Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The possibility to create a delta-like, interface-near Ge nanocluster band in a 20 nm thin SiO2 layer by ion beam synthesis is demonstrated. The role of the post implantation annealing conditions for the formation of Ge nanoclusters in the centre of the layer, near the interface or in both regions is discussed. The presence of hydrogen in the annealing atmosphere accelerates the redistribution of Ge in SiO2. By applying a two-step annealing process, preannealing in hydrogen containing at low temperature followed by a rapid thermal annealing at high temperature, the controlled fabrication of a single delta-like, interface-near Ge nanocluster band was achieved. In some clusters <100> lattice planes of Ge were observed. From this and similar contrast situation for amorphous clusters it is concluded that the inerface near clusters consist of elementary germanium.

Die zeitaufgelöste optische Spektroskopie mit Femtosekunden Laserpulsen ermöglicht die Untersuchung der Dynamik von Elektronen und Phononen und deren Wechselwirkung in Halbleitern in Echtzeit. Ein besonderes Objekt des Interesses sind Bloch Oszillationen, die ein Faszinosum der Festkörperphysik darstellen. Bereits in frühen Arbeiten von Bloch und Zener wurde die Vorhersage gemacht, dass ein Elektron in einem periodischen Potential eines Festkörpers unter dem Einfluß eines statischen elektrischen Feldes oszilliert, wobei die Oszillationsfrequenz linear vom elektrischen Feld abhängt. In Abwesenheit von Streuprozessen hätte dies die Konsequenz, dass kein elektrischer Strom fließen würde. Anfang der 90er Jahre gelang es, künstliche Kristallgitter - sogenannte Halbleiter-Übergitter - mit hinreichender Qualität herzustellen, in denen Bloch Oszillationen in optischen Experimenten mit sub-Pikosekunden Zeitauflösung beobachtet werden konnten. Diese Halbleiter Übergitter sind ein Modellsystem für die Untersuchung kohärenter Wellenpakete und deren Dephasierung in Halbleiter Heterostrukturen. Von besonderem Interesse ist hierbei die Wechselwirkung der oszillierenden Elektronen mit optischen Phononen. Diese konnte kürzlich unter resonanten Bedingungen, d.h. bei Abstimmung der Bloch Frequenz auf die optische Phononfrequenz, untersucht werden, was Aufschluß über einen neuen Mechanismus zur Anregung kohärenter optischer Phononen gab.

Inorganic colloids in mine waters are mainly produced by the formation of oxyhydroxides and oxyhydroxy sulfates of iron(III) and aluminum due to the oxidation of Fe2+ and the hydrolysis of Fe3+ and Al3+. They are of relevance as they are able to influence heavy metal transport (emphasis is laid on the behavior of uranium here). Two extremely different types of mine waters can be observed:

(i) Type "acidic pore water"
These waters possess high salt concentrations and are very acidic (pH 1 to 3). Ultrafine particles of <5 nm are the main colloidal component. The colloid concentration reaches the range of >1 g/L. The particles consist mainly of H-jarosite and schwertmannite. As and Pb show a high tendency to adsorb onto these particles.

(ii) Type "bulk water"
This type of waters mainly refers to the flowing mine waters like adit waters which possess a near-neutral pH. Typical colloid contents of such waters are about 1 mg/L, typical particle sizes are 100 to 300 nm. The particles consist of Fe(III) and Al oxyhydroxides. Their electrostatic stabilization is weak, i. e. they show a larger tendency to coagulate. Contaminants such as As, Pb, Cu, Th, U(IV) and Po are bound onto these particles. Uranium(VI) adsorption is often suppressed due to the formation of uranyl carbonato complexes in mine waters.

An interesting colloid chemistry is observed during the transition of type (i) waters to type (ii) waters (flooding of abandoned ore mines). Huge amounts of iron(III) particles with a size of 100 to 300 nm are formed under such conditions. The adsorption rises drastically when the pH reaches the near-neutral region. Uranyl adsorption to the iron(III) particles is neither suppressed by high acidity nor by uranyl carbonate complexation in the pH region 4 to 6. Therefore, most of the uranium(VI) is colloid-borne in waters of the transition type.

The effect of radiation embrittlement has high safety significance for Russian VVER reactor pressure vessel steels. Heats of base and weld metal of the as-received state, irradiated state and post-irradiation annealed state were investigated by SANS to get insights about the microstructural features caused by fast neutron irradiation. The SANS intensities increase in the momentum transfer range between 0.8 and 3 nm-1 for all material compositions in the irradiated state. The size distribution function of the irradiation-induced defect clusters has a pronounced maximum at 1 nm in radius. Their content varies between 0.1 and 0.7 vol.% dependent on material composition and increases with the neutron fluence. The comparison of nuclear and magnetic scattering indicates that the defects differ in their composition. Thermal annealing reduces volume fraction of irradiation defect cluster.

Cu is especially suitable to decorate defects in silicon. The Cu decoration technique has been
applied for the detection of point defect clusters in the RP/2 region of Si+ ion implanted silicon. The results of
this technique are compared with the results obtained by other analysis techniques. Nanocavities at RP/2
could be observed only in cross section transmission electron microscopy specimen prepared by cleavage
technique. These nanocavities are probably the dominant gettering centres for Cu at RP/2. Small interstitial
clusters may exist there as well. The conditions for the formation and for the annealing of the gettering layer
at RP/2 have been determined. Impurity gettering at RP/2 can be prevented by a sequence of additional Si+
implantations to balance implantation-induced excess vacancies which are the origin of the nanocavities.

The radiochemistry experimental station at ROBL has been designed to perform environmentally relevant experiments on radionuclides, in particular actinides, using X-ray absorption fine structure spectroscopy. The technical concepts and the layout of this experimental station, where radioactive solids and liquids with activities of up to 185 MBq can be studied, are presented. The radiological safety of experimenters, equipment, and of the environment are ensured by the specially developed radiochemistry safety system.

A computer program is presented that is able to connect (to "splice") two EXAFS spectra of the same sample if they have an overlapping energy region. This tool will be useful in many situations when it is impossible to measure a spectrum over the desired energy range in a single scan.
Technical details of the SPLICE program are described to overcome the difficulties concerning the adjustment of different EXAFS spectra containing information about the same sample at different energies. The SPLICE program was tested at the U LIII edge using EXAFS spectra of an uranyl arsenate sample measured up to k of 22 Å -1 at a temperature of 15 K.

The abandoned uranium mines in the Western Erzgebirge in Germany are mostly related to the rock phyllite. Currently, many of these mines are being flooded. The flood water, which contains concentration of uranium penetrates through cracks and fissures of the phyllite and leads to a dissolution of several minerals. One of the major components in the phyllite is an iron-rich chlorite [1], which dominates the sorption behaviour for heavy metals.
During the dissolution of the chlorite a reaction causes the loss of octahedral layer cations, primarily Fe. Ferrous iron is released in the aqueous solution, where it is oxidized rapidly to ferric iron. Hydrolysis of ferric iron leads to Fe-oxyhydroxide, which precipitates from the solution as due to the low solubility of iron in the pH region higher 4 [2]. By scanning electron microscopy, these precipitates of Fe-oxyhydroxide are detected as small spherical particles of ferrihydrite that are preferentially situated as immobile coatings on the most reactive edge surfaces of the chlorite crystals. During the dissolution of chlorite a mobile component of ferrihydrite is formed, too. These are colloids, which are found under similar geochemical conditions. The mobile colloids are aqueous species that do not adsorb to rock surfaces. The adsorption of contaminants, for example uranium onto the colloidal particles of ferrihydrite influences and enhances the rate of contaminant transport. In previous investigations the uptake of uranium on ferrihydrite reaches almost 95-100 % in a pH range from 5.0 to 7.5 [1]. Conclusively, the formation of secondarily formed ferrihydrite as mobile colloids and as immobile coatings during the dissolution of chlorite in the rock phyllite is an important process which has to be considered in risk management.
References:
[1] Arnold, T. et al. (1998): Chemical Geology 151,
129-141.
[2] Zänker, H. et al. (2000): Aquatic Geochemistry
(submitted).

Das Erdmagnetfeld ensteht durch Strömungen im flüssigen äußeren Erdkern, welche durch Auftriebskräfte und die Rotation der Erde angetrieben werden. Trotz der Fortschritte, die insbesondere im letzten Jahrzehnt bei der numerischen Behandlung des gekoppelten Systems von Induktionsgleichung und Navier-Stokes-Gleichung gemacht worden sind, ist eine realistische Berechnung der Vorgänge im Erdinneren in absehbarer Zukunft nicht möglich. Flüssigmetallexperimente liefern einen komplementären Zugang zum Verständnis homogener Dynamos. Im Vortrag werden die Ergebnisse der jüngsten Rigaer Dynamoexperimente vorgestellt und mit den numerischen Prognosen verglichen.

Als Quelle kosmischer Magnetfelder wird heute einhellig der homogene Dynamoeffekt in elektrisch leitfähigen Fluiden angesehen. Im Gegensatz zu der inzwischen weit entwickelten Theorie und Numerik dieses Effektes war die experimentelle Untersuchung bis vor kurzem nicht möglich gewesen. Am 11.11.1999 wurde an der Rigaer Natriumanlage erstmalig der homogene Dynamoeffekt in einem Flüssigmetall-Experiment nachgewiesen. Weitere Messungen im Juli 2000 haben die Vorhersagen der kinematischen Dynamotheorie gut bestätigt und eine umfangreiche Datenbasis für das Regime der nichtlinearen Rückwirkung geliefert.

This thesis is focused on quantum fluctuations in rotating nuclei and on the effect they have on observables such as relative energy and angular momentum. The study of the nucleus under extreme conditions has been one of the main sources of information about nuclear structure over the last decades. Nuclei at high angular momenta are studied by means of modern gamma-detector arrays. Among the phenomena studied in such experiments are the phase transition from superfluid to normal phase, orientation changes in rotating nuclei, shape changes in rotating nuclei, super deformation etc.

The most powerful method to calculate nuclear properties is the mean field approach known as Hartree-Fock or Hartree-Fock-Bogoliubov method. Within this method the two-body interaction is replaced by a selfconsistent one-body potential which is calculated in an iterative way.

The nuclear mean field breaks a series of symmetries present in any realistic two-body Hamiltonian. One motivation to include effects that go beyond the mean field is to restore these symmetries. Two methods of restoring symmetries are used in this thesis, namely, the projection method and the random phase approximation (RPA).

An advanced quantum mechanical description of a nuclei should take into account quantum fluctuations around the mean field minimum. The quantal fluctuations do not only lead to a series of collective excitations like vibrations and rotations but also add correlations to the mean field ground state. The correlation energy gained by these quantum fluctuations is, in general, state dependent and is important when describing observables like the moment of inertia, the ordering and relative energies between states.

The report gives an overview on the activities of the Institute of Safety Research in 2000.

PIII was used to dope Si (001) wafers with nitrogen and carbon at high doses, relying on two PIII systems: one at the FZR and the other at INPE.

Nitrogen was implanted in (001) silicon wafers using 12 kV pulses in a glow-discharge PIII system and at 35 keV in an ECR PIII facility.

Porous silicon samples were prepared on (100) monocrystalline silicon wafers and implanted with nitrogen by PIII and analyzed by AES and reflectance measurements.

Co/Cu multilayers were prepared by cross-beam pulsed laser deposition and characterised by high-angle X-ray diffraction as well as specular and off-specular reflection before and after annealing (500 °C, 2h). Using synchrotron radiation at the K-edge energy of Co and Cu to enhance the scattering contrast, the study shows that annealing does not enlarge the interface roughness but strongly influences the interface morphology. In the fractal model of self-affine structures the latter is expressed by the drastic reduction of the extremely large lateral roughness correlation length parameter from about 4 µm in the as-deposited state to about 20 nm after annealing. High-angle X-ray diffraction indicates that the reduction of lateral roughness correlation length is caused by grain coarsening due to growth of crystallites and grain boundaries. Thermal treatment enhances the separation of Co and Cu at the interface, i.e. the initially very jagged (roughness exponent between 0.15 and 0.3) structure is smoothed (roughness exponent between 0.6 and 0.7).

Atomic calculations, based on empirical potentials and the method of homogeneous deformation, are presented for the elastic properties of as-deposited amorphous carbon at 0 K. Several structural models of amorphous carbon generated by a realistic molecular-dynamics simulation of ion-beam deposition were studied. The models yield intrinsic compressive stresses of approximately 10 GPa. Here, we examine the dependence of the second-order elastic constants of amorphous carbon on the intrinsic stress, as well as on hydrostatic pressure. Different sets of elastic constants describing the behaviour of a solid under stress are considered. The nonlinear effects are shown to become appreciable at a pressure of 10 GPa, whereas the difference between the elastic constants in the equations of motion and the Lagrangian elastic constants is not large.

Contactless melt flow control is important in many crystal growth technologies. Typically, steady magnetic fields are used to damp convective flow. On the other hand active flow driving forces like in a rotating magnetic field can be of stabilizing character, too. We present numerical results for the combined action of steady and alternating magnetic fields for the silicon Czochralski crystal growth process. The melt flow is determined by various flow driving sources: besides the thermal convection and rotation of crystal and crucible, there are also the influence of driving and/or damping electromagnetic forces and the thermocapillary-driven flow at the free deformable melt surface.

16-Alpha-[¹⁸F]Fluoroestradiol-3,17-Beta-disulphamate ([¹⁸F]FESDS) has recently been discovered to display affinity to carbonic anhydrase (CA) and estrone sulfatase (ES), enzymes which are expressed in the CNS and suggested to play a regulatory role in various brain diseases. In this study the radioligand was used to provide quantitative data on the regional distribution of these enzymes in the rat brain. The expression of CA I, CA II and ES has been studied in rat brain regions with RT-PCR. CA II and ES but not CA I has been detected in all regions. About 80-90 % of the total binding of [¹⁸F]FESDS to brain slices represents binding to CA (displaceable with acetazolamide). Binding of [¹⁸F]FESDS to ES was studied with selective inhibition of CA using acetazolamide. B_max values of between 0.3 pmol/mg (pons) and 11.5 pmol/mg (striatum) were obtained in various brain regions. The K_d and B_max values of ES binding were used as constants to calculate K_d and B_max of CA binding from inhibition studies with FESDS. B_max values of between 6.2 pmol/mg protein (striatum) and 14.6 pmol/mg (cerebellum) were obtained. The K_d-values varied between 33 nM and 166 nM, which is similar to the K_d of [¹⁸F]FESDS binding to purified human CA-II (54 nM). The affinity of FESDS to ES is lower by about factor 5. Furthermore, the enzymatic activity of ES in six rat brain regions was determined and found to be correlated to the corresponding [¹⁸F]FESDS binding. It is concluded, that [¹⁸F]FESDS can be used for mapping of CA and ES in vitro. The in vivo use of the radioligand may be limited because of its bipolar binding profile.

This paper reports synthesis, biological evaluation, in vitro and ex vivo autoradiography of the first Tc-99m ligand with subnanomolar affinity for the 5-HT_1A receptor and a remarkably high affinity for the alpha1-adrenergicreceptor. The neutral "3+1" mixed-ligand complex combines 4-(6-mercaptohexyl)-1-(2-methoxyphenyl)piperazine as monodentate and 3-(N-methyl)azapentane-1,5-dithiol as tridentate unit with oxotechnetium(V). The analogous rhenium complex was synthesized for complete structural characterization and used in receptor binding assays. In competition experiments both complexes display subnanomolar affinity for the 5-HT_1A receptor (IC₅₀ 0.24 nM for Re, 0.13 nM for Tc) but also very high affinities for the alpha1-adrenergic receptor (IC₅₀ 0.05 nM for Re, 0.03 nM for Tc). Biodistribution studies show a brain uptake in rat of 0.22 % ID five minutes post injection. In vitro autoradiographic studies in rat brain and postmortem human brain indicate the accumulation of the Tc-99m complex in brain areas which are rich in 5-HT_1A receptors or in alpha1-adrenergic receptors. This in vitro enrichment can be blocked respectively by the 5-HT_1A receptor agonist 8-OH-DPAT or by prazosin hydrochloride, an alpha1-adrenergic receptor antagonist. Ex vivo autoradiographic studies in rats show a slight accumulation of the Tc-99m complex in 5-HT_1A receptor-rich areas of the brain which could not be blocked, as well as in regions rich in alpha1-adrenergic receptors, which could be blocked by prazosin hydrochloride.

We present a method to calculate macroscopic bulk stresses in tetrahedral amorphous carbon (ta-C) films grown by a realistic atomic scale simulation of ion-beam deposition. Similar to real as-deposited films, the simulated films have a high content of sp3 bonded atoms and large intrinsic compressive stresses. Deriving atomic stresses from an interatomic potential and averaging them over slices inside the film, we show that average stresses in the inner film region converge to realistic values (~10 GPa) as the thickness of the slices exceeds 1 nm. The analysis of stress variation with depth reveals that in amorphous films deposited with low energy (20-30 eV) ions the highest compressive stress is attained in the region of steady-state growth, while in films grown with 80 eV ions it reaches a maximum in an intermediate layer adjacent to the crystalline substrate. The transition from graphitic carbon to ta-C is found to occur at a threshold stress of about 13 GPa

6H-SiC n-type wafers were implanted with Al+ and N+ ions in two steps: first Al+ double implantation (100 keV, 5x1016 cm-2 and 160 keV, 1.3x1017 cm-2 ) followed by N+ double implantation (65 keV, 5x1016 cm-2 , 120 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 computer-controlled 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.

This research is supported by the Deutsche Forschungsgemeinschaft (DFG) under
Grant No. Br 1250/13-1 and Br 1250/13-2.

Uranium is one of the main potential contaminants in East Germany's former mining areas. Under reducing conditions uranium(IV) is stable and can be complexed by phosphate and arsenate at low pH. Due to their low water solubility no thermodynamic complex formation constants are available for the uranium(IV)-phosphate and arsenate complexes.. For example, the solubility product /1/ of U(HPO4)2·4H2O limits the uranium(IV) concentration in 1 M perchloric acid to less than 1.2 x 10-4 M. Moreover there is a general lack of information on the aqueous chemistry and thermodynamics of tetravalent actinides.
We studied the formation of these complexes at uranium concentrations between 2 x 10-6 M and 1 x 10-4 M by Laser-Induced Photoacoustic Spectroscopy and UV-vis spectroscopy in acid media. To determine the complex formation constant we measured and analyzed the spectra from 600 nm to 690 nm. The spectra were corrected for the absorption of the solvent water. The solvated uranium(IV) shows a very intensive absorption band with a maximum at 650 nm and a smaller maximum at 672 nm. We found a shoulder at 630 nm deconvoluting the absorption spectrum.
The spectrum changes with increasing phosphate and arsenate concentration. Two isosbestic points were determined at 661 nm and 670 nm in the phosphate system. In the arsenate system three isosbestic point were found to be at 628 nm, 660 nm and 667 nm.
From measurements with variable ionic strength, ligand and proton concentration the complexation reaction according to
U4+ + H3LO4 <=> UH2LO43+ + H+ (L = P, As)
was quantified
The stoichiometry of the formed phosphate and arsenate complexes was confirmed by slope analysis. The formation constant at infinite dilution in the phosphate system was found to be log b0 = 3.52 ± 0.18 using the SIT extrapolation. For the arsenate system we found the complex formation constant to be log b0 = 2.13 ± 0.32.

Poster -
Combination of EXAFS and powder diffraction for solving heavy-atom structures

In this paper the luminescence properties of thin thermally grown SiO2 layers implanted with silicon and carbon ions are explored. The doses and energies were chosen in such a way that the resulting peak concentration of excess Si and C amounts to 5...10 % in a depth region of 60 to 180 nm below the surface. The microstructure was investigated by Auger electron spectroscopy and transmission electron microscopy. Amorphous nanostructures with a size between 2 and 3.5 nm were found in depth region between 80 and 150 nm below the oxide surface. Strong photoluminescence around 2.1 and 2.7 eV has been observed after excitation at 4.77 eV. SiyC1-yOx complexes with x<2 are assumed to cause the observed PL in the blue spectral region.

The second report from the Project-Group ESRF-Beamline of the Forschungszentrum Rossendorf covers the period from July 1999 until December 2000. The ROssendorf BeamLine (ROBL) at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France performed quite well during this time. In the beamtime used by the FZR and collaborating institutes 44 scheduled experiments were performed, while in the ESRF scheduled beamtime 12 experiments. Additionally, a distinct amount of beamtime was devoted to in-house research of the FZR and methodical experiments.
Since February 2000 ROBL is part of the European Commission’s programme ”Access to Research Infrastructure” which supports user groups from member and associated states of the EU during experiments at ROBL. In the year 2000 ROBL hosted 6 groups for experiments.

The report is organised in three main parts. The first part contains extended contributions on results obtained at ROBL. The second part gives an overview about the scheduled experiments, publications, guests having visited ROBL with support of the EC, and some other information. Finally, the third part collects the experimental reports of the user groups received.

Unsaturated flows within subsurface regions control many large-scale hydrological
and environmental processes. This contribution presents and discusses the results of numerical calculations dealing with the flow of water, the chemical reaction at the water-mineral interface and the transport of chemical species caused by such flows. The reason for the water flow through the soil is solely the rainfall.
The water motion is calculated for two different soil classes and for a typical annual precipitation. The transport of chemical species is described by a set of partial differential equations, and the homogeneous chemical processes, under the assumption of equilibrium, are described by a set of nonlinear algebraic equations. The source terms of these partial differential equations are given by rate laws of chemical weathering. Rainfall and chemical weathering are therefore the reason of the transport of reactive multispecies in this model.

Si+ ion implantation into Si under inclined incidence angle was applied to demonstrate that Cu gettering in the region around half of the projected ion range, RP/2, of ion-implanted Si is controlled by the same mechanism working for excess vacancy generation. The obtained results directly relate the appearance of the RP/2 gettering effect to radiation-induced excess vacancies. Excess vacancies were found to be origin for the dominating gettering sites of Cu at RP/2. Moreover, it was shown that the undesired impurity trapping at RP/2 can be prevented by means of additional Si+ implantation into the vacancy-rich region of ion-implanted Si to balance the excess of vacancies. The parameters were determined for the additional Si+ implantation to remove Cu gettering at RP/2. If the threshold fluence necessary to remove the Cu gettering at RP/2 is exceeded, the excess vacancies are overcompensated and new interstitial-type dislocation loops form.

In diesem Report wird eine Niederenergie-Implantationskammer (NEI-Kammer) beschrieben, die im Forschungszentrum Rossendorf entwickelt und aufgebaut wurde. Die Kammer ermöglicht es, die Implantation von Ionen bei niedrigen Energien (< 30 keV) mit einer Implantationsanlage für mittlere Energien durchzuführen. In der Kammer werden der Ionenstrahl, den der Implanter liefert, auf die erwünschte niedrige Energie abgebremst. Dazu wird ein elektrostatisches Bremslinsensystem eingesetzt, das auf einem neuartigen Prinzip basiert. Das System besteht aus einer Sammellinse und einer Zerstreuungslinse, wobei die Öffnungsfehler beider Linsen entgegengesetzte Vorzeichen besitzen und sich gegenseitig kompensieren. Dadurch ist es möglich, Wafer gebräuchlicher Größe bei geringer Energie mit hoher Dosishomogenität zu implantieren. Die NEI-Kammer ist insbesondere für Forschungseinrichtungen eine vorteilhafte Lösung, da sie eine wesentlich kostengünstigere und flexiblere Alternative zur Anschaffung einer Niederenergie-Implantationsanlage darstellt.

The development of optimized processes for p-type doping of SiC by ion implantation and subsequent annealing is a remaining challenge to SiC-device technology. Al is a promising acceptor in SiC. Compared to B it has a shallower acceptor level and a stronger tendency to occupy atomic sites in the Si sublattice which makes it more suitable for the production of heavily doped, low resistivity layers. However, also in the case of Al very high acceptor concentrations (>1019 cm-3) are necessary to obtain SiC layers with low resistivities (<1 cm). The physical consequences of such high impurity concentrations in SiC for the annealing of implantation damage and the electrical activation will be discussed. A survey of the results of several implantation and annealing schemes is presented.

Ion beam induced crystallization (IBIC) of preamorphized surface layers on 6H-SiC has been stimulated by high dose Al implantation (0.3 - 3 E17 cm-2) at elevated temperatures (300 -500°C). Randomly oriented 3C-SiC nanocrystals withn diameters between 2 and 25 nm are formed depending on the implantation parameters as proved by XRD and XTEM. Spreading resistance measurements have been performed at bevelled as-implanted and annealed (1500°C, 10 min) samples in order to study the electrical behaviour of the Al acceptors in the nanocrystalline layer. Reference experiments have been carried out on single crystalline 6H- SiC crystals implanted at the similar conditions. It has been found that in the as-implanted state Al doped fine granular SiC has much lower spreading resistance than the corresponding single crystalline SiC. Only minor differences have been observed between the nano- and single crystalline samples after annealing.

Focused ion beam implantation of cobalt at 35 keV into 6H:SiC is used to investigate a possible ion beam synthesis of CoSi2 micro-structures. The pattern were studied using SEM and EDX measurements. The resistivity of the implanted test-structures was determined as a function of dose, implantation and annealing temperature. For room temperature irradiated samples after a 1150°C annealing resistivities of about 100 µScm could be achieved and a diode like behaviour influenced by parasitic resistors between structure and bulk was found.

The focused ion beam is a very useful tool to sputter holes with well defined dimensions which can be easily analysed by surface profiling measurements. Applying this the sputte-ring yields of 6H:SiC were -measured for 35 and 70 keV Si, Co, Ge, Nd and Au ions from a mass separated focused ion beam. Additionally, the sputtering yield was determin-ed as a function of the angle of incidence and the target temperature for gold ions. The swelling due to ion implantation will be discussed.

The absolute amount of deuterium in amorphous deuterated carbon (a-C:D) layers has been measured by six laboratories with different techniques, such as MeV ion beam analysis, secondary ion mass spectrometry (SIMS), and thermal desorption spectrometry (TSD). The a-C:D layers have been deposited from a CD4 glow discharge plasma onto carbon and silicon substrates. The results for the absolute numbers obtained with the different analysing techniques show a scatter of up to about 35% around the average value. The deviations are larger than the errors stated by the experimentalists and indicate possible systematic uncertainties in some of the experiments.

A short description of the Rossendorf AMS system is given and first experimental results are presented. The planned applications are listed.

The Tritium Laboratory Karlsruhe (TLK) has mainly designed for the conduction of technological experiments relevant to fusion under simulation of the conditions actually expected in the various tritium processing systems. Presently ongoing experimental and design work is almost exclusively oriented towards the needs of JET and ITER-H-FEAT. Basic research, while increasing in importance, plays predominatly a complementary role. This paper presents the most recent progress and developments related to the technological and applied experiments at the TLK.

Das Mitte der 90er Jahre im KKW Saporoshje als Pilotprojekt für den 5. Block eingerichtete Fernüberwachungssystem wurde auf alle Blöcke der KKW Saporoshje und Rovno (Ukraine) erweitert und mittels moderner Kommunikationstechnik an das Informations- und Krisenzentrum der ukrainischen Aufsichtsbehörde in Kiew angeschlossen. Nach entsprechender Weiterentwicklung der Software für die Informationsverarbeitung, -übertragung und -bewertung können von diesen KKW-Blöcken sicherheitsrelevante betriebliche und radiologische Messwerte kontinuierlich erfasst, vor Ort in Form von Tabellen, Grafiken und Schemata online dargestellt sowie nach Kiew übertragen und dort visualisiert und bewertet werden.

Es wird ein System zur Überwachung technologischer Parameter für Blöcke ukrainischer Kernkraftwerke beschrieben. Die Autoren erläutern die theoretischen Grundlagen der Fernüberwachung sowie Aufbau und Wirkungsweise des Systems. Nachfolgend wird seine Einordnung in die ukrainischen kerntechnischen Aufsichtsbehörden dargelegt. Die Bestandteile der speziell für diese Anwendung entwickelten Software werden anhand von Beispielen erklärt und die Implementierung auf die Hardware beschrieben. Erste Erprobungsergebnisse und Vorschläge zur Erweiterung des Systems beenden den Artikel.

A successful application of the Ultrasound Doppler Velocimetry (UDV) in liquid sodium flows is described.
To get sufficient Doppler signals different problems had to be solved: the transmission of the ultrasonic
beam through the channel wall made of stainless steel, the acousting coupling between transducer and
channel wall and the wetting of the inner surface of the wall by the liquid metal, respectively.
A sodium flow in a square duct exposed to a transverse magnetic field is investigated. According to the
existing knowledge about MHD channel flows we found the velocity profiles modified to a M-shape due to
the effect of an inhomogeneous magnetic field.

Self-organized nanostructures produced by far-from-equilibrium processing of semiconductor materials with ion beams can be applied in microelectronics (e.g. nanocluster memories), optoelectronics (luminescence from Si nanocrystals) and photonics (plasmonic devices using Au nanoclusters). Our recent experimental, theoretical and computer simulation work, which aimed at optimization and improved fundamental understanding of these processes, will be reviewed.
Two different regimes of self-organization will be distinguished: (i) Relaxation regime: Ion implantation of impurity atoms may produce extremely supersaturated solid solutions. During subsequent annealing this far-from-equilibrium state relaxes towards equilibrium by phase separation (nucleation, growth) and minimization of interface energy (Ostwald ripening, coalescence). Self-organization phenomena (e.g. pattern formation during spinodal decomposition, Rayleigh or pearling instability during interface minimization) are observed. (ii) Driven system: Interfaces or compounds like SiO2 can be driven into a steady state far from equilibrium by ion irradiation. The steady state is established by a competition between collisional mixing, diffusion and re-formation of the compound. The application of resulting effects like nanocluster d-layer formation and ''inverse'' Ostwald ripening for devices will be discussed.

Dissertation

Die Migration von Uranspezies durch geologische Formationen wird durch die mineralogische Zusam-mensetzung der Gesteine sowie durch die che-mischen Eigenschaften der wässrigen Lösung bestimmt. In Abhängigkeit von den chemisch-physikalischen Bedingungen wird Uran an den Mineralen sorbiert. Um diese Bedingungen näher einzugrenzen, wurden Batchexperimente im Labor durchgeführt, die die natürlichen Bedingungen simulieren. Als Gesteinsprobe wurde der Granit von Eibenstock ausgewählt, der als geologische Formation einen großen Bereich der ehemaligen Uranbergbauregion im westlichen Erzgebirge bestimmt. Die mineralogischen Bestandteile des Eibenstocker Granits sind Quarz (45 %), Orthoklas (35 %), Albit (7,5 %), Biotit (7,5 %) sowie Muskowit (4 %). Für die Batchexperimente wurden 0,5 g der Granitprobe (63-200 µm Körnung) sowie 0,5 g der einzelnen Mineralkomponenten des Granits mit jeweils 40 ml 0,1 M NaClO4-Lösung der Verwitterung über mehrere Wochen ausgesetzt. Im Anschluß an die Stabilisierung der eingestellten pH-Werte erfolgte die Zugabe einer 1.10-6 M UO2(ClO4)-Lösung. Nach einer Sorptionsdauer von 2,5 Tagen wurde der Urangehalt in den Lösungen massenspektrometrisch bestimmt.
Die Ergebnisse zeigen eine hohe Sorption von U(VI) am Granit in einem pH-Bereich von 5 bis 7 mit einer maximalen Sorption von 94,62 % bei einem pH von 6.57. Bei einem pH < 5 sowie > 7 nimmt die Sorption stark ab. Unterhalb pH 4, bzw. oberhalb pH 8.5 ist die Sorption < 1 %. Im Vergleich zu anderen Gesteinen des Erzgebirges ist die U(VI)-Sorption am Granit deutlich auf einen kleinen pH-Bereich beschränkt [1]. Die Sorption an den Mineralkomponenten des Granits zeigt eine ähnliche Tendenz, wobei die Schichtsilikate Muskowit und Biotit durch ihre im Vergleich zu den Feldspäten höhere Sorption dominieren [2].

Literatur:

[1] Krawczyk-Bärsch, E. (2000): Final Report DFG (Ni 210/5-1).
[2] Arnold, T. et al. (1998): Chemical Geology 151, 129-141.

Cu is especially suitable to decorate defects in silicon. The Cu decoration technique has been applied for the detection of point defect clusters in the RP/2 region of Si+ ion implanted silicon. The results of this technique are compared with the results obtained by other analysis techniques. Nanocavities at RP/2 could be observed only in cross section transmission electron microscopy specimen prepared by cleavage technique. These nanocavities are probably the dominant gettering centres for Cu at RP/2. Small interstitial clusters may exist there as well. The conditions for the formation and for the annealing of the gettering layer at RP/2 have been determined. Impurity gettering at RP/2 can be prevented by a sequence of additional Si+ implantations to balance implantation-induced excess vacancies which are the origin of the nanocavities.

This article describes the crystal selection and quality control utilized to develop and calibrate a high resolution array of CsI(TI) scintillator crystals for the detection of energetic charged particles. Alpha sources are used to test the light output variation due to thallium doping gradients. Selection of crystals with better than 1% non-uniformity in light output is accomplished using this method. Tests with 240 MeV alpha beam reveal that local light output variations within each of the tested CsI(TI) crystals limit the resolution to about 0.5%. Charge and mass dependences in the energy - light output relationship are determined by calibrating with energetic projectile fragmentation beams.

Particle Induced X-ray Emission (PIXE) at the external proton beam has proved ideal to study the individual techniques used for creating art objects. In particular, PIXE is tailored for examining paintings because of the low level of background produced by organic components like binders and paper backings. Thus, even traces of pigments as deposited by pens on cardboard can be identified by this method. The combination of PIXE with external Rutherford Backscattering Spectrometry (RBS) allows non-destructive gain of knowledge on near-surface and thin film arrangements of paint materials. Thicker but less complex layers of oil paintings can be identified by special procedures of depth resolved PIXE investigation. In this case, RBS provides additional information on organic coverings like madder lake or varnishes.

Die Nutzung der seit Jahrhunderten bekannten Windkraft zur Erzeugung von
Strom hat im letzten Jahrzehnt eine dynamische Entwicklung erfahren. Basierend
vor allem auf den erreichten Fortschritten in der Technologie der Windenergie-
anlagen (WEA) und den damit verbundenen erheblichen Kostensenkungen steht
die Windenergienutzung heute an der Schwelle zur Wirtschaftlichkeit. Diese ent-
scheidende Voraussetzung hat besonders in Deutschland zur zunehmenden, in
einigen Gebieten sogar massenhaften Nutzung der Windenergie geführt. Die
wichtigsten technischen Entwicklungen der WEA im letzten Jahrzehnt werden
im Beitrag vorgestellt.
Gefördert wurde diese Entwicklung durch verschiedene größere Vorhaben des
Bundes und einzelner Länder. Hervorzuheben sind hier das 250-MW-Programm
sowie das Stromeinspeisegesetz. In den 90er Jahren bestanden somit stabile
Rahmenbedingungen für die Entwicklung der Windenergie. Die installierte WEA-
Leistung in Deutschland stieg von weniger als 30 MW im Jahr 1989 auf etwa
6000 MW zum Jahresende 2000. Im Jahr 2001 wird in Deutschland eine
Strommenge durch WEA erzeugt werden, die etwa 50% der aus Wasserkraft-
werken erzeugten Strommenge oder der Stromerzeugung des größten deutschen
Kernkraftwerkes entspricht.
Nach anfänglicher Zurückhaltung der meisten Energieversorgungsunternehmen
(EVU) erwägen derzeit auch diese ein Engagement in der Windkraftnutzung.
Dennoch werden sich die in den letzten Jahren erreichten Zuwachsraten mittel-
fristig nicht aufrechterhalten lassen. Ein absehbarer Leistungszuwachs bei den
Einzelanlagen auf bis zu 3 MW führt zwar zu einer Entlastung bei den benötigten
Standorten, die aus objektiven und subjektiven Gründen folgende Begrenzung
der nutzbaren Standorte limitiert jedoch insgesamt die Ausschöpfung der vor-
handenen Potenziale. Ein wesentliches begrenzendes Element ist bereits heute
der vermeintliche Widerspruch zwischen dem durch den Einsatz von WEA beför-
derten Umweltschutz (CO2-Problem) und dem Naturschutz in vielen Gebieten
(Landschaftsschutz), der auf der zuständigen kommunale Ebene kaum aufgelöst
werden kann.
Dennoch rechnet der Autor mit einer Verdoppelung der durch WEA erzeugten
Strommenge bis zum Jahr 2010 durch Neuinstallation bzw. Ersatz alter WEA auf
der Landfläche Deutschlands. Dies würde – bei unverändertem Stromverbrauch
– einem Anteil der Windkraft am Stromverbrauch von etwa 5 % entsprechen.
Etwa die gleiche Strommenge könnte um das Jahr 2015 durch offshore-WEA in
der Nord- und Ostsee erzeugt werden, so dass künftig mit einem „Windstroman-
teil“ von 10% in Deutschland gerechnet werden kann.

The unsteady flow field has been studied experimentally in a cold metal
model of an existing 10 kHz induction furnace for the inter-metallic fibre
extraction process in presence of a DC magnetic field. It has been shown
that a vertical DC magnetic field normal to the free liquid metal surface
efficiently decreases turbulence in the melt volume and suppresses surface
deformations. Whereas the turbulence and free surface deformations were not
suppressed by a DC field parallel to the free surface.

Our first in-beam PET measurements of the beta+activation induced by proton irradiation are presented.
Monoenergetic proton beams in the energy and intensity range suited for the treatment of deep-seated tumours were delivered by the synchrotron of the Gesellschaft fuer Schwerionenforschung (GSI) at Darmstadt. They were stopped in PMMA blocks placed in the centre of the field of view of the positron camera that is installed in the heavy ion tumour treatment facility at GSI.
The beta+ activity signal was found to be three times larger than that produced by carbon ions at the same range and applied physical dose. The reconstructed spatial beta+ activity distributions were analysed and compared with the production of positron emitters predicted by a calculation based on experimental cross-sections and on the proton flux given by the FLUKA Monte Carlo code. The shape of the depth-activity-profiles was well reproduced by the model and the correlation with the proton
range and the depth-dose-distributions was carefully investigated. Despite the nontrivial range determination from the beta+ activity distribution in the proton case, our experimental investigation supports the feasibility of an in-situ proton therapy monitoring by means of in-beam PET, as already clinically implemented for the monitoring of carbon ion therapy at GSI Darmstadt.

An important component of nuclear safety research is the analysis of abnormal transients and accident scenarios in nuclear power plants. In the presented work the ATHLET code was used for thermohydraulic calculations of small and intermediate break loss of coolant accident experiments, which were performed at the Hungarian test facility PMK-2. In the experiments different kinds of natural circulation instabilities could be observed. Such instabilities play an important role in the behaviour of the primary circuit, because the instabilities can disturb the heat removal from the reactor core. The aim of the presented calculations is to investigate whether the code is capable of modelling natural circulation phenomena in VVER-440-type reactors. It could be shown, that ATHLET can calculate the accident behaviour in good agreement with the experimental data. All significant phenomena, such as hot and cold leg loop seal clearing, stagnation of the natural circulation and especially the natural circulation instabilities are calculated very well. Calculations for a VVER-reactor show that the instabilities can also appear in a real plant.

Die systematische Weiterentwicklung der gekoppelten neutronenkinetischen und thermohydraulischen Codes (DYN3D-ATHLET) erfordert den Einsatz von dreidimensionalen Vermischungsmodellen.

CFX-4-Nachrechnungen experimenteller Daten der Vermischungsanlage ROCOM ergeben im hochturblenten Bereich eine gute Übereinstimmung mit den Messdaten.

- Vierschleifenbetrieb:

- Sektorformation am Kerneintritt
- zeitliche Schwankungen der Konzentrationsprofile an den Sektorgrenzen

- Anlaufen der Kühlmittelzirkulation:

- Unterschiedliche Vermischungsbilder je nach Durchsatz und Anfahrvorgang
- Eintritt des Pfropfens in den Kern in den Randzonen der gegenüberliegenden Seite

In dem vorliegenden Bericht wird die Erstellung eines Containmenteingabedatensatzes für das Kernkraftwerk Stade (KKW Stade) für das von der Gesellschaft Anlagen- und Reaktorsicherheit (GRS) entwickelte Programmsystem RALOC (Radiolyse und lokalen Konzentrationen (der Gase, z. B. Wasserstoff) im Containment beschrieben und der Aufbau des Eingabedatensatzes, erste Rechnungen zum Nachweis der Lauffähigkeit, der Einbau der Rekombinatoren in den Datensatz sowie erste Testläufe dokumentiert. In einem ersten Bericht sind im Detail die verwendete Nodalisierung, d.h. die Unterteilung des Contaniments in Zonen, Verbindungen und Strukturen beschrieben

Zur Validierung der thermohydraulischen Wirksamkeit der im SWR 1000 verwendeten passiven Sicherheitssysteme zur Nachwärmeabfuhr aus dem Reaktordruck-sowie dem Sicherheitsbehälter bei Störfällen wurden in den Versuchsanlagen PANDA (PSI / Schweiz) und NOKO (Forschungszentrum Jülich / Deutschland) umfangreiche Versuchsserien durchgeführt. Das Experimentalprogramm beinhaltete im Detail Versuche zum Notkondensator (zwei verschiedene Bündel), zum Passiven Flutsystem sowie dem Gebäudekondensator, der sowohl in NOKO (als Einzeleffektversuch) als auch in PANDA (als Systemversuch) getestet wurde. Zusätzlich wurden in NOKO noch mehrere Bauformen Passiver Impulsgeber erprobt. Allen Versuchen war gemein, dass die zu untersuchenden Systeme in Originalabmessungen sowie -materialien nachgebildet und unter adäquaten thermohydraulischen Randbedingungen getestet wurden. Die Versuchsergebnisse bestätigen ausnahmslos die Funktionalität und Effektivität der passiven Sicherheitssysteme.
Die Wärmeabfuhr in den Not- und Gebäudekondensatoren wurde mit den weltweit zur Sicherheitsanalyse von Reaktoren etablierten 1D-Thermohydraulikprogrammsystemen nachgerechnet. Die Ergebnisse der mit den unterschiedlichen Codes berechneten, integral durch Notkondensatoren abgeführten Energie stimmen sowohl untereinander als auch mit den Experimenten gut überein.
Bei den Gebäudekondensatoren konnten ebenfalls die globalen Werte mit den gebräuchlichen 1D-Containmentprogrammsystemen berechnet werden. Aufgrund der lokalen Anordnung der Gebäudekondensatoren stellen sich im Sicherheitsbehälter jedoch mit diesen 1D-Codes nicht beschreib- und somit modellierbare dreidimensionale Strömungs- und Temperaturfeldern (speziell Stratifizierungen) ein. Diese konnten zwar durch moderne Computational Fluid Dynamic (CFD) Codes punktuell wiedergegeben werden, zur Nachrechnung vollständiger Störfallsequenzen sind jedoch weitere Codeverbesserungen sowie schnellere Computer notwendig.

A German/Russian irradiation experiment has been performed at the pressurised water reactor VVER-70 of the Rheinsberg NPP (Germany). The programme aims at the evaluation of neutron embrittlement and annealing behaviour in dependence on the content of alloying elements and impurities. Charpy V-notch, SENB, tensile, and CT-type specimens have been irradiated.
Specimens have been subjected to instrumented Charpy V impact and fracture mechanical toughness testing according to the ASTM E 1921-97 standard for reference temperature, T0, de-termination. The results of Charpy-V testing were presented on the IAEA Specialist’s Meeting in Madrid 1999. This paper continues the presentation with reference temperature testing and results of microstructural investigations. The microstructure is analysed using SANS technique.
The Charpy-V transition temperature shifts due to neutron irradiation could be confirmed by the reference temperatures T0 shifts. Furthermore, the SANS experiments provide a clear evidence of irradiation-induced microstructural features. Between a microstructural and an embrittlement based radiation coefficient, there is a obvious correlation. The main parameters of influence are the neutron fluence and the nickel content.

Es wird eine Übersicht über die Arbeiten zur Magnetofluiddynamik gegeben.
Die wesentlichen Effekte bestehen in der strömungsantreibenden Wirkung von
magnetischen Wechselfeldern und der dämpfenden Wirkung von Gleichfeldern.
Die Kombination beider Felder erlaubt meist die Entwicklung einer
Feldkonfiguration, die eine maßgeschneiderte Wirkung auf Strömung sowie
Wärme- und Stofftransport des jeweiligen Prozesses gestattet. Dafür werden
Beispiele aus Kristallzüchtung und Metallurgie angegeben.

Today there are two developments for an inverse approach to liquid metal
magnetohydrodynamics. At first, the reconstruction of a three-dimensional
velocity field out of external magnetic field measurements. At second, the
design of tailored magnetic field actions specific for the heat- and mass
transfer needs of the corresponding process. Results for both methods are
presented. The application to the steel flow in the mould are discussed.

Ziel:

Das Aminosäurederivat 3-O-methyl-6-[¹⁸F]fluoro-L-DOPA ([¹⁸F]OMFD) zeigt eine hohe Aufnahme in Hirntumoren im Gegensatz zum normalen Hirngewebe. Ziel dieser Arbeit war die Generierung parametrischer Datensätze des Tracer-Verteilungsraumes in der Positronen-Emissions-Tomographie (PET).
Methodik:
Nach vorangegangener Transmissionsmessung für die Schwächungs- und Streukorrektur wurden dynamische PET-Aufnahmen mit 34 Frames innerhalb von 90 Minuten auf einem hochauflösenden Scanner ECAT EXACT HR+ nach der intravenösen Gabe von 330 MBq [¹⁸F]OMFD akquiriert. Zur Reduktion des Rauschens wurden die Bilder nach der iterativen Rekonstruktion mit einem Savitzky-Golay-Filter geglättet. Die Angebotsfunktion wurde entweder extern aus gemessenen venösen Blutproben oder nichtinvasiv aus der A. carotis interna bestimmt. Eine Korrektur auf Metabolite ist bei
[¹⁸F]OMFD nicht erforderlich. Für die Erzeugung parametrischer Bilder wird das Eingewebs-Kompartimentmodell zur Beschreibung des kinetischen Verhaltens reversibler Tracer benutzt. Pixelweise werden die Einstromkonstante K₁, die Eliminationskonstante k₂ und das anteilige Blutvolumen fbv geschätzt. Das Verteilungsraumvolumen V_d des Tracers wird als Quotient von k₁ und k₂ bestimmt.
Ergebnisse:
In den parametrischen Bildern des Verteilungsraumvolumens ist eine klarere Abgrenzung maligner Areale als in den Aktivitätsverteilungen möglich. Der Wert von V_d ist ein Indikator für die Aminosäuretransporteraktivität in den Zellen, von der angenommen wird, dass sie in Tumorzellen gegenüber Normalgewebe erhöht ist. Das Verhältnis der V_d-Werte von Tumor zu Nichttumor lag bei dem untersuchten Patientenkollektiv zwischen 2,2 : 1 und 3,2 : 1.
Schlussfolgerungen:
Die Berechnung der Verteilungsraumkoeffizienten V_d führt zu einer Quantifizierung onkologischer PET-Studien mit [¹⁸F]OMFD, mit der zahlenmäßige Aussagen bei Verlaufskontrollen und interindividuelle Vergleiche möglich werden.

The temperature and boron concentration fields established by the coolant mixing during nominal and transient flow conditions in the reactor pressure vessel of the PWR Konvoi were analyzed by numerical and experimental studies. The validation of the CFD results (CFD-code CFX-4) was carried out at the Rossendorf mixing test facility ROCOM. ROCOM is a 1:5 scaled Plexiglas model of the PWR Konvoi allowing velocity measurements by the LDA technique. Plugs of coolant with low boron acid concentration and/or different temperature are simulated by salt water injection. The CFD calculations were based on the assumption of incompressible turbulent flow. The turbulence was considered by an k--model. The perforated drum, as well as the reactor core with core internals, were represented by the model of a porous body. Calculations were performed for constant flow in the loops as well as for the scenario of an onset of the circulation. For transient CFD-calculation sensitivity studies were performed to check the numerical diffusion and the choice of different turbulence models.

Grundlage für die Erstellung des Eingabedatensatzes ist die Nodalisierung, eine Unterteilung des Containments in Bilanzräume (sog. Zonen), die über definierte Strömungswege (sog. Junctions) miteinander verbunden sind. Für die Zonen werden während einer Rechnung Massen- und Energiebilanzen, für die Verbindungen hingegen Impulsbilanzen aufgestellt und gelöst. Zusätzlich können mit Hilfe von sog. wärmeleitenden Strukturen Wärmequellen und -senken definiert werden. Diese erlauben die Modellierung der Zufuhr von Wärme in bzw. die Abfuhr von Wärme aus einzelnen Zonen sowie die Berechnung von Temperaturprofilen in festen Materialien (z. B. Wänden, Einbauten, Armaturen, Leitungen, Komponenten) sowie des Wärmeübergangs an deren Oberflächen.

ZIEL:

Patientinnen (Pat.) mit hochgradigem V.a. Mamma-CA wurden präoperativ mit FES oder FDG untersucht. Ziel war die Beurteilung von Multizentrizität, axillärem Lymphknotenbefall und Estrogenrezeptorstatus (ER) bzw. metabolischen Aktivität mittels PET sowie der Vergleich mit den histologischen Befunden incl. Estrogenrezeptorstatus.

METHODIK:

Die Pat. wurden radomisiert mit FDG oder FES im klinischen Stadium =pT2 an einem dedizierten PET-System (ECAT EXACT HR⁺, SIEMENS/CTI) untersucht. FES: Injektion von ca. 220 MBq i.v., 2 bed positions ab Axiallae bis Oberbauch in Bauchlage (Lagerungshilfe) ab 90 min p.i., anschließend ab prox. Oberschenkel bis Schädelbasis in Rückenlage, jeweils mit gemessener Transmissionskorrektur im 2D-Modus. FDG: Injektion von 290-370 MBq i.v., ab 60 min p.i. gleiche Aufnahmeparameter wie bei FES.

ERGEBNISSE:

Es wurden bisher 5 Pat. mit FES und 4 Pat. mit FDG untersucht (Tabelle). Erste Daten zeigen für FES und FDG eine positive Carcinomdarstellung auch bei Multizentrizität. Bei einer Pat. fand sich mittels FES ein falsch-positiver bzw. ein falsch negativer Befund bezüglich der axillären LK und des Estrogenrezeptorstatus.

Lfd...Diagnose postoperativ....Präparat......PET:... .ER.. ..Vergleich PET - Histologie
Nr.........................................................T/LK_all...[%]
....................................................................................T.......MZ.......LK_ax......ER......SUV

1......pT4NxM1G3L1 (MZ)......FDG.............+/-........0.......RP......RP.......(FN).................2,0
2......pT4bN1M1G2...............FES..............-/-........0.......RN......RN........RN.......RN.......0,2
3......pT2N0M0G2L0V0.........FDG..............+/-.......0.......RP......RN........RN...................6,8
4......pT2N1M0G3L1 (MZ)......FES..............+/+...>80......RP......RP........RP.......RP.......4,3
5......pT2M0M0G2L0V0.........FES..............+/-....>80......RP......RN........RN.......RP.......1,5
6......pT4N1M1G3L1.............FDG..............+/+.....20......RP......RP........RP..................4,5
7......pT2N0M0 Dcis (MZ)......FDG..............+/-.......0.......RP......RN........RN..................1,8
8......pT2N1M0L1V1 (MZ)......FES..............+/-.......0.......RP......RP........FN.......FP.......1,6
9......pT4NxM1 (MZ).............FES..............+/+....>90......RP......RP.......(RP)......RP.......7,3

SCHLUSSFOLGERUNGEN:

Erste mittels FES in Deutschland durchgeführte Untersuchungen weisen auf die Eignung zur präoperativen Diagnostik des Mamma-CA hin. Eine abschließende Beurteilung ist bei kleiner Fallzahl noch nicht möglich.

In November 2000, the 4th Workshop on Measurement Techniques for Stationary and Transient Multiphase Flows took place in Rossendorf. Three previous workshops of this series were national meetings; this time participants from different countries took part. The programme comprised 14 oral presentations, 9 of which are included in these proceedings in full length. A special highlight of the meeting was the main lecture "Ultrasonic doppler method for bubbly flow measurement" of Professor Masanori Aritomi, Dr. Hiroshige Kikura and Dr. Yumiko Suzuki, which was read by Dr. Hiroshige Kikura. The workshop again dealt with high-resolution phase distribution and phase velocity measurement techniques based on electrical conductivity, ultrasound, laser light and high-speed cinematography. A number of presentations were dedicated to the application of wire-mesh sensors developed by FZR for different applications used by the Technical Universities of Delft and Munich and the Tokyo Institute of Technology. The presentations were in particular:

M. Aritomi, H. Kikura, Y. Suzuki (Tokyo Institute of Technology): Ultrasonic doppler method for bubbly flow measurement

V. V. Kontelev, V. I. Melnikov (TU Nishny Novgorod): An ultrasonic mesh sensor for two-phase flow visualisation

A. V. Duncev (TU Nishny Novgorod): Waveguide ultrasonic liquid level transducers for power generating equipment

H.-M. Prasser, E. Krepper, D. Lucas, J. Zschau (FZR), D. Peters, G. Pietzsch, W. Taubert, M. Trepte (Teletronic Ingenieurbüro GmbH), Fast wire-mesh sensors for gas-liquid flows and decomposition of gas fraction profiles according to bubble size classes

D. Scholz, C. Zippe (FZR): Validation of bubble size measurements with wire-mesh sensors by high-speed video observation

A. Manera, H. Hartmann, W.J.M. de Kruijf, T.H.J.J. van der Hagen, R.F. Mudde, (TU Delft, IRI): Low-pressure dynamics of a natural-circulation two-phase flow loop

H. Schmidt, O. Herbst, W. Kastner, W. Köhler (Siemens AG KWU): Measuring methods for the investigation of the flow phenomena during external pressure vessel cooling of the boiling water reactor SWR1000

A. Traichel, W. Kästner, S. Schefter, V. Schneider, S. Fleischer, T. Gocht, R. Hampel (HTWS Zittau/Görlitz - IPM): Verification of simulation results of mixture level transients and evaporation processes in level measurement systems using needle-shaped probes

S. Richter, M. Aritomi (Tokyo Institute of Technology): Methods for studies on bubbly flow characteristics applying a new electrode-mesh tomograph

Electrical properties of 20 ... 30 nm gate oxides implanted with Si+ ions are investigated using MOS capacitors and transistor structures. The observed programmming window can reach several volts and the structures exhibit good retention behavior. A first 256k - nvSRAM is demonstrated showing a programming window >1V for write pulses of 12V / 8 ms.

Das untersuchte Flutungswasser (pH 5,5) enthält Fe(II), welches bei Sauerstoffzutritt Fe(III)-Oxyhydroxidpartikel bildet. Diese Partikel adsorbieren Radionuklide wie Po-210 und Pb-210. Im pH-Bereich von 4 bis 6 wird auch der größte Teil des Urans, welches in sechswertiger Form vorliegt, sorbiert. Radium dagegen ist kaum kolloidgetragen.

The present report contains the User Manual of the FZR version of the dynamic binary-collision computer simulation code TRIDYN. The present version of the code is based on TRIDYN Vs. 4.0 by W.Möller and W.Eckstein, Department of Surface Physics, Max-Planck Institute of Plasma Physics, Boltzmannstraße 2, 85748 Garching, Germany (1989). Modifications, in particular for PC implementation, quasi-dynamic display and the input dialog have been performed at the Institute of Ion Beam Physics and Materials Research by V.Kharlamov, T.Schwieger, M.Posselt, and W.Möller (1995-2001).

The structural and phase transformations occurring in the near-surface layers of pre-quenched high-speed steel subjected to pulsed electron beam melting have been investigated. Melting was induced by a low-energy (20–30 keV), high-current electron beam with a pulse duration of 2.5 µs and an energy densities ranging from 3 to 18 J/cm2. Using electron microscopy and x-ray diffraction it has been revealed that with increasing beam energy density gradual liquid-phase dissolution of initial globular M6C carbide particles occurs in the near-surface layer of thickness up to ~1 µm. This process is accompanied by formation of martensite crystals (gamma-phase) and an increase of residual austenite (alpha-phase) content. When the carbide particles are completely dissolved, martensitic transformation is suppressed. In this case, a nonmisoriented structure is formed consisting predominantly of submicron cells of -phase separated by nanosized carbide interlayers. Irradiation of cutting tools (drills) in a mode corresponding to an abrupt decrease in the content of M6C particles due to their liquid-phase dissolution enhances the wear resistance of the drills by a factor of 1.7. This is associated with the fixation of undissolved particles in the matrix, the formation of residual compressive stresses and of dispersed M3C carbide particles as well as the high (~50 %) content of the metastable -phase in the surface layer.

please contact the author

Ordered quantum dot patterns are generated on GaSb and InSb surfaces due to a
surface instability induced by Ar+ ion sputtering under normal incidence.
The characteristic length of the generated patterns scales with the square
root of the ion energy over the energy range of 75 - 1800 eV. This energy
dependence is compared to the solutions of the isotropic Kuramoto-Sivashinsky
equation and allows the determination of the lateral width of the energy
distribution deposited by the incident ions in the very low energy range. We
show that the observed energy dependence is in agreement with the linear
continuum theory under the assumption that the dominant smoothing process is
due to effective ion induced diffusion without mass transport on the surface.

Summary of the Scientific Activities of the Institute in 2000

Modern trends in investigating the phytotoxic effects of trichloroacetic acid (TCA) have initiated an actual interest in [1,2-14C]TCA with specific activities > 3.7 GBq/mmol. One-pot synthesis starting from potassium [1,2-14C]acetate yielding 80% of [1,2-14C]TCA is described. The specific activity of the product corresponds to that of the potassium or sodium [1,2-14C]acetate and the radiochemical purity is higher than 98%. The synthesis method is usable for the synthesis scale < 1 mmol.

The Forschungszentrum Rossendorf has built a synchrotron radiation beamline at the ESRF, Grenoble, for radiochemistry and materials research. The radiochemistry set-up at ROBL is the only dedicated station in Europe for XAS experiments on actinides in solid or liquid samples. The materials end station is mainly for diffraction and reflectometry studies on thin films and has capabilities for in-situ experiments in film growth or temperature induced structural changes. The possibilities for materials research at ROBL are demonstrated by some experiments performed.

During growth the micro-structural development of TiN films was studied – especially the change in texture with film thickness. The films were deposited by use of a magnetron sputtering source in a vacuum chamber equipped with two magnetron sources and mounted on a goniometer located at a synchrotron radiation beam line. X-ray diffraction and reflectivity measurements were carried out in situ to follow the microstructure as a function of film thickness. With the deposition parameters that were chosen, a crossover was observed: grains with a (002) plane parallel to the film surface dominate at small thickness, while, at larger thickness, (111) grains dominate. Recrystallization was identified as a mechanism that controls this texture development. The driving force for change of orientation of the individual grains arise from minimalization of the sum of the surface energy and the strain energy of the individual grains.

A focused ion beam system is applied to study the dose dependence of the shape of Ge channeling implantation profiles at two very different dose rates (10¹⁸ and 10¹¹ cm^-2 s^-1), and for implantation temperatures of 250⁰C and RT. A simple model for the buildup of radiation damage is developed to describe the dechanneling effect of defects formed during ion bombardment. The use of this model in atomistic computer simulations yields Ge depth profiles which agree well with measured data. The lifetime of ion-beam-induced defects at 250⁰C was estimated to be in the order of 100 s. At RT, some defect relaxation was found between 10 microseconds and 100 s after ion impact.

Currently effects related to carrier confinement in nanometer sized silicon structures are extensively studied. So it has been shown that Si in spite of its indirect band
gap can efficiently emit photons due to carrier recombination provided that low dimensionality is achieved. Further a novel Si-nanocrystal floating gate MOSFET
memory structure has been proposed. In all these applications the formation of Si-quantum dots is a critical step being tackled using a variety of methods. Our
approach is rf magnetron sputtering, a popular thin film preparation technique compatible with conventional Si-technology and providing an elegant way to prepare
device quality SiO2 thin-films, but also SiO2/nanocrystalline (nc)-Si/SiO2 thin-film systems. SiO2 films were prepared by sputtering from an high purity quartz
target and characterized by TEM, FTIR, Current-Voltage and Capacitance-Voltage measurements. The electrical properties of the sputtered oxide films are
comparable to those of thermally grown oxides. By alternate sputtering from Si and SiO2-targets thin-film systems have been prepared. For the latter charge
storage in the nc-Si-floating gate has been demonstrated.

The temperature dependent morphological evolution of Pt(111) under 1 keV Xe normal
incidence ion bombardment has been investigated up to 600 monolayers removed.
Coarsening of the surface structures during erosion and a qualitative change in
roughness evolution between 650 and 700 K are found to be caused by different
atomic processes: the former by diffusion of atoms along steps, the latter by the
onset of step atom detachment.

Nanoparticles can be formed in a variety of substrates by ion implantation and
thermal annealing. These particles range from a few to several hundred nanometers
in diameter and may be metals or semiconductors containing either single or multiple elements. Particles formed in this way are not uniform in size and are randomly
distributed throughout the implant region. The purpose of this work is to make
uniformly spaced lattices of colloidal particles of more uniform size by using a finely
focused ion beam to implant ions only into a microscopic region at each point of
a two-dimensional array. Simulations using a kinetic
lattice Monte Carlo code indicate that such implants should form localized distributions of colloids that may Ostwald ripen into a single large colloid at each
lattice site. Such a composite would exhibit greatly improved optical characteristics. Initial work is being done with 30 keV Ga and As in Si. Particle formation
as a function of implant and annealing conditions will be discussed

The blue-violet electroluminescence (EL) of Sn-implanted SiO2 layers thermally grown on crystalline Si has been investigated at room temperature and compared with the corresponding photoluminescence (PL) spectra. It was shown that power efficiencies up to 2.5·10-4 can be achieved, and that the power efficiency slightly decreases for high injection currents. Because of the excellent correspondence between the EL and the PL spectra we interpreted the EL as due to a radiative triplet-singlet transition of a Sn-related oxygen deficiency center. Based on the electrical measurements, we assume that the luminescence centers will be excited either by impact excitation of hot electrons moving in the conduction band of SiO2 or by field ionization of luminescence centers in conjunction with hopping conduction.

Ion nitriding of Al has been performed by a N2 reactive ion beam using a hot filament ion source. Quantitative determination of N incorporation and loss has been estimated at a beam energy of 1.6 keV with two ion current densities of 0.1 and 0.2 mA/cm2 and substrate temperature of 350°C. For this purpose, a characterisation of the ion beam has been carried out by an energy selective mass spectrometer. The analysis shows that the beam consists solely of N2+ and N+ ions with a composition of about 80 % and 20 %, respectively. The ion energy distribution of both N2+ and N+ consists of a single narrow peak with a full width at half maximum of about 10 eV and a mean ion energy corresponding to the applied beam potential. From the beam parameters, N loss due to sputtering and backscattering has been calculated using dynamic binary collision computer simulations. After an initial transient, the stationary partial sputtering yield of N is predicted to be 0.45, while the amount of backscattered N is about 5 % of the incident N fluence. The N loss obtained from the simulation is consistent with the incident fluence and the total amount of incorporated N measured by Nuclear Reaction Analysis (NRA).

Frühere Untersuchungen haben gezeigt, dass im Verlaufe sozialer Isolation - tierexperimentelles Modell gestörten Sozialkontaktes - serotonerge Alterationen Anteil an den neurobiologischen Veränderungen haben, die den auffälligen Verhaltensänderungen
zugrunde liegen. Die durch Bindungsassays nachgewiesenen Veränderungen von K_D und B_max Werten serotonerger Rezeptorpopulationen deuten an, dass eine Reihe lokaler quantitativer Veränderungen serotonerger Rezeptoren in verschiedenen Hirnregionen zu erwarten sind .
Mittels autoradiographischer Untersuchungen wurde die lokale Verteilung von spezifischen Rezeptorpopulationen, insbesondere von 5-HT_1A und 5-HT_2A Rezeptoren im Cortex, Hippocampus, Amygdala, Striatum und N. acccumbens verfolgt. Nach 28 Tagen zeigt sich eine massive Abnahme der 5-HT_1A Rezeptordichte im Cortex, Hippocampus, Substantia nigra und in der Amygdala , die auch weitestgehend nach 12 Wochen Isolation noch nachweisbar ist. Die Dichte der 5-HT_2A Rezeptoren ist ebenfalls nach 28 Tagen in den untersuchten Hirnregionen signifikant vermindert, während nach 12 Wochen kaum noch Veränderungen nachgewiesen werden können. In der Tendenz ist im Striatum und im N.accumbens sogar eine up-Regulation zu erkennen. Die Ergebnisse werden in Beziehung zu neurochemischen und Verhaltensveränderungen diskutiert.

The instrumented impact test is suitable for the determination of fracture mechanical pa-rameters. In this paper the determination of the dynamic fracture toughness values in the lower ductile-to-brittle transition region is presented. The fracture toughness is determined at the onset of cleavage fracture and evaluated by the Master Curve (MC) concept. The MC concept allows to quantify the variation of fracture toughness with the temperature within the lower ductile-to-brittle transition region. Limit curves of fracture toughness for defined fail-ure probabilities and a reference temperatures can be determined using this method. This paper presents the application of the master curve concept to the reference temperature de-termination through the thickness of reactor pressure vessel (RPV) steel plate. The reference temperatures determined with dynamic fracture toughness values (T0dy) are compared with quasi-static reference temperatures (T0st) and Charpy-V transition temperatures (TT). The T0dy, T0st and TT increase from the surface to the middle of the RPV steel plate. Compared with T0st, the T0dy values are higher approximately 70 to 90 K.

After successful synthesizing 16alpha-[¹⁸F]fluoroestradiol-3,17beta-disulphamate in an automatic procedure, we studied the conditions for obtaining 16alpha- [¹⁸F]fluoroestradiol-mono-sulphamates in a similar manner. The described procedure can simultaneously provide approximately 3 GBq of 16alpha-[¹⁸F]fluoroestradiol-3-sulphamate and 1 GBq of 16alpha-[¹⁸F]fluoroestradiol-17beta-sulphamate of high radiochemical purity. By treating 16alpha-[¹⁸F]fluoroestradiol-3,17beta-disulphamate with Kryptofix 2.2.2 and potassium carbonate, 16alpha-[¹⁸F]fluoroestradiol-17beta-sulphamate also becomes available at high radioactivity.

Multi-crown-dendrimers of four different generations have been synthesized by grafting 4, 8, 16 and 32 benzo[15]crown-5 units at the periphery of POPAM-dendrimers. The binding of sodium pertechnetate and mercury(II) chloride by the multi-crown-dendrimers has been studied by liquid-liquid extraction using the radioactive probes ²²Na⁺, ⁹⁹TcO₄ ^-, and ²⁰³Hg²⁺. The third- and fourth-generation dendrimers 3 and 4, in particular, are capable of extracting mercury(II) with high efficiency ( ca. 12 Hg^II ions per dendrimer molecule, even at low generation). It has been shown that the guest molecules investigated preferentially encapsulated inside the dendrimers.

The most frequently used technetium compounds suitable for coupling the metal to biologically active molecules are square-pyramidal oxo complexes based on tetradentate N₂S₂ ligands (1). Properties and thus the in vivo behaviour of such complexes are strongly influenced by the presence of the quite polar [Tc=O]³⁺ unit. Whether such a polarity is beneficial or not is not obvious and depends on the requirements for specific radiotracers, e.g. for receptor-targeting agents or for metabolic tracers. Another crucial point in tracer design is the stability of the respective Tc chelate towards ligand exchange in vivo. Recently it was shown that the applicability of the "3+1" mixed-ligand Tc(V) chelates is limited because of their reaction with glutathione in vivo (2,3). So there is a considerable interest in alter-native chelate systems that combine lower polarity with enhanced in vivo stability. Such systems are based on oxo-free Tc cores at lower oxidation state.
Here we describe novel types of Tc(III) mixed-ligand complexes. Both chelate systems fulfil the requirements for a lipophilic, non-polar building block stable against ligand exchange reaction in vivo. They offer the advantage of high versatility in conjugating biomolecules as described for the "3+1"-series (4).

Despite tremendous effort in the development of Tc-99m complexes to image post-synaptic CNS receptors, various attempts failed so far (1). The combination of sufficient brain uptake and high affinity to the receptors (IC₅₀ < 1 nM) seems to be crucial. Our studies are focused on complexes for serotonin 5-HT_1A and 5-HT_2A receptors. Recently we succeeded in synthesizing of complex I, which is a high affinity Tc-99m ligand for the 5-HT_1A receptor derived from the well known serotonin 5-HT_1A antagonist WAY 100635 and shows a subnanomolar affinity (0.13 nM) and a brain uptake of 0.20 % ID in rats, 5 min post injection (2). Figure 1 shows the structure of the complex I.

Here we report on the synthesis of new high-affinity Tc-99m ligands for the 5-HT_1A receptor with improved brain uptakes. The complexes are evaluated in receptor binding assays, by in vitro autoradiography in post mortem human brain and by in vivo studies.

Uransekundärminerale sind in verschiedenen Uranerzbergbaugebieten (u. a. Schneeberg; Joachimstal, Adrinapole, Arizona) nachgewiesen worden. Aus der Kenntnis der Bildung von Erdalkaliuranylcarbonaten wie Bayleyit (M = Mg) und Liebigit (M = Ca) können wichtige Hinweise über den Transport und die Immobilisierung von Uran unter umweltrelevanten Bedingungen abgeleitet werden.
Ein Ziel der Arbeit war es, Syntheseverfahren für Ca-, Mg-, Sr- und Ba-Uranyltricarbonate zu erarbeiten bzw. zu optimieren und die Syntheseprodukte physikalisch-chemisch zu charakterisieren. Als Analysemethoden wurden Röntgendiffraktometrie, Elementaranalyse, ICP-MS, Thermoanalyse [1] durchgeführt. Desweiteren wurden die Produkte mit spektroskopischen Methoden wie IR, Raman, TRLFS und EXAFS untersucht.
Die Synthesen erfolgten in der Regel durch die Umsetzung von Uranylnitratlösung mit Erdalkalinitrat- oder -chloridlösung und Natriumcarbonat im pH-Bereich von 7 bis 8 [2]. Die charakterisierten Substanzen wurden für die Bestimmung ihrer Löslichkeit und für Speziationsuntersuchungen verwendet.
Hauptziel dieser Arbeit war die Bestimmung der Löslichkeit dieser Uranminerale, da bisher keine Daten bekannt sind. Die Löslichkeitsexperimente wurden bei 25°C im pH-Bereich von 7,0 bis 9,0 in 0,1 M NaClO4 - Lösung durchgeführt. Unter Gleichgewichtsbedingungen wurden die Festphasen mittels Röntgendiffraktometrie und die Lösungen mit TRLFS und EXAFS analysiert. Die Ergebnisse zeigten, daß bei pH 7,0 bis 9,0 die Minerale als Festphase vorliegen. Mittels TRLFS wurden in den Lösungen auch M2UO2(CO3)3-Komplexe nachgewiesen.
Die Löslichkeit der Erdalkaliuranyltricarbonate vermindert sich in der Reihe von Magnesiumuranyltricarbonat (0.230 mol/l pH: 8,0) zum Bariumuranyltricarbonat (1.31x10-3 mol/l pH: 8,0) entscheidend [3]. Analoges Verhalten zeigt die Löslichkeit der entsprechenden Erdalkalicarbonate.

Literatur:

[1] J. Cejka; Reviews in Mineralogy (Uranium: Mineralogy, Geochemistry and the
Environment) volume 38,(1999) 521-622
[2] M. Bachelet , Cheylon E., Douis M.and Goulette G.; Bull. Soc. Chim. France 19 (3),
(1952) 565
[3] S. Amayri; Dissertation an der TU-Dresden in Vorbereitung (2001)

Carbonate and bicarbonate are the common anions found in significant concentrations in many natural waters, and they are strong complexation agents for actinide ions. Seepage, flooding and mining waters from the uranium mining area in the southeast of Germany (Saxony and Thuringia), contain relatively high amounts of magnesium, calcium, carbonate and sulfate ions. In these waters the pH values range from 7.0 to 8.0 and the uranium content is about 0.02 mmol/L where magnesium, calcium and carbonate concentrations are 11.6 mmol/L, 6.9 mmol/L and 3.9 mmol/L, respectively /1/.
Recently we were able to confirm the existence of the natural complexes Ca2UO2(CO3)3(aq) and Mg2UO2(CO3)3(aq) by spectroscopic measurements /2/.
We performed Extended X-ray Absorption Fine Structure (EXAFS) measurements at the uranium LIII- edge to study the structures of these complexes. The obtained results by EXAFS of these complex solutions are compared with those from the corresponding EXAFS and XRD data related to the secondary minerals of uranium, liebigite, Ca2[UO2(CO3)3]×10H2O and bayleyite, Mg2[UO2(CO3)3]×10H2O and they are in good agreement.

References:

/1/ Bernhard, G., G. Geipel, V. Brendler, H. Nitsche: Uranium speciation in waters of different
uranium mining areas, J. of Alloys and Compounds 201 (1998) 271-273.
/2/ Bernhard, G., G. Geipel, V. Brendler, H. Nitsche: Speciation of Uranium in Seepage Waters of a
Mine Tailing Pile Studied by Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS),
Radiochim. Acta 74 (1996), 87-91.

The retained fraction of the potential energy of argon ions incident on copper has been measured using stationary calorimetry at charge states up to 9+ and kinetic energies ranging from 75 eV and 240 eV per ionic charge. An average fraction of 30% to 40% is found with little dependence on the charge number and on the kinetic energy. The retention of the total energy ranges 60% to 75% and can mainly be accounted for by the retained fraction of the potential energy and the collisional energy lost by reflected ions and sputtered target atoms.

It is demonstrated that the intrinsic stress in cubic boron nitride films can be significantly relaxed during growth by simultaneous medium energy ion implantation. The stress in the growing film has been studied in-situ using cantilever curvature measurements and has been reduced to below 2 GPa by simultaneous Ar+ or N+ ion implantation with an energy of 70 keV and 35 keV, respectively. The resulting cubic boron nitride films show an increased long term stability. The results reveal that the stress in cBN is not reduced due to segregation of boron at grain boundaries.

The interaction of uranium with cells of three recently described eco-types of Acidithiobacillus ferrooxidans recovered from uranium mining wastes was studied. The uranium sorption studies demonstrated that the strains from these types possess different capability to accumulate and tolerate uranium. The amount of uranium biosorbed by all A. ferrooxidans strains increased with increasing the concentration of uranium. We have found that the representatives of type II accumulate significantly higher amounts of uranium in comparison to the other A. ferrooxidans strains. The investigations of the tolerance to uranium showed that the types I and III are resistant to 8 and 9 mM of uranium respectively, whereas the type II does not tolerate more than 2 mM of uranium. The recovery of the accumulated uranium by desorption was investigated using various desorbing agents as sodium carbonate, sodium citrate and EDTA at different concentrations. Sodium carbonate was the most efficient desorbing agent, removing 97% of the uranium sorbed from the cells of A. ferrooxidans type III, and 88.33 and 88.50% from the cells of the types I and II, respectively.

Mobilization of heavy metals in the environment due to industrial activities is of serious concern due to the toxicity of these metals in humans and other forms of life. Uranium is an example of these metals, and is considered one of the most seriously threatening heavy metals mainly because of its high toxicity, not so much radioactivity. Activities associated with the nuclear industry, mining and wastewater treatment have brought excessive amounts of uranium into the environment. In uranium deposits a number of acidophilic chemolithoautotrophic ( Acidithiobacillus ferrooxidans, for instance) bacteria have been identified which are able to oxidise sulphide minerals, elemental sulfur, ferrous iron. Sequence analysis of the 16S rRNA genes of several reference strains and uranium mining waste pile isolates of A. ferrooxidans revealed specific signatures which distinguish three types within the species. These types differ in their capability to accumulate and tolerate uranium /1/.
Uranium (VI) complexes formation at cell surfaces of A. ferrooxidans types was studied using uranium LIII-edge Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. In all samples uranium is coordinated by two axial oxygen atoms (Oax) at distance of 1.77-1.78 Å. The average distance between uranium and the equatorial oxygen atoms (Oeq) is 2.35 Å. The coordination number for Oeq is 5-6.
Using U-C and U-P phase and amplitude functions, the third and the fourth peak in the FT of A. ferrooxidans give a distance of 2.91 and 3.58 ± 0.02Å, respectively. The latter is the same U-P bond distance as for the organic uranyl phosphate (U(VI)-ATP complex). But we do not exclude the possibility of implication of sulfur because these 2 elements (P and S) are close each other in the periodic system of elements and EXAFS can not distinguish between them. In addition, the P (or S) is bonded in a monodentate mode to the uranyl ion. A bidentate bounding would give a atomic distance of approximately 3.2 Å.
Moreover, no structural differences were observed between the uranium complexes formed by the 3 types of A. ferrooxidans. However, the EXAFS spectra are indicating a formation of uranium complexes which are different from those formed by Bacilli /2/.

/1/ M. Merroun et al., Interaction of three types of Acidithiobacillus ferrooxidans with uranium, Biometals (in preparation).
/2/ C. Hennig et al., EXAFS investigation of uranium(VI) complexes formed at Bacillus cereus and Bacillus sphaericus surfaces, Radiochim. Acta (in press).

In den vergangenen Jahren wurde grundsätzlich akzeptiert, dass Kolloide unter bestimmten Randbedingungen einen erheblichen Beitrag zum Transport von Stoffen in aquatischen Systemen leisten können. Nach wie vor ist jedoch umstritten, welche Relevanz der kolloidale Transport bei einer Vielzahl von Fragestellungen hat.

Plasma immersion ion implantation (PIII) from a chlorine containing plasma has been used in order to improve the high temperature oxidation behavior of titanium aluminide alloys. This process is promising since the subsurface Cl concentration, which is needed for optimum protection against oxidation, can be quickly obtained (approx. fluence 1·1016 Cl/cm-2) in a PIII process.
A PIII system being resistant against the strongly etching Cl2 plasma is presented. Plasma diagnostics of the Cl2 plasma sustained by an ICP source using Langmuir probe measurements is discussed. For the electro-negative Cl plasma, the measurements are examined regarding the influence of negative ions. The implantation of Cl is correlated to the plasma parameters using AES depth profiling of the surface after implantation. The high temperature oxidation behavior is tested using thermogravimetrical analysis (TGA) in air at 900 °C and microstructural investigations of the oxide scale. PIII implantations of Cl2 with 30 kV HV pulses (effective energy 15 keV) show a strong reduction of the oxidation at 900 °C in air, which is comparable to conventional beam line im-plantations of Cl at 15 keV.

Due to the spontaneous heat release during the initiation of the strongly exothermic Grignard reaction, these reactions dispose of considerable harzard potentials. Therefore, the knowledge of thermody-namic and thermokinetic parameters is one of the prerequisites for safe formation of Grignard rea-gents in production plants. To obtain more accurate results, these studies on the formation of Grignard reagents were carried out in a closed reaction calorimeter by dosing the pure bromobenzene deriva-tive for the first time. The molar reaction enthalpy per mole bromobenzene derivative was determined with a standard deviation of about 5%.

We show that coherent optical phonons in GaAs multiple quantum wells are generated in a completely different way compared to bulk GaAs. Unlike in GaAs where the ultrafast screening of electric fields by photogenerated charge carriers is known to be dominant, three distinctive generation mechanisms contribute simoultaneously in multiple quantum wells.

Natural convection is a basic principle for a lot of industrial processes. As an example for the investigation of natural convection phenomena, the paper describes investigations of a passive heat removal system in advanced designs of nuclear power plants. The SWR1000 concept of Siemens AG includes emergency condensers. In the Research Centre Jülich at the NOKO test facility experiments were performed, to investigate the heat transfer capability under different operation modes. In the last time the heating up phenomena on the secondary side were investigated in detail. The paper describes simulations performed in the Forschungszentrum Rossendorf using the CFD-code CFX-4 of AEA-Technology and comparisons to the experiments. Performing additional calculations, measures to avoid undesired temperature stratification were investigated.

The irradiation sensibility and the annealing behaviour were studied on seven different heats from VVER 440 and VVER 1000-type reactor pressure vessel steels. The specimens were irradiated at the Rheinsberg prototype VVER 2 reactor to mean neutron fluences between 43 - 127.6A1018 n/cm² [E > 0.5 MeV] and afterwards toughness and strength properties were determined. In addition the microstructure was analysed using SANS technique. There is an obvious trend regarding the correlations between the irradiation-induced changes of transition temperature, hardness and volume fraction of microstructural features of the radius near of approx. 0 to 2 nm. The main parameters of influence are the neutron fluence and the nickel content. The nickel-containing VVER 1000-type pressure vessel steel is more sensible against irradiation than the VVER 440-type steel which has a low content of nickel. For the last one the sensibility against radiation embrittlement depends on content of copper and phosphorus. Annealing at 475 °C (100 h) reduces the irradiation effect but not completely in every case.

Experiments with 3 MW deuterium injection have been carried out in the Gas Dynamic Trap (GDT) to simulate the axial profile of the fusion reaction intensity in the proposed neutron source based on the GDT. Quite narrow angular distribution function of the fast ions produced by an oblique neutral beam injection results in a peaked axial profile of the fusion yield. This strong peaking is essential to produce an intense neutron flux in the testing zones of the GDT-based neutron source.
The scintillation counters were installed in the central cell of the device to monitor the DD fusion reaction products: neutrons (2.45 MeV) and protons (3,02 MeV). They were closely located to the plasma column inside of the vacuum chamber in oreder to avoid contribution from the scattered neutrons and to improve the spatial resolution of the measurements. The axial profiles of the fusion neutrons and protons have been measured in the high-beta regime of the GDT operation.
In the paper the experimental data are compared with the results of numerical simulations. The conclusion may be drawn that the kinetics of the fast ion relaxation and scattering is determined by classical Coulomb collisions.

Laser induced spectroscopic methods are an excellent tool for the study of complex formation of actinides with various ligands at relatively low concentrations. Laser-induced Photoacoustic spectroscopy and Time-resolved Laser-induced Fluorescence spectroscopy are well-known methods. These methods are inappropriate for metal ions which show no change in their spectroscopic properties with complexation. In the case of organic actinide complexes it is possible to use the dependence of fluorescence of the organic ligands on actinide concentration in order to determine complex formation constants. The fluorescence lifetimes of organic ligands in aqueous solution at room temperature are below 20 ns. To study fluorescence properties of theses organic substances laser systems with ultrashort pulses are inevitable. We, therefore, have installed a femtosecond-laser-induced fluorescence spectroscopy system in our laboratory.
The lasersystem provides femtosecond laserpulses in the wavelength range from 250 nm to 10 µm and a pulse duration of 130 fs. The repetition rate is 1 kHz. The emitted fluorescence signal is detected with an intensified CCD camera, with gate width between 80 ps and 6 ns. The delay for time resolved spectra can be adjusted between 0 and 20 ns after the laser pulse with stepwidth down to 25 ps.
We validated this time-resolved laser-induced fluorescence system by studying the fluorescence behavior of salicylic acid and 5-sulfosalicylic acid at pH 4.0 as function of the uranium(VI) concentration. Using a static quenching mechanism the complex formation constants are calculated to be log KI=0.1M= -1.12 ± 0.03 for salicylic acid and log KI=0.1M= -0.67 ± 0.08 for 5-sulfosalicylic acid, respectively, assuming a 1:1 complex formation. The data from the NIST database /1/ are log KI=0.1M= -1.0 and log KI=0.1M= -0.72, respectively. For the actinides neptunium and plutonium much less data are available. Complex formation constants of various substituted benzoic acids with these actinide elements are reported.

/1/ A.E. Martel, R.M. Smith and R.J. Motekaitis: NIST Critically Selected Stability Constants of Metal
Complexes Database Version 5.0; 1998

The effect of plasma immersion ion implantation of chlorine on the high temperature oxidation of titanium aluminides alloys was investigated. PIII implantations of Cl2 at 30 kV (effective energy 15 keV) show a strong reduction of the oxidation at 900°C in air, which is comparable to conventional beam line im-plantations of Cl at 15 keV. A specialized PI³ system for the strongly etching Cl2 plasma was set up. The chamber is coated inside with aluminum foil, in order to protect the chamber and to avoid contamination of the plasma except with Al. The pumping system is chemically resistant. First implantations and plasma diagnostic of an ICP source sustained Cl2 plasma are discussed. The effect on the high temperature oxidation behavior is tested using thermogravimetrical analysis and microstructural investigations

The Paks Nuclear Power Plant is equipped with VVER-440/V213-type pressurised water reactors. As known, these reactors have a number of special features, therefore the transient behaviour should be different from PWRs of usual design.
To study the transient behaviour of this type of NPPs an integral-type facility called PMK-2, a scaled-down model of the Paks NPP was designed and constructed in the middle of 1980s and several experiments of different types have been performed.
In the framework of a European Union financed Phare project an upgrading of PMK-2 was performed. Equipments installed are as follows: needle-shaped void-probes for local void measurements, full-flow turbines for velocity measurements, micro-turbines for two-phase flow measurements, three beam gamma densitometer to measure coolant density and to identify flow patterns, and in addition a new data acquisition system has been installed.
This paper deals with the application of void probes for the evaluation of the results of a loss of coolant accident.

The paper presents a method to prevent the water hammer by an adaptive control of the valve closing process. For this purpose, the valve is equipped with a brake system that acts onto the rotation axis of the valve flap. The brake cylinder of the applied hydraulic disk brake is connected to the pipeline just upstream the valve, so that the fluid pressure may activate the brake. By this means the closing is interrupted when the pressure of the fluid increases due to the water hammer. The pressure peak is limited to a maximum pressure given by the user.
The described system does not need any external energy source. Furthermore, it adapts to changes of the pipe system parameters, such as varying pipeline length (e.g. liquid supplied from tanks with a different distance from the valve), fluid velocity or physical properties of the fluid. These are major advantages compared to traditional damping systems, which delay valve closing in a fixed manner.