Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Gold nanoparticle arrays manufactured by a modified Electron Beam Lithography method are presented. The method allows to write highly ordered dot structures with a dot size of 50 nm and total area of 4 x 4 mm in a reasonable time.

The arrays are evaluated with respect to the desired application as plasmonic sensors. Therefore the uniformity of the particles created by the modified method is investigated. Using far-field optical spectroscopy the sprectral position and FWHM of the surface plasmon resonance (SPR) of the arrays are determined. Influences of plasmonic coupling effects on the SPR properties of closely packed array structures are elucidated by comparing the results to single particle SPR spectra. The experiments are conducted on arrays with different interparticle spacings.

We present results on dielectron production in Ar+KCl collisions at 1.76A GeV. For the first time $\omega$ mesons could be reconstructed in a heavy-ion reaction at a bombarding energy which is well below the production threshold in free nucleon-nucleon collisions. The omega multiplicity has been extracted and compared to the yields of other particles, in particular of the phi meson. At intermediate e+e- invariant masses, we find a strong enhancement of the pair yield over a reference spectrum from elementary nucleon-nucleon reactions suggesting the onset of non-trivial effects of the nuclear medium. Transverse-mass spectra and angular distributions have been reconstructed in three invariant mass bins. In the former unexpectedly large slopes are found for high-mass pairs. The latter, in particular the helicity-angle distributions, are largely consistent with expectations for a pair cocktail dominated at intermediate masses by delta Dalitz decays.

Recent investigations of Al-doped ZnO (AZO) thin films using techniques based on synchrotron radiation show that formation of metastable homologous phase (ZnO)3Al2O3 is the reason for the observed deterioration of the film electrical properties at deposition temperatures higher than certain optimum value [1]. The effect of this phase formation on the AZO film optical properties has not been studied yet. Moreover, little is known about optical properties of ZnO-Al2O3 solid solutions in general and (ZnO)3Al2O3 phase in particular, although this information might facilitate in situ diagnostics of the film properties evolution. The present work is focused on characterization of AZO and undoped ZnO films by spectroscopic ellipsometry in a wide spectral range (0.73-5.8 eV). For selected samples, ellipsometric measurements were combined with reflection and transmission measurements. The films with defined Al concentrations (cFAl=0-20 at.%) grown by reactive pulsed magnetron sputtering at temperatures ranging from RT to 550 °C were investigated.

The complex dielectric function of AZO films was obtained using a general oscillator model which combines Drude term in order to account for the free electron absorption with parameterized semiconductor oscillator model (PSEMI) [2] to account for interband transitions. The comparison of undoped ZnO and AZO films with the highest crystallinity shows that an addition of ~1 at.% of Al leads to the lowest electrical resistivity and to substantial decrease of the refractive index in the whole spectral range. This is accompanied by broadening of the PSEMI oscillator around the fundamental transition energies. It is characteristic of ZnO with high defect concentrations and is consistent with observed presence of the (ZnO)3Al2O3 phase-related peaks in x-ray absorption near edge structures (XANES) of Al K-edge. The AZO films remain conductive with cFAl values increasing up to ~8-10 at.%, while their (ZnO)3Al2O3 phase-related peaks in Al K-edge spectra scale with cFAl. In this case, refractive index decreases and PSEMI oscillator broadens further which is in agreement with deteriorating film crystallinity.

Finally, increasing cFAl>10 at.% leads to formation of insulating nanocrystalline films, which show even more intense (ZnO)3Al2O3 phase-related XANES peaks. These films have the lowest refractive index, which, however, is still substantially higher than that of amorphous Al2O3. It is observed that these films have significantly lower amplitude and a blue-shifted PSEMI oscillator compared to conductive AZO films. The latter may be explained neither by the Burstein-Moss shift because the films are insulating nor by effective medium approximation using optical constants of ZnO and Al2O3. Instead, it is explained in analogy to optical properties of the metastable wurtzite Mg(x)Zn(1-x)O alloys.

[1] M. Vinnichenko, R. Gago, S. Cornelius, N. Shevchenko, A. Rogozin, A. Kolitsch, F. Munnik, and W. Möller, Appl. Phys. Lett. 96, 141907 (2010).
[2] B. Johs, C.M. Herzinger, J.H. Dinan, A. Cornfeld, and J.D. Benson, Thin Solid Films 313-314, 137 (1998).

This seminar gives an overview on recent experimental studies involving terahertz (THz) and mid-infrared radiation from photoconducting antennae and from the free-electron laser in Dresden, Germany. In particular, microstructured scalable antennae for photoconductive THz emitters and semiconductor quantum well detectors for quadratic autocorrelation of pulsed THz and mid-infrared radiation will be discussed. The final part of my talk will concentrate on nonlinear THz spectroscopy, in particular THz sideband generation and coherent dynamics of excitons dressed by strong THz beams.

The LIMMCAST program at HZDR models the flow fields in mould, tundish and nozzle using low-melting liquid metals. It provides detailed flow measurements which may serve for the validation of related codes. Here we present numerical simulations using the CFX code for the influence of an electromagnetic brake on single- and two-phase flows in the mould. These simulations are done in close relation to LIMMCAST experiments. Contrary to the expectation, the local flow around the jets was intensified remarkably and lead to an asymmetric flow at the center plane in the presence of the magnetic field in case of electrically insulating mould walls. For electrically conducting walls, the jet becomes rather stable. It turns out that the electrically conducting boundary conditions have a great impact on the flow structure with the imposition of an external static magnetic field. For the two-phase case of injected argon bubbles, the model problem of a rising bubble driven flow in an external magnetic field is considered.

The few-group cross section libraries, used by reactor dynamics codes, are affected by the spectral history effect – a dependence of fuel cross sections not only on burnup, but also on local spectral conditions during burnup. A cross section correction method based on Pu-239 concentration was implemented in the reactor dynamic code DYN3D.
This paper describes the influence of a cross section correction on full-core calculation results. Steady-state and burnup characteristics of a PWR equilibrium cycle, calculated by DYN3D with and without cross section corrections, are compared. A study has shown a significant influence of spectral history on axial power and burnup distributions as well as on calculated cycle length. An impact of the correction on transient calculations is studied for a control rod ejection example.

Magnetic excitations in copper pyrimidine dinitrate, a spin-1/2 antiferromagnetic chain with alternating g-tensor and Dzyaloshinskii-Moriya interactions that exhibits a field-induced spin gap, are probed by means of pulsed-field electron-spin-resonance spectroscopy. In particular, we report on a minimum of the gap in the vicinity of the saturation field H_sat = 48.5 T associated with a transition from the sine-Gordon region (with soliton-breather elementary excitations) to a spin-polarized state (with magnon excitations). This interpretation is fully confirmed by the quantitative agreement over the entire field range of the experimental data with the density matrix renormalization group calculations for a spin-1/2 Heisenberg chain with a staggered transverse field.

We present magnetic-torque measurements of the organic superconductor κ-(BEDT-TTF)₂Cu(NCS)₂ for inplane magnetic fields up to 32 T. In this layered two-dimensional compound the superconductivity can persist even in fields above the Pauli limit of about 21 T. There, a pronounced upturn of the upper-critical-field line occurs and the superconducting phase-transition line splits and forms an additional high-magnetic-field phase. κ-(BEDT-TTF)₂Cu(NCS)₂ is a spin-singlet superconductor; therefore, such a superconducting high-field phase beyond the Pauli limit can originate only from Cooper pairing with finite center-of-mass momentum. The measurements are discussed in connection with a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, in accordance with earlier specific-heat observations. The torque experiments allow us to investigate the high-magnetic-field phase diagram and the FFLO state of κ-(BEDT-TTF)₂Cu(NCS)₂ in great detail.

Contemporary particle accelerators for fundamental research in particle physics like Fermilab's Tevatron and CERN's Large Hadron Collider (LHC) provide researchers with higher and higher luminosities. This sets the pace for the need for radiation hard detector materials for both beamline instrumentation and the physics experiments themselves.
Silicon pixel and silicon microstrip detectors are well developed devices for tracking applications in these high-energy physics experiments. However, these detectors are expected to reach the end of their lifetime within a few years due to their exposure to harsh radiation, of which the yearly level amounts to up to several 10¹⁴ hadrons/cm² during the foreseen 10 years of operation in the case of LHC experiments.
In order to protect sensitive experimental devices from adverse beam conditions, chemical vapor deposition (CVD) diamond, an artificially generated diamond material, is more and more being used in systems called Beam Condition Monitors
(BCM). The radiation level these sensors are exposed to is even higher than in the case of position sensitive tracking detectors. An example are the CVD diamond sensors of the BCM of the LHCb experiment at CERN, which is meant to withstand 10¹⁵ hadrons/cm² during 10 years.
Preparation of CVD diamond sensors for BCM applications are discussed in detail, together with the properties of this new material as a candidate for position sensitive devices in high energy physics experiments, addressing also operational questions like the appearance of erratic dark currents in polycrystalline diamond bulks. Other new materials for position sensitive devices such as CdZnTe and CdTe are discussed as well and compared to the well established silicon, together with a compilation of their properties relevant to particle detection.
Recent advances in the field of passive radiation monitors, where thermoluminescent sensors made from lithium fluoride now cover a dynamic range from several µGy up to 10⁵Gy, are also discussed briefly.

Ausgehend von Fragen wie „Was ist Masse?“ oder „Was passierte beim Urknall?“ erläutert der Beitrag Ziele und Methoden der Forschung am Large Hadron Collider (LHC). CERN, das Europäische Labor für Teilchenphysik, betreibt diesen größten Teilchenbeschleuniger der Welt in der Nähe von Genf. Angereichert mit zahlreichen Fakten wird dabei einerseits der bisherige Kenntnisstand dargestellt, andererseits aber auch die Theorien, welche man momentan am CERN der experimentellen Prüfung unterzieht. In zusätzlichen Info-Kästen wird genauer auf das Standardmodell der Elementarteilchenphysik, die einzelnen Experimente LHC und die Physik des Higgs-Bosons eingegangen. Eine umfangreiche Literaturliste, die sowohl neue Bücher als auch Webseiten mit Bezug zum Thema enthält, rundet den Artikel ab.

We report resistivity and upper critical field B_c2 (T) data for disordered (As-deficient) LaO_0.9F_0.1 FeAs_1-delta in a wide temperature and high field range up to 60 T. These samples exhibit a slightly enhanced superconducting transition at T_c = 28.5 K and a significantly enlarged slope dB_c2/dT = -5.4 T/K near T_c which contrasts with a flattening of B_c2(T) starting near 23 K above 30 T. The latter evidences Pauli-limiting behaviour (PLB) with B_c2(0) approximate to 63 T. We compare our results with B_c2(T)-data from the literature for clean and disordered samples. Whereas clean samples show almost no PLB for fields below 60-70 T, the hitherto unexplained pronounced flattening of B_c2(T) for applied fields H vertical bar ab observed for several disordered closely related systems is interpreted also as a manifestation of PLB. Consequences are discussed in terms of disorder effects within the frames of (un)conventional superconductivity, respectively.

The complexation of uranyl ions with lipopolysaccharide (LPS), the main component of the cell wall of Gram-negative bacteria, was investigated on a molecular level with U LIII edge extended X-ray absorption fine structure (EXAFS) and attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy over a wide pH range (2.6 to 7.0). For the first time, structural determinations of uranyl complexes with cell wall compounds were extended from acidic up to neutral pH. The main functionalities responsible for uranyl binding are phosphoryl and carboxyl groups. At an excess of LPS, related to environmental conditions, the uranyl ion is mainly complexed by phosphoryl groups four-fold monodentately coordinated in the equatorial plane of the uranyl dioxo cation UO₂ ²⁺ showing great homologies to the uranyl mineral phase meta-autunite in the EXAFS spectra. At equimolar ratios of uranyl and functional groups of LPS, according to a slight deficit of phosphoryl groups, additional carboxyl coordination in a bidentate manner becomes important as it is shown by IR spectroscopy. From the vibrational spectra, a mixed coordination of UO₂ ²⁺ with both phosphoryl and carboxyl groups is derived. The coordination of uranyl ions to the LPS molecule is obviously mainly controlled by the U/LPS concentration ratio, and the influence of pH is only of minor significance at the investigated range.

Time-resolved Laser-induced Fluorescence Spectroscopy (TRLFS) is a very helpful tool with an extremely low detection limit for analyzing speciation of certain radioactive heavy metal ions like uranium (VI). Thus this technique is preferential appropriate for detection of speciation from that ions in environmental relevant concentrations. So TRLFS can be useful in safety assessment concerning migration behaviour of radioactive elements.
In this presentation is shown, that the uranium speciation in natural occurring seepage water samples, and in soil water samples, all samples collected from test site “Gessenwiese” close to Ronneburg in Eastern Thuringia (Germany), were analyzed by TRLFS. This test site was installed as a part of a research program of the Friedrich Schiller University Jena for investigations within the area of recultivated former uranium mining heaps.
The TRLFS measurements on water samples collected within test site Gessenwiese revealed that the uranium speciation in that seepage water is dominated by the hydrolyzed and monomer uranium (VI) sulfate species UO2SO4(aq). This results presented here are a convincing example for the suitability of TRFLS in analyzing the speciation of uranium from natural occurring water samples with pH values between 3.2 and 4.0.

In this work we report the effect of FeCo atomic fraction (0.33 < x < 0.54) and temperature on the electrical, magnetic and tunneling magnetoresistance (TMR) properties of FeCo-Si-O granular films prepared by atom beam sputtering technique. GAXRD and TEM studies reveal that films are amorphous in nature. The dipole-dipole interactions (particle-matrix mixing) is evident from Zero-field cooled (ZFC) and field-cooled (FC) magnetic susceptibility measurements and the presence of oxides (mainly Fe- related) is observed by XPS analysis. The presence of Fe-oxides is responsible for the observed reduction of saturation magnetization and rapid increase in coercivity below 50 K. TMR has been observed in a wide temperature range and a maximum TMR of -4.25 % at 300 K is observed for x = 0.39 at a maximum applied field of 60 kOe. The fast decay of maximum TMR at high temperatures and lower TMR values at 300 K as compared to , where PFeCo is the spin polarization of FeCo are in accordance with a theoretical model that includes spin-flip scattering processes. The temperature dependent study of TMR effect reveals a remarkably enhanced TMR at low temperatures. The TMR value varies from -2.1% at 300 K to -14.5% at 5 K for x = 0.54 and a large MR value of -18.5% at 5 K for x = 0.39 is explained on the basis of theoretical models involving Coulomb blockade effects. Qualitatively particle-matrix mixing and presence of Fe-oxides seems to be the source of spin-flip scattering, responsible for fast decay of TMR at high temperatures. A combination of higher order tunneling (in Coulomb blockade regime) and spin flip scattering (high temperature regime) explains the temperature dependent TMR of these films.

The demand for certified reference materials for chemical and structural microanalysis of geological samples is growing continuously. The fact that there are no certified materials currently available, for which the chemical homogeneity has been documented at the micrometer- and submicrometer level [1] reinforces the need of producing them. A collaboration involving several German scientific institutions has now received funding from the Free State of Saxony and the European Union Social Fund with the objective of providing synthetic, adequately homogeneous minerals with appropriate contents of economically important trace elements that could be certified as reference materials for methods employing sub-ng sampling masses.

Due to such geological processes as crystallization, metasomatism and weathering, specific elemental exchange vectors and substitution mechanisms may be triggered [2, 3] (as shown in Fig. 1), causing elements in minerals to be spatially, heterogeneously distributed at the micrometer scale [4] (e.g. zonation, see Fig. 2). An awareness of naturally occurring solid solutions as well as different structural characters in the lattice of minerals must, therefore, form a foundation for any attempt at producing synthetic mineral materials, which according to this project’s objective, should be free of any compositional and structural inhomogeneities at such a sampling scale.

Prior to the synthesis of any minerals, a thorough crystal-chemical characterization of their natural analogs should be performed. A certain spatial variation in the concentration of major and trace elements in natural mineral samples may be revealed using microanalytical techniques of varied sensitivity. One way to perceive homogeneity is as the function of the size of the studied analytical volume, which is largely determined by the spatial resolution of the probe. For example, a material rated homogenous by optical microscopy and EPMA may demonstrate inhomogeneity when tested using nanoSIMS because of the better spatial resolution and detection limits provided by this method. On the other hand, an isotopically homogenous material may exhibit heterogeneity in the major and/or trace element distributions [5].

In order to test such variances and relationships in selected natural analogs of synthetic reference materials as a function of analytical method, we designed a series of chemical and structural homogeneity–check measurements of sanidine, tantalite, columbite and pyrite. We are using several different imaging and spectroscopic techniques, starting from optical polarizing and reflected microscopy, BSE and CL imaging, EBSD, IR, Raman, EPMA, µPIXE coupled with µPIGE, SIMS and synchrotron µXRF. Establishing a rapid, economical and robust homogeneity testing procedure is essential for achieving the overall goals of this project. In order to meet these criteria, a reasonable sequence of measurements is devised starting from simple techniques (i.e., optical microscopy) and move toward the more complex (i.e. SIMS and µXRF). This first phase will contribute towards optimizing our homogeneity testing procedure, assuring that our approach will be suitable for our ultimate certification plan.

Present work reports the elongation of spherical Ni nanoparticles (NPs) parallel to each other, due to bombardment with 120 MeV Au⁺⁹ ions at a fluence of 5 × 10¹³ ions/cm². The Ni NPs embedded in silica matrix have been prepared by atom beam sputtering technique and subsequent annealing. The elongation of Ni NPs due to interaction with Au⁺⁹ ions as investigated by cross-sectional transmission electron microscopy (TEM) shows a strong dependence on initial Ni particle size and is explained on the basis of thermal spike model. Irradiation induces a change from single crystalline nature of spherical particles to polycrystalline nature of elongated particles. Magnetization measurements indicate that changes in coercivity (Hc) and remanence ratio (Mr/Ms) are stronger in the ion beam direction due to the preferential easy axis of elongated particles in the beam direction.

The international development of the Lead-cooled Fast Reactor (LFR) had an early start in the Soviet Union in the 1960s where reactors cooled by Lead-Bismuth Eutectic (LBE) were developed and deployed for use in submarine propulsion. More recently, the Generation IV International Forum (GIF) Technology Roadmap identified the LFR as a technology with great promise to provide small-unit electricity generation as well as large, grid-connected power. Since then, considerable effort has been devoted to the development of new concepts.

The focus of the experimental and numerical study presented here is on the bulk flow within a swirling liquid metal column driven by a rotating magnetic field (RMF), whereas the free surface of the melt was covered by a distinct oxide layer. Flow measurements revealed an anomalous behaviour of the flow: Pronounced oscillations of both the primary swirling and the secondary recirculating flow occur spontaneously. This peculiarity can be attributed to the influence of the oxide layer at the surface of the metal. The motion of the covering layer is determined by the strength of the fluid flow and the properties of the layer and may exhibit three different states of motion: permanent rotation, intermittent rotation or the quiescent state. The regime of an intermittent oxide layer rotation reveals a striking influence on the bulk flow of the liquid metal. The amplitude of the velocity oscillations observed appears to be at least one order of magnitude larger than those of turbulent fluctuations in a steady RMF-driven flow. Essential features of the phenomenon observed were reproduced by a simple numerical model.

Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications. Water model experiments are of limited value, particularly in the cases of strong temperature gradients, two-phase flows or flows exposed to electromagnetic fields. We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400°C. The parameters of the facility and the dimensions of the test sections will be given, and the possibilities for flow investigations in tundish, submerged entry nozzle and mould will be discussed. In addition, the smaller set-up Mini-LIMMCAST will be presented, which works with the room-temperature liquid alloy GaInSn. The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements with a reasonable spatial and temporal resolution. New ultrasonic and electromagnetic techniques for measuring the velocity in liquid metal flows came up during the last decade allowing for a satisfying characterisation of flow quantities in the considered temperature range up to 400°C. First results from LIMMCAST and Mini-LIMMCAST will be presented covering the following phenomena: fully contactless electromagnetic tomography of the flow in the mould, mould flow monitoring by a multitude of ultrasonic sensors and analysis of the flow in the mould under the influence of an electromagnetic brake: intensification of the flow turbulence contrary to the expected flow damping, injection of argon bubbles through the stopper rod: occurrence of pressure oscillations. In addition, numerical simulations using ANSYS-CFX will be presented which basically confirm the measuring results.

We present model experiments with low melting point liquid metal two-phase flows using the setup of the Mini-LIMMCAST facility at HZDR. Argon gas was injected at the tip of the stopper rod. The flow field and the gas distribution were measured in the submerged entry nozzle (SEN) and in the mould by means of electromagnetic and/or ultrasonic techniques. Data sets were recorded for the pressure at the gas injection point and for the levels of the liquid metal surface in the tundish and the mould, respectively. The investigations showed that not all the gas injected forms bubbles or slugs within the SEN. In all likelihood, gas layer were formed around the stopper rod and a part of the gas escapes along the stopper rod towards the free surface in the tundish. The flow experiments delivered a strong indication for the occurrence of a slug flow inside the SEN manifested by simultaneous, coherent oscillations of the pressure at the injection point and the liquid metal level in the mould. Further systematic experiments are necessary to figure out the occurrence of different flow regimes in the SEN depending on the ratio of liquid and gas flow rates.

This paper is concerned with experimental and numerical investigations focusing on the fluid flow in the continuous casting process under the influence of an external DC magnetic field. Systematic measurements of the mould flow were carried out using the eutectic alloy GaInSn inside a plexiglass model at room temperature. The jet flow discharging from the submerged entry nozzle was exposed to a level magnetic field spanning across the entire wide side of the mould. The ultrasound Doppler velocimetry (UDV) was applied to obtain a detailed experimental data base with respect to the mean values and transient properties of the velocity fields occurring in the mould. Numerical calculations were performed by means of the software package CFX with an implemented RANS-SST turbulence model. The non-isotropic nature of the MHD turbulence was taken into account by specific modifications of the turbulence model. The comparison between our numerical calculations and the experimental results displays a very well agreement. An important result of our study was the feature that a static magnetic field may give rise to non-steady, non-isotropic large-scale flow perturbations.

Rotating magnetic fields (RMF’s) are meanwhile widely used in metallurgy. The RMF eliminates flow asymmetries and allows for the control of heat and mass transfer, and hence of the evolving microstructure during solidification processes. In an extension of previous works, devoted to the unidirectional solidification in both constant and temporarily modulated RMF’s, we now analyze the solidification driven by a radial heat flux. The model geometry is a cylinder filled with a binary aluminum-silicon alloy. The outer walls of the cylinder are held on a constant temperature of 20°C while its lower surface is adiabatic. The top surface of the alloy is free.
The numerical simulations employ a hybrid solidification model which is implemented into a 2D Navier-Stokes solver based on the SIMPLE algorithm. We first re-investigate the spin-up problem, given by the simultaneous start of both cooling and acceleration of the melt, for different thermal conditions. Second, we compare the numerical results with corresponding experiments in the same model geometry which have been performed at the Helmholtz-Zentrum HZDR.

An undesired phenomenon associated with natural convection in the mushy zone is the formation of segregations channels, the so-called chimneys. We investigated the influence of melt flow on the solidification of a Ga-25wt.In alloy, if the buoyancy-driven flow is interfered by a much stronger electromagnetically-driven flow. For visualizing the process we apply the X-ray radiography which enables a general intuitional understanding of the interaction between solidification and melt flow. The main effect of the flow is determined by the flow-induced redistribution of solute concentration. The consequences are a change of the grow direction of the dendrites and the preference of secondary arm branches for and accelerated and decelerated growth, respectively. The present study demonstrates that a dominating electromagnetic stirring may provoke a unidirectional solute transport in the mushy zone which in turn causes the formation of spacious segregation pattern.

Electromagnetic stirring during solidification has been proved to be a striking method for achieving a purposeful alteration of the microstructure of casting ingots, such as grain refinement or the promotion of a transition from a columnar to an equiaxed dendritic groth (CET). However, the imposition of a rotating (RMF) or a travelling magnetic field (TMF) also causes problems like the occurrence of typical segregation pattern or a deflection of the upper free surface. A permanent radial inward (RMF and downward TMF) or outward (upward TMF) flow along the solidification front is responsible for the transport of solute to the axis or the wall of the ingot resulting in typical freckle segregation pattern filled with alloy of eutectic composition. It was shown, that modulated AC magnetic fields are appropriate to overcome these problems.
This present study examines the directional solidification of SnPb alloys from a water cooled copper chill. Time-modulated combinations of rotating and travelling magnetic field are used to agitate the melt. Our results reveal the potential of modulated magnetic fields to realize an effective flow control for achieving grain refinement without the formation of segregation freckles.

The kinetics of solidification as well as the resulting microstructure are significantly affected by convection occurring in the liquid phase. Therefore, the application of electro-magnetic fields to control solidification processes has received a growing interest. We study the grain growth in various metal alloys under the influence of a rotating magnetic field (RMF) which generates a melt flow aligned mainly perpendicular to the solidification front. Previous investigations showed an inclination of the columnar structure towards the incident flow. The tilting of the columnar grains can be explained by the transport of solute, however, the influence of the flow on the crystal orientation has not been examined so far.
Within the present study directional solidification experiments were performed in PbSn and AlSi alloys applying a sudden onset of the electromagnetic force. Just be-fore and after the initiation of the magnetic field the grain structure was analyzed. Electrolytical etching was used to identify grains having different orientations and related EBSD measurements provided quantitative values for the crystallographic orientation of the grains. Whereas a distinct asymmetric grain growth or a deflection of the columnar grains becomes obvious in case of forced melt flow, a perceivable modification of the crystal orientation cannot be detected by our measurements.

In times of scarce resources and increasing demands, an optimum IT support requires a greater service orientation and a more systematic description and management. While IT Service Management (ITSM) previously in the industry has become a standard, there are so far, only few best practice examples at universities and research institutions. The essential characteristic of this paradigm shift in the way of IT provisioning is to align IT with the specific business processes of the organization.

This paper proposes an approach to ITSM for research institutes that achieves an IT and business alignment in the context of an IT service orientation, based on ITIL v3. Starting with a description of the business processes in the context of research institutions the required IT services structure can be derived. A draft of a generic business process map providing the basis for the definition and design of IT services has been found. The resulting IT service and IT function catalogues combine the business and technical view. This provides the first step towards the development of a standardized and efficient implementation reference model for ITSM in the research area. The goal of this ongoing project is to develop a practical framework for the ITSM of research institutes and an IT management information system prototype.

Uranium exist in low concentrations overall in the environment. Despite this ground level of uranium distribution the use of this metal in nuclear industry, agriculture, and as depleted uranium in weapons caused widespread additional contamination of this element in the environment. Depleted uranium ammunition can form uranium minerals by weathering, which later decompose and may increase the uranium concentration in the ground water [1].
This dissolved uranium may be bio-available and can be incorporated by microorganism, biofilms, algae, fungi and plants. In this way uranium reaches the food chain and can be incorporated also by the human.
Due to the extraordinary properties of uranium it is possible to study the speciation of this element under natural conditions and up to extremely low concentrations of about 50 ng/L by time-resolved laser-induced fluorescence spectroscopy.
We could show that the uranium speciation in compartments of living organism differ strongly. As example we follow the theoretical way of the uranium from the mineral phases after weathering to cell compartments of Arabidopsis halleri, grown on a mine tailing pile in Johanngeorgenstadt.
We could show that the uranium speciation changes from the uranium mineral phase like sabugalit to carbonate species in the aqueous environment. This dissolved uranium may be up taken by roots of plants and transported into the plant cells [2]. Compounds with phosphate and carboxylate ligands in different compartments of the living organisms were expected. By fractionation of the plant cells the uranium speciation in the several compartments was studied. Other bioligands play an additional role by reducing the hexavalent uranium .

[1] Schimmack, W.; Gerstmann, U.; Schultz, W.; Geipel, G.: Radiation and Environmental Biophysics 46(2007), 221-227
[2] Viehweger, K.; Geipel, G.: Environmental and Experimental Botany 69(2010), 39-46

The relaxation dynamics in graphene is of key importance for understanding the basic material properties as well as for high-frequency electronic and opto-electronic device applications. In addition to single colour pump-probe experiments in the THz range (photon energy: 14-30 meV) without magnetic field, we performed experiments at a photon energy of 18 meV in magnetic fields up to 1.34 T. For photon energies larger than twice the Fermi energy (approx. 10 meV) positive pump-probe signals were observed while for smaller photon energies pump-induced absorption occurred due to carrier heating. Relaxation times were around 30 ps. At magnetic fields around 0.23 T the pumpprobe signal increases by a factor of 2.5. At this field the splitting of the zeroth to first Landau level is resonant with the photon energy.

In addition to salt and crystalline rock, argillaceous rock is investigated as potential host rock and backfill material for nuclear waste repositories. For safety assessment, knowledge on the migration behavior of potentially released actinides in these environments is required. Clay rock contains natural organic matter. Low molecular weight organic acids such as acetate, lactate, propionate and formate as well as fulvic and humic acids can be released from clay under certain conditions [1, 2]. In continuation of our former study where the retention properties of the natural clay rock Opalinus Clay (Mont Terri, Switzerland) towards U(VI) were investigated [3], we studied the influence of various organic ligands on the sorption of U(VI) (1•10-6 M) onto Opalinus Clay under aerobic conditions applying synthetic Opalinus Clay pore water (I = 0.36 M, pH 7.6 [4]) as background electrolyte. It was found that the low U(VI) sorption onto Opalinus Clay in the absence of ligands (Kd = (0.0222 ± 0.0004) m³/kg [3]) further decreases with increasing concentration of low molecular weight organic acids (1•10-5 to 1•10-2 M) due to complex formation in aqueous solution. The mobilizing effect of the organic ligands on U(VI) increases in the following sequence: formate < lactate ~ acetate ~ propionate < tartrate < citrate. For instance, in the presence of citrate (1•10-2 M), which has been identified as important ligand in radioactive waste problems, the Kd value for U(VI) amounts to only (0.0011 ± 0.0003) m³/kg. The influence of the organic ligands on the U(VI) sorption onto Opalinus Clay correlates with the stability of the respective U(VI) complexes. In contrast, humic acid (< 50 mg/L) does not change U(VI) sorption [3]. A reduction of U(VI) to U(IV) was not detected.
Since elevated temperatures are expected for the disposal of high-level nuclear waste in clay formations, the influence of temperature on the U(VI) sorption onto Opalinus Clay was studied in the temperature range from 10 to 60°C. In the absence of organic ligands, the U(VI) sorption increases with increasing temperature. For U(VI), the apparent endothermic sorption enthalpy amounts to 34 ± 1 kJ/mol. The temperature dependence of the U(VI) sorption onto Opalinus Clay is almost not influenced by lactate and humic acid (50 mg/L), however, slightly changed by citrate, when present in the concentration range from 1•10-5 to 1•10-2 M.
For interpretation of the sorption results, the U(VI) speciation in aqueous solution has to be known. Therefore, we studied the U(VI) complexation by lactic acid (pH 3) and citric acid (pH 1-10) in the temperature range from 7 to 65°C. Species distribution and complex formation constants were determined by means of UV-Vis and time-resolved laser-induced fluorescence spectroscopy. The complex formation between U(VI) and these ligands was found to be endothermic and entropy-driven.
Finally, the diffusion of U(VI) (1•10-6 M) in intact bore core samples was studied under anaerobic conditions in the absence and presence of humic acid (10 mg/L) both at 25°C and at 60°C. After three months of diffusion time, the U(VI) and humic acid diffusion profiles were determined. Both an influence of the temperature and of humic acid on U(VI) diffusion was detected. Currently, diffusion and distribution coefficients are determined by fitting the U(VI) and humic acid diffusion profiles using the modeling software COMSOL Multiphysics 3.3 [5].
The results show that the sorption and diffusion behavior of U(VI) in the system Opalinus Clay/Opalinus Clay pore water is influenced by natural organic matter and temperature. Especially strongly complexing low molecular weight organic acids can enhance the mobility of U(VI) in clay.

[1] Courdouan, A., Christl, I., Meylan, S., Wersin, P., Kretschmar, R.: Characterization of dissolved organic matter in anoxic rock extracts and in situ pore water of the Opalinus Clay. Appl. Geochem. 22, 2926-2939 (2007).
[2] Claret, F., Schäfer, T., Bauer, A., Buckau, G.: Generation of humic and fulvic acid from Callovo-Oxfordian clay under high alkaline conditions. Sci. Total Environ. 317, 189-200 (2003).
[3] Joseph, C., Schmeide, K., Sachs, S., Brendler, V., Geipel, G., Bernhard, G.: Sorption of uranium(VI) onto Opalinus Clay in the absence and presence of humic acid in Opalinus Clay pore water. Chem. Geology 284, 240-250 (2011).
[4] Pearson, F.J.: Opalinus Clay experimental water: A1Type, Version 980318, PSI Internal Report TM-44-98-07. Paul Scherrer Institut, Villigen, Switzerland (1998).
[5] Finite-element software package. http://www.comsol.com.

The production of phi mesons in the collisions of 2.83 GeV protons with C, Cu, Ag, and Au at forward angles has been measured via the phi→K⁺K⁻ decay using the COSY-ANKE magnetic spectrometer. The phi meson production cross section follows a target mass dependence of A^0.56±0.03 in the momentum region of 0.6–1.6 GeV/c. The comparison of the data with model calculations suggests that the in-medium phi width is about an order of magnitude larger than its free value.

With the HADES spectrometer at GSI we have studied dilepton production in various collision systems from elementary N+N, over p+A, up to the medium-heavy Ar+KCl system. We have confirmed the puzzling results of the former DLS collaboration at the Bevalac. While we have traced the origin of the excess pair yield in C+C collisions to elementary p+p and n+p processes, we find a significant contribution from the dense phase of the collision in larger Ar+KCl system. From recently obtained e+e- pair spectra in p+p and p+Nb interactions at 3.5 GeV kinetic beam energy the inclusive production cross sections for neutral pions, η , ω and ρ mesons are extracted for the first time at this beam energy. Furthermore, the production mechanisms of the vector mesons, which are not known at these energies, are investigated. The direct comparison of p+p and p+Nb data allows us to investigate in-medium mass modifications of vector mesons at nuclear ground state density.

The preliminary results on charged pion production in np collisions at an incident beam energy of 1.25 GeV measured with HADES are presented. The np reactions were isolated in dp collisions at 1.25 GeV/u using the Forward Wall hodoscope, which allowed to register spectator protons. The results for np -> pppi-, np -> nppi+pi- and np -> dpi+pi- channels are compared with OPE calculations. A reasonable agreement between experimental results and the predictions of the OPE+OBE model is observed.

Results on Λp femtoscopy are reported at the lowest energy so far. At a beam energy of 1.76A GeV, the reaction Ar+KCl was studied with HADES at SIS18/GSI. A high-statistics and high-purity Λ sample was collected, allowing for the investigation of Λp correlations at small relative momenta. The experimental correlation function is compared to corresponding model calculations allowing the determination of the space-time extent of the Λp emission source. The Λp radius is found significantly smaller than that for Au+Au/Pb+Pb collisions in the AGS, SPS and RHIC energy domains, but larger than that for electroproduction from He. Taking into account all available data, we find the Λp source radius to increase almost linearly with the number of participants to the power of one-third.

Due to their redox reactivity, surface sorption characteristics, and ubiquity as corrosion products or as minerals in natural sediments, iron(II)-bearing minerals control to a large extent the environmental fate of actinides. Pu-LIII-edge XANES and EXAFS spectra were used to investigate reaction products of aqueous ²⁴²Pu(III) and ²⁴²Pu(V) reacted with magnetite, mackinawite, and chukanovite under anoxic conditions. As Pu concentrations in the liquid phase were rapidly below detection limit, oxidation state and local structure of Pu were determined for Pu associated with the solid mineral phase. Pu(V) was reduced in the presence of all three minerals. A newly identified, highly specific Pu(III)-sorption complex formed with magnetite. Solid PuO₂ phases formed in the presence of mackinawite and chukanovite; in the case of chukanovite, up to one-third of plutonium was also present as Pu(III). This highlights the necessity to consider, under reducing anoxic conditions, Pu(III) species in addition to tetravalent PuO₂ for environmental risk assessment. Our results also demonstrate the necessity to support thermodynamic calculations with spectroscopic data.

Super-homogenisation (SPH) factors were generated by a modified version of the code DYN3D for PWR fuel assemblies in hot-zero-power states defined in the OECD MOX/UO2 Benchmark. SPH factors averaged for each pin-material type and factors for each individual pin position were produced. The application of the SPH factors improves the accuracy of DYN3D calculations, especially for configurations with control rods inserted.

Sorption is one of the key retardation processes considered in safety assessment of radioactive waste repositories. Whereas most often conventional distribution coefficients (KD values) are utilized, additionally taking credit from mechanistic sorption models (Surface Complexation Models, SCM) helps to increase confidence both in the underlying basic chemical processes and in their numerical representation. Quality-assurance of long-term safety assessment studies requires the identification of the most sensitive geochemical and thermodynamic model input parameters [1] by means of sensitivity analysis (SA) and uncertainty analysis (UA). Such an approach is tested here rigorously for a variety of test cases: Se(IV/VI) sorption onto goethite, Np(V) sorbed onto hematite, and U(VI) sorption onto a simplified aquifer material resembling the overburden of a salt-rock repository.

In each case KD computations were based on a 1-site, 2pK Diffuse Double Layer Model. A component-additivity approach was used for the simplified aquifer. The mineral characterization comprised selected values for the specific surface area (SSA, typically following a log-normal error distribution function − EDF) and the surface site protolysis constants pK1 and pK2. The data selection was based on the mineral-specific sorption database RES³T [2] as were the decisions about the most relevant surface species and their formation constants. All surface reaction constants were assumed to be Gaussian distributed and were normalized to a reference site density of 2.31 sites/nm². The aqueous speciation of selenate and selenite (basically the hydrolysis steps of H2SeO4 and H2SeO3) as well as the more complex aqueous speciation for Np and U was based on the respective NEA TDB reviews [3,4].

Computations for the single-mineral systems were performed with the code FITEQL [5] as the innermost routine for calculating the speciation and subsequently deriving KD values. The outermost shell was a specially programmed tool to generate the necessary parameter variations and to derive statistical evaluations, namely variances as a function of the input parameter set, from the associated Kd distribution. There is also an option available to introduce correlated variables in the form of a correlation matrix. The coupling between these two codes is performed by UCODE [6]. The simplified aquifer was analysed by a combination of PhreeqC [7] for the geochemical speciation, interfaced by UCODE with the SimLab package [8] for SA/UA.

The SCM for the case of Se sorption onto goethite used an of 44.0 ± 2.8 m²/g, pK1 = 7.04 ± 0.15 and pK2 = 9.41 ± 0.24. Based on the available literature, for both Se oxidation states a protonated and an unprotonated inner-sphere surface complex was selected as most probable species: »Fe SeO3 , »Fe HSeO3, »Fe SeO4 , and »Fe HSeO4 with the following respective formation constants log K: 13.79 ± 0.40, 20.36 ± 0.24, 7.69 ± 0.39, and 14.36 ± 0.60. SA and UA were performed on six different pH levels (4 – 9), for two total selenium concentrations (10-4 M and 10-7 M), and for two redox scenarios (+300 mV and +800 mV), the solid-liquid ratio was set to 10 g/L, and atmospheric carbonate was excluded. Sensitivity analysis of its sorption onto goethite revealed that namely the uncertainty of the unprotonated inner-sphere surface complexes affects the overall uncertainty of the distribution coefficient KD, independent from the redox state. Moreover, the uncertainty of the computed KD values is in the order of about 5-30 %.

The system Np(V)-hematite was investigated based on the following parametrization: SSA = 22.5 ± 1.9 m²/g, pK values of 7.23 ± 0.40 and 9.49 ± 0.44 for the 1st and 2nd surface protolysis steps, and complex formation constants of -2.61 ± 0.21, -4.57 ± 0.18, 3.64 ± 0.28, and -10.53 ± 0.9 for the surface species »Fe–O–NpO2, »Fe–O–COO−, »Fe–O–COOH, and »Fe–O–NpO2(HCO3)22−, respectively. Total Np(V) concentration was set to 10−7 M and the geochemical environment characterized as oxidizing with ambient air and temperature, with a pH stepping from 4 to 9. It turned out that log K for the formation of the ternary surface complex »Fe O NpO2 is the input parameter influencing strongest the overall KD values in this system.

Concerning the most complex case, the aquifer model (composition: 85% quartz, 10% feldspar, 0.5% muscovite, 0.5% gibbsite, 0.5% goethite, 2% calcite, and 1.5% kaolinite) the varied input factors for the KD computations were solely geochemical parameters (contrary to the above cases), namely the pH value, the carbonate content, the ionic strength, the total concentrations of calcium, aluminium, and of uranium. Whereas the first two parameters followed a trigonal EDF, the latter four were log-trigonal distributed (all based on geochemical analyses of more than hundred samples). The most influential factors were identified to be the pH, the Ca content, and the carbonate content.

Based on these examples and further test cases, a generalization of application areas and limits for SA and UA applied to sorption phenomena will be discussed, considering both thermodynamic and environmental parameters.

[1] Ochs, M., Payne, T.E., Brendler, V. (2011). Thermodynamic Sorption Modeling in Support of Radioactive Waste Disposal Safety Cases, NEA Report, Paris.
[2] Brendler, V., Vahle, A. Arnold, T. Bernhard, G. and Fanghänel, T. (2002). „RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics“, J. Contam. Hydrol. 61, 281-291.
[3] Olin, Å., Noläng, B. Öhman, L.-O. Osadchii, E., Rosén, E., (2005). Chemical thermodynamics of selenium. Chemical Thermodynamics Vol. 7 (OECD NEA ed.), Elsevier, Amsterdam.
[4] Guillaumont, R., Fanghänel, T., Fuger, J., Grenthe, I., Neck, V., Palmer, D.A., Rand, M.H (2003). Update on the chemical thermodynamics of uranium, neptunium, plutonium, americium and technetium. Chemical Thermodynamics Vol. 5 (OECD NEA ed.), Elsevier, Amsterdam.
[5] Herbelin, A. L. et al. (1999). FITEQL 4.0 Report 99-01, Dept. Chemistry, Oregon State University, Corvallis.
[6] Poeter, E.P.; Hill, M.C. (1998). Documentation of UCODE, a computer code for universal inverse modeling: U.S.G.S. Water-Resources Investigations Report 98-4080, 122 p.
[7] Parkhurst, D.L.; Appelo, C.A.J. (1999). User’s guide to PHREEQC (Version 2) - A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations: U.S.G.S. Water-Resources Investigations Report 99-4259, 312 p.
[8] Saltelli, A., Tarantola, S. SimLab, http://simlab.jrc.ec.europa.eu/

Financial support through the NEA Sorption Project Phase III and the German Federal Ministry of Economics (Contract 02 E 10528) is gratefully acknowledged.

The metal complexation properties of the naturally occurring Maillard reaction product isomaltol HL² are investigated by measurement of its stability constants with copper(II), zinc(II), and iron(III) using potentiometric pH titrations in water, by structural and magnetic characterization of its crystalline complex, [Cu(L²)₂] 3 8H₂O, and by density functional theory calculations. Strong complexation is observed to form the bis(isomaltolato)copper(II) complex Zincorporating copper in a typical (pseudo-)square-planar geometry. In the solid state, extensive intra- and intermolecular hydrogen bonding involving all three oxygen functions per ligand assembles the complexes into ribbons that interact to form two-dimensional arrays; further hydrogen bonds and π interactions between the furan moiety of the anionic ligands and adjacent copper(II) centers connect the complexes in the third dimension, leading to a compact polymeric three-dimensional (3D) arrangement. The latter interactions involving copper(II), which represent an underappreciated aspect of copper(II) chemistry, are compared to similar interactions present in other copper(II) 3D structures showing interactions with benzene molecules; the results indicate that dispersion forces dominate in the π system to chelated copper(II) ion interactions.

The THEREDA project develops a consistent and quality assured thermodynamic reference database for modeling geochemical processes in waste disposal sites. It offers evaluated thermodynamic data for all relevant elements, covering both radioactive waste and chemo-toxic substances, see table 1 for a detailed list. All host rocks currently discussed as candidates for waste repositories in Germany are considered. Thus, parameters for a variety of models describing interactions in mixed phases are included. Here, namely the Pitzer- and SIT-formalisms to describe activity coefficients of hydrated ions and molecules are supported. Provision is made to include parameters for solid solution models and non-ideal gas models at a later stage. Both thermodynamic and interaction parameters can be described by (flexible) temperature functions.
An essential topic in the context of nuclear waste is public confidence building on scientific responsibility. This is addressed by a detailed scheme of quality assurance (QA), incorporating elements such as data categorization (review quality, original publication type, experimental category, and uncertainty level), validity limits, full bibliographic tracking, formalized data evaluation procedures, internal consistency checks (coupled to the concepts of dependent data sets and alternatives), data audits, benchmark test cases, and finally external feedback enabled through free access (www.thereda.de) combined with a variety of communication tools. Each part of THEREDA and its accompanying QA, as well as all technologic details, are fully documented.
Another important topic is that THEREDA strives for a broad coverage of all relevant reactions and species by making use of estimation methods, ranging from chemical analogy to LFER and fractional group algorithms. Such values are clearly labeled, also carry uncertainties, and have validity limits assigned.
To ease the use of the THEREDA data pool both “fixed” complete and consistent databases (updated twice a year) as well as user-specified ones can be downloaded directly form the project’s webpage. Available formats are a generic ASCII type, and formats as required by the geochemical speciation codes PhreeqC, EQ3/6, ChemApp and Geochemist’s workbench.

wird nachgereicht

Strong decrease in the carrier mobility of the nanometer-thick silicon films imposes a limitation on the application of Silicon-On-Insulator SOI structures in the current planar CMOS technology. The formation of heterostructures-on-insulator is a way to increase the carrier mobility in the nanometer-scale layers. We have already shown that formation of Ge/Si on SiO₂ heterostructure leads to increasing of holes mobility [1]. It is known that electron mobility in bulk InSb is about 77000 cmy²/Vs. This is about 50 times more than that in bulk silicon. The formation of Si/InSb on insulator heterostructures may provide an increase of effective electron mobility in the nanometer scale SOI films. The main goal of this work was a study of nucleation and growth of monocrystalline indium antimonide thin film at the Si/SiO₂ grain boundary.

DYN3D is a nodal diffusion code for 3D steady-state and transient analysis of Light Water Reactor (LWR) cores with hexagonal or square fuel element geometry. In addition to the neutron kinetics, it comprises of a thermal-hydraulics model for flow in parallel coolant channels. Macroscopic cross section data libraries generated with variation of burn-up, reactor poisons concentrations and thermal-hydraulic feedback parameters are linked to the code. Two-group and multi-groups versions of the code are available.
Currently, at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the DYN3D code is being extended and adopted for the application to block-type High Temperature Gas-Cooled Reactors (HTGR). In this paper, we give an overview of the latest developments of DYN3D concerning block-type HTGR.
The simplified P3 (SP3) transport approximation is implemented into the multi-group DYN3D code to take anisotropy of the neutron flux and heterogeneity of the core more precisely into account. The SP3 method previously implemented into DYN3D for square fuel element geometry of LWR is being extended for hexagonal geometry of the graphite blocks, where the hexagons are subdivided into triangular nodes to be able to perform a systematic mesh refinement.
One of the main challenges in cross section generation for the HTGR core calculations is the treatment of the so-called “double heterogeneity”. The modified Reactivity-Equivalent Physical Transformation (RPT) approach is applied in order to eliminate the double-heterogeneity of HTGR fuel elements in the deterministic lattice calculations. The main steps of the RPT method are described. The use of the method for the cross section generation of a simplified HTGR core including its verification is presented.
A 3D heat conduction module coupled with a channel-type coolant flow model is implemented to take the temperature reactivity feedback to neutronics physically correctly into account. It is shown that there is significant redistribution of the produced heat by heat conduction between the graphite blocks.

The disposal of nuclear waste including the assessment of long-term safety is still an open question in Germany. In addition to the still pending decision about the repository host rock (salt, granite, or clay) the basic necessity of a consistent and obligatory thermodynamic reference database persists. Such a database is essential to assess potential failure scenarios accurately and to make well founded predictions about the long-term safety. Specific needs for waste repository and remediation projects in Germany are comprehensive datasets also covering high temperatures and high salinities. Against this background, available databases do not suffice and are limited in their use, partly because of high restrictions and resulting incompleteness of reactions. Other databases rely on heterogeneous and therefore inconsistent data leading to incorrect model calculations. Due to these deficiencies THEREDA, a joint project of institutions leading in the field of safety research for nuclear waste disposal in Germany, was started in 2006 [1,2].
THEREDA contains a relational databank whose structure has been designed in a way that promotes the internal consistency of thermodynamic data. Data considered cover the needs of Gibbs Energy Minimizers and Law-of-Mass-Action programs alike. Parameters for a variety of models describing interactions in mixed phases are included. Namely the Pitzer- and SIT-parameters to describe activity coefficients of hydrated ions and molecules are considered. Provision is made to include parameters for solid solution models and non-ideal gas models at a later stage. Both thermodynamic and interaction parameters can be described by temperature functions.
THEREDA offers evaluated thermodynamic data for all compounds (solid phases, aqueous species, or constituents of the gaseous phase) of elements, which according to the present state of research are relevant. In particular, all oxidation states expected for disposal site conditions are covered.
The guidelines developed by the NEA form the basis for those for THEREDA. They were extended to cover also areas such as nomenclature, interaction coefficients, temperature and pressure functions, and quality assurance (QA). The latter contains an internal review where correctness, plausibility an completeness of documentation are checked.
An important step is the data assessment. It involves subdividing the data according to

• Class: distinction between “real” datum, chemical analogue, or estimated value
• Category: type of experiment from which the datum was derived
• Quality: reliability of the datum derived from its numerical uncertainty
• Source: type of literature from which the value was adopted (international reviews, based on the analysis of many papers, internal value…)

An einem Gas-Aerosol-Versuchsstand wurden die Strömungseigenschaften mit dem Messverfahren Particle Image Velocimetry (PIV) untersucht. Die Experimente erfolgten jeweils bei den drei Reynolds-Zahlen Re = 8 900, 27 950 und 44250 an einem Windkanal (d = 10 cm) ohne und mit Einbauten. Für die Strömung ohne Kanaleinbauten wurde die Strömungsentwicklung untersucht und dokumentiert. Dabei konnte festgestellt werden, dass ab der Strömungslänge von x = 15 d die Gesetzmäßigkeiten einer voll entwickelten Strömung anwendbar sind. Als Kanaleinbauten wurden periodische Stufen der Höhe H = 10 mm und Breite B = 100 mm mit einem Abstand von P = 100 mm sowie Zylinderstümpfe mit der Höhe H = 10 mm und Durchmesser d = 20 mm in Noppenstruktur (Vierecksanordnung, Abstand zueinander 20 mm) am Kanalboden verwendet. An verschiedenen Positionen im Bereich der Strömungshindernisse wurden die Geschwindigkeiten in den Strömungsfeldern gemessen und dargestellt. Im Vergleich mit publizierten Daten wurden für die ungestörte Strömung und die Umströmung von Stufen sehr gute Übereinstimmungen gefunden. Die dargestellten Ergebnisse können als Referenz für die weitere Erforschung des Depositions- und Resuspensionsverhaltens von Graphitstaub verwendet werden.
Die Messungen erfolgten mit einem 2C2D-PIV-Messystem. Die ermittelten Messunsicherheiten für die Geschwindigkeit beträgt etwa vier Prozent des Messwertes bei einer messkonfurationsabhängigen Ortsauflösung des Vektorfeldes zwischen 0,4 und 0,8 mm.

The turbulent flow was studied in small-scale gas-aerosol test facility using a particle image velocimetry (PIV) system. The experiments were conducted at Reynolds numbers Re = 8900, 27950 and 44250 in a square duct (d = 10 cm) without and with generic obstacles. The flow formation in the inlet was measured and documented without obstacles. It could be shown that the laws of a well developed turbulent boundary layer are applicable downstream of x = 15 d. Periodic steps (height H = 10 mm, channel width, pitch P = 100 mm) and cylindrical stumps (Ø 20 cm, H = 10 cm, P = 20 cm, square structure) were mounted on the bottom of the channel in order to study more complex flow phenomena. The time averaged mean flow field was illustrated at miscellaneous positions around the obstacles. It agrees well with published data. The showed results can be used for fundamental research on deposition and resuspension of aerosol particles.
The measurement uncertainty of the 2C2D-PIV-system tots up for about 4 percent of the measured value. The resolution of the vector field accounts between 0,4 and 0,8 mm.

Microorganisms like bacteria, algae and fungi have a significant influence on the immobilization, mobilization and transport of radionuclides like uranium and other heavy metals in the biological and geological environment via the soil and water path. To understand the mechanisms of uptake, transport, deposition, degradation and the behavior of actinides in different biological and geological systems structural knowledge about the formed actinides species are of great importance and are essential for a reliable assessment of these processes.
Arthrobacter (bacteria), Chlorella vulgaris (green algae) and Schizophyllum commune (fungi) interact in different ways with uranium and are therefore used as model organisms to study different interaction mechanisms and binding forms of uranium, including possibly also so far unknown uptake processes into living cells. Hence the aim of this study was to localize the uranium(VI) on/inside the cells using microscopic methods. Furthermore, experiments with a combination of different spectroscopic techniques were performed to obtain first information about the kind and structure of the formed uranium species and to identify the functionalities, which are responsible for the binding of uranium on/inside the living cells.
All investigated organisms bind significant amounts of uranium(VI) in the pH range from 4 to 7 and contact time of 48 hours. Arthrobacter oxygen and A. nicotinae have binding capacities of 50 – 95 mg U/g biomass dry weight at a uranium concentration of 1∙10-4 M and are thus comparable with that of Schizophyllum cells binding 75 mg U/g bio dry weight independent of the pH value. In contrast to this, metabolic active Chlorella cells bind only up to 30 mg U/g dry biomass under the same experimental conditions. At a more environmentally relevant uranium concentration of 5∙10-6 M in mineral medium and during ongoing cultivation, a mobilization of the algae-bound uranium occurred. At uranium concentrations higher than 1∙10-4 M algal cells died, whereas fungal cells tolerated even high uranium concentrations and were able to accumulate up to 280 mg U/ g biomass dry weigth at pH 5 and 6. At pH 4 and 7, Schizophyllum cells bound only 130 to 150 mg U/ g biomass dry weight. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) combined with EDX analyses were used for the localization of formed uranyl species in the biomass of all investigated organisms. TEM micrographs of thin sections of uranium containing Arthrobacter and Chlorella cells show uranium mainly bound on parts of the cell wall. In some cases uranium containing accumulates were found inside the cells. However, it remains to be resolved if these cells are still alive and possess intact cell walls. In contrast, SEM pictures of transparent fungal cells clearly show uranium containing accumulates inside originally living cells and on their cell surface. Therefore, further research is needed to identify involved uptake mechanisms.
For the determination of the functionalities, which are important for the immobilization of uranium, the interaction of uranium(VI) with metabolic active bacterial, algal and fungal cells was investigated by means of time-resolved laser-induced fluorescence spectroscopy (TRLFS) and X-ray absorption fine structure spectroscopy (EXAFS). The measured luminescence spectra of uranyl containing cell species of all investigated organisms show bathochromic shifts of the uranyl emission bands in comparison to the corresponding emission signals of the uranyl species in the initial solution independent of the uranium concentration and the pH value of the solution (Fig. 1). Obtained results demonstrated a change of the uranyl speciation during the sorption processes. The carboxylic and organic/inorganic phosphate groups are responsible for uranium binding on the biomass with varying contributions dependent on the microbial biomass, cell status and uranium concentration in the initial sorption solution. The dominant interaction of uranium(VI) with organic/inorganic phosphate groups could be verified by EXAFS investigations.

The piezoresistance effect of silicon has been widely used in MEMS sensors [1-3]. Strain engineering is now considered to be the one of the most promising strategies for developing high performance sub-10-nm silicon devices [4]. Strain silicon sensors show typically a gauge factor of below 100, depending on temperature, orientation, doping level and stress direction. Interesting electromechanical properties have been observed in silicon nanowires [5] and carbon nanotubes [6]. This new materials show an unusual large piezoresistance effect compared with bulk silicon. One of disadvantages of using this new materials is the complicated and expensive manufacturing. In this paper we report on the first realized pressure sensor approach, which uses the proposed metal-semiconductor (silicon) hybrid structures in order to achieve higher Kfactor.

New macrocyclic 1,4,8,11-tetraazacyclotetradecane (cyclam) derivatives with 1, 2 and 4 neurotensin(8-13) units 4, 5 and 7 have been synthesized. Compounds 4 and 5 were prepared by the reaction of non-stabilized neurotensin(8-13) and cyclam tetrapropionic acid 2 using 1-ethyl-3-(3-dimethylaminocarbonyl)carbodiimide hydrochloride and N-hydroxysulfosuccinimide. The tetrameric compound 7 was synthesized by Michael addition of neurotensin(8-13) acrylamide 6 and cyclam 1. The copper(II) complexation behavior of 4, 5 and 7 was investigated by UV/visible spectrophotometry and shows that the metal center resides inside the N4 chromophore with additional apical interactions established with pendant arms. The novel tetrabranched neurotensin(8-13) cyclam 7 with nanomolar binding affinity to the neurotensin receptor 1 was efficiently radiolabeled with ⁶⁴Cu under mild conditions. ⁶⁴Cu⊂7 showed slow transchelation in the presence of a large amount of cyclam as competing ligand, while it completely remains intact in the presence of EDTA. The in vivo behavior of ⁶⁴Cu⊂7 was studied in rats and mice. The metabolic stability in rodent models was high with a half-life of intact ⁶⁴Cu⊂7 in plasma of 34 min in rats and 60 min in the mice, respectively. The binding affinity was high enough to demonstrate in vivo binding of ⁶⁴Cu⊂7 to NTR1 overexpressing HT-29 tumor xenotransplants in nude mice. Regarding elimination, ⁶⁴Cu⊂7 showed a substantial renal and reticuloendothelial accumulation. On the other hand, metabolization of the compound in vivo with a resulting metabolite – postulated to be the ⁶⁴Cu-cyclam-tetraarginine complex – also showed long retention in the circulating blood, preventing a better contrast of tumor imaging.

⁶¹Cu (T_1/2 = 3,32 h, E_β+ = 1,22 MeV 60%) ist ein Positronenstrahler aus der großen Auswahl medizinisch nutzbarer Kupfer-Radioisotope. Seine nuklearen Eigenschaften und die relativ einfache Herstellung machen es zu einem geeigneten Radionuklid für die Anwendung in der Positronen-Emissions-Tomografie.
Die ⁶⁴Zn(p,α)⁶¹Cu-Reaktion mit angereichertem ⁶⁴Zn als Targetmaterial scheint für die Routineproduktion von ⁶¹Cu noch geeigneter zu sein als die ⁶¹Ni(p,n)⁶¹Cu-Reaktion. Den Hauptgrund dafür stellen die hohen Kosten des angereicherten⁶¹Ni dar. Der hohe Anteil von ⁶⁴Zn in natürlichem Zink (48,8%) macht angereichertes⁶⁴Zn mit gerade einmal 1,50 $/mg relativ billig im Vergleich zu angereichertem ⁶¹Ni (40 $/mg). Die⁶⁴Zn(p,α)⁶¹Cu-Reaktion liefert im Energiebereich von 19→10 MeV adäquate Ausbeuten an ⁶¹Cu.
Bisher wurde ⁶¹Cu fast ausschließlich aus Nickeltargets hergestellt und die ⁶⁴Zn(p,α)⁶¹Cu-Reaktion mit angereichertem ⁶⁴Zn nur auf geschichteten Folientargets zur Bestimmung von Wirkungsquerschnitten durchgeführt. Mit dieser Arbeit werden ein Targetsystem und die dazugehörige radiochemische Trennmethode für die Routineherstellung von ⁶¹Cu über die ⁶⁴Zn(p,α)⁶¹Cu-Reaktion bei niedrigen Protonenenergien präsentiert

Einleitung:

Eine außerordentlich sensitive und spezifische Diagnose und Therapie selbst mikroskopisch kleiner Tumorherde ist durch radionuklidmarkierte monoklonale Antikörper zu realisieren. Der mit Y-90 gelabelte, gegen den epithermalen Wachstumsfaktor gerichtete Antikörper Cetuximab eignet sich zur Therapie von Patienten mit einem Plattenepithelkarzinom im Kopf-Hals-Bereich.
Radiopharmaka dieser Art gewährleisten eine deutlich effizientere, d. h. eine für den Patienten schonendere Therapie mit besonders hohem Potential der Kuration.

Experimentelles:

Zur Kontrolle der Konjugationsausbeute, bei der ein Isothiozyanat-DOTA-Derivat an zugängliche Lysinaminogruppen des monoklonalen Antikörpers Cetuximab gekuppelt wird, liefert die MALDI-TOF-Analyse ein erstes Indiz. Die Bestimmung der durchschnittlichen Anzahl von DOTA-Chelatoren pro Antikörpermolekül wird dabei wie folgt vorgenommen: Die Differenz der Masse des DOTA-Cetuximab-Konjugates und unverändertem Cetuximab wird mit dem molekularen Gewicht des verwendeten DOTA-Chelators ins Verhältnis gesetzt.
Um Massendifferenzen zwischen den Kupplungsprodukten reproduzierbar quantifizieren zu können ist eine Kalibrierung selbstverständlich unerlässlich.
Alternativ lässt sich die Anzahl der DOTA-Chelatoren pro Antikörpermolekül auch durch Kombination aus einer Proteinbestimmung des Konjugates und dessen Titration mit einem Radionuklid ermitteln.

Vorläufige Daten:

Beim Einsatz von 25 Äquivalenten des DOTA-Chelators zur Konjugation an Cetuximab resultiert eine statistische Produktverteilung mit überwiegend sechs DOTA-Chelatoren pro monoklonalem Antikörper.

Tetravalent actinides are able to form polynuclear comlexes with carboxylate ligands. The resulting structure types will be discussed.

Due to their low solubility actinides An(IV) are usually assumed to be immobile in natural water sources. At the other hand, it is also well known that solid precipitates can be mobilized if they occur as colloids. Pure An(IV) oxyhydroxides and An(IV) colloids in presence of silica were investigated.

Bakterien können auf sehr unterschiedliche Art und Weise mit Metallen wechsel wirken. Dies ist nicht nur von Relevanz für deren Überleben in der Natur, sondern bietet auch ein enormes Potenzial für die Entwicklung innovativer Recyclingstrategien für strategisch relevante Metalle. Im Rahmen des Vortrags werden aktuelle Forschungsarbeiten des Instituts für Radiochemie in diesem Bereich vorgestellt und das Potenzial mikrobiologisch basierter Verfahren aufgezeigt.

In the context of nuclear waste management, long-term safety assessments have shown that selenium-79, released from the solid waste matrix, could be one of the major isotopes contributing to the global radioactivity potentially reaching the biosphere. Selenium has a quite complex speciation, with four main oxidation states, depending on both the pH and the redox potential of the surrounding environment. Thus, it is of great importance to characterize the relevant processes occurring at mineral-water interfaces.
Heat emitted by high level and long-lived radioactive waste is well-known to increase the temperature at the vicinity of the waste disposal site for at least 10,000 years. Such a thermal effect raises the question how the retention of selenium is influenced at elevated temperatures. However, so far, only a few sorption studies, which were performed at higher temperatures with single oxides like goethite [1,2], ferromanganese nodules [3] and TiO2 nanoparticles [4], are available. They showed a lowering of Se sorption with increasing temperature. However, no information and insights about mechanisms involved at higher temperatures were provided.
The present study focuses on the impact of temperature on the sorption of selenium oxyanions, i.e. selenium(VI) and selenium(IV), onto pure anatase (TiO2). Because of its abundance in soils and its well-known crystal structure, anatase represents an ideal model system for the study of sorption behavior of Se onto transition metal oxide phases. This will also lead to a completion of thermodynamic databases used for safety assessments of water contamination.
To get a better understanding of involved sorption mechanisms, a combined approach of both macroscopic and microscopic techniques was applied. To avoid an activation of anatase photocatalytic properties, all tubes were covered by aluminum foil. Batch experiments results performed at room temperature showed that anatase has a higher affinity towards selenium(IV) compared to selenium(VI), which is in agreement with former studies on iron, aluminum and titanium oxides [6,7,8]. Selenium(VI) and selenium(IV) sorption onto anatase were strongly dependent on the pH of the suspension. Sorption of both oxyanions was at a maximum in the acidic pH range and decreased when the pH became more alkaline. Sorption of selenium(VI) onto anatase was dependent on the ionic strength of the suspension, while no influence could be noticed for selenium(IV). No reduction of Se oxyanions at both homogenous and heterogeneous levels was noticed during HG-AAS and XPS measurements. Electrophoresis measurements have also been performed during this work. No shift of the isoelectric point of anatase (pHIEP) upon selenium(VI) sorption was observed. On the contrary, selenium(IV) sorption clearly shifted the pHIEP of anatase to lower pH values. Based on EXAFS and ATR FT-IR spectroscopic observations, we concluded that selenium(VI) is sorbed onto anatase as outer-sphere surface complexes, while the sorption of selenium(IV) proceeds via the formation of inner-sphere complexes, at room temperature.
Furthermore, batch sorption experiments of selenium(VI) and selenium(IV) onto anatase at different temperatures ranging from 25 to 60°C have been performed in NaCl. As shown in Fig.1, the influence of the pH on the sorption of selenium(VI) onto anatase shows a similar general tendency, i.e. a decrease of the sorption with increasing pH. However, the sorption capacity of anatase towards selenium(VI) is lowered at higher temperatures. The thermodynamic parameters, i.e. ΔRH°, ΔRS° and ΔRG° for Se sorption onto anatase were determined from the temperature dependence sorption data using the van´t Hoff equation and the exothermic/endothermic and spontaneous sorption characteristics were discussed.
Finally, in situ ATR FT-IR measurements have been performed using an experimental design which allows data collection at elevated temperatures up to 60°C. In the IR spectrum of selenium(VI) sorbed onto anatase obtained at room temperature, the asymmetric v3(Se-O) stretching mode located at 880 cm−1 was significantly shifted to higher wavenumbers compared to the ν3 mode of the free SeO42− species in solution observed at 867 cm−1, indicating the formation of outer-sphere complexes on the anatase surface. At higher temperatures, ATR FT-IR measurements evidenced a decrease of selenium(VI) sorption onto anatase (Fig. 2), in agreement with batch experiments investigations. Additionally, a small blue shift (885 cm−1) of the asymmetric v3(Se-O) stretching mode was noticed when the temperature was increased. However, no significant changes on the sorbed selenium(VI) surface complexes appeared at higher temperatures.

The science case and feasibility for experimental study of several nuclear reactions important for stellar helium burning will be reviewed. The cases of the ¹⁵N(alpha,gamma)¹⁹F, ¹⁶O(alpha,gamma)²⁰Ne, and ¹⁸O(alpha,gamma)²²Ne reactions will be discussed in detail. It is shown that a study of these reactions at an underground accelerator will allow to significantly improve the nuclear reaction rate input for astrophysics.

The status of the effort to install a possible accelerator in the shallow-underground laboratory Felsenkeller/Dresden will be reviewed.

TiC_x/Al bilayer thin films were synthesized using combinatorial magnetron sputtering to study the influence of C content on the reaction products at different annealing temperatures. Based on energy dispersive X-ray analysis calibrated by elastic recoil detection analysis data, x in TiC_x was varied from 0.4 to 1.0. Film constitution was studied by X-ray diffraction before and after annealing at temperatures from 500 to 1000°C. The formation of TiC_x and Al in the as-deposited samples over the whole C/Ti range was identified. Upon annealing TiC_x reacts with Al to form the Ti-Al based intermetallics. Already at 700°C, the formation of MAX phases (space group P63/mmc) is observed at x≤0.7. Based on the comparison between the C content induced changes in the lattice spacing of TiC_x and Ti₂AlC as well as Ti₃AlC₂, we infer the direct formation of MAX phases by Al intercalation into TiC_x for x≤0.7.

no abstract available

Argillaceous rocks, like the Opalinus clay formation (OPA) in Switzerland are potential host rocks for nuclear waste repositories. The OPA can contain up to 1% dissolved organic matter. It consists of small organic molecules like formiate, citrate or lactate. Such small organic molecules can like the ubiquitous humic acid influence the migration behaviour of radionuclides.

The understanding of the complex behaviour of radionuclides with such natural organic matter and the thermodynamic quantification of the interaction is of great importance to simulate and predict their migration behaviour in the environment. Additionally, it is crucial to study the complex behaviour of radionuclides at elevated temperatures, because especially in the near field of nuclear waste disposals higher temperatures are prevailing.

We investigated the complex behaviour of Am(III) complexes with lactate and substituted benzoic acids like pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid, BTC) which serve as model compounds for humic substances at ambient and elevated temperatures with time-resolved laser-induced fluorescence spectroscopy (TRLFS).

TRLFS has been extensively used as a sensitive and selective technique to analyze actinide complexation with inorganic and organic ligands in trace metal concentrations. However, the application of TRLFS onto Am(III) complex systems was up to now limited because of the much lower luminescence intensity and much shorter lifetime in comparison to U(VI) or Cm(III).

Using the emission of the 5D1-7F1 transition at around 690 nm, spectral data like luminescence lifetimes and maxima and complex stability constants were calculated. Temperature dependent stability constants were determined to estimate thermodynamic data (enthalpy, entropy).
The Am(III) aquo ion shows at pH 4-5 a luminescence lifetime of 23 ns, corresponding to approximately 9 coordinating water molecules. Complexation with BTC shows no change of the emission maximum but an increase of the luminescence intensity and lifetime. The luminescence lifetime was prolonged to 27 ns, corresponding to 8 remaining water molecules in the first coordination shell. This indicates an exchange of 1 water molecule with 1 coordination site of the ligand, resulting in an Am-BTC 1:1 complex. In contrast, complexation with lactate causes additionally a red shift of the luminescence maximum of about 5 nm. The luminescence lifetime is prolonged up to 37 ns which corresponds to 5-6 remaining water molecules, indicating an exchange of about 3-4 water molecules with coordination sites of ligand molecules which implies the formation of 1:1, 1:2 and 1:3 complexes. The stability constants increase with rising temperature which is consistent with an endothermic complexation reaction.

TRLFS investigations with the inactive lanthanide analogue Eu(III) and the same ligands resulted in similar complex behaviour of Am(III) and Eu(III). This fact permits performing further investigations concerning the complex behaviour of trivalent actinides at elevated temperatures exemplarily with Eu(III). Temperature-dependent isothermal titration calorimetry (ITC) shows with rising temperature a stepwise polymerization between Eu(III) and BTC. ATR FT-IR (attenuated total reflection Fourier transform infrared spectroscopy) in combination with DFT (density functional theory) calculations was used to determine main structural features of the monomer and the polymer. In principle, we found monodentate coordination of one carboxylate group of BTC to one Eu(III) with a small fraction of chelating coordination mode of two neighbouring carboxylate groups.

The results suggest that the migration of actinides will be strongly influenced by organic matter. Small organic molecules can enhance the mobility with rising temperature due to higher complexation ability. In contrast, complex organic materials like humic substances are able to immobilize radionuclides under certain conditions due to the possibility of polymerization.

Nuclear aerosol deposition and the assessment of its resuspension during a design basis accident in the primary circuit are a key issue in the development and certification of advanced (Very) High Temperature Reactors ((V)HTRs). It is of general interest how much of these nuclear aerosol particles escape from the primary circuit into the containment during a depressurization scenario. The knowledge about the amount of resuspended material will allow detailed estimate
of dose escaping the primary circuit (Fontanet et al. (2009)).
Kissane (2009) and Moormann (2008) list different sources of radioactive graphite dust production. Regarding pebble bed HTRs, there is mechanical movement and thereby friction between the pebbles due to loading and unloading of the core. Furthermore, different kind of impurities such as oil, water and air ingresses lead to dust production due to oxidation and peeling of the pebble surfaces. Referring to VAMPYR filter experiments at AVR J¨ulich, Moormann (2008) reports about airborne concentration (C = 0..50 μg/m³), geometrical size distribution (dP = 0.1..50 μm) and chemical composition of graphite dust. Annual amount of dust production in the AVR is estimated to be around 5 kg/yr and surface loading is calculated to be approximately 10 g/m² after 16 years operation. Furthermore, Kissane (2009) expects that the partially graphitized binder is a major source of carbonaceous dust production. Scaling these dust production contributions up to a 400 MWt pebble bed core, the annual dust production is around 100 kg/yr. The graphite dust particles circulate in helium pressure boundary (HPB) which is characterized by a cooling pressure of about 11 to 55 bar and coolant temperature up to 950°C. Flow conditions range from laminar flows in the recuperator to turbulent high Reynolds number flows in pipes and ducts. Depending on the local conditions, there is deposition and esuspension of graphite dust mainly moderated by diffusion, thermophoresis, turbophoresis, particle inertia, gravitational settling and electrostatic precipitation. In order to investigate transport, deposition and resuspension phenomena, we focus on single effect studies of nuclear aerosol particles in a well developed turbulent flow field.

Der Vortrag gibt einen Einblick in hochauflösende Zweiphasenmesstechnik mit dem Schwerpunkt Gas-Flüssig-Systeme. Vorgestellt werden Nadelsonden, Gittersensoren, Gammadensitometrie sowie Gammastrahlen- und Röntgentomographie-Verfahren. Neben den physikalischen Messprinzipien werden Einsatzgebiete und Grenzen sowie Methoden zur Datenverarbeitung und Datenanalyse vorgestellt.

The presentation introduces into gamma ray and x-ray tomography as sophisticated tomographic imaging techniques applicable in multiphase flow studies and process imaging. Both techniques have recently been developed at HZDR and have been usedin different scientific applications, such as steam-water two phase flow studies in nuclear safety research and multiphase flow studies in process technology. The presentation both gives an overview over physical measuring principles along with different and unique applications in science and industry.

Mehrphasenströmungen finden sich in einer Vielzahl von Prozessen und Apparaten der chemischen Industrie. Sie treten in vielfältigen Formen, wie etwa als disperse Gas-Flüssigkeits-Strömungen in Blasensäulenreaktoren, Gas-Feststoff-Strömungen in Wirbelschichtapparaten oder Blasen-, Schwall- und Filmströmungen in Destillationskolonnen auf. Charakteristisch für Mehrphasenströmungen ist, dass sie messtechnisch schwer erfassbar, theoretisch schwer modellierbar und numerisch schwer berechenbar sind. Ihre Beobachtung und Beschreibung in sowohl industriellen Apparaten als auch in kleinskaligen Versuchsanlagen erfordert Messverfahren, die in der Lage sind, mit hoher räumlicher und zeitlicher Auflösung Phasenverteilungen, Phasengrenzflächendichten, Turbulenz- und Geschwindigkeitsparameter in Kontinuumsphasen, als auch Wärme-, Stoff- und Impulstransport zwischen den beteiligten Phasen abzubilden. Da Mehrphasenströmungen im Allgemeinen opak sind, ist dies mit den sonst in der Strömungsmechanik üblichen optischen Messverfahren nur begrenzt möglich. Dazu kommt, dass gerade in der Verfahrenstechnik viele Prozesse bei hohen Drücken und Temperaturen und in Gefäßen mit dicken Metallwänden und Einbauten ablaufen, was die Möglichkeiten der Instrumentierung einschränkt und hohe Anforderungen an die Robustheit von Messsystemen stellt.

In der jüngeren Vergangenheit wurden am Helmholtz-Zentrum Dresden-Rossendorf verstärkt Anstrengungen unternommen, tomographische bildgebende Messverfahren zu entwickeln, mit denen eine Aufklärung von Mehrphasenströmungen mit hoher räumlicher und zeitlicher Auflösung möglich ist. Ergebnisse dieser Entwicklungen, wie die Gittersensortechnik, die Gamma- und Röntgentomographie, werden im Vortrag vorgestellt. Mit dem Gittersensor wurde erstmalig die Untersuchung transienter Gas-Flüssigkeits-Strömungen mit Bildraten von bis zu 10.000 Bildern pro Sekunde bei einer räumlichen Auflösung von ca. 2 mm möglich. Für druckführende Apparate und Apparate mit Einbauten steht die hochauflösende Gammatomographie zur Verfügung, die eine räumliche Auflösung von ebenfalls ca. 2 mm erreicht. Schließlich vereint die ultraschnelle Röntgentomographie einige vorteilhafte Eigenschaften, wie die berührungsfreien Messung mit hoher räumlicher (~1 mm) und zeitlicher (~10.000 Bilder pro Sekunde) Auflösung sowie die Abbildung opaker und sowie feststoffhaltiger Medien. Der Vortrag stellt die genannten Messverfahren hinsichtlich ihrer physikalischen und messtechnischen Grundprinzipien dar und gibt einen Einblick in potenzielle Anwendungen und Methoden für die Bilddatenanalyse.

Microorganisms moderate local chemical conditions and alter forms of metals indirectly or directly to meet their cellular, species, and consortia needs. The diversity of microorganisms and the complexity of biogeochemical systems ensures that bacterially mediated processes yield a wide range of products, which await discovery by material scientists. Few types of materials produced by environmental bacteria have been analyzed by modern chemical and material science methods. Research on actinide biomaterials has focused on the biomineralization of a few chemical forms of uranium, neptunium, and plutonium. The materials produced are molecular complexes, microcrystalline minerals (most commonly oxides and phosphates) within cells and biofilms, and mineral adsorbates. The actinide biomaterials that emerge from this new research area will impact nuclear waste isolation and increase our understanding of environmental and geological metal cycles and may yield new bioremediation methods and industrially useful materials.

BACKGROUND
Serum aldosterone is a causative factor for various metabolic and cardiovascular disorders. Low-density lipoprotein (LDL) is a major cholesterol source for aldosterone steroidogenesis; however, the effect of oxidative modification of LDL on aldosterone release is not known. We studied the effect of hypochlorite-oxidized LDL (oxLDL) on adrenal aldosterone secretion.
METHODS
LDL (native LDL (natLDL)) was obtained from healthy volunteers and oxidatively modified in vitro. NCI-H295R cells were stimulated with natLDL and oxLDL, and the aldosterone release was quantified by radioimmunoassay. Molecular changes were studied with western blot analysis and quantitative RT-PCR analysis.
RESULTS NatLDL and oxLDL caused dose-dependent increase in aldosterone release up to threefold. However, the stimulatory effects of modified LDL on aldosterone secretion decreased with increasing degree of LDL oxidation. 24-h incubations with natLDL, mild- and medium-oxidized LDL sensitized the adrenocortical cells to subsequent angiotensin II (Ang II) stimulations by 2.9-, 2.8-, and 2.5-folds, respectively. Heavily oxidized LDL did not sensitize the cells to Ang II stimulations to a similar extent. At the molecular level, the ERK pathway was activated within a minute by both natLDL and oxLDL; however, oxLDL showed a stronger (2.75-fold at 1 and 15 min) and longer (15 min) activation of ERK than natLDL (twofold).
CONCLUSIONS This study demonstrates the following: (i) both natLDL and hypochlorite-oxidized LDL utilize ERK pathway to mediate aldosterone release; (ii) mildly oxidized LDL sensitizes the adrenocortical cells to further stimulations by Ang II similar to natLDL that may have a role in pathological processes; (iii) extensive LDL oxidation counteracts adrenocortical aldosterone release.

In this work, samples of 316L, an austenite stainless steel, have been irradiated with a low-energy high-current electron beam of microsecond duration after that these samples were implanted at 150 keV by chromium ions. Implantation doses varied between 2.0 ⋅ 10¹⁶ and 2.0 ⋅ 10¹⁷ ions/cm². The structure of the irradiated and implanted layer was examined by grazing incidence X-ray diffraction analysis. At 2.0 ⋅ 10¹⁶ ions/cm² X-ray diffraction analysis of the phase composition in the surface layer revealed no difference between initial and irradiated-implanted samples. Above 2.0 ⋅ 10¹⁶ ions/cm² a new bcc ferrite structure appeared. Higher implantation dose leads to a larger fraction of the ferritic phase. Irradiation with a low-energy high-current electron beam (LEHCEB) followed by ion beam implantation results in complete dissolution of inclusions and leads to the formation of ompletely homogeneous surface layer. It was also revealed that the surface layer homogeneity doesn't depend on implantation dose.

This paper replaces the paper published in the journal by Deendarlianto et al. (2008). Because of an error in the implementation of the air flow meter some of the data given by Deendarlianto et al. (2008) are wrong. They are corrected within the present paper. The general results and conclusions remain unchanged.
An experimental investigation on the air/water counter-current two-phase flow in a horizontal rectangular channel connected to an inclined riser has been conducted. This test-section representing a model of the hot leg of a pressurized water reactor is mounted between two separators in a pressurized experimental vessel. The cross-section and length of the horizontal part of the test-section are (0.25 m × 0.05 m) and 2.59 m, respectively, whereas the inclination angle of the riser is 50. The flow was captured by a high speed camera in the bended region of the hot leg, delivering a detailed view of the stratified interface as well as of dispersed structures like bubbles and droplets. Countercurrent flow limitation (CCFL), or the onset of flooding, was found by analyzing the water levels measured in the separators. The counter-current flow limitation is defined as the maximum air mass flow rate at which the discharged water mass flow rate is equal to the inlet water mass flow rate.
From the high-speed observations it was found that the initiation of flooding coincides with the formation of slug flow. Furthermore, a hysteresis was noticed between flooding and deflooding. The CCFL data was compared with similar experiments and empirical correlations available in the literature. Therefore, the Wallis-parameter was calculated for the rectangular cross-sections by using the channel height as length, instead of the diameter. The agreement of the CCFL curve is good, but the zero liquid penetration was found at lower values of the Wallis parameter than in most of the previous work. This deviation can be attributed to the special rectangular geometry of the hot leg model of FZD, since the other investigations were done for pipes.

Research into gas-liquid countercurrent two-phase flow in a model of pressurized water reactor (PWR) hot leg has been carried out over the last several decades. An extensive experimental data base has been accumulated from these studies, leading to the development of phenomenological correlations and scaling parameters of the countercurrent flow limitation (CCFL). However, most the proposed correlations apply under a relatively narrow range of conditions, generally limited to the test section conditions and/or geometry. Moreover the development of mechanistic models based on the underlying physical processes has been limited. In contrast to this mechanistic form of modelling, the implementation of computational fluid dynamic (CFD) techniques has also been pursued, but the numerical approach for this application should be improved to reduce the computational cost.

This paper presents a comprehensive review of research work on countercurrent gas-liquid two-phase flow in a PWR hot leg and provides direction regarding future research on this topic. In the introductory section, the problems facing current research are described. In the following sections, recent experimental as well as theoretical research achievements are overviewed. In the last section, the problems that remain unsolved are discussed, along with some concluding remarks. It was found that only limited theoretical developments exist in the literature, however highly reliable experimental data are needed to support this effort. Additional work, both analytical and experimental, needs to be carried out on the effects of mass transfer on countercurrent flow limitation to improve the existing correlations and analytical models.

In 1992, strainers on the suction side of the ECCS pumps in Barsebäck NPP Unit 2 became partially clogged with mineral wool because after a safety valve opened the steam impinged on thermally-insulated equipment and released mineral wool. This event pointed out that strainer clogging is an issue in the course of a loss-of-coolant accident. Modifications of the insulation material, the strainer area and mesh size were carried out in most of the German NPPs. Moreover, back flushing procedures to remove the mineral wool from the strainers and differential pressure measurements were implemented to assure the performance of emergency core cooling during the containment sump recirculation mode. Nevertheless, it cannot be completely ruled out, that a limited amount of small fractions of the insulation material is transported into the RPV. During a postulated cold leg LOCA with hot leg ECC injection, the fibers enter the upper plenum and can accumulate at the fuel element spacer grids, preferably at the uppermost grid level. This effect might affect the ECC flow into the core and could result in degradation of core cooling.
It was the aim of the numerical simulations presented to study where and how many mineral wool fibers are deposited at the upper spacer grid. The 3D, time dependent, multi-phase flow problem was modelled applying the CFD code ANSYS CFX. The CFD calculation does not yet include steam production in the core and also does not include re-suspension of the insulation material during reverse flow. This will certainly further improve the coolability of the core.
The spacer grids were modelled as a strainer, which completely retains all the insulation material reaching the uppermost spacer level. There, the accumulation of the insulation material gives rise to the formation of a compressible fibrous cake, the permeability of which to the coolant flow is calculated in terms of the local amount of deposited material and the local value of the superficial liquid velocity.
Before the switch over of the ECC injection from the flooding mode to the sump mode, the coolant circulates in an inner convection loop in the core extending from the lower plenum to the upper plenum. The CFD simulations have shown that after starting the sump mode, the ECC water injected through the hot legs flows down into the core at so-called “breakthrough channels” located at the outer core region where the downward leg of the convection roll had established. The hotter, lighter coolant rises in the centre of the core. As a consequence, the insulation material is preferably deposited at the uppermost spacer grids positioned in the breakthrough zones. This means that the fibers are not uniformly deposited over the core cross section.
When the inner recirculation stops later in the transient, insulation material can also be collected in other regions of the core. Nevertheless, with a total of 2.7 kg fiber material deposited at the uppermost spacer level, the pressure drop over the fiber cake is not higher than 8 kPa and all the ECC water could still enter the core.

In order to improve the understanding of counter-current two-phase flows, a CFD simulation of 1/3rd scale model of the hot leg of a German Konvoi PWR with rectangular cross section was performed. A selected air-water counter-current flow limitation (CCFL) experiment at the Forschungszentrum Dresden-Rossendorf (FZD) at 0.306 MPa and room temperature (experimental running of 30-05) was calculated with three-dimensional two-fluid models of computer code ANSYS CFX 13. It was simulated using the multi-fluid Euler-Euler modeling approach. The transient calculation was carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a SST turbulence model for each phase. In the simulation, the surface drag was approached by a new correlation inside the Algebraic Interfacial Area Density (AIAD) model. The AIAD model allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows also a good qualitative agreement (Fig. 1). The results indicated also that quantitative agreement of the CCFL characteristics between calculation and experimental data was obtained.

In order to improve the understanding of counter-current two-phase flows and to validate new physical models, CFD simulations of 1/3rd scale model of the hot leg of a German Konvoi PWR with rectangular cross section was performed. Selected counter-current flow limitation (CCFL) experiments at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) were calculated with ANSYS CFX 12.1 using the multi-fluid Euler-Euler modeling approach. The transient calculations were carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a SST turbulence model for each phase. In the simulation, the surface drag was approached by a new correlation inside the Algebraic Interfacial Area Density (AIAD) model. The AIAD model allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows a good qualitative agreement. The results indicated that quantitative agreement of the CCFL characteristics between calculation and experimental data was obtained.

Coolant mixing in the cold leg, downcomer and the lower plenum of pressurized water reactors is an important phenomenon mitigating the reactivity insertion into the core. Therefore, mixing of the deborated slugs with the ambient coolant in the reactor pressure vessel was investigated at the four loop 1:5 scaled ROCOM mixing test facility. Thermal hydraulics analysis showed, that weakly borated condensate can accumulate in the pump loop seal of the loops. After refilling of the primary circuit, natural circulation in the stagnant loops which do not receive safety injection can re-establish and the deborated slugs are shifted towards the reactor pressure vessel (RPV). In the ROCOM experiments, the length of the flow ramp and the initial density difference between the slugs and the ambient coolant was varied. From the test matrix experiments with 0-2% density difference between the deborated slugs and the ambient coolant were used to validate the CFD software ANSYS CFX. To model the effects of turbulence on the mean flow a higher order Reynolds stress turbulence model was employed and a mesh consisting of 6.4 million hybrid elements was utilized. Only the experiments and CFD calculations with modeling density differences show stratification in the downcomer. Depending on the degree of density differences the less dense slugs flow around the core barrel at the top of the downcomer. On the opposite side the lower borated coolant is entrained and borated by the colder safety injection water and transported to the core. The validation proves that ANSYS CFX is able to simulate appropriately the flow field and mixing effects of coolant with different densities.

Ga-rich layers in Si were fabricated by 80 keV Ga implantation through a 30 nm SiO₂ cover layer and subsequent rapid thermal annealing for 60 s in a temperature range between 500°C and 1000°C. Fluences of 2x10¹⁶cm^-2 and 4x10¹⁶cm^-2, leading to Ga peak concentrations of 8 at.% and 16 at.%, are chosen. Residual damage in the implanted layers and the Ga distribution were investigated by Rutherford-backscattering spectrometry in combination with ion channeling, cross-sectional electron microscopy and X-ray photoelectron spectroscopy. Temperature dependent Hall-effect measurements were carried out in order to determine the electrical properties of the implanted layers. It is shown that annealing at temperatures up to 800°C leads to the formation of poly-crystalline layers containing random distributed amorphous clusters. At the Si/SiO₂ interface a dense and narrow band of Ga-rich clusters is observed. For 4x10¹⁶cm^-2 the amount of mobile Ga is higher than for 2x10¹⁶cm^-2 and an increase of the cluster density at the Si/SiO₂ interface was found. Due to the higher cluster density for 4x10¹⁶cm^-2 this interface layer can become superconducting below 7 K with critical fields exceeding 9 T at optimized annealing conditions. Critical currents are above 1 kA/cm² and therefore this seems to be a possible material system for future microelectronic applications. After annealing at 900°C and above, the implanted layers are single crystalline and no amorphous precipitates were found.

Recent experiments at the Experimental Storage Ring (ESR) at GSI have shown that relativistic Li-like carbon (C3+) ion beams can be laser-cooled to an un-precedented momentum spread of Δp/p ≈ 10-7. Here, a single-frequency laser was tuned to the Doppler-shifted 1s22s → 1s22p (2P1/2 and 2P3/2) transitions. These results encourage the application of laser cooling to beams of other Li- and Na-like ions at even higher energies, as will e.g. be available at FAIR.

The application of nanomaterials (NMs) in biomedicine is increasing rapidly and offers excellent prospects for the development of new non-invasive strategies for the diagnosis and treatment of cancer. In this review, we provide a brief description of cancer pathology and the characteristics which are important for tumor-targeted NM design, followed by an overview of the different types of NMs explored to date, covering synthetic aspects and approaches explored for their application in unimodal and multi-modal imaging, diagnosis and therapy. Significant synthetic advances now allow for the preparation of NMs with highly controlled geometry, surface charge and physicochemical properties, and the decoration of their surfaces with polymers and bioactive molecules in order to improve biocompatibility and achieve active targeting. This is stimulating the development of a diverse range of nano-sized objects that can recognize cancer tissue, enabling visualization of tumors, delivery of anti-cancer drugs and/or the destruction of tumors by different therapeutic techniques.

Different ion implantation techniques for the fabrication of shallow boron doped layers used as piezoresistors have been evaluated. In the present case the corresponding process parameters have been optimized to meet demands for high deflection sensitivity of piezoresistive AFM cantilevers. Boron doped layers with decreased pn-junction depths down to ~ 20 nm has been fabricated showing increased deflection sensitivities of (10-20)x106 Ωm-1 compared to conventional implanted resistors. The used ion beam technique fulfills requirements for pn-junctions in terms of small junction depth and low sheet resistance. Additionally, the piezoresistor fabrication processes was evaluated in combination with other ion implanted elements integrated in AFM cantilevers.

Gewöhnlich wird davon ausgegangen, dass tetravalente Actiniden, An(IV), wegen ihrer Schwerlöslichkeit in natürlichen Wässern immobil sind. Es ist jedoch auch gut bekannt, dass unlösliche Fällungsprodukte mobil sein können, wenn sie als Kolloide auftreten. Für An(IV)-Oxyhydroxide wurde dieses Phänomen umfassend studiert.Hier beschreiben wir einen neuen Typ von An(IV)-Kolloiden. Mit Hilfe von Photonenkorrelationsspektroskopie (PCS), Ultrafiltration und Ultrazentrifugation wird nachgewiesen, dass Uran(IV) silikathaltige Kolloide bilden kann. Diese U(IV)-Silica-Partikel entstehen in nahneutralen bis leicht alkalischen Lösungen mit Inhaltsstoffen geogener Natur (Carbonat, Silikat, Natriumionen). Unter Luftausschluss bleiben sie über Jahre in wässriger Suspension stabil. Es wurde eine Konzentration von bis zu 10 hoch -3 M an kolloidgetragenem U(IV) beobachtet, was eine deutlich höhere Konzentration als die bisher für den nahneutralen pH-Bereich berichteten Konzentrationen echt gelöster oder kolloidal suspendierter An(IV)-Spezies darstellt. Die vorherrschende Größe der Nanopartikel hängt von der Silikatkonzentration sowie vom pH-Wert ab und liegt unter 20 nm. Mit Laser-Doppler-Velocimetrie wurde gefunden, dass die Partikel durch elektrostatische Abstoßung infolge eines durch das Silikat negativeren Zetapotenzials im wassergetragenen Zustand stabilisiert werden. Messungen mittels Extended X-ray absorption fine structure (EXAFS) spectroscopy zeigten, dass U-O-Si-Bindungen, welche mit steigender Silikatkonzentration die U-O-U-Bindungen des amorphen U(IV)-Oxyhydroxids ersetzen, die innere Struktur der Kolloide bilden. Die Next-neighbor-Koordination des U(IV) ist vergleichbar mit der des Coffinits, USiO4.

Eingeladener Key Note Vortrag: 20. Symposium zur Experimetellen Strahlentherapie und Klinischen Strahlenbiologie

Nuclear Transmutation Research at nELBE

Experience during percutaneous ion beam therapy at Gesellschaft für Schwerionenforschung showed that the treatment can be improved by in-vivo dose monitoring that is independent of the irradiation device and based on positron emission tomography. It has been studied whether a similar technique can be implemented for high energy photon therapy. Simulation shows that the dose is closely related to the distribution of the annihilation points of positrons emerging from pair production. Design parameters of a detector system have been assessed which is capable of registering annihilation radiation during treatment. A test system has been assembled which can be operated with various scintillator crystals and avalanche photodiodes. A custom digital signal processing
system has been implemented. Phantom experiments at a clinical linear accelerator disclosed a severe background that does not solely stem from scattered primary photons but from radiation directly emitted from the treatment head. It was not possible to shield the detectors sufficiently and thus there was no success in identifying annihilation radiation.

A study of the ion implantation of Cu⁺, Ag⁺ or Au⁺ ions into different types of silicate glasses is reported. The energy of the implanted ions was 330 key and the implantation fluence was kept at 1 x 10¹⁶ cm^-2. The samples were characterised by various analytical methods: Rutherford backscattering spectrometry for the concentration depth profiles of the implanted atoms, Raman spectroscopy for the structure of the samples and also by UV-VIS absorption spectroscopy. The obtained data were evaluated on the bases of the structure of the glass matrix and the relations between the structural changes and optical properties, important for photonics applications, were formulated.
The main focus was the impact of various types and concentrations of glass network modifiers (e.g. Li, Na, K, Mg, Ca or Zn) as well as glass network formers (Si, and B) on the projected range of the implanted ions. Interesting results were also provided by a study of the annealing of the as-implanted samples in various types of glass substrates. The study showed that each of the implanted ions migrated in the substrates with different glass structures via unique mechanisms.

With conventional methods the sound velocity c in fluids can be determined using the back wall echo. This paper proposes a novel technique, in which the signals reflected by scattering particles suspended in the fluid are analysed instead. The basic idea is that the particles generate the strongest echo signal when being located in the sound field maximum. Therefore the position of the echo signal maximum is a measure for the sound propagation time to the sound field maximum. Provided that calibration data or sound field simulations for the ultrasonic transducer are available, this propagation time suffices to determine both the sound velocity and the location of the sound field maximum. The feasibility of the new approach is demonstrated by different kinds of experiments: (i) Measurements of the sound velocity in four fluids covering the wide range between c = 1116 m/s and 2740 m/s. The results show good agreement with values published elsewhere. (ii) Using the dependence of the sound velocity on temperature, it is possible to vary c over the comparatively small range between 1431 m/s and 1555 m/s with increments of less than 10 m/s. The measured statistical variation of 1.4 m/s corresponds to a relative uncertainty not worse than 0.1%. (iii) The focus position, i. e. the distance of the maximum of the sound field from the transducer, was varied by time-shifted superposition of the receive signals belonging to the different elements of an annular array. The results indicate that the novel method is even capable of measuring profiles of the sound velocity along the ultrasonic beam non-invasively.

Hydrogen plays an important role in many areas of material sciences. For example, hydrogen is an abundant impurity in thin-film materials - depending on the deposition process - and has great influence on the chemical, physical and electrical properties of many materials. Therefore, hydrogen analysis is of particular importance and it is often necessary to obtain a depth profile of the H-concentration. Best-suited methods for depth-resolved hydrogen analysis are ion beam techniques such as elastic recoil detection (ERD) and nuclear reaction analysis (NRA). In principle, both methods can be performed as primary - reference material free - methods.

The method with the best depth resolution is NRA using the 6385 keV resonance of the ¹H(¹⁵N,αγ)¹²C nuclear reaction. The correct quantification of the depth scale in the measured hydrogen profiles essentially relies on accurate stopping power values. The most commonly used stopping power values are from the SRIM program [1]. Here, the stopping power for heavy ions is calculated using the stopping power for hydrogen and an effective charge. The parameters for the effective charge are based on a fit of experimental data. Due to the lack of reliable experimental data, the uncertainty in the stopping powers, thus obtained, can be quite large and is only known in the widest sense (as the average deviation between experiment and SRIM for all elements or all ions). Therefore, we present a new method to deduce these values from a unique combination of two techniques: NRA and X-ray reflectometry (XRR), also a primary method. This method is applied to the determination of the accurate stopping power of ~6.4 MeV ¹⁵N ions in H-containing amorphous Si-layers (a-Si:H).

The samples are prepared by magnetron sputtering of a-Si in an Ar/H₂-atmosphere on a Cr-layer, which is needed as contrast material for XRR. The energy loss in the layers is measured by NRA at HZDR and the H-content has also been determined by NRA [2]. The layer thickness, density and roughness are determined by XRR using synchrotron radiation. XRR measurements were performed at the electron storage ring BESSY at the hard X-ray beamline BAMline [3]. The beam was monochromatised to 10 keV using a Si[111]-double-crystal monochromator. The reflected photons of the θ-2θ-scans from the 6-circle goniometer are counted by a scintillation detector and a photodiode, respectively. Data analysis is performed by the IMD 4.1 software package [4].

The combination of results from NRA and XRR allows the accurate calculation of the mass stopping power independent of the density of the material. The results for the H-containing amorphous Si-layers are presented, including a discussion of the uncertainty budget. Stopping powers at different H concentrations, ranging from 6 at.% to 14 at.%, are determined with an overall uncertainty of 3%. The preliminary results show a reasonable agreement with the SRIM values, thereby increasing the confidence in the results obtained by NRA.
[1] J. F. Ziegler, J. P. Biersack and U. Littmark, “The Stopping and Range of Ions in Solids", Pergamon Press, New York, 2009, http://www.srim.org.
[2] D. Grambole et al, Nucl. Instr. Meth. B 210 (2003) 526.
[3] W. Görner et al., Insight-Non-Destr. Test. Cond. Monit. 48 (2006) 540.
[4] D.L. Windt, Comp. in Physics 12 (1998) 360.

At the superconducting electron linear accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf the neutron time-of-flight facility nELBE has become operational. Fast neutrons in the energy range from 200 keV to 10 MeV are produced by the pulsed electron beam from ELBE impinging on a liquid lead circuit as a radiator. The short beam pulses of 10 ps provide the basis for an excellent time resolution for neutron time-of-flight experiments, giving an energy resolution of about <1% at 1 MeV with a short ight path of 5 m. The neutron intensity on target is ≈ 4*10^4 n/(cm2s) using an electron bunch charge of 77 pC and 100 kHz pulse repetition rate. The energy range of the neutrons produced is well suited for neutron cross section measurements relevant for the development of Generation IV reactor systems and for the transmutation of nuclear waste. First measurements of inelastic neutron scattering cross sections have been performed and will be presented.

A global parameterization is presented for the electromagnetic strength in heavy nuclei which gives a rather good fit to respective data in nuclei with mass numbers A between 50 and 240. It relies on a Lorentzian description of the isovector giant dipole resonance and it needs only a very small number of parameters to describe the electric dipole strength down to low excitation energy of importance for radiative capture processes. The resonance energies are chosen to be in accordance to liquid drop model parameters adjusted to ground state masses and to rotation invariant determinations of ground state deformation and triaxiality. By a straightforward use of this information a surprisingly smooth variation of the GDR width with A and Z is found and a full agreement to the predictions of the electromagnetic sum rule is assured. Predictions for radiative neutron capture cross sections compare well to respective data, when the proposed photon strength function is combined with standard prescriptions for the level density in the product nuclei.

The Electron-Ion Scattering experiment ELISe at the International Facility for Antiproton and Ion Research (FAIR) – a conceptual design study

The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of U 238 projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify 40 new heavy neutron-rich nuclei: Pt 205 , Au 207−210 , Hg 211−216 , Tl 214−217 , Pb 215−220 , Bi 219−224 , Po 223−227 , At 225−229 , Rn 230,231 , and Fr 233 . The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.

Measurement of the inelastic neutron scattering cross section of 56Fe

Operation of the liquid lead loop at nELBE

The nELBE neutron time of flight facility

Inelastic neutron scattering measurements at the photoneutron source nELBE

Transmutation radioaktiven Abfalls - Grundlagen, Methoden, Perspektiven

Es handelt sich um einen vertraulichen Bericht, deshalb kein Abstract.

First results of the differential cross section in dp elastic scattering at 1.25 GeV/u measured with the HADES over a large angular range are reported. The obtained data corresponds to large transverse momenta, where a high sensitivity to the two-nucleon and three-nucleon short-range correlations is expected.

Molecular-scale knowledge of U(VI) sorption reactions at the water-mineral interface is important for predicting U(VI) transport processes in the environment. In this work, in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy was used in a comprehensive investigation of the sorption processes of U(VI) onto TiO₂. The high sensitivity of the in situ ATR FT-IR technique allows the study of U(VI) concentrations down to the low micromolar range, which is relevant to most environmental scenarios.
A set of highly purified and well characterized TiO₂ phases differing in their origin, the ratio of the most stable polymorphs (anatase and rutile), in specific surface area, isoelectric points and in particle size distribution was investigated. Irrespective of the composition of the mineral phase, it was shown that U(VI) forms similar surface complexes, which was derived from the antisymmetric stretching mode υ₃(UO₂) showing a characteristic shift to lower wavenumbers compared to the respective aqueous species at a similar low concentration level.
The availability of a fast scanning IR device makes it feasible to perform time-resolved experiments of the sorption processes with a time resolution in the sub-minute range. It is shown that during the early stages of the U(VI) uptake a surface species on the mineral phase is formed characterized by a significantly red-shifted absorption maximum which is interpreted as a bidendate inner-sphere complex. After prolonged sorption, the IR spectra indicate the formation of a second surface species showing a smaller shift compared to the aqueous species. These findings were verified by a series of spectroscopic experiments performed on a U(VI)-saturated surfaces.
Further ATR FT-IR spectroscopic experiments focused on the impact of the U(VI) concentration, the pH value and the exclusion of atmospheric carbonate on the sorption process. The results confirm the presence of two surface species, occurring sequentially as a function of U(VI) surface loading.
This work provides new insights into the sorption processes of U(VI) on titanium dioxide on a molecular level. Basic thermodynamic ideas of surface complexation are substantiated by in situ infrared spectroscopy.

Two free-electron lasers (FELBE; 4-21 μm and 18-250 μm, respectively) have been in routine user operation for a wide range of IR experiments at the radiation source ELBE in the Forschungszentrum Dresden-Rossendorf for several years. The lasers are driven by a superconducting RF linac that permits the generation of a cw-beam with a repetition rate of 13 MHz and a high average beam power. In addition, operation in a macropulse modus (pulse duration >100 µs, repetition rate ≤ 25 Hz) is possible. A few important experiments using the cw-operation are discussed.

The Radboud University in Nijmegen received funding to realize a narrow-band THz laser system and a 45 T hybrid magnet system. In this paper we present the technical solutions for realization of the main system components. We present the details of the RI Research Instruments GmbH (a former ACCEL Instruments GmbH activity) LINAC system. Operation of the full system (including the electron source) at 3 GHz is desirable and deemed feasible after first experimental studies. As the Nijmegen FEL will operate at wavelength up to 1.5 mm, the cavity will be fully waveguided, complicating the incorporation of an intra-cavity Fox-Smith interferometer required to induce coherence between micropulses and a Michelson interferometer as most ideal outcoupler. The optical distribution system comprises 150 m of vacuum tubing with 25 cm effective diameter (planar and refocusing) mirrors. A robust yet cost efficient realization taking boundary conditions on optical beam parameters at diagnostics station and user stations into account is foreseen.

no abstract available

Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) is a very sensitive technique to characterize the degree of molecular ordering in thin films on metallic surfaces. This is the first report of the coupling of a PM-IRRAS microscope to a free electron laser (FEL), a light source of highest brilliance. Some FELs emit in the infrared region and permit the mapping of molecular properties at high lateral resolution. We studied the molecular orientation of octadecanephosphonic acid (OPA) attached to a gold surface with microstructured aluminum oxide islands on the gold. The spatial resolution achieved is 12 μm which corresponds to the diffraction limit of the infrared light used in this study. This is a substantial improvement compared to previous studies using a PM-IRRA accessory together with a commercial Fourier transform infrared spectrometer, where the lateral resolution is noise-limited rather than diffraction-limited. The spectral maps reveal that OPA is preferably attached to the aluminum oxide islands via the bidentate binding mode whereas the tridentate mode is dominating in case of OPA attached to the gold areas.

For a risk assessment for released radionuclides a comprehensive elucidation of the migration behavior of uranium is necessary. Therefore not only the uranium interactions with the geosphere but also with the biosphere have to be investigated.
The aim of the study was to characterize the sorption of U(VI) by living Chlorella vulgaris and Schizophyllum commune and the molecular structure of formed complexes.
Both organisms bind significant amounts of U(VI) dependent on applied uranium concentration and pH in the range from 4 to 7. At uranium concentration of 0.2 mM Schizophyllum shows binding capacities of around 130 mg U/g dry weight independent of pH value. A higher initial uranium concentration leads to higher binding capacities of 230-280 mg U/g dry weight at pH 5 and 6 for still living Schizophyllum biomass. In contrast to that, Chlorella binds at a uranium concentration of 0.5 mM 75 mg U/g dry weight (pH 4.4). Furthermore, Chlorella cells die at concentration higher than 0.1 mM within 48 h. Therefore further experiments were carried out at a concentration of 5 µM. Under this condition living algae firstly bind almost all uranium within 5 min of incubation, but then again mobilize up to 80% of the bound uranium during ongoing incubation. The release of metabolism related substances is suggested to cause this mobilization of uranium. As potential leachates for algal-bound uranium oxalate, citrate and ATP were tested and found to be able to mobilize 55-87% of the algal-bound uranium within 24 h.
Differences in complexation of uranium by active and inactive algae cells as well as fungal biomass were investigated with a combination of different spectroscopic techniques. Obtained results demonstrated an involvement of carboxylic and organic/inorganic phosphate groups in the uranium complexation with varying contributions dependent on microbial biomass, cell status, uranium concentration and pH.

Nowadays AFM becomes a more and more attractive method for microbiologists to investigate Microorganisms. The technique allows imaging over a broad magnitude scale and is not confined by the diffraction limit. Sometimes it is interesting to measure the dimensions of an organism. The other time the question is about surface properties of a cell. The scanning principle makes the AFM technique comparatively slow and the specimen has to be fixed on a flat surface during the scans. It is quite simple to dry the samples on a surface. Drying leads to a good immobilization but also to drying artifacts like denaturation of Proteins and shrinkage of the whole cell due to the loss of water. Therefore it is advantageous for most biological questions to do the imaging in liquids. Immobilization is not trivial as result of the heterogeneous surface properties of different micro organisms. Existing preparation methods are mostly utilizing coated surfaces or lithographicaly prepared surfaces. While lithography is not an option for everyone there is a variety of coatings available for instance poly-L-lysine or gelatine which work quite good with some microorganisms. A new method based on polyelectrolyte coated surfaces combined with centrifugal sedimentation shows promising results regarding the efficiency of immobilization. A variety of micro organisms were tested with the new method showing universality for many organisms. The samples were prepared with and without fixation. Of course fixation simplifies the imaging by enhancing the stability of the samples. But even unfixed Microorganisms can be imaged which opens the field for investigations in respect to cell division or other dynamic processes of living cells.