Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41809 Publications

Force-free and contactless sensor for electromagnetic flowrate measurements

Priede, J.; Buchenau, D.; Gerbeth, G.

Abstract

We present a novel design of a contactless flowmeter using a single cylindrical permanent magnet magnetised perpendicularly to its axis, about which it can freely rotate, and placed close to a duct with a liquid metal flow. The electromagnetic torque on the magnet caused by the liquid metal flow sets the magnet into rotation. The equilibrium rotation rate, which is attained at a vanishing net electromagnetic torque on the magnet, depends only on the flowrate and the geometry of the system while it is independent of the electromagnetic torque itself. A laboratory model of such a flowmeter has been built and tested at a liquid metal flow.

  • Magnetohydrodynamics 45(2009)3, 451-458

Permalink: https://www.hzdr.de/publications/Publ-12361


Design, Synthese und Anwendungsmöglichkeiten radiomarkierter Verbindungen

Stephan, H.

  • Invited lecture (Conferences)
    Universität Duisburg-Essen, Institut für Organische Chemie, 05.02.2009, Essen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12360


Role of D(E)RY motif in switching mechanism of G protein-coupled receptors studied by ITC

Eichler, S.; Fahmy, K.

Abstract

Membrane proteins, especially GPCRs (G-protein coupled receptors), play a fundamental role in many physiological processes. Their function is based on the ability to switch between different structures. Due to the low dielectricity of the lipidic environment, side chain charges contribute to the energetics of such transitions much more than in purely aqueous environment.
Our aim is to understand the functional implication of charged amino acids in the conformational control of membrane-spanning protein domains.
We used Isothermal Titration Calorimetry (ITC) to study proton uptake from the buffer by the class-defining and highly conserved D(E)RY motif in a synthetic peptide derived from rhodopsin transmembrane (TM) helix 3. By adding a negatively charged molecule (SDS) the pKA of the peptide is expected to be shifted and proton uptake from the buffer by glutamic acid in the D(E)RY motif is assumed to occur depending on pH. Thus the heat of buffer ionization depending on pH and buffer ionization enthalpy is measured according to Baker and Murphy. First experiments in phosphate buffer at pH 4.8 showed promising results, i.e. a titration curve with stoichiometry around 1:1 (SDS:peptide) and ∆H in good agreement to buffer ionization heat of phosphate buffer. However the buffer ionization heat of phosphate buffer is comparatively low and so are other buffers at that pH. Thus these results were not sufficiently reproducible and following experiments were performed at pH 6 and 8 with Imidazole buffer, PIPES and TRIS. These results were good reproducible but no buffer ionization could be shown. A pKA shift in our model peptide introduced by an additional charge (SDS) could not be proved by means of ITC. Thus, there is no evidence for breakage of the internal Glu-Arg salt bridge by competition with an Arg-sulfate interaction.

Keywords: GPCR; D(E)RY motif; Isothermal Titration Calorimetry

  • Poster
    18. Ulm-Freiberger Kalorimetrietage, 18.-20.03.2009, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12359


Instability of the melt flow in VGF growth with a traveling magnetic field

Grants, I.; Klyukin, A.; Gerbeth, G.

Abstract

The linear instability of a thermally stratified melt flow in the VGF configuration driven by a traveling magnetic field (TMF) is considered numerically and experimentally. The dependency of the instability threshold on the governing parameters is found for several cuts through the parameter space covering a wide range of possible applications. In a first approximation the linear instability occurs when the dimensionless TMF forcing parameter reaches the magnitude of the Grashof number. This is particularly true in a medium-sized crucible where the first instability is axisymmetric and sub-critical. As the Grashof number increases the flow develops self-similar boundary layers and the instability becomes three-dimensional. The instability originates in the bottom boundary layer where the convection tends to suppress the imposed temperature gradient in the central part of the melt zone. It is shown that the TMF may serve as a tool to control the phase interface shape without causing flow instationarity when the crucible diameter exceeds a certain value. This value is estimated to be around 5-6 cm for GaAs. The flow stays stable if the TMF is used for a reversal of the meridional flow with the aim to remove a possible dopant concentration peak on the axis.

  • Journal of Crystal Growth 311(2009)17, 4255-4264

Permalink: https://www.hzdr.de/publications/Publ-12358


Growth and Electrical Properties of the (Si/Ge)-on-Insulator Structures Formed by Ion Implantation and Subsequent Hydrogen-Assisted Transfer

Tyschenko, I. E.; Voelskow, M.; Cherkov, A. G.; Popov, V. P.

Abstract

Systematic features of endotaxial growth of intermediate germanium layers at the bonding interface
in the silicon-on-insulator structure consisting of buried SiO2 layer implanted with Ge+ ions are studied in relation to the annealing temperature. On the basis of the results for high-resolution electron microscopy and thermodynamic analysis of the Si/Ge/SiO2 system it is assumed that the endotaxial growth of the Ge layer occurs via formation of a melt due to enhanced segregation and accumulation of Ge at the Si/SiO
interface. Effect of germanium at the bonding interface on the Hall mobility of holes in silicon layers with nanometer-scale thickness is studied. It is found that the structures including the top silicon layer with the thickness 3–20 nm and incorporating germanium feature the hole mobility that exceeds by a factor of 2–3 the hole mobility in corresponding Ge-free silicon-on-insulator structures.

Keywords: Si/Ge; Electrical Properties; Ion Implantation; Hydrogen Transfer

  • Semiconductors 43(2009)1, 52-56
  • Fizika i Tekhnika Poluprovodnikov 43(2009)1, 58-63

Permalink: https://www.hzdr.de/publications/Publ-12357


Evidence for an FFLO state in layered organic superconductors

Wosnitza, J.

Abstract

In the so-called FFLO state, named after Fulde, Ferrell, Larkin, and Ovchinnikov, the superconducting state can survive even at high magnetic fields above the Pauli paramagnetic limit. The quasi-two-dimensional (2D) organic superconductors have been suggested as good candidates for exhibiting the FFLO state. When applying the magnetic field exactly parallel to the conducting layers the orbital pair breaking is greatly suppressed and the Pauli limit is reached. We performed high-resolution specific-heat and torque-magnetization experiments in magnetic fields up to 28 T for different 2D organic superconductors. In a very narrow region close to parallel orientation we observe additional anomalies below the upper critical field signalling the existence of an additional superconducting phase. The specific-heat data for kappa-(BEDT-TTF)2Cu(NCS)2 with Tc = 9.1 K show that the superconducting transition becomes first order for fields above 21 T indicating that the Pauli limit is reached. Below about 3 K, the upper critical field increases sharply and a second first-order transition appears within the superconducting phase. Our results give strong evidence for the realization of the FFLO state in organic superconductors.

  • Invited lecture (Conferences)
    10th German-Japanese Symposium "Collective Quantum Phenomena in Correlated Condensed Matter Systems", 28.09.-01.10.2008, Ringberg Castle, Rottach-Egern, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12356


Magnetic quantum oscillations in strongly correlated metals - experimental data meet theoretical predicitons

Wosnitza, J.

Abstract

hat nicht vorgelegen

  • Invited lecture (Conferences)
    DFT Meets Experiment & 7th Tutorial Hand-on-FPLO, Workshop at the IFW Dresden, 25.-28.08.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12355


Calorimetric Evidence for an FFLO superconducting state in the layered organic superconductor κ-(BEDT-TTF)2Cu(NCS)2

Wosnitza, J.

Abstract

hat nicht vorgelegen

  • Invited lecture (Conferences)
    The 63rd Calorimetry Conference, 02.-06.07.2008, Jersey City, New Jersey, USA

Permalink: https://www.hzdr.de/publications/Publ-12354


Amorphous clusters in Co implanted ZnO induced by boron pre-implantation

Potzger, K.; Shalimov, A.; Zhou, S.; Schmidt, H.; Mücklich, A.; Helm, M.; Fassbender, J.; Arenholz, M.; Liberati, E.

Abstract

We demonstrate the formation of superparamagnetic/ferromagnetic regions within ZnO(0001) single crystals sequentially implanted with B and Co. While the pre-implantation with B plays a minor role for the electrical transport properties, its presence leads to the formation of amorphous phases. Moreover, B acts strongly reducing on the implanted Co. Thus, the origin of the ferromagnetic ordering in local clusters with large Co concentration are itinerant d-electrons as in the case of metallic Co. The amorphous Co-based phases are non-detectable by common X-ray diffraction.

Keywords: ZnO; DMS; Ion implantation

  • Journal of Applied Physics 105(2009)12, 123917

Permalink: https://www.hzdr.de/publications/Publ-12353


Static and dynamic magnetization processes in magnetic property patterned thin films

McCord, J.; Hamann, C.; Martin, N.; Mönch, I.; Kaltofen, R.; Schultz, L.; Strache, T.; Fassbender, J.; Mattheis, R.

Abstract

The control of the effective magnetic anisotropy, saturation magnetization as well as the dynamic magnetic properties in ferromagnetic thin films is of significant importance for most applications in spin electronics. Usually, the magnetic anisotropy, e.g. uniaxial anisotropy or unidirectional anisotropy (exchange bias), in ferromagnetic single or multi-layers is initialized by applying a magnetic field during film deposition or by a magnetic field anneal, which results in an anisotropy aligned along the applied field direction. The saturation magnetization is mainly determined by the film's composition. Whereas anisotropy and saturation magnetization together determine the precessional frequency of the films, the magnetic damping parameter cannot easily be varied in a controlled way.

We demonstrate different ways to pattern soft magnetic magnetic films in terms of laterally varying magnetic properties [1]. In distinction from conventionally patterned systems, the magnetic behavior of these hybrid property films is strongly influenced by the direct exchange interaction across the (now) magnetic property element's borders. Therefore, the effects are directly correlated with the magnetic feature size. Below a critical magnetic feature size, a transition from a magnetic two-phase material to an effective magnetic meta material occurs. This makes them in some sense comparable to magnetic multilayer structures. However, the lateral 'layers' permit access to spatially resolved characterization methods.

Different samples of anisotropy [1,2], exchange bias [1,3], and saturation magnetization [4] modulated thin films are prepared by local oxidation, introducing local stress variation [5], or local ion irradiation. The magnetization reversal processes in the two-phase materials exhibit unique features, some of them so far only known from magnetic multilayer samples. The main emphasis is on the role of magnetic domain formation and domain wall effects in stripe-like magnetic hybrid structures on the overall magnetization properties. Quasi-cubic anisotropies and bi-directional anisotropies, as well as lateral exchange spring behavior are derived from hysteresis loop measurements and magnetic domain imaging. Effects from the introduced quasi-domains, which are related to the domain wall structure and the corresponding wall interaction, will be discussed. In addition, data regarding the influence of pattern density on precessional frequency and effective damping parameter will be shown.

The presented paths of film preparation provide additional degrees of freedom for the tailoring of magnetic properties and functionality of soft-magnetic thin films. Some of the presented methods allow for a local setting of magnetic properties without irreversible structural and magnetic alterations.

Financial support from the Deutsche Forschungsgemeinschaft DFG is highly acknowledged.

References:

[1] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320, 579 (2008)
[2] J. McCord, I. Mönch et al., J. Phys. D: Appl. Phys., accepted (2009)
[3] C. Hamann, I. Mönch et al., J. Appl. Phys. 104, 13926 (2008)
[4] J. McCord, L. Schultz et al., Adv. Mat. 20, 2009 (2008)
[5] N. Martin, J. McCord et al., Appl. Phys. Lett., accepted (2009)

Keywords: magnetism; ion irradiation; ion implantation; magnetic domains; magnetization processes; property patterning

  • Invited lecture (Conferences)
    International Magnetics Conference, 04.-08.05.2009, Sacramento, USA

Permalink: https://www.hzdr.de/publications/Publ-12352


Engineering surfaces, interfaces and structural phases to tailor magnetic properties

Fassbender, J.

Abstract

Surfaces and interfaces play an important role in order to determine the overall properties of ultrathin magnetic films and multilayers. In particular, the morphology and roughness of the surface and the sharpness of mutual interfaces between magnetic and non-magnetic thin films are crucial. All these parameters are easily accessible by means of ion irradiation [1,2], ion implantation [2,3] and ion erosion approaches [4]. Also structural phase transitions can be accompanied by magnetic ones [5] which allow the creation of nanomagnets in the sub-100 nm regime [6]. In this talk I am going to present a survey of ion beam modifications of magnetic materials with special emphasis on the basic phenomena including some technological applications. Supported by DFG FA 314/3-1, FA 314/6-1 and FA 314/7-1.

[1] J. Fassbender, D. Ravelosona, Y. Samson, J. Phys. D 37, R179 (2004).
[2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320, 579 (2008).
[3] J. McCord, L. Schultz, J. Fassbender, Adv. Mater. 20, 2090 (2008).
[4] M. O. Liedke et al., Phys. Rev. B 75, 220407(R) (2007).
[5] J. Fassbender et al., Phys. Rev. B 77, 174413 (2008).
[6] E. Menendez et al., Small, in press.

Keywords: magnetism; ion irradiation; ion implantation; interface; phase transition

  • Invited lecture (Conferences)
    Gaede-Preis-Vortrag auf der Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 22.-27.03.2009, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12351


Atembewegungskorrektur von listmode-basierten Ganzkörperuntersuchungen mit dem PET-Scanner ECAT Exact HR+

Mölle, H.; Langner, J.; Beuthien-Baumann, B.; Hofheinz, F.; Will, E.; van den Hoff, J.

Abstract

Ziel/Aim:

Die Messzeit bei Ganzkörperuntersuchungen (GKU) am PET-Scanner ECAT Exact HR+ beträgt 6-8 Minuten pro Bettposition. Atembewegungen des Patienten sind während einer solchen Aufnahme unvermeidbar, woraus unter anderem eine lageabhängige Beeinträchtigung der Tumorabbildung resultiert. Hieraus ergibt sich insbesondere eine Verfälschung quantitativer Parameter wie des SUV und des scheinbaren Tumorvolumens, die unter anderen im Rahmen der Therapieresponse und Follow-up Untersuchungen von Bedeutung sind. Daher ist es wünschenswert die atmungsbedingte Unschärfe bei GKU in der klinischen Routine zu korrigieren.

Methodik/Methods:

Es wurden Methoden für die Durchführung listmode-basierter GKU implementiert (Akquisition der Listmodedaten für jede Bettposition, Steuerung des Bettvorschubs, Eintrag der Datensätze in die ECAT-Datenbank). Das Verfahren wurde bisher bei 32 klinischen Untersuchungen eingesetzt. Gleichzeitig erfassten Infrarot-Tracking-Kameras die Brustkorbbewegung der Patienten. Anhand der Bewegungsamplitude erfolgte die Einteilung der Listmodedaten in einzelne Atemphasen (Gates). Mit Hilfe eines Atembewegungsmodells, das die Atembewegung im inneren des Körpers vereinfacht modelliert, wurden alle Atemphasen auf eine einzige Atemphase abgebildet.

Ergebnisse/Results:

Erstmals konnten listmode-basierte GKU (6-8 Bettpositionen) mit gleichzeitiger Atembewegungserfassung am PET-Scanner ECAT Exact HR+ in der klinischen Routine durchgeführt werden. Dadurch wird eine Atembewegungskorrektur bei GKU ermöglicht. Um die Größe der Korrektur zu prüfen, wurde die Organbewegung der Patienten bestimmt. Vorläufige Ergebnisse zeigen eine mittlere transaxiale Bewegung der Niere von 0.93 ± 0.43 cm. Die Bewegung war so groß, dass bei den meisten Patienten eine Korrektur sowohl im Bereich des Thorax als auch im Abdomen notwendig ist. Die bewegungskorrigierten GKU enthalten nur noch minimale Bewegungen, wodurch eine bessere Quantifizierung des Tumorvolumens und des SUV im Tumor möglich ist.

Schlussfolgerungen/Conclusions:

Die hier vorgestellte Methode der Atembewegungskorrektur bei GKU mit dem PETScanner ECAT Exact HR+ führt zu einer deutlichen Verbesserung der Bildqualität. Die Bewegungskorrektur erfolgt weitestgehend automatisch, wodurch ein Einsatz in der klinischen Routine problemlos möglich ist.

  • Lecture (Conference)
    47. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 22.-25.04.2009, Leipzig, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 48(2009)2, A21
    ISSN: 0029-5566

Permalink: https://www.hzdr.de/publications/Publ-12350


Atomistic simulation of amorphous germanium and its solid phase epitaxial recrystallization

Posselt, M.; Gabriel, A.

Abstract

Amorphous Ge and its recrystallization are investigated by molecular dynamics simulations using a Stillinger-Weber-type interatomic potential. Unlike previously used parametrizations of this potential the parameter set employed in this work yields a reasonable description of all condensed phases of Ge. The preparation of amorphous Ge is performed by cooling from the molten state. Structural and thermal properties of the amorphous phase such as the pair correlation function, the atomic density as well as the melting temperature are calculated and a good agreement with experimental data is found. In order to obtain the initial atomic configuration for the simulation of recrystallization of amorphous Ge, a simulation cell that contains an amorphous and a crystalline layer is carefully prepared by melting a part of a primarily crystalline simulation cell and by cooling the liquid in a similar manner as in the preparation of bulk amorphous Ge. The recrystallization is simulated in the temperature range between 600 and 950 K. The simulation cell is built in such a manner that the main regrowth direction is parallel to [100]. Using an efficient characterization method the configuration of the current amorphous-crystalline interface, its average position with respect to the [100] direction and its roughness given by the rms deviation of this position are determined throughout the simulations. Consistently with former models for Si it is found that recrystallization of amorphous Ge occurs mainly at small {111} facets and is characterized by a sequential local rearrangement of atomic bonds and positions. In very good agreement with experiments the dependence of the velocity of solid phase epitaxial recrystallization on temperature can be approximated by a straight line in an Arrhenius plot. However, the absolute value of the velocity is too high compared to the experimental data. The main reason for this discrepancy may be the overestimation of the flexibility of atomic bonds by the present interatomic potential which leads to an underestimation of the activation energy. Similar to the state of the art in atomistic simulations of solid phase epitaxial regrowth in Si, there is not yet a suitable interatomic potential which allows a consistent quantitative modeling of both the condensed phases and the solid phase epitaxial recrystallization.

Keywords: solid phase epitaxy; atomistic simulation; germanium

  • Physical Review B 80(2009), 045202

Permalink: https://www.hzdr.de/publications/Publ-12349


Boron activation and diffusion in silicon and strained silicon-on-insulator by rapid thermal and flash lamp annealing

Lanzerath, F.; Buca, D.; Trinkaus, H.; Goryll, M.; Mantl, S.; Knoch, J.; Breuer, U.; Skorupa, W.; Ghyselen, B.

Abstract

We present experimental results on the activation and diffusion behaviors of boron in silicon-on-insulator and strained silicon-on-insulator using standard rapid thermal processing treatments as well as flash lamp annealing. After boron implantation at different doses and at a low energy of 1 keV, samples were annealed to activate the dopants, and secondary ion mass spectrometry and Hall measurements were carried out to determine boron diffusion and the amount of activated dopants, respectively. In contrast to rapid thermal annealing, flash lamp annealing enables the activation without significant diffusion of dopants. In addition, we investigated the effect of coating the samples with antireflection layers to increase the absorbed energy during flash annealing. As a result, the activation was increased significantly to values comparable with the activation obtained with standard annealing. Furthermore, the relation between the observed boron diffusion and activation as a function of the implantation and annealing parameters is discussed in terms of the kinetics of the defects involved in these processes.

Keywords: silicon-on-insulator; strained silicon-on-insulator; flash lamp annealing; rapid thermal annealing; Boron implantation; electrical activation

  • Journal of Applied Physics 104(2008), 044908-1-044908-7

Permalink: https://www.hzdr.de/publications/Publ-12348


Ion beam analysis (IBA) and accelerator mass spectrometry (AMS) with the new 6 MV accelerator at FZ Dresden-Rossendorf

Neelmeijer, C.; Grambole, D.; Grötzschel, R.; Merchel, S.; Munnik, F.

Abstract

Since more than 30 years IBA is performed at the Forschungszentrum Dresden-Rossendorf (FZD) for the determination of element distributions. Due to continuous upgrades of the different experimental set-ups, we are able to routinely perform:

• Rutherford Backscattering Spectrometry (RBS) & Channeling (C-RBS)
• Nuclear Reaction Analysis (NRA)
• Elastic Recoil Detection Analysis (ERDA)
• Particle-Induced X-Ray (PIXE) and Gamma-Emission (PIGE)
Most of our applications lie within material sciences. We are able to measure non-destructively “all natural” elements, i.e. H to U; most elements with lateral, some in 3-D resolution with the following typical parameters (matrix- and analyte-depending):
• depth resolution: 0.5-30 nm
• depth range: nm-µm
• lateral resolution: few µm
• usual mapping area: 2x2 mm2
• maximum sample size: 3x10 cm2 (vacuum) & “unlimited” (external beam)
• detection limits: ~10 µg/g (H); 500 µg/g – 1% (He-F); 10-100 µg/g (Na-U)
In summer 2009, our 5 MV van-de-Graaff accelerator will be replaced by a 6 MV Tandetron model [1], which is even more sophisticated than the lately installed 5 MV one in France [2]. The new accelerator will need less maintenance allowing more beam time. It might be also possible to expand from two to three 8-hour-shifts a day with the new fully automatic system. The main scientific advantages are an increased depth range by a factor of two for ERDA and improved detection limits for NRA. The high energy resolution also provides the ion optical requirements for a MeV-ion nanoprobe for selective in vivo-irradiation of cell nuclei at the nanometre-scale.
In addition, the machine will have special equipment for AMS [3]. There is a main advantage of using 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 (isotope ratios: 10-10-10-15).
In contrast to common low-energy AMS facilities, which have mainly specialized in radiocarbon analyses, the FZD-AMS is the first modern-type facility in the EU that will run at a terminal voltage of 6 MV. Especially in environmental and geosciences, the determination of long-lived (t1/2 > 0.3 Ma) cosmogenic radionuclides like 10Be, 26Al, and 36Cl became more and more important within the last decades [4]. Using these nuclides dating of e.g. volcanic eruptions, rock avalanches, earth quakes, and glacier movements is possible.
References: [1] A. Gottdang et al., Nucl. Instr. and Meth. B 2002, 190, 177. [2] M.G. Klein et al., Nucl. Instr. and Meth. B 2008, 266, 1828. [3] http://www.fzd.de/ams. [4] J.C. Gosse and F.M. Phillips, Quat. Sci. Rev. 2001, 20, 1475.

Keywords: ion beam analysis; accelerator mass spectrometry

  • Poster
    GDCh-Wissenschaftsforum Chemie 2009, 30.08.-02.09.2009, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12347


Radio-induced alteration in cordierite – Implications for petrology, gemmology and materials science

Krickl, R.; Nasdala, L.; Grambole, D.; Kaindl, R.

Abstract

Cordierite is a common metamorphic and magmatic mineral, which is used as petrologic tool for reconstructing the history of its host rock. Further applications include cordierite gemstones and the use of synthetic analogs in ceramics. Cordierite is stable over a wide temperature and pressure range and relatively resistant to chemical alteration; however, its properties can be significantly changed upon the impact of external irradiation.
In the course of a comprehensive study, natural radiohaloes in cordierite (a widespread feature caused by the impact of alpha-particles originating from radioactive inclusions) as well as artificial analogs produced by implantation of 8.8 MeV He2+ ions were investigated using modern micro-techniques. Additional irradiation experiments were performed using O6+ ions, electrons and gamma-rays.
Ion irradiation causes yellow colouration that is strongly pleochroic, and fades at higher doses. The possibility of radiation-treatment for enhancing the quality of gem-cordierite is discussed. While samples remain crystalline up to doses of 1016 He2+ /cm², the same material is fully amorphised when irradiated with the same dose of 30 MeV O6+ ions. These different observations may help to estimate the performance assessment of cordierite-ceramics in radiated environments.
A most important result concerning the petrological use of cordierite is the radio-induced transformation of channel constituents: Inside the irradiated areas the vibrational bands of CO2 decrease in intensity, whereas two new bands appear at 2135 cm-1 (both IR and Raman; cf. Nasdala et al., 2006) and 1550 cm-1 (Raman only). They are assigned to stretching vibrations of carbon monoxide and molecular oxygen, respectively, thus indicating a radio-chemical transformation 2CO2 → 2CO + O2 in alpha-irradiated cordierite. This study yields the first spectroscopic evidence for the irradiation-induced formation of molecular oxygen in cordierite. Polarised vibrational spectra of oriented samples give evidence that not only CO2 but also CO and O2 are preferentially oriented parallel [100], most probably being located at the Ch0 position in the large channel cavities. Carbon monoxide and O2 molecules seem to coexist in artificially irradiated cordierite without any sign of back reaction. Investigations on natural CO2 -bearing cordierite from different localities show that the 2CO2 → 2CO + O2 transformation is ubiquitous in radiohaloes.
Up to date, the detection of CO in cordierite has solely been ascribed to a reducing environment during crystal formation (Khomeko & Langer, 2005). In contrast, this present study shows that CO can also be produced by the action of radioactivity. This, as well as the production of radiogenic O2 , has to be taken into account in reconstructing palaeofluid compositions from molecules trapped in the structural channels of cordierite.

Khomenko VM, Langer K (2005): Carbon oxides in cordierite channels: Determination of CO2 isotopic species and CO by single crystal IR spectroscopy. Am Mineral 90: 1913-1917
Nasdala L, Wildner M, Wirth R, Groschopf N, Pal DC, Möller A (2006): Alpha particle haloes in chlorite and cordierite. Mineral Petrol 86: 1-27

  • Poster
    General Assembly 2009 of the European Geosciences Union (EGU), 19.-24.04.2009, Vienna, Austria
  • Open Access Logo Abstract in refereed journal
    Geophysical Research Abstracts 11(2009), EGU2009-2657-2

Permalink: https://www.hzdr.de/publications/Publ-12346


Binding Form of Uranium in Environmental Relevant Compartments

Bernhard, G.; Geipel, G.

Abstract

wird nachgereicht

  • Invited lecture (Conferences)
    School cum Workshop on Trace Element Speciation (SEISS-08), 21.-29.11.2008, Kolkata, India

Permalink: https://www.hzdr.de/publications/Publ-12345


Chemistry of Actinides

Bernhard, G.; Geipel, G.

Abstract

wird nachgereicht

  • Invited lecture (Conferences)
    School cum Workshop on Trace Element Speciation (SElS-08), 24.-28.11.2008, Kolkata, India

Permalink: https://www.hzdr.de/publications/Publ-12344


Subsecond melt processing for achieving SiGe surface layers

Voelskow, M.; Kanjilal, A.; Skorupa, W.

Abstract

High dose germanium (Ge) ion implantation in silicon (Si) substrate in combination with flash lamp irradiation was used to produce a thin SiGe surface layer. Due to the reduced melting temperature of the SiGe alloys, the possibility to form an undesirable facetted liquid/solid interface, well known for pulse melting in the millisecond time regime, was found to decrease significantly using ion beam implantation technique. The formation of a dislocation network in the surface SiGe layer and strain were evidenced by transmission electron microscopy and -Raman spectroscopy measurements, respectively.

Keywords: SiGe; FLA; RBS; Raman spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-12343


Planned experiment on 40Ca(alpha,gamma)44Ti in Dresden

Bemmerer, D.

Abstract

The 40Ca(alpha,gamma)44Ti nuclear reaction is important for the production of 44Ti in the alpha-rich freezeout in supernovae. The decay of 44Ti has been observed in several staellite-based gamma observatories for the Cas A supernova remnant, but surprisingly not in other cases. A new 40Ca(alpha,gamma)44Ti cross section measurement planned in Dresden is briefly described in the talk. The irradiations are to be performed at the FZD 3 MV Tandetron. Besides in-beam gamma-spectrometry and accelerator mass spectrometry, the main detection method will be an activation measurement. The weak activated 44Ti samples will be counted in the Felsenkeller underground low-level counting facility.

  • Invited lecture (Conferences)
    Research Day "44Ti" of the Excellence cluster "Origin and structure of the universe", 15.01.2009, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12342


Comparison of two dedicated 'in beam' PET systems via simultaneous imaging of 12C-induced β+-activity

Attanasi, F.; Belcari, N.; Del Guerra, A.; Enghardt, W.; Moehrs, S.; Parodi, K.; Rosso, V.; Vecchio, S.

Abstract

The selective energy deposition of hadrontherapy has led to a growing interest in quality assurance techniques such as ‘in-beam’ PET. Due to the current lack of commercial solutions, dedicated detectors need to be developed. In this paper, we compare the performances of two different ‘in-beam’ PET systems which were simultaneously operated during and after lowenergy carbon ion irradiation of PMMA phantoms at GSI Darmstadt. The results highlight advantages and drawbacks of a novel in-beam PET prototype against a long-term clinically operated tomograph for ion therapy monitoring.

  • Physics in Medicine and Biology 54(2008), n29-n35

Permalink: https://www.hzdr.de/publications/Publ-12341


Direct measurement of the 15N(p,gamma)16O total cross section at novae energies

Bemmerer, D.; Caciolli, A.; Bonetti, R.; Broggini, C.; Confortola, F.; Corvisiero, P.; Costantini, H.; Elekes, Z.; Formicola, A.; Fulop, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyurky, G.; Junker, M.; Limata, B.; Marta, M.; Menegazzo, R.; Prati, P.; Roca, V.; Rolfs, C.; Alvarez, C. R.; Somorjai, E.; Straniero, O.

Abstract

The 15N(p,gamma)16O reaction controls the passage of nucleosynthetic material from the first to the second carbon-nitrogen-oxygen (CNO) cycle. A direct measurement of the total 15N(p,gamma)16O cross section at energies corresponding to hydrogen burning in novae is presented here. Data have been taken at 90-230 keV center-of-mass energy using a windowless gas target filled with nitrogen of natural isotopic composition and a bismuth germanate summing detector. The cross section is found to be a factor two lower than previously believed.

Keywords: Nuclear astrophysics; Nova burning, CNO cycle; gas target; BGO detector; LUNA

Permalink: https://www.hzdr.de/publications/Publ-12340


First 4D in-beam PET measurement for beam tracking of a moving phantom with a scanned carbon ion beam

Parodi, K.; Saito, N.; Richter, C.; Chaudhri, N.; Enghardt, W.; Rietzel, E.; Bert, C.

Abstract

More than 10 years of clinical operation of in-beam PET at GSI Darmstadt have proven its positive impact on quality assurance of carbon ion therapy, mostly for head-and-neck sites. Due to the promise of ion beam therapy for indications such as lung and liver tumors which are influenced by respiratory motion we started to investigate the potential of time-resolved, 4D in-beam PET. 4D in-beam PET is expected to facilitate in-vivo assessment of tumor miss or unwanted involvement of nearby critical structures in the presence of organ motion. In a first experiment performed at GSI, in-beam PET was used in combination with beam tracking. A homogeneous PMMA phantom was placed in the center of the field of view of the PET camera and moved parallel to the two detector heads (left-right in beam's eye view, amplitude: 3 cm peak-to-peak, period: ~ 3 s). Dose was delivered by beam tracking as a two-dimensionally spread-out Bragg-peak of 5 x 5 cm2 extension, centered at a depth of 10 cm in the central plane of the phantom. The dynamic PET acquisition was performed during the 6 min of beam delivery and for 25 min after irradiation. The data stream was synchronized with the time course of the dynamic beam application and with the phantom motion. Additional 18 min of decay were acquired with the activated phantom kept steady, for comparison with a separate measurement of the same treatment field without motion. Reconstruction of the data taken with a steady phantom yielded comparable activation patterns for beam tracking and stationary irradiation. 4D PET reconstruction is currently in progress. Motion phase sorted data as well as results for imaging performance in dependence on the amount of reconstructed events will be presented. First conclusions on the feasibility of in-beam PET for monitoring ion treatment of moving targets will be discussed.

  • Lecture (Conference)
    IEEE MIC 2008, 19.-25.10.2008, Dresden, Deutschland
  • Contribution to proceedings
    IEEE Dresden 2008, 19.-25.10.2008, Dresden, Deutschland
    IEEE Conference Report

Permalink: https://www.hzdr.de/publications/Publ-12339


Phasenkorrelierte Schwächungskorrektur von 4D-PET mit Hilfe von 4D-CT

Richter, C.; Just, U.; Pönisch, F.; Enghardt, W.

  • Poster
    OncoRay Retreat 2008, 08.-09.01.2008, Gröditz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12338


Phase-Correlated Attenuation Correction (PC-AC) for 4D-PET/4D-CT

Richter, C.

  • Lecture (others)
    3rd Meeting of the Scientific Advisory Board of OncoRay, 28.02.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12337


On the multivariate nature of brain metabolic impairment in Alzheimer's disease

Salmon, E.; Kerrouche, N.; Perani, D.; Lekeu, F.; Holthoff, V.; Beuthien-Baumann, B.; Sorbi, S.; Lemaire, C.; Herholz, K.

Abstract

We used principal component analysis to decompose functional images of patients with AD in orthogonal ensembles of brain regions with maximal metabolic covariance. Three principal components explained 38% of the total variance in a large sample of FDG-PET images obtained in 225 AD patients. One functional ensemble (PC2) included limbic structures from Papez's circuit (medial temporal regions, posterior and anterior cingulate cortex, thalamus); its disruption in AD patients was related to episodic memory impairment. Another principal component (PC1) illustrated major metabolic variance in posterior cerebral cortices, and patients’ scores were correlated to instrumental functions (language and visuospatial abilities). PC3 comprised frontal, parietal, temporal and posteromedial (posterior cingulate and precuneus) cortices, and patients’ scores were related to executive dysfunction and global cognitive impairment. The three main metabolic covariance networks converged in the posterior cingulate area that showed complex relationships with medial temporal structures within each PC. Individual AD scores were distributed as a continuum along PC axes: an individual combination of scores would determine specific clinical symptoms in each patient.

Keywords: Alzheimer; Dementia; PET; Brain imaging; Multivariate; PCA

Permalink: https://www.hzdr.de/publications/Publ-12336


Magnetic Structure of RuSr2GdCu2O8 Determined by Resonant X-Ray Diffraction

Bohnenbuck, B.; Zegkinoglou, I.; Strempfer, J.; Nelson, C. S.; Wu, H.-H.; Schüßler-Langeheine, C.; Reehuis, M.; Schierle, E.; Leininger, P.; Herrmannsdörfer, T.; Lang, J. C.; Srajer, G.; Lin, C. T.; Keimer, B.

Abstract

X-ray diffraction with photon energies near the Ru L2-absorption edge was used to detect resonant
reflections characteristic of a G-type superstructure in RuSr2GdCu2O8 single crystals. A polarization
analysis confirms that these reflections are due to magnetic order of Ru moments, and the azimuthal-angle
dependence of the scattering amplitude reveals that the moments lie along a low-symmetry axis with
substantial components parallel and perpendicular to the RuO2 layers. Complemented by susceptibility
data and a symmetry analysis of the magnetic structure, these results reconcile many of the apparently
contradictory findings reported in the literature

  • Physical Review Letters 102(2009), 037205

Permalink: https://www.hzdr.de/publications/Publ-12335


Magnetic field control of the pouring process in aluminium investment casting

Gerbeth, G.; Eckert, S.; Galindo, V.; Willers, B.; Hewelt, U.; Hornung, B.

Abstract

The mould filling process of aluminium investment casting consists basically of the flow in a U-bend showing a high pouring velocity at the beginning and decreasing velocity values during the course of the process. The high velocities during the starting phase are supposed to cause distinct problems like bubble or inclusion entrapment.
We present results on the design and application of a DC magnetic field to control the pouring velocity. Numerical 3d transient calculations were performed to simulate the filling process and the effect of the magnetic field. In parallel, model experiments with a plexiglas model have been performed using the low melting eutectic GaInSn. Ultrasonic Doppler velocimetry was applied to carry out detailed velocity measurements in the model. These measurements served for the validation of the numerical calculations, thus allowing to scale up the simulations to the realistic aluminium casting process.
The developed DC field system has been tested under industrial conditions. The amplitude of the DC field was tuned during the process as the braking action is only needed during the first part of the process. In this way, a clear reduction of the peak velocities is obtained without a significant prolongation of the overall filling time. A multitude of investment casting units have been produced showing a significant diminishment of defects due to the magnetic field control of the pouring process.

  • Contribution to proceedings
    11th International Conference on Aluminium Alloys, 22.-26.09.2008, Aachen, Germany
    Aluminium Alloys, Eds.: J. Hirsch, B. Skrotzki, G. Gottstein: Wiley-VCH, 427-433
  • Lecture (Conference)
    11th International Conference on Aluminium Alloys, 22.-26.09.2008, Aachen, Germany

Permalink: https://www.hzdr.de/publications/Publ-12334


Synthesis and cyclooxygenase inhibition of various (aryl-1,2,3-triazole-1-yl)-methanesulfonylphenyl derivatives

Wuest, F.; Tang, X.; Knieß, T.; Pietzsch, J.; Suresh, M.

Abstract

A series of 1,4- and 1,5-diaryl substituted 1,2,3-triazoles was synthesized by either Cu(I)-catalyzed or Ru(II)-catalyzed 1,3-dipolar cycloaddition reactions between 1-azido-4-methane-sulfonylbenzene 9 and a panel of various para-substituted phenyl acetylenes (4-H, 4-Me, 4-OMe, 4-NMe2, 4-Cl, 4-F). All compounds were used in in vitro cyclooxygenase (COX) assays to determine the combined electronic and steric effects upon COX-1 and COX-2 inhibitory potency and selectivity. Structure-activity relationship studies showed that compounds having a vicinal diaryl substitution pattern showed more potent COX-2 inhibition (IC50 = 0.03–0.36 µM) compared to their corresponding 1,3-diaryl-substituted counterparts (IC50 = 0.15 to >10.0 µM). In both series, compounds possessing an electron-withdrawing group (Cl and F) at the para-position of one of the aryl rings displayed higher COX-2 inhibition potency and selectivity as determined for compounds containing electron-donating groups (Me, OMe, NMe2). The obtained data show, that the central carbocyclic or heterocyclic ring system as found in many COX-2 inhibitors can be replaced by a central 1,2,3-triazole unit without losing COX-2 inhibition potency and selectivity. The high COX-2 inhibition potency of some 1,2,3-triazoles having a vicinal diaryl substitution pattern along with their ease in synthesis through versatile Ru(II)-catalyzed click chemistry make this class of compounds interesting candidates for further design and synthesis of highly selective and potent COX-2 inhibitors.

Keywords: Click chemistry; Cyclooxygenase-1 and -2 inhibitors; Triazoles

Permalink: https://www.hzdr.de/publications/Publ-12332


Co-localization of hypoxia and perfusion markers with parameters of glucose metabolism in human tumour xenografts

Yaromina, A.; Zips, D.; Quennet, V.; Meyer, S.; Shakirin, G.; Mueller-Klieser, W.; Baumann, M.

Abstract

Tumour hypoxia measured by biochemical markers such as pimonidazole and parameters of the glucose metabolism such as lactate concentration have been shown to correlate with outcome after fractionated radiotherapy in experimental and clinical tumours and might serve as potential candidates for treatment individualization. High resolution imaging of tumour pathophysiology allows to study not only average values per tumour but also to investigate the spatial variations in hypoxia, perfusion, and energy metabolism. To examine relationships between hypoxia marker pimonidazole, perfusion marker Hoechst and the parameters of metabolic micromilieu such as glucose and lactate at the microregional level serial histological sections were explored for co-localization in 3 different human squamous cell carcinomas (hSCC) growing in nude mice

Keywords: hypoxia; hSCC; pefusion

  • Poster
    International Workshop "Radiation and Multidrug Resistance Mediated via the Tumor Microenvironment", 09.-10.02.2009, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12331


Anwendung zeitmodulierter Magnetfelder zur Strömungskontrolle während der gerichteten Erstarrung metallischer Legierungen

Eckert, S.; Nikrityuk, P. A.; Räbiger, D.; Willers, B.; Eckert, K.

Abstract

In dieser Arbeit wird die Wirkung des elektromagnetischen Rührens der Restschmelze bei der gerichteten Erstarrung einer Al-Si-Legierung untersucht. Dabei wird eine neue Methode zum elektromagnetischen Rühren unter Nutzung eines rotierenden Magnetfeldes (RMF) und eines wandernden Magnetfeldes (TMF) vorgeschlagen, bei der beide Felder einzeln aufeinanderfolgend in Form von Rechteckpulsen angewandt werden. Beim konventionellen elektromagnetischen Rühren mit kontinuierlich wirkenden Feldern treten oft strömungsinduzierte Entmischungen im Gefüge auf. Mit der Strategie der Nutzung zeitmodulierter Felder sollen diese bekannten Nachteile vermieden werden. Die Ergebnisse zeigen, dass das Rühren unter Anwendung eines modulierten magnetischen Feldes Möglichkeiten zur Beeinflussung des Erstarrungsgefüges durch eine effiziente Kontrolle des Strömungsfeldes vor der Erstarrungsfront bietet. Eine erfolgreiche Anwendung erfordert eine dem jeweiligen Prozess angepasste Optimierung der Magnetfeldparameter.

Keywords: solidification; electromagnetic stirring; rotating magnetic field; traveling magnetic field; macrosegregation

  • Berg- und hüttenmännische Monatshefte 154(2009)3, 117-120

Permalink: https://www.hzdr.de/publications/Publ-12330


Coprecipitation of Arsenate with Metal Oxides. 3. Nature, Mineralogy, and Reactivity of Iron(III)-Aluminum Precipitates.

Violante, A.; Pigna, M.; Del Gaudio, S.; Cozzolino, V.; Banerjee, D.

Abstract

Coprecipitation involving arsenic with aluminum or iron has been studied because this technique is considered particularly efficient for removal of this toxic element from polluted waters. Coprecipitation of arsenic with mixed iron-aluminum solutions has received scant attention. In this work we studied
(i) the mineralogy, surface properties, and chemical composition of mixed iron-aluminum oxides formed at initial Fe/Al molar ratio of 1.0 in the absence or presence of arsenate [As/Fe+Al molar ratio (R) of 0, 0.01, or 0.1] and at pH 4.0, 7.0, and 10.0 and aged for 30 and 210 days at 50 °C and
(ii) the removal of arsenate from the coprecipitates after addition of phosphate. The amounts of short-range ordered precipitates (ferrihydrite, aluminous ferrihydrite and/or poorly crystalline boehmite) were greater than those found in iron and aluminum systems (studied in previous works), due to the capacity of both aluminum and arsenate to retard or inhibit the transformation of the initially formed precipitates into well-crystallized oxides (gibbsite, bayerite, and hematite). As a consequence, the surface areas of the iron-aluminum oxides formed in the absence or presence of arsenate were usually much larger than those of aluminum or iron oxides formed under the same conditions. Arsenate was found to be associated mainly into short-rangeorderedmaterials. Chemicalcompositionofallsamples was affected by pH, initial R, and aging. Phosphate sorption was facilitated by the presence of short-range ordered materials, mainly those richer in aluminum, but was inhibited by arsenate present in the samples. The quantities of arsenate replaced by phosphate, expressed as percentages of its total amount present in the samples, were particularly low, ranging from 10% to 26%. A comparison of the desorption of arsenate by phosphate from aluminum-arsenate and iron-arsenate (studied in previous works) and iron-aluminum-arsenate coprecipitates evidenced that phosphate has a greater capacity to desorb arsenate from aluminum than iron sites.

Keywords: Arsenic; XPS; Coprecipitate

Permalink: https://www.hzdr.de/publications/Publ-12329


Was tut ein Medizinphysikexperte? Der Masterstudiengang „Medical Radiation Sciences“ an der medizinischen Fakultät“

Enghardt, W.

Abstract

Was tut ein Medizinphysikexperte? Der Masterstudiengang „Medical Radiation Sciences“ an der medizinischen Fakultät“

  • Invited lecture (Conferences)
    Uni-Tag der TU Dresden, 31.05.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12328


Neue Anwendungen ionisierender Strahlen in der Medizin

Enghardt, W.

Abstract

1. Motivation für neue Therapiestrahlen
2. Physikalische Eigenschaften von Ionenstrahlen
3. Biologische Eigenschaften von Ionenstrahlen
4. Technologische Umsetzung
5. Klinische Ergebnisse

  • Invited lecture (Conferences)
    1. Strahlenschutzseminar für Führungskräfte in Sachsen, 13.10.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12327


Erste dosimetrische und strahlenbiologische Experimente an Laser beschleunigten Elektronenstrahlen

Enghardt, W.

Abstract

1. Laser Beschleuniger für die Strahlentherapie
2. Das Verbundprojekt onCOOPtics (Jena – Dresden)
3. Dosimetrie Laser beschleunigten Elektronenstrahlen
4. Strahlenbiologische Experimente

  • Invited lecture (Conferences)
    Radioonkologisches Kolloquium, 02.04.2008, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12326


Der Masterstudiengang „Medical Radiation Sciences“und die Ausbildung von MPE an der medizinischen Fakultät der TU Dresden

Enghardt, W.

Abstract

Der Masterstudiengang „Medical Radiation Sciences“und die Ausbildung von MPE an der medizinischen Fakultät der TU Dresden

  • Invited lecture (Conferences)
    39. Wissenschaftliche Jahrestagung der DGMP 2008 Medizinische Physik, 13.09.2008, Oldenburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12324


Monitoring of Hadron Therapy by means of PET Techniques

Enghardt, W.

Abstract

1. PET and hadron therapy (PT-PET)
2. Clinical implementation
3. Results and conclusions

  • Invited lecture (Conferences)
    ESTRO 27, 16.09.2008, Göteborg, Schweden

Permalink: https://www.hzdr.de/publications/Publ-12323


Erfahrungen zum und künftige Anforderungen an das Verhältnis zwischen großen Forschungseinrichtungen und dem Rechnungshof

Joehnk, P.

Abstract

Neues Steuerungsmodell in der Wissenschaft und die Rolle der Rechnungshöfe

  • Invited lecture (Conferences)
    Veranstaltung des ZWM Wissenschaftsmanagement Speyer, 29.-30.01.2009, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-12322


The detector system for measurement of multiple cosmic muons in the central detector of KASCADE

Bozdog, H.; Elzer, M.; Gils, H.; Haungs, A.; Herm, F.; Koepernik, H.; Kohler, K.; Kretschmer, M.; Leibrock, H.; Mathes, H.; Petcu, M.; Proehl, D.; Rebel, H.; Wentz, J.; Wolf, A.; Zagromski, S.

Abstract

A detector system for directional and time correlation measurements of multiple cosmic muons has been set up within the extensive air shower experiment KASCADE. The system consists of two layers (129 m(2) area each) of position-sensitive multiwire proportional chambers (MWPC) triggered by a layer of segmented plastic scintillation counters placed upon an iron/concrete shielding above the MWPCs. Operation conditions and performance of the MWPCs have been studied by means of a prototype arrangement consisting of a stack of four detectors and two trigger layers. Results of the detailed prototype studies are presented and discussed. In particular, it has been found that for the present purposes an operation with a commonly used argon-methane gas mixture instead of previously used argon-isobutane leads to an excellent performance. The chambers are integrated into the KASCADE experiment as described and are in continuous operation since 1996. Some typical measurements with the full detector assembly are used to illustrate which features of extensive air showers can be studied. (C) 2001 Elsevier Science B.V. All rights reserved.

Keywords: multiwire proportional chambers; data processing; extensive air showers; cosmic muons; extensive air showers

  • Nuclear Instruments and Methods in Physics Research A 465(2001)2-3, 455-471
    ISSN: 0168-9002

Permalink: https://www.hzdr.de/publications/Publ-12321


In-beam PET for moving targets in particle therapy

Laube, K.; Bert, C.; Chaudhri, N.; Fiedler, F.; Parodi, K.; Rietzel, E.; Saito, N.; Enghardt, W.

Keywords: in-beam PET; moving targets; ion therapy

  • Poster
    OncoRay, Retreat, 14.-15.01.2009, Bautzen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12320


PET-CT Co-Registrierung for In-Beam PET

Fiedler, F.; Sobiella, M.; Enghardt, W.

Keywords: in-beam PET

  • Poster
    Oncoray, Retreat, 14.-15.01.2009, Bautzen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12319


In-beam PET for ion therapy monitoring

Fiedler, F.

Keywords: in-beam PET

  • Lecture (others)
    Oncoray-Meeting, 03.06.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12318


Local setting of magnetic anisotropy in amorphous films by Co ion implantation

McCord, J.; Mönch, I.; Fassbender, J.; Gerber, A.; Quandt, E.

Abstract

The local setting of magnetic anisotropy by low fluence Co ion implantation in amorphous magnetic thin films is demonstrated. For a wide range of ion fluences no structural changes occur and the adjustment of anisotropy is reversible. A quantitative relationship between the anisotropy change and the atomic displacements is found. Magnetic domain investigations of the purely magnetically patterned stripes reveal an effective quasi-cubic anisotropy below a critical width for orthogonal magnetic anisotropy alignment. The method of ion-annealing allows for a local setting of anisotropy without irreversible structural and magnetic alterations.

Keywords: magnetism; ion implantation; amorphous films; patterning; anisotropy

Permalink: https://www.hzdr.de/publications/Publ-12317


Local stress engineering of magnetic anisotropy in soft magnetic thin films

Martin, N.; McCord, J.; Gerber, A.; Strache, T.; Gemming, T.; Mönch, I.; Farag, N.; Schäfer, R.; Fassbender, J.; Quandt, E.; Schultz, L.

Abstract

The magnetic anisotropy of amorphous thin films was modified laterally by masked ion irradiation without alteration of the intrinsic magnetic properties. The changes were introduced by local ion implantation in a protection layer, causing additional stress-induced magnetic anisotropy in the magnetostrictive layer. The underlying local variation of magnetic anisotropy was modelled and confirmed experimentally. The described method, relying purely on magneto-elastics, introduces a new path to the alteration of magnetic properties subsequent to magnetic film preparation. With the use of the resulting artificial magnetization patterns it is possible to tailor the ferromagnetic thin film structure used in magneto-electronic applications.

Keywords: magnetism; ion irradiation; amorphous films; magneto-elastic; patterning

Permalink: https://www.hzdr.de/publications/Publ-12316


Künstliche magnetische Materialien durch Nanostrukturierung

Fassbender, J.

Abstract

Nanostrukturierte magnetische Materialien wurden in den letzten 15 Jahren intensiv untersucht. In den allermeisten Fällen handelte es sich dabei um magnetische Inseln die mittels Lithographietechniken auf einem unmagnetischen Substrat hergestellt wurden. Eine völlig neuartige Klasse von Materialien entsteht, wenn anstelle einer topographischen eine rein magnetische Strukturierung verwendet wird. Dies geschieht durch lokale Modifikation der Oberflächenrauhigkeit oder Grenzflächenschärfe bei Vielfachschichtsystemen. Derartige Modifikationen können leicht mittels Ionenbestrahlung [1], Ionenimplantation [2,3] oder Ionenstrahlerosion [4] erzielt werden. Alternativ können auch strukturelle Phasenübergänge, die mit magnetischen Phasenübergängen einhergehen realisiert werden [5], die die Erzeugung magnetischer Nanostrukturen im sub-100 nm Bereich zulassen [6]. Der Vortrag gibt einen Überblick über die auftretenden physikalischen Phänomene unter Einbezug einiger Anwendungsbeispiele.

[1] J. Fassbender, D. Ravelosona, Y. Samson, J. Phys. D: Applied Physics 37, R179 (2004).
[2] J. Fassbender, J. McCord, J. Magn. Magn. Mater. 320, 579 (2008).
[3] J. McCord, L. Schultz, J. Fassbender, Advanced Materials 20, 2090 (2008).
[4] M. O. Liedke, B. Liedke, A. Keller, B. Hillebrands, A. Mücklich, S. Facsko, J. Fassbender, Phys. Rev. B 75, 220407(R) (2007).
[5] J. Fassbender, M. O. Liedke, T. Strache, W. Möller, E. Menendez, J. Sort, K. V. Rao, S. C. Deevi, J. Nogues, Phys. Rev. B 77, 174430 (2008).
[6] E. Menendez, J. Sort, M. O. Liedke, J. Fassbender, T. Gemming, A. Weber, L. J. Heydermann, S. Surinach, K. V. Rao, S. C. Deevi, M. D. Baro, J. Nogues, Small 5, 229 (2009).

Keywords: magnetism; ion irradiation; implantation; patterning; nano; ion erosion

  • Invited lecture (Conferences)
    Kolloquiumsvortrag, Universität Mainz, 16.02.2009, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12315


Superconductivity in heavily Ga-doped Ge

Heera, V.; Herrmannsdörfer, T.; Heinig, K.-H.; Ignatchik, O.; Mücklich, A.; Posselt, M.; Schmidt, B.; Skrotzki, R.; Skorupa, W.; Uhlarz, M.; Voelskow, M.; Wündisch, C.; Helm, M.; Wosnitza, J.

Abstract

Recently, superconductivity was detected in heavily boron doped group IV semiconductors like diamond (cB=2.8 at%, TC=4 K) [1] and silicon (cB=1.2 at%, TC=0.34 K) [2]. These unexpected results initiated a new debate about the possibility and the mechanism of superconductivity in doped semiconductors. Theoretical calculations, based on the classical electron-phonon coupling mechanism, demonstrated that critical temperatures in diamond can clearly exceed 1 K for acceptor concentrations higher than 5 at% [3]. However, unrealistic high doping concentrations are predicted for observable superconductivity in Si or even Ge. It was an open question whether superconductivity can be achieved in doped Ge.
In order to fabricate group IV semiconductors with acceptor concentrations much higher than their equilibrium solid solubility exotic doping methods like high-pressure-high-temperature synthesis [1] or gas immersion laser doping [2] were applied. We used a more conventional doping process consisting of high dose implantation and 3 ms flash lamp or 60 s rapid thermal annealing in order to form Ge layers with Ga concentrations up to 6 at%. According to Hall effect measurements the hole concentrations are in the range between 0.3x1021 and 1.4x1021 cm-3. Superconductivity was found in the Ga-doped Ge samples below critical temperatures between 0.1 and 0.5 K in dependence on the annealing conditions.

References
[1] E. A. Ekimov et al., Nature 428 (2004) 542
[2] E. Bustarret et al., Nature 444 (2006) 465
[3] L. Boeri, J. Kortus, O. K. Anderson, J. Phys. Chem. Solids 67 (2006) 552

Keywords: Ga doped Ge; Ga implantation; flash lamp annealing; Hall effect measurements; superconductivity

  • Lecture (Conference)
    Workshop Ionenstrahlphysik, 06.-08.04.2009, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12314


Synthesis, Modification and Applications of Ge Nanoclusters Embedded in SiO2 Films

von Borany, J.; Beyer, V.; Heinig, K.-H.; Mücklich, A.; Schmidt, B.; Skorupa, W.

Abstract

Due to their quantum confinement properties and the large surface-to-volume-ratio, semiconductor and metal nanoparticles embedded in a matrix play a significant role for new functional materials. Among them, Si, Ge, or SiC nanoclusters (-or crystals) are of particular interest for future (opto)electronic devices due to the full compatibility with semiconductor technology.
The contribution focus on recent studies on Ge nanoparticles embedded in dielectric films (mainly SiO2). Based on phase separation of supersaturated solid solutions, Ge nanocluster have been fabricated using ion beam synthesis or magnetron sputtering techniques. The size, density, density and position of the Ge nanocrystals can be varied in a technological relevant way by the degree of supersaturation and the spatial distribution of the Ge. Moreover, subsequent thermal or ion-beam processing enables to tailor nanocluster properties like shape, size or composition. Taking into account the ion beam interaction at interfaces, the generation of delta-like nanocluster bands has been successfully demonstrated. For Ge nanocrystals formation, relatively low process temperatures (< 950°C) are characteristic, but careful processing remains necessary to avoid Ge loss in thin films due to the formation of volatile GeO components. Some conceivable (opto)electronic applications of Ge nanoclusters will be discussed more in detail. Thin gate oxides containing ion beam synthesized Ge nanoclusters have been applied to study “non-volatile” me¬mory with low-field programming (< 5 MV/cm) capability. The violet luminescence in Ge doped SiO2 films was investigated with respect to their possible use to fabricate luminescence or opto-coupling devices. Finally, nanocluster films offer a new interesting approach for light absorption in bandgap engineered absorber materials designed for next generation solar cells.

Keywords: Ion beam synthesis; Ge nanoclusters; Nanocrystal memory; Bandgap engineering; Photovoltaics

  • Invited lecture (Conferences)
    The IUMRS International Conference in Asia 2008 (IUMRS-ICA2008), Session M "Innovative Material Technologies Utilizing Ion Beams", 08.-13.12.2008, Nagoya, Japan

Permalink: https://www.hzdr.de/publications/Publ-12313


Evidence of a thermally stimulated charge transfer mechanism and interface defect formation in metal-oxide-semiconductor structures with germanium nanocrystals

Beyer, R.; von Borany, J.

Abstract

The trapping of charge carriers and the mechanism of the charge transfer were examined in metal-oxide-semiconductor structures with germanium nanocrystals embedded in a 20 nm silicondioxide layer. The nanoclusters were generated by ion beam synthesis. Capacitance-voltage (C-V) measurements exhibit a hysteresis loop due to the charge trapping and detrapping. Effective oxide trap densities were derived and could be related to the nanoclusters. A strong temperature dependence of the C-V loop indicates, that a thermally stimulated process is involved in the charge transfer between the clusters and the interface, thus ruling out direct tunneling. The application of deep level transient spectroscopy revealed a large amount of interface states in the Ge implanted samples, including a distinct trap state at 0.32 eV above the valence band edge with a concentration up to 2e13 /(cm²eV), which is much likely involved in the emission of carriers from cluster related states in a two stage process.

Keywords: Ion beam synthesis; Ge nanocrystals; CV characteristics

Permalink: https://www.hzdr.de/publications/Publ-12312


X rays from relaxation of slow highly charged ions hitting thin metallic foils: emission depth and time

PešIć, Z. D.; Vikor, G.; Schuch, R.

Abstract

Nanotechnological devices are reaching the size of few molecules and there is a quest for new nanoscale materials. It has been prompted already in the eighties that the high potential energy carried by highly charged ions (HCIs) might be exploited for surface modifications . For example, the use of potential sputtering for nanostructuring would avoid unwanted damage caused by fast ions. Therefore, the knowledge of the exact time and depth scale for the energy deposition is essential.
Apart from the work reported in, there are very few direct experimental determinations of the relaxation time in the bulk. Recently, we introduced a method to determine the relaxation time of the innermost vacancies for highly ionized heavy ions moving through the bulk . The method compares the intensities of photons emitted through the front and back-side of a thin metal foil. Using foils with known thickness and x-ray absorption cross-sections, we obtained directly the mean x-ray emission depth, and thereafter the mean relaxation time.
The experiment was performed at the Manne Siegbahn Laboratory in Stockholm. Two Si(Li) detectors were used to measure X-rays emitted following the impact of 8.5xq keV and 23.5xq keV Pbq+ ions (q=53-58) on thin Ta foils oriented 45o relative to the ion-beam direction. This geometry allowed simultaneous detection of photons that escape through the back and the front surface of the foil.
The difference of the intensities of front- and back-side x-ray spectra is caused by different path lengths through the absorbing material (Ta foil) as well as by different detection efficiencies of the two Si(Li) detectors. The fitting procedure is illustrated in Fig.1, clearly showing that it is necessary to correct both spectra for the proper absorption by the Ta foil.
The experimental results of the emission depth are combined with a trajectory simulation to obtain the slowing down of the ion in the solid, to get the range and to convert the length scale to a time scale. We found that the relaxation time ranges from 30-60 fs.
The extracted mean relaxation time is compared with the prediction of the rate-equations model that incorporates radiative and non-radiative transitions, combined with a molecular orbital (MO) calculation for the Pb-Ta collision system which gives the projectile levels that are filled in close collisions with target atoms. The calculated mean relaxation time is found to be in fair agreement with the experimental results.

  • Invited lecture (Conferences)
    IISC-17, 17th International Workshop on Inelastic Ion-Surface Collisions, 21.-26.09.2008, Porquerolles, France

Permalink: https://www.hzdr.de/publications/Publ-12311


Fragmentation of Water Molecule by Slow Multiply Charged Ions

PešIć, Z. D.; Hellhammer, R.; Sulik, B.; Stolterfoht, N.

Abstract

Fragmentation of molecules subsequent to the interaction with ions has been studied intensively in the last decade, with the focus on relatively fast projectiles (the interaction time is 1-2 orders of magnitude smaller than the dissociation time). If the projectile is slow that the interaction time is comparable with the dissociation time, it strongly alters the angular and energy distribution of ionic fragment.

The energy and angular distribution of ionic fragments from water molecules formed upon impact of highly charged 1-220 keV Xeq+ ions (q=10, 15 and 22) was studied. These results are compared with our previous studies of water fragmentation induced by He1,2+, Ne(3-9)+ and Ar13+ ions [1-3]. A strong difference of the intensities and kinetic energy of ions scattered in forward and backward directions is observed as a function of the ion velocity. The data are interpreted by means of a classical trajectory simulation within the framework of a Coulomb Explosion.

  • Invited lecture (Conferences)
    RADAM 2008 - Radiation Damage in Biomolecular Systems, 13.-15.06.2008, Debrecen, Hungary
  • Contribution to proceedings
    RADAM 2008 - Radiation Damage in Biomolecular Systems, 13.-15.06.2008, Debrecen, Hungary
    Proceedings of the 5th International Conference (RADAM 2008), Melville, New York: American Institute of Physics, 978-0-7354-0611-7, 88-97

Permalink: https://www.hzdr.de/publications/Publ-12310


Strong Forward-Backward Asymmetry of Water Ionic Fragments by Slow Highly Charged Ions Impact

Peić, Z. D.; Hellhammer, R.; Sulik, B.; Stolterfoht, N.

Abstract

Fragmentation of molecules subsequent to the interaction with ions has been studied intensively in the last decade. If the projectile is fast that the interaction time is orders of magnitude smaller than the dissociation time, the collision can be considered as a two-step process . On the other hand, for slow (v < 1 a. u.), highly charged projectiles the energy and angular distribution of fragments is determined by the energy and momentum transferred from the projectile, in addition to the energy gained by the repulsive dissociation of the molecule.
We present the results of the fragment ion spectroscopy studies of water molecules subsequent to impact of highly charged 1-220 keV Xeq+ ions (q=10, 15 and 22). We observed a strong forwardbackward asymmetry in the emission of the ionic fragments. For example, the ion yield in the forward direction is almost completely suppressed for the impact of below 10 keV Xe22+ ions.

These results are compared with our previous studies of water fragmentation induced by He1,2+ and Ne(3-9)+ ions . For projectiles with low charge state, the final kinetic energy is apparently determined by the related Franck-Condon transition. In order to guide the interpretation of the experimental data, we performed a classical trajectory simulation within the framework of a Coulomb Explosion model wherein a satisfactory agreement is achieved. Finally, the integrated cross sections over all fragmentation channels are compared with results of the semiempirical scaling law deduced from a multi-electron capture model.

  • Lecture (Conference)
    HCI 2008, 14th International Conference on the Physics of Highly Charged Ions., 01.-05.09.2008, Tokyo, Japan

Permalink: https://www.hzdr.de/publications/Publ-12309


Measurements of electron bunch lengths

Debus, A.

Abstract

Particle-in-Cell (PIC) simulations suggest that laser accelerated electron bunches have pulse lengths down to below 10fs. Classic approaches known from the accelerator community are known to be limited to longer electron bunches. An all-optical, single-shot approach is presented that shows how the spectral analysis of the coherent transition radiation from a thin foil in the mid-infrared can be used to extract the electron bunch length on a scale from 8fs to 50fs.

Keywords: electron bunch lengths; transition radiation; laser wakefield accelerated electrons; ultrashort electrons

  • Lecture (others)
    3rd PhD Seminar of FZD, 27.-29.8.2008, Feriendorf Hoher Hain, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12308


Synchrotron radiation from laser-accelerated monoenergetic electrons

Schlenvoigt, H.-P.; Haupt, K.; Debus, A.; Budde, F.; Jaeckel, O.; Pfotenhauer, S.; Gallacher, J. G.; Brunetti, E.; Shanks, R. P.; Wiggins, S. M.; Jaroszynski, D. A.; Rohwer, E.; Schwoerer, H.

Abstract

In this paper, we report on the generation of incoherent synchrotron radiation in the visible spectral range which is produced by laser-accelerated electrons with 55-75-MeV energy as they propagate through an undulator. Simultaneous detection of electron and photon spectra allows for precise comparison between experimental results and undulator theory. First- and second-order undulator radiation was detected. The agreement between experiment and theory and the exclusion of other effects proves that the observed radiation is generated in the undulator. Beyond that, this experiment introduces laser-accelerated electrons into the radio-frequency accelerator domain of synchrotron light sources. This marks a noticeable step toward a new, compact, and brilliant short-wavelength light source.

  • IEEE Transactions on Plasma Science 36(2008)4, 1773-1781
    ISSN: 0093-3813

Permalink: https://www.hzdr.de/publications/Publ-12307


4D in-beam PET of moving targets for different irradiation scenarios

Laube, K.; Bert, C.; Chaudhri, N.; Fiedler, F.; Parodi, K.; Rietzel, E.; Saito, N.; Enghardt, W.

Keywords: in-beam PET; moving targets; ion therapy

  • Contribution to external collection
    in: GSI Scientific Report 2008, Darmstadt: GSI, 2009

Permalink: https://www.hzdr.de/publications/Publ-12306


Characterization of neutron-irradiated ferritic model alloys and a RPV steel from combined APT, SANS, TEM and PAS analyses

Meslin, E.; Lambrecht, M.; Hernández-Mayoral, M.; Bergner, F.; Malerba, L.; Pareige, P.; Radiguet, B.; Barbu, A.; Gomez-Briceno, D.; Ulbricht, A.; Almazouzi, A.

Abstract

Understanding the behaviour of reactor pressure vessel (RPV) steels under irradiation is a mandatory task that has to be elucidated in order to be able to operate safely a nuclear power plant or to extend its lifetime. To build up predictive tools, a substantial experimental data base is needed at the nanometre scale to validate the theoretical models and to extract quantitative information on neutron irradiated materials. To reach this experimental goal, ferritic model alloys and French RPV steel were neutron irradiated in a test reactor at an irradiation flux of 9 x 1017 n.m-2.s, doses from 0.18 to 1.3 x 1024 n.m-2 and 300°C. The main goal of this paper is to report the characterisation of the radiation induced microstructural change in the materials by using the state of the art of characterisation techniques available in Europe at the nanometre scale. Possibilities, limitations and complementarities of the techniques to each other are highlighted.

  • Journal of Nuclear Materials 406(2010), 73-83
  • Lecture (Conference)
    15th Workshop of the International Group on Radiation Damage Mechanisms in Pressure Vessel Steels (IGRDM-15), 11.-16.10.2009, Budapest, Ungarn

Permalink: https://www.hzdr.de/publications/Publ-12305


On the correlation between irradiation-induced microstructural features and the hardening of reactor pressure vessel steels

Lambrecht, M.; Meslin, E.; Malerba, L.; Hernández-Mayoral, M.; Bergner, F.; Pareige, A. P.; Radiguet, B.; Almazouzi, A.

Abstract

A correlation is attempted between microstructural observations by various complementary techniques, which have been implemented within the PERFECT project and the hardening measured by tensile tests of reactor pressure vessel steel and model alloys after irradiation to a dose of ~71019 n cm-2. This is done, using the simple hardening model embodied by the Orowan equation and applying the most suitable superposition law, as suggested by a parametric study using the DUPAIR line-tension code. It is found that loops are very strong obstacles to dislocation motion, but due to their low concentration, they only play a minor role in the hardening itself. For the precipitates, the contrary is found, although they are quite soft (due to their very small sizes and their coherent nature), they still play the dominant role in the hardening. Vacancy clusters are important for the formation of both loops and precipitates, but they will play almost no role in the hardening by themselves.

  • Journal of Nuclear Materials 406(2010), 84-89

Permalink: https://www.hzdr.de/publications/Publ-12304


Cyclotron resonance absorption of 2D holes in strained InGaAs/GaAs quantum wells under high magnetic fields

Drachenko, O.; Kozlov, D.; Gavrilenko, V.; Maremyanin, K.; Ikonnikov, A.; Zvonkov, B.; Goiran, M.; Leotin, L.; Fasching, G.; Winnerl, S.; Schneider, H.; Wosnitza, J.; Helm, M.

Abstract

We report a systematic study of the cyclotron resonance (CR) absorption of two dimensional (2D) holes in strained InGaAs/GaAs quantum wells (QWs) in the quantum limit. The energies of CR transitions are traced as a function of magnetic field up to 55 T. A remarkable CR line splitting was evidenced when the resonant field exceeds 20 T. We analyze our date with a 4x4 Luttinger Hamiltonian including strain and QW potentials and find excellent agreement in the positions of the resonances. On the other hand, the spectral weight distribution of the split components suggests an inverted position of the two first Landau levels compared to the theoretical model.

Keywords: cyclotron resonance; strain; 2D holes; quantum wells

  • Poster
    Workshop of GDR-E "Semiconductor sources and detectors of THz frequencies", 26.-27.09.2008, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-12302


On the accuracy of range determination from in-beam PET data

Fiedler, F.; Shakirin, G.; Skowron, J.; Braess, H.; Crespo, P.; Kunath, D.; Pawelke, J.; Pönisch, F.; Enghardt, W.

Keywords: in-beam PET

  • Contribution to external collection
    in: GSI Scientific Report 2008, Darmstadt: GSI, 2009

Permalink: https://www.hzdr.de/publications/Publ-12301


Advanced laser driven accelerator concepts at the FZD

Schramm, U.

Abstract

Summary of laser acceleration projects to be performed at FZD

Keywords: laser particle acceleration; ELBE

  • Lecture (others)
    Laser Physics Seminar Univ. Twente, NL, 28.01.2009, Enschede, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-12299


Laser-accelerated ion beams for future medical applications

Kraft, S.

Abstract

Recent success in laser-driven particle acceleration has increased interest in laser-generated “accelerator-quality” beams, for example, protons and ions have been produced with up to several tens of MeV per nucleon, and with extremely low emittance (<0.01 mm mrad, normalized). Compact, high-gradient laser-accelerators are therefore now being discussed as a potentially viable technology for a host of particle-beam applications, including future compact medical accelerators for medical diagnostics and therapy. After commissioning of a 150 TW laser system at the FZD, a joint research center for radiation therapy with laser-accelerator ions is being established together with the OncoRay Center for Radiation Research in Oncology, and the University Clinic of the Technical University of Dresden. The present status and future plans of the center, and the results from first proton acceleration experiments at FZD will be presented.

  • Lecture (Conference)
    Second Internatioanl Symposium on Laser-Driven Relativistic Plasma Applied to Science, Industry and Medicine, 19.-23.01.2009, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-12298


Physikalisch- technische Vorbereitung von Zellbestrahlungen am intensiven Channeling-Röntgenstrahl der Strahlungsquelle ELBE

Zeil, K.

Abstract

Derzeit erfolgt im Forschungszentrum Dresden-Rossendorf (FZD) die schrittweise Inbetriebnahme und Erprobung der Strahlungsquelle ELBE, welche unter anderem intensive quasimonochromatische und in der Energie durchstimmbare Röntgenstrahlung durch Channeling relativistischer Elektronen in Diamantkristallen erzeugt. Im Rahmen strahlenbiologischer invitro Experimente soll diese zur Bestimmung der relativen biologischen Wirksamkeit (RBW) von Photonenstrahlung in Abhängigkeit von der Photonenenergie eingesetzt werden. Die hierzu notwendige Durchführung strahlenbiologischer Experimente und die Bestimmung von Dosis-Effekt-Kurven unter Berücksichtigung der Diversität lebender Zellen erfordern die Bestrahlung einer größeren Anzahl von Zellproben mit verschiedenen vorgegebenen Dosiswerten (ca. 0, 5 − 10 Gy) und für praktikable Bestrahlungsdauern eine Dosisleistung von 1 Gy/min. Gleichzeitig muss die auf die Zellproben übertragene Dosis exakt bestimmt und ihre räumliche sowie spektrale Verteilung charakterisiert werden. ...

  • Diploma thesis
    HU Berlin, 2007
    100 Seiten

Permalink: https://www.hzdr.de/publications/Publ-12297


Oncoray Retreat 2008: Laserteilchenbeschleunigung

Zeil, K.

Abstract

Presentation der Aktivitäten der Gruppe Laserteilchenbeschleunigung am FZD.

  • Invited lecture (Conferences)
    Oncoray Retreat 2009, 15.1.2009, Bautzen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12296


Detector response to ps electron bunches with high bunch charge

Zeil, K.

Abstract

Presentation of the scientific program of the Laser Particle Acceleration Group at the FZD as well as the status of the Laser lab. Then the major topic of the talk are measurements of detector response calibration to ps - pulses from the ELBE electron source with different electron bunch charges.

  • Invited lecture (Conferences)
    Radiation Protection Workshop, 16.12.2008, Chamonix, France

Permalink: https://www.hzdr.de/publications/Publ-12295


In-Medium QCD Sum Rules for omega Meson, Nucleon and D Meson

Thomas, R.

Abstract

The modifications of hadronic properties caused by an ambient nuclear medium are investigated within the scope of QCD sum rules. This is exemplified for the cases of the ω meson, the nucleon and the D meson. By virtue of the sum rules, integrated spectral densities of these hadrons are linked to properties of the QCD ground state, quantified in condensates. For the cases of the ω meson and the nucleon it is discussed how the sum rules allow a restriction of the parameter range of poorly known four-quark condensates by a comparison of experimental and theoretical knowledge. The catalog of independent four-quark condensates is covered and relations among these condensates are revealed. The behavior of four-quark condensates under the chiral symmetry group and the relation to order parameters of spontaneous chiral symmetry breaking are outlined. In this respect, also the QCD condensates appearing in differences of sum rules of chiral partners are investigated. Finally, the effects of an ambient nuclear medium on the D meson are discussed and relevant condensates are identified.

  • Other report
    Dresden: Technische Universität Dresden, 2008
    105 Seiten

Permalink: https://www.hzdr.de/publications/Publ-12294


QCD equation of state of hot deconfined matter at finite baryon density - A quasiparticle perspective

Bluhm, M.

Abstract

The quasiparticle model, based on quark and gluon degrees of freedom, has been developed for the description of the thermodynamics of a hot plasma of strongly interacting matter which is of enormous relevance in astrophysics, cosmology and for relativistic heavy-ion collisions as well. In the present work, this phenomenological model is extended into the realm of imaginary chemical potential and towards including, in general, different and independent quark flavour chemical potentials. In this way, nonzero net baryon-density effects in the equation of state are selfconsistently attainable. Furthermore, a chain of proximations based on formal mathematical manipulations is presented which outlines the connection of the quasiparticle model with the underlying gauge field theory of strong interactions, QCD, putting the model on firmer ground.
A comparison of quasiparticle model results with available lattice QCD data for, e. g., basic bulk thermodynamic quantities and various susceptibilities such as
diagonal and off-diagonal susceptibilities, which provide a rich and sensitive testing ground, is found to be successful. Furthermore, different thermodynamic quantities and the phase diagram for imaginary chemical potential are faithfully described. Thus, the applicability of the model to extrapolate the equation of state known from lattice QCD at zero baryon density to nonzero baryon densities is shown. In addition, the ability of the model to extrapolate results to the chiral limit and to asymptotically large temperatures is illustrated by confrontation with available first-principle lattice QCD results. These extrapolations demonstrate the predictive power of the model.
Basing on these successful comparisons supporting the idea that the hot deconfined phase can be described in a consistent picture by dressed quark and gluon degrees of freedom, a reliable QCD equation of state is constructed and baryon-density effects are examined, also along isentropic evolutionary paths. Scaling properties of the equation of state with fundamental QCD parameters such as the number of active quark flavour degrees of freedom, the entering quark mass parameters or the numerical value of the deconfinement transition temperature are discussed, and the robustness of the equation of state in the regions of small and large energy densities is shown. Uncertainties arising in the transition region are taken into account by constructing a family of equations of state whose members differ from each other in the specific interpolation prescription between large energy density region and a realistic hadron resonance gas equation of state at low energy densities.
The obtained family of equations of state is applied in hydrodynamic simulations, and the implications of variations in the transition region are discussed by considering transverse momentum spectra and differential elliptic flow of directly emitted hadrons, in particular of strange baryons, for both, RHIC top energy and LHC conditions. Finally, with regard to FAIR physics, implications of the possible presence of a QCD critical point on the equation of state are outlined both, in an exemplary toy model and for an extended quasiparticle model.

  • Other report
    Dissertation: Technische Universität Dresden, 2008
    155 Seiten

Permalink: https://www.hzdr.de/publications/Publ-12293


Uran(VI)-Sorption an Ton in An- und Abwesenheit von Huminsäure

Joseph, C.; Schmeide, K.; Sachs, S.; Bernhard, G.

Abstract

Die Endlagerung radioaktiver Abfälle steht im Mittelpunkt vieler politischer Debatten. Neben Salzstöcken (Gorleben, Asse) kommen in Deutschland auch Ton und Granit als Wirtsgestein für ein Endlager in Frage. Ton und Salz werden favorisiert und für eine bessere Entscheidungsfindung werden die Untersuchungen am Ton derzeit intensiviert. Schwerpunkt unserer Untersuchungen ist die Wechselwirkung von Uran(VI) mit Ton (Referenzton: Kaolinit; natürlicher Ton: Opalinuston, Mont Terri, Schweiz). Natürliche Tone können organische Substanzen, wie z. B. Humin- und Fulvinsäuren, enthalten. Aufgrund dessen wird in unseren Versuchen der Einfluss von Huminsäure auf die Uran(VI)-Ton-Wechselwirkung untersucht.

Zunächst wurde der Einfluss des Elektrolyten auf die Uran(VI)-Sorption an Kaolinit erforscht. Neben dem bisher in unseren Experimenten verwendeten NaClO4 [1], wurde synthetisches Opalinustonporenwasser (I = 0.42 M, pH 7.6) [2] untersucht. Es zeigte sich, dass bei Verwendung von Opalinustonporenwasser weniger Uran(VI) an Kaolinit sorbiert. Dieses Verhalten kann mit der Uran(VI)-Speziation erklärt werden. Der im Opalinustonporenwasser bei pH 7.6 vorliegende neutrale Ca2UO2(CO3)3-Komplex sorbiert schlechter als die in 0.42 M NaClO4-Lösung gebildeten geladenen Uranspezies UO2(CO3)34-, (UO2)2CO3(OH)3- und UO2(CO3)22-. Bei Anwesenheit von Huminsäure wird weniger Uran(VI) im NaClO4-System sorbiert, da es durch die Bildung von Uran(VI)-Humat-Komplexen mobilisiert wird und die Huminsäure mit dem Uran(VI) um Bindungsplätze auf dem Ton konkurriert. Durch Huminsäuresorption auf dem Ton stehen wiederum zusätzliche Uran(VI)-Bindungsstellen zur Verfügung und die Menge an sorbiertem Uran(VI) steigt mit steigender Huminsäurekonzentration. Im Opalinustonporenwassersystem ist jedoch kein signifikanter Einfluss von Huminsäure auf die Menge an sorbiertem Uran(VI) zu beobachten, da die Huminsäure keinen Einfluss auf die Uranspeziation in Opalinustonporenwasser bei pH 7.6 nimmt. Weiterhin wurden Kaolinit und Opalinuston hinsichtlich ihres Uran(VI)-Sorptionsvermögens in Opalinustonporenwasser verglichen. Es zeigt sich, dass mehr Uran(VI) an Kaolinit (2.8 ± 0.2 µg/m2) sorbiert als an Opalinuston (0.049 ± 0.002 µg/m2). Dieses Ergebnis ist unerwartet, da Opalinuston einerseits eine größere spezifische Oberfläche als Kaolinit besitzt, andererseits mehr Eisenminerale enthält, die sehr gut Uran(VI) sorbieren [3] können (Opalinuston: BET = 42 m2/g, 5 Gew.-% Fe; Kaolinit: BET = 11.7 m2/g, 0.27 Gew.-% Fe [1]). Der Grund für diesen Unterschied scheint somit im Anteil an Uran(VI) schlecht sorbierenden Mineralen im Opalinuston zu liegen, möglicherweise an Quarz [3].

[1] A. Křepelová et al., Radiochim. Acta 2007, 94, 825. [2] F.J. Pearson, PSI Internal Report TM-44-98-07 1998, Paul Scherrer Institut, Villigen, Schweiz. [3] K. Schmeide et al., Radiochim. Acta 2000, 88, 723.

Keywords: uranium(VI); clay; kaolinite; opalinus clay; sorption; speciation; opalinus clay pore water; humic acid

  • Lecture (Conference)
    Fachgruppentagung der GDCh-Fachgruppe Nuklearchemie, 30.08.-02.09.2009, Frankfurt/Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12290


Komplexierung von Curium(III) und Europium(III) mit organischen Liganden unter physiologischen Bedingungen – erste Hinweise auf ihre Speziation in Biofluiden

Heller, A.; Barkleit, A.; Bernhard, G.

Abstract

Curium und Europium sind zwei f-Elemente, deren Metabolismus im Biosystem bis heute nicht vollständig geklärt ist. Um diese Wissenslücke zu schließen, wurde das Komplexbildungsverhalten beider Metalle mit relevanten organischen Substanzen unter physiologischen Bedingungen bestimmt. Außerdem wurde die Speziation beider Ele-mente im menschlichen Urin untersucht.
Da Curium innerhalb des Kernbrennstoffzyklus gebildet wird und nur radioaktive Isotope aufweist, stellt es im Falle einer Kontamination oder unfallbedingter Freisetzung in die Umwelt eine ernste Gefahr für die Gesundheit dar. Um mögliche Dekontaminationsmittel zu erforschen, müssen daher sein Metabolismus und die Bindungsform in Biofluiden bekannt sein. Im Gegensatz dazu ist Europium nicht radioaktiv und gewinnt in der Medizin immer mehr an Bedeutung als Bestandteil von Kontrastmitteln in der bildgebenden Diagnostik. Trotz seiner wachsenden Applikation ist auch der Metabolismus dieses Metalls bisher unbekannt.
Beide Elemente weisen ähnliche Eigenschaften auf, da sie in Form ihrer dreiwertigen Ionen vergleichbare Elektronenkonfigurationen besitzen. Aufgrund seiner besseren Handhabbarkeit wird Europium daher oft als Analogon für Curium verwendet. Darüber hinaus weisen beide Elemente einzigartige Fluoreszenzeigenschaften auf. Dies erlaubt Untersuchungen mittels zeitaufgelöster laserinduzierter Fluoreszenzspektroskopie im Spurenkonzentrationsbereich.
Urin ist das Hauptausscheidungsmedium im menschlichen Körper und besteht zu über 90 % aus Harnstoff. Mögliche Reaktionen mit dieser Matrixkomponente wurden daher zuerst untersucht. Beide Metalle bilden Komplexe vom Typ ML 3+ und MLOH 2+, was zu signifikanten Änderungen in den Lumineszenzspektren führt, allerdings nur bei sehr hohem Harnstoffüberschuss Dies spricht ebenso für schwache Komplexe wie die sehr niedrigen Komplexbildungskonstanten.
Ein weiterer biologisch relevanter, organischer Ligand ist Citronensäure. Auch hier führte die Bildung verschiedener Komplexe vom Typ MLH2 2+, MLH +, ML2H 2- und ML bei beiden Elementen zu deutlichen Veränderungen im Lumineszenzspektrum, im Gegensatz zu Harnstoff aber schon bei der kleinsten Ligandkonzentration. Berücksichtigt man, dass Citronensäure in der Biosphäre weitverbreitet ist, spricht dies zusammen mit den hohen Komplexbildungskonstanten dafür, dass Citronensäure eine Hauptrolle bei der Curium- und Europiumspeziation in Biofluiden spielt.
Erste Aufnahmen von Lumineszenzspektren natürlicher, menschlicher Urinproben, die in vitro mit einem der beiden Elemente versetzt wurden, zeigen, dass bei niedrigeren pH-Werten Komplexe mit Citronensäure die Speziation dominieren. Im Gegensatz dazu scheinen bei höheren pH-Werten Komplexe mit anorganischen Liganden, die noch näher untersucht werden müssen, vorzuherrschen. Allgemein weisen Curium und Europium ähnliche Komplexbildung und Speziation auf, wobei das Lanthanid aber etwas stärkere Komplexe bildet als das Actinid.

Keywords: curium(III); europium(III); TRLFS; complexation; human biofluids; heavy metal speciation

  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2009, 30.08.-02.09.2009, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12289


Total neutron cross section measurements at nELBE

Junghans, A. R.; Altstadt, E.; Bemmerer, D.; Beyer, R.; Galindo, V.; Grosse, E.; Hannaske, R.; Marta, M.; Matic, A.; Nair, C.; Naumann, B.; Schilling, K. D.; Schneider, S.; Schlenk, R.; Schwengner, R.; Wagner, A.; Weiss, F.-P.; Mosconi, M.; Nolte, R.; Röttger, S.

Abstract

Total neutron cross section measurements at nELBE

  • Lecture (Conference)
    EFNUDAT progress and general assembly meeting, 01.-03.10.2008, Uppsala, Schweden

Permalink: https://www.hzdr.de/publications/Publ-12288


The fate of uraniumin phosphate-rich soils

Read, D.; Black, S.; Beddow, H.; Trueman, E.; Arnold, T.; Baumann, N.

Abstract

A number of industrial processes concentrate natural radionuclides to levels that cannot be disregarded on health or environmental grounds. These activites include mining of metalliferous and non-metalliferous ores; ore processing; oil and gas extraction; metal smelting and power production from coal (IAEA 2003; Ceccarello et al. 2004; Read et al. 2004). The phosphate industry, which encompasses fertilizer production, is another. Concern has been raised that the radiological consequences of such processes have been underestimated. While this is undoubtedly true in many cases, there is considerable debate as to whether the widespread application of fertilizer has any significant effect on human exposure or the broader environment. This paper adds to the debate by addressing the likely fate of uranium in phosphate-rich soil media.

  • Contribution to external collection
    L. J. De Kok, E. Schnug: Loads and Fate of Fertilizer-derived Uranium, AH Leiden: Backhuys Publishers BV, 2009, 978-90-5782-193-6, 65-71

Permalink: https://www.hzdr.de/publications/Publ-12287


P0703 - Verfahren zur Messung von lokalen Strömungsgeschwindigkeiten in flüssigen Schmelzen

Eckert, S.; Gerbeth, G.; Gundrum, T.

Abstract

Die Erfindung betrifft ein Verfahren zur Messung der Strömungsgeschwindigkeit in flüssigen Schmelzen in einem Temperaturbereich oberhalb von 200°C mit einem Ultraschallgenerator sowie zugehörigem Ultraschall-Wellenleiter nach dem Ultraschall-Doppler-Verfahren.
Mit der Erfindung soll eine gute Signalein- und -auskopplung gewährleistet werden. Erreicht wird das durch Herstellen der Benetzbarkeit der Stirnfläche des Ultraschallwellenleiters vor dem Messvorgang, anschließendes direktes Einkoppeln von Ultraschall-Messsignalen in die Schmelze unter einem Winkel verschieden von 90°, indem zumindest die Stirnfläche des Ultraschallwellenleiters in die Schmelze eingetaucht wird, und Auskoppeln der in der Schmelze reflektierten Ultraschallsignale über die Stirnfläche des Ultraschallwellenleiters und Weiterleitung derselben an eine Auswerteschaltung. Die Herstellung der Benetzbarkeit erfolgt durch mechanisches und chemisches Reinigen der Stirnfläche und nachfolgendes Beschichten derselben mit einem geeigneten Material.

  • Patent
    DE 10 2007 027 392 B3 - 2009.01.15
  • Patent
    WO 00 2008 152 025 A2 - 2008.12.18
  • Patent
    US 7950293 B2 - 31.05.2011
  • Patent
    KR101196407B1 - 25.10.2012

Permalink: https://www.hzdr.de/publications/Publ-12286


Inverse Compton backscattering source driven by the multi-10 TW laser installed at Daresbury

Priebe, G.; Laundy, D.; Macdonald, M.; Diakun, G.; Jamison, S.; Jones, L.; Holder, D.; Smith, S.; Phillips, P.; Fell, B.; Sheehy, B.; Naumova, N.; Sokolov, I.; Ter-Avetisyan, S.; Spohr, K.; Krafft, G.; Rosenzweig, J.; Schramm, U.; Gruner, F.; Hirst, G.; Collier, J.; Chattopadhyay, S.; Seddon, E.

Abstract

Inverse Compton scattering is a promising method to implement a high brightness, ultra-short, energy tunable X-ray source at accelerator facilities. We have developed an inverse Compton backscattering X-ray source driven by the multi-10 TW laser installed at Daresbury. Hard X-rays, with spectral peaks ranging from 15 to 30 keV, depending on the scattering geometry, will be generated through the interaction of laser pulses with electron bunches delivered by the energy recovery linac machine, initially known as energy recovery linac prototype and subsequently renamed accelerators and lasers in combined experiments. X-ray pulses containing 9 × 107 photons per pulse will be created from head-on collisions, with a pulse duration comparable to the incoming electron bunch length. For transverse collisions 8 × 106 photons per pulse will be generated, where the laser pulse transit time defines the X-ray pulse duration. The peak spectral brightness is predicted to be ~1021 photons/(s mm2 mrad2 0.1% Δλ/λ).

Keywords: ALICE; Compton scattering; Compton synchrotron radiation; Energy recovery linac; ERLP; Laser Compton scattering; Laser synchrotron radiation; Thomson scattering; Ultra-short X-ray pulses; X-ray source

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Permalink: https://www.hzdr.de/publications/Publ-12285


S-Layer basierte Forschungsarbeiten zur Eliminierung von Organika in Wasser

Raff, J.; Pollmann, K.

Abstract

Vorstellung der S-Layer basierten Forschungsarbeiten am Institut für Radiochemie zur Eliminierung von Organika in Wasser über fotokatalytische Verfahren

  • Lecture (others)
    Vortrag im Rahmen des Besuchs der IBL Umwelt- und Biotechnik GmbH, 21.01.2009, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12284


Anisotropic ion-enhanced diffusion during ion nitriding of single-crystalline austenitic stainless steel

Martinavicius, A.; Abrasonis, G.; Möller, W.; Templier, C.; Riviere, J. P.; Declemy, A.; Chumlyakov, Y.

Abstract

Nitrogen diffusion is investigated in single crystalline austenitic stainless steel AISI 316L (ASS) during ion beam nitriding and subsequent annealing at different crystalline orientations. After nitriding at 400ºC and ion energy of 1 keV, the N penetration depth depends significantly on the crystalline orientation, with the highest penetration depth for (001) orientation. The experimental observations are quantitatively reproduced by fitting using the model of diffusion under the influence of traps. During subsequent isothermal annealing, the N diffusion becomes significantly slower than during nitriding and independent of the orientation. Possible mechanisms of the anisotropic ion enhanced N diffusion are discussed.

Keywords: Stainless steel; Ion nitriding; AISI316L single crystal

  • Journal of Applied Physics 105(2009)9, 093502

Permalink: https://www.hzdr.de/publications/Publ-12283


Native Sn-Pb droplets in a zeolitic amygdale (Isle of Mull, Inner Hebrides)

Dekov, V. M.; Hålenius, U.; Billström, K.; Kamenov, G. D.; Munnik, F.; Eriksson, L.; Dyer, A.; Schmidt, M.; Botz, R.

Abstract

Despite the particular scientific interest in the elements with high affinity to S and O2, but found in zero-valence state in nature, the origin of these native minerals has been little explored and remains obscure. Here we describe unique Sn-Pb droplets found in a closed analcime-calcite amygdale collected from a basaltic unit cropping out at Carsaig Bay (Isle of Mull, Inner Hebrides). The droplets consist of intimate intergrowths of nearly pure Sn0 and Pb0 domains in proportion 88:12 and are enveloped in a thin, brownish, amber-like film of organic composition, which gives the impression of metallic “embryos” in organic “placenta”. The occurrence of the Sn-Pb droplets in a closed amygdale, their relationship with the host analcime+calcite and their Pb isotope composition (which does not match any known anthropogenic Pb source) rule out the possibility of anthropogenic contamination and support the natural origin of the Sn-Pb alloy.
The variable isotope (Pb, Sr, Nd) compositions in different members of the host basaltic sequence suggest that a parent basaltic magma was modified by crustal assimilation and post-emplacement alteration processes. Considering all possible scenarios, it appears that the most likely source of Pb for the Sn-Pb alloy is a discrete basaltic unit with an isotopic composition comparable to the Antrim basalts (Northern Ireland). The amygdale phases, on the other hand, show isotopic evidence for incorporation of elements from both local basaltic and sedimentary units. The apparent isotopic disequilibrium between Sn-Pb droplets and amygdale phases indicates a complex, multi-stage fluid evolution. The occurrence of Sn-Pb droplets in organic capsules suggests that the droplets and the enveloping organic substances are co-precipitates. This implies that the transportation and deposition of Sn and Pb might have occurred through organometallic compounds. We assume interaction of seawater fluids carrying metals leached from basaltic rocks with hydrocarbons from sedimentary units as a prerequisite for the formation of the organometallic complexes. The zeolites lining the basaltic vesicles might have destabilized the migrating organo- Sn and Pb compounds causing their breakdown and precipitation of Sn-Pb alloy.

Keywords: Sn-Pb alloy; organometallic compounds; Isle of Mull; Inner Hebrides

Permalink: https://www.hzdr.de/publications/Publ-12282


Tracked megawatt PV plants: Operation results 2008 in Germany and Spain

Rindelhardt, U.; Dietrich, A.; Rösner, C.

Abstract

An increasing number of 2-axis tracked Megawatt PV plants have been put into operation during the last years. The higher final yield of such plants (compared to plants with fixed generator orientation) must be paid with higher plant costs and larger area consumption. The absolute yield is determined by the insolation conditions at the sites. The paper compares design and operation results of four 2-axis tracked plants operating in Germany and Spain in 2008, which are representative PV sites in Europe.

The plant locations are distributed between 37 and 50 degrees northern latitude (Fig.1), in South Spain and Central Germany. Some technical features of the investigated plants are given in the table below.

plant total power /MW tracker Plant area/m² module supplier
Borna 3.44 Solon 210000 Solon
Penig 0,2 Deger 22000 Sanyo,Sharp,SunLink
Alqueria 1.02 Solon 125000 Solon
Ventanas 1.01 Solon 102000 Solon

The used tracker systems differ in their construction and in the applied tracking principle. Whereas the Solon mover (Fig. 2) follows every 10 minutes the astronomic sun path, the Deger tracker (Fig. 3) tries to find the optimal generator position also at cloudy conditions. The tracker distance varies between the both used tracker types and the sites. The most plants started their operation in 2007. The operation of the plants was monitored by the owners or by professional service providers.

The operation results of the year 2008 are exemplarily presented. The solar irradiance in 2008 in Germany was higher than the long year average, similar to the years before. The final yield of the both plants is about 1300 kWh/kW (Fig. 4), with an advantage of 8 % for the plant using Deger trackers. The annual performance ratio was fond to be 82 %.
The yields of the Spain plants exceed the yield of the German plants with 2250 kWh/kW by more than 70 %. Only in one month (May) the yield of the German reaches the yield of the Spain plants due to the extraordinary insolation in Germany (high) and Spain (low), respectively. The performance ratios of the Spain plants were also about 82 %.
A number of operation details will be given.
Finally a long term estimation of the yield for the different plants will be given.

Keywords: PV plants; tracked systems; performance

  • Lecture (Conference)
    24th European Photovoltaic Solar Energy Conference and Exhibition, 21.-25.09.2009, Hamburg, Deutschland
  • Contribution to proceedings
    24th European Photovoltaic Solar Energy Conference and Exhibition, 21.-25.09.2009, Hamburg, Deutschland
    Proceedings CD-ROM, contribution 5AO.8.5, 3-936338-25-6

Permalink: https://www.hzdr.de/publications/Publ-12281


Beltline welding seam and base metal investigations of a WWER-440/230 reactor pressure vessel from the former Greifswald NPP

Rindelhardt, U.; Schuhknecht, J.; Viehrig, H.-W.

Abstract

Nuclear plants operators must demonstrate that the structural integrity of the nuclear reactor pressure vessel (RPV) is assured during routine operations or under postulated accident conditions. Russian type WWER reactors are operated in Russia and many other European countries like Ukraine, Finland, Czech Republic and Hungary. Surveillance specimens programmes for inspection of aging of the RPV materials were implemented for the second generation (213) of WWER-440 reactors.
The paper presents results of the circumferential core weld SN0.1.4 and the base metal ring 0.3.1 of the RPV from the unit 1 of the Greifswald WWER-440/230. The investigated trepans represent the irradiated-annealed-re-irradiated (IAI) condition. The working program is focussed on the characterisation of the RPV steels through the RPV wall. The key part of the testing is aimed at the determination of the reference temperature T0 following the ASTM Test Standard E1921-05 to determine the fracture toughness in different thickness locations. It is shown that the Master Curve approach as adopted in ASTM E1921 is applicable to the investigated original WWER-440 weld and base metal.
The evaluated T0 varies through the thickness of the welding seam. The lowest T0 value was measured in the root region of the welding seam representing a uniform fine grain ferritic structure. The highest T0 of the weld seam was not measured at the inner wall surface. This is important for the assessment of ductile-to-brittle temperatures measured on sub size Charpy specimens made of weld metal compact samples removed from the inner RPV wall. Our findings imply that these samples may not represent the most conservative condition. The Charpy transition temperature TT41J estimated with results of sub size specimens after the recovery annealing was confirmed by the testing of standard Charpy V-notch specimens. The evaluated transition temperature of 51°C is close to the estimated critical embitterment temperature for the initial condition TK0 of the welding seam SN0.1.4.
The T0 from the trepan 1-4 of base metal ring 0.3.1 varies through the thickness of the welding seam. T0 decreases from -124°C at the inner surface to -90°C at a distance of 33 mm from it and again to -113°C at the outer RPV wall. The KJc values generally follow the course of the MC, although the scatter is large. The re-embrittlement during 2 campaigns operation can be assumed to be low. Hence, the variation of T0 measured through the thickness of the base metal ring 0.3.1 results basically from differences in the structure. With metallographic characterization the scatter of the MC will be investigated.
The Charpy transition temperature TT41J estimated with results of sub size specimens after the recovery annealing was confirmed by the testing of standard Charpy V-notch specimens.

Keywords: Russian WWER-type reactor; WWER; reactor pressure vessel steel; weld metal; trepans; fracture toughness; Master Curve

  • Lecture (Conference)
    6th International Scientific and Technical Conference “Safety Assurance of NPP with WWER”, 26.-29.05.2009, Podolsk, Russian Federation
  • Contribution to proceedings
    6th International Scientific and Technical Conference “Safety Assurance of NPP with WWER”, 26.-29.05.2009, Podolsk, Russian Federation
    Conference CD, Podolsk

Permalink: https://www.hzdr.de/publications/Publ-12280


Neutron fluence calculations for embrittlement surveillance specimens in VVER-1000

Konheiser, J.; Mittag, S.; Zaritsky, S.

Abstract

Neutron fluence spectrum calculations have been performed for the reactor pressure vessel of a VVER-1000, applying the Monte Carlo code TRAMO. Activities measured earlier in Balakovo-1 by fluence monitors, placed in special Charpy surveillance containers, are compared to TRAMO results. The average deviation from the measurements is about 5 %. A good agreement of the fluence spectra near the RPV inner side, at the height of the core beltline, to the spectra at the Charpy probe positions on top of the radial reflector has been demonstrated.

Keywords: Neutron Fluence Calculation; Surveillance specimens; VVER-1000; Monte-Carlo; TRAMO

  • Annals of Nuclear Energy 36(2009)8, 1235-1241

Permalink: https://www.hzdr.de/publications/Publ-12279


High pressure materials for energy storage. The case of V2O5

Arroyo-De Dompablo, M. E.; Amador, U.; Gallardo–Amores, J. M.; Baehtz, C.; Biskup, N.; Morán, E.

Abstract

The high pressure polymorph of V2O5 is investigated as example of a high-pressure material (HP-V2O5) with potential applications in electrochemical devices, such as lithium batteries. HP-V2O5 reversibly intercalates up to 2 lithium ions down to 1 Volt vs Li+/Li. The typical voltage-composition profile of HP-V2O5 shows distinct features than that of the ambient pressure polymorph, AP-V2O5. Remarkably, the specific capacity retention with cycling of HP-V2O5 // Li cells (250 Ah/Kg at a C/3.5 rate) is comparable to that of the ambient pressure polymorph. Furthermore, the measured resistivities at room temperature (10000 Ωcm in AP and 400 Ωcm in HP) reveal that HP-V2O5 is a better electronic conductor than AP-V2O5. The enhanced electronic conductivity of HP-V2O5 is an advantage for electrochemical applications.

Keywords: in-situ diffraction; lithium ion battery; synchrothron

Permalink: https://www.hzdr.de/publications/Publ-12278


Thermal “order-disorder” behaviour in (Na1-xKx)4B8O14 solid solutions investigated by X-ray powder diffraction

Georgievskaya, M.; Albert, B.; Bubnova, R.; Cordier, G.; Baehtz, C.; Filatov, S.

Abstract

In the potassium-rich part of the binary system Na4B8O14-K4B8O14 solid solutions have been found that can be described with the formula (Na1-xKx)4B8O14 with 0.45 ≤ x < 1.0. The crystal structures of (Na0.25K0.75)4B8O14 and (Na0.45K0.55)4B8O14 were refined at room temperature by the Rietveld method. The solid solutions crystallize like K4B8O14 in the triclinic crystal system, space group P-1, with K partially substituted for Na.
An ordered distribution of the alkali atoms over the four cation sites at room temperature has been discovered. The structure of (Na0.25K0.75)4B8O14 was also refined for data collected at 300 and 500°C. The refinements show that sodium and potassium atoms are less ordered at higher temperatures.

Keywords: borates; solid solutions; Rietveld refinement; structure refinement; high temperatures

Permalink: https://www.hzdr.de/publications/Publ-12277


TOPFLOW hot leg model experiments: Overview, examples, status of data analysis and future work

Vallee, C.; Seidel, T.; Lucas, D.

Abstract

The presentation gives an overview about the experiments performed in the hot leg model built in in the pressure vessel of the TOPFLOW facility.
These experiments were conducted in a flat test-section representing a model of the hot leg of a pressurised water reactor. The region of the elbow and of the steam generator inlet chamber is equipped with glass side walls in order to allow high-speed video observations of the two-phase flow in this region. The used fluids were air and water at ambient temperature and pressures up to 0.5 MPa as well as steam and saturated water at pressures up to 5.0 MPa and temperatures up to 264°C. Four types of experiments were performed: experiments without water circulation, co-current flow experiments, steady counter-current flow experiments and counter-current flow limitation (CCFL) experiments. The test procedures, detailed test matrices and selected examples of the measurements are shown.
The current status of data analysis is presented. Data sheets were arranged in order to give an overview of the 191 runs. The water level measured during co-current flow experiments was analysed over probability distributions. Furthermore, the flooding characteristics of the hot leg model was determined and a new parameter is proposed to correlate the data. Finally, a first approach for the interface detection in high-speed camera images was presented.
In the next future, the acquired data will be compared with CFD calculations for validation purposes.

Keywords: hot leg; pressurised water reactor; PWR; two-phase flow; counter-current flow; counter-current flow limitation; CCFL

  • Lecture (others)
    15th Meeting of the German CFD Network, 21.-22.01.2009, Garching, Germany

Permalink: https://www.hzdr.de/publications/Publ-12276


High-temperature thermal expansion and structural behaviour of stromeyerite, AgCuS

Trots, D. M.; Senyshyn, A.; Mikhailova, D. A.; Knapp, M.; Baehtz, C.; Hoelzel, M.; Fuess, H.

Abstract

Results of simultaneous thermal analysis, synchrotron and neutron powder diffraction in the range from room temperature up to the melting point at 936 K on non-superionic orthorhombic β-AgCuS as well as on superionic hexagonal α- and cubic δ-AgCuS are reported. On heating the sample is only stable in argon. The following phase transitions occur in AgCuS at elevated temperatures: β 361 K −→ α 399 K −→ α + δ 439 K −→ δ. The volume changes at the superionic β −→ α and α −→ δ phase transitions are about 2.3 and 0.6%. The volume thermal expansion coefficients are 26 × 10−6, 130 × 10−6 and 85 × 10−6 K−1 for the pure β-, α-and δ-phases, respectively. Models forthe average structures of α-and δ-AgCuS are proposed and discussed. Ionic conductivity in δ-AgCuS may originate from cation jumps in ‘skewed’ (100) directions between nearest-neighbour tetrahedral sites via the peripheries of the octahedral cavities. A correlation between the temperature dependence of the cation redistribution in δ-AgCuS and the temperature dependence of the ionic conductivity is assumed. A two-dimensional nature of the ionic conductivity due to cation jumps in slabs perpendicular to the c-direction is supposed for α-AgCuS. There is no evidence for ionic diffusion through the (1/2, 1/2, 1/2) site in (111) directions in either superionic α-or δ-phases.

Keywords: XRD phase transition AgCuS

Permalink: https://www.hzdr.de/publications/Publ-12275


Annual Report 2007 - Institute of Radiation Physics

Kämpfer, B.

Abstract

activities etc. in line of previous reports. In 2007, the various research directions were organized and performed in four departments: radiation physics, biophysics (both belonging to the program Life Science), nuclear physics and hadron physics (both belonging to Structure of Matter). A substantial part of the institute’s tasks is the performance and further development of the radiation source ELBE, for which a fifth department is responsible. Besides providing secondary beams for radiation physics and biology, nuclear and hadron physics, ELBE is used by groups from other institutes of the Forschungszentrum Dresden-Rossendorf, too in parts in common projects and by external users. Beamtime is used extensively by outside users while all beam time requests have been rated by an international advisory committee.
Some highlights in 2007 related to ELBE have been: first electron beam from superconducting HF gun, first pulsed fast neutron beams from nELBE, and first experiments with single electron pulses of high bunch charge (cell irradiation for radiobiological studies). These achievements are not yet documented in this report.

  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2008
    72 Seiten
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-12274


Labeling of peptides and proteins with 18F via click chemistry using a novel prosthetic group 4-[18F]fluoro-N-methyl-N-(prop-2-ynyl)benzenesulfonamide

Ramenda, T.; Knieß, T.; Steinbach, J.; Wüst, F.

Abstract

Ziel/Aim:

The radiolabeling of peptides or proteins with the short-lived positron emitter 18F requires rapid and mild reaction conditions compatible with the structural and functional integrity of these biopolymers. Over the last two years several approaches have been published focusing on the application of copper(I)-mediated 1,3-dipolar [3+2]cycloaddition of azides and alkynes for labeling peptides with 18F. The peptides were functionalized with an azide- or alkyne group to be reacted with an appropriately 18F-labeled azide or alkyne, respectively. We report on the radiosynthesis of a novel alkine containing 18F-labeled prosthetic group having the advantage of a stable aromatic 18F-label and low lipophilicity caused from the sulfonamide backbone. First applications for click chemistry by labeling azide-functionalized phosphopeptides and human serum albumin (HSA) are demonstrated.

Methodik/Methods:

Two labeling precursors containing different leaving groups (nitro- and trimethylammoniumtriflate) and the reference substance were prepared by the reaction of N methylpropargylamine with the corresponding sulfonic acid chlorides. Radiofluorination was performed in a single step on an automated synthesizer. After purification on semi-preparative HPLC click reaction was performed with a phosphopeptide and the HSA protein. Peptide and protein have been modified with an azide linker. Click reaction occurs in the presence of copper(I) salts and in combination with different copper-chelating ligand systems.

Ergebnisse/Results:

The radiolabeled sulfonamide can be obtained in radiochemical yields of 19 % (d. c.) in high radiochemical purity of > 99 % after HPLC purification within 84 min. First promising results in labeling an azide modified phosphopeptide and protein via click chemistry gave labeling yields about 42 % for posphopeptides after semi-preparative HPLC and about 31 % for HSA after size exclusion chromatography.

Schlussfolgerungen/Conclusions:

The novel prosthetic group 4-[18F]fluoro-N-methyl-N-(prop-2-ynyl)benzenesulfonamide for peptide and protein labeling with 18F via click chemistry can be prepared in reasonable radiochemical yields and high radiochemical purity. Moreover, by this method for the first time click chemistry was successfully applied to the 18F-labeling of a phosphopeptide and a protein. The radiopharmacological investigation of the 18F-labeled phoshopeptides and HSA including metabolic stability, biodistribution and cell uptake studies is in progress.

  • Lecture (Conference)
    47. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 22.-25.04.2009, Leipzig, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 48(2009)2, A38
    ISSN: 0029-5566

Permalink: https://www.hzdr.de/publications/Publ-12273


Die Relevanz der Borflüchtigkeit bei Langzeittransienten in einem mit Bor vergifteten Siedewasserreaktor

Laczko, G.; Böhlke, S.; Ohlmeyer, H.; Schuster, C.; Hurtado, A.

Abstract

Die Analyse der Reaktivitätswirksamkeit der Boreinspeisung am SWR erfolgt im Rahmen einer sich im Abschluss befindlichen Dissertation an der Technischen Universität Dresden. Die Finanzierung dieses Vorhabens nahm Vattenfall Europe Nuclear Energy (VENE) GmbH über den Kompetenzverbund Kerntechnik wahr. Innerhalb dieses Projektes wurde die Flüchtigkeit des Bors aus Boratlösungen in Abhängigkeit der Einflussgrößen Borkonzentration, Temperatur, pH-Wert und Volumendampfgehalt aus Zweiphasenströmungen experimentell bestimmt. Aus den Messwerten erfolgte die Ableitung empirischer Funktionen, welche für Simulationsrechnungen mit System-Codes und einfache Abschätzungen nutzbar sind [BoB08].

Keywords: Boreinspeisung am SWR; Zweiphasenströmung; Simulationsrechnung

  • Lecture (Conference)
    Jahrestagung Kerntechnik 2009, 12.-14.05.2009, Dresden, Deutschland
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2009, 12.-14.05.2009, Dresden, Deutschland
    Tagungsband der Jahrestagung Kerntechnik 2009, paper 311, Berlin: INFORUM GmbH

Permalink: https://www.hzdr.de/publications/Publ-12272


Im Kern - Energie

Weiß, F.-P.; Hurtado, A.

Abstract

Weltweit sind derzeit 439 Kernkraftwerke in Betrieb, in Deutschland waren es noch 17 Anlagen. Diese 17 Anlagen haben im Jahre 2007 22,1% des gesamten in Deutschland erzeugten Stromes geliefert. An der Grundlast macht der Strom aus Kernenergie sogar 45% aus.
Die Bundesregierung hat den Ausstieg aus der Nutzung der Kernenergie zum Zwecke der Stromerzeugung beschlossen, weltweit zeichnet sich jedoch ein erheblicher Ausbau der Kernenergie ab. Im Oktober 2008 waren 36 Anlagen im Bau und 99 weitere in Planung.
Vor diesem Hintergrund geht der Vortrag auf die physikalischen und technischen Grundlagen der friedlichen Nutzung der Kernenergie, der Sicherheitsprinzipien sowie auf die mit dem Betrieb von Kernkraftwerken verbundenen Risiken im Vergleich zu anderen Formen der Stromerzeugung ein. Dabei wird auch der Beitrag der Kernenergie zu CO2-Vermeidung dargestellt. Darüber hinaus werden Aspekte der Brennstoffversorgung, insbesondere der Reichweiter des Urans, und der Abfallentsorgung beleuchtet.

Keywords: Strom aus Kernenergie; Brennstoffversorgung; CO2-Vermeidung; Abfallentsorgung

  • Invited lecture (Conferences)
    Im Kern - Energie Veranstaltungsreihe der Katholischen Akademie, 11.11.2008, Katholische Akademie Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12271


Impossibility to describe repulsion with contact interaction

Morawetz, K.; Maennel, M.

Abstract

Contact interactions always lead to attractive behaviour. Arguments are presented to show why a repulsive interacting system, e.g. Bose gases, cannot be described by contact interactions and corresponding treatments are possibly obscured by the appearance of bound states.

Permalink: https://www.hzdr.de/publications/Publ-12270


Application of a step-wise verification and validation procedure to the 3D neutron kinetics code DYN3D within the European NURESIM project

Rohde, U.; Mittag, S.; Grundmann, U.; Petkov, P.; Hadek, J.

Abstract

The generic strategy of core physics codes benchmarking which has been elaborated within the European NURESIM code platform development was applied to benchmarking of the 3D neutron kinetics code DYN3D for applications to VVER-type reactors. Numerical and experimental benchmark problems were considered for code verification and validation.
Mathematical problems with given cross sections are used for the verification of the mathematical methods applied e.g. in nodal codes against finite difference solutions.
After minimisation of numerical errors, modelling errors have to be considered. Diffusion approximation and homogenisation error are due to simplified physical approaches and can be estimated by comparing diffusion solutions with more accurate Monte Carlo or deterministic transport solutions.
A series of 2D whole core benchmarks for different core loadings and operational conditions for VVER-1000 reactors was defined for this purpose. Reference transport solutions were calculated by the MARIKO and APOLLO codes based on Method of Characteristics. Homogenised two-group and few-group diffusion parameters were derived from the reference solutions and used as cross section data for the nodal diffusion code DYN3D. The DYN3D solutions were compared to the reference solution. It was shown that the homogenisation error can be significantly reduced, if Assembly Discontinuity Factors (ADF) and Reference Discontinuity Factors (RDF) which are obtained from the transport solution by applying equivalence theory are used.
A study using the multi-group version of DYN3D has shown that increasing the number of groups in the considered cases has only a small effect in comparison with homogenisation error.
Experimental problems are used for code validation. Experimental data for VVER reactors, which were used for the benchmarking of the DYN3D code within NURESIM, are power distribution measurements at the full-size (VVER-1000) experimental facility V-1000, which have been well documented within the EC project VALCO, and kinetic experiments at the LR-0 zero power reactor in NRI Řež.
The code DYN3D has proved to be an effective tool for steady-state and kinetics core calculations. The high accuracy of the code is based on the advanced nodal method “HEXNEM2”, multi-group approach, applying discontinuity factors, and intra-nodal flux reconstruction.

Keywords: reactor physics; neutron kinetics; verification; validation; benchmarking; diffusion theory; homogenisation

  • Lecture (Conference)
    17th International Conference on Nuclear Engineering ICONE17, 12.-17.07.2009, Brussels, Belgium
  • Contribution to proceedings
    17th International Conference on Nuclear Engineering ICONE-17, 12.-16.07.2009, Brussels, Belgium
    CD-ROM paper 75446

Permalink: https://www.hzdr.de/publications/Publ-12269


Switching Ti Valence in SrTiO3 by a dc Electric Field

Leisegang, T.; Stöcker, H.; Levin, A. A.; Weißbach, T.; Zschornak, M.; Gutmann, E.; Rickers, K.; Gemming, S.; Meyer, D. C.

Abstract

A (001) SrTiO3 wafer has been investigated in situ at room temperature under application of a static electric field of varying polarity by the fluorescence X-ray Absorption Near Edge Structure (XANES) analysis at the Sr-K and Ti-K absorption edges. The XANES spectra show a clear shift of the Ti-K absorption edge energy. The shift is attributed to a change of the Ti valence state in a volume invoked by diffusion of the oxygen ions and vacancies. No shift was observed for the Sr-K absorption edge energy. Theoretical calculations support these findings.

Keywords: functional oxide; density-functional; XANES; electric field; strontium titanate

Permalink: https://www.hzdr.de/publications/Publ-12268


On the effect of spatial discretization in integral transport calculations with HELIOS 1.9

Merk, B.; Weiß, F. P.

Abstract

In this study the consequences of the discretization effect is investigated for the full calculation chain starting with the steady state calculation continuing with the burnup calculations and finishing with the evaluation of the safety coefficients. The investigation is based on Mixed Oxide (MOX) Fuel with reactor grade Plutonium. Detailed evaluation of the convergence behavior, the influence of the discretization on the neutron spectrum and the isotopic composition during burnup is given. Finally the influence on the few group cross section preparation and an estimation of the influence of discretization on the safety coefficients is shown.

Keywords: Cell- and Lattice calculation; cross section preparation; HELIOS; Discretization; Burnup calculation; Depletion; Safety coefficients

  • Contribution to proceedings
    XXI International Conference on Transport Theory, 12.-17.07.2009, Torino, Italy

Permalink: https://www.hzdr.de/publications/Publ-12267


A three scale expansion solution for the Telegrapher’s equation with external source: development and first application

Merk, B.; Glivici, V.; Weiß, F. P.

Abstract

This work presents a improved onset for the analysis of experiments by the development of an analytical approximation solution for a space-time dependent P1 neutron transport problem in a one dimensional system consisting of homogenized medium with a central external source with Green's functions. The delayed neutron production is implemented in two additional time scales with the multiple scale expansion method. The approximation solutions are developed for the switch off of the source. First applications are shown for the analysis of the YALINA Booster experiment.

Keywords: Time dependet neutron transport; Accelerator driven system; Experimental analysis; Green's funtion expansion; YALINA experiment

  • Contribution to proceedings
    XXI International Conference on Transport Theory, 12.-17.07.2009, Torino, Italy
  • Lecture (Conference)
    XXI International Conference on Transport Theory, 12.-17.07.2009, Torino, Italy

Permalink: https://www.hzdr.de/publications/Publ-12266


ATWS analysis for PWR using the coupled code system DYN3D/ATHLET

Kliem, S.; Mittag, S.; Rohde, U.; Weiß, F.-P.

Abstract

The ATWS transient “Loss of main feed water supply” in a generic four-loop PWR at the nominal power of 3750 MW was analyzed using the coupled code system DYN3D/ATHLET. A variation of the MOX-fuel-assembly portion in the core has an effect on the reactivity coefficients of the fuel temperature and the moderator density. These two parameters mainly influence the behaviour of the coolant pressure, which is safety-relevant. It has been demonstrated that the pressure maximum decreases with an increasing portion of MOX. For all core loadings considered, both primary-circuit mechanical integrity and sufficient core cooling are guaranteed.

Keywords: reactor safety; MOX, reactivity; temperature-feedback; thermal-hydraulics; transient

Permalink: https://www.hzdr.de/publications/Publ-12265


Evaluation leistungsbezogener Budgetierungsmodelle

Gilge, B.; Joehnk, P.

Abstract

Wird die an öffentlich finanzierten außeruniversitären Forschungseinrichtungen zunehmend wichtiger werdende Programmbudgetierung durch eine leistungsbezogene Budgetierung ergänzt, kann die durch das Neue Steuerungsmodell geforderte Wirkungsorientierung der Ressourcenallokation forciert werden. Darüber hinaus ermöglicht die Übernahme von Kriterien der externen Evaluierung in die budgetierungsrelevanten Leistungsindikatoren eine Verknüpfung zwischen externen Anforderungen der Träger der Einrichtungen und internen Leistungsanreizen. Mit dem vorliegenden Beitrag wird eine Evaluationskonzeption vorgestellt, mit welcher das leistungsbezogene Budgetierungsmodell einer öffentlich finanzierten außeruniversitären Forschungseinrichtung bewertet sowie verbessert werden kann.

  • Wissenschaftsmanagement 4(2008), 12-19

Permalink: https://www.hzdr.de/publications/Publ-12264


Preparatory Grants for Collaboratory European Research Projects

Joehnk, P.

  • Lecture (Conference)
    Bioingteh - The exploratory Workshop on Advanced Materials & Technologies in Biology and Medicine, 18.-20.09.2008, Poiana Brasov, Romania

Permalink: https://www.hzdr.de/publications/Publ-12263


High-resolution hydrogen profiling in AlGaN/GaN heterostructures grown by different epitaxial methods

González-Posada Flores, F.; Redondo-Cubero, A.; Gago, R.; Bengoechea, A.; Jiménez, A.; Grambole, D.; Braña, A. F.; Muñoz, E.

Abstract

Hydrogen (H) incorporation into AlGaN/GaN heterostructures used in high electron mobility transistors, grown by different methods, is studied by high-resolution depth profiling. Samples grown on sapphire and Si(1 1 1) substrates by molecular-beam epitaxy and metal–organic vapour phase epitaxy; involving H-free and H-containing precursors, were analysed to evaluate the eventual incorporation of H into the wafer. The amount of H was measured by means of nuclear reaction analysis (NRA) using the 1H(15N,αγ )12C reaction up to a depth of ∼110 nm into the heterostructures. Interestingly, the H profiles are similar in all the samples analysed, with an increasing H content towards the surface and a negligible H incorporation into the GaN layer (0.24 ± 0.08 at%) or at the AlGaN/GaN interface. Therefore, NRA shows that H uptake is not related to the growth process or technique employed and that H contamination may be due to external sources after growth. The eventual correlation between topographical defects on the AlGaN surface and the H concentration are also discussed. (Some figures in this article are in colour only in the electronic version)

Keywords: PACS: GaN; AlGaN; Hydrogen; NRA; HEMT; AFM; MOCVD; MBE

Permalink: https://www.hzdr.de/publications/Publ-12262


Experimental studies and CFD calculations for buoyancy driven mixing phenomena

Da Silva, M. J.; Thiele, S.; Höhne, T.; Vaibar, R.; Hampel, U.

Abstract

In nuclear reactor safety the mixing of borated and deborated water is a critical issue that needs investigation, assessment and prediction. Such mixing is buoyancy driven and numerical codes must correctly model momentum transfer between components of different density. To assess and develop CFD models for buoyancy driven mixing we set up a simple vertical mixing test facility (VeMix) and equipped it with a newly developed planar electrical imaging sensor. This imaging sensor acquires conductivity images of the liquid at the rear channel wall with a speed of 2,500 frames per second. By adding NaCl tracer to the denser component we were able to visualize the mixing process in high spatial and temporal detail. Furthermore, an image processing algorithm based on the optical flow concept was implemented and tested which allows the measurement of flow pattern velocities. Selected experiments at different Richardson numbers were run with two components of different density (pure water and glucose-water mixture) simulating borated and deborated water in a light water reactor scenario. These experiments were compared to CFD calculations using standard turbulence models. Good agreement between experimental data and first CFD simulations was found.

Keywords: buoyancy driven flow; mixing; deborated water; flow visualization; CFD; simulation; planar array sensor

  • Nuclear Engineering and Design 240(2010)9, 2185-2193

Permalink: https://www.hzdr.de/publications/Publ-12261


Collisional Energy Loss: A Welcoming Component for Jet Quenching Phenomenology in Heavy-Ion Collisions

Mustafa, M.

  • Lecture (others)
    Universität Gießen, 10.09.2008, Gießen, Deutschland
  • Lecture (others)
    Seminar am Max-Planck-Institut fuer extraterrestrische Physik, 11.09.2008, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12260


Strongly Coupled QGP - Equation of State

Bluhm, M.

  • Lecture (Conference)
    Workshop of the European Network SIM, 08.-12.09.2008, Villasimius, Italien

Permalink: https://www.hzdr.de/publications/Publ-12259


Nuclear data needs for transmutation of nuclear waste

Ignatyuk, A.

  • Lecture (others)
    Seminar FWK, 10.04.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12258


Quantal Rotation: Molecular view on nuclei

Frauendorf, S.

  • Lecture (others)
    Seminar FWK, 30.04.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12257


Exotic modes of rotation

Frauendorf, S.

  • Lecture (others)
    Seminar FWK, 04.06.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12256


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