Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41809 Publications

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

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

Abstract

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

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Permalink: https://www.hzdr.de/publications/Publ-33271


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

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

Abstract

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

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

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Permalink: https://www.hzdr.de/publications/Publ-33270


Gas permeability and selectivity of a porous WS₂ monolayer

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

Abstract

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

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

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


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

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

Abstract

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

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

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

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


Data for "Sauerstoffeintragstechnologien für die biologische Abwasseraufbereitung"

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

Abstract

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

Keywords: Aeration; Bubble size; Dynamic operation

Involved research facilities

  • TOPFLOW Facility

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Permalink: https://www.hzdr.de/publications/Publ-33265


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

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

Abstract

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

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

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Permalink: https://www.hzdr.de/publications/Publ-33264


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

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

Abstract

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

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

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

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

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

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


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

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

Abstract

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

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

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


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

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

Abstract

raw data and processed data for the publication.

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

Involved research facilities

  • TOPFLOW Facility

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


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

Matschiavelli, N.

Abstract

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

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

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


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

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

Abstract

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

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

Involved research facilities

  • TOPFLOW Facility

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


Sauerstoffeintragstechnologien für die biologische Abwasseraufbereitung

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

Abstract

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

Keywords: Belüftung; Sauerstoffeintragseffizienz; Blasengröße; Dynamischer Betrieb

Involved research facilities

  • TOPFLOW Facility

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

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


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

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

Abstract

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

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


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

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

Abstract

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

References:

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

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

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


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

Wulf, T.

Abstract

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

for publication

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

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

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Permalink: https://www.hzdr.de/publications/Publ-33253


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

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

Abstract

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

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Permalink: https://www.hzdr.de/publications/Publ-33251


alpaka-group/alpaka: alpaka 0.7.0: Maximum Warp

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

Abstract

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

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

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


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

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

Abstract

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

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  • Secondary publication expected from 04.08.2024

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


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

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

Abstract

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

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

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

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


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

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

Abstract

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

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

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


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

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

Abstract

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

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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


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

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

Abstract

TRLFS spectra; NMR spectra; QMMM data

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


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

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

Abstract

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

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  • High Magnetic Field Laboratory (HLD)

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Permalink: https://www.hzdr.de/publications/Publ-33242


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

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

Abstract

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

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Permalink: https://www.hzdr.de/publications/Publ-33241


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

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

Abstract

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

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

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


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

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

Abstract

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

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

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

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


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

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

Abstract

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

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

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

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


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

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

Abstract

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

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

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

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


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

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

Abstract

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

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

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

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


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

Krönke, T.

Abstract

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

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

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

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


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

Mamat, C.

Abstract

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

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

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

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


Implementing the Variability of Crystal Surface Reactivity in Reactive Transport Modeling

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

Abstract

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

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

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


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

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

Abstract

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

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

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


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

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

Abstract

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

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


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

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

Abstract

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

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

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

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

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

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

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


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

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

Abstract

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

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


WP7 Task 3 Current Activities

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

Abstract

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

Keywords: compression; pipelines

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


Ein Modellierungsansatz zur numerischen Simulation disperser und aufgelöster Strukturen mit Morphologieübergang

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

Abstract

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

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

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


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

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

Abstract

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

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

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


Low-energy magnetic dipole strength in cadmium isotopes

Schwengner, R.

Abstract

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

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

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


HSQ-based process to integrate vertical nanoscale devices

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

Abstract

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

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

Involved research facilities

Related publications

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

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


Coupling of atomic states to particle in cell simulations

Marre, B. E.

Abstract

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

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

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


Compatibility of CMOS technology with QD-based devices

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

Abstract

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

Keywords: single electron transistor; quantum dot; CMOS

Involved research facilities

Related publications

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

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


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

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

Abstract

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

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

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

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


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

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

Abstract

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

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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


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

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

Abstract

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

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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


Optical Readout of the Néel Vector in the Metallic Antiferromagnet Mn2Au

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

Abstract

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

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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


MoP3SiO11: A 4d3 honeycomb antiferromagnet with disconnected octahedra

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

Abstract

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

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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


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

Hampel, U.

Abstract

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

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

Involved research facilities

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

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


Fast tomographic imaging of multiphase flow

Hampel, U.

Abstract

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

Keywords: multiphase flows; computed tomography; imaging

Involved research facilities

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

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


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

Li, R.

Abstract

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

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

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

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


UMB-II: 2nd video conference workshop

Matschiavelli, N.

Abstract

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

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

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


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

Mayordomo, N.

Abstract

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

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

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

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

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


Technetium immobilization by chloride green rust

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

Abstract

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

Keywords: Technetium; Reductive immobilization; Sorption; LDH

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Related publications

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

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


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

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

Abstract

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

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

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

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


Rhamnolipid as an ion collector in bioionflotation

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

Abstract

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

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

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

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


Optimized laser ion acceleration at the relativistic critical density surface

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

Abstract

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

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


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

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

Abstract

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

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


Recovery of nanodiamonds from dynamically shock-compressed hydrocarbon samples

Schuster, A.

Abstract

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

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

Involved research facilities

Related publications

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

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


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

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

Abstract

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

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

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

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


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

Raff, J.

Abstract

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

Keywords: Bioleaching; uramium ores

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

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


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

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

Abstract

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

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

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

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

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

Abstract

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

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

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


Künstliche Intelligenz im Gesundheitswesen

Steinbach, P.

Abstract

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

Keywords: KI; Medizin; Gesundheitswesen; Maschinelles Lernen

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


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

Wulf, T.

Abstract

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

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

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

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

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

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

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

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

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


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

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

Abstract

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

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

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


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

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

Abstract

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

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

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

Abstract

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

Prerequesites

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

Python: 3.8.6

Scholarly: 1.2.0

Pyzotero: 1.4.24

Numpy: 1.20.1

Fitz: 1.19.1

Contents

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

scripts/ : Contains scripts to perform the citation analysis.

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

Usage

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

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


Volume 141: European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases, 14 September 2020, Virtual Conference

Bischl, B.; Guhr, O.; Seibold, H.; Steinbach, P.

Abstract

Proceedings of Machine Learning Research

Keywords: teaching; machine learning; ECML/PKDD 2020

  • Open Access Logo Book (Editorship)
    www: PMLR, 2021

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Permalink: https://www.hzdr.de/publications/Publ-33193


Machine Learning for Accelerator Physics and Engineering

Steinbach, P.; Hoffmann, H.; Schmerler, S.; Starke, S.

Abstract

Helmholtz AI has been available for members of ARD since its inception 2019/20. In this presentation, I'd like to present the current status of Helmholtz AI consultancy for matter research in Helmholtz. I'd provide sneak previews into past and ongoing vouchers we embarked upon for the accelerator physics community. Last but not least, I'll discuss challenges we faced along the way and will highlight some future directions if time allows.

Keywords: machine learning; Helmholtz AI; accelerator physics; seminar

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    MT ARD ST3 Meeting 2021 in Hamburg, 29.09.-01.10.2021, virtuell, Germany
    DOI: 10.6084/m9.figshare.16709350.v2

Permalink: https://www.hzdr.de/publications/Publ-33192


Predicting the shoe size of workshop participants

Starke, S.; Schmerler, S.; Steinbach, P.

Abstract

A jupyter notebook that can predict the shoe size of a person based on their gender, height and weight. This is a notebook meant for training purposes to show case how public data can be used to train a machine learning predictor.

This notebook uses a public crowd-sourced dataset from https://doi.org/10.5281/zenodo.5541145 to conduct the training.

Keywords: jupyter notebook; notebook; machine learning; scikit-learn; shoe size; csv

Permalink: https://www.hzdr.de/publications/Publ-33191


crowdsourced body parameters of workshop attendants at the Helmholtz MT ARD ST3 meeting

Steinbach, P.; Schmerler, S.

Abstract

This data set was crowdsourced at the 2021 Helmholtz MT ARD ST3 meeting from attendants of the Machine Learning Tutorial on Sep 30, 2021. For more details on the event, see
https://indico.desy.de/event/28823/

Keywords: shoe size; body height; body mass; gender; crowdsource; csv

Permalink: https://www.hzdr.de/publications/Publ-33190


Publishing the (PaN) Experiment

Knodel, O.

Abstract

The talk gives an overview on the publication of an (PaN) experiment in general, including data and software publication. An additional overall workflow describes the dependencies between all data objects with the aim to create a comprehensible experiment. The live demo introduces our training catalogue developed in WP5 with the special workflow feature.

Keywords: ExPaNDS; Data Management; PaN Training Catalogue

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    ExPaNDS Symposium for Librarians and Data Managers, 30.09.2021, online, online

Permalink: https://www.hzdr.de/publications/Publ-33189


Demonstrator for using e-learning platforms for PaN

Knodel, O.; Konrad, U.

Abstract

A definition of the most suitable training materials for PaN communities in accordance with the requirements and recommendations made by the targeted e-platform providers.

A demonstrator for using e-learning platforms was developed and provided by HZDR in the frame of the ExPaNDS project.

Keywords: ExPaNDS; E-learning; Photon and Neutron

Permalink: https://www.hzdr.de/publications/Publ-33188


Solid-phase synthesis of selectively mono-fluorobenz(o)ylated polyamines as a basis for for the Development of 18F-Labeled Radiotracers

Wodtke, R.; Pietzsch, J.; Löser, R.

Abstract

Polyamines are highly attractive vectors for tumor targeting, particularly with regards to the development of radiolabeled probes for imaging by positron emission (PET) and single-photon emission computed tomography (SPECT). However, the synthesis of selectively functionalized derivatives remains challenging owing to the presence of multiple amino groups of similar re-activity. In this work, we established a synthetic methodology for the selective mono-fluorobenz(o)ylation of various biogenic diamines and polyamines as lead compounds for the perspective development of substrate-based radiotracers for targeting polyamine-specific membrane transporters and enzymes such as transglutaminases. To this end, the polyamine scaffold was constructed by solid-phase synthesis of the corresponding oxopolyamines and subsequent re-duction with BH₃/THF. Primary and secondary amino groups were selectively protected using Dde and Boc as protecting groups, respectively, in orientation to previously reported proce-dures, which enabled the selective introduction of the reporter groups. For example, N¹-FBz-spermidine, N⁴-FBz-spermidine, N⁸-FBz-spermidine, and N¹-FBz-spermine and N⁴-FBz-spermine (FBz=4-fluorobenzoyl) were obtained in good yields by this approach. The advantages and disadvantages of this synthetic approach are discussed in detail and its suitability for radiolabeling was demonstrated for the solid-phase synthesis of N¹-[¹⁸F]FBz-cadaverine.

Keywords: amide bond reduction; reductive alkylation; ¹⁸F-labeling; prosthetic groups; site-selective chemical modification; transglutaminases; polyamine transport system; substrate-based probes; PET tracers; tumor targeting

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  • PET-Center

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Permalink: https://www.hzdr.de/publications/Publ-33187


Limitations and gaps in global bat wing morphology trait data

Matt, C.; Simoes Silva, I. M.; Matthew, J. G.; George, A. G.

Abstract

Species’ life-history traits have a wide variety of applications in ecological and conservation research, particularly when assessing threats. The development and growth of global species’ trait databases are critical for improving trait-based analyses; however, it is vital to understand the gaps and biases in the available data.
We reviewed bat wing morphology data, specifically mass, wingspan, wing area, wing loading, and aspect ratio, to identify issues with data reporting and ambiguity. Additionally, we aimed to assess taxonomic and geographic biases in trait data coverage. We found that most studies used similar field methodology, but that data reporting and quality were inconsistent/poor. Additionally, we noted several issues regarding semantic ambiguity in trait definitions, specifically around what constitutes wing area. Globally, we found that bat wing morphology trait coverage was low. Only six bat families had ≥40% trait coverage, and, of those, none consisted of more than 11 species in total. We found similar biases in trait coverage across International Union for Conservation of Nature Red List categories, with threatened species having lower coverage.
Geographically, North America, Europe, and the Indomalayan regions exhibited higher overall trait coverage, while both the Afrotropical and Neotropical ecoregions showed poor trait coverage.
The underlying biases and gaps in bat wing morphology data have implications for researchers conducting global trait-based assessments. Implementing imputation techniques may address missing data, but only for smaller regional subsets with substantial trait coverage. Due to generally low overall trait coverage, increasing species’ representation in the database should be prioritised. We suggest adopting an Ecological Trait Standard Vocabulary to reduce semantic ambiguity in bat wing morphology traits, to improve data compilation and clarity. Additionally, we advocate that researchers adopt an Open Science approach to facilitate the growth of a bat wing morphology trait database.

Keywords: open science; ecology; bats; aspect ratio; reproducibility; data availability; spatial biases; species traits

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Permalink: https://www.hzdr.de/publications/Publ-33186


Emerging opportunities for wildlife with sustainable autonomous transportation

Simoes Silva, I. M.; Calabrese, J.

Abstract

Autonomous vehicles (AV) are expected to play a key role in the future of transportation, introducing a disruptive yet potentially beneficial change for vehicle-wildlife interactions. However, this assumption has not been critically examined. Here, we introduce a new conceptual framework covering the intersection between AV technological innovation and wildlife conservation to reduce wildlife-vehicle collisions. We suggest future research within this framework to focus on developing robust warning systems and animal detection methods for AV systems, and to incorporate wildlife-vehicle interactions into decision-making algorithms. With large-scale deployment a looming reality, it is vital to incorporate conservation and sustainability into the societal, ethical, and legal implications of AV technology. We appeal for further debate and interdisciplinary collaborations between scientists, developers, and policymakers.

Keywords: conservation; autonomous vehicles; ecology; sustainability; self-driving cars; automated vehicles; traffic accidents; animal-vehicle collisions; wildlife-vehicle collisions; conceptual framework

Permalink: https://www.hzdr.de/publications/Publ-33185


Defect characterization using positron annihilation spectroscopy on laser ablated surfaces

Hosemann, P.; Auguste, R.; Lam, S.; Butterling, M.; Liedke, M. O.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.; Grigoropoulos, C. P.; Selim, F.; Uberuaga, B. P.

Abstract

In recent years, short, pulsed laser ablation has been gaining popularity for machining small scale test geometries from bulk samples and for efficient serial sectioning. These laser-based techniques are being added to the toolbox in material science, which makes it necessary to understand the changes in the material that occur from the laser-material interaction. Positron annihilation spectroscopy is a unique, nondestructive technique to investigate small defects in materials difficult to investigate by other tools. In this work, Doppler broadening and positron lifetime annihilation spectroscopy are utilized to help quantify the damage in materials treated with short, pulsed lasers. Using a femtosecond laser on single crystal silicon, this manuscript shows that clusters of vacancy-like defects and small voids increase systematically with laser power. The damage induced by the laser can also reach to micrometer depths.

Keywords: Si; fs-laser; positron annihilation spectroscopy; Doppler broadening; pores

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Permalink: https://www.hzdr.de/publications/Publ-33184


Using of light and heavy ion beams in modern FIBs

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

Abstract

The incident ion defines the interaction mechanism with the sample surface caused by the energy deposition and thus has significant consequences on resulting nanostructures [1]. Therefore, we have extended the FIB technology towards the stable delivery of multiple ion species by liquid metal alloy ion sources (LMAIS) [2].
These LMAIS provides single and multiple charged ion species of different masses. As an example we introduce the GaBiLi LMAIS [3]. Such “universal” source enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from the same ion source. Light ions are of
increasing interest due to the available high resolution in the nanometer range and their special chemical and physical behavior in the substrate. We compare helium and neon ion beams from a helium ion microscope with beams such as lithium, boron, and silicon, obtained from a mass-separated FIB using a LMAIS with respect
to the imaging and milling resolution, as well as the current stability [4]. The bombardment of solids by poly-atomic (cluster) ions leads to nonlinear collision cascades in near-surface regions. In comparison with linear cascades by monoatomic ions, much higher energy deposition occurs up to local surface melting [5]. Here, we also report the study on the sputter yield of Si under the bombardment by atomic Bi+ and cluster Bin+ (n = 2-4) ions with the same specific energy related to one incidence single atom [6].
[1] P. Mazarov, V. Dudnikov, A. Tolstoguzov, Electrohydrodynamic emitters of ion beams, Phys. Usp. 63
(2020) 1219.
[2] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative
for Focused Ion Beam Technology, Appl. Phys. Rev. 3 (2016) 021101.
[3] W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium ion beams from liquid metal
alloy ion sources, JVSTB 37(2), Mar/Apr (2019) 021802.
[4] N. Klingner, G. Hlawacek, P. Mazarov, W. Pilz, F. Meyer, L. Bischoff, Imaging and Milling Resolution
of Light Ion Beams from HIM and Liquid Metal Alloy Ion Source driven FIBs, Beilstein J. Nanotechnol. 11
(2020) 1742.
[5] L. Bischoff, K.-H. Heinig, B. Schmidt, S. Facsko, and W. Pilz, Self-organization of Ge nanopattern under
erosion with heavy Bi monomer and cluster ions, Nucl. Instr. Meth. B 272 (2012) 198.
[6] A. Tolstogouzov, P. Mazarov, A. Ieshkin, S.Belykh, N. Korobeishchikov, V. Pelenovich, D.J. Fu,
Sputtering of silicon by atomic and cluster bismuth ions: An influence of projectile nuclearity and specific
kinetic energy on the sputter yield, Vacuum 188 (2021) 110188.

Keywords: liquid metal alloy ion source; FIB technology; nanostructures; poly-atomic ions

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  • Lecture (Conference)
    4th EuFN and FIT4NANO Joint Workshop / Meeting, 27.-30.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-33183


Investigation of Boron Liquid Metal Alloy Ion Sources for Focused Ion Beam Applications

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

Abstract

Focused Ion Beam (FIB) processing is established as a well-suited and promising technique in R&D in nearly all fields of nanotechnology for patterning and prototyping on the μm-scale and below. Liquid Metal Alloy Ion Sources (LMAIS) represent an alternative to expand the FIB application fields beside all other source concepts [1]. Due to the interest on light elements, especially boron, various alloys were investigated and characterized. In this contribution we will describe Co31Nd64B5 as the most promising alloy in more detail. The mass spectrum of such a source was obtained in a VELION FIB-SEM system (Raith GmbH) [2]. The source operation life time was longer than 600 μAh and a first imaging characterization showed a lateral resolution of (30 ± 5) nm so far. This LMAIS is suited for several mass-filtered FIB applications like implantation, high rate sputtering, surface patterning or ion lithography [3]. The switching between the certain ion species. B – very light, suitable for ion lithography or writing p-type doping. Co – medium mass for applications in the field of nano-magnetics or CoSi2 for ion beam synthesis of conductive nano-structures on Si. Finally Nd as double charged heavy ion for ion sputtering. The change between ion species can be done in seconds and leads to remarkable expansion of the application spectrum of FIB technology.
[1] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources - An Alternative for Focused Ion Beam Technology; Appl. Phys. Rev. 3 (2016) 021101.
[2] L. Bischoff, N. Klingner, P. Mazarov, W. Pilz, and F. Meyer, Boron Liquid Metal Alloy Ion Sources for special FIB applications, JVST B 38 (2020) 042801.
[3] L. Bruchhaus, P. Mazarov, L. Bischoff, J. Gierak, A. D. Wieck, and H. Hövel, Comparison of Technologies for Nano Device Prototyping with a Special Focus on Ion Beams – A Review,
Appl. Phys. Rev. 4 (2017), 011302.

Keywords: Focused Ion Beam; Liquid Metal Alloy Ion Source; boron; mass filter

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  • Lecture (Conference)
    4th EuFN and FIT4NANO Joint Workshop / Meeting, 27.-30.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-33182


Data driven high resolution modeling and spatial analyses of the COVID-19 pandemic in Germany

Schüler, L.; Calabrese, J.; Attinger, S.

Abstract

The SARS-CoV-2 virus has spread around the world with over 100 million infections to date, and currently many countries are fighting the second wave of infections. With neither sufficient vaccination capacity nor effective medication, non-pharmaceutical interventions (NPIs) remain the measure of choice. However, NPIs place a great burden on society, the mental health of individuals, and economics. Therefore the cost/benefit ratio must be carefully balanced and a target-oriented small-scale implementation of these NPIs could help achieve this balance. To this end, we introduce a modified SEIRD-class compartment model and parametrize it locally for all 412 districts of Germany. The NPIs are modeled at district level by time varying contact rates. This high spatial resolution makes it possible to apply geostatistical methods to analyse the spatial patterns of the pandemic in Germany and to compare the results of different spatial resolutions. We find that the modified SEIRD model can successfully be fitted to the COVID-19 cases in German districts, states, and also nationwide. We propose the correlation length as a further measure, besides the weekly incidence rates, to describe the current situation of the epidemic.

Keywords: COVID-19; Germany; Epidemiology; Pandemics; SARS-CoV-2; Death rates; Spatial epidemiology

Permalink: https://www.hzdr.de/publications/Publ-33181


Far-infrared Near-field Optical Imaging and Kelvin Probe Force Microscopy of Laser-crystallized and amorphized Phase Change Material Ge₃Sb₂Te₆

Barnett, J.; Wehmeier, L.; Heßler, A.; Lewin, M.; Pries, J.; Wuttig, M.; Klopf, J. M.; Kehr, S. C.; Eng, L. M.; Taubner, T.

Abstract

Chalcogenide phase change materials reversibly switch between non-volatile states with vastly different optical properties, enabling novel active nanophotonic devices. However, a fundamental understanding of their laser-switching behavior is lacking and the resulting local optical properties are unclear at the nanoscale. Here, we combine infrared scattering-type scanning near-field optical microscopy (SNOM) and Kelvin probe force microscopy (KPFM) to investigate four states of laser-switched Ge3Sb2Te6 (as-deposited amorphous, crystallized, reamorphized, and recrystallized) with nanometer lateral resolution. We find SNOM especially sensitive to differences between crystalline and amorphous states, while KPFM has higher sensitivity to changes introduced by melt-quenching. Using illumination from a free-electron laser, we employ that far-infrared (THz) SNOM is more sensitive to free charge carriers compared to mid-infrared SNOM and prove that the local conductivity of crystalline states depends on the switching process. This insight into the local switching of optical properties is essential for developing active nanophotonic devices.

Keywords: scattering-type scanning near-field optical microscopy; free-electron laser; phase change material; Kelvin probe force microscopy; GST; optical switching; metavalent bonding

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Permalink: https://www.hzdr.de/publications/Publ-33180


Dosimetric benefit of 4D robustly optimized proton plans for NSCLC patients with intrafractional motion above 5 mm

Spautz, S.; Haase, L.; Tschiche, M.; Makocki, S.; Troost, E. G. C.; Richter, C.; Stützer, K.

Abstract

Background: We analyse the benefit of 4D robust plan optimization (RO) for proton therapy treatments of NSCLC patients with pronounced breathing-induced anatomical variations.

Methods: Eight NSCLC patients with relevant maximal intrafractional motion of the primary (CTVp; 5.6-24.5mm) and/or nodal CTV (CTVn; 5.8-17.3mm) on the planning 4DCT (pCT) were included. We optimized three robust normo-fractionated plans with a criterion of 5mm setup and 3.5%+2mm range uncertainty: RO on the AverageCT with iGTVp density override (3DRO); RO on the AverageCT and three 4DCT phases (4DRO3); and RO on the AverageCT and all eight 4DCT phases (4DRO8). Setup and range error scenarios were analysed on the pCT. To assess robustness against intra- and inter-fractional changes, 4D doses were calculated on the pCT and up to two control 4DCTs (cCTs) assuming equal weights between breathing phases. Interplay effects were simulated on the pCT from patient breathing signals and machine logfiles of plan deliveries with and without 5 layered rescans. Fractionation effects were emulated by accumulating four interplay scenarios with different starting times.

Results: All nominal plans fulfilled target coverage (D98%>95%) and OAR sparing; CTVp/CTVn coverage failed setup and range robustness in 12%/35% (3DRO), 14%/18% (4DRO3) and 13%/20% (4DRO8) of the scenarios (Fig1a), respectively. 4D dose target coverage on the pCT was >94% for all plans; interfractional changes in the cCTs reduced the CTVp coverage by about 2pp (Fig1b). Interplay analyses (Fig1c) revealed a mean CTVp/CTVn coverage loss by 3.4pp/2.4pp, 3.0pp/2.3pp, and 2.9pp/3.2pp in single scenarios of 3DRO, 4DRO3 and 4DRO8 plans, respectively. D98% values were improved on average by 1.0pp with rescanning, but were even worsened in some scenarios. Irrespective of rescanning, the simulated fractionation fullfilled the target coverage in all cases.

Conclusion: 3DRO and 4DRO showed similar robustness against different motion effects. 4DRO provides benefits for some patients, but 3DRO demands less workload.

  • Poster
    4D treatment workshop on particle therapy, 12.-13.11.2021, Delft, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-33179


Solar selective coatings and materials for high-temperature solar thermal applications

Escobar Galindo, R.; Krause, M.; Niranjan, K.; Barshilia, H.

Abstract

In this chapter, we will present and summarize the latest innovative materials science approaches devoted to increase the CSP plant efficiency by implementing higher operation temperatures and reducing the levelized costs of electricity (LCOE). The chapter is organized as follows: The first section provides statistical data (Section 13.3.1) and the basic knowledge (Section 13.3.2) necessary to understand the state-of-the-art and the recent R&D directions of the field “high-temperature solar thermal applications”. In the second section 13.2 we introduce the concept of solar selectivity. Based on realistic operational parameters of CSP plants, their potentials and limitations are discussed and graphically illustrated. State-of-the-art results from the last decade are briefly reviewed in the third section for: absorber paints (Section 13.3.1), solar selective coatings (SSCs) (Section 13.3.2), and volumetric receivers (Section 13.3.3). The fourth Section 13.4 focuses on the need of comparable stability studies of newly developed SSCs and materials along with the demand and the criteria for standardized characterization protocols.

Keywords: Solar thermal; Concentrated solar power; High-temperature energy conversion; High-temperature materials

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Permalink: https://www.hzdr.de/publications/Publ-33178


A Hybrid Radiomics Approach to Modeling Progression-free Survival in Head and Neck Cancers

Starke, S.; Thalmeier, D.; Steinbach, P.; Piraud, M.

Abstract

We present our contribution to the HECKTOR 2021 challenge.
We created a Survival Random Forest model based on clinical features, and a few radiomics features that have been extracted with and without using the given tumor masks, for Task 3 and Task 2 of the challenge, respectively.
To decide on which radiomics features to include into the model, we proceeded both to automatic feature selection, using several established methods, and to literature review of radiomics approaches for similar tasks.
Our best performing model includes one feature selected from the literature (Metabolic Tumor Volume derived from the FDG-PET image), one via stability selection (Inverse Variance of the Gray Level Co-occurrence Matrix of the CT image), and one selected via permutation-based feature importance (Tumor Sphericity).
This hybrid approach turns-out to be more robust to overfitting than models based on automatic feature selection.
We also show that simple ROI definition for the radiomics features, derived by thresholding the Standard Uptake Value in the FDG-PET images, outperforms the given expert tumor delineation in our case. Team name on the AIcrowd platform: ia-h-ai.

Keywords: Head and Neck Cancer; Radiomics; Survival analysis; CT; PET

  • Contribution to proceedings
    HECKTOR Challenge 2021 - Head and Neck tumor segmentation and outcome prediction in PET/CT images, 27.09.2021, Strasbourg, France
    Lecture Notes in Computer Science: Springer, 978-3-030-98252-2
    DOI: 10.1007/978-3-030-98253-9_25
    Cited 6 times in Scopus
  • Open Access Logo Lecture (Conference) (Online presentation)
    24th International Conference on Medical Image Computing & Computer Assisted Intervention (MICCAI 2021), 27.09.-01.10.2021, Strasbourg, France
    DOI: 10.5281/zenodo.5606514

Permalink: https://www.hzdr.de/publications/Publ-33177


Laser-Ion Acceleration in the Optimized TNSA-Regime via Temporal Pulse Shaping

Garten, M.; Göthel, I.; Wetzel, J.; Miethlinger, T.; Ziegler, T.; Püschel, T.; Bock, S.; Zeil, K.; Marre, B. E.; Bussmann, M.; Cowan, T.; Schramm, U.; Kluge, T.

Abstract

Establishing precise control over the beam parameters of laser-accelerated ions from the interaction of ultrashort ultra-high intensity (UHI) laser pulses with ultrathin foils has been the major goal of the last 20 years since the first description of the TNSA process. Especially the quest for repeatable, highest maximum energies continues to be challenging as the spatiotemporal coupling of laser-pulse- and target parameters down to the femtosecond-nanometer level was found to be decisive for the overall acceleration performance. In particular, precise control and metrology of the driving UHI laser pulses are paramount to achieving this goal. We present a multi-parameter-space study, bridging the scales from picosecond preplasma formation over transient, non-equilibrium dynamics of the tens of femtosecond laser duration down to attosecond plasma oscillations performed through 1D– up to 3D particle-in-cell simulations. By taking into account realistic temporal intensity contrast features of the last picosecond prior and up to the first picosecond after the main pulse peak, we show how temporal pulse shaping optimizes the TNSA process.

Keywords: laser ion acceleration; TNSA; particle-in-cell; PIConGPU; Smilei; temporal laser contrast

  • Poster (Online presentation)
    47th EPS Conference on Plasma Physics, 21.-25.06.2021, online, online
  • Poster
    17th International Conference on the Physics of Non-Ideal Plasmas, 19.-24.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33176


Hydrothermal wall rock alteration related to Late Variscan Pb-Zn-Ag-(Au) mineralisation and its implication for exploration in the Freiberg District, Germany

Birtel, S.; Gutzmer, J.

Abstract

Although epithermal Pb-Zn-Ag-(Au) vein-hosted mineralisation in the Freiberg District, Germany, has been widely studied, closely associated wall rock alteration remains hardly understood. In order to deduce alteration stages in the proximity to mineralised veins, suites of wall rock samples ranging from least altered to intensely altered were studied from two localities in the central part of the district in order to describe and quantify the effects of hydrothermal wall rock alteration.

Least altered host rocks at both localities are medium to coarse- grained biotite –plagioclase orthoclase augengneisses. In weakly altered samples the foliation, and the primary assemblage are well preserved with typical alteration assemblages comprising of fine-grained carbonate, kaolinite, epidote, sericite and chlorite. This alteration assemblage dominates also in moderately altered samples, with metamorphic quartz and the original foliation partly preserved. Intensively altered samples, in contrast, comprise a massive fabric with globular quartz and fine-grained sericite that are very finely intergrown arsenopyrite and/or pyrite occur finely disseminated in this alteration assemblage. Fe-Mn-rich carbonates also occur in the matrix or as thin veinlets in the altered wall rock. In hand specimen, this strongly sericitized rock is of light green to yellow colour.

Hydrothermal alteration related to vein-hosted magmatic-hydrothermal mineralization in the Freiberg District is best described as fabric destructive with distinct discoloration, an effect that can be simply detected visually in core. Sericitization and silicification are dominant – and appear limited to the immediate vicinity around and within relevant structural zones and veins. Visual core inspection, possibly complemented by hyperspectral drill core scanning and whole rock geochemistry (by pXRF) are simple tools that can be used to trace this alteration during ongoing exploration efforts in the district.

Keywords: host rock alteration; exploration; mineralisation in Freiberg District

  • Contribution to proceedings
    16th Biennial meeting SGA 2022, 28.-31.03.2022, Rotorua, New Zealand
    Christie AB (ed.), Proceedings of the 16th SGA Biennial Meeting

Permalink: https://www.hzdr.de/publications/Publ-33174


Effect of the deposition method and ageing in atmosphere on the optical properties of tetraphenylporphyrins (TPPs) films

Lungwitz, F.; Fronk, M.; Richter, P.; Mende, C.; Rüffer, T.; Gordan, O. D.; Himcinschi, C.; Zahn, D. R. T.; Lang, H.; Salvan, G.

Abstract

In this work thin films of 5,10,15,20-tetraphenylporphyrin (H2TPP) and 5,10,15,20-tetrakis(4-methoxyphenyl)porpyhrin (H2TMPP)) were prepared by organic molecular beam deposition (OMBD). In addition, spin coating was applied as an alternative preparation technique for thin films of H2TPP to investigate the influence of the deposition method on the optical properties. The preservation of the molecular structure was proven by comparative Raman spectroscopy studies between films and powder. Modelling of the spectroscopic ellipsometry data yields a uniaxial anisotropy of the optical constants for the films of both molecules deposited by OMBD, which was used to determine the relative orientation of the molecules with respect to the substrate. The effect of the storage in air on the optical properties of the OMBD films was investigated using the example of H2TMPP. The molecular order in the films was found to decrease while the film roughness increased compared to samples stored in nitrogen.

Keywords: Tetraphenylporphyrin; Tetramethoxyphenylporpyhrin; Organic molecular beam deposition; Spin coating; Optical constants; Atmosphere exposure

Permalink: https://www.hzdr.de/publications/Publ-33173


Neural Solvers

Stiller, P.; Zhdanov, M.; Rustamov, J.; Bethke, F.; Hoffmann, N.

Abstract

Neural Solvers are neural network-based solvers for partial differential equations and inverse problems. The framework implements scalable physics-informed neural networks Physics-informed neural networks allow strong scaling by design. Therefore, we have developed a framework that uses data parallelism to accelerate the training of physics-informed neural networks significantly. To implement data parallelism, we use the Horovod framework, which provides near-ideal speedup on multi-GPU regimes.

Keywords: PINNs; PDEs; Neural Solver; Scalable AI

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Permalink: https://www.hzdr.de/publications/Publ-33172


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

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

Abstract

The ion-induced nanoscale pattern formation on a crystalline Ge(001) surface is observed in-situ by means of Grazing Incidence Small Angle X-ray Scattering (GISAXS). Analysis of the GISAXS intensity maps yields the temporal develoment of geometric parameters characterizing the changing pattern morphology. In comparison with theoretical predictions and with simulations of the patterning process based on a continuum equation we find good agreement for the temporal evolution of the polar facet angle, characteristic length, and surface roughness in the non-linear regime. To achieve this agreement, we included an additional term in the continuum equation which adjusts the pattern anisotropy.

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-33171


Real-Time Observation of Temperature-Induced Surface Nanofaceting in M-Plane α-Al2O3

Erb, D.; Perlich, J.; Roth, S.; Röhlsberger, R.; Schlage, K.

Abstract

The spontaneous crystal surface reconstruction of M-plane Al₂O₃ is employed for nanopatterning and nanofabrication in various fields of research including, among others, magnetism, superconductivity, and optoelectronics. However, investigating this reconstruction process from a planar surface to one with a nanoscale ripple topography is challenging, since it occurs at high temperatures above approximately 1000 °C. This contribution presents an approach combining ex-situ Atomic Force Microscopy with in-situ and simulated Grazing Incidence Small Angle X-ray Scattering to further elucidate this morphological transition. It provides time-resolved information on all relevant morphological characteristics required to trace the surface topography during recon-
struction and thereby offers a comprehensive picture of this process on a nanometer scale.

Keywords: crystal surface reconstruction; nanofaceted Al₂O₃; pattern formation; in-situ GISAXS; AFM

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33170


The role of data science and machine learning to achieve sustainable mineral exploration

Lorenz, S.

Abstract

Europes’ journey towards a sustainable and digitized future relies fundamentally on the secured supply with critical raw materials. Lithium, Rare Earths, Indium and Tungsten, to name a few, are fundamental requisites for green and smart technologies, e-mobility and the energy transition. Securing the access to such materials is one of the fundamental questions for Europes ambition to deliver the Green Deal. Fast, versatile and accurate but at the same time socially acceptable and less invasive mineral exploration technologies are required to meet this goal. Innovative sensors and acquisition platforms for spectral imaging allow to gain insights on the composition of materials without destroying or even touching them. The complexity, diversity and sheer amount of respective data produced in a typical exploration scenario require a joint understanding of geoscience, image processing and machine learning to retrieve geologically meaningful results in a reasonable time. The presentation will give an overview on our current research highlighting important challenges in modern mineral exploration in regards to image processing, multi-sensor data fusion, data classification and real-time processing.

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Women in Machine Learning & Data Science (WiMLDS) Meetup, 17.03.2021, online, online

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Permalink: https://www.hzdr.de/publications/Publ-33169


Targeted mapping using self-organizing drone swarms

Lorenz, S.

Abstract

Drohnen unterstützen heutzutage viele Anwendungsfelder als preiswerte und flexible Flugplattformen. Durch die fortschreitende Entwicklung miniaturisierter Sensorik können Drohnen inzwischen auch für komplexe Observierungsaufgaben eingesetzt werden. Sie unterstützen auf diese Weise Wissenschaft und Industrie bei der Analyse schwer erreichbarer Ziele, zum Beispiel in Bergbau, Landwirtschaft oder Bauindustrie. Der notwendige Kompromiss zwischen Zuladung und Flugzeit ist dabei für die zivile Drohnenanwendung nach wie vor eine große Herausforderung. Mit seiner neuesten Projektidee zu autonomen, selbstorganisierten Drohnenverbänden will die Abteilung Erkundung des Helmholtz-Institutes Freiberg für Ressourcentechnologie Abhilfe schaffen: Scouting-Drohnen mit langer Flugzeit und leichten multispektralen Sensoren übernehmen eine Vorab-Analyse des Zielgebietes in Echtzeit. Anhand der Ergebnisse koordinieren sie selbsttätig weitere Drohnen ihres Verbandes für eine detaillierte Analyse ausgewählter kleinerer Zielpolygone. Jene mit schwereren, aber genaueren Sensoren ausgerüsteten Drohnen sparen so nicht nur Flugzeit ein, sondern nehmen auch nur dort detaillierte Daten auf wo sie wirklich benötigt werden. Neben der Entwicklung der Drohnen- und Multisensortechnologie sind Echtzeitverarbeitung und künstliche Intelligenz die Kernherausforderungen des Projektes.

  • Lecture (Conference) (Online presentation)
    Silicon Saxony Day, 27.05.2021, virtual, Germany

Permalink: https://www.hzdr.de/publications/Publ-33168


Hyper 3D-AI: Artificial Intelligence for 3D multimodal point cloud classification

Lorenz, S.

Abstract

Independent of the application field, spatially detailed information is commonly provided in the form of image data. Accordingly, major developments in image processing and artificial intelligence (AI) for image data interpretation are based on an image-like data structure, i.e. a spatially two-dimensional data grid with a custom number of informative layers. While sufficient for large-scale geographical data, this approach has major flaws when applied in any oblique-angle scenario, in particular as it inherently distorts the spatial characteristics of the observed target (virtual vs. real-world neighborhood relationships, occlusions). Todays’ most crucial image data applications (e.g., resources, energy, mobility, medicine), however, heavily rely on the accurate interpretation of the spatial relationship of objects in all three dimensions. It has been shown that the upscaling of 2D-images to multi-feature attributed 3D point clouds boosts the interpretational value of the dataset. This approach is not only beneficial for the fusion of image data with 3D-information (such as orientation, shape, and surface roughness), but also offers a straightforward solution for the fusion of higher dimensional multi-sensor data. Although point clouds or meshes are routinely used as 3D analogues of real-world targets, the processing of multi-feature point clouds in terms of clustering, classification or material characterization is still in its infancy. Innovative AI approaches such as PointNets or 3D-CNN have shown great potential for point cloud clustering using the spatial relationships of the individual points. However, classifications based on both spatial and auxiliary, high-dimensional point information such as spectral signatures or compositional characteristics is yet to be developed. The proposed project aims at the development of advanced machine (deep) learning approaches to fill this exact gap. These approaches comprise both the challenging fusion of multiple sensors as well as the subsequent classification and segmentation. Besides the algorithm design, the testing on representative scenarios from different application fields is a main work package, including the creation of reusable benchmark datasets for the validation and future development of algorithms. If successful, the project will improve the characterization of objects and surfaces for a wide range of potential applications such as exploration and mining, recycling, autonomous systems, quality assessment, sorting systems or detection of falsified objects. From a resource perspective, an enhanced material characterization will directly contribute to making processes more material and energy efficient. Regarding autonomous systems, the project will advance the research and implementation of methods for robust sensor fusion of multimodal sensors. Due to the versatility in application, the project outcome could support any process that requires a multi-sensor-based discrimination of objects and materials.

  • Invited lecture (Conferences) (Online presentation)
    Helmholtz Imaging Virtual Conference, 23.09.2021, virtual, Germany

Permalink: https://www.hzdr.de/publications/Publ-33167


Quasi‑1D XY antiferromagnet Sr2Ni(SeO3)2Cl2 at Sakai‑Takahashi phase diagram

Kozlyakova, E. S.; Moskin, A. V.; Berdonosov, P. S.; Gapontsev, V. V.; Streltsov, S. V.; Uhlarz, M.; Spachmann, S.; Elghandour, A.; Klingeler, R.; Vasiliev, A. N.

Abstract

Uniform quasi-one-dimensional integer spin compounds are of interest as a potential realization of the Haldane conjecture of a gapped spin liquid. This phase, however, has to compete with magnetic anisotropy and long-range ordered phases, the implementation of which depends on the ratio of interchain J′ and intrachain J exchange interactions and both uniaxial D and rhombic E single-ion anisotropies. Strontium nickel selenite chloride, Sr2Ni(SeO3)2Cl2, is a spin-1 chain system which passes through a correlations regime at Tmax ~ 12 K to long-range order at TN = 6 K. Under external magnetic field it experiences the sequence of spin-flop at Bc1 = 9.0 T and spin-flip transitions Bc2 = 23.7 T prior to full saturation at Bsat = 31.0 T. Density functional theory provides values of the main exchange interactions and uniaxial anisotropy which corroborate the experimental findings. The values of J′/J = 0.083 and D/J = 0.357 place this compound into a hitherto unoccupied sector of the Sakai-Takahashi phase diagram.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-33164


THEREDA - Thermodynamic Reference Database

Gaona, X.; Bok, F.; Freyer, D.; Moog, H. C.; Wissmeier, L.

Abstract

Part of the process to ensure the safety of radioactive waste disposal is the predictive modelling of the solubility of all relevant toxic components in a complex aqueous solution. To ensure the reliability of thermodynamic equilibrium modelling as well as to facilitate the comparison of such calculations done by different institutions it is necessary to create a mutually accepted thermodynamic reference database. To meet this demand several institutions in Germany joined efforts and created THEREDA [1].

THEREDA is a suite of programs at the base of which resides a relational databank. Special emphasis is put on thermodynamic data along with suitable Pitzer coefficients, which allow for the calculation of solubilities in high-saline solutions. Registered users may either view single thermodynamic data and Pitzer interaction parameters or download ready-to-use parameter files for the geochemical speciation codes PHREEQC, Geochemist’s Workbench, CHEMAPP, or TOUGHREACT. The dataset can also be downloaded in a generic JSON-format to allow the import into other codes. The database can be accessed via the World Wide Web: www.thereda.de

Prior to release, the released part of the database is subjected to many tests. Results are compared to results from earlier releases and among the different codes. This is to ensure that by additions of new and modification of existing data no adverse side effects on calculations are caused. Furthermore, our website offers an in-creasing number of examples for applications, including graphical representation, which can be filtered by com-ponents of the calculated system.

REFERENCES
[1] Moog, H. C., Bok, F., Marquardt, C. M., and Brendler, V.: Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem., 55, 72-84, 2015

Keywords: THEREDA; Thermodynamic Reference Database; Solubility; Modelling; Pitzer

  • Poster (Online presentation)
    Processes Influencing Radionuclide Transport and Retention - Investigations Across Scales (TransRet2020), 12.-13.10.2021, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33162


Effects of hydrogen absorption on magnetism in Ni80Fe20/Y/Pd trilayers

Weiss, C.; Hübner, R.; Saunders, M.; Semisalova, A.; Ehrler, J.; Schmidt, N.; Seyd, J.; Albrecht, M.; Anwar, S.; Lindner, J.; Potzger, K.; Kostylev, M.

Abstract

The effects of hydrogen absorption on the effective magnetization (4πMeff), gyromagnetic ratio (γ), Gilbert damping constant (αG), and the inhomogeneous linewidth broadening in Py(x)/Y(16 nm)/Pd(15 nm) trilayer films (x = 2, 3, 5, 8, 10, 20, 40 nm) were investigated with ferromagnetic resonance (FMR), transmission electron microscopy, and vibrating sample magnetometry. In the presence of a hydrogen atmosphere, the samples show a reduction of their FMR linewidth which is found to stem purely from a reduction of the inhomogeneous linewidth broadening. This is attributed to a rearrangement of atoms at the Py/Y interface in the presence of hydrogen, making the Py/Y interface more homogeneous. In addition, a reduction of 4πMeff was seen for all samples in the hydrogen atmosphere which is typical for an increase of the interfacial perpendicular magnetic anisotropy at the Py/Y interface.

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-33161


Trident process in laser pulses

Dinu, V.; Torgrimsson, G.

Abstract

We study the trident process in laser pulses. We provide exact numerical results for all contributions, including the difficult exchange term. We show that all terms are in general important for a short pulse. For a long pulse, we identify a term that gives the dominant contribution even if the intensity is only moderately high, a0≳1, which is an experimentally important regime where the standard locally constant field (LCF) approximation cannot be used. We show that the spectrum has a richer structure at a0∼1, compared to the LCF regime a0≫1. We study the convergence to LCF as a0 increases and how this convergence depends on the momentum of the initial electron. We also identify the terms that dominate at high energy.

Permalink: https://www.hzdr.de/publications/Publ-33160


Large linear non-saturating magnetoresistance and high mobility in ferromagnetic MnBi

He, Y.; Gayles, J.; Yao, M.; Helm, T.; Reimann, T.; Strocov, V. N.; Schnelle, W.; Nicklas, M.; Sun, Y.; Fecher, G. H.; Felser, C.

Abstract

A large non-saturating magnetoresistance has been observed in several nonmagnetic topological Weyl semi-metals with high mobility of charge carriers at the Fermi energy. However, ferromagnetic systems rarely display a large magnetoresistance because of localized electrons in heavy d bands with a low Fermi velocity. Here, we report a large linear non-saturating magnetoresistance and high mobility in ferromagnetic MnBi. MnBi, unlike conventional ferromagnets, exhibits a large linear non-saturating magnetoresistance of 5000% under a pulsed field of 70 T. The electrons and holes’ mobilities are both 5000 cm2V−1s−1 at 2 K, which are one of the highest for ferromagnetic materials. These phenomena are due to the spin-polarised Bi 6p band’s sharp dispersion with a small effective mass. Our study provides an approach to achieve high mobility in ferromagnetic systems with a high Curie temperature, which is advantageous for topological spintronics.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-33159


Approximating higher-order nonlinear QED processes with first-order building blocks

Dinu, V.; Torgrimsson, G.

Abstract

Higher-order tree-level processes in strong laser fields, i.e., cascades, are in general extremely difficult to calculate, but in some regimes the dominant contribution comes from a sequence of first-order processes, i.e., nonlinear Compton scattering and nonlinear Breit-Wheeler pair production. At high intensity the field can be treated as locally constant, which is the basis for standard particle-in-cell codes. However, the locally-constant-field (LCF) approximation and these particle-in-cell codes cannot be used when the intensity is only moderately high, which is a regime that is experimentally relevant. We have shown that one can still use a sequence of first-order processes to estimate higher orders at moderate intensities provided the field is sufficiently long. An important aspect of our new “gluing” approach is the role of the spin and polarization of intermediate particles, which is more nontrivial compared to the LCF regime.

Permalink: https://www.hzdr.de/publications/Publ-33158


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