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41419 Publications

Laser-plasma proton acceleration with a combined gas-foil target

Levy, D.; Bernert, C.; Rehwald, M.; Andriyash, I. A.; Assenbaum, S.; Kluge, T.; Kroupp, E.; Obst-Huebl, L.; Pausch, R.; Schulze-Makuch, A.; Zeil, K.; Schramm, U.; Malka, V.

Laser-plasma proton acceleration was investigated in the target normal sheath acceleration regime with a target composed of a gas layer and a thin foil. The laser's shape, duration, energy and frequency are modified as it propagates in the gas, altering the laser-solid interaction leading to proton acceleration. The modified properties of the laser were assessed by both numerical simulations and by measurements. The 3D particle-in-cell simulations have shown that a nearly seven-fold increase in peak intensity at the foil plane is possible. In the experiment, maximum proton energies showed high dependence on the energy transmission of the laser through the gas and a lesser dependence on the size and shape of the pulse. At high gas densities, where high intensity was expected, laser energy depletion and pulse distortion suppressed proton energies. At low densities, with the laser focused far behind the foil, self-focusing was observed and the gas showed a positive effect on proton energies. The promising results of this first exploration motivate further study of the target.

Keywords: laser plasma; TNSA; self focusing; PIConGPU

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Permalink: https://www.hzdr.de/publications/Publ-31881
Publ.-Id: 31881


Status Report of GaN photocathode

Schaber, J.; Xiang, R.; Teichert, J.; Arnold, A.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.

Particle accelerators are always looking for new materials which can promise high quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance. Semiconductors such as GaN as novel materials for photocathodes are showing an enormous potential.
Activated with a thin alkali metal layer, like caesium (Cs), p-GaN has the ability to lower the surface work function to produce a negative electron affinity (NEA). Requirements on the instrumentation is to avoid any oxygen contamination before, during and after the activation with caesium, so the activation process takes place in a UHV chamber.
At the beginning of 2020 the first activation of GaN on sapphire substrate was successfully done and meanwhile more activations could be implemented. The activation process is influenced by many parameters like Cs-flux, heat-cleaning temperature, conductivity, anode material, vacuum and the substrate. All of these parameters have an influence on the photocathodes quality and its lifetime, which are studied and compared.

Keywords: GaN photocathode; III-V semiconductor; caesium activation; NEA cathode; Quantum efficiency

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  • Open Access Logo Lecture (others) (Online presentation)
    High Brightness Electron beams generated from novel THermal resistant photocathodes (BETH) 2nd Collaboration Meeting, 10.07.2020, Siegen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31880
Publ.-Id: 31880


Status Report of ELBE and GaN

Xiang, R.; Teichert, J.; Arnold, A.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.; Schaber, J.

The SRF Gun has been running stabile using a magnesium cathode in the last year. Over 200 hours beam time have been provided in CW operation in 2019.
The magnesium bulk cathodes work routinely in ELBE and are polished and chemical cleaned before inserting them into the SRF Gun II, where they are again cleaned with an UV drive laser. Magnesium cathodes derives usually quantum effeciencies (QE) between 0.3 to 0.5% in SRF Gun II and offer a low risk of contaminations and an extreme long lifetime. The UV drive laser cleaning can be repeated several times to guarantee an high quality working cathode.
However, the particle accelerator community is always looking for new materials which can promise high quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance. Semiconductors such as GaN as novel materials for photocathodes are showing an enormous potential.
GaN is a semi-conductive material and well known for its high QE when illuminated with UV light. For the activation only caesium is required.
At the beginning of 2020 the first activation of GaN on sapphire substrate was successfully done. At first the GaN is heat treated at 610°C for 15 min and then activated with caesium to form a negative electron affinity surface. With 0.5 % quantum efficiency the first activation is all in all a successfully step for further promising GaN photocathodes.

Keywords: GaN; photocathode; SRF Gun; III-V semiconductor photocathode; Mg cathode

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  • Open Access Logo Lecture (others)
    High Brightness Electron beams generated from novel THermal resistant photocathodes (BETH) Meeting, 20.-21.01.2020, Siegen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31879
Publ.-Id: 31879


C. elegans possess a general program to enter cryptobiosis that allows dauer larvae to survive different kinds of abiotic stress

Gade, V. R.; Traikov, S.; Oertel, J.; Fahmy, K.; Kurzchalia, T. V.

All organisms encounter abiotic stress but only certain organisms are able to cope with extreme conditions and enter into cryptobiosis (hidden life). Previously, we have shown that C. elegans dauer larvae can survive severe desiccation (anhydrobiosis), a specific form of cryptobiosis. Entry into anhydrobiosis is preceded by activation of a set of biochemical pathways by exposure to mild desiccation. This process called preconditioning induces elevation of trehalose, intrinsically disordered proteins, polyamines and some other pathways that allow the preservation of cellular functionality in the absence of water. Here, we demonstrate that another stress factor, high osmolarity, activates similar biochemical pathways. The larvae that acquired resistance to high osmotic pressure can also withstand desiccation. In addition, high osmolarity significantly increases the biosynthesis of glycerol making larva tolerant to freezing. Thus, to survive abiotic stress, C. elegans activates a combination of genetic and biochemical pathways that serve as a general survival program.

Keywords: calorimetry; anhydrobiosis; metabolic monitoring; osmmotic stress

Permalink: https://www.hzdr.de/publications/Publ-31878
Publ.-Id: 31878


Current status of the simulations on Wu et al. using fbpic and PIConGPU

Pausch, R.; Döpp, A.

A brief summary to drive a discussion regarding the Wu et al. paper and a possible reply to it.

Keywords: PIConGPU; LWFA; PWFA; fbpic

  • Lecture (others)
    hybrid meeting, 06.02.2020, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-31877
Publ.-Id: 31877


Data for: "First-principles modeling of plasmons in aluminum under ambient and extreme conditions"

Ramakrishna, K.; Cangi, A.; Dornheim, T.; Vorberger, J.; Baczewski, A.

The theoretical understanding of plasmon behavior is crucial for an accurate interpretation of inelastic
scattering diagnostics in many experiments. We highlight the utility of linear-response time-dependent density
functional theory (LR-TDDFT) as a first-principles framework for consistently modeling plasmon properties.
We provide a comprehensive analysis of plasmons in aluminum from ambient to warm dense matter conditions
and assess typical properties such as the dynamical structure factor, the plasmon dispersion, and the plasmon
lifetime. We compare our results with scattering measurements and with other TDDFT results as well as models
such as the random phase approximation, the Mermin approach, and the dielectric function obtained using static
local field corrections of the uniform electron gas parametrized from path-integral Monte Carlo simulations. We
conclude that results for the plasmon dispersion and lifetime are inconsistent between experiment and theories
and that the common practice of extracting and studying plasmon dispersion relations is an insufficient procedure
to capture the complicated physics contained in the dynamic structure factor in its full breadth.
 

Keywords: Warm dense matter; TDDFT

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Permalink: https://www.hzdr.de/publications/Publ-31876
Publ.-Id: 31876


Probing ultrafast magnetic-field generation by current filamentation instability in femtosecond relativistic laser-matter interactions

Raj, G.; Kononenko, O.; Gilljohann, M. F. F.; Doche, A.; Davoine, X.; Caizergues, C.; Chang, Y.-Y.; Couperus Cabadağ, J. P.; Debus, A.; Ding, H.; Förster, M.; Goddet, J.-P.; Heinemann, T.; Kluge, T.; Kurz, T.; Pausch, R.; Rousseau, P.; San Miguel Claveria, P.; Schöbel, S.; Siciak, A.; Steiniger, K.; Tafzi, A.; Yu, S.; Hidding, B.; Martinez De La Ossa, A.; Irman, A.; Karsch, S.; Döpp, A.; Schramm, U.; Gremillet, L.; Corde, S.

The current filamentation instability is a key phenomenon underpinning various processes in astrophysics, laboratory laser-plasma, and beam-plasma experiments. Here we show that the ultrafast dynamics of this instability can be explored in the context of relativistic laser-solid interactions through deflectometry by low-emittance, highly relativistic electron bunches from a laser wakefield accelerator. We present experimental measurements of the femtosecond timescale generation of strong magnetic-field fluctuations, with a measured line-integrated B field of 2.70±0.39kTμm. Three-dimensional, fully relativistic particle-in-cell simulations demonstrate that such fluctuations originate from the current filamentation instability arising at submicron scales around the irradiated target surface, and that they grow to amplitudes strong enough to broaden the angular distribution of the probe electron bunch a few tens of femtoseconds after the laser pulse maximum. Our results open a branch of physics experiments investigating the femtosecond dynamics of laser-driven plasma instabilities by means of synchronized, wakefield-accelerated electron beams.

Keywords: current filamentation; laser plasma

Permalink: https://www.hzdr.de/publications/Publ-31875
Publ.-Id: 31875


Review on the Compositional Variation of Eudialyte-Group Minerals in the Ilímaussaq Complex (South Greenland)

Marks, M. A. W.; Eggenkamp, H. G. M.; Atanasova, Petya; Mundel, F.; Kümmel, S.; Hagen, M.; Wenzel, T.; Markl, G.

We review the compositional variation of eudialyte-group minerals (EGM) from the Ilímaussaq complex in South Greenland. Investigated samples cover all major rock units and associated pegmatites and aplites. The whole data set (>3000 analyses from>250 samples) exhibits variable XMn (0.1–0.5), REE (0.2–1.7 apfu), Nb (0.1–0.4), and Cl contents (0.4–1.6 apfu). Most EGM compositions are Na-rich (13–15 apfu), while deviations to Na-rich but also to Na-poor compositions occur because of a combination of primary features (peralkalinity, water activity) and secondary alteration. During magma evolution, REE contents in EGM cores generally increase and reach their highest contents in the most evolved rock units of the complex. This points to the moderate compatibility of REE in EGM and a bulk D (cEGM/cmelt) value of <1 during magma differentiation. Chlorine contents in EGM cores continuously decrease, and are lowest at the rims of individual crystals, suggesting a continuous decrease of Cl activity in the magmas by large-scale EGM and sodalite extraction during the orthomagmatic stage and water enrichment during the late-magmatic stage. The overall variations of XMn across stratigraphy are only minor and likely influenced bythe co-crystallization of sodic pyroxene and amphibole (c.f. aegirine, arfvedsonite) and local phaseproportions. Similarly, Nb and Ti contents are influenced by co-crystallizing aenigmatite, rinkite, and others. Their presence buffers Ti and Nb contents to rather constant and low values, while their absence may cause variable enrichment on a local scale. Very low Sr contents (<0.1 apfu) in magmatic EGM from Ilímaussaq are related to the basaltic nature of the parental magmas of the complex, as large-scale plagioclase fractionation occurred prior to the formation of the Ilímaussaq magmas, effectively removing Sr from the system. This is in line with very strong negative Eu anomalies in EGM from Ilímaussaq. Consistently, Sr contents in EGM from alkaline complexes, for which foiditic parental magmas are assumed, are much higher and, in such cases, negative Eu anomalies aregenerally absent.

Keywords: Ilimaussaq; differentiation; eudialyte-group minerals; mineral chemistry

Permalink: https://www.hzdr.de/publications/Publ-31874
Publ.-Id: 31874


PIConGPU - a highly-parallel 3D3V particle-in-cell code

Pausch, R.; Bastrakov, S.; Debus, A.; Garten, M.; Huebl, A.; Marre, B.-E.; Meyer, F.; Steinger, K.; Widera, R.; Bussmann, M.

This talk will introduce the basic concepts of how particle-in-cell codes model plasma dynamics and discuss their implementation in the open-source code PIConGPU, focusing on how parallelism can be exploited to enable efficient scaling on today's largest HPC systems. Furthermore, the problem of IO limitations with larger simulations is discussed and the plugin method for in-situ data analysis in PIConGPU is presented to overcome these limitations. Finally, an overview of different physics cases simulated with PIConGPU is presented, ranging from small-scale laser-plasma accelerators to plasma jets in astrophysics.

Keywords: PIConGPU; LWFA; TNSA; alpaka; ISAAC; KHI

  • Lecture (others) (Online presentation)
    CASUS Seminar, 08.09.2020, Görlitz, Deutschland
  • Lecture (others)
    Seminar Series 'Hardware & Numerics', 24.11.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31873
Publ.-Id: 31873


Changes in Halogen (F, Cl, Br, and I) and S Ratios inRock-Forming Minerals as Monitors for MagmaticDifferentiation, Volatile-Loss, and HydrothermalOverprint: The Case for Peralkaline Systems

Eggenkamp, H. G. M.; Marks, M. A. W.; Atanasova, Petya; Wenzel, T.; Markl, G.

We determined the halogen (F, Cl, Br, and I) and sulfur (S) concentrations in Cl-rich rock-forming minerals from five peralkaline complexes. We investigated sodalite (N=42), eudialyte-group minerals (N=84), and tugtupite (N=8) from representative rock samples derived from Ilímaussaq (South Greenland), Norra Kärr (Sweden), Tamazeght (Morocco), Lovozero, and Khibina (Russian Federation). Taken together, sodalite and eudialyte-group minerals dominate the Cl and Br budget of the investigated rocks. For F, however, several other phases (e.g., amphibole, fluorite, villiaumite, and minerals of the rinkite group and the apatite supergroup) are additional sinks, and parts of the S may be scavenged in generally rare sulfides. The investigated minerals contain Cl at the wt.% level, F and S concentrations are in the hundreds to thousands of μg/g-range, Br is less common (0.2–200μg/g) and I is rare (mostly well below 1μg/g). Normalized to Cl, sodalite prefers Br relative to eudialyte-group minerals, while F is always enriched in the latter. Our data show that both F and S may represent important components in eudialyte-group minerals, sometimes at similar levels as Cl, which normally dominates. Sulfur reveals redox-dependent behavior: Under reduced crystallization conditions, S is more compatible in eudialyte-group minerals (EGM) than in sodalite, which flips to the opposite under water-rich and presumably more oxidized conditions. We investigate the applicability of F/Cl, Br/Cl, and S/Cl ratios in these minerals in peralkaline systems to better understand the interplay of magmatic differentiation, fluid loss and hydrothermal overprint. Similar to apatite in metaluminous systems, fractionation of sodalite, and eudialyte-group minerals in peralkaline magmas leads to decreasing Br/Cl ratios. The data presented in this study bear implications for the mineral chemistry and compositional variation of sodalite and especially EGM in general. Volatile components in EGM that are not normally considered, such as F and S, can reach concentrations of thousands of μg/g. Especially in the case of F, with its low atomic weight, the results obtained in this study indicate that it is very significant for formulae calculations, neutral charge-balance, and similar aspects at such concentration levels. This study demonstrates that halogen contents and ratios are sensitive monitors for a variety of processes in magmatic-hydrothermal systems, including magmatic fractionation, volatile loss, and fluid–rock interaction.

Keywords: eudialyte group minerals; sodalite; tugtupite; chloride; fluoride; bromide; sulfur; Ilímaussaq; peralkaline rocks

Permalink: https://www.hzdr.de/publications/Publ-31872
Publ.-Id: 31872


Design study for a compact laser-driven source for medical x-ray fluorescence imaging

Brümmer, T.; Debus, A.; Pausch, R.; Osterhoff, J.; Grüner, F.

Thomson scattering sources with their hard x-ray pencil beams represent a promising candidate to drive high-resolution X-ray Fluorescence Imaging (XFI). As XFI is a scanning imaging modality, it specifically requires pencil-beam geometries along with a high beam mobility. In combination with laser-wakefield acceleration (LWFA) such sources could provide the compactness needed for a future transition into clinical application. A sufficient flux within a small bandwidth could enable in-vivo high-sensitivity XFI for early cancer diagnostics and pharmacokinetic imaging. We thus report on a specific all-laser driven source design directed at increasing the photon number within the bandwidth and opening angle defined by XFI conditions. Typical parameters of driver lasers and electron bunches from LWFA are utilized and controlled within realistic parameter regions on the basis of appropriate beam optics. An active plasma lens is implemented for chromatic focal control of the bunch. Source performance limits are identified and compared to existing x-ray sources with regard to their potential to be implemented in future clinical XFI.

Keywords: Thomsons scattering; x-ray; light source; ClaRa2

Permalink: https://www.hzdr.de/publications/Publ-31871
Publ.-Id: 31871


Uranium(VI) reduction by a sulphate-reducing microorganism in Opalinus Clay pore water

Hilpmann, S.; Drobot, B.; Steudtner, R.; Bok, F.; Stumpf, T.; Cherkouk, A.

1 Introduction
Clay formations are potential host rocks for the long-term storage of high-level radioactive waste in a deep geological repository in Germany, besides salt and crystalline rock. A multi-barrier system is fa-vored, consisting of the technical (container with the waste), the geotechnical (sealing and backfilling material, e.g. bentonite) and the geological barrier (host rock) to isolate it from the biosphere.
Different studies showed that sulphate-reducing microorganisms, especially Desulfosporosinus species, occur in various clay formations, as well as in bentonite [1,2]. Desulfosporosinus hippei DSM 8344 is an anaerobic spore-forming microorganism isolated from permafrost soil [3] and a close phylogenetic relative of the Desulfosporosinus species detected in clay formations. Therefore, this strain was selected to study the reduc-tion of uranium(VI) to the less mobile uranium(IV).

2 Results
A time-dependent experiment in artificial Opalinus Clay pore water [4] (100 µM uranium(VI), pH 5.5) revealed a 95 % removal of uranium from the supernatant within 24 h. The corresponding microscopy of live/dead stained cells showed the formation of agglomerates and an increasing number of dead cells within the incubation time. The black colouring of the agglomerates already provided hints of the occur-ring reduction of uranium(VI).
Different aqueous species including uranyl(VI) lactate and uranyl(VI) carbonate complexes are present in the supernatant, as determined by time-resolved laser-induced luminescence spectroscopy. The assign-ment of the different species was possible by comparison with reference spectra. While the amount of the uranyl(VI) lactate complex decreased with the incubation time, the uranyl(VI) carbonate fraction re-mained almost constant. This leads to the assumption, that the cells reduce only the uranyl(VI) lactate complex. This conclusion can be supported by the fact that the reduction process did not take place in bicarbonate buffer, where the uranyl(VI) carbonate complexes are dominant, using the same microor-ganism.
The comparison of the UV/VIS band positions of the dissolved cell pellets with the spectra of pure uranium(IV) and uranyl(VI) samples provides clear evidence of the formed uranium(IV). Furthermore, bands of uranyl(VI) occur in the spectrum, as well. Therefore, a combination of a sorption and reduction processes is assumed. These findings offer new insights into the microbe-actinide interactions relevant to high-level radioactive waste disposal in clay rock.

The authors gratefully acknowledge the funding provided by the German Federal Ministry of Education and Research (BMBF) (Grant 02NUK053E) and The Helmholtz Association (Grant SO-093).

References
[1] A. Bagnoud et al., “Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock”, Nat. Commun. 7, 1–10 (2016)
[2] N. Matschiavelli et al., “The year-long development of microorganisms in uncompacted Bavarian bentonite slurries at 30 °C and 60 °C”, Environ. Sci. Technol. 53, 10514–10524 (2019).
[3] A. Vatsurina et al., “Desulfosporosinus hippei sp. nov., a mesophilic sulfate-reducing bacterium isolated from permafrost”, Int. J. Syst. Evol. Microbiol. 58, 1228–1232 (2008).
[4] P. Wersin et al. “Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland”, Appl. Geochemistry 26, 931–953 (2011).

Keywords: uranium(VI) reduction; sulphate-reducing bacteria; clay rock

  • Lecture (Conference) (Online presentation)
    Tage der Standortauswahl Freiberg 2021, 11.-12.02.2021, Freiberg, Deutschland
  • Poster (Online presentation)
    Tage der Standortauswahl Freiberg 2021, 11.-12.02.2021, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31870
Publ.-Id: 31870


Wire-mesh sensor data set of gas-water flow in a horizontal pipe

de Assis Dias, F.; Pipa, D. R.; Morales, R. E. M.; Da Silva, M. J.

Wire-mesh sensor raw data of gas-water pipe flow. The experiments were performed at the Federal University of Paraná in a setup located at the NUEM (Núcleo de Escoamento Multifásico). The flow loop is composed of a horizontal pipe of 26 mm inner diameter and 9 m long. The data set are measurements of wire-mesh sensors with the following resolutions: 12x12, 8x8, 6x6, 4x4 and 2x2.

Keywords: wire-mesh sensor; multiphase flow

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Permalink: https://www.hzdr.de/publications/Publ-31869
Publ.-Id: 31869


First-principles modeling of plasmons in aluminum under ambient and extreme conditions

Ramakrishna, K.; Cangi, A.; Dornheim, T.; Vorberger, J.

The numerical modeling of plasmon behavior is crucial for an accurate interpretation of inelastic scattering diagnostics in many experiments. We highlight the utility of linear-response time-dependent density functional theory (LR-TDDFT) as an appropriate first-principles framework for a consistent modeling of plasmon properties. We provide a comprehensive analysis of plasmons from ambient throughout warm dense conditions and assess typical properties such as the dynamical structure factor, the plasmon dispersion, and the plasmon width. We compare them with experimental measurements in aluminum accessible via x-ray Thomson scattering and with other dielectric models such as the Lindhard model, the Mermin approach based on parametrized collision frequencies, and the dielectric function obtained using static local field corrections of the uniform electron gas parametrized from path integral Monte Carlo simulations both at the ground state and at finite temperature. We conclude with the remark that the common practice of extracting and employing plasmon dispersion relations and widths is an insufficient procedure to capture the complicated physics contained in the dynamic structure factor in its full breadth.

Keywords: Warm dense matter

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Permalink: https://www.hzdr.de/publications/Publ-31868
Publ.-Id: 31868


Attenuating the fermion sign problem in path integral Monte Carlo simulations using the Bogoliubov inequality and thermodynamic integration

Dornheim, T.; Invernizzi, M.; Hirshberg, B.; Vorberger, J.

Accurate thermodynamic simulations of correlated fermions using path integral Monte Carlo (PIMC) methods are of paramount importance for many applications such as the description of ultracold atoms, electrons in quantum dots, and warm-dense matter. The main obstacle is the fermion sign problem (FSP), which leads to an exponential increase in computation time both with increasing the system-size and with decreasing temperature. Very recently, Hirshberg et al.[J. Chem. Phys. 152, 171102 (2020)] have proposed to alleviate the FSP based on the Bogoliubov inequality. In the present work, we extend this approach by adding a parameter that controls the perturbation, allowing for an extrapolation to the exact result. In this way, we can also use thermodynamic integration to obtain an improved estimate of the fermionic energy. As a test system, we choose electrons in 2D and 3D quantum dots and find in some cases a speed-up exceeding 10^ 6, as compared to standard PIMC, while retaining a relative accuracy of ~0.1%. Our approach is quite general and can readily be adapted to other simulation methods.

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Permalink: https://www.hzdr.de/publications/Publ-31866
Publ.-Id: 31866


Finite-size effects in the reconstruction of dynamic properties from ab initio path integral Monte Carlo simulations

Dornheim, T.; Vorberger, J.

We systematically investigate finite-size effects in the dynamic structure factor S(q,ω) of the uniform electron gas obtained via the analytic continuation of ab initio path integral Monte Carlo data for the imaginary-time density–density correlation function F(q,τ). Using the recent scheme by Dornheim et al. [Phys. Rev. Lett. 121, 255001 (2018)], we find that the reconstructed spectra are not afflicted with any finite-size effects for as few as N=14 electrons both at warm dense matter (WDM) conditions and at the margins of the strongly correlated electron liquid regime. Our results further corroborate the high quality of our current description of the dynamic density response of correlated electrons, which is of high importance for many applications in WDM theory and beyond.

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Permalink: https://www.hzdr.de/publications/Publ-31865
Publ.-Id: 31865


Effective Static Approximation: A Fast and Reliable Tool for Warm-Dense Matter Theory

Dornheim, T.; Cangi, A.; Ramakrishna, K.; Böhme, M.; Tanaka, S.; Vorberger, J.

We present an effective static approximation (ESA) to the local field correction (LFC) of the electron gas that enables highly accurate calculations of electronic properties like the dynamic structure factor S(q,ω), the static structure factor S(q), and the interaction energy v. The ESA combines the recent neural-net representation by T. Dornheim et al., [J. Chem. Phys. 151, 194104 (2019)] of the temperature-dependent LFC in the exact static limit with a consistent large wave-number limit obtained from quantum Monte Carlo data of the on-top pair distribution function g(0). It is suited for a straightforward integration into existing codes. We demonstrate the importance of the LFC for practical applications by reevaluating the results of the recent x-ray Thomson scattering experiment on aluminum by Sperling et al. [Phys. Rev. Lett. 115, 115001 (2015)]. We find that an accurate incorporation of electronic correlations in terms of the ESA leads to a different prediction of the inelastic scattering spectrum than obtained from state-of-the-art models like the Mermin approach or linear-response time-dependent density functional theory. Furthermore, the ESA scheme is particularly relevant for the development of advanced exchange-correlation functionals in density functional theory.

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Permalink: https://www.hzdr.de/publications/Publ-31864
Publ.-Id: 31864


Pump-probe response of correlated materials under high pressures

Pashkin, O.

Time-resolved optical spectroscopy is a very powerful tool for studying the photoinduced phase transitions and ultrafast dynamics in strongly correlated electronic systems. We reinforce this method by combining it with the high-pressure technique which allows to tune the strength of electronic correlations and Fermi surface nesting in a system. Several application examples for the investigation of the pressure-induced phenomena such as the metallization in VO2 and the suppression of the charge-density wave in CeTe3 and the spin-density wave in BaFe2As2 will be discussed.

  • Lecture (others) (Online presentation)
    Elasto-Q-Mat Colloquia, 10.12.2020, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31863
Publ.-Id: 31863


Protein-Assisted Room-Temperature Assembly of Rigid, Immobile Holliday Junctions and Hierarchical DNA Nanostructures

Ramakrishnan, S.; Subramaniam, S.; Kielar, C.; Grundmeier, G.; Stewart, A. F.; Keller, A.

Immobile Holliday junctions represent not only the most fundamental building block of structural DNA nanotechnology but are also of tremendous importance for the in vitro investigation of genetic recombination and epigenetics. Here, we present a detailed study on the room-temperature assembly of immobile Holliday junctions with the help of the single-strand annealing protein Red beta. Individual DNA single strands are initially coated with protein monomers and subsequently hybridized to form a rigid blunt-ended four-arm junction. We investigate the efficiency of this approach for different DNA/protein ratios, as well as for different DNA sequence lengths. Furthermore, we also evaluate the potential of Red beta to anneal sticky-end modified Holliday junctions into hierarchical assemblies. We demonstrate the Red beta-mediated annealing of Holliday junction dimers, multimers, and extended networks several microns in size. While these hybrid DNA-protein nanostructures may find applications in the crystallization of DNA-protein complexes, our work shows the great potential of Red beta to aid in the synthesis of functional DNA nanostructures under mild reaction conditions.

Keywords: DNA nanotechnology; Holliday junctions; atomic force microscopy; single-strand annealing proteins

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Permalink: https://www.hzdr.de/publications/Publ-31862
Publ.-Id: 31862


Alginite rock as effective demulsifier to separate water from various crude oil emulsions

Ahmed, S. S.; Hippmann, S.; Roode-Gutzmer, Q. I.; Fröhlich, P.; Bertau, M.

Due to environmental restriction laws in oil production and processing, there is a high demand for the oil industry to reduce the use of chemical demulsifiers and to employ safer, less toxic materials. The purpose of this research is to investigate whether Alginite, a naturally occurring and abundant oil-shale rock, can be utilised as an alternative, environmentally friendly and low-cost material to demulsify various water-in-crude oil emulsions (W/O). Three W/O emulsions were prepared using saline water with respectively light, medium and heavy crude oils. The properties of the crude oils were analysed and the effectiveness of Alginite to demulsify the corresponding W/O emulsions was investigated. The results confirm that naturally occuring Alginite exhibits exceptional water-removing capacity even from emulsions containing heavy crude oil, leaving only < 1.0 wt.-% water in the remaining demulsified oil, which satisfies the required specification for industrial applications. Alginite was shown to reduce viscosity and to deform the dispersed phase in W/O emulsions even in the absence of flow. The results of this work indicate that Alginite is of significant interest in petroleum research, in industrial oil processing as well as in environmental remediation.

Keywords: Alginite rock; natural demulsifier; crude oil; viscosity; water droplet

Permalink: https://www.hzdr.de/publications/Publ-31861
Publ.-Id: 31861


Characterization of the porous network structure of concrete

Roode-Gutzmer, Q. I.; Kulenkampff, J.

The porosity and specific surface area of a small intact core of concrete (~ 0.2 g) was characterized non-destructively by micro-computed tomography (µ-CT), N₂/BET and destructively by Mercury Intrusion Porosimetry (MIP).

Keywords: irradiated concrete; porosity; mercury intrusion porosimetry; micro computed tomography

  • Contribution to HZDR-Annual report
    Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-113 Februar 2021, 75-75
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-31860
Publ.-Id: 31860


Solventextraktion von Rhenium und Molybdän - Trennung durch selektive Reextraktion

Göthel, J.

Die Anwendungen der Solventextraktion finden sich in der anorganischen, organischen und analytischen Chemie, in den pharmazeutischen und biochemischen Industrien sowie in der Abfallbehandlung und ist eine der groß angelegten industriellen Trennungs-verfahren. In der metallurgischen Aufbereitung von Rohstoffen ist die Solventextraktion durch die Interdisziplinarität von hydrometallurgischer Verfahrenstechnik und anorganisch-organischer Chemie geprägt. Bei der Extraktion anionischer Metallspezies aus wässriger Lösung finden unter anderem aliphatische Amine eine breite Anwendung. Die wirtschaftsstrategischen Refraktärmetalle Rhenium und Molybdän wurden in den 1980er Jahren hinsichtlich ihrer selektiven Trennung durch eine Kombination von sekundären Aminen (R2NH) als Extraktionsmittel und Phosphinoxid (R3PO) als Additiv beschrieben. Bisher wurden keine Untersuchungen des Extraktionssystems gegenüber Eisen (III), der Coextraktion vom Mo (VI) und Re (VII) aus stark verdünnten Lösungen und dem Vergleich zu anderen sekundären Aminen durchgeführt sowie den Einfluss des Lösungsmittels untersucht (vgl. KÄHLER und GOCK). Die Untersuchungen zum System Rhenium und Molybdän im Rahmen dieser experimentellen Studienarbeit haben gezeigt, dass das Additiv TOPO mit dem Extraktionsmittel DTDA die Extraktion von Rhenium verbessert. Das Extraktionsmittel DTDA führt aufgrund seiner langkettigen Alkylreste im Vergleich zu DOA zu größeren Extraktionsergebnissen. Mit dem Extraktionsmittel DOA treten vermehrt dritte Phasen bei der Extraktion auf. Das Extraktionssystem zeichnet sich durch eine Gesamtbeladungs-kapazität aus, wobei Sulfatspezies und auch Wasser coextrahiert werden können. Das Lösungsmittel Chloroform verschlechtert die Extraktion von Rhenium durch seine abschirmenden polaren Wechselwirkungen und der Konkurrenzsituation bei der Ausbildung von Wasserstoffbrückenbindungen. Molybdän scheint für die Extraktion keine signifikante Abhängigkeit vom Lösungsmittel (Kerosin, Toluol und Chloroform) zu zeigen. Molybdän und Rhenium lassen sich selektiv von Kupfer und Zink extrahieren, jedoch nicht von Eisen (III). Eisen kann mit Salzsäure zu über 60 % von der beladenen Organik unter Verlust von Molybdän gewaschen werden. Mittels Schwefelsäure kann Eisen vollständig von der Organik, aber mit noch höheren Molybdänüberführungen, gewaschen werden. Eine befriedigende Trennung ergibt sich nicht. Rhenium kann von Molybdän selektiv unter dem Einfluss von TOPO bereits bei geringen TOPO-Konzentrationen reextrahiert werden. Diese Selektivität zeigt sich deutlicher im Lösungsmittel Chloroform als im Lösungsmittel Kerosin.

  • Other
    TU Bergakademie Freiberg, 2020
    Mentor: Toni Helbig

Permalink: https://www.hzdr.de/publications/Publ-31858
Publ.-Id: 31858


Accelerating Finite-temperature Kohn-Sham Density Functional Theory with Deep Neural Networks

Ellis, J. A.; Cangi, A.; Modine, N. A.; Stephens, J. A.; Thompson, A. P.; Rajamanickam, S.

Output from electronic structure code (Quantum Espresso) that serves as training data for the machine-learning workflow of the related scientific publication (https://arxiv.org/abs/2010.04905).

Keywords: machine learning; neural networks; materials science; density functional theory

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Permalink: https://www.hzdr.de/publications/Publ-31857
Publ.-Id: 31857


Defects in Functional Materials

Ling, F. C.-C.; Zhou, S.; Kuznetsov, A.

The research of functional materials has attracted extensive attention in recent years, and its advancement nitrifies the developments of modern sciences and technologies like green sciences and energy, aerospace, medical and health, telecommunications, and information technology. The present book aims to summarize the research activities carried out in recent years devoting to the understanding of the physics and chemistry of how the defects play a role in the electrical, optical and magnetic properties and the applications of the different functional materials in the fields of magnetism, optoelectronic, and photovoltaic etc.

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Permalink: https://www.hzdr.de/publications/Publ-31856
Publ.-Id: 31856


Volume expansion of quartz aggregate in ion-irradiated concrete

Roode-Gutzmer, Q. I.; Schymura, S.; Lippold, H.

Quartz aggregate in concrete irradiated by Si-ions with a fluence of 5·10¹⁴ ions/cm² at 300 keV exhibited an out-of-plane expansion of ~ 80 nm.

Keywords: irradiated concrete; quartz aggregate; volume expansion

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  • Contribution to HZDR-Annual report
    Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-113 Februar 2021, 76-76
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-31855
Publ.-Id: 31855


Making 2D topological polymers a reality

Jing, Y.; Heine, T.

First-principles calculations predicted electronic topological properties for 2D honeycomb–kagome polymers, which have been now confirmed experimentally thanks to improvements in on-surface synthesis.

Keywords: 2D polymers; topological polymers

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Permalink: https://www.hzdr.de/publications/Publ-31854
Publ.-Id: 31854


Benchmark of Simplified Time-Dependent Density Functional Theory for UV–Vis Spectral Properties of Porphyrinoids

Batra, K.; Zahn, S.; Heine, T.

Time-dependent density functional theory is thoroughly benchmarked for the predictive calculation of UV–vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density functional theory, including the simplified Tamm–Dancoff approximation, are compared. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm–Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ≈0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ≈0.04 eV).

Keywords: density functional theory; UV–Vis; porphyrinoids; spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-31853
Publ.-Id: 31853


Blue Phosphorene Bilayer Is a Two-Dimensional Metal and an Unambiguous Classification Scheme for Buckled Hexagonal Bilayers

Arcudia, J.; Kempt, R.; Eduardo Cifuentes-Quintal, M.; Heine, T.; Merino, G.

High-level first-principles computations predict blue phosphorene bilayer to be a two-dimensional metal. This structure has not been considered before and was identified by employing a block-diagram scheme that yields the complete set of five high-symmetry stacking configurations of buckled honeycomb layers, and allows their unambiguous classification. We show that all of these stacking configurations are stable or at least metastable both for blue phosphorene and gray arsenene bilayers. For blue phosphorene, the most stable stacking arrangement has not yet been reported, and surprisingly it is metallic, while the others are indirect band gap semiconductors. As it is impossible to interchange the stacking configurations by translations, all of them should be experimentally accessible via the transfer of monolayers. The metallic character of blue phosphorene bilayer is caused by its short interlayer distance of 3.01 Å and offers the exceptional possibility to design single elemental all-phosphorus transistors.

Keywords: 2D materials; phosphorus; nanoelectronics; first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-31852
Publ.-Id: 31852


RBS raw data for publication "Tuning the Co/Sr stoichiometry of SrCoO2.5 thin films by RHEED assisted MBEgrowth"

Schöffmann, P.; Pütter, S.; Schubert, J.; Zander, W.; Barthel, J.; Zakalek, P.; Waschk, M.; Heller, R.; Brückel, T.

RBS raw date for publication "Tuning the Co/Sr stoichiometry of SrCoO2.5 thin films by RHEED assisted MBEgrowth"

Simulation results using SIMNRA included as well

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Permalink: https://www.hzdr.de/publications/Publ-31851
Publ.-Id: 31851


Tuning the Co/Sr stoichiometry of SrCoO2.5 thin films by RHEED assisted MBEgrowth

Schöffmann, P.; Pütter, S.; Schubert, J.; Zander, W.; Barthel, J.; Zakalek, P.; Waschk, M.; Heller, R.; Brückel, T.

Strontium cobaltite (SrCoO2.5+δ, SCO) is a fascinating material because of its topotactic structural phase transition caused by a change in oxygen stoichiometry. In the brownmillerite phase (δ = 0) it is an insulating antiferromagnet whereas in the perovskite phase (δ = 0.5) it is a conducting ferromagnet. In contrast, the impact of the varying Co/Sr stoichiometry on the structure has not yet been studied in SCO thin films. Using molecular beam epitaxy we have fabricated SCO thin films of varying Co/Sr stoichiometry. Films with Co excess exhibit a brownmillerite crystal structure with CoO precipitates within the thin film and on the surface. Co deficient films are amorphous. Only for 1:1 stoichiometry a pure brownmillerite structure is present. We find a clear dependence of the Reflection High Energy Electron Diffraction (RHEED) pattern of these thin films on the stoichiometry. Interestingly, RHEED is very sensitive to a Co excess of less than 12% while x-ray diffraction fails to reveal that difference. Hence, using RHEED, the stoichiometry of SCO can be evaluated and tuned in-situ to a high degree of precision, which allows for a quick adjustment of the growth parameters during a sample series.

Keywords: This films; SrCoO; Rutherford Backscattering; RHEED; MBE; growth

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Permalink: https://www.hzdr.de/publications/Publ-31850
Publ.-Id: 31850


MEIS raw data and maps for publication "Stopping and straggling of 60–250-keV backscattered protons on nanometric Pt films"

Selau, F. F.; Trombini, H.; Marmitt, G. G.; de Andrade, A. M. H.; Morais, J.; Grande, P. L.; Alencar, I.; Vos, M.; Heller, R.

MEIS raw data and maps for publication "Stopping and straggling of 60–250-keV backscattered protons on nanometric Pt films"

Including stiched spectra and 2D ESTAT maps

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Permalink: https://www.hzdr.de/publications/Publ-31849
Publ.-Id: 31849


Stopping and straggling of 60–250-keV backscattered protons on nanometric Pt films

Selau, F. F.; Trombini, H.; Marmitt, G. G.; de Andrade, A. M. H.; Morais, J.; Grande, P. L.; Alencar, I.; Vos, M.; Heller, R.

The stopping power and straggling of backscattered protons on nanometric Pt films were measured at low to medium energies (60–250 keV) by using the medium-energy ion scattering technique. The stopping power results are in good agreement with the most recent measurements by Primetzhofer Phys. Rev. B 86, 094102 (2012) and are well described by the free electron gas model at low projectile energies. Nevertheless, the straggling results are strongly underestimated by well-established formulas up to a factor of two. Alternatively, we propose a model for the energy-loss straggling that takes into account the inhomogeneous electron-gas response, based on the electron-loss function of the material, along with bunching effects. This approach yields remarkable agreement with the experimental data, indicating that the observed enhancement in energy-loss straggling is due to bunching effects in an inhomogeneous electron system. Nonlinear effects are of minor importance for the energy-loss straggling.

Keywords: Stopping cross sections; Rutherford Backscattering; Medium Energy Ion Scattering; Energy Straggling

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Permalink: https://www.hzdr.de/publications/Publ-31848
Publ.-Id: 31848


RBS raw data for publication "Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites"

Zehner, J.; Soldatov, I.; Schneider, S.; Heller, R.; Khojasteh, N. B.; Schiemenz, S.; Fähler, S.; Nielsch, K.; Schäfer, R.; Leistner, K.

RBS raw data for publication "Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites"

Simulation results using SIMNRA are included as well

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Permalink: https://www.hzdr.de/publications/Publ-31847
Publ.-Id: 31847


Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites

Zehner, J.; Soldatov, I.; Schneider, S.; Heller, R.; Khojasteh, N. B.; Schiemenz, S.; Fähler, S.; Nielsch, K.; Schäfer, R.; Leistner, K.

High energy efficiency of magnetic devices is crucial for applications such as data storage, computation, and actuation. Redox‐based (magneto‐ionic) voltage control of magnetism is a promising room‐temperature pathway to improve energy efficiency. However, for ferromagnetic metals, the magneto‐ionic effects studied so far require ultrathin films with tunable perpendicular magnetic anisotropy or nanoporous structures for appreciable effects. This paper reports a fully reversible, low voltage‐induced collapse of coercivity and remanence by redox reactions in iron oxide/iron films with uniaxial in‐plane anisotropy. In the initial iron oxide/iron films, Néel wall interactions stabilize a blocked state with high coercivity. During the voltage‐triggered reduction of the iron oxide layer, in situ Kerr microscopy reveals inverse changes of coercivity and anisotropy, and a coarsening of the magnetic microstructure. These results confirm a magneto‐ionic deblocking mechanism, which relies on changes of the Néel wall interactions, and of the microstructural domain‐wall‐pinning sites. With this approach, voltage‐controlled 180° magnetization switching with high energy‐efficiency is achieved. It opens up possibilities for developing magnetic devices programmable by ultralow power and for the reversible tuning of defect‐controlled materials in general.

Keywords: iron films; magnetic domains; magnetoelectrics; magneto‐ionic mechanisms

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Permalink: https://www.hzdr.de/publications/Publ-31846
Publ.-Id: 31846


RBS raw data for publication "High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy "

Bommanaboyena, S. P.; Bergfeldt, T.; Heller, R.; Kläui, M.; Jourdan, M.

RBS raw data for publication "High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy "

Simulation results using SINRA are included as well.

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Permalink: https://www.hzdr.de/publications/Publ-31845
Publ.-Id: 31845


High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy

Bommanaboyena, S. P.; Bergfeldt, T.; Heller, R.; Kläui, M.; Jourdan, M.

The recently discovered phenomenon of Néel spin-orbit torque in antiferromagnetic Mn2Au [Bodnar et al., Nat. Commun. 9, 348 (2018); Meinert et al., Phys. Rev. Appl. 9, 064040 (2018); Bodnar et al., Phys. Rev. B 99, 140409(R) (2019)] has generated huge interest in this material for spintronics applications. In this paper, we report the preparation and characterization of high quality Mn2Au thin films by molecular beam epitaxy and compare them with magnetron sputtered samples. The films were characterized for their structural and morphological properties using reflective high-energy electron diffraction, x-ray diffraction, x-ray reflectometry, atomic force microscopy, and temperature dependent resistance measurements. The thin film composition was determined using both inductively coupled plasma optical emission spectroscopy and Rutherford backscattering spectrometry techniques. The MBE-grown films were found to show a superior smooth morphology and a low defect concentration, resulting in reduced scattering of the charge carriers.

Keywords: Atomic force microscopy; Electron diffraction; Epitaxy; Inductively coupled plasma atomic emission spectroscopy; Thin films; Rutherford backscattering spectrometry

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Permalink: https://www.hzdr.de/publications/Publ-31844
Publ.-Id: 31844


Explicit algebraic relation for calculating Reynolds normal stresses in flows dominated by bubble-induced turbulence

Ma, T.; Lucas, D.; Bragg, A. D.

Two new algebraic turbulence models for flows dominated by bubble-induced turbulence (BIT) are presented. They combine different elements of existing models that are considered superior to their alternatives. Both models focus on the core region of a channel flow, where the flow can be assumed to be in local equilibrium and the void fraction is approximately homogeneous. The first model, referred to as the algebraic Reynolds normal stress model, is derived from the differential Reynolds stress model of Ma et al. [J. Fluid Mech. 883, A9 (2020)]. The second model utilizes the original two-equation turbulence model for bubbly flows [Ma et al., Phys. Rev. Fluids 2, 034301 (2017)] to achieve algebraic expressions for k and ε in BIT-dominated cases. If both models are combined, it results in a purely algebraic (i.e. not involving any differential equations), explicit relation for the Reynolds normal stresses, which depends only on the mean flow parameters, namely, the mean gas void fraction and mean liquid and gas velocities. We find that the model can well predict the Reynolds normal stresses, compared with direct numerical simulation and experimental data.

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Permalink: https://www.hzdr.de/publications/Publ-31843
Publ.-Id: 31843


RBS raw data for publication "Solid–liquid interface analysis with in‐situ Rutherford backscattering and electrochemical impedance spectroscopy "

Bergmann, U.; Apelt, S.; Khojasteh, N. B.; Heller, R.

RBS raw data for publication "Solid–liquid interface analysis with in‐situ Rutherford backscattering and electrochemical impedance spectroscopy "

Simulation results using SIMNRA-Code also included

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Permalink: https://www.hzdr.de/publications/Publ-31842
Publ.-Id: 31842


Solid–liquid interface analysis with in‐situ Rutherford backscattering and electrochemical impedance spectroscopy

Bergmann, U.; Apelt, S.; Khojasteh, N. B.; Heller, R.

A novel Rutherford backscattering spectrometry (RBS) method is presented to investigate the interface between a solid surface and a surrounding liquid. The introduced measurement system allows to observe and quantify adsorption at the solid–liquid interface and the formation of the electrochemical double layer (EDL). BaCl2 as a bicomponent electrolyte and a Si3N4 membrane surface are chosen as a model system to prove the capabilities of the setup. The results of these RBS measurements are combined with electrochemical impedance spectroscopy (EIS) to validate the findings for the solid–liquid interface under study. Complementary results and discrepancies regarding the formation of the EDL are discussed.
Author keywords: electrochemical double layer, electrochemical impedance spectroscopy, Rutherford backscattering spectroscopy, silicon nitride

Keywords: Rutherford backscattering spectrometry; electrochemical double layer; electrochemical impedance spectroscopy; point of zero charge

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Permalink: https://www.hzdr.de/publications/Publ-31841
Publ.-Id: 31841


RBS Raw data for publication: ""Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas"

Mientus, R.; Weise, M.; Seeger, S.; Heller, R.; Ellmer, K.

Raw data for pub. "Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas"

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Permalink: https://www.hzdr.de/publications/Publ-31840
Publ.-Id: 31840


Tantalum recycling from pyrometallurgical residues (Tantalrecycling aus pyrometallurgischen Rückständen)

Reuter, M.; Taube, M. C.; Adamczyk, B.; Adam, C.; Feldmann, I.; Ostermann, M.; Stelter, M.

An existing pyrometallurgical process for tantalum and niobium recovery, mainly from low grade pyrometallurgical residues, was investigated. Melting experiments were carried out in a pilot-scale electric arc furnace to study the material system during the reduction process caused by blowing coke into the liquid mineral melt. During the pyrometallurgical treatment refractory metals such as tantalum and niobium are converted into their carbides and enriched in the molten iron-based metal phase.Titanium is also enriched in the metal phase as an unwanted accompanying element, but most of it remains in oxidic form in the slag and is mainly bound in the mineral perovskite. Cooled down slag samples were analysed using XRF, XRD, SEM and EDX to investigate the formation of mineral phases rich in tantalum during various stages of the reduction process. The results show that the settling of the tantalum-rich iron droplets in the molten slag into the metal phase may play a greater role for the kinetics than the actual reduction reaction caused by blowing in coke.

Keywords: tantalum; niobium; pyrometallurgical

  • World of Metallurgy - Erzmetall 73(2020)4, 196-205

Permalink: https://www.hzdr.de/publications/Publ-31839
Publ.-Id: 31839


Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas

Mientus, R.; Weise, M.; Seeger, S.; Heller, R.; Ellmer, K.

By reactive magnetron sputtering from a ceramic SnO2:Ta target onto unheated substrates, X-ray amorphous SnO:Ta films were prepared in gas mixtures of Ar/O2(N2O, H2O). The process windows, where the films exhibit the lowest resistivity values, were investigated as a function of the partial pressure of the reactive gases O2, N2O and H2O. We found that all three gases lead to the same minimum resistivity, while the width of the process window is broadest for the reactive gas H2O. While the amorphous films were remarkably conductive (ρ ≈ 5 × 10−3 Ωcm), the films crystallized by annealing at 500 °C exhibit higher resistivities due to grain boundary limited conduction. For larger film thicknesses (d ≳ 150 nm), crystallization occurs already during the deposition, caused by the substrate temperature increase due to the energy influx from the condensing film species and from the plasma (ions, electrons), leading to higher resistivities of these films. The best amorphous SnO2:Ta films had a resistivity of lower than 4 × 10−3 Ωcm, with a carrier concentration of 1.1 × 1020 cm−3, and a Hall mobility of 16 cm2/Vs. The sheet resistance was about 400 Ω/□ for 100 nm films and 80 Ω/□ for 500 nm thick films. The average optical transmittance from 500 to 1000 nm is greater than 76% for 100 nm films, where the films, deposited with H2O as reactive gas, exhibit even a slightly higher transmittance of 80%. These X-ray amorpous SnO2:Ta films can be used as low-temperature prepared transparent and conductive protection layers, for instance, to protect semiconducting photoelectrodes for water splitting, and also, where appropriate, in combination with more conductive TCO films (ITO or ZnO).

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Permalink: https://www.hzdr.de/publications/Publ-31838
Publ.-Id: 31838


Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Kaden, P.; Kupka, N.

NMR dataset to the publication:
Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Keywords: NMR; acidified water glass; scheelite calcite separation; froth flotation; mechanism

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Permalink: https://www.hzdr.de/publications/Publ-31837
Publ.-Id: 31837


Timing and correlation of glacial and glaciofluvial sediments in the German Alpine Foreland

Hofmann, F.; Hildebrandt, D.; Merchel, S.; Rugel, G.; Lachner, J.; Friedrich, A. M.

Multiple periods of advance and retreat of piedmont glaciers in the German Alpine Foreland due to changing climatic conditions were classically defined by Penck and Brückner in 1909. However, a robust absolute chronology has not yet been established. Age assignments in previous studies have mostly been based on the interpretation of terrace deposits as a result of periods of glacier advance and retreat and correlation with periods of globally low temperatures. Intercorrelation between these discontinuous deposits has mainly been done by using morphological, petrographical, and hypsometric characteristics. We measure absolute cosmogenic ³⁶Cl exposure ages of glacial erratics and ¹⁰Be/²⁶Al isochron burial ages of till and glaciofluvial deposits, which have previously been interpreted as Würmian (ultimate) and Rissian (penultimate glacial period). This establishes an absolute chronology for these periods and enables the correlation of moraines, which are direct products of advancing and retreating glaciers, with indirect glaciofluvial deposits in the foreland. The absolute chronology of this study sheds light on the development of Central European climatic trends and enables the correlation to global climate.

Keywords: AMS; cosmogenic radionuclide; dating; burial age; glacier; climate; exposure age

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  • Poster (Online presentation)
    American Geophysical Union (AGU) Fall Meeting, 01.-17.12.2020, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-31836
Publ.-Id: 31836


Nanoscale‐Confined Terahertz Polaritons in a van der Waals Crystal

de Oliveira, T. V. A. G.; Nörenberg, T.; Álvarez‐Pérez, G.; Wehmeier, L.; Taboada‐Gutiérrez, J.; Obst, M.; Hempel, F.; Lee, E. J. H.; Klopf, J. M.; Errea, I.; Nikitin, A. Y.; Kehr, S. C.; Alonso‐González, P.; Eng, L. M.

Electromagnetic field confinement is crucial for nanophotonic technologies, since it allows for enhancing light–matter interactions, thus enabling light manipulation in deep sub‐wavelength scales. In the terahertz (THz) spectral range, radiation confinement is conventionally achieved with specially designed metallic structures—such as antennas or nanoslits—with large footprints due to the rather long wavelengths of THz radiation. In this context, phonon polaritons—light coupled to lattice vibrations—in van der Waals (vdW) crystals have emerged as a promising solution for controlling light beyond the diffraction limit, as they feature extreme field confinements and low optical losses. However, experimental demonstration of nanoscale‐confined phonon polaritons at THz frequencies has so far remained elusive. Here, it is provided by employing scattering‐type scanning near‐field optical microscopy combined with a free‐electron laser to reveal a range of low‐loss polaritonic excitations at frequencies from 8 to 12 THz in the vdW semiconductor α‐MoO3. In this study, THz polaritons are visualized with: i) in‐plane hyperbolic dispersion, ii) extreme nanoscale field confinement (below λo ⁄75), and iii) long polariton lifetimes, with a lower limit of >2 ps.

Keywords: THz; FEL; s-SNOM; phonon polaritons; field confinement

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Permalink: https://www.hzdr.de/publications/Publ-31835
Publ.-Id: 31835


68Ga, 44Sc and 177Lu-labeled AAZTA5-PSMA-617: synthesis, radiolabeling, stability and cell binding compared to DOTA-PSMA-617 analogues

Sinnes, J.; Bauder-Wüst, U.; Schäfer, M.; Moon, E.; Kopka, K.; Rösch, F.

Background: The AAZTA chelator and in particular its bifunctional derivative AAZTA5 was recently investigated to demonstrate unique capabilities to complex diagnostic and therapeutic trivalent radiometals under mild conditions. This study presents a comparison of 68Ga, 44Sc and 177Lu-labeled AAZTA5-PSMA-617 with DOTA-PSMA-617 analogues. We evaluated the radiolabeling characteristics, in vitro stability of the radiolabeled compounds and evaluated their binding affinity and internalization behavior on LNCaP tumor cells in direct comparison to the radiolabeled DOTA-conjugated PSMA-617 analogs.
Results: AAZTA5 was synthesized in a five-step synthesis and coupled to the PSMA-617 backbone on solid phase. Radiochemical evaluation of AAZTA5-PSMA-617 with 68Ga, 44Sc and 177Lu achieved quantitative radiolabeling of > 99% after less than 5 min at room temperature. Stabilities against human serum, PBS buffer and EDTA and DTPA solutions were analyzed. While there was a small degradation of the 68Ga complex over 2 h in human serum, PBS and EDTA/DTPA, the 44Sc and 177Lu complexes were stable at 2 h and remained stable over 8 h and 1 day. For all three compounds, i.e. [natGa]Ga-AAZTA5-PSMA-617, [natSc]Sc-AAZTA5-PSMA-617 and [natLu]Lu-AAZTA5-PSMA-617, in vitro studies on PSMA-positive LNCaP cells were performed in direct comparison to radiolabeled DOTA-PSMA-617 yielding the corresponding inhibition constants (Ki). Ki values were in the range of 8-31 nM values which correspond with those of [natGa]Ga-DOTA-PSMA-617, [natSc]Sc-DOTA-PSMA-617 and [natLu]Lu-DOTA-PSMA-617, i.e. 5-7 nM, respectively. Internalization studies demonstrated cellular membrane to internalization ratios for the radiolabeled 68Ga, 44Sc and 177Lu-AAZTA5-PSMA-617 tracers (13-20%IA/10^6 cells) in the same range as the ones of the three radiolabeled DOTA-PSMA-617 tracers (17-20%IA/10^6 cells) in the same assay.
Conclusions: The AAZTA5-PSMA-617 structure proved fast and quantitative radiolabeling with all three radiometal complexes at room temperature, excellent stability with 44Sc, very high stability with 177Lu and medium stability with 68Ga in human serum, PBS and EDTA/DTPA solutions. All three AAZTA5-PSMA-617 tracers showed binding affinities and internalization ratios in LNCaP cells comparable with that of radiolabeled DOTA-PSMA-617 analogues. Therefore, the exchange of the chelator DOTA with AAZTA5 within the PSMA-617 binding motif has no negative influence on in vitro LNCaP cell binding characteristics. In combination with the faster and milder radiolabeling features, AAZTA5-PSMA-617 thus demonstrates promising potential for in vivo application for theranostics of prostate cancer.

Keywords: AAZTA; AAZTA5-PSMA-617; Gallium-68; Lutetium-177; PET; PSMA-617; Scandium-44; Theranostics

Permalink: https://www.hzdr.de/publications/Publ-31834
Publ.-Id: 31834


UAS-Based Hyperspectral Environmental Monitoring of Acid Mine Drainage Affected Waters

Flores Rojas, H. M.; Lorenz, S.; Jackisch, R.; Tusa, L.; Contreras Acosta, I. C.; Zimmermann, R.; Gloaguen, R.

The exposure of metal sulfides to air or water, either produced naturally or due to mining activities, can result in environmentally damaging acid mine drainage (AMD). This needs to be accurately monitored and remediated. In this study, we apply high-resolution unmanned aerial system (UAS)-based hyperspectral mapping tools to provide a useful, fast, and non-invasive method for the monitoring aspect. Specifically, we propose a machine learning framework to integrate visible to near-infrared (VNIR) hyperspectral data with physicochemical field data from water and sediments, together with laboratory analyses to precisely map the extent of acid mine drainage in the Tintillo River (Spain). This river collects the drainage from the western part of the Rio Tinto massive sulfide deposit and discharges large quantities of acidic water with significant amounts of dissolved metals (Fe, Al, Cu, Zn, amongst others) into the Odiel River. At the confluence of these rivers, different geochemical and mineralogical processes occur due to the interaction of very acidic water (pH 2.5–3.0) with neutral water (pH 7.0–8.0). This complexity makes the area an ideal test site for the application of hyperspectral mapping to characterize both rivers and better evaluate contaminated water bodies with remote sensing imagery. Our approach makes use of a supervised random forest (RF) regression for the extended mapping of water properties, using the samples collected in the field as ground-truth and training data. The resulting maps successfully estimate the concentration of dissolved metals and related physicochemical properties in water, and trace associated iron species (e.g., jarosite, goethite) within sediments. These results highlight the capabilities of UAS-based hyperspectral data to monitor water bodies in mining environments, by mapping their hydrogeochemical properties, using few field samples. Hence, we have demonstrated that our workflow allows the rapid discrimination and mapping of AMD contamination in water, providing an essential basis for monitoring and subsequent remediation.

Keywords: hyperspectral; remote sensing; machine learning; unmanned aerial system; acid mine drainage; random forest regression; post-mining

Permalink: https://www.hzdr.de/publications/Publ-31833
Publ.-Id: 31833


Online Detuning Computation and Quench Detection for Superconducting Resonators

Bellandi, A.; Butkowski, Ł.; Dursun, B.; Eichler, A.; Gümüs, C.; Kuntzsch, M.; Nawaz, A.; Pfeiffer, S.; Schlarb, H.; Schmidt, C.; Zenker, K.; Branlard, J.

Superconducting cavities are responsible for beam acceleration in superconducting linear accelerators. Challenging cavity control specifications are necessary to reduce RF costs and to maximize the availability of the accelerator. Cavity detuning and bandwidth are two critical parameters to monitor when operating particle accelerators. Cavity detuning is strongly related to the power required to generate the desired accelerating gradient. Cavity bandwidth is related to the cavity RF losses.
A sudden increase in bandwidth can indicate the presence of a quench or multipacting event. Therefore, calculating these parameters in real-time in the low-level RF system is highly desirable. A real-time estimation of the bandwidth allows a faster response of the machine protection system in case of quench events, whereas the estimation of cavity detuning can be used to drive piezoelectric tuner-based resonance control algorithms. In this proceeding, a new FPGA-based estimation component is presented. Such a component is designed to be used either in continuous wave or pulsed operation mode with loaded quality factors between 10^6 and 10^8 . Results of this component with FLASH, EuXFEL, CMTB, and ELBE are presented.

Keywords: Particle accelerators; Parameter estimation; Superconducting cavities; ELBE

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Permalink: https://www.hzdr.de/publications/Publ-31832
Publ.-Id: 31832


Curvilinear One-Dimensional Antiferromagnets

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

Antiferromagnets host exotic quasiparticles, support high frequency excitations and are key enablers of the prospective spintronic and spin−orbitronic technologies. Here, we propose a concept of a curvilinear antiferromagnetism where material responses can be tailored by a geometrical curvature without the need to adjust material parameters. We show that an intrinsically achiral one-dimensional (1D) curvilinear antiferromagnet behaves as a chiral helimagnet with geometrically tunable Dzyaloshinskii−Moriya interaction (DMI) and orientation of the Né el vector. The curvature-induced DMI results in the hybridization of spin wave modes and enables a geometrically driven local minimum of the low-frequency branch. This positions curvilinear 1D antiferromagnets as a novel platform for the realization of geometrically tunable chiral antiferromagnets for antiferromagnetic spin−orbitronics and fundamental discoveries in the formation of coherent magnon condensates in the momentum space.

Keywords: antiferromagnetism; curvilinear spin chain; Dzyaloshinskii-Moriya interaction; spin-orbitronics

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Permalink: https://www.hzdr.de/publications/Publ-31831
Publ.-Id: 31831


Data Fusion Using a Multi-Sensor Sparse-Based Clustering Algorithm

Rafiezadeh Shahi, K.; Ghamisi, P.; Rasti, B.; Jackisch, R.; Scheunders, P.; Gloaguen, R.

The increasing amount of information acquired by imaging sensors in Earth Sciences results in the availability of a multitude of complementary data (e.g., spectral, spatial, elevation) for monitoring of the Earth’s surface. Many studies were devoted to investigating the usage of multi-sensor data sets in the performance of supervised learning-based approaches at various tasks (i.e., classification and regression) while unsupervised learning-based approaches have received less attention. In this paper, we propose a new approach to fuse multiple data sets from imaging sensors using a multi-sensor sparse-based clustering algorithm (Multi-SSC). A technique for the extraction of spatial features (i.e., morphological profiles (MPs) and invariant attribute profiles (IAPs)) is applied to high spatial-resolution data to derive the spatial and contextual information. This information is then fused with spectrally rich data such as multi- or hyperspectral data. In order to fuse multi-sensor data sets a hierarchical sparse subspace clustering approach is employed. More specifically, a lasso-based binary algorithm is used to fuse the spectral and spatial information prior to automatic clustering. The proposed framework ensures that the generated clustering map is smooth and preserves the spatial structures of the scene. In order to evaluate the generalization capability of the proposed approach, we investigate its performance not only on diverse scenes but also on different sensors and data types. The first two data sets are geological data sets, which consist of hyperspectral and RGB data. The third data set is the well-known benchmark Trento data set, including hyperspectral and LiDAR data. Experimental results indicate that this novel multi-sensor clustering algorithm can provide an accurate clustering map compared to the state-of-the-art sparse subspace-based clustering algorithms.

Keywords: multi-sensor data fusion; subspace-based clustering; sparse representation; hierarchical representation; remote sensing

Permalink: https://www.hzdr.de/publications/Publ-31830
Publ.-Id: 31830


A New Spectral-Spatial Subspace Clustering Algorithm For Hyperspectral Image Analysis

Rafiezadeh Shahi, K.; Ghamisi, P.; Jackisch, R.; Khodadadzadeh, M.; Lorenz, S.; Gloaguen, R.

In the past decade, hyperspectral imaging techniques have been widely used in various applications to acquire high spectral-spatialresolution images from different objects and materials. Although hyperspectral images (HSIs) are useful tools to obtain valuableinformation from different materials, the processing of such data is challenging due to several reasons such as the high dimension-ality and redundancy of the feature space. Therefore, advanced machine learning algorithms have been developed to analyse HSIs.Among the developed algorithms, unsupervised learning techniques have become popular since they are capable of processing HSIswithout having prior knowledge. Generally, unsupervised learning algorithms analyse HSIs based on spectral information. How-ever, in many applications, spatial information plays an eminent role, in particular when the input data is of high spatial resolution.In this study, we propose a new clustering approach by utilizing the sparse subspace-based concept within the hidden Markov ran-dom field (HMRF) structure to process HSIs in an unsupervised manner. The qualitative analyses of the obtained clustering resultsshow that the proposed spectral-spatial clustering algorithm outperforms the sparse subspace-based clustering algorithm that onlyuses spectral information.

Keywords: Hyperspectral image analysis; Subspace clustering; Sparse representation; Hidden Markov random field; UAV data

Permalink: https://www.hzdr.de/publications/Publ-31829
Publ.-Id: 31829


Geochemical and mineralogical characterisation of Historic Zn-Pb Mine Waste, Plombières, East Belgium

Bevandic, S.; Blannin, R.; Vander Auwera, J.; Delmelle, N.; Caterina, D.; Nguyen, F.; Muchez, P.

Mine wastes and tailings derived from historical processing may contain significant contents of valuable metals due to processing being less efficient in the past. The Plombières tailings pond in eastern Belgium was selected as a case study to determine mineralogical and geochemical characteristics of the different mine waste materials found at the site. Four types of material were classified: soil, metallurgical waste, brown tailings and yellow tailings. The distribution of the mine wastes was investigated with drill holes, pit-holes and geophysical methods. Samples of the materials were assessed with grain size analysis, mineralogical and geochemical techniques. The mine wastes dominantly consist of SiO2, Al2O3 and Fe2O3. The cover material, comprising soil and metallurgical waste is highly heterogeneous in terms of mineralogy, geochemistry and grain size. The metallurgical waste has a high concentration of metals (Zn: 0.1 to 24 wt% and Pb: 0.1 to 10.1 wt%). In the tailings materials, Pb and Zn vary from 10 ppm to 8.5 wt% and from 51 ppm to 4 wt%, respectively. The mining wastes comprises mainly quartz, amorphous phases and phyllosilicates, with minor contents of Fe-oxide, Pb- and Zn-bearing minerals. Based on the mineralogical and geochemical properties, the different potential applications of the four waste material types were determined. Additionally, the theoretical economic potential of Pb and Zn in the mine wastes was established.

Permalink: https://www.hzdr.de/publications/Publ-31828
Publ.-Id: 31828


The 2021 Magnonics Roadmap

Barman, A.; Gubbiotti, G.; Ladak, S.; Adeyeye, A. O.; Krawczyk, M.; Gräfe, J.; Chumak, A. V.; Khitun, A.; Nikonev, D.; Young, I. A.; Vasyuchka, V. I.; Hillebrands, B.; Nikitov, S. A.; Yu, H.; Grundler, D.; Sadovnikov, A. V.; Grachev, A. A.; Sheshukova, S. E.; Duquesne, J.-Y.; Marangolo, M.; Csaba, G.; Porod, W.; Demidov, V. E.; Urazhdin, S.; Demokritov, S. O.; Albisetti, E.; Petti, D.; Bertacco, R.; Schultheiß, H.; Kruglyak, V. V.; Poimanov, V. D.; Sahoo, S.; Sinha, J.; Moriyama, T.; Mizukami, S.; Yang, H.; Münzenburg, M.; Landeros, P.; Gallardo, R. A.; Carlotti, G.; Kim, J.-V.; Stamps, R. L.; Camley, R. E.; Rana, B.; Otani, Y.; Yu, W.; Yu, T.; Bauer, G. E. W.; Back, C.; Uhrig, G. S.; Dobrovolskiy, O. V.; van Dijken, S.; Budinska, B.; Qin, H.; Adelmann, C.; Cotofana, S.; Naeemi, A.; Zingsem, B. W.; Winklhofer, M.

Magnonics is a rather young physics research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. After several papers and review articles published in the last decade, with a steadily increase in the number of citations, we are presenting the first Roadmap on Magnonics. This a collection of 22 sections written by leading experts in this field who review and discuss the current status but also present their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and the interconnections to standard electronics. In this respect, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This Roadmap represents a milestone for future emerging research directions in magnonics and hopefully it will be followed by a series of articles on the same topic.

Keywords: magnonics; spin waves; roadmap; spin textures; skyrmions; computing

Permalink: https://www.hzdr.de/publications/Publ-31827
Publ.-Id: 31827


A mechanistic model for bubble formation from microscale orifices under constant gas flow conditions

Mohseni, E.; Bauermann Lang, G.; Reinecke, S.; Hampel, U.

We studied the bubble formation at micro-scale orifices in the range from 0.03 mm to 0.193 mm under the constant gas flow conditions. Furthermore, we investigated the evolution of individual forces applied on the bubble surface during its formation. We observed a different mechanism of the bubble formation compared with millimeter range orifices. This mechanism is highly influenced by the capillary pressure and gas kinetic energy. The latter results in a sequence of coalescence events of the bubbles in the vicinity above the orifice, even at significantly low gas flow rates. Studying the individual forces acting on the bubble revealed that the mechanism of bubble formation at micro-orifices is highly dependent on the gas momentum force and the liquid inertia force. Accordingly, we propose a new mechanistic model that precisely predicts the bubble size generated at micro-orifices. In addition to the influential forces, the model includes the influence of both the bubble base expansion and the relative bulk liquid velocity. Experimental validation of the model confirms that the maximum relative error of the model is less than 10%.

Keywords: Bubble Formation; Micro-orifices; Bubbling Regime; Numerical Model; Stainless Steel Orifice

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Permalink: https://www.hzdr.de/publications/Publ-31826
Publ.-Id: 31826


MicroTCA.4 based low level RF for continuous wave mode operation at the ELBE accelerator

Gümüş, Ç.; Hierholzer, M.; Kuntzsch, M.; Pfeiffer, S.; Schmidt, C.; Steinbrück, R.; Zenker, K.; Michel, P.; Schlarb, H.; Schurig, R.

At the superconducting linear accelerator ELBE electrons with an energy of up to 40 MeV can be generated. ELBE is operated in continuous wave mode. The acceleration is achieved using superconducting RF cavities, which are driven by an analogue low level RF system and solid state based RF amplifiers. The analogue low level RF system was transformed to a digital system based on the MicroTCA standard. It is in user operation since 2020. Here the new digital system and its integration in the ELBE control system is described. Furthermore, the system is characterised by noise measurements, which result in a RMS field stability of the digital low level RF system of 0.01 ◦ in phase and 0.005 % in amplitude. In addition, an algorithm for compensating long term drifts is presented and characterised.

Keywords: ELBE; ChimeraTK; MicroTCA.4; LLRF; OPC UA

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Permalink: https://www.hzdr.de/publications/Publ-31825
Publ.-Id: 31825


Multi-scale, multi-sensor data integration for automated 3-D geological mapping

Thiele, S. T.; Lorenz, S.; Kirsch, M.; Contreras Acosta, I. C.; Tusa, L.; Herrmann, E.; Möckel, R.; Gloaguen, R.

Enhanced digital outcrop models attributed with hyperspectral reflectance data, or hyperclouds, provide a flexible, three-dimensional medium for data-driven mapping of geological exposures, mine faces or cliffs. In this contribution we present an open-source python workflow, hylite, for creating hyperclouds by seamlessly fusing geometric information with data from a variety of hyperspectral imaging sensors and applying necessary atmospheric and illumination corrections. These rich datasets can be analysed using a variety of techniques, including minimum wavelength mapping and spectral indices to accurately map geological objects from a distance. Reference spectra from spectral libraries, ground or laboratory measurements can also be included to derive supervised classifications using machine learning techniques. We demonstrate the potential of the hypercloud approach by integrating hyperspectral data from laboratory, tripod and unmanned aerial vehicle acquisitions to automatically map relevant lithologies and alterations associated with volcanic hosted massive sulphide (VHMS) mineralisation in the Corta Atalaya open-pit, Spain. These analyses allow quantitative and objective mineral mapping at the outcrop and open-pit scale, facilitating quantitative research and smart-mining approaches. Our results highlight the seamless sensor integration made possible with hylite and the power of data-driven mapping approaches applied to hyperclouds. Significantly, we also show that random forests (RF) trained only on laboratory data from labelled hand-samples can be used to map outcrop scale data.

Permalink: https://www.hzdr.de/publications/Publ-31823
Publ.-Id: 31823


Liquid Metal Batteries for cheap stationary electricity storage

Weber, N.; Weier, T.

Liquid metal batteries are discussed as cheap stationary energy storage. Built as a stable density stratification of two liquid metals separated by a molten salt, they offer excellent charge transfer kinetics, extreme current densities and a very long lifetime. Using earth-abundant and cheap raw materials allows potentially reaching a storage price of 1-5 ct/kWh/cycle.
The talk will give an overview of LMB research at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Special focus will be given to the Li-Bi and Na-Bi systems, and the importance of fluid dynamics for the efficient and safe operation of the cells. Finally, an outlook on the Horizon 2020 project “Solstice”, which aims in developing Na-Zn molten salt batteries, will be given.

  • Open Access Logo Lecture (Conference)
    I Meeting on Energy Conversion and Storage Electrochemical Devices, 28.-29.01.2021, Madrid, Spanien

Permalink: https://www.hzdr.de/publications/Publ-31822
Publ.-Id: 31822


Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Kupka, N.; Kaden, P.; Jantschke, A.; Schach, E.; Rudolph, M.

Sodium silicate is one of the main depressants against calcite and fluorite in the scheelite flotation industry. In the first part of this article, the authors acidified sodium silicate (AWG) with three acids (sulfuric, oxalic and hydrochloric) to improve its performance. Results showed that acidified water glass outperforms alkaline water glass in terms of selectivity: it increases mainly the grade by further depressing silicates and calcium-bearing minerals. In most cases, AWG requires lower dosages to do so. The effect of acidified water glass is evaluated through Mineral Liberation Analysis (MLA), froth analysis, Raman and Nuclear Magnetic Resonance (NMR) spectroscopy in order to hypothesize its mechanism. MLA shows that AWG affects silicates and sulfides more intensely than semi-soluble salt-type minerals. Froth observations indicate other species in solution associated to the acid having an impact on the flotation results. Raman spectroscopy and NMR measurements indicate that the solution undergoes deep depolymerization when water glass is acidified. Lower molecular weight silica species, specifically Si-O monomers such as SiO(OH)3- will be responsible for the depression of the gangue minerals and are the drivers of the selectivity of AWG, more than orthosilicic acid. Depolymerization is more or less effective depending on the mass ratio of the acid to water glass and depending on the acid.

Keywords: acidified water glass; scheelite calcite separation; froth flotation; mechanism; mineral processing

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Permalink: https://www.hzdr.de/publications/Publ-31821
Publ.-Id: 31821


Coordination of Trivalent Lanthanum and Cerium, and Tetravalent Cerium and Actinides (An = Th(IV), U(IV), Np(IV)) by a 4-Phosphoryl 1H-Pyrazol-5-olate Ligand in Solution and the Solid State

Kaden, P.; Roßberg, A.

This dataset is a subset of the complete data used in the original publication. It contains NMR and XAS data and there simulation. Based on this original data, conlcusions are drawn in the linked publication. For the full data, please refer to the corresponding author of the full publication.

Abstract of the publication:

Structural investigations of three actinide(IV) 4-phosphoryl 1H-pyrazol-5-olate complexes (An = Th(IV), U(IV), Np(IV)) and their cerium(IV) analogue display the same metal coordination in the solid state. The mononuclear complexes show the metal centre in a square antiprismatic coordination geometry composed by the two O-donor atoms of four deprotonated ligands. Detailed solid state analysis of the U(IV) complex shows that in dependence of the solvent used altered arrangements are observable, resulting in a change in the coordination polyhedron of the U(IV) metal centre to bi-capped trigonal prismatic. Further, single crystal analyses of the La(III) and Ce(III) complexes show that the ligand can also act as a neutral ligand by protonation of the pyrazoyl moiety. All complexes were comprehensively characterized by NMR, IR and Raman spectroscopy. A single resonance in each of the 31P NMR spectra for the La(III), Ce(III), Ce(IV), Th(IV) and Np(IV) complex indicates the formation of highly symmetric complex species in solution. Extended X-ray absorption fine structure (EXAFS) investigations provide evidence for the same local structure of the U(IV) and Np(IV) complex in toluene solution, confirming the observations made in the solid state.

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Permalink: https://www.hzdr.de/publications/Publ-31820
Publ.-Id: 31820


Uncertainties in quantitative mineralogical studies using scanning electron microscope-based image analysis

Blannin, R.; Frenzel, M.; Tusa, L.; Birtel, S.; Ivășcanu, P.; Baker, T.; Gutzmer, J.

Scanning electron microscope-based automated mineralogy studies are readily associated with quantitative results, providing one of the foundations for geometallurgical studies. Despite the importance of quantitative data for such studies, and efforts to reduce statistical errors, the reporting of uncertainties is rare. This contribution illustrates how bootstrap resampling can be used to provide robust estimates of statistical uncertainties for the modal mineralogy, metal deportment and all relevant textural attributes of a sample, or series of samples. Based on a case study of the Bolcana Au-Cu porphyry deposit in the South Apuseni Mountains, Romania, the impact of insufficient sampling statistics on quantitative mineralogical studies is illustrated. Quantitative analyses of the mineralogy and microfabric of milled ore samples from seven 40 m drill core intervals from the Bolcana Prospect were conducted using a Mineral Liberation Analyser (MLA), complemented by electron probe micro-analysis. Bootstrap resampling was then applied to assess how many grain mount surfaces should be analysed to achieve statistically robust results for both Cu and Au mineralogy, deportment and textural attributes. Despite variable mineralogy, grades and mineralisation styles, estimated statistical uncertainties on Cu deportment are consistently low. In contrast, uncertainties for Au deportment are so high that most reported values for important characteristics are statistically meaningless. This is mainly attributed to the pronounced nugget effect for Au mineralisation, exacerbated by the small sample size analysed by MLA. An unfeasible number of measurements would be necessary to provide robust figures for the deportment of minor/trace elements and minerals, along with other tangible mineralogical properties, such as mineral associations. The results of this case study demonstrate that statistical uncertainties need to be carefully incorporated when considering the results of automated mineralogical studies and their impact on geometallurgical models. This is particularly relevant for studies of precious metal ores.

Keywords: Geometallurgy; Automated mineralogy; Nugget effect; Uncertainty estimation; Bootstrap resampling

Permalink: https://www.hzdr.de/publications/Publ-31819
Publ.-Id: 31819


Zero Net Flux MRI Turbulence in Disks: Sustenance Scheme and Magnetic Prandtl Number Dependence

Mamatsashvili, G.; Chagelishvili, George; Pessah, Martin E.; Stefani, F.; Bodo, Gianluigi

We investigate sustenance and dependence on magnetic Prandtl number (Pm) for magnetorotational instability (MRI)-driven turbulence in Keplerian disks with zero net magnetic flux using standard shearing box simulations. We focus on the turbulence dynamics in Fourier space, capturing specific/noncanonical anisotropy of nonlinear processes due to disk flow shear. This is a new type of nonlinear redistribution of modes over wavevector orientations in Fourier space—the nonlinear transverse cascade—which is generic to shear flows and fundamentally different from the usual direct/inverse cascade. The zero flux MRI has no exponentially growing modes, so its growth is transient, or nonmodal. Turbulence self-sustenance is governed by constructive cooperation of the transient growth of MRI and the nonlinear transverse cascade. This cooperation takes place at small wavenumbers (on the flow size scales) referred to as the vital area in Fourier space. The direct cascade transfers mode energy from the vital area to larger wavenumbers. At large Pm, the transverse cascade prevails over the direct one, keeping most of modes' energy contained in small wavenumbers. With decreasing Pm, however, the action of the transverse cascade weakens and can no longer oppose the action of the direct cascade, which more efficiently transfers energy to higher wavenumbers, leading to increased resistive dissipation. This undermines the sustenance scheme, resulting in the turbulence decay. Thus, the decay of zero net flux MRI turbulence with decreasing Pm is attributed to the topological rearrangement of the nonlinear processes when the direct cascade begins to prevail over the transverse cascade.

Keywords: Stellar accretion disks; Magnetohydrodynamics; Plasma astrophysics; Magnetic fields; Interplanetary turbulence; Instabilities

  • Open Access Logo Astrophysical Journal 904(2020)1, 47
    Online First (2020) DOI: 10.3847/1538-4357/abbd42
    Cited 5 times in Scopus
  • Open Access Logo Contribution to WWW
    arXiv:2009.14736 [astro-ph.HE]: https://arxiv.org/abs/2009.14736
  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    DAMTP Astro Seminars, 26.04.2021, Cambridge, UK, (https://sms.cam.ac.uk/media/3503403)
  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    CAS Seminar at ESO Garching, 06.09.2021, Garching, Germany
  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Astrophysics Colloquium, 15.02.2021, Tübingen, Germany

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Permalink: https://www.hzdr.de/publications/Publ-31818
Publ.-Id: 31818


Stress-controlled zero-field spin splitting in silicon carbide

Breev, I. D.; Poshakinskiy, A. V.; Yakovleva, V. V.; Nagalyuk, S. S.; Mokhov, E. N.; Hübner, R.; Astakhov, G.; Baranov, P. G.; Anisimov, A. N.

We report the influence of static mechanical deformation on the zero-field splitting of silicon vacancies in silicon carbide at room temperature. We use AlN/6H-SiC heterostructures deformed by growth conditions and monitor the stress distribution as a function of distance from the heterointerface with spatially-resolved confocal Raman spectroscopy. The zero-field splitting of the V1/V3 and V2 centers in 6H-SiC, measured by optically-detected magnetic resonance, reveal significant changes at the heterointerface compared to the bulk value. This approach allows unambiguous determination of the spin-deformation interaction constant, which turns out to be 0.75 GHz for the V1/V3 centers and 0.5 GHz for the V2 centers. Provided piezoelectricity of AlN, our results offer a strategy to realize the on-demand fine tuning of spin transition energies in SiC by deformation.

Keywords: Silicon carbide; spins; qubits; magnetic resonance; wide bandgap semiconductors; heterointerface

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Permalink: https://www.hzdr.de/publications/Publ-31817
Publ.-Id: 31817


The EU’s metallurgical infrastructure is a cornerstone of the EU Green Deal and the Agenda 2030 realization

Abadias Llamas, A.; Bartie, N. J.; Meskers, C. E. M.; Reuter, M.

The European metallurgical industries are the enablers for the realization of the goals of the EU Green Deal and the Agenda 2030 for Sustainable Development. The realization of these goals requires a metallurgical industry that is even more resource-efficient, eco-friendly and responsible than it is today. Accordingly, the metallurgical industry and system must be protected and strengthened, rather than having its socioeconomic importance undermined because of misconceptions about its residue generation, energy consumption, and environmental impacts. To understand and quantify the opportunities and limits associated with creating more circular and sustainable metallurgical infrastructure systems, rigorous digitalization is imperative. The European Training Network SOCRATES has taken this up by developing ground-breaking metallurgical processes for the valorization of industrial intermediate products. Additionally, this project quantified the impact of its developed metallurgical processes on the sustainability of the current material and metal supply chain through the creation of large simulation-based digital twins of the metallurgical system.

  • Communication & Media Relations
    SOCRATES Policy Brief 01.09.2020

Permalink: https://www.hzdr.de/publications/Publ-31816
Publ.-Id: 31816


Quantication of Valuable Chemical Elements present in Recyclable Printed Circuit Boards using Spectrum Radiography

Bhayani, G. S.

As of 2016, gold from electronic scrap was estimated to value almost e 19,000 million of the global e-waste [1]. This thesis aims at quantication of gold in scrap Printed Circuit Boards using Spectrum Radiography. The thesis is divided into two main sections- rst is where calibration of the detector takes place in order to estimate amount of x-rays that are transmitted through dierent thicknesses of gold and the second section is based on the results from scrap PCBs. The nal focus is to use the calibration, to quantify gold in Printed Circuit Board sample. Spectrum Radiography can help obtain the transmission of x-rays by a sample and based on the k-edge absorption theory, one can identify the element present in the sample.
The amount of transmission was estimated to relate to the thickness of the sample and the calibration data showed that with increasing sample thickness, gradual reduction in transmission was observed with the Spectrum Radiography. Hence, the thesis was based on quantifying elements based on k-edge transmission spectra. The resolution limit of the detector comes along, contributing to errors in quantication.
The thesis enlists and elaborates the statistical approaches for the quantication of gold using the radiographs obtained from the new prototype Spectral Detector and concludes the correlation of results obtained for geometrically analogous sample to x-ray beam orientations and also concludes the inapplicability of this method for samples with inhomogeneous thickness across the x-ray beam path.

Keywords: spectral CT; energy bins; 3D image; k-edge quantification

  • Master thesis
    Technical University Chemnitz, 2020
    Mentor: Jose R. A. Godinho

Permalink: https://www.hzdr.de/publications/Publ-31815
Publ.-Id: 31815


Automated Mineral Classification

Gupta, S.

A photon counting detector gives X-ray transmission radiographs of a slice of a sample in which transmission is resolved into 128 bins of X-ray energies from 20 keV to 160 keV. After plotting the graph of transmission over energy bins, the K-edge can be traced. By using machine learning and computer vision techniques on these ‘energy bins vs derivative of X-ray transmission’ information, slices were not only classified much faster in an automated way but also performed better when compared to the manual classification of minerals by using intensities or gray scale values of particles.
Machine learning was implemented on the slices of manually prepared sample containing gold and lead particles, Printed Circuit Board (PCB) and a rock sample. Slices were also classified by implementing machine learning on intensity properties of gold and galena to further confirm an advantage of using spectrum information. Results helped to understand the challenges in the project and thus paved a way for advanced research.

Keywords: spectral CT; Machine learning; 3D imaging

  • Master thesis
    Ernst-Abbe-Hochschule Jena University of Applied Sciences, 2020
    Mentor: Jose R. A. Godinho

Permalink: https://www.hzdr.de/publications/Publ-31814
Publ.-Id: 31814


Comparison of 3D (X-ray computed tomography) vs 2D (mineral liberation analysis) particle information in mineral processing simulations

Siddique, A.

Processing behaviour of a mineral resource highly depends on the characteristics of particles such as shape, size and composition. Therefore, comprehensive particle characterization is crucial to understand and optimize processing behaviour to enhance recoveries and reduce waste production. Nevertheless, despite the obvious importance of particle characteristics, current analysis techniques are restricted to two-dimensional (2D) particle characterization. In order to have advance three-dimensional (3D) characterization, this study aims to present a new X-CT methodology for single particle characterization with a special sample preparation method to reduce the X-CT artefacts.
A homogenous and dispersed particle sample reduce the X-CT artefacts and ease the segmentation process for individual particle labelling. This labelled data then further used for image processing combined with a new single particle peak analysis method for enhanced mineral classification based on greyscale. Classification of mineral phases for X-CT data was performed with the correlation of Mineral Liberation Analyzer (MLA). All the major mineral phases present in the ore were successfully classified except the gold grains. Characterization using 2D (MLA) and 3D (X-CT) was compared and mineralogy difference of around 2% observed. The effect of particle properties measured by both methods also investigated in processing simulation

Keywords: Mineral processing; 3D Particle characterization; X-ray computed tomography; Mineral Liberation Analysis; Single particle peak analysis; Flotation simulation

  • Master thesis
    Technical University Freiberg, 2020
    Mentor: Jose R. A. Godinho

Permalink: https://www.hzdr.de/publications/Publ-31813
Publ.-Id: 31813


Tetranuclear Lanthanide Complexes Supported by Hydroxyquinoline-Calix[4]arene-Ligands: Synthesis, Structure, and Magnetic Properties of [Ln₄(H₃L)₂(µ-OH)₂(NO₃)₄] (Ln = Tb, Dy, Yb) and [Dy₂(H₄L)₂(NO₃)](NO₃)

Jäschke, A.; Stumpf, T.; Aliabadi, A.; Büchner, B.; Kataev, V.; Hahn, T.; Kortus, J.; Kersting, B.

The coordination behavior of the calixarene-based N4O4 donor ligand H6L bearing two pendant 8-hydroxyquinoline-2-hydrazone arms towards the lanthanide ions Tb3+, Dy3+, and Yb3+ has been investigated. H6L was found to support tetra- and dinuclear mixed-ligand complexes with the pendant hydrazone units in a deprotonated enolate and/or a neutral amide form. The direct reaction of H6L with Ln(NO3)3(H2O)6 and NEt3 in a 1:1:2 molar ratio leads to tetranuclear [Ln4(H3L)2(µ-OH)2(η2-NO3)4] complexes {Ln = Tb (1), Dy (2), Yb (3)} containing a rectangular arrangement of four eight-coordinate Ln3+ ions bridged by two hydroxido- and four quinolinolato-O atoms as established by X-ray crystallography. Degradation of 2 occurs upon addition of further equiv. of H6L to give dinuclear [Dy2(H4L)(NO3)2(MeCN)2]NO3 (4) with eight- and ten-coordinated Dy3+ ions. ESI-MS studies reveal that such dinuclear species exist also in the solution state. The results of variable temperature direct and alternating current magnetic susceptibility measurements for 1–4 and high frequency EPR study on 4 are also reported.

Permalink: https://www.hzdr.de/publications/Publ-31812
Publ.-Id: 31812


Printable and Stretchable Giant Magnetoresistive Sensors for Highly Compliant and Skin-Conformal Electronics

Ha, M.; Canon Bermudez, G. S.; Kosub, T.; Mönch, J. I.; Zabila, Y.; Oliveros Mata, E. S.; Illing, R.; Wang, Y.; Faßbender, J.; Makarov, D.

Highly compliant electronics, naturally conforming to human skin, represent a paradigm shift in the interplay with the surroundings. Solution-processable printing technologies are yet to be developed to comply with extreme requirements to mechanical conformability of on-skin appliances. Here, it is demonstrated that high-performance spintronic elements can be printed on ultrathin 3 μm thick polymeric foils enabling the mechanically imperceptible printed magnetoelectronics. Benefiting from their extreme compliancy, the printed magnetic-field sensors well adapt to the periodic buckling surface to be biaxially stretched over 100% of strain rate. They constitute the first example of printed and stretchable giant magnetoresistive sensors, revealing 2 orders of magnitude improvements in mechanical stability and sensitivity at small magnetic fields, compared to the state-of-the-art printed magnetoelectronics. The key aspect of this performance enhancement is the use of elastomeric triblock copolymers as a binder for the magnetosensitive paste. Even when bent to a radius of 16 μm, the sensors screen printed on ultrathin foils remain fully intact and possess unmatched sensitivity for printed magnetoelectronics of 3 T-1 in a low magnetic field of 0.88 mT. With this performance, the compliant printed sensors can be used as components of on-skin interactive electronics as it is demonstrated with a touchless control of virtual objects including zooming in and out of interactive maps and scrolling through electronic documents.

Keywords: magnetoresistive; printable; sensor; skin-conformal; stretchable

Permalink: https://www.hzdr.de/publications/Publ-31811
Publ.-Id: 31811


Determination of the optimal sensor for ore sorting

Kern, M.; Tusa, L.; Khodadadzadeh, M.; Leißner, T.; Gloaguen, R.; van den Boogaart, K. G.; Gutzmer, J.

Ore sorting is a technology that is increasingly used to process primary raw materials. Time-consuming and expensive empirical state-of-the-art test work is carried out to assess whether the use of ore sorting for the enrichment of a particular ore makes technical and economic sense. With the innovative simulation-based approach presented here, it is possible to direct the selection of a suitable sensor based on quantitative mineralogical and textural data, thus avoiding much of the empirical studies. Required data can be collected quickly and cost-effectively using available methods of automated mineralogy. The obtained parameters such as mineral grain size distribution, modal mineralogy, mineral area and mineral density distribution have been utilized in this study to simulate the prospects of success of ore sorting applying different types of sensors. Empirical tests with commercially available sensor systems have been conducted to experimentally validate the predictions of the simulations. The estimation of the target mineral grade can be further optimized by the use of machine learning algorithms for the integration of automated mineralogy data and sensor data. The approach can easily be adapted to other types of raw materials and thus has great potential to become a key technology for the optimization of processing experiments.

Keywords: Automated Mineralogy; hyperspectral imaging; machine learning; ore sorting

  • Contribution to proceedings
    IMPC 2020, 18.-22.04.2021, Online, Online
    IMPC 2020 Proceedings

Permalink: https://www.hzdr.de/publications/Publ-31810
Publ.-Id: 31810


The optimal sensor for ore sorting

Kern, M.

Presentation about optimal sensor for ore sorting

  • Invited lecture (Conferences)
    EIT Raw Materials Expert Forum, 15.-18.01.2020, Leoben, Österreich

Permalink: https://www.hzdr.de/publications/Publ-31809
Publ.-Id: 31809


Beyond seeing the target: taking into account new parameters to measure the efficiency of exploration technologies

Ajjabou, L.; Kirsch, M.; Lorenz, S.; Gloaguen, R.

The INFACT project (Innovative, Non-Invasive and Fully Acceptable Exploration Technologies) aims to change raw material exploration in a way that it becomes socially accepted, environmentally-friendly and technologically advanced. It strives to establish a view of the best practices for exploration that is shared by civil society, state and industry. A set of permanent reference sites representing a variety of social, physical and technical challenges in the EU are used to conduct stakeholder dialogue and to provide an industry-relevant environment for the development of non-invasive exploration methods.

  • Contribution to proceedings
    KEGS Symposium 2020 "Success from Innovation", 29.02.2020, Toronto, Canada
  • Invited lecture (Conferences)
    KEGS Symposium 2020 "Success from Innovation", 29.02.2020, Toronto, Canada

Permalink: https://www.hzdr.de/publications/Publ-31808
Publ.-Id: 31808


Liquid metal batteries

Weber, N.; Weier, T.

Liquid metal batteries (LMBs) are introduced as future candidates for grid scale electricity storage. Their completely liquid cell interior entails a prominent role of fluid mechanics to understand and model their behaviour. We describe the equations used to compute electrochemical reactions, heat and mass transfer, electromagnetic fields, and fluid flow and explain the simplifications that can be made in the case of LMBs. The implementation of solution algorithms in OpenFOAM pertaining to domain coupling, multiphase simulations, mesh mapping, and operator discretisation are discussed in detail and accompanied by example code.

Related publications

  • Book chapter
    Steven B. Beale, Werner Lehnert: Electrochemical Cell Calculations with OpenFOAM, N/A: Springer, 2022, 978-3-030-92178-1, 193-212
    DOI: 10.1007/978-3-030-92178-1_7
  • Software in external data repository
    Publication year 2022
    Programming language: C++
    System requirements: OpenFOAM 6.0
    License: GNU General Public License version 3
    DOI: 10.1007/978-3-030-92178-1_7

Permalink: https://www.hzdr.de/publications/Publ-31807
Publ.-Id: 31807


FLUKA simulations for the Mu2e experiment

Müller, S.; Ferrari, A.

Presentation at FLUKA collaboration meeting (virtual), December 4, 2020

Keywords: FLUKA; Mu2e

  • Lecture (Conference) (Online presentation)
    FLUKA collaboration meeting, 03.-04.12.2020, Milan, Italy

Permalink: https://www.hzdr.de/publications/Publ-31806
Publ.-Id: 31806


HELmholtz ScIentific Project WORkflow PlaTform - Status and Roadmap 2020

Knodel, O.

The talk gives an overview on status and recent developments of the "HELmholtz ScIentific Project WORk-flow PlaTform" called HELIPORT. The idea is it to accommodate the complete life cycle of a scientific project and to links all corresponding programs and systems. The HELIPORT architecture has a modular structure such that the core application can be used in different Helmholtz centers and only individual components have to be replaced or added. HELIPORT is based on modern web technologies and can be used on different platforms. In addition to the entire project flow, computational workflows are also managed via the system in order to document all work steps as seamlessly as possible according to the FAIR principles and to publish them later.

Keywords: data management; workflow

  • Open Access Logo Lecture (others) (Online presentation)
    Meeting Helmholtz Zentrum Berlin (HZB), 04.12.2020, online, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31805
Publ.-Id: 31805


Generation of biological hypotheses by functional imaging links tumor hypoxia to radiation induced tissue inflammation/ glucose uptake in head and neck cancer

Zschaeck, S.; Zöphel, K.; Seidlitz, A.; Zips, D.; Kotzerke, J.; Baumann, M.; Troost, E. G. C.; Löck, S.; Krause, M.

Background and purpose: Positron emission tomography (PET) is a functional imaging modality which is able to deliver tracer specific biological information, e.g. about glucose uptake, inflammation or hypoxia of tumors. We performed a proof-of-principle study that used different tracers and expanded the analytical scope to non-tumor structures to evaluate tumor-host interactions.
Materials and Methods: Based on a previously reported prospective imaging study on 50 patients treated with curative intent chemoradiation (CRT) for head and neck squamous cell carcinoma, PET-based hypoxia and normal tissue inflammation measured by repeat 18F-fluoromisonidazole (FMISO) PET and 18F-fluorodesoxyglucose (FDG) PET, respectively, were correlated using the Spearman correlation coefficient R. PET parameters determined before and during CRT (week 1, 2 and 5), were associated with local tumor control and overall survival.
Results: Tumor hypoxia at all measured times showed an inverse correlation with mid-treatment FDG-uptake of non-tumor affected oral (sub-)mucosa with R values between -0.35 and -0.6 (all p<0.05). Mucosal FDG-uptake and mucosal hypoxia correlated positively but weaker (R values between 0.2 and 0.45). More tumor hypoxia in FMISO-PET (week 2) and less FDG-uptake of (sub-)mucosa in FDG-PET (week 4) were significantly associated with worse LC (FMISO TBRpeak: HR=1.72, p=0.030; FDG SUVmean: HR=0.23, p=0.025) and OS (FMISO TBRpeak: HR=1.71, p=0.007; FDG SUVmean: HR=0.30, p=0.003). Multivariable models including both parameters showed improved performance, suggesting that these modalities still bear distinct biological information despite their strong inter-correlation.
Conclusion: We report first clinical evidence that tumor hypoxia is inversely correlated with increased FDG-uptake during radiation, potentially expressinginflammation. This observation merits further research and may have important implication for future research on tumor hypoxia and radio-immunology. Our study demonstrates that functional imaging can be utilized to assess complex tumor-host interactions and generate novel biological insights in vivo vero.

Keywords: FDG PET; FMISO PET; inflammation; hypoxia; head and neck cancer; radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-31804
Publ.-Id: 31804


Protonentherapie intrathorakaler Tumoren – aktueller Stand und Ausblick

Troost, E. G. C.

Conventional external beam radiation therapy with high-energy photons is one of the pillars of treatment for patients with intrathoracic tumors. Due to technical advances, e.g., highly conformal, image-guided irradiation techniques, it has been possible to increase local tumor control while simultaneously reducing treatment-associated side effects. In recent years, proton beam therapy has become an alternative at an increasing number of national and international sites. At present, only four German sites offer protons for treatment of tumors outside of the eye, but the demand is increasing continually. Due to the physical characteristics of protons, i.e., the steep dose fall-off beyond the point of maximum dose deposition that is normally located in the tumor, normal tissue and organs at risk beyond the tumor can be spared. This review highlights the value of proton beam therapy for intrathoracic tumors.

Keywords: Radiotherapy; Esophageal carcinomas; Small cell lung cancer; Non- small cell lung cancer; Proton beam therapy

Permalink: https://www.hzdr.de/publications/Publ-31803
Publ.-Id: 31803


Role of radiotherapy in the management of brain metastases of NSCLC – Decision criteria in clinical routine

Glatzer, M.; Faivre-Finn, C.; De, R. D.; Widder, J.; Van, H. P.; Troost, E. G. C.; Slotman, B. J.; Ramella, S.; Pöttgen, C.; Peeters, S.; Nestle, U.; McDonald, F.; Le Pechoux, C.; Dziadziuszko, R.; Belderbos, J.; Ricardi, U.; Manapov, F.; Lievens, Y.; Geets, X.; Dieckmann, K.; Guckenberger, M.; Andratschke, N.; Süveg, K.; Putora, P. M.

Background: Whole brain radiotherapy (WBRT) is a common treatment option for brain metastases secondary to non-small cell lung cancer (NSCLC). Data from the QUARTZ trial suggest that WBRT can be omitted in selected patients and treated with optimal supportive care alone. Nevertheless, WBRT is still widely used to treat brain metastases secondary to NSCLC. We analysed decision criteria influencing the selection for WBRT among European radiation oncology experts.
Methods: Twenty-two European radiation oncology experts in lung cancer as selected by the European Society for Therapeutic Radiation Oncology (ESTRO) for previous projects and by the Advisory Committee on Radiation Oncology Practice (ACROP) for lung cancer were asked to describe their strategies in the management of brain metastases of NSCLC. Treatment strategies were subsequently converted into decision trees and analysed for agreement and discrepancies.
Results: Eight decision criteria (suitability for SRS, performance status, symptoms, eligibility for targeted therapy, extra-cranial tumour control, age, prognostic scores and ‘‘Zugzwang” (the compulsion to treat)) were identified. WBRT was recommended by a majority of the European experts for symptomatic patients not suitable for radiosurgery or fractionated stereotactic radiotherapy. There was also a tendency to use WBRT in the ALK/EGFR/ROS1 negative NSCLC setting.
Conclusion: Despite the results of the QUARTZ trial WBRT is still widely used among European radiation oncology experts.

Keywords: WBRT; Decision-making; Decision tree; QUARTZ; NSCLC

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Permalink: https://www.hzdr.de/publications/Publ-31802
Publ.-Id: 31802


An improvement on selective separation by applying ultrasound to rougher and re-cleaner stages of copper flotation

Hassanzadeh, A. A.; Sajjady, S. A. B.; Gholami, H. C.; Amini, S. B.; Özkan, S. G. D.

It has been known that the power ultrasound is used as a pretreatment and rarely applied as a simultaneous method to improve grade and recovery during froth flotation processes. This work aimed at investigating the impact of simultaneously used ultrasonic waves under variant operating configurations on the flotation of representative porphyry copper ore during rougher and re-cleaner stages. For this purpose, four different operating outlines were examined as (I) conventional flotation, (II) homogenizer, (III) ultrasonic bath, and (IV) combination of a homogenizer and an ultrasonic bath. The ultrasonic vibration was generated by the homogenizer (21 kHz, 1 kW) in the froth zone and ultrasonic bath (35 kHz, 0.3 kW) in the bulk zone. The rougher and re-cleaner flotation experiments were conducted using Denver-type mechanically agitated cells with 4.2 and 1 L capacities, respectively. The results showed that using the homogenizer (at 0.4 kW) slightly affected the selectivity separation index of chalcopyrite and pyrite, although it positively increased the grade of chalcopyrite from 21.5% to 25.7%. The ultrasonic-assisted flotation experiments with the ultrasonic bath and its combination with the homogenizer (0.4 kW) (i.e., configurations III and IV) led to an increase of approximately 16.1% and 26.9% in the chalcopyrite selectivity index compared to the conventional flotation, respectively. At the cleaning stage, a lower grade of aluminum silicate-based minerals was obtained desirably in every ultrasonic-treated configuration, which was supported with the water recoveries. Finally, applying the homogenizer and its combination with the ultrasonic bath were recommended for re-cleaner and rougher stages, respectively. Further fundamental and practical knowledge gaps required to be studied were highlighted.

Keywords: Copper flotation; Ultrasonic pretreatment; Simultaneous ultrasonic treatment; Rougher and re-cleaner stages; Homogenizer

Permalink: https://www.hzdr.de/publications/Publ-31801
Publ.-Id: 31801


Helium Ion Microscopy to address relevant questions in the impact of nanomaterials on lung epithelium – correlative microscopy approach

Podlipec, R.; Krišelj, A.; Pirker, L.; Klingner, N.; Hlawacek, G.; Strancar, J.; von Borany, J.

Helium Ion Microscopy (HIM) has not been thoroughly exploited for biological studies addressing relevant questions that range from the cellular to the subcellular level. One of the benefits of HIM compared to other high-resolution imaging techniques is definitely the large depth of focus, sub-nm resolution, nm surface sensitivity, and especially that no sample coating is needed that can change the nanostructure morphology on the surface. The prerequisite to getting the most from the technique is thus the appropriate sample preparation. Besides, to get the most from understanding the addressed biological question, a successful correlative microscopy approach is necessary. This is best shown in our recently published study (H Kokot, Advanced Materials, 2020), where we have addressed one of the most critical issues in toxicology, that is the poor understanding of chronic inflammation initiation in lung tissue caused by inhaled nanoparticles, with the correlative microscopy approach using advanced multimodal optical microscopy and HIM. HIM nicely revealed the TiO2 nanotube organization and passivation on the cell surface and confirmed lipid and protein binding to the TiO2 surface (Figure below), identified as well by in silico simulations. In brief, HIM is an extremely powerful technique for the surface, and in the case of porous samples also in-depth morphology characterization on an nm scale. In combination with complementary imaging techniques and proper sample preparation, many relevant biological questions can be addressed and solved. Still, there are many limitations and challenges in cell preparation and imaging using helium ions, such as imaging of internal structures, definitely pursuing discussions and new developments in the future.

Related publications

  • Lecture (Conference) (Online presentation)
    IAEA Technical Meeting on Imaging Using Ionizing Radiation to Address Biological Challenges, 30.11.-03.12.2020, Virtual Event, Virtual Event

Permalink: https://www.hzdr.de/publications/Publ-31800
Publ.-Id: 31800


Validation of a morphology adaptive multi-field two-fluid model considering counter-current stratified flow with interfacial turbulence damping

Tekavčič, M.; Meller, R.; Schlegel, F.

Stratified flows are one of the most important multiphase flow regimes for safety analyses of the loss-of-coolant accident in pressurized water reactors. The present paper considers simulations of an isothermal counter-current stratified flow case in the channel of the WENKA experiment using a morphology adaptive multi-field two-fluid modelling framework. A consistent momentum interpolation approach is applied together with the partial elimination algorithm, as it is required for strong momentum coupling, which enforces the no-slip condition at the interface and mirrors the behaviour of a homogeneous model. To model the turbulent flow conditions near an interface, the framework is extended with a turbulence damping model based on the damping scale formulation from the literature, which is introduced into the k-w SST (Shear Stress Transport) turbulence model. The presented modelling approach is validated with experimental data for the pressure difference and vertical profiles of volume fraction, velocity and turbulent kinetic energy. Results of a mesh sensitivity study of the model are presented. Simulations were performed on two- and three-dimensional models of the channel geometry. Two turbulence damping strategies are investigated: symmetric, with damping in both phases, and asymmetric with damping only in the gas phase. The comparison shows that the asymmetric approach offers improved prediction of turbulent kinetic energy on the liquid side of the interface, but with a cost of diminished accuracy of the predicted velocity profiles on the gas side.

Keywords: stratified flow; CFD; two- fluid model; turbulence damping

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31799
Publ.-Id: 31799


Gating of charge sensitive preamplifiers for the use at pulsed radiation sources.

Urlaß, S.; Junghans, A.; Mingrone, F.; Peronnard, P.; Stach, D.; Tassan-Got, L.; Weinberger, D.; The, Ntof Collaboration

The development of a switch circuit to gate charge sensitive preamplifiers for use at pulsed radiation sources will be presented.This development was used for the 16O(n,alpha)13C reaction measurement with a Double Frisch Grid Ionization Chamber (DFGIC) at the neutron time-of-flight facility CERN nTOF in Geneva, Switzerland. The so-called gamma-flash, which is produced in the spallation target of the nTOF facility can saturate charge sensitive preamplifiers and prevent signals from being registered in the detection system. The switch circuit made it possible for the first time to perform a measurement with the DFGIC with gamma-flash gated off at nTOF in November 2018. Nano-second gating of charge sensitive preamplifiers has a wide range of applicability at pulsed radiation sources, where short burst of radiation must be gated off to avoid saturation, e.g. with HPGe detectors for gamma-ray detection. Nano-second gating requires the stray-capacitance of the wideband reflective switch to be compensated to avoid a strong signal during the switch operation. Spectral analysis of the switch circuit shows that additional noise is insignificant.

Keywords: ToF facility; Neutron time of flight; Switch; gamma flash; gated preamplifier

Permalink: https://www.hzdr.de/publications/Publ-31798
Publ.-Id: 31798


Digital LLRF at ELBE: Performance and first impressions of user operation

Gümüş, Ç.; Hierholzer, M.; Kuntzsch, M.; Pfeiffer, S.; Schmidt, C.; Steinbrück, R.; Zenker, K.

A digital LLRF control has been implemented at the CW linac ELBE at Helmholtz-Zentrum Dresden-Rossendorf. The system is based on the MicroTCA.4 standard and drives four superconducting TESLA cavities and two normal conducting buncher cavities. The system enables a higher flexibility of the field control, improved diagnostics and field stability compared to the analogue system which was used before. The presentation will give an overview on the system performance in terms of noise measurements. In addition a review of the user operation started in August 2020 will be given. Finally, planned future features are presented.

Keywords: ELBE; ChimeraTK; MicroTCA.4; LLRF; OPC UA

Related publications

  • Invited lecture (Conferences) (Online presentation)
    Virtual MT ARD ST3 Meeting 2020, 23.-24.09.2020, Karlsruhe, Detuschland

Permalink: https://www.hzdr.de/publications/Publ-31797
Publ.-Id: 31797


The MicroTCA.4 based LLRF system for CW operation at ELBE

Gümüş, Ç.; Hierholzer, M.; Kuntzsch, M.; Pfeiffer, S.; Schmidt, C.; Steinbrück, R.; Zenker, K.

A digital LLRF control has been implemented at the CW linac ELBE at Helmholtz-Zentrum Dresden-Rossendorf. The system is based on the MicroTCA.4 standard and drives four superconducting TESLA cavities and two normal conducting buncher cavities. The system enables a higher flexibility of the field control, improved diagnostics and field stability compared to the analogue system which was used before. The presentation will give an overview on the system, its performance and a review of the user operation started in August 2020.

Keywords: ELBE; MicroTCA.4; LLRF; OPC UA; ChimeraTK

Related publications

  • Invited lecture (Conferences) (Online presentation)
    9th Virtual MicroTCA Workshop for Industry and Research, 01.-03.12.2020, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31796
Publ.-Id: 31796


Mineralogy, geochemistry and genesis of agate - a review

Götze, J.; Möckel, R.; Pan, Y.

Agate - a spectacular form of SiO2 and a famous gemstone - is commonly characterized as banded chalcedony. In detail, chalcedony layers in agates can be intergrown or intercalated with macrocrystalline quartz, quartzine, opal-A, opal-CT, cristobalite and/or moganite. In addition, agates often contain considerable amounts of mineral inclusions and water as both interstitial molecular H2O and silanol groups. Most agate occurrences worldwide are related to SiO2-rich (rhyolites, rhyodacites) and SiO2-poor (andesites, basalts) volcanic rocks, but can also be formed as hydrothermal vein varieties or as silica accumulation during diagenesis in sedimentary rocks. It is assumed that the supply of silica for agate formation is often associated with late-or post-volcanic alteration of the volcanic host rocks. Evidence can be found in association with typical secondary minerals such as clay minerals, zeolites or iron oxides/hydroxides, frequent pseudomorphs (e.g., after carbonates or sulfates) as well as the chemical composition of the agates. For instance, elements of the volcanic rock matrix (Al, Ca, Fe, Na, K) are enriched, but extraordinary high contents of Ge (>90 ppm), B (>40 ppm) and U (>20 ppm) have also been detected. Calculations based on fluid inclusion and oxygen isotope studies point to a range between 20 and 230◦C for agate formation temperatures. The accumulation and condensation of silicic acid result in the formation of silica sols and proposed amorphous silica as precursors for the development of the typical agate micro-structure. The process of crystallisation often starts with spherulitic growth of chalcedony continuing into chalcedony fibers. High concentrations of lattice defects (oxygen and silicon vacancies, silanol groups) detected by cathodoluminescence (CL) and electron paramagnetic resonance (EPR) spectroscopy indicate a rapid crystallisation via an amorphous silica precursor under non-equilibrium conditions. It is assumed that the formation of the typical agate microstructure is governed by processes of self-organization. The resulting differences in crystallite size, porosity, kind of silica phase and incorporated color pigments finally cause the characteristic agate banding and colors.

Keywords: agate; quartz; chalcedony; silica minerals; micro-structure; trace elements; O-isotopes; paragenetic minerals

Permalink: https://www.hzdr.de/publications/Publ-31795
Publ.-Id: 31795


Example videos of particles colliding with a rising bubble

Sommer, A.-E.; Heitkam, S.; Eckert, K.

These videos are related to the publication "Collision phenomena between inertialess particles and bubbles: An experimental study with 4D PTV and tomographic PIV", submitted on the XXX to the Journal of Fluid Mechanics. They are the underlying raw videos of an exemplary leading and tailing edge collision trajectory which are analzed in Figure 7 and 8, respectivly.

Keywords: Froth Flotation; 4D Particle Tracking Velocimetry (PTV); Bubble-Particle Collision; Rising bubble chain

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Permalink: https://www.hzdr.de/publications/Publ-31794
Publ.-Id: 31794


Correlated pion-proton pair emission off hot and dense QCD matter

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

In this letter we report the first multi-differential measurement of correlated pion-proton pairs from 2 billion Au+Au collisions at \sqrt{s_{NN}} = 2.42 GeV collected with HADES. In this energy regime the population of \Delta(1232) resonances plays an important role in the way energy is distributed between intrinsic excitation energy and kinetic energy of the hadrons in the fireball. The triple differential d3N/dM{\pi}pdpTdy distributions of correlated {\pi}p pairs have been determined by subtracting the {\pi}p combinatorial background using an iterative method. The invariant-mass distributions in the \Delta(1232) mass region show strong deviations from a Breit-Wigner function with vacuum width and mass. The yield of correlated pion-proton pairs exhibits a complex isospin, rapidity and transverse-momentum dependence. In the invariant mass range 1.1 < Minv (GeV/c2) < 1.4, the yield is found to be similar for {\pi}+p and {\pi}-p pairs, and to follow a power law ^{\alpha}, where is the mean number of participating nucleons. The exponent {\alpha} depends strongly on the pair transverse momentum (pT) while its pT-integrated and charge-averaged value is {\alpha} = 1.5 \pm 0.08stat \pm 0.2sys.

Permalink: https://www.hzdr.de/publications/Publ-31793
Publ.-Id: 31793


Metabolic targeting of cancer stem cells

Mukha, A.; Dubrovska, A.

Most human tumors possess a high heterogeneity resulting from both clonal evolution and cell differentiation program. The process of cell differentiation is initiated from a population of cancer stem cells (CSCs), which are enriched in tumor‐regenerating and tumor‐propagating activities and responsible for tumor maintenance and regrowth after treatment. Intrinsic resistance to conventional therapies, as well as a high degree of phenotypic plasticity, makes CSCs hard-to-target tumor cell population. Reprogramming of CSC metabolic pathways plays an essential role in tumor progression and metastatic spread. Many of these pathways confer cell adaptation to the microenvironmental stresses, including a shortage of nutrients and anti-cancer therapies. A better understanding of CSC metabolic dependences as well as metabolic communication between CSCs and the tumor microenvironment are of utmost importance for efficient cancer treatment. In this mini-review, we discuss the general characteristics of CSC metabolism and potential metabolic targeting of CSC populations as a potent strategy to enhance the efficacy of conventional treatment approaches.

Keywords: Cancer Stem Cells; therapy resistance; metabolic targeting

Permalink: https://www.hzdr.de/publications/Publ-31792
Publ.-Id: 31792


Amino acid transporters on the guard of cell genome and epigenome

Kahya, U.; Köseer, A. S.; Dubrovska, A.

Tumorigenesis is driven by metabolic reprogramming. Oncogenic mutations and epigenetic alterations that cause metabolic reprogramming may also upregulate the reactive oxygen species (ROS). Precise regulation of the intracellular ROS levels is critical for tumor cell growth and survival. High ROS production leads to the damage of vital macromolecules, such as DNA, proteins, and lipids, causing genomic instability and further tumor evolution. One of the hallmarks of cancer metabolism is deregulated amino acid uptake. In fast-growing tumors, amino acids are not only the source of energy and building intermediates but also critical regulators of redox homeostasis. Amino acid uptake regulates the intracellular GSH levels, endoplasmic reticulum stress, unfolded protein response signaling, mTOR-mediated antioxidant defense, and epigenetic adaptations of tumor cells to oxidative stress. This review summarizes the role of amino acid transporters as the defender of tumor antioxidant system and genome integrity and discusses them as promising therapeutic targets and tumor imaging tools.

Keywords: amino acid transporters; reactive oxygen species (ROS); α-ketoglutarate (AKG); the mammalian target of rapamycin (mTOR); epigenetic regulation; xCT/SLC7A11; ASCT2/SLC1A5; EZH2; oxidative stress; glutathione (GSH)

Permalink: https://www.hzdr.de/publications/Publ-31791
Publ.-Id: 31791


Kinetic (Lattice) Monte Carlo for Helical Molecules and Magnetic Substrates

Kelling, J.

In the investigation of the mutual interaction of self-assembled monolayers (SAMs) of helical organic molecules with metal surfaces, the goals are both to understand how surface properties, like magnetisation, influence the formation of the SAM and how the ensemble of electron-spin selective molecules influences magnetic properties of the carrier materials, specifically on a buried ferromagnetic layer.

The phenomenology of the effects on both sides can be modelled via kinetic Metropolis Monte Carlo (KMC) simulations in different ways. In both cases, this class of simulations models the kinetics of non-equilibrium systems based on local interaction energies using stochastic cellular automata based on non-equilibrium thermodynamics. This stochastic modeling replaces the physical dynamics simulated in, e.g., molecular dynamics (MD) simulations. Such a simplification is often necessary when simulating large ensembles required to observe phase ordering processes in order make these simulations possible or achieve sufficient throughput to create parameter maps like phase diagrams.

Keywords: Kinetic Metropolis Monte Carlo; GPU; Self Organization

Permalink: https://www.hzdr.de/publications/Publ-31790
Publ.-Id: 31790


Experimental liquid concentration distribution for air-led stripping of isobutyl acetate in sieve tray column

Marchini, S.; Vishwakarma, V.; Schubert, M.; Hampel, U.

This data contain the outcome of absorbance measurements performed via UV-Spectroscopy on liquid samples containing isobutyl acetate in various concentration. The liquid samples have been taken from several deck positions on a distillation sieve tray to determine the liquid concentration distribution and have been used to determine tray and point efficiency in a post-processing stage.

Keywords: distillation; concentration distribution; sieve tray; point efficiency; tray efficiency

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Publ.-Id: 31789


Magnetic field dependence of low-energy magnons, anisotropic heat conduction, and spontaneous relaxation of magnetic domains in the cubic helimagnet ZnCr2Se4

Inosov, D. S.; Onykiienkko, Y. O.; Tymoshenko, Y. V.; Akopyan, A.; Shukla, D.; Prasai, N.; Doerr, M.; Gorbunov, D.; Zherlitsyn, S.; Voneshen, D. J.; Boehm, M.; Tsurkan, V.; Felea, V.; Loidl, A.; Cohn, J. L.

Anisotropic low-temperature properties of the cubic spinel helimagnet ZnCr2Se4 in the single-domain spinspiral state are investigated by a combination of neutron scattering, thermal conductivity, ultrasound velocity, and dilatometry measurements. In an applied magnetic field, neutron spectroscopy shows a complex and nonmonotonic evolution of the spin-wave spectrum across the quantum-critical point that separates the spin-spiral phase from the field-polarized ferromagnetic phase at high fields. A tiny spin gap of the pseudo-Goldstone magnon mode, observed at wave vectors that are structurally equivalent but orthogonal to the propagation vector of the spin helix, vanishes at this quantum critical point, restoring the cubic symmetry in the magnetic subsystem. The anisotropy imposed by the spin helix has only a minor influence on the lattice structure and sound velocity but has a much stronger effect on the heat conductivities measured parallel and perpendicular to the magnetic propagation vector. The thermal transport is anisotropic at T ≲ 2K, highly sensitive to an external magnetic field, and likely results directly from magnonic heat conduction. We also report long-time thermal relaxation phenomena, revealed by capacitive dilatometry, which are due to magnetic domain motion related to the destruction of the single-domain magnetic state, initially stabilized in the sample by the application and removal of magnetic field. Our results can be generalized to a broad class of helimagnetic materials in which a discrete lattice symmetry is spontaneously broken by the magnetic order.

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Publ.-Id: 31788


Influence of the martensitic transformation kinetics on the magnetocaloric effect in Ni-Mn-In

Pfeuffer, L.; Gottschall, T.; Faske, T.; Taubel, A.; Scheibel, F.; Karpenkov, A. Y.; Ener, S.; Skokov, K. P.; Gutfleisch, O.

The inverse magnetocaloric effect in Ni-Mn based Heusler compounds occurs during the magnetostructural transition between low-temperature, low-magnetization martensite and high-temperature, high-magnetization austenite. In this study, we analyze the metamagnetic transformation of a Ni49.8Mn35In15.2 compound by simultaneous adiabatic temperature change ΔTad and strain Δl/l0 measurements in pulsed magnetic fields up to 10 T. We observe a ΔTad of −10 K and a Δl/l0 of −0.22% when the reverse martensitic transition is fully induced at a starting temperature of 285 K. By a variation of the magnetic field-sweep rates between 316, 865, and 1850 T s−1, the transitional dynamics of the reverse martensitic transformation have been investigated. Our experiments reveal an apparent delay upon the end of the reverse martensitic transformation at field rates exceeding 865 T s−1 which is related to the annihilation of retained martensite. As a consequence, the field hysteresis increases and higher fields are required to saturate the transition. In contrast, no time-dependent effects on the onset of the reverse martensitic transformation were observed in the studied field-sweep range. Our results demonstrate that kinetic effects in Heusler compounds strongly affect the magnetic cooling cycle, especially when utilizing a multicaloric “exploiting-hysteresis cycle” where high magnetic field-sweep rates are employed.

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Publ.-Id: 31787


Competing Effect of Transport versus Surface Reactivity on Mineral Dissolution Rates

Schabernack, J.; Fischer, C.

Mineral dissolution plays a key role in many environmental and technical fields, e.g., weathering, reservoir and host rock characterization, as well as building materials. The rate of mineral dissolution in water is determined by two parameters: (1) transport of dissolved species over and from the interface determined by advective fluid flow and diffusion (transport control) and (2) crystal surface reactivity (surface reactivity control). Current reactive transport models (RTM) simulating species transport commonly calculate mineral dissolution by using rate laws (e.g., Agrawal et al., 2020). These rate laws solely depend on species concentration in the fluid and therefore do not include intrinsic surface reactivity. Experimental studies at surface reactivity controlled conditions have shown a heterogeneous distribution of reaction rates (e.g., Bibi et al., 2018). This rate heterogeneity is caused by nanotopographical structures on the crystal surface, such as steps and etch pits that are generated at lattice defects. At these structures, the high density of reactive kink sites is leading to a local increase in dissolution rates.
In this study, we test whether experimentally observed rate heterogeneities can be reproduced by using current RTMs. We apply a standard RTM approach combined with the measured surface topography of a calcite single crystal (Bibi et al., 2018). The calculated surface dissolution rate maps are compared to experimentally derived rate maps. The results show that the measured rate heterogeneities cannot be reproduced with the existing RTM approach. To improve the predictive capabilities of RTMs, the surface reactivity that is intrinsic to the mineral needs to be implemented into dissolution rate calculations. We discuss parameterization of surface reactivity via proxy parameters, such as surface roughness or surface slope.

Agrawal, P., Raoof, A., Iliev, O. and Wolthers, M. (2020): Evolution of pore-shape and its impact on pore conductivity during CO2 injection in calcite: Single pore simulations and microfluidic experiments. Advances in Water Resources, 136, 103480.
Bibi, I., Arvidson, R.S., Fischer, C. and Lüttge, A. (2018): Temporal Evolution of Calcite Surface Dissolution Kinetics. Minerals, 8, 256

Keywords: Reactive Transport Model; Mineral Dissolution; Crystal Surface Topography

  • Poster (Online presentation)
    DMG VIRTUAL POSTER-SESSION 2020, 30.11.-03.12.2020, Virtuell, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31786
Publ.-Id: 31786


Process simulation: NdFeB permanent magnet production

Belo Fernandes, I.; Abadias Llamas, A.; Reuter, M.
ContactPerson: Ivan Belo Fernandes; Researcher: Alejandro ABADIAS LLAMAS; Supervisor: Markus Andreas REUTER; WorkPackageLeader: Sandra BIRTEL

This file contains an HSC model for NdFeB permanent magnet production, from ore processing to magnet production and two possible recycling routes. Data to build the model is found in key literature studies and from internal project data obtained by the various partners in four work packages (rare earth oxide separation, reduction and purification, alloy design, and powder magnet production).

The model was used to perform a resource efficiency, including exergy, and environmental impact (LCA) evaluation of the life cycle of a NdFeB permanent magnet produced from primary and secondary resources. This work has been submitted to JOM, in its special edition “Thermodynamic modeling of sustainable non-ferrous metals production” and has been accepted for publication with a digital object identifier (DOI): https://doi.org/10.1007/s11837-020-04185-6. Detailed information about the literature sources used for developing the model can be found in the original research paper. The model was built using HSC Chemistry version 9.9 (https://www.outotec.com/products-and-services/technologies/digital-solutions/hsc-chemistry/).

Keywords: NdFeB magnet production; resource efficiency; exergetic life cycle assessment; process simulation; geometallurgy; large systems design

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Publ.-Id: 31785


Smart Kd-concept as efficient approach to improve geochemistry in reactive transport modelling for repository safety assessment

Stockmann, M.; Noseck, U.; Flügge, J.; Gehrke, A.; Brendler, V.

A key component of performance assessment (PA) for radioactive waste repositories in deep geological formations is the forecast of potential radionuclide transport through the repository system. Understanding and appropriate modelling of all relevant (hydro-)geochemical processes is essential for predicting the migration of radionuclides. One important retardation process is sorption on mineral surfaces of the host rock or sedimentary overburden. For the quantification of the radionuclide retention the solid/liquid distribution coefficients (Kd-values) calculated for a given groundwater/rock system are traditionally used in reactive transport modelling (RTM) and most often considered as a constant value due to the large temporal and spatial scales considered in PA. Such a conventional concept has the advantage to be simple and computationally fast but cannot reflect changes in geochemical conditions that are expected during the evolution of the repository system caused by climatic or geological changes. Due to the German safety criteria with an assessment period of one million years it is necessary to consider the impact of such hydrogeological and geochemical changes on the radionuclide transport and retardation. The challenge for large-scale RTM is the integration of important geochemical parameters and processes at affordable computational costs into the codes. Most often a full direct coupling of a transport code with a geochemical speciation code, however, leads to unacceptably long computational times for PA relevant systems.
As an effective way to integrate variable geochemistry in RTM, we developed the smart Kd-concept (www.smartkd-concept.de), a mechanistic approach mainly based on surface complexation models and implemented it into a transport code [1], [2]. The philosophy behind this approach is to compute a-priori multidimensional look-up tables with distribution coefficients (referred to as smart Kd-values as they are based on mechanistic sorption models) for a wide range of important environmental input parameters. Such parameters are typically pH, ionic strength, concentration of competing cations and complexing ligands such as calcium (Ca) and dissolved inorganic carbon (DIC). These smart Kd-values can be accessed during each transport simulation step. Equations describing pH and concentrations of ions as a function of mineral phases are implemented into the transport code, and the resulting values are used to obtain the corresponding smart Kd-values from the look-up table. The smart Kd values are calculated using the geochemical code PHREEQC [3] with a bottom-up approach, i.e. the mineral-specific sorption of dissolved species on each single mineral phase contributes to the distribution coefficient for the whole sediment. Parameter variation was performed with the numeric tool UCODE [4].
The capability of this approach is demonstrated for the sorption of repository-relevant radionuclides (isotopes of Am, Cm, Cs, Ni, Np, Pu, Ra, Th and U) and possible migration scenarios through a typical sedimentary rock system covering potential repository host rocks, namely salt and clay formations in Northern Germany as natural geological barrier for a deep geological repository site. This serves as a comprehensive proof-of-concept and demonstrates the capability to describe the sorption behaviour in dependence of changing geochemical conditions quite well. As a side-effect, the large Kd-matrices that were computed can be further analysed by sensitivity and uncertainty analysis (SA/UA) as provided by SimLab2.2/4 [5], [6].
Results of this case study showed that the smart Kd approach goes considerably beyond the conventional concepts. We can illustrate that constant Kd values previously used in transport simulations, here exemplarily shown for uranium U(VI) (Figure 1, right, green line [7]), are a rough approximation, as in reality they rather range over several orders of magnitude. Moreover, with the results from SA, those input parameters influencing strongest the radionuclide retardation variation can be identified (key parameters of the model). The calculated sensitivity indices allowed us to rank all parameters with respect to sensitivity on Kd. From the visualized smart Kd matrix for U(VI) (Figure 1, left) it is obvious that mainly the pH value and the DIC determine the sorption of U(VI) under the given conditions. SA is a useful means for reducing the complexity of a geochemical model by focusing on the most important input parameters.

Keywords: Distribution coefficient; Radionuclides; Performance assessment; Sorption; Speciation

  • Lecture (Conference)
    Tage der Standortauswahl 2021, 11.-12.02.2021, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31784
Publ.-Id: 31784


Silicon-based Intermediate-band Infrared Photodetector realized by Te Hyperdoping

Wang, M.; García-Hemme, E.; Berencén, Y.; Hübner, R.; Xie, Y.; Rebohle, L.; Xu, C.; Schneider, H.; Helm, M.; Zhou, S.

Si-based photodetectors satisfy the criteria of low-cost and environmental-friendly, and can enable the development of on-chip complementary metal-oxide-semiconductor (CMOS)-compatible photonic systems. However, extending their room-temperature photoresponse into the mid-wavelength infrared (MWIR) regime remains challenging due to the intrinsic bandgap of Si. Here, we report on a comprehensive study of a room-temperature MWIR photodetector based on Si hyperdoped with Te. The demonstrated MWIR p-n photodiode exhibits a spectral photoresponse up to 5 µm and a slightly lower detector performance than the commercial devices in the wavelength range of 1.0-1.9 μm. We also investigate the correlation between the background noise and the sensitivity of the Te-hyperdoped Si photodiode, where the maximum room-temperature specific detectivity is found to be 3.2 × 1012 cmHz1/2W-1 and 9.2 × 108 cmHz1/2W-1 at 1 µm and 1.55 µm, respectively. This work contributes to pave the way towards establishing a Si-based broadband infrared photonic system operating at room temperature.

Keywords: Si photonics; mid-wavelength infrared photodetector; hyperdoping; ion implantation; CMOS compatible

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Permalink: https://www.hzdr.de/publications/Publ-31782
Publ.-Id: 31782


Advanced Magnetic Resonance Studies of Tetraphenylporphyrinatoiron(III) Halides

Tin, P.; Stavretis, S. E.; Ozerov, M.; Krzystek, J.; Ponomaryov, O.; Zvyagin, S.; Wosnitza, J.; Chen, C.-C.; Chen, P. P.-Y.; Telser, J.; Xue, Z.-L.

High-Frequency and -Field EPR (HFEPR) studies of Fe(TPP)X (X = F, Cl, Br; I, TPP2−=meso-tetraphenylporphyrinate dianion) and far-IR magnetic spectroscopic (FIRMS) studies of Fe(TPP)Br and Fe(TPP)I have been conducted to probe magnetic intra- and inter-Kramers doublet transitions in these S = 5/2 metalloporphyrin complexes, yielding zero-field splitting (ZFS) and g parameters for the complexes: Fe(TPP)F, D = +4.67(1) cm−1, E = 0.00(1) cm−1, g = 1.97(1), g = 2.000(5) by HFEPR; Fe(TPP)Cl, D = +6.458(2) cm−1, E = +0.015(5) cm−1, E/D = 0.002, g = 2.004(3), g|| = 2.02(1) by HFEPR; Fe(TPP)Br, D = +9.03(5) cm−1, E = +0.047(5) cm−1, E/D = 0.005, giso = 1.99(1) by HFEPR and D = +9.05 cm−1, giso = 2.0 by FIRMS; Fe(TPP)I, D = +13.84 cm−1, E = +0.07 cm−1, E/D = 0.005, giso = 2.0 by HFEPR and D = +13.95 cm−1, giso = 2.0 by FIRMS (the sign of E was in each case arbitrarily assigned as that of D). These results demonstrate the complementary nature of field- and frequency-domain magnetic resonance experiments in extracting with high accuracy and precision spin Hamiltonian parameters of metal complexes with S > 1/2. The spin Hamiltonian parameters obtained from these experiments have been compared with those obtained from other physical methods such as magnetic susceptibility, magnetic Mössbauer spectroscopy, inelastic neutron scattering (INS), and variable-temperature and -field magnetic circular dichroism (VT-VH MCD) experiments. INS, Mössbauer and MCD give good agreement with the results of HFEPR/FIRMS; the others not as much. The electronic structure of Fe(TPP)X (X = F, Cl, Br, I) was studied earlier by multi-reference ab initio methods to explore the origin of the large and positive D-values, reproducing the trends of D from the experiments. In the current work, a simpler model based on Ligand Field Theory (LFT) is used to explain qualitatively the trend of increasing ZFS from X = F to Cl to Br and to I as the axial ligand. Tetragonally elongated high-spin d5 systems such as Fe(TPP)X exhibit D > 0, but X plays a key role. Spin delocalization onto X means that there is a spin–orbit coupling (SOC) contribution to D from X, as opposed to none from closed-shell X. Over the range X = F, Cl, Br, I, X character increases as does the intrinsic SOC of X so that D increases correspondingly over this range.

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Publ.-Id: 31781


Process Simulation: Zinc and Cadmium production, Lead refining

Bartie, N. J.; Heibeck, M.
Researcher: Bartie, Neill Jacques; Researcher: Heibeck, Magdalena

A process simulation model for the production and purification of Zinc via the Roast-Leach-Electrowinning (RLE) process and the subsequent production of its byproduct, Cadmium. It also includes a process for the precipitation of jarosite, and produces residues that can be further processed for the production of Copper and Cobalt. The refining of crude Lead (Pb) bullion is included as a separate stand-alone section.

The simulation was created using flowsheet configurations and operating parameters available in the public domain. Feed and product stream compositions are therefore metallurgically sound and representative of industrial operations that use the processes modelled. The simulation remains an abstraction of reality, however, and should be verified and adopted to the specific operation under consideration. 

The model was developed using the HSC Sim Flowsheet Module in HSC Chemistry 10 (version 10.0.0.5).

(https://www.outotec.com/products-and-services/technologies/digital-solutions/hsc-chemistry/)

Note: The authors do not accept responsibility for any errors. The onus is on the user to verify and validate results against the system being investigated, as system configurations and operating parameters differ from site to site.

Keywords: Process Simulation; Metal production; Zinc; Cadmium; Lead; Copper; Cobalt; Jarosite

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Publ.-Id: 31779


Justification of best-estimate transient calculations in comparison to the steady-state bounding-case approach

Sangiorgi, M.; Carenini, L.; Brumm, S.; Le Tellier, R.; Viot, L.; Wu, Z.; Xia, S.; Bakouta, N.; Ederli, S.; Mascari, F.; Harti, M.; Lecomte, M.; Sagan, M.; Pandazis, P.; Jobst, Matthias; Gencheva, R.; Groudev, P.; Barnak, M.; Matejovic, P.; Villanueva, W.; Chen, Y.; Ma, W.; Bechta, S.; Kaliatka, A.; Valinius, M.; Kostka, P.; Techy, Z.; Vorobyov, Y.; Thomas, R.; Vokac, P.; Kotouc, M.; Korpinen, A.; Fichot, F.

In the scope of the European IVMR (In-Vessel Melt Retention) project, calculations of In-Vessel retention (IVR) strategy with state of the art Severe Accident (SA) computer codes were performed, including the integral codes ASTEC, ATHLET-CD, MAAP, MELCOR and RELAP5/SCDAPSIM. Further codes dedicated to the study of lower plenum behaviour were also included. Simulations were performed for several types of reactors (PWR, VVER-440, VVER-1000, BWR) and several severe accident scenarios (Station Blackout (SBO) accidents and Loss-Of-Coolant accidents of several leak sizes combined with SBO). The code improvements for IVR simulation, implemented during the project, are summarized and the results obtained with the improved codes are presented in the paper.

Keywords: In-vessel melt retention; Severe Accidents; PWR; VVER-1000; VVER-440; BWR; Accident Management Measures; SBO; LOCA

  • Contribution to proceedings
    International Seminar “In-vessel retention: outcomes of IVMR project”, 20.-21.01.2020, Juan-les-Pins, France

Permalink: https://www.hzdr.de/publications/Publ-31778
Publ.-Id: 31778


Structural and magnetic properties of swift heavy-ion irradiated SiC

Zhang, X.; Zhang, Z.; Akhmadaliev, S.; Zhou, S.; Wu, Y.; Guo, B.

Ferromagnetism has been observed in ion and neutron irradiated SiC single crystals. In this paper, we present a structural and magnetic investigation on 6H–SiC irradiated by swift heavy ions. The co-exist of paramagnetism, superparamagnetism and ferromagnetism is revealed by using different magnetometry methods. The ferromagnetic component persists well above room temperature. This study confirms the general existence of defect-induced magnetism in SiC.

Keywords: Ferromagnetism Magnetometry; Heavy ions; Silicon carbide; Superparamagnetism; Ferromagnetic component; Induced magnetism; Neutron irradiated SiC single crystals; Structural and magnetic properties; Swift heavy ions; Silicon compounds

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Permalink: https://www.hzdr.de/publications/Publ-31777
Publ.-Id: 31777


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