Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34133 Publications

Kinetic Modelling of Neurokinin-1 Receptor Studies in Human Brain

Hinz, R.

(no abstract available)

  • Lecture (others)
    PET Methodology Seminar, Imaging Research Solutions Limited, London, UK 14 December 2001

Publ.-Id: 4267

Kinetic Modelling of NK1 Receptor Studies in Human Brain

Hinz, R.

(no abstract available)

  • Lecture (others)
    National Institutes of Health, Positron Emission Tomography Department Bethesda, Maryland, USA, November 2, 2001

Publ.-Id: 4266

Gamma and Neutron Spectra Investigations in Iron-Water Benchmark Configurations for the Verification of Monte Carlo Calculations in Reactor Material Dosimetry

Böhmer, B.; Grantz, M.; Hansen, W.; Hinke, D.; Konheiser, J.; Mehner, H.-C.; Noack, K.; Schneider, R.; Stephan, I.; Unholzer, S.

In order to validate Monte Carlo calculations for coupled neutron/gamma problems in reactor dosimetry an experimental benchmark programme at two low power reactors was started to measure both, neutron and gamma flux spectra behind and inside of transmission modules consisting of variable iron and water slabs. The comparison of the first series of experiments with MCNP calculations is presented.

Keywords: reactor dosimetry; neutron spectrometry; gamma spectrometry; reactor pressure vessel; steel embrittlemen; coupled neutron; gamma fluence calculations; benchmark

  • Lecture (Conference)
    Jahrestagung Kerntechnik 2002, Stuttgart, 14.-16. Mai 2002, Proceedings pp. 511-514
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2002, Stuttgart, 14.-16. Mai 2002, Proceedings pp. 511-514

Publ.-Id: 4265

Detection and Characterization of ultrafine Fe-As-Pb colloids in acid rock drainage solution from an ore mine

Zänker, H.; Moll, H.; Richter, W.; Brendler, V.; Hennig, C.; Reich, T.; Kluge, A.; Hüttig, G.

The processes of sulfide oxidation, water acidification and water mineralization in abandoned ore mines is closely associated with the existence of gangue fissures in the host rock that contain clay minerals and finely-divided sulfide ores. These fis-sures release highly mineralized, red-colored acid rock drainage (ARD) solutions which can easily be collected from pools in front of the fissures. ARD solution from an abandoned Zn-Pb-Ag mine at Freiberg, Germany, (pH 2.7, sulfate concentration 411 mmol/l, Fe concentration 93,5 mmol/l) was investigated by photon correlation spec-troscopy, centrifugation, filtration, ultrafiltration, scanning electron microscopy, ICP-MS, AAS, ion chromatography, TOC analysis, and X-ray absorption fine structure (EXAFS) spectroscopy. The question was if this ARD solution contains colloidal par-ticles of the lower nanometer range or if it is particle-free after the common filtration through a 450-nm filter. We found that the solution contains a small amount (about 20 mg/l) of submicron particles of about 100 nm in size. However, the major colloidal component was shown to be a population of ultrafine particles of less than 5 nm. The concentration of these particles is about 1 g/l. They consist of Fe, As and Pb com-pounds. According to EXAFS spectroscopy, the most probable mineralogical compo-sition of these particles is a mixture of hydronium jarosite (HFe3(SO4)2(OH)6) and schwertmannite (ideally Fe8O8(OH)6SO4). We also observed the formation of a rela-tively coarse precipitate of a similar mineralogy in the colloidal solution over a time span of months. The ultrafine colloids are obviously an intermediate in the formation process of the long-term precipitate. The arsenic is probably bound onto the ultrafine colloidal particles as a bidentate binuclear arsenate surface complex (inner-sphere complex). However, the transformation of the colloids to the more aggregated long-term precipitate leads to the incorporation of the arsenic into the interior of the iron hydroxy sulfate structures. The mechanism of this incorporation could be the substi-tution of arsenate for sulfate in the jarosite structure and/or the formation of very small scorodite clusters as occlusions within the oxyhydroxysulfate structures. The lead might occur as anglesite (PbSO4).

Keywords: colloids; ultrafiltration; EXAFS; acid rock drainage; jarosite; schwertmannite; arsenate

  • Lecture (Conference)
    XXVII General Assembly of the European Geophysical Society. Nice, France, 21 - 26 April 2002

Publ.-Id: 4260

Synthesis and structural characterization of two cis-dioxorhenium(V) ReO2[SN][P] mixed-ligand complexes

Bouziotis, P.; Papagiannopoulou, D.; Pirmettis, I.; Pelecanou, M.; Raptopoulou, C. P.; Stassinopoulou, C. I.; Terzis, A.; Friebe, M.; Spies, H.; Papadopoulos, M.; Chiotellis, E.

Two novel five-coordinate cis-dioxorhenium(V) complexes of the general formula ReO2[R2NCH2CH2S][PPh3] (R2N=Et2N, complex 1 and R2N=(o-CH3O-C6H4N(CH2CH2)2N, complex 2) have been synthesized by reacting ReOCl3(PPh3)2 with the respective bidentate ligands R2NCH2CH2SH. The complexes have been characterized by elemental analysis, IR, NMR spectroscopies and X-ray crystallography. X-ray crystallographic studies showed that the coordination geometry around rhenium is distorted trigonal bipyramidal. the basal plane is defined by the two doubly bonded oxygen atoms and the sulfur of the bidentate ligand, while the nitrogen of the ligand and the phosphorus occupy the apical positions.

Keywords: Crystal structures; Rhenium complexes; Dioxo complexes

  • Inorganica Chimica Acta 320 (2001) 174-177

Publ.-Id: 4259

Simulation of two surge line break experiments at the PMK-2 Test Facility using the code ATHLET

Schäfer, F.; Krepper, E.; Prasser, H.-M.; Szabados, L.; Ezsöl, G.

Results of two surge line break experiments, which were conducted at the PMK-2 test facility, are presented. The thermo-hydraulic computer code ATHLET, which was developed by GRS (Gesellschaft für Anlagen- und Reaktorsicherheit) mbH, was used for post-test calculations. The experiments simulate a break of the pressurizer surge line in the hot leg of a VVER-440-type reactor with different injection modes from the ECC systems. The main phenomena of the experiments are discussed and in case of selected events a more detailed interpretation with help of the measured void fraction, obtained with a special measurement device, is given. The results of the experiments and the ATHLET calculations are compared. In both experiments natural circulation instabilities could be observed. The physical mechanisms of the instabilities are discussed and it could be shown, that ATHLET can calculate the instabilities in good agreement with the experimental data.

Keywords: Thermo-hydraulics; Simulations; Instabilities; ATHLET

  • Lecture (Conference)
    Annual Meeting on Nuclear Technology, May 14-16, 2002, Stuttgart, Germany
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology, May 14-16, 2002, Stuttgart, Germany

Publ.-Id: 4258

Experimental analysis of crossflow in the reactor core geometry.

Kliem, M.

A new method for the thermal-hydraulic calculations in the reactor core using a porous media approach is presented in this paper.
The Core Crossflow Experimental Facility (CCEF) was built for the validation of this method.
The comparison of the calculations using this method with the experimental data from CCEF are also presented.

Keywords: reactor core; crossflow; CCEF

  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 2002, Stuttgart, Germany, May 14-16, 2002 Proceedings pp. 55-58
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 2002, Stuttgart, Germany, May 14-16, 2002 Proceedings pp. 55-58

Publ.-Id: 4257

High-spin structure of the spherical nucleus 90Y

Rainovski, G.; Schwengner, R.; Schilling, K. D.; Wagner, A.; Jungclaus, A.; Galindo, E.; Thelen, O.; Napoli, D. R.; Ur, C.; de Angelis, G.; Axiotis, M.; Gadea, A.; Marginean, N.; Martinez, T.; Kröll, T.

High-spin states in 90Y were populated in the 82Se(11B,3n)
reaction at a beam energy of 37 MeV. Gamma rays were detected with the spectrometer GASP. The level scheme of 90Y was extended up to J^\pi = (18^+) at 9.6 MeV. Mean lifetimes of four levels were determined using the Doppler-shift-attenuation method. The structure of 90Y was
interpreted in terms of the shell model. The calculations were performed in the model space \pi(0f_{5/2},1p_{3/2},1p_{1/2},0g_{9/2})
\nu(1p_{1/2},0g_{9/2},1d_{5/2}) and in an extended space including the \nu(0g_{7/2})$ orbital as well. The calculations in the extended model space reveal a correspondence between states in ^{90}Y and ^{89}Y. Moreover, a combination of the predicted states with J^\pi \geq 14^(+) can be found
that reproduces the large B(M1) values of up to about 1 W.u.

Keywords: Nuclear structure; In-beam gamma-ray spectroscopy; Shell model

  • Physical Review C, Vol. 65, 044327

Publ.-Id: 4256

Synthetic Humic Acids A Useful Tool to Study the Interaction of Humic Acids with Actinides in the Environment

Sachs, S.; Schmeide, K.; Heise, K.-H.; Bernhard, G.

The present work gives a detailed overview about our motivation for the synthesis of humic acid model substances. Exemplary for one synthetic humic acid (type M42), which is synthesized from xylose, glutamic acid and water [1], the synthesis, 14C-labeling ([14C]M42) and modification (M42-PB) of humic acids are described. We will discuss the characterization of these synthetic humic acids in comparison to natural humic acids from the literature as well as to natural humic acid Kranichsee [2]. This humic acid was isolated from surface water of the mountain bog "Kleiner Kranichsee" (Johanngeorgenstadt, Western Saxony, Germany) applying standard isolation techniques for humic acids.
The application of synthetic humic acid model substances will be presented with two examples. First, we will demonstrate the use of humic acid type M42 and humic acid type M42 with blocked phenolic and other blocked acidic OH groups (M42-PB) as model substances for the investigation of the neptunium(V) complexation by humic acids.
Secondly, we will discuss the application of 14C-labeled synthetic humic acid type M42 in batch and column experiments. The intend of these investigations is to improve the knowledge about the influence of humic acids on the mobilization or immobilization of actinides under natural conditions.
In addition to humic acid-like melanoidins, we synthesize humic acid model substances with distinct redox functionalities. Applying these model substances, detailed investigations with regard to the redox behavior of humic acids as well as to the redox stability of actinide humate complexes can be performed. In the present work we will give an brief overview about the synthesis, characterization and application of humic acids with pronounced redox functionalities.

[1] S. Pompe (Sachs), M. Bubner, K. Schmeide, K.H. Heise, G. Bernhard, H. Nitsche, 'Influence of Humic Acids on the Migration Behavior of Radioactive and Non-radioactive Substances under Conditions Close to Nature. Synthesis, Radiometric Determination of Functional Groups, Complexation', Report FZR-290, Rossendorf, 2000.
[2] K. Schmeide, H. Zänker, K.H. Heise, H. Nitsche, in Report FZKA 6124, G. Buckau (ed.), Karlsruhe, 1998, p. 161.

Keywords: Humic Acid; Synthesis; Modification; Labeling; Characterization; Complexation; Actinides; Neptunium; Migration

  • Lecture (Conference)
    20th Anniversary Conference of the International Humic Substances Society, July 21-26, 2002, Northeastern University Boston, Massachusetts, USA

Publ.-Id: 4255

Studies on interactions of actinides with organic ligands using femtosecond-laser-induced spectroscopy

Geipel, G.; Bernhard, G.; Fanghänel, T.

Polyelectrolytic organic macromolecules, like humic substances, are important complexing agents towards actinide metal ions. Due to these properties humic substances are possible carriers for the migration of actinides in the environment. The study of the high molecular compounds is very complex. Therefore the investigation of simple model ligands would give a more detailed description of the binding behavior of humic substances. Especially the different bonding of carboxylic and phenolic group and the discrimination between them is of interest to get more detailed information about the complex formation. The various hydroxy benzoic acids allow the investigation of these differences.
To study the complex formation of actinides with such organic ligands we used the new, recently developed tool of femtosecond laser-induced time-resolved fluorescence spectroscopy. The method uses the fluorescence properties of organic ligands with p-electron systems and their change by interaction with metal ions to study the complex formation of these systems.
The method was validated by study of the deprotonation of 2,3 dihydroxybenzoic acid. Within the error limits a very good agreement of the third protonation constant was found.
The studies of the complex formation of uranium(VI) with 2,3 dihydroxybenzoic acid in the pH range from 3.0 to 4.5 showed an one to one complex. The dependence of the complex formation on pH leads to the conclusion that besides the carboxylic group one of the two phenolic OH-groups contributes to the complex formation. The formation constant was determined to be log K(I=0.1M) = - 3.02 ± 0.09.
Studies of the complex formation in the system neptunium(V)-2,3 dihydroxybenzoic acid showed a completely different behavior. At low pH values also an one to one complex formation was found. This complex formation was not dependent on pH. That means complexes with the deprotonated carboxylic group were formed.
The formation constant was determined to be log K(I=0.1M) = 0.11 ± 0.04. With increasing pH the complex reaction changes. An intermediate complex can be observed by its own fluorescence properties. At pH values higher then six an one to two complex will be formed. The complex formation constants and the stoichiometry of the complex reaction will presented.

  • Lecture (Conference)
    14th Radiochemical Conference, Marianzke Lazne, 14-19. April 2002

Publ.-Id: 4254

Inner-sphere, outer-sphere and ternary surface complexes: a TRLFS study of the sorption process of Eu(III) onto smectite and kaolinite

Stumpf, T.; Bauer, A.; Coppin, F.; Fanghänel, T.; Kim, I.

Summary. The surface sorption process of Eu(III) onto smectite and kaolinite was investigated by time-resolved laser fluorescence spectroscopy (TRLFS) in the trace concentration range. The experiments were performed in 0.025 M and 0.45 M NaClO4. The sorption process of Eu(III) onto smectite was obtained by TRLFS under atmospheric conditions and in absence of CO2. The pH was varied between 3.5 and 9 at a fixed metal ion concentration of 3.3x10-6 mol/L Eu(III). At low pH (< 4) the metal ion keeps its complete hydration sphere indicating outer-sphere complexation. With increasing pH the formation of an inner-sphere Eu(III) surface complex was observed. The differences in the spectra and the fluorescence emission lifetimes of the surface sorbed Eu(III) in presence and absence of carbonate indicate the formation of ternary clay/Eu(III)/carbonate complexes. The different europium/clay surface complexes were characterized by their fluorescence emission spectra (5D0®7F1/5D0®7F2 intensity ratio) and their fluorescence emission lifetime.

  • Radiochimica Acta

Publ.-Id: 4253

Analyse der Schädigung eines Druckbehälters in Simulationsexperimenten von nuklearen Kernschmelzunfällen

Böhmert, J.; Müller, G.; Willschütz, H.-G.; Sehgal, B. R.

Das Verhalten eines Reaktordruckbehälters bei Kernschmelzunfällen ist von hoher sicherheitstechnischer Bedeutung für die Beherrschung derartiger Störfälle. An der Königlich-Technischen Hochschule Stockholm werden in einem umfangreichen Programm (FOREVER - Failure Of REactor VEssel Retention) die Verformung und das Versagenverhalten des Druckbehälters unter der thermischen Belastung einer oxidischen Schmelze untersucht. Die Experimente werden begleitet durch Finite-Element-Modell-Vorausrechnungen und durch metallografische Nachuntersuchungen. Die Gefügeänderungen geben Hinweise auf die aufgetretenen Maximaltemperaturen und Temperaturgradienten, auf die Wechselwirkungen mit der Schmelze und der umgebenden Atmosphäre sowie auf den Versagensmechanismus. Am Beispiel eines FOREVER-Experimentes werden die Ergebnisse der Nachtestuntersuchungen mit den FE-Modellrechnungen verglichen. Die metallografischen Befunde bestätigen die FEM-Vorausrechnungen.

  • Lecture (Conference)
    DGM-Tagung Werkstoffprüfung 2001, Bad Nauheim, 6. - 7. 12. 2001

Publ.-Id: 4252

Separation Control On A NACA 0015 Hydrofoil Using Lorentz Forces

Weier, T.; Gerbeth, G.; Mutschke, G.; Lielausis, O.; Lammers, G.

The use of electromagnetic forces to control the flow of electrically
conducting fluids is mostly associated with highly conducting liquids
like liquid metals and semiconductor melts. Only recently,
Electro-magnetic Flow Control for fluids of low electrical
conductivity like seawater has gained increasing interest. Most of the
published experimental and numerical work in this emerging field is
dedicated to skin friction reduction in turbulent boundary layers.

The present paper is focused on utilizing the accelerating effect of a
streamwise Lorentz force to prevent flow separation at the suction
side of a NACA 0015 hydrofoil. While the basic effects of
separation suppression and circulation enhancement have been
shown in [1], we will concentrate on the comparison of the
experimental results with such of separation control by steady
blowing. For this purpose, the Lorentz force strength will be given in
terms of an electromagnetic momentum coefficient C_EMHD, describing
the ratio of the total electromagnetic force imposed on the flow to
the product of dynamic pressure and wing area. Force measurements in
the Reynolds number range 2.9 10E4 < Re < 3.7 10E5, obtained with 3
different hydrofoils will be used to give a first approximation of the
maximum lift gain in dependence upon Reynolds number and Lorentz
force. Again, the electromagnetic momentum coefficient seems to be an
acceptable correlation factor to describe the control effect of the
Lorentz force in different flow configurations.

  • Lecture (Conference)
    12th European Drag Reduction Meeting, 18-20 April 2002, Herning, Denmark

Publ.-Id: 4251

Die kolloidalen Bestandteile von Lettenwasser (Acid Rock Drainage) aus der Himmelfahrt Fundgrube in Freiberg/Sa.

Zänker, H.; Moll, H.; Richter, W.; Brendler, V.; Hennig, C.; Reich, T.; Kluge, A.; Hüttig, G.

Es wurde gezeigt, daß das Lettenwasser eine kleine Menge (ca. 20 mg/l) an Submicronpartiklen von etwa 100 nm Größe enthält. Die kolloidale Hauptkomponente sind jedoch ultrafeine Partikel einer Größe von weniger als 5 nm. Sie weisen eine Konzentration von ca. 1 g/l auf. Diese Partikel bestehen wahrscheinlich aus einem Gemisch von H-Jarosit und Schwertmannit und sind ein Zwischenprodukt bei der Ausscheidung gröberkristalliner Präzipitate. Außerdem tragen sie Arsen und Blei. Das As ist offensichtlich als Arsenat-Oberflächenkomplex an die ultrafeinen Partikel gebunden. Bei der Ausscheidung von gröberkristallinen Fe-Oxyhydroxisulfatpräzipitaten scheint dann auch Arsenateinbau in das Innere der Oxyhydroxisulfatstrukturen eine Rolle zu spielen.

Keywords: Acid Rock Drainage; Kolloide; Eisenoxyhydroxysulfate; Arsenat

  • Lecture (Conference)
    Jahrestagung der Wasserchemischen Gesellschaft, Eichstätt/Altmühltal, 6.-8. Mai 2002

Publ.-Id: 4245

Acceptance and count rate estimates for experiments on subthreshold Phi meson production in central collisions of C + C at 2 AGeV

Kotte, R.; Kämpfer, B.

Monte-Carlo estimates of the subthreshold Phi meson production are performed for the reaction 12C + 12C at 2 AGeV assuming the Phi's to be emitted isotropically and distributed thermally in the center-of-mass system of the colliding nuclei. Different scenarios involving the detector installations FOPI and HADES at SIS/GSI are considered to determine the expected yields of Phi(1020) mesons identified via the K+K- and e+e- decay channels.

Keywords: PACS. 25.75.-q; 25.75.Dw

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-339 Januar 2002
    ISSN: 1437-322X


Publ.-Id: 4244

phi puzzle in heavy-ion collisions at 2 AGeV: how many K^- from phi decays?

Kämpfer, B.; Kotte, R.; Hartnack, C.; Aichelin, J.

The preliminary experimental data on phi production in the reaction Ni(1.93 AGeV) + Ni point to a puzzling high phi yield which can not be reproduced with present transport codes. We survey the experimental situation and present prospects for dedicated measurements of the phi multiplicities with the $K^+ K^-$ and $e^+ e^-$ channels at HADES and FOPI.

Keywords: Haevy-ion collisions; kaon production; phi mesons

  • J.Phys.G28:2035-2040,2002 arXiv: nucl-th/0112040

Publ.-Id: 4243

Ion Induced Formation of Regular Nanostructures on Amorphous GaSb Surfaces

Facsko, S.; Bobek, T.; Kurz, H.; Dekorsy, T.; Kyrsta, R.; Cremer, R.

Crystalline and amorphous GaSb surfaces are compared concerning their response
to sputter erosion with low-energy Ar$^+$-ions under normal incidence. We show
that the formation of regular nanostructures on GaSb is basically independent
on whether the initial material is crystalline or amorphous. The similarity in
the temporal and spatial evolution demonstrates that the dynamics of the
morphology evolution is entirely controlled by a thin amorphous
nonstoichiometric surface layer.

Keywords: self organization; ion induced surface modification; quantum dots; nanotechnology

  • Applied Physics Letters 80 (2002) 130-132

Publ.-Id: 4242

Two crossovers in the pseudogap regime of YBa$_2$Cu$_3$O$_{7-x}$ superconductors observed by ultrafast spectroscopy

Misochko, O. V.; Georgiev, N.; Dekorsy, T.; Helm, M.

We have investigated the temperature dependence of the optical reflectivity on
a femtosecond scale in a near-optimally doped YBa$_2$Cu$_3$O$_{7-x}$
superconductor. The combined study of the lattice and carrier dynamics at
temperatures above T$_c$ allows us to identify two crossover temperatures in
the normal state giving evidence for an inhomogeneity of the pseudogap regime.
These crossovers exhibit a clear hysteresis behavior depending on the direction
of temperature change. The carrier and lattice dynamics within the crossover
regimes show distinct differences from and similarities to the superconducting
state, which may help in choosing between the competing theories for the
pseudogap state.

Keywords: HTSC; coherent phonons; pseudogap; femtosecond spectroscopy

  • Physical Review Letters 89 (2002) 067002-067005

Publ.-Id: 4241

Prophylaxis of restenosis with 186Re-labeled stents in a rabbit model

Tepe, G.; Dinkelborg, L. M.; Brehme, U.; Muschick, P.; Noll, B.; Dietrich, T.; Greschniok, A.; Baumbach, A.; Claussen, C. D.; Duda, S. H.

Intraluminal beta-irradiation has been shown to decrease neointimal proliferation after angioplasty in experimental models. The purpose of this study was to test the technical feasibility and biological effects of 186Re-labeled stents.

Methods and results:
Thirty-four New Zealand White rabbits were fed a 0.5% cholesterol diet before balloon angioplasty and insertion of Palmaz stents in the infrarenal aorta. The animals were killed 7 weeks after stent implantation. Two of 34 animals died prematurely (aortic leak, pneumonia). Control stents (n=7) were compared with 186Re stents (2.6 MBq [n=6], 8.1 MBq [n=5], 16 MBq [n=6], and 25.3 MBq [n=8]). Stent application was successful in all cases. No thrombus occlusion was observed. After 7 weeks, neointima formation was 2.2±0.2 mm2 in the control group. In the treatment groups, a dose-dependent neointima reduction was detectable (0.5±0.5 mm2 [2.6 MBq], 0.4±0.4 mm2 [8.1 MBq], and 0 mm2 [16.0 MBq, 25.3 MBq]). No induction of neointimal formation was observed at the edges of the stents. Radiation resulted in delayed reendothelialization.

186Re stents were capable of reducing neointima formation in a dose-dependent fashion. 186Re stents did not cause late thrombosis or neointimal induction at the stent margins in the observation period of 7 weeks.

Keywords: atherosclerosis; angioplasty; hypertension; restenosis; radioisotopes; stents

  • Circulation 104 (2001) 480-485

Publ.-Id: 4240

Magnetic and collective rotation in 79Br

Schwengner, R.; Dönau, F.; Servene, T.; Schnare, H.; Reif, J.; Winter, G.; Käubler, L.; Prade, H.; Skoda, S.; Eberth, J.; Thomas, H. G.; Becker, F.; Fiedler, B.; Freund, S.; Kasemann, S.; Steinhardt, T.; Thelen, O.; Härtlein, T.; Ender, C.; Köck, F.; Reiter, P.; Schwalm, D.

Excited states of the nucleus 79Br were investigated via the reaction
76Ge(7Li,4n) at 35 MeV. Coincidence data of emitted gamma rays
were measured with an arrangement of six EUROBALL CLUSTER detectors.
The E2 bands built on the 9/2+ and 3/2- states were extended up to
J = 37/2 at E \approx 8.8 MeV. The M1 band starting with a 15/2-
state at 2.6 MeV was extended to J = (29/2) at E = 6.4 MeV. Cross-over
E2 transitions within this band were observed for the first time. Mean
lifetimes of 17 levels were deduced using the Doppler-shift-attenuation method.
The M1 band can be described within theTilted-Axis-Cranking model on the
basis of the tilted three-quasiparticle configuration
pi(g9/2) nu (g9/2) nu (fp) which has a triaxial shape. This band
appears as a mixed case including contributions of both, magnetic and
collective rotation.

Keywords: Nuclear spectroscopy; Cluster detectors; Magnetic and collective rotation; Tilted-axis cranking model

  • Physical Review C, Vol. 65, 044326

Publ.-Id: 4239

On parabolic potential profile in ion sheaths

Mukherjee, S.

Parabolic potential profiles are commonly used in ion sheaths as it simplifies the mathematical formulation and is observed in limited experimental observations, where measurement uncertainties justify it. However, before using the parabolic potential profile assumption in all cases, there are other factors that needs to be concerned. The article highlights these factors for collisionless and collisional ion sheaths.

Keywords: parabolic potential profile; ion sheath; ion matrix

  • PHYS SCRIPTA 66 (2): 165-167 AUG 2002

Publ.-Id: 4238

Fluid-Structure Interaction Experiments at the Cold Water Hammer Test Facility (CWHTF) of the FZ-Rossendorf

Altstadt, E.; Carl, H.; Weiß, R.

In existing NPPs water hammers can occur in case of an inflow of sub-cooled water into pipes or other parts of the equipment, which are filled with steam or steam-water mixture. They also may appear as the consequence of valve closing or opening actions or of breaks in pipelines, with single phase or two-phase flow. The influence of the fluid-structure interaction on the magnitude of the loads on pipe walls and support structures is not yet completely understood. The lack of experimental data obtained at well defined geometric boundary conditions is a significant obstacle for the validation of codes which consider fluid-structure interaction. Furthermore, up to now the feedback from structural deformations to the fluid mechanics is not fully implemented in existing calculation software codes. Therefore, at FZR a cold water hammer test facility (CWHTF) was designed and built up.

Keywords: fluid-structure interaction; waterhammer

  • Lecture (Conference)
    Jahrestagung Kerntechnik 2002, Stuttgart, Tagungsband S. 59-64, May 14-16, 2002
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2002, Stuttgart, Tagungsband S. 59-64, May 14-16, 2002

Publ.-Id: 4237

The influence of the N=50 neutron-core on dipole excitations in 87Rb

Käubler, L.; Schilling, K. D.; Schwengner, R.; Dönau, F.; Grosse, E.; Belic, D.; von Brentano, P.; Bubner, M.; Fransen, C.; Grinberg, M.; Kneissl, U.; Kohstall, C.; Linnemann, A.; Matschinsky, P.; Nord, A.; Pietralla, N.; Pitz, H. H.; Scheck, M.; Stedile, F.; Werner, V.

Dipole excitations in the semimagic N=50 nucleus ^{87}Rb were investigated at the Stuttgart Dynamitron
facility using bremsstrahlung with an endpoint energy of 4.0 MeV. The widths Gamma or the reduced excitation probabilities B(Pi 1)uparrow of 19 states were determined for the first time. The magnetic dipole excitations
are well reproduced in the framework of the shell model, however, these calculations cannot describe the observed electric dipole excitations.The 1/2^+ state at 3060 keV is proposedto be the weak coupling of an f_{5/2} proton hole to the 3^- octupole vibrational state in the N=50 core ^{88}Sr. The relatively strong E1 transition from that state to the ground state is explained as mainly the neutron h_{11/2} \rightarrow g_{9/2} transition. The breakup of the N=50 core and neutron excitations into the h_{11/2} shell are essential to describe electric dipole excitations, but neutron-core excitations do not play an important role for the structure of magnetic dipole excitations.

  • Physical Review C, Vol. 65, 054315

Publ.-Id: 4233

Analysis and insights about FE-Calculations of the EC-Forever-Experiments

Willschütz, H.-G.; Altstadt, E.; Weiß, F.-P.; Sehgal, B. R.

To get an improved understanding and knowledge of the melt pool convection and the vessel creep and possible failure processes and modes occurring during the late phase of a core melt down accident the FOREVER-experiments are currently underway at the Division of Nuclear Power Safety of the Royal Institute of Technology Stockholm. These experiments are simulating the behaviour of the lower head of the RPV under the thermal loads of a convecting melt pool with decay heating, and under the pressure loads that the vessel experiences in a depressurization scenario.
Due to the multi axial creep deformation of the vessel with a non-uniform temperature field these experiments are on the one hand an excellent source of data to validate numerical creep models which are developed on the basis of uniaxial creep tests. On the other hand the results of pre-test calculations can be used to optimize the experimental procedure and can help to make on-site decisions during the experiment.
Therefore a Finite Element model is developed based on a multi-purpose code. After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Additionally metallographic post test investigations of the experiments are conducted to improve the numerical damage model and to adjust the correlation between the metallographic observations and the calculated damage. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios.
After analysing the calculations, it seems to be advantageous to introduce a vessel support which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it is possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.

Keywords: Scaled Core Melt Down Experiments; FEM Calculations; Advanced Creep Modelling; Metallographic Investigations; Vessel Support as Accident Mitigation Measure

  • Lecture (Conference)
    10th International Conference on Nuclear Engineering, Arlington, VA, USA, April 14-18, 2002, Proceedings on CD-ROM, Paper No. 22262
  • Contribution to proceedings
    10th International Conference on Nuclear Engineering, Arlington, VA, USA, April 14-18, 2002, Proceedings on CD-ROM, Paper No. 22262

Publ.-Id: 4232

Scaled vessel failure experiment analysis and investigation of a possible vessel support

Willschütz, H.-G.; Altstadt, E.; Weiß, F.-P.; Sehgal, B. R.

Scaled coupled melt pool convection and vessel creep failure experiments are being performed in the FOREVER program at the Royal Institute of Technology, Stockholm. These experiments are simulating the lower head of a pressurized reactor vessel under the thermal load of a melt pool with internal heat sources [1]. Due to the multi axial creep deformation of the three-dimensional vessel with a highly non-uniform temperature field these experiments offer an excellent opportunity to validate numerical creep models. A Finite Element model is developed and using the Computational Fluid Dynamic module, the melt pool convection is simulated and the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a new creep modeling procedure. Additionally, the material damage is evaluated considering the creep deformation as well as the prompt plasticity [2, 3].
Pre- and post-test calculations of at least 4 FOREVER experiments have been performed successfully [4]. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios.
After analyzing the calculations, it seems to be advantageous to introduce a vessel support which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it is possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.

Keywords: LWR scaled vessel failure experiments; FE-simulation; vessel support as accident mitigation strategy

  • Lecture (Conference)
    Jahrestagung Kerntechnik 2002, Stuttgart, May 14-16, 2002, Tagungsband S. 173-178
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2002, Stuttgart, May 14-16, 2002, Tagungsband S. 173-178

Publ.-Id: 4231

First measurement of beta-decay properties of the proton drip-line nucleus 60Ga

Mazzocchi, C.; Janas, Z.; Döring, J.; Axiotis, M.; Batist, L.; Borcea, R.; Cano-Ott, D.; Caurier, E.; de Angelis, G.; Farnea, E.; Fassbender, A.; Gadea, A.; Grawe, H.; Jungclaus, A.; Kapica, M.; Kirchner, R.; Kurcewicz, J.; Lenzi, S.; Mart'Inez, T.; Mukha, I.; N'Acher, E.; Napoli, D. R.; Roeckl, E.; Rubio, B.; Schwengner, R.; Tain, J. L.; Ur, C. A.

By using the fusion-evaporation reaction 28Si(36Ar,p3n) and spectroscopy of beta-delayed gamma rays and charged particles on mass-separated sources, beta-decay properties of the neutron-deficient isotope 60Ga were studied for the first time. The half-life of 60Ga was determined to be 70(15) ms, and, based on gamma-gamma coincidences, the isobaric-analogue state in 60Zn was identified at 4851.9(7) keV. A semiempirical proton separation energy value of 40(70) keV was deduced for 60Ga. The experimental results on half-life, mass excess, proton separation energy, and structure of the 60Zn daughter states are discussed in comparison with various model predictions, including large scale shell model calculations.

Keywords: Properties of nuclei; nuclear energy levels; Beta decay; 21. Shell model

  • European Physical Journal A 12, 269-277 (2001)

Publ.-Id: 4230

Vacancy-type defects in 6H-SiC caused by N+ and Al+ high fluence co-implantation

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

6H-SiC n-type wafers were implanted with Al+ and N+ ions in two steps: first N+ double implantation (65 keV, 5x1016 cm-2 , 120 keV, 1.3x1017 cm-2 ) followed by Al+ double implantation (100 keV, 5x1016 cm-2 and 160 keV, 1.3x1017 cm-2 ). The implantation was carried out at a substrate temperature of 800 0C in order to avoid amorphisation. In this way a buried SiC1-x(AlN)x layer could be created. Variable-energy positron Doppler broadening measurements were performed at room temperature using a magnetic transport beam system in order to characterize the vacancy-type defects created by ion implantation. Depth profiles could be evaluated from the measured Doppler broadening profiles. The defect distribution and the defect size after the complete co-implantation are discussed and the contribution of the different implantation steps to the evolution of this defect structure is shown.

Keywords: 6H-SiC; N+ and Al+ co-implantation; vacancy-type defects; slow positron spectroscopy

  • Applied Surface Science 194 (2002) 131-135
  • Poster
    9th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces, Dresden, Germany, September 16-22, 2001

Publ.-Id: 4229

The influence of substrate temperature on the evolution of ion implantation induced defects in epitaxial 6H-SiC

Anwand, W.; Brauer, G.; Wirth, H.; Skorupa, W.; Coleman, P. G.

An epitaxial n-type 6H-SiC layer has been fourfold implanted with Al+ ions at temperatures ranging from room temperature to 1200 oC in order to create a buried p-doped layer from 200 nm to 600 nm below the surface. The defects induced by the ion implantation at different temperatures have been investigated by Slow Positron Implantation Spectroscopy. Higher substrate temperatures were found to lead to a significant reduction in the depth of the damage. However, this is accompanied by the formation of vacancy clusters of sizes up to seven Si-C divacancies. Only at 1200 ºC does the vacancy agglomeration disappear in the implanted region, and larger agglomerates are formed immediately below the surface. Furnace annealing at 1650 ºC was found to be insufficient to remove all damage.

Keywords: epitaxial 6H-SiC; Al implantation; vacancy-type defects; slow positron spectroscopy

  • Applied Surface Science 194 (2002) 127-130
  • Poster
    9th International Workshop on Slow Positron Beam Techniques for Solids and Surfaces, Dresden, Germany, September 16-22, 2001

Publ.-Id: 4228

Investigation of ion implantation induced damage in the carbon and silicon sublattices of 6H-SiC

Zolnai, Z.; Khánh, N. Q.; Szilágyi, E.; Kótai, E.; Ster, A.; Posselt, M.; Lohner, T.; Gyulai, J.

Single crystal 6H-SiC samples were irradiated at room temperature with 200 keV Al+ ions at fluences ranging from 3.5x1013 to 2.8x1014 ion/cm2. Depth profiles of crystal defects both in the C and Si sublattices were measured by Backscattering Spectrometry combined with channeling technique (BS/C) at 3550 keV 4He+ ion beam energy along the <0001> axial channeling direction. Damage in the carbon sublattice was found to be higher than in the silicon one. Moreover, C/Si damage ratio decreased with increasing fluence. The crystal defect profiles can be well simulated both by full-cascade SRIM and Crystal-TRIM programs. Effective displacement energies for carbon and silicon sublattices in the applied fluence range of Al implantation were determined by comparing SRIM simulations to BS/C results.

Keywords: Silicon carbide; Ion implantation; Backscattering Spectrometry; Defects

  • Lecture (Conference)
    12th European Conf. on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide, September 2-7, 2001, Budapest, Hungary
  • Diamond and Related Materials 11 (2002) 1239-1242

Publ.-Id: 4227

Einfluss von Wasserstoff auf die Zähigkeit von Reaktordruckbehälterstählen

Uhlemann, M.; Böhmert, J.; Müller, G.

Niedriglegierte ferritische Stähle gelten ebenso wie die hochlegierten austentischen Stähle als anfällig gegen Wasserstoffversprödung. Im Kernreaktor können Korrosion oder Radiolyse zur Bildung von atomaren Wasserstoff an der inneren Oberfläche des Reaktordruckbehälters und folglich zur Wasserstoffaufnahme während des Reaktorbetriebes führen. Der Beitrag stellt Ergebnisse zum Wasserstoffdiffusionsverhalten, zur Wasserstofflöslichkeit und zum Einfluss des Wasserstoffs auf die mechanischen Eigenschaften vor. Sie wurden an unbestrahlten Druckbehälterstählen unterschiedlicher Art gewonnen und beziehen sich auf solche Bedingungen, die denen im DWR nahe kommen.

  • Lecture (Conference)
    Jahrestagung Kerntechnik 2002, Tagungsbericht, 14.-16.05.2002, Stuttgart, S. 609
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2002, Tagungsbericht, 14.-16.05.2002, Stuttgart, S. 609

Publ.-Id: 4226

ROCOM experiments on the influence of density differences on the coolant mixing inside the reactor pressure vessel of a PWR

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

During emergency core cooling (ECC) injection into the cold leg of a PWR an incomplete mixing of the injected water with the natural circulation flow in the loop takes place. Due to the higher density of the ECC water a streak of cold water is flowing downwards the downcomer. This causes thermal loads on the reactor pressure vessel wall. Furthermore, the core behaviour is determined by the resulting parameter distributions at the core inlet.
An experimental study was carried out at the ROCOM test facility, a fluid dynamic model of a German type PWR (KONVOI 1300 MWe) in the scale of 1:5. Natural circulation conditions in one loop were approximated by running the corresponding pump at low rotation speed by means of a frequency transformer system. The higher density of the injected water was simulated by adding sugar. The evolution of the spatial distribution of the ECC water was measured by tracering with sodium chloride. Conductivity distributions reflecting the share of ECC water present at given time and location were measured by electrode mesh sensors, one close to the reactor inlet nozzle (16 x 16 measuring points), two sensors in the upper and lower part of the downcomer (2D grids of 4 radial and 64 angular measuring positions) and one sensor at the core entrance (inlets of each of 193 fuel elements).
The paper presents visualisations of the streak effect in the downcomer. The transition from momentum driven flow in the downcomer to a density driven regime was identified (critical Froude number). In the experiments the relative density difference was varied between 0 and 10 % and the loop flow rate between 0 and 15 % of the nominal. The streak effect is more pronounced at higher density differences.

  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 2002, Stuttgart, Germany, May 14-16, 2002 Proceedings pp. 65-69
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 2002, Stuttgart, Germany, May 14-16, 2002 Proceedings pp. 65-69

Publ.-Id: 4225

Syntheses and first crystal structures of rhenium complexes derived from omega-functionalized fatty acids as model compounds of technetium tracers for myocardial metabolism imaging

Jung, C. M.; Kraus, W.; Leibnitz, P.; Pietzsch, H.-J.; Kropp, J.; Spies, H.

In an attempt to develop new technetium-based radiopharmaceuticals for the non-invasive diagnosis of myocardial metabolism, we have synthesized three examples of novel metal-containing fatty acid derivatives according to the '3+1' mixed-ligand and the Schiff Base/tricarbonyl design. The chelates contain the metal core in the oxidation states +5 and +1 respectively, and were attached to the ending position of a fatty acid chain. The complex formation was accomplished by ligand exchange reactions using three different rhenium precursors, whereas the inactive rhenium metal was utilized as surrogate of the technetium radionuclide. The molecular structures of the fatty acid complexes 7, 10 and 14 were determined by single-crystal X-ray diffraction analyses and show impressively a general problem in technetium tracer research, namely the significant structural alterations of bioactive molecules by coordination even to small-sized metal chelates.

Keywords: rhenium; technetium; fatty acid; drug research, radiopharmaceuticals

  • European Journal of Inorganic Chemistry (2002) 1219-1225

Publ.-Id: 4224

Linear three-dimensional instability of a magnetically driven flow

Grants, I.; Gerbeth, G.

The instability of a rotating magnetic field driven liquid metal flow in a finite cylinder with respect to infinitesimal azimuthally periodic
perturbations is studied numerically. This instability is observed to set in prior to its axisymmetric counterpart with relatively low frequency at diameter-to-height ratios between 0.5 and 2. The both, axisymmetric and three-dimensional instabilities have similar characteristic features. The instability originates in the cross-section of the horizontal and vertical rotating boundary layers and excites inertial waves in the inviscid core.

  • Journal of Fluid Mechanics (2002), vol. 463, pp. 229-239

Publ.-Id: 4223

Targeting of human gamma-glutamyltransferase with mAb 138H11 in a new renal cell carcinoma mouse model

Zimmermann, J.; Sachsinger, J.; Ivancevic, V.; Künstler, J.-U.; Michael, R.; Knoll, K.; Reszka, R.; Seifert, S.; Krause, H.; Munz, D. L.; Heicappell, R.; Fischer, P.

Renal cell carcinoma (RCC) belongs to the 12 most frequent tumors in Germany. Its incidence increases worldwide. 30% to 40% of patients already have metastases when the tumor is diagnosed and further 50% develop metastases after tumor resection. Radiotherapy or chemotherapy have no therapeutic effect against RCC. Systematic therapy of RCC with immunostimulatory cytokines is limited by dose due to serious side effects. A tumor targeting antibody offers the possibility to achieve efficient local doses of cytotoxic or immunostimulating reagents within the tumor without high systemic burden.

Our approach is to treat metastatic RCC with immunoactive agents coupled to our mAb 138H11 specific for human GGT (gamma-glutamyltransferase) which has the ability to target human clear cell and papillary RCC. In extracorporeal transfusion experiments with human RCC-bearing kidney 99m-Tc-labeled 138H11 was enriched up to 20-fold in the tumor. Treatment of nude mice bearing human RCC xenografts with a highly cytotoxic drug (Calicheamicin theta) conjugated to mAb 138H11 led to a significant shrinkage of tumor mass (Cancer Res. 2000, 60, 6089-6094). However, these nude mice are not useful for evaluating ADCC of naked 138H11 or immunoactive conjugates.

For creating a syngeneic immunocompetent mouse model bearing a tumor sensitive to mAb 138H11, we stably transfected the murine RCC RENCA cell line with the human GGT-gene. FACS-analyses revealed that transfected cells were positive for mAb 138H11, in contrast to wild type cells. The transfected cells were growing s.c. in Balb/c Mice without signs of rejection by the host. The mice showed a higher uptake of 99m-Tc-labeled 138H11 in the GGT positive RENCA tumors compared to the wild type tumors.

  • Abstract in refereed journal
    Immunobiology 204 (2001) 308-309
  • Poster
    32nd Annual Meeting of the German Society of Immunology, September 2001

Publ.-Id: 4222

EXAFS Analyses in Radiopharmaceutical Research: Stability Studies of Technetium(I) Carbonyl Complexes in Solution

Seifert, S.; Künstler, J.-U.; Gupta, A.; Funke, H.; Reich, T.; Hennig, C.; Roßberg, A.; Pietzsch, H.-J.; Alberto, R.; Johannsen, B.

Nowadays, the majority of radiopharmaceuticals used in routine nuclear medicine imaging procedures are 99mTc labelled compounds, and intensive research is in progress to design new 99mTc radiopharmaceuticals. Investigation of Tc and Re carbonyl chemistry has led to an organometallic M(I) aqua ion, M(CO)3(H2O)3]+
(M = Tc, Re), as a precursor for the preparation of complexes containing the small [M(CO)3]+ moiety. Tc(I) and Re(I) tricarbonyl complexes represent a new and promising approach to low-valent, non-polar and inert compounds. Complexes with N-donor or S-donor chelating ligands coordinated to the M(I) tricarbonyl moiety with high stability in aqueous solution may serve in the design of radiopharmaceuticals [1, 2].

The aim of this work was to investigate the stability of a model Tc(I) dithioether-tricarbonyl complex, Tc1, in aqueous solution and to estimate structural
parameters for the dissolved compounds. Owing to the extremely small concentration of the radionuclide present in the radiopharmaceutical preparation (10­6 ­ 10­8 M), XAS studies as well as most other chemical investigations employ the long-lived isotope 99Tc (K-edge at 21.044 keV). We found that the complex Tc1 is reversibly transformed into the complex Tc1a in aqueous solution (Figure 24).

Fig. 24: Reversible transformation of the complex Tc1 in aqueous solution.

Chemical investigations were performed both at the 99Tc and 99mTc levels. The change of charge of the complexes was determined by electrophoresis. Mass-spectrometric analyses and EXAFS measurements confirmed the composition of the compounds. EXAFS analyses were carried out at BM20 (Rossendorf CRG beamline, ROBL) [3]. 99Tc solutions of Tc1 and Tc1a were prepared by dissolving solid Tc1 in water/methanol and adding chloride or Ag+, respectively. With an excess of sodium chloride the equilibrium (Figure 24) is on the side of the Tc1 complex. If chloride is removed from the equilibrium by precipitation as AgCl, Tc1a is the species in solution. To obtain a satisfactory evaluation of the EXAFS spectra and the Fourier transforms, single-scattering paths including the C, O and S/Cl coordination shells and multiple-scattering paths to model the oxygen atom of the carbonyl group were taken into account (Figure 25). The estimated atomic distances are 1.92 Å (Tc­C), 2.49 Å (Tc­S or Tc­Cl), 2.19 Å (Tc­Oaq) and 3.06 Å (Tc­OCO). The coordination numbers agree with the molecular structure represented in Figure 24. EXAFS analysis of Tc1a shows the same structural parameters for the C, S/Cl and CO coordination shells as Tc1 except that the coordination number for the S/Cl coordination shell is lowered by approximately one. In addition, the detection of 1.2 ± 0.3 oxygen atoms at 2.19 Å proves the substitution of chlorine by water. This can be seen in Figure 25 as a reduction of the magnitude of the second peak in the Fourier transform since electron back-scattering from the oxygen atom is weaker than from the chlorine atom.

Fig. 25: Tc K-edge k3-weighted EXAFS spectra and the corresponding Fourier transforms of Tc1 and Tc1a (solid line: experimental data, dotted line: fit), transmission mode, sample concentration 3.5 x 10-2 M, sample thickness 1 cm, room temperature.

EXAFS analyses were successfully used to determine structural parameters of Tc(I) tricarbonyl complexes in solution. In connection with chromatographic,
electrophoretic and mass-spectrometric methods, it was found that Tc(I) tricarbonyl complexes containing a bidentate thioether ligand are able to react with water by
exchange of chlorine.

[1] R. Alberto et al., Coordination Chem. Rev., 190-192, 901 (1999).
[2] H.-J. Pietzsch et al., Bioconj. Chem., 11, 414 (2000).
[3] W. Matz et al., J. Synchrotron Rad., 6, 1076 (...

  • Contribution to external collection
    ESRF Highlights 2000 (2001) 22-23

Publ.-Id: 4221

Anordnung zur quantitativen Bildrekonstruktion

Hoppe, D.; Christen, M.

Die Erfindung betrifft Materialuntersuchungen mit Hilfe der Tomographie.
Der Erfindung liegt die Aufgabe zugrunde, auch dann eine quantitative Bildrekonstruktion durchführen zu können, wenn im zu untersuchenden Objekt kein Gebiet bekannter Absorption vorhanden ist.

  • Patent
    DE 101 44 261 A1 - 10. April 2003
  • Patent
    DE 101 44 261 B4 - 20. Dezember 2007

Publ.-Id: 4220

Schichtmaterial für optische Informationsträger und Lichtmasken sowie ein Verfahren zur Herstellung des Schichtmaterials

Teichert, J.; Bischoff, L.; Tsvetkovam, T.

Der Erfindung liegt die Aufgabe zugrunde, ein neues Schichtmaterial für optische Informationsträger und Lichtmasken sowie ähnlich gelagerte Anwendungen vorzuschlagen. Außerdem wird ein einfaches Verfahren zur lokalen Veränderung der optischen Absorption in diesem Schichtmaterial angegeben, mit dem Strukturgrößen erreichbar sind, wie sie die fortgeschrittene Halbleiterindustrie fordert.
Das Schichtmaterial besteht aus amorphem, hydroxierten Siliciumkarbid der Form a-SiC:H, die Schichtbereiche hoher optischer Absorption enthalten Metallatome, vorzugsweise Gallium oder Zinn.

  • Patent
    Patentanmeldung Az 101 43 616.5
  • Patent
    DE 101 43 616 A 1

Publ.-Id: 4219

Biomaterial und Verfahren zu dessen Herstellung

Pham, M. T.; Maitz, M. F.

Die Erfindung betrifft ein Biomaterial und ein Verfahren zu dessen Herstellung. Potentielle Anwendungen sind medizinische Implantologie, Gewebezüchtung, Biotechnologie und Pharmazeutik.
Der Erfindung liegt die Aufgabe zugrunde, ein Biomaterial für Anwendungen in medizinischer Implantologie, Gewebezüchtung, Biotechnologie und Pharmazeutik zu schaffen, das eine gute Strukturbildung und Haftfestigkeit aufweist sowie die zellbiologischen Aspekte berücksichtigt.
Der Erfindung obliegt auch die Aufgabe, ein einfaches und anwendungswirksames Verfahren zur Herstellung des genannten Biomaterials vorzuschlagen.

  • Patent
    Patentanmeldung Az 101 43 410.3
  • Patent
    DE 101 43 410 A 1

Publ.-Id: 4218

Radioaktiv markierte 3-O-Methyl-6-halogen-L-DOPA- Verbindung, (3-O-Methyl-6-halogen-L-4-hydroxyphenylalanin, 3-(2-Halogen-4-hydroxy-5-methoxy-phenyl)-2-amino-propansäure) und deren Verwendung zur Diagnose und Therapie von Tumoren sowie ein Verfahren zu ihrer Herstellung

Füchtner, F.; Bergmann, R.; Steinbach, J.; Wunderlich, G.; Bredow, J.

Aufgabe der Erfindung ist es Substanzen vorzuschlagen, die zur Diagnose und Therapie von Tumoren in der Nuklearmedizin geeignet sind und ein Verfahren zur Herstellung der Substanzen anzugeben.

  • Patent
    DE 101 27 835 A 1

Publ.-Id: 4217

Verfahren und Schaltungsanordnung zur Regelung von Extremwerten

Herbrand, F.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren und eine Schaltungsanordnung vorzuschlagen, mit denen der Extremwert einer Größe, oft als Gütegröße bezeichnet, auch bei sehr kleinen Stellbewegungen zu finden und zu halten ist und bei denen der Suchverlust durch die Suchbewegungen konstant gehalten werden kann.

  • Patent
    Patentanmeldung Az 101 27 878.0
  • Patent
    DE 101 27 878 A1
  • Patent
    EP 1 267 228 A2

Publ.-Id: 4216

Verfahren zur Behandlung heteroepitaktischer Halbleiterschichten auf Siliziumsubstraten

Gebel, T.; Heera, V.; Panknin, D.; Skorupa, W.; Voelskow, M.; Eickhoff, M.

Die Erfindung betrifft ein Verfahren zur Behandlung heteroepitaktisch auf Siliziumsubstraten abgeschiedener Halbleiterschichten. Die Erfindung soll insbesondere für die Herstellung elektronischer Bauelemente eingesetzt werden.

  • Patent
    Patentanmeldung Az 101 27 073.9
  • Patent
    DE 101 27 197 A1
  • Patent
    EP 1 263 030 A2

Publ.-Id: 4215

Verfahren zur Behandlung heteroepitaktischer Halbleiterschichten auf Silicon-on-insulator(SOI)-Substraten

Gebel, T.; Heera, V.; Panknin, D.; Skorupa, W.; Voelskow, M.; Eickhoff, M.

Die Erfindung betrifft ein Verfahren zur Behandlung heteroepitaktisch auf SOI-Substraten abgeschiedener Halbleiterschichten. Die Erfindung soll insbesondere für die Herstellung elektronischer Bauelemente eingesetzt werden.

  • Patent
    Patentanmeldung Az 101 27 074.7
  • Patent
    DE 101 27 074 A 1

Publ.-Id: 4214

Anordnung zur tomographischen Bildrekonstruktion

Hoppe, D.

Der Erfindung liegt die Aufgabe zugrunde, dass bei Auftreten von Fluid-Gas-Gemischen (2-Phasen-Gemischen) für das Rekonstruktionsobjektbild die Fehler verringert oder vermieden werden.

  • Patent
    Patentanmeldung Az 101 21 998.9
  • Patent
    DE 101 21 998 A1
  • Patent
    DE 101 21 998 B4

Publ.-Id: 4213

Anordnung zur messtechnischen Erfassung einer Projektion des Strahlungsabsorptionsvermögens eines periodisch veränderlichen Messobjekts

Prasser, H.-M.; Zschau, J.

Die Anwendung ist insbesondere als tomographische Anordnung zur Erzeugung von Schnittbildern von Objekten gegeben, deren Gestalt beziehungsweise Zusammensetzung schnellen Änderungen unterworfen ist, und zwar für den Fall, dass die Änderungen sich zeitlich periodisch wiederholen.
Aufgabe der Erfindung ist es, eine Anordnung vorzuschlagen, die auch bei Objekten, deren Gestalt beziehungsweise Zusammensetzung schnellen, sich periodisch wiederholenden Änderungen unterworfen sind, die Ermittlung von Projektionen gestattet, die einen Momentanzustand oder eine Abfolge von Momentanzuständen der periodisch veränderlichen Verteilung des Absorptionsverhaltens repräsentieren und aus denen sich die Verteilungen selbst rekonstruieren lassen und die dabei mit einer kontinuierlich Strahlung aussendenden Gammaquelle auskommt.

  • Patent
    Patentanmeldung Az 101 17 569.8
  • Patent
    DE 101 17 569 C1
  • Patent
    WO 02/080772 A1

Publ.-Id: 4212

Structure and evolution of electric dipole strength in 204,206,208 Pb below the neutron emission threshold

Enders, J.; von Brentano, P.; Eberth, J.; Fitzler, A.; Fransen, C.; Herzberg, R.-D.; Kaiser, H.; Käubler, L.; von Neumann-Cosel, P.; Pietralla, N.; Ponomarev, V. Y.; Prade, H.; Richter, A.; Schnare, H.; Schwengner, R.; Skoda, S.; Thomas, H. G.; Tiesler, H.; Weisshaar, D.; Wiedenhöver, I.

Not available

  • Physics Letters B 486 (2000) 279-285

Publ.-Id: 4210

Experimental Investigation of the Emergency Condenser of the SWR1000

Schaffrath, A.; Hicken, E. F.; Prasser, H.-M.; Palavecino, C.

The experimental investigations of the emergency condenser of the SWR1000 done at Forschungszentrum Jülich is described in detail. After the description of the emergency condenser operation mode and the NOKO Test facility the performance and the evaluation of several bundle tests are presented. From the bundle tests a thermal and a hydraulic condition are developed. Single tube test results are remarked at the end of the presentation.

  • Lecture (others)
    Centro Atomico Bariloche, Argentinien, 28.11.-04.12.2001

Publ.-Id: 4209

Modeling of Condensation inside Horizontal Tubes

Schaffrath, A.; Krüssenberg, A.-K.; Alt, S.

In the presentation the modeling of condensation inside horizontal tubes is described. The differences between condensation in vertical tubes and in horizontal tubes is explained in detail. The development of the improvement KONWAR for the German thermohydraulic program system ATHLET is decribed in detail. Afterwards the validation of this improvement with the two different experiments NOKO (Forschungszentrum Jülich GmbH) and HORUS (Universität Zittau/Görlitz) is presented.

  • Lecture (others)
    Centro Atomico Bariloche, Argentinien, 28.11.-04.12.2001

Publ.-Id: 4208

Investigation of Two Phase Flow in Vertical Pipes

Schaffrath, A.; Krüssenberg, A.-K.; Prasser, H.-M.

In the presentation a description of the investigations concerning flowmaps for vertical pipes done at the institute of safety research are given. That means, the test facility MTLOOP of the institute with its measurement techniques and the test matrix is described in detail. From these experiments a new criterium for the bubble to slug flow transition is presented. Afterwards, the comparison of this criterium to existing flow maps is done.

  • Lecture (others)
    Centro Atomico Bariloche, Argentinien, 28.11.-04.12.2001

Publ.-Id: 4207

TOPFLOW - a new multipurpose test facility for the investigation of transient two phase flows

Schaffrath, A.; Krüssenberg, A.-K.; Weiß, F.-P.; Prasser, H.-M.

In the presentation a description of the new multipurpose thermohydraulic test facility TOPFLOW is given including the construction phase and the main working fields. Then, after the details about flow diagram and facility loayout as well as the building layout the chosen documentatin form via internet and intranet is presented. Ideas concerning possible CAREM system tests in TOPFLOW are summarized, too.

  • Lecture (others)
    Centro Atomico Bariloche, Argentinien, 26.11.-04.12.2001

Publ.-Id: 4206

Spectroscopy of 44,46Ti with the Binary Reaction Spectrometer and Euroball

Thummerer, S.; Gebauer, B.; Bohlen, H. G.; von Oertzen, W.; Bazzacco, D.; Lenzi, S. M.; Algora, A.; de Angelis, G.; Gadea, A.; Napoli, D. R.; Borcan, C.; Dönau, F.; Käubler, L.; Schnare, H.; Schwengner, R.; Peter, I.; Beck, C.; Bhattacharya, C.; Rousseau, M.; Noucier, R.; Lisle, J.

Not available

  • Physica Scripta T 88 (2000) 114

Publ.-Id: 4205

Magnetic rotation in the A = 80 region: M1 bands in heavy Rb isotopes

Schwengner, R.; Schnare, H.; Frauendorf, S.; Dönau, F.; Käubler, L.; Prade, H.; Grosse, E.; Jungclaus, A.; Lieb, K. P.; Lingk, C.; Skoda, S.; Eberth, J.; de Angelis, G.; Gadea, A.; Farnea, E.; Napoli, D. R.; Ur, C. A.; Lo Bianco, G.

We have studied the isotopes 82Rb45, 83Rb46, and 84Rb47 to search for magnetic rotation which is predicted in the tilted-axis cranking model for a certain mass region around A = 80. Excited states in these nuclei were populated via the reaction 11B + 76Ge with E = 50 MeV at the XTU tandem accelerator of the LNL Legnaro. Based on a -coincidence experiment using the spectrometer GASP we have found magnetic dipole bands in each studied nuclide. The regular M1 bands observed in the odd-odd nuclei 82Rb and 84Rb include B(M1)/B(E2) ratios decreasing smoothly with increasing spin in a range of 13-≤Jπ≤16-. These bands are interpreted in the tilted-axis cranking model on the basis of four-quasiparticle configurations of the type π(fp) πg9/22 vg9/2. This is the first evidence of magnetic rotation in the A ≈ 80 region. In contrast, the M1 sequences in the odd-even nucleus 83Rb are not regular, and the B(M1)/B(E2) ratios show a pronounced staggering.

Keywords: in-beam gamma-spectroscopy; magnetic dipole bands

  • Journal of Research of the National Institute of Standards and Technology 105, 133 (2000) 133
    DOI: 10.6028/jres.105.017

Publ.-Id: 4204

Three-quasiparticle excitations in $^{77}$Br

Döring, J.; Funke, L.; Schwengner, R.; Winter, G.

Not available

  • Physical Review C 48 (1993) 2524-2547

Publ.-Id: 4203

Quadrupole moments of high-spin isomers: Test of the tilted-axis cranking model

Balabanski, D. L.; Vyvey, K.; Neyens, G.; Almehed, D.; Blaha, P.; Borremans, D.; Chmel, S.; Coulier, N.; Coussement, R.; de Clercq, W.; Frauendorf, S.; Georgiev, G.; Hubel, H.; Lepine-Szily, A.; Mineva, M.; Nenoff, N.; Pancholi, S.; Rossbach, D.; Schwengner, R.; Teughels, S.; Walker, P.

We report the results of recent measurements of the spectroscopic quadrupole moments of high-spin isomers. For the K-pi = 35/2(-) five-quasiparticle isomer in W-179 we measured Q(B) =4.00 ((+0.83)(-1.06)) eb. It corresponds to a smaller deformation compaxed to the ground states of the W isotopes and is in disagreement with the current theoretical predictions. We also measuredthe quadrupole moment of the I-pi = 11(-) isomer in Pb-196, Q(s) = (-)3.41(66) eb. It has the same proton (s(1/2)(-2)h(9)/(2)i(13/2)) configuration as the one suggested for the 11 = 16(-) magneticbandhead which allows to deduce the quadrupole moment of the 16(-) state as Q(s) = -0.316(97) eb. This small value proves the near sphericity of the bandhead.

  • Acta Physica Polonica B 32 (2001) 2655

Publ.-Id: 4202

Synthesis and biological evaluation of technetium(III) mixed-ligand complexes with high affinity for the cerebral 5-HT1A receptor and the alpha1-adrenergic receptor

Drews, A.; Pietzsch, H.-J.; Syhre, R.; Seifert, S.; Varnäs, K.; Hall, H.; Halldin, C.; Kraus, W.; Karlsson, P.; Johnsson, C.; Spies, H.; Johannsen, B.

Tc(III) and Re(III) complexes [M(NS3)(CNR)] (M = Re, 99mTc, NS3 = 2,2',2''-nitrilotris(ethanethiol), CNR = functionalized isocyanide bearing a derivative of WAY 100635) have been synthesized and characterized. Re was used as Tc surrogate for chemical characterization and in vitro receptor-binding studies. For two representatives subnanomolar affinities for the 5-HT1A as well as for the alpha1-adrenergic receptor were reached. Biodistribution studies in rats of the 99mTc complexes showed brain uptakes between 0.3 and 0.5 % ID/organ (5 min p.i.). In vitro autoradiography of one 99mTc representative in sections of post mortem human brain indicate its accumulation in 5-HT1A receptor-rich brain regions. However, addition of the specific 5-HT1A receptor agonist 8-OH-DPAT as well as the alpha1-adrenoceptor antagonist prazosin could not substantially block this tracer accumulation. A preliminary SPET study in a monkey showed negligible brain uptake.

  • Nuclear Medicine and Biology 29 (2002) 389-398

Publ.-Id: 4201

Kühlmittelvermischung in Druckwasserreaktoren Teil 1: Möglichkeiten geschlossener analytischer Lösungen und Simulation der Vermischung mit CFX-4

Grunwald, G.; Höhne, T.; Prasser, H.-M.; Rohde, U.

Ziel des Vorhabens war die analytische und numerische Simulation der Kühlmittelvermischung im Ringraum und unteren Plenum von Druckwasserreaktoren. Generell ist die Kühlmittelvermischung relevant für zwei große Störfallgruppen - Borsäureverdünnungsstörfälle und Kaltwassertransienten. Zur Untersuchung der Vermischungsphänomene aus diesen Störfallszenarien wurde die Rossendorfer Versuchsanlage ROCOM konzipiert, die ein 1:5 skaliertes Plexiglasmodell des DWR Konvoi darstellt, in dem auch Geschwindigkeitsmessungen mit Hilfe von LDA-Technik möglich sind. Konstruktion, Errichtung und meßtechnische Ausstattung von ROCOM erfolgten in einem 2. Teil des Vorhabens. Im Vorfeld der Errichtung des ROCOM-Versuchsstandes wurden mit Hilfe des dreidimensionalen Strömungsberechnungsprogrammes CFX-4 Skalierungseffekte untersucht. Die Vergleichsrechnungen belegten, daß eine 1:5 Skalierung ausreichend ist. Nach dem Aufbau des Versuchsstandes und der Inbetriebnahme im 2. Teil des Vorhabens wurden die Vorausberechnungen anhand von experimentellen Ergebnissen bestätigt. Es wurde weiterhin ein Verfahren zur vereinfachten analytischen 2D-Beschreibung des Strömungsfeldes im Ringraum von Druckwasserreaktoren aufgestellt. Es beruht auf der Potentialtheorie, wobei Quellen an den Kühlmitteleintrittspositionen und Wirbel unter Beachtung der Randbedingungen der typischen Ringspaltgeometrie von DWR überlagert wurden. Der Schwerpunkt des Projektes lag jedoch in der numerischen Simulation der Kühlmittelvermischung unterschiedlicher Reaktoranlagen mit CFX-4 und der Validierung des Rechenprogramms anhand von Vermischungsexperimenten. Dabei wurden sowohl stationäre Schleifendurchsätze bei Nominalbetrieb und Teilschleifenbetrieb bzw. transiente Strömungsbedingungen der Reaktortypen DWR Konvoi und WWER-440 untersucht. Die Ergebnisse der CFX-4 Rechnungen im Vergleich mit den Leitfähigkeits- bzw. LDA-Messungen sind im Abschlußbericht dokumentiert. Grundlage für diesen Abschlußbericht ist eine Promotionsarbeit von T. Höhne zum gleichnamigen Thema im Rahmen des Kompetenzerhaltungsprogrammes Kerntechnik.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-335 Oktober 2001
    ISSN: 1437-322X


Publ.-Id: 4200

Jahresbericht 2. Halbjahr 1999/2000 Forschungszentrum Rossendorf

Ottow, S.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-327 August 2001
    ISSN: 1437-322X


Publ.-Id: 4199

Group-IV Nanocluster Formation by Ion Beam Synthesis

Skorupa, W.; Rebohle, L.; Gebel, T.

A short review of our investigations devoted to the use of ion beam synthesized nanoclusters for silicon based light emission and nonvolatile memory effects is presented. Blue-violet light emission is demonstrated basing on Ge-implanted silicon dioxide layers thermally grown on silicon substrates. This version of silicon-based light emission relies on Ge-related defects in the amorphous -Si-O-Si- network. The photo (PL) - and electroluminescence (EL) is excited by a singlett S0-S1 transition of neutral oxygen vacancy and by electron injection from the silicon substrate into the silicon dioxide layer, respectively. Whereas the PL excitation is a well-known mechanism, for the case of electroluminescence an interpretation was performed for the first time in the course of our studies. It is found that the most probable way to excite luminescence centers is the impact excitation by hot electrons. Whereas the injection is explained by trap assisted tunneling of electrons from the substrate into the oxide, the electrons will be transported via traps or in the SiO2 conduction band. The application of the silicon-based light emitting devices for an optocoupler arrangement are described. Another application of nanoclusters is basing on the investigation of thin Si-implanted silicon dioxide layers for nonvolatile memory applications. First promising results demonstrated that the observed programming window can reach several volts and the devices exhibit excellent retention behavior. A 256k-nv-SRAM is demonstrated showing a programming window >1V for write pulses of 12V/8ms.

Keywords: ion implantation; ion beam synthesis; silicon dioxide; silicon; germanium; tin; charge trapping; photoluminescence; electroluminescence; integrated optocoupler; nonvolatile memory device

  • Applied Physics A Volume 76(2003)1049-1059

Publ.-Id: 4198

Doppeldiffusive Instabilität beim Flüssig-Flüssig-Stoffübergang: Simulation und Experiment

Grahn, A.

Der Stofftransport über Flüssig-Flüssig-Phasengrenzen führt sehr oft zu hydrodynamischen Instabilitäten und zur Bildung von dissipativen, d. h. konvektiven Strukturen. Zwei Mechanismen liegen diesen Instabilitäten zurunde. Der erste ist mit dem Wirken von Grenzflächenspannungsgradienten in Systemen mit flüssigen oder flüssig-gasförmigen Grenzflächen verbunden und wird als Marangoniinstabilität bezeichnet. Der zweite, als Rayleigh-Bénard-Instabilität bezeichnete Mechanismus wird durch Auftriebskräfte aufgrund lokaler Dichteunterschiede verursacht. In diesem Beitrag soll über experimentelle und numerische Untersuchungen berichtet werden, die an Systemen vorgenommen wurden, bei denen die übergehende Komponente eine chemischen Reaktion an der Grenzfläche eingeht und Auftriebskräfte bei der Ausbildung der Instabilität dominieren.

  • Lecture (Conference)
    GVC/DECHEMA-Jahrestagungen 2002, Wiesbaden, 11.-13.6.2002 Chemie-Ingenieur-Technik 74 (2002), S. 570
  • Contribution to proceedings
    GVC/DECHEMA-Jahrestagungen 2002, Wiesbaden, 11.-13.6.2002 Chemie-Ingenieur-Technik 74 (2002), S. 570

Publ.-Id: 4196

Beta decay of 56Cu

Borcea, R.; Äystö, J.; Caurier, E.; Dendooven, P.; Döring, J.; Gierlik, M.; Górska, M.; Grawe, H.; Hellström, M.; Janas, Z.; Jokinen, A.; Karny, M.; Kirchner, R.; La Commara, M.; Langanke, K.; Martínez-Pinedo, G.; Mayet, P.; Nieminen, A.; Nowacki, F.; Penttilä, H.; Plochocki, A.; Rejmund, M.; Roeckl, E.; Schwengner, R.; Schlegel, C.; Schmidt, K.; Sawicka, M.

The proton-rich isotope 56Cu was produced at the GSI On-Line Mass Separator by means of the 28Si(32S, p3n)
fusion¯evaporation reaction. Its -decay properties were studied by detecting -delayed rays and protons. A half-life of
93±3 ms was determined for 56Cu. Compared to the previous work, six new rays and three new levels were assigned to the
daughter nucleus 56Ni. The measured Gamow¯Teller strength values for five 56Ni levels are compared to shell-model

  • Nuclear Physics A 695 (2001) 69-81

Publ.-Id: 4195

Double-diffusive instability during liquid-liquid mass transfer---simulation and experiment

Grahn, A.

Mass transfer across interfaces in liquid-liquid systems may give rise to hydrodynamic instability and the formation of various dissipative, i. e. convective, structures. There are two basic mechanisms leading to instability. The first one is related to the action of surface tension gradients in systems with free interfaces and is referred to as Marangoni effect while the second one is related to buoyancy forces and is referred to as Rayleigh-B'enard instability. Convection at the interface and in the bulk of the liquids greatly enhances mass transfer rates. This paper reports on experimental and numerical studies which have been carried out on systems where the transferred species undergoes a chemical reaction at the interface and buoyancy forces predominate.

Keywords: double-diffusive instability; hydrodynamic instability; convective instability; buoyancy; liquid-liquid mass transfer; fingers; fingering; fingering criterion; interface; interfacial reaction; simulation; CFD; visualization

  • Lecture (Conference)
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, pp. 293-300
  • Contribution to proceedings
    HEAT 2002: Third International Conference Transport Phenomena in Multiphase Systems, Baranow Sandomierski, Poland, June 24-27, 2002, pp. 293-300

Publ.-Id: 4194

Numerical investigation and measurement of transient two-phase boiling flow

Yeoh, G. H.; Tu, J. Y.; Krepper, E.; Prasser, H.-M.

Transient boiling is examined for conditions related to the hypothetical heating of liquids in a storage tank by an external fire, with the potential for evaporation of the liquids and the release of toxic gases into the environment. Temperature and void fraction distribution data were obtained from an experiment on water heated in a tank. Numerical simulations were also performed. These generally agreed reasonably well with measurements.

  • Lecture (Conference)
    14th Australasian Fluid Mechanics Conference, Adelaide Australia, 10-14 December 2001, Proceedings pp. 865-868
  • Contribution to proceedings
    14th Australasian Fluid Mechanics Conference, Adelaide Australia, 10-14 December 2001, Proceedings pp. 865-868

Publ.-Id: 4193

Jahresbericht 1999/2000 Abteilung Kommunikation und Datenverarbeitung, FZR-324

Fülle, R.

Bericht über Dienste und Weiterentwicklung der IT-Infrastruktur des FZR im Zeitraum 1999 bis 2000 in den Tätigkeitsbereichen Zentrale Server, Datennetz und Benutzerservice.

Keywords: IT-Infrastruktur; Server; Datennetze; Benutzerservice

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-324 Juli 2001
    ISSN: 1437-322X


Publ.-Id: 4192

On back-reaction effects in the Riga dynamo experiment

Gailitis, A.; Lieleausis, O.; Platacis, E.; Gerbeth, G.; Stefani, F.

The most prominent back-reaction effects observed in the Riga dynamo experiment are presented and a preliminary interpretation of them is given.

  • Magnetohydrodynamics, Vol. 38, No. 1/2 (2002), pp. 15-26

Publ.-Id: 4191

Microscopy of ion-beam generated fluorescent color-center patterns in LiF

Martin, J.; Bischoff, L.; Wannemacher, R.

Color centers have been generated on [100] surfaces of LiF crystals by irradiation with a focussed beam of 35 keV Ga+ ions at room temperature and at 240 K. The luminescence of two centers at 655 and 540 nm, ascribed to F2 and F3+ centers, respectively, has been detected and spatially resolved, with spatial resolution in the range of 1 µm, by imaging microscopy, as well as by laser scanning confocal microscopy. Diffusion and pinning of color centers have been observed directly in this way. Due to the high intensity in the focal spot of the confocal microscope nonlinear photophysical and photochemical processes are observed. For example an additional emission at 775 nm could be detected at high excitation density. The luminescence band is tentatively ascribed to radiative triplet-triplet emissions of F2 centers after recombination of F2+ centers with an electron.

Keywords: color centres; laser; LiF

  • Optics Communications 188 (1-4) (2001) 119-128

Publ.-Id: 4190

Complex Formation of Uranium(VI) with Fructose and Glucose Phosphates

Koban, A.; Geipel, G.; Bernhard, G.; Fanghänel, T.

The uptake of heavy metals into plants is commonly quantified by the soil-plant transfer factor. Up to now little is known about the chemical speciation of actinides in plants. To compare the obtained spectroscopic data of uranium complexes in plants with model compounds, we investigate the complexation of uranium with relevant bioligands of various functionalities. A very important class of ligands are phosphate esters, which serve as phosphate group and energy transmitters as well as energy storage mediums in biological systems. Heavy metal ions bound to the phosphate esters can be transported into living cells and than deposited.
Therefore, in our study we present the results of uranium complexation with glucose-6-phosphate (G6P), and fructose-6-phosphate (F6P) obtained by time-resolved laser-induced fluorescence spectroscopy (TRLFS). The experiments were performed at a fixed uranyl concentration (10-5 M) as a function of the ligand concentrations (10-5 to 10-3 M) in a pH range from 2 to 4.5.
For the glucose phosphate system we observed, using increasing ligand concentrations, a decreased fluorescence intensity and a small red shift of the emission bands. From this we conclude that the complexed uranyl glucose phosphate species either show only minor or no fluorescence properties. The TRLFS spectra of the glucose phosphate samples indicated the presence of only one species with fluorescence properties. This species has a lifetime of approximately 1.5µs and was identified as the free uranyl ion.
An opposite phenomenon was observed for the fructose phosphate system: There was no decrease of fluorescence intensity. However, a strong red shift of the spectra was observed illustrating the fluorescence properties of the uranyl fructose phosphate complex. The TRLFS spectra of the fructose phosphate system showed a second lifetime (<1µs) belonging to the complexed species.
The concentration of the free uranyl ion was determined on the basis of the measured fluorescence spectra. These data were used to calculate the corresponding concentrations of the uranyl sugar phosphate complexes and the non complexed ligands. The complex formation reaction is assumed to be:
x lig + UO22+ <==> UO2(lig)x(2-y)+ + y H+ (lig = sugar phosphate)
Applying the mass action law and transformation to the logarithmic scale, we obtain:
log {[UO2(lig)x(2-y)+] / [UO22+]} = x log[lignonkomplexed] - y log[H+] + logK

From this we conclude, that 1:1 uranyl sugar phosphate species UO2(ROPO3) (R is either glucose or fructose) has formed. Using these data complex formation constants for the complexes were calculated to be in the range of logK=3.7 for G6P and 3.2 for F6P.

Keywords: uranium complexes; sugar phosphates; complex formation constants

  • Lecture (Conference)
    14th Radiochemical Conference Marianske Lazne, Czech Republic, 14 - 18 April 2002

Publ.-Id: 4186

Tomographisches Messverfahren für die Gasverteilung in einer Axialpumpe bei Zweiphasenbetrieb

Baldauf, D.; Christen, M.; Fietz, J.; Hampel, U.; Hoppe, D.; Prasser, H.-M.; Will, G.; Zippe, C.; Zschau, J.

Bei einer Vielzahl von natürlichen und technischen Strömungsvorgängen besteht das strömende Medium aus mehreren Phasen. Bei der Förderung derartiger Medien mit Kreiselpumpen führen bislang nicht genügend bekannte Vorgänge bei bestimmten Betriebsbedingungen zu einer starken Verringerung der Förderleistung und einem Anstieg des Leistungsbedarfs. Bei der Förderung von gasbeladenen Flüssigkeiten kann ein zu hoher Gasanteil zum vollständigen Zusammenbruch der Förderung führen. Zusätzlich führt die erosive Wirkung von Kavitation zu einer starken Minderung der Lebensdauer der Pumpe.

Diese Arbeit beschreibt ein neuartiges Verfahren, das es erstmals gestattet, die Methode der Gamma-Tomographie zur Bestimmung der örtlichen Phasenverteilung innerhalb von rotierenden Pumpenläufern und ähnlichen Bauteilen anzuwenden. Dabei wird eine Zeitauflösung von ca. 100 µs erreicht, mit der die Gasverteilung wesentlich genauer als bisher erfaßt werden kann. Mit dem Tomographen wurden die Vorgänge innerhalb des Läufers einer Axialpumpe bei Förderung eines Luft-Wasser-Gemischs visualisiert. Es wird gezeigt, wie sich die Änderung äußerer Strömungsparameter und die Variation des Arbeitspunktes auf die räumliche Phasenverteilung innerhalb des Läufers auswirkt.

Keywords: Tomographie; Gamma-Tomographie; Kreiselpumpe; Axialpumpe; Phasenverteilung; Gasverteilung; Mehrphasenströmung; Zweiphasenströmung

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-336 November 2001
    ISSN: 1437-322X


Publ.-Id: 4184

Structure of high-spin states in 91Sr and 92Sr

Stefanova, E.; Danchev, M.; Schwengner, R.; Balabanski, D.; Carpenter, M.; Djongolov, M.; Fischer, S.; Hartley, D.; Janssens, R.; Mueller, W.; Nisius, D.; Reviol, W.; Riedinger, L.; Zeidan, O.

The nuclei $^{91}$Sr and $^{92}$Sr were produced at high spin as fission fragments following the fusion reaction $^{36}$S + $^{159}$Tb at 165 MeV. Gamma rays were detected with the Gammasphere array. The level schemes of
$^{91}$Sr and $^{92}$Sr were extended up to $E \approx$ 6 MeV and $E \approx$ 8 MeV, respectively. Level structures in $^{91}$Sr and $^{92}$Sr were interpreted in terms of the shell model. The calculations were performed in the configuration space $(0f_{5/2}, 1p_{3/2}, 1p_{1/2}, 0g_{9/2})$ for the
protons and $(1p_{1/2}, 0g_{9/2}, 1d_{5/2})$ for the neutrons. Negative-parity states in the yrast sequences are described in these calculations by coupling $3^-$ proton excitations to the unpaired $1d_{5/2}$ neutrons. A possible reduction of the gap between the proton $1p_{3/2}$ and $1p_{1/2}$ orbitals in
$^{92}$Sr is discussed.

Keywords: Nuclear structure; In-beam spectroscopy; Gammasphere detector array; Shell-model calculations

  • Physical Review C, Vol. 65, 034323

Publ.-Id: 4182

TOPFLOW - a new multipurpose thermalhydraulic test facility for the investigation of steady state and transient two phase flow phenomena

Schaffrath, A.; Krüssenberg, A.-K.; Weiß, F.-P.; Hicken, E.-F.; Beyer, M.; Carl, H.; Prasser, H.-M.; Schuster, J.; Schütz, P.; Tamme, M.

The Forschunszentrum Rossendorf (FZR) e.V. is constructing a new large-scale test facility, TOPFLOW, for thermalhydraulic single effect tests. The acronym stands for Transient Two Phase Flow Test Facility. It will mainly be used for the investigation of generic and applied steady state and transient two phase flow phenomena and the development and validation of models of Computational Fluid Dynamic (CFD) Codes.

Keywords: TOPFLOW; thermalhydraulic test facility

  • Kerntechnik 66 (2001) 4 209-212

Publ.-Id: 4181

Simulation of subcooled flow instability for high flux research reactors with ATHLET

Hainoun, A.; Schaffrath, A.

The ATHLET code has been improved and validated for the safety analysis of high flux research reactors against experimental data of the Thermalhydraulic Test Loop of Oak Ridge National Laboratory (ORNL). Therefore, an extensive series of "stiff mode" experiments were recalculated. The comparison between experiments and ATHLET posttest calculations shows that the extended code simulates accurately the thermalhydraulic conditions and the flow instabilities in a wide range of inlet velocity, head and mass flux.

Keywords: research reactor; ATHLET; flow instability

  • Kerntechnik 66 (2001) 4,214-216

Publ.-Id: 4180

Solution of the 6. Dynamic AER Benchmark Using the Coupled Code DYN3D/ATHLET

Seidel, A.; Kliem, S.

The 6th dynamic benchmark is a logical continuation of the work to validate systematically coupled neutron kinetics / thermohydraulics code systems for the estimation of the transient behaviour of VVER type nuclear power plant which was started in the 5th dynamic benchmark. This benchmark concerns a double ended break of one main steam line (asymmetrical MSLB) in a VVER-440 plant. The core is at the end of first cycle in full power conditions. The asymmetric leak causes a different depressurization of all steam generators. New features in comparison to the 5th dynamic benchmark were included: asymmetric operation of the feed water system, consideration of incomplete coolant mixing in the reactor vessel, and the definition of a fixed isothermal recriticality temperature for normalising the nuclear data.

The solution of this benchmark was obtained by means of coupled code system DYN3D/ATHLET. There, the whole core including neutron kinetics and thermohydraulics processes was calculated by three dimensional neutron kinetics core model DYN3D. The thermal hydraulics behaviour of primary and secondary circuit was modelled by the system code ATHLET.
For the purpose of realisation of the fixed isothermal recriticality temperature Trecrit = 210°C the cross section data of absorber were adapted.

During the transient calculation of MSLB scenario, the reactor scram was initiated with the assumption that two of the most reactive control rods in the sector of highest overcooling are stuck at their fully withdrawn position. Accordingly, the power is decreased due to reactor scram. Thereafter, the reactivity feedback caused by the decrease of coolant temperature entailed the increase of the reactor power. Based on an assumed delayed start of the high pressure safety injection, the recriticality of the shut-off reactor is achieved. The value of total power in the second maximum is about 80 MW.

In this paper the behaviour of the main thermohydraulic and neutron kinetic parameters is presented.

  • Lecture (Conference)
    11. AER Symposium on VVER Reactor Physics and Reactor Safety, Csopak, Hungary, September 24-28, 2001, Proceedings pp. 251-267
  • Contribution to proceedings
    11. AER Symposium on VVER Reactor Physics and Reactor Safety, Csopak, Hungary, September 24-28, 2001, Proceedings pp. 251-267

Publ.-Id: 4179

Complex formation between uranium(VI) and calix[6]arenes studied by time-resolved laser-induced fluorescence spectroscopy

Schmeide, K.; Geipel, G.; Keil, D.; Heise, K. H.; Bernhard, G.; Gloe, K.

Seepage and mine waters of the abandoned uranium mining and milling sites in Saxony and Thuringia are contaminated by uranium and its decay products. Therefore, efficient water purification technologies are necessary.
The separation of uranium(VI) from aqueous solution by calixarenes by means of solvent extraction is described in the literature. Calixarenes are macrocyclic molecules formed by 4, 6 or 8 para-substituted phenolic units linked by methylene bridges ortho to the OH functions. Thus, molecules of different ring sizes are formed. Especially calix[6]arenes functionalized with carboxylic or hydroxamic groups on the lower rim are suitable to separate uranium from aqueous solution.
In the present work, the extraction efficiency of various carboxylate derivatives of calix[6]arene, e.g., carboxymethoxy-p-tert-octyl-calix[6]arene, including their selectivity towards uranium(VI) is studied in a two phases solvent extraction system in dependence on pH value and the amount of competing ions in aqueous solution as well as in dependence on ligand concentration and solvent. The complex formation between uranium(VI) and calix[6]arenes is further studied by means of time-resolved laser-induced fluorescence spectroscopy (TRLFS). Uranium species are identified, complex formation constants are determined, and reaction mechanisms are discussed. The suitability of the calix[6]arenes as efficient reagents for selective separation of uranium from aqueous solution, even in the acidic pH region, is shown.

Keywords: Uranium; calixarene; complexation; solvent extraction; TRLFS; laser spectroscopy

  • Invited lecture (Conferences)
    14th Radiochemical Conference, 14.-19.04.2002, Mariánské Lázné, Czech Republic

Publ.-Id: 4178

Schwingungsmodellierung von WWER-Reaktoren zur Untersuchung von Störfallszenarien

Werner, M.; Altstadt, E.; Perov, S.

In einem gemeinsamen Vorhaben mit dem Diagnosezentrum für russische Kernkraftwerke (DIAPROM Moskau) wurde ein Beitrag zur verbesserten Beurteilung der mechanischen Integrität von Reaktoren der russischen WWER-Baureihen, insbesondere zur empfindlichen Früherkennung und Lokalisation mechanischer Schädigungen an Reaktorkomponenten mit Hilfe schwingungsdiagnostischer Methoden geleistet. Zu diesem Zweck wurde für den WWER-440 und WWER-1000 das mechanische Schwingungsverhalten aller Primärkreiskomponenten mit finiten Elementen (FE) modelliert. Dafür wurde das Programmpaket ANSYS® genutzt.
Der Einfluss des strömenden Kühlmittels auf die schwingenden mechanischen Strukturen ist im Rahmen der Fluid-Struktur-Interaktion (FSI) berücksichtigt worden. Die Berechnungsmodelle wurden mit Ergebnissen experimenteller Schwingungsuntersuchungen justiert. Zum Teil konnte auf aktuelle Messungen zurückgegriffen werden. Die Modelle können als weitgehend verifiziert gelten. Diese wurden in der Hauptsache genutzt, um zu klären, wie sich unterstellte mechanische Defekte von Reaktoreinbauten auf die Schwingungen der Gesamtanlage auswirken. Diese Schadenssimulation ist besonders geeignet, empfindliche Messpositionen für die on-line Überwachung zu finden und physikalisch fundierte Grenzwerte zu definieren.
Die entwickelten Modelle sind grundsätzlich auch geeignet, um Lastabschätzung für die Reaktorkomponenten bei Einwirkung von außen (Explosion, Erdbeben) vorzunehmen.

  • Lecture (Conference)
    27. MPA-Seminar, Sicherheit und Verfügbarkeit in der Energietechnik, Band 1 und 2, Stuttgart, 4 .- 5. 10. 2001, Artikel 9
  • Contribution to proceedings
    27. MPA-Seminar, Sicherheit und Verfügbarkeit in der Energietechnik, Band 1 und 2, Stuttgart, 4 .- 5. 10. 2001, Artikel 9

Publ.-Id: 4176

Memory properties of Si+ implanted gate oxides: From MOS capacitors to nvSRAM

von Borany, J.; Gebel, T.; Stegemann, K.-H.; Thees, H.-J.; Wittmaack, M.

Charge storage properties of 20-30 nm gate oxides implanted with Si+ ions are investigated using MOS capacitors, single transistor structures and a non-volatile memory. The observed programming window can reach several volts for programming with electric fields of about 4-7 MV/cm. The structures exhibit good retention (250°C, 280h) and the endurance (>106 w/e-cycles) considerably exceeds the typical values of present EEPROM technologies. The capability of Si implanted SiO2 films as gate dielectrics for a real non-volatile memory is demonstrated for the first time by a 256k - nvSRAM showing a programming window of larger than 1 volt.

Keywords: ion implantation; nanoclusters; non-volatile memory

  • Solid State Electronics 46 (2002) 1729-1737

Publ.-Id: 4175

Radiobiological hypoxia, oxygen tension, interstitial fluid pressure and relative viable tumour area in two human squamous cell carcinomas in nude mice during fractionated radiotherapy.

Baumann, M.; Appold, S.; Zimmer, J.; Scharf, M.; Beuthien-Baumann, B.; Dubben, H. H.; Enghardt, W.; Schreiber, A.; Eicheler, W.; Petersen, C.

no abstract

Keywords: Radiobiological Hypoxia; Oxygen Tension; Human Squamous Cell Carcinomas

  • Acta Oncologica, Vol. 40, No. 4 (2001) 519-528

Publ.-Id: 4174

Fast wire-mesh sensors for gas-liquid flows and decomposition of gas fraction profiles according to bubble size classes

Prasser, H.-M.; Krepper, E.; Lucas, D.

The wire-mesh sensor developed by the Forschungszentrum Rossendorf produces measuring sequences of instantaneous gas fraction distributions in a cross section at a rate of up to 10 000 frames per second and a spatial resolution of about 2-3 mm. This sensor was applied to an upwards air-liquid flow in a vertical channel. After a brief introduction of the functioning of the sensor, the paper presents results obtained at a rate of 1200 frames per second, which were used to study the evolution of bubble size distributions and radial gas fraction profiles along the pipe, starting at a relative distance of L/D=0.6 above the gas injection and ending at L/D=60. The developed bubble identification algorithm allows to select bubbles of a given range of the effective diameter and to calculate partial gas fraction profiles for this diameter range. In this way, the different behaviour of small and large bubbles in respect to the action of the lift force was observed in a mixture of small and large bubbles. Furthermore, the paper presents results of a flow visualisation at the rate of 10 000 frames per second, showing details of the flow structure in the region of transition to annular flow.

Keywords: two-phase flow; gas-liquid flow; bubble size; bubbly flow; wire-mesh sensor; void fraction measurement

  • Lecture (Conference)
    5th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, Thessalonoki, Greece, 24-28 September 2001, Vol. 2, pp. 1135 - 1140.
  • Contribution to proceedings
    5th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, Thessalonoki, Greece, 24-28 September 2001, Vol. 2, pp. 1135 - 1140.

Publ.-Id: 4173

Methods for studies on bubbly flow characteristics applying an electrode-mesh tomograph

Richter, S.; Aritomi, M.; Prasser, H.-M.; Hampel, R.

For studies on the characteristics of bubble flow in a rectangular channel (20x100mm) an electrode-mesh tomograph has been applied. The measuring principle is based on local conductivity measurement. The applied sensor scans the local void fraction distribution in 2 parallel planes, separated 1.5mm in flow direction, with a resolution of 6.1x2.2mm and an overall sampling rate of 1200Hz (all 256 points). Algorithms for the calculation of the local instantaneous void fraction distribution and the true gas velocity are presented. Based on these values the approximate shape of bubbles has been reconstructed and the gas volume flow through the sensor evaluated. The superficial gas velocity as well as the local distribution of the gas volume flux was
calculated. Finally, bubble diameter spectra have been obtained and the statistical behavior of the bubble rising velocity in its dependency from bubble diameter in a turbulent flow of high void fraction has been investigated. An extensive sensitivity study illustrating the applicability and accuracy is presented, based on experimental observations as well as theoretical considerations. The evaluated results are compared with high-speed video observations of the flow field as well as data comparing the reconstructed volume flow with measurements by a laminar flow meter. Good agreement can be stated.

Keywords: two-phase flow; void fraction measurement; wire-mesh sensor; bubbly flow

  • Lecture (Conference)
    Vortrag und Beitrag zu Sammelwerken (Proc., etc.): 4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001. Proc. CD-ROM, paper 848.
  • Contribution to proceedings
    Vortrag und Beitrag zu Sammelwerken (Proc., etc.): 4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001. Proc. CD-ROM, paper 848.

Publ.-Id: 4171

Dynamo experiments at the Riga sodium facility

Gailitis, A.; Lielausis, O.; Platacis, E.; Dement'Ev, S.; Cifersons, A.; Gerbeth, G.; Gundrum, T.; Stefani, F.; Christen, M.; Will, G.

We summarize the history and the results of the first successful hydromagnetic dynamo experiment which was prepared and run at the Institute of Physics in Riga, Latvia.

  • Magnetohydrodynamics, Vol. 38, No. 1/2 (2002), pp. 5-14

Publ.-Id: 4170

Subband physics in semiconductor quantum structures and the Rossendorf FEL programme

Helm, M.

The electronic confinement in semiconductor quantum wells gives rise to the formation of electronic subbands within the conduction or valence band. Due to the same curvature of initial and final subband, intersubband optical transitions (within one band) exhibit a quasi-zero-dimensional joint density of states and therefore resemble atomic transitions in some way. The typical energy spacing from 10 to a few 100 meV corresponds to the far- and mid infrared spectral range. Thus, for the study of nonlinear or time resolved phenomena in these structures, IR free-electron lasers are among the most – or the only – suitable light sources.

As an example, I will review some experiments on the energy relaxation of electrons in wide GaAs/AlGaAs quantum wells, performed with FELIX.

Transitions between minibands in strongly coupled superlattices exhibit a one-dimensional joint density of states, and I will show how the dispersion along the growth axis can be employed to study the electron distribution function.

Finally I will present the status of the ELBE project at the Forschungszentrum Rossendorf near Dresden. This project comprises a superconducting electron accelerator, providing the electron beam for two undulators. The latter form the heart of the FELs, which are planned to operate from 5 to 25 microns and 20 to 100 (or 150) microns, respectively. First lasing is expected for early 2002.

Keywords: semiconductor

  • Lecture (Conference)
    Mini-symposium on "Applications of Free Electron Lasers" (17.-20.9.2001), Grasmere, UK

Publ.-Id: 4169

Infrared spectroscopy of semiconductor quantum structures and the ion-beam and free-electron-laser facilities at Rossendorf

Helm, M.

First I will give a brief overview of my institution, the Research Center Rossendorf near Dresden. Though much smaller than LBNL, its activities also cover a wide range from Nuclear Physics over Materials Science to Radiochemistry and Biomedical Research. The Institute of Ion Beam Physics and Materials Research accommodates a large ion beam center (with ions from eV to MeV available), other local groups have been involved in the construction of the superconducting electron accelerator ELBE, which will, apart from other applications, be the basis of an infrared free-electron laser (FEL). This FEL, whose first lasing is expected in early 2002, will be used for semiconductor spectroscopy as well as for studies on biological samples.

In the second part of my talk I will stroll around two of the main playgrounds for infrared spectroscopy of semiconductor quantum structures: the physics of intersubband transitions in quantum wells, which have brought us novel infrared lasers and detectors, and the physics of Bloch oscillations in superlattices, which are supposed to bring us a tunable THz source at some point. Finally I will present some infrared experiments concerning the electron distribution function in superlattices, performed with a step-scan FTIR with sub-microsecond time resolution, and will be touching on the issue of appropriate narrow- and broad-band infrared and THz sources.

Keywords: semiconductor; infrared

  • Lecture (others)
    Vortrag am Lawrence Berkeley National Laboratory (6.9.2001)

Publ.-Id: 4168

Structural and micromechanical properties of ion-beam mixed tungsten-on-steel system

Jagielski, J.; Piatkowska, A.; Matz, W.; Richter, E.; Gawlik, G.; Turos, A.

Structural and micromechanical properties of ion-beam mixed tungsten layers were studied. 45 nm thick W layers deposited on HSS substrates were Kr-ion-beam mixed at temperatures ranging from RT up to 450°C. The samples mixed at RT are amorphous. Increase of the process temperature results in the formation of crystalline layers. Amorphous layer are characterized by low friction coefficient and relatively low hardness. Crystallization of layers results in the increase of their hardness and friction coefficient. Wear rates of ion-beam mixed layers are always lower when compared with untreated steel substrates. The results are discussed in the frames of the model assuming the presence of thin, soft layer on hard substrate.

Keywords: ion-beam mixing; amorphous metals; friction; hardness; wear; x-ray diffraction

  • Vacuum 63 (2001) 671-677

Publ.-Id: 4167

Hardness in Ag/Ni, Au/Ni and Cu/Ni multilayers

Schweitz, K. O.; Chevallier, J.; Bottiger, J.; Matz, W.; Schell, N.

By use of nanoidentation, the hardness was measured in dc-magnetron sputterd Ag/Ni, Au/Ni and Cu/Ni multilayers as a function of the modulation period. In a limited modulation period range, the expression k*lambda**(-n) where k and n are fitting parameters and lambda is the modulation period, was fitted to the curves of hardness versus modulation period for the three types of multilayer. The exponent n of Ag/Ni was found to deviate by a factor of three from the n value of Au/Ni, which is surprising since no significant difference exists between the lattice parameters, shear moduli, morphologies and microstructures of the two systems. The results are discussed considering theoretical models and published experimental data.

Keywords: multilayers; hardness; X-ray diffraction; synchrotron radiation; ROBL

  • Philosophical Magazine A, 81 (2001) No. 8, 2021-2032

Publ.-Id: 4166

Comparison of the Results of the 6. Dynamic AER Benchmark - Main Steam Line Break in a NPP with VVER-440

Kliem, S.; Seidel, A.

The sixth dynamic AER benchmark is used for the continuation of a systematic validation of coupled 3D neutron kinetic/thermohydraulic system codes. In this benchmark, a hypothetical double ended break of one main steam line (asymmetric MSLB) at full power in a VVER-440 plant is investigated. The main thermohydraulic features are the consideration of incomplete coolant mixing inside the reactor pressure vessel and an asymmetric operation of the feed water system. For the tuning of the different nuclear cross section data used by the participants, an isothermal recriticality temperature was defined.

Solutions were received from VTT Energy Espoo (HEXTRAN/SMABRE), Kurchatov Institute Moscow (BIPR8/ATHLET), KFKI AEKI Budapest (KIKO3D/ATHLET), NRI Rez (RELAP-3D) and Forschungszentrum Rossendorf (DYN3D/ATHLET). This paper gives an overview on the behaviour of the main thermohydraulic and neutron kinetic parameters in the provided solutions. In all calculations, the overcooling after leak opening leads to a power rise and the activation of the reactor scram. The continuing overcooling after reactor scram results in a second power rise in all calculations. This power rise is eventually stopped by the injected highly-borated water from the high pressure injection system. Differences in the gradient of overcooling and different moderator temperature coefficients (MTC) in the used nuclear data are responsible for a spreading of the time of scram activation over several seconds in the various calculations. Differences in the thermohydraulic behaviour of the secondary side (modeling of the steamgenerator and the critical flow) together with the mentioned different MTC cause significant differences in the value of the second power peak.

  • Lecture (Conference)
    11. AER Symposium on VVER Reactor Physics and Reactor Safety, Csopak, Hungary, September, 24-28, 2001, Proceedings pp. 295-329
  • Contribution to proceedings
    11. AER Symposium on VVER Reactor Physics and Reactor Safety, Csopak, Hungary, September, 24-28, 2001, Proceedings pp. 295-329

Publ.-Id: 4165

The Saturation Regime of the Riga Dynamo Experiment: Observational Facts and their Interpretation

Gailitis, A.; Lielausis, O.; Platacis, E.; Gerbeth, G.; Stefani, F.

In the Riga dynamo experiment, a helical flow with a velocity up to 15 m/s is produced by a motor driven propeller. This flow is free enough to be modified by the Lorentz forces in a non-trivial manner.
In addition to the increase of the necessary motor power due to the axial components of the Lorentz force, we observed a significant deformation of the magnetic field structure and a shift of the eigenvalue. Both observations can be explained by the downward accumulating brake effect of the azimuthal Lorentz force component.
The occurence of a triple frequency in the magnetic field spectrum gives indications for the action of the non-axisymmetric parts of the Lorentz forces on the flow.

  • Lecture (Conference)
    4. MHD-Tage, Ruhr-Universität Bochum, 01-02 Oktober 2001

Publ.-Id: 4162

Development and Application of a Fast Running Model for the Description of Coolant Mixing Inside the Pressure Vessel of Pressurized Water Reactors

Kliem, S.; Prasser, H.-M.; Höhne, T.; Rohde, U.

An efficient semi-analytical model for the description of the coolant mixing during stationary and transient processes inside the reactor pressure vessel (RPV) of pressurised water reactors (PWR) has been developed. Both boron concentration and coolant temperature mixing are described by a dimensionless mixing scalar which is transported with the fluid and is subject of turbulent dispersion, but does not affect the flow field. This model is based on the technique of linear superposition of response functions on Dirac impulse shaped perturbations of the mixing scalar. In the model, the RPV is represented formally by a group of transfer systems (for each combination of inlet nozzle position and fuel element position one) with one input and one output each. These systems have different transfer properties which are determined by the flow field and turbulent mixing being strongly dependent on geometrical details of the flow domain. In this work, one way of obtaining the transfer properties is shown on the example of the German PWR KONVOI. The validation of the model against experimental data from the 1:5 scaled coolant mixing test facility ROCOM is presented.
The semi-analytical model for the description of coolant mixing has been used in combination with the 3D reactor dynamics code DYN3D for the analysis of a hypothetical boron dilution event after start-up of the first main coolant pump (MCP) in a generic four-loop PWR. The model provides realistic time-dependent boron concentration fields at the core inlet. By varying the initial plug volume it was found, that for the given core configuration plugs of less than 20 m3 did not lead to a re-criticality of the shut-off reactor.
Besides the modelling of the coolant mixing inside the RPV, a proper description of the boron transport in the reactor core in the considered case was absolutely necessary to calculate the neutron kinetic behaviour of the core correctly. Otherwise the numerical diffusion distorts the boron front and the reactivity insertion is smoothed artificially. In DYN3D, a particle-in-cell method is used to describe the boron transport without numerical diffusion.
The semi-analytical model is not restricted to one reactor type. The transfer properties used in the model can be explored also by means of computational fluid dynamics codes (CFD). The use of calculated response functions allows to apply the model for the description of coolant mixing in different geometry (i.e. RPV of VVER) and under various conditions without performing additional experiments.

  • Lecture (Conference)
    11. AER Symposium on VVER Reactor Physics and Reactor Safety, Csopak, Hungary, September 24-28, 2001, Proceedings pp. 449-463
  • Contribution to proceedings
    11. AER Symposium on VVER Reactor Physics and Reactor Safety, Csopak, Hungary, September 24-28, 2001, Proceedings pp. 449-463

Publ.-Id: 4161

Information About a New Neutron-Gamma Reactor Experiment

Böhmer, B.; Hansen, W.; Konheiser, J.; Mehner, H.-C.; Noack, K.; Unholzer, S.

Presently, no experimental benchmark data are available allowing to test calculations of gamma spectra in neutron-gamma reactor environments. As newer findings indicate a possible influence of gamma radiation on reactor pressure vessel embrittlement, a neutron-gamma experiment using NE213 scintillation spectrometry to measure gamma and neutron spectra in iron-water slabs has been started at the training reactors of the Technical University Dresden and the University of Applied Sciences Zittau/Goerlitz. The measured data will be used to test the accuracy of Monte Carlo Calculations of gamma and neutron spectra in environments typical for pressure vessel dosimetry applications. Particularly, the code Monte Carlo code TRAMO will be validated in connection with the nuclear data library ENDF/B-VI. After a description of the experimental facilities, the schedule of measurements and the applied measurement and calculation methods are described.

Keywords: Gamma fluence spectrum; neutron fluence spectrum; benchmark experiment; NE-213 scintillation spectrometer; nuclear data

  • Lecture (Conference)
    WGRD VVER Meeting, April 23 -25, 2001, Rez, Czech Republic

Publ.-Id: 4160

Dort-MCNP Discrepancies for a Simple Testing Model - Proposal of a Calculational Neutron-Gamma Benchmark.

Böhmer, B.; Borodkin, G.; Kumpf, H.

Discrepancies found between DORT and MCNP calculation results for neutron and gamma fluxes in the surveillance and PV regions of a PWR gave the impulse for this work. As nuclear data were suspected to be the reason for these discrepancies a simple 2-zone one-dimensional cylindrical model was defined, allowing to exclude modeling uncertainties and to calculate fluxes in outer zones made of pure materials, as H2O, Fe, Cr, Ni. Compared were the neutron flux integrals over energy regions E<0.414 eV, E >0.0, 0.1, 0.5, 1.0, 3.0 MeV and the gamma flux integrals over energy regions E>0.0, 1.0, 3.0 MeV calculated with DORT-3D-synthesis/BUGLE-96 and MCNP-4B/ENDF/-B-VI at 12-15 radial points in core and outer zones. The reasons of the found discrepancies are not simply to understand. One important difference is the group approximation in DORT/BUGLE and the different treatment of resonance effects. Another is the different treatment of cross sections in the thermal region.
As the used model is supposed to be of general interest for testing codes and data , a detailed specification of the model is given as appendix. It is proposed to be used as benchmark model for coupled neutron-gamma flux calculations, including comparisons with the presented calculation results.

Keywords: Neutron and gamma spectra; coupled neutron-gamma flux calculations; benchmark model; nuclear data

  • Lecture (Conference)
    WGRD VVER Meeting, April 23 -25, 2001, Rez, Czech Republic

Publ.-Id: 4158

Fehlerermittlung mit neuronalen Netzen

Schmitt, W.

Es werden die Grundlagen der Fehlerermittlung an technischen Anlagen und Prozessen mit Hilfe von neuronalen Netzen vorgestellt. Vor ihrer Anwendung als Fehlerklassifikator müssen neuronale Netze zunächst mit den Messdaten der normalen und gestörten Betriebszustände unter Zuhilfenahme von Expertenwissen trainiert werden, um das Anlagen- und Prozessverhalten bis hin zum Entscheidungsresultat zu implementieren. Nach diesem überwachten Lernprozess kann das trainierte Netz zur Fehlerermittlung genutzt werden.
Da diese Methode ohne die zeit- und kostenintensive analytische Modellierung des Anlagen- und Prozessverhaltens auskommt, können neuronale Netze vor allem bei komplexen, nichtlinearen Prozessen vorteilhaft zur Fehlerermittlung eingesetzt werden. Die Methodik und die Probleme bei der Anwendung in der industriellen Praxis werden am Beispiel dreischichtiger Perceptron-Netze ausführlich beschrieben.

  • Lecture (Conference)
    DECHEMA-Kursus "Sicherheitstechnik in der chemischen Industrie", 17.09. - 21.09.2001, Universität Dortmund, in Modul II: Methoden der Schwachstellen- und Risikoanalyse, S. 1-20

Publ.-Id: 4156

Innovationskolleg "Magnetofluiddynamik elektrisch leitfähiger Flüssigkeiten"

Gerbeth, G.; Eckert, S.; Stefani, F.; Cramer, A.; Weier, T.

no abstract delivered from author

  • Other report
    Abschlußbericht, Juli 2001 zu den FRZ-Teilprojekten A3,A4,B1,B3,C4,D3

Publ.-Id: 4155

Einfluß von Huminstoffen auf das Wechselwirkungsverhalten von Uran(VI) unter naturnahen Bedingungen

Sachs, S.; Schmeide, K.; Artinger, R.; Heise, K.-H.; Bernhard, G.

Die zuverlässige Prognose der Langzeitsicherheit von ober- und untertägigen Einrichtungen des ehemaligen Uranerzbergbaus sowie von Endlagern für radioaktiven Abfall erfordert die detaillierte Untersuchung der Ausbreitung von radioaktiven und toxischen Metallionen in der Umwelt. Die Ausbreitung dieser Schadstoffe über den Wasserpfad wird durch eine Vielzahl von Prozessen beeinflußt, wobei die Wechselwirkung mit Huminstoffen dabei eine wesentliche Rolle spielt.
Huminstoffe sind ubiquitär in der Natur vorkommende organische, polyelektrolytische Makromoleküle, die beim Abbau von Biomasse gebildet werden. Aufgrund der Vielzahl an Ausgangsstoffen kann der natürliche Huminstoffbildungsprozess nicht durch einfache chemische und biochemische Reaktionen beschrieben werden. In Abhängigkeit von ihrer Herkunft zeigen Huminstoffe unterschiedliche strukturelle und funktionelle Eigenschaften. Huminstoffe können aufgrund ihrer Löslichkeit bei verschiedenen pH-Werten operationell in drei Fraktionen eingeteilt werden [1]. Humin repräsentiert die Fraktion, die bei allen pH-Werten unlöslich ist, wohingegen Huminsäuren bei pH-Werten > 3.5 und Fulvinsäuren bei allen pH-Werten löslich sind.
Innerhalb natürlicher Wechselwirkungsprozesse können Huminsäuren aufgrund ihrer guten Löslichkeit bei pH-Werten natürlicher Wässer eine entscheidende Rolle spielen. Huminsäuren sind in der Lage Metallionen, z.B. Actinidionen, zu komplexieren. Sie beeinflussen somit deren Speziation und auch deren Mobilisierung bzw. Immobilisierung in der Umwelt. Aufgrund der großen strukturellen und funktionellen Heterogenität von Huminsäuren ergeben sich zahlreiche Probleme bei der thermodynamischen Beschreibung ihres Wechselwirkungsverhaltens in natürlichen Systemen.
Die vorliegende Arbeit gibt einen Überblick zu Untersuchungen, die zur Erlangung detaillierter Kenntnisse zum Wechselwirkungsverhalten von Huminsäuren mit Uran(VI) unter natürlichen Bedingungen durchgeführt wurden [2]. Es werden Ergebnisse zum Komplexbildungsverhalten von Huminsäuren mit Uran(VI) sowie zum Einfluß von Huminstoffen auf das Migrationsverhalten von Uran vorgestellt.

[1] Choppin, G.R.: The Role of Natural Organics in Radionuclide Migration in Natural Aquifer Systems. Radiochim. Acta 58/59, 113 (1992).
[2] Pompe, S., Bubner, M., Schmeide, K., Heise, K.H., Bernhard, G., Nitsche, H.: Influence of Humic Acids on the Migration Behavior of Radioactive and Non-Radioactive Substances under Conditions Close to Nature. Wissenschaftlich-Technische Berichte, FZR-290, Rossendorf 2000.

Keywords: Huminstoffe; Huminsäuren; Uran; Migration; Sorption

  • Lecture (others)
    1. GK-Kolloquium für Geoumweltforschung, Kontamination aus der Nutzung von Ressourcen: Probleme und Lösungen, TU Bergakademie Freiberg, 07.12.2001

Publ.-Id: 4154

Synthese und Charakterisierung Tetradentater Tc-99m Liganden mit hoher Affinität zum 5-HT1A Rezeptor

Heimbold, I.; Drews, A.; Syhre, R.; Kretzschmar, M.; Pietzsch, H.-J.; Johannsen, B.

In diesem Beitrag werden Tetradentate Tc-99m Liganden mit hoher Affinität zum 5-HT1A Rezeptor vorgestellt. Die Verbindungen weisen sowohl eine moderate Selektivität gegenüber dem alpha1-adrenergen Rezeptor als auch eine verbesserte Hirnaufnahme auf. Sie leiten sich strukturell von den PET-Liganden WAY 100635 und DWAY ab. Als Chelatorensystem für Oxotechnetium(V) wird Bis(aminoethanthiol) (BAT) genutzt welches über Spacer unterschiedlicher Länge mit der Phenylpiperazineinheit verknüpft ist.
Der Beitrag behandelt die Ligandsynthese, die Markierung mit Technetium sowie die biologische Evaluierung der Komplexe (in vitro Rezeptorbindungsstudien, Bioverteilungen und Autoradiographische Untersuchungen).

  • Poster
    Jahrestagung Gesellschaft Deutscher Chemiker, Würzburg, 23.-29.9.2001

Publ.-Id: 4153

Improvement of Ta-based thin film barriers on copper by ion implantation of nitrogen and oxygen

Wieser, E.; Peikert, M.; Wenzel, C.; Schreiber, J.; Bartha, J. W.; Bendjus, B.; Melov, V. V.; Reuther, H.; Mücklich, A.; Adolphi, B.; Fischer, D.

Magnetron sputtered polycrystalline Ta and Ta(Si) barriers for copper metallization schemes were modified by nitrogen or oxygen high dose ion implantation to improve their thermo-mechanical stability. The ion bombardment changes the initially polycrystalline microstructure to amorphous-like. In contrast to pure Ta, Ta(Si) layers are already X-ray amorphous after deposition. Here the implantation enhances the recrystallization temperature by about 100 K. In order to demonstrate the improvement in the barrier properties of the implanted Ta films the intermixing of Ta and Cu at the interface of corresponding layer structures was measured by AES depth profiling as a function of the annealing temperature. The thermal stability of Ta and Ta(Si) barriers increases from 6000C/ 1h for the non-implanted layers up to 750° C/1h after implantation of nitrogen or oxygen.

Keywords: Ion implantation; diffusion barrier; tantalum

  • Thin Solid Films 410 (2002) 121-128
  • Thin Solid Films 410 (2002) 121-128

Publ.-Id: 4152

Promoted calcium-phosphate precipitation from solution on titanium for improved biocompatibility by ion implantation

Maitz, M. F.; Pham, M.-T.; Matz, W.; Reuther, H.; Steiner, G.

Calciumphosphates are the main component of bone and as a coating they promise optimal bone integration of an implant. Titanium as a leading implant material does not support calciumphosphate precipitation on its surface. The aim is to modify the titanium surface for spontaneous deposition of calciumphosphate out of a solution and to demonstrate its biocompatibility. Non treated, Na implanted (3.2 x 1017 Na cm-2), or NaOH (10 mol/L) etched Ti samples were used. Bone forming SAOS-2 cells were seeded out on the surface. After 3, 14, and 28 days samples were investigated for cell count and morphology, biochemical markers and ratio of Ca and P as a hint for the type of calciumphosphate. For a second series calciumphosphate was precipitated by incubation in a simulated body fluid prior to cell culture. On Na implanted Ti without treatments in simulated body fluid, cells grow more oriented in comparison to pure or etched Ti and the cell count was higher, but the cells did not cover the whole surface. Characteristic markers for bone cell metabolism did not differ significantly between the samples. Apatite formation was low but increased in experiments after calciumphosphate precipitation out of solution. The cell morphology improved when the cells were grown on samples after treatment with simulated body fluid. Na implantation can enhance calciumphosphate precipitation on Ti and this way promote the growth of bone forming cells.

Keywords: Biomaterials; Titanium; Hydroxyapatite; cell culture; Simulated Body Fluid

  • Surface and Coatings Technology 158-159C (2002) 151-156
  • Lecture (Conference)
    12th International Conference on Surface Modification by Ion Beams, Marburg., September 9-14 2001

Publ.-Id: 4151

Kolloidchemische Untersuchungen an Umweltwässern unter anoxischen Bedingungen

Richter, W.; Zänker, H.; Hüttig, G.

Kolloidchemische Untersuchungen an Umweltwässern unter anoxischen Bedingungen

  • Poster
    DFG Tagung Berlin 13.-14.9.2001

Publ.-Id: 4150

Magnetic Characterization of the Hybrid Undulator U27 for the ELBE-Project

Gippner, P.; Grosse, E.; Pflüger, J.; Schamlott, A.; Seidel, W.; Wolf, U.; Wünsch, R.

At the Dresden Radiation Source ELBE an intense IR beam in 3 - 30 µm range will be produced in the undulator U27. It consists of two 34-pole sections, allowing to insert a magnetic chicane in between. The undulator structure has a period of 27.3 mm and consists of NdFeB permanent magnets and poles of decarborized iron, mounted on two carriages such that the distance between the two sections is adjustable for phase-matching. The gaps of both sections can be varied independently to eventually produce two IR-colours at the same electron energy. For high-gain lasing one can introduce a tapering of the field.

Keywords: Hybrid undulator; hall probe measurement; pulsed wire method; field tapering; phase matching

  • Poster
    Proc. 23th Int. Conf. on Free Electron Lasers, Darmstadt 2001 pp II-55
  • Contribution to external collection
    Proc. 23th Int. Conf. on Free Electron Lasers, Darmstadt 2001 pp II-55

Publ.-Id: 4149

Ion Acoustic Microscope based on IMSA-100 Focused Ion Beam system

Akhmadaliev, C.; Bischoff, L.; Teichert, J.; Kazbekov, K.

An intensity modulated focused ion beam (FIB) which is hitting the surface of a solid, leads to a small temperature variation in the near subsurface region which is sufficient for thermal elastic wave generation. The measurement of these waves can be used for analysis and imaging of surface as well as near subsurface structures in the material. The modified FIB equipment IMSA-100 working with 35 keV Ga+ and Au+ ions and a current of about 3 nA was employed to obtain acoustic images from structures on silicon, aluminum and glass targets. The acoustic signals were detected using a PZT transducer delivering an output voltage of 50 - 100 nV at modulation frequency of 100kHz. The frequency was varied in the range of 60kHz - 2MHz. The obtained lateral resolution of the ion acoustic images at 80 kHz was about 16 µm on silicon and about 7µm on glass and at 2 MHz it decreases to 5 µm and 3 µm, respectively.

Keywords: Focused Ion Beam; Ion Acoustic Microscopy; Piezoelectric Transducer

  • 12th International School on Vacuum, Electron and Ion Technologies 17 –21 September, 2001, Varna, Bulgaria / Vacuum 69 (2003) 431 - 435
  • Vacuum 69 (2003) 431 - 435

Publ.-Id: 4148

Subthreshold phi meson production in heavy-ion collisions

Barz, H. W.; Zetenyi, M.; Wolf, G.; Kämpfer, B.

Within a transport code of BUU type the production of phi mesons in the reactions Ni + Ni at 1.93 AGeV and Ru + Ru at 1.69 AGeV is studied. New elementary reaction channels rho N Delta to phi N and pi N(1520) to phi N are included. In spite of a substantial increase of the phi multiplicities by these channels the results stay below the tentative numbers extracted from experimental data.

Keywords: phi-meson; subthreshold production; heavy-ion collisions

  • Nucl.Phys.A705:223-235,2002 nucl-th/0110013

Publ.-Id: 4145

Spectroellipsometric, AFM and XPS probing of stainless steel surfaces subjected to biological influences

Vinnichenko, M.; Chevolleau, T.; Pham, M.-T.; Poperenko, L.; Maitz, M. F.

Surface modification of austenitic stainless steel 316L due to incubation in growing cell cultures and cell culture media as control has been studied. The following treatments were applied: mouse fibrosarcoma cells L929 during 3 and 7 days, polymorphonuclear neutrophils 3 and 7 days and human osteosarcoma cells SAOS-2 in during 7 and 14 days. Cells were enzymatically removed in all cases. The modified surfaces were probed in comparison with untreated ones by means of spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS shows the appearance of the peak of bonded nitrogen at 400.5 eV characteristic for adsorbed proteins on the surface for each type of cells and for the cell-free medium. Migration of Ni in the adsorbed layer is observed in all cases for samples after the cell cultures. The protein layer thickness is ellipsometrically determined to be within 2.5-6.0 nm for all treated samples with parameterization of its optical constants in Cauchy approach. The study showed that for such biological treatments of the stainless steel the protein adsorption is the dominating process in the first two weeks, which could play a role in the process of corrosion by complex forming properties with metal ions.

Keywords: stainless steel; biocorrosion; optical constants; spectroscopic ellipsometry; X-ray photoelectron spectroscopy; atomic force microscopy

  • Applied Surface Science 201 (2002)41-50

Publ.-Id: 4144

Application of Focused Ion Beams in Materials Research

Bischoff, L.; Teichert, J.

With the invention of the liquid metal ion source (LMIS) in the sixties the focused ion beam (FIB) technique started an impressive development from the laboratory level to high performance industrial equipments. At present, the FIB is a very useful and versatile tool in microelectronics industry for mask and integrated circuit repair and modification, failure analysis or TEM specimen preparation, as well as in the material science for radiation damage and sputtering investigations, for grain size and distribution analysis in metals and alloys, for the formation of silicides or the fabrication of micro-tools. A modern FIB column which is operated with gallium liquid metal ion souces (LMIS) only reaches a spot size in the range of 10 nm and current densities of more than 10 A/cm2 .

For special purposes in the field of research and development, like writing ion implantation or ion mixing in the µm- or sub-µm range other ion species than Ga are needed. Therefore alloy LMIS are used. The energy distribution of the ions from an alloy LMIS is one of the determining factors for the performance of the source in the FIB equipment, in other words, the obtainable spot size. Different source materials like the alloys Au73Ge27 (Tm = 366°C), Au77Ge14Si9 (Tm = 365°C), Co36Nd64 (Tm = 566°C), Er69Ni31 (Tm = 765°C), and Er70Fe22Ni5Cr3 (Tm = 862°C) were investigated and compared with respect to the energy spread of the different ion species depending on the operation parameters emission current I, ion mass m and temperature T. For single charged ions the predicted dependence of the energy spread according to DE µ I2/3 m1/3 T1/2 found for Ga could be confirmed in reasonable agreement. Due to the ion mass, for doubly charged ions a weaker and for clusters a stronger slope was found. The temperature dependence of the source behaviour is strongly related to the surface tension coefficient of the used alloy.

The alloy LMIS`s discussed above have been used in the Rossendorf FIB system IMSA-100 especially for writing implantation to fabricate sub-µm pattern without any lithographic steps. So a Co-FIB was applied for the ion beam synthesis of CoSi2 micro-structures with a minimum feature size of 60 nm. Additionally, the possibility of varying the current density with the FIB by changing the pixel dwell-time was used for radiation damage investigations in Si and SiC at elevated implantation temperatures. Furthermore, a broad spectrum of ions was employed to study the sputtering process depending on temperature, angle of incidence and ion mass on a couple of target materials using the volume loss method. The effective erosion properties of the FIB were exploided in fabricating micro-tools with dimensions smaller than 40 µm from WC(Co) and HSS steel. The application of the FIB as a scanning ion microscope with high topographic resolution of the sample surface can be used to study the grain size and distribution of metals and alloys as well as micoelectronic structures on the surface and also, after sputtering, in deeper layers. The sputtered holes can also be imaged after polishing with the FIB and tilding as a cross section by SEM. All the examples underline the importance of a FIB in modern research.

Keywords: focused ion beam; alloy liquid metal ion source; materials research; ion milling; writing implantation

  • Invited lecture (Conferences)
    Proceedings of the 12th International School on Vacuum, Electron and Ion Technologies, 17 - 21 September, 2001, Varna, Bulgaria (invited)

Publ.-Id: 4143

Molecular cloning and functional characterization of the OCTN2 transporter at the RBE4 cells, an in vitro model of the blood-brain barrier

Friedrich, A.; Prasad, P. D.; Freyer, D.; Et, A.

The transport of L-carnitine (4-N-trimethylamino-3-hydoxybutyric acid), a compound known to be transported by the organic cation transporter / carnitine transporter OCTN2, was studied in immortalized rat brain endothelial cells (RBE4). The cells were found to take up L-carnitine by a sodium-dependent process. This uptake process was saturable with an apparent Michaelis-Menten constant for L-carnitine of 53.8 ± 9.8 µM and a maximal velocity of 214.5 ± 34.7 pmol/mg protein/h. Besides L-carnitine, the cells also took up acetyl-L-carnitine and propionyl-L-carnitine in a sodium-dependent manner and TEA in a sodium-independent manner. RT-PCR with primers specific for the rat OCTN2 transporter revealed the existence of OCTN2 mRNA in RBE4 cells. Screening of a cDNA library from RBE4 cells with rat OCTN2 cDNA as a probe identified a positive clone which showed, when expressed in HeLa cells, the functional characteristics of OCTN2. The HeLa cells expressing the RBE4 OCTN2 cDNA showed a six-fold increase in L-carnitine uptake and a four-fold increase in TEA uptake in a sodium-containing buffer. Typical inhibitors for organic cation transporters (e.g., MPP+ or TEA) showed an inhibitory effect on the transport of L-carnitine and TEA into the transfected cells. Similarly, unlabeled L-carnitine inhibited the transport of [3H]-L-carnitine and [14C]TEA in transfected HeLa cells. It is concluded that RBE4 cells, a widely used in vitro model of the blood-brain barrier (BBB), express the organic cation/carnitine transporter OCTN2.

  • Brain Research 968: 69-79 2003

Publ.-Id: 4142

Ion beam synthesis of semiconductor nanoclusters in SiO2 films for opto- and microelectronic applications

von Borany, J.; Heinig, K.-H.; Klimenkov, M.; Rebohle, L.; Schmidt, B.; Skorupa, W.; Stegemann, K.-H.

The contribution will review recent results to the fabrication and investigation of semiconductor nanoclusters (Si, Ge, Sn) embedded in SiO2 films. Due to quantum confinement effects or the large surface/volume ratio of such clusters typical dimensions of only few nanometers exhibit remarkable properties which differ to that of the bulk values. Among different fabrication techniques the ion beam synthesis offers specific advantages to realize a large density of tiny (2-4 nm) nanoclusters and to fulfil the requirements of CMOS technology. The results of presented experiments clearly indicate that the size, density and distribution of clusters are strongly influenced by the implantation and annealing conditions. Taking these influences into account it is possible to realize desired nanocluster distributions in the SiO2 layer, e.g. the fabrication of wide regions with homogeneously distributed clusters or d-like nanocluster bands in thin SiO2 films.
The specific features of semiconductor nanoparticles in SiO2 films comprise an enormous potential for future opto- and microelectronics.
In general, group IV nanocluster containing SiO2 films can emit light in a wide wavelength region. The topic of light emission from ion beam synthesized nanoclusters is focused on recent success in extracting intensive violet/blue photo- and electroluminescence (EL) from Si-, Ge- or Sn implanted SiO2 layers which can be attributed to a specific defect formed after the IBS process. A power efficiency up to 0,5 % for EL has been established using MOS structures. Among possible applications the properties of a monolithically integrated optocoupler with ultra low power consumption will be discussed.
Based on a FET structure with semiconductor nanocluster containing gate oxide, a new non-volatile memory cell has been designed which makes use from the charge storage ability of small quantum dots. The advantages of this memory are attributed to the features, that (i) the nanoclusters act as an ensemble of single storage elements, and (ii) the charge transfer during programming occurs preferably by direct tunnelling. Therefore, lower programming voltages and considerably increased endurance (1010 w/e-cycles) in comparison to the present (Flash)- EEPROM technique is expected. Routes towards the fabrication of a shallow band of nanoclusters in the gate oxide of a FET very close, but well separated to the Si/SiO2-interface will be discussed in detail. CV or IV measurements reveal the charge storage effect of cluster containing thin SiO2 films by a remarkable shift of the flatband or threshold voltage of MOS or FET-structures, respectively. Recently, Zentrum Mikroelektronik Dresden has been successfully realized the first 256 nv-SRAM based on ion beam modified gate oxides.

  • Invited lecture (Conferences)
    12th International School on Vacuum, Electron and Ion Technologies, VEIT'01, September 17-21, 2001, Varna, Bulgaria (Invited Lecture)

Publ.-Id: 4141

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