Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Nuclear reactions power our Sun, and they create the chemical ele- ments that are necessary for human life. In order to correctly under- stand what happens in stars, one needs astronomical observations, but also nuclear physics data. For a number of astrophysical scenarios such as the Big Bang and our Sun, precise astronomical data are now avail-able. This calls for new nuclear reaction data of similar precision.
The nuclear reactions that are important for hydrogen burning in the Sun and for Big Bang nucleosynthesis have to be studied by low- energy experiments with intensive beams of stable ions. Due to the low cross sections involved, the experiments are usually performed in a low-background environment, such as an underground laboratory. The results obtained in the last decade at the pioneering LUNA 0.4 MV accelerator deep underground in the Gran Sasso laboratory, Italy, will be summarized, as well as related studies at surface-based ion accelerators.
New, higher-energy underground accelerators are necessary to ex- tend the energy range of the solar fusion data, and to address stellar helium and carbon burning. Relevant projects are underway both at LUNA and at the Dresden Felsenkeller.

The nuclear physics processes taking place in the first three minutes of the universe are reviewed, from an experimental perspective

The nuclear fusion processes in the center of our Sun are reviewed

The large deposits of Kupferschiefer in Middle Europe involve the northeastern part of Saxony, the Upper Lusatia. The regional copper shale raised again interest of both industry and science because it’s copper content constitutes the most important natural copper resource in this region. Due to the complex composition of the shale including copper and sulfide rich ores, carbonates and organic compounds, there is no efficient biotechnological approach applied yet. Bioleaching, which means the use of microorganisms and their metabolites to extract metals from their ores, reduces costs of high energy input and avoids the usage of toxic chemicals thus benefitting environment (Narayan 2009) and employees.
Raman spectroscopy enables a fast and specific chemical identification of minerals and ores (Hope 2001) as well as changes e.g. caused by oxidation (García-Meza 2012). Also Raman spectroscopic imaging of biotic components such as biofilms has already been performed (Virdis 2012).
We aim to use Raman spectroscopy to investigate the interactions of microorganisms and ore surface: Different polished sections of bornite, chalcopyrite (both from Henderson Mine, Namagualand, South Africa), chalcosite (Japan) and copper shale (Polkovice, Poland) were analysed by polarising microscopy to ensure correct spectra assignment (Fig. 1/2). Subsequently identic areas were analysed by Raman imaging using 2D scanning function (Fig. 3 - 5). After incubation with microorganisms the sections will be investigated again in order to evaluate chemical changes of the ore surfaces, biofilm formation and to monitor bioleaching processes.

The state of the art of nuclear physics for solar neutrinos is reviewed.

Workshop - eingeladener Vortrag

Veröffentlichung

Vortrag im Rahmen des FM – Nutzerkongresses, Düsseldorf

The concept of geological disposal of nuclear waste comprises a detailed knowledge concerning potential host rock formations. One of such formations is the Opalinus Clay geologic layer of the Mont Terri Underground Rock Laboratory (Switzerland). Dominant bacterial strains from sites destined for future nuclear waste deposition have to be identified and investigated regarding their interaction mechanisms with soluble actinide ions.
For the first time microbial total DNA (tDNA) was isolated from 50 g unperturbed Mont Terri Opalinus Clay. Analysis of the tDNA revealed that the bacterial community of the unperturbed Opalinus Clay is dominated by representatives of Firmicutes, Betaproteobacteria, and Bacteriodetes. Representatives of Firmicutes completely overgrow the other members of the community after treatment of the clay with R2A medium. Bacteria isolated from Mont Terri Opalinus Clay on R2A medium were affiliated with different Sporomusa spp., Paenibacillus spp., and Clostridium spp..
After isolation, characterization, and cultivation, we studied the unknown interaction between plutonium in mixed oxidation states and cell-suspensions of one of the Sporomusa sp. MT-2 isolates. Accumulation experiments were performed in order to obtain information about the amount of Pu bound by the bacteria in dependence on the contact time and the initial plutonium concentration. The 242-Pu present in blank (no cells added), supernatant, and washed biomass suspension at pH 0 was analyzed using UV-vis-NIR spectroscopy, solvent extraction, and liquid scintillation counting (LSC). In addition experiments were performed by adding an electron donor (Na-pyruvate) in two concentrations 0.1 mM and 10 mM.
The amount of Pu sorbed by Sporomusa sp. cells increased with time. Steady state conditions were reached after approximately 200 h. The data could be successfully fitted to a bi-exponential law. The amount of Pu associated with Sporomusa sp. cells depends on the initial 242-Pu concentration. In the first step, a fast binding of the Pu(VI) and Pu(IV)-polymers onto the biomass occurred. Solvent extractions showed that 92 % of the initially present Pu(VI) is reduced to Pu(V) due to the activity of the cells within the first 48 h of contact time (no electron donor added). The corresponding redox potential in the cell suspensions dropped down to 300 mV compared to 780 mV measured in the blanks. Most of the formed Pu(V) dissolves from the cell envelope back to the aqueous solution due to the weak complexing properties of Pu(V). Good binding properties of Pu(IV)-polymers on functional groups of the Sporomusa sp. cell envelope were found (immobilization). In contrast to earlier measurements with Pseudomonas fluorescens (CCUG 32456A) cells clear indications for increased amounts of Pu(IV) and Pu(III) on the Sporomusa biomass were observed. The Pu oxidation state distributions as a function of time will be discussed in detail and the results of the system without addition of electron donors will be compared with the electron donor supplemented systems. Here differences in the Pu interaction mechanism were found.

Laser-wakefield accelerators (LWFA) feature electron bunch durations ranging from several fs to tens of fs. Knowledge and control of the electron bunch duration is vital to the design of future table-top, X-ray
light-sources for laser-synchronized pump-probe experiments, ranging from betatron radiation, Thomson scattering to FELs. Due to the nonlinear nature of the laser-wakefield electron injection and small changes in initial experimental conditions the electron bunch properties are often subject to large shot-to-shot variations, which requires diagnostics working not only at ultrashort time-scales but also at single-shot.
We aim for measurements of the LWFA electron bunch duration and bunch substructure at single-shot by analysing the coherent and incoherent transition radiation spectrum. Our ultra-broadband spectrometer ranges from the UV (200 nm) to the mid-IR (12 µm), which allows to resolve time-scales from 0.7 to 40 fs. The prims and grating-based spectrometer divides and maps the spectrum onto three detector systems (UV/VIS;NIR;MIR) of staggered, increasing resolution towards lower wavelengths. Here we present the experimental approach, scope and current status of our spectrometer project.

This study aims at elucidating the mechanisms leading to the incorporation of cations (Eu and Ni) into carbonates (CaCO3). These minerals are present in the French Callovo Oxfordian shales where the radioactive waste should be disposed of. Europium is a long lived fission product that can also be used as analogue of trivalent actinides. Nickel is a long lived activation product. Therefore, for safety reasons, the evaluation of the retention capabilities of calcite with respect to these radionuclides has to be checked. Calcite powders or calcite single crystals (some mm sized) have been put into contact with inactive Europium or Nickel enriched solutions. The concentrations ranged from 10-3 to 10-5 mol/L for Eu and 10-3 mol/L for Ni and the sorption durations ranged from one week to one month. In order to elucidate the incorporation mechanisms of these elements on calcite, Rutherford Backscattering Spectrometry (RBS) experiments have been carried out using an alpha particle millibeam at the 4 MV Van de Graaff accelerator of IPNL. This technique is well adapted to discriminate incorporation processes such as: (i) adsorption or co precipitation at the mineral surfaces or, (ii) incorporation into the mineral structure (through diffusion for instance). For the single crystals, complementary Scanning Electron Microscopy (SEM) observations of the mineral surfaces at low voltage have also been carried out. Moreover, for Europium incorporation, using its fluorescence properties, the results have been compared to those obtained by Time-resolved laser fluorescence spectroscopy (TRLFS). Results on single crystals show different sorption behavior for Ni and Eu. Ni accumulates at the calcite surface whereas Eu is also incorporated at a greater depth. Eu seems therefore to be incorporated into two different states in calcite: (i) heterogeneous surface accumulation and (ii) incorporation at depth greater than 160 nm after 1 month of sorption.

Anisotropic magneto resistance (AMR) sensors are widely used in daily life. Nevertheless, the influence of magnetic domains on the AMR is still not fully understood. AMR depends on the angle between applied current and the direction of the internal magnetization, which is equal to the sum of all magnetic domains. For the understanding of the AMR it is important to know the domain structure.
In this experiment Kerr microscopy is used for the observation of the magnetic domains while at the same time the AMR is measured. The investigated permalloy films are stripe patterned by Cr+ implantation. Amongst other effects the implantation leads to a lower saturation magnetization in the implanted stripes compared to the non-implanted ones.
Our measurements show a clear correlation between AMR and the magnetic domain structure. It is also possible to correlate stripe parameters to different domain types.
This work is supported by DFG grant FA316/3-2.

The present work is concerned with the growth of small-diameter single intermetallic compound crystals by the floating-zone method using a radio frequency RF induction heating. In order to maintain a convex solidification interface, which is required for the growth of single crystals, we have developed a novel two-phase inductor comprising a secondary coil, which is short-circuited through capacitor and resistor. The former is adjusted to have resonance in the secondary circuit, which results in a 90 degrees phase lag of the secondary current relative to the primary one. However, it is not always possible to tune the secondary circuit into the resonance as it turns out to be incompatible with the operation of contemporary self-tuning RF-generators. We show that the resonance frequency is unstable unless the resistance of the secondary circuit is made high enough. Analytical results are confirmed by both numerical simulation of the circuit system using the Simulink and measurements on the floating-zone crystal growth facility equipped with a two-phase inductor.

We have investigated the interlayer exchange coupling in Fe (4nm)/Cr (x nm)/Fe (4nm) thin film trilayers (x=0–5 nm) deposited on rippled amorphous silicon substrates. The substrate surface was periodically modulated (periods of 22 nm and 37 nm) by Ar+ ion erosion. The influence of the resulting surface and interface structure on the magnetic properties has been investigated by magneto-optical Kerr effect (MOKE). We found an orange peel type coupling, predicted by N´eel’s theory and, due to the morphology of the magnetic layers, a strong uniaxial magnetic anisotropy in the system.
This work is supported by DFG grant FA 314/6-1.

SrTiO3 (STO) films have been grown on TiO2-buffered GaN(0002) substrates. The deposition process was in-situ monitored by reflective high energy electron diffraction (RHEED). The deposition rate and in-plane lattice parameter of TiO2 were calculated from the oscillation curve and RHEED patterns, respectively. It was found that the TiO2 lattice parameter changed as the thickness increased, which indicated a strain relaxation process of TiO2 buffer layers during the deposition. We show that the thickness of TiO2 can significantly influence the STO growth mode, surface morphology and crystalline quality. As the TiO2 thickness increased, the STO growth mode is changed from 3D island to 2D growth mode and finally to S.K mode as revealed by RHEED. The growth mode evolution shows close relation with the surface morphology and crystalline quality of STO. STO films deposited on 2nm thick TiO2 film show 2D growth mode and have smoothest surface and smallest full width at half magnitude of the STO rocking curve. Our investigation hints towards to a general approach to optimize the crystalline quality of STO can be optimized by adjusting the strain state of TiO2 buffer layer.

In the Travelling-wave Thomson-scattering (TWTS) scheme ultrashort and narrow-band light pulses in the X-Ray region of the spectrum are created by scattering high intensity laser pulses from relativistic electron bunches. TWTS uses lasers with a pulse front tilt in a side-scattering geometry to scale the interaction length into the centimeter to meter range. This is crucial for allowing the scattered radiation to act back on the electrons which eventually can lead to coherent amplification of the radiation as in a free electron laser (FEL). We study the electron dynamics in the laser field including back reaction effects and discuss the applicability of TWTS as a SASE-FEL.

Beschleunigermassenspektrometrie (AMS, accelerator mass spectrometry) ist eine höchstsensitive Methode, um langlebige Radionuklide mit einer Halbwertszeit von 100 Jahren und länger zu messen. Der Aufbau der AMS-Anlage DREAMS (DREsden AMS), die seit August 2011 in Betrieb ist, ist in Abbildung 1 dargestellt.
Aus der zu analysierenden – bereits chemisch aufbereiteten – Probe werden in einer Cäsium-Sputterionenquelle negative Ionen (Moleküle oder Elemente) extrahiert. Diese einfach negativ geladenen Ionen werden in einem Niederenergie-Massenspektrometer nach ihrer Energie und Masse analysiert und gelangen nachfolgend in den Tandem-Beschleuniger, wo sie durch eine positive Hochspannung (im Bereich von MV) beschleunigt werden. Beim Durchgang durch Argon-Gas werden den Ionen Elektronen abgestreift, dadurch Moleküle zerstört, und die nun positiven Ionen ein zweites Mal beschleunigt. Im Hochenergie-Massenspektrometer werden die Radionuklide dann mit einem geeigneten Detektionssystem identifiziert. Mit diesem Aufbau lassen sich Isobare effizient, sowie molekularer Untergrund vollständig unterdrücken.
Momentan werden an DREAMS Routinemessungen der Nuklide ¹⁰Be, ²⁶Al und ⁴¹Ca durchgeführt [1]. Die Nachweisgrenze liegt im Bereich von 10^-15 – 10^-16 Radionuklid zu stabilem Nuklid, was Aktivitäten im Bereich von nBq entspricht. Zu Messungen volatiler Elemente wie Chlor (³⁶Cl) siehe [2].
DREAMS wird um eine Flugzeitstrecke (time-of-flight (TOF)) erweitert, um schwere Nuklide wie Aktinide messen zu können. Neben der vollständigen Molekülunterdrückung und dem geringeren Präparationsaufwand von Proben liegt der Vorteil der AMS darin, Isotope wie ²³⁹Pu und ²⁴⁰Pu unterscheiden zu können, was mittels Alphaspektrometrie nicht möglich ist.
Durch den Anbau einer kommerziellen SIMS (SIMS = Secondary ion mass spectrometry) Anlage an den Beschleuniger wird DREAMS zu einer Super-SIMS erweitert. Damit sollen Verhältnisse stabiler Elemente im Bereich von 10^-9-10^-12 unter Beibehaltung der Ortsauflösung einer SIMS-Anlage gemessen werden.
[1] S. Akhmadaliev et al., Nucl. Instr. Meth. B 294 (2013) 5.
[2] S. Pavetich, Poster, 7. Workshop RCA.

High-power superconducting linear electron accelerators allow producing a variety of secondary beams. At the Helmholtz-Zentrum Dresden-Rossendorf a 40 MeV superconducting electron accelerator is operated at beam currents up to 1.6 mA in continous-wave mode delivering neutrons from photo-production off lead, tunable coherent laser light from free-electron lasers, intense Bremsstrahlung for nuclear (astro-) physics, and positrons from pair production. New developments now enable for the first time positron annihilation lifetime experiments in bulk materials, fluids, gases and organic tissue. A 3-D tomographic annihilation lifetime imaging systems has been developped for new classes of experiments for quantitative and qualitative crystal-defect characterizations, chemsitry of positronium in insulators and porous materials. Some recent applications will be presented.

We consider equations of the kinematic mean-field alpha^2-dynamo with the spherically-symmetric alpha-profile that depends only on the radial coordinate. We study spectrum of the non-self-adjoint boundary eigenvalue problem for the corresponding operator matrix with the boundary conditions associated either with a perfect electrically conducting surrounding or with an insulating one. In the first case we demonstrate that the operator is self-adjoint in a Hilbert space with the indefinite metric (i.e. in the Krein space). Moreover, if, additionally, the alpha-profile is constant (the problem A), the eigenvalues are real-valued linear functions of alpha; hence, only non-oscillatory instability is possible. However, with non-constant alpha-profiles and insulating boundary conditions, oscillatory dynamo regimes can become dominant (the problem B). With the use of the perturbation theory of multiple eigenvalues we explicitly demonstrate how from the real spectrum of the problem A one can get the complex eigenvalues of the problem B due to variation of alpha-profile and interpolation between the two types of boundary conditions.

We consider rotating flows of an electrically conducting, viscous and resistive fluid in an external magnetic field with arbitrary combinations of axial and azimuthal components. Within the short-wavelength approximation, the local stability of the flow is studied with respect to perturbations of arbitrary azimuthal wavenumbers. In the limit of vanishing magnetic Prandtl number (Pm) we find that the maximum critical Rossby number (Ro) for the occurrence of the magnetorotational instability (MRI) is universally governed by the Liu limit which is below the value for Keplerian rotation.

Ein gegebener schneller Röntgentomograph mit zwei parallelen Messebenen dient zur örtlich aufgelösten Messung von Geschwindigkeiten. Seine Aufgabe soll ohne technischen Zusatzaufwand auf zeitlich aufgelöste Messungen ausgedehnt werden. Der Ebenenabstand ist dafür aber zu groß. Deshalb wird zusätzlich eine indirekte Messebene definiert, indem diejenige Strahlung ausgenutzt wird, die sich im Tomographen zwischen den regulären Ebenen ausbreitet. Die neue Messebene hat zu einer der regulären Ebenen einen genügend kleinen Abstand. Wie damit gemessen werden kann, verdeutlicht ein praktisches Beispiel.

A given fast X-ray tomograph with two parallel measuring planes is used for spatially resolved measurements of flow velocities by design. Now it is to be extended to time-resolved measurements avoiding any additional technical effort. But the spacing between the planes is too big. Thus, an additional indirect measuring plane is defined utilizing radiation which propagates between the regular planes during the tomographic scan. This indirect plane is close enough to one of the regular planes. A practical example illustrates the mode of measurement using the new method.

The reactor dynamics code DYN3D is a three-dimensional best-estimate tool for simulating steady states and transients of light-water reactors and innovative reactor designs. An overview of the DYN3D features is provided. This paper further focuses on the recently developed trigonal-geometry diffusion model DYN3D-TRIDIF including a description of the underlying nodal approach and the characteristics of trigonal geometries. Via a mesh refinement study by means of a VVER-1000-type core benchmark using a fine-mesh diffusion reference solution, DYN3D-TRIDIF shows spatial convergence. Furthermore, the performance of DYN3D-TRIDIF is verified by means of a single-assembly problem on pin-cell level. Good agreement between DYN3D-TRIDIF and the detailed-geometry transport reference is achieved with an average deviation in power of less than 1 %.

In this talk, I will introduce our work on magnetic semiconductors using ion beams. We can (1) prepare ferromagnetic III-V:Mn with different bandgaps and (2) change the hole concentration while keeping Mn concentration constant by ion irradiation. Both possibilities are unique and may lead to a better understanding of magnetic semiconductors.

Ridge waveguides have been fabricated in Nd:YAG crystals by using ion irradiation and precise diamond blade dicing. Continuous-wave lasers at ~1064 nm have been realized in the ridge waveguides through optical pumping at 808 nm at room temperature. The ridge guiding structure shows superior lasing performance with respect to the planar counterpart with a slope efficiency of 43% and a maximum output power of 84 mW.

Our objective was to develop and evaluate Ga-68- and Cu-64-labeled albumin conjugates for PET imaging of sentinel lymph nodes. Four different albumin conjugates were prepared starting from NOTA-HSA.The lymph node uptake of Ga-68- and Cu-64-labeled albumin conjugates was investigated after subcutaneous injection into the foot pad of Wistar rats. A pig model was utilized for further biological evaluation of the lymph node uptake. For all the four conjugates, radiolabeling with Ga-68 and Cu-64 resulted in >95% radiochemical yield. Denatured and mannosylated Ga-68 NOTA-HSA revealed the highest popliteal lymph node uptake in rats (2.78%±0.38% IDand 6.13%±1.13%ID 10 min and 60 min p.i., resp.).Thepopliteal lymph node reached its maximumactivity after approximately 120 min and remained constant for denatured and mannosylated Cu-64 NOTA-HSA at least up to 240 min p.i. In a pig model, 2% of the injected dose of this compound was found in the sentinel lymph node 60 min after subcutaneous injection. In conclusion, PET imaging of sentinel lymph nodes with Ga-68- and Cu-64-labeled denatured NOTA-Man-HSA could be successfully demonstrated and deserves further investigations.

Measuring the transient plasma density structures of Laser-wakefield accelerators (LWFA) that are shorter than the drive laser on a µmfs-scale is experimentally challenging, which complicates comparisons of these results with numerical models from 3D-PIC simulations. Radiation spectra from LWFA plasmas on the other hand are straightforward to measure, but hard to calculate in realistic detail because it is computationally expensive (both CPU and memory) to calculate the radiation emitted by a complete PIC simulation. However, it would be very useful to know where to look for "good" radiation signatures that show quantitative details on the electron dynamics at electron injection.
Here we present a highly-scalable, classical radiation code based on Liénard-Wiechert potentials, which runs on high-performance computing clusters using GPUs. The memory and disk-space footprint is reduced by directly integrating into the 3D-PIC code PIConGPU. With this new code, it is possible to calculate logarithmic-scaled spectra from IR to X-ray wavelengths in arbitrary observation directions. In this talk we put the emphasis on the code architecture, the verification of the physics and on some first results.

In the last decade focused ion beams (FIB) became an irrecoverable instrument in research and industry. Sample preparation, local ion implantation and ion analysis are the main application topics. Most of the systems are equipped with a gallium liquid metal ion source (LMIS). But, modern trends in nanotechnology require more extended properties like variable ion species, non-contaminating milling at higher rates or higher lateral resolution in the field of ion microscopy.
In this presentation the assembly and the mode of operation as well as the application of alloy LMIS in mass separated FIB systems are introduced. A brief survey about the history and fabrication technology of LMIS is given. Finally, new developments including sources in the field of FIB applications in the nanotechnology are discussed.

Microorganisms in a soil sample from the uranium mining waste Johanngeorgenstadt, Germany and an Opalinus clay sample from the Mont Terri rock laboratory were investigated by culture-independent and culture-dependent methods. In addition, the interactions of an Arthrobacter sp. from the uranium mining waste and a Sporomusa sp. clay isolate with Uranium(VI) will be shown. The studies demonstrated that different microorganisms are present in these two different environments and in both cases indigenous microorganisms have the potential to interact with heavy metals and uranium.

Membrane proteins fulfil vital functions in cellular signalling and ion exchange across cell membranes. Their function originates in well defined structural transitions of transmembrane and extramembraneous protein domains. The latter experience aqueous and hydrophobic solvation forces, respectively. We have used time-resolved FTIR spectroscopy coupled to static fluorescence measurements to study how this solvation balance at the membrane water interface affects membrane protein structure. Transmembrane peptides derived from rhodopsin, a prototypical G protein-coupled receptor (GPCRs), exhibit solvent-accessible stretches which couple protonation and hydration to local helical structure: protonation of a conserved cytosolic site in helix 3 (Glu-134) causes side chain partitioning at the water lipid interface [1]. Vice versa, the side chain charge affects structural transitions that are induced by transients (seconds) of interfacial water potential. These local processes depend on the hydrophobic context of the amino acid sequence. Opsin mutants containing amino acid replacements of the same carboxyl side chain also exhibit altered responses of their structure to water potential. The data indicate that the conserved carboxyl in helix 3 of GPCRs is a protonation-controlled hydration site that regulates the partial entry of water at the protein lipid interface, thereby contributing to the free enthalpy difference between active and inactive structures of the receptor.

Si films sputter deposited on SiO₂ substrates are enriched with Ga by ion implantation through a capping SiO₂ layer. The morphology and the electrical transport properties of these films are investigated after rapid thermal annealing. Amorphous, Ga rich nanograins are embedded in a nanocrystalline Si matrix. The nanograins are metallic in the normal state and superconducting below 7 K. They form a random network of junctions to heavily doped Si crystallites. Small modifications of the junction properties, e.g. by annealing or current pulses, can dramatically change the electronic transport in the film. Ga rich Si films show a wealth of low-temperature transport phenomena which have been known until now only from granular metals or high temperature superconductors: superconductor-insulator transition, quasi-reentrant superconductivity and current controlled sheet resistance. The possibility to fabricate and tailor films of Ga rich Si with microelectronics compatible technology make it a promising material for the integration of superconducting circuits into Si devices.

As nanotechnology increasingly finds its way into everyday applications the risk assessment of a potential nanoparticle (NP) release into the environment becomes mandatory. Though, NPs are notoriously difficult to trace in such complex environments as the geosphere, ground and surface waters or organisms, especially at the predicted low concentrations that nevertheless might be environmentally relevant. Radiolabeling of NPs provides a possibility to overcome this problem. However, radiolabeling itself bears the danger of changing the particle properties, leading to uncertainties in the interpretation of experimental results. We here present radiolabelling strategies for TiO2, Ag0 nanoparticles and carbon nanotubes (CNTs) that were developed with a minimum of NP property alteration in mind.

TiO2 and Ag0 NPs were radiolabeled using an in-diffusion technique resulting in the incorporation of radionuclides of the respective element in the NPs. Briefly, radionuclide stock solutions containing 45Ti or 110mAg were applied to dry nanoparticle powder followed by a low temperature annealing for diffusive introduction of the radionuclides into the NPs. A stable radiolabeling was achieved with no significant change in particle properties detectable in the range of our experimental conditions.

CNTs were radiolabelled using the one-pot Iodogen reaction for introduction of radioactive iodine 125/131I onto the CNT side wall. The radiolabel proved to be stable in the absence of light and no changes of the particle properties could be measured. The potential employment of 124I opens the possibility for positron emission tomography studies and therefore the localisation of radiolabeled CNTs in complex matrices such as rock materials.

The employment of radiotracers is a versatile tool for the detection of nano-particulate materials in complex systems such as environmental samples or organisms. With the increasing usage of nanoparticles (NPs) in applications outside of research laboratories a careful risk assessment of their release into the environment becomes mandatory. However the monitoring of nanoparticles in such complex natural systems as geological formations or ground water is nearly impossible using conventional methods, especially at environmentally relevant concentrations. This obstacle can be overcome by radiolabelling, which may be of crucial value in enabling such research. We present here two different radiolabelling strategies for Ag0-NP, TiO2-NP and MWCNTs.

Both strategies involve proton bombardment using a cyclotron and cause the incorporation of radioactive isotopes inside the NPs. The first option is to directly activate the NPs by proton irradiation, which proved useful for MWCNTs and TiO2-NP. 12C gets activated using a (p,3d) nuclear reaction to 7Be while 48Ti gets activated to 48V by a (p,n) reaction.
The second option, which is generally adoptable for NPs that do not show useful nuclear reactions, is to mix the NP powder with a lithium containing compound like LiH and irradiate it to create 7Be out of 7Li via a (p,n) reaction. The recoil of the 7Be from the nuclear reaction causes the incorporation of the radiotracer into the structure of the NP.
The methods were tested for labelling yield, achievable activity concentration, pH-dependent stability of the labeling and the influence on NP-properties. Data thus obtained enables the selection of a radiolabelling method appropriate for different experimental conditions.
48V labeled TiO2-NPs were successfully employed to study the NP release out of surface coatings not measurable using conventional methods.

Der Vortrag fasst Ergebnisse zu mikrostrukturellen Untersuchungen an neutronenbestrahlten WWER440 RDB-Stählen mittels Neutronen-Kleinwinkelstreuung zusammen.
The presentation summarizes results of microstructural invetigations on WWER440 -type RPV steels by means of SANS.

For the modeling of different chemical aspects of a salt repository for nuclear waste, the Pitzer formalism is necessary. Therefore, a comprehensive database with the relevant aqueous and mineral species, the corresponding reaction constants and associated ion-ion interaction parameters are required.
A number of different Pitzer databases are available for, or even delivered with various geochemical speciation codes such as EQ3/6, PHREEQC, Geochemist’s Workbench® (GWB) or ChemApp. In this work we performed comparative calculations for well-defined chemical systems on the base of these Pitzer databases. In Addition, for a more comprehensive view experimentally measured values from the literature were included in the comparisons.

Fast neutron irradiation of low-Cu reactor pressure vessel (RPV) steels gives rise to the formation of solute clusters and a degradation of mechanical properties. A remarkable acceleration of cluster formation was identified in a previous investigation of low-Cu steels irradiated at 255 degrees C. The thermal stability of the observed features at a typical RPV operation temperature (290 degrees C) is of particular interest. Small-angle neutron scattering experiments for three low-Cu materials irradiated at 255 degrees C and exposed to post-irradiation annealing at 290 degrees C are reported. The results indicate stability of the irradiation-induced features at a temperature of 290 degrees C for all three materials. In two cases, even an increase in scattering intensity upon post-irradiation annealing has been observed. The effect of the annealing treatment on the nature of clusters is discussed and a model of the cluster-matrix interface is introduced to rationalize the observed increase in scattering intensity. The role of the residual elements is discussed.

Reactor pressure vessel (RPV) steel, when exposed to fast neutron irradiation, leads to the formation of nano-sized clusters [1]. These clusters can cause an overall degradation in mechanical properties, which is a safety issue. Small-angle neutron scattering (SANS) is a commonly used technique to determine the irradiation-induced cluster volume fraction and cluster size distribution in the material.
However, in the case of modern RPV steels, standard data treatment [2] for back-transforming the SANS scattering curves to real space can lead to unstable results. These are highly dependent on renormalisation parameters to be chosen by the user.
Here, a Monte Carlo fitting (MCF) algorithm based on [3] is presented. No renormalisation parameter is needed. The algorithm is optimized to get a robust determination of small cluster volume fractions (≈ 0.01 %) and cluster radii (≈ 0.7 nm), which are typical for modern RPV steels. The significance of the resulting data can be evaluated by an automatic error analysis. Using simulated scattering curves, the MCF is able to deliver a good reconstruction of the cluster size distribution and volume fraction in the vicinity of the SANS detection limit. Furthermore, the algorithm is tested with experimental scattering curves of neutron-irradiated RPV steels. The MCF transformation yields in physical meaningful, non-divergent results. Comparisons between analyses performed by the standard methods [2] and the MCF algorithm are drawn. The stability of the results and the limits of information to be extracted from the experimental data are discussed.

References
[1] G.R. Odette, B.D. Wirth, Handbook of Materials Modeling, Springer Netherlands, 999–1037 (2005)
[2] S. Hansen, J.S. Pedersen, J.Appl.Crystallogr. 24, 541–548 (1991)
[3] S. Martelli, P.E. Di Nunzio, Part.Part.Syst.Char. 19, 247–255 (2002)

Fe-14 Cr based ODS alloys are candidates for nuclear applications such as cladding tubes. One of the main issues is the fabrication of dense material with uniformly dispersed nanometer-size oxide particles. In order to investigate the influence of the fabrication route on the microstructure of the material the samples with Yttria contents of 0…0.6wt% were produced by mechanical alloying and subsequent consolidation via spark plasma sintering (SPS). The microstructure was characterized concerning the grain and particle size by means of electron backscatter diffraction (EBSD) and atom probe tomography (APT).

Ferritic Fe14Cr based oxide dispersion strengthened (ODS) alloys are promising candidates for components of GEN IV reactors. Due to their high Cr content high corrosion resistance is provided and the austenite phase transformation is prevented. Matrix compositions containing Ti in combination with yttria as reinforcing constituent tend to the formation of complex Y-Ti oxides that are known for their small particle sizes. High creep resistance and yield strength as well as an improved resistance against radiation induced He embrittlement are expected improvements to be achieved by ODS.
The considered fabrication process consists of a mechanical alloying step and the subsequent consolidation. During these steps an evolution of the added yttria particles (≈30 nm) towards much smaller Ti-Y-O nanoclusters (2-5 nm) has been observed [ ; ]. However, the mechanisms of dissolution and especially the re-precipitation during the consolidation process are not well known yet.
In order to evaluate the influence of the processing parameters, powders of different compositions (0….0.6wt% Y2O3) are fabricated applying different milling times (20h; 30h). These powders are consolidated via spark plasma sintering (SPS). The sintered material has been characterized with respect to porosity, microstructure, spatial distribution of composition and Vickers hardness. Ongoing research is focussed on the characterization of the oxide particles at the nanometre scale.

Sn(II) is a contaminant of general environmental interest, but little is known about its interaction and retention by mineral surfaces. We have selected the redox-inactive mineral anatase (TiO2) to study the surface complexation mechanism by combining EXAFSderived surface structures with surface complexation modeling to model the macroscopic sorption behavior. Three adjustable parameters required for diffuse double layer model were determined in this study: the surface site density (16 sites/nm2), and two log K+ values (4.76 ± 0.36 and −9.90 ± 0.42) of the protolysis reactions. EXAFS spectra show Sn(II)–Ti distances at 3.26 and 3.60 Å indicating the formation of monodentate and bidentate inner-sphere sorption complexes. Four surface complexes, Anat_sOSn+, Anat_sSnOH,
Anat_sOH(Anat_sO)Sn+, and (Anat_sO)2Sn, with log K values of 3.66, 3.68, 4.63, and 4.41, respectively,
were required to model the sorption data.

The present historical organs are musical instruments, which provide sound impression of divine music spanning six centuries. Unfortunately, organ pipes, traditionally made of PbSn alloys, have been severely affected by corrosion in the last couple of centuries, and particularly over the last decades. A major threat to the historical organs is harmful indoor environments. Thus, it is necessary to develop a method of protecting the organ pipes, so that the significant cultural heritage obtained over many centuries does not get lost. A new conservation concept based on nanotechnology using plasma immersion ion implantation (PIII) is proposed here for the protection of PbSn alloys exposed to high levels of acetic acid vapors.

LaLuO3 and LaScO3 high-k layers were treated by flash lamp annealing (FLA) at temperatures between 1000°C and 1200°C for 3 or 20 ms. This procedure mimics the effect of an source/drain activation annealing by FLA on the electrical and microstructural properties of these alternative high-k dielectrics in a gate-first processing sheme. Related MOS capacitors with a TiN metal gate were processed in a gate first like processing scheme. It is shown that 3 nm thick oxide layers resist crystallization even at 1200°C for 3 ms, while nanocrystallites are formed in thicker layers. The influence of the FLA treatment on capacitance-voltage (C-V) and current-voltage (I-V) characteristics are investigated. From these measurements, the effects on the relative dielectric constant (k), the fixed oxide charge density (Qox) as well as the leakage current through the insulators are deduced.

CFD simulations of dispersed bubbly flow on the scale of technical equipment are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, accurate numerical predictions rely on suitable closure models. A large body of work using different closure relations of varying degree of sophistication exists, but no complete, reliable, and robust formulation has been achieved so far.
As a step towards this goal, an attempt is made here to collect the best available description for all aspects known to be relevant for adiabatic bubbly flows where only momentum is exchanged between liquid and gas phases. Apart from interest in its own right, results obtained for this restricted problem also provide a good starting point for the investigation of more complex situations including heat and mass transport and possibly phase change or chemical reactions.
Aspects requiring closure for the case under consideration are: (i) the exchange of momentum between liquid and gas phases, (ii) the effects of the dispersed bubbles on the turbulence of the liquid carrier phase, and (iii) processes of bubble coalescence and breakup that determine the distribution of bubble sizes. All of these aspects are coupled and therefore in principle have to be considered as a whole.
To validate the overall model, simulation results are compared against experimental data taken from the literature for bubble columns in various settings. In the present study the focus is on the homogeneous regime where the assumption of a monodisperse bubble size distribution is reasonable and coalescence and breakup need not be considered. From the observed level of agreement between simulation and experiment, issues requiring further investigation will be identified. Necessary extensions to the heterogeneous regime will be discussed but remain to be worked out in the future.

The talk gives an overview about high energy ion-induced anisotropic deformation of nanostructures, also called ion beam shaping, especially of different nanoparticles embedded in silica. For selected examples, swift-heavy-ion-induced deformation of spherical Au and Ge nanoclusters (NCs) embedded in SiO2 was studied experimentally and theoretically. Ge NC shaping is size dependent under irradiation with 38 MeV iodine ions and with 89 and 185 MeV gold ions. Large NCs don’t deform, smaller ones become discus-shaped, and very small ones show Ge loss at their equator. Small Au NCs deform into rods and wires, and, rather exotic, at critical NC size Au wires are squeezed out of the poles of the Au spheres.
Experimental results are compared with modeling and atomistic computer simulations. The model describes the ion-induced shape evolution of different elements for different ion species, energies and fluences even quantitatively, where only one fit parameter describes all experiments. It is based on classical thermodynamics and hydrodynamics only.

Positron emission tomography (PET) is widely used in radiology to visualized cancer cells and infections in human tissue. This functional imaging technique is commonly used in order to visualize processes in the body with the help of radioactive substances. In addition, this method has been used for the investigation of transport processes in geological materials [1].
The aim of our work is the development of a method for the application of PET for geo-microbial research. We will use this technique for the spatio-temporal visualization of the mobility of bacteria in geological matrices. The visualization of the formation of biofilms and their influence on flow paths in different matrices is an important aspect as well. In addition, it offers the possibility to get insights into microbial processes (e.g. bioleaching) in opaque materials.
Some basic investigations for the experimental set-up are necessary. First, the method requires an efficient non-toxic method that allows the selective labeling of bacteria without interfering with the geological matrix. Currently, we are investigating a selection of antimicrobial peptides for their use as appropriate marker. Second, appropriate bacteria are selected for further investigation. Pseudomonas fluorescens and Lysinibacillus sphaericus JG-A12 were chosen as typical organisms living in soil. Third, the interactions of the different compounds and the influence of experimental parameters need to be tested. For further experiments it is very important to examine the stability of the label as well as adsorption and desorption processes of the PET nuclides and of the labeled substances in conjunction with different matrices. The characterisation of model columns that are filled with quartz gravel or copper ore needs to be investigated as well. Fluid dynamics and structural parameters like porosity and the internal surface area have to be investigated.
In this study we present our recent results on the development of a PET-method that allows the in-situ labeling of bacteria and the visualization of their mobility in geological matrices.

[1] Gründig, M., M. Richter, et al. (2003). Positron Emission Tomography for investigation of water flow in soil columns. Geochemical Processes in Soil and Groundwater. H. D. Schulz. Weinheim, Wiley-VCH: 550-559.

Bacterial cell walls have great potential to influence the speciation and mobility of actinides and lanthanides in the environment. This study explores the unknown interaction between Cm(III)/Eu(III) and cell-suspensions of Sporomusa sp. MT-2.99, a novel isolate originating from Opalinus Clay (Mont Terri, Switzerland).
The Cm(III)/Eu(III) binding by the cell surface functional groups was studied by potentiometry combined with time-resolved laser-induced fluorescence spectroscopy (TRLFS). This paper provides stability constants of Cm(III)/Eu(III) complexed by cell surface functional groups. It could be shown that as a function of pH Cm(III)/Eu(III) binding occurred to hydrogen phosphoryl, carboxyl and deprotonated phosphoryl sites. Both metals showed a similar interaction process consisting of surface complexation (major) with high thermodynamic stability and immobilization within the cell envelope (minor).

To optimize the semi-preparative separation of a ¹⁸F-labeled PET radiotracer from its nitro precursor in a recently developed radiosynthesis, we performed an analytical HPLC study using the unlabeled reference compound and the corresponding nitro precursor. Several RP phases as well as a bare silica column were investigated with ACN and MeOH as organic modifiers and aqueous NH₄OAc because of the basic character of the analytes. Four types of separation were observed based on different interaction mechanisms. When ACN/20 mM NH₄OAc aq. was used mainly cationic-exchange and hydrophobic interactions contribute to the retention. A reversal of elution order could be observed starting from 95% ACN and subsequent increasing of the water content. This phenomenon was observed for all RP phases and seems to be independent of the different spacers bound to the silica. By contrast, using MeOH/20 mM NH₄OAc aq. the elution order depends on the phase material. Two columns with the potential to perform π-π interactions showed different separation behavior compared to the other RP phases.

Tetrahedral amorphous carbon (ta-C) coatings have attracted high scientific attention in recent years due to their outstanding low friction coefficients in lubricated environments and their superior resistance to abrasive as well as adhesive wear. Consequently, they are highly suitable as protective coatings in automotive components such as combustion engines to reduce wear and friction. Nevertheless, ta-C abrade under extreme conditions and an atomistic understanding of the wear processes in ta-C is crucial for optimizing its wear resistance. The present study employs atomic-scale simulations to investigate the basic principles of wear between hydrogen- free tetrahedral-amorphous carbon (ta-C) films, which are modeled state-of-the-art by an improved version of the well-known Brenner bond-order potential. During tribological contact, these mainly sp3 hybridized films tend to form an amorphous carbon (a-C) tribomaterial mainly consisting of carbon atoms in sp2 configuration. Furthermore, the observed tribolayer grows faster than the a-C between diamond surfaces under similar conditions, which can be explained by easy breaking of weak bonds in a finite ta-C region triggered by plasticity in the adjacent a-C while the diamond/a-C transition occurs at an atomically sharp interface. The difference in the a-C tribofilm formation between ta-C and diamond is in agreement with near-edge x-ray absorption fine structure spectroscopy (NEXAFS) studies published recently.

Nanocoatings have the potential to improve the surface properties of various materials. They are of extreme importance for surfaces in sliding contact such as highly stressed automotive engine parts. Here, nanocoatings have to be optimized with respect to low friction properties and a high wear resistance to enhance the energetic and environmental efficiency. The present study employs atomic-scale simulations to investigate the basic principles of wear and friction between hydrogen-free tetrahedral-amorphous carbon (ta-C) films. The ta-C films are modeled state-of-the-art by an improved version of the well-known Brenner bond-order potential, which had been successfully applied to elucidate the wear processes during diamond polishing.

We start our work by the preparation of the ta-C film structure, which is then characterized with respect to local and global film properties in comparison to experiments. After validating our ta-C nanocoatings with the help of experimental data, we perform computational sliding experiments to investigate mechanisms of friction and wear between interacting ta-C surfaces. During tribological contact, these diamond-like films (mainly sp3 hybridized) tend to form a soft-amorphous or graphite-like tribomaterial mainly consisting of carbon atoms in sp2 configuration. The sp3 to sp2 transition originates from atom-by-atom extraction events occurring at the sp3/sp2 interface. We discuss the underlying mechanisms by focusing on associated triboreactions and tribological properties such as shear forces.

Beschleunigermassenspektrometrie (AMS - Accelerator Mass Spectrometry) ist eine hochsensitive Methode zur Bestimmung der Häufigkeit von Radioisotopen. Dabei werden Radionuklide immer relativ zu den stabilen Isotopen des jeweiligen Elements gemessen. Da bei der AMS radioaktive Atome nicht durch ihren Zerfall detektiert werden, sondern direkt gezählt werden, eignet sich die Methode in erster Linie für langlebige Radionuklide (t_1/2 > 100 a). Dabei können je nach Element Isotopenverhältnisse von 10^-15-10^-16 (entspricht nBq) gemessen werden, wobei die Messzeit ca. 1 h pro Probe beträgt. Im Wesentlichen besteht eine AMS-Anlage aus einer Ionenquelle (üblicherweise Cs-Ionensputterquelle) zur Extraktion negativer Ionen aus dem Probenmaterial (< 10 mg), zwei Massenspekrometern (Injektormagnet und Analysiermagnet) zum Filtern der Ionen nach ihrer Energie, ihrem Impuls und Ladungszustand, einem Beschleuniger der die Ionen auf die für die finale Separation notwendigen Energien (MeV) beschleunigt und durch das sogenannte „Stripping“ für eine totale Unterdrückung des molekularen Isobarenhintergrundes sorgt und einem Detektor zum Zählen der Radioisotope bzw. Faraday-Cups zur Messung des Stromes der Stabilisotope.

Die AMS-Anlage DREAMS (DREsden AMS) ist seit August 2011 in Betrieb [1]. Momentan werden bei DREAMS Routinemessungen der Nuklide ¹⁰Be, ²⁶Al und ⁴¹Ca durchgeführt [2]. Bei den volatilen Element Cl und I werden Präzisionsmessungen noch durch Langzeit- und Probe-zu-Probe-Kontaminationseffekte in der Ionenquelle verhindert [3]. Kooperationen mit der TU Bergakademie Freiberg einerseits und dem UFZ Leipzig (Helmholtz-Zentrum für Umweltforschung) andererseits bei denen Proben aus der Salar de Uyuni (Salzwüste in Bolivien) und von unterirdischen Wasserläufen im Oman untersucht wurden, haben gezeigt, dass die Bestimmung von ³⁶Cl-Konzentrationen dennoch auf einem Level von einigen 100 nBq zurzeit schon möglich ist. Die Entwicklung einer neuen Ionenquelle für volatile Elemente, die in ersten Versuchen vielversprechende Ergebnisse geliefert hat, wird noch präzisere AMS-Messungen von ³⁶Cl bei DREAMS ermöglichen.

Danksagungen: Prof. Dr. Broder J. Merkel und Anna Seither, TU Bergakademie Freiberg
Dr. Gerhard Strauch und Thomas Müller, Helmholtz-Zentrum für Umweltforschung Leipzig

[1] S. Akhmadaliev et al., Nucl. Instr. Meth. B 294 (2013) 5
[2] G. Rugel, Vortrag, 7. Workshop RCA
[3] R. Finkel et al., Nucl. Instr. Meth. B 294 (2013) 121

The DREAMS (DREsden Accelerator Mass Spectrometry) facility [1] went operational in August 2011. It is based on a state-of-the-art 6 MV Tandetron. The target wheels of the two Cs sputter ion sources can be loaded with up to 200 samples each. A fast bouncing system at the 90° injection magnet allows almost simultaneous measurements of the radioisotope and its stable isotope(s). For the measurement of ¹⁰Be and ³⁶Cl a 1 µm Si₃N₄-post-acceleration stripping-foil in combination with a 35° ESA suppresses their stable isobars ¹⁰B and ³⁶S. An ionization chamber with four anodes is used for the final identification of the radioisotopes.

At the moment routine measurements of ¹⁰Be, ²⁶Al and ⁴¹Ca are performed at DREAMS. In the case of volatile elements like Cl and I, the key issue for precise AMS-measurements is the understanding and minimization of ion source memory effects [2,3]. For this purpose the main focus for ³⁶Cl-measurements at DREAMS was set to the mechanical modification and improvement of the original SO110 ion source from High Voltage Engineering (HVE) [4]. The new DREAMS design has a more open geometry to improve the vacuum level and a modified target loading and positioning system, which allows exchanging the individual cathode aperture with each target.

In order to evaluate this improvement in comparison to other up-to-date ion sources, an interlaboratory comparison with three AMS labs had been initiated. The long-term memory effect in the four Cs sputter ion sources of VERA [5] (Vienna Environmental Research Accelerator, NEC ion source: MC-SNICS), ASTER [3] (Accélérateur pour les Sciences de la Terre, Environnement, Risques, modified HVE SO110) and DREAMS (original HVE SO110 and modified HVE SO110 ion source) had been investigated by running samples of natural ³⁵Cl/³⁷Cl-ratio and samples containing highly-enriched ³⁵Cl (³⁵Cl/³⁷Cl > 500). We choose to perform these measurements with the two stable Cl isotopes instead of using ³⁶Cl standards and blanks to avoid limitations of accuracy by counting statistics on low level ³⁶Cl samples.

The primary goals of these experiments are the determination of the time constants of the recovery from the contaminated sample ratio to the initial ratio of the sample and the level of the long-term memory effect in the sources.

[1] S. Akhmadaliev et al., Nucl. Instr. Meth. B 294 (2013) 5.
[2] R. Finkel et al., Nucl. Instr. Meth. B 294 (2013) 121.
[3] M. Arnold et al., Nucl. Instr. Meth. B 294 (2013) 24.
[4] M.G. Klein et al., Nucl. Instr. Meth. B 249 (2006) 764.
[5] M. Martschini et al., Nucl. Instr. Meth. B 269 (2011) 3188.

Complex formation between uranyl(VI) ion and formic acid was studied by infrared absorption (IR) and X–ray absorption (EXAFS) spectroscopy as well as density functional theory (DFT) calculations. In contrast to the acetate ion which forms exclusively bidentate complex with uranyl(VI), formate ion binds to uranyl(VI) in unidentate fashion. The photochemistry of the uranyl(VI)–formic acid system was explored by DFT calculations and photoreduction of uranyl(VI) in the presence of formic acid was found to occur via an intermolecular process, that is hydrogen abstraction from hydrogenformate by the photo–excited uranyl(VI). There is no photo–induced decarboxylation of uranyl(VI) formate via an intramolecular process, presumably due to lack of a C=C double bond.

Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-burning regions. In particular, low-energy nuclear resonances in the Mg-25(p,gamma)Al-26 reaction affect the production of radioactive Al-26(gs) as well as the resulting Mg/Al abundance ratio. Reliable estimations of these quantities require precise measurements of the strengths of low-energy resonances. Based on a new experimental study performed at the Laboratory for Underground Nuclear Astrophysics, we provide revised rates of the Mg-25(p,gamma)Al-26(gs) and the Mg-25(p,gamma)Al-26(m) reactions with corresponding uncertainties. In the temperature range 50-150 MK, the new recommended rate of Al-26(m) production is up to five times higher than previously assumed. In addition, at T = 100 MK, the revised total reaction rate is a factor of two higher. Note that this is the range of temperature at which the Mg-Al cycle operates in a H-burning zone. The effects of this revision are discu!
ssed. Due to the significantly larger Mg-25(p,gamma)Al-26(m) rate, the estimated production of Al-26(gs) in H-burning regions is less efficient than previously obtained. As a result, the new rates should imply a smaller contribution from Wolf-Rayet stars to the galactic Al-26 budget. Similarly, we show that the asymptotic giant branch (AGB) extra-mixing scenario does not appear able to explain the most extreme values of Al-26/Al-27, i.e., > 10(-2), found in some O-rich presolar grains. Finally, the substantial increase of the total reaction rate makes the hypothesis of self-pollution by massive AGBs a more robust explanation for the Mg-Al anticorrelation observed in globular-cluster stars.

In this paper, we report on a long, ms range, hole spin relaxation time in InGaAs/GaAs quantum wells probed by cyclotron resonance spectroscopy in pulsed magnetic fields. In our experiments, we found strong hysteresis in the spectral weights of cyclotron resonance absorption lines when rapidly changing magnetic field is used for the experiment. The hysteresis vanishes when a much slower changing magnetic field is used. We attribute this behavior to a long energy relaxation time between the two lowest spin-split hole Landau levels, i.e., a long hole spin relaxation time. We also present transition frequencies calculated using a 4×4 Luttinger Hamiltonian, which confirm our findings.

This talk summarizes recent magneto-optical activities at Dresden high magnetic field laboratory. The first part reports a correction to the model potential of the Ga acceptor in germanium, evidenced by high-magnetic-field photoconductivity measurements. It was found that under high magnetic fields the chemical shift of the binding energy of Ga acceptors vanishes, contrary to the results given by the generally accepted theory. To fit our data, we found that the central-cell correction should contain a repulsive part (i.e., it must be bipolar), in contrast to the purely attractive screened point-charge potential widely used in the literature.
In the second part, we report long, ms range, hole spin relaxation time in InGaAs/GaAs quantum wells probed by cyclotron- resonance spectroscopy in pulsed magnetic fields. In our experiments, we found strong hysteresis in the spectral weights of cyclotron resonance absorption lines when rapidly changing magnetic field is used for the experiment. The hysteresis vanishes when a much slower changing magnetic field is used. We attribute this behavior to a long energy relaxation time between two lowest spin-split hole Landau levels, i.e. a long hole spin relaxation time. We also present transition frequencies calculated using a 4x4 Luttinger Hamiltonian, which confirm our findings.

• Limits today in simulating horizontal two phase flow: no special turbulence treatment at the surface Turbulence Damping,
• Introduction of a symmetric damping procedure (Egorov) for the solid wall-like damping of turbulence in both gas and liquid phases Subgrid wave turbulence (SWT),
• Waves created by Kelvin-Helmholtz instabilities that are smaller than the grid size are neglected - Influence on the turbulence kinetic energy of the liquid side can be significantly large,
• A region of marginal breaking is defined according Brocchini and Peregrine (2001) and added as a source term in the turbulent kinetic energy equation,
• Verification and Validation is going on – more experimental data are required for the validation

Demineralisation plants of power stations are not able to remove organics in all cases to a satisfied degree. The present work focuses on natural organic matter (NOM) and its interaction with anion exchanger and adsorber resins to optimize organics uptake. In this study, four different starches (one of them 14C-labelled) with different molecular size distributions were selected as model substances for the biopolymer fraction of NOM. Their uptake by various anion exchangers and adsorbers was measured in column experiments. Results are discussed in terms of size exclusion, anion exchange, adsorption, and hydrophilic/hydrophobic repulsion. In summary, at neutral pH, starch has been removed preferably by size-exclusion followed by adsorption, whereas anion exchange resins show higher uptake capacities than “pure” adsorber resins caused by stronger attraction between starch and polar functional groups of the anion exchangers. At acidic pH, the uptake of sulphate, as competitive adsorptive, leads to an earlier starch breakthrough at anion exchangers. Therefore, adsorbers are more effective. It was found, that the higher the water content of the resins, the more effective the uptake is.

Functional DNA origami nanostructures for single-molecule experiments and novel nanomaterials

An optical technique to study the longitudinal distribution of ions in a bunched ion beam circulating in a storage ring is presented. It is based on the arrival-time analysis of photons emitted after collisional excitation of residual gas molecules. The beam-induced fluorescence was investigated in the ultraviolet regime with a channeltron and in the visible region using a photomultiplier tube. Both were applied to investigate the longitudinal shape of bunched and electron-cooled 209Bi80+ ion beams at about 400 MeV/u in the experimental storage ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Bunch lengths were determined with an uncertainty of about 0.5 m using the UV-sensitive channeltron and with slightly lower accuracy from the photomultiplier data due to the slower transitions in the red region of the spectrum. The Gaussian shape of the longitudinal distribution of ions inside the bunch was confirmed. With the information of the transverse beam size that can be measured simultaneously by a newly installed ionization profile monitor (IPM) at the ESR, an accurate determination of the ion density in the bunched beam will be allowed.

We present a novel technique for quantitative unmixing of primary and secondary ferrimagnetic minerals in sediments. Hysteresis and high-resolution first-order reversal curve (FORC) measurements are performed on sediment samples before and after digestion in a citrate-bicarbonate-dithionite (CBD) solution optimized for maximum selective extraction of secondary fine-grained iron oxides. The difference between magnetic measurements of untreated and CBD-treated sample materials is used to calculate the original magnetic signature of CBD-extractable minerals. Combination of selective chemical extraction and magnetic measurements suited for the detection of single-domain particles provides a cross-check between chemical and magnetic unmixing of primary and secondary iron-oxides and resolves the non-uniqueness of numerical unmixing methods. A fully quantitative magnetic characerization of secondary ferrimagnetic minerals in a magnetofossil-rich pelagic carbonate is presented for the first time. It can be used for calibartion of recently developed fast magentic unmixing techniques. CBD-based Fe extraction from sediments with minimal clascic and/or aeolian inputs, such as pelagic carbonates, is partcularly suited for the detection of cosmogenic ⁶⁰Fe signatures from supernova explosions, because ⁶⁰Fe dilution by dissolved primary Fe-bearing minerals is minimized.

Multilayer particle deposition and resuspension between periodic steps in a turbulent channel flow was experimentally studied. A particle laden turbulent flow in a horizontal channel was generated by means of a small-scale wind tunnel. Periodic steps were placed on the channel floor to induce a complex flow field characterized by flow separations, recirculation and reattachment zones.
The turbulent flow field was recorded by means of a stereoscopic Particle Image Velocimetry system. The dimensions of the flow field structures agree well with the specifications from comparable studies. Polydisperse graphite particles were injected into the flow field during a pure deposition regime. The multilayer build up between the periodic steps was measured using a laser distance sensor coupled with a linear stage. The particle layer build up shows a linear tendency against time and the deposition velocities are in good agreement with similar investigations. After the deposition scenario the particle dispersion was switched off and particle resuspension was induced by the stepwise increase of the fluid velocity. The particle resuspension was found to begin in clusters close to the recirculation zones and was accomplished at lower friction velocities than necessary for single particle resuspension. Surface roughness analysis of the multilayer interface characterizes the growth of the loose particle agglomerates during particle deposition and the instant removal of these structures during particle resuspension. Furthermore, particle bed porosity measurements were performed by gravimetrical and x-ray methods to characterize the packing properties. Spatial correlations between the turbulent flow field and the multilayer thickness distribution indicate the influence of inertia impaction, turbulent dispersion and gravitational settling on the particle deposition process. The multilayer particle resuspension seems to be influenced by the mean and fluctuating flow field structures. The results indicate similarities between single particle and multilayer particle formation during particle deposition and resuspension processes.

Bacterial isolates from the uranium mining waste pile Haberland (Johanngeorgenstadt, Saxony) possess high affinities for heavy metals [1]. Binding sites are predominantly provided by the components of the bacterial cell wall, mainly by surface layer proteins, but also from other parts of the cell wall e.g. membrane lipids.

A deeper understanding of the metal interaction with the biosphere is important not only from an ecological point of view but also from an application oriented one.
Parts of our investigations focused on surface layer proteins (S-layers). They represent the outermost cell envelope of many eubacteria and archaea forming highly ordered paracrystalline lattices not only on the living cell, but also after isolation on various technical surfaces by self-assembling processes [2]. Such biological structures can be used e.g. as filter materials for waste water treatment and as templates for synthesis of bio-based sensory layer or chemical catalysts [3]. Nevertheless, the investigation of interactions of the cell wall components like S-layer, peptidoglycan, lipids and secondary cell wall polymers (SCWP) with metals and nanoparticles both as molecules and as intact layers on a molecular level remains challenging.

In addition, to standard bio-analytical methods the quartz crystal microbalance with dissipation monitoring (QCM-D) represents a versatile tool to track and control the biological layer formation, metal interaction and nanoparticle deposition as well as adsorption kinetics. This method allows the real time detection of sorption processes on a molecular level and gives further information of the viscoelasticity [4].

Aim of our study was the investigation of layer adsorption of isolated cell wall components on technical surfaces such as glass or silicon using a simplified model derived from Gram-positive bacteria in order to get basic information about multilevel processes in complex natural systems. The sorption behavior of metals with these components will be investigated by QCM-D. The results were evaluated by supporting atomic force microscopy (AFM).

[1] J. Raff et al. (2003), Chem. Mater. 15, 240-244.
[2] Sleytr, U. B. et al. (2007), FEMS Microbiology Letters 267(2), 131-144.
[3] K. Pollmann et al. (2006), Biotechnol. Adv. 24, 58– 68.
[4] A. E. Lopez et al. (2010), Small 6 (3), 396 -403.

Background:

- a 3½-cell SRF gun was developed and commissioned in HZDR
- the SRF gun needs further optimization and refinement

Aim:

In this study we describe the performance and workflow of the commercially available small animal sequential PET/MR system, the Mediso nanoScan^®.

Material and Methods:

The system consists of a PET scanner (Mediso Ltd. Budapest, Hungary) based on LYSO crystals (1.12 x 1.12 x 13mm) with an axially FOV of 94.7mm and a 1 tesla permanent magnet (Aspect Imaging, Toronto, Canada). The fringe fields of this magnet enable the use of Position Sensitive PMTs (PSPMTs) for the PET gantry.
The PET performance was assessed by using NEMA NU 4-2008 standard to derive the sensitivity and spatial resolution. The MR based attenuation correction for this device is tested by using different homogenous volumes (syringes); the activity is reconstructed and compared to the uncorrected data to determine the impact of this method. The image quality of the system is presented in through different MR scans of rat and mice as well as in coregistered PET/MR images.

Conclusion:

The PET performance has no visible influence by the MRI system. The first results deliver an absolute sensitivity of 8.4% and an axial resolution of 1.1mm FWHM (radial 1.5, tangential 1.3). Anatomic good quality brain images are obtained in 20 minutes and a basic 3D scout in 4.5 minutes. The reproduced activity of the attenuation corrected data verifies the efficiency of the implemented method, while the residual deviation in homogenous phantoms is +1.3% (5ml, 10ml and 20ml syringes).
The nanoScan^® PET/MR scanner allows fast, high resolution anatomical MR- and precise PET-imaging with a special regard to brain studies.

Research fields for the HED Instrument at the European XFEL
with the Helmholtz-Beamline add-on

Research fields for the HED Instrument at the European XFEL with the Helmholtz-Beamline add-on

Providing additional instrumentation to the HED instrument via a User-Consortium to a world-unique combination.

The article deals with the formal reguirements for an effective risk management system. After summing up the definition of risk and risk management and the description of the objectives and tasks, the idea of the process steps of a risk management system with significant methods and instruments follows. Finally, an organizational integration will be shown.

The article describes the different aspects of crisis management. The term corporate crisis and its typical phases will be defined as well as the essential measures, which can be used to avoid or manage a crisis situation in a company. A particular focus is placed on measures of reorganisation as a part of reactive crisis management. Three particular measures of reorganisation management will be present.

Seminarvortrag zu:

• Switching – Electrostatic field at interfaces
• Strontium Titanate & Defects
• Aluminium Oxide Boundaries - Quantification by DFT – EELS – HRTEM

Several differently substituted 1,4-bis(phenylethynyl)benzene molecules have been analyzed regarding their suitability as nano-electrical devices. Since the molecules have the same fully conjugated backbone and only differ in their side groups it has been possible to study the influence of such side groups. First, the contact stability of the molecules was investigated by molecular dynamics simulations. Not only the energetically optimized contact geometries, but also energetically less favorable contract geometries remained contacted. In the next step, the density-functional-based tight-binding method was employed to analyze the density of states as well as the charge transport properties of both molecules. This investigation showed that the side group effect reduces the energy gap between the highest occupied and the lowest unoccupied molecular orbital. However, the charge transport was lowered by the influence of the side group. Furthermore, the molecular density of states gets significantly changed if the molecule is contacted by metallic leads.

Nanocoatings have the potential to improve the surface properties of various materials. They are of extreme importance for surfaces in sliding contact such as highly stressed automotive engine parts. Here, nanocoatings have to be optimized with respect to low friction properties and a high wear resistance to enhance the energetic and environmental efficiency.
The present study employs atomic-scale simulations to investigate the basic principles of wear and friction between hydrogen-free tetrahedral-amorphous carbon (ta-C) films. The ta-C films are modeled state-of-the-art by an improved version of the well-known Brenner bond-order potential [1,2], which had been successfully applied to elucidate the wear processes during diamond polishing[3].

Our work starts with the preparation of ta-C film structures with different atomic densities, which are then characterized with respect to local and global film properties in comparison to experimental data. With these prepared nanocoatings, we perform computational sliding experiments to investigate mechanisms of friction and wear between interacting ta-C surfaces. Dry and lubricated sliding is considered. Especially for dry sliding and during tribological contact, these diamond-like films (mainly sp3 hybridized) tend to form a soft-amorphous or graphite-like tribomaterial mainly consisting of carbon atoms in sp2 configuration. We discuss underlying mechanisms of the dynamic triboreactions and investigate tribological properties such as shear forces at the sliding interface.

Several differently substituted 1,4-bis(phenylethynyl)benzene molecules have been analyzed regarding their suitability as nano-electrical devices. Since the molecules have the same fully conjugated backbone and only differ in their side groups it has been possible to study the influence of such side groups. First, the contact stability of the molecules was investigated by molecular dynamics simulations. Not only the energetically optimized contact geometries, but also energetically less favorable contract geometries remained contacted. In the next step, the density-functional-based tight-binding method was employed to analyze the density of states as well as the charge transport properties of both molecules. This investigation showed that the side group effect reduces the energy gap between the highest occupied and the lowest unoccupied molecular orbital. However, the charge transport was lowered by the influence of the side group. Furthermore, the molecular density of states gets significantly changed if the molecule is contacted by metallic leads.

A story of personal experience is presented which will be illustrated by several photographs taken in the course of design, construction and final use of the positron beam "SPONSOR" at Rossendorf. In particular, the important role of and very fruitful cooperation with Professor Paul Coleman will be outlined and honoured.

The determination and verification of thermodynamic and kinetic parameters of complexation, redox and sorption processes will improve the safety assessment of nuclear waste disposal sites. Sorption processes of U(VI) on mineral surface were traditionally investigated as a function of different reaction parameters (pH, I, T, Eh, c, atm., gs) by employing batch sorption experiments and surface complexation modeling (SCM). In the last decades, the batch sorption experiments were additionally investigated by the application of different spectroscopic techniques (TRLFS, EXAFS, ATR FT-IR). Especially the in situ ATR FT-IR experiments provide an online monitoring of the absorption changes of the sorption processes by the formation of the U(VI) surface complexes. The main objective of this study is to demonstrate the possibility of laser fluorescence spectroscopy for in situ monitoring and characterization of U(VI) sorption reactions. Therefore we investigated the sorption of an aqueous solution of U(VI) onto SiO2. In analogy to the in situ ATR FT-IR measurements, three subprocesses (conditioning, sorption, flushing) are performed in in situ laser fluorescence experiments, as shown in Fig. 1. The resulting fluorescence spectra showed significantly different fluorescence characteristics between the aquoues U(VI) and the sorbed U(VI) species. These preliminary results show that the application of the in situ laser fluorescence spectroscopy is a new alternative technique for identification and characterization of U(VI) complexes at mineral-water interfaces on a molecular level. Furthermore, the time-resolution in the sub-minute range allows kinetic studies of the surface reactions.

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Physical models with anti-linear symmetries can often be described by differential operators self-adjoint in suitably chosen Krein spaces.
In the first lecture, we briefly comment on the spectral properties of some specific operators self-adjoint in Krein spaces and related effects:
1) the operator of the Bender-Boettcher model of PT Quantum Mechanics and its historical background in the 2D Ising model, the Lee-Yang model, Yang-Lee edge singularities, conformal field theory and the theory of phase transitions
2) the operator of the hydrodynamic Squire equation, its scaling behavior and mapping to the operator of the Bender-Boettcher model of PT Quantum Mechanics,
3) the cusp-type spectral properties in the vicinity of third-order exceptional points (algebraic branch points),
4) the unfolding of higher-order exceptional points of the spectrum of Hamiltonians in PT-symmetric Bose-Hubbard models described with the help of Puiseux series expansions and Newton polygon techniques.
The second lecture comprises the following three main subjects:
1) the eigenvector isotropization in the vicinity of exceptional points (algebraic branch points) of the spectra of parameter dependent operators and matrices, and underlying Lie group structures of such isotropizations. For simple toy model matrix Hamiltonians we demonstrate the structural analogy to Lorentz boost transformations of chiral spinors and the naturally emerging SO(N,C) group structure of these boosts. It will be shown that normalization divergencies of the eigenvectors can be simply resolved via projective extensions and the use of different affine charts of the corresponding projective spaces. For gauged PT-symmetric systems we demonstrate the occurrence of Lie triple systems (ternary Lie algebraic structures) as well as of a hidden Clifford algebra.
2) We briefly explain the basic features of the so-called quantum brachistochrone problem for Hamiltonians self-adjoint in Hilbert spaces and in Krein spaces and demonstrate their interrelation geometrically in terms of contraction-dilation maps in projective Hilbert spaces and via positive operator-valued measures (POVMs) and Naimark dilation.
3) Finally, we briefly comment on recent experimental findings in PT-symmetric (i.e. Krein-space related) physics, especially in optical wave-guide systems and microwave cavities.

The current work combines numerical and experimental investigations based on a small-scale mockup using the eutectic alloy GaInSn. The jet flow discharging from the submerged entry nozzle was exposed perpendicularly to a DC magnetic field across the entire wide face of the mold. Numerical calculations were performed by using the commercial package CFX with an implemented RANS-SST turbulence model. The anisotropic properties of the MHD turbulence were taken into account by specific modifications of the turbulence model. The comparison between our numerical calculations and the experimental results shows a very well agreement. In particular, the modified RANS-SST turbulence model is capable to reconstruct the peculiar phenomenon of the excitation of non-steady, non-isotropic large-scale flow perturbations caused by the application of the DC magnetic field. Another important finding of our study is the feature that the electrical boundary conditions, namely the wall conductivity ratio, have a great impact on the mold flow subjected to an external magnetic field.

Purpose: The development of proton and ion acceleration by ultra high intensity lasers for cancer therapy promises the realization of compact and economic particle accelerators that can be integrated in already existing clinics. For translational research towards clinical application the radiobiological consequences of laser accelerated and therewith ultra-short pulsed particle beams with high pulse dose have to be investigated. After extensive in vitro dose response studies with laser driven electron and proton beams, in vivo experiments have been performed within the joint research project “onCOOPtics” as next translational step.

Material/Methods: A mouse tumor model suitable for currently available low energy laser protons was developed, tested and successfully used. The already in vitro established laser based irradiation technology was further developed for the animal model in terms of beam transport, beam monitoring, dose delivery and dosimetry allowing to apply a prescribed dose to each tumor and to determine the absolute dose received. For precise and reproducible positioning at the irradiation site a system for mouse fixation, tumor positioning and position verification was implemented as described in [Schürer et al 2012]. Experiments were carried out at the 30 Terawatt Jena Titanium:Sapphire (JeTi) laser system. Laser pulses of 28 fs duration were focused into a hydrogen gas jet accelerating electrons to energies of up to a few 10 MeV. In vivo tumor irradiation was realized for murine sarcoma KHT and human squamous cell carcinoma FaDu. Doses up to 14 Gy were applied at mean dose rates of 1-2 Gy/min and irradiation induced tumor growth delay was investigated. Comparison irradiations were performed at a conventional therapy LINAC with the same setup for irradiation and absolute dose determination.
Results: The reliability and stability of all implemented setup components and methods were proven by numerous irradiations over a period of several months. Dose response curves of tumor growth delay were generated for direct comparison of ultra short pulsed laser accelerated and conventional continuous electron beam. The ongoing data evaluation by now shows no significant difference in RBE for laser driven electrons.
Conclusion: The successful establishment of all technical requirements for and the world wide first performance of systematic animal studies with laser accelerated electrons mark an important step towards the clinical application of laser accelerated particle beams. The realization of in vivo studies with laser driven proton beams is now feasible.
The authors thank for the contribution of the Jeti accelerator crew at Friedrich-Schiller-University Jena, Ralf Bergmann (HZDR) and for the support by the German Ministry of Education and Research (BMBF) Grant Nr 03Z1N511.

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The principles and data needs of nuclear transmutation are explained. The nELBE neutron time-of-flight facility and the different types of experiments with fast neutrons are presented.

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The development of proton and ion acceleration by ultra-high intensity lasers for cancer therapy promises the realization of compact and economic particle accelerators that can be integrated in already existing clinics. However, particle acceleration with high intensity lasers, in comparison to the conventional used acceleration technique, leads to ultra-short beam pulses, generated with low pulse frequency, that apply a very high pulse dose. Prior to a clinical application the radiobiological consequences of laser accelerated and therewith ultra-short pulsed particle beams have to be investigated.
After extensive in vitro dose response studies, for several cell lines and endpoints with laser driven electron and proton beams, the translational step to perform in vivo experiments has been taken. A tumor model suitable for currently available low energy laser protons was developed, tested and successfully used. The already in vitro established laser based irradiation technology was further developed for the animal model in terms of beam transport, beam monitoring, dose delivery and dosimetry, allowing to apply a prescribed dose to each tumor and to determine the absolute dose received. The utilized high power laser system delivered a stable and reproducible particle beam over a period of months to allow systematic in vivo dose response studies of a human xenograft line. 300 mice hosting two different tumor lines were irradiated with various defined doses and monitored for several weeks to determine tumor growth delay.
In parallel irradiation by a continuous beam of a conventional accelerator has been performed. Results of the still ongoing data evaluation will be presented and discussed.

Experiments were carried out within the onCOOPtics project in cooperation between Oncoray Dresden and Ultraoptics Jena. The work was supported by the German Ministry of Education and Research (BMBF), grant no. 03ZIK445

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Die vorliegende Erfindung betrifft die Verwendung ne und Nanopartikel umfasst, sowie ein Verfahren zur Entfernung von Arsenverunreinigungen aus Wasser. Die erfindungsgemäße Verwendung bzw. das erfindungsgemäße Verfahren eignen sich zur Verwendung in der Grund-, Trink-, Brauch- und Abwasseraufbereitung. In Versuchen der Erfinder konnten Abtrennleistungen von bis zu 5,3 mg Arsen/g Biokompositmateria erzielt werden. Dies entspricht nahezu der doppelten Menge im Vergleich zum kommerziellen Arsen-Adsorbens Ferrosorp®, einem Eisenhydroxidgranulat. Damit übersteigt die Bindungsfähigkeit des erfindungsgemäß verwendeten Biokompositmaterial für Arsen (V) deutlich die Summe der Bindungswerte der Einzelkomponenten (S-Layer und Nanopartikel).

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Die Erfindung betrifft neue Chinazolinderivate, die als Diagnostika sowie Therapeutika geeignet sind und insbesondere zur Diagnose und Behandlung neurodegenerativer und psychiatrischer Erkrankungen, z. B. Schizophrenie verwenden werden können. Die neuen Chinazolinderivate zeichnen sich durch eine hohe Affinität und Selektivität für PDE10A aus und dadurch dass sie mindestens einen Halogensubstituierten Substituenten am Chinazolinrest aufweisen.