Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31738 Publications
Development and validation of models for bubble coalescence and breakup
Liao, Y.; Lucas, D.;
New models were prosposed for bubble coalescence and breakup. They were implemented and validated for the case of air-water pipe flow in the Test Solver and CFX, respectively. The results were compared with the TOPFLOW L12 experimental data as well as the standard models in CFX. It was observed that good agreements with experimental data and substantial improvements in contrast to the standard models were achieved. In addition, the influence of bubble-induced turbulence models was studied. Large discrepancies show that modeling of bubble induced turbulence through additional source terms is still an open question.
Keywords: new models, bubble coalescence and breakup, validation, CFX, Test solver
  • Lecture (Conference)
    3rd Milestone-Workshop, CFD-Network on Nuclear Reactor Safety Research, 23.09.2010, Grosshartpenning (bei Holzkirchen), Germany

Publ.-Id: 14562 - Permalink


TOPFLOW-II - Aktueller Stand, wichtige Ergebnisse und Pläne zur Weiterführung der Arbeiten
Lucas, D.; Beyer, M.; Schmidtke, M.; Zhang, D.; Krepper, E.; Höhne, T.; Deendarlianto, F. B.; Seidel, T.; Vallée, C.; Schleicher, E.; Zippe, C.; Weiß, F.-P.;
Im Vortrag wird ein Überblick über den aktuellen Bearbeitungsstand des Vorhabens "TOPFLOW-Experimente, Modellentwicklung und Validierung von CFD-Codes für Dampf/Wasser-Strömungen mit Phasenübergang " (gefördert durch das BMWi, Projektnummer 150 1329) sowie über wichtige, im letzten Jahr erreichte Ergebnisse und Pläne zur Weiterführung des Vorhabens gegeben.
Keywords: Zweiphasenströmung, Experiment, CFD
  • Lecture (others)
    3. Meilenstein-Workshop des CFD-Forschungsverbunds "Entwicklung und Anwendung von Computational Fluid Dynamics (CFD) Programmen für Phänomene im Kühlkreislauf und Sicherheitseinschluss von Leichtwasserreaktoren", 23.09.2010, Großhartpenning, Deutschland

Publ.-Id: 14561 - Permalink


Hardening and microstructure of neutron- and ion-irradiated Fe-Cr alloys
Heintze, C.; Altstadt, E.; Bergner, F.; Hernández Mayoral, M.; Xie, M.; Birkenheuer, U.;
Understanding the irradiation behaviour of binary Fe-Cr alloys is basic for the optimization of ferritic/martensitic chromium steels for future applications under conditions of high neutron exposures. In this work self-ion irradiation with the ion beam scanned over the sample was used in order to simulate neutron damage in Fe-12.5at%Cr. The material irradiated at 300°C up to a damage level of 1 dpa was exposed to isochronal annealing treatments in the range from 300 to 550°C and the indentation hardness was measured as a function of annealing temperature. We have found the presence of two recovery steps. The first one takes place at 300°C, i.e. at irradiation temperature, and gives rise to a 45% recovery of the irradiation-induced hardness increase. The second step occurs in the range from 400 to 550°C and gives rise to full recovery. The findings are discussed in terms of the dissolution of hardening features, such as dislocation loops and ’-phase particles. In addition, rate theoretical considerations were used to investigate possible flux effects caused by the pulsed irradiation experienced by the material due to the scanning ion beam. It was found, that no significant additional flux effects arise from the pulsing.
  • Contribution to proceedings
    OECD Nuclear Energy Agency International Workshop on Structural Materials for Innovative Nuclear Systems (SMINS-2), 31.08.-03.09.2010, Daejeon, Republic of Korea

Publ.-Id: 14560 - Permalink


Simulation der Einströmung des heißseitig eingespeisten Notkühlwassers in den Kern mit Faserablagerungen
Höhne, T.;
In 1992, strainers on the suction side of the ECCS pumps in Barsebäck NPP Unit 2 became partially clogged with mineral wool after a safety valve opened because steam impinged on the thermally-insulated equipment and released mineral wool. This event pointed out that strainer clogging in the course of a loss-of-coolant accident is an issue. Modifications of the insulation material, the strainer area and mesh size were carried out in most of the German NPPs, since the Barsebäck event . Moreover, back flushing procedures to remove the mineral wool from the strainers and differential pressure measurement were implemented to assure the performance of emergency core cooling during the containment sump recirculation mode. Nevertheless, it cannot be completely ruled out, that a limited amount of small fractions of the insulation material is transported into the RPV. During a postulated cold leg LOCA with hot leg ECC injection, the fibres enter the upper plenum and can accumulate at the fuel element spacer grids, preferably at the uppermost grid level. This effect might affect the ECC flow into the core and could result in degradation of core cooling.
The CFD simulations show that after starting the sump mode, the ECC water injected through the hot legs flows down into the core at so-called “brake through channels” located at the outer core region where the downward leg of the convection role had established. The hotter, lighter coolant rises in the center of the core. As a consequence, the insulation material is preferably deposited at the uppermost spacer grids positioned in the break through zones. This means that the fibres are not uniformly deposited over the core cross section.
Keywords: Strainer, Core, RPV, CFD
  • Lecture (others)
    Fachkolloquium zum BMWi-Vorhaben 150 1363 "Isolationsmaterialbelastete Kühlmittelströmung", 03.03.2010, Forschungszentrum Dresden-Rossendorf, Deutschland

Publ.-Id: 14559 - Permalink


Scaling of proton energies in ultrashort pulse laser plasma acceleration
Zeil, K.; Kraft, S.; Metzkes, J.; Richter, T.; Bock, S.; Helbig, U.; Bussmann, M.; Kluge, T.; Schramm, U.; Cowan, T.; Sauerbrey, R.;
We present a systematic investigation of ultra-short pulse laser acceleration of protons yielding unprecedented maximum proton energies of 17 MeV using the Ti:Sa lased high power laser of 100 TW Draco at the Research Centre Dresden-Rossendorf. For plain few micron thick foil targets a linear scaling of the maximum proton energy with laser power is observed and attributed to the short acceleration period close to the target rear surface. Although excellent laser pulse contrast was available slight deformations of the target rear were found to lead to a predictable shift of the direction of the energetic proton emission away from target normal towards the laser direction. The change of the emission characteristics are compared to analytical modelling and 2D PIC simulations.
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) 2010, 10.03.2010, Hannover, Deutschland

Publ.-Id: 14558 - Permalink


Ionenimplantierte Halbleiterstrukturen fuer die Strahlungssensorik
von Borany, J.; Schmidt, B.;
Die Anwendung der Ionenimplantation und anderer halbleitertechnologischer Prozessschritte hat die Fertigungstechnologie von Silizium-Detektoren für die Strahlungssensorik in den zurueckliegenden Jahren wesentlich vorangetrieben. Dies ermöglicht einerseits die kostenguenstige Herstellung von „Standard“-Sensoren, andererseits aber die Entwicklung anwendungsspezifischer Sonderkonfigurationen oder die Umsetzung innovativer neuer Loesungen. Der Vortrag gibt einen kurzgefassten Ueberblick über die Arbeiten des FZD bei der Entwicklung und Fertigung von ionenimplantierter Strahlungsdetektoren fuer ionisierende Teilchen und Photonen. Im Mittelpunkt stehen dabei Loesungen fuer die Spektroskopie von Alpha-Teilchen mit bester Energieaufloesung und Fotodioden mit angepasster spektraler Empfindlichkeit. Die Erzeugung und Optimierung dotierter Gebiete in den Detektorstrukturen mittels spezieller Implantationstechniken (flache pn-Uebergaenge, vergrabene Strukturen) und Kurzzeit- Temperverfahren ist oftmals von ausschlaggebender Bedeutung. Bedingt durch die Verfuegbarkeit elektrostatischer Beschleuniger ist die Anwendung der Hochenergie-Ionenimplantaion fuer spezielle Detektorstrukturen zu einem Markenzeichen der Rossendorfer Entwicklungen geworden. Dazu zaehlen Detektoren für schwere Ionen, Elektronenstrahlen hoher Intensitaet oder spezielle Avalanche- Photodetektoren. Der Vortrag skizziert an einigen praxisrelevanten Beispielen die Anwendung dieser Detektoren auf verschiedenen Gebieten der Sensorik.
Keywords: silicon radiation detectors, high-energy implantation
  • Lecture (others)
    Innovationsforum Sonden fuer Hydrogeologie und Rohstofferkundung, 24.09.-25.10.2010, Dresden, Deutschland

Publ.-Id: 14557 - Permalink


Versuchsanlagen für die Untersuchung von Korrosionsprozessen
Kryk, H.; Hoffmann, W.; Härting, H.-U.;
Das Ziel des BMWi-Forschungsvorhabens besteht in der Beschreibung von Kühlmittelströmungen mit Feststoffpartikeln (Isolationsmaterial und Korrosionsprodukte) im Sumpf (DWR) oder der Kondensationskammer (SWR) eines LWR. Dabei stehen die Entwicklung und Validierung von CFD-Modellen hinsichtlich Fasertransport, Agglomeration/Resuspension sowie Sieb- und Sumpfgeometrie-Modellierung auf Basis der Ergebnisse von Experimenten an Großversuchsanlagen des Projektpartners HS Zittau/Görlitz im Vordergrund. Weiterhin sollen CFD-Modellkomponenten entwickelt werden, die die Verblockungseigenschaften von mit Isoliermaterial belegten Sumpfansaugsieben durch partikelförmige Korrosionsprodukte unter Einbeziehung vereinfachter Modelle der Korrosionsprozesse beschreiben. Zur Aufklärung der Korrosions- und Verblockungsmechanismen werden Einzeleffekt-Experimente im FZD durchgeführt, wofür drei spezielle Versuchsanlagen im Labormaßstab entwickelt und errichtet wurden. In einer Batch-Versuchsanlage (Rührkesselreaktor) werden grundlegende Untersuchungen zu elektrochemischen Korrosionsmechanismen und zur Wasserchemie durchgeführt. Ein Korrosionsversuchsstand für Langzeit-Experimente dient der Aufklärung der Korrosions- und Partikelbildungsvorgänge unter prozessähnlichen Bedingungen sowie dem Monitoring des Differenzdruckaufbaus an den Sumpfansaugsieben. Die Experimente zur Parametrierung und Validierung von Tiefenfiltrationsmodellen für die numerische Beschreibung der Partikelanlagerung an die Sumpfansaugsiebe und dem daraus folgenden Differenzdruckaufbau werden an einem speziellen Tiefenfiltrationsversuchsstand durchgeführt. Im Rahmen des Vortrages werden, ausgehend von grundlegenden Korrosionsmechanismen, Versuchsstrategien vorgestellt und die Versuchsanlagen, Versuchsparameter und Versuchsdurchführungen detailliert erläutert.
  • Lecture (Conference)
    Fachkolloquium zum BMWi-Vorhaben 150 1363 „Isolationsmaterialbelastete Kühlmittelströmung“, 03.03.2010, Rossendorf, Deutschland
  • Contribution to proceedings
    Fachkolloquium zum BMWi-Vorhaben 150 1363 „Isolationsmaterialbelastete Kühlmittelströmung, 03.03.2010, Rossendorf, Deutschland

Publ.-Id: 14554 - Permalink


Use of superconducting LINACs for positron generation
Krause-Rehberg, R.; Jungmann, M.; Werlich, B.; Pohl, A.; Brauer, G.; Anwand, W.; Butterling, M.; Krille, A.; Buettig, H.; Kosev, K. M.; Wagner, A.; Cowan, T. E.;
Recently, superconducting LINACs became available to obtain high-energy electron beams [1]. The advantage of these rather compact accelerators is the high electron bunch charge at very high repetition rates up to > 20 MHz under cw operating conditions. Moreover, the electron bunch length is extremely short (< 5 ps). A single accelerator stage containing several RF cavities may supply beam energies as large as 20 MeV. Thus, such electron beams are ideal hosts for the generation of bunched, intense sources of either slow or fast positrons. The Radiation Source ELBE [2] at the Research Centre Dresden-Rossendorf (FZD) has two accelerator stages providing an electron beam of 40 MeV with 26 MHz maximum repetition rate, and an average electron current of 1 mA. In close collaboration of the University Halle and the FZD the positron source EPOS (ELBE Positron Source) is under construction [3]. The recent progress of the EPOS project will be demonstrated. EPOS consists of a digital, pulsed monoenergetic positron beam (MePS), a conventional lifetime/Doppler spectrometer (CoPS), and a setup for gamma-induced positron annihilation spectroscopy (GiPS). While the CoPS and GiPS systems are available for user operation, the MePS system is still under construction. First positrons were moderated and fed into the positron lab. In the moment, the chopper/buncher/accelerator system is under assembly. The GiPS system has now been used in several regular user sessions. Positrons are generated inside the sample by an intense, pulsed photon beam (up to 20 MeV). Thus, the whole sample volume will be investigated even for rather thick samples up to a sample volume of 20x20x20 mm3. This is very useful for liquids, coarse powders, biological tissue, NDT experiments, and other bulky samples. GiPS as well as CoPS are operated in the moment with analogue detector systems. However, the development of digital systems is close to be completed.
[1] http://elan.desy.de/
[2] http://www.fzd.de/db/Cms?pNid=144
[3] http://positron.physik.uni-halle.de/EPOS/
  • Invited lecture (Conferences)
    12th International Workshop on Positron Beam Techniques for Solids and Surfaces (SLOPOS 12), 01.-06.08.2010, Magnetic Island/North Queensland, Australia

Publ.-Id: 14553 - Permalink


Enhanced laser ion acceleration from mass-limited foils
Kluge, T.; Enhardt, W.; Kraft, S. D.; Schramm, U.; Zeil, K.; Cowan, T. E.; Bussmann, M.;
This paper reports on simulations of solid mass-limited targets (MLT) via electrodynamic 2D3V particle-in-cell simulations. The interaction with long (300 fs) high intensity (1020 W/cm²) laser pulses with targets of diameter down to 1 m is described in detail with respect to electron dynamics and proton and ion acceleration. Depending on the foil diameter, different effects consecutively arise. Electrons laterally recirculate within the target, smoothening the target rear accelerating sheath and increasing the hot electron density and temperature. Our results suggest that the most significant ion energy enhancement to should be expected for MLT with diameter below the laser focal spot size. The spread of energetic protons is decreased for medium sized foils while it is greatly increased for foils of size near the focal spot size.

Publ.-Id: 14552 - Permalink


Theoretical Understanding of Enhanced Proton Energies from Laser-Cone Interactions
Kluge, T.; Gaillard, S. A.; Bussmann, M.; Flippo, K. A.; Burris-Mog, T.; Gall, B.; Geissel, M.; Kraft, S. D.; Lockard, T.; Metzkes, J.; Offermann, D. T.; Rassuchine, J.; Schollmeier, M.; Schramm, U.; Sentoku, Y.; Zeil, K.; Cowan, T. E.;
For the past ten years, the highest proton energies accelerated with high-intensity lasers was 58 MeV, observed in 2000 at the LLNL NOVA Petawatt laser, using flat foil targets. Recently, 67.5 MeV protons were observed in experiments at the Los Alamos National Laboratory (LANL) Trident laser, using one-fifth of the PW laser pulse energy, incident into novel conical targets. We present a focused study of new theoretical understanding of this measured enhancement from collisional Particle-in-Cell simulations, which shows that the hot electron temperature, number and maximum energy, responsible for the Target Normal Sheath Acceleration (TNSA) at the cone-top, are significantly increased when the laser grazes the cone wall. This is mainly due to the extraction of electrons from the cone wall by the laser electric field, and their boost in the forward direction by the v×B term of the Lorentz force. This result is in contrast to previous predictions of optical collection and wall-guiding of electrons in angled cones. This new wall-grazing mechanism offers the prospect to linearly increase the hot electron temperature, and thereby the TNSA proton energy, by extending the length over which the laser interacts in a grazing fashion in suitably optimized targets. This may allow achieving much higher proton energies for interesting future applications, with smaller, lower energy laser systems that allow for a high repetition rate.
Keywords: laser, proton, ion, acceleration, flat top cone, maximum energy
  • Contribution to proceedings
    Advanced Accelerator Concepts Workshop, 13.-19,06,2010, Annaplolis, USA
    1299: AIP Conference Proceedings, 715

Publ.-Id: 14551 - Permalink


Stretching the Neck Towards Higher Energies
Kluge, T.; Gaillard, S.; Flippo, K.; Kraft, S. D.; Metzkes, J.; Zeil, K.; Schramm, U.; Enghardt, W.; Sauerbrey, R.; Bussmann, M.; Cowan, T.;
We present a new theoretical understanding of and selected results from experiments performed in 2009 at the TRIDENT laser at Los Alamos National lab. Those experiments yielded the wolrd's highest proton energies from laser-solid interaction and were based on novel flat-top copper cone targets. Simulations show that a new mechanism of laser-plasma interaction was responsible for the observed high proton energies and suggest that an optimization of the cone geometry may further enhance the achievable proton energies.
  • Poster
    FZD PhD Seminar, 22.-24.09-2010, Krögis, Deutschland

Publ.-Id: 14550 - Permalink


A comprehensive study of the p-type conductivity formation in radio frequency magnetron sputtering grown arsenic-doped ZnO film
Fan, J. C.; Zhu, C. Y.; Yang, B.; Fung, S.; Beling, C. D.; Brauer, G.; Anwand, W.; Grambole, D.; Skorupa, W.; Wong, K. S.; Zhong, Y. C.; Ling, C. C.;
As-doped ZnO films were grown by the radio frequency magnetron sputtering method at different substrate temperature TS. For each of the TS’s, the average carrier concentration and mobility were obtained from samples grown by eight independent runs of growth through the Hall measurement. ZnO films grown on SiO2, Si and glass exhibited similar conductivity dependence on TS. As a typical example shown in the figure illustrating the carrier concentration of ZnO:As/SiO2, n-type high resistive films were yielded at low TS (i.e. 200°C). Those grown at TS=350°C and 400°C were p-type, though had large deviations from individual runs of growth. Reproducible p-type films having h~6x1017cm-3 and µ~6 cm2V-1s-1 were fabricated at high enough TS of 450°C. Conversion of the n-type ZnO:As film grown at TS=200°C to p-type film (p~1017cm-3) was observed upon the 450°C post-growth annealing in Ar.
The ZnO:As films grown at different TS’s were studied by X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), positron annihilation spectroscopy (PAS) and nuclear reaction analysis (NRA). The XPS and the 10K PL results showed that majority of the As-atoms occupied the Zn-site of the lattice and the As-related acceptor had an activation energy Ea=155 meV. The correlated increase of S-parameter (obtained from the PAS study) showed that the p-type conductivity was associated with the Vzn-related defect and/or its increased open volume. These results were in consistent with Limijumnong et al’s AsZn-2VZn shallow acceptor model [Phys. Rev. Lett. 92, 155504 (2004)], which proposed an Ea=0.15 eV and a VZn volume increase due to atomic relaxation. An anti-correlation between the H-density and the p-type conductivity was also observed in the NRA study. Our results thus suggested that the p-type conductivity was associated with the thermally induced AsZn-2VZn shallow acceptor formation and the H-donor reduction.

This work was supported by the GRF (No.7031/08P) of RGC HKSAR, G_HK026/07 of RGC HKSAR and DAAD Germany, and the UDF of HKU HKSAR.
  • Invited lecture (Conferences)
    6th International Workshop on Zinc Oxide and Related Materials, 05.-07.08.2010, Changchun, China

Publ.-Id: 14549 - Permalink


Nanocap arrays of granular CoCrPt:SiO2 films on silica particles: tailoring of the magnetic properties by Co+ irradiation
Krone, P.; Brombacher, C.; Makarov, D.; Lenz, K.; Ball, D.; Springer, F.; Rohrmann, H.; Fassbender, J.ORC; Albrecht, M.
An approach for tailoring the magnetic properties by ion irradiation of granular perpendicular CoCrPt:SiO2 films grown on silica particles with sizes down to 10 nm was investigated. The as-prepared samples reveal an intriguing scaling dependence of the coercive field and remnant magnetization: both parameters are found to decrease with decreasing particle size. However, Co+ irradiation at a low fluence of 0.5 x 1014 cm-2 already results in an opposite scaling behavior. It is assumed that this modification is due to the enhancement of the intergranular magnetic exchange coupling of the granular CoCrPt:SiO2 film initiated by Co+ irradiation resulting in a modified reversal behavior. Further increase of the irradiation fluence beyond 1.6 x 1014 ions cm-2 leads to a degradation of the magnetic layer properties, lowering the remnant magnetization and the coercive field in the easy-axis direction. Moreover, the local magnetic properties of the samples were analyzed by magnetic force microscopy revealing magnetic multi-domain cap structures.
Keywords: magnetism granular media perpendicular recording ion irradiation

Publ.-Id: 14548 - Permalink


Developing Highly Scalable Particle-Mesh Codes for GPUs: A Generic Approach
Juckeland, G.; Bussmann, M.;
Dive deep into a multi-parallel Particle in Cell code that utilizes MPI, pthreads, and CUDA. Around this specific application a general C++ framework for transparent data transfers between GPUs has been developed and will be presented. Further techniques employed include interleaving of communication and computation, particle tiling and a study of how well CUDA performance can be transferred to OpenCL.
Keywords: gpu, particle-in-cell, pic, algorithm, cuda, simulation, performance, current deposition, cluster, mpi, opencl

Publ.-Id: 14546 - Permalink


Arsenic speciation in sulfidic waters: Consolidation of contradictory spectroscopic and chromatographic evidence
Planer‐Friedrich, B.; Suess, E.; Scheinost, A. C.; Wallschläger, D.;
In recent years, analytical methods have been developed that have demonstrated that soluble arsenic‐sulfur species constitute a major fraction of dissolved arsenic in sulfidic waters. However, an intense debate is going on about the exact chemical nature of these compounds, since X‐ray absorption spectroscopy (XAS) data generated at higher (mmol/L) concentrations suggest the presence of (oxy)thioarsenites in such waters, while ion chromatographic (IC) and mass spectroscopic data at lower (μmol/L to nmol/L) concentrations indicate the presence of (oxy)thioarsenates. In this contribution, we connect and explain these two apparently different types of results. We show by XAS that thioarsenites are the primary reaction products of arsenite and sulfide in geochemical model experiments in the complete absence of oxygen. However, thioarsenites are extremely instable towards oxidation, and convert rapidly into thioarsenates when exposed to atmospheric oxygen, e.g. while waiting for analysis on the chromatographic autosampler. This problem can only be eliminated when the entire chromatographic process is conducted inside a glove box. We also show that thioarsenites are instable towards sample dilution, which is commonly employed prior to chromatographic analysis when ultra‐sensitive detectors like ICP‐MS are used. This instability has two main reasons: if pH changes during dilution, then equilibria between individual arsenic‐sulfur species rearrange rapidly due to their different stability regions within the pH range, and if pH is kept constant during dilution, then this changes the ratio between OH‐ and SH‐ in solution, which in turn shifts the underlying speciation equilibria. This problem is avoided by analyzing samples undiluted. Our studies show that thioarsenites appear as thioarsenates in IC analyses if oxygen is not excluded completely, and as arsenite if samples are diluted in alkaline anoxic medium. This also points out that thioarsenites are necessary intermediates in the formation of thioarsenates.
Keywords: arsenic XAFS IC-ICP-MS speciation

Publ.-Id: 14544 - Permalink


3D-Visualisierung und Quantifizierung von Fluidströmungen in Salinargestein mittels Positronen-Emissions-Tomographie
Wolf, M.; Kulenkampff, J.; Enzmann, F.; Gründig, M.; Richter, M.; Lippmann-Pipke, J.; Mittmann, H.;
Anhand der Bergbaufolgeschäden des ehemaligen Kali- und Steinsalzbergbau im Raum Staßfurt (Sachsen-Anhalt) wurden im Rahmen des Forschungsverbundvorhaben Dynamik abgesoffener oder gefluteter Salzbergwerke und ihres Deckgebirgsstockwerks Ursachen, Prozesse und Auswirkungen der Bergschäden exemplarisch und umfassend untersucht.
Ein verbessertes Prozessverständnis, das auf kleinskaligen experimentellen Untersuchung der Strukturen und Prozesse im Labormaßstab und damit verbundenen Modellierungen beruht, soll zur Aufklärung des Geschehens und möglicher Folgen beitragen.
Zu diesem Zweck wurde in enger Zusammenarbeit mit dem Teilvorhaben zur strukturbezogenen Prozessmodellierung eine Methode zur direkten räumlich aufgelösten und quantitativen Prozessbeobachtung entwickelt und angewendet. Hierfür wurde als bildgebendes Verfahren die Positronen-Emissions-Tomographie (PET) eingesetzt. Hierfür wird ein Teil des injizierten Fluids mit Spuren eines Radiotracers markiert. Die Tracerkonzentration kann zerstörungsfrei, mit höchstmöglicher Empfindlichkeit und einem geeignetem Auflösungsvermögen in Raum und Zeit abgebildet werden. Der Prozess wird durch den Tracer auf geringst mögliche Weise beeinflusst und es wird ein realistisches Bild der Tracerverteilung, bzw. des Fließverhaltens, mit einer räumlichen Auflösung von 1 mm und einer zeitlichen Auflösung von 60s erzeugt.
Dieses Fließverhalten lässt sich mit räumlich heterogenen und prozessabhängigen Verteilungen von Parametern, wie effektiven Volumina, Permeabilitäten, Abstandsgeschwindigkeiten und Dispersionsraten beschreiben. Einem besseren Prozessverständnis dient insbesondere der Abgleich mit mit Lattice-Boltzmann-Simulationen der Fließprozesse, die auf hochauflösenden computertomographischen (µXCT) Messungen der internen Struktur der identischen Bohrkerne beruhen. Dieser Vergleich von PET-Messdaten mit Lattice-Boltzmann - Simulationsdaten, der zugleich eine Skalenübertragung um etwa drei Größenordnungen bedeutet, erfolgt mit geostatistischen Methoden.
Nicht in jedem Fall war dieser Abgleich zwischen Simulation und Experiment möglich: Während in klüftig-porösen Materialien gewöhnlich mit beiden Methoden räumlich stark differenzierte präferentielle Fließwege im Kluftsystem gefunden wurden, konnte in eher mikrostrukturell ausgeprägten Materialien trotz messbarer Permeabilität gelegentlich kein verbundener Porenraum aus den CT-Bildern segmentiert und somit keine LBM-Simulation durchgeführt werden. In diesem Fall zeigte die PET-Untersuchung ein diffuses Ausbreitungsverhalten des Tracers.
Keywords: positron emission tomography, imaging, saline rock, Lattice Boltzmann simulation, preferential flow
  • Contribution to proceedings
    Staßfurt 2010 - Erkennen, analysieren, bewerten und prognostizieren der zukünftigen Entwicklung der Bergbaufolgeschäden, 18.-20.11.2010, Staßfurt, Deutschland
    EDGG Exkursionsführer & Tagungspublikationen 244(2010), Hannover: Deutschen Gesellschaft für Geowissenschaften e.V, ISBN: 978-3-986944-028-6, 200-212

Publ.-Id: 14543 - Permalink


Optimization of induction heating for container-less melt extraction from a metallic sheet
Park, J.-S.; Pal, J.; Cramer, A.; Gerbeth, G.;
This work examines the induction heating of a metal sheet to be used for multiple instance melt extraction from the lower edge. The task formulation of heating the edge in first place while keeping the release of Joule heat along that edge as homogeneous as possible, i.e., the avoidance of end effects, is solved numerically with a parametric study. A set of factors is also modeled physically in the framework of an experimental series. Subject to variation are (1) the extension of the copper block, which simulates the extraction wheel, in both directions parallel and perpendicular to the inductor; (2) the protrusion depth of the edge of the sheet below the lower face of the inductor; and (3) the shape of the inductor. It is shown that this shape adopted from the floating zone crystal growth technique in a previous work,[1] albeit acting effectively, is removed from optimum. In this article, a more efficient solution is proposed. The numerical simulations also suggest that the vertical position of the inductor must be significantly above that one in Reference 1 to increase the efficiency of the process. Reasonable conformity may be stated between the calculated and the experimental results.
Keywords: container-less melt extraction, induction heating

Publ.-Id: 14541 - Permalink


Transport of hot electron currents in solid targets irradiated by high intensity short laser pulses
Antici, P.; Andebert, P.; Borghesi, M.; Cowan, T.; Gremillet, L.; Sentoku, Y.; Fuchs, J.;
Abstract. We have analyzed the transport of hot electrons generated in the interaction between a short-pulse, ultra-high intensity laser beam (pulse duration t1018 W.cm-2.μm2) and a solid or dense target through the use of proton emission imaging. We used targets of different material (Cu, Al, Au) with a regularly modulated rear target surface in order to compare the electron transport in different conditions. As result, we see that the electron transport depends on the target material and on the interaction conditions.

Publ.-Id: 14540 - Permalink


Proton acceleration from ultrahigh-intensity short-pulse lasermatter interactions with Cu micro-cone targets at an intrinsic ~10-8 contrast
Gallard, S. A.; Flippo, K. A.; Lowenstern, M. E.; Mucino, J. E.; Rassuchine, J. M.; Gautier, D. C.; Workman, J.; Cowan, T. E.;
Abstract. In this paper, we report on experiments comparing various geometries of conical Cu targets to Cu flat foils, which were performed on the 200 TW Trident laser (~80 J, 600 fs, ~7 μm spot size, S-polarization and ~1.5×1020 W/cm2) at an intrinsic (to the system’s regenerative amplifier) ASE contrast of 10-8. The current work builds on previous results obtained on Trident (~20 J, ~14 μm spot size, P-polarization, ~1019 W/cm2, also at the intrinsic contrast of 10-8) demonstrating enhanced proton energies and laser-proton conversion efficiencies (η) using Flat Top Cone (FTC) targets [1]. An electron spectrometer and a Cu K alpha imaging diagnostic were added to respectively assess the electron population, and determine the characteristics of laser absorption in FTCs. Results indicate a linear correlation between electron temperatures and proton energies, as well as laser absorption taking place in a preplasma filling the cone, preventing the previously observed enhancement in proton energies.
Keywords: Proton acceleration, Cu micro-cone targets

Publ.-Id: 14539 - Permalink


Bioaccumulation of U(VI) by Sulfolobus acidocaldarius at moderate acidic conditions.
Reitz, T.; Merroun, M. L.; Rossberg, A.; Steudtner, R.; Selenska-Pobell, S.;
U(VI) accumulation by the acidothermophilic archaeon Sulfolobus acidocaldarius at pH 4.5 and 6 was investigated. These pH values are relevant for some heavy metal and uranium polluted environments where populations of S. acidocaldarius were found to persist. We demonstrate that at these pH values U(VI) is rapidly complexed by the archaeal cells. A combination of X-ray absorption spectroscopy and time-resolved laser induced fluorescence spectroscopy revealed that at pH 4.5 both, organic phosphate and carboxylic groups are involved in the U(VI) complexation. In addition, at this pH, part of the added U(VI) was precipitated in inorganic uranyl phosphate mineral phases. These mineral phases were the most predominant uranium complexes found after the treatment of the cells with U(VI) at pH 6. Transmission electron microscopic analysis of the cells treated at pH 4.5 showed extracellular and intracellular U(VI) accumulates. The extracellular complexes represented mainly inorganic uranyl phosphate complexes. The formation of the intracellular uranyl phosphate deposits is attributed to uncontrolled uptake of U(VI) as a result of the increased cell permeability, most likely due to the stress of the non-optimal pH and uranium toxicity. Our results demonstrate that at moderate acidic conditions S. acidocaldarius immobilizes U(VI) via biosorption and biomineralization processes.
Keywords: Sulfolobus acidocaldarius DSM 639, Interactions with U(VI), X-ray absorption spectroscopy, Time-resolved laser-induced fluorescence spectroscopy, Transmission electron microscopy

Publ.-Id: 14538 - Permalink


Studying Hadron Properties in Baryonic Matter with HADES
Kugler, A.; Balanda, A.; Belver, D.; Belyaev, A. V.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Díaz, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O. V.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Gil, A.; Golubeva, M.; González-Díaz, D.; Guber, F.; Hennino, T.; Holzmann, R.; Huck, P.; Ierusalimov, A. P.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Kraza, A.; Krizek, F.; Krücken, R.; Kühn, W.; Kurepin, A.; Kählitz, P. K.; Lamsa-Verde, J.; Lang, S.; Lange, J. S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Morinière, E.; Mousa, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roskoss, J.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Siebenson, J.; Simon, R.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Weber, M.; Wisniowski, M.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y. V.;
The HADES spectrometer installed at GSI Darmstadt is a second generation experiment to study production of lepton pairs from proton, pion and nucleus induced reactions at the SIS/BEVALAC energy regime. The HADES study of the light C+C system at 1 and 2 AGeV confirms former finding of the DLS collaboration. Further studies of the reaction p+p and d+p allowed to reveal contribution to the above mentioned data of di-leptons produced during first chance collision. Finally, the results of the study of heavier system Ar+KCl indicates possible nonlinear dependence of the observed excess over the known long lived sources of di-leptons on the number of participants.

Publ.-Id: 14537 - Permalink


Hydrogen evolution under the influence of a magnetic field
Koza, J. A.; Mühlenhoff, S.; Zabinski, P.; Nikrityuk, P.; Eckert, K.; Uhlemann, M.; Gebert, A.; Weier, T.; Schultz, L.; Odenbach, S.;
The effect of a uniform magnetic field on the hydrogen evolution reaction (HER) during water electrolysis in 0.1 M Na2SO4 solution was investigated. Irrespective of the magnetic field orientation with respect to the electrode surface, the desorption of hydrogen is enhanced by the presence of the magnetic field. This effect is displayed by a reduction of the mean bubble size as well as a narrower bubble size distribution in a magnetic field. Moreover, it is shown that in the presence of an external magnetic field the fractional bubble coverage is strongly retarded. As a consequence the current density is increased since more active sitesare available for the reduction processes. These effects are discussed with respect to the Lorentz force driven convection induced by a magnetic field. In order to resolve further the influence of a magnetic field applied in the perpendicular-to-electrode configuration, where the bulk Lorentz force is negligible, a numerical study has been performed. This revealed the mechanism of the improved desorption of a hydrogen bubble from the electrode surface. The numerical study has been validated by a model experiment. Most importantly, it is clearly demonstrated that a magnetic field superposed during water decomposition is a very effective method to intensify hydrogen evolution processes, and it should be possible to significantly improve the energetic efficiency of the hydrogen production via water electrolysis in a magnetic field.
Keywords: Lorentz force; Water electrolysis; MHD effect; micro-MHD; Desorption of hydrogen

Publ.-Id: 14536 - Permalink


Geogas transport in fractured hard rock - correlations with mining seismicity at 3.54 km depth, TauTona gold mine, South Africa
Lippmann-Pipke, J.; Erzinger, J.; Zimmer, M.; Kujawa, C.; Boettcher, M.; van Heerden, E.; Bester, A.; Moller, H.; Stroncik, N. A.; Reches, Z.;
An on-site gas monitoring study has been conducted in the framework of an earthquake laboratory (the international NELSAM-DAFGAS projects) at the TauTona Gold mine, South Africa. Extensive underground activities began in 2004 with the establishment of a 25 m² cubby and the drilling of five boreholes up to 60 m apart within the Pretorius Fault zone at 3.54 km depth. Instruments for chemical and seismic monitoring were then installed within the cubby and boreholes. Since 2007 sensitive gas monitoring devices have been continuously improved to enable the direct observation of geogas concentration variations in the DAFGAS borehole. The major gas concentrations are constant and air-like with about 78% N2, 21% O2, 1% Ar, while the geogas components CO2, CH4, He and H2 show most interesting trends and variations on the minute-by-minute basis. Time series and cross correlation analysis with meteorologic and seismic data allow the identification of two different gas components (geogas and tunnel air) and the identification of the two most significant processes influencing the borehole gas composition: 1) pumping-induced tunnel air breakthrough events through networks of initially water-saturated fault fractures; and 2) blasting induced permeability enhancement of the fault fractures to above ~5*10-10 m². The current set-up of the gas monitoring system is sensitive enough to quantify the resulting geogas transport during periods of intense blasting activities (including recorded blasts with seismic moment ≤ 1*109 Nm, located within 1000 m of the cubby) – and, we suggest, also during induced earthquakes – a final goal of the project.
Keywords: Gas transport, gas permeability of faults, gas breakthrough, mining, seismicity, DAFSAM, NELSAM

Publ.-Id: 14535 - Permalink


First in vitro cell experiments with laser-accelerated protons
Naumburger, D.; Baumann, M.; Beyreuther, E.; Bock, S.; Cowan, T. E.; Dammene, Y.; Enghardt, W.; Helbig, U.; Karsch, L.; Kraft, S. D.; Laschinsky, L.; Lessmann, E.; Metzkes, J.; Richter, C.; Sauerbrey, R.; Schramm, U.; Schürer, M.; Sobiella, M.; Woithe, J.; Zeil, K.; Pawelke, J.;
Background: The novel technology of laser particle acceleration, which promises ion radiotherapy accelerators of compact size and reasonable costs, generates ultra-short pulsed particle beams (~ 100 fs) with very high pulse dose rate (more than 1012 Gy/min). The development of this new technology for radiotherapy application is the aim of the joint research project onCOOPtics – High intensity lasers for radiooncology. One important step before potential medical application is the radiobiological characterization of this new radiation quality starting with in vitro cell experiments.

Material and Methods: Cell irradiations have been performed with protons generated at the 150 TW laser system Draco installed at the FZD. Before starting irradiation experiments the laser particle accelerator had to be optimized with respect to intensity, energy distribution, spot size, stability and reliability of the proton beam. Furthermore, beam filtering and transport to an in-air irradiation site and a dosimetry system were developed and realised. For a precise dose measurement, low energy protons were filtered out by a permanent magnet system. At cell irradiation site the proton beam possessed an energy spectrum of 6 to 18 MeV with a maximum at 7 MeV resulting in a minimal penetration depth in water of approximately 500 µm. To avoid stopping of protons within the bottom of the cell culture vessel or the cell monolayer, dedicated material for cell cultivation and irradiation had to be established to minimize material on the proton path. Cells of the radiosensitive tumour cell line SKX were seeded at thin biofilm (50 µm thickness) in place of conventional cultivation vessels. To quantify the irradiation damage, residual DNA double strand breaks were detected using the immunofluorescence H2AX/53BP1 staining technique 24 h after irradiation, optimized for the special cell carrier material. Cell samples were irradiated with three different doses applied by different proton pulse numbers and controlled by online dose measurement. As online dosimetry system an ionization chamber was used, cross-calibrated against Gafchromic EBT radiochromic films and a Faraday cup to provide precise dose determination at the cell site.

Results: The successful in vitro cell irradiation by laser-accelerated protons represents an important milestone on the long term development of laser ion acceleration for clinical radiotherapy. The laser accelerator generated a stable and reproducible proton beam over the whole experiment time. The measurement of the ionization chamber as online dosimeter showed a stable mean dose per pulse of (0.1370.039) Gy during all irradiations. The EBT films verified a homogeneous dose distribution at the cell location. The irradiated tumour cells demonstrated a clear trend in the number of DNA double-strand breaks in accordance with delivered dose.

Conclusion: Systematic cell irradiation experiments with laser-accelerated protons has been started determining dose-effect curves for both tumour and normal tissue cell lines and also including the cell surviving assay as second biological endpoint. In addition to the experiments with laser-accelerated proton pulses reference cell irradiations are performed using a continuous proton beam at a conventional tandem accelerator.

Funding: This work was supported by the BMBF (no. 03ZIK445).
  • Poster
    13. Jahrestagung der Gesellschaft für Biologische Strahlenforschung GBS, 01.-02.09.2010, Hamburg, Deutschland

Publ.-Id: 14534 - Permalink


Flow modelling with relevance to Vertical Gradient Freeze crystal growth under the Influence of a travelling magnetic field
Niemietz, K.; Galindo, V.; Pätzold, O.; Gerbeth, G.; Stelter, M.;
Results on the experimental and numerical modelling of the melt flow typically observed in Vertical Gradient Freeze (VGF) crystal growth with a Travelling Magnetic Field (TMF) are presented. Particular attention is paid on the transition from a laminar to a time-dependent flow, which represents a crucial problem in VGF growth. Low-temperature model experiments at around 80°C were performed using a GaInSn melt in a resistance furnace with concentric, separately adjustable heating zones. The TMF was created by an external coil system, and the flow velocity was measured by means of the Ultrasonic Doppler Velocimetry (UDV). The melt flow was simulated numerically using a finite volume code based on the open source code library OpenFOAM. As a criterion for the stability of the flow the turbulent kinetic energy was calculated under the influence of the TMF and thermal buoyancy. The results obtained are compared to isothermal TMF flow modelling at ambient temperature. The stability limit of the melt flow is found to be significantly influenced by the mutual interaction of buoyant and TMF-driven flows. Both experimental and numerical results show the stabilizing effect of a natural, VGF-type buoyancy on the TMF-induced flow.
Keywords: fluid flows; magnetic fields; stirring; vertical gradient freeze technique; numerical simulation
  • Journal of Crystal Growth 318(2011), 150-155
    DOI: 10.1016/j.jcrysgro.2010.10.077
  • Lecture (Conference)
    The 16th International Conference on Crystal Growth(ICCG-16), 08.-13.08.2010, Beijing, China

Publ.-Id: 14533 - Permalink


Investigation of dipole strength up to the neutron-separation energy at the ELBE accelerator
Massarczyk, R.; Bemmerer, D.; Beyer, R.; Birgersson, E.; Dönau, F.; Grosse, E.; Hannaske, R.; Hartmann, A.; Junghans, A.; Kempe, M.; Kögler, T.; Matic, A.; Rusev, G.; Schilling, K.-D.; Schramm, G.; Schwengner, R.; Wagner, A.;
At the bremsstrahlung facility of the ELBE accelerator there exists the possibility to investigate dipole strength distributions up to the neutronseparation energies with photon energies up to 18 MeV. The facility and various results for nuclides measured during recent years will be presented. One example is the study of 86Kr that complements a systematic study of stable isotones at the shell closure of neutron number N = 50. As a special feature, a high-pressure gas target was used in this experiment. The other presented example is an experiment on 136Ba. GEANT4 simulations were performed to detremine the non-nuclear background that has to be removed from the measured spectra. This opens up the possibility to take into account also the strength of unresolved transitions. Simulations of gamma-ray cascades were carried out that consider the transitions from states in the quasicontinuum and allow us to estimate their branching ratios. As a result, the photoabsorption cross sections obtained from corrected intensities of ground-state transitions are combined with existing data from (gamma,n) experiments and are compared with theoretical predictions.
Keywords: Nuclear structure, gamma-ray spectroscopy, gamma-ray strength functions
  • Lecture (Conference)
    Workshop on Gamma Strength and Level Density in Nuclear Physics and Nuclear Technology, 30.08.-03.09.2010, Dresden, Deutschland

Publ.-Id: 14532 - Permalink


Photon strength function deduced from photon scattering and neutron capture
Massarczyk, R.; Birgersson, E.; Schramm, G.; Schwengner, R.; Belgya, T.; Beyer, R.; Grosse, E.; Hannaske, R.; Junghans, A. R.; Matic, A.; Szentimiklosi, L.; Weil, J.; Wagner, A.;
The dipole strength function of 78Se and 196Pt are investigated by two different experimental methods, capture of cold neutrons in 77Se and 195Pt, and photon scattering experiments on 78Se and 196Pt. Considering the different ways of excitation, the strength function deduced from the results are expected to agree. The report shows the status of the data analysis and presents first preliminary results.
Keywords: Nuclear structure, gamma-ray spectroscopy, gamma-ray strength functions, neutron capture
  • Contribution to proceedings
    EFNUDAT Users and Collaboration Workshop "Measurement and Models of Nuclear Reactions", 25.-27.05.2010, Paris, France
    European Physics Journal Web Conferences 8 (2010), 07008
  • Lecture (Conference)
    EFNUDAT Users and Collaboration Workshop "Measurement and Models of Nuclear Reactions", 25.-27.05.2010, Paris, France

Publ.-Id: 14531 - Permalink


Prediction of polydisperse steam bubble condensation in sub-cooled water using the Inhomogeneous MUSIG model
Lifante, C.; Frank, T.; Burns, A. D.; Lucas, D.; Krepper, E.;
The aim of this paper is to present the validation of a new methodology implemented in ANSYS CFX (ANSYS, 2009), that extends the standard capabilities of the inhomogeneous MUltiple-SIze Group model (MUSIG) by additionally accounting for bubble size changes due to heat and mass transfer. Bubble condensation plays an important role in sub-cooled boiling or steam injection into pools among many other applications of interest in the Nuclear Reactor Safety (NRS) area and other engineering areas. Since the mass transfer rate between phases is proportional to the interfacial area density, a polydisperse modelling approach considering different bubble sizes is of main importance, because an accurate prediction of the bubble diameter distribution is required.
The standard MUSIG approach is an inhomogeneous one with respect to bubble velocities, which combines the size classes into different so-called velocity groups to precisely capture the different behaviour of the bubbles depending on their size. In the framework of collaboration between ANSYS and the Forschungszentrum Dresden-Rossendorf (FZD) an extension of the MUSIG model was developed, which allows to take into account the effect of mass transfer due to evaporation and condensation on the bubble size distribution changes in addition to breakup and coalescence effects.
After the successful verification of the model, the next step was the validation of the new developed model against experimental data. For this purpose an experiment was chosen, which was investigated in detail at the TOPFLOW test facility at FZD. It consists of a steam bubble condensation case at 2MPa pressure in 3.9K sub-cooled water at a large diameter (DN200) vertical pipe. Sub-cooled water flows into the 195.3 mm wide and 8 m height pipe, were steam is injected at z=0.0 m and is recondensing. The experimental results are published in (Lucas, et al., 2007). Using a wire-mesh sensor technique the main characteristics of the two-phase flow were measured, i.e. radial steam volume fraction distribution and bubble diameter distribution at different heights and cross-sections.
ANSYS CFX 12.0 was used for the numerical prediction. A 60 degrees pipe sector was modelled in order to save computational time, discretized into a mesh containing about 260.000 elements refined towards the pipe wall and towards the location of the steam injection nozzles. Interfacial forces due to drag, lift, turbulent dispersion and wall lubrication force were considered. The numerical results were compared to the experimental data. The agreement is highly satisfactory, proving the capability of the new MUSIG model extension to accurately predict such complex two-phase flow.
Keywords: polydisperse, bubble, condensation, phase transfer, CFD
  • Contribution to proceedings
    CFD4NRS-3, Workshop on Experimental Validation and Application of CFD and CMFD Codes to Nuclear Reactor Safety Issues, paper 13.3, 14.-16.09.2010, Washington D.C., USA
  • Lecture (Conference)
    CFD4NRS-3, Workshop on Experimental Validation and Application of CFD and CMFD Codes to Nuclear Reactor Safety Issues, 14.-16.09.2010, Washington D.C., USA

Publ.-Id: 14530 - Permalink


Dipole strength in 136Ba up to the neutron-separation energy
Massarczyk, R.; Schwengner, R.; Beyer, R.; Hannaske, R.; Junghans, A.; Kempe, M.; Kosev, K.; Marta, M.; Matic, A.; Nair, C.; Rusev, G.; Schilling, K. D.; Stach, D.; Trompler, E.; Wagner, A.; Yakorev, D.;
The dipole-strength distribution of 136Ba has been investigated at the bremsstrahlung facility at the ELBE accelerator of the Forschungszentrum Dresden-Rossendorf. The photon-scattering experiment was carried out at an electron beam energy of 10.9 MeV in order to study the energy region up to the neutron separation. GEANT4 simulations were performed to subtract the atomic background from the measured spectrum and deduce the intensity of the resonantly scattered gammarays. Considering the transitions from states in the quasicontinuum, simulations of gammaray cascades were carried out to estimate branching ratios. As a result the photoabsorption cross section obtained from transitions to the ground state are combined with existing data from photoneutron experiments.
Keywords: Nuclear structure, gamma-ray spectroscopy, gamma-ray strength functions
  • Lecture (Conference)
    74. Jahrestagung der DPG und DPG Frühjahrstagung der Fachverbände 2010, 15.-19.03.2010, Bonn, Deutschland

Publ.-Id: 14529 - Permalink


Kohlenstoff-Nanoröhren und die Umwelt
Zänker, H.;
Es wird das Verhalten von Carbon Nanotubes in Umweltwässern analysiert. Insbesondere werden die Mobilität in wässriger Suspension und die Adsorption von Schwermetallen (Uran) diskutiert.
Keywords: Carbon Nanotubes
  • Open Access LogoGIT Labor-Fachzeitschrift 4(2010), 310

Publ.-Id: 14528 - Permalink


An integrated dosimetry and cell irradiation device for in vitro experiments with laser accelerated protons
Richter, C.; Beyreuther, E.; Baumann, M.; Dammene, Y.; Enghardt, W.; Karsch, L.; Kraft, S.; Laschinsky, L.; Lessmann, E.; Metzkes, J.; Naumburger, D.; Schramm, U.; Schürer, M.; Sobiella, M.; Weber, A.; Zeil, K.; Pawelke, J.;
Purpose: The novel technology of laser based particle acceleration promises accelerators of compact size and reasonable costs that may significantly contribute to a widespread use of ion radiotherapy. Although some basic properties of laser acceleration are reasonably well known from theory, simulations and fundamental experiments, several demands have to be fulfilled for its medical application. Moreover, the ultra-short pulsed particle beams with resulting high pulse dose-rate have to be characterized with regard to their radiobiological properties. Therefore, a precise dosimetry is necessary that considers the special characteristics of the laser accelerated protons. Special attention has to be drawn on the low energy (<10 MeV), the exponential energy spectrum, the low repetition rate and the pulse-to-pulse fluctuations of the available laser accelerated proton beams.

Material & Methods: An Integrated Dosimetry and Cell Irradiation Device (IDCID) for systematic in vitro and in vivo experiments with laser accelerated protons was developed and characterized. The IDCID (Fig. 1) consists of a kapton vacuum window, an ionisation chamber consisting of ultra-thin foils (22.5 µm) for online dose information and a Faraday cup inset for absolute dosimetry that can be replaced by an inset for cell or even mouse model irradiation. Radiochromic films, i.e. GafChromic EBT, or CR-39 solid state track detectors can be included matching the plane of the cell monolayer. For the use of the Faraday Cup (FC) for absolute dosimetry and cross-calibration of the ionisation chamber, an accurate FC calibration is necessary. Therefore, three independent ways were chosen: (1) electronic calibration by applying a defined charge to the FC amplifier, (2) dose calibration against a clinical established absolute dosimetry and (3) calibration with CR-39 solid state track detectors. The dose calibration was performed at the proton therapy facility at the Helmholtz Zentrum Berlin, where also EBT and EBT2 films were calibrated for determination of 2D dose distribution. Moreover, the FC calibration with the help of CR-39 was carried out at the Tandem accelerator of the Forschungszentrum Dresden-Rossendorf.

Results: Successfully, the functional capability of the IDCID was thoroughly tested and precisely calibrated with three independent methods. EBT / EBT2 films were calibrated for several proton beam qualities with mean energies between 5 - 62 MeV. As next step, first systematic in vitro cell irradiations were performed for a human squamous cell carcinoma (FaDu) cell line irradiated with 7 MeV monoenergetic protons.

Conclusion: Both the dosimetric and radiobiological requirements for systematic cell irradiations with laser accelerated protons have been fulfilled.

Supported by the BMBF, grant 03ZIK445


Fig. 1: Integrated dosimetry and cell irradiation device (a) with Faraday cup inset, (b) with cell holder inset
  • Poster
    ESTRO 29 - Conference of the European Society for Therapeutic Radiology and Oncology, 12.-16.09.2010, Barcelona, Spanien
  • Abstract in refereed journal
    Radiotherapy and Oncology 96(2010)Suppl. 1, S533-S534

Publ.-Id: 14527 - Permalink


Phase Segregation and Transformations in Arsenic-Implanted ZnO Thin Films
Krause, M.; Vinnichenko, M.; Shevchenko, N.; Mücklich, A.; Gemming, S.; Munnik, F.; Rogozin, A.; Kolitsch, A.; Möller, W.;
The conversion of ZnO into a p-type semiconductor remains a major challenge for its application in optoelectronic devices, since up to now neither the suitable type of defects nor the possible role of secondary phase formation during doping has been clarified. Here, the implantation of arsenic into epitaxial ZnO thin films on Alpha-Al2O3 (0001) and subsequent isothermal annealing in high vacuum are studied by particle induced X-ray emission, X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The as-implanted ZnO:As films are single phase and exhibit a locally disordered ZnO lattice structure. Zn3As2 nanocrystals segregate at 700°C. Due to annealing at 800°C, Alpha-As and Alpha-As2O3 are formed. The study demonstrates the role of solid state reactions and secondary phase formation for group V element doping of ZnO that is a promising route to convert this material into a p-type semiconductor.
Keywords: Transparent Conductive Oxides - ZnO - Arsenic Doping - Secondary Phase Formation - Ion Implantation

Publ.-Id: 14526 - Permalink


Carbon:Vanadium (C:V) nanocomposite filmsfor tribological applications
Krause, M.; Abrasonis, G.; Mücklich, A.; Kolitsch, A.; Möller, W.;
Nanocomposites are heterogeneous materials wherein the lateral extension of at least one component is lower than 100 nm.[1] They represent a new class of functional materials, whose properties cannot be predicted from those of their constituents alone. Among the various classes of nanocomposites, metal-containing nano-particles embedded in a carbon matrix have recently attracted considerable interest regarding their structure and properties.[2,3]
This study focuses on the structure and the mechanical properties of C:V nanocomposites. A series of C:V films with a varying vanadium concentration of 2 at.% ≤ xv ≤ 50 at.% was grown on silicon by DC dual magnetron sputtering. Depending on the metal concentration, significant structural variations were observed within both phases (dispersed phase and matrix) of the nanocomposite. At low vanadium concentrations, an amorphous metal rich and an amorphous carbon phase are formed. An increasing metal content promotes the formation of cubic VC and a graphitic carbon phase. With optimized deposition parameters, the hardness of the C:V nanocomposite films is higher then 10 GPa, and the elastic modulus achieves values of about 130 GPa. The friction coefficients for sliding conditions are as good as 0.1.

[1] P. M. Ajayan, L.S. Schadler, P.V. Braun, Nanocomposites Science and Technology, Wiley, 2005
[2] T. Hayashi, S. Hirono, M. Tomita, S. Umemura, Nature 381, 772-774 (1996)
[3] M. Krause et al., Phys. Stat. Sol. (B), 244, 4236-4239 (2007); G. Abrasonis et al. Carbon, 45, 2995-3006 (2007); M. Berndt et al., Plasma Process. Polym. 6, S902–S906 (2009); C. Adelhelm et al., J. Appl. Phys. 105, 033522 (2009); M. Magnuson et al. Phys. Rev. B, 80, 235108 (2009).
  • Poster
    12th International conference on Plasma Surface Engineering, 13.-17.09.2010, Garmisch-Partenkirchen, Deutschland

Publ.-Id: 14525 - Permalink


Roughness evolution in amorphous silicon films grown by (biased) DC magnetron sputtering
Gago, R.; Redondo-Cubero, A.; Vinnichenko, M.; Vazquez, L.;
Control over surface roughness (σ) is a critical issue in many physical, chemical, biological and technological processes. Regarding relevant systems, silicon is a model material that finds a wide range of applications in microelectronic and photovoltaic devices. Further, the growth of amorphous silicon (a-Si) could yield ultrasmoothness, a keystone for the production of ultrathin films, in analogy to amorphous diamond-like carbon [1]. Based on this motivation, we have studied the roughness evolution of a-Si films prepared by DC magnetron sputtering at low (LP) and high (HP) plasma pressures (10-3 and 3×10-3 mbar, respectively). The morphological analysis was carried out by atomic force microscopy and interpreted in the framework of dynamic scaling concepts [2]. The film thickness evolution was analyzed by ex-situ spectroscopic ellipsometry, providing also information on the disorder character of the films. Smooth (σ<0.2nm) films were produced at LP whereas rougher surfaces were grown at HP. The growth exponent [σ(t)~tβ] was close to 0.25 at LP, compatible with a morphology controlled by surface diffusion relaxation processes, whereas HP yielded considerably higher β characteristic of unstable growth. The distinct evolution should be related to the lower mean free path in the gas phase at HP, which alters the incidence angle and/or size of the particles condensing at the substrate and can result in shadowing effectsduring growth [3]. Finally, a negative DC bias voltage (-400V) applied to the substrate at HP changes drastically the surface morphology to ultrasmooth (σ~0.12 nm) during the whole temporal window sampled, resulting in β~0 (i.e. suppressing surface roughening). The latter could be consistent with the Edwards-Wilkinson interface equation [2]. This evident surface smoothing could be ascribed to ion-induced downhill currents that preferentially erode prominent features [1].
REFs.: [1] M. Moseler, P. Gumbsch, C. Casiraghi, A.C. Ferrari, and J. Robertson, Science 309, 1545 (2005); [2] A.L. Barabasi, and H.E. Stanley, Fractal Concepts in Surface Growth (Cambridge Univ. Press, 1995); [3] J.T. Drotar et al., Phys. Rev. B 62, 2118 (2000).
Keywords: Roughness, AFM, dynamic scaling, smoothness, shadowing
  • Lecture (Conference)
    12th International Conference on Plasma Surface Engineering, 13.-17.09.2010, Garmisch-Partenkirchen, Germany

Publ.-Id: 14523 - Permalink


Thermally-induced formation of secondary phases in ZnO:Al films grown by reactive pulsed magnetron sputtering
Vinnichenko, M.; Gago, R.; Cornelius, S.; Rogozin, A.; Shevchenko, N.; Munnik, F.; Kolitsch, A.; Moeller, W.;
Segregation of Al2O3 or ZnAl2O4 in Al-doped ZnO (AZO) is often discussed as a reason for deterioration of the film electrical properties during growth at temperatures above a certain optimum value (150-300 °C). However, conclusive evidence of these phase segregation in AZO is lacking since electrical properties and crystallinity of the films deteriorate simultaneously and, the disordered structure precludes a proper analysis using conventional methods. The present work overcomes these limitations using characterization techniques based on synchrotron radiation, such as X-ray diffraction and X-ray absorption near edge structures. These studies were combined with investigations by spectroscopic ellipsometry, Hall effect measurements and elastic recoil detection analysis. The AZO films grown by reactive pulsed magnetron sputtering at substrate temperatures, Ts, ranging from RT to 550 °C, were investigated. It is found that Al-sites in an insulating metastable homologous (ZnO)3Al2O3 phase are favored above an optimum Ts value (200-400 °C), which depends on the metal/oxygen flux ratio. Energy deposition during growth due to the elevated TS and from the flux of energetic particles incident on the substrate causes preferential Zn desorption. Thus, increasing TS above the optimum value leads to a higher Al concentration (cFAl) in the films, as compared with that of the sputter targets. It exceeds the solubility limit and triggers the formation of this phase, whose volume fraction scales with increasing cFAl. This impedes crystal growth, causes a significant increase of free electron scattering, and results in an increase of the film electrical resistivity. It is shown that one can grow low-resistivity AZO films in a wider range of TS using lower metal/oxygen flux ratios during deposition. This may be suggested as an approach to minimizing the effect of such undesirable phase formation on AZO film electrical properties.
Keywords: Transparent conductive oxides, Al-doped ZnO, Reactive pulsed magnetron sputtering, X-ray absorption near edge structure (XANES), Phase composition
  • Lecture (Conference)
    12th International Conference on Plasma Surface Engineering, 13.-17.09.2010, Garmisch-Partenkirchen, Germany

Publ.-Id: 14522 - Permalink


Study of dipole strength distributions at the ELBE accelerator
Schwengner, R.;
Abstract not available.
  • Invited lecture (Conferences)
    Seminar im Institut für Kernphysik der TU Darmstadt, 11.05.2010, Darmstadt, Deutschland

Publ.-Id: 14521 - Permalink


Enhancement of dipole strength below the neutron-separation energy in 139La
Schwengner, R.;
Abstract not available
  • Lecture (Conference)
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 15.-19.03.2010, Bonn, Deutschland

Publ.-Id: 14520 - Permalink


On the action of magnetic gradient forces in micro-structured copper deposition
Mutschke, G.; Tschulik, K.; Weier, T.; Uhlemann, M.; Bund, A.; Fröhlich, J.;
Magnetic fields allow to study distinct magnetic effects in various electrochemical systems. Lorentz forces can be utilized to tailor convection and mass transfer in electrolytic cells, thereby influencing for example the morphology and the structure of the electrodeposits [1]. Recently, the influence of magnetic gradient forces on the preparation of microstructured metal deposits on field-gradient electrodes has been discussed in the literature [2]. The presentation summarizes new experimental results, analytical findings and numerical simulations in order to discuss the influence of different magnetic forces involved and the prospects towards smaller deposition structures.

[1] G. Mutschke, A. Hess, A. Bund, J. Fröhlich,
On the origin of horizontal counter-rotating electrolyte flow during
copper magnetoelectrolysis.
Electrochimica Acta 55 (2010) 1543-1547.

[2] K. Tschulik, J. Koza, M. Uhlemann, A. Gebert, L. Schultz,
Effects of well-defined magnetic field gradients on the electrodeposition
of copper and bismuth.
Electrochemistry Communications 11 (2009) 2241-2244.
Keywords: magnetic gradient forces, structured deposition
  • Lecture (Conference)
    61st Annual Meeting of the International Society of Electrochemistry, 26.09.-01.10.2010, Nizza, Frankreich
  • Contribution to proceedings
    61st Annual Meeting of the International Society of Electrochemistry, 26.09.-01.10.2010, Nizza, Frankreich

Publ.-Id: 14518 - Permalink


Surface tension and density of liquid Bi-Pb, Bi-Sn and Bi-Pb-Sn eutectic alloys
Plevachuk, Y.; Sklyarchuk, V.; Gerbeth, G.; Eckert, S.; Novakovic, R.;
Surface tension and density measurements of liquid Bi-Pb, Bi-Sn and Bi-Pb-Sn eutectic alloys were carried out by the large drop method in the temperature range 350 - 750 K. The regular solution model is used in conjunction with Butler's equation to calculate the surface tension of binary and ternary alloys of the Bi-Pb-Sn system, while the surface tension of ternary alloys is also predicted by geometric models. The new experimental results were compared with the calculated values of the surface tension as well as with the data available in literature.
Keywords: surface tension, density eutectic alloys, large drop method, bismuth, lead, tin
  • Surface Science 605(2011), 1034-1042

Publ.-Id: 14517 - Permalink


Quantitative characterization of melt flows in AC magnetic fields
Eckert, S.; Zhang, C.; Grants, I.; Gerbeth, G.;
This presentation considers various situations where the flow inside a liquid metal column is driven by different configurations of AC magnetic fields. The ultrasonic Doppler method has been used to determine profiles of the fluid velocity in the ternary alloy GaInSn. The azimuthal and vertical velocity components have been measured allowing for an analysis of both a swirling flow in the horizontal planes and the flow pattern in the radial-meridional plane. In particular, we consider here transient liquid metal flows generated inside a cylindrical container by the superposition of a rotating magnetic field (RMF) and a travelling magnetic field (TMF). The application of the magnetic body forces can be used to create a tornado-like vortex in a closed volume of liquid metal. Moreover, the case of an RMF-driven flow will be discussed which is influenced by an oxide layer at the free surface of the metallic melt. The oxide layer feels the effect of the viscous force arising from the moving liquid beneath and the friction force from the side walls. A complex interaction occurs if the both forces are in the same order of magnitude. In that case, our measurements demonstrate that the occurrence of the oxide layer may lead to an unexpected oscillating behaviour of the bulk flow.
Keywords: liquid metal, electromagnetic stirring, rotating magnetic field, ultrasound Doppler velocimetry
  • Lecture (Conference)
    4th Asian Workshop on Electromagnetic Processing of Materials, 03.-06.10.2010, Jeju, South Korea
  • Contribution to proceedings
    4th Asian Workshop on Electromagnetic Processing of Materials, 03.-06.10.2010, Jeju, South Korea, 172-175

Publ.-Id: 14516 - Permalink


Effect of the substrate on the insulator-metal transition of vanadium dioxide films
Kovacs, G.; Buerger, D.; Skorupa, I.; Schmidt, H.;
Single-phase vanadium dioxide films grown on (0001) sapphire and (001) silicon substrates show very different insulator-metal electronic transition. A detailed description of the growth mechanisms and the substrate-film interaction is given, and the characteristics of the electronic transition are described by the morphology and grain boundary structure. (Tri-)epitaxy-stabilized columnar growth of VO2 takes place on the sapphire substrate, while on silicon the expected Zone II growth is identified. We have found that in the case of the Si substrate the reasons for the broader hysteresis and the lower switching amplitude are the higher average oxygen vacancy concentration and the VxSiyO built up in the grain boundaries. These phenomena are the result of the material transport between the silicon substrate and the growing film.
Keywords: memristor, insulator-metal transition, vanadium dioxide
  • Journal of Applied Physics 109(2011)6, 063708

Publ.-Id: 14515 - Permalink


Design, Synthese und Anwendungsmöglichkeiten von Radiometallverbindungen
Stephan, H.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Kolloquium Universität Heidelberg, Institut für Anorganische Chemie, 13.08.2010, Heidelberg, D

Publ.-Id: 14514 - Permalink


The Master Curve approach an approved fracture mechanics test method for more than one decade
Viehrig, H.-W.;
The paper gives an overview about the development of the Master Curve approach since the first version of the appropriate test standard ASTM E1921 was issued. The main focus is on the application of ASTM E1921 for the determination of fracture toughness values applied in the nuclear reactor pressure vessel integrity assessment. Test parameters influencing the reference temperature were assessed.
Keywords: fracture toughness, ductile-to-brittle transition, reactor pressure vessel steel
  • Invited lecture (Conferences)
    COMAT 2010 RECENT TRENDS IN STRUCTURAL MATERIALS, 25.-26.11.2010, Plzen, Czech Republic
  • Contribution to proceedings
    COMAT 2010 RECENT TRENDS IN STRUCTURAL MATERIALS, 25.-26.11.2010, Plzen, Czech Republic
    Proceedings of COMAT 2010 Recent Trends in Structural Materials, Plzen: COMTES FHT a.s.

Publ.-Id: 14513 - Permalink


FLUKA capabilities and CERN applications for the study of radiation damage to electronics at high energy hadron accelerators
Battistoni, G.; Boccone, V.; Broggi, F.; Brugger, M.; Campanella, M.; Carboni, M.; Cerutti, F.; Empl, A.; Fassò, A.; Ferrari, A.; Ferrari, A.; Gadioli, E.; Garzelli, M.; Kramer, D.; Lantz, M.; Lebbos, E.; Mairani, A.; Margiotta, A.; Mereghetti, A.; Morone, C.; Muraro, S.; Parodi, K.; Patera, V.; Pelliccioni, M.; Pinsky, L.; Ranft, J.; Roeed, K.; Roesler, S.; Rollet, S.; Sala, P. R.; Santana, M.; Sarchiapone, L.; Sioli, M.; Smirnov, G.; Sommerer, F.; Theis, C.; Trovati, S.; Versaci, R.; Villari, R.; Vincke, H.; Vincke, H.; Vlachoudis, V.; Vollaire, J.; Zapp, N.;
The assessment of radiation damage to electronics is a complex process and requires a detailed description of the full particle energy spectra, as well as a clear characterization of the quantities used to predict radiation damage. FLUKA, a multi-purpose particle interaction and transport code, is capable of calculating proton-proton and heavy ion collisions at LHC energies and beyond. It correctly describes the entire hadronic and electromagnetic particle cascade initiated by secondary particles from TeV energies down to thermal neutrons, and provides direct scoring capabilities essential to estimate in detail the possible risk of radiation damage to electronics. This paper presents the FLUKA capabilities for applications related to radiation damage to electronics, providing benchmarking examples and showing the practical applications of FLUKA at CERN facilities such as CNGS and LHC. Related applications range from the study of device effects, the detailed characterization of the radiation field and radiation monitor calibration, to the input requirements for important mitigation studies including shielding, relocation or other options.
Keywords: Radiation Damage to Electronics, FLUKA, CERN, LHC
  • Contribution to proceedings
    Joint International Conference on Supercomputing in Nuclear Applications and Monte Carlo 2010 (SNA + MC2010), 17.-21.10.2010, Tokyo, Japan
    Progress in Nuclear Science and technology 2(2011), 948-954

Publ.-Id: 14512 - Permalink


The application of the Monte Carlo code FLUKA in radiation protection studies for the Large Hadron Collider
Battistoni, G.; Broggi, F.; Brugger, M.; Campanella, M.; Carboni, M.; Empl, A.; Fassò, A.; Gadioli, E.; Cerutti, F.; Ferrari, A.; Ferrari, A.; Garzelli, M.; Lantz, M.; Mairani, A.; Margiotta, A.; Morone, C.; Muraro, S.; Parodi, K.; Patera, V.; Pelliccioni, M.; Pinsky, L.; Ranft, J.; Roesler, S.; Rollet, S.; Sala, P. R.; Santana, M.; Sarchiapone, L.; Sioli, M.; Smirnov, G.; Sommerer, F.; Theis, C.; Trovati, S.; Villari, R.; Vincke, H.; Vincke, H.; Vlachoudis, V.; Vollaire, J.; Zapp, N.;
The multi-purpose particle interaction and transport code FLUKA is integral part of all radiation protection studies for the design and operation of the Large Hadron Collider (LHC) at CERN. It is one of the very few codes available for this type of calculations which is capable to calculate in one and the same simulation proton-proton and heavy ion collisions at LHC energies as well as the entire hadronic and electromagnetic particle cascade initiated by secondary particles in detectors and beam-line components from TeV energies down to energies of thermal neutrons. The present paper reviews these capabilities of FLUKA in giving details of relevant physics models along with examples of radiation protection studies for the LHC such as shielding studies for underground areas occupied by personnel during LHC operation and the simulation of induced radioactivity around beam loss points. Integral part of the FLUKA development is a careful benchmarking of specific models as well as the code performance in complex, real life applications which is demonstrated with examples of studies relevant to radiation protection at the LHC.
Keywords: radiation protection, shielding calculations, activation, FLUKA
  • Contribution to proceedings
    Joint International Conference on Supercomputing in Nuclear Applications and Monte Carlo 2010 (SNA + MC2010), 17.-21.10.2010, Tokyo, Japan
    Progress in Nuclear Science and Technology 2(2011), 358-364

Publ.-Id: 14511 - Permalink


Status of the PTS Experiment at TOPFLOW
Beyer, M.; Schleicher, E.; Pietruske, H.; Seidel, T.; Szalinski, L.; Hampel, U.; Weiß, F.-P.;
After a short description of the aim and tasks of the project the experimental setup and the measurement technique were explained. Futhermore, the two executed air/water measurement series were specified. On the one hand, the behaviour of the flow through an Emergency Core Cooling (ECC) line into a Cold Leg of a Pressurized Water Reactor was investigated in dependence on some thermo hydraulic parameters. On the other hand, the occureance of thermal stratification inside the Cold Leg during ECC injection with different mass flows was analysed. An explanation of the next steps for the steam/water tests and an outlook completed the presentation.
Keywords: Pressurized Thermal Shock, Emergency Core Cooling, Pressurized Water Reactor, thermal stratification, mixing phenomena
  • Lecture (others)
    Steering Committee Meeting on R&D Cooperation between Forschungszentrum Dresden-Rossendorf and AREVA NP GmbH, 20.09.2010, Dresden, Deutschland

Publ.-Id: 14510 - Permalink


Measurement of the neutron detection efficiency of a 80% absorber - 20% scintillating fiber calorimeter
Anelli, M.; Bertolucci, S.; Bini, C.; Branchini, P.; Corradi, G.; Curceanu, C.; Dezorzi, G.; Di Domenico, A.; Di Micco, B.; Ferrari, A.; Fiore, S.; Gauzzi, P.; Giovannella, S.; Happacher, F.; Iliescu, M.; Luca', A.; Martini, M.; Miscetti, S.; Nguyen, F.; Passeri, A.; Prokoviev, A. V.; Sarra, I.; Sciascia, B.; Sirghi, F.; Tagnani, D.;
The neutron detection efficiency of a sampling calorimeter made of 1 mm diameter scintillating fibers embedded in a lead/bismuth structure has been measured at the neutron beam of the Svedberg Laboratory at Uppsala. A significant enhancement of the detection efficiency with respect to a bulk organic scintillator detector with the same thickness is observed.
Keywords: Neutron detection, calorimetry, scintillating fibers

Publ.-Id: 14509 - Permalink


Experimentelle Ergebnisse im Rahmen des TOPFLOW-II Projektes
Beyer, M.; Szalinski, L.; Barthel, F.; Lucas, D.; Weiß, F.-P.;
Der Vortrag beschreibt die im TOPFLOW-II Projekt erzielten Ergebnisse und den Realisierungsstand der Arbeiten. Nach einer kurzen Einführung zu Ziel und Aufgabenstellung des Projektes, werden detailliert die Resultate der Kondensationsexperimente und erste Auswertungen der Messdaten erläutert. Hierbei wird auch zum Teil auf Einzeleffekte eingegangen und die Reproduzierbarkeit der Ergebnisse nachgewiesen. Eine Beschreibung der Druckentlastungsversuche und die Darstellung ausgewählter Messdaten sowie Vorschläge zur Datenauswertung schließen sich an. Nachfolgend wird der erreichte Stand bei den Messungen mit dem Schnellen Röntgentomographen an der Teststrecke Ti-Rohr DN50 für aufwärtsgerichtete Luft/Wasser-Strömungen vorgestellt. Eine Zusammenfassung und ein Überblick zur Projektrealisierung beenden den Vortrag.
Keywords: TOPFLOW, wire-mesh sensor, ROFEX, X-ray tomograph, CFD, two-phase flow, steam condensation, pressure release
  • Lecture (others)
    CFD-Forschungsverbund, Entwicklung und Anwendung von Computational Fluid Dynamics (CFD) Programmen für Phänomene im Kühlkreislauf und Sicherheitseinschluss von Leichtwasserreaktoren, 23.09.2010, Grosshartpenning, Deutschland

Publ.-Id: 14508 - Permalink


Shielding aspects of the new nELBE photo-neutron source
Ferrari, A.; Beyer, R.; Birgersson, E.; Claussner, J.; Grosse, E.; Hannaske, R.; Junghans, A.; Kögler, T.; Kösterke, I.; Massarczyk, R.; Matic, A.; Schilling, K.-D.; Schramm, G.; Schwengner, R.; Wagner, A.; Weiss, F.-P.;
The nELBE beamline at Forschungszentrum Dresden-Rossendorf (FZD) provides intense neutron beams by stopping a primary electron beam in a liquid lead radiator and producing then neutrons by bremsstrahlung photons through (gamma,n) reactions. To increase the neutron yield through the electron energy enhancement (from the current 40 MeV limit up to 50 MeV), to optimize the neutron/photon ratio and to minimize several source of background at the present time, a new neutron beamline with a new, larger experimental room has been designed. Extensive simulations with the particle interaction and transport code FLUKA have been performed to assess all the shielding aspects of the design. Starting from the primary electron beam, both the photon and neutron secondary radiation fields have been fully characterized. To have a cross-check of the results, the calculated values of the neutron yields at different energies of the primary beam have been compared with an independent simulation with the MCNP code, obtaining a very satisfactory agreement at the level of few percent. The photoproduction area has been studied in a mixed field condition, while, for statistical reasons, the penetration of the beam through the collimator and then in the neutron experimental room has been studied by writing a separate source term for the photon and the neutron radiation component. The results for the nELBE shielding, together with some aspects of the optimization of the photo-neutron beamline, are here presented and discussed.
Keywords: neutron time-of-flight superconducting electron linear accelerator, shielding assessment
  • Contribution to proceedings
    10th Conference of the Task Force on Shielding Aspects of Accelerators, Targets and Irradiation Facilities, SATIF-10, 02.-04.06.2010, Geneva, Switzerland
    Shielding Aspects of Accelerators, Targets and Irradiation Facilities - SATIF 10, Paris: OECD Nuclear Energy Agency Publications, 9789264096509 (PDF) ; 9789264034679 (print), 97-106
  • Lecture (Conference)
    10th Conference of the Task Force on Shielding Aspects of Accelerators, Targets and Irradiation Facilities, SATIF-10, 02.-04.06.2010, Geneva, Switzerland

Publ.-Id: 14507 - Permalink


Shielding assessment for the ELI high intensity laser beamline facility in Czech Republic
Ferrari, A.; Cowan, T.; Margarone, D.; Prokupek, J.; Rus, B.;
The production of laser-accelerated, high energy and high current particle beams requires a proper shielding assessment, especially when high intensity laser systems operate in repetition rate. The ELI (Extreme Light Infrastructure) future european facility in Czech Republic, where different optional laser beamlines are foreseen, will offer versatile electron and proton/ion sources, emitting in an unprecedented energy range (up to about 40 GeV for the electron case). For this facility a first extensive study that includes shielding and activation calculations for the 300 J laser beamline, which is the most critical for electron acceleration experiments, has been performed. Starting from analytical calculations, as well as from dedicated simulations, the main radiation fields produced in the laser-matter interaction have been defined. These fields have been then characterized as "source terms" in a full simulation with the Monte Carlo code FLUKA, where the produced secondary radiation has been studied to assess a proper shielding. The first results for the ELI shielding for the electron case, together with the activation calculations that drove several material solutions, are here presented and discussed.
Keywords: laser-accelerated electron and proton beams, shielding assessment
  • Contribution to proceedings
    10th Conference of the Task Force on Shielding Aspects of Accelerators, Targets and Irradiation Facilities, SATIF-10, 02.-04.10.2010, Geneva, Switzerland
    Shielding Aspects of Accelerators, Targets and Irradiation Facilities - SATIF 10, Paris: OECD Nuclear Energy Agency Publications, 9789264096509 (PDF) ; 9789264034679 (print), 87-96
  • Lecture (Conference)
    10th Conference of the Task Force on Shielding Aspects of Accelerators, Targets and Irradiation Facilities, SATIF-10, 02.-04.06.2010, Geneva, Switzerland

Publ.-Id: 14506 - Permalink


Rare and strange probes in relativistic Heavy-Ion Collisions
Schade, H.; Kämpfer, B.;
Mit Hilfe eines Transportmodells vom Boltzmann-Ühling-Uhlenbeck (BUU)-Typ wird die Dynamik von Strangeness-Freiheitsgraden in relativistischen Schwerionenstößen studiert. Insbesondere werden die $K^+$, $K^-$ und $\phi$ Multiplizitäten sowie Transversalimpuls- und Rapiditätsspektren mit aktuellen HADES Daten (Ar+KCl bei einer kinetischen Strahlenergie von 1.756 AGeV) erfolgreich verglichen und damit deren Medium-Modifikationen (zunächst durch effektive Massenverschiebungen parametrisiert) bestimmt. Die Rolle des $\phi$ Zerfalls und des Strangeness-Transfer-Kanals für die $K^-$ Produktion wird quantifiziert. Weiterhin wird die Empfindlichkeit des doppelt seltsamen Hyperons $\Xi^-$ (Ausbeute und Spektren) auf die nukleare Zustandsgleichung getestet.
  • Lecture (Conference)
    74. Jahrestagung der DPG und DPG Frühjahrstagung der Fachverbände 2010, 15.-19.03.2010, Bonn, Deutschland

Publ.-Id: 14505 - Permalink


Strangeness - phi mesons in pA reactions
Schade, H.; Kämpfer, B.;
Recent experiments of the ANKE collaboration concerning the phi meson production in pA-reactions p (2.83 GeV) + C, Cu, Ag and Au are appropriate for the absorptive phi-N interaction within the trancparency ratio. With the aim of analyzing the amount of phi absorption we applied our well confirmed transport model of Boltzmann-Ühling-Uhlenbeck (BUU) type on this scenario. The results seem to point to an absorption cross section of 18 \pm 3 mb only when accounting for secundary phi production processes as well as isospin asymmetry and ANKE acceptance conditions.
  • Invited lecture (Conferences)
    International Workshop on Hot and Cold Baryonic Matter, 15.-19.08.2010, Budapest, Ungarn

Publ.-Id: 14503 - Permalink


Optimization aspects of the new nELBE photo-neutron source
Ferrari, A.; Beyer, R.; Birgersson, E.; Claussner, J.; Grosse, E.; Hannaske, R.; Junghans, A.; Kempe, M.; Kögler, T.; Massarczyk, R.; Matic, A.; Schilling, K.-D.; Schramm, G.; Schwengner, R.; Wagner, A.; Weiss, F.-P.; Yakorev, D.;
The nELBE beamline at Forschungszentrum Dresden-Rossendorf (FZD) provides intense neutron beams by stopping primary electrons in a liquid lead target, where neutrons are produced by bremsstrahlung photons via (gamma,n) reactions. With the aim to increase the neutron yield through the enhancement of the electron beam energy (from the current 40 MeV limit up to 50 MeV), as well as to minimize several sources of background that are presently affecting the measurements, a new neutron beam-line and a new, larger neutron experimental room have been designed. The optimization of the neutron/photon ratio, the minimization of the backscattered radiation from the walls and the possibility to have better experimental conditions are the main advantages of the new design. To optimize the beamline, extensive simulations with the particle interaction and transport code FLUKA have been performed. Starting from the primary electron beam, both the photon and neutron radiation fields have been fully characterized. To have a cross-check of the results, the calculated values of the neutron yields at different energies of the primary beam have been compared both with an independent simulation with the MCNP code and with analytical calculations, obtaining a very satisfactory agreement at the level of few percent. The evaluated radiation fields have been used to optimize the direction of the new neutron beamline, in order to minimize the photon flash contribution. A general overview of the new photo-neutron source, together with all the steps of the optimization study, is here presented and discussed.
Keywords: neutron time-of-flight superconducting electron linear accelerator, photo-nuclear cross sections
  • Open Access LogoContribution to proceedings
    Measurements and Models of Nuclear Reactions, EFNUDAT Users and Collaboration Workshop, 25.-27.05.2010, Paris, France
    European Physical Journal, Web of Conferences 8(2010), 05002, DOI:10.1051/epjconf/20100805002, 978-2-7598-0585-3
  • Lecture (Conference)
    Measurements and Models of Nuclear Reactions, EFNUDAT Users and Collaboration Workshop, 25.-27.05.2010, Paris, France

Publ.-Id: 14502 - Permalink


Phase resolved x-ray ferromagnetic measurements in fluorescence yield
Marcham, M. K.; Keatley, P. S.; Neudert, A.; Hicken, R. J.; Cavill, S. A.; Shelford, L. R.; van der Laan, G.; Telling, N. D.; Childress, J. R.; Katine, J. A.; Shafer, P.; Arenholz, E.;
Phase resolved X-ray Ferromagnetic Resonance (XFMR) has been measured in fluorescence yield, widening the application of XFMR to opaque samples on opaque substrates. Magnetization dynamics were excited in a Co50Fe50(0.7)/Ni90Fe10(5) bilayer by means of a continuous wave microwave excitation, while X-ray Magnetic Circular Dichroism (XMCD) spectra were measured stroboscopically at different points in the precession cycle. By tuning the x-ray energy to the L3 edge of Ni or Fe, the dependence of the real and imaginary components of the magnetic susceptibility upon the strength of an externally applied static was determined. First results from measurements on a Co50Fe50(0.7)/Ni90Fe10(5)/Dy(1) sample confirm that enhanced damping results from the addition of the Dy cap.
Keywords: Phase resolved X-ray Ferromagnetic Resonance Magnetization Dynamics

Publ.-Id: 14499 - Permalink


A nodal SP3 approach for reactors with hexagonal fuel assemblies
Duerigen, S.; Grundmann, U.; Mittag, S.; Merk, B.; Kliem, S.;
The neutronics model of the nodal reactor dynamics code DYN3D developed for 3-D analyses of steady states and transients in light-water reactors has been extended by a simplified P3 (SP3) neutron transport option to overcome the limitations of the diffusion approach. To provide a method being applicable to reactors with hexagonal fuel assemblies and furthermore allowing flexible mesh refinement, the nodal SP3 method has been
developed on the basis of a flux expansion in trigonal-z geometry. Dividing a hexagonal fuel assembly into six triangular nodes, steady-state test calculations for one assembly as well as for a 'minicore' consisting of seven fuel assemblies have been performed, in which both a symmetric and an asymmetric material composition are chosen to be compared with more accurate HELIOS transport calculations in each case.
Keywords: nodal simplified P3 SP3 DYN3D trigonal hexagonal
  • Contribution to proceedings
    20th Symposium of AER on VVER Reactor Physics and Reactor Safety, 20.-24.09.2010, Hanasaari, Espoo, Finland
  • Lecture (Conference)
    20th Symposium of AER on VVER Reactor Physics and Reactor Safety, 20.-24.09.2010, Hanasaari, Espoo, Finland

Publ.-Id: 14498 - Permalink


Proteinbasierte Biokompositmaterialien zur Behandlung schadstoffhaltiger Wässer
Raff, J.; Weinert, U.; Lehmann, F.; Günther, T.; Matys, S.; Kutschke, S.; Pollmann, K.;
Bakterielle Hüllproteine, sogenannte S-Layer, bilden eine intelligente Grenzschicht zwischen Zellen und ihrer Umwelt. Diese erlauben es Bakterien auf Uranabfallhalden, giftige Schwermetalle am Eindringen in die Zelle zu hindern, während lebensnotwendige Spuren¬elemente die Barriere passieren können. Verantwortlich für die genannte Eigenschaft ist eine gitterförmige und hochgeordnete Ausprägung des Proteinpolymers und damit verbunden eine regelmäßige und definierte Anordnung zahlreicher funktioneller Gruppen auf der Polymeroberfläche. Letztere ist ursächlich für die selektive Bindung bestimmter Metalle. Darüber hinaus bilden S-Layer-Proteine spontan monolagige Schichten an Grenzflächen und auf Oberflächen. Diese Kombination von Eigenschaften machen S-Layer sehr interessant für die Entwicklung neuer Biokompositwerkstoffe für technische Anwendungen und insbe¬sondere für die Wasserbehandlung. Zur Beschichtung und Funktionalisierung technischer Träger mit S-Layern werden Layer-by-Layer-Techniken genutzt. Derartige Biokomposite dienen gegenwärtig der Entwicklung von selektiven Filtern, von Biosensoren und von Fotokatalysatoren zur Detektion und Entfernung von anorganischen sowie organischen Schadstoffen aus Wasser.
Keywords: S-layer, bio-composite
  • Lecture (Conference)
    7. Max-Bergmann-Symposium, 16.11.2010, Dresden, Deutschland

Publ.-Id: 14497 - Permalink


The electromagnetically forced flow over a backward-facing step
Weier, T.; Albrecht, T.; Gerbeth, G.; Metzkes, H.; Stiller, J.;
The flow over a backward-facing step is a prototype of a separating and reattaching shear flow. Here we investigate the influence of time periodic electromagnetic forces on different flow features by time resolved Particle Image Velocimetry. As integral measure, the reattachment length is used, which shortens for increasing amplitude of the forcing. The maximum reduction of the rezirculation zone is found for an excitation frequency equal to the most amplified frequency of the separating shear layer.
Keywords: backward-facing step, flow control, Lorentz force
  • Open Access LogoContribution to proceedings
    Seventh International Symposium On Turbulence and Shear Flow Phenomena (TSFP-7), 28.-31.07.2011, Ottawa, Kanada
    Proceedings of the 7th International Symposium On Turbulence and Shear Flow Phenomena (TSFP-7)
  • Poster
    Seventh International Symposium On Turbulence and Shear Flow Phenomena (TSFP-7), 28.-31.07.2011, Ottawa, Canada

Downloads:

Publ.-Id: 14496 - Permalink


First identification of the tridymite form of AlPO4 in a municipal sewage sludge ash
Peplinski, B.; Adam, C.; Reuther, H.; Vogel, C.; Adamczyk, B.; Menzel, M.; Emmerling, F.; Simon, F.-G.;
  • Poster
    European Powder Diffraction Conference EPDIC 12, 27.-30.08.2010, Darmstadt, Deutschland
  • Zeitschrift für Kristallographie Proceedings 1(2011), 443-448
    DOI: 10.1524/zkpr.2011.0067

Publ.-Id: 14495 - Permalink


Innovation Information Technology in the service of research at the FZD
Konrad, U.;
Large research facilities, such as the Forschungszentrum Dresden-Rossendorf (FZD), provide the scientific work environment for employees, guests and students from all over the world.
To manage research projects, achieve new insights and visualize the results innovative information technology has to be applied for the communication, information and collaboration infrastructure as well as for the scientific equipments. Managing such a dynamic environment in a networked world is a challenging task. This paper describes some solutions and implementation aspects of innovative information technology for a large scale research facility developed in Dresden. The solutions are illustrated using some examples out of the areas of High Performance Computing (HPC), Virtual Reality (VR) and Collaboration in Virtual Institutes.
  • Contribution to proceedings
    International Workshop "Innovation Information Technologies: Theory and Practice", 06.-10.09.2010, Dresden, Deutschland
    Proceedings of the International Workshop "Innovation Information Technologies: Theory and Practice", Dresden: Forschungszentrum Dresden-Rossendorf, 978-3-941405-10-3, 10-12

Publ.-Id: 14494 - Permalink


Progress Report: Cold quarks stars from hot lattice QCD
Schulze, R.; Kämpfer, B.;
Based on a quasiparticle model for �� stable and electrically neutral deconfined matter we address the mass-radius relation of pure quark stars. The model is adjusted to recent hot lattice QCD results for 2+1 flavors with almost physical quark masses [1].We find rather small radii and masses of equilibrium configurations composed of cold deconfined matter, well distinguished from neutron or hybrid stars.
[1] Bazavov et al., Phys. Rev. D 80 (2009) 014504.
  • Lecture (Conference)
    74. Jahrestagung der DPG und DPG Frühjahrstagung der Fachverbände, 15.-19.03.2010, Bonn, Germany

Publ.-Id: 14493 - Permalink


Multiphase flow measurement techniques in industrial safety analysis
Pöpping, U.; Thiele, S.; Bärtling, Y.; Hampel, U.;
Multiphase flows play a major role in many industrial fields, such as in chemical and mineral oil industry and energy power production. Industrial processes run at high pressures and temperatures and involve hazardous materials, such as toxic chemicals or radioactive products. Hence, they must be operated in a safe way under all circumstances, not only in the operational plant mode but also for accident scenarios. Therefore the Institute of Safety Research at Forschungszentrum Dresden-Rossendorf (FZD) spends great effort in the investigation of multiphase flow behavior in industrial plants under such conditions. Understanding the physics of multiphase processes and flows requires special instrumentation of industrial plant components as well as dedicated test facilities.

The expertise at FZD covers the identification of different phases and temperatures employing measurement techniques for permittivity and conductivity as well as ultrafast electron beam X-ray tomography. Many measurement systems, like wire-mesh sensors, needle probes and flow microscopes have been developed and are continuously improved. Especially the existing expertise is the basis for the research on new multiphase measurement technologies, for example autonomous sensors but also a multi-phase flow meter and a filling level sensor.

The poster describes some of the available measurement technologies and outlines future developments.
Keywords: multiphase flow measurement technologies, industry safety analysis
  • Poster
    6th Dresden Symposium, "HAZARDS DETECTION AND MANAGEMENT", 20.-24.09.2010, Dresden, Deutschland

Publ.-Id: 14492 - Permalink


Fast Neutron Cross-Section Measurements with the nELBE Neutron Time-of-Flight Facility
Wagner, A.; Bemmerer, D.; Beyer, R.; Birgersson, E.; Ferrari, A.; Grosse, E.; Hannaske, R.; Junghans, A. R.; Kempe, M.; Kögler, T.; Marta, M.; Matic, A.; Nolte, R.; Schilling, K. D.; Schramm, G.; Schwengner, R.; Weiss, F.-P.; Yakorev, D.;
At the Forschungszentrum Dresden-Rossendorf a new neutron time-of-flight facility has been set up. Fast neutrons in the energy range from 0.1 MeV to 10 MeV are produced using pulsed electron beams from a superconducting electron linear accelerator. Short beam pulses of less than 10 ps allow high-resolution time-of-flight experiments with the aim to determine interaction cross sections of neutrons with reactor structural materials and actinides at energies matching the neutron energies in fast reactors. Following experiments using a thermionic electron injector a new superconducting radio-frequency injector has been built which will allow average beam currents of 0.5 mA at a repetition rate of 500 kHz.
Meanwhile, first experiments on inelastic neutron scattering cross sections on 56Fe and total neutron cross sections on aluminium and tantalum have been performed as benchmark experiments. While photons from the de-exciting transitions are being detected using a 16-element BaF2 scintillator array, neutrons are measured with five low-threshold plastic scintillation detectors. Beam normalisation is done using a calibrated 235U fission chamber. The preparation of actinide targets for neutron induced fission cross section measurements is under way.
Keywords: neutron time-of-flight superconducting electron linear accelerator interaction cross sections reactor structural materials actinides inelastic neutron scattering
  • Contribution to proceedings
    18th International Seminar on Interaction of Neutrons with Nuclei: "Neutron Spectroscopy, Nuclear Structure, Related Topics", 26.-29.05.2010, Dubna, Russia
    ISINN-18: Neutron Spectroscopy, Nuclear Structure, Related Topics, Dubna, Russia: Joint Institute for Nuclear Research, 978-5-9530-0277-6, 127-134
  • Lecture (Conference)
    18th International Seminar on Interaction of Neutrons with Nuclei: "Fundamental Interactions & Neutrons, Nuclear Structure, Ultracold Neutrons, Related Topics", 26.05.2010, Dubna, Russia

Publ.-Id: 14491 - Permalink


Grain growth induced by focused ion beam irradiation in thin magnetic films
Roshchupkina, O. D.; Grenzer, J.; Strache, T.; Fritzsche, M.; Fassbender, J.ORC
Focused ion beam irradiation can be used as a tool for creation of magnetic nanos-tructures. Previous studies have shown that FIB irradiation of thin metallic films could induce significant grain growth and therefore modify magnetic properties [1-2]. In this work we compare X-ray diffraction studies with magnetic properties that were characterized by magneto-optic Kerr effect sensing both the in-plane and the out-of-plane components of the magnetization.
A 50nm thick permalloy layer (Ni80Fe20) irradiated with different fluences of Ga+ ions was chosen for the investigations of grain size and microstrain. Due to the small irradiated areas produced by FIB irradiation XRD measurements were carried out on an optimized X-ray laboratory setup with a focused X-ray beam of 200µm as well as on the ESRF ID01 facility using a 1µm focused beam. Figure 1a shows rocking curves of the (111) permalloy reflection and demonstrates the material texturing with increase of ion fluence as there is a narrowing in FWHM and a rise of intensity. Low irradiation fluences up to 6.24*10E15 ions/cm2 modify the material and induce crystal-lite growth, whereas larger fluences completely destroy the crystalline structure. A further material crystallization should improve the magnetic properties. Due to the incorporation of Ga+ ions into the lattice additional softening of the permalloy film occurs and leads to the degradation of magnetic properties. In figure 1b a corre-sponding saturation Kerr rotation measurement is shown. It demonstrates a decrease of the magnetic moment with increasing ion fluence.


[1] C.M. Park and J. A. Bain., J. of Appl. Phys. 91, 6830 (2002).
[2] W.M. Kaminsky et al., Appl. Phys. Lett. 78, 1589 (2001).
Keywords: Focused ion beam irradiation, permalloy
  • Poster
    XTOP 2010 / 10th Biennial Conference on High Resolution X-Ray Diffraction and Imaging, 20.-23.09.2010, University of Warwick, UK

Publ.-Id: 14490 - Permalink


Transporting radioactive samples from the laboratory to the ESRF
Venault, L.; Den Auwer, C.; Moisy, P.; Colomp, P.; Scheinost, A. C.; Hennig, C.;
Desription of safety efforts required to transport radioactive samples
Keywords: The Rossendorf beamline EXAFS XANES radionuclides actinides
  • Communication & Media Relations
    ESRF News Nr. 54 15.06.2010
    1 Seiten

Publ.-Id: 14487 - Permalink


High-field metamagnetic transitions in Rare-Earth Transition-metal ferrimagnets
Skourski, Y.;
hat nicht vorgelegen
  • Lecture (Conference)
    Joint European Magnetic Symposia (JEMS 2010), 23.-28.08.2010, Krakow, Poland

Publ.-Id: 14486 - Permalink


3D-observation of heterogeneous transport and comparison to Lattice-Boltzmann modelling
Wolf, M.;
This thesis is located at the Institute of Radiochemistry, FZD Research Site Leipzig for Interdisciplinary Isotope Research, Reactive Transport Division (FWRT). The main focus of this division is the investigation of transport processes in geosystems by means of radiotracer applications. The main topic of the thesis is the visualization of transport processes in geologic material by means of the in-house development of the GeoPET-method. This work is conducted as part of the scientific joint venture: „Dynamik abgesoffener oder gefluteter Salzbergwerke und ihres Deckgebirgsstockwerks“ („Dynamic of drowned or flooded salt mines and their overburden“), coordinated by the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR).

Since the late 19. century drowned salt mines cause severe mining damages in the city of Stassfurt (Saxony-Anhalt). Sink hole depressions and subsidence of the surface below the groundwater table destroyed large parts of the down town. The general causation was lack of experience with salt mines and mining in gypsum karst in the 19. century. The causation in detail why and how exactly salt rock has washed out is more complicated to identify, as streaming mechanisms at the small scale level are partly still unclear; the general fluid dynamics at small scales is partly unknown.

To reveal these processes and mechanisms the behaviour of salt brines at the millimetre scale in drilling cores of the different geological units of the salt rock and its surrounding is examined by three-dimensional visualization of the distribution of radioactive labelled water measured with PET. Mechanisms at millimetre scale control mechanisms at the kilometre scale and are of utmost importance for the principal understanding of fluid dynamics. In the laboratory you can have „a look into the rock“. In the field this is not possible this way.

Combining PET data with high resolution CT-scans of the samples (conducted by the cooperation partners JGU Mainz and BAM Berlin) allows an alignment of processes of the fluid flow and its associated hydraulic pathway structures. This matching is important for understanding and for generalized conclusion about ongoing processes and is a necessary preparatory work for computer modelling.

Lattice-Boltzmann-simulations of velocity fields and streaming patterns based on CT-data are compared with PET-data derived from the same samples. This comparison of the flow patterns is done by means of geostatistic methods that allows scale independant spatial correlation of the patterns and therefore provide scale indpendant parameters like correlation lengths that are a necessity for upscaling.

Short term objective is the improvement and validation of parameters and fluid flow concepts derived from small scale simulations. Long term objective is the improvement of upscaling of parameters and concepts to the field scale and a better understanding and prediction of mining damages and groundwater behaviour.
  • Lecture (others)
    FZD Doktorandenseminar, 22.-24.09.2010, Krögis (Meissen), Deutschland

Publ.-Id: 14485 - Permalink


Environmental Sciences at the ESRF
Cotte, M.; Auffan, M.; Degruyter, W.; Fairchild, I.; Newton, M.; Morin, G.; Sarret, G.; Scheinost, A. C.;
In the past several years, environmental sciences have increased their share in the research portfolios of many synchrotrons, not least for their topicality from a societal point of view. As this field overlaps with many other disciplines, the ESRF decided to establish, in 2005, a dedicated Review Panel for Environmental Science and Cultural Heritage.
This facility report summarizes recent trends and results from the ESRF to highlight the different disciplines, techniques and topics. It should also be noted that environmental studies encompass both a better understanding of natural phenomena and monitoring the impact of human activity on nature.
Keywords: synchrotron radiation XAFS environmental research

Publ.-Id: 14483 - Permalink


The use of ionization chambers for short-pulsed radiation fields with high pulse dose
Karsch, L.; Richter, C.; Pawelke, J.;
no abstract available
Keywords: ionization chamber, saturation correction
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 186(2010)Suppl. 1, 93-93
  • Poster
    16. Jahreskongress der Deutschen Gesellschaft für Radioonkologie, 03.-06.06.2010, Magdeburg, Deutschland

Publ.-Id: 14482 - Permalink


Characterization and optimization of the imaging and dosimetric properties of a image-guided precision irradiation device for small animals
Tillner, F.; Hietschold, V.; Khaless, A.; Pawelke, J.; Thute, P.; Enghardt, W.;
no abstract available
Keywords: IGRT, small animal
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 186(2010)Suppl. 1, 105-105
  • Poster
    16. Jahreskongress der Deutschen Gesellschaft für Radioonkologie, 03.-06.06.2010, Magdeburg, Deutschland

Publ.-Id: 14481 - Permalink


The Influence of the temperature on the carbonate complexation of Uranium(VI) - a spectroscopic study
Götz, C.; Geipel, G.; Bernhard, G.;
The interaction of uranium(VI) with carbonate ions was studied with absorption spectroscopy and time resolved laser induced fluorescence spectroscopy due to the importance of these complexes in environmental relevant waters. In the pH range from 2 to 11 the influence of the temperature on the spectra was studied to check changes in the abundances of several binding forms. It was found that several binding forms are predominant at different temperatures and pH values. This observation can be explained by speciation changes due to the dependence of chemical equilibria on the temperature.
Furthermore photoluminescence spectra of aqueous solutions of uranyl carbonate complexes were observed at ambient temperatures for the first time and single component absorption spectra of the uranyl carbonate complexes UO2(CO3)34- and UO2(CO3)22- were derived.
Keywords: Uranium(VI), carbonate complexation, absorption spectroscopy, time resolved laser induced fluorescence spectroscopy, temperature, chemical equilibrium

Publ.-Id: 14479 - Permalink


Instantaneous shape sampling: A model for the gamma-absorption cross section of transitional nuclei
Bentley, I.; Brant, S.; Dönau, F.; Frauendorf, S.; Kämpfer, B.; Schwengner, R.; Zhang, S. Q.;
The influence of the quadrupole shape fluctuations on the dipole vibrations in transitional nuclei is investigated in the framework of the instantaneous-Shape Sampling (ISS) Model, which combines the Interacting Boson Model for the slow collective quadrupole motion with the Random Phase Approximation for the rapid dipole vibrations. Coupling to the complex background configurations is taken into account by folding the results with a Lorentzian with energy dependent width (collisional damping CD).
The low-energy energy portion of the gamma absorption cross section, which is important for photo-nuclear processes, is studied for the isotop series of Kr, Xe, Ba, and Sm. The experimental cross sections are well reproduced. The low-energy dipole strength is determined by the Landau fragmentation of the dipole strength and its redistribution caused by the shape fluctuations. CD only wipes out fluctuations of the absorption cross section, generating the smooth energy dependence observed in experiment. In the case of semi magical nuclei, shallow pygmy resonances are found in correspondence with experiment.
Keywords: Dipole strength, absorption cross section, interacting boson model, quasiparticle random-phase-approximation.
  • Physical Review C 83(2011), 014317

Publ.-Id: 14478 - Permalink


Experimentelle und analytische Untersuchungen zu passiven Komponenten des KERENA TM Konzeptes im Versuchsstand INKA
Willschütz, H.-G.; Diercks, F.; Leyer, S.; Krüssenberg, A.-K.; Schäfer, F.; Hristov, H. V.;
Das KERENA TM - Konzept ist eine kontinuierliche Weiterentwicklung der seit Jahren bewährten (deutschen) Siedewassertechnologie der "Baulinie 72". Die Kombination von betriebserprobten aktiven Sicherheitssystemen mit neu hinzugekommenen passiven Sicherheitssystemen setzt die Forderungen der "Defense in Depth"-Philsophie konsequent um. Insbesondere für die neu eingeführten passiven Sicherheitssysteme muss das Betriebsverhalten durch experimentelle Untersuchungen validiert und die thermohydraulischen Berechnungsprogramme müssen qualifiziert werden, so dass sie die auftretenden Naturumlaufphänomene korrekt berechnen können. Mit den vorliegenden Arbeiten wird die Eignung des Thermohydraulikprogrammsystems ATHLET der Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH als ein Programm, das im Genehmigungs- und Aufsichtsverfahren in verschiedenen Ländern eingesetzt wird, zur Berechnung des Betriebsverhalten der passiven Komponenten untersucht. Dazu wurde ein Modell für die Versuchsanlage INKA (INtegral test facility in KArlstein) entwickelt, mit dem sowohl Vorausrechnungen des Kennfelds der passiven Komponenten Notkondensator und Gebäudekondensator als auch Nachrechnungen zu Experimenten durchgeführt wurden.
Keywords: KERENA, ATHLET, Boiling Water Reactor
  • Contribution to proceedings
    42. Kraftwerkstechnisches Kolloquium 2010, 12.-13.10.2010, Congress Center Dresden, Deutschland
    Experimentelle und analytische Untersuchungen zu passiven Komponenten des KERENA TM Konzeptes im Versuchsstand INKA
  • Lecture (Conference)
    42. Kraftwerkstechnisches Kolloquium 2010, 12.-13.10.2010, Congress Center Dresden, Deutschland

Publ.-Id: 14476 - Permalink


4D-in-beam-PET für periodisch bewegte Phantome bei Bestrahlung mit einem mitbewegten 12C-Strahl
Laube, K.; Bert, C.; Chaudhri, N.; Fiedler, F.; Parodi, K.; Rietzel, E.; Saito, N.; Enghardt, W.;
Fragestellung
In-beam-PET ist die bislang einzige Methode zur in vivo und in situ Überwachung der Dosisapplikation bei der Ionenstrahltherapie. Sie wurde in einem Pilotprojekt am GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt bei der 12C-Bestrahlung von über 400 Patienten mit unbeweglichen Tumoren im Kopf-Halsbereich erfolgreich eingesetzt. Die geplante Anwendung der Ionenstrahltherapie auf, v. a. atmungsbedingt, intrafraktionell bewegliche Tumoren erfordert eine Erweiterung der in-beam-PET-Datenrekonstruktion. Die Notwendigkeit einer zeitaufgelösten (4D) Auswertung und die Qualität der damit reproduzierbaren Aktivitätsverteilung werden anhand experimenteller Daten dargestellt.

Methodik
Ein PMMA-Phantom wurde mittig im Gesichtsfeld des Doppelkopf-PET-Scanners BASTEI am ehemaligen medizinischen Bestrahlungsplatz der GSI positioniert und senkrecht zur Einstrahlrichtung periodisch (sinusförmig, Amplitude = 10 mm, Periode ≈ 3,5 s) ausgelenkt. Mit einem monoenergetischen 12C-Bleistiftstrahl wurde eine im Bereich des Bragg-Peaks homogene, linienförmige Dosisverteilung parallel zur Bewegungsrichtung im Target appliziert. Für die Bestrahlung wurde ein neuartiges Tracking-System benutzt, welches die Strahlrichtung der aktuellen Phantomauslenkung anpasst. Im Verlauf der Bestrahlung entsteht durch Kernfragmentierungen eine der Dosisverteilung ähnliche +-Aktivitätsverteilung aus v. a. 11C und 15O. Die entsprechende Annihilationsstrahlung sowie die Targetbewegung werden während der Bestrahlung (≈ 85 s) und weitere 5 min danach detektiert. Die gemessenen Ereignisse werden unter Berücksichtigung der Detektoreffektivität und einer Schwächungskorrektur rückprojiziert und mit einer Referenzaktivität aus einer zweiten, identischen Bestrahlung und Aktivitätsmessung jedoch ohne Phantombewegung verglichen. Für eine 4D-Auswertung werden zuerst in einem zusätzlichen Zwischenschritt die Koinzidenzen entsprechend der Bewegungsamplitude oder -phase sortiert und die einzelnen Rückprojektionen werden anschließend zusammengeführt.

Ergebnis
Ohne Berücksichtigung der Phantombewegung ist die Aktivitätsverteilung entlang der Bewegungsrichtung über die Targetgrenzen hinaus verschmiert. Sie weicht im Hochdosisbereich bis zu 22 % von der statischen Referenz ab und die Breite des lateralen 80–20%-Aktivitätsabfalls vergrößert sich von 7,6 mm für die Referenz auf 17,2 mm. Bei der 4D-in-beam-PET bleibt diese mit 8,3 mm innerhalb der Fehlergrenzen erhalten und der maximale Unterschied zur Referenz beträgt nur 4 %.

Schlussfolgerung
Bereits bei geringen Bewegungsamplituden ist eine 4D-Rekonstruktion erforderlich, da andernfalls nicht die tatsächlich applizierte Dosisverteilung verifiziert werden kann. Bei genauer Kenntnis des Bewegungsverlaufes reproduziert die vorgestellte 4D-in-beam-PET die Aktivitätsverteilung im Phantom innerhalb statistischer Schwankungen. Weitere Experimente für komplexe Targetgeometrien, Dosisverteilungen und Bewegungsabläufe sind erforderlich.
Keywords: in-beam PET, moving targets, ion beam therapy
  • Poster
    16. Jahreskongress der Deutschen Gesellschaft für Radioonkologie, 03.-06.06.2010, Magdeburg, Deutschland

Publ.-Id: 14475 - Permalink


Atomic Layer Deposition of CaB2O4 Films Using Bis(tris(pyrazolyl)borate)calcium as a Highly Thermally Stable Boron and Calcium Source
Saly, M. J.; Munnik, F.; Winter, C. H.;
The atomic layer deposition of CaB2O4 was carried out using bis(tris(pyrazolyl)borate)calcium (CaTp2) and water as precursors. CaTp2 melts at 280 °C, undergoes solid state thermal decomposition at 385 °C, and sublimed on a preparative scale at 180 °C/0.05 Torr in about 3 hours with 99.7% recovery and 0.2% nonvolatile residue. Self-limited ALD growth was established at 350 °C with CaTp2 pulse lengths of ≥ 2.0 s. An ALD window was observed from 300 to 375 °C, in which the growth rate was between 0.34 and 0.36 Å/cycle. The thin film compositions were assessed by elastic recoil detection analysis (ERDA) and X-ray photoelectron spectroscopy (XPS). The B/Ca ratios for CaB2O4 films deposited at 275, 325, 350, and 400 °C were 1.84(11), 1.85(11), 1.89(13), and 1.42(10), respectively, as determined by ERDA. Within the ALD window, hydrogen concentrations ranged from 0.22(2) to 0.35(4) atom % and the carbon and nitrogen concentrations were below the detection limits. XPS analyses on representative CaB2O4 thin films showed all expected ionizations. X-ray diffraction experiments revealed that the as-deposited films were amorphous. The surface morphology was assessed by atomic force microscopy and scanning electron microscopy. The rms surface roughness of a typical 2 μm x 2 μm area for films deposited at 325 and 350 °C was 0.3 nm. Scanning electron micrographs of these films showed no cracks or pinholes.
Keywords: group 2 ALD precursors, calcium borate, tris(pyrazolyl)borate, bimetallic ALD precursors, atomic layer deposition

Publ.-Id: 14474 - Permalink


All-Optical Ion Beam Cooling and Online Diagnostics at Relativistic Energies
Bussmann, M.; Schramm, U.; Nörtershäuser, W.; Novotny, C.; Geppert, C.; Walther, T.; Birkl, G.; Winters, D. F. A.; Kühl, T.; Kozhuharov, C.; Steck, M.; Nolden, F.; Dimopoulou, C.; Stöhlker, T.;
Recent experiments at the Experimental Storage Ring (ESR) at GSI have shown that relativistic Li-like C3+ ion beams can be cooled to an unprecedented momentum spread of dp=p ~ 10-7 using a single-frequency laser tuned to the Doppler-shifted 2S1/2 -> 2P1/2 and 2S1/2 -> 2P3/2 atomic transitions. Although these results encourage the application of laser cooling to beams of other Li-like and Na-like ions at even higher energies as will be available at future storage rings at FAIR (Facility for Antiproton and Ion Research), two major concepts have to be demonstrated experimentally: First, efficient laser cooling of ion beams with large initial momentum spread, thus avoiding additional electron cooling to match the large momentum spread to the usually small momentum acceptance of the laser force. Second, all-optical measurements of the relevant beam parameters, thus overcoming the limited resolution of standard storage ring detectors such as the Schottky pickup electrode at ultra-low momentum spreads. The aim of this paper is to discuss the technical realization of these concepts as planned for an upcoming beam time at ESR.
Keywords: laser cooling, relativistic, energy beam, ion, laser, optical diagnostics, storage ring, esr, gsi, c3+
  • Contribution to proceedings
    Workshop on Beam Cooling and Related Topics 2009, COOL 2009, 31.08.-04.09.2009, Lanzhou, China
    All-Optical Ion Beam Cooling and Online Diagnostics at Relativistic Energies: Atomic Energy Press, 978-7-5022-4871-0, 22-26

Publ.-Id: 14473 - Permalink


DREAMS at FZD: The new accelerator mass spectrometry facility
Akhmadaliev, S.; Heller, R.; Kolitsch, A.; Merchel, S.; Möller, W.;
The installation of a new 6 MV-Tandetron accelerator opens a new topic of research at FZ Dresden-Rossendorf: Accelerator mass spectrometry (AMS). The Dresden AMS facility (DREAMS) will be mainly used for measurements of the long-lived radionuclides 10Be, 26Al, 36Cl, 41Ca and 129I (T1/2 = 0.1-15.7 Ma) in the isotopic ratio range of 10-10- 10-16. The same accelerator will be partially also used for spatial- and depth-resolved chemical analysis using ion beam techniques such as Rutherford Backscattering Spectrometry (RBS), Elastic Recoil Detection (ERD), Particle-induced X-ray and Gamma-ray emission (PIXE/PIGE) and Nuclear Reaction Analysis (NRA). Using these methods, we are able to measure nondestructively "all natural" elements, i.e. H to U; most elements with lateral, some in 3D resolution. Additionally, materials modification via high energy ion implantation is possible.
The AMS injector consist of two Cs-sputter ion sources SO-110 with wheels for up to 200 sputter targets, a 54° electrostatic analyzer (ESA) and a 90° bouncer magnet for sequential acceleration of stable isotopes and radionuclides. In contrast to common low-energy AMS facilities, which have mainly specialized in radiocarbon analyses (14C), the FZD-AMS is the first modern type facility in the EU that will run at a terminal voltage of 6 MV. The electrostatic accelerator operates with a Cockcroft-Walton type high voltage cascade for generating the terminal voltage. The high-energy part of the system consists of a 90° analyzing magnet, a set of precise Faraday cups with energy slits for measuring the stable nuclides and stabilising the terminal voltage, a set of absorber foils for isobar suppression, a 35° ESA, and a 30° vertical magnet for suppressing interfering species. The radionuclides will be finally detected by a ΔE/E gas ionisation chamber containing four anodes. There is a main advantage of us-ing a high-energy accelerator for mass spectrometry: The background and interfering signals, resulting from molecular ions and ions with similar masses (e.g. isobars) are nearly completely eliminated. Thus, AMS provides much lower detection limits compared to conventional mass spectrometry.
The benefits from using AMS for radiation protection, nuclear safety, nuclear waste, radioecology, phytology, nutrition, toxicology, and pharmacology research are obvious and manifold: Smaller sample sizes, easier and faster sample preparation, higher sample throughput and the redundancy for radiochemistry la-boratories will largely reduce costs. Lower detection limits will widen applications to shorter and longer time scales and to sample types which could never been investigated before. Especially in environmental and geosciences, the determination of long-lived cosmogenic radionuclides like 10Be, 26Al, and 36Cl became more and more important within the last decades. Using these nuclides dating of suddenly occurring prehistoric mass movements, e.g. volcanic eruptions, rock valanches, tsunamis, meteor impacts, earth quakes and glacier movements, is possible. Additionally, glacier movements and data from ice cores give hints for the reconstruction of historic climate changes and providing information for the validation of climate model predicting future changes. Taking the advantage of location into account DREAMS will soon also focus on applications of radionuclides of anthropogenic origin such as plutonium isotopes and 129I.
Investment and maintenance costs of a high-energy AMS facility are much higher compared to e.g. methods determining radionuclides via their decay. All methods including AMS need sophisticated radiochemical separation procedures. However, for several nuclides the requirements with respect to the purity of the final sample to be measured are much lower for AMS. As it is the case for most destructive analytical methods AMS chemical sample preparation takes much longer and is more expensive that the actual measurement, which takes about 10 - 60 min.
Keywords: AMS, Ion Beam Analysis, Tandetron
  • Lecture (Conference)
    6. Workshop Radiochemische Analytik bei Betrieb und Rückbau kerntechnische Anlagen, der Deklaration von Abfällen und im Schtrahlenschutz und 23.Seminar Aktivierungsanalyse und Gammaspektroskopie, 06.-08.09.2010, Dresden, Deutschland

Publ.-Id: 14472 - Permalink


Simulation of advanced, laser-driven radiation sources at FZD
Bussmann, M.;
In this talk I will present an overview of the activities at the Forschungszentrum Dresden-Rossendorf (FZD) focusing on laser ion acceleration, x-ray generation via Thomson scattering and medical beam line design for tumor therapy with laser-driven particle beams.
Optimization and precise control of the properties of laser-driven radiation sources using large-scale realistic simulations and direct comparison to experiment play a key role in the research program at FZD.
I will show some recent results obtained at FZD and give an outlook on future work, with an emphasis on the development of new simulation tools.
Keywords: laser, particle, acceleration, x-ray, radiation, source, overview, simulation
  • Invited lecture (Conferences)
    Seminar of the Shanghai Institute of Optics and Fine Mechanics (SIOM), 30.08.2010, Shanghai, China

Publ.-Id: 14471 - Permalink


Experimental Design of Traveling-Wave Thomson Scattering
Debus, A.; Bussmann, M.; Jochmann, A.; Siebold, M.; Cowan, T.; Schramm, U.; Sauerbrey, R.;
Traveling-wave Thomson scattering is a novel interaction design that allows circumventing the Rayleigh limit in optical undulators, which is interesting for possible realizations of Thomson scattering sources with photon yields per pulse that are orders of magnitudes beyond current designs. The resulting radiation reaction could even be strong enough for driving an FEL instability. Here we present details on how a Traveling-wave setup has to be implemented in experiment. An emphasis is put on the use of varied-line spacing (VLS) gratings for spatio-temporal beam shaping at large interaction angles to achieve optimal overlap. At the FZD we are using the high-power laser system DRACO (250TW) to realize a Thomson source with electrons from the linear accelerator ELBE or laser-plasma accelerated electrons. We present the current status and further progress towards a head-on Thomson source and a Traveling-Wave Thomson scattering source aiming for high photon yields per pulse.
Keywords: Traveling-wave Thomson scattering, free electron laser, FEL, xray, EUV
  • Poster
    32nd International Free Electron Laser Conference FEL 2010, 23.-27.08.2010, Malmö, Sweden

Publ.-Id: 14470 - Permalink


Traveling-wave Thomson scattering for scaling optical undulators towards the FEL regime
Debus, A. D.; Bussmann, M.; Jochmann, A.; Siebold, M.; Cowan, T.; Schramm, U.; Sauerbrey, R.;
We present a novel concept for optical undulators that avoids the restrictions by the Rayleigh limit and thus allows to define interaction length and diameter independent of each other. With an ultrashort, high-power laser pulse in an oblique angle scattering geometry using tilted pulse fronts, electrons and laser remain overlapped while both beams travel over distances much longer than the Rayleigh length. For small scattering angles (<10°), where dispersive effects become negligible and interaction lengths scale up to the meter range, we discuss with the help of 1D-calculations the possibility of entering the SASE-FEL regime using optical undulators driven by existing lasers.
Keywords: Traveling-wave Thomson scattering, free electron laser, xray, EUV
  • Poster
    32nd International Free Electron Laser Conference FEL 2010, 23.-27.08.2010, Malmö, Sweden

Publ.-Id: 14469 - Permalink


A Virtual Firefighting Simulator
Schmeißer, N.;
A simulator will be presented which employs VR techniques in order to provide a training environment for re-ghters. While existing systems for re-brigade training do focus on tactics and command training, this simulator targets the training of the re attack group. It provides scenarios for search & rescue operations, direct reghting using water and foam as well as radiation source search operations. Visual, audio and haptic feed-back is provided. The system supports immersive displays (HMD) as well as standard techniques (monoscopic big-wall). It implements a walking paradigm, which enables the trainee to move around freely. The simulator uses extended reality features in order to improve the handling (nozzles, dose meter, ...). The trainee can use the system fully equipped, even using the respiratory protection, in order to provide a realistic feeling. Several physical models are used to provide eects closed to reality, namely:
  • heat release rate is used to model the energetic behavior of a fire, fl ame size etc.
  • a simple energetic model for re-extinction by cooling
  • water and foam ejection (depending on pressure, volume, form of jet, agent)
  • a smoke system (visibility equivalent to height of eye)
  • superposition of radiation sources (no shielding) and detection by Teleprobe FH40G
The simulation is supervised by an instructor, each action, e.g. radio traffc, movements is logged for analysis.
Keywords: simulation fire fire-fighting extinction radioton search rescue
  • Contribution to proceedings
    3rd International Workshop "Innovation in Information Technologies - Theory and Practice", September 6th-10th, Dresden, Germany, 2010, 06.-10.9.2010, Dresden, BRD
    A Virtual Firefighting Simulator, Dresden: Forschungszentrum-Rossendorf e. V., 978-3-941405-10-3, 76-82

Publ.-Id: 14468 - Permalink


Cold quark stars from hot lattice QCD
Schulze, R.; Kämpfer, B.;
Based on a quasiparticle model for \beta stable and electrically neutral deconfined matter we address the possibility of pure quark stars. The model is adjusted to recent hot lattice QCD results for 2+1 flavors with almost physical quark masses. Using stability and binding arguments general statements can be made concerning the existence of such compact stellar objects.
Keywords: QCD, quasiparticle model, quark stars, quark gluon plasma
  • Invited lecture (Conferences)
    Hot and Cold Baryonic Matter 2010, 15.-20.08.2010, Budapest, Hungary

Publ.-Id: 14467 - Permalink


Schlagende Herzen und rasante Strömungen - Schnelle bildgebende Messverfahren in Technik und Medizin
Hampel, U.;
Der Vortrag gibt einen Einblick in die Nutzung schneller tomographischer Bildgebungsverfahren in der Medizin und Technik.
Keywords: fast tomography methods, medicine, engineering
  • Invited lecture (Conferences)
    Dresdner Seniorenakademie, 09.09.2010, Dresden, Germany

Publ.-Id: 14465 - Permalink


Steam bubble condensation in polydispersed flow experiments and CFD simulations
Krepper, E.; Schmidtke, M.; Lucas, D.; Beyer, M.;
Bubble condensation in sub-cooled water is a complex process, to which various phenomena contribute. Since the condensation rate depends on the interfacial area density, bubble size distribution changes caused by breakup and coalescence play a crucial role.
Experiments on steam bubble condensation in vertical co-current steam/water flows have been carried out in a 8m long vertical DN200 pipe. Steam is injected into the pipe and the development of the bubbly flow is measured at different distances to the injection using a wire mesh sensor. By varying the steam nozzle diameter the initial bubble size can be influenced. Larger bubbles come along with a lower interfacial area density and therefore condensate slower. Steam pressures between 1-2 MPa and sub-cooling temperatures from 2 to 6 K were applied. Due to the drop of hydrostatic pressure along the pipe, the saturation temperature falls towards the upper pipe end. This affects the sub-cooling temperature and can even cause re-evaporation in the upper part of the test section. The experimental configurations are simulated with the CFD code CFX using an extended MUSIG approach, which includes the bubble shrinking or growth due to condensation or re-evaporation. The development of the vapour phase along the pipe with respect to vapur void fractions and bubble sizes is qualitatively well reproduced in the simulations. For a better quantitative reproduction, reliable models for the heat transfer at high Reynolds number as well as for bubble breakup and coalescence are needed.
Keywords: two phase flow, experiments, CFD simulation, population balance models, mass transfer
  • Contribution to proceedings
    Int. Conf. "Nuclear Energy for New Europe", 06.09.-09.10.2010, Portoz, Slovenien
  • Lecture (Conference)
    Int. Conf. "Nuclear Energy for New Europe", 06.-09.09.2010, Portoz, Slovenien

Publ.-Id: 14464 - Permalink


Computing the KPZ Equation Using GPU Acceleration
Schulz, H.; Odor, G.; Kelling, J.; Heinig, K.-H.; Liedke, B.; Schmeißer, N.;
In this talk we present an approach for fast parallel computation of the Kardar-Parisi-Zhang equation (KPZ). Acceleration of these computations is always a major task since the run time of the simulations representing sequential algorithms is in the range of several months. We developed an implementation for the KPZ equation on graphics processing units (GPU) using the Compute Unified Device Architecture (CUDA). Experimental results show a significant speed-up compared to implementations on conventional processors.
  • Contribution to proceedings
    Innovation Information Technologies - Theory and Practice, 06.-10.09.2010, Dresden, Deutschland
    Computing the KPZ Equation Using GPU Acceleration, Dresden: FZD, 978-3-941405-10-3, 46-48

Publ.-Id: 14463 - Permalink


Raster-Kelvinkraft-Mikroskopie zur quantitativen Dotierprofilierung an dotiertem Silizium und Mn-implantiertem Germanium
Baumgart, C.; Zhou, S.; Helm, M.; Schmidt, H.;
Am Beispiel von dotierten Halbleitern konnte gezeigt werden, dass es mit Hilfe der korrekten Interpretation von KPFM-Daten möglich ist, die gemessene KPFM-Spannung mit der Ladungsträger-Konzentration in den untersuchten Halbleitern zu korrelieren. Die präsentierten Ergebnisse an dotiertem Silizium und Mn-implantiertem Germanium legen nahe, dass die Modellierung der KPFM-Spannung auf alle dotierten Halbleitermaterialien angewandt werden kann, solange die intrinsische Ladungsträgerkonzentration geringer als die Dotierkonzentration ist. Wir erwarten, dass in Zukunft die KPFM-Methode auch zur quantitativen Untersuchung der elektrischen Eigenschaften anderer Materialsysteme eingesetzt wird. Grundlage dafür ist immer das Verständnis der Ursache der mittels KPFM detektierten elektrostatischen Kräfte und die damit verbundene korrekte Interpretation der KPFM-Spannung.

Publ.-Id: 14462 - Permalink


Enhanced nucleation of vortices in soft magnetic disks prepared by silica nanosphere lithography
Martin, N.; Bigall, N. C.; Mönch, I.; Gemming, T.; Eychmüller, A.; Mattheis, R.; Schäfer, R.; Schultz, L.; McCord, J.;
Magnetic vortices show promise as data storage structures, however the vortex formation process imposes a lower limit on the element’s size. In this article a technique is presented, which application increases the probability of nucleating of magnetic vortices in sub-micron sized soft magnetic thin film elements. By tailoring the edge geometry of the elements, the symmetry of their magnetic configuration is broken in a manner which favors vortex nucleation. Micromagnetic simulations are presented, which demonstrate this effect in soft-magnetic disks with beveled edges. The favored edge geometry was realized by applying nanosphere lithography directly on top of a ferromagnetic thin film material. The resulting magnetic reversal loops show that in both magnetically isolated as well as in closely packed arrays of beveled disks, vortex formation takes place. The technique presented facilitates the vortex formation even in closely packed and small elements. The lowering of the minimum critical diameter for vortex formation enables a significant increase of data storage density in devices based on magnetic vortices.
Keywords: nanoparticles, patterned arrays, magnetic materials, thin films, magnetic vortex

Publ.-Id: 14459 - Permalink


Synthesis and Radiofluorination of Iodophenyl Esters as Tool for the Traceless Staudinger Ligation
Pretze, M.; Flemming, A.; Köckerling, M.; Mamat, C.;
A new synthetic pathway for the preparation of ω-functionalized 2-iodophenyl esters as starting materials for the synthesis of substituted phosphanes is described. A radiolabeling of these esters with fluorine-18 has led to building blocks which were reacted with HPPh2 in a Pd-catalyzed P-C cross coupling to establish new phosphanes. These compounds can be applied as mild and bioorthogonal radiolabeling agents by means of the traceless Staudinger ligation. A route to access this class of compounds has been established.
Keywords: Staudinger Ligation, Traceless, Bioorthogonal, Radiofluorination, PET, X-Ray Structure
  • Zeitschrift für Naturforschung Section B - A Journal of Chemical Sciences 65(2010), 1128-1136

Publ.-Id: 14458 - Permalink


A Compton Imager for in-vivo Dosimetry of Proton Beams
Enghardt, W.; Golnik, C.; Kormoll, T.; Wüstemann, J.; Fiedler, F.; Müller, A.; Schöne, S.;
no abstract available
Keywords: in-vivo dosimetry, proton irradiation, ion irradiation
  • Lecture (others)
    WP 3 Meeting, ENVISION, 04.09.2010, Stockholm, Schweden

Publ.-Id: 14457 - Permalink


High-precision ( p,t) reaction to determine 25Al( p,γ )26Si reaction rates
Matic, A.; van den Berg, A. M.; Harakeh, M. N.; Wörtche, H. J.; Berg, G. P. A.; Couder, M.; Görres, J.; Leblanc, P.; O’Brien, S.; Wiescher, M.; Fujita, K.; Hatanaka, K.; Sakemi, Y.; Shimizu, Y.; Tameshige, Y.; Tamii, A.; Yosoi, M.; Adachi, T.; Fujita, Y.; Shimbara, Y.; Fujita, H.; Wakasa, T.; Brown, B. A.; Schatz, H.;
Since the identification of ongoing 26Al production in the universe, the reaction sequence 24Mg(p,γ )25Al(β+ν)25Mg(p,γ )26Al has been studied intensively. At temperatures where the radiative capture on 25Al (t1/2 = 7.2 s) becomes faster than the β+ decay, the production of 26Al can be reduced due to the depletion of 25Al. To determine the resonances relevant for the 25Al(p,γ )26Si bypass reaction, we measured the 28Si(p,t )26Si reaction with high-energy precision using the Grand Raiden spectrometer at the Research Center for Nuclear Physics, Osaka. Several new energy levels were found above the p threshold and for known states excitation energies were determined with smaller uncertainties. The calculated stellar rates of the bypass reaction agree well with previous results, suggesting that these rates are well established.
Keywords: 26Al 24Mg(p,γ )25Al(β+ν)25Mg(p,γ )26Al Grand Raiden spectrometer

Publ.-Id: 14456 - Permalink


Analysis of Design Basis Accidents
Weiss, F.-P.; Schaefer, F.; Kliem, S.; Tusheva, P.;
The safety philosophy of nuclear reactors aims at maintaining the barriers for the retention of radioactivity. The safety functions required to achieve this fundamental protection goal are implemented by the operational and safety systems. All these systems are elements in a staggered safety concept, known as the defence in depth (DiD) concept which is meant to optimize the interaction of the manifold systems in respect to their effect on the safety of the nuclear power plant. On the first two levels of the DiD concept, i.e. at normal and abnormal or disturbed operation, the operational as well as the limitation and protection systems are designed to keep the plant at normal operation or to return to normal operation after a disturbance had occurred. Only in case of a failure of these systems or by effect of external events, an operational disturbance might develop into an accident. Accident scenarios which have been considered in the plant design are called design basis accidents. Safety systems and measures are arranged at level 3 of the DiD concept to control the design basis accidents and to bring the reactor back to a safe state.
  • Lecture (Conference)
    FJOH Summer School 2010, 24.-26.08.2010, Aix-en-Provence, Frankreich
  • Contribution to proceedings
    Analysis of Design Basis Accidents, 24.-26.08.2010, Aix-en Provence, Frankreich

Publ.-Id: 14455 - Permalink


Experiments and numerical simulations of horizontal two-phase flow regimes using an interfacial area density model
Höhne, T.; Vallee, C.;
Stratified two-phase flow regimes can occur in the main cooling lines of Pressurized Water Reactors, Chemical plants and Oil pipelines. A relevant problem occurring is the development of wavy stratified flows, which can lead to slug generation. In the last decade, stratified flows have increasingly been modelled with computational fluid dynamics (CFD) codes. In CFD, closure models are required that must be validated. Recent improvements of the multiphase flow modelling in the ANSYS CFX code, now make it possible to simulate these mechanisms in detail. In order to validate existing and further developed multiphase flow models, a high spatial and temporal resolution of measurement data are required. For the experimental investigation of co-current air/water flows, the HAWAC (Horizontal Air/Water Channel) was built. The channel allows in particular the study of air/water slug flow under atmospheric pressure. Parallel to the experiments, CFD calculations were carried out. The two-fluid model was applied with a special turbulence damping procedure at the free surface. An Algebraic Interfacial Area Density (AIAD) model based on the implemented mixture model was introduced, which allows the detection of the morphological form of the two-phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result, this model can distinguish between bubbles, droplets and the free surface using the local value of the volume fraction of the liquid phase. The behaviour of slug generation and propagation was qualitatively reproduced by the simulation, while local deviations require a continuation of the work.
Keywords: CFD, AIAD, TOPFLOW
  • Contribution to proceedings
    ANSYS Conference & 28. CADFEM Users´ Meeting 2010, 03.-05.11.2010, Aachen, Deutschland
    CD-ROM
  • Invited lecture (Conferences)
    ANSYS Conference & 28. CADFEM Users´ Meeting 2010, 03.-05.11.2010, Aachen, Deutschland
  • The Journal of Computational Multiphase Flows 2(2010)3, 131-143

Publ.-Id: 14454 - Permalink


Thermodynamical limits of diluted (magnetic) semiconductors
Bürger, D.; Seeger, M.; Zhou, S.; Skorupa, W.; Helm, M.; Schmidt, H.;
The incorporation of transition metal dopants in semiconductors above their solubility limit is the main challenge for the fabrication of diluted magnetic semiconductors. Dietl et al. have predicted the Curie temperature of different p-type conducting semiconductors alloyed with 5 at. % Mn [1]. This work motivated experimental efforts focused on the fabrication of highly diluted magnetic semiconductors. Unfortunately, such highly diluted magnetic semiconductors are metastable alloys and try to reach their thermodynamical equilibrium by the diffusion of the incorporated magnetic dopants leading to spinodal decomposition and secondary phase formation. There exist classical models which describe the kinetics of phase transitions and secondary phase formation for large clusters consisting of 100, 1000 or more atoms. However, electronic properties like carrier concentration strongly depend on the fraction of unclustered dopant atoms. Especially, in diluted magnetic semiconductors the formation of such clusters has to be prevented and growth techniques far from thermodynamical equilibrium are necessary.
Besides the LT-MBE process, the magnetic dopant implantation followed by pulsed laser annealing (PLA) appears to be a promising route for the fabrication of ferromagnetic semiconductors. The fast temperature quenching during PLA suppresses the diffusion of magnetic dopant atoms, i.e. diffusion via random hopping of these dopants is frozen and metastable diluted magnetic semiconductors are formed.
In this contribution we present the results from combined random-walk simulations and heat-flow calculations to describe the initial cluster formation for different magnetic semiconductors being characterized by a large variation of diffusion coefficients of the magnetic dopants. Under the assumption that the de-clustering probability of neighbouring dopants is lower than the clustering probability, we can explain the successful fabrication of GaAs:Mn and the impossibility to fabricate diluted ferromagnetic Si:Mn with LT-MBE or Mn implantation followed by PLA. Especially, our modelling approach can be used to estimate first clustering events during the re-crystallization after PLA. Within this picture, we conclude that for the preparation of diluted ferromagnetic semiconductors the basic diffusion parameters and the room temperature solubility of the magnetic dopants are reasonable parameters to estimate the chance for a successful preparation of different kinds of diluted systems.
[1] T. Dietl et al. Science 287 1019 (2000)
Keywords: ferromagnetic semiconductors, pulsed laser annealing, metastable, manganese
  • Poster
    30th International Conference on the Physics of Semiconductors (ICPS 2010), 25.-30.07.2010, Seoul, Südkorea

Publ.-Id: 14453 - Permalink


Characterization of mesoporous ZnO:SiO2 films obtained by the sol-gel method
Martins, R. M. S.; Musat, V.; Mücklich, A.; Franco, N.; Fortunato, E.;
ZnO:SiO2 films are intensively investigated for optical and electronic applications. Additionally, porous ZnO:SiO2 films are of great interest as catalyst and gas-sensing materials. The sol–gel method is an efficient and low-cost process for the deposition of meso- and microporous silica-based films. The present paper studies the effect of the withdrawal speed on the microstructure and optical properties of mesoporous ZnO:SiO2 films obtained by the sol–gel method. The morphology of the films was investigated by atomic force microscopy and the overall structure was studied by X-ray diffraction. The structure and size of the zinc oxide nanoparticles embedded in the silica matrix were investigated in more detail by transmission electron microscopy. These techniques showed ZnO:SiO2 films with crack-free mesoporous morphology and highly efficient embedding of ZnO nanoparticles with (100) preferred orientation. Furthermore, the optical transmittance (in the visible and near infrared regions) and the optical band gap value were observed to vary with withdrawal speed. It is shown that ZnO:SiO2 nanocomposites films which possess ZnO particles exhibiting a (100) orientation, with possible special applications in non-linear optics, could be prepared by the low-temperature crystallization sol–gel method.
Keywords: sol–gel, Zinc oxide, nanoparticles, silica matrix, thin films, mesoporous films, optical and electrical properties, X-ray diffraction, atomic force microscopy

Publ.-Id: 14450 - Permalink


3D QSAR study, synthesis and in vitro evaluation of (+)-5-FBVM as potential PET radioligand for the Vesicular AcetylCholine Transporter (VAChT)
Kovac, M.; Mavel, S.; Deuther-Conrad, W.; Méheux, N.; Glöckner, J.; Wenzel, B.; Anderluh, M.; Brust, P.; Guilloteau, D.; Emond, P.;
Located in presynaptic cholinergic nerve terminals, the vesicular acetylcholine transporter (VAChT) represents a potential target for quantitative visualization of early degeneration of cholinergic neurons in Alzheimer´s disease using PET. Benzovesamicol derivatives are proposed as radioligands for this purpose. We report QSAR studies of vesamicol and benzovesamicol derivatives taking into account the stereoselectivity of the VAChT binding site. Use of different data sets and different models in this study revealed that both enantiomers of 5-fluoro-3-(4-phenyl-piperidin-1-yl)-1,2,3,4-tetrahydro-naphthalen-2-ol (5-FBVM) are promising candidates, with predicted VAChT affinities between 6.1 and 0.05 nM. The synthesis of enantiopure (R,R)- and (S,S)-5-FBVM and their corresponding triazene precursors for future radiofluorination is reported. Both enantiomers exhibited high in vitro affinity for VAChT [(+)-5-FBVM: Ki = 6.95 nM and (-)-5-FBVM: Ki = 3.68 nM] and were selective for s2 receptors (~70-fold), only (+)-5-FBVM is selective for s1 receptors (~5-fold). These initial results suggest that (+)-(S,S)-5-FBVM warrants further investigation as a potential radioligand for in vivo PET imaging of cholinergic nerve terminals.
Keywords: Benzovesamicol derivative; VAChT; triazene; fluoro-dediazoniation, 3D QSAR

Publ.-Id: 14449 - Permalink


Actinide Interactions with Bacteria
Moll, H.; Bernhard, G.;
Microbes are widely distributed in nature also under harsh conditions (e.g., high salinity; low permeability; high and low temperatures). They can strongly influence the migration of hazardous actinides in the environment once they have been released. This is demonstrated by an increased interest in studies exploring the interaction processes involving actinides and bacteria during the last years. However, worldwide only little detailed information is available about the biodiversity and microbial influences on radionuclide migration under the conditions of a deep nuclear repository.
The presentation covers the broad topic of actinide interactions with bacteria. A short overview about the determination of the microbial diversity giving the dominant bacterial strains will be given. In more detail, the manifold interaction process of bacteria with actinides will be highlighted based on selected examples.
With this presentation we want to point out the importance of actinide-microbe interactions for the disposal of nuclear waste.
Keywords: microbes, actinides, nuclear waste disposal
  • Lecture (Conference)
    Actinide and Brine Chemistry in a Salt-Based Repository (ABC-SALT) International Workshop, 15.-17.09.2010, Carlsbad, New Mexico, USA

Publ.-Id: 14448 - Permalink


Terahertz nonlinear optics using intraexcitonic quantum well transitions: sideband generation and AC Stark splitting
Wagner, M.; Schneider, H.; Stehr, D.; Winnerl, S.; Andrews, A. M.; Schartner, S.; Strasser, G.; Helm, M.;
Intense THz electric fields coupling to intraband excitations can modify the interband absorption of semiconductors. A classical nonlinear mixing process is the sideband generation, where a ps NIR laser beam is mixed with the THz beam to generate sidebands at ωNIR ± n × ωTHz (integer n). In an undoped GaAs/AlGaAs multi quantum well film (substrate etched away) we observe several even-order sidebands using an all-normal-incidence geometry for the NIR and THz laser pulses [1]. Varying THz and NIR frequencies, we identify several resonances, where the intraexciton 1s-2p transition (at ~9 meV) makes the strongest contribution. Fig. 1(a) shows a typical NIR transmission spectrum with the NIR fundamental at the hh(1s) state and the resulting even-order sidebands.
In a second experiment we monitor the sample’s broadband transmission under THz pumping. THz light can couple and “dress” two resonant states, giving rise to the Autler-Townes or AC Stark effect [2, 3]. Fig. 1(b) shows the measured transmission spectra without (dashed line) and with (solid line) THz light at a THz peak intensity of 220 kW/cm² for THz pumping above (14 meV), near (10.5 meV) and below (6.1 meV) resonance. Near resonance (10.5 meV) we observe a distinct line splitting (see arrows), which represents the first clear evidence of the Autler-Townes effect in an intraexcitonic transition. Above and below resonance, low- and high-energy shoulders, respectively, are observed (see arrows). We discuss our findings on the basis of a simple two-level model that describes the situation surprisingly well near resonance up to a THz field strength of 10 kV/cm, corresponding to a Rabi energy of 0.6 times the 1s-2p transition energy. This is already well beyond the rotating-wave approximation of our model. Observed deviations would have to be addressed within a full many-body theory dealing with the complete set of excitonic states as well as with the possibility of exciton field ionization. Note that for the above parameters the ponderomotive energy is 3 meV, comparable to the exciton transition/ionization energy and the Rabi energy, an extremely non-perturbative regime with a Keldysh parameter near unity.

References:
[1] M. Wagner et al., Appl. Phys. Lett. 94, 241105 (2009).
[2] S. H. Autler and C. H. Townes, Phys. Rev. 100, 703 (1955).
[3] S. G. Carter et al., Science 310, 651 (2005).
Keywords: AC Stark effect, Autler Townes effect, excitons, terahertz, sideband generation, nonlinear optics
  • Lecture (Conference)
    NOEKS 10 - 10th International workshop on Nonlinear Optics and Excitation Kinetics in Semiconductors, 16.-19.08.2010, Paderborn, Deutschland

Publ.-Id: 14447 - Permalink


Terahertz induced intra-excitonic Autler-Townes effect in semiconductor quantum wells
Wagner, M.; Schneider, H.; Stehr, D.; Winnerl, S.; Helm, M.; Roch, T.; Andrews, A. M.; Schartner, S.; Strasser, G.;
When light is resonant with a material excitation the optical Stark or Autler-Townes (AT) effect couples the involved energy states and alters their energy, i.e. the states get “dressed” by the light-matter interaction. This fundamental quantum-mechanical feature of light-matter interaction was originally observed in atomic spectroscopy [1]. However, despite some theoretical work, it took a long time to the first observation of the AT effect for terahertz (THz) light coupled to hole [2] and electron [3] intersubband transitions in semiconductor quantum wells.
Here, we report clear evidence of the intra-excitonic AT effect. In our experimental work we study the NIR transmission at low temperature of a GaAs/AlGaAs multiple quantum well film (substrate etched away) exposed to strong picosecond THz pulses from the free-electron laser (FEL) at FZD. NIR spectra are recorded for a series of different THz frequencies and intensities. When tuning the THz photon energy in the range from 6 to 17 meV around the 1s-2p intra-excitonic transition energy that lies at ~9 meV, we observe a line splitting when pumping near resonance, and low- and high-energy shoulders, respectively, when pumping off resonance. This behavior is consistent with the AT effect. In Fig. 1 the measured absorption around the heavy-hole 1s exciton is displayed for different THz photon energies, showing the two dressed states and their expected anticrossing behavior. We discuss our experimental evidence of a coupling between the NIR “bright” 1s state and the NIR “dark” 2p state on the basis of a two-level model. Near resonance (10.5 meV) we find that our simplified model describes the situation surprisingly well up to a THz field strength of 10 kV/cm (I = 650 kW/cm2), corresponding to a Rabi energy of 0.6 times the 1s-2p transition energy. This is already well beyond the limits of the rotating-wave approximation. At the highest field strengths, the Rabi sidebands appear to start interacting with other exciton states. A full many-body theory would have to deal with the complete manifold of excitonic states as well as with the possibility of exciton field ionization. Note that for the above parameters in our case the ponderomotive energy is 3 meV and thus of the same order as the exciton transition/ionization energy (i.e. Keldysh parameter near unity) and the Rabi energy, an extremely non-trivial regime.
Using picosecond THz pulses we finally demonstrate that the induced absorption change occurs adiabatically only during the THz pulse. This ultrashort change that corresponds to an up to 20-fold increase in transmission can in principle be exploited in NIR modulators or switches.

[1] S. H. Autler and C. H. Townes, Phys. Rev. 100, 703 (1955).
[2] S. G. Carter et al., Science 310, 651 (2005).
[3] J. F. Dynes, M. D. Frogley, M. Beck, J. Faist, and C. C. Phillips, Phys. Rev. Lett. 94, 157403 (2005).
Keywords: AC Stark effect, Autler Townes effect, excitons, terahertz, sideband generation, nonlinear optics
  • Lecture (Conference)
    ICPS 2010, 30th International Conference on the Physics of Semiconductors, 25.-30.07.2010, Seoul, Südkorea
  • Contribution to proceedings
    ICPS 2010, 30th International Conference on the Physics of Semiconductors, 25.-30.07.2010, Seoul, Südkorea
    AIP Conference Proceeding 1399 (2011) 479-480; doi: 10.1063/1.3666462

Publ.-Id: 14446 - Permalink


Interaction of U(VI) with Schizophyllum commune
Günther, A.; Roßberg, A.; Raff, J.; Bernhard, G.;
Biosorption processes of heavy metals and actinides like uranium by fungal cells play an important role in the mobilisation or immobilisation of these elements in nature. Different sorption experiments of U(VI) with Schizophyllum commune at different initial uranium concentrations and therewith connected varying initial uranium speciation showed high uranium sorption capacities in the pH range from 4 to 7. Formed uranium complexes were investigated by means of time-resolved laser-induced fluorescence spectroscopic measurements (TRLFS). The obtained spectra show clearly differences between the emissions properties of the uranium species on fungi and the dissolved uranium species in the initial mineral medium. While the oxidation state of uranium remained unchanged during the sorption process, the uranium speciation changes significantly. Extra- and/or intracellular phosphate groups are the predominant binding places of uranium due to our first spectroscopic results. X-ray absorption fine structure spectroscopic measurements (EXAFS) were performed for a structural characterisation of formed uranium-fungi species and a verification of the TRLFS results.
Keywords: Uranium(VI), fungi, TRLFS, EXAFS
  • Lecture (Conference)
    9th Symposium on remediation in Jena, "Jenaer Sanierungskolloquium", 04.-05.10.2010, Jena, BRD

Publ.-Id: 14445 - Permalink


Nanostructuring of BaF2 (111) surfaces by single slow highly charged ions
El-Said, A. S.; Heller, R.; Facsko, S.;
The creation of surface nanostructures in BaF2 (111) surfaces was studied after irradiation with slow highly charged Xe ions from the Dresden-EBIT (Electron Beam Ion Trap). After irradiation, the crystals were investigated by scanning force microscopy (SFM). Using specific ion parameters, the topographic images show nanohillocks emerging from the surface. Additionally, we used the technique of selective chemical etching to reveal the lattice damage created by ion energy deposition below and above threshold needed for surface hillocks formation. The role of both potential and kinetic energy as well as a comparison with results for swift heavy ion irradiations of BaF2 single crystals are presented.
Keywords: highly charged ions, nanostructures
  • Nuclear Instruments and Methods in Physics Research B 269(2011), 901-904

Publ.-Id: 14444 - Permalink


Ion-Induced Nanoscale Ripple Patterns on Si Surfaces - Theory and Experiment
Keller, A.; Facsko, S.;
Nanopatterning solid surfaces by low-energy ion bombardment has received considerable interest in the recent years. This interest was partially motivated by promising applications of nanopatterned substrates in the production of functional surfaces. Especially nanoscale ripple patterns on Si surfaces have attracted attention both from a fundamental and an application related point of view. This paper summarizes the theoretical basics of ion-induced pattern formation and compares the predictions of the various continuum models to experimental observations with special emphasis on the morphology development of Si surfaces during sub-keV ion sputtering.
Keywords: nanopatterning; ion sputtering; surface morphology; continuum theory

Publ.-Id: 14443 - Permalink


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