Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

A phenomenological quasiparticle model, featuring dynamically generated self-energies of excitation modes, successfully describes lattice QCD results relevant for the QCD equation of state and related quantities both at zero and non-zero net baryon density. Here, this model is extended to study bulk and shear viscosities of the gluon-plasma within an effective kinetic theory approach. In this way, the compatibility of the employed quasiparticle ansatz with the apparent low viscosities of the strongly coupled deconfined gluonic medium is shown.

We analyze mu⁺mu^- pair production generated by high-energy electrons emerging from a laser-wakefield accelerator. The mu⁺mu^- pairs are created in a solid thick high-Z target, following the electron accelerating plasma region. Numerical estimates are presented for electron beams obtained presently in the LBL TW laser experiment \cite{C2} and possible future developments. Reactions induced by the secondary bremsstrahlung photons dominate the dimuon production. According to our estimates, a 20 pC electron bunch with energy of 1 (10) GeV may create about 200 (6000) muon pairs. The produced mu(+/-) can be used in studying various aspects of muon-related physics in table top installations. This may be considered as an important step towards the investigation of more complicated elementary processes induced by laser driven electrons.

Self-ion irradiation in combination with nanoindentation offers the possibility to characterize irradiation damage in a broad range of irradiation temperature and fluence. Nanoindentation results are reported for Fe-2.5at%Cr, Fe-9at%Cr and Fe-12.5at%Cr irradiated at room temperature, 300°C and 500°C. Special features of this work are roughly rectangular damage profiles and exploitation of the full load dependence of hardness. The effects of Cr content, fluence and irradiation temperature are discussed. Cases of both broad consistence with and deviations from reported trends are found. Hardening features were characterized by means of TEM also taking into account SANS data reported for neutron-irradiated conditions of the same alloys. A tentative two-feature hardening model was applied.

Due to the high sensitivity of Ni–Ti films to environmental changes, e.g. thermal, and/or to stress, they are ideal materials for applications on micro-sensors. It was aimed to obtain Ni–Ti films exhibiting the beginning of the B25R-phase transformation between room temperature (RT) and 0°C. Thus, films with a slightly Ni-rich composition were prepared by sputtering, without intentional heating of the substrate. The Ni–Ti films were deposited on an Si₃N₄ intermediate layer previously deposited on naturally oxidized Si(100). The crystallization behaviour of the samples (at a constant temperature of 430°C) was studied by X-ray diffraction in grazing incidence geometry off-plane (GIXD) at a synchrotron-radiation beamline. The GIXD patterns obtained during the annealing process of the Ni–Ti polycrystalline films revealed mainly an austenitic structure (B2 phase) and the precipitation of Ni₄Ti₃. The results have also shown that the presence of an intermediate layer of Si₃N₄ enhances the crystallization process of the Ni–Ti sputtered films when compared to the films deposited directly on single-crystal Si (with native oxide).
The phase transformation behaviour of the Ni–Ti film on Si₃N₄ was evaluated by XRD in off-plane Bragg–Brentano geometry during cooling (RT-> -40°C) and heating (-40°C ->RT). It has been observed that a high fraction of the Ni–Ti film is already transformed to R-phase at 9°C (austenitic at RT), as well as a very small temperature hysteresis for the B25R-phase transformation.
After the characterization described above, the film was removed from the substrate. The free-standing film showed a pronounced ‘‘two-way’’ shape memory effect (SME). In the austenitic state the film presents a flat shape. During cooling, by reducing its distance from ice cubes (i.e., decreasing the surrounding temperature), the film starts bending exhibiting a final curled shape (yet without touching the ice). On heating it recovers its flat shape. The authors attribute the nature of this ‘‘two-way’’ SME to the Ni₄Ti₃ precipitates that formed during the heat treatment.

Nominally undoped, hydrothermally grown ZnO single crystals have been investigated after doping in remote H plasma. Characterizations have been made by positron annihilation (slow positron implantation spectroscopy, lifetime, coincidence Doppler broadening), temperature-dependent Hall and photoluminescence measurements. The H content before and after the doping has been determined using nuclear reaction analysis. In addition, changes of the polished surface of the crystals have been monitored by atomic force microscopy.
H plasma doping produced a metallic conducting near-surface layer. It is discussed if this is due to an increased H and zinc incorporation into pre-existing zinc vacancy – H complexes, as this also could explain the occurrence of a second positron lifetime component in the volume of the crystals, from which a bulk positron lifetime of (153 +/- 2) ps for ZnO is derived in very good agreement with previous experiments and theoretical calculations.

We have investigated the magnetic properties of pure ZnO thin films grown under N2 pressure on a-, c- and r-plane Al2O3 substrates by pulsed laser deposition. The substrate temperature and the N2 pressure were varied from room temperature to 570 °C and from 0.007 mbar to 1.0 mbar, respectively. The magnetic properties of bare substrates and ZnO films were investigated by SQUID magnetometry. ZnO films grown on c- and a-plane Al2O3 substrates did not show significant ferromagnetism. However, ZnO films grown on r-plane Al2O3 showed reproducible ferromagnetism at 300 K when grown at 300¡400 °C and 0.1-1.0 mbar N2 pressure. Positron annihilation spectroscopy measurements as well as density functional theory calculations suggest that the ferromagnetism in ZnO films is related to Zn vacancies.

We investigate theoretically the electron dynamics in a single-channel mesoscopic ring with a localized impurity subjected to picosecond linearly polarized asymmetric electromagnetic pulses. A nonequilibrium coherent population of electronic states that possesses a time-dependent polarization is induced. The associated radiation emission decays on a time scale determined by the system relaxation and hence lasts long, after the pulses have perished. We derive analytically and confirm numerically that the presence of an impurity influences strongly the time-dependent charge polarization and allows the generation of higher harmonics in the terahertz range.

To activate silica optically our investigations are extended to ion implantation, mainly to overstoichiometric injection or isoelectronic substitution of the both constituents silicon or oxygen, i.e. by ions of the group IV (C, Si, Ge, Sn, Pb) or the group VI (O, S, Se). Such implantation produce new luminescence bands in silica layers, partially with optical electronic–vibronic transitions and respective multimodal spectra. In this context, special interest should be directed to low-dimension nanocluster formation in silica layers. Cathodoluminescence, high resolution transmission (HR-TEM) and scanning transmission electron microscopy (STEM), and energy dispersive X-ray analysis (EDX) have been used to investigate Si and Ge cluster formation in amorphous silicon dioxide layers and their respective luminescence behavior.

This paper describes the home-made MULTIpurpose MAGnetic field system MULTIMAG, a facility composed of compact coil systems carrying high currents. Prominent features of MULTIMAG are (i) The large bore of 400 mm in height and 365 mm in diameter, which supports, in conjunction with the high current densities, the attainability of similarity criteria in the industrial range. (ii) Because the use of ferromagnetic material was strictly avoided in the construction, the rotating, travelling, pulsating, and DC in either homogeneous or cusp configuration magnetic fields may be superimposed linearly. (iii) In order to have as flexible as possible spatio-temporal distributions of the magnetic fields, the power supplies are realised as amplifiers. Each of the seven phases, three for the rotating and the travelling field, respectively, and one for the pulsating field, comprises a pulse width modulated power amplifier controlled by its own freely programmable frequency synthesizer.

The verification of design improvements of a fuel assembly of a nuclear reactor core and their influence on the critical heat flux require expensive experiments. Therefore the supplementation or even the replacements of experiments by numerical analyses are of relevant interest in fuel assembly design. The CFD modeling has the potential of simulation independent on the certain geometry.
The presentation describes the actual state of CFX modeling of subcooled boiling and their possible contribution for rod bundle design. The comparative investigation of different designs is possible at least qualitatively. For more quantitatively reliable results the models have to be improved. In the presentation the demands on the accuracy of measured values are established. The usage of model fluids enables the enlargement of the investigated geometry. The most promising results are expected by tomographic methods like gamma tomography or especially by fast X-ray tomography.

The verification of design improvements of a fuel assembly of a nuclear reactor core and their influence on the critical heat flux require expensive experiments. Therefore the supplementation or even the replacements of experiments by numerical analyses are of relevant interest in fuel assembly design. The CFD modeling has the potential of simulation independent on the certain geometry.
The presentation describes the actual state of CFX modeling of subcooled boiling and their possible contribution for rod bundle design. The comparative investigation of different designs is possible at least qualitatively. For more quantitatively reliable results the models have to be improved. In the presentation the demands on the accuracy of measured values are established. The usage of model fluids enables the enlargement of the investigated geometry. The most promising results are expected by tomographic methods like gamma tomography or especially by fast X-ray tomography.

The investigation of insulation debris generation, transport and sedimentation becomes important with regard to reactor safety research for PWR and BWR, when considering the long-term behaviour of emergency core cooling systems during all types of loss of coolant accidents (LOCA). A joint research project on such questions is being performed in cooperation between the University of Applied Sciences Zittau/Görlitz and the Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow and the development of CFD models for its description. While the experiments are performed at the University at Zittau/Görlitz, the theoretical modelling efforts are concentrated at Forschungszentrum Dresden-Rossendorf.
In the current paper the basic concepts for CFD modelling are described and feasibility studies are presented.

The investigation of insulation debris generation, transport and sedimentation becomes important with regard to reactor safety research for PWR and BWR, when considering the long-term behavior of emergency core cooling systems during all types of loss of coolant accidents (LOCA). The insulation debris released near the break during a LOCA incident consists of a mixture of disparate particle population that varies with size, shape, consistency and other properties. Some fractions of the released insulation debris can be transported into the reactor sump, where it may perturb/impinge on the emergency core cooling systems.
Open questions of generic interest are the sedimentation of the insulation debris in a water pool, its possible re-suspension and transport in the sump water flow and the particle load on strainers and corresponding pressure drop. A joint research project on such questions is being performed in cooperation between the University of Applied Sciences Zittau/Görlitz and the Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow and the development of CFD models for its description. While the experiments are performed at the University at Zittau/Görlitz, the theoretical modeling efforts are concentrated at Forschungszentrum Dresden-Rossendorf.
In the current paper the basic concepts for CFD modeling are described and feasibility studies including the conceptual design of the experiments are presented.

This experimental work is concerned with optimisation of the Czochralski crystal growth process. With respect to the shape of the solidification front and the related mono-crystalline growth, the ratio of the horizontal and the vertical temperature gradient r* = DTh /DTv at the triple point liquid-solid-atmosphere is thought of being a crucial magnitude, which desirably should be in the order of unity. A liquid metal model experiment was therefore built that allows studying this ratio under the influence of magnetic fields applied to the melt. The cylindrical liquid metal column was homogeneously heated from below, whereas on top the heat was extracted in a concentrical region covering only about one third of the surface in order to simulate the growing crystal. It was shown that the native, i. e. without flow control, r* ≈ 3 is far removed from unity. In a first series of measurements, it was then possible to reach the target value r* = 1 for any temperature difference between the bottom and the top at a moderate field strength while applying a rotating magnetic field.

The solubility limit of Cr in Fe (a-Fe-Cr) at lower temperatures is a matter of debate. We report a direct estimation of the solubility limit at 300°C from SANS data obtained for neutron-irradiated Fe-Cr alloys. The SANS results indicate that the equilibrium concentration of a’ was reached via irradiation-enhanced diffusion. The solubility limit was estimated using an iterative approach based on the SANS invariant and the lever rule of phase equilibrium

Defects in zinc-implanted and thermally annealed ZnO thin films were investigated by means of capacitance-voltage spectroscopy (C-V), thermal admittance spectroscopy (TAS), deep level transient spectroscopy (DLTS), and photoluminescence (PL) spectroscopy. The authors report on the formation of two donor states approximately 35 and 190 meV below the conduction band edge, observed by TAS and DLTS, respectively. In the PL spectra of a reference sample a peak at 3.366 eV was present, which diminished after the implantation, while a new peak at 3.364 eV was observed only in the spectrum of the implanted sample. Since only intrinsic ions were implanted, the authors consider the defects formed by the zinc implantation and annealing to be intrinsic.

Dendritic microstructure is one of the major microstructural constituents of peritectic alloys. In the present work, the effect of melt convection on the secondary dendritic arm spacing (SDAS) and volume fraction of properitectic alpha-Fe was investigated during solidification of stoichiometric Nd-Fe-B alloys under forced crucible rotation technique. The resulting microstructure of the alloy in consideration of melt convection has been investigated using scanning electron microscopy and optical microscopy. The average SDAS was determined for each sample from the whole cross-section of the cylindrical test samples using image analyzing software LEICA QWIN. A detailed statistical analysis of the spacing distribution was performed on the basis of the variation of SDAS values averaged from about 80 to 120 dendrites in different zones. The a-Fe volume fraction measured by vibrating sample magnetometer (VSM) reduces with increasing crucible rotation frequency. Similarly, the SDAS values decrease with increasing rotation frequency. These results are explained from the viewpoint of a reduced melt convection state under steady forced crucible rotation leading to a reduced effective mass transfer coefficient.

AlYB₁₄ (Imma) thin films were synthesized by magnetron sputtering. Based on X-ray diffraction, no phases other than crystalline AlYB₁₄ could be identified. According to electron probe microanalysis, energy dispersive X-ray analysis and elastic recoil detection analysis, the Al and Y occupancy varies in the range of 0.73 to 1.0 and 0.29 to 0.45, respectively. Density functional theory based calculations were carried out to investigate the effect of occupancy on the stability of Al_xY_yB₁₄ (x, y = 0.25, 0.75, 1). The mean effective charge per icosahedron and the bulk moduli were also calculated. It is shown that the most stable configuration is Al_0.5YB₁₄, corresponding to a charge transfer of 2 electrons to the boron icosahedra. Furthermore, it is found that the stability of a configuration is increased if the charge is homogeneously distributed within the icosahedra. The bulk moduli for all investigated configurations are in the range between 196 and 220 GPa, rather close to known hard phases such as α-Al₂O₃.

We have measured the temperature and frequency-dependant transmission and phase shift through LuNi₂B₂C thin films on MgO substrates at terahertz frequencies. From the measured data, we could accurately determine the complex dielectric constant, epsilon, the complex optical conductivity, sigma, and the penetration depth, gamma. Comparing our measured results with theory, we find strong deviations from the standard one-band BCS predictions. These deviations can be attributed to the multiband nature of the superconducting state in LuNi₂B₂C.

Impact of a highly charged ion upon a solid surface can induce dramatic changes in the morphology only by the release of its potential energy. Hillocks and mono-atomic deep pits have been observed on the surfaces of CaF2 and KBr, respectively. For both processes a threshold in the potential energy exists for the creation of these nanostructures. Above this threshold the structure size increases linearly with potential energy. The mechanisms for the formation of hillocks and pits are discussed and a rst attempt to present a unied microscopic picture is made.

In diesem Vortrag wird Beschleunigermassenspektrometrie am FZD vorgestellt.

Outline
Ion – Solid interaction
Experimental
RBS + high resolution
ERDA + high resolution
H analysis
Summary

Abstract is not available

Abstract is not available

not available. will be published later

The novel technology of particle acceleration based on high intensity laser systems promises accelerators of compact size and reasonable costs and may significantly contribute to a widespread use of high precision hadron radiotherapy. Although some basic properties of laser acceleration are reasonably well known from theory, simulations and fundamental physical experiments, several further requests have to be fulfilled for its medical application such as supply of a stable and reliable particle beam with reproducible properties and precise delivery of dose in an appropriate irradiation time with required exposure of a desired irradiation field. Moreover, the ultra-short pulsed (in the region of 100 fs) particle beams with resulting high pulse dose-rate (in the order of 1012 Gy/min) have to be characterized with regard to their radiobiological properties.
First in-vitro cell irradiations with laser accelerated electrons have been performed at the Jena Titanium:Sapphire (JeTi) 10 terawatt laser system and dose-effect-curves were obtained for four cell lines and two endpoints. Laser pulses (80 fs duration, 2.5 Hz repetition rate) were focused into a helium gas jet, accelerating electrons to energies of up to 20 MeV. Before irradiation, the JeTi system was optimized for cell experiments: the electron spectrum was limited to a minimum energy of 3 MeV, the beam spot size was adjusted and the dose rate and homogeneity were improved. Each cell sample was equipped with two Gafchromic EBT radiochromic films, one in front and one behind the cell monolayer, used for retrospective precise dose determination. A Roos ionization chamber and a Faraday Cup monitored the beam providing on-line dose information necessary for irradiation control. Moreover the energy spectrum was measured both with an electromagnetic spectrometer and by analyzing film stack measurements. Following to the irradiation the cell survival fraction was determined using clonogenic survival assay. In addition, DNA double strand breaks present in cell 24 h after irradiation were analyzed.
Normally used for physical single-shot experiments, the JeTi was customized for a long-time cell irradiation. 163 Samples were irradiated at 13 experiment days over a period of 10 weeks with doses between 0.3 and 10 Gy. A reasonably stable and reproducible beam was achieved. Dose homogeneity was examined for all samples within the target area and the inhomogeneity obtained was less than 10 % for all days and all applied doses. Although still preliminary, the dose-effect-curves obtained show in general a lower biological effectiveness for the laser accelerated electron beams in comparison with conventional x-rays.

A concentrated vortex with properties similar to a tornado may be created by magnetic body forces. We study this phenomenon experimentally by applying combined travelling and rotating magnetic fields to a liquid metal cylinder. The bulk velocity is measured by ultrasound Doppler velocimetry and the surface velocity is reconstructed by particle image velocimetry. The travelling magnetic field (TMF) creates an axial body force with a parabolic radial profile. The induced meridional flow follows the field at the rim and returns through the central part. Thus an intense converging flow is created at one end of the cylinder. The additionally superimposed rotating magnetic field (RMF) with a substantially different frequency sets the flow into rotation. The angular momentum conservation forces the rotation to intensify towards the centre of the converging flow. The swirl intensification is limited by the centrifugal force which stops the radial inflow at some equilibrium radius. The resulting concentrated vortex is unstable but persistent. We determine conditions of its formation in terms of the ratio of the two magnetic body forces. It turns out that the maximum strength of the vortex is determined by the TMF but its structure is governed by a much weaker RMF. The maximum time-averaged swirl is observed at a force ratio of about 100. A pronounced two-cell vortex with a reversed meridional circulation in the inner core is observed at a force ratio of about 50. The inner core is encircled then by a number of smaller vortices resembling a large wedge-shaped tornado or eye of a tropical cyclone. As the force ratio is further increased the inner core expands until it occupies the entire cylinder. The flow is then essentially controlled by the RMF despite the TMF might be still much stronger. The phenomenon may be useful to stir floating particles into the melt. A related sink-vortex may occur over a drain-hole in various technological processes. Magnetic body forces can be used to alter or eliminate it.

This paper describes laboratory experiments for investigations of flow structures in liquid metal bubbly flows under the influence of a travelling magnetic field (TMF). The melt flow is driven by central gas injection into a cylindrical container filled with the low melting point alloy GaInSn. Velocity fields of the liquid were measured non-intrusively using the ultrasound Doppler method. Depending on the travelling direction of the magnetic field, the TMF mainly imposes either a co-current or counter flow with respect to the original bubble-driven circulation. The application of a downward TMF significantly increases the liquid velocity all over the fluid volume. An upward TMF gives rise to more complex structures of the velocity field resulting in alternately arranged up- and downstream regions. Both the upward and downward TMF promote the occurrence of non-steady motions with distinct velocity fluctuations leading to an intensification of related transport processes in the melt and providing the perspective of enhanced mixing efficiencies.

Radiotherapy is a mainstay of cancer treatment. More than 50 % of tumour patients in developed countries receive radiotherapy, either as the only method of treatment or as a crucial component in combination with surgery and/or systemic treatment. However, in many cases, especially for compact, deep-seated, radiation-resistant tumours growing in close vicinity to organs at risk, state-of-the-art radiotherapy which is based on photon or electron beams delivered by compact electron linear accelerators comes to its limits. Considerably improved conformance of radiation dose to the tumour volume with simultaneous preservation of surrounding healthy tissue will derive from utilization of ions whose favourable physical and radiobiological properties have already been demonstrated in clinical application [1, 2]. However, only a few ion therapy facilities are running worldwide, due to their complexity, large scale and high investment cost linked to present radiofrequency accelerator technology. Laser-based particle acceleration is a rapidly evolving new technology [3-9]. It promises the development of compact ion accelerators with reasonable costs, which may be integrated into existing hospitals since they are based on compact table-top multi-terawatt laser systems and the acceleration process takes place within micrometer distances. This novel technology appears to be a key that many more patients could benefit from ion radiotherapy and its favourable properties.

The MLLTRAP at the Maier-Leibnitz-Laboratory (Garching) is a new Penning trap facility designed to combine several novel technologies to decelerate, charge breed, cool, bunch and purify the reaction products and perform high-accuracy nuclear and atomic mass measurements. It is now in the commissioning phase, achieving a mass-resolving power of about 105 in the purification trap for stable ions.

Was sind Magnetfelder? Wo findet man sie? Wie erzeugt man sie und zu was sind sie nutze? Antworten auf diese Fragen sollen in dem Vortrag durch Vorstellung der weltweiten Bestrebungen, immer höhere Magnetfelder zu erreichen, gegeben werden. Ähnlich wie z. B. Druck und Temperatur haben magnetische Felder einen tief greifenden Einfluss auf den Zustand und Zustandsänderungen der Materie. Untersuchungen von Materialien in hohen Magnetfeldern sind daher mittlerweile Standard und eine Vielzahl von Anwendungen in unserem täglichen Leben sind ohne Magnetfeldeffekte undenkbar. In der Forschung wird der stetig wachsende Bedarf an möglichst großen Magnetfeldstärken durch Hochfeldlaboratorien abge-deckt. In dem neu aufgebauten Hochfeld-Magnetlabor Dresden sollen demnächst gepulste Magnetfelder bis zu 100 Tesla erzeugt werden. Erste Hochfeldmagnete sind in Betrieb und seit 2007 hat neben der Eigenforschung der Nutzerbetrieb begonnen. Der momentane Status des Labors, die Schwierigkeiten, die zur Erzeugung so hoher Magnetfelder überwunden werden müssen, und exemplarische wissenschaftliche Ergebnisse aus Hochfeldstudien sollen vorgestellt werden.

One of the most powerful methods to determine important bulk band-structure parameters in metals is the measurement of magnetic quantum oscillations. By applying high magnetic fields, this can be done e.g. by detecting the oscillations in the field-dependent magnetization, called de Haas-van Alphen (dHvA) effect, or by resolving Shubnikov-de Haas (SdH) oscilla-tions in the field-dependent resistivity. The combination of such kind of experimental data with sophisticated band-structure calculations often is a necessary prerequisite to gain a deeper understanding of the electronic properties of metals. One example for such a joint ef-fort of experimental and theoretical work is the finding and explanation of the field-induced band-structure change in CeBiPt [1]. In this material, a drastic change of the electronic band structure, as seen in the SdH and Hall signals, is found above about 25 T. This field-induced Lifshitz transition can be understood by the splitting of the Ce-5d bands close to the Fermi energy due to the exchange interaction with the polarized Ce-4f states. Another example where dHvA measurements were successfully combined with highly precise full-potential local-orbital calculations is the borocarbide superconductor LuNi₂B₂C [2]. By carefully com-paring the experimentally extracted effective masses with the calculated bare masses the many-body mass enhancements could be determined independently for several bands and for different directions.

The temperature dependences of the electric-transport properties of the two-dimensional organic conductors β"--(BEDT-TTF)₂SF₅CH₂CF₂SO₃, β"-(d₈-BEDT-TTF)₂SF₅CH₂CF₂SO₃, and β"-(d₈-BEDTTTF)₂SF₅CH₂CF₂SO₃ are measured by dc methods in and perpendicular to the highly conducting plane. Microwave measurements are performed at 24 and 33.5GHz to probe the high-frequency behavior from room temperature down to 2 K. Superconductivity is observed in β"-(BEDT-TTF)₂SF₅CH₂CF₂SO₃ and its deuterated analogue. Although all the compounds remain metallic down to low-temperatures, they are close to a charge-order transition. This leads to deviations from a simple Drude behavior of the optical conductivity which become obvious already in the microwave range. In β"-(BEDT-TTF)₂SF₅CH₂CF₂SO₃, for instance, charge fluctuations cause an increase in microwave resistivity for T < 20K which is not detected in dc measurements. β"-(BEDT-TTF)₂SF₅CHFSO₃ exhibits a simple metallic behavior at all frequencies. In the dc transport, however, we observe indications of localization in the perpendicular direction.

We report on precise low-temperature specific-heat measurements, C(T), of YbRh₂Si₂ in the vicinity of the antiferromagnetic phase transition on a single crystal of superior quality (residual resistivity ratio of ~150).We observe a very sharp peak at TN = 72 mK with absolute values as high as C/T = 8 J/molK². A detailed analysis of the critical exponent α around T_N reveals α ≤ 0.38 which differs significantly from those of the conventional universality classes in the Ginzburg-Landau theory, where α ≤ 0.11. Thermal-expansion measurements corroborate this large positive critical exponent. These results provide insight into the nature of the critical magnetic fluctuations at a temperature-driven phase transition close to a quantum critical point.

We demonstrate that the third elemental group-IV semiconductor, germanium, exhibits superconductivity at ambient pressure. Using advanced doping and annealing techniques of state-of-the-art semiconductor processing, we have fabricated a highly Ga-doped Ge (Ge:Ga) layer in near-intrinsic Ge. Depending on the detailed annealing conditions, we demonstrate that superconductivity can be generated and tailored in the doped semiconducting Ge host at temperatures as high as 0.5 K. Critical-field measurements reveal the quasi-two-dimensional character of superconductivity in the ~60 nm thick Ge:Ga layer. The Cooper-pair density in Ge:Ga appears to be exceptionally low.

Large-scale ab initio molecular dynamics simulations of ion-solid interactions in SiC reveal that significant charge transfer occurs between atoms, and defects can enhance charge transfer to surrounding atoms. The results demonstrate that charge transfer to and from recoiling atoms can alter the energy barriers and dynamics for stable defect formation. The present simulations illustrate in detail the dynamic processes for charged defect formation. The averaged values of displacement threshold energies along four main crystallographic directions are smaller than those determined by empirical potentials due to charge-transfer effects on recoil atoms.

Understanding the dynamics of metals and radionuclides in soil environments is necessary for evaluating risks to pristine sites. An iron-rich creek soil of a former uranium-mining district (Ronneburg, Germany) showed high porewater concentrations of heavy metals and radionuclides. Thus, this study aims i) to evaluate metal dynamics during terminal electron accepting processes (TEAPs) and ii) to characterize the active microbial populations in biostimulated soil microcosms using a stable isotope probing (SIP) approach. In biostimulated soil slurries, concentrations of soluble Co, Ni, Zn, As, and unexpectedly U increased during Fe(III)-reduction. This suggests that there was a direct reduction of As and a release of sorbed metals during reductive dissolution of Fe(III)-oxides. Subsequent sulfate-reduction was concurrent with a decrease of U, Co, Ni, and Zn concentrations. The relative contribution of U(IV) in the solid phase changed from 18.5 to 88.7% after incubation. The active Fe(III)-reducing population was dominated by δ-Proteobacteria (Geobacter) in 13C-ethanol amended microcosms. A more diverse community was present in 13C lactate amended microcosms including taxa related to Acidobacteria, Firmicutes, δ- Proteobacteria, and β-Proteobacteria. Our results suggested that biostimulated Fe(III)-reducing communities facilitated the release of metals including U to groundwater which is in contrast to other studies.

The successful use of picosecond-pulse free-electron-laser (FEL) radiation for the continuous-wave terahertz-range electron spin resonance (ESR) spectroscopy has been demonstrated. The combination of two linac-based FELs (covering the wavelength range of 4–250 µm) with pulsed magnetic fields up to 70 T allows for multifrequency ESR spectroscopy in a frequency range of 1.2–75 THz with a spectral resolution better than 1%. The performance of the spectrometer is illustrated with ESR spectra obtained in the 2,2-diphenyl-1-picrylhydrazyl and the low-dimensional organic material (C₆H₉N₂)CuCl₃

The stopping of high-energy light ions in a host solid is characterised by a very high ratio of electronic to nuclear stopping powers. Consequently, alpha particles (⁴He cores whose energies range between 3.9 and 8.8 MeV) penetrating into a host mineral cause tremendous amounts of lattice ionisation, whereas they are rather marginally efficient in generating atomic displacements. Radiohaloes in rock-forming minerals are therefore mostly characterised by relatively low levels of structural radiation damage [1,2]. It is well known, however, that ion-beam irradiation may not only create defects, but it may also cause structural reconstitution [3-5]. It has been suspected that the electronic excitation by the alpha particles may result in radiation-enhanced annealing of pre-existing radiation damage, as for instance the bulk metamictization or fission tracks [6] in minerals.
The present study aimed at checking the principal effect of alpha particles on the self-irradiation damage (i.e., predominantly alpha-recoil damage) in U- and Th-bearing accessory minerals. Three hypothetical possibilities had to be considered, namely, (i) the creation of additional damage, (ii) structural reconstitution of the pre-existing damage, or (iii) insignificant effects on the structural state. For this, a suite of well-characterised zircon and monazite samples, covering the entire range from well-crystallised to fully metamict, were irradiated with 8.8 MeV ⁴He²⁺ ions (which are the analogue of alpha particles generated in the ²¹²Po ---> ²⁰⁸Pb decay in the Th chain). Fluences were varied in the range 10¹² - 10¹⁷ He ions/cm². In the case of He-irradiated metamict (i.e., amorphous) samples, no indication of recrystallisation or nucleation was found. For all non-amorphous starting materials, we found that the degree of structural damage has always notably increased after the He irradiation. Consequently, alpha particles do create structural damage not only in well-crystallised but also in mildly to highly radiation-damaged zircon and monazite. In contrast, the hypothetical ability of alpha particles to assist damage annealing is not supported.
Our observations do not seem to confirm results of dual-beam ion irradiation experiments (i.e., the simultaneous irradiation of a solid with a heavy ion beam with relatively high nuclear excitation, and a second beam with high electronic excitation, such as high-energy light ions or electrons). Such experiments suggested that the simultaneous, intense electronic excitation may retard or prevent amorphisation by heavy ions [7]. The apparent contrast to our results may perhaps be explained by the consideration that self-irradiating minerals do virtually never experience genuine dual irradiation. Due to their generally low irradiation rates (averaging a few events per minute and mm³), alpha recoils and alpha particle irradiation in the very same volume area do not occur simultaneously but successively.

References:

[1] Nasdala, L., Wildner, M., Wirth, R., Groschopf, N., Pal, D.C., Möller, A. (2006) Mineral. Petrol. 86, 1-27
[2] Krickl, R., Nasdala, L., Götze, J., Grambole, D., Wirth, R. (2008) Eur. J. Mineral. 20, 517-522
[3] Priolo, F., Spinella, C., Rimini, E. (1990) Phys. Rev. B 41, 5235-5242
[4] Heera, V., Kögler, R., Skorupa, W., Grötzschel, R. (1993) Nucl. Instr. Meth. Phys. Res. B80/81, 538-542
[5] Som, T., Ghatak, J., Sinha, O.P., Sivakumar, R., Kanjilal, D. (2008) J. Appl. Phys. 103, 123532
[6] Hendricks B.W.H., Redfield, T.F. (2005) Earth Plan. Sci. Lett. 236, 443-458
[7] Devanathan, R., Sickafus, K.E., Weber, W.J., Nastasi, M. (1998) J. Nucl. Mat. 253, 113-119

The underlying motivation of this work is the tailored growth of Ge nanocrystals (NC) for photovoltaic applications. The use of superlattices (SL) delivers a reliable method to control the Ge NC size after phase separation. In this contribution we report the deposition of (GeOx-SiO2) SL via reactive dc magnetron sputtering and the self-ordered Ge NC formation during subsequent annealing. Main attention is directed to define proper deposition conditions for tuning the GeOx composition between elemental Ge (x = 0) and GeO2 (x = 2) by the variation of the deposition temperature and the oxygen partial pressure. A convenient process window has been found which allows sequential GeOx-SiO2 deposition without changing the oxygen partial pressure during deposition. The phase separation and Ge NC formation after subsequent annealing were investigated with in−situ X-ray scattering, Raman spectroscopy and electron microscopy. By these methods the existence of 2-5 nm Ge NC at annealing temperatures of 600-750°C has been confirmed which is within the SL stability range. The used technique allows to produce SL stacks with very smooth interfaces (roughness <1 nm), thus the Ge NC layers could be separated by very thin SiO2 films (d > 3 nm) which offers interesting possibilities for charge transport via direct tunneling.

High quality Al_1-xIn_xN/GaN bilayers, grown by Metal Organic Chemical Vapour Deposition (MOCVD), were characterized using structural and optical techniques. Compositional analysis was performed using Rutherford Backscattering Spectrometry (RBS) and Elastic Recoil Detection Analysis (ERDA). The InN molar fraction x decreased approximately linearly with increasing growth temperature and ranged from x=0.13 to 0.24. Up to x=0.20 the layers grow pseudomorphically to GaN with good crystalline quality. These layers show a smooth surface with V-shaped pits. Two layers with InN contents around 24% showed partial strain relaxation. However, the mechanisms leading to relaxation of compressive strain are very different in the two samples grown both at low temperature but with different growth rate. One sample shows a decreased c/a ratio, as expected for relaxation of the compressive strain, while In was shown to be homogeneously distributed with depth. Another sample started to grow with x=0.24 but relaxed mainly by reduction of the incorporated InN content towards the lattice-match composition of x~0.17. Both samples have an increased surface roughness. All samples show strong Al_1-xIn_xN band edge luminescence with large bowing parameter and Stokes’ shifts.

A MoS₂ microtube synthesized by chemical transport reaction was studied by Raman line scan mapping. The Raman spectrum of the MoS₂ microtube closely resembles that of a MoS₂ single crystal. In both, first order A_1g and E_2g Raman lines are observed with equal wave numbers, while line widths are slightly larger in the microtube spectrum, which can be attributed to defects. In the line scan along the tube axis the wave numbers of first order peaks are constant, while a slight up-shift of the Raman lines is observed in a line scan perpendicular to the tube. Possible mechanisms are discussed and the heating effect is proposed. Line scan approach over the edge of an object thus enables accurate determination of positions of first order peaks in highly absorbing materials.

The effect of the tube diameter and of the surface layer on the Raman spectra of WS₂ nanotubes is investigated. With decreasing diameter, a disorder-induced line in the A_1g mode range, the D-A_1g line, is selectively enhanced. This enhancement is attributed to an increasing structural disorder in smaller nanotubes. On the other hand, no significant effect on the D-A_1g / A_1g intensity ratio is observed for a Raman scan perpendicular to a 290 nm diameter tube. Therefore the enhancement of the disorder induced line is an intrinsic property of WS₂ nanostructures and not a surface layer effect.

Two methods based on bremsstrahlung were applied to the stable even Mo isotopes for the experimental determination of the photon strength function covering the high excitation energy range above 4 MeV with its increasing level density. Photon scattering was used up to the neutron separation energies Sn and data up to the maximum of the isovector giant resonance(GDR) were obtained by photo-activation. After a proper correction for multi-step processes the observed quasi-continuous spectra of scattered photons show a remarkably good match to the photon strengths derived from nuclear photo effect data obtained previously by neutron detection and corrected in absolute scale using the new activation results. The combined data form an excellent basis to derive a shape dependence of the E1 strength in the even Mo isotopes with increasing deviation from the N = 50 neutron shell, i.e. with the impact of quadrupole deformation and triaxiality. The wide energy coverage of the data allows for a stringent assessment of the dipole sum-rule, and a test of a novel parameterization developed previously which is based upon. This parameterization for the electric dipole strength function in nuclei with A>80 deviates significantly from prescriptions generally used previously. In astrophysical network calculations it may help to quantify the role the p-process plays in the cosmic nucleosynthesis. It also has impact on the accurate analysis of neutron capture data of importance for future nuclear energy systems and waste transmutation.

Recent success in laser-driven particle acceleration has increased interest in laser-generated “accelerator-quality” beams, for example, protons and ions have been produced with up to several tens of MeV per nucleon, and with extremely low emittance (<0.01 mm mrad, normalized). Compact, high-gradient laser-accelerators are therefore now being discussed as a potentially viable technology for a host of particle-beam applications, including future compact medical accelerators for medical diagnostics and therapy. After commissioning of a 150 TW laser system at the FZD, a joint research center for radiation therapy with laser-accelerator ions is being established together with the OncoRay Center for Radiation Research in Oncology, and the University Clinic of the Technical University of Dresden. The present status and future plans of the center, and the results from first proton acceleration experiments at FZD will be presented.

Introduction to Ion Beam Materials Analysis (IBA)
Characterisation of thin films by Ion Beam Materials Analysis (IBA)
Research topics for Ion Beam Materials Analysis (IBA)

Polychromatic decorations of ancient Egyptians tombs and temples have a long tradition over three millennia but are hard to identify because many pigments have been subjected to severe chemical reactions, which have entirely changed their original colours. Optical microscopy, PIXE and microbeam-PIXE have been used for determination of the nature of pigments, their chronology, and identification of domestic and imported materials. Paint flakes from various archeological sites in Egypt were analyzed: we report the results of the analysis of samples which were collected at the Mortuary Temple of Ramesses III (Habu Town), and the tombs of Tuthmosis III (Valley of the Kings) and Sennefer (Valley of the Noblemen). The paint is composed of grains of sizes typically ranging from 50 μm to 300 μm embedded in binding material and has great non-uniformity of pigment depth and lateral distributions and discontinuity of the paint layers. Qualitative analysis using broad beam PIXE has been performed to allow determination of the average composition of both support and pigments. Microbeam-PIXE has been used for mapping of selected grains. Goethite FeO(OH) (yellow), orpiment As₂S₃ (green), and the two blues: Egyptian Blue CaCuSi₄O₁₀ and Green Frit CaCuSiO₃ (mixed with the red haematite Fe₂O₃) were identified, and interesting details of the painting technique of ancient masters, like blending of pigments and the use of multilayer structures, were revealed.

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Rossendorf als lebendiger und attraktiver Standort für Wissenschaft und Wirtschaft

Problem: The goal of this study is to prepare novel chelators suitable for conjugation to vector molecules which can be labeled by yttrium or copper in order to achieve high specific activities and to improve pharmacokinetics. In this context, new water soluble bifunctional DOTA- and bis (2-pyridylmethyl)triazacyclocyclononane (DMPTACN)-based chelators have been synthesized and conjugated to the monoclonal antibody Cetuximab which binds to HER2 of the epithelial growth factor receptor (EGFR) family which is over-expressed by various tumors.

Material and Method: Both chelators have been conjugated to Cetuximab via thiourea-bridging. Radiolabeling of DOTA derivatives has been performed in aqueous ammonium acetate solution at r.t. using ⁸⁶YCl₃ or ⁹⁰YCl₃. Radiolabeling of DMPTACN conjugates with ⁶⁴Cu was achieved in MES buffer solution at 50°C using ⁶⁴CuCl₂. The affinity of the bioconjugates towards EGFR was determined by ELISA.

Results: The ELISA test showed that the affinity of the bioconjugates has decreased compared to native Cetuximab. A chelator/antibody molar ratio of 4 was achieved as determined by MALDI-TOF-MS for the DOTA-Cetuximab conjugate. Radiolabeling of DOTA-conjugates with ⁸⁶Y and ⁹⁰Y at 37°C requires optimization to improve radiochemical yield. DMPTACN-Cetuximab conjugates can be rapidly labeled with 64Cu under mild conditions in almost quantitative yield.

Conclusions: DMPTACN- and DOTA-ligands are attractive bifunctional chelating agents which can be conjugated to vector molecules for PET-imaging and radiotherapy. In the near future, the work with the ligands investigated will be extended using the pre-labeling approach.

Thermoelectromagnetic convection in cubic containers was studied experimentally. Two opposing side walls were cooled and heated, respectively, to produce an uniform temperature gradient. Inhomogeneous magnetic field distributions were achieved either with a permanent magnet or with specifically shaped pole shoes of an electromagnetic system. Ultrasonic Doppler velocimetry demonstrated that even a moderate temperature gradient may drive distinct convection. Two different flow regimes were investigated with the permanent magnet. Located at an isothermal wall, it produced a single vortex spreading the whole container while the flow was relatively stable. Moving the magnet to the center altered the flow structure. Four vortices developed and the velocity fluctuations were intensified. The more generic case realised with the electromagnet provided a gradient of the magnetic field only in one direction. Since the field strength and the area of impact on the melt were larger, developed turbulent regimes were accomplished.

Atomic layer deposition (ALD) of rhodium oxide thin films has been studied using Rh(acac)₃ (acac = acetylacetonato) and ozone as precursors. Amorphous Rh₂O₃ thin films were deposited between 160 and 180 °C. The sublimation temperature of Rh(acac)₃ set the low temperature limit for the oxide film deposition, while the high temperature limit was governed by the partial reduction of the film to metallic rhodium. The rhodium oxide films were successfully deposited on Al₂O₃ nucleation layers, soda lime glasses, and native oxide covered silicon substrates. The films demonstrated excellent conformality as characteristic for ALD. The films were not uniform across the substrate, which was most likely due to the catalyzing effect of Rh₂O₃ for ozone decomposition. The nonuniformity was repeatable and could be simply compensated in the cross-flow reactor. By splitting the deposition in two stages with 180° substrate rotation in between, good uniformity across the substrate was accomplished. The resistivities of about 80 nm thick Rh₂O₃ films were from 5 to 8 mΩcm.

Wurtzite GaN(001)-films were implanted with 195 keV 57Fe ions with a fluence Φ = 4*10^{16 cm-2} at room temperature. No secondary phase was detected in as implanted state. In order to reduce the implantation damage and to investigate the formation of secondary phases the implanted samples were annealed at 1073 K in a reduced N2-atmosphere (0.5 bar) for several cycles in a minute range. The formation of secondary phases in Fe implanted GaN upon annealing was detected by means of in-situ x-ray diffraction and conversion electron Mössbauer spectroscopy (CEMS). In contrast to our previous experiments with the annealing in a N2-flow at 1.1 bar pressure [3] no α-Fe cluster were found, but Fe3N. The repeatable phase change from Fe3N at room temperature and Fe3-xN at 1023 K was observed by means of in-situ x-ray diffraction. The diffusion of Fe during the annealing process limits the availability of secondary phase and hence the repeatability. The annealing process is accompanied by a strong diffusion of Fe and dissolution of GaN. Oxygen contamination promotes the dissolution of GaN and the formation of β-Ga2O3. The oxidation is confirmed by CEMS. The ferromagnetism in the samples is related to the presence of Fe3-xN. No DMS related phenomena have been observed. The results demonstrate that by variation of pressure phase compositions, other than α-Fe, are possible. It is expected that by the proper choice of annealing conditions specific secondary phases can be created, leading to different electronic, magnetic and other properties.

In this study, we report the unequivocal demonstration of midinfrared mode-locked pulses from quantum cascade lasers. The train of short pulses was generated by actively modulating the current and hence the gain of an edge-emitting quantum cascade laser (QCL). Pulses with duration of about 3 ps at full-width-at-half-maxima and energy of 0.5 pJ were characterized using a second-order interferometric autocorrelation technique based on a nonlinear quantum well infrared photodetector. The modelocking dynamics in the QCLs was modeled based on the Maxwell-Bloch equations in an open two-level system. Our model reproduces the overall shape of the measured autocorrelation traces and predicts that the short pulses are accompanied by substantial wings as a result of strong spatial hole burning. The range of parameters where short mode-locked pulses can be formed is found.

The neutron deficient p-nuclei are shielded from the s- or r-process by stable isotopes. P-nuclei are likely to be formed in high temperature cosmic scenarios like exploding supernovae by photodisintegration reactions on heavy r- or s- seed nuclei. The lack of experimental information on energy-dependent cross sections especially for (gamma,p) and (gamma,gamma) reactions reduces the applicability of nucleosynthesis models. Using intense bremsstrahlung produced at the superconducting electron linear accelereator ELBE at Forschungszentrum Dresden-Rossendorf we investigated (gamma,n), (gamma,p) and (gamma,alpha) reactions for the medium-mass p-nuclei 92Mo and 144Sm, as well as (gamma,n) reactions for 100Mo and 154Sm by photo-activation. The lowest photoactivation yields have been measured in an underground laboratory. The photodisintegration of 197Au serves as a benchmark and it is compared to data measured previously with the positron annihilation technique.

This talk summarizes our activities in nonlinear laser spectroscopy using the free-electron laser at FZD and tabletop lasers. Our research concentrates on III-V semiconductor quantum wells and superlattices. In particular, I will focus on pump-probe spectroscopy, two-photon absorption, and photocurrent autocorrelation involving intersubband transitions in quantum wells at mid-infrared wavelengths, and discuss a concept for scalable photoconductive Terahertz emitters.

Quantum well infrared photodetectors (QWIPs) provide unique opportunities for high-performance thermal imaging. Due to their narrow absorption bands with relative spectral widths of the order of 10%, QWIPs are particularly suitable for thermal imaging applications involving several atmospheric transmission bands or several colors within the same band. For dual-band/dual-color FPAs, QWIP technology has the unique property that the active region for the long-wavelength band is transparent for the short-wavelength band. Narrow intersubband transition linewidths also enable us to enhance resonantly the cross section for two-photon-absorption by several orders of magnitude. This approach results in particularly sensitive quadratic two-photon detectors, which are useful for pulse diagnostics and photon correlation measurements of mid-infrared laser sources. In the first part of this talk, I will report on QWIP structures optimized for thermal imaging applications and on the performance of QWIP thermal imagers which were jointly realized by the Fraunhofer-Institute for Applied Solid State Physics (Freiburg, Germany) and AIM Infrarot-Module GmbH (Heilbronn, Germany). In particular, a dual-band QWIP FPA with 384x288 pixels detecting simultaneously in the 8 – 12 µm long-wavelength infrared (LWIR) and 3 – 5 µm mid-wavelength infrared (MWIR) regimes was found to exhibit a noise-equivalent temperature difference as low as 20.6 mK in the LWIR and 26.7 mK in the MWIR spectral bands. The array, which is based on a photoconductive QWIP for the MWIR and a photovoltaic "low-noise" QWIP for the LWIR, allows for synchronous and pixel-registered image acquisition in both bands. This functionality yields several advantages, including better distinction between target and background clutter, operation in a much wider range of ambient conditions, and the ability of remote absolute temperature measurement. The second part of my talk will address quadratic detection involving two-photon transitions in specially designed QWIP structures. These two-photon QWIPs are exploited in autocorrelation measurements of pulsed infrared sources including the free-electron laser FELBE in Dresden.

The possibility of detecting ³⁶Cl for geological exposure dating has been explored for several years at VERA (the Vienna Environmental Research Accelerator). First results on real samples were obtained with an ionization chamber (developed at the ETH/PSI, Zürich, Switzerland) with two anodes. To improve the suppression of ³⁶S, we equipped the ionization chamber with an exit window and added a Time-of-Flight (TOF) system with a double-sided silicon strip detector (50x50 mm²) as stop detector. We optimized the TOF setup by using silicon nitride foils to reduce scattering tails in the energy spectra.
At 3 MV terminal voltage, corresponding to a particle energy of 24 MeV of ³⁶Cl⁷⁺, we achieved a ³⁶S7+-suppression of 21500 (50% ³⁶Cl-detector-efficiency).

The EC-funded project SPIRIT (Support of Public and Industrial Research using Ion beam Technology) [1] started in March 2009. It will provide free transnational access to European ion beam infrastructures for users from research and industry. Besides we will improve the methods and tools for ion-beam based analysis and processing of materials by helping European researchers to carry out state-of-the-art multidisciplinary scientific and technological research.
SPRIT partners are eleven leading ion beam facilities, i.e.
• FZD Dresden-Rossendorf (management), Germany*
• Centre d’Etudes Nucléaires de Bordeaux-Gradignan, France*
• Centre de Recherche sur les Ions, les Matériaux et la Photonique, Caen & Service de Recherche en Métallurgie Physique, Saclay, France*
• Instituto Tecnológico e Nuclear, Portugal
• Jožef Stefan Institute, Ljubljana, Slovenia*
• Katholieke Universitet Leuven, Belgium*
• Ruđer Bošković Institute, Zagreb, Croatia
• Surrey Ion Beam Centre, University of Surrey, Great Britain*
• Swiss Federal Institute of Technology, Zurich, Switzerland
• Universität der Bundeswehr, München, Germany*
• Université de Pierre et Marie Curie, Paris, France
Within the project the partners use and provide fast ions (10 keV-100 MeV) for the purpose of modification and analysis of surfaces, interfaces, thin films and nanostructured systems. The partners themselves and their external users focus on fundamental and applied research spanning from material sciences over life, environmental and Earth sciences to investigations of objects from art and cultural heritage.
For example, element distributions can be determined non-destructively and standard-free by mean of ion beam analysis (IBA) including Rutherford Backscattering Spectrometry (RBS), Nuclear Reaction Analysis (NRA), Elastic Recoil Detection Analysis (ERDA), Particle-Induced X-Ray (PIXE) and Gamma-Emission (PIGE) [2]. All natural-occurring elements are accessible; most elements with lateral, some in 3-D resolution (depth-range: nm-µm; depth-resolution: 0.5-30 nm). Typical detection limits are 10 µg/g (H), 500 µg/g - 1% (He-O), 1 µg/g (F), 10-100 µg/g (Na-U).
Seven SPIRIT partners – those marked above with a * – provide transnational access to researchers from the European Community. Help is provided to external users during planning, performance and evaluation of their research projects. Proposals [3] for running experiments in person (“hands-on”) or remote services are selected after a formal reviewing and ranking following scientific criteria as innovation/originality by an international expert panel. All costs including travel for external users are covered by the EC.
References: [1] www.spirit-ion.eu, contract number 227012. [2] C. Neelmeijer et al., this meeting. [3] http://www.spirit-ion.eu/Project/Transnational-Access/Application-Form.html.

no abstract available

Saturable absorption mode-locking based on intersubband transitions in quantum wells at 2 μm.

The formation of Fe-filled carbon nanotubes by thermal decomposition of ferrocene combined with a Fe-catalyst-nanostructuring on an oxidized Si substrate is investigated in the temperature range of 1015 – 1200 K. The optimal growth conditions for aligned and homogeneous carbon nanotubes are found at 1100 K. Mössbauer spectroscopy (both in transmission geometry and CEMS) was used to analyze and quantify the different formed Fe-phases. In general, a-Fe, g-Fe and Fe3C are found to form within the carbon nanotubes. Depending on the growth conditions their fractions vary strongly. Moreover, an alignment of the a-Fe in the tubes could be detected.

Kaons and Antikaons in Nuclear Matter: AA vs. pA Collisions

Transport model calculations for HADES

Transport Models for Heavy-Ion Collisions

The coordination of the limiting U(IV) carbonate species in aqueous solution was investigated by comparing its structure parameters with those of the complex preserved in a crystal structure. The solution species was obtained in a aqueous solution of 0.05 M U(IV) and 1 M NaHCO3. Single crystals of Na6[U(CO3)5]•12H2O were obtained directly from this mother solution. The U(IV) carbonate complex in the crystal structure was identified as [U(CO3)5]6 anionic complex. This monomeric complex forms a network with charge compensating Na+ cations and H2O ligands. The interatomic distances around the U(IV) coordination polyhedron show average distances of U-O = 2.461(8) Å, U-C = 2.912(4) Å and U-Odist = 4.164(6) Å. U L3edge EXAFS spectra were collected from the solid Na6[U(CO3)5]•12H2O and the corresponding solution. In both samples, the first shell of the Fourier transforms (FTs) revealed ten oxygen atoms at an average distance of 2.450.02 Å, the second shell originates from five carbon atoms with a U-C distance of 2.910.02 Å, and the third shell was fit with single and multiple scattering paths of the distal oxygen at 4.170.02 Å. These data indicate the identity of the [U(CO3)5]6 complex in solid and solution state. The high negative charge of the [U(CO3)5]6 anion is compensated by Na+ cations. In solid state the Na+ cations form a bridging network between the [U(CO3)5]6 units, while in liquid state they seem to be located closer at the anionic complex. The average metal-oxygen distances of the coordination polyhedron show a linear correlation to the radius contraction of the neighbour actinide(IV) ions and indicate the equivalence of the [An(CO3)5]6 coordination within the series of thorium, uranium, neptunium and plutonium.

The L3-edge x-ray absorption spectrum of the aqua trivalent Cm ion in aqueous solution exhibits a double photoexcitation involving 2p and 4f electrons. The sharp resonance structure of the multielectron excitation reveals a shake-up process at 508.110 eV. The data indicate a monotonic increase of the [2p4f] excitation energy between elements of sixth period (Au, Hg, Pb, and Bi) and the early actinides (Th, Pa, U, Np, Pu, Am and Cm).

It is our pleasure to publish the Proceedings of the 16th International Conference on Ion Beam Modification of Materials (IBMM 2008), which was held at the Lecture Hall Centre of the Technische Universität at Dresden, Germany, from August 31 to September 5, 2008, under the common organization by the Forschungszentrum Dresden-Rossendorf, Dresden, Germany and the Leibniz-Institut für Oberflächenmodifizierung, Leipzig, Germany.
The biannual IBMM International Conference Series looks back on a 30-years history starting in 1978, being considered as the major international forum to present and discuss recent results in ion-related materials research and to point into the future of the field. It assembles physicists, chemists, material scientists and engineers from all over the world and along the whole chain from basic research to industrial production.

Microorganisms, microbial components, biopolymers and bioligands secreted by microbes have a great potential to influence the behavior of actinides in the environment. Functional groups provided by both lipopolysaccharide (LPS: main part of the cell wall of Gram-negative bacteria), and peptidoglycan (PG: main part of the cell wall of Gram-positive bacteria) are very effective in complexing uranium(VI) over a wide pH range (2.0 to 9.0) [1, 2]. The main functionalities for uranyl binding are phosphoryl and carboxyl groups of LPS and carboxyl groups of PG. The aerobic soil bacterium Pseudomonas fluorescens (CCUG 32456 A) isolated from the aquifers at the Äspö Hard Rock Laboratory, Sweden secretes pyoverdins. These unique bioligands have a high potential to bind uranium(VI) and curium(III) mainly due to their hydroxamate and catecholate functionalities [3, 4]. However, the interaction of neptunium(V) with both microbial cell wall components (LPS, PG) and secreted bioligands (PYO) are unknown. To address this lack, we thus present findings regarding the complexation of neptunium(V) with LPS, PG, and P. fluorescens (CCUG 32456) pyoverdins (PYO) obtained using near-infrared (NIR) absorption spectroscopy.
The spectrophotometric titrations of the Np(V)-LPS system showed a dominant neptunyl(V) coordination to phosphoryl groups between pH 4 and 8 followed by hydroxyl interactions in the alkaline pH range. A very low affinity of Np(V) to interact with the carboxyl groups of PG was measured. Strong Np(V)-pyoverdin species of the type MxLyHz could be identified from the spectrophotometric titrations. Remarkable was that the influence of Np(V)-pyoverdin species could already be detected under equimolar conditions.
Estimates are possible, on the basis of the determined stability constants, if neptunium(V) prefers to interact with the microbial cell wall (LPS), with biopolymers (PG) or with the secreted pyoverdin bioligands (PYO). The calculations were performed using nearly equimolar conditions of Np(V) and functional groups of the biosystems. More than 80% of all Np(V) is bound to pyoverdin species at pH 8 compared to ~37% bound to LPS and less than 1% bound to PG. This shows both the high affinity of neptunium(V) to bioligands containing hydroxamate and catecholate groups and the importance of indirect interaction processes between neptunium(V) and bioligands secreted by resident microbes.

[1] A. Barkleit, H. Moll, G. Bernhard, Dalton Trans. 2879-2886 (2008).
[2] A. Barkleit, H. Moll, G. Bernhard, Dalton Trans. published online: DOI 10.1039/b818702a (2009).
[3] H. Moll, M. Glorius, G. Bernhard, A. Johnsson, K. Pedersen, M. Schäfer, H. Budzikiewicz, Geomicrobiol. J. 25, 157-166 (2008).
[4] H. Moll, A. Johnsson, M. Schäfer, K. Pedersen, H. Budzikiewicz, G. Bernhard, Biometals 21, 219-228 (2008).

This work was funded by the BMWi under contract number: 02E9985.

Seit langem ist bekannt, dass die Magnetfelder von Planeten, Sternen und Galaxien durch den hydromagnetischen Dynamoeffekt erzeugt werden. Weniger bekannt ist die erstaunlich aktive Rolle, die Magnetfelder in der kosmischen Strukturbildung spielen. So sind die hohen Wachstumsraten von Sternen und Schwarzen Löchern nur erklärbar, wenn die Akkretionsscheiben, aus denen sie gefüttert werden, turbulent sind und damit Drehimpuls effektiv nach außen transportieren können. Die Ursache dieser Turbulenz liegt in der destabilisierenden Wirkung von Magnetfeldern auf rotierende Strömungen, die als Magnetorotationsinstabilität (MRI) bezeichnet wird. Der Vortrag gibt eine kurze Einführung in die Theorien zur Entstehung und Wirkung kosmischer Magnetfelder. Im Mittelpunkt stehen aber die Flüssigmetall-Experimente der letzten zehn Jahre, in denen Dynamoeffekt bzw. MRI untersucht worden sind, insbesondere das PROMISE-Experiment am Forschungszentrum Dresden-Rossendorf.

The charge retention characteristics of SONOS (silicon-oxide-nitride-oxide-silicon) nonvolatile memory cells at elevated temperatures were investigated. Assuming the thermal excitation model to be the dominant charge loss mechanism, the trap energy distribution in the nitride was determined. We present an improved model which includes the influence of subsequent tunneling of the charge carriers through the bottom oxide after being thermally emitted into the conduction band of the silicon nitride. The trap energy distribution was evaluated from samples with different bottom oxide thicknesses. Using this model it was found that the detected trap energy distribution is nearly identical despite the different tunneling probabilities from the various bottom oxide thicknesses.

The oxygen content of binary Ti₄₅Al₅₅ and ternary Ti₄₄Al₅₂Nb₄ single crystals and polycrystalline alloys
was quantified with secondary ion mass spectrometry (SIMS) using Cs⁺ primary ions. The SIMS measurements
were calibrated with respect to concentration and depth scale using oxygen implanted samples.
The measurements revealed considerably lower oxygen content in the ternary alloy indicating a protecting
impact of the Nb addition in grain boundaries against oxygen contamination. The relative strong
surface oxide layer thickness of the investigated samples was determined to about 1µm.

Electrostatic charging changes the critical temperature of superconducting thin layers. To understand the basic mechanism, it is possible to use the Ginzburg-Landau theory with the boundary condition derived by de Gennes from the BCS theory. Here we show that a similar boundary condition can be obtained from the principle of minimum free energy.
We compare the two boundary conditions and use the Budd-Vannimenus theorem as a test of approximations.

Magnetic characterization is shown to be a highly effective, nondestructive, and commonly available method to accurately assess dehydrogenation temperatures and further clarify the reaction mechanisms during dehydrogenation in systems with superconducting or ferromagnetic constituents. As examples, the dehydrogenation temperature of NaBH4 in a nanostructured NaBH4/MgH2 system and the dehydrogenation process of nanostructured Mg2CoH5, based on the superconducting and ferromagnetic properties of MO, and Co, respectively, are determined.

A selfconsistent T-matrix theory of many-Fermion systems is proposed. In the normal state the theory agrees with the Galitskii-Feynmann approximation, in the superconducting state it has the form of the renormalized Kadanoff-Martin approximation. The two-particle propagator satisfies the Baym-Kadanoff symmetry condition which guarantees that the theory conserves the number of particles, momentum and energy. The theory is developed for retarded interactions leading to the Eliashberg theory in the approximation of a single pairing channel.

Hydrogen (H) is continuously produced by the large dose fast neutron irradiation on fusion reactor material. The concentration, diffusion and evolution of H in the structure material may cause H-embrittlement. Ion beam analysis is one of the most useful methods for studying the micro-kinetics of H in solids. In this work, the H-distribution in titanium (Ti) has been studied by resonance nuclear reaction analysis (resonance-NRA) and micro-elastic recoil detection analysis (micro-ERDA). The evolution of H-depth-profile in titanium samples has been studied versus the change of normal stress. Evident H diffusion has been observed, while a normal stress is changed in the range of 107-963 MPa. The H diffusion is related to the concentration of H in samples.

It is well known that oblique low and medium energy (typically 0.1 – 100 keV) ion erosion of solid surfaces can lead to the formation of periodic ripple patterns with wavelengths ranging from 10 to 1000 nm. These ripple structures have been found on a large variety of materials, including semiconductors, metals, and insulators. The formation and early evolution of the ripple patterns can be described by a linear continuum equation derived by Bradley and Harper. At longer times, however, nonlinear terms have to be taken into account, leading to nonlinear models based on the Kuramoto-Sivashinsky equation.
This talk will provide an overview of ion-induced pattern formation and summarize the theoretical basics. Recent experimental results on the evolution of nanoscale ripple patterns on silicon surfaces during high-fluence ion sputtering will be presented and compared to the predictions of different continuum models. In addition, promising applications of nanorippled substrates as templates in thin film growth will be discussed.

Silicon ion implantation effects on the optical and photoluminescence (PL) properties of polymethylmethacrylate (PMMA) have been studied. Low-energy ion implantation (E = 30-50 keV) was carried out over a range of different ion fluences (D = 10(13)-10(17) cm(-2)). Visible PL and optical transmission spectra in the range (330-800 nm) have been measured. The existing visible range PL emission in the unimplanted PMMA samples is clearly affected by the Si+ ion implantation and the observed modification effect of photoluminescence enhancement (PLE) is essentially dependent on the implantation fluence. For certain fluences, dependent on the ion energy, the overall amplitude of the PL emission has a several times (similar to 5 times) increase. Optical absorption also gradually increases with the fluence.

We present extended experimental material about optical and mechanical properties of oxide optical coating materials, deposited by electron beam evaporation, ion and plasma ion assisted evaporation, sputtering and ion plating. A clear correlation between these experimental data is established and understood as being caused by the different degree of the porosity of the films. This assumption has been verified by investigation of the layer structure and accompanying simulations of the effect of porosity on refractive index, layer stress and thermal shift. As a practical conclusion, we find that a certain pore fraction in the films is essential in order to get a valuable balance between optical and mechanical coating properties.

Nanostructured NaBH4/MgH2 composites have established themselves as promising materials for hydrogen storage applications due to their high gravimetric capacity, large hydrogen volumetric density and rather low dehydrogenation temperature compared to that one corresponding to the single compounds. Actually, further research on the NaBH4/MgH2 system could lead to an enhanced understanding of more complex reactive hydride composites, such as Ca(BH4)2/MgH2 or LiBH4/MgH2.

As-received NaBH4 and MgH2 powders were mixed, in a 2 to 1 molar ratio (2NaBH4/MgH2) and ball-milled to obtain nanostructured composites. The milling processes were carried out for diverse times, under Ar atmosphere, in a Spex mill with a ball-to-powder mass ratio of 10:1.

In-situ synchrotron x-ray powder diffraction indicates that the dehydrogenation process starts at around 210 C, with the desorption of the MgH2 to Mg, and rpoceeds with the chemical dismutation of NaBH4 in NaH and a possible intermediate specie, such as Na2B12H12. In fact, solid-NMR seems to confirm the existence of the transitional compound. However, the temperature onset of the dehydrogenation process of the NaBH4 counterpart has not yet been fully elucidated and, since it is difficutls to establish from either x-ray diffraction or thermogravimetric analyiss, magnetic hcaracterization is proposed as an alternative technique, which takes advantage of the superconducting nature of the MgB2 phase, to further study dehydrogenation processes.

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Over the last two decades, radiolabeled antibodies and peptides have been introduced in research and in clinical application of nuclear medicine. Such substances are utilized for tumor targeting as radiotracers and for therapeutic purposes as well. Labelling of such substances with PET radionuclides such as F-18 offers the chance of introduction the label without drastic changes of the molecular properties in conjunction with highest image quality, i.e. high diagnostic value. Radiometal-labeled bioactive substances offer both: The possibility of diagnostics and therapeutic intervention as well. However, the labelling procedure is a considerable alteration of the molecules radiopharmacological properties. This is due to the need of introducing a chelating moiety to bind the radiometals kinetically and thermodynamically inert. Beside this geometric impact, the labelling conditions are of highest importance. Whereas peptides may withstand rather drastic conditions, proteins e.g. antibodies need ambient labelling conditions such as aqueous solution, room temperature, near physiological pH. Furthermore, various proteins tend to coagulate in the presence of heavy metals as radio-copper.
The talk will present such results of scientific investigations at the Institute of Radiopharmacy during the last five years. This involves the application of established methods such as the use of [¹⁸F]SFB (N-succinimidyl-4-[¹⁸F]fluorobenzoate) for labelling of biomolecules, the development of alternative labelling agents/prosthetic groups as well as current efforts to establish methods for pre- and postlabelling with radiometals. All these investigations are directed to corresponding applications with biomolecules and bioactive compounds, respectively.

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This paper considers the directional solidification of Al-Si alloys from a water cooled copper chill. Melt stirring during solidification has been realised by utilising time-modulated AC magnetic fields in two different variants: (1) an RMF applied in form of a pulse sequence with a periodic inversion of the direction of rotation between two consecutive pulses and (2) a combination of rotating (RMF) and travelling magnetic fields (TMF), whereas both fields are implemented subsequently in form of rectangular pulses. Our results demonstrate that the melt agitation using modulated magnetic fields offers a considerable potential for a well-aimed modification of casting properties by an effective control of the flow field, but, this goal requires an optimisation of the magnetic field onfiguration with respect to the particular solidification parameters.

he structure of C:Ni nanocomposite thin films grown by ion beam sputtering (IBS) and pulsed filtered cathodic vacuum arc (PFCVA) is compared. The films were grown in the temperature (T) and Ni concentration ranges of RT-500C and 7-40 at.%, respectively. The composition of the films and elemental depth profiles were determined by elastic recoil detection analysis (ERDA). The morphology and phase composition were investigated by transmission electron microscopy and x-ray diffraction, respectively. Independent of the growth method the Ni dispersed phase is carbidic for T<=300C and mostly fcc metallic at higher deposition temperatures. In the C:Ni films grown by IBS the transition from globular towards columnar growth occurs at 200

The present study concerns the directional solidification of grain-refined and non-refined AlSi7 alloys under the influence of a travelling magnetic field (TMF). An upwards travelling field has been applied to provide a forced convection within the solidifying melt. The formation of a fine equiaxed structure is favoured by both the addition of grain refining AlTi5B1-particles and electromagnetic stirring as well, whereas the addition of grain refiners into the melt appears to be more efficient for achieving a reduction of the mean grain size. A minimum grain size has been observed of the electromagnetic agitation of a grain-refined alloy. A melt stirring by a sufficiently high magnetic field provides a homogeneous grain size distribution in the sample volume.

This experimental study is concerned with the secondary meridional flow during the time if the fluid spins up from rest. A cylindrical cavity with an aspect ratio of unity is filled with liquid metal and suddenly exposed to an azimuthal body force generated by a rotating magnetic field (RMF). Vertical profiles of the axial velocity have been measured by means of the ultrasound Doppler velocimetry. Our experimental results show an excellent agreement with recently published numerical results with respect to the laminar spin-up and the onset of linear three-dimensional instabilities in RMFdriven flows.

The aim of a combination of magnetic spectrometers with ion beam analysis techniques is to measure concentration profiles in thin layers with sub-nanometer depth resolution. For these measurements heavy ions from a MV-ion accelerator are directed to the sample. Scattered primary ions or ejected recoil atoms are detected and energy analysed under forward angles. The depth resolution depends directly on the energy resolution of the spectrometer. High energy resolution can only be obtained using magnetic particle spectrometers, where the energy measurement is transformed into a position measurement at the focal plane.
The depth scale is provided by the stopping power of energetic heavy ions moving in matter. The yet produced data are only valid for dynamic charge state equilibrium due to electron loss and capture along the ion trajectory. In the case of ultra thin layers the path length of the particles are too short to achieve this equilibrium. Since magnetic spectrometers separate particles with identical energy but different charge states, it is necessary to consider charge state dependent stopping cross sections for quantitative data analysis. Here only very few data are available in the literature.
In this work, we introduce quantitative ion beam analysis of ultra thin films with magnetic spectrometers.
1. the Quadruple-Quadrupole-Dipole-Sextupole spectrometer “Little John” to measure concentration profiles and charge state distribution of light ions.
2. The Browne-Buechner spectrometer, which is designed to measure samples with heavy atoms.

Die quantitative Elementanalytik von Schichten und Schichtabfolgen im Dickenbereich weniger Nanometer ist in den letzten Jahren in den Fokus aktueller Forschung gerückt. Im Mittelpunkt dieser materialwissenschaftlichen Fragestellungen steht die Bestimmung von Tiefenverteilungen von Elementen in dünnen Schichten, die durch spezielle Abscheideverfahren oder nachfolgende Prozessschritte wie Temperung erzielt werden, aber auch der Nachweis unbeabsichtigter Kontamination in den Schichten. Daraus können Informationen im Hinblick auf gezielte Materialentwicklung gewonnen werden und die Qualität bestehender Prozessführungen lässt sich bewerten.
Die meisten konventionellen (nicht nuklearen) Analyseverfahren sind zur Quantifizierung ihrer Ergebnisse in der Regel auf Referenzmaterialien (gleicher Matrix) angewiesen. Im Gegensatz dazu kann die Ionenstrahlanalyse (ion beam analysis, IBA) standardfrei betrieben werden. Der physikalische Prozess, auf der alle Methoden der IBA beruhen, ist die binäre Wechselwirkung von MeV-Ionen mit den Atomkernen in den Schichten. Diese Wechselwirkung, elastische Streuung oder Kernreaktion, ist einfach und genau beschreibbar; kollektive Matrixeffekte treten dabei nicht auf.
Am Ionenstrahlzentrum des Forschungszentrums Dresden-Rossendorf kommen hauptsächlich drei Analysemethoden zur Anwendung:
• Kernreaktionsanalyse (Nuclear Reaction Analysis, NRA) zum tiefenabhängigen Nachweis von Wasserstoff über die resonante Kernreaktion ¹H(¹⁵N,αγ)¹²C*
• Rutherford-Rückstreuspektrometrie (Rutherford Backscattering Spectrometry, RBS) insbesondere zur Detektion von Elementen mit Ordnungszahlen Z > 14
• Detektion elastisch rückgestossener Atome (Elastic Recoil Detection Analysis, ERDA) zum Nachweis leichter Elemente mit Z = 2-14 (He-Si)
Die zur Messung ultradünner Schichten mit RBS und ERDA erforderliche Tiefenauflösung (< 1 nm) kann mit Teilchenspektrometern mit höchster Energieauflösung erreicht werden.
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The modified QQDS magnetic spectrometer “Little John” [1] at the Forschungszentrum Dresden-Rossendorf is aimed to measure concentration profiles of light elements in thin layers with sub-nanometre depth resolution by Elastic Recoil Detection Analysis (ERDA). Of particular interest are various ultra thin films of metal oxides, nitrides and of carbon compounds. For these measurements heavy ions from the 5 MV-Tandem accelerator are directed to the sample. The ejected recoil atoms are detected and their energy is analysed under forward angles (15°, 30°, 45°, or 60°). Due to the low solid angle of the QQDS spectrometer of about 0.5 msr rather high fluences of initial heavy ions have to be applied. Therefore, special care must be taken to minimize layer deterioration and decomposition by preferential release of elements from the film. To identify optimum measurement conditions and perform final corrections for quantification of high resolution results, we studied the release of oxygen as a function of beam fluence. Thus, different oxides have been irradiated with Cl-, Cu- and I-ions in the energy range from 15 to 40 MeV. We could validate the earlier reported [2] dependency of oxygen loss on
• angle of incidence
• kind and energy of incoming ion
• stopping power
• layer thickness
for SiO2. Similar results have been yet found for La2O3. Further experiments on materials relevant for microelectronics as e.g. high k-dielectrics as HfO2 or ZrO2 are foreseen for the very near future and, thus, will be presented.

References: [1] H.J. Gils et al., Nucl. Instr. and Meth. A276 (1989) 151. [2] W.M. Arnoldbik et al., Nucl. Inst. and Meth. B203 (2003) 151.
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Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows being relevant for metallurgical applications. In this paper we present the new experimental facility CONCAST for modeling the continuous casting process of steel by using the low melting point alloy SnBi. The facility operates at temperatures of 200°C-400°C. Main parameters of the facility and dimensions of the test sections will be shown. The resultant possibilities with respect to flow investigations in tundish, submerged entry
nozzle and mould will be discussed.

The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements with a reasonable spatial and temporal resolution. First experimental results will be presented which have been obtained using a small-scale experimental set-up with the room temperature alloy GaInSn. Measurements of the liquid flow in the mold will be compared with accompanying numerical calculations. According to the concept of the electromagnetic brake the impact of a DC magnetic field on the outlet flow from the submerged entry nozzle (SEN) has been studied.

The systematic development and improvement of a methodology for mild radiolabeling of both native and modified proteins with the short-lived positron emitter fluorine-18 (¹⁸F) under physiological conditions is reported. The presented methodology is an attractive alternative to protein and lipoprotein radiolabeling methods using iodine or metal radionuclides and, particularly, can be applied for functional characterization of both native and oxidized protein species in vivo by means of positron emission tomography (PET).

The sorption of Np(V) and Np(IV) onto kaolinite has been studied in the absence and presence of humic acid (HA) in a series of batch equilibrium experiments under different experimental conditions: [Np]0: 1.0x10-6 or 1.0x10-5 M, [HA]0: 0 or 50 mg/L, I: 0.01 or 0.1 M NaClO4, solid to liquid ratio: 4 g/L, pH: 6-11, anaerobic or aerobic conditions.
The results showed that the Np(V) sorption onto kaolinite is effected by solution pH, ionic strength, Np concentration, presence of carbonate and HA. In the absence of carbonate, the Np(V) uptake increased with pH up to ~ 96% at pH 11. HA further increased the Np(V) sorption between pH 6 and 9 but decreased the Np(V) sorption between pH 9 and 11. In the presence of carbonate, the Np(V) sorption increased with pH and reached a maximum of 54% between pH 8.5 and 9. At higher pH values, the Np(V) sorption decreased due to the presence of dissolved neptunyl carbonate species with a higher negative charge that were not sorbed onto the kaolinite surface which is negatively charged in this pH range. HA again decreased the Np(V) uptake in the near-neutral to alkaline pH range due to formation of aqueous neptunyl humate complexes. The decrease of the initial Np(V) concentration from 1.0x10-5 M to 1.0x10-6 M led to a shift of the Np(V) adsorption edge to lower pH values. A higher ionic strength increased the Np(V) uptake onto kaolinite in the presence of carbonate but had no effect on Np(V) uptake in the absence of carbonate.
To the best of the author`s knowledge, the sorption of Np(IV) onto kaolinite in the presence of HA was studied the first time. For this, a synthetic HA with pronounced reducing properties was applied. This HA effectively reduced Np(V) to Np(IV) and stabilized the tetravalent oxidation state during sorption experiments over a wide pH range. The Np(IV) uptake onto kaolinite is strongly effected by HA. Especially in the near-neutral pH range the Np(IV) uptake was found to be very low in the presence of HA which was attributed to the strong Np(IV) humate complexation in solution.
Thus, depending on the prevailing geochemical conditions, HA has an immobilizing as well as a mobilizing effect on Np(V). In case of Np(IV), the mobilizing effect predominates.

We present an experimental study on efficient second order sideband generation in symmetric undoped GaAs/AlGaAs multiple quantum wells. A near-infrared laser tuned to excitonic interband transitions is mixed with an in-plane polarized terahertz beam from a free-electron laser. The terahertz beam is tuned either to the intraexcitonic heavy-hole 1s-2p transition or to the interexcitonic heavy-hole light-hole transition. We find strong evidence that the intraexcitonic transition is of paramount influence on n=+-2 sideband generation, leading to an order-of-magnitude resonant enhancement of the conversion efficiency up to 0.1% at low temperature. At room temperature, the efficiency drops only by a factor of 7 for low terahertz powers.

The application of a novel wire-mesh sensor based on electrical capacitance (permittivity) measurements for the investigation of gas-oil two-phase flow in a vertical pipe of 67 mm diameter under industrial operating conditions is reported in this article. The employed wire-mesh sensor can be operated at up to 5,000 frames per second acquisition speed and at a spatial resolution of 2.8 mm. By varying gas and liquid flow rates different flow patterns, such as bubbly, slug and churn flow, were produced and investigated. From the images of gas void fraction distribution quantitative flow structure information, such as time series of cross-sectional void fraction, radial void fraction profiles and bubble size distributions, was extracted by special image processing algorithms.