Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Using the FOPI facility at GSI, charged particles (1\leqZ\leq6) produced in the Au(150 A MeV)+Au reaction have been measured at laboratory angles 1.20 these central collisions, have been extracted: the intensity ratio deduced for a transverse to longitudinal emission is found to be R=1.4+0.2-0.4. Model comparisons using QMD are presented. The value of R appears to depend sensitively on the nucleon-nucleon cross section, nn. Within this model, a value of nn=25±5 mb is derived.

Charged pions are measured with the 4 pi detector FOPI at GSI using the Au on Au reaction at 1.06 AGeV bombarding energy. The pion multiplicities n(pi) increase with the number of participants A(part). The average pion multiplicities per participant are / = 0.0308 and / = 0.0182. These values are only half as large as extrapolated from the low-mass systems studied by Harris et al. The ratio n(pi-)/n(pi+) increases with A(part) and decreases with the pion kinetic energies. The pion kinetic energy spectra have concave shapes, their parametrization in terms of thermal Boltzmann distributions yields a low (T-l,T- pi) and high (T-h,T- pi) temperature which change with the cm emission angle Theta of the pions. In the angular range 45 degrees < Theta < 135 degrees the low temperature is larger than , the high temperatures , are, within experimental uncertainties, the same. The inclusive polar angular distributions of pions are anisotropic, d sigma/d Omega increases for forward and backward angles. The forward - backward enhancements are independent of the pion kinetic energies or the number of participants. In addition to the preferred forward - backward emission, also the enhanced emission into the transverse direction Theta = 90 degrees is observed for pions with high energies or for pions from near-central collisions. These observations and the shape of the rapidity spectra suggest that pions, emitted from the central rapidity region, are partly rescattered by spectator matter. The strength of the rescattering process depends only weakly on the number of participants. The experimental data are compared to the results of IQMD/GEANT calculations using momentum dependent NN interactions and a hard equation of state. The calculated pion multiplicities are approximately 50% larger than experimentally determined; the existence of secondary pion sources is reproduced by the calculation, but their predicted strengths are larger than experimentally observed.

Semi-inclusive triple differential multiplicity distributions of positively charged kaons have been measured over a wide range in rapidity and transverse mass for central collisions of 58Ni with 58Ni nuclei. The transverse mass (mt) spectra have been studied as a function of rapidity at a beam energy 1.93 A GeV. The mt distributions of K+ mesons are well described by a single Boltzmann-type function. The spectral slopes are similar to that of the protons indicating that rescattering plays a significant role in the propagation of the kaon. Multiplicity densities have been obtained as a function of rapidity by extrapolating the Boltzmann-type fits to the measured distributions over the remaining phase space. The total K+ meson yield has been determined at beam energies of1.06, 1.45, and 1.93 A GeV, and is presented in comparison to existing data. The low total yield indicates that the K+ meson can not be explained within a hadro-chemical equilibrium scenario, therefore indicating that the yield does remain sensitive to effects related to its production processes such as the equation of state of nuclear matter and/or modifications to the K+ dispersion relation.

We present new experimental results concerning the azimuthal distributions of proton-likes, light and intermediate mass fragments at midrapidity for Au(100-800 A MeV)+Au collisions measured with the FOPI phase-I detector at GSI in Darmstadt. The azimuthal distributions are investigated as a function of the collision centrality, the incident energy, the fragment charge and transverse momentum. The azimuthal anisotropy is maximum for impact parameters around 7 fm. Intermediate mass fragments present a stronger out-of-plane emission signal than light fragments and a saturation is reached for Z 4. The azimuthal anisotropy increases with the fragment transverse momentum and decreases as the incident energy increases. The azimuthal anisotropy of Z = 2 particles investigated as a function of the scaled fragment transverse momentum follows an universal curve for bombarding energies between 250-800 A MeV. A signature for a transition from in-plane to out-of-plane emission is evidenced at the lowest beam energies.

Collisions of Au on Au at incident energies of 150, 250 and 400 A·MeV were studied with the FOPI-facility at GSI Darmstadt. Nuclear charge (Z15) and velocity of the products were detected with full azimuthal acceptance at laboratory angles 1lab30. Isotope separated light charged particles were measured with movable multiple telescopes in an angular range of 6-90. Central collisions representing about 1% of the reaction cross section were selected by requiring high total transverse energy, but vanishing side flow. The velocity space distributions and yields of the emitted fragments are reported. The data are analysed in terms of a thermal model including radial flow. A comparison with predictions of the quantum molecular model is presented.

Using the FOPI detector at GSI Darmstadt, excitation functions of collective flow components were measured for
the Au+Au system, in the reaction plane and out of this plane, at seven incident energies ranging from 100A MeV
to 800A MeV. The threshold energies, corresponding to the onset of sideward-flow (balance energy) and
squeeze-out effect (transition energy), are extracted from extrapolations of these excitation functions toward
lower beam energies for charged products with Z>= 2. The transition energy is found to be larger than the balance
energy. The impact parameter dependence of both balance and transition energies, when extrapolated to central
collisions, suggests comparable although slightly higher values than the threshold energy for the radial flow. The
relevant parameter seems to be the energy deposited into the system in order to overcome the attractive nuclear
forces.

The hydrolysis of uranium(VI) has been the subject of extensive studies since 50 years and is relatively well-known under acidic and near-neutral conditions. A comprehensive discussion and review of the thermodynamic data is published in [1]. At total uranium(VI) concentrations above 10-4 M and in a slightly acidic (pH: 2 to 5) aqueous media, polymeric cations [e.g., (UO2)2(OH)22+, (UO2)3(OH)5+] are the major species. Structure investigations of such hydrolysis products of uranyl in solutions at environmental relevant uranium concentrations are rare [2].
We investigated the structure of dioxouranium(VI) as a function of pH at different (CH3)4N-OH concentrations with the aid of U LIII EXAFS. Polynuclear hydroxo species were identified by an U-U interaction at 3.808 Å at pH = 4.1.
The speciation of uranium(VI) in the neutral and slightly alkaline pH region is dominated by the precipitation of schoepite. The EXAFS measurements performed at the precipitate formed at pH = 7 showed a schoepite like structure.
The investigation of uranyl hydroxide complexes in alkaline solutions is challenging due to the formation of highly insoluble alkali metal mono- and polyuranate salts. Mononuclear species, UO2(OH)3- and UO2(OH)42-, have been identified mainly by solubility experiments [3] to be the major uranium(VI) complexes at pH > 12. Several attempts have been made to characterize the structure of uranyl complexes under highly alkaline conditions using potentiometric titrations, EXAFS, NMR techniques and quantum chemical methods [4-6]. In solution at high pH [0.5M (CH3)4N-OH], our EXAFS data are consistent with the formation of a monomeric four coordinated uranium(VI) hydroxide complex UO2(OH)42- of octahedral geometry. The first shell contains two O atoms with a U=O distance of 1.830 Å, and four O atoms were identified at a U-Oeq distance of 2.266 Å.
We have extended a previous study [6] by determining the structure of uranium(VI) at (CH3)4N-OH concentration below 1 M over a broad pH-range. The objective was to decide if binary polynuclear hydroxo species also occur in (CH3)4N-OH media. Additional information is provided by comparing the EXAFS results with new 17O-NMR measurements. In strong alkaline solutions [> 1 M (CH3)4N)-OH], 17O-NMR spectra indicate the presence of two species, presumably UO2(OH)42- and UO2(OH)53-, which are in rapid equilibrium with one another at 268 K in aqueous solution. New EXAFS and 17O-NMR data will be presented.

References
1. Grenthe, I., Fuger, J., Konings, R.J.M., Lemire, R.J., Muller, A.B., Nguyen-Trung C., Wanner, H., in: Wanner, H. and Forrest, I. (eds.): Chemical Thermodynamics of Uranium, NEA OECD, Issy-les-Moulineaux, France, p. 241ff (1992).
2. Dent, A.J., Ramsay, J.D.F., Swanton, S.W.: J. Colloid Interface Sci. 150, 45-60 (1992).
3. Yamamura, T., Kitamura, A., Fukui, A., Nishikawa, S., Yamamoto, T., Moriyama, H.: Radiochim. Acta 83, 139-146 (1998).
4. Palmer, D.A., Nguyen-Trung, C.: J. Solution Chem. 24, 1281-1291 (1995).
5. Clark, D.L., Conradson, S.D., Donohoe, R.J., Keogh, D.W., Morris, D.E., Palmer, P.D., Rogers, R.D., Tait, C.D.: Inorg. Chem. 38, 1456-1466 (1999).
6. Wahlgren, U., Moll, H., Grenthe, I., Schimmelpfennig, B., Maron, L., Vallet, V., Gropen, O.: J. Phys. Chem. A103, 8257-8264 (1999).

To get an improved understanding and knowledge of the processes and phenomena during the late phase of a core melt down accident the FOREVER-experiments (Failure of Reactor Vessel Retention) are currently underway. These experiments are simulating the lower head of a reactor pressure vessel under the load of a melt pool with internal heat sources. The geometrical scale of the experiments is 1:10 compared to a common Light Water Reactor. During the first series of experiments the Creep behaviour of the vessel is investigated.
Due to the multi-axial creep deformation of the three-dimensional vessel with a non-uniform temperature field these experiments are on the one hand an excellent possibility to validate numerical creep models which are developed on the basis of uniaxial creep tests. On the other hand the results of pre-test calculations can be used for an optimized experimental procedure.
Therefore a Finite Element model is developed on the basis of the multi-purpose commercial code ANSYS/Multiphysics®. Using the Computational Fluid Dynamic module the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are performed applying a creep model which is able to take into account great temperature, stress and strain variations within the model domain. The new numerical approach avoids the use of a single creep law with constants evaluated for a limited stress and temperature range. Instead of this a three-dimensional array is developed where the creep strain rate is evaluated according to the actual total strain, temperature and equivalent stress for each element.
Performing post-test calculations for the FOREVER-C2 experiment it was found that the assessment of the experimental data and of the numerical results has to be done very carefully. A slight temperature increase during the creep deformation stage of the experiment for example could explain the creep behaviour which appears to be tertiary because of the accelerating creep strain rate. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios.

A joint German/Russian irradiation programme was performed at the prototype pressurized water reactor VVER-2 of the Rheinsberg nuclear power plant (Germany). The experiment comprises about 800 Charpy V-notch, SENB and CT specimens made from 24 different heats of Russian VVER type reactor pressure vessel base and weld metals. The testing of these specimens were performed at Forschungszentrum Rossendorf e.V. (FZR), MPA Stuttgart and the KFA Jülich. This paper presents the results of Charpy V tests performed by FZR. On the base of these results the neutron embrittlement sensitivity and the annealing behaviour are evaluated.

Der Erfindung betrifft ein Verfahren zur Implantation von Ionen gasförmiger Elemente in leitende bzw. halbleitende Werkstücke mittels Plasmaimmersionsimplantation ( PIII ) das ohne aufwendige Hochspannungspulser zu guten Implantationsergebnissen führt.
Das erfindungsgemäße Verfahren besteht darin, daß an die zu implantierenden Werkstücke eine DC-Hochspannung (Gleichspannung > 5kV ) angelegt und das Plasma gepulst wird.
Zur Erzeugung des Plasmas wird vorteilhaft eine Anordnung mit geheizten Filamenten oder eine ECR-Quelle eingesetzt. Das Plasma wird gepulst, indem die Bogenspannung an den Filamenten gepulst wird, oder aber der Mikrowellengenerator der ECR-Quelle im Pulsbetrieb betrieben wird.
Um zu verhindern, daß das das vom auf Hochspannung liegenden Werkstück ausgehende elektrische Feld bis auf die Ionenquelle durchgreift, dort den Austritt von Elektronen unterdrückt und die Zündung des Plasmas erschwert, wird die Plasmaquelle geometrisch so angeordnet bzw. gegenüber der Hochspannung abgeschirmt, daß der Durchgriff der Hochspannung auf die Plasmaquelle minimal ist. Konkret kann dies z. B. dadurch erfolgen, daß die Plasmaquelle an die Implantationskammer mit einem genügend tiefen Hals angeflanscht wird, oder daß zwischen Plasmaquelle und Werkstück in Abständen von einigen cm dünne geerdete Drähte gespannt werden.

Workshop on X-rays from electron beams with special emphasis on possible developments at ELBE

The diagnosis and staging of breast cancer could be improved by the development of imaging radiopharmaceuticals that provide a noninvasive determination of the estrogen receptor status in the tumor cells. Toward this goal, we have synthesized a number of novel Re-containing 7alpha-substituted estradiol complexes. The introduction of the 7alpha side chain involves the alkylation of tetrahydropyranyloxy-protected 6-keto estradiol. The methods used to introduce the rhenium metal involve "3+1" and "4+1" mixed ligand complexes (2a-c and 5, respectively), tricarbonyl dithioether complexes (3), and the cyclopentadienyltricarbonylmetal organometallic system (4ab, 6, 7). These complexes showed binding affinities for the estrogen receptor (as high as 45% for the "3+1" complex 2c) when compared to the native ligand estradiol. The polarity of some complexes (4ab) was modified to improve biodistribution properties by introducing (poly)ether linkages into the 7alpha side chain (6, 7). These complexes provide a further refinement of our understanding of ligand structure-binding affinity correlations for the estrogen receptor, and they furnish the synthetic groundwork for the synthesis of the analogous Tc-99m complexes for evaluation as breast tumor imaging agents.

In a former study we investigated the influence of phenolic OH groups on the complexation behavior of humic acids (HAs) with uranium(VI) using chemically modified synthetic HA (type M1) as well as modified natural HAs (Aldrich and Kranichsee) with blocked phenolic OH groups. These modified HAs were synthesized by permethylation of the original HAs with diazomethane, which converts carboxyl groups to methyl esters and acidic (phenolic) OH groups to methyl ethers and subsequent alkaline saponification of the permethylated HAs. This results in the hydrolysis of ester groups, whereas phenolic OH groups remain blocked.
In continuation, we performed in the present study comparative 13C-CP/MAS-NMR measurements of the modified and unmodified HAs type M1, Aldrich and Kranichsee to verify that there are no significant structural changes of the HAs during their modification. We also studied NMR spectra of alkaline treated HAs type M1, Aldrich and Kranichsee to determine potential structural changes of the HAs which may occur during the alkaline treatment of the permethylated HAs. In addition to the modified and unmodified HAs with carbon-13 at natural abundance we investigated 13C-labeled modified HAs type M1 (permethylated, phenolic OH groups blocked, partly methylated) that were synthesized using [13C]diazomethane as methylation reagent. These studies were performed to verify the modification process and to determine which functional groups of the HAs show the highest affinity for methylation with diazomethane.
From our studies we conclude that only carboxyl and acidic (phenolic) OH groups are methylated with diazomethane, whereby carboxyl groups show the highest affinity for methylation. The alkaline hydrolysis of diazomethylated HAs results in HAs with blocked phenolic OH groups. No significant changes of the overall HA structure occur. This method offers the possibility to synthesize selective modified HAs that can be used to study the influence of various functional groups on the complexation behavior of HAs with metal ions.

We studied the influence of sulfate on the kinetics of uranium(VI) sorption onto ferrihydrite both in the absence and presence of humic acid at pH 6.5 under aerobic conditions since seepage waters from uranium mine tailing piles in Saxony and Thuringia (Germany) contain up to 3·10-2 M sulfate. The sequence in which sulfate, uranium and humic acid were added to the ferrihydrite suspensions was varied in order to obtain more detailed information on the sorption mechanisms. The uranium(VI) and humic acid concentration was 1·10-6 M and 5 mg/L, respectively. As humic acid, we applied the 14C-labeled synthetic humic acid 14C-M1. Two different sulfate concentrations were applied (0.005 and 0.02 M Na2SO4). The ionic strength was always 0.1 M.
The influence of sulfate, present at naturally relevant concentrations (0.005 or 0.02 M), on uranium sorption was found to be different in the absence and presence of humic material.
In the absence of humic acid, both the uranium sorption rate and the total uranium sorption in equilibrium decreased with increasing sulfate concentration. The reason is that the number of strong ferrihydrite sorption sites, accessible for uranium, is reduced upon sulfate adsorption. This leads to an increased availability of uranium.
In the presence of humic acid, and especially in the presence of higher amounts of uranyl humate complexes in solution, the influence of sulfate on uranium sorption is smaller. The reducing effect of sulfate on the total uranium sorption is almost counterbalanced by humic acid.

Summary of the Scientific Activities of the Institute in 1999: Highlight Reports / Short Contributions / Statistics

Basing on data obtained by the incomplete fusion reactions 7Li (43 AMeV) + 232Th and 14N (34 AMeV) + 197Au, the energy dependence of the variance of the fragment mass in fission of highly heated nuclei has been investigated for total excitation energies ranging from 50 up to 350 MeV. This dependence shows some unexpected features when the total excitation energy exceeds a value of about 70 MeV. After this value the steady increase of the variance expected from its temperature dependence changes to some kind of plateau between 100 and 200 MeV. Further on, at energies in excess of about 250 MeV, the variance is found to increase again sharply. In order to analyze this behaviour quantitatively, a dynamical stochastic model has been developed. The model employs the one-body dissipation mechanism and describes the decay of highly excited and rotating nuclei by fission and light particle evaporation. It satisfactory explains the measured prior-to-scission neutron multiplicities and the experimental mass variances up to an energy of about 250 MeV, but the stochastic treatment does not reveal any increase at higher excitation energies in contradiction with the data.

The photoluminescence (PL) and PL excitation (PLE) properties of Sn-implanted SiO2 layers thermally grown on crystalline Si has been investigated and compared with those from Ge- and Si-implanted SiO2 layers. In detail, the violet PL of Sn-implanted SiO2 layers is approximately 2 and 20 times higher than those of Ge- and Si-implanted SiO2 layers, respectively. Based on PL, PLE and decay time measurements the violet PL is interpreted as due to a triplet-singlet transition of the neutral oxygen vacancy (NOV) typical for Si-rich SiO2 and similar Ge- and Sn-related defects in Ge- and Sn-implanted SiO2 films. The enhancement of the blue-violet PL within the isoelectronic row of Si, Ge and Sn will be explained by means of the heavy atom effect.

The microstructural, optical and electrical properties of Si-, Ge- and Sn-implanted silicon dioxide layers were investigated. It was found, that these layers exhibit strong Photoluminescence (PL) around 2.7 eV (Si) and between 3 and 3.2 eV (Ge, Sn) at room temperature (RT), which is accompanied by an UV emission around 4.3 eV. This PL is compared with that of Ar-implanted silicon dioxide and that of Si- and Ge-rich oxide made by rf magnetron sputtering. Based on PL and PL excitation (PLE) spectra we tentatively interpret the blue-violet PL as due to a T1®S0 transition of the neutral oxygen vacancy typical for Si-rich SiO2 and similar Ge- or Sn-related defects in Ge- and Sn-implanted silicon dioxide. The differences between Si, Ge and Sn will be explained by means of the heavy atom effect. For Ge-implanted silicon dioxide layers a strong electroluminescence (EL) well visible with the naked eye and with a power efficiency up to 5·10-4 was achieved. The EL spectrum correlates very well with the PL one. Whereas the EL intensity shows a linear dependence on the injection current over three orders of magnitude, the shape of the EL spectrum remains unchanged. The I-V dependence exhibiting the typical behavior of Fowler-Nordheim tunneling shows an increase of the breakdown voltage and the tunnel current in comparison to the unimplanted material. Finally, the suitability of Ge-implanted silicon dioxide layers for optoelectronic applications is briefly discussed.

A joint German/Russian irradiation programme was performed at the prototype pressurized water reactor VVER-2 of the Rheinsberg nuclear power plant (Germany). The experiment comprises about 800 Charpy V-notch, SENB and CT specimens made of 24 different heats of Russian VVER type reactor pressure vessel base and weld metals. The testing of these specimens was performed at Forschungszentrum Rossendorf e.V. (FZR), MPA Stuttgart and the KFA Jülich. This paper presents the results of Charpy V and fracture toughness tests performed by FZR. On the base of these results the neutron embrittlement sensitivity and the annealing behaviour are evaluated.

The potential of radiolabelled neurotensin ana-logues for in vivo imaging of neurotensin (NT) receptor overexpressing tumours by PET was studied.
Methods: Three newly synthesised ¹⁸F-radiolabelled NT(8-13) agonists, characterised by HPLC, mass spectrometry, and NMR were used for in vitro binding and internalisation stud-ies with HT-29 or WiDr cells. Ca²⁺ mobilisation was investigated using FLIPR measurements. Biodistribution studies were performed in nude mice bearing HT-29 or WiDr tumours without and with blocking of the NT receptors. Biokinetic studies were done in Wistar rats using PET. The specificity of the peptide binding to the tu-mour cells was studied in receptor blocking ex-periments.
Results: The K_D's of the NT analogues were in the nanomolar range. The Ca²⁺ mobilisation ef-fect of the compounds were between 99% and 129% compared to NT with EC50 between 17nM and 120nM. The tumour uptake of the peptides was moderate and was highest for the double stabi-lised peptide {4-[¹⁸F]fluoro-benzoyl-Arg-Psi-(CH2-NH)-Arg-Pro-Phe¹¹-T-Leu¹²-Leu-OH (FB-P3)} (3.5% ID/g tissue 10 min p.i.). It was specifically accumulated in vitro and also in vivo in the tumours (70% inhibition by NT(8-13)). In nude mice the tumour was clearly visible with PET if the location was distant from the excre-tory organs.
Conclusion: The ¹⁸F-labeled stabilised NT analogues are NT agonists and potential radiotrac-ers for imaging of neurotensin receptor ex-pressing tumours. However, structural optimisa-tion is still needed.
(supported by the EC, Contract No. BMH4-CT98-3198)

High-spin states in 72Br were studied with the EUROBALL III spectrometer . The negative-parity band
observed in this experiment displays a signature inversion around spin I = 16. The interpretation within cranked Nilsson-Strutinsky approach shows that this signature pattern is a signal of a substantial triaxial shape change with increasing spin where the nucleus evolves from a triaxial shape with rotation around the intermediate axis at low spin
through an axially symmetric prolate one to a triaxial shape
but with rotation around the shortest principal axis at high spin.
This is the first case in which signature inversion was clearly related to varying gamma deformation.

We report on a nuclear resonance fluorescence experiment on the semi-magic odd-mass fp-shell nucleus 51V. The
detected dipole strength distribution is discussed on the basis of modern shell-model calculations employing a
model space allowing for excitations of protons and neutrons from the 1f7/2 to the (2p1/2,2p3/2,1f5/2) shells. The
calculations indicate that the main body of transitions is of magnetic dipole type, and they are capable of
reproducing the observed distribution well. Possible electric dipole and quadrupole contributions are also
discussed.

We investigate the application of LSO and YSO scintillating crystals for Positron Emission Tomography (PET). Properties such as light output, energy resolution, detection efficiency for various energy threshold, and timing resolution are presented. These data allow us to evaluate the usage of finger-like LSO:Ce and YSO:Ce crystals coupled to photomultiplier tube, and to establish optimal operating conditions for high-resolution PET. Both crystals have advantages over BGO currently used in PET and LSO is considered as a possible replacement for BGO based systems.

Natural IIa diamond was implanted at 90 keV to 1 1015 N+/cm2 and subsequently at 150 keV to 3 1017 Si+/cm2 at a temperature of 900°C. The structure of the implanted diamond region was investigated by high resolution cross-sectional transmission electron microscopy, Raman- and infrared absorption spectrometry. A buried layer with crystalline 3C-SiC domains in perfect epitaxial relation to the diamond substrate was detected. Amorphization and graphitization was completely prevented by the elevated temperature during the implantation. Resistance measurements demonstrated low electrical resistivity in the implanted regions.

A method for the prediction of the radial gas profile for a given bubble size distribution is presented. It is based on the assumption of the equilibrium of the forces acting on a bubble perpendicularly to the flow direction. These forces strongly depend on the bubble size. For the simulation of transient flow regime effects, the modelling of several bubble classes in an 1D model and consideration of their radial profiles seems to be more promising than a detailed 3D modelling.
The radial profile of the liquid velocity is calculated by the model of Sato. On the basis of this velocity profile, radial distributions are calculated separately for all bubble classes according to the given bubble size distribution. The sum of these distributions is the radial profile of the gas fraction. It is used in an iteration process to calculate a new velocity profile. There is a strong interaction between the profiles of liquid velocity and gas volume fraction. The model is the basis of a fast running one-dimensional steady state computer code. The results are compared with experimental data obtained for a number of gas and liquid volume flow rates. There is a good agreement between experimental and calculated data. In particular the change from wall peaking to centre peaking gas fraction distribution is well predicted.

The hydrothermal treatment of zeolite powder leads to the strong changes in the morphology of zeolite particles. In the particles characterised by homogeneous structure before thermal treatment the formation of holes after thermal treatment was observed. These changes lead to the enrichment of zeolite with titanium that enhance its catalytic activity. The titanium surplus precipitates as small TiO2 anatase particles within the holes

Rotational bands in 73Br have been investigated
up to spins of 65/2 using the EUROBALL
III spectrometer. One of the
negative-parity bands displays the highest rotational
frequency 1.85 MeV reported to date in nuclei heavier than 25.
At high frequencies, the experimental dynamic moment of inertia for all bands decrease to very low values, indicating
a lose of collectivity. The bands are described in the configuration-dependent cranked
Nilsson-Strutinsky model. The calculations indicate that
one of the negative-parity bands is observed up to its terminating single-particle state at spin 63/2.
This result establishes the first band termination in the
A =70 mass region.

The stability and reactivity of mixed-ligand ^99mTc complexes of the general formula [^99mTcOL¹L², where L¹H₂ is either an N-substituted bis-(2-mercaptoethyl]amine [SNMeS] or 3-thiapentane-1,5-dithiol [SSS] and L²H is a monodentate thiol [RS], were investigated. The complexes undergo transchelation reactions with glutathione and other SH-group containing blood constituents. The reactions are reversible and can be inhibited by addition of diethylmaleate. Challenge experiments were performed with a broad set of ^99mTc mixed-ligand complexes to investigate the influence of both tridentate ligand and the monodentate ligand on the stability of this type of complex. The occurence of ligand exchange reactions with glutathione depends on the donor set of the tridentate ligands as well as the structure of the monodentate ligands.Especially the stability of complexes containing a monodentate ligand with an amine nitrogen in the side chain can be increased by lengthening the carbon chain between the sulfhydryl group and the nitrogen. Thus, it might be possible to improve their in vivo performance.

Energy filtered TEM (EFTEM) has been applied to study ion beam syn-thesized Ge nanoclusters in 30nm SiO2 thin film thermally grown on Si(100). After thermal annealing the implanted Ge, as show the RBC measurements, was redistributed in to two spatial well separated layers - around the center of SiO2 film and near the SiO2/Si interface. The Ge in the middle of SiO2 film build the well detectable with a bright field TEM the cluster band. But the conventional TEM methods (bright, dark field and EDX line scans) are not able to determine exact Ge location related to the interface the closed cluster band. The energy filtered TEM investigations show that the interface Ge completely located in the Si substrate. The study enable conclusions about influence of the protection layer on Ge distribution in SiO2/Si.

Usually, the microstructure cannot be absolutely surely reconstructed from the small angle scattering pattern produced by it. The small angle neutron scattering curves measured at four C-poor ternary iron alloys were used to demonstrate the effect of the analysis method and the applied assumption on the microstructure analysis. Apart from the mean size of the scatterer, the size distribution as well as the shape of the scatterer affect the results. As a consequence, even well-proved methods as the indirect transformation method developed by Glatter can fail. The application of additional evaluation procedures or the use of information obtained by non-small angle scattering methods increases the chance to derive plausible structure models. In the paper a fit two-parameter method, the ratio between nuclear and magnetic scattering cross section and results from atom probe field ion microscopy are used for that. In this way it is shown that one of the four alloys exhibits another type of irradiation defects. Furthermore, modelling of the mechanical behaviours can also be helpful.

Co/Cu multilayers were prepared by crossed-beam pulsed laser deposition and
characterized by high-angle X-ray diffraction as well as specular and non-specular reflection. The as-deposited structure has
a higher rms roughness than magnetron sputtered Co/Cu multilayer. In
general the roughness of the interface is described by a very large lateral correlation length and a high jaggedness.
Ion-beam mixing of the multilayers with 150 keV Cu ions and a fluence of
up to 5e15 Cu/cm^2 leads to the formation of a granular system of superparamagnetic Co clusters in Cu, as it is shown by magnetic
measurements.

Natural circulation is a basic physical principle for a lot of industrial applications. The paper describes two examples of investigations of natural circulation phenomena. The first example is drawn from the task of the safety assessment of the danger of storage tanks of hazardous fluids under the influence of an external heat source. Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external. As a consequence of an external fire, the heat-up of the inventory may lead to the evaporation of the liquid and to release of significant quantities of dangerous gases into the environment. Several tests were performed both with heating from the bottom and with heating from the side walls. The paper presents experimental and numerical investigations of single and two phase heating up processes of tanks with side wall heating. The measurement of the temperature and of the void fraction makes interesting phenomena evident, which could be explained by an own 2D model.
The second example concerns with investigations of the investigation of passive heat removal systems in advanced designs of nuclear power plants. The heating up processes on the large pool on the secondary side of a test facility NOKO were analysed using the CFD code CFX.

Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external heat source. As a consequence of an external fire, the heat-up of the inventory may lead to the evaporation of the liquid and to release of significant quantities of dangerous gases into the environment. Several tests were performed both with heating from the bottom and with heating from the side walls. In recent tests in addition to thermocouples, the tank was equipped with needle probes for measuring of the local void fraction.
The paper presents experimental and numerical investigations of single and two phase heating up processes of tanks with side wall heating. The measurement of the temperature and of the void fraction makes interesting phenomena evident, which could be explained by an own 2D model. The gained experimental results may be used for the validation of boiling models in 3D CFD codes.

The amorphous non-equilibrium state of the system Fe/Al is studied in bulk and thin-film systems. For bulk samples prepared by ion-beam mixing of laser-deposited multilayers, a bcc solid solution is found
for alloys with up to 70 at.% Al. Around 75 at.% Al a Fe2Al5-like crystalline phase is found. An amorphous state with Fe2Al5-like short-range order is found for 80 at.% Al. In thin films, e.g. the amorphous Al-rich transition layer of a laser-deposited Fe/Al multilayer, the amorphous state can exist for
up to 30 at.% Fe due to the high interfacial energy. By ion-beam mixing at low temperatures (about 140 K) an oversaturation of 40 at.% Fe could be achieved.

Since seepage and flood waters of abandoned uranium mines in Saxony and Thuringia (Germany) contain relatively high amounts of sulfate, we studied the influence of sulfate on the kinetics of uranium(VI) adsorption onto ferrihydrite both in the absence and presence of humic acid at pH 6.5 under aerobic conditions. The sequence in which sulfate, uranium and humic acid were added to the ferrihydrite containing solutions was varied in order to obtain indications to sorption mechanisms. Two different sulfate concentrations were applied (0.005 and 0.02 M Na₂SO₄). The ionic strength was held constant at 0.1 M as sum of NaClO₄ and Na₂SO₄. The uranium(VI) concentration was 1·10^-6 M and the humic acid concentration was 5 mg/L.
In the absence of humic acid, the uranium sorption rate and the total uranium sorption in equilibrium decreased with increasing sulfate concentration due to blocking of strong ferrihydrite surface sites by sorbed sulfate. This leads to an increased availability of uranium. Variations of the order of addition of uranium and sulfate primarily affected the initial uranium sorption rate but not its sorption capacity. Direct competition of uranium and sulfate for strong ferrihydrite surface sites predominates electrostatic effects due to changes in net surface charge of ferrihydrite upon sulfate sorption.
In experiments with humic acid, the competitive effect of sulfate on humic acid sorption at pH 6.5 is small. This is attributed to a higher sorption affinity of humic acid for ferrihydrite surface sites compared to that of sulfate. The initial humic acid sorption rate was not affected by sulfate, only the total humic acid sorption was somewhat reduced by sorbed sulfate. Since the total number of potential binding sites for uranyl ions is increased by sorbed humic acid, more uranium is sorbed in the presence than in absence of humic acid. Thus, the influence of sulfate on uranium sorption is smaller when humic acid is present in solution. This effect becomes even more pronounced with increasing amounts of uranyl humate complexes in solution.

We studied the kinetics of uranium(VI) and humic acid adsorption by the rock material phyllite and by the minerals ferrihydrite and muscovite at pH 6.5 under aerobic conditions. The sequence in which uranium and humic acid were added to the solid containing solutions was varied in order to obtain more detailed information on the sorption mechanisms. The results showed that sorption of uranium and humic acid onto phyllite and ferrihydrite is rapid, that onto muscovite is slower. The initial uranium sorption rates were found to depend on the sequence of addition of uranium and humic acid. For ferrihydrite the initial uranium sorption rate decreased with increasing amounts of uranyl humate complexes in solution. In contrast, addition of humic acid to muscovite resulted in a faster uranium sorption, since the amount of easily accessible surface sites for uranyl ions is enhanced largely by sorbed humic acid. Phyllite showed an overlapping of different processes which is attributed to the complex nature of the phyllite rock. The total uranium uptake decreased in the following order: ferrihydrite > phyllite > muscovite. The results have shown that the amount of uranium sorbed on minerals in equilibrium is determined by the total number of surface sites as well as their affinity and accessibility to solutes. For ferrihydrite indications to mineral dissolution in the presence of humic acid were found. The results of the kinetic experiments confirm that the sorption behavior of phyllite to uranium and humic acid is dominated by minor amounts of ferrihydrite, that is formed as secondary mineral phase due to weathering of phyllite. The contribution of minerals, naturally present in the rock material phyllite, to the total sorption behavior of phyllite could also be shown.
Furthermore, we compared the sorption behavior of two different humic acids, a natural humic acid Kranichsee HA and a 14C-labeled synthetic humic acid type M1, onto phyllite in the pH range 3.5 to 9.5 by batch experiments. Their influence on uranium(VI) sorption onto phyllite was also studied and compared to uranium sorption in the absence of humic acid. Results revealed that sorption of humic acids and their effect on uranium sorption is influenced by the total content of humic acid functional groups and its fractions that are actually involved in sorption reactions or are available for binding of uranyl ions, together with the molecular size and the amount of aromatic structural elements of humic acids. The results also confirmed that the synthetic humic acid 14C-M1 is suitable for experiments studying the kinetics and reversibility of uranium and humic acid sorption onto minerals in the pH range 3.5 to 7.5 since its sorption behavior and its influence on uranium sorption is comparable to that of natural humic acids.

Bei der Charakterisierung der Kolloidpartikel in Bergwerkswässern stehen sowohl die Partikelgröße als auch die chemische Zusammensetzung der Partikel im Zentrum des Interesses. Die Kolloidunter-suchungen an Bergwerkswässern, die den "Bulk" der fließenden Wässer darstellen (Stollenwässer, Flutungswässer), wurden fortgesetzt. Die bevorzugte Partikelgröße von 100 bis 300 nm bestätigte sich für die "Bulk"-Wässer. Bezüglich der chemischen Aspekte stand, neben dem Verhalten des As, Pb und Cu, besonders das Verhalten des U im Blickpunkt. Es tritt sehr oft "nichtkolloidal" auf, im pH-Bereich zwischen 5 und 6 kann es jedoch auch an Eisenoxyhydroxidpartikel gebunden sein und sich dann zu erheblichen Anteilen "kolloidal" verhalten.

Mit der Untersuchung von Acid Rock Drainage (ARD), deutsch "Lettenwasser", wurden die kol-loidchemischen Arbeiten auf ein andersartiges Bergwerkswasser ausgedehnt. Lettenwässer spielen eine Schlüsselrolle bei der Wassermineralisierung in Altbergwerken. Frage war, ob ein Lettenwasser aus der Himmelfahrt Fundgrube Freiberg (pH 2,7; Sulfatkonzentration 39,5 g/l) Kolloidteilchen des unteren Nanometerbereichs enthält, oder ob es nach gängiger Filtration über ein 0,45-µm-Filter parti-kelfrei ist. Wir fanden eine kleine Menge (weniger als 30 mg/l) an leichtnachweisbaren Kolloidpartikeln von 70 bis 250 nm Größe. Wichtiger war jedoch eine zweite kolloidale Komponente, welche schwerer zu detektieren ist: eine Population von ultrafeinen Partikeln einer Größe von weniger als 5 nm. Die Konzentration dieser Komponente ist ca. 1 g/l. Die ultrafeinen Partikel konnten mit Hilfe der Photonenkorrelationsspektroskopie (PCS) nach "Demaskierung" durch Filtration über Nuclepore-Filter nachgewiesen werden (die Detektion von extrem kleinen Partikeln mittels PCS wird bei Anwesenheit größerer Submicron-Partikel durch optische Maskierung verhindert, denn die Streulichtintensität hängt im Partikelgrößenbereich der Rayleigh-Streuung von der sechsten Potenz des Partikelradius ab). Die feinen Partikel wurden gründlicher mittels Ultrafiltration untersucht. Dabei ergab sich, daß mindestens 15 % des Eisens, 50 % des Arsens und 80 % des Bleis im Letten-wasser kolloidales Verhalten zeigen.

Um die röntgenamorphen, schwer untersuchbaren ultrafeinen Partikel der ARD-Lösung näher zu cha-rakterisieren, versuchten wir, mit thermodynamischen Rechnungen (EQ3/6) die übersättigten Minera-lien festzustellen (dies sind die potentiellen Kolloidbildner). Folgende Substanzen/Systeme kommen als Kolloidbildner in Frage. Für Fe: Ferrihydrit, Schwertmannit, Jarosit oder Hydroniumjarosit. Für Pb: Anglesit (PbSO4) oder Plumbojarosit. Für As: Skorodit oder adsorptive Arsenatbindung durch Oberflä-chenkomplexierung (Inner-Sphere-Komplexe). Eine weitergehende Eingrenzung der chemischen Ver-hältnisse in den Partikeln ist mit EQ3/6-Rechnungen nicht möglich.

Die Aufklärung von Bindungszuständen in den Kolloidpartikeln unterschiedlicher Bergwerkswässer (Lettenwässer, "Bulk"-Wässer) ist das Ziel von XAFS-Messungen an der Rossendorfer Beamline (ROBL) am Synchrotron der ESRF in Grenoble die im Februar 2000 angelaufen sind. Das Problem der Unterscheidung zwischen Partikeln und Mutterlösung wollen wir bei diesen in-situ-Messungen durch Vergleich der EXAFS-Spektren von Lösungen unterschiedlichen Filtrationsgrades zu lösen ver-suchen: a) unfiltrierte Lösungen, b) stark angereichertes Kolloid (Retentate der Ultrafiltration) und c) stark abgereichertes Kolloid (Fitrate der Ultrafiltration). Aussagen über die Bindungszustände in den Partikeln möchten wir dann durch Vergleich mit Spektren von definierten Referenzsystemen gewin-nen. Folgende Referenzsysteme wurden vorbereitet: Schwertmannit, Jarosit, Goethit, Skorodit, Bukowskyit, Arsenat sorbiert an Goethit und Bleisulfat.

Im Laufe von 10 Monaten schied sich aus dem untersuchten Lettenwasser eine makros-kopische Sekundärmineralphase aus. Es handelt sich im wesentlichen um das sulfatreiche Mineral H-Jarosit. Kleine Mengen an schlecht kristallinen Phasen, wie Schwertmannit, können nicht ausgeschlossen werden. Der H-Jarosit bindet signifikante Mengen an As und Blei. Die XRD ergab aber keine Hinweise auf Skorodit oder Bleiminerale.
Die ultrafeinen Partikel (<5nm) in ARD Lösungen könnten ein Zwischenprodukt im Bildungsprozeß des H-Jarosits sein. Dann könnte die Charakterisierung des Niederschlags im gealterten Lettenwasser Hinweise auf die Zusammensetzung der ultrafeinen Partikel im frischen Lettenwasser geben. EXAFS-Messungen zur Aufklärung der chemischen Bindungsverhältnisse in Kolloidpartikeln (<5nm) sind in Arbeit.

Real time ellipsometry in conjunction with real time stress and evaporation rate measurement is applied to ion beam assisted deposition of boron nitride films. Information on the reactivity of boron with water vapor is obtained from in situ ellipsometry data and conclusions concerning the stability of BN films are drawn. Damage formation in the Si substrate in the beginning of the deposition process is revealed. Real time stress measurement in combination with ellipsometry shows, that stress buildup occurs in the end-of-range region of the plating ions and not in the whole collision cascade or thermal spike region. Information on dynamic densification of tBN, derived from real time ellipsometry and evaporation rate measurement, is reported for the first time. A new model for cBN growth is proposed: instead of compressive stress, a certain level of tBN densification is required for cBN to nucleate. It is shown that tBN density and compressive stress are not necessarily correlated parameters.

A DC glow discharge source with controlled plasma potential was developed for application in plasma immersion ion implantation processing of materials.

Iron was implanted with 50 keV Si ions. The depth distribution of the formed Fe-Si phases was investigated by depth selective conversion electron Mossbauer spectroscopy.

Durch Ionenstrahlverfahren hergestellte Eisensilizidproben wurden mittels XPS und AES untersucht.

In Pressurised Water Reactors (PWRs) the parameters of the coolant may differ from one loop to another and change in time during transients. In case of an undesired decrease of the boron acid concentration we speak about boron dilution transients. In other cases also the coolant temperature may be affected, e.g. by overcooling of a loop if a main steam line break happens. Both kinds of transient lead to a positive reactivity insertion, which may cause a dangerous power excursion. For the analysis of the core behaviour during boron dilution transients and main steam line breaks, coupled neutron kinetic / thermal hydraulic codes are necessary. These codes must contain models of the coolant mixing on its way from the inlet nozzles to the core entrance, because the reactivity insertion strongly depends on the distribution of these parameters at the core inlet. The coolant mixing mainly happens in the three-dimensional flow field inside the complex geometry of the downcomer and lower plenum. It depends signifi-cantly on the construction of the reactor vessel. The modelling of coolant mixing was carried out by detailed computational fluid dynamics (CFD) calculations with the code CFX 4.2. For the validation of the computational results, the ROCOM test facility was built, a fluid dy-namic model of the reactor in the scale of 1:5. The reactor vessel is made of Plexiglas for flow visualisation and LDA measurements. The four loops dispose of separately controllable main coolant pumps. Plugs of coolant with low boron acid concentration are modelled by salt water injection. The use of a system of wire-mesh sensors allows to measure salt concentra-tions at over 1000 locations with a maximum time resolution of 200 Hz. Measuring locations are at the reactor inlet, at the core inlet as well as in the upper part and at the lower end of the downcomer. The experiments as well as the calculations have shown, that the mixing is in-complete. In case of stationary coolant flow in all loops a disturbance of boron concentration or temperature is transferred to a sector of the core inlet plane, which corresponds to the loca-tion of the inlet nozzle. In the steady state, the concentration respectively temperature in the centre of the sector almost reaches the amplitude of the disturbance at the inlet nozzle. A short plug of boron diluted water experiences a better mixing: due to the vortices in the downcomer different portions of the disturbance are transported with different velocities. This causes a dispersion of the front and the end of the plug (axial mixing). If the plug is short enough, the maximum concentration decreases. Further, experiments and calculations are going on to be performed for the investigation of mixing under transient conditions (start of circulation). Response functions will be calculated for the development of a fast running mixing model.

A DC glow charge plasma source was used to implant various types of materials (Al, SS 304, Si) with nitrogen.

High-resolution x-ray diffraction methods have been used to characterize nitrogen-doped silicon obtained by plasma immersion ion implantation.

The formation of iron disilicides by ion implantation at room temperature and the subsequent ion beam induced epitaxial crystallization process was studied by conversion electron Mössbauer spectroscopy. Implantation with 195 keV Fe ions with doses from 7 x 1015cm-2 to 2 x 1017cm-2 at room temperature leads to an amorphized top layer of about 300 nm thickness. The concentration profiles determined by Auger electron sputter depth profiling have maximum iron concentrations from 0.7 at.% for the lowest dose up to 21.1 at.% for the highest dose at about 100 nm depth. The Mössbauer spectra show similar broad quadrupole doublets for each dose which could not be attributed to any known amorphous or crystalline iron silicide phase. The subsequent irradiation with 1 x 1016cm-2 500 keV Si ions at 350°C induces the formation of iron disilicide phases and the crystallization of the Si substrates. For the samples containing the lowest iron content of 0.7, 2 and 5 x 1016cm-2 the metastable g-FeSi2 is produced whereas for doses of 1 x 1017cm-2 and higher the formation of a phase mixture of a- and b-FeSi2 is found.

Magnesium and aluminum were alloyed by implantation with iron ions. The implantation energy was 200 keV while the ion doses ranged over several decades up to 9x1017 cm-2. In this way it was possible to obtain highly disordered alloyed layers with up to 90 at.% iron [1]. To study possible ordering and redistribution processes samples were annealed in vacuum at subsequently increasing temperatures up to 600 °C for aluminium and up to 400 °C for magnesium. The annealing process was observed by conversion electron Mössbauer spectroscopy, Auger electron depth profiling, and x-ray diffraction. In the case of the Fe-Al system iron aluminides are formed. In the case of the Fe-Mg system (insoluble with each other), a-iron is precipited in small clusters.
[1] H. Reuther, M. Betzl, W. Matz, E. Richter, Hyperfine Interactions 113 (1998) 391

Four different combinations of ⁹⁶ ₄₄Ru and ⁹⁶ ₄₀Zr nuclei, both as projectile and target, were investigated at the same bombarding energy of 400 AMeV using a 4pi detector. The degree of isospin mixing between projectile and target nucleons is mapped across a large portion of the phase space using two different isospin-tracer observables, the number of measured protons and the t/³He yield ratio. The experimental results show that the global equilibrium is not reached even in the most central collisions. Quantitative measures of stopping and mixing are extracted from the data. They are found to exhibit a quite strong sensitivity to the in-medium (n,n) cross section used in microscopic transport calculations.

To date most Tc compounds suitable for coupling to biologically active molecules, e.g. CNS receptor targeted agents, are square-pyramidal complexes of the oxo ion [Tc=O]³⁺. However, the properties and thus the in vivo behaviour of such complexes are strongly influenced by the quite polar Tc=O unit offering a free position trans to the oxo ligand for further reaction in vivo. The stricter the requirements for specific agents, the more important is the question whether such a polarity is beneficial or not. Alternatives are oxo-free lower oxidation states. Here we report on prototypic trigonal-bipyramidal mixed-ligand complexes 1, 2 and 3 which are neutral, non-polar and robust since they contain sterically well shielded oxo-free Tc(III). We describe the syntheses and structural analyses of ⁹⁹Tc complexes with simple co-ligands serving as models for functionalized derivatives, the no-carrier-added preparation of the analogous ^99mTc-complexes as well as their stability in aqueous solution and in plasma, and their biodistribution in rats.

Auf dem Wege zu einer ökonomischen und sicheren Energietechnologie muß die Fusionsforschung Materialien entwickeln, die möglichst hohen Strahlenbelastungen standhalten und ein Minimum an langlebiger Aktivierung produzieren. Dazu ist eine geeignete Neutronenquelle als Bestrahlungsgerät unerläßlich. Neben dem Projekt IFMIF bleibt der Vorschlag des Budker-Instituts Novosibirsk für eine Neutronenquelle auf der Grundlage einer gasdynamischen Falle aktuell. Prinzipiellen Vorteilen dieses Quelltyps steht der Nachteil gegenüber, dass seine Funktionsfähigkeit durch die bisher verfügbare Datenbasis noch nicht ausreichend belegt werden kann. Der Vortrag gibt eine Einführung in das Konzept dieser Neutronenquelle und legt die Forschungsergebnisse dar, die in den letzten Jahren, teilweise in Kollaboration mit dem Forschungszentrum Rossendorf, erzielt wurden.

The confinement of the fast, anisotropic ions is one of the basic objectives of the GDT experimental research program. The approach consists in comparing the measured ion parameters with those predicted by computer simulations based on the theory of Coulomb collisions. A broad set of diagnostics for measurements of fast ion parameters has been developed. In particular, it includes the measurement of the local energy distribution function. In parallel the Monte Carlo transport code FIT, which simulates fast ion histories in the frame of the lassical theory has been developed. The comparison of the measured and computed parameters clearly shows that the energy confinement time of the fast ions is governed by Coulomb collisions only and significant anomalous ion losses were not yet observed in GDT experiments up to the present plasma parameters.

Electromagnetic levitation is a well-known technique for containerless processing of metallic samples. If the sample is melted the electromagnetic forces cause a melt motion inside the droplet. This motion is of interest since it influences shape oscillations or heat transfer within the droplet, or may even effect the stability behaviour of the droplet at all. First, the axisymmetric case is considered allowing no variations of quantities around the vertical axis which is the pronounced axis due to the symmetry of the levitating or heating magnetic fields. Typical mean flow strucures are calculated depending on the skin-depth parameter and the magnetic field interaction parameter for the two cases of a uniform or linear magnetic field. The stability of this axisymmetric flow is analyzed showing that those flow fields become unstable only at high numbers of the magnetic field interaction parameter N. This is in contrast to a few experimental observations indicating that oscillatory motions take place already at much lower values of N.
Therefore, the three-dimensional stability of the flow is investigated. This stability analysis is performed using spectral methods. As expected the first instability is characterized by an azimuthal wave number of one. But it is found that the most dangerous three-dimensional instability occures at relatively small interaction parameters being by orders of magnitude lower than the critical values of the axisymmetric case.

This work presents a numerical and experimental study of the growth of single intermetallic-compound crystals by the floating-zone method using a radio frequency (RF) heating magnetic field. The quality of the grown crystals depends strongly on the growth conditions, particularly on the shape of solidification front. To obtain single crystals of complex composition, a convex to the melt growth interface is desirable. The shape of the solid-liquid interface can be strongly influenced by the convective heat transport in the melt. There is a number of mechanisms driving the melt convection: differential rotation of the crystal and the seed, buoyancy, thermocapillarity and electromagnetic forces due to the RF heating. The aim of this work is to find out the growth parameters ensuring a desired shape of the crystalization front. The numerical study consists of two major parts - finding of the electromagnetic field induced by the RF-heater coil and the solution of the coupled heat and hydrodynamic problems. For the solution of the electromagnetic problem a novel boundary-integral method is developed. This method involving integration only along the surfaces is easily applicable to complex geometries at arbitrary skin depth. The heat and hydrodynamic problems are solved by a numerical code based on the control volume technique using a triangular finite-element-like mesh adapting to the solid-liquid interfaces. For small-diameter crystals considered here, only the thermocapillary and electromagnetically-driven convections turn out to be significant for the heat transport. Pure heat diffusion is found to result in the interfaces which are slightly convex over most of the diameter except close to the crystal surface where the interface is always concave to the solid phase. Such a form of the interface is determined by the Ohmic dissipation in the skin-layer and the heat radiation from the surface. A part of the produced heat is emitted directly from the liquid zone that makes the surface colder than the underlaying melt. Therefore the interface is concave in the vicinity of the surface. The rest of the heat released in the skinlayer is conducted radially inwards into the melt from where it enters the crystal to be emitted further away from the liquid zone. This inward heat flux is responsible for the central convex part of the interface. The numerical results give evidence that at the minimal length of the liquid zone, electromagnetically-driven convection may be so weak that it has no significant effect on the heat transfer. Strength of the forced convection rapidly increases with the heating power resulting in a concave interface over the whole diameter. Thermocapillary convection is found to be significant at smaller crystal diameters where it can substantially counterbalance the electromagnetically-driven convection in the bulk of the melt. Numerically found interface shapes are compared with experimental results obtained on a model system of Ni crystals.

Shape oscillations of electromagnetically-levitated metal droplets can be used to measure the surface tension and viscosity of liquid metals. The first determines the frequency while the second accounts for the attenuation rate of the oscillations. Until now the effect of the magnetic field on the frequency spectrum has been considered only in the perfect-conductor approximation where the action of the magnetic field reduces to the magnetic pressure on the liquid surface. In this approximation, magnetic field influences droplet oscillations in two ways. First, it causes a static deformation of the droplet. So the oscillations in the magnetic field occur about an aspheric basic shape. Second, the coupling between the shape variation and the magnetic field gives rise to a new oscillation mode called hydromagnetic surface wave. For small droplets magnetic field causes a slight perturbation of oscillations with both aforementioned effects resulting in the same order small corrections to the frequency spectrum of an inviscid spherical droplet. Magnetic field yields the same order relative correction also for the damping rate of oscillations of a viscous droplet. But there is no direct influence of the magnetic field on the damping rate of oscillations that is a serious drawback of the perfect-conductor approximation. Since for low-viscosity metal droplets the damping rate itself is small, even a weak direct effect of the magnetic field might be significant.
This work is dealt with the effect a high-frequency alternating magnetic field on the damping of the shape oscillations of viscous metal droplet. Conversely to the viscosity, high-frequency magnetic field is found to reduce the damping of the oscillations. We find the leading order solution of the damping rate by assuming the viscosity to be small but the frequency of the magnetic field to be high. The magnetic pressure is considered to be small with respect to the capillary pressure so that the static deformation of the droplet may be neglected. Besides, we assume the Reynolds number of the fluid flow driven by the magnetic field at finite skin depth in the droplet to be small so that the coupling between the base flow and shape oscillations may be neglected. Under these assumptions we formulate a theory for the case when both the magnetic field and oscillations are axisymmetric. The theory is applied to calculate the effect of a uniform magnetic field on the damping of the axisymmetric fundamental mode.

An axially symmetric isothermal liquid metal flow induced by a low frequency low induction rotating magnetic field in a cylindrical cavity is considered. This problem has already been addressed by several investigations but the existing results are still contradicting. We consider the problem numerically employing highly accurate spectral methods. We seek for the steady solution in vorticity-stream function formulation in space of base functions build up from Chebyshev polynomials to satisfy appropriate boundary conditions. The dynamical system is obtained and the spectrum of the linearized problem is found gradually increasing the forcing parameter. We evaluate the critical magnetic Taylor number for the basic solution in 0.1% accuracy as 166300 (for a diameter to height ratio 1). The oscillatory instability is found to be of another type than the expected Taylor-Goertler vortices. Several additional monotonically unstable steady solutions are detected in the range where the basic solution is stable. These additional solutions are marked by an additional couple of secondary vortices counter-rotating in the meridional plane near the side wall at the mid-height. Some of the additional steady solutions are particularly close to the basic steady state and therefore take high spatial resolution to be distinguished. We consider also the time dependent solution that allows much higher spatial resolution. The linear stability results were verified comparing to the dynamical parameters of the time evolution in the near-critical regime. This comparison shows 0.1% agreement. The unstable additional steady solutions close to the basic steady state indicate instability to small finite size perturbations. The closest one gives an estimate from above for the minimum energy of the unstable finite perturbation. This estimate is improved considerably by series of numerical time-dependent solutions developing from additional steady states. The basic state is found to be unstable with respect to a finite size Taylor-Goertler type perturbation of less than 3.0E-8 size (in relative energy terms). Such a small perturbation excites long-lasting non-linear oscillations already at 3/4 of the critical forcing. This excited regime in turn is found to be unstable to another instability that finally reestablishes the basic state. These results predict the possibility of an unpredictably oscillating flow already in the linearly stable regime. The results indicate that an experimental observation of the linear instability is hardly possible. The obtained results also explain the big differences in previous numerical results concerning the stability of the rotating magnetic field driven flow.

Lorentz forces can be used to control the near wall flow of low conducting liquids like sea-water. To achieve force densities strong enough to influence the flow, both magnetic and electric fields have to be applied to the fluid. Here the wall parallel Lorentz force in streamwise direction was generated by means of periodically arranged electrodes and permanent magnet strips of alternating polarity and magnetization direction, respectively. In a first approximation the resulting force is independent of the spanwise coordinate and decays exponentially with the wall distance. Such a force distribution acts as a source of momentum to the flow. It gives the possibility to compensate for viscous losses and to counteract adverse pressure gradients, thereby stabilizing the boundary layer and preventing separation.
Experimental results on the control of a flat plate boundary layer in a sodium chloride solution up to Re=9·105 will be given. LDA measurements show the effect of the Lorentz force on the boundary layer profile. At moderate force strength the mean velocity profiles are characterized by momentum thicknesses smaller than in the unforced case, at high enough Hartmann numbers a wall jet develops. Additionally, a turbulent, but practically non growing boundary layer has been observed for a special combination of Reynolds and Hartmann number. The fluctuating streamwise velocity component is slightly damped due to the accelerating action of the Lorentz force. Force balance measurements on the controlled flat plate show a reduction of the total drag by up to 80% compared to the uncontrolled case. The sole reason for this dramatic drag reduction is the momentum gain caused by the Lorentz force. From the velocity profiles one can conclude on a skin friction increase in the forced cases. However, the momentum gain overcomes the skin friction increase.
The effect of a suction-side, streamwise Lorentz force on a NACA-0017-like hydrofoil is quantified by means of force balance measurements for chord-length Reynolds numbers of 3 to 8·104. Depending on the angle of attack, two different effects are observed. (1) At small angles of incidence, a moderate increase in lift due to additional circulation is observed. Simultaneously, a decrease in the drag of the hydrofoil is caused by the added momentum. (2) At higher angles of attack, where the unforced hydrofoil would normally stall, a more pronounced lift increase (90% at Re=3·104) and a corresponding drag reduction are observed due to separation prevention.
Direct numerical simulations at low Reynolds numbers confirm the physical tendencies of the experiments.

A contactless control of melt convection is important for many crystal growth technologies. Typically steady magnetic fields are used to damp such flows and, in particular, turbulent fluctuations. Surprisingly, active flow driving forces due to alternating magnetic fields can be of stabilizing character, too. We present numerical results for the combined action of steady and alternating magnetic fields taking into account rotating, pulsating and travelling magnetic fields. Results will be given for the silicon Czochralski and the vertical Bridgman crystal growth process. For given thermal conditions of the process a typical buoyancy convection takes place. In case of the Czochralski process the convection is additionally determined by crystal and crucible rotations and the thermocapillary driven flow at the free melt surface. We study the influence of different magnetic field combinations on these melt convections. Results will be presented in which way different combinations of fields change the mean flow structure and influence the level of turbulent fluctuations. In order to limit the computational effort, we apply first a zero equation turbulence model based on the Prandtl mixing length hypothesis and afterwards a standard two equations turbulence model (k-omega).

Usually, MHD is understood as the forward problem of determiningvelocity and magnetic fields in the sense of solving the coupled system of Navier-Stokes equations and induction equation if some boundary conditions or types of forcing are given. For most laboratory and technical applications with small magnetic Reynolds number Rm the magnetic field is disturbed only slightly by the flow whereas it can modify the latter significantly via Lorentz forces. For higher Rm, however, the fluid flow can change the magnetic field drastically or can even lead to self-excitation of a magnetic field via the dynamo effect.

In the inverse problems approach one strives to get information about the distribution of certain material parameters or temperature and velocity fields inside the fluid from measurements of appropriate quantities at the fluid boundary and/or outside the fluid. We restrict our interest on the spatial reconstruction of the velocity field (or of related mean-field quantities) purely from magnetic fields and electric potentials which can be measured outside the fluid body and at its boundary, respectively.

For the case of small Rm, which is most interesting for a number of technological applications like metal casting and crystal growth, it is necessary to apply external magnetic fields and to measure the flow induced magnetic fields and electric potentials. Analytical results concerning the uniqueness problem of velocity reconstruction /1/ as well as numerical illustrations /2/ are presented. The need of regularization of the inverse problem is discussed.

Some aspects of generalizing the method to high Rm, i.e. to an inverse dynamo theory, are also discussed. In particaluar, considering a modified Krause-Steenbeck dynamo model with radially varying alpha we show how this radial dependence can be inferred from the growth rates of several magnetic field modes. The connection of this problem with similar problems in quantum mechanics, like isospectral potential deformations, is worked out.

A set of electric arc evaporators has been installed inside the gas dynamic trap experimental facility of the Budker Institute Novosibirsk. It is used for fast Ti-coating of the inner chamber surface. In this way the vacuum conditions could be substantially improved. Under the new conditions special experiments were carried out to measure the temporal and spatial variation of the neutral gas density during typical shots. The results of these measurements are presented and compared with those of numerical simulations by means of the Monte Carlo code TUBE.

The paper reports on the investigations of the confinement of neutral beam heated, high-ß and two-component plasmas in the Gas Dynamic Trap. The set of diagnostic methods which have been developed enabled the characterization of different energy loss channels. To analyze the plasma heating the energy balance models were applied. The measurements of the local energy and angular distributions of the fast ion minority are described and their results are presented. These measurements were done by injecting a focused, diagnostic neutral beam to produce a local charge-exchange target for the fast ions. The resulting charge-exchange atoms were registered by an electrostatic analyzer. The energy distribution function obtained was compared with the results of Monte Carlo and Fokker-Planck simulations.

This report summarizes the results of experimental investigations obtained during the last five years at the Gas Dynamic Trap experimental facility of the Budker Institute Novosibirsk. Due to an essential upgrade of the main components performed in this period, the following plasma parameters have been achieved: electron temperature - 90-110 eV, fast ion density - up to 0.8*10^13 cm^-3, mean energy of fast ions - 5-8 keV, plasma-ß - 15-20%. The paper describes the following investigations: effect of wall conditioning on neutral gas dynamics, longitudinal electron heat flux, confinement of the high-ß two-component plasma, fast ion parameters under high-ß conditions, fueling of the target plasma by gas puffing. It presents results of measurements and of calculations.

By upgrading the high-energetic neutral beam injection system of the gas dynamic trap (GDT) experimental facility of the Budker Institute Novosibirsk the plasma heating could be substantially improved. Now an electron temperature up to 120 eV is attainable compared to 70 eV before. Under the new conditions various heating scenarios and the plasma confinement were studied.

Übersicht über die Methoden und Einsatzmöglichkeiten der Röntgenreflektometrie (XRR). Diskussion der Anwendungen der XRR bei Herstellung und Charakterisierung dünner Schichten und von Vielschichtsystemen. Als Beispiele wurden u. a. Ergebnisse eigener Messungen an der Rossendorfer Beamline (ROBL/ESRF)in Grenoble herangezogen.

Semiconductor nanoclusters embedded in a dielectric matrix are of great interest for future optical and electrical applications in microelectronic circuits. The contribution is focused on the study of Ge-nanoclu-sters generated by ion beam synthesis (IBS) in thermally grown thin SiO2 layers (20-50 nm). TEM and RBS analysis show, that the cluster formation and the elemental Ge distribution is strongly influenced by the annealing condi-tions, which is described in detail for furnace and rapid thermal processing (800°C-1100°C). TEM investigation revealed that in dependence on specific implantation and annealing conditions a broad nanocluster band in the centre of SiO2-layer or a d-like one in the distance of 5-7 nm from the SiO2/Si interface can be generated. HRTEM characterisation of samples emerge that the Ge clusters in the thin SiO2 films are amorphous opposite to earlier results were crystalline Ge nano-cluster were created in 500 nm SiO2 layers [1]. Long-term stability of grown clusters is an important feature for their further use in microelectronics. We identified the preparation conditions where the Ge nanocluster have a high stability and do not change with time and where the cluster are unstable and disappear completely after 2 month storage without any thermal treatment. Experiments with strong electron irradiation performed in a TEM with a FEG show the possibility of in-situ crystallisation of existing cluster as well as crystalline cluster formation in the samples where clusters before irradiation were not observed.
[1] J. v. Borany, R. Grötzschel, K.H. Heinig, A. Markwitz, W. Matz, B. Schmidt and W. Skorupa "Multimodal impurity redistribution and nanocluster formation in Ge implanted silicon dioxide films", Appl. Phys. Lett. 71 (22) 3215 (1997)

We have shown that holes with diameters in the nanometer range may be created in the Al2O3/NiAl(110) substrate if metal clusters deposited on it are irradiated by the intense convergent electron beam in TEM. The localisation and size of holes can be controlled to some extend. The formation of holes can be interrupted by lowering the beam intensity below a critical value. It can be continued by increasing the intensity above the threshold value. We have also disclosed the necessity of clusters' presence on the surface for the start of holes' formation.

Studies of the relaxation and confinement of hot anisotropic ions are considered to be the key elements of the gas dynamic trap (GDT) experimental research programme. The method of confinement study described consists essentially in the comparison of measured ion parameters with those predicted by computer simulations. To realize this approach a set of diagnostics for the measurements of local and global parameters of the fast ions has been developed. In particular, this set includes diagnostics to measure the local energy and the angular distribution functions. For numerical studies of the fast ion dynamics a Monte Carlo code based on the theory of two body Coulomb collisions has been elaborated. Comparison of the experimental data with the results of the simulation clearly demonstrates that the fast ion characteristic relaxation times in the warm target plasma are close to those determined by binary Coulomb collisions. Significant anomalous energy losses or scattering of fast ions have not been observed as yet. The measurements provide a maximum density of the fast ions with mean energy of about 8 keV up to 10E+13/cm^3, in good agreement with computer simulations. The increase of the neutral beam power and improved vacuum conditions of GDT made possible the access to plasma ß of as high as 30%.

ZrO2 layers stabilized with 9mol% Y2O3 of 35-100 nmthickness were deposited by sputtering on 200 nm thick Fe layers on Si/SiO2. Ion beam mixing induced by 300 keV Kr ions and 1.5 MeV Br ions bombardement was studied at temperatures ranging from 100 to 300 K. Samples were analysed by means of RBS, GXRD, and SEM techniques. RBS analysis revealed important atomic transport across the ZrO2/Fe interface. The amount of intermixed atoms increases with increasing ion dose. Ion beam mixing was observed at low temperaturesw. Upon 300 keV Kr-ion bombardment the tetragonal structure of as-deposited ZrO2(Y2O3) layers was transformed into the cubic one. High energy ion bombardment produces only transformations of the crystalline structure without any visible atomic transport and the formation of the rare FeO-wuestite phase. Kr blistering was observed from samples implanted with 300 keV Kr ions to fluences exceeding 1e16 at/cm2 at 100 K and 5e16 at/cm2 at RT.

Interface mixing between ZrO2 and Fe by Kr ion irradiation was studies in order to understand atomic effects of adhesion of ceramics on metals. No formation of new phases was observed. The main effect is connected with the redistribution of oxygen near the interface. It was followed with RBS and TEM.

The report gives an overview on the activities of the Institute of Safety Research in 1999.

Ion implantation of Ca and/or P into Ti or Ti alloys is of interest in order to enhance mechanical properties and biocompatibility for medical applications . With this motivation the microstructural changes of the implanted surface layer were studied. Surface near implantation of high doses of calcium results in an oxidation of the modified layer and the formation of CaO. For deeper calcium implantations, precipitation of the metastable hexagonal modification of calcium has been observed instead of the cubic equilibrium phase. Beside these new phases partial amporphization is observed. High dose implantation of phosphorus leads mainly to amorphization of the implanted layer. This hinders the reaction with oxygen during implantation and room temperature aging. High dose double implantation with P followed by Ca also leads to partial amorphization. No indication for new phases containing Ca and P is found.

Overview about the Materials Research Hutch and its instrumentation. Representation of results gained in the first year of operation: powder diffraction on HTSC; formation of SiC in Si; reflectometry on multilayers using anomalous scattering; H in Nd thin films; in-situ study of structural changes in TiAlV;

Populärwissenschaftliche Darstellung von ROBL. Beispiele zu Experimente im Bereich der Ökoradiochemie (Abwässer des Uranbergbaus) und der Materialforschung.

Erzeugung und Eigenschaften von Synchrotronstrahlung und Infrarotstrahlung aus FEL; Ausgewählte Anwendungsbeispieöle aus Physik, Werkstofforschung, Umweltstudien und Medizin.

Description of the experimental set-up of the Materials Research Hutch. Report of first results from structural follow-up during in-situ annealing experiments. Discussion of possibilities for a in-situ deposition chamber.

Description of the Materials Research Set-up of ROBL. Presentation of the results obtained in the first year of operation.

Description of ROBL, its experimental possibilities and the research oppotunities for east European scientist under EC funding.

The project contributed to answer issues which are identified for future BWR plants:

• The design of innovative components
• An enlarged assesment of the performances
• A better understanding of the underlying physical phenomena.

The results of an intercomparison of neutron dosimetry measurements in the ex-vessel cavity of VVER-1000 type reactor are submitted. A good agreement of measured results of different independent participants was found for the different activation reactions. Evaluated absolute dosimetry data are presented. Also good agreement of neutron transport calculation results obtained by as Sn and Monte Carlo methods by independent laboratories with measurements is demonstrated.

: The KORPUS irradiation experiment has been used to test and demonstrate improvements of the pressure vessel dosimetry methodology developed in Rossendorf. The Monte Carlo Code TRAMO has been recently supplied with a new data treatment procedure for elastic scattering and with extended geometries. The new code version has been used to accurately calculate absolute neutron fluence spectra at detector positions in the KORPUS irradiation facility at the RIAR in Dimitrovgrad. The influence of used approximations on the obtained fluences was investigated with calculations for different model variants.
The activation rates calculated with these spectra have been compared with results of activation measurements with detectors irradiated at the International Dosimetry Benchmark at the KORPUS facility. Based on the measured data the calculated fluence spectra have been adjusted with help of the adjustment code system COSA3, a newly extended multispectrum version of COSA2. A comprehensive uncertainty analysis was accomplished for the fluence calculations and the measurements.

The assessment of the uncertainties of neutron transport calculation results caused by uncertainties of the input data is important for the direct use of the calculated fluences and even indispensable for the further improvement of the data by spectrum adjustment on the basis of experimental results. A former work of two of the authors has approached this topic first for a VVER-1000 using a one-dimensional reactor model and applying spectrum adjustment in a single spectrum approximation. In the present work 2D/1D-SN-synthesis calculations have been used to determine the neutron group spectrum covariances including cross-correlations between interesting positions. As possible sources of uncertainties neutron data and reactor model parameters were considered, whereas the uncertainties caused by the calculational method were considered negligible in view of the now available precision of Monte Carlo simulations. The input data uncer-tainties have been updated including newer information.
The calculated absolute group fluence spectra have been adjusted to measured ex-vessel cavity activation rates with help of the COSA3 generalized least squares multispectrum adjustment code. Adjusted fluences for different detector positions have been compared with corresponding fluences obtained with single spectrum adjustments. The results are discussed and conclusions have been drawn. Results obtained with Russian LUND- and ENDF/B-VI-based cross section and fission spectrum covariance data have been compared.

A series of oxorhenium(V) SNS/S mixed ligand complexes [ReO(Lⁿ/L)] carrying different types of tridentate ligand [L¹: C₂H₅N(CH₂CH₂S)₂, L²: (C₂H₅)₂NCH₂CH₂N(CH₂CH₂S)₂, L³: C₂H₅SCH₂CH₂N(CH₂CH₂S)₂ and L⁴: 2,6-(SCH₂)₂NC₅H₃] and the same monodentate coligand (L: C₆H₅S) have been synthesized and characterized by spectroscopic methods and elemental analyses. X-ray structure determination was performed for complexes 3 and 4. Complex 3 adopts the expected distorted trigonal bipyramidal geometry around the metal in a syn configuration, while complex 4, due to the aromatic character of the nitrogen of the SNS donor-atom set, exhibits a distorted square pyramidal geometry. The interaction of complexes 1 - 4 with glutathione (GSH) was studied by high performance liquid chromatography (HPLC), revealing the rapid formation of the respective daughter complexes 5 - 8, wherein the L coligand has been substituted by GS. The daughter complexes 5 - 8 have been characterized by ES-MS and a battery of NMR measurements involving HETCOR, COSY and NOESY procedures. Kinetic aspects of the interaction of complexes 1 ¾ 3 with GSH have been studied by isothermal titration microcalorimetry providing direct measurements of the interaction rate constants as well as the total enthalpy change. The reaction of complex 1 is characterized by the slowest and that of complex 2 by the fastest rate. This is in agreement with previously reported trends for analogous ^99mTc complexes.

3D synthesis based on detailed and improved calculations by SN-codes DORT, ANISN and the BUGLE-96 library has been validated using reference activation data from the Balakovo-3 ex-vessel dosimetry benchmark. The 3D spatial neutron source distribution including pin-to-pin power variations and the complex baffle construction were modeled in detail. All particulars of reactor operation such as coolant temperature changes, assembly power asymmetry and fuel burnup influence on space-energy neutron source distributions were taken into account.
The discrepancies found do not exceed 10%. The average relation between calculated and measured valuse is 0,99. The calculated results show a systematic underestimation for 237Np(n,f) ( -6% on the average), 93Nb(n,n') ( -8%) and systematic overestimation for 58Ni(n,p) and 54Fe(n,p) ( +7%). Generally, the agreement between experiment and calculation is even closer as expected from uncertainty considerations.

A high dose of 1x1018 cm-2, 60 keV carbon ions was implanted into single crystalline 6H silicon carbide (SiC) at elevated temperatures. The formation of carbon phases in the crystalline SiC lattice was investigated by cross sectional transmission electron microscopy. An amorphous, carbon rich phase was produced at 300oC. Precipitates of graphite were obtained at 600oC, whereas at 900oC small diamond grains were produced. These grains are in perfect epitaxial relation with the surrounding SiC lattice.

Pt films on alumina substrates, both in their as-received and annealed states, have been extensively characterized by slow positron implantation spectroscopy (SPIS). Bulk Pt samples have been investigated by conventional positron annihilation spectroscopy (PAS) as well as by SPIS. A variety of state-of-the-art theoretical calculations have been performed to aid the interpretation of experimental findings. The research shows that a re-interpretation of earlier defect studies of bulk Pt by PAS is required in order to achieve a satisfactory agreement with the present experimental findings and theory.

A full power MSLB analysis for the TMI-1 NPP using the coupled code DYN3D/ATHLET was performed in the frame of the OECD Benchmark for coupled neutron kinetics/thermohydraulics codes. The analysis shows a return-to-power after the scram. The impact of the description of coolant mixing inside the reactor pressure vessel was investigated. The exclusion of the coolant mixing enhances this second power peak by about a factor of two in comparison to the first calculation, where the coolant mixing is treated by means of an experimentally determined mixing ratio. The neglection of mixing applied in point kinetics calculations with compatible feedback coefficients shows the opposite effect on the obtained reactor power.

DYN3D is a three-dimensional computer code for calculating transients in light-water reactor cores with quadratic (version DYN3D/R) or hexagonal (version DYN3D/H) fuel assembly geometry. Starting from the critical state (keff - value, critical boron concentration or critical power) the code allows to simulate the neutroniand thermal-hydraulic core response to reactivity changes caused by control rod movements and/or changes of the coolant core inlet conditions. Burn-up calculations can be performed. The depletion state can used as starting point for the transient. The steady state and transient Xe and Sm concentrations can be analyzed. The decay heat is takeinto account.

Extended duality (i.e. the replacement of the thermal dilepton emissivity of hadron matter by that of q bar q annihilation)
is used to explain the dilepton data of heavy-ion experiments at CERN-SPS. Taking into account the background contributions (hadronic cocktail, Drell-Yan, semileptonic open charm decays) the spectral shapes of the CERES, NA38/50 and HELIOS-3 data in experiments with lead and sulfur beams can be well described while the normalizations of the sulfur beam data is problematic.

The structure of dioxouranium(VI) as a function of pH at different (CH3)4N-OH concentrations has been investigated with the aid of U LIII EXAFS. Polynuclear hydroxo species were identified by an U-U interaction at 3.808 Å at pH = 4.1. The precipitate formed at pH = 7 has a schoepite like structure. In solution at high pH [0.5M (CH3)4N-OH], the EXAFS and data are consistent with the formation of a monomeric four coordinated uranium(VI) hydroxide complex UO2(OH)42- of octahedral geometry. The first shell contains two O atoms with a U=O distance of 1.830 Å, and four O atoms were identified at a U-O distance of 2.266 Å.
In strong alkaline solutions [> 1 M (CH3)4N)-OH], 17O-NMR spectra indicate the presence of two species, presumably UO2(OH)42- and UO2(OH)53-, which are in rapid equilibrium with one another at 268 K in aqueous solution.

We analyze the production of Φ mesons in πN and NN reactions in the near-threshold region, using throughoutly the conventional "non-strange'' dynamics based on such processes which are allowed by the non-ideal ω - Φ mixing.
We show that the occurrence of the direct Φ NN interaction may show up in different unpolarized and polarization observables in π N to NΦ reactions. We find a strong non-trivial difference between observables in the reactions pp to ppΦ and pn to pnΦ caused by the different role of the spin singlet and triplet states in the entrance channel for the Φ meson production mechanisms. A series of predictions for the experimental study of this effect is presented.

A covariant model based on the Bethe-Salpeter formalism is proposed for investigating the near-threshold deuteron disintegration via electromagnetic and weak interactions. The solar proton burning process $pp\to De^+\nu_e$ and
its astrophysical low-energy cross section factor $S_{pp}$ areconsidered within this formalism as well.
Results of numerical calculations of the energy dependence of relevant cross sections and of $S_{pp}$ are presented.
Our results confirm previous canonical values. The energy dependence of the $S_{pp}$ factor is rather close to phenomenological extrapolations commonly adopted in computations of solar nuclear reaction rates.

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