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41396 Publications

Super-SIMS @ DREAMS: status of a challenging initiative

Rugel, G.; Ziegenrücker, R.; Lachner, J.; Vivo Vilches, C.; Renno, A.; Wallner, A.; Wiedenbeck, M.

At the DREAMS (DREsden AMS) facility [1,2] we are implementing a so-called Super-SIMS (SIMS = Secondary Ion Mass Spectrometry) device [3] for specialized applications. The system combines the spatial resolution capability of a commercial SIMS (CAMECA IMS 7f-auto) with AMS capability, which should suppress molecular isobars in the ion beam allowing for the quantification of elemental abundances down to ~ E-9 – E-12. This would be more than an order of magnitude improvement over traditional dynamic SIMS (e.g. [4,5]). We aim to use this for the highly sensitive analysis of geological samples in the context of resource technology.

In the present setup, high efficiency transmission in the low-energy ion optics segment remains a challenge, as the beam needs to traverse two existing magnet chambers without deflection, where no steering or lens elements are available over a flight distance of 4 m. We have now improved the low-energy injection just after the ion beam exits the 7f-auto, upgrading the steerers directly after the SIMS and by adding a beam intensity attenuator. This provides both more stable conditions for instrument tuning and simplifies transition between measurements of the beam intensity in Faraday cups and the gas ionization chamber. Regarding the measurement of C, N and O in silicon, we found that a simple Wien-filter using permanent magnets for the primary Cs-sputter beam significantly reduces the background at the detector, as the 7f-auto uses a Cs₂CO₃ source – rather than metallic Cs – for the generation of the primary positive Cs beam.

Once the remaining issues associated with ion beam-path are fully addressed, we will still need to tackle the issue of establishing suitable, well characterized reference materials needed for our first suite of resource and geoscience applications (e.g., halides in naturally occurring sulphide minerals). We present ongoing developments and results, as well as plans for extending to other matrices and isotope systems.

[1] S. Akhmadaliev et al., NIMB 294 (2013) 5. [2] G. Rugel et al. NIMB 370 (2016) 94. [3] J. M. Anthony, D. J. Donahue, A. J. T. Jull, MRS Proceedings 69 (1986) 311-316. [4] C. Maden, PhD thesis, ETH Zurich 2003. [5] S. Matteson, Mass Spectrom. Rev., 27 (2008) 470.

Related publications

  • Poster (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-33303
Publ.-Id: 33303


Holmium-166m measurements with AMS for the ECHo-project

Rugel, G.; Berndt, S.; Düllmann, C. E.; Dorrer, H.; Forstner, O.; Kieck, T.; Kneip, N.; Lachner, J.; Merchel, S.; Vivo Vilches, C.; Wallner, A.; Wendt, K.

The Electron Capture in ¹⁶³Ho experiment (ECHo) aims at measuring the mass of the electron neutrino by analysing the EC spectrum of the long-lived radionuclide ¹⁶³Ho (T_1/2 = 4570 a) with a metallic magnetic calorimeter (MMC). For the determination of a reasonable upper limit for the neutrino mass it is mandatory to keep the contamination with the long-lived radionuclide ¹⁶⁶mHo (T_1/2 = 1132.6 a) nine orders of magnitude below the ¹⁶³Ho content. The ion-implantation of ultra-pure ¹⁶³Ho into a MMC for the experiment is carried out by the RISIKO (Resonance Ionization Spectroscopy in KOllinear geometry) mass separator. The separation from ¹⁶⁶mHo, however, cannot be guaranteed to such low levels as needed in this project, it can only be estimated. Here we present our approach to determine the corresponding low isotopic ratio with accelerator mass spectrometry (AMS). Of course, this requires the formation of negative ions, where we find the highest negative ion yield for the anion HoO₂−. For first tests, stable ¹⁶⁵Ho was implanted by RISIKO into various different metal foils and we studied the overall Ho detection efficiency for our setup. We will present first results and estimates of the expected detection limit for the ¹⁶⁶mHo/¹⁶³Ho isotope ratio.

Related publications

  • Lecture (Conference) (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-33302
Publ.-Id: 33302


High electron mobility in strained GaAs nanowires

Balaghi, L.; Shan, S.; Fotev, I.; Moebus, F.; Rana, R.; Venanzi, T.; Hübner, R.; Mikolajick, T.; Schneider, H.; Helm, M.; Pashkin, O.; Dimakis, E.

Novel transistor concepts based on semiconductor nanowires promise high performance, lower energy consumption and better integrability in various platforms in nanoscale dimensions. Concerning the intrinsic transport properties of electrons in nanowires, relatively high mobility values that approach those in bulk crystals have been obtained only in core/shell heterostructures, where electrons are spatially confined inside the core. Here, it is demonstrated that the strain in lattice-mismatched core/shell nanowires can affect the effective mass of electrons in a way that boosts their mobility to unprecedented levels. Specifically, electrons inside the hydrostatically tensile-strained gallium arsenide core of nanowires with a thick indium aluminium arsenide shell exhibit mobility values 30 – 50 % higher than in equivalent unstrained nanowires or bulk crystals, as measured at room temperature. With such an enhancement of electron mobility, strained gallium arsenide nanowires emerge as a unique means for the advancement of transistor technology.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33301
Publ.-Id: 33301


Data publication: Flow morphology of high-pressure steam condensation in an inclined tube at low inlet steam qualities

Boden, S.; Moonesi Shabestary, A.; Bieberle, A.; Pietruske, H.; Hampel, U.

This archive contains the processed X-ray data of the measurement campaign "Investigation of flow morphology and heat transfer in an inclined tube", which was conducted between June 2020 and June 2021 at the thermal hydraulic test facility COSMEA (COndenSation test rig for flow Morphology and hEAt transfer studies) at Helmholtz-Zentrum Dresden - Rossendorf (HZDR). The flow morphology of high-pressure (up to 65 bar) steam condensation in a slightly inclined tube at low inlet steam qualities (down to 2.8%) were are studied. Both X-ray computed tomography as well as X-ray radioscopy have been applied. The results include images of the local condensate distribution in selected cross-sections of the condenser tube as well as time resolved projections of the condensate distribution.

Keywords: steam condensation; two-phase flow; X-ray tomography; X-ray radioscopy

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Permalink: https://www.hzdr.de/publications/Publ-33300
Publ.-Id: 33300


Universal Liquid Metal Alloy Ion Sources for FIB nanofabrication

Richter, T.; Mazarov, P.; Meyer, F.; Pilz, W.; Bischoff, L.; Klingner, N.

The incident ion defines the interaction mechanism with the sample surface caused by the energy deposition and thus has significant consequences on resulting nanostructures [1]. In addition, nanofabrication requirements for FIB technologies are specifically demanding in terms of patterning resolution and stability [2].
Therefore, we have extended the technology towards a stable supply of multiple ion species selectable into a nanometer scale focused ion beam by employing a liquid metal alloy ion source (LMAIS) [3]. This LMAIS provides single and multiple charged ion species of different masses, resulting in significantly different interaction mechanisms. Nearly half of the elements of the periodic table are thus made available in the FIB technology because of continuous research in this area [4]. This range of ion species with different mass or charge can be beneficial for various nanofabrication applications. Recent developments could make these sources to an alternative technology feasible for nanopatterning challenges. In this contribution, the operation principle, first results and prospective domains for modern FIB applications will be presented. As examples, we will introduce the AuGeSi and GaBiLi LMAIS [5, 6]. Both sources provide light and heavy ions available from a single source to tailor chemical and physical properties of resulting nanostructures. GaBiLi enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from one ion source. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB could benefit of providing additional ion species in a mass separated FIB without changing the ion source.
[1] P. Mazarov, V. Dudnikov, A. Tolstoguzov, Electrohydrodynamic emitters of ion beams, Phys. Usp. 63, 1219 (2020).
[2] L. Bruchhaus, P. Mazarov, L. Bischoff, J. Gierak, A. D. Wieck, and H. Hövel, Comparison of technologies for nano device prototyping with a special focus on ion beams: A review, Appl. Phys. Rev. 4, 011302 (2017).
[3] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative for Focused Ion Beam Technology, Appl. Phys. Rev. 3, 021101 (2016).
[4] J. Gierak, P. Mazarov, L. Bruchhaus, R. Jede, L. Bischoff, Review of electrohydrodynamical ion sources and their applications to focused ion beam technology, JVSTB 36, 06J101 (2018).
[5] W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium ion beams from liquid metal alloy ion sources, JVSTB 37, 021802 (2019).
[6] N. Klingner, G. Hlawacek, P. Mazarov, W. Pilz, F. Meyer, and L. Bischoff, Imaging and milling resolution of light ion beams from helium ion microscopy and FIBs driven by liquid metal alloy ion sources, Beilstein J. Nanotechnol. 11, 1742 (2020).

Keywords: Liquid Metal Alloy Ion Sources; FIB; nanofabrication

Related publications

  • Lecture (Conference) (Online presentation)
    34th International Microprocesses and Nanotechnology Conference (MNC 2021), 26.-29.10.2021, Osaka, Japan

Permalink: https://www.hzdr.de/publications/Publ-33299
Publ.-Id: 33299


Retention of redox-sensitive Tc(VII) and Se(IV) on Fe(II)/Fe(III) bearing clay minerals

Qian, Y.; Grangeon, S.; Scheinost, A. C.; Hoving, A.; Greneche, J. M.; Marques Fernandes, M.

Clay minerals, as main components of the engineered barrier in deep geological repositories, are not only highly effective sorbents for a wide range of (cationic) contaminants, but due to their structural iron content, they can also modify the mobility and (bio)availability of redox-sensitive elements by changing their oxidation state. Here we will systematically address the retention of the redox-sensitive fission products Tc and Se by FeII/FeIII containing clays. The mobility of Tc and Se strongly depends on their oxidation states. The specific chemical form of Tc and Se is governed by many factors, such as pH, redox potential (Eh), solubility, mineralogical and chemical composition of the environment, biological (microbial) interactions and (redox) reaction kinetics. The most considerable influence, however, is exerted by redox potential, pH and solubility.
Tc(VII) in its anionic form (TcO4-) is highly mobile whereas under reducing conditions the mobility of Tc is decreased when it is reduced to Tc(IV). A few studies have shown that TcVII can be reduced to TcIV by Fe-bearing minerals, mainly forming TcO2.nH2O surface precipitates[1]. Most of these studies, however, were carried out at rather high Tc loadings. The focus of this study is on low to very low Tc loadings, which are more environmentally relevant.
Selenate (SeO42−, Se(VI)) and selenite (SeO32−, Se(IV)) are favoured under oxidizing conditions. Selenate reduction is kinetically hindered and very slow (high activation energy). Hence, the study focuses on selenite. There is little data on the retention of Se(IV) by Fe(II) bearing clay minerals. Reductive precipitation of Se(IV) to nanoparticulate Se(0) was observed when dissolved Fe(II) is sorbed onto synthetic montmorillonite[2].
By combining Tc and Se sorption experiments on native and reduced smectite clay samples with different FeII/FeIII ratios with Tc/Se K-edge extended X-ray absorption fine structure (EXAFS), mediated oxidation and reduction experiments (MEO/MER), Mössbauer spectrometry and microscopy, we aim at discriminating the contributions of the different available Fe sources to the overall adsorption and reduction of Tc and Se and to identify the surface products. The ultimate aim is to correlate mineral properties with respect to their redox reactive iron content, the degree of Tc and Se reduction and the molecular scale surface speciation, in order to improve the understanding of the coupled adsorption and electron transfer reactions contributing to the retention of Tc and Se on FeII/FeIII bearing clay minerals, and thus to contribute to a more reliable prediction of the Tc and Se retention in nuclear waste repositories.

1. Jaisi, D.P., et al., Reduction and long-term immobilization of technetium by Fe(II) associated with clay mineral nontronite. Chemical Geology, 2009. 264(1): p. 127-138.
2. Charlet, L., et al., Electron transfer at the mineral/water interface: Selenium reduction by ferrous iron sorbed on clay. Geochimica et Cosmochimica Acta, 2007. 71(23): p. 5731–5749.

Keywords: Technetium; Selenium; Clay Minerals; Redox; XAFS

Related publications

  • Lecture (Conference)
    Clay Conference 2022, 13.-16.06.2022, Nancy, France
  • Poster
    EURADWASTE'22, 30.05.-03.06.2022, Lyon, France
  • Lecture (Conference)
    ATAS-AnXAS 2022, 17.-21.10.2022, Grenoble, France
  • Invited lecture (Conferences)
    ROBL-Workshop, 25.01.2023, Dresden, Germany
  • Invited lecture (Conferences)
    EURAD Annual Meeting, 14.-16.03.2023, Larnaca, Cyprus

Permalink: https://www.hzdr.de/publications/Publ-33298
Publ.-Id: 33298


Redox-active iron in different types of clay minerals – mediated electrochemical characterization and reactivity towards Se(IV)

Hoving, A. L.; Qian, Y.; Marques Fernandes, J. M.; Griffioen, J.; Behrends, T.; Scheinost, A. C.

Clay minerals are ubiquitous in the environment and are an important reactant to pollutants including radionuclides. Besides their adsorptive capacity, clay minerals can also participate in redox reactions due to the presence of iron (Fe) in their structure and can thereby influence the mobility of redox-active compounds such as technetium, selenium and uranium. However, not all Fe(II) or Fe(III) in the structure of clay minerals may be accessible for redox reactions. The redox activity of Fe can depend on the quantity and coordination of Fe in the clay mineral structure. Research on the redox activity of structural Fe in clay minerals has mainly focused on smectites whereas other types of clay minerals have received less attention. In this study we measured redox-activity of a variety of clay minerals, i.e. illites, chlorites, glauconites and mixed-layered illite-smectites. The redox-activity of the clay minerals was investigated by mediated electrochemistry. To examine the relation between electrochemically active structural Fe(II) in these clay minerals and their reactivity towards radionuclides, batch experiments were performed with selenite, a redox-active, mobile, long-lived radionuclide in radioactive waste. Both pristine (oxidized) clay minerals and chemically reduced clay minerals were tested. Results from mediated electrochemical oxidation and reduction show that all clay minerals have electrochemically active Fe to some extent, but there is a large variation in the fractions of electrochemically-active Fe between the different clay minerals, e.g. around 100% redox-active Fe in smectites, <20% redox-active Fe for the tested illites. K-edge XAFS spectroscopy of these batch experiment samples reveals that these different types of chemically reduced clay minerals reduce selenite to elemental selenium.

Keywords: redox; clay minerals; Mediated Electrochemistry; XAFS; Selenium

Related publications

  • Lecture (Conference)
    Clay Conference 2022, 13.-16.06.2022, Nancy, France

Permalink: https://www.hzdr.de/publications/Publ-33297
Publ.-Id: 33297


Towards multiscale ab-initio simulations: size transferability of density functional theory surrogates

Fiedler, L.

Density Functional Theory (DFT) is one of the most important computational tools for materials science, as it combines high accuracy with general computational feasibility. However, applications important to scientific progress can pose problems to even the most advanced and efficient DFT codes due to size and/or complexity of the underlying simulations. Namely the modeling of materials across multiple length and time scales at ambient or extreme conditions, necessary for the understanding of important physical phenomena such as radiation damage in fusion reactor walls, evade traditional ab-initio treatment.
DFT surrogate models are a useful tool in achieving this goal by reproducing DFT results at drastically reduced computational cost due to using machine learning methods. In order to successfully model on multiple length and time scales, these models have to be transferable with respect to their size. Here, we present results of such an investigation, by showing how models trained on small numbers of atoms (e.g., 128) can be used to accurately calculate energies of much larger simulation cells (e.g., 1024 atoms). The models are based upon the Materials Learning Algorithms (MALA) package and the LDOS-based machine-learning workflow implemented therein.

Keywords: Density Functional Theory; Machine Learning; Surrogate Model

  • Lecture (Conference)
    8th International Symposium on Optics & its applications, 19.-22.10.2021, Rostock, Dresden

Permalink: https://www.hzdr.de/publications/Publ-33296
Publ.-Id: 33296


Investigation of transferability in LDOS based DFT surrogate models for multiscale simulations

Fiedler, L.; Cangi, A.

Density Functional Theory (DFT) is one of the most important computational tools for materials science, as it combines high accuracy with general computational feasibility. However, applications important to scientific progress can pose problems to even the most advanced and efficient DFT codes due to size and/or complexity of the underlying simulations. Namely the modeling of materials across multiple length and time scales at ambient or extreme conditions, necessary for the understanding of important physical phenomena such as radiation damages in fusion reactor walls, evade traditional ab-initio treatment.
DFT surrogate models are a useful tool in achieving this goal by reproducing DFT results at drastically reduced computational cost by using machine learning methods. Yet, a lack of transferability of many approaches lead to repeated and costly training data generation procedures. Here, we present results of an investigation to transfer such machine learning DFT surrogate models between different simulation cell sizes, with the goal of reducing the overall amount of computational time for training data generation. The models are based upon the Materials Learning Algorithms (MALA) package [1] and the therein implemented LDOS based machine learning workflow [2].
[1]: https://github.com/mala-project
[2]: J. A. Ellis et al., Phys. Rev. B 104, 035120, 2021

Keywords: Machine Learning; Density Functional Theory; Surrogate Model

  • Lecture (Conference) (Online presentation)
    84. Jahrestagung der DPG und DPG-Tagung der Sektion Kondensierte Materie (SKM), 27.09.-01.10.2021, online, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33295
Publ.-Id: 33295


Materials Learning Algorithms (MALA): An Efficient Surrogate for Ab-initio Simulations

Fiedler, L.

Ab-initio simulations are crucial tools for many scientific applications, from materials science to drug discovery. This is due to powerful simulation techniques such as Density Functional Theory (DFT), that combine high accuracy with computational feasibility. Yet, there exist applications unattainable to even the most performant of DFT programs. A prominent example is the modeling of materials on multiple time and length scales, especially under ambient or extreme conditions. While these simulations hold the potential to both further our understanding of important physical phenomena such as planetary formation or radiation damages in fusion reactor wall, they evade traditional ab-initio approaches due to their size and complexity.
Surrogate models can mitigate these computational restrictions, by reproducing DFT-level results at a fraction of the cost. Here, were present the Materials Learning Algorithms (MALA) package, an open source python package for building neural network based surrogate models for materials science. MALA provides easy-to-use functions to process DFT data, build models and use these models to replace DFT calculations, as shown for simulations of Aluminium at both 298K and 933K, as well as Iron at 3000K. The source code for MALA is publicly available on Github and developed by the Center for Advanced Systems Understanding (CASUS), Sandia National Laboratories, and Oak Ridge National Laboratory.

Keywords: Density Functional Theory; Machine Learning; Surrogate Model

  • Lecture (Conference)
    17th International Conference on the Physics of Non-Ideal Plasmas, 20.-24.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33294
Publ.-Id: 33294


Preliminary Results of Contactless Inductive Flow Tomography for Rayleigh- Bénard Convection Cell with an Aspect Ratio of 0.5

Mitra, R.; Sieger, M.; Galindo, V.; Schindler, F.; Vogt, T.; Stefani, F.; Eckert, S.; Wondrak, T.

The focus of this presentation is on the numerical study of CIFT on the same RB cell, for an experimentally feasible case of 7x6 sensor configuration and developing the measurement system based on the applicability. The two excitation magnetic fields were kept in the order of 1 mT during the simulation. Sensors are kept outside the RB cell to detect the flow-induced perturbations. The original velocity fields were simulated using OpenFoam solver with a high temporal resolution of 0.5 seconds for 8000 seconds. For reconstruction, only the transient condition between 7000th to 8000th second was considered. Torsional mode analysis is also reported.

Keywords: Contactless inductive flow tomography; Rayleigh-Bénard convection; Liquid metal measurement

  • Contribution to proceedings
    10th World Congress on Industrial Process Tomography, 13.-16.09.2021, Online, Online
  • Lecture (Conference) (Online presentation)
    10th World Congress on Industrial Process Tomography, 13.-16.09.2021, online, online

Permalink: https://www.hzdr.de/publications/Publ-33293
Publ.-Id: 33293


Rapid Iron(III)-Fluoride Mediated Hydrogen Atom Transfer

Panda, C.; Doyle, L. M.; Gericke, R.; McDonald, A. R.

We anticipate high-valent metal fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H–F bond (in the product) that drives HAT oxidation. We prepared a dimeric Fe(III)(F)–F–Fe(III)(F) complex (1) by reacting Fe(II)(NCCH₃)₂(TPA) where X = F/OTf. 1 and 2 were characterised using NMR, EPR, UV-vis, and FT-IR spectroscopies and mass spectrometry. 2 was a remarkably reactive Fe III reagent for oxidative C–H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive Fe III and Fe IV oxidants.

Keywords: high-valent oxidants; biomimetic; proton coupled electron transfer; fluoride oxidant

Permalink: https://www.hzdr.de/publications/Publ-33292
Publ.-Id: 33292


Comparing Metal–Halide and −Oxygen Adducts in Oxidative C/O–H Activation: Au(III)–Cl versus Au(III)–OH

Lovisari, M.; Gericke, R.; Twamley, B.; McDonald, A. R.

High-valent metal−halides have come to prominence as highly effective oxidants. A direct comparison of their efficacy against that of traditional metal−oxygen adducts is needed. AuIII(Cl)(terpy)](ClO₄)₂ (1; terpy = 2,2′:6′,2-terpyridine) readily oxidized substrates bearing O−H and C−H bonds via a hydrogen atom transfer mechanism. A direct comparison with [AuIII(OH)(terpy) showed that 1 was a kinetically superior oxidant with respect to 2 for all substrates tested. We ascribe this to the greater thermodynamic driving force imbued by the Cl ligand versus the OH ligand.

Keywords: Bond dissociation free energy; Hydrocarbons; Ligands; Gold; Oxidation

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Permalink: https://www.hzdr.de/publications/Publ-33291
Publ.-Id: 33291


Migration kinetics of surface ions in oxygen-deficient perovskite during topotactic transitions

Cao, L.; Petracic, O.; Wei, X.-K.; Zhang, H.; Duchoň, T.; Gunkel, F.; Koutsioubas, A.; Zhernenkov, K.; Rushchanskii, K. Z.; Hartmann, H.; Wilhelm, M.; Li, Z.; Xie, Y.; He, S.; Weber, M. L.; Veltruská, K.; Stellhorn, A.; Mayer, J.; Zhou, S.; Brückel, T.

Oxygen diffusivity and surface exchange kinetics underpin the ionic, electronic, and catalytic functionalities of complex multivalent oxides. Towards understanding and controlling the kinetics of oxygen transport in emerging technologies, it is highly desirable to reveal the underlying lattice dynamics and ionic activities related to oxygen variation. In this study, the evolution of oxygen content is identified in real-time during the progress of a topotactic phase transition in La0.7Sr0.3MnO3-δ epitaxial thin films, both at the surface and throughout the bulk. Using polarized neutron reflectometry, a quantitative depth profile of the oxygen content gradient is achieved, which, alongside atomic-resolution scanning transmission electron microscopy, uniquely reveals the formation of a novel structural phase near the surface. Surface-sensitive x-ray spectroscopies further confirm a significant change of the electronic structure accompanying the transition. The anisotropic features of this novel phase enable a distinct oxygen diffusion pathway in contrast to conventional observation of oxygen motion at moderate temperatures. The results provide insights furthering the design of solid oxygen ion conductors within the framework of topotactic phase transitions.

Keywords: oxygen vacancy ordering; topotactic transition; defect chemistry; polarized neutron reflectometry; X-ray absorption

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33290
Publ.-Id: 33290


Effects of torsion and curvature in antiferromagnetic spin chains

Pylypovskyi, O.; Kononenko, D. Y.; Yershov, K.; Roessler, U.; Tomilo, A.; Faßbender, J.; van den Brink, J.; Makarov, D.; Sheka, D.

Antiferromagnets represent a wide class of technologically promising materials for spintronic and spinorbirtonic devices with multiple magnetic sublattices [1]. An efficient manipulation of antiferromagnetic textures requires the presence of the Dzyaloshinskii-Moriya interaction (DMI), which is present in crystals of special symmetry, and thus limits the number of available materials. In contrast to antiferromagnets, it is already established that in ferromagnetic thin films and nanowires chiral responses can be tailored relying on curvilinear geometries [2]. Here, we explore curvature effects in curvilinear antiferromagnets which are stemming from exchange interaction [3]. It is shown that intrinsically achiral curvilinear antiferromagnetic spin chains behave as a biaxial chiral helimagnet with a curvature-tunable anisotropy and DMI. In contrast to ferromagnetic spin chains, the dipolar interaction leads to the hard-axis anisotropy. This allows to observe the effects of geometry even in chains with small curvature and torsion because of absence of other competing easy axis anisotropies except the geometry-induced one. The latter determines the homogeneous antiferromagnetic state at low curvatures and the gap for spin waves. The geometry-driven DMI determines the helimagnetic phase transition and leads to the appearance of the region with the negative group velocity at the dispersion curve. We note, that the anisotropy in curvilinear antiferromagnetic spin chains is an additional source of geometry-driven effects on magnetic textures [4].

Keywords: antiferromagnetism; curvilinear magnetism; spin chains

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33289
Publ.-Id: 33289


Parallel computation of 3D magnetic structures

Tomilo, A.; Pylypovskyi, O.; Yershov, K.; Sheka, D.

Intensive experimental and theoretical research for novel materials introduces new architectures for magnetic devices, where shape and topology plays a crucial role [1]. A powerful way to study them as well as confirm analytical predictions is to compute the corresponding equations of motion numerically. Here, we present a spin-lattice simulation suite SLaSi, which can address flexible magnetic one- and two- dimensional spin lattices. They can represent soft wires and ribbons, where the coupling between magnetic and mechanical subsystem results into spontaneous deformations and symmetry breaks [2]. The SLaSi is a C-written program, where exchange, single-ion anisotropy, Zeeman energy, dipolar interaction, and Dzyaloshinskii-Moriya interaction are taken into account for the description cubic, square, and triangular lattices. Dynamics of the mechanical sub-system is modelled by the overdamped Newton equations, while magnetic sub-system is modelled by LLG. Speedup of the computations is achieved by parallelization using MPI and CUDA frameworks.

Keywords: curvilinear magnetism; computations; CUDA; MPI

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33288
Publ.-Id: 33288


Nanoscale mechanics of antiferromagnetic domain walls in Cr2O3

Hedrich, N.; Wagner, K.; Lehmann, P.; Pylypovskyi, O.; Shields, B. J.; Kosub, T.; Sheka, D.; Makarov, D.; Maletinsky, P.

Magneto-electric antiferromagnets hold promise for future spintronic devices, as they offer magnetic field hardness, high switching speeds combined with electric and magnetic control of their order parameters, owing to the magneto-electric coupling [1]. As information and functionality is encoded in the antiferromagnetic order parameter, its manipulation, read-out and nanoscale texture are paramount for device operation, as well as interesting from a fundamental point of view. E.g. spin-textures in such materials are theorized to carry an intrinsic magnetization [2]. Here we study a single crystal ‘textbook’ magneto-electric antiferromagnet, Cr2O3, by nanoscale imaging of its surface magnetization via magnetic stray field imaging by scanning nitrogen vacancy magnetometry [3]. This surface magnetization is directly linked to the bulk Neel vector of Cr2O3 and thereby allows for nanoscale imaging of antiferromagnet spin textures. After confirming magneto-electric poling [4], local electrodes are utilized to nucleate single domain walls, which we then study on the nanometer scale. Manipulation of the domain wall is demonstrated both by local laser heating [5], as well as the creation of an energy landscape for the domain wall via topographic structuring [3]. We analyze the interaction of the domain wall with topographic islands both experimentally and in simulations. This analysis yields information about the domain wall boundary conditions at topographic edges and an estimate of the full 3D-profile of the texture based on minimizing the domain walls surface energy. A Snell like refraction of the domain wall path is found, that can be represented in an analytical approximation as a ‘refractive index’ for a given island dimension as demonstrated for a range of incidence angles.

We then observe bistable domain wall paths configurations and switching between them is demonstrated and imaged experimentally. This pinning and control of the domain wall position constitutes the main ingredients for logic devices based on domain walls in magneto-electric antiferromagnets and their fundamental study.

Keywords: antiferromagnetism; Cr2O3; mesa; NV magnetometry

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33287
Publ.-Id: 33287


Ground states of the antiferromagnetic spin rings in strong magnetic fields

Borysenko, Y.; Pylypovskyi, O.; Faßbender, J.; Sheka, D.; Makarov, D.

Antiferromagnetic (AFM) materials have distinct advances compared to ferromagnets, that allow to use them in variety of spintronic applications [1,2]. Antiferromagnetically coupled curvilinear spin chains are of fundamental interest as simplest systems possessing interplay between the geometry and magnetic subsystem [3].

In this work, we analyze the ground states of AFM ring-shaped spin chain with the nearest-neighbour Heisenberg exchange and single-ion anisotropy in presence of external magnetic field. The direction of magnetic field coincides with the symmetry axis of the ring. Collinear two-sublattice 1D curved AFM chain with even number of spins is considered, and the hard axis of anisotropy is oriented tangentially to the chain.

Within the classical continuum approach its magnetic state is described by two order parameters, the Néel and ferromagnetism vector fields. In the ground state, the Néel vector is oriented perpendicularly to the ring plane.

The magnetic field applied along the ring normal allows to observe spin-flop and spin-flip orientational phase transitions. We determine the dependency of spin-flop and spin-flip transition fields on the ring curvature and the critical curvature which separates two topologically different ground states above spin-flop transition. The first one with the Néel order parameter within the normal plane is mainly determined by the anisotropy at small curvatures. The second ground state at large curvatures is represented by onion ordering of the Néel vector. With the applied fields larger than critical spin-flip transition field Néel order parameter vanishes, which leads to ferromagnetic ground state. The phase diagram of AFM as a function of applied field intensity and the ring curvature is developed.

Keywords: antiferromagnetism; spin-flop; curvilinear magnetism

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33286
Publ.-Id: 33286


Challenges Porting a C++ Template-Metaprogramming Abstraction Layer to Directive-based Offloading

Kelling, J.; Bastrakov, S.; Debus, A.; Kluge, T.; Leinhauser, M.; Pausch, R.; Steiniger, K.; Stephan, J.; Widera, R.; Young, J.; Bussmann, M.; Chandrasekaran, S.; Juckeland, G.

HPC systems employ a growing variety of compute accelerators with different architectures and from different vendors. Large scientific applications are required to run efficiently across these systems but need to retain a single code-base in order to not stifle development. Directive-based offloading programming models set out to provide the required portability, but, to existing codes, they themselves represent yet another API to port to. Here, we present our approach of porting the GPU-accelerated particle-in-cell code PIConGPU to OpenACC and OpenMP target by adding two new backends to its existing C++-template metaprogramming-based offloading abstraction layer alpaka and avoiding other modifications to the application code. We introduce our approach in the face of conflicts between requirements and available features in the standards as well as practical hurdles posed by immature compiler support.

Keywords: C++; OpenACC; OpenMP; Offloading

  • Contribution to WWW
    https://arxiv.org/abs/2110.08650
  • Lecture (Conference) (Online presentation)
    Eighth Workshop on Accelerator Programming Using Directives (WACCPD) @SC21, 14.11.2021, St. Louis, USA
  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    SC21 - The International Conference for High Performance Computing, Networking, Storage, and Analysis: OpenMP Offloading and the 5.2 API Birds-of-a-Feather, 14.-19.11.2021, St. Louis, MO, USA
  • Contribution to proceedings
    8th International Workshop, WACCPD 2021, 14.11.2021, St. Louis, USA
    Accelerator Programming Using Directives, Cham: Springer, 978-3-030-97758-0
    DOI: 10.1007/978-3-030-97759-7

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Permalink: https://www.hzdr.de/publications/Publ-33285
Publ.-Id: 33285


Geometrical symmetry breaking in nanomagnets

Pylypovskyi, O.

Three-dimensional ferro- and antiferromagnetic nanoarchitectures possess a special interplay between their geometrical (topological) properties and the magnetic order parameter. The emergent chiral and anisotropic responses extend the intrinsic material properties and pave the way to novel functionalities of spintronic and spin-orbitronic devices.

Keywords: curvilinear magnetism; ferromagnets; antiferromagnets

  • Invited lecture (Conferences) (Online presentation)
    META 2021 The 11th International Conference on Metamaterials, Photonic Crystals and Plasmonics, 20.-23.07.2021, Warsaw (Online event), Poland

Permalink: https://www.hzdr.de/publications/Publ-33284
Publ.-Id: 33284


A community data mining approach for surface complexation database development

Zavarin, M.; Chang, E.; Wainwright, H.; Parham, N.; Kaukuntla, R.; Zouabe, J.; Deinhart, A.; Genetti, V.; Shipman, S.; Bok, F.; Brendler, V.

This paper presents a comprehensive data-to-model workflow, including a findable, accessible, interoperable, reusable (FAIR) community sorption database (newly developed LLNL Surface Complexation/Ion Exchange (L-SCIE) database) along with a data fitting workflow to efficiently optimize surface complexation reaction constants with multiple surface complexation model (SCM) constructs. This workflow serves as a universal framework to mine, compile, and analyze large numbers of published sorption data as well as to estimate reaction constants for parameterizing reactive transport models. The framework includes (1) data digitization from published papers, (2) data unification including unit conversions, and (3) data-model integration and reaction constant estimation using geochemical software PHREEQC coupled with the universal parameter estimation code PEST. We demonstrate our approach using an analysis of U(VI) sorption to quartz based on a first L-SCIE implementation, concluding that a multisite SCM construct with carbonate surface species yielded the best fit to community data. Surface complexation reaction constants extracted from this approach captured all available sorption data available in the literature and provided insight into previously published reaction constants and surface complexation model constructs. The L-SCIE sorption database presented herein allows for automating this approach across a wide range of metals and minerals and implementing novel machine learning approaches to reactive transport in the future.

Keywords: Surface Complexation Modelling; Database; Sorption; Data Mining; Raw Data

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Publ.-Id: 33283


Prompt-gamma imaging for prostate cancer proton therapy: CNN-based detection of anatomical changes

Pietsch, J.; Nick, P.; Berthold, J.; Khamfongkhruea, C.; Thiele, J.; Hölscher, T.; Traneus, E.; Janssens, G.; Smeets, J.; Stützer, K.; Löck, S.; Richter, C.

Purpose & Objective
A clinical study (PRIMA) regarding the potential of range verification in proton therapy by prompt-gamma imaging (PGI) is carried out at our institution. As a step towards the automatic evaluation of the measured PGI data, we present an approach to detect anatomical changes in prostate cancer patients from realistically simulated PGI data using convolutional neural networks (CNNs).

Materials & Methods
In-room control CTs (cCTs) were acquired in treatment position before monitoring 146 field deliveries of 10 hypo-fractioned (3Gy/fraction) prostate cancer patients with a PGI slit camera (range: 8-18 fields/patient). After manual CT registration and dose recalculation, spot-wise shifts of integrated depth-dose (IDD) profiles between cCTs and planning CTs were extracted at the 80% distal falloff position and used for ground-truth classification. Treatment fields were considered to be affected by relevant anatomical changes of the patient if >0.1% of all spots (with at least 0.1% of the total monitor units per field) had absolute IDD shifts above 5 mm. These parameters lead to a field-wise IDD ground-truth classification in optimal agreement with a prior manual field-wise classification based on dose difference maps.
Based on the cCTs, we simulated realistic PGI profiles, including Poisson noise and a positioning uncertainty of the PGI slit camera, and extracted spot-wise range shifts by comparison with the expected reference profiles for the planning CT. Spots with reliable PGI information (inside field-of-view and >5E7 protons), were considered with their Bragg peak position for generating two independent 3D spatial maps of 161616 voxels (0.740.740.66 cm3): (1) The PGI-determined range shift in each voxel is the weighted average taking the spot-wise proton number into account. (2) The proton number in each voxel is summed over all respective spots and normalized per field (Fig. 1).
With these maps and the IDD classification, 3D-CNNs (6 convolutional & 2 downsampling layers) were trained using patient-wise 10-fold cross-validation on the binary task to detect anatomical changes.

Results
The CNNs achieved a mean training and validation accuracy of 0.85 (range: 0.77-0.91) and 0.83 (0.70-0.93), respectively (Fig. 2). Based on the validation results, anatomical changes were detected with a sensitivity of 0.88 and a specificity of 0.76.

Conclusion
Our work shows that CNNs can reliably detect anatomical changes in prostate cancer patients from realistically simulated PGI data of clinical irradiations. While a validation on measured PGI data is the next step, this study highlights the potential of an automatic interpretation of PGI data, which is highly desired for routine clinical application and required for the inclusion of PGI in an automated feedback loop for online adaptive proton therapy.

Keywords: range verification; prompt gamma imaging; proton therapy; artificial intelligence; machine learning

  • Lecture (Conference)
    ESTRO 2022, 06.-10.05.2022, Kopenhagen, Dänemark
  • Abstract in refereed journal
    Radiotherapy and Oncology 170(2022)Supplement, 546-548
    DOI: 10.1016/S0167-8140(22)02642-1

Permalink: https://www.hzdr.de/publications/Publ-33282
Publ.-Id: 33282


Skin-conformal flexible and printable magnetoelectronics for human-machine interfaces and soft robotics

Makarov, D.

Motion sensing is the primary task in numerous disciplines including industrial robotics, prosthetics, virtual and augmented reality appliances. In rigid electronics, rotations, displacements and vibrations are typically monitored using magnetic field sensors prepared on flat and rigid substrates. Extending 2D structures into 3D space relying on the flexible and printed electronics approaches allows to enrich conventional or to launch novel functionalities of spintronic-based devices by tailoring geometrical curvature and 3D shape. We developed shapeable magnetoelectronics [1] – namely, flexible, stretchable [2] and even printable [3] skin-conformal magnetosensitive elements. The technology platform relies on high-performance magnetoresistive and Hall effect sensors fabricated on ultrathin polymeric foils based on thin film technologies or printing methods. These mechanically shapeable magnetosensitive elements enable touchless interactivity with our surroundings based on the interaction with magnetic fields, which is relevant for smart skins, soft robotics and human-machine interfaces. With these activities, we extended the use of high quality magnetic thin films to new research and technology fields. This topic is gaining visibility in the interdisciplinary community of physicists, chemists, mechanical and electrical engineers working on the fabrication of 3D shaped magnetic functional membranes, develops methods for their characterisation and theoretical frameworks for their description as well as puts forth concepts for the technological implementation of shapeable magnetoelectronics in different application fields. Here, we will review technological platforms allowing to realize mechanically imperceptible electronic skins for interactive electronics, which enable perception of the geomagnetic field, but also enable sensitivities down to ultra-small fields of sub-50 nT. These devices allow humans to orient with respect to earth’s magnetic field ubiquitously. Furthermore, biomagnetic orientation enables novel interactivity concepts for virtual and augmented reality applications. We showcase this by realizing touchless control of virtual units in a game using omnidirectional magnetosensitive skins [2]. This concept was further extended by demonstrating a flexible magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [4]. This is crucial for smart home applications, interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly conformal integrated feedback system [5] as well as in medicine for physicians and surgeons. In 2019, we brought these research activities to the next level in the frame of the Helmholtz Innovation Lab FlexiSens. FlexiSens bridges fundamental and application-oriented activities with the focus on the transfer of the thin film fabricated sensor technologies for flexible and printable electronics to the market. For this purpose, together with Scia Systems GmbH, we establish a 300 mm grade production line (thin film deposition, lithography, chemical processing of 300 mm wafers) to bring the our sensor technologies to the industry-relevant scale. Flexible magnetic field sensors are offered to industry partners either directly via the HZDR or via the company HZDR Innovation GmbH and already bring financial benefit to the group. The fundamental and application-oriented aspects of this technology will be discussed in the presentation.

[1] D. Makarov, M. Melzer, D. Karnaushenko, O. G. Schmidt, Applied Physics Reviews, 2016, 3, 011101.
[2] G. S. Cañón Bermúdez, H. Fuchs, L. Bischoff, J. Fassbender, D. Makarov, Nature Electronics, 2018, 1, 589.
[3] M. Ha, G. S. Cañón Bermúdez, T. Kosub, I. Mönch, Y. Zabila, E. S. Oliveros Mata, R. Illing, Y. Wang, J. Fassbender, D. Makarov, Advanced Materials, 2021, 33, 2005521.
[4] J. Ge, X. Wang, M. Drack, O. Volkov, M. Liang, G. S. Cañón Bermúdez, R. Illing, C. Wang, S. Zhou, J. Fassbender, M. Kaltenbrunner, D. Makarov, Nature Communications, 2019, 10, 4405.
[5] M. Ha, G. S. Cañón Bermúdez, J. A.-C. Liu, E. S. Oliveros Mata, B. A. Evans, J. B. Tracy, D. Makarov, Advanced Materials, 2021, 33, 2008751.

Keywords: flexible electronics; printed electronics; magnetic field sensing; human-machine interfaces; soft robotics

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  • Invited lecture (Conferences) (Online presentation)
    Advanced Nanomaterials Congress, 24.-27.10.2021, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-33281
Publ.-Id: 33281


Effect of Nozzle Geometry on Centerline Gas Holdup in Submerged Gas Injection

Xiao, J.; Yan, H.; Schubert, M.; Liu, L.; Döß, A.; Schleicher, E.; Hampel, U.

Non-circular nozzle geometries are widely used in many industrial processes with submerged gas injection for altering the centerline gas holdup to intensify the reaction process. However, the effect of the nozzle geometry on the centerline gas holdup is rarely investigated. In this work, hollow circular-shaped, gear-shaped, four-flower-shaped and multi-hole-shaped nozzle geometries are utilized to investigate the centerline gas holdup by wire-mesh sensors and
digital image processing. The results reveal that the centerline gas holdup is influenced by nozzle geometry, axial distance and gas flow rate. The centerline gas holdup for hollow circular-shaped,four-flower-shaped and multi-hole-shaped nozzles is larger than that of the gear-shaped nozzle.
The correlations for the centerline gas holdup are obtained based on modified Froude number Frm and dimensionless axial distance o via regression analysis. The correlations for hollow circular-shaped nozzle geometry obtained in this study are validated with experimental data
from this study and the literature.

Permalink: https://www.hzdr.de/publications/Publ-33280
Publ.-Id: 33280


Block model of passive seismic shear velocity and airborne electromagnetic resistivity in the Geyer area, Erzgebirge, Germany

Ryberg, T.; Kirsch, M.; Haberland, C.; Tolosana Delgado, R.; Viezzoli, A.; Gloaguen, R.

As a means of investigating the structure of the geological subsurface and delineating Sn-W-Li greisen-hosted mineral deposits in the Geyer-Ehrenfriedersdorf area, Central Erzgebirge, Germany, we collected an ambient noise dataset which was supplemented and analysed together with airborne time-domain electromagnetic data. The here presented dataset is a combined three-dimensional block model containing the following parameters:

(X), (Y), (Z) – Coordinates of the block model center nodes in ETRS89 UTM33N coordinates.

(PS_vel) – Shear wave velocity based on ambient noise data from a dense "LARGE-N" network comprising 400 low-power, short-period seismic stations tomographically inverted based on Bayesian statistics.

(logVTEM_res) – Logarithm of resistivity based on airborne time-domain electromagnetic data acquired using the Geotech Versatile Time Domain (VTEM™ ET) system and inverted using a layered earth approach.

(class_K-means) – Class labels of a spatially constrained clustering using K-means with 26 immediate neighbours performed on the bivariate velocity-resistivity 3D dataset.

Keywords: Ambient seismic noise; Airborne electromagnetics; Mineral exploration

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Publ.-Id: 33279


Garnet major-element composition as an indicator of host-rock type: a machine learning approach using the random forest classifier / supplementary data

Schoenig, J.; von Eynatten, H.; Tolosana Delgado, R.; Meinhold, G.

The database includes 13615 garnet compositions of eight oxides commonly analysed in lab routines: SiO2, TiO2, Al2O3, Cr2O3, FeOtotal, MnO, MgO, and CaO (in wt%). These are complemented by the following covariables:

setting and metamorphic facies class: code indicating the geologic/tectonic setting of the host rock

composition class: code indicating the compositional class of the host rock

author: authors of the original paper providing the data

journal: journal of the original paper

region: origin of the data, in the format "region, country"

sample name: sample ID in the original paper

Pavg(kbar): if available, indicated pressure

Tavg(°C): if available, indicated temperature

host-rock type and/or metamorphic facies: facies indication of host rock

lithology and/or protolith: composition indication of host rock

SiO2: wt%

TiO2: wt%

Al2O3: wt%

Cr2O3: wt%

FeOtotal: wt%

MnO: wt%

MgO: wt%

CaO: wt%

This research was funded by DFG grant EY 23/27-1.

Keywords: garnet major-element composition; host-rock discrimination

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Publ.-Id: 33278


Energy Flexibility Chances for the Wastewater Treatment Plant of the Benchmark Simulation Model 1

Parra Ramirez, M. A.; Reinecke, S.; Skouteris, G.; Hampel, U.

Future energy systems must mainly generate electricity from renewable resources. To
deal with the fluctuating availability of wind and solar power, new versatile electricity markets and
sustainable solutions concentrating on energy flexibility are needed. In this research, we investigated
the potential of energy flexibility achieved through demand-side response for the wastewater treat-
ment plant of the Benchmark Simulation Model 1. First, seven control strategies were simulated and
assessed. Next, the flexibility calls were identified, two energy flexibility scenarios were defined and
incorporated into the model, and the control strategies were evaluated anew. In this research, the
effluent ammonia concentration needed to be maintained within the limits for as long as possible.
Strategy 5, which controlled ammonia in Tank 5 at a low value and did not control any nitrate
in Tank 2, of Scenario 1, which was characterized by an undetermined on/off aeration cycle, was
then found to be the best. Although this control strategy led to high total energy consumption,
the percentage of time during which aeration was nearly suspended was one of the highest. This
work proposes a methodology that will be useful to plant operators who should soon reduce energy
consumption during spikes in electricity prices.

Keywords: Energy flexibility; Wastewater treatment plant; Benchmark Simulation Model 1; Control strategies; Aeration; Water quality

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Permalink: https://www.hzdr.de/publications/Publ-33277
Publ.-Id: 33277


Intraindividual comparison of [68Ga]-Ga-PSMA-11 and [18F]-F-PSMA-1007 in prostate cancer patients: a retrospective single-center analysis.

Hoberück, S.; Löck, S.; Borkowetz, A.; Sommer, U.; Winzer, R.; Zöphel, K.; Fedders, D.; Michler, E.; Kotzerke, J.; Kopka, K.; Hölscher, T.; Braune, A.

Background: The analysis aimed to compare the radiotracers [68Ga]-Ga-PSMA-11 and [18F]-F-PSMA-1007 intraindividually in terms of malignant lesions, mi(molecular-imaging)TNM staging and presumable unspecific lesions retrospectively as used in routine clinical practice.
Methods: A retrospective analysis of 46 prostate cancer patients (median age: 71 years) who underwent consecutive [68Ga]-Ga-PSMA-11- and [18F]-F-PSMA-1007-PET/CT or PET/MRI within a mean of 12 ± 8.0 days was performed. MiTNM staging was performed in both studies by two nuclear medicine physicians who were blinded to the results of the other tracer. After intradisciplinary and interdisciplinary consensus with two radiologists was reached, differences in both malignant and presumable nonspecific tracer accumulation were analyzed.
Results: Differences in terms of miTNM stages in both studies occurred in nine of the 46 patients (19.6%). The miT stages differed in five patients (10.9%), the miN stages differed in three patients (6.5%), and different miM stages occurred only in one patient who was upstaged in [18F]-F-PSMA-1007 PET. Concordant miTNM stages were obtained in 37 patients (80.4%). There was no significant difference between [18F]-F-PSMA-1007 and [68Ga]-Ga-PSMA-11 in the SUVmax locally (31.5 vs. 32.7; p = 0.658), in lymph node metastases (28.9 vs. 24.9; p = 0.30) or in bone metastases (22.9 vs. 27.6; p = 0.286). In [18F]-F-PSMA-1007 PET, more patients featured presumable unspecific uptake in the lymph nodes (52.2% vs. 28.3%; p: < 0.001), bones (71.7% vs. 23.9%; p < 0.001) and ganglia (71.7% vs. 43.5%; p < 0.001). Probable unspecific, exclusively [18F]-F-PSMA-1007-positive lesions mainly occurred in the ribs (58.7%), axillary lymph nodes (39.1%) and cervical ganglia (28.3%).
Conclusion: In terms of miTNM staging, both tracers appeared widely exchangeable, as no tracer relevantly outperformed the other. The differences between the two tracers were far more common in presumable unspecific lesions than in malignant spots. A routinely performed two-tracer study could not be shown to be superior. Since it seems at least challenging for most nuclear medicine departments to provide both [18F]-F-PSMA-1007 and [68Ga]-Ga-PSMA-11, it appears reasonable to choose the PSMA radiotracer depending on local availability with attention to the greater occurrence of nonspecific bone findings with [18F]-F-PSMA-1007.

Keywords: PET; PSMA; Prostate cancer; [18F]F-PSMA-1007; [68Ga]Ga-PSMA-11; miTNM

Permalink: https://www.hzdr.de/publications/Publ-33276
Publ.-Id: 33276


Fermi-surface reconstruction at the metamagnetic high-field transition in uranium mononitride

Hamann, S.; Förster, T.; Gorbunov, D.; König, M.; Uhlarz, M.; Wosnitza, J.; Helm, T.

We report on the electronic and thermodynamic properties of the antiferromagnetic metal uranium mononitride with a Néel temperature TN ≈ 53 K. The fabrication of microstructures from single crystals enables us to study the low-temperature metamagnetic transition at approximately 58 T by high-precision magnetotransport, Halleffect, and magnetic-torque measurements.We confirm the evolution of the high-field transition from a broad and complex behavior to a sharp first-order-like step, associated with a spin flop at low temperature. In the high-field state, the magnetic contribution to the temperature dependence of the resistivity is suppressed completely. It evolves into an almost quadratic dependence at low temperatures indicative of a metallic character. Our detailed investigation of the Hall effect provides evidence for a prominent Fermi-surface reconstruction as the system is pushed into the high-field state.

Permalink: https://www.hzdr.de/publications/Publ-33274
Publ.-Id: 33274


Underground measurements and simulations on the muon intensity and 12C-induced nuclear reactions at low energies

Ludwig, F.

The reaction 12C(α,γ)16O is of paramount importance for the nucleosynthesis of heavier elements in stars. It takes place during helium burning and determines the abundance of 12C and 16O at the end of this burning stage and therefore influences subsequent nuclear reactions. Currently the cross section at astrophysically relevant energies is not known with satisfactory precision.
Due to the low cross section of the reaction, low background, high beam intensities and target thicknesses are necessary for experiments. Therefore a new laboratory hosting a 5 MV ion accelerator, was built in the shallow-underground tunnels of Felsenkeller. The main background component in such laboratories was investigated with a muon telescope in this thesis. It was found, that the rock overburden of about 45 m vertical depth reduces the muons by a factor of about 40 compared to the surface. Furthermore the results of the measurements were compared to a simulation based on the geometry of the facility and showed good agreement.
In the next step the accelerator was put into operation. Since the experiment on 12C(α,γ)16O will be done in inverse kinematics, an intense carbon beam is necessary to reach sufficient statistics. For this, the creation and extraction of carbon ions in an external ion source was improved. The external source now provides steady currents of 12C− of above 100 μA.
In the following the transmission through the accelerator and the high-energy beamline was tested with a beam restricted in width. The pressure of the gas stripper in the centre of the accelerator and the parameters of different focusing elements after the accelerator were varied. It was found, that for a desired carbon beam energy of below 9 MeV, the 2+ charge state is suited best, where up to 35% of the inserted beam could be transmitted.
To ease the planning of future experiments and aid the analysis of the data, the target chamber and two different kinds of cluster detectors were modelled in Geant4. The low-energy region was verified by comparing the simulations to measurements with radioactive calibration sources. Deviations for the detectors were below 10% without target chamber, and up to 30% for individual germanium crystals of the Cluster Detectors with the target chamber.
A first test measurement was undertaken to investigate the capabilities of the new laboratory. Solid tantalum targets implanted with 4 He were prepared. An ERDA analysis of the used solid targets showed contaminations with carbon and oxygen. These led to beam-induced background in the region of interest during the irradiation.
Then the targets were irradiated with a carbon beam at two different energies. While no clear signal of 12C(α,γ)16O could be observed, the beam could be steered on the target for the whole duration of the beam time spanning five days. Problems during this test, like low beam current, were identified. These could be partly remedied in the scope of this thesis. Suggestions for improvements for a second test run were developed as well.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-116 2021
    ISSN: 2191-8708, eISSN: 2191-8716

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The Future of Solar Neutrinos

Orebi Gann, G. D.; Zuber, K.; Bemmerer, D.; Serenelli, A.

In this article we review the current state of the field of solar neutrinos, including flavour oscillations, non-standard effects, solar models, cross section measurements, and the broad experimental program thus motivated and enabled. We discuss the historical discoveries that contributed to current knowledge, and define critical open questions to be addressed in the next decade. We discuss the state of the art of standard solar models, including uncertainties and problems related to the solar composition, and review experimental and model solar neutrino fluxes, including future prospects. We review the state of the art of the nuclear reaction data relevant for solar fusion in the proton-proton chain and carbon-nitrogen-oxygen cycle. Finally, we review the current and future experimental program that can address outstanding questions in this field.

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Direct Measurement of the 13C(α ,n)16O Cross Section into the s-Process Gamow Peak

Ciani, G. F.; Csedreki, L.; Rapagnani, D.; Aliotta, M.; Balibrea-Correa, J.; Barile, F.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Cavanna, F.; Chillery, T.; Colombetti, P.; Corvisiero, P.; Cristallo, S.; Davinson, T.; Depalo, R.; Di Leva, A.; Ferraro, F.; Fiore, E.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Lugaro, M.; Marigo, P.; Masha, E.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Paticchio, V.; Perrino, R.; Piatti, D.; Prati, P.; Schiavulli, L.; Stöckel, K.; Straniero, O.; Szücs, T.; Takacs, M. P.; Terrasi, F.; Vescovi, D.; Zavatarelli, S.; Elekes, Z.

One of the main neutron sources for the astrophysical s process is the reaction C 13 (α ,n )O 16 , taking place in thermally pulsing asymptotic giant branch stars at temperatures around 90 MK. To model the nucleosynthesis during this process the reaction cross section needs to be known in the 150-230 keV energy window (Gamow peak). At these sub-Coulomb energies, cross section direct measurements are severely affected by the low event rate, making us rely on input from indirect methods and extrapolations from higher-energy direct data. This leads to an uncertainty in the cross section at the relevant energies too high to reliably constrain the nuclear physics input to s -process calculations. We present the results from a new deep-underground measurement of C 13 (α ,n )O 16 , covering the energy range 230-300 keV, with drastically reduced uncertainties over previous measurements and for the first time providing data directly inside the s -process Gamow peak. Selected stellar models have been computed to estimate the impact of our revised reaction rate. For stars of nearly solar composition, we find sizeable variations of some isotopes, whose production is influenced by the activation of close-by branching points that are sensitive to the neutron density, in particular, the two radioactive nuclei Fe 60 and Pb 205 , as well as Gd 152 .

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Publ.-Id: 33271


Low-energy resonances in the 18O(p,γ)19F reaction

Pantaleo, F. R.; Boeltzig, A.; Best, A.; Perrino, R.; Aliotta, M.; Balibrea-Correa, J.; Barile, F.; Bemmerer, D.; Broggini, C.; Bruno, C. G.; Buompane, R.; Caciolli, A.; Cavanna, F.; Chillery, T.; Ciani, G. F.; Corvisiero, P.; Csedreki, L.; Davinson, T.; Deboer, R. J.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Fiore, E. M.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Kochanek, I.; Lugaro, M.; Masha, E.; Menegazzo, R.; Mossa, V.; Paticchio, V.; Piatti, D.; Prati, P.; Rapagnani, D.; Schiavulli, L.; Stöckel, K.; Straniero, O.; Szücs, T.; Takács, M. P.; Trezzi, D.; Wiescher, M.; Zavatarelli, S.; Derasmo, G.

Background: Shell hydrogen burning during the asymptotic giant branch (AGB) phase through the oxygen isotopes has been indicated as a key process that is needed to understand the observed 18O/16O relative abundance in presolar grains and in stellar atmospheres. This ratio is strongly influenced by the relative strengths of the reactions 18O(p ,α )15N and 18O(p ,γ )19F in low-mass AGB stars. While the former channel has been the focus of a large number of measurements, the (p ,γ ) reaction path has only recently received some attention and its stellar reaction rate over a wide temperature range rests on only one measurement.

Purpose: Our aim is the direct measurement of states in 19F as populated through the reaction 18O(p ,γ )19F to better determine their influence on the astrophysical reaction rate, and more generally to improve the understanding of the nuclear structure of 19F.
Method: Branchings and resonance strengths were measured in the proton energy range Eplab=150 -400 keV , using a high-purity germanium detector inside a massive lead shield. The measurement took place in the ultra-low-background environment of the Laboratory for Underground Nuclear Astrophysics (LUNA) experiment at the Gran Sasso National Laboratory, leading to a highly increased sensitivity.
Results: The uncertainty of the γ branchings and strengths was improved for all four resonances in the studied energy range; many new transitions were observed in the case of the 334 keV resonance, and individual γ decays of the 215 keV resonance were measured for the first time. In addition a number of transitions to intermediate states that decay through α emission were identified. The strengths of the observed resonances are generally in agreement with literature values.
Conclusions: Our measurements substantially confirm previous determinations of the relevant resonance strengths. Therefore the 18O(p ,γ )19F reaction rate does not change with respect to the reaction rate reported in the compilations commonly adopted in the extant computations of red-giant branch and AGB stellar models. Nevertheless, our measurements definitely exclude a nonstandard scenario for the fluorine nucleosynthesis and a nuclear physics solution for the 18O depletion observed in Group 2 oxygen-rich stardust grains.

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Publ.-Id: 33270


Gas permeability and selectivity of a porous WS₂ monolayer

Hassani, N.; Ghorbani Asl, M.; Radha, B.; Drndic, M.; Krasheninnikov, A.; Neek-Amal, M.

Atomically thin porous membranes display high selectivity for gas transport and separation. To create such systems, defect engineering of 2D materials, e.g., via ion irradiation, provides an efficient route. Here,first-principles calculations are used to study permeability of He, H₂, N₂, CO₂, and CH₄ molecules through WS₂ monolayers containing vacancy-type defects. We found that i) for most pores, regardless of the pore size, H₂ exhibits large permeability (~10⁵ GPU), ii) dissociation of H₂ molecules and edge saturation occurs when they approach the angstrom-size pores, iii) the 1W6S pore (one W and six S atoms are removed from WS₂ monolayer) can separate H₂ and N₂ gases with high selectivity, and iv) the 2W6S pore exhibits exceptionally high selectivity for separation of H2/CO2 (~10¹³) and H₂/CH₄ (~10⁹).

Keywords: selectivity; permeance; translocation energy barrier; interaction energy; porous monolayer WS2

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Permalink: https://www.hzdr.de/publications/Publ-33268
Publ.-Id: 33268


Real-time tracking of fast-moving objects using ultrafast electron beam X-ray computed tomography

Windisch, D.; Barthel, F.; Hampel, U.; Bieberle, A.

Ultrafast electron beam X-ray computed tomography (UFXCT) allows for non-invasive investigation of multi-phase flows with frame rates up to 8,000 slice images per second and a spatial resolution down to 1 mm (see Fig. 1). With the current detector electronics, however, the scanner is limited to offline image reconstruction after the data acquisition which limits its applicability. Nevertheless, especially real-time process and scanner control are of high interest in multi-phase flow investigations. For this, we redesigned the detector electronics firmware, enhanced data transfer, and implemented real-time image reconstruction and analysis. We finally conducted a demonstration experiment in which the position of a moving test object is dynamically controlled using the online analysis of UFXCT images.

Keywords: Image-based real-time process control; ultrafast computed tomography

  • Lecture (Conference) (Online presentation)
    World Congress on Industrial Process Tomography (WCIPT-10), 13.-16.09.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33266
Publ.-Id: 33266


Data for "Sauerstoffeintragstechnologien für die biologische Abwasseraufbereitung"

Parra Ramirez, M. A.; Ristau, F.; Mohseni, E.; Herrmann-Heber, R.; Reinecke, S.; Hampel, U.

Data set for the publication in the wwt modernisierung magazine with the tittle "Sauerstoffeintragstechnologien für die biologische Abwasseraufbereitung".

Keywords: Aeration; Bubble size; Dynamic operation

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Publ.-Id: 33265


Atomistic simulations on the relationship between solid-phase epitaxial recrystallization and self-diffusion in amorphous silicon

Posselt, M.; Bracht, H.; Radic, D.

Recent experimental results on self-diffusion (SD) in amorphous silicon (a-Si) [J. Kirschbaum et al. Phys. Rev. Lett. 120, 225902 (2018)] indicate that the atomic mechanism of this process is akin to that of solid-phase epitaxial recrystallization (SPER). In this work this relationship is investigated by classical molecular dynamics (MD) simulations using selected interatomic potentials. At the beginning an overview on the status of the present knowledge on SPER and SD is given. Then properties of a-Si are determined for Stillinger-Weber(SW)-type and Tersoff(T)-type potentials. In all cases a good or satisfactory agreement with structural data measured at room temperature is obtained, in particular with the experimental static structure factor. On the other hand, deviations are found for thermal properties. These studies are followed by extraordinarily extensive MD simulations of SPER and SD which reveal that the temperature dependence of those processes can be described by a simple Arrhenius relation. This corresponds to the results of the measurements. However a fully quantitative agreement cannot be found in the case of the interatomic potentials considered. On the other hand, for a given potential the activation enthalpies of both SPER and SD are rather equal. Therefore, the simulated atomic-level processes are obviously very similar. This is consistent with earlier qualitative discussions of results of SPER and SD experiments. The quantitative agreement with measured data for SPER and SD can be improved for certain SW-type potentials if for a-Si an increased value of the three-body parameter is used.

Keywords: Amorphous silicon; Solid phase epitaxial recrystallization; Self-diffusion; Atomistic simulation

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Publ.-Id: 33264


A multifunctional, theranostic approach for universal CAR T cell therapy, targeted alpha-therapy and imaging of prostate cancer

Arndt, C.; Bergmann, R.; Máthé, D.; Berndt, N.; Loureiro, L. R.; Szöllősi, D.; Kovács, N.; Hegedűs, N.; Kovács, T.; Feldmann, A.

Background
Chimeric antigen receptor (CAR) T-cells are living drugs successfully applied for treatment of patients with hematological malignancies. However, clinical translation towards solid tumor therapy faces several challenges and does not result in durable responses. In order to improve CAR T-cells´ therapeutic efficiency, combinations with other treatment and imaging modalities are intensively investigated.

Methods
For prostate cancer theranostics we developed a novel, multifunctional IgG4-based antibody construct directed against the prostate stem cell antigen (PSCA). Due to equipment with the UniCAR-tag E5B9 it can be used as a target module (TM) for the well-established UniCAR T-cell approach [1]. Functionality of the PSCA-IgG4 antibody was investigated in vitro by conducting co-cultivation assays with UniCAR T-cells and PSCApos/PSCAneg prostate cancer cells. After radiolabeling with copper-64 or actinium-225, imaging and radioimmunotherapeutic potential of the PSCA-IgG4 antibody were studied using NMRI Foxn1 nu/nu mice.

Results
UniCAR T-cells were specifically activated upon cross-linkage with PSCApos tumor cells via the novel PSCA-IgG4 antibody, which resulted in the secretion of pro-inflammatory cytokines and an efficient tumor cell lysis with EC50 values in the picomolar range. 64Cu- or 225Ac-labeled PSCA-IgG4 antibodies were successfully applied for PET imaging and radioimmunotherapy of prostate tumors in experimental mice. Antibodies specifically enriched at the tumor side whereby maximal tumor accumulation and optimal tumor-to-background ratios were reached after 31 hours. Treatment of tumor-bearing mice with 225Ac-labeled PSCA-IgG4 antibody further resulted in significant lower tumor sizes compared to the control group after 40 days.

Conclusions
We here present a novel, multifunctional PSCA-IgG4 antibody construct for prostate cancer theranostics that facilitates not only UniCAR T-cell immunotherapy, but is also a suitable tool for targeted alpha-therapy and imaging of prostate cancer. This opens the door for a combined radioimmunotherapeutic and imaging approach of prostate cancer that may help to overcome present hurdles in solid tumor therapy.

  • Poster (Online presentation)
    World Immunotherapy Council’s (WIC) 4th Young Investigators Symposium during 36th Annual Meeting & Pre-Conference Programs (SITC 2021), 10.11.2021, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-33263
Publ.-Id: 33263


Towards Scalable Reconfigurable Electronics: Fabrication of Schottky Barrier Field-Effect Transistors using Flash Lamp Annealing

Khan, M. B.; Ghosh, S.; Prucnal, S.; Hübner, R.; Erbe, A.; Georgiev, Y.

To complement the scaling down of complementary metal-oxide-semiconductor (CMOS), new device concepts have been introduced. One such concept is the reconfigurable field-effect transistor (RFET). In the most general case, an RFET is a silicon nanowire (SiNW) based device. The SiNW is silicided at both ends, which results in silicide-Si-silicide Schottky junctions. Typically, two distinct gate electrodes are placed on silicide-Si junctions. By controlling the electrostatic potential on the gate electrodes, the RFET is programmed to the p- or n- polarity. We report on the fabrication and electrical characterization of top-down fabricated SiNW based RFETs. Flash lamp annealing based silicidation process is developed, which enables control over the silicidation process. Uni-polar transfer characteristics are obtained using two top-gates. The effect of implementing various gate dielectric materials (SiO2, Al2O3 and hBN) is studied to enhance device electrostatics.

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  • Poster (Online presentation)
    84th Annual DPG Meeting, 27.09.2021, Virtual, Germany

Permalink: https://www.hzdr.de/publications/Publ-33262
Publ.-Id: 33262


Data for: Bubble formation from sub-millimeter orifices: experimental analysis and modeling

Mohseni, E.; Eduarda Chiamulera, M.; Reinecke, S. F.; Hampel, U.

raw data and processed data for the publication.

Keywords: Bubble formation; Sub-millimeter orifice; Gas reservoir; Bubble dynamics; Modeling

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Permalink: https://www.hzdr.de/publications/Publ-33261
Publ.-Id: 33261


Analyzing the microbial influence on corrosion at the bentonite-canister interface in a repository of high-level radioactive waste

Matschiavelli, N.

The talk gives an overview about some microbiological-related experimental work in the FWOB-department. The talk focusses on the microbial influence on different barrier materials in a repository for high-level radioactie waste.

  • Lecture (others) (Online presentation)
    HIF-FWOB joint seminar, 02.12.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33260
Publ.-Id: 33260


Bubble formation from sub-millimeter orifices: experimental analysis and modeling

Mohseni, E.; Chiamulera, M.; Reinecke, S.; Hampel, U.

We developed a theoretical model that estimates the bubble size from sub-millimeter orifices under variable gas flow conditions. The model is successfully tested for orifices with diameters in the range of 0.2 mm to 1 mm under both quasi-static and dynamic bubbling regimes. The model is able to predict the final bubble radius with an accuracy better than 20% compared with the experimental results. Moreover, we explicitly look into the influence of the gas reservoir volume V_c upstream of the orifice on the gas reservoir pressure P_c by simultaneously monitoring the events, i.e. changes in the state of bubble, upstream and downstream of orifices. We found that, variations in P_c reduce as V_c increases. Analysis of the dynamics of the dominating forces acting on a bubble show that, enlarging V_c mainly amplifies the gas momentum force and the liquid inertia force. Hence, the bubble detachment mechanism may no longer be only buoyancy driven.

Keywords: Bubble formation; Sub-millimeter orifice; Gas reservoir; Bubble dynamics; Modeling

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Permalink: https://www.hzdr.de/publications/Publ-33258
Publ.-Id: 33258


Sauerstoffeintragstechnologien für die biologische Abwasseraufbereitung

Parra Ramirez, M. A.; Ristau, F.; Mohseni, E.; Herrmann-Heber, R.; Reinecke, S.; Hampel, U.

In entwickelten Ländern ist die Abwasseraufbereitung für etwa 1 % des gesamten elektrischen Energieverbrauchs verantwortlich, wobei die biologische Behandlung in Belebungsbecken bis zu 80 % des gesamten Energieverbrauchs ausmacht. Zudem wird für die nahe Zukunft ein Anstieg des Energieverbrauchs im Wassersektor um 80 % prognostiziert. Ein wesentlicher Faktor dabei ist die Verwendung energieintensiver Druckbelüftungssysteme, um den für die biologische Aktivität notwendigen Sauerstoff bereitzustellen. Wissenschaftler des Helmholtz-Innovationslabors CLEWATER arbeiten daran, die Effizienz des Belüftungsprozesses deutlich zu steigern. In diesem Artikel werden die aktuellen Fortschritte bei zwei von CLEWATEC vorgeschlagenen Ansätzen zur effizienten Belüftung vorgestellt.

Keywords: Belüftung; Sauerstoffeintragseffizienz; Blasengröße; Dynamischer Betrieb

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  • Contribution to external collection
    in: wwt Modernisierungsreport, Frankfurt am Main: Deutscher Fachverlag GmbH, 2021

Permalink: https://www.hzdr.de/publications/Publ-33256
Publ.-Id: 33256


Data publication: In-situ GISAXS observation of ion-induced nanoscale pattern formation on crystalline Ge(001) in the reverse epitaxy regime

Erb, D.; Myint, P.; Evans-Lutterodt, K.; Ludwig, K.; Facsko, S.

experimental raw data: in-situ Grazing Incidence Small Angle X-ray Scattering (GISAXS), ex-situ Atomic Force Microscopy (AFM); simulated raw data: surface topography (RIDO)

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Permalink: https://www.hzdr.de/publications/Publ-33255
Publ.-Id: 33255


Unvailing charge storage and degradation mechanisms of electrochemical energy storage systems via ex-situ and in-situ analyses

Lee, J.; Monrrabal, G.; Landgraf, S.; Weber, N.; Weier, T.

In recent decades, a wealth of new electrochemical energy storage systems have emerged as well as a variety of novel and advanced materials for conventional systems. Once new systems and materials are introduced, they are often challenged by performance degradation such as capacity loss and the increase in cell resistance. Since degradation processes could also raise safety issues such as gas evolution and short-circuiting events, understanding charge storage and degradation mechanisms plays a crucial role in further development. In this work, some of the progress on unvailing charge storage and degradation mechanisms for various electrochemical energy storage systems will be presented. In particular, relying on ex-situ and in-situ technologies, X-ray diffraction, scanning transmission electron microscopy, neutron radiography, degradation processes of advanced electrode materials such as layered nickel-rich cathodes [1-3] and MXene [4] in lithium-ion batteries will be discussed. Additionally, some of the critical limitations of in-situ technologies, such as the radiolysis process in transmission electron microscopy, will be introduced, including the simulation work based on the reaction-diffusion model. [5, 6] Finally, we introduce our recent work on understanding the charge storage mechanism of membrane-free alkali metal-iodide (A-AI) batteries relying on ex-situ neutron radiography.
Acknowledgement:
This project has received funding from the European Union’s Horizon 2020 research and innovation
programme under grant agreement No 963599.

References:

1. C. Xu, K. Marker, J. Lee, A. Mahadevegowda, P. J. Reeves, S. J. Day, M. F. Groh, S. P. Emge, C. Ducati, B. Layla Mehdi, C. C. Tang and C. P. Grey, Nat. Mater., 2021, 20, 84-92.
2. W. Li, I. Siachos, J. Lee, S. A. Corr, C. P. Grey, N. D. Browning and B. Layla Mehdi, Microsc. Microanal., 2021, 27, 1254-1255.
3. J. Lee, H. Amari, M. Bahri, Z. Shen, C. Xu, Z. Ruff, C. P. Grey, O. Ersen, A. Aguadero, N. D. Browning and B. L. Mehdi, Batteries & Supercaps, 2021, DOI: 10.1002/batt.202100110.
4. J. Lee, D. Spurling, O. Ronan, W. Li, I. Siachos, V. Nicolosi and B. Layla Mehdi, Microsc. Microanal., 2021, 27, 1976-1977.
5. J. Lee, D. Nicholls, N. D. Browning and B. L. Mehdi, Phys. Chem. Chem. Phys., 2021, 23, 17766-17773.
6. D. Nicholls, J. Lee, H. Amari, A. J. Stevens, B. L. Mehdi and N. D. Browning, Nanoscale, 2020, 12, 21248-21254.

  • Lecture (Conference)
    Europe-Korea Conference on Science and Technology 2021, 10.10.2021, BEW, Essen, Germany

Permalink: https://www.hzdr.de/publications/Publ-33254
Publ.-Id: 33254


Data publication: B₁₂X₁₁(H₂)⁻: Exploring the limits of isotopologue selectivity of hydrogen adsorption

Wulf, T.

Sample ORCA 4.2.1 input files (TXT);
atomic coordinates and NEB paths (XYZ);
vibration files (7-column XYZ)

for publication

T. Wulf, J. Warneke, T. Heine: B₁₂X₁₁(H₂)⁻: exploring the limits of isotopologue selectivity of hydrogen adsorption. RSC Advances, 11:46 (2021), 28466–28475, doi:10.1039/d1ra06322g

Keywords: hydrogen adsorption,closo-dodecaborates,hydrogen isotopes,boron clusters

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Publ.-Id: 33253


Effect of Mechanical Stress on the Splitting of Spin Sublevels in 4H-SiC

Breev, I. D.; Likhachev, K. V.; Yakovleva, V. V.; Veishtort, I. P.; Skomorokhov, A. M.; Nagalyuk, S. S.; Mokhov, E. N.; Astakhov, G.; Baranov, P. G.; Anisimov, A. N.

The effect of static mechanical strain on the splitting of spin sublevels of color centers based on spin 3/2 silicon vacancies in silicon carbide at room temperature has been shown. The deformed heterointerface of the AlN/4H-SiC structure has been studied. Stresses near the heterointerface have been determined using con- focal Raman spectroscopy. The spin–strain coupling constants −0.1 GHz/strain and −0.8 GHz/strain for the V2 center in 4H-SiC have been experimentally determined for the first time using the optically detected magnetic resonance method. The results obtained can be used to control spin states in SiC by means of the controlled piezoelectric strain in AlN and to estimate the fine-structure parameter D of spin centers using Raman scattering. Such an estimate makes it possible to forecast magnetometric parameters of nanosensors based on SiC nanocrystals.

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Publ.-Id: 33251


alpaka-group/alpaka: alpaka 0.7.0: Maximum Warp

Worpitz, B.; Bastrakov, S.; Ehrig, S.; Gruber, B. M.; Hübl, A.; Kelling, J.; Rogers, D. M.; Stephan, J.; Widera, R.

The alpaka library is a header-only C++14 abstraction library for accelerator development. Its aim is to provide performance portability across accelerators through the abstraction (not hiding!) of the underlying levels of parallelism.

Keywords: CUDA; HPC; alpaka; OpenMP; HIP; C++; GPU; heterogeneous computing; performance portability

Permalink: https://www.hzdr.de/publications/Publ-33250
Publ.-Id: 33250


Strong Dipolar Repulsion of One-Dimensional Interfacial Excitons in Monolayer Lateral Heterojunctions

Yuan, L.; Zheng, B.; Zhao, Q.; Kempt, R.; Brumme, T.; Kuc, A. B.; Ma, C.; Deng, S.; Pan, A.; Huang, L.

Repulsive and long-range exciton-exciton interactions are crucial for the exploration of one-dimensional (1D) correlated quantum phases in the solid state. However, the experimental realization of nanoscale confinement of 1D dipolar exciton has thus far been limited. Here, we demonstrated atomically precise lateral heterojunctions based on transitional-metal dichalcogenides (TMDC) as a new platform for 1D dipolar excitons. The dynamics and transport of the interfacial charge transfer excitons in a type II WSe2-WSSe lateral heterostructure were spatially and temporally imaged using ultrafast microscopy. The expansion of the exciton cloud driven by dipolar repulsion was found to be strongly density dependent and highly anisotropic. The interaction strength between the 1D excitons was determined to be ~3.9 × 10^-14 eV cm^-2 corresponding to a dipolar length of 310 nm, which is a factor of 2-3 larger than the interlayer excitons at two-dimensional van der Waals vertical interfaces. These results suggest 1D dipolar excitons with large static in-plane dipole moment in lateral TMDC heterojunctions as a new system for investigating quantum many-body physics.

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  • Secondary publication expected from 04.08.2024

Permalink: https://www.hzdr.de/publications/Publ-33249
Publ.-Id: 33249


Flow Feature Extraction with Contactless Inductive Flow Tomography in Presence of the Variable Magnetic Field of an Electromagnetic Brake

Glavinic, I.; Stefani, F.; Eckert, S.; Wondrak, T.

Continuous casting is the primary means of production of steel semi-products. It is of paramount importance to keep the quality of the produced stock constantly at a high level to meet the tight margins of the steel industry. Flow conditions in the mould, where the solidification process starts, significantly impact the quality of the end product. Unfortunately, the harsh industrial environment limits the applicable measurement methods to detect any undesired flow conditions, thus limiting the viable control strategies.Contactless Inductive Flow Tomography (CIFT) was previously proposed to identify flow features in the mould of a continuous caster. While the Electromagnetic Brake (EMBr) is a common way to influence the flow, it has a disturbing influence on CIFT measurements which, however, can be compensated. In this work, we introduce the experimental setup, measurement technique, and discuss the control strategy derived from the CIFT flow reconstruction.

Keywords: Contactless Inductive Flow Tomography; Continuous casting; Electromagnetic Brake

  • Lecture (Conference) (Online presentation)
    10th World Congress on Industrial Process Tomography, 13.09.2021, Tianjin, China
  • Contribution to proceedings
    10th World Congress on Industrial Process Tomography, 13.-16.09.2021, Tianjin, China

Permalink: https://www.hzdr.de/publications/Publ-33248
Publ.-Id: 33248


Resistivity contrast imaging in semiconductor structures using ultra-low energy scanning electron microscopy

Jozwik, I.; Jagielski, J.; Dumiszewska, E.; Kaminski, M.; Kentsch, U.

The damage-induced voltage alteration (DIVA) contrast mechanism in scanning electron microscope (SEM) has been studied in broad range of the primary electron beam energies, with a special emphasis on the ultra-low energy range. The SEM imaging contrast related to resistivity changes in the In(0.55)Al(0.45)P irradiated with He2+ ions of 600 keV was subjected to an analysis in a range of 10 keV down to 10 eV of primary electron energies. The problem of specimen charging in ultra-low energy range and its effect on the contrast in SEM images has been tackled for the first time. Contrary to expectations based on the classical total emission yield approach, the potentials formed at the highly resistive part of irradiated area led to dramatic increase in the intensity of registered signal for primary electron energies below E1, which can be explained as signal saturation due to potential on the specimen surface acting as repeller for primary electrons. Nevertheless, the experimental data presenting the influence of the beam energy on the potential formation on the surface of an insulating material under electron irradiation have been presented for the first time in ultra-low energy regime.

Keywords: Ion damage; Ion irradiation; Low-kV SEM; Semiconductors

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Permalink: https://www.hzdr.de/publications/Publ-33247
Publ.-Id: 33247


New insights into REE mineralisation of Storkwitz carbonatite

Loidolt, C.; Zimmermann, R.; Tusa, L.; Lorenz, S.; Ebert, D.; Gloaguen, R.; Broom-Fendley, S.

The Storkwitz carbonatite breccia, located near Delitzsch, Germany, is one of the few domestic potential rare earth elements (REE) deposits located in Europe. The complex is understudied when compared to other potential European REE sources due to the presence of more than 100 m of Cenozoic glacio-fluvial sedimentary cover. We present the results of a mineralogical and geochemical investigation of the recently acquired ~700 m deep SES 1/2012 borehole. The Storkwitz breccia is composed of clasts of country rocks and carbonatites ranging from <1 mm to ~30 cm in size, cemented by ankeritic carbonatite. Extensive fenitisation and biotitisation mainly affects clasts of coarse-grained granitoids and medium-grained, plutonic dolomite-calcite-carbonatites. The 425 m to 542 m interval of the core shows an intersection of the Storkwitz breccia with local REE-enrichment. REE mineralisation is predominantly contained within an REE-fluorcarbonate bearing mineral assemblage, which locally forms hexagonal pseudomorphs in clasts of fine-grained ankerite-carbonatite. The predominance of pseudomorphic REE minerals in the ankerite-carbonatite fits with recent experimental and fluid inclusion data suggesting formation from an evolved ‘brine-melt’ phase, which occurred prior to brecciation. Our findings suggest that REE mineralisation occurs post-brecciation within the ankerite-carbonatite groundmass of the breccia and as rare REE-fluorcarbonate rims around clasts in the breccia matrix.

Keywords: REE; carbonatite; Storkwitz

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-33246
Publ.-Id: 33246


Influence of Cr substitution on the reversibility of the magnetocaloric effect in Ni-Cr-Mn-In Heusler alloys

Salazar Mejia, C.; Devi, P.; Singh, S.; Felser, C.; Wosnitza, J.

We present the effect of substitution-induced pressure on the reversibility of the magnetocaloric effect (MCE) in Ni2CrxMn1.4−xIn0.6 (x = 0.1, 0.2, 0.3) alloys, through characterization in pulsed magnetic fields.We measured the adiabatic temperature change ΔTad directly during applied magnetic field pulses of 2 and 6 T. We paid special attention to the reversibility of ΔTad. The substitution of Mn by Cr in Ni2Mn1.4In0.6 leads to a negative pressure, as evidence by the increase of the lattice parameters, which shifts the martensitic transition towards lower temperatures and enhances the ferromagnetism of the martensite phase.We found a large value of ΔTad = −7 K at T = 270 K for the sample with x = 0.1 for a field change of 6 T. We discuss the reversibility of the MCE in these alloys in terms of the Clausius-Clapeyron equation.

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Permalink: https://www.hzdr.de/publications/Publ-33244
Publ.-Id: 33244


Data publication: Structure and Thermodynamics of Eu(III) and Cm(III) Complexes with Glucuronic Acid

Reese, S.; Kaden, P.; Taylor, C. J.; Kloditz, R.; Schmidt, M.

TRLFS spectra; NMR spectra; QMMM data

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Permalink: https://www.hzdr.de/publications/Publ-33243
Publ.-Id: 33243


Planar triangular S = 3/2 magnet AgCrSe2: Magnetic frustration, short range correlations, and field-tuned anisotropic cycloidal magnetic order

Baenitz, M.; Piva, M. M.; Luther, S.; Sichelschmidt, J.; Ranjith, K. M.; Dawczak-Debicki, H.; Ajeesh, M. O.; Kim, S.-J.; Siemann, G.; Bigi, C.; Manuel, P.; Khalyavin, D.; Sokolov, D. A.; Mokhtari, P.; Zhang, H.; Yasuoka, H.; King, P. D. C.; Vinai, G.; Polewczyk, V.; Torelli, P.; Wosnitza, J.; Bukhardt, U.; Schmidt, B.; Rosner, H.; Wirth, S.; Kühne, H.; Nicklas, M.; Schmidt, M.

Single crystals of the hexagonal triangular lattice compound AgCrSe2 have been grown by chemical vapor transport. The crystals have been carefully characterized and studied by magnetic susceptibility, magnetization, specific heat, and thermal expansion. In addition, we used Cr-electron spin resonance and neutron diffraction to probe the Cr 3d3 magnetism microscopically. To obtain the electronic density of states, we employed x-ray absorption and resonant photoemission spectroscopy in combination with density functional theory calculations. Our studies evidence an anisotropic magnetic order below TN = 32 K. Susceptibility data in small fields of about 1 T reveal an antiferromagnetic (AFM) type of order for H ⊥ c, whereas for H II c the data are reminiscent of a field-induced ferromagnetic (FM) structure. At low temperatures and for H ⊥ c, the field-dependent magnetization and AC susceptibility data evidence a metamagnetic transition at H+ = 5 T, which is absent for H II c. We assign this to a transition from a planar cycloidal spin structure at low fields to a planar fanlike arrangement above H+. A fully ferromagnetically polarized state is obtained above the saturation field of H⊥S = 23.7 T at 2K with a magnetization of Ms = 2.8 μB/Cr. For H II c, M(H) monotonically increases and saturates at the same Ms value at HIIS = 25.1 T at 4.2 K. Above TN , the magnetic susceptibility and specific heat indicate signatures of two dimensional (2D) frustration related to the presence of planar ferromagnetic and antiferromagnetic exchange interactions. We found a pronounced nearly isotropic maximum in both properties at about T = 45 K, which is a clear fingerprint of short range correlations and emergent spin fluctuations. Calculations based on a planar 2D Heisenberg model support our experimental findings and suggest a predominant FM exchange among nearest and AFM exchange among third-nearest neighbors. Only a minor contribution might be assigned to the antisymmetric Dzyaloshinskii-Moriya interaction possibly related to the noncentrosymmetric polar space group R3m. Due to these competing interactions, the magnetism in AgCrSe2, in contrast to the oxygen-based delafossites, can be tuned by relatively small, experimentally accessible magnetic fields, allowing us to establish the complete anisotropic magnetic H-T phase diagram in detail.

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Publ.-Id: 33242


Structure and Thermodynamics of Eu(III) and Cm(III) Complexes with Glucuronic Acid

Reese, S.; Kaden, P.; Taylor, C. J.; Kloditz, R.; Schmidt, M.

Complexation by small organic ligands controls the bioavailability of contaminants and influences their mobility in the geosphere. We have studied the interactions of Cm3+, as a representative of the trivalent actinides, and Eu3+, as an inactive homologue, with glucuronic acid (GlcA) a simple sugar acid. Time-resolved laser-induced luminescence spectroscopy (TRLFS) shows that complexation at pH 5.0 occurs only at high ligand to
metal ratios in the form of 1:1 complexes with standard formation constants log β0 = 1.84 ± 0.22 for Eu3+ and log β0 = 2.39 ± 0.19 for Cm3+. A combination of NMR, QMMM, and TRLFS reveals the structure of the complex to be a half-sandwich structure wherein the ligand binds through its carboxylic group, the ring oxygen, and a hydroxyl group in addition to five to six water molecules. Surprisingly, Y3+, which was used as a diamagnetic reference in NMR, prefers a different coordination geometry with bonding through at least two hydroxyl groups on the opposite side of a distorted GlcA molecule. QMMM simulations indicate that the differences in stability among Cm, Eu, and Y are related to ring strain induced by smaller cations. At higher pH a stronger complex was detected, most likely due to deprotonation of a coordinating OH group.

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Publ.-Id: 33241


Microstructure-informed prediction and measurement of nanoindentation hardness of an Fe-9Cr alloy irradiated with Fe-ions of 1 and 5 MeV energy

Kapoor, G.; Chekhonin, P.; Kaden, C.; Vogel, K.; Bergner, F.

Hardening of Fe-9%Cr alloys exposed to irradiation with Fe²⁺ ions of two different energies, 1 and 5 MeV, is investigated using nanoindentation. The limited penetration depth of the ions causes steep damage gradients in the near-surface volumes of the irradiated samples. This damage gives rise to graded microstructures resulting in depth-dependent irradiation hardening. Nanoindentation integrates the depth-dependent hardness over the indentation plastic zone. Our study combines quantitative analysis of the ion-irradiated microstructures with the determination of the full depth dependence of irradiation hardening. The microstructure-informed model incorporates direct experimental evidence revealed by a former investigation using cross-sectional scanning transmission electron microscopy. For both ion energies, the observed microstructures consist of dislocation loops with band-like distributions and are concluded to be the dominant source of the measured irradiation-induced hardening. The model predictions are found to be in reasonable agreement with the as-measured nanoindentation response. The comparison of hardening predictions with different kinds of superposition rules of hardening contributions suggests linear superposition as the most appropriate selection under the present conditions. The possible transferability of these results to neutron irradiation is also discussed.

Keywords: Fe-Cr alloys; Ion irradiation; Scanning TEM; Dislocation loops; Nanoindentation; Irradiation hardening

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Permalink: https://www.hzdr.de/publications/Publ-33240
Publ.-Id: 33240


Contactless Inductive Flow Tomography for control of liquid metal flow with electromagnetic actuators

Glavinic, I.; Ratajczak, M.; Stefani, F.; Eckert, S.; Wondrak, T.

To achieve an optimal flow pattern in the mould of a continuous caster, it is desirable to use a tailored control of the flow using electromagnetic actuators (e.g. electromagnetic brakes or stirrers) based on the current flow condition in the mould. However, the rough environment provides a challenge. Contactless Inductive Flow Tomography (CIFT) is a technique that can provide information about the flow structure by visualizing the full velocity field in the mould. In order to reconstruct the flow, the perturbation of an applied magnetic field by the flow is measured. It is obvious that every change of the strength of the magnetic field of an electromagnetic brake influences the measured values. In this paper we cover the challenges of measuring the flow induced magnetic field in the range of nT in the presence of varying magnetic field of the electromagnetic actuators in the range of 100 mT.

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

  • Lecture (Conference) (Online presentation)
    TMS2021 Annual Meeting & Exhibition, 16.03.2021, Orlando, Florida, United States of America

Permalink: https://www.hzdr.de/publications/Publ-33239
Publ.-Id: 33239


Control of liquid metal flow in a laboratory model of a continuous caster with Electromagnetic Brake and Contactless Inductive Flow Tomography

Glavinic, I.; Eckert, S.; Stefani, F.; Wondrak, T.

The quality of steel produced by a continuous caster depends on the flow condition during initial solidification in the mould. While the understanding of the flow and its effects is highly desirable, high temperature, opaqueness of the liquid steel and harsh conditions during the production limit viable measurement methods. Contactless Inductive Flow Tomography (CIFT) can provide information about the dominant flow structure in the mould in real time. This information can be used in a control loop for the Electromagnetic Brake (EMBr). Due to the inductive nature of CIFT, every change of the magnetic field strength of the EMBr has a strong influence on the measurements. Changing the strength of the EMBr alters the magnetization vector in its ferromagnetic yoke, which, in turn, generates a signal up to a thousand times higher than the flow induced magnetic field.
In this paper, we present a way to compensate these effects of EMBr on CIFT by filling a database containing compensation values. We will also present the preliminary results of a controller that utilizes CIFT and EMBr to actively control the flow in the mould during casting. The experiments are conducted on the Mini-LIMMCAST facility, a laboratory model of the mould of a continuous caster with the rectangular cross-section of 300 × 30 mm2. It is operated with the eutectic ally GaInSn.

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

  • Lecture (Conference) (Online presentation)
    SteelSim2021, 06.10.2021, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-33238
Publ.-Id: 33238


alpaka-group/alpaka: Version 0.6.1: Fix CPU shared memory and rework OpenMP scheduler configuration

Worpitz, B.; Bastrakov, S.; Ehrig, S.; Gruber, B. M.; Hübl, A.; Kelling, J.; Krude, J.; Stephan, J.; Widera, R.

The alpaka library is a header-only C++14 abstraction library for accelerator development. Its aim is to provide performance portability across accelerators through the abstraction (not hiding!) of the underlying levels of parallelism.

Keywords: CUDA; HPC; alpaka; OpenMP; HIP; C++; GPU; heterogeneous computing; performance portability

  • Software in external data repository
    Publication year 2021
    Programming language: C++
    System requirements: OS: Linux, Windows, or OSX requirements: C++14 compiler, boost 1.65.1+
    License: MPL-2.0
    Hosted on https://github.com/alpaka-group/alpaka/tree/0.6.1: Link to location
    DOI: 10.5281/zenodo.5040809

Permalink: https://www.hzdr.de/publications/Publ-33237
Publ.-Id: 33237


alpaka-group/alpaka: Version 0.6.0: New Backends and Useability Improvements

Worpitz, B.; Widera, R.; Bastrakov, S.; Hübl, A.; Ehrig, S.; Gruber, B. M.; Kelling, J.; Krude, J.; Stephan, J.

The alpaka library is a header-only C++14 abstraction library for accelerator development. Its aim is to provide performance portability across accelerators through the abstraction of the underlying levels of parallelism.

Keywords: CUDA; HPC; alpaka; OpenMP; HIP; C++; GPU; heterogeneous computing; performance portability

  • Software in external data repository
    Publication year 2021
    Programming language: C++
    System requirements: OS: Linux, Windows, or OSX requirements: C++14 compiler, boost 1.65.1+
    License: MPL-2.0
    Hosted on https://github.com/alpaka-group/alpaka/tree/0.6.0: Link to location
    DOI: 10.5281/zenodo.4452636

Permalink: https://www.hzdr.de/publications/Publ-33236
Publ.-Id: 33236


Synthese von Bispidinen für die Radiomarkierung mit Quecksilber-197(m)

Krönke, T.

In der Nuklearmedizin werden Radionuklide für die Diagnose oder die Therapie von Tumoren verwendet. Das Quecksilberisotop 197Hg und das dazugehörige metastabile 197mHg wecken großes Interesse in diesem Gebiet. Ziel dieser Arbeit ist es daher, Moleküle, basierend auf einem Bispidingrundgerüst zu synthetisieren, die eine kovalente Bindung von Hg2+ über Phenylgruppen ermöglichen, um so eine Freisetzung und damit verbundene unspezifische Anreicherung des Quecksilbers in vivo zu verhindern. Der Schwerpunkt liegt dabei auf der Funktionalisierung eines spezifischen Bispidolderivates, um dieses an ein biologisches Molekül knüpfen zu können. Letztendlich soll eine Synthesestrategie erarbeitet werden, die eine Herstellung dieser Bispidole ermöglicht.

Keywords: Quecksilber-197(m); Bispidine; Diagnose; Theranostisches Konzept

  • Bachelor thesis
    TU Dresden / Fakultät Chemie und Lebensmittelchemie, 2021
    Mentor: Dr. Constantin Mamat
    59 Seiten

Permalink: https://www.hzdr.de/publications/Publ-33235
Publ.-Id: 33235


On the Way to Radium-223- and Actinium-225-Radiopharmaceuticals for Targeted Alpha Therapy

Mamat, C.

This talk is fossued on current strategies and future perspectives using the alpha-emitters actinium-225 and radium-223/-224 for targeted alpha therapy.

Keywords: alpha therapy; actinium-225; radium-223; theranostic concept

  • Invited lecture (Conferences) (Online presentation)
    PiDD - Perspectives on interdisciplinary Drug Development | Promote Synergies! in the research landscape Leipzig/Dresden, 01.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33234
Publ.-Id: 33234


Implementing the Variability of Crystal Surface Reactivity in Reactive Transport Modeling

Prill, T.; Fischer, C.; Gavrilenko, P.; Iliev, O.

Current reactive transport model (RTM) uses transport control as the sole arbiter of differences in reactivity. For the simulation of crystal dissolution, a constant reaction rate is assumed for the entire crystal surface as a function of chemical parameters. However, multiple dissolution experiments conirmed the existence of an intrinsic variability of reaction rates, spanning two to three orders of magnitude. Modeling this variance in the dissolution process is vital for predicting the dissolution of minerals in multiple systems. Novel approaches to solve this problem are currently under discussion. Critical applications
include reactions in reservoir rocks, corrosion of materials, or contaminated soils. The goal of this study is to provide an algorithm for multi-rate dissolution of single crystals, to discuss its software implementation, and to present case studies illustrating the diference between the single rate and multi-rate dissolution models. This improved model approach is applied to a set of test cases in order to illustrate the diference between the new model
and the standard approach. First, a Kossel crystal is utilized to illustrate the existence of critical rate modes of crystal faces, edges, and corners. A second system exempliies the efect of multiple rate modes in a reservoir rock system during calcite cement dissolution in a sandstone. The results suggest that reported variations in average dissolution rates can be explained by the multi-rate model, depending on the geometric conigurations of the crystal surfaces.

Keywords: Reactive transport modeling; Surface reactivity; Rate map; Rate spectra

Permalink: https://www.hzdr.de/publications/Publ-33233
Publ.-Id: 33233


High-Gradient Magnetic Separation of Compact Fluorescent Lamp Phosphors: Elucidation of the Removal Dynamics in a Rotary Permanent Magnet Separator

Boelens, P.; Lei, Z.; Drobot, B.; Rudolph, M.; Li, Z.; Franzreb, M.; Eckert, K.; Lederer, F.

In an ongoing effort towards a more sustainable rare-earth element market, there is a high potential for an efficient recycling of rare-earth elements from end-of-life compact fluorescent lamps by physical separation of the individual phosphors. In this study, we investigate the separation of five fluorescent lamp particles by high-gradient magnetic separation in a rotary permanent magnet separator. We thoroughly characterize the phosphors by ICP-MS, laser diffraction analysis, gas displacement pycnometry, surface area analysis, SQUID-VSM, and Time-Resolved Laser-Induced Fluorescence Spectroscopy. We present a fast and reliable quantification method for mixtures of the investigated phosphors, based on a combination of Time-Resolved Laser-Induced Fluorescence Spectroscopy and parallel factor analysis. With this method, we were able to monitor each phosphors’ removal dynamics in the high-gradient magnetic separator and we estimate that the particles’ removal efficiencies are proportional to (d².χ)^(1/3). Finally, we have found that the removed phosphors can readily be recovered easily from the separation cell by backwashing with an intermittent air–water flow. This work should contribute to a better understanding of the phosphors’ separability by high-gradient magnetic separation and can simultaneously be considered to be an important preparation for an upscalable separation process with (bio)functionalized superparamagnetic carriers.

Keywords: rare-earth elements; compact fluorescent lamp phosphors; time-resolved laser-induced fluorescence spectroscopy (TRLFS); parallel factor analysis (PARAFAC); rotary permanent magnet separator; high-gradient magnetic separation; kelvin force

Permalink: https://www.hzdr.de/publications/Publ-33231
Publ.-Id: 33231


Near-Infrared-Emitting CdxHg1−xSe-Based Core/Shell Nanoplatelets

Mitrofanov, A.; Prudnikau, A.; Di Stasio, F.; Weiß, N.; Hübner, R.; Dominic, A. M.; Borchert, K. B. L.; Lesnyak, V.; Eychmüller, A.

The anisotropy in semiconductor nanoplatelets (NPLs) is reflected in the anisotropy of their crystal structure and organic ligand shell, which can be used for creating new semiconductor heterostructures. This work demonstrates the synthesis of core/shell NPLs containing zero-dimensional (0D) CdxHg1−xSe domains embedded in CdSe NPLs via cation exchange. The strategy is based on the different accessibility of definite regions of the NPLs for incoming cations upon time-limited reaction conditions. The obtained heterostructures were successfully overcoated with a CdyZn1−yS shell preserving their two-dimensional (2D) morphology. The NPLs exhibit bright photoluminescence in the range of 700-1100 nm with quantum yields up to 55%, thus making them a prospective material for light-emitting applications in the near-infrared spectral range.

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Permalink: https://www.hzdr.de/publications/Publ-33230
Publ.-Id: 33230


Examining alkali silica reaction of radiation-damaged quartz and feldspar minerals

Roode-Gutzmer, Q. I.; Rößler, C.; Akhmadaliev, S.; Schymura, S.; Barkleit, A.; Stumpf, T.

Quartz and feldspar in end-of-life biological shielding concrete in nuclear power plants exhibit a maximum volume expansion at a neutron fluence of 10⁹ n/cm² of 17.8 % and 7.7 % respectively. [1] To simulate neutron-radiation damage, shallow ion-penetration depths in the order of a few hundred nanometers are optimal for 2D examinations of radiation-induced structural changes in silicate minerals and subsequent hydraulic weathering under aqueous alkaline conditions.

Using vertical scanning interferometry (VSI) we observed an out-of-plane expansion for quartz within concrete equivalent to 18.8 vol. % using Si-ion radiation with a fluence of 5·10¹⁴ ions/cm² and an energy of 300 keV. This agrees well with results recently acquired by Luu et al. (2021), [2] who achieved 18.1 vol. % using a Si-ion fluence and beam energy each an order of magnitude higher (6·10¹⁵ ions/cm², 3000 keV). These irradiation conditions correspond to penetration depths calculated in SRIM [3] of respectively 430 nm and 2000 nm.

By virtue of the resistance to polishing exhibited by feldspars, it is difficult to reduce the inherent surface roughness down to submicron relief required for VSI and even finer for electron backscatter diffraction (EBSD). Furthermore, structural relaxation in feldspar begins further away from the surface than quartz. We polish mineral specimen surfaces using a low-energy and -incident Ar+ broad ion beam (Ar-BIB) prior to Si-ion irradiation. In addition to depth profile changes due to radiation-induced structural relaxation and subsequent aqueous alkaline dissolution using VSI, we examine structural changes using EBSD in conjunction with electron scanning microscopy (SEM).

[1] Le Pape et al. (2018) J. Adv. Conc. Technol. 16 191-209
[2] Luu et al. (2021) J. Nucl. Mat. 545 152734
[3] Ziegler et al. (2010) Nucl. Instrum. Methods Phys. Res. B268 1818-1823 (http://www.SRIM.org)

Keywords: alkali silica reaction; radiation damage; quartz; feldspar; biological shield concrete

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  • Lecture (Conference)
    20th International Conference on Environmental Degradation of Materials in Nuclear Power Systems -- Water Reactors, 17.-21.07.2022, Snowmass Village, Colorado, USA

Permalink: https://www.hzdr.de/publications/Publ-33229
Publ.-Id: 33229


Drag and lift forces on a rigid sphere immersed in a wall-bounded linear shear flow

Shi, P.; Rzehak, R.; Lucas, D.; Magnaudet, J.

We report on a series of fully resolved simulations of the flow around a rigid sphere translating steadily near a wall, either in a fluid at rest or in the presence of a uniform shear. Non-rotating and freely rotating spheres subject to a torque-free condition are both considered to evaluate the importance of spin-induced effects. The separation distance between the sphere and wall is varied from values at which the wall influence is weak down to gaps of half the sphere radius. The Reynolds number based on the sphere diameter and relative velocity with respect to the ambient fluid spans the range 0.1 - 250, and the relative shear rate defined as the ratio of the shear-induced velocity variation across the sphere to the relative velocity is varied from -0.5 to +0.5, so that the sphere either leads the fluid or lags behind it. The wall-induced interaction mechanisms at play in the various flow regimes are analyzed qualitatively by examining the flow structure, especially the spanwise and streamwise vorticity distributions. Variations of the drag and lift forces at low-but-finite and moderate Reynolds number are compared with available analytical and semiempirical expressions, respectively. In more inertial regimes, empirical expressions for the two force components are derived based on the numerical data, yielding accurate fits valid over a wide range of Reynolds number and wall-sphere separations for both non-rotating and torque-free spheres.

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Permalink: https://www.hzdr.de/publications/Publ-33228
Publ.-Id: 33228


WP7 Task 3 Current Activities

Steinbach, P.; Gernhardt, F. P. D.

Presentation given to report the current status on our activities in the LEAPS-INNOV WP7 task 3. For the agenda, see https://events.hifis.net/event/210/

Keywords: compression; pipelines

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Permalink: https://www.hzdr.de/publications/Publ-33227
Publ.-Id: 33227


Ein Modellierungsansatz zur numerischen Simulation disperser und aufgelöster Strukturen mit Morphologieübergang

Schlegel, F.; Krull, B.; Lehnigk, R.; Meller, R.; Tekavcic, M.

Die numerische Simulation hat sich in den letzten Jahrzehnten stetig weiterentwickelt und ist im Bereich der Aerodynamik und der Hydrodynamik zu einem etablierten Werkzeug für die Auslegung und Fehleranalyse von Bauteilen herangereift. Der Schwerpunkt der Forschung verlagert sich daher zunehmend auf die numerische Simulation mehrphasiger Strömungen. Derartige Mehrphasenströmungen zeichnen sich durch eine hohe Dynamik, komplexe physikalische Vorgänge und eine große Spanne an Längenskalen aus, die überwiegend mit den sich ausbildenden Grenzflächen zusammenhängen. Insbesondere in der Chemie- und Verfahrenstechnik sind solche Problemstellungen häufig anzutreffen und entsprechend viel Forschungsbedarf ist vorhanden. Allerdings liegt der Schwerpunkt der jeweiligen Forschungsarbeit und Modellentwicklung jeweils auf numerischen Simulationen für eine spezifische Morphologie: a) Verfahren zur Simulation von dispersen Strukturen, bei welchen die Grenzflächen durch das numerische Gitter nicht erfasst werden (Euler-Euler, Euler-Lagrange) und b) Verfahren, bei welchen die Grenzflächen aufgelöst werden (Volume-of-Fluid, Level-Set). Jedoch gibt es eine Vielzahl von technischen Fragestellungen, bei denen die auftretenden Morphologien – und damit das am besten geeignete Verfahren – nicht a priori bekannt sind. Hierzu gehören u. a. Flotationszellen, Kältemaschinen, biologische und chemische Reaktoren, Destillationskolonnen, Drall-basierte Abscheider oder Fliehkraftpumpen für mehrphasige Strömungen. Seit einiger Zeit werden für derartige Problemstellungen spezielle hybride Simulationsmethoden entwickelt: 2-Feld-Ansätze mit entsprechendem Morphologieblending, 4-Feld-Ansätze mit spezifischen numerisch motivierten Phasen, Drift-Flux-Methoden auf Volume-of-Fluid-Basis oder auch das Blending zwischen Simulationsmethoden wie Euler-Euler und Level-set.
Der vorliegende Beitrag stellt einen 4-Feld-Ansatz vor, welcher seit einiger Zeit am Helmholtz-Zentrum Dresden-Rossendorf in der quelloffenen Bibliothek OpenFOAM entwickelt und validiert wird. Die wesentlichen Entwicklungskriterien und -ziele sind:

  • robuste Anwendbarkeit für ingenieurstechnische Fragestellungen in der Chemie- und Verfahrenstechnik,
  • Anwendung eines einheitlichen Satzes von Gleichungen, welcher die verschiedenen Simulationsmethoden enthält (kein Blending zwischen den Methoden),
  • für hochauflösende numerische Gitter sollen die Ergebnisse für aufgelöste Grenzflächen denen einer algebraischen Volume-of-Fluid-Simulation entsprechen,
  • für niedrigauflösende Gitter sollen die Ergebnisse für disperse Strukturen denen des Euler-Euler-Verfahrens entsprechen,
  • Phasen, welche eine aufgelöste Grenzfläche ausbilden, und Phasen, welche dispers in einer anderen Phase vorliegen, sind eigenständige numerische Phasen,
  • ein Morphologieübergang zwischen aufgelösten und dispersen Strukturen soll über entsprechende Massentransfermodelle zwischen den numerischen Phasen realisiert werden und
  • disperse Phasen sollen mit aufgelösten Grenzflächen interagieren können (Übergang, Aufplatzen, Schaumbildung).
Der derzeitige Entwicklungsstand umfasst u. a. die Modellierung aufgelöster Grenzflächen im Euler-Euler-Modell, die erfolgreiche Verifikation anhand von Volume-of-Fluid-Simulationen, die Modellierung aufgelöster Strukturen auf zu groben Gittern durch entsprechende Schließungsmodelle, die Stabilisierung des Euler-Euler-Verfahrens für disperse Strukturen auf zu feinen Gittern und einfache Massentransfermodelle für den Morphologieübergang. Die Fähigkeiten des Modellansatzes für mehrphasige Strömungen mit Morphologieübergang werden anhand einer Sprudelschicht und eines Drall-basierten Abscheiders für Gasblasen demonstriert.
Eine wesentliche Intention des Beitrages ist es, die am Helmholtz-Zentrum Dresden-Rossendorf entwickelte Simulationstechnologie der deutschen Chemie- und Verfahrenstechnik vorzustellen, um für die Weiterentwicklung Kooperationspartner und Anwendungsfälle zu finden. Vertrauensvolle Partnerschaften zwischen Forschungszentren und Industrie sollen es der Spitzenforschung der Helmholtz-Gemeinschaft ermöglichen, die Technologieführerschaft der deutschen Chemie und Verfahrenstechnik langfristig sicherzustellen., Dazu sollen Schwachstellen in der Modellierung mit komplexen, realistischen Anwendungsfällen identifiziert werden und die Robustheit der Methode soll durch ein großes Spektrum von Anwendungsfällen gewährleistet werden.
  • Poster (Online presentation)
    Jahrestreffen der ProcessNet-Fachgruppen Mehrphasenströmungen, Mechanische Flüssigkeitsabtrennung sowie Zerkleinern und Klassieren, 21.-22.02.2022, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33226
Publ.-Id: 33226


Neutron capture cross sections of light neutron-rich nuclei relevant for r-process nucleosynthesis

Bhattacharyya, A.; Datta, U.; Rahaman, A.; Chakraborty, S.; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chartier, M.; Cortina-Gil, D.; Das, P.; Angelis, G. D.; Diaz Fernandez, P.; Emling, H.; Geissel, H.; Gonzalez-Diaz, D.; Heine, M.; Johansson, H.; Jonson, B.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Langer, C.; Le Bleis, T.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Plag, R.; Reifarth, R.; Ricciardi, M. V.; Rigollet, C.; Rossi, D.; Scheidenberger, C.; Scheit, H.; Simon, H.; Togano, Y.; Typel, S.; Utsuno, Y.; Wagner, A.; Wamers, F.; Weick, H.; Winfield, J. S.

The measurements of neutron capture cross sections of neutron-rich nuclei are challenging but essential for understanding nucleosynthesis and stellar evolution processes in the explosive burning scenario. In the quest of r-process abundances, according to the neutrino-driven-wind model, light neutron-rich unstable nuclei may play a significant role as seed nuclei that influence the abundance pattern. Hence, experimental data for neutron capture cross sections of neutron-rich nuclei are needed. Coulomb dissociation of radioactive ion beams at intermediate energy is a powerful indirect method for inferring capture cross section. As a test case for validation of the indirect method, the neutron capture cross section (n, γ ) for 14C was inferred from the Coulomb
dissociation of 15C at intermediate energy (600A MeV). A comparison between different theoretical approaches and experimental results for the reaction is discussed. We report for the first time experimental reaction cross sections of 28Na(n, γ ) 29Na, 29Na(n, γ ) 30Na, 32Mg(n, γ ) 33Mg, and 34Al(n, γ ) 35Al. The reaction cross sections were inferred indirectly through Coulomb dissociation of 29,30Na, 33Mg, and 35Al at incident projectile energies around 400–430 A MeV using the FRS-LAND setup at GSI, Darmstadt. The neutron capture cross sections were obtained from the photoabsorption cross sections with the aid of the detailed balance theorem. The reaction rates for the neutron-rich Na, Mg, Al nuclei at typical r-process temperatures were obtained from the measured (n, γ ) capture cross sections. The measured neutron capture reaction rates of the neutron-rich nuclei, 28Na, 29Na, and 34Al are significantly lower than those predicted by the Hauser-Feshbach decay model. A similar trend was observed earlier for 17C and 19N but in the case of 14C(n, γ ) 15C the trend is opposite. The situation is more complicated when the ground state has a multi-particle-hole configuration. For 32Mg, the measured cross section is about 40–90% higher than the Hauser-Feshbach prediction.

Keywords: Neutron capture; neutron-rich nuclei; r-process nucleosynthesis; Hauser-Feshbach

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Permalink: https://www.hzdr.de/publications/Publ-33224
Publ.-Id: 33224


Low-energy magnetic dipole strength in cadmium isotopes

Schwengner, R.

Magnetic dipole strength functions have been deduced from averages of large numbers of M1 transition strengths calculated within the shell model for the nuclides 105Cd, 106Cd 111Cd, and 112Cd. Enhancements of the M1 strengths toward low transition energy have been found for all nuclides considered. These properties are compared with those of experimental photon strength functions obtained from (3He,3He') experiments, which seem to indicate
a disappearance of the low-energy enhancement in the heavier isotopes.

Keywords: Nuclear structure; Electromagnetic transitions; Photon strength functions; Shell model

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Permalink: https://www.hzdr.de/publications/Publ-33223
Publ.-Id: 33223


HSQ-based process to integrate vertical nanoscale devices

Amat, E.; Del Moral, A.; Engelmann, H.-J.; Borany, J.; Heinig, K.-H.; Pourteau, M.-L.; Rademaker, G.; Tiron, R.; Bausells, J.; Perez-Murano, F.

The inherent three-dimensional topology of vNWs imposes several constraints to their fabrication and their integration in other circuits. We present here the use of Hydrogen silsesquioxane (HSQ) for the fabrication of single electron transistors (SETs) based on vNWs.

Keywords: single electron transistor; quantum dot; CMOS; Si nanowire; fabrication

Related publications

  • Open Access Logo Lecture (Conference) (Online presentation)
    47th international conference on Micro and Nano Engineering, 20.-23.09.2021, Turin, Italy

Permalink: https://www.hzdr.de/publications/Publ-33222
Publ.-Id: 33222


Coupling of atomic states to particle in cell simulations

Marre, B. E.

Master Thesis discussing approaches to including atomic physics in PIC simulations for transient non-thermal plasmas and developing new approaches and algorithms for doing so.

Keywords: PIC; atomic physics; picongpu; plasma; Particle in Cell; simulation; Markov-Chain rate solver; Monte-Carlo rate solver

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Permalink: https://www.hzdr.de/publications/Publ-33221
Publ.-Id: 33221


Compatibility of CMOS technology with QD-based devices

Alberto, D. M.; Amat, E.; Quirion, D.; Torres, N.; Engelmann, H.-J.; Borany, J.; Heinig, K.-H.; Rademaker, G.; Pourteau, M.-L.; Tiron, R.; Bausells, J.; Perez-Murano, F.

This work reports the CMOS compatible and monolithic fabrication of a conventional planar field effect transistor (FET) co-integrated with a quantum dot (QD) based single electron transistor (SET). The FET process fabrication is adapted to fulfill the restrictions imposed by the pre-fabricated SET, such as reduced thermal budget, extra protection layers and modified doping in order to obtain low threshold voltage. The resulting FET presents good subthreshold characteristics and the SET preserves its integrity at the end of the fabrication.

Keywords: single electron transistor; quantum dot; CMOS

Related publications

  • Lecture (Conference) (Online presentation)
    Micro and Nano Engineering Conference, 20.-23.09.2021, Turin, Italy

Permalink: https://www.hzdr.de/publications/Publ-33220
Publ.-Id: 33220


The RE-MINING Approach - Utilization and Rehabilitation of Tailings through Bioleaching and Metal Recovery

Dirlich, S.; Reichel, S.; Thürigen, F.; Aubel, T.; Meißner, S.; Werner, A.; Helbig, T.

The extraction of metals such as copper or indium is essential for the economy, but inevitably associated with the generation of vast amounts of tailings. Especially flotation tailings lead to huge land consumption and are a potential source of environmental hazards. However, due to limited processing technologies in the past such mining waste typically contains remarkable concentrations of valuable elements. Therefore, it is sensible to combine modern resource with environmental technologies to supplement the recovery of valuables with the removal of hazardous substances such as arsenic or cadmium. In the ideal scenario the residues can be utilized for underground backfilling or dump construction.
The project partners GEOS, SAXONIA and HIF have started to develop, build and optimize a pilot plant for the processing of material from primary and secondary sources using bioleaching, metal extraction and elimination of hazardous components based on various research projects. The pilot plant, consisting of different modules, combines biotechnology with physical separation and processing technologies in an innovative and sophisticated way to recover valuables and remove pollutants. The bioleaching module leaches tailings in an airlift reactor by means of selected microorganisms under specific process conditions (pH, temperature, etc.). The obtained yields of up to 90% indium and 85-90% copper indicate the promising potential of this bioleaching technique. For the metal recovery module, it is planned to integrate the following main processing stages: solvent extraction, absorber columns (e.g. activated carbon, IX resin) and electrolysis. The so-called environmental module is designed as classical precipitation, flocculation and sedimentation unit for treatment of remaining process streams from the metal recovery module to eliminate hazardous substances. A future aim is running the mobile pilot plant directly at the tailings site.
An overview on the development of the modules, the equipment and the results that were obtained so far will be presented.

Keywords: remining; bioleaching; pilot plant; metal extraction; primary resources; secondary resources; tailings; flotation; critical raw materials

  • Lecture (Conference) (Online presentation)
    World Resources Forum 2021, 12.-14.10.2021, Accra, Ghana

Permalink: https://www.hzdr.de/publications/Publ-33219
Publ.-Id: 33219


Magnetocaloric effect in the Laves-phase Ho1−xDyxAl2 family in high magnetic fields

Bykov, E.; Liu, W.; Skokov, K.; Scheibel, F.; Gutfleisch, O.; Taskaev, S.; Khovaylo, V.; Plakhotskiy, D.; Salazar Mejia, C.; Wosnitza, J.; Gottschall, T.

Hydrogen has the largest gravimetric energy density among all chemical fuels. At the same time, the density of gaseous H2 is extremely low, which makes its compression to high pressures, liquefaction, or solid-state storage necessary for transport purposes. Liquid hydrogen (LH2) can be transported in a dewar under atmospheric pressure, but this requires energy-intensive cooling down to 20 K. Magnetocaloric materials have great potential to revolutionize gas liquefaction to make LH2 more competitive as fuel. In this paper, we investigate a series of Laves-phase materials regarding their structural, magnetic, and magnetocaloric properties in high magnetic fields. The three compounds HoAl2, Ho0.5Dy0.5Al2, and DyAl2 are suited for building a stack for cooling from liquid-nitrogen temperature (77 K) down to the boiling point of hydrogen at 20 K. This is evident from our direct measurements of the adiabatic temperature change in pulsed magnetic fields, which we compare with calorimetric data measured in a static field. With this methodology, we are now able to study the suitability of magnetocaloric materials down to low temperatures up to the highest magnetic fields of 50 T.

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Permalink: https://www.hzdr.de/publications/Publ-33218
Publ.-Id: 33218


Magnetic Field Induced Quantum Spin Liquid in the Two Coupled Trillium Lattices of K2Ni2(SO4)3

Zivkovic, I.; Favre, V.; Salazar Mejia, C.; Jeschke, H. O.; Magrez, A.; Dabholkar, B.; Noculak, V.; Freitas, R. S.; Jeong, M.; Hegde, N. G.; Testa, L.; Babkevich, P.; Su, Y.; Manuel, P.; Luetkens, H.; Baines, C.; Baker, P. J.; Wosnitza, J.; Zaharko, O.; Iqbal, Y.; Reuther, J.; Ronnow, H. M.

Quantum spin liquids are exotic states of matter that form when strongly frustrated magnetic interactions induce a highly entangled quantum paramagnet far below the energy scale of the magnetic interactions. Three-dimensional cases are especially challenging due to the significant reduction of the influence of quantum fluctuations. Here, we report the magnetic characterization of K2Ni2(SO4)3 forming a three-dimensional network of Ni2+ spins. Using density functional theory calculations, we show that this network consists of two interconnected spin-1 trillium lattices. In the absence of a magnetic field, magnetization, specific heat, neutron scattering, and muon spin relaxation experiments demonstrate a highly correlated and dynamic state, coexisting with a peculiar, very small static component exhibiting a strongly renormalized moment. A magnetic field B ≳ 4 T diminishes the ordered component and drives the system into a pure quantum spin liquid state. This shows that a system of interconnected S = 1 trillium lattices exhibits a significantly elevated level of geometrical frustration.

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Permalink: https://www.hzdr.de/publications/Publ-33217
Publ.-Id: 33217


Optical Readout of the Néel Vector in the Metallic Antiferromagnet Mn2Au

Grigorev, V.; Filianina, M.; Bodnar, S. Y.; Sobolev, S.; Bhattacharjee, N.; Bommanaboyena, S.; Lytvynenko, Y.; Scurschii, I.; Fuchs, D.; Kläui, M.; Jourdan, M.; Demsar, J.

Metallic antiferromagnets with broken inversion symmetry on the two sublattices, strong spin-orbit coupling, and high Neel temperatures offer alternative opportunities for applications in spintronics. Especially Mn2Au, with a high Neel temperature and high conductivity, is particularly interesting for real-world applications. Here, manipulation of the orientation of the staggered magnetization, (i.e., the Neel vector) by current pulses was recently demonstrated, with the readout limited to studies of anisotropic magnetoresistance or x-ray magnetic linear dichroism. Here we report on the in-plane reflectivity anisotropy of Mn2Au(001) films, which are Neel vector aligned in pulsed magnetic fields. In the near-infrared region, the anisotropy is approximately 0.6%, with higher reflectivity for the light polarized along the Neel vector. The observed magnetic linear dichroism is about 4 times larger than the anisotropic magnetoresistance. This suggests the dichroism in Mn2Au is a result of the strong spin-orbit interactions giving rise to anisotropy of interband optical transitions, which is in line with recent studies of electronic band structure. The considerable magnetic linear dichroism in the near-infrared region could be used for ultrafast optical readout of the Neel vector in Mn2Au.

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Permalink: https://www.hzdr.de/publications/Publ-33216
Publ.-Id: 33216


MoP3SiO11: A 4d3 honeycomb antiferromagnet with disconnected octahedra

Badrtdinov, D. I.; Ding, L.; Ritter, C.; Hembacher, J.; Ahmed, N.; Scurschii, I.; Tsirlin, A. A.

We report the crystal structure and magnetic behavior of the 4d3 spin-3/2 silicophosphate MoP3SiO11 studied by high-resolution synchrotron x-ray diffraction, neutron diffraction, thermodynamic measurements, and ab initio band-structure calculations. Our data revise the crystallographic symmetry of this compound and establish its rhombohedral space group (R¯3c) along with the geometrically perfect honeycomb lattice of the Mo3+ ions residing in disconnected MoO6 octahedra. Long-range antiferromagnetic order with the propagation vector k = 0 observed below TN = 6.8 K is a combined effect of the nearest-neighbor in-plane exchange coupling J ≃ 2.6 K, easy-plane single-ion anisotropy D ≃ 2.2 K, and a weak interlayer coupling Jc ≃ 0.8 K. The 12% reduction in the ordered magnetic moment of the Mo3+ ions and the magnon gap of Δ ≃ 7 K induced by the single-ion anisotropy further illustrate the impact of spin-orbit coupling on the magnetism. Our analysis puts forward single-ion anisotropy as an important ingredient of 4d3 honeycomb antiferromagnets despite their nominally quenched orbital moment.

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Permalink: https://www.hzdr.de/publications/Publ-33215
Publ.-Id: 33215


Einsatz bildgebender Messverfahren und numerischer Modellierungswerkzeuge für die Verbesserung der Energieeffizienz industrieller Mehrphasenprozesse

Hampel, U.

Stoff- und Energieumwandlungsprozesse in technischen Apparaten sind oft an Mehrphasenströmungen gekoppelt. Beispiele dafür sind Chemiereaktoren, Stoffaustauschapparate, Kraftwerksanlagen oder Abwasserbehandlungsanlagen. Für die Modellierung der Strömungsvorgänge wurden in der jüngeren Vergangenheit numerische Berechnungsverfahren der Computational Fluid Dynamics entwickelt. Für diese besteht immer wieder die Aufgabe, sie mit realen Messdaten aus Strömungsexperimenten unter prozessähnlichen Bedingungen zu validieren bzw. aus solchen Messdaten Modelle und Korrelationen abzuleiten.
Der Vortrag gibt einen Einblick in die Nutzung innovativer schneller Bildgebungsverfahren für Mehrphasenströmungen für diesen Zweck. Vorgestellt werden die Gittersensortechnik sowie die ultraschnelle Röntgentomographie, welche am Helmholtz-Zentrum Dresden-Rossendorf entwickelt wurden. Mit beiden Bildgebungsverfahren ist die tomographische Analyse von Mehrphasenströmungen mit Bildraten von mehr als 1000 Bildern pro Sekunde sowie einer räumlichen Auflösung im Millimeterbereich möglich. Ihre Anwendung wird anhand verschiedener Beispiele für die Optimierung energieintensiver Prozesse, wie etwa Destillation und Abwasserbehandlung, exemplarisch diskutiert.

Keywords: Energieeffizienz; Industrieprozesse; Mehrphasenströmungen; Bildgebende Messverfahren; Modellierung

  • Lecture (Conference) (Online presentation)
    Deutsche Physikalsiche Gesellschaft ‚Berliner‘ (Online) Tagung, Arbeitskreis Energie, 27.-28.09.2021, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33214
Publ.-Id: 33214


Fast tomographic imaging of multiphase flow

Hampel, U.

Multiphase flows are to be found in many production processes in the process industry. Examples are bubble column reactors, distillation columns, fluidized beds and many more. Measuring process parameters in such systems is very difficult because most sensors are disturbed in their fundamental measuring principles by the presence of particles and interfaces. Especially in fundamental fluid mechanics science, there is a growing need for imaging techniques for studying multiphase flows. There, the derivation of so-called CFD-grade data from fluid dynamics experiments requires imaging techniques with high spatial resolution, non-intrusiveness and ability to deal with the opacity of multiphase mixtures, walls and inserts in process vessels and their mock-ups. The presentation will give an overview of the state of the art of selected tomographic imaging techniques and discuss their application in solving chemical engineering problems.

Keywords: multiphase flows; computed tomography; imaging

  • Invited lecture (Conferences) (Online presentation)
    Symposium of the International Joint Research Center, 03.09.2021, Tianjin, China
  • Invited lecture (Conferences) (Online presentation)
    ChemE Faculty Colloquium, 27.09.2021, Delft, The Netherlands
  • Invited lecture (Conferences) (Online presentation)
    Webinatr Series: Innovation in the multiphase flow technology, 21.09.2021, Yogyakarta, Indonesia

Permalink: https://www.hzdr.de/publications/Publ-33213
Publ.-Id: 33213


Image features for vision-based robot manipulation based on deep reinforcement learning

Li, R.

Deep Reinforcement Learning (DRL) provides a potential toolset that enables industrial robots to autonomously learn manipulation skills, but the learning efficiency (success rate within certain learning episodes) is the bottleneck. In this work, we ascertained well-designed environmental observations to be vital for improving efficiency. To determine the impacts of different observations, we conducted simulation experiments of robots grasping, and evaluated three popular categories of environment observations -positions of the Tool-Center-Point, raw images from a fixed viewpoint camera, and image features (Sobel, Laplacian, HOG, LBP). The results indicate “image features” proved to be superior to the others, they contribute to higher success rate and learning speed.

Keywords: Machine Learning for Robot Control; Reinforcement Learning; Simulation and Animation

  • Lecture (Conference) (Online presentation)
    International Conference on Intelligent Computer Communication and Processing 2021, 28.-30.10.2021, Cluj-Napoca, Romania

Permalink: https://www.hzdr.de/publications/Publ-33212
Publ.-Id: 33212


UMB-II: 2nd video conference workshop

Matschiavelli, N.

In this first UMB-II project-meeting, the results of the first 6 months are summerized and presented. HZDR fucusses on the set up of microcosm-experiments and presents the first data.

  • Lecture (others) (Online presentation)
    UMB-II project meeting, 06.10.2021, Braunschweig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33211
Publ.-Id: 33211


The importance of understanding Technetium environmental chemistry- research at Institute of Resource Ecology

Mayordomo, N.

Technetium (Tc) is a radioactive element, 99-Tc being its most abundant isotope. 99-Tc is mainly generated by anthropogenic sources like nuclear power plants, nuclear weapon detonations (99-Tc is the fission product of 235-U and 239-Pu), and hospitals due to its use in radiodiagnostics (99-Tc is the daughter of 99m-Tc). The emission of 99-Tc is of environmental concern since it is a b- emitter with a long life time (0.213 million years) and a high mobility in groundwater under oxic conditions. Therefore, a deep understanding of the environmental behavior of Tc is crucial to ensure a safe Tc storage in a nuclear waste repository and the protection of the environment.

The environmental behavior of Tc, its bioavailability, and its mobility in groundwater are ruled by environmental conditions like redox conditions, pH, presence of ions or minerals, and temperature among others. The knowledge about basic Tc chemistry helps to identify and understand the environmental conditions under which Tc migration is limited. Additionally, it allows for the development of possible Tc scavengers for remediation of polluted sites.

At the Institute of Resource Ecology (IRE) we study Tc immobilization by various natural materials such as pyrite (FeS₂) and materials found in nuclear waste repositories, such as green rust (Fe(II)-Fe(III) hydroxide). To answer the question, how Tc interacts with these materials, we employ a multitude of experimental techniques including X-ray diffraction, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), Raman microscopy, scanning electron microscopy (SEM), and geochemical modeling approaches. This allows us to obtain an in-depth understanding of Tc chemistry, which can be used to develop and improve Tc scavengers and to build a safe nuclear waste repository.

  • Lecture (others) (Online presentation)
    Research Talk at Helmholtz-Zentrum Dresden - Rossendor, 23.06.2021, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-33209
Publ.-Id: 33209


Technetium immobilization by chloride green rust

Mayordomo, N.; Rodriguez Hernandez, D. M.; Schild, D.; Roßberg, A.; Scheinost, A.; Brendler, V.; Müller, K.

Techntium-99 (⁹⁹Tc) is one of the most concerning fission products due to its long half-life (2.14∙105 years) and the high mobility of the anion pertechnetate (TcO₄⁻).
Tc migration decreases when Tc(VII) is reduced to Tc(IV). This scavenging step is carried out by Fe(II) minerals, which have been widely studied due to their versatility, low cost and ubiquity. Green rust is a Fe(II)-Fe(III) hydroxide that possesses adsorption, anion exchange and reduction capabilities. Its presence is expected in the near- and far-field of a nuclear waste repository because it is an iron corrosion product, and it is also formed in the environment when Fe²⁺ interacts with Fe(III) minerals. Thus, further studies are needed to both identify the optimal Tc scavenging conditions by green rust and the mechanism responsible of Tc retention. Batch contact studies have been performed under a wide range of conditions, i.e. pH (3-11), Tc concentration (nM-mM), and ionic strength (0-0.1 M). X-ray powder diffraction, Raman microscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) provided information on Tc oxidation state and speciation as well as on secondary redox products related to the Tc interaction with chloride green rust (GR(Cl)). In addition, re-oxidation experiments have been performed for one year to analyze the Tc retention reversibility. The results show that GR(Cl) removes Tc from solution with efficiencies between 80% (Kd = 8.0∙10³ mL/g) and ≈100% (Kd = 9.9∙10⁵ mL/g) for pH > 6.0.
In contrast, Tc removal for pH < 6.0 drops with decreasing pH, and ranges from 80% to 50% (Kd = 2.0∙10³ mL/g), reaching a minimum at pH 3.5. XPS analysis reveals the predominance of Tc(IV) at all evaluated pH values (3.5 to 11.5), supporting that Tc reductive immobilization is the main retention mechanism. Re-oxidation experiments show that Tc is slowly solubilized when time increases.
The analysis of the extended X-ray absorption fine structure (EXAFS) reveals a change on Tc(IV) environment depending on pH and Tc loading. The most probable structural rearrangements are represented by Tc(IV) sorption on Fe(III) minerals formed as secondary phases with Tc polynuclear species contribution.

Keywords: Technetium; Reductive immobilization; Sorption; LDH

Related publications

  • Lecture (Conference) (Online presentation)
    TransRet2020, 12.-13.10.2021, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-33208
Publ.-Id: 33208


Microbial consortium as an effective biocatalyst for the decolorization of textile dyes wastewater

Kurade, M.; Waghmode, T.; Chakankar, M. V.; Awasthi, M.; Dawkar, V.; Jeon, B.-H.

Microbial consortia are proven to be one of the most effective tools for the decolorization of textile industrial dyes and effluent. The microbial consortium offers several benefits in bioremediation, some of them include the faster rate of dye degradation and high efficiency, tolerance to drastic environmental changes, possession of concerted metabolic activities due to presence of multiple microbial species that carry out maximum catalysis of dye molecule or sometimes complete mineralization, and its feasibility in practical scale operations due to less requirements of sterile conditions and cost effectiveness. This chapter critically summarizes the basic principles of microbial interactions such as mutualism and commensalism as the most valuable microbial relationships within the consortium that are beneficial for the bioremediation of wastewater. Several different microbial consortia which combined the microbial species of bacteria, fungus, yeast, along with algae and plants which have been used for the treatment of textile dyes/effluent have been thoroughly evaluated. All combinations have their own advantages and disadvantages, which have been explored herein. Bacterial species are fast growing microorganisms while fungal species contain highly catalytic enzymatic system, thus their combinations have been quite successful. Microalgae and plants have recently attracted researcher because of their potential of bioremediation and subsequent utilization of their biomass in biofuel generation which is commercially beneficial along with environmentally sustainable approach. Moreover, this chapter provides a brief introduction on newly emerging high-throughput techniques that deal with the engineering of synthetic microbial consortium for bioremediation and environmental cleanup.

Keywords: Microbial consortium; Biodegradation; Bioremediation; Decolorization; Dye degradation; Textile industry wastewater; Synthetic microbial consortium

  • Book chapter
    Sanjay Govindwar, Byong-Hun Jeon, Mayur Kurade, Ashok Pandey: Advances in Eco-friendly and Sustainable Technologies for the Treatment of Textile Wastewater, Amsterdam: Elsevier, 2023, 978-0-323-91235-8, 473-511
    DOI: 10.1016/C2020-0-04450-6
    Cited 5 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-33207
Publ.-Id: 33207


Rhamnolipid as an ion collector in bioionflotation

Chakankar, M. V.; Oestreich, A.; Pollmann, K.; Rudolph, M.

Objective: Industrial wastewaters are secondary sources of many critical and base metals. Recovering these metals from such waste streams helps in resource recycling and reduce the environmental burden. However, such a recovery is challenging due to the low concentration of target metals and the presence of other unwanted metals at higher concentrations. Ion flotation is a promising separation process for resource recycling of metals from secondary sources. However, secondary pollution by used chemicals and low selectivity amongst ionic species limit its practical application so far. Thus, there is a need to develop new ion collectors, which are highly selective, efficient, and ecofriendly. Microbial biomolecules, which can act as complexing agent and can bind selectively to specific metal ionic species are attractive alternative. Biosurfactants are microbial surface-active molecules having both hydrophilic and hydrophobic groups, and therefore have surface activity and metal complexing ability making them an interesting candidate for flotation reagent. Rhamnolipid, a glycolipid type of biosurfactant, is reported to complex with variety of metals. In order to improve the application of biosurfactant in these processes, a comprehensive and systematic investigation of their performance and behavior as an ion collector is required. Our objective is to provide an insight into the surface activity, foamability and foam characterization for rhamnolipid for their application in bioionflotation. In the current study, rhamnolipid was investigated for its application as an ion collector in BioIonFlotation for Ga recovery.
Results: Rhamnolipid exhibits extensive foaming over a wide range of pH. Foam produced by rhamnolipid alone has higher foam stability making it difficult to collect the
flotation concentrates. Addition of 1,2-decanediol introduces the little destability to this foam and also aids in concentrate collection.
Aggregation studies – Mixing of rhamnolipid and Ga solutions resulted in colloidal suspension. These colloidal interactions were studied in presence and absence of Ga and/or 1,2 decaneciol by dynamic light scattering. The aggregate size of rhamnolipid molecules was largely influenced by the presence of Ga and/or 1,2 decanediol. Increase in aggregate size, indicated that interaction of rhamnolipid with either or both of them boosted the aggregation process.
Dynamic surface activity – Presence and absence of Ga and/or 1,2 decaneciol had significant impact on dynamic surface activity of rhamnolipid. Presence of Ga shifted the surface activity curve of rhamnolipids. This change in trend can be attributed to the complexation of rhamnolipid with Ga that lead to longer diffusion at the sub-surface and then to interface resulting in higher surface ages. Addition of 1,2 decanediol had no such effect, whereas presence of both contributed in further shifting of the surface activity curve (Fig. 1).
Foam characterization – Foam produced by rhamnolipid was characterized by dynamic foam analyzer. Interaction of rhamnolpid with Ga and 1,2 decanediol or both, changed the foaming behavior of rhamnolipid. Images of foam revealed the differences in size and shape of bubbles as well as their development.
Conclusion: The study investigated the role of rhamnolipid biosurfactant as an ion collector for its application in flotation. The influence of Ga, as target metal and 1,2 decanediol as additional frother on properties of rhamnolipid were evaluated and found to have a significant impact. Such studies provide in-depth insights on the parameters influencing the properties of flotation collectors and provide the basis for the development of the bioionflotation process.

Keywords: Rhamnolipid; Ion collector; Bioionflotation; Gallium; Foam; Surface tension

  • Lecture (Conference) (Online presentation)
    13th European Congress of Chemical Engineering and 6th European Congress of Applied Biotechnology, 20.-23.09.2021, Frankfurt am Main, Germany

Permalink: https://www.hzdr.de/publications/Publ-33206
Publ.-Id: 33206


Optimized laser ion acceleration at the relativistic critical density surface

Göthel, I.; Bernert, C.; Bussmann, M.; Garten, M.; Miethlinger, T.; Rehwald, M.; Zeil, K.; Ziegler, T.; Cowan, T.; Schramm, U.; Kluge, T.

In the effort of achieving high-energetic ion beams from the interaction of ultrashort laser pulses with a plasma, volumetric acceleration mechanisms beyond Target Normal Sheath Acceleration have gained attention.
A relativisticly intense laser can turn a near critical density plasma slowly transparent, facilitating a synchronized acceleration of ions at the moving relativistic critical density front. While simulations promise extremely high ion energies in in this regime, the challenge resides in the realization of a synchronized movement of the ultra-relativistic laser pulse ($a_0\gtrsim 30$) driven reflective relativistic electron front and the fastest ions, which imposes a narrow parameter range on the laser and plasma parameters. We present an analytic model for the relevant processes, confirmed by a broad parameter simulation study in 1D- and 3D-geometry. By tayloring the pulse length and plasma density profile at the front side, we can optimize the proton acceleration performance and extend the regions in parameter space of efficient ion acceleration at the relativistic relativistic density surface.

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Permalink: https://www.hzdr.de/publications/Publ-33205
Publ.-Id: 33205


Software for "Optimized laser ion acceleration at the relativistic critical density surface"

Göthel, I.; Bernert, C.; Bussmann, M.; Garten, M.; Miethlinger, T.; Rehwald, M.; Zeil, K.; Ziegler, T.; Cowan, T. E.; Schramm, U.; Kluge, T.

In the effort of achieving high-energetic ion beams from the interaction of ultrashort laser pulses with a plasma, volumetric acceleration mechanisms beyond Target Normal Sheath Acceleration have gained attention.
A relativisticly intense laser can turn a near critical density plasma slowly transparent, facilitating a synchronized acceleration of ions at the moving relativistic critical density front. While simulations promise extremely high ion energies in in this regime, the challenge resides in the realization of a synchronized movement of the ultra-relativistic laser pulse ($a_0\gtrsim 30$) driven reflective relativistic electron front and the fastest ions, which imposes a narrow parameter range on the laser and plasma parameters.  We present an analytic model for the relevant processes, confirmed by a broad parameter simulation study in 1D- and 3D-geometry. By tayloring the pulse length and plasma density profile at the front side, we can optimize the proton acceleration performance and extend the regions in parameter space of efficient ion acceleration at the relativistic relativistic density surface.

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Permalink: https://www.hzdr.de/publications/Publ-33204
Publ.-Id: 33204


Recovery of nanodiamonds from dynamically shock-compressed hydrocarbon samples

Schuster, A.

Hydrocarbons are abundant in icy giant planets like Uranus and Neptune. Their interiors are governed by extreme conditions with pressures of hundreds of gigapascals and temperatures of thousands of kelvins. It is possible to generate such extreme conditions in materials on a nanosecond timescale via laser-driven shock compression in the laboratory. A simple representative of hydrocarbons for use in the laboratory is polystyrene (C₈H₈). The formation of nanodiamonds from laser-induced shock compression of polystyrene was demonstrated at the Linac Coherent Light Source (LCLS) via 𝘪𝘯 𝘴𝘪𝘵𝘶 X-ray diffraction (XRD). This technique is based on driving two time-delayed shock waves through the material, such that they overlap at the sample rear side. Subsequently, a rarefaction wave releases the material at hypervelocity. The goal of the current work is the physical capture, extraction and characterisation of those generated nanodiamonds to better understand their formation process. In a larger framework, the project pursues the long-standing goal in condensed matter physics to recover metastable structures that form under extreme pressure and temperature conditions. This work presents an analysis of 𝘪𝘯 𝘴𝘪𝘵𝘶 XRD data deducing estimates of nanodiamond nucleation rates relevant to planetary interiors observed in the above mentioned experiment at LCLS and compares them to the latest theoretical model. Furthermore, seven recovery experiments, among them four recovery-only campaigns, were designed, prepared and conducted with the support of our working group and an eighth one was designed and prepared. High speed recordings were obtained giving unprecedented insights into the dynamics of the hypervelocity ejecta cloud and its impact into the various catcher types made from different materials. First analysis campaigns including chemical procedures for sample preparation, Raman spectroscopy, X-ray diffraction, dynamic light scattering, scanning and transmission electron microscopy, and tomography were arranged and some performed. Various collaborations were initiated, that among others enabled the usage of state-of-the-art materials and diagnostics, access to other facilities and support through simulations. The thesis provides a solid foundation for further research taking on the challenging task of recovering the nanodiamonds formed via laser-induced shock compression of hydrocarbons. This research can have crucial implications for planetary interior models of the icy giant planets.

Keywords: nanodiamonds; recovery; laser-induced shock compression; laboratory astrophysics; warm dense matter; high energy density

Related publications

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-115 2021
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-33203
Publ.-Id: 33203


Transparent conductive oxides on top of a black body absorber as alternative concept for high-temperature-stable solar-selective coatings

Krause, M.; Lungwitz, F.; Mendez, A.; Hoppe, M.; Sonnenberg, J.; Garcia-Valenzuela, A.; Munnik, F.; Grenzer, J.; Hübner, R.; Escobar Galindo, R.

After a short overview about the activities of our research group the concept of selective transmitter coatings on top of black body absorbers for the use in high-temperature solar thermal applications will be introduced.[1,2] Solar selective transmitters, which are also called heat mirrors, are characterized by a high solar transmittance and a high thermal reflectance. They can consist either of dielectric/metal/dielectric multilayers or of transparent conductive oxides (TCOs),[3] but only the latter one’s are suitable for high-temperature applications. The design of a TCO on top of a black body has a series of advantages compared to multilayer- or cermet-based solar-selective coatings (SSCs). Bare absorbers can be transformed into selective ones, the functionality is almost independent on film thicknesses, the fabrication is relatively easy and the concept is adaptable to specific requirements with respect to the operation temperature of the solar-thermal application.
The conceptual introduction will be followed by a review of recent developments in the field, which include the excellent high-temperature in-air stability of such type of solar coating when based on Sn-doped In₂O₃ (ITO).[4] In the main part of the talk, the development, optical modelling, properties and thermal stability of another TCO, Ta-doped SnO₂, are reported.[5] Its cutoff, i.e. the wavelength where it changes from transmitting to reflecting, is tunable from 1.7 µm to 2.4 µm. The optical properties of SnO₂:Ta are almost independent on the film thickness. The TCO is stable up to 800 °C in high vacuum and in air for 12 hours (at least) as shown by ion beam analysis, X-ray diffraction, ellipsometry and reflectometry. When the SnO₂:Ta is deposited on silicon and glassy carbon transforms these bare absorbers into selective ones. Finally, as part of the whole SSC concept, the formation, structure, and optical properties of dense, PVD-grown CuCr₂O₄ thin films is reported. This potential high-temperature absorber is obtained in high purity from as-deposited samples by a simple in-air annealing step at 800 °C and absorbs light in the whole solar range from 300 nm to 2500 nm.[6]

[1] Kennedy, C. E. Review of Mid- to High-Temperature Solar Selective Absorber Materials. Report No. NREL/TP-520-31267, (NREL - National Renewable Energy Laboratory, Golden, Colorado, USA, 2002).
[2] Granqvist, C. G. Transparent conductors as solar energy materials: A panoramic review. Solar Energy Materials and Solar Cells 91, 1529-1598, doi:10.1016/j.solmat.2007.04.031 (2007).
[3] Fan, J. C. C. & Bachner, F. J. TRANSPARENT HEAT MIRRORS FOR SOLAR-ENERGY APPLICATIONS. Applied Optics 15, 1012-1017, doi:10.1364/ao.15.001012 (1976).
[4] Wang, H., Haechler, I., Kaur, S., Freedman, J. & Prasher, R. Spectrally selective solar absorber stable up to 900 degrees C for 120 h under ambient conditions. Solar Energy 174, 305-311, doi:10.1016/j.solener.2018.09.009 (2018).
[5] Lungwitz, F. et al. Transparent conductive tantalum doped tin oxide as selectively solar-transmitting coating for high temperature solar thermal applications. Solar Energy Materials and Solar Cells 196, 84-93, doi:10.1016/j.solmat.2019.03.012 (2019).
[6] Krause, M. et al. Formation, structure, and optical properties of copper chromite thin films for high-temperature solar absorbers. Mater. 18, doi:10.1016/j.mtla.2021.101156 (2021).

Related publications

  • Invited lecture (Conferences) (Online presentation)
    2021 Iberian Vacuum Meeting - RIVA Online, 04.-06.10.2021, Online, Spanien/ Portugal

Permalink: https://www.hzdr.de/publications/Publ-33202
Publ.-Id: 33202


Bioleaching of uranium ores - microbiology, technical processes and resulting challenges

Raff, J.

The presentation will give a brief overview of microbial leaching in general and uranium ore leaching in particular. The microbial metabolism and its influencing variables as well as the chemistry and the actual technical process will be discussed. Finally, the advantages and disadvantages of the biotechnological process are compared to a conventional process and the main challenges in this context are mentioned.

Keywords: Bioleaching; uramium ores

  • Invited lecture (Conferences) (Online presentation)
    57th Meeting of the Joint OECD/NEA-IAEA Uranium Group, 03.-05.11.2021, Paris, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-33201
Publ.-Id: 33201


Challenges to TEM sample preparation of stacked Si/SiO2/Si nanopillars for SETs using Focused Ion Beam

Engelmann, H.-J.; Bischoff, L.; Hübner, R.; Heinig, K.-H.; Hlawacek, G.; Borany, J.; Pourteau, M. L.; Rademaker, G.

Single Electron Transistors (SETs) open the way to semiconductor devices with extremely low power consumption. Quantum mechanical effects are used in such transistors: field-controlled tunneling of single electrons from a source to a drain via a quantum dot. SETs can be manufactured as thin Si pillars (source and drain) with a Si oxide layer in-between containing one Si quantum dot (Fig. 1). After SiOx formation by ion beam mixing, a thermally activated phase separation including Ostwald ripening results in a self-organization of Si nanocrystals in the SiO2 layer acting as Si quantum dots (Si NDs). For SET operation at room temperature, the diameter of the Si pillars needs to be < 12 nm, the Si ND diameter must be in the range of 2…3 nm and the distances between Si NDs and source/drain cannot be larger than 1.5 nm allowing quantum mechanical tunneling of the electrons.
Thus, Transmission Electron Microscopy (TEM) must be used for the structural characterization of these SETs. Si NDs inside the SiO2 matrix can only be detected by using the Si plasmon loss in the energy-filtered TEM mode. TEM sample preparation is challenging because of the very small 3D structure of the pillars (Fig.2) and the need for very thin TEM lamellae (30…40 nm in thickness). The Focused Ion Beam (FIB) lift-out technique can be used to prepare such samples. Setting markers and gradual thinning of the lamella from both sides (with TEM inspection in between) is necessary.
Surprisingly, comprehensive TEM studies uncovered that the oxide layer of a Si/ SiO2/Si layer stack can become dramatically thinner in pillars fabricated from this stack by Reactive Ion Etching (RIE). The oxide layer thinning depends on the pillar diameter. For instance, an originally 8 nm thick SiO2 layer is reduced to 2.6 nm in 15 nm diameter pillars. In order to prove that this oxide shrinkage is caused by RIE and not by sample preparation the most critical process in the FIB preparation - which is the electron-beam-assisted carbon-protection-layer deposition - was analyzed in detail: pillars were irradiated with different electron doses and then, the SiO2 thickness was measured in the TEM. As can be seen in Fig. 3 there is a clear influence of the electron dose on the oxide thickness. This can be explained by charge accumulation in pillar Si caps (drain), followed by dielectric breakdowns through filament formation across the SiO2 layer accompanied by Si oxide dissociation and oxygen emanation from the SiO2 disc rim of the pillars. However, as can be seen in Fig. 3 the FIB-caused contribution to the oxide thickness reduction is only a small part. The main contribution comes from the pillar RIE process based on the same physical reason (charging of the pillar Si caps).
This work was supported by the European Union’s H-2020 research project ‘IONS4SET’ under Grant Agreement No. 688072

Keywords: Single Electron Transistor (SET); Structural Characterization; Plasmon Loss Energy-Filtered TEM; TEM Sample Preparation; Focused Ion Beam; Si Oxide Layer Thickness Reduction

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  • Lecture (Conference) (Online presentation)
    FIT4NANO/Eu-F-N workshop, 27.-30.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-33200
Publ.-Id: 33200


Data publication: Formation and time dynamics of hydrogen-induced vacancies in nickel

Chiari, L.; Kojima, K.; Endo, Y.; Teshigahara, H.; Butterling, M.; Liedke, M. O.; Hirschmann, E.; Elsherif, A. G. A.; Wagner, A.; Fujinami, M.

Die Daten umfassen: - original-Daten für die zeitabhängige Messung der Positronen-Annihilations-Lebensdauer - Verwendete Ergebnisse der Daten-Analyse für die Publikation

Keywords: hydrogen; nickel; vacancies; positron annihilation spectroscopy; positron annihilation lifetime spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-33199
Publ.-Id: 33199


Künstliche Intelligenz im Gesundheitswesen

Steinbach, P.

Künstliche Intelligenz als Überbegriff steht schon länger im Fokus von Klinikern, Gesundheitsökonomen und medizinischen Wissenschaftlern. Entdeckungen in diesem weiten Feld sind aber nur vereinzelt im klinischen Alltag sichtbar, da insbesondere die diagnostische Entscheidungshoheit dem Menschen zugestanden wird. Doch steht schon heute fest: Der Einsatz von künstlicher Intelligenz wird nach und nach zu einem Wandel in der Medizin führen.

Keywords: KI; Medizin; Gesundheitswesen; Maschinelles Lernen

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Permalink: https://www.hzdr.de/publications/Publ-33198
Publ.-Id: 33198


The role of adsorption strength and quantum confinement on the isotopologue selectivity of H₂ complexation

Wulf, T.

Heavy hydrogen isotopes are an essential resource with multiple applications in energy production, medicine and science. Unfortunately, the relative scarcity of heavy hydrogen in comparison to the much more abundant light hydrogen makes the enrichment of the heavy isotopes extremely challenging. State-of-the-art separation methods based on chemical exchange remain energy-consuming processes. In this thesis, density functional and ab initio methods are used to make several contributions to the investigation of one alternative approach to isotope separation: the isotopologue-selective adsorption of hydrogen at undercoordinated metal sites based on the different zero-point energy of adsorption of the isotopologues.

Because the zero-point energy is proportional to the curvature of the potential energy surface, which in turn correlates with the adsorption energy, stronger adsorption should in principle also lead to higher selectivity. Therefore, in the first part, the prerequisites for a high adsorption energy are investigated. It is concluded that main contributors are the chemical nature of the metal site (presence of d orbitals) and very acute ligand-metal-ligand angles, whereas the nature of the ligands seems to play a minor role.

The second part focuses on the selectivity-enhancing effect of confinement introduced by a pore around the adsorption site. It is found that confinement does not play a significant role in Cu(I)-MFU-4l. Although some confinement may be introduced via appropriate modifications of the linker, it is found that this comes at the cost of a sharp loss in H₂ affinity. Studying a more strongly binding model, it is nevertheless concluded that confinement can indeed significantly enhance H₂ isotopologue selectivity at very strong adsorption sites.

B₁₂X₁₁⁻ (X = H, F, Cl, Br, I, CN), a system showing very strong H₂ adsorption and a high D₂ /H₂ selectivity is investigated in the third part.

In the fourth part, the CoRE MOF database is screened for potential H₂-affine sites based on geometric criteria. Some promising adsorption site motifs are identified, studied with preliminary DFT calculations and their deeper investigation in future works is envisioned.

To conclude, this thesis advances the field of isotopologue-selective H₂ adsorption by identifying both general structural prerequisites for high selectivity as well as specific model systems and structural motifs worthy of further study.

Keywords: hydrogen; isotopes; separation; adsorption; open metal sites

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  • Doctoral thesis
    Universität Leipzig, 2022
    Mentor: Thomas Heine
    134 Seiten

Permalink: https://www.hzdr.de/publications/Publ-33197
Publ.-Id: 33197


Sc3Ir4Si13+x and Sc4Ir7Ge6 – the perovskite-related crystal structures

Levytskyi, V.; Wagler, J.; Hennig, C.; Feig, M.; Weigel, T.; Leithe-Jasper, A.; Meyer, D. C.; Gumeniuk, R.

The crystal structure of Sc3Ir4Si13+x (x = 0.22) [space group Pm3 ̅n, a = 8.4651(1) Å] is found to be a new disordered variant of the primitive cubic Yb3Rh4Sn13 Remeika prototype. The silicide is stable in the narrow temperature range of 1283-1397 °C and reveals metallic properties. The crystal structure of Sc4Ir7Ge6 [U4Re7Si6 type, space group Im3 ̅m, a = 8.1397(8) Å] is refined for the first time. The electronic band structure calculations reveal that the properties of this germanide can be explained based on the free electron gas model. Both compounds reveal close structural relationships to the simple perovskite structure.

Keywords: crystal structure; single crystal; X-ray diffraction; synchrotron studies; electronic structure; magnetic susceptibility

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Permalink: https://www.hzdr.de/publications/Publ-33196
Publ.-Id: 33196


Uranium remobilisation in anoxic deep rock-groundwater system in response to late Quaternary climate changes – Results from Forsmark, Sweden

Suksi, J.; Tullborg, E.-L.; Pidchenko, I.; Krall, L.; Sandström, B.; Kaksonen, K.; Vitova, T.; Kvashnina, K. O.; Göttlicher, J.

Unusually high uranium (U) concentrations (up to 175 μg/L) have been measured in groundwater at depths between 400 and 650 m at the Forsmark site, eastern Sweden. Since it is unlikely that such high concentrations formed under the stagnant and low redox groundwater conditions that currently prevail, this study employs U-series isotopes to understand how the recent evolution (<1 Ma) of the flow system has influenced the observed U distribution. Material from fractures as deep as 700 m along the assumed flow route was subject to U-series disequilibrium (USD) measurements, as well as sequential extractions (SE) and U redox-state analyses that revealed the U-series activity ratios in the bulk and soluble fraction of the fracture precipitates. Uranium isotope data collected over several years of annual groundwater monitoring were scrutinized to evaluate the U sources and U exchange in fractures located in high-U groundwater sections. Numerical simulations with the experimental data were used to study evolution of U-series isotope composition in a fracture in the highest U section at ~500 m depth under various U mobility scenarios. The results show that U redistribution in fractures with certain dissolution/deposition flux ratios during periodic water intrusions, driven by glaciation and deglaciation events during the last 120 ka, can explain the U anomaly in the groundwater.

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Permalink: https://www.hzdr.de/publications/Publ-33195
Publ.-Id: 33195


Dataset and scripts for A Deep Dive into Machine Learning Density Functional Theory for Materials Science and Chemistry

Fiedler, L.; Shah, K.; Cangi, A.; Bussmann, M.

This dataset contains additional data for the publication "A Deep Dive into Machine Learning Density Functional Theory for Materials Science and Chemistry". Its goal is to enable interested people to reproduce the citation analysis carried out in the aforementioned publication.  

Prerequesites

The following software versions were used for the python version of this dataset:

Python: 3.8.6

Scholarly: 1.2.0

Pyzotero: 1.4.24

Numpy: 1.20.1

Fitz: 1.19.1

Contents

results/ : Contains the .csv files that were the results of the citation analysis.  Paper groupings follow the ones outlined in the publication.

scripts/ : Contains scripts to perform the citation analysis.

Zotero.cached.pkl : Contains the cached Zotero library.

Usage

In order to reproduce the results of the citation analysis, you can use citation_analysis.py in conjunction with cached Zotero library. Manual additions can be verified using the check_consistency script.
Please note that you will need a Tor key for the citation analysis, and access to our Zotero library if you don't want to use the cached version. If you need this access, simply contact us.

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Permalink: https://www.hzdr.de/publications/Publ-33194
Publ.-Id: 33194


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