; Faulhaber, E.; Law, J. M.;
Field-induced magnetic ordering in the Haldane chain compound SrNi2V2O8 and the effect of anisotropy have been investigated using single crystals. Static susceptibility, inelastic neutron scattering, high-field magnetization, and low-temperature heat-capacity studies confirm a nonmagnetic spin-singlet ground state and a gap between the singlet ground state and triplet excited states. The intrachain exchange interaction is estimated to be J ∼ 8.9 ± 0.1meV. Splitting of the dispersions into two modeswithminimum energies 1.57 and 2.58 meV confirms the existence of single-ion anisotropy D(Sz)2. The value of D is estimated to be −0.51 ± 0.01 meV and the easy axis is found to be along the crystallographic c axis. Field-induced magnetic ordering has been found with two critical fields (μ0Hc⊥c = 12.0 ± 0.2 T and μ0HcIIc = 20.8 ± 0.5 T at 4.2 K). Field-induced three-dimensional magnetic ordering above the critical fields is evident from the heat-capacity, susceptibility, and high-field magnetization study. The phase diagram in the H-T plane has been obtained from the high-field magnetization. The observed results are discussed in the light of theoretical predictions as well as earlier experimental reports on Haldane chain compounds.

Publ.-Id: 19385 - Permalink


Measurement of the dipole polarizability of the unstable neutron-rich nucleus 68Ni
Rossi, D. M.; Adrich, P.; Aksouh, F.; Alvarez-Pol, H.; Aumann, T.; Benlliure, J.; Böhmer, M.; Boretzky, K.; Casarejos, E.; Chartier, M.; Chatillon, A.; Cortina-Gil, D.; Datta Pramanik, U.; Emling, H.; Ershova, O.; Fernandez-Dominguez, B.; Geissel, H.; Gorska, M.; Heil, M.; Johansson, H. T.; Junghans, A.; Kelic-Heil, A.; Kiselev, O.; Klimkiewicz, A.; Kratz, J. V.; Krücken, R.; Kurz, N.; Labiche, M.; Le Bleis, T.; Lemmon, R.; Litvinov, Y. A.; Mahata, K.; Maierbeck, P.; Movsesyan, A.; Nilsson, T.; Nociforo, C.; Palit, R.; Paschalis, S.; Plag, R.; Reifarth, R.; Savran, D.; Scheit, H.; Simon, H.; Sümmerer, K.; Wagner, A.; Walus, W.; Weick, H.; Winkler, M.;
The E1 strength distribution in 68Ni has been investigated using Coulomb excitation in inverse kinematics at the R3B-LAND setup and by measuring the invariant mass in the one and two Neutron decay channels.The GDR and a low-lying peak (PDR) have been observed at 17.1(2) and 9.55(17) MeV, respectively. The measured dipole polarizability is compared to relativistic RPA calculations yielding a neutron-skin thickness of 0.175(21) fm. A method and analysis applicable to neutron-rich nuclei has been developed, allowing for a precise determination of neutron skins in nuclei as a function of neutron excess.
Keywords: strength distribution 68Ni Coulomb excitation inverse kinematics invariant mass GDR PDR dipole polarizability neutron skin

Publ.-Id: 19384 - Permalink


Re-examining the doping effect on the performance of quantum well infrared photodetectors
Hao, M. R.; Zhang, S.; Zhang, Y. H.; Shen, W. Z.; Schneider, H.; Liu, H. C.;
This paper investigates the dependence of background limited performance (BLIP) temperature of quantum well infrared photodetectors (QWIPs) on doping density. In contrast to the generally accepted optimal doping condition EF = k_B TBLIP, our theoretical prediction shows that lower doping densities should slightly increase the BLIP temperature TBLIP taking into account the temperature dependence of the Fermi energy EF, a factor neglected in previous analyses. Numerical modeling results are used to reinterpret the reported TBLIP measurements for a series of QWIPs of typical design for 9 μm peak wavelength with different doping values. In addition, based on the same general expression for the Fermi energy, the optimized sheet doping concentration to achieve maximum detectivity is given by EF = 1.37 kBT, a revision to the previous EF = 2kBT condition.
Keywords: Quantum well infrared photodetector, QWIP, background limited performance, detectivity

Publ.-Id: 19383 - Permalink


Investigation of Structure, Adsorption Free Energy, and Overcharging Behavior of Trivalent Yttrium Adsorbed at the Muscovite (001)–Water Interface
Lee, S. S.; Schmidt, M.; Laanait, N.; Sturchio, N. C.; Fenter, P.;
The speciation, coverage, and thermodynamics of trivalent Y3+ adsorbed at a negatively charged muscovite (001)–water interface were measured to investigate electrostatic ion–ion correlations in a strong coupling regime. In situ specular crystal truncation rod and resonant anomalous X-ray reflectivity data show that Y3+ adsorbs as three distinct species (inner-sphere, adsorbed outer-sphere, and extended outer-sphere) among which the fractional coverage of the inner-sphere species (10%) is the smallest. Uptake measurements show that the maximum Y3+ coverage is higher by 50% than the amount needed to satisfy the muscovite surface charge in the absence of background electrolyte, but this overcharging is largely suppressed in the presence of 0.1 m NaCl. The measured intrinsic standard-state Gibbs free energy for Y3+ adsorption (−36.9 ± 0.9 kJ/mol) is smaller than that expected solely on the basis of its charge, and this discrepancy can be partly explained by the difference in adsorbed cation speciation at the charged interface.

Publ.-Id: 19382 - Permalink


Interfacial Reactivity of Pu and Th at the Muscovite (001) Basal Plane
Schmidt, M.; Lee, S. S.; Knope, K. E.; Bellucci, F.; Soderholm, L.; Fenter, P.;
The geochemistry of the actinides is of utmost importance in understanding and predicting their behavior in contaminated legacy sites as well as nuclear waste storage facilities. The unique chemistry of this group of elements including strong hydrolysis, complex redox chemistry, and the potential for polymerization reactions in combination with the actinides’ inherent radioactivity and toxicity makes studies challenging. However, especially for artificial elements like Pu and other transuranics, no natural analogues are available and homologues frequently fall short in accurately reproducing the actinides’ behavior.
We will present and discuss recent results from in situ resonant anomalous x-ray reflectivity (RAXR) and crystal truncation rod (CTR) experiments, shedding light on the inter-action of Th(IV) as well as Pu(III) and Pu(IV) with the negatively charged muscovite (001) basal plane. The example of Th(IV) demonstrates how the strong hydration of the highly charged cations prevents a close approach to the surface, instead favoring adsorption as a highly hydrated extended outer sphere complex. Subsequently, it will be shown how similar adsorption behavior in combination with the complex redox chemistry of plutonium, leads to a surface-enhanced formation of nanoparticles.
Results from surface x-ray scattering will be supplemented by ex situ alpha-spectrometry quantification and atomic force microscopy (AFM), to yield a more complete understanding of the interfacial structure.
Keywords: Plutonium, Sorption, RAXR, CTR, AFM
  • Invited lecture (Conferences)
    247th ACS National Meeting, 16.-20.03.2014, Dallas, Texas, USA

Publ.-Id: 19381 - Permalink


Exploiting Memristive BiFeO3 Bilayer Structures for Compact Sequential Logics
You, T.; Shuai, Y.; Luo, W.; Du, N.; Bürger, D.; Skorupa, I.; Hübner, R.; Henker, S.; Mayr, C.; Schüffny, R.; Mikolajick, T.; Schmidt, O. G.; Schmidt, H.;
Abstract: Resistive switching devices are considered as one of the most promising candidates for the next generation memories and nonvolatile logic applications. In this paper, we present BiFeO3:Ti/BiFeO3 (BFTO/BFO) bilayer structures with optimized BFTO/BFO thickness ratio which show symmetric, bipolar, and nonvolatile resistive switching. The resistive switching mechanism is understood by a model of flexible top and bottom Schottky-like barrier heights in the BFTO/BFO bilayer structures. For the nonvolatile logic applications, the polarity of reading bias can be used as an additional logic variable, which makes it feasible to program and store all 16 Boolean logic functions into a single cell of a BFTO/BFO bilayer structure in three logic cycles. In comparison to standard logic hardware solutions, the proposed memristive bilayer structures allow for simplified parallel, sequential, and looped logical processing.
Keywords: memristor, resistive switching, BiFeO3, boolean logic functions, reconfigurable nonvolatile logics

Publ.-Id: 19380 - Permalink


Resonance THz spectroscopy in high magnetic fields
Barra, A.-L.; Goiran, M.; Sessoli, R.; Zvyagin, S. A.;
The employment of the high-magnetic-field resonance spectroscopy to probe magnetic excitations in the THz frequency range is reported. To illustrate the great potential of this technique in solid state physics, we present results of recent electron spin resonance studies of the quantum-tunneling effect in the single-molecule magnet Mn12tba and of the soliton–magnon crossover in Cu-PM, a spin-1/2 Heisenberg chain system with a staggered transverse field. Among others, we report on the successful use of the THz-range timedomain and free electron laser spectroscopy to study magnetic excitation spectra in pulsed magnetic fields.

Publ.-Id: 19379 - Permalink


CFD for subcooled flow boiling: Analysis of DEBORA tests
Krepper, E.; Rzehak, R.;
In this work we investigate the present capabilities of CFD for wall boiling. The computational model used combines the Euler / Euler two-phase flow description with heat flux partitioning. Very similar modelling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant non-dimensional numbers have been realized in the DEBORA tests using Dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, liquid temperature and bubble size.
Robust predictive capabilities of the modelling require that it is validated for a wide range of parameters. In previous studies (Krepper and Rzehak, 2011, 2013) it was shown that a careful calibration of correlations used in the wall boiling model is necessary to obtain agreement with the measured data. We here consider tests under a variety of conditions concerning liquid subcooling, flow rate and heat flux. It is investigated to which extent a set of calibrated model parameters suffices to cover at least a certain parameter range.
In the paper the potential of the application of a population balance model is demonstrated. The measured gas bubble size profiles show an increase of the bubble size with increased distance from the heated wall caused by bubble coalescence. Furthermore the model framework is shown to be able to describe a shift from wall peak to core peak in the radial gas volume fraction profiles with increasing inlet temperature respective decreasing subcooling temperature, which was observed in some test series.
Keywords: CFD, wall boiling, DEBORA tests, population balance model, model calibration, model validation

Publ.-Id: 19377 - Permalink


Development of fluorinated CB2 receptor agonists for PET studies
Lueg, C.; Schepmann, D.; Günther, R.; Brust, P.; Wünsch, B.;
A convergent strategy was followed to modify systematically carbazole based CB2 receptor ligands. The length of the N-(fluoroalkyl) group (n in 7), the length of the alkanamide (m in 7) and the substitution pattern of the phenyl moiety (X and Y in 7) were varied systematically. The highest CB2 affinity was found for the 2-fluoroethyl substituted carbazole derivative 20a (Ki = 5.8 nM) containing the propionamide and the 2-bromo-4-fluorophenyl moiety. According to docking studies 20a fits nicely into the binding pocket of the CB2 receptor, but elongation of the fluoroethyl side chain leads to a different binding mode of the ligands. The high CB2 affinity together with the high selectivity over the CB2 subtype qualifies the fluoroethyl derivative 20a to be developed as a PET tracer.
Keywords: CB2 receptor ligands Carbazole derivatives Fluorinated ligands Structure affinity relationships PET Docking

Publ.-Id: 19376 - Permalink


DREAMS: Die Zauberkugel für die Vergangenheit
Merchel, S.; Akhmadaliev, S.; Pavetich, S.; Rugel, G.; Ziegenrücker, R.;
ohne Abstract, da eingeladener Vortrag
Keywords: AMS, cosmogenic radionuclides
  • Invited lecture (Conferences)
    WiN-Mitgliederversammlung (2. Runde WiN-Germany-Preis 2013), 22.11.2013, Kernkraftwerk Obrigheim, Deutschland

Publ.-Id: 19375 - Permalink


Super-radiant Linac-based THz Sources in 2013
Gensch, M.;
These proceedings shall give an overview over the rapidly growing number of super-radiant linac-based THz sources which have been developed and designed over the past 13 years following the seminal pilot experiment at the Jefferson lab energy recovery linac in 2001 [1]. More than 20 super-radiant THz facilities already exist or are planned worldwide and are listed together with a set of fundamental parameters in the appendix of this paper.

[1] G.L. Carr et. al., “High power terahertz radiation from relativistic electrons” Nature 420 (2001), 153.
  • Open Access LogoContribution to proceedings
    FEL13 - 35th International Free-Electron Laser Conference, 25.-30.08.2013, New York, USA
    Proceedings of FEL13

Publ.-Id: 19374 - Permalink


Magnetization dynamics in periodically modulated nanostructures
Lenz, K.;
Periodical arrangements of magnetic nanostructures offer very exciting and new features that do not exist in thin films. They range from dipolar interactions leading to two-magnon scattering in periodically perturbed films to the opening of magnonic band gaps in a magnonic crystal acting as e.g. filters - analog to a photonic crystal.
I will present experimental data from ferromagnetic resonance (FMR) experiments of two types of periodic nanostructures, which depict the transition region from a thin film to an array of separated magnetic elements. The structures were created (i) by ion beam erosion in a self-organizing process or (ii) by local magnetic property patterning using ion beam implantation in conjunction with lithographic masks. Both methods allow for easy tailoring of the magnetic dimensions.
The FMR data shows a splitting of the uniform resonance mode into several modes due to the dipolar stray fields of the nanostructures, which can be imaged by transmission electron holography. The results are corroborated by an analytical perturbation theory of two-magnon scattering developed by P. Landeros and D.L. Mills. This extended model allows for calculating the resonance response function of 1D and 2D periodically perturbed ferromagnetic films in almost perfect agreement to the FMR experiments.
Keywords: ferromagnetic resonance, magnetism, dynamics, spinwaves, magnons
  • Lecture (others)
    Physikalisches Kolloquium, Technische Universität Chemnitz, 30.10.2013, Chemnitz, Deutschland

Publ.-Id: 19373 - Permalink


Channeling radiation with low-energy electron beams: Experimental plans & status at FERMILAB
Blomberg, B.; Brau, C. A.; Choi, B. K.; Gabella, W. E.; Ivanov, B.; Mendenhall, M.; Mihalcea, D.; Panuganti, H.; Piot, P.; Wagner, W.;
Channeling radiation is an appealing radiation process to produce x-ray radiation with low-energy electron beams.
In this contribution we describe the anticipated performance and preliminary results from a channeling-radiation experiment
to produce ~1,2-keV radiation from a ~4-MeV electron beam at Fermilab’s high-brightness electron source lab (HBESL).
We also discuss plans to produce x-ray radiation ([10; 80]-keV photon energy) at Fermilab’s advanced superconducting
test accelerator (ASTA).
Keywords: channeling radiation, X-rays, electron beam
  • Open Access LogoContribution to proceedings
    35th International Free-Electron-Laser Conference, 25.-30.08.2013, New York, USA
    Proceedings of FEL2013: www.jacow.org, MOPSO07

Publ.-Id: 19372 - Permalink


Accelerated simulations for plasma physics - Understanding and probing plasmas on the atomic scale
Bussmann, M.;
Modern compute hardware allows for simulating laser plasma interaction interactively and for integrating physical effects that could not be accounted for previously. I will show how efficient plasma simulations may pave the way towards predictive simulations of laser matter interaction.
Keywords: simulation, plasma, x-ray, laser, ultrashort, dynamics
  • Invited lecture (Conferences)
    Seminar of the Shanghai Institute of Optics and Fine Mechanics (SIOM), 13.11.2013, Shanghai, China

Publ.-Id: 19371 - Permalink


Laser cooling of relativistic heavy ion beams at the ESR and CSRe
Wen, W.; Siebold, M.; Schramm, U.; Ma, X.; Bussmann, M.;
We present results on laser cooling of heavy ion beams at ESR and discuss prospects for laser cooling at CSRe.
Keywords: laser, cooling, heavy, ion, beam, storage ring
  • Lecture (Conference)
    Chinese-German Workshop on "High Precision Experiments with Stored Exotic and Stable Ions", 06.-11.11.2013, Lanzhou, China

Publ.-Id: 19370 - Permalink


Laser cooling experiments in storage rings
Bussmann, M.; Siebold, M.; Schramm, U.;
We present results on laser cooling of ion beams at storage rings and discuss their relevance for future facilities.
Keywords: laser, cooling, storage ring, ion, beam
  • Invited lecture (Conferences)
    Chinese-German Workshop on "High Precision Experiments with Stored Exotic and Stable Ions", 06.-11.11.2013, Lanzhou, China

Publ.-Id: 19369 - Permalink


Twinkle, Twinkle Little Star - Using 18.000 GPUs to Simulate Jets in the Cosmos
Bussmann, M.; Burau, H.; Cowan, T. E.; Debus, A.; Huebl, A.; Juckeland, G.; Kluge, T.; Nagel, W. E.; Pausch, R.; Schmitt, F.; Schramm, U.; Schuchart, J.; Widera, R.;
In order to understand what happens when jets of hot, streaming gas are ejected at high speed into the cosmos, we are bound to rely on m easuring the radiation emitted by the particles in the jet. Astrophysical jets can originate from a variety of sources such as stars, black holes and even galaxies. In such jets, the plasma flow can become unstable, generating characteristic patterns of p article flows. Using our particle-in-cell code PIConGPU utilizing the complete TITAN supercomputer system at Oak Ridge National Laboratory, we were able, for the first time, to not only simulate the particle dynamics but also the radiation emitted during the formation of such an instability, the Kelvin-Helmholtz instability.
Keywords: kelvin-helmholtz-instability, plasma, simulation, jet, astrophysics, gpu, titan, ornl, picongpu, particle-in-cell, pic, simulation, khi
  • Invited lecture (Conferences)
    GPU Technology Theatre at the SC'13, The International Conference for High Performance Computing, Networking, Storage and Analysis, 17.-22.11.2013, Denver, CO, United States of America

Publ.-Id: 19368 - Permalink


Radiative Signatures of the Relativistic Kelvin-Helmholtz Instability
Bussmann, M.; Burau, H.; Cowan, T. E.; Debus, A.; Huebl, A.; Juckeland, G.; Kluge, T.; Nagel, W. E.; Pausch, R.; Schmitt, F.; Schramm, U.; Schuchart, J.; Widera, R.;
We present a particle-in-cell simulation of the relativistic Kelvin-Helmholtz Instability (KHI) that for the first time delivers angularly resolved radiation spectra of the particle dynamics during the formation of the KHI. This enables studying the formation of the KHI with unprecedented spatial, angular and spectral resolution. Our results are of great importance for understanding astrophysical jet formation and comparable plasma phenomena by relating the particle motion observed in the KHI to its radiation signature. The innovative methods presented here on the implementation of the particle-in-cell algorithm on graphic processing units can be directly adapted to any many-core parallelization of the particle-mesh method. With these methods we see a peak performance of 7.176 PFLOP/s (double-precision) plus 1.449 PFLOP/s (single-precision), an efficiency of 96% when weakly scaling from 1 to 18432 nodes, an efficiency of 68.92% and a speed up of 794 (ideal: 1152) when strongly scaling from 16 to 18432 nodes.
Keywords: picongpu, titan, ornl, kelvin-helmholtz-instability, khi, pflop, gpu, simulation, plasma, performance, gordon bell prize
  • Invited lecture (Conferences)
    SC'13, The International Conference for High Performance Computing, Networking, Storage and Analysis, 17.-22.11.2013, Denver, CO, United States of America
  • Open Access LogoContribution to proceedings
    SC13: International Conference for High Performance Computing, Networking, Storage and Analysis, 17.-22.11.2013, Denver, CO, United States of America
    Proceedings of SC13, New York, NY, USA: ACM, 978-1-4503-2378-9, 5-1
    DOI: 10.1145/2503210.2504564

Publ.-Id: 19367 - Permalink


Concurrent visualisation for PIC simulations on Titan
Bussmann, M.; Schneider, B.; Grottel, S.; Gumhold, S.;
We present live visualization of large-scale plasma simulations with PIConGPU.
Keywords: visualization, in-situ, live, interactive, supercomputing, picongpu, gpu, simulation
  • Invited lecture (Conferences)
    HBP Workshop on Interactive Supercomputing, IASC 2013, 30.09.-01.10.2013, Frankfurt am Main, Deutschland

Publ.-Id: 19366 - Permalink


Playing with Petaflops - Interactive, large-scale Plasma Simulations with GPUs
Bussmann, M.;
We present results of our PIConGPU KHI simulation on TITAN at ORNL.
Keywords: hpc, titan, khi, plasma, petaflop, gpu, picongpu, simulation
  • Invited lecture (Conferences)
    NVIDIA Application Lab at Jülich: 1st Annual Workshop, 08.-09.07.2013, Jülich, Deutschland

Publ.-Id: 19365 - Permalink


Laser cooling of relativistic ion beams with broad initial momentum spread
Bussmann, M.; Siebold, M.; Schramm, U.;
One of the key requirements to using laser cooling at future high energy storage rings is to address the entire and initially broad spectrum of a bunched ion beam with a single cooling laser system.
Recent experiments at ESR have shown that this can indeed be realized by scanning the frequency of a single cw laser over a broad frequency range.
By this technique, each part of the phase space of the ions in the bucket potential can be subjected to the same cooling force, resulting in efficient cooling over the whole bucket acceptance.
Cooling times are thus limited prominently by the duration of the frequency scan and can be in the order of seconds.
In my talk I will present recent results from our experiments at ESR but will also give an outlook on what to do next - and how large-scale beam dynamics simulations can help in making the best use of laser cooling.
Keywords: laser, cooling, ion, beam, storage ring
  • Invited lecture (Conferences)
    GSI Atomphysikseminar, 02.07.2013, Darmstadt, Deutschland

Publ.-Id: 19364 - Permalink


The future of Laser-Plasma-Simulations - A personal view
Bussmann, M.;
Simulations of laser plasma interaction face several challenges. The most important one is having predictive capabilities. While qualitative agreement between experiments and simulations is frequently seen, quantitative agreement is scarce. Predictive capability requires defining your simulated system as accurately as possible and using numerical methods that do not alter your results in an unphysical manner. I'll present how these requirements influence your simulation codes and what role next-generation computers play in the game.
Keywords: picongpu, gpu, laser, plasma, acceleration, simulation, modeling
  • Invited lecture (Conferences)
    Institutsseminar Helmholtz-Institut Jena, 26.06.2013, Jena, Deutschland

Publ.-Id: 19363 - Permalink


Large-scale particle-in-cell simulations scaling up to 18432 GPUs on TITAN
Bussmann, M.;
An overview of our Petaflop simulations on the ORNL TITAN HPC system.
Keywords: titan, pflop, picongpu, plasma, simulation, gpu
  • Invited lecture (Conferences)
    ISC'13, GPU Supercomputing for Physics & Astrophysics – a Road to Exascale, 16.-20.06.2013, Leipzig, Deutschland

Publ.-Id: 19362 - Permalink


Summary “Data Analysis and Simulations”
Bussmann, M.;
A summary of data analysis and simulations with regard to the Helmholtz Beamline at XFEL
Keywords: xfel, hibef, data analysis, simulation
  • Lecture (Conference)
    Kick Off Meeting for the Helmholtz International Beamline for Extreme Fields, 02.-05.06.2013, Hamburg, Deutschland

Publ.-Id: 19361 - Permalink


Petaflop Plasma Physics: Pursuing Particle Paths
Bussmann, M.;
We present first results on radiative signatures of the Kelvin-Helmholtz Instability in relativistic streams. Large-scale simulations enable us to follow particle trajectories through turbulent plasma flows by computing the radiation of the charged particles inside the plasma. This allows imaging the plasma particle flow with unprecedented resolution by detecting the far field radiation coming from the plasma. Our results bring forward the understanding of the complex dynamics of plasmas especially in situations where direct plasma probing is impossible.
Keywords: picongpu, petaflop, gpu, plasma, astrophysics
  • Invited lecture (Conferences)
    1st Dresden CCoE GPU Programming Workshop, 27.-29.05.2013, Dresden, Deutschland

Publ.-Id: 19360 - Permalink


Towards Exascale Simulations of Laser-Driven Accelerators, Ultra-Short Solid Density Plasma Dynamics and Plasma Astrophysics
Bussmann, M.;
With new compute hardware existing today, interactive simulations of large-scale plasma dynamics have become possible. Moreover, speed ups of two orders of magnitude allow to integrate new physics into our simulations. I will present recent advances in particle-in-cell codes running on GPUs and other hardware platforms and discuss applications in laser-driven particle acceleration, ultra-short plasma phenomena at solid density and astrophysics.
Following the lessons learned from these examples I will show how gaming and file sharing may pave a path towards Exascale simulations and what the Zebra fish might have to do with this.
Keywords: picongpu, gpu, plasma, astrophysics, laser, acceleration, simulation
  • Invited lecture (Conferences)
    Seminarreihe "Aktuelle Probleme der Beschleuniger-, Plasma- und Astrophysik", 24.05.2013, Frankfurt am Main, Deutschland

Publ.-Id: 19359 - Permalink


Laser cooling of relativistic heavy ion beams at the CSRe and the ESR
Wen, W.; Siebold, M.; Schramm, U.; Zhang, D.; Ma, X.; Bussmann, M.;
An overview of laser cooling experiments at ESR/GSI and CSRe/IMPCAS Lanzhou.
Keywords: laser, cooling, esr, csre, impcas, lanzhou, ion, beam, storage ring
  • Lecture (Conference)
    China-Germany Symposium for “Laser Cooling at Storage Rings”, 06.-10.05.2013, Lanzhou, China

Publ.-Id: 19358 - Permalink


Bringing Crystalline Ion Beams from PALLAS to FAIR
Bussmann, M.; Schramm, U.;
An overview of our work on crystalline ion beams and how it applies to large-scale storage rings.
Keywords: crystalline, ion, beam, laser, cooling, storage ring
  • Invited lecture (Conferences)
    China-Germany Symposium for “Laser Cooling at Storage Rings”, 06.-10.05.2013, Lanzhou, China

Publ.-Id: 19357 - Permalink


Laser Cooling at current and future Storage Rings: From ESR to FAIR
Bussmann, M.; Siebold, M.; Schramm, U.;
A history and outlook of laser cooling of relativistic ion beams
Keywords: ion, beam, laser, cooling, storage ring, relativistic
  • Invited lecture (Conferences)
    China-Germany Symposium for “Laser Cooling at Storage Rings”, 06.-10.05.2013, Lanzhou, China

Publ.-Id: 19356 - Permalink


Large-scale simulations of laser-plasma interaction: state of the art and next steps
Bussmann, M.; Burau, H.; Widera, R.; Hübl, A.; Pausch, R.; Debus, A.; Kluge, T.; Schramm, U.; Cowan, T. E.; Schmitt, F.; Juckeland, G.; Nagel, W. E.;
We present new results on PIConGPU, a GPGPU implementation of a relativistic 3D3V particle-in-cell implementation. We show weak and strong scalings for PIConGPU on large GPU clusters and discuss the techniques used to achieve such scalability.
We furthermore introduce new physics and analysis modules added to PIConGPU that have previously not been seen in laser-plasma interaction simulations. The new analysis modules help to better conduct large parameter surveys and increase the usability of the code. One of the special features of these analysis models is that all of them are in-memory and thus allow for live generation of simulation videos at frames per second time step rates. The new physics modules focus on the generation of radiation during the laser-plasma interaction and the inter-particle interactions.
We finally discuss new techniques to scale PIConGPU and other particle-in-cell codes to Exaflop performance and the possible benefits of such extreme scaling performance.
Keywords: picongpu, particle-in-cell, simulation, laser-matter interaction, plasma
  • Invited lecture (Conferences)
    SPIE 2013 Optics+Optoelectronics, 15.-18.04.2013, Praha, Tschechische Republik

Publ.-Id: 19355 - Permalink


Aplicacion de la tecnica de espectrometria de masas con aceleradores en el estudio de la dinamica de sedimentos submarinos
Application of the accelerator mass spectrometry technique to the study of the marine sediments dynamic

Rodrigues, D.; Korschinek, G.; Merchel, S.; Rugel, G.; Arazi, A.; Marti, G. V.;
Utilizando la técnica de Espectrometría de Masas con Aceleradores se ha determinado la relación entre el radionucleido 10Be (T½ = 1,39 Ma) y su isótopo estable 9Be en siete muestras de sedimentos submarinos. Estas muestras, con relaciones isotópicas 10Be/9Be del orden de 10-8, constituyen un primer perfil de 275 m de profundidad cercano al punto donde confluyen las placas tectónicas de Nazca, Antártica y Sudamericana. Debido a su decaimiento, la concentración del 10Be disminuye con la edad del sedimento, y esta última, se espera que se corresponda linealmente con la profundidad de los mismos. Sin embargo, en este trabajo se encontraron discontinuidades en la concentración de 10Be entre los 100 y 150 metros y entre los 200 y 250 metros de profundidad con un comportamiento opuesto al esperado. Este resultado es consistente con un perfil de sedimentos estratificado en capas de edades semejantes producido por un proceso de plegamiento.

Using the accelerator mass spectrometry technique, the ratio between the radionuclide 10Be (T½ = 1.39 Ma) and its stable isotope 9Be in seven submarine sediment samples has been determined. These samples, with 10Be/9Be isotopic ratios of the order of 10-8, constitute a first 275 m-deep profile near the point where Nazca, Antarctica and South American tectonic plates join each other. Due to the decay of 10Be, its concentration decreases with the age of the sediment, which is expected to vary linearly with the depth. However, in this study we found discontinuities in the 10Be concentration between 100 and 150 meters and between 200 and 250 meters of depth. This result is consistent with a stratified sediment profile in layers with similar ages produced by a plication process.
Keywords: AMS, sediments, geochronology, site 860 ODP, plication
  • ANALES AFA 25(2014), 51-55

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Publ.-Id: 19354 - Permalink


How to test and verify radiation diagnostics simulations within particle-in-cell frameworks
Pausch, R.; Debus, A.; Widera, R.; Steiniger, K.; Huebl, A.; Burau, H.; Bussmann, M.; Schramm, U.;
The particle-in-cell code PIConGPU provides the feature of calculating angular resolved radiation spectra in the far field based on Liénard-Wiechert potentials for all macro particles of a plasma simulation. In order to verify the physics of our code we present a series of physics test scenarios, which compare numerical results to analytic solutions of nonlinear Thomson scattering at relativistic electrons. These scenarios range from single particle and electron bunch tests to full-scale laser-plasma simulations that include the collective effects of a plasma, as well as coherent and incoherent superposition of radiation of many particles. For the calculated test cases good agreement to the theoretical results with respect to absolute spectral intensities was found in all observation directions. In an electron density scan of a laser-plasma scenario, we reproduce a second-harmonic intensity scaling also observed in experiment.
Keywords: Liénard-Wiechert potentials, Thomson scattering, laser wakefield acceleration, particle-in-cell codes, radiation, synthetic diagnostics
  • Contribution to proceedings
    1st European Advanced Accelerator Concepts, 02.-06.06.2013, La Biodola, Isola d'Elba, Italy
    Proceedings of the 1st European Advanced Accelerator Concepts, Amsterdam: Elsevier
    DOI: 10.1016/j.nima.2013.10.073
  • Nuclear Instruments and Methods in Physics Research A 740(2014), 250-256
    DOI: 10.1016/j.nima.2013.10.073

Publ.-Id: 19353 - Permalink


The electromagnetic sky-map radiated by the Kelvin-Helmholtz instability
Pausch, R.; Huebl, A.; Schmitt, F.; Burau, H.; Widera, R.; Pugmire, D.; Debus, A.; Juckeland, G.; Nagel, W. E.; Bussmann, M.;
We present angularly resolved spectra from a Kelvin-Helmholtz instability (KHI) simulated at an unprecedented spatial, spectral and angular resolution.
This KHI simulated is a model of those KHIs expected to occur in active galactic nuclei and the afterglow of gamma-ray bursts. Our 3D, fully relativistic particle-in-cell simulation is initialized with two neighboring, counter-propagating plasma streams with initially sharp surfaces. During the simulation, a relativistic KHI extending over 9 vortices at an unprecedented resolution of 0.06 classical skin depths developed. The strong magnetic fields occurring in the KHI are a possible mechanism behind the non-thermal electromagnetic emissions from gamma-ray bursts. By simulating the far field radiation of this collisionless plasma shock using Liénard-Wiechert potentials, we obtained spectra for one quarter of the full sky map. Unique radiation signatures were linked to the particle dynamics during the formation of the relativistic, fully-3D KHI.
Keywords: Kelvin-Helmholtz instability, KHI, angularly resolved spectra, sky-map, electromagnetic radiation, Liénard-Wiechert potentials, PIConGPU
  • Poster
    Astrophysical Turbulence: From Galaxies to Planets, 07.-11.10.2013, Dresden, Deutschland

Publ.-Id: 19352 - Permalink


First observation of the ground-state hyperfine transition in 209Bi80+
Nörtershäuser, W.; Lochmann, M.; Jöhren, R.; Geppert, C.; Andelkovic, Z.; Anielski, D.; Botermann, B.; Bussmann, M.; Dax, A.; Frömmgen, N.; Hammen, M.; Hannen, V.; Kühl, T.; Litvinov, Y. A.; Volbrecht, J.; Stöhlker, T.; Thompson, R. C.; Weinheimer, C.; Wen, W.; Will, E.; Winters, D.; Sánchez, R. M.;
The long sought after ground-state hyperfine transition in lithium-like bismuth 209Bi80+ was observed for the first time using laser spectroscopy on relativistic ions in the experimental storage ring at the GSI Helmholtz Centre in Darmstadt. Combined with the transition in the corresponding hydrogen-like ion 209Bi82+, it will allow extraction of the specific difference between the two transitions that is unaffected by the magnetic moment distribution in the nucleus and can therefore provide a better test of bound-state QED in extremely strong magnetic fields.
Keywords: ground state, transition, bismuth, lithium-like, spectroscopy, storage ring, laser, highly charged ions

Publ.-Id: 19351 - Permalink


Longitudinal dynamics of RF-bunched and electron-cooled ion beam at the CSRe
Wen, W. Q.; Ma, X.; Bussmann, M.; Yuan, Y. J.; Zhang, D. C.; Winters, D. F. A.; Zhu, X. L.; Li, J.; Liu, H. P.; Zhao, D. M.; Wang, Z. S.; Mao, R. S.; Zhao, T. C.; Wu, J. X.; Ma, X. M.; Yan, T. L.; Li, G. H.; Yang, X. D.; Liu, Y.; Yang, J. C.; Xia, J. W.; Xu, H. S.;
Abstract: The longitudinal dynamics of RF-bunched and electron cooled ion beams have been studied at the experimental cooler storage ring (CSRe), at IMP Lanzhou. By RF-bunching the ion beam at the 50th and 100th harmonic of the revolution frequency, the longitudinal momentum spread and the bunch length of the 22Ne10+ ion beam with an energy of 70 MeV/u were measured by the new resonant Schottky pick-up and the capacitive pick-up, respectively. A minimum momentum spread of Δp/p=1.6×10−5 has been reached with less than 107 ions stored in the ring. By using the harmonic potential extracted from the Taylor expansion and the real sinusoidal potential of the bucket, the trend of momentum spread and synchrotron frequency as well as the bunch length as a function of beam current can be interpreted very well. According to this experiment, the RF-buncher is suitable for upcoming experiments on laser cooling of relativistic heavy ion beams at the CSRe.
Keywords: storage ring, ion beam, electron cooling, rf bunching, schottky

Publ.-Id: 19350 - Permalink


Preparations for laser cooling of relativistic heavy-ion beams at the CSRe
Wen, W.; Ma, X.; Zhang, D.; Bussmann, M.; Zhu, X.; Winters, D.; Meng, L.; Liu, H.; Zhao, D.; Wang, Z.; Li, J.; Mao, R.; Zhao, T.; Wu, J.; Li, G.; Yang, X.; Liu, Y.; Yang, J.; Yuan, Y.; Xia, J.; Xu, H.;
Laser cooling is one of the most promising techniques to reach high phase-space densities for relativistic heavy-ion beams. Preparations for laser cooling of relativistic lithium-like ions, such as C 3+ and N 4+ , are being made at the experimental cooler storage ring (CSRe) in Lanzhou, China. In December 2011, a new buncher was installed and tested with a 70 MeV u-1 22 Ne 10+ ion beam by electron cooling at the CSRe. The longitudinal momentum spread of the bunched ion beam was measured by the new resonant Schottky pick-up. As a result, d” p / p ~‰ˆ 2 x— 10^-ˆ’5 has been reached at ion numbers less than 107 . According to this test result, the RF-buncher is suitable for the upcoming experiment of laser cooling at the CSRe. Laser cooling of heavy-ion beams will also be applied at future storage ring facilities, e.g. FAIR in Darmstadt, and HIAF in Lanzhou.
Keywords: rf bunching, ion beam, storage ring, schottky

Publ.-Id: 19349 - Permalink


A 23Na Magic Angle Spinning Nuclear Magnetic Resonance, XANES, and High Temperature X-Ray Diffraction Study of NaUO3, Na4UO5, and Na2U2O7
Smith, A. L.; Raison, P. E.; Martel, L.; Charpentier, T.; Farnan, I.; Prieur, D.; Hennig, C.; Scheinost, A. C.; Konings, R. J. M.; Cheetham, A. K.;
The valence state of uranium has been confirmed for the three sodium uranates NaUVO3/[Rn](5f1), Na4UVIO5/[Rn](5f0), and Na2UVI2O7/[Rn](5f0), using X-ray absorption near-edge structure (XANES) spectroscopy. Solid-state 23Na magic angle spinning nuclear magnetic resonance (MAS NMR) measurements have been performed for the first time, yielding chemical shifts at −29.1 (NaUO3), 15.1 (Na4UO5), and −14.1 and −19 ppm (Na1 8-fold coordinated and Na2 7-fold coordinated in Na2U2O7), respectively. The [Rn]5f1 electronic structure of uranium in NaUO3 causes a paramagnetic shift in comparison to Na4UO5 and Na2U2O7, where the electronic structure is [Rn]5f0. A 23Na multi quantum magic angle spinning (MQMAS) study on Na2U2O7 has confirmed a monoclinic rather than rhombohedral structure with evidence for two distinct Na sites. DFT calculations of the NMR parameters on the nonmagnetic compounds Na4UO5 and Na2U2O7 have permitted the differentiation between the two Na sites of the Na2U2O7 structure. The linear thermal expansion coefficients of all three compounds have been determined using high-temperature X-ray diffraction: αa = 22.7 × 10–6 K–1, αb = 12.9 × 10–6 K–1, αc = 16.2 × 10–6 K–1, and αvol = 52.8 × 10–6 K–1 for NaUO3 in the range 298–1273 K; αa = 37.1 × 10–6 K–1, αc = 6.2 × 10–6 K–1, and αvol = 81.8 × 10–6 K–1 for Na4UO5 in the range 298–1073 K; αa = 6.7 × 10–6 K–1, αb = 14.4 × 10–6 K–1, αc = 26.8 × 10–6 K–1, αβ = −7.8 × 10–6 K–1, and αvol = −217.6 × 10–6 K–1 for Na2U2O7 in the range 298–573 K. The α to β phase transition reported for the last compound above about 600 K was not observed in the present studies, either by high-temperature X-ray diffraction or by differential scanning calorimetry.
Keywords: XANES NMR XRD uranates

Publ.-Id: 19348 - Permalink


Cetuximab Attenuates Its Cytotoxic and Radiosensitizing Potential by Inducing Fibronectin Biosynthesis
Eke, I.; Storch, K.; Krause, M.; Cordes, N.;
Inherent and acquired resistance to targeted therapeutics continues to emerge as a major clinical obstacle. For example, resistance to EGF receptor targeting occurs commonly, more so than was expected, on the basis of preclinical work. Given emerging evidence that cancer cell-substrate interactions are important determinants of therapeutic sensitivity, we examined the impact of cell-fibronectin interactions on the efficacy of the EGF receptor antibody cetuximab, which is used widely for lung cancer treatment. Our results revealed the potential for cell-fibronectin interactions to induce radioresistance of human non-small cell lung cancer cells. Cell adhesion to fibronectin enhanced tumor cell radioresistance and attenuated the cytotoxic and radiosensitizing effects of cetuximab. Both in vitro and in vivo, we found that cetuximab treatment led to a remarkable induction of fibronectin biosynthesis. Mechanistic analyses revealed the induction was mediated by a p38-MAPK-ATF2 signaling pathway and that RNAi-mediated inhibition of fibronectin could elevate the cytotoxic and radiosensitizing potential of cetuximab. Taken together, our findings show how cell adhesion blunts cetuximab, which, by inducing fibronectin, generates a self-attenuating mechanism of drug resistance.
Keywords: GROWTH-FACTOR RECEPTOR; EXTRACELLULAR-MATRIX COMPONENTS; SQUAMOUS-CELL CARCINOMA; LUNG-CANCER; GENE-EXPRESSION; BREAST-CANCER; IN-VITRO; EGFR; TUMOR; TRANSCRIPTION

Publ.-Id: 19347 - Permalink


Influence and Compensation of Truncation Artifacts in MR-Based Attenuation Correction in PET/MR
Schramm, G.; Langner, J.; Hofheinz, F.; Petr, J.; Lougovski, A.; Beuthien-Baumann, B.; Platzek, I.; van den Hoff, J.;
The goal of this article is to quantify the influence of truncation artifacts in the magnetic resonance (MR)-based attenuation map (MRMap) on reconstructed positron emission tomography (PET) image volumes and to propose a new method for minimizing this influence. Methods: PET data sets of 20 patients investigated in a Philips Ingenuity PET/MR were reconstructed with and without applying two different methods for truncation compensation (TC1 vendor-provided, TC2 newly developed). In this patient group, the extent of truncation artifacts and quality of the truncation compensation (TC) was assessed visually in the MRMaps. In three additional patients MRMaps generated by algorithm TC2 could be compared to the ground truth of transmission-based attenuation maps obtained with a Siemens ECAT {rm HR}^{+} scanner. The influence of truncation on regional SUVs in lesions, other hot structures (bladder, kidney, myocardium) and the arms was assessed in suitable volume of interests (VOI). Results: Truncation compensated MRMaps exhibited residual artifacts in the arms in 16 patients for algorithm TC1 and to a lesser extent in eight patients for algorithm TC2. Compared to the transmission-based attenuation maps algorithm TC2 slightly overestimated the size of the truncated arms by 0.3 cm in the radial direction. Without truncation compensation, VOIs located in the trunk showed an average {rm SUV}_{max} underestimation of less than 5.4% relative to the results obtained with TC2. Inside the patients' arms underestimations up to 46.5% were found. Conclusion: In the trunk, standardized uptake values (SUV) underestimations due to truncation artifacts in the MRMap are rather small. Inside the arms, severe SUV underestimations can occur. Therefore, reliable TC is mandatory and can be achieved by applying the newly developed algorithm TC2 which has y- elded promising results so far. Implementation of the proposed method is straightforward and should be easily adaptable to other PET/MR systems.

Publ.-Id: 19346 - Permalink


Atomic layer deposition of TiO2 from tetrakis(dimethylamino) titanium and H2O
Abendroth, B.; Moebus, T.; Rentrop, S.; Strohmeyer, R.; Vinnichenko, M.; Weling, T.; Stocker, H.; Meyer, D. C.;
The atomic layer deposition (ALD) of TiO2 from tetrakis(dimethylamino) titanium(TDMAT) and water was studied in the substrate temperature (T-S) range of 120 degrees C to 330 degrees C.
The effect of deposition temperatures on the resulting layer microstructure is investigated. Based on the experimental results, possible interaction mechanisms of TDMAT and H2O precursor molecules and the TiO2 surface at different temperatures are discussed. The TiO2 layers were characterized with respect to microstructure, composition and optical properties by glancing angle x-ray diffraction and reflectometry, x-ray fluorescence analysis, photoelectron spectroscopy and spectroscopic ellipsometry. A constant layer growth with increasing number of ALD cycles was achieved for all investigated deposition temperatures, if the inert gas purge time after the H2O pulse was increased from 5 s at temperatures below 250 degrees C to 25 s for T-S >= 320 degrees C. In the investigated temperature range, the growth per cycle varies between 0.33 and 0.67 angstrom/cycle with a minimum at 250 degrees C. The variations of the deposition rate are related to a change from a surface determined decomposition of TDMAT to a gas phase decomposition route above 250 degrees C. At the same temperature, the microstructure of the TiO2 layers changes from amorphous to predominately crystalline, where both anatase and rutile are present.

Publ.-Id: 19345 - Permalink


An automatic method for accurate volume delineation of heterogeneous tumors in PET
Hofheinz, F.; Langner, J.; Petr, J.; Beuthien-Baumann, B.; Steinbach, J.; Kotzerke, J.; van den Hoff, J.;
Purpose: Accurate volumetric tumor delineation is of increasing importance in radiation treatment planning. Many tumors exhibit only moderate tracer uptake heterogeneity and delineation methods using an adaptive threshold lead to robust results. These methods use a tumor reference value R (e. g., ROI maximum) and the tumor background Bg to compute the volume reproducing threshold. This threshold corresponds to an isocontour which defines the tumor boundary. However, the boundaries of strongly heterogeneous tumors can not be described by an isocontour anymore and therefore conventional threshold methods are not suitable for accurate delineation. The aim of this work is the development and validation of a delineation method for heterogeneous tumors.

Methods: The new method (voxel-specific threshold method, VTM) can be considered as an extension of an adaptive threshold method (lesion-specific threshold method, LTM), where instead of a lesion-specific threshold for the whole ROI, a voxel-specific threshold is computed by determining for each voxel Bg and R in the close vicinity of the voxel. The absolute threshold for the considered voxel is then given by T-abs = T x (R - Bg) + Bg, where T = 0.39 was determined with phantom measurements. Validation: 30 clinical datasets from patients with non-small-cell lung cancer were used to generate 30 realistic anthropomorphic software phantoms of tumors with different heterogeneities and well-known volumes and boundaries. Volume delineation was performed with VTM and LTM and compared with the known lesion volumes and boundaries.

Results: In contrast to LTM, VTM was able to reproduce the true tumor boundaries accurately, independent of the heterogeneity. The deviation of the determined volume from the true volume was (0.8 +/- 4.2)% for VTM and (11.0 +/- 16.4)% for LTM.

Conclusions: In anthropomorphic software phantoms, the new method leads to promising results and to a clear improvement of volume delineation in comparison to conventional background-corrected thresholding. In the next step, the suitability for clinical routine will be further investigated. (C) 2013 American Association of Physicists in Medicine.
Keywords: PET, ROI delineation, heterogeneous tumors

Publ.-Id: 19344 - Permalink


GaPN dilute nitride fabricated by ion-implantation and pulsed laser melting
Gao, K.; Prucnal, S.; Baehtz, C.; Skorupa, W.; Helm, M.; Zhou, S.;
It is challenging to achieve luminescence from GaP due to its indirect bandgap. This restricts the application of GaP for photonic devices.
In this contribution we present the broad-band luminescence from a multi-energy-level structure based on GaP. Such optically active layer is performed by nitrogen-implantation into commercial (100) GaP wafers followed by nanosecond-range pulsed laser melting. The microstructural and optical properties of the fabricated GaPN/GaP samples were investigated by means of X-ray diffraction (XRD), micro-Raman spectroscopy, photoluminescence (PL) and photoreflectance (PR) spectroscopy. The XRD results indicate that the pulsed laser treatment leads to the recrystallization of the implantation-induced amorphous layer and the incorporation of nitrogen into the GaP lattice. The PL spectra confirm directly the formation of optically active diluted nitride layer. Moreover, the obtained multi-band PL and micro-Raman spectra suggest a local enrichment of nitrogen in the implanted layer, i.e., the formation of GaN/GaN1-xPx crystallites, which are embedded in a porous GaP1-yNy/GaP layer. Such system exhibits a wide range of strong luminescence and absorption from 380 nm to 700 nm. The structure has promising prospects in photovoltaic and white-light-emitting applications.
Keywords: GaPN, ion-implantation, pulsed laser melting
  • Lecture (Conference)
    E-MRS 2013 Fall Meeting, 16.-20.09.2013, Warsaw, Poland

Publ.-Id: 19342 - Permalink


Radionuclide impurities in [F-18]F- and [F-18]FDG for positron emission tomography
Koehler, M.; Degering, D.; Zessin, J.; Fuechtner, F.; Konheiser, J.;
The paper describes radionuclide impurities (gamma-emitters and H-3) in proton irradiated O-18 enriched water from an Nb target vessel with Nb entrance window, their distribution in different synthesis steps and finally in the PET radiopharmaceuticals [F-18]Fluoride and [F-18]FDG.
Keywords: 18F, PET, radionuclidic purity

Publ.-Id: 19341 - Permalink


Insitu STXM imaging and resistance measurements of trilayer vortices
Banholzer, A.; Wintz, S.; Fowley, C.; Deac, A.; Raabe, J.; Lenz, K.; Lindner, J.; Fassbender, J.ORC
We investigate a trilayer vortex system by simultaneous scanning trans-mission X-ray microscopy (STXM) and in-situ giant magnetoresistance (GMR) measurements. Our aim is to correlate the magnetic conguration of both magnetic layers with the corresponding magneto-resistance effects.
The sample is a Co/Cu/NiFe cylindrical trilayer, with 2 micrometer diameter. Top and bottom contacts allow to apply a perpendicular DC current to measure the resistance. Simultaneously the magnetic conguration of each element of the disc is imaged using STXM. This is performed at the Paul Scherrer Institute. The vortex core formation in both magnetic layers and the position of the vortex core can be controlled by applying an in-plane external magnetic eld. When the cores are at the edge, and the magnetization state resembles that of two in-plane magnetized disks, the GMR is low, as both cores move towards the center. With decreasing field the resistance increases, as the cores move beyond the center and towards the opposite side, the resistance decreases again. We investigate the resistance at different DC currents in dependency on the swept magnetic fields.
Keywords: vortex, STXM, GMR
  • Poster
    17. Deutsche Physikerinnentagung, 31.10.-03.11.2013, Heidelberg, Deutschland

Publ.-Id: 19340 - Permalink


Automated evaluation of setup errors in carbon ion therapy using PET: feasibility study
Kuess, P.; Helmbrecht, S.; Fiedler, F.; Birkfellner, W.; Enghardt, W.; Hopfgartner, J.; Georg, D.;
Purpose: To investigate the possibility of detecting patient mispositioning in carbon-ion therapy with particle therapy PET in an automated image registration based manner.
Methods: Tumors in the head and neck (H&N), pelvic, lung and brain region were investigated. Biologically optimized carbon ion treatment plans were created with TRiP98. From this treatment plans the reference +-activity distributions were calculated using a Monte Carlo simulation. Setup errors were simulated by shifting or rotating the CT. The expected + activity was calculated for each plan with shifts. Finally, the reference particle therapy PET images were compared to the "shifted" +-activity distribution simulations using the Pearson's correlation coecient (PCC). To account for dierent PET monitoring options the in-beam PET was compared to three dierent in-room scenarios. Additionally the dosimetric eects of the CT misalignments were investigated.
Results: The automated PCC detection of patient mispositioning was possible in the investigated indications for cranio-caudal shifts of 4 mm and more, except for prostate tumors. In the rather homogeneous pelvic region the generated +-activity distribution of the reference and compared PET image were to much alike. Thus setup errors in this region could not be detected. Regarding lung lesions the detection strongly depended on the exact tumor location: in the center of the lung tumor misalignments could be detected down to 2 mm shifts while resolving shifts of tumors close to the thoracic wall was more challenging. Rotational shifts in the H&N and lung region of +6 and more could be detected using in-room PET and partly using in-beam PET. Comparing in-room PET to in-beam PET no obvious trend was found. However, among the in-room scenarios a longer measurement time was found to be advantageous.
Conclusion: This study scopes the use of various particle therapy PET verication techniques in four indications. The automated detection of patients' setup errors was investigated in a broad accumulation of data sets. The evaluation of introduced setup errors is performed automatically, which is of utmost importance to introduce highly required particle therapy monitoring devices into the clinical routine.
Keywords: in-beam PET, PT-PET, Pearson's correlation coefficient, in-vivo Dosimetry, TRiP98

Publ.-Id: 19339 - Permalink


Charakterisierung der Wechselwirkung von Selen mit dem Bakterium Azospirillum brasilense
Maffert, A.;
In der vorliegenden Arbeit konnte gezeigt werden, dass das Wachstum von Azospirillum brasilense durch die Selenoxianionen Selenat und Selenit unterschiedlich beeinflusst wird. Selenat hatte im Rahmen der untersuchten Bedingungen kein Einfluss auf das Bakterium und wurde auch nicht reduziert. Dahingegen konnte beobachtet werden, dass das Bakterium sensitiv gegenüber Selenit ist. Im über die optische Dichte der Zellkultur und die Gesamtzellproteinkonzentration dokumentierten Wachstumsverlauf wurde ersichtlich, dass die Kultur in Gegenwart von Selenit erst nach vergleichsweise langer lag-Phase wächst und auch mit der Reduktion des Selenits zu elementarem Selen beginnt. Die sphärische nanopartikuläre Form des mikrobiell gebildeten elementaren Selens konnte über verschieden mikroskopische Techniken dargestellt werden. Im Folgenden ist es gelungen die Nanopartikel durch Adaption einer aus der Literatur bekannten Methode von den Bakterienzellen zu separieren. Über Elektronenmikrokopie gekoppelt mit Elementanalysen sowie die Ramanspektroskopie konnte die Zusammensetzung und Struktur der Nanopartikel als Selen- und Schwefel-haltig analysiert werden. Zudem konnte über dynamische Lichtstreuung und Zetapotentialmessungen Aussagen über die mittlere Größe der Partikel von 400 nm und das negative Oberflächenpotential getroffen werden.
Keywords: selenium, micobial reduction, selenite
  • Master thesis
    Internationales Hochschulinstitut Zittau, 2013
    77 Seiten

Publ.-Id: 19338 - Permalink


Magnetic-polaron–induced colossal magnetocapacitance in CdCr2S4
Xie, Y. M.; Yang, Z. R.; Zhang, Z. T.; Yin, L. H.; Chen, X. L.; Song, W. H.; Sun, Y. P.; Zhou, S.; Tong, W.; Zhang, Y. H.;
The origin of colossal magnetoresistance and colossal magnetocapacitance in a CdCr2S4 system was investigated. Thermoelectric-power and electronic spin resonance spectra reveal that the magnetic polaron is responsible for the colossal magnetoresistance in the n-type sample. The existence of magnetic polarons in the paramagnetic insulting matrix forms an intrinsic Maxwell-Wagner system, leading to the appearance of colossal magnetocapacitance. Being consistent with the evolution of magnetic polarons upon cooling, the Maxwell-Wagner system is valid around insulator-metal transition, where the resistance derived from impedance spectroscopy matches perfectly with DC resistance.

Publ.-Id: 19337 - Permalink


Establishment of two complementary in vitro assays for radiocopper complexes
Kubeil, M.; Zarschler, K.; Stephan, H.;
kein Abstract verfügbar
  • Lecture (Conference)
    2nd Annual Meeting Helmholtz Virtual Institute, 06.-08.10.2013, Heidelberg, Deutschland

Publ.-Id: 19336 - Permalink


64Cu-Markierung eines Cyclampropionsäure-Peptid-Konjugats zum EGFR-Targeting
Kubeil, M.; Viehweger, K.; Steinbach, J.; Stephan, H.;
Für die Entwicklung von 64Cu-basierten-Radiopharmaka erweisen sich makrocyclische Tetraamin-Chelatoren als überaus interessant. Sie bieten die Möglichkeit, Kupferradionuklide stabil zu binden und erlauben die Einführung von zielsuchenden Einheiten (Peptide, Proteine, Antikörper) an das Grundgerüst, um ein pharmazeutisches Targeting zu erzielen. Es ist bekannt, dass Cyclam-Monopropionsäure (TE1P) stabile Kupfer(II)-Komplexe bildet [1]. Komplexe mit Radiokupfer sind bisher nicht beschrieben worden. Dieses Chelatorsystem eignet sich für eine Mehrfachfunktionalisierung mit zielsuchenden Einheiten und damit ergibt sich die Möglichkeit, multivalente Wechselwirkungen mit Rezeptoren auszunutzen. Das kann zum einen zu einer höheren Bindungsaffinität und zum anderen zu einer Erhöhung der metabolischen Stabilität führen. Exemplarisch wird als rezeptorbindende Einheit das Dodecapeptid GE11 (YHWYGYTPQNVI) verwendet, welches spezifisch am epidermalen Wachstumsfaktor Rezeptor (Epidermal-Growth-Factor-Receptor, EGFR) bindet [2].
Es werden die Synthese zur Mehrfachfunktionalisierung der Cyclam-Monopropionsäure (TE1P) mit einem EGFR-spezischen Peptid (GE11) vorgestellt sowie radiochemische Aspekte bezüglich der Markierung mit 64Cu diskutiert. Darüber hinaus werden Aussagen zur metabolischen Stabilität und zur Bindungsaffinität gegenüber dem EGFR getroffen, um das Potenzial dieses 64Cu-markierten Konjugats für eine radiopharmazeutische Anwendung zu bewerten.

Literatur:
[1] T. A. Kaden et al., Helv. Chim. Acta, 1986, 69, 2081. [2] Z. Li et al., Faseb J. 2005,
19, 1978.
  • Poster
    GDCh-Wissenschaftsforum Chemie 2013, 01.-04.09.2013, Darmstadt, Deutschland

Publ.-Id: 19335 - Permalink


High-yield production of functional soluble single-domain antibodies in the cytoplasm of Escherichia coli
Zarschler, K.; Witecy, S.; Kapplusch, F.; Foerster, C.; Stephan, H.;
Background
For their application in the area of diagnosis and therapy, single-domain antibodies (sdAbs) offer multiple advantages over conventional antibodies and fragments thereof in terms of size, stability, solubility, immunogenicity, production costs as well as tumor uptake and blood clearance. Thus, sdAbs have been identified as valuable next-generation targeting moieties for molecular imaging and drug delivery in the past years. Since these probes are much less complex than conventional antibody fragments, bacterial expression represent a facile method in order to produce sdAbs in large amounts as soluble and functional proteins.

Results
By the combined use of high cell density cultivation media with a genetically engineered E. coli mutant strain designed for the cytoplasmic formation of proper disulfide bonds, we achieved high level of intracellular sdAb production (up to 200 mg/L). Due to a carboxyterminal hexahistidine epitope, the soluble recombinant sdAbs could be purified by one-step immobilized metal affinity chromatography to apparent homogeneity and easily radiolabeled with 99mTc within 1 h. The intradomain disulfide bridge being critical for the stability and functionality of the sdAb molecule was shown to be properly formed in ~96% of the purified proteins. In vitro binding studies confirmed the high affinity and specificity of the expressed sdAb 7C12 towards its molecular target.

Conclusions
Our study demonstrates an efficient cultivation and expression strategy for the production of substantial amounts of soluble and functional sdAbs, which may be adopted for high-yield production of other more complex proteins with multiple disulfides as well.

Publ.-Id: 19334 - Permalink


Damage accumulation in pure iron and high concentrated Fe–12.5 at% Cr alloy: comparison between object kinetic Monte Carlo and cluster dynamics
Gokhman, A.; Caturla, M.; Bergner, F.;
A comparison between object kinetic Monte Carlo (OKMC) and cluster dynamics (CD) simulations of damage accumulation has been made in the domain of low (77–150 K) temperatures for electronirradiated and then annealed pure iron as well as at 573K temperature for neutron-irradiated high concentrated Fe–12.5 at% Cr alloy. Findings indicate that an increase in the size of the simulation box up to 300 nm × 300 nm × 300 nm in OKMC simulation and direct integration of master equation of CD provide the quantitative agreement results of these methods among themselves as well as with the experimental data of microstructure evolution of Fe–12.5 at% Cr alloy and qualitative agreement for the case of pure iron electron irradiated at 77K and then annealed at temperatures between 77 and 150 K.
Keywords: irradiation; pure iron; Fe–Cr alloy; cluster dynamics; object kinetic Monte Carlo

Publ.-Id: 19333 - Permalink


Critical assessment of Cr-rich precipitates in neutron-irradiated Fe–12 at%Cr: Comparison of SANS and APT
Bergner, F.; Pareige, C.; Kuksenko, V.; Malerba, L.; Pareige, P.; Ulbricht, A.; Wagner, A.;
Neutron irradiation at 300 °C up to 0.6 dpa of an industrial purity Fe–12at%Cr alloy gives rise to the formation of Cr-rich precipitates of radii of about 1 nm. Small-angle neutron scattering (SANS) and atom probe tomography (APT) applied to the same material should reveal consistent characteristics of the irradiation-induced features. They roughly do so with respect to size and volume fraction, but they do not with respect to the composition of the precipitates or clusters. The discrepancy was expressed in terms of the Porod invariant of nuclear SANS. This quantity can be determined directly by integrating the measured nuclear difference scattering cross section or, alternatively, estimated from the APT results. Both
estimates were compared taking into account all potential sources of deviation including error propagation. We have found that the deviation is significant and can be progressively removed by artificially reducing the Fe fraction in the Cr-rich clusters with respect to the measured value. A well-known effect of this kind is the different evaporation fields of Cr-rich clusters and the Fe-rich matrix and resulting ion trajectory overlaps in APT. State-of-the-art consideration of this effect indicates, however, that it is not sufficient to remove the observed discrepancy.
Keywords: Small-angle neutron scattering, Atom probe tomography, Fe-Cr alloys. Irradiation effects

Publ.-Id: 19332 - Permalink


PIConGPU - Ultrafast OpenSource Plasma Physics
Bussmann, M.; Burau, H.; Cowan, T. E.; Debus, A.; Helm, A.; Huebl, A.; Juckeland, G.; Kluge, T.; Nagel, W. E.; Pausch, R.; Schmitt, F.; Schneider, B.; Schramm, U.; Steiniger, K.; Widera, R.;
PIConGPU is a fully relativistic 3D3V particle-in-cell (PIC) code for studing laser-plasma physics. Todays GPUs can be used as hardware accelerators, approaching a new era of fast in situ plasma simulations.

PIC codes became the working-horses for theoretical studies of laser-plasma interactions. PIConGPU has been developed for ion and electron acceleration experiments as well as for studing plasma instabilities. It is accompanied by a still-growing set of live-analysis plugins, e.g. far-field radiation diagnostics and live 3D imaging.

With its outstanding performance up to 8 PFlops/s on the TOP2 supercomputer Titan (Oak Ridge National Lab), PIConGPU is one of the Gordon-Bell-Prize finalists 2013. It has been shown that it runs efficiently on up to 18,000 GPUs, utilizing a total of 50 million multi-processors.

Its OpenSource development is carried out by the Junior Group Computational Radiation Physics at the Institute for Radiation Physics at HZDR in close collaboration with the Center for Information Services and High Performance Computing (ZIH) of the Technical University Dresden (TUD).
  • Invited lecture (Conferences)
    Plasma Seminar October 2013, 23.10.2013, Rehovot, Israel

Publ.-Id: 19331 - Permalink


Networks of silicon nanowires: a large-scale atomistic electronic structure analysis
Keles, U.; Liedke, B.; Heinig, K.-H.; Bulutay, C.;
Networks of silicon nanowires possess intriguing electronic properties surpassing the predictions based on quantum confinement of individual nanowires. Employing large-scale atomistic pseudopotential computations, as yet unexplored branched nanostructures are investigated in the subsystem level, as well as in full assembly. The end product is a simple but versatile expression for the bandgap and band edge alignments of multiply-crossing Si nanowires for various diameter, number of crossings, and wire orientations. Further progress along this line can potentially topple the bottom-up approach for Si nanowire networks to a top-down design by starting with functionality and leading to an enabling structure.
Keywords: nanowire networks, branched nanowires, nanoscale silicon, electronic structure

Publ.-Id: 19330 - Permalink


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