Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34118 Publications

Compact, high-yield incoherent and coherent X-ray sources by Traveling-Wave Thomson-Scattering

Steiniger, K.; Loeser, M.; Albach, D.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.; Debus, A.

In Traveling-Wave Thomson-Scattering pulse-front tilted, petawatt class laser pulses are scattered off relativistic electrons to realize compact optical free-electron lasers or brilliant incoherent X-ray sources with state-of-the-art electron accelerators and high-power laser systems. Example setups of TWTS OFELs providing ultraviolet radiation are presented together with an optical setup to compensate laser dispersion.

  • Invited lecture (Conferences)
    Visions on Future Laser-based X-ray Science and Technology, 19.-20.11.2018, Castelldefels, Spain

Publ.-Id: 28239

Irradiation tests at HZDR

Müller, S. E.; Ferrari, A.

Irradiation tests at HZDR in the framework of the MUSE project are presented

  • Lecture (Conference)
    MUSE meeting, 22.10.2018, Fermilab, USA

Publ.-Id: 28238

FLUKA simulations for the Mu2e experiment

Müller, S. E.; Ferrari, A.

FLUKA simulations for the Mu2e experiment are presented

  • Lecture (Conference)
    MU2E collaboration meeting, 18.10.2018, 18.10.2018, Fermilab, USA

Publ.-Id: 28237

Laser-driven plasma pinching in e−e+ cascade

Efimenko, E. S.; Bashinov, A. V.; Gonoskov, A. A.; Bastrakov, S. I.; Muraviev, A. A.; Meyerov, I. B.; Kim, A. V.; Sergeev, A. M.

The cascaded production and dynamics of electron-positron plasma in ultimately focused laser fields of extreme intensity are studied by 3D particle-in-cell simulations with the account for the relevant processes of quantum electrodynamics (QED). We show that, if the laser facility provides a total power above 20 PW, it is possible to trigger not only a QED cascade but also pinching in the produced electron-positron plasma. The plasma self-compression in this case leads to an abrupt rise of the peak density and magnetic (electric) field up to at least 10^28 cm^−3 and 1/20 (1/40) of the Schwinger field, respectively. Determining the actual limits and physics of this process might require quantum treatment beyond the used standard semiclassical approach. The proposed setup can thus provide extreme conditions for probing and exploring fundamental physics of the matter and vacuum.

Publ.-Id: 28236

Unconventional trace elements in sphalerite – Clues to fluid origin?

Frenzel, M.; Slattery, A.; Wade, B.; Gilbert, S.; Ciobanu, C. C.; Cook, N. J.; Voudouris, P.

It is well known that the trace element content of sphalerite correlates with the conditions of ore formation (T, fS2). However, the suite of trace elements analysed in geological studies is generally restricted to the chalcophile and siderophile elements (Ag, As, Cd, Co, Fe, Ga, Ge, In, Mn, Sb, Se etc.). This may limit the inferences that can be made about the chemistry of the ore-forming fluids.

We used an integrated analytical approach consisting of electron probe micro-analysis, laser-ablationinductively coupled plasma-mass spectrometry, scanning electron microscopy and transmission electron microscopy to investigate the incorporation of the halogens Cl and Br, as well as the alkali metals Na and K into natural sphalerite from a range of deposits. This allowed us to study element distribution at length scales from >1 mm down to ~1 nm.

We found that Cl, Br, Na and K occur in measurable concentrations (100s to 1000s of ppm) in samples from several deposits. Chlorine occurs as either atomic substitutions in the sphalerite lattice or as a mixture of substitution and nano-inclusions. Unfortunately, analytical limitations mean that an investigation of the nanoscale distribution of Br, Na and K was not possible. However, concentrations of these elements (determined by LA-ICP-MS) correlate with Cl concentrations suggesting that they may be present together
with Cl in the sphalerite lattice.

The levels of trace elements present as atomic substitutions are generally related to the chemistry of the oreforming fluids. Therefore, our findings raise the possibility to measure Cl concentrations as well as Cl/Br ratios in natural sphalerite, and use these measurements to constrain fluid salinity and origin. However, more work will be required to constrain the relevant thermodynamic relationships and improve the detection limits of Cl and Br before such measurements can become a standard tool in economic geology.

  • Lecture (Conference)
    SEG 2018 conference, Keystone, 24.09.2018, Keystone, Colorado, United States of America

Publ.-Id: 28235

Criticality - What makes a raw material critical?

Frenzel, M.; Kullik, J.; Reuter, M. A.; Gutzmer, J.

A key to the current debate on the supply security of mineral raw materials is the concept of 'criticality'. This presentation provides a brief review of the criticality concept, as well as the methodologies used in its assessment, including a critical evaluation of their validity. Furthermore, it discusses several risks present in global raw materials markets that are not captured by most criticality assessments. The key result is that current assessments of raw material criticality are fundamentally flawed in several ways. This is mostly due to a lack of adherence to risk theory, and highly limits their applicability. Many of the raw materials generally identified as critical may not be critical, meaning that new assessments are urgently required.

While these are important results for policy makers, it is not necessarily clear what their implications are for geoscientific research on critical element deposits, the topic of this session. Therefore, this question will briefly be explored in the second part of the presentation.

  • Invited lecture (Conferences)
    GeoBonn, 05.09.2018, Bonn, Deutschland

Publ.-Id: 28233

Investigation of 18F-labelled pyrazolo[2,3-d]pyrimidines for molecular imaging of the adenosine A2A receptor with positron emission tomography (PET)

Lai, T. H.; Moldovan, R.-P.; Brust, P.

Objectives: The adenosine A2A receptor (A2AR) is a promising target for the development of PET radiotracers for molecular imaging of neurodegenerative diseases and cancer. Based on binding-affinities the 4 and 2-fluorobenzyl derivatives 1 (Ki(hA2A) = 5.3 nM) and 2 (Ki(hA2A) = 2.1 nM) were chosen for radiofluorination. Methods: Three different strategies for the synthesis of [18F]1 have been investigated. The first two are using [18F]fluorobenzaldehyde, which was applied either in a reductive amination or in a reduction followed by an Appel and benzylation reaction. The third strategy is based on a one-step radiolabelling starting from a boronic acid pinacol ester precursor employing [18F]TBAF and Cu(OTf)2(py)4 in n-BuOH/DMA. The specific binding of [18F]1 and [18F]2 on mice brain slices was evaluated by in vitro autoradiography. Results: The two- and four-step labelling strategies resulted in a radiochemical yield (RCY) of only 1.4% or 10% [18F]1 (non-isolated). Thus, [18F]1 and [18F]2 were prepared by a one-step procedure with a RCY of 52+7 or 9+1% (EOB), a molar activity of 135+64 or 132 GBq/µmol (EOS) and a radiochemical purity of >98%. In vitro autoradiography performed with [18F]2 demonstrated high binding to the striatum, a brain region with high density of A2AR, which could be blocked by selective A2A ligands. Conclusions: An efficient copper-mediated one-step radiolabelling procedure was established for two new highly affine A2A radiotracers. The first in vitro study with [18F]2 demonstrated excellent potential for the imaging of adenosine A2AR. Current work focuses on further in vitro and in vivo investigations.

Keywords: adenosine A2A; PET; radiotracer; 18F

  • Poster
    15th Research Festival Leipzig 2019, 18.01.2019, Leipzig, Deutschland

Publ.-Id: 28232

The geometallurgical assessment of by-products - Geochemical proxies for the complex mineralogical deportment of indium at Neves-Corvo, Portugal

Frenzel, M.; Bachmann, K.; Carvalho, J. R. S.; Relvas, J. M. R. S.; Pacheco, N.; Gutzmer, J.

Many by-productmetals are classified as critical.However, they are only ofmarginal interest tomanymining companies and are rarely part of detailed resource statements or geometallurgical assessments. As a result, there is a general lack of reliable quantitative data on the mineralogy and spatial distribution of these metals in ore deposits—hampering assessments of future availability.We propose here an innovative approach to integrate by-product metals into geometallurgical assessments. As an example, we use the distribution and deportment of indium at Neves-Corvo, a major European base-metal mine (Cu + Zn), and one of the largest and richest volcanichosted massive sulfide (VHMS) deposits in the world. Based on a combination of bulk-ore geochemistry and mineralogical and microanalytical data, this study is the first to develop a quantitativemodel of indium deportment inmassive sulfide ores, demonstrating how regularities in indium partitioning between different minerals can be used to predict its mineralogical deportment in individual drill-core samples. Bulk-ore assays of As, Cu, Fe, Pb, S, Sb, Sn, Zn, and In are found to be sufficient for reasonably accurate predictions. The movement of indium through the ore processing plants is fully explained by its mineralogical deportment, allowing for specific mine and process planning. The novel methodologies implemented in this contribution for (1) the assessment of analytical uncertainties, (2) the prediction of complex mineralogical deportments from bulk geochemical data, and (3) the modeling of byproduct recoveries from individual mining blocks, are of general applicability to the geometallurgical assessment of many other byproduct metals in polymetallic sulfide ores, including Ga, Ge, Mo, Re, Se, Te, as well as the noble metals.

Keywords: Geometallurgy; By-products; Trace elements; Automated mineralogy; Mineral balances; VMS deposits; VHMS deposits


Publ.-Id: 28231

Simulation-based exergy, thermo-economic and environmental footprint analysis of primary copper production

Abadías Llamas, A.; Reuter, M. A.; Valero Capilla, A.; Torres Cuadra, C.; Peltomäki, M.; Stelter, M.; Valero Delgado, A.; Roine, A.; Hultgren, M.

The transition from a Linear to Circular Economy has become a societal challenge to be tackled. However, the increasing complexity of materials and products increases also the sophistication of the circular economy systems required to deal with them. These systems are very resource consuming, therefore, a rigorous evaluation of the impact of every “actor” in circular economy must be done at design and operation stages to ensure the sustainability of the metal-production value chain.

A circular economy system implies, among others, low consumption of energy and material resources and low production of wastes or pollutant emissions. Its sustainability cannot therefore be evaluated just with one indicator. In this paper, we integrate indicators such as recovery rates, environmental impact indicators, as well as the quantities and qualities of the flows, losses and emissions, quantified through exergy. These must all be considered and evaluated simultaneously to perform a rigorous sustainability analysis.

The challenges of achieving a circular processing system and society are illustrated using a unique copper flowsheet that covers the complete processing chain from ore to refined metal including among others minor elements refining, scrap recycling, residue processing, steam utilization, sulphur capture and power generation in 129 unit operations linked by 289 streams and all the compositional and thermochemical detail. Using a simulation-based approach, two scenarios have been studied and compared: (i) a representative primary copper flowsheet and (ii) excluding all waste treatment processes. This unique simulated flowsheet permits a complete evaluation of various scenarios of all copper related processing options (while any additional unit operations can also be added) and also rigorously permits an allocation of impacts of all flows, products, residues etc. as a function of the complete mineral composition.

This approach to evaluating systems shows how to estimate the true losses from a system and will be a key approach to evaluate the true circularity of the circular economy system.

Keywords: Circular economy; Metallurgical process simulation; Thermoeconomics; Exergy; Copper production; Life Cycle Assessment (LCA); System design

Publ.-Id: 28230

Application of Layered Double Hydroxides for 99Tc remediation

Daniels, N.; Franzen, C.; Kvashnina, K.; Petrov, V.; Torapava, N.; Bukaemskiy, A.; Kowalski, P.; Hölzer, A.; Walther, C.

The present study investigates possible use of Layered Double Hydroxides (LDH) for Tc(VII) remediation. Mg/Al- and Mg/Fe-LDH were obtained by a hydrothermal route and thermally activated at 450°C, which was shown to significantly improve the Tc(VII) removal efficiency. Based on XRD investigation of Tc-LDH phases, the Tc(VII) uptake follows the restoring of an LDH structure. X-ray absorption spectroscopy demonstrates that Tc ions interact solely via the Tc-O bond, leaving no evidences of farther atomic interactions with, e.g., layers of LDH. The presence of competing anions, like NO3-, or CO32- in the solution decreases Tc(VII) uptake by LDH. Presently investigated thermally activated Mg0.67/Al0.33-LDH revealed a maximum uptake capacity of up to 1.27 mol/kg (or 20 wt.%), which is higher than that of the Mg0.75/Fe0.25-LDH (0.9 mol/kg). In agreement with these findings, theoretical simulations predicted incorporation energies for Mg0.67/Al0.33-LDH and Mg0.75/Fe0.25-LDH of -128 kJ/mol and -110 kJ/mol, respectively. Investigation of Tc-LDH in different leaching media demonstrated a rather high Tc(VII) stability in LDH in contact with diluted solutions containing Cl- and OH-, however, in a high saline solution, like Q-brine a rather fast release of TcO4- occurs due to anionic exchange with Cl-.

Keywords: Technetium; Layered Double Hydroxides; uptake; disposal


  • Secondary publication expected

Publ.-Id: 28229

Developments in the estimation of tensile strength by small punch testing

Holmström, S.; Simonovski, I.; Baraldi, D.; Bruchhausen, M.; Altstadt, E.; Delville, R.

The Small Punch (SP) test is a relatively simple test well suited for material ranking and material property estimation in situations where standard testing is not possible or considered too material consuming. The material tensile properties, e.g. the ultimate tensile strength (Rm) and proof strength (Rp02) are usually linearly correlated to the force-deflection behaviour of a SP test. However, if the test samples and test set-up dimensions are not according to standardized dimensions or the material ductility does not allow the SP sample to deform to the pre-defined displacements used in these correlations, the standard formulations can naturally not be used. Also, in cases where no supporting Rm data is available the applied correlation factors cannot be verified. In this paper a formulation is proposed that enables the estimation of Rm without supporting uniaxial tensile strength data for a range of materials, both for the soon to be standardized flat samples as well as for curved (tube section) samples. The proposed equations are based on the classical and recent SP and Small Punch Creep (SPC) formulations. It is claimed that the both equivalent stress in small punch creep and tensile strength can be robustly estimated with the same type of equations at least for ductile and semi-ductile ferritic/martensitic and austenitic steels. It is also shown that the same equations can be applied on non-standard test samples and test set-ups. The tensile strength of semi-ductile materials such as 46% cold worked 15-15Ti cladding steel tubes are successfully estimated by correcting the correlations for the curvature of the samples. The usability of the SP testing and assessment method for estimating tensile strength of engineering steels in general and for nuclear claddings in specific has been verified.

Keywords: small punch testing; tensile strength; models; fuel claddings

Publ.-Id: 28228

Dancing performance of organic droplets in aqueous surfactant solutions

Cejkova, J.; Schwarzenberger, K.; Eckert, K.; Tanaka, S.

Droplet systems remain the subject of a constant fascination in science and technology. Here we focus on organic droplets floating on the surface of aqueous surfactant solutions. These droplets can exhibit intriguing interactions. Recently we have found independently in two laboratories that we can observe almost the same complex collective behaviour in two different droplet systems. The aim of this paper is to compare both droplets systems, present their differences and show their similar oscillatory behaviour. The first system consists of decanol droplets floating on sodium decanoate solution. In the second one, the droplets consist of a mixture of ethyl salicylate and liquid paraffin and they are placed on the surface of aqueous sodium dodecyl sulphate solution. Although the mechanism of these spatio-temporal interactions of droplets is not fully understood yet, we believe that this behaviour is based on the same phenomena.

Publ.-Id: 28227

Materials research in high magnetic fields

Wosnitza, J.

  • Invited lecture (Conferences)
    12th Annual Matsurf Seminar, 05.11.2018, Turku, Finnland

Publ.-Id: 28226

FFLO states in organic superconductors − Modulated order parameter

Wosnitza, J.

  • Invited lecture (Conferences)
    Workshop on “Emergent Phenomena in Strongly Correlated Quantum Matter”, 26.-31.08.2018, Natal, Brasilien

Publ.-Id: 28225

"Superconductivity under Extreme Conditions” (Discussion Leader of this Session)

Wosnitza, J.

  • Invited lecture (Conferences)
    Gordon Research Conference on Conductivity and Magnetism in Molecular Materials, 12.-17.08.2018, Smithfield, USA

Publ.-Id: 28224

Spin-imbalanced superconductivity in layered organic superconductors

Wosnitza, J.

  • Invited lecture (Conferences)
    International Conference on Science and Technology of Synthetic Metals 2018 (ICSM 2018), 01.-06.07.2018, Busan, Korea

Publ.-Id: 28223

Frustrated and low-dimensional magnets in high magnetic fields

Wosnitza, J.

  • Invited lecture (Conferences)
    12th International Conference on Research in High Magnetic Fields (RHMF 2018), 24.-28.06.2018, Santa Fe, USA

Publ.-Id: 28222

Kinetic concepts for quantitative prediction of fluid-solid interactions

Lüttge, A.; Arvidson, R. S.; Fischer, C.; Kurganskaya, I.

In a unique “perspectives” format that examines both past and future, we appraise the field of crystal dissolution kinetics, showing how the last century’s strong progress in experimental discovery has both driven, and been driven by, the tandem evolution of basic theory. To provide context for examining the current state-of-the-art in this critical field, we highlight the key milestones that have punctuated our progress in understanding the dynamics of crystalline surfaces. For crystal growth, these are the energy relations between kinks on stepped surfaces, and the phenomena of screw dislocations sustaining steady state growth at low thermodynamic overstep. For crystal dissolution, the corresponding recognition is the tie between defects, hollow cores, and macroscopic etch pits. These latter relationships have been more recently formalized in the stepwave model, incorporating etch pit nucleation, step generation, and global retreat of the crystal surface: the total dissolution rate. All these conceptual advances contain an assertion of a link, fundamental but often implicit, between mass action and kinetics, where chemical potential is the primary driver of rates of physical process. This link is inherent in many “classical” rate equations, whose parameterization is often the endgame of laboratory observations.
Today, this extant framework serves as the conceptual basis for organizing the data available from a sophisticated suite of analytical and experimental instrumentation. These resources permit ever-increasing resolution of reacting surfaces in breathtaking detail, often under in situ conditions. These direct observations are now further enhanced by powerful computer-driven simulation and numerical modeling, allowing the virtual exploration of complex reaction systems, ranging from isolated single crystals to porous, multiphase networks. Despite the exhilarating breadth and detail of these accomplishments, it is also becoming increasingly apparent that we are moving further, not closer, from the goal of predictive understanding, a goal that is an increasingly vital social responsibility of our science. A major source of this divergence reflects the fact that at key intersecting points of study, our prowess in technical observation has effectively outpaced our theoretical understanding. In confronting the daunting complexity of these systems, we must be careful to first identify major vacancies in theory. Until we resolve these deficits, more observations may be of only limited utility.
In assessing this problem, a major uncertainty is how to properly reconcile thermodynamics, by its very nature a macroscopic formalism, with our current focus on atomic scales of reaction. This may be a problem unique to crystalline materials and their interactions with phases whose components are otherwise mobile. Detailed balancing and related microscopic reversibility, the implicit link referred to above, is often used to form a mechanistic bridge between the macroscopic distribution of energy and microscopic heterogeneity of events in crystal surfaces, but its employment creates two problems: spatial and temporal. First, reaction mechanism is truly atomic in dimension, involving actual, nondegenerate collisions at crystal surface sites, whereas 〖∆G〗_r or ∆μ is macroscopic. Second, the rate at which a crystal surface dissolves reflects both the chemical composition of the ambient fluid and the distribution of surface energy. Reaction towards “equilibrium”, involving the typically slow redistribution of surface energy, may thus inherit topography inconsistent with the computed “driving force”. This reactivity mismatch yields surfaces that evolve over time, producing a heterogeneous distribution of rates. This distribution can be efficiently characterized by rate spectra: the span of non-steady-state rates reflecting diversity of reactive sites established under previous 〖∆G〗_r regimes. We use these spectra as a basic compact variable: a signal that encodes the complex link between site-specific surficial energy distributions, solution and surface chemistry, and the cumulative rate that results. Because this encoding is efficiently captured by numerous surface analytical microscopies (VSI, AFM), this approach permits the testing of hypotheses regarding the probabilistic nature of rate distributions, a process we hope the community will embrace, serving ultimately as a key step forward in establishing useful predictive approaches. We illustrate this potential with a series of case studies that target a range of composition, space, and time scales.

Publ.-Id: 28221

Neutronic analyses of the FREYA experiments in support of the ALFRED LFR core design and licensing

Sarotto, M.; Firpo, G.; Kochetkov, A.; Krása, A.; Fridman, E.; Cetnar, J.; Domanska, G.

During the EURATOM FP7 project FREYA, a number of experiments was performed in a critical core assembled in the VENUS-F zero-power reactor able to reproduce the ALFRED lead-cooled fast reactor spectrum in a dedicated island. The experiments dealt with the measurements of integral and local neutronic parameters, such as: the core criticality, the control rod and the lead void reactivity worth, the axial distributions of fission rates for the nuclides of major interest in a fast spectrum, the spectral indices of important actinides (U238, Pu239, Np237) respect to U235. With the main aim to validate the neutronic codes adopted for the ALFRED core design, the VENUS-F core and its characterisation measurements were simulated with both deterministic (ERANOS) and stochastic (MCNP, SERPENT) codes, by adopting different nuclear data libraries (JEFF, ENDF/B, JENDL, TENDL). This paper summarises the main results obtained and points out a general agreement between measurements and simulations, with few discrepancies for some parameters that are here discussed. Additionally, a sensitivity and uncertainty analysis was performed with deterministic methods for the core reactivity: it clearly indicates that the calculation accuracy of the different codes/libraries resulted to be lower than the uncertainties due to nuclear data.

Keywords: FREYA EU FP7 project; ALFRED LFR, VENUS-F reactor; Measurements of neutronic parameters; ERANOS deterministic code; MNCP and SERPENT stochastic codes

  • Journal of Nuclear Engineering and Radiation Science 6(2020)1, 011402
    DOI: 10.1115/1.4044000


  • Secondary publication expected

Publ.-Id: 28219

Wasserstoffbrennen in der Sonne: Die 12C(p,γ)13N-Reaktion und die Radiofrequenz-Ionenquelle für den Felsenkeller-Beschleuniger

Reinicke, S.

Die Reaktion 12C(p,γ)13N bestimmt die Rate des Bethe-Weizsäcker-Zyklus in der anfänglichen Entwicklungsphase von Sternen und am äußeren Rand der Sonne. Eine genaue Kenntnis der Reaktionsrate ist somit für die Entwicklung von stellaren Modellen erforderlich. Über das Verhältnis der Raten von den Protoneneinfangreaktionen von 12C und 13C kann außerdem das entsprechende Isotopenverhältnis in Sternen bestimmt werden. Eine Revision der Rate von 12C(p,γ)13N könnte damit einen unerwartet hohen Isotopenanteil von 13C erklären, der in verschiedenen Meteoriteneinschlüssen gemessen wurde und mit den existierenden stellaren Modellen nicht hinreichend in Konsistenz gebracht werden kann.
Für den S-Faktor der Reaktion existieren im Energiebereich unterhalb von 190 keV nur Messdaten aus den 1950er Jahren. Bei der Untersuchung von ähnlichen Reaktionen des Wasserstoffbrennens wurden die mit der verwendeten Messtechnik erlangten Messdaten durch moderne Experimente teilweise um einen Faktor zwei oder höher revidiert.
Ziel der gegenwärtigen Arbeit war das Messen von S-Faktor-Werten in einem weiten Energiebereich von 130 keV bis 450 keV zur Überprüfung der alten Messdaten und um eine zukünftige präzisere Extrapolation zu astrophysikalisch relevanten Energien hin zu ermöglichen. Dabei wurde eine Messung in inverser Kinematik, eine Methode, für die bisher keine publizierten Daten zu der Reaktion existieren, am HZDR 3 MV Tandetron Beschleuniger durchgeführt mit TiH2-Proben, die mit 12C2+-Ionen bestrahlt wurden. Die Reaktion wurde mittels Gammaspektrometrie ausgewertet und die Proben durch die Methode der Nuklearen Resonanz-Reaktionsanalyse charakterisiert.
Die neuen Messdaten sind im Energiebereich von 130 keV bis 170 keV im Mittel etwa 20 % höher als die Werte eines existierenden Fits an die bestehenden Messdaten, im Rahmen der Messunsicherheiten aber mit diesen konsistent. Im Energiebereich der Resonanz oberhalb von 420 keV wurde eine Diskrepanz zu den alten Messwerten festgestellt. Die neuen Werte liegen in diesem Bereich systematisch bis zu 50 % unterhalb der alten Messwerte.
Als weiteres Ziel dieser Arbeit wurde mithilfe von ionenoptischen Simulationen mit SIMION 8.1 ein elektrostatischer Deflektor und eine Einzellinse für eine RadiofrequenzIonenquelle entwickelt, die im Inneren des Hochspannungsterminals des Felsenkeller Beschleunigers eingesetzt werden soll. Durch die Erkenntnisse der Simulationen konnte ein Deflektor gebaut und getestet werden, der unter den Bedingungen auf dem Beschleuniger-Terminal funktionsfähig ist und zusammen mit der Ionenquelle einen intensiven Strahl von Wasserstoff oder Helium in die Beschleunigungsstrecke umlenken kann. Die Simulationen sagen Strahlverluste von maximal 10 % für Wasserstoff und 1.5 % für Helium voraus, womit, basierend auf den Messungen an einem Vakuumteststand und den Angaben des Herstellers der Ionenquelle, Strahlströme von 80 µA für 4He+ und über 100 µA für Protonen nach Verlassen des Beschleunigers zu erwarten sind. Der Untertage-Beschleuniger am Felsenkeller und die Radiofrequenz-Ionenquelle können zu einer weiteren Messung der Reaktion 12C(p,γ)13N mit besserer Statistik und einem zu niedrigeren Energien erweiterten Messbereich verwendet werden.

The reaction 12C(p,γ)13N determines the rate of the Bethe-Weizsäcker cycle in the initial development phase of stars and near the surface of the Sun. An exact knowledge of the reaction rate is thus required for the development of precise stellar models. In addition, the ratio of the rates of the proton capture reactions of 12C and 13C is used to determine the corresponding isotopic ratio in stars. A revision of the rate of 12C(p,γ)13N might help to explain an unexpectedly high isotopic abundance of 13C, which was measured in presolar grains and cannot be sufficiently explained with the existing stellar models.
For the S-factor of 12C(p,γ)13N in an energy range below 190 keV, the only existing data were measured in the 1950s. For similar reactions of hydrogen burning, data obtained with these measuring techniques were revised by a factor of two or higher by modern experiments.
The aim of the present thesis was to measure S-factor data in a wide energy range from 130 keV to 450 keV in order to verify the old data and to allow a more precise extrapolation towards astrophysically relevant energies in the future. A measurement in inverse kinematics, a method for which no published data on the reaction exist, was performed at the HZDR 3 MV Tandetron accelerator with a 12C2+ ion beam and the use of TiH2 targets. Gamma spectroscopy was used to measure the yield and the targets were characterized with nuclear resonant reaction analysis (NRRA).
In the energy range from 130 keV to 170 keV, the new values are on average about 20 % higher than the values of a recent fit to the old data, but they are consistent within uncertainties. In the energy range of the resonance above 420 keV, a discrepancy to the old data was found. The new values in this region are up to 50 % lower than the values from previous measurements.
Another goal of this work was the development of an electrostatic deflector and an einzel lens for a radio frequency ion source inside the high voltage terminal of the Felsenkeller accelerator. For this purpose, ion-optics simulations with SIMION 8.1 were performed, which lead to a design choice for the deflector allowing the transmission of intensive beams through the accelerator. The simulation predicts beam losses of less than 10 % for hydrogen and less than 1.5 % for helium, which based on easurements with a vacuum test chamber leads to expected beam currents of 80 µA for 4He+ at the exit of the acceleration tube. According to the data sheet of the radio frequency ion source, proton beams of more than 100 µA are to be expected.
The Felsenkeller underground accelerator and its radio frequency ion source can be used to perform further measurements of the reaction 12C(p,γ)13N with improved statistical uncertainties and an extension of the energy region towards lower energies.

  • Doctoral thesis
    TU Dresden, 2018
    Mentor: Prof. Dr. Kai Zuber, PD Dr. Daniel Bemmerer
    171 Seiten
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-095 2019
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 28218

Physical and electrical properties of nitrogen-doped hydrogenated amorphous carbon films

Fenker, M.; Julin, J.; Petrikowski, K.; Richter, A.

Nitrogen-doped hydrogenated amorphous carbon films (a-C:H:N) have been prepared by a plasma-activated chemical vapor deposition technique (PACVD) by using a plasma beam source (PBS). The properties of the a-C:H:N films were changed by varying the total pressure, the substrate temperature (100 °C, 300 °C) and nitrogen partial pressure p(N₂) by adding nitrogen to the precursor acetylene (C₂H₂). For the investigations, a-C:H:N films have been deposited onto glass slides and doped silicon wafers. The deposition rate decreased with increasing nitrogen content in the N₂/C₂H₂ gas mixture and with decreasing total pressure. The elemental composition of two sample series (300 °C) has been analyzed with Elastic Recoil Detection Analysis (ERDA). The highest N content and N/C ratio was estimated to be 16 at.% and 0.25 at the highest p(N₂), respectively. Microhardness measurements showed that the hardness decreased with increasing p(N₂). Electrical resistance of the a-C:H:N films was measured by 4-point probe. Electrically conductive coatings have been obtained by nitrogen-doped a-C:H films at higher substrate temperature (300 °C). The electrical resistance of the a-C:H:N films also decreases with ecreasing total pressure, with the lowest value being about 1 Ohm cm. The film density was determined by means of X-ray reflectometry (XRR).

Keywords: PACVD; DLC; carbon films; carbon nitride films; XRR; electrical conductivity

Publ.-Id: 28217

Measurement of the prompt fission γ-ray spectrum of 242Pu

Urlass, S.; Beyer, R.; Junghans, A. R.; Kögler, T.; Schwengner, R.; Wagner, A.

The prompt γ-ray spectrum of fission fragments is important in understanding the dynamics of the fission process, as well as for nuclear engineering in terms of predicting the γ-ray heating in nuclear reactors. The γ-ray spectrum measured from the fission fragments of the spontaneous fission of 242Pu will be presented here. A fission chamber containing in total 37mg of 242Pu was used as active sample. The γ-quanta were detected with high time- and energy-resolution using LaBr3 and HPGe detectors, respectively, in coincidence with spontaneous fission events detected by the fission chamber.
The acquired γ-ray spectra were corrected for the detector response using the spectrum stripping method. About 70 million fission events were detected which results in a very low statistical uncertainty and a wider energy range covered compared to previous measurements. The prompt fission γ-ray spectrum measured with the HPGe detectors shows structures that allow conclusions about the nature of γ-ray transitions in the fission fragments. The average photon multiplicity of 8.2 and the average total energy release by prompt photons per fission event of about 6.8 MeV were determined for both detector types.

Keywords: nELBE; prompt fission; gamma-rays; plutonium; 242Pu; fission chamber

Publ.-Id: 28216

Calcium molybdate, CaMoO₄: a promising target material for 99m-Tc and its potential applications in nuclear medicine and nuclear waste disposal

Johnstone, E. V.; Czerwinski, K. R.; Hartmann, T.; Poineau, F.; Bailey, D. J.; Hyatt, N. C.; Mayordomo, N.; Nuñez, A.; Tsang, F. Y.; Sattelberger, A. P.; German, K. E.; Mausolf, E. J.

Calcium molybdate (CaMoO₄ ) is a robust, inorganic material known for its favorable physicochemical properties making it ideal for a wide scope of applications concerning optics (i.e., phosphors, scintillators, laser hosts, etc.), nuclear waste encapsulation and disposal, corrosion inhibition, etc. Calcium molybdate occurs in nature as the mineral Powellite, and the compound adopts the scheelite (CaWO₄ ) structure-type with Mo fully oxidized in the +6-oxidation state. This Mo-containing ceramic phase exhibits limited insoluble in aqueous environments and relative thermal stability at elevated temperatures. In the laboratory, CaMoO₄ can be synthesized straightforward from the stoichiometric solid-state reaction MoO₃ with the respective calcium oxide or carbonate, e.g., CaO or CaCO₃, at elevated temperatures, or alternatively via co-precipitation, sol-gel, or mechanochemical methods. Depending on synthetic conditions, single phase nano-powders to monoliths can be generated and tailored for its successive application. Likewise, the scheelite structure type can incorporate different doping elements into the host lattice, such as Pb2+ or elements arising from the lanthanoid series, which are used for applications with phosphors. , ,
On the periodic table, Mo (Z = 42) is located on the 5th row within the transition metals and precedes the lightest, inherently radioactive element, technetium (Tc, Z = 43). Molybdenum is characterized by an assortment of naturally occurring isotopes (i.e., 92Mo 14.53%, 94Mo 9.16%, 95Mo 15.84%, 96Mo 16.67%, 97Mo 9.60%, 98Mo 24.39%, and 100Mo 9.82%) making it a suitable starting material for the transmutation to an array of different Tc isotopes depending on isotope enrichment, particle beam type (e.g., proton, deuteron, electron, neutron, photon, etc.), and beam energy. One of the most recognized Mo-Tc radionuclidic parent-daughter couples is 99Mo-99mTc, where the daughter isotope 99mTc has been notoriously branded as the workhorse of the nuclear diagnostic imaging industry used worldwide in 30 to 40 million procedures annually, i.e., ~ 9,000 6-day Ci at end of processing (EOP) per week. As the international geopolitical attitude towards using highly enriched uranium (HEU) for the production of 99Mo begins to shift, the use of non-fission sources for the production of 99mTc is becoming increasingly more vital, and new methods for production and separation are desperately being sought. For example, the United States of America currently has no domestic supply in place for the production of 99mTc, although it is responsible for half of the world’s usage.
When considering both, the isotopic and physicochemical composition and properties of Mo and CaMoO₄, strong arguments can be made to pursue the better understanding of CaMoO₄ and its relationship as a host material for direct transmutation of Mo → Tc and / or post-processing integration of Tc, specifically 99mTc at the atomistic level to weight percentages in its fundamental structure for applications such as nuclear waste disposal and radiopharmaceuticals. In this work, the synthesis and irradiation of CaMoO₄ using a modular, fusion-based neutron source and its successive characterizations are reported. Further discussions are presented considering these empirical data and their context with potential applications in the realms of nuclear medicine and materials.

Keywords: technetium; waste disposal encapsulation; molybdate; ceramics; post-irradiation

  • Contribution to proceedings
    10th Symposium on Technetium and Rhenium science and application, 03.-06.10.2018, Moscow, Russia
    10th Symposium on Technetium and Rhenium science and application, 978-5-9933-0132-7
  • Lecture (Conference)
    10th Symposium on Technetium and Rhenium science and application, 03.-06.10.2018, Moscow, Russia

Publ.-Id: 28215

Effects of gamma-alumina nanoparticles on strontium sorption in smectite: additive model approach

Mayordomo, N.; Alonso, U.; Missana, T.

Strontium sorption was analysed in binary mixtures of smectite and γ-alumina nanoparticles under different pH, ionic strength and Sr concentration. The aims were to verify if γ-alumina nanoparticles enhance Sr sorption in smectite and to analyse whether a component additive model satisfactorily described Sr sorption in the mixtures.
In smectite, Sr sorption mainly occurs by cation exchange but surface complexation was also accounted for. In both solids, surface complexation was described with a non-electrostatic model.
The addition of γ-Al₂O₃ nanoparticles to smectite improved Sr uptake under alkaline pH and high ionic strength, and the additive model successfully reproduced experimental data. In contrast, under acid pH and low ionic strength, no sorption improvement was observed upon adding the nanoparticles and the additive model overestimated Sr sorption. The competition of Al(III) ions, coming from γ-Al₂O₃ dissolution, partially explained the differences between data and model. Nevertheless, surface interactions between alumina particles and smectite layers may be shielding the charge, hindering contaminant access to exchangeable sites in smectite.

Keywords: Strontium; smectite; alumina; nanoparticles; sorption modelling; additive model

Publ.-Id: 28214

Is It Here/There Yet? - Real Life Experiences of Generating/Evaluating Extreme Data Sets Around the World

Juckeland, G.; Huebl, A.; Bussmann, M.

Large scale simulations easily produce vast amounts of data that cannot always be evaluated in-situ. At that point parallel file systems come into play, but their per node performance is essentially limited to about the speed of a USB 2.0 thumb drive (e.g. the Spider file system at OLCF provides over 1 TB/s write bandwidth, but with 18000+ nodes of Titan writing simultaneously, this number is reduced to about 50 MB/s per node). Making the most out of such a limited resource requires I/O libraries that actually scale. In addition such libraries also offer on the fly data transformations (e.g. compression) to better utilize the raw I/O bandwidth, albeit, opening a new can of worms by trading compression throughput with compression ratios for performance. We will present a detailed study of I/O performance and various compression techniques at OLCF and compare them against smaller local I/O installations, demonstrating the highest achieved I/O performance for real world applications at OLCF. Furthermore, we demonstrate that the best performing I/O setup can be determined prior to starting the job based on hardware characteristics.
Now that you have your data on disk the clock starts ticking and you are fighting against the deadline until your data will be purged, since most centers only offer the high performing storage spaces on a temporary basis. Extracting all valuable information out of a petabyte sized data set requires parallel processing as well and induces wait times until the resources are available and quite naturally a lot of trial-and-error for the evaluation. The time constraint for keeping the temporary data becomes even more troublesome when trying to compare multiple large simulations that naturally have a delay of multiple days until they are scheduled and write their results. And ideally analysis could embrace the data of multiple simulations of a quarterly accounted, yet year-long computing campaign. Another challenge for actually conducting scientific discoveries comes when utilizing multiple compute sites. This seems to be rather usual for research groups as they will use all the compute clock cycles they
can get wherever that may be. For comparative studies the data sets now need to be available at the same time for analysis, e.g. via archiving solutions or transfer to one location. The achievable transfer bandwidth between data centers is in our experience still much lower than expected. The talk will also present on the experiences of evaluating petabyte sized data sets in such a diverse environment.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-09-18
    DOI: 10.14278/rodare.70
    License: CC-BY-4.0


Publ.-Id: 28213

Neutron flux and spectrum in the Dresden Felsenkeller underground facility studied by moderated He-3 counters

Grieger, M.; Hensel, T.; Agramunt, J.; Bemmerer, D.; Degering, D.; Dillmann, I.; Fraille, L. M.; Köster, U.; Marta, M.; Müller, S.; Taín, J. L.; Zuber, K.

Ambient neutrons may cause significant background for underground experiments. Therefore, it is necessary to investigate their flux and energy spectrum in order to devise a proper shielding. Here, two sets of altogether ten moderated ³He neutron counters are used for a detailed study of the ambient neutron background in tunnel IV of the Felsenkeller facility, underground below 45 meters of rock in Dresden/Germany. One of the moderators is lined with lead and thus sensitive to neutrons of energies higher than 10 MeV. For each ³He counter-moderator assembly, the energy dependent neutron sensitivity was calculated with the FLUKA code. The count rates of the ten detectors were then fitted with the MAXED and GRAVEL packages. As a result, both the neutron energy spectrum from 10⁻⁹ MeV to 300 MeV and the flux integrated over the same energy range were determined experimentally.
The data show that at a given depth, both the flux and the spectrum vary significantly depending on local conditions. Energy integrated fluxes of (0.61±0.05), (1.96±0.15), and (4.6±0.4)×10⁻⁴ cm⁻² s⁻¹, respectively, are measured for three sites within Felsenkeller tunnel IV which have similar muon flux but different shielding wall configurations.
The integrated neutron flux data and the obtained spectra for the three sites are matched reasonably well by FLUKA Monte Carlo calculations that are based on the known muon flux and composition of the measurement room walls.

Keywords: Underground; Felsenkeller; Neutron Flux; FLUKA

Publ.-Id: 28212

Cross section and neutron angular distribution measurements of neutron scattering on natural iron

Pirovano, E.; Beyer, R.; Dietz, M.; Junghans, A. R.; Müller, S. E.; Nolte, R.; Nyman, M.; Plompen, A. J. M.; Röder, M.; Szücs, T.; Takacs, M. P.

New measurements of the neutron scattering double differential cross section of iron were carried out at the neutron time-of-flight facilities GELINA and nELBE. A neutron spectrometer consisting of an array of up to 32 liquid organic scintillators was employed, which was designed to measure the scattering differential cross section at eight scattering angles and to simultaneously determine the integral cross section via numerical quadrature. The separation of elastic from inelastic scattering was achieved by analysing the time-of-flight dependent light-output distributions to determine the scattered neutron energy. The method was validated by studying elastic scattering on carbon and it was proved to work well for the determination of the elastic cross section. Here, the possibility to extend it to inelastic scattering was investigated too. For these experiments a sample of natural iron was used and the results cover the incident neutron energy range from 2 to 6~MeV. Both the differential and the integral elastic cross sections were produced for Fe, while for inelastic scattering, partial angular distributions for scattering from the first excited level of Fe could be determined.

Keywords: GELINA; nELBE; fast neutron scattering; cross section; angular distribution; iron

Related publications

Publ.-Id: 28211

Radiosynthesis and preliminary biological evaluation of a novel 18F-labeled MCT1/MCT4 inhibitor for tumor imaging by PET

Sadeghzadeh, M.; Moldovan, R.-P.; Wenzel, B.; Deuther-Conrad, W.; Toussaint, M.; Fischer, S.; Ludwig, F.-A.; Teodoro, R.; Kranz, M.; Spalholz, T.; Gurrapu, S.; Steinbach, J.; Drewes, L. R.; Brust, P.

Aim: Monocarboxylate transporters (MCTs) are integral plasma membrane proteins that bi-directionally transport lactate and ketone bodies and are highly expressed in non-hypoxic regions of human colon, brain, breast, lung and other tumors.[1] Transporter inhibition leads to intracellular lactate accumulation, acidosis and cell death especially in glioma cell lines.[2] Accordingly, MCT1/MCT4 inhibitors are regarded to be of potential clinical use. In the current study a new 18F-labeled MCT1/MCT4 inhibitor was developed for in vivo PET imaging of MCT1/MCT4-overexpressing brain tumors.

Methods: (E)-2-Cyano-3-{4-[(3-fluoropropyl)(propyl)amino]-2-methoxyphenyl}acrylic acid (CAPAA) was synthesized from m-anisidine in three consecutive steps with 50% overall yield. Similar strategy was carried out to synthesize the mesylated precursor for radiosynthesis. Radiosynthesis of [18F]CAPAA was achieved by a two-step reaction, starting with the nucleophilic substitution of fluorine-18 on the alkyl chain using [18F]TBAF followed by removal of the protecting group by TFA at room temperature. [18F]CAPAA was isolated by semi-preparative HPLC eluting with 46% CH3CN/aq. 20 mM NH4HCO2 (Reprosil-Pur C18-AQ column, 250 × 10 mm), purified via Sep-Pak® C18 light cartridge and formulated in 10% EtOH/saline solution. LogD was assessed by the shake-flask method. The average IC50 values for MCT1 and MCT4 were evaluated via [14C]lactate uptake assay on the rat brain cerebrovascular endothelial cell line RBE4. The apparent affinity of [18F]CAPAA (KD) was determined using brain homogenate obtained from female CD1 mouse. The radiotracer metabolism was investigated in female CD1 mice by radio-HPLC of plasma and brain samples obtained at 30 min p.i. Plasma obtained at 60 min p.i. was used to measure the in vivo plasma free fraction.

Results: During radiosynthesis, a radiolabeled intermediate was obtained by an optimized procedure (CH3CN, 50µl of TBAHCO3-, 2-5 GBq of K[18F]F, 100 ̊C, 15 min) with 55-70% yield (n=8, non-isolated) determined by radio-HPLC analysis. Deprotection of tert-Bu group was accomplished with TFA in acetonitrile at r.t. for 15 min with 65-73% yield (n=10, radio-HPLC, non-isolated). The radiotracer was obtained in 42-65% radiochemical yield (RCY) with >98% radiochemical purity (RCP). The radioligand was highly stable in saline and PBS (>95%) up to 60 min. LogD was determined as 0.42 which reveals the tracer has moderate lipophilicity. CAPAA showed high MCT1 and MCT4 inhibition activity (IC50 = 11 and 6.4 nM respectively). [18F]CAPAA binds with an apparent KD value of ~30 nM in a saturable manner to a binding site in the brain of healthy mice. In vivo studies showed >99% of intact tracer in plasma at 30 min p.i. and a free fraction in plasma of ~3% at 60 min p.i.

Conclusions: [18F]CAPAA was achieved in high RCY and RCP and showed considerable in vitro and in vivo stability. Accordingly, the newly developed MCT1/MCT4 radioligand is anticipated to be a useful agent for imaging of tumors by PET. Animal PET imaging on healthy and brain tumor-bearing mice is currently performed.

Keywords: Radiofluorination; MCT1; Tumor imaging

  • Contribution to proceedings
    26. Jahrestagung Arbeitsgemeinschaft Radiochemie und Radiopharmazie (AGRR2018), 20.-22.09.2018, Aachen, Deutschland

Publ.-Id: 28210

Paramagnetic NMR investigations of metal-organic complexes of soft donor ligands and the tetravalent actinides

Schöne, S.; Radoske, T.; Felsner, B.; Köhler, L.; Patzschke, M.; März, J.; Kaden, P.

NMR spectroscopy of metal-organic complexes of the f-element metal ions is often challenging due to additional chemical shifts and enhanced relaxation close to the paramagnetic metal center. These effects originate from electronic interactions between metal and ligand and often result in large additional NMR chemical shifts, compared to isostructural diamagnetic complexes, ob-served on the resonances of the ligands’ nuclei. The major two contributors to these paramag-netic chemical shifts are Fermi-contact shifts (FCS) and pseudo-contact shifts (PCS). FCS are due to delocalization 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 paramagnetic contributions can be mathematical separated provided that a suitable diamag-netic reference is available in order to subtract non-paramagnetic contributions. For the trivalent actinides no diamagnetic reference in the same series is available in milligram scale. Further-more, all available theories behind mathematical disentangling of contributions to the paramag-netic 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 studies of isostructural diamagnetic complexes of both f-element series of tetravalent metal ions (Ce(IV) and Th(IV)) allow for an es-timation of additional influences to the chemical shifts and the effect of contributions usually omitted by commonly used mathematical theories.

With Th(IV) as a diamagnetic reference in the same series, studying paramagnetic metal-organic complexes of the tetravalent actinides (An(IV)) allows to assess the chemical bonding situation via the influences on NMR chemical shifts (via FCS) and additionally allows to exploit the geo-metrical information which can be extracted from dipolar interactions (via PCS). These structural properties of the complexes as derived from PCS contributions can be compared to single crys-tal X-ray diffraction structures enabling a comparison of solution state and solid state structure of the metal-organic complexes under investigation. Herein we report the first results of investiga-tions of N- and N,O-donor ligand complexes of the An(IV) series (Th(IV), U(IV) and Np(IV)).

Keywords: NMR; actinides; paramagnetic; metal organic; Th; U; Np; Pu; Thorium; Uranium; Neptunium; Plutonium; diamagnetic

  • Lecture (Conference)
    ATAS - 4th International Workshop on Advanced Techniques in Actinide Spectroscopy, 06.-09.11.2018, Nice, France

Publ.-Id: 28209

Development of the first 18F-labeled MCT1/MCT4 lactate transport inhibitor: Radiosynthesis and preliminary in vivo evaluation in mice

Sadeghzadeh, M.; Moldovan, R.-P.; Wenzel, B.; Kranz, M.; Deuther-Conrad, W.; Toussaint, M.; Fischer, S.; Ludwig, F.-A.; Teodoro, R.; Gurrapu, S.; Drewes, L. R.; Brust, P.

Objectives: Although, lactate is occasionally considered as a waste in physiological cell metabolism, it is also known as an important substrate that fuels the oxidative metabolism of oxygenated tumor cells. Therefore, tumor cells express a set of plasma membrane transporters for lactate. Those monocarboxylate transporters (MCTs) are regarded as functional biomarkers for the metabolic symbiosis between glycolytic and oxidative tumor cells [1]. Overexpression of MCT1 and MCT4 has been shown for a variety of human cancers (e.g. colon, brain, breast, and kidney) [2]. Experimentally, inhibition of MCT1/MCT4 resulted in intracellular lactate accumulation, acidosis and cell death. In the current study, the first 18F-labeled MCT1/MCT4 inhibitor was developed for potential in vivo imaging of MCT expression in cancer.
Methods: Fluorinated α-CHC derivatives (FACH and tert-Bu-FACH) were synthesized and the inhibitory activity of FACH towards MCT1 and MCT4 was estimated by [14C]lactate uptake assays using an immortalized rat brain endothelial cell line (RBE4). For the radiosynthesis of [18F]FACH, a protected mesylate precursor was developed to prevent any possible effect on the labeling reaction. [18F]FACH was produced via a two-step radiosynthesis approach, starting with the nucleophilic substitution on the alkyl chain using [18F]TBAF followed by removal of the protecting group by trifluoroacetic acid (TFA) at room temperature (Figure 1A).
Isolation of [18F]FACH was performed by semi-preparative HPLC (Reprosil-Pur C18-AQ column, 250 × 10 mm, 46% CH3CN/aq. 20 mM NH4HCO2, pH = 4-5, flow 3.5 mL/min). The tracer was finally purified via solid-phase extraction (Sep-Pak® C18 light cartridge) and formulated in 10% EtOH/saline solution. In vitro stability tests were performed in pig plasma, saline, PBS and n-octanol. The LogD value was assessed by the shake-flask method. The in vivo metabolism of the radiotracer was investigated in female CD-1 mice at 30 min p.i. The biodistribution of [18F]FACH and the inhibitory effects of FACH and α-CHC were investigated by dynamic PET imaging (60 min, nanoScan® PET/MRI, MEDISO, Budapest, Hungary) of female CD-1 mice (Figure 1B).
Results: FACH showed strong inhibition of MCT1 and MCT4 (IC50 = 11 and 6.4 nM respectively). The intermediate [18F]tert-Bu-FACH was obtained by an optimized procedure (CH3CN, 3.75 µmol of TBAHCO3, 2-5 GBq of K[18F]F, 100 ̊C, 15 min) with 55-85% radiochemical yield (n = 10, non-isolated). [18F]FACH was obtained after deprotection of [18F]tert-Bu-FACH with TFA in acetonitrile at room temperature for 15 min. After purification and formulation, the novel radiotracer could be achieved with a RCY of 39 ± 3% (n = 10, EOB), molar activity of 42-100 GBq/µmol (EOS), and RCP >98%. The measured logD value (0.42) reveals moderate lipophilicity of the radiotracer. [18F]FACH was highly stable in saline (>98%) up to 60 min. In vivo metabolite studies showed >98% of intact tracer in plasma, brain, liver and kidney at 30 min p.i. Beside [18F]FACH, a few polar metabolites were also found in urine after 30 min p.i. The organ distribution pattern of [18F]FACH in healthy mice corresponds to the specific expression of MCT1 and MCT4 in kidney, lung, pancreas and liver. In these tissues, a moderate to high reduction of uptake was observed after after pre-injection of FACH and α-CHC, respectively.
Conclusions: The high uptake of [18F]FACH in kidney and other peripheral MCT-expressing organs together with the strong inhibition by specific drugs provide evidence that the new MCT1/MCT4-targeting radiotracer could be proven in ongoing studies to be useful for imaging of solid tumors with PET.

Keywords: Monocarboxylate transporter; Radiofluorination; PET; [18F]FACH

  • Contribution to proceedings
    23rd International Symposium on Radiopharmaceutical Sciences (ISRS2019), 26.-31.05.2019, Beijing, China

Publ.-Id: 28208

The Unofficial "Green HPCG"

Huebl, A.

An unofficial list of HPC systems, compiled from the HPCG Benchmark and TOP500 in order to explore an alternative metric for the Green500.

Keywords: hpc; manycore; top500; computing; hardware; energy efficiency

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-11-18
    DOI: 10.14278/rodare.68
    License: CC-BY-4.0


Publ.-Id: 28207

FMR Linewidth Variation with Distance from Lateral Antiferromagnet/Ferromagnet Interfaces

Usami, T.; Bali, R.; Lindner, J.; Itoh, M.; Taniyama, T.

B2-ordered FeRh alloys show a fascinating first-order magnetic phase transition from the antiferromagnetic (AFM) to the ferromagnetic (FM) state at around 380 K[1]. Recently, the AFM/FM phase transition and its related phenomena have been extensively studied; the transition temperature can be manipulated by substituting ions[2], introducing disorder via ion irradiation[3], injecting a spin-polarized current[4], and applying an electric field[5]. These experimental demonstrations would provide a fundamental basis for the use of FeRh in practical novel spintronic applications such as magnetic recordings, AFM memory resistors, and magnonic devices. Also, we have shown a long-range propagation of spin waves in a ferromagnetic Fe60Rh40 thin wire, demonstrating that FeRh has its potential of an alternative material for magonics [6]. In this study, we report ferromagnetic resonance (FMR) in the proximity of lateral AFM/FM FeRh interfaces that are generated by Ne+ ion irradiation. From the FMR measurements, we find a unique dependence of linewidth of the FMR spectra as a function of distance between the rf-antenna and the AFM/FM interface.

  • Poster
    Magnetics and Optics Research International Symposium 2018, 07.-10.01.2018, New York, United States of America

Publ.-Id: 28206

Measurement of Diamond Nucleation Rates from Hydrocarbons at Conditions Comparable to the Interiors of Icy Giant Planets

Schuster, A. K.; Hartley, N. J.; Vorberger, J.; Döppner, T.; van Driel, T.; Falcone, R. W.; 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.; Pak, A.; Prencipe, I.; Rohatsch, K.; Saunders, A. M.; Sun, P.; Kraus, D.

We present measurements of the nucleation rate into a diamond lattice in dynamically compressed polystyrene obtained in a pump-probe experiment using a high energy laser system and in situ femtosecond X-ray diffraction. Different temperature-pressure conditions that occur in planetary interiors were probed. For a single shock reaching 70GPa and 3000K no diamond formation was observed while with a double shock driving polystyrene to pressures around 150GPa and temperatures around 5000K nucleation rates between 1029 m-3s-1 and 1034 m-3s-1 were recorded. These nucleation rates do not a agree with predictions of recent theoretical models for carbon-hydrogen mixtures by many orders of magnitude. Our data suggests that there is indeed significant diamond formation to be expected inside icy giant planets like Neptune and Uranus.

Publ.-Id: 28205

The role of fluid flow in heat and mass transport in Liquid Metal Batteries

Personnettaz, P.; Landgraf, S.; Nimtz, M.; Weber, N.; Weier, T.

Liquid metal batteries (LMBs) are suggested as a promising energy storage technology. An LMB is a three liquid layers concentration cell: two liquid metal electrodes are divided by a molten salt electrolyte. The relatively simple composition and geometry, the occurrence of multi-physics phenomena and the completely liquid nature of the active material have made the LMB an interesting candidate for continuum mechanics studies, ranging from magnetohydrodynamics to transport phenomena, such as Marangoni convection. The cell is in fact subject to a simultaneous transport of charge, heat, mass and momentum together with electrochemical reactions. The fluid flow can be beneficial if it is able to enhance the mixing at the electrolyte interfaces, thereby preventing the formation of intermetallic solid phases. However, a vigorous flow can also be detrimental to the safe operation of the battery, leading to short circuit induced by the rupture of the thin electrolyte layer. In our work the attention is focused on the role of fluid flow in heat and mass transport.
Thermally driven convection is investigated in a three layer Li||Bi LMB with an extended version of the VOF solver multiphaseInterFOAM. A relevant flow is discovered in the pure negative electrode, however it is too weak to deform the liquid interface. Moreover mass transfer is studied in the positive electrode with a single-phase CFD solver. The presence of solutal convection is numerically confirmed during the charge of the cell. The flow structures and the effects on cell efficiency are presented, the modeling limitations and the future developments are discussed.

Keywords: LMB; mass transport; heat transfer; openFoam; CFD

  • Poster
    MHD Days and GDRI Dynamo Meeting, 26.-28.11.2018, Dresden, Germany

Publ.-Id: 28204

Ion induced ferromagnetism combined with self-assembly for large area magnetic modulation of thin films

Krupinski, M.; Bali, R.; Mitin, D.; Sobieszczyk, P.; Gregor-Pawlowski, J.; Zarzycki, A.; Böttger, R.; Albrecht, M.; Potzger, K.; Marszałek, M.

A highly versatile and scalable path to obtain buried magnetic nanostructures within alloy thin films, while maintaining a flat topography, is described. A magnetic pattern of nanoscale periodicity is generated over ∼cm 2 areas by employing a B2 → A2 structural transition in the prototype Fe 60 Al 40 thin alloy films. The phase transition was induced in the confined regions via ion-irradiation through self-assembled nanosphere masks. In this way, large area patterns of a hexagonal symmetry of ferromagnetic nanostructures embedded within a paramagnetic Fe 60 Al 40 thin film are realized. The depth and lateral distribution of the induced magnetization was investigated by magnetometry and microscopy methods. Magnetic contrast imaging as well as simulations shows that the obtained magnetic structures are well defined, with the magnetic behavior tunable via the mask geometry.

Keywords: self-assembly; magnetic nanostructures; chemical disorder; magnetic patterning; ion irradiation

Publ.-Id: 28203

Identical pion intensity interferometry in central Au+Au collisions at 1.23A GeV

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Kühn, W.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K. N.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.

For the first time, identical pion HBT intensity interferometry is investigated for a large heavy ion collision system in the energy region of 1 GeV per nucleon. High-statistics π−π− and π+π+ data are presented for central Au+Au collisions at 1.23A GeV, measured with HADES at SIS18/GSI. The radius parameters, derived from the correlation function depending on relative momenta in the longitudinal-comoving system and parametrized as three-dimensional Gaussian distribution, are studied as function of transverse momentum. A substantial charge-sign difference of the source radii is found, particularly pronounced at low transverse momentum. The extracted Coulomb-corrected source parameters agree well with a smooth extrapolation of the center-of-mass energy dependence established at higher energies, extending the corresponding excitation functions down towards a very low energy. Our data would thus rather disfavour any strong energy dependence of the radius parameters in the low energy region.

Publ.-Id: 28202

High-field ESR in low-dimensional spin systems

Zvyagin, S.

Electron spin resonance (ESR) is traditionally recognized as one of the most sensitive tools for probing magnetic excitations in strongly-correlated spin systems. Among other exchange-coupled spin systems, low-dimensional magnets serve as almost ideal paradigmatic models in quantum magnetism, exhibiting highly unusual ground-state properties and spin dynamics. Here, I review results of our recent high-field ESR studies of some low-dimensional magnets, including quantum spin chains [1], quantum antiferromagnets on triangular lattice [2], Heisenberg spin ladders [3], and quasi-two-dimensional magnets on a honeycomb lattice [4]. In addition, I will give a brief introduction into the high-field ESR facilities at the Dresden High Magnetic Field Laboratory, which allows for multi-frequency ESR experiments in a very broad frequency range (ca 50 GHz - 9 THz) in magnetic fields up to 60 T and above.

  • Invited lecture (Conferences)
    Third Joint Conference of the Asia-Pacific EPR/ESR Society and The International EPR (ESR) Society (IES) Symposium, 23.-27.09.2018, Brisbane, Australia

Publ.-Id: 28200

TEM investigation of irradiation-induced defects in an ion-irradiated Fe-9Cr ODS steel

Vogel, K.; Duan, B.; Heintze, C.; Bergner, F.

Oxide dispersion strengthened (ODS) steels are promising candidate materials for structural components in nuclear power generators. Here we report on our preliminary results of TEM investigations of irradiation-induced defects in an ion-irradiated Fe-9Cr ODS steel. A cross-sectional TEM sample prepared by focused ion beam (FIB) was studied in a FEI Talos F200X transmission electron microscope by imaging under various diffraction conditions in bright- and dark-field mode. The TEM micrographs show a defect-rich band of about 400 nm width. The band is aligned parallel to the specimen surface and its position corresponds to the position of the peaks in the damage and/or injected interstitials profiles. Therefore we conclude that the defects within the band are caused by the ion irradiation. In higher magnified images of the band we observe a large number of defects, which appear as "black dots" showing a high contrast under kinematic bright-field conditions. We assume that these defects are interstitial loops, however this assumption has to be proved by further investigations. Additionally we observe some strongly curved dislocation segments, which will also be a subject of our further TEM studies.

Keywords: Transmission Electron Microscopy; Irradiation-induced defects

  • Poster
    Microscopy of Radiation Damage 2018, 21.-23.03.2018, Oxford, United Kingdom

Publ.-Id: 28199

Effect of Tb for Gd substitution on magnetic and magnetocaloric properties of melt-spun (Gd1-xTbx)3Co alloys

Shishkin, D. A.; Volegov, A. S.; Ogloblichev, V. V.; Mikhalev, K. N.; Gerasimov, E. G.; Terentev, P. B.; Gaviko, V. S.; Gorbunov, D. I.; Baranov, N. V.

The melt-spun (Gd1-xTbx)3Co alloys (0≤x≤1) have been obtained and studied by X-ray diffraction, ac-susceptibility, magnetization in steady and pulse magnetic fields, and NMR measurements. A comparison of the results obtained on melt-spun alloys with their crystalline analogs has revealed a strong impact of amorphization on the magnetic state and magnetocaloric properties. The Gd-rich amorphous (Gd1-xTbx)3Co alloys (x≤0.1) exhibit increased magnetic ordering temperatures in comparison with the crystalline compounds, which is attributed to the appearance of a magnetic moment on Co atoms. The substitution of Tb for Gd results in the growth of the ratio of local anisotropy to exchange. The melt quenching of the (Gd1-xTbx)3Co alloys allows improving their magnetocaloric properties in the temperature range from 80 K up to 170 K.

Publ.-Id: 28198

Cm complexation with aqueous phosphates at elevated temperatures

Huittinen, N.; Jordan, N.; Demnitz, M.; Lösch, H.; Starke, S.; Brendler, V.

Orthophosphate ions (H2PO4-, HPO42-, and PO43-) are ubiquitous in the environment and may originate from the natural decomposition of rocks and minerals (e.g. monazite or apatite), agricultural runoff, or from wastewater treatment plants. Furthermore, the potential use of monazite (LnPO4) ceramics for the immobilization of specific actinide-containing waste streams may become an important source of phosphates in the future [1–2]. Among the inorganic ligands, phosphates are strong complexants and can be expected to influence the speciation of dissolved radioactive contaminants when present in solution. However, very little data is available on the complexation of especially actinides with aqueous phosphates, even though these complexation reactions precede any aqueous synthesis of monazite ceramics and are expected to occur in natural waters as well as in the proximity of monazite-containing high-level waste repositories. The existing data also suffers from an almost systematic absence of independent spectroscopic validation of the stoichiometry of the proposed complexes.
In the present work, time-resolved laser fluorescence spectroscopy (TRLFS) has been employed to study the complexation of the actinide Cm3+ (5×10-7 M) as a function of total phosphate concentration (0–0.5 M Σ(PO4)) in the temperature regime 25–80°C, using NaClO4 as a background electrolyte (0.5–2.1 M). The studies have been conducted in the acidic pH-range ( log[H+] = 1–2.5) to avoid precipitation of solid Cm rhabdophane (CmPO4×nH2O). Under these experimental conditions, the trivalent actinide cation was found to form a complex with the anionic H2PO4- species, i.e. CmH2PO42+ and Cm(H2PO4)2+, depending on the solution pH and the total phosphate concentration, Figure 1.
The complexation reaction occurs at lower total phosphate concentration when increasing the ionic strength or the temperature. Using specific ion interaction theory (SIT) and the Van’t Hoff equation, obtained conditional constants at varying ionic strengths and temperatures have been extrapolated to infinite dilution (logβ0) and values for the enthalpy ΔRH° (assumed constant between 25 to 80 °C) and entropy ΔRS° of reaction have been acquired. The results of the extrapolations are shown exemplarily for the CmH2PO42+ species in Figure 2.
The new thermodynamic data derived in this fundamental study will contribute to a fundamental process understanding necessary to critically assess the environmental fate of actinides in the environment.

  • Lecture (Conference)
    Radiation in the environment – scientific achievements and challenges for the society, 16.-17.04.2018, Helsinki, Finland

Publ.-Id: 28197

Spectroscopic investigations of Cm3+ incorporation in lanthanide orthophosphates

Huittinen, N.; Scheinost, A. C.; Ji, Y.; Kowalski, P. M.; Arinicheva, Y.; Neumeier, S.

Monazites (LnPO4) are envisioned as potential immobilization matrices for high-level radioactive wastes produced e.g. during the nuclear fuel cycle [1–2]. Hydrated rhabdophane (LnPO4×0.67H2O) is a precursor phase during monazite synthesis and a potential solubility-limiting solid phase under nuclear waste storage conditions [3–4]. Thus, for a reliable long-term safety assessment of nuclear waste repositories for conditioned radioactive waste, a fundamental understanding of the radionuclide incorporation process in both the pristine monazite ceramics and their alteration products is required.
In the present study [5] we have combined two spectroscopic methods, (1) time-resolved laser fluorescence spectroscopy (TRLFS) and (2) extended x-ray absorption fine structure spectroscopy (XAFS) with density functional theory-based ab initio calculations to investigate the incorporation of the actinide curium (Cm) in (La,Gd)PO4 monazite and rhabdophane solid phases. Spectroscopic methods allow for direct probing of the dopant and its local environment in host matrices, providing a better understanding of potential lattice defect formations, lattice strain or disordering phenomena, and site population deviances with regard to the composition of the host structure, which may occur in the solid phase upon introduction of the dopant. Ab initio calculations can further deliver descriptions and explanations for spectroscopic findings, thus, contributing to a better understanding of the incorporation processes on a molecular level.
The solid phases were synthesized by addition of phosphoric acid to a solution containing La3+ and Gd3+ in desired relative concentrations and a small amount of the actinide (248Cm), until a white precipitate of La1-xGdxPO4 rhabdophane doped with approximately 50 ppm Cm3+ was obtained. An aliquot of the obtained solid phase was thereafter sintered at 1450°C to acquire the crystalline monazite ceramic. Structural refinement of collected XRD data for both rhabdophane and monazite solids show a linear dependency of lattice parameters as a function of Gd3+ substitution according to Vegard’s law.
Our combined spectroscopic results show that Cm3+ is incorporated in the monazite end-members (LaPO4 and GdPO4) on one specific, highly ordered lattice site. In the intermediate solid solution compositions, an increasing disorder around the Cm3+ dopant can be seen as a result of a broader distribution of possible Cm∙∙∙O bond-lengths in comparison to the end-member compositions with very well-defined nearest neighbour distances. Despite this local structural disordering, homogenous solid solutions were obtained for all synthesized monazite compositions without the formation of dopant clusters that could potentially hamper the performance of the monazite ceramics for the immobilization of minor actinide containing wastes.
The hydrated rhabdophane lattice comprises two different site types that could accommodate the actinide dopant: a 9-coordinated “hydrated” site amounting to two thirds (2/3) of the total number of lanthanide sites in the solid structure, where one coordinating oxygen atom originates from a water molecule, and an 8-fold coordinated “non-hydrated” site (1/3 of available Ln sites) where all oxygen atoms are provided by phosphate groups [4]. Based on our laser spectroscopic investigations, curium incorporation on both site types can be confirmed, however, the site occupancy is not in agreement with the hydrated rhabdophane structure. In contrast, a preferential incorporation of curium on non-hydrated lattice sites can be seen, especially for the La-rich rhabdophane compositions, implying that structural substitution reactions cannot be predicted based on the structure of the host matrix only.

  • Lecture (Conference)
    4th International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 06.-09.11.2018, Nice, France

Publ.-Id: 28196

Inverted hysteresis and negative remanence in a homogeneous antiferromagnet

Opherden, L.; Billitewski, T.; Hornung, J.; Herrmannsdörfer, T.; Samartzis, A.; Islam, A. T. M. N.; Anand, V. K.; Lake, B.; Moessner, R.; Wosnitza, J.

Magnetic remanence—found in bar magnets or magnetic storage devices—is probably the oldest and most ubiquitous phenomenon underpinning the technological applications of magnetism. It is a macroscopic nonequilibrium phenomenon: A remanent magnetization appears when a magnetic field is applied to an initially unmagnetized ferromagnet, and then taken away. Here, we present an inverted magnetic hysteresis loop in the pyrochlore compound Nd2Hf2O7: The remanent magnetization points in a direction opposite to the applied field. This phenomenon is exquisitely tunable as a function of the protocol in field and temperature, and it is reproducible as in a quasiequilibrium setting.


Publ.-Id: 28195

Quantitative Modelling and Assessment for Circular Economy Systems

Bartie, N.; Fröhling, M.; Reuter, M. A.

Minerals and metals required to produce renewables and everyday electric and electronic technologies are extracted from both geological (primary) and urban (secondary, recycling) mines. Extraction and recycling process complexity is often neglected in impact assessments. Treatment of interconnected components in isolation is physically impossible, and should be reflected in impact assessments. Claims of completely closed loops neglect irreversible losses governed by the thermodynamics. Aggregation of complex processes into average “black boxes” reduces resolution, removing the ability to allocate impacts and optimise circular economy systems that are often geographically and temporally dispersed. We aim to expand and integrate existing frameworks, models and tools, including fundamental thermochemistry, process simulation, life cycle inventory and impact assessment, costing and thermoeconomics, and to utilise multi-criteria optimisation to conduct holistic assessments and optimisation of resource efficiency, losses and impacts of entire circular economies at high resolution. This will benefit stakeholders from operational through to policy-making levels.

Keywords: Life cycle; Recycling; Metals; Exergy; Thermodynamics; Holistic analysis

  • Poster
    Sustainable Minerals 2018, 14.-15.06.2018, Windhoek, Namibia

Publ.-Id: 28194

HILIC - A simple method to determine [18F]fluoride in plasma and tissue samples

Wenzel, B.; Moldovan, R.; Teodoro, R.; Deuther-Conrad, W.; Brust, P.

Objectives: The investigation of the metabolism of 18F-labeled radiotracers is a crucial step in the development process. Most often radio-defluorination as well as O- and N-dealkylation are observed resulting in the formation of very polar radiometabolites such as [18F]fluoride, [18F]fluoroethanol or [18F]fluoroacetic acid. Due to their high polarity these compounds are not easy to separate and analyze by the routinely used reversed phase HPLC. In a recent study we were faced with the problem of finding a high fraction of a very polar radiometabolite in brain samples of mice obtained after injection of a newly developed radiotracer, which seemed to be [18F]fluoride. However, as [18F]fluoride is not able to penetrate the blood-brain barrier to a considerable amount, we were interested to investigate the identity of this radiometabolite in the brain samples.

Methods: Hydrophilic interaction chromatography (HILIC) was selected as HPLC method since the elution order is more or less the reverse of the elution order in RP-HPLC. This is achieved by the use of a polar stationary phase and an aqueous mobile phase with a high content of organic solvent. In the present study, the retention and elution profile of [18F]fluoride was investigated by using a Nucleodur HILIC column (250 × 4.6 mm; Macherey-Nagel GmbH, Germany) and modifying the following parameters: i) organic solvent (e.g. CH3CN, CH3OH, THF), ii) pH value of the eluent, iii) concentration and nature of buffer additives (e.g. ammonium acetate, ammonium formate) and iv) isocratic and gradient mode. Typical investigated conditions comprised eluent compositions of 86-70% organic solvent/14-30% water, buffer concentrations ranging from 5 to 100 mM and acid concentrations of 0.05%.

The type of the organic solvent strongly influenced the retention of [18F]fluoride. Best results could be achieved with CH3CN, while with CH3OH almost no retention could be obtained. Also the pH value of the eluent played a crucial role. By using 0.05% trifluoroacetic acid (pH ~2) or formic acid (pH ~3) in the eluent, [18F]fluoride strongly retained on the stationary phase and eluted only at long retention times as very broad peak. The use of buffer systems at pH 6 to 8 improved the retention and the peak shape. Comparing ammonium formate and ammonium acetate the latter gave so far the best results. For example, under isocratic conditions at 74% CH3CN/20 mM NH4OAcaq, [18F]fluoride eluted at a retention time of 14 min while more lipophilic compounds such as typical 18F-labeled radiotracers elute close to the dead time of the column (A in Figure 1). Subsequently, this method was used to investigate homogenates of ex vivo brain samples of our newly developed P2Y1 receptor radiotracer [18F]1 (1-{2-[2-(tert-butyl)phenoxy]pyridin-3-yl}-3-[4-[18F](2-fluoroethyl)phenyl]urea) [1], and it could be demonstrated that the main radiometabolite observed in the brain after 30 min p.i. is indeed [18F]fluoride (B in Figure 1).

Figure 1: A) HILIC radio-chromatogram of a mixture of [18F]1 and [18F]fluoride, B) HILIC radio-chromatogram of a mouse brain sample at 30 min p.i. of [18F]1; conditions: Nucleodur HILIC, 250 x 4.6 mm, 74% CH3CN/20 mM NH4OAcaq, flow 1.0 mL/min.

Hydrophilic interaction chromatography is a simple and useful method to determine [18F]fluoride in biological samples such as plasma and brain homogenates. Further investigation is ongoing to further improve the retention profile and to use this method also for other typical polar radiometabolites such as [18F]fluoroacetic acid and [18F]fluoroethanol.

References: [1] Moldovan et al. Eur. J. Med. Chem. (in revision) "Studies towards the development of a PET radiotracer for imaging of the P2Y1 receptors in the brain: synthesis, 18F labeling and preliminary biological evaluation".

  • Lecture (Conference)
    ISRS 2019, 26.05.-01.06.2019, Beijing, China

Publ.-Id: 28193

Association of Eu(III) and Cm(III) onto an extremely halophilic archaeon

Bader, M.; Moll, H.; Steudtner, R.; Lösch, H.; Drobot, B.; Stumpf, T.; Cherkouk, A.

Regarding the final storage of high-level radioactive waste in a deep geological repository next to geological, geochemical and geophysical also microbial aspects have to be taken into account. Rock salt is a potential host rock formation for the repository. One in rock salt common indigenous microorganism is the halophilic archaeon Halobacterium noricense DSM15987T, which was used in our study to investigate its interactions with the trivalent actinide curium and its inactive analogue europium as function of time and concentration. Time-resolved laser-induced fluorescence spectroscopy was applied to characterize formed species in the µM europium concentration range. An extended evaluation of the data with parallel factor analysis revealed the association of Eu(III) to a phosphate compound released by the cells (F2/F1 ratio: 2.50) and a solid species (F2/F1 ratio: 1.80). The association to an aqueous phosphate species and a solid species could be proven with the site-selective TRLFS. Experiments with Cm(III) in the nM concentration range showed a time- and pCH+-dependent species distribution. These species were characterized by red shifted emission maxima, 600 – 602 nm, in comparison to the free Cm(III) aqueous ion, 593.8 nm. After 24 h 40 % of the luminescence intensity was measured on the cells corresponding to 0.18 µg Cm(III)/gDBM. Our results demonstrate that Halobacterium noricense DSM15987T interacts with Eu(III) by the formation of phosphate species, whereas for Cm(III) also a complexation with carboxylic functional groups was observed.

Publ.-Id: 28192

Experimental investigation on the buoyancy-induced flow in a model of the Czochralski crystal growth process

Pal, J.; Franke, S.; Eckert, S.; Gerbeth, G.

Within this paper we present a model experiment focusing on investigations of the flow field in a Czochralski puller. Low melting point liquid metals as GaInSn are an important tool to investigate the flow structure for such industrial processes. The topology of the prevailing thermally-driven convection might be very complex and is mainly determined by the aspect ratio of the liquid volume and the strength of the convection described by the characteristic dimensionless Grashof number. The measurements of the fluid flow have been conducted by means of the ultrasound Doppler velocimetry (UDV) with and without the influence of external magnetic fields. Two kinds of sensor configurations were used to investigate the flow. Firstly, measurements of the radial velocity component by means of single UDV transducers were carried out shortly below the melt surface across the entire diameter of the cylindrical liquid column at various azimuthal angles. Secondly, a vertically arranged UDV array was applied at the side of the cylinder to obtain more detailed information about the radial velocities in the covered meridional plane. The results reveal the complex flow structure of natural convection in a Czochralski crucible which gains in complexity with applied external magnetic fields.

Keywords: Czochralski crystal growth process

  • Lecture (Conference)
    Electromagnetic Processing of Materials 2018, 14.-18.10.2018, Awaji, Japan
  • Open Access Logo IOP Conference Series: Materials Science and Engineering 424(2018), 012011
    DOI: 10.1088/1757-899X/424/1/012011

Publ.-Id: 28191

The challenge of digitalising lead smelting with technology elements

Schalkwyk, R. F. Van; Reuter, M. A.; Stelter, M.

Technology elements (e.g. Te, Se, Ge) are crucial to the creation of complex products, e.g. photovoltaic cells, which also drive the circular economy. However, these elements introduce complexity when the waste materials (slags, flue dusts or electronic wastes) that contain them are treated in lead smelters. This strategy of treating wastes in lead smelters is followed to utilise existing infrastructure as far as possible. In order to address the complex metallurgy, a dynamic model of the furnaces that are operative in lead metallurgy is required. This project focuses on the laboratory measurements of thermodynamic and kinetic parameters that will be used to create a dynamic model of a Top Submerged Lance furnace.

Keywords: Top Submerged Lance furnace; Kinetics; Technology Elements; Modeling

  • Lecture (Conference)
    GDMB Lead Experts Meeting, 26.04.2018, Freiberg, Deutschland

Publ.-Id: 28190

Digitalizing the circular economy: Behaviour of technology elements during lead smelting

Schalkwyk, R. F. Van; Reuter, M. A.; Stelter, M.

Lead pyrometallurgical infrastructure plays an important role in the circular economy, due to the application of existing lead infrastructure and smelters for processing of secondary materials (e.g. electronics, flue dusts and waste slags). However, as the proportion of non-traditional secondary feed materials to smelters increases, so does the complexity. Better understanding is required of non-traditional and minor elements in lead metallurgy, e.g. Se.
During direct lead smelting, molten metal and slag phases form and minor elements are distributed amongst these. Se typically reports to the lead bullion and is removed from the bullion during refining stages. It is important to determine the metal/slag distribution in order to understand downstream process impacts and to avoid contamination of the final product.
Equilibration experiments are carried out in a laboratory furnace to determine slag/metal distributions of minor elements. At thermodynamic equilibrium, the distribution is affected by the temperature, slag composition, oxygen potential and interactions between elements in the melt. Results from equilibrium measurements and process implications will be discussed.

Keywords: Lead; Equilibrium; Selenium; Technology Elements; Circular Economy

  • Poster
    Sustainable Minerals, 14.-15.06.2018, Namibia, Namibia

Publ.-Id: 28189

Two-dimensional Pd3P2S8 Semiconductors as Photocatalysts for Solar Oxygen Evolution Reaction: A Theoretical Investigation

Jing, Y.; Heine, T.

On the basis of first principles calculations, we propose Pd3P2S8 monolayer and bilayer, two-dimensional semiconductors, whose layered bulk parent crystals are experimentally reported, as promising photocatalysts for the solar-driven oxygen evolution reaction. The monolayer is kinetically and thermodynamically stable and shows a small cleavage energy of 0.35 J m−2, suggesting that it can be prepared by exfoliation from its bulk material, and exhibits a direct band gap of 2.98 eV, which can be engineered by applying strain. The Pd3P2S8 bilayer is an indirect band gap semiconductor with a slightly smaller band gap of 2.83 eV. The photoexcited holes generate favorable driving forces for promoting the specific solar-driven O2 evolution reaction. The extraordinary electronic properties, pronounced light harvesting capability in the visible and ultraviolet regions and active surface sites render the Pd3P2S8 monolayer and bilayer as compelling 2D materials with interesting application potential for photocatalytic and photoelectrocatalytic water splitting.


  • Secondary publication expected

Publ.-Id: 28188

Cavitation energies can outperform dispersion interactions

He, S.; Biedermann, F.; Vankova, N.; Zhechkov, L.; Heine, T.; Hoffman, R. E.; de Simone, A.; Duignan, T. T.; Nau, W. M.

In this work we prepare Langmuir–Blodgett monolayers with a trifunctional amphiphilic anthraphane monomer. Upon spreading at the air/water interface, the monomers self-assemble into 1 nm-thin monolayer islands, which are highly fluorescent and can be visualized by the naked eye upon excitation. In situ fluorescence spectroscopy indicates that in the monolayers, all the anthracene units of the monomers are stacked face-to-face forming excimer pairs, whereas at the edges of the monolayers, free anthracenes are present acting as edge groups. Irradiation of the monolayer triggers [4 + 4]-cycloadditions among the excimer pairs, effectively resulting in a two-dimensional (2D) polymerization. The polymerization reaction also completely quenches the fluorescence, allowing to draw patterns on the monomer monolayers. More interestingly, after transferring the monomer monolayer on a solid substrate, by employing masks or the laser of a confocal scanning microscope, it is possible to arbitrarily select the parts of the monolayer that one wants to polymerize. The unpolymerized regions can then be washed away from the substrate, leaving 2D macromolecular monolayer objects of the desired shape. This photolithographic process employs 2D polymerizations and affords 1 nm-thin coatings.

Keywords: 2D polymerization; air/water interface; anthracene; fluorescence; photolithography; self-assembled monolayers


Publ.-Id: 28187

PtTe Monolayer: Two-Dimensional Electrocatalyst with High Basal Plane Activity toward Oxygen Reduction Reaction

Wang, Y.; Li, Y.; Heine, T.

PtTe is a layered bulk material that was discovered in 1897. According to first-principles calculations, it is one of the few layered materials that maintains structure and metallic character when thinned down to the monolayer. Interlayer energy is small enough to allow for chemical exfoliation techniques. Our calculations show that monolayer PtTe is a candidate to substitute Pt electrodes, and we computationally studied its catalytic performance in the oxygen reduction reaction (ORR). Remarkably, the basal plane of a PtTe monolayer exhibits excellent catalytic activity toward ORR, with a positive half-wave potential (∼0.90 V) and a high four-electron reduction pathway selectivity. These characteristics suggest that it outperforms Pt electrodes as catalyst, has a reduced Pt content, high Pt utilization, and a high surface area, and is a promising candidate for fuel cell components.


Publ.-Id: 28186

Target volumes in adaptive treatment of NSCLC show large discrepancies among experts

Apolle, R.; Appold, S.; Bussink, J.; Faivre-Finn, C.; Khalifa, J.; Lievens, Y.; de Ruysscher, D.; van Elmpt, W.; Troost, E. G. C.

Purpose or Objective
Target volume delineation is subject to inter-observer variability (IOV) and thus a major source of uncertainty in radiation treatment planning. IOV in the context of treatment adaptation is largely unknown. We analysed IOV of the primary gross tumour volume (GTV) and clinical target volume (CTV) in locally advanced NSCLC delineated by experts in the pre- and mid-treatment (PT and MT) setting.

Material and Methods
Five patients from routine clinical practice, who underwent repeat imaging, were selected such that a variety of features likely to prompt adaptation, e.g. atelectasis, central primary tumour, was included. Brief case reports and CT imaging data were sent to six observers, supplemented with FDG-PET studies in two cases at PT and three at MT. Observers received PT and MT imaging data at least one week apart and were asked to delineate the GTV and CTV in their own treatment planning system and to comment on their delineation process, i.e. on how GTV to CTV expansion and adaptation were performed. Delineations were rasterised on a 1mm³ grid and their compatibility assessed with the Generalised Conformity Index (CIgen). Differences in IOV between PT and MT were probed with Wilcoxon signed-rank tests and the correlation between GTV and CTV IOV evolution with Spearman rank correlation. While it is respectively impossible and very difficult for these tests to show two-sided α=0.05 significance at n=5, more powerful parametric alternatives cannot credibly be employed.

A total of 109/120 delineations were received and analysed. Figure 1 shows an overview of IOV in terms of volume overlap. All but one case saw a reduction of CIgen when transitioning from PT to MT (p=0.125 for both GTVs and CTVs). Agreement in corresponding GTV and CTV delineations was generally comparable at individual time points, and there was a trend of a correlation between GTV and CTV CIgen changes (ρ=0.9, p=0.083). This behaviour is consistent with almost all observers adopting an isotropic GTV to CTV expansion of 5 mm with rare editing for anatomical boundaries at either time point. MT GTV delineations were only occasionally adopted from PT after image registration (9/28 analysed observers and cases), the remainder contoured anew. Post-transfer adaptation to changed anatomy was performed by one observer, and inclusion of PT GTV in MT CTV by two. Figure 2 shows the two cases demonstrating the most extreme changes in IOV (improvement and deterioration). In both cases large volumes of consolidated lung lead to increased IOV, but at different time points. Shortcomings of this in silico contouring challenge were incomplete FDG-PET availability and a lack of contrast-enhanced CT, both current clinical standard. Modern MRI would also have been welcomed by many.

Differing approaches of reacting to intra-therapeutic changes further increase IOV in target volume delineation in the adaptive setting. Consensus guidelines and in-depth analysis of per-treatment tumour shrinkage patterns are urgently needed.

Keywords: Delineation

  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Mailand, Italien

Publ.-Id: 28185

Target volume delineation for adaptive treatment in HNSCC is highly variable among experts

Apolle, R.; Bijl, H. P.; Blanchard, P.; Laprie, A.; Madani, I.; Ruffier, A.; van Elmpt, W.; Troost, E. G. C.

Purpose or Objective
Inter-observer variability (IOV) in target volume delineation is a well-documented phenomenon and a major source of uncertainty in radiation treatment (RT) planning. The increasing adoption of adaptive RT adds a dynamic component to IOV, which is largely unknown. We analysed IOV in the pre- and mid-treatment (PT and MT) setting using expert primary gross tumour volume (GTV) and clinical target volume (CTV) delineations in locally advanced HNSCC.

Material and Methods
Five patients from routine clinical practice, who underwent repeat imaging, were selected such that a variety of features likely to prompt adaptation were included. Brief case reports and CT imaging data were sent to five observers, the latter supplemented with pre-therapeutic FDG-PET in four cases. Observers received PT and MT imaging data at least one week apart and were asked to delineate the GTV and CTV in their own treatment planning system and to comment on their delineation process, i.e. on how GTV to CTV expansion and adaptation were performed. Delineations were rasterised on a 1mm³ grid and their compatibility assessed with the Generalised Conformity Index (CIgen). Differences in IOV between PT and MT were probed with Wilcoxon signed-rank tests and the correlation between GTV and CTV IOV evolution with Spearman rank correlation. While it is respectively impossible and very difficult for these tests to show two-sided α=0.05 significance at n=5, more powerful parametric alternatives cannot credibly be employed. Delineations were processed with ITK and statistical analyses performed in R.

A total of 82/100 delineations were received and analysed. Figure 1 shows an overview of IOV in terms of volume overlap. All cases and volumes suffered a reduction of CIgen when transitioning from PT to MT (p=0.063 for both CTVs and GTVs). There was generally better agreement in CTV than GTV delineations at individual time points, and the correlation between GTV and CTV CIgen changes was very weak (ρ=0.5, p=0.45). This comparative robustness of CTV delineations might stem from GTV to CTV expansion practices, which overwhelmingly employed sizeable isotropic margins (mean: 7.6 mm) and additional editing for anatomical boundaries at both time points. Figure 2 shows a case in which CIgen for CTVs remains stable despite deteriorating IOV in the primary GTV. MT GTV delineations were often based on PT delineations after image registration (14/24 analysed observers and cases), the remainder contoured de novo. Post-transfer adaptation to changed anatomy was performed by two observers and inclusion of the PT GTV in the MT CTV by one. Shortcomings of this contouring challenge are a lack of MRI and contrast-enhanced CT at both time points.

IOV in target volume delineation increases during treatment, where a disparity in institutional adaptation practices adds to the static causes of IOV. Consensus guidelines are urgently needed and should recommend scope, frequency, and quality of MT imaging alongside adaptation strategies.

Keywords: Delineation

  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Mailand, Italien

Publ.-Id: 28184

Correction of Geometrical Effects of a Knife-Edge Slit Camera for Prompt Gamma-Based Range Verification in Proton Therapy

Petzoldt, J.; Janssens, G.; Nenoff, L.; Richter, C.; Smeets, J.

Prompt gamma (PG) based range verification can potentially reduce the safety margins in proton therapy. A knife-edge slit camera has been developed in this context using analytical PG simulations as reference for absolute range verification during patient treatment. Geometrical deviations between measurement and simulation could be observed and have to be corrected for in order to improve the range retrieval of the system. A geometrical correction model is derived from Monte Carlo simulations in water. The influence of different parameters is tested and the model is validated in a dedicated benchmark experiment. We found that the geometrical correction improves the agreement between measured and simulated PG profiles resulting in an improved range retrieval and higher accuracy for absolute range verification. An intrinsic offset of 1.4 mm between measurement and simulation is observed in the experimental data and corrected in the PG simulation. In summary, the absolute range verification capabilities of a PG camera have been improved by applying a geometrical correction model.


Publ.-Id: 28183

Rare-Earth orthophosphates from atomistic simulations

Ji, Y.; Kowalski, P. M.; Kegler, P.; Huittinen, N.; Marks, N.; Vinograd, V.; Arinicheva, Y.; Neumeier, S.; Bosbach, D.

Lanthanide phosphates (LnPO4 ) are considered as a potential nuclear waste form for immobilization of Pu and minor actinides (Np, Am and Cm). In that respect, in the recent years we have applied advanced atomistic simulation methods to investigate various properties of these materials on the atomic scale. In particular, we computed several structural, thermochemical, thermodynamic and radiation damage related parameters. From a theoretical point of view, these materials turn out to be excellent systems for testing quantum mechanics-based computational methods for strongly correlated electronic systems. On the other hand, by conducting joint atomistic modeling and experimental research, we have been able to obtain enhanced understanding of the properties of lanthanide phosphates. Here we discuss joint initiatives directed at understanding the thermodynamically driven long-term performance of these materials, including long-term stability of solid solutions with actinides and studies of structural incorporation of f elements into these materials. In particular, we discuss the maximum load of Pu into the lanthanide-phosphate monazites. We also address the importance of our results for applications of lanthanide-phosphates beyond nuclear waste applications, in particular the monazite-xenotime systems in geothermometry. For this we have derived a stateof-the-art model of monazite-xenotime solubilities. Last but not least, we discuss the advantage of usage of atomistic simulations and the modern computational facilities for understanding of behavior of nuclear waste-related materials.

Keywords: Rare-earth phosphates; Atomistic simulations; Monazite; Xenotime; nuclear waste management; Ceramics; Thermodynamics; solid solutions

Publ.-Id: 28182

Experimental Analysis of the effect of column feed pipe configurations on the flow morphology

Döß, A.; Schubert, M.; Hampel, U.

Droplets entrained by the vapor phase can drastically reduce the separation capacity of distillation columns and cause severe corrosion problems, process instabilities as well as higher emissions due to droplet carry-over into the downstream process units.
Intensive interactions between vapor and liquid phases favor droplet formation. Feed pipe and feed inlet are prone positions for such droplet formation, depending on flow rates, phase change and pipe geometry resulting in characteristic morphologies.
Several models are available to predict the flow regime for known liquid and vapor flow rates. However, these models and flow maps are often restricted to fully developed flows in straight pipes of small diameter only and do not account for the effects of various entrance lengths, larger diameters as well as bends found in industry. Thus, an experimental analysis is performed to study the effect of column feed pipe configurations on the evolving flow regime using the wire-mesh sensor technique (Fig. 1). Wire-mesh sensors visualize the dynamic flow structure in the pipe cross-section at high spatiotemporal resolution (1 to 3 mm, up to 10,000 Hz). This work is supported by the Federal Ministry for Economic Affairs and Energy (BMWi) based on a decision by the German Bundestag (FKZ 03ET1395D).

Keywords: Two-phase flow morphology; Horizontal feed pipe; Wire-mesh sensor; Pipe configuration

  • Poster
    ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018, 10.-13.09.2018, Aachen, Deutschland
    DOI: 10.1002/cite.201855425

Publ.-Id: 28181

Dynamic Aeration for Improved Oxygen Mass Transfer in the Wastewater Treatment Process

Herrmann-Heber, R.; Reinecke, S.; Hampel, U.

Wastewater treatment is responsible for about 1% of the total electric energy consumption in developed countries. The dynamic aeration method, which applies oscillations to the gas flow, shows a high potential for increase of oxygen mass transfer and energy efficiency of the biological wastewater treatment process. We investigated the mass transfer of pulsed aeration modes in comparison to constant flow aeration in a test geometry in a numerical study. The effects of flow rate, pulsation frequency, bubble size and injection depth on mass transfer were studied. Gas was pulsated with a square wave pattern in on/off mode for the application in aeration basins of wastewater treatment plants. A geometry with up to 4 m aeration depth was investigated. The air supply was pulsed with frequencies in the range of 0.1 to 4 Hz. An increase of oxygen mass transfer rate by up to 24% is determined compared to continuous aeration. Moreover, comparable mass transfer rates are achieved for lower gas mass flow rates during pulsation. Thus, air demand in compression and energy consumption can be reduced when dynamic aeration is applied.

Keywords: Wastewater aeration; pulsed aeration; oxygen mass transfer; CFD

  • Open Access Logo Chemical Engineering Journal 386(2020), 122068
    DOI: 10.1016/j.cej.2019.122068
  • Lecture (Conference)
    14th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS-14), 30.05.-03.06.2019, Guilin, China


Publ.-Id: 28180

Flow morphology in feed pipes: theoretical analysis and experimental investigation

Döß, A.; Schubert, M.; Hampel, U.; Schleicher, E.; Geipel, C.; Mehringer, C.; Flegiel, F.

Efficient separation in distillation columns driven by the thermodynamic non-equilibrium between vapor and liquid phase is achieved by high turbulence as well as large interfacial area. At the same time, intensive interactions between vapor and liquid phases result in the formation of droplets, whose entrainment by the vapor phase may drastically reduce the separation capacity. The feed pipe is a prone position for such droplet formation. Besides the flash evaporation, the evolving flow morphology in the feed pipe is decisive for the droplet generation.The flow morphology in pipes depends on fluid flow rates and properties as well as on the pipe geometry. Several models and flow regime maps for fully developed flows in small pipe diameters exist, relating operating conditions and flow morphology. However, industrial feed pipe configurations with larger diameters and bends are so far not studied.
Thus, an experimental study in feed pipes of 50 mm and 200 mm diameter is performed using the wire-mesh sensor technique (Fig. 1). The wire-mesh sensor visualizes the dynamic flow structure in the pipe cross-section at high spatiotemporal resolution (1 to 3 mm, up to 10,000 Hz). The obtained data are compared with the
state-of the art models to assess their applicability for feed pipes. This project is supported by the Federal Ministry for Economic Affairs and Energy (BMWi) based on a decision by the German Bundestag (FKZ 03ET1395D).

Keywords: Two-phase flow morphology; Horizontal feed pipe; Wire-mesh sensor

  • Lecture (Conference)
    ACHEMA 2018, Session: TERESA – Droplet entrainment and droplet reduction in mass transfer devices, 11.-15.06.2018, Fankfurt am Main, Deutschland

Publ.-Id: 28179

PREFACE: American Journal of Science, Vol. 318, November, 2018

Fischer, C.; Arvidson, R. S.; (Editors)

Research in fluid-solid interaction processes has expanded tremendously over the past few decades, with key fronts ranging from fundamental understanding of reaction kinetics to detailed predictions involving the release, migration, and retention of environmentally important components. This special issue of AJS showcases the diversity and progress of this research in a series of invited papers that also illustrate core problems and solutions.
A central theme is the challenge involved in the integration of reaction processes over length and time scales that span many orders of magnitude. At one end of this spectrum, both theoretical and modeling approaches have evolved to describe the very brief interactions at the molecular scale, allowing key insights into details of reaction mechanism. At the other, modeling approaches have focused on the longer reaction times and lengths that characterize macroscopic systems. Experimental and analytical observations are also now able to map the dynamics and reactivity of reacting surfaces at the pore scale and above, providing these modeling approaches with essential feedbacks towards validation of predictions and identification of aspects where improvement is needed.
The strong coupling between the two “worlds” of experimental and simulation approaches is perhaps the most important result of the last years of research in our field. A primary motivation for this special issue was to highlight this productive interaction. A second motivation was to mark the 60th birthday of Professor Andreas Lüttge. Starting his scientific work at Tübingen University, followed by appointments at Yale University, Rice University, and now at the University of Bremen, he has continued to pursue the productive synergy of these two activities via pioneering work combining kinetic Monte Carlo simulations with complementary observations of reacting mineral surfaces.

This special issue is published in two parts. This first part begins with theoretical work by Bender and Becker, involving the kinetics of interactions between redox-sensitive plutonyl species, iron, and hydroxyl radical. This work nicely illustrates a divide-and-conquer approach, elucidating the stepwise reaction sequence involved in the formation and configuration of various complexes. In so doing, it also provides a potential framework for approaching related problems in the context of interactions at mineral surfaces. The second contribution, by Churakov and Prasianakis, combines thermodynamic calculations and kinetic simulations. Here the authors use the scale of the pore itself as a central connector to elegantly link the atomistic description of mineral surface reactivity with structural and compositional heterogeneities of real materials. The third contribution, by Kim, Marcano, Ellis, and Becker, presents experimental data on the photocatalytic role of TiO2 nanoparticles in uranyl reduction, using a diverse array of organic ligands as electron donors. This study demonstrates the importance of understanding the environmental specificity of reactions at surfaces, documenting the sensitivity of reduction efficiency to both ligand and UV wavelength. The last paper in this special issue’s first part, by Gebauer, Raiteri, Gale, and Cölfen, provides insight into current discussions concerning the birth of crystal nuclei during homogeneous precipitation in solution. They provide a nice summary of the ongoing debate, and stimulate further examination of true nature of these processes, arguing that the “critical” aspect of these clusters lies not in their size, but in their dynamics.
This last point also bears on a larger fundamental problem: how to resolve our new and increasing knowledge of the kinetics of these microscopic interactions, with the conventional thermodynamic framework that has long guided our interpretations of interactions at the mineral-fluid interface, but which is also largely macroscopic in origin. In the near future, we will announce the second part of this special issue, with a specific focus on new experimental results that challenge conventional model predictions.

  • Book (Editorship)
    New Haven, Connecticut: American Journal of Science, Yale University, 2018
    DOI: 10.2475/09.2018.01

Publ.-Id: 28178

Use of immobilizing individual abdominal corset in patients with upper-GI tumors treated with proton beam irradiation

Thiele, J.; Schneider, S.; Valentini, C.; Lohaus, F.; Stefanowicz, S.; Haak, D.; Krause, M.; Hoffmann, A. L.; Troost, E. G. C.

Purpose/Objective: The irradiation of tumors, which are subject to respiration-induced motion is challenging for pencil beam scanning (PBS) based proton therapy due to the interplay effect and the temporally varying tissue densities along the beam path. Here, we report on the feasibility, tolerability and setup reproducibility of an individualized immobilization device for patients with tumors in the upper abdomen, who are treated with PBS.

Material/Methods: Since January 2018, nine patients with tumors in the upper abdomen (pancreas, liver and gall bladder) have been treated with PBS at our department. All patients eligible for this study underwent the following procedure within 10-days: (1) intra-tumoral implantation of three fiducial markers for target localization, (2) design of an individualized abdominal corset for motion reduction by abdominal compression, (3) abdominal MRI scan with intravenous contrast agent (c.a.) for target volume definition and tumor motion quantification, and (4) 4D-CT scan with c.a. for treatment planning. CT simulation and irradiation was performed with a vacuum mattress (Fig.1). Before each treatment fraction, the position of the target volume was verified with orthogonal X-ray imaging. First, a 2D/2D match with the DRRs was performed and then the position of the fiducial markers was verified (tolerance level: 3-5mm). In case this tolerance level was exceeded, a CT scan was performed in-room and the dose distribution was recalculated for plan comparison; in case of clinically relevant changes in the dose distribution, a new plan was calculated.

Result: All patients tolerated the marker implantation, the abdominal corset and the treatment well with no treatment interruptions. In 4 out of the 300 applied fractions (1,3%) the tolerance level of the fiducial markers was exceeded. For these fractions, the recalculated dose distribution nevertheless showed sufficient target coverage (Fig. 2). The entire treatment fraction (including patient positioning, setup verification and dose delivery) did not exceed the standard time slot of 30 minutes.

Conclusion: This study demonstrates that PBS-based proton therapy with an abdominal corset to reduce breathing motion of GI-tumors is feasible, well-tolerated by patients and provides a reproducible setup without prolonging the daily treatment time.

Publ.-Id: 28177

Implementation of CT-based attenuation maps of RT positioning devices in PET/MRI - online vs offline

Täubert, L.; Pfaffenberger, A.; Berker, Y.; Beuthien-Baumann, B.; Hoffmann, A. L.; Troost, E. G. C.; Koerber, S. A.; Kachelrieß, M.; Gillmann, C.

Purpose or Objective
Integrating PET/MR hybrid imaging into radiation treatment (RT) planning has great potential to improve tumor delineation and dose prescription. Since these scans must be acquired under treatment conditions, attenuation correction of RT positioning devices is necessary. Attenuation maps can be implemented either online (directly at the PET/MRI scanner) or offline (at another PC). In this study, we compare both methods and assess their impact on PET image quality using a CT-based user-generated attenuation map of an RT table overlay.
Material and Methods
CT images of an RT table overlay (in-house construction) were acquired on a stand-alone CT (Somatom Definition Flash, Siemens Healthineers, Erlangen, Germany) at 120 kV and 360 mAs. Based on the CT images, an attenuation map of the RT table overlay was calculated via the bilinear approach [1]. The RT table overlay was then mounted onto the patient table of the PET/MRI (Biograph mMR, Siemens Healthineers) and two sets of PET-measurements were taken using an active 68Ge phantom (32 MBq, 10 min scan time). The phantom was scanned with the RT table overlay (RT scan), and without the RT table overlay (reference scan). PET reconstructions of the phantom scans were performed online at the PET/MRI scanner and offline using the e7tools (Version VA20, Siemens Healthineers) with identical reconstruction parameters. For the PET-reconstructions of the RT scan, the attenuation map of the RT table overlay was implemented. Attenuation correction accuracy was evaluated by comparing PET activities between RT and reference scans in 10 ROIs placed every 10 slices along the phantom in longitudinal direction, both for the online and the offline reconstruction methods.
The RT table overlay attenuation map was successfully added to the hardware attenuation maps produced online and offline. Table 1 compares measured PET activities. For the online reconstruction, a mean percentage difference of 0.7% was found between the reference and the RT scan. For the offline reconstruction, a mean percentage difference of 1.4% was found. A systematic difference of around 500 Bq/ml was found between the online and offline reconstructions.
For the integration of PET/MRI in RT planning, attenuation correction of RT positioning devices is viable. The online reconstruction seems to be more accurate, but it has the disadvantage that the attenuation map must be removed from the system after every RT measurement to prevent an incorrect reconstruction of patient data that were not scanned in RT setup. Alternatively, offline reconstruction can be implemented at any PC via e7tools, and the reconstruction could be automated, thereby diminishing human error. The cause of the systematic signal difference in online and offline reconstruction needs to be investigated further.

Publ.-Id: 28176

Development of an anthropomorphic multimodality pelvis phantom for PET/MRI- and CT-based RT planning

Homolka, N.; Pfaffenberger, A.; Beuthien-Baumann, B.; Mann, P.; Schneider, V.; Johnen, W.; Runz, A.; Echner, G.; Hoffmann, A. L.; Troost, E. G. C.; Koerber, S. A.; Seco, J.; Gillmann, C.

The aim of the study is the further development of an anthropomorphic multimodality pelvis phantom (ADAM, [1]) for the integration of PSMA-PET/MRI-based treatment planning of prostate cancer patients.
CT and 3T-MRI characteristics of different tissue types are mimicked using agarose gels (Agarose NEEO Ultra-Qualität Carl Roth GmbH + Co. KG, Germany) mixed with different concentrations of Gadolinium (Gd, MultiHance® 0.5 M, Bracco Imaging Deutschland GmbH) and sodium fluoride (NaF, Carl Roth GmbH + Co. KG). Gels were scanned using a 3T PET/MRI (Biograph mMR, Siemens Healthineers, Erlangen, Germany) using a saturation recovery sequence with multiple inversion times and a spin-echo sequence with multiple echo times. Based on the resulting images, T1- and T2-relaxation times were determined using in-house written software. CT scans of the agarose mixtures were performed on a stand-alone CT scanner (Somatom Definition Flash, Siemens Healthineers) at 120kV and 390 mAs.
The gels can be doped with radioactive tracers to simulate tumors in PET. Agarose mixtures that agreed best with reference values derived from literature data [2-4] were subsequently doped with patient-specific activity concentrations of 18F and 68Ga (e.g. 3kBq/ml 68Ga and 11kBq/ml 18F for the primary tumor). Organ shells (prostate with two intraprostatic lesions,
ESTRO abstract Noa Homolka, Physics Track lymph nodes and bone metastases) were printed using a 3D printer (Stratasys Objet 300 Connex 3, print material: VeroClear). The doped, liquid agarose gels were filled into the organ shells where they solidified within seconds. Organ shells were scanned at the 3T PET/MRI scanner (PET acquisition time: 10 min, MRI: T2-weighted morphological sequence).
The final compositions of agarose gels are the following (given as mass fractions of agarose/NaF/Gd): Prostate (1.35%/3.2%/0.011%), tumor (2.25%/3.2%/0.0085%), lymph nodes (3.2%/1.4%/0.025%).
T1- and T2-relaxation times and CT numbers of the developed agarose gels fit well to reference values (Figure 1). Exemplary PET- and MR-images of a prostate with two intraprostatic lesions doped with 11 kBq/mL 18F are shown in Figure 2. The PET signal can be detected and the tumors appear hypointense on T2-weighted MRI.
Agarose gel mixtures with organ-specific MR-relaxation times at 3T and CT numbers have been developed and doped with radioactive tracers. The gels will be used in the pelvis phantom which will be central to simulate and optimize the technical workflow for the integration of PSMA-PET/MRI-based RT planning of prostate cancer patients.

Publ.-Id: 28175

Modelling of Complex Flow Sheets

van den Boogaart, K. G.; Kern, M.; Schach, E.; Krupko, N.; Hannula, J.; Menzel, P.; Prior, A.; Tolosana Delgado, R.

Complex multi-element ores, like the skarn ores from the AFK project and the Tellerhäuser pilot plant, are difficult to process due to their complex and fine-grained mineralogy. The valuable elements are enriched in various scales. The deposit hosts a very large, high-grade tin orebody, which is challenging to process because of the high energy consumption during grinding and the very fine-grained tin mineralisation. Traditional way of processing such ores would consist of a milling to desired liberation size, followed by a separation of cassiterite based on density or floatability properties. As it has been done historically due to the specific properties of the ore this approach however requires a selection between very intensive grinding with lots of fines, or less grinding with insufficient liberation, both approaches essentially leading to low final concentrate grades.
Unlike many other deposits, the Tellerhäuser skarn ore has a much more complex structure, which can be exploited with more advanced flow sheets. Additionally to the tin mineralization there is a substantial enrichment in multiple potential by-products. The fine-grained tin mineralization itself is locatedin lithologies (units of consistent geometallurgical, mineralogical and physical characteristics) dominated by tin free minerals. Despite a background concentration of unrecoverable tin as a trace element in the whole skarn body, the cassiterite mineralisation is localized within the ore body at mining block scale. It is thus possible to reject gangue material at various scales: Exploration based on mineralogical information allows distinguishing processable ore from gangue. A separation based on mineral groups allows to reject unmineralized skarns at various scales and to enrich preconcentrates for various by-products before cassiterite is liberated.
Applied in the right way, automated mineralogy data allows characterizing the spatial and mineralogical structure and physical properties of particles at various scales from mining blocks (selective processing), through cm-scale (sensor sorting), sub mm-scale (physical processing) down to µm scale (ultra-fine processing). This allows the prediction of potential separation behaviour of complex processing chains and thus to infer optimal separation criteria, separation thresholds, milling targets, mass streams, savings potential and environmental properties of all processing steps from mine to final concentrate.
In this way, the detailed understanding of the deposit and ore structure allows to model the different processing steps in an optimal scale and detail, combined to one flowsheet. The effect of imperfect processing behaviour can be quantified and understood in particle-level detail and used to determine suitable processing equipment.

Keywords: Automated Mineralogy; Particle Based Simulation

  • Invited lecture (Conferences)
    FAME Closure Conference, 05.-06.12.2018, London, Great Britain

Publ.-Id: 28174

Microbial diversity in an arid, naturally saline environment

Bachran, M.; Kluge, S.; Lopez-Fernandez, M.; Cherkouk, A.

The Arava Valley in Israel is a rock desert within the Great African Rift valley. Soil from this area is covered with a salt crust. Here, we report microbial diversity from arid, naturally saline samples collected near Ein Yahav from the Arava Valley by culture-independent as well as culture-dependent analysis. High-throughput sequencing of the hypervariable region V4 of the 16S rRNA gene revealed that the microbial community consists of halophiles from the domain Bacteria as well as Archaea. Bacterial diversity was mainly represented by the genus Salinimicrobium of the order Flavobacteriales within the phylum Bacteroidetes, from the gammaproteobacterial orders Alteromonadales and Oceanospirillales as well as representatives from the order Bacillales of the phylum Firmicutes. Archaeal diversity was dominated by euryarchaeal Halobacteria from the orders Halobacteriales, Haloferacales and Natrialbales. But more than 40 % of the sequences affiliated with Archaea were assigned to unknown or unclassified archaea. Even if taxonomic resolution of the 16S rRNA gene V4 region for Archaea is limited, this study indicates the need of further and more detailed studies of Archaea. By using culture-dependent analysis bacteria of the order Bacillales as well as archaea from all three halobacterial orders Halobacteriales, Haloferacales and Natrialbales including potentially novel species from the genera Halorubrum and Haloparvum were isolated.

Publ.-Id: 28173

Ultrasonic measurements of the flow field in foam and froth

Heitkam, S.; Nauber, R.; Richter, T.; Büttner, L.; Czarske, J.; Eckert, K.

In this work, the non-invasive Ultrasound-Doppler velocimetry has been used to measure the velocity distribution inside a liquid foam bulk for the first time. The foam flows upward in a transparent channel. Optical correlation algorithms and conductivity measurement provide reference data. An array of ultrasound transducers is mounted within the channel, sending bursts along the main flow axis and receiving the echoes. The penetration depth equals up to 0.2 meters. With purposely designed flows it is demonstrated, that the velocity uncertainty is below 15 percent and the spatial resolution better than 1 cm. In static experiments, the applicability to particle laden foam and froth has been estimated. These parameters allow for monitoring of industrial processes as well as scientific investigation of three-dimensional foam and froth flow on medium scales.

Keywords: Ultrasound Doppler Velocimetry; Foam flow

  • Lecture (Conference)
    ISUD 11 - 11th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 06.09.2018, Berlin, Germany

Publ.-Id: 28171

Neutron Imaging of Foam and Froth

Heitkam, S.; Lappan, T.; Rudolph, M.; Trtik, P.; Eckert, S.; Eckert, K.

The present contribution reports on the investigation of particle movement and drainage in unsteady foam and froth using Neutron Imaging (NI) (S. Heitkam et al. "Neutron imaging of froth structure and particle motion." Minerals Engineering, vol. 119, pp. 126-129, 2018.)

Froth flotation is one of the major separation processes in mining. Billions of tons per year of ore are treated by flotation worldwide. Despite the industrial relevance, measurement techniques for the observation of particle movement and liquid distribution inside the froth are limited.

In this situation, NI can reveal new insights on the mechanisms in froth flotation. NI is similar to radiography, but X-rays are replaced by neutrons. The neutrons pass through the measurement object, being partially attenuated. Then they hit a scintillator, generating photons that are observed by a high-speed camera. The advantage of NI in froth research is, that some materials (e.g. gadolinium) offer extremely high attenuation of neutrons. And also water attenuates neutrons about 30 times stronger than X-rays.

Keywords: Neutron Imaging; Foam; Froth

  • Lecture (Conference)
    EUFOAM, 10.07.2018, Liege, Belgium

Publ.-Id: 28170

Ultrasonic measurements of the velocity distribution inside foam

Heitkam, S.; Nauber, R.; Büttner, L.; Czarske, J.; Eckert, K.

The flowing behavior of liquid foam and froth is not yet well investigated. One reason for that is, that adequate measurement techniques are scarcely available. Also, industrial foam applications could be improved by monitoring the foam flow in the process.

In this work, the ultrasound Doppler velocimetry is used to measure the velocity distribution inside liquid foam. (Nauber et al. “Ultrasonic measurements of the bulk flow field in foams.”, Physical Review E, vol. 97 (1), pp 013113, 2018). To that end, an array of five ultrasound transducers is positioned inside a foam channel. One transducer sends pulses into the foam and the others receive the echoes. Sound pulses are reflected at moving particles and air-liquid interfaces. The echoes reveal the longitudinal velocity distribution along the beam axis. Multiplexing of the array allows for 2D-1C measurement.

Keywords: Ultrasound Doppler Velocimetry; Foam flow

  • Lecture (Conference)
    EUFOAM, 10.07.2018, Liege, Belgium

Publ.-Id: 28169

Phase-resolving simulation of dense bubble clusters under periodic shear

Heitkam, S.; Fröhlich, J.

The paper studies the response of a cluster of bubbles to osmotic pressure, and steady and oscillatory shearing by resolved numerical simulations. In contrast to other investigations, the movement of the interstitial fluid is fully resolved. To that end, an immersed-boundary method is employed, yielding the trajectory of each bubble and the flow and pressure field of the fluid. Additionally, a physically motivated collision model ensures realistic bubble interactions. Furthermore, a suitable numerical configuration is proposed which allows imposing osmotic pressure and shear in a way that integrates well into the simulation without generating artefacts. This method allows for the realistic investigation of the compression of bubbles across the jamming limit, demonstrating the influence of the inertia of the interstitial fluid. Applying oscillatory shearing with varying osmotic pressure, shear stress and frequency, the occurrence of shear bands is demonstrated and the influence on rheometric measurements is discussed.

Keywords: Bubbles; Simulation; Rheology; Foam


Publ.-Id: 28168

Improving the range accuracy in particle therapy: Wrap up of the workshop

Richter, C.

Summary of the workshop results

  • Lecture (Conference)

Publ.-Id: 28167

Improving range accuracy in particle therapy: Introduction of the workshop

Richter, C.

Introduction of the workshop

  • Lecture (Conference)

Publ.-Id: 28166

Hochpräzisions-Strahlentherapie: Mit Protonen gegen Krebs

Richter, C.


  • Invited lecture (Conferences)
    50. Kraftwerkstechnisches Kolloquium, 23.-24.10.2018, Dresden, Deutschland

Publ.-Id: 28165

Dual-energy CT for automatic organ at risk segmentation in brain tumor patients using a multi-atlas and deep-learning approach

van der Heyden, B.; Wohlfahrt, P.; Troost, E.; Terhaaf, K.; Eekers, D.; Richter, C.; Verhaegen, F.

In radiotherapy, computed tomography (CT) datasets are frequently used to calculate radiation treatment plans to interpret dose evaluation metrics in healthy surrounding organs that need to be spared, the organs at risk (OARs). Based on CT scan and/or magnetic resonance images, the OARs have to be delineated by hand which is one of the most time-consuming tasks in the clinical radiotherapy workflow. Recent multi-atlas (MA) or deep learning (DL) based methods aim to improve the clinical workflow by automatically segment the OARs on a CT dataset. However, no studies investigated the performance of these MA or DL methods on dual-energy CT datasets which have been shown to improve the image quality compared to 120 kVp single-energy CT. In this study, the in-house developed MA method and the DL method (two-step three dimensional U-net) are described first. Then, the performance of both approaches (MA and DL) was quantitatively and qualitatively evaluated on various dual-energy CT datasets, more specifically on pseudo-monoenergetic CT dataset that were generated between 40 keV and 170 keV.

Publ.-Id: 28164

Log file based dose reconstruction and accumulation for 4D adaptive pencil beam scanned proton therapy in a clinical treatment planning system: Implementation and proof-of-concept

Meijers, A.; Jakobi, A.; Stützer, K.; Marmitt, G.; Both, S.; Langendijk, J.; Richter, C.; Knopf, A.

Background and Purpose
Motion induced uncertainties hamper the clinical implementation of pencil beam scanning proton therapy (PBS-PT). Prospective pre-treatment evaluations only provide multi-scenario predictions without giving a clear conclusion for the actual treatment. Therefore, in this proof-of-concept study we present a methodology for a fraction-wise retrospective 4D dose reconstruction and accumulation aiming at the evaluation of treatment quality during and after treatment.
Material and Methods
We implemented an easy-to-use, script-based 4D dose assessment of PBS-PT for patients with moving tumours in a commercially available treatment planning system. This 4D dose accumulation uses treatment delivery log files and breathing pattern records of each fraction as well as weekly repeated 4D-CT scans acquired during the treatment course. The approach was validated experimentally and was executed for an exemplary data set of a lung cancer patient.
The script-based 4D dose reconstruction and accumulation was implemented successfully, requiring minimal user input and a reasonable processing time (around 10 minutes for a fraction dose assessment). An experimental validation using a dynamic CIRS thorax phantom confirmed the precision of the 4D dose reconstruction methodology. In a proof-of-concept study, the accumulation of 33 reconstructed fraction showed a linear increase of D98 values. Projected treatment course D98 values revealed a CTV under dosage after fraction 25. This loss of target coverage was confirmed in a DVH comparison of the nominal, the projected (after 16 fractions) and the accumulated (after 33 fractions) dose distribution.
The presented method allows for the assessment of the conformity between planned and delivered dose as the treatment course progresses. The implemented approach considers the influence of changing patient anatomy and variations in the breathing pattern. This facilitates treatment quality evaluation and supports decisions regarding plan adaptation. In a next step, this approach will be applied to a larger patient cohort to investigate its capability as 4D quality control and decision support tool for treatment adaptation.


Publ.-Id: 28163

Large refrigerant capacity induced by table-like magnetocaloric effect in amorphous Er0.2Gd0.2Ho0.2Co0.2Cu0.2 ribbons

Li, L.; Xu, C.; Yuan, Y.; Zhou, S.

The microstructure, magnetism, and magnetocaloric properties in melt-spun Er0.2Gd0.2Ho0.2Co0.2 Cu0.2 ribbons were reported. The ribbons are fully amorphousized and all the constituent elements are distributed uniformly. The large table-like magnetocaloric effect (MCE) from 25 to 75 K has been observed, resulting in a large value of refrigerant capacity (RC). With the magnetic field change (μ0H) of 0–5 T, the values of maximum magnetic entropy change (−Smax M ) reaches 11.1 J/kg K, and the corresponding value of RC are as large as 806 J/kg, make the amorphous Er0.2Gd0.2Ho0.2Co0.2Cu0.2 ribbons extremely attractive for cryogenic magnetic refrigeration.

Keywords: Table-like magnetocaloric effect; Er0.2Gd0.2Ho0.2Co0.2Cu0.2 amorphous ribbons; large refrigeration capacity

Publ.-Id: 28162

Dual-energy computed tomography for improved delineation in postoperative brain-tumor patients

Wohlfahrt, P.; Agolli, L.; Pilz, K.; Richter, C.; Troost, E.

The clinical use of dual-energy CT (DECT) contributes to an improved accuracy in proton treatment planning compared to single-energy CT (SECT) as demonstrated in recent studies. A precise delineation of tumor volumes and organs at risk (OARs) is essential in particular for emerging high-conformal treatment techniques. Since DECT provides additional tissue information and allows for the generation of various tissue contrasts, we assessed its influence on the intra- and inter-observer delineation variability.
Two cohorts of 10 postoperative brain-tumor patients each, receiving either a 120kVp SECT or 80/140kVp DECT scan with identical total dose, were evaluated. Pseudo-monoenergetic CT (MonoCT) datasets of 50, 60, 70 and 79keV, representing several tissue contrasts, were derived from DECT scans processed in syngo.via (Siemens Healthineers). Three radiation oncologists with different levels of experience in neuro-oncology delineated the postoperative tumor bed volume (TBV) and OARs (brainstem, parotid and lacrimal glands, eyes, lenses, optic nerves, and chiasm) on each dataset, at least two-weeks apart per patient. Relevant image information was blinded. The delineations on SECT datasets were repeated once to assess the intra-observer variability. Finally, the delineation was also performed on T1/T2 MR scans as clinical reference.
The contour conformity was quantified by the Jaccard index (JI) and Hausdorff distance (HD) between the intersection and union of the respective contours (Fig. 1).
The median inter-observer TBV conformity (Fig. 2A) was almost independent from the CT dataset (HD=6-9mm, JI=61-66%) and comparable to MR scans (HD=6-7mm, JI = 66-67%). The consistency of brainstem contours (Fig. 2B) was best at the lowest energy of MonoCT datasets (median HD=2.8mm, JI=81%). In contrast, the contour conformity of the parotid glands (Fig. 2C) gained slightly from an increased energy (median HD reduction of 0.6mm, JI increase of 1%) and also led to better results as MR scans. For these OARs, using the most suitable MonoCT instead of SECT resulted in smaller interobserver variations. No relevant differences between SECT and MonoCT were determined for the other OARs, potentially due to their small volume.
The intra-observer TBV variability obtained on SECT did not depend on clinical experience. However, the contouring of less experienced clinicians is more affected by different image contrasts introduced by MonoCT of different energies (Fig. 2D).
For postoperative brain-tumor patients, DECT-derived MonoCT datasets can improve the intra- and inter-observer delineation conformity compared to the currently used SECT. Moreover, they in part led to similar or better results as the gold standard MR. The most suitable image contrast to meet individual delineation requirements of anatomical structures can be chosen after CT acquisition. Future studies need to show whether the advantages can also be translated to other tumor entities and body regions.

  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Milano, Italia
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 133(2019), S559-S560
    DOI: 10.1016/S0167-8140(19)31432-X

Publ.-Id: 28161

Glassy formation ability, magnetic properties and magnetocaloric effect in Al27Cu18Er55 amorphous ribbon

Li, L.; Xu, C.; Yuan, Y.; Zhou, S.

In this work, we have fabricated the Al27Cu18Er55 amorphous ribbon with good glassy formation ability by melt-spinning technology. A broad paramagnetic (PM) to ferromagnetic (FM) transition (second ordered) together with a large reversible magnetocaloric effect (MCE) in Al27Cu18Er55 amorphous ribbon was observed around the Curie temperature TC 11 K. Under the magnetic field change (DH of 0–7 T, the values of MCE parameter of the maximum magnetic entropy change (DSM max) and refrigerant capacity (RC) for Al27Cu18Er55 amorphous ribbon reach 21.4 J/kg K and 599 J/kg, respectively. The outstanding glass forming ability as well as the excellent magneto-caloric properties indicate that Al27Cu18Er55 amorphous could be a good candidate for low temperature magnetic refrigeration.

Keywords: Al27Cu18Er55 amorphous ribbon; Magnetocaloric effect; Magnetic properties; Magnetic refrigeration

Publ.-Id: 28160

Range verification in proton therapy: Can prompt-gamma imaging identify the source of deviation?

Khamfongkhruea, C.; Janssens, G.; Petzoldt, J.; Smeets, J.; Pausch, G.; Richter, C.

Purpose/ Objective
In-vivo prompt-gamma imaging (PGI) is a promising method for directly assessing deviations in the proton range during proton therapy. However, several effects that can cause range shifts in patients need to be distinguished, e.g. global errors in CT conversion to stopping power ratio (SPR), variations in patient setup, and changes in the patient anatomy. Here, we evaluate if the source of range deviation in proton pencil-beam scanning (PBS) can be distinguished based on PGI information using a slit camera [1].
Material and Methods
For a virtual head-and-neck tumor in an anthropomorphic head phantom, a PBS treatment plan with simultaneous integrated boost (3 beams, 70Gy and 57Gy in 33 fractions) was generated. For all PBS spots in the investigated beam, PGI profiles were simulated using a verified analytical model of the slit camera [2, 3] for the reference scenario as well as for different error scenarios: SPR change of ±1.0, ±2.0 and ±3.5%, setup error in beam direction of ±1mm and ±3mm, and 10 scenarios of realistic anatomical changes (Fig. 1). A decision-tree approach was proposed to classify different groups of error sources. This included preceding filtering of PBS spots containing reliable PGI information for range verification. For simplification and better hypothesis generation, the head phantom was first overridden with water density. Afterwards, the real phantom anatomy including all heterogeneities was analyzed. It was evaluated whether the different error scenarios could be classified correctly.

An automated filter to identify reliable PBS spots was developed, e.g. assuring that the spot position is within the effective field of view (FOV) of the camera and that the fall-off of the PGI profile is completely included in the FOV – even in case of range shifts. For subsequent decision-tree-based error source classification (Fig. 2), the following parameters were selected: The coefficient of determination (R2), the slope and intercept of the linear regression between range shift and penetration depth as well as the 2D range shift map. With this approach, 27 of 30 error scenarios could be identified correctly. However, the three error scenarios with anatomical changes in the nasal cavity could not be identified because the automated filtering approach had removed most relevant spots in this region.
An automated classification approach was introduced to identify the source for range deviation solely from prompt-gamma information. Based on phantom data, including simulation of realistic anatomical variation, the results are promising. Further refinement of this initial approach might be beneficial. An extension of the validation with patient CT data is in preparation. In the future, an application of the approach on clinically measured PGI data is planned. Also other classification methods could be evaluated.

  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Milano, Italia
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 133(2019), S296-S297
    DOI: 10.1016/S0167-8140(19)30986-7

Publ.-Id: 28159

Neutronen-Imaging von partikelbeladenen Schäumen

Heitkam, S.; Rudolph, M.; Lappan, T.; Sarma, M.; Eckert, S.; Trtik, P.; Lehmann, E.; Vontobel, P.; Eckert, K.

Die Flotation ist ein Trennverfahren mit großer industrieller Bedeutung, beispielsweise in der Gewinnung von Elementen aus Erzen. Dabei werden die Erze gemahlen und in Wasser suspendiert. Durch Zugabe geeigneter oberflächenaktiver Substanzen werden die gewünschten Partikel selektiv hydrophobisiert. Dadurch haften sie an eingebrachten Gasblasen an, werden an die Oberfläche transportiert und dort in sich bildenden Schaum eingelagert. Der Schaum wird abgezogen und man erhält gewünschte Partikel in hoher Konzentration.

Keywords: Neutron Imaging; Froth flotation

  • Lecture (Conference)
    Dechema Jahrestreffen, 06.03.2018, Bremen, Deutschland

Publ.-Id: 28158

p-type co-doping effect in (Ga,Mn)As: Mn lattice location and magnetic phase transition

Xu, C.; Yuan, Y.; Wang, M.; Zhou, S.; Helm, M.

III-Mn-V based diluted magnetic semiconductors offer an opportunity to explore various aspects of carrier transport in the presence of cooperative phenomena [1]. In this work, we demonstrate the efficiency of an alternative approach to control the carrier state through involving one magnetic impurity Mn and one electrically active dopant Zn. Mn-doped and Zn co-doped GaAs films have been prepared by combining ion implantation and pulsed laser melting, followed by a systematic investigation on the magnetic and transport properties of (Ga,Mn)As by varying Mn concentration as well as by Zn co-doping. Changes of electrical, magnetic and magneto-transport behavior of the investigated (Ga,Mn)As were observed after co-doping with Zn. The changes are caused by interstitial Mn atoms which are transferred from substitutional sites or formation of Mn-Zn dimers.

Keywords: Dilute ferromagnetic semiconductor; ion implantation; co-doping; magnetic properties

  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft 2018, 11.-16.03.2018, Berlin, Deutschland
  • Lecture (Conference)
    Ion Implantation and other Applications of Ions and Electrons 2018, 18.06.-21.11.2018, Kazimierz Dolny, Poland

Publ.-Id: 28157

Tracking of particles in froth using neutron imaging

Heitkam, S.; Lappan, T.; Eckert, S.; Trtik, P.; Eckert, K.

In this study, neutron imaging is employed to investigate the movement of hydrophobic particles in a rising froth column. A cylindrical batch-flotation cell is mounted to a rotary stage, allowing for three-dimensional analysis. Gadolinium particles of 200 μm diameter are hydrophobized and floated by means of small air bubbles. The generated froth is investigated by neutron imaging. Using particle-tracking and a reconstruction algorithm for the third dimension, the movement of particles in the froth is analyzed. Varying the concentration of the frother sodium oleate, different froth stabilities are compared. It has been found, that with decreasing froth stability bubble rupture leads to higher horizontal diffusion of particles and to higher agglomeration of particles.

Keywords: Froth; Particle laden Foam; Particle Tracking; Neutron Radiography; Neutron Imaging


Publ.-Id: 28156

All-optical structuring of laser-driven proton beam profiles

Obst-Hübl, L.; Ziegler, T.; Brack, F.-E.; Branco, J.; Bussmann, M.; Cowan, T. E.; Curry, C. B.; Fiuza, F.; Garten, M.; Gauthier, M.; Göde, S.; Glenzer, S. H.; Huebl, A.; Irman, A.; Kim, J. B.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Pausch, R.; Prencipe, I.; Rehwald, M.; Rödel, C.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

Extreme field gradients intrinsic to relativistic laser-interactions with thin solid targets enable compact MeV proton accelerators with unique bunch characteristics. Yet, direct control of the proton beam profile is usually not possible. Here we present a readily applicable all-optical approach to imprint detailed spatial information from the driving laser pulse onto the proton bunch. In a series of experiments, counter-intuitively, the spatial profile of the energetic proton bunch was found to exhibit identical structures as the fraction of the laser pulse passing around a target of limited size.
Such information transfer between the laser pulse and the naturally delayed proton bunch is attributed to the formation of quasi-static electric fields in the beam path by ionization of residual gas. Essentially acting as a programmable memory, these fields provide access to a higher level of proton beam manipulation.

Keywords: laser plasma interaction; laser particle acceleration; novel accelerator concepts; high performance computing; high power lasers

Related publications

  • Open Access Logo Nature Communications 9(2018), 5292
    DOI: 10.1038/s41467-018-07756-z
  • Lecture (Conference)
    Advanced Accelerator Concepts Workshop 2018, 13.-17.08.2018, Breckenridge, USA
  • Poster
    Advanced Accelerator Concepts Workshop 2018, 13.-17.08.2018, Breckenridge, USA
  • Lecture (Conference)
    Matter and Technologies Annual Meeting, 12.-14.06.2018, Berlin, Deutschland
  • Lecture (Conference)
    Matter and Technology Meeting, 06.03.2019, Jena, Deutschland

Publ.-Id: 28155

Nematicity of correlated systems driven by anisotropic chemical phase separation

Yuan, Y.; Hübner, R.; Birowska, M.; Xu, C.; Wang, M.; Prucnal, S.; Jakiela, R.; Potzger, K.; Böttger, R.; Facsko, S.; Majewski, J. A.; Helm, M.; Sawicki, M.; Zhou, S.; Dietl, T.

The origin of nematicity, i.e., in-plane rotational symmetry breaking, and in particular the relative role played by spontaneous unidirectional ordering of spin, orbital, or charge degrees of freedom, is a challenging issue of magnetism, unconventional superconductivity, and quantum Hall effect systems, discussed in the context of doped semiconductor systems such as Ga1−xMnxAs, CuxBi2Se3, and Ga(Al)As/AlxGa1−xAs quantum wells, respectively. Here, guided by our experimental and theoretical results for In1−xFexAs, we demonstrate that spinodal phase separation at the growth surface (that has a lower symmetry than the bulk) can lead to a quenched nematic order of alloy components, which then governs low-temperature magnetic and magnetotransport properties, in particular the magnetoresistance anisotropy whose theory for the C_2v symmetry group is advanced here. These findings, together with earlier data for Ga1−xMnxAs, show under which conditions anisotropic chemical phase separation accounts for the magnitude of transition temperature to a collective phase or merely breaks its rotational symmetry. We address the question to what extent the directional distribution of impurities or alloy components setting in during the growth may account for the observed nematicity in other classes of correlated systems.


Publ.-Id: 28154

Modeling the gluon and ghost propagators in Landau gauge by truncated Dyson-Schwinger equations

Kaptari, L. P.; Kämpfer, B.; Zhang, P.

We suggest a framework based on the rainbow approximation with effective parameters adjusted to lattice data. The analytic structure of the gluon and ghost propagators of QCD in Landau gauge is analyzed by means of numerical solutions of the coupled system of truncated Dyson-Schwinger equations. We find that the gluon and ghost dressing functions are singular in complex Euclidean space with singularities as isolated pairwise conjugated poles. These poles hamper solving numerically the Bethe-Salpeter equation for glueballs as bound states of two interacting dressed gluons. Nevertheless, we argue that, by knowing the position of the poles and their residues, a reliable algorithm for numerical solving the Bethe-Salpeter equation can be established.


Publ.-Id: 28153

Towards Measuring Vacuum Birefringence

Schlenvoigt, H.-P.

We will present a design study how one could detect vacuum birefringence when combining an ultra-intense optical laser and an X-ray free electron laser. By means of precision X-ray polarimetry, one may detect the polarization flip of X-ray photons induced by the ultra-strong laser fields as a signature of vacuum birefringence. We will discuss crucial experimental parameters and provide a comprehensive model to study the experimental feasibility.

Keywords: Hibef

  • Lecture (Conference)
    27th Annual International Laser Physics Workshop, 16.-20.07.2018, Nottingham, UK

Publ.-Id: 28151

Oxygen diffusion in bcc Fe under the influence of foreign atoms and vacancies

Wang, X.; Posselt, M.; Faßbender, J.

A multiscale approach including Density Functional Theory (DFT) and Atomistic Kinetic Monte Carlo (AKMC) simulations is applied to investigate the diffusion of oxygen in bcc Fe under the influence of substitutional foreign atoms or solutes (Al, Si, P, S, Ti, Cr, Mn, Ni, Y, Mo, W) and vacancies. The solutes can be assumed to be immobile since their diffusion coefficient is much smaller than that of oxygen. On the other hand, the vacancy mobility must be considered in the calculations because it is comparable to that of oxygen. The most stable state of oxygen in pure bcc Fe is the octahedral interstitial configuration. Recently, jumps of oxygen in pure bcc Fe, between first-, second-, and third-neighbor octahedral interstitial sites were investigated by DFT. It was found that the first-neighbor jump is most relevant. The second-neighbor jump consists of two consecutive first-neighbor jumps whereas the barrier of the third-neighbor jump is too high to be significant for the diffusion process. In this work DFT is used to determine the modified migration barriers in the presence of solutes. It is found that Si, P, Ni, Mo and W have some effect on the migration barriers of oxygen and their interaction with O is mainly repulsive. Al, Cr and Mn have a significant influence on the barriers and they exhibit strong attractive interactions with O. The most important modification of the barriers is found for S, Ti, and Y where deep attractive states exist. The barriers for oxygen jumps near a vacancy and barriers for vacancy jumps in the environment of oxygen are also calculated by DFT. Based on the migration barriers obtained by DFT, AKMC simulations on a rigid lattice are employed to determine the diffusion coefficient of oxygen in a dilute iron alloy containing different substitutional foreign atoms. It is found that Si, P, Ni, Mo, and W have almost no influence on the diffusivity of O. The presence of Al, Cr, Mn, S, Ti, and Y causes a significant reduction of the mobility of oxygen. Another version of the AKMC code is applied to investigate the mutual influence of oxygen and vacancy diffusion as well as the migration of the oxygen-vacancy pair.

Keywords: oxygen; diffusion; bcc-Fe; Density Functional Theory; Atomistic Kinetic Monte Carlo simulations

  • Lecture (Conference)
    9th Int. Multiscale Materials Modeling conference (MMM 2018), 28.10.-02.11.2018, Osaka, Japan

Publ.-Id: 28150

Transmission Electron Microscopy at the Helmholtz-Zentrum Dresden-Rossendorf

Hübner, R.

Transmission Electron Microscopy at the Helmholtz-Zentrum Dresden-Rossendorf

  • Lecture (others)
    Forschungsseminar Nanochemie, Physkalische Chemie, Technische Universität Dresden, 05.11.2018, Dresden, Deutschland

Publ.-Id: 28149

Operating three research infrastructures at one site: electrons & photons, ions, magnetic fields

Helm, M.

Operating three research infrastructures at one site: electrons & photons, ions, magnetic fields

Keywords: research infrastructure; large-scale facility

  • Invited lecture (Conferences)
    Conference on International Cooperation of Science Centers, 19.10.2018, Huairou, China

Publ.-Id: 28147

Review of the International Standard ISO 2975 on Tracer methods for the measurement of single-phase flows in closed conduits

Jentsch, T. B. O.; Thereska, J.; Brisset, P.

Flow rate measurement is the most applied radiotracer method for online calibration and mass balance control in industrial processing. Better than 1-2% accuracy is achievable.

ISO Standards for measurements of fluid flows with tracer methods drafted years ago have been as follows:
ISO 2975 Measurement of water flow in closed conduits-Tracer methods, which consists of 7 parts, some of them never applied and others became obsolete.
ISO 4053 Measurement of gas flow in conduits -Tracer methods, which has been withdrawn for unknown reasons in 2003 leaving a void on this subject.

It is due time to review the existing ISO 2975, in the light of new development in radiotracer methods and industrial processing market.

The Sub Committee (SC) 5 of Technical Committee (TC) 30 of International Standardization Organization (ISO) - shortly: ISO/TC 30/SC 5 - is responsible for periodically reviewing ISO standard in the field of fluid flow measurements. Currently, the SC5 consists of 25 P member states and 11 observing member states (O-members).

Every five years the ISO TC30 SC5 initiates a so-called systematic review of each ISO standard. The last one for the ISO 2975 standard was carried out in 2018.

American Society of Mechanical Engineers (ASME) has adopted the American National Standard MFC-13M – 2006, which merges both ISO 2975 and ISO 4035. This Standard defines the terms and principles needed for intelligent consideration of tracer methods for any application, it can be serving as a good model for reviewing the ISO 2975.

The International Atomic Energy Agency (IAEA) and the International Society of Tracer and Radiation Applications (ISTRA) invites experts from all over the world to participate in the reviewing process of the existing ISO standards, formulating a more comprehensive, simple and universal ISO standard in this field. The new Standard on tracer methods for the measurement of single-phase fluid (gas or liquid) flows in closed conduits, will respond to the demand of industrial end-users.

Keywords: ISO 2975; International standard; fluid flow; measurement; mass flow rate; radiotracer

  • Lecture (Conference)
    Tracer8: The 8th International Conference on Tracers and Tracing Methods, 26.-28.02.2019, Đà Nẵng‎, Vietnam

Publ.-Id: 28146

Strategien zur Darstellung eines neuen 18F-markierten Adenosin-A2A-Rezeptorliganden zur PET-Bildgebung von Hirntumoren [1]

Lai, T. H.; Schröder, S.; Ludwig, F.-A.; Fischer, S.; Moldovan, R.-P.; Scheunemann, M.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Brust, P.

Ziel: Auf Grundlage einer Pyrazolo[2,3-d]pyrimidin-Leitverbindung[2] wurden 21 fluorierte Derivate synthetisiert. Basierend auf den dazu ermittelten Affinitäts- und Selektivitätsdaten für den humanen Adenosin-A2A-Rezeptor wurde das potente 4-Fluorbenzyl-Derivat 1 (Ki(A2A) = 5,3 nM; Ki(A1) = 220 nM) für die 18F-Markierung zur Darstellung eines neuen potentiellen A2A Radiotracers ausgewählt. Die gewünschte Position in 1 ist jedoch nicht für eine nukleophile aromatische Substitution gegen [18F]Fluorid aktiviert, sodass die Zielstellung in der Entwicklung einer geeigneten Radiosynthese von [18F]1 besteht.

Methodik: Es wurden drei Strategien zur Radiosynthese von [18F]1 verfolgt. Ausgehend vom Trimethylammonium-Präkursor 2 erfolgte die 18F-Markierung zum [18F]Fluorbenzaldehyd [18F]3. Dieser wurde entweder direkt über eine reduktive Aminierung oder nach Reduktion und anschließender Bromierung über eine Benzylierung mit dem Pyrazolo[2,3-d]pyrimidin-Baustein 4 zu [18F]1 umgesetzt. Parallel dazu wurde die direkte 18F-Markierung des Boronsäurepinacol-Präkursors 5 bearbeitet.

Ergebnisse: Ausgehend von 2 wurde [18F]1 nach der zweistufigen Radiosynthese mit nur 1,5% radiochemischer Ausbeute in der Reaktionsmischung detektiert (Radio-HPLC). Diese konnte mittels der vierstufigen Methode auf 49% gesteigert werden. In beiden Verfahren wurde eine hohe Anzahl an 18F-Nebenprodukten nachgewiesen, welche die Isolierung von [18F]1 mittels semi-präparativer HPLC erschweren. Die direkte 18F-Markierung von 5 führte zu einer radiochemischen Ausbeute von 80-90% an [18F]1 in der Reaktionsmischung (Radio-DC/-HPLC), wobei lediglich ein 18F-Nebenprodukt (< 5%) detektiert wurde.

Schlussfolgerungen: Aufgrund dieser Ergebnisse wird ausschließlich die einstufige Strategie zur Darstellung des neuen potentiellen A2A-Radiotracers [18F]1 ausgehend von 5 weiterverfolgt. Für die geplante biologische Evaluierung (in vitro und in vivo) werden derzeit geeignete Methoden zur Isolierung, Konzentration und Formulierung von [18F]1 erarbeitet.

[1] Allard et al., Immunol. Cell. Biol. 2017, 95(4), 333-339
[2] Gillespie et al., Bioorg. Med. Chem. Lett. 2008, 18, 2924-2929

Keywords: Adenosin A2A Rezeptor; Radiotracer; 18F; PET; Hirntumor

  • Lecture (Conference)
    26. Jahrestagung der AGRR, 20.-22.09.2018, Aachen, Deutschland

Publ.-Id: 28145

Poly-disperse simulation of flash evaporation of water inside a large vertical pipe using class method of population balance

Liao, Y.; Lucas, D.

Flash evaporation of superheated liquid to vapour by depressurization is frequently encountered in the nature and technology, but computational fluid dynamics modelling and simulation of such scenarios is still at the embryo stage. Attempts having been made before are all based on the assumption of mono-disperse bubbles by prescribing either the size or number density, which deviates largely from the physical picture. In the present work the poly-disperse multiple-size-group approach is used for the first time to simulate the water evaporation process under pressure release transients. Complex bubble dynamics and non-equilibrium processes such as bubble nucleation, growth, coalescence and breakup as well as interfacial heat transfer are accounted for. The comparison with experimental data demonstrates that the model is effective in capturing the temporal course of vapour bubbles’ generation and growth as well as their spatial distribution. The agreement between measured and simulated cross-section averaged flow parameters such as void fraction, liquid temperature and bubble size distribution is satisfying.

Keywords: bubble coalescence; bubble nucleation; flash evaporation; interfacial heat transfer; poly-disperse


  • Secondary publication expected

Publ.-Id: 28144

1-Dimensional inorganic double helices as candidates for information storage materials

Springer, M.; Kuc, A.; Vankova, N.; Heine, T.

Alkali metal monopnictides contain one-dimensional chains with a double-helical structure. In this work, we report about their possible use as information storage materials. We investigated computationally fundamental properties of hetero- and homocationic systems and ways towards the application. It was shown, that the phosphorous backbone is capable of stabilising cationic chains of different composition and thus allows encoding of information.

  • Poster
    Computational Spectroscopy: Bridging Theory and Experiment, 09.-14.09.2018, Como, Italien
  • Poster
    13th HZDR PhD seminar, Ustí, 05.-07.11.2018, Ustí nad labem, Tschechische Republik
  • Poster
    JCF-Frühjahrssymposium, 20.-23.03.2019, Bremen, Deutschland

Publ.-Id: 28143

Theoretical and simulation study of ‘Comb’ electron beam and THz generation

Joshi, V.; Lehnert, U.; Karmakar, J.; Kumar, N.; Karmakar, B.; Tripathi, S.; Aryshev, A.; Gosh, S.; Urakawa, J.; Bhandari, R. K.; Kanjilal, D.

A compact accelerator based super-radiant THz source is under development at Inter University Accelerator Centre (IUAC), New Delhi. The facility is based on the principle of pre-bunched Free Electron Laser (FEL) which will produce THz radiation in the range of 0.18 to 3 THz from a modulated electron beam. A photocathode electron gun will generate a short train of micro-bunches (a ‘‘comb’’ beam) driven by a fibre laser system capable of producing multi micro-pulse laser beam with variable separation (‘‘comb’’ laser pulse). Upon acceleration, the electron beam will be injected in to a compact undulator magnet tuned to the same frequency as the separation of the electron micro-bunches. The paper discusses the process of enhancement of super-radiant emission of radiation due to modulation in the comb beam and the conditions required to achieve maximum enhancement of the radiation power. The feasibility study of generating a comb beam at the photocathode and its transport through the beamline while preserving its temporal structure has been reported. To evaluate the characteristics of the radiation emitted from the comb beam, a 𝐶++ based particle tracker and Lienard–Wiechert field solver has been developed. The conceptual understanding of the emission of radiation from comb beam is shown to conform with the numerical results. The code has been used to calculate the radiation pulse energy emitted into the central cone of undulator for various comb beam configurations.

Keywords: linear accelerator; THz; THz source; radiation source; comb beam; pre-bunched beam; radiation emission; undulator radiation; super-radiant emission


Publ.-Id: 28142

Dissecting spin-phonon equilibration in ferrimagnetic insulators by ultrafast lattice excitation

Maehrlein, S. F.; Radu, I.; Maldonado, P.; Paarmann, A.; Gensch, M.; Kalashnikova, A. M.; Pisarev, R. V.; Wolf, M.; Oppeneer, P. M.; Barker, J.; Kampfrath, T.

To gain control over magnetic order on ultrafast time scales, a fundamental understanding of the way electron spins interact with the surrounding crystal lattice is required. However, measurement and analysis even of basic collective processes such as spin-phonon equilibration have remained challenging. We directly probe the flow of energy and angularmomentum in the model insulating ferrimagnet yttriumiron garnet. After ultrafast resonant lattice excitation, we observe thatmagnetic order reduces on distinct time scales of 1 ps and 100 ns. Temperature-dependentmeasurements, a spin-coupling analysis, and simulations show that the two dynamics directly reflect two stages of spinlattice equilibration. On the 1-ps scale, spins and phonons reach quasi-equilibrium in terms of energy through phonon-induced modulation of the exchange interaction. This mechanism leads to identical demagnetization of the ferrimagnet’s two spin sublattices and a novel ferrimagnetic state of increased temperature yet unchanged total magnetization. Finally, on the much slower, 100-ns scale, the excess of spin angular momentum is released to the crystal lattice, resulting in full equilibrium. Our findings are relevant for all insulating ferrimagnets and indicate that spin manipulation by phonons, including the spin Seebeck effect, can be extended to antiferromagnets and into the terahertz frequency range.

Keywords: THz control; ultra-fast; magnetism

Publ.-Id: 28141

Effect of anisotropic microstructure of ODS steels on small punch test results

Altstadt, E.; Bergner, F.; Das, A.; Houska, M.

Hot rolling and hot extrusion of oxide-dispersion strengthened (ODS) ferritic steels give rise to anisotropic microstructures and mechanical properties and may provoke related phenomena such as secondary cracking. In this study, we consider the small punch (SP) test – a method, applicable in the case of small amounts of available material and well established for isotropic materials. The SP test was applied to investigate the effect of sample orientation on deformation and cracking for one hot-rolled and two hot-extruded ODS ferritic steels. Existing microstructural evidence is used to rationalize the observed anisotropic fracture behaviour. The SP test results are compared with those from existing fracture mechanics tests based on sub-sized C(T) samples. The applicability of the empirical conversion of SP-based into Charpy-based transition temperatures is evaluated. The fractographic manifestation of load drops in SP load-displacement curves is identified and the analogy to secondary cracking in fracture mechanics tests is shown.

Keywords: small punch test; ductile-to-brittle transition temperature; oxide dispersion strengthened steel; pop-ins


Publ.-Id: 28140

Fuzzy flow pattern identification in horizontal air-water two-phase flow based on wire-mesh sensor data

Wiedemann, P.; Döß, A.; Schleicher, E.; Hampel, U.

Online monitoring of two-phase flow patterns is an essential need in various chemical engineering applications, since the reliability of prediction methods is limited. Therefore, the present study aims at developing a practically applicable algorithm for identifying flow patterns in horizontal gas-liquid flows on the basis of wire-mesh sensor data. Experiments were conducted in a 50mm i. d. pipe over a wide range of superficial velocities of an air-water mixture. Characteristic features involving the influence of gravity and the spatio-temporal behavior of the flows were derived from tomographic phase fraction data and used as input for fuzzy clustering. Three differently determined sets of cluster centers are compared against a reference classification by human specialist through reclassifying the measurements with the aid of defuzzyfication and, alternatively, by means of a novel visualization technique, that retains the fuzziness of the results. With respect to the latter one, best agreement is reached with cluster centers from fuzzy c-means clustering using all recorded measurements. As a special emphasis is put to the identification of transitional flow patterns, the performance of the algorithm at pseudo-dynamic operation is demonstrated, finally.

Keywords: gas-liquid flow; fuzzy c-means clustering; polar visualization technique; regime transition; wire-mesh sensor

Publ.-Id: 28139

Visualisation of the large scale circulation in Rayleigh-Bénard convection using contactless inductive flow tomography

Wondrak, T.; Stefani, F.; Galindo, V.; Eckert, S.

Rayleigh-Bénard (RB) convection plays an important role in geo- and astrophysics as well as in many metallurgical applications. At sufficiently high values of the Rayleigh number, a large scale circulation (LSC) is formed whose dynamics had turned out to be surprisingly rich. In this paper, the applicability of the contactless inductive flow tomography (CIFT) for the detection of the torsional mode of the LSC is investigated. CIFT enables the three-dimensional reconstruction of flow structures in liquid metals by applying one or more magnetic fields and measuring the flow induced perturbations of those fields outside the melt. Additionally, preliminary measurements of the flow induced magnetic field with a similar sensor arrangement will be presented.

Keywords: flow measurement techniques; Rayleigh-Bénard convection

  • Lecture (Conference)
    9th international symposium on electromagnetic processing of materials (EPM2018), 14.-18.10.2018, Awaji Yumebutai International Conference Center, Japan
  • Open Access Logo IOP Conference Series: Materials Science and Engineering 424(2018), 012007
    DOI: 10.1088/1757-899X/424/1/012007

Publ.-Id: 28138

Real-time control of the mould flow in a model of continuous casting in frame of the TOMOCON project

Wondrak, T.; Hampel, U.; Ratajczak, M.; Glavinić, I.; Stefani, F.; Eckert, S.; van der Plas, D.; Pennerstorfer, P.; Muttakin, I.; Soleimani, M.; Abouelazayem, S.; Hlava, J.; Blishchik, A.; Kenjeres, S.

In continuous casting, the flow structure of the liquid steel in the mould and the two-phase distribution in the submerged entry nozzle (SEN) are crucial for the quality of the produced steel. In order to effectively control the flow in the mould by electromagnetic brakes (EMBrs) and the injection of gas into the SEN, even a rough knowledge of the flow structure would be very helpful. In the framework of the TOMOCON project, the contactless inductive flow tomography (CIFT) and the mutual inductance tomography (MIT) will be integrated into a control loop for slab casters. This control loop will be developed and implemented at the Mini-LIMMCAST facility, which is available at the Helmholtz-Zentrum Dresden – Rossendorf. In this paper a short overview of this project will be given.

Keywords: continuous casting; electromagnetic brake; inductive measurement techniques; flow control

  • Lecture (Conference)
    9th international symposium on electromagnetic processing of materials (EPM2018), 14.-18.10.2018, Awaji Yumebutai International Conference Center, Japan
  • Open Access Logo IOP Conference Series: Materials Science and Engineering 424(2018), 012003
    DOI: 10.1088/1757-899X/424/1/012003

Publ.-Id: 28137

All-optical structuring of laser-driven proton beam profiles data sets

Obst-Huebl, L.; Ziegler, T.; Brack, F.-E.; Branco, J.; Bussmann, M.; Cowan, T. E.; Curry, C. B.; Fiuza, F.; Garten, M.; Gauthier, M.; Göde, S.; Glenzer, S. H.; Huebl, A.; Irman, A.; Kim, J. B.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Pausch, R.; Prencipe, I.; Rehwald, M.; Rödel, C.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

This data repository contains analyzed data files of the shown figures and simulation input files.

Please see the according README.txt files in the individual directories and the original manuscript for guidance.

Manuscript title:
  All-optical structuring of laser-driven proton beam profiles

  Lieselotte Obst, Tim Ziegler, Florian-Emanuel Brack, Joao Branco, Michael Bussmann, Thomas E. Cowan, Chandra B. Curry, Frederico Fiuza, Marco Garten, Maxence Gauthier, Sebastian Göde, Siegfried H. Glenzer, Axel Huebl, Arie Irman, Siegfried H. Glenzer, Axel Huebl, Arie Irman, Jongjin B. Kim, Thomas Kluge, Stephan Kraft, Florian Kroll, Josefine Metzkes-Ng, Richard Pausch, Irene Prencipe, Martin Rehwald, Christian Rödel, Hans-Peter Schlenvoigt, Ulrich Schramm, Karl Zeil

Submitted to:
  Nature Communications (2018)

Responsible for the data repository:
  Lieselotte Obst-Huebl, TU Dresden and HZDR
  Axel Huebl, TU Dresden and HZDR
  Tim Ziegler, TU Dresden and HZDR
  Thomas Kluge, HZDR


Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-10-30
    DOI: 10.14278/rodare.65
    License: CC-BY-4.0


Publ.-Id: 28136

Contactless inductive flow tomography for models of continuous casting and crystal growth

Ratajczak, M.; Wondrak, T.; Glavinić, I.; Stefani, F.

Contactless inductive flow tomography (CIFT) enables the reconstruction of the major flow structure in electrically conducting liquids, like molten steel or silicon. It is based on the permeation of the melt by an external primary magnetic field and the subsequent induction of currents, which generate a flow-induced secondary magnetic field. The measured secondary field allows for reconstruction of the flow by solving the underlying linear inverse problem. We present results for the application of CIFT for two lab-scale model experiments of (a) continuous steel casting in the presence of an electromagnetic brake and (b) Czochalski crystal growth with a thermally driven convection. In the first scenario (a), the electromagnetic brake poses the biggest challenge, since its strong static magnetic field of about 300 mT superimposes the flow-induced field of about 100 nT, and the brake’s ferromagnetic parts distort the CIFT excitation field. We show how this can be overcome by simulations and adequate instrumentation using gradiometric induction coil sensors, which enables correct flow reconstructions in this scenario. In the second setup (b) the biggest challenges arise from the long measurement times of up to 12 hours together with thermal expansion and contraction of the setup mounting due to the intrinsic temperature gradient of the melt. Here an optimized experimental construction is necessary to enable successful measurements magnetic field measurements with Fluxgate sensors. The experimental data reveal plausible stationary and transient phenomena in accordance with numerical
flow simulations.

Keywords: metallurgy; contactless inductive flow tomography; magnetic field measurement; flow measurement

  • Contribution to proceedings
    9th world congress on industrial process tomography, 02.-6.9.2018, Bath, UK
    Proceedings of the 9th world congress on industrial process tomography, 978 0 85316 3497, 839-845
  • Lecture (Conference)
    9th world congress on industrial process tomography, 02.-6.9.2018, Bath, UK

Publ.-Id: 28135

Numerical aspects of contactless inductive flow tomography for crystal growth

Wondrak, T.; Jacobs, R. T.; Galindo, V.; Stefani, F.

The flow structure of liquid silicon in the crucible for Czochralski (Cz) crystal growth is important for the quality of the silicon crystal. However, the high temperature and the required cleanliness of the melt represent a challenge for any flow measurement device. A promising technique to reconstruct the flow of a conducting liquid is contactless inductive flow tomography (CIFT). The procedure relies on the measurement of the flow induced perturbation of a primary magnetic field and the inversion of the corresponding integral equation system. In this paper, the numerical challenges for the application of CIFT to Cz crystal growth will be investigated. This includes the treatment of the singularities of the integral equation system as well as the selection of appropriate integration techniques. The paper concludes with numerical investigation of the expected flow induced magnetic field for a reversal of the rotation in simple model of a typical crucible.

Keywords: contactless inductive flow tomography; Czochralski crystal growth; flow measurement; liquid metal

  • Contribution to proceedings
    9th world congress on industrial process tomography, 02.-6.9.2018, Bath, UK
    Proceedings of the 9th world congress on industrial process tomography, 978 0 85316 3497, 451-456
  • Lecture (Conference)
    9th world congress on industrial process tomography, 02.-6.9.2018, Bath, UK

Publ.-Id: 28134

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