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41396 Publications

Free and silica-gel bound tetraazamacrocycles as complexing agents of actinide cations: a XAFS investigation of the solid-state coordination scheme

Giachini, L.; Faure, S.; Meyer, M.; Vi Nguyen, L.; Batifol, B.; Chollet, H.; Guilard, R.; Hennig, C.; Scheinost, A. C.

There is a continuous need for processes aimed at the selective uptake of toxic metal ions from dilute wastewaters and industrial process streams. Insofar, solid-liquid extraction processes using chelating agents grafted onto hydrophilic supports are appealing. The Institut de Chimie Moléculaire de l'Université de Bourgogne has designed a series of hybrid organic-inorganic materials for the selective uptake of toxic metal ions, including actinides [1]. These extracting agents are obtained by grafting functionalized tetraazamacrocyclic ligands (cyclen and cyclam derivatives) on the surface of silica-gel beads. In collaboration with the Commissariat à l'Energie Atomique (CEA Center of Valduc), one of these modified gel has been prepared on a semi-industrial scale and used in the final decontamination step of real effluents for removing the residual -emitters (U, Pu, Am) contained at the sub-g/L level. This process allowed the successful decontamination of more than 50 m3 wastewaters, with a residual radioactivity level of less than 5 Bq/m3.
We have used XAFS to investigate the coordination scheme of UO22+ and Pu4+ cations at the surface of the organic-inorganic hybrid materials. The results show that surface complexes are formed through a combined action between the reactive solid support, namely amorphous silica, and the chelating groups appended on the immobilized ligands [2].

[1] F. Barbette, F. Rascalou, H. Chollet, J. L. Babouhot, F. Denat, R. Guilard, Anal. Chim. Acta, 502, 179-187, 2004.
[2] L. Giachini, S. Faure, M. Meyer, L.V. Nguyen, B. Batifol, H. Chollet, R. Guilard, A.C. Scheinost, C. Hennig, Proceedings of the 5th Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources (Actinide XAS 2008), in press.

Keywords: macrocycles; actinides; cyclen; cyclam; nuclear waste; EXAFS

  • Lecture (Conference)
    The 14th International Conference on X-ray Absorption Fine Structure (XAFS14), 26.-31.07.2009, Camerino, Italy

Permalink: https://www.hzdr.de/publications/Publ-12518
Publ.-Id: 12518


THEREDA – A thermodynamic reference database for nuclear waste disposal in Germany

Gester, S.; Altmaier, M.; Brendler, V.; Hagemann, S.; Herbert, H.-J.; Marquardt, C.; Moog, H. C.; Neck, V.; Richter, A.; Scharge, T.; Voigt, W.; Wilhelm, S.; Willms, T.; Wollmann, G.

The long-term safety of radioactive waste disposal in deep geological repositories with respective reliable predictions is an important fact in the disposal site selection process. To ensure the safety geochemical modeling calculations using comprehensive and consistent thermodynamic data are required.
The relational databank THEREDA will provide such thermodynamic datasets. It takes into account specific German requirements (high ionic strengths in salt host rocks) and temperatures up to 100°C. Available databases do not suffice these needs because of very restrictive data selection procedures or heterogeneous and inconsistent data. THEREDA mainly builds on data derived from solution experiments with a focus on ternary and higher systems.
The application of referential integrity, thermodynamic dependencies, alternative datasets and uncertainty estimates allows THEREDA to deliver tailor-made parameter files for use in geochemical modeling software like EQ3/6, GWB and ChemApp.
To enhance public use THEREDA is accessible via internet.

Keywords: THEREDA; database; nuclear waste disposal; long-term safety; reliable predictions; thermodynamic data; high ionic strength; Pitzer; SIT; solution experiments; alternative datasets; referential integrity; uncertainty estimates; geochemical modelling; EQ3/6; GWB; ChemApp

  • Lecture (Conference)
    238th ACS National Meeting & Exposition (Fall 2009), 16.-20.08.2009, Washington DC, United States
  • Abstract in refereed journal
    American Chemical society: Abstracts of scientific papers 238(2009), 58-NUCL
    ISSN: 978-0-8412-0005-0

Permalink: https://www.hzdr.de/publications/Publ-12516
Publ.-Id: 12516


THEREDA – A thermodynamic reference database for nuclear waste disposal in Germany

Gester, S.; Altmaier, M.; Brendler, V.; Hagemann, S.; Herbert, H.-J.; Marquardt, C.; Moog, H. C.; Neck, V.; Richter, A.; Scharge, T.; Voigt, W.; Wilhelm, S.; Willms, T.; Wollmann, G.

THEREDA provides consistent thermodynamic datasets to assist the long-term safety assessment of nuclear waste repositories. It meets specific German requirements (high salinities and temperatures). THEREDA is build on a relational SQL-database. The application of referential integrity, thermodynamic dependencies, alternative datasets and uncertainty estimates allows to deliver tailor-made parameter files for use in geochemical modelling software like EQ3/6, GWB and ChemApp covering law-of-mass-action and Gibbs-energy-minimization codes.

Keywords: THEREDA; database; nuclear waste disposal; long-term safety; thermodynamic data; high saline systems; Pitzer; SIT; alternative datasets; referential integrity; uncertainty estimates; geochemical modelling; EQ3/6; GWB; ChemApp

  • Lecture (Conference)
    SIAM Conference on Mathematical & Computational Issues in the Geosciences (GS 09), 15.-18.06.2009, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12515
Publ.-Id: 12515


The role of colloids in uranium transport: Facilitating and impeding effects

Zänker, H.; Brendler, V.

Tetravalent uranium is generally regarded as sparingly soluble and hence immobile in the aquatic environment. The solubility product of UO2·xH2O was determined by laser-induced breakdown detection (LIBD). For the given reaction, UO2·xH2O + 4 H+ = U4+ + (2+x) H2O, a value of log Ksp0 = -54.30 ± 1.0 was found (cf. [1]). It results in U(IV) solubilities of about 10-8 M in the near-neutral pH region. On the other hand, hexavalent uranium is much more soluble, in particular if carbonate is present in a water. Calculations with the EQ3/6 geochemical speciation software (thermodynamic data from the NEA data base) were performed for a typical oxic groundwater in equilibrium with air CO2 and varying pH. They yielded uranium solubilities of as much as 10-5 M in the near-neutral pH region. Normally, uranium is regarded as mobile under typical groundwater conditions in geochemistry.
However, this apparently clear picture can be counteracted if colloids come into the play. By our laboratory experiments (cf. [2]) the formation of intrinsic U(IV) colloids in the presence of silicate was demonstrated. The possibility that U(IV) forms colloids can not be ruled out also in the aquatic environment. In the colloidal form U(IV) is “undissolved” in the thermodynamic sense of the word but nevertheless mobile. Second, the high mobility of U(VI) in groundwaters or mine waters can be significantly reduced by scavenging and co-precipitation of U(VI) due to the formation of pseudocolloids with unstable (coagulating) ferrihydrite colloids. Laboratory mine flooding simulation experiments were carried out and it was found that more than 98 % of the U(VI) present was scavenged by such colloids ([3, 4]). It follows that both transport-facilitating effects of colloids on “immobile” contaminants such as U(IV) and transport-impeding effects on “mobile” contaminants such as U(VI) may play a part. It is the geochemical ambiance that decides which effect prevails. A comparison of geochemical cases (uranium mine / nuclear waste depository, oxidizing/reducing, acidic/near-neutral) is given.

[1] Opel K., Weiß S., Hübener S., Zänker H., Bernhard G., Radiochim. Acta 95 (2007) 143-149.
[2] Zänker, H., Opel, K., Weiß, S., Hübener, S., Bernhard, G., 2nd Annual Workshop of the IP FUNMIG, 21.-23.11.2006, Stockholm.
[3] Zänker, H., Richter, W., Hüttig, G., Coll. Surf. A: Physicochem. Eng. Aspects 217 (2003) 21-31.
[4] Ulrich, K.-U., Rossberg, A., Foerstendorf, H., Zänker, H., Scheinost, A., Geochim. Cosmochim. Acta 70 (2006) 5469-5487.

Keywords: uranium(IV); uranium(VI); intrinsic colloids; pseudocolloids

  • Poster
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, USA

Permalink: https://www.hzdr.de/publications/Publ-12514
Publ.-Id: 12514


Sorption of uranium(VI) on clay in absence and presence of humic acid

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

In Germany, the investigated host rocks for nuclear waste disposal in deep geological formations are salt, crystalline rock and argillaceous rock. Natural clay contains organic matter, such as humic acid (HA), which has an influence on the sorption of metal ions. In this work, we studied the uranium(VI) sorption onto the reference clay mineral kaolinite and the natural opalinus clay in absence and presence of HA. The results are compared with our previous studies focused on kaolinite [1].
The influence of the background electrolyte on uranium(VI) sorption onto kaolinite was investigated. The NaClO4 electrolyte previously used [1] was compared with synthetic opalinus clay pore water (I = 0.42 M, pH 7.6) [2]. The experiments show that a lower amount of uranium(VI) is adsorbed onto the clay when the opalinus clay pore water is used. This behavior can be explained with the uranium(VI) speciation. At pH 7.6, the speciation in opalinus clay pore water is dominated by the neutral aquatic Ca2UO2(CO3)3 complex, which has a lower sorption affinity towards kaolinite than the charged UO2(CO3)34-, (UO2)2CO3(OH)3- and UO2(CO3)22- species formed in the NaClO4 system (I = 0.42 M) at pH 7.6.
In the presence of HA (10 mg/L, 50 mg/L), in opalinus clay pore water a lower percental amount of uranium(VI) is adsorbed onto kaolinite. But the concentration of HA has no influence on the amount of sorbed uranium(VI). The reason is that HA has no influence on the uranium(VI) speciation in opalinus clay pore water at pH 7.6, thus, no uranium(VI) humate complexes are formed. The decrease of sorbed uranium(VI) in presence of HA is only due to the competition for surface binding sites between uranium(VI) and HA. These results are in contrast to the results obtained in the NaClO4 system (I = 0.1 M) [1]. There, the speciation of uranium(VI) in NaClO4 changes because aqueous uranium(VI) humate complexes are formed. Due to this and due to a competition for surface binding sites, the percental amount of sorbed uranium(VI) decreases. This effect is increased with increasing HA concentration.
Furhermore, the uranium(VI) sorption onto kaolinite and opalinus clay in opalinus clay pore water was compared. Results show a stronger sorption of uranium(VI) onto kaolinite (2.8 ± 0.2 µg/m2) than onto opalinus clay (0.049 ± 0.002 µg/m2). Since opalinus clay has a higher specific surface area than kaolinite (opalinus clay: Asp = 42 m2/g; kaolinite: Asp = 11.7 m2/g [1]), and contains a higher amount of iron-containing minerals (opalinus clay: 5 wt.% Fe; kaolinite: 0.27 wt.% Fe [1]), which are able to sorb uranium(VI) very well [3], this result is unexpected. To clarify this observation, leaching experiments with opalinus clay applying the two background electrolytes are performed in order to determine the release of ions into the solution in dependence on time and pH and to investigate their influence on the uranium(VI) sorption. We studied the pH dependence of the uranium(VI) sorption onto opalinus clay in absence and presence of HA, and compared this with previous results obtained for kaolinite [1].

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

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

  • Contribution to proceedings
    12th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA
  • Poster
    12th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere, 20.-25.09.2009, Kennewick, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-12513
Publ.-Id: 12513


Ion Bombardment induced self-organization of nanopattern studied by 3D lattice kinetic MC simulation

Numazawa, S.; Heinig, K.-H.

The surface damage (sputtered atoms, adatoms, surface vacancies) produced by ion impact is determined by random displacement of the atom at impact point. Using the statistics of this damage for multiple ion impacts in 3D kinetic lattice Monte Carlo simulations, the self-organization of nano-scale surface pattern by the competition between damage creation and damage diffusion/annealing is studied. Especially, anisotropic displacement of surface atoms creates ripple formation even sputtering is suppressed. The ripple wavelength follows a power low of fluence and temperature of substrate. Local temperature enhancement of impact points refers also Frenkel-pair and ripples on f.c.c.(110) surface. The direction of ripples depends on the temperature of migration atoms which is corresponding to the experimental result of Ag(110) ion bombardment.

  • Poster
    The CCP5 Molecular Simulation Summer School 2008, 07.-15.7.2008, Sheffield, UK
  • Poster
    16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Germany
  • Poster
    IUMRS-ICA 2008, 09.-13.12.2008, Nagoya, Japan

Permalink: https://www.hzdr.de/publications/Publ-12512
Publ.-Id: 12512


Sorption of U(VI) onto TiO2. A vibrational spectroscopic analysis of the sorption processes

Foerstendorf, H.; Müller, K.; Meusel, T.; Brendler, V.; Comarmond, J.; Payne, T.; Lefèvre, G.

A detailed knowledge of the sorption processes of uranium(VI) onto titanium(IV) dioxide (TiO2) can serve as a model for the elucidation of molecular processes on more complex mineral surfaces. Because of the high stability, low solubility over a wide pH range and the well-known structure of TiO2, sorption studies with U(VI) can be carried out throughout a large range of experimental parameters [1-3].

In this work, we used attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy in an in situ investigation of the sorption processes of U(VI) onto TiO2. A set of highly purified and well characterized TiO2 phases from different origins differing in the ratio of the most stable polymorphs, i.e. anatase and rutile, in specific surface area and in particle size distribution was investigated. Irrespective of the composition of the mineral phase, it was shown that U(VI) mainly forms a similar inner sphere complex, showing an absorption maximum shifted of about 20 cm−1 to lower wavenumbers compared to the aqueous species.

The influence of the aqueous speciation on the sorption process was studied using different concentrations of the actinide ions and at different pH values. The high sensitivity of the in situ ATR FT-IR technique allows the study of U(VI) concentrations down to the lower micromolar range. From these results, it is concluded that only one significant surface U(VI) complex forms in the pH range between 4 and 7, and across a range of aqueous uranyl concentrations. The surface speciation of uranyl therefore involves fewer species than the aqueous speciation in these experimental systems, as is consistent with the findings of a previous study [4].

Furthermore, the capability of a fast scanning of IR spectra makes it feasible to carry out time-resolved experiments of the sorption processes with a time resolution in the sub-minute time range. It is shown that in the early steps of the U(VI) sorption a transient species is formed on the mineral phase showing a clearly red-shifted absorption maximum. After prolonged sorption the IR spectra indicate the formation of a stable surface species which is commonly found on TiO2 phases. These findings give new insights into the surface complex formation of U(VI) on titanium dioxide at a molecular level.

[1] Den Auwer, C., Drot, R., Simoni, E., Conradson, S. D., Gailhanou, M. and de Leon, J. M. (2003) "Grazing incidence XAFS spectroscopy of uranyl sorbed onto TiO2 rutile surfaces." New J. Chem. 27, 648-655.
[2] Wazne, M., Meng, X. G., Korfiatis, G. P. and Christodoulatos, C. (2006) "Carbonate effects on hexavalent uranium removal from water by nanocrystalline titanium dioxide." J. Hazard. Mater. 136, 47-52.
[3] Vandenborre, J., Drot, R. and Simoni, E. (2007) "Interaction mechanisms between uranium(VI) and rutile titanium dioxide: From single crystal to powder." Inorg. Chem. 46, 1291-1296.
[4] Lefèvre, G., Kneppers, J. and Fédoroff, M. (2008) "Sorption of uranyl ions on titanium oxide studied by ATR-IR spectroscopy." J. Colloid Interface Sci. 327, 15-20.

  • Poster
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, U.S.A.

Permalink: https://www.hzdr.de/publications/Publ-12511
Publ.-Id: 12511


J-self-adjointness, Krein spaces and related physics

Günther, U.

As brief introduction, a few basic aspects of the theory of J-self-adjoint operators and matrices are sketched as well as their natural relation to Krein spaces --- Hilbert spaces with indefinite metric structures. The mathematical facts are then illustrated by some recent results from PT quantum mechanics:
  • the highly nontrivial spectral behavior of a quantum mechanical Hamiltonian with x2(ix)ν potential in the sector of spontaneously broken PT-symmetry, the form invariant resolution of the spectral singularity in the limit ν → -1 and a hidden UV-IR duality
  • the unfolding of higher-order branch-points (exceptional points) in PT-symmetric Bose-Hubbard models and the relevance of the underlying Hessenberg type of perturbation matrices
  • the Naimark dilation of the PT-symmetric quantum brachistochrone solution with the unexpected physical result of inducing ultra-fast (wormhole-like) evolution regimes via fine-tuned entanglement
The talk concludes with briefly indicating further applications and possible future developments.

Keywords: J-self-adjoint operators; Krein space; PT quantum mechanics; spontaneously broken symmetry; UV-IR duality; Bose-Hubbard model; Bose-Einstein condensate; exceptional point; branch point; brachistochrone; entangled states; ultra-fast evolution; wormhole-like behavior

  • Invited lecture (Conferences)
    Editorial Board Meeting; Journal of Physics A: Mathematical and Theoretical, 23.-24.04.2009, London, UK

Permalink: https://www.hzdr.de/publications/Publ-12510
Publ.-Id: 12510


Radiation-induced defect centers: Luminescence and optical absorption study of helium-irradiated diamond and zircon

Nasdala, L.; Grambole, D.; Wildner, M.; Zaitsev, A. M.; Götze, J.; Kempe, U.; Hanchar, J. M.; Harris, J. W.

The impact of radioactivity can generate optically active defect centers in minerals. These defects may first affect light absorption, i.e., they may cause radio-coloration or -de-coloration. Second, radio-induced defects may enhance or suppress luminescence emissions of their host minerals. The action of such centers is, for instance, seen in spotted diamond specimens showing green or brown radio-coloration (the latter is typically associated with yellowish-green photoluminescence). Another example is the yellow broad-band luminescence emission of zircon, which is commonly observed in cathodo- and photoluminescence spectra of this mineral. So study whether, and how, natural alpha radiation generates and affects such centers, flat polished diamond and zircon samples were irradiated in a tandem accelerator facility with 8.8 MeV He2+ ions, which are the analog of alpha particles generated in the 212Po α-decay (Th decay chain).
Helium ions were found to penetrate 29 μm into diamond and 32 μm into zircon, respectively, which corresponds very well to ranges predicted by Monte Carlo simulations using the SRIM code. Notable pale green coloration of diamond was observed to start at 1014 to 1015 He/cm². Spots irradiated with 1017 He/cm² appeared dark green and were found to show initial amorphization. Green colors transformed to orange-brown through heat-treatment at about 550 °C, which is mainly due to the disappearance of the ∼16,000 cm-1 GR1 band. The latter process was found to be associated with the appearance of intense green UV-induced photoluminescence. Associated observations include strong volume expansion due to the accumulated radiation-damage, which may result in notable up-doming of radiohaloes. First studies of He-implanted zircon indicated a similar luminescence behavior, with an irradiation-induced broad-band yellow emission at 575 nm. This emission band decreases in intensity in samples that were affected by natural radiation damage prior to the He irradiation experiment.
The observed depth profiles of the luminescence emission intensity in the two minerals correspond to the calculated defect distribution profiles but not to the ionization distribution profiles. This suggests that ionization alone is insufficient to create optically active centers. Additional carbon- (diamond) and oxygen-irradiation experiments (zircon) were done to generate similar structural damage with an elemental species which is already present in the respective host mineral. Observations on these samples are largely similar to those on He-irradiated samples. Consequently, optically active centers are related to structural point defects that are created by atomic knock-ons whereas our observations did not yield independent evidence which suggests that He ions themselves might be optically active species.

  • Lecture (Conference)
    AGU Joint Assembly 2009 - The Meeting of the Americas, 24.-27.05.2009, Toronto, Canada

Permalink: https://www.hzdr.de/publications/Publ-12509
Publ.-Id: 12509


DYN3D - Advanced Reactor Simulations in 3D

Rohde, U.; Grundmann, U.; Kliem, S.

DYN3D is a three-dimensional core model for dynamic and depletion calculations in light water reactor cores with quadratic or hexagonal fuel assembly geometry. The neutron kinetic model is based on the solution of the three dimensional two-group neutron diffusion equation by nodal expansion methods. The thermal hydraulic model of the reactor core and the fuel rod model are implemented in the module FLOCAL, which is a part of DYN3D.
The paper gaves an overview on the application possibilities of DYN3D.

  • Nuclear Energy Review 2(2007), 28-30
    ISSN: 1753-3910

Permalink: https://www.hzdr.de/publications/Publ-12508
Publ.-Id: 12508


Phi decay: A relevant source for K- production at energies available at the GSI Schwerionen-Synchrotron (SIS)?

Agakishiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Bielcik, J.; Blanco, A.; Bortolotti, A.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Chernenko, S.; Christ, T.; Coniglione, R.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Duran, I.; Dybczak, A.; Eberl, T.; Fabietti, L.; Fateev, O.; Ferreira-Marques, R.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krasa, A.; Krizek, F.; Krücken, R.; Kühn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lapidus, K.; Lopes, L.; Lorenz, M.; Maier, L.; Maiolino, C.; Mangiarotti, A.; Marin, J.; Markert, J.; Metag, V.; Michalska, B.; Michel, D.; Moriniere, E.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Perez Cavalcanti, T.; Piatelli, P.; Pietraszko, J.; Pospisil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Sapienza, P.; Schmah, A.; Schröder, C.; Schwab, E.; Simon, R.; Smolyankin, V.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.

We present phase space distributions and multiplicities of K+, K- and phi mesons produced in Ar+KCl reactions at a kinetic beam energy of 1.756 AGeV and measured with the HADES spectrometer. The inverse slope parameters and yields of kaons supplement the systematics of previous measurements. The percentage of K- mesons coming fromphi decay is found to be 18+- 7%.

  • Physical Review C 80(2009)2, 025209

Permalink: https://www.hzdr.de/publications/Publ-12507
Publ.-Id: 12507


The High-Acceptance Dielectron Spectrometer HADES

Agakishiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Bielcik, J.; Blanco, A.; Bortolotti, A.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Chernenko, S.; Christ, T.; Coniglione, R.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Duran, I.; Dybczak, A.; Eberl, T.; Fabietti, L.; Fateev, O.; Ferreira-Marques, R.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krasa, A.; Krizek, F.; Krücken, R.; Kühn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lapidus, K.; Lopes, L.; Lorenz, M.; Maier, L.; Maiolino, C.; Mangiarotti, A.; Marin, J.; Markert, J.; Metag, V.; Michalska, B.; Michel, D.; Moriniere, E.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Perez Cavalcanti, T.; Piatelli, P.; Pietraszko, J.; Pospisil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Sapienza, P.; Schmah, A.; Schröder, C.; Schwab, E.; Simon, R.; Smolyankin, V.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.

HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion induced collisions. Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and dense hadronic matter. The detector system is characterized by an 85% azimuthal coverage over a polar angle interval from 18 to 85 degree, a single electron efficiency of 50% and a vector meson mass resolution of 2.5%. Identification of pions, kaons and protons is achieved combining time-of-flight and energy loss measurements over a large momentum range. This paper describes the main features and the performance of the detector system.

Permalink: https://www.hzdr.de/publications/Publ-12506
Publ.-Id: 12506


Measurement of charged pions in 12C + 12C collisions at 1A GeV and 2A GeV with HADES

Agakishiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Bielcik, J.; Blanco, A.; Bortolotti, A.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Chernenko, S.; Christ, T.; Coniglione, R.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Duran, I.; Dybczak, A.; Eberl, T.; Fabietti, L.; Fateev, O.; Ferreira-Marques, R.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krasa, A.; Krizek, F.; Krücken, R.; Kühn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lapidus, K.; Lopes, L.; Lorenz, M.; Maier, L.; Maiolino, C.; Mangiarotti, A.; Marin, J.; Markert, J.; Metag, V.; Michalska, B.; Michel, D.; Moriniere, E.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Perez Cavalcanti, T.; Piatelli, P.; Pietraszko, J.; Pospisil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Sapienza, P.; Schmah, A.; Schröder, C.; Schwab, E.; Simon, R.; Smolyankin, V.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.

We present the results of a study of charged pion production in 12C + 12C collisions at incident beam energies of 1A GeV and 2A GeV using the HADES spectrometer at GSI. The main emphasis of the HADES program is on the dielectron signal from the early phase of the collision. Here, however, we discuss the data with respect to the emission of charged hadrons, specifically the production of pi+- mesons, which are related to neutral pions representing a dominant contribution to the dielectron yield. We have performed the first large-angular range measurement of the distribution of pi+- mesons for the 12C + 12C collision system covering a fairly large rapidity interval. The pion yields, transverse-mass and angular distributions are compared with calculations done within a transport model, as well as with existing data from other experiments. The anisotropy of pion production is systematically analyzed.

  • European Physical Journal A 40(2009), 45-59

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Permalink: https://www.hzdr.de/publications/Publ-12504
Publ.-Id: 12504


Study of the role of sulfur functionalities in humic acids for uranium(VI) complexation

Sachs, S.; Reich, T.; Bernhard, G.

Humic substances influence the speciation and migration behavior of toxic and radiotoxic metal ions, such as actinides, in the environment. Depending on their origin, humic substances contain different amounts of sulfur ranging from 0.1 to 3.6% and 0.5 to 1.43% in soil and aquatic humic substances, respectively [1]. Reduced, intermediately oxidized and highly oxidized sulfur functionalities occur in humic substances [1]. Although sulfur functionalities occur in small concentrations, they can play an important role in the complexation of selected metal ions. Knowledge about the impact of sulfur functionalities on the metal ion complexation by humic substances and their significance compared to oxygen- and nitrogen-containing functional groups helps to improve complexation models for humic substances. Consequently, this contributes to a more reliable geochemical modeling of the interaction processes between humic matter and metal ions in the environment.
In the present work sulfur-containing humic acid (HA) model substances have been synthesized to study the influence of sulfur functionalities on the metal ion complexation by HA. HA type M1-S with different sulfur contents was synthesized from xylose, phenylalanine, glycine, and cysteine and the resulting products were characterized. The identity of the sulfur species was determined by X-ray photoelectron spectroscopy (XPS). XPS results of HA M1-S with 1.94 wt-% sulfur indicate the occurrence of at least two different sulfur species. About 82% of sulfur occurs in form of reduced sulfur species (e.g., thiols, dialkylsulfide and/or disulfides) and about 18% of sulfur is attributed to sulfoxides.
The uranium(VI) complexation of HA with different sulfur contents (0, 1.94 and 3.94 wt-%) has been studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS) and TRLFS with ultrafast pulses. Applying the metal ion charge neutralization model [2] comparable complexation constants with a mean value of logβ0.1M = 6.3 ± 0.1 were determined by TRLFS. However, with increasing sulfur content of the HA an increase in the uranium(VI) loading capacities from 26 ± 4 to 37 ± 2% (pH 3.8) was observed. This indicates that with increasing amounts of sulfur functionalities more sites become available for the complexation of uranium(VI) by HA.

Keywords: Humic substances; humic acids; complexation; functional groups; sulfur; uranium(VI); XPS; TRLFS; fs-TRLFS

  • Contribution to proceedings
    12th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA
  • Lecture (Conference)
    12th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-12503
Publ.-Id: 12503


Complexation of low-valent actinides (uranium(IV), plutonium(III)) by organic model ligands and humic acid in aqueous solution

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

Risk assessments predicting the transport of actinides under environmentally relevant conditions require basic knowledge of their solubility, their interaction with complexing ligands, their sorption and redox behavior as well as their ability to form colloids. Under reducing conditions as prevalent in deep underground nuclear waste repositories and in the depth of flooded uranium mines, actinide species occur in lower oxidation states. Both the speciation and the mobility of actinides in aquatic systems strongly depend on their oxidation state. For instance, in contrast to the soluble and mobile uranium(VI), uranium(IV) is much less mobile due to the low solubility of uranium(IV) hydrous oxide (UO2•xH2O(am)). However, in the presence of inorganic and organic ligands also uranium(IV) may become mobile due to formation of soluble complexes. Also the mobility of plutonium depends strongly on the existing oxidation states and the chemical species formed. Thus, the speciation of low-valent actinides in aqueous solution has to be studied to predict their migration behavior in natural environments.
Data for the complexation of uranium(IV) and plutonium(III) with inorganic and organic ligands are scarce or vary strongly. In the present study, the complexation behavior of the model ligands citric acid, succinic acid, mandelic acid and glycolic acid is studied and compared to that of humic acid. These model ligands stand for a variety of organic ligands in aqueous systems. The actinide complexation by model ligands and humic acid is studied applying UV-vis absorption spectroscopy and ultrafiltration, respectively.
The stability constants for 1:1 and 1:2 uranium(IV) citrate complexes of the type MpHqLr were determined with log ß101 = 13.5 ± 0.2 and log ß102 = 25.1 ± 0.2 [1]. This shows a strong interaction between uranium(IV) and the ligand. The uranium(IV) complexation with mandelic and glycolic acid is weaker. Stability constants for 1:1 and 1:2 uranium(IV) ligand complexes of the type MpHqLr were determined with log ß101 = 4.53 ± 0.09 and log ß102 = 8.02 ± 0.13 for mandelate and with log ß101 = 4.71 ± 0.08 and log ß102 = 8.25 ± 0.15 for glycolate (I = 1.0 M). Speciation calculations show that due to complexation with organic ligands the solubility and thus, the mobility of uranium(IV) in aquatic systems is increased.
Also plutonium(III) is strongly complexed by organic ligands and humic acid under environmentally relevant conditions which shows the need for speciation studies of plutonium in aqueous solutions containing various complexing agents.

[1] Schmeide, K., Bernhard, G.: Spectroscopic Study of the Uranium(IV) Complexation by Organic Model Ligands in Aqueous Solution. In: Uranium, Mining and Hydrogeology (Merkel, B.J.; Hasche-Berger, A. eds.), Springer Verlag, Berlin, 591-598 (2008).

Keywords: uranium; tetravalent; citric acid; succinic acid; mandelic acid; glycolic acid; plutonium; humic acid; stability constants; speciation

  • Contribution to proceedings
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA
  • Poster
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-12502
Publ.-Id: 12502


Terahertz two-photon quantum well infrared photodetector

Schneider, H.; Liu, H. C.; Winnerl, S.; Song, C. Y.; Walther, M.; Helm, M.

A two-photon detector based on intersubband transitions in GaAs/AlGaAs quantum wells operating in the Terahertz regime below the Reststrahlenband is reported. Resonantly enhanced optical nonlinearities enables sensitive quadratic detection at pJ pulse energies. We demonstrate its use in a quadratic autocorrelator for far-infrared picosecond pulses at around 7 THz.

Keywords: Quantum well infrared photodetector; two-photon intersubband transition; GaAs/AlGaAs quantum well; quadratic autocorrelation

Permalink: https://www.hzdr.de/publications/Publ-12501
Publ.-Id: 12501


UV-vis spectroscopy of Eu(III) and Am(III) complexation with small organic acids at low concentrations and variable temperatures

Müller, M.; Acker, M.; Barkleit, A.; Taut, S.; Bernhard, G.

The long-term safety analysis of nuclear waste disposals in clay formations requires detailed knowledge of the interaction of actinides at relevant temperatures (up to 100 °C). It is well known that the migration behaviour of the actinides is strongly influenced by natural organic matter (NOM) from the clay. However, the current thermodynamic database is lacking fundamental data about the temperature-dependent complexation of americium (and its analogue europium) with small organic acids, which are structural similar components of natural organic matter in the clay.

We present our results for the complexation of both Am(III) and Eu(III) with 2-hydroxybenzoic acid (salicylic acid), 1,2,4,5-benzentetracarboxylic acid (pyromellitic acid) and 2,3-dihydroxbutanedioic acid (L-tartaric acid) in the temperature range from 20 to 50°C, at ionic strength of 0.1 mol/l NaClO4 and pH below 6.

For the first time, temperature-dependent UV-Vis spectroscopic measurements with a Liquid Waveguide Capillary Cell were used for complexation investigations. Due to the long optical path length of the capillary cell (up to 2 m) very low americium and europium concentrations can be measured. Thus, the presented absorption measurements were carried out at Am(III) concentrations below 5e-7 mol/l and Eu(III) concentration below 5e-4 mol/l. For all investigated model ligands we observed a slight shift of the absorption maxima of Eu(III) (394 nm) and Am(III) (504 nm) spectra of 0.5 to 2 nm to higher wavelengths due to the complexation.
We first validated the method with europium: at 25°C the determined constants for the 1:1 complexes of europium salicylate, europium pyromellitate and europium L tartrate with logß111=15.4+/-0.06, logß112 = 14.3 +/-0.2, logß111=7.9+/-0.3 respectively, are in good agreement with the literature values [1], [2].
For the americium salicylate system, both a 1:1 complex and a 1:2 complex were observed at pH 4. The stability constants of these complexes are logß111= 15.42+/-0.06 and logß122=30.98+/-0.05 and comparable to the reported ones for the analogous complexes with europium [1]. With increasing temperature, the stability constants for both complex systems increase, indicating an endothermic complexation reaction. The same behaviour is expected for the americium pyromellitate system, where just a 1:1 complex with log ß112=15.03+/-0.1 can be reported until now.

The temperature dependence and the interaction of americium with L-tartrate is presently under investigation. The stability constants and thermodynamic parameters (enthalpy, entropy, Gibbs energy) of all above investigated systems are reported.

[1] Aoyagi, N. et al. Radiochemica Acta, Vol. 92, 2004, 589-593
[2] R. Kulshrestha, S. Sengar, M. Singh, Indian J. of Chemistry 26A, 1987, 940-943

  • Poster
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-12500
Publ.-Id: 12500


Optimized Detector Configurations for Particle Therapy Positron Emission Tomography

Fiedler, F.; Braess, H.; Kunath, D.; Laube, K.; Parodi, K.; Priegnitz, M.; Shakirin, G.; Enghardt, W.

no abstract available

Keywords: PT PET; ion therapy

  • Lecture (Conference)
    Heavy Ions in Therapy and Space Symposium 2009, 06.-10.07.2009, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12499
Publ.-Id: 12499


Atomistic simulation of ion-erosion-induced surface patterning

Numazawa, S.; Posselt, M.; Heinig, K.-H.

Kinetic 3D lattice Monte-Carlo simulation of ion beam induced surface modification was performed for f.c.c. (100) surface and preliminary Crystal-TCAS calculations of 5keV As+ on Si(001) have been simulated. By KMC, the observed surface patterning was depending on the incidence angle even the direction of ion-induced surface atom displacement is arbitrary next lattice position. Angular dependency of the sputtering yield by the Crystal-TCAS calculation has been studied.

Keywords: TRIM; Kinetic Monte-Carlo; nanopatterninig

  • Lecture (others)
    Seminar of DFG project FOR845, 06.-07.05.08, Münster, Germany

Permalink: https://www.hzdr.de/publications/Publ-12498
Publ.-Id: 12498


Polyhedral Surface Approximation of Non-Convex Voxel Sets and Improvements to the Convex Hull Computing Method

Schulz, H.

In this paper we introduce an algorithm for the creation of polyhedral approximations for objects represented as strongly connected sets of voxels in three-dimensional binary images. The algorithm generates the convex hull of a given object and modifies the hull afterwards by recursive repetitions of generating convex hulls of subsets of the given voxel set or subsets of the background voxels. The result of this method is a polyhedron which separates object voxels from background voxels. The objects processed by this algorithm and also the background voxel components inside the convex hull of the objects are restricted to have genus 0. The second aim of this paper is to present some improvements to our convex hull algorithm to reduce computation time.

Keywords: digital geometry; surface approximation; abstract cell complex; polyhedron; voxel

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZD-514 2009
    ISSN: 1437-322X

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Publ.-Id: 12497


Photoeffects on U(VI) sorption onto TiO2 studied by in situ ATR FT-IR spectroscopy.

Müller, K.; Meusel, T.; Steudtner, R.; Foerstendorf, H.; Brendler, V.; Bernhard, G.

Uranium(VI), is known to be the most stable oxidation state of uranium in oxygenated waters, with the uranyl ion UO22+ forming soluble hydroxo and carbonate complexes [1, 2]. Thermodynamic unstable U(IV) complexes might be formed in oxygenated waters by photoreduction of U(VI) supplied by solar radiation. Although U(VI) photoinduced reduction is reported to occur in acidic solutions, it is prevented at neutral conditions because of structural arrangements resulting from hydrolysis reactions. However, sorbed U(VI) species at the water-mineral interface on particles with semiconducting properties, e.g. TiO2 have shown different redox behavior than solution species [3-5].

TiO2 is the material mostly applied for the investigation of photocatalysis, due to its exceptional optical and electronic properties, chemical stability and low cost. Anatase was found photocatalytically more active than rutile [6]. The mixed sample of 80% antase and 20% rutile Degussa P-25 was investigated for U(VI) photoreduction using laser fluorescence spectroscopy [3, 4]. ATR FT-IR spectroscopy, which was applied to photoreactions of oxalic acid, has not been applied for U(VI), yet.

We investigated the effects of UV-visible light on the sorption processes of U(VI) onto TiO2 by application of in situ ATR FT-IR spectroscopy. Thus, changes of the excitation wavelength and the TiO2 phase, namely anatase, rutile, and a mixture of both (P-25), were considered. Furthermore, the results were compared to photoeffects observed for U(VI) sorption onto ZnO.

From the obtained spectra different photoinduced effects on U(VI) sorption onto different TiO2 phases are derived. Photocatalysis is clearly suggested for the P-25 sample. In contrast, pure anatase and rutile did not show spectral differences for the sorption mechanisms under dark and light conditions. Furthermore, the photoreaction was found to be limited to incident light with wavelengths below 580 nm. The comparison between TiO2 and ZnO evidence a higher photoactivity for TiO2.

1.Guillaumont, R.; Fanghänel, T.; Fuger, J.; Grenthe, I.; Neck, V.; Palmer, D. A.; Rand, M. H., Update on the Chemical Thermodynamics of U, Np, Pu, Am and Tc. Elsevier: Amsterdam, 2003.
2.Müller, K.; Brendler, V.; Foerstendorf, H., Inorganic Chemistry 2008, 47, (21), 10127-10134.
3.Eliet, V.; Bidoglio, G., Environmental Science & Technology 1998, 32, (20), 3155-3161.
4.Selli, E.; Eliet, V.; Spini, M. R.; Bidoglio, G., Environmental Science & Technology 2000, 34, (17), 3742-3748.
5.Amadelli, R.; Maldotti, A.; Sostero, S.; Carassiti, V., Journal of the Chemical Society-Faraday Transactions 1991, 87, (19), 3267-3273.
6.Litter, M. I., Applied Catalysis B-Environmental 1999, 23, (2-3), 89-114.

  • Poster
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA
  • Contribution to proceedings
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 169-170

Permalink: https://www.hzdr.de/publications/Publ-12496
Publ.-Id: 12496


Sorption of Np(V) onto metal oxide surfaces: An in situ ATR FT-IR spectroscopic study.

Müller, K.; Foerstendorf, H.; Brendler, V.; Bernhard, G.

Neptunium (Np) is one of the most important components of nuclear waste to consider for the long-term safety assessment of nuclear waste repositories and hence, great attention is paid to its geochemistry and migration behavior [1]. Among the various geochemical processes, the migration of actinides in the environment is strongly affected by molecular reactions at the solid-water interface, e.g. sorption onto mineral phases, surface precipitation, and colloid formation [2]. In aqueous solution the pentavalent form dominates the neptunium speciation under a wide range of environmental conditions [1]. Thus, reliable results of Np(V) sorption data and its molecular speciation at the water-mineral interface are crucial to allow an improved modeling of Np migration in the environment. Vibrational spectroscopy is a useful tool for the in situ identification of molecular species in aqueous solution and sorbed onto mineral surfaces [3, 4]. Using attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy, the type of the sorbed species, e.g. inner- and outer-sphere complex, can be elucidated by shifts of the antisymmetric stretching vibration ν3 of the Np=O bond compared to the aqueous species.

In this study, we investigated the Np(V) speciation in aqueous solution and upon sorption onto oxides of titanium, silicon, and zinc at a micromolar concentration level by application of NIR and ATR FT-IR spectroscopy.

The obtained spectra of aqueous 50 µM Np(V) solution confirmed the predominance of the fully hydrated neptunyl(V) species NpO2+ up to pH 7.7 at inert gas atmosphere, excluding atmospheric CO2, as was predicted by the updated NEA thermodynamic database [5]. Upon sorption of 50 µM Np(V) on TiO2 at pH 7.6 at inert gas atmosphere, NpO2+ forms stable surface species. The formation of an inner-sphere complex can be derived from the significant shift of the band representing the antisymmetric stretching vibration ν3 of the NpO2+ ion. Furthermore, since the spectra of the sorption processes show no significant deviations within the pH range from 4 to 7.6, and no indications of aqueous NpO2+ species are obtained, the formation of outer-sphere complexes can be neglected. Additionally, from the on-line monitored measurements it is obvious that only one Np(V) surface species is formed during the sorption experiments.

A comparative in situ ATR FT-IR investigation of Np(V) sorption onto TiO2, SiO2 and ZnO indicates the formation of structurally similar inner-sphere surface complexation. From minor spectral deviations of the ν3 band representing the Np(V) surface species bidentate complexes can be suggested.

For future spectroscopic investigations of neptunyl sorption at the water-mineral interface the present work may provide vibrational reference data for the interpretation of more complex systems relevant for environment.

1.Kaszuba, J. P.; Runde, W. H., Environmental Science & Technology 1999, 33, (24), 4427-4433.
2.O'Day, P. A., Reviews of Geophysics 1999, 37, (2), 249-274.
3.Lefevre, G., Advances in Colloid and Interface Science 2004, 107, (2-3), 109-123.
4.Müller, K.; Brendler, V.; Foerstendorf, H., Inorganic Chemistry 2008, 47, (21), 10127-10134.
5.Guillaumont, R.; Fanghänel, T.; Fuger, J.; Grenthe, I.; Neck, V.; Palmer, D. A.; Rand, M. H., Update on the Chemical Thermodynamics of U, Np, Pu, Am and Tc. Elsevier: Amsterdam, 2003.

  • Contribution to proceedings
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 170-171
  • Poster
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-12495
Publ.-Id: 12495


Time resolved fluorescence spectroscopy of Eu(III) complexes with benzoic acid derivatives at different temperatures

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

Humic acids have a great influence on the migration of actinides and heavy metals. To get a quantitative understanding of the humic acid / actinide interaction on a molecular level, we investigate the complexation behavior of trivalent lanthanides and actinides with different functionalized benzoic acids as model compounds for humic acids. Our primary objective is to determine the temperature dependence of the complexation behavior, because in radioactive waste repositories one can observe elevated temperatures and concerning this matter only few investigations are known.

In this study, we present the reaction of Eu(III) with 2-hydroxybenzoate (salicylate), 2,5-dihydroxybenzoate and 1,2,4,5-benzenetetracarboxylate (pyromellitate), investigated with time-resolved laser-induced fluorescence spectroscopy (TRLFS) at different temperatures (10-50°C).

The Eu pyromellitate complex system shows strong luminescence behavior. The intensity of the 5D0 7F2 transition band increases with increasing ligand concentration. With increasing temperature, the total emission intensity decreases slightly. At lower pH (around 3) a MHL complex species with a stability constant of logK = 3.92 (25°C) could be determined. The lifetime of about 125 µs indicates, according to the equation of Kimura et al. (n(H2O) = 1.07 x (1/t -0.62) [1]), the exclusion of 1 water molecule from the first shell, implying an inner sphere complex with monodentate coordination. At pH around 5, a ML complex species (logK = 4.74, 25°C) was identified. The lifetime of about 135 µs stands for the substitution of 2 water molecules, according to an inner sphere complex with bidentate coordination. The lifetimes remain constant over the determined temperature range, as well as the lifetime of the free Eu3+(aq) ion. With increasing temperature, the stability constants increase, indicating an endothermic complexation reaction. The thermodynamic parameters of the Eu pyromellitate complexes were calculated to be ΔH = 9.4 kJ mol-1, ΔG = 22.3 kJ mol-1, ΔS = 106 J mol-1 K-1 (MHL; 25 °C) and ΔH = 15.2 kJ mol-1, ΔG = 28.1 kJ mol-1, ΔS = 145 J mol-1 K-1 (ML; 25 °C); these values are in good agreement with the literature [2]. The Eu complexes with salicylate and 2,5-dihydroxybenzoate show no luminescence behavior; only static and dynamic quenching is observable. For both ligands, the complex stability constants for a 1 : 1 complex species each could be determined. With increasing temperature, the stability constant also increases in both cases, indicating again an endothermic complexation reaction. The stability constants and thermodynamic parameters of these complexes are reported and compared with those determined by UV-vis spectroscopy with a liquid waveguide capillary cell (LWCC).

[1] T. Kimura, G.R. Choppin, Y. Kato, Z. Yoshida, Radiochim. Acta 72 (1996) 61-64.
[2] G.R. Choppin, E.N. Rizkalla, T.A. El-Ansi, A. Dadgar, J. Coord. Chem. 31 (1994) 297-304.

  • Poster
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-12494
Publ.-Id: 12494


Interaction of uranium(VI) and europium(III) with alpha-amylase

Barkleit, A.; Jähnigen, P.; Hennig, C.; Rossberg, A.

The calcium-binding protein α-amylase (α-1,4 glucan-4-glucanhydrolase) catalyzes the degradation of starch and glycogen. It is widely distributed in plants, animals, and microorganisms. In saliva and pancreas it is a main enzyme which is built in high amounts. Incorporated heavy metals like actinides firstly come into contact with saliva. In order to explore the origin of the well known toxic effect of these metals we investigate the interaction between UO22+ and Eu3+ (as an inactive analogue for threefold actinides) with the main constituents of saliva like α-amylase.

The influence of UO22+ and Eu3+ on the enzyme activity was tested with the α-amylase assay method by Bernfeld [1]. Both metal ions have a strong inhibition effect even at very low metal to α-amylase ratios. Sorption experiments showed a high binding capacity of α-amylase and that in the sorption maximum (pH 6-7) the protein can bind up to a tenfold molar excess of the metal ions. Both metal ions displace the Ca2+ ion, which is the central metal ion in the protein, even at equimolar amounts. UO22+ and Eu3+ seem to occupy first the Ca2+ binding place and then other potential metal binding sites in the protein. The binding process occurs in a short time, so that after 5 minutes the main metal amount is accumulated by α-amylase.

The UO22+ and Eu3+ α-amylase complexes were investigated using time-resolved laser-induced fluorescence spectroscopy (TRLFS) and extended x-ray absorption fine structure (EXAFS) spectroscopy. In case of UO22+ and TRLFS, we observed in the pH range 3-7 a red shift of the peak maxima and two different luminescence lifetimes, indicating the formation of two different UO22+ protein complex types. With EXAFS spectroscopy two different binding types were identified. At equimolar metal to ligand ratio we identified a fourfold coordination of UO22+ with only monodentate binding carbonyl groups. With excess of UO22+ the binding properties changes and higher coordination numbers are observed with indication of monodentate and bidentate binding carbonyl and carboxylate groups. For the Eu3+ α-amylase complex, the luminescence lifetimes show that 2 or 3 water molecules remain in the first coordination sphere. EXAFS measurements points at the presence of monodentate and bidentate coordinated carbonyl or carboxylate groups.

[1] P. Bernfeld, Methods in Enzymology 1(1955) S. 149-158

  • Poster
    12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere 2009, 20.-25.09.2009, Kennewick, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-12493
Publ.-Id: 12493


EXAFS study of the structural phase transition in the americium zirconate pyrochlore

Martin, P. M.; Belin, R. C.; Valenza, P. J.; Scheinost, A. C.

The 241Am2Zr2O7 phase undergoes a structural transition from pyrochlore to defect fluorite driven by alpha self-irradiation. In an effort to better understand the underlying phenomena of this order-disorder transition, powder X-ray diffraction (PXRD) and X-ray absorption fine-structure (XAFS) spectroscopy experiments were conducted on two samples aged for 40 days (0.02 dpa) and 370 days (0.21 dpa), respectively. While the XAFS data support the phase transition observed by XRD, they reveal different local coordinations of americium and zirconium. The transition occurs through oxygen Frenkel and cation antisite formation. The XAFS, clearly showed that the ZrO polyhedron is stable against irradiation, probably a main factor explaining the excellent resistance to amorphization observed for americium zirconia defect fluorite structures.

Keywords: Rietveld; XRD; EXAFS; americium; zirconia; transmutation; nuclear waste

  • Journal of Nuclear Materials 385(2009), 126-130

Permalink: https://www.hzdr.de/publications/Publ-12492
Publ.-Id: 12492


Implementation of a pressure drop model for the CFD simulation of clogged containment sump strainers

Grahn, A.; Krepper, E.; Weiß, F.-P.; Alt, S.; Kästner, W.; Kratzsch, A.; Hampel, R.

The present study aims at modelling the pressure drop of flows across growing cakes of compressible, fibrous materials which may form on the upstream side of containment sump strainers after a loss-of-coolant accident (LOCA). The model developed is based on the coupled solution of a differential equation for the change of the pressure drop in terms of superficial liquid velocity and local porosity of the fibre cake and a material equation that accounts for the compaction pressure dependent cake porosity. Details of its implementation into a general-purpose three-dimensional computational fluid dynamics code (CFD) are given. An extension to this basic model is presented, which simulates the time dependent clogging of the fibre cake due to capturing of suspended particles as they pass trough the cake. The extended model relies on empirical relations which model the change of pressure drop and removal efficiency in terms of particle deposit in the fibre cake.

Keywords: CFD; pressure drop; strainer clogging; LOCA; containment sump

  • Contribution to proceedings
    17th International Conference On Nuclear Engineering ICONE 17, 12.-16.07.2009, Brussels, Belgium
    Implementation of a pressure drop model for the CFD simulation of clogged containment sump strainers
  • Lecture (Conference)
    17th International Conference On Nuclear Engineering ICONE 17, 12.-16.07.2009, Brussels, Belgium
  • Journal of Engineering for Gas Turbines and Power - Transactions of the ASME 132(2010), 082902
    DOI: 10.1115/1.4000365
    Cited 7 times in Scopus

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Permalink: https://www.hzdr.de/publications/Publ-12491
Publ.-Id: 12491


P0713 - Anordnung zur Röntgen-Computertomographie mit elektromagnetisch abgelenktem Elektronenstrahl

Bieberle, M.; Hampel, U.; Schleicher, E.

Aufgabe der vorliegenden Erfindung ist es, eine Anordnung zur Röntgen-Computertomographie anzugeben, die ohne einen axialen Versatz zwischen Brennfleckbahn und Röntgendetektorbogen auskommt und dennoch einen im Sinne der tomographischen Bildrekonstruktion vollständigen Projektionsdatensatz liefert. Gelöst wurde die Aufgabe durch die Kombination zweier Target-Detektor-Einheiten, die mit einem geringen axialen Versatz in zwei Ebenen angeordnet sind.
Der hauptsächliche Vorteil der beschriebenen Anordnung zur Röntgen-Computertomographie mit zwei Tomographieebenen besteht darin, dass Target- und Röntgendetektorbogen jeder Einheit vollständig innerhalb einer axialen Ebene angeordnet werden können und durch die Kombination beider Datensätze eine vollständige tomographische Datenaufnahme von einer axialen Ebene des Untersuchungsobjektes möglich ist. Damit wird eine höchstmögliche Bildqualität und axiale Ortsauflösung erreicht. Die Anordnung kann insbesondere für Elektronenstrahltomographen oder andere Computertomographie-Scanner mit feststehendem Quell-Detektorverbund angewendet werden. Besonders vorteilhaft ist sie für sich axial bewegende Objekte, zum Beispiel Rohrströmungen, da dort die Bewegung zwischen den Ebenen dem Untersuchungsobjekt inhärent ist und somit ohne zusätzlichen Aufwand sehr schnelle Prozesse mit hoher lateraler und axialer Ortsauflösung sowie hoher zeitlicher Auflösung abgebildet werden können.

  • Patent
    DE 10 2007 040 778 A1 - 2009.03.05

Permalink: https://www.hzdr.de/publications/Publ-12490
Publ.-Id: 12490


The Potential of In-beam Positron Emission Tomography within Image-Guided Radiation Therapy

Kunath, D.

Presentation about in-beam PET in the context of IGRT

  • Lecture (Conference)
    4th International Conference on Translational Research and Pre-Clinical Strategies in Radiation Oncology, 11.-13.03.2009, Genf, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-12489
Publ.-Id: 12489


Xenobiotics tolerant bacteria in soils near a Pb-Zn smelter in Bulgaria as estimated via the 16S rRNA gene approach

Satchanska, G.; Golovinski, E.; Selenska-Pobell, S.

Microbial diversity in xenobiotics polluted soils was investigated by the 16S rRNA gene approach. The samples studied were collected from the vicinity of a Pb-Zn (KCM) smelter and pesticides manufacturing plant situated in South Bulgaria. ICP-MS analyses showed that some metals such as Zn, Pb, Cu, Cd, As, Ni and Hg exceeded in high extent the maximum permission standard. Two 16S rRNA gene clone banks were constructed – KCM-B and KCM-C. The main part of the studied microbial communities consisted of members of Proteobacteria (and ) - 42 % for KCM-B and 72 % for the KCM-C sample. In both soils Proteobacteria were registered in equal content of 28 %. Acidobacteria, Holophaga, Cytophaga/Flavo-bacterium/Bacteroides, AD1 and other novel divisions were represented as well.
Most of the identified bacterial groups were closely related to bacteria inhabiting other extreme environments such as uranium mill-tailings, sulphide mines, mine drainages and dumps, metal-rich sediments, soils contaminated with polychlorinated hydrocarbons, deserts, and Antarctic permafrost. Some of the closest relatives of several identified groups were xenobiotics-degrading bacteria inhabiting a hexane-degrading biofilm, 1,2-dichloropropan transforming bacteria and phosphorous eliminating bacteria.

  • Contribution to proceedings
    Ecology Seminar of the "Ecological Engineering and Environmental protection", 23.-24.04.2009, Sofia, Bulgaria

Permalink: https://www.hzdr.de/publications/Publ-12488
Publ.-Id: 12488


Deposition of functional coatings on polyethylene terephthalate films by magnetronplasma-enhanced chemical vapour deposition

Fahland, M.; Vogt, T.; Meyer, B.; Fahlteich, J.; Schiller, N.; Vinnichenko, M.; Munnik, F.

Magnetron-plasma enhanced chemical vapour deposition (PECVD) is a process tool which allows the deposition of plasma polymer coatings at process pressures below 1 Pa. The striking features of this technology are the relatively easy realisation of large area deposition as well as the possibility of the combination with sputtering processes for multilayer coating designs. SiOxCy coatings were deposited on polymer film in a roll-to-roll deposition machine. Dynamic deposition rates as high as 120 nm*m/min were achieved. The process was set up with both the monomer hexamethyldisiloxane and the monomer tetraethylorthosilicate (TEOS) and with mixtures thereof. The coatings were analysed by Fourier transform infrared spectroscopy. This method identifies the existence of different types of Si–O bonding in the layer. The results show how the layer properties are linked to the plasma parameters of the deposition process. The properties were compared to sputtered SiO2 and to layers obtained by other PECVD processes. Elastic recoil detection analysis (ERDA) was used in order to determine the composition of the samples. Both IR spectroscopy and ERDA revealed that the usage of TEOS provided more SiO2-like layers. The process was applied to the deposition of optical multilayer coating in a roll-to-roll coating system.

Keywords: Sputtering; Web coating; Plasma-enhanced chemical vapour deposition; Magnetron

Permalink: https://www.hzdr.de/publications/Publ-12487
Publ.-Id: 12487


Study of photo-proton reactions driven by bremsstrahlung radiation of high-intensity laser generated electrons

Spohr, K. M.; Shaw, M.; Galster, W.; Ledingham, K. W. D.; Robson, L.; Yang, J. M.; Mc Kenna, P.; Mc Canny, T.; Melone, J.; Amthor, K.-U.; Ewald, F.; Liesfeld, B.; Schwoerer, H.; Sauerbrey, R.

Photo-nuclear reactions were investigated using a high power table-top laser. The laser system at the University of Jena (I ~ 3-5×1019 W cm-2) produced hard bremsstrahlung photons (kT~2.9 MeV) via a laser-gas interaction which served to induce (γ, p) and (γ, n) reactions in Mg, Ti, Zn and Mo isotopes. Several (γ, p) decay channels were identified using nuclear activation analysis to determine their integral reaction yields. As the laser-generated bremsstrahlung spectra stretches over the energy regime dominated by the giant dipole resonance (GDR), these yield measurements were used in conjunction with theoretical estimates of the resonance energies Eres and their widths Γres to derive the integral reaction cross-section σint(γ,p) for 25Mn, 48, 49Ti, 68Zn and 97, 98Mo isotopes for the first time. This study enabled the determination of the previously unknown cross-section ratios for these isotopes. The experiments were supported by extensive model calculations (Empire) and the results were compared to the Thomas-Reiche-Kuhn (TRK) dipole sum rule as well as to the experimental data in neighboring isotopes and good agreement was observed. The Coulomb barrier and the neutron excess strongly influence the ratios for increasing target proton and neutron numbers.

Permalink: https://www.hzdr.de/publications/Publ-12486
Publ.-Id: 12486


Electric events synchronized with laser filaments in thunderclouds

Kasparian, J.; Ackermann, R.; André, Y.; Méchain, G.; Méjean, G.; Prade, B.; Rohwetter, P.; Salmon, E.; Stelmaszczyk, K.; Yu, J.; Mysyrowicz, A.; Sauerbrey, R.; Woeste, L.; Wolf, J.

We investigated the possibility to trigger real-scale lightning using ionized filaments generated by ultrashort laser pulses in the atmosphere. Under conditions of high electric field during two thunderstorms, we observed a statistically significant number of electric events synchronized with the laser pulses, at the location of the filaments. This observation suggests that corona discharges may have been triggered by filaments.

  • Optics Express 16(2008)8, 5757-5763
    ISSN: 1094-4087

Permalink: https://www.hzdr.de/publications/Publ-12485
Publ.-Id: 12485


Void measurement using high-resolution gamma-ray computed tomography

Bieberle, A.; Hoppe, D.; Schleicher, E.; Hampel, U.

We present a high-resolution gamma-ray computed tomography (CT) system for the measurement of cross-sectional time-averaged void distributions in thermo hydraulic facilities. The system has been carefully designed for harsh operating conditions, such as varying temperature fields and strong magnetic fields, typically produced by thermal hydraulic test loops with direct electric bundle heating. Measurements are non invasive, thus the two-phase flow in the test section is not influenced. The gamma-ray CT system consists of a collimated 137Cs isotopic source, a gamma radiation detector arc including 320 single elements, a pulse processing unit and a thermal stabilisation unit. The spatial resolution of the CT system is about 2 mm in plane. Recently, the thermal design of the detector arc is improved to secure maintenance of constant temperature of thermally sensitive components under changing environmental conditions. This turned out to be a key issue for achieving accurate quantitative measurements. First results of laboratory measurements on a bundle mock-up with this improved system are presented.

Keywords: Gamma-ray computed tomography

Permalink: https://www.hzdr.de/publications/Publ-12484
Publ.-Id: 12484


Ultra-fast evolution via PT-symmetry and entanglement: extending the BBJM brachistochrone

Günther, U.; Samsonov, B.

The basics of quantum mechanical brachistochrones are briefly sketched for Hermitian systems as well as for PT-symmetric systems --- as the latter have been recently proposed by Bender, Brody, Jones and Meister (BBJM) in [C. M. Bender et al, Phys. Rev. Lett. 98, 040403 (2007)]. Using a mainly geometric approach, the hidden new features of this PT-symmetric brachsistochrone with its close relation to non-diagonalizable operator realizations with non-trivial Jordan block structures and spectral singularities (spectral exceptional points) are discussed. Furthermore the Naimark dilation technique as basic tool for an extension toward possible experimental implementations is explained. The remarkable links to wormhole-type setups and entangled states (Einstein's 'spooky action') are highlighted and sketched geometrically. The talk is mainly based on [Phys. Rev. Lett. 101, 230404 (2008)].

Keywords: quantum brachistochrone; quantum computing; PT quantum mechanics; strongly non-Hermitian regime; exceptional point; Anandan-Aharonov lower bound; ultra-fast evolution; POVM; Naimark dilation; Naimark extension; entangled state; two-qubit system; wormhole; Einstein's spooky action

  • Invited lecture (Conferences)
    Quantum Mechanics in the Complex Domain (QMCD09), 27.-28.03.2009, St. Louis, USA

Permalink: https://www.hzdr.de/publications/Publ-12483
Publ.-Id: 12483


Be-10 and Cl-36 interlaboratory comparisons: Implications for terrestrial production rates?

Merchel, S.; Bremser, W.; Alfimov, V.; Arnold, M.; Aumaître, G.; Benedetti, L.; Bourlès, D. L.; Braucher, R.; Caffee, M.; Christl, M.; Fifield, L. K.; Finkel, R. C.; Freeman, S. P. H. T.; Ruiz-Gómez, A.; Kubik, P. W.; Rood, D. H.; Sasa, K.; Steier, P.; Tims, S. G.; Wallner, A.; Wilcken, K. M.; Xu, S.

Driven by the progress in accelerator mass spectrometry (AMS) and its spreading application within geosciences, the number of samples with low isotopic ratios will increase. Therefore, we have examined the linearity of 10Be/9Be as a function of isotope ratio by distributing three secondary standards (dilutions of NIST4325: 10-12-10-14) to nine AMS labs. The problem of low ratio samples is even more crucial for 36Cl. Thus, we have prepared large quantities of three 36Cl/Cl solutions from a certified 36Cl activity (NIST4943) by dilution with NaCl. AgCl precipitated from these solutions (10-11-10-13) has been distributed to nine AMS labs. We are still awaiting some final results, but first results from eight labs for each nuclide show that these interlaboratory exercises are very valuable, as they show maximum differences between individual AMS labs up to 35% for 10Be, and 25% for 36Cl, respectively.
Our data indicate that actual 36Cl measurements at LLNL, PRIME Lab and ANU can differ by more than 10%. The implications of this for 36Cl in-situ production rates, determined earlier at these facilities, cannot be ignored. Some, although not all, of the current disagreement concerning 36Cl production rates may result from these discrepancies. However, we are assuming that our new data at the 10-12-10-13 level are still representative for earlier measurements of in-situ samples at that level.
This work was partially funded by CRONUS-EU (Marie-Curie Action, 6th FP #511927).

Keywords: accelerator mass spectrometry

  • Abstract in refereed journal
    Geochimica et Cosmochimica Acta 73(2009)13, A871
    DOI: 10.1016/j.gca.2009.05.011
    ISSN: 0016-7037
  • Poster
    19th V.M. Goldschmidt™ conference, 21.-26.06.2009, Davos, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-12482
Publ.-Id: 12482


X-ray Spectromicroscopy of Carbon Nanotubes

Sedlmair, J.; Gleber, S.-C.; Zänker, H.; Thieme, J.

The analysis of pristine and functionalized carbon nanotubes by X-ray spectromicroscopy was demonstrated. It was shown that both the generation of COOH groups due to functionalization and the reaction of these groups with hexavalent uranium (surface complexation) influenses the NEXAFS spectra. The method may become a promising tool for "mapping" chemical properties such as the presence or absence of chemical elements or the type of binding between these elements on the surface of carbon nanotubes.

Keywords: Carbon nanotubes; X-ray spectromicroscopy; carboxylic groups; uranium; sorption

  • Poster
    Wasser 2009 - Jahrestagung der Wasserchemischen Gesellschaft, 18.-20.05.2009, Stralsund, Deutschland
  • Contribution to proceedings
    Wasser 2009 - Jahrestagung der Wasserchemischen Gesellschaft, 18.-20.05.2009, Stralsund, Deutschland
    Wasser2009, ISBN 978-3-936028-56-0, 345-346

Permalink: https://www.hzdr.de/publications/Publ-12481
Publ.-Id: 12481


Influence of specimen type, crack length and evaluation method on quasi-static and dynamic fracture toughness properties

Zurbuchen, C.

For up-to-date safety analyses and lifetime assessments of nuclear power plants (NPPs) fracture mechanical based methods are indispensable. When two Swiss NPPs were planned in the 1970s, no standards existed concerning the geometry or testing of pre-cracked Charpy-V-size surveillance specimens. Therefore, the guideline HSK-AN-425 was drafted for fracture toughness evaluation by dynamic testing. Before becoming a Swiss standard it is to be thoroughly checked for potential pitfalls. Furthermore, it has to be verified that surveillance specimens of those NPPs with shorter cracks than recommended in present standards are eligible for fracture mechanics assessment.

Experiments were performed on unirradiated commercial NPP steel 22NiMoCr3-7.
Quasi-static Master Curve (MC) reference temperature T0 were evaluated according to ASTM E1921 on Charpy-size (width B=0.4T, 1T=1 inch=25.4mm) single edge bend (SE(B)) specimens with crack lengths of 3 mm and 5 mm as well as 1T-C(T) specimens. Furthermore, transferability of surveillance specimen results to heavy-walled structures was checked with SE(B) specimens of B=0.4T, 0.8T, 1.6T and 3.2T. Dynamic MC results were retrieved from instrumented impact tests performed at 1.2 to 2.4 m/s in which T0 was calculated according to HSK-AN-425 and also by a modified ASTM 1921 method. Quasi-static J resistance curves were obtained according to standards ASTM E1820, ISO12135 and ESIS-P2.

In quasi-static MC tests it could be demonstrated that SE(B) specimens with 3 mm and 5 mm fatigue cracks yield the same T0 of ca. -80°C. Thus, surveillance 0.4T-SE(B) specimens with 3 mm crack length may be used for safety assessment without further modifications. The transferability of small-scale results to structural behaviour was proven. T0 obtained from 1T-C(T) specimens is 15K above T0 from 0.4T-SE(B) specimens.

The dynamic MC T0 (v=2.4m/s) is nearly equal for 0.4T-SE(B) specimens of both crack lengths but is ca. 80K above the quasi-static T0.

Small surveillance specimens do not yield valid quasi-static J resistance curve crack initiation values as requirements based on size unnecessarily invalidate all of the results. The idea of using a size criterion to limit J values should be re-evaluated. Ductile crack initiation values are highly dependent on the evaluation standard used. Ordered from highest to lowest, JIc(E1820) > J0.2BL(ISO 12135) > J0.2(ESIS-P2) > Ji(stretch zone width, ISO 12135). Ji is said to be a physically sound crack initiation value but numerous problems arise in stretch zone width determination. It is often not traceable throughout the whole crack front, affected by subjectivity and intricate for irradiated material.

Keywords: fracture mechanics; Master Curve; JR curve; constraint; E1921; E1820; ISO12135; HSK-AN-425

  • Lecture (Conference)
    2009 ASME Pressure Vessels and Piping Division Conference, 26.-30.07.2009, Prag, Czech Republic
  • Contribution to proceedings
    2009 ASME Pressure Vessels and Piping Division Conference, 26.-30.07.2009, Prag, Czech Republic
    2009 Proceedings of the ASME Pressure Vessels and Piping, West Conshohocken: ASME, 9780791838549

Permalink: https://www.hzdr.de/publications/Publ-12480
Publ.-Id: 12480


Infrared solid state spectroscopy using a free-electron laser

Helm, M.

I will introduce the free electron laser at the Forschungszentrum Dresden-Rossendorf, which covers a wavelength range between 3 and 200 micrometers with picosecond pulses. Then I will discuss a few experiments which focus on temporal and spatial resolution, respectively. The former refers to pump-probe experiments on semiconductor quantum structures and the latter to near-field spectro-microscopy on ferroelectrics.

Keywords: free electron alser; semiconductor quantum structures; pump-probe; near-field; infrared

  • Lecture (others)
    Seminarvortrag bei ANKA, 02.03.2009, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12479
Publ.-Id: 12479


Enhanced blue-violet emission by inverse energy transfer to the Ge-related oxygen deficiency centers via Er3+ ions in metal-oxide semiconductor structures

Kanjilal, A.; Rebohle, L.; Voelskow, M.; Skorupa, W.; Helm, M.

It is generally believed that the 1.5 um Er luminescence is enhanced by transferring energy from Si nanocrystals to the nearest Er3+ ions in Er-doped Si-rich SiO2 layers during optical pumping. Here, the influence of Ge nanocrystals instead of excess Si in the same environment is studied using electroluminescence technique on metal-oxide-semiconductor structures. An increase of the 400 nm electroluminescence intensity with a concomitant reduction of the Er-related emission is observed. This is explained in the light of an inverse energy transfer process from Er3+ to the Ge-related oxygen-deficiency centers.

Keywords: EL; Er; Ge; Nanocrystals; MOS

Permalink: https://www.hzdr.de/publications/Publ-12478
Publ.-Id: 12478


Buckling Stabilization and Stress Reduction in SiC on Si by i-FLASiC Processing

Andreadou, A.; Pezoldt, J.; Förster, C.; Polychroniadis, E. K.; Voelskow, M.; Skorupa, W.

One of the main challenging tasks in the prospective technology is the buckling suppression of the 3C-SiC film due to the melting and solidification process and the stress relief as a consequence of the short time Si melting during the Flash Lamp Annealing. To overcome this effect and to stabilize a flat surface morphology an alternative i-FlASiC process was developed. This work refers to the influence of the layer stack modifications by doping and meltstop formation by ion implantation on the wafer buckling. The samples were studied by transmission electron microscopy, high resolution x-ray diffraction and infrared ellipsometry. The aim was to optimize the doping and flash lamp annealing conditions in relation to the i-FLASiC layer stack modification.

Keywords: Characterization; 3C-SiC; Flash Lamp Annealing; Buckling

  • Materials Science Forum 600-603(2009), 239-242

Permalink: https://www.hzdr.de/publications/Publ-12477
Publ.-Id: 12477


Redox stability of neptunium(V) and neptunium(IV) in the presence of humic substances of varying functionality

Schmeide, K.; Bernhard, G.

The reducing properties of humic substances (humic acid (HA) and fulvic acid (FA)) of varying functionality towards Np(V) have been studied under anaerobic conditions between pH 3.5 and pH 9.0 in batch experiments. For Np redox speciation in solution solvent extraction, NIR absorption spectroscopy and ultrafiltration were applied. The reduction rate varied with type of humic substances, solution pH, HA to Np concentration ratio, and equilibration time. In comparison to natural humic substances, synthetic HA with designed redox properties lead to a stronger reduction of Np(V) to Np(IV). The reducing capacities of humic substances towards Np(V) could be correlated to their phenolic/acidic OH group content, which includes both hydroquinone-like moieties and non-quinonoid phenols. By applying a synthetic HA with blocked phenolic/acidic OH groups, the dominance of phenolic/acidic OH groups as the redox-active moieties of humic substances was verified.
The Np(IV) formed in the course of the experiments is predominantly humic colloid-bound. Np(IV) oxo/hydroxide colloids, that might be formed in addition, are stabilized by adsorbed humic substances. The remaining Np(V) occurs as NpO2 + ion or Np(V) humate depending on pH. The ability of synthetic HA to effectively maintain Np in the tetravalent state during complexation experiments could be shown.

Keywords: Neptunium; Tetravalent; Humic acid; Reduction; Reducing capacity; Redox speciation; Redox process; Np(V); Np(IV)

Permalink: https://www.hzdr.de/publications/Publ-12476
Publ.-Id: 12476


SANS investigation of a neutron-irradiated Fe-9at%Cr alloy

Ulbricht, A.; Heintze, C.; Bergner, F.; Eckerlebe, H.

Available experimental results indicate that the addition of Cr to Fe and steels significantly influences the response of Fe-Cr alloys and ferritic/martensitic high-Cr steels to neutron irradiation. A level of 9 at% Cr is of particular interest because this composition is close to the boundary of the Fe-Cr miscibility gap. Furthermore, it corresponds to the composition of several candidate steels for application in nuclear technology. However, experimental evidence has been incomplete so far. The reported study by means of small-angle neutron scattering is devoted to the effect of neutron irradiation at 300°C up to fluences of 0.6 and 1.5 dpa on the microstructure of an Fe-9at%Cr alloy. We have observed a pronounced irradiation-induced increase of scattering cross-sections for both magnetic and nuclear scattering. Bimodal size distributions of irradiation-induced defect-solute clusters have been reconstructed. The restrictions on the composition of these clusters have been discussed in terms of the scattering contrast. We have found that vacancy clusters and alpha’-particles alone cannot explain the full set of experimental findings. The remaining inconsistency can be solved by taking into account a contribution of impurity carbon.

Keywords: SANS; Fe-Cr alloy; irradiation-induced defect-solute cluster

Permalink: https://www.hzdr.de/publications/Publ-12475
Publ.-Id: 12475


SANS investigation of irradiation-induced phase separation in a binary Fe-Cr alloy

Ulbricht, A.; Bergner, F.; Heintze, C.

Ferritic-martensitic chromium steels are candidate materials for future applications in both Gen-IV fi ssion and fusion technology. Investigations of binary Fe-Cr alloys will contribute to the understanding of the behaviour of more complex alloys. The presented SANS results are focused on a Fe-9at%Cr alloy neutron-irradiated up to neutron doses of 0.6 and 1.5 dpa. We have observed a pronounced increase of scattering cross-sections for both magnetic and nuclear scattering. The A-ratio is about 2.8 for both irradiation conditions. This value is far from a value of 1.45 corresponding to nanovoids as scattering objects. This indicates that the irradiation-induced clusters are different from pure nanovoids and must contain Cr-atoms with the same or very similar average composition for both irradiation conditions. The composition of the clusters will be discussed in more detail. The size distributions of irradiation-induced defects have been calculated. The volume fraction of clusters increases slightly with neutron dose.

Keywords: SANS; Fe-Cr alloy; irradiation-induced defect-solute cluster

  • Poster
    TMS 2009, Symposium Material Characterization: Microstructural Processes in Irradiated Materials, 15.-19.02.2009, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-12474
Publ.-Id: 12474


QCD sum rules for D and B mesons in nuclear matter

Hilger, T.; Thomas, R.; Kämpfer, B.

QCD sum rules for D and B mesons embedded in cold nuclear matter are evaluated. We quantify the mass splitting of D - D-bar and B - B-bar mesons as a function of the nuclear matter density; extrapolated to saturation density it is in the order of 60 and 130 MeV driven essentially by the condensates , and . The genuine chiral condensate , amplified by heavy-quark masses, enters the Borel transformed sum rules for the mass splitting beyond linear density dependence. Including strange quark condensates reveals a umerically smaller and opposite effect for the Ds - Ds-bar mass splitting.

  • Physical Review C 79(2009), 025202
  • Lecture (Conference)
    XLVII International Winter Meeting on Nuclear Physics, 26.-30.01.2009, Bormio, Italien
  • Lecture (Conference)
    40. Arbeitstreffen Kernphysik in Schleching, 02.-06.03.2009, Schleching, Deutschland
  • Lecture (Conference)
    DPG Spring Meeting 2009 (Hadronic and Nuclear Physics) in conjunction with the European Nuclear Physics Conference (EuNPC) (Nuclear Physics Board of the European Physical Society (EPS)), 16.-20.03.2009, Bochum, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12468
Publ.-Id: 12468


Bioaktive Oberflächen

Raff, J.

Bioaktive Oberflächen lassen sich auf ganz unterschiedliche Art und Weise herstellen. Am Institut für Radiochemie werden insbesondere S-Layer-Proteine verschiedener Naturisolate zur Beschichtung und Funktionalisierung verschiedenere Trägermaterialien genutzt. Durch die Verwendung dieser monolagigen Proteinschicht können nicht nur vielfältige Biomoleküle sehr regelmäßig, in großer Dichte und mit unterschiedlichen Funktionen auf den Trägern immobilisiert werden, sondern auch mit anorganischen Nanopartikeln, z. B. mit (foto)katalytischen Eigenschaften, kombiniert werden. Auf diese Weise können neuartige intelligente Materialien für technische Anwendungen entwickelt werden. Beispielhaft werden diesbezüglich Arbeiten zur Entwicklung von Filtermaterialien, (Foto)kalysatoren und Sensoren vorgestellt.

  • Lecture (others)
    Vortrag bei GMBU e.V., Arbeitsgruppe "Funktionelle Schichten", 04.03.2009, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12456
Publ.-Id: 12456


Methodik, Zielstellung und Möglichkeiten der PET/CT bei kongenitalem Hyperinsulinismus

Blankenstein, O.; Mohnike, K.; Barthlen, W.; Füchtner, F.

kein Abstract verfügbar

  • Lecture (Conference)
    6. Berliner PET/CT Symposium, 07.05.2008, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12455
Publ.-Id: 12455


Micro-elemental Analysis of some Transylvanian Meteorites and Lunar Samples

Vasilescu, A.; Constantinescu, B.; Bugoi, R.; Ceccato, D.; Grambole, D.; Herrmann, F.

Micro-PIXE investigations on some Transylvanian chondritic meteorite fragments and on small Moon soil pieces from the LUNA-16 mission were performed at the Legnaro and Rossendorf proton microprobes. The most exciting finding of the study was the presence of Pt grains in the Moci meteorite. The results are compared to previously published data.

Keywords: micro-PIXE; elemental analysis; meteorites; lunar soil

  • Lecture (Conference)
    ICNMTA2008 - 11th International Conference on Nuclear Microprobe Technology and Applications, 20.-25.07.2008, Debrecen, Hungary
  • Nuclear Instruments and Methods in Physics Research B 267(2009), 2233-2235
    DOI: 10.1016/j.nimb.2009.03.017
    Cited 2 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-12454
Publ.-Id: 12454


Ergebnisse der multzentrischen Gruppe im internationalen Vergleich

Mohnike, K.; Blankenstein, O.; Barthlen, W.; Füchtner, F.

kein Abstract verfügbar

  • Lecture (Conference)
    6. Berliner PET/CT Symposium, 07.05.2008, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12453
Publ.-Id: 12453


The First Octahedral Cluster Complexes With Terminal Formate Ligands: Synthesis, Structure, and Properties of K4[Re6S8(HCOO)6] and Cs4[Re6S8(HCOO)6]

Brylev, K. A.; Mironov, Y. V.; Kozlova, S. G.; Fedorov, V. E.; Kim, S.-J.; Pietzsch, H.-J.; Stephan, H.; Ito, A.; Ishizaka, S.; Kitamura, N.

The hexarhenium anionic cluster complex with terminal formate ligands [Re6S8(HCOO)6]4- was obtained by the room-temperature reaction between [Re6S8(OH)6]4- and formic acid in an aqueous solution. The cluster was crystallized as a potassium or cesium salt and characterized by X-ray single-crystal diffraction and elemental analyses, IR, 1H NMR, UV/vis, and luminescence spectroscopies. In particular, the emission quantum yield of the potassium salt of the Re6 cluster anion in the solid phase was determined for the first time. The electronic structures of [Re6S8(HCOO)6]4- and [Re6S8(OH)6]4- were also elucidated by DFT calculations.

Permalink: https://www.hzdr.de/publications/Publ-12452
Publ.-Id: 12452


Hexadentate Bispidine Derivatives as Versatile Bifunctional Chelate Agents for Copper(II) Radioisotopes

Juran, S.; Walther, M.; Stephan, H.; Bergmann, R.; Steinbach, J.; Kraus, W.; Emmerling, F.; Comba, P.

The preparation and use of bispidine derivatives (3,7-diazabicyclo[3.3.1]nonane) as chelate ligands for radioactive copper isotopes for diagnosis (64Cu) or therapy (67Cu) are reported. Starting from the hexadentate bispidine-based bis(amine)tetrakis(pyridine) ligand 1 with a keto and two ester substituents, the corresponding mono-ol 2 and two dicarboxylic acid derivatives 3 and 5 have been synthesized. A range of techniques, including single-crystal X-ray structure analysis, UV/vis spectroscopy, cyclic voltammetry, thin-layer- (TLC), and high-performance liquid chromatography (HPLC), have been used to characterize the structure and stability of the copper(II)-bispidine complexes. A rapid formation (within 1 min) of stable copper(II)-bispidine complexes under mild conditions (ambient temperature, aqueous solution) has been observed. Challenge experiments of these complexes in the presence of a high excess of competing ligands, such as glutathione, cyclam, or superoxide dismutase (SOD), as well as in rat plasma, gave no evidence of demetalation or transchelation. The bifunctional bispidine derivative 5 can be readily functionalized with biologically active molecules at the pendant carboxylate groups. The coupling of a bombesin analogue ßhomo-Glu-ßAla-ßAla-[Cha13,Nle14]BBN(7-14), by condensation of a carboxylate of the bispidine backbone with the N-terminus of the peptide produced the bifunctional ligand 6. The radiocopper(II) complex of this bombesin-bispidine conjugate has a considerable hydrophilicity (log Do/w < -2.4), and this leads to a very fast blood clearance (blood: 0.28 +/- 0.02 SUV, 1 h p.i.), low liver tissue accumulation (liver: 1.20 +/- 0.27 SUV, 1 h p.i.), and rapid renal-urinary excretion (kidneys: 6.06 +/- 2.96 SUV, 1 h p.i.) as shown by biodistribution studies of 64Cu-6 in Wistar rats. Preliminary in vivo studies of 64Cu-6 in NMRI nu/nu mice, bearing the human prostate tumor PC-3 showed an accumulation of the conjugate in the tumor (2.25 +/- 0.13 SUV, 12.5 min p.i.; 0.94 +/- 0.05 SUV, 55 min p.i.) and allowed a clear visualization of the gastrin-releasing peptide receptor distribution by positron emission tomography (PET).

Permalink: https://www.hzdr.de/publications/Publ-12451
Publ.-Id: 12451


Multiple condensed phases in attractively interacting Bose systems

Männel, M.; Morawetz, K.; Lipavsky, P.

We investigate a Bose gas with finite-range interaction using a scheme to eliminate unphysical repeated collisions in the T-matrix approximation. In this way the corrected T-matrix becomes suitable to calculate properties below the critical temperature. For attractive interaction, the Evans-Rashid transition occurs from the quasi-ideal Bose gas to the BCS-like phase with a gaped dispersion. The gap decreases with increasing density and vanishes at a critical density where the single-particle dispersion becomes linear for small momenta indicating Bose-Einstein condensation.

  • Open Access Logo New Journal of Physics 12(2010), 033013

Permalink: https://www.hzdr.de/publications/Publ-12450
Publ.-Id: 12450


Ion beam-induced hydrogen migration in a SiO2/a-Si:H/SiO2 layer stack

Pantchev, B.; Danesh, P.; Schmidt, B.; Grambole, D.; Möller, W.

The phenomenon of radiation-induced hydrogen migration has been studied in hydrogenated amorphous silicon (a-Si:H) using layer stacks of SiO2/a-Si:H/SiO2. The top and bottom SiO2 layers were deposited by magnetron sputtering at room temperature. The intermediate a-Si:H layers were deposited using plasma-enhanced chemical vapor deposition at three temperatures - room temperature, 150 ◦C and 270 ◦C. The samples were irradiated with MeV 15N+ ions during nuclear reaction analysis of hydrogen concentration. It has been established that the irradiation leads to hydrogen migration and redistribution, which depend on the a-Si:H deposition temperature. The symmetric hydrogen concentration profile in the as-prepared layer stack becomes asymmetric after the irradiation due to increase in the hydrogen concentration in the bottom SiO2 layer. Hydrogen concentration in the layer stacks decreases during the initial irradiation stage and then remains constant. In contrast, hydrogen loss from the a-Si:H layer proceeds gradually and continuously with increasing radiation fluence. It has been suggested that the hydrogen atoms liberated by the MeV ion irradiation do not recombine in molecules and that the hydrogen migration in a-Si:H is related to the diffusion of the hydrogen atoms. The radiation-induced asymmetry of the hydrogen profiles in the layer stack implies that there is a difference in the diffusion parameters at the inner and outer interface.

Keywords: hydrogenated amorphous silicon (a-Si:H); nuclear reaction analysis of hydrogen (NRA); radiation-induced hydrogen migration

Permalink: https://www.hzdr.de/publications/Publ-12449
Publ.-Id: 12449


Simulation studies for the positron source EPOS

Butterling, M.; Jungmann, M.; Krille, A.; Anwand, W.; Krause-Rehberg, R.

  • Poster
    XVth International Conference on Positron Annihilation (ICPA-15), 18.-23.01.2009, Kolkata, India

Permalink: https://www.hzdr.de/publications/Publ-12448
Publ.-Id: 12448


Hydrogen-induced defects in Pd films

Melikhova, O.; Cizek, J.; Kuriplach, J.; Prochazka, I.; Cieslar, M.; Brauer, G.; Anwand, W.

  • Poster
    XVth International Conference on Positron Annihilation (ICPA-15), 18.-23.01.2009, Kolkata, India

Permalink: https://www.hzdr.de/publications/Publ-12447
Publ.-Id: 12447


Quenched-in vacancies in Fe-Al alloys

Melikhova, O.; Cizek, J.; Kuriplach, J.; Prochazka, I.; Cieslar, M.; Brauer, G.; Anwand, W.

  • Poster
    XVth International Conference on Positron Annihilation (ICPA-15), 18.-23.01.2009, Kolkata, India

Permalink: https://www.hzdr.de/publications/Publ-12446
Publ.-Id: 12446


Defects in nanostructured Yttria-stabilized zirconia studied by positron annihilation spectroscopy

Prochazka, I.; Cizek, J.; Melikhova, O.; Kuriplach, J.; Kuzel, R.; Brauer, G.; Anwand, W.; Konstantinova, T. E.; Danilenko, I. A.

  • Lecture (Conference)
    XVth International Conference on Positron Annihilation (ICPA-15), 18.-23.01.2009, Kolkata, India

Permalink: https://www.hzdr.de/publications/Publ-12445
Publ.-Id: 12445


Positron Annihilation Spectroscopy in connection with activities towards p-type doping of ZnO

Brauer, G.

  • Lecture (Conference)
    Seminar an der University of Orissa (Institute of Physics), 16.01.2009, Bhubaneswar, India

Permalink: https://www.hzdr.de/publications/Publ-12443
Publ.-Id: 12443


Analytische HPLC synthetischer Sparteinabkömmlinge

Fähnemann, S.; Matterna, M.

kein Abstract verfügbar

  • Lecture (others)
    2. Workshop "Möglichkeiten und Grenzen der HPLC in den Lebenswissenschaften", 20.02.2009, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12442
Publ.-Id: 12442


From experiment to clinical application: particle therapy PET solution

Shakirin, G.

A knowledge transfer of particle therapy PET applications to industry is discussed

Keywords: PET; particle therpay

  • Invited lecture (Conferences)
    4th Meeting of the Scientific Advisory Board of OncoRay, 26.02.2009, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12441
Publ.-Id: 12441


Spectroscopic identification of ternary carbonate complexes upon U(VI) sorption onto ferrihydrite

Foerstendorf, H.; Heim, K.

The sorption processes of uranium(VI) onto ferrihydrite (Fh) were investigated by in situ Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR) spectroscopy. This technique provides structural information of the molecular complexes occurring during the sorption processes of actinide ions on mineral phases in aqueous solution [1].
The influence of the presence of atmospheric carbon dioxide during the sorption processes of the actinide ions was studied by sorption experiments which were carried out under inert gas conditions and in an ambient atmosphere.
The spectra demonstrate that the uranyl ion recovers in a similar molecular environment irrespective to the prevailing atmospheric conditions. However, the carbonate ions sorbed to the mineral phase in ambient atmosphere undergo significant structural changes upon the sorption of the actinide ions. While carbonate binds monodentately to the pristine Fh-surface, it forms bidendate surface complexes upon the sorption of U(VI). Moreover, the formation of ternary inner-sphere complexes can be derived from spectra recorded during the sorption processes of atmospheric carbonate onto a Fh-film which was preloaded with U(VI) under inert gas conditions. With respect to the absorption frequency of the uranyl ion sorbed onto Fh under different conditions, we suggest the formation of [Fh•••UO2•••O2CO] complexes. Surface complexes with carbonate serving as a bridging ligand between Fh and UO22+ ions were not found in our experiments. These findings are in good agreement with recent EXAFS results [2].
Furthermore, we investigated the sorption processes at acidic (5.5) and at ambient (7.8) pH values. No significant differences were observed in the spectra. However, the sorption processes obviously occur with reduced velocity at higher pH values which might be due to the dominating aqueous U(VI) species at different pH values [3].

[1] Lefèvre (2004) Adv. Colloid Interface Sci. 107, 109-123. [2] Rossberg et al. (2009) Environ. Sci. Technol. (in press). [3] Müller et al. (2008) Inorg. Chem. 47, 10127-10134.

  • Poster
    Goldschmidt™2009 - "Challenges to Our Volatile Planet", 21.-26.06.2009, Davos, Switzerland
  • Geochimica et Cosmochimica Acta 73(2009)13, A386-A386
    ISSN: 0016-7037

Permalink: https://www.hzdr.de/publications/Publ-12440
Publ.-Id: 12440


Investigation of fuel assembly design options for high conversion thorium fuel cycle in PWRs

Fridman, E.; Shwageraus, E.; Volaski, D.

This study explores the basic possibility of achieving a self-sustainable Th-U233 fuel cycle that can be adopted in the current generation of Pressurized Water Reactors. This study outlines some fuel design strategies to achieve (or to approach as closely as possible) a sustainable fuel cycle. Major design tradeoffs in the core design are discussed. Preliminary neutronic analysis performed on the fuel assembly level with BOXER computer code suggests that net breeding of U233 is feasible in principle within a typical PWR operating envelope. However, some reduction in the core power density and/or shorter than typical fuel cycle length would most likely be required in order to achieve such performance.

Keywords: thorium fuel cycle; high conversion reactor

  • Contribution to proceedings
    Advances in Nuclear Fuel Management IV, 12.-15.04.2009, Hilton Head Island, South Carolina, USA

Permalink: https://www.hzdr.de/publications/Publ-12439
Publ.-Id: 12439


Growth Aspects of Iron-Filled Carbon Nanotubes Obtained by Catalytic Chemical Vapor Deposition of Ferrocene

Müller, C.; Leonhardt, A.; Kutz, M. C.; Büchner, B.; Reuther, H.

The thermal decomposition of ferrocene combined with an Fe-catalyst nanostructuring on an oxidized Si
substrate is investigated in the temperature range of 1015-1200 K. The optimal growth conditions for aligned
and homogeneous Fe-filled carbon nanotubes are found at 1100 K. From the nanostructures the corresponding
growth rates are determined, and the activation energy of carbon diffusion is calculated to be ∼0.4-0.5
eV/atom. Further, the Fe particle size on the substrate after pretreatment in different gas atmospheres is studied
and compared with the nanotube dimensions. With these data the diffusion coefficient of carbon in the catalyst
particle amounts to 0.5-1.5 × 10-9 m2/s. Such values prove the formation of liquid catalyst particles during
the nanotube growth. Mo¨ssbauer spectroscopy was utilized to analyze and quantify the different Fe phases.
In conclusion we propose a simple base-growth model from the experimental results.

  • Journal of Physical Chemistry C 113(2009)7, 2736-2740

Permalink: https://www.hzdr.de/publications/Publ-12438
Publ.-Id: 12438


Experimental Conditions in Underground Measurements

Bemmerer, D.

I will summarize technical aspects relevant to the measurement of extremely small cross sections at accelerator facilities deep underground, with a focus on the laboratory background observed in gamma-ray detectors.

Keywords: underground nuclear astrophysics

  • Invited lecture (Conferences)
    Nuclear Astrophysics Opportunities at the Underground Laboratory in Canfranc, 19.-20.02.2009, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-12437
Publ.-Id: 12437


Study of high temperature and high density plasmoids in axially symmetrical magnetic fields

Anikeev, A. V.; Bagryansky, P. A.; Prikhodko, V. V.; Soldatkina, E. I.; Tsidulko, Y. A.; Kolesnikov, E. Y.; Lizunov, A. A.; Noack, K.; Konheiser, J.; Berger, T.

Within the framework of an Institutional Partnership of the Alexander von Humboldt Foundation, the Budker Institute of Nuclear Physics Novisibirsk (BINP) and Forschungszentrum Dresden-Rossendorf worked together in a joint project devoted to the research at the coupled GDT-SHIP facility of the BINP with the focus on the study of plasma phenomena within the SHIP mirror section. The project began at July 1st, 2005 and ended on August 30th, 2008. It included work packages of significant theoretical, computational and analyzing investigations.
The focus of this final report is on the presentation of results achieved whereas the work that was done is described briefly only. Chapter 2 illustrates the GDT-SHIP facility and describes shortly the planned topics of the SHIP plasma research. Chapter 3 explains the main extensions and modifications of the Integrated Transport Code System (ITCS) which were necessary for the calculations of the fast ion and neutral gas particle fields in SHIP, describes briefly the scheme of computations and presents significant results of pre-calculations from which conclusions were drawn regarding the experimental program of SHIP. In chapter 4, the theoretical and computational investigations of self-organizing processes in two-component plasmas of the GDT-SHIP device are explained and the results hitherto achieved are presented. In chapter 5, significant results of several experiments with moderate and with enhanced plasma parameters are presented and compared with computational results obtained with the ITCS. Preparing neutron measurements which are planned for neutron producing experiments with deuterium injection, Monte Carlo neutron transport calculations with the MCNP code were also carried out. The results are presented. Finally, from the results obtained within the joint research project important conclusions are drawn in chapter 6.

Keywords: fusion neutron source; gas dynamic trap; synthesized hot ion plasmoid

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZD-513 2009
    ISSN: 1437-322X

Downloads

Permalink: https://www.hzdr.de/publications/Publ-12436
Publ.-Id: 12436


Aktivitäten des FZD für die (Dünnschicht) Photovoltaik

von Borany, J.

Kurze Übersicht der PV-Aktivitäten im FZD.

Keywords: Photovoltaik; Ionentechniken; dünne Schichten; Magnetohydrodynamik

  • Lecture (others)
    EFDS Fachausschuss "Großflächenbeschichtung für solar- und lichttechnische Anwendungen", 10.07.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12435
Publ.-Id: 12435


In-situ study of film growth by synchrotron radiation scattering

Martins, R.M.S; Schell, N.; von Borany, J.; Bähtz, C.

The possibilities of in-situ X-ray investigations at ROBL for the study of thin films growth are summarized.

Keywords: ROBL; X-ray studies; thin films; microstructure

  • Poster
    2008 International Conference for Shape Memory and Superelatic Technologies (R&D Exhibition Event), 21.-25.09.2008, Stresa, Italy

Permalink: https://www.hzdr.de/publications/Publ-12434
Publ.-Id: 12434


Texture development and phase transformation behaviour of sputtered Ni-Ti films

Martins, R. M. S.; Schell, N.; Silva, R.; Pereira, L.; Mahesh, K. K.; Braz Fernandes, F. M.

The technological importance of thin films has led to an unabated interest in the detailed characterization of their structure, morphology, and their interfaces. A real understanding of the underlying growth mechanisms and their microstructural development requires sophisticated in situ techniques. X-ray diffraction with high-brilliance beams is such a powerful technique, as it is demonstrated here for the study of Ni-Ti films.
Numerous examples of investigations on Ni-Ti films can be found in the literature but it has been reported that the deposition of Ni-Ti films with definite stoichiometry and high purity remains a challenge, and important issues like formation of film texture and its control are still unresolved.
It is essential to identify and control their preferential orientation since it is a crucial factor in determining the shape memory behaviour. Widening the scope of our previous experiments concerning the influence of the deposition parameters on the structure of the Ni-Ti films, the incorporation of a TiN buffer layer has been tested.
Here, it is established a clear relationship between the TiN substrates and Ni-Ti texture development (B2 phase) and it is shown that the distinct crystallographic orientations of the Ni-Ti films influence their phase transformation behaviour. The influence of a substrate bias voltage on the preferential orientation of the B2 phase and transformation temperatures is as well revealed. A lower biaxial stress state and lower phase transformation temperatures have been observed for the films deposited with bias (-45 and -90V). Therefore, the control of the energy of the bombarding ions could be used as a tool for the manipulation of the transformation temperatures.

Keywords: NiTi; shape memory alloys; texture; X-ray diffraction

  • Lecture (Conference)
    2008 International Conference for Shape Memory and Superelastic Technologies, 21.-25.09.2008, Stresa, Italy
  • Journal of Materials Engineering and Performance 18(2009), 543-547
    ISSN: 1059-9495

Permalink: https://www.hzdr.de/publications/Publ-12433
Publ.-Id: 12433


Texture development and phase transformation behaviour of sputtered Shape Memory Alloy Ni-Ti films

Martins, R. M. S.; Schell, N.; Silva, R.; Pereira, L.; Mahesh, K. K.; Braz Fernandes, F. M.

Ni-Ti SMA films are attractive materials for microfabrication and integration in micro-miniature systems composed of mechanical elements, actuators, sensors and electronics made on one chip. However, there are still important issues unresolved like formation of film texture and its control as well as substrate effects. It is essential to identify and control their preferential orientation since it is a crucial factor in determining the shape memory behaviour. Widening the scope of previous experiments concerning the influence of the deposition parameters on the Ni-Ti films structure, the incorporation of a TiN intermediate layer was tested.
Here, it is established a clear relationship between the TiN substrates and Ni-Ti texture development (B2 phase) and it is shown that the distinct crystallographic orientations of the Ni-Ti films influence their phase transformation behaviour. The influence of a substrate bias voltage on the preferential orientation of the B2 phase and transformation temperatures is as well revealed.

Keywords: NiTi; shape memory alloys; texture; x-ray diffraction

  • Poster
    ESRF User Meeting 2008, 05.-07.02.2008, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-12432
Publ.-Id: 12432


Speciation and Structural Study of U(IV) and -(VI) in Perchloric and Nitric Acid Solutions

Ikeda-Ohno, A.; Hennig, C.; Tsushima, S.; Scheinost, A. C.; Bernhard, G.; Yaita, T.

In order to elucidate the uranium solution chemistry at the high HNO3 concentrations typically employed for the reprocessing of spent nuclear fuels, speciation and complex structures of UIV and UVI are studied in aqueous HNO3 solutions, as well as in HClO4 solutions, by means of UV-visible-near-infrared and X-ray absorption spectroscopies and density functional theory calculations. In 1.0 M HClO4, UIV exists as a spherical cation of U4+, which is surrounded by 9-10 water molecules in the primary coordination sphere, while it forms a colloidal hydrous oxide, UIVO2 nH2O, at a lower acidic concentration of 0.1 M HClO4. UVI exists as a transdioxo uranyl cation, UO2 2+, and forms a 5-fold pure hydrate complex of [UVIO2(H2O)5]2+ in 1.0M HClO4. With increasing HNO3concentration, the water molecules of the UIV and UVI hydrate complexes are successively replaced by planar bidentate coordinating nitrate ions (NO3 -), forming dominant species of [UIV(H2O)x(NO3)5]- in 9.0 M HNO3 and [UVIO2(NO3)3]- in 14.5 M HNO3, respectively. The present multitechnique approach also suggests the formation of two intermediate UVI species, a 5-fold mononitrato complex ([UVIO2(H2O)32-NO3)]+) and a 6-fold dinitrato complex ([UVIO2(H2O)22-NO3)2]0), involving an increase in the total coordination number on the uranyl(VI) equatorial plane from 5 to 6 with increasing HNO3 concentration. The presence of unidentate coordinate nitrato complexes or tetranitrato UVI complexes is less probable in the present HNO3 system.

Permalink: https://www.hzdr.de/publications/Publ-12431
Publ.-Id: 12431


Persistent decoupling of valence neutrons toward the dripline: Study of C-20 by gamma-spectroscopy

Elekes, Z.; Dombrádi, Z.; Aiba, T.; Aoi, N.; Baba, H.; Bemmerer, D.; Brown, B. A.; Furumoto, T.; Fülöp, Z.; Iwasa, N.; Kiss, Á.; Kobayashi, T.; Kondo, Y.; Motobayashi, T.; Nakabayashi, T.; Nannichi, T.; Sakuragi, Y.; Sakurai, H.; Sohler, D.; Takashina, M.; Takeuchi, S.; Tanaka, K.; Togano, Y.; Yamada, K.; Yamaguchi, M.; Yoneda, K.

he very neutron-rich nucleus 20C has been investigated by inelastic scattering on 208Pb and liquid hydrogen targets. Through distorted wave analysis, the reduced electric quadrupole transition probability B(E2;02)<18.4 (stat) e2 fm4 and the neutron transition probability M=292±52 (stat) fm4 have been derived. A simple shell model calculation has shown a need for a factor of about 0.4 decrease of the normal polarization charges to elucidate the results. This is interpreted as a decoupling of the valence neutrons from the nuclear core in carbon isotopes heavier than 14C.

Permalink: https://www.hzdr.de/publications/Publ-12430
Publ.-Id: 12430


The sulfate coordination of Np(IV), Np(V) and Np(VI) in aqueous solution

Hennig, C.; Ikeda-Ohno, A.; Tsushima, S.; Scheinost, A.

Coordination and redox behavior of Np(IV), Np(V) and Np(VI) sulfate in aqueous solution has been investigated by Np L3-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, cyclic voltammetry and density functional theory (DFT) calculations. The sulfate coordination mode, i.e. monodentate or bidentate, has been determined from neptunium-sulfur distances RNp-S and coordination numbers NS obtained by EXAFS. Np(VI) is coordinated by sulfate in bidentate (RNp-S = 3.12  0.02 Å) and monodentate (RNp-S = 3.61  0.02 Å) modes at a low sulfate concentration of [SO4 2-]/[NpO2 2+] = 1. At higher [SO4 2-]/[NpO2 2+] ratios bidentate coordination prevails. Approximately two bidentate sulfate groups are coordinated to Np(VI) at 2.0 M SO4 2- and pH 1.1. Np(V) is coordinated by sulfate in bidentate (RNp-S = 3.16  0.02) and monodentate (RNp-S = 3.67  0.02 Å) modes. However, sulfate coordination is less pronounced here and does not exceed in total one SO4 2- ligand in a solution of 2.0 M SO4 2-. The redox couple Np(VI)/Np(V) is reversible at low [SO4 2-]/[NpO2 2+] ratio and becomes irreversible at high sulfate concentration due to structural rearrangement of the sulfate ligands. Finally, Np(IV) also shows bidentate (RNp-S = 3.06  0.02 Å) and monodentate (RNp-S = 3.78  0.02 Å) coordination modes. The sulfate coordination increases with increasing [SO4 2-]/[Np4+] ratio. A comparison of other tetravalent actinides reveals that the monodentate sulfate coordination decreases whereas the bidentate coordination increases along the series Th(IV) - U(IV) - Np(IV). This trend was studied by DFT calculations and is discussed in terms of solvation energy and covalency of the molecular bonds.

Keywords: EXAFS; DFT; Neptunium; Sulfat

Permalink: https://www.hzdr.de/publications/Publ-12429
Publ.-Id: 12429


Electroluminescence (at 316 nm) and electrical stability of a MOS light-emitting device operated at different temperatures

Prucnal, S.; Rebohle, L.; Skorupa, W.

The influence of the operating temperature on the electrical and optical stability of the Metal-Oxide-Silicon-based light-emitting device (MOSLED) with Gd and Gd plus K implanted SiO2 layers was investigated. An increase of the temperature from room temperature up to 423 K reduces the gate voltage by about 8 V due to the Auger de-excitation mainly. It increases the rate of the EL quenching process and the degradation of the MOSLED structure by a factor of three. On the other hand, the MOSLED structure containing Gd and K atoms shows that an increase of the operating temperature leads to a threefold decrease of the decay time what was not observed in the gadolinium-implanted sample. The decrease of the operating temperature down to 70 K leads to an increase of the EL intensity and the operating time in both cases.

Keywords: electroluminescence; gadolinium; MOS device; K codoping; operation temperature dependence

Permalink: https://www.hzdr.de/publications/Publ-12428
Publ.-Id: 12428


U(VI) sorption on granite: prediction and experiments

Nebelung, C.; Brendler, V.

The sorption characteristics of U(VI) on granite was investigated in batch experiments for understanding the far-field behaviour in granitic geological nuclear repositories. The granite (from Eibenstock, Germany) was a mixture of quartz (40.9%) albite (26.7%), orthoclase (14.0%), biotite (2.0%), rubicline (0.7%), muscovite (14.7%), and hematite (1.0%) according to the ICP-MS after digestion. Except hematite and rubicline all components were found by XRD. The surface area (N2-BET) of the granite was 0.35 m2/g. The sorption conditions were ambient atmosphere, 0.1M NaClO4, sorption time 5 d for pH dependence (pH 3-11, at U(VI) 10-6 M), and U(VI) concentration dependence (10-9-10-3 M, at pH 5).

A scientifically founded description of sorption processes at the mineral-liquid surface is possible with the surface complexation models (SCM), the ion adsorption on surface sites as complexation reaction. The approach to real systems is the component additivity, the superposition of simultaneous sorption and competition reactions based on mineralogical composition. We used the diffuse double layer model (DDL) to predict the sorption with the code MINTEQA2 (Version 4.03, US EPA May 2006), thermodynamic data of aqueous and solid species from the NEA-TDB [1], and the respective protolysis data and surface complex constants for all mineralogical components of granite.

The prediction of U(VI) sorption on granite vs. pH was very good. Even the increased retention at pH 11 can be explained as precipitation of uranophane by calculation with the measured CO2 (lower than the equilibrium CO2). The modelling of the sorption on granite vs. U(VI) concentration shows a good agreement of measured and predicted values. At high concentrations the precipitation of well crystallized schoepite was predicted. Such a well crystallized mineral is unlikely after only 5 days sorption time. Excluding schoepite, the precipitation of metaschoepite was predicted for concentrations >10-4 mol/L U(VI).

[1] Guillaumont, R. et al. (2003) "Update on the chemical thermodynamics of U, Np, Pu, Am, Tc. Chemical Thermodynamics", Vol. 5 (OECD Nuclear Energy Agency, ed.), Elsevier, Amsterdam.

Acknowledgement
Funding by the BMBF and BMWA (02C1144) is gratefully acknowledged.

Keywords: sorption; sorption prediction; surface complex model; granite

  • Lecture (Conference)
    Migration '09 12th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 20.-25.09.2009, Kennewick, Washington,, USA
  • Radiochimica Acta 98(2010)9-11, 621-625

Permalink: https://www.hzdr.de/publications/Publ-12427
Publ.-Id: 12427


Validation of DYN3D pin-power calculation against experimental VVER-full-core benchmark

Hádek, J.; Mittag, S.

The EU NURESIM V1000-VALCO-STAT benchmark is focused on three-dimensional VVER-1000 steady-states with assembly-averaged and fine-mesh power distributions. Calculation results are compared with measurements from the Moscow zero-power critical facility V-1000, which was used as a full-scale mock-up of the Russian VVER-1000 reactor core. A very low moderator temperature and radial-reflector asymmetries were significant for this core. The calculations are performed with the reactor dynamic nodal code DYN3D. The usual node-averaged approach is applied in the first step. Then, an intra-nodal pin-wise power reconstruction method and its combination with the pin-powers from the lattice code HELIOS zero-net-current fuel-assembly calculations are applied. The power distributions calculated by pin-wise reconstruction show better agreement with the measurement than the node-averaged values, which is particularly obvious for fuel assemblies with inserted control clusters.

Keywords: benchmark; NURESIM; VVER; DYN3D; pin-power reconstruction

  • Lecture (Conference)
    International Conference on Mathematics, Computational Methods & Reactor Physics (M&C 2009), 03.-07.05.2009, Saratoga Springs, New York, USA
  • Contribution to proceedings
    International Conference on Mathematics, Computational Methods & Reactor Physics (M&C 2009), 03.-07.05.2009, Saratoga Springs, New York, USA
    Proceedings on CDROM: paper 200483, La Grange Park, USA: ANS

Permalink: https://www.hzdr.de/publications/Publ-12426
Publ.-Id: 12426


Hydrogen-vacancy complexes in electron-irradiated niobium

Cizek, J.; Procházka, I.; Daniš, S.; Brauer, G.; Anwand, W.; Gemma, R.; Nikitin, E.; Kirchheim, R.; Pundt, A.; Islamgaliev, R. K.

The aim of the present work was to investigate the microstructure of bulk niobium irradiated by 10 MeV electrons. Positron-annihilation spectroscopy was employed as a principal technique for the characterization of irradiation-induced defects. Experimental results were compared to first-principles theoretical calculations of positron characteristics. In addition to extended positron-annihilation studies, the specimens were characterized also by x-ray diffraction. It was found that irradiation-induced vacancies are surrounded by hydrogen. Complexes consisting of a Nb vacancy surrounded by one and two H atoms were identified in the irradiated specimens. The concentration of these vacancy-hydrogen complexes was estimated to be (18–24)x10^−5 at. %. Vacancy-2H complexes are found to represent the dominating type of defects. Hydrogen atoms surrounding a Nb vacancy cause a shortening of the lifetime of trapped positrons. Moreover, it was demonstrated that hydrogen attached to Nb vacancy can be identified by coincidence Doppler broadening technique. The effect of a thin Pd (or Cr) overlayer on the irradiation-induced defects was investigated also. It was found that the relative fraction of vacancy-2H complexes is higher in the specimens irradiated with such an overlayer.

  • Physical Review B 79(2009), 054108

Permalink: https://www.hzdr.de/publications/Publ-12425
Publ.-Id: 12425


Spezialsensorik für die Prozessindustrie - Technologietransfer aus der Sicherheitsforschung

Da Silva, M. J.; Thiele, S.; Schleicher, E.; Hauptmann, T.; Schmid, R.; Hampel, U.

Der Vortrag gibt einen Überblick über bedeutende Sensorkonzepte aus dem Bereich der Abteilung "Experimentelle Thermofluiddynamik". Die Zielgruppe des Vortrages sind potentielle Interessenten aus der Industrie, welche im Rahmen des FORMAT-Projektes kontaktiert wurden.

Keywords: sensor concepts; process industry; FORMAT

  • Lecture (others)
    Informationsveranstaltung bei CHOREN Fuel Freiberg GmbH & Co. KG, 06.02.2009, Freiberg, Deutschland
  • Lecture (others)
    Informationsveranstaltung bei EBZ GmbH, 27.01.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung für Sick Engineering GmbH, 04.02.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung bei der GlaxoSmithKline GmbH & Co. KG, 16.02.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung für die Umwelt- und Ingenieurtechnik GmbH Dresden, 17.02.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung für Roxar ASA, 23.02.2009, Bergen, Norwegen
  • Lecture (others)
    Informationsveranstaltung für Statoil Hydro, 24.02.09, Porsgrunn, Norwegen
  • Lecture (others)
    Informationsveranstaltung für die Lechler GmbH, 10.03.2009, Metzingen (Württ), Deutschland
  • Lecture (others)
    Informationsveranstaltung für die Riesaer Brennstoffzellentechnik GmbH, 18.02.2009, Riesa, Deutschland
  • Lecture (others)
    Informationsveranstaltung für LyondellBasell Industries, 11.03.2009, Ferrara, Italien
  • Lecture (others)
    Informationsveranstaltung für Bayer Technology Services GmbH, 13.03.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung für die Evonik Oxeno GmbH, 30.03.2009, Marl, Deutschland
  • Lecture (others)
    Informationsveranstaltung für das Institut für Leichtbau und Kunststofftechnik (ILK) der TU-Dresden, 26.02.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung bei Endress + Hauser - Conducta Gesellschaft für Mess- und Regeltechnik mbH u. Co.KG, 30.03.2009, Waldheim, Deutschland
  • Lecture (others)
    Informationsveranstaltung bei der Dow Olefinverbund GmbH, 31.03.2009, Schkopau, Deutschland
  • Lecture (others)
    Informationsveranstaltung für das "Institute of Nuclear Safety System" (INSS), 26.05.2009, Dresden, Deutschland
  • Lecture (others)
    Informationsveranstaltung für die Firma DuPont (USA), 18.04.2009, Tokyo, USA

Permalink: https://www.hzdr.de/publications/Publ-12424
Publ.-Id: 12424


Atomic layer deposition of MgF2 thin films using TaF5 as a novel fluorine source

Pilvi, T.; Puukilainen, E.; Kreissig, U.; Leskela, M.; Ritala, M.

Magnesium fluoride is one of the most important optical thin film materials due to the good light transparency down to the vacuum ultraviolet (UV) range. A novel atomic layer deposition (ALD) process was developed for depositing MgF2 thin films. Instead of the previously used fluorine sources, namely HF or TiF4, we used TaF5 as the fluorine precursor for the first time in ALD. The films were grown in a temperature range of 225-400 degrees C. The films were characterized by X-ray diffraction, X-ray reflection, atomic force microscopy, scanning electron microscopy, spectrophotometer, and elastic recoil detection analysis. Optical and electrical properties of the films were also studied. The films grew in columnar fashion onto silicon and all the films were polycrystalline. The film densities were close to bulk MgF2. Films with a good stoichiometry and low impurity levels were achieved. The refractive indices were between 1.36 and 1.38 at lambda = 580 nm. The permittivity of a film grown at 300 degrees C was 5.0. The transmittance of a film deposited at 350 degrees C was good even in the deep UV range. This type of novel ALD process using the new fluorine precursor TaF5 is a convenient method also for depositing other metal fluoride thin films.

Keywords: CHEMICAL-VAPOR-DEPOSITION; OPTICAL COATINGS; ASSISTED DEPOSITION; LASER INTERACTION; ALD PROCESS; PRECURSOR; MICROSCOPY; EPITAXY; SI2H6; TIF4

  • Chemistry of Materials 20(2008)15, 5023-5028
    ISSN: 0897-4756

Permalink: https://www.hzdr.de/publications/Publ-12423
Publ.-Id: 12423


Modelling of stratified two phase flows using an interfacial area density model

Höhne, T.; Vallee, C.

Stratified two-phase flow regimes can occur in chemical plants, nuclear reactors and oil pipelines. A relevant problem is the development of wavy stratified flows which can lead to slug generation. The slug flow regime is characterized by an acceleration of the gaseous phase and by the transition of fast liquid slugs, which carry a significant amount of liquid with high kinetic energy. It is potentially hazardous to the structure of the system due to the strong oscillating pressure levels formed behind the liquid slugs as well as the mechanical momentum of the slugs. Because these flow conditions cannot be predicted with the required accuracy and spatial resolution by the one-dimensional system codes, the stratified flows are increasingly modelled with computational fluid dynamics (CFD) codes. In CFD, closure models are required that must be validated. The recent improvements of the multiphase flow modelling in the ANSYS CFX code make it now possible to simulate these mechanisms in detail. In order to validate existing multiphase flow models and to further develop these, measurement data with a high-resolution in time and also in space are needed. For the experimental investigation of co-current air/water flows, the HAWAC (Horizontal Air/Water Channel) was built. The channel allows in particular the study of air/water slug flow under atmospheric pressure. Parallel to the experiments, CFD calculations were carried out. The two-fluid model was applied with a special turbulence damping procedure at the free surface. An Algebraic Interfacial Area Density (AIAD) model on the basis of the implemented mixture model was introduced, which allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface. The behaviour of slug generation and propagation at the experimental setup was qualitatively reproduced by the simulation, while local deviations require a continuation of the work. The creation of small instabilities due to pressure surge or an increase of interfacial momentum should be analysed in the future. Furthermore, experiments with pressure and velocity measurements are planned and will allow quantitative comparisons, also at other superficial velocities.

Keywords: CFD; stratified flow; slug flow; HAWAC

  • Contribution to proceedings
    Fifth International Conference on Computational and Experimental Methods in Multiphase and Complex Flow, 15.-17.06.2009, New Forest, Großbritannien
    CD-ROM
  • Lecture (Conference)
    Fifth International Conference on Computational and Experimental Methods in Multiphase and Complex Flow, 15.-17.06.2009, New Forest, Großbritannien
  • WIT Transactions on Engineering Sciences Volume 63(2009), 123-135
    ISSN: 1746-4471

Permalink: https://www.hzdr.de/publications/Publ-12422
Publ.-Id: 12422


Spectroscopic comparison of aqueous Np(VI) and U(VI) species

Müller, K.; Foerstendorf, H.; Tsushima, S.; Brendler, V.; Bernhard, G.

The distribution of aqueous species of actinide(VI) ions primarily defines their geochemical reactions and, thus, influences their migration behaviour in the environment. In aqueous solution, uranium and neptunium exist as actinyl ions AnO22+ (An = U, Np). They form different complexed species depending on their concentration level, pH range and the presence of potential ligands, such as carbonate. In recent years, the aqueous U(VI) system has been investigated intensively, in contrast to Np(VI). However, the thermodynamic data often arise from non-spectroscopic experiments mostly performed in the millimolar concentration range. [1] Up to now, a verification of the data of the different actinyl species by spectroscopic techniques providing direct molecular structural information is still incomplete. In particular, actinide solutions at lower concentrations and at neutral pH values, reasonably in an environmental context, were addressed seldom. [2]
In this study, the Np(VI) speciation at a submillimolar concentration range was investigated applying ATR FT-IR and NIR absorption spectroscopy, and computed modeling of updated NEA thermodynamic data. The findings are comparatively discussed with results obtained from U(VI) under identical conditions.
At ambient atmosphere, the formation of similar actinyl(VI) species can be derived from IR spectroscopic results at pH ≤ 4, namely the fully hydrated AnO22+ (An = U, Np) and monomeric hydrolysis products. At higher pH, the spectra evidence structurally different species contributing to the speciation of both actinides. At pH 5, the formation of (NpO2)2CO3(OH)3− probably occurs which is supported by modeling NEA data and results from NIR spectroscopy. For uranium, the presence of additional hydroxo complexes is assumed in this pH range.
1. Guillaumont, R. et al. Update on the Chemical Thermodynamics of U, Np, Pu, Am and Tc. Elsevier: Amsterdam, 2003; p 970.
2. Müller, K. et al. Inorganic Chemistry 2008, 47, (21), 10127-10134.

  • Lecture (Conference)
    Goldschmidt 2009 - "Challenges to Our Volatile Planet", 21.-26.06.2009, Davos, Schweiz
  • Geochimica et Cosmochimica Acta 73(2009)13S, A914

Permalink: https://www.hzdr.de/publications/Publ-12421
Publ.-Id: 12421


Blasenmitriss durch Impinging Jets

Schmidtke, M.; Danciu, D.

Der Gaseintrag durch impinging jets wird mittels Experimenten und CFD-Simulationen untersucht. In den Experimenten wird die Düsenhöhe über dem Waserbecken und die Wassergeschwindigkeit in der Düse variiert. Der Blasenmitriss durch den Wasserstrahl wird mittels einer Hochgeschwindigkeits-Video-Kamera beobachtet. Quantitative Daten zu Blasengrößen so wie Geometrien der Blasenfahne werden durch Bildverarbeitung aus den Videofilmen gewonnen. Zusätzlich wird die Entwicklung zweiphasiger Jets unter Wasser mittels CFD untersucht, unter Verwendung des Euler-Euler Ansatzes. Es wird ein Kriterium für die Eindringtiefe definert, und die simulierten Blasenfahnen werden mit den experimentell beobachteten hinsichtlich der Eindringtiefe verglichen.

The gas entrainment by impinging water jets is studied by the means of experiments and CFD simulations. In the experiments, the nozzle height above the water pool and the water velocity inside the nozzle is varied and the bubble entrainment below the jet is observed with a video camera. Quantitative data for bubble sizes and the geometry of the bubble plume are obtained by image processing. The development of two phase jets under water is also studied with CFD, using the Euler-Eulerian approach. Defining a criterion for an average penetration depth, the simulated plumes are compared with those observed in the experiments.

Keywords: impinging jets; bubble entrainment; gas carryunder; multiphase; penetration depth; plunging

  • Lecture (Conference)
    Jahrestreffen der Fachausschüsse Mehrphasenströmungen und Wärme- und Stoffübertragung, 03.-05.03.2009, Bad Dürkheim, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12420
Publ.-Id: 12420


Air entrainment by impinging jets. Experimental identification of the key phenomena and approaches for their modelling.

Schmidtke, M.; Danciu, D.; Lucas, D.

The gas entrainment by impinging water jets is studied by the means of experiments and CFD simulations. In the experiments, the nozzle height above the water pool and the water velocity inside the nozzle is varied and the bubble entrainment below the jet is observed with a video camera. Quantitative data for bubble sizes and the geometry of the bubble plume are obtained by image processing. The development of two phase jets under water is also studied with CFD, using the Euler-Eulerian approach. Defining a criterion for an average penetration depth, the simulated plumes are compared with those observed in the experiments

Keywords: impinging jets; plunging; gas entrainment; bubble; carryunder; plume; multiphase; CFD

  • Contribution to proceedings
    17th International Conference on Nuclear Engineering ICONE 17, 12.-16.7.2009, Brussels, Belgium
  • Lecture (Conference)
    17th International Conference on Nuclear Engineering ICONE 17, 12.-16.07.2009, Brussels, Belgium

Permalink: https://www.hzdr.de/publications/Publ-12419
Publ.-Id: 12419


Studies on oxygen concentrations in uranium contaminated biofilms: Comparing electrochemical and fiber-optic sensors

Krawczyk-Bärsch, E.

Within the framework of ReCosy first comparative investigations of electrochemical and fiber-optic sensors were performed in collaboration with the University Potsdam (UPPC). Fiber-optic sensor measurements in biofilms have some advantages compared to those made by electro-chemical microelectrodes. As described in Beyenal et al. (2000) fiber-optic sensors are immune to environmental changes in pH, salinity, and ionic strength and immune to interference from moisture, carbon dioxide, methane, and other substances. A range of fiber-optic sensor studies were carried out to measure in situ geochemical gradients in biofilms. To our knowledge optical sensors applied to biofilm samples exposed to heavy metals are so far not reported in the literature. In our first collaboration with the UPPC we compared the oxygen concentration profiles obtained by electrochemical and optical microsensors, respectively. Oxygen concentration profiles were measured in the biofilms by electrochemical microsensors of the Clark design (Unisense, Denmark). These Clark-type oxygen microsensors are generally used for microbial ecology studies and contain a guard electrode. They have a tip diameter of 10 µm, a stirring sensitivity of <1–2%, and a response time of <1 s. The used multispecies biofilms (microbial diversity described in Krawczyk-Bärsch et al., 2008) were cultivated in the laboratory under non-sterile conditions in different biofilm reactors. One biofilm reactor was adjusted to a uranium concentration of (1x10-6 M), which is typical for uranium contaminated sites. The data achieved from both sensor methods are directly comparable. Fiber-optic sensor measurements showed high concentrations of oxygen over the total thickness of the biofilms, which were not in contact with uranium. In contrast, biofilms exposed to uranium revealed a much lower oxygen concentration in the bottom parts of the biofilm as described before in Krawczyk-Bärsch et al. (2008). Already at a depth of approximately 400 µm no oxygen was detectable. The comparative studies revealed that depending on the existing environmental conditions during the measurements a decision for the appropriate method is possible. However, further developments, e.g. miniaturization of the sensor equipments, are needed and aimed for within ReCosy.

References:

Beyenal, H. et al. (2000) Appl Opt 39, 3408.
Krawczyk-Bärsch, E. et al. (2008) Geochimica et Cosmochimica Acta 72, 5251–5265

  • Lecture (Conference)
    1st Annual Workshop of the Recosy Project, 10.-12.02.2009, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-12418
Publ.-Id: 12418


The influence of charge-transfer complexes on the copolymerization behavior of cyclic maleic acid derivatives with donor monomers

Schmidt-Naake, G.; Drache, M.; Leonhardt, K.

  • wird nachgereicht
  • Macromolecular Chemistry and Physics 199(1998)3, 353-361

Permalink: https://www.hzdr.de/publications/Publ-12417
Publ.-Id: 12417


First reporting of the scientific-technical outcome of WP 4.2: Chemical and redox behavior of the investigated radionuclides in the different systems through microbial mediated processes

Krawczyk-Bärsch, E.

Within the framework of ReCosy redox processes in biofilms, grown in-situ in radionuclide contaminated environments, will be studied by oxygen and redox potential microsensors. First in-situ measurement activities have already taken place in a former uranium mine in Saxony (Germany). Since the mining activities had stopped in 1990, the uranium mine has been partially flooded for remediation. This resulted in encroaching release of heavy metals and radionuclides as contaminants in acid, sulphate-rich waters. Huge biofilms with a thickness of more than 10 centimeters are currently growing in drainage channels (so far not flooded) under acid conditions and in the presence of uranium concentrations of approximately 1x10-4 M. Concentration profiles of oxygen were measured in these biofilms in-situ by means of electrochemical microsensors of the Clark design (Unisense, Denmark) with a tip diameter of 10 µm. The sensors were connected to a picoammeter and fixed in a holder on a motor-driven micromanipulator stage, connected with a motor controller, for a precise small-scale positioning and for automated measurements in 50 µm steps in Z-axis. Due to the hetero-geneities of the biofilm, numerous microprofiles were measured at different points of the biofilm. The results revealed a fast decrease of the oxygen concentration in the biofilm profiles. Already at a depth of approximately 2 mm no oxygen was detectable. It can be assumed that the microorganisms of the biofilm battle the toxic effects of aqueous uranium in a similar way as the biofilms described in Krawczyk-Bärsch et al. (2008). The biofilm community is reacting to the exposition of uranium in environmentally relevant concen-trations with an increase of the respiratory activity of the microorganisms. The increased metabolic activity of the microorganisms, as a result of an activation of heavy metal resistance mechanisms, will lead to larger anoxic zones (reducing zones) within the biofilms, which may induce redox processes. In these zones uranium (VI) can be reduced to highly insoluble uranium (IV) through abiotic processes. The precipitations of uranium (IV) solids will result in an increased removal of uranium and immobilisation of uranium from the solution.

References:

Krawczyk-Bärsch, E. et al. (2008) Geochimica et Cosmochimica Acta 72, 5251–5265

  • Lecture (Conference)
    1st Annual Workshop of the Recosy Project, 10.-12.02.2009, Barcelona, Spain
  • Contribution to proceedings
    1st Annual Workshop of the Recosy Project, 10.-12.02.2009, Barcelona, Spain
    Collaborative Project "Redox Phenomena Controlling Systems", Karlsruhe: Forschungszentrum Karlsruhe GmbH, KIT Report FZKA 7466 Dezember 2009, 43-46

Permalink: https://www.hzdr.de/publications/Publ-12416
Publ.-Id: 12416


Zur Anwendung von Schwerionen und Protonen in der Strahlentherapie

Enghardt, W.

no abstract available

  • Lecture (others)
    34. Seminar für Mitarbeiter von Landesbehörden, Landesanstalt für Personendosimetrie und Strahlenschutzausbildung Mecklenburg-Vorpommern, 13.11.2008, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12415
Publ.-Id: 12415


Cell response to laser-accelerated electron beams.

Pawelke, J.

wird nachgereicht

  • Invited lecture (Conferences)
    N4 Workshop on Radiation Protection Issues, 14.-17.12.2008, Chamonix, France

Permalink: https://www.hzdr.de/publications/Publ-12414
Publ.-Id: 12414


Neue Entwicklungen im Strahlenschutz in der Forschung.

Pawelke, J.

wird nachgereicht

  • Invited lecture (Conferences)
    2. Strahlenschutzseminar für Lehrer im Freistaat Sachsen, 18.11.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12413
Publ.-Id: 12413


Mensch und Strahlung – Wie verstehen wir die Wirkung der zur Krebstherapie eingesetzten Strahlen auf menschliche Zellen?

Pawelke, J.

wird nachgereicht

  • Lecture (others)
    Lange Nacht der Wissenschaften, 04.07.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12412
Publ.-Id: 12412


Laser Radiooncology.

Pawelke, J.

wird nachgereicht

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

Permalink: https://www.hzdr.de/publications/Publ-12411
Publ.-Id: 12411


Ultra fast electron beam x-ray computed tomography for two-phase flow measurement

Fischer, F.; Hampel, U.

Electron beam X-ray CT is a new technique for a fast measurement of multiphase flows with frame rates of 1000 images per second and more. It gives, in principle, quantitatively accurate images of the flow at high spatial resolution and it is non-intrusive since moderately radiation absorbing vessel walls can be penetrated by X-rays. However, on the road to a technical realisation of such a technique within a computed tomography system many problems have to be solved. As a first prototype for scientific flow measurement studies we devised and built a fast scanned electron beam X-ray tomography scanner. The scanner consists of an electron beam unit that can be operated at up to 150 kV acceleration voltage and up to 65 mA electron beam current, with the required electron optics for beam adjustment, beam focussing and beam deflection unit and a fast circular CZT detector comprising 240 elements of 1.5 mm × 1.5 mm × 1.5 mm active pixel area. X-ray radiation is produced on a circular water cooled tungsten target. The CT system achieves up to 7000 frames per second with a spatial resolution of 1 millimetre. First two-phase flow experiments have been carried out on gas-water flows in bubble columns. Further, a vertical test section made of titanium alloy has been installed at the TOPFLOW facility and will be used in the future to study the evolution of two-phase gas-water pipe flow at high pressures and temperatures.

Keywords: Two-phase flow; electron beam tomography; CFD code validation

Permalink: https://www.hzdr.de/publications/Publ-12410
Publ.-Id: 12410


Implications of three dimensional velocity distributions on the generation of magnetic fields in the Von-K\'arm\'an-Sodium dynamo experiment.

Giesecke, A.; Stefani, F.; Gerbeth, G.

Numerical simulations of the kinematic induction equation have been carried out in a cylindrical domain that resembles the configuration of the VKS dynamo experiment. Primary objective are investigations of non-axisymmetric source terms and their impact on the critical Reynolds number as well as onthe structure of the field geometry.

In case of an axisymmetric velocity distribution the resulting magnetic field is always determined by an azimuthal m=1-mode which is in contradiction to the experimental realization that is dominated by an axisymmetric field.

A simple non-axisymmetric contribution can be parameterized by a localized $\alpha$-effect which arises from the induction action of radially oriented helical outflow between the impeller blades that drive the flow. However, it turns out, that the amplitude of $\alpha$ which is necessary to obtain an axisymmetric field is far above realistic values.

Further potential contributions involve a time dependent non-axisymmetric velocity component in form of azimuthal drifting equatorial vortices as they have been found in water experiments. These structures provide a coupling between different field modes, but the m=1 mode still remains dominant. Resonance effects provide a strong increment of the field growthrate if the vortex drift motion proceeds phase synchronous with a drift of the magnetic field caused by equatorial symmetry braking of the velocity distribution. Presumably this phenomenon is not relevant in the experiment, as the drift of the eigenfield is very small so that resonance would require a much slower vortex drift velocity than it is observed.

So far, non-axisymmetric source terms in the induction equation are not able to explain the dominance of the m=0 mode, however it remains still possible that a quite exotic dynamo mechanism is operating which is essentially based on induction terms generated by the azimuthal variation of the permeability introduced by the ferrous impellers.

Keywords: dynamo; alpha-effect; induction; kinematic simulations

  • Lecture (Conference)
    Frontiers in Dynamo Theory, 16.-20.03.2009, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-12409
Publ.-Id: 12409


Mensch und Strahlung – Forschung an ELBE.

Pawelke, J.

wird nachgereicht

  • Lecture (others)
    Lehrerfortbildung 2007/2008 im FZD: „Moderne Beschleunigerkonzepte und ihre Anwendung in der Medizin“, 15.02.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12408
Publ.-Id: 12408


Weltweit erste Zellbestrahlungsexperimente mit laserbeschleunigten Teilchenstrahlen.

Pawelke, J.

wird nachgereicht

  • Invited lecture (Conferences)
    Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität, 21.01.2008, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12407
Publ.-Id: 12407


Therapie von Tumorerkrankungen mit laserbeschleunigten Teilchenstrahlen.

Pawelke, J.

wird nachgereicht

  • Invited lecture (Conferences)
    OncoRay, Strategie-Meeting, 08.-09.01.2008, Gröditz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12406
Publ.-Id: 12406


Präzisions-Strahlentherapie mit Laser-Ionenbeschleunigern.

Karsch, L.; Messner, L.; Pawelke, J.; Richter, C.; Schüttig, R.

wird nachgereicht

  • Poster
    Tag der Gesundheitsforschung, 17.02.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12405
Publ.-Id: 12405


Auf dem Weg zu einer neuen Strahlentherapie mit laserbeschleunigten Teilchen – Erste Experimente mit Elektronen.

Karsch, L.; Hümmerich, J.; Beyreuther, E.; Lessmann, E.; Pawelke, J.; Nicolai, M.; Schlenvoigt, H.

wird nachgereicht

  • Poster
    OncoRay, Strategie-Meeting, 08.-09.01.2008, Gröditz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12404
Publ.-Id: 12404


Mit laserbeschleunigten Teilchen gegen Tumore – Erste in vitro Experimente an laserbeschleunigten Elektronenstrahlen.

Naumburger, D.; Beyreuther, E.; Enghardt, W.; Karsch, L.; Lessmann, E.; Messner, L.; Nicolai, M.; Pawelke, J.; Richter, C.; Sauerbrey, R.; Schlenvoigt, H.; Baumann, M.

wird nachgereicht

  • Lecture (Conference)
    11. Jahrestagung der Gesellschaft für Biologische Strahlenforschung (GBS), 06.-08.10.2008, Tübingen, Deutschland
  • Contribution to proceedings
    11. Jahrestagung der Gesellschaft für Biologische Strahlenforschung (GBS), 06.-08.10.2008, Tübingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12403
Publ.-Id: 12403


Implementation of a High Level Hands-on-Training at an Experimental PET Scanner.

Würschig, T.; Kluge, T.; Enghardt, W.

The remarkable increase of medical imaging within the last decade demands the implementation of teaching programs for experts and students. Such courses must achieve both the realization of theoretical basics and an understanding of its implementation within real systems. This accounts for positron emission tomography (PET) as well. PET is, among other techniques like computer tomography (CT) or magnetic resonance imaging (MRI), one of the key technologies for biological and medical imaging. To teach and demonstrate the fundamentals of CT and the physical background of PET as well as to illustrate the signal processing of a coincidence measurement and the data processing of multi-parameter, list-mode data sets, the experimental PET scanner PET-TW05 has been developed. It is a simplified but still fully functional scanner consisting of two commercial BGO block-detectors. They are fixed in opposite to each other and can be moved along a linear axis and rotated around the field of view (FOV). The hardware layout and the software performance of the PET-TW05 scanner support the demonstration of important process steps of PET imaging like (i) system calibration, (ii) detector efficiency measurements, (iii) determination of time and spatial resolution of a PET scanner, (iv) list-mode data acquisition, (v) tomographic reconstruction by means of filtered backprojection, (vi) the effect of different filter kernels as well as of time and energy windows on the image quality, (vii) the influence of scatter on the image quality. Furthermore, the principle of time-of-flight PET can be experimentally demonstrated.

Keywords: PET; education; filtered backprojection; BGO block detector; list-mode data acquisition

  • Poster
    IEEE NSS-MIC Nuclear Science Symposium Conference Record M06-147, 19.-25.10.2008, Dresden, Deutschland
  • Contribution to proceedings
    IEEE NSS-MIC Nuclear Science Symposium Conference Record M06-147, 19.-25.10.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12402
Publ.-Id: 12402


Considerations on the Biological Effect of Laser Induced Radiation with High Dose Rates.

Khaless, A.; Karsch, L.; Enghardt, W.

wird nachgereicht

  • Lecture (Conference)
    IEEE NSS-MIC Nuclear Science Symposium Conference Record N51-5, 19.-25.10.2008, Dresden, Deutschland
  • Contribution to proceedings
    IEEE NSS-MIC Nuclear Science Symposium Conference Record N51-5, 19.-25.10.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12401
Publ.-Id: 12401


Dosimetric comparison between gated and steady photon and electron beams delivered by the Siemens ONCOR linear accelerator.

Wieczorkowski, L.; Hoinkis, C.; Lehmann, D.; Enghardt, W.

Objective: The gated irradiation technique is a sophisticated tool for focusing the prescribed dose to periodically moving target volumes while sparing the surrounding healthy tissue. Thus, gated irradiation is predominantly applied to organ motion caused by breathing. The tumour is irradiated in a specific phase of its motion. This requires to switch on and off the beam periodically. The beam-on time may change in a certain range depending on the individual breathing curve, site specific conceptions and the tumour dose conformity required. The latter will be increased for a short beam-on time, however, causing an increase in the number of irradiation cycles for reaching the prescribed dose. Prior to the therapeutic application of gated irradiation, the dose distributions delivered for photons and electrons in steady and gated mode in static phantoms were measured.

Materials: Photon and electron beams were delivered by a Siemens ONCOR Impression linear accelerator. The gating signal was provided by a commercial respiratory gating system based onto a pressure belt feedback mechanism in combination with a respiratory phantom (AZ-733, Anzai Medical). For measurements in stationary phantom linear diode array BMS 96 (Schuster Medizinische Systeme GmbH) was used to measure beam profiles and a solid water phantom (RW3, PTW) with ionization chamber (0.6 cm3 Farmer, PTW) were used to measure the depth dose at different depths. Respiratory frequency were set to 10 and 15 min-1 and beam-on time to 1, 2 and 3 s. Different field sizes (5 × 5, 10 × 10 and 20 × 20 cm2) for 6 and 15 MV photons and 10 × 10 cm2 for 9 and 12 MeV electrons were used.

Results: Depth doses maximum deviation for gated photon and electron beams is up to 0.8 % in comparison to non-gated beams. The maximum deviation between gated and non-gated dose profiles has been found to be less than 3 % and is located in the penumbra region. Deviations are randomized and do not depend on the photon and electron energy. Minor dependence of field size was observed but in most cases, the results for the 10 × 10 cm2 field were more accurate. None respiratory frequency dependence was noticed as well.

Conclusion: To evaluate more realistic cases with respect to therapy the dosimetric and geometric verification using a moving phantom will also been done.

  • Poster
    39. Jahrestagung Deutsche Gesellschaft für Medizinische Physik e.V. Oldenburg, 10.-13.09.2008, Oldenburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12400
Publ.-Id: 12400


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