Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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Only approved publications

29892 Publications
Large-scale self-organized gold nanostructures with bidirectional plasmon resonances for SERS
Schreiber, B.; Gkogkou, D.; Dedelaite, L.; Kerbusch, J.; Hübner, R.; Sheremet, E.; Zahn, D. R. T.; Ramanavicius, A.; Facsko, S.; Rodriguez, R. D.
Efficient substrates for surface-enhanced Raman spectroscopy (SERS) are under constant development, since time-consuming and costly fabrication routines are often an issue for high-throughput spectroscopy applications. In this research, we use a two-step fabrication method to produce self- organized parallel-oriented plasmonic gold nanostructures. The fabrication routine is ready for wafer-scale production involving only low-energy ion beam irradiation and metal deposition. The optical spectroscopy features of the resulting structures show a successful bidirectional plasmonic response. The localized surface plasmon resonances (LSPRs) of each direction are independent from each other and can be tuned by the fabrication parameters. This ability to tune the LSPR characteristics allows the development of optimized plasmonic nanostructures to match different laser excitations and optical transitions for any arbitrary analyte. Moreover, in this study, we probe the polarization and wavelength dependence of such bidirectional plasmonic nanostructures by a complementary spectroscopic ellipsometry and Raman spectroscopy analysis. We observe a significant signal amplification by the SERS substrates and determine enhancement factors of over a thousand times. We also perform finite element method-based calculations of the electromagnetic enhancement for the SERS signal provided by the plasmonic nanostructures. The calculations are based on realistic models constructed using the same particle sizes and shapes experimentally determined by scanning electron microscopy. The spatial distribution of electric field enhancement shows some dispersion in the LSPR, which is a direct consequence of the semi-random distribution of hotspots. The signal enhancement is highly efficient, making our SERS substrates attractive candidates for high-throughput chemical sensing applications in which directionality, chemical stability, and large-scale fabrication are essential requirements.

Publ.-Id: 27608 - Permalink


Implanting Germanium into Graphene
Tripathi, M.; Markevich, A.; Böttger, R.; Facsko, S.; Besley, E.; Kotakoski, J.; Susi, T.
Incorporating heteroatoms into the graphene lattice may be used to tailor its electronic, mechanical and chemical properties, although directly observed substitutions have thus far been limited to incidental Si impurities and P, N and B dopants introduced using low-energy ion implantation. We present here the heaviest impurity to date, namely 74Ge+ ions implanted into monolayer graphene. Although sample contamination remains an issue, atomic resolution scanning transmission electron microscopy imaging and quantitative image simulations show that Ge can either directly substitute single atoms, bonding to three carbon neighbors in a buckled out-of-plane configuration, or occupy an in-plane position in a divacancy. First-principles molecular dynamics provides further atomistic insight into the implantation process, revealing a strong chemical effect that enables implantation below the graphene displacement threshold energy. Our results demonstrate that heavy atoms can be implanted into the graphene lattice, pointing a way toward advanced applications such as single-atom catalysis with graphene as the template.
Keywords: heteroatom doping; ion implantation; molecular dynamics; scanning transmission electron microscopy

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Publ.-Id: 27605 - Permalink


Wechselwirkungs- und Transportuntersuchungen dreiwertiger Radiometalle in Ton unter Berücksichtigung des Einflusses von Fulvinsäure und erhöhten Salinitäten
Poetsch, M.
The storage of radioactive waste demands for evidence of security over a long period. Mainly because of its high sorption capacity as well as favourable geomechanical properties, clay is being explored as one of the potential host rocks for a final repository. This work contributes to the understanding of interactions between trivalent lanthanides (as analogues for trivalent actinides), fulvic acid and Opalinus clay regarding high ionic strength. High salinity and natural organic matter are both known to facilitate migration of toxic or radioactive metals in geochemical systems, but little is known on their combined effect.
The complex system was split into three binary systems with the following interactions: lanthanides (Tb, Eu) and Opalinus clay, lanthanides and fulvic acid, Opalinus clay and fulvic acid.
The binary systems were investigated at pH of 5 and 7 with variable amounts of NaCl, MgCl2 or CaCl2 within a range of 0 - 4 mol L-1. The sorption of the lanthanides and fulvic acid onto the Opalinus clay was investigated in batch experiments, employing 160Tb, 152Eu and 14C as radiotracers. For the investigation of the complexation behaviour of Tb(III) and Eu(III) with fulvic acid, time-resolved laser-induced fluorescence spectroscopy was used.
A combined Kd approach (Linear Additive Model) was tested for suitability in predicting solid-liquid distribution of metals in the presence of organic matter based on the interactions in the constituent subsystems. The metal-ion interactions with fulvic acid were modelled by using the NICA-Donnan approach. To reproduce the migration behaviour of lanthanides in clay, a diffusion-based process was modelled.
This study has shown that there is no synergism in the mobilising effects of fulvic acid and electrolytes at in-situ pH. On the contrary, a mitigating effect of ionic strength was evidenced, based on the fact that metal binding is suppressed while adsorption of humic matter is hardly influenced.
  • Doctoral thesis
    Universität Leipzig, 2018
    Mentor: Lippold, Holger
    106 Seiten

Publ.-Id: 27603 - Permalink


THz spectroscopy of solids with a free-electron laser
Helm, M.
I will start describing the Dresden free-electron laser FELBE as an intense, tunable, pulsed and narrowband source of infrared and THz radiation and the unique opportunities it offers for the spectroscopy of low-energy excitations in solids. In particular, the FEL can be used for nonlinear optical experiments, for time-resolved pump-probe studies, and also for near-field microscopy. I will mainly discuss nonlinear experiments on excitons in semiconductor quantum wells and pump-probe studies of the relaxation dynamics in graphene. If time permits, I will also introduce the new superradiant THz radiation source TELBE.
Keywords: free electron laser, terahertz, graphene
  • Lecture (others)
    Kolloquium am Max-Born-Institut Berlin, 13.06.2018, Berlin, Germany

Publ.-Id: 27602 - Permalink


cupla - C++ User interface for the Platform independent Library Alpaka
Widera, R.ORC
cupla [qχɑpˈlɑʔ] is a simple user interface for the platform independent parallel kernel acceleration library alpaka. It follows a similar concept as the NVIDIA® CUDA® API by providing a software layer to manage accelerator devices. alpaka is used as backend for cupla.
  • Software in the HZDR data repository RODARE
    Publication date: 2018-06-10
    DOI: 10.14278/rodare.29
    License: LGPL-3.0

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Publ.-Id: 27585 - Permalink


C++ & Python API for Scientific I/O with openPMD
Koller, F.ORC; Huebl, A.ORC

openPMD is an open metadata format for open data workflows in open science. This library provides a common high-level API for openPMD writing and reading. It provides a common interface to I/O libraries and file formats such as HDF5 and ADIOS. Where supported, openPMD-api implements both serial and MPI parallel I/O capabilities.

Keywords: openpmd; open science; hdf5; adios; data; mpi; hpc; research; file-format; file-handling; open data
  • Software in the HZDR data repository RODARE
    Publication date: 2018-06-07
    DOI: 10.14278/rodare.27
    License: LGPL-3.0

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Publ.-Id: 27579 - Permalink


Amphiphilic Siderophore Marinobactin for Froth Flotation Process
Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.
The consumption of metallic raw materials increased in the last years. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, some new ways have to be gone, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application in the classic froth flotation process. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants to equalize the low bioavailability of iron in their environment. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate groups, is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
This work includes on the one hand the biotechnological production of the marine siderophore marinobactin for the first time using a bioreactor and optimized conditions to make the production more efficient. On the other hand, the produced siderophore is tested in different froth flotation micro scale experiments like “Bubble-pick-up-test” and micro flotation in the Halimond Tube. These results show for the first time that amphiphilic siderophores are working in the froth flotation process and supply first concepts about the required concentration of siderophores in this processing process. In addition, the results also include interaction studies of different metals.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the bioflotation process. This will reduce the usage of other chemical agents. Moreover the specific metal binding of siderophores changes flotation in a more purposeful and efficient process.
Keywords: Bioflotation, Flotation, Siderophore, Marinobactin
  • Lecture (Conference)
    Applied Biotechnology in Mining, 25.-27.04.2018, Dnipro, Ukraine

Publ.-Id: 27577 - Permalink


Re-irradiation of recurrent gliomas: pooled analysis and validation of an established prognostic score-report of the Radiation Oncology Group (ROG) of the German Cancer Consortium (DKTK)
Combs, S.; Niyazi, M.; Adeberg, S.; Bougatf, N.; Kaul, D.; Fleischmann, D.; Gruen, A.; Fokas, E.; Rodel, C.; Eckert, F.; Paulsen, F.; Oehlke, O.; Grosu, A.; Seidlitz, A.; Lattermann, A.; Krause, M.; Baumann, M.; Guberina, M.; Stuschke, M.; Budach, V.; Belka, C.; Debus, J.; Kessel, K.
The heterogeneity of high-grade glioma recurrences remains an ongoing challenge for the interdisciplinary neurooncology team. Response to re-irradiation (re-RT) is heterogeneous, and survival data depend on prognostic factors such as tumor volume, primary histology, age, the possibility of reresection, or time between primary diagnosis and initial RT and re-RT. in the present pooled analysis, we gathered data from radiooncology centers of the DKTK Consortium and used it to validate the established prognostic score by Combs et al. and its modification by Kessel et al. Data consisted of a large independent, multicenter cohort of 565 high-grade glioma patients treated with re-RT from 1997 to 2016 and a median dose of 36 Gy. Primary RT was between 1986 and 2015 with a median dose of 60 Gy. Median age was 54 years; median follow-up was 7.1 months. Median OS after re-RT was 7.5, 9.5, and 13.8 months for WHO IV, III, and I/II gliomas, respectively. All six prognostic factors were tested for their significance on OS. Aside from the time from primary RT to re-RT (P = 0.074) and the reresection status (P = 0.101), all factors (primary histology, age, KPS, and tumor volume) were significant. Both the original and new score showed a highly significant influence on survival with P < 0.001. Both prognostic scores successfully predict survival after re-RT and can easily be applied in the routine clinical workflow. Now, further prognostic features need to be found to even improve treatment decisions regarding neurooncological interventions for recurrent glioma patients.
Keywords: Outcome, prognostic score, recurrent glioma, re-irradiation

Publ.-Id: 27576 - Permalink


Atomic scale reversible opto-structural switching of few atom luminescent silver clusters confined in LTA zeolites
Aghakhani, S.; Grandjean, D.; Baekelant, W.; Coutiño-Gonzalez, E.; Fron, E.; Kvashnina, K.; Roeffaers, M. B. J.; Hofkens, J.; Lievens, B. F.; Sels, P.
Luminescent silver clusters (AgCLs) stabilized inside partially Ag exchanged Na LTA zeolites show a remarkable reversible on–off switching of their green-yellowish luminescence that is easily tuned by a hydration and dehydration cycle, making them very promising materials for sensing applications. We have used a unique combination of photoluminescence (PL), UV-visible-NIR Diffuse Reflectance (DRS), X-ray absorption fine structure (XAFS), Fourier Transform-Infrared (FTIR) and electron spin resonance (ESR) spectroscopies to unravel the atomic-scale structural changes responsible for the reversible optical behavior of the confined AgCLs in LTA zeolites. Water coordinated, diamagnetic, tetrahedral AgCLs [Ag4(H2O)4]2+ with Ag atoms positioned along the axis of the sodalite six-membered rings are at the origin of the broad and intense green-yellowish luminescence in the hydrated sample. Upon dehydration, the luminescent [Ag4(H2O)4]2+ clusters are transformed into non-luminescent (dark), diamagnetic, octahedral AgCLs [Ag6(OF)14]2+ with Ag atoms interacting strongly with zeolite framework oxygen (OF) of the sodalite four-membered rings. This highly responsive on–off switching reveals that besides quantum confinement and molecular-size, coordinated water and framework oxygen ligands strongly affect the organization of AgCLs valence electrons and play a crucial role in the opto-structural properties of AgCLs.

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  • Secondary publication expected from 04.06.2019

Publ.-Id: 27571 - Permalink


Flow Structures in a Weakly Turbulent Rayleigh-Bénard Convection affected by a Horizontal Magnetic Field
Vogt, T.; Yanagisawa, T.; Ishimi, W.; Tasaka, Y.; Eckert, S.
MHD Rayleigh-Bénard convection was studied experimentally using the eutectic metal alloy GaInSn inside a box having a square horizontal cross section and an aspect ratio of 5. Flow measurements were performed by means of ultrasound Doppler velocimetry that can capture time variations of instantaneous velocity profiles. Applying a horizontal magnetic field organizes the convective motion into a flow pattern of quasi-two dimensional rolls arranged parallel to the magnetic field [1], [2]. If the Rayleigh number (Ra) is increased over a certain threshold Ra/Q, whereby Q is the Chandrasekhar number, the flow undergoes a transition to turbulence. Besides the primary convection rolls the measurements reveal regular flow oscillations arising from 2D and 3D deformations of the rolls, Ekman-pumping induced flow as well as smaller side vortices that develop around the convection rolls [3]. Our findings demonstrate the importance to take 3D flow effects into account in order to explain the observed flow structures, which are often considered as quasi 2D. The comparison between the experiments and accompanying direct numerical simulations shows a very good agreement.
  • Lecture (Conference)
    INTERNATIONAL CONFERENCE ON RAYLEIGH BÉNARD TURBULENCE, 14.-18.05.2018, Enschede, Netherlands
  • Open Access LogoContribution to proceedings
    INTERNATIONAL CONFERENCE ON RAYLEIGH BÉNARD TURBULENCE, 14.-18.05.2018, Enschede, Netherlands

Publ.-Id: 27570 - Permalink


Large-scale circulations of turbulent Rayleigh-Bénard convection in a finite liquid metal layer
Akashi, M.; Tasaka, Y.; Yanagisawa, T.; Vogt, T.; Murai, Y.; Eckert, S.
Large-scale circulations of Rayleigh-Bénard convection in a finite liquid metal layer were examined experimentally by means of ultrasonic Doppler velocimetry. The fluid layer with aspect ratio of five and L = 40 mm in height was filled with eutectic alloy of GaInSn (Prandtl number, Pr = 0.03), and multiple ultrasonic transducers for the velocimetry were mounted in the side wall of the vessel to capture 3D structures of the convection.
  • Lecture (Conference)
    INTERNATIONAL CONFERENCE ON RAYLEIGH BÉNARD TURBULENCE, 14.-18.05.2018, Enschede, Netherlands

Publ.-Id: 27569 - Permalink


LSC Oscillations in a Liquid Metal
Vogt, T.; Horn, S.; Grannan, A.; Aurnou, J.
We present experimental results of liquid metal Rayleigh Bénard convection in a Gamma = D/H = 2 cylindrical tank. The tank is filled with liquid gallium that has a Prandtl-number Pr = 0.03. Ultrasound Doppler velocimetry is used in this study to measure the instantaneous velocity distribution along four different measuring lines. This technique is a useful tool to measure the velocities in opaque fluids, such as liquid metals non-invasively. Furthermore, a total number of 29 thermocouples is used to monitor the temperature in the experiment. Thus, the experimental set-up allows for a simultaneous analysis of the velocity and temperature field. We observed a strong oscillatory behaviour of the LSC in both, the velocity and temperature signal whose characteristic behaviour remains unchanged over the investigated range of 7x10^4 < Ra < 6x10^6. We analysed the three dimensional structure of the oscillation and compare the results to direct numerical simulation, which are in excellent agreement to the experimental observation.
  • Lecture (Conference)
    INTERNATIONAL CONFERENCE ON RAYLEIGH BÉNARD TURBULENCE, 14.-18.05.2018, Enschede, Netherlands
  • Open Access LogoContribution to proceedings
    INTERNATIONAL CONFERENCE ON RAYLEIGH BÉNARD TURBULENCE, 14.-18.05.2018, Enschede, Netherlands

Publ.-Id: 27568 - Permalink


Parametric resonances in periodically perturbed dynamo models
Giesecke, A.; Stefani, F.
I present results on kinematic dynsamo models driven by an axisymmetric large scale flow impacted by periodic perturbations due to azimuthally propagating vortices. I found a strong impact on growth rates and frequencies with regimes of parametric resonances whenn the frequency of the perturbation is twice the frequency of the unperturbed case. These models behave similar to rotating mechanical systems subject to periodic distortions that are described by the Matthieu equation. A possible application are dynamo experiments like VKS dynamo in Cadarache or convection driven planetary dynamos that are influenced by tidal forces.
Keywords: dynamo DRESDYN
  • Lecture (Conference)
    Planetary-Stellar Connection: The Sun's Lesson, 07.-09.05.2018, Freiburg, Deutschland

Publ.-Id: 27559 - Permalink


Temporal Evolution of Calcite Surface Dissolution Kinetics
Bibi, I.; Arvidson, R. S.; Fischer, C.; Luttge, A.
This brief paper presents a rare dataset: a set of quantitative, topographic measurements of a dissolving calcite crystal over a relatively large and fixed field of view (~400 μm) and long total reaction time (>6h). Using a vertical scanning interferometer and patented fluid flow cell, surface height maps of a dissolving calcite crystal were produced by periodically and repetitively removing reactant fluid, rapidly acquiring a height dataset, and returning the sample to a wetted, reacting state. These reaction-measurement cycles were accomplished without changing the crystal surface position relative to the instrument’s optic axis, with an approximate frequency of one data acquisition per six minutes’ reaction (~10/h). In the standard fashion, computed differences in surface height over time yield a detailed velocity map of the retreating surface as a function of time. This dataset thus constitutes a near-continuous record of reaction, and can be used to both understand the relationship between changes in the overall dissolution rate of the surface and the morphology of the surface itself, particularly the relationship of a) large, persistent features (e.g., etch pits related to screw dislocations; b) small, short-lived features (e.g., so-called pancake pits probably related to point defects); c) complex features that reflect organization on a large scale over a long period of time (i.e., coalescent “super” steps), to surface normal retreat and stepwave formation. Although roughly similar in frequency of observation to anin situ AFM fluid cell, this VSI method reveals details of the interaction of surface features over a significantly larger scale, yielding insight into the role of various components in terms of their contribution to the cumulative dissolution rate as a function of space and time.

Publ.-Id: 27556 - Permalink


Self-Diffusion in Amorphous Silicon by Local Bond Rearrangements
Kirschbaum, J.; Teuber, T.; Donner, A.; Radek, M.; Bougeard, D.; Lundsgaard Hansen, J.; Nylandsted Larsen, A.; Posselt, M.; Bracht, H.; Böttger, R.
Experiments on self-diffusion in amorphous silicon (Si) were performed at temperatures between 460 to 600° C. The amorphous structure was prepared by Si ion implantation of single crystalline Si isotope multilayers epitaxially grown on a silicon-on-insulator wafer. The Si isotope profiles before and after annealing were determined by means of secondary ion mass spectrometry. Isothermal diffusion experiments reveal that structural relaxation does not cause any significant intermixing of the isotope interfaces whereas self-diffusion is significant before the structure recrystallizes. The temperature dependence of self-diffusion is described by an Arrhenius law with an activation enthalpy Q =2.70 +- 0.11eV and preexponential factor D0=5.5(+11.1 -3.7) × 10−2 cm2 s−1. Remarkably, Q equals the activation enthalpy of hydrogen diffusion in amorphous Si, the migration of bond defects determining boron diffusion, and the activation enthalpy of solid phase epitaxial recrystallization reported in the literature. This close agreement provides strong evidence that self-diffusion is mediated by local bond rearrangements rather than by the migration of extended defects as suggested by Strauß et al. (Phys. Rev. Lett. 116, 025901 (2016)).
Keywords: amorphous Si, self-diffusion, isotope multilayers

Publ.-Id: 27555 - Permalink


Design, validation and testing of new receiver coatings for concentrated solar power
Krause, M.; Heras, I.; Lungwitz, F.; Wenisch, R.; Schumann, E.; Janke, D.; Guillén, E.; Munnik, F.; Azkona, I.; Gemming, S.; Escobar-Galindo, R.
Increasing central receiver solar plant’s operation temperature from 550°C to about 800°C would improve the energy conversion efficiency by 15 to 20%. Absorber coatings appropriate for such conditions have to outperform the state-of-the-art pigment paint Pyromark® that has an absorptivity α > 95% but a high emittance (ε ~ 80%). The development of environmentally stable solar-selective coatings (SSC) for these temperatures requires new concepts of design and thermal testing. Multilayer SSC based on [AlyTi1-y(OxN1-x)] absorbers were designed after an extensive microstructural characterization and optical simulations. Based on excellent simulation performance values of α = 88-94% and εRT = 4.8-13.6%, complete coating stacks were experimentally validated and tested in vacuum and in air up to temperatures of 800°C [1]. Thermal stability in vacuum up to 800°C is shown by in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry (SE) for individual layers as well as for complete SSC. Regarding in-air stability, the most stable SSC fulfilled the standard performance criterion PC ≤ 5% for 300 symmetric, 3 hours long cyclic tests between 300°C and 600°C. Another promising and simpler coating concept to be presented is based on a metal-doped transparent conductive oxide acting as solar-selective transmitter on top of a blackbody. The onset of the infrared reflectivity is tuneable by variation of the parameters during reactive magnetron sputtering deposition, thus matching the specific temperature requirements during solar applications. Thermal stability up to 800°C in vacuum is demonstrated by in situ RBS and SE.

Financial support by the EU, grant No. 645725, project FRIENDS2, and the HGF via the W3 program (S.G.) is gratefully acknowledged.

[1] I. Heras, et al. , Design of high-temperature solar-selective coatings based on aluminium titanium oxynitrides [AlyTi1-y(OxN1-x)]. Part 1: Advanced microstructural characterisation and optical simulation. Solar Energy Materials and Solar Cells 176 (2018) 81-92
Keywords: Solar selective coatings, oxynitrides, TCO's, thermosolar energy, in situ analysis, cluster tool
  • Invited lecture (Conferences)
    5th European Conference in Nanofilms (ECNF), 20.-22.03.2018, Cranfield, United Kingdom

Publ.-Id: 27553 - Permalink


Synthesis and radiofluorination of a novel monocarboxylate transporter 1 inhibitor for tumor imaging by PET
Sadeghzadeh, M.; Moldovan, R.-P.; Wenzel, B.; Fischer, S.; Teodoro, R.; Ludwig, F.-A.; Gurrapu, S.; Drewes, L. R.; Brust, P.
Monocarboxylate transporter 1 (MCT1) is an integral plasma membrane protein that bi-directionally transports lactate and ketone bodies and is highly expressed in non-hypoxic regions of human colon, brain, breast, lung and other tumors. Accordingly, MCT1 inhibitors are regarded to be of potential clinical use. In the current study we developed a new 18F-labeled radioligand for in vivo imaging of MCT1-overexpressing brain tumors by PET.
A new fluorinated analogue of α-cyano-4-hydroxycinnamic acid (RM231) was synthesized from m-anisidine via alkylation, ortho formylation and Knoevenagel condensation in 50% overall yield. Its MCT1 inhibition activity was evaluated via [14C]lactate uptake assay on rat brain endothelial 4 cells. The mesylated precursor was similarly prepared in 52% overall yield. Radiosynthesis of [18F]RM231 was achieved by a two-step reaction, starting with the radiofluorination using [18F]-K2CO3-K222 complex followed by protective group removal via hydrolysis under optimized reaction conditions.
RM231 showed relatively high MCT1 inhibition activity (IC50 = 12 nM). The radiolabeled intermediate was obtained by an optimized procedure (acetonitrile, 5.5 mg of K222, 0.7 mg of K2CO3, 12-15 GBq of K18F, 100 ̊C, 8 min) with 44-50% yield determined by radio-HPLC analysis (N=3, non-isolated). The final product was obtained by hydrolysis with TFA in dry dichloromethane at room temperature for 10 minutes with 29% yield (radio-HPLC, non-isolated).[18F]RM231 could be obtained after separation using semi-preparative HPLC (RP C18 column; 30% ACN, 20 mM NH4CO2H). Currently, attempts are made to stabilize and formulate the final product appropriately for biological investigation. The newly developed MCT1 radioligand is anticipated to be a useful agent for imaging of the tumors with PET. Accordingly, animal studies on the new radiotracer are currently under investigation.
Keywords: Monocarboxylate transporter 1, α-Cyanocinnamic acid derivatives, Radiofluorination, Fluorine-18, Brain tumors.
  • Lecture (Conference)
    18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Czeck Republic

Publ.-Id: 27549 - Permalink


Inductive System for Reliable Magnesium Level Detection in a Titanium Reduction Reactor
Krauter, N.; Eckert, S.; Gundrum, T.; Stefani, F.; Wondrak, T.; Frick, P.; Khalilov, R.; Teimurazov, A.
The determination of the Magnesium level in a Titanium reduction retort by inductive methods is often hampered by the formation of Titanium sponge rings which disturb the propagation of electromagnetic signals between excitation and receiver coils. We present a new method for the reliable identification of the Magnesium level which explicitly takes into account the presence of sponge rings with unknown geometry and conductivity. The inverse problem is solved by a look-up-table method, based on the solution of the inductive forward problems for several tens of thousands parameter combinations.
Keywords: titanium, Kroll process, level detection, inductive measurements

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Publ.-Id: 27532 - Permalink


Environmental fate of fission products: a comprenhensive study
Mayordomo, N.; Rodríguez, D. M.; Müller, K.ORC
Assuring a safe long-term nuclear waste management implies extensive knowledge on the fundamental behaviour of fission products in the surroundings of the feasible repository. This includes the radionuclide speciation, their migration, and their possible interaction with compartments of the technical and geological barriers, and biota.
Fission products, although generated in low yield, posse radiotoxicity and their half-life can be high (10^5 years). Among them, Se and Tc are especially relevant because some of their species are assumed highly mobile in water, since their interaction with the barrier materials (like clay) is considered negligible, as they are mainly found as anionic species [1].
We carry out a comprehensive study to fill the existing gaps of knowledge about the thermodynamic parameters and the molecular level information related to Tc and Se interaction with minerals. Our approach consist on having a global view of the interaction by combining experiments and theoretical tools [2]. On one hand the experiments consists on batch sorption experiments (to obtain the trend of sorption with pH, ionic strength or time) and on spectroscopic experiments (to get the information of the interaction at a molecular level). On the other hand, the theoretical tool consists on developing complexation models that allow the prediction of fission product-mineral interaction under given conditions and that can be adapted to other environments.
In this talk we focus on the Tc(VII) interaction with alumina. Alumina has been selected not only for its model character for complex minerals, but also because of its high affinity for anions, as Se(IV) [2].

This work has been developed in the frame of VESPA II project (02E11607B), supported by the German Ministry of Economy and Energy (BMWi).

[1] K.H. Lieser, et al. Radiochim. Acta. 42 (1987) 205–213.
[2] N. Mayordomo, et al. Environ. Sci. Technol. (2018) 581–588.
Keywords: Technetium, alumina, retention
  • Invited lecture (Conferences)
    Goldschmidt 2018, 12.-17.08.2018, Boston, USA

Publ.-Id: 27529 - Permalink


Radiopharmaceutical evaluation of novel bifunctional chelators and bioconjugates for tumor imaging and therapy
Stephan, H.
The development of multi-functional complexing agents for radiometal nuclides with a view of nuclear medical application represents a field of research that is intensively dealt with and has rapidly been developing. In this context, ligands that form highly stable metal complexes and additionally possess several different functional groups are of particular interest. This enables the simultaneous introduction of targeting, solubilizing and, for example, fluorescent units into the relevant metal complexes. In this perspective, bifunctional chelating agents (BFCAs) based on 3,7-diazabicyclo[3.3.1]nonane (bispidine) and 1,4,7-triazacyclononane (TACN) are discussed. Examples of target-specific peptides and bio(nano)materials equipped with bispidine and TACN ligands for labeling with 64Cu as an ideal positron emitter are presented. This enables tumor imaging and the biodistribution of the materials to be studied over a period of days via positron emission tomography (PET). This lecture will also give an insight into the pre-targeting strategy using complementary oligonucleotides such as peptide nucleic acid (PNA) derivatives. The pre-targeting strategy allows for the rational use of long circulating, high affinity antibodies for both non-invasive cancer radioimmunodetection (RID) and –therapy (RIT).
  • Invited lecture (Conferences)
    IsoSiM Summer School 2018, Medical Isotope Production and Applications, 03.-07.06.2018, Harrison Hot Springs, Canada

Publ.-Id: 27525 - Permalink


From Point to Line Defects in Two-Dimensional Transition Metal Dichalcogenides: Insights from Transmission Electron Microscopy and First-Principles Calculations
Komsa, H.-P.; Krasheninnikov, A. V.ORC
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have recently received great deal of attention due to their unique properties associated with the reduced dimensionality of the system. The properties of these materials have been shown to be affected by atomic defects in the atomic network. The very structure of these materials which are composed from three atomic layers only, combined with dramatic improvements in microscopy techniques, made it possible to study the behavior of defects in these systems with unprecedented accuracy. Various point and line defects were identified, and their effects on the properties of the systems were accessed. It was demonstrated that point defects induced by electron beam irradiation coalesce in line defects, but their quasi-one dimensional atomic structure varies from member to member in the transition metal dichalcogenides family. In this review, we summarize recent experimental and theoretical findings in this area, discuss how the line structures appear due to the agglomeration of point defects, and dwell upon how line defects can be used to engineer properties of 2D TMDs. Finally, we address the challenges in this field and issues which still lack the explanation.
Keywords: 2D materials
  • Book chapter
    Vittorio Morandi, Luca Ottaviano: Carbon nanostructures book series (CARBON), EU: Springer, 2017, 71-85
    DOI: 10.1007/978-3-319-58134-7_6

Publ.-Id: 27520 - Permalink


Ring-like spatial distribution of laser accelerated protons in the ultra-high-contrast TNSA-regime
Becker, G. A.; Tietze, S.; Keppler, S.; Reislöhner, J.; Bin, J. H.; Bock, L.; Brack, F.-E.; Hein, J.; Hellwing, M.; Hilz, P.; Hornung, M.; Kessler, A.; Kraft, S. D.; Kuschel, S.; Liebetrau, H.; Ma, W.; Polz, J.; Schlenvoigt, H.-P.; Schorcht, F.; Schwab, M. B.; Seidel, A.; Zeil, K.; Schramm, U.; Zepf, M.; Schreiber, J.; Rykovanov, S.; Kaluza, M. C.
The spatial distribution of protons accelerated from submicron-thick plastic foil targets using multi-terawatt, frequency-doubled laser pulses with ultra-high temporal contrast has been investigated experimentally. A very stable, ring-like beam profile of the accelerated protons, oriented around the target's normal direction has been observed. The ring's opening angle has been found to decrease with increasing foil thicknesses. Two-dimensional particle-in-cell simulations reproduce our results indicating that the ring is formed during the expansion of the proton density distribution into the vacuum as described by the mechanism of target-normal sheath acceleration. Here - in addition to the longitudinal electric fields responsible for the forward acceleration of the protons - a lateral charge separation leads to transverse field components accelerating the protons in the lateral direction.
Keywords: laser-plasma interaction, proton acceleration, proton beam profile, target normal sheath acceleration

Publ.-Id: 27519 - Permalink


Paramagnetic NMR investigations in metal-organic complexes of tetravalent actinides with soft-donor ligands
Schöne, S.ORC; Radoske, T.; Felsner, B.; Patzschke, M.ORC; März, J.ORC; Kaden, P.ORC
Electronic interactions between metal and ligand are the origin of additional NMR chemical shifts observed on nuclei of the ligand in paramagnetic metal-organic complexes. The major two contributors to these paramagnetic chemical shifts are Fermi-contact shifts (FCS) and pseudo-contact shifts (PCS). FCS are due to delocalisation of unpaired electron density in molecular orbitals involving both metal and ligand orbitals and thus report on the bond properties. PCS are originating from distance- and angle-dependent dipolar coupling of electron spins through space and are therefore bearing structural information.
The mathematical separation of paramagnetic contributions in complexes relies on the availability of a suitable diamagnetic reference to subtract non-paramagnetic contributions. For the trivalent actinides no diamagnetic reference in the same series is available in milligram scale. Furthermore, all available theories behind mathematical disentangling of contributions to the paramagnetic chemical shift, even for the lanthanide series, omit the influence of spin-orbit effects that might have a sizeable contribution as well. [1,2]
Comparing isostructural diamagnetic complexes of both f-element series of tetravalent metal ions (Ce(IV) and Th(IV)) allows for an estimation of additional influences to the chemical shifts and the effect of contributions usually omitted by commonly used mathematical theories.
To assess the chemical bonding situation via the influences on NMR chemical shifts (via FCS) we started to study paramagnetic metal-organic complexes of the tetravalent actinides (An(IV)). With increasing number of unpaired electrons throughout the 5f-series additional effects to the observed chemical shift are expected. Structural properties of the complexes as derived from PCS contributions can be compared to single crystal X-ray diffraction structures. Herein we report the first results of investigations of N- and N,O-donor ligand complexes of the An(IV) series.

References
1 C. Adam, P. Kaden, B. B. Beele, U. Müllich, S. Trumm, A. Geist, P. J. Panak, M. A. Denecke, “Evidence for covalence in a N-donor complex of americium(III)”, Dalton Trans., 42, 14068-14074 (2013).
2. C. Adam, B. B. Beele, A. Geist, U. Müllich, P. Kaden, P. J. Panak, “NMR and TRLFS studies of Ln(III) and An(III) C5-BPP complexes”, Chemical Science, 6, 1548-1561 (2015).
Keywords: NMR, paramagnetic, Actinide, N-donor, FCS, PCS, structure determination, solution
  • Lecture (Conference)
    18th Radiochemical Conference - RadChem 2018, 13.-18.05.2018, Mariánské Lázně, Tschechische Rupublik
  • Contribution to proceedings
    18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Tschechische Rupublik
    Czech Chemical Society Symposium Series 2

Publ.-Id: 27517 - Permalink


Critical heat flux as a mass flux dependent local or global phenomenon: Theoretical analysis and experimental confirmation
Ding, W.; Geißler, T.; Krepper, E.; Hampel, U.
In this article, we report on a theoretical analysis and experimental investigations on critical heat flux (CHF) in subcooled flow boiling. Commonly, CHF is considered as a local phenomenon. A validated CHF- concept recently developed in our group indicated that CHF may be initiated in two different ways, that is, locally and globally. We designed and conducted an experiment to verify this hypothesis. The experimental results agree well with the expectations from our CHF- modelling and confirm the two mechanisms. Following that, we continued to clarify the role of different parameters, such as channel orientation, channel length and hydraulic diameter. The new concept of CHF is useful to explain and predict CHF at conditions of low pressure and low fluid velocity.
Keywords: boiling, critical heat flux, initiation mechanisms

Publ.-Id: 27515 - Permalink


Long-term quality of life in inoperable non-small cell lung cancer patients treated with conventionally fractionated compared to hyperfractionated accelerated radiotherapy - Results of the randomized CHARTWEL trial
Hechtner, M.; Krause, M.; Konig, J.; Appold, S.; Hornemann, B.; Singer, S.; Baumann, M.
Background and purpose: To evaluate the quality of life (QoL) of patients with inoperable non-small cell lung cancer treated with conventionally fractionated radiotherapy (CF) vs. continuous hyperfractionated accelerated radiotherapy weekend-less (CHARTWEL).
Material and methods: The largest monocentric subgroup of the phase III CHARTWEL trial was analyzed up to three years after randomization. QoL was assessed with the European Organization for Research and Treatment of Cancer QoL Core Questionnaire (QLQ-C30) and lung cancer module (QLQ-LC13) and compared using linear mixed models. QoL interrelations with recurrence, metastasis, and death were explored by multi-state modeling.
Results: 160 patients (98%) provided at least one QoL assessment.
Average treatment differences of CF vs. CHARTWEL over three years were -5.4 points (95%CI [-13.6,2.8], p = 0.19) in global QoL, 11.9 ([2.8,21.0], p = 0.01) in fatigue, 13.4 ([3.5,23.3], p = 0.009) in pain, 10.5 ([1.3,19.6], p = 0.03) in dyspnea, and 5.2 ([-2.7,13.0], p = 0.19) in dysphagia. At 12 months, the probabilities of being disease-free with good, good or moderate, any global QoL, or alive were 5.1%, 20.3%, 34.2%, 54.4% under CF and 10.4%, 21.0%, 37.5%, 65.3% under CHARTWEL.
Conclusions: Over three years, QoL was similar or more favorable under CHARTWEL compared to CF. Modeling QoL together with disease states provided additional insight into treatment comparisons.
Keywords: Quality of life Non-small cell lung cancer Accelerated radiotherapy Hyperfractionation Randomized trial Multi-state model

Publ.-Id: 27513 - Permalink


Cognitive deficits following brain tumor radiation therapy
Buthut, M.; Haussmann, R.; Seidlitz, A.; Krause, M.; Donix, M.
Brain radiation is an important treatment option for malignant and benign brain diseases. The possible acute or chronic impact of radiation therapy on cognitive performance is important for daily functioning and quality of life. A detailed evaluation of cognitive impairment is important in the context of how to control disease progression. The susceptibility of the hippocampus to radiation-induced neuronal damage and its important role in memory highlight that therapeutic strategies require precision medicine.

Publ.-Id: 27512 - Permalink


Magnetohydrodynamic Simulation: Liquid Metal Batteries, Crystal Growth & Steel Casting
Weber, N.; Beckstein, P.; Galindo, V.; Giesecke, A.; Liu, K.; Pal, J.; Personnettaz, P.; Stefani, F.; Timmel, K.; Weier, T.
Der Vortrag gibt einen Überblick über numerische Simulationen der Abteilung Magnetohydrodynamik am HZDR.
  • Lecture (Conference)
    OpenFOAM Stammtisch United, 24.05.2018, Dresden, Deutschland

Publ.-Id: 27511 - Permalink


Quantum Criticality of an Ising-like Spin-1/2 Antiferromagnetic Chain in a Transverse Magnetic Field
Wang, Z.; Lorenz, T.; Gorbunov, D.  I.; Cong, P.  T.; Kohama, Y.; Niesen, S.; Breunig, O.; Engelmayer, J.; Herman, A.; Wu, J.; Kindo, K.; Wosnitza, J.; Zherlitsyn, S.; Loidl, A.
We report on magnetization, sound velocity, and magnetocaloric-effect measurements of the Ising-like spin-1/2 quantum antiferromagnetic chain BaCo$_2$V$_2$O$_8$ as a function of temperature down to 1.3~K and applied transverse magnetic field up to 60~T. While across the Ne\'{e}l temperature of $T_N\sim5$~K anomalies in magnetization and sound velocity confirm the antiferromagnetic ordering transition, at the lowest temperature in the field-dependent measurements we find a sharp softening of sound velocity and a clear temperature minimum at $B^{c,3D}_\perp=21.4$~T, indicating suppression of the antiferromagnetic order. At higher fields, magnetocaloric-effect measurements reveal a broad temperature minimum at $B^c_\perp = 40$~T, accompanied by a broad minimum of sound velocity and a saturation-like level-off in magnetization. These features signal a quantum phase transition that is further quantified by the divergent behavior of Gr\"{u}neisen parameter $\Gamma_B \propto (B-B^{c}_\perp)^{-1}$. By contrast, at the critical field the Gr\"{u}neisen parameter converges to a constant as temperature decreases towards zero, which is a distinct characteristics of the one-dimensional transverse-field Ising quantum critical point.
Keywords: Spin chain, quantum critical point, transverse field Ising model, BaCo2V2O8, magnetization, sound velocity, magnetocaloric effects

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Publ.-Id: 27509 - Permalink


SRF gun II - status as of April 2018
Arnold, A.; Teichert, J.; Xiang, R.; Murcek, P.
In May 2014 the 1st superconducting photo injector (SRF gun) at HZDR was replaced by a new gun, featuring a new resonator and a new cryostat. The intention for this upgrade was to reach higher beam energy, higher bunch charge and lower emittance at the same time. With the improved parameters user experiments of the superconducting CW accelerator ELBE are to be served, that benefit from an increased average beam current at a given repetition rate of some hundred kHz. Although the cavity performance stays behind its specifications, the SRF gun has been optimized for an operation mode at 200 pC and a repetition rate of 100 kHz to generate four times more THz pulse energy then possible by ELBE's thermionic injector. Because of this significant improvement, the new gun has been recently used for first user shifts at the THz facility at ELBE. In this contribution we will report on first results and operational experiences.
Keywords: SRF gun, superconducting RF injector, ELBE, electron source
  • Lecture (others)
    HOPE II Projekttreffen im Rahmen BMBF Verbundforschungsinitiative, 16.04.2018, Mainz, Deutschland

Publ.-Id: 27506 - Permalink


Pushing the limits of applicability of REBCO coated conductor films through fine chemical tuning and nanoengineering of inclusions
Rizzo, F.; Augieri, A.; Kursumovic, A.; Bianchetti, M.; Opherden, L.; Sieger, M.; Hühne, R.; Hänisch, J.; Meledin, A.; van Tendeloo, G.; Macmanus-Driscol, J. L.; Celentano, G.
An outstanding current carrying performance (namely critical current density, Jc) over a broad temperature range of 10–77 K for magnetic fields up to 12 T is reported for films of YBa2Cu3O7−x with Ba2Y(Nb,Ta)O6 inclusion pinning centres (YBCO-BYNTO) and thicknesses in the range of 220–500 nm. Jc values of 10 MA cm−2 were measured at 30 K – 5 T and 10 K – 9 T with a corresponding maximum of the pinning force density at 10 K close to 1 TN m−3. The system is very flexible regarding properties and microstructure tuning, and the growth window for achieving a particular microstructure is wide, which is very important for industrial processing. Hence, the dependence of Jc on the magnetic field angle was readily controlled by fine tuning the pinning microstructure. Transmission electron microscopy (TEM) analysis highlighted that higher growth rates induce more splayed and denser BYNTO nanocolumns with a matching field as high as 5.2 T. Correspondingly, a strong peak at the B||c-axis is noticed when the density of vortices is lower than the nanocolumn density. YBCO-BYNTO is a very robust and reproducible composite system for high-current coated conductors over an extended range of magnetic fields and temperatures.

Publ.-Id: 27503 - Permalink


Anomalous Hall effect in fully compensated half-metallic Mn₂RuₓGa thin films
Fowley, C.; Rode, K.; Lau, Y. C.; Thiyagarajah, N.; Betto, D.; Borisov, K.; Atcheson, G.; Kampert, E.; Wang, Z.; Yuan, Y.; Zhou, S.; Lindner, J.; Stamenov, P.; Coey, J. M. D.; Deac, A. M.
High-field magnetotransport is investigated in thin films of half-metallic ferrimagnet Mn₂RuₓGa. A non-vanishing Hall signal is observed over a broad temperature range, spanning the compensation temperature (155K), where the net magnetic moment is strictly zero, the Hall conductivity is 6673 Ohm⁻¹ m⁻¹ and the coercivity exceeds 9T. Molecular field modelling is used to determine the intra- and inter-sublattice exchange constants and from the spin-flop transition we infer the anisotropy of the electrically active sublattice to be 216 kJm⁻³ and predict the magnetic resonances frequencies. Exchange and anisotropy are comparable and hard-axis applied magnetic fields result in a tilting of the magnetic moments from their collinear ground state. Our analysis is applicable to collinear ferrimagnetic half-metal systems.
Keywords: Ferrimagnetism, Magnetotransport, Half-metals, Anomalous Hall effect, Magnetic anisotropy, Exchange interaction
  • Invited lecture (Conferences)
    Intermag 2018, 23.-27.04.2018, Singapore, Singapore

Publ.-Id: 27502 - Permalink


Features of magnetization behavior in the rare-earth intermetallic compound (Nd0.5Ho0.5)2Fe14B
Kostyuchenko, N. V.; Tereshina, I. S.; Gorbunov, D. I.; Tereshina-Chitrova, E. A.; Andreev, A. V.; Doerr, M.; Politova, G. A.; Zvezdin, A. K.
The crystal-electric field parameters are determined for the (Nd0.5Ho0.5)2Fe14B compound by analyzing experimental magnetization curves obtained in magnetic fields up to 60 T. The values of the crystal-field parameters B20, B40, B60, B44, B64 are 56.3, −73.2, −10.74, −8.9, 0 cm−1 for Nd3+ ion and 312.38, −176.78, 89.2, −88.43, 0 cm−1 for Ho3+ ion. The transition from the ferri- to the field-induced ferromagnetic state has been studied in detail.

Publ.-Id: 27501 - Permalink


Magnetic and magnetocaloric properties of single Crystal (Nd0.5Pr0.5)2Fe14B
Politova, G. A.; Tereshina, I. S.; Gorbunov, D. I.; Paukov, M. A.; Andreev, A. V.; Grechishkin, R. M.; Rogacki, K.
In this work the magnetic and magnetocaloric properties of a (Nd0.5Pr0.5)2Fe14B single crystal have been investigated in a wide range of temperatures and magnetic fields. Magnetic phase transition temperatures (spin-reorientation transition (SRT) at TSR = 73 K and Curie point at Tc = 570 K) were determined together with the values of saturation magnetization Ms and magnetocrystalline anisotropy constants K1 and K2. In the vicinity of a spin-reorientation magnetic phase transition, the value of the magnetocaloric effect was determined as an isothermal magnetic entropy change (DSM). The universal curve of ΔS´(ʘ) around TSR under various magnetic field changes has been constructed by using a phenomenological procedure. It is found that this approach is applicable to materials with a second-order spin-reorientation phase transition.

Publ.-Id: 27500 - Permalink


Complex magnetic order in the kagome ferromagnet Pr3Ru4Al12
Henriques, M. S.; Gorbunov, D. I.; Andreev, A. V.; Fabrèges, X.; Gukasov, A.; Uhlarz, M.; Petricek, V.; Ouladdiaf, B.; Wosnitza, J.
In the hexagonal crystal structure of Pr3Ru4Al12, the Pr atoms form a distorted kagome lattice, and their magnetic moments, are subject to competing exchange and anisotropy interactions.We performed magnetization, magnetic-susceptibility, specific-heat, electrical-resistivity, and neutron-scattering measurements. Pr3Ru4Al12 is a uniaxial ferromagnet with TC = 39 K that displays a collinear magnetic structure (in the high-temperature range of the magnetically ordered state) for which the only crystallographic position of Pr is split into two sites carrying different magnetic moments. A spin-reorientation phase transition is found at 7 K. Below this temperature, part of the Pr moments rotate towards the basal plane, resulting in a noncollinear magnetic state with a lower magnetic symmetry. We argue that unequal RKKY exchange interactions competing with the crystal electric field lead to a moment instability and qualitatively explain the observed magnetic phases in Pr3Ru4Al12.

Publ.-Id: 27499 - Permalink


Bethe‐Strings: Exotische Anregungen in Spinsystemen
Wang, Z.; Loidl, A.
Hans Bethe sagte 1931 in einer fundamentalen Arbeit die Existenz von stark gebundenen Zuständen von Quasiteilchen voraus. Nun konnte eine internationale Kooperation erstmals derartige Bethe‐Strings in einem Kristall nachweisen.
Keywords: Spin Kette, Quasiteilchen, String Erregungen, Hans Bethe

Publ.-Id: 27497 - Permalink


Stability and instability of hydromagnetic Taylor–Couette flows
Rüdiger, G.; Gellert, M.; Hollerbach, R.; Schultz, M.; Stefani, F.
Decades ago S. Lundquist, S. Chandrasekhar, P. H. Roberts and R. J. Tayler first posed questions about the stability of Taylor–Couette flows of conducting material under the influence of large-scale magnetic fields. These and many new questions can now be answered numerically where the nonlinear simulations even provide the instability-induced values of several transport coefficients. The cylindrical containers are axially unbounded and penetrated by magnetic background fields with axial and/or azimuthal components. The influence of the magnetic Prandtl number Pm on the onset of the instabilities is shown to be substantial. The potential flow subject to axial fields becomes unstable against axisymmetric perturbations for a certain supercritical value of the averaged Reynolds number (with Re the Reynolds number of rotation, Rm its magnetic Reynolds number). Rotation profiles as flat as the quasi-Keplerian rotation law scale similarly but only for Pm >> 1 while for the instability instead sets in for supercritical Rm at an optimal value of the magnetic field. Among the considered instabilities of azimuthal fields, those of the Chandrasekhar-type, where the background field and the background flow have identical radial profiles, are particularly interesting. They are unstable against nonaxisymmetric perturbations if at least one of the diffusivities is non-zero. For Pm << 1the onset of the instability scales with Re while it scales with Rm for Pm >> 1. Even superrotation can be destabilized by azimuthal and current-free magnetic fields; this recently discovered nonaxisymmetric instability is of a double-diffusive character, thus excluding Pm=1 . It scales with Re for Pm -> 0 and with Rm for Pm -> infinity.
The presented results allow the construction of several new experiments with liquid metals as the conducting fluid. Some of them are described here and their results will be discussed together with relevant diversifications of the magnetic instability theory including nonlinear numerical studies of the kinetic and magnetic energies, the azimuthal spectra and the influence of the Hall effect.

Publ.-Id: 27496 - Permalink


A Cu Photocathode for the Superconducting RF Photoinjector of BERLinPro
Kühn, J.; Bürger, M.; Frahm, A.; Jankowiak, A.; Kamps, T.; Klemz, G.; Kourkafas, G.; Neumann, A.; Ohm, N.; Schmeißer, M.; Schuster, M.; Völker, J.; Murcek, P.; Teichert, J.
The initial commissioning of the Superconducting RF (SRF) photoinjector is achieved with a Cu photocathode due to its robustness with respect to interactions with the SRF cavity of the injector. Here we present the preparation and characterization of a Cu photocathode plug and the diagnostics to insert the photocathode in the back wall of the SRF cavity. A polycrystalline bulk Cu plug was polished, particle free cleaned and characterized by x-ray photoelectron spectroscopy. During the transfer of the photocathode insert into the gun module the whole process was controlled by several diagnostic tools monitoring the insert position as well as RF, vacuum and cryogenic signals. We discuss the challenges of the photocathode transfer into an SRF cavity and how they can be tackled.
Keywords: electron source, photocathode, Cu, SRF gun, superconducting RF
  • Poster
    9th International Particle Accelerator Conference IPAC´18, 29.04.-04.05.2018, Vancouver, Canada

Publ.-Id: 27493 - Permalink


Reply to “Comment on Methodological accuracy of image-based electron density assessment using dual-energy computed tomography” [Med. Phys. 44, 2429-2437 (2017)]
Möhler, C.ORC; Wohlfahrt, P.ORC; Richter, C.; Greilich, S.ORC
To the editor,
In his recent letter, Dr. Bouchard expressed his concern that our article on electron density (ED) assessment with dual-energy computed tomography (DECT) contained “some errors and speculative arguments”. We are aware that any study — no matter how carefully conducted — can exhibit erroneous aspects. In this case, however, we concluded that most of the statements and additional data provided by Dr. Bouchard in fact support the key findings of our paper, while other points raised can be attributed to a different use of concepts and to occasional overinterpretation. We therefore firmly reject his assertion. In this reply we provide our response to the criticism
raised:
Keywords: dual-energy CT, electron density, proton therapy

Publ.-Id: 27492 - Permalink


EOS at cw beam operation at Elbe
Schneider, C.; Gensch, M.; Kuntzsch, M.; Michel, P.; Seidel, W.; Kaya, K.; Al Shemmary, A.; Stojanovic, N.; Evtushenko, P.
The ELBE accelerator is a super conduction electron cw machine located at the Helmholtz Center Dresden Rossendorf Germany with 1 mA current, now tested for up to 2 mA. Besides other important diagnostics for setting up the machine for user beam time and further improvement of the machine – a THz source is momentary under commissioning – a EOS measuring station for bunch length measurements is locate right behind the second super conducting Linac. Measuring with a crystal in the vicinity of an up to 2 mA cw beam implies higher beam loss and also higher radiation exposure of the crystal and hence also a safety risk for the UHV conditions of the super conducting cavities in the case of crystal damage. Therefore the EOS measuring principle is adapted to larger measuring distances and also for beam requirements with lower bunch charge at ELBE. A description of the setup, considerations of special boundary conditions and as well results for 13 MHz cw beam operation are presented.
  • Open Access LogoContribution to proceedings
    IPAC2014 - 5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Germany

Publ.-Id: 27491 - Permalink


Microresonator-ferromagnetic resonance investigation of thermal spin-transfer torque in Co2FeAl/MgO/CoFeB magnetic tunnel junctions
Cansever, H.ORC; Narkowicz, R.; Lenz, K.; Fowley, C.; Ramasubramanian, L.; Yildirim, O.; Niesen, A.; Huebner, T.ORC; Reiss, G.; Lindner, J.; Fassbender, J.; Deac, A. M.
Similar to electrical currents flowing through magnetic multilayers [1,2], thermal gradients applied across the barrier of a magnetic tunnel junction may induce pure spin currents and generate ‘thermal’ spin-transfer torques large enough to induce magnetization dynamics on the free layer [3, 4]. The relation of spin current, charge current and heat current was theoretically described by Bauer et al. using Onsager’s reciprocity rule [5]. According to Onsager’s law, spin currents can be produced by bias voltages or thermal gradients and investigated in terms of spin-Seebeck effect in magnetic multilayers.
First, Hatami et al. theoretically studied the spin-Seebeck effect in spin-valves and introduced the concept of thermal spin-transfer torques. They predicted that the thermally induced spin current creates an imbalance on the interface between non-magnetic and ferromagnetic layers due to collisions (electron-electron and electron-phonon interactions) [3]. Thermal spin-transfer torques were studied experimentally within asymmetric Co/Cu/Co nanowire spin-valves which exhibit switching field changes under varying a.c. currents causing Joule heating [6]. In magnetic tunnel junctions, it was theoretically predicted that temperature differences of around 10 K over an ultrathin barrier (1 nm) can create magnetization dynamics in Fe/MgO/Fe magnetic tunnel junctions [4]. The spin-Seebeck effect has been studied on CoFeB/MgO/CoFeB magnetic tunnel junctions using different heating methods such as Joule heating, heating with Peltier elements, as well as laser heating [8-14]. Recently, it was shown that using Co2FeAl as a reference layer improves tunneling magneto-Seebeck (TMS) in magnetic tunnel junctions [7].
Here, we describe a novel experimental approach and setup to observe effects of thermal gradients within magnetic tunnel junctions with Heusler compounds by using the microresonator ferromagnetic resonance (µR-FMR) method under laser heating. Initially, microresonators (shown in figure 1) were introduced by Narkowicz et al. for electron paramagnetic resonance (EPR) experiments to achieve optimal sensitivity for small objects [8]. Detecting the FMR signal of nano- to micron-sized samples in conventional cavities (cm3) is not possible, due to the too small ferromagnetic volume, and therefore low filling factor. A planar microresonator, by definition, is a two-dimensional structure, its diameter can be tailored to match the order of the sample’s size (shown as a black ellipse in the microresonator loop in figure 1). Two stubs are attached to the inductive loop. The capacitive radial stub in first approximation may be viewed as an element to tune the loop to the operation frequency, while the rectangular stub matches the structure to the 50 Ω impedance of the microstrip feedline.

Figure 1: Layout of a planar microresonator with simulated electric field distribution at the resonance frequency. The inset shows the current and magnetic field distribution (out-of-plane direction) in the loop containing a sample (black ellipse).
We investigated magnetic tunnel junctions (MTJs) fabricated out of Co2FeAl/MgO/CoFeB stacks. The sample and microresonator fabrication consist of multiple steps of lithography, ion etching and lift-off processes. The sample is finally patterned into a 6x9 µm2 elliptical shape using electron beam lithography (EBL) and ion beam etching is used to etch down the sample to the substrate. Microresonators are then fabricated around the sample using UV lithography. For laser heating, a continuous-wave (CW) laser at 532 nm wavelength and with tunable power up to 33 mW is focused on the sample.
“Hot-FMR” measurements were performed on unpatterned multilayers between 300 K and 450 K (figure 2) to understand the effect of global heating. It is clearly seen that the FMR signal of Co2FeAl exhibits a shift with increasing temperature. As seen in the inset graph, it is difficult to quantify the changes for the CoFeB signal, due to its small intensity. Subsequent, measurements in the presence of a thermal gradient were performed on 6x9 µm2 MTJs, integrated into microresonator loops with an inner diameter of 20 µm. The MTJs were submitted to laser irradiation, up to a maximum power of 33 mW. Unlike the Hot-FMR measurements, the resonance field and linewidth did not show clear changes with increasing laser power. The results suggest that the laser power is neither sufficient to induce magnetization dynamics via thermal gradients across the barrier, nor lead to significant changes of the magnetic parameters due to global heating of the sample.
Figure 2: FMR spectra of the extended films of Co2FeAl / MgO / CoFeB measured in the in-plane direction at different temperatures
As a conclusion, the effect of a global temperature change on the resonance frequency and linewidth of Co2FeAl was analyzed. With regards to the µR-FMR results, higher laser power is needed to induce magnetization dynamics. Moreover, the lateral heat transport might reduce the vertical thermal gradients, thus similar measurements on smaller structures are required.
This study was funded by the German Research Foundation (DFG) via priority program SpinCaT (SPP 1538). We thank H. Schultheiss for helping with the optical part of the experimental setup and S. Zhou for giving the access to the VSM setup.
[1] J.C. Slonczewski, J. Magn. Magn. Mater. 159, L1, (1996).
[2] L. Berger, Phys. Rev. B 54, 9353, (1996).
[3] M. Hatami, G.E.W. Bauer, Q. Zhang and P.J. Kelly, Phys. Rev. Lett. 99, 066603 (2007).
[4] X. Jia, K. Xia and G.E.W. Bauer, Phys. Rev. Lett. 107, 176603 (2011).
[5] G.E.W. Bauer, E. Saitoh and B.J. van Wees, Nature Mater. 11, 391, (2012).
[6] H. Yu, S. Granville, D.P. Yu and J.-Ph. Ansermet, Phys. Rev. Lett. 104, 146601 (2010).
[7] A. Boehnke, U. Martens, C. Sterwerf, A. Niesen, T. Huebner, M. von der Ehe, M. Meinert, T. Kuschel, A. Thomas, C. Heiliger, M. Münzenberg M, Nature Communications 8,(1),1626, (2017).
[8] R. Narkowicz, D. Suter and R. Stonies, J. Magn. Reson.175, 275 (2005).
Keywords: thermal spin transfer torque, ferromagnetic resonance, microresonator, magnetic tunnel junctions
  • Lecture (Conference)
    INTERMAG 2018 Singapore, 23.-27.04.2018, Singapore, Singapore

Publ.-Id: 27490 - Permalink


Radiation Tests Of Aerospace Components At Elbe
Schneider, C.; Bemmerer, D.; Michel, P.; Stach, D.
The cw electron accelerator ELBE operates mainly in the beam energy range 6 to 32 MeV and beam current range 1μA to 1mA. For most experiments a thermionic gun is used as electron source. The cw electron pulse structure so as the pulse charge is realized by applying electrical pulses with specific amplitudes and frequencies on the grid of the gun. The standard cw operation frequency is 13 MHz but can be divided sequentially by the factor 2 down to 101 kHz. For very special pulse structures a so called single pulser module exist performing different patterns also with dark current suppression via a macro pulser gate. For evaluating the performance and hardness under irradiation of e.g. aerospace components much lower doses resp. currents lower than the μA range are required. Furthermore reproducible and stable doses in a specific area for consecutively radiation of samples are necessary. In the presentation the investigations and concepts used at ELBE for the irradiation of different aerospace components are described.
  • Open Access LogoContribution to proceedings
    IPAC2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark

Publ.-Id: 27489 - Permalink


Design Of A Stripline Kicker For The Elbe Accelerator
Schneider, C.; Arnold, A.; Hauser, J.; Michel, P.; Staats, G.
ELBE is a linac based cw electron accelerator serving different secondary beams one at a time. Depending on the user demand the bunch repetition rate may vary from single pulse up to 13 MHz. For the future different end stations should be served simultaneously, hence specific bunch patterns have to be kicked into different beam-lines. To use e.g. one bunch out of the bunch train very short kicking durations have to be realized. The variabil-ity of the bunch pattern and the frequency resp. switching time are one of the main arguments for a stripline-kicker combined with high voltage (HV)-switches as basic con-cept. A nearly homogenous field in the kicker has to be realized for uniform deflection of the electron bunch and keep the emittance growth of the bunch as low as possi-ble. Furthermore the fast switching ability of the kicker demands for a fast decay of the HV-pulse resp. its reflec-tions in the structure implying a specific design of the kicker elements. For this reason a design with two tapered active electrodes and two ground fenders was optimized in time and frequency domain with the software package CST. Additionally a first prototype was manufactured for laboratory and first beam-line tests.
  • Open Access LogoContribution to proceedings
    IPAC2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark

Publ.-Id: 27487 - Permalink


Strain and order-parameter coupling in Ni-Mn-Ga Heusler alloys from resonant ultrasound spectroscopy
Salazar Mejia, C.; Born, N.-O.; Schiemer, J. A.; Felser, C.; Carpenter, M. A.; Nicklas, M.
Resonant ultrasound spectroscopy and magnetic susceptibility experiments have been used to characterize strain coupling phenomena associated with structural and magnetic properties of the shape-memory Heusler alloy series Ni50+xMn25−xGa25 (x=0, 2.5, 5.0, and 7.5). All samples exhibit a martensitic transformation at temperature TM and ferromagnetic ordering at temperature TC, while the pure end member (x=0) also has a premartensitic transition at TPM, giving four different scenarios:
Tc > TPM > TM, TC > TM without premartensitic transition, TC ≈ TM, and TC < TM. Fundamental differences in elastic properties, i.e., stiffening versus softening, are explained in terms of coupling of shear strains with three discrete order parameters relating to magnetic ordering, a soft mode, and the electronic instability responsible for the large strains typical of martensitic transitions. Linear-quadratic or biquadratic coupling between these order parameters, either directly or indirectly via the common strains, is then used to explain the stabilities of the different structures. Acoustic losses are attributed to critical slowing down at the premartensite transition, to the mobility of interphases between coexisting phases at the martensitic transition, and to mobility of some aspect of the twin walls under applied stress down to the lowest temperatures at which measurements were made.

Publ.-Id: 27478 - Permalink


Investigating spin-transfer torques induced by thermal gradients in magnetic tunnel junctions by using micro-cavity ferromagnetic resonance
Cansever, H.; Narkowicz, R.; Lenz, K.; Fowley, C.; Ramasubramanian, L.; Yildirim, O.; Niesen, A.; Huebner, T.; Reiss, G.; Lindner, J.; Fassbender, J.; Deac, A. M.
Similar to electrical currents flowing through magnetic multilayers, thermal gradients applied across the barrier of a magnetic tunnel junction may induce pure spin-currents and generate ‘ thermal’ spin-transfer torques large enough to induce magnetization dynamics in the free layer. In this study, we describe a novel experimental approach to observe spin-transfer torques induced by thermal gradients in magnetic multilayers by studying their ferromagnetic resonance response in microwave cavities. Utilizing this approach allows for measuring the magnetization dynamics on micron/nano-sized samples in open-circuit conditions, i.e. without the need of electrical contacts. We performed first experiments on magnetic tunnel junctions patterned into 6×9μm2 ellipses from Co2FeAl/MgO/CoFeB stacks. We conducted microresonator ferromagnetic resonance (FMR) under focused laser illumination to induce thermal gradients in the layer stack and compared them to measurements in which the sample was globally heated from the backside of the substrate. Moreover, we carried out broadband FMR measurements under global heating conditions on the same extended films the microstructures were later on prepared from. The results clearly demonstrate the effect of thermal spin-torque on the FMR response and thus show that the microresonator approach is well suited to investigate thermal spin-transfer-driven processes for small temperatures gradients, far below the gradients required for magnetic switching.
Keywords: thermal spin transfer torque, microresonator, ferromagnetic resonance, magnetic tunnel junction

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  • Secondary publication expected from 14.05.2019

Publ.-Id: 27477 - Permalink


Magnetocaloric materials for refrigeration near room temperature
Waske, A.; Gruner, M. E.; Gottschall, T.; Gutfleisch, O.
This article overviews the current status of magnetocaloric materials for room-temperature refrigeration. We discuss the underlying mechanism of the magnetocaloric effect and illustrate differences between fi rst- and second-order type materials starting with gadolinium as a reference system. Beyond the key functional properties of magnetocaloric materials, the adiabatic temperature, and entropy change, we briefl y address the criticality of the most promising materials in terms of their supply risk. Looking at practical applications, suitable geometries and processing routes for magnetocaloric heat exchangers for device implementation are introduced.

Publ.-Id: 27476 - Permalink


Spatially Nonuniform Superconductivity in Quasi-Two-Dimensional Organic Charge-Transfer Salts
Wosnitza, J.
In the following, a brief overview on the recently found robust experimental evidence for the existence of the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state in layered organic superconductors is given. These electronically quasi-two-dimensional (2D) clean-limit superconductors are ideally suited for observing FFLO states. Applying a magnetic field parallel to the layers suppresses orbital effects and superconductivity is observed beyond the Pauli paramagnetic limit. Both, thermodynamic as well as microscopic experimental data show the existence of an additional high-field low-temperature superconducting state having a one-dimensionally modulated order parameter.

Publ.-Id: 27475 - Permalink


Fermi-surface topology of the heavy-fermion system Ce2PtIn8
Klotz, J.; Götze, K.; Green, E. L.; Demuer, A.; Shishido, H.; Ishida, T.; Harima, H.; Wosnitza, J.; Sheikin, I.
Ce2PtIn8 is a recently discovered heavy-fermion system structurally related to the well-studied superconductor CeCoIn. Here we report on low-temperature de Haas–van Alphen-effect measurements in high magnetic fields in Ce2PtIn8 and Pr2PtIn8. In addition, we performed band-structure calculations for localized and itinerant Ce-4f electrons in Ce2PtIn8. Comparison with the experimental data of Ce2PtIn8 and of the 4f -localized Pr2PtIn8 suggests the itinerant character of the Ce-4f electrons. This conclusion is further supported by the observation of effective masses in CePtIn8, which are strongly enhanced with up to 26 bare electron masses.

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Publ.-Id: 27474 - Permalink


Crystal-field effects in the kagome antiferromagnet Ho3Ru4Al12
Gorbunov, D. I.; Nomura, T.; Ishii, I.; Henriques, M. S.; Andreev, A. V.; Doerr, M.; Stöter, T.; Suzuki, T.; Zherlitsyn, S.; Wosnitza, J.
In Ho3Ru4Al12, the Ho atoms form a distorted kagome lattice. We performed magnetization, magnetic-susceptibility, specific-heat, and ultrasound measurements on a single crystal. We find that the magnetic and magnetoelastic properties of Ho3Ru4Al12 result from an interplay between geometric frustration and crystalelectric-field (CEF) effects. The Ho atoms order antiferromagnetically at TN = 4.5 K with reduced magnetic moments. In applied field, the magnetization shows anomalies that can be explained by CEF level crossings. We propose a CEF level scheme for which the ground-state doublet and the first two excited singlets at about 2.7 K form a quasiquartet. Indirect interlevel transitions allow for a quadrupolar interaction. This interaction explains well changes in the elastic shear modulus C44 as a function of temperature and magnetic field.

Publ.-Id: 27473 - Permalink


Search for multipolar instability in URu2Si2 studied by ultrasonic measurements under pulsed magnetic field
Yanagisawa, T.; Mombetsu, S.; Hidaka, H.; Amitsuka, H.; Cong, P. T.; Yasin, S.; Zherlitsyn, S.; Wosnitza, J.; Huang, K.; Kanchanavatee, N.; Janoschek, M.; Maple, M. B.; Aoki, D.
The elastic properties of URu2Si2 in the high magnetic field region above 40 T, over a wide temperature range from 1.5 to 120 K, were systematically investigated by means of high-frequency ultrasonic measurements. The investigation was performed at high magnetic fields to better investigate the innate bare 5f -electron properties, since the unidentified electronic thermodynamic phase of unknown origin, the so-called “hidden order” (HO), and associated hybridization of conduction and f electrons (c-f hybridization) are suppressed at high magnetic fields. From the three different transverse modes we find contrasting results; both the Γ4(B2g) and Γ5(Eg) symmetry modes C66 and C44 show elastic softening that is enhanced above 30 T, while the characteristic softening of the Γ3/B1g) symmetry mode (C11 - C12)/2 is suppressed in high magnetic fields. These results underscore the presence of a hybridization-driven Γ3(B1g) lattice instability in URu2Si2. However, the results from this work cannot be explained by using existing crystalline electric field schemes applied to the quadrupolar susceptibility in a local 5f2 configuration. Instead, we present an analysis based on a band Jahn-Teller effect.

Publ.-Id: 27472 - Permalink


Data for publication
Kluge, T.ORC; Rödel, M.; Metzkes, J.; Pelka, A.; Garcia, A. L.; Prencipe, I.; Rehwald, M.; Nakatsutsumi, M.; Mcbride, E. E.; Schönherr, T.; Garten, M.; Hartley, N. J.; Zacharias, M.; Erbe, A.; Georgiev, Y. M.; Galtier, E.; Nam, I.; Lee, H. J.; Glenzer, S.; Bussmann, M.; Gutt, C.; Zeil, K.; Rödel, C.; Hübner, U.; Schramm, U.; Cowan, T. E.

Raw data, lineouts and fits for the publication

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-05-09
    DOI: 10.14278/rodare.23

Downloads:

Publ.-Id: 27465 - Permalink


Sulfonated calix-baskets for complexation of Barium and Radium
Mamat, C.ORC; Reissig, F.ORC; Bauer, D.ORC; Pietzsch, H.-J.ORC; Steinbach, J.ORC
Understanding the coordination chemistry of heavy group 2 metals, especially of barium as surrogate for radium, is mandatory not only for radiopharmaceutical applications of radium. This is from high importance since radium-223 is the only approved therapeutic alpha-emitter (by EMA and FDA). Unfortunately, the applications are limited. To date, radium-223 is only in use as RaCl2 for the treatment of bone cancer metastases. To overcome this limitation, which is also true for other group 2 metals, special cage-like compounds have to be developed as ligands like sulfonated calix[4]crowns to stably bind the Ba2+ and Ra2+ to avoid a release in vivo. This will be the basis for a future application of heavy group 2 metals and not only of radium to treat other cancer entities than bone metastases. Ra2+ can then be included in radiopharmaceuticals which contain a chelator and a biologically active molecule part to find the tumor cell.
For this purpose, a series of modified calix[4]crown-6 derivatives was synthesized to chelate barium, which serves as non-radioactive surrogate for radium-223/-224. These calixcrowns were functionalized sulfonate moieties including deprotonable groups and the corresponding barium complexes were synthesized. Stability constants of these complexes were measured using UV/Vis titration experiments to determine logK values. Further extraction studies were performed with [133Ba]Ba2+ and [224Ra]Ra2+ to further characterize the binding affinity of calixcrowns.
  • Lecture (Conference)
    RadChem - 18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Czech Republic
  • Open Access LogoContribution to proceedings
    RadChem - 18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázne, Czech Republic
    Czech Chemical Society Symposium Series, Praha: Czech Chemical Society (CCS), 228-229

Publ.-Id: 27462 - Permalink


Modelling and Simulation of Severe Accidents in Pressurized Water Reactors
Wilhelm, P.; Schäfer, F.; Jobst, M.; Kozmenkov, Y.; Kosowski, K.
Modelling and Simulation of Severe Accidents in Pressurized Water Reactors
  • Lecture (Conference)
    NUGENIA Annual Forum 2018/Nuclear Days 2018, 10.-12.04.2018, Prague, Czech Republic

Publ.-Id: 27458 - Permalink


Tests of MACACO Compton telescope with 4.44MeV gamma rays
Muñoz, E.; Barrio, J.; Bemmerer, D.; Etxebeste, A.; Fiedler, F.; Hueso-González, F.; Lacasta, C.; Oliver, J. F.; Römer, K.; Solaz, C.; Wagner, L.; Llosá, G.
Hadron therapy offers the possibility of delivering a large amount of radiation dose to tumors with minimal absorption by the surrounding healthy tissue. In order to fully exploit the advantages of this technique, the use of real-time beam monitoring devices becomes mandatory.
Compton imaging devices can be employed to map the distribution of prompt gamma emission during the treatment and thus assess its correct delivery. The Compton telescope prototype developed at IFIC-Valencia for this purpose is made of three layers of LaBr3 crystals coupled to silicon photomultipliers. The system has been tested in a 4.44 MeV gamma field at the 3 MV Tandetron accelerator at HZDR, Dresden. Images of the target with the system in three different positions separated by 10 mm were successfully reconstructed. This indicates the ability of MACACO for imaging the prompt gamma rays emitted at such energies.
Keywords: Compton imaging; Instrumentation for hadron therapy; Gamma detectors (scintillators, CZT, HPG, HgI etc); Photon detectors for UV, visible and IR photons (solid-state) (PIN diodes, APDs, Si-PMTs, G-APDs, CCDs, EBCCDs, EMCCDs

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Publ.-Id: 27456 - Permalink


Ion Sources for Focused Ion Beam Applications
Bischoff, L.; Mazarov, P.; Pilz, W.; Gierak, J.
One of the most important elements of a Focused Ion Beam (FIB) system is the ion source which has to guarantee a stable, long life working in the needed application field with the required properties. Main points are the achievable focus of the spot, the ion current, the energy and also the ion species itself. At present nearly half of elements of the periodic table can be used in FIB equipment to modify or tune locally electrical, optical, mechanic or magnetic properties. Depending on the special task very different types of ion sources can be found. Among them the Liquid Metal Ion Sources (LMIS) mostly used for Ga and derived from that the Liquid Metal Alloy Ion Sources (LMAIS) [1] are most popular ones having a brightness of 106 A/cm² sr. The obtainable resolution is a few nm with ion currents of some pA. In a similar manner Ionic Liquid Ion Sources (ILIS) work using salts or certain compounds from which positive and negative mono- and polyatomic ions can be emitted [1,2]. Due to the limited ion current in such sources to lower than 100 nA and so applications like larger volume removing are restricted. ECR or RF plasma sources can fill the gap working with heavy Xe ions and currents up to 2 µA [3,4]. In the last decade a long known source was rediscovered – the Gas Field Ion Source (GFIS) and generate the initial point for the successful development of the Helium Ion Microscope (HIM) [5]. A final lateral spot size of about half nm opens new prospects in the field of ion microscopy and nano-engineering. Another modern and interesting approach is the magneto-optical trap ion source (MOTIS) successful demonstrated for Cr and Li ions [6].
All ion sources used in FIB systems will be compared, characterized, discussed and described with a typical application.

[1] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative for Focused Ion Beam Technology, Appl. Phys. Rev. 3 (2016) 021101.
[2] A. N. Zorzos and P. Lozano, The use of ionic liquid ion sources in focused ion beam applications, J. Vac. Sci. Technol. B 26 (2008) 2097.
[3] A. Delobbe, O. Salord, T. Hrncir, A. David, P. Sudraud and F. Lopour, High Speed TEM Sample Preparation by Xe FIB, Microsc. Microanal. 20 (2014) 298.
[4] T.L. Burnetta, R. Kelley, B. Winiarski, L. Contreras, M. Daly, A. Gholinia, M.G. Burke, and P.J. Withers, Large volume serial section tomography by Xe Plasma FIB dual beam Microscopy, Ultramicroscopy 161 (2016) 119.
[5] G. Hlawacek, V. Veligura, R. van Gastel, and B. Poelsema, Helium ion microscopy, J. Vac. Sci. Technol. B 32 (2014) 020801.
[6] B. Knuffman, A. V. Steele, J. Orloff, M. Maazouz, and J. J. McClelland, A Focused Ion Beam Source Based On Laser-Cooled Atoms, AIP Conference Proceedings 1395 (2011) 85.
Keywords: Focused Ion Beam, Plasma Ion Sources, LMAIS, MOTIS
  • Lecture (Conference)
    MAT Science Week, 24.-27.04.2018, Darmstadt, Germany

Publ.-Id: 27452 - Permalink


Metallic twin boundaries boost the hydrogen evolution reaction on the basal plane of molybdenum selenotellurides
Kosmala, T.; Diaz, H. C.; Komsa, H.-P.; Ma, Y.; Krasheninnikov, A. V.ORC; Batzill, M.; Agnoli, S.
The hydrogen evolution reaction (HER) is a fundamental process that impacts several important clean energy technologies. Great efforts have been taken to identify alternative materials that could replace Pt for this reaction or that may present additional functional properties such as optical activity and advanced electronic properties. Herein, a comparative study of the HER activity for ultrathin films of MoTe2, MoSe2, and their solid solutions on highly oriented pyrolytic graphite is reported. Combining advanced characterization techniques and density functional theory calculations with electrochemical measurements, it is shown that the chemical activity of the scarcely reactive 2H phases can be boosted by the presence of metallic twin boundaries. These defects, which are thermodynamically stable and naturally present in Mo-enriched MoTe2 and MoSe2, endow the basal plane of the 2H phase with a high chemical activity, which is comparable to the metastable 1T polymorph.
Keywords: 2D materials, hydrogen evolution reaction, first-principles calculations

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  • Secondary publication expected from 14.04.2019

Publ.-Id: 27449 - Permalink


Post-synthesis modifications of two-dimensional MoSe2 or MoTe2 by incorporation of excess metal atoms into the crystal structure
Coelho, P. M.; Komsa, H.-P.; Diaz, H. C.; Ma, Y.; Krasheninnikov, A. V.ORC; Batzill, M.
Phase engineering has extensively been used to achieve metallization of two-dimensional (2D) semiconducting materials, as it should boost their catalytic properties or improve electrical contacts. In contrast, here we demonstrate compositional phase change by incorporation of excess metals into the crystal structure. We demonstrate post-synthesis restructuring of the semiconducting MoTe2 or MoSe2 host material by unexpected easy incorporation of excess Mo into their crystal planes, which causes local metallization. The amount of excess Mo can reach values as high as 10% in MoTe2 thus creating a significantly altered material compared to its parent structure. The incorporation mechanism is explained by density functional theory in terms of the energy difference of Mo atoms incorporated in the line phases as compared to Mo ad-clusters. Angle resolved photoemission spectroscopy reveals that the incorporated excess Mo induces band gap states up to the Fermi level causing its pinning at these electronic states. The incorporation of excess transition metals in MoTe2 and MoSe2 is not limited to molybdenum, but other transition metals can also diffuse into the lattice, as demonstrated experimentally by Ti deposition. The mechanism of incorporation of transition metals in MoSe2 and MoTe2 is revealed, which should help to address the challenges in synthesizing defect-free single layer materials by, for example, molecular beam epitaxy. The easy incorporation of metal atoms into the crystal also indicates that the previously assumed picture of a sharp metal/2D- material interface may not be correct, and at least for MoSe2 and MoTe2, in-diffusion of metals from metal-contacts into the 2D material has to be considered. Most importantly though, the process of incorporation of transition metals with high concentrations into pristine 2D transition-metal dichalcogenides enables a pathway for their post-synthesis modifications and adding functionalities.
Keywords: 2D materials, defects, first-principles simulaitons

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  • Secondary publication expected from 09.04.2019

Publ.-Id: 27448 - Permalink


Synthesis and structural characterization of the first neptunium based metal-organic frameworks incorporating {Np6O8} hexanuclear cluster
Martin, N. P.ORC; März, J.; Feuchter, H.; Duval, S.; Roussel, P.; Henry, N.; Petricek, V.; Ikeda-Ohno, A.ORC; Loiseau, T.ORC; Volkringer, C.ORC
Successful synthesis of the first transuranium Metal-Organic Frameworks (MOFs) involving neptunium(IV) (Np(IV) is reported. These compounds were obtained from the controlled hydrolysis of Np(IV) in the presence of dicarboxylate ligands. The final structures contain the [Np6O4(OH)4(H2O)6]12+ unit, which were never cristallized before with tetravalent neptunium
Keywords: actinides, neptunium, metal-organic frameworks, carboxylate, coordination chemistry, structure, X-ray diffraction

Publ.-Id: 27442 - Permalink


Flow Measurements in a Liquid Metal Model for Continuous Casting of Steel
Schurmann, D.; Willers, B.; Eckert, S.; Hackl, G.; Nitzl, G.
Poster for the Graduate Student Poster Contest of the AISTech 2018 Conference in Philadelphia, USA.
Related publications
Gyro Nozzle – An innovative Submerged Entry Nozzle Design… (Id 27128) is supplemented by this publication
  • Poster
    AISTech 2018, 07.-10.05.2018, Philadelphia, USA

Publ.-Id: 27436 - Permalink


Origin and Manipulation of Stable Vortex Ground States in Permalloy Nanotubes
Zimmermann, M.; Gerhard-Meier, T. N.; Dirnberger, F.; Kákay, A.; Decker, M.; Wintz, S.; Finizio, S.; Josten, E.; Raabe, J.; Kronseder, M.; Bougeard, D.; Lindner, J.; Back, C. H.
We present a detailed study on the static magnetic properties of individual permalloy nanotubes (NTs) with hexagonal cross-sections. Anisotropic magnetoresistance (AMR) measurements and scanning transmission X-ray microscopy (STXM) are used to investigate their magnetic ground states and its stability. We find that the magnetization in zero applied magnetic field is in a very stable vortex state. Its origin is attributed to a strong growth-induced anisotropy with easy axis perpendicular to the long axis of the tubes. AMR measurements of individual NTs in combination with micromagnetic simulations allow the determination of the magnitude of the growth-induced anisotropy for different types of NT coatings. We show that the strength of the anisotropy can be controlled by introducing a buffer layer underneath the magnetic layer. The magnetic ground states depend on the external magnetic field history and are directly imaged using STXM. Stable vortex domains can be introduced by external magnetic fields and can be erased by radio-frequency magnetic fields applied at the center of the tubes via a strip line antenna.
Keywords: Nanotube, anisotropic magnetoresistance, permalloy, vortex, ground state

Publ.-Id: 27435 - Permalink


Functional thiols as repair and doping agents of defective MoS2 monolayers
Förster, A.; Gemming, S.; Seifert, G.
Recent experimental and theoretical studies indicate that thiols (R-SH) can be used to repair sulfur vacancy defects in MoS2 monolayers (MLs). This density functional theory (DFT) study investigates how the thiol repair mechanism process can be used to dope MoS2 MLs. Fluorinated thiols as well as amine-containing ones are used to p- and n-dope the MoS2 ML, respectively. It is shown that functional groups are only physisorbed on the repaired MoSS2 surface. This explains the reversible doping with fluorinated thiols.
Keywords: 2D materials, desnsity functional theory, DFT, defects, thiols, repair, doping, tuning

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  • Secondary publication expected from 17.05.2019

Publ.-Id: 27430 - Permalink


Freisetzung und Rückhaltung von Radionukliden in Systemen mit Zementphasen, Zuschlagstoffen und Tongestein.
Wolter, J.-M.; Philipp, T.; Schmeide, K.; Schymura, S.; Huittinen, N.; Stumpf, T.
Leaching experiments of uranium(VI) and Cm(III) doped calcium-silicate-hydrate (CSH) phases with various calcium to silicon ratios were carried out in NaCl, NaCl/Na2SO4, NaCl/NaHCO3 and NaHCO3 containing solutions to study the time-dependent release of Ca, Si, U and Cm. Potential changes of the U(VI) and Cm(III)-CSH binding induced by leaching were monitored with time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD).
Furthermore, investigations of the Eu(III) sorption on Ca-bentonite in the presence of high ionic strengths and superplasticizer were carried out.
Additionally, the U(VI) binding to the Ca-bentonite surface in the hyper-alkaline pH region was studdied with EXAFS.
Keywords: Cm(III), U(VI), Eu(III), TRLFS, IR, EXAFS, PXRD, CSH, Ca-bentonite, NaCl, Na2SO4, NaHCO3, CaCl2
  • Lecture (others)
    6. Workshop des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“, 25.-26.04.2018, Karlsruhe, Deutschland

Publ.-Id: 27425 - Permalink


Phytotoxicity of tin mine waste and accumulation of involved heavy metals in common buckwheat (Fagopyrum esculentum Moench)
Franzaring, J.; Damsohn, W.; Fangmeier, A.; Schlosser, S.; Kurz, H.; Büttner, P.
Extraction and processing of cassiterite (SnO2) left large tailings with high concentrations of tin, tungsten, molybdenum and lithium. Information on the phytotoxicity of mine waste is important with regard to ecological hazards. Exposure studies help to identify plants useful for the stabilization of waste tips and the phytomining of metals. A greenhouse study was performed using a dilution series of mine waste and four crops, a halophytic and a metallophytic species to derive dose response curves. Based on effective doses for growth reductions, sensitivity increased in the following order: maize > common buckwheat > quinoa > garden bean. Element analyses in different species and compartments of common buckwheat grown in a mixture of standard soil and 25% of the mine waste showed that only low levels of the metals were taken up and that transfer to seed tissues was negligible. As indicated by soil metal levels prior to and after the experiment, only lithium and arsenic proved to be plant available and reached high levels in green tissues while seed levels were low. The experiment confirmed differences in the uptake of metals with regard to elements and species. Common buckwheat is a suited candidate for cultivation on metal polluted soils. © 2018 Taylor & Francis Group, LLC.
Keywords: bioaccumulationdose-response, curvessoil, contaminationsoil, reclamation

Publ.-Id: 27420 - Permalink


Controlled Nickel Silicidation of Silicon Nanowires for Fabrication of Reconfigurable Field Effect Transistors
Khan, M. B.; Deb, D.; Georgiev, Y. M.; Prucnal, S.; Voelskow, M.; Erbe, A.
Physical scaling down of field effect transistors (FET) is reaching its end. To meet the consistent demand for faster, smaller and energy efficient transistors, new concepts which include new materials, new architectures, new computation principles and enhanced functionality are under research. Focus of this work is to fabricate devices with enhanced functionality, the so called reconfigurable FET (RFET) which can be configured as p- or n-channel FET. These FETs are realized by fabricating silicon nanowires (SiNWs) on Si on insulator (SOI) substrates. These NWs are subsequently nickel silicided at both ends to form Si-NiSi2-Si Schottky junctions. Control over silicide length is important to scale Si channel and to have symmetric contacts on both sides of nanowires. Focus of our recent work is achieve this control over silicidation by using flash lamp annealing (FLA). Comparison between silicidation using flash lamp annealing (FLA) and rapid thermal annealing (FLA) along with the resulting electrical characteristics of these devices will be presented at the conference.
  • Poster
    DPG-Frühjahrstagung 2018, 11.-16.03.2018, Berlin, Germany

Publ.-Id: 27418 - Permalink


Profiling of RT-PICLS Code
Kelling, J.; Juckeland, G.ORC

It was observed, that the RT-PICLS code ran by FWKT on the hypnos cluster was producing an unusual amount of system load, according to Ganglia metrics. Since this may point to an IO-problem in the code, this code was analyzed more closely.

RT-PICLS was run with additionally provided input data on 64 CPU cores (AMD Opteron) in a single node of the hypnos cluster. Score-P 4.0 with IO-tracing support was used for profiling and tracing of the application. A developer version of Vampir 9.2 [3] enabled graphical analysis of the traces.

Different file systems were evaluated for storing the output:

  • bigdata: the high-performance file system of the cluster based on GPFS.
  • nfs: a loop-mounted EXT4 image mounted to the current compute node via NFS.
  • scr: the local scratch file-system of the compute node.
  • tmpfs: a virtual filesystem, physically located in the main memory of the compute node.

The trace files that were used to compile the referenced report are collected in this upload.

Keywords: Scorep; Vampir; Tracing; Profiling
Related publications
Profiling of RT-PICLS Code (Id 25474) is a supplement to this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-04-25
    DOI: 10.14278/rodare.15
    License: CC-BY-4.0

Downloads:

Publ.-Id: 27417 - Permalink


Time-delayed multiple shocks
Kraus, D.
Time-delayed multiple shocks
  • Invited lecture (Conferences)
    Workshop on Dynamic Laser Compression Experiments at the HED instrument at European XFEL, 12.-14.09.2016, Hamburg, Deutschland

Publ.-Id: 27416 - Permalink


Structural transitions in shock-compressed (hydro) carbon(s)
Kraus, D.
Structural transitions in shock-compressed (hydro) carbon(s)
  • Invited lecture (Conferences)
    Workshop on High Pressure, Planetary and Plasma Physics, 14.-16.09.2016, Hamburg, Deutschland

Publ.-Id: 27415 - Permalink


Phase separation of hydrocarbons at conditions relevant to planetary interiors and the first shock in ICF
Kraus, D.
Phase separation of hydrocarbons at conditions relevant to planetary interiors and the first shock in ICF
  • Invited lecture (Conferences)
    4th High Power Laser Workshop, 03.-04.10.2016, Menlo Park, USA

Publ.-Id: 27414 - Permalink


Diagnostics of shock-compressed matter at X-ray facilities
Kraus, D.
The combination of pulsed high-energy lasers with highly brilliant X-ray sources has started to provide unprecedented in situ diagnostics of dynamically compressed materials. Combining various diagnostic techniques will be crucial in order to obtain an improved understanding of the extreme states of matter that are investigated in such experiments. This talk will discuss diagnostics that are planned for HPLF at ESRF in the context of other X-ray facilities that also provide high-energy laser systems.
  • Invited lecture (Conferences)
    2nd Workshop on "Studies of dynamically compressed matter with X-rays", 29.-30.03.2017, Grenoble, Frankreich

Publ.-Id: 27413 - Permalink


X-ray scattering and diffraction from samples driven by ultra-intense lasers
Kraus, D.
The combination of X-ray free electron lasers and ultra-intense optical lasers promises unprecedented opportunities to investigate matter at most extreme pressures and temperatures on ultra-short timescales, particularly accessing and resolving non-equilibrium dynamics. Recent experiments at LCLS and SACLA have demonstrated this great potential, but also identify certain technical challenges that need to be addressed for high-precision experiments. This talk will discuss exemplary X-ray diffraction and X-ray scattering results obtained with ultra-intense optical lasers at LCLS and SACLA.
  • Invited lecture (Conferences)
    Workshop on High Intensity Laser Science at the HED instrument at the European XFEL, 05.-06.04.2017, Hamburg, Deutschland

Publ.-Id: 27412 - Permalink


In situ investigation of nanodiamonds formed in shock compressed plastics
Kraus, D.
In situ investigation of nanodiamonds formed in shock compressed plastics
  • Invited lecture (Conferences)
    5th High-Power Laser Workshop, 27.-28.09.2017, Menlo Park, USA

Publ.-Id: 27411 - Permalink


Probing C-H mixtures at conditions relevant to planetary interiors and inertial confinement fusion
Kraus, D.
Carbon-hydrogen (C-H) mixtures at extreme pressure and temperature conditions are highly relevant for the interiors of icy giant planets like Neptune and Uranus where pressures of several Mbar are present in their deep interiors. Moreover, C-H is used as ablator material in contemporary inertial confinement fusion concepts. Here, the ablator material passes various warm dense matter and dense plasma states up to the Gbar regime. Experiments at state-of-the-art facilities allow for insights of unprecedented quality into such extreme states of matter. At the Linac Coherent Light Source (LCLS), we have investigated C-H mixtures at conditions comparable to planetary interiors [1] and the very first compression stages of ICF showing structural transitions and chemical activity applying various X-ray diagnostic techniques in one experiment. In other experiments, performed at the National Ignition Facility and using spectrally resolved X-ray scattering in combination with radiography, we have investigated the ionization balance of warm and hot dense C-H at conditions that comparable to later compression stages of ICF as well the interiors of Brown Dwarfs or small stars. These results indicate that, particularly for mixtures, standard ionization models may require revisions in the regime of warm and hot dense matter [2].

[1] D. Kraus et al., Nature Astronomy 1, 606-611 (2017).
[2] D. Kraus et al., Physical Review E 94, 011202(R) (2016).
  • Invited lecture (Conferences)
    3rd International Conference on Matter and Radiation at Extremes, 06.-11.05.2018, Qingdao, China

Publ.-Id: 27410 - Permalink


Experimental Investigation of Diamond Precipitation inside Giant Planets
Kraus, D.; Vorberger, J.; Pak, A.; Hartley, N. J.; Fletcher, L. B.; Frydrych, S.; Galtier, E.; Gamboa, E. J.; Gericke, D. O.; Glenzer, S. H.; Granados, E.; Macdonald, M. J.; Mackinnon, A. J.; Mcbride, E. E.; Nam, I.; Neumayer, P.; Roth, M.; Saunders, A. M.; Schuster, A. K.; Sun, P.; van Driel, T.; Doeppner, T.; Falcone, R. W.
The effects of hydrocarbon reactions and diamond precipitation on the internal structure and evolution of icy giant planets like Neptune and Uranus have been discussed for more than three decades. Inside these celestial bodies, gravity compresses mixtures of light elements to densities of several grams per cubic centimeter while the temperature reaches thousands of kelvins resulting in thermal energies on the order of chemical bond energies and above. Under these conditions, simple hydrocarbons like methane, which are highly abundant in the atmospheres, are believed to undergo structural transitions that release hydrogen from deeper layers and may lead to compact stratified cores. Indeed, the isentropes of Uranus and Neptune intersect a temperature-pressure regime where first polymerization occurs, whereas in deeper layers, a phase separation into diamond and hydrogen may be possible. Here we show experimental evidence for this phase separation process obtained by in situ X-ray diffraction from polystyrene (C8H8)n samples dynamically compressed to conditions around 150 GPa and 5000 K, which resembles the environment ~10,000 km below the surfaces of Neptune and Uranus [1]. Our findings demonstrate the necessity of high pressures for initiating carbon-hydrogen demixing and imply that diamond precipitation may require ~10x higher pressures than previously suggested by static compression experiments. In addition to their relevance for planetary modelling, by showing the formation of nanodiamonds from laser-irradiated plastic, our results identify a possible method to produce diamond nanoparticles for material science and industrial applications.
  • Invited lecture (Conferences)
    55th European High Pressure Research Group Meeting, 04.-08.09.2017, Poznan, Polen

Publ.-Id: 27409 - Permalink


Dense Plasma Chemistry of Hydrocarbons at Conditions Relevant to Planetary Interiors and ICF
Kraus, D.
Carbon-hydrogen demixing and subsequent diamond precipitation has been predicted to strongly participate in shaping the internal structure and evolution of icy giant planets like Neptune and Uranus. The very same dense plasma chemistry is also a potential concern for CH plastic ablator materials in inertial confinement fusion (ICF) experiments where similar conditions are present during the first compression stage of the imploding capsule. Here, carbon-hydrogen demixing may enhance the hydrodynamic instabilities occurring in the following compression stages. First experiments applying dynamic compression and ultrafast in situ X-ray diffraction at SLAC’s Linac Coherent Light Source demonstrated diamond formation from polystyrene (CH) at 150 GPa and 5000 K [1]. Very recent experiments have now investigated the influence of oxygen, which is highly abundant in icy giant planets on the phase separation process. Compressing PET (C5H4O2) and PMMA (C5H8O2) we find again diamond formation at pressures above ~150 GPa and temperatures of several thousand kelvins, showing no strong effect due to the presence of oxygen. Thus, diamond precipitation deep inside icy giant planets seems very likely. Moreover, small-angle X-ray scattering (SAXS) was added to the platform, which determines an upper limit for the diamond particle size, while the width of the diffraction features provides a lower limit. We find that diamond particles of several nanometers in size are formed on a nanosecond timescale. Finally, spectrally resolved X-ray scattering is used to absolutely scale amorphous diffraction signals and additionally allows for determining the amount of carbon-hydrogen demixing inside the compressed samples even if no crystalline diamond is formed. This whole set of diagnostics provides unprecedented insights into the nanosecond kinetics of dense plasma chemistry.
[1] D. Kraus et al., “Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditions”, to appear in Nature Astronomy (2017)
  • Invited lecture (Conferences)
    APS DPP Meeting, 23.11.2017, Milwaukee, USA

Publ.-Id: 27407 - Permalink


Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditions
Kraus, D.
The effects of hydrocarbon reactions and diamond precipitation on the internal structure and evolution of icy giant planets such as Neptune and Uranus have been discussed for more than three decades. Inside these celestial bodies, simple hydrocarbons such as methane, which are highly abundant in the atmospheres, are believed to undergo structural transitions that release hydrogen from deeper layers and may lead to compact stratified cores. Indeed, from the surface towards the core, the isentropes of Uranus and Neptune intersect a temperature–pressure regime in which methane first transforms into a mixture of hydrocarbon polymers, whereas, in deeper layers, a phase separation into diamond and hydrogen may be possible. Here we show experimental evidence for this phase separation process obtained by in situ X-ray diffraction from polystyrene, PET ant PMMA samples dynamically compressed to conditions around 150 GPa and 5,000 K; these conditions resemble the environment around 10,000 km below the surfaces of Neptune and Uranus. Our findings demonstrate the necessity of high pressures for initiating carbon–hydrogen separation and imply that diamond precipitation may require pressures about ten times as high as previously indicated by static compression experiments. Our results will inform mass–radius relationships of carbon-bearing exoplanets, provide constraints for their internal layer structure and improve evolutionary models of Uranus and Neptune, in which carbon–hydrogen separation could influence the convective heat transport. In addition to their relevance for planetary modelling, by showing the formation of diamonds that are possibly a few nanometers in size from laser-irradiated plastic, our results may identify a new method to produce diamond nanoparticles for material science and industrial applications.

*We acknowledge support by the U.S. DOE under awards DE-FG52-10NA29649 and DE-NA0001859 as well as the Helmholtz Association under award VH-NG-1141.
  • Invited lecture (Conferences)
    APS March Meeting, 05.-09.03.2018, Los Angeles, USA

Publ.-Id: 27406 - Permalink


Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditions
Kraus, D.
High-energy laser systems can be used to mimic extreme states of matter, as found in the interior of various celestial bodies, in the laboratory. Combining such laser systems with extremely bright X-ray sources, particularly X-ray free electron lasers (XFELs), allows for studying exotic physical processes in real-time. This includes high-pressure phase separation reactions, such as diamond precipitation from liquid hydrocarbons, which has been predicted to happen deep inside Neptune and Uranus, and many other interesting phenomena.

At the Linac Coherent Light Source (LCLS), we obtained experimental results from hydrocarbon samples that were laser-compressed to the extreme pressure and temperature conditions found in the deep interiors of such ‘icy’ giant planets [1]. The extreme brightness of the XFEL source enables unprecedented in situ snapshots of the induced chemical reactions and shows that diamond nucleation is initiated on sub-nanosecond timescales at ~150 GPa and ~5000 K. Combining several X-ray and optical diagnostic methods, we obtain high-quality constraints for theoretical models of the involved physical processes: X-ray diffraction records the formation of solid diamond structures, Small angle X-ray scattering determines the size distribution of the growing nanodiamonds while spectrally resolved X-ray scattering provides an absolute scale for the diffraction pattern giving the absolute amount of the reacting material that undergoes species separation. Optical velocimetry is used to characterize and optimize the laser-driven compression waves and optical reflectometry indicates that the isolated hydrogen produced by the phase separation reaction is in a metallic state. All these diagnostics can be used with single-shot quality in the same experiment and provide unprecedented insights into the nanosecond kinetics of chemical reactions at extreme pressures and temperatures.

Besides underlining the general importance of chemical processes inside giant planets, our results
will inform mass-radius relationships of carbon-bearing exoplanets, provide constraints for their internal layer structure and improve evolutionary models of Uranus and Neptune, where carbon-hydrogen separation could significantly influence the convective heat transport. Finally, our experiments may identify a new method to produce diamond nanoparticles for material science and
industrial applications.

[1] D. Kraus et al., Nature Astronomy 1, 606-611 (2017)
  • Invited lecture (Conferences)
    European XFEL Users Meeting, 22.-25.01.2018, Hamburg, Deutschland

Publ.-Id: 27405 - Permalink


A Maximum-Likelihood Timing Resolution Estimation algorithm for TOF-PET
Nikulin, P.ORC; Lougovski, A.; Hofheinz, F.ORC; Maus, J.ORC; van den Hoff, J.ORC
Timing resolution in time-of-flight (TOF) PET is known to be to a different extend count-rate dependent, while using the actual timing resolution during TOF-PET image reconstruction is crucial for achieving high contrast recovery. However, a count-rate dependent TOF-resolution calibration procedure is usually not provided by the vendor. We therefore developed such a procedure which is compatible with clinical routine and is also applicable retrospectively to existing data.

We propose a novel Maximum-Likelihood Timing Resolution Estimation algorithm that maximizes likelihood by updating activity image and TOF-kernel width alternately. For activity update TOF-MLEM was used and quadratic surrogate based maximization of the likelihood was performed to update timing resolution.

The algorithm was integrated into our previously developed reconstruction tool THOR, see ref. (1), and evaluated using the Philips Ingenuity TF PET/MR scanner and phantom and patient studies covering a large range of count-rates. Studies were grouped by imaging protocol ("brain" and "whole-body", covering different transaxial fields of view). Within each group a linear dependency of timing resolution on count-rate was observed which is in correspondence with reports by other groups. The timing resolution degradation value approaches 150 ps (~25% of initial TOF-kernel width) for clinical relevant count-rates. No difference in estimated timing resolution between the study groups was encountered.

Our preliminary results indicate that the proposed algorithm is capable of realistic timing resolution estimation. The timing resolution of the Philips Ingenuity TF PET/MR degrades rapidly with count-rate. This should be accounted for during image reconstruction.

(1) A. Lougovski, F. Hofheinz, J. Maus, et al., Physics in Medicine and Biology 59(3), 561 (2014)
Keywords: PET, MLEM, MLTRE, image reconstruction, TOF-PET, calibration, TOF-resolution
  • Poster
    56. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 18.-21.04.2018, Bremen, Deutschland

Publ.-Id: 27403 - Permalink


Characterization of the cesium sputter ion source for the new Felsenkeller 5 MV underground accelerator
Ludwig, F.; Koppitz, M.; Bemmerer, D.; Zuber, K.
In order to determine the cross section of the ¹²C(α,γ)¹⁶O reaction at astrophysically relevant energies, an accelerator with a stable and intensive ¹²C ion beam in an ultra low background environment is needed. For this purpose a 134-MC-SNICS cesium sputter ion source is going to be part of the Felsenkeller shallow underground accelerator facility. To determine the characteristics of this ion source overground tests were undertaken at HZDR. The contribution will report on long time measurements of the ion current and the beam emittance.
  • Lecture (Conference)
    DPG Frühjahrstagung, 26.02.-02.03.2018, Bochum, Deutschland

Publ.-Id: 27402 - Permalink


Prognostische Relevanz von FDG-PET/CT-basierten Biomarkern bei Kopf-Hals-Tumoren: Total Lesion Glycolysis (TLG) übertrifft klinische Parameter
Weidt, D.; Spanier, G.; Meier, J.; Hofheinz, F.; Reichert, T.; Hellwig, D.; Grosse, J.
Ziel/Aim:
Ziel der retrospektiven Studie war die Evaluation der prognostischen Relevanz der FDG-PET/CT-basierten Biomarker maximaler und mittlerer SUV (SUVmax, SUVmean), metabolisches Tumorvolumen (MTV) und total lesion glycolysis (TLG) im Primarius bei Erstdiagnose eines oralen Plattenepithelkarzinoms (OSSC). Der Einfluss auf das Gesamtüberleben (OS) wurde mit etablierten Prognoseparametern verglichen.

Methodik/Methods:
Einschluss von 127 Patienten mit zwischen 2006 und 2013 bioptisch gesichertem OSCC und präoperativer FDG-PET/CT (3 MBq/kg Körpergewicht, Start 60 min p.i., Biograph 16, Siemens). Messung von SUVmax, SUVmean, MTV (Schwellenwert: 41% SUVmax) und TLG im Primarius mittels ROVER (ABX, Radebeul). Berechnung des OS nach Kaplan-Meier. Analyse prognostischer Parameter mit uni-/multivariater Cox-Regression.

Ergebnisse/Results:
In der Nachbeobachtung starben 52 (41%) der Patienten (Status aller Patienten über mindestens 36 Monate bekannt). Das mediane OS war länger bei geringerem MTV (≤5,3 ml: >95 Monate; >5,3 ml: 59 Monate; p=0,006) oder TLG (≤38,7 g: 95 Monate; >38,7 g: 47 Monate; p<0,001). SUVmax und SUVmean hatten keinen Einfluss auf das OS (p>0,05). Die univariate Cox-Regression identifizierte MTV (Hazard Ratio [HR]=2,260, p=0,005), TLG (HR=2,808, p=0,001), Lymphknoten (LK)-Status (HR=2,234, p=0,005) und UICC-Stadium (HR=2,095, p=0,021) als Prognosefaktoren, nicht jedoch Geschlecht, Alter (>60 J), oder Tabak-/Alkoholabusus. Multivariat erwiesen sich nur MTV (HR=1,991, p=0,019) und TLG (HR=2,808, p=0,001) als unabhängige Prognosefaktoren.

Schlussfolgerungen/Conclusions:
MTV und TLG des Primarius sind Prognosefaktoren für das OS bei Patienten mit Erstdiagnose eines OSCC. TLG ist der stärkste unabhängige Prognosefaktor für das OS und übertrifft etablierte klinische Parameter.
  • Lecture (Conference)
    Jahrestagung der DGN, 19.-21.04.2018, Bremen, Deutschland

Publ.-Id: 27394 - Permalink


Assessment of in vivo PET quantification accuracy using image derived arterial blood SUVs
Maus, J.ORC; Hofheinz, F.; Apostolova, I.; Kreissl, M. C.; Kotzerke, J.; van den Hoff, J.
Aim: Accurate calibration is a prerequisite for SUV quantification in PET and usually performed via phantom measurements. However, such a calibration is only valid for the used phantom since attenuation and scatter correction limitations affect quantification accuracy (QA) in-vivo. In recent studies in-vivo QA was assessed using bladder image vs. urine samples comparisons and showed a systematic underestimate of SUVs when relying on phantom-based calibration. A notable disadvantage of this approach is that it requires additional effort, making it unattractive for clinical use. The goal of this work was evaluation of an alternative method utilizing image-derived arterial blood SUVs (BSUV) averaged over a sufficiently large number of subjects.

Methods: We analyzed 681 patient scans from 3 sites which underwent routine 18F-FDG PET/CT or PET/MR. BSUVs were determined in the descending aorta using a roughly cylindrical ROI (delineated in the attenuation image and spatially transferred to PET). Minimum ROI volume was 5 mL and a safety margin used to avoid partial volume effects. Mean BSUVs, standard deviation (SD), and standard error of the mean (SEM) were computed for subgroups corresponding to 3 scanner calibrations of each site (9 subgroups, n=54–100). Intra- and inter-site variability was computed.

Results: Relative SD (SEM) of BSUV in the subgroups ranged 14.3%–20.7% (2.8%–4.8%). BSUV-differences between intra-site groups were 1.8%–6.4% and mostly (5/6) insignificant. Inter-site BSUV-differences were significant and much larger (12.6%–25.1%, P<0.001).

Conclusions: Due to low inter-site BSUV-variability, group-averages can be computed with high statistical accuracy (<5%) in groups of ~70 patients and used for comparison of relative in-vivo QA. For multi-center trials this method can reveal inter-site differences at the 10% level and might even be used to calibrate image data between sites.
Keywords: PET; quantification; blood SUV; standardization; multicenter; in vivo
Related publications
Monitoring scanner calibration using the image derived… (Id 27358) is supplemented by this publication

Publ.-Id: 27391 - Permalink


An Overview of High Energy Density Sciences in HiBEF Project
Huang, L. G.
This talk will give an overview of high energy density (HED) researches in the frame of Helmholtz International Beamline for Extreme Fields (HiBEF) project leading by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The HiBEF user consortium is aiming to contribute and operate different experimental setups at the HED beamline of the European XFEL with worldwide unique ultrashort and extremely bright X-ray flashes.
Three main kinds of HED experiments including relativistic laser solid targets interactions to understand the plasma heating and ionization dynamics, high energy long pulse laser shocked warm dense matters to understand the stellar structures, intense XFEL-matter interactions to understand the effect of crystal structure on the rapidly melting and heating process performed by our group at LCLS and SACLA will be reviewed in this talk. All these experiments take advantages of the ultra-short and intense coherent XFEL beam as a probe to achieve nanometer and femtosecond resolutions simultaneously. Furthermore, to design and under the HED experiments, we will also present the theoretical and simulation studies based on the particle-in-cell (PIC) code, atomic collisional- radiative code and density function theory (DFT) code.
Keywords: High Energy Density; HiBEF; XFEL; High Power Laser; High Energy Laser.
  • Invited lecture (Conferences)
    The 3rd International symposium series on High Power Laser Science and Engineering, 09.-13.04.2018, Suzhou, China

Publ.-Id: 27388 - Permalink


Activation of acceptor levels in Mn implanted Si by pulsed laser annealing
Li, L.; Bürger, D.; Shalimov, A.; Kovacs, G. J.; Schmidt, H.; Zhou, S.
In this paper, we report the magnetic and electrical properties of Mn implanted nearly intrinsic Si wafers after subsecond thermal treatment. Activation of acceptors is realized in pulsed laser annealing (PLA) films with a free hole concentration of 6.29  ×  10^20 cm−3 while the sample annealed by rapid thermal annealing (RTA) shows n-type conductivity with a much smaller free electron concentration in the order of 10^15 cm−3. Ferromagnetism is probed for all films by a SQUID magnetometer at low temperatures. The formation of ferromagnetic MnSi1.7 nanoparticles which was proven in RTA films can be excluded in Mn implanted Si annealed by PLA.

Downloads:

  • Secondary publication expected from 19.03.2019

Publ.-Id: 27387 - Permalink


Effect of ausforming temperature on creep strength of G91 investigated by means of small punch creep tests
Vivas, J.; Capdevila, C.ORC; Altstadt, E.ORC; Houska, M.; Serrano, M.ORC; De-Castro, D.; San-Martin, D.
The stability of the martensitic microstructure in ferritic/martensitic G91 steel at operating temperatures up to 700 ºC might be improved by means of ausforming thermomechanical treatments. The goal sought is to promote the formation of a high number density of MX nanoprecipitates in the martensitic microstructure obtained after a subsequent tempering. This work is focused on the effect of the ausforming temperature. The results show that the lower the ausforming temperature is the higher is the dislocation density obtained in ausformed fresh martensite and the larger the number density of MX carbonitrides after tempering are. Creep strength, evaluated by Small Punch Creep Tests has allowed us to conclude that the best creep behavior was obtained for the steel ausformed at lower the temperature due to the higher pinning force for dislocation motion triggered by the distribution of MX. The creep results obtained on the ausformed samples were compared with those after the conventional heat treatment, showing that the high density of MX carbonitrides after an ausforming thermomechanical treatment is a promising processing to raise the operation temperature of this steel.
Keywords: Creep resistant steels; carbonitrides precipitation; martensite; tempering; small punch creep tests; ausforming

Downloads:

  • Secondary publication expected from 01.06.2019

Publ.-Id: 27384 - Permalink


Importance of austenitization temperature and ausforming on creep strength in 9Cr ferritic/martensitic steel
Vivas, J.; Capdevila, C.ORC; Altstadt, E.ORC; Houska, M.; San-Martin, D.
Small Punch Creep technique was used as a screening procedure to evaluate the creep properties of different microstructures developed in a thermomechanical simulator. The goal seek was to generate alternative microstructures in a conventional ferritic-martensitic G91 steel grade which boost thermal stability at temperatures as high as 700ºC. The developed microstructures allow studying the effect of the austenitization temperature optimized by thermodynamic calculations and the ausforming on the creep strength and ductility. The improvement in creep strength recorded was attributable to a higher number density of MX precipitates. By contrast, these microstructures showed an important reduction in creep ductility.
Keywords: Small Punch Creep Tests; MX nanoprecipitates; creep ductility; ausforming; creep resistant steels

Downloads:

  • Secondary publication expected from 01.05.2019

Publ.-Id: 27383 - Permalink


The multi-purpose electron accelerator ELBE and its applications, with a focus on THz spectroscopy
Helm, M.
I will introduce the superconducting electron accelerator ELBE (Electron Linear accelerator with high Brilliance and low Emittance) as a source for different types of secondary radiation, including low- (meV) and high- (MeV) energy photons, positrons and neutrons. Being a solid-state spectroscopist, I will then focus on research we have performed using the terahertz free-electron laser FELBE. Here the high peak power can be employed for nonlinear optical experiments in the THz range, whereas the picosecond pulse structure enables time-resolved studies of relaxation processes.
Keywords: electron accelerator, free electron laser, THz spectroscpy
  • Lecture (others)
    Kolloquium am Max-Planck-Institut für Plasmaphysik (IPP), 19.04.2018, Munich, Germany

Publ.-Id: 27382 - Permalink


Agile Software Development using GitLab and GitLab CI
Juckeland, G.ORC; Frust, T.ORC
This talk presents how the GitLab Community Edition installation at HZDR is used to map components of agile programming and also motivates why most scientific programming is agile.
  • Lecture (Conference)
    SEI-Tagung 2018, 16.-18.04.2018, Dresden, Deutschland

Publ.-Id: 27373 - Permalink


Superior electrical conduction of a water repelling 3D interconnected nano-network
Dhal, S.; Das, P.; Rajbhar, M. K.; Chatterjee, S.; Möller, W.; Chatterjee, S.; Ramgir, N.
A three-dimensional (3D) network of interconnected nanowires of functional materials possesses huge potential for device fabrication since it hinders sluggish interfacial charge carrier transport owing to reduced contact resistance. In the present work, the formation of a highly porous 3D interconnected nano-network by Na+ ion irradiation is demonstrated. The mechanism of solid junction formation at very low energy is established using the results obtained from TRI3DYN computer simulation studies. The formation of a 3D interconnected network resulted in a significant improvement in the electrical conduction as compared to that observed for the pristine nanotube mesh. Further, contact angle measurement shows a transition from "superhydrophilic" nature, as observed for pristine nanotubes, to "superhydrophobic" nature for the 3D nano-network. The superhydrophobicity of the 3D nano-network is expected to find application in miniaturized electronic devices, wherein water condensation and related effects such as short-circuits and erroneous signal output can be significantly minimized.

Publ.-Id: 27370 - Permalink


Nanofabrication activities at HZDR
Georgiev, Y. M.ORC
During this talk I will first briefly introduce the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the Institute of Ion Beam Physics and Materials Research as well as the Ion Beam Centre as a user facility run by the Institute.

Next, I will present some of the equipment available at the nanofabrication facility in Rossendorf (NanoFaRo), in particular electron beam lithography (EBL) systems as well as tools for thin film deposition and reactive ion etching (RIE), paying special attention on their capabilities.

I will then go through the most important nanofabrication projects, both internal and external, run lately at NanoFaRo, including top-down fabrication and electrical characterisation of silicon (Si) nanowire (NW) reconfigurable field effect transistors (RFETs) together with detailed study of nickel (Ni) silicidation of Si NWs; top-down fabrication of a large number of gratings with different periodicity on 2 µm thick Si membranes for laser targets; electrical contacting of randomly distributed nanostructures (bottom-up grown VO2 and hyperdoped Si NWs, DNA origami, flakes of 2D materials, etc.); top-down fabrication of four-terminal Si NW test devices for modulation doping experiments; nanopatterning of polymer brushes by reactive writing with EBL; bevel formation by EBL and RIE for dopant/conductance profiling of thin films and NWs by conductive atomic force microscopy (C-AFM); top-down fabrication of Si NWs hyperdoped with selenium (Se) as well as of plasmonic antennas on Si hyperdoped with tellurium (Te); fabrication and electrical characterisation of FETs on 2D materials, etc. Concluding this part of my talk, I will draw your attention to some highlights of our activities, focussing mostly on processes for high-resolution patterning as well as on high-precision electrical contacting of randomly distributed nanostructures.

Finally, I will discuss possibilities for collaboration between HZDR and UCC/Tyndall in the field of our activities.
Keywords: nanofabrication, electron beam lithography, reactive ion etching, silicon nanowires, reconfigurable field effect transistors, nickel silicidation, silicon gratings, silicon membranes, laser targets, DNA origami, 2D materials, conductive atomic force microscopy, hyper doped silicon nanowires, plasmonic antennas
  • Lecture (others)
    Seminar of the School of Chemistry, University College Cork, 22.03.2018, Cork, Ireland

Publ.-Id: 27368 - Permalink


Group IV Semiconductor Nanowires for Sensing and Nanoelectronic Applications
Georgiev, Y. M.ORC
During the last decade, semiconductor nanowires (NWs) have received significant academic and commercial attention due to their attractive electrical and mechanical properties and large surface area to volume ratios. They have a variety of possible applications including nanoelectronics, nanophotonics, photovoltaics, sensorics, etc. Among all semiconductor NWs the ones based on group IV materials have the added value of being the most silicon (Si) compatible. This would allow their relatively easy integration into the existing semiconductor technology platform.

In my talk I will first present the NWs that we are working with. These include top-down fabricated Si and germanium (Ge) NWs having widths down to 6-7 nm as well as bottom-up grown alloyed germanium-tin (Ge1-xSnx) NWs with x = 0.07-0.1, diameters of 50-70 nm and lengths of 1 to 3 µm. In the future we plan to work also with alloyed SiGe and SiGeSn NWs with varying content of the different materials.

I will next discuss the innovative devices that we are targeting, namely junctionless nanowire transistors (JNTs) and reconfigurable field effect transistors (RFETs). In particular, we are interested in Si JNTs for sensing application as well as in Ge and GeSn JNTs for digital logic. Concerning RFETs, we are currently working on Si RFETs and commencing activities on Ge RFETs. In the future we are planning to work also on GeSn RFETs.

Finally, I will pay a special attention to a novel device that we recently invented: group IV heterostructure band-to-band tunnel FET (TFET). We are planning to fabricate this device with a scalable and fully CMOS compatible process and expect it to demonstrate high Ion together with low Ioff and hence steep subthreshold slopes.
Keywords: semiconductor nanowires, nanoelectronics, silicon, germanium, germanium-tin, junctionless nanowire transistors, reconfigurable field effect transistors, heterostructure band-to-band tunnel field effect transistors
  • Lecture (others)
    Science Meets Industry, 08.03.2018, Dresden, Germany

Publ.-Id: 27367 - Permalink


Formation of a new type of {U38} cluster based on a controlled release of water via esterification reaction
Martin, N. P.ORC; Volkringer, C.ORC; Henry, N.; Trivelli, X.; Stoclet, G.; Ikeda-Ohno, A.ORC; Loiseau, T.ORC
A new strategy for the synthesis of large poly-oxo cluster bearing 38 tetravalent uranium atoms {U38} has been developed by controlling the water release from the esterification reaction between carboxylic acid and alcohol. The molecular entity [U38O56Cl40(H2O)2(ipa)20]·(ipa)x (ipa = isopropanol) was crystallized from the solvothermal reaction of the mixture of UCl4 and benzoic acid in isopropanol at temperature ranging from 70 to 130°C. Its crystal structure reveals the molecular assembly of the UO2 fluorite-like inner core {U14} with oxo groups bridging the uranium centers. The {U14} core is further surrounded by six tetrameric sub-units of {U4} to form the {U38} cluster. Its surface is decorated by either bridging- and terminal chloride anions or terminal isopropanol molecules. Another synthesis using the same reactant mixture at a room temperature resulted in the crystallization of discrete dinuclear complex [U2Cl4(bz)4(ipa)4] (bz = benzoate), in which each uranium center is coordinated by two chlorine atoms, four oxygen atoms from carboxylate groups and two additional oxygen atoms from isopropanol. The slow production of water released from the esterification of isopropanol allows the formation of the giant cluster with oxo bridges linking the uranium atoms at a temperature above 70°C, whereas no such oxo groups are present in the dinuclear complex formed at a room temperature. The kinetic of {U38} crystallization as well as the ester formation are analyzed and discussed. SAXS experiments indicate that the {U38} species are not dominant in the supernatant, but hexanuclear entities which are closely related to the [U6O8] type are formed.
Keywords: Actinides, uranium, cluster, polymer, coordination, solid-state chemistry, structure characterisation, solution speciation

Publ.-Id: 27366 - Permalink


Bentonite – a natural source for sulfate-reducing bacteria
Matschiavelli, N.; Kluge, S.; Cherkouk, A.
In order to analyze the potential influence of natural occuring microorganisms within the bentonite on the properties of the bentonite barrier, we set up microcosm-experiments. Two different Bavarian bentonites (a natural and an industrial one) were supplied with an anaerobic, synthetic Opalinus-clay pore water solution under an N2/CO2-atmosphere and were incubated for one year at 30 °C and 60 °C. To some set ups organics (acetate or lactate) or H2 were supplemented. During the incubation time samples were analyzed for several biogeochemical parameters and the evolution of microbial community.
Our results clearly demonstrate, that natural occuring microbes affect geochemical parameters. Set ups containing the industrial bentonite supplemented with lactate or H2 show the most striking effects. The respective batches were dominated (up to 81 %) by Desulfosporosinus spp. after 6 months – spore-forming, strictly anaerobic, sulfate-reducing organisms, able to survive under very harsh conditions. Concomitantly, an increase of ferrous iron and a simoultaneous decrease of ferric iron was observed as well as a decrease in sulfate – alterations that could effect different properties of and reactions within the barrier system of an HLW.
Keywords: Bentonite, sulfate-reduction, Desulfosporosinus spp.
  • Lecture (Conference)
    MIND-Project Annual Meeting 2018, 07.-09.05.2018, Lausanne, Switzerland

Publ.-Id: 27362 - Permalink


Shibboleth-Authenticator for Invenio
Frust, T.ORC

The shibboleth-authenticator module for Invenio provides web browser single sign-on via the SAML protocol. It is based on the python3-saml module and supports the usage of multiple identity providers at the same time.


Related publications
Invenio Shibboleth-Authenticator (Id 26045) is identical to this publication
  • Software in the HZDR data repository RODARE
    Publication date: 2018-04-18
    DOI: 10.14278/rodare.13
    License: GPL-3.0

Downloads:

Publ.-Id: 27360 - Permalink


Monitoring scanner calibration using the image derived arterial blood SUV in whole-body FDG-PET
Maus, J.ORC; Hofheinz, F.; Apostolova, I.; Kreissl, M. C.; Kotzerke, J.; van den Hoff, J.
Background:
The current de facto standard for quantification of tumor metabolism in oncological whole-body PET is the standardized uptake value (SUV) approach. SUV determination requires accurate scanner calibration. Residual inaccuracies of the calibration lead to biased SUV values. Especially, this can adversely affect multicenter trials where it is difficult to ensure reliable cross-calibration across participating sites. The goal of the present work was the evaluation of a new method for monitoring scanner calibration utilizing the image-derived arterial blood SUV (BSUV) averaged over a sufficiently large number of whole-body FDG-PET investigations.

Data of 681 patients from three sites which underwent routine 18F-FDG PET/CT or PET/MR were retrospectively analyzed. BSUV was determined in the descending aorta using a three-dimensional ROI concentric to the aorta’s centerline. The ROI was delineated in the CT or MRI images and transferred to the PET images. A minimum ROI volume of 5 mL and a concentric safety margin to the aortic wall was observed. Mean BSUV, standard deviation (SD), and standard error of the mean (SE) were computed for three groups of patients at each site, investigated 2 years apart, respectively, with group sizes between 53 and 100 patients. Differences of mean BSUV between the individual groups and sites were determined.

Results: SD (SE) of BSUV in the different groups ranged from 14.3 to 20.7% (1.7 to 2.8%). Differences of mean BSUV between intra-site groups were small (1.1–6.3%). Only one out of nine of these differences reached statistical significance. Inter-site differences were distinctly larger (12.6–25.1%) and highly significant (P<0.001).

Conclusions: Image-based determination of the group-averaged blood SUV in modestly large groups of whole-body FDG-PET investigations is a viable approach for ensuring consistent scanner calibration over time and across different sites. We propose this approach as a quality control and cross-calibration tool augmenting established phantom-based procedures.
Keywords: PET; Quantification; Blood SUV; Standardization; Multicenter; In vivo
Related publications
Assessment of in vivo PET quantification accuracy using… (Id 27391) is a supplement to this publication

Publ.-Id: 27358 - Permalink


Massive Parallel Computing on GPU Architectures
Frust, T.ORC
Graphics processing units (GPU) have evolved to massively parallel processors for general-purpose computing during the last couple of years. They are now available in small and energy-efficient embedded systems, too. This talk gives a brief overview about GPU computing and introduces the NVIDIA Jetson platform as an example for a GPU powered embedded system.
Keywords: GPU; Embedded systems; Parallel computing
  • Lecture (others)
    TOMOCON Kick-Off Meeting, 18.04.2018, Technische Universtität Dresden, Deutschland

Publ.-Id: 27357 - Permalink


Research Data Management
Frust, T.ORC
The importance of research data and research data management (RDM) in the research lifecycle is growing. This talk provides an overview about data management in research projects. The goal is to make research data FAIR (Findable, Accessible, Interoperable and Retrievable) by starting early with a Data Management Plan (DMP) and making research data available in appropriate data repositories.
Keywords: Data Management; Data Management Plan; FAIR; RODARE; Zenodo
  • Lecture (others)
    TOMOCON Kick-Off Meeting, 18.04.2018, Technische Universität Dresden, Deutschland

Publ.-Id: 27356 - Permalink


Liquid metal batteries - activities at the Helmholtz-Zentrum Dresden - Rossendorf
Weier, T.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Stefani, F.; Weber, N.
The talk will provide an overview of the liquid metal battery (LMB) related activities at Helmholtz-Zentrum Dresden - Rossendorf (HZDR) with a focus on magnetohydrodynamic aspects of future large scale LMBs. High current densities in the range of 4 up to 130 kA/m-2, as typical for LMBs, together with cells of large cross section will result in substantial currents accompanied by considerable magnetic fields. Thus electromagnetically driven flows and instabilities should be of concern for large enough installations, especially when the thin electrolyte layers necessitated by the limited open circuit voltages are taken into account. Beneficial effects of mild electromagnetically driven flows are to be expected for the cathodes were mixing should improve cell performance.
Keywords: liquid metal batteries, magnetohydrodynamics, Tayler instability, sloshing
  • Lecture (others)
    Seminar, 12.04.2018, Cambridge, United Kingdom

Publ.-Id: 27354 - Permalink


Liquid metal batteries - stationary storage for fluctuating renewable energy sources
Weier, T.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Stefani, F.; Weber, N.
Liquid metal batteries are introduced as a potential means to future economic large-scale electricity storage indispensable for energy systems with high penetration of fluctuating sources. The talk will concentrate on the role of electrodynamics and fluid mechanics in the design of large single cells, discussing a few instability mechanisms that should be taken into account.
Keywords: liquid metal batteries, magnetohydrodynamics, instabilities
  • Invited lecture (Conferences)
    Battery Application and Energy Storage, 11.04.2018, London, United Kingdom

Publ.-Id: 27353 - Permalink


Layer-by-Layer assembly of heparin and peptide-polyethylene glycol conjugates to form hybrid nanothin films of biomatrices
Thomas, A. K.; Wieduwild, R.; Zimmermann, R.; Lin, W.; Friedrichs, J.; Bickle, M.; Fahmy, K.; Werner, C.; Zhang, Y.
We investigated the utility of a heparin/peptide-polyethylene glycol conjugate system to build Layer-by-Layer (LbL) structures, to assemble tailored multilayer-biomatrices for cell culture. The LbL assembly balances the advantages of polyelectrolyte systems and protein-based systems. Human umbilical vein endothelial cells showed distinct responses to: the film thickness and structure; the presence, density and spatial arrangement of a cell adhesion ligand within the nanothin film; and the pretreatment of the film with morphogens. The LbL technique presents a versatile tool for modifying cell culture substrates with defined and diverse biochemical and structural features, for investigating cell-material interactions.
Keywords: extracellular matrix, layer-by-layer, nano thin, heparin, biomimetic, Fourier transform infrared

Publ.-Id: 27352 - Permalink


Influence of thin film morphology and stacking sequence on Ni-catalyzed graphitization of thin amorphous carbon films
Janke, D.; Wenisch, R.; Munnik, F.; Julin, J.; Hübner, R.; Gemming, S.; Rafaja, D.; Krause, M.
Metal-induced crystallization with layer exchange (MIC w LE) reduces the crystallization temperature of group 14 elements significantly. This is especially interesting for device fabrication on substrates with limited thermal stability. In this contribution, MIC w LE is applied on Ni and C thin film stacks with different stacking sequences. The influence of the thin film morphology and stacking on the layer exchange degree αLE and the graphitic ordering is studied comprehensively in situ and ex situ.
During annealing of the thin films at up to 700 °C, film morphology and stacking sequence had a significant impact on αLE, showing an incomplete LE for the C/Ni stack. The highest αLE of 96%, determined by RBS and ERDA, was achieved for the smoothest samples and Ni/C stacking sequence. Raman spectroscopy and TEM demonstrated the formation of 2D crystalline carbon structures independently of the stacking sequence, while the degree of graphitic ordering increased with decreasing surface roughness. The simultaneous occurrence of LE and graphitization has been demonstrated in situ by RBS and Raman, giving insights into mechanism responsible for carbon crystallization in this system.
Keywords: metal-induced crystallization, layer exchange, amorphous carbon, Rutherford backscattering spectrometry, Raman spectroscopy, elastic recoil detection
  • Poster
    International Winterschool on Electronic Properties of Novel Materials, 17.-24.03.2018, Kirchberg in Tirol, Österreich

Publ.-Id: 27337 - Permalink


Data set to illustrate advanced process-synchronized computed tomography for the investigation of periodic processes
Bieberle, A.; Neumann, M.

This data set contains raw data and data read-in routines used for the publication:
"Advanced process-synchronized computed tomography for the investigation of periodic processes"

Object of investigation: A centrifugal pump that impeller rotates at 1480 rpm and that is operated in gas-liquid two phase flow.
Used CT imaging system: HireCT (high resolution gamma-ray computed tomography) scanner of the HZDR

Keywords: Tomographic imaging, synchronized data acquisition, multiphase flow, centrifugal pump
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-04-12
    DOI: 10.14278/rodare.7
    License: CC-BY-4.0

Downloads:

Publ.-Id: 27335 - Permalink


Fabrication of Y128-and Y36-cut lithium niobate single-crystalline thin films by crystal-ion-slicing technique
Shuai, Y.; Gong, C.; Bai, X.; Wu, C.; Luo, W.; Böttger, R.; Zhou, S.; Tian, B.; Zhang, W.
Y128- and Y36-cut single-crystalline lithium niobate (LN) thin films are fabricated by the crystal-ion-slicing (CIS) technique onto LN substrates. The conditions for the successful exfoliation of submicron-thick LN thin films are independent of the wafer orientation used in the present work. Wafer bonding using benzocyclobutene (BCB) is adopted to transfer LN thin films onto substrates, instead of the generally used hydrophilic bonding, which does not need a strict surface polishing process before the bonding. A noncontact polishing method involving low-energy Ar+ irradiation is adopted to treat the sliced LN thin films. The atomic force microscopy result shows that the surface roughness of the LN thin film is reduced from 10.6 to 6.4nm.
Keywords: Lithium niobate, Crystal-ion-slicing, ion implantation

Publ.-Id: 27334 - Permalink


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