Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

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

This is a comprehensive study of the characteristics of an AuGeSi and CoNd liquid metal alloy ion sources [Focused ion beams from liquid metal ion sources, 1991]. Such characteristics include current-voltage curves and ion beam mass-spectra. A careful investigation has been undertaken where the temperature is one of the main variable experimental parameters. Theoretical models support the experimental results.

Chemical vapor deposited (CVD) diamond films thermochemically polished on cylindrical steel plates are subjected to Rutherford Backscattering Spectrometry (RBS) and Scanning Electron Microscopy - Energy Diffractive X-ray Spectrometry (SEM-EDX). A diamond film polished for 25 hours at 950 °C is etched in chromic acid (K2Cr2O7 + H2SO4 + H2O) prior to RBS measurement while two other films also polished at 950 °C for 8 and 25 hours, respectively are analyzed as polished. The RBS spectra of as-polished diamond films contain peaks of iron contaminant while the surface of the etched film is devoid of iron. Moreover, the concentration/magnitude of the contaminant on the film polished for 25 hours is about 2-fold that of the film polished for 8 hours. SEM-EDX spectra taken from dark and bright spots manifest the presence of iron contaminant in as-polished films but its absence in the etched film regardless of the surface topology. Thus, the depth measured by the RBS is assumed to represent the characteristic thickness of the non-diamond carbon layer in which the iron contaminant originating from the polishing plate are embedded. The presence of silicon and oxygen bands in the SEM-EDX spectra of both as-polished and etched diamond films is attributed to their inclusion during film deposition.

Temperature and strain rate change tensile tests were performed at two VVER 1000-type reactor pressure vessel welds with different content of nickel in unirradiated and irradiated conditions in order to determine the activation parameter of the contribution of the thermally activated deformation. There are no differences in the activation parameters in the unirradiated and the irradiated condition as well as for the two different materials. This shows irradiation hardening preferentially results from a friction hardening mechanism by long-range obstacles.

In the Forschungszentrum Rossendorf (FZR), an infrared FEL at the radiation source ELBE is under construction. For the measurements of the electron beam position in the undulator, two systems will be used. The first one consists of seven insertable beryllium OTR (Optical Transition Radiation) view screens, which will also be used for the alignment of the FEL optical resonator. The second one will use a single moveable YAG (Yttrium Aluminium Garnet activated by Cerium) screen, which can travel within the undulator vacuum chamber such that the electron beam position can be measured at any place in the undulator.

Annual Report 2000
Institute of Radiochemistry

Für den 3. Block vom KKW Rovno - WWER-1000/W-320 - wurde in Analogie zu den 6 typengleichen Blöcken des KKW Saporoshje eine verbesserte betriebliche Überwachung eingerichtet. Dazu werden der Aufsichtsbehörde vor Ort und in Kiew einmal pro Minute 57 aktuelle sicherheitsrelevante Parameter zur Erfassung und Bewertung mittels moderner technischer Mittel on-line zur Verfügung gestellt. Die entwickelte Auswertesoftware gestattet die Darstellung der Bewertungsergebnisse in Form von Tabellen, Grafiken und Schemata, wobei durch einen Archivmodus auch Trendanalysen von allen Parametern möglich sind. Des Weiteren wurde die Leistungsfähigkeit und Zuverlässigkeit des gesamten Fernüberwachungssystem weiter erhöht, so dass derzeit mehr als 60 % der ukrainischen KKW-Kapazität unter einer deutlich verbesserten behördlichen Aufsicht stehen.

Die genaue Messung der Lamb-Verschiebung stark gebundener Elektronen in Zusammenhang mit Tests der Quantenelektrodynamik (QED) in starken Feldern in hochgeladenen Ionen ist eines der Hauptthemen der heutigen Atomphysik. Die gegenwärtig durchgeführten Hochpräzisionsmessungen erfordern eine hohe Genauigkeit in den theoretischen Berechnungen der Lamb-Verschiebung. Diese Genauigkeit impliziert eine Berücksichtigung aller QED-Korrekturen der Ordnung α und α², aber exakt in allen Ordnungen in Zα. In den zurückliegenden Jahren sind die meisten dieser QED-Korrekturen sowohl in 1. Ordnung als auch in 2. Ordnung Störungstheorie berechnet worden. Der Beitrag der Zwei-Photonen-Selbstenergie konnte jedoch bisher nicht ausgewertet werden und stellte somit die größte Ungenauigkeit in der Vorhersage der Lamb-Verschiebung für wasserstoffartige Systeme dar. In dieser Arbeit wird der Beitrag dieser Prozesse zur Lamb-Verschiebung untersucht. Darüber hinaus werden erstmals renormierte Ausdrücke der Zwei-Photonen-Vakuumpolarisation und der Selbstenergie-Vakuumpolarisation hergeleitet. Bisher konnten diese Beträge nur in Uehling-Näherung ausgewertet werden.

The Rossendorf electrostatic accelerator facility, consisting of three accelerators with rated voltages of 2 -5 MV, has been extended by a 100 kV tandem accelerator for tritium depth profiling by AMS and by concentration of two implanters at the same location. Two experimental chambers were installed, which give the possibility of dual beam experiments using the beams from the 3 MV tandetron and from the 500 kV implanter. At the 5 MV tandem the original inclined field acceleration tubes were exchanged by straight field tubes with spiraling magnetic field. First results of the accelerator modernisation and of the beam line extension are presented.

Recent findings indicate that gamma radiation can contribute to the embrittlement of reactor materials. On this background an experimental benchmark programme at two low power reactors was started to measure both, neutron and gamma spectral fluences behind and inside of transmission modules consisting of variable iron and water slabs using a NE213 scintillation spectrometer and partly a HPGe detector. The experimental results are used to validate Monte Carlo calculation methods in reactor dosimetry for coupled neutron/gamma problems. The experiment and results of a first series of measurements and comparisons to MCNP calculations for neutron and gamma energy spectra are presented. The investigations will be continued with an extension and validation of the Monte Carlo transport code TRAMO.

Within a transport code of BUU type the production of Φ mesons in the reactions Ni+Ni at 1.93 A GeV and Ru + Ru at 1.69 A GeV is studied.
New elementary reaction channels ρN(Δ) → ΦN and πN(1520)→ ρN are included.
In spite of a substantial increase of the Φ multiplicities by these channels the results stay below the tentative numbers extracted from experimental data.

Physical vapor deposition (PVD) processes are nowadays common in synthesis of hard coatings like cubic boron nitride (cBN). Precise knowledge of plasma characteristics (ion flux, ion energy distribution and plasma composition) is crucial for understanding and controlling cBN thin film growth. This work is devoted to the characterization of an unbalanced RF magnetron Ar/N2 discharge using a Langmuir probe and an energy selective mass spectrometer. RF power and total pressure were varied from 50 to 300 W and from 0.1 to 0.5 Pa respectively for different Ar/N2 mixtures. Main ionic species are found to be Ar+ and N2+ with a very low fraction of N+. The ion density increases with RF power, pressure and Ar content. The ion energy distribution consists of one single narrow peak with full width at half maximum of a few eV. The main neutral species are Ar and N2. Atomic nitrogen could not be detected by mass spectrometry, indicating a low fraction of this species in the discharge.

In der vorliegenden Arbeit wird die methodische Entwicklung eines Ultraschall-Einprobenverfahrens zur Erfassung duktilen Rissfortschritts im quasistatischen Dreipunktbiegeversuch auf der Grundlage eines Ultraschallverfahrens vorgestellt. Das Verfahren wird an Werkstoffen unterschiedlichen Zähigkeits-Festigkeitsverhältnisses erprobt.
Das Messverfahren beruht auf der wiederholten Messung der Laufzeit des von einem Sendewandler auf die Rissspitze gerichteten und dort in Richtung Empfangswandler gebeugten Ultraschallimpulses. Als Voraussetzung für die In-situ-Rissfortschrittsmessung auf der Grundlage der Signallaufzeitmessung wurde die Schallwellenausbreitung und Signalbildung mittels Schallfeldsimulationen anhand der Elastodynamischen Finiten Integrationstechnik modelliert und zusätzlich durch stroboskopische Messungen der Schallfeldausbreitung experimentell bestätigt. Zur Kalibrierung des Messverfahrens wurde ein analytischer Zusammenhang entwickelt, der die eindeutige Zuordnung der Signallaufzeit zum gesuchten Rissfortschritt gestattet und den Einfluss der während des Dreipunktbiegeversuches stattfindenden plastischen Verformungen berücksichtigt. Das Ultraschall-Laufzeit-Beugungsverfahren wurde für den Einsatz an bruchmechanischen Kleinproben (ISO-V-Geometrie) spezifiziert. Die in den Prüfvorschriften formulierte Genauigkeitsanforderung an ein Einprobenverfahren kann mit dem ULB-Verfahren erfüllt werden. Die erreichbare Messpunktdichte des Rissfortschritts ermöglicht eine nahezu kontinuierliche Darstellung resultierender J-Risswiderstandskurven.

The fast neutron induced embrittlement of the reactor pressure vessel (RPV) is the main cause limiting the lifetime of many types of nuclear reactors, especially of the VVER type, produc-ing most of the nuclear energy in Russia and seven other countries. Uncertainty estimations show that the largest contribution to the uncertainty of calculated fluences is the uncertainty of the neutron cross section data. In the present work, different aspects of uncertainties of neutron fluence determination connected with the neutron data for transport calculations, data preparation methods and activation dosimetry cross sections have been investigated by com-parison of calculations with data from different libraries and by comparison of calculated and measured activation rates. The main object of these investigations was the VVER-1000 type reactor Balakovo-3. The tested libraries were the ENDF/B-VI based 47n/20g-group library BUGLE-96, the Russian 299n/15g-group library ABBN-93 (v. 99.01) and two modifications of the ABBN library: ABBN/B-VI and ABBN/JEF-2.2. In these modifications the cross sec-tion data of Fe, Cr and Ni are replaced by data based on the evaluated nuclear data libraries ENDF/B-VI and JEF-2.2, respectively. This allows to investigate the influence of the data of the elements most critical for the RPV fluence. Although thermal neutrons contribute only negligible to the embrittlement they are a strong source of gamma irradiation, which is proba-bly contributing noticeable to RPV embrittlement, as newer results showed. Therefore, the influence of different treatment of neutron data in the thermal energy region was investigated by calculations with and without upscattering in the region below 5 eV, as well as with and without consideration of core heterogenity effects. The neutron transport calculations were performed by the discrete ordinate code DORT using a 3D synthesis of (r-*)-, (r-z)- and r-calculations. Results obtained with the Monte Carlo codes MCNP and TRAMO with ENDF/B-VI data, were used to validate the DORT-results. The results of calculations at ex-vessel positions were compared with reference data of the Interlaboratory Experiment at Balakovo-3. The best agreement between results of calculations (C) and experiments (E) was obtained for BUGLE-96 and ABBN/B-VI, and 3D TRAMO results for all used reactions: 237Np(n,f), 93Nb(n,n'), 238U(n,f), 58Ni(n,p), 54Fe(n,p), 46Ti(n,p) and 63Cu(n,a). Further, the in-fluence of using different dosimetry cross sections, from IRDF-90v2, JENDL/D-99, RRDF-98 and a new Russian evaluation for 237Np(n,f), was investigated. The systematic calcula-tional underestimation of 237Np(n,f) reaction rates in case of IRDF-90v2, observed also by other investigators, can be removed using JENDL/D-99 or the new Russian evaluation. A similar underestimation for 93Nb(n,n') is reduced largely if JENDL/D-99 data are used. To evaluate the influence of cross sections of individual elements and of water on neutron and gamma fluence calculations, a simple two-zone cylindrical model was defined. The inner zone simulates the reactor core, the outer consists of H2O or Fe or Cr or Ni. In addition to DORT calculations with different libraries MCNP calculations with ENDF/B-VI were per-formed, to test the influence of point-wise data representation. The found discrepancies should be investigated further.

Introduction

If a fluid is electrically conductive, its flow may be controlled using electromagnetic forces. Meanwhile, this technique is a recognized tool even on an industrial scale for handling highly conductive materials like liquid metals.
However, also fluids of low electrical conductivity as considered in the present study, like sea--water and other electrolytes, permit electromagnetic flow control. Experimental results on the prevention of flow separation by means of a streamwise, wall parallel Lorentz force acting on the suction side of inclined flat plates and hydrofoils will be presented.

Force Configuration
The stripwise arrangement of permanent magnets and electrodes of alternating magnetization direction and polarity shown in Fig. 1 was proposed by Gailitis and Lielausis (1961). It generates a wall parallel force with a maximum value directly at the wall, decaying exponentially with the wall distance. Due to the low electrical conductivity, both electric and magnetic fields have to be applied to generate a Lorentz force of adequate strength. The width of the electrodes is equal to that of the magnets and
determines the penetration of the force into the flow. The ratio of electromagnetic to inertial force can be characterized by the interaction parameter. In analogy to the terminology used in separation control by blowing, one may also define an electrohydrodynamic momentum coefficient.

Results and Discussion
A downstream directed force adds momentum to the flow and accelerates the fluid in the vicinity of the wall. This flow acceleration may be used to counteract the energy loss due to friction and adverse pressure gradients. Actually, a streamwise Lorentz force has already been successfully applied to control the flow around a circular cylinder in Weier et al. (1998). The two inserts in Fig. 2 show the flow around an inclined flat plate. In the lower left photograph, the unforced separated flow is visible, whereas the upper subfigure depicts the fully attached flow under the action of a suction side Lorentz force. The graph indicates that the interaction
parameter, necessary to completely suppress separation, decreases with increasing chord length Reynolds number. The effect of a suction side Lorentz force on lift and drag of NACA--0017--like hydrofoils has been quantified by means of force balance measurements. Depending on the inclination angle, two different effects are observed. At small angles of incidence, a moderate lift increase due to additional circulation is observed. Simultaneously, caused by the added momentum, the drag is decreased. At higher angles of attack, where the unforced hydrofoil would normally stall, a more pronounced lift increase occurs.
Fig. 3 shows the lift gained by the suction side Lorentz force at a fixed inclination angle of 17. Here delta CL is the difference of the lift coefficients of the forced and the unforced hydrofoil at the specified chord length Reynolds number. The shape of the curve as well as the total values of the lift gain and the momentum coefficient resemble the behavior found in separation control experiments with steady blowing. In the presentation, a complementary discussion on scaling issues based on experiments with a NACA 0015 hydrofoil will be given.

Monte Carlo simulations have been used to optimize the monochromator shielding of the polarized cold neutron triple axis spectrometer PANDA at the Munich high flux reactor FRM-II. By using the Monte Carlo program MCNP-4B the destiny of the total spectrum of incoming neutron and gamma radiation from the beam tube SR-2 have been determined during the 3-dimensional diffusion process in different types of heavy concrete and other absorbing material. Special attention has been paid to build a compact and highly efficient shielding, partially non-magnetic, with a total biological radiation dose of less than 10 µSv/h at its outsides. Specially considered was the construction of an albedo reducer, which serves to reduce the background in the experiment outside the shielding.

We present new experimental data obtained with the FOPI detector at SIS, for the Au+Au heavy-ion collisions at 400 AMeV incident energy. The sideward flow, determined from a method without reaction-plane reconstruction, and the nuclear stopping are studied as a function of the centrality of the collisions. In order to study the nuclear in-medium effects, which act on the NN cross sections and potential and hence on experimental observables like the nuclear-matter flow and stopping, these results are compared with the predictions of two different QMD versions. The first one offers a fully microscopic calculation of the cross sections and potential in the G-matrix formalism and naturally includes the in-medium effects (this version is for the first time confronted with experiment). The second one uses a standard Skyrme potential plus a momentum-dependent term in order to mimic the in-medium effects.

The ratio of the total charge bound in fragments with Z between 2 and 15 to the hydrogen yield has been measured, and the neutron-to-proton ratio n/p has been estimated from the data of central Au+Au reactions between 100 and 400 AMeV, measured with the phase I setup of the detector system FOPI at the GSI, Darmstadt, in the polar angle range between 7^o and 30^o. These two quantities were used to determine the entropy per nucleon S/A by comparing them with the predictions of the FREESCO code. The analysis allows the simultaneous extraction of the values of the baryonic entropy, temperature, and collective flow. The extracted values are in good agreement with the values obtained in earlier FOPI studies and, for the baryonic entropy, with recent hydrodynamic caculations.

Light-particle emission from Au+Au collisions has been studied in the bombarding-energy range 100-250 AMeV, using Delta-E-E_R telescopes in coincidence with the FOPI detector in its phase I configuration. Center-of-mass energy spectra have been measured for Z=1, 2 isotopes emitted in central colisions at CM polar angles between 60^o and 90^o. Evidence for a collective expansion is reported, on the basis of the mean kinetic energies of hydrogen isotopes. Comparison is presented with statistical calculations (WIX code). For CM kinetic energy spectra, fair agreement is found between data and a recently developed transport model.

Inorganic colloids are ubiquitous in mine waters. They are primarily 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+. Colloidal particles are able to adsorb heavy metals and to influence trace heavy metal transport as for instance the transport of uranium. However, colloid formation and heavy metal adsorption are strongly dependent on pH. From a colloid-chemical point of view it can be differentiated between two principal types of mine waters:

(i) Type "acidic pore water" [1]
These waters can be separated from the rock by centrifugation or can be collected in the mines as acid rock drainage (ARD) samples. The waters possess high salt concentrations and are very acidic (pH 3 to 1). Ultrafine particles of <5 nm in size are the main colloidal component (based on photon correlation spectroscopy and ultrafiltration). The colloid concentration reaches the g/L range. The particles consist mainly of hydronium jarosite and schwertmannite (based on EXAFS). As and Pb show a high tendency to adsorb onto these particles.

(ii) Type "bulk water" [2]
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 (based on photon correlation spectroscopy and scanning electron microscopy). The particles consist of Fe(III) and Al oxyhydroxides (ferrihydrite, alumogel). Their electrostatic stabilization is weak (zeta potential only about -10 mV), i. e. they show a larger tendency to coagulate and aggregate than the colloids found in the type (i) waters. Contaminants such as As, Pb, Cu, Th, U(IV), Po, and in the absence of carbonate complexation also U(VI), are strongly bound onto these particles. Uranium(VI) adsorption is often suppressed due to the formation of dissolved uranyl carbonato complexes in mine waters [2].

Important colloid-chemical processes are observed during the transition of type (i) waters to type (ii) waters which occurs in the course of the flooding of abandoned ore mines (dilution of the type (i) waters). Huge amounts of iron(III) particles with a size of 100 to 300 nm are formed under such conditions due to O2 ingress and pH increase. The adsorption rises drastically when the pH reaches the near-neutral region (cf. [3]). The sorption behavior of U(VI) in flooding waters differs significantly from that of U(VI) in both typical "acidic pore waters" and typical steady-state "bulk waters". Typical pH values of the flooding waters are in the range between 4 and 6 after some flooding time. Uranyl adsorption to the iron(III) particles is neither suppressed by high acidity nor by uranyl carbonate complexation in this pH region and the assumption of an unretarded migration of uranyl is "over-conservative". Scavenging by Fe(III) particles and colloid coagulation plus sedimentation can significantly immobilize the U(VI) in waters of the transition type. This scavenging mechanism refers also to trace elements such as Cu, As, Mo, Sb, Y, and Ce. Also the radiotoxic heavy metals Po, Pb, Th and Ac are colloid-borne above pH 4. Ra is usually truly dissolved.

[1] Zänker, H.; Moll, H.; Richter, W.; Brendler, V.; Hennig, C.; Reich, T.; Kluge, A.; Hüttig, G. (2001)
The colloid chemistry of acid rock drainage solution from an abandoned Zn-Pb-Ag mine. Appl. Geochem. (accepted).

[2] Zänker, H.; Richter, W.; Brendler, V.; Nitsche, H. (2000)
Colloid-borne uranium and other heavy metals in the water of a mine drainage gallery. Radiochim. Acta 88, 619-624.

[3] Hsi, C.-K. D.; Langmuir, D. (1985)
Adsorption of uranyl onto ferric oxyhydroxides: Application of the surface complexation site-binding model. Geochim. Cosmochim. Acta 49, 1931-1941.

The entropy per nucleon (S/A) has been extracted for the Au (150-800 AMeV)+Au reaction by using the phase I setup of the 4pi facility at GSI, Darmstadt. The entropy has been obtained from the comparison of various observables characterizing the dM/dZ fragment multiplicity distribution, extending up to Z=15, with those calculated with the quantum statistical model. It is the first time that S/A values are determined by considering the full ensemble of charged products detected in the reaction. Consistent values of S/A are found from different methods. These entropy values are shown to be fairly independent of the volume of the "participant" region considered. They are somewhat lower than those extracted in earlier works but are in good agreement with hydrodynamic calculations and suggest a low viscosity for the hot and dense nuclear matter.

Charged particles have been observed in collisions of Au+Au at an incident energy of 150 AMeV using a high-granularity detector system covering approximately the forward hemisphere in the center-of-mass system. Highly central collisions have been studied using a double selection criterion which combines large charged-particle multiplicities with small transverse-momentum directivities. In this class of events about one-quarter of the total nuclear charge emerges as intermediate-mass fragments with nuclear chages Z>2. These fragments are centered at midrapidity and are produced with large transverse velocities.

At the SIS/ESR accelerator facility at GSI in Darmstadt the 4pi-detector system FOPI is under construction at present. It is designed for the investigation of central collisions of heavy ions in the energy range up to 2 AGeV. As phase I of this detector a forward wall has been built and used in various experiments. It comprizes a total number of 764 scintillators with an additional shell of 188 thin Delta-E-detectors in front of it and covers the full azimuth of the polar angles from 1 to 30 degrees. the velocity and the nuclear charge of the fragments are determined by a combined time-of-flight and Delta-E measurement.

Using the FOPI facility at GSI Darmstadt, complete data of Au+Au collisions at 150 AMeV were collected for charged products (Z=1-15) at laboratory angles from 1 to 30 degrees. Central collisions were selected by applying various criteria. The kinentic energy spectra of fragments from an isolated midrapidity source are investigated in detail for center-of-mass angles from 25 to 45 degrees. The heavy products (Z>=3) are used to determine the collective energy which is found to be at least 10 AMeV.

Complete distributions of the light and intermediate mass fragments (Z=1-6) produced within the polar angle range of 1 to 30 degrees in highly central collisions of 250 AMeV Au+Au are presented. The results of this measurement and a model analysis are used to study the expansion and clustering of the hot and compressed transient state formed in central collisions of such a heavy system. The influence of the initial conditions on the final observables is discussed.

Particles with strange quark content produced in the system 1.93 AGeV ⁵⁸Ni on ⁵⁸Ni have been investigated at GSI Darmstadt with the FOPI detector system. The correlation of these produced particles was analyzed with respect to the reaction plane. Lambda baryons exhibit a very pronounced sideward flow pattern which is qualitatively similar to the proton flow. However, the kaon (K⁺,K_s ⁰) flow patterns are significantly different from that of protons, and their form may be useful to restrict theoretical models on the form of the kaon potential in the nuclear medium.

Charged pion spectra measured in ⁵⁸Ni+⁵⁸Ni collisions at 1, 06, 1.45 and 1.93 AGeV are interpreted in terms of a thermal model including the decay of Delta resonances. The transverse momentum spectra of pions are well reproduced by adding the pions originating from the Delta-resonance decay to the component of thermal pions, deduced from the high transverse momentum part of the pion spectra. about 10 and 18% of the nucleons are excited to Delta states at freeze-out for beam energies of 1 and 2 AGeV, respectively

The Mössbauer spectra of single crystals of the iron silicides e-FeSi, ß-FeSi2 and a-FeSi2 are collected by conversion electron Mössbauer spectroscopy at room temperature. Measurements were performed at different angles between the propagation direction of the exciting g-radiation and the crystal axis of the single crystals.
The hyperfine parameters are determined with high accuracy. Moreover, the signs of the quadrupole splittings and the direction of the main axis of the electric field gradient in regard to the crystal orientation was determined for the disilicides. For the monosilicide, this was impossible because of the particular crystal symmetry.

Im Rahmen eines vom BMBF/BMWi geförderten WTZ-Vorhabens wurde dem Institute for Nuclear Research and Nuclear Energy (INRNE) in Sofia der Programmcode DYN3D sowie der gekoppelte Programmkomplex ATHLET-DYN3D verfügbar gemacht. Dabei stellt dieser Programmkomplex eine Anbindung des im FZR entwickelten 3D Kernmodells DYN3D an den thermohydraulischen Systemcode ATHLET der GRS dar.
Zur Validierung dieser Programmcodes wurde eine Messdatensammlung zu einem Inbetriebnahmeexperiment am Block 6 des KKW Kozloduj (WWER-1000/320) erstellt. Die Ergebnisse der durchgeführten Validierungsrechnungen wurden mit den Messwerten aus der Datensammlung verglichen.
In den Programmcode DYN3D wurde von den bulgarischen Experten ein vereinfachtes Modell zur Simulation von Querströmungen zwischen den Brennelementen integriert. Dieses Querströmungsmodell ermöglicht es, Prozesse mit asymmetrischen Randbedingungen realistischer zu betrachten. Eine erste Bewertung des implementierten Strömungsmodells erfolgt durch Vergleichsrechnungen zwischen dem modifizierten DYN3D Code und dem Unterkanalanalyse-Code COBRA-4I sowie auf der Grundlage von verfügbaren Messdaten aus dem KKW Kozloduj.

Two models of material damage occuring with viscoplasticity are presented:

1. accumulation model based on rupture strain
2. constitutive model based on the volume fraction of creep cavities

The creep model for porous material is developed by numerical simulation experiments with a FE model representing the simplified microstructure of a representative volume element.

The damage accumulation model is integrated into ANSYS via the user programmable features.

The efficiency as diffusion barrier of RF-Magnetron sputtered Ta-layer modified by ion implantation has been studied using Auger electron spectroscopy and X-ray diffraction. Two systems were prepared : 50nm-Ta/500nm-Cu/50nm-Ta/ on SiO2 and 200nm-Cu/50nm-Ta/ on SiO2. The samples were annealed at temperatures from 600 to 850°C in a vacuum of 2 x 10-4 Pa. The thermal stability was determined by interdiffusion of Cu into the diffusion barrier. The as-deposited Ta barriers are polycrystalline. After annealing at 600°C for 1 hour interdifusion of Cu is observed for the non-implanted barrier. Ion implantation of nitrogen into the Ta layer leads to a nanocrystalline or amorphous-like structure with an important improvement of the barrier effect. The nitrogen implanted 50 nm Ta-barrier on Cu is stable up to 750°C for 1h. A higher thermal stability reveals the Ta layers between the Cu and SiO2. Cu/Ta/SiO2 system shows beginning of copper diffusion and a strong interaction between Ta and SiO2 after annealing at 800°C without implantation. The implanted Ta-barriers in this system are still effective, after annealing with 850°C for 3h.

Acidic pore waters are the waters of most chemical importance in abandoned ore mines before the mines' flooding. These waters possess high concentrations of sulfuric acid and reach pH values of 3 to 1. In particular in the case of the Königstein uranium mine they contain high amounts of sulfuric acid because of the former ore extraction technology (acidic underground leaching with sulfuric acid). Typically, acidic pore waters have iron concentrations of the range of grams per liter. This iron is partly dissolved and partly colloidal (particle size < 5 nm, cf. [1]). Most of the heavy metals, including U(VI), are truly dissolved in acidic pore waters. Only As and Pb have been found in a colloid-borne form [1].

From a chemical point of view, the flooding of a mine is primarily the dilution of the pore waters by groundwaters. The following concomitant phenomena are accompanying this process in the Königstein mine: a decrease in heavy metal concentrations, a decrease in H2SO4 concentration (increase of the pH), an ingress of oxygen and an ingress of carbonate. This gives rise to chemical reactions such as the neutralization of sulfuric acid by carbonate, the degassing of carbonate as CO2, the oxidation of Fe2+ into Fe3+ and the hydrolysis of Fe3+, i.e. the formation of Fe(III) particles. We asked ourselves what the interactions of the radiotoxic heavy metals with these Fe(III) particles are and what the behavior and later fate of the particles (possibly carrying radiotoxic heavy metals) is.

According to the existing knowledge there should not be much interaction between the < 5 nm Fe(III) particles and the radiotoxic heavy metals in the acidic pore waters (exception: 210Pb). With increasing pH, elements such as Th, Po, Ac etc. begin to adsorb strongly onto the particles. Also the uranyl increasingly tends to sorb onto the particles with increasing pH. However, uranyl adsorption to the particles is counteracted by carbonate complexation in the solution the importance of which also increases with increasing pH. Therefore, uranyl is often assumed to be truly dissolved under the conditions of real mine waters, either due to high acidity (low pH region) or due to carbonate complexation (higher pH). It remains to be elucidated if there is a pH region where also the uranyl occurs colloid-borne in a mine.

We investigated flooding waters from the Königstein mine by light scattering, centrifugation, filtration, ultrafiltration, scanning electron microscopy, laser doppler electrophoresis, ICP-MS, AAS, ion chromatography and diverse radiometric methods. The waters had a pH of 5.6 and an Eh of 450 mV, the concentrations of important constituents were CCa 0.9 mM, CFe 0.3 mM, CU 0.05 mM, Csulfate 1.2 mM, Ccarbonate 1,0 mM and CO2 0.11mM. Almost 90 % of the iron was divalent. Because of the Eh value we assume that the uranium was hexavalent. Colloid concentrations in the range of 2 to 3 mg/L were found; they rose rapidly if the access of oxygen was allowed. The particle size was about 100 nm. We measured a zeta potential of only -7.5 mV, i.e. the electrostatic stabilization of the particles was weak. Therefore the particles showed a pronounced tendency to aggregate and sediment. Strongly-sorbing radionuclides such as 210Po and 210Pb, but also significant fractions of the uranyl (up to 100 %) were colloid-borne. The amount of the sorbed uranyl was very sensitive to pH changes of only few tenth of pH units. This senstivity is obviously attributable to the fact that the pH of the water was in the vicinity of the point of inflection of the uranyl - Fe oxyhydroxide "adsorption edge". The uranium and the other radiotoxic heavy metals studied, with the exception of radium, followed the tendency of the iron(III) particles to aggregate and sediment.

We conclude that there is a pH range where the U(VI) occurs colloid-borne in mine waters, even if carbonate is present. This range is pH 4 to 6 (see also [2]). The assumption of an unretarded m...

We present experimental data on directed flow in semi-central Au+Au collisions at incident energies from 90 to 400 AMeV. For the first time for this energy domain, the data are presented in a transverse momentum differential way. We study the first order Fourier coefficient v1 for different particle species and establish a gradual change of its pattern as function of incident energy and for different regions in rapidity.

New oxorhenium complexes with 2(diphenylphosphanyl)-N-(1-thioethyl)benzamide (H₂PNS) and 2-(diphenylphosphanyl)-N-(2-hydroxyethyl)bezamide (H₂PNO) and various monodentate thiols as co-ligands are reported. These new complexes, 1-6, have been prepared by reacting [ⁿBu₄][Re(O)Cl₄] or [Re(O)Cl₃(PPh₃)₂] with the tridentate H₂PNX (X=O, S) ligands and different monothiols. The characterization of the complexes involved IR. ¹H and ³¹PNMR spectroscopy and x-ray crystallographic analysis in the case of 1 and 2. Complexes [Re(O)(kappa³-PNO)(SPh)] (1), and [Re(O)(kappa³-PNS)(SPh)] (2), adopt a distorted square pyramidal geometry (delta=3.0°, 1 and delta=1.3° for 2), with the oxo group in the axial position and the equatorial plane being defined by the phosphorus, nitrogen and oxygen (1) or sulfur (2) atoms of the tridentate chelate and by the sulfur atom of the monothiol.

Der Zugang zu diagnostisch relevanten Komplexverbindungen des Tc-99m wird in der Kopplung des Metalls an biologisch aktive Moleküle gesucht. Bisher dominieren Tc(V)-Chelate mit charakteristischem [Tc=O]³⁺ core. Die hohe Polarität der Metall-Sauerstoff-Bindung sowie die Austauschfähigkeit der Liganden in vivo stimulieren die Suche nach stabilen Systemen auf niederen Oxidationsstufen.
Wir beschreiben hier zwei neue Typen von Tc(III)-Komplexen. Sie erfüllen die Forderung nach niedriger Polarität und hoher in-vivo-Stabilität.
Gekoppelte Substitutions-Reduktionsreaktionen von Tc(V)-Verbindungen 1 mit zwei-zähnigen PS-Liganden führen zu Tc(III)-Komplexen der Struktur 2.
Die Reduktion von Pertechnetat mit tertiären Phosphinen in Gegenwart des tripodalen Liganden Tris(2-mercaptoethyl)amin ergibt Gemischtligandkomplexe 3 mit NS₃/P-Koordination. Der monodendate Phosphinligand kann in einfacher Weise durch Isocyanide unter Bildung der Spezies 4 substituiert werden.
Die neuen Tc(III)-Chelate 2 und 4 zeichnen sich durch eine hohe Variabilität hinsichtlich des zu koppelnden Biomoleküls (R) aus. Challenge-Experimente mit Glutathion unter physiologischen Bedingungen belegen die hohe in-vivo-Stabilität der Verbindungen.

By virtue of its ideal nuclear physical characteristics for routine nuclear medicine diagnostics and its ready availability, technetium-99m (^99mTc) is of outstanding interest in the development of novel radiopharmaceuticals. The potential of developing ^99mTc-based radioligands also for studying the receptor function in the central nervous system (CNS) is well recognized despite the difficulties to be overcome. A fundamental challenge is the pharmacologically acceptable integration of the transition metal technetium with its peculiar coordination chemistry into the molecular entity of CNS receptor ligands. Conceptually, the ligand molecule can be assembled by three building blocks: a small neutral chelate unit, an organic linker that may also serve as pharmacological modifier and a receptor-binding region derived from selective receptor antagonists. The recent introduction of novel technetium chelate units, particularly mixed-ligand complexes and low-valency organometallic compounds of technetium, provides an impetus for the further development of CNS receptor ligands. Moreover, progress in receptor pharmacology and experience gained with PET radiotracers have facilitated the design of numerous ^99mTc-based CNS receptor ligands. The formidable challenge of developing ^99mTc probes as SPET imaging agents targeting CNS receptors can be meet with optimism in view of the successful development of [^99mTc]TRODAT-1 as a ^99mTc complex for imaging dopamine transporters in the brain, although there are a number of receptor-specific imaging agents that have so far resisted all efforts to develop them.
This review presents recent advances and discusses the remaining hurdles in the design of ^99mTc-based CNS receptor imaging agents.

The vacany clusters (VC) evolution in the neutron-irradiated VVER-type reactor pressure vessel steels is investigated, beginning at the nucleation stage and finishing in the coarsening stage. For this, characteristic VVER-type reactor conditions are considered. VC evolution in the nucleation stage is analysed on the basis of the computer simulation data. During the deterministic and the coarsening stage, elastic interaction between iron matrix and VC is accounted, that provides the stability of the peak of the size distribution function under the condition of increasing neutron fluence in correspondence to the experiments.The results are compared with the results of SANS experiments which were carried out on specimens irradiated at surveillance positions of VVER reactors. The presented approach may be used for analyses of the small inhomogeneities (about 1 nm) in the irradiated damage structure of the VVER-type steels.

The Master Curve concept (MC) allows to quantify the variation of fracture toughness with the temperature through-out the ductile-to-brittle transition region. Limit curves of fracture toughness for defined failure probabilities and a reference temperatures can be determined using this method. Thus, fracture mechanical values can be supplied for an integrity assessment of structural components.
The paper links MC concept and Charpy-V impact test to determine dynamic fracture mechanical parameters of ASTM A 533 B Cl. 1 nuclear pressure vessel steel. The MC based reference temperature, T0dy, is measured under impact loading using the instrumented impact test. The change in T0dy is determined in dependence on the thickness position of a steel plate and compared with the quasi-static reference temperature, T0st, and the Charpy-V transition temperature (TT). All three parameters increase from the surface to the middle of the steel plate in the same course. However, in the middle section of the plate T0dy is in average approximately 38 K higher than TT and 88 K higher than T0st. The results show that the MC concept is applicable for the fracture mechanical characterisation of material with different microstructure using Charpy size specimens.

Cylindrical steel plates used for the thermochemical polishing of CVD diamond films at elevated temperatures are investigated regarding their carbon content using X-ray and ion beam analysis. The surface distribution of carbon is investigated at randomly selected areas on two plates - one virgin and another on which a CVD diamond film is polished for one hour at 950°C. The investigation is carried out with a Scanning Electron Microscope (SEM) operated at an energy of 5 keV. Analysis of the SEM-EDX spectra manifest inhomogeneity in the surface distribution of carbon on both steel samples. Moreover, the absolute concentration of carbon on the steel plate on which diamond is polished for one hour almost triples that of the virgin sample. Elastic Recoil Detection Analysis (ERDA) depth profiling is performed on several steel plates used to polish as grown CVD diamond films for periods between 0.5-8 hours at 950°C. ERDA carbon profiles show inhomogeneity for three samples on which polishing is successively done for 8 hours. Raman spectra of post-polished steel plates reveal graphite bands and C-Hn complexes at exactly the wave numbers they appear on the diamond samples. This is a clear manifestation that the steel surfaces do not necessarily contain only atomic carbon after thermochemical polishing.

Aufgabe des Projektes war die Entwicklung einer neuen Technologie zur Probenpräparation für die Transmissions-Elektronenmikroskopie (TEM) auf der Basis der Ionenfeinstrahlbearbei-tung. Dazu wurden Prozesse der ionenstrahlgestützten Abtragung (Sputtern), der Abschei-dung, des Probenhandling sowie systemeigener Komponenten untersucht. Als Alternative zur Ga- Quelle wurde eine Flüssigmetall-Ionenquelle auf der Basis einer AuGeSi Legierung entwi-ckelt, charakterisiert und in der FIB 4400 eingesetzt.
Um eine automatische Bearbeitung bei der Herstellung von TEM-Lamellen zu ermöglichen, erfolgte eine Modifikation der FIB-4400 Software. Das LabView Programm wurde entsprechend modifi-ziert und zusätzlich um nützliche Komponenten ergänzt.
Abtragsraten auf der Basis der Volumenverlustmethode wurden experimentell bestimmt. Diese Werte dienen als Ausgangspunkt für eine weiter ausbaubare Datensammlung, die die entwi-ckelte Prozessautomatisierung verfeinert.
Für den Tranfer von TEM -Lamellen, die aus dem Volumen präpariert werden, wurde ein spe-zieller lift-off Manipulator entwickelt, gebaut und getestet.
Es wurde ein Angebotskatalog erarbeitet, der anhand von Applikationsbeispielen mit verschie-denen Anforderungen (raue Oberflächen, Hochauflösung, poröse Materialien, Materialien mit verminderter Leitfähigkeit) die Kooperationsmöglichkeiten im Dresdener Raum im Rahmen des Materialforschungsverbundes aufzeigt.

In früheren Kolloquien des Schwerpunktprogramms berichteten wir über den Einfluß von Kolloidpartikeln auf das Spurenmetallverhalten in Acid Rock Drainage (vgl. auch Zänker et al., 2001) sowie in "Bulk-Wasser" (Stollenwasser) aus einem Bergwerk (vgl. Zänker et al., 2000). Flutungswässer sind, chemisch gesehen, zwischen die Zustände "Acid Rock Drainage" und "Bulk-Wasser" einzuordnen. Die Flutung eines Bergwerks stellt eine Verdünnung von Acid-Rock-Drainage-Lösungen dar. Sie ist mit wichtigen kolloidchemischen Vorgängen verbunden.

Wir untersuchten Flutungswasser aus der Urangrube Königstein (Sachsen), wobei in der Hauptsache die Streulichtmessung, die Zentrifugation, die Filtration, die Ultrafiltration, die Rasterelektronenmikroskopie, die Laser-Doppler-Elektrophorese, die ICP-MS, die AAS, die Ionenchromatographie sowie diverse radiometrische Meßmethoden zum Einsatz kamen. Das Wasser besaß einen pH-Wert von 5,6 und einen Eh-Wert von 450 mV; die Konzentrationen wichtiger Wasserinhaltstoffe waren CCa 0,9 mM, CFe 0,3 mM, CU 0,05 mM, CSulfat 1,2 mM, CCarbonat 1,0 mM und CO2 0,11 mM. Nahezu 90% des Eisens waren zweiwertig. Die Kolloidkonzentration lag im Bereich von 2 bis 3 mg/l, die Partikelgröße war ca. 100 nm. Eisen(III)verbindungen stellten den Hauptbestandteil der Kolloidmatrix dar. Mit einem Zetapotential von -7,5 mV wiesen die Partikel eine nur schwache elektrische Ladung auf; sie neigten stark zur Flockulation und Sedimentation. Neben stark adsorbierenden Radionukliden wie 210Po und 210Pb waren auch erhebliche Anteile des Urans kolloidgetragen (auf Grund des Eh-Wertes gehen wir davon aus, daß das Uran sechswertig vorlag).

Der Zutritt von Luftsauerstoff beeinflußte die Proben erheblich. Durch die Oxidation des Fe2+ stieg der Gehalt an Fe(III)-Partikeln (ca. Faktor 10). Trotz der höheren Trägerkolloidkonzentration sank der filtrierbare (kolloidgetragene) Uranylanteil zunächst. Grund war der pH-Abfall (bis auf etwa 4,5), den die Fe-Oxidation verursacht; durch die Fe(III)-Hydrolyse werden Protonen freigesetzt. Mit einiger Verzögerung stieg der pH-Wert wieder, weil die Carbonatkonzentration durch CO2-Entgasung sinkt; der Gehalt an Carbonat/Hydrogencarbonat fiel bis auf <0,05 mM. Dies bewirkte einen Anstieg des filtrierbaren Urananteils auf fast 100%. Das Uran und alle anderen analysierten radiotoxischen Schwermetalle mit Ausnahme des Radiums folgten in dieser Situation der Neigung der Eisen(III)-Partikel zur Aggregation/Sedimentation. Alle hier im Labor beobachteten Vorgänge (O2-Zutritt, pH-Variationen, CO2-Entgasung, Eisen(III)-Sedimentation) spielen auch im Bergwerk eine Rolle.

Die oft getroffene Annahme einer ungehinderten Migration von Uranyl in gelöster Form ist für pH-Werte von 4 bis 6 "überkonservativ". Scavening durch Fe(III)-Partikel und Kolloidkoagulation plus Sedimentation kann in diesem pH-Bereich das U(VI) in erheblichem Maße immobilisieren (Natural Attenuation).

ZÄNKER, H.; MOLL, H.; RICHTER, W.; BRENDLER, V.; REICH, T.; KLUGE, A.; HÜTTIG, G. (2001):

The colloid chemistry of acid rock drainage solution from an abondaned Zn-Pb-Ag mine. Appl. Geochem. (accepted).

ZÄNKER, H.; RICHTER, W.; BRENDLER, V.; NITSCHE, H. (2000): Colloid-borne uranium and other heavy metals in the water of a mine drainage gallery. Radiochim. Acta 88 (2000) 619-624.

The Budker Institute of Nuclear Physics Novosibirsk develops a project of an intense 14 MeV neutron source (NS) based on a gas dynamic trap (GDT) which is mainly intended for fusion material irradiation. Its actual disadvantage is the lack of data for the parameter range of the projected GDT-NS which does not yet allow a reliable interpolation from the parameters of the existing GDT experimental facility to the neutron source. At present, experimental and computational researches are carried out to complete the required data base.
So far, rather promising results have been achieved concerning the main plasma-physical issues like MHD stability, longitudinal confinement, cross-field transport and the fast ion behaviour [1,2]. For the investigations in the latter field the Integrated Transport Code System (ITCS) has been used [3,4]. These investigations must be extended to a higher level of plasma parameters. To this end a substantial upgrade of the GDT facility is planned. The main subsystems which are to be upgraded are the neutral beam injection (NBI) system and the magnetic field power supply. The higher power and the longer duration of the injection will provide a substantially higher energy content of the fast ions and, consequently, will increase the electron temperature.
During the last years several transport codes have been developed and applied for computational studies in parallel to the experimental research. They have been coupled by appropriate data file transfers to the ITCS. The report is focused on the application of the code system to study possible operation regimes of the upgraded GDT. The results of numerical simulations enable us to conclude that an electron temperature of 250-300 eV can be achieved in the GDT-Upgrade with a NBI of 10 MW and a duration of 3-6 ms. The maximum fast ion density in the region of their turning points is estimated at ~5x1013 cm-3.

Low energy ion implantation into SiO2 causes a damaged layer near the surface. The high amount of broken bonds due to displaced Si and O atoms forms a more or less "open glassy network" in which moisture from the ambient can be absorbed. Therefore chemical reactions of the implanted impurities with hydrogen and oxygen must be expected during subsequent annealing. Water absorption in heavy ion damaged SiO2 layers has been studied by hydrogen depth profiling using the Nuclear Reaction Analysis (NRA). SiO2 was implanted with ions of different mass (Si, Ge, Sn) and doses in the range 1013...1016 cm-2. H depth profiles were measured after a certain storage under clean room conditions (40 % rel.hum.) and after additional wet cleaning as well as after certain annealing. At the surface and in the region of the implanted profile the H concentration reaches (5...10) at% after storage and increases during wet chemical cleaning up to 12 at% for implantation doses > 1*1014 cm-2.

16alpha-Fluoroestradiol-3,17beta-disulfamate (FESDS) strongly inhibits estrone sulfatase (ES), an enzyme which is also present in the brain. The enzyme is probably involved in important regulatory functions of neurosteroids which may be disturbed in certain brain diseases. In the present study [¹⁸F]FESDS was used to measure the amount of ES in various rat brain regions using quantitative in vitro autoradiography. The obtained values vary between 0.29 pmol (mg protein)^-1 (pons) and 11.5 pmol (mg protein)^-1 (striatum). They are positively correlated with the enzyme activity measured in homogenates of the corresponding regions. Because this radiotracer binds also to carbonic anhydrase in the brain it is only limited use for in vivo imaging studies.

Azacage compounds have been investigated in order to find typical structure extractability relationships towards selected metal ions [Ag(I), Hg(II), Ni(II), Zn(II), Co(II), Cu(I) and Cu(II)] and anions [I, Cl, SO₄ ^2-, TcO₄ ^-]. The influence of different parameters [concentration, pH, diluent, time, temperature] on the extraction equilibrium will be discussed. The complexation and extraction behaviour observed will be interpreted using ESI mass spectroscopic studies, cyclovoltammetric measurements and molecular modeling calculations.

The precise knowledge of the solar thermonuclear fusion reaction of ⁷Be(p, γ)⁸B is crucial for estimating the ⁸B solar neutrino flux and the predicted neutrino rates in terrestrial neutrino detectors. The flux of ⁸B solar neutrinos is particularly important for the results of the Homestake, Super-Kamiokande, and SNO experiments, because they measure high-energy solar neutrinos mainly or solely from the ⁸B decay.

We have measured the Coulomb dissociation of ⁸B into ⁷Be and proton on a ²⁰⁸Pb target at 254 MeV/nucleon using the large acceptance focusing spectrometer KaoS at GSI. Since the dissociation process can be regarded as absorption of a virtual photon, the Coulomb dissociation cross section is converted to the photo-absorption ⁸B( γ,p)⁷Be cross section which is directly related to the ⁷Be(p, γ)⁸B cross section.

In a first experiment the astrophysical S factor for the ⁷Be(p,γ)⁸B reaction is extracted to be S17(0)=20.6 ±1.2(exp) ±1.0(theo) eV-b for 0.25-2.78 MeV (1). This result agrees with the presently adopted zero-energy S17 factor obtained in direct-reaction measurements and with the results of other Coulomb dissociation studies performed at 46.5 and 51.2 A MeV. A second run allowed to also obtain information on the E1/E2 ratio by analysing the angular correlation of ⁷Be and the proton.

A modified method for the synthesis of the intermediate product N-Boc-3,4-di(Boc-O)-6-iodo-L-phenylalanine ethyl ester of the [¹⁸F]FDOPA precursor preparation was developed. With the application of bis-(trifluoroacetoxy)-iodobenzene for the iodination step with elemental iodine the yield of the intermediate can be increased from 12% to 50-60%. By replacing silica-gel-based RP HPLC column by a polymer-based column for semi-preparative purification of [¹⁸F]FDOPA from the reaction mixture the radiochemical purity of the final product can be increased up to > 99 %. For the determination of the radiochemical impurity [¹⁸F]fluoride a HPLC method using a column with polymer-based RP material was introduced.

Scaled coupled melt pool convection and vessel creep failure experiments are being performed in the FOREVER program at the Royal Institute of Technology, Stockholm. These experiments are simulating the lower head of a pressurized reactor vessel under the thermal load of a melt pool with internal heat sources. Due to the multi axial creep deformation of the three-dimensional vessel with a highly non-uniform temperature field these experiments offer an excellent opportunity to validate numerical creep models. A Finite Element model is developed and using the Computational Fluid Dynamic module, the melt pool convection is simulated and the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a new creep modelling procedure. Additionally, the material damage is evaluated considering the creep deformation as well as the prompt plasticity.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios.

The FOREVER (Failure Of REactor VEssel Retention) program is concerned with the phenomena of melt-vessel interactions during a postulated severe accident in a light water reactor. The objectives of the FOREVER program are to obtain data and develop validated models on (i) the melt coolability process inside the vessel, in the presence of water (in particular on the efficacy of the postulated gap cooling to preclude vessel failure) and (ii) the lower head failure due to the creep process in the absence of water inside or outside of the lower head.
Integral experiments were performed in a 1/10 scaled carbon steel vessels of 0.4 m diameter, 15 mm thickness and 60 mm height. Up to 20 litres of binary oxide melt (30wt% CaO -70wt% B2O3 ) was poured into the vessel and maintained at about 1300 °C by a specially designed electrical heater operating at about 40 kW. The melt pool undergoes natural con-vection as it would in the prototypic scenario and the vessel wall temperatures vary from ~ 600 to 1000 °C azimuthally. The pressure inside the vessel was maintained at about 2.6 MPa. The main diagnostics were several types of thermocouples and linear position transducers (LPT) which measure the displacement of the vessel due to its creep deformation.
The first three experiments, described here, are focussed on vessel creep and failure.The FOREVER/CI test was performed with the German steel (15Mo3) lower head, at about 25 bars of internal pressure and at the input power level of 22 kW. The maximum essel wall temperature was about 800 °C. A sizable database was obtained for the creep deformation rates over a period of 24 hours and the maximum creep strain obtained was about 5 %. The second test FOREVER/C2 employed a French reactor vessel steel (16MND5) lower head, and a power level of 40 kW. The maximum vessel wall temperature was measured to be about 1000 °C and the maximum creep strain obtained was about 10 %. The test ended without the failure of the lower head as the heater failed due to its unconvering from the melt as the melt level receded due to vessel expansion.
The third test, the EC-FOREVER-I, incorporated higher initial melt level to avoid heater failure. Although, the heater power level was maintained same, at about 40 kW, the internal pressure was increased to 28 bars in order to obtain the lower head failure. The lower head failure was achieved, albeit, at a lower than expected creep strain of only 6%. The failure site was located just above the welding joint between the hemispherical part and the cylindrical part. The cause for this mode of failure is being investigated.
A coupled thermal-structural analysis of these FOREVER tests was performed with the ANSYS Multiphysics code. An improvised creep model was incorporated into this code which avoids the use of a single creep law for the entire lower head. Instead, a three dimensional array was developed where the creep strain is evaluated according to the actual total strain, temperature and equivalent stress for each element. The material damage is evaluated considering the creep and the prompt plastic deformations. The calculated results for the creep strain and vessel failure time are in good agreement with those from the experiments.

Scaled coupled melt pool convection and vessel creep failure experiments are being performed in the FOREVER program at the Royal Institute of Technology, Stockholm. These experiments are simulating the lower head of a pressurized reactor vessel under the thermal load of a melt pool with internal heat sources. Due to the multi axial creep deformation of the three-dimensional vessel with a highly non-uniform temperature field these experiments offer an excellent opportunity to validate numerical creep models. A Finite Element model is developed and using the Computational Fluid Dynamic module, the melt pool convection is simulated and the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a new creep modelling procedure. Additionally, the material damage is evaluated considering the creep deformation as well as the prompt plasticity.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the forthcoming experiments are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios. After analysing the calculations, it seems to be advantageous to introduce a vessel support which can unburden the vessel from a part of the mechanical load and, therefore, avoid the vessel failure or at least prolong the time to failure. This can be a possible accident mitigation strategy. Additionally, it is possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in the event of a core melt down.

Im Beitrag wird die Nutzung erneuerbarer Energiequellen zur Stromerzeugung bis Ende 2000 im Einzelnen dargestellt sowie auf die möglichen Perspektiven eingegangen. Die Entwicklung in Ostdeutschland war einerseits durch einige - historisch bedingte - Besonderheiten geprägt, spiegelt aber andererseits auch generelle Tendenzen bei der Nutzung von erneuerbaren Energien zur Stromerzeugung in Deutschland wider.
Im Jahr 2000 wurde aus erneuerbaren Energien in Ostdeutschland eine Strommenge von 3,5 TWh erzeugt, was einem Anteil von 4,8 % am Nettostromverbrauch (abzüglich Netzverluste) entsprach. Mit Abstand dominierende erneuerbare Energie ist mit 70 % die Windenergie, gefolgt von Biomasse und Wasserkraft mit je 15 %. Die Photovoltaik spielt nur eine marginale Rolle. Der Anteil erneuerbarer Energien kann sich in diesem Jahrzehnt verdoppeln.

The code DYN3D coupled with the thermal-hydraulic plant model ATHLET was used for the analysis of the OECD Main Steam Line Break (MSLB) Benchmark which is based on real plant design and operational data of the TMI-1 PWR. DYN3D is a three-dimensional core model for steady-state and transient analyses of thermal reactors with quadratic or hexagonal fuel as-semblies. The neutron kinetic model is based on the solution of the three-dimensional two-group neutron diffusion equation by nodal expansion. Models for the thermal hydraulics of the reactor core and the fuel pins are implemented in the DYN3D. The reactor core is modeled by parallel cooling channels which can describe one or more fuel elements. DYN3D can be used as a stand alone code with given thermal-hydraulic boundary conditions of the core. Besides the standard simulation given by the specification, modifications are introduced for sen-sitivity studies. The results presented here show the influence of a reduced number of thermal-hydraulic channels for the core for the exercise 2 and the influence of coolant mixing inside the reactor pressure vessel exercise 3. Based on the presented investigations, it can be concluded that the maximum values of local parameters as fuel temperatures are not conservative, if a few number of coolant channels is used for the simulation of the reactor core. If coolant mixing in the reactor vessel is modeled, the accident consequences are mitigated.

The high intrinsic stresses in as-deposited cBN films are relaxed employing thermal treatment and ion implantation. In-situ stress measurement and ex-situ polarized infrared reflection spectroscopy are utilized to study correlations between stress and cBN TO phonon energy. The in plane TO phonon energy of cBN films is found to be not unambiguously dependent upon the film stress in contrast to the dependence of the phonon energy of cBN crystallites upon hydrostatic pressure. Factors affecting the relation between stress and phonon position are discussed.

The sorption of uranyl(VI) on muscovite was studied with the diffuse double layer model (DDLM). The required values for the surface site density, the surface acidity constants, the specific surface area, and the experimental sorption data were determined in [1].
The modeling favored the formation of two uranyl surface complexes. Both surfave complexes were simultaneously calculated with FITEQL [2]. The first one is a monodentate mononuclear surface complex:

XOH + UO22+ = (XO-UO22+)+ + H+

The second surface complex is a bidentate mononuclear surface complex:

X(OH)2 + UO22+ = (XO22-UO22+)+ + 2 H+

The results of the SCM (surface complexation model) modeling were compared with results obtained from extended x-ray absorption fine structure spectroscopy (EXAFS), high-resolution transmission electron microscopy (HRTEM), and time resolved laser induced fluorescence spectroscopy (TRLFS).
An EXAFS sample representing the sorption of U(VI) on muscovite at pH 5.8 with an initial U concentration of 1H10-4 M indicated that U(VI) is bound to the muscovite surface as an outer-sphere complex, as indicated by the missing Si/Al to U distance.
HRTEM investigations, representing the sorption of uranium on muscovite at pH 6.5 using an initial U concentration of 5H10-4 M, showed sorbed uranium particles on the muscovite surface. The particles were 5 to 10 nm in diameter. Diffraction patterns of these nano-sized particles gave indication for schoepite and metallic uranium.
TRLFS studies conducted with a muscovite suspension at pH 6.5 using an initial uranium concentration of 1×10-5 M revealed the presence of an uranium-muscovite surface species with a fluorescence lifetime of 120 ns ± 10 ns.

References

[1] Arnold, T. et al. (2001) Sorption Behavior of U(VI) on Phyllite: Experiment and Modeling. Journal of Contaminant Hydrology 47, 219-231.

[2] Herbelin, A. and Westall, J. (1996) FITEQL A Computer Program for Determination of Chemical Equilibrium Constants from Exp. Data, Version 3.2. Rep. 96-01, Dep. of Chem., Oregon St. Uni., Corvallis, Oregon.

Nuclear temperatures were determined from yields of isotopes with 1<Z<14 accompanying the spontaneous and neutron-induced fission of heavy elements. The mean temperature derived from the corresponding temperature distributions amounts to 1.10 +- 0.15 MeV.

The Forschungszentrum Rossendorf (FZR) e.V. is building the large-scale test facility TOPFLOW for thermal hydraulic single effect tests. The acronym TOPFLOW stands for Transient Two Phase Flow Test Facility. It will mainly be used for the investigation of generic and applied steady state and transient two phase flow phenomena in power- and process industries. Main research activities are the investigation of:

• transient flow regimes in horizontal, vertical and inclined tubes,
• the dynamic behaviour of interphase areas in gas-liquid flows,
• critical mass flows and oscillations during depressurization of chemical reactors,
• natural convection in large pools with local heating,
• natural convection in parallel channels and feed pipes and
• condensation phenomena.

CAE tools were consequently established for planning and construction of the facility. This includes e.g. in the basic/detail engineering phase pipe and process flow diagrams, three dimensional plot plans and isometric projections for construction. The 3D model of the facility was used for generation of cutaway sectional drawings, determination of connecting points of components, collision checking and generation of reports such as data sheets and part lists. At last the plant model will be used for the documentation of the built isometric projection. From this version a VRML-model will be created. It will be used for presentation in an immersive virtual-reality environment which was developed at FZR. Alternatively the model can be inspected by any web browser with a standard VRML viewer like CosmoPlayer.

In diesem Artikel werden die erforderliche Technik, die Strahlenschutz- und Genehmigungsbedingungen und die methodische Ausrichtung der Labors in diesem radiochemischen Laborgebäude für den Umgang mit Radionukliden, insbesondere Actiniden vor dem Hintergrund aktueller Forschungen beschrieben. Sowohl für Forschungen auf dem Gebiet der Radiopharmazie wie auch auf dem Gebiet der Grundlagen der Radiochemie und Radioökologie (z. B. für die Erforschung der Speziation und Migration von Radionukliden/Actiniden in Gebieten des ehemaligen Uranerzbergbaues, in radioaktiv kontaminierten Umgebungen resultierend aus Nuklearunfällen, im Nah- und Fernfeld potentieller nuklearer Endlager) sind radiochemische Laboratorien unabdingbar.
Im Forschungszentrum Rossendorf wurde ein radiochemisches Laborgebäude errichtet, in dem nach Paragr. 3 der Strahlenschutzverordnung mit einer Vielzahl radioaktiver Nuklide (170 Nuklide) in einer maximalen Aktivität für jedes Nuklid von 10E11Bq umgegangen werden kann. Das Laborgebäude hat 24 radiochemische Labors und 10 Service Raume. Die Labors sind mit einer Vielzahl von Abzügen, Laminarboxen und mit 22 Glove Boxen für den Umgang mit Gramm-Mengen von Actiniden ausgerüstet. Das gesamte Gebäude bildet einen Kontrollbereich und bietet Arbeitsplätze für 50 Mitarbeiter/innen. Moderne Analytische und spektroskopische Verfahren sind installiert, z. B. verschiedene Laserspektroskopische Verfahren, ICP-MS, FTIR, NMR, UV/Vis, chromatographische und elektrochemische Verfahren und a,ß,y - Spektrometrie.

Silicon-based light emission is a key feature to make a real step into the world of integrated optical systems, laboratory-on-chip applications and high performance optical communication. One of the most promising approaches is ion implantation into thin SiO2 films. In this paper the electroluminescence (EL) properties of Sn-implanted SiO2 layers are investigated and compared with those of Ge-implanted SiO2 layers. Strong EL in the blue-violet spectral region with a power efficiency of 0.025 % is extracted from Sn-implanted oxide layers. Similar to the case of Ge, the main emission at 3.2 eV is attributed to a radiative T1®S0 transition of a Sn-related oxygen deficiency center, the EL intensity increases linearly over several orders of magnitude and the stability reaches comparable values. In contrast to the case of Ge, a low energy shoulder appears in the EL spectrum of Sn-implanted oxides. Finally, the suitability of Sn-implanted oxides for optoelectronic applications is discussed.

Strukturbestimmende Bestandteile biologisch aktiver Verbindungen sind häufig meta-bolisch stabile aromatische Fragmente, die für die Positronen-Emissions-Tomographie (PET) von Interesse sein können. Dementsprechend wurden Markierungstechniken zur Einführung des kurzlebigen Radionuklids ¹¹C (T_1/2 = 20 min) in aromatische und hetero-aromatische Grundverbindungen entwickelt.

¹¹C-kernmarkierte Benzolderivate

* Das Syntheseprinzip der synchronen Sechs-Elektronen-Cyclisierung von Hexatrien-Systemen ^[1] wird zur Darstellung von [¹¹C]-Aromaten genutzt. In Anwesenheit einer Base lassen sich durch Umsetzung von Nitro-[¹¹C]-methan mit Pentamethiniumsalzen ¹¹C-kernmarkierte Nitrobenzole herstellen ^[2-4]. Diese Nitro-[1-¹¹C]ben-zole können mit Na₂S zu den entsprechenden [1-¹¹C]Anilinen reduziert werden. Aus [1-¹¹C]Anilin ist durch Diazotierung und Verkochen des gebildeten Diazoniumsalzes [1-¹¹C]Phenol zu-gänglich ^[5]. Analoge Umsetzungen mit ¹³C wurden demonstriert.

* In Übertragung der bekannten Kondensation von Nitro-methan mit Pyryliumsalzen ^[6] konnten 4-Nitro-[4-¹¹C]anisol sowie zwei 2,4,6-trisubstituierte Nitro-[1-¹¹C]ben-zole syn-thetisiert werden^[7]. Das Verfahren wurde methodisch auf Arbeiten mit ¹³C ausgeweitet.

¹¹C-kernmarkierte N-Heteroaromaten

* Die Synthese von [¹¹C]Pyridin und Cyano-[¹¹C]pyridinen gelang durch Pyrolyse von N-[¹¹C]Methylpyrrolen ^[8].
Das Indolgerüst wurde durch zwei verschiedene Synthesewege mit ¹¹C markiert:

* [2^-11C]Indol ist durch Kondensation von Nitro-[¹¹C]-methan mit o-Nitrobenzaldehyd und nachfolgender Reduktion des gebildeten ß,2-Dinitro-[ß-¹¹C]styrols zugänglich ^[9].

* Ein neuer¹¹C-Baustein, das Triphenylarsonium-[¹¹C]methylid, das in situ aus [¹¹C]-Methyltriphenylarsoniumiodid unter Baseneinwirkung gebildet wird, lässt sich durch Reaktion mit o-Aminobenzoyl-Verbindungen direkt zu [2-¹¹C]Indolen ^[10] kondensieren. Diese Umsetzung unterscheidet sich vom normalen Verlauf der Wittig-Reaktion ^[11].

[1] Ch. Jutz, Angew. Chem. 1972, 84, 299.
[2] J. Steinbach, J. Label. Compds. Radiopharm. 1995, 36, 33.
[3] P. Mäding, J. Label. Compds. Radiopharm. 1997, 39, 585.
[4] P. Mäding, J. Label. Compds. Radiopharm.1998, 41, 647.
[5] P. Mäding, J. Label. Compds. Radiopharm., 2000, 43, 557.
[6] K. Dimroth, Angew. Chem. 1960, 72, 331.
[7] P. Mäding, J. Label. Compds. Radiopharm., 2000, 43, 565.
[8] J. Steinbach, J. Label. Compds. Radiopharm. 1995, 37, 613.
[9] J. Zessin, J. Label. Compds. Radiopharm., 1998, 41, 669.
[10] J. Zessin, J. Label. Compds. Radiopharm., 1999, 42, 725.
[11] P. Bravo, Tetrahedron Lett. 1970, 52, 4535.

Based on a high affinity to the enzyme estrone sulfatase (ES) 16alpha-[¹⁸F]fluoroestradiol-3,17beta-disulfamate ([¹⁸F]FESDS) has been suggested as a potential PET tracer for imaging steroid-dependent breast tumours. The distribution of [¹⁸F]FESDS was studied in rats, tumour-bearing nude mice and piglets. In all species evidence for tracer binding to a second target, the enzyme carbonic anhydrase (CA), was obtained. ES and CA inhibitors significantly reduced the radiotracer uptake in various organs but not in tumours. It is concluded that [¹⁸F]FESDS binds to ES and CA in vivo but this binding is not strong enough to allow tumour imaging with positron emission tomography (PET)..

The thickness dependencies and depth distributions of hydrogen and intrinsic mechanical stress are studied for a-Si:H films prepared with 10% silane in hydrogen. Nuclear reaction analysis has been used to establish the total concentration of the incorporated hydrogen. It has been shown that the hydrogen distribution in the films is uniform and does not depend on the film thickness. On contrary, the intrinsic stress depends on the film thickness and has a nonuniform depth distribution, as the stress increase linearly in the direction from the substrate/film interface to the film surface. The obtained results are discussed in view of the hydrogen-related processes and structural improvement of the silicon network during the film growth.

We present the first all-silicon integrated optocoupler, whose fabrication, using ion implantation into SiO2, is completely compatible with standard Si technology. It is based on Ge-implanted SiO2 layers as light emitter exhibiting bright blue-violet electroluminescence light with a record wall-plug efficiency of 0.5%. The electroluminescence is explained with a model in which electrons enter the SiO2 layer via tunnel injection and excite the luminescence centers by impact excitation or field ionization. A radiative T1-S0 transition of these luminescence centers is then causing the observed electroluminescence. Finally we show, that these optocoupling devices hold great promise for integrated optoelectronic applications, especially in the field of sensor and biotechnology.

For the realization of good quality 3C-SiC films epitaxially grown on Si the perfection of the film during the early stage of growth is substantial. In this paper the beneficial role of Flash Lamp Annealing (FLA) for the elimination of the defects in the SiC film and the strain reduction at the SiC/Si interface is discussed. FLA is a highly transient process, having a flash duration of a few milliseconds. When the energy density is sufficient high, it melts the silicon at the SiC/Si interface increasing the temperature there well above the melting point of the silicon. The melted Si dissolves the 3C-SiC near the interface. Additionally, the uppermost part of the 3C-SiC film is annealed due to the heat dissipation during the flash duration and the solidification of the molten region. During the solidification of the C-rich Si melt SiC grows by liquid phase epitaxy at the annealed uppermost 3C-SiC film which act as a seed. This process results in a substantial improvement of the SiC film, eliminating also the cavities and the stress at the interface.

The charge-state distributions of Li, C, and F ions after a single collision with Au atoms deposited at a sub-monolayer coverage on Si were measured at energies below 500 keV/amu and compared to the equilibrium charge-state distributions. The influence of the surface on the charge state of the outgoing ions is demonstrated for Li ions at 3 MeV. It is found that the charge state distribution does not generally reach equilibrium after a single collision.

In dem Vortrag wird der Stand der Arbeiten zur Errichtung der Versuchsanlage TOPFLOW (Transient Two Phase Flow Test Facility) präsentiert. Hierbei werden u. a. das Design der Anlage, die geplanten Experimente, die Dokumentation, das Internetprotal sowie der Zeitplan im Detail vorgestellt.

Im Rahmen des Seminars des Lehrstuhls Nukleare und Neue Energiesysteme der Ruhr-Universität Bochum wurden ausgewählte experimentelle Untersuchungen von aufwaertsgerichteten Luft-Wasser Strömungen in vertikalen Rohren vorgestellt. Ein besonderes Kennzeichen dieser Untersuchungen ist der Einsatz von fortschrittlicher Zweiphasenmesstechnik, die am Institut für Sicherheitsforschung entwicklet wird.

The need of the experimental support for validation of the computational tools to be applied to analyze the mixing of diluted slugs has been recognized in various countries. The test series for the International Standard Problem ISP-43 provides a platform for experiences to be applied to the simulation of a well-defined test series. Test A and B of the UM2x4 loop test facility were calculated with the CFD Code CFX-4.3. Sensitivity studies were made to analyze the used turbulence model and numerical errors. The results show good agreement with the experimental data for both tests.

The paper comprises a short overview about the work in the Institute of Safety Research on CFD-modelling of natural convection and on subcooled boiling

Industrial applications of magnetic field systems require tailored solutions
for the specific requirements of each technological process in order to keep
the effort, i.e. the magnetic field strength or the power consumption of the
control unit, as low as possible. In case of magnetic field control of
liquid metal processes this results often in combined systems of AC and DC
magnetic fields. The lecture presents examples for this approach.

Die verschiedenen heutzutage gebräuchlichen tomographischen Verfahren (CT, MRT, PET, SPECT) ergänzen sich vorzüglich in ihren Anwendungsmöglichkeiten. Informationen über die Struktur der Gewebe und Organe werden komplettiert durch Informationen zu deren Funktion und Biochemie. Letzteres ist die Domäne der Nuklearmedizin, die auf der Anwendung radioaktiver Substanzen beruht. Derartige radioaktive Substanzen fungieren in der Diagnostik als "molekulare Sonden" (Radiotracer), die in den Körper gebracht werden und in Form der nach außen dringenden Strahlung über ihre Verteilung, Reaktion mit Körperbestandteilen und Ausscheidung informieren. Radiotracermethoden machen so den Körper biochemisch transparent. Im Vortrag werden anhand von Beispielen radiopharmazeutische Arbeitsrichtungen vorgestellt. Kurzlebige Positronenstrahler, wie Kohlenstoff-11 und Fluor-18, ermöglichen die Entwicklung von molekularen Sonden für zahlreiche bio-chemische Prozesse. Neurologisch/psychiatrische und onkologische Fragestellungen sind derzeit dominierend in der klinischen Forschung mit Hilfe der Positronen-Emissions-Tomographie (PET). Der eine kostenintensive Infrastruktur erfordernden PET steht die Tomographie mit gammastrahlenden Isotopen (SPECT) gegenüber, insbesondere, wenn ein einfaches Generatorsystem die Erzeugung der kurzlebigen Radionuklide vor Ort in der Klinik ermöglicht und die anschließende Radiopharmakaherstellung problemlos erfolgen kann. Das Generatornuklid Technetium-99m ist das "Arbeitspferd" der nuklearmedizinischen Routinediagnostik. Als Übergangsmetall erfordert es eine koordinationschemische Arbeitsweise bei der Radiodiagnostikherstellung. Bei anspruchsvollen biochemischen Fragestellungen besteht die Herausforderung, den grundsätzlich unphysiologischen Verbindungen dieses Metalls eine solche Gestalt, Größe und Reaktivität zu verleihen, dass sie Biomoleküle ausreichend imitieren können.

We studied the coordination environment of neptunium(IV) in complexes with various natural and synthetic humic and fulvic acids at pH 1 by X-ray absorption fine structure (XAFS) spectroscopy. The results were compared to those obtained for the interaction of neptunium(IV) with Bio-Rex70, a cation exchange resin having solely carboxylic groups as metal binding functional groups. In both neptunium humate complexes and neptunium Bio-Rex70 sorbates, Np4+ is surrounded by about 10 oxygen atoms at an average distance of 2.36 ± 0.02 Å. This verifies that the carboxylic groups are the main complexing sites of the humic substances responsible for binding neptunium(IV) in the acidic pH range. The data suggest a predominant monodentate coordination of the carboxylate groups to neptunium(IV) ions.

Risswiderstandskurven haben sich zur zähbruchmechanischen Charakterisierung des duktilen Verformungsverhaltens metallischer Werkstoffe bewährt. Eine geeignete Methode zur Ermittlung von Risswiderstandskurven ist die Compliance-Methode, bei der Risswachstum aus der Veränderung der Probennachgiebigkeit bei Zwischenentlastungen ermittelt wird. Voraussetzung für die Methode ist eine hochgenaue Mes-sung der Rissöffnung. Üblicherweise werden dazu mechanische Wegaufnehmer (Clip-on-Gage) verwendet. Die Messung mit einem Laserextensometer eröffnet neue Anwendungsfelder.
Für eine erste Erprobung werden Risswiderstandskurven an Proben aus hochzähen ferritischen Stählen mit Charpy-Geometrie und unter 3-Punkt-Biegebelastung gleichzeitig mit einem Laserextensometer und einem mechanischen Wegaufnehmer er-mittelt. Die erreichte Endrisslänge am Ende des Versuches wird optisch ausgemessen und mit der aus der Probennachgiebigkeit ermittelten verglichen.
Es gelingt mit dem Laserextensometer die Rissöffnung so empfindlich auszumessen, dass Risswiderstandskurven ermittelt werden können. Die Streuungen zwischen den einzelnen Messschritten sind dabei leicht größer, aber vergleichbar mit den Streuungen gemäß dem Standardverfahren.
Für hochzähen Stahl unterscheiden sich jedoch die mit beiden Wegmessern ermittelten Risswiderstandskurven signifikant. Der Unterschied ist nicht im Wegaufnehmer, sondern versuchsmethodisch begründet.
Die mit dem Laserextensometer bestimmten Endrisslängen liegen innerhalb der vom Standard zugelassenen Abweichung und sind überwiegend besser als die mit dem mechanischen Wegaufnehmer ermittelten.
Messungen bei Prüftemperaturen unter- oder oberhalb Raumtemperatur unter Ver-wendung einer Temperierkammer stellen hohe Anforderungen an die Stabilität des optischen Übertragungsweges und führen zu stärkeren Streuungen der Messergebnisse. An der Lösung dieses Problems muss weiter gearbeitet werden.

The properties of advanced CMOS transistors are strongly influenced by the dopant distribution in the transition region between the source (drain) and the channel. The tailoring of this distribution is achieved by appropriate halo and extension implants and subsequent annealing. Process and device simulations are performed to investigate the influence of the corresponding process parameters. The boundary condition used throughout the simulations is to keep the threshold voltage VTsat for the nominal nMOS transistor (sub-70 nm gate length) at 0.2 V. The following process conditions are studied:

(i) B+ halo implant: energy below 10 keV, tilt 45 degree, rotation 4x90 degree, dose varied to achieve VTsat = 0.2 V
(ii) As+ extension implant: 0.5, 1.0, 2.0 keV, tilt 0 degree, 1015 cm-2, and 2 keV, 1015 cm-2, tilt 20 degree, rotation 4x90 degree
(iii)RTA after both implants with special emphasis on soak and spike anneals (950...1100 degree C)
The model parameters employed in the simulation of the formation of the ultra-shallow extension profiles are calibrated using SIMS profiles of as-implanted and annealed samples, and sheet resistance data. The VTsat vs. LGate curve of the nMOS transistor is calculated. The dependence of the roll-off and roll-on behaviour on the process conditions considered is discussed.

For advanced technologies there is a lack of experimental data and calibrated physical models which enable accurate simulation of CMOS technologies down to channel lengths of 100 nm and below. This work aims to develop predictive modeling of USJ profiles for state-of-the-art and next generation CMOS devices.
Profiles were created by As (0.2-10 keV), B (0.2-10 KeV) and BF2(1-25 keV) ion implantation and annealed at various times and temperatures including typical drain extension spike anneals. B and BF2 profiles are investigated with and without pre-amorphization by implantation of Si or Ge.
The calibration is based on SIMS and SRP profiles as well as XTEM pictures. The BC code Crystal-TRIM was calibrated for ultra-low energy implantation. Annealing is simulated within the pairdiffusion framework of the process simulator DIOS, including first order reaction equations for interstitials and dopant clustering and a new model for dose loss, where impurities are stored in a thin surface layer on top of the silicon.

Depth profiling measurements of tritium at carbon samples have been performed during the past seven years at the AMS facility installed at the Rossendorf 3 MV tandetron. The samples have been cut from the inner wall of the fusion experiments ASDEX-upgrade/Garching and JET/Culham. The increasing amounts of tritium inside the samples from JET have been required a dedicated AMS facility to prevent any contamination of the versatile 3 MV tandetron. On base of an air-insulated 100 kV tandem accelerator equipped with a gas stripper a small dedicated AMS facility for tritium depth profiling was installed, tested and used for routinely measurements. After successful tests of diamond-like carbon (DLC) stripper foils at this accelerator a small and compact SF6-insulated 100 kV tandem accelerator with a DLC-stripper has been installed at the AMS facility. Results measured with the different tandem accelerators are presented.

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.