Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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Fragestellung
There is evidence that σ1 receptors are involved in the cognitive impairment found in neurodegenerative diseases. Because of considerable drawbacks of the currently used PET ligand for neuroimaging of σ1 receptors, [C-11]SA4503, we have recently developed a new spirocyclic piperidine derivative: [F-18]WMS1813 ([F-18]1'-benzyl-3-(3-fluoropropyl)-3H-spiro[[2]benzofuran-1,4'-piperidine]) with high affinity and selectivity for σ1 receptor binding site (1). Further SAR studies on the fluoroalkyl chain provided three other promising analogues, bearing either fluoromethyl- (WMS1850), fluoroethyl- (WMS1828) or fluorobutyl-(WMS1847) moieties. Herein, we report on radiosyntheses and biological evaluation of these candidates for PET imaging of σ1 receptors.

Methodik
Radiosyntheses of [F-18]WMS1850, [F-18]WMS1828, and [F-18]WMS1847 were performed by direct nucleophilic substitution of corresponding aliphatic tosylate precursors, using the K[F-18]F-K222-carbonate complex. Biodistribution studies and ex vivo brain autoradiography of the radiotracers were performed in female CD-1 mice. Target specificity was validated by pre-treatment with 1 mg/kg i.p. of the σ1 receptor antagonist haloperidol. In vivo metabolism of each radiotracer was evaluated by radio- TLC/-HPLC.

Ergebnis
The three radiotracers were obtained with radiochemical yields of 35-53%, radiochemical purities >98.5%, and high specific activities ≥150 GBq/μmol. In mice, they rapidly accumulated in brain tissue. [F-18]WMS1828 was superior with a brain uptake value of 4.71 ± 1.39 %ID/g (30 min p.i.) in comparison to [F-18]WMS1813, [F-18]WMS1847 and [F-18]WMS1850 (3.18±0.68; 1.78±0.16; 2.65±0.68 %ID/g respectively). For all radiotracers, uptake in brain as well as in peripheral σ1 receptor expressing organs was significantly inhibited by haloperidol. At 30 min p.i., more than 75% of the radioactivity detected in plasma samples corresponded to native [F-18]WMS1850, [F-18]WMS1828 and [F-18]WMS1847. None of the radiometabolites observed crossed the blood-brain barrier. Results of ex vivo autoradiography of brain slices revealed resemblance between radioactivity distribution pattern of all radiotracers and regions with known high σ1 receptors density. The highest target (facial nucleus)-to-nontarget (olfactory bulb) tissue ratio was determined for [F-18]WMS1828 (4.69 at 45 min p.i.).

Schlussfolgerungen
Within the series of σ1 receptor-specific radiotracers studied, [F-18]WMS1828 ([F-18]fluspidine) appears to be the most promising candidate for PET imaging with even better pharmacological profile than the lead compound WMS1813. Hence, [F-18]fluspidine radiosynthesis is selected for transfer onto an automated radiosynthesis module for further (pre)clinical development.

Literatur
(1) Maestrup E G et al. J Med Chem 2009; 52, 6062-6072.

The nonaxisymmetric Tayler instability of toroidal magnetic fields due to axial electric currents is studied for conducting incompressible fluids between two coaxial cylinders without endplates. The inner cylinder is considered as so thin that the limit of Rin → 0 can be computed. The magnetic Prandtl number is varied over many orders of magnitudes but the azimuthal mode number of the perturbations is fixed to m = 1. In the linear approximation the critical magnetic field amplitudes and the growth rates of the instability are determined for both resting and rotating cylinders. Without rotation the critical Hartmann numbers do not depend on the magnetic Prandtl number but this is not true for the corresponding growth rates. For given product of viscosity and magnetic diffusivity the growth rates for small and large magnetic Prandtl number are much smaller than those for Pm = 1. For gallium under the influence of a magnetic field at the outer cylinder of 1 kG the resulting growth time is 5 s. The minimum electric current through a container of 10 cm diameter to excite the instability is 3.20 kA. For a rotating container both the critical magnetic field and the related growth times are larger than for the resting column.

Fragestellung
Neurologische und psychiatrische Erkrankungen, wie Schizophrenie und Psychosen werden in Zusammenhang mit Beeinträchtigungen der Aktivität der Phosphodiesterease 10A (PDE10A) gebracht. Selektive und hirngängige PDE10A-Inhibitoren sind daher Ziel der Entwicklung hochwirksamer Therapeutika (1) und geeigneter Diagnostika für die molekulare Bildgebung (2).
Ein Papaverin-basierter chiraler 6,7-Dimethoxychinazolin-Ligand diente in den vorliegenden Arbeiten als Leitstruktur für die Entwicklung eines 7-(2-[F-18]Fluorethoxy)-Analogons [F-18]I zur Darstellung der PDE10A mit PET.

Methodik
Die Referenzverbindung I sowie die Markierungsvorläufer II und III wurden in Mehrstufen-Synthesen dargestellt und der logD7,0 mittels HPLC ermittelt. Für eine zweistufige Radiosynthese wurde 1,2-Bistosyloxyethan nach einem Standardverfahren zu 2-[F-18]Fluorethyltosylat [F-18]IV umgesetzt und [F-18]IV ohne Aufarbeitung weiterverwendet. Deprotonierung des 7-Hydroxy-Synthesevorläufers II mittels K.222/K2CO3 (2-3 h, 50-60°C, MeCN) und anschließende Veretherung (2 mg; K.222/K2CO3, MeCN/80°C) mit [F-18]IV führten zur Zielverbindung [F-18]I. Die direkte Radiofluorierung erfolgte über Substitution des 7-(2-Tosyloxyethyl)-Präkursors III mit n.c.a. [F-18]F- (2-3 mg; K.222/K2CO3, MeCN/80°C). Nach Aufarbeitung mit FPE (RP-18, MeCN) folgte semipräparative Radio-HPLC (RP-18, 45-50% MeCN, 20 mM NH4OAc) und Formulierung in MeCN, MeOH, EtOH oder wässrigem Puffer. Mit [F-18]I-Lösungen wurde die Stabilität bei 40 und 80°C untersucht sowie der logD7,2-7,4 mittels Extraktion in n-Octanol/Puffer-Systemen bestimmt.

Ergebnis
[F-18]IV konnte in 5 min mit Markierungsausbeuten (MA, DC/HPLC) von 50-76% dargestellt werden. Hiermit wurde II in 15-20 min zu 30-45% MA an [F-18]I umgesetzt. Die radiochemische Ausbeute (RCA) betrug nach 2-3 h ohne Aufarbeitung 18-29%.
Mittels Tosylat III wurde n.c.a. [F-18]I in 15 min mit MA von 42-72%, einer chemischen und radiochemischen Reinheit ≥99% (DC/HPLC) sowie spezifischen Aktivität von 110-1110 GBq/μmol (HPLC) erhalten. Die RCA betrug nach 3-4 h Gesamtsynthesedauer 17-40%. Für die Zielverbindung I/[F-18]I wurden ein logD7,0 von 2,63±0,01 mittels HPLC und ein logD7,2-7,4 von 2,59±0,46 mittels Extraktion ermittelt. [F-18]I ist bei 40°C nur in ethanolischer KOH labil und erweist sich in EtOH und MeCN bei 80°C auch nach 120 min als stabil.

Schlussfolgerungen
Die Zielverbindung konnte sowohl in einer zweistufigen als auch direkten Radiofluorierung dargestellt werden, wobei letztere eine höhere radiochemische Ausbeute lieferte. Ein logD von ∼ 2,6 stellt eine gute Voraussetzung für eine gute Hirnaufnahme des Radioliganden bei ausreichend niedriger unspezifischer Bindung dar. Weiterführende Experimente sind geplant, um die Organverteilung des Radioliganden sowie Bindung in vitro und in vivo zu untersuchen.

Literatur
(1) Chappie T A et al. J Med Chem 2007; 50: 182-185
(2) Celen S et al. J Nucl Med 2010; 51: 1584-1591

Tetrahedral amorphous carbon (ta-C) films with high sp3 content produced by mass filtered vacuum arc deposition were modified by Ga+ FIB irradiation. Surface swelling occurs as a function of fluence, caused by ion induced conversion of sp3 to sp2 hybridized carbon atoms. A model [1] for diamond swelling was applied to ta-C films to estimate the swelling for fluences up to 1 x 10¹⁶ cm^-2. For higher fluences data from TRIDYN simulations were included due to sputtering in a good agreement with the experiments. Van der Pauw structures were produced by means of Ga+ FIB lithography. A decrease of the sheet resistance with increasing fluence due to the evolution of graphitic regions was observed. The lowest value of 290 Ohm/sq was achieved at 1.6 x 10¹⁷ cm^-2. Investigations of the conduction mechanism were done by Hall-mobility measurements on Van der Pauw and Hall test structures. Additionally, conducting graphitic wires were produced (length: 10 µm, width: 200 nm to 5 µm). The wire resistivity was measured within 130 kOhm (5 µm width) and 0.3 GOhm (300 nm width). Ion induced graphitization of ta-C films by FIB offers prospective applications in nano technology to fabricate conductive nanostructures in an insulating thin film.
[1] F. Bosia et al. Nucl. Instrum. Meth. B 268 (2010) 2991.

Die Phosphodiesterase 10A (PDE10A) terminiert die Signalübertragung der Second messenger cAMP und cGMP durch Hydrolyse und wird vorrangig in Gehirn (Striatum) und Schilddrüse exprimiert. Veränderungen der Aktivität der PDE10A werden in Zusammenhang mit Schizophrenie und Psychosen gebracht. Selektive und hirngängige PDE10A-Inhibitoren sind daher Ziel der Entwicklung hochwirksamer Therapeutika und geeigneter Diagnostika für die molekulare Bildgebung, wie unser 7-(2-[18F]Fluorethoxy)-6-methoxychinazolin-Derivat zur Visualisierung der PDE10A mit Positronen-Emissions-Tomographie (PET). Die zur Analytik erforderliche nichtradioaktive Referenzverbindung und die Ausgangsverbindungen für die 18F-Markierung wurden in Mehrstufen-Synthesen dargestellt. Für die 18F-Markierung wurde zunächst ein schneller zugängliches zweistufiges Verfahren entwickelt. Eine verbesserte Darstellung erfolgte anschließend im Einstufenverfahren über die direkte Umsetzung des entsprechenden 7-(2-Tosyloxyethyl)-Präkursors mit trägerfreiem [18F]F-. Die Markierungsausbeute betrug 42-72%, die chemische und radiochemische Reinheit ≥99% und die spezifische Aktivität 110-1110 GBq/µmol. Die zerfallskorrigierte radiochemische Ausbeute lag nach 3-4 h Gesamtsynthesedauer bei 17-40%. Als Kriterium für die Qualität der Hirnaufnahme wurde die Lipophilie des Radioliganden bei pH 7 bis 7,4 mittels HPLC und extraktiven Methoden bestimmt. Ein logD7,0-7,4  2,6 weist auf eine gute Hirnaufnahme bei ausreichend niedriger unspezifischer Bindung hin. Weiterführende Experimente sind geplant, um die Organverteilung des Radioliganden sowie Bindung in vitro und in vivo zu untersuchen.

The regularly structured paracrystalline surface layers (S-layers) of prokaryotic microorganisms are promising biological templates for production of metal nanoclusters for biotechnological applications. Formerly, we have demonstrated that some bacterial S-layers can effectively bind noble metals and can be used for preparation of palladium, platinum, and gold nanoclusters by using different reduction agents (1, 2) or electron beam (3).
In this work Au-nanoclusters were produced on the extremely stable (against high temperatures, acidity, proteases, and mechanic stress) S-layer of the acidothermophilic Archaeon Sulfolobus acidocaldarius. One additional important characteristic feature of this S-layer, called recently SlaA (4) is the presence of the sulfur containing amino acid cystein in its primary structure. This is in contrast to the above mentioned bacterial S-layers and is of great importance for the effective binding and deposition of Au cations. The purified SlaA-layer fraction was treated initially with tetrachloroauric (III) acid solution. Afterwards the deposited Au(III) cations were reduced to Au(0) by using dimethylaminoburane. The analysis of the obtained Au-nanoclusters by using Transmission Electron Microscopy combined with Energy Dispersive X-ray analyses (TEM-EDX) demonstrated that the nanoclusters have a size in the range of 2-3.5 nm and that they are associated with sulfur atoms (Fig. 1). As measured via SQUID Magnetometer they possess magnetic properties (Fig. 2). No magnetic properties were observed in the case of the Au-nanoparticles formed on the bacterial S-layers possessing no sulfur. We suggest that the sulfur atoms are possibly contributing to the observed magnetic properties. However, the number of sulfur atoms implicated in the Au complexation is extremely low (only a few atoms per nano-particle). On the other hand, the size of the nanoparticles formed on the archaeal SlaA-layer is significantly bigger (about 3 nm) in comparison to those formed on the bacterial S-layer (less then 1 nm). The size difference in the two kinds of nano-particles can be explained with the different size of the pores of the two S-layer lattices, where the initial deposition of the metal cations occurs. The archaeal SlaA-layer possesses p3 lattice symmetry and significantly larger pores (4) then the bacterial S-layer which has p4 symmetry (1, 2). The size of the Au-nanoclusters may play also a role for their magnetic properties. Efforts to understand the reasons for the observed unexpected magnetic behavior of the newly constructed bio-Au nanoparticles are in progress.
To our knowledge, this is the first report on constructing of highly ordered Au nanoparticles on an archaeal S-layer. These bio-Au structures possess some advantageous properties, such as high stability to high temperatures, acidic and mechanical stress, in comparison to those formerly constructed on bacterial S-layers. Moreover, in contrast to Au as a bulk noble metal and to bacterial bio-Au, the archaeal bio-Au nanoparticles possess unique magnetic properties.
References
1. Fahmy K, Merroun M, Raff J, Pollmann K, Hennig Ch, Savchuk O, Selenska-Pobell S (2006) Biophys J 91:996-1007.
2. Merroun M, Rossberg A, Hennig C, Scheinost A, Selenska-Pobell S (2007) Mater Sci & Engin C27, 188-192
3. Wahl R, Mertig M, Raff J, Selenska-Pobell S, Pompe W (2001) Adv Mater 13, 736-740
4. Veith A, Klingl A, Zolghadr B, Lauber K, Mentele R, Lottspeich F, Rachel R, Alberts S-V, Kletzin A (2009) Mol Microbiol 73, 58-72

An Integrated DOsimetry and Cell Irradiation System (IDOCIS) with laser-accelerated proton beams was developed, characterized, calibrated and successfully used for systematic in vitro experiments. Due to the broad exponentially shaped energy spectrum, the low energy range of the protons (< 20 MeV) and the high pulse dose, the absolute dosimetry for this beam quality is challenging. Therefore, a dedicated Faraday cup is used as an energy and dose rate independent absolute dosimeter that has been calibrated consistently with three independent methods. A transmission ionization chamber providing online relative dose information is cross-calibrated against the Faraday cup. Providing both online and absolute dose information the IDOCIS allows for quantitative dosimetric and radiobiological studies at current low-energy laser-accelerated proton beams. Finally, first dosimetric characterizations of a laser-accelerated proton beam with the IDOCIS are presented.

Neptunyl, Np(V)O₂ ⁺, along with the other actinyl ions U(VI)O₂ ²⁺ and Pu(V,VI)O₂ ^+,2+, is considered to be highly mobile in the geosphere, while interaction with mineral surfaces (inner- or outer-sphere adsorption, ion-exchange, coprecipitation/structural incorporation) may retard its migration. Detailed information about the exact interaction mechanisms including the structure and stoichiometry of the adsorption complexes is crucial to predict the retention behavior in diverse geochemical environments. Here, we investigated the structure of the neptunyl adsorption complex at the calcite-water interface at pH 8.3 in equilibrium with air by means of low-temperature (15 K) EXAFS spectroscopy at the Np-L_III edge. The coordination environment of neptunyl consists of two axial oxygen atoms at 1.87(±0.01) Å, and an equatorial oxygen shell of six atoms at 2.51(±0.01) Å. Two oxygen backscatterers at 3.50(±0.04) Å along with calcium backscatterers at 3.95(±0.03) Å suggest that neptunyl is linked to the calcite surface through two monodentate bonds towards carbonate groups of the calcite surface. Two additional carbon backscatterers at 2.94(±0.02) Å are attributed to two carbonate ions in bidentate coordination. This structural environment is conclusively interpreted as a ternary surface complex, where a neptunyl biscarbonato complex sorbs through two monodentate carbonate bonds to steps at the calcite (104) face, while the two bidentately coordinated carbonate groups point away from the surface. This structural information is further supported by Mixed Flow Reactor (MFR) experiments. They show a significant decrease of the calcite growth rate in the presence of neptunyl(V), in line with blockage of the most active crystal growth sites, step and kink sites, by adsorption of neptunyl. Formation of this sorption complex constitutes an important retention mechanism for neptunyl in calcite-rich environments.

Many microorganisms like bacteria developed during evolution highly effective mechanisms and structures to survive at the most forbidding, uninviting places on Earth. One example, intensively studied at the Institute of Radiochemistry of the Forschungszentrum Dresden-Rossendorf, is the binding of heavy metals and actinides by cell surface proteins of uranium mining waste pile isolates. The so called surface layer (S-layer) proteins (figure 1) bind toxic metals and metalloids and thusly protect the cells from being damaged by these elements and their compounds. On other cells, S-layers may act as immobilization matrix for exoenzymes, as molecular sieve, as ion and molecule trap or they protect the cell from being affected by the immune defense of host organism, by other bacteria or by lytic enzymes. These properties makes S-layer, together with their capability to self-assemble in suspension, on surfaces and at interfaces, very interesting building blocks for the construction of new bioinspired nanomaterials for different technical applications. Using the two-dimensional protein arrays, different kinds of surfaces can be nanostructured and multiple functionalized by a layer-by-layer technique. This interdisdisciplinary approach allows the design of novel bio-inorganic hybrid materials. Currently under development are three kinds of materials, namely metal filters, nanocatalysts and sensors. Regarding metal filters the aim is the development of selective materials for the removal of toxic metals and metalloids or the recovery of precious metals. In the case of nanocatalysts, the research is focused on the development of highly efficient catalysts or photocatalysts on the basis of immobilized and regular arranged metal or metal oxide nanoparticles for organic synthesis or the elimination of organic pollutants. S-layer based biosensors were under development to detect chemicals or pharmaceuticals by combining highly specific receptors like aptamers with stable fluorescence dyes.

This paper reviews the advances that millisecond thermal processing using flash lamps and lasers brings to the processing of the most advanced semiconductor materials, namely silicon and germanium, thus enabling the fabrication of novel microelectronic structures and materials. It will be demonstrated how such developments can translate into important practical applications leading to a wide range of technological benefits. Opportunities in ultra-shallow junction formation for silicon-on-insulator, superconducting Ge and Si, and diluted ferromagnetic Ge, along with the technical reasons for using annealing times in the ms range are discussed in the context of state-of-the-art materials processing. Whereas these examples base on solid phase processing, the more sophisticated approach regards on working with the liquid phase at the surface of solid substrates. As a recent example the controlled surface melting of a Ge enriched silicon substrate is reported.

Abstract not available.

Nucleophilic ring-opening reactions of three 1-aralkyl-3,4-epoxy piperidines with a series of aliphatic and aromatic amines have been investigated. Reactions in protic solvents, preferably 2-propanol, gave rise to 3-amino-piperidin-4-ols in ratios up to 20:1. Accordingly, the highly VAChT affine 4-fluorobenzyltrozamicol was obtained directly from an epoxide ring opening in one step, without the need of chromatographic separation. Reactions in acetonitrile assisted by Li-salts, most suitable with LiBr, led regioselectively to trans-4-amino-piperidin-3-ols in high yields. N-Phenethyl substituted anilino-piperidinols as easily obtained by this method were converted into a series of new β-hydroxy substituted anilidopiperidines.

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Es ist kein Abstract vorhanden.

VC_xN_y films with a wide range of chemical composition were grown onto silicon and high-speed steel substrates using reactive unbalanced magnetron sputtering from V targets in an Ar/N₂/C₂H₂ atmosphere at a substrate temperature of 500°C. A solid solution of VN and VC is formed for N₂ and C₂H₂ addition, with increasing fractions of an additional amorphous carbon phase for increasing C₂H₂ flow ratios. While an increase in hardness is observed for low carbon contents due to solid solution hardening, raising the amorphous carbon phase fraction results in a hardness reduction. Dry-sliding ball-on-disc tests yield low friction coefficients with values of 0.22 for those films with the highest content of amorphous carbon phase, while the lowest wear is observed for films with dominating vanadium carbonitride solid solution. The low friction behavior is attributed to the formation of tribo-layers with easy-shearable C-H bonds formed in humid atmospheres, and is not observed in dry nitrogen and synthetic air.

On a continuous 20 nm thick Permalloy film, magnetically softer and harder stripes, which are in direct lateral contact by means of exchange coupling, were fabricated by focused Ga+ irradiation. The irradiation dose was 6.00 x 1015 Ga/ions and the width of the alternative exposed and unexposed stripes were varied from 1000nm to 200nm. Low angle electron diffraction experiment confirmed that due to this amount of ion dose, saturation magnetic induction of the irradiated stripe is reduced to 70 % of the unirradiated stripe, assuming a thickness reduction of 2.5 nm determined by AFM. Magnetisation reversal experiments were carried out using high resolution Lorentz microscopy. For a stripe width of 1000 nm a pronounced 2 step reversal with an intermediate antiparallel orientation of magnetisation in neighboring stripes is found. Differential phase contrast (DPC) images demonstrate a transition from the discrete switching of the wider nanostripes to the collective switching of the narrower stripes of width 200 nm. This can be attributed to the local modification of the magnetic thin film parameters below the intrinsic magnetic length scales associated with the domain wall width. By using DPC mode of Lorentz microscopy, domain wall width was calculated and compared with theory for 20 nm thick continuous Permalloy film.

The reconstruction of past climate changes in the Pamir Mountains has high potential for identifying the dynamics of circulation systems in Asia and for understanding global environmental changes during the Late Quaternary. The Pamir Mountains are situated in a climatic transition zone between mid-latitude westerlies, the Indian summer monsoon and the Siberian High. Today main moisture to the Pamir comes with SW- cyclones along the westerly jetstream whereas the influence of the Indian monsoon typically ends south of the NW-Himalaya. Up to now the impact of the Indian monsoon on former glaciations of the Pamir Mountains has not yet been adequately examined. Even chronological information about former glaciations in the Pamir is still sparse. The objectives of our study are: To upgrade the present glacial chronology by dating glacial successions along a moisture gradient from the north-western to the southern Pamir Mountain ranges. We present preliminary ¹⁰Be ages from moraine successions of three study sites (Iskenderkul area, Muksu-Kyzlsu area, Alichur area). Our first results from the southern Pamir (Alichur area) corroborate and refine previously published findings: Extensive glaciation occurred during MIS 4 and during MIS 2. However our data indicate that glaciers in the southern Pamir also advanced during ~50 to 40 ka. Rapid deglaciation occurred after ~18 ka. So far there is no evidence for glacier advances during the Holocene. Overall, we conclude that the glacial chronology of the Pamir seems to be mainly controlled by temperature, with maxima during ~70 to 60 ka, ~50 to 40 ka and ~20 ka. Because during climatic cold phases the Indian Monsoon was weakened, we assume that glacier advances in the Pamir Mountains during the Last Glacial cycle were mainly triggered by westerly moisture supply. Analyses of further samples, from both the Muksu-Kyzlsu area and the Iskenderkul area are in progress.

At GSI Darmstadt targets of different materials have been irradiated with carbon ions in order to verify an approach for the prediction of positron emitter distribution based on experimental yields. Depth dependent thick target yields calculated with this approach are presented and compared to experimental results.

The (n,n'g) cross section to the 1st excited state of Fe-56 has been measured at the neutron time-of-flight facility nELBE of the Forschungzentrum Dresden-Rossendorf.
The nELBE neutron source delivers neutrons with energies from 100 keV up to 10 MeV. By means of a "double time-of-flight" setup the inealstic scattering cross section of the 1st excited state could be measured over the whole energy range independently of the knowledge about cross sections of higher levels. Plastic scintillators were used to detect the inelastically scattered neutron and BaF2 detectors to detect the correlated gamma-ray. The time of detection of the gamma-ray defines the time-of-flight of the incoming neutron. The time difference between gamma- and neutron-detection gives the energy of the scattered neutron. By this method the excitation of the 1st level can be identified independently from the emitted gamma-ray energy.

It will described how nuclear transmutation will help to reduce the radiotoxicity of nuclear waste.

The dipole strength function strongly influences neutron capture processes in heavy nuclei and it is of great importance for photon induced processes like electromagnetic disintegration and nuclear resonance fluorescence. Above 10 MeV the absolute value and energy dependence are well known from (g,n) experiments usually described by the Lorentzian shape of the Giant Dipole Resonance (GDR). Below the threshold photon scattering studies on nuclei above mass 80 indicate no decrease of the spreading width with falling energy allows to describe its shape by a continuation of the GDR Lorentzian with constant width. The constant width is in accordance to primary photons observed after neutron capture in deformed nuclei which show a clear double peak structure. Capture data taken for nearly spherical nuclei seem to show a one-component Lorentzian shape with width varying with the square of the gamma-energy Eg. This apparent disaccord between more or less deformed nuclei is reinvestigated with the aid of Average Resonance Capture (ARC) data measured for various transitional nuclei. Our suggestion, a 3-fold Lorentzian for all kinds of deformation, will be explained.

Presenation of latest experiments done at the nELBE facility at Forschungszentrum Dresden-Rossendorf. Preliminary results on Fe-56 and Na-23 inelastic neutron scattering will be shown.

At the superconducting electron linear accelerator ELBE at Forschungszentrum Dresden-Rossendorf the neutron time-of-flight facility nELBE has become operational.
Fast neutrons in the energy range from ca. 0.1 to 10 MeV are produced by the pulsed electron beam from ELBE impinging on a liquid lead circuit as a radiator.
The short beam pulses of ~10 ps provide the basis for an excellent time resolution for neutron time-of-flight experiments, giving an energy resolution of about < 1~\% at 1 MeV with a short flight path of ~ 5 m.
The neutron intensity on target is ca. 4*10⁴ n/s/cm² using an electron bunch charge of 77 pC and 203 kHz pulse repetition rate.
The energy range of the neutrons produced is well suited for neutron cross section measurements relevant for the development of Generation IV reactor systems and for the transmutation of nuclear waste.
First measurements of inelastic scattering cross section on natural Fe have been performed using a double time-of-flight method. The cross section for the first excited level of Fe-56 and Fe-54 could be determined.

At the nELBE facility at Forschungszentrum Dresden-Rossendorf fast neutrons with kinetic energies of 0.1 to 10 MeV will be used to deliver nuclear data on neutron induced reactions necessary for the development of future nuclear transmutation facilities and new types of nuclear reactors. Electrons from the superconducting electron linac ELBE are shot onto a liquid lead target where they produce Bremsstrahlung which in turn liberates neutrons via (gamma,n) reactions. The short pico-second pulse structure of the electron beam enables neutron time-of-flight experiments with very short flight paths of 4-7 meters obtaining energy resolutions of about 1 %.

First experiments on inelastic neutron scattering on ⁵⁶Fe where performed using a double time-of-flight setup based on proton recoil detectors [2] and an array of 42 BaF$_2$ crystals to detect the emitted photons and neutrons in coincidence. First results will be presented.

As a first step towards using world-wide a common ³⁶Cl standard-type material for the normalization of ³⁶Cl AMS results, we have initiated an interlaboratory comparison, but with differences in the execution of the project compared to other round-robin exercises: a) participants have given up anonymity to better optimize discussion and conclusions, b) preliminary results have been shown at various scientific meetings and workshops to discuss first trends and to increase the number of participants, c) participants had the possibility to repeat their AMS measurements and/or change measurement setups or data evaluation to improve individual data [e.g. 1]. We are aware and acknowledge that these later changes by some of the participants, which led to different overall data compared with the initial results, are not fully consistent with the idea of a normal proficiency test layout. However, these data changes were accepted to better meet the main objectives of the intercomparison: to identify and eliminate differences between AMS laboratories, thus, improving the ³⁶Cl data quality world-wide as soon as possible.
The evaluation of the final results of the eight participating AMS laboratories for three synthetic AgCl samples with ³⁶Cl/Cl ratios at the 10^-11 (SM-Cl-11), 10^-12 (SM-Cl-12), and 10^-13 (SM-Cl-13) level shows no difference in the sense of simple statistical significance [2]. However, more detailed statistical analyses indicate a certain interlaboratory bias and an under-estimation of uncertainties by some of the laboratories. The round-robin data demonstrate that ³⁶Cl/Cl results from two individual AMS laboratories can differ by up to 17% (Fig. 1). Thus, the necessity for further work on harmonizing the ³⁶Cl business on a world-wide scale and on improving the measurements is obvious.

Fig. 1: Regression of normalized results for the three investigated samples in the order of ascending average.
[1] V. Alfimov et al., Ion Beam Physics, ETH Zurich, Annual Report (2009) 13.
[2] S. Merchel et al., Anal. Bioanal. Chem., submitted.

The Pamir Mountains have been extensively glaciated several times in the past. As glaciers are mainly sensitive to variations in temperature and precipitation, they reflect changes in large-scale atmospheric circulation patterns. The Pamir Mountains are situated in a climatic transition zone between mid-latitude westerlies, the Indian summer monsoon and the Siberian High. Today main moisture to the Pamir comes with SW-cyclones along the westerly jetstream. Up to now the impact of the Indian monsoon on former glaciations of the Pamir Mountains has not yet been adequately examined. Even chronological information about former glaciations in the Pamir are still sparse. The objective of our study is: To upgrade the present glacial chronology by ¹⁰Be surface exposure dating of erratic boulders on top of moraines along a moisture gradient from the north-western to the southern Pamir Mountain ranges. We present preliminary ¹⁰Be ages from moraine successions of three study sites (Iskenderkul area, Muksu-Kyslsu area, Alichur area).
Our first results from the southern Pamir (Alichur area) corroborate and refine previously published findings: Extensive glaciation occurred during MIS 4 and during MIS 2 coinciding with lower insolation intensity. Because during climatic cold phases the Indian Monsoon was weakened we assume that these glacier advances were mainly triggered by westerly moisture supply. However, our data indicate that glaciers in the southern Pamir also advanced during ~58 to ~45 ka as also observed in monsoonal influenced Karakoram and eastern Hindu Kush regions. Our surface exposure ages point to rapid deglaciation after ~18 ka. So far there is no evidence for glacier advances during the Holocene. Analyses of further samples, from both the Muksu-Kyzlsu area and the Iskenderkul area are in progress.

At the Forschungszentrum Dresden-Rossendorf (FZD), the Light Water Reactor (LWR) dynamics code DYN3D is extended and adopted for the application to block-type High Temperature Gas-Cooled Reactor (HTGR). DYN3D is a two-group diffusion code for 3D steady-state and transient core calculations based on nodal expansion methods. In addition to the neutron kinetics, it comprises of a thermal-hydraulics model for flow in parallel coolant channels. Macroscopic cross section data libraries precalculated with variation of burn-up, reactor poisons concentrations and thermal-hydraulic feedback parameters are linked to the code. Recently, a multi-group version of the code was developed.
In this paper, we give an overview of the latest developments of DYN3D concerning block-type HTGR.
The SP3 transport approximation is implemented into the multi-group DYN3D code to take anisotropy of the neutron flux and heterogeneity of the core more precisely into account. The SP3 method previously implemented into DYN3D for square fuel element geometry of LWR is being extended for hexagonal geometry of the graphite blocks, where the hexagons are subdivided into triangular nodes to be able to perform a systematic mesh refinement.
The main challenge in cross section generation for the HTGR core calculations is the treatment of the so-called “double heterogeneity”. The Reactivity-Equivalent Physical Transformation (RPT) approach is applied in order to eliminate the double-heterogeneity of HTGR fuel elements in HELIOS calculations. The main steps of the RPT method are presented. A 3D heat conduction module coupled with a channel-type coolant flow model is implemented to take the temperature reactivity feedback to neutronics physically correctly into account. It is shown that there is significant redistribution of the produced heat by heat conduction between the graphite blocks.

The correlation between the grain orientation and the magnetic and elastic properties of plasma nitrided polycrystalline 316L austenitic stainless steel (ASS) is investigated.Plasma nitriding was performed at 400°C for 30 minutes under a pressure of 7.5 Pa using a 60 sccm N2 and 40 sccm H2 mixture. The grain orientation in a delimited area was obtained from electron backscatter diffraction (EBSD). The magnetic properties of the assessed grains were locally investigated by polar magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM). Young's modulus Ehkl cartography was obtained in 3D using nanoindentation tomography. Plasma nitriding results in the nitrogen incorporation into the octahedral sites and expansion of the ASS lattice. This induces ferromagnetism at room temperature due to the formation of expanded austenite, where the diverse grains exhibit different magnetic properties, with a resulting effective magnetic easy axis along an unusual direction. Moreover, nitriding results in a complete reversal of the elastic behavior anisotropy: while the non-nitrided 316L ASSshows the typical elastic anisotropy of fcc-type metals with a maximum of Ehkl for the <111> oriented grains, the maximum of Ehkl is observed for the <100> oriented grains in the expanded austenite. These observations are discussed on the basis of the expansion due to the nitrogen incorporation and associated lattice rotation and residual stress effects.

At the nELBE facility at Forschungszentrum Dresden-Rossendorf fast neutrons with kinetic energies of 0.1 to 10 MeV will be used to deliver nuclear data on neutron induced reactions.
First experiments on inelastic neutron scattering on 56Fe where performed using a double time-of-flight detector setup. This setup is based on proton recoil detectors and an array of 42 BaF2 crystals. The emitted photons and neutrons can be detectd in coincidence. First results will be presented.

Ionenstrahlinduzierte Oberflächenstrukturen von bisher nicht erreichter Qualität wurden Ende 2009 am FZD bei der routinemäßigen Untersuchung der Oberflächenerosion von Ge mit schweren Bi2+ und Bi3++ Ionen-Clustern entdeckt. Die neue Qualität betrifft die sehr gute Nahordnung und die große Amplitude der „Dot“-Muster, die deutlich über dem bisher Erreichten liegt (siehe Abb.). Das implantierte Bi ist in den Dots angereichert.
Auch ein qualitativer Sprung wird bei der Cluster-Ionenerosion beobachtet: Während bei senkrechter Fokussed-Ion-Beam-Bestrahlung mit Bi+-Ionen die Ge-Oberflächenschicht die bekannte Schwammstruktur erhält, finden wir mit Bi3++-Clustern bei gleicher Energie pro Bi-Atom (10 keV) selbstorganisierte (kristalline) „Dots“, deren Abstand untereinander weniger als 50nm beträgt und die 30-40nm hoch sind.
Die von uns entdeckte Selbststrukturierung basiert also auf einem Clustereffekt, nicht auf Einzel-Ioneneinschlägen. Das Kuramoto-Sivashinsky Modell ist daher nicht anwendbar, anders als für die reguläre Selbststrukturierung von Ge mit 3-4nm flachen Löchern durch Beschuss mit 5keV Ga-Ionen (Wei et al., Adv. Mat. 21 (2009) 2865).
Erste theoretische Analysen zeigen, dass die durch die Stoßkaskade deponierte Energiedichte einen Schwellwert überschreiten muss um den neuartige Selbststrukturierungsprozess auszulösen. Der Schwellwert koinzidiert mit der pro Atom benötigten Energie zum Schmelzen des Ge, d.h. jeder Bi-Clustereinschlag erzeugt einen Ge-Schmelzpool von einigen 100nm3. Unsere erste Modellvorstellung erklärt die Bi-Konzentrierung in „Punkte“ durch eine Bi-Ge-Entmischung der Oberflächenschicht mittels vielfacher Bi-Segregation in den erstarrenden Schmelzpools. Die topografische Aufwölbung in den „Punkten“ wird durch die ca. 5%ige Ge-Volumenänderung beim Schmelzen bewirkt. Die Bi-konzentrationsabhängigen Schmelztemperatur des Ge führt zu einem asymmetrischen Erstarren der Schmelzpools und wegen der Volumenänderung zu einem Ge-Massentransport in Richtung hoher Bi-Konzentration.

During the last decades, the focused ion beam (FIB) became a very useful and versatile tool in microelectronics industry, as well as in the field of basic and applied research and derived an exceedingly importance with the development of the ano-technology. For special purposes like writing ion implantation for doping or ion beam synthesis (IBS) in the µm- as well as in the nm-range without any lithographic steps ion species other than gallium become more and more relevant. Therefore mass separated FIB systems equipped with alloy liquid metal ion sources (LMIS) play an increasing role.
Modern FIB systems and related liquid metal ion sources are introduced in detail and the broad spectrum of applications, like processes for the fabrication of nanstructures, templating, 3D ion milling or the combination of FIB implantation and wet chemical anisotropic etching as well as sample preparation techniques will be presented and discussed.

Recently a lot of research has been done in revealing the nature of intrinsic superconductivity in highly p-type doped silicon and germanium. However, the studies presented here, demonstrate the feasibility of embedding extrinsic superconducting nanolayers in commercial (100) silicon wafers due to Ga precipitation. With the ion implantation technique a high Ga fluence (2x10¹⁶ cm^-2 or 4x10¹⁶ cm^-2) is introduced in Si through a 30 nm SiO2 cover layer. This leads to amorphous layers containing Ga peak concentrations far beyond the equilibrium solid solubility limit. To initiate Ga precipitation and recrystallization rapid thermal annealing (RTA) is used. At optimized processing conditions (4x10¹⁶ cm^-2, 600 - 700°C) the samples become superconducting. Critical temperatures of 7 K and in plane critical fields up to 14 T are reached [1]. A detailed investigation of the layer microstructure by means of RBS/C and TEM will be presented. These structural investigations reveal polycrystalline Si layers containing amorphous Ga-rich precipitates and that the superconductivity arises because of a high density of precipitates at the Si/SiO2 interface. As the ion implantation with subsequent annealing is compatible with standard microelectronic technology it could be possible to develop new superconducting devices, which operate above liquid He temperature.
[1] Skrotzki R. et al., Appl. Phys. Lett. 97 (2010) 192505

We present a novel ultrasound Doppler system for fluid flow engineering being able to determine two-dimensional, two-component velocity fields. Electromagnetically-driven liquid metal flows appear as an attractive application field for such a measuring system. Two linear ultrasound transducer arrays each equipped with 25 transducer elements are used to measure the flow field in a square plane of 67 x 67 mm². The application of advanced processing techniques like a simultaneous excitation of multiple transducer elements and a segmented array technique enable high data acquisition rates as well as a high spatial resolution, which have not been obtained so far for flow measurements in liquid metals. Essential operation principles such as the multiplexing electronic concept will be presented within this paper. The capabilities of the measuring system makes it suitable for investigations of nontransparent, turbulent flows. Here, we present measurements of liquid metal flows in a rotating magnetic field for demonstration purposes. The measuring setup realized here delivers details of the swirling fluid motion in a horizontal section of a cube. Frame acquisition rates up to 30 fps were achieved for a complete two-dimensional flow mapping.

Innovative Mixed OXide (MOX) (U,Pu)O2-x fuels for Sodium Fast neutron Reactors (SFR’s) systems are studied within the framework of GEN-IV nuclear reactor systems. SFRs will also be able to burn long-lived minor actinides (MA) such as Am, Np and Cm. Among MA, americium is of main concern. One solution currently considered is to homogeneously add americium in small amount to the fuel. Because it significantly affects sintering properties as well as irradiation performances, the oxygen to metal (O/M) ratio is an important factor to be considered when designing oxide fuels. Therefore, a thorough knowledge of the correlation between oxygen potential fixed during fuel sintering and O/M ratio is essential. The aim of this work is to follow the chemistry of uranium, plutonium and americium in (U0.750Pu0.246Am0.004)O2-x samples sintered for 4 h at 1700°C in various moisture-added Ar containing 5% of H2 atmospheres Thanks to XAS experiments performed at U, Pu and Am edges, the O/M ratio values were determined and are in very good agreement with those derived from XRD analysis. Furthermore, both XANES and EXAFS results show that O/M evolution in MOX samples is only supported by the reduction of plutonium. Thus, with this methodology, we are able to obtain O/M ratio without further thermal treatment as opposed to TGA. By using thermochemical modeling based on Lindemer and Besmann formalism [1], determination of thermodynamical conditions leading to these O/M values are estimated. Our results are compared to the study of Osaka et al. [2] highlighting a discrepancy between modeled and experimental oxygen potential vs. O/M ratio curve for Am-doped MOX system.

[1] T.B. Lindemer and T.M. Besmann, J. Nucl. Mat. 130, 489-504 (1985).
[2] M. Osaka et al., J. Alloys Comp. 428, 355-361 (2007).

The investigation of insulation debris transport, sedimentation, penetration into the reactor core and head loss build up becomes important to reactor safety research for PWR and BWR, when considering the long-term behaviour of emergency core cooling systems during loss of coolant accidents. Research projects are being performed in cooperation between the University of Applied Sciences Zittau/Görlitz and the Forschungszentrum Dresden-Rossendorf. The projects include experimental investigations of different processes and phenomena of insulation debris in coolant flow and the development of CFD models. Generic complex experiments serve for building up a data base for the validation of models for single effects and their coupling in CFD codes. This paper includes the description of the experimental facility for complex generic experiments (ZSW), an overview about experimental boundary conditions and results for upstream and down-stream phenomena as well as for the long-time behaviour due to corrosive processes.

Photoexcitation of uranyl(VI) ion occurs via singlet-to-singlet transition. After rapid internal conversion and intersystem crossing, it converges to the lowest-lying triplet state which has relatively long lifetime of ~ μs. The relaxation process of excited state uranyl(VI) has been a subject of investigation by Ghosh et al. [1] using picosecond transient absorption spectroscopy. Time-resolved X-ray absorption spectroscopy is well-suited for such investigation, however, to the best of my knowledge there has been no such application to uranyl(VI) systems.
Here, excited state chemistry of uranyl(VI) has been explored by density functional theory calculations mainly focusing on the lowest-lying triplet states. The structures of the lowest-lying triplet states were found to predict photochemical reactivities of uranyl(VI) complexes, e.g. photochemical reduction [2], luminescence quenching [3], and photochemical decomposition [4]. The lowest-lying triplet state of uranyl(VI) ion in the presence of ethanol was found to have an asymmetric bond distances in its transdioxo O-U-O unit with the U-O distances of 1.791 and 1.962 Å, and the formal oxidation state of uranium was found to be U(V). These theoretical findings were experimentally confirmed by Ghosh et al. using transient absorption spectroscopy [1].
[1] R.Ghosh et al., J. Phys. Chem. A 114, 5263-5270 (2010).
[2] S.Tsushima, Inorg. Chem. 48, 4856-4862 (2009).
[3] S.Tsushima et al., Chem. Eur. J. 16, 8029-8033 (2010).
[4] S.Tsushima et al., Dalton Trans. 39, 10953-10958 (2010).

Current-induced domain wall motion for systematic studies of spin momentum transfer requires the reliable preparation of domain walls. Since high current densities can change or destroy the structures investigated, weak pinning potentials allowing the controlled and reliable depinning of domain walls at low current densities are desirable. A prerequisite for the preparation of a domain wall at such pinning sites is, that the domain wall nucleates at fields smaller than the field required to depin the domain wall. We suggest methods to tune the nucleation field of lithographically patterned Co/Pt multilayer wires. An up to fourfold reduction of the nucleation field could be achieved through altering the lateral shape of the wires or by depositing iron stripes on top. Furthermore we explored the applicability of geometric constrictions and ion implantation for the creation of pinning sites. The magnetization reversal of the structures was imaged by transmission X-ray microscopy at the Advanced Light Source in Berkeley, CA, USA. The authors gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft via SFB 668 and GrK 1286 as well as by the DOE.

The controlled motion of magnetic domain walls in nanowires is of scientific and technological relevance since it is necessary for new concepts of ultrafast, high-density, and nonvolatile data storage devices. Locally well-defined confining potentials, e.g., created by notches, act as pinning sites for individual domain walls. Magnetic configurations can be manipulated by external magnetic fields and by spin-polarized currents via transfer of spin-angular momentum.
The local modification of magnetic properties by ion irradiation opens the possibility to create pinning sites without geometric constrictions. Implantation of chromium ions into permalloy nanowires causes alloying and structural defects which leads to a reduction of the Curie temperature and the saturation magnetization Ms as well as small changes of the magnetocrystalline anisotropy.
The energy associated with the domain wall is locally reduced and a position at the so-called magnetic soft spot is energetically favorable in comparison to the environment, Field- driven pinning and depinning of a domain wall at the soft spots has been directly observed using magnetic transmission soft X-ray microscopy (MTXM) at beamline 6.1.2. of the Advanced Light Source in Berkeley, CA, USA. Magnetic contrast is provided via X-ray magnetic circular dichroism (XMCD) at the Ni L3-absorption edge. We have shown that the strength of the pinning potential and thus the depinning field can be tuned by the chromium ion fluence applied to induce the soft spots.

Micromagnetic structures have been a focus of both fundamental and technological research for several decades. As a part of this effort, spin vortices (which are characterized by an in-plane magnetization curl and a small out-of-plane core region) have attracted much attention due to their chiral nature and the variety of dynamic phenomena associated with them. Although the static and dynamic properties of individual vortices are now reasonably well understood, there have been relatively few studies addressing their mutual interactions, particularly for the case of a vertically stacked arrangement. Here we present experimental findings on vortex coupling in trilayer elements, where two ferromagnetic layers are separated by a nonmagnetic spacer. For these systems the relative configurations of the in-plane flux senses (circulations) as well as the core orientations (polarities) of layered vortices have been identified by means of scanning transmission x-ray microscopy (STXM). The dominant coupling mechanisms here are the magneto-dipolar interaction and interlayer exchange coupling (IEC).

The joint research project „Dynamics of drowned and flooded salt mines and their overlaying rocks“ aimed at exemplarily and comprehensively clarifying causes, processes and effects of damages caused by abandoned historical potassium mining in Staßfurt, Germany [1]. Funded by the BMBF (Bundesministerium für Bildung und Forschung) ten universities, research facilities and companies were coordinated by the BGR (Bundesanstalt für Geowissenschaften und Rohstoffe). The IRC - Research Site Leipzig contributed small scale laboratory experiments of flow and transport process observations in drilling cores from hydrologic relevant regional lithologies and the matching of fluid flow patterns with high resolution CT imaging data and structure-controlled model simulations obtained and conducted by colleagues from JGUM [2]. This close collaboration aimed at enhancing the comprehension of small scale fluid flow in heterogeneous natural porous media.

Visualization of fluid flow in homogeneous porous as well as in fractured heterogeneous media was conducted with a preclinical PET scanner with a spatial resolution of 1 mm and a temporal resolution of 1 minute [3]. Drill cores from anhydrite, sandstone and rock salt formations of the Staßfurt salt dome were examined with continuous flow-through experiments. Pulses of radiotracer solutions ([18-F]KF and [124-I]KI) were injected and in situ PET-observations of the tracer propagation were conducted throughout the course of several hours and weeks, depending on the sample permeability. The flow behavior can be described with heterogeneous and process-dependent parameter distributions, like effective volume, permeability and dispersion rates. Based on µXCT measurements with a spatial resolution of 65.3 µm the percolating pore space, including all connected pores and fractures and the maximal inner surface, was quantified [2].

This “GeoPET” method is an excellent tool for direct quantitative spatiotemporal visualization of tracer transport in heterogeneous rocks on core scale [3, 4]. Combined interpretation of µXCT PET data enables deepened understanding on causes and effects of the structural constraints (pore space, cleavages etc.) and fluid flow patterns, enables to stereotype combined structural characteristics and flow path topologies and to determine the ratio between total and effective pore volume. The latter is for instance revealed by observable fingering phenomena in extended fractures. The fraction of the internal surface of a rock sample in contact with the mobile fluid – the effective reactive surface area – decreases with increasing localization of actual transport paths. Therefore, combined PET-CT data interpretation enables to realistically describe the considerably narrowed potential of dissolution and sorption reactions in heterogeneous and fractured media. In combination with simulated data the flow velocity patterns were quantified along the pathways, and they appeared highly variable within the fractures. In saline rocks we observed that localized high flow velocities may locally stimulate the salt dissolution and cause the widening of fracture cross sections. Such self energizing mechanisms may lead to increasing permeabilities, flow velocities and flow rates.

The complex flow patterns and the different resolutions of the data sets require scale independent comparison methods. We thus applied variography [4], which also could be applicable as simple method for upscaling to the field scale.

[1] Gerardi, J. (2006) Report BGR, p. 79.
[2] Enzmann, F. et al. (2010) EDGG, 244, p. 213-224.
[3] Kulenkampff, J. et al. (2008) Phys. Chem. Earth, 33, p. 937-942.
[4] Wolf, M. et al. (2010) EDGG, 244, p. 200-212.

Backround:

Molecular targeting is a novel approach in radiotherapy with great potential to increase local tumour control. The epidermal growth factor receptor (EGFR) is a suitable target for such strategies, due to its overexpression in many solid tumours.
The aim of the project is an increased inactivation of tumour cells, including EGFR overexpressing metastases. Therefore the radioactive isotope 90Yttrium was bound to the EGFR directed antibody Cetuximab (C225). This allows a specific induction of DNA damage in EGFR overexpressing tumour cells with low side effects in normal tissue expressing low EGFR.
In this study double strand breaks (DSB) induced by ⁹⁰YDTPA-Cetuximab were determined. Therefore γH2AX foci formation in human squamous cell carcinoma cells of head and neck differing in EGFR expression were detected after treatment with ⁹⁰Y-DTPA-Cetuximab.

Summary & Conclusion:

• The binding of Cetuximab to cells depends on their membranous EGFR expression level.
• The chelator DTPA attached to the antibody Cetuximab reduces the affinity to EGFR about 30% compared to native Cetuximab. This effect can be avoided by using saturating concentrations of antibody.
• ⁹⁰Y-DTPA-Cetuximab induces DNA double strand breaks in human squamous cell carcinoma cell lines.
• The dose applied by ⁹⁰Y-DTPA-Cetuximab, and thereby the amount of DNA double strand breaks induced, depends on the time of treatment and seems to be related to the membranous EGFR expression.
• The repair of DNA double strand breaks in human squamous cell carcinoma cell lines shows comparable kinetics after treatment with ⁹⁰Y-DTPA-Cetuximab and irradiation with X-ray.

The control of the magnetic properties like magnetic anisotropy, saturation magnetization, and especially the dynamic magnetic properties in ferromagnetic thin films are of significant importance for spintronics applications. For instance, the magnetic anisotropy, e.g. uniaxial anisotropy or unidirectional anisotropy, in ferromagnetic single or multi-layers is initialized by applying a magnetic field during film deposition or by a magnetic field anneal.
Here, we give an overview on novel ways of tailoring ferromagnetic thin film properties by ion irradiation. In addition, additional tuning is obtained by patterning the magnetic films in terms of laterally varying magnetic properties [1]. Results from different samples patterned in terms of anisotropy [1, 2, 3], exchange bias [1, 4], and saturation magnetization [5] are presented. The main emphasis of the investigations is on the role of magnetic domain formation and domain wall effects in stripe-like magnetic hybrid structures on the overall static and especially dynamic magnetic properties [6, 7].
The presented paths of ferromagnetic film preparation provide an additional degree of freedom for the tailoring of magnetic properties and functionality of soft-magnetic thin films

Dipole strength functions up to the neutron-separation energies S_n of the N=50 isotones 88Sr , 89Y, 90Zr, the even-mass Mo isotopes from 92Mo to 100Mo, the N=82 nuclide 139La and the doubly magic 208Pb have been studied in photon-scattering
experiments using the bremsstrahlung facility [8] at the superconducting electron accelerator ELBE of the Forschungszentrum Dresden-Rossendorf. To estimate the distribution of inelastic transitions from high-lying levels at high level density to low-lying levels, simulations of $\gamma$-ray cascades were performed. On the basis of these simulations, intensities of inelastic transitions were subtracted from the experimental intensity distributions that include the resolved peaks as well as a quasicontinuum formed by unresolved transitions, and the intensities of elastic transitions to the ground state were corrected for their branching ratios.
The photoabsorption cross sections obtained in this novel way are combined with (gamma,n) and (gamma,p) data and give detailed information about the dipole strength functions in the energy range from about 4 MeV up to the
giant dipole resonance (GDR). In all nuclides enhanced strength compared to Lorentzian-like approximations of the tail of the GDR is found in the energy range from about 5 MeV up to about the respective particle thresholds.
Calculations in the framework of the quasiparticle-random-phase approximation (QRPA) underestimate the dipole strength at low energy and show strong fluctuations in the whole energy range up to the giant dipole resonance (GDR). A new approach is presented that calculates the dipole strength for nuclei with shape fluctuations by combining the interacting boson approximation (IBA) with
QRPA. Based on the slow shape dynamics and the fast dipole vibrations an Instantaneous Shape Sampling (ISS) is performed that describes the photoabsorption at a fixed shape with QRPA with probabilities given by IBA.
The ISS-QRPA improves the description of the experimental photoabsorption cross sections but still requires additional smearing. Predictions of ISS-QRPA for isotopic chains with changing nuclear deformation are presented.
Shell-model calculations including (2p-2h) excitations performed for the case of 208Pb show that the higher-order excitations are the main mechanism for the fragmentation of the strength and hence for the spreading of the GDR.

The paper presents initial results of the post mortem investigations performed on the reactor pres-sure vessels (RPV) of 1st generation WWER-440/V-230 reactors. Trepans were taken from the beltline weld and the base metal of the units 1, 2 and 4 RPVs, which represent different material conditions (irradiated, annealed and re-irradiated. From the trepans were manufactured standard SE(B) and Charpy V-notch specimens and investigated by Master Curve (MC) and Charpy V-notch testing. Specimens from defined locations through the thickness of the welding seam and the base metal ring were tested. The reference temperature T0 was calculated using the measured fracture toughness values KJc at brittle failure of the specimen. In addition Charpy V-notch specimens were tested in order to determine the Charpy-V ductile-to brittle transition temperatures.

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An extensive experimental database comprising air-water as well as steam-water upwards vertical pipe flows for a pressure up to 6.5 MPa was used to investigate the effect of the lateral lift force on turbulent poly-dispersed flows with medium or high gas volume fraction. It was clearly shown that the lift force plays an important role also in such flows. Dynamic effects such as bubble coalescence and breakup as well as fast rising large bubbles which push small bubbles towards the pipe wall superpose the effect of the lift force but can be separated from this effect. The predictions of the correlation by Tomiyama et al. (2002) on the critical bubbles size at which the lift force changes its sign are obviously also valid for turbulent air-water and steam-water flows with medium and high void fraction and a broad spectrum of bubbles sizes. The values for this critical bubble diameter are confirmed by the experimental data within the frame of the uncertainty of the data. Consequences of the action of the lateral lift force on flow structures in different flow situations are discussed. From the investigations can be concluded that the lift force including the bubble size dependent change of its sign should be considered in a proper numerical 2D or 3D-simulation on flows in which bubbles in the range of several millimeters are present.

Hydrodynamics of a periodically operated trickling packed bed was studied with a high-speed wire-mesh sensor technique based on direct measurement of cross-sectional distributed local capacitances Liquid cycles in the alumina packing were generated by periodic induction of gas and/or liquid phase in distinctive slow-mode Hydrodynamics were characterized with respect to liquid saturation and liquid saturation distribution varying period length split and time-averaged superficial gas and liquid velocities The sensors technique allows direct access to local phenomena during liquid pulse breakthrough to distribution patterns and their reproducibility at different cycle positions that were studied based on transient liquid saturation distribution data of different periodicity variables Due to simultaneous measurement at four different axial reactor positions pulse attenuation along the reactor and pulse velocity could be analyzed Furthermore hydrodynamics of different modes of gas-induced periodic cycling e. g. gas cycling only asynchronous and synchronous cycling of gas and liquid flow rate and alternating gas-liquid cycling were studied.

The distribution of erosion in the Himalayas is mainly controlled by the spatial distribution of relief and possibly precipitation intensity. However, both parameters might depend on each other. Today we do not have a good understanding of the effects of this controlling parameters on erosion in complex topographic settings and active mountain belts such as the Himalayas. The conjunction of independent erosion proxies can help to understand recent (today-10⁴ years) erosion distribution and its eventual dependency on topography, precipitation and uplift.

For our analysis we have validated the precipitation dataset APHRO_MA_V1003R1 (Asian Precipitation Highly Resolved Observational Data Integration Towards Evaluation of Water Resources, Monsoon Asia, Version 10, hereafter referred to as APHRO), which is interpolated from rain gauging stations. It was evaluated to be the best dataset of precipitation estimates at the scale of the Himalayas. APHRO data, with a daily temporal resolution and 0.25° spatial resolution, is available since 1951.

Here, we present a compiled analysis of spatio-temporal erosion evaluation from suspended river discharge fluxes, its relation with precipitation and rainfall induced landsliding. The analysis is based on data from 14 hydrological stations in Nepal, which cover nearly all major rivers, spanning a rainfall gradient from East to West along the Himalayan front. The annual hydrograph of the Himalayan rivers is controlled by the South Asian summer monsoon. The average increase of discharge during monsoon is one to two orders of magnitude with respect to winter base-flow. Considerable suspended concentrations (10²–10³ mg/l) are observable during monsoon season. Short lasting events, however, can catapult concentrations for few short periods above 10³ mg/l. In general, few above 95 % quantile events account for more than the half of all suspended material transported in one year. These above threshold events are generated by precipitation driven landslides. A direct linkage between annual suspended fluxes and precipitation intensity distribution is also observed. Denudation rates calculated from suspended sediment fluxes are in the range of 2.1 to 5.6x³ t km^-2 a^-1.

We will present cosmogenic erosion rates, deduced from ¹⁰Be analyses from quartz, for several small and associated large catchments across the Himalayan range. Sample locations for large river basins correspond with the hydrological station location mentioned above. Our cosmogenic erosion rates are in the same range as the ones derived from suspended sediment fluxes, 1-4 mm/a. In general, erosion rates are higher within the Himalayan range close to the Himalayan ride crest.

The combination of these methods gives a good overview on the erosion processes and its distribution across the Himalayan mountain belt. Mass wasting is indeed the dominant process driving erosion and shaping topography. Furthermore, the source and transport pathways can be determined, which is a first step to understand the linkage between topography and precipitation distribution on a large scale.

Acknowledgments: Beryllium-10 measurements by accelerator mass spectrometry at the French CEREGE-ASTER-LN2C is highly appreciated.

Overview of the physical basics of in-beam PET and SPECT during proton and ion therapy. Current investigations of signal prediction and preliminary results are presented.

Starting with the Riga and Karlsruhe liquid sodium experiments, the last decade has seen great progress in the laboratory modeling of dynamo action and related magnetohydrodynamic instabilities such as the magnetorotational instability (MRI) and the Tayler instability (TI). We summarize the recent experimental achievements, and we present our plans for a large scale precession dynamo experiment and a combined MRI/TI experiment in the framework of the DRESDYN project at Helmholtz-Zentrum Dresden-Rossendorf.

The expansion dynamics of hot electron-positron-photon plasma droplets is dealt with within relativistic hydrodynamics. Such droplets, envisaged to be created in future experiments by irradiating thin foils with counterpropagating ultraintense laser beams, are sources of flashes of gamma radiation. Warm electron-positron plasma droplets may be identified and characterized by a broadened 511 keV line. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3499410]

Cosmonuclide concentrations in surface samples are function of both duration of exposure to cosmic radiation and surface stability. From the measurement of a single cosmonuclide concentration in a single surface sample, it is thus impossible to quantify simultaneously the exposure duration and the denudation rate affecting the studied object. In the case of a simple exposure history, measurements of two cosmonuclide concentrations within the same surface sample may however theoretically be used to estimate both unknowns.
A more constraining approach to accurately quantify both exposure time and denudation rate is to take advantage of the fact that the effective production attenuation length of neutrons is significantly shorter than that of muons. The neutron-induced cosmonuclide concentrations thus reach steady-state with respect to denudational loss much more rapidly than the muon induced ones. Consequently, the near-surface cosmonuclide concentrations mainly resulting from interactions with neutrons might be used to estimate the denudation rates while the several meters depth concentrations mainly resulting from interactions with muons might be used to estimate the exposure duration. A unique well constrained depth profile thus permits determination of both the exposure time and the denudation rate. In the case of abandoned material, inheritance due to previous exposition to cosmic rays can be revealed.
Multi-nuclide depth profiles are also excellent tools for better deducing the physical parameters of the particles involved in the production of these cosmogenic radionuclides. This approach has been applied twice: 1.) ¹⁰Be and ²⁶Al along a 25 meters pure quartz core from Galicia, Spain, and 2.) ¹⁰Be, ²⁶Al and ³⁶Cl along a ~11 meters carbonate and quartzose conglomerates core from La Ciotat, S.E. France. Both projects confirm that the density of the material is one of the most sensitive parameters. The latter study also allows to precise the still debatable spallation production rate of ³⁶Cl from Ca.

Medium-energy AMS facilities such as the British 5 MV-NEC machine at “SUERC”, the French 5 MV-HVEE-machine “ASTER” and the two German 6 MV-HVEE-machines “DREAMS” at Dresden [1] and “Cologne AMS” have been recently installed in Central Europe. Of course, these machines need physicists to get them running but also scientists to establish AMS chemistry on-site. As it is not advisable to change simultaneously two ”things”, i.e. machine and chemistry, a close cooperation with the teams of ASTER and VERA helped to check the new sample preparation laboratories of DREAMS.

Generally, a ”good” AMS sample has two features: high stable isotope current and low isobar concentration. High chemical yields and low concentrations of other elements originating from the matrix or chemical products used are less important, but may play a role if e.g. a matrix contains Ti being introduced into BeO-targets as shown by µ-XRF [2] and recent µ-PIXE analyses of final AMS-targets at HZDR. A processing blank with low radionuclide/stable nuclide ratio is, however, essential for projects near the detection limit. For high sample throughput and reasonable costs a fast, easy and cheap chemical separation is also favourable.

The results from first samples processed at DREAMS are excellent: For ¹⁰Be-AMS-targets isolated from quartz-rich river sediments (Himalaya, erosion rate study) ⁹Be-currents had been as high as ASTER standards and machine blanks. Corresponding processing blanks were in the same order as the machine blank (1x10^-15), thus, more than one order of magnitude lower than the lowest sample ratio. Chlorine-36 targets originating from calcite-rich boulders from a medieval rockfall had been well-measurable with blank-corrections lower than 8 %. Finally, ³⁶Cl prepared from river terraces (Anatolian Plateau, Turkey, uplift rate study) showed also perfect performance at VERA.

References: [1] Akhmadaliev et al., this meeting. [2] S. Merchel et al., NIMB 266 (2008) 4921.

Acknowledgments: Thanks to T. Schildgen and C. Yildirim (Potsdam) performing 36Cl chemistry tests at DREAMS.

Since the acceptance tests of ASTER in March 2007, routine measurement conditions for the long-lived radionuclides ¹⁰Be and ²⁶Al have been established. Sample throughput as high as over 3300 unknowns has been reached for ¹⁰Be in 2010. Steady numbers for ²⁶Al within the last three years settle down ~300 real samples.

Unacceptable cross-contamination for volatile elements has been largely solved by an ion source upgrade [1]. Thus, the second frequent nuclide measured at ASTER in 2010 is ³⁶Cl with ~480 sample targets. The enhancement with respect to immediate short-term sample to sample by the new ion source is impressive allowing minimal measurement time losses such as for initial burn-in periods of 5 min for virgin targets and waiting periods between data acquisition of two sample runs of 2 min. However, recent long-term tests using ³⁵Cl/³⁷Cl samples with strongly varying ratios have shown that identical targets lead to different ³⁵Cl/³⁷Cl results at the 2-4% level when being measured after a time gap of 24 hours while the source is running other samples. Reasons for this such as source memory, time dependent mass fractionation, drift of the Faraday-cup measurement system or something else are not yet clear.

Finally, after establishing quality assurance at ASTER by cross-calibration of secondary in-house ²⁶Al and ⁴¹Ca standards [1] and taking part in round-robin exercises of ¹⁰Be and ³⁶Cl, we performed a two-step cross-calibration of secondary in-house ¹²⁹I standards. The two ampoules of NIST 3231 containing ¹²⁹I/¹²⁷I at 0.981x10^-6 have been used for step-wise dilution with NaI (MERCK, suprapur, 99.99 %) to get gram-quantities of lower-level standards for every-day use. The material SM-I-9 (~1x10^-9) has been measured vs. AgI produced from the two NIST ampoules with (0.982+0.012)x10^-8 solution using minimum chemistry. In a second stage, SM-I-10 and SM-I-11 with ratios of ~1x10^-10 and ~1x10^-11, respectively, have been cross-calibrated against SM-I-9. Individual uncertainties of the traceable secondary standards are around 1.5 %, mainly originating from the given uncertainty of the primary NIST 3231 at 10^-8.

References: [1] M. Arnold et al., NIMB 268 (2010) 1954.

The most abundant presolar grains in primitive meteorites are nanodiamonds. These grains survived the formation of the solar system and kept their own individuality. However, existing measurements of their isotopic pattern do not allow for a consistent understanding of their origin. The reasons are mainly due to their small size (nm) and the low abundance of trace elements. Most likely, such nanodiamonds were formed in a supernova environment. Positive measurements of trace-element isotopic signatures will help understanding heavy element nucleosynthesis in massive stars and dust formation from their ejecta. They will also enable testing predictions of r-process nucleosynthesis and understanding the uniformity of the “main r-process”.
A first approach applying AMS to measure Pt in nanodiamonds was performed at TU Munich [1]. We have continued our search for stable isotope anomalies in nanodiamonds at VERA. Recent experience showed that AMS provides the required measurement precision together with a low Pt machine background. Moreover, we observed for the first time enhancements of ¹⁹⁸Pt/¹⁹⁵Pt isotope ratios in two diamond residues from the Allende meteorite, which were prepared by different separation techniques. Variations in other isotopic ratios were within analytical uncertainty, and no anomaly was identified in a third diamond fraction. An enhanced ¹⁹⁸Pt/¹⁹⁵Pt ratio is predicted by models that either include or exclude a simultaneous negative anomaly in ¹⁹⁴Pt/¹⁹⁵Pt. This negative anomaly, however, was not observed via AMS and is in contrast to data obtained for tellurium.
The robustness of these first results needs to be verified by detailed and systematic studies of possible mass-fractionation effects and potential scatter due to inhomogeneities within samples. We will present our measurement approach and plans for other isotopes. The latter is part of the Eurogenesis programme organized by the European Science foundation.

[1] S. Merchel et al., Geochim et Cosmochim Acta 67 (2003) 4949.

Pressurized Thermal Shock (PTS) occurs in Pressurized Water Reactors (PWR) during hypothetical Small Break Loss of Coolant Accidents (SBLOCA) with the action of the Emergency Core Cooling System (ECCS). For reactor designs where cold water is injected into the cold leg, insufficient mixing can lead to critical thermal stress in the hot RPV wall. The mixing process involves several thermal hydraulic phenomena, such as direct contact condensation (DCC), entrainment of steam bubbles and multi-scale momentum transfer, and is therefore difficult to model. Conventional 1D system codes are not designed to resolve flows, which are governed by 3D multiphase phenomena. Therefore Computational Fluid Dynamics (CFD) codes are currently being qualified for such problems.
For the validation of CFD models and simulations related to PTS problems, the TOPFLOW-PTS project is running in cooperation with AREVA, CEA, EDF, ETHZ, IRSN and PSI. There, an experimental installation was implemented inside the TOPFLOW pressure tank to run scaled down steam-water and air-water experiments. The PTS assembly is a model of a French 900 MWe PWR including downcomer, cold leg with ECC injection and a pump simulator - all scaled at 1:2.5. (See [1] for details) The setup is highly instrumented with sophisticated special instrumentation. Temperature profiles in the flow domain are measured with about 200 distributed thermocouples and the cold leg wall is observed by an infrared camera system. Furthermore high-speed camera observation and wire mesh sensors record the flow structure in the cold leg.
In a first project phase several air-water experiments have been carried out which were intended to give a general insight into the flow structures for some parameter variations. These experiments indicated the flow stratification phenomena in the ECC line and thermal mixing in the cold leg in dependence on the ECC mass flow rate, the system pressure (gas density) and other parameters. One of the most important determinants for thermal mixing is the jet momentum at the impact position, which mainly depends on the jet’s mass flow rate. It turned out that there can be different flow regimes in the ECC line which need to be considered in boundary condition definitions for CFD calculations. Therefore this effect was particularly studied utilizing an ultrasound sensor together with simultaneous high-speed camera observations of the impingement point and the water surface. A digital bubble tracking velocimetry method was then applied to compare different flow regimes in the cold leg.

Quartz (SiO2) glass was implanted with 5-9x1016 57Fe ions/cm² at a substrate temperature of 500°C, and annealed at temperatures between 700 and 950°C. The implanted and annealed plates were characterized by conversion electron Mössbauer spectroscopy (CEMS), and measured by a Kerr effect magnetometer or a vibration sample magnetometer. Kerr effect measurement of as-implanted SiO2 glass showed ferromagnetism at room temperature. CEM spectrum of the as-implanted glass consisted of magnetic relaxation peaks of finely dispersed metallic Fe species, and paramagnetic doublets of Fe3+ and Fe2+ species. The sample heated at 700°C contained large grains of metallic Fe and a lot of oxidation products of Fe2+ species. After oxidation at temperatures higher than 800°C, the samples showed also ferromagnetism, which was attributed mainly to ferromagnetic e-Fe2O3 precipitated in SiO2 matrix. Small amounts of a-Fe2O3 were produced at 950°C. The results suggest that ion implantation and oxidation make a transparent ferromagnetic glass possible.

Talk on the applicability of laser accelerated proton beams for radiotherapy and current status of the HZDR activities.

We present recent studies on laser proton acceleration experiments using mass limited silicon targets. Small micro machined silicon foils with 2 µm thickness and 20x20 µm2 to 100x100µm2 size mounted on very tiny stalks were shot with ultra short laser pulses 30 fs of the new 150 TW DRACO Laser facility of the Research Centre Dresden-Rossendorf. The experiments were carried out using high contrast level 10-10. Proton spectra have been measured with magnetic spectrometers and radio chromic film stacks. The scaling of the maximum proton energy as function of the target size was investigated and strong influence of the stalk as well as the target edges was found.

Overview of the cell irradiation measuremants and the new Center for high power radiation sources

In the last years, high power laser systems in the 100 TW range with ultrashort pulses (~30 fs) and repetition rates of up to 10 Hz have come into operation. In order to investigate the laser proton acceleration in this laser regime we have performed a series of experiments using plain few-micron-thick metal targets and mass-limited silicon targets. The targets were irradiated with 30 fs pulses from the new 150 TW DRACO Laser facility at the Forschungszentrum Dresden-Rossendorf which show a contrast level of 10^-10 in the picosecond and 10^-9 up to 10^-10 in the nanosecond range.

For both target types, proton spectra have been measured with a magnetic spectrometer and radiochromic film stacks. In addition, two magnetic electron spectrometers at different angles have yielded information on the electrons emitted from the non-irradiated target rear side.

Using plain metal foil targets, we have observed a linear scaling of the maximum proton energy with laser power and could show that this behaviour is explained consistently by Schreiber’s analytical scaling model [1] in the limiting case of ultrashort laser pulses [2]. Despite the high laser contrast we have found that a slight deformation of the target rear side results in a predictable deflection of the emission of energetic protons away from the target normal direction [2].

The mass limited targets tested in the experiment were micromachined silicon foils with lateral sizes of 20x20 µm2 to 100x100 µm2 mounted on tiny stalks. Their thickness of 2 μm corresponded to the optimum target thickness for proton acceleration at DRACO. Depending on the size of the targets strong influences of the stalks as well as the target edges were found which could both increase or decrease the maximum proton energy in comparison to a plain foil.

[1] J. Schreiber et al., PRL 97, 045005 (2006)
[2] K. Zeil et al., NJP 12, 045015 (2010)

The 14N(p,γ)15O is the bottleneck reaction of the hydrogen burning CNO cycle. Although it contributes only 0.8% to energy production in our Sun, the CNO cycle is responsible for neutrino fluxes from the decay of 13N and 15O, which can be detected by underground laboratories as Borexino and SNO+. The interpretation of these data requires more precise nuclear reaction cross section data.
Recent experiments on 14N(p,γ)15O focused mainly in the region 70 < E < 500 keV. Only one set of data extends up to 2 MeV. However, also high energy data are important for the S-factor extrapolation towards lower energies.
The present experiment re-studied the reaction cross section in the energy region from E = 0.6 to 2 MeV, including the resonance at E = 0.987 MeV. New resonance strength and off-resonance S-factors will be presented.

Future accelerator based radiation sources need high-brightness electron beams with high average currents and pulse repetition rates in the megahertz rage. Electron guns which can provide beams with these properties are still under development. The most promising candidate is the superconducting photo electron injector (SRF gun). The SRF gun operation basic principle is the direct production of short electron pulses by laser pulse irradiation of a photocathode which is placed in radio frequency resonator. The RF field ensures an instantaneous and strong acceleration of the electron bunches. The superconducting RF resonator has an extremely high quality factor of about 1010 and thus very low thermal losses which allows for a continuous operation. The SRF gun has highest gradient and acceleration voltages combination of all CW electron guns. Due to the low RF power losses, nearly all of the RF power is consumed for beam acceleration. The SRF gun vacuum is ideal with an enormous cryopumping speed to provide best lifetime for sensitive photo cathodes.

Recently a collaboration network has been formed by the four German Institutes DESY, FZD, HZB, and MBI, called SRF gun cluster, with the aim to commonly work in the research and development of SRF guns. The guns are needed for accelerator projects in Germany as the extension of the ELBE accelerator as a part of the high-intensity radiation center at FZD, the construction of compact energy recovery linac at HZB, and the continuous wave upgrade of the European XFEL at DESY. The involved institutes has longstanding experiences, know-how and capacities in the fields of superconducting radio frequency, electron gun and photo cathode development, cryogenics, electron beam diagnostics, and UV laser development. Specific common activities which have been started are focused on the SRF gun cavity development and test with a superconducting lead cathode, the cryomodule development for SRF guns, and on the semiconductor photo cathode preparation and characterization.

Two-phase flows are of primary importance in the understanding of thermal hydraulic phenomena in nuclear light water reactors. The qualification of CFD codes for the simulation of stationary and even transient two-phase flows in complex three dimensional geometries requires extending our knowledge toward the details of the flow structure under various thermal hydraulic conditions. At Helmholtzzentrum Dresden-Rossendorf the thermal hydraulic test facility TOPFLOW is currently extensively used to conduct two-phase flow experiments which aim at the disclosure of fine flow structure details in generic and also more complex geometries. Especially for upward adiabatic two-phase pipe flows in the bubbly to churn turbulent flow regimes valuable experimental data of the flow structure was generated in the past using the wire-mesh sensor technology. A known drawback of the wire mesh sensor is its intrusiveness.
Consequently, we have extended our measurement technology for two-phase flow to high-speed X-ray tomography which offers non-intrusive flow measurement at a speed comparable to the wire-mesh sensor. X-ray CT as an imaging modality is highly advantageous due to its non-invasiveness and its ability to penetrate opaque wall materials. One essential disadvantage of classical CT systems is the requirement for a rotating object or source-detector setup. To measure multiphase flows in a flow velocity range of up to 1 meter per second frame rates of up to 1000 frames per second are required. To achieve this, mechanically rotating parts are to be avoided. Scanned electron beam technology provides a mean to circumvent this problem. Instead of mechanical rotation of scanner components an electron beam is rapidly swept across an X-ray target using deflection coils. This technology has been introduced in medicine more than two decades ago were it is mainly used for cardiovascular diagnostics. However, medical systems with frame rates of about 20 fps are still too slow for technical flow diagnostic problems. For that reason we have developed a scanned electron beam X-ray CT apparatus “ROFEX” which can today already perform cross-sectional imaging at high frame rates and will in the future be extended to other measurement features, such as multi-plane tomography, phase velocity measurement, higher scanning diameters and high energy X-rays. This paper introduce the scanner design, discuss major performance parameters along with the application example of air-water two-phase flow measurements in a DN50 vertical test section of the TOPFLOW facility. Furthermore preparations for steam-water-experiments @70bar/286°C will be discussed.

Die Entwicklung und Validierung von CFD-Codes (computational fluid dynamics) für zweiphasige Anwendungsfälle, wie sie in der Reaktorsicherheit vorkommen, erfordern dedizierte experimentelle Daten. Mit diesem Hintergrund wurden im Helmholtz-Zentrum Dresden Rossendorf (HZDR) geschichtete Gas/Flüssikeits-Strömungen in verschiedenen Versuchsanlagen mit horizontalen Teststrecken untersucht. Diese Kanäle wurden mit rechteckigem Querschnitt konstruiert, um optimale Beobachtungsbedingungen für die Anwendung optischer Messmethoden zu erreichen. So wurde die lokale Strömungsstruktur mit einer Hochgeschwindigkeitskamera visualisiert, welche die für die CFD-Validierung benötigten Daten mit hoher räumlicher sowie zeitlicher Auflösung liefert.

Generische Gleichstromexperimente wurden im Strömungskanal HAWAC (Horizontal Air/Water Channel) mit Luft und Wasser bei Atmosphärendruck und Raumtemperatur durchgeführt. Der hydraulische Sprung, der den quasistationären diskontinuierlichen Übergang zwischen schießender und Flussströmung darstellt, wurde in diesem geschlossenen Kanal studiert. Zudem wurde das zur Schwallströmung führende instabile Wellenwachstum vom Teststreckeneintritt an untersucht. Für quantitative Analysen der optischen Messungen wurde ein Algorithmus entwickelt, um die stratifizierte Phasengrenze in den Kamerabildern zu erkennen und damit statistische Auswertungen für den Vergleich mit Ergebnissen aus CFD-Rechnungen zu ermöglichen. Anwendungsnahe Untersuchungen erfolgten im Heißstrangmodell der TOPFLOW-Anlage. Dieser Versuchsaufbau wurde in einer Druckkammer installiert, um es auch bei reaktortypischen Bedingungen im Druckgleichgewicht mit der Innenatmosphäre des Druckbehälters betreiben zu können. Die Teststrecke bildet ein flaches Modell des heißen Strangs eines deutschen Konvoi Druckwasserreaktors (DWR) im Maßstab 1:3 nach und ist für visuelle Beobachtungen mit großflächigen Glaswänden ausgestattet. Die Experimente erfolgten mit Luft und Wasser bei Raumtemperatur und Drücken von maximal 3 bar sowie mit Dampf und Wasser bei bis zu 50 bar und 264°C. Es werden Ergebnisse aus Gleichstromexperimente präsentiert, die den zweiphasigen Naturumlauf im Primärkreislauf eines DWRs simulieren. Zudem wird detailliert auf das Flutverhalten des Heißstrangmodells eingegangen, welches bei speziellen Gegenstrombegrenzungsexperimenten untersucht wurde. Nicht zuletzt weisen verschiedene Vergleichsbeispiele zwischen Experiment und Simulation nach, welche Möglichkeiten die Daten für die Unterstützung der CFD-Entwicklung und Validierung bieten.

The optical synchronization of two passively mode-locked erbium fiber lasers in a master-slave geometry is presented. Both lasers were mode-locked via nonlinear polarization rotation and used a shared semiconductor saturable absorber mirror for synchronization. Tight synchronization and transfer of the repetition frequency stability were shown. The contributions of several physical mechanisms to the change in roundtrip time during synchronization are investigated by analyzing the change of different pulse parameters in synchronized state, including carrier envelope offset frequency and spectrum.

The NURISP project (Nuclear Reactor Integrated Simulation Project) is focused on the further development of the European NUclear REactor SIMulation (NURESIM) platform for advanced numerical reactor design and safety analysis tools. NURESIM is based on an open source platform – called SALOME – that offers flexible and powerful capabilities for pre- and post processing as well as for coupling of multi-physics and multi-scale solutions. The developments within the NURISP project are concentrated in the areas of reactors physics, thermal hydraulics, multi-physics, and sensitivity and uncertainty methodologies. The aim is to develop experimentally validated advanced simulation tools including capabilities for uncertainty and sensitivity quantification. A unique feature of NURESIM is the flexibility in selecting the solvers for the area of interest and the interpolation and mapping schemes according to the problem under consideration. The Sub Project 3 (SP3) of NURISP is focused on the development of multi-physics methodologies at different scales and covering different physical fields (neutronics, thermal hydraulics and pin mechanics). One of the objectives of SP3 is the development of multi-physics methodologies beyond the state-of-the-art for improved prediction of local safety margins and design at pin-by-pin scale. The Karlsruhe Institute of Technology (KIT) and the Research Center Dresden-Rossendorf (FZD) are involved in the integration of the reactor dynamics code DYN3D into the SALOME platform for coupling with a thermal hydraulic sub-channel code (FLICA4) at fuel assembly and pin level. In this paper, the main capabilities of the SALOME platform, the steps for the integration process of DYN3D as well as selected preliminary results obtained for the DYN3D/FLICA4 coupling are presented and discussed. Finally the next steps for the validation of the coupling scheme at fuel assembly and pin basis are given.

Semiconductor quantum posts (QPs) – nanowire-like InGaAs heterostructures [1] in a GaAs matrix – resemble many properties of regular self-assembled quantum dots (QDs), to which they are closely related. Due to their increased size as compared to QDs, QPs have proven to be suitable for very low threshold interband lasers [2]. However, their well controllable height makes them attractive for precise tuning of the interband energy spacing that in QDs can only be achieved via post-growth annealing. Specifically, the 1s – 2p transition energy is expected to drop below LO-phonon energies at post heights of more than 30 nm, making them attractive as frequency-agile structures at terahertz frequencies.
In the work presented here we explore the capture dynamics of QP structures after photoexcitation into the GaAs matrix. While the combined electron-hole dynamics are studied using time-resolved photoluminescence spectroscopy, optical pump - THz probe experiments were performed in order to solely study the electron dynamics. The results of the THz experiment show that after ultrafast excitation, electrons relax within a few picoseconds into the quantum posts, which act as efficient traps [3]. The saturation of the quantum post states, probed by photoluminescence, was reached at approximately ten times the quantum post density in the samples. Recently, we also studied the response of possible electronic resonances after direct photoexcitation into QPs where a broad absorption around 1.5 THz was observed.
[1] J. He et al., Nano Lett. 7, 802 (2007).
[3] D. Stehr et al. Appl. Phys. Lett. 95, 251105 (2009).

THz radiation in the range from 0.2 – 10 THz, generated by ultrafast lasers via optical rectification or highly excited dipole antennas typically consist of 0.5 to 2 cycles of light and therefore cover a broad frequency range. This makes these pulses ideal for broadband spectroscopic applications, where spectra can be acquired at the highest possible time-resolution. For applications such as free space imaging or intense driving of a specific resonance, such THz pulses are less useful due to water absorption and quantitative studies become difficult. In these cases narrowband sources such as Free-Electron Lasers proved to be the ideal light source, as well as cw-sources (e.g. quantum cascade lasers) and photomixers for imaging. However, utilizing the broad spectra of ultrafast lasers, one technique to generate narrowband THz radiation is based on mixing two time- delayed linearly chirped pulses in a nonlinear media: Narrowband, tunable THz pulses up to 780 GHz were successfully generated in a dipole antenna [1] via a fast oscillating current induced by the beat frequency of the mixed laser pulses. Higher frequency pulses were recently demonstrated in ZnTe, where a second order process is utilized [2]. In this work we show that an Auston-switch based emitter concept can serve as a high frequency emitter for narrowband THz pulses. We use our recently introduced concept of a large area emitter with interdigitated electrodes, based on low-temperature grown and semi-insulating substrates. The two pulses for THz generation as well as the probe pulses for electro-optic sampling were taken from a 250 kHz regenerative Ti:sapphire amplifier, whose output was positively chirped to a pulse duration of 3.3 ps. These pulses were split into three beams, where one, undergoing compression in a grating compressor, serves as the probe pulse for field-resolved detection. The other two pulses are sent – with an adjustable optical delay in one of the arms – to a combining beamsplitter and to the THz emitter. The beat frequency – set by the delay in the interferometer – now controls the emission frequency of the emitter, while the length of the input pulse gives the spectral width. The normalized spectra of the pulses for different delays are presented in Fig. 1 and show a frequency coverage from 0.35 to 2.3 THz. All spectra have a spectral width (FWHM) of about 200 GHz which could be further reduced by employing longer driving pulses. Fig. 2 demonstrates the excellent tuning behavior of the emitter, which is perfectly linear with the given time-delay (black dots). The maximum power is obtained around 1 THz and steeply drops towards higher frequencies (red dots) and resembles the power distribution of the emitter excited with a single 50 fs pulse.
[1] A. S. Weling and D. H. Auston, J. Opt. Soc. Am. B 13, 2783 (1996). [2] J. R. Danielson et al., J. Appl. Phys. 104, 033111 (2008).

Driving a two-level system with intense light can lead to non-perturbative phenomena like Rabi oscillations. The frequency-domain equivalent is the Autler-Townes or AC Stark effect where dressed light-matter states of a resonantly driven two-level scheme occur. Known from molecular spectroscopy [1] the effect exhibits an absorption line splitting whose magnitude is proportional to the field strength, whereas the symmetry of the splitting depends on the detuning from the resonance case. For atomic or molecular resonances the line widths are much smaller compared to solid state systems like semiconductors, making it much easier to observe the effect in the first case. While only recently the effect has been investigated in quantum well intersubband transitions [2, 3], we present strong evidence for the THz induced intraexciton AC Stark effect using the hydrogen-like 1s and 2p levels of the quantum well heavy-hole exciton [4]. Despite its similarity to the hydrogen problem (except the energy is scaled down by a factor of 1000) we can reach a regime where the Keldysh parameter is comparable to the transition energy and the Rabi energy, a regime not easily accessible for atomic systems.In the experiment an undoped GaAs/AlGaAs multiple quantum well (substrate etched away) is illuminated under normal incidence with intense THz pulses from the Dresden Free-Electron Laser FELBE. At the same time we probe the low-temperature transmission with a broadband femtosecond laser. Tuning the THz photon energy around the measured 1s-2p resonance energy of 9 meV (at 3 meV line width) we observe characteristic absorption changes at the hh(1s) exciton line (see Fig. 1). Below resonance (6.1 meV) an additional high-energy peak or Rabi sideband occurs, while above resonance (14 meV) a low-frequency shoulder is seen. On resonance we have a nearly symmetric splitting. From the two-line fit of Fig. 1 we find an anticrossing for various THz photon energies around the undriven exciton line (marked as dashed vertical line). Moreover, with increasing THz field strength the splitting on resonance increases linearly up to a field of 10 kV/cm with a Rabi energy as large as 60% of the resonance energy. We explain our findings qualitatively on the basis of a simple two-level model, though the underlying rotating-wave approximation breaks down in this regime. Observed deviations would have to be addressed within a full many-body theory. Shifting the NIR probe pulses in time with respect to the THz pulses has been found to change the transmission adiabatically on a time scale of several picoseconds only during the THz pulse. In connection with the observed up to 20-fold transmission change at the hh(1s) exciton, this temporal behavior promises ultrafast optical modulation based on the AC Stark effect.
In conclusion, our experimental data provides the first unambiguous evidence for the intraexciton Autler-Townes effect with its characteristic intensity-dependent line splitting on resonance and its frequency-dependent anticrossing behavior.

[1] S. H. Autler and C. H. Townes, Phys. Rev. 100, 703 (1955).
[2] S. G. Carter et al., Science 310, 651 (2005).
[3] J. F. Dynes et al., Phys. Rev. Lett. 94, 157403 (2005).
[4] M. Wagner et al., Phys. Rev. Lett. 105, 167401 (2010).

Over the last decade, the optoelectronic properties of self-assembled semiconductor quantum dots (QDs) have been studied intensely. Quantum dots confine carriers in the conduction and valence band three dimensionally, acting as artificial atoms with energy levels that are tunable based on the dot’s geometry and material parameters. We have recently introduced a novel quantum dot based nanostructure grown by molecular beam epitaxy [1] called the quantum post (QP). These structures - whose height can be controlled with nanometer precision - form short cylindrical structures (average composition In.4Ga.6As) aligned along the growth direction. The QPs are embedded in an In.1Ga.9As quantum well (QW) of the same height as the QPs. The three dimensional confinement of the post structures produces quantized states. The energies of these states relative to the Fermi level of the structure are strongly dependent on the amount of charge in the QPs. This strong dependence is due to the similarity of the electron-electron Coulomb repulsion energies in the QPs and the spacing between their electronic states (~10 meV).
Here we report absorption from electrons transitioning from three dimensionally confined QP states to one dimensionally confined states of the two dimensional electron gas in the surrounding QW. For the absorption experiments, a single QP layer was embedded between an n-doped back- gate and a Schottky-contact, allowing for controllable loading of electrons into the QPs and surrounding quantum well. The electronic loading behavior was studied by capacitance- voltage spectroscopy, which shows distinct loading-features of electrons into the QPs and the QW. The absorption measurements were performed at a voltage where the posts are completely filled (~6 electrons per post) and the well is filled to a sheet charge density of ~2.4x1011/cm². Absorption measurements were taken in an FTIR with the THz light polarized parallel to the growth direction to couple only to states arising from vertical confinement. Comparison of spectra from a sample containing quantum posts and a reference quantum well sample show an absorption feature due to the QPs entirely absent in the QW sample.
Temperature dependent absorption measurements show that this absorption is due to a transition that begins in the QP. Using 8 band k.p calculations of post and well energies as a function of the number of electrons in the posts, the absorption is determined to be from an ionizing transition from the posts to the well. The highest filled state in the posts absorbs a terahertz photon, making a transition to a weakly bound unfilled post state ~20 meV higher. From this state, the electron quickly scatters into the quantum well matrix. The Coulomb repulsion of the QP electrons locally depopulates the quantum well states, leaving open states for the electrons to scatter into despite the well’s large average charge density. These results represent a promising structure for investigation of Coulomb blockade physics, as well as the physics of ionizing transitions that occur when Coulomb effects are on the same energy scale as the ionizing transition, a regime only accessible in these artificial atom systems. Additionally, these ionizing transitions hold promise for use in terahertz infrared photodetectors with their three dimensional confinement giving reduced sensitivity to temperature compared to their quantum well based equivalents.
This work is supported by the NSF NIRT grant No. CCF 0507295 and the Alexander von Humboldt Foundation.
References [1] Krenner, H. J. & Petroff, P. M., Sol. St. Comm. 149, 1386 (2009).

Semiconductor heterostructures are attractive for investigating intense light-matter interactions since the quantum energy levels and effective masses can be engineered at the growth stage, while the dimensionality of the system can be uniquely controlled by quantum confinement. With intense electromagnetic fields tuned resonantly to a two-level quantum transition, Autler and Townes found that absorption of a weak probe from a third state split into two symmetric peaks. Autler-Townes splitting has been studied in atomic and molecular systems for decades but has only recently been observed in the solid state in low dimensional semiconductors and in superconducting quantum systems. In semiconductors, effects such as Coulomb interactions between electrons and holes offer an interesting deviation from effects in atomic systems.
The Autler-Townes effect in a three-level system can be exactly calculated within the rotating wave approximation (RWA). In this model, the splitting in the absorption spectrum is symmetric when the driving frequency ωTHz is resonant with the transition frequency ω2-1. With a non-resonant driving frequency, the symmetry of the absorption spectrum is broken and the relative peak amplitudes are determined by the detuning, ωTHz - ω2-1. A positive (negative) detuning results in a larger (smaller) peak at higher energy. In the RWA model, ω2-1 is independent of the strength of the driving field.
The effect of abandoning the RWA was first studied by Bloch and Siegert in a two-level system. They found a blue shift to the energy of the two-level system ħω2-1 with increasing EM field amplitude. As the E-M field amplitude is increased in the three-level system, the amplitude of the higher energy Autler-Townes peak will decrease as a result of the Bloch-Siegert blue shift. A systematic investigation of Autler-Townes splitting for several quantum well systems demonstrated that the amplitude of the peak at higher energy increases with increasing terahertz intensity, indicating a red shift of the two-level transition energy ω2-1. At first sight this reverse Bloch-Siegert shift is a complete surprise. Only by solving a full four-subband semiconductor Bloch model outside the RWA are we able to achieve theoretical results that are in good agreement with experiment (Figure 1).We have observed large red shifts - exceeding 12% of the transition energy - in THz driven quantum wells. A non-RWA four subband model based on the full semiconductor Bloch equations including Coulomb effects was developed and calculations are shown to have excellent agreement with experimental data. We demonstrate that terahertz-driven quantum wells are an ideal system to investigate strong light-matter interactions on a quantitative level and to controllably explore the regime outside the three-level model and beyond the RWA.

Mostly common for THz spectroscopy systems is the use of a single ultrafast laser where the original laser beam is split into a part for THz generation and a part for probing. The latter can be mechanically delayed in time to sample the electric field of the THz pulses which is usually realized by a motorized translation stage. An alternative to this approach is the use of fast-scanning devices such as loudspeaker membranes or spring- loaded stages that can achieve scan rates of 10-30 Hz, barely reaching video-rate operation. However, having two synchronized lasers with high timing precision available, it is possible to overcome this mechanical limit. With the technique called asynchronous optical sampling (ASOPS), where one laser has a constant offset in the repletion rate, it was shown that kHz scan rates are possible [1], enabling high speed THz spectroscopy.
Here we demonstrate the operation of a robust and true turnkey fiber-laser based ASOPS system that is used for THz spectroscopy. The laser system consists of two amplified Er-doped fiber lasers (TWIN M-Fiber A, Menlo Systems), emitting 80 fs pulses centered at 1550 nm at a repetition rate fREP of 250 MHz. The repetition rates of both lasers are frequency stabilized and a frequency synthesizer can add an adjustable (1 Hz- 10 kHz) frequency offset Δf to Laser A for ASOPS operation. In ASOPS operation, the entire time between adjacent pulses (1/fREP=4 ns) is scanned during the inverse of the offset frequency, a fact that often has been criticized as for THz spectroscopy usually only a few tens of picoseconds are needed. To circumvent this, the technique called electronically controlled optical sampling (ECOPS) has been proposed: here, both lasers are set to the same repetition rate and one of the laser’s phase relative to the timing stabilization gets modified. By this, a smaller time-window can be selected and electronically sampled.
For efficient THz generation, we excite an interdigitated large-area photoconductive antenna (PCA) with the second harmonic output of one of the lasers and employ electro-optic sampling in a 500 μm thick <110> ZnTe crystal for detection. The result of a single ECOPS scan at a rate of 2.5 kHz is presented in Fig. 1 and shows a signal-to-noise ratio of the electric field of greater than 50. When averaging is applied, the noise floor drops (Fig. 2, solid line) and the dynamic range reaches 50 dB. To compare the ASOPS with the ECOPS technique, the spectrum of an ASOPS scan with identical acquisition time (Δf=2.5 kHz, 1000 averages) is shown as the dashed line. It can be seen that ECOPS reaches a higher signal-to-noise ratio in this case. Also shown in Fig. 2 is the amplitude spectrum of a 680 μm thick DAST crystal excited at 1550 nm as the dotted curve. It demonstrates that using the fundamental wavelength of the lasers can actually enhance the accessible frequency range, a feature only available for fiber-laser based systems.
[1] A. Bartels et al., Rev. Sci. Instrum. 78, 35107 (2007).

“Quantum posts” are roughly-cylindrical semiconductor nanostructures that are embedded in an energetically shallower “matrix” quantum well of comparable thickness. We report measurements of voltage-controlled charging and THz absorption of 30 nm thick InGaAs quantum wells and posts. Under flat-band (zero-electric field) conditions, the quantum posts each contain ~6 electrons, and an additional ~2.4x1011 cm^-2 electrons populate the quantum well matrix. In this regime, absorption spectra show peaks at 3.5 and 4.8 THz (14 and 19 meV) whose relative amplitude depends strongly on temperature. These peaks are assigned to intersubband transitions of electrons in the quantum well matrix. A third, broader feature has a temperature-independent amplitude and is assigned to an absorption involving quantum posts. Eight-band k·p calculations incorporating the effects of strain and Coulomb repulsion predict that the electrons in the posts strongly repel the electrons in the quantum well matrix, “perforating” the electron gas. The strongest calculated transition, which has a frequency close to the center of the quantum post-related absorption at 5 THz (20 meV), is an ionizing transition from a filled state to a quasi-bound state that can easily scatter to empty states in the quantum well matrix.

We investigate the near infrared interband absorption of semiconductor quantum wells driven by intense terahertz (THz) radiation in the regime of ultrastrong coupling, where the Rabi frequency is a significant fraction of the frequency of the strongly driven transition. With the driving frequency tuned just below the lowest frequency transition between valence subbands, a particularly interesting phenomenon is observed. As the THz power increases, a new peak emerges above the frequency of the undriven exciton peak, which grows and eventually becomes the larger of the two. This reversal of relative peak intensity is inconsistent with the Autler–Townes effect in a three-state system while within the rotating wave approximation (RWA). In the samples investigated, the Bloch–Siegert shift (associated with abandoning the RWA), exciton binding energy, the Rabi energy, and non-resonant ac Stark effects are all of comparable magnitude. Solution of a semiconductor Bloch model with one conduction and multiple valence subbands indicates that the ac Stark effect is predominantly responsible for the observed phenomenon.

The safe and reliable operation of liquid metal systems requires corresponding measuring systems and control units, both for the liquid metal single-phase flow as well as for bubble-laden liquid metal two-phase flows. However, velocity measurements in opaque liquid metal flows still represent a challenging task as commercial measuring systems are not available for such fluids.
The paper reports on established methods and new developments in the field of measuring techniques for liquid metal flows. The presentation is focussed on measurements of the flow rate and the local velocity field as well as on the characterization of liquid metal two-phase flows. During the last two decades considerable effort was spent by miscellaneous researcher groups to provide new solutions for measurements of flow fields in liquid metals. This paper intends to summarize different approaches and tempts to account on perspectives, particularly in view of some recent developments (ultrasonic techniques, magnetic tomography).

A first international ³⁶Cl interlaboratory comparison has been initiated. Evaluation of the final results of the eight participating accelerator mass spectrometry (AMS) laboratories on three synthetic AgCl samples with ³⁶Cl/Cl ratios at the 10^-11, 10^-12, and 10^-13 level shows no difference in the sense of simple statistical significance. However, more detailed statistical analyses demonstrate certain interlaboratory bias and underestimation of uncertainties by some laboratories. Subsequent remeasurement and reanalysis of the data from some AMS facilities, the round-robin data indicates that ³⁶Cl/Cl data from two individual AMS laboratories can differ by up to 17%. Thus, the demand for further work on harmonising the ³⁶Cl-system on a world-wide scale and enlarging the improvement of measurements is obvious.

The solubility and environmental mobility of the actinides under reducing conditions is a widely discussed issue. Tetravalent actinides show a strong tendency towards hydrolysis followed by the formation of oligomers and colloids. However, An(IV) oxohydroxide colloids easily precipitate already at low pH values. We found that silica is able to stabilize such colloids at neutral pH through modification of the inner structure and by influencing the surface charge [1]. The internal structure of the particles can be characterized by An-O(H)-Si bonds that replace the An-O(H)-An bonds of the oxyhydroxide structure. The structure and the formation process were investigated with EXAFS, LIBD, XPS, HEXS, UV-Vis and NMR. The results suggest that the assessment of actinide behaviour in the aquatic environment should take the possible existence of An(IV)-silica colloids into consideration.

es hat kein Abstract vorgelegen!

We report on semiclassical angle-dependent magnetoresistance oscillations and the Shubnikov–de Haas effect in the electron-overdoped cuprate superconductor Nd_2-xCe_xCuO₄. Our data provide convincing evidence for magnetic breakdown in the system. This shows that a reconstructed multiply connected Fermi surface persists, at least at strong magnetic fields, up to the highest doping level of the superconducting regime.

We have measured the complex dynamical conductivity, sigma = sigma₁+i sigma₂, of superconducting Ba(Fe_0.9Co_0.1)₂As₂ (T_c = 22 K) at terahertz frequencies and temperatures 2–30 K. In the frequency dependence of sigma₁ below T_c, we observe clear signatures of the superconducting energy gap opening. The temperature dependence of sigma₁ demonstrates a pronounced coherence peak at frequencies below 15 cm⁻¹ (1.8 meV). The temperature dependence of the penetration depth, calculated from sigma₂, shows power-law behavior at the lowest temperatures. Analysis of the conductivity data with a two-gap model, gives the smaller isotropic s-wave gap of Delta_A = 3 meV, while the larger gap is highly anisotropic with possible nodes and its rms amplitude is Delta₀ = 8 meV. Overall, our results are consistent with a two-band superconductor with an s± gap symmetry.

We present magnetic-torque experiments on the organic superconductor κ-(BEDT-TTF)₂Cu(NCS)₂ for magnetic fields applied parallel to the 2D superconducting layers. The experiments show a crossover from a second-order to a first-order transition when the upper critical field reaches 21 T. Beyond this field, which we interpret as the Pauli limit for superconductivity, the upper critical field line shows a pronounced upturn and a phase transition line separates the superconducting state into a low- and a high-field phase. We interpret the data in the framework of a Fulde–Ferrell–Larkin–Ovchinnikov state.

Uranium (U) as a redox-active heavy metal can cause various redox imbalances in plant cells. Measurements of the cellular glutathione/glutathione disulfide (GSH/GSSG) by HPLC after cellular U contact revealed an interference with this essential redox couple. The GSH content remained unaffected by 10 µM U whereas the GSSG level immediately increased. In contrast, higher U concentrations (50 µM) drastically raised both forms. Using the Nernst equation, it was possible to calculate the half-cell reduction potential of 2GSH/GSSG. In case of lower U contents the cellular redox environment shifted towards more oxidizing conditions whereas the opposite effect was obtained by higher U contents. This indicates that U contact causes a consumption of reduced redox equivalents such as GSH, NAD(P)H. Artificial depletion of GSH by chlorodinitrobenzene and measuring the cellular reducing capacity by tetrazolium salt reduction underlined the strong requirement of reduced redox equivalents.
An additional element of cellular U detoxification mechanisms is the complex formation between the heavy metal and carboxylic functionalities of GSH. Because two GSH molecules catalyze electron transfers each with one electron forming a dimer (GSSG) two UO₂ ²⁺ are reduced to each UO₂ ⁺ by unbound redox sensitive sulfhydryl moieties. UO₂ ⁺ subsequently disproportionates to UO₂ ²⁺ and U⁴⁺. This explains that in-vitro experiments revealed a reduction to U(IV) of only around 33 % of initial U(VI). Cellular U(IV) was transiently detected with the highest level after 2 hours of U contact. Hence, it can be proposed that these reducing processes are an important element of defense reactions induced by this heavy metal.

The influence of a steady magnetic field on the spatio-temporal structure of the mold flow in a physical model of the continuous casting process is studied. The velocity field is measured by an array of ultrasound sensors. The application of the magnetic field provokes a strong recirculation flow at the upper part of the nozzle outlet. The inclination of the jet becomes flatter, and its up- and downturn leads to large scale oscillations of the local velocity.

A new analytical method is described to deal with the Leakage Environmental Effect. The method is based on the analytical solution of the two group diffusion equation for two adjacent fuel elements. The quality of the results for this highly efficient method is demonstrated on a homogeneous test case and on a heterogeneous combination of two fuel elements described in the PWR MOX/UO2 CORE TRANSIENT BENCHMARK.

The scattering of temporally shaped intense laser pulses off electrons is discussed by means of manifestly covariant quantum electrodynamics. We employ a framework based on Volkov states with a time dependent laser envelope in light-cone coordinates within the Furry picture. An expression for the cross section is constructed unambiguously with respect to the pulse length. A broad distribution of scatted photons with a rich pattern of subpeaks like that obtained in Thomson scattering is found. These broad peaks may overlap at sufficiently high laser intensity, rendering inappropriate the notion of individual harmonics. The limit of monochromatic plane waves as well as the classical limit of Thomson scattering are discussed. As a main result, a scaling law is presented connecting the Thomson limit with the general result for arbitrary kinematics. In the overlapping regions of the spectral density, the classical and quantum calculations give different results, even in the Thomson limit. Thus, a phase space region is identified where the differential photon distribution is strongly modified by quantum effects.

We discuss the progress of the prototyping effort for an MRPC-based solution for the NeuLAND detector for 1 GeV neutrons at FAIR.

Due to the suppression by the Coulomb barrier, the cross sections of astrophysically relevant nuclear reactions are very low at the stellar energy. Therefore they can only be directly measured in a low-background environment. For more than a decade now, the LUNA collaboration has pursued this approach with a 0.4 MV accelerator in the Gran Sasso underground laboratory in Italy. It was highly successful in studying the nuclear physics of the Sun and of the Big Bang.

However, the energy range of LUNA is not sufficient to address the nuclear reactions of stellar helium and carbon burning and the neutron source reactions for the astrophysical s-process. Therefore, in the 2010 NuPECC Long Range Plan for nuclear physics in Europe, it is recommended to install one or more accelerators with higher energy underground.

I will discuss the feasibility and science program of a possible accelerator to be placed in the Felsenkeller underground facility in Dresden/Germany

Due to the suppression by the Coulomb barrier, the cross sections of astrophysically relevant nuclear reactions are very low at the stellar energy. Therefore they can only be directly measured in a low-background environment. For more than a decade now, the LUNA collaboration has pursued this approach with a 0.4 MV accelerator in the Gran Sasso underground laboratory in Italy. It was highly successful in studying the nuclear physics of the Sun and of the Big Bang.

However, the energy range of LUNA is not sufficient to address the nuclear reactions of stellar helium and carbon burning and the neutron source reactions for the astrophysical s-process. Therefore, in the 2010 NuPECC Long Range Plan for nuclear physics in Europe, it is recommended to install one or more accelerators with higher energy underground.

I will discuss the methodology and main results of LUNA, and then review projects for new accelerators that are under discussion in Italy (Gran Sasso), Spain (Canfranc), Britain (Boulby), and recently also in Germany (Felsenkeller). Analogous efforts are being made in the US (DUSEL).

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Objectives:

Post mortem studies have shown a degeneration of cholinergic neurons in the brain of AD-patients. Further evidence suggests that the loss of nAChRs is a major contributor to the cognitive deterioration in AD, whereby the alpha4beta2-nAChR subtype is thought to be the most severely reduced in the onset of AD. Using 2-[18F]F-A85380 PET we showed a significant decline in alpha4beta2-nAChRs in early AD-patients which correlated significantly with the loss of cognitive function (1, 2). However, this tracer was not well suited as a biomarker in a routine clinical set-up for early AD-diagnosis because of unfavourable properties (slow kinetics, long acquisition times up to 7 hours, limited alpha4beta2-receptor selectivity). We, therefore, developed the new radiotracer [18F]NCFHEB (epibatidine derivative without toxicity in humans) with significantly improved brain uptake, nAChR affinity and selectivity (3). Here, we present the results of the worldwide first ongoing NCFHEB-PET study in humans.
Methods:
6 mild AD-patients (NINCDS-ADRDA, age 76.7±5.9, MMSE 23.8±3.0) and 5 age-matched healthy controls (HC, age 71.1±5.3, MMSE 28.4±1.1) underwent NCFHEB-PET (370 MBq, 3D-acquisition, ECAT Exact HR+). All were nonsmokers and naïve for central acting medication. In each subject, 4 scans (41 frames) were acquired from 0-270 min post injection and motion correction was performed with SPM2. Kinetic modelling was applied to the VOI-based tissue-activity curves generated for 29 brain regions (irregularly anatomically defined via MRI co-registration) using a one tissue compartment model with measured arterial input-function. Total distribution volume (DV) and binding potential (BP, reference region: corpus callosum) werde used to characterize specific binding. Additionally, parametric images of DV were computed (Logan plot).
Results:
Image quality of NCFHEB scans was clearly superior to 2-[18F]F-A85380, and a 20 minutes scan already adequate for visual analysis. All 29 regions were well described with one tissue compartment. PET data acquired over only 90 minutes were sufficient to estimate all kinetic parameters precisely indicating a fast receptor binding kinetic (much faster than for 2-[18F]F-A85380). DVs in HCs increase as expected with receptor density: Corpus callosum (DV: 4.81±0.32), posterior cingulate (8.92±0.66), temporal (9.03±0.44), pons (11.00±1.19), thalamus (24.32±2.96). The AD-patients showed extensive BP reductions in frontal, parietal, temporal, anterior and posterior cingulated cortices, caudate, and hippocampus (all p<0.05) compared to HCs.
Conclusions:
Due to the significant shorter acquisition time and superior image quality NCFHEB appears to be a much more valuable tracer than 2-[18F]F-A85380 to image alpha4beta2-nAChRs in humans. Early AD-patients show significant declines of alpha4beta2-nAChRs in brain regions typically affected by AD-pathology. These results indicate that NCFHEB-PET has a great potential to be tested as a biomarker for early AD-diagnosis.
References:
1. O. Sabri,..P. Brust: Acetylcholine receptors in dementia and mild cognitive impairment. Eur J Nucl Med Mol Imaging 2008; 35 (Suppl. 1): 30-45.
2. K. Kenziorra,..O. Sabri: Decreased cerebral α4β2 nicotinic acetylcholine receptors in living patients with mild cognitive impairment and Alzheimer disease with positron emission tomography.
Eur J Nucl Med Mol Imaging 2010; DOI 10.1007/s00259-010-1644-5.
3. P. Brust,..O. Sabri: In-vivo measurement of nicotinic acetylcholine receptors with [18F]norchloro-fluoro-homoepibatidine (NCFHEB). Synapse 2008; 62: 205-218.

The electroluminescence properties of rare earth–doped SiO2 layers are known to deteriorate markedly at room temperature due to rare earth clustering. The key challenge is therefore to probe ongoing processes at microscopic level and the subsequent impact on the optical response with increasing rare earth concentration. Positron annihilation spectroscopy, especially Doppler Broadening Spectroscopy, was applied in order to clarify the structural changes in Ge and Er doped SiO2 layers in dependence on the Er concentration. The obtained results will be compared with Transmission Electron Microscopy investigations and with conclusions in recently published papers. Finally, an outlook about future applications of luminescent SiO2 will be given.

Granite is the aspired potential host rock material for future nuclear waste storage in Sweden. The Äspö Hard Rock Laboratory (Äspö HRL) today is an interdisciplinary research facility for geological disposal in granite rock. The research within the Äspö HRL programme involves international cooperation with various countries including Germany.
This presentation drafts the operations done at Äspö and the contribution by the IRC. Here the objectives and results of the study on the interaction of uranium(VI) with Pseudomonas fluorescens, a strain that has been isolated at the Äspö site, are presented. Explicitly results about the accumulation capability of the strain and TRLFS investigations are shown.

The increase of integration density in modern nano-electronics demands the shrinking of device dimensions in lateral directions as well as in depth. Ultra-shallow p-n junctions in semiconducting materials are vital for this technology [1].
Low-energy ion implantation is a feasible way to incorporate dopant elements such as boron, phosphorous or antimony in the near-surface region of the substrate material. Characterisation of these implants, especially the depth profile of the implant, is important for evaluating the specific process parameters. However, there are not many analysis techniques that can provide depth profiles of nanometre resolution at the very surface of a sample. Secondary Ion Mass Spectrometry (SIMS) is a well established technique for such measurements, but in the near-surface region SIMS encounters problems due to the so-called transient effects, which distort the measured atomic concentrations in that area. [2]. Therefore, complementary techniques capable of providing accurate depth profiles in the upper few nanometres are required.
High depth resolution Elastic Recoil Detection (ERD) is able to provide these depth profiles. ERD in conjunction with a magnetic spectrometer for high depth resolution (setup developed at HZDR, see. Fig. 1) has been performed to evaluate boron implant profiles in silicon for different implantation parameters [3]. Experimental conditions have been optimised to minimise sample damage while measuring. Boron recoil ions are detected using 6.5 MeV chlorine ions. Under those conditions no beam damage could be detected during measurement. Undistorted near-surface depth profiles of the boron implants can be reconstructed.
Acknowledgments: We thank B. Beckhoff (PTB Berlin) for providing the samples and W. Möller for very helpful discussions.

[1] L. Shao, J.R. Liu, Q.Y. Chen, W.K. Chu, Materials Science & Engineering R-Reports 42 (2003) 65-114.
[2] D. Avau,W. Vandervorst, H.E. Maes, Surf. Interf. Anal. 11 (1988) 522–528.
[3] P. Hönicke, B. Beckhoff, M. Kolbe et al., Anal. Bioanal. Chemistry 396 (2010) 2825-2832.

The implementation of an Fe buffer layer is a promising way to obtain epitaxial growth of Co-doped BaFe2As2 (Ba-122). However, the crystalline quality and the superconducting properties of Co-doped Ba-122 are influenced by the Fe buffer layer thickness, d(Fe). The well-textured growth of the Fe/Ba-122 bilayer with d(Fe) = 15 nm results in a high J(c) of 0.45 MA cm(-2) at 12 K in self-field, whereas a low J(c) value of 61 000 A cm(-2) is recorded for the bilayer with d(Fe) = 4 nm at the corresponding reduced temperature due to the presence of grain boundaries. (C) 2010 American Institute of Physics. [doi:10.1063/1.3509418]

Lateral patterning of thin ferromagnetic films allows the modification of the magnetic parameters below certain intrinsic magnetic length scales like the domain wall width. In contrast to the creation of isolated micro- and nanostructures, magnetic patterning by means of local ion irradiation results in direct exchanged coupled regions in the thin film, which have different magnetic properties. At the lateral interfaces of these regions magnetic domain walls can be trapped and thus easily investigated. The modification of the material properties, e.g. saturation magnetization and magnetic anisotropy, also directly affects the intrinsic length scales. As a model system periodic patterns of Ni80Fe20 stripes with alternating saturation magnetization value located either inside a Ni80Fe20 matrix or isolated are used. During the magnetic reversal with the external field parallel to the stripes, magnetic domain walls are created between adjacent stripes due to a noneparallel alignment of the stripe’s magnetization
(Fig. 1). Fig. 1: Magnetization distribution in periodic pattern of 10 μm wide stripes with alternating saturation magnetization value. The magnetization directions are indicated by arrows. (Non-) irradiated regions with (unchanged) decreased saturation magnetization are indicated with (gray) white shaded areas at the bottom. The location of a 180° domain wall is indicated by the green rectangle. As the wall profile for stripe widths in the sub-μm regime is not easily accessible in experiment, changes of the possible orientations of the magnetization inside the stripes with respect to the stripe orientation are used to obtain informations about the domain walls. For special pattern configurations these domain walls are able to mediate an exchange spring behavior through the storage of energy [1]. By scaling the stripes width down, a crossing between the patterning size and the intrinsic length scales associated with the domain walls is expected. This is combined with a transformation to an effective magnetic medium, showing neither the properties of the fully irradiated nor the unirradiated material (so-called hybrid material). Local ion irradiation is accomplished by irradiation in combination with a lithographically defined mask or the by the use of a focused ion beam. For comparision the ion energies for both methods are choosen to be 30 keV. For a Ni80Fe20 film thickness of 20 nm the resulting penetration depths of the ions cover the complete film as well as the interface to the seed layer. In order to understand the ion irradiation induced changes in the magnetic parameters of the film, ions of different species (Ar+, Ga+, Cr+, Ni+, Co+, Si+, O+) as well as different seed layers are used. Changes of the magnetic and structural properties are studied as function of ion species, fluence and seed layer material. The uniaxial magnetic anisotropy of the Ni80Fe20 film is not affected by the implanted ion species, but by the species of the recoils originating from the seed layer. Using SiO2 as seed layer material, the anisotropy can be successively annihilated with increasing fluence. Irradiation using a Ga+ focused ion beam with its high current density induces a grain growth to the material [2], limiting therefore also the minimum patterning size (Fig. 2). Fig. 2: Bright field plane view TEM image of 200 nm wide stripes. The focused ion beam irradiated areas are observable by the increased grain size.
References: [1] McCord J. et al. Advanced Materials 20 (2008) 2090. [2] Ozkaya D.L. et al. Journal of Applied Physics 91 (2002) 9937.

Lateral patterning of thin magnetic films allows structuring on dimensions below certain intrinsic length scales like the domain wall width. By means of magnetic patterning using local ion irradiation periodic patterns of stripes with alternating saturation magnetization value were created in a ferromagnetic Ni80Fe20 matrix. The domain configuration during magnetization reversal was investigated using Kerr microscopy, scanning transmission x-ray microscopy, as well as Lorentz microscopy. The reversal mechanisms in the stripe panels are influenced by the domain configuration of the surrounding film. Starting from 1 um stripe width, changes in the micromagnetic behavior with respect to decreasing width are investigated. Special emphasis is put on the formation of 180∘ walls between adjacent stripes with different saturation magnetization, on the orientation of the magnetization inside the stripes with respect to the stripe axis orientation, as well as on the transition of the patterned material to an effective medium.

Ni-doped CdS thin films were prepared by 90 keV Ni⁺ implantation at room temperature. Ni-ion implantation induced modifications in structural, optical, and morphological properties are studied for a wide range of impurity concentrations (1.86–10.19 at.%). Addition of Ni⁺ ions does not lead to any structural phase transformation or formation of metallic clusters or secondary phase precipitates. However, it induces structural disorder leading to a reduction in the optical band gap from 2.39 to 2.28 eV following Ni implantation up to 3 × 10¹⁶ ions cm⁻². This is addressed on the basis of band tailing due to the creation of localized energy states and implantation induced grain growth. Moreover, Ni-doping is found to modify the luminescence properties by creating shallow acceptor states.