Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34800 Publications

The Waldenburg beakers and Johann Kunckel: Analytical and technological study of four corner-cut colored glasses

Richter, R.; Neelmeijer, C.

The provenance of at least five out of seven variously colored glass beakers in the collection of the Naturalienkabinett Waldenburg (Saxony) indicates their relation to the famous glass chemist Johann Kunckel. The technological characteristics of four corner-cut glasses, which show a ruby-rose, transparent blue-green, transparent dark purple, respectively an opaque striated brownish-red color, are described. Crizzling phenomena, cracking due to frozen strains and inhomogeneous coloring were closer examined with a light microscope and under a short-wave UV-lamp.
Combined simultaneous PIXE and PIGE analysis conducted at the Helmholtz-Zentrum Dresden-Rossendorf allowed the detection of all glass constituents from lead up to boron in elemental concentrations above c. 0.01 w%. Different types of potassium-rich crystal glasses with varying amounts of calcium, arsenic and lead were found. There is evidence for the use of highly refined raw materials and the addition of various ionic and colloidal glass colorants.
The Waldenburg beakers seem to be early examples of Kunckel’s experimental efforts to establish elevated standards for the production of luxury glass in northern Europe, as additionally supported by accounts in his publications from the years between 1678 and 1716.

Keywords: Waldenburg; Kunckel; glass; beakers; PIXE; PIGE; ion beam analysis

  • Lecture (Conference)
    IIC Congress - The Decorative: Conservation and the Applied Arts, 10.-14.09.2012, Wien, Österreich
  • Studies in Conservation 57(2013)S1, 234-243
    DOI: 10.1179/2047058412Y.0000000033

Publ.-Id: 16143

Techniques for image based in-vivo dosimetry: from particle therapy PET to in-beam prompt gamma imaging

Fiedler, F.; Dersch, U.; Golnik, C.; Helmbrecht, S.; Kormoll, T.; Kunath, D.; Laube, K.; Müller, A.; Priegnitz, M.; Rohling, H.; Schöne, S.; Enghardt, W.

Radiation therapy is an important treatment modality in cancer therapy. New radiation species, like protons and light ions have the potential to increase tumor conformality of irradiation. Because of the way these particles deposit energy on their path through tissue they allow for an increased dose deposition in the tumor volume and reduce the damage of the surrounding normal tissue.
Such high precision radiotherapy treatment requires efficient quality assurance techniques. Small changes in the irradiated volume will lead to a mismatch of the deposited dose maximum and the tumor. This causes missing dose in the tumor volume and potential damage to healthy tissue. Therefore, a dose monitoring system is highly desirable. Between 1997 and 2008, the in-beam Positron Emission Tomography (PET) method was used at the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany, for monitoring the dose delivered by 12C beams (cf. figure 1). The spatial distribution of positron emitters generated via nuclear interactions between projectile ions and atomic nuclei of the tissue is measured during and shortly after the irradiation. Due to different physical processes for dose deposition and activity production a simulation of the expected activity is required. By means of a comparison between measured and simulated activity distribution conclusions on the accuracy of the dose localization can be drawn. Since ion therapy is normally applied during a fractionated treatment over more than 15 days, detected deviations can be corrected for in the following fractions. Different modalities of PET, i.e. measuring during the irradiation versus taking data after the treatment have been compared. Since the positive clinical impact of the method has been shown, an in-room PET/CT will be installed for the same purpose at the Dresden Proton Therapy facility. Recent investigation and limits of the PET method used for in vivo dose monitoring at ion beams will be presented and discussed.

Due to inherent physical restrictions of this method, a direct quantification of the delivered dose is not feasible. Therefore, another approach based on dose monitoring by detection of prompt gamma rays is currently under investigation. In contrast to PET this method relies on the detection of prompt gamma rays emitted almost instantaneously during the therapeutic irradiation. These gammas are expected to possess a wide energy range between 0 and 10 MeV. To measure these photons a Compton camera design was evaluated with respect to the special requirements and conditions that arise from this application (cf. figure 1). Different concepts were compared by means of simulation. The complete chain from simulation based on the treatment plan to the iterative reconstruction of the data was developed and is now under optimization. First measurements have been successfully performed with radioactive sources and ion beams. Results of the first test of this prototype at a proton beam will be shown.

Keywords: in vivo dosimetry; ion beam therapy

  • Lecture (Conference)
    International Conference on Translational Research in Radio-Oncology and Physics for Health in Europe ICTR-PHE, 27.02.-02.03.2012, Geneva, Switzerland
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 102(2012), S40-S41

Publ.-Id: 16142

Photon induced positron annihilation spectroscopy: A nondestructive method for assay of defects in large engineering materials

Pujari, P. K.; Sudarshan, K.; Tripathi, R.; Dutta, D.; Maheshwari, P.; Sharma, S. K.; Srivastava, D.; Krause-Rehberg, R.; Butterling, M.; Anwand, W.; Wagner, A.

This paper describes a new methodology for volumetric assay of defects in large engineering materials nondestructively. It utilizes high energy photons produced by nuclear reaction to create positrons in situ whose fate is followed using conventional positron spectroscopic techniques. The photon induced positron annihilation (PIPA) spectroscopy system has been set-up using a Folded Tandem Ion Accelerator (FOTIA). Possibility of using prompt gamma-rays produced in nuclear reactions 27Al (1H,γ)28Si and 19F(1H,γ)16O have been examined. The reaction 19F(1H,γ)16O is seen to provide higher photon flux and measurements have been carried out in large samples of metals and polymers. We could establish good sensitivity of the technique as well as reproducibility in a number of samples. This technique has been used to carry out defect studies in cold worked Zircaloy-2 plates. The measured S-parameter, indicative of defect concentration, was seen to correlate well with the measured residual stress using X-ray technique. The results were validated by gamma-induced positron annihilation lifetime measurements at ELBE LINAC based GiPS facility.

Keywords: Photon induced positron annihilation; defects; 19F(1H; alphaγ)16O reaction; large samples; in- situ positron production

Publ.-Id: 16141

Crystallographic superstructure in R2PdSi3 compounds (R=heavy rare earth)

Tang, F.; Frontzek, M.; Dshemuchadse, J.; Leisegang, T.; Zschornak, M.; Mietrach, R.; Hoffmann, J.-U.; Löser, W.; Gemming, S.; Meyer, D. C.; Loewenhaupt, M.

The R2PdSi3 intermetallic compounds have been reported to crystallize in a hexagonal AlB2-derived structure, with the rare earth atoms on the Al sites and Pd and Si atoms randomly distributed on the B sites. However, the intricate magnetic properties observed in the series of compounds have always suggested complications to the assumed structure. To clarify the situation, x-ray and neutron diffraction measurements were performed on the heavy rare earth compounds with R=Gd, Tb, Dy, Ho, Er, Tm, which revealed the existence of a crystallographic superstructure. The superstructure features a doubled unit cell in the hexagonal basal plane and an octuplication along the perpendicular c direction with respect to the primitive cell. No structural transition was observed between 300 and 1.5 K. Extended x-ray absorption fine structure (EXAFS) analysis as well as density functional theory (DFT) calculations were utilized to investigate the local environments of the respective atoms. In this paper the various experimental results will be presented and it will be shown that the superstructure is mainly due to the Pd-Si order on the B sites. A structure model will be proposed to fully describe the superstructure of Pd-Si order in R2PdSi3. The connection between the crystallographic superstructure and the magnetic properties will be discussed in the framework of the presented model.


Publ.-Id: 16140

Multifunctional oxides and the influence of defects on the ferroic properties

Gemming, S.; Weissbach, T.; Zschornak, M.; Stöcker, H.; Meyer, D. C.; Leisegang, T.; Ronneberger, I.; Potzger, K.

Transition metal oxides exhibit a wealth of physical phenomena, among them ferroic properties such as ferroelasticity, ferroelectricity and ferromagnetism, or their combination in multiferroics. In addition, transition metal oxides are sensitive to the chemical environment via the external partial pressure of oxygen; changes induce stoichiometry deviations, which cause conductivity changes and modify the ferroic characteristics. Ternary and quaternary compounds from the perovskite family will be discussed as examples, which correlate local changes due to point and planar defects with changes of the elastic, polarization and magnetic properties. The microscopic interactions are determined by density functional calculations, which yield the basis for more large-scale simulations with effective Hamiltonian approaches. Under oxygen-poor conditions, oxygen vacancies in SrTiO3 accumulate in an external electric field and reduce the hardness. In an Sr/O-rich environment the phases SrO(SrTiO3)n are formed, which yield a distinct change of the X-Ray reflectivity due to the regular arrangement of extrinsic SrO(001) stacking faults. YMn2O5 has a series of complex antiferromagnetic phases in coexistence with ferroelectricity. In YFeMnO5, only one commensurable ferrimagnetic phase was found and ferroelectricity is absent. Based on spin-polarized DFT calculations a Heisenberg model yields the coupling constants of the Fe-substituted and the mangenese-only compounds and relates them to
crystal-field interactions. BiFeO3 is a rhombohedral multiferroic with several domain wall configurations. Among them, the 109° and 180º degrees walls have a significant change in the component of their polarization perpendicular to the wall; the corresponding step in the electrostatic potential is consistent with a recent report of electrical conductivity at the domain walls. Changes in the Fe-O-Fe bond angles at the walls change the canting of the Fe magnetic moments which can enhance the local magnetization.

Keywords: multiferroic; ferroelectric; perovskite; defects; domain wall; boundary; point defect; conductance; density-functional theory; ion-beam

  • Poster
    Joint Meeting of the DGK, DMG and ÖMG, 20.-24.09.2011, Salzburg, Österreich

Publ.-Id: 16139

Modeling Bubbly-Cap Flows Using Two-Group Average Bubble Number Density

Yeoh, G. H.; Cheung, S.; Tu, J.; Krepper, E.; Lucas, D.

The basic concept of two-group average bubble number density equations along with three-fluid model has been demonstrated for vertical gas-liquid flow. Specifically, the current study focused on:
(i) classification of bubble interaction between spherical bubbles (Group-1) and cap bubbles (Group-2),
(ii) preliminary consideration of source and sink terms in the averaged bubble number density equations via the model of Hibiki and Ishii [1] and (iii) assessment by means of experimental data sets at bubbly-to-cap flow transition. Reasonable agreement was achieved between measured and predicted distributions of void fraction, interfacial area concentration (IAC) and volume equivalent bubble diameter.

Keywords: CFD; two-phase flow; bubble number density

  • Contribution to proceedings
    The 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14, 25.-30.09.2011, Toronto, Canada
    Proceedings of the 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics (NURETH-14)

Publ.-Id: 16138

Bio-precipitation of uranium by two bacterial isolates recovered from extreme environments as estimated by potentiometric titration, TEM and X-ray absorption spectroscopic analyses

Merroun, M. L.; Nedelkova, M.; Ojeda, J. J.; Reitz, T.; Fernandez, M. L.; Arias, J. M.; Romero-Gonzalez, M.; Selenska-Pobell, S.

This work describes the mechanisms of uranium biomineralization at acidic conditions by Bacillus sphaericus JG-7B and Sphingomonas sp. S15-S1 both recovered from extreme environments. The U bacterial interaction experiments were performed at low pH values (2.0-4.5) and using 0.1 M NaClO4 as electrolyte background where the uranium aqueous speciation is dominated by the free uranyl ion. As demonstrated by X-ray absorption (XAS) studies, the cells of the studied strains precipitated uranium at pH 3.0 and 4.5 as a uranium phosphate mineral phase belonging to the meta-autunite group. The observed U(VI) biomineralization was associated with the activity of indigenous acid phosphatase detected at these pH values without the supply of an organic phosphate substrate. At pH 2.0, however, no uranium biomineralization occurred, and U(VI) formed complexes with organically bound phosphates of the cells. Transmission electron microscopic (TEM) analyses showed strain-specific localization of the uranium precipitates. In the case of B. sphaericus JG-7B U(VI) was bound to the cell wall while in the case of Sphingomonas sp. S15-S1, U(VI) precipitates were found not only on the cell surface but also intracellularly. This study contributes to the expansion of the number of bacterial strains that have been demonstrated to precipitate uranium phosphates at acidic conditions via the activity of acid phosphatase.

Keywords: Uranium biomineralization; Potentiometric titration; XAS; TEM/EDX; Acid phosphatase

Publ.-Id: 16137

Chemische Aspekte der Korrosion von feuerverzinkten Einbauten im Containment eines Druckwasserreaktors nach einem Kühlmittelverluststörfall

Hoffmann, W.; Kryk, H.

Bei einem Kühlmittelverluststörfall (Loss of coolant Accident LOCA) eines Druckwasserreaktors (DWR) können sich in der Anfangsphase an den Sumpfansaugsieben des Notkühlsystems Mineralwolleablagerungen aus dem Isolationsmaterial der Anlagenkomponenten bilden und dadurch die Notkühlung beeinträchtigen. Im weiteren Verlauf des Störfalles verursacht das borsäurehaltige Primärkühlmittel eine Korrosion an Einbauten im Containment, die überwiegend aus feuerverzinktem Stahl bestehen. Feste Korrosionsprodukte bewirken in diesem Falle durch Anlagerung an die Mineralwolleablagerungen einen Anstieg des Differenzdrucks über den Sumpfansaugsieben, der bis zur Blockade und dem Ausfall der Notkühlung führen kann.
Zur Untersuchung der chemischen Aspekte dieses Vorgangs wurde im HZDR eine Laborversuchsanlage (KorrVA) errichtet, in welcher die Korrosion verzinkter Materialproben unterschiedlicher Größe und Geometrie bei verschiedenen Anströmbedingungen des borsäurehaltigen Kühlmittels und bei Temperaturen bis 70°C untersucht werden kann. Volumen, Durchfluss, Größe von Proben und Sumpfansaugsieb sowie dessen Belegung wurden skaliert an den Verhältnissen eines typischen DWR-Sumpfes nach einem LOCA.
Dabei sind verschiedene Einflüsse auf die Korrosion zu beobachten, die von der Zusammensetzung des Mediums (Borsäurekonzentration, pH-Anhebung durch LiOH-Zusatz), Temperatur des Mediums, Größe und Geometrie der Probe sowie auch von der Anströmung durch das Medium abhängen und einen unterschiedlichen Differenzdruckverlauf bewirken.
Ausgehend vom Schichtaufbau der Feuerverzinkung konnte der Ablauf der Korrosion aufgeklärt werden, wobei zunächst lösliche Korrosionsprodukte des Zinks entstehen und erst nach Freilegung von Stahl Rost gebildet wird, der sich am Faserbett anlagern kann. Die Ergebnisse, die auf den Analysen von Lösungen und Ablagerungen auf den Faserbetten und den Untersuchungen der Metallproben nach Ende der Versuche beruhen, stehen in Übereinstimmung mit dem Differenzdruckanstieg als technisch wichtigem Parameter, der im Wesentlichen durch Rost verursacht wird. Die anfangs starke Korrosion unter Bildung von Zinkionen bedingt eine Zunahme des pH-Werts, die aber zu einer wesentlichen Verringerung der Korrosionsrate führt. Bei ausreichender Zinkmenge kommt die Korrosion nahezu zum Erliegen. Im weiteren Verlauf bilden sich aber auch an der Oberfläche des Zinks weiße Korrosionsprodukte.
Entscheidend für den Ablauf der Korrosion sind neben dem Angebot an Zinkoberfläche besonders die Strömungsverhältnisse und die Zusammensetzung des Primärkühlmittels nach lokaler Freilegung des Basismaterials. Verursacht wird eine Verblockung des Faserbetts nicht nur durch eine Bildung von Rost sondern erst durch dessen Transport und Ablagerung am Fasermaterial.

Keywords: LOCA; corrosion; galvanized steel; boric acid; sumpscreen clogging

  • Invited lecture (Conferences)
    Zittauer Kraftwerkschemisches Kolloquium, 22.-23.09.2011, Lückendorf, Deutschland
  • Contribution to proceedings
    Zittauer Kraftwerkschemisches Kolloquium, 22.-23.09.2011, Lückendorf, Deutschland
    Tagungsband zu Aspekte der Kerntechnikforschung

Publ.-Id: 16136

Intersubband transitions and quantum cascade lasers

Helm, M.

Intersubband transitions and quantum cascade lssers

Keywords: intersubband transition; qantum cascade laser; infrared; terahertz

  • Invited lecture (Conferences)
    TeraNano PIRE Kickoff meeting, 07.-08.10.2011, Houston, USA

Publ.-Id: 16135

Flow accelerated corrosion of galvanized steel in boric acid solution

Hoffmann, W.; Kryk, H.

Corrosion products of hot-dip galvanized steel containment internals may cause serious problems during a loss-of-coolant accident (LOCA) at a nuclear power plant by clogging insulation debris laden sump strainers of the emergency core cooling system. The chemical and physical conditions influence the formation and deposition of the sparingly soluble corrosion products. In nearly neutral boric acid media, the corrosion starts by a dissolution process of zinc. A fast local coolant flow accelerates the dissolution of Zn (flow accelerated corrosion) and leads to rust formation on steel rapidly. Additionally, the local flow conditions prevent the known cathodic protection mechanism of zinc on steel. Furthermore, a sufficient flow impact is presumed to transport the rust particles into the insulation fibres mats on the strainers where they may blocked in the worst case. As a result of fibre bed analyses, corrosion products of iron and not of zinc are regarded as the main source of clogging. The mechanism of zinc dissolution in the absence of other anions can be explained by formation of borate ions originate from boric acid as a coolant ingredient in pressurized water reactors (PWR).

Keywords: flow accelerated corrosion; zinc; boric acid; LOCA

  • Poster
    EUROCORR 2011, 04.-08.09.2011, Stockholm, Sweden
  • Contribution to proceedings
    EUROCORR 2011, 04.-08.09.2011, Stockholm, Sweden

Publ.-Id: 16134

Microbial structure of biofilm communities in an uranium contaminated acid mine drainage environment

Wobus, A.; Zirnstein, I.; Meierhöfer, C.; Arnold, T.; Krawczyk-Bärsch, E.; Röske, I.

Investigations of bacterial composition of biofilm samples from uranium contaminated underground mine Königstein by molecular methods and FISH.

  • Poster
    Jahrestagung der Vereinigung für Allgemeine und Angewandte Mikrobiologie (VAAM), 03.-06.04.2011, Karlsruhe, Germany

Publ.-Id: 16133

Dose controlled radiobiological experiments with an ultra-short pulse laser accelerated proton beam

Schramm, U.

Talk on prospects of laser proton acceleration for applications in oncology.

Keywords: Laser accelerated protons; oncology; cell irradiation

  • Invited lecture (Conferences)
    2nd ELI beamlines scientific challenges meeting, 05.-06.10.2011, Prague, Czech Republic

Publ.-Id: 16132

S-layer proteins as binding matrix for sensory layers

Weinert, U.; Müller, N.; Günther, T.; Pollmann, K.; Raff, J.

The idea is use S-layer proteins as binding matrix to couple aptamers and fluorescence dyes in a sequential way. This sensory layer will be able to detect very small amounts of analyte in aqueous environment. The fluorophores which are able to perform a FRET serve as optical system whereas aptameres work as specific receptor for one analyte.

Keywords: S-layer proteins; sensory layer; FRET; aptamer

  • Poster
    6th PhD Seminar, 05.-07.10.2011, Sporthotel Rabenberg, Deutschland

Publ.-Id: 16131

Bio-basierte Konzepte zur Gewinnung von Metallen aus Mineralien

Pollmann, K.; Raff, J.; Kutschke, S.

Biotechnologische Methoden zur Metallgewinnung; Vortrag zum 1. Workshop des Innovationsforums Geobiotechnologie

  • Invited lecture (Conferences)
    1. Workshop des Innovationsforums Geobiotechnologie, 10.-11.10.2011, Aue, Deutschland

Publ.-Id: 16130

Comparison of dopamine turnover, dopamine influx constant and activity ratio of striatum and occipital brain with F-18-dopa brain PET in normal controls and patients with Parkinson's disease

Oehme, L.; Perick, M.; Beuthien-Baumann, B.; Wolz, M.; Storch, A.; Loehe, M.; Herting, B.; Langner, J.; van den Hoff, J.; Reichmann, H.; Kotzerke, J.

The aim of the study was to estimate normal ranges and test-retest measures for various parameters characterising dopamine metabolism from a prolonged F-18-dopa positron emission tomography (PET) measurement using a reference tissue model and compare their value for the detection of early Parkinson's disease (PD).
Healthy volunteers (n = 9) and patients (n = 36) in an early stage of PD underwent an F-18-dopa PET measurement lasting 4 h. The influx rate constant k(occ) and the effective distribution volume ratio (EDVR, its inverse is an indicator for dopamine turnover) were estimated by a graphical approach using dynamic data in the striatum and, as a reference region, the occipital cortex. Furthermore, ratios of activity concentrations between striatum and occipital brain taken for three time intervals completed the data analysis. All parameters were determined both in eight small volumes of interest placed in the striatum as well as averaged for caudate nucleus and putamen. For the control group, reproducibility was checked in a second study 3 months later and ranges for normal values were derived from mean +/- 2 standard deviations. Receiver-operating characteristic (ROC) analyses were performed to assess the value of the parameters for diagnostic purposes.
Patients with early-stage PD and healthy volunteers could be separated by the values of the putamen, not the caudate nucleus. The normal ranges of the putamen were 0.0151-0.0216/min for the influx rate constant k(occ) and 2.02-3.00 for EDVR. For the various time intervals used the striato-occipital ratios yielded 2.24-3.06, 2.43-3.42 and 2.35-3.21, respectively. Patients were characterised by significantly lower values (p < 0.001) and significant differences between ipsi- and contralateral sides (p < 0.001) with regard to their clinical symptoms and a rostrocaudal gradient. EDVR as well as k(occ) for the putamen were able to effectively differentiate between groups (sensitivity > 97%, specificity 100%). In contrast, striato-occipital ratios showed a sensitivity of about only 85%.
For clinical applications, our data do not demonstrate any superiority of the EDVR determination compared to influx rate constant, while requiring long and tedious acquisition protocols. The normal range estimates do not represent absolute quantitative measures for dopamine metabolism but are specific for the chosen acquisition and processing procedures.

Keywords: F-Dopa; PET; Normal values; Parkinson’s disease; Dopamine turnover

Publ.-Id: 16129

Coordination chemistry of bis(2-pyridylimine) ligands with Ag(I): formation of two structurally different coordination polymers and one metallocycle controlled by linker and the solvent system

Jeazet, H. B. T.; Mizera, J.; Doert, T.; Gloe, K.; Heine, A.; Bernhard, G.; Gloe, K.

Reaction of equimolar amounts of AgCIO and bis[4-(2-pyridylmethyleneamino)phenyl] methane (L1) or bis[4-(2-pyridylmethyleneamino)phenyl] ether (L2) in a 1:1 solvent mixture of CH3CN and CH2CL2 leads to the formation of two infinite coordination polymers of the composition {[Ag(L1)]ClO4•CH3CN}n (1) and {[Ag(L2)]ClO4•CH2Cl2}n (2). Whereas 1 represents a homochiral single-stranded helicate the related complex 2 shows a typical zigzag chain arrangement. Both structures are characterized by a distorted tetrahedral coordination environment of the Ag(I) centres each based on a N4 coordination pattern of two ligand molecules. The resulting strands are connected by a hydrogen bonding network including ClO4¯ anions and solvent molecules forming 2-D layers. Additional π-π and CH- π interactions between the aromatic parts of the ligand molecules give a 3-D arrangement of the packing. In contrast, a discrete dinuclear metallocycle, [Ag2(L2)2](ClO4)2•CH3OH (3), has been formed by reaction of AgClO4 with L2 when CH2Cl2 in the solvent mixture was replaced by CH3OH. Again each Ag(I) has a distorted tetrahedral geometry and is coordinated to two pyridylimine units of two ligand molecules. Additional weak hydrogen bonds involving perchlorate and solvent molecules as well as edge-to-face and face-to-face π-π interactions allow a 3-D packing arrangement.

Publ.-Id: 16128

Revisiting temporal accuracy in neutronics/T-H code coupling using the NURESIM LWR simulation platform

Zerkak, O.; Gajev, I.; Manera, A.; Kozlowski, T.; Gommlich, A.; Zimmer, S.; Kliem, S.; Crouzet, N.; Zimmermann, M.

The first part of the paper reviews the different temporal coupling methodologies that are currently employed for the transient simulation of LWR cores. The second part shows preliminary results from the implementation of some suggested coupling improvements, including high-order corrections to the exchanged coupling fields and a dynamic time step control technique.

  • Lecture (Conference)
    14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14, 25.-30.09.2011, Toronto, Canada
  • Contribution to proceedings
    14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14, 25.-30.09.2011, Toronto, Canada
    Proceedings of the 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, paper 484

Publ.-Id: 16127

GDCh Working Group “Analytical Methods using Radionuclides and High-performance Sources”

Denecke, M. A.; Merchel, S.; Eberhardt, K.

The working group “Analytical Methods using Radionuclides and High-performance Sources” (in German: Analytik mit Radionukliden und Hochleistungsstrahlenquellen, ARH) of the German Chemical Society (in German: Gesellschaft Deutscher Chemiker, GDCh) is supported by the GDCh Groups Nuclear Chemistry, Analytical Chemistry, Macromolecular Chemistry, Solid State Chemistry and Materials Research and the Wöhler Association of Inorganic Chemistry.

The ARH working group aims at promoting and supporting the use of radionuclides especially for quality assurance of other analytical methods and analytical methods using large research facilities including synchrotron, neutron and ion sources. The main specific objectives and tasks of ARH are:

  • Dissemination of scientific methodology and experience, knowledge transfer
  • Coordination and promotion of analytical work with radioactive substances
  • Utilization of radio-analytical methods by improving access to radiation facilities, associated instrumentation and isotope laboratories
  • Facilitate access to high-performance radiation sources
  • Contribution to quality assurance and validation in analytical methods
  • Establishment and reinforcing contacts with other scientific associations
  • Organization of scientific conferences and meetings

The ARH is continually growing, with the largest relative growth of student members over the past six years. You can become a member of the ARH working group if you belong to one of the supporting GDCh Groups listed above, are an interested company, which is a corporate GDCh member, or are an associated GDCh member in Germany or abroad (note, this is with limited member rights). Members of the German Physical Society (DPG) are also welcome to join the ARH working group with guest status.

More information can be found at our website

Keywords: neutron source; accelerator; synchrotron radiation

  • Poster
    3rd ANKA / KNMF Joint Users Meeting, 13.-14.10.2011, Karlsruhe-Neureut, Deutschland

Publ.-Id: 16126

Using Monte-Carlo Simulations to implement corrections for I-124 as a non-pure positron emitter in small animal and human PET imaging

Sauerzapf, S.; Thomas, L.; Behe, M.; Weber, W.; Pietrzyk, U.; Zakhnini, A.; Mix, M.

Using I-124 for PET imaging applications implies some difficulties concerning the image quality: The resolution is degraded by the large maximum positron energy of 2.1 MeV and the resultant long positron range. In addition I-124 is a non-pure PET isotope exhibiting additional gamma ray emissions with high contributions to the total decay scheme: 602.72 keV with 63% and 722.78 keV with 10.35%. These fractions cannot be quantified exactly in PET measurements. Therefore in our work we utilized GATE 6.1 [1] to investigate the effects of these supplementary “false” coincidences on a spectral, sinogram- and image-based basis. Three PET systems were modeled with GATE and confirming measurements were accomplished on them: Two small animal PET scanners (ClearPET and MicroPET) and one human scanner (Gemini TF). Derived from the simulated energy spectra, we propose narrower energy window configurations for the ClearPET and the Gemini TF in order to minimize the amount of false coincidences. Separating the simulated sinograms for true and false coincidences revealed that a two-component correction for I-124 has to be implemented. A homogenous background subtraction has to be amended by a part which considers an additional portion within the phantom borders.
[1] S. Jan et al.: GATE V6: a major enhancement of the GATE simulation platform enabling modelling of CT and radiotherapy. Phys. Med. Biol. (56) (2011) 881-901

  • Poster
    2011 IEEE Nuclear Science Symposium and Medical Imaging Conference, 23.-29.10.2011, Valencia, Spain

Publ.-Id: 16125

Optimierung der Kleintierbildgebung mit nichtreinen Positronenstrahlern

Sauerzapf, S.; Zakhnini, A.; Behe, M.; Weber, W.; Pietrzyk, U.; Mix, M.

Die lange Halbwertszeit des Radionuklids I-124 (4,18d) ermöglicht es langsame biochemische Prozesse über einen längeren Zeitraum zu quantifizieren, als dies mit herkömmlichen reinen Positronenstrahler, wie beispielsweise F-18, der Fall ist. Nachteilig beim komplexen Zerfallsschema von I-124 sind neben der geringen Positronenausbeute von 22,8% zusätzlich koinzident emittierte Gammalinien. Mit Energien von z.B. 602.72keV und 722.78keV liegen sie in den Energiefenstern der verwendeten Kleintier-PET-Scannern. Ziel dieser Arbeit war es, einerseits die Datenakquisition bzgl. der Wahl des Energiefensters zu optimieren und andererseits Korrekturen zur Bildverbesserung direkt in die Datenrekonstruktion einzuarbeiten.

  • Lecture (Conference)
    Dreiländertagung der ÖGMP, DGMP und SGSMP, 28.09.-01.10.2011, Wien, Österreich

Publ.-Id: 16124

Nanoscale characterization of ODS Fe-9%Cr model alloys compacted by spark plasma sintering

Heintze, C.; Hernández-Mayoral, M.; Ulbricht, A.; Bergner, F.; Shariq, A.; Weissgärber, T.; Frielinghaus, H.

Ferritic/martensitic high-chromium steels are leading candidates for fission and fusion reactor components. Oxide dispersion strengthening is an effective way to improve properties related to thermal and irradiation-induced creep and to extend their elevated temperature applications. An extensive experimental study focusing on the microstructural characterization of oxide-dispersion strengthened Fe-9wt%Cr model alloys is reported. Several material variants were produced by means of high-energy milling of elemental powders of Fe, Cr and commercial yttria powders. Consolidation was based on spark plasma sintering. Special emphasis is placed on the characterization of the nano-particles using transmission electron microscopy, small-angle neutron scattering and atom probe tomography. The microstructure of the investigated alloys and the role of the process parameters are discussed. Implications for the reliability of the applied characterization techniques are also highlighted.

Publ.-Id: 16123

Nanoindentation of ion-irradiated FeCr alloys

Heintze, C.

Ferritic/martensitic high-chromium steels are candidate structural materials for future nuclear applications for reasons such as resistance to swelling, irradiation creep and oxidation but suffer hardening and embrittlement due to neutron irradiation. Ion irradiation has been proven to be a useful tool to simulate neutron irradiation effects without the drawbacks of producing radioactive material and being restricted to time consuming and expensive in-reactor irradiations. In the present work ion-irradiation in combination with nanoindentation has been applied to study the irradiation-induced hardening of binary Fe-Cr alloys and 9% Cr steels. The details of the approach are specified and the effects of Cr content and irradiation conditions including both single-beam and dual-beam irradiations are considered. Transmission electron microscopy is used to characterize irradiation-induced defects. Ion-irradiation-induced hardening is compared to hardening observed after neutron irradiation at similar conditions and dominant hardening mechanisms are identified in terms of obstacle strength.

  • Invited lecture (Conferences)
    Workshop on Ion Implantation as a Neutron Irradiation Analogue, 26.-28.09.2011, Oxford, United Kingdom

Publ.-Id: 16122

Nanoindentation of Fe-Cr alloys ion-irradiated up to 50 dpa

Heintze, C.

Ferritic/martensitic high-chromium steels are candidate structural materials for future nuclear applications such as fusion and generation IV fission reactors. Nevertheless these steels suffer hardening and embrittlement due to neutron irradiation. Ion irradiation is an efficient tool to simulate neutron irradiation effects without the drawbacks of producing radioactive material. In the present work ion-irradiation in combination with nanoindentation has been applied to study the irradiation-induced hardening of binary Fe-Cr alloys and 9% Cr steels. The details of the approach are specified and the effects of Cr content and irradiation conditions including both single-beam and dual-beam irradiations are considered. Transmission electron microscopy is used to characterize irradiation-induced defects. Ion-irradiation-induced hardening is compared to hardening observed after neutron irradiation at similar conditions and dominant hardening mechanisms are identified.

  • Lecture (Conference)
    18th Workshop on Multiscale Modelling and Basic Experiments of Iron-Chromium Alloys for Nuclear Applications, 04.-05.05.2011, Dresden, Deutschland

Publ.-Id: 16121

ECCS strainer clogging due to corrosion of hot-dip galvanized steel containment internals

Kryk, H.; Hoffmann, W.

Damage to fibrous insulation materials located near to a LWR primary circuit coolant leak may compromise the operation of the emergency core cooling system, if insulation fibers are transported to the containment sump strainers, where they may block or penetrate the strainers. Beside insulation material, other forms of debris may influence the sump strainer clogging behavior as well as the cooling water chemistry. Especially, the long-term contact of the water jet from the leak with hot-dip galvanized steel grating treads installed in the containment may cause corrosion of the corresponding materials. Subsequently, the formation of particulate corrosion products may occur by spalling of solid corrosion products from the metallic surfaces or precipitation of solids from the liquid phase. In the event of a LOCA, such processes may lead to an accelerated clogging of the fiber-laden sump strainers. This is especially important in PWRs, where post-LOCA corrosion is accelerated due to the specific primary coolant water chemistry.
Detailed experimental investigations regarding the influence of corrosion processes on the chemical composition of the coolant as well as on the strainer clogging behavior were established within a research project funded by the BMWi, where the priority of the presented investigations is given to the mechanisms that cause sump strainer clogging. As a result of corrosion experiments in the lab-scale KorrVA test facility using hot-dip galvanized steel as well as pure steel samples, it was found that the increase of the head loss is mainly caused by the flow-accelerated corrosion of the base material (steel) whereas the corrosion of the zinc coating leads to soluble corrosion products influencing the cooling water chemistry. Depending on the hydrodynamic conditions, the particulate corrosion products may be removed from the surface and suspended in the coolant, which may lead to further increase of the head loss. In addition, the water chemistry as well as the ratio of coolant volume to corrosion material surface affects the corrosion and clogging behavior significantly.

  • Lecture (Conference)
    Jahrestagung Kerntechnik 2011, 17.-19.05.2011, Berlin, Deutschland
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2011, 17.-19.05.2011, Berlin, Deutschland
    Jahrestagung Kerntechnik 2011, CD-ROM

Publ.-Id: 16120

Studies on Boiling Water Reactor Design with Reduced Moderation and Analysis of Reactivity Accidents using the Code DYN3D-MG

Rohde, U.; Pivovarov, V.; Matveev, Y.

The multi-group version of DYN3D code was used for calculations of a new concept of boiling water reactor with a tight lattice of fuel rods and reduced neutron moderation. For that purpose a 5-group cross section library was prepared and connected to the DYN3D code. Comparison calculations with the steady-state finite-difference code ACADEM showed a very good agreement.

The capability of the DYN3D multi-group code in modeling transients in boiling water reactors with tight fuel element lattices was demonstrated by the analysis of two reactivity accidents initiated by the ejection of one control rod and unauthorized withdrawal of a control rod bank from the reactor core. The corresponding analyses were performed for begin of cycle conditions, when the considered control rods are at their maximum insertion depth.

Keywords: boiling water reactor; high conversion; reduced moderation; reactor dynamics; code validation; transient analysis

  • Lecture (Conference)
    21st Symposium of Atomic Energy Research, 19.-23.09.2011, Dresden, Deutschland
  • Contribution to proceedings
    21st Symposium of Atomic Energy Research, 19.-23.09.2011, Dresden, Deutschland
    Proceedings of the twenty-first Symposium of AER, Budapest: MTA KFKI Atomenergia Kutatointezet, 978-963-372-646-4, 579-593

Publ.-Id: 16119

Nanoindentation and TEM applied to ion-irradiated Fe-Cr alloys

Bergner, F.; Hernández-Mayoral, M.; Heintze, C.

9-18% Cr steels and oxide dispersion strengthened (ODS) steels being candidate structural materials for future nuclear applications for reasons such as resistance to swelling, irradiation creep and oxidation suffer hardening and embrittlement due to neutron irradiation. Ion irradiation has proven useful to simulate neutron irradiation effects without the drawbacks of producing radioactive material and being restricted to time consuming and expensive in-reactor irradiations. We have applied ion irradiation in combination with nanoindentation to study the irradiation-induced hardening of binary Fe-Cr alloys, 9% Cr steels and experimental ODS alloys. The details of the approach are specified and the effects of Cr content and irradiation conditions including dual-beam irradiations are considered. Transmission electron microscopy is used to characterize nanoscale oxide particles and irradiation-induced dislocation loops. The dimensionless obstacle strength is estimated. On a scale assigning unity to non-shearable obstacles, we have found a ranking from about 0.012 for Cr-rich α’-phase particles, 0.1 to 0.2 for ODS nanoparticles up to about 0.5 for dislocation loops.

Keywords: nanoindentation; TEM; ion irradiation; irradiation effects; iron-chromium alloys; oxide-dispersion strengthening

  • Poster
    ECI Conference on Nanomechanical Testing in Materials Research and Development, 09.-14.10.2011, Lanzarote, Espania

Publ.-Id: 16117

Perrhenate Complexation by Uranyl in Traditional Solvents and in Ionic Liquids: A Joined Molecular Dynamics/Spectroscopic Study

Chaumont, A.; Klimchuk, O.; Gaillard, C.; Billard, I.; Ouadi, A.; Hennig, C.; Wipff, G.

The complexation of perrhenate (ReO4-) anions by the uranyl (UO22+) cation is investigated by joined molecular dynamics simulations and spectroscopic (UV-Vis, TRLFS and EXAFS) studies in aqueous solution, acetonitrile and three ionic liquids (ILs), namely [Bmi][Tf2N], [Me3BuN][Tf2N] and [Bu3MeN][Tf2N] that are based on the same Tf2N- anion (bis(trifluoromethylsulfonyl)imide) and either Bmi+ (1-butyl,3-methylimidazolium), Me3BuN+ or Bu3MeN+ cations. They show that ReO4- behaves as a weak ligand in aqueous solution and as a strong ligand in acetonitrile and in the ILs. In aqueous solution, the simulated UO2(ReO4)2 complex quickly dissociates to form the UO2(H2O)52+ species, while in acetonitrile the simulated UO2(ReO4)53- complex forms from dissociated ions and remains stable along 100 ns of dynamics. When the UO2(ReO4)n2-n complexes (n = 1 to 5) are simulated in the ILs, the uranyl cation remains coordinated to the ReO4- ligands, and to additional OTf2N oxygens when n < 5. To assess the relative stabilities of these complexes, we computed the free energy profiles for stepwise ReO4- complexation by uranyl (PMF calculations). In the two studied ILs, perrhenate complexation is favoured, leading to the UO2(ReO4)53- species in [Bmi][Tf2N] and to UO2(ReO4)42- in [Bu3MeN][Tf2N]. Furthermore, in both acetonitrile and [Bmi][Tf2N] solutions, MD and PMF simulations support the formation of dimeric uranyl complexes [UO2(ReO4)4]24- with two bridging ReO4- ligands. The simulation results are qualitatively consistent with spectroscopic observations in the different solvents, without firmly concluding, however, on the precise composition and structure of the complexes in the solutions.

Keywords: Molecular Dynamics; EXAFS; UV-Vis; TRLFS; uranium; rhenium

Publ.-Id: 16116

Two-photon Compton process in pulsed intense laser fields

Seipt, D.; Kämpfer, B.

Based on strong-field QED in the Furry picture we use the Dirac-Volkov propagator to derive a compact expression for the differential emission probability of the two-photon Compton process in a pulsed intense laser field. The relation of real and virtual intermediate states is discussed, and the natural regularization of the on-shell contributions due to the finite laser pulse is highlighted. The inclusive two-photon spectrum is two orders of magnitude stronger than expected from a perturbative estimate.

Publ.-Id: 16115

Study of amorphous lithium silicate thin films grown by atomic layer deposition

Hämäläinen, J.; Munnik, F.; Hatanpää, T.; Holopainen, J.; Ritala, M.; Leskelä, M.

Lithium silicate thin films, which are interesting materials for example in lithium ion batteries, were grown by the atomic layer deposition technique from lithium hexamethyldisilazide [LiHMDS, Li(N(SiMe3)2)] and ozone precursors. Films were obtained at a wide deposition temperature range between 150 and 400 °C. All the films were amorphous except at 400 °C, where partial decomposition of LiHMDS was also observed. The growth behavior was examined in detail at 250 °C, and saturation of growth rates and refractive indices with precursor doses was confirmed, thereby verifying self-limiting surface reactions. Likewise, the linear thickness dependence of the films with the number of deposition cycles was verified. Strong dependence of growth rate and film composition on deposition temperature was also seen. Overall, the amorphous films grown at 250 °C had a stoichiometry close to lithium metasilicate (Li2.0SiO2.9) with 0.7 at. % carbon and 4.6 at. % hydrogen impurities. The corresponding growth rate and refractive index (n580) were 0.8 A/cycle and about 1.55.

Publ.-Id: 16114

Evidence for chirped Auger electron emission

Schütte, B.; Bauch, S.; Frühling, U.; Wieland, M.; Gensch, M.; Plönjes, E.; Azima, A.; Bonitz, M.; Drescher, M.

Auger decay, i.e. the spontaneous emission of an electron upon relaxation of the atomic shell, carries valuable information about the electronic structure and dynamics of atoms and their compounds. While the energetic properties are well investigated, little is known about the detailed temporal profile of Auger electron wave packets. Here we furnish evidence, that under certain conditions Auger electrons are subject to an energetic chirp imprinting a non-linear change of energy over time on the escaping wave packet. The origin of this unexpected finding is shown to be the exchange of energy between the Auger electron and a slightly earlier emitted photoelectron in the presence of a laser field. The interpretation in terms of this long-range electron correlation is substantiated by fs-time-resolved experiments on the xenon NOO and Kr MNN Auger decay together with extensive theoretical modelling using semi-classical as well as quantum-mechanical simulations.

Publ.-Id: 16113

Characterization of Ce(IV) Hydrolytic Species in Aqueous Solution by X-ray Absorption Spectroscopy, High Energy Solution X-ray Scattering, and Dynamic Light Scattering

Ikeda-Ohno, A.; Weiss, S.; Bernhard, G.; Hennig, C.

Tetravalent cerium (Ce(IV)) is known to be one of the most commonly-used oxidizing agents in various chemical studies, such as organic synthesis. Furthermore, it recently draws considerable attention to its catalytic applications to water oxidation or biotechnology. As a versatile catalytic oxidant, Ce(IV) is often employed in the form of aqueous solution. Therefore, fundamental knowledge of Ce(IV) species in aqueous solution is essential not only for discussing its functionality in the applied systems, but also for further developing its applications; nevertheless, the nature of Ce(IV) species in aqueous solution is far less well understood. In this context, the present study aims to elucidate the chemical speciation and complex structure of soluble Ce(IV) species formed on hydrolysis, which is the most fundamental reaction of metal cations in the aqueous solution system, by employing X-ray absorption spectroscopy (XAS), high energy solution X-ray scattering (HEXS), and dynamic light scattering (DLS).
The obtained XAS data have clearly showed the systematic growing of Ce–Ce bonding in the soluble Ce(IV) hydrolytic species, as an increase in pH. This indicates that some soluble polymeric or cluster complexes are formed on the hydrolysis of Ce(IV). The diffraction patterns of Ce(IV) hydrolytic species have further revealed that the observed polymeric or cluster complex has a crystalline structure, not the amorphous one. The results of the detailed analysis on XAS and HEXS data will be presented on site, along with the DLS data for discussing the size of Ce(IV) hydrolytic polymers/clusters and its aging effect.

Keywords: Lanthanides; Cerium(IV); hydrolysis; aqueous solution; XAS; HEXS; DLS

  • Poster
    Workshop on Analysis of Diffraction Data in Real Space (ADD2011), 12.-14.10.2011, ILL, Grenoble, France

Publ.-Id: 16112

Control of the migration behaviour of radiotoxic heavy metals by means of calixarenes

Paulik, S.; Mansel, A.

Es ist kein Abstract vorhanden.

  • Poster
    HZDR-Doktorandenseminar, 05.-07.10.2011, Rabenberg, Deutschland

Publ.-Id: 16111

Erratum: “Direct observation of antiferromagnetically oriented spin vortex states in magnetic multilayer elements” [Appl. Phys. Lett. 98, 232511 (2011)]

Wintz, S.; Strache, T.; Körner, M.; Fritzsche, M.; Markó, D.; Mönch, I.; Mattheis, R.; Raabe, J.; Quitmann, C.; McCord, J.; Erbe, A.; Fassbender, J.

Keywords: magnetic vortex

Publ.-Id: 16110

The influence of microbes on radionuclide speciation concerning nuclear waste disposal

Frost, L.

Granite is the aspired potential host rock material for future nuclear waste storage in Sweden. The Äspö Hard Rock Laboratory (Äspö HRL) today is an interdisciplinary research facility for geological disposal in granite rock. The research within the Äspö HRL programme involves international cooperation with various countries including Germany.
This presentation drafts the operations done at Äspö and the contribution by the IRC. Here the objectives and results of the study on the interaction of uranium(VI) with Pseudomonas fluorescens, a strain that has been isolated at the Äspö site, are presented. Explicitly results about the accumulation capability of the strain, TRLFS investigations and potentiometric titration results are shown.

Keywords: Uranium(VI); speciation; Pseudomonas fluorescens; Äspö; nuclear waste repository

  • Lecture (others)
    6. Ph.D. Seminar HZDR, 05.-07.10.2011, Rabenberg, Deutschland

Publ.-Id: 16109

Computer simulation of the radiation of electrons axially channeled in a thin Ge single crystal

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

The radiation emitted by axially channeled electrons has been investigated by computer simulations. Using the Doyle-Turner approximation for the atomic scattering factor and taking thermal vibrations of the crystal atoms into account, two-dimensional continuous potentials for the <100> and <110> crystallographic axes of a thin Ge single crystal have been calculated. The trajectories, velocities and accelerations of channeled electrons are obtained by solving numerically the classical equations of motion in three dimensions. In the framework of classical electrodynamics, these data allow realistic simulations of spectral-angular distributions and energy spectra of axial channeling radiation as well.

Keywords: channeling radiation; axial channeling

Publ.-Id: 16108

Prototyping and tests for an MRPC-based time-of-flight detector for 1 GeV neutrons

Yakorev, D.; Aumann, T.; Bemmerer, D.; Boretzky, K.; Caesar, C.; Ciobanu, M.; Cowan, T.; Elekes, Z.; Elvers, M.; Gonzalez Diaz, D.; Hannaske, R.; Hehner, J.; Heil, M.; Kempe, M.; Maroussov, V.; Nusair, O.; Simon, H.; Sobiella, M.; Stach, D.; Wagner, A.; Zilges, A.

The NeuLAND detector at the R3B experiment at the future FAIR facility in Darmstadt aims to detect fast neutrons (0.2–1.0 GeV) with high time and spatial resolutions . This task can be performed either with a scintillator or based on the multigap resistive plate chamber (MRPC) technology. Here, prototyping and test for an MRPC-based solution are discussed. In order to reach 90% detection efficiency, the final detector must consist of 50 consecutive MRPC stacks. Each stack contains a 4 mm thick anode made of iron converter material, with an additional 4 mm of converter material between two stacks. The secondary charged particles stemming from hadronic interactions of the high energetic neutrons in the converter will be detected in the MRPCs. As part of the ongoing development effort, a number of prototypes for this detector have been developed and built. They have been tested in experiments with a single-electron beam with picosecond resolution at the superconducting linac ELBE (Dresden, Germany). The results of the tests are presented here, and an outlook is given.

Keywords: MRPC; Multigap resistive plate chamber; R3B; FAIR; ELBE; Time resolution; Neutron detection

Publ.-Id: 16107

Revision of the 15N(p,γ)16O reaction rate and oxygen abundance in H-burning zones

Caciolli, A.; Mazzocchi, C.; Capogrosso, V.; Bemmerer, D.; Broggini, C.; Corvisiero, P.; Costantini, H.; Elekes, Z.; Formicola, A.; Fulop, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyurky, G.; Imbriani, G.; Junker, M.; Lemut, A.; Marta, M.; Menegazzo, R.; Palmerini, S.; Prati, P.; Roca, V.; Rolfs, C.; Rossi Alvarez, C.; Somorjai, E.; Straniero, O.; Strieder, F.; Terrasi, F.; Trautvetter, H. P.; Vomiero, A.

The NO cycle takes place in the deepest layer of a H-burning core or shell, when the temperature exceeds T {\simeq} 30 {\cdot} 106 K. The O depletion observed in some globular cluster giant stars, always associated with a Na enhancement, may be due to either a deep mixing during the RGB (red giant branch) phase of the star or to the pollution of the primordial gas by an early population of massive AGB (asymptotic giant branch) stars, whose chemical composition was modified by the hot bottom burning. In both cases, the NO cycle is responsible for the O depletion. The activation of this cycle depends on the rate of the 15N(p,{\gamma})16O reaction. A precise evaluation of this reaction rate at temperatures as low as experienced in H-burning zones in stellar interiors is mandatory to understand the observed O abundances. We present a new measurement of the 15N(p,{\gamma})16O reaction performed at LUNA covering for the first time the center of mass energy range 70-370 keV, which corresponds to stellar temperatures between 65 {\cdot} 106 K and 780 {\cdot}106 K. This range includes the 15N(p,{\gamma})16O Gamow-peak energy of explosive H-burning taking place in the external layer of a nova and the one of the hot bottom burning (HBB) nucleosynthesis occurring in massive AGB stars. With the present data, we are also able to confirm the result of the previous R-matrix extrapolation. In particular, in the temperature range of astrophysical interest, the new rate is about a factor of 2 smaller than reported in the widely adopted compilation of reaction rates (NACRE or CF88) and the uncertainty is now reduced down to the 10% level.

Publ.-Id: 16106

Is it Possible to Study the 44Ti(α,p)47V Reaction with a Radioactive Target?

Al-Abdullah, T.; Bemmerer, D.; Schmidt, K.; Ayranov, M.; Dressler, R.; Schumann, D.

The 44Ti(alpha,p)47V reaction is of crucial importance for the destruction of Ti-44 in the alpha-rich freezeout of a supernova. Here I report on a feasibility study. Using radioactive Ti-44 and alpha-emitting sources and sputtering simulations, I study the feasibility and safety of a possible experiment using an alpha-beam from an accelerator and a radioactive Ti-44 target.

  • Lecture (Conference)
    ERAWAST2: 2nd workshop on exotic radionuclides from accelerator waste for science and technology, 30.08.-02.09.2011, Villigen, Schweiz

Publ.-Id: 16105

Interaction of Uranium(VI) with Schiff Bases in organic solvents

Lindner, K.; Günther, A.; Bernhard, G.

Presentation of the complexation of Uranium(VI) with selected Schiff bases in methanol investigated by UV/Vis spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS)

Keywords: Uranium(VI); Schiff bases; UV/Vis; TRLFS

  • Poster
    6th Graduate Students Seminar, 05.-07.10.2011, Breitenbrunn, Germany

Publ.-Id: 16104

Online Irradiation Control by means of PET

Fiedler, F.; Kunath, D.; Priegnitz, M.; Enghardt, W.

Positron emission tomography (PET) is a dedicated tool for quality assurance in ion beam therapy. By measuring the spatial distribution of positron emitters generated via nuclear interactions between projectiles and atomic nuclei of the tissue during the therapeutic irradiation, conclusions on the accuracy of the dose localization can be drawn. In the following, the physical background as well as the technical realization of PET is depicted. Furthermore, current PET installations for quality assurance of proton and ion beam therapy are presented.

  • Book chapter
    Ute Linz: Ion Beam Therapy: Fundamentals, Technology, Clinical Applications, Berlin: Springer, 2012, 3642214134, 527-543

Publ.-Id: 16103

Stable-ion beam experiments for nuclear astrophysics

Bemmerer, D.

I will review the state of the art of stable-ion beam experiments for nuclear astrophysics. Special mention will be made of the so-called solar abundance problem and the contributions that experimental nuclear astrophysics may make to solve it. Topics where ERAWAST nuclides have played a special role will be mentioned.

  • Lecture (Conference)
    ERAWAST2: 2nd workshop on exotic radionuclides from accelerator waste for science and technology, 30.08.-02.09.2011, Villigen, Schweiz

Publ.-Id: 16102

Hydrogen burning in the CNO cycles

Bemmerer, D.

I will review the status of the standard solar model, with special mention given to the so-called solar abundance problem that ha recently developed. Then, I will discuss the experimental status of the nuclear reactions of the carbon-nitrogen-oxygen (CNO) cycle of hydrogen burning.

  • Invited lecture (Conferences)
    Helmholtz International Summer School "Nuclear Theory and Astrophysical Applications", 24.07.-02.08.2011, Dubna, Russland

Publ.-Id: 16101

Numerical and experimental modelling of VGF-type buoyant flow under the influence of travelling and rotating magnetic fields

Galindo, V.; Niemietz, K.; Pätzold, O.; Gerbeth, G.

Numerical and experimental modelling of a VGF-type (VGF - Vertical Gradient Freeze) buoyant flow under the influence of both travelling and rotating magnetic fields (TMF and RMF, respectively) is presented. Low-temperature flow experiments were carried out using a GaInSn alloy as model fluid. Radial heating and cooling of the melt leading to a meridional double vortex flow like in typical VGF growth, was introduced using a double-walled melt container. The flow was found to be significantly influenced by the mutual interaction of buoyant and electromagnetically driven forces. With increasing axial temperature difference, the buoyant flow becomes more concentrated in the upper and lower part of the melt leaving an extended melt zone with low flow velocity around the mid-height. Furthermore, VGF-type buoyancy is found to stabilize TMF- and RMF-induced melt flows. Besides, the time evolution of the flow just above the stability threshold is studied. In the case of combined VGF-type/RMF flow complex fluctuation patterns are observed, which depends sensitively on the applied thermal field.

Keywords: Fluid flows; Magnetic fields; Vertical gradient freeze technique; numerical simulation

Publ.-Id: 16100

LUNA: Underground for Nuclear Astrophysics

Bemmerer, D.

The international LUNA collaboration studies nuclear reactions at very low energy, directly relevant to the Sun. To this end, it uses a 0.4 MV accelerator deep underground in the Gran Sasso laboratory in Italy. I will review the motivations, techniques and achievements of LUNA.

  • Invited lecture (Conferences)
    Helmholtz International Summer School "Nuclear Theory and Astrophysical Applications", 24.07.-02.08.2011, Dubna, Russland

Publ.-Id: 16099

Kinetic and structural studies on the adsorption of metals and actinides on cell surfaces by using multi-layer systems as a model of bacterial cell walls

Suhr, M.; Günther, T.; Raff, J.; Pollmann, K.

Bacterial isolates from the uranium mining waste pile Haberland (Johanngeorgenstadt, Saxony) possess high affinities to heavy metals and uranium. This binding effect is caused by the components of the bacterial cell wall, mainly effected by surface layer proteins.
Aim of this work is the construction of a stable multi-layer system for the simulation of cell walls of Gram-positive bacteria and the investigation of metal interactions with single compounds and whole complex systems.
The quartz crystal microbalance (QCM-D) and atomic force microscopy (AFM) is used to track and control this multi-layer formation.
First result of these tasks is the proof of recrystallization of S-layer proteins as part of the cell wall of Bacillus spec. JG-B53 via QCM-D and AFM.

Keywords: QCM-D; S-Layer; polyelectrolytes; bacteria; adsorption; metals; actinides

  • Poster
    6th PhD Seminar, 05.-07.10.2011, Rabenberg, Deutschland

Publ.-Id: 16097

Angewandte Naturwissenschafler in der Forschung

Beyreuther, E.

no abstract;
Vortrag ohne Abstrakt!

  • Lecture (others)
    Absolvententreffen 55 Jahre Chemie und 15 Angewandte Naturwissenschaften an der TU Bergakademie Freiberg, 23.-24.09.2011, Freiberg, Deutschland

Publ.-Id: 16096

Heterologous expression of surface layer proteins

Lederer, F.; Günther, T.; Pollmann, K.

Heterologous expression is a common method of molecular biology, which finds applications for example in up scaling of protein production and structural analyses of naturally unexpressed proteins. An experimental setup is started by the amplification of the template gene. Afterwards this gene is cloned into coiled DNA, called vectors and transformed into the host organism. The desired protein, which is encoded by the cloned gene, is produced inside the host organism. Host strains are for example Escherichia coli, Lactococcus lactis or Pichia pastoris.

Keywords: Heterologous expression; Escherichia coli; Lactococcus lactis

  • Poster
    Doktorandenseminar 2011, 05.-07.10.2011, Breitenbrunn, Deutschland

Publ.-Id: 16095

Investigation of actinides behaviour under specific environmental conditions

Fischer, S.; Husar, R.

Presentation of motivation and objectives of the PhD theses “Spectroscopic characterization of trivalent actinides Am and Cm on bacterial cell walls” and “Evidence and characterization of silica-containing colloids of tetravalent Th, U, Np”.

Keywords: Actinides; trivalent; tetravalent; spectroscopy; bacterial cell walls; silica-containing colloids

  • Poster
    6th PhD Seminar HZDR, 05.-07.10.2011, Rabenberg, Deutschland
  • Poster
    Doktorandenseminar - Kompetenzzentrum Ost für Kerntechnik, 08.12.2011, Zittau, Deutschland

Publ.-Id: 16094

Nonlinear transmission dynamics in graphene close to the Dirac point

Winnerl, S.; Orlita, M.; Plochocka, P.; Kossacki, P.; Potemski, M.; Winzer, T.; Malic, E.; Knorr, A.; Sprinkle, M.; Berger, C.; de Heer, W. A.; Schneider, H.; Helm, M.

We report on carrier relaxation dynamics close to the Dirac point in epitaxially grown graphene under pulsed excitation with 10 – 250 meV photons. With decreasing photon energy, we identify different regimes – induced transmission with bi- and single-exponential decay as well as induced absorption - and discuss their physical origin.

Keywords: graphene; pump-probe experiment; free-electron laser

  • Contribution to proceedings
    36th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2011), 02.-07.10.2011, Houston, USA
    IEEE-2011 36th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2011): IEEE Xplore Digital Library, doi: 10.1109/irmmw-THz.2011.6105036
  • Lecture (Conference)
    36th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2011), 02.-07.10.2011, Houston, TX, USA

Publ.-Id: 16093

Strong-field terahertz spectroscopy of semiconductor quantum structures

Schneider, H.

This seminar gives an overview on our recent experimental studies involving terahertz (THz) and mid-infrared radiation from the free-electron laser facility FELBE in Dresden, Germany. In particular, cyclotron resonance spectroscopy and aperture-less near-field microscopy will be addressed as examples for linear measurements. Moreover, nonlinear THz photocurrents originating from two-photon excitation between subbands in semiconductor quantum wells allow for measurements of intersubband relaxation and dephasing times and for quadratic autocorrelation of THz pulses. The final part of my talk will concentrate on nonlinear two-color THz spectroscopy, in particular THz sideband generation and coherent dynamics involving excitons dressed by strong THz beams.

Keywords: nonlinear terahertz spectroscopy; THz; semiconductor quantum well; sideband generation; excitons

  • Lecture (others)
    Physics Colloquium, Shanghai Jiao Tong University, 07.09.2011, Shanghai, China

Publ.-Id: 16092

Jena's Impact on the High Intensity Laser Community

Cowan, T. E.

Gründungsveranstaltung Abbe Center of Photonics

  • Invited lecture (Conferences)
    Gründungsveranstaltung Abbe Center of Photonics, 10.12.2010, Jena, Deutschland

Publ.-Id: 16091

High Intensity Laser- and Plasma Physics in collaboration with Helmholtz Institute Jena

Cowan, T. E.

High Intensity Laser- and Plasma Physics in collaboration with Helmholtz Institute Jena

  • Lecture (Conference)
    Scientific Council Helmholtz Institute Jena, 29.-30.06.2010, Jena, Deutschland

Publ.-Id: 16090

Maximizing the energy of laser-accelerated protons and ions within Target Normal Sheath Acceleration

Cowan, T. E.; Bussmann, M.; Gaillard, S.; Kluge, T.; Kraft, S.; Metzkes, J.; Zeil, K.; Schramm, U.

The Target Normal Sheath Acceleration mechanism is perhaps the most robust, and certainly the most studied, process by which protons and ions are accelerated to multi-MeV energies in ultra-intense laser-matter interactions. It is characterized by the generation of superstrong TV/m ambipolar electric fields in the relativistic electron sheath on the rear-surface of laser-irradiated thin foils, and the subsequent quasi-neutral plasma expansion driven by the electron thermal pressure. The maximum achievable ion energies should increase with increasing hot electron temperature and density, depending upon the laser pulse parameters and the geometry of the target and laser-plasma interaction. To date, proton energies of up to 67.5 MeV have been observed. In this talk, techniques to further increase the proton and ion energies from TNSA will be reviewed, with emphasis on experimental results from the FZD Draco Ti:Sa laser and with our collaboration partners working at several higher energy Nd:glass lasers world-wide. Scaling of the proton energy with the laser pulse energy and intensity, pulse length and contrast, and by variation of the target geometry and properties, such as thickness, transverse size, and by target shaping, will be discussed.

  • Invited lecture (Conferences)
    4th International Conference on Superstrong Fields In Plasmas, 03.-09.10.2010, Varenna, Italy

Publ.-Id: 16089

Enhanced Positron Creation in Ultra-Intense Laser-Matter Interactions

Cowan, T. E.; Nakashima, K.; Sentoku, Y.; Takabe, H.; Brown, C.; Cassidy, D.; Christl, M.; Fountain, W.; Hunt, A. W.; Johnson, J.; Kühl, T.; Parnell, T.; Patterson, W. S.; Pennington, D. M.; Perry, M. D.; Phillips, T. W.; Roth, M.; Takahashi, Y.; Wilks, S. C.

Enhanced Positron Creation in Ultra-Intense Laser-Matter Interactions

  • Invited lecture (Conferences)
    Antimatter Creation Using Ultra-Intense Lasers Workshop, 27.-28.04.2010, Berkeley, USA

Publ.-Id: 16088

FZD (HZDR) contribution to Laser-Accelerated Proton Test Stand Project

Cowan, T. E.

Milestones and perspectives of the projected test stand to capture and transport laser-accelerated proton beams. Workshop GSI Darmstadt

  • Lecture (Conference)
    Milestones and perspectives of the projected test stand to capture and transport laser-accelerated proton beams, 06.08.2010, Darmstadt, Deutschland

Publ.-Id: 16087

Proton acceleration from engineered laser beams

Cowan, T. E.; Roth, M.; Bagnound, V.; Zielbauer, B.; Brabetz, C.; Kester, O.; Lei, A.; Schramm, U.

Proposal for PHELIX Experiment Time, GSI-PPAC

  • Lecture (Conference)
    5th Meeting of the Phelix and Plasmaphysics Program Advisory Committee, 08.-09.11.2010, Darmstadt, Deutschland

Publ.-Id: 16085

Determination of the Degree of Quasineutrality of Laser-accelerated Proton Pulses

Cowan, T. E.; Margarone, D.; Burris, T.; Bussmann, M.; Krasa, J.; Roth, M.; Harres, K.; Nürnberg, F.; Busold, S.; Deppert, O.; Boine-Frankenheim, O.; Kornilov, V.; Zsolt, L.; Zielbauer, B.

Proposal for PHELIX Experiment Time, GSI-PPAC

  • Lecture (Conference)
    5th Meeting of the Phelix and Plasmaphysics Program Advisory Committee, 08.-09.11.2010, Darmstadt, Deutschland

Publ.-Id: 16084

Baryonic resonances close to the Kbar N threshold: the case of Σ(1385)+ in pp collisions

Agakishiev, G.; Balanda, A.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Castro, E.; Chen, J. C.; Chernenko, S.; Christ, T.; Destefanis, M.; Dohrmann, F.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Lalik, R.; Lang, S.; Lange, J. S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Moriniere, E.; Mousa, J.; Müntz, C.; Naumann, L.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

We present results of an exclusive measurement of the first excited state of the Σ hyperon, Σ(1385)+, produced in p+p->Σ++K++n at 3.5 GeV beam energy. The extracted data allow to study in detail the invariant mass distribution of the Σ(1385)+. The mass distribution is well described by a relativistic Breit-Wigner function with a maximum at m0=1383.2±0.9 MeV/c2 and a width of 40.2±2.1 MeV/c2. The exclusive production cross-section comes out to be 22.27±0.89±1.56+3.07−2.10 μb. Angular distributions of the Σ(1385)+ in different reference frames are found to be compatible with the hypothesis that 33% of Σ(1385)+ result from the decay of an intermediate Δ++ resonance.

Publ.-Id: 16082

Superconducting states of flash-lamp annealed Ga implanted Ge

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

Since superconductivity has been discovered one century ago, scientists search for new materials that show this fascinating ground state of matter. Recent investigations on superconductivity of elemental group-IV semiconductors like diamond [1] and silicon [2] lead to a new debate about the mechanism and technological potential of these unusual superconductors.
In our previous work, we have shown the possibility of creating highly Ga doped Ge layers via Ga-ion implantation and subsequent short-time annealing. As a consequence of the high doping level, these layers are intrinsically superconducting below 1 K [3]. Furthermore we investigated the feasibility of embedding superconducting layers in Si-SiO2 heterostructures not via doping but by Ga precipitation reaching critical temperatures of 7 K [4] with equivalent processing steps.
From these investigations, the question arises if it is possible to combine highly doped semiconducting regions with intrinsic and extrinsic superconducting structures having different critical temperatures. We used again Ga implantation in Ge covered by a 30 nm SiO2 layer and flash-lamp annealing to create a complex layer structure showing various transitions in different superconducting states. The first transition occurs at 7 K and can be attributed to Ga-rich precipitates at the Ge-SiO2 interface. Due to the superconductivity of the underlying highly doped germanium layer, a second transition is observed at around 1 K. Recent results on the structural and electrical properties of the heterostructures will be presented.

[1] E. A. Ekimov et al., Nature (London) 428, 542 (2004).
[2] E. Bustarret et al., Nature 444, 465 (2006).
[3] T. Herrmannsdörfer et al., Phys, Rev. Lett. 102, 217003 (2009); V. Heera et al., Journal of Applied Physics 107, 053508 (2010).
[4] J. Fiedler et al., Phys. Rev. B 83, 214504 (2011); R. Skrotzki et al., Appl. Phys. Lett. 97 192505 (2010).

  • Lecture (Conference)
    subtherm; International Topical Workshop on Subsecond Thermal Prosessing of advanced Materials, 25.-27.10.2011, Dresden, Deutschland
  • Poster
    subtherm; International Topical Workshop on Subsecond Thermal Prosessing of advanced Materials, 25.-27.10.2011, Dresden, Deutschland

Publ.-Id: 16081

A new route towards a silicon based quantum computer? - About superconducting layers in semiconductors

Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.

Es hat kein Abstract vorgelegen.

  • Lecture (others)
    6th PhD Seminar HZDR, 05.-07.10.2011, Rabenberg, Deutschland

Publ.-Id: 16080

Phenomenology of pattern formation on Si(001) with and without impurities

Michely, T.; Macko, S.; Engler, M.; Frost, F.; Müller, S.; Förster, D.; Höche, T.; Hirsch, D.; Fritzsche, M.; Mücklich, A.; Grenzer, J.

Pattern formation on Si(001) through 2 keV Kr+ ion beam erosion under ultra high vacuum conditions is investigated by in situ scanning tunneling
microscopy, ex situ atomic force microscopy and electron microscopy. Under these conditions, at room temperature for fluences up to ≈ 2×10^22 ions m^-2 no ion beam patterns develop for angles ϑ <= 55° with respect to the global surface normal. Only for shallow incidence with 60° <= ϑ <= 81° pronounced patterns form. These patterns expose facets for which the ion beam angle q with respect to the local surface normal of each facet is in the stable range, i.e. outside 60° <= q <= 81°. Analysis of the fluence dependence of pattern formation was conducted in the unstable range with ϑ = 63° and ϑ = 75°. While the speed of pattern evolution depends strongly on the angle of incidence, the sequence does not. The flat surface evolves via small amplitude, regular ripple patterns to large amplitude, irregular facet patterns. The regular ripple pattern transforms through a coarsening mechanism to a facetted pattern.
Co-deposition of stainless steel during ion beam erosion results in well developed hole, dot and ripple patterns already for small ion fluences. Codeposition induced pattern formation does not depend on the deposition method as it takes place for both, co-sputter deposition and co-evaporation. The key factor selecting the type of pattern realized is the ion-to-impurity arrival ratio. While in a broad range from 150 K to 440 K pattern formation is rather temperature independent, dramatic changes take place above a threshold temperature ≈ 600 K, when structures of crystalline iron silicide are shaped on the surface. For these high temperatures needles and sponge patterns with amplitudes of the order of 100 nm and directed towards the ion beam evolve. Variation of the angle between ion beam and impurity source has a significant effect on pattern formation. The larger this angle, the more efficient is pattern formation. This observation points to the relevance of shadowing.

  • Invited lecture (Conferences)
    Nanoscale Pattern Formation at Surfaces, 18.-22.09.2011, El Escorial, Spain

Publ.-Id: 16079

Comparison of pattern formation by Focused Ion Beam and Broad Beam Sputtering

Fritzsche, M.; Facsko, S.; Mücklich, A.

Under specific conditions low energy ion beam sputtering of surfaces leads to self-organized periodic patterns. These can be ripple patterns with periodicities in the nanometer range for oblique ion incidence or hexagonal dot patterns on compound materials for normal ion incidence. Recently, periodic nanohole patterns were observed on Ge surfaces when sputtered at normal incidence using a 5 keV Ga+ focused ion beam (FIB) [1]. These patterns resemble the dot patterns on GaSb mirrored with respect to the surface plane, suggesting a similar formation mechanism.
In this work we studied the pattern formation using FIB and compared the results with patterns produced by sputtering with a broad beam. In case of the focused beam a variation of the incidence angle as well as a variation in the energy of the incoming Ga+ ion on a Ge substrate was done. Using a broad Ga+ beam leads to the same pattern formation on Ge independent of scanning. Additionally GaSb dot patterns were produced using a broad beam of Ar+ and the size dependence of the energy of the incoming ion was studied. A comparison of both patterns shows no flux dependence in case of Ga+ sputtered on Ge (neither for FIB nor for broad beam), whereas the size and also the shape of the GaSb dots changes with flux.
[1] Q. Wei, X. Zhou, B. Joshi, Y. Chen, K. Li, Q. Wei, K. Sun, and L. Wang, Adv. Mater. 21, 2865 (2009).

  • Poster
    Nanoscale Pattern Formation at Surfaces, 18.-22.09.2011, El Escorial, Spain

Publ.-Id: 16078

Tailoring Spin Dynamics by Magnetic Nanopatterning Using Ion Irradiation

Lenz, K.; Körner, M.; Banholzer, A.; Liedke, M. O.; Grebing, J.; Fassbender, J.; Barsukov, I.; Römer, F. M.; Lindner, J.

Various elements like Pd, Cr, Ta, as well as several rare-earth elements can be used to modify the magnetic properties of thin ferromagnetic films. They are incorporated either by co-sputtering or ion implantation and are well known to reduce the Curie temperature, saturation magnetization, anisotropy and damping [1,2]. In combination with lithographic masking this allows for magnetic property patterning at the nanoscale [3]. In thin ferromagnetic films, the magnetization dynamics are governed by
intrinsic effects like Gilbert damping and spin-pumping but also by extrinsic effects like two-magnon scattering due to inevitable defect structures. By lithographic nanopatterning or by using ion-eroded, nanoscale periodically modulated substrates (ripples) as templates we are able to artificially create and thus control those defect structures necessary to induce two-magnon scattering. The damping contributions are disentangled from linewidth measurements by broadband ferromagnetic resonance technique.

Keywords: Ferromagnetic resonance; damping; relaxation; ripples; ion irradiation; nanostructures

  • Poster
    2nd international workshop on magnonics: From Fundamentals to Applications, 07.-10.08.2011, Recife, Brasilien

Publ.-Id: 16077

Tailoring Magnetization Dynamics at the Nanoscale

Barsukov, I.; Rubacheva, A.; Melnichak, N.; Römer, F. M.; Meckenstock, R.; Lindner, J.; Wende, H.; Farle, M.; Lenz, K.; Banholzer, A.; Fassbender, J.; Mankovsky, S.; Ebert, H.; Landeros, P.; Mills, D. L.

Controlling spin relaxation is essential for spintronic and spin torque applications. Manipulating spin relaxation allows the adjustment of magnetization reversal speed at microwave frequencies. Moreover, the critical current in spin torque devices can be reduced and tuned. In the experiment it is possible to distinguish between the intrinsic and extrinsic relaxation channels. The latter can be tailored with respect to the intensity and anisotropic behaviour. In particular, methods for inducing elementary relaxation channels of uniaxial symmetry and their impact on the magnetization dynamics are discussed in this presentation. Fe-based thin films have been studied by means of the ferromagnetic resonance technique, by which the intrinsic and extrinsic relaxation processes can be disentangled. While the former are rather isotropic and can be adjusted via spin-orbit interaction, the latter can be modified in an advanced way. It is shown, how crystalline defects, inhomogeneities of chemical composition, and interface modifications can induce the 2-magnon scattering. Control and systematic manipulation of these parameters allow tailoring the overall spin relaxation in a desired manner with respect to the direction of magnetization and precessional frequency.

Keywords: ferromagnetic resonance; damping; relaxation

  • Poster
    2nd international workshop on magnonics: From Fundamentals to Applications, 07.-10.08.2011, Recife, Brasilien

Publ.-Id: 16076

Herstellung von 61Cu mit hoher spezifischer Aktivität über die 64Zn(p,α)61Cu-Reaktion

Thieme, S.; Walther, M.; Rajander, J.; Pietzsch, H.-J.; Solin, O.; Steinbach, J.

Die Herstellung von 61Cu hoher spezifischer Aktivität erfordert besonders aufwändige Maßnahmen, um Metallkontaminationen sowohl durch Cu-Isotope als auch durch andere Metalle zu minimieren. Dementsprechend müssen die herkömmlichen Methoden ververfeinert werden, um 61Cu sowohl in hoher Qualität als auch effektiv herstellen zu können. Vergleichswerte über spezifische Aktivitäten von 61Cu sind in der Literatur selten zu finden. McCarthy et al. [1] berichten zu spez. Aktivitäten von 61Cu im Bereich von 47 bis 190 GBq/µmol; erzeugt durch 61Ni(p,n)61Cu und 60Ni(d,n)61Cu-Reaktion. Eine Alternative dazu stellt die 64Zn(p,α)61Cu-Reaktion dar [2]. Das hierfür genutzte Targetmaterial 64Zn (99,3% Isotopenanreicherung) ist im Vergleich zu angereichertem 61Ni weitaus weniger kostenintensiv.

Für die Bestrahlung am Zyklotron wird ein massiver Targetträger aus Gold verwendet, auf dem ca. 100 mg angereichertes 64Zn (99,3% Isotopenanreicherung) abgeschieden sind. Die radiochemische Trennung erfolgt über Ionenaustauschtechniken nach Literaturangaben [3-8]. Die angewandte Methode nutzt eine Ionenaustauscherkaskade, die aus zwei Kationenaustauscher-Säulen und einer Anionenaustauscher-Säule besteht. Dabei sorgt der doppelte Kationenaustauscherschritt für die effektive Abtrennung von Galliumisotopen (66/67/68Ga) und die Anionenaustauscher-Säule für die Trennung des 61Cu vom Zn-Targetmaterial. Der Gesamtprozess zur Gewinnung des gereinigten 61Cu dauert eine Stunde. Die Methode umfasst die Wiedergewinnung des eingesetzten 64Zn, welches danach zur erneuten Verwendung zur Verfügung steht. Das optimierte Verfahren nutzt kleinere Ionenaustauschersäulen als bisher und ausschließlich wässrige Salzsäure; Details vgl. Thieme et al. [2]. Die Ermittlung der spezifischen Aktivität erfolgt über TETA-Titrationen und ICP-MS-Analysen. Es wurden Bestrahlungen an zwei verschiedenen Zyklotronen durchgeführt: am Cyclone 18/9 (IBA, Belgien) des Instituts für Radiopharmazie, Dresden-Rossendorf und am CC 18/9 (Efremov Institut, St. Petersburg, Russland) des Turku PET Centre in Turku, Finnland.

Die Bestrahlungen mit dem Cyclone 18/9 wurden mit 12 µA und 16 MeV durchgeführt. Dies führte innerhalb von 30 Minuten zu Ausbeuten von ca. 300 MBq 61Cu (EOB). Am CC 18/9 wurde mit 30 µA, 13 MeV, 30 Minuten gearbeitet. Dabei wurden ebenfalls 330-400 MBq 61Cu (EOB) erzeugt, bei einer Bestrahlungszeit von 3 Stunden bis zu 1150 MBq61Cu (EOB). Am CC 18/9 wurde eine extrem hohe spezifische Aktivität des 61Cu von über 1000 GBq/µmol erreicht. Demgegenüber fielen die spezifischen Aktivitäten am Cyclone 18/9 deutlich ab, es konnte nur eine spezifische Aktivität von ca. 2 GBq/µmol erzielt werden. Wahrscheinlich tritt in diesem Fall eine Kontamination mit stabilem Kupfer schon während der Bestrahlung auf. Möglicherweise geht diese von der Targethalterung am Zyklotron aus, da sie nicht wie beim CC 18/9 komplett aus Aluminium, sondern größtenteils aus Messing besteht. Bisherige Versuche zum Schutz des Targetträgers und des Targetmaterials vor derartigen Kontaminationen bzw. der Versuch, Kontaminationen während des Trennprozesses zu verhindern, blieben erfolglos.

Schlussfolgerungen: Die Ergebnisse zeigen, dass es prinzipiell möglich ist, 61Cu mit hoher spezifischer Aktivität mit Hilfe der 64Zn(p,α)61Cu-Reaktion herzustellen. Die genutzte radiochemische Trennmethode bietet sich hervorragend für eine routinemäßige Herstellung von 61Cu an.

[1] McCarthy, D. W.; Bass, L. A.; Cutler, P. D.; Shefer, R. E.; Klinkowstein, R. E.; Herrero, P.; Lewis, J. S.; Cutler, C. S.; Anderson, C. J.; Welch, M. J. (1999) Nucl. Med. Biol. 26, 351-358
[2] Thieme, S.; Walther, M.; Pietzsch, H.-J.; Steinbach, J. in: Technetium and other radiometals in chemistry and medicine (Mazzi, U.; Eckelman, W. C.; Volkert, W. A. eds.), pp 475-478, SGE Editoriali, Padova, Italy
[3] Kraus, K. A.; Moore, G. E. (1953) J. Am. Chem. Soc. 75, 1460-1462
[4] O'Brien, H. A. (1969) Int. J. Appl. Radiat. Isot. 20, 121-124
[5] Neirinckx, R. D. (1977) Int. J. Appl. Radiat. Isot. 28, 802-804
[6] Jamriska, D. J.; Taylor, W. A.; Ott, M. A.; Heaton, R. C.; Phillips, D. R.; Fowler, M. M. (1995) J. Radioanal. Nucl. Chem. Art. 195, 263-270
[7] Smith, S. V.; Waters, D. J.; Di Bartolo, N. (1996) Radiochim. Acta 75, 65-68
[8] Rowshanfarzad, P.; Sabet, M.; Jalilian, A. R.; Kamalidehghan, M. (2006) Appl. Radiat. Isot. 64, 1563-1573

  • Lecture (Conference)
    19. Jahrestagung der AG Radiochemie/Radiopharmazie der DGN, 15.-17.09.2011, Ochsenfurt, D

Publ.-Id: 16075

Spectroscopic Characterization of Eu(III) and Am(III) Complexes with Small Organic Molecules at Elevated Temperatures

Barkleit, A.; Geipel, G.; Acker, M.; Taut, S.

Clay minerals which are components of potential host rock formations for nuclear waste repositories can contain small organic molecules like formate, citrate or lactate. Such small organic molecules can like the ubiquitous humic acids influence the migration behavior of radionuclides. Different substituted benzoic acids can mimic the main functionalities and are often used as model compounds for humic substances.
The understanding of the complex behavior of radionuclides with such natural organic matter and the thermodynamic quantification of the interaction especially at elevated temperatures is of great importance to simulate and predict their migration behavior in the environment, particularly in the near field of nuclear waste disposals where higher temperatures are prevailing.
We present the investigation of the complex behavior of Am(III) and Eu(III) with lactate and salicylate at ambient and elevated temperatures with time-resolved laser-induced fluorescence spectroscopy (TRLFS) and the resulting thermodynamic data (reaction enthalpy, reaction entropy). Whereas the complexation with lactate is for both cations nearly temperature independent, is the complexation with salicylate clearly an endothermic reaction.

Keywords: Americium; Europium; Lactate; Salicylate; TRLFS; High Temperatures

  • Contribution to proceedings
    HiTAC - High Temperature Aqueous Chemistry, 09.11.2011, Karlsruhe, Deutschland
    Proceedings of the International Workshops ABC-Salt(II) and HiTAC 2011, KIT Scientific Reports 7625, 978-3-86644-912-1, 173-174

Publ.-Id: 16074

Status of the FZD lab combining beams of the 150 TW laser Draco and the superconducting 40 MeV electron linac ELBE

Jochmann, A.; Couperus, J. P.; Debus, A.; Erler, C.; Irman, A.; Kraft, S.; Bussmann, M.; Cowan, T.; Sauerbrey, R.; Zeil, K.; Schramm, U.

Important questions regarding the scaling of laser plasma (wakefield) electron acceleration are if, as in conventional architectures, a number of plasma accelerators can be staged and if it can be combined with conventional accelerators with reasonable efficiency and stability.
At the FZD, we are therefore combining the 150 TW laser beam of the Ti:Sapphire system Draco (up to 4 J on target in about 25 fs pulse duration [1] and to be upgraded to at least 500 TW until 2012) with the electron beam of the superconducting linear accelerator ELBE in the energy range between 15 and 35 MeV. ELBE routinely provides bunches of up to 70 pC charge with a pulse duration in the ps range, which is obviously not well matched to the laser pulse parameters, but will serve as a starting point for first experiments. Pulse compression techniques combined with the use of the recently installed photo electron gun should ultimately provide bunches in the 100 fs and nC range. A fully shielded target area has been set up allowing for co- and counter-propagating laser and electron beams. Currently pulse synchronization issues are examined experimentally.

Moreover, Thomson scattering of the laser light from the relativistic electron bunch [2] can be used for the generation of hard X-rays (few ten keV) without the need for electron acceleration to the GeV level. Although in the common head-on geometry and in the linear regime only about 10^6 photons per laser pulse can be expected. This number should be sufficient for applications in pump probe experiments. A significant increase in the rate can be expected when for short electron pulses the matching of the temporal overlap is improved by a tilted pulse front approach [3] which has been extensively simulated.

[1] K. Zeil, et al., New Journal of Physics, 12, special issue to appear in april 2010
[2] for an overview with respect to ELBE parameters, see A. Debus, et al., Proc. SPIE, 9780819476333, 735908 (2009) and refs. therein.
[3] A. Debus, et al., Applied Physics B in press (2010)

  • Lecture (Conference)
    14th Advanced Accelerator Concepts Workshop, 13.-19.06.2010, Annapolis, USA

Publ.-Id: 16073

Physik und Technologie der Strahlentherapie mit Protonen und Ionen

Kunath, D.

Vortrag über die Grundlagen der Ionentherapie

  • Invited lecture (Conferences)
    3 Ländertagung der ÖGMP, DGMP und SGSMP, 28.09.-01.10.2011, Wien, Österreich

Publ.-Id: 16072

Relativistic positron production with ultra-intense short-pulse lasers

Cowan, T. E.

Ultra-intense laser interactions with solid foils are studied as a means to produce relativistic positron plasmas, which has been proposed as a potential laboratory for understanding positron-electron plasma aspects of gamma-ray bursts [1]. Initial experiments with high energy Nd:glass lasers have revealed a strong dependence of the positron yield, and energy distribution, on the thin-foil target thickness [2]. This arises from the contribution of so-called “trident” electro-production positrons, beyond the photo-production which dominates in thick targets [3]. Prospects for thin-target positron production and detection in 100 TW-class ultra-short pulse laser experiments will be presented

[1] E.P. Liang, S.C. Wilks and M. Tabak, Phys. Rev. Lett. 81, 4887 (1998).
[2] T. E. Cowan et al., Laser Part. Beams 17, 773 (1999).
[3] H. Chen et al., Phys. Rev. Lett. 102, 105001 (2009).

  • Poster
    8th International Conference on High Energy Density Laboratory Astrophysics, 15.-18.03.2010, Pasadena, USA

Publ.-Id: 16071

Impact of functionalized coligands on the pharmacokinetics of 99mTc(III) ‘4+1’ mixed-ligand complexes conjugated to bombesin

Künstler, J.-U.; Bergmann, R.; Gniazdowska, E.; Kozminski, P.; Walther, M.; Pietzsch, H.-J.

Bombesins (BN) containing 99mTc ‘4+1’ complexes may be useful to detect tumors expressing the gastrinreleasing peptide receptor (GRPR). Derivatives of the formula [99mTc(NS3R)(L2-BNst)] were synthesized, in which Tc(III) is coordinated by an isocyanide L2-BNst bearing the peptide (BNst=βAla-βAla-Gln-Trp-Ala-Val-Gly-His-Cha-Nle-NH2) and a tetradentate chelator NS3R. NS3R consists of 2,2′,2″-nitrilotriethanethiol (NS3) bearing a crown ether (NS3crown), an aliphatic amine (NS3en) and a tricarboxylic acid (NS3(COOH3). Nonradioactive Re compounds were prepared and analysed by electrospray ionization mass spectrometry. The structural similarity to the 99mTc conjugates was demonstrated by their identical HPLC elution profiles. The lipophilicity of [99mTc(NS3R)(L2-BNst)] decreased depending on the coligands NS3crown (log DO/W, pH=7.4, 0.98±0.11), NS3en (−0.49±0.07) and NS3(COOH)3 (−2.01±0.09). Biodistribution in normal rats was characterized by an increasing kidney uptake and a decreasing uptake into the liver corresponding to the reduced lipophilicity of the conjugates. The pancreatic uptake expressed by the organ/blood ratio of standardized uptake values at 60 min p.i. in rats was 8.6±1.2 for [99mTc(NS3en)(L2-BNst)] and higher compared to the other conjugates. The pancreas/liver ratio of the SUV at 60 min p.i. in rats was highest for [99mTc(NS3(COOH)3)(L2-BNst)] at 8.4±1.3. [99mTc(NS3en)(L2-BNst)] was further studied in tumor-bearing mice and its pancreas/blood and pancreas/liver ratios were lower, however the pancreas/kidney ratios were higher in mice compared to rats. The activity uptake of [99mTc(NS3en)(L2-BNst)] into the PC-3 tumor xenografts was low (%ID/g: 0.83±0.18 at 60 min; SUV: 0.21±0.05 at 60 min) but specific.

Keywords: Technetium; ‘4+1’ mixed-ligand complex; Peptide; Bombesin; Metabolism

Publ.-Id: 16070

Interaction of an edge dislocation with Cu–Ni-vacancy clusters in bcc iron

Terentyev, D.; Malerba, L.; Bonny, G.; Al-Motasem, A. T.; Posselt, M.

In this work we studied the interaction of a ½〈1 1 1〉{1 1 0} edge dislocation with Cu-rich precipitates, mimicking those that are known to form in RPV steels. We have applied a combination of Monte Carlo and molecular dynamics techniques to explore the structure and obstacle strength of Cu–Ni-vacancy clusters of nanometric size below the resolution limit of transmission electron microscopy. The results show that the strength of Cu-vacancy, Cu–Ni and Cu–Ni-vacancy clusters is comparable or even smaller than that of pure Cu clusters, but considerably smaller than the strength of pure vacancy clusters or nanovoids. Thus, the enrichment of small Cu precipitates by Ni atoms and/or a small amount of vacancies does not increase their obstacle strength, at least in the case of edge dislocations.


Publ.-Id: 16069

Radiobiological applications of ultrashort pulse laser-accelerated proton beams

Zeil, K.; Kraft, S.; Bussmann, M.; Cowan, T. E.; Kluge, T.; Metzkes, J.; Richter, T.; Sauerbrey, R.; Schramm, U.; Richter, C.; Beyreuther, E.; Enghardt, W.; Karsch, L.; Laschinsky, L.; Naumburger, D.; Pawelke, J.

Ultrashort pulse laser proton acceleration is demonstrated to yield energies hitherto only accessible with high energy lasers. Up to 20 MeV protons are observed with the FZD Draco Ti:Sa laser with ~30 fs pulses and only 2 J. This proton energy range allows for first well controlled applications. The radiation dose per shot observed for energies above 10 amounts to few Gy and thus provides excellent starting conditions for the irradiation of in vitro tumour cells with the aim of determining dose dependent biological damage. A first experiment demonstrates the availability of all components indispensable for systematic radiobiological studies: A laser-plasma accelerator providing stable proton spectra with maximum energy exceeding 15MeV over hundreds of pulses and applicable doses of a few Gy within few minutes, a beam transport and filtering system, an in-air irradiation site, a dedicated dosimetry system providing both online dose monitoring and a precise absolute dose information applied to the cell sample, and the full infrastructure for analysing radiation induced damage in cells.

[1] S.D. Kraft, K. Zeil, et al., New J. Phys. 12, 085003 (2010).

  • Poster
    52nd Annual Meeting of the APS Division of Plasma Physics, 08.-12.11.2010, Chicago, USA

Publ.-Id: 16068

Progress towards laser-driven Particle Therapy accelerators

Cowan, T. E.; Schramm, U.; Bussmann, M.; Burris, T.; Fiedler, F.; Gaillard, S.; Herrmannsdoerfer, T.; Kluge, T.; Kraft, S. D.; Metzkes, J.; Sauerbrey, R.; Zeil, K.; Baumann, M.; Enghardt, W.; Pawelke, J.

Recent successes in laser-ion acceleration have motivated research towards laser-driven compact accelerators for medical therapy. Realizing laser-ion acceleration for medical therapy will require adapting both the laser-ion acceleration to the medical requirements, as well as the treatment methodology to the foreseeable laser constraints. Three key scientific and technological challenges are identified: increasing laser-accelerated proton energies to 250 MeV; developing compact, strong field magnetic beam manipulation systems; and development of real-time in-vivo dosimetry to enable pulse-by-pulse active feedback and control. Progress in each of these key areas are reviewed, with special emphasis on the prospect of increasing the energy of laser accelerated protons by modifications of the Target Normal Sheath Acceleration process.

  • Poster
    52nd Annual Meeting of the APS Division of Plasma Physics, 08.-12.11.2010, Chicago, USA

Publ.-Id: 16067

Energy scaling of laser accelerated protons, and performance of reduced mass targets

Metzkes, J.; Zeil, K.; Kraft, S. D.; Bock, S.; Bussmann, M.; Helbig, U.; Kluge, T.; Cowan, T. E.; Sauerbrey, R.; Schramm, U.

Proton acceleration from thin foils and reduced mass targets is studied with the 150 TW Ti:Sa DRACO Laser at FZD. DRACO has ~30 fs pulses, with up to 5 J at 10 Hz, and a contrast of 1e-10 in the ps regime, and 1e-9 to 1e-10 in the ns regime. Proton spectra are measured in radiochromic film stacks and magnetic spectrometers. Flat metallic foils exhibit a near-linear scaling of the maximum proton energy with laser power, consistent with [1] in the limiting case of ultrashort laser pulses [2]. Despite the high laser contrast, a slight deformation of the target rear surface results in a reproducible deflection of the emission of energetic protons away from the target normal direction [2]. The mass limited targets of 2 μm thick Si, were fabricated by MEMS techniques and ranged from 20x20 µm2 to 100x100 µm2 lateral size. Significant influence of the target edge and supporting stalks is observed, which depending on size can both both increase or decrease the maximum proton energy in comparison to a flat foil.

[1] J. Schreiber et al., PRL 97, 045005 (2006).
[2] K. Zeil et al., NJP 12, 045015 (2010)

  • Poster
    52nd Annual Meeting of the APS Division of Plasma Physics, 08.-12.11.2010, Chicago, USA

Publ.-Id: 16066

Theoretical understanding of record proton energies from laser acceleration with cone targets and future prospects

Kluge, T.; Gaillard, S. A.; Flippo, K.; Bussmann, M.; Burris, T.; Gall, B.; Geissel, M.; Lockard, T.; Metzkes, J.; Offermann, D. T.; Rassuchine, J.; Schollmeier, M.; Schramm, U.; Sentoku, Y.; Zeil, K.; Cowan, T. E.

The laser-acceleration of protons to 67.5 MeV has recently been observed at the LANL Trident laser using novel cone targets [1]. The measured enhancement in proton energy is understood from collisional Particle in Cell simulations, which show that the hot electron temperature, responsible for the Target Normal Sheath Acceleration at the cone-top, is significantly increased when the laser grazes the cone wall. This is due to the extraction of electrons from the cone wall by the laser electric field, and their boost in the forward direction by the vxB term of the Lorentz force. This is in contrast to previous predictions of optical collection and wall-guiding of electrons in angled cones [2]. This new mechanism should enable new and more robust target designs for reaching high laser-accelerated proton energies.

[1] S.A. Gaillard, invited talk NI3.00004.
[2] Y. Sentoku et al, Phys. Plasmas 11, 3083 (2004).

  • Poster
    52nd Annual Meeting of the APS Division of Plasma Physics, 08.-12.11.2010, Chicago, USA
  • Invited lecture (Conferences)
    52nd Annual Meeting of the APS Division of Plasma Physics, 10.11.2010, Chicago, USA

Publ.-Id: 16065

The electrical and electroluminescence properties of rare earth implanted MOS light emitting devices in the near infrared

Rebohle, L.; Lehmann, J.; Prucnal, S.; Helm, M.; Skorupa, W.

In the past, the suitability of Er for Si-based light emission was already investigated in detail. However, much less attention has been paid to Nd and Ho which exhibit several emission lines in the near infrared according to their 4f energy level scheme. In this work we measure the electrical and electroluminescence properties of Nd- and Ho-implanted MOS structures and compare them with the corresponding properties of Er-implanted devices. Based on these results their suitability for integrated photonic devices is discussed.

Keywords: Electroluminescence; Erbium; Neodymium; Holmium; Rare Earth; Optoelectronic Device; Si-based light emission

  • Lecture (Conference)
    EMRS Fall Meeting, 19.-23.09.2011, Warsaw, Poland
  • Journal of Luminescence 132(2012), 3151-3153
    DOI: 10.1016/j.jlumin.2011.11.024

Publ.-Id: 16064

Inclusive e+e pair production in p+p and p+Nb collisions at Ekin = 3.5 GeV

Weber, M.; Agakishiev, G.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Cabanelas, P.; Chernenko, S.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Hennino, T.; Holzmann, R.; Huck, P.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Kozuch, A.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lang, S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

We report on recent data of e+e- pair emission in proton nucleus collisions at energies above the light vector meson production thresholds. Invariant mass distributions for the p+Nb system at Ekin = 3.5 GeV are compared to data from elementary p+p reactions at the same beam energy. We observe a constant π0/ω yield ratio for both systems but an excess in the mass region above the π0 mass. Furthermore we present here the normalization procedure that was applied to p+Nb collisions by measuring the production of negative pions in the HADES acceptance.

Publ.-Id: 16063

Locally Adaptive Filtering for Edge Preserving Noise Reduction on Images with low SNR in PET

Langner, J.; Hofheinz, F.; Beuthien-Baumann, B.; van den Hoff, J.

As well known, the signal-to-noise ratio (SNR) of PET images can be considerably low. This is especially true for whole-body examinations of heavy patients, for respiratorygated studies, and dynamic studies with short frames. In these cases linear smoothing filters (LF) such as a Gaussian filter are applied in order to achieve an acceptable SNR. Image resolution is, however, considerably reduced by these LFs. This affects detectability and quantification of small structures. Interesting
alternatives to LFs are non-linear, locally adaptive filters (NLF), which enable noise reduction while preserving sharp edges.
It was the aim of this study to investigate the performance of a special NLF (bilateral filter, BF) when applied to images with a low SNR. In three phantom studies using a cylinder phantom with sphere inserts different signal-to-background ratios have been investigated. In addition, images with different noise levels were generated. Finally, respiratory-gated whole-body studies were analyzed. All data were filtered, both with BF and LF. The results were analyzed regarding noise level, image resolution and relative signal recovery.
In the phantom studies BF is able to preserve the spatial resolution near the edges of the spheres while improving the noise characteristics. Signal recovery even of small spheres is not significantly reduced. Using LF compromises the spatial
resolution and leads to unacceptable reduction of signal recovery. The positive properties of BF were also apparent when applying it to single gates of respiratory-gated studies, which otherwise were not suitable for visual inspection.
NLF is a powerful alternative to LFs commonly used in PET. For studies with high noise and high signal-to-background ratios using NLFs represents a suitable filter for edge preserving image enhancement. Its performance, however, is critically dependent on a sensible choice of its intensity and spatial dependent part.

  • Poster
    IEEE Nuclear Science Symposium and Medical Imaging Conference, 23.-29.10.2011, Valencia, Spain

Publ.-Id: 16062

Isothiocyanate containing bifunctional chelating ligands for copper(II) based on the 1,4,7-triazacyclononane (TACN) skeleton

Ruffani, A.; Stephan, H.; Steinbach, J.

The aim of this work is the development of bifunctional chelating agents (BFCAs) for mild and selective labelling of proteins with copper radioisotopes. In this perspective, the triazacyclononane derivative with two pyridyl pendant arms 1
(DMPTACN) seems to be useful. DMPTACN 1 and its bombesin conjugates can readily form very stable radiocopper(II) complexes under physiological conditions.1 The remaining secondary amine group of ligand 1 may be utilized to introduce the isothiocyanate group allowing the conjugation to appropriate biomolecules, e.g. proteins/antibodies by thiourea-bridging.
Results and Discussion:
Compound 1 was synthesized by a eleven-step sequence according to the previously published procedure.1 Treating the secondary amino group of 1 with 2-bromoacetamide reagents gave the appropriate N-Boc protected predecessors 2 (Figure 1). Subsequent cleavage of the Boc protection group with trifluoroacetic acid led smoothly to the 4-aminophenyl and 4-aminobenzyl derivatives of DMPTACN 3. In the last step, the isothiocyanates 4, synthesized by the reaction of
2 with thiophosgen proved to be high yielding. First labelling experiments of DMPTACN isothiocyanates 4 with [64Cu]CuCl2 were performed in 0.1M MES/NaOH buffer at a pH = 6.2 and 251C, resulting in a radiochemical purity of higher than 99% within few minutes. The reactivity of the 64Cu-labeled isothiocyanates with primary amino groups was tested using glycine as model compound. Applying a ten-fold excess of glycine, the reaction was completed after 4 h at room temperature. To prove the potential to label proteins, the monoclonal antibody C225 was investigated. In a first approach, ligands 4 were radiolabelled with 64Cu, and subsequently conjugated to C225. For this pre-labelling strategy, a specific activity of 2.5 GBq/mmol was obtained. The post-labelling approach is more practical. The achievable ligand-toantibody ratios were 5:1, analyzed by Maldi-Tof mass spectrometry. Rapid labelling of the DMPTACN-containing antibody with [64Cu]CuCl2 was achieved to give a specific activity of 304 GBq/mmol.
DMPTACN isothiocyanates are attractive bifunctional agents for the radiocopper(II)-labelling of proteins featuring very high chemical stabiliy.
[1] G. Gasser, L. Tjioe, B. Graham, M. J. Belousoff, S. Juran, M. Walther, J.-U. Ku¨ nstler, R. Bergmann, H. Stephan, L. Spiccia, Bioconjugate Chem. 2008, 9, 719–730.

Keywords: TACN; copper-64; isothiocyanate; C225

  • Lecture (Conference)
    17th Workshop of the International Isotope Society – Central European Division. The Synthesis and Applications of Isotopes and Isotopically Labelled Compounds, 23.-24.09.2010, Bad Soden, D
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), 281-282
    DOI: 10.1002/jlcr.1859

Publ.-Id: 16061

New maleimide functionalized NOTA-derivatives: Synthesis and 64Cu/68Ga labelling of thiol modified L-oligonucleotides

Schubert, M.; Förster, C.; Bergmann, R.; Klussmann, S.; Pietzsch, H.-J.; Steinbach, J.

The macrocyclic chelator 1,4,7–triazacyclononane triacetic acid (NOTA) is very suitable to label molecules with 64Cu or 68Ga due to its fast complex formation resulting in thermodynamically and kinetically stable complexes. Here we describe a convenient synthesis procedure for maleimide-functionalized NOTA derivatives for stable binding thiol groups of carrier molecules such as peptides, oligonucleotides or antibodies. This principle is examplified by coupling of thiol-modified L-oligonucleotides which are of great interest for pre-targeting approaches in radio-immunotherapy 1.
Results and discussion:
NOTA-monomaleimide 3 and NOTA-bismaleimide 4 were synthesized by nucleophilic addition of aminoethyl maleimide 1 or bismaleimide 2 to p–SCN-Bn-NOTA. At the next reaction step the NOTA-maleimides were conjugated
with a 50-mercaptohexyl-modified L-oligonucleotide.
64Cu or 68Ga labelling of conjugates 5 and 6 occurred very fast and with good radiochemical yields in NH4OAc buffer. The specific activities resulted in 13.0 GBq/mmol for [64Cu]Cu5, 6.7 GBq/mmol for [68Ga]Ga5, 5.8 GBq/mmol for [64Cu]Cu6 and 2.6 GBq/mmol for [68Ga]Ga6. Small animal PET imaging in mice with [64Cu]Cu5 showed that after 2 hours most of the injected activity was located in the bladder.
The new ligand systems show advantages which make them interesting for further biological studies, namely the easy synthesis procedure, the fast labelling with 64Cu or 68Ga and the transferability of the conjugation principle to other carrier molecules such as peptides or antibodies.
[1] J. Schlesinger et al., Bioconjugate Chem. 2008, 19, 928–939.

  • Lecture (Conference)
    17th Workshop of the International Isotope Society – Central European Division. The Synthesis and Applications of Isotopes and Isotopically Labelled Compounds, 23.-24.09.2010, Bad Soden, D
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), 279-280
    DOI: 10.1002/jlcr.1859

Publ.-Id: 16060

Mono- and bis-maleimido-functionalized NOTA for site-specific modifications

Förster, C.; Schubert, M.; Pietzsch, H.-J.; Steinbach, J.

The purpose was to develop applicable synthetic strategies for the preparation of new NOTAmaleimides for site-specific introduction into radiopharmaceutically relevant (macro)molecules. This approach should be characterized by low synthetic effort and high grade of flexibility concerning length and chemical nature of spacer units connecting the NOTA to the maleimide entities.
To translate the idea and above stated requirements, the commercially available 1 and 2 were used as starting NOTA compounds. For the covalent attachment of maleimide derivatives with different linkers (aliphatic C2 to C6 as well as PEG28), two synthetic pathways were investigated (scheme 1). The first is based on nucleophilic addition reaction of an aromatic isothiocyanate with a primary amino group. Due to the limited availability of amino functionalized maleimides, a second protocol was developed. Therefore, the aromatic amino group of 2 was used for coupling reactions with NHS-ester functionalized maleimide derivatives. After establishment of these two
methods, a selection of products was engaged in coupling reactions with thiol modified L-oligonucleotides (L-DNA) for tumor pretargeting studies.

The high sensitivity of the starting materials as well as the products 3a-b and 4a-e in terms of hydrolyzation side reactions necessitated optimization of reaction parameters (solvent, pH value, stoichiometry, reaction time, etc.). Yields of 30-40 % and 83-86 % for 3a-b and 4a-d were achieved, respectively. A yield of 50 % was attained for the PEG28 derivative 4e. High specific activities resulted upon labeling different L-DNA-NOTA conjugates with 64Cu and 68Ga for biodistribution studies in Wistar rats.
As a proof of concept, we demonstrate the practicability of these two methods by engaging various linkers. The broad variety of commercially available NHS-ester modified maleimides in respect to different spacer length, shape, and polarity emphasizes the high flexibility for the design of tailored NOTA-maleimides for diverse applications.

  • Poster
    19th International Symposium on Radiopharmaceutical Sciences, 28.08.-02.09.2011, Amsterdam, The Netherlands
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), S324

Publ.-Id: 16059

Synthesis and in vitro characterisation of complementary L-oligonucleotides and their antibody conjugates

Schubert, M.; Förster, C.; Bergmann, R.; Vonhoff, S.; Klussmann, S.; Walther, M.; Pietzsch, J.; Pietzsch, H.-J.; Steinbach, J.

Complementary L-oligonucleotides (L-ONs) are characterized by high metabolic stability and low immunogenicity, in combination with the absence of natural hybridization targets and therefore represent a potential effector and conjugated with the targeting antibody as binding pairs in pretargeting technologies. PEG modification of the L-DNA will allow the pharmacokinetic tailoring of the effector molecules. Therefore we studied the effect of various sizes of PEG conjugates on the hybridisation of the L-DNA molecules with the complementary L-DNA-Cetuximab conjugates.
Cetuximab as targeting probe for the endothelial growth factor receptor was a) modified with 1,4,7 triazacyclononane-1,4,7-triacetic acid (NOTA), b) modified with maleimide moieties by conjugation of the bifunctional cosslinker 4 maleimidobutyric acid N-hydroxysuccinimide ester (GMBS), c) conjugated with the complementary thiol-bearing single strand 17mer-c-L-DNA-SH. The degree of bound NOTA, maleimide and c-L DNA were determined by MALDI-TOF or UV/VIS spectroscopy. HS-PEG-L-DNAs with PEG sizes of 2, 5 and 10 kDa were conjugated with NOTA-maleimide and labelled with 64Cu++. The hybridisation was carried out in vitro with the radiolabeled L-DNA in different stoichiometrical ratios to NOTA-c-L-DNA-Cetuximab and analysed by agarose gel electrophoresis or UV-spectroscopy.
Four different L-DNA-Cetuximab-conjugates bearing 2.2±0.8, 2.9±1.1, 4.9±1.4 and 9±2 L-DNA chains (mean±SEM, n=3) were synthesized. PEGs with molecular masses of 2, 5 and 10 kDa did not clearly influence the hybridization of the 64Cu-NOTA-PEG-L-DNA-conjugates with the complementary DNA-Cetuximab in vitro. Maximal hybridisation was reached in ratios equal and larger than 1:1 calculated from the DNA amount. The number of bound c-L-DNA on Cetuximab in the radioactive titration experiments were 2, 2.5, 5 and 9.5, which well agreed with 2.2, 2.9, 4.9 and 9, respectively, determined by direct UV/VIS spectroscopy of the c-L-DNA-NOTA-Cetuximab-conjugates.
The effector 64Cu-NOTA-PEG-L-DNA and the targeting probe NOTA-c-L-DNA-Cetuximab were synthesised, characterized and tested. The number of c-L-DNA on the Cetuximab was sufficient for in vitro hybridisation. The size of the PEG spacer did not clearly influence the in vitro hybridisation of the c-L-DNA-NOTA-Cetuximab-conjugates. This characteristic of the studied L-ON derivatives seems to be suitable for in vivo application. The potential of this L-ON approach in the pretargeting technology is currently under in vitro and in vivo investigation.

  • Poster
    19th International Symposium on Radiopharmaceutical Sciences, 28.08.-02.09.2011, Amsterdam, The Netherlands
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 54(2011), S405

Publ.-Id: 16058

Neue Entwicklungen in der PET/CT Hybridbildgebung: Nutzen für die Strahlentherapie?

Hofheinz, F.; Perrin, R.; van den Hoff, J.; Zips, D.

Die kombinierte PET/CT Bildgebung hat nach ihrer klinischen Einführung im Jahr 2001 in kurzer Zeit große Bedeutung in der Onkologie und Strahlentherapie erlangt (siehe z.B. [1-7]). Die Fähigkeit zur quasi-simultanen akkuraten morphologischen CT- und funktionellen PET-Bildgebung bei methodenbedingt gewährleisteter guter räumlicher Korrespondenz der beiden tomographischen Bilddatensätze ist der wesentliche Grund hierfür.

Die Gerätetechnik hat sich in diesen rund zehn Jahren kontinuierlich fortentwickelt. CT-seitig erfolgte hier ein Übergang von den initial verwendeten Einzeilengeräten zu den heute üblichen 64-128-Zeilengeräten, welche die im Vergleich zur PET ohnehin gute Ortsauflösung der CT weiter verbessern, v.a. aber die Untersuchungszeiten deutlich verkürzen. Auch PET-seitig wurden und werden große Fortschritte in der Gerätetechnik erreicht, die im folgenden noch näher diskutiert werden sollen, da insbesondere die kontinuierliche Verbesserung der PET-Bildgebung für den prospektiven Nutzen der PET/CT für die Belange der Strahlentherapie von entscheidender Bedeutung ist.

Maßgebliches Interesse besteht aus strahlentherapeutischer Sicht daran, die durch die PET gelieferte Information hinsichtlich verschiedener relevanter Parameter wie Tumorstoffwechsel und -hypoxie in eine individualisierte Bestrahlungsplanung optimal einzubringen. Aus messtechnischer Sicht sind die hauptsächlichen Anforderungen an die funktionelle PET/CT-Bildgebung in diesem Zusammenhang: Gewährleistung der bestmöglichen Koregistrierung von CT- und PET-Bilddaten, hohe Genauigkeit der quantitativen funktionellen PET-Parameter (z.B. SUV-Werte und Targetvolumen) und möglichst hohe (praktisch nutzbare) räumliche Auflösung der PET.

Publ.-Id: 16057

Instability types at ion-assisted alloy deposition: from two-dimensional to three-dimensional nanopattern growth

Abrasonis, G.; Morawetz, K.

Ion irradiation during film growth has a strong impact on structural properties. Linear stability analysis is employed to study surface instabilities during ion-assisted growth of binary alloys. An interplay between curvature-dependent ion-driven and deposition-driven instabilities is investigated. We demonstrate that ion irradiation of growing binary alloys leads to the formation of composition-modulated surface patterns. It is shown that the ion-to-atom arrival ratio R is the pattern control parameter. Close to the instability threshold we identify different regimes of instabilities driven by ion- or deposition-induced surface roughness processes, or roughness-composition feedback interactions. In particular, the synergistic effects of the curvature-dependent displacement and deposition coupling to the preferential sputtering or to the preferential diffusivity are found to induce instabilities and pattern formation. Depending on the film growth and ion-irradiation conditions, the instabilities show stationary or oscillating behavior. The latter one is exclusively connected with ion irradiation. The corresponding phase diagrams are presented in terms of experimentally accessible parameters. This shows an alternative way to control surface patterning and to grow three-dimensional laterally or vertically ordered nanostructures.

Publ.-Id: 16056

Supernovae im Labor

Schmidt, K.; Akhmadaliev, C.; Anders, M.; Bemmerer, D.; Boretzky, K.; Caciolli, A.; Elekes, Z.; Fülöp, Z.; Gyürky, G.; Hannaske, R.; Junghans, A.; Marta, M.; Schwengner, R.; Szücs, T.; Wagner, A.; Zuber, K.

Das Nuklid 44Ti (Halbwertszeit 59 Jahre) wird in Supernovae erzeugt. Die Gamma-Strahlung aus seinem Zerfall lässt sich in weltraumgestützten Gamma-Teleskopen nachweisen und kann als Werkzeug zum Test von Supernova-Modellen genutzt werden. Hierfür ist eine genaue Kenntnis der Kernreaktionsraten für die Erzeugung und Zerstörung von 44Ti erforderlich. Die 40Ca(alpha,gamma)44Ti-Reaktion dominiert die Erzeugung von 44Ti. Ihre Rate wird von einer Vielzahl von Resonanzen bestimmt. Um präzise Daten zu gewinnen, wurde die Stärke des Resonanztripletts bei 4.5MeV Gamma-Energie am Dresdner 3MV Tandetron sowohl mittels in-beam Gamma-Spektrometrie als auch durch eine Aktivierungsmessung im Felsenkeller-Niederniveaumesslabor gemessen. Eine Untersuchung der bestrahlten Proben mittels Beschleunigermassenspektrometrie ist geplant. – Gefördert von der EU (FP7-SPIRIT 227012) und der DFG (BE 4100/2-1).

Keywords: 44Ti Supernova 40Ca(alpha; gamma)44Ti 3MV Tandetron Felsenkeller

  • Poster
    9. Dresdner Lange Nacht der Wissenschaften, 01.07.2011, Dresden, Deutschland

Publ.-Id: 16055

Ion-Assisted Physical Vapor Deposition: Principles and Applications

Abrasonis, G.

Many physical vapor deposition (PVD) methods involve the energetic particle bombardment of growing film surfaces. While the source, energy and flux of such energetic particles strongly depend on the PVD method, the basic processes they induce on the film surface are similar. Such an irradiation has a beneficial effect on different structural properties of coatings or thin films such as densification, grain morphology, adhesion, texture. This has a direct impact on the mechanical, tribological, electrical, optical or chemical performance of such films.

The aim of this talk is to give a brief overview on (i) different PVD techniques involving energetic particles and (ii) basic ion-solid interaction processes and how they influence the thin film growth process. Some recent results of our group on the ion-assisted growth of nanocomposite thin films will be also presented.

  • Invited lecture (Conferences)
    The 13th International Conference - School Advanced Materials and Technologies, 27.-31.08.2011, Palanga, Lithuania

Publ.-Id: 16052

Current driven flow instabilities in large scale liquid metal batteries and their management

Weier, T.; Stefani, F.; Gundrum, T.; Gerbeth, G.

Liquid metal batteries, i.e. batteries in which both electrodes as well as the electrolyte are in the liquid state, usable for grid-scale energy storage have received considerable attention recently . A current and comprehensive account focusing on their applicability in future large scale storage systems is provided by Bradwell, earlier investigations of the technology were oriented on smaller units and thermally regenerative electrochemical systems.

A battery with fully liquid active inventary has a number of advantages: when densities are chosen properly, the battery is self-assembling due to stable stratification. Liquid-liquid interfaces allow for very fast kinetics and thereby rapid charging and discharging. Structureless (liquid) electrodes are insusceptible to aging providing nearly unlimited cyclability. Liquid metal batteries may be built from abundant and cheap feedstock. NaS and ZEBRA batteries share several of the advantages mentioned above, but require large initial investments due to their complicated construction, which is mainly dictated by the fragile ceramic electrolyte. In any case, scalability is a key enabler for cheap grid storage and ease of scale-up is one of the main underlying assumptions of liquid metal battery development. However, large electrode areas and high current densities imply large total current per cell and here electromagnetics together with fluid mechanics - i.e. magnetohydrodynamics - comes into play.

Aluminium reduction cells - which are often mentioned to have sparked the idea for large scale energy storage using liquid metals, see, e.g., - suffer from an interfacial instability which puts a constraint on the minimum electrolyte thickness. While this limitation has also to be considered, our focus is on another kind of instabilty, which limits the upper size of liquid metal batteries and is known in astrophysics under the label Tayler instability (TI). In our context, the TI is a kink-type (i.e. non-axisymmetric) instability that occurs if the current through a column of liquid metal exceeds some critical value in the order of kA, depending on the material properties. If this current threshold is exceeded, the TI would lead to a stirring of the battery inventory destroying the stable density stratification and short-circuiting the electrodes. Due to its potentially dramatic consequences, the TI should definitely be avoided during liquid metal battery operation.

One possibility to circumvent the instability is to use cells with a central bore. Depending on the ratio of bore to cell diameter, the instability can be shifted to higher total currents. Feeding a current through the bore opposing the current in the cell is a means to suppress the TI totally and would therefore be preferred in practical settings.

Keywords: liquid metal battery; Tayler instability; magnetohydrodynamics; energy storage

  • Poster
    6th International Renewable Energy Storage Conference and Exhibition (IRES 2011), 28.-30.11.2011, Berlin, Deutschland

Publ.-Id: 16051

Photoluminescence dynamics in GaAs/AlGaAs quantum wells under pulsed intersubband excitation

Zybell, S.; Schneider, H.; Winnerl, S.; Köhler, K.; Helm, M.

The photoluminescence (PL) emission of semiconductor quantum wells (QWs) at low temperatures for low and intermediate excitation densities shows long rise times, as only zero-momentum states can directly couple to the photons. The relaxation of the electron-hole plasma into the k=0 state and the binding of free electron-hole pairs into excitons has been extensively studied and debated in literature. Amo et al. [1] studied the effects of the sudden warming of the relaxing carrier distribution by applying a second, time-delayed interband excitation pulse.
We present a detailed study on time-resolved photoluminescence from an undoped GaAs/AlGaAs multiple QW sample quenched by a time-delayed mid-infrared (MIR) pulse causing an intersubband transition. Our experimental technique is based on the synchronization of a pulsed table-top Ti:sapphire laser with a free-electron laser (FEL) operating in continuous pulsing mode (13 MHz). The user facility FELBE at Helmholtz-Zentrum Dresden-Rossendorf is tunable and covers a wavelength range from 4 to 280 µm. The picosecond Ti:sapphire laser pulses operating at a photon energy of 1.64 eV create a free-carrier density of approximately 5x1010 cm-2 per well in the MQW structure via interband excitation. The PL is detected by a streak camera attached to a grating spectrometer, which allows for spectral and temporal resolution of the signal (see Fig. 1b). PL quenching is induced by a delayed MIR pulse from the FEL tuned to the intersubband energy of the sample of 172 meV (7.2 µm). Since the MIR pulses (~2 ps) are much shorter than the PL recovery time, a clear sharp dip appears in the PL transient at the arrival time of the MIR pulse. The PL recovers to a slightly higher intensity as compared to the unperturbed case due to particle conservation (see Fig. 1b). As no carriers are newly injected, the carrier dynamics can be directly studied from the PL recovery within the time resolution of our experimental setup (~ 25 ps).
The experimental data can be accurately described by a rate-equation model, where possible states in the conduction band are reduced to two effective levels. The PL recovery time was found to be the same as the PL rise time for all studied MIR fluences and temporal positions of the dip. This implies that the PL recovery accounts for the cooling of the carrier distribution rather than the formation of radiative states. The observed cooling time linearly decreases with MIR fluence due to lattice heating induced by the FEL. Performing polarization sensitive measurements, we were able to discriminate the contributions of free-carrier absorption from that of intersubband absorption, where the latter is 20 times more efficient than the free-carrier absorption (see Fig. 2). This approach also provides a new method to investigate the strictness of the polarization selection rules for intersubband absorption.

[1] A. Amo, D. Ballarini, D. Sanvitto, E. Kozhemyakina, L.Vina, A. Lemaitre, D. Bajoni, and J. Bloch, Appl. Phys. Lett 92, 061912 (2008).

Keywords: quantum wells; intersubband transition; time-resolved photoluminescence

  • Lecture (Conference)
    The 11th International Conference on Intersubband Transitions in Quantum Wells (ITQW 2011), 11.-17.09.2011, Le Dune Resort & Spa Badesi, Sardinia, Italia

Publ.-Id: 16050

Reynolds Averaged Navier-Stokes (RANS) und Large Eddy Simulations (LES) of the air-water TOPFLOW-PTS experiment

Niceno, B.; Lumpp, T.; Apanasevich, P.; Lucas, D.

The occurrence of a PTS in a reactor vessel is an important phenomenon for assessing nuclear reactor safety. New experiment was conducted at HZDR, focused on thermal mixing processes in the cold leg and the downcomer of two-phase PTS case. Present work reports CFD analysis of steady-state air-water case. CFD analysis was conducted with two turbulence-modeling approaches, RANS and LES. Multiphase situation was modeled with VOF approach. Simulations were performed using the ANSYS Fluent 12 package. Comparison of computed temperatures results and measurements along the thermo-couple lines revealed results depend on the turbulence model used.

Keywords: CFD; Pressurized thermal shock; LES; RANS

  • Contribution to proceedings
    The 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14), 25.-30.09.2011, Toronto, Canada
    Proceedings of the 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics (NURETH-14)
  • Lecture (Conference)
    The 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14), 25.-30.09.2011, Toronto, Canada

Publ.-Id: 16049

The free-electron laser as a tool for time-resolved, nonlinear, and near-field spectroscopy

Helm, M.

We present three examples of infrared spectroscopic investigations of semiconductors: exciton dressed states in quantum wells, pump-probe measurements on graphene, and near-field spectroscopy of buried quantum dots.

Keywords: free-electron laser; pump-probe; quantum dots; graphene; exciton

  • Invited lecture (Conferences)
    36th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2011), 02.-07.10.2011, Houston, USA
  • Contribution to proceedings
    36th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2011), 02.-07.10.2011, Houston, USA: IEEE, E-ISBN : 978-1-4577-0508-3, 6105078
    DOI: 10.1109/irmmw-THz.2011.6105078

Publ.-Id: 16048

Coherent switching of a THz intersubband polarization in a quantum well

Wagner, M.; Helm, M.; Sherwin, M. S.; Stehr, D.

Using low-frequency terahertz pulses we present ultrafast optical switching of a coherent intersubband polarization in a semiconductor quantum well.

Keywords: terahertz; intersubband; quantum well; coherent

  • Lecture (Conference)
    11th International Conference on Intersubband Transitions in Quantum Wells (ITQW 2011), 11.-17.09.2011, Badesi, Italy

Publ.-Id: 16047

Numerical simulations of the TOPFLOW-PTS steam-water experiment

Apanasevich, P.; Lucas, D.; Hoehne, T.

The correct analysis of the Pressurized Thermal Shock requires the simulation of the thermal mixing that occurs when cold Emergency Core Cooling (ECC) water is injected into the cold leg, where it flows to the downcomer and mixes with the hot coolant present in the primary circuit. In the framework of the NURISP (NUclear Reactor Integrated Simulation Project) project attempts are being made to improve the CFD modeling for two-phase PTS scenarios. For this purpose, two steady-state reference cases from the TOPFLOW-PTS experimental program were defined: one for air-water and one for steam-water flow. The current paper focuses only on the steam-water reference case. The pre-test simulations were performed with the commercial CFD code ANSYS CFX 12.0. The simulations of the steam-water reference test predicted a thermal stratification in the cold leg at the entrance into the downcomer and in the downcomer itself.

Keywords: Stratified flow; Direct contact condensation; CFD; Pressurized thermal shock

  • Contribution to proceedings
    The 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14), 25.-30.09.2011, Toronto, Canada
    Proceedings of the 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics (NURETH-14)
  • Lecture (Conference)
    The 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14), 25.-30.09.2011, Toronto, Canada

Publ.-Id: 16046

Dreams for DREAMS - The DREsden Accelerator Mass Spectrometry facility

Merchel, S.; Akhmadaliev, S.; Pavetich, S.; Rugel, G.

Eingeladener Vortrag ohne Abstract

Keywords: accelerator mass spectrometry; AMS

  • Invited lecture (Conferences)
    Graduiertenkollegseminar des Graduiertenkolleg "Elementspeziation", 16.-18.10.2011, Bad Münster am Stein, Deutschland

Publ.-Id: 16045

Uranium(VI) speciation in natural occurring water samples at pH 3 – 4, determined by TRLFS

Baumann, N.; Arnold, T.

Knowledge in speciation is a requirement in investigations about migration paths of heavy metal con-taminations in the natural environment. A very helpful tool with an extremely low detection limit for analyzing speciation of certain radioactive heavy metal ions like uranium (VI) is the Time-resolved Laser-induced Fluores-cence Spectroscopy (TRLFS). This technique is particularly useful for detection of speciation from those ions in very low, but environmental relevant concentrations. So TRLFS can be useful in safety assessment concerning migration behaviour of fluorescent and radioactive elements.
In this study, TRLFS was applied to determine the uranium speciation in natural occurring seepage water sam-ples, and in soil water samples, all samples collected from test site “Gessenwiese” close to Ronneburg in Eastern Thuringia (Germany), were analyzed by TRLFS. This test site was installed as part of a research program of the Friedrich Schiller University Jena for investigations within the area of recultivated former uranium mining heaps.
The TRLFS measurements on water samples collected within test site Gessenwiese revealed that the uranium speciation in these seepage waters and soil waters is dominated by the hydrolyzed and monomer uranium (VI) sulfate species UO2SO4(aq). The analysis were based on the position of the peak maxima from the fluorescence signal, and their mono-exponential decay curve. Despite of the presence of high amounts of well-known fluores-cence quenchers like iron (up to 18.3 ppm) and manganese (up to extend of 97.4 ppm), the obtained uranium (VI) fluorescence signals from the natural surface and soil water samples showed sufficiently high intensity and thus could be analysed.
The here presented results are a convincing example for the suitability of TRFLS in analyzing the speciation of uranium from natural occurring water samples with pH values between 3.2 and 4.0. They were published in [1] and via Open Access.

[1] N. Baumann, T. Arnold and M. Longschinski, J Radioanal Nucl Chem, accepted Aug. 2011

  • Contribution to proceedings
    10. Jenaer Sanierungkolloquium, 04.-06.10.2011, Dornburg, Deutschland
    Konferenzband zum 10. Jenaer Sanierungskolloquim

Publ.-Id: 16044

Synergistic Approach of Structure-Based and Ligand-Based Drug Design for the Development of selective Cannabinoid Receptor Ligands

Günther, R.; Brust, P.

Cannabinoid receptors (CB) are G-protein coupled receptors involved in many physiological processes, like learning, appetite, nociception and others. Two subtypes (termed CB1 and CB2) are involved in slightly different processes [1]. Thus, it is important to gain more insight into the the cannabinoid receptor system and the potential effects of cannabinoid therapeutics.

By combining [2] 3D-QSAR, pharmacophore modeling, comparative modeling and molecular docking we could identify features responsible for receptor subtype specificity. Various pharmacophore models were derived from in-house libraries and data available in the literature. 3D structures of both receptor subtypes were created employing comparative modeling methods. The models were subjected to molecular simulations in solvated lipid bilayers to sample different receptor conformations. The models were used for molecular docking studies with small compound libraries.
Employing the data obtained in the pharmacophore/3D-QSAR studies as additional constraints delivered valuable information on affinity and selectivity of the compounds towards CB1 and CB2. The results from this synergistic modeling approach could improve our understanding of the protein–ligand interactions involved.
[1] Pertwee, RG. Ligands that target cannabinoid receptors in the brain: from THC to anandamide and beyond Addict Biol 2008, 13:147–159.
[2] This synergistic approach has been implemented into the MOE modeling package (MOE: Chemical Computing Group Inc. Montreal. H3A 2R7 Canada.

  • Poster
    7th German Conference on Chemoinformations, 06.-08.11.2011, Goslar, Deutschland

Publ.-Id: 16042

Depth-filtration model for compressible fibrous cakes

Grahn, A.; Kryk, H.; Kästner, W.; Alt, S.; Kratzsch, A.

Flow through fibrous materials is encountered in a number of industrial applications, such as paper making, air and liquid filtration or manufacture of composite materials. Particle retention and pressure drop in beds of fibrous materials are difficult to predict because such beds easily compact under the action of fluid drag forces and thus exhibit significant variations of hydraulic and filtration properties along the flow direction and with time. This study proposes a semi-empirical model to calculate the time dependent clogging of compressible fibrous cakes due to the capturing of suspended particles as they pass through the cake. An experimental and a data evaluation procedure are suggested for determining the empirical parameters of the model equations.

Keywords: depth filtration; pressure drop; compressible fibre cake

Publ.-Id: 16041

Study on severe accidents and countermeasures for VVER-1000 reactors using the integral code ASTEC

Tusheva, P.; Schäfer, F.; Reinke, N.; Altstadt, E.; Kliem, S.

The research field focussing on the investigations and the analyses of severe accidents is an important part of the nuclear safety. To maintain the safety barriers as long as possible and to retain the radioactivity within the airtight premises or the containment, to avoid or mitigate the consequences of such events and to assess the risk, thorough studies are needed. On the one side, it is the aim of the severe accident research to understand the complex phenomena during the in- and ex-vessel phase, involving reactor-physics, thermal-hydraulics, physico-chemical and mechanical processes. On the other side the investigations strive for effective severe accident management measures.

This paper is focused on the possibilities for accident management measures in case of severe accidents. The reactor pressure vessel is the last barrier to keep the molten materials inside the reactor, and thus to prevent higher loads to the containment. To assess the behaviour of a nuclear power plant during transient or accident conditions, computer codes are widely used, which have to be validated against experiments or benchmarked against other codes. The analyses performed with the integral code ASTEC cover two accident sequences which could lead to a severe accident: a small break loss of coolant accident and a station blackout. The results have shown that in case of unavailability of major active safety systems the reactor pressure vessel would ultimately fail. The discussed issues concern the main phenomena during the early and late in-vessel phase of the accident, the time to core heat-up, the hydrogen production, the mass of corium in the reactor pressure vessel lower plenum and the failure of the reactor pressure vessel. Additionally, possible operator’s actions and countermeasures in the preventive or mitigative domain are addressed. The presented investigations contribute to the validation of the European integral severe accidents code ASTEC for VVER-1000 type of reactors.

Keywords: Severe accidents; severe accident management; SBLOCA; SBO; primary side depressurization; vessel failure; ASTEC

  • Kerntechnik 77(2012)4, 271-277

Publ.-Id: 16040

Microbial Life in Uranium-contaminated Milieus

Zirnstein, I.; Gagell, C.; Arnold, T.; Krawczyk-Bärsch, E.; Röske, I.

Microorganisms often form communities, so-called biofilms, in its natural habitats. In every territory of the world they play an important role. Biofilms contain different types of microorganisms e.g. bacteria, fungi, amoebae, algae etc. Together with the self-produced matrix, called EPS (extracellular polymeric substances), they constitute a kind of microenvironment. The supply of nutrients is mediated by open water channels. Just the same way toxic heavy metals could possibly infiltrate the biofilm. In order to understand the migration and transport processes of uranium in nature it is necessary to study the interaction of uranium with biofilms.
Biofilms are located in the former uranium mine Königstein (Saxony) in a depth of 250 m. There are two types of biofilms: stalactite-like biofilms and drainage biofilms. The water is characterized by high concentrations of uranium, protons and sulfate ions. The microscopic and genetic analysis of the Königstein biofilms revealed a rich diversity of microorganisms within the biofilm. Astonishing, we also found fungi and eukaryotes such as amoebae, insects, ciliates among bacteria to live under the extreme conditions of the mine.
Königstein mine was flooded last year (2010). Other mining sites of Saxony were flooded a long time ago. Recent studies compare the microbial diversity after (selected mining sites) and before (Königstein mine) flooding. The aim of the work is to visualize the whole biofilm and to analyze its interaction with uranium.

  • Poster
    6th PhD Seminar HZDR, 05.-07.10.2011, Rabenberg, Germany

Publ.-Id: 16039

Intelligente Strömungsfolger zur räumlichen Parametererfassung in großskaligen Behältern

Reinecke, S.; Kryk, H.; Hampel, U.

Die räumliche Erfassung relevanter Prozessparameter wird bei einer Vielzahl industrieller Anwendungen durch den begrenzten Zugang zum Prozess erschwert. Beispiele sind Reaktoren mit Rührwerken, Bioreaktoren, Fermenter und Schüttgutbehälter. In solchen Behältern ist die Installation von fest angebrachten Sensoren und Kabelverbindungen oft nicht realisierbar oder unerwünscht. Herkömmliche Messsonden werden üblicherweise nur lokal installiert, womit die Erfassung räumlich verteilter Parameter nur eingeschränkt möglich ist. Zudem sind räumlich auflösende Apparate, wie Kameras oder Tomographiemesssysteme, meist nicht anwendbar. Daher bietet die Überwachung der räumlichen Verteilung relevanter Prozessparameter ein hohes Potential für die verbesserte Untersuchung und die Optimierung der Anlagen und Prozesse.
Speziell für Fermenter sind der lokale Vergärungsgrad von Biomasse, Temperaturprofile, pH-Wertverteilungen, Gas- und Flüssigkeitsbestandteile im Substrat sowie lokale Strömungscharakteristiken (Geschwindigkeitsprofile, Totzonen, Kurzschlussströmungen) für die Einschätzung der Prozesseffizienz von Interesse. Dabei kann es oft ausgehend von wenigen physikalischen Basisparametern, wie Temperatur und Druck, Rückschlüsse auf die Effektivität der Heiz- und Rührregime geben. Autonome Sensortechnologien ermöglichen die messtechnische Erfassung verteilter Parameter durch den Einsatz intelligenter Strömungsfolger und gewinnen deshalb zunehmend an Bedeutung für Anwendungen in der Prozessindustrie.
Zur Erfassung räumlich verteilter Parameter in Prozessbehältern wurde ein Schwarm autonomer Sensorkapseln mit einer zugehörigen Basiseinheit entwickelt und getestet. Die Validierung des Messsystemes erfolgte unter realen Strömungsbedingungen in einem Pilotfermenter. Die aufgenommenen Messdaten und die daraus extrahierten Parameterprofile liefern neuwertige und verlässliche Informationen über den Zustand im Prozess und die vorherrschenden Strömungsbedingungen.

  • Lecture (Conference)
    Mess- und Regelungskonzepte in der Lebensmittel- und Umweltbiotechnologie, 18.10.2011, Gerlingen, Deutschland
  • Contribution to proceedings
    Mess- und Regelungskonzepte in der Lebensmittel- und Umweltbiotechnologie, 18.10.2011, Gerlingen, Deutschland, 18.10.2011, Gerlingen, Deutschland
    Fachgruppentagung Mess- und Regelungskonzepte in der Lebensmittel- und Umweltbiotechnologie

Publ.-Id: 16038

Biofilms growing in an underground Uranium mine

Zirnstein, I.; Gagell, C.; Arnold, T.; Krawczyk-Bärsch, E.; Röske, I.

The eukaryotic diversity of biofilm microorganisms in the underground uranium mine Königstein in Saxony/Germany was studied by molecular methods and microscopy. The Königstein mine is currently in the process of remediation. Due to technical leaching with sulphuric acid, the mine water is characterized by low pH, high concentrations of toxic heavy metals and uranium (up to 3×10-4 M) (Arnold et al. 2010). Biofilms in the Königstein mine grew underground in the mine galleries in a depth of 250 m (50 above sea level) either as stalactite-like slime communities or as acid streamers in the drainage channels. Previously conducted studies on the bacterial diversity in both biofilm communities in the uranium mine Königstein showed that beta-proteobacterium affiliated with Ferrovum myxofaciens, also designated “Ferribacter polymyxa” were identified as dominating bacterial species (Brockmann et al. 2010).
Biofilms are not only composed of bacteria, but may also include archaea and eukaryotic organisms. The eukaryotic diversity of the Königstein biofilms was analysed by molecular methods, i.e. 18S rDNA PCR, cloning and sequencing, which were used to determine the DNA-fragments of the microorganism, and by microscopic investigations. It was found that the eukaryotic biofilm communities of the Königstein environment showed a limited number of different heterotrophic species and consist of a variety of lineages belonging to nine major taxa: Ciliates, Flagellates, Amoebae, Heterolobosea, Fungi, Apicomplexa, Stramenopiles, Rotifers and Arthropoda and in addition a large number of uncultured eukaryotes, denoted as acidophilic eukaryotic cluster (AEC). As dominant eukaryotic species in the underground Königstein environment were identified Vahlkampfia species, Bodo species, and Oxytricha species. Flagellates, e.g. Bodo saltans, Stramenopiles, e.g. Diplophrys archeri and Rotifers were discovered for the first time in acid mine drainage (AMD) milieus characterized by high concentrations of uranium.
These eukaryotes in the studied biofilms are part of a biofilm community and represent a cycle of a food chain. This study shows that not only bacteria and archaea were identified in extreme AMD environments, but also eukaryotic species were found. These observed eukaryotes may influence significantly carbon cycling and metal immobilization within biofilms.

Keywords: Eukaryote; uranium; acid mine drainage; biofilm; microbial diversity; snottite; acid streamer; 18S rDNA PCR; Light microscopy

  • Lecture (Conference)
    10th symposium on remediation, 04.-05.10.2011, Jena, Germany

Publ.-Id: 16037

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