Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32337 Publications
Lift Forces on Solid Spherical Particles in Unbounded Flows
Shi, P.ORC; Rzehak, R.
The present work is concerned with the lift forces acting on particles immersed in an unbounded fluid. Both mechanisms due to rotation of the particle and vorticity of the fluid flow are considered. Focus is on solid spherical particles at Reynolds numbers up to 103 which are relevant for particulate flows in chemical and minerals engineering. A comprehensive review of existing results from analytical, numerical, and experimental studies is given. In particular in the simulation area many new data have appeared in the past 10 years since the earlier review of Loth [AIAA Journal 46 (2008), 801–809]. The available correlations are critically assessed by comparison to data from experiment and direct numerical simulation. Based on the comparison new correlations are proposed and gaps or inconsistencies in the data are identified. The case of wall-bounded flows will be considered in a sequel.
Keywords: lift force, particles, shear flow, particle rotation, correlation

Publ.-Id: 29402 - Permalink


Nanoscale n++-p junction formation in GeOI probed by tip-enhanced Raman spectroscopy and conductive atomic force microscopy
Prucnal, S.; Berencen, Y.; Wang, M.; Georgiev, Y.; Erbe, A.; Khan, M. B.; Böttger, R.; Hübner, R.; Schönherr, T.; Kalbacova, J.; Vines, L.; Facsko, S.ORC; Engler, M.; Zahn, D. R. T.; Knoch, J.; Helm, M.; Skorupa, W.; Zhou, S.ORC
Ge-on-Si and Ge-on-insulator (GeOI) are the most promising materials for the next-generation nanoelectronics that can be fully integrated with silicon technology. To this day, the fabrication of Ge-based transistors with a n-type channel doping above 5 × 1019 cm−3 remains challenging. Here, we report on n-type doping of Ge beyond the equilibrium solubility limit (ne ≈ 6 × 1020 cm−3) together with a nanoscale technique to inspect the dopant distribution in n++-p junctions in GeOI. The n++ layer in Ge is realized by P+ ion implantation followed by millisecond-flashlamp annealing. The electron concentration is found to be three times higher than the equilibrium solid solubility limit of P in Ge determined at 800 °C. The millisecond-flashlamp annealing process is used for the electrical activation of the implanted P dopant and to fully suppress its diffusion. The study of the P activation and distribution in implanted GeOI relies on the combination of Raman spectroscopy, conductive atomic force microscopy, and secondary ion mass spectrometry. The linear dependence between the Fano asymmetry parameter q and the active carrier concentration makes Raman spectroscopy a powerful tool to study the electrical properties of semiconductors.
We also demonstrate the high electrical activation efficiency together with the formation of ohmic contacts through Ni germanidation via a single-step flashlamp annealing process.
Keywords: GeOI, ion implantation, flash lamp annealing, doping, TERS

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  • Secondary publication expected from 28.06.2020

Publ.-Id: 29401 - Permalink


PIConGPU: Predictive Simulations of Laser-Particle Accelerators with Manycore Hardware
Huebl, A.ORC
The presented thesis establishes simulations on modern massively parallel computing hardware to investigate relativistic laser-driven plasmas. The latter are of special interest as they may provide a compact source for energetic ion beams. Computer simulations provide valuable insight into ultrafast plasma processes, evolving in the ultrahigh intensity (I0 ≫ 1018 W/cm2) focus of the ultrashort (𝜏0=30-500 fs) laser pulses driving the interaction. Such simulations require high numerical resolution and full geometric treatment for reliable predictions, which can only be addressed with high-performance computing. The open source particle-in-cell code PIConGPU, which is developed in the framework of this thesis, answers these demands, providing speed and scalability to run on the world's largest supercomputers. PIConGPU is designed with a modular and extensible implementation, allowing to compute on current and upcoming hardware from a single code base. Furthermore, challenges arising for generated data rates, reaching 1 PByte per simulation, are resolved with scalable data reduction techniques and novel workflows, such as interactive simulations.

Numerical studies are performed on two novel targets for laser-proton acceleration with near-critical and mass-limited properties. A micrometer-scale spherical target is explored with realistic temporal laser contrast, providing an interpretation for experimental results collected at the PW-class laser system PHELIX (𝜏0=500 fs pulse length). In this study, 3D modeling with the GPU supercomputer Titan enabled the identification of pre-expansion to near-critical target conditions, which uncovers a regime of volumetric laser-electron interaction generating a highly directed proton beam. Furthermore, a novel cryogenic hydrogen jet target is researched in close collaboration to experiments at the laser system DRACO (𝜏0=30 fs). This target system provides a unique setup for the isolated investigation of multi-species effects and their influence on the generated ion energy distribution. A novel analytical model provides a link between characteristic modulations in the ion energy spectra and ensemble properties of the microscopic electron distribution. In view of a potential experimental realization, parametric scans are performed confirming the feasibility of the proposed setup.
Keywords: laser-plasma acceleration, modeling, HPC, GPU, laser-ion acceleration, exascale computing, open source, open data
  • Doctoral thesis
    TU Dresden, 2019
    Mentor: Prof. Dr. Ulrich Schramm
    171 Seiten
    DOI: 10.5281/zenodo.3266820
  • Lecture (others)
    Dissertationsverteidigung, 25.06.2019, Dresden, Deutschland

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Publ.-Id: 29400 - Permalink


Joint project: Umwandlungsmechanismen in Bentonitbarrieren - Subproject B: Einfluss von mikrobiellen Prozessen auf die Bentonitumwandlung
Matschiavelli, N.; Drozdowski, J.; Kluge, S.; Arnold, T.; Cherkouk, A.ORC
Concerning the deep geological disposal of high-level radioactive waste (HLW), bentonite can be used because of its high swelling capacity and its low hydraulic conductivity as geo-technical barrier and buffering material in between the waste-containing canister (technical barrier) and the surrounding host rock (geological barrier). There are still many gaps in process understanding of bentonite transformations, especially in dependence of different temperatures and pore waters. Within the joint-project UMB (“Umwandlungsmechanismen in Bentonitbarrieren”), the co-operation partner Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH (Repository Safety Analysis), the University of Greifswald (Institute for Geography and Geology), the Federal Institute for Geosciences and Natural Resources (BGR, section of technical mineralogy), the Technical University of Munich (TUM; chair of theoretical chemistry, quantum chemistry) and the Helmholtz-Center Dresden-Rossendorf (HZDR, Institute of Resource Ecology) are supposed to define criteria which facilitate the selection of suitable bentonites in order to use them in the deep geological repository of high-level radioactive waste. HZDR analyzed two different bentonites (B36 and SD80) regarding their microbial diversity and potential microbial activity. In dependence of repository-relevant parameters (temperature, pore water, presence of substrates), microcosm experiments were set up at the GRS, containing the respective bentonites and Opalinus Clay pore water or cap rock solution, respectively. The long-term batches were incubated one year and two years at different temperatures (25 °C, 60 °C and 90 °C) in gastight bottles. Additionally, HZDR set up B36 short-term microcosms with Opalinus Clay pore water, which incubated for three month at 30 °C with six sampling points monitoring the microbial diversity and geochemical parameters.
After one and two years of incubation at 25 °C, respectively, supplemented SD80 microcosms containing Opalinus Clay pore water showed the formation of black precipitates and fissures as well as the dominance of sulfate-reducing and spore-forming bacteria. The detected genera are able to reduce the present sulfate in order to form hydrogen sulfide. XRF spectroscopy analysis, done at the University of Greifswald, showed a decrease in sulfate concentration in the respective SD80 microcosms, supporting this surveillance. Similar observations were made for the two-year incubations. The microbial diversity of the B36 bentonite raw material is much different from the SD80 bentonite raw material. Similar to the diversity of SD80 bentonite, the microbial community of the B36 bentonite long-term incubations changed with respect to the applied pore water. Spore-forming organisms dominated the set ups which were supplied with Opalinus Clay pore water solution whereas halophilic microorganisms were found in set ups containing diluted cap rock solution. We were also successful in showing the dominance of thermophilic bacteria in Opalinus clay pore water-containing microcosms that incubated at 60 °C for two years. Additionally, we were able to enrich microorganism from Opalinus Clay pore water of both, B36 and SD80 bentonite long-term incubations. Similar to the long-term analysis, substrate-containing B36 short-term microcosms, containing Opalinus Clay pore water, showed also the dominance of spore-forming bacteria after three months of incubation. Furthermore, a slight decrease in lactate-concentration as well as an increase in ferrous iron and acetate-concentration was observed in the respective B36 microcosms. The presence of substrates and mesophilic incubation temperatures of 25 °C or 30 °C, respectively, promoted the growth of “microbial generalists” that are able to exist in a vegetative state. Extreme environmental conditions as elevated temperatures (60 °C) or high-salt concentrations promote the dominance of highly specialized microorganisms. Our data show, that the microbial diversity in the analyzed bentonites and, furthermore, the evolution of the respective microbial communities differs significantly from each other. Since not that much is known about intrinsic extremophilic microorganisms (metabolic activity and potential influence on the bentonite barrier material), our data stress the importance of further microbial investigations in order to prevent and reduce potential risks (e.g. corrosion, mineralogical changes), due to microbial activity within the repository.
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-103 2019

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Publ.-Id: 29398 - Permalink


Making a cool choice: the materials library of magnetic refrigeration
Gottschall, T.ORC; Skokov, K. P.; Fries, M.; Taubel, A.; Radulov, I.; Scheibel, F.; Benke, D.; Riegg, S.; Gutfleisch, O.
The phase-down scenario of conventional refrigerants used in gas-vapor compressors and the demand for environmentally friendly and efficient cooling makes the search for alternative technologies more important than ever. Magnetic refrigeration utilizing the magnetocaloric effect of magnetic materials could be that alternative. However, there are still several challenges to be overcome before we have devices that are competitive with those based on the conventional gas-vapor technology. In this paper we present a rigorous assessment of the most relevant examples of 14 different magnetocaloric material families and compare them in terms of their adiabatic temperature and isothermal entropy change under cycling in magnetic-field changes of 1 and 2 T, criticality aspects and the amount of heat that they can transfer per cycle. The work is based on magnetic, direct thermometric and calorimetric measurements made under similar conditions and in the same devices. Such a wide-ranging study has not been carried out before. This data sets the basis for more advanced modelling and machine learning approaches in the near future.

Publ.-Id: 29397 - Permalink


Multiferroic spin-superfluid and spin-supersolid phases in MnCr2S4
Ruff, A.; Wang, Z.; Zherlitsyn, S.ORC; Wosnitza, J.; Krohns, S.; Krug Von Nidda, H.-A.; Lunkenheimer, P.; Tsurkan, V.; Loidl, A.
Spin supersolids and spin superfluids reveal complex canted spin structures with independent order of longitudinal and transverse spin components. This work addresses the question whether these exotic phases can lead to spin-driven ferroelectricity. Here we report the results of dielectric and pyrocurrent measurements of MnCr2S4 as function of temperature and magnetic field up to 60 T. This sulfide chromium spinel exhibits a Yafet-Kittel type spin structure at low temperatures. As function of external magnetic field, the manganese spins undergo a sequence of ordering patterns of the transverse and longitudinal spin components, which can be mapped onto phases as predicted by lattice-gas models including solid, liquid, super-fluid, and supersolid phases. By detailed dielectric and pyrocurrent measurements, we document a zoo of multiferroic phases with sizable ferroelectric polarization strongly varying from phase to phase. Using lattice-gas terminology, the title compound reveals multiferroic spin-superfluid and spin-supersolid phases, while the antiferromagnetic solid is paraelectric.

Publ.-Id: 29396 - Permalink


Biologische Wege zur Rohstoffsicherung – vom Nobelpreis zum Recycling
Lederer, F.ORC
Im Jahr 1985 entwickelte der Wissenschaftler George P. Smith eine Methode zur Identifizierung von kurzen Eiweißbruchstücken, die gezielt und selektiv ein Zielmaterial binden können. Für diese Methode der Evolution im Reagenzglas, welche auf der Verwendung von Bakteriophagen basiert, erhielt er im Jahr 2018 den Chemienobelpreis. Damals half ihm die Methode, Antikörper für bestimmte Krebszellen zu identifizieren. Die Wissenschaftler des Helmholtz-Instituts Freiberg für Ressourcentechnologie nutzen die Phage Surface Display genannte Methode für die Entwicklung hochspezifischer Bioangeln zum seletiven Recycling von Seltenen Erden aus Elektroschrott.
Keywords: Biotechnologie, Phage Surface Display, Bioangeln
  • Lecture (others)
    Lange Nacht der Wissenschaften 2019 in Dresden, 14.06.2019, Dresden, Deutschland

Publ.-Id: 29395 - Permalink


Metallgewinnung durch Mikrobiologie – Biologisch assistierte Prozesse in der Rohstofftechnologie
Lederer, F.ORC
Präsentation der Arbeitsbereiche Bioflotation, Biosorption und Biolaugung, die in der Abteilung Biotechnologie des HIF Schwerpunktmäßig untersucht werden. Vorstellung der Nachwuchsgruppe BioKollekt
Keywords: Phage Surface Display, BioKollekt, Bioflotation, Biolaugung, Biosorption
  • Lecture (others)
    Lehrveranstaltung Industrielle Mikrobiologie im Fachbereich Technische Mikrobiologie, 24.06.2019, Senftenberg, Deutschland

Publ.-Id: 29394 - Permalink


Fermi surface investigation of the semimetal TaAs2
Butcher, T.; Hornung, J.; Förster, T.; Uhlarz, M.; Klotz, J.; Sheikin, I.; Wosnitza, J.; Kaczorowski, D.;
The transversal magnetoresistance associated with the semimetal TaAs2 shows a parabolic field dependence that rises unrestrictedly to 2800 at 14 T and 1.8 K. Here, we report the results of a comprehensive quantum-oscillation study. Angular-dependent de Haas–van Alphen (dHvA) data were obtained with the method of cantilever-torque magnetometry. These were compared with the results of density-functional theory calculations, which predict a Fermi surface with two kinds of electron pockets, as well as two types of hole pockets. Only the electron pockets could be xperimentally verified, whereas no evidence for the hole pockets is present in the measured dHvA frequencies.

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Publ.-Id: 29393 - Permalink


Fermi surface studies of the skutterudite superconductors LaPt4Ge12 and PrPt4Ge12
Bergk, B.; Klotz, J.; Förster, T.; Gumeniuk, R.; Leithe-Jasper, A.; Lorenz, V.; Schnelle, W.; Nicklas, M.; Rosner, H.; Grin, Y.; Wosnitza, J.;
We report on comprehensive de Haas–van Alphen (dHvA) and electronic band-structure studies of the superconducting skutterudites LaPt4Ge12 (Tc = 8.3 K) and PrPt4Ge12 (Tc = 7.9 K). Both materials show very rich spectra of dHvA oscillations with similar and only slightly varying angular-dependent frequencies. The spectral richness can partly be rationalized by the elaborated electronic band structures resulting in several Fermi surfaces built by six different bands. The effective cyclotron masses of both superconductors lie between about 0.5 and 1.1 times the free-electron mass. Although these values are small, we find moderate mass enhancements between about 2 and 4 when comparing to the calculated masses. Our results evidence the localized character of the 4f electrons in the Pr compound and are in line with an electron-phonon mediated multiband superconductivity, largely identical for both compounds.

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Publ.-Id: 29392 - Permalink


Hole compensation effect in III-Mn-V dilute ferromagnetic semiconductors
Xu, C.ORC; Wang, M.ORC; Yuan, Y.; Larkin, G.; Helm, M.; Zhou, S.
A systematic study of hole compensation effect on magnetic properties, which is controlled by defect compensation through ion irradiation, in (Ga,Mn)As, (In,Mn)As and (Ga,Mn)P is represented in this work. In all materials, both Curie temperature and magnetization decrease upon increasing the hole compensation, confirming the description of hole mediated
erromagnetism according to the p -d Zener model. The material dependence of Curie temperature and magnetization versus hole compensation reveals that the manipulation of magnetic properties in III-Mn-V dilute ferromagnetic semiconductors by ion irradiation is strongly influenced by the energy level location of the produced defect relative to the band edges in
emiconductors.
Keywords: dilute ferromagnetic semiconductors, the Curie temperature, magnetization, compensation effect, ion irradiation

Publ.-Id: 29391 - Permalink


Presenting Non-Invasive and Fully Acceptable Exploration Technologies - The INFACT Project
Viezzoli, A.; Roffey, S.; Wijns, C.; Fernandez, I.; Blanco Gonzalez, J. M.;
Despite its rich history of mining and residual mineral wealth, current conditions within the EU present a number of social, political, legislative, cost, technical and physical obstacles to raw material exploration: obstacles to be overcome by innovation, dialogue, and reform. The Innovative, Non-invasive and Fully Acceptable Exploration Technologies (INFACT) project, within the Horizon 2020 program, will work to mitigate each and every one of these obstacles.
Specific to exploration geophysics, the project will facilitate the development of innovative airborne geophysical and remote sensing technologies (less-invasive than classical exploration methods) that promise to penetrate to new depths, reach new sensitivities and resolve new parameters. The project will also set the EU as a leader on the world stage by establishing permanent infrastructure (reference sites) to drive innovation in the next generation of exploration tools: tools that are cost-effective, designed for EU conditions and its raw materials strategy, and high-performing in terms of minimum environmental impact, social acceptability, and technical performance. These reference sites will provide long-term targets over which successive new technologies can be tested against previous ones.
  • Poster
    2nd Conference on Geophysics for Mineral Exploration and Mining, 09.-12.09.2018, Porto, Portugal
    DOI: 10.3997/2214-4609.201802752

Publ.-Id: 29390 - Permalink


Investigations on potential methods for the long-term monitoring of the state of fuel elements in dry storage casks: recent results
Hampel, U.ORC; Wagner, M.; Schmidt, S.; Fiß, D.; Reinicke, S.; Kratzsch, A.
Until a repository is available in deep geological formations, there is a need in Germany for the safe interim storage of spent fuel elements at the power plant sites. It is assumed that considerable periods of more than 50 years will have to be taken into account. Spent fuel elements are stored in Germany in transport and storage casks of the CASTOR type.
A material-scientific question currently being investigated in depth internationally concerns the long-term integrity of the fuel rod cladding tubes during dry storage and thus the safety during transport to the final repository and during secondary packaging. The absorption of hydrogen in the cladding tube during reactor operation leads to the precipitation of hydrides. If the cladding tube temperature increases during reloading or dry storage, a radial reorientation of the hydrides is conceivable due to the tangential stresses caused by the internal rod pressure. This type of hydride arrangement considerably reduces the brittle fracture toughness. A long-term cladding tube failure is conceivable due to a long-term increase in the internal rod pressure (production of gaseous fission products) and a long-term decrease in the cladding tube temperature (reduction of brittle fracture toughness).
Due to the existing uncertainties with regard to the concrete physical processes, the question arises as to the possibility of monitoring the cask contents. Invasive procedures, such as internal probes, are mainly ruled out for reasons of licensing. On the other hand, the massive construction of the containers with a wall thickness of at least 47 cm on all sides limits the spectrum of non-invasive testing and condition monitoring procedures that can be used. Within the DCS-Monitor project, four non-invasive measuring methods are investigated with regard to their suitability for the condition monitoring of the cask inventory by simulations and experiments. For this purpose, damage scenarios of the cask inventory were assumed in a CASTOR V/19, which were identified on the basis of investigations on damage mechanisms. In the following, the recent investigation results of the project are presented.
  • Contribution to proceedings
    3rd Workshop on Safety of Extended Dry Storage of Spent Nuclear Fuel, 05.-07.06.2019, Garching, Deutschland
  • Lecture (Conference)
    3rd Workshop on Safety of Extended Dry Storage of Spent Nuclear Fuel, 05.-07.06.2019, Garching, Deutschland

Publ.-Id: 29389 - Permalink


Phase Transition Induced Carrier Mass Enhancement in 2D Ruddlesden-Popper Perovskites
Baranowski, M.; Zelewski, S. J.; Kepenekian, M.; Traoré, B.; Urban, J. M.; Surrente, A.; Maude, D. K.; Kuc, A. B.ORC; Booker, E. P.; Stranks, S. D.; Plochocka, P.
The variety of possible ways to tune the optical properties of 2D perovskites is their huge advantage, while at the same time, the mutual dependence between different tuning parameters hinder our fundamental understanding of their properties. In this work, we attempt to address this issue for (CnH2n+1NH3)2PbI4 (with n=4,6,8,10,12) using optical spectroscopy in high magnetic fields up to 67T. Our experimental results, supported by DFT calculations, clearly demonstrate that the reduced mass of the exciton increases by around 30% in the low temperature phase. This is reflected by a 2-3 fold decrease of the diamagnetic coefficient. Our studies shows that the effective mass which is essential parameter for optolectronic device operation can be tuned by the variation of organic spacers and/or moderate cooling achievable using Peltier coolers. Moreover, we show that the complex absorption features visible in absorption/transmission specta track each other in magnetic field providing strong evidence for the phonon related nature of the observed side bands.

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  • Secondary publication expected from 04.09.2020

Publ.-Id: 29386 - Permalink


Tunable large field magnetoconductance of ZnO, ZnMnO, and ZnCoO thin films
Vegesna, S. V.; Bürger, D.; Patra, R. K.; Dellith, J.; Abendroth, B.; Skorupa, I.; Schmidt, O. G.; Schmidt, H.;
Magnetoconductivity of ten ZnO, Zn1-x Cox O, and Zn1-x MnxO thin films with nominal concentrations of 2.0 at.% and 0.1 at.% of Co2+ and Mn2+ ions, respectively, has been analyzed in the temperature range from 5 K to 200 K in in-plane and out-of-plane magnetic fields up to 6 T. The formation of a highly conducting surface layer can be controlled during thin film deposition, leading to a large variation of the sheet resistance, namely, from 2 × 103 ω /□ to 1 × 10 5 ω/□ at room temperature. Depending on the thickness of the highly conducting surface layer, a single two-dimensional (2D), a single three-dimensional (3D), or a two-dimensional and three-dimensional (2D + 3D) parallel conducting model was chosen to analyze the measured magnetoconductivity of the magnetic ZnO thin films with different electron spins (S = 5 / 2 for Zn 1 - x Mn x O and S = 3 / 2 for Zn1-x Cox O) and with different Landé g -factors (isotropic for 3D Zn1-x Mnx O and 2D Zn1-x Cox O and anisotropic for 2D Zn1-x Mnx O and 3D Zn1-x Cox O).

Publ.-Id: 29383 - Permalink


Fundamentals and Applications of Hybrid LWFA-PWFA
Hidding, B.; Beaton, A.; Boulton, L.; Corde, S.; Doepp, A.; Habib, F. A.; Heinemann, T.; Irman, A.ORC; Karsch, S.; Kirwan, G.; Knetsch, A.; Manahan, G. G.; Martinez De La Ossa, A.; Nutter, A.; Scherkl, P.; Schramm, U.ORC; Ullmann, D.
Fundamental similarities and differences between laser-driven plasma wakefield acceleration (LWFA) and particle-driven plasma wakefield acceleration (PWFA) are discussed.
The complementary features enable the conception and development of novel hybrid plasma accelerators, which allow previously not accessible compact solutions for high quality electron bunch generation and arising applications. Very high energy gains can be realized by electron beam drivers even in single stages because PWFA is practically dephasing-free and not diffraction-limited.
These electron driver beams for PWFA in turn can be produced in compact LWFA stages. In various hybrid approaches, these PWFA systems can be spiked with ionizing laser pulses to realize tunable and high-quality electron sources via optical density downramp injection (also known as plasma torch) or plasma photocathodes (also known as Trojan Horse) and via wakefield-induced injection (also known as WII). These hybrids can act as beam energy, brightness and quality transformers, and partially have built-in stabilizing features. They thus offer compact pathways towards beams with unprecedented emittance and brightness, which may have transformative impact for light sources and photon science applications. Furthermore, they allow the study of PWFA-specific challenges in compact setups in addition to large linac-based facilities, such as fundamental beam–plasma interaction physics, to develop novel diagnostics, and to develop contributions such as ultralow emittance test beams or other building blocks and schemes which support future plasma-based collider concepts.
Keywords: plasma physics; accelerators; electron beams; light sources; photon science

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Publ.-Id: 29382 - Permalink


Which transition metal atoms can be embedded into two-dimensional molybdenum dichalcogenides and add magnetism?
Karthikeyan, J.; Komsa, H.-P.; Batzill, M.; Krasheninnikov, A. V.ORC
As compared to bulk solids, large surface-to-volume ratio of two-dimensional (2D) materials may open new opportunities for post-synthesis introduction of impurities into these systems by, e.g., vapor deposition. However, it does not work for graphene or h-BN, as the dopant atoms prefer clustering on the surface of the material instead of getting integrated into the atomic network. Using extensive first-principles calculations, we show that counterintuitively most transition metal (TM) atoms can be embedded into the atomic network of the pristine molybdenum dichalcogenides (MoDCs) upon atom deposition at moderate temperatures either as interstitials or substitutional im- purities, especially in MoTe2, which has the largest spacing between the host atoms. We further demonstrate that many impurity configurations have localized magnetic moments. By analyzing the trends in energetics and values of the magnetic moments across the periodic table, we rationalize the results through the values of TM atomic radii and the number of (s + d) electrons available for bonding, and suggest the most promising TMs for inducing magnetism in MoDCs. Our results are in line with the available experimental data and should further guide the experimental effort towards a simple post-synthesis doping of 2D MoDCs and adding new functionalities to these materials.
Keywords: 2D materials, electronic structure calcualtions

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  • Secondary publication expected from 24.06.2020

Publ.-Id: 29380 - Permalink


Analysing tumour growth delay data from animal irradiation experiments with deviations from prescribed dose
Karsch, L.; Beyreuther, E.; Eger Passos, D.; Pawelke, J.; Löck, S.;
Abstract: The development of new radiotherapy technologies is a long-term process, which requires proving the general concept although clinical requirements with respect to beam quality and controlled dose delivery may not yet be fulfilled. Exemplarily, the necessary radiobiological experiments with laser-accelerated ion beams are challenged by fluctuating beam intensities. Based on tumour-growth data and dose values obtained in an in-vivo trial comparing the biological efficacy of laser-driven and conventional Linac electrons [2], different statistical approaches for analysis were compared. In addition to the classical averaging per dose point, which excludes animals with high dose deviations, multivariable linear regression, Cox regression and a Monte-Carlo-based approach were tested as alternatives that include all animals in statistical analysis. The four methods were compared based on experimental and simulated data. All applied statistical approaches revealed a comparable radiobiological efficacy of laser-driven and conventional Linac electrons, confirming the experimental conclusion. However, in the simulation study, significant differences in dose-response were observed by all methods except for the conventional method. Thereby, these statistical approaches may allow for reducing the total number of required animals in future pre-clinical trials.
Keywords: pre-clinical studies; statistical analysis; experimental beams; radiotherapy

Publ.-Id: 29379 - Permalink


Comparative effect of trivalent lanthanides and actinides on a rat kidney cell line
Heller, A.; Acker, M.; Barkleit, A.ORC; Bok, F.; Wober, J.
Exposure to trivalent lanthanides (Ln) and actinides (An) poses a serious health risk to animals and humans. Since both Lan and An are mainly excreted with the urine, we investigated the effect of La, Ce, Eu, and Yb (as representatives of Ln) as well as Am (as representative of An) exposure on a rat renal cell line (NRK-52E) for 8, 24, and 48 h in vitro. Cell viability studies using the XXT assay and fluorescence microscopic investigations were combined with solubility and speciation studies using ICP-MS and time-resolved laser-induced fluorescence spectroscopy (TRLFS). Thermodynamic modeling was applied to predict the speciation of Ln and Am in cell culture medium.
All Ln show a concentration- and time-dependent effect on NRK-52E cells with Ce being the most potent element. Effective Ln concentrations reducing the cell viability to 50 % (EC50 values) range from 340 µM for Ce to 1.1 mM for Eu. In general, light and heavy Ln seem to exhibit a greater effect than middle Ln.
In cell culture medium with 10 % fetal bovine serum (FBS), the Ln are completely soluble and complexed with proteins from FBS. Ln speciation is time-independent. Comparative experiment with Am are ongoing and will reveal analogies and differences in the effect of trivalent Ln and An on rat kidney cells.
The results of this study underline the importance of combining biological, chemical, and spectroscopic methods in studying the effect of Ln and An on cells in vitro and may contribute to the improvement of the current risk assessment for Ln in the human body. Furthermore, they demonstrate that Ln seem to have no effect on rat renal cells in vitro at environmental trace concentrations. Nevertheless, especially Ce has the potential for harmful effects at elevated concentrations observed in mining and industrial areas.

References:
[1] A. Heller, Ecotox. Environ. Safe. 2019, 173.
  • Lecture (Conference)
    GDCh-Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Publ.-Id: 29378 - Permalink


Calculation of neutron fluence distribution in components in the reactor vicinity and their validation on experiments as a basis for activity calculations
Barkleit, A.ORC; Konheiser, J.
Due to the “German Energiewende”, all nuclear power plants (NPPs) in Germany will be shut down by the end of 2022. Consequently, the safe and sustainable decommissioning and dismantling of the NPPs will be an important challenge for the next decades.
The aim of the project EMPRADO (“Entwicklung einer Methode zur Pre-Aktivitäts- und Dosisleistungsberechnung von reaktornahen Bauteilen auf Basis von Neutronen-fluenzverteilungen” – “Development of a method for pre-activity and dose rate calculations of components in the reactor vicinity based on neutron fluence distributions”) is to develop a standardized method to calculate the specific and temporal progression of activation for reactor components and near-reactor concrete as well as construction elements based on the power history of a nuclear reactor. A non-destructive early radiological characterization in the region of the reactor core is thus possible, which is required for an optimal planning of the dismantling. This can make a significant contribution to minimize the radioactive waste and the radiation exposure of personnel during the decommissioning.
The exact 3D neutron fluence calculations are carried out by Monte-Carlo simulations using the international widely used program MCNP6. For validation of the calculation results neutron flux measurements on the basis of activation foils (monitors) are carried out at several German NPPs which are still in operation.
The monitors used in this project are thin metal foils (10 × 10 × 0.1 mm) of Ti, Fe, Ni, Cu, Zn, Nb, Pd, In, and Sn. They are placed during the annual revision of the NPP at different construction elements, for instance near the reactor pressure vessel and at the first concrete wall, the biological shield, at different heights. At these positions the monitors remain during one working cycle of the NPP; that is approximately one year. After recovery, the neutron activation products are analyzed qualitatively and quantitatively by gamma spectroscopy and liquid scintillation counting (LSC). The experimentally determined activities are compared with the calculated ones in order to optimize the simulation procedure.
First experimental results of a feasibility study carried out in NPP Grohnde will be presented and compared to the available literature.
  • Poster
    Jahrestagung der Fachgruppe Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Publ.-Id: 29377 - Permalink


Application of Magnetism on Curved Surfaces
Makarov, D.;
Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system. On the other hand, we explore the application potential of these 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics for automotive but also virtual and augmented reality appliances.
Keywords: flexible magnetoelectronics, virtual reality
  • Invited lecture (Conferences)
    European Forum for Science, Research and Innovation, 24.-25.06.2019, Dresden, Germany

Publ.-Id: 29375 - Permalink


A series of tetravalent Pu, Np, U and Th complexes of a salen type ligand
Radoske, T.ORC; Kaden, P.ORC; Walter, O.; Kloditz, R.; Patzschke, M.ORC; Stumpf, T.; März, J.ORC
Fundamental actinide (An) coordination chemistry is still rather scarcely explored though it can provide a deep insight into the bonding situation and bonding trends across the An series. Characteristic of actinides is their huge variety of possible oxidation states, typically ranging from +II to +VII for early An. A suitable approach to explore fundamental physical-chemical properties of actinides is to study series of isostructural An compounds in which the An possesses the same oxidation state. Changes in e.g. the binding situation or magnetic effects among the An series allow insights into their unique electronic properties mainly originating from the 5f-electrons. The tetravalent actinides (An(IV)) are particularly suitable for this kind of systematic studies, as this is the largest accessible series within the early actinides.
Against this background, we performed the current study focusing on a systematic comparison of isostructural An(IV) complexes of Th, U, Np and Pu with a salen type ligand (H2L).
All syntheses and characterizations are conducted under inert, water-free nitrogen atmosphere. SC-XRD results prove that an isostructural complex series was achieved with a molecular unit where two ligands coordinate tetradentately to the An with all oxygen and nitrogen donor atoms. The resulting eightfold coordination environment exhibits a distorted square antiprismatic coordination geometry around the An center. Moreover, the relevant complexes are characterized in solution by NMR spectroscopy displaying characteristic paramagnetic effects according to the unpaired f-electrons. Interestingly, the paramagnetic contributions to the 1H and 13C NMR chemical shifts reach their maximum with [NpL2], and are drastically lower for [PuL2]. The acquired experimental results are further supported by quantum chemical calculations to study the electronic structure of the complexes.
Keywords: tetravalent actinide complexes coordination chemistry paramagnetic effects
  • Lecture (Conference)
    49èmes Journées des Actinides, 14.-18.04.2019, Erice, Italy

Publ.-Id: 29374 - Permalink


Cerebral Oxygen Metabolism Measurements with MRI in Adults with Sickle Cell Disease: PF742
Vaclavu, L.; Petersen, E.; Mutsaerts, H.; Petr, J.; Majoie, C.; Wood, J.; Vanbavel, E.; Nederveen, A.; Biemond, B.;
MRI studies have demonstrated a high prevalence of silent cerebral infarcts (SCI) in both children and adults with sickle cell disease (SCD). SCI are associated with cognitive impairment and lesion progression in adults with SCD. Disrupted oxygen transport can contribute to cerebral ischemic lesions, despite the compensatory elevation in cerebral blood flow (CBF) in SCD. Investigating the cerebral metabolic rate of oxygen (CMRO2) may therefore give insight into the hemodynamic etiology of SCI in SCD patients. We hypothesized that CMRO2 is reduced in adult patients with SCD as a result of chronic anemia and that vasodilation can improve CMRO2 by generating an increase in blood and oxygen flow.
  • Open Access LogoPoster
    24th Annual Congress of the European Hematology Association, 13.06.2019, Amsterdam, The Netherlands
  • Open Access LogoContribution to proceedings
    24th Annual Congress of the European Hematology Association, 13.06.2019, Amsterdam, The Netherlands
    Hemasphere, 324-325
    DOI: 10.1097/01.HS9.0000561252.50212.c6

Publ.-Id: 29373 - Permalink


Using Agile Development Platforms for Continuous Integration, Code Review and Collaboration
Schlegel, F.;
The reality of scientific software development is of a more or less agile nature. As such, modern code development platforms such as GitHub or GitLab are a great fit to support this process. With their components (issues, projects, continuous integration, etc.) they match the agile development components, merge request enforce a cross-check for all code changes. While a lot of other development workflows are possible, this talk will present the best practice established for large and small projects at HZDR for using these platforms for software development projects.
  • Lecture (Conference)
    Platform for Advanced Scientific Computing (PASC) Conference 2019, 12.-14.06.2019, Zürich, Schweiz

Publ.-Id: 29372 - Permalink


Synthesis and Reactivity of Tetravalent Actinide Amidinates
Schöne, S.ORC; März, J.; Kaden, P.
A series of tetravalent actinide amidinates was synthesized and characterized in solution and in solid state. Quantum chemical calculations support findings based on bonding analysis. Furthermore the reactivity of the complexes is presented.
  • Lecture (others)
    FENABIUM Projekttreffen März 2019, 27.02.2019, Dresden, Deutschland

Publ.-Id: 29371 - Permalink


Enantiopure Tetravalent Actinide Amidinates – Synthesis and Reactivity
Schöne, S.ORC; Kloditz, R.; März, J.; Kaden, P.; Patzschke, M.; Roesky, P. W.; Stumpf, T.
In contrast to the dominant trivalent state for the lanthanide series (Ln(III)), a wide variety of oxidation states (from II to VII) of actinides (An) makes their chemistry intricate but attractive. Especially the early An thorium (Th), uranium (U), neptunium (Np), and plutonium (Pu) form highly charged cations with the oxidation state +IV (An4+), which are of particular interest for coordination chemistry due to their strong interaction with ligands.
The focus of our investigations lies in the comprehensive characterization of An(IV) complexes with ligands bearing soft donor atoms, such as nitrogen (N), both in the solid state and in solution. The present study focuses particularly on the interaction of An(IV) (Th, U, Np) with N-donor ligands of amidinate type, which could be considered as a simplified model of naturally occurring N-donor organic compounds.
Recently, the trivalent lanthanide complexes with the chiral benzamidine, (S,S)-N,N‘-Bis-(1-phenylethyl)-benzamidine ((S)-HPEBA), have been successfully synthesized.[1,2] Mono- and bis-amidinate complexes of the later lanthanides (Er, Yb, Lu) were obtained using a salt metathesis approach. Only for the larger samarium(III) a homoleptic tris-amidinate was accessible.
We have extended this approach to the tetravalent An, and successfully synthesized the first transuranic amidinate complexes. Moreover, we have obtained the first enantiopure amidinate complexes of An(IV) [AnCl((S)-PEBA)3] (An = Th, U, and Np) as well as the analogous Ce(IV) compound, a chemical analog of An(IV). The tris-amidinate complexes have been structurally characterized in solid state and in solution showing a comparable complex geometry.
Due to the presence of a Cl- ligand in the An coordination sphere, it could be speculated that the complex should be reactive. Thus, the reactivity of the complexes has been demonstrated by successful reduction with potassium graphite to homoleptic trivalent actinide amidinates [An((S)-PEBA)3] (An = U, Np).
  • Lecture (Conference)
    Journées des Actinides 2019, 14.-18.04.2019, Erice, Italien

Publ.-Id: 29370 - Permalink


Comprehensive real space bonding analysis of tetravalent f-element complexes with Schiff-base ligands
Kloditz, R.; Radoske, T.; Patzschke, M.; Stumpf, T.;
The contribution of the f-orbitals to chemical bonding leads to the rich chemistry of the actinides. This is in contrast to the lanthanides, where it is known that this contribution is less important. Of special interest is the influence of these orbitals on the bonding character of actinides and lanthanides with organic ligands reflecting natural binding motifs.
This study compares the different bonding behavior of tetravalent actinides and lanthanides with the Schiff base salen (see Fig. 1, left) by means of real-space bonding analysis. Our approach makes use of the quantum theory of atoms in molecules (QTAIM), plots of the non-covalent interactions (NCI) and density differences complemented by natural population analysis (NPA). Especially the local properties at the bond critical points (Fig. 1, right), for instance charge, density, ellipticity and others, can be used to characterize a bond’s order, strength, and covalent contribution. In addition, thermodynamic calculations on the stability of these complexes are presented since the difference in stability is a direct consequence of the different interaction strengths of the f elements.
First results reveal a strong interaction of the actinides, i.e. Th to Pu, with the oxygen of salen characterized by a high electron density concentration between the atoms. In contrast, the interaction between the actinides and the nitrogen of salen is much weaker. The delocalization index, density and Laplacian reveal a significant increase of covalency for Pa to Pu compared to Th and Ce being an indicator of the contribution of the f-electrons. Tetravalent Ce as a lanthanide analogue of Th is expected to show a similar bonding behavior, but, surprisingly, this is not the case for all investigated bonding properties.
Such a detailed analysis of the electronic properties of actinide compounds will help to improve understanding of their behavior in the environment as well as in technical processes and leads to the possibility to predict properties of unknown complexes.
Keywords: Actinides, Quantum chemistry, DFT, Bonding, Covalency
  • Lecture (Conference)
    Journees des Actinides, 14.-18.04.2019, Erice, Italien

Publ.-Id: 29369 - Permalink


Hybrid LWFA–PWFA staging as a beam energy and brightness transformer: conceptual design and simulations
Martinez De La Ossa, A.; Assmann, R. W.; Bussmann, M.; Corde, S.; Couperus Cabadağ, J. P.; Debus, A.; Döpp, A.; Ferran Pousa, A.; Gilljohann, M. F.; Heinemann, T.; Hidding, B.; Irman, A.; Karsch, S.; Kononenko, O.; Kurz, T.; Osterhoff, J.; Pausch, R.; Schöbel, S.; Schramm, U.ORC
We present a conceptual design for a hybrid laserdriven plasma wakefield accelerator (LWFA) to beam-driven plasma wakefield accelerator (PWFA). In this set-up, the output beams from an LWFA stage are used as input beams of a new PWFA stage. In the PWFA stage, a new witness beam of largely increased quality can be produced and accelerated to higher energies. The feasibility and the potential of this concept is shown through exemplary particle-in-cell simulations.
In addition, preliminary simulation results for a proof-of-concept experiment in Helmholtz-Zentrum Dresden-Rossendorf (Germany) are shown.
Keywords: laser plasma accelerator, LWFA, PWFA

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  • Secondary publication expected from 25.06.2020

Publ.-Id: 29368 - Permalink


Dynamics of Charges in Superlong Blacklight-Emitting CaB2O4:Ce3+ Persistent Phosphor
Sharma, S. K.; Bettinelli, M.; Carrasco, I.; Beyer, J.; Gloaguen, R.; Heitmann, J.;
The optical and persistent luminescence properties of CaB2O4:Ce3+ phosphor are presented. The optical emission for excitation in the 250–340 nm wavelength region is dominated by two bands at 365 and 460 nm. Lifetime measurements suggested that the 365 nm emission band is due to interconfigurational Ce3+ 5d → 4f transitions. Upon excitation with a 254 nm UV lamp, a superlong persistent luminescence in the UVA1 region (340–400 nm, blacklight) was observed, lasting for at least 15 h, and with excellent reproducibility, which is perfectly suitable for phototherapy application. The initial-rise method was applied on the thermoluminescence glow curves to determine the trap distribution and trap depth. The results suggest that one distinct trap, with an activation energy of ∼0.52 eV, was solely responsible for the persistent luminescence in the CaB2O4:Ce3+ phosphor. The other traps had a quasi-continuous distribution, with activation energies between 0.56 and 1.15 eV. The proposed persistent luminescence and the thermoluminescence mechanisms are elucidated using experimental parameters obtained from the optical and thermoluminescence results and the theoretically calculated electronic structure of the Ce3+ ion in CaB2O4. The lowest Ce3+ 5d1 level was found to be ∼0.97 eV below the conduction band, and the persistent luminescence/thermoluminescence emission was dominated by the radiative transitions between Ce3+ energy levels, 5d → 2F5/2,7/2.
Keywords: Rare earth luminescence, long persistence, photoluminescence, thermoluminescence, mechanism

Publ.-Id: 29367 - Permalink


Nanoscale modification of one-dimensional single-crystalline cuprous oxide
Das, P.; Raibhar, M. K.; Elliman, R. G.; Möller, W.; Facsko, S.; Chatterjee, S.;
In this work we report for the first time a method to modify the surface of Cu2O nanowires in a controllable way and physically weld them into a network form, which contributes to higherelectrical conductivity as well as a strong water-repelling nature. We have used state-of-the-art theoretical calculations to support our experimental observations. We demonstrate how varying the irradiation fluence can modulate the surface and decorate the nanowire with a uniformdistribution of Cu8O nanocrystals due to referential sputtering. While several well studied joining techniques are available for carbon and metal-based nanowires, the same information forceramic nanowires is scarce at present. The current study sheds light into this and a state-of-the art 3D simulation technique predicts most of the modifications including surface modulation, oxygen depletion and welding. The welded network shows higher electrical conductivity than the unwelded assembly. With Cu2O being of p-type the current ion beam joining technique shows a novel path for fabricating p-i-n junctions or solar cell devices through bottom-up approach. Furthermore, we have explored the response of this network to moisture. Our calculation based on density functional theory predicts the hydrophilic nature of individual copper oxide nanowires both before and after irradiation. However, the network shows a strong water-repelling nature, which has been explained quantitatively using the Cassie–Baxter model.
Keywords: copper oxide, superhydrophobic, ion irradiation, nanowire, welding

Publ.-Id: 29366 - Permalink


Ab initio path integral Monte Carlo approach to the static and dynamic density response of the uniform electron gas
Groth, S.; Dornheim, T.; Vorberger, J.;
In a recent Letter [T. Dornheim et al., Phys. Rev. Lett. 121, 255001 (2018)] we have presented ab initio results for the dynamic structure factor S(q,ω) of the uniform electron gas for conditions ranging from the warm dense matter regime to the strongly correlated electron liquid. This was achieved on the basis of exact path integral Monte Carlo data by stochastically sampling the dynamic local field correction G(q,ω). In this paper we introduce in detail this reconstruction method and provide several practical demonstrations. Moreover, we thoroughly investigate the associated imaginary-time density-density correlation function F(q,τ). The latter also gives us access to the static density-response function χ(q) and static local field correction G(q), which are compared to standard dielectric theories like the widespread random phase approximation. In addition, we study the high-frequency limit of G(q,ω) and provide extensive results for the dynamic structure factor for different densities and temperatures. Finally, we discuss the implications of our findings for warm dense matter research and the interpretation of experiments.
Keywords: electron gas, warm dense matter, response function, structure factor, local field correction, quantum Monte Carlo

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Publ.-Id: 29365 - Permalink


Investigations of the interactions of a Halobacterium isolate with uranium using different microscopic and spectroscopic methods
Hilpmann, S.; Bader, M.; Bachran, M.; Steudtner, R.; Schmidt, M.; Stumpf, T.; Cherkouk, A.;
Rock salt formations can serve as potential host rocks for the long-term storage of high-level radioactive waste in a deep geological repository. Haloarchaea are widespread under these highly saline conditions. However, there exists a lack of knowledge about the interactions of these microorganisms with radionuclides especially concerning the chemical speciation. Therefore, the interactions of an extremely halophilic archaeon, Halobacterium sp. GP5 1-1 with uranium, one of the major radionuclides of concern, were investigated in detail. This haloarchaeon was isolated from a German rock salt sample. Different microscopic and spectroscopic techniques were used to get an overall image of the occurring processes on a molecular level.
Time-dependent association experiments with two different U(VI) concentrations were performed, to investigate the interaction kinetics of U(VI) with the cells of the haloarchaeon. The amount of bioassociated U(VI) increased with the incubation time at both concentrations. However, the association process at the lower concentration (10 µM) was much faster than at the higher U(VI) concentration (30 µM). Overall, the association process is not exclusively biosorption, being a passive process and normally finished after a short time of incubation (0 – 2 h) [1].
Scanning electron microscopy coupled with energy-dispersive X-ray absorption spectroscopy indicates different interaction mechanisms of the cells at different U(VI) concentrations. It was found that at a concentration of 10µM U(VI) preferentially biomineralization takes place, whereas biofilm-like structures are formed at a concentration of 30µM.
With the help of time-resolved laser-induced luminescence spectroscopy, different aqueous U(VI) species could be extracted from the supernatant. These species differ slightly in dependence of the U(VI) concentration. In general, the formation of a uranyl-carbonate-complex was observed. This could be the result of microbial released CO2 during the process. In contrast to the higher U(VI) concentration, a phosphate species was formed at a U(VI) concentration of 10 µM.
These findings offer new insights into the microbe-actinide interactions at highly saline conditions relevant to high-level radioactive waste disposal in rock salt formations.

[1] J. R. Lloyd, L. E. Macaskie (2002) in “Interactions of Microorganisms with Radionuclides” (Eds.: M.J. Keith-Roach, F. R. Livens), Elsevier, pp. 313-381
  • Poster
    Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Publ.-Id: 29364 - Permalink


Selective leaching of rare earth elements (REEs) from eudialyte concentrate after sulfation and thermal decomposition of non-REE sulfates
Balinski, A.; Petya, A.; Wiche, O.; Kelly, N.; Reuter, M. A.; Scharf, C.;
Eudialyte, a sodium rich zirconosilicate, is one of the promising sources for REEs, particularly for HREEs+Y. The key challenge by hydrometallurgical processing is the prevention of silica gel formation and REE separation from resulting multi-element leach solutions. This study deals with the selective leaching of REEs from eudialyte concentrate after sulfation and thermal decomposition of non-REE sulfates. We demonstrate how to select the parameters in each process stage to achieve high yields of REEs and to separate them from Zr⁴⁺(+Hf⁴⁺), Nb⁵⁺, Al³⁺ and Fe³⁺. The best result in terms of the separation and the REE yield was achieved with the following parameters: acid addition: 15 mmol/g; roasting temperature: 750 °C; roasting time: 2 h; pulp density: 25 kg/m³; leaching temperature: 20 °C; leaching time: 24 h; stirring speed: 300 rpm. For sufficient conversion of REEs into sulfates H₂SO₄ was added in excess, approximately twice as high as the acid consumption. Water leaching at high solid/liquid ratios caused decrease in the separation factor and REE losses resulting from formation of double sulfates and gypsum.
Keywords: eudialyte concentrate, rare earth elements, separation, sulfation, selective roasting, thermal stability of sulfates, leaching, silica stability during leaching

Publ.-Id: 29363 - Permalink


Relation between topology and electronic structure of 2D polymers
Springer, M.; Kuc, A.; Heine, T.;
New 2D materials open access to a whole new world of compounds and properties. Graphene monolayer is such a material, since it has special electron transport features due to its honeycomb topology. Apart from the honeycomb net, there are many more topologies, which promise a manifold of new properties, e.g. the kagomé or the Lieb lattice. As recently shown in the case of the kagomé net, 2D polymers (covalent organic frameworks) can be designed in a way, that their geometric and electronic structures match the desired topology.[1] Other nets, e.g. the Lieb lattice, can at the moment only be realized as optical lattices or via adsorption of molecules on a surface.[2]
In this project, we want to work out the relation between topology and electronic properties. For this purpose, we employ a tight-binding model. In Fig. 1, exemplary results for the aforementioned kagomé and Lieb lattices are shown. Based on these findings, we want to propose new 2D polymers with the desired structures and new properties using density- functional theory.
[1] Y. Jing, T. Heine, J. Am. Chem. Soc. 141, 2, 743 (2019)
[2] S. Mukherjee et al., Phys. Rev. Lett. 114, 245504 (2015); S. Taie et al., Sci. Adv. 1, e1500854 (2015); M. R. Slot et al., Nat. Phys. 13, 672 (2017)
  • Poster
    Flatlands Beyond Graphene 2019, Toulouse, 02.-06.09.2019, Toulouse, France
  • Poster
    European Conference On Chemistry Of Two-Dimensional Materials, 03.-06.09.2019, Dresden, Deutschland
  • Poster
    55th Symposium on Theoretical Chemistry, 22.-26.09.2019, Rostock, Deutschland

Publ.-Id: 29360 - Permalink


Tetranuclear Cu(II)-chiral complexes: Synthesis, characterization and biological activity
Peewasan, K.; Merkel, M. P.; Zarschler, K.; Stephan, H.; Anson, C. E.; Powell, A. K.;
Tetranuclear chiral Cu(II)-Schiff-base complexes S-1 and R-1, were synthesised using enantiomerically pure (S)-H2L and (R)-H2L ligand respectively in the ratio of 1:1 of Cu(NO3)2 to (S/R)-H2L in MeOH at room temperature. A pair of polynuclear chiral Cu(II)-cluster complexes were characterized using single-crystal X-ray diffraction, elemental analysis, infrared and CD spectroscopy. The results revealed the importance of these chiral ligands encouraging the arrangement of copper metal in non-centrosymmetric polar packing. The potential of the novel Cu(II)-H2L complexes as biologically active compounds was assessed in particular regarding their anti-proliferative and anti-microbial properties.
Keywords: Metal-based drugs; Polynuclear Cu(II)-cluster; Enantiomerically pure Schiff-base ligand; Cell viability; Single-crystal X-ray diffraction

Publ.-Id: 29357 - Permalink


Bakterien als Alleskönner
Lederer, F.;
Bakterien sind Lebewesen, die unser tägliches Leben ganz entscheidend prägen. Ob Käse, Sauerkraut oder Wein - viele Delikatessen werden für uns durch diese kleinen Alleskönner produziert. Obwohl Bakterien häufig als Krankheitserreger verschrien sind, sind viele von ihnen wichtige Unterstützer unserer Gesundheit - was wir oft erst dann merken, wenn sie weg sind. Eine gesunde Darmflora aus Millionen von Bakterien ist entscheidend für die Produktion und Aufnahme vieler Vitamine in unserem Körper und für unser körperliches Wohlbefinden.
Auch in der Forschung werden Bakterien mit ihren vielen Eigenschaften gerne eingesetzt. Am Helmholtz-Zentrum Dresden-Rossendorf studiert man unter anderem ihre Fähigkeiten, sich fehlende Metalle aus der Umgebung zu besorgen und nutzt diese mikrobiellen Komplexbildner zur Rohstoffrückgewinnung aus Industrieabwässern.
Der Vortrag wird Bakterien als Alleskönner aus verschiednen Perspektiven beleuchten.
Keywords: Bakterien
  • Lecture (others)
    Seniorenakademie, 11.4.2019, Dresden, Deutschland

Publ.-Id: 29356 - Permalink


Gezieltes selektives Herauslösen von Substanzen aus Roh- und Reststoffen mit biologisch basierten Aufbereitungstechnologien
Lederer, F.;
Gast-Vorlesung an der BTU Cottbus-Senftenberg in der Fakultät Umweltwissenschaften und Verfahrenstechnik im Modul "Stoffliche Nutzung nachwachsender Rohstoffe"
Keywords: Mikrobiologie, Phage Surface Display
  • Lecture (others)
    Stoffliche Nutzung nachwachsender Rohstoffe, 17.01.2019, Cottbus, Deutschland
  • Lecture (others)
    Vorlesung im Modul "Stoffliche Nutzung nachwachsender Rohstoffe", 17.01.2019, Cottbus, Deutschland

Publ.-Id: 29355 - Permalink


Ultrafast X-ray tomography raw-data of bubbly two-phase pipe flow around a ring shaped obstacle
Neumann-Kipping, M.ORC; Hampel, U.ORC

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow obstacles were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.

The provided data set contains tomography raw-data for the experimental series L30 that uses a ring shaped flow obstacle with a blockage ratio of 0.5. 

For visualization, the data might be opend with Fiji. Therefore choose Import->Raw... In the following window specify "Image type" as 16-bit Unsigned, "Width" as 288 pixels and "Height" as 500 pixels for 2x1000Hz measurement or 200 pixels for 2x2500Hz measurement. Make sure that "Little-endian byte order" is checked. A data set contains image frames of both scvanning planes in alternating order. Therefore, if only a single scanning plane is required, the offset and gap parameters need to be set to 288000 bytes for 2x1000Hz measurement or 115200 bytes for 2x2500Hz measurement.

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-06-18
    DOI: 10.14278/rodare.124
    License: CC-BY-4.0

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Publ.-Id: 29354 - Permalink


Ultrafast X-ray tomography raw-data of bubbly two-phase pipe flow around a semi-circular obstacle
Neumann-Kipping, M.ORC; Hampel, U.ORC

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow obstacles were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.

The provided data set contains tomography raw-data for the experimental series L30 that uses a semi-circular flow obstacle with a blockage ratio of 0.5. 

For visualization, the data might be opend with Fiji. Therefore choose Import->Raw... In the following window specify "Image type" as 16-bit Unsigned, "Width" as 288 pixels and "Height" as 500 pixels for 2x1000Hz measurement or 200 pixels for 2x2500Hz measurement. Make sure that "Little-endian byte order" is checked. A data set contains image frames of both scvanning planes in alternating order. Therefore, if only a single scanning plane is required, the offset and gap parameters need to be set to 288000 bytes for 2x1000Hz measurement or 115200 bytes for 2x2500Hz measurement.

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-06-26
    DOI: 10.14278/rodare.122
    License: CC-BY-4.0

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Publ.-Id: 29353 - Permalink


Scalable, Data Driven Plasma Simulations with PIConGPU
Huebl, A.ORC; Widera, R.ORC; Garten, M.ORC; Pausch, R.ORC; Steiniger, K.ORC; Bastrakov, S.ORC; Meyer, F.; Bastrakova, K.; Debus, A.ORC; Kluge, T.ORC; Ehrig, S.ORC; Werner, M.; Worpitz, B.; Matthes, A.ORC; Rudat, S.; Starke, S.ORC; Bussmann, M.ORC

PIConGPU is an open source, multi-platform particle-in-cell code scaling to the fastest supercomputers in the TOP500 list. We present the architecture, novel developments, and workflows that enable high-precision, fast turn-around computations on Exascale-machines. Furthermore, we present our strategies to handle extreme data flows from thousands of GPUs for analysis with in situ processing and open data formats (openPMD). PIConGPU is since recently furthermore natively controlled by a Python Jupyter interface and we research just-in-time kernel generation for C++ with our Cling-CUDA extensions.

Keywords: LPA; laser-plasma; particle-in-cell; HPC; manycore; GPU; simulation; interactive; big data
Related publications
Scalable, Data Driven Plasma Simulations with PIConGPU (Id 29350) is supplemented by this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-06-13
    DOI: 10.14278/rodare.130
    License: CC-BY-4.0

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Publ.-Id: 29351 - Permalink


Scalable, Data Driven Plasma Simulations with PIConGPU
Huebl, A.ORC; Widera, R.ORC; Garten, M.ORC; Pausch, R.ORC; Steiniger, K.ORC; Bastrakov, S.ORC; Meyer, F.; Bastrakova, K.; Debus, A.ORC; Kluge, T.ORC; Ehrig, S.ORC; Werner, M.; Worpitz, B.; Matthes, A.ORC; Rudat, S.; Starke, S.ORC; Bussmann, M.ORC
PIConGPU is an open source, multi-platform particle-in-cell code scaling to the fastest supercomputers in the TOP500 list. We present the architecture, novel developments, and workflows that enable high-precision, fast turn-around computations on Exascale-machines. Furthermore, we present our strategies to handle extreme data flows from thousands of GPUs for analysis with in situ processing and open data formats (openPMD). PIConGPU is since recently furthermore natively controlled by a Python Jupyter interface and we research just-in-time kernel generation for C++ with our Cling-CUDA extensions.
Keywords: LPA, laser-plasma, particle-in-cell, HPC, manycore, GPU, simulation, interactive, big data
Related publications
Scalable, Data Driven Plasma Simulations with PIConGPU (Id 29351) is a supplement to this publication
  • Invited lecture (Conferences)
    Platform for Advanced Scientific Computing (PASC) Conference (PASC19), 12.-14.06.2019, Zürich, Schweiz
    DOI: 10.14278/rodare.131

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Publ.-Id: 29350 - Permalink


AMS measurements of cosmogenic nuclide concentrations resolve mountain landscape evolution and the glacial history in the Pamir, Central Asia
Stübner, K.; Bookhagen, B.; Merchel, S.ORC; Rugel, G.; Lachner, J.
Secondary cosmic rays interact with terrestrial materials in the atmosphere and near the Earth's surface to produce cosmogenic radionuclides. The production and accumulation of cosmogenic ¹⁰Be and ²⁶Al in quartz allows geologists to investigate processes of landscape evolution such as erosion, landsliding, sediment transport and deposition on time scales of thousands to few millions of years. The Pamir mountains at the western end of the India-Asia collision zone have been in the focus of geologic research since the early 2000s. While the tectonic evolution of the Pamir is increasingly well understood, the drivers of Pamir landscape evolution remain elusive. The western Pamir is characterized by an extreme topographic relief with summit and valley elevations of 6-7 km and 2-3 km, respectively; the eastern Pamir is a low-relief plateau at ~4 km. This contrast may be attributed to higher precipitation in the western Pamir driving faster river incision and erosion compared to the arid east. Alternatively, the relief may be controlled by spatially variable, tectonically forced surface uplift. Field observations suggest that Pleistocene glaciation of the Pamir was much more extensive than modern glaciation, and that glaciation had a significant impact on the evolution of the Pamir landscape.

We use cosmogenic ¹⁰Be and ²⁶Al concentrations in moraine boulders, glacially polished bedrock and glacio-alluvial sediment deposits to determine the timing and extent of past glacial stages with the goal to better understand what controls landscape evolution in the Pamir. Our results indicate that early Holocene (~10 ka) glaciation was more extensive than previously thought, and that at that time the western Pamir was much more strongly glaciated than the east. The most widespread glaciation occurred at ≥200 ka covering most of the western Pamir and possibly also much of the east Pamir plateau. These results strengthen our hypothesis that the glacial history of the Pamir had a significant impact on its landscape evolution.
Keywords: AMS, tectonics, geomophology
  • Lecture (Conference)
    Heavy Ion Accelerator Symposium on Fundamental and Applied Science (HIAS), 09.-13.09.2019, Canberra, Australia

Publ.-Id: 29349 - Permalink


Mass transport induced asymmetry in charge/discharge behavior of liquid metal batteries
Personnettaz, P.; Landgraf, S.; Nimtz, M.; Weber, N.; Weier, T.;
Mass and charge transport in liquid metal batteries are closely intertwined because of the fully liquid interior of the cells. We found that charging and discharging cycles may show pronounced asymmetries. They are caused by the presence (charge) or absence (discharge) of solutal convection. While the direction of thermal gradients in the positive electrode of a liquid metal battery depend on boundary conditions and thermodynamics in a non-trivial manner, the solutal gradient predictably changes direction from charge to discharge. The unstable density distribution during charge drives a flow strong enough to prevent any concentration polarization. In contrast, during discharge, the stable density gradient suppresses convection and leads to a substantial mass transport overvoltage. We illustrate this scenario by experimental data, numerical simulations and a physical model.
Keywords: electrorefining, liquid electrode, liquid metal batteries, mass transport, overvoltage, solutal convection

Publ.-Id: 29348 - Permalink


Heavy ion irradiation damage in Zr2AlC MAX phase
Qarra, H. H.; Knowles, K. M.; Vickers, M. E.; Akhmadaliev, S.; Lambrinou, K.;
Zr2AlC MAX phase-based ceramic material with 33 wt% ZrC has been irradiated with 22 MeV Au7+ ions between room temperature and 600 °C, achieving a maximum nominal midrange dose of 3.5 displacements per atom. The response of the material to irradiation has been studied using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Under room temperature irradiation, the ions caused a partial amorphisation of the MAX phase. At high temperatures, irradiated Zr2AlC remained crystalline, but developed an increased density of dislocations and stacking faults in the (0001) basal planes. The irradiated material also exhibited a temperature-dependent microcracking phenomenon similar to that previously reported in other MAX phase materials.

Publ.-Id: 29346 - Permalink


Advanced characterization methods for electrical and sensoric components and devices at the micro and nanoscale
Sheremet, E.ORC; Meszmer, P.ORC; Blaudeck, T.ORC; Hartmann, S.; Wagner, C.ORC; Ma, B.; Hermann, S.; Wunderle, B.; Schulz, S. E.; Hietschold, M.; Rodriguez, R. D.; Zahn, D. R. T.
This feature article covers the nano-analysis methods for four key material characteristics: electrical and electronic properties, optical, stress and strain, and chemical composition. With the downsizing of the geometrical dimensions of electronic, optoelectronic, and electromechanical devices from the micro to the nanoscale at the one hand and the increase of functionality density at the other, the previous generation of micro-analysis methods is no longer sufficient. Therefore, the metrology of materials’ properties with nanoscale resolution has become prerequisite in materials research and development. The article shortly reviews the standard analysis methods and focuses on advanced methods with a nanoscale spatial resolution based on atomic force microscopy (AFM): current-sensing AFM (CSAFM), Kelvin probe force microscopy (KPFM), and hybrid optical techniques coupled with AFM including tip-enhanced Raman spectroscopy (TERS), photothermal-induced resonance (PTIR) characterization methods (nano-Vis, nano-IR), photo-induced force microscopy (PIFM) and photothermal microspectroscopy (PTMS). The simultaneous acquisition of multiple parameters (topography, charge and conductivity, stress and strain, chemical composition) at the nanoscale is a key for exploring new research on structure-property relationships of nanostructured materials such as carbon nanotubes (CNTs) and nano/microelectromechanical systems (N/MEMS). Advanced nanocharacterization techniques foster the design and development of new functional materials for flexible hybrid and smart applications.
Keywords: Scanning probe microscopy, Kelvin probe force microscopy, nanoanalysis, Raman spectroscopy, atomic force microscopy

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  • Secondary publication expected

Publ.-Id: 29345 - Permalink


RF Controls Towards Femtosecond and Attosecond Precision
Zenker, K.; Ludwig, F.; Branlard, J.; Butkowski, L.; Czwalinna, M. K.; Hoffmann, M.; Killenberg, M.; Lamb, T.; Mavric, U.; Mueller, J. M.; Pfeiffer, S.; Schlarb, H.; Schmidt, C.; Springer, L.; Kuntzsch, M.; Hierholzer, M.; Marjanovic, J.;
In the past two decades, radio-frequency (RF) controls have improved by two orders in magnitude achieving meanwhile sub-10 fs phase stabilities and 0.01% amplitude precision. Advances are through improved field detection methods and extensive usage of digital signal processing on very powerful field programmable gate arrays (FPGAs). The question rises, what can be achieved in the next 10 years? In this paper, a review is given of existing systems and strategies, current stability limitations of RF control systems and new technologies with the potential to achieve attosecond resolutions.
  • Open Access LogoContribution to proceedings
    10th International Particle Accelerator Conference, 19.-24.05.2019, Melbourne, Astralia: JACoW, 978-3-95450-208-0, 3414-3418
    DOI: 10.18429/JACoW-IPAC2019-THYYPLM2

Publ.-Id: 29344 - Permalink


Super-SIMS at HZDR - first steps: measurements on halogens
Rugel, G.; Renno, A. D.; Wiedenbeck, M.; Ziegenrücker, R.ORC
The integration of an ion source with very high spatial resolution with a tandem accelerator is a long-standing concept for improving analytical selectivity and sensitivity by orders of magnitude [1-3]. Translating this design concept to reality has its challenges [e.g. 4-6]. Supporting a strong focus on natural, metallic and mineral resources the Helmholtz Institute Freiberg for Resource Technology installed such a system at the Ion Beam Centre at HZDR. This so-called Super-SIMS will be at the core of a comprehensive pallet of micro-analytical methods devoted to the characterization of minerals and ores. Secondary ion beam from a CAMECA IMS 7f-auto are injected into the pre-existing 6MV Dresden Accelerator Mass Spectrometry facility [7,8], which quantitatively eliminates isobaric molecular species from the ion beam.
Our SIMS component can function as either a stand-alone device or can be used to inject the negatively charged secondary ions at energies of up to 40 keV (to match the acceptance conditions) into the accelerator.
We will present the current status of this initiative and will report first results from halogen determinations (F – I) in sphalerite and galena. These data demonstrate a systematic and significant change in the counting rates of all halogens in mineralogically clearly distinguishable areas of both minerals. Furthermore first attempts on quantification with reference materials are given in [8].

[1] K. Purser et al. Surface and Interface Analysis 1(1), 1979, 12.
[2] J. M. Anthony, D. J. Donahue, A. J. T. Jull, MRS Proceedings 69 (1986) 311-316.
[3] S. Matteson, Mass Spectrom. Rev., 27 (2008) 470.
[4] Ender et al. NIMB 123 (1997) 575.
[5] C. Maden, PhD thesis, ETH Zurich 2003.
[6] A. J. Fahey et al. Analytical Chemistry 88(14), 2016, 7145.
[7] Sh. Akhmadaliev et al., NIMB 294 (2013) 5. [8] G. Rugel et al. NIMB 370 (2016) 94.
[8] R. Ziegenrücker et al., this conference.
Keywords: SIMS, Super-SIMS, AMS, accelerator, Beschleuniger, Flur, Flourine, Sphalerit, sphalerite
  • Poster
    Ion Beam Physics Workshop 2019, 24.-26.06.2019, Dresden, Deutschland

Publ.-Id: 29342 - Permalink


Continuous Documentation for Users, Developers and Maintainers
Frust, T.ORC
This talk covers the often neglected and “hated” aspect of software documentation that is indispensable in a sustainable research software development process. A good, up-to-date and easily accessible software documentation lays the foundation for broader usage and collaboration. Software documentation usually covers three different components: user documentation, instructions how to modify and contribute to the software and a low-level API documentation. When starting developing a new research software, the documentation should be considered from the very beginning. Maintaining an up-to-date software documentation with good coverage in an exascale ready scientific software stack is only achievable, if the contribution process clearly includes a check for documentation adding or updates. This check can only be automated partially and usually requires a manual review process. All contributions must be made with the understanding, that documentation is a key aspect of any contribution. Things get never cleaned up later. Recurrent tasks should be automated wherever possible to reduce the impact of manual errors, e.g. the deployment of software documentation. This talk provides a set of best practices for software documentation in science combined with concrete examples from real-world scientific software solutions.
Keywords: Documentation; Software; Best Practices; CI; CD; Continuous Integration; API
  • Open Access LogoInvited lecture (Conferences)
    Platform for Advanced Scientific Computing (PASC) Conference 2019, 12.-14.06.2019, Zürich, Schweiz
    DOI: 10.5281/zenodo.3247324

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Publ.-Id: 29338 - Permalink


Entwicklung induktiver Strömungs- und Füllstandssensoren für flüssige Metalle
Krauter, N.;
In dieser Arbeit werden die Weiterentwicklung bestehender und die Entwicklung neuer Sensoren für die induktive Strömungs- und Füllstandsmessung in flüssigen Metallen sowie die zugehörigen Simulations- und Messergebnisse vorgestellt: Dabei handelt es sich um die Entwicklung und Charakterisierung eines miniaturisierten Eddy Current Flow Meters, das z.B. als Bestandteil der Sicherheitstechnik in flüssigmetallgekühlten Reaktoren zur Überwachung der Kühlmittelströmung bei hohen Umgebungstemperaturen eingesetzt werden kann. Außerdem wird das im Rahmen dieser Arbeit entwickelte Immersed Transient Eddy Current Flow Meter vorgestellt, welches eine direkte und kalibrierungsfreie Fließgeschwindigkeitsmessung ermöglicht und damit einen entscheidenden Vorteil gegenüber herkömmlichen induktiven Strömungssensoren besitzt. Anschließend werden neue Konzepte und ein Sensor für die Füllstandsüberwachung bei industriellen Prozessen, hier am Beispiel der Aluminium-Elektrolyse bei Temperaturen bis zu 1000 °C und der Titanherstellung vorgestellt.
Keywords: Induktive Messverfahren, Fließgeschwindigkeitsmessung, Füllstandsmessung
  • Doctoral thesis
    TUDpress, 2019
    Mentor: Prof. Dr. Uwe Hampel und Dr. Frank Stefani
    248 Seiten

Publ.-Id: 29336 - Permalink


Local inductive flow measurements
Krauter, N.; Stefani, F.;
An overview of current research on inductive local flow rate measurement techniques in liquid metals at the HZDR.
Keywords: Inductive Flow Measurements, Eddy Current Flow Meter, Immersed Transient Eddy Current Flow Meter
  • Lecture (Conference)
    ESFR-SMART European Workshop on Instrumentation for the Safety of Liquid Metal Facilities, 10.-12.04.2019, Dresden, Deutschland

Publ.-Id: 29335 - Permalink


Inductive Level Sensors
Krauter, N.; Stefani, F.; Zürner, T.; Wondrak, T.; Ratajczak, M.;
An overview of current research on inductive level measurement techniques in liquid metals at the HZDR.
Keywords: Eddy Current Level Sensor, Free Surface Detection, Look-Up-Table Method
  • Lecture (Conference)
    ESFR-SMART European Workshop on Instrumentation for the Safety of Liquid Metal Facilities, 10.-12.04.2019, Dresden, Deutschland

Publ.-Id: 29334 - Permalink


Simultaneous determination of flow velocity and electrical conductivity of a liquid metal using an eddy current flow meter in combination with a look-up-table method
Krauter, N.; Stefani, F.;
Eddy Current Flow Meters (ECFM) are inductive sensors that are commonly used to measure the local flow rate or flow velocity of liquid metals in the vicinity of the sensor. One disadvantage of the ECFM is, that the measured voltage signals depend on the magnetic Reynolds number i.e. they are not only depending on the flow velocity but also on the electrical conductivity of the liquid metal. For applications where the temperature (and therefore also the electrical conductivity) is fluctuating significantly, the ECFM has to be calibrated in order to be able to distinguish between the influence of the flow velocity and the temperature on the measured signals. In this paper we present a method that allows the simultaneous measurement of electrical conductivity and flow velocity by using a so called Look-Up-Table method. When using this method, there is no need to calibrate the ECFM.
Keywords: Eddy current, inductive flow measurement, look-up-table
  • Contribution to proceedings
    11th Pamir International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich
  • Lecture (Conference)
    11th Pamir International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich

Publ.-Id: 29333 - Permalink


I-BEAT: Ultrasonic method for online measurement of the energy distribution of a single ion bunch
Haffa, D.; Yang, R.; Bin, J.; Lehrack, S.; Brack, F.-E.; Ding, H.; Englbrecht, F.; Gao, Y.; Gaus, L.; Gebhard, J.; Gilljohann, M.; Götzfried, J.; Hartmann, J.; Herr, S.; Hilz, P.; Kraft, S.; Kreuzer, C.; Kroll, F.; Lindner, F. H.; Metzkes-Ng, J.; Ostermayr, T. M.; Ridente, E.; Rösch, T. F.; Schilling, G.; Schlenvoigt, H.-P.; Speicher, M.; Taray, D.; Würl, M.; Zeil, K.; Schramm, U.ORC; Karsch, S.; Parodi, K.; Bolton, P.; Schreiber, J.; Assmann, W.
the shape of a wave carries all information about the spatial and temporal structure of its source, given that the medium and its properties are known. Most modern imaging methods seek to utilize this nature of waves originating from Huygens’ principle. We discuss the retrieval of the complete kinetic energy distribution from the acoustic trace that is recorded when a short ion bunch deposits its energy in water. this novel method, which we refer to as Ion-Bunch energy Acoustic tracing (I-BeAt), is a refinement of the ionoacoustic approach. With its capability of completely monitoring a single, focused proton bunch with prompt readout and high repetition rate, I-BeAt is a promising approach to meet future requirements of experiments and applications in the field of laser-based ion acceleration. We demonstrate its functionality at two laser-driven ion sources for quantitative online determination of the kinetic energy distribution in the focus of single proton bunches
Keywords: laser ion acceleration, ion spectrometer

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Publ.-Id: 29332 - Permalink


Direct Observation of Plasma Waves and Dynamics Induced by Laser-Accelerated Electron Beams
Gilljohann, M. F.; Ding, H.; Döpp, A.; Götzfried, J.; Schindler, S.; Schilling, G.; Corde, S.; Debus, A.; Heinemann, T.; Hidding, B.; Hooker, S. M.; Irman, A.; Kononenko, O.; Kurz, T.; Martinez De La Ossa, A.; Schramm, U.ORC; Karsch, S.
Plasma wakefield acceleration (PWFA) is a novel acceleration technique with promising prospects for both particle colliders and light sources. However, PWFA research has so far been limited to a few large-scale accelerator facilities worldwide. Here, we present first results on plasma wakefield generation using electron beams accelerated with a 100-TW-class Ti:sapphire laser. Because of their ultrashort duration and high charge density, the laser-accelerated electron bunches are suitable to drive plasma waves at electron densities in the order of 1019  cm−3. We capture the beam-induced plasma dynamics with femtosecond resolution using few-cycle optical probing and, in addition to the plasma wave itself, we observe a distinctive transverse ion motion in its trail. This previously unobserved phenomenon can be explained by the ponderomotive force of the plasma wave acting on the ions, resulting in a modulation of the plasma density over many picoseconds. Because of the scaling laws of plasma wakefield generation, results obtained at high plasma density using high-current laser-accelerated electron beams can be readily scaled to low-density systems. Laser-driven PWFA experiments can thus act as miniature models for their larger, conventional counterparts. Furthermore, our results pave the way towards a novel generation of laser-driven PWFA, which can potentially provide ultralow emittance beams within a compact setup.
Keywords: laser wakefield, plasma wakefield electron acceleration, high power laser, advanced accelerator

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Publ.-Id: 29331 - Permalink


A new method for the production of CeO2-base nanograined high capacity absorbent
Bonani, W.; Walter, O.; Cologna, M.; Prieur, D.; Beck, A.; Vitova, T.; Martin, P.; Störmer, H.; Popa, K.;
Due to the broad range of applications (e.g.: catalyst, polishing agents, in fuel cells, pollutant adsorbed, in medicine), ceria is one of the most engineered oxides at nano- and micro-scale. The present research demonstrates highly reactive, nearly mono-dispersed metal oxides NPs with very large specific surface area (>300 m /g). The size of the NPs can be tailored by controlling the temperature and the pressure of the process. This research project explores applications of high quality CeO nanomaterials towards safe management of liquid radioactive wastes contributing to the environmental protection, resources, energy consumption optimisation, and circular economy.
  • Poster
    Nano Today Conference, 17.-21.06.2019, Lisbon, Portugal

Publ.-Id: 29330 - Permalink


How do actinyls interact with hyperphosphorylated yolk protein Phosvitin ?
Kumar, S.; Creff, G.; Hennig, C.; Rossberg, A.; Steudtner, R.; Raff, J.; Vidaud, C.; Oberhaensli, F. R.; Bottein, Y.; Den Auwer, C.;
We carried out a multi-techniques spectroscopic investigation to reveal the coordination geometry of actinyl ions (U(VI), Np(V)) in speciation with phosvitin protein. Like other protein molecules, phosvitin has carboxylic, phosphoryl and amide functional groups, but it has clustered serine residues and all the serine residues are phosphorylated to make it a hyperphosphorylated protein. IR spectroscopic study revealed phosphoryl groups as the main functional group interacting with uranyl ions. This was confirmed in the U(VI)-phosvitin fluorescence spectroscopic investigation and Np(V)-phosvitin UV-visible studies. Further, the existence of U(VI)-phosvitin system in a single speciation was found by the analysis of uranyl ion fluorescence decay data. Interestingly, X-ray absorption fine structure spectroscopic data for U/Np LIII edge revealed small contribution of bidentate binding present along with predominantly monodentate binding of phosphoryl groups in speciation of Uranyl ions with phosvitin protein. Signature of only bidentate binding was found in speciation of Np(V)-phosvitin system. In view of (de)phosphorylation as an important step of functional expression of various human body proteins, this study adds significant details to the molecular description of the toxicity of actinyl ions in biosphere.

Publ.-Id: 29329 - Permalink


Instant kit preparation of 68Ga-radiopharmaceuticals via the hybrid chelator DATA: clinical translation of [68Ga]Ga-DATA-TOC
Sinnes, J. P.; Nagel, J.; Waldron, B. P.; Maina, T.; Nock, B. A.; Bergmann, R. K.; Ullrich, M.; Pietzsch, J.ORC; Bachmann, M.; Baum, P. B.; Rösch, F.
PURPOSE:
The widespread use of 68Ga for positron emission tomography (PET) relies on the development of radiopharmaceutical precursors that can be radiolabelled and dispensed in a simple, quick, and convenient manner. The DATA (6-amino-1,4-diazapine-triacetate) scaffold represents a novel hybrid chelator architecture possessing both cyclic and acyclic character that may allow for facile access to 68Ga-labelled tracers in the clinic. We report the first bifunctional DATA chelator conjugated to [Tyr3]octreotide (TOC), a somatostatin subtype 2 receptor (SST2)-targeting vector for imaging and functional characterisation of SSTR2 expressing tumours.

METHODS:
The radiopharmaceutical precursor, DATA-TOC, was synthesised as previously described and used to complex natGa(III) and 68Ga(III). Competition binding assays of [natGa]Ga-DATA-TOC or [natGa]Ga-DOTA-TOC against [125I-Tyr25]LTT-SS28 were conducted in membranes of HEK293 cells transfected to stably express one of the hSST2,3,5 receptor subtypes (HEK293-hSST2/3/5 cells). First in vivo studies were performed in female NMRI-nude mice bearing SST2-positive mouse phaeochromocytoma mCherry (MPC-mCherry) tumours to compare the in vivo SST2-specific tumour-targeting of [68Ga]Ga-DATA-TOC and its overall pharmacokinetics versus the [68Ga]Ga-DOTA-TOC reference. A direct comparison of [68Ga]Ga-DATA-TOC with the well-established PET radiotracer [68Ga]Ga-DOTA-TOC was additionally performed in a 46-year-old male patient with a well-differentiated NET (neuroendocrine tumour), representing the first in human administration of [68Ga]Ga-DATA-TOC.

RESULTS:
DATA-TOC was labelled with 68Ga with a radiolabelling efficiency of > 95% in less than 10 min at ambient temperature. A molar activity up to 35 MBq/nmol was achieved. The hSST2-affinities of [natGa]Ga-DATA-TOC and [natGa]Ga-DOTA-TOC were found similar with only sub-nanomolar differences in the respective IC50 values. In mice, [68Ga]Ga-DATA-TOC was able to visualise the tumour lesions, showing standardised uptake values (SUVs) similar to [68Ga]Ga-DOTA-TOC. Direct comparison of the two PET tracers in a NET patient revealed very similar tumour uptake for the two 68Ga-radiotracers, but with a higher tumour-to-liver contrast for [68Ga]Ga-DATA-TOC.

CONCLUSION:
[68Ga]Ga-DATA-TOC was prepared, to a quality appropriate for in vivo use, following a highly efficient kit type process. Furthermore, the novel radiopharmaceutical was comparable or better than [68Ga]Ga-DOTA-TOC in all preclinical tests, achieving a higher tumour-to-liver contrast in a NET-patient. The results illustrate the potential of the DATA-chelator to facilitate the access to and preparation of 68Ga-radiotracers in a routine clinical radiopharmacy setting.
Keywords: DATA-TOC; DOTA-TOC; Gallium-68; Molecular imaging; NET; PET-CT; Somatostatin receptor

Publ.-Id: 29328 - Permalink


High-field magnetoresistance of graphite revised
Barzola-Quiquia, J.; Esquinazi, P. D.; Precker, C. E.; Stiller, M.; Zoraghi, M.; Förster, T.; Herrmannsdörfer, T.; Coniglio, W. A.;
A detailed magnetoresistance (MR) study of bulk and microflake samples of highly oriented pyrolytic graphite in a broad temperature 240 ≳ T ≳ 1 K and magnetic field μ0H ≼ 62 T range, reveals the existence of three independent phenomena, the contributions of which are observed at different temperatures and fields. The identification of the three phenomena was possible by studying the MR of samples with thickness of 25 μm to 23 nm. At temperatures T ≳ 100 K the MR is mainly given by the semiconducting stacking order regions. At lower temperatures the contribution of the internal interfaces of graphite to its MR is clearly observable. These interfaces are the origin of the commonly observed electronic phase transitions at fields 35 ≲ μ0H ≲ 55 T at T ≲ 10 K as well as a background MR in the whole field range that resembles the MR measured in granular superconductors.

Publ.-Id: 29327 - Permalink


Bedtime stories from space - Cosmogenic nuclides investigated by accelerator mass spectrometry
Merchel, S.ORC; Rugel, G.; Wallner, A.; DREAMS-Friends/Users
High-energy particles as part of the cosmic ray spectrum are constantly bombarding Earth and induce nuclear reactions in the atmosphere and the Earth’s surface. The reaction products can be determined by sophisticated analytical methods such as mass spectrometry (noble gases), radioactivity counting (short-lived radionuclides) or accelerator mass spectrometry (long-lived radionuclides). Their concentrations allow us to date and quantify geomorphological processes like Earth quakes, rock avalanches, glacier movements, volcanic eruptions, tsunamis, and meteoroid impacts, which have happened hundred to million years ago. Combined with stable isotope data, we can reconstruct the Sun’s activity, the Earth’s magnetic field and temperature of the past.

Additionally, meteorites found on Earth also contain the same nuclear reaction products induced mainly by the galactic cosmic radiation but at much higher concentrations as they have not been shielded by the Earth’s atmosphere and magnetic field while irradiated. These data provide information about the exposure history of the individual meteorite and the cosmic radiation itself.

Last but not least, terrestrial archives from the deep-sea or from remote areas like Antarctica contain traces of cosmic events like supernovae explosions or stellar collisions. Identifying those long-lived radionuclides, produced not only long-time ago but also at a far-distance in the interstellar space, gives hints about these amazing astrophysical events.

For many of these interdisciplinary research areas accelerator mass spectrometry (AMS) being able to determine long-lived radionuclides at the ultra-trace level, i.e. isotopic ratios (radioactive/stable) as low as 10-16, is nowadays the analytical method-of-choice. Thus, DREsden AMS (DREAMS) and other European AMS facilities offer external users free measurements via a Trans-National-Access proposal program (www.ionbeamcenters.eu) and also national access (www.hzdr.de/ibc; DREAMS only).
Keywords: AMS, cosmic radiation
  • Invited lecture (Conferences)
    Colloquium Analytische Atomspektroskopie 2019 (canas 2019), 23.-26.09.2019, Freiberg, Deutschland

Publ.-Id: 29326 - Permalink


Extremely high conductivity observed in the triple point topological metal MoP
Kumar, N.; Sun, Y.; Nicklas, M.; Watzmann, S. J.; Young, O.; Leermakers, I.; Hornung, J.; Klotz, J.; Gooth, J.; Manna, K.; Süß, V.; Guin, S. N.; Förster, T.; Schmidt, M.; Muechler, L.; Yan, B.; Werner, P.; Schnelle, W.; Zeitler, U.; Wosnitza, J.; Parkin, S. S. P.; Felser, C.; Shekhar, C.;
Weyl and Dirac fermions have created much attention in condensed matter physics and materials science. Recently, several additional distinct types of fermions have been predicted. Here, we report ultra-high electrical conductivity in MoP at low temperature, which has recently been established as a triple point fermion material. We show that the electrical resistivity is 6 nΩ cm at 2 K with a large mean free path of 11 microns. de Haas-van Alphen oscillations reveal spin splitting of the Fermi surfaces. In contrast to noble metals with similar conductivity and number of carriers, the magnetoresistance in MoP does not saturate up to 9 T at 2 K. Interestingly, the momentum relaxing time of the electrons is found to be more than 15 times larger than the quantum coherence time. This difference between the scattering scales shows that momentum conserving scattering dominates in MoP at low temperatures.

Publ.-Id: 29325 - Permalink


Ultrafast Response of Photoexcited Carriers in Transition Metal Oxides under High Pressure
Braun, J. M.;
In this work, optical pump – near-infrared probe and near-infrared pump – mid-infrared probe spectroscopy are used for the investigation of pressure-induced insulator-tometal transitions in transition metal oxide compounds. The materials under study are a-Fe₂O₃, also known as hematite, and VO₂. Both materials undergo pressureinduced metallization. However, the physical mechanisms of this phase transition are very different for these systems and have not been fully understood up to now. Using ultrafast pump-probe spectroscopy we obtain an insight into the evolution of the band structure and electron dynamics across the insulator-to-metal transition.
In the case of VO₂, our near-infrared pump – mid-infrared probe experiments reveal a non-vanishing pumping threshold for photo-induced metallization even at our highest pressures around 20 GPa. This demonstrates the existence of localized charge carriers and the corresponding persistence of a band gap. Besides the threshold behaviour for photo-induced metallization, the carrier relaxation time scale, and the linear reflectivity and transmissivity have been studied under pressure increase. An anomaly in the threshold behaviour as well as the linear reflectivity and transmissivity at a critical pressure around 7 GPa indicates band gap filling under pressure. This is further supported by results obtained under decompression, where the changes of the linear reflectivity turned out to be almost fully reversible. The observations on VO₂ are highly reproducible and can be explained in terms of a pressure-induced bandwidth-driven insulator-to-metal transition.
Fe₂O₃ has been studied via optical pump – near-infrared probe spectroscopy up to pressures of 60 GPa. In the pressure range up to 40 GPa, the changes of the response can be explained by photo-induced absorption and bleaching. The pressure-dependent study of the relaxation dynamics allows to identify cooling of the electron system as origin of the picosecond relaxation process. A sharp anomaly found in the response of Fe₂O₃ at 40 GPa indicates a strong rearrangement of the electronic band structure which could be explained by an insulator-to-metal phase transition induced by pumping.
The successful demonstration of pump-probe experiments in diamond anvil cells using pulses from optical to mid-infrared wavelengths and reaching pressures of several tens of GPa is a good basis for further experimental high-pressure studies. Our results obtained on VO₂ and Fe₂O₃ can serve as a benchmark for the development of advanced material models.
Keywords: metal-insulator transition; high-pressure; ultrafast spectroscopy; correlated oxides
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-101 2019

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Publ.-Id: 29324 - Permalink


Cytocompatible, Injectable, and Electroconductive Soft Adhesives with Hybrid Covalent/Noncovalent Dynamic Network
Xu, Y.; Patsis, P. A.; Hauser, S.; Voigt, D.; Rothe, R.; Günther, M.; Cui, M.; Yang, X.; Wieduwild, R.; Eckert, K.; Neinhuis, C.; Akbar, T. F.; Minev, I. R.; Pietzsch, J.ORC; Zhang, J.
Synthetic conductive biopolymers have gained increasing interest in tissue engineering, as they can provide a chemically defined electroconductive and biomimetic microenvironment for cells. In addition to low cytotoxicity and high biocompatibility, injectability and adhesiveness are important for many biomedical applications but have proven to be very challenging. Recent results show that fascinating material properties can be realized with a bioinspired hybrid network, especially through the synergy between irreversible covalent crosslinking and reversible noncovalent self-assembly.
Herein, a polysaccharide-based conductive hydrogel crosslinked through noncovalent and reversible covalent reactions is reported. The hybrid material exhibits rheological properties associated with dynamic networks such as self-healing and stress relaxation. Moreover, through fine-tuning the network dynamics by varying covalent/noncovalent crosslinking content and incorporating electroconductive polymers, the resulting materials exhibit electroconductivity and reliable adhesive strength, at a similar range to that of clinically used fibrin glue. The conductive soft adhesives exhibit high cytocompatibility in 2D/3D cell cultures and can promote myogenic differentiation of myoblast cells. The heparin-containing electroconductive adhesive shows high biocompatibility in immunocompetent mice, both for topical application and as injectable materials. The materials could have utilities in many biomedical applications, especially in the area of cardiovascular diseases and wound dressing.
Keywords: 3D cell culture, adhesion, biocompatibility, PEDOT, small animal magnetic resonance imaging

Publ.-Id: 29323 - Permalink


Exciton localization in MoSe₂ monolayer induced by adsorbed gas molecules
Venanzi, T.; Arora, H.ORC; Erbe, A.; Pashkin, O.ORC; Winnerl, S.; Helm, M.; Schneider, H.ORC
Lattice defects and dielectric environment play a crucial role for 2D materials. Gas molecules can get physisorbed easily on the surface through van der Waals forces and can modify dramatically the electronic and optical properties. In this work we investigate the impact of the physisorbed gas molecules on the optical properties of MoSe₂ monolayers by means of low-temperature photoluminescence (PL). More specifically we focus on the physics of excitons localized by gas molecules. The associated PL peak is observed to show a systematic and large red-shift with temperature and a blue-shift with laser irradiation. Both energy shifts are explained in terms of thermal instability of the localization in combination with hopping effects. Finally a model is presented which can reproduce the experimental data with excellent agreement.
Keywords: MoSe2, photoluminescence, localized excitons, TMD, physisorption

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  • Secondary publication expected from 03.05.2020

Publ.-Id: 29321 - Permalink


XAFS Spectroscopy Study of Microstructure and Electronic Structure of Heterosystems Containing Si/GeMn Quantum Dots
Erenburg, S. B.; Trubina, S. V.; Zvereva, A.; Zinoviev, A.; Katsyuba, V.; Dvurechenskii, V.; Kvashnina, K. O.; Voelskow, M.;
Using X-ray absorption near edge structure spectroscopy, extended X-ray absorption fine structure spectroscopy, atomic force microscopy, and Rutherford backscattering spectroscopy, the features of the microstructure and elemental composition of Si/GeMn magnetic systems obtained by molecular beam epitaxy and containing quantum dots are studied. Intense mixing of Ge and Si atoms is found in all samples. The degree of mixing (diffusion) correlates with the conditions of synthesis of Si/GeMn samples. For these systems, direct contacts of germanium atoms with manganese atoms are characterized and the presence of interstitial manganese with tetrahedral coordination and substitution of manganese for germanium and silicon in the lattice sites is found. The presence of stoichiometric phases Ge8Mn11, Ge3Mn5 is not detected. The correlations of the Ge, Si, and Mn coordination numbers in the Ge environment are determined both with the Mn flux value (evaporator temperature) and with the temperature at which quantum dots are grown, as well as with other synthesis conditions. The manganese concentration in the samples is determined.

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Publ.-Id: 29320 - Permalink


Viscosity measurements in pulsed magnetic fields by using a quartz-crystal microbalance
Nomura, T.; Zherlitsyn, S.ORC; Kohama, Y.; Wosnitza, J.
Viscosity measurements in combination with pulsed magnetic fields are developed by use of a quartz-crystal microbalance (QCM). When the QCM is immersed in liquid, the resonant frequency, f0, and the quality factor, Q, of the QCM change depending on (pn)0.5, where p is the mass density and n the viscosity. During the magnetic-field pulse, f0 and Q of the QCM are simultaneously measured by a ringdown technique. The typical resolution of (pn)>sup>0.5 is 0.5%. As a benchmark, the viscosity of liquid oxygen is measured up to 55 T.

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Publ.-Id: 29319 - Permalink


Spin Textures as Sources for Magnons with Short Wavelengths and 3D Mode Profiles
Sluka, V.; Wintz, S.;
In this chapter, we will give an overview of contemporary methods for spin-wave excitation and propagation. We will focus on the exploitation of spin textures for the generation and propagation of spin waves with very short wavelengths as well as on the 3D nature of such excited waves.
Keywords: spin waves, excitation, 3D
  • Book chapter
    Gianluca Gubbiotti: Three-Dimensional Magnonics, Singapur: Jenny Stanford Publishing, 2019, 9789814800730, 219-259

Publ.-Id: 29318 - Permalink


A model of a tidally synchronized solar dynamo
Stefani, F.; Giesecke, A.ORC; Weier, T.
We discuss a solar dynamo model of Tayler–Spruit type whose Omega-effect is conventionally produced by a solar-like differential rotation but whose alpha-effect is assumed to be periodically modulated by planetary tidal forcing. This resonance-like effect has its rationale in the tendency of the current-driven Tayler instability to undergo intrinsic helicity oscillations which, in turn, can be synchronized by periodic tidal perturbations. Specifically, we focus on the 11.07-years alignment periodicity of the tidally dominant planets Venus, Earth, and Jupiter, whose persistent synchronization with the solar dynamo is briefly touched upon. The typically emerging dynamo modes are dipolar fields, oscillating with a 22.14-years period or pulsating with a 11.07-years period, but also quadrupolar fields with corresponding periodicities. In the absence of any constant part of alpha, we prove the sub-critical nature of this Tayler–Spruit type dynamo. The resulting amplitude of the alpha oscillation that is required for dynamo action turns out to lie in the order of 1 m/s, which seems not implausible for the Sun. When starting with a more classical, non-periodic part of alpha, even less of the oscillatory alpha part is needed to synchronize the entire dynamo. Typically, the dipole solutions show butterfly diagrams, although their shapes are not convincing yet. Phase coherent transitions between dipoles and quadrupoles, which are reminiscent of the observed behavior during the Maunder minimum, can easily be triggered by long-term variations of dynamo parameters, but may also occur spontaneously even for fixed parameters. Further interesting features of the model are the typical second intensity peak and the intermittent appearance of reversed helicities in both hemispheres.

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  • Secondary publication expected from 22.05.2020

Publ.-Id: 29317 - Permalink


Micro-scale isotopic variability of low-temperature pyrite in fractured crystalline bedrock ― A large Fe isotope fractionation between Fe(II)aq/pyrite and absence of Fe-S isotope co-variation
Yu, C.; Drake, H.; Lopez Fernandez, M.ORC; Whitehouse, M.; Dopson, M.; Åström, M. E.
This study assessed Fe-isotope ratio (56Fe/54Fe, expressed as δ56Fe relative to the IRMM-014 standard) variability and controls in pyrite that has among the largest reported S-isotope variability (maximum δ34S: 140‰). The pyrite occurs as fine-grained secondary crystals in fractures throughout the upper kilometer of granitoids of the Baltic Shield, and was analyzed here for δ56Fe by in situ secondary ion mass spectrometry (SIMS). Part of these pyrite crystals were picked from borehole instrumentation at depths of >400 m below sea level (m.b.s.l.), and thus are modern (known to have formed within 17 years) and can be compared with the δ56Fe of the source dissolved ferrous iron. The δ56Fe values of the modern pyrite crystals (−1.81‰ to +2.29‰) varied to a much greater extent than those of the groundwaters from which they formed (−0.48‰ to +0.13‰), providing strong field evidence for a large Fe isotope fractionation during the conversion of Fe(II)aq to FeS and ultimately to pyrite. Enrichment of 56Fe in pyrite relative to the groundwater was explained by equilibrium Fe(II)aq-FeS isotope fractionation, whereas depletion of 56Fe in pyrite relative to the groundwater was mainly the result of sulfidization of magnetite and kinetic isotopic fractionation during partial transformation of microsized FeS to pyrite. In many pyrite crystals, there is an increase in δ34S from crystal center to rim reflecting Rayleigh distillation processes (reservoir effects) caused by the development of closed-system conditions in the micro-environment near the growing crystals. A corresponding center-to-rim feature was not observed for the δ56Fe values. It is therefore unlikely that the groundwater near the growing pyrite crystals became progressively enriched in the heavy Fe isotope, in contrast to what has been found for the sulfur in sulfate. Other pyrite crystals formed following bacterial sulfate reduction in the time period of mid-Mesozoicum to Quaternary, had an almost identical Fe-isotope variability (total range: −1.50‰ to +2.76‰), frequency-distribution pattern, and relationship with δ34S as the recent pyrite formed on the borehole instrumentation. These features suggest that fundamental processes are operating and governing the Fe-isotope composition of pyrite crystals formed in fractured crystalline bedrock over large time scales.
Keywords: Pyrite Iron isotopes Equilibrium Fe-isotope fractionation Magnetite sulfidization Partial pyritization Fractured crystalline bedrock

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  • Secondary publication expected from 28.05.2020

Publ.-Id: 29315 - Permalink


Horizon-2020 ESFR-SMART project on SFR safety: status after first 15 months
Mikityuk, K.; Girardi, E.; Krepel, J.; Bubelis, E.; Fridman, E.; Rineiski, A.; Girault, N.; Payot, F.; Buligins, L.; Gerbeth, G.; Chauvin, N.; Latge, C.; Guidez, J.;
Devoted to the Generation-IV European Sodium Fast Reactor safety, the Horizon-2020 ESFR-SMART project was launched in September 2017. Selected results and milestones achieved during the first fifteen months of the project are briefly reviewed in the paper, including 1)proposal of new safety measures for ESFR; 2)evaluation of ESFR core performance; 3) benchmarking of codes; 4) experimental programs; and 5) education and training.
  • Contribution to proceedings
    27th International Conference on Nuclear Engineering - ICONE27, 19.-24.05.2019, Ibaraki, Japan

Publ.-Id: 29314 - Permalink


Benchmarking KENO-VI against MCNP/Serpent using a simplified SFR pin cell problem
Fridman, E.; Jiménez-Carrascosa, A.; García-Herranz, N.; Alvarez-Velarde, F.; Romojaro, P.; Bostelmann, F.;
  • Lecture (Conference)
    OECD/NEA UAM Workshop 2019, 13.-17.05.2019, Oak Ridge National Laboratory, USA

Publ.-Id: 29313 - Permalink


Initial solution of the SFR-UAM Exercises I-1 and I-2 with Serpent
Fridman, E.;
Initial solution of the SFR-UAM Exercises I-1 and I-2 with Serpent
  • Lecture (Conference)
    OECD/NEA UAM Workshop 2019, 13.-17.05.2019, Oak Ridge National Laboratory, USA

Publ.-Id: 29312 - Permalink


About the impact of the Unresolved Resonance Region in Monte Carlo simulations of Sodium Fast Reactors
Jiménez-Carrascosa, A.; Fridman, E.ORC; García-Herranz, N.; Alvarez-Velarde, F.; Romojaro, P.; Bostelmann, F.
In the last few years, and within the framework of different European projects, KENO-VI code from SCALE system has been employed to perform detailed continuous-energy Monte Carlo transport calculations for advanced fast reactors. The core characterization of both the sodium-cooled ASTRID and the lead-cooled ALFRED reactors was performed during the FP7 cross-cutting ESNII+ project; more recently, core calculations for the sodium-cooled Superphénix reactor and the improved European Sodium Fast Reactor design were performed within the HORIZON2020 ESFR-SMART project. In all cases, the effective multiplication factor predicted by KENO-VI was systematically higher (around 400-500 pcm) than the values computed by MCNP and Serpent Monte Carlo codes, using the same nuclear data library.

In order to provide insight into the origin of the observed discrepancies, a simplified 2D MOX-fueled SFR pin-cell benchmark has been launched. The multiplication factor, as well as 1-group and VITAMINJ 175-group cross-sections computed by KENO-VI, Serpent and MCNP codes employing ENDF/B-VII.1 data library, have been compared.

Significant differences between KENO-VI and the other codes have been found in the unresolved resonance regions of 239Pu and 241Pu capture and production cross sections, while negligible differences appeared outside those energy ranges. On the other hand, calculations without using probability tables have shown very good agreement. Quantita-tive comparison is presented and analyzed, along with a discussion of the impact of the probability-table treatment in the three codes for MOX-fueled systems with typical SFR spectrum.
Keywords: Unresolved Resonance Region, Probability Tables, Monte Carlo simulations of SFR
  • Contribution to proceedings
    ICAPP 2019 – International Congress on Advances in Nuclear Power Plants, 12.-15.05.2019, Juan-les-pins, France
    Proceedings of ICAPP 2019

Publ.-Id: 29311 - Permalink


In-house reference materials for the determination of low titanium concentration in SiO2 by secondary ion mass spectrometry
Ziegenrücker, R.ORC; Belokonov, G.; Böttger, R.; Couffignal, F.; Munnik, F.ORC; Renno, A.; Wiedenbeck, M.; Wu, H. S.
Secondary ion mass spectrometry (SIMS) is routinely used for geochemical and mineralogical applications, but quantification is still the major challenge of this method. Each analysed matrix needs its own matrix-matched reference material (RM). However, the list of available reference materials is short compared to the needs.

One approach for the production of suitable RMs is the use of ion implantation to introduce a known amount of an isotope into a matrix-matched material. This is widely used for SIMS applications in materials science, but rarely for geochemical problems. Bumett et al. (2014) [1] demonstrated the principal appropriateness and ways to calibrate nominal implant fluence. We choose the more elaborate way of implanting a box profile to allow an effectivly homogeneous distribution of the respective isotope in all three dimensions.

Silicon dioxide SiO2, a “simple” mineralogical and chemical system, can record scientificly important data e.g. the Ti-in-quartz geothermometer [2, 3]. 47Ti respectively 48Ti were implanted into synthetic ultra-high purity silica glass. Box profiles with concentrations between 10 and 1000 ppm and a maximum depth of homogeneous 47/48Ti distribution between 200 and 500 nm were produced at the Ion Beam Center in Dresden-Rossendorf. Single implantation steps with different ion-energies and –doses were simulated with the SRIM (Stopping and Range of Ions in Matter) software [4] and optimized to the target concentrations, implantation-depths and technological limitations of the implanter.

Several different implanted test-samples were characterized by means of SIMS, atomic force microscopy (AFM) and other analytical techniques. These showed that Ti is homogeneously distributed in the glass structure within ± 5% uncertainty in all 3 dimensions, while the surface-roughness remains suitable for SIMS depth profiling.

Such reference materials are also very promising for the quantification of Super-SIMS measurements [5].


[1] Bumett, D.S., et al. (2014). Ion Implants as Matrix-Appropriate Calibrators for Geochemical Ion Probe Analyses. Geostandards and Geoanalytical Research, 39(3), 265-276.
[2] Wark, D. A., Watson E. B. (2006). TitaniQ: a titanium-in-quartz geothermometer. Contributions to Mineralogy and Petrology, 152(6), 743-754.
[3] Thomas, J. B., Watson E. B., et al. (2010). TitaniQ under pressure: the effect of pressure and temperature on the solubility of Ti in quartz. Contributions to Mineralogy and Petrology, 160(5), 743–759.
[4] Ziegler, J. F. (2004). SRIM-2003. Nuclear Instruments and Methods in Physics Research Section B, 219-220, 1027-1036.
[5] Rugel, G., et al, this conference.
Keywords: Implantation, SIMS, Titanium, Quartz, Quarz, Reference material, Referenz Material
  • Poster
    Ion Beam Physics Workshop 2019, 24.-26.06.2019, Dresden, Germany

Publ.-Id: 29310 - Permalink


Preparation of non-oxidized Ge quantum dot lattices in amorphous Al2O3, Si3N4 and SiC matrices
Nekić, N.; Šarić, I.; Salamon, K.; Basioli, L.; Sancho-Parramon, J.; Grenzer, J.; Hübner, R.; Bernstorff, S.; Petravić, M.; Mičetić, M.;
The preparation of non-oxidized Ge quantum dot (QD) lattices embedded in Al2O3, Si3N4, SiC matrices by self-assembled growth was studied. The materials were produced by magnetron sputtering deposition, using different substrate temperatures. The deposition regimes leading to the self-assembled growth type and the formation of three-dimensionally ordered Ge QD lattices in different matrices were investigated and determined. The oxidation of the Ge QDs in different matrices was monitored and the best conditions for the production of non-oxidized Ge QDs were found. The optical properties of the Ge QD lattices in different matrices show a strong dependence on the Ge oxidation and the matrix type.
Keywords: Ge QD lattices, Ge oxidation, self-assembled growth, influence of matrix

Publ.-Id: 29309 - Permalink


The magnetic structure of L10 ordered MnPt at room temperature determined using polarized neutron diffraction
Solina, D.; Schmidt, W.; Kaltofen, R.; Krien, C.; Lai, C.-H.; Schreyer, A.;
Neutron scattering studies have been carried out on single crystal films of [001] orientated L10 ordered MnPt grown epitaxially onMgO(001) usingDCmagnetron sputtering. Polarized neutron diffraction studies at room temperature show that the moments in ordered MnPt are aligned perpendicular to the [001] axis with a tilt of 45° to the [100] axis and not parallel to [100] as inferred from previous powder neutron diffraction measurements.
Keywords: antiferromagnetic, neutron diffraction, platinum alloys

Publ.-Id: 29308 - Permalink


Fast neutron inelastic scattering from ⁷Li
Beyer, R.ORC; Frotscher, A.; Gyürky, G.; Junghans, A.ORC; Nolte, R.; Nyman, M.; Olacel, A.; Pirovano, E.; Plompen, A.; Röttger, S.; Grieger, M.; Hammer, S.; Kögler, T.ORC; Ludwig, F.; Müller, S.ORC; Reinicke, S.; Schulz, S.; Schwengner, R.ORC; Trinh, T. T.; Turkat, S.; Urlaß, S.; Wagner, A.ORC
The inelastic scattering of fast neutrons from 7Li nuclei was investigated at the nELBE neutron-time-of-flight facility. This process has technological implications in fusion and fission reactors. In the former it could create an intense γ-ray field causing heating and radiation damage, in the latter it could strongly influence the neutron energy spectrum and therefore the neutronics of e.g. novel reactor concepts like the molten salt reactor. Furthermore the γ-ray production cross section of 7Li is a very good case to be used as an alternative for neutron fluence determination to enable relative measurements of neutron-induced reactions. Inelastic neutron scattering on 7Li leads to the production of a 478 keV γ-ray from the first excited state of 7Li. The next higher lying state in this nucleus at 4630 keV already undergoes break up into an α-particle and a triton. The angular distribution of the γ-rays after inelastic neutron scattering is isotropic and has negligible internal conversion. The threshold energy is low enough to be able to cover a large range of neutron energy and the cross section of about 0.2 barn is reasonably high to enable good statistics within a feasible measurement time.
At nELBE the photon production cross section was determined by irradiated a disc of LiF with a neutrons of energies ranging from 100 keV to about 10 MeV. The target position was surounded by a setup of 7 LaBr3 scintillation detectors and 4 high-purity germanium detectors to detect the 478 keV de-excitation gamma-rays. A 235U fission chamber was used to determine the incoming neutron flux. All details of the experiment and the data analysis will be explained. The final results will be compared to previous measurement done e.g. at the GELINA facility.
Keywords: fast neutron inelastic scattering, ⁷Li, nELBE
Related publications
Messung des 478 keV Gammaproduktionsquerschnitts nach … (Id 27814) HZDR-primary research data are used by this publication
  • Lecture (Conference)
    2019 International Conference on Nuclear Data for Science and Technology, 19.-24.05.2019, Beijing, China

Publ.-Id: 29307 - Permalink


Detection of ultra-low protein concentrations with the simplest possible field effect transistor
Georgiev, Y.ORC; Petkov, N.; Yu, R.; Nightingale, A. M.; Buitrago, E.; Lotty, O.; Demello, J. C.; Ionescu, A.; Holmes, J. D.
Silicon nanowire (Si NW) sensors have attracted great attention due to their ability to provide fast, low-cost, label-free, real-time detection of chemical and biological species. Usually configured as field effect transistors (FETs), they have already demonstrated remarkable sensitivity with high selectivity (through appropriate functionalisation) towards a large number of analyses in both liquid and gas phases. Despite these excellent results, Si NW FET sensors have not yet been successfully employed to detect single molecules of either a chemical or biological target species. Here we show that sensors based on silicon junctionless nanowire transistors (JNTs), the simplest possible transistors, are capable of detecting the protein streptavidin at a concentration as low as 580 zM closely approaching the single molecule level. This ultrahigh detection sensitivity is due to the intrinsic advantages of junctionless devices over conventional FETs.

Apart from their superior functionality, JNTs are much easier to fabricate by standard microelectronic processes than transistors containing p-n junctions. The ability of JNT sensors to detect ultra-low concentrations (in the zeptomolar range) of target species, and their potential for low-cost mass production, will permit their deployment in numerous environments, including life sciences, biotechnology, medicine, pharmacology, product safety, environmental monitoring and security.
Keywords: Si nanowire biosensor, junctionless nanowire transistor, ultrahigh detection sensitivity, protein, streptavidin, single-molecule detection

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  • Secondary publication expected from 08.05.2020

Publ.-Id: 29306 - Permalink


Development of nuclear and optical dual-labelled agents for cancer imaging
Stephan, H.ORC
For the past decade, nuclear and optical dual-labelled imaging agents have attracted enormous attention. Applied to cancer imaging, tumours can be tracked down by nuclear techniques such as single-photon emission tomography (SPECT) and positron emission tomography (PET), and subsequently resected using image-guided surgery with the appropriate fluorophores. Moreover, the high spatial resolution of fluorescence imaging permits the elucidation of cell-biological events and thereby gaining a deeper insight into in vitro and in vivo processes. The development of dual imaging probes can be achieved using sophisticated low-molecular compounds that combine moieties for the desired imaging modalities, e.g. dyes for fluorescence optical imaging, and appropriate bifunctional chelator agents (BFCAs) for radiometals enabling SPECT or PET. We have developed BFCAs based on bis(2-pyridylmethyl)-1,4,7-triazacyclononane (DMPTACN) and 3,7-diazabicyclo[3.3.1]nonane (bispidine) that rapidly form stable 64CuII complexes under mild conditions. These BFCAs are well-suited for in vivo application in cancer imaging. Since they are also relatively easy to functionalize with multiple modalities, they are ideal chelators for the design of targeted dual-labelled imaging agents (PET, fluorescence imaging). Moreover, these chelating agents can be easily grafted on the surface of nanomaterials that are equipped with a multitude of different functionalities, such as targeting units, solubility enhancer and fluorescent tags. Hence, higher sensitivity can be achieved compared to small molecules, and there is an almost infinite variability regarding the surface functionalization.
Examples of target-specific peptides and bio(nano)materials equipped with DMPTACN/bispidine ligands for labelling with 64Cu as an ideal positron emitter are discussed. This enables tumour imaging and the biodistribution of materials can be studied over a period of days via positron emission tomography (PET). The additional introduction of fluorescence labels allows for optical imaging with high spatial resolution, and offers the possibility to visualize cellular processes by fluorescence microscopy.
  • Lecture (Conference)
    Seventh International Conference on Radiation in Various Fields of Research, 10.-14.06.2019, Herceg Novi, Montenegro

Publ.-Id: 29305 - Permalink


Evidence for Recent Interstellar ⁶⁰Fe on Earth
Koll, D.; Faestermann, T.; Feige, J.; Fifield, L. K.; Froehlich, M. B.; Hotchkis, M. A. C.; Korschinek, G.; Merchel, S.ORC; Panjkov, S.; Pavetich, S.; Tims, S. G.; Wallner, A.
Over the last 20 years the long-lived radionuclide ⁶⁰Fe with a half-life of 2.6 Myr was shown to be an expedient astrophysical tracer to detect freshly synthesized stardust on Earth. The unprecedented sensitivity of Accelerator Mass Spectrometry for ⁶⁰Fe at The Australian National University (ANU) and Technical University of Munich (TUM) allowed us to detect minute amounts of ⁶⁰Fe in deep-sea crusts, nodules, sediments and on the Moon [1-5]. These signals, around 2-3 Myr and 6.5-9 Myr before present, were interpreted as a signature from nearby Supernovae which synthesized and ejected ⁶⁰Fe into the local interstellar medium.
Triggered by these findings, ANU and TUM independently analyzed recent surface material for ⁶⁰Fe, deep-sea sediments and for the first time Antarctic snow, respectively [6, 7].
We find in both terrestrial archives corresponding amounts of recent ⁶⁰Fe.
We will present these discoveries, evaluate the origin of this recent influx and bring it into line with previously reported ancient ⁶⁰Fe findings.
[1] K. Knie et. al. “Indication for supernova produced ⁶⁰Fe activity on Earth”, Phys. Rev. Lett. 83 (1999) 18.
[2] K. Knie et. al. “⁶⁰Fe anomaly in a deep-sea manganese crust and implications for a nearby supernova source”, Phys. Rev. Lett. 93 (2004) 171103.
[3] P. Ludwig et. al. “Time-resolved 2-million-year-old super-nova activity discovered in Earth's microfossil record”, PNAS 113 (2016) 9232.
[4] A. Wallner et. al. “Recent near-Earth supernovae probed by global deposition of interstellar radioactive ⁶⁰Fe”, Nature 532 (2016) 69.
[5] L. Fimiani et. al. “Interstellar ⁶⁰Fe on the surface of the Moon”, Phys. Rev. Lett. 116 (2016) 151104.
[6] D. Koll et. al. “Interstellar ⁶⁰Fe in Antarctica”, Phys. Rev. Lett., submitted
[7] A. Wallner et al. in preparation
Keywords: AMS, supernova, Antarctica, radionuclide, ⁶⁰Fe
  • Lecture (Conference)
    Heavy Ion Accelerator Symposium on Fundamental and Applied Science (HIAS), 09.-13.09.2019, Canberra, Australia

Publ.-Id: 29304 - Permalink


Effect of trivalent lanthanides and actinides on a rat kidney cell line
Heller, A.; Acker, M.; Barkleit, A.ORC; Bok, F.; Wober, J.
Exposure to trivalent lanthanides (Ln) and actinides (An) poses a serious health risk to animals and humans. Since both Ln and An are mainly excreted with the urine, we investigated the effect of La, Ce, Eu, and Yb (as representatives of Ln) as well as Am (as representative of An) exposure on a rat kidney cell line (NRK-52E) for 8, 24, and 48 h in vitro. Cell viability studies using the XTT assay and fluorescence microscopic investigations were combined with solubility and speciation studies using ICP-MS and time-resolved laser-induced fluorescence spectroscopy (TRLFS). Thermodynamic modeling was applied to predict the speciation of Ln and Am in cell culture medium.
All Ln show a concentration- and time-dependent effect on NRK-52E cells with Ce being the most potent element. Effective Ln concentrations reducing the cell viability to 50 % (EC50 values) range from 340 µM for Ce to 1.1 mM for Eu. In general, light and heavy Ln seem to exhibit a greater effect than middle Ln.
In cell culture medium with 10 % fetal bovine serum (FBS), the Ln are completely soluble and complexed with proteins from FBS. Ln speciation is time-independent. Comparative experiments with Am are ongoing and will reveal analogies and/or differences in the effect of trivalent Ln and An on rat kidney cells.
This is the first study revealing the effects of Ln onto mammalian kidney cells. Furthermore, our laboratory is one of the few worldwide, which is able to perform cell culture studies using radioactive elements like Am.
The results of this study underline the importance of combining biological, chemical, and spectroscopic methods in studying the effect of Ln and An on cells in vitro and may contribute to the improvement of the current risk assessment for Ln in the human body. Furthermore, they demonstrate that Ln seem to have no effect on rat renal cells in vitro at environmental trace concentrations. Nevertheless, especially Ce has the potential for harmful effects at elevated concentrations observed in mining and industrial areas.
Keywords: cytotoxicity, f-elements, XTT, TRLFS
  • Lecture (Conference)
    5th International Conference on Environmental Radioactivity, ENVIRA 2019, 08.-13.09.2019, Prag, Tschechische Republik

Publ.-Id: 29302 - Permalink


Influence of common decorporation agents on the speciation of trivalent f-elements in serum – a luminescence spectroscopic study
Barkleit, A.ORC; Heller, A.
The accidental release of radionuclides, especially actinides (An), in a nuclear facility or in the environment increases the risk of incorporation of these elements into the human body. Irrespective of the uptake pathway, via inhalation, ingestion, or through wounds or the skin, An are resorbed and transported by the bloodstream. Eventually, they are deposited in target organs (e.g., bone, liver or kidney) or partially excreted with urine or faeces. Fast and effective decorporation or chelation therapy is very important to minimize the health risk. To improve decorporation efficiency by choosing the right chelating agent or by designing new efficient chelators for different An, the understanding of their chemical speciation on a molecular level is crucial.
In this study, we investigate the chemical speciation of Cm(III) (as representative of An) and Eu(III) (as non-radioactive analogue for trivalent An) in blood serum. Subsequently, the alterations in speciation after spiking with common chelating agents often used for decorporation purposes, such as ethylenediaminetetraacetic acid (EDTA), or diethylenetriaminepentaacetic acid (DTPA), were studied and compared to biological ligands, such as citrate. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used to perform the speciation investigations. Thermodynamic calculations were carried out to support the experimental results.
The dominant chemical species of Eu in serum were identified by comparing the Eu luminescence spectra and lifetimes in serum with those obtained in reference solutions with individual components of the serum, such as the proteins albumin and transferrin as well as the inorganic anions phosphate and carbonate. Linear combination fitting analysis (LCFA) on the sample spectra indicated that Eu is mainly coordinated by albumin (~50 %) and transferrin (~35 %), and to a lesser extent by inorganic anions like carbonate (~15 %).
The shape of the Eu luminescence spectrum in serum was only slightly influenced by adding citrate and EDTA, whereas the shapes of the pure ligand spectra differ strongly. This indicates that the speciation of Eu in serum was only slightly changed by these ligands. In contrast, DTPA caused a splitting of both the 7F1 and 7F2 peak, which is very similar to the Eu spectrum with the pure DTPA ligand, indicating a strong change of the Eu speciation in serum towards Eu-DTPA complexation. LCFA indicated that about 50 % of the Eu was coordinated by DTPA. The luminescence lifetimes and thermodynamic calculations as well as the Cm luminescence data show similar tendencies. Our results follow the trend of the respective complex stability constants of Am(III) complexes with chelating agents and the findings from 241Am experiments with animals.
This study combining TRLFS and thermodynamic calculations demonstrates a fast and easy way to screen the effect of several chelating agents towards (luminescent) An in vitro. In future, this could be a useful tool to improve decorporation methods.
Keywords: serum proteins, EDTA, DTPA, laser fluorescence spectroscopy
  • Contribution to proceedings
    5th International Conference on Environmental Radioactivity, ENVIRA 2019, 08.-13.09.2019, Prag, Tschechische Republik
  • Lecture (Conference)
    5th International Conference on Environmental Radioactivity, ENVIRA 2019, 08.-13.09.2019, Prag, Tschechische Republik

Publ.-Id: 29300 - Permalink


Transverse electron beam dynamics in the beam loading regime
Köhler, A.;
GeV electron bunches accelerated on a centimeter scale device exemplify the extraordinary advances of laser-plasma acceleration. The combination of high charges from optimized injection schemes and intrinsic femtosecond short bunch duration yields kiloampere peak currents. Further enhancing the current while reducing the energy spread will pave the way for future application, e.g. the driver for compact secondary radiation sources such as high-field THz, high-brightness x-ray or gamma-ray sources. One essential key for beam transport to a specific application is an electron bunch with high quality beam parameters such as low energy spread as well as small divergence and spot size. The inherent micrometer size at the plasma exit is typically sufficient for an efficient coupling into a conventional beamline. However, energy spread and beam divergence require optimization before the beam can be transported efficiently. Induced by the high peak current, the beam loading regime can be used in order to achieve optimized beam parameters for beam transport.

In this thesis, the impact of beam loading on the transverse electron dynamic is systematically studied by investigating betatron radiation and electron beam divergence. For this reason, the bubble regime with self-truncated ionization injection (STII) is applied to set up a nanocoulomb-class laser wakefield accelerator. The accelerator is driven by 150TW laser pulses from the DRACO high power laser system. A supersonic gas jet provides a 3mm long acceleration medium with electron densities from 3 × 10^18 cm^−3 to 5 × 10^18 cm^−3. The STII scheme together with the employed setup yields highly reproducible injections with bunch charges of up to 0.5 nC. The recorded betatron radius at the accelerator exit is about one micron and reveals that the beam size stays at the same value. The optimal beam loading, which is observed at around 250 pC to 300 pC, leads to the minimum energy spread of ~40MeV and a 20% smaller divergence. It is demonstrated that an incomplete betatron phase mixing due to the small energy spread can explain the experimentally observed minimum beam divergence.
Keywords: Laser wakefield acceleration, laser plasma accelerator, self-truncated ionization injection, high x-ray flux, high bunch charge, beam loading, bunch size measurement, betatron radiation, betatron spectroscopy, Transverse phase space dynamic, beam divergence, beam decoherence, betatron phase mixing, betatron decoherence
Related publications
Minimizing betatron coupling of energy spread and … (Id 29188) HZDR-primary research data are used by this publication
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-102 2019

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Publ.-Id: 29299 - Permalink


Extracting the Dynamic Magnetic Contrast in Time-Resolved X-ray Transmission Microscopy
Schaffers, T.; Feggeler, T.; Pile, S.; Meckenstock, R.; Buchner, M.; Spoddig, D.; Ney, V.; Farle, M.; Wende, H.; Wintz, S.; Weigand, M.; Ohldag, H.; Ollefs, K.; Ney, A.;
Using a time-resolved detection scheme in scanning transmission X-ray microscopy (STXM) we measured element resolved ferromagnetic resonance (FMR) at microwave frequencies up to 10 GHz and a spatial resolution down to 20 nm at two different synchrotrons. We present different methods to separate the contribution of the background from the dynamic magnetic contrast based on the X-ray magnetic circular dichroism (XMCD) effect. The relative phase between the GHz microwave excitation and the X-ray pulses generated by the synchrotron, as well as the opening angle of the precession at FMR can be quantified. A detailed analysis for homogeneous and inhomogeneous magnetic excitations demonstrates that the dynamic contrast indeed behaves as the usual XMCD effect. The dynamic magnetic contrast in time-resolved STXM has the potential be a powerful tool to study the linear and non-linear magnetic excitations in magnetic micro- and nano-structures with unique spatial-temporal resolution in combination with element selectivity.
Keywords: x-ray microscopy, magnetic imaging

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Publ.-Id: 29297 - Permalink


Editorial for special issue "Jörg Steinbach"
Mamat, C.ORC
This special issue of Journal of Labelled Compounds and Radiopharmaceuticals is dedicated to commemorate the outstanding scientific work of Jörg Steinbach, former director of the Institute of Radiopharmaceutical Cancer Research at the Helmholtz‐Zentrum Dresden‐Rossendorf (HZDR) and full professor for Bioinorganic and Radiopharmaceutical Chemistry at the Technical University Dresden. Current legal regulations brought to an end the formal attachment of Professor Steinbach to the TU Dresden as well as the directorship of the institute within his 65th birthday. A festive symposium has been held at the HZDR on the occasion of his retirement on September 5th, 2018, one day after the inauguration of the new Centre for Radiopharmaceutical Tumor Research at the HZDR.
  • Journal of Labelled Compounds and Radiopharmaceuticals 62(2019)8, 350-351
    DOI: 10.1002/jlcr.3773

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  • Secondary publication expected from 12.07.2020

Publ.-Id: 29295 - Permalink


Prompt-gamma based range verification in proton therapy: Can we do better? Shall we do better?
Pausch, G.ORC
Prompt gamma-ray imaging (PGI) with a knife-edge slit camera has proven to be useful for range monitoring in proton therapy (PT). It is meanwhile applied in a prostate patient study at OncoRay. Together with an improved range prediction based on dual-energy CT and robust planning methods it could finally allow reducing the range margins, thus saving normal tissue in PT treatments. Translating these emerging techniques in clinical routine is a long but important process that will require considerable efforts.
Nevertheless we are also dealing with the far end of the translational conveyer, asking if and how in-vivo range verification could be improved. So far, PGI does not allow measuring range deviations of single pencil beams with the necessary precision. The reason is the short delivery time of such a beam spot, and the poor event statistics that can be accessed in this period. It is obvious to exploit not only spatial, but also spectroscopic and timing information of the gamma rays registered for range verification. The prompt gamma-ray spectroscopy method developed at MGH in Boston and the prompt gamma-ray timing technique explored at OncoRay in Dresden represent reasonable alternatives to PGI; but can these approaches be combined in a single, preferable simple and light-weight, clinically applicable system distinguished by minimum interference with beam and patient couch? Could such a combination improve the accuracy and allow single-spot range verification, maybe even for the non-distal spots comprising much less protons?
The talk will present our thoughts and approaches to answer this question. This includes recent results concerning prompt gamma-ray timing (PGT) and single-plane Compton imaging (SPCI). Part of the research performed in this context could also affect gamma-ray imaging in nuclear medicine.
Keywords: PGI, PGT, prompt gamma ray, proton therapy, range verification, treatment verification
  • Lecture (others)
    Medizinphysik-Seminar, 12.06.2019, Heidelberg, Deutschland

Publ.-Id: 29293 - Permalink


THEREDA - Achievements, present activities, and future developments
Moog, H. C.; Altmaier, M.; Bok, F.; Brendler, V.; Freyer, D.; Gaona, X.; Marquardt, C.; Richter, A.; Scharge, T.; Seher, H.; Thoenen, T.; Voigt, W.;
INTRODUCTION
Five institutions are actively maintaining the thermodynamic reference database THEREDA aiming at the calculation of solubilities in high-saline solutions. The database is designed for applications in the context of the disposal of radioactive waste in rock salt formations and clay formations featuring solutions with a higher ionic strength [1]. The project is striving to provide an internally consistent set of data, formatted for the use by several widely-used geochemical codes. With the focus on high ionic strength systems, THEREDA complements other database projects focussing on low-saline solutions, such as THERMOCHIMIE [2] or the PSI/Nagra Chemical Thermodynamic Data Base [3].
In practical terms, work for THEREDA comprises several aspects. Most importantly, the database is continuously maintained and extended, based on annual contributions to the project. Other aspects concern the implementation of internal calculation routines, export functions and measures for quality assurance.

RECENT ACTIVITIES
Data releases
In 2018 a new release (R-12) was issued covering phosphate in high-saline solutions [4-5]. Pitzer interaction coefficients were optimized using osmotic coefficients, activity coefficients, and solubility data in binary and ternary systems. To test the obtained database, experimental data from quaternary systems were successfully modelled.
Supplementary to the phosphate release, an earlier uranium release was upgraded by adding several solid phases with phosphate (R-09.1). Available experimental data for respective aqueous complexes with phosphate in high-saline solution are currently under inspection.

CURRENT ACTIVITIES
Data releases
THEREDA is working on new thermodynamic data sets, in part as extensions to existing releases, and in part representing new systems, hitherto not covered by THEREDA. In short, the systems currently in preparation are:
• Solubility of molecular oxygen (polythermal)
• Se(+VI,+IV,0,-II) – Na, K, Mg, Ca – Cl, SO4 – H2O (partially polythermal)
• Solubility of carbonates up to 100°C (upgrade for R-03)
• Extensions for the systems Na, Mg, Cl, OH- - H2O (Sorel phases)
• Cs – K, Na, Mg, Ca, – Cl, SO4 – H2O (polythermal upgrade for R-05)
• Rb - K, Na, Mg, Ca, – Cl, SO4 – H2O (25°C)
• U(VI) hydrolysis and solubility in NaCl, KCl and MgCl2 systems (25°C, upgrade of R-09.1)
• Implementation of CEMDATA 18 [8]; will not work with GWB and TOUGHREACT as they cannot handle solid solutions yet.

Preparation of new release mode
THEREDA ensures that all issued parameter files yield the results as laid out in the release papers available at the project website. To optimize the workload, we will abstain from producing release papers in the future and establish a new procedure for data releases, which ensures a high quality of issued parameter files. Future data releases will move along the following steps.
• 1. addition and modification of data sets in THEREDA;
• 2. “feature freeze” of the database: no new data sets are added, and no existing data sets modified;
• 3. All test calculations (at present 192) are automated for all supported codes, producing (at present 1131) individual results to be compared with the ones from previous releases;
• 4. If significant deviations occur, “debugging” and repetition of test calculations is started.
5. Release of one cumulative parameter file (covering all supported systems) for each supported code.

Supported codes
Due to a significantly decreasing number of downloads, the support for EQ3/6 has been abandoned. GEM-Selektor [9] is now able to import the generic JSON-export from THEREDA. As to GWB beside the traditional “Oct84” the “Jul17” format is supported.
At present we are working on the support for TOUGHREACT [10].

Assessment of current state of THEREDA
By the end of the year the management board of THEREDA is required to submit an assessment as to whether the database, related to supported systems, still represents the state-of-the-art, or to which extent updates are appropriate.

CONCLUSION
THEREDA aims for implementing additional thermodynamic data (Pitzer) for radionuclides and key matrix elements in future data releases. While THEREDA is particularly focusing on Germany, it is open for international exchange and exploiting synergies with the international scientific/technical community.

ACKNOWLEDGMENTS
THEREDA is funded by the German “Bundesgesellschaft für Endlagerung (BGE)”, contract number 45162393 (8998-3).

REFERENCES
1. H. C. MOOG et al.: Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem., 55, 72-84 (2015).
2. E. GIFFAUT et al.: Andra thermodynamic data for performance assessment: ThermoChimie. Appl. Geochem., 49, 225–236 (2014).
3. T. THOENEN et al.: The PSI/Nagra Chemical Thermodynamic Database 12/07. PSI Bericht Nr. 14-04, Paul Scherrer Institut, ISSN 1019-0643 (2014). https://www.psi.ch/en/les/database
4. T. SCHARGE et al.: Thermodynamic modelling of high salinary phosphate solutions. I. Binary systems. J. Chem. Thermodynamics, 64, 249–256 (2013).
5. T. SCHARGE et al.: Thermodynamic modeling of high salinary phosphate solutions II. Ternary and higher systems. J. Chem. Thermodynamics, 80, 172-183 (2015).
6. A. P. SOLOV’JEV et al.: Rastvorimost‘ v ctevernych vzainych vodnych sistemach iz chloridov i fosfatov natrija i kalija pri 25°C, Sb. Naucn. Tr. Jarosl. Gos. Ped. Inst., 164, 136-142 (1977).
7. G. BRUNISHOLZ et al.: Contribution à L'étude du système quinaire H+-Na+-K+-Cl--PO43--H2O II. Le diagramme de solubilité du système quaternaire Na+-K+-Cl--H2PO4--H2O, Helv. Chim. Acta, 46, 2575-2587 (1963).
8. B. LOTHENBACH et al.: Cemdata18: A chemical thermodynamic database for hydrated Portland cements and alkali-activated materials. Cem. Concr. Res., 115, 472-506 (2019).
9. D. A. KULIK et al.: GEM-Selektor geochemical modeling package: revised algorithm and GEMS3K numerical kernel for coupled simulation codes. Comp. Geosc., 17, 1-24 (2013).
10: TIANFU XU et al.: TOUGHREACT—A simulation program for non-isothermal multiphase reactive geochemical transport in variably saturated geologic media: Applications to geothermal injectivity and CO2 geological sequestration. Comp.Geosc., 32, 145-165 (2006).
Keywords: THEREDA, Database, Geochemical Modelling, Thermodynamic, Nuclear Waste Repository, Pitzer
  • Lecture (Conference)
    Actinide Brine Chemistry (ABC-Salt) VI Workshop 2019, 25.-26.06.2019, Karlsruhe, Deutschland

Publ.-Id: 29292 - Permalink


Band gap renormalization in n-type GeSn alloys made by ion implantation and flash lamp annealing
Prucnal, S.; Berencén, Y.; Wang, M.; Rebohle, L.; Kudrawiec, R.; Polak, M.; Zviagin, V.; Schmidt-Grund, R.; Grundmann, M.; Grenzer, J.; Turek, M.; Droździel, A.; Pyszniak, K.; Zuk, J.; Helm, M.; Skorupa, W.; Zhou, S.;
The last missing piece of the puzzle for the full functionalization of group IV optoelectronic devices is a direct bandgap semiconductor made by CMOS compatible technology. Here, we report on the fabrication of GeSn alloys with Sn concentrations up to 4.5% using ion implantation followed by millisecond-range explosive solid phase epitaxy. The n-type single crystalline GeSn alloys are realized by coimplantation of Sn and P into Ge. Both the activation of P and the formation of GeSn are performed during a single-step flash lamp annealing for 3 ms. The bandgap engineering in GeSn as a function of the doping level and Sn concentration is theoretically predicted by density functional theory and experimentally verified using ellipsometric spectroscopy. We demonstrate that both the diffusion and the segregation of Sn and P atoms in Ge are fully suppressed by millisecond-range nonequilibrium thermal processing.
Keywords: ion implantation, flash lamp annealing, Ge, GeSn, n-type doping

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  • Secondary publication expected from 30.05.2020

Publ.-Id: 29290 - Permalink


Benchmarking ATHLET against TRACE as applied to Superphénix start-up tests
Di Nora, V. A.; Fridman, E.; Mikityuk, K.;
ATHLET is a thermal-hydraulic (TH) system code developed at the GRS for the modeling of Light Water Reactors (LWRs). To extend the applicability of ATHLET to the analyses of Sodium Fast Reactors (SFRs), the code was recently upgraded with the thermal-physical properties of the liquid sodium. The new extension is still under verification and validation phases. The present work contributes to the verification efforts. This study investigated the perfor-mance of the extended version of ATHLET as applied to the transient analysis of a set of start-up tests conducted at the Superphénix SFR. The specifications of the corresponding tests such as the simplified SPX reactor core models and the set of reactivity coefficients were adopted primarily from a previous dedicated study performed at PSI and at KIT. The reactivity effects accounted for by ATHLET included fuel Doppler effect and thermal expansion effects of sodium, fuel, diagrid, control rods driveline, strongback, and reactor vessel. The results obtained by ATHLET for main stationary TH parameters, power evolutions, and reactivity feedback components were benchmarked against the reference solutions provided by TRACE. Employing an identical set of reactivity coefficients, either in steady-state or transient calculations, the codes produce consistent and close results.
Keywords: ATHLET against TRACE; ATHLET verification; Superphénix start-up tests;
  • Contribution to proceedings
    International Congress on Advances in Nuclear Power Plants - ICAPP2019, 12.-15.05.2019, Juan-les-Pins, France

Publ.-Id: 29289 - Permalink


Photon diagnostics at the FLASH THz beamline
Pan, R.; Zapolnova, E.; Golz, T.; Krmpot, A. J.ORC; Rabasovic, M. D.; Petrovic, J.; Asgekar, V.ORC; Faatz, B.; Tavella, F.; Perucchi, A.; Kovalev, S.; Green, B.ORC; Geloni, G.; Tanikawa, T.ORC; Yurkov, M.; Schneidmiller, E.; Gensch, M.; Stojanovic, N.
The THz beamline at FLASH, DESY, provides both tunable (1–300 THz) narrow-bandwidth (∼10%) and broad-bandwidth intense (up to 150 uJ) THz pulses delivered in 1 MHz bursts and naturally synchronized with free-electron laser X-ray pulses. Combination of these pulses, along with the auxiliary NIR and VIS ultrashort lasers, supports a plethora of dynamic investigations in physics, material science and biology. The unique features of the FLASH THz pulses and the accelerator source, however, bring along a set of challenges in the diagnostics of their key parameters: pulse energy, spectral, temporal and spatial profiles. Here, these challenges are discussed and the pulse diagnostic tools developed at FLASH are presented. In particular, a radiometric power measurement is presented that enables the derivation of the average pulse energy within a pulse burst across the spectral range, jitter-corrected electro-optical sampling for the full spectro-temporal pulse characterization, spatial beam profiling along the beam transport line and at the sample, and a lamellar grating based Fourier transform infrared spectrometer for the on-line assessment of the average THz pulse spectra. Corresponding measurement results provide a comprehensive insight into the THz beamline capabilities.
Keywords: Electro-optic, FLASH, FTIR, Intense THz, THz diagnostic

Publ.-Id: 29288 - Permalink


Cross section of 3He(α , γ)7Be around the 7Be proton separation threshold
Szücs, T.ORC; Kiss, G. G.; Gyürky, G.; Halász, Z.; Szegedi, T. N.; Fülöp, Z.
Background: The 3He(α,γ)7Be reaction is a widely studied nuclear reaction; however, it is still not understood with the required precision. It has a great importance both in Big Bang nucleosynthesis and in solar hydrogen burning. The low mass number of the reaction partners makes it also suitable for testing microscopic calculations.

Purpose: Despite the high number of experimental studies, none of them addresses the 3He(α,γ)7Be reaction cross sections above 3.1-MeV center-of-mass energy. Recently, a previously unobserved resonance in the 6Li(p,γ)7Be reaction suggested a new level in 7Be, which would also have an impact on the 3He(α,γ)7Be reaction in the energy range above 4.0 MeV. The aim of the present experiment is to measure the 3He(α,γ)7Be reaction cross section in the energy range of the proposed level.

Method: For this investigation the activation technique was used. A thin window gas-cell target confining 3He gas was irradiated using an α beam. The 7Be produced was implanted into the exit foil. The 7Be activity was determined by counting the γ rays following its decay by a well-shielded high-purity germanium detector.

Results: Reaction cross sections have been determined between Ecm=4.0and4.4 MeV with 0.04-MeV steps covering the energy range of the proposed nuclear level. One lower-energy cross-section point was also determined to be able to compare the results with previous studies.

Conclusions: A constant cross section of around 10.5 μb was observed around the 7Be proton separation energy. An upper limit of 45 neV for the strength of a 3He(α,γ)7Be resonance is derived.
Keywords: Nuclear Astrophysics, alpha induced reaction, light element nucleosynthesis

Publ.-Id: 29287 - Permalink


Electromagnetic forcing of a flow with the azimuthal wavenumber m=2 in cylindrical geometry
Stepanov, R.; Stefani, F.;
In this paper, we consider a liquid metal flow generated in a cylindrical volume by AC currents in various coil configurations. The final aim of this study is to design and optimize a Rayleigh-Bénard experiment with a large scale circulation, the helicity oscillation of which is synchronized by a periodically modulated tide-like m=2 perturbation.
Keywords: Rayleigh-Bénard

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  • Secondary publication expected from 10.05.2020

Publ.-Id: 29286 - Permalink


Incorporation of Europium into GaN Nanowires by Ion Implantation
Faye, D. N. A.; Biquard, X. B.; Nogales, E. C.; Felizardo, M. A.; Peres, M. A.; Redondo-Cubero, A. A.; Auzelle, T. B.; Daudin, B.; Tizei, L. H. G.; Kociak, M.; Ruterana, P.; Möller, W.; Méndez, B.; Alves, E.; Lorenz, K.;
Rare earth (RE)-doped GaN nanowires (NWs), combining the well-defined and controllable optical emission lines of trivalent RE ions with the high crystalline quality, versatility, and small dimension of the NW host, are promising building blocks for future nanoscale devices in optoelectronics and quantum technologies. Europium doping of GaN NWs was performed by ion implantation, and structural and optical properties were assessed in comparison to thin film reference samples. Despite some surface degradation for high implantation fluences, the NW core remains of high crystalline quality with lower concentrations of extended defects than observed in ion-implanted thin films. Strain introduced by implantation defects is efficiently relaxed in NWs and the measured deformation stays much below that in thin films implanted in the same conditions. Optical activation is achieved for all samples after annealing, and while optical centers are similar in all samples, Eu 3+ emission from NW samples is shown to be less affected by residual implantation damage than for the case of thin films. The incorporation of Eu in GaN NWs was further investigated by nano-cathodoluminescence and X-ray absorption spectroscopy (XAS). Maps of the Eu-emission intensity within a single NW agree well with the Eu-distribution predicted by Monte Carlo simulations, suggesting that no pronounced Eu-diffusion takes place. XAS shows that 70-80% of Eu is found in the 3+ charge state while 20-30% is 2+ attributed to residual implantation defects. A similar local environment was found for Eu in NWs and thin films: for low fluences, Eu is mainly incorporated on substitutional Ga-sites, while for high fluences XAS points at the formation of a local EuN-like next neighbor structure. The results reveal the high potential of ion implantation as a processing tool at the nanoscale.

Publ.-Id: 29285 - Permalink


Electron Paramagnetic Resonance in Ge/Si Heterostructures with Mn-Doped Quantum Dots
Zinovieva, A. F.; Zinovyev, V. A.; Stepina, N. P.; Katsuba, A. V.; Dvurechenskii, A. V.; Gutakovskii, A. K.; Kulik, L. V.; Bogomyakov, A. S.; Erenburg, S. B.; Trubina, S. V.; Voelskow, M.;
Ge/Si quantum dot (QD) structures doped with Mn have been tested by the EPR method to find the optimal conditions for formation of the diluted magnetic semiconductor (DMS) phase inside QDs. The effect of Mn doping has been studied for two series of samples: series A with QDs grown at 450 degrees C and varied Mn concentration and series B with QDs grown at different temperature with Mn concentration x = 0.02. Several effects of modification of the EPR spectra due to Mn presence in the samples have been obtained. These effects are related to (i) strain reduction due to GeSi intermixing, (ii) QD enlargement and change in QD shape, (iii) presence of an additional magnetic field produced by Mn atoms incorporated in QDs. The data obtained allow us to understand the reasons for irreproducibility of the results available in the literature on the creation of magnetic Ge1 - xMnx quantum dots.

Publ.-Id: 29283 - Permalink


Optimizing the Utilization of Heterogeneous Systems Using a Single-Source Approach with Dynamic Resource Mapping
Knodel, O.ORC; Charaf, N.; Stephan, J.; Göhringer, D.
The efficient execution of applications on various heterogeneous resources is an emerging challenge in the heterogeneous landscape of ongoing processing architectures. Especially the mapping of applications to available hardware --regarding to real time requirements, energy parameters, hardware resources and various other system parameters-- is a major academic mission. Based on a single-source C++ software application --only containing SYCL directives-- kernels are generated for different specialized hardware accelerators (e.g. multicore processors, Graphics Processing Units (GPUs) and Field Programmable Gate Arrays (FPGAs)). With the help of hardware emulation the behavior of the execution on different hardware platforms is simulated and a survey is created. While taking additional user objectives and demands (e.g. execution time, hardware resources, power consumption, ...) into account, a virtual Heterogeneous System (vHS) is constructed and then deployed inside a data center or resource-limited edge board. To achieve high system utilization dynamic task offloading between different accelerators and kernel migration is also considered.
Keywords: Heterogeneous Systems; Virtualization; Cloud; Edge Computing; Reconfigurable
  • Poster
    ACACES - Advanced Computer Architecture and Compilation for High-Performance and Embedded Systems, 14.-20.07.2019, Fiuggi, Italy

Publ.-Id: 29282 - Permalink


Numerical modelling of air-breathing PEMFC
Weber, N.; Chaparro, A.; Ferreira-Aparicio, P.;
Übersicht über die Simulation von Luft atmenden Brennstoffzellen mit OpenFOAM
  • Lecture (others)
    Vortrag am IEK3 des Forschungszentrums Jülich, 22.05.2019, Jülich, Deutschland

Publ.-Id: 29279 - Permalink


Improved 242Pu(n,γ) thermal cross section combining activation and prompt gamma analysis
Lerendegui-Marco, J.; Guerrero, C.; Belgya, T.; Maróti, B.; Eberhardt, K.; Düllmann, C. E.; Junghans, A. R.; Mokry, C.; Quesada, J. M.; Runke, J.; Thörle-Pospiech, P.;
A good knowledge of the radiative capture cross section of 242Pu is required for innovative nuclear reactor studies, especially for MoX fuel reactors. However, the experimental data available show discrepancies in the energy regions of interest: the thermal point and the keV region. Previous experimental results of the thermal cross section deviate from each other by 20% and these discrepancies are reflected also in the evaluated libraries, each of them giving more credit to different data sets. A recent measurement by Genreith et al. did not succeed to solve the existing discrepancy due to the large uncertainties and correction factors in the analysis. This work presents a new measurement of the thermal capture cross section of 242Pu carried out in the Budapest Research Reactor using the same thin targets of a previous measurement at n_TOF-EAR1, each containing 30mg of 99.995% pure 242Pu . The combined analysis of the full prompt γ-ray spectrum and the 243Pu decay has led to three compatible values for the thermal cross section. Their average value, 18.9(9)b, has an improved accuracy compared to recent measurements. Leaving aside the activation value of Genreith using an outdated intensity value for the 84 keV decay line of 243Pu , our average result is in very good agreement with the JEFF-3.2 evaluation and all the previous measurements, with the exception of the highest value 22.5(11)b reported by Marie et al., which has a strong influence in the ENDF evaluation.242
Keywords: neutron capture cross section, 242Pu, thermal neutron spectrum

Publ.-Id: 29278 - Permalink


Analysis of studies and research projects regarding the detection of nanomaterials in different environmental compartments and deduction of need for action regarding method development
Hildebrand, H.; Franke, K.; Fischer, C.; Schymura, S.;
Exertengespräch und Präsentation der Ergebnisse aus der Literaturstudie zum Nachweis von Nanomaterialien in den verschiedenen Umweltkompartimenten, Projekt NanoExperte
Keywords: nanomaterials in environemtal media, detection, quantification
  • Invited lecture (Conferences)
    Abschlusspräsentation des Sachverständigengutachtens „NanoExperte“, 17.04.2019, Dessau-Roßlau, Deutschland

Publ.-Id: 29277 - Permalink


Specific ion effects directed noble metal aerogels: Versatile manipulation for electrocatalysis and beyond
Du, R.; Hu, Y.; Hübner, R.; Joswig, J.-O.; Fan, X.; Schneider, K.; Eychmüller, A.;
Noble metal foams (NMFs) are a new class of functional materials featuring properties of both noble metals and monolithic porous materials, providing impressive prospects in diverse fields. Among reported synthetic methods, the sol-gel approach manifests overwhelming advantages for versatile synthesis of nanostructured NMFs (i.e., noble metal aerogels) under mild conditions. However, limited gelation methods and elusive formation mechanisms retard structure/composition manipulation, hampering on-demand design for practical applications. Here, highly tunable NMFs are fabricated by activating specific ion effects, enabling various single/alloy aerogels with adjustable composition (Au, Ag, Pd, and Pt), ligament sizes (3.1 to 142.0 nm), and special morphologies. Their superior performance in programmable self-propulsion devices and electrocatalytic alcohol oxidation is also demonstrated. This study provides a conceptually new approach to fabricate and manipulate NMFs and an overall framework for understanding the gelation mechanism, paving the way for on-target design of NMFs and investigating structure-performance
relationships for versatile applications.

Publ.-Id: 29276 - Permalink


Eu3+ incorporation into xenotime LnPO4: the effect of local distortion on long term stability
Schmidt, M.ORC; Lösch, H.; Hirsch, A.; Holthausen, J.; Peters, L.; Xiao, B.; Neumeier, S.; Huittinen, N.
Ceramic matrices are considered for the immobilization of specific nuclear waste streams. Recently, our group has studied the suitability of orthophosphates with monazite structure for this purpose, and found generally good exchangeability between host and guest cation and a corresponding high stability of the materials. Nonetheless, it was evident that both bulk structure and the local coordination environment of the guest cation need to be studied in order to assess the structural strain in the ceramic
material on the molecular level. Here, we present an in-depth study of the incorporation of Eu3+ as a luminescent homologue for the trivalent actinides, such as Am3+, into xenotime orthophosphates. We combine XRD with laser-induced luminescence spectroscopy (TRLFS) as a method to probe the local structure, to understand the impact of the substitution process.
Polarization-dependent TRLFS studies with single crystalline materials show that Eu3+ occupies identical lattice sites in Tb, Y, Ho, Er, and YbPO4. The site has a distinct lower symmetry than the crystallographic cation lattice site, indicating local distortion. In LuPO4, the material with the smallest host cation, this distortion is no longer viable and Eu3+ occupies a less distorted site with similar geometry to the crystallographic lattice site. The very small site enforces a strong overlap of ligand and metal orbitals, inducing strong spectral shifts as well as coupling to lattice phonons.[1] Characterization of polycrystalline materials reveals a more complex mineralogy, including an anhydrite-type phase and monazite in addition to xenotime. Eu3+ distribution indicates a clear aversion for the xenotime lattice when other phases are present. In the absence of other phases, Eu3+ is incorporated into xenotime initially, but long term studies reveal a complex unmixing process[2].
[1] Xiao, B. et al., (2018), Chem Eur J., 24, 13368-77.
[2] Lösch, H. et al., (2019), Front. Chem., 7, 94.
Keywords: xenotime, TRLFS, luminescence, lanthanides
  • Lecture (Conference)
    Goldschmidt 2019, 18.-23.08.2019, Barcelona, Espana

Publ.-Id: 29274 - Permalink


Uranium toxicity on plant cells: Isothermal microcalorimetric studies for the differentiation between chemotoxic and radiotoxic effects of uranium
Sachs, S.; Oertel, J.; Fahmy, K.;
The transfer of radionuclides into the food chain is a central concern in the safety assessment of both nuclear waste repositories and remediation strategies in radioactively contaminated sites, such as legacies of the former uranium mining. The uptake and translocation of radionuclides, e.g., uranium, is speciation dependent and induces several stress response reactions, which changes the plant metabolism. Correlating molecular information on radionuclide speciation and biomolecular interactions with physiological performance is a major challenge for radioecology.
In our previous work we applied isothermal microcalorimetry as a sensitive real-time monitor to study the interaction of U(VI) with canola (Brassica napus) cells (Sachs et al., 2017). Applying this method we were able to monitor the metabolic activity of the cells in the presence of U(VI) and to determine the U(VI) toxicity in B. napus cells. Those was correlated with the oxidoreductase activity of the cells and the U(VI) speciation in solution. Based on this work we are currently investigating the differentiation between chemotoxic and radiotoxic effects of uranium on B. napus cells applying natural uranium as well as 233U as alpha emitter. To discriminate between these effects, the metabolic heat flow of the cells at a constant total uranium concentration of 50 µmol/L is monitored by isothermal microcalorimetry applying increasing concentrations of 233U (1-15 µmol/L), which correspond to increasing radiation doses. Applying liquid scintillation counting (LSC) we determine the amount of uranium that is bioassociated to the plant cells and estimate the respective 233U doses for the cells.
Mc values provide a quantitative ranking of metabolic activities that is independent of cell number and largely unaffected by normal variations between experiments (Sachs et al., 2017). Our data are normalized to Mc values of B. napus cells that were exposed to natural uranium only. In the presence of 2 µM 233U a slight increase in the Mc values was observed, which indicates a slightly higher metabolic activity of the cells. Probably, this is an indication for a stress response of the cells to the radiotoxic effect of 233U. With increasing 233U concentration only a slight decrease of the Mc values was observed. This indicates only a slight effect of the alpha radiation on the cells compared to those cells that were exposed to natural uranium, which exhibits a predominant chemotoxic effect. These first results point to a high resistance of B. napus cells to the radiotoxicity of 233U.
This presentation will demonstrate the potential of life cell microcalorimetry for radioecological studies. We will present the calorimetric determination of the U(VI) toxicity in B. napus cells that correlates with oxidoreductase activity and U(VI) speciation and will focus on the differentiation between chemotoxic and radiotoxic effects of uranium.

Sachs, S., Geipel, G., Bok, F., Oertel, J., Fahmy, K. 2017. Calorimetrically determined U(VI) toxicity in Brassica napus correlates with oxidoreductase activity and U(VI) speciation. Environ. Sci. Technol. 51, 10843-10849.
Keywords: uranium, plant cells, toxicity, isothermal microcalorimetry
  • Lecture (Conference)
    ENVIRA 2019, 5th International Conference on Environmental Radioactivity, 08.-13.09.2019, Prague, Czech Republic

Publ.-Id: 29272 - Permalink


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