Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Many tasks in different sectors of dosimetry are very complex and highly sensitive to changes of the radiation field, e. g. dose estimations in microdosimetry. Often experimental measurements are only available for particular conditions or at single target points. Thus only the simulation of radiation transport is capable of describing the radiation field completely. Different approaches for solving the radiation transport problem as e.g. FEM can be used. In particular the Monte Carlo (MC) method is very useful for high-dimensional problems, and it is accepted as a standard method for this purpose.
Down to sub cellular dimensions the energy deposition by cascades of secondary electrons is the main pathway for damage induction in matter. A high number of interactions is taking place until such an electron is slowed down to thermal energies. For this reason the non-analog Monte Carlo program AMOS has been developed for photon and electron transport. The advanced MC algorithms implemented are able to handle a large number of histories at reasonable performance even for time consuming single scattering models. They facilitate the calculation of photon dose distributions at up to 10^6 points.
Modeling the dose distribution of a 125-I brachytherapy source has proven the high efficiency of this MC approach. Further on results achieved by AMOS for the transport of electrons with low energies (E < 100 keV) in matter with low atomic numbers were compared to measured data from the literature. It has been proven that the program code produces results in rather well agreement to the experiments also for small target structures of about one micrometre. This is especially important for the application to cell irradiation experiments as they are carried out at the FZ Rossendorf. As another example of application a simulation of the whole spectral detector response of an HPGe detector will be presented.

Femtosecond pump-probe measurements of reflection from crystallographic planes are performed to investigate lattice relaxation dynamics in the NdBa2Cu3O7-x high-temperature superconductor. Ultrafast phonon response is examined over a wide temperature range for various orientations of the pump and probe polarization vectors with respect to particular crystallographic axes. The initial phases of coherent phonons are measured, and hysteretic behavior is revealed in the transition between two temperature regions above T-c for the ac plane.

Coherent folded longitudinal acoustic phonons in a GaAs/AlAs long-period superlattice (SL) have been investigated by using a reflection-type two-color pump-probe technique under the condition that the wave vector of the probe pulse in the sample exceeds the mini-Brillouin zone. The coherent oscillations observed in the time-domain signals indicate the propagation of the phonon wave packet through the whole SL layer. The Fourier transform spectrum of the time-domain signals is compared with the dispersion relation of the folded longitudinal acoustic phonons in the long-period SL calculated using a transfer matrix method on the bases of an elastic continuum model. This comparison indicates that the folded longitudinal acoustic phonons in the long-period SL are observed through the umklapp process.

Structural materials, such as ferritic and austenitic steels and aluminium alloys, as used in the nuclear and aircraft industry are subject to external stresses which may lead to the nucleation of cracks. The damage zone ahead of a crack tip introduced as a result of static deformation was investigated in an Al-2024 and Al-6013 alloy and in a 10 CrMo9 10 reference steel by means of small angle X-ray scattering. A robust parameter, the anisotropy parameter, describing the damage region was developed. Further parameters were exployed. The data, supported by electron microscopy investigations point to large oriented dislocation networks. Finite element calculations show a good correspondence in the shape and size of the damage zone.

Konstruktionswerkstoffe, z. B. ferritische Stähle, austenitische Stähle und Aluminiumlegierungen mit Anwendung in der Kernenergie- und Luftfahrttechnik, sind hohen äußeren Belastungen ausgesetzt, die zur Rissbildung führen können. Die Schädigungszone vor der Spitze von Rissen, die durch quasistatische Belastung in Materialproben der Aluminiumlegierungen Al-2024 und Al-6013 und des warmfesten Stahls 10 CrMo9 10 eingebracht worden waren, wurde mittels Röntgenkleinwinkelstreuung punktweise erfasst und abgerastert. Aus den Streubildern wurden mehrere verschiedene Streuparameter abgeleitet, von denen sich der Anisotropieparameter als besonders robust erwies. Die Ergebnisse deuten, gestützt durch elektronenmikroskopische Untersuchungen, auf grobe orientierte Versetzungsnetzwerke. Finite-Elemente-Rechnungen zeigen eine gute Übereinstimmung hinsichtlich Form und Größe der Schädigungszone.

An assessment of void fraction correlations and drift-flux models applied to stationary and transient flashing flows in a vertical pipe has been performed. Experiments have been carried out on a steam/water loop that can be operated both in forced and natural-circulation conditions. Advanced instrumentation, namely wire-mesh sensors, has been used to obtain a detailed picture of the void-fraction development in the system. On the basis of experimental data collected, three-dimensional flow-pattern visualization was achieved.

A benchmark of some codes developed for the neutronic analysis of molten-salt reactors is presented. The results of the calculations are compared to the experimental data reported for the Molten Salt Reactor Experiment performed at Oak Ridge National Laboratory in the 60's. Both static and time-dependent situations are considered. The phenomena connected to the motion of the multiplying material are investigated. The results presented show a good agreement among the codes and with the available experimental data, thus providing the adequateness of the computational tools for the simulation of molten-salt system.

The CIRCUS test facility has been built to study the start-up phase of a natural-circulation BWR. During the start-up so called flashing-induced instabilities can arise. These instabilities are induced by flashing, due to steam production in the long adiabatic riser section, which is placed above the core to enhance the flow rate. Flashing occurring in the riser causes an unbalance between driving force and pressure losses in the natural-circulation loop, giving rise to flow oscillations.

This paper gives an overview about experimental results and the physics of the instabilities. The thermo-hydraulic code ATHLET is used to investigate the dynamic behavior of the CIRCUS test facility and the results of the calculations are compared with the experimental data.

This work is part of the NACUSP project (Natural Circulation and Stability Performance of BWRs) within the European-Union 5th Framework Programme.

Die experimentellen Arbeiten zur Kühlmittelvermischung in einem Druckwasserreaktor vom Typ KONVOI an der Versuchsanlage ROCOM werden vorgestellt. Weiterhin sind die parallel zu den Experimenten durchgeführten theoretischen Arbeiten zur Anwendung und Validierung des CFD-Codes CFX-4 Bestandteil des Beitrages.

Positron emission tomography is currently the only feasible method for in-situ and non-invasive 3D monitoring of the precision of the treatment in highly conformal ion therapy. Its positive clinical impact has been proven for fractionated carbon ion therapy of head and neck tumours at the experimental facility at the Gesellschaft für Schwerionenforschung Darmstadt (GSI), Germany. Following previous promising experiments, the possible extension of the method to the monitoring of proton therapy has been investigated further in extensive in-beam measurements at GSI. Millimetre accuracy for verification of the lateral field position and for the most challenging issue of range monitoring has been demonstrated in mono-energetic and SOBP proton irradiation of PMMA targets. The irradiation of an inhomogeneous phantom with tissue equivalent inserts in combination with further dynamic analysis has supported the extension of such millimetre precision to real clinical cases, at least in regions of interest for low perfused tissues. All the experimental investigations have been reproduced by the developed modeling rather well. This indicates the possible extraction of valuable clinical information as particle range in-vivo, irradiation field position and even local deviations from the dose prescription on the basis of the comparison between measured and predicted b+-activity distributions. Hence, the clinical feasibility of in-beam PET for proton therapy monitoring is strongly supported.

The relaxation dynamics of charge carriers in an epitaxial La0.7Ca0.3MnO3 film was studied by the light reflection method with a femtosecond time resolution in a wide temperature range. The relaxation of time-resolved photoinduced reflections was shown to be two-component in the whole temperature range including the paramagnetic dielectric-ferromagnetic metal transition at Tapproximate to150-160 K. The fast relaxation component had a maximum lifetime (tausimilar to500 fs) in the transition region, and its contribution to relaxation increased as temperature decreased. The lifetime of the slow component was minimum (tausimilar to15 ps) in the transition region. In addition, fast oscillations assigned to coherent phonons appeared in photoinduced responses at T<200 K. The dephasing time of these oscillations increased as temperature decreased, whereas their frequency changed insignificantly.

HADES is a second generation experiment designed to study dielectron production in proton, pion and heavy ion induced reactions at the GSI accelerator facility in Darmstadt. The physics programme of HADES is focused on in-medium properties of the light vector mesons. In this contribution we discuss relevance of dielectron spectroscopy to the problem of hadron mass origin. We present status of the HADES experiment, demonstrate ists capability to identify rare dielectron signal and show first experimental results obtained from C+C reations at 2 AGeV.

The lowest-order induced soft gluon radiation processes of heavy quarks are considered with the aim to quantify the dead cone effect. The dead cone effect is expected to suppress significantly the energy loss of charm quarks passing an amorphous colour-neutral deconfined medium, as anticipated in recent experiments at RHIC.

Using molecular-dynamics (MD) techniques and a hydrocarbon potential of Brenner with an increased C-C interaction range, we investigate kinetics of relaxation processes in tetrahedral amorphous carbon films (ta-C) with high sp³ fractions. The structural models for as-grown non-equilibrium ta-C networks were generated using MD film deposition simulation with ion energy of 80 eV. The results of MD simulations of low temperature annealing show that both film stress and energy behave with annealing time t as a+bexp(-t/t₁ ). This exponential dependency is interpreted in terms of structural transformations in the amorphous carbon networks. It is also shown that the relaxation times for the energy and stress do not coincide, indicating that some atomic rearrangements in the networks may reduce their energy without changing the stress. At the annealing temperature of 1000 K, the relaxation constant t₁ for energy was found to be in the range of 0.5-0.7 ns, depending on the simulation parameters. It considerably exceeds an estimate of 10 ps for the thermalization stage of the subplantation model for ta-C film formation from energetic C ions. A decrease in the ta-C energy during the first 10 ps of the simulated annealing is much larger than that predicted by the exponential law with the relaxation constant t₁ .

The Molecular Microbiological Group at the Institute of Radiochemistry, Research Centre Rossendorf nearby Dresden, performs as part of an institute from the Wissenschaftsgemein-schaft Gottfried Wilhelm Leibniz e.V. basic and applied research. Main interests are

• bacterial diversity of soil and water

• investigation and characterization of

• development of novel bacteria-based bioremediation strategies for cleaning contaminated wastewater
• use of bacteria or bacterial components as biotemplates for the formation of nanoclusters for biotechnological applications

Bacteria consist of only one single cell, but apart from their simple organisation and their small size they are an unbelievable complex and highly efficient group of creatures. Some bacteria are able to thrive at the most forbidding, uninviting places on Earth: they live in hot springs, in extremely alkaline or acid waters, in muds of marshes or even at the bottom of the ocean. For production of energy they can use different kinds of organic and inorganic matter or sun light. Against this background, investigation of bacteria recovered from extreme environments shows a great promise to discover novel and yet unknown properties of this interesting group of organisms.

TiN and Ti1-xAlxN coatings were deposited on Al substrates using the plasma immersion ion implantation and deposition technique, employing a filtered Ti and Ti0.5Al0.5 cathodic arc in a nitrogen atmosphere. Negative pulsed bias voltages between 0 to –4.0 kV were applied with varying duty cycles, at a constant time-averaged bias. Stress measurements using X-ray diffraction reveal an increase and then a decrease in the intrinsic compressive stress at increasing on-time bias, more pronounced for Ti1-xAlxN coatings. A bias dependent preferred orientation is observed for both the coatings, with [200] being the preferred orientation at higher bias. The hardness always reduces for TiN coatings with increase in bias, whereas for Ti1-xAlxN it shows a reverse trend. The results are qualitatively explained by the role played by Al in Ti1-xAlxN. The results indicate that the peak bias plays a more dominant role than time averaged bias.

The structures, formation energies and stable configurations of elementary defects (vacancies, antisite defects and self-interstitials) in 3C- and 4H-SiC are studied using classical molecular dynamics simulation with a recently developed interatomic potential. The defect structures in 3C-SiC are relatively simple, but those in 4H-SiC are more complex. The interstitials between hexagonal and trigonal rings are characteristic for 4H-SiC and other hexagonal polytypes, but not for 3C-SiC. The number of non-equivalent defects in 4H-SiC is much higher than that in 3C-SiC, and a considerable difference is found for some complex and anisotropic defects, in particular for the dumbbells D1Si+Si, D1Si+C and D2Si+C. The lattice deformation beyond the first nearest neighbor shell, which depends strongly on the polytype structure, plays an important role on these effects. However, the polytypism does not have a significant influence on the structure and energetics of the more compact and isotropic defects, such as vacancies and antisite defects. Despite the complexity of defect configurations, the tetrahedral interstitials have very similar properties in 3C- and 4H-SiC because their first, second and third nearest neighbor shells are identical.

We devised and tested a novel computed tomography approach that utilises a scanned electron beam X-ray source to produce fast sequences of tomographic images of transient density distributions. In contrary to classical electron beam tomography we used a linear deflection pattern for the electron beam and a non-annular detector arc to record transmission data of an object from different projection angles. This approach gives the highest achievable axial resolution and is comparatively moderate in effort and costs. For the inverse problem we applied iterative image reconstruction techniques to reconstruct the density distribution from a limited data set. The method has been experimentally tested on static and dynamic phantoms with a frame rate of 1000 images per second and a spatial resolution of approximately 1 mm in plane and axial.

Intermetallic Rare-Earth-Transition-Metall compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of massive single crystals is very often unsuccessful due to an unfavourable solid-liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds. This control is provided by a tailored design of the electromagnetic field and the resulting electromagnetically driven convection. Numerical simulations for the determination of the electromagnetic field configuration induced by the RF heater coil and the solution of the coupled heat and hydrodynamic equations were done for the model substance Ni with and without additional magnetic field. As a result, an innovative magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards/outwards flows to flows almost at rest. The selection of parameters necessary for the desired fluid flow is determined from numerical simulation. The basis for the calculations are the process-related fluid flow conditions which are determined by the mode of heating, heat radiation at the free surface and material parameters. This treatment of the problem leads to the customised magnetic field for the special intermetallic compound. The application of the new magnetic system leads to a distinct improvement of the solid-liquid interface validated on experiments with the model substance Nickel.

Intermetallic Rare-Earth-Transition-Metall compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of massive single crystals is very often unsuccessful due to an unfavourable solid-liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds. This control is provided by a tailored design of the electromagnetic field and the resulting electromagnetically driven convection. Numerical simulations for the determination of the electromagnetic field configuration induced by the RF heater coil and the solution of the coupled heat and hydrodynamic equations were done for the model substance Ni with and without additional magnetic field. As a result, an innovative magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards/outwards flows to flows almost at rest. The selection of parameters necessary for the desired fluid flow is determined from numerical simulation. The basis for the calculations are the process-related fluid flow conditions which are determined by the mode of heating, heat radiation at the free surface and material parameters. This treatment of the problem leads to the customised magnetic field for the special intermetallic compound. The application of the new magnetic system leads to a distinct improvement of the solid-liquid interface validated on experiments with the model substance Nickel.

Self-aligned Si nanocluster (NC) formation in thin MOSFET gate oxides by means of ion beam mixing and post-irradiation annealing of SiO₂-Si interfaces is proven for the first time by cross-section TEM. This study proves a recent prediction based on kinetic Monte Carlo (KLMC) simulations that a delta-layer of tiny Si NCs in SiO₂, located 2…3nm apart from the SiO₂-Si interface, can be fabricated by ion irradiation [1]. Such a self-aligned NC delta-layer configuration meets the requirements of non-volatile multi-dot floating-gate memory transistors [2], on which immense research effort has been spent in recent years.
By conventional TEM techniques the delta-layer of Si NCs in SiO₂ can not be observed due to the low mass contrast between Si and SiO₂ and the tininess of the Si NCs which have a mean diameter of 1.5nm. Here we present a method of mass contrast enhancement of such tiny Si NCs by alloying them with Ge. For this purpose, a thin Ge layer was embedded into the oxide far above the SiO₂-Si interface, i.e. outside the mixing range of the SiO₂-Si interface in order not to interfere with the original Si NC formation process. During post-irradiation annealing, diffusing Ge atoms are captured by the Si NCs due to the strong Si-Ge bond.

Nanoscale metallic multilayers have been deposited by a pulsed double-cathodic arc deposition with varying thicknesses of each layer from a few to tens of angstroms and examined by cross-sectional transmission electron microscopy (XTEM). TRIDYN computer simulations are performed to get a better understanding of the nanoscale deposition of multilayers during the cathodic arc deposition process. Their results are compared with the experimental data. For the higher ion fluence ( > 1.e16 ions/cm**2 ) and larger bilayer thickness ( > 2 nm), the periodicity of multilayers was good. However, the results of the simulations for the lower ion flux and smaller bilayer thickness reveal that the individual layers are intermixed and diffused. The experimental results are in good agreement with those of simulations that the limit of bilayer period of the ultra-thin multilayers is approximately 2 nm in the present case.

Newborn (7-10 days old) and young (6-8 weeks old) pigs were used to study the metabolism of 6-[F-18]fluoro-L-DOPA (FDOPA) in various brain regions with positron emission tomography (PET). Compartmental modeling of PET data was used to calculate the rate constants for the decarboxylation of FDOPA (k(3)) and for the metabolism of the resulting [F-18]fluoro-dopamine (k(cl)). Whereas general physiological parameters such as cerebral blood flow, cerebral oxygen uptake, arterial blood gases and glucose concentration remained unchanged in young pigs as compared to newborns, a 50-200% increase of k(3) in frontal cortex, striatum and mesencephalon was found. Also a 60% enhancement of k(cl) in the frontal cortex was measured, which is related to changes of the catechol-O-methyl-transferase (COMT) activity and implies a special function of this enzyme in the development of this brain region. In addition, measurement of plasma metabolites of FDOPA with HPLC was performed. The metabolism of FDOPA in young pigs was significantly faster than in newborns. Calculation of the rate constant for O-methylation of FDOPA by COMT revealed a significant elevation of this enzyme activity in young pigs compared to newborns. The increase of AADC and COMT activity with brain development is considered to be associated with special stages of neuronal maturation and tissue differentiation.

There is evidence that the dopaminergic system is sensitive to traumatic brain injury (TBI). However, the age-dependency of this sensitivity has not been studied together with brain oxidative metabolism. We postulate that the acute effects of severe TBI on brain dopamine turnover are age-dependent. Therefore F-18-labelled 6-fuoro-L-3,4-dihydroxyphenylalanine (FDOPA) together with Positron-Emission-Tomography (PET) was used to estimate the activity of the aromatic amino acid decarboxylase (AADC) in the brain of Ill newborn piglets (7-10 days old) and nine juvenile pigs (6-7 weeks old). Six newborn and five juvenile animals were subjected to a severe fluid-percussion (FP) induced TBI. The remaining animals were used as sham operated untreated control groups. Simultaneously, the regional cerebral blood flow (CBF) was measured with colored microspheres and the cerebral metabolic rates of oxygen and glucose were determined. At 1 h after FP-TBI, [F-18]FDOPA was infused and PET sca! nning was performed for 2 h. At 2 h after FP-TBI administration, a second series of measurements of physiological values including CBF and brain oxidative metabolism data had been obtained. Severe FP-TBI elicited a marked increase in the rate constant for fluorodopamine production (k(3)(FDOPA)) in all brain regions of newborn piglets studied by between 97% (mesencephalon) and 143% (frontal cortex) (p < 0.05). In contrast, brain hemodynamics and cerebral oxidative metabolism remained unaltered after TBI. Furthermore, the permeability-surface area product of FDOPA (PSFDOPA) was unchanged. In addition, regional blood flow differences between corresponding ipsi- and contralateral brain regions did not occur after TBI. Thus, it is suggested that severe FP-TBI induces an upregulation off AADC activity of newborn piglets that is not related to alterations in brain oxidative metabolism.

Schaumbildung in Chemiereaktoren ist eine oft unerwünschte Begleiterscheinung bei mehrphasigen Prozessen und Anlagenstörfällen. Die hier vorgestellte Experimentiertechnik gestattet die berührungslose Messung von Phasen- und Konzentrationsverteilungen mittels PET und wurde für Grundlagenuntersuchungen zum Verhalten von Tensiden bei Schaumbildungs- und Zerfallsprozessen in rohrförmigen Reaktionsgefäßen entwickelt und erprobt.

Small-angle correlations of pairs of protons emitted in central collisions of Ca + Ca, Ru + Ru and Au + Au at beam energies from 400 to 1500 MeV per nucleon are investigated with the FOPI detector system at SIS/GSI Darmstadt. Dependences on system size and beam energy are presented which extend the experimental data basis of pp correlations in the SIS energy range substantially. The size of the proton-emitting source is estimated by comparing the experimental data with the output of a final-state interaction model which is processing either static Gaussian sources or the one-body phase-space distribution of protons provided by the BUU transport approach. The trends in the experimental data, i.e. system-size and beam energy dependences, are well reproduced by this hybrid model. However, the pp correlation function is found rather insensitive to the stiffness of the equation of state entering the transport model calculations.

We describe two-flavor QCD lattice data for the pressure at a nonzero temperature and vanishing chemical potential within a quasiparticle model. Relying only on thermodynamic consistency, the model is extended to nonzero chemical potential. The results agree with lattice calculations in the region of a small chemical potential.

Summary. Bifunctional ligands able to form neutral complexes with radioactive technetium and rhenium and to couple to biological relevant anchor groups play an important role in the design of new radiopharmaceuticals for diagnosis and therapy. A novel tetradentate amide thioether dithiolate ligand HS-CH₂CH₂-S-CH₂CONH-CH(COOR)CH₂SH(H₃SNSS) with R = CH₃, C₁₀H₂₁ was synthesized that forms stable complexes with technetium and rhenium in oxidation state V. The molecular structures of the rhenium and technetium complexes MO(SNSS) were determined by X-ray structural analysis and show that the metal coordination number is five and the coordination polyhedron is between square-pyramidal and trigonal-bipyramidal. The pendent ester group allows coupling of the chelate unit at biologically relevant anchor groups. As a relevant representative the X-ray structural analysis of the rhenium decylester complex was carried out. The complex formation with Tc at teh n.c.a. level and ¹⁸⁶Re at 10^-10M level is described.

The trigonal-bipyramidal Re(III) and Tc(III) mixed-ligand complexes of the general formula [M^III(Lⁿ)(L^m)] (M = Tc, Re; Lⁿ = 2,2‘,2“-nitrilotris-(ethanethiol) NS₃ or NS3-COOH; L^m = isocyanide or phosphine) are stable against ligand exchange with cysteine or glutathione and in vitro in incubations with plasma as well as whole blood of rats and represent therefore an alternative to the more unstable ‘3+1‘ Re(V) or Tc(V) complexes concerning the possibilities of designing biologically interesting ^99mTc or ¹⁸⁸Re labelled compounds¹. Improved methods for their preparation are presented. To avoid the unrequested formation of reduced-hydrolysed species of both metals the preparation of complexes is performed in a two-step procedure.
At first the Tc(III)- or Re(III)-EDTA complex is formed which reacts in a second step with the tripodal ligand NS₃ or its carboxyl derivative NS₃-COOH and the monodentate phosphine or isocyanide ligands to the so-called ‘4+1’ complexes. Copper(I) isocyanide complexes are used for preparing the ‘4+1’ complexes. That facilitates storage stability and allows kit formulations. Moreover, using that stabilized form of isocyanides enables the formation of ¹⁸⁸Re complexes in acidic solution. Only micromolar amounts of the monodentate ligand are needed and that results in high specific activity labelling of interesting molecules. The stability of the ^99mTc and ¹⁸⁸Re preparations is discussed. The introduction of a carboxyl group into the tetradentate ligand and/or the monodentate ligands enables the conjugation of biomolecules and controlling of lipophilicity.

Technetium and rhenium mixed-ligand complexes represent an important approach to the development of radiotracers for diagnostic and therapeutic application because of the many possibilities to vary their biobehaviour. The trigonal-bipyramidal Re(III) and Tc(III) complexes of the general formula [M^III(Lⁿ)(L^m)] (M = Tc, Re; Lⁿ = 2,2‘,2“-nitrilotris-(ethanethiol) NS₃ or NS₃-COOH; L^m = isocyanide or phosphine) are stable against ligand exchange with cysteine or glutathione and in vitro in incubations with plasma as well as whole blood of rats and represent therefore an alternative to the more unstable ‘3+1‘ Re(V) or Tc(V) complexes concerning the possibilities of designing biologically interesting ^99mTc or ¹⁸⁸Re labelled compounds. Improved methods for their preparation are presented. To avoid the unrequested formation of reduced-hydrolyzed species of both metals the preparation of complexes is performed in a two-step procedure. At first the Tc(III)- or Re(III)-EDTA complex is formed which reacts in a second step with the tripodal ligand NS₃ or its carboxyl derivative NS₃-COOH and the monodentate phosphine or isocyanide ligands to the so-called ‘4+1’ complexes. Copper(I) isocyanide complexes are used for preparing the ‘4+1’ complexes. That facilitates storage stability and allows kit formulations. Moreover, using that stabilized form of isocyanides enables the formation of ¹⁸⁸Re complexes in acidic solution. Only micromolar amounts of the monodentate ligand are needed and that results in high specific activity labeling of interesting molecules. The stability of the ^99mTc and ¹⁸⁸Re preparations is discussed. The introduction of a carboxyl group into the tetradentate ligand and/or the monodentate ligands enables the conjugation of biomolecules and controlling of lipophilicity.

Besides promising applications for electronic nanostructures or nonlinear optical devices nanocrystalline Au may be used as efficient catalysis material (e.g. chemisorption of CO or hydrocarbons). The catalytic reaction is often very sensitive to the structure and size of the metal crystallites and their crystallographic orientation Both conditions may be controlled by growing the nanocrystals in a single crystalline non-metallic matrix.
Here, Au nanocrystals were generated inside rutile TiO2 by implantation of 260 keV Au ions. The growth in a matrix allows to stabilize the precipitates structurally. Furthermore, no impurities were introduced because of mass separation during the process. However, the host crystal is damaged by the ion impact processes. This damage may be reduced by in situ or post-implantation annealing.
Various x-ray scattering techniques were used for the structural characterization of the material: specular reflection for surface and near-surface studies, diffraction for determination of strain and crystal size, pole figure measurements to reveal the orientation relationship.
In the as-implanted state randomly oriented crystals with a size of 5 … 7 nm as well as crystals oriented in a fibre texture with axis parallel to the rutile surface normal have been obtained. Annealing at 1000 K let the nanocrystals grow to 15 nm; simultaneously the amount of epitaxially oriented Au crystals increases. The orientation relationship is controlled by the crystallographic axis of the rutile matrix surface so that the ensemble of the Au nanocrystals fits to the crystal symmetry of the matrix:

• the surface normal is the two-fold rutile [100] direction:

• the surface normal is the four-fold rutile [001] direction:

Feinfokussierte Ionenstrahlen dienen in den Gebieten der Halbleiterindustrie und Materialforschung der Mikro- und Nanostrukturierung. Die vorliegende Arbeit beschäftigt sich mit den beiden Hauptanwendungen von fokussierten Ionenstrahlen, dem Materialabtrag und der ionenstrahlinduzierten Materialabscheidung. Dabei wird die hochauflösende Ionensäule CANION 31Z der Firma Orsay Physics mit Stromdichten von bis zu 10 A/cm2 und mit integriertem Gassystem eingesetzt. Es wird ausführlich auf Anwendungsbeispiele von Fokussierten Ionenstrahlsystemen im Bereich der Industrie und Forschung eingegangen.
Schwerpunktmäßig wird die Abscheidung von Wolfram aus dem Precursorgas W(CO)6 (Wolframhexacarbonyl) auf Si und SiO2 als Substrat untersucht, mit dem Ziel, gut leitfähige Drähte (hier im Sinne von Leiterbahnen) mit minimalem Querschnitt herzustellen. Die Optimierung der Ionenstrahl-Parameter dieser Feinfokussierten Ionenstrahlanlage bezüglich der Abscheidung steht im Vordergrund. Dabei wird ein kurzer Einblick in die Theorie der Schichtentstehung beim Abscheidevorgang gegeben. Untersuchungen der erzeugten Strukturen entsprechend der Schichtqualität und der Strukturabmessungen werden erläutert und die Ergebnisse diskutiert. Es konnten Wolframdrähte mit einer Länge von 20 ... 100 µm, einer Breite von minimal 150 nm und einer Höhe von maximal 600 nm angefertigt werden. Die Zusammensetzung der Drähte in Abhängigkeit der Prozessparameter wurde mittels AES bestimmt. Im optimalen Fall wurden die Schichtanteile zu 80% W, 5% O, 6% C und 9% Ga ermittelt (Angaben in Atomprozent). Der spezifische Widerstand der Wolframdrähte ist im Bereich 150 ... 320 µWcm gemessen worden.

The linear three-dimensional instability of the flow due to a low frequency traveling magnetic field in a regular cylinder is studied numerically for height-to-diameter ratios in the range [0.5:2.5]. The first instability has the form of a non-rotating azimuthal wave with wave numbers between 1 and 6 depending on the aspect ratio. It is shown that the flow is stable if the Reynolds number is below 290. Even stronger stationary flows may be obtained in a flattened cylinder.

In a recent work [1], a combined simulation method was applied to investigate ion-beam-induced defect formation in silicon. BCA simulations were used to treat the ballistic processes, whereas the subsequent fast relaxation and the first stage of thermally activated processes were described by classical MD calculations. It was found that the metastable defect structure formed immediately after ion impact consists not only of isolated vacancies and self-interstitials but also of complex defects. A more detailed analysis of the results shows, that at elevated implantation temperatures or during the annealing of the defect structures obtained at room temperature, di- and tri-interstitials are formed. In some cases a high mobility of these defects is observed. In agreement with former studies [2,3], the di-interstital is found to move relatively fast. The present contribution deals with systematic investigations on the migration of di- and tri-interstitials. The classical MD simulations allow direct investigations of the motion of defects and its atomic mechanisms. Particular attention is paid to the role of transformations between different modifications of di- or tri-interstitials. These transformations may lead to an substantial increase or decrease of the defect mobility. The present results are compared with the few literature data obtained by tight-binding and density-functional methods which employ mainly static potential energy calculations.
[1] M. Posselt, Mat. Res. Soc. Symp. Proc. 647 (2001) O2.1.1.
[2] G. H. Gilmer, T. Diaz de la Rubia, D. M. Stock, M. Jaraiz, Nucl. Instr. Meth. Phys. Res. B 102 (1995) 247.
[3] M. Hane, T. Ikezawa, G. H. Gilmer, Proc. SISPAD 2000, IEEE Catalog Number 00TH8502, p. 119 , IEEE, Piscataway, 2000.

Advanced technologies use successive implantations of p- and/or n-dopants without any intermediate annealing steps. A characteristic example is the engineering of the regions of source, drain, extension and halo. The sequence of the implantations may influence the final distribution of dopants and radiation damage. In particular it affects the as-implanted distribution of dopants if in one or more implantation steps the direction of ion incidence is close to a major crystallographic axis of the silicon substrate. For example, extension implantations are often performed perpendicularly to the wafer surface, i.e. nearly parallel to the [100] axis. The defect production in previous implantations influences the shape of dopant and damage profiles in a subsequent channeling implantation step, since these defects may lead to increased dechanneling. Furthermore, the amorphization dose in a certain implantation step may be affected by the level of radiation damage formed during the previous steps. The present work deals with the simple example of two consecutive implantations in order to demonstrate the effects mentioned above. Two implantation sequences are investigated: (i) 35 keV B followed by 50 keV As into the [100] channel direction, (ii) 50 keV As followed by 35 keV B [100] channeling implantation. The depth profiles of B and As are measured by SIMS. The as-implanted damage is determined by RBS/C. The experimental data can be reproduced by atomistic computer simulations using the Crystal-TRIM code with an improved phenomenological model for damage buildup during multiple implantations. The present results contribute to a better understanding of ion-beam-induced defect formation and to progress in TCAD.

The paper deals with the problematic of determination of the crack initiation for three point bend specimens during fracture toughness testing of materials in the upper transition and upper shelf region. In the presented study was developed Induced Current Focussed Potential Drop method for the fracture mechanics tests of Single Edge Notched Bend specimens of Charpy size. The performance of the newly developed technique is shown here. Obtained crack initiation integrals are compared with Stretch Zone Width based crack initiation integrals.

Positron emission tomography (PET) imaging of the radioactivity distributions induced by therapeutic irradiation is at present the only feasible method for an in-situ and non-invasive monitoring of radiooncology treatments with ion-beams. The clinical implementation of this imaging technlogy at the experimental carbon ion therapy facility at the Gesellschaft für Schwerionenforschung (GSI) at Darmstadt, Germany is outlined and an interactive approach for a PET guided quantification of local dose deviations with respect to the treatment plan is presented.

Es wird ein entwickeltes Überwachungssystem vorgestellt, das zum Online-Monitoring sicherheitstechnisch schwieriger chemischer Reaktionen in Rührkesselreaktoren entwickelt wurde. Die Industrieerprobung erfolgte an einer Mehrzweckanlage der Degussa AG.
Betriebserfahrungen und der praktische Nutzen werden am Beispiel des Semibatch-Betriebes eines heterogenen exothermen Hydrierprozesses aufgezeigt und diskutiert.

Stationary and time periodic wall parallel Lorentz forces in streamwise direction have been used to control the suction side flow
of NACA 0015 and PTL IV hydrofoils. Experimental results, consisting of flow visualizations and force measurements in the low Reynolds number range $Re=0.5 \dots 1.5 \times 10^5$ will be presented.
A stationary Lorentz force may increase lift by two mechanisms: 1) reattaching the separated flow and therefore increasing the critical angle and 2) introducing circulation due to acceleration of the attached suction side flow. Periodic excitation by oscillatory Lorentz forces near the leading edge is able to reattach the separated flow with much less momentum input then required for stationary forcing. However, to increase the maximum lift gain requires a comparable expenditure for both methods. The action of a wall parallel Lorentz force compares well to that of momentum input by blowing.

Electromagnetic flow control is a viable option, if the fluid in question is electrically conducting. In the case of liquid metals or
semiconductor melts, this control method is being used on an industrial scale. The application of Lorentz forces to fluids of low
electrical conductivity like seawater and other electrolytes is less common, although first efforts date back to the 1950s [1]. The present talk gives a short overview on separation control with steady wall parallel Lorentz forces [2], while the main part reports on recent activities on time periodic forces. The latter topic reveals certain parallels to current aerodynamic research on separation control by oscillatory blowing. The main motivation to investigate time periodic Lorentz forces is that periodic input of momentum has proven to be around two orders of magnitude more efficient than steady blowing [3].

An electromagnetic body force F results from the vector product of current density j and magnetic induction B. For fluids of low
electrical conductivity (10 S/m) as seawater and other electrolytes, the currents due to the induced voltages are generally very low for magnetic fields of moderate strength (1 T). Consequently, the Lorentz force due to these currents is negligible. In order to obtain current densities large enough for flow control purposes it is therefore necessary to additionally apply an electric field.

There are several distinct features, that make the Lorentz force an attractive actuator: momentum is directly generated in the fluid
without associated mass flux; its frequency response is practically unlimited; virtually any excitation wave form might be realized by
feeding the electrodes with appropriate current. On the other hand, efficiency of momentum generation by weak magnetic and strong electric fields is generally small, since Joule losses dominate in electrically low conducting fluids.

For the experiments described in the following, an arrangement of flush mounted electrodes and permanent magnets producing a streamwise wall parallel Lorentz force has been used. The Lorentz force decays exponentially with the wall distance. The characteristic parameter to describe the Lorentz force action on the suction side flow is the effective momentum coefficient cµ. It relates the rms­value of the momentum injected by the Lorentz force to the freestream dynamic pressure multiplied by the foil area. Since the mechanism of periodic forcing is supposed to be connected to shear layer excitation (see [3]), the actuator should be placed near the separation line. A sketch of the NACA 0015 equipped with permanent magnets and electrodes is given in Fig. 1. Flow visualizations on an inclined flat plate (Fig. 2) show, that the otherwise fully separated flow can be reattached in an averaged sense by a time periodic Lorentz force acting near the leading edge. A characteristic feature of the flow are the vortices moving along the plate. F+ is the excitation frequency nondimensionalized by chord length and freestream velocity. Direct force measurements on the stalled NACA 0015 reveal that the maximum lift gain occurs around F+ 1, the forcing effect decays relatively
rapidly for higher frequencies. A specific lift increase at a constant angle of attack and relativ to the value for the separated flow can be obtained by oscillatory forcing with fractions of the momentum input necessary for steady Lorentz forces. In contrast, an equal increase of the maximum lift gain requires a similar expenditure of momentum for both control methods.

Direct numerical simulations (DNS) at lower Reynolds numbers have been performed by using an well-established spectral element method [4]. The results obtained confirm the experimental findings in a qualitative sense. Figure 3 shows a snapshot of velocity contours (gray) and streamtraces of the controlled flow around an hydrofoil of 30o angle of attack at Re = 500, cµ = ...

First efforts on using Lorentz forces to control the flow of electrically low conducting fluids date back to the 1950s [1]. The
present talk reports on recent activities to delay transition in flat plate boundary layers and to control separation at hydrofoils by means of streamwise, wall parallel Lorentz forces. The actuator consists of a strip­like arrangement of permanent magnets and electrodes as proposed by [2].

Direct Numerical Simulations (DNS) by means of a spectral element method investigate the stability of a flat plate boundary layer under the influence of the Lorentz force. The evolution of Tollmien­Schlichting waves and proper 3­D disturbances is reported. A
stabilizing effect of the mean profile modification due to the Lorentz forces applied was found, verifying the assumption of [2].

Separation control at hydrofoils is undertaken by means of steady [3] as well as time periodic Lorentz forces. The latter topic reveals certain parallels to current aerodynamic research on separation control by oscillatory blowing. The main motivation for applying time periodic momentum input is that efficiency can be around two orders of magnitude higher than in case of steady blowing [4]. Since the mechanism of periodic forcing is supposed to be connected to shear layer excitation (see [4]), the Lorentz force actuator is placed in the nose region of the NACA 0015 investigated here. Direct force measurements on the stalled NACA 0015 reveal that the maximum lift gain occurs around a nondimensionalized excitation frequency of F+ 1, decaying rapidly for larger frequencies. For stalled hydrofoils, the same lift increase can be obtained by oscillatory forcing with only fractions of the momentum input necessary for steady forcing. In contrast, an equal increase of the maximum lift gain requires a similar expenditure of momentum for both control methods. DNS at lower Reynolds numbers confirm the experimental findings in a qualitative sense.

[1] Resler, E.L., Sears, W.: The prospects for
magneto­aerodynamics. J. Aero. Sci. 25, 235­245, 1958.

[2] Gailitis, A., Lielausis, O.: On a possibility to reduce the
hydrodynamic resistance of a plate in an electrolyte. Applied
Magnetohydrodynamics. Reports of the Physics Institute, 12, 143­146,
1961 (in Russian).

[3] Weier, T., Gerbeth, G., Mutschke, G., Lielausis, O., Lammers, G.:

Control of Flow Separation Using Electromagnetic Forces. Flow,
Turbulence and Combustion, 71, 5-17, 2003.

[4] Greenblatt, D., Wygnanski, I.J.: The control of flow separation by
periodic excitation. Prog. Aero. Sci., 36, 487­545, 2000.

The use of flash lamp annealing for processing semiconductor materials is outlined. Specific applications include ultra-shallow junction formation and heteroepitaxial growth of improved quality thin films of cubic silicon carbide. It is demonstrated that flash lamp annealing holds great promise as a technique for fabricating novel devices.

When a moving electrically conducting fluid is exposed to an applied magnetic field, electrical currents are induced that give rise to an additional magnetic field. The ratio of the induced field to the applied field is determined by the magnetic Reynolds number Rm. If Rm is not too small, the induced field can be measured in the exteriour of the fluid. Applying the imposed magnetic fields in different directions and measuring the respective induced fields one can gather sufficient information to reconstruct, at least approximatively, the velocity structure of the fluid. The theory of such a contactless inductive flow tomography (CIFT) is delineated, and its practical feasibility is demonstrated in a liquid metal experiment. Qualitative as well as quantitative changes of the flow field were resolved by the CIFT method in a reasonable and reproducible way.

Examplified by three case studies, we address the problem on how flow structures can be inferred from various magnetic field constraints. At first, we present the contactless inductive flow tomography in which we reconstruct the three-dimensional velocity field from externally measured induced magnetic fields. At second, we reconsider the optimization problem for the sodium flow in the Riga dynamo experiment. The third example concerns the special inverse spectral dynamo problem on how a spherically symmetric alpha^2 dynamo can become oscillatory.

Non-normal nonlinear transition of a linearly stable liquid metal flow driven by a rotating magnetic field is simulated numerically. Three dimensional Navier-Stokes equations are solved by a highly accurate spectral methods. Response of the flow to noise is simulated introducing a random body force. We observe four flow regimes. At a low control parameter the flow response does not differ from the response of a fluid at rest. In the second regime the amplitude of response is considerably higher though it scales linearly with the noise amplitude. Nonlinear intermittent outbursts are observed in the third regime. Duration of outbursts increases with noise amplitude until they merge in a continuous series in the fourth regime. We demonstrate that direct numerical simulation of the flow response to random forcing can uncover mechanisms which lead to transition in linearly stable flows.

We report on an experimental study of the influence of technical frequency pulsating magnetic field on a liquid metal volume. Such single-phase a.c. fields are widely used in metallurgy. Ultrasonic Doppler Velocimetry (UDV) has been used to determine the topology of the flow in a liquid metal column contained in a cylindrical vessel. Profile-scan-rates exceeding 25 Hz permit to acquire sequential time series for different radial co-ordinates which in turn allow to map the statistical properties of the flow. Concerning the sensitivity of UDV it was possible to measure values of the velocity down to a few mm/s. Even the flow is no more laminar in this regime almost any industrial situations are more turbulent. Limited by the maximum current which can be supplied to our magnet a range nearly spanning one order of magnitude of the driving magnetic field strength could be investigated. By that scaling laws derived analytically can be checked over a wide parameter range of industrial interest. The characteristic velocity was estimated from the time averaged mean profile in the centre of the container. Here the maximum absolute values of the vertical velocity component are found throughout the whole vessel in the up-stream in the upper half and the downstream in the lower half. Both local maxima scale nearly perfectly linear with the applied magnetic induction. This characteristic is similar to that of classical turbulent shear flows, even here the skin depth is not large compared to the dimension of the bath.

Potential difference probes and ultrasound have been employed to investigate liquid metal flows in cylindrical containers.
The fluid motion was driven by either a rotating or a pulsating magnetic field. Experimental results containing flow mapping and scaling of mean velocities for very small driving forces will be presented. We report on our new MULTIMAG facility which allows for almost any combination of rotating, traveling, pulsating and d.c. magnetic fields in extended geometries for industrially relevant regimes.

An experimental and numerical study with respect to the influence of a rotating magnetic field (RMF) on the directional solidification of a Pb-Sn alloys is reported. A cylindrical crucible with a diameter of 50 mm was positioned on a water cooled copper chill thus inducing an axial heat transfer from the mold. The electromagnetically driven convection shows a distinct effect on the solidification parameters such as the cooling rate, the temperature gradient or the growth velocity of the liquidus isotherm resulting in significant modifications of the observed macro- and microstructures. The fluid flow promotes the heat transfer rate and decreases the temperature gradients in the melt. Analyzing the columnar-equiaxed transition (CET) a dependence of the CET position and shape on the applied Taylor number was demonstrated. The experiments also revealed that the permanent modification of the fluid volume due to the movement of the solidification front prevents the development of stationary flow pattern as known for the isothermal case.

A tin liquid metal ion source contaminated with led has been studied. From a detailed analysis of the source mass spectra as a function of emission current it is established that while Sn+, Sn++ and Pb+are directly field-evaporated from the liquid surface, Pb++ forms by the post-ionisation of Pb+. Moreover, our results for, the Pb++/Pb+ ratio are in excellent agreement with those of Komuro (1983), obtained with a pure led LMIS.

Excited levels in ⁶⁹Se have been studied using the ⁴⁰Ca(³²S,2pn)⁶⁹Se reaction at 95- and 105-MeV beam energy. γ-rays have been detected with the EUROBALL spectrometer operated in conjunction with the wall and the charged-particle detector array EUCLIDES. New level sequences with positive and negative parities have been identified from n-γγ and n-γγγ coincidences. Spins have been assigned to many of the levels on the basis of angular distribution and directional correlation measurements. Excitation energies of the positive-parity yrast band and the branching ratios of its decay are compared with the predictions of the rigid triaxial rotor plus particle model.

This prospective study assessed the impact of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) on the staging an d possible consequential changes of treatment regimen in patients with Hodgkin´s lymphoma (HL). A total of 88 consecutive patients with histologically verified Hodgkin´s lymphoma underwent a PET scan in addition to conventional staging procedures. Treatment was based on the conventional staging only, and the results of the FDG-PET did not affect the treatment strategy. The evaluation focused on the suggested change in clinical stage according to the Ann Arbor classification and on the suggested change in treatment strategy rather than on a lesion-by-lesion analysis. Using all the methods performed as the standard of reference, ¹⁸F-FDG-PET staging was concordant with conventional staging in 70 out of 88 patients (80 %). ¹⁸F-fluorodeoxyglucose positron emission tomography suggested a change to a different clinical stage in 18 patients (20 %). Management would have been changed in 16 patients (18 %): intensification of treatment in nine patients (10 %) and minimisation of treatment in seven patients (8 %). In the 44 patients with early disease (stage IA - IIB), treatment would have benn intensified in nine out of 44 patients (20 %). ¹⁸F-fluorodeoxyglucose postitron emission tomography is a relevant noninvasive method that supplements conventional staging procedures and should therefore be used routinely to stage Hodgkin´s lymphoma, particularly in patients with an early stage.

Focused ion beams from liquid metal ion sources (LMISs) have become of increasing interest in recent years. A promising source is one of Ge ions, important in the semiconductor technology; e.g., local doping of SixGe1-x structures. The beam energy spread, ΔE½, of the source - which, through the chromatic aberrations of the system determines the final spot size at the target - and the peak energy deficit (PED), as well as the mass spectra of a Au73Ge27 eutectic liquid metal alloy ion source were investigated. Source temperature was the main experimental parameter. The melting point of the eutectic was determined as 366oC. ΔE½, measured with a retarding field analyser, is expressed as the full width of the distribution at half its maximum height (FWHM). Doubly-charged ions attain twice the energy of singly-charged ions, for a given voltage drop, and this has to be taken into account when determining the value of ΔE½ and the PED. Ge was found to be much more abundant in the doubly-charged state, in accordance with Brandon`s criterion [1]. From PED measurements we conclude that Ge++ as well as Au+ and Ge+ are directly field-evaporated, whereas Au++ is post-ionized from the singly-charged state. As expected for liquid metals that display a linear decrease of their surface tension coefficient with temperature, the liquid metal ion source under investigation shows an increase in emission current with increasing temperature. This is in contrast to Si containing metallic glass alloys, e.g., AuSi or AuGeSi, that have an anomalous surface tension coefficient [2]. The mass spectra, where obtained with an ExB filter. Alongside the main monomer species, cluster ions, the result of droplet disintegration, were identified. The conclusions drawn from a study of the ratio of the abundance of doubly to singly-charged monomer ions, support our deductions from PED measurements, as far as the mechanisms of creation of the monomer ions are concerned.
[1] D.G. Brandon, Surf. Sci. 3 (1964) 1.
[2] L. Bischoff and G.L.R. Mair, Recent Res. Devel. Appl. Phys. 6 (2003) 123.

Die Kühlmittelvermischung im Primärkreislauf von Druckwasserreaktoren (DWR) ist für zwei Klassen von hypothetischen Störfällen relevant: Borverdünnungsstörfälle und Kaltwassertransienten. Ausgehend von den Vermischungsphänomenen, die für diese Szenarien bedeutsam sind, wurde die Versuchsanlage ROCOM (Rossendorf Coolant Mixing Facility) konzipiert und aufgebaut. Die Untersuchung der Vermischung erfolgt anhand eines Tracers (verdünnte Salzlösung) und der Messung der Leitfähigkeit des Fluids. Die experimentellen Ergebnisse wurden auf Grundlage eines blockstrukturierten Gitters mit CFX-4 (450000 Nodes) bzw. eines unstrukturierten, tetraederbasierten Gitters mit CFX-5 (5 Mio. Tetraeder) unter Zuhilfenahme des k,e Turbulenzmodells nachgerechnet. Dabei mussten Einbauten im strukturierten Gitter mit Hilfe des Modells des porösen Körpers und Einführung von richtungsabhängigen Körperkräften modelliert werden, während im unstrukturierten Gitter die Geometrie komplett abgebildet werden konnte. Die Rechnungen wurden auf einem LINUX-Cluster im Parallelmode durchgeführt. Die Experimente an der ROCOM-Anlage zur stationären Kühlmittelzirkulation bei Betrieb aller Schleifen zeigen übereinstimmend mit den numerischen Berechnungen eine Beschränkung der Verteilung des eingespeisten Tracers am Kerneintritt überwiegend auf den Quadranten der mit dem Tracer beaufschlagten Schleife. Für turbulente Strömungen konnten die Berechnungscodes somit anhand von Experimenten validiert werden und steht für weitere Untersuchungen in der Reaktorsicherheitsforschung zur Verfügung. Die Ergebnisse der Experimente und CFD-Rechnungen fließen in ein Modul ein, welches in Computercodes für Störfallanalysen integriert wird. Über eine verbesserte Beschreibung der Vermischung wird dadurch eine realistische Störfallsimulation erreicht.

Partial depletion of the primary circuit during a hypothetical small break loss of coolant accident can lead to interruption of one-phase flow natural circulation. In this case, the decay heat is removed from the core in the reflux-condenser mode. Thermal hydraulics analyses using the system code ATHLET showed for the scenario of hot leg side leak and hot leg safety injection, that weakly borated condensate can accumulate in particular in the pump loop seal of those two loops, which do not receive safety injection. According to these ATHLET-calculations, one-phase flow is maintained in the remaining two loops at high residual heat conditions because of the entrainment of safety injection coolant into the steam generators. After refilling of the primary circuit, the natural circulation in the two stagnant loops simultaneously re-establishes and the de-borated slugs are shifted towards the reactor pressure vessel (RPV). Mixing in the downcomer and the lower plenum is an important phenomenon mitigating the reactivity insertion into the core in this postulated scenario.
Therefore, the mixing of the de-borated slugs with the ambient coolant in the RPV was investigated at the four loop 1:5 scaled Mixing Test Facility ROCOM.
Based on the ATHLET-calculations, a volume flow rate of 5 % of the nominal rate was set in the loops running in one-phase flow. The volume flow rate in the two restarting loops increases from zero to 6 %. In these two loops, de-borated slugs of 7.2 m3 were assumed corresponding to the volume of the whole loop seal. An experimental parameter study was carried out with different duration of the flow ramp and variation of the density difference between de-borated slug and ambient coolant due to differences in boron concentration and temperature.
The variation of the density difference significantly changes the mixing behavior. With no density differences, the weakly borated coolant almost perpendicularly flows down in the downcomer and a maximum of 64 % of the initial perturbation is detected in the core entry section below the loops where the slugs were formed. Increasing the density difference, a stratification is observed in the downcomer. The less dense slugs flow around the core barrel at the top of the downcomer. At the opposite side the lower borated coolant is entrained by the colder safety injection water and transported to the core. This entrainment effect leads to the admixture of boron from the safety injection to the under-borated slugs. Consequently, the maximum of under-boration at the core entry is lower. For the maximum density difference of 2 % investigated in the frame of this work, a value of 31 % only of the initial perturbation was measured.

Modification of semiconductor materials by ion implantation is a well-established technological process. It can modify semiconductor material by producing crystal lattice defects as well as by alloying the substrate with the implant. The first introduces stress/strain into material or mixing of the constituents. The second effect leads to semiconductor doping or creation of new phases. Precise control of structural properties are crucial for technological applications. We present here, how various methods of x﷓ray scattering can be used for structural studies on such materials for optimization of the ion beam treatment of semiconductors. In some cases also complementary techniques like RBS/c were used.
As+ ions with an energy of 1.2 MeV were implanted into InP single crystals and epitaxial layers. Due to the ion induced strain, interplanar spacing in the growth direction decreases with increasing ion dose. Important recovery of radiation damage was observed upon prolonged storage at RT. Furthermore, patterned ion implantation is used for modification of lateral regions. XRD revealed that the presence of a masked region produces strain variations across the sample. RBS/c analysis showed that such an edge effect is independent on implantation conditions.
Silicon carbide and diamond are semiconductor materials for high temperature, high frequency and high power applications. However, a heavy p-type doping of SiC is difficult and a sufficient n-type doping of diamond was not yet realized. Therefore, the fabrication of diamond-SiC heterostructures by ion beam synthesis (IBS) is a new approach to novel devices. It was found that the synthesized nanocrystals grow in the surrounding single crystalline matrix highly oriented. The crystal size and shape, their strain and strain fluctuation vary in dependence on the implantation parameters like dose, dose rate and substrate temperature. The lattice damage of the matrix may be minimized by high temperature treatment.

This review covers a part of the current general directions in radiopharmaceutical research and development, being the design of ^99mTc-containing steroids capable of binding and imaging the estrogen receptor, progesterone receptor or androgen receptor. The non-physiological metal technetium has to be adapted to the biological environmental by means of coordination chemistry. As a d-block transition metal, technetium must be incorporated into small-molecule receptor ligands like steriods by some chelation system, which may involve multiple heteroatom coordination of the formation of stable organometallic species. The review will also address examples of rhenium-containing steroids as non-radioactive models for the radiopharmaceutically relevant ^99mTc compounds.

Aus Gründen der Anlagensicherheit und der Sicherung einer hohen Ausbeute und Produktqualität ist die frühzeitige Erkennung von unerwünschten Prozessabweichungen bei Batch- und Semibatchprozessen von besonderer Bedeutung. Aufgrund der instationären Prozessführung sind diese oft nicht aus den Prozesssignalverläufen eindeutig erkennbar. Ziel war deshalb die Entwicklung eines Online-Monitoring-Systems, das dem Operator Informationen über die Konzentrationsverläufe und den Prozessfortschritt zur Verfügung stellt.
Die Bewertung des Prozesszustandes erfolgte bisher in der Regel auf Grundlage der Prozessdatenverläufe (z. B. Temperaturen und Drücke) unter Einbeziehung von Erfahrungswissen, wobei Konzentrationsmessungen erst nach dem Prozessende im Rahmen von Qualitätskontrollen oder während des Prozesses stichprobenartig offline durchgeführt wurden. Der Aufwand bezüglich Probenahme und Handling ist hierbei erheblich. Alternativ ist die Nutzung einer Online-Analytik möglich, die jedoch sehr hohe Investitions- und Betriebskosten verursacht.
Das Online-Monitoring-System MoSys ist ein auf adaptiven Stoff- und Energiebilanzen basierendes Softwaresystem, das dem Operator Informationen über den Prozessfortschritt, das voraussichtliche Reaktionsende und die Konzentrationen der Reaktionsmedien zur Verfügung stellt. Die Berechnungen erfolgen online auf Grundlage von Prozessmessdaten und Zusatzinformationen über den Prozess. Der Einsatz einer Online-Analytik ist nicht erforderlich. Die Ergebnisse sind an den Terminals des Prozessleitsystems abrufbar.
Die Entwicklung richtet sich in erster Linie an Anlagenbetreiber der Feinchemie und der pharmazeutischen Industrie. Ein derartiges Online-System ist bei allen ausreichend exothermen Batch- und Semibatch-Prozessen einsetzbar, wenn die Nutzinformationen in den Wärme- und Stoffbilanzen enthalten sind. Neben einer Erhöhung der Anlagen- und Umweltsicherheit wird durch den Einsatz des Systems weiterführendes Prozesswissen generiert, das als Grundlage für eine Prozessoptimierung genutzt werden kann.

On the basis of detailed experimental data obtained for stationary bubbly flow in vertical pipes with an inner diameter of 51.2 mm and 194.1 mm, analytical investigations on scaling effects were made. Because of the interaction between the phases the scaling behavior is very complex in case of two phase flow. Similarity can only be achieved regarding selected parameters. Thus the modeling of scaling effects has to be based on local models for the phase interaction. A simplified model, introduced earlier, is used for the validation of such models by consideration of scaling effects. Because of the strong influence of the bubble size distribution on the flow, the model considers a number of bubble classes. Models for the non-drag forces acting on bubbles were validated for the small pipe and afterwards used for the prediction of radial gas volume profiles in the large pipe. The comparison with measured profiles shows that there is a generality of these models. Even more complex is the situation regarding the development of the flow along the pipe. Here bubble coalescence and break-up are important. There is still a need for an improvement of these models.

Annealing or increasing growth temperature enhance interface fluctuations, causing drastic influence on GMR and interlayer coupling. The present X-ray measurements were aimed to study the influence of the sapphire substrate temperature during MBE on the in-plane layer stress and the degree of orientation in the Fe/Cr multilayers (MLs). A series of five samples was investigated, grown in the range 60-240°C on the oriented substrate, having a Cr buffer layer in the assembly Al₂O₃/Cr(8nm)/[Fe(3nm)/Cr(1.2nm)]x8. The data were received with Cu radiation using a standard goniometer setup. At the sapphire R-plane the Fe/Cr multilayers grow in [100] direction. The orientation distribution in the layers was analyzed by rocking curves of the (200) reflection. The layer stress could be determined from the (200) reflection, measured in ML normal direction, and the perpendicularly measured reflections (020) and (002). The studies reveal that the sharpness of the (200) Fe/Cr orientation is proceedingly reduced with increasing substrate temperature. This is accompanied by a drastic relaxation of the tensile in-plane layer stress.

Bacterial diversity was assessed in water samples collected from two uranium mill tailings, one in Germany and one in the USA, by using the 16S rDNA retrieval. Mainly individual RFLP types were found in the 16S rDNA library constructed for the samples of the German tailings, Gittersee/Coschütz, that indicated a high bacterial diversity. Several small groups of Proteobacteria and of Cytophagales were identified in those samples as well. Significantly lower bacterial diversity was demonstrated in the samples collected from the Shiprock tailings in the USA, which were predominated by a few large populations of gamma-Proteobacteria.
Key words: bacterial diversity, 16S rDNA, uranium mill tailings
Introduction: Bacteria significantly influence the migration and the toxicity of heavy metals and radionuclides in nature due to their ability to biotransform and accumulate them [1,2]. Uranium mining wastes are contaminated with radionuclides and other toxic metals [2]. The toxicity of uranium is primarily attributed to its chemical properties rather than to its radioactivity [3]. As in other extreme environments, most parts of the indigenous bacterial populations in the uranium mining wastes are not yet cultured due to the limited knowledge of their life necessities. The problems of culturability in the analysis of bacterial diversity were overcome during the last decade by the application of direct molecular methods for analysis, such as the 16S rDNA retrieval [4]. This molecular method was successfully used for compositional analysis of the natural microbial communities in many different environments [5,6,7]. The aim of the present work was to assess bacterial diversity in water samples collected from two uranium wastes by using the 16S rDNA retrieval.
Materials and methods. Samples collection. Samples were collected from two uranium mill tailings: Gittersee/Coschütz, a former uranium-coal mine, near the town of Dresden in Germany and Shiprock, New Mexico, in the USA, located in north western New Mexico,

Structures of the natural bacterial and archaeal communities in soil and water samples from three U wastes in Germany and from two in the USA were compared by using the 16S rDNA and the RISA retrievals. We found that the composition of the bacterial communities is very diverse and site-specific. However, several particular groups of bacteria including also novel lineages were identified in the samples of all habitats. Some of the retrieved 16S rDNAs were related to sequences already found in other heavy metal contaminated environments and it seems that they represent not yet cultured bacterial populations characteristic for the latter.
A quantitative analysis of the Geobacter sp. populations demonstrated that they are present in low but site-specific number at the studied environments.
The archaeal populations in the studied environments were, in contrast to the bacterial, not very dense and they were limited to only two lineages of not yet cultured groups of Crenarchaeotae. Only in one of the samples studied representatives of methanogenic Euryarchaeotae were identified.
Chemolithoautotrophic strains involved in U mobilization and also heterotrophic U reducing and immobilizing strains were cultured from the samples from the U wastes. In addition, several ultramicrobacterial isolates were cultured on oligotrophic media. These isolates were characterized morphologically and physiologically. Their interactions with U and several other metals were studied by using ICP-MS, EXAFS, and IR spectroscopy.

Microbial diversity was studied in water samples collected from depths of 290 to 324 m near the radioactive waste injection site Tomsk-7 in Siberia, Russia. The biomass from the samples was concentrated via consequent filtration on filters with pore sizes of 1.2, 0.45 and 0.22 µm. 16S rDNA clone libraries were constructed for total DNA recovered simultaneously from the three filters and also for the DNA extracted individually from 0.45 and 0.22 µm filters in parallel. The analysis of the 16S rDNA libraries demonstrated that the estimation of microbial diversity strongly depends on the way of collecting the biomass.
About 65% of the clones retrieved in the total DNA were affiliated to the Rhodocyclus group. The rest of the clones represented very diverse bacterial groups. Euryarchaeota and Grenarchaeota were also identified in this total DNA.
No archaeal sequences were amplified in the 0.45 and 0.22 µm filter DNA. This indicates that the archaea were associated (possibly with some bacteria) with the larger aquatic particles.
In the 0.45 mm library the representatives of the Rhodocyclus group represented 30% of the total number of clones. Another 20% of the clones were affiliated with a low identity to a novel cyanobacteria related lineage.
Sequences representing the same "cyanobacteria-like" lineage were also found in the 0.22 µm library. However, populations of possibly oligotrophic Cytophagales were the most predominant in the latter library and represented about 55% of the clones. Microdiverse ultramicrobacterial isolates were cultured from one 0.22 µm filter and characterized morphologically and physiologically.

RBS - Channeling - Messungen werden routinemäßig zur Untersuchung von Kristallqualität und -defekten genutzt, wobei die Größe des Ionenstrahls üblicherweise im mm-Bereich liegt. Durch eine Verkleinerung des Strahldurchmessers in den µm-Bereich erschließen sich Möglichkeiten der Untersuchung von Mikrokristallen. Damit verbunden ist jedoch eine starke Erhöhung der notwendigen Fluenz des Ionenstrahles, die zu einer verstärkten Kristallschädigung während der Analyse führt.
Im Vortrag werden nach der Vorstellung der Rossendorfer Mikrochanneling-Apparatur die durch den Mikrostrahl erzeugten Kristallschädigungen diskutiert und daraus Grenzen für die Anwendung abgeleitet. Ein erstes Untersuchungsbeispiel soll die Möglichkeiten von Channeling-Messungen mit dem Mikrostrahl verdeutlichen.

Fourier transform (FT) is a fundamental step for the data reduction and interpretation of extended x-ray absorption fine structure (EXAFS) spectra. The FT separates backscattering atoms by their radial distance from the absorbing atom (so-called shells). We suggest to routinely complement the FT by a wavelet transform (WT), which provides not only radial distance resolution, but resolves in k space. This information eases the discrimination of atoms by their elemental nature, especially if these atoms are at the same distance. We present an in-depth analysis of the Morlet wavelet, which has specific advantages for EXAFS analysis, including the possibility to estimate Morlet parameter values optimized either for elemental or for spatial resolution. Using an experimental spectrum of Zn-Al layered double hydroxide, we demonstrate the discrimination of Al and Zn at a similar crystallographic position, in spite of destructive interference substantially reducing signal information. Finally, the extension to multiple scattering paths leads to a deeper understanding of the resolution properties of the WT.

The high-acceptance dielectron spectrometer HADES has become operational at GSI. Its physics program is reviewed with special emphasis on the planned studies of hadron properties in proton- and pion-induced reactions. The relevance of these data for the interpretation of dilepton data from heavy-ion reactions is stressed as well.

A general framework is presented for the modeling of turbulent dispersion in Eulerian Multi-Phase Flows. The approach is based on a double averaging procedure of the local instant equations. We start with the ensemble averaged equations of Eulerian multi-phase flow. We perform a second time average of these, in order to form equations which may be used to model turbulent multi-phase flows. These are conveniently expressed in terms of Favre or Mass averaged variables. Turbulent dispersion is modeled by performing a time average of the interphase drag term in its modeled form, and expressing it in terms of Favre averaged variables. The resulting double averaged momentum equations contain additional terms which account for a turbulent dispersion force. We call the resulting model the Favre Averaged Drag (FAD) model for turbulent dispersion. It is first presented in a general form which may be used in conjunction with any Reynolds averaged turbulence model, and for an arbitrary number of phases with arbitrary morphologies. For the purposes of this study, we make two further specializations, to poly-dispersed multiphase flows, and to turbulence models which employ the eddy diffusivity hypothesis. The resulting model is compared to several other models that have appeared in the literature, We show that all are special cases of the FAD model, within certain physical and mathematical limitations. Hence the FAD model encompasses all of these models, but has a potentially wider range of universality. The FAD model has been implemented in the commercial CFD package, CFX-5, and tested against a range of dispersed multiphase flows, including bubbly flows in vertical pipes, and liquid-solid flows in mixing vessels. The FAD model is shown to yield superior predictions in all cases.

The C+C reaction at 2 A GeV has been recently studied using the HADES spectrometer installed at GSI Darmstadt,with the main aim to reconstruct the dielectron signal from the decay of low mass vector mesons.We have analyzed the data with respect to emission of charged hadrons,in order to study production of ð mesons from excited nuclear matter with high temperature and high energy density.
Efficient hadron identification is also important for dielectron analysis.The main source of electron pairs at this energy is the neutral ð meson Dalitz decay,so normalization of its yield to charged ð mesons is a natural way for data presentation.Analysis of produced hadrons also allows event characterization,and check of the detector performance. The particle identification method (PID),based on a likelihood technique to select the most probable particle type,is described.In case of hadrons,the particle momentum,velocity and energy loss are used for the PID decision.The performance of the method is evaluated in detailed simulations.
Preliminary results of analysis of charged hadron production are presented.The particle yields and transverse mass distributions are shown and interpreted in terms of the thermal model.Results are compared with existing data from previous experiments.

This work shows that self-assembled molecular (SAM) films of silanes and alkanethiolates can be used as surface active agents for direct 50 nm pattern transfer from a metallic or semiconductor master to metallic surfaces. The patterned metallic surfaces can be modified again by alkanethiolate SAMs to be used as a further mold for master replication. It is also demonstrated that the patterned metallic surfaces are excellent templates to produce nanopatterned metal-semiconductor hybrid surfaces by controlled chemical reactions.

The propagation of surface plasmons in thin silver films and their interaction with defined surface grooves are presented. Of interest to photonic structures are both the optical transmission across barriers and other structures, but also the coupling to free-space electromagnetic waves. We present results on plasmon transmission and reflection at grooves written with a focused ion beam (FIB) into a thin silver film. In order to monitor the optical properties of travelling plasmons excited in attenuated total eflection (ATR), we apply near-field optical microscopy using a dielectric fiber tip. Our results agree well with former theoretical redictions.
Furthermore, we report on optical observation of plasmons propagating at the silver-glass interface rather than the silver-air interface as usually monitored. This manifests itself in a very exciting beating phenomenon between plasmon modes running at the silver-air and silver-glass interface.

Using scanning near-field optical microscopy for probing surface plasmon fields, we show that energy can be transferred from the plasmon propagating on one interface to the mode bound to the other interface of a thin metal film. This coupling is mediated by a narrow groove interrupting the silver film. Excitation of the second plasmon mode is detected by mapping the spatial intensity modulation induced by the interfering fields of the two plasmons. A quantitative analysis provides detailed knowledge about the degree of coupling. Our inter-pretation of the experimental results is confirmed by a numerical simulation of the field distribution.

The e ffect on source stability of removing the extractor electrode from a liquid metal ion source system has been investigated.The noise of the current and the corresponding frequency spectra were carefully studied. The findings in
the two cases,i.e.with and without an extractor electrode,were found to be very different.The explanation for this is given in terms of different droplet emission mechanisms being operative in the two cases.The liquid emitter used was a AuGeSi alloy.Focused Ge and Si ion beams are important for icroelectronics applications.Thus,an understanding of the mechanisms that lead to source instability is essential.

During the last decades, the focused ion beam (FIB) became a very useful and versatile tool in the microelectronics industry, as well as in the field of research and development. For special purposes like writing ion implantation or ion mixing in the µm- or sub-µm range ion species other than gallium are needed. Therefore alloy liquid metal ion sources (LMIS) were developed. The energy distribution of the ions from an alloy LMIS is one of the determining factors for the performance of an FIB column. Different source materials like Au73Ge27, Au82Si18, Au77Ge14Si9, Co36Nd64, Er69Ni31, and Er70Fe22Ni5Cr3 were investigated with respect to the energy spread of the different ion species as a function of emission current I, ion mass m and emitter temperature T. For singly charged ions a predicted dependence of the energy spread, DE µ I2/3 m1/3 T1/2 found for Ga could be reasonable confirmed. The alloy LMIS`s discussed above have been used in the Rossendorf FIB system IMSA-100 as well as in recent time in the new IMSA-OrsayPysics FIB especially for writing implantation to fabricate sub-µm pattern without any lithographic steps. A Co-FIB obtained from a Co36Nd64 alloy LMIS was applied for the ion beam synthesis of CoSi2 micro-structures down to 60 nm. Additionally, the possibility of varying the current density of the FIB by changing the pixel dwell-time was used for investigations of radiation induced damage and its dynamic annealing 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. Especially this direct patterning 3D technique was used for the fabrication of various kinds of micro-tools.
Running and future activities will be discussed which are focused to the preparation and investigation of plasmonic structures, like nano-wires and nano-chains in the sub-micron scale down to a few ten nanometers.
All these examples underline the importance of FIBs in modern research and the new possibilities opened up by a mass separated system applying a broad spectrum of ion species.