Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31860 Publications
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 LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-453 2006


Publ.-Id: 8380 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

Annual Report 2005 - Institute of Ion Beam Physics and Materials Research
von Borany, J.; Heera, V.; Helm, M.; Möller, W.; (Editors)
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-448 2006


Publ.-Id: 8363 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 LogoActa Physica Polonica B 37(2006)1, 139

Publ.-Id: 8337 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

Mixing and subsequent amorphization of ultrathin Ni81Fe19/Ta bilayers by 30 keV Ni implantation
Fassbender, J.ORC; 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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-443 2006


Publ.-Id: 8326 - Permalink

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 LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-441 2005


Publ.-Id: 8325 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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
  • International Journal of Modern Physics E 15(2006)4, 761-851
    DOI: 10.1142/S021830130600465X

Publ.-Id: 8320 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

Ion beam induced destabilization of icosahedral structures in gas phase prepared FePt nanoparticles
Dmitrieva, O.; Acet, M.; Liedke, M. O.; Rellinghaus, B.; Fassbender, J.ORC
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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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.ORC; 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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

Ultraschnelle optoelektronische und Materialeigenschaften von Stickstoff-haltigem GaAs
Sinning, S.;
no abstract available
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-450 2006


Publ.-Id: 8299 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

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 - Permalink

Ion-based materials research at FZR
Möller, W.;
no abstract available
  • Lecture (others)
    Laboratory of Ion Beam Physics and Materials Research, University of Lanzhou, 23.09.05, Lanzhou, China

Publ.-Id: 8292 - Permalink

Fast ions for nano technology
Möller, W.;
no abstract available
  • Lecture (others)
    Fraunhofer Center of Nanoelectronic Technologies, 13.10.05, Dresden, Germany

Publ.-Id: 8291 - Permalink

Deposition and characterization of nitride MAX phase thin films
Möller, W.;
no abstract available
  • Lecture (others)
    CSIC-ICMM, 13.12.05, Madrid, Spain

Publ.-Id: 8290 - Permalink

EPOS - An intense positron beam project at the ELBE radiation source in Rossendorf
Krause-Rehberg, R.; Sachert, S.; Brauer, G.; Rogov, A.; Noack, K.;
EPOS, the acronym of ELBE Positron Source, describes a running project to build an intense pulsed beam of mono-energetic positrons (0.2-40 keV) for materials research. Positrons will be created via pair production at a tungsten target using the pulsed 40 MeV electron beam of the superconducting electron linac with high brilliance and low emittance (ELBE) at Forschungszentrum Rossendorf (near Dresden, Germany). The chosen design of the system under construction is described and results of calculations simulating the interaction of the electron beam with the target are presented, and positron beam formations and transportation are also discussed.
Keywords: Positron beam, Intense positron source

Publ.-Id: 8289 - Permalink

Influence of bacteria on migration of uranium from uranium mining wastes
Selenska-Pobell, S.;
Our studies on bacterial diversity in waters, sediments and soils of different uranium mining wastes and repositories in Germany and in the USA demonstrated that these extreme environments are populated by dense groups of various bacteria, most of which are site-specific [14, 16, 17]. Recently we have found that these bacterial populations respond very vigorously to the addition of uranyl or sodium nitrate to their natural habitats [5, 6]. The predominant bacterial groups in the original, untreated samples, which contained about 26 mg U/kg, were rapidly replaced after the supplementations by bacteria, which were underrepresented in the untreated samples. The shifting in the structure of the natural bacterial community was dependent on the salt solution added, on the aeration conditions, and on the duration of the experiments...
  • Invited lecture (Conferences)
    Fachdiskussion: "Mikrobiologie in Halden und Absetzanlagen", 09.02.2006, Berlin, Germany

Publ.-Id: 8288 - Permalink

Synthesis and evaluation of Ga-68 labeled Y2-selective peptides for in vivo receptor targeting using small animal PET
Zwanziger, D.; Khan, I.; Schlesinger, J.; Bergmann, R.; Beck-Sickinger, A.;
Peptide YY (PYY) is a 36 amino acid peptide amide that belongs to the PP-hormone family. It selectively binds to at least two G-protein coupled receptors named Y2- and Y5-receptor. These receptors are overexpressed in various tumors like neuroblastomas and nephroblastomas. With regard to clinical applications, NPY2 and NPY5 receptors may act as in vivo targets for receptor-directed therapy and diagnosis of the tumors, however there are specific and in vivo stabile ligands still required. The aim of the work was to synthesize receptor ligands, which could be radioloabeled with the positron emitting nuclides Ga-68 for small animal positron emission tomography (PET).
PYY derivatives were synthesized by solid-phase peptide synthesis, characterized by HPLC/MALDI techniques, purified by preparative HPLC and linked to DOTA (1,4,7,10-tetraazacyclotetradecane-N, N´,N´´,N´´´tetraacetic acid) as chelator for the 68Ga(III). The in vitro binding affinity of the peptides was studied in SMS-KAN cells expressing NPY2 receptors by competitive receptor binding assays. Two Ga-68 labeled derivatives were studied in vivo by small animal PET in rats and mice. The activity was fast eliminated into the urine. One hour after injection was only in the kidneys remaining activity detected.
Optimized Y2-selective and in vivo stabile peptides will be developed and tested for tumor targeting.
  • Lecture (Conference)
    2nd Fabisch Symposium for Cancer Research and Molecular Cell Biology, 30.03.-01.04.2006, Berlin, Germany

Publ.-Id: 8287 - Permalink

Optimierung einer Zellmarkierungs-Strategie für die Magnetresonanzbildgebung
Wolf, G.; Strobel, K.; Gruener, S.; Koch, A.; Abolmaali, N.;
Mit Hilfe moderner Scannertechnologien und hohen Magnetfeldstärken erreicht die Magnetresonanzbildgebung (MRT) eine nahezu zelluläre Auflösung. Damit bietet sie eine zerstörungsfreie, nicht-invasive und wiederholbare Möglichkeit zur Verfolgung einzelner Zellen oder kleiner Gruppen von Zellen nach deren Transplantation oder Injektion in lebende Organismen. Dafür müssen die Zellen mit einem geeigneten MRI-Kontrastmittel (KM) markiert sein, um sie in vivo vom umgebenden Gewebe unterscheiden zu können.
In der vorliegenden Studie haben wir MRT-Messungen an KM-markierten Zellen des nicht-kleinzelligen Lungenkarzinoms (NSCLC) bei Magnetfeldstärken von 1,5 T und 7 T durchgeführt. Systematisch bestimmten wir die Zellmarkierungseffizienz von gadolinium- und Mangan-basierten KM in Abwesenheit und gegenwart verschiedener Transfektionsmittel (TM). Das Ziel der Studie war, diejenige Kombination von KM und TM zu finden, welche den besten Kontrast in der MRT liefert.
  • Lecture (Conference)
    15. Symposium "Experimentelle Strahlentherapie und Klinische Strahlenbiologie", 02.-04.03.2006, Dresden, Germany
  • Contribution to proceedings
    15. Symposium "Experimentelle Strahlentherapie und Klinische Strahlenbiologie", 02.-04.03.2006, Dresden, Germany, ISSN 1432-864X, 165

Publ.-Id: 8285 - Permalink

Optimization of a Cell Labeling Strategy for Magnetic Resonance Imaging
Wolf, G.; Strobel, K.; Gruener, S.; Koch, A.; Hietschold, V.; Abolmaali, N.;
With the currently available scanner technology and high field strengths, magnetic resonance imaging (MRI) allows a near cellular resolution and, thus, provides a non-invasive and repetitive means of tracking single cells or small groups of cells after their transplantation or injection in living organisms. Therefore, cells need to be labeled with a suitable MRI contrast agent (CA) in order to differntiate them from surrounding tissue in vivo. Using CA labeled tumor cells it would be possible to follow tumor progression over time with MRI after transplantation or injection.
  • Poster
    ISMRM 14. Scientific Meeting & Exhibition, 06.-12.05.2006, Seatle, USA
  • Contribution to proceedings
    ISMRM 14. Scientific Meeting, 06.-12.05.2006, Seatle, USA
    Proceedings of the International Society for Magnetic Resonance in Medicine 14, 1864

Publ.-Id: 8284 - Permalink

Two- and Threefold Intramolecular Bridging p-tert- Butylcalix[8]arene Triphosphates – Synthesis, Structure and Stereochemistry
Gloede, J.; Ozegowski, S.; Keitel, I.; Gruner, M.; Costisella, B.; Pritzkow, W.; Stephan, H.; Bartoschek, M.;
The phosphorylation of p-tert-butylcalix[8]arene (1) with phosphorus pentachloride and hydrolysis gives intramolecular bridging tert-butylcalix[8]arene triphosphates. The reactivity (esterification, dehydratisation, complexation), the structure (nmr and x-ray), and stereochemical behaviour of the phosphates will be discussed.
  • Zeitschrift für Anorganische und Allgemeine Chemie (2006)632, 123-132

Publ.-Id: 8283 - Permalink

Hunting Medium Modifications of the Chiral Condensate
Thomas, R.; Zschocke, S.; Hilger, T.; Kämpfer, B.;
With QCD sum rule evaluations, spectral changes of hadrons inside nuclear matter are considered, which shed light on QCD condensates and thus on the non-perturbative structure of the QCD ground state. For some light quark configurations, omega meson and nucleon, the relevance of four-quark condensates is compared; the D meson as a representative of heavy-light quark systems is also briefly discussed.
Keywords: QCD Sum Rules, Chiral Condensate
  • Contribution to proceedings
    44th International Winter Meeting on Nuclear Physics, 29.01.-05.02.2006, Bormio, Italy
  • Lecture (others)
    Int. Wintermeeting on Nuclear Physics, 20.01.-05.02.2006, Bormio, Italy

Publ.-Id: 8282 - Permalink

The growth and microstructure of magnetron sputtered Ti2AlN MAX phase thin films characterized by in-situ x-ray diffraction
Beckers, M.; Schell, N.; Martins, R. M. S.; Mücklich, A.; Möller, W.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    14th International Summer School on Vacuum, Electron and Ion Technologies (VEIT), 12.-16.09.2005, Sunny Beach, Bulgaria

Publ.-Id: 8281 - Permalink

Amorphous-crystalline ripple formation in ion beam induced Si wafers
Grigorian, S.; Pietsch, U.; Grenzer, J.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    348. Heraeus-Seminar "Ions at Surfaces: Patterns and Processes", 19.-23.06.2005, Bad Honnef, Germany

Publ.-Id: 8280 - Permalink

Modelling of differential pressure buildup during flow through beds of fibrous materials
Grahn, A.; Krepper, E.; Alt, S.; Kästner, W.;
The present paper reports on our efforts in modelling the pressure drop buildup across beds of fibrous materials at strainers. Special attention is drawn to the compressibility of the fibrous filter cake. The influence of penetration depth of sludge particles onto the overall pressure drop in conjunction with the thin-bed effect has been investigated. Numerical results are compared with pressure drop measurements.
Keywords: pressure drop, strainer blockage, fibrous filter cakes, compressible filter cakes

Publ.-Id: 8279 - Permalink

Formation of Au nanocrystals in TiO2, SrTiO3 and MgO by ion implantation
Fromknecht, R.; Linker, G.; Sun, K.; Zhu, S.; Wang, L. M.; van Veen, A.; van Huis, M. A.; Weimann, T.; Wang, J.; Niemeyer, J.; Eichhorn, F.; Wang, T.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    10th Int. Symposium on Advanced Physical Fields (APF-10) "Nano-Fabrication and Nano-Characterization of Nanomaterials", 07.-10.03.2005, Tsukuba, Japan

Publ.-Id: 8278 - Permalink

Molecular structure and electronic properties of poly(3-hexylthiophene)
Zen, A.; Saphiannikova, M.; Neher, D.; Grenzer, J.; Pietsch, U.; Asawapirom, U.; Scherf, U.;
Kein Abstract vorhanden.
  • Lecture (Conference)
    DPG Frühjahrstagung, 04.-09.03.2005, Berlin, Germany

Publ.-Id: 8277 - Permalink

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