Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

35175 Publications

Die Zweiquellenanlage des Forschungszentrum Rossendorf - Neue Möglichkeiten für Experimente mit hochgeladenen Ionen

Kost, D.; Facsko, S.; Heller, R.; Schlenk, R.; Wustmann, B.; Zschornack, G.

Die Rossendorfer Zweiquellenionenstrahlanlage stellt eine weltweit einmalige Kombination aus einer Elektron-Zyklotron-Resonanz-Ionenquelle mit einer bei Raumtemperatur arbeitenden Elektronenstrahl-Ionenquelle, der Dresden EBIT, dar. Die Ionenstrahlen beider Quellen münden in eine gemeinsame Targetkammer und stehen dort für Experimente zur Verfügung. Die erreichbaren Ladungszustände, die Ionenströme sowie die Energien der Ionen aus beiden Quellen unterscheiden sich aufgrund der verschiedenen Wirkungsprinzipien und gewährleisten so ein breites Spektrum an Experimenten. Die Gesamtanlage kann gegenüber der Targetkammer auf ein negatives Potential gebracht werden, wodurch sich die Ionen beider Quellen bis auf Energien unter q*100V abbremsen lassen. Die Untersuchung der Wechselwirkung langsamer hochgeladener Ionen mit Festkörperoberflächen, insbesondere der Einfluss der Potentialenergie der Ionen, ist neben der Ionenquellendiagnostik Gegenstand aktueller Forschungen an der Rossendorfer Zweiquellenanlage.

  • Lecture (Conference)
    Energiereiche Atomare Stöße, 06.-10.02.2006, Riezlern, Östereich

Publ.-Id: 8397

Potential Energy Retention of Slow Highly Charged Ar-Ions in Chemical Clean Silicon Surfaces

Kost, D.; Facsko, S.; Tyrroff, H.; Zschornack, G.; Möller, W.

Highly charged ions (HCI) carry a large amount of potential energy, which is defined as the sum of the binding energies of all electrons that are removed from the atom. In the case of low velocities of the ions this energy is equal or can exceed the kinetic energy of the ions. Retaining such a large energy in a very small surface area of typically about 1-10nm^2 and in a very short interaction time of typically 5-10fs an enormous power flux of 10^13 W/cm^2 is given. In respect of this, high yields of photons and electrons have been observed, which carry away a fraction of the potential energy. Some experiments give a quantitative estimation of an energy reemission coefficent in the order of only 10%. In our experiment we determine the fraction of the retained potential energy of the ions by a calorimetric measurement.

For improved calorimetric measurements of the retention of the potential energy of highly charged ions a UHV device with a base pressure of p<10^-9mbar was constructed and connected to the 7.5 GHz ECR ion source at the Forschungszentrum Rossendorf. The ECR ion source is equipped with a sector field magnetic separation and a beam deceleration system. The ions are accelerated with a voltage of 5 kV and after beam transport decelerated to final kinetic energies down to 60eVxq.

By using a calorimetric setup the increase of the target temperature is measured during the irradiation with argon ions.
The retained energy of Ar q+ (q= 1 up to 9) ions into the Si(100) surface is determined at kinetic energies between 60 eVxq and 200 eVxq. By extrapolation to zero kinetic energy the retained fraction of the potential energy is obtained.

For absolute calorimetric measurements a small resistive heater is used for the calibration of the calorimetric setup. Using the resistive heater a function between the temperature increase and the deposited electrical power of the heater is obtained. Assuming that the electrical power is equivalent to the retained power of the incident ions the retained power of the ions can obtained from the temperature increase.

By sputtering with Ar+ the silicon surface is cleaned before the measurement. The chemical state of the target surface is controlled by AES using LEED
optics. Once being clean there are no other Auger electron signals in spite of silicon signals detectable over a time of 7 hours.

The obtained retained potential energy of the different charge states of the argon ions is related to the total potential energy. The potential energy retention coefficient results as 0.7 +/- 0.2 and decreases weakly with increasing charge state. This values are compared with earlier measurements [1] on a copper surface. The potential energy retention coefficient for silicon is about three times larger than the results with the copper surface.

[1] U. Kentsch, H. Tyrroff, G. Zschornack, and W. Möller, Retention of the potential energy of multiply charged argon ions incident on copper, Phys. Rev. Lett. 87(10), 4273 (2001).

  • Poster
    International Conference on Photonic, Electronic and Atomic Collisions, 23.-29.07.2003, Stockholm, Schweden

Publ.-Id: 8395

Excursions into reversals

Stefani, F.; Gerbeth, G.; Günther, U.; Xu, M.

Despite the recent success of fully coupled three-dimensional numerical models of the geodynamo, the very nature of field reversals is still a matter of controversy. A mean-field dynamo model with a spherically symmetric helical turbulence parameter alpha serves us as a sort of minimum dynamo model that exhibits a number of typical reversal features. These include the asymmetry of reversals, the correlation between field strength and interval length, the existence of an inhibition time, and the bimodal field distribution. We identify the existence of a branch point of the spectrum of the non-selfadjoint dynamo operator as the essential ingredient for reversals to happen (Phys. Rev. Lett. 94 (2005), 184506). We present some evidences for a self-tuning mechanism of highly supercritical dynamos that tend to saturate into a reversal-prone state by driving the branch point and its nearby local maximum of the growth rate towards the zero line (Earth Planet. Sci. Lett. 143 (2006), 828-840). The high supercriticality can also explain the typical time-scales of asymmetric reversals (, without taking resort to a turbulent resistivity. The role of the inner core to increase the ratio of excursions to reversals is discussed in the framework of resonant appearance of branch points in dependence on the wavelength of the dynamo source (

  • Poster
    10th Symposium of SEDI, 09.-14.07.2006, Prague, Czech Republic

Publ.-Id: 8394

Influence of colloids on uranium transport in nuclear waste repositories and abandoned uranium mines – a critical comparison

Zänker, H.; Ulrich, K.-U.; Opel, K.; Brendler, V.

It is widely recognized that colloids can influence the migration of toxic and radiotoxic elements such as uranium. There are transport-facilitating and transport-impeding effects caused by colloids.
The most common scenario assumed in performance assessment for nuclear waste repositories is contaminant transport through anoxic aquifers. Only transport-facilitating effects of colloids are usually taken into consideration for this case. For abandoned uranium mines, retarding influences of colloids, apart from mobilizing ones, are also of high interest since they have the potential of causing “natural attenuation” of the environmental hazard.
The formation of colloids containing U(IV) and U(VI) was studied by laboratory experiments and by comparing the results with field experience. It is shown that there may be transport-stimulating effects of colloids on the “immobile” contaminant U(IV) and transport-impeding effects on the “mobile” contaminant U(VI).
A key factor in assessing the impact of colloids in a geochemical setting is the timescale that needs to be taken into account. Very long periods of time must be considered for nuclear waste repositories. Here, the point in time at which a certain colloid-borne contaminant such as uranium reaches the biosphere depends on the moment at which spent fuel container leakage begins, the water flow velocity, the concentration and mobility of potential carrier colloids, the hindrance of colloidal transport by barrier materials, and the persistence (reversibility vs. irreversibility) of the binding of the contaminant onto the colloids. In the case of mines, the phase critical for the environment occurs when the flood water reaches the level where first connections to unprotected surface waters or underground drinking water resources occur. This phase is characterized by the „first flush“ of the mine; the maximum release rate of contaminants such as U from the mine to the environment can be reduced by colloids via the flattening of the release rate profile. Whereas the timescale of critical contaminant release is in the range of centuries for the nuclear waste repositories, it lies in the range of only few years for abandoned uranium mines.
It is primarily the different dynamics of the processes behind these two different timescales that causes the different role of colloids for uranium migration in nuclear waste repositories and in abandoned uranium mines.

Keywords: nuclear waste repositories; abandoned uranium mines; uranium; colloids

  • Lecture (Conference)
    16th Goldschmidt Conference 2006, 27.08.-01.09.2006, Melbourne, Australia
  • Abstract in refereed journal
    Geochimica et Cosmochimica Acta 70(2006)18, A731
    DOI: doi:10.1016/j.gca.2006.06.1314

Publ.-Id: 8393

Calculation of the VVER-1000 Coolant Transient Benchmark using the Coupled Code Systems DYN3D/RELAP5 and DYN3D/ATHLET

Kozmenkov, Y.; Kliem, S.; Grundmann, U.; Rohde, U.; Weiss, F.-P.

Plant-measured data provided by the OECD/NEA VVER-1000 coolant transient benchmark programme were used to validate the DYN3D/RELAP5 and DYN3D/ATHLET coupled code systems. Phase 1 of the benchmark (V1000CT-1) refers to an experiment that was conducted during the commissioning of the Kozloduy NPP Unit 6 in Bulgaria. In this experiment, the fourth main coolant pump was switched on whilst the remaining three were running normal operating conditions. The experiment was conducted at 27.5 % of the nominal level of the reactor power. The transient is characterized by a rapid increase in the primary coolant flow through the core, and as a consequence, a decrease of the space-dependent core inlet temperature. The control rods were kept in their original positions during the entire transient. The coupled simulations performed on both DYN3D/RELAP5 and DYN3D/ATHLET were based on the same reactor model, including identical main coolant pump characteristics, boundary conditions, benchmark-specified nuclear data library and nearly identical nodalization schemes. In addition to validation of the coupled code systems against measured data, a code-to-code comparison between simulation results has also been performed to evaluate the respective thermal hydraulic models of the system codes RELAP5 and ATHLET.

Keywords: Coupled code systems; 3D neutron kinetics; code validation; code-to-code comparison; VVER-1000 model; coolant transient benchmark; main coolant pump

Publ.-Id: 8392

Atomic-level simulations of ion implantation, defect formation and defect migration

Posselt, M.

for further information, please contact the author

Keywords: ion implantation; defect formation; defect migration; atomic-level simulations

  • Invited lecture (Conferences)
    Seminar, 05.04.2006, Zürich, Switzerland

Publ.-Id: 8391

Interaction of Cu(II) with dendritic ligands studied by TRLFS

Geipel, G.

  • Lecture (Conference)
    Supraphone Meeting 2006, 04.-06.05.2006, Lissabon, Portugal

Publ.-Id: 8390

Comparison of in vitro and in vivo properties of 99mTc-RGD peptides for targeting tumour angiogenesis labelled using different novel technetium-cores

Decristoforo, C.; Rey, A.; Künstler, U.; Pietzsch, H.-J.; Galamba, J.; Santos, I.; Smith, J.; Faintuch, B.; Hernandez-Gonzales, I.; Rupprich, M.; Alberto, R.; Haubner, R.

1. Introduction
Integrins are cell surface transmembrane glycoproteins that are found as αβ heterodimers. The αvβ3 integrin is known to be over-expressed in many tumour types and sprouting blood vessels in the tumour, but expressed at lower levels in normal tissues. Peptides containing the Arg-Gly-Asp (RGD) sequence, bind with high affinity to αvβ3 and have found increasing interest for radiolabelling to target v3 receptors and for imaging angiogenesis. Recently, it was demonstrated using [18F]Galacto-RGD and PET that monitoring of αvβ3 is possible in animal models as well as in humans (1). Recent advances in organometallic chemistry enable 99mTc-labelling of biomolecules with high specific activity and high stability. The aim of this study was to use a cyclic RGD derivative, c(RGDyK), containing a Lys residue for derivatisation with different moieties for labelling with 99mTc using novel technetium-cores, such as HYNIC, Tc(CO)3, and Tc(4+1) approaches and to compare chemical and biological properties in vitro and in vivo.

2. Materials & Methods:
c(RGDyK) (RGD) was derivatised with HYNIC (1), Cys (2), 3, 5–Me2 –pyrazol-1-yl-ethyldiamine –RGD (PZ1, 3) and an isonitrile moiety (L3, 4) at the terminal lysine group of c(RGDyK) using standard fmoc chemistry (examples see Fig1). 99mTc-labelling was performed using both Tricine as well as EDDA as coligands for HYNIC-RGD, [99mTc(CO)3(H2O)3]+ was used for labelling Cys-, PZ1 and HYNIC-RGD and Aminotrithiols as coligangds for L3-RGD at high specific activities. Radiolabelled peptides were characterised concerning lipophilicity (octanol/PBS coefficient, RP-HPLC), protein binding using SEC, stability in buffer, serum and tissue homogenates and tested for stability in PBS, Cystein and Histidine solutions, tissue homogenates and serum up to 6 h. Integrin receptor activity was determined in internalisation assays using v3 receptor positive M21 and negative M21-L melanoma cells. Biodistribution and in vivo tumour uptake was evaluated in nude mice carrying M21 and M21-L tumours for selected compounds.

3. Results
All peptides could be labelled at high specific activities and revealed high stability in various solvents. Both lipophilicity as determined by HPLC retention times and log P values (-0.92 to -3.57) and binding to serum proteins (2-32%) varied considerably All 99mTc-labelled peptides showed specific uptake in αvβ3 positive cells with comparable values for all compounds around 1% of total/mg protein except for 99mTc-L1 and L3-RGD with lower values of less than 0.5%. In a mouse tumour model great variations in pharmacokinetic behaviour was found ranging from predominant renal excretion up to predominant hepatobiliar eliminiation. Highest specific values of tumour uptake were found for 99mTc-EDDA/HYNIC-RGD and 99mTc(CO)3-PZ1-RGD (see Fig. 2) with about 2.5% uptake in M21 receptor positive tumours and <1% in receptor negative M21-L tumours with lower intestinal uptake of 99mTc-EDDA/HYNIC-RGD.

4. Discussion/Conclusion
Our study provides for the first time data on chemical and biological characterisation of the same peptide labelled with 99mTc using different technetium-cores. It shows the decisive influence of labelling approaches on imaging properties of 99mTc-labelled peptides and the necessity to use different in vitro assays to predict targeting properties in vivo.

5. References:
(1) Haubner R, Weber WA, Beer AJ, Vabuliene E, Reim D, Sarbia M, Becker KF, Goebel M, Hein R, Wester HJ, Kessler H, Schwaiger M. [2005] PLoS Medicine. 2(3):e70.

6. Acknowledgements:
This work is part of the CRP “Development of Tc-99m based small bio-molecules using novel 99mTc cores” of the IAEA

  • Lecture (Conference)
    European Symposium on Radiopharmacy and Radiopharmaceuticals - ESRR 06, 30.03.-02.04.2006, Lucca, Italy
  • Abstract in refereed journal
    Quarterly Journal of Nuclear Medicine and Molecular Imaging 50(2006)Suppl. 1, 19

Publ.-Id: 8389

Towards Tc(III)- and Re(III)-labelled peptides with tunable lipophilicity

Gniazdowska, E.; Künstler, J.-U.; Stephan, H.; Pietzsch, H.-J.

1 Introduction
Organometallic Tc and Re (III) compounds in terms of so called “4+1” complexes enable high specific labelling of biomolecules, e.g., peptides under mild conditions and exhibit high complex stability [1, 2]. However, 99mTc-labelled peptides containing a “4+1” complex as in 99mTc(NS3)(CN-GGY) (Fig. 1) showed a high liver uptake [1]. To improve the biobehavior of such compounds a new hydrophilic “4+1” complex bearing three carboxyl groups was introduced and evaluated coupled to a model peptide.

2 Results
The carboxyl-groups bearing ligand NS3(COOH)3 was synthesized by conjugation (DCC) of the dendritically functionalized amine H2N-C(-CH2-O-CH2-CH2-COO-Me)3 [3] to the S-benzyl protected NS3COOH [1] followed by deprotection.
The isocyanide group was coupled to the model peptide Gly-Gly-Tyr via an aliphatic linker (CN-BFCA). For 99mTc-labelling a two-step procedure [1] was applied using 99mTc-EDTA/mannitol (400 MBq) which was reacted with 20 µg isocyanide-modified peptide and 300 µg NS3(COOH)3. 99mTc-labelling resulted in a radiochemical yield of app. 25 % (HPLC), Fig. 2. The yield can be increased by using a higher peptide amount. 99mTc(NS3(COOH)3)(CN-GGY) showed a high in vitro stability (> 90 % in PBS after 24 h).
To verify the identity of the 99mTc-labelled peptide, the analogous "4+1" Re compound Re(NS3(COOH)3)(CN-GGY) was synthesized (Fig. 1).

For a convenient synthesis of peptides containing the new hydrophilic Re “4+1” complex, the active ester Re(NS3(COOMe)3)(CN-BFCA) as shown in Fig. 1 was prepared starting from NS3(COOH)3, [Re(tu-S)6]Cl3 and PMe2Ph followed by ligand exchange with CN-BFCA. Reaction of Re(NS3(COOMe)3)(CN-BFCA) with the peptide and hydrolysis of the methyl ester gave the desired peptide derivative.
The increased hydrophilicity of the new “4+1” complex was shown by HPLC investigations (Fig. 2) and determination of the partition coefficient (logD, octanol/PBS, pH 7.4).
99mTc(NS3(COOH)3)(CN-GGY) showed a logD value of -2.6 ± 0.3 (n = 3) compared with the logD value of -1.5 ± 0.2, 99mTc(NS3)(CN-GGY).

3 Conclusion
A new hydrophilic “4+1” complex characterized by a dendritically modified tetradentate ligand was synthesized and has been introduced for peptide labelling. Increasing generation of dendritic branches will be grafted on the chelating unit in order to tune the lipophilicity. As a next step peptides bearing the new modified “4+1” compound have to be evaluated in animal experiments.

4 References
[1] Seifert S., Künstler J.-U., Schiller E., Pietzsch H.-J., Pawelke B., Bergmann R. and Spies H. [2004] Bioconjugate Chem. 15: 856-863.
[2] Schiller E., Seifert S., Tisato F., Refosco F., Kraus W., Spies H. and Pietzsch H.-J. [2005] Bioconjugate Chem. 16: 634-643.
[3] Newkome G. R., Lin X. and Young J. K. [1992] Synlett 1: 53-54.

5 Acknowledgements
The work was performed in the framework of the project “Chemical Studies for Design and Production of New Radiopharmaceuticals” (No MTKD-CT-2004-509224 (POL-RAD-PHARM)) supported by the European Community within the 6th Framework Programme Marie Curie: Host Fellowships for Transfer of Knowledge.

  • Poster
    European Symposium on Radiopharmacy and Radiopharmaceuticals - ESRR 06, 30.03.-02.04.2006, Lucca, Italy
  • Abstract in refereed journal
    Quarterly Journal of Nuclear Medicine and Molecular Imaging 51(2007)1, 92

Publ.-Id: 8387

Zerstörungsfreie, quantitative Wasserstoff-Analytik mittels Ionenstrahlen

Grambole, D.

In der Einleitung wird das Rossendorfer Ionenstrahllabor mit allen zur Verfügung stehenden ionenstrahl-analytischen Methoden zur Elementanalyse im oberflächennahen Bereich von Festkörpern kurz vorgestellt.
Die physikalischen Grundlagen zur Wasserstoffanalytik mittels resonanter Kernreaktion (RNRA) und elastischer Rückstoßstreuung (ERDA) werden erläutert. Es werden die notwendigen Voraussetzungen zur Berechnung der H-Konzentration und – tiefenprofile diskutiert. Die folgenden Anwendungsbeispiele sollen die Leistungsfähigkeit und Grenzen beider Methoden verdeutlichen. So wird die H-Konzentration in SiO2 – Schichten untersucht, die durch nasschemische Oxidation von Si erzeugt wurden. Hierbei wird darauf hingewiesen, wie wichtig die Kontrolle eines eventuellen H-Verlustes während der Analyse ist, um Fehlmessungen auszuschließen. Die mit RNRA erreichte Tiefenauflösung von 1 nm macht die Untersuchung der H-Verteilung in ca. 10 nm dünnen ZrO2– und Al2O3-Schichten möglich. Es wird über den Versuch berichtet, H-Monolagen zu untersuchen.
ERDA am Mikrostrahl (micro ERDA) machte erstmalig die Messung von dreidimensionalen H-Verteilungen möglich, die in H-implantierten Ti-Blechen mit und ohne Biegespannung untersucht wurde.

  • Lecture (others)
    Seminar, 04.04.2006, Karlsruhe, Deutschland

Publ.-Id: 8386

Extraction Methods

Stephan, H.; Juran, S.; Antonioli, B.; Gloe, K.; Gloe, K.

Molecular recognition, binding and transport of different chemical species represents an aspect of supramolecular chemistry that has relevance to a number of areas that include biochemical processes, analytical techniques, recycling and environmental processes as well as aspects of catalysis and medicine. Over the years a large number of both efficient and selective receptors for cations, anions, salts and zwitterions based on different architectures and binding modes have been developed and studied. Among the manifold experimental techniques employed for the application of such receptors has been the investigation of the distribution of species between two immiscible solutions, normally an aqueous and an organic phase, under the influence of the receptor in the organic phase. Such a procedure has often allowed characterization of the receptor’s complexation behaviour towards individual species as well as enabling an evaluation of its suitability for species monitoring, separation and/or concentration; especially with respect to possible analytical applications as well as for use in extraction and membrane transport processes.

  • Contribution to external collection
    C. Schalley: Analytical Methods in Supramolecular Chemistry, Weinheim: Wiley-VCH, 2007, 978-3-527-31505-5, 79-103

Publ.-Id: 8385

Strukturelle Charakterisierung neuer Bispidinderivate und iher Kupfer(II)-Komplexe

Kraus, W.; Juran, S.; Emmerling, F.; Stephan, H.

Radioaktive Kupfer(II)-Komplexe weisen ein hohes inhärentes Anwendungspotential für radiopharmazeutische Anwendungen in Diagnostik und Therapie auf. In diesem Zusammenhang zeigen sechszähnige Derivate des Bispidins (3,7-Diazabicyclo[3.3.1]nonan) aussichtsreiche Eigenschaften. Sie bilden insbesondere mit Kupfer(II) Komplexe hoher Stabilität. Um eine selektive Anreicherung der radioaktiven Kupferkomplexe im Zielgewebe zu erzielen, ist es notwendig, Biomoleküle an das Ligandgrundgerüst anzukoppeln.

  • Poster
    14. Jahrestagung der Deutschen Gesellschaft für Kristallographie 2006, 03.-06.04.2006, Freiburg, Deutschland
  • Abstract in refereed journal
    Zeitschrift für Kristallographie 24(2006)Suppl., 105

Publ.-Id: 8384

Carbon-11 Labelling Chemistry Based upon [11C]Methyl Iodide

Wüst, F.; Berndt, M.; Knieß, T.

Radiochemistry with the short-lived positron emitter carbon-11 (t1/2 = 20.38 min) represents special challenges in terms of synthesis time and the labelling techniques. The recent developments in carbon-11 radiochemistry have steadily expanded the number of carbon-11 labelled compounds. The review wants to address selected chemical and technical aspects of carbon-11 chemistry based on the readily available labelling precursors [11C]methyl iodide and, to some lower extent, [11C]methyl triflate. Special emphasis is attributed to heteroatom methylation reactions and 11C-C bond formations.

  • Contribution to external collection
    P.A. Schubiger, L. Lehmann, M. Friebe: E.Schering Research Foundation Workshop,Vol. 62,PET Chemistry,The Driving Force in Molecular Imaging, Berlin, Heidelberg: Springer Verlag, 2006, 10-3-540 326 23-5, 183-213

Publ.-Id: 8383

On Krein space related perturbation theory for MHD α²-dynamos

Kirillov, O.; Günther, U.

The spectrum of the spherically symmetric α²-dynamo is studied in the case of idealized boundary conditions. Starting from the exact analytical solutions of models with constant α-profiles a perturbation theory and a Galerkin technique are developed in a Krein-space approach. With the help of these tools a very pronounced α-resonance pattern is found in the deformations of the spectral mesh as well as in the unfolding of the diabolical points located at the nodes of this mesh. Non-oscillatory as well as oscillatory dynamo regimes are obtained. An estimation technique is developed for obtaining the critical α-profiles at which the eigenvalues enter the right spectral half-plane with non-vanishing imaginary components (at which overcritical oscillatory dynamo regimes form).

Keywords: Krein space; MHD dynamo; diabolical point; spectral deformation; perturbation theory; resonance; Galerkin method; spectral phase transition

Publ.-Id: 8382

Spectroscopic ellipsometry of ZnO thin films grown by pulsed reactive magnetron sputtering at elevated temperatures

Vinnichenko, M.; Rogozin, A.; Shevchenko, N.; Ozerov, M.; Kolitsch, A.; Möller, W.; (Editors)

Understanding of the growth process of undoped ZnO thin films is important for optoelectronic applications of the material. In this study, ZnO layers were deposited at single crystalline Al2O3 (0001) substrates by pulsed reactive magnetron sputtering. Oxygen partial pressure, base pressure and the substrate temperature (Ts) were varied systematically. The films were characterized by spectroscopic ellipsometry (SE), Seebeck effect measurements and X-ray diffraction (XRD). SE data were analyzed by using graded layer model for the film with Lorentz oscillator parameterization of the ZnO optical constants. The films produced at low temperatures always have negative Seebeck voltage, while at Ts>540 °C it changes to low positive values, which, however, degrade to negative values within several hours. The Lorentz oscillator broadening for the films grown at these temperatures increases with oxygen flow which points to a formation of more disordered structure inside ZnO grains in this case. XRD analysis yields decreasing grain size and increasing rocking curve full width on a half maximum with oxygen flow enhancement at the same Ts.

Keywords: zinc oxide thin films; dielectric function; spectroscopic ellipsometry; x-ray diffraction

  • Lecture (Conference)
    DPG Spring Meeting, 27.-31.03.2006, Dresden, Germany

Publ.-Id: 8381

Untersuchungen an neutronenbestrahlten Reaktordruckbehälterstählen mit Neutronen-Kleinwinkelstreuung

Ulbricht, A.

In dieser Arbeit wurde die durch Bestrahlung mit schnellen Neutronen bedingte Materialalterung von Reaktordruckbehälterstählen untersucht. Das Probenmaterial umfasste unbestrahlte, bestrahlte und ausgeheilte RDB-Stähle russischer und westlicher Reaktoren sowie Eisenbasis-Modelllegierungen. Mittels Neutronen-Kleinwinkelstreuung ließen sich bestrahlungsinduzierte Leerstellen/Fremdatom-Cluster unterschiedlicher Zusammensetzung mit mittlerem Radius um 1.0 nm nachweisen. Ihr Volumenanteil steigt mit der Strahlenbelastung monoton, aber im allgemeinen nicht linear an. Der Einfluss der Elemente Cu, Ni und P auf den Prozess der Clusterbildung konnte herausgearbeitet werden. Eine Wärmebehandlung oberhalb der Bestrahlungstemperatur reduziert den Anteil der Strahlendefekte bis hin zu deren vollständiger Auflösung. Die Änderungen der mechanischen Eigenschaften der Werkstoffe lassen sich eindeutig auf die beobachteten Gefügemodifikationen zurückführen. Die abgeleiteten Korrelationen können als Hilfsmittel zur Vorhersage des Materialverhaltens bei fortgeschrittener Betriebsdauer von Leistungsreaktoren mit herangezogen werden.

Keywords: small-angle neutron scattering; irradiation-induced microstructure; ageing of reactor pressure vessel steels under neutron irradiation

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZR-453 2006
    ISSN: 1437-322X


Publ.-Id: 8380

Luminescence spectrum of uranyl(V) in 2-propanol perchlorate solution

Steudtner, R.; Arnold, T.; Großmann, K.; Geipel, G.; Brendler, V.

The luminescence spectrum of uranyl U(V) in aqueous perchlorate solution was detected for the first time at room temperature in the UV-Vis region with a peak maxima at 440 nm and a fluorescence lifetime of 1.1 +/- 0.021 mu s using an excitation wavelength of 255 nm.

  • Inorganic Chemistry Communications 9(2006)9, 939-941

Publ.-Id: 8379

Uranium(VI) Complexation by Humic Acid under Neutral pH Conditions Studied by Laser-Induced Fluorescence Spectroscopy

Sachs, S.; Brendler, V.; Geipel, G.

The complexation of U(VI) with Aldrich humic acid (HA) was studied at pH 7 under exclusion of CO2. Using two independent laser-induced spectroscopic methods, time-resolved laser-induced fluorescence spectroscopy (TRLFS) and TRLFS with ultrafast pulses (fs-TRLFS), the formation of the ternary U(VI) mono hydroxo humate complex UO2(OH)HA(I) by reaction of UO2OH+ with HA was studied. Assuming that all proton exchanging functional groups of the HA are able to contribute to the complex formation, a mean stability constant of 6.58 ± 0.24 was derived for UO2(OH)HA(I). Alternatively, the analytical data were evaluated based on the metal ion charge neutralization model resulting in a complexation constant of 6.95 ± 0.10 and a loading capacity of 0.76 ± 0.28. An overall complexation constant of log b0.1M = 14.89 ± 0.54 was calculated for the total reaction of U(VI) with HA starting from the non-hydrolyzed UO22+ ion. This value agrees very well with literature data. Taking into account the UO2(OH)HA(I) complex, the speciation of U(VI) in presence of HA was recalculated. It was found, that the formation of UO2(OH)HA(I) can significantly influence the U(VI) distribution in the environmentally relevant pH region. As a consequence, the mobility of U(VI) in natural aquifer systems could be enhanced.

Keywords: Humic Acid; Complexation; Uranium(VI); Ternary Complexes; TRLFS; fs-TRLFS

Publ.-Id: 8378

Beta decay of the proton-rich nuclei 102Sn and 104Sn

Karny, M.; Batist, L.; Banu, A.; Becker, F.; Blazhev, A.; Brown, B. A.; Brüchle, W.; Döring, J.; Faestermann, T.; Gorska, M.; Grawe, H.; Janas, Z.; Jungclaus, A.; Kavatsyuk, M.; Kavatsyuk, O.; Kirchner, R.; La Commara, M.; Mandal, S.; Mazzocchi, C.; Miernik, K.; Mukha, I.; Muralithar, S.; Plettner, C.; Plochocki, A.; Roeckl, E.; Romoli, M.; Rykaczewski, K.; Schädel, M.; Schmidt, K.; Schwengner, R.; Zylicz, J.

The decays of 102 Sn and 104 Sn were studied by using high-resolution germanium detectors as well as a Total Absorption Spectrometer (TAS). For 104 Sn, with three new beta-delayed gamma rays identified, the total Gamow-Teller strength (BGT) value of 2.7(3) was obtained. For 102Sn, the gamma-gamma coincidence data were collected for the first time, allowing us to considerably extend the decay scheme. This scheme was
used to unfold the TAS data and to deduce a BGT value of 4.2(8) for this decay. This result is compared to
shell model predictions, yielding a hindrance factor of 3.6(7) in agreement with those obtained previously for 98Cd and 100In. Together with the latter two, 102 Sn completes the triplet of Z < 50, N > 50 nuclei
with two proton holes, one proton hole and one neutron particle, and two neutron particles with respect to the doubly magic 100Sn core.

Keywords: Nuclear structure; Gamma-ray spectroscopy; Beta decay; Gamov-Teller strength; Shell model

Publ.-Id: 8377

Electronic structure of highly ordered Sr2FeMoO6: XPS and XES studies

Kuepper, K.; Kadiroglu, M.; Postnikov, A. V.; Prince, K. C.; Matteucci, M.; Galakhov, V. R.; Hesse, H.; Borstel, G.; Neumann, M.

We have investigated the electronic structure of Sr2FeMoO6. In order to probe the partial densities of states we applied soft x-ray emission spectroscopy (XES) to the Fe L, the Mo M and the O K edges. We discuss the results in the light of complementary measurements of the valence band by means of x-ray photoelectron spectroscopy (XPS) and first-principles generalized gradient approximation (GGA) and LDA + U band structure calculations [1].
[1] K. Kuepper et al., J. Phys.: Condens. Matter 17, 4309 (2005).

Keywords: Sr2FeMoO6; double perovskite; electronic structure; x-ray photoelectron spectroscopy; x-ray emission spectroscopy

  • Lecture (Conference)
    DPG - spring meeting of the Division Condensed Matter, 26.-31.03.2006, Dresden, Germany

Publ.-Id: 8376

Investigation of orbital ordering in La7/8Sr1/8MnO3 by means of x-ray linear dichroism at the Mn L edge

Kuepper, K.; Bondino, F.; Prince, K. C.; Zangrando, M.; Zacchigna, M.; Takacs, A. F.; Matteucci, M.; Parmigiani, F.; Winiarski, A.; Galakhov, V. R.; Mukovskii, Y. M.; Neumann, M.

We have investigated for the first time the orbital ordering in a three dimensional colossal magneto resistance manganite, namely
La7/8Sr1/8MnO3, by applying soft x-ray linear dichroism (XLD) to the Mn L edge [1]. We found that the cooperative Jahn Teller distorted orthorhombic phase, which is present at a temperature of 240 K, is probably accompanied by a predominantly cross type (x2−z2)/(y2−z2) orbital ordering. This result is discussed in the light of previous results obtained by means of resonant x-ray scattering at the Mn K edge and different exchange interaction models.
[1] K. Kuepper et al., J. Phys. Chem. B 109, 15667 (2005)

Keywords: LaMnO3; La1-xSrxMnO3; colossal magneto resistance; orbital ordering; x-ray linear dichroism

  • Poster
    DPG - spring meeting of the Division Condensed Matter, 26.-31.03.2006, Dresden, Germany

Publ.-Id: 8375

Microstructural anisotropy at the ion-induced rippled amorphous – crystalline interface of silicon

Grigorian, S.; Grenzer, J.; Datta, D. P.; Hazra, S.; Chini, T. K.; Sanyal, M. K.; Pietsch, U.

The mechanism of ion-induced ripple-like structure formation at top-surface
and at buried crystalline surface is being studied extensively by several techniques. Using the technique of grazing incidence x-ray scattering, we have measured the degree of amorphization in the region between buried-crystalline and top-surface ripples in silicon as a function of argon-ion dose. Two broad peaks of the amorphous scattering profiles were probed by varying the penetration depth of x-ray and revealed short-range ordering. Our results show that the strong damage of crystalline structure caused by ion bombardment takes place along particular crystallographic directions and displays ion dose dependent behavior.

Keywords: grazing incidence scattering; ion beam irradiation

  • Applied Physics Letters 89(2006)23, 231915

Publ.-Id: 8374

Organic Field-Effect Transistors Utilising Oligothiophene Based Swivel Cruciform

Zen, A.; Pingel, P.; Neher, D.; Grenzer, J.; Zhuang, W.; Rabe, J. P.; Bilge, A.; Galbrecht, F.; Nehls, B.; Farrell, T.; Scherf, U.; Abellons, R. D.; Grozema, F. C.; Siebbeles, L. D. A.

Two types of highly soluble oligothiophene based swivel cruciform are presented as semiconducting materials in OFETs. Transistor made from one of these oligomers exhibited mobilities of more than 0.01 cm^2/Vs and current on/off ratio of >105. This is among the highest values reported to date for wet processed OFETs utilizing oligothiophenes. In fact, the OFET-mobilities are comparable to values extracted from pulse-radiolysis time resolved microwave conductivity (PR-TRMC) experiment, indicating that carrier trapping is insignificant. In depth examination of the morphological, optical characteristics and thermal stability of the materials were carried to obtain information on the packing of the oligomers in the layer. Finally, the correlation between the transistor performance and the crystallinity of the layers is addressed.

Keywords: organic field effect transistors; semiconducting polymers

  • Chemistry of Materials (2007)
  • Poster
    DPG - spring meeting of the Division Condensed Matter, 27.-31.03.2006, Dresden, Germany

Publ.-Id: 8373

Ripple morphology versus Ar+ implantation dose in silicon

Grigorian, S.; Grenzer, J.; Pietsch, U.

Investigations of ripples morphology of Ar+ implanted silicon are presented. Particularly we have measured the degree of amorphization as a function of implantation dose by means of x-ray grazing amorphous scattering (GIAS). For perfect silicon crystals GIAS shows monotone decreasing background intensity versus the 2theta scattering angle. For implanted samples we find two broad peaks indicating short-range ordering of amorphous material changing with the penetration depth of probing x-ray. The appearance of embedded crystalline domains is indicated by additional sharp peaks on top of the amorphous scattering. 2theta- scans taken at different azimuthal angles of sample display strong anisotropy of amorphous scattering which only slightly changes with dose. Based on these results we suggest a model of dose-dependent amorphization. The strong damage of crystalline structure takes place along particular crystallographic directions and strongly reveal for low doses, before it becomes complete amorphous and mostly uniform at high doses of implantation. This mechanism can be used as a hint for the appearance of a ripples amorphous-crystalline interface found at these structures.

We would like to thank S. Hazra and T.K. Chini for research collaborations.
This work was supported by the DST-DAAD India-Germany

Keywords: Granzing incidence amorphous scattering; ion beam irradiation

  • Lecture (Conference)
    DPG - spring meeting of the Division Condensed Matter, 27.-31.03.2006, Dresden, Germany

Publ.-Id: 8372

Alkaline earth uranyl compounds – from solution to mineral phases

Geipel, G.; Bernhard, G.

The uranyl tricarbonato complex is one of the most important uranyl species under environmental conditions. The tendency to form stable metal-uranyl tricarbonato complexes was found particularly for the interaction with alkaline earth elements. We studied chemical behavior of these compounds in aqueous solution by time-resolved laser-induced fluorescence spectroscopy (TRLFS). However, under comparable chemical conditions the formation of these complexes is very different. While magnesium tends mainly to the formation of a MgUO2(CO3)32+ - complex, in the case of calcium the Ca2UO2(CO3)3(aq.) complex is the most stable. The stability constant for the Ca2UO2(CO3)3 – complex is derived to be log β°213 = 30.90 ± 0.25 [1]. In the corresponding systems with strontium as well as for barium only the MeUO2(CO3)32+ - complex is formed. The stability constants of the MeUO2(CO3)32+ - complexes are determined to be log β°113 = 26.13 ± 0.27 and 26.24 ± 0.31 for the alkaline earth elements Sr and Ba, respectively. The Me2UO2(CO3)3 – complexes for Mg and Ca form stable minerals as bayleyite and liebigite. However several other mineral modifications as zellerite, fontanite, sharpite and rabbittite underline the geochemical importance of this class of compounds.
Analogous phenomena can be expected in the alkaline earth uranyl phosphate systems. Therefore we studied the interaction of alklaine earth metal ione with UO2(PO4)- at pH 7.0. From the fluorescence data the formation of MeUO2(PO4)+ complexes in solution can be concluded. The stability constants are derived to be β°111 = 16.85 ± 0.16, 16.62 ± 0.15, 17.4 ± 0.4 and 16.9 ± 0.4 for Mg, Ca, Sr and Ba, respectively. The formation of complexes with the common formula Me(UO2)2(PO4)2aq has not yet been obeserved due to the low solubility of these componds. In the case of Mg and Ca the fluorescence data will be compared to the correspondong minerals saleiite and autunite [2].

Keywords: uranium; minerals; fluorescence; complex formation

  • Lecture (Conference)
    Goldschmidt Conference, 27.08.-1.9.2006, Melbourne, Australia
  • Geochimica et Cosmochimica Acta 70(2006)18, Supl.1, 10
    DOI: 10.1016/j.gca.2006.06.396

Publ.-Id: 8371

Complex formation of uranium(VI) with 4-hydrosy-3-methoxybenzoic acid and related compounds

Vulpius, D.; Geipel, G.; Baraniak, L.; Rossberg, A.; Bernhard, G.

The complex formation of uranium(VI) with 4-hydroxy-3-methoxybenzoic acid as well as with benzoic acid and 3-hydroxybenzoic acid was studied. In aqueous solution weak carboxylic 1:1 complexes, in which the carboxyl group is bidentately coordinated to the metal atom, are formed. The logarithmic stability constants of these complexes regarding the reaction of the uranyl ion with the single charged anion of the respective ligands are 2.78 ± 0.04, and 2.71 ± 0.04 at an ionic strength of 0.1 mol/l (NaClO4) and at 25 °C.
Bis(4-hydroxa-3-methoxybenzoato)dioxouranium(VI) was obtained as a crystalline complex if the concentrations of the starting compounds for the synthesis are increased. The monoclinic compound has a reflections-rich X-ray powder diffraction pattern. The lattice constants are a = 13.662(9) Å, b = 21.293(7) Å, c = 11.213(3) Å, b = 107.49(4)°, and V = 3111(2) Å3.

  • Journal of Radioanalytical and Nuclear Chemistry 270(2006)3, 661-667

Publ.-Id: 8370

Monitoring Carbon Ion Tumor Therapy with In-Beam Positron Emission Tomography: Status and Trends

Crespo, P.

Within the tumor treatment pilot project running at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, in-beam positron emission tomography (in-beam PET) is used to clinically monitor every patient irradiation with carbon ion beams. The physical, technical and radiobiological rationale for heavy ion tumor therapy will be shortly outlined, together with a comparison of clinical results obtained with carbon therapy versus other forms of radiotherapy.
In-beam PET, installed at GSI by the team from the Forschungszentrum Rossendorf, will then be presented in this clinical context, followed by a description of the technological solutions already achieved, as well as by the challenges to take into consideration in order to extend the in-beam PET method onto future radiotherapy facilities delivering also other ion species.

Keywords: PET

  • Lecture (others)
    Seminar on Molecular Life Sciences and Imaging, 28.02.2006, Forschungszentrum Rossendorf, Dresden, Deutschland

Publ.-Id: 8369

New developments in detectors for in-beam PET

Crespo, P.; Barthel, T.; Kapusta, M.; Heidel, K.; Moszynski, M.; Pawelke, J.; Enghardt, W.

State-of-the-art technology has outperformed the efficiency of the positron emission tomograph installed at the Gesellschaft für Schwerionenforschung for monitoring, in-beam, ion radiation therapy. In addition, the special requirements of in-beam PET have been better understood. We explain these special requisites and present dedicated in-beam PET readout solutions, either tested in-beam or under development. Experimental results obtained with two multi-pixel, gamma-ray detectors consisting of lutetium oxyorthosilicate (LSO) coupled to avalanche photodiode arrays (APDA) show that this detector provides a good solution for improved, next-generation in-beam PET scanners.
Nevertheless, we extrapolate recent detector and scintillator developments, enabling sub-nanosecond coincidence time resolution (T), onto a possile in-beam time-of-flight (TOF) PET scanner. We show that T < 200 ps full-width-at-half-maximum allows:
(1) images to be shown to the radiooncologist in real-time,
(2) artifact-free images to be obtained from dual-head tomographs,
(3) an absolute quantification of image intensity and
(4) to obtain optimum PET images corrected from biological washout mechanisms.

Keywords: PET; TOF-PET

  • Lecture (Conference)
    DPG Frühjahrstagung, 13.-15.03.2006, Heidelberg, Deutschland

Publ.-Id: 8368

Reaction Pathways of a Regular Disintegration of Nanowires by Thermocapillarity

Röntzsch, L.; Heinig, K.-H.

Surface free energy minimization driven by capillary forces leads to morphological changes of wires, e.g. disintegration into a droplet chain – known as Rayleigh instability. At the nano-scale, capillary effects are much more pronounced than in macroscopic systems due to the large surface-to-volume ratio. However, capillary-driven self-organization processes are subject to increasing fluctuations with decreasing dimensions, which mostly prevent the formation of regular structures with long-range order. In this contribution, we predict by means of kinetic Monte Carlo simulations a novel method to fabricate size-controlled chains of nanodroplets. Our prediction rests on the temperature dependence of surface tension – the origin of thermocapillarity. Uncompensated forces occur due to surface temperature gradients. These forces lead to material transport and structure formation on short time and length scales. A surface tension gradient triggers the biased migration of atoms from hot to cold regions by surface diffusion. A periodic temperature gradient along a nanowire might be achieved by a surface-plasmon-polariton (SPP) wave. For SPP excitations with long wavelengths (e.g. by a CO2 laser), sufficiently strong steady-state temperature gradients may be produced. However, pulsed operation might be necessary for shorter wavelengths. We predict that the regularity of nanodroplet chains, that form during a self-organized disintegration of nanowires, might be considerably improved by SPPs. If the SPP wavelength is commensurable with the inherent Rayleigh wavelength of the nanowire disintegration, the SPP-induced temperature undulations control the Rayleigh instability. Thus, a regular and long-range order in nanodroplet size and position may be achieved.

Keywords: Rayleigh instability; nanowire; thermocapillarity; disintegration; long-range order

  • Poster
    DPG Frühjahrtagung 2006, 26.-31.03.2006, Dresden, Deutschland

Publ.-Id: 8367

Experimental investigation of coolant mixing in the RPV of PWR in the late phase of a SBLOCA event

Kliem, S.; Prasser, H.-M.; Sühnel, T.; Weiss, F.-P.; Hansen, A.

Partial depletion of the primary circuit of a pressurized water reactor during a postulated small break loss of coolant accident can lead to interruption of one-phase flow natural circulation. In this case, the decay heat is removed from the core in the reflux-condenser mode. In this operation mode, slugs of lower borated water can accumulate in the cold legs. After refilling of the primary circuit, the natural circulation in the two loops not receiving emergency core cooling injection (ECC) re-establishes and the lower borated slugs are shifted towards the reactor pressure vessel (RPV). Entering the core, the lower borated water causes a reactivity insertion. Mixing inside the RPV is an important phenomenon limiting the reactivity insertion and preventing a re-criticality.
The mixing of these lower borated slugs with the ambient coolant in the RPV was investigated at the 1:5 scaled coolant mixing test facility ROCOM. Wire mesh sensors based on electrical conductivity measurement are used in ROCOM to measure in detail the spreading of a tracer solution in the facility. The mixing in the downcomer was observed with a sensor which spans a measuring grid of 64 azimuthal and 32 positions over the height. The resulting distribution of the boron concentration at the core inlet was measured with a sensor integrated into the lower core support plate providing one measurement position at the entry into each fuel assembly.
The boundary conditions for the mixing experiment were taken from an experiment at the thermal-hydraulic test facility PKL operated by FANP Germany. The slugs, which have a lower density, accumulate in the upper part of the downcomer after shifting into the RPV. The ECC-water injected into the RPV falls almost straight down through the lower borated water and accelerates. On the outer sides of the ECC-streak, lower borated coolant admixes and flows together with the ECC-water downwards. This is the only mechanism of transporting the lower borated water into the lower plenum. All these effects could be visualized and quantified by the downcomer sensor. On the way to the core, the lower borated water is effectively mixing with the ambient, high borated water. Therefore, in the core inlet plane, lower borated water is detected only in the outer part. The minimum boron concentration, measured at one fuel element inlet position at one certain time point, was 71 % of the initial 2500 ppm. There is no change of the initial boron concentration in the inner part of the core inlet plane during the whole transient at all.

  • Lecture (Conference)
    International Conference on Nuclear Engineering ICONE-14, 17.-20.07.2006, Miami, United States
  • Contribution to proceedings
    International Conference on Nuclear Engineering ICONE-14, 17.-20.07.2006, Miami, United States
    Proceedings paper 89472: ASME, 0-7918-3783-1

Publ.-Id: 8366

Atomistic study of bulk properties and point defects in Ge

Geßner, H.; Posselt, M.

Different parametrizations for the Stillinger-Weber potential are used to determine the elastic properties and the melting point of Ge as well as the stability, the structure and the energetics of potential vacancy and self-interstitial configurations. The results are compared with literature data obtained from experiments and by tight-binding and density-functional theory calculations. Furthermore, the vacancy and self-interstitial migration is investigated for temperatures between 600 and 1200 K. The defect diffusivity, the self-diffusion coefficient per defect and the corresponding effective migration barriers are determined. These results are compared with experimental data on self-diffusion in Ge.

Keywords: atomistic simulation; germanium; point defects; bulk properties

  • Poster
    DPG/AKF Frühjahrstagung and 21st General Conference of the EPS Condensed Matter Division, 27.-31.03.2006, Dresden, Germany

Publ.-Id: 8365

Sigma-2 selective fluorinated ligands: Synthetic method and optimization of decarbonylation for radiolabeling.

Seo, J. W.; Chi, D. Y.; Luyt, L. G.; Wüst, F.; Dence, C. S.; Sharp, T. L.; Mach, R. H.; Welch, M. J.; Katzenellenbogen, J. A.

Sigma receptors are membrane-bound proteins having high affinities for a variety psychotropic
drugs with opiate-type structures. The sigma receptor subtypes, sigma-1 and sigma-2, have different molecular weights and pharmacological roles.1 Many cancer cell lines (breast, melanoma, prostate cancer) express high levels of sigma receptors,2,3 and proliferative tumor cells express much higher levels of sigma-2 receptors than quiescent cells.4,5 Thus, the sigma-2 receptor has been proposed as a suitable target for imaging proliferative tumor cells.

While many ligands are selective for the sigma-1 receptor or are nonselective, very few ligands
are selective for the sigma-2 receptor. A radiopharmaceutical based on an azabicyclo[3.3.1]nonane framework was developed by Mach,6 who demonstrated that the rhenium surrogate showed exceptional sigma-2 selectivity; later this agent was labeled with technetium-99m by Kung for tissue distribution studies.7 In considering potential fluorine-18
labeled sigma-2 receptor ligands, our attention focused on members of an indole piperidine series, especially 1 (LU 28-179), which is reported to have a remarkably high sigma-2 binding affinity and selectivity.8,9 Figure 1. The structure of indole piperidine ligands and their inhibition constants toward sigma receptors.

Target compounds 1 and 2 were prepared in several steps by a route based on a previously
described method,7 with modifications making it more efficient for the synthesis of the precursor molecule (3); compounds 1 and 2 showed high binding affinity and good selectivity (6 fold) for the sigma-2 receptor (Figure 1). The preparation of [18F]-labeled indole piperidine [18F]1 was achieved in two steps from a o-nitroaldehyde precursor (3). Aromatic [18F]fluorination was not reproducible when 3 was treated with F-18 fluoride in the presence of Bu4NOH under microwave heating conditions. However, by using F-18, K2CO3 and kryptofix[2.2.2] under microwave heating, we obtained radiochemical yields of 5-50%. The final decarbonylation step with Wilkinson’s catalyst was studied in various solvents. Decarbonylation using dioxane as solvent produced [18F]1, but with toluene, extensive decomposition resulted. Herein, we present the synthesis of precursor 3, optimization of [18F]fluorination, and decarbonylation to produce [18F]Lu 28-179 (Scheme 1). Future work to prepare [18F]1 will be done using an alternate synthetic route.10
Supported by DOE grants 86ER60401 (to JAK) and 84ER60218 (to MJW).
1. Vilner, B. J. et al. Cancer Res. 55: 408-413 (1995)
2. John, C. S. et al. Cancer Res. 59: 4578-4583 (1999)
3. Quirion, R. et al. Trends Phrmacol. Sci. 13: 85-6 (1992)
4. Mach, R. H. et al. Cancer Res. 57: 156-161 (1997)
5. Wheeler, K. T. et al. Br. J. Cancer 82: 1223-1232 (2000)
6. Mach et al., J. Labelled Cmpds Radiopharm 2001; 44: 899-908
7. Choi, S.-R. Nucle. Med. Biol. 28: 657-666 (2001)
8. Perregaard, J. J. Med. Chem. 38: 1998-2008 (1995)
9. Moltzen, E. K. J. Med. Chem. 38: 2009-2017 (1995)
10. Wüst, F. et al. J. Label. Compd. Radiopharm. 48: 31-43 (2005)

  • Poster
    International Symposium on Radiopharmaceutical Chemistry (IRSC 2005), 24.-28.06.2005, Iowa City, Iowa, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 48(2005), S170

Publ.-Id: 8364

Annual Report 2005 - Institute of Ion Beam Physics and Materials Research

von Borany, J.; Heera, V.; Helm, M.; Möller, W.; (Editors)

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZR-448 2006
    ISSN: 1437-322X


Publ.-Id: 8363

Response of bacterial strains isolated from a uranium mining waste to heavy metal stress

Merroun, M.; Geissler, A.; Regenhardt, D.; Selenska-Pobell, S.

Two bacterial strains, Iso2 and Iso3, were cultured from a uranium mining waste pile near the town of Johanngeorgenstadt, Germany. The 16S rRNA gene sequence analysis demonstrated that these strains belong to the genus Arthrobacter of Actinobacteria. In this work, a combination of wet chemistry, spectroscopic, microscopic and microbiological methods were used to assess the stress response of these strains to heavy metals. The studied strains, Arthrobacter sp. Iso2 and Iso3, tolerate -lead, -nickel, and -uranium in concentrations up to 0.5 mM, 18 mM, and 1 mM respectively. As was demonstrated by X-ray powder diffraction (XRD) analysis, the cells of these two strains precipitate lead as lead sulfide (galena). Transmission electron microscope (TEM) showed that these precipitates are localized mainly at the cell surface. Dead/live staining indicated that 60% of the lead-treated cells are viable. Polyacrylamide gel electrophoretic (PAGE) analysis of total bacterial proteins showed different profiles between the Pb-treated and the -untreated (control) cells. The amount of a 55 kDa protein was higher in lead-treated cultures than in the control cultures. The origin of sulfide involved in lead precipitation will be discussed in term of microbial activity .

  • Lecture (Conference)
    FEMS 2006, 2nd Congress of European Microbiologists, 04.-08.07.2006, Madrid, Spain
  • Contribution to proceedings
    FEMS 2006, 2nd Congress of European Microbiologists, 04.-08.07.2006, Madrid, Spain, 299

Publ.-Id: 8362

AMOS - An Effective Tool for Adjoint Monte Carlo Photon Transport

Gabler, D.; Henniger, J.; Reichelt, U.

In order to expand the photon version of the Monte Carlo transport program AMOS PE to an adjoint photon version the theory of adjoint radiation transport is resumed and evaluated in this regard. All relevant photon interactions, photoelectric effect, coherent scattering, incoherent scattering and pair production, are taken into account as proposed in the EPDL 97. In order to simulate pair production and to realise physical source terms with discrete energy levels, an energy point detector is used. To demonstrate the qualification of AMOS Pt a simple air-over ground problem is simulated by both the forward and the adjoint programs. The results are compared and total agreement is shown.

Keywords: Monte Carlo; Radiation Transport; Adjoint; Air-Over-Ground

Publ.-Id: 8361

Antisite pair recombination in SiC by a modified concerted exchange mechanism

Posselt, M.; Gao, F.; Weber, W. J.

for further information, please contact the author

Keywords: defects; SiC; atomistic simulations

  • Lecture (Conference)
    44. Arbeitskreis "Punktdefekte", 23.-25.03.2006, Dresden, Germany

Publ.-Id: 8360

Optical properties of PECVD deposited DLC films prepared with air addition

Tinchev, S. S.; Dyulgerska, Y.; Nikolova, P.; Grambole, D.; Kreissig, U.; Babeva, T.

Diamond-like carbon (DLC) films with addition of atmospheric air to benzene were prepared by DC discharge plasma enhanced chemical vapor deposition (PECVD). These films were compared with films made from benzene/argon mixture. Some properties of the films including their optical transmission, hydrogen content and Raman spectra were investigated. It was found that such films fabricated with air addition (even at low vacuum) exhibit properties suitable for optical applications.

Keywords: Diamond-like carbon; Thin films; PECVD

  • Journal of Optoelectronics and Advanced Materials 8(2006)1, 308-311

Publ.-Id: 8359

Stability and Molecular Speciation of Colloid-borne Uranium

Ulrich, K.-U.; Weiss, S.; Rossberg, A.; Foerstendorf, H.; Zänker, H.

Mining on uranium ores in Eastern Germany produced 220,000 metric tons of uranium (U) in addition to ~5•108 metric tons of radioactive waste on 3000 dumps and 20 tailings, and leaving a total subsurface void volume of >1•108 m3 to be flooded. For a reliable assessment of the U migration, knowledge on the molecular speciation and complex stability is crucial. Starting from field studies and mesocosm-scaled simulation of a mine flooding scenario, we performed coprecipitation batch experiments with U(VI) and newly formed, initially colloidal 2-line ferrihydrite at different pH and ion matrix conditions. The talk presents major results of the colloid characterization, and of spectroscopic investigations on the molecular bonding of the colloid-borne U using Extended X-ray Absorption Fine Structure (EXAFS) and Attenuated Total Reflectance Infrared (ATR IR) spectroscopy. The influence of carbonate on the U(VI)-ferrihydrite surface complex formation will be discussed.
In addition, some U-loaded precipitates and a sediment sample from a uranium mine were subjected to consecutive leaching experiments and thermally induced aging. These experimental approaches aimed at determining the kinetics of U desorption processes and obtaining preliminary information on the long-term stability of U-binding. According to our results, part of the adsorbed uranium seems to be bound irreversibly within the bulk precipitate, especially when the U-sorbing ferrihydrite phase altered to hematite.
In summary, the presented results show that the interaction of U(VI) and highly reactive functional groups of colloidal and aggregated ferrihydrite surfaces can play a major role in lowering or delaying the release of toxic U from flooded uranium mines into adjacent groundwater aquifers or surface waters.

  • Lecture (Conference)
    Water Quality SuperGroup meeting at the School of Engineering & Applied Science, 31.03.2006, St. Louis, United States

Publ.-Id: 8358

Entwicklung und Validierung von CFD-Modellen fürZweiphasenströmungen

Frank, T.; Lucas, D.; Prasser, H.-M.; Krepper, E.; Shi, J.-M.

CFD-Codes ist der Oberbegriff für Rechenprogramme zur mehrdimensionalen numerischen Strömungssimulation. Mit der heute verfügbaren Rechentechnik und fortgeschrittenen numerischen Methoden können bereits komplizierte Strömungsfelder, wie sie unter anderem in der Automobil- und Luftfahrtindustrie auftreten, berechnet werden. Von dem, was bei reinen Gas- oder Flüssigkeitsströmungen schon breite Anwendung findet, ist man im Fall zwei- oder mehrphasiger Strömungen jedoch noch weit entfernt. Wenn, wie beispielsweise in einem Kernreaktor, ein Zweiphasengemisch aus Dampf und Wasser die Brennelemente kühlt, dann müssen zusätzlich die Wechselwirkungen zwischen den beiden beteiligten Phasen beschrieben werden. Im Rahmen einer Initiative des BMWA zur "Entwicklung und Anwendung von CFDProgrammen für Phänomene im Kühlkreislauf von Leichtwasserreaktoren" werden Arbeiten zur Ertüchtigung des CFD-Codes CFX von ANSYS gemeinsam vom Institut für Sicherheitsforschung des Forschungszentrum Rossendorf (FZR) und dem Codeentwickler, der ANSYS Germany GmbH durchgeführt. Ausgehend von experimentellen Daten, die an der TOPFLOW-Versuchsanlage des FZR mit innovativer, hochauflösender Messtechnik gewonnen werden, erfolgt die Entwicklung neuer Modelle und Konzepte. Diese werden mit vereinfachten Methoden getestet und nach erfolgreichem Test vom Codeentwickler in CFX implementiert. Anschließend erfolgt die gemeinsame Validierung der Modelle an Hand experimenteller Daten. Dieses Vorgehen wird am Beispiel der der Modellentwicklungen für Blasenströmungen demonstriert.

Keywords: CFD; Bubbly flow; MUSIG

  • Contribution to proceedings
    Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland, KTG-Fachtagung, 03.-04.04.2006, Dresden, Germany
  • Invited lecture (Conferences)
    Aktuelle Themen der Reacktorsicherheitsforschung in Deutschland, KTG-Fachtagung, 03.-04.04.2006, Dresden, Germany

Publ.-Id: 8357

Effect of pH on the speciation of uranium(VI) associated with bacterial strains isolated from extreme habitats: Spectroscopic and microscopic studies

Merroun, M.; Nedelkova, M.; Rossberg, A.; Hennig, C.; Selenska-Pobell, S.

This paper deals with the speciation of U(VI) associated with the cells of bacterial strains isolated from extreme habitats as function of pH. For this propose, a combination of synchrotron-based X-ray absorption spectroscopy (XAS), time-resolved laser-induced fluorescence spectroscopy (TRLFS), transmission electron microsocpe (TEM) coupled with energy dispersive-X ray (EDX) analysis and electron diffraction were used. XAS analysis indicated that the effect of pH on the local coordination of U in the U-complexes formed by the different bacterial strains is species specific. No structural differences were found between the U complexes formed by three different exo-types of Acidothiobacillus ferrooxidans at pH 2, 3 and 4.5. In contrast, the cells of Bacillus sphaericus JG-B7, Microbacterium oxydans M2, and Sphingomonas sp. S15-S1 precipitate U(VI) as a meta-autunite-like phase at pH 4.5, probably due to the release of the inorganic phosphate from the cells. At pH 2, the U is coordinated to the organic phosphate groups of the cells of the listed bacteria. Both organic and inorganic uranyl / bacterial complexes were formed at pH 3. TEM/EDX analysis confirm these results and showed strain-specific extracellular and/or intracellular uranium accumulation to varying degrees. We applied Iterative Target Test Factor Analysis to determine the uranium speciation at different pH values quantitatively from the EXAFS spectra. Different hypothesis explaining the different coordination chemistry of uranium to bacteria as a function of pH of uranium solution in terms of solubility of m-autunite and/or microbial activity will be discussed.

  • Lecture (Conference)
    11th International Symposium on Microbial Ecology, ISME-11, 20.-25.08.2006, Vienna, Austria

Publ.-Id: 8356

Erste Experimente zu in-beam PET mit harter Photonenstrahlung

Möckel, D.; Pawelke, J.; Sommer, M.; Will, E.; Enghardt, W.

In-beam PET als eine Möglichkeit zur Qualitätssicherung für die Bestrahlung hat sich bereits in der Therapie mit Schwerionen bewährt. Für Protonen und Helium wurden erfolgreich Experimente durchgeführt. Da die Strahlentherapie mit Photonenstrahlung auch auf Photonen hoher Energien (größer 20 MeV) ausgeweitet wird, könnte in-beam PET dabei eingesetzt werden. Erste Experimente dazu wurden an ELBE (Elektronen Linearbeschleuniger für Strahlen hoher Brillianz und niedriger Emittanz) im Forschungszentrum Rossendorf durchgeführt. Durch Auftreffen der Elektronen (I = 80 µA) auf ein Aluminium-Target wurde Bremsstrahlung erzeugt und sowohl homogene PMMA-, als auch inhomogene gewebeäquivalente Phantome bestrahlt. Nach Ende der Bestrahlung wurde die Verteilung der im Phantom erzeugten Positronenemitter in einem PET-Scanner (Siemens ECAT EXACT HR+) ausgemessen. Die im Phantom applizierte Dosis wurde mittels optisch stimulierter Lumineszenzdosimeter (BeO) ermittelt. In insgesamt 16 Experimenten konnten die Abhängigkeiten der erzeugten Aktivität von der Elektronenenergie (E = 21 ... 34 MeV), der Dosis (D = 1 ... 10 Gy), der Kollimation des Photonenstrahls, sowie des Phantommaterials untersucht werden. Die Experimente und die Ergebnisse für Produktionsrate und dosisbezogene Aktivitätskonzentration werden vorgestellt.

Keywords: in-beam PET; hard photons

  • Lecture (Conference)
    DPG-Frühjahrstagung, 13.-15.03.2006, Heidelberg, Deutschland

Publ.-Id: 8355

Stability analysis of an electromagnetically levitated sphere

Priede, J.; Gerbeth, G.

We present a combined numerical and analytical approach to analyze the static and dynamic stability of an electromagnetically levitated spherical body depending on the ac frequency and the configuration of a three-dimensional (3-D) coil made of thin winding which is modelled by linear current filaments. First, we calculate numerically the magnetic vector potential in grid points on the surface of the sphere and then use Legendre and fast Fourier transforms to find the expansion of the magnetic field in terms of spherical harmonics. Second, we employ a previously developed gauge transformation to solve analytically the 3-D electromagnetic problem in terms of the numerically obtained expansion coefficients. Using this solution, we obtain the electromagnetic reaction force due to both a small displacement of the sphere from its equilibrium position and its velocity of motion which are defined by symmetric stiffness and damping matrices, respectively. Eigenvalues and eigenvectors of the stiffness matrix yield three principal stiffness coefficients, which all have to be positive for the equilibrium state to be statically stable, and three mutually orthogonal directions of principal oscillations. Dynamic instabilities are characterized by critical ac frequencies which, when exceeded, may result either in a spin-up or oscillations with increasing amplitude. The effective electromagnetic damping coefficients are found by using a classical eigenvalue perturbation theory. A new theoretical approach based on the vector field transformation by a small rotation in combination with a parametric frequency derivative is introduced to find the electromagnetic reaction torque due to a slow rotation of the sphere in a 3-D ac magnetic field.

  • Journal of Applied Physics 100(2006), 054911

Publ.-Id: 8353

Experimental study of the suppression of Rayleigh--Benard instability in a cylinder by combined rotating and static magnetic fields

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

We consider experimentally transitions in a liquid metal cylinder heated from below and subject to superimposed rotating and static magnetic fields. Being itself unstable, a strong enough rotating magnetic field driven flow suppresses considerably the temperature fluctuations due to the thermo-gravitational convection. The remaining fluctuations are caused by unsteady Taylor vortices generated near the side wall. Our experiment shows that the superimposed static `cusp' field further reduces the amplitude and characteristic period of these remaining temperature fluctuations while a superimposed uniform axial field has no such effect. The observed behavior agrees quantitatively with the differing effects of various static fields on the additional unstable Taylor vortex type solutions, which bifurcate sub-critically and actually govern the transition in the RMF driven flow. Thus, the observations are consistent with the description of a turbulent shear flow as a trajectory wound irregularly on the skeleton of the additional unstable flow states. If this `skeleton' is compressed by an external influence (the `cusp' static field in our case), then also the averaged amplitude of turbulent fluctuations decreases by the same factor.

  • Physics of Fluids 18(2006), 124104
  • Lecture (Conference)
    2nd International Symposium "Instabilities and Bifurcations in Fluid Dynamics", 15.-18.08.2006, Copenhagen, Denmark

Publ.-Id: 8352

Towards CFD modelling of critical heat flux in fuel rod bundles

Krepper, E.; Egorov, Y.; Koncar, B.

The paper describes actual CFD approaches to subcooled boiling and investigates their capability to contribute to fuel assembly design. In a prototype version of the CFD code CFX a wall boiling model is implemented based on a wall heat flux partition algorithm. It can be shown, that the wall boiling model is able, to calculate the cross sectional averaged vapour volume fraction with good agreement to published measurements. The most sensitive parameters of the model are identified. Needs for more detailed experiments are established which are necessary to support further model development. Nevertheless in the paper the model is applied for the investigation of the phenomena inside a hot channel in a fuel assembly. Here the essential parameter is the critical heat flux. Although subcooled boiling represents only a preliminary state toward critical heat flux essential parameters like the swirl, the cross flow between adjacent channels and concentration regions of bubbles can be determined. By calculating the temperature at the rod surface the critical regions can be identified which might later on lead to departure from nucleate boiling and possible damage of the fuel pin. The application of up-to-date CFD with a subcooled boiling model for the simulation of a hot channel enables the comparison and the evaluation of different geometrical designs of the spacer grids of a fuel rod bundle.

Keywords: Wallboiling; CFD; Validation; Fuel Rod Bundle

  • Contribution to proceedings
    International Congress on Advances in Nuclear Power Plants ICAPP06, 04.-08.06.2006, Reno, United States
  • Lecture (Conference)
    International Congress on Advances in Nuclear Power Plants ICAPP06, 04.-08.06.2006, Reno, United States

Publ.-Id: 8351

CFD Simulation of forced convective boiling in heated channels

Koncar, B.; Krepper, E.

In this paper a forced convective boiling of Refrigerant R-113 in a vertical annular channel has been simulated by a custom version of the CFX-5 code. The employed subcooled boiling model uses a special treatment of the wall boiling boundary, which assures the grid invariant solution. The simulation results have been validated against the published experimental data. In general a good agreement with the experimental data has been achieved, which shows that the current model may be applied for the Refrigerant R-113 without significantly changing the model parameters. The influence of non-drag forces, bubble diameter size and interfacial drag model on the numerical results has been investigated as well.

Keywords: forced convective boiling; refrigerant R-113; CFD simulations; validation

  • Contribution to proceedings
    OECD/NEA International Workshop on The Benchmarking of CFD Codes for Application to Nuclear Reactor Safety (CFD4NRS), 05.-09.09.2006, Garching, Germany
  • Lecture (Conference)
    OECD/NEA International Workshop on The Benchmarking of CFD Codes for Application to Nuclear Reactor Safety (CFD4NRS), 05.-09.09.2006, Garching, Germany

Publ.-Id: 8350

CFD-Simulation von Mineralwollpartikeln in der Sumpfströmung

Krepper, E.; Grahn, A.; Kästner, W.

Die Untersuchung der Freisetzung, des Transports und der Sedimentation von Mineralwollpartikeln in der Sumpfströmung gewinnt wachsende Beachtung bezüglich des Langzeitverhaltens der Notkühlsysteme von Druck- und Siedewasserreaktoren. Das bei einem Leck freigesetzte Isolationsmaterial besteht bezüglich Größe, Form, Konsistenz und anderen Eigenschaften aus einem Gemisch von sehr unterschiedlichen Partikeln. Ein Teil dieser freigesetzten Fasern kann in den Sumpf gelangen und durch Anlagerung an den Sumpfsieben die Notkühlung beeinträchtigen. Offene Fragen von allgemeinem Interesse sind z.B. die Ablagerung von Isolationsmaterial, die mögliche Re-Suspension und der Transport in einer Wasserströmung, die Anlagerung des Isolationsmaterials an die Sumpfsiebe und der daraus resultierende Differenzdruck.
Ein gemeinsames durch das BMWA gefördertes Forschungsprojekt in Zusammenarbeit mit dem Institut für Prozesstechnologie, Automatisierung und Messtechnik (IPM) in Zittau befasst sich mit der experimentellen Untersuchung und der Entwicklung von CFD-Modellen zur Beschreibung von Partikeltransportphänomenen in der Kühlmittelströmung. Während die Experimente am IPM Zittau durchgeführt werden, ist die theoretische Arbeit am Forschungszentrum Rossendorf konzentriert.
In der vorliegenden Arbeit werden die grundlegenden Konzepte der CFD-Modellierung beschrieben und erste Ergebnisse einschließlich Machbarkeitsstudien beschrieben.

Keywords: Emergency core cooling; Fibres of isolation material; water flow; sedimentation; re-suspension; strainer clogging; CFD; experiments

  • Contribution to proceedings
    Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland, 03.-04.04.2006, Dresden, Germany
  • Lecture (Conference)
    Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland, 03.-04.04.2006, Dresden, Germany

Publ.-Id: 8349

Surface modification of Si(111) substrate by iron ion implantation: Growth of a thin beta-FeSi2 layer

Ayache, R.; Bouabellou, A.; Eichhorn, F.; Richter, E.; Mücklich, A.

The processes in the synthesis of a thin layer of the semiconducting iron silicide (beta-FeSi2) on the surface of a single-crystal Si(111) substrate by implantation of 195 keV Fe ions with a dose of 8×1017 cm–2 are investigated. Using Rutherford backscattering spectrometry, x-ray diffraction and cross-sectional transmission electron microscopy, the structure and the phase composition of the synthesized layers are studied. The infrared transmittance spectra show the absorption at 310 cm–1 as an indication of the initial nucleation of beta-FeSi2 precipitates during the implantation of iron into silicon substrate.

Keywords: beta-FeSi2; Si111; ion beam synthesis; RBS; XRD; TEM

Publ.-Id: 8348

Einfluss von Huminstoffen auf die Migration von Uran und Neptunium im Ton

Sachs, S.; Krepelova, A.; Mibus, J.; Schmeide, K.; Brendler, V.; Bernhard, G.

Im Vortrag werden Ergebnisse der Arbeiten des Instituts für Radiochemie im Rahmen des vom BMWi-geförderten Huminstoff-Verbundprojekts "Migration von Actiniden im System Ton, Huminstoff, Aquifer" vorgestellt.

Keywords: Humic substances; humic acid; migration; actinides; uranium; neptunium; complexation; clay; sorption; diffusion

  • Lecture (others)
    Workshop zum Forschungsvorhaben "Migration von Actiniden im System Ton, Huminstoff, Aquifer", 28.-29.03.2006, Mainz, Germany

Publ.-Id: 8347

Krein space related perturbation theory for MHD α²-dynamos and resonant unfolding of diabolical points

Kirillov, O.; Günther, U.

The spectrum of the spherically symmetric α²-dynamo is studied in the case of idealized boundary conditions. Starting from the exact analytical solutions of models with constant α²-profiles a perturbation theory and a Galerkin technique are developed in a Krein-space approach. With the help of these tools a very pronounced α²-resonance pattern is found in the deformations of the spectral mesh as well as in the unfolding of the diabolical points located at the nodes of this mesh. Non-oscillatory as well as oscillatory dynamo regimes are obtained. A Fourier component based estimation technique is developed for obtaining the critical α²-profiles at which the eigenvalues enter the right spectral half-plane with nonvanishing imaginary components (at which overcritical oscillatory dynamo regimes form). Finally, Fréchet derivative (gradient) based methods are developed, suitable for further numerical investigations of Krein-space related setups like MHD α²-dynamos or models of PT-symmetric quantum mechanics.

Keywords: Krein space; MHD dynamo; diabolical point; exceptional point; spectral deformation; perturbation theory; resonance; Galerkin method

  • Lecture (Conference)
    International Congress of Mathematicians, 22.-30.08.2006, Madrid, Spain

Publ.-Id: 8346

Krein space related perturbation theory for MHD α²-dynamos

Kirillov, O.; Günther, U.

The mean field α²-dynamo of magnetohydrodynamics (MHD) plays a similarly paradigmatic role in MHD dynamo theory like the harmonic oscillator in quantum mechanics. In its kinematic regime this dynamo is described by a linear induction equation for the magnetic field. For spherically symmetric α²-profiles α(r) the vector of the magnetic field can be decomposed into poloidal and toroidal components and expanded in spherical harmonics. In the present contribution the spectrum of the spherically symmetric α²-dynamo is studied in the case of idealized boundary conditions. Starting from the exact analytical solutions of models with constant α²-profiles a perturbation theory and a Galerkin technique are developed in a Krein-space approach. With the help of these tools a very pronounced α²-resonance pattern is found in the deformations of the spectral mesh as well as in the unfolding of the diabolical points located at the nodes of this mesh. Non-oscillatory as well as oscillatory dynamo regimes are obtained. Finally, Fréchet derivative (gradient) based methods are developed, suitable for further numerical investigations of Krein-space related setups like MHD α²-dynamo or models of PT−symmetric quantum mechanics.

Keywords: Krein space; MHD dynamo; diabolical point; exceptional point; spectral deformation; perturbation theory; resonance; Galerkin method

  • Lecture (Conference)
    77th Annual Meeting of the Gesellschaft für Angewandte Mathematik und Mechanik e.V. (GAMM), 27.-31.03.2006, Berlin, Germany

Publ.-Id: 8345

Concept of deterministic single ion doping with sub-nm spatial resolution

Meijer, J.; Vogel, T.; Burchard, B.; Rangelow, I. W.; Bischoff, L.; Wrachtrup, J.; Domhan, M.; Jelezko, F.; Schnitzler, W.; Schulz, S. A.; Singer, K.; Schmidt-Kaler, F.

We propose a method for deterministic implantation of single atoms into solids which relies on a linear ion trap as an ion source. Our approach allows a deterministic control of the number of implanted atoms and a spatial resolution of less than 1 nm. Furthermore, the method is expected to work for almost all chemical elements. The deterministic implantation of single phosphor or nitrogen atoms is interesting for the fabrication of scalable solid state quantum computers, in particular for silicon and diamond based schemes. A wide range of further applications is expected for the fabrication of nano and sub-nano electronic devices.

Keywords: Single ion implantation; linear ion trap; quantum computer

Publ.-Id: 8344

S-trityl protected mercaptoacetyl-glycyl-glycine - A useful purification handle for oligonucleotide-chelator conjugates as precursors for radiolabeling of aptamers with Tc(V) and Re(V)

Friebe, M.; Hecht, M.; Graham, K.; Stephens, A. W.; Hilger, C. S.; Johannsen, B.; Dinkelborg, L. M.

kein Abstract vorhanden

  • Poster
    International Symposium on Radiopharmaceutical Chemistry (IRSC 2005), 24.-28.08.2005, Iowa City, Iowa, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 48(2005), S242

Publ.-Id: 8343

Quadrupole moment of the 8+ yrast state in 84Kr

Schwengner, R.; Balabanski, D. L.; Neyens, G.; Benouaret, N.; Borremans, D.; Coulier, N.; de Rydt, M.; Georgiev, G.; Mallion, S.; Rainovski, G.; Rusev, G.; Teughels, S.; Vyvey, K.

The quadrupole moment of the 8+ yrast state in 84Kr was measured using the level-mixing spectroscopy technique to be Q = 36(4) efm2. The result is compared with predictions of the shell model using common sets of effective charges. The comparison of experimental quadrupole moments with calculated values for 8+ states in Kr, Sr and Zr isotopes with N = 48, 50 and for 9/2+ states in isotopes with N = 47, 49 suggests a modification of the effective charges used in this region.

Keywords: Nuclear structure; nuclear quadrupole moments; level-mixing spectroscopy; shell model

Publ.-Id: 8342

Local structure and oxidation state of uranium in some ternary oxides: X-ray absorption analysis

Soldatov, A. V.; Lamoen, D.; Konstantinovic, M. J.; van den Berghe, S.; Scheinost, A. C.; Verwerft, M.

We investigated the local atomic and electronic structures of two related systematic sets of ternary uranium oxides, NaUO3 - KUO3 - RbUO3 and BaUO3 - Ba2U2O7 - BaUO4, by measuring the X-ray absorption near edge structure (XANES). The results are compared with calculations based on self-consistent real space full multiple scattering analysis. We found a very good agreement between measured and calculated spectra, which indicates that the uranium ions are in pure U5+ oxidation state in these compounds. The low energy shoulder observed in the U L3 edge XANES is an intrinsic feature of the uranium unoccupied 3d electronic state of the U5+ ions. Specific double shoulder features in the higher energy range of the U L3 edge XANES can be interpreted as indicative of the pure cubic perovskite structure.

Keywords: XAFS; XANES; uranium; ternary uranium oxides; oxidation state; pentavalent

  • Journal of Solid State Chemistry 180(2007), 53-60

Publ.-Id: 8341

Phase stability of epitaxially grown Ti2AlN thin films

Beckers, M.; Schell, N.; Martins, R. M. S.; Mücklich, A.; Möller, W.

The preferred orientation and thermal stability of MAX phase (M: early transition metal; A: A group element; X: C and/or N) Ti2AlN thin films sputtered onto MgO(111) and Al2O3(0001) substrates have been investigated by in situ x-ray diffraction and Rutherford backscattering (RBS). Low-temperature deposition results in epitaxial growth with inclined basal planes. An increased substrate temperature changes the preferred orientation to a parallel basal plane growth. In contrast to high bulk thermal stability, thin films decompose in vacuum already at 800°C by outward Al diffusion, followed by de-twinning of the remaining Ti2N slabs and concurrent TiN and Ti4AlN3 formation.

Keywords: Nucleation and growth; Ti Al N MAX phases; sputter deposition; in situ x ray diffraction

Publ.-Id: 8340

Uranium speciation of environmentally related waters

Geipel, G.; Bernhard, G.

In the environment uranium is one of the ubiquitous elements. One million tons of uranium metal have been produced so far. Between 1945 and 1990 about one quarter of the total world production of uranium have been mined and milled in Eastern Germany. Especially these former intense uranium mining and milling activities have caused contaminations within urban areas.

In the hexavalent oxidation state uranium is soluble in aqueous media. The determination of different species with non-invasive methods can be performed by Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLIFS) under natural conditions. This is due to the different fluorescence emission and fluorescence lifetime of the varying uranium species.
The concentration of uranium ranges from the upper ng/L scale for table waters to the mg/L scale for mining related seepage and surface waters of the tailing ponds. From speciation calculations uranium in the most of these waters should be found as carbonate species. Unfortunately the carbonate species show poor fluorescence properties under ambient temperatures. By cooling of the samples to temperatures below 220 K an increase in the fluorescence intensity and lifetime can be observed. The dynamic quench effect of the carbonate ion decreases with decreasing temperature. Therefore the direct determination of the uranium speciation also in drinking waters can be performed. Examples of uranium carbonate speciation in a wide variety of natural waters will be given.

As an example, the dependence of the uranium speciation on pH of a tailing pond water was detected in detail by TRLIFS measurements. This water contains complexing anions like carbonate, phosphate, arsenate and sulphate. The uranium speciation in this surface water is strongly changed with pH. At pH 5 uranium arsenate species are dominating. The fluorescence emission of this species is in good agreement with data obtained from the uranium mineral troegerite.

Keywords: uranium; speciation; fluorescence; spectroscopy

  • Invited lecture (Conferences)
    Western Pacific Geophysics Meeting, 24.-27.07.2006, Beijing, China
  • Contribution to proceedings
    Western Pacific Geophysics Meeting, 27.07.2006, Beijing, China
    Uranium speciation of environmentally related waters

Publ.-Id: 8339

Dynamics of molten salt reactors

Krepel, J.; Rohde, U.; Grundmann, U.

Dynamics of the Molten Salt Reactor, one of the 'Generation IV International Forum' concepts, was studied in this paper. The graphite-moderated channel type MSR was selected for the numerical simulation. The MSR represents a liquid fueled reactor and its dynamics is very specific because of two physical peculiarities: the delayed neutrons precursors are drifted by the fuel flow and the fission energy is immediately released directly into the coolant. Presently, there are not many accessible numerical codes appropriate for the MSR simulation, therefore the DYN3D-MSR code was developed based on the Light Water Reactor dynamics code DYN3D. It allows calculating of full 3D transient neutronics in combination with parallel channel type thermal-hydraulics. The code was validated on experimental results of Molten Salt Reactor Experiment (from Oak Ridge National Laboratory) and applied to several transients typical for the liquid fuel system. Those transients were initiated by reactivity insertion, by overcooled or overfueled fuel slug, by the fuel pump start-up or coast-down, or by the blockage of single fuel channels. In these considered transients, the response of the MSR is characterized by the immediate change of the fuel temperature according to the power level. This causes fast feedback reactivity insertion, which is negative in the case of power increase. On the other hand, the graphite response is slower and its feedback coefficient is in some cases positive. The addition of erbium to the graphite can ensure the negative feedback and inherent safety features. The DYN3D-MSR code has been shown to be an effective tool for MSR dynamics studies.

Keywords: MSR; molten; salt; reactor; dynamics; MSRE; MSBR

  • Contribution to proceedings
    International Congress on Advances in Nuclear Power Plants - ICAPP 2006, 04.-08.06.2006, Reno, United States
  • Lecture (Conference)
    International Congress on Advances in Nuclear Power Plants - ICAPP 2006, 04.-08.06.2006, Reno, United States

Publ.-Id: 8338

HADES Experiment: Di-Lepton Spectroscopy in p+p (2.2 GeV) and C+C (1 and 2 A GeV) Collisions

Przygoda, W.; Agakishiev, G.; Agodi, C.; Alvarez-Pol, H.; Balanda, A.; Bassini, R.; Bellia, G.; Belver, D.; Bielcik, J.; Blanco, A.; Boehmer, M.; Boiano, C.; Bortolotti, A.; Boyard, J.; Brambilla, S.; Braun-Munzinger, P.; Cabanelas, P.; Chernenko, S.; Christ, T.; Coniglione, R.; Dahlinger, M.; Diaz, J.; Djeridi, R.; Dohrmann, F.; Duran, I.; Eberl, T.; Enghardt, W.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Froehlich, I.; Garzon, J.; Gernhaeuser, R.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Heinz, T.; Hennino, T.; Hlavac, S.; Hoffmann, J.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jaskula, M.; Jurkovic, M.; Kajetanowicz, M.; Kaempfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B.; Kopf, U.; Kotte, R.; Kotulic-Bunta, J.; Kruecken, R.; Kugler, A.; Kuehn, W.; Kulessa, R.; Lang, S.; Lehnert, J.; Maier, L.; Maier-Komor, P.; Maiolino, C.; Marin, J.; Markert, J.; Metag, V.; Montes, N.; Moriniere, E.; Mousa, J.; Muench, M.; Muentz, C.; Naumann, L.; Novotny, R.; Novotny, J.; Ott, W.; Otwinowski, J.; Pachmayer, Y.; Perez, T.; Pechenov, V.; Pietraszko, J.; Pinhao, J.; Pleskac, R.; Pospisil, V.; Pullia, A.; Rabin, N.; Ramstein, B.; Riboldi, S.; Ritman, J.; Rosier, P.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Sapienza, P.; Schmah, A.; Schoen, W.; Schroeder, C.; Schwab, E.; Senger, P.; Simon, R.; Smolyankin, V.; Smykov, L.; Spataro, S.; Spruck, B.; Stroebele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tiflov, V.; Tlusty, P.; Toia, A.; Traxler, M.; Tsertos, H.; Turzo, I.; Wagner, V.; Walus, W.; Willmott, C.; Winkler, S.; Wisniowski, M.; Wojcik, T.; Wuestenfeld, J.; Zanevsky, Y.; Zumbruch, P.

The HADES (High Acceptance Di-Electron Spectrometer) is a tool designed for lepton pair (e+e-) spectroscopy in pion, proton and heavy ion induced reactions in the 1-2 A GeV energy range. One of the goals of the HADES experiment is to study in-medium modifications of hadron properties like effective masses, decay widths, electromagnetic form factors etc. Such effects can be probed with vector mesons (rho , omega , phi ) decaying into e+e- channel. The identification of vector mesons by means of a HADES spectrometer is based on invariant mass reconstruction of e+e- pairs. The combined information from all spectrometer sub-detectors is used to reconstruct the di-lepton signal. The recent results from 2.2 GeV p+p, 1 A GeV and 2 A GeV C+C experiments are presented.

Keywords: PACS numbers: 25.75.Dw; 13.60.Le

  • Open Access Logo Acta Physica Polonica B 37(2006)1, 139

Publ.-Id: 8337

Uranium and cesium sorption on montmorillonite and bentonite

Nebelung, C.; Brendler, V.; Brockmann, S.; Mibus, J.

The sorption characteristics of U and Cs on bentonite and montmorillonite were investigated in batch experiments to understand the near-field behaviour in geological nuclear repositories. The pH dependence and the retention of Cs are small and only caused by cation exchange. For the U sorption, maxima were found between pH 5.5 to 6.0 and at pH > 10.5. The linear sorption isotherm indicates only one binding type.
The retention of Cs in the concentration range between 3·E-9 and 1·E-4 mol/L on bentonite and montmorillonite (KD between 30 and 189 mL/g, retention from 7 to 31 %) is low compared to U (KD between 430 and 31500 mL/g, retention from 50 to 100 %)

This work is supported by the European Commission (NF-PRO C2-ST-C-01)

Keywords: Keywords: Sorption; Bentonite; Montmorillonite; Uranium; Cesium

  • Contribution to proceedings
    1st European Chemistry Congress, 27.-31.08.2006, Budapest, Hungary
  • Poster
    1st Europaen Chemistry Congress, GDCh, RS*C, sfc, 27.-31.08.2006, Budapest, Hungary

Publ.-Id: 8336

Uranium(VI) sorption onto kaolinite in the presence and absence of humic acid

Krepelova, A.; Sachs, S.; Bernhard, G.

We studied the U(VI) sorption onto kaolinite in batch experiments in the absence and presence of humic acid (HA) under different experimental conditions: [U]0 = 1×10-6M or 1×10-5 M, [HA]0 = 10 or 50 mg/L, I = 0.1 M or 0.01 M NaClO4, pH = 3 – 10, CO2 or N2 atmosphere. The study showed that the U(VI) sorption onto kaolinite is influenced by pH, CO2 and HA presence. In the absence of CO2, the U(VI) uptake increases with increasing pH value up to pH 6. Above pH 6 it remains unchanged. Because of the formation of negatively charged uranyl carbonate complexes, the decrease in the U(VI) sorption onto the negative surface of kaolinite was observed above pH 8 in the presence of CO2. In presence of HA, the adsorption of U(VI) closely follows the adsorption of HA. In the acidic pH range the U(VI) uptake is enhanced compared to the system without HA due to the formation of additional binding sites for U(VI) coming from HA adsorbed onto kaolinite. The formation of aqueous uranyl humate complexes reduces the U(VI) sorption in the near neutral pH range. The enhancement of the U(VI) concentration from 1×10-6 M to 1×10-5 M results in the shift of the sorption pH edge by one pH unit to higher pH values. The ionic strength has only a slight influence on the U(VI) sorption onto kaolinite, whereas the HA sorption shows a dependence on the ionic strength.

Keywords: Humic Acid; Uranium; Kaolinite; Sorption

  • Radiochimica Acta 94(2006), 825-833

Publ.-Id: 8335

Electroproduction of light hypernuclei on Helium

Dohrmann, F.

Overview of electroproduction experiments on light nuclei

  • Invited lecture (Conferences)
    PANDA collaboration meeting Dresden, 09.-10.03.2006, Dresden, Deutschland

Publ.-Id: 8334

Testing sub-100ps RPC detectors at ELBE

Dohrmann, F.; Kotte, R.; Naumann, L.

Report on RPC test at the FZ Rossendorf ELBE linac

  • Lecture (Conference)
    7th CBM collaboration meeting, 28.02.-03.03.2006, GSI Darmstadt, Deutschland

Publ.-Id: 8333

Complex formation of curium(III) with amino acids of different functionalities: L-Threonine and O-Phospho-L-Threonine.

Moll, H.; Bernhard, G.

The speciation of curium(III) with L-Threonine and O-Phospho-L-Threonine was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS) at trace Cm(III) concentrations (3x10-7 M).
Curium species of the type MpHqLr were identified in the L-Threonine- and O-Phospho-L-Threonine system. These complexes are characterized by their individual luminescence spectra and luminescence lifetimes. The following formation constants were determined a) for L-Threonine: log β101 = 6.72 ± 0.07, log β102 = 10.22 ± 0.09, and log β1-22 = -(7.22 ± 0.19) at ionic strength I = 0.5 M and b) for O-Phospho-L-Threonine: log β121 = 18.03 ± 0.13 and log β111 = 14.17 ± 0.09 at ionic strength I = 0.154 M. Possible structures of the identified curium species will be discussed on the basis of the luminescence lifetime measurements and the magnitude of the formation constants.

Keywords: Complexation; L-Threonine; O-Phospho-L-Threonine; TRLFS; Curium

Publ.-Id: 8332

Mixing and subsequent amorphization of ultrathin Ni81Fe19/Ta bilayers by 30 keV Ni implantation

Fassbender, J.; Mücklich, A.; Potzger, K.; Möller, W.

The ion implantation induced interfacial mixing and subsequent amorphization of ultrathin Ni81Fe19/Ta bilayers has been investigated by TRIDYN simulations and cross-sectional transmission electron microscopy. Due to the 30 keV Ni implantation the initially sharp interface between Ni81Fe19 and Ta broadens and an intermixing between both layers is observed. Consequently the Ni81Fe19 layer is increasingly doped with Ta in the interface near region. For the region exhibiting a Ta concentration above a threshold value of about 20 atom-% irradiation induced amorphization takes place. For an increasing Ni implantation fluence this region is succeedingly enlarged. A quantitative agreement between simulations and experimental data is found.

Keywords: irradiation induced mixing; irradiation induced amorphization; metal amorphization; TRIDYN

Publ.-Id: 8331

Der Washout der Positronenemitter bei in-beam PET

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

Der Washout der Positronenemitter bei in-beam PET

In-beam PET wird am experimentellen Schwerionentherapieplatz an der Gesellschaft für Schwerionenforschung (GSI) Darmstadt bereits erfolgreich eingesetzt. Durch Vergleich der simulierten Positronen-emitterverteilung mit der gemessenen sind Aussagen zur Reichweite des Kohlenstoffstrahls möglich, es können anatomische Veränderungen detektiert werden und die Feldlage kann beurteilt werden. In der Simulation werden alle Prozesse von der Erzeugung der Positronenemitter bis zum Nachweis der Photonen im Detektor behandelt. Im lebenden Gewebe jedoch nehmen die Positronenemitter an metabolischen Vorgängen teil. Es kommt zum Transport und der Annihilationsort kann vom Erzeugungsort verschieden sein.
Durch Auswertung von Messungen an Patienten kann eine effektive Halbwertszeit bestimmt werden, die sich aus der physikalischen und der biologischen Halbwertszeit zusammensetzt. Die physikalische Halbwertszeit wird nur durch die Stöchiometrie des Gewebes und die Bestrahlungsdauer determiniert. Die biologische Halbwertszeit unterliegt dagegen vielfältigen Einflüssen, die in der vorliegenden Arbeit untersucht wurden. Die Berücksichtigung der effektiven Halbwertszeiten verbessert die Simulation.

Keywords: in-beam PET; ion therapy; washout

  • Lecture (Conference)
    DPG Frühjahrstagung, 13.-15.3.2006, Heidelberg, Deutschland

Publ.-Id: 8330

In-beam PET für die Qualitätssicherung der Ionentherapie - Möglichkeiten und Grenzen

Fiedler, F.

Bei der Radiotherapie von Tumoren erlauben Ionenstrahlen auf Grund ihrer physikalischen und biologischen Eigenschaften ein höheres Maß an Präzision und Wirksamkeit als die konventionellen Strahlenmodalitäten, Photonen und Elektronen. Ein in-situ Monitoring der Dosisapplikation ist deshalb für die Qualitätssicherung der Ionentherapie in hohem Maße wünschenswert. Das einzige gegenwärtig bekannte, dafür geeignete Verfahren ist die in-beam Positronen-Emissionstomographie (PET). Dabei werden während der Tumorbestrahlungen Annihilationsereignisse registriert, die in Folge des Zerfalls von Positronenemittern auftreten, welche durch nuklare Wechselwirkungen zwischen den Projektilen des Therapiestrahles und den Atomkernen des Gewebes erzeugt werden. In die experimentelle Ionentherapie-Anlage an der Gesellschaft für Schwerionenforschung Darmstadt wurde ein in-beam PET-Scanner integriert und die Methode erstmals klinisch angewendet. An dieser Anlage wurden seit 1997 etwa 300 Patienten, vornehmlich mit stahlenresistenten Tumoren in komplizierten anatomischen Positionen im Kopf-Hals-Bereich mit Kohlenstoff-Ionenstrahlen behandelt. Alle Bestrahlungen wurden mit PET kontrolliert.Die nunmehr vorliegenden Erfahrungen erlauben gesicherte Aussagen zum Potential der in-beam PET für die Qualitätssicherung der Ionentherapie.

Keywords: in-beam PET; ion therapy

  • Lecture (Conference)
    DPG Frühjahrstagung, 13.-15.3.2006, Heidelberg, Deutschland

Publ.-Id: 8329

Highlights from the 14th International Summer School on Vacuum, Electron and Ion Technologies (VEIT 2005)

Guerassimov, N.; Möller, W.; (Editors)

Abstract not available

  • Plasma Processes and Polymers 3(2006)2, 87-261

Publ.-Id: 8328

Determination of value of mass transfer coefficient electromagnetic stirred liquid metal phase

Adler, K.; Blacha, L.; Galindo, V.; Schwarze, R.

The paper presents the method of determination of mass transfer coefficient in electromagnetic stirred liquid phase based on Lamont, Scott and Kolmogorov turbulent models. For this purpose the numerical model allowing the determination of electromagnetic force and turbulent filed was utilized. As result the values of Lorentz forces and metal surface velocity have been determined. Calculations were made for IS5/III Leybold Heraeus induction furnace.

Keywords: mass transfer coefficient; electromagnetic stirred molten metal; numerical simulation; turbulent flow; induction furnaces

  • Hutnik, wiadomosci hutnicze (2006)1, 23-27

Publ.-Id: 8327

Annual Report 2005 - Institute of Radiochemistry

Bernhard, G.; Foerstendorf, H.; Mibus, J.; Richter, A.; Ulrich, K.-U.; (Editors)

The Institute of Radiochemistry (IRC), one of the six institutes of the Forschungszentrum Rossendorf (FZR), performs application-oriented research in the fields of radiochemistry and radioecology. Motivation and background of our research are environmental processes relevant for the installation of nuclear waste repositories, for remediation of uranium mining and milling sites, and for radioactive contaminations caused by nuclear accidents and fallout. Due to their high radiotoxicity and long half-life the actinides are of special interest. Hence our research focuses on the chemical behavior of actinides at the molecular level in order to predict the relevant macroscopic processes in the environment.
Within this framework, special emphasis is on the interface between geological and biological systems.
In the last year our research topics were as follows:
– Aquatic chemistry of actinides
– Actinides in bio-systems
– Interaction of actinides with solid phases
– Reactive transport of actinides
About 60 scientists, technicians and PhD students are employed in the Institute of Radiochemistry.
We have achieved a wide range of new scientific results in the past year, which are presented in this Annual Report. Among them only a few can be highlighted here in this preface. For the first time it was possible to determine uranium speciation in situ in drinking and mineral waters e.g. by a dedicated fluorescence spectrometer at lowest μg/L concentrations. This methodical progress is an important prerequisite to study the uranium toxicity and its dependence on chemical speciation. We were very successful in the determination of formation pathways and structure of various actinide complexes, e.g., the surface complexes of uranium (VI) onto mica and iron hydroxides over a wide range of pH and carbonate concentration. These results contribute to a better understanding of actinide speciation in geo- and bio-systems, especially with respect to the chemical processes on the interfaces.
Studies to the interaction of uranium with biofilms, green algae and bacteria coming from extreme habitats extended our research on the field of bio-systems.
Major progress in the structural analysis of multiple uranium species has been achieved by applying Monte Carlo simulations and iterative transformation factor analysis to EXAFS spectroscopy.
Furthermore, our new radiochemical experimental station at the Free Electron Laser of the Rossendorf accelerator ELBE is now in full operation. We have started first experiments on the uranium and neptunium complexation on selected mineral surfaces.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZR-443 2006
    ISSN: 1437-322X


Publ.-Id: 8326

Establishment of the Physical and Technical Prerequisites for the Determination of the Relative Biological Effectiveness of Low-energy Monochromatic X-rays

Lehnert, A.

A superconducting electron linear accelerator of high brilliance and low emittance (ELBE) is under operation at Forschungszentrum Rossendorf since January 2003. The first stage of ELBE is based on an electron energy of 20 MeV, whereas in the future a 40 MeV beam will be provided. The relativistic electron beam is used to drive various kinds of secondary radiation sources. Among all, X-rays in a wide energy range can be obtained. One method for production of intensive, quasi-monochromatic Xrays in the energy range 10 - 100 keV, tunable in photon energy, is by channeling of relativistic electrons in a perfect crystal. This unconventional photon source with variable time structure will be optimised and used for radiobiological studies. Its first test operation was in October 2003. This thesis is part of the first radiobiological project – the determination of relative biological effectiveness (RBE) of the X-rays in this energy range.
The most important aspects of medical application of low-energy X-rays are imaging and radiation therapy, but they can also be helpful in the study of radiation effects in living matter. However, the RBE depends on the photon energy, dose range, cell line and biological endpoint. Up to now no definitive conclusions can be made about their biological effectiveness due to the large spread of the published data. Therefore, in order to precisely determine the RBE, studies have to be performed at an intensive, tunable photon source, for several practically relevant cell lines and biological endpoints. The possibility of using channeling radiation (CR) for medical applications has been widely discussed in the literature, but building and optimisation of a dedicated source is for the first time performed at the ELBE accelerator.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZR-441 2005
    ISSN: 1437-322X


Publ.-Id: 8325

Reversals in nature and the nature of reversals

Stefani, F.; Günther, U.; Gerbeth, G.

One of the most interesting features of Earth's magnetic field reversals is their asymmetric shape including a rather slow decay of a given axial dipole and a very fast recreation of the dipole with opposite polarity. With focus on this asymmetry, we consider a simple mean-field dynamo model with a spherically symmetric isotropic helical turbulence parameter alpha that is quenched by the magnetic field energy and subjected to some noise. With an appropriate radial dependence of alpha(r) (including at least one sign change), this dynamo model exhibits typical features of reversals. The asymmetric shape and the very fast recreation are attributed to the dynamical behaviour in the vicinity of a branching point of square root type (exceptional point) of the spectrum of the non-selfadjoint dynamo operator. Other features, like the possible correlation of magnetic field amplitude and reversal rate, the bimodal field distribution, and the inhibition time are also addressed within our simple model. We discuss a tendency of highly supercritical dynamos to self-tune into reversal prone states, and hypothesize that reversing dynamos might be much more common in nature than what could be expected from a purely kinematic perspective.

  • Invited lecture (Conferences)
    AIMS' Sixth International Conference on Dynamical Systems, Differential Equations and Applications, 25.-28.06.2006, Poitiers, France

Publ.-Id: 8324

In-medium effects on phase space distributions of antikaons measured in proton-nucleus collisions

Scheinast, W.; Böttcher, I.; Debowski, M.; Dohrmann, F.; Förster, A.; Grosse, E.; Koczon, P.; Kohlmeyer, B.; Laue, F.; Menzel, M.; Naumann, L.; Schwab, E.; Senger, P.; Shin, Y.; Ströbele, H.; Sturm, C.; Surówka, G.; Uhlig, F.; Wagner, A.; Walus, W.; Kämpfer, B.; Barz, H. W.

Differential production cross sections of K± mesons have been measured in p+C and p+Au collisions at 1.6, 2.5, and 3.5 GeV proton beam energy. At beam energies close to the production threshold, the K- multiplicity is strongly enhanced with respect to proton-proton collisions. According to microscopic transport calculations, this enhancement is caused by two effects: the strangeness exchange reaction NY-->K-NN and an attractive in-medium K-N potential at saturation density.

  • Physical Review Letters 96(2006), 072301

Publ.-Id: 8323

Testing timing RPC detectors at the Rossendorf electron linac ELBE

Kotte, R.; Dohrmann, F.; Hutsch, J.; Naumann, L.; Stach, D.

The timing performance of various multigap resistive plate chambers (MRPCs) has been tested at the Rossendorf electron linac ELBE. Electrons with energies of 20-40 MeV have been used to mimic minimum ionizing hadrons to be detected in large-scale time-of-flight (TOF) detectors for future heavy-ion collision experiments. Referencing the TOF measurement to the accelerator radio frequency, no fast start detector was necessary. A typical time resolution (including contributions from front-end electronics) of about 70 ps has been achieved for individual strips of the multistrip-anode MRPCs. Rate dependencies and detection efficiencies have been investigated.

Keywords: gaseous detectors; RPC; time resolution

Publ.-Id: 8321

Production of strangeness in hot and cold nuclear matter induced by both leptonic and hadronic projectiles

Dohrmann, F.

Strangeness production by both hadronic and leptonic projectiles with beam energies of up to a few GeV is reviewed. The focus is on the production of strangeness using proton and ion beams, as well as the photo- and electroproduction of strangeness, as observed at modern facilities. The elementary production of K+- and phi mesons as well as Lambda, Sigma hyperons on the nucleon is described. Based on these results, the production of strange mesons and strange baryons on nuclear targets, as well as the creation of light hypernuclei is discussed, emphasizing the influence of the nuclear medium.

  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2006
    129 Seiten
    ISSN: 1437-322X
  • International Journal of Modern Physics E 15(2006)4, 761-851
    DOI: 10.1142/S021830130600465X

Publ.-Id: 8320

Further indication of a low quartz structure at the SiO2/Siinterface from coincidence Doppler broadening spectroscopy

Brauer, G.; Becvar, F.; Anwand, W.; Skorupa, W.

Results from coincidence Doppler broadening (CDB) measurements on various Si samples and Brazilian quartz having low quartz structure are presented with the aim to give further strong indication of the existence of a low quartz structure, but not of Si divacancies as frequently considered, at the SiO2/Si interface.

Keywords: Slow-positron spectroscopy; Coincidence Doppler broadening; Silicon; Brazilian quartz; Silicon divacancy; SiO2/Si interface

  • Applied Surface Science 252(2006), 3368-3371

Publ.-Id: 8318

Sachsens größte Forschungsinvestition Die Strahlungsquelle ELBE im Forschungszentrum Rossendorf

Michel, P.

kein Abstract vorhanden

  • Invited lecture (Conferences)
    Symposium, 21.04.2005, Dresden, Germany

Publ.-Id: 8317

The Radiation Source ELBE and its Research Programm in Nuclear Physics

Lehnert, U.

kein Abstract vorhanden

  • Invited lecture (Conferences)
    Third Sandanski Coordination Meeting on Nuclear Science, 26.-30.09.2005, Albena, Bulgary

Publ.-Id: 8316

Experiments at the mixing test facility ROCOM for benchmarking of CFD-codes

Kliem, S.; Sühnel, T.; Rohde, U.; Höhne, T.; Prasser, H.-M.; Weiß, F.-P.

For the validation of Computational Fluid Dynamics (CFD) codes experimental data with high resolution in time and space are needed.
ROCOM (Rossendorf Coolant Mixing Model) is a test facility for the investigation of coolant mixing in the primary circuit of pressurized water reactors. This facility describes the primary circuit of a German KONVOI type reactor. All important details of the reactor pressure vessel are modelled in a linear scale of 1:5. The facility is characterized by flexible possibilities of operation in a wide variety of flow regimes and boundary conditions. The flow path of the coolant from the cold legs through the downcomer until the inlet into the core is equipped with high resolution measurement technique. Especially, wire mesh sensors in the downcomer of the vessel with a mesh of 64 x 32 measurement positions and in the core inlet plane with one measurement position for the entry into each fuel assembly allow to carry out high-level CFD code validation. The measured data can contribute significantly to the validation of the CFD-codes.

  • Contribution to proceedings
    OECD/NEA & IAEA Workshop: "Benchmarking of CFD Codes for Application to Nuclear Reactor Safety", 05.-07.09.2006, Garching, Germany
    Proceedings CD-ROM paper A4-17, Issy-les-Moulineaux, France: OECD NEA
  • Lecture (Conference)
    OECD/NEA & IAEA Workshop: "Benchmarking of CFD Codes for Application to Nuclear Reactor Safety", 05.-07.09.2006, Garching, Germany
  • Nuclear Engineering and Design 238(2008), 566-576
    DOI: 10.1016/j.nucengdes.2007.02.053

Publ.-Id: 8315

Ion beam induced destabilization of icosahedral structures in gas phase prepared FePt nanoparticles

Dmitrieva, O.; Acet, M.; Liedke, M. O.; Rellinghaus, B.; Fassbender, J.

Multiply twinned FePt nanoparticles with icosahedral structures were prepared by dc magnetron sputtering in argon. The icosahedral structure of these particles is known to be very stable against structural transformations into both the face-centered cubic phase (fcc, A1) and the chemically ordered tetragonal L10 phase upon in-flight or post-deposition thermal annealing. Irradiation of these multiply twinned FePt particles with 5 keV He ions, however, resulted in a transformation into predominantly single crystalline fcc particles at high ion fluences of f>1017 ions/cm2. Adjacent particles were observed to coalesce under the effect of He irradiation, and the size of individual particles was found to be slightly reduced, which indicates a high atomic mobility owing to temporarily enhanced defect concentrations caused by the ion bombardment. Strikingly, there was no indication for the occurrence of L10 ordered FePt nanoparticles upon ion irradiation in these samples.

Keywords: magnetism; nanoparticles; FePt; hard magnetic materials; He ion irradiation; structural phase transformation

  • Journal of Applied Physics 97(2005), 10N112

Publ.-Id: 8314

The multipurpose thermalhydraulic test facility TOPFLOW: an overview on experimental capabilities, instrumentation and results

Prasser, H.-M.; Beyer, M.; Carl, H.; Manera, A.; Pietruske, H.; Schütz, P.; Weiß, F.-P.

A new multipurpose thermalhydraulic test facility TOPFLOW (TwO Phase FLOW) was built and put into operation at Forschungszentrum Rossendorf in 2002 and 2003. Since then, it has been manly used for the investigation of generic and applied steady state and transient two phase flow phenomena and the development and validation of models of Computational Fluid Dynamic (CFD) codes in the frame of the German CFD initiative. The advantage of TOPFLOW consists in the combination of a large scale of the test channels with a wide operational range both of the flow velocities as well as of the system pressures and temperatures plus finally the availability of an special instrumentation that is capable in high spatial and temporal resolving two phase flow phenomena, for example the wire-mesh sensors.

Keywords: two-phase flow; wire-mesh sensor; TOPFLOW; emergency condenser; CCFL

  • Kerntechnik 71(2006)4, 163-173

Publ.-Id: 8313

Solid-state nanocluster formation of praseodymium compounds in silicon and silicon dioxide

Kögler, R.; Mücklich, A.; Eichhorn, F.; Posselt, M.; Reuther, H.; Skorupa, W.

Nanocluster of Pr compounds were formed in a silicon-on-insulator (SOI) structure by ion beam synthesis. The processes of ion-induced atomic mixing, phase segregation, texturing, and nanocluster formation were investigated by transmission electron microscopy, Auger electron spectroscopy and X-ray diffraction. After annealing at 900°C an array of Si precipitates is formed in SiO2. The size distribution of Si precipitates corresponds to the concentration profile of excess Si atoms in SiO2. Implanted Pr atoms are trapped at the Si/SiO2 interface around the Si precipitates and decorate them. During annealing at 1100°C crystalline nanocluster of Pr9.33Si6O26 or Pr2Si2O7 silicate are formed. In the top-Si-layer a narrow layer of Pr compound nanocluster is formed by self-organization rather equidistant of the Si/SiO2 interface. Pr oxide (Pr2O3), the most desired high-k material, was not definitely verified. The predominant process in solid-state synthesis of Pr compounds is Pr silicate formation. It provides both, a high atomic package density and a low reordering energy.

Keywords: Ion beam synthesis; high-k materials; Pr compounds; Si; nanocluster

  • Journal of Applied Physics 100(2006), 104314

Publ.-Id: 8312

Evaluation of a limited angle scanned electron beam X-ray CT approach for two-phase pipe flows

Bieberle, M.; Hampel, U.

We investigated the imaging capability of a fast linearly scanned electron-beam X-ray tomography approach with respect to the phase structure recovery for two-phase flows in a cylindrical pipe. As a consequence of the suggested linear electron beam deflection pattern we need to solve an inverse problem of the limited-angle type which introduces some artefacts in the reconstructed images. To reduce these artefacts we have devised a modified iterative image reconstruction algorithm denoted as binary ART including a level-set based image smoothing operation. To assess the achievable quality of spatial phase structure recovery from the limited-angle data we performed a simulation study on three-dimensional flow data sets obtained with a fast and high-resolution conductivity wire-mesh sensor under real two-phase flow conditions. The simulations revealed that the reconstruction error remains below 2% for up to 1% of Gaussian noise in the projection data and even for up to 5% noise in the case of the bubble diameters below 3 mm.

Keywords: limited-angle tomography; two-phase flow; scanned electron beam; fast tomography

  • Measurement Science and Technology 17(2006), 2057-2065

Publ.-Id: 8311

The coordination of uranium in solution –what can we learn from EXAFS spectroscopy?

Hennig, C.

EXAFS gives average values of all neighbor distances as a radial distribution function. The determination of the coordination number has a relative high error (10-25%), therefore the structure interpretation is strongly focused onto distance determination (delta R ± 0.01Å). EXAFS combined with Factor analysis allows separation of different species from solutions. EXAFS allows to korrelate structural features to thermodynamically proposed solution species.

  • Invited lecture (Conferences)
    Katholieke Universiteit Leuven, Molecular Design and Synthesis Group, 2.3.2006, Leuven, Belgium

Publ.-Id: 8310

On the application of CFD modeling for the prediction of the degree of mixing in a PWR during a boron dilution transient

Lycklama À. Nijeholt, J.-A.; Höhne, T.

In a Pressurized Water Reactor, negative reactivity is present in the core by means of Boric acid as a soluble neutron absorber in the coolant water. The main functions of the boric acid are to compensate for the fuel burn up and Xenon poisoning during normal operation and to provide the required sub-criticality of reactor shutdown during refueling and maintenance. During a so called Boron Dilution Transient (BDT), the borated coolant water is diluted by mixing with unborated water. The resulting decrease in the boron concentration leads to an insertion of positive reactivity in the core, which may lead to a reactivity excursion. The associated power peak may damage the fuel rods.

The most severe BDT involves scenarios in which a slug of unborated water has been formed in a cold leg in a stationary (Main Coolant Pumps are down) primary circuit. An inadvertent start-up of the MCP of the affected loop causes the transport of the unborated slug into the Reactor Pressure Vessel (RPV). The resulting positive reactivity insertion in the core is governed by the degree of mixing of the unborated slug and the borated water in the cold leg, the downcomer and the lower plenum. This mixing of borated and unborated water is an important process, because it mitigates and determines the degree of reactivity insertion.

The objective of the present study is to develop a validated Computational Fluid Dynamics (CFD) model for the prediction of the boron concentration distribution in the RPV as function of time during a BDT. This CFD model has been validated using the measurement data from the Rossendorf coolant mixing model (ROCOM) experiment. The ROCOM test facility represents the primary cooling system of a KONVOI type of PWR (1300 MWel). The linear scale of the ROCOM experimental facility is 1:5. The RPV is connected with four circulation loops. Various experiments on boron dilution scenarios have been performed. For the pump start-up experiments the following boundary conditions were varied: the length of the pump ramp, the final mass flow rate of the loop with the start–up pump, the volume of the deborated slug and initial position in the cold leg and the status of the unaffected loops.

A detailed CFD model of the RPV including the inlet nozzles, the downcomer, and the lower plenum has been developed to predict the mixing of deborated and borated water in this RPV. The validation of the model has been achieved by comparison of the calculated and measured relative boron concentration at the core inlet plane as function of time. For code validation a slug mixing experiment with 14 s ramp length, 185 m³/h final flow rate, 4 m³ slug volume and 10 m initial slug position was taken. The unaffected loops were open. In spite of the complicated spatial, temporal, and geometrical aspects of the flow in the RPV, the agreement between the calculated and the experimental data is good. The minimal relative boron concentration measured at the core inlet is 64% and the calculated minimum value is 60%.

Keywords: PWR; Boron Dilution; CFD

  • Contribution to proceedings
    ICAPP ’06, 04.-08.06.2006, Reno, United States
    Proceedings, paper 6155
  • Lecture (Conference)
    ICAPP ’06, 04.06.2006, Reno, United States

Publ.-Id: 8309

Structural and magnetic properties of Mn-implanted Si

Zhou, S.; Potzger, K.; Mücklich, A.; Eichhorn, F.; Schell, N.; Grötzschel, R.; Schmidt, B.; Skorupa, W.; Helm, M.; Fassbender, J.; Geiger, D.

Structural and magnetic properties in Mn-implanted, p-type Si were investigated. High resolution structural analysis techniques such as synchrotron x-ray diffraction revealed the formation of MnSi1.7 nanoparticles already in the as-implanted samples. Depending on the Mn fluence, the size increases from 5 nm to 20 nm upon rapid thermal annealing. No significant evidence is found for Mn substituting Si sites either in the as-implanted or annealed samples. The observed ferromagnetism yields a saturation moment of 0.21µB per implanted Mn at 10 K, which could be assigned to MnSi1.7 nanoparticles as revealed by a temperature-dependent magnetization measurement.

Keywords: Diluted magnetic semiconductor; Si; Ion implantation

Publ.-Id: 8308

CFD für Sicherheitsventile und andere Anwendungen

Höhne, T.

Mit dem CFX-Code wurden Nachrechnungen von Durchsatzparametern eines Leser Sicherheitsventils mit einem Gitter von 1 Million Hexaeder Zellen vorgestellt. Sehr gute Übereinstimmung wurde bei den Durchsatzkennlinien der vom Hersteller angegebenen Charakteristiken für Luft und Wasser erzielt, es existierte jedoch eine systematische Abweichung bei Luft im Falle hoher Ansprechdrücke durch Realgasverhalten und das Auftreten hohe Ma-Zahlen. Eine CFX-Rechnung mit einem Zweiphasengemisch bei 2 bar Überdruck, 1 mm Blasendurchmesser und 4% Gasanteil ergab eine realistische Erhöhung des Volumenanteils der Gasphase in Abhängigkeit von der Druckabsenkung. Weitere Untersuchungen, insbesondere das Verhalten bei Sattdampf und bei Stoffgemischen im Vergleich mit Experimenten sind geplant.

Keywords: Sicherheitsventil; CFD

  • Invited lecture (Conferences)
    GVC-Arbeitsausschuß “Sicherheitsgerechtes Auslegen von Chemieapparaten“ 61. Sitzung, 08.-09.03.2006, Dresden, Germany

Publ.-Id: 8307

CFD-Analysen zur Kühlmittelvermischung in DWR

Höhne, T.; Kliem, S.; Rohde, U.; Weiß, F.-P.

Auftriebsgetriebene Strömungen in Druckwasserreaktoren stellen sich in einer Vielzahl von sicherheitsrelevanten Szenarien, insbesondere unter Naturumlaufbedingungen z.B. nach einem postulierten Leckstörfall bzw. bei “pressurized thermal shocks (PTS)” Szenarien, wie der Einspeisung von kaltem Notkühlwasser in die noch heissen Loops in, ein. Bei der Untersuchung dieser Klasse von Strömungen mit numerischen Tools zeigte sich, dass vor allem die vorhandenen Turbulenz- und Zweiphasenmodelle noch weiterzuentwickeln sind. Die umfangreichen Messdaten der Versuchsanlage ROCOM bieten eine Grundlage für die Validierung von CFD-Codes. Zur Bewertung der Güte der Modelle wurden quantitative Vergleiche zwischen Rechnung und Messung durchgeführt.

Im ersten Teil des Vortrages erfolgt eine Vorstellung von Nachrechnungen dichtegetriebener Experimente an der ROCOM-Versuchsanlage. Im zweiten Teil wird näher auf Simulationen eines Auffüllvorganges eines Notkühlbehälters mit deborierten Kühlmittel eingegangen.

Hierbei werden Fortschritte in der CFD-Modellierung der letzten Jahre, der Einbezug von sogenannten Best Practice Guidelines in der CFD-Modellierung in der Reaktorsicherheitsforschung aber auch bestehender Forschungsbedarf und Grenzen der Modellierung dargestellt.

Keywords: Born Dilution; PWR; Safety tank; CFD; ROCOM

  • Invited lecture (Conferences)
    Fachtagung der KTG-Fachgruppen "Sicherheit kerntechnischer Anlagen„ „Thermo- und Fluiddynamik“ und "Betrieb von kerntechnischen Anlagen", 03.-04.04.2006, Dresden, Germany
  • Contribution to proceedings
    Fachtagung der KTG-Fachgruppen "Sicherheit kerntechnischer Anlagen„ „Thermo- und Fluiddynamik“ und "Betrieb von kerntechnischen Anlagen", 03.-04.04.2006, Dresden, Germany
    Wissenschaftlich-technische Berichte FZR 455, 1437-322X, III-14

Publ.-Id: 8306

Diffusion of humic acid in compacted clay

Mibus, J.; Sachs, S.; Krepelova, A.

Clay minerals and organic substances are common components of soils, sediments, and rocks. Little is known, however, on the migration behavior of humic substances in clay formations. Here, we studied the diffusion of humic acid (HA) in clay at different porosities to understand the migration of organic colloids in narrow pore systems.
The migration behavior of HA in compacted clay has to be understood as the diffusion of a size distributed matter, which is affected by filtration effects, size exclusion, the conformity of HA as a function of pH, and probably the distribution of functional groups in the different molecular fractions.

Keywords: humic acid; clay; diffusion

  • Contribution to proceedings
    Bridging Clays, 03.-07.06.2006, Ile d'Oléron, France
  • Lecture (Conference)
    Bridging Clays, 03.-07.06.2006, Ile d'Oléron, France

Publ.-Id: 8305

Strahlungsdetektoren für astrophysikalische Messungen

Crespo, P.; Erhard, M.

In diesem Vortrag sollte dargestellt werden, mit welchen Methoden sich die Astrophysik Information über den Kosmos beschafft und welche Vor- und Nachteile erdgebundene gegenüber weltraumgestützten Beobachtungen haben. Dabei wurde insbesondere auf den Nachweis elektromagnetischer Strahlung und kosmischer Teilchen eingegangen.
Ein Teil des elektromagnetischen Spektrums wird durch die Erdatmosphäre absorbiert und geladene Teilchen werden bis zu einer bestimmten Energie durch das Erdmagnetfeld abgelenkt. Hochenergetische Teilchen können jedoch in der Atmosphäre Teilchenschauer auslösen, die mit verschiedenen Detektortypen am Erdboden nachgewiesen werden können, wobei unterschiedliche physikalische Prozesse ausgenutzt werden. Als Beispiele wurde die Funktionsweise von Radioantennen, CCD-Kameras (Charge-Coupled Device), des Chandra-Röntgenteleskops und EGRET (Energetic Gamma Ray Experiment Telescope) für den Nachweis elektromagnetischer Strahlung, sowie des AMS-Experimentes (Alpha Magnetic Spectrometer) mit seinen vielfältigen Detektortypen zum Nachweis kosmischer Teilchen vorgestellt.
Ohne die Resultate dieser Messungen wäre die Entwicklung kosmolgischer Modelle nicht möglich. Gleichzeitg werden dadurch neue Fragen aufgeworfen, die Anstoß zur Verbesserung und Entwicklung neuer Detektortypen liefern.

  • Lecture (others)
    Lehrerfortbildung 2005/2006 - Astrophysik, 17.02.2006, Forschungszentrum Rossendorf, Dresden, Deutschland

Publ.-Id: 8304

VVER-1000 radial reflector modeling by diffusion nodes

Petkov, P. T.; Mittag, S.

The two commonly used approaches to describe the VVER radial reflectors in diffusion codes, by core-reflector albedos and by a ring of diffusion assembly size nodes, are discussed. The advantages and disadvantages of the first approach are presented first, then the Koebke's equivalence theory is outlined and its implementation for the VVER radial reflectors is discussed. Results for the VVER-1000 reactor are presented.

  • Progress in Nuclear Energy 48(2006), 764-772

Publ.-Id: 8303

Growth of sputter-deposited Ni-Ti thin films: effect of a SiO2 buffer layer

Martins, R. M. S.; Schell, N.; Beckers, M.; Mahesh, K. K.; Silva, R. J. C.; Fernandes, F. M. B.

In-situ x-ray diffraction (XRD) during the growth of Ni-Ti thin films was chosen in order to investigate their texture development using a deposition chamber installed at a synchrotron radiation beamline. Near-equiatomic films were co-sputtered from Ni-Ti and Ti targets. The texture evolution during deposition is clearly affected by the substrate type and the ion bombardment of the growing film. On naturally oxidized Si(100) substrates the NiTi B2 phase starts by stacking onto (h00) planes, and as the thickness increases evolves into a (110) fiber texture. For the deposition on thermally oxidized Si(100) substrates, this pronounced cross-over is only observed when a substrate bias voltage (-45 V) is applied. The oxide layer plays an important role on the development of the (100) orientation of the B2 phase during deposition on heated substrates (≈ 470ºC). If this layer is not thick enough (naturally oxidized Si substrate) or if a bias voltage is applied, a cross-over and further development of the (110) fiber texture is observed,which is considered as an orientation that minimizes surface energies. Electrical resistivity measurements showed different behaviour during phase transformation for the NiTi film deposited on thermally oxidized Si without bias and those on thermally oxidized Si(100) with bias and on naturally oxidized Si(100) without bias. This is related to stresses resultant from the fact that the NiTi films are attached to the substrates as well as with the existence of distinct textures.

Keywords: Ni-Ti; Sputter deposition; In-situ x-ray diffraction; Texture development

  • Applied Physics A 84(2006)3, 285-289

Publ.-Id: 8302

Migration von Actiniden im System Ton, Huminstoff, Aquifer

Bernhard, G.

  • wird nachgereicht
  • Lecture (Conference)
    Forschungsförderung zur Entsorgung gefährlicher Abfälle in tiefen geologischen Formationen - 7. Projektstatusgespräch, 03.-04.05.2006, Karlsruhe, Germany

Publ.-Id: 8301

Experimente an der Versuchsanlage ROCOM zur Kühlmittelvermischung bei Wiederanlauf der Naturzirkulation

Kliem, S.; Sühnel, T.; Prasser, H.-M.; Weiß, F.-P.

Ein kleiner Leckstörfall kann im Druckwasserreaktor unter bestimmten Bedingungen zum Abriss der einphasigen Naturzirkulation in einer oder mehrerer Schleifen führen. Bei einem bestimmten Druckniveau ist der Massenstrom der Noteinspeisung groß genug, um die Leckverluste wieder zu kompensieren. Der Primärkreislauf wird aufgefüllt und der einphasige Naturumlauf springt wieder an. Minderborierte Kondensatpfropfen, die sich in der vorhergehenden Reflux-Condenser-Phase gebildet haben, werden in Richtung Reaktorkern transportiert. Basierend auf aus PKL-Experimenten abgeleiteten Randbedingungen wurden an ROCOM Experimente zur Quantifizierung der Vermischung innerhalb des Druckbehälters durchgeführt.

  • Contribution to proceedings
    KTG-Fachtag "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", 03.-04.04.2006, Dresden, Germany
    Tagungsband FZR-455, 1437-322X, I-6
  • atw - International Journal for Nuclear Power (2007), 352-360
  • Invited lecture (Conferences)
    KTG-Fachtag "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", 03.-04.04.2006, Dresden, Germany

Publ.-Id: 8300

Ultraschnelle optoelektronische und Materialeigenschaften von Stickstoff-haltigem GaAs

Sinning, S.

no abstract available

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZR-450 2006
    ISSN: 1437-322X


Publ.-Id: 8299

Reactive ion plasma immersion implantation for surface passivation

Möller, W.; Shevchenko, N.; Yankov, R. A.; Rogozin, A.; Maitz, M. F.; Richter, E.; Donchev, A.; Schütze, M.

no abstract available

  • Invited lecture (Conferences)
    8th International Workshop on Plasma-Based Ion Implantation and Deposition, 18.-22.09.05, Chengdu, China

Publ.-Id: 8298

Ion-induced stress release in hard coatings

Möller, W.

no abstract available

  • Invited lecture (Conferences)
    14th International Summer School on Vacuum, Electron, and Ion Technologies, 12.-16.09.05, Sunny Beach, Bulgaria

Publ.-Id: 8297

Plasma immersion ion implantation: Process, promises and prospects

Möller, W.

no abstract available

  • Invited lecture (Conferences)
    15th International Colloquium on Plasma Processes, 05.-09.06.05, Autrans, France

Publ.-Id: 8296

Ion bombardment for stress release in cubic boron nitride thin films

Möller, W.; Abendroth, B.; Gago, R.; Kolitsch, A.

no abstract available

  • Invited lecture (Conferences)
    International Conference on Metallurgical Coatings and Thin Films, 02.-06.05.05, San Diego, USA

Publ.-Id: 8295

Ion beam synthesis of nanostructures with keV/amu ions

Möller, W.; Heinig, K.-H.; Müller, T.; Röntzsch, L.; Schmidt, B.

no abstract available

  • Invited lecture (Conferences)
    Indo-German Workshop "Synthesis and Modification of Nanostructured Materials by Energetic Ion Beams", 21.-24.02.05, New Delhi, India

Publ.-Id: 8294

Plasma surface interaction and ion bombardment

Möller, W.

no abstract available

  • Invited lecture (Conferences)
    International School "Nanostructuring by Ion Beams", 18.-19.02.05, New Delhi, India

Publ.-Id: 8293

Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208] [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247] [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258] [259] [260] [261] [262] [263] [264] [265] [266] [267] [268] [269] [270] [271] [272] [273] [274] [275] [276] [277] [278] [279] [280] [281] [282] [283] [284] [285] [286] [287] [288] [289] [290] [291] [292] [293]