Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34118 Publications

Transmission electron microscopy investigation of the microstructure of Fe-Cr alloys induced by neutron and ion irradiation at 300ºC

Hernández-Mayoral, M.; Heintze, C.; Onorbe, E.

Four Fe-Cr binary alloys, with Cr content from 2.5 up to 12wt%, were neutron or ion irradiated up to a dose of 0.6 dpa at 300ºC. The microstructural response to irradiation has been characterised using Transmission Electron Microscopy (TEM). Both, neutrons and ions, gave rise to the formation of dislocation loops. The most striking difference between ion and neutron irradiation is the distribution of these loops in the sample. Except for the lowest Cr content, loops are distributed mainly along grain boundaries and dislocations in the neutron irradiated samples. The inhomogeneous distribution of dislocation loops could be related to the presence of α’ precipitates in the matrix. In contrast, a homogeneous distribution is observed in all ion irradiated samples. This important difference is attributed to the orders of magnitude difference in dose rate between these two irradiation conditions. Moreover, the density of loops depends non-monotonically on Cr content in case of neutron irradiation, while it seems to increase with Cr content for ion implantation. Differences are also observed in terms of cluster size, with larger sizes for neutron irradiation than for ion implantation, again pointing towards an effect of the dose rate.

Keywords: transmission electron microscopy (TEM); neutron irradiation; ion irradiation; ferritic and martensitic steels; Fe-Cr alloys

Publ.-Id: 23267

A record of paleofluid circulation in faults revealed by hematite (U-Th)/He and apatite fission-track dating: an example from Gower Peninsula fault fissures, Wales

Ault, A. K.; Frenzel, M.; Reiners, P. W.; Woodock, N. H.; Thomson, S. N.

Fault-related fissures on the Gower Peninsula, Wales, preserve evidence of faulting, hematite-calcite mineralization, sediment infill, and paleofluid flow. We combine hematite (U-Th)/He (He) dating with sandstone apatite fission-track (AFT) and apatite and zircon (U-Th)/He (He) thermochronology to constrain the timing of fluid circulation in these structures. Hematite He dates from 141.0 ± 5.1 Ma to 119.9 ± 5.0 Ma overlap with a 131.4 ± 20.1 Ma sandstone infill AFT date. Individual zircon He dates are ~402-260 Ma, reflecting source material erosion, and imply a maximum late Permian infill depositional age. Burial history reconstruction reveals modern exposures were not reheated to temperatures sufficient to reset the AFT or hematite He systems in the Triassic-Early Cretaceous, and thus these dates cannot reflect cooling due to erosion alone. Hot fluids circulating through fissures in the Early Cretaceous reset the AFT system. Hematite was either also reset by fluids or precipitated from these fluids. Similar hematite He dates from fault-related mineralization in south Glamorgan (Wales), and Cumbria (England) imply concomitant regional hot groundwater flow along faults. Hydrothermal fluid circulation, coeval with North Atlantic rifting, occurred in these higher permeability fissures and fault veins long after they initially formed.

Keywords: hematite (U-Th)/He dating; low temperature thermochronology; fluid flow; Gower Peninsula; fault; fissure fills

Publ.-Id: 23266

Ion heating, Compression, Instability, Mixing, Interpenetrating and Stagnating of Ultrafast Relativistic Laser Produced Solid Plasmas

Huang, L. G.; Kluge, T.; Bussmann, M.; Cowan, T. E.

We presented ion dynamics in ultrafast relativistic laser produced solid plasmas, which include ionh eating, compression, instability, mixing, interpenetrating and stagnating.

Keywords: Ion dynamics; heating; compression; instability; mixing; interpenetrating; stagnating

  • Poster
    2016 European XFEL Users' Meeting and Satellite Meetings, 27.-29.01.2016, Hamburg, Germany

Publ.-Id: 23265

On the electrolyte convection around a hydrogen bubble evolving at a microelectrode under the influence of a magnetic field

Baczyzmalski, D.; Karnbach, F.; Yang, X.; Mutschke, G.; Uhlemann, M.; Eckert, K.; Cierpka, C.

The flow around an evolving hydrogen bubble on a microelectrode (0.1 mm in diameter) under the influence of an electrode-normal magnetic field was investigated to clarify the effect of the imposed flow on the detachment of the bubble from the electrode. Therefore, water electrolysis was carried out in a 1 M H2SO4 solution under potentiostatic conditions for different potentials in the presence of a magnetic field normal to the horizontal electrode surface. Measurements of the current oscillations and microscopic high-speed imaging were used to analyze the periodic bubble growth. The three-dimensional flow in the bulk of the cell and around the evolving bubble was measured in parallel by applying different particle imaging and tracking techniques. In addition, a numerical study of the flow was conducted to support the experimental results. The results demonstrate that the hydrodynamic force imposed by the Lorentz-force-driven-convection has a very small stabilizing effect on the bubble. However, a strong flow in the vicinity of the bubble was observed that may reduce the local supersaturation of dissolved hydrogen. Furthermore, large flow velocities close to the bubble surface indicate a strong motion of the mobile liquid-gas interface that might be significant for the bubble evolution process.

Keywords: electrolysis; gas evolution; hydrogen; magnetic field; Lorentz force; PIV; numerical simulation

Publ.-Id: 23262

Monazite characterization in a carbonatite weathering profile – a new tool for landscape geochronology

Le Bras, L.; Renno, A.; Haser, S.; Ziegenruecker, R.; Atanasova, P.; Gutzmer, J.

The Post-Gondwana geology of South Africa is marked by two prominent planation surfaces. These are the result of two distinct phases of uplift and erosion processes that took place under tropical and subtropical conditions: the first of these took place during the mid and late Cretaceous (African planation) whilst the second is tentatively placed into the Miocene (Post-African I planation) [1] or Oligocene [2]. Humid and warm climatic conditions along the African and Post-African I planation surfaces are evidenced by deep lateritic weathering columns of suitable lithologies. The ancient nature of the weathering residues has been well documented by Ar-Ar geochronology on supergene Mn-oxihydroxides [3]. The present study is carried out to test the suitability of U-Th-Pb dating on supergene monazite as a geochronometer for landscape formation and the downward progression of chemical weathering processes.

The study is carried out on material from the Zandkopsdrift carbonatite, Namaqualand, South Africa. The Zandkopsdrift carbonatite is a pipe-shaped intrusion located in the Northern Cape Province of South Africa. Its age of intrusion has been determined as being Eocene (54-56 Ma) [3]. The carbonatite has a well developed lateritic cap that is more than 80 m thick in places. This lateritic cap is greatly enriched in REE – hosted mostly by very fine crystalline monazite that is presumably of supergene origin. Due to the fact that the age of intrusion postdates the African planation surface, the lateritic cap almost certainly marks the Post-African I erosion surface.

There is pre-existing information for the development of the Post-African I planation from geological, paleontological [1] and geochronological evidence [2] [4]. The Post-African I planation surface was carved into the African surface as a consequence of renewed uplift and westward tilting of the African Plate. Climatic conditions during the development of the Post-African I planation surface remained at first humid and warm, but subsequently became more arid and thus less conducive to chemical weathering. The onset and duration of the Post-African I cycle of erosion remains uncertain.

The latter question will be addressed by the current study by dating supergene monazite from different depth in the Zandkopsdrift laterite cap – as intersected in exploration drill core. A detailed description of the petrographic and mineralogical attributes was used to identify the most promising samples for chemical dating using secondary ion mass spectrometry (SIMS). A detailed description of the internal structure, microporosity and inclusions as well as intergrowths and pseudomorphic mineral formations of each analysed monazite crystal allowed us to interpret and evaluate the respective results. The results describe the alteration of the REE minerals, the weathering process as well as the stabilization of the weathering column during arid climatic conditions. These data set important anchor points for the reconstruction of the landscape evolution in South Africa.

[1] Partridge and Maud (1987) S Afr J Geol 90:197-208
[2] Burke (1996) S Afr J Geol 99:339-409
[3] Gutzmer et al. (2012) Ore Geology Reviews 47:136-153
[4] Verwoerd (1993) S Afr J Geol 96(3):75-95

Keywords: African Landscape; Geochronology; Supergene Alteration; Monazite

  • Poster
    35th International Geological Congress, 27.08.-04.09.2016, Cape Town, Republic of South Africa

Publ.-Id: 23261

Alternative fabrication routes toward oxide dispersion strengthened steels and model alloys

Bergner, F.; Hilger, I.; Virta, J.; Lagerbom, J.; Gerbeth, G.; Connolly, S.; Hong, Z.; Grant, P. S.; Weissgärber, T.

The standard powder metallurgy (PM) route for the fabrication of oxide-dispersion-strengthened (ODS) steels involves gas atomization to produce a prealloyed powder, mechanical alloying (MA) with fine oxide powders, consolidation, and finally thermal/thermomechanical treatment (TMT). It is well established that ODS steels with superior property combinations, for example, creep and tensile strength, can be produced by this PM/MA route. However, the fabrication process is complex and expensive, and the fitness for scaling up to the industrial scale is limited. At the laboratory scale, production of small amounts of well-controlled model systems continues to be desirable for specific purposes, such as modeling-oriented experiments. Thus, from the laboratory to industrial application, there is growing interest in complementary or alternative fabrication routes for ODS steels and related model systems, which offer a different balance of cost, convenience, properties, and scalability. This article reviews the state of the art in ODS alloy fabrication and identifies promising new routes toward ODS steels. The PM/AM route for the fabrication of ODS steels is also described, as it is the current default process. Hybrid routes that comprise aspects of both the PM route and more radical liquid metal (LM) routes are suggested to be promising approaches for larger volumes and higher throughput of fabricated material. Although similar uniformity and refinement of the critical nanometer-sized oxide particles has not yet been demonstrated, ongoing innovations in the LM route are described, along with recent encouraging preliminary results for both extrinsic nano-oxide additions and intrinsic nano-oxide formation in variants of the LM route. Finally, physicochemical methods such as ion beam synthesis are shown to offer interesting perspectives for the fabrication of model systems. As well as literature sources, examples of progress in the authors’ groups are also highlighted.

Keywords: ODS steel; Fabrication; Powder metallurgy; Liquid metal; Hybrid routes


Publ.-Id: 23260

A synchronous Gigabit Ethernet protocol stack for high-throughput UDP/IP applications

Födisch, P.; Lange, B.; Sandmann, J.; Büchner, A.; Enghardt, W.; Kaever, P.

State of the art detector readout electronics require high-throughput data acquisition (DAQ) systems. In many applications, e. g. for medical imaging, the front-end electronics are set up as separate modules in a distributed DAQ. A standardized interface between the modules and a central data unit is essential. The requirements on such an interface are varied, but demand almost always a high throughput of data. Beyond this challenge, a Gigabit Ethernet interface is predestined for the broad requirements of Systems-on-a-Chip (SoC) up to large-scale DAQ systems. We have implemented an embedded protocol stack for a Field Programmable Gate Array (FPGA) capable of high-throughput data transmission and clock synchronization. A versatile stack architecture for the User Datagram Protocol (UDP) and Internet Control Message Protocol (ICMP) over Internet Protocol (IP) such as Address Resolution Protocol (ARP) as well as Precision Time Protocol (PTP) is presented. With a point-to-point connection to a host in a MicroTCA system we achieved the theoretical maximum data throughput limited by UDP both for 1000BASE-T and 1000BASE-KX links. Furthermore, we show that the random jitter of a synchronous clock over a 1000BASE-T link for a PTP application is below 60 ps.

Keywords: Data acquisition circuits; Data acquisition concepts


Publ.-Id: 23259

Ein VHDL basierter Gigabit Ethernet Protokollstapel für FPGAs

Födisch, P.; Lange, B.; Kaever, P.

Mit diesem Beitrag wird ein Protokollstapel für einen ethernet-basierten Datenaustausch mit einem FPGA vorgestellt. Für den schnellen und verbindungslosen Datenaustausch ist das User Datagram Protocol (UDP) ein schlankes Protokoll der Transportschicht. Die dynamische Erzeugung der UDP Paketrahmen benötigt eine vollständige Abbildung der zugrunde liegenden Netzwerkschichten (Internetschicht und Netzwerkschicht). Es wird eine VHDL basierte Architektur für einen Protokollstapel vorgestellt, welche die Protokolle UDP, IP, ICMP und ARP in einem FPGA integriert. Der Schichtenaufbau soll den maximalen Datendurchsatz ermöglichen. Es werden die Ergebnisse der Implementierung und Tests auf unterschiedlichen FPGA Plattformen gezeigt.

  • Contribution to proceedings
    106. Tagung der Studiengruppe elektronische Instrumentierung im Frühjahr 2015, 02.-04.03.2015, Zeuthen, Deutschland, Hamburg: Verlag Deutsches Elektronen-Synchrotron, 978-3-935702-96-6, 52-76


Publ.-Id: 23257

Droplet-confined alternate pulsed epitaxy of GaAs nanowires on Si substrates down to CMOS-compatible temperatures

Dimakis, E.; Balaghi, L.; Tauchnitz, T.; Hübner, R.; Bischoff, L.; Schneider, H.; Helm, M.

The self-catalyzed epitaxial growth of free-standing GaAs nanowires on Si substrates by molecular beam epitaxy typically requires high enough temperatures, where the Ga adatoms can diffuse efficiently along the surface of the substrate and the nanowire sidewalls before their incorporation into the liquid Ga droplets at the top of the nanowires. On the other hand, the use of high temperatures imposes several limitations concerning the interruption and resumption of the growth in an accurate and defect-free way, the realization of well-defined composition or doping profiles in axial heterostructures and, finally, the compliance with the thermal budget restrictions of fully-processed Si-CMOS circuits that is necessary for the integration of the two material technologies. Here, we introduce the droplet-confined alternate pulsed epitaxy for the self-catalyzed growth of GaAs nanowires on Si(111) substrates in the temperature range from 550 °C down to 450 °C. This unconventional growth mode is a modification of the migration-enhanced epitaxy, where alternating pulses of Ga and As4 are employed instead of a continuous supply. The enhancement of the diffusion length of Ga adatoms on the {1-10} nanowire sidewalls allows for their targeted delivery to the Ga droplets at the top of the nanowires and, thus, for a highly directional growth along the nanowire axis even at temperatures as low as 450 °C. We demonstrate that the axial growth can be controlled with the ultimate accuracy of one monolayer, while it can be simply and abruptly interrupted at any time without the formation of any defects. Taking advantage of these unique possibilities, we were able to probe the growth mechanisms in specially designed experiments and describe quantitatively the population dynamics of As inside the Ga droplets.

Keywords: Nanowire; self-catalyzed; alternate pulsed epitaxy; GaAs; Si substrate

Publ.-Id: 23256

Early and late effects of radiochemotherapy on cerebral blood flow in glioblastoma patients measured with non-invasive perfusion MRI

Petr, J.; Platzek, I.; Seidlitz, A.; Mutsaerts, H. J. M. M.; Hofheinz, F.; Schramm, G.; Maus, J.; Beuthien-Baumann, B.; Krause, M.; van den Hoff, J.

Background and purpose: To provide a systematic measure of changes of brain perfusion in healthy tissue following a fractionated radiotherapy of brain tumors.
Materials and methods: Perfusion was assessed before and after radiochemotherapy using arterial spin labeling in a group of 24 patients (mean age 54.3±14.1 years) with glioblastoma multiforme. Mean relative perfusion change in gray matter in the hemisphere contralateral to the tumor was obtained for the whole hemisphere and also for six regions created by thresholding the individual dose maps at 10 Gy steps.
Results: A significant decrease of perfusion of -9.8 ± 20.9% (p = 0.032) compared to the pre-treatment baseline was observed 3 months after the end of radiotherapy. The decrease was more pronounced for high-dose regions above 50 Gy (-16.8 ± 21.0%, p = 0.0014) than for low-dose regions below 10 Gy (-2.3 ± 20.0%, p = 0.54). No further significant decrease compared to the post-treatment baseline was observed 6 months (-0.4 ± 18.4%, p = 0.94) and 9 months (2.0 ± 15.4%, p = 0.74) after the end of radiotherapy. Conclusions: Perfusion decreased significantly during the course of radiochemotherapy. The decrease was higher in regions receiving a higher dose of radiation. This suggests that the perfusion decrease is at least partly caused by radiotherapy. Our results suggest that the detrimental effects of radiochemotherapy on perfusion occur early rather than later.

Keywords: ASL; Arterial spin labeling; Cerebral blood flow; Radiotherapy; Brain tumor; Perfusion

Publ.-Id: 23255

A fluorescence anisotropy-based assay for determining the activity of tissue transglutaminase

Hauser, C.; Wodtke, R.; Löser, R.; Pietsch, M.

Tissue transglutaminase (TGase 2) is the most abundantly expressed enzyme of the transglutaminase family and involved in a large variety of pathological processes, such as neurodegenerative diseases, disorders related to autoimmunity and inflammation as well as tumor growth, progression and metastasis. As a result, TGase 2 represents an attractive target for drug discovery and development, which requires assays that allow for the characterization of modulating agents and are appropriate for high-throughput screening. Herein, we report a fluorescence anisotropy‐based approach for the determination of TGase 2’s transamidase activity, following the time-dependent increase in fluorescence anisotropy due to the enzyme-catalyzed incorporation of fluorescein‐ and rhodamine B‐conjugated cadaverines 1-3 (acyl acceptor substrates) into N,N-dimethylated casein (acyl donor substrate). These cadaverine derivatives 1-3 were obtained by solid‐phase synthesis. To allow efficient conjugation of the rhodamine B moiety, different linkers providing secondary amine functions, such as sarcosyl and isonipecotyl, were introduced between the cadaverine and xanthenyl entities in compounds 2 and 3, respectively, with acyl acceptor 3 showing the most optimal substrate properties of the compounds investigated. The assay was validated for the search of both irreversible and reversible TGase 2 inhibitors using the inactivators iodoacetamide and a recently published L‐lysine-derived acrylamide and the allosteric binder GTP, respectively. In addition, the fluorescence anisotropy-based method was proven to be suitable for high-throughput screening (Z’ factor of 0.86) and represents a non-radioactive and highly sensitive assay for determining the active TGase 2 concentration.

Keywords: Active-site titration; Cadaverine; Enzyme inhibition; Fluorescent labeling; Transglutaminases; Xanthene dyes


Publ.-Id: 23254

Liquid metal experiments on astrophysical magnetic fields

Giesecke, A.; Gundrum, T.; Herault, J.; Stefani, F.

Cosmic magnetic fields are ubiquitous phenomena that are observed on all scales, from planets and stars to galaxies and clusters of galaxies. The origin of these fields involves the formation of electrical currents by means of complex flows of conducting fluids or plasmas. Magnetic fields may also be important for cosmic structure formation by destabilizing rotational flows that would otherwise be hydrodynamically stable with the magnetorotational instability (MRI)in accretions disks as the most prominent example. Both processes, magnetic field generation (the so called dynamo effect), and magnetic field induced instabilities have also been observed in experiments, which, however, require considerable technical efforts due to the significantly smaller scales available in the laboratory.

In my talk I will briefly summarize the essential outcome of past, present, and future liquid metal experiments on magnetohydrodynamic dynamos and instabilities. The focus will be on the project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies), a new platform for a variety of liquid sodium experiments devoted to problems of geo- and astrophysical magnetohydrodynamics conducted at Helmholtz-Zentrum Dresden-Rossendorf. Most ambitious experiments will be a large-scale precession driven dynamo experiment and a combined set-up for investigating different versions of the magnetorotational instability and the Tayler instability, a current driven kink-like instability. For both experiments, recent results of preparatory studies are presented, and the scientific prospects for the final set-ups are delineated.

Keywords: dynamo; dresdyn

  • Invited lecture (Conferences)
    Physikalisches Kolloquium, 18.04.2016, Bochum, Germany

Publ.-Id: 23253

Joint project: Retention of radionuclides relevant for final disposal in natural clay rock and saline systems - Subproject 2: Geochemical behavior and transport of radionuclides in saline systems in the presence of repository-relevant organics

Schmeide, K.; Fritsch, K.; Lippold, H.; Poetsch, M.; Kulenkampff, J.; Lippmann-Pipke, J.; Jordan, N.; Joseph, C.; Moll, H.; Cherkouk, A.; Bader, M.

The objective of this project was to study the influence of increased salinities on interaction processes in the system radionuclide – organics – clay – aquifer. For this purpose, complexation, redox, sorption, and diffusion studies were performed under variation of the ionic strength (up to 4 mol/kg) and the background electrolyte.
The U(VI) complexation by propionate was studied in dependence on ionic strength (up to 4 mol/kg NaClO4) by TRLFS, ATR FT-IR spectroscopy, and DFT calculations. An influence of ionic strength on stability constants was detected, depending on the charge of the respective complexes. The conditional stability constants, determined for 1:1, 1:2, and 1:3 complexes at specific ionic strengths, were extrapolated to zero ionic strength.
The interaction of the bacteria Sporomusa sp. MT-2.99 and Paenibacillus sp. MT-2.2 cells, isolated from Opalinus Clay, with Pu was studied. The experiments can be divided into such without an electron donor where biosorption is favored and such with addition of Na-pyruvate as an electron donor stimulating also bioreduction processes. Moreover, experiments were performed to study the interactions of the halophilic archaeon Halobacterium noricense DSM-15987 with U(VI), Eu(III), and Cm(III) in 3 M NaCl solutions.
Research for improving process understanding with respect to the mobility of multivalent metals in systems containing humic matter was focused on the reversibility of elementary processes and on their interaction. Kinetic stabilization processes in the dynamics of humate complexation equilibria were quantified in isotope exchange studies. The influence of high salinity on the mobilizing potential of humic-like clay organics was systematically investigated and was described by modeling.
The sorption of Tc(VII)/Tc(IV) onto the iron(II)-containing minerals magnetite and siderite was studied by means of batch sorption experiments, ATR FT-IR and X-ray absorption spectroscopy. The strong Tc retention at these minerals could be attributed to surface-mediated reduction of Tc(VII) to Tc(IV). An influence of ionic strength was not observed.
The influence of ionic strength (up to 3 mol/kg) and background electrolyte (NaCl, CaCl2, MgCl2) on U(VI) sorption onto montmorillonite was studied. The U(VI) sorption is influenced by the background electrolyte, the influence of ionic strength is small. Surface complexation modeling was performed applying the 2SPNE SC/CE model. Surface complexation constants were determined for the NaCl and CaCl2 system and were extrapolated to zero ionic strength. Surface complexation in mixed electrolytes can be modeled applying surface complexation constants derived for pure electrolytes.
The influence of citrate on U(VI) diffusion in Opalinus Clay was studied using Opalinus Clay pore water as background electrolyte. The diffusion parameter values obtained for the HTO through-diffusion and the U(VI) in-diffusion in the absence of citric acid were in agreement with literature data. In the presence of citric acid, U(VI) diffusion was significantly retarded, which was attributed to a change in speciation, probably U(VI) was reduced to U(IV).
Larger-scale heterogeneous material effects on diffusive transport were investigated with PET. Diffusion parameters were derived by optimum fit of a FEM-model to the measurement. These parameters are in accordance with the results from 1D-through-diffusion experiments. Deviations from the simple transversal-isotropic behavior, which are identified as residuals from the model, are indications for heterogeneous transport on the mm-scale.
PET measurements were also conducted in order to display the improvement of the EDZ with waterglass injections. These experiments enable to draw conclusions on the complex reactive transport process and thus an estimation of the achieved improvement of the barrier function. The image reconstruction procedure was largely improved, mainly with the aid of Monte-Carlo simulations, and now allows quantitative analysis and error estimation.

Keywords: actinides; uranium; curium; technetium; terbium; europium; clay; Opalinus Clay; montmorillonite; clay organics; model ligands; complexation; reduction; sorption; diffusion; heterogeneity; upscaling; migration; repository

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-068 2016
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 23251

Centrality dependence of subthreshold φ meson production in Ni+Ni collisions at 1.9A GeV

Piasecki, K.; Tyminski, Z.; Herrmann, N.; Averbeck, R.; Andronic, A.; Barret, V.; Basrak, Z.; Bastid, N.; Benabderrahmane, M. L.; Berger, M.; Buehler, P.; Cargnelli, M.; Caplar, R.; Cordier, E.; Crochet, P.; Czerwiakowa, O.; Deppner, I.; Dupieux, P.; Dzelalija, M.; Fabbietti, L.; Fodor, Z.; Gasik, P.; Gasparic, I.; Grishkin, Y.; Hartmann, O. N.; Hildenbrand, K. D.; Hong, B.; Kang, T. I.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Kis, M.; Koczon, P.; Korolija, M.; Kotte, R.; Lebedev, A.; Leifels, Y.; Le Fevre, A.; Liu, J. L.; Lopez, X.; Mangiarotti, A.; Manko, V.; Marton, J.; Matulewicz, T.; Merschmeyer, M.; Münzer, R.; Pelte, D.; Petrovici, M.; Rami, F.; Reischl, A.; Reisdorf, W.; Ryu, M. S.; Schmidt, P.; Schüttauf, A.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczynska, K.; Smolyankin, V.; Stoicea, G.; Suzuki, K.; Wagner, P.; Weber, I.; Widmann, E.; Wisniewski, K.; Xiao, Z. G.; Xu, H. S.; Yushmanov, I.; Zhang, Y.; Zhilin, A.; Zinyuk, V.; Zmeskal, J.

We analysed the φ meson production in central Ni+Ni collisions at the beam kinetic energy of 1.93A GeV with the FOPI spectrometer and found the production probability per event of [8.6 +- 0.9 (stat) +- 1.5 (syst)] x 10-4. This new data point allows for the first time to inspect the centrality dependence of the subthreshold φ meson production in heavy-ion collisions. The rise of φ meson multiplicity per event with mean number of participants can be parametrized by the power function with exponent α = 1.6 +- 0.5. The ratio of φ to K- production yields seems not to depend within the experimental uncertainties on the collision centrality, and the average of measured values was found to be 0.37 +- 0.05.


Publ.-Id: 23248

Numerische Simulation von Flüssigmetallbatterien

Weber, N.; Galindo, V.; Landgraf, S.; Starace, M.; Stefani, F.; Weier, T.; Nore, C.; Herreman, W.

Flüssigmetallbatterien bestehen aus einer stabilen Dichteschichtung zweier Metalle, welche durch eine flüssige Salzschicht getrennt sind. Die einfache Skalierbarkeit, die hohen Stromdichten und insbesondere der geringe Preis solcher Zellen machen sie zu einem idealen stationären Energiespeicher.
Fluidströmungen in komplett flüssigen Batterien können im Extremfall zum Kurzschluss der Batterie führen – eine Verbesserung des Wirkungsgrads der Zellen ist aber gleichfalls (durch Durchmischung) möglich. Strömungsphänomene, mit denen zu rechnen ist, sind Naturkonvektion, Maragonikonvektion und Magnetohydrodynamische Instabilitäten. Für letztere wurde ein numerischer Löser in OpenFOAM entwickelt. Der Vortrag bietet einen kurzen Überblick über Aufbau und Funktionsweise von Flüssigmetallbatterien, relevante Strömungsphänomene, Implementierung der Löser und eine Auswahl von Ergebnissen.

  • Lecture (others)
    Professur für Strömungsmechanik, TU Dresden, 03.03.2016, Dresden, Deutschland

Publ.-Id: 23247

Calculation of the rockwall recession rate of a limestone cliff, affected by rockfalls, using cosmogenic chlorine-36. Case study of the Montsec Range (Eastern Pyrenees, Spain)

Domènech, G.; Corominas, J.; Mavrouli, O.; Merchel, S.; Abellán, A.; Pavetich, S.; Rugel, G.

The erosion of the cliffs may be a major problem in settled areas affecting to their population and producing economic and ecological losses. In this paper we present a procedure to alculate the long-term retreat rate of a cliff affected by rockfalls in the Montsec range, Eastern Pyrenees (Spain). It is composed of low densely fractured limestones and the rockwall is affected by rockfalls of different sizes. The rockfall scars are clearly distinguishable by their regular boundaries and by their orange colour which show a clear contrast with the greyish old reference surface of the cliff face. We have dated different stepped surfaces of the rockwall, including the old reference surface, using cosmogenic 36Cl. The total amount of material released by rockfall activity was calculated using a high definition point cloud of the slope face obtained with a Terrestrial Laser Scanner (TLS). The present rockwall surface has been subtracted from the reconstructed old cliff surface. This has allowed the calculation of the total volume released by rockfalls and of the retreat rate. The latter, range from 0.31 to 0.37 mm · a-1.
This value is of the same order of magnitude as the obtained by other researchers in neighbouring regions in Spain, having similar geology and affected by rockfalls.

Keywords: Rockwall retreat rate; Terrestrial Cosmogenic Nuclide (TCN); Terrestrial Laser Scanning (TLS); Rockfall; accelerator mass spectrometry; AMS

Publ.-Id: 23246

Application of Si3N4/SiC composite for particle detectors in harsh radiation environment

Naumann, L.; Laso Garcia, A.; Akindinov, A.; Dreyer, J.; Fan, X.; Kämpfer, B.; Kotte, R.; Kugler, A.; Malkevich, D.; Martin, H. P.; Naumann, B.; Stach, D.; Svoboda, O.; Sultanov, R.

Si3N4/SiC composite is a possible candidate for floating electrodes in resistive plate chambers (RPC).
This detector type has been used in different nuclear physics experiments with soda lime glass electrodes at particle fluxes below 10E3 cm-2 s-1. Future experiments, e.g. at CBM-FAIR, demand a two orders of magnitude higher rate capability. This implies a proportional reduction of the RPC time constant. A manufacturing process has been developed to produce ceramic electrodes with a bulk resistivity varying between 10E8 and 10E12 Ω cm [2].
RPC detector prototypes of different sizes from 2x2 cm2 up to 20x20 cm2 and different bulk resistivity have been exposed with relativistic electrons, protons and ions. Detection efficiencies of 95% have been obtained for minimum ionizing particles at fluxes of up to 5x10E5 cm-2 s-1. The design of different ceramic RPC detectors and their working characteristics will be presented.
Finally, the radiation hardness of the ceramics electrodes has been investigated by neutron exposure with fluxes from 10E10 to 10E14 neq cm-2.

Keywords: Si3N4/SiC; RPC; neutron exposure; radiation hardness

  • Invited lecture (Conferences)
    Application of Si3N4/SiC Composite for Particle Detectors in Harsh Radiation Environment/ Energy Materials Nanotechnology - EMN Ceramics Meeting 2016, 25.-28.01.2016, Hong Kong, Hong Kong/SAR China

Publ.-Id: 23245

Evolution of the western Namibian drainage systems since Eocene times – a multi-methodical approach

Gärtner, A.; Linnemann, U.; Merchel, S.; Niedermann, S.; Gerdes, A.; Nguno, A.; Rugel, G.; Scharf, A.; Le Bras, L.; Hofmann, M.; Zieger, J.; Krause, R.; Harazim, S.; Stutzriemer, M.; Rothe, J.

The recent stream network of western Namibia is characterised by numerous non-perennial rivers with relatively small catchment areas, framed by the perennial Kunene and Orange Rivers. Most of them originate in the hinterland of the Great Escarpment. Studies based on terrestrial cosmogenic nuclides (TCN) revealed very low erosion rates of 3-16 m/Ma since the end of the Eocene within the proposed field area, which is consistent with the estimated long-term exhumation rates of 2 to 14 m/Ma derived by fission track studies [1,2]. Rates of ca. 10 m/Ma are also supposed for the escarpment retreat [1,3]. Thus, the relief of this region is inferred to have changed little since the Eocene [4]. Such low erosion provided excellent conditions for the preservation of fluvial sedimentary records derived by older river systems. They occur mostly as terrace conglomerates in higher positions of recent valleys. The river incision into the subjacent rocks was likely caused by recurrent tectonic events along the Etosha-Griqualand-Transvaal axis, which resulted in the uplift of the Great Escarpment [e.g. 5,6]. But the uplift possibly also caused changes of the atmospheric circulation and the hydrologic cycle [7]. Tectonic events and climate changes are supposed to be responsible for several variations in the direction of flow and dimension of the catchment areas, e.g. for the Kunene and Orange Rivers, since Palaeogene times.

The present study aims to constrain the evolution of the western Namibian drainages since the Eocene. Therefore, fluvial sediments of the Kunene, Ugab, Swakop, Kuiseb, Tsondab, and Orange Rivers, as well as their precursors were sampled. In order to obtain precise surface exposure ages of the various terrace levels the routinely used TCN 10Be, 21Ne and 26Al from quartz were applied either on surface samples or on depth-profiles consisting of 3 to 5 depth sample spots. Additionally, first results of 36Cl in calcite and U-Pb SSI (small scale isochrones) ages of calcareous matrices from pedogenic calcretes will be presented.

The provenance of the sediments was studied by detrital zircon geochronology using U-Th-Pb and Lu-Hf isotope systematics as well as single grain morphometrics. Preliminary results from several river terraces indicate differences in the detrital zircon pattern through time. This combination of methods facilitates the recognition of potential changes in the fluvial sediment provenance of a catchment area at certain points in time with high resolution. Thus, this combined approach has huge potential for revealing the palaeohydrological history. All this information can be used to estimate amplitudes and processing speeds of past events like incision rates, changing sizes of catchment areas or discharge, which is of particular interest for modelling the palaeoclimate and palaeogeography.

[1] Cockburn HAP, Brown RW, Summerfield MA, Seidl MA (2000) Earth Planet Sci Lett, 179: 429-435
[2] Bierman PR, Caffee M (2001) Am J Sci, 301: 326-358
[3] Matmon A, Bierman P, Enzel Y (2002): Geology, 30: 1135-1138
[4] Fujioka T, Chappell J (2011): Aeolian Res, 3:157-164
[5] Haddon IG, McCarthy TS (2005): J Afr Earth Sci, 43: 316-333
[6] Burke K, Gunnell Y (2008): GSA Memoirs, 201: 1-66
[7] Hay WW (1996): Geol Rundsch, 85: 409-437

Keywords: accelerator mass spectrometry; AMS; TCN; geochronology; Namibia; provenance; zircon; palaeoclimate

  • Lecture (Conference)
    35th International Geological Congress, 27.08.-04.09.2016, Cape Town, South Africa

Publ.-Id: 23244

Determination of the Maxwellian-averaged cross section of 35Cl(n,gamma)

Pavetich, S.; Akhmadaliev, S.; Dillmann, I.; Fifield, K.; Halfon, S.; Heftrich, T.; Käppeler, F.; Lederer, C.; Martschini, M.; Merchel, S.; Paul, M.; Reifarth, R.; Rugel, G.; Steier, P.; Tessler, M.; Tims, S.; Wallner, A.; Weigand, M.; Weissman, L.

In stellar environments neutron capture reactions produce 99% of all elements heavier than iron. In the slow neutron capture process (s-process) lighter isotopes, especially those with high abundances and large neutron capture cross sections, act as “neutron poisons” by reducing the number of available neutrons and hence, decreasing the production of the heavier nuclei. 35Cl, which is produced in advanced burning phases of stars, contributes to the poisoning effect. Accordingly, its Maxwellian-averaged cross section (MACS) is of significant astrophysical interest.
A combination of activation technique and accelerator mass spectrometry (AMS) was used for the determination of the MACS of 35Cl(n,gamma)36Cl. NaCl pellets were irradiated at KIT and SARAF-LiLiT (Soreq Applied Research Accelerator Facility-Liquid-Lithium Target) with a quasi-Maxwellian neutron energy distribution of 25 keV. The neutron fluence was monitored by gold foils. AMS measurements at VERA (Vienna Environmental Research Accelerator), the DREAMS (DREsden AMS) facility and the ANU Heavy Ion Accelerator Facility quantified the 36Cl/35Cl ratio of the samples. The product of the neutron fluence and the isotopic ratio gives the spectrum-averaged cross section of the reaction. By normalizing this value to a real Maxwellian spectrum a new value for the 25 keV MACS of (9.5±0.4) mb for the reaction 35Cl(n,gamma)36Cl was obtained. This is ~16% lower than the previously determined value in Guber et al [1].

[1] K. H. Guber et al., Phys. Rev. C 65, 058801 (2002).

Keywords: accelerator mass spectrometry; AMS; MACS; s-process

  • Poster
    XIV Nuclei in the Cosmos (NIC), 19.-24.06.2016, Toki Messe, Niigata, Japan

Publ.-Id: 23243

The link between the Local Bubble and radioisotopic signatures on Earth

Feige, J.; Breitschwerdt, D.; Wallner, A.; Schulreich, M. M.; Dettbarn, C.; Fifield, K.; Fuchs, B.; Merchel, S.; Rugel, G.; Steier, P.; Tims, S.; Winkler, S. R.; Golser, R.

The terrestrial 2-3 Myr old 60Fe signal has been probed to be a global phenomenon [1]. Even lunar samples show an 60Fe excess pointing towards a recent injection into the solar system [2]. The most likely sources are stellar explosions within a moving group that passed the solar neighborhood, and whose surviving members are now in the Sco-Cen association [3]. We have traced the trajectories of those stars back in time and, by analyzing the uncertainties of the stellar positions, calculated the most probable explosion sites of the perished stars. By determining their masses and explosion times, we found a sequence of supernovae starting 13 Myr ago. We used analytical and numerical methods to generate the Local Superbubble, as well as its neighboring Loop I Superbubble, and link its formation to the 60Fe signature. Similar calculations with 26Al show only a marginal signal due to its shorter half-life and the broad extension of the supernova signal of ~1.5 Myr. Recent AMS measurements of 26Al contents in four deep-sea sediment cores from the Indian Ocean confirm this result. The data show an exponential decrease towards larger depths as expected from atmospherically-produced 26Al. This terrestrial concentration overwhelms a possible signature from nearby supernovae. With 60Fe data determined from the sediment samples [1] lower limits of 60Fe/26Al ratios were calculated. These are in line with gamma-line flux ratios from SPI/INTEGRAL data in the interstellar medium [4].
[1] A. Wallner et al., this conference.
[2] L. Fimiani et al., in Proceedings of the Lunar and Planetary Science Conference, Texas, 2014, p. 1778.
[3] B. Fuchs et al., MNRAS 373, 993 (2006).
[4] W. Wang, Proceedings of the International Astronomical Union, China, 2008, p. 333.

Keywords: accelerator mass spectrometry; AMS; supernova

  • Lecture (Conference)
    XIV Nuclei in the Cosmos (NIC), 19.-24.06.2016, Toki Messe, Niigata, Japan

Publ.-Id: 23242

Atomistic simulation of copper-vacancy clusters in bcc-Fe

Talati, M.; Al-Motasem, A. T.; Bergner, F.; Bonny, G.; Posselt, M.

We have investigated how the lattice vibrations affect the thermodynamics of nanosized coherent clusters in bcc-Fe consisting of vacancies and/or copper. The study is carried out within the harmonic approximation. We have applied a combination of on-lattice simulated annealing based on Metropolis Monte Carlo simulations and off-lattice relaxation by molecular dynamics in order to find the most stable cluster configurations at 0 K. We have used the most recent interatomic potential built within the framework of the embedded-atom method for the Fe–Cu system. For finite temperatures, we determined the total free energy of pure bcc-Fe and fcc- Cu as well as the total formation free energy and the total binding free energy of the vacancy–copper clusters. Our results are compared with the available data from previous investigations performed using many-body interatomic potentials and first-principles methods.

Keywords: Atomistic simulation; nanoclusters

  • Lecture (Conference)
    International Conference: Women in Science & Technology: Creating Sustainable Career, 28.-30.01.2016, Ahmedabad, India

Publ.-Id: 23241

A gradiometric version of contactless inductive flow tomography: theory and first applications

Ratajczak, M.; Wondrak, T.; Stefani, F.

The contactless inductive flow tomography (CIFT) is a measurement technique that allows reconstructing the flow of electrically conducting fluids by measuring the flow-induced perturbations of one or various applied magnetic fields and solving the underlying inverse problem. One of the most promising application fields of CIFT is the continuous casting of steel, for which the online monitoring of the low in the mould would be highly desirable. In previous experiments at a small-scale model of continuous casting, CIFT has been applied to various industrially relevant problems, including the sudden changes of flow structures in case of Argon injection and the influence of a magnetic stirrer at the submerged entry nozzle (SEN).

The application of CIFT in the presence of electromagnetic brakes (EMBr), which are widely used to stabilize the flow in the mould, has turned out to be more challenging due to the extreme dynamic range between the strong applied brake field and the weak flow induced perturbations of the measuring field. In the present paper, we present a gradiometric version of CIFT (G-CIFT), relying on gradiometricfield measurements, that is capable to overcome those problems and which seems, therefore, a promising candidate for applying CIFT in the steel casting industry.

Keywords: contactless inductive flow tomography; CIFT; continuous casting; magnetic field measurement; gradiometric sensor; electromagnetic brake

Publ.-Id: 23240

Untersuchungen zur selektiven Anreicherung sehr feiner Partikel an Öl/Wasser-Grenzflächen

Leistner, T.; Rudolph, M.; Peuker, U.

Die Entwicklung und Erforschung von Prozessen, die eine selektive Trennung feinstpartikulärer Systeme im Größenbereich von 0,1 bis 10 µm ermöglichen, stößt auf anhaltendes Interesse im Bereich der Aufbereitung. Einen vielversprechenden Prozessansatz in diese Richtung stellt dabei der Einsatz einer unpolaren, mit Wasser nicht-mischbaren Ölphase dar. In einer Partikelmischung in der nur ausgewählte Partikel von einer Ölphase benetzt werden, können durch selektive Anreicherung an der Öl/Wasser-Grenzfläche bzw. durch den Partikeltransfer aus der wässrigen Suspension in die Ölphase theoretisch Partikel/Öl-Aggregate mit einem hohen Grad an Selektivität erzeugt werden. Die Grundlage dieses Prozesses steht im direkten Zusammenhang mit der Stabilisierung von Emulsionen mithilfe sehr feiner Feststoffpartikel.
Im Rahmen dieser Studie werden Untersuchungen zur selektiven Steuerung des Partikel/Öl-Aggregationsmechanismus an verschiedenen sehr feinen Modellpartikelsystemen (< 10 µm) durchgeführt. Als unpolare Ölphase wird Isooktan eingesetzt. Das Prozessverhalten wird in Abhängigkeit von ausgewählten Prozessparametern, u. a. dem pH-Wert der wässrigen Suspension, dem Elektrolytgehalt sowie der Zugabe von grenzflächenmodifizierenden Substanzen, untersucht und quantitativ dargestellt.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Agglomerations- und Schüttguttechnik, Lebensmittelverfahrenstechnik mit Lebensmittelbiotechnologie, Grenzflächenbestimmte Systeme und Prozesse, 16.-18.03.2015, Magdeburg, Germany

Publ.-Id: 23239

Investigating the recovery of (ultrafine) cassiterite from tailings disposals using oil-assisted flotation methods

Leistner, T.; Embrechts, M.; Chereh Chelgani, S.; Rudolph, M.; Peuker, U.

As a consequence of historic tin-mining activities up until late 1980s, several mining disposals exist in the German Erzgebirge (Ore Mountains). These disposals still contain substantial amounts of cassiterite (mainly as ultrafine particles) resulting either from de-sliming steps or from tailings of separation methods, which were not sensitive enough for fine particles. Based on industrial demands, there is a considerable interest to reprocess these disposals using beneficiation methods for ultrafine particles.
In this paper we report on the reprocessing of material from one exemplary heap applying oil-assisted flotation methods (oil agglomeration flotation and two-liquid flotation). Isooctane as a non-polar oil was used to promote the collection of cassiterite either by selective aggregation or as carriers. Recovery and product quality are investigated with different process parameters: various collectors (e.g. sulphosuccinamates and phosphonic acids), particle sizes, oil dosage, oil/pulp agitation time and pulp density. Furthermore, a comparison between these results with conventional flotation tests without using oil as process aid is presented.

  • Lecture (Conference)
    MEI Flotation '15, 16.-19.11.2015, Cape Town, South Africa

Publ.-Id: 23238

Aufbereitung Ehrenfriedersdorfer Spülsande - Untersuchungen zur Anwendung von Dichtetrennung und Flotationsmethoden zur Kassiteritgewinnung im Fein- und Feinstkornbereich

Leißner, T.; Leistner, T.; Embrechts, M.; Michaux, B.; Osbahr, I.; Möckel, R.; Rudolph, M.; Gutzmer, J.; Peuker, U.

Jahrhundertelanger Bergbau im Erzgebirgsraum hat neben einer welterbewürdigen Montanregion auch viele Bergbauhalden zurück gelassen. Unter aktuellen Rohstoffpolitischen Gesichtspunkten können diese Halden potentiellen Ressourcen darstellen. So wurde zum Beispiel im Ehrenfriedersdorfer Revier bis zum Jahr 1990 Zinn und Wolfram gewonnen. Mithilfe eines vielstufigen Verfahrens aus Zerkleinerung, Klassierung und Dichtetrennung wurden Schwermineralmischkonzentrate gewonnen, die in nachfolgenden Trennschritten in ein Kassiterit- und ein Wolframkonzentrat sowie die störenden arsenhaltigen Minerale zerlegt wurden. Beim Erzeugen der Mischkonzentrate über Dichtesortierprozesse von klassiertem Material fielen Bergefraktionen verschiedener Körnungen an. Während die Abgänge der Mittel- und Grobkornsetzmaschinen als Split verkauft wurden, sind die feinkörnigeren Abgänge der Herdwäsche den Spülhalden zugeführt worden. In dem Betriebszeitraum von 1949 bis 1990 wurden ein Zinnausbringen zwischen 58 und 75 Prozent erreicht. Ein nennenswerter Anteil des Zinns ging als feinkörniges, nicht-aufbereitbares Material in den Spülsand verloren, entweder als fein- bis feinstkörniger, freier Kassiterit, welcher nicht durch die Herde gewonnen werden konnte oder als feinkörniger, mit Bergemineralen verwachsener Kassiterit, der aufgrund des unzureichenden Aufschlusses in die Abgänge gelangte.
Im Rahmen des internationalen EMerald-Masterprogramms wurden zwei Abschlussarbeiten angefertigt, die sich mit Untersuchungen zur Aufbereitbarkeit des Ehrenfriedersdorfer Spülsands befassen. Hierbei lag der Fokus im Erhalt von Aussagen zur möglichen Gewinnung des fein- und feinstkörnigen Kassiterits durch Feinstkorndichtetrennung mittels Sortierzentrifugen (Falcon Separator) sowie durch verschiedene Flotationsmethoden (konventionelle Schaumflotation und Agglomerationsflotation). Basierend auf Ergebnissen der Aufschlussanalyse (Mineral Liberation Analyzer, MLA) wurden verschiedene Trennschnitte festgelegt und mittels Querstromklassierung Probenmaterial in definierten Größenklassen erzeugt. Die experimentellen Untersuchungen erfolgten am klassierten Material. Aussagen zum Ausbringen und zur Anreicherung des Kassiterits in den einzelnen Prozessschritten wurde durch Gehaltsbestimmung der Prozessprodukte mittels Röntgenfluoreszenzanalyse (XRF) gewonnen.

  • Lecture (Conference)
    Jahrestagung 2015 "Aufbereitung und Recycling", 11.-12.11.2015, Freiberg, Germany

Publ.-Id: 23237

Metal pad roll instability in liquid metal batteries

Weber, N.; Stefani, F.; Weier, T.

Liquid metal batteries, built as a stable density stratification of two liquid metals and a molten salt are considered as a promising candidate for grid-scale energy storage in the future.
Long-wave interface instabilities, as known from aluminium smelters, may short-ci rcuit a liquid metal battery and must therefore be avoided. First simulations of this instability, carried out in the free CFD library OpenFOAM, are presented.

  • Lecture (Conference)
    Journée de Dynamique des Fluides du Plateau de Saclay, 09.02.2016, Orsay, Frankreich

Publ.-Id: 23236

Surface sealing using self-assembled monolayers and its effect on metal diffusion in porous low-k dielectrics studied using monoenergetic positron beams

Uedono, A.; Armini, S.; Zhang, Y.; Kakizaki, T.; Krause-Rehberg, R.; Anwand, W.; Wagner, A.

Surface sealing effects on the diffusion of metal atoms in porous organosilicate glass (OSG) films were studied by monoenergetic positron beams. For a Cu(5 nm)/MnN(3 nm)/OSG(130 nm) sample fabricated with pore stuffing, C4F8 plasma etch, unstuffing, and a self-assembled monolayer (SAM) sealing process, it was found that pores with cubic pore side lengths of 1.1 and 3.1 nm coexisted in the OSG film. For the sample without the SAM sealing process, metal (Cu and Mn) atoms diffused from the top Cu/MnN layer into the OSG film and were trapped by the pores. As a result, almost all pore interiors were covered by those metals. For the sample damaged by an Ar/C4F8 plasma etch treatment before the SAM sealing process, self-assembled molecules diffused into the OSG film, and they were preferentially trapped by larger pores. The cubic pore side lengths in these pores containing self-assembled molecules was estimated to be 0.7 nm. Through this work, we have demonstrated that monoenergetic positron beams are a powerful tool for characterizing capped porous films and the trapping of atoms and molecules by pores.

Keywords: Positron annihilation low-k OSG SAM

Publ.-Id: 23235

Laser Cooling of Ion Beams at Relativistic Energies

Bussmann, M.

Laser cooling of ion beams can achieve unprecedented low momentum spreads and is strong enough to overcome intra-beam scattering and induce beam crystallization. When compared to stochastic cooling and electron cooling, laser cooling promises to show better performance than the latter two in cooling highly relativistic ion beams.

Thus, laser cooling at future facilities such as FAIR and HIAF has come into the focus of ion accelerator research.
This work is intended to give the reader a comprehensive overview of laser cooling at relativistic energies and related experiments at the storage rings ESR at GSI Darmstadt, S-LSR at ICR Kyoto and CSRe at IMP Lanzhou.

Keywords: laser; cooling; storage; ring

  • Open Access Logo Contribution to external collection
    Y. Zhang, W. Zhou: ICFA Beam Dynamics Newsletter No. 65, Newport News, CA, USA: International Committee for Future Accelerators, 2014, 8-21

Publ.-Id: 23234

Steering laser plasma simulations towards reliable predictions: how to use accelerated computing for particle accelerators

Bussmann, M.

Overview on HZDR simulation codes

Keywords: laser; plasma; simulation

  • Invited lecture (Conferences)
    SPIE Optics + Optoelectronics, 13.-16.04.2016, Praha, Ceska republika

Publ.-Id: 23233

Data- and hardware-independent methods for parallel analysis algorithms: Alpaka, GrayBat and other strange animals

Bussmann, M.

We present abstract methods for parallel algorithms developed at HZDR

Keywords: hpc

  • Lecture (Conference)
    PNI-HDRI Spring meeting 2015, 13.-14.04.2015, Hamburg, Deutschland

Publ.-Id: 23232

High performant, staged data I/O and analysis: Say ADIOS to your data

Bussmann, M.

Overview on data intensive computing at HZDR

Keywords: big data; hpc

  • Lecture (Conference)
    PNI-HDRI Spring meeting 2015, 13.-14.04.2015, Hamburg, Deutschland

Publ.-Id: 23231

Compact Cancer Killers ─ Simulating Next-Generation Laser-Driven Ion Accelerators

Bussmann, M.; Huebl, A.

We present recent results on simulations of laserd riven ion acceleration for cancer therapy

Keywords: simulation; gpu; picongpu; titan; cancer; radiation; therapy

  • Lecture (Conference)
    GPU Technology Conference 2015, 17.-20.03.2015, San Jose, CA, United States of America

Publ.-Id: 23230

Breaking the Simulation/Analysis Chain

Bussmann, M.; Huebl, A.; Schmitt, R. W. F.; Podhorszki, S. G. N.; Pugmire, D.; Klasky, S.

We discuss the future of simulation and data analysis

Keywords: hpc; data analysis; simulation

  • Invited lecture (Conferences)
    Supercomputing Frontiers 2015, 17.-20.03.2015, Singapore, Singapore

Publ.-Id: 23229

Femtosecond probing of fast transient plasma processes in high-power laser interaction with solids

Kluge, T.; Huang, L.; Gutt, C.; Bussmann, M.; Chung, H.; Zacharias, M.; Schramm, U.; Cowan, T.

Ultra-intense laser-matter interactions are a major research area in in modern plasma physics. One of the essential elements is the relativistic electron generation and transport dynamics. At present, a predictive understanding of high-intensity laser-matter interactions is severely hampered by the lack of self-consistent models for the ionization dynamics, coupled with the complex electron transport.

We establish the feasibility of using XFEL femtosecond X-ray sources to probe the spatial correlations inside of the solid-density plasma using small angle X-ray scattering (SAXS) and resonant SAXS, to obtain for the first time information on the spatial and temporal evolution of the electron density and ionization dynamics with few fs and few nm resolution. The local and instantaneous ionization state can be measured when the X-ray beam is tuned to a bound-bound resonance of a particular charge state. The atomic scattering factor at the threshold of core electron excitation increases for example at Kα excitations in highly ionized Cu to a magnitude of more than 100 times the Thomson cross section per ion.

Keywords: xfel; saxs; laser; plasma

  • Lecture (Conference)
    DPG-Frühjahrstagung Bochum, 02.-05.03.2015, Bochum, Deutschland

Publ.-Id: 23228

Laser Cooling of High Energy Ion Beams - from ESR and CSRe to FAIR and HIAF

Bussmann, M.; Wen, W.; Winters, D.; Dimopoulou, C.; Nolden, F.; Steck, M.; Sanjari, S.; Giacomini, T.; Litvinov, Y.; Kozhuharov, C.; Kühl, T.; Lochmann, M.; Ullmann, J.; Sanchez, R.; Nörtershäuser, W.; Stöhlker, T.; Beck, T.; Rein, B.; Walther, T.; Tichelmann, S.; Birkl, G.; Wang, H.; Zhang, D.; Huang, Z.; Hai, B.; Yuan, Y.; Ma, X.; Löser, M.; Siebold, M.; Schramm, U.

We present results from laser cooling experiments at ESR, GSI Darmstadt and CSRe, IMP Lanzhou. We show that with a cw laser system it is possible to cool ion beams with large initial momentum spread and that laser cooling can overcome intra-beam scattering, regardless of the initial ion beam current.

We furthermore discuss first laser cooling tests with a pulsed laser system and present an outlook on how to optimize laser cooling for heavy ion beams at highly-relativistic energies, focusing not only on laser technologies but also on optical beam diagnostics.

Keywords: laser cooling; relativistic; ion beam; storage rings

  • Lecture (Conference)
    DPG-Frühjahrstagung Wuppertal, 09.-13.03.2015, Wuppertal, Deutschland

Publ.-Id: 23227

Don’t forget the wire

Bussmann, M.; Zacharias, M.; Schöne, S.; Jung, F.; Vogt, S.; Widera, R.; Lieber, S.; Konrad, U.; Kaever, P.; Bieberle, A.; Wagner, A.; Fiedler, F.

Overview of HZDR DTS Activities in Parallel Data Analyis

Keywords: dts; data; analysis; parallel

  • Lecture (Conference)
    Matter and Technologies Kickoff Meeting, 23.-26.02.2015, Hamburg, Deutschland

Publ.-Id: 23226

Laser Cooling of Relativistic Ion Beams Recent Results and Future Perspectives

Bussmann, M.; Löser, M.; Seltmann, M.; Siebold, M.; Schramm, U.; Beck, T.; Rein, B.; Walther, T.; Tichelmann, S.; Birkl, G.; Sanchez-Alarcon, R.; Ullmann, J.; Lochmann, M.; Nörtershäuser, W.; Eidam, L.; Boine-Frankenheim, O.; Winters, D.; Kozhuharov, C.; Sanjari, S.; Litvinov, Y.; Giacomini, T.; Steck, M.; Dimopoulou, C.; Nolden, F.; Shevelko, S.; Stöhlker, T.; Spiller, P.; Wen, W.; Yang, J.; Zhang, D.; Ma, X.; Hannen, V.

We discuss recent results and future perspectives of laser cooling of relativistic ion beams

Keywords: laser cooling; storage ring; relativistic; ion; beam

  • Invited lecture (Conferences)
    COOL Workshop 2015, 28.09.-02.10.2015, Newport News, VA, United States of America

Publ.-Id: 23225

Synthetic Diagnostics for kinetic Laser Plasma Interaction Resonant Coherent X-Ray Diffraction

Bussmann, M.; Kluge, T.; Huebl, A.; Chung, H. K.; Gutt, C.; Huang, L. G.; Schramm, U.; Zacharias, M.; Cowan, T. E.

Overview on Resonant Coherent X-Ray Diffraction Simulations of Laser Plasma Interaction

Keywords: rcxdi; cfel; laser; plasma

  • Poster
    XFEL User Meeting, 28.-30.01.2015, Hamburg, Deutschland
  • Poster
    3rd International Conference on “Correlation Effects in Radiation Fields”, CERF'15, 13.-18.09.2015, Rostock, Deutschland

Publ.-Id: 23224

Alpaka, GrayBat and other spiritual animals that will help you survive in the dangerous world of HPC

Bussmann, M.; Eckert, C.; Huebl, A.; Jung, F.; Widera, R.; Worpitz, B.; Zacharias, M.; Zenker, E.; Juckeland, G.; Knüpfer, A.; Nagel, W.

Implementing codes for simulations or large-scale, high rate data analysis on modern compute hardware can take much of the time that you initially wanted to spend on something entirely else. We present our tool box of simple yet powerful solutions for writing hardware-independent, scalable and performant codes that are maintanable and can survive the next compute hardware update. We show that with modern programming techniques it is possible to implement abstract interfaces that provide sustainable concepts for parallel programming while at the same time allowing for performance optimization. This talk is about real life applications that need to work. But it will also be cool.

Keywords: hpc; c++; simulation; plasma; imaging; abstraction

  • Invited lecture (Conferences)
    ZIH-Kolloquium, 28.01.2016, Dresden, Deutschland

Publ.-Id: 23223

Titan Targets Tumors

Gedenk, E.; Bussmann, M.

German team makes large computational gains in laser-driven radiation therapy of cancer

Keywords: titan; supercomputer; radiation therapy; tumor; laser; ion; acceleration

Publ.-Id: 23222

Graphene-based fibers for supercapacitor applications

Chen, L. L.; Liu, Y.; Zhao, Y.; Chen, N.; Qu, L. T.

Energy conversion and storage devices play an important role in industry and society with the rapid growth of energy consumption. Supercapacitors are very attractive due to their superior power density, fast charge/discharge rates and long cycle lifetime. Graphene fiber (GF), a fascinating material, has drawn considerable attention and shown great potential as an active material in the field of supercapacitors owing to its unique and tunable nanostructure, high electrical conductivity, excellent mechanical flexibility, light weight, and ease of functionalization. This review focuses on the recent significant advances in the fabrication and application of graphene-based fiber as electrode material in supercapacitors. The synthetic strategies and application in the supercapacitor are presented, accompanied with the summary and outlook for the future development of GFs.

Keywords: flexible electronics; graphene fiber; supercapacitor

Publ.-Id: 23221

Efficient laser-driven proton acceleration for radiobiological studies using ultra short laser pulses

Zeil, K.; Schlenvoigt, H.-P.; Brack, F.; Metzkes, J.; Kluge, T.; Bussmann, M.; Cowan, T. E.; Kraft, S. D.; Sauerbrey, R.; Schramm, U.; Becker, G.; Hornung, M.; Lötzsch, R.; Kaluza, M.; Kämpfer, T.; Reislöhner, J.; Uschmann, I.

Presentation about laser-proton acceleration at HZDR with 100 TW Laser, cell irradiation experiments, study on filamented proton beam profiles and reduced mass targets.

  • Invited lecture (Conferences)
    Laser Plasma Acceleration Workshop, 15.5.2015, Guadeloupe, France

Publ.-Id: 23220

Laser proton acceleration of mass-limited-targets of different materials

Zeil, K.; Schlenvoigt, H.-P.; Brack, F.; Metzkes, J.; Kluge, T.; Bussmann, M.; Cowan, T. E.; Kraft, S. D.; Sauerbrey, R.; Schramm, U.; Becker, G.; Hornung, M.; Lötzsch, R.; Kaluza, M.; Kämpfer, T.; Reislöhner, J.; Uschmann, I.

Reproducible series of mass-limited targets, manufactured with lithographic techniques, and varying in size, thickness, and mounting geometry were irradiated at the 150 TW Draco Laser facility of the Helmhotz-Zentrum Dresden-Rossendorf with ultrashort (30 fs) laser pulses of intensities of about 8 · 10^20 W/cm^2. A robust maximum energy enhancement of almost a factor of two was found when compared to reference irradiations of plain foils of the same thickness and material. The performance gain was, however, restricted to lateral target sizes of about 50 μm which was attributed to edge and mounting structure influences. In a recent experiments these mass-limited targets of similar size and thickness but different materials, such as Al, Ti and Au were irradiated at the diode-pumped high-power laser system POLARIS at the Helmholtz-Zentrum Jena, in order to study the influence of the material on to the laser proton acceleration performance. The effect of target size dependent bulk heating was studied with characteristic X-ray imaging and spectroscopy.

  • Lecture (Conference)
    Laser Plasma Targetry Workshop, 21.4.2015, Paris, France

Publ.-Id: 23219

Effect of superimposed DC magnetic field on an AC induction semi-levitated molten copper droplet

Bojarevics, A.; Beinerts, T.; Grants, I.; Kaldre, I.; Sivars, A.; Gelfgat, Y.; Gerbeth, G.

While a piece of copper on a ceramic substrate was inductively melted by a 9 to 18 kHz AC magnetic field with an axial magnetic DC field superimposed, the liquid metal stably semi-levitated in the expected free surface shape. The diameter of the liquid metal at the base was 30 mm, the volume more than 20 cm3. Replacing the ceramic substrate with a non-wetted glassy carbon crucible causes instability of the semi-levitated copper droplet. In the absence of the DC field severe chaotic instabilities of the liquid metal shape occurred, causing splashes and uncontrolled contact with the crucible walls. When an axial DC magnetic field with induction 0.35T was superimposed, the liquid metal droplet exhibited a harmonic azimuthal wave deformation of the free surface. Higher frequencies lead to smaller characteristic wavelength. The transverse DC magnetic field direction suppressed the travelling wave deformations of the droplet shape. The stabilizing effect of the DC magnetic field during induction melting has been shown for axial and transverse directions of the DC magnetic field. These results experimentally demonstrate the possibilities to improve the stability of levitated metal volumes by a superimposed DC magnetic.

  • Magnetohydrodynamics 15(2015), 437-443

Publ.-Id: 23218

Time evolution of Kelvin-Helmholtz vortices associated with collisionless shocks in laser produced plasmas

Kuramitsu, Y.; Mizuta, A.; Sakawa, Y.; Tanji, H.; Ide, T.; Sano, T.; Koenig, M.; Ravasio, A.; Pelka, A.; Takabe, H.; Gregory, C. D.; Woolsey, N.; Moritaka, T.; Matsukiyo, S.; Matsumoto, Y.; Ohnishi, N.

We report experimental results on Kelvin-Helmholtz (KH) instability and resultant vortices in laser-produced plasmas. By irradiating a double plane target with a laser beam, asymmetric counterstreaming plasmas are created. The interaction of the plasmas with different velocities and densities results in the formation of asymmetric shocks, where the shear flow exists along the contact surface and the KH instability is excited. We observe the spatial and temporal evolution of plasmas and shocks with time resolved diagnostics over several shots. Our results clearly show the evolution of transverse fluctuations, wavelike structures and circular features, which are interpreted as the KH instability and resultant vortices. The relevant numerical simulations demonstrate the time evolution of KH vortices and show qualitative agreements with experimental results. Shocks and thus the contact surfaces are ubiquitous in the universe; our experimental results show general consequences where two plasmas interact.

Keywords: Plasmas; Instabilities; Vortices; Turbulence; Waves; Laboratory astrophysics

Publ.-Id: 23216

Lithium/Sulfur Batteries Upon Cycling: Structural Modifications and Species Quantification by In Situ and Operando X-Ray Diffraction Spectroscopy

Walus, S.; Barchasz, C.; Bouchet, R.; Leprêtre, J.-C.; Colin, J.-F.; Martin, J.-F.; Elkaïm, E.; Baehtz, C.; Alloin, F.

A quantitative analysis of in situ and operando X-ray diffraction studies allows for deeper insight into the mechanism of Li2S formation and consumption. A two-step reaction process is proposed for both discharge and charge. Changing selectivity for Li2S formation is estimated, with solely Li2S being formed during the earliest step, followed by possible concurrent formation of Li2S2 intermediate in the further step of discharge.

Keywords: Lithium/Sulfur Battery; x-Ray diffraction, XRD, EXAFS, in operando

Publ.-Id: 23215

Pulsed Power Technology in the Field of Laser Plasma Physics

Kroll, F.

The presented work will summarize the development of pulsed high-field magnets and power converter technology at HZDR in 2014 for application in laser-plasma physics. The talk will focus on miniature magnetic solenoids, pulsed multipole magnets and the generation of high-current pulses.

  • Lecture (others)
    Annual Meeting of the LIGHT collaboration, 12.-13.01.2015, GSI Darmstadt, Deutschland

Publ.-Id: 23214

Influence of microstructure and mechanical stress on behavior of hydrogen in 500 nm Pd films

Vlcek, M.; Lukác, F.; Vlach, M.; Wagner, S.; Uchida, H.; Baehtz, C.; Shalimov, A.; Pundt, A.; Cízek, J.

Pd films can be used as a model system to examine the influence of microstructure and stress on the hydrogen absorption. In this work we study 500 nm Pd films deposited on different substrates with different binding strengths. The films were electrochemically loaded with hydrogen up to hydride concentration. Development of lattice constant during hydrogen loading of Pd films was investigated by in situ X-ray diffraction using synchrotron radiation. The influence of microstructure and mechanical stress in the films on the phase transition from Pd to Pd hydride was examined.

Keywords: Hydrogen; Palladium; Thin films

Publ.-Id: 23213

Thermal expansion of polycrystalline gallium nitride: an X-ray diffraction study

Minikayev, R.; Paszkowicz, W.; Piszora, P.; Knapp, M.; Bähtz, C.; Podsiadlo, S.

Gallium nitride is studied at ambient and nonambient temperatures by powder X-ray diffraction followed by Rietveld refinement of the structure. The structure is reported for the ambient temperature on the basis of laboratory data. The diffraction data collected using a synchrotron beam serve for derivation of the lattice parameter and thermal expansion dependencies on temperature. The variation of unit-cell size on temperature was studied in detail in a broad range 11 K < T < 1073 K. The obtained dependencies of a, c and V and thermal expansion coefficients are smooth, and the results are consistent with previously collected data. The c/a ratio shows an almost linear decreasing trend with rising temperature. The magnitude of thermal expansion obtained in the described experiments is similar to a recently reported theoretical one.

Keywords: Thermal expansion; x-ray diffraction; gallium nitride

Publ.-Id: 23212

Characterization of laser driven ions

Brack, F.-E.; Kraft, S. D.; Kroll, F.; Metzkes, J.; Obst, L.; Rehwald, M.; Schlenvoigt, H.-P.; Zeil, K.; Schramm, U.

Durch die Fokussierung eines ultrakurzen und hochintensiven Laserpulses auf ein Festkörpertarget können Pulse von Protonen und anderen positiv geladenen Ionen erzeugt werden. Auf Basis des etablierten TNSA (target-normal sheath acceleration) Prozesses konnten am Helmholtz-Zentrum Dresden-Rossendorf mit dem 150 TW Ultrakurzpulslaser Draco Protonenpulse mit Energien bis zu 20 MeV erzeugt und charakterisiert werden. Die Charakterisierung dieser Teilchenstrahlung erfordert die Identifizierung der Ionenspezies und die Bestimmung ihrer spektralen Verteilung möglichst nach jedem Puls, wofür standardmäßig Thomsonspektrometer verwendet werden. In den letzten Jahren wurde das DRACO-Lasersystem bis zu einer Pulsleistung über 500 TW erweitert. Aufbauend auf dem bisherigen Spektrometerdesign wurde in dieser Arbeit ein kompaktes Spektrometer für einen höheren Energiebereich bis über 80 MeV entworfen. Besonders wichtig dabei ist die Identifizierung möglicher das Messergebnis verfälschender Sekundärstrahlungsquellen, die mit Hilfe von Monte-Carlo Simulation analysiert werden müssen.

  • Lecture (Conference)
    DPG-Frühjahrstagung Wuppertal 2015, 09.-13.03.2015, Wuppertal, Deutschland

Publ.-Id: 23211

Reflective probing of laser-driven plasma for ion acceleration

Rehwald, M.; Metzkes, J.; Zeil, K.; Kraft, S.; Schramm, U.

Plasmas driven by intense, ultra-short laser pulses can support electrical field strengths of up to TV/m, making this concept promising for compact particle accelerators in which ions can gain MeV energies on a micrometer scale. For the acceleration, the laser pulse is focused onto a thin target which quickly ionized and transformed into a plasma in which electrons gain MeV energies in the laser field. These electrons leave the target volume and thereby create quasi-static charge-separation fields along the target surfaces in which the ion acceleration takes place. The acceleration is strongly influenced by the plasma conditions at the target during the main pulse interaction, which are determined by light preceding the intense main pulse or by the rising edge of the main pulse itself.

In this talk, we present a reflective pump probe method which allows to temporally resolve the lateral and longitudinal expansion of the critical plasma density. First experimental results with a pure imaging technique will be shown, in which the front and rear surface plasma were characterized. This technique is currently developed to include interferometry, in that way increasing the sensitivity in longitudinal direction. We will discuss the simulation results and a corresponding experimental setup.

  • Lecture (Conference)
    DPG-Frühjahrstagung Wuppertal 2015, 09.-13.03.2015, Wuppertal, Deutschland

Publ.-Id: 23210

Phase transformations in Ni/Ti multilayers investigated by synchrotron radiation-based x-ray diffraction

Cavaleiro, A. J.; Ramos, A. S.; Martins, R. M. S.; Braz Fernandes, F. M.; Morgiel, J.; Baehtz, C.; Vieira, M. T.

X-ray diffraction using synchrotron radiation was used for real-time investigation of the phase evolution of Ni/Ti multilayer thin films during annealing. These multilayers were deposited onto Tie6Ale4V substrates by dc magnetron sputtering from pure Ni and Ti targets. The deposition parameters were adjusted in order to obtain a near equiatomic chemical composition and modulation periods (L) below 25 nm. Along the entire thickness of the films, well-defined structures with alternate Ni- and Ti-rich layers are observed, even for L ¼ 4 nm. In this case, a halo characteristic of an amorphous structure is obtained, while for L of 12 and 25 nm the as-deposited thin films are nanocrystalline being possible to identify the (111) Ni and (002) Ti diffraction peaks. The nanolayered structure vanishes during annealing due to interdiffusion followed by reaction. The reaction between Ni and Ti to produce NiTi in the cubic B2 structure occurs in a short delay of time and within a narrow temperature range. For L of 25, 12 and 4 nm, the reaction temperature is close to 320, 350 and 385 C, respectively. For higher temperatures, in addition to the austenitic phase, the NiTi2 phase is identified. The diffusion of Ti from the substrate and Ni towards the substrate could favour the precipitation of NiTi2.

Keywords: Thin films; Transition metal alloys and compounds; Vapour deposition; Phase transition; Synchrotron radiation; Transmission electron microscopy

Publ.-Id: 23209

High-repetition-rate laser-proton acceleration employing a cryogenic hydrogen jet as a target

Rehwald, M.; Göde, S.; Obst, L.; Sommer, P.; Brack, F.; Schramm, U.; Gauthier, M.; Macdonald, M.; Roedel, C.; Glenzer, S.; Zeil, K.; Metzkes, J.; Schumaker, W.; Schlenvoigt, H.-P.

Applications of laser-accelerated protons demand a stable, high-energy and high-repetition rate particle source. We present the results of our experimental campaign in cooperation with the HED group at SLAC, performed at the 10 Hz Ti:Sa laser Draco of Helmholtz-Zentrum Dresden-Rossendorf (HZDR), employing a cryogenic Hydrogen jet as a renewable target. Draco delivers pulses of 30 fs and 5 J at 800 nm, focussed to a 3 µm spot by a F/2.5 off-axis parabolic mirror. The cylindrical jet has a diameter of 2 µm or 5 µm and a nominal electron density of 30 times the critical density. Preliminary results show a mono-species proton acceleration in a solid angle of at least +/-45° with respect to the incoming laser beam and proton energies exceeding 10 MeV. Radiochromic film stacks in forward direction show signatures of two acceleration mechanisms, one being the conventional TNSA and a second one leading to filament-like structures, possibly stemming from an instability within the plasma. Among other results, an on-shot monitoring of the stability of the jet by means of a temporally synchronized probe beam will be shown in the presentation.

  • Lecture (Conference)
    2nd European Advanced Accelerator Concepts Workshop, 13.-19.09.2015, La Biodola, Isola d'Elba, Italien

Publ.-Id: 23208

Nucleation Control for Large, Single Crystalline Domains of Monolayer Hexagonal Boron Nitride via Si-Doped Fe Catalysts

Caneva, S.; Weatherup, R. S.; Bayer, B. C.; Brennan, B.; Spencer, S. J.; Mingard, K.; Cabrero-Vilatela, A.; Baehtz, C.; Pollard, A. J.; Hofmann, S.

The scalable chemical vapor deposition of monolayer hexagonal boron nitride (h-BN) single crystals, with lateral dimensions of ∼0.3 mm, and of continuous h-BN monolayer films with large domain sizes (>25 μm) is demonstrated via an admixture of Si to Fe catalyst films. A simple thin-film Fe/SiO 2/Si catalyst system is used to show that controlled Si diffusion into the Fe catalyst allows exclusive nucleation of monolayer h-BN with very low nucleation densities upon exposure to undiluted borazine. Our systematic in situ and ex situ characterization of this catalyst system establishes a basis for further rational catalyst design for compound 2D materials.

Keywords: Hexagonal boron nitride (h-BN); chemical vapor deposition (CVD); borazine (HBNH)3; in situ X-ray diffraction (XRD); secondary ion mass spectrometry (SIMS); Fe catalyst

Publ.-Id: 23207

Spin waves going 3D - chiral effects in curved magnetic nanowires

Otalora, J. A.; Yan, M.; Lindner, J.; Fassbender, J.; Hertel, R.; Kakay, A.

Recent progress in material science has enabled the first experimental studies concerning the static magnetization characterization of samples with tubular geometry to be carried out [1]. Although investigating spin-wave and domain-wall dynamics remains a challenge from an experimental point of view, theory predicts that it is fundamentally different than in previously investigated flat geometries. Here, we discuss the effect of the curvature on the dynamics of domain walls and spin waves. Using extensive finite element micromagnetic simulations, we demonstrate that a typical vortex-type domain wall formed in a ferromagnetic tube exhibits advantageous properties regarding the domain wall speed and stability. For topological reasons, these robust domain walls do not encounter the Walker breakdown in certain nanotubes and can propagate with velocities faster than the spin wave phase velocity [2]. Above a critical velocity, the domain wall triggers a Cherenkov-type spin wave radiation. A characteristic of ferromagnetic nanotubes is that the chiral symmetry of the domain wall propagation is broken [3]. This is attributed to the lack of local inversion symmetry due to the curved surface of the nanotube [4]. Our micromagnetic as well as analytical studies show that this lack of inversion symmetry leads to a non-reciprocal dispersion relation for the spin waves with regards to the sign of the propagation vector k. The split in the frequencies for spin waves traveling in opposite directions is of the order of several GHz for tubes below 100 nm in diameter. This effect is the largest when the nanotube radius is comparable with the wavelength of the traveling spin waves and is already present for bended thin films that form a half or even less than a half nanotube only. The split and the minima of the dispersion, however, can be tuned with a circular field. The analytical formula obtained for the dispersion allows for a systematic study of the dispersion relation of nanotubes with different geometry, material parameters, applied circular and/or axial fields, without the need for the expensive 3 dimensional finite element micromagnetic simulations.
[1] R. Streubel, et al., Nano Lett. 14, 3981 (2014)
[2] M. Yan et al., Appl. Phys. Lett. 99, 122505 (2011)
[3] M. Yan et al., Appl. Phys. Lett. 100, 25402 (2012)
[4] R. Hertel, SPIN 3, 1340009 (2013)

Keywords: Nanotube; chiral; curved; spin waves; Cherenkov; non-reciprocal

  • Invited lecture (Conferences)
    603. WE-Heraeus-Seminar: Magnonics – Spin Waves Connecting Charges, Spins and Photons, 05.-08.01.2016, Bad Honnef, Deutschland

Publ.-Id: 23206

Non-reciprocal spin-wave dispersion in bent thin-film stripes

Zahn, F.; Lindner, J.; Fassbender, J.; Kakay, A.

Spin waves are considered as promising candidates to carry information in future technology applications, therefore in the last decades they have been studied intensively in ferromagnetic thin films. Recent developments in material research enabled the manufacturing of more complex structures than planar thin films; especially nanotubes and bent structures of varying curvature can be produced. It has recently been shown by theory that in nanotubes the curvature has an impact on both the domain wall and spin-wave propagation [1][2]. Moreover, the dispersion relation in nanotubes is non-reciprocal regarding the sign of the propagation vector. These effects are attributed to the lack of local inversion symmetry due to the curved surface of the nanotube [3]. As predicted by theory the spin-wave dynamics is fundamentally different from that known from thin films. Here, we studied the spin-wave propagation and the spin-wave dispersion in bent Permalloy thin-film stripes in the form of quarter-tubes, half-tubes and threequarter tubes. Compared to nanotubes, these systems only posses the curvature but not the specific boundary condition of nanotubes. For the simulations we used our GPU accelerated Finite Element micromagnetic code TetraMag [4]. The partial tubes had a homogenous magnetization along the circumference or azimuthal direction in cylindrical coordinates. The spin waves are excited with an external field applied in the radial direction at the middle of the sample. Therefore the spin waves propagate toward the ends of the considered structures, in a Damon-Eshbach geometry. For a given frequency the simulation is run until the steady state is reached. The wave vector correponding to this excitation frequency is determined by a Fourier analysis of the radial component of the magnetization along the z-axis, using a given snapshot in time. The resulting dispersion relations show a non-reciprocity regarding the sign of the propagation vector, similarly to those reported for nanotubes. The spin wave assymetry, defined as the ratio between the difference of the frequencies and their sum for a given wave vector but with opposite signs, can be as high as 5%. This is equivalent to a difference of about 500MHz for spin waves travelling with a given wave vector but opposite signs. We believe this assymetry can be verified experimentally, providing further prospects for research.
[1] M. Yan et al., Appl. Phys. Lett. 99, 122505 (2011)
[2] M. Yan et al., Appl. Phys. Lett. 100, 25402 (2012)
[3] R. Hertel, SPIN 3, 1340009 (2013)
[4] A. Kakay et al., IEEE Trans. Magn. 46, 2303 (2010)

Keywords: Spin waves; non-reciprocal; dispersion; curvature induced

  • Poster
    603. WE-Heraeus-Seminar: Magnonics – Spin Waves Connecting Charges, Spins and Photons, 05.-08.01.2016, Bad Honnef, Deutschland

Publ.-Id: 23205

An affine equivariant multivariate normal score transform for compositional data

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

The geostatistical treatment of continuous variables often includes a step of transformation to normal scores. In the case of analysing a composition, it has been suggested that standard methods can be applied to (isometric) logratio transformed compositions. Several logratio transformations are available and invariance of the final results under the choice of logratio transform is desirable. Unfortunately, a geostatistical procedure which includes marginal normal scores transformations of the individual logratio scores via quantile matching will not have this invariance property, nor will the resulting vectors of scores show a joint multivariate normal distribution. In this paper an affine-equivariant normal score transform is proposed. The method is based on a continuous deformation of the underlying logratio space to a Gaussian space. The properties and performance of this method are illustrated and positively compared with existing alternatives using a simulated setting and a case study from a banded iron formation ore mining operation from Western Australia. The proposed method is also suitable for the study of other multivariate non-compositional cases.

Keywords: additive logratio transform; alr; flow; Gaussian anamorphosis; ordinary differential equation

Publ.-Id: 23204

PENELOPE laser system update – on the way to first light

Albach, D.; Siebold, M.; Loeser, M.; Roeser, F.; Eiselt, P.; Schramm, U.

We present the current status of the PENELOPE laser system presently under construction at the Helmholtz-Zentrum Dresden-Rossendorf. We aim for the activation of the first major amplification stage boosting available energies to the Joule-level, as well as initial results for the stretcher-compressor module. An update on the development status of the last amplification stage and future front end improvements will be given.

Keywords: Penelope; laser; Ytterbium; diode pumping; CaF2

  • Lecture (Conference)
    The 5th Advanced Lasers and Photon Sources (ALPS’16), 17.-20.05.2016, Yokohama, Japan

Publ.-Id: 23203

An imaging technique for characterization of fluid flow pattern on industrial-scale column sieve trays

Schubert, M.; Piechotta, M.; Beyer, M.; Schleicher, E.; Hampel, U.; Paschold, J.

Non-uniform flow patterns on distillation trays can result in significant losses in separation efficiency compared to conditions with straight chordal flow paths. To improve flow pattern via tray design revamps as well as for more accurate prediction of achievable separation efficiency, better understanding of the flow formation is required. This is, however, not straight forward since the evolving patterns depend on column and tray design as well as on operating conditions and may cover configurations with continuous liquid being pushed through a curtain of rising bubbles (bubble regime) or a continuous gas phase carrying the liquid as droplets (spray regime).
In this study, the wire-mesh sensor technique was used to visualize flow patterns on larger trays. The technique tracks conductivity tracer pulses during their passage across the tray. A proper calibration routine was developed and a methodology is proposed to determine point liquid residence time distributions and weir-to-weir liquid velocities. Experiments were carried out in a tray column of 800 mm diameter. The feasibility study included experiments at different liquid capacities and various outlet weir obstructions. Tray benchmark data at high spatio-temporal resolution were obtained, which are suitable for validation of CFD models for flow simulation of industrial-scale sieve trays.

Keywords: distillation column; sieve tray; wire-mesh sensor; tray flow pattern; residence time distribution; liquid velocity

Publ.-Id: 23202

Liquid metal two-phase flows

Strumpf, E.; Roshchupkina, O.; Shevchenko, N.; Eckert, S.; Gerbeth, G.

The ascents of single Argon bubbles and bubble chains are investigated by means of Ultrasound Doppler Vecolimetry and X-ray radiography. A cuboid benchmark experiment of dimensions 144 x 144 x 12 mm³ is used and filled with eutectic alloy GaInSn. Furthermore the effects on the bubble behaviour and flow structure is investigated by superimposing a strong magnetic transversal DC field up to 1.1 T.

Keywords: liquid metal; two phase flow; bubble; magnetic field; UDV; X-ray

  • Poster
    LIMTECH midterm evaluation, 28.-30.09.2015, Dresden, Deutschland

Publ.-Id: 23201

Liquid metal two-phase flows

Strumpf, E.; Roshchupkina, O.; Shevchenko, N.; Eckert, S.; Gerbeth, G.

The ascents of single Argon bubbles and bubble chains are investigated by means of Ultrasound Doppler Vecolimetry and X-ray radiography. A cuboid benchmark experiment of dimensions 144 x 144 x 12 mm³ is used and filled with eutectic alloy GaInSn. Furthermore the effects on the bubble behaviour and flow structure is investigated by superimposing a strong magnetic transversal DC field up to 1.1 T.

Keywords: liquid metal; two phase flow; bubble; magnetic field; UDV; X-ray

  • Poster
    LIMTECH annual meeting 2015, 16.-17.11.2015, Hannover, Deutschland

Publ.-Id: 23200

Magnetische Momente und mächtige Magnete

Wosnitza, J.

es hat kein Abstract vorgelegen

  • Invited lecture (Conferences)
    „Physik am Samstag“ der Fachrichtung Physik der TU Dresden, 05.12.2015, Dresden, Deutschland
  • Invited lecture (Conferences)
    Vorlesung im Studium Generale "Naturwissenschaften Aktuell", 20.10.2016, Dresden, Deutschland

Publ.-Id: 23199

AIDA – Apparatus for In-situ Defect Analysis

Trinh, T. T.

AIDA – Apparatus for In-situ Defect Analysis

  • Lecture (Conference)
    PhD-Seminar of HZDR, 06.10.2015, Altenberg, Germany

Publ.-Id: 23198

Spin-lattice interactions of frustrated magnets in high magnetic fields

Wosnitza, J.

es hat kein Abstract vorgelegen

  • Invited lecture (Conferences)
    SFB 1143 Retreat workshop, 21.-23.09.2015, Krippen, Deutschland

Publ.-Id: 23197

Apparatus for In-situ Defect Analysis (AIDA) Investigations by Positron Annihilation Spectroscopy

Trinh, T. T.; Liedke, M. O.; Anwand, W.; Wagner, A.; Potzger, K.; Krause-Rehberg, R.

A unique high vacuum system for defect manipulation and analysis has been developed and installed at the Helmholtz-Zentrum Dresden-Rossendorf. The setup combines several experimental techniques for that purpose, e.g., material evaporation, ion beam modifications, and temperature treatment with the positron annihilation spectroscopy, and sheet resistance measurements.

AIDA utilizes a monoenergetic positron beam which is tungsten moderated, magnetically guided and pre-accelerated in the range of 30 eV to 35 keV. The positron beam is extracted from an intense 22Na source and enables sample depth profiling by Doppler broadening spectroscopy. The coincidence Measurements are performed by two HPGe detectors with energy resolution of (780 ± 20) eV at 511 keV, whereas the standard single HPGe detector Doppler broadening with energy resolution of (1.09 ± 0.001) keV is applicable for the varied energy scans. AIDA consist of a load lock chamber mechanism for halogen preliminary heating up to 150°C and loading a sample holder through a linear transfer to the MBE chamber by a basic pressure of 10-7 mbar. The sample holder is then mounted on a sophisticated 5 axis manipulator which is available for resistometry investigations by a 4-point probe module during isochronal annealing by a resistive heater at a base pressure of about 10-8 mbar. Thus, defects can be annealed up to 1300 K or stabilized down to 50 K and meanwhile residual resistivity measurements can be performed. In order to determine influence of vacancy complexes and their distribution onto magnetic, structural, and morphological sample properties, simultaneously ion irradiation by an energy range from (0.001 – 5) keV can be realized. The Ion Source is suitable for depth profiling and enables operation with reactive and noble gases by a current density of <200 µA/cm2. A Quartz oscillator provides a useful and progressive indication of coating thickness during the deposition process. Eventual, defect role during a dynamic formation of nanostructures on the semiconductor surface, e.g. Si or Ge, can be investigated during ion irradiation.

Keywords: Positron Annihilation Spectroscopy; In-situ

  • Poster
    28th International Conference on Defects in Semiconductors, 27.07.2015, Espoo, Finland

Publ.-Id: 23196

Magnetic and structural studies of Mg2Fe(x)Si(1-x) – hydrides

Trinh, T. T.; Yildirim, O.; Anwand, W.; Liedke, O. M.; Grenzer, J.; Potzger, K.; Lindner, J.; Asano, K.; Dam, B.; (Editors)

Mg2Fe(x)Si(1-x) – hydride is a promising multifunctional material in terms of magnetic applications due to a dramatic change in their magnetic, optical and electronic properties upon hydrogen loading. Therefore they are capable of potential applications, e.g. hydrogen sensors for use as safety monitors wherever hydrogen is used, stored, or produced and storage devices.
In order to understand the physical background of Mg2(FeSi) based systems as well as their hydrides, comprehensive investigations were performed on as-grown and hydrogen loaded 250 nm thick Mg2Fe(x)Si(1-x) (x= 0; 0.25; 0.50; 0.75; 0.90; 1.00) films using magnetometry, X-ray diffraction (XRD) and positron annihilation spectroscopy (PAS).
Magnetometry results revealed that upon hydrogen loading volume magnetic properties of the system transforms from superparamagnetic- and spin glass-like behavior to ferromagnetic behavior with high Curie temperature. Likewise, it is found that the hydrogen loading and Fe concentration have direct consequences on the structural properties, these can be explained either by an amorphisation process or by the formation of very small nanocrystalline particles probed by XRD measurements. Furthermore, different sizes and chemical decoration of open-volume defects has been observed by PAS.
The knowledge gained from these studies can be use for monitoring those characteristics that change in the presence of hydrogen.

Keywords: Magnetic application; positron annihilation spectroscopy

  • Poster
    Gordon research conference on hydrogen-metal systems, 12.-17.07.2015, Easton, MA, USA

Publ.-Id: 23195

Mg2FexSi1-x thin films: The interplay between the defects and magnetic structure properties of hydrogenation

Trinh, T. T.; Munnik, F.

Mg2Fe hydride belongs to the most promising candidates for application as light weight storage material in a future hydrogen economy. Recently, it has also been shown that due to chemochromism, Mg2Fe is a low-cost and rare-earth-free candidate for switchable mirrors upon hydrogen loading. Besides the Mg2Fe hydride, a new compound of Mg2FexSi1-x will be presented. The additional content of Si promises an optimization of hydrogen absorption and desorption processes. Comprehensive investigations at the facilities of HZDR on Mg2FexSi1-x system showed that hydrogen induced changes in structure, electronic, optical and magnetic properties. I.e., volume magnetic properties transform from superparamagnetism to ferromagnetism with a high Curie temperature.
As a member of the Helmholtz Association, HZDR provides a unique infrastructure for researchers. Large scale research facilities, i.e. the ion beam center and the linear electron accelerator ELBE of the HZDR are also briefly presented. A suite of materials analysis techniques based on ion beams and the generated radiation of the electron beam is available. A few methods are introduced such as Rutherford Backscattering Spectrometry (RBS), Resonant Nuclear Reaction Analysis (NRA) and Positron annihilation spectroscopy (PAS), which enable the cross-disciplinary collaboration between researchers.

Keywords: Metal hydride; switchable mirror; Superparamagnetism

  • Invited lecture (Conferences)
    ENERGYPOLIS Seminar, 12.11.2015, Sion, Switzerland

Publ.-Id: 23194

Luminescence mechanism for Er3+ ions in a silicon-rich nitride host under electrical pumping

Berencén, Y.; Illera, S.; Rebohle, L.; Ramírez, J. M.; Wutzler, R.; Cirera, A.; Hiller, D.; Rodríguez, J. A.; Skorupa, W.; Garrido, B.

A combined experimental and theoretical study on the electroluminescent excitation mechanism for trivalent erbium (Er3+) ions in a silicon-rich nitride (SiNx) host is presented. Direct impact by hot electrons is demonstrated to be the fundamental excitation mechanism. The Er3+ excitation by energy transfer from silicon nanostructures and/or defects is shown to be marginal under electrical pumping. A bilayer structure made of a SiO2 electron-accelerating layer and an Er-implanted SiNx layer has been sandwiched between a metal–insulator–semiconductor structure with a highly doped N-type silicon substrate and an indium–tin–oxide window functioning as a transparent electrode. Monte Carlo (MC) simulations are used to model hot electron transport in the proposed device structure. Acoustic, polar and non-polar optical electron–phonon scattering mechanisms are considered as well as a new scattering process related to the trapping/detrapping on energetically shallow traps in the band gap of silicon nitride. For SiO2 layers around 20 nm-thick and beyond, the number and kinetic energy of hot electrons before entering the SiNx layer are maximal. A significant enhancement of the 1.54 μm electroluminescence power efficiency of two orders of magnitude is observed in devices composed of a 20 nm-thick SiO2 layer compared to those composed of 10 nm-thick SiO2. We demonstrate by MC simulations that such a difference, in terms of power efficiency, is ascribed to the high-energy tail of the hot electron energy distribution, which becomes more pronounced as the SiO2 electron-accelerating layer thickness increases. It is also unveiled that direct excitation of the 1.54 μm Er3+ main radiative transition requiring an excitation energy of only 0.8 eV is inefficient, and that the major part of the Er3+ ions are excited via higher level energy states. The obtained results are sufficiently consistent to be extended to other trivalent rare-earth ions inside similar insulating material environments.

Keywords: erbium; silicon-rich nitride; hot electrons; electroluminescence; direct impact excitation; Monte Carlo; light emitting devices

Publ.-Id: 23193

Die Jagd nach dem Feldrekord - Europas höchste Magnetfelder

Wosnitza, J.

es hat kein Abstract vorgelegen

  • Lecture (others)
    Dresden-Open-Minded, Culture Container Festival, 12.-23.02.2015, Dresden, Deutschland

Publ.-Id: 23192

Investigation of single bubbles and bubble chains in liquid metal under the influence of magnetic fields

Strumpf, E.; Roshchupkina, O.; Shevchenko, N.; Eckert, S.

In the present study the ascents of single bubbles and of bubble chains in a liquid metal are investigated. For this purpose a benchmark experiment is set up, a cuboid vessel of the dimensions 144 x 144 x 12 mm³, which is filled with eutectic alloy GaInSn. A transversal magnetic field up to 1.1 T is imposed to this vessel. Ultrasound Doppler Velocimetry (UDV) is used to map the flow in the continuous phase of bubble chain regimes as well as the ascent velocity of single bubbles. X-ray radioscopy is applied to obtain detailed information within the disperse phase of bubble chains, such as bubble diameter, shape, trajectory etc.

Keywords: liquid metal; bubble; magnetic field; UDV; X-ray; two-phase flows

  • Lecture (Conference)
    MHD Days 2015, 07.-09.12.2015, Ilmenau, Deutschland

Publ.-Id: 23191

Mono-energetic Positron Source (MePS) – a large-scale facility for Porosimetry at ELBE

Trinh, T. T.; Liedke, M. O.; Anwand, W.; Wagner, A.; Krause-Rehberg, R.

Positron annihilation lifetime spectroscopy serves as an excellent tool for studies of open-volume defects in solid materials such as vacancies, vacancy agglomerates, dislocations, pores and voids. The intense mono-energetic positros beamline (MePS) at the ELBE accelerator developed for positron life-time and conventional Doppler Broadening experiments offers a non-destructive investigation method to study of porous media as well as thin film as a function of thickness.

Keywords: Positron annihilation lifetime spectroscopy; Doppler Broadening; Porous

  • Poster
    Porosimetry Workshop, 21.10.2015, HZDR, Germany

Publ.-Id: 23190

From anti‐dots to sponge: Positron Annihilation Spectroscopy of Ge+ irradiated Ge

Liedke, M. O.; Böttger, R.; Liedke, B.; Facsko, S.; Anwand, W.; Wagner, A.

Ion irradiation of Ge drives the surface morphology throughout a rich variety of nanostructure formations, i.e., from ordered nanohole and nanodot patterns to nanoporous and sponge-like structures [1]. Moreover, due to ion energy depth resolution functional modifications of Ge are not only limited to the surface but extend easily to several tens of nm depth. That is especially relevant for fuel [2], and solar cells [3], as well as for filters [4], and gas sensors [5] applications. Possible fundamental implications are under a debate as well, e.g., does the mechanism for porous Ge formation originate mainly from the vacancy clustering [1] or microexplosions [6]? In addition, surprisingly porous structures have not been found in ion irradiated Si that is in appearance virtually a very similar material to Ge.
The driving force for the irradiation induced morphology evolution is mainly related to the kinetics of ion beam induced defects. For Ge+ self-irradiation with low ion energies the sample surface remains first (i) smooth (EGe<4keV), followed by (ii) the self-organized formation of nanoholes (EGe=5-7keV), and finally (iii) at EGe>8keV porous/sponge structures develop. Increasing ion energy allows to tailor depth and porosity. For Bi+ irradiation surface morphology evolves in a similar fashion besides for EBi=7-12keV, where initial hexagonally ordered nanohole patterns reorganize into homogeneously distributed nanodots [1]. Again for larger ion energies porous and sponge-like structures evolve. The kinetics beneath ion irradiation of Ge can be drawn as follows: (i) defect distribution and number at a certain sample depth scales with ion energy, whereas (ii) increasing ion fluence forms amorphous Ge layer due to continuous creation of interstitials and vacancies. The former (iii) because of their mobility, formation volume and energy compare to interstitials can cluster and grow into pores. Once, such a small void is created and is far enough from the surface it grows by attracting additional vacancies [7]. The overall surface morphology evolution has been simulated by means of kinetic Monte Carlo (kMC) modeling [1]. Both hole and sponge structures have been visualized without, however, hexagonal ordering of patterns nor the nanodot formation found from Bi+ irradiation could be realized.
Positron annihilation lifetime spectroscopy (PALS) and Doppler Broadening (DB) measurements will allow to probe the open-volume distribution and its complexes as well as the pores size as a function of depth. Thus, it should give an insight into the evolution of surface morphology during ion irradiation of semiconductors. These results can be of importance for further kMC modeling. Preliminary investigations by DB will be performed at the SPONSOR/AIDA setup in order to estimate positron annihilation line parameters as a function of positron energy.

  • Lecture (Conference)
    Treffen deutscher Positronengruppen (TdP‐2015), 12.-13.11.2015, München, Deutschland

Publ.-Id: 23189

Open volume defects and magnetic phase transition in Fe60Al40 transition metal aluminide

Liedke, M. O.; Anwand, W.; Bali, R.; Cornelius, S.; Butterling, M.; Trinh, T. T.; Wagner, A.; Salamon, S.; Walecki, D.; Smekhova, A.; Wende, H.; Potzger, K.

Magnetic phase transition in the Fe60Al40 transition metal aluminide from the ferromagnetic disordered A2-phase to the paramagnetic ordered B2-phase as a function of annealing up to 1000°C has been investigated by means of magneto-optical and spectroscopy techniques, i.e., Kerr effect, positron annihilation and Mössbauer spectroscopy. The positron annihilation spectroscopy (PAS) has been performed in-situ sequentially after each annealing step at the Apparatus for In-situ Defect Analysis (AIDA) that is a unique tool combining positron annihilation spectroscopy with temperature treatment, material evaporation, ion irradiation, and sheet resistance measurement techniques. The overall goal was to investigate importance of the open volume defects onto the magnetic phase transition.
Magneto-optical measurements of the ordered Fe60Al40 as well as disordered sample after each annealing step have been done ex-situ at room temperature. A set of magnetization reversal loops is presented in Figure 1(a). The ordered sample shows no magnetic signal at room temperature at all, whereas the disordered one is represented by a magnetic reversal curve with coercivity of about 65 Oe. Due to annealing both the remanence and coercivity drop significantly and already at 500°C the magnetic signal vanishes. The SEM images [see inset of Fig. 1(a)] reveal continuous film surface at 500°C, whereas at 1000°C darker and bright island-like regions were found that possibly correspond to the former FeAl film and Al-AlO segregations, respectively. The light gray color surrounding the island-like regions in the 1000°C case represents most probably the SiO2 substrate.

Two different positron annihilation spectroscopy (PAS) measurement types have been utilized for defect analysis after each temperature step: (i) room temperature standard Doppler broadening as a function of positron energy E for depth profiling, (ii) RT coincident Doppler broadening measurements at fixed energy after each temperature step that can in detail reveal information of the chemical environment of defects with higher energy resolution [Fig. 1(b)]. In both cases two specific annihilation line parameters have been extracted: (i) the shape parameter S that corresponds to the fraction of positrons annihilating with the low-momentum electrons localized close to the middle of the annihilation line, and (ii) the wing parameter W that takes into appoint positron annihilation with high-momentum electrons at the outer region of the annihilation line. In general, the S parameter is sensitive to the open volume defects amount and their size, whereas the W parameter is a fingerprint of the annihilation site chemical environment, thus defects decoration by neighboring matrix elements [1].

cDB results are summarized in Figure 1(b), where the annihilation line parameters are plotted as a function of the annealing temperature. We can clearly see that up to 600°C both S and W parameters are more or less constant, whereas a jump followed by another plateau in the S parameter value for higher temperatures is visible. The jump of the S parameter can correspond to a slight increase of the open volume number and/or its size, whereas the decrease of W shifts the defect decoration in direction of Al. The S parameter difference at the jump is of about 1.5% that can be considered as low, nevertheless a step-like dependence is visible. A drop of about 5.5% in W cannot be neglected. Moreover W recovers to its original value at 1000°C that suggests larger occupation of the neighboring defect sites with Fe as well as a slight change of film stoichiometry due to annealing.

Summarizing, no evidence of variation in the vacancy concentration in matching the magnetic phase transition temperature range (400-600°C) has been found, whereas higher temperatures showed an increase in the vacancy concentration. Still, in the surface region of the sample reasonably large annihilation line parameters variations have been found showing sufficient sensitivity of our experimental tools, and ruling out possible signal saturation due to too high vacancies concentration. At higher temperatures a slightly larger defect concentration as well as different defect decorations were found that is likely a result of temperature driven material decomposition leading to a complete film melt at 1000°C. Magnetic and structural changes have been tracked using PAS, XRD, and CEMS measurements. The magnetic phase transition from para- to ferro-magnetic behavior appears to be driven by chemical disordering alone, and is independent of the vacancy concentration. These results help understand the role of defects in materials that show disorder-induced ferromagnetism.

This work has been partially financed by the Initiative and Networking Fund of the German Helmholtz Association, Helmholtz Virtual Institute MEMRIOX (VH-VI-442).

[1] - R. Krause-Rehberg and H. Leipner, Positron Annihilation in Semiconductors, Solid-State Sciences. Berlin: Springer, vol. 127 (1999)

  • Poster
    22nd International Colloquium on Magnetic Films and Surfaces, 12.-17.07.2015, Kraków, Polska

Publ.-Id: 23188

Nature of low-lying electric dipole resonance exditations in 74Ge

Negi, D.; Wiedeking, M.; Lanza, E. G.; Litvinova, E.; Vitturi, A.; Bark, R. A.; Bernstein, L. A.; Bleuel, D. L.; Bvumbi, S.; Bucher, T. D.; Daub, B. H.; Dinoko, T. S.; Erasmus, N.; Easton, J. L.; Görgen, A.; Guttormsen, M.; Jones, P.; Kheswa, B. V.; Khumalo, N. A.; Larsen, A. C.; Lawrie, E. A.; Lawrie, J. J.; Majola, S. N. T.; Masiteng, L. P.; Nchodu, M. R.; Ndayishimye, J.; Newman, R. T.; Noncolela, S. P.; Orce, J. N.; Papka, P.; Pellegri, L.; Renstrom, T.; Roux, D. G.; Schwengner, R.; Shirinda, O.; Siem, S.; Sithole, P. S.; Uwitonze, P. C.

Isospin properties of dipole states in 74Ge are investigated using the (alpha,alpha') reaction and compared to (gamma,gamma') data. The results indicate that the dipole states in the excitation energy region of 6 to 8 MeV adhere to the scenario of the recently found splitting of the region of dipole states into two separated parts: one at low energy being populated by both isoscalar and isovector probes and the other at high energy excited only by the electromagnetic probe. RQTBA calculations show a reduction in the isoscalar E1 strength with an increase in excitation energy which is consistent with the measurement.

Keywords: Alpha-particle scattering; cross sections; E1 strength; RQTBA calculations

Publ.-Id: 23187

High energy Yb:YAG active mirror laser system for transform limited pulses bridging the picosecond gap

Siebold, M.; Loeser, M.; Röser, F.; Albach, D.; Bussmann, M.; Eckhardt, S.; Lasagni, A.-F.; Sauerbrey, R.; Schramm, U.

We present a diode-pumped Yb:YAG MOPA-System for the unprecedented generation of variable pulse duration transform limited pulses in the range between 10ps and 100ps. First applications relying on unique pulse parameters as modulation free spectrum, tunability and coherence length, namely the direct laser interference patterning (DLIP) and laser cooling of stored relativistic ion beams are highlighted. Pulses are generated by a mode-locked fs-oscillator while the spectral bandwidth is narrowed in the subsequent regenerative amplifier by an intra-cavity grating monochromator. Two alternative booster amplifiers were added to increase the pulse energy to 100µJ and 10mJ, respectively.

Keywords: Lasers, ytterbium; Laser amplifiers; Pulse shaping; Diffraction gratings

Publ.-Id: 23186

Local probe of disorder-induced magnetism in Fe60Al40 thin films by CEMS

Smekhova, A.; Walecki, D.; Salamon, S.; Bali, R.; Potzger, K.; Cornelius, S.; Liedke, M. O.; Lindner, J.; Wende, H.

The phenomenon of chemical disorder-induced magnetism in the bulk FeAl system is known for decades [e.g. Ref.1] and has been intensively studied by Mössbauer spectroscopy. The majority of literature reports are dedicated to studies of ball-milled FeAl alloys of different stoichiometry that exhibit a hyperfine field splitting depending on the milling time and temperature. Nowadays it is possible to create such a disorder in a much more controlled and delicate manner also in thin films: the ion beam irradiation technique allows to effectively vary the number of Fe nearest-neighbors and interatomic distances by increasing either the ion energy or the irradiation dose.
Fe60Al40 (40nm and 250nm)/SiO2/Si thin films have been prepared by magnetron sputtering with further annealing and 20 keV Ne+ irradiation as reported in [2]. XRD scans demonstrate that the irradiation destroys the chemical ordering but preserves the structural integrity. MOKE and VSM magnetometry measurements confirm that chemically disordered films (A2 phase) are clearly ferromagnetic contrary to the annealed ones (B2 phase).
CEMS studies of as-prepared, annealed and irradiated thin films of 40nm were performed at room and low (80K) temperatures in normal or “magic angle” incidence geometry. The evident paramagnetic-ferromagnetic phase transition is shown in Fig.1: the experimental single line from an annealed sample (B2 phase) is replaced by a sextet with a hyperfine field distribution from the irradiated one (A2 phase). Measurements performed at 80K revealed further transformation of the subspectra: the subspectrum related to the paramagnetic phase almost vanishes while the subspectrum related to the ferromagnetic phase exhibits an enlarged hyperfine field splitting. Such a behavior may be attributed to the enhanced contribution of ferromagnetic Fe-rich areas in the sample [as in Ref. 3] that could have different Curie temperatures below RT. For 250nm thick samples annealed at 500°C or 1000°C, the parameters of the CEMS subspectra (isomer shifts, quadrupole splitting and doublet intensity ratio) obtained within a model suggested in [4] could be interpreted as an indication of different amounts of thermal vacancies in the samples studied. A comparison of results from CEMS and X-ray element-specific spectroscopy is in progress and will be reported.
[1] G. P. Huffman et al., J.Appl. Phys. 38, 735 (1967).
[2] R. Bali et al, Nano Lett. 14, 435 (2014).
[3] L. Zamora et al., Phys. Rev. B 79, 094418 (2009).
[4] J. Bogner et al., Phys. Rev. B 58, 14922 (1998).

  • Poster
    The International Conference on the Applications of the Mössbauer Effect (ICAME), 13.-18.09.2015, Hamburg, Deutschland

Publ.-Id: 23184

Electron beam final focus system for Thomson scattering

Krämer, J.; Jochmann, A.; Lehnert, U.; Budde, M.; Irman, A.; Schramm, U.

Electron beam final focus system for Thomson scattering experiments is presented.

  • Poster
    2nd European Advanced Accelerator Concepts Workshop, 13.-19.09.2015, La Biodola, Isola d'Elba, Italia

Publ.-Id: 23183

Developing the current experimental research into laser acceleration to a pre-commercial level

Krämer, J.; Lehnert, U.; Irman, A.; Budde, M.; Schramm, U.

One of the main challenges in the field of laser acceleration is the beam transport of laser accelerated beams with a large energy spread. The same applies to a final focus system (FFS) for the high-flux laser-Thomson x-ray source at the conventional electron accelerator ELBE, where beams are chirped for longitudinal bunch compression. We found a telescope system consisting of four permanent quadrupole magnets to address the energy spread significantly better than a quadrupole triplet. We present the design of the system, magnet test results and emittance measurements at the interaction point.

  • Lecture (Conference)
    Laser Applications at Accelerators, 24.-27.03.2015, Palmanova, Spain

Publ.-Id: 23182

Linear and nonlinear Thomson scattering from the PHOENIX xray source

Krämer, J.; Jochmann, A.; Couperus, J. P.; Köhler, A.; Zarini, O.; Pausch, R.; Debus, A.; Wagner, A.; Lehnert, U.; Budde, M.; Bødker, F.; Kristensen, J.; Michel, P.; Irman, A.; Schramm, U.

Development of advanced x-ray sources based on the laser-Thomson scattering mechanism is becoming important pushed by a strong demand for ultrashort hard x-ray pulses. These can serve as a tool for structural analysis of complex systems with unprecedented temporal and spatial resolution. We explored the spectral shape and bandwidth of the x-ray beam as a result from the interaction of electron and laser beam. The intensity dependence of the backscattered photon spectrum is investigated and compared to full-physics 3D ab-initio simulations. The realization of a non-linear Thomson scattering source qualifies as an initial step towards strong field physics research.

  • Lecture (Conference)
    International Conference on Extreme Light (ICEL), 23.-27.11.2015, Bucharest, Romania
  • Lecture (Conference)
    2nd European Advanced Accelerator Concepts Workshop, 13.-19.09.2015, La Biodola,Isola d'Elba, Italia

Publ.-Id: 23181

Radiobiological characterization of laser driven particles

Beyreuther, E.; Baumann, M.; Brüchner, K.; Cowan, T.; Gotz, M.; Kaluza, M.; Karsch, L.; Krause, M.; Laschinsky, L.; Leßmann, E.; Oppelt, M.; Schmidt, M.; Schramm, U.; Schürer, M.; Pawelke, J.

The long-term aim of developing laser based particle acceleration towards clinical application requires not only substantial technological progress, but also new technical solutions for dose delivery and quality assurance as well as comprehensive research on the radiobiological consequences of ultra-short radiation pulses with high pulse dose.
During the last years the laser driven technology was developed at such a rate that cell samples and small animals can be irradiated. Within the joint research project “onCOOPtics” extensive in vitro studies with several human tumor and normal tissue cells were already performed revealing comparable radiobiological effects of laser driven and conventional electron and proton beams1,2. Using the same cell lines, these results were substantiated comparing the radiobiological response to ultra-short pulsed electron bunches (pulse dose rates of ≤1012 Gy/min) and continuous electron delivery at the radiation source ELBE3.
In a second translational step, in vivo experiments were established. Although the experiments were motivated by future proton trials, first attempts were performed with electrons at the laser system JETI4, since the delivery of prescribed homogeneous doses to a 3D target volume is easier for electrons than for protons. A full scale animal experiment was realized for the HNSCC FaDu grown on nude mice ear. The radiation induced tumor growth delay was determined and compared to those obtained after similar treatment at a conventional clinical LINAC. Again, no significant difference in the radiation response to both radiation qualities was revealed, whereas the successful performance of such a comprehensive experiment campaign underlines the stability and reproducibility of all implemented methods and setup components5.
During this experiment campaign the changing tumour take rate and a high rate of secondary tumours were identified as limitations of the model that have to be improved before proton experiments and tumour control studies can be performed. In order to optimize the model Matrigel as medium for tumor cell injection and the glioblastoma cell line LN229 as interesting entity for proton treatment were introduced. Results of this optimization process and the status of the experiments with laser driven protons at the laser system DRACO will be presented.
The work was supported by the German Government, Federal Ministry of Education and Research, grant nos. 03ZIK445 and 03Z1N511.

1Laschinsky L, Baumann M, Beyreuther E, Enghardt W, Kaluza M et al. (2012) Radiobiological effectiveness of laser accelerated electrons in comparison to electron beams from a conventional linear accelerator. J. Radiat. Res. 53(3): 395-403.
2Zeil K, Baumann M, Beyreuther E, Burris-Mog T, Cowan TE et al. (2012) Dose-controlled irradiation of cancer cells with laser-accelerated proton pulses. Appl. Phys. B 110(4): 437-444.
3Beyreuther E, Karsch L, Laschinsky L, Leßmann E, Naumburger D et al. (2015) Radiobiological response to ultra-short pulsed megavoltage electron beams of ultra-high pulse dose rate. Int. J. Radiat. Biol. 91(8): 643-652.
4Brüchner K, Beyreuther E, Baumann M, Krause M, Oppelt M et al. (2014) Establishment of a small animal tumour model for in vivo studies with low energy laser accelerated particles. Radiat. Oncol. 9(1): 57.
5Oppelt M, Baumann M, Bergmann R, Beyreuther E, Brüchner K et al. (2015) Comparison study of in vivo dose response to laser-driven versus conventional electron beam. Radiat. Environ. Biophys. 54(2): 155-166.

  • Lecture (Conference)
    ELIMEDICS Workshop, 03.-04.03.2016, Prag, Tschechische Republik
  • Open Access Logo Abstract in refereed journal
    Journal of Nuclear Medicine & Radiation Therapy 7(2016)4, 56
    DOI: 10.4172/2155-9619.C1.005

Publ.-Id: 23179

Geochemical transfer and preliminary health risk assessment of thallium in a riverine system in the Pearl River Basin, South China

Liu, J.; Wang, J.; Chen, Y.; Lippold, H.; Xiao, T.; Li, H.; Shen, C.-C.; Xie, L.; Xie, X.; Yang, H.

Thallium is a highly toxic element, whose geochemical dispersion, transfer and potential health risks in aquatic systems are far from understood. This study aims to investigate the distribution of Tl in the surface water from an ultra-large Tl-bearing pyrite open-mining site and its associated riverine system of Yunfu city, western of the Pearl River Basin (PRB). Concentrations of 2.75–194.4 μg/L of Tl were found in the surface water from the mining site. Compared with other trace metals measured (Al, As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn), Tl experienced little precipitation by conventional lime-dosing treatment of mine water and readily moved through the river trace. The distribution of Tl in the river watershed during both the dry season (Tl: 0.01–9.15 μg/L) and wet season (Tl: 0.03–1.92 μg/L) generally followed a decreasing concentration pattern downstream of the pyrite mining site for the upper and middle reaches. However, some unexpected Tl elevations were observed in the lower reaches. Concentrations of Tl correlated well with concentrations of Ca, Mn, Sr, sulfate, total dissolved solids and water conductivity values for both the dry season and the wet season. Finally, health risk assessment suggests that Tl may pose non-carginogenic health risks to local residents over a long time. This study highlights not only anthropogenically-induced but also hidden naturally-occurring Tl enrichment in the hydrosphere of the PRB, and enhances the understanding of aqueous geochemistry of Tl.

Keywords: thallium; water safety; pyrite; health risk assessment; trace metal

Publ.-Id: 23178

Glutamic acid leaching of synthetic covellite – A model system combining experimental data and geochemical modeling

Barthen, R.; Karimzadeh, L.; Gründig, M.; Grenzer, J.; Lippold, H.; Franke, K.; Lippmann-Pipke, J.

For Kupferschiefer mining established pyrometallurgical and acidic bioleaching methods face numerous problems. This is due to the finely grained and dispersed distribution of the copper minerals, the complex mineralogy, comparably low copper content, and the possibly high carbonate and organic content in this ore. Leaching at neutral pH seemed worth a try: At neutral pH the abundant carbonates do not need to be dissolved and therewith would not consume excessive amounts of provided acids. Certainly, copper solubility at neutral pH is reduced compared to an acidic environment; however, if copper complexing ligands would be supplied abundantly, copper contents in the mobile phase could easily reach the required economic level. We set up a model system to study the effect of parameters such as pH, microorganisms, microbial metabolites, and organic ligands on covellite leaching to get a better understanding of the processes in copper leaching at pH ≥ 6. With this model system we could show that glutamic acid and the microbial siderophore desferrioxamine B promote covellite dissolution. Both experimental and modeling data showed that pH is an important parameter in covellite dissolution. An increase of pH from 6 to 9 could elevate copper extraction in the presence of glutamic acid by a factor of five. These results have implications for both development of a biotechnological process regarding metal extraction from Kupferschiefer, and for the interaction of bacterial metabolites with the lithosphere and potential mobilization of heavy metals in alkaline environments.

Keywords: Covellite; Glutamic acid; Desferrioxamine B; Modeling; Neutrophilic bioleaching; Copper

Publ.-Id: 23177

Thallium transformation and partitioning during Pb-Zn smelting and environmental implications

Liu, J.; Wang, J.; Chen, Y.; Xie, X.; Qi, J.; Lippold, H.; Luo, D.; Wang, C.; Su, L.; He, L.; Wu, Q.

Thallium (Tl) is a toxic and non-essential heavy metal. Raw Pb-Zn ores and solid smelting wastes from a large Pb-Zn smelting plant - a typical thallium pollution source in South China, were investigated in terms of Tl distribution and fractionation. A modified IRMM (Institute for Reference Materials and Measurement, Europe) sequential extraction scheme was applied on the samples in order to uncover the geochemical behavior and transformation of Tl during Pb-Zn smelting and to assess the potential environmental risk of Tl arising from this plant. Results showed that the Pb-Zn ore materials were relatively enriched with Tl (15.1-87.7 mg kg−1), while even higher accumulation existed in the electrostatic dust (3280-4050 mg kg−1) and acidic waste (13300 mg kg−1). A comparison of Tl concentration and fraction distribution in different samples clearly demonstrated the significant role of the ore roasting in Tl transformation and mobilization, probably as a result of alteration/decomposition of related minerals followed by Tl release and subsequent deposition/co-precipitation on fine surface particles of the electrostatic dust and acidic waste. While only 10-30% of total Tl amounts was associated with the exchangeable/acid-extractable fraction of the Pb-Zn ore materials, up to 90% of total Tl was found in this fraction of the electrostatic dust and acidic waste. Taking into account the mobility and bioavailability of this fraction, these waste forms may pose significant environmental risk.

Keywords: thallium fraction; Pb-Zn smelting; electrostatic dust; acidic waste; IRMM sequential extraction

Publ.-Id: 23176

Al in ZnO - From doping to alloying: An investigation of Al electrical activation in relation to structure and charge transport limits

Cornelius, S.; Vinnichenko, M.

The electrical activation of Al in ZnO thin films grown by pulsed reactive magnetron sputtering is quantified experimentally for a wide range of Al concentrations. We find that the activation does not exceed 35% remaining constant for growth temperatures below a certain optimum value at which the highest free electron density and mobility are achieved. Above this temperature, the Al activation decreases rapidly, while Al is accumulating in the films and their micro-structure as well as electrical properties deteriorate significantly. The analysis of possible mechanisms of Al deactivation suggests that the observed effects may be explained only by considering Al doped ZnO as metastable solid solution showing a tendency to segregation of Al into secondary phases

Keywords: Sputtering; Transparent conductive oxide

Publ.-Id: 23175

Neue Lasermaterialien für Petawatt – Laser: Anforderungen und Erkenntnisstand

Röser, F.; Löser, M.; Albach, D.; Siebold, M.; Schramm, U.

  • Lecture (others)
    2. Projekttreffen des VP5 „Hochreine Gläser“ im Rahmen des Wachstumskerns Pades, 04.03.2015, Dresden, Deutschland

Publ.-Id: 23174

Laserlab Europe – ILAT kick-off

Siebold, M.; Röser, F.; Löser, M.; Albach, D.; Harzendorf, G.; Nehring, H.; Eiselt, P.; Schramm, U.

Laserlab Europe – ILAT kick-off presentation HZDR

  • Lecture (others)
    Laserlab Europe, 24.11.2015, Mailand, Italien

Publ.-Id: 23173

Stereotactic radiotherapy augments the immune response / Die stereotaktische Strahlentherapie unterstützt die Immunantwort

Troost, E. G. C.

there ist no abstract

Publ.-Id: 23172

Plug Transfer System for GaAs Photocathodes

Murcek, P.; Arnold, A.; Teichert, J.; Xiang, R.; Burrill, A.

The transport and exchange technology of Cs2Te photocathode for the ELBE superconducting rf photoinjector (SRF gun) has been successfully developed and tested at HZDR. The next goal is to realize the transport of GaAs photocathode into SRF gun, which will need a new transfer system with XHV 10-11 mbar. The key component of the system is the transfer chamber and the load-lock system that will be connected to the SRF-gun. In the carrier four small plugs will be transported, and one of them will be plug on the cathode-body and inserted into the cavity. The new transport chamber allows the transfer and exchange of plugs between HZDR, HZB and other cooperating institutes. In HZDR this transfer system will also provide a direct connection between the SRFGUN and the GaAs preparation chamber in the Elbe-accelerator hall.

Keywords: SRf gun; photo injector; GaAs photo cathode

  • Poster
    17th International Conference on RF Superconductivity SRF 2015, 13.-18.09.2015, Whistler, Canada

Publ.-Id: 23171

Preclinical Assessment of Efficacy of Radiation Dose Painting Based on Intratumoral FDG-PET Uptake.

Trani, D.; Yaromina, A.; Dubois, L.; Granzier, M.; Peeters, S. G.; Biemans, R.; Nalbantov, G.; Lieuwes, N.; Reniers, B.; Troost, E. G. C.; Verhaegen, F.; Lambin, P.


We tested therapeutic efficacy of two dose painting strategies of applying higher radiation dose to tumor subvolumes with high FDG uptake (biologic target volume, BTV): dose escalation and dose redistribution. We also investigated whether tumor response was determined by the highest dose in BTV or the lowest dose in gross tumor volume (GTV).

FDG uptake was evaluated in rat rhabdomyosarcomas prior to irradiation. BTV was defined as 30% of GTV with the highest (BTVhot) or lowest (BTVcold) uptake. To test efficacy of dose escalation, tumor response (time to reach two times starting tumor volume, TGTV2) to Hot Boost irradiation (40% higher dose to BTVhot) was compared with Cold Boost (40% higher dose to BTVcold), while mean dose to GTV remained 12 Gy. To test efficacy of dose redistribution, TGTV2 after Hot Boost was compared with uniform irradiation with the same mean dose (8 or 12 Gy).

TGTV2 after 12 Gy delivered heterogeneously (Hot and Cold Boost) or uniformly were not significantly different: 20.2, 19.5, and 20.6 days, respectively. Dose redistribution (Hot Boost) with 8 Gy resulted in faster tumor regrowth as compared with uniform irradiation (13.3 vs. 17.1 days; P = 0.026). Further increase in dose gradient to 60% led to a more pronounced decrease in TGTV2 (10.9 days; P < 0.0001).

Dose escalation effect was independent of FDG uptake in target tumor volume, while dose redistribution was detrimental in this tumor model for dose levels applied here. Our data are consistent with the hypothesis that tumor response depends on the minimum intratumoral dose. Clin Cancer Res; 21(24); 5511-8. ©2015 AACR.

Publ.-Id: 23170

HPV and beyond-looking out for biomarkers for distinguishing the good prognosis from the bad prognosis group in locally advanced and clinically high risk HNSCC.

Lohaus, F.; Linge, A.; Baumann, M.

There is no abstract

Publ.-Id: 23169

Annual Report 2015 Institute of Resource Ecology

Stumpf, T.; Foerstendorf, H.; Bok, F.; Richter, A.; (Editors)

The Institute of REsource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden – Rossendorf (HZDR). The research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”...

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-067 2016
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 23168

Cancer stem cell related markers of radioresistance in head and neck squamous cell carcinoma.

Kurth, I.; Hein, L.; Mäbert, K.; Peitzsch, C.; Koi, L.; Cojoc, M.; Kunz-Schughart, L.; Baumann, M.; Dubrovska, A.

Despite recent advances in understanding of the molecular pathogenesis and improvement of treatment techniques, locally advanced head and neck squamous cell carcinoma (HNSCC) remains associated with an unfavorable prognosis. Compelling evidence suggests that cancer stem cells (CSC) may cause tumor recurrence if they are not eradicated by current therapies as radiotherapy or radio-chemotherapy. Recent in vitro studies have demonstrated that CSCs may be protected from treatment-induced death by multiple intrinsic and extrinsic mechanisms. Therefore, early determination of CSC abundance in tumor biopsies prior-treatment and development of therapeutics, which specifically target CSCs, are promising strategies to optimize treatment. Here we provide evidence that aldehyde dehydrogenase (ALDH) activity is indicative for radioresistant HNSCC CSCs. Our study suggests that ALDH+ cells comprise a population that maintains its tumorigenic properties in vivo after irradiation and may provide tumor regrowth after therapy. We found that ALDH activity in HNSCC cells can be attributed, at least in part, to the ALDH1A3 isoform and inhibition of the ALDH1A3 expression by small interfering RNA (siRNA) decreases tumor cell radioresistance. The expression dynamic of ALDH1A3 upon irradiation by either induction or selection of the ALDH1A3 positive population correlates to in vivo curability, suggesting that changes in protein expression during radiotherapy are indicative for tumor radioresistance. Our data indicate that ALDH1A3+ HNSCC cells may contribute to tumor relapse after irradiation, and inhibition of this cell population might improve therapeutic response to radiotherapy.

Keywords: aldehyde dehydrogenase; cancer stem cells; head and neck squamous cell carcinoma (HNSCC); radioresistance

Publ.-Id: 23167

Acceleration of volume decomposition of supersaturated Al+4 wt.% Cu solid solution under irradiation with Ar+ ions

Gushchina, N. V.; Ovchinnikov, V. V.; Mücklich, A.

Effect of irradiation with Ar+ ions on the decomposition processes of model precipitation-hardening alloy Al+4wt.% Cu has been studied. Using X-ray diffraction, high-resolution electron microscopy methods and micro hardness measurements, it was established, that, already at low temperatures (T<60°C), ion irradiation causes accelerated decomposition of solid solution, with precipitation of θ′- and θ-phase particles at a depth greatly exceeding the Ar+ ions projected range.

Keywords: Aluminum alloy; Ion irradiation; Long-range effect; Supersaturated solid solution decomposition

Publ.-Id: 23166

Global Task Force on Radiotherapy for Cancer Control.

Jaffray, D. A.; Knaul, F. M.; Atun, R.; Adams, C.; Barton, M. B.; Baumann, M.; Lievens, Y.; Lui, T. Y.; Rodin, D. L.; Rosenblatt, E.; Torode, J.; van Dyk, J.; Vikram, B.; Gospodarowicz, M.

there is no abstract

Publ.-Id: 23165

SRF Gun Characterization – Phase Space and Dark Current Measurement at ELBE

Panofski, E.; Jankowiak, A.; Kamps, T.; Lu, P.; Teichert, J.

RF photoelectron sources with superconducting cavities provide the potential to generate high quality, high brightness electron beams for future accelerator applications. At Helmholtz-Zentrum Dresden Rossendorf, such an electron source was operated for many years. The commissioning of an improved SRF Gun with a new high-performance gun cavity with low field emission and a superconducting solenoid inside the gun cryomodule (SRF Gun II) has started in June 2014. Simulations of the experimental set-up with ASTRA and ELEGANT were performed. First low current measurements as well as studies of unwanted beam transport using SRF Gun II with Cu photocathode and an acceleration gradient up to 9 MV/m will be presented. First beam characterization of the SRF Gun in combination with ELBE, a two-stage superconducting linear accelerator will be discussed.

Keywords: electron source; SRF gun; photo injector; superconducting RF

  • Poster
    International Beam Instrumentation Conference IBIC2015, 13.-17.09.2015, Melbourne, Australia
  • Open Access Logo Contribution to proceedings
    International Beam Instrumentation Conference IBIC2015, 13.-17.09.2015, Melbourne, Australia
    Proceedings of the IBIC 2015: Jacow

Publ.-Id: 23164

Increased evidence for the prognostic value of primary tumor asphericity in pretherapeutic FDG PET for risk stratification in patients with head and neck cancer.

Hofheinz, F.; Lougovski, A.; Zöphel, K.; Hentschel, M.; Steffen, I. G.; Apostolova, I.; Wedel, F.; Buchert, R.; Baumann, M.; Brenner, W.; Kotzerke, J.; van den Hoff, J.


In a previous study, we demonstrated the first evidence that the asphericity (ASP) of pretherapeutic FDG uptake in the primary tumor provides independent prognostic information in patients with head and neck cancer. The aim of this work was to confirm these results in an independent patient group examined at a different site.

FDG-PET/CT was performed in 37 patients. The primary tumor was delineated by an automatic algorithm based on adaptive thresholding. For the resulting ROIs, the metabolically active part of the tumor (MTV), SUVmax, SUVmean, total lesion glycolysis (TLG) and ASP were computed. Univariate Cox regression with respect to progression free survival (PFS) and overall survival (OS) was performed. For survival analysis, patients were divided in groups of high and low risk according to the parameter cut-offs defined in our previous work. In a second step, the cut-offs were adjusted to the present data. Univariate and multivariate Cox regression was performed for the pooled data consisting of the current and the previously described patient group (N = 68). In multivariate Cox regression, clinically relevant parameters were included.

Univariate Cox regression using the previously published cut-off values revealed TLG (hazard ratio (HR) = 3) and ASP (HR = 3) as significant predictors for PFS. For OS MTV (HR = 2.7) and ASP (HR = 5.9) were significant predictors. Using the adjusted cutoffs MTV (HR = 2.9/3.3), TLG (HR = 3.1/3.3) and ASP (HR = 3.1/5.9) were prognostic for PFS/OS. In the pooled data, multivariate Cox regression revealed a significant prognostic value with respect to PFS/OS for MTV (HR = 2.3/2.1), SUVmax (HR = 2.1/2.5), TLG (HR = 3.5/3.6), and ASP (HR = 3.4/4.4).

Our results confirm the independent prognostic value of ASP of the pretherapeutic FDG uptake in the primary tumor in patients with head and neck cancer. Moreover, these results demonstrate that ASP can be determined unambiguously across different sites.

Publ.-Id: 23163

Proton therapy of pediatric rhabdomyosarcoma: Same tumor control as photon therapy, with less adverse effects / Protonentherapie von Rhabdomyosarkompatienten im Kindesalter: Gleiche lokale Tumorkontrolle wie bei Photonentherapie mit weniger Nebenwirkungen

Gurtner, K.; Baumann, M.

there is no abstract

Publ.-Id: 23162

Comprehensive analysis of signal transduction in three-dimensional ECM-based tumor cell cultures.

Eke, I.; Hehlgans, S.; Zong, Y.; Cordes, N.

Analysis of signal transduction and protein phosphorylation is fundamental to understanding physiological and pathological cell behavior and identifying novel therapeutic targets. Despite the fact that the use of physiological three-dimensional cell culture assays is increasing, 3D proteomics and phosphoproteomics remain challenging due to difficulties with easy, robust and reproducible sample preparation. Here, we present an easy-to-perform, reliable and time-efficient method for the production of 3D cell lysates that does not compromise cell adhesion before cell lysis. The samples can be used for western blotting as well as phosphoproteome array technology. This technique will be of interest for researchers working in all fields of biology and drug development.

Keywords: 3D cell culture; extracellular matrix; phosphoproteomics; protein analysis; signaling

Publ.-Id: 23161

Cell-ECM interactions control DDR

Dickreuter, E.; Cordes, N.

there ist no abstract

Keywords: DNA repair; cell-ecm interactions; integrins

  • Open Access Logo Oncoscience 2(2015)8, 679-680

Publ.-Id: 23160

Hyperfractionated accelerated radiation therapy (HART) of 70.6 Gy with concurrent 5-FU/Mitomycin C is superior to HART of 77.6 Gy alone in locally advanced head and neck cancer: long-term results of the ARO 95-06 randomized phase III trial.

Budach, V.; Stromberger, C.; Poettgen, C.; Baumann, M.; Budach, W.; Grabenbauer, G.; Marnitz, S.; Olze, H.; Wernecke, K. D.; Ghadjar, P.


To report the long-term results of the ARO 95-06 randomized trial comparing hyperfractionated accelerated chemoradiation with mitomycin C/5-fluorouracil (C-HART) with hyperfractionated accelerated radiation therapy (HART) alone in locally advanced head and neck cancer.

The primary endpoint was locoregional control (LRC). Three hundred eighty-four patients with stage III (6%) and IV (94%) oropharyngeal (59.4%), hypopharyngeal (32.3%), and oral cavity (8.3%) cancer were randomly assigned to 30 Gy/2 Gy daily followed by twice-daily 1.4 Gy to a total of 70.6 Gy concurrently with mitomycin C/5-FU (C-HART) or 16 Gy/2 Gy daily followed by twice-daily 1.4 Gy to a total dose of 77.6 Gy alone (HART). Statistical analyses were done with the log-rank test and univariate and multivariate Cox regression analyses.

The median follow-up time was 8.7 years (95% confidence interval [CI]: 7.8-9.7 years). At 10 years, the LRC rates were 38.0% (C-HART) versus 26.0% (HART, P=.002). The cancer-specific survival and overall survival rates were 39% and 10% (C-HART) versus 30.0% and 9% (HART, P=.042 and P=.049), respectively. According to multivariate Cox regression analysis, the combined treatment was associated with improved LRC (hazard ratio [HR]: 0.6 [95% CI: 0.5-0.8; P=.002]). The association between combined treatment arm and increased LRC appeared to be limited to oropharyngeal cancer (P=.003) as compared with hypopharyngeal or oral cavity cancer (P=.264).

C-HART remains superior to HART in terms of LRC. However, this effect may be limited to oropharyngeal cancer patients.

Publ.-Id: 23159

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