Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Plasmagestütztes Randaufsticken ist eine erfolgversprechende Technologie zur Verbesserung der Verschleiß- und der Korrosionseigenschaften von Bauteilen aus nichtrostendem Stahl. Bei moderaten Temperaturen (ca. 400°C) kann eine Randschicht mit einem hohem Gehalt an gelöstem Stickstoff (ca. 20at.%) erzeugt werden. Diese Randschicht weist eine deutlich erhöhte Härte und Verschleißbeständigkeit und eine hervorragende Korrosionsbeständigkeit auf. Die Prozesse, die zur Bildung dieser Randschicht führen, sind weitgehend unverstanden. Um den Einfluß der passivierenden Oxidschicht auf die Bildung der stickstoffreichen Randschicht zu untersuchen, ist ein in-situ Experiment mit einer gekreuzten Strahlgeometrie aufgebaut worden. Bei kontrollierten Restgaszusammensetzungen wird während des plasmagestützten Randaufstickens zeit- und tiefenaufgelöste Elementanalyse betrieben. Dabei wird zum Randaufsticken eine Hochstrom-Ionenquelle und zur tiefenaufgelöste Elementanalyse „elastic recoil detection analysis“ (ERDA) verwendet. ERDA ist sensitiv auf die leichten Elemente und wurde hier hinsichtlich schneller Datenaufnahme optimiert. Quantitative zeitaufgelöste Messungen der Elementverteilungen werden für verschiedene Sauerstoffpartialdrücke vorgestellt. Die Bildung der stickstoffreichen Randschicht ist stark mit der Reduzierung der Oxidschicht korreliert. Hohe Sauerstoffpartialdrücke stabilisieren die Oxidschicht. Dieses Ergebnis stimmt gut überein mit einem einfachen Transportmodell, das die Sauerstoffadsorptionsrate und die Zerstäubungsrate berücksichtigt.

The moderator temperature coefficient (MTC) of a 1400 MW pressurized water reactor (PWR) has been measured from neutron and temperature fluctuations in different reactor positions. In order to explain the deviations observed between the estimations, numerical evaluations of the MTC were performed using the 3D two energy groups DYN3D code for a prototype PWR. The differences between the experimental MTC estimations can be partially explained considering that the numerical MTC evaluations show a definite devitation of the neutronics from point kinetics.

The effect of chromium implantation and subsequent annealing
on the hardness and wear behaviour of a silicon nitride-based ceramic is
investigated. Implantation energies were 200, 400, 1000 and 2000 keV, the
fluence was 1017 Cr+ ions cm-2 in all cases. The annealing temperatures
were 800 C, 1000 C and 1200 C. The phase composition was determined with
X-ray diffraction. Annealing at 800 C does not affect the crystal structure.
At 1000 C the -Si3N4-phase is formed for 1 and 2 MeV implantation energy.
At 1200 C, Cristobalite and Keiviite are formed at the lower implantation
energies; at higher energies -Si3N4 is formed. We discuss the phase formation
for the different implantation energies and annealing temperatures and
the relationship with the observed hardness and wear.

Surfaces of SiO2, Si3N4, Ta2O5 and glass were implanted
with Ag+ ions. Studies using X-ray diffraction (XRD) and atomic force microscopy
(AFM) show that the surface morphology is dominated by metallic silver
features consisting of regularly shaped, mostly spherical, Ag particles
spanning a size range from some nanometers to some 100 nm in diameter.
The particle size metrics, distribution, shape, and their density are shown
to be controlled by the process paramters ion dose, dose rate, and ion
energy. Adjusting the energy of the incident ions results in various degrees
of submerging into the substrate including exposed Ag features anchored
onto the surface or buried Ag particles overcoated by a thin layer of the
matrix material. The substrate material differs by its ability of stabilizing
the dispersion and blocking the Ag movement. Ta2O5 and glass substrates
provide more homogeneously dispersed Ag particles, much smaller in size
and regularly shaped compared to SiO2 and Si3N4 substrate systems. Potential
application refers to surface enhanced Raman scattering.

Plasma immersion ion implantation was used to implant
oxygen into silicon with nominal doses ranging from 2 x 1016 to 2 x 1017/cm2.
Positive Ions, O+2 and O+, with a continuous energy distribution between
0 and 40 keV were implanted. The plasma parameters and the geometrical
configuration of the implantation were chosen in order to follow closely
the assumptions of a theoretical model, which allowed to calculate the
energy distribution of the incident ions. Computer simulations were performed
to derive the resulting theoretical oxygen depth distribution. The agreement
found with the experimental depth profiles, measured by elastic recoil
detection analysis, is good. The small discrepancy observed is discussed
in terms of the shortcomings of the model used.

no abstract

U LIII Polarized XAFS studies on Ba[UO2PO4]2·8H2O
C. Hennig 1, M. A. Denecke 1, A. Roßberg 1, G. Zahn 2,
T. Reich 1, H. Nitsche1
1 Forschungszentrum Rossendorf, Institut für Radiochemie,
PF 510119, D-01314 Dresden
2 Technical University of Dresden, Institute of Crystallography
and Solid State Physics, Zellescher Weg 16,
D-01062 Dresden

An experimental and theoretical study of the U LIII -edge polarization dependent XANES and EXAFS is presented for a single crystal of barium uranyl phosphate hydrate. Ba[UO2PO4]2·8H2O is built up by layers of [UO2]2+ and equatorial coordinated [PO4]3- tetrahedra. Layers are bridged by Ba2+, H+ and H3O+ cations giving an overall tetragonal (or nearly tetragonal) symmetry. The orientation of a crystal obtained by cleaving a larger crystal and used for the XAFS measurements was determined by x-ray diffraction. The layered structure of Ba[UO2PO4]2·8H2O exhibits preferred cleavage along {001} and parallel to {100}. Linear uranyl units are aligned parallel to [001]. {100} represents the least squares plane for the equatorial oxygen atoms. XAFS measurements were performed with the polarization vector aligned in the equatorial plane (parallel to [100] and [110]), as well as with the polarization vector oriented perpendicular to [010], with 90°, 60°, 45°, and 30° angles to [001].
Two different explanations of the resonance » 15 eV above the LIII -edge white-line maximum have been discussed. One explanation, based on pressure dependent measurements of UO3, attributed this feature to shake-up processes [1]. The other interpretation stems from ab initio multiple-scattering calculations using the FEFF program package. These calculations identify this feature as a multiple-scattering resonance associated with the axial U-O bonds in various uranium compounds [2], [3]. Our experimental investigations show that the relative intensity of this resonance increases if the polarization vector is aligned along the axial U-O bonds. This observation confirms the multiple-scattering assignment of this feature and is supported by our own theoretical FEFF calculations.
The U LIII -edge EXAFS show a strong polarization dependence, especially evident in the Fourier transforms at distances corresponding to uranyl axial oxygen atoms and equatorial atoms. This dependence strongly influences the effective coordination numbers, Ni, obtained in the data analysis.
The marked characteristics of such polarization-dependent XAFS spectra renders them useful as a unique indicator of uranyl orientation. For example, the specific binding sites and orientation of sorbed uranyl (actinyl) ions onto mineral surfaces can be determined with this method.

[1] Bertram, S., Kaindl, G., Jové, J., Pagès, M., Gal, J.: Phys.
Rev. B 52 (1989) 2680
[2] Hudson, E.A., Rehr, J.J., Buchner, J.J.: Phys. Rev. B 52
(1995) 13815
[3] Hudson, E.A., Allen, P.G., Terminello, L.J., Denecke, M.A.,
Reich, T.: Phys. Rev. B 54 (1996) 156

The alteration of the shape of one-dimensional, two-dimensional (2D), and three-dimensional (3D) range distributions with growing dose as well as the extension of amorphous zones formed at high doses is studied for 15 keV BF₂ ⁺ and 30 keV P⁺ implantations into (100)Si using the dynamic binary collision code Crystal-TRIM. The range and damage profiles are calculated for the area 97.74 (parallel to [010]) × 97.74 (parallel to [001]) nm² at the target surface irradiated by the ion beam and surrounded by impenetrable masks. The change of the shape of the 2D and 3D distributions in the lateral direction is less pronounced than in the depth direction. At low doses the lateral profile branches are determined by rechanneled particles, at high doses the enhanced dechanneling is the reason for the increased lateral straggling. The latter effect is responsible for the relatively large lateral extension of the amorphous zone beneath the masks. The simulated depth profiles of boron and phosphorus and the predicted thickness of the amorphous layer are in good agreement with experimental data.

In früheren Untersuchungen haben wir nachgewiesen, dass Oxorhenium(V)-Komplexe mit Ketanserin-, Cisaprid- und MDL72832-ähnlicher Struktur hohe Affinität zu Serotoninrezeptoren des Gehirns aufweisen, womit die analogen ^99mTc-Verbindungen als potentielle Radiopharmaka von Interesse sind. Ihre Struktur ließ auch inhibitorische Wirkung auf die Serotonin abbauende Monoaminoxidase (MAO) vermuten. In Untersuchungen an Rattenhirnhomogenaten mit 1mM Tryptamin als Substrat beider Isoenzyme MAO A und MAO B, bzw. 1 mM Phenylethylamin als spezifisches Substrat für MAO B hemmt die Mehrheit der untersuchten Komplexe mit IC₅₀ Werten zwischen 10^-4 und 10^-6 M das Enzym. Die höchste Affinität besitzt der abgebildete Komplex mit IC₅₀=7*10^-7±2 M.
Die räumliche Anordnung des protonierbaren Stickstoffs im Molekül ist dabei kritisch. Die Ergebnisse zeigen, daß bei der Bewertung von Radiotracern für das serotonerge System potentielle Wechselwirkungen mit der MAO berücksichtigt werden müssen.

Das P-Glycoprotein (Pgp) ist ein energieabhängiges Efflux-Transportsystem für ein breites Pharmaka-Spektrum, welches in bestimmten Tumoren, aber auch in normalen Geweben, z. B. den Endothelzellen des Gehirns exprimiert wird. Die Pgp-Bewertung in Tumoren mit lipophilen Kationen (^99mTc-MIBI, ^99mTc-Tetrafosmin) wird durch verschiedene biochemische Veränderungen (z. B. des Energiestoffwechsels) erschwert. In Multitracerexperimenten an Hirnendothelzellen untersuchten wir die Veränderungen im Membranpotential (^99mTc-MIBI, ^99mTc-Tetrafosmin), des Glukoseumsatzes ([¹⁸F]FDG) und der Pgp-Aktivität ([³H]Vinblastin) unter dem Einfluß verschiedener Pgp-Inhibitoren (u. a. Verapamil, Vinblastin,Valinomycin). Die Zellaufnahme der Pgp-Substrate ([³H]Vinblastin, ^99mTc-MIBI, ^99mTc-Tetrafosmin) korrelliert unter Kontrollbedingungen mit dem Glucosemetabolismus ([¹⁸F]FDG). Bei Hemmung des Pgp zeigte sich allerdings in den meisten Fällen eine Verminderung der Akkumulation von FDG. Das Ionophor Valinonycin löst dagegen einen dramatischen Anstieg des Glucoseumsatzes aus, gleichzeitig ist die MIBI oder Tetrafosmin-Aufnahme verringert obwohl die [³H]Vinblasin-Akkumulation unverändert bleibt. Das zeigt, daß bei der Untersuchung von Pgp-Transportprozessen Sekundäreffekte auftreten können (hier Veränderungen des Energiestoffwechsels), die bei der Interpretation der Daten zu berücksichtigen sind.

Abstract
The first series of experiments at the FOBOS detector, using beams of the U-400M cyclotron of the Flerov Laboratory of Nuclear Reactions, was devoted to few-fragment decays of equilibrated systems. To exclude deep inelastic collisions or quasifission as sources of massive fragments, hot heavy nuclei were produced in the very asymmetric reactions ⁷Li (43 AMeV) + ²³²Th, ¹⁴N (34 AMeV) + ¹⁹⁷Au, and ¹⁴N (53 AMeV) + ¹⁹⁷Au, ²³²Th. Two- and three-fragment events were analysed on the base of masses and velocity vectors measured independently for each fragment. The events were sorted into excitation energy bins according to the linear momentum transfer following the massive transfer approach. Binary events were treated as fission. Fragment mass distributions as well as total kinetic energies were studied for an excitation energy range of 100 - 500 MeV. A new TKE parametrisation is proposed extending the Viola systematics to large mass asymmetries. With rising excitation energy the mass dispersion develops unexpectedly. Two new effects have been fourid and are discussed as consquences of the cooling down during the slow fission process at moderate E*, and of a strong decrease of the fission time at large E*. Ternary events were analysed by comparing measured velocity correlations with results of Coulomb trajectory simulations. If one fragment has intermediate mass (A = 10...30), two components in the relative velocities and the Z/A ratios confirm a sequential and a neck mechanism. For events with three fragments of comperable size neither the assumption of two sequential independent fission acts nor a nlultifragnlentaion-like scenario can reproduce the data. Agreement is achieved if these three-fragment decays are characterized by a collinear intermediate state followed by two scissions separated by no more than 280 fm/c, a very short time scale compared with usual saddle-to-scission intervals.

Abstract
A method for the intrinsic energy calibration of photomultiplier-coupled CsI(Tl) detectors is described. A simple empirical model of the scintillation light pulse-shape of CsI(Tl) crystals for light charged particles has been applied to simulate the particle identification matrix as it follows from the pulse-shape analysis method. The calibration procedure for the large-area CsI(Tl) detectors of the scintillator shell of the 4 π - array FOBOS for ions with Z < 4 at energies below 100 AMeV is based on the energies of the particle punch-through points.

Cobalt disilicide layers were formed by ion beam synthesis using 35 keV Co+ focused ion beam (FIB) implantation into silicon. A strong influence of the pixel dwell time on the layer formation was found. Only for short pixel dwell-times (about 1µs) closed layers with sufficient quality for device application could be formed. To understand the dwell-time effect the as-implanted samples were examined by Rutherford backscattering (RBS) and channeling analysis. A method is presented which allows quantitative measurements of samples where the implanted areas are smaller than the diameter of the RBS beam. Evidence has been obtained that the silicon crystal damage is less for short dwell-times.

Abstract
The elastic proton-deuteron backward reaction is analyzed within a covariant approach based on the Bethe-Salpeter equation with realistic meson-exchange interaction. Lorentz boost and other relativistic effects in the cross section and spin correlation observables, like tensor analyzing power and polarization transfer etc., are investigated in explicit form. Results of numerical calculations for a compbte set of polarization observables are presented.

Different benchmarks for reactors with quadratic fuel assemblies were calculated with the code DYN3D/R. In this report comparisons with the results of the reference solutions are carried out. The results of DYN3D/R and the reference calculation for the eigenvalue keff and the power distribution are shown for the steady-state 3-dimensional IAEA-Benchmark. The results of NEACRP-Benchmarks on control rod ejections in a standard PWR were compared with the reference solutions published by the NEA Data Bank. For assessing the accuracy of DYN3D/R results in comparison to other codes the deviations to the reference solutions are considered. Detailed comparisons with the published reference solutions of the NEA-NSC Benchmarks on uncontrolled withdrawal of control rods are made. The influence of the axial nodalization is also investigated. All in all, a good agreement of the DYN3D/R results with the reference solutions can be seen for the considered benchmark problems.

In diesem Abschlußbericht wird ein Fördervorhaben beschrieben, welches auf die Unterstützung von 6 russischen Wissenschaftlern aus drei unterschiedlichen Institutionen abzielte. Ihre Arbeiten zur Anlagendiagnostik / Schadensfrüherkennung dienen der Erhöhung der Sicherheit von WWER-Reaktoren.
Das Vorhaben leistet einen Beitrag zur verbesserten Beurteilung der mechanischen Integrität von Reaktoren der russischen WWER-440 und WWER-1000 Baureihe, insbesondere zur empfindlichen Früherkennung und Lokalisation mechanischer Schädigungen an Reaktorkomponenten mit Hilfe schwingungsdiagnostischer Methoden. Zu diesem Zweck wurde das Finite-Element-Modell zur Simulation des mechanischen Schwingungsverhaltens aller Primärkreiskomponenten eines WWER-1000 erstellt. Dafür wurde das Programmpaket ANSYS® genutzt.
Das Berechnungsmodell zum WWER-440 wurde mit neueren Ergebnissen experimenteller Schwingungsuntersuchungen weiter justiert. Das Modell kann in der Hauptsache genutzt werden, um zu klären, wie sich unterstellte mechanische Defekte von Reaktoreinbauten auf die Schwingungen der Gesamtanlage auswirken. Diese Schadenssimulation ist besonders geeignet, empfindliche Meßpositionen für die on-line Überwachung zu finden und physikalisch fundierte Grenzwerte zu definieren.

As the scaling of silicon devices to 100 nm channel length requires the formation of ultra-shallow (< 60 nm) junctions, high depth resolution analytical techniques become necessary for the characterization of the dopant and damage distributions. In situ single wavelength Ellipsometric
Etch Depth Profiling (EEDP) and non-destructive Variable Angle of incidence Spectroscopic Ellipsometry (VASE) have been used to obtain accurate and quantitative information on the depth profiles of radiation damage produced by low energy, room temperature ion implantation of B⁺ into Si.

The interaction of radium with characteristic sediments of the upper Saxon Elbe river valley was investigated with the
aim to provide key data for transport modelling within the framework of mining site restoration. Adsorption
measurements therefore were carried out on site-specific sediments (different kinds of sandstone, claystone and lime
marl) using (1) acidic mine water coming from sulfuric acid residues of the former in-situ leaching process, (2)
groundwater that is inflowing into the mine and (3) mixtures of both which simulates certain stages of the mine flooding process. The distribution ratios were determined by batch experiments using an eight-week equilibration at aquifer temperature (14 °C). Radium adsorption from acidic mine water onto different kinds of sandstone is characterized by high distribution ratios (3400 mL/g). When contacted with groundwater, the sorption is decreased more than 20-fold (60-180 mL/g). For claystone and lime marl the distribution ratios amount to 130 and 480 mL/g, respectively, and they are nearly constant in the mine flooding process. The main adsorption mechanisms on the leached sandstone and the clayey sediments were identified as coprecipitation and ion exchange, respectively. The long-term migration behaviour in the aquifers of the south-east Saxon Elbe basin was calculated on the basis of Hadermanns' equation, considering retardation, dispersion and radioactive decay.

The E1 response of the semi-magic nucleus ¹⁴⁰Ce below the particle
threshold was measured in a (gamma, gamma') experiment utilizing the new
Euroball Cluster detector at the S-DALINAC. While the energy averaged data
are in good agreement with the tagged photon results, here they are resolved
for the first time into 54 individual transitions. A quasiparticle-phonon
model calculation including up to three-phonon configurations compares
well to the extracted strength distribution. The interference between one-
and two-phonon contributions is essential for a quantitative reproduction.

Excited states of the nuclei ¹²²Te, ¹²⁶Te and ¹³⁰Te
were populated via the (gamma,gamma') reaction at endpoint energies of
the bremsstrahlung between 4.5 and 5.5 MeV. Gamma rays were detected with
a EUROBALL-CLUSTER detector and a single detector. In all nuclei several
dipole transitions were identified at energies around 3 MeV. The lowest
corresponding J = 1 states are interpreted as two-phonon excitations. Quasiparticle-phonon-model
calculations predict one 1^- state arising from the coupling
of the first quadrupole and the first octupole phonon and one 1⁺
state arising from the coupling of the first and the isovector second quadrupole
phonon at about 3 MeV. The calculated transition strengths are compatible
with experimental one.

At the new heavy ion tumor therapy facility of the Gesellschaft für Schwerionenforschung at Darmstadt positron emission tomography (PET) has been implemented for in-beam and in-situ therapy control, i.e. during the tumor irradiation. The components necessary for this dedicated PET-imaging and their integration into the framework of therapy planning and quality assurance of heavy ion cancer treatments are presented. Results of the first application of this PET-method to patient treatments are reported.

The results of the 4th AER dynamic benchmark obtained by the use of the code DYN3D in the Research Centre Rossendorf are presented. The benchmark comprises the modeling of a boron dilution transient caused by switching on the first main coolant pump of a loop containing a plug of partially undiluted water. Therefore, the course of the transient is significantly affected by correct modeling of the boron transport. The results of studies on the influence of numerical diffusion during boron transport are presented. Consequently, a new numerical model based on the particle­in­cell method has been developed and implemented into DYN3D. The basic features of this model are described. It allows the complete suppression of numerical diffusion and to take into account the effect of boron enrichment in the liquid water phase in the case of boiling in a simple manner. Another important feature of the benchmark task was that each participant had to use his own macroscopic cross section library. In our analysis the MAGRU library for VVER­440 was used. A few reactor­physical key parameters had been given in the benchmark definition for optional adoptation of the cross section data. The presented analysis was carried out with a minimum amount of adoptations. Finally, only the static supercriticality of the boron dilution was given an the Doppler feedback was adopted. Some interesting thermo­hydraulic effects are discussed, which can be used for a deeper comparative analysis of the thermo­hydraulics models of the codes. Due to the low mass flow rate and high heat flux densities occuring, vapour generation during the transient is significantly affected by subcooled boiling under thermodynamic non­equlibrium conditions.

A method for the in-situ control of the heavy-ion tumour therapy by means of positron emission tomography is introduced. This method is founded on the measurement of the dynamic spatial distributions of beta+-emitters generated by nuclear fragmentation during the irradiation and their relation to the dose. In order to study this relationship and to derive the dose distribution from the measured beta+-activity distribution, a framework of model calculations is used. Results of phantom experiments with ¹²C ion beams will be presented, demonstrating good agreement between experiment and calculation as well as the possibilities and limits of the PET-technique for treatment plan verification and beam monitoring.

Excited states in ¹¹⁰Sb have been identified for the first time
in a series of gamma-spectroscopy experiments using both thin and backed
targets, including neutron-fold and recoil-mass measurements to provide
unambiguous channel identification. The three decoupled intruder bands
observed in ¹¹⁰Sb are based upon configurations involving 2p-2h
excitations across the Z=50 shell gap and show the features of smooth band
termination. The yrast intruder band, which has been connected to the low-spin
levels, is tentatively identified up to its predicted termination at I^Pi=45⁺.
Excellent agreement with configuration-dependent cranked Nilsson-Strutinsky
calculations is obtained for the high-spin states near termination.

ß-FeSi2 was produced by ion beam assisted deposition
(IBAD). The influence of the deposition parameters on the structure was
studied by Rutherford backscattering, X-ray diffraction, cross section
transmission electron microscopy, and scanning electron microscopy. The
samples grow in a columnar way with pin-holes and their surface is rough.
A soft IBAD process with low Ar energy (EAr = 200 eV) and low Ar ion to
Fe atom ratio (IAr/AFe = 0.16) improves the layer structure in comparison
to samples prepared without Ar irradiation. Less pin-holes are formed,
and the roughness shows a minimum. The roughness increases for larger EAr
and larger IAr/AFe. All samples are polycrystalline but with a pronounced
texture. The preferential orientation is also enhanced by the IBAD process.
The electrical properties of the layers were characterized by Hall effect
measurements and measurements of the I-V characteristics of simple diode
structures. The results are discussed in relation with the influence of
the ion beam.

Im Bericht werden die Potentiale zur Elektroenergieerzeugung aus verschiedenen erneuerbaren Energiequellen in Sachsen zusammengestellt. Dabei werden natürliche Potentiale und - wo möglich - technische Potentiale sowie wirtschaftliche Potentiale unterschieden. Das ermittelte technische Potential (ohne Biomasse) entspricht etwa einer Elektroenergieproduktion von 7400 GWh jährlich. Davon entfallen etwa 2/3 auf die Windenergie und der Rest zu gleichen Teilen auf die Wasserkraft und die Photovoltaik.
Die Erschließung der Potentiale seit 1990 wird im Einzelnen dargestellt. Neben der seit langem genutzten Wasserkraft entwickelt sich insbesondere die Windenergie sehr dynamisch. Die Windenergie wird noch 1997 die Wasserkraft als bedeutendste erneuerbare Energie in Sachsen ablösen. Die weitere Nutzung dieser beiden Energiequellen stößt allerdings auf zunehmende ökologische Bedenken bzw. Widerstände.
Der Anteil der erneuerbaren Energiequellen am Elektroenergieverbrauch in Sachsen erreichte 1996 etwa 1,3 %. Bis zum Jahr 2000 erscheint eine Vergrößerung dieses Anteils auf ca. 5 % möglich.

Abstract
In this article we present results concerning the extraction of light charged particle multiplicities in incomplete fusion-fission reactions with a moving source fitting procedure. To demonstrate the feasibility and reliability of the procedure we have used simulated events of known multiplicity to construct kinetic energy distributions at different angles that are fitted assuming several pre- and post-scission sources. In particular, we show that it is necessary to include at least two pre-equilibrium sources in order to extract correctly the known pre-equilibrium proton multiplicity. These two sources are characterized by high ernission temperatures, low emission barriers and high velocities, having ~ 70% and ~ 25% of the beam velocity along the beam axis, respectively The former source is naturally dominant at forward angles due to the strong focusing effect of its high velocity, Contrary to normal expectations, however, the slower pre-equilibrium source is present with considerable yield at the most backward angles θ ~ 145° where it is normally assumed only evaporative components are present. The estracted proton multiplicities are well reproduced by the moving source procedure, as well as fitting parameters with physical relevance.

The Siemens AG is developing the new innovative boiling water
reactor concept SWR1000. New features are the passive safety
systems (e.g. emergency condensers, building condensers, passive
pressure pulse transmitters).
For the experimental investigation of the emergency condenser
effectiveness, the NOKO test facility has been constructed at
the Forschungszentrum Jülich in cooperation with Siemens. The
facility has an operating pressure of 10 MPa and a maximum power
of 4 MW for steam production. The condenser bundle consists of 8
tubes and is fabricated with the geometry and material as planned
for the SWR. In more than 200 experiments, the emergency condenser
capacity was tested as a function of pressure, water level and
concentration of noncondensables in the pressure vessel as well as
pressure, water level and temperature in the condenser.
Posttest calculations of NOKO experiments were performed with an
improved version of ATHLET. To calculate the heat transfer coefficients
during condensation in horizontal tubes the module KONWAR has been
developed and implemented in ATHLET. KONWAR is based on the flow regime
map of Tandon and includes several semiempirical correlations for the
determination of the heat transfer coefficients. The presented comparison
between calculations and experiments shows a good agreement

Analysis and calculation of an abnormal event which occurred in 1989 at the NPP Greifswald (VVER-440/213) are reported about. This event was a scram failure at about 50% nominal power with two of six working main coolant pumps (MCP). The analysis revealed remarkable differences between the active and passive loops due to non-homogeneous coolant mixing in the downcomer and lower plenum in the initial state before the accident. An existing input data deck for the coupled code DYN3D/ATHLET was modified to carry out calculations of this accident. On account of the absence of a mixing model considering loops with forward and loops with backward flow at the same time, the six reactor loops were modeled by a 3-fold (passive), a 2-fold (active) and a single (with the MCP to be switched-off at the beginning of the transient) loop. The comparison of the stationary calculation with the reported data shows a good agreement taking into account the mentioned deviations between the loops. Most of the calculated thermohydraulic parameters during the accident are very close to the measured data. Deviations in the loop temperatures can be explained by the differences in the measured stationary data and by the fact of non-homogeneous coolant mixing in the downcomer and the lower plenum. A small, but continuous power increase was observed during the whole time in the calculation while the measured power was remaining nearly constant. The power behaviour was brought into agreement with the measured data by a correction of the moderator temperature coefficient within the accuracy recommendations of the Atomic Energy Research (AER).
The calculation of this accident is an important contribution to the validation of the coupled code DYN3D/ATHLET. It demonstrated problems of the analysis of real abnormal events on NPP`s.

On the NOKO (emergency condenser) test station constructed at Jülich Research Centre, the operating performance and effectiveness of the emergency condenser of the boiling water reactor 1000 have been determined in well over 200 tests. It has been possible to check that the tests were in close agreement with a modified version of ATHLET

Der Stand und die Perspektiven der Windenergienutzung in den neuen Bundesländern unterscheidet sich nicht grundsätzlich von der Situation in den alten Ländern. In einigen Fragen (flächendeckende Potentialerhebungen, durchschnittliche WEA-Größe) ist der Stand sogar höher zu bewerten. Die weitere Entwicklung der Windenergienutzung wird bestimmt durch
- die mittelfristig mögliche Senkung der Stromgestehungskosten (Anforderungen an die Standortwahl und Standortnutzung),
- den praktischen Nachweis von Zuverlässigkeit und Lebensdauer der eingesetzten Anlagen,
- den künftigen ordnungspolitischen Rahmen für die Windenergienutzung (Zielkonflikt Liberalisierung der Strommärkte und Reduktion CO2-Ausstoß) sowie
- die politische und soziale Akzeptanz der Windenergienutzung.
Neben Wissenschaftlern und Technikern steht hier auch die Politik vor einer großen Herausforderung.

The fifth dynamic benchmark defined in this paper is the first benchmark for coupled thermohydraulic system/three-dimensional neutron kinetic core models. In this benchmark the interaction between the components of a VVER-440 NPP with the reactor core should be investigated.

The initiating event is a symmetrical break of the main steam header (MSH) at the end of the first fuel cycle and hot shutdown conditions with one stuck out control rod group. The main purpose is the investigation of recriticality. For this reason, the calculation should be continued until the power excursion is eventually terminated by high-borated water from the high pressure injection system.

The participants of the benchmark should use own input data decks developed according to the needs of their own codes. The main geometrical parameters and characteristics of control and safety systems to be considered in this benchmark will be given to bring into agreement the data decks. Own best estimate nuclear cross section data should be used in the calculation. Only the initial subcriticality at the beginning of the transient will be given to made the results more comparable.

Abstract
Within a covariant effective one-boson exchange model for the T matrix of NN interactions we present detailed calculations of bremsstrahlung cross sections for proton - proton and proton - neutron reactions at beam energies in the 1 GeV region. Besides pure bremsstrahlung processes we consider photons from ∆ decays and contributions from the η → γγ process. At beam energies above 700 MeV the ∆ decay channel dominates the spectra at large photon energies, where the interference between non-resonance processes and the ∆ decay channel becomes also important. Low energy photons stem from pure bremsstrahlung processes. The available experimental data at 730 MeV beam energy is well described. We extrapolate the model down to 280 MeV, where more detailed experimental data exist, and find agreement with angular distributions.

The report gives an overview on the scientific work of the Institute of Safety Research in 1996.

Abstract
The spectra of lepton pairs from correlated open charm and bottom decays in ultrarelativistic heavy-ion collisions are calculated. Our approach includes energy loss effects of the fast heavy quarks in deconfined matter which are determined by temperature and density of the expanding parton medium. We find a strong suppression of the initial transverse momentum spectrum of heavy quarks due to the energy lass at LHC conditions. Within the central rapidity covered by the ALICE detector system, the dominant contribution from bottom decays to the high invariant mass dielectron spectrum is predicted.

Abstract.

Exploiting a unique set of parton distribution functions we estimate hard processes for open charm, dilepton and mini-jet production. Assuming rapid thermalization within the mini-jet plasma we follow the evolution (expansion and chemical equilibration) of the parton matter and calculate the energy loss of charm quarks in this environment. A substantial part of charm is espected to thermalize. We try to estimate the thermalized open charm component in the final hadron spectra.

Minimizing the consequences of loss of vacuum and loss of coolant into vacuum accidents with respect to fusion reactor design requires the choice of materials as oxidation resistant as possible. In continuation to the testing of carbon candidate materials under oxidizing conditions (oxygen and steam) in collaboration with NET the carbon compound Aerolor AO5 of Carbone Lorraine has been examined in detail in the test facilities INDEX 2 and SPALEX at Forschungszentrum Jülich. The parameters for these oxidation experiments in the in-pore diffusion controlled regime are temperature (from 973 K up to 1173 K for oxygen, from 1173 K up to 1423 K for steam) and reaction gas concentration (1 vol.-% - 20 vol.% oxygen in argon, 5 vol.% - 100 vol.% steam in argon). The deducted equations for the primary oxidation reactions consider the dependence of the reaction rate on temperature, partial pressure and burn-off of the material.

The Siemens AG is developing the new innovative boiling water reactor
concept SWR1000. New features are the passive safety systems (e.g.
emergency condensers, building condensers, passive pressure pulse
transmitters, gravitydriven core flooding lines).

For the experimental investigation of the emergency condenser effectiveness,
the NOKO test facility has been constructed at the Forschungszentrum Jülich
in cooperation with Siemens. This test facility has an operating pressure of
10 MPa and a maximum power of 4 MW for steam production. The emergency
condenser bundle consists of eight tubes and is fabricated with planned
geometry and material of the SWR1000. In more than 200 experiments, the
emergency condenser capacity was tested as a function of pressure, water
level and concentration of noncondensables in the pressure vessel as well
of pressure, water level and temperature in the condenser.

Post test calculations of NOKO experiments were performed with an improved
version of ATHLET. To calculate the heat transfer coefficients during
condensation in horizontal tubes the module KONWAR has been developed
and implemented in ATHLET. KONWAR is based on the flow regime map of
Tandon and includes several semiempirical correlations for the determination
of the heat transfer coefficients. The comparison between calculations and
experiments shows a good agreement.

Molecular-dynamics simulations on ion-beam deposition
of boron nitride are presented. A realistic Tersoff-like potential energy
function for boron nitride, which was specially fitted to ab initio-data,
has been used. The impact of energetic boron and nitrogen atoms on a c-BN
target is simulated with energies ranging from 10 to 600 eV. The structural
analysis of the grown films shows, that a loose, dominantly sp²-bonded
structure arises at high ion flux. In no case the formation of a sp³-bonded
phase is observed, but the obtained films partially reveal textured basal
planes as found in experiment. Two different growth regimes are identified
for ion energies above and below 100 eV.

Im Rahmen des Forschungsvorhabens "Berechnung des passiven Notkondensators eines mit Naturumlauf arbeitenden innovativen Siedewasserreaktors (SWR600) mit ATHLET", das eng mit dem Forschungsvorhaben 15 NU 9050 "Notkondensator für einen Siedewasserreaktor mittlerer Leitung - Versuche zur Ermittlung der Leistung" verknüpft ist, wurden seitens des Forschungszentrums Rossendorf (FZR) e.V. im Rahmen eines F&E-Vertrages Auswertungen und Interpretationen von Messungen zu Strömungsformen und Kondensationsvorgängen im NOKO-Versuchsstand durchgeführt. Neben den Bündelversuchen wurden im NOKO-Versuchsstand mehrere Experimente im einem separaten, seitlich vom Bündel angeordneten und umfangreich instrumentierten Einzelrohr durchgeführt, um die Aussagesicherheit der Notkondensatorexperimente zu erhöhen und zusätzlich experimentelle Daten für die Validierung von Thermohydraulikprogrammsystemen (u. a. den ATHLET-Code) bereitzustellen. Hierbei geht es speziell um die Untersuchung der transienten Zweiphasenströmung innerhalb der Notkondensatorrohre hinsichtlich der dort anzutreffenden Strömungsformen, sowie die Bestimmung des volumentrischen Gasgehaltes an verschiedenen Stellen auf der Sekundärseite im Bündel bei unterkühltem und gesättigtem Sieden. Das NOKO-Einzelrohr wurde hierzu mit nadelförmigen Voidsonden ausgestattet. Durch die Nutzung von jeweils mehreren Sonden in zwei ausgewählten Strömungsquerschnitten wurde die Phasenverteilung während der Füllstandsabsenkung, d.h. beim Durchgang des Flüssigkeitsspiegels an den Sondenpositionen, in-stationär gemessen. Daraus läßt sich die Form der Phasengrenzfläche rekonstruieren. Neben den Messungen im Einzelrohr fanden, ebenfalls mit Nadelsonden, Messungen auf der Sekundärseite des NOKO-Bündels statt. Die Einzelrohr-Versuche an der NOKO-Anlage in Jülich haben gezeigt daß bei entsprechend geringer Konzentration von nichtkondensierbaren Gasen Schwälle und Pfropfen im Ansatz zu beobachten sind, die Vorhersagen bekannter Strömungskarten jedoch nicht zutreffen. Dort werden Schwälle und Pfropfen in wesentlich größerem Aumaß vorhergesagt. Die Aufstellung und Validierung eines einfachen Modells zur Berechnung des Druckverlustes im Wärmeübertragerrohr ist gelungen. Damit kann der Differenzdruck zwischen den Kollektoren ober besser ein an den Wärmeübertragerrohren direkt gemessener Differenzdruck zur Füllstandsmessung auf der Primärseite des Notkondensators herangezogen werden. Bei der Validierung mußten jedoch die experimentell ermittelten Volumina des nichtkondensierbaren Gases in die Berechnung einfließen. Der Mechanismus der Kondensationsbehinderung durch das nichtkondensierbare Gas wurde durch Gegenüberstellung der Sondendaten mit den Meßwerten der Thermoelemente im Einzelrohr im Detail untersucht.

High current ion nitriding of austenitic stainless steel at temperatures of about 400°C leads to the formation of a surface layer, called expanded austenite. The formation of this layer is not well understood. Deuterium induced nuclear reaction analyses have been performed on austenitic stainless steel samples that were subsequently high current ion nitrided with low energy ion implantation of 15 N and 14 N. The obtained depth profiles yield criteria for the formation process of the expanded austenite. A trapping mechanism cannot be confirmed.

Abstract
We consider a chiral one-loop hedgehog soliton of the bosonized SU(2)_f Nambu & Jona-Lasinio model which is embedded in a liot medium of constituent quarks. Energy and radius of the soliton are determined in self-consistent mean-field approximation. Quasi-classical corrections to the soliton energy are derived by means of the pushing and cranking approaches. The corresponding inertial parameters are evaluated. It is shown that the inertial mass is equivalent to the total internal energy of the soliton. Corrected nucleon and ∆ isobar masses are calculated in dependence on temperature and density of the medium. As a result of the internal structure of the soliton which is controlled by the self-consistent mean field, the scaling between constituent quark mass and soliton mass is noticeable disturbed.

The synthesis route to n.c.a. 3-nitro-[3-C-11]anisole (3) by use of the principle of synchronous six-electron cyclization of hexatriene systems into aromatics is described and discussed. Nitro-[C-11]-methane (1) reacts with the prepared precursor 5-dimethylamino-2-methoxy-penta-2,4-dienylidene-1-dimethylammonium tetrafluoroborate (2b) in the presence of BuLi to form 1-dimethylamino-4-methoxy-6-nitro-[6-C-11]hexatriene (IA, IB), followed by cyclization/ aromatization into 3. Starting from 1, 3-nitro-[3-C-11]anisole of a radiochemical purity of about 65 % and a mean specific radioactivity of 1 Ci/mu mol was obtained within 10 min. Related to [C-11]CH3NO2, the reproducible radiochemical yield of 3 (decay-corrected) was 60+/-5 %. Reduction of 3 by heating the above reaction mixture with aqueous Na2S gave 3-amino-[3-C-11]anisole (4) of a radiochemical purity of about 50 %. The reproducible radiochemical yield of 4 (decay-corrected) in relation to 1 was 45+/-5 %, the synthesis time from 1 was 16 min.