Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

35814 Publications

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

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

raw data and processed data for the publication.

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

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-10-18
    DOI: 10.14278/rodare.1211

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


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

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

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

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-12-31
    DOI: 10.14278/rodare.1209
    License: CC-BY-4.0
    Embargo: 31.12.2022

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


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

Wulf, T.

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

for publication

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

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

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-09-16
    DOI: 10.14278/rodare.1207
    License: CC-BY-4.0

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


alpaka-group/alpaka: alpaka 0.7.0: Maximum Warp

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

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

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

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


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

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

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

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

  • Lecture (Conference) (Online presentation)
    10TH WORLD CONGRESS ON INDUSTRIAL PROCESS TOMOGRAPHY, 13.09.2021, Tianjin, China

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


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

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

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

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  • Secondary publication expected

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


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

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

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

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


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

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

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

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

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

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


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

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

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

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

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

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


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

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

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

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

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

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


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

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

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

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

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

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


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

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

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

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


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

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

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

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

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


HSQ-based process to integrate vertical nanoscale devices

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

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

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

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

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


Coupling of atomic states to particle in cell simulations

Marre, B. E.

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

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

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-10-07
    DOI: 10.14278/rodare.1202
    License: CC-BY-4.0

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


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

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

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

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


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

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

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

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


Optical Readout of the Néel Vector in the Metallic Antiferromagnet Mn2Au

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

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

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


MoP3SiO11: A 4d3 honeycomb antiferromagnet with disconnected octahedra

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

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

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


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

Hampel, U.

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

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

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

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


Fast tomographic imaging of multiphase flow

Hampel, U.

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

Keywords: multiphase flows; computed tomography; imaging

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

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


UMB-II: 2nd video conference workshop

Matschiavelli, N.

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

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

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


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

Mayordomo, N.

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

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

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

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

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


Technetium immobilization by chloride green rust

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

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

Keywords: Technetium; Reductive immobilization; Sorption; LDH

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

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


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

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

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

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

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

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


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

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

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

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

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

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


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

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

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

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

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-10-05
    DOI: 10.14278/rodare.1200

Downloads:

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


Künstliche Intelligenz im Gesundheitswesen

Steinbach, P.

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

Keywords: KI; Medizin; Gesundheitswesen; Maschinelles Lernen

Downloads:

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


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

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

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

Prerequesites

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

Python: 3.8.6

Scholarly: 1.2.0

Pyzotero: 1.4.24

Numpy: 1.20.1

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.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-10-01
    DOI: 10.14278/rodare.1196
    License: CC-BY-4.0

Downloads:

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

Proceedings of Machine Learning Research

Keywords: teaching; machine learning; ECML/PKDD 2020

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

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


Machine Learning for Accelerator Physics and Engineering

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

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
Publ.-Id: 33192


Predicting the shoe size of workshop participants

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

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
Publ.-Id: 33191


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

Steinbach, P.; Schmerler, S.

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
Publ.-Id: 33190


Publishing the (PaN) Experiment

Knodel, O.

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
Publ.-Id: 33189


Demonstrator for using e-learning platforms for PaN

Knodel, O.; Konrad, U.

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
Publ.-Id: 33188


Using of light and heavy ion beams in modern FIBs

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

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

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

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


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

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

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

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

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


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

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

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

  • Book chapter
    in: Sustainable Material Solutions for Solar Energy Technologies - Processing Techniques and Applications, Amsterdam: Elsevier, 2021, 978-0-12-821592-0, 383-427
    DOI: 10.1016/B978-0-12-821592-0.00011-X

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


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.

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
Publ.-Id: 33176


Neural Solvers

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

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

  • Software in the HZDR data repository RODARE
    Publication date: 2021-09-06
    DOI: 10.14278/rodare.1193
    License: CC-BY-1.0

Downloads:

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


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

Lorenz, S.

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

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


Targeted mapping using self-organizing drone swarms

Lorenz, S.

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
Publ.-Id: 33168


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

Lorenz, S.

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
Publ.-Id: 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.

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.

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


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.

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.

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


Trident process in laser pulses

Dinu, V.; Torgrimsson, G.

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
Publ.-Id: 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.

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.

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


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

Dinu, V.; Torgrimsson, G.

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
Publ.-Id: 33158


The High Energy Density Scientific Instrument at the European XFEL

Zastrau, U.; Appel, K.; Bähtz, C.; Bähr, O.; Batchelor, L.; Berghäuser, A.; Banjafar, M.; Brambrink, E.; Cerantola, V.; Cowan, T.; Damker, H.; Dittrich, S.; Di Dio Cafiso, S. D.; Dreyer, J.; Engel, H.-O.; Feldmann, T.; Findeisen, S.; Foese, M.; Fulla-Marsa, D.; Göde, S.; Hassan, M. K. Y.; Hauser, J.; Herrmannsdörfer, T.; Höppner, H.; Kaa, J.; Kaever, P.; Knöfel, K.; Konopkova, Z.; Laso García, A.; Liermann, H.-P.; Mainberger, J.; Makita, M.; Martens, E.-C.; McBride, E. E.; Möller, D.; Nakatsutsumi, M.; Pelka, A.; Plueckthun, C.; Prescher, C.; Preston, T. R.; Röper, M.; Schmidt, A.; Seidel, W.; Schwinkendorf, J.-P.; Schoelmerich, M. O.; Schramm, U.; Schropp, A.; Strohm, C.; Sukharnikov, K.; Talkovski, P.; Thorpe, I.; Toncian, M.; Toncian, T.; Wollenweber, L.; Yamamoto, S.; Tschentscher, T.

The European XFEL delivers up to 27000 intense (>1012 photons) pulses per second, of ultrashort (≤50 fs) and transversely coherent X-ray radiation, at a maximum repetition rate of 4.5 MHz. Its unique X-ray beam parameters enable groundbreaking experiments in matter at extreme conditions at the High Energy Density (HED) scientific instrument. The performance of the HED instrument during its first two years of operation, its scientific remit, as well as ongoing installations towards full operation are presented. Scientific goals of HED include the investigation of extreme states of matter created by intense laser pulses, diamond anvil cells, or pulsed magnets, and ultrafast X-ray methods that allow their diagnosis using self-amplified spontaneous emission between 5 and 25 keV, coupled with X-ray monochromators and optional seeded beam operation. The HED instrument provides two target chambers, X-ray spectrometers for emission and scattering, X-ray detectors, and a timing tool to correct for residual timing jitter between laser and X-ray pulses.

Permalink: https://www.hzdr.de/publications/Publ-33157
Publ.-Id: 33157


Nonlinear trident in the high-energy limit: Nonlocality, Coulomb field and resummations

Torgrimsson, G.

We study nonlinear trident in laser pulses in the high-energy limit, where the initial electron experiences, in its rest frame, an electromagnetic field strength above Schwinger’s critical field. At lower energies the dominant contribution comes from the “two-step” part, but in the high-energy limit the dominant contribution comes instead from the one-step term. We obtain new approximations that explain the relation between the high-energy limit of trident and pair production by a Coulomb field, as well as the role of the Weizsäcker-Williams approximation and why it does not agree with the high-χ limit of the locally-constant-field approximation. We also show that the next-to-leading order in the large-a0 expansion is, in the high-energy limit, nonlocal and is numerically very important even for quite large a0. We show that the small-a0 perturbation series has a finite radius of convergence, but using Padé-conformal methods we obtain resummations that go beyond the radius of convergence and have a large numerical overlap with the large-a0 approximation. We use Borel-Padé-conformal methods to resum the small-χ expansion and obtain a high precision up to very large χ. We also use newer resummation methods based on hypergeometric/Meijer-G and confluent hypergeometric functions.

Permalink: https://www.hzdr.de/publications/Publ-33156
Publ.-Id: 33156


Nonlinear photon trident versus double Compton scattering and resummation of one-step terms

Torgrimsson, G.

We study the photon trident process, where an initial photon turns into an electron-positron pair and a final photon under a nonlinear interaction with a strong plane-wave background field. We show that this process is very similar to double Compton scattering, where an electron interacts with the background field and emits two photons. We also show how the one-step terms can be obtained by resumming the small- and large-\chiχ expansions. We consider a couple of different resummation methods, and also propose new resummations (involving Meijer-G functions) which have the correct type of expansions at both small and large \chiχ. These new resummations require relatively few terms to give good precision.

Permalink: https://www.hzdr.de/publications/Publ-33155
Publ.-Id: 33155


Loops and polarization in strong-field QED

Torgrimsson, G.

In a previous paper we showed how higher-order strong-field-QED processes in long laser pulses can be approximated by multiplying sequences of ‘strong-field Mueller matrices’. We obtained expressions that are valid for arbitrary field shape and polarization. In this paper we derive practical approximations of these Mueller matrices in the locally-constant- and the locally-monochromatic-field regimes. The spin and polarization can also change due to loop contributions (the mass operator for electrons and the polarization operator for photons). We derive Mueller matrices for these as well, for arbitrary laser polarization and arbitrarily polarized initial and final particles.

Permalink: https://www.hzdr.de/publications/Publ-33154
Publ.-Id: 33154


Resummation of Quantum Radiation Reaction in Plane Waves

Torgrimsson, G.

We propose a new approach to obtain the momentum expectation value of an electron in a high-intensity laser, including multiple photon emissions and loops. We find a recursive formula that allows us to obtain the O(αn) term from O(αn-1), which can also be expressed as an integro-differential equation. In the classical limit we obtain the solution to the Landau-Lifshitz equation to all orders. We show how spin-dependent quantum radiation reaction can be obtained by resumming both the energy expansion as well as the α expansion.

Permalink: https://www.hzdr.de/publications/Publ-33153
Publ.-Id: 33153


Resummation of quantum radiation reaction and induced polarization

Torgrimsson, G.

In a previous paper we proposed a new method based on resummations for studying radiation reaction of an electron in a plane-wave electromagnetic field. In this paper we use this method to study the electron momentum expectation value for a circularly polarized monochromatic field with a0=1, for which standard locally constant-field methods cannot be used. We also find that radiation reaction has a significant effect on the induced polarization, as compared to the results without radiation reaction, i.e., the Sokolov-Ternov formula for a constant field, or the zero result for a circularly monochromatic field. We also study the Abraham-Lorentz-Dirac equation using Borel-Padé resummations.

Permalink: https://www.hzdr.de/publications/Publ-33152
Publ.-Id: 33152


High-field soft-x-ray dichroism of a hard ferrimagnet with easy-plane anisotropy

Yamamoto, S.; Gorbunov, D.; Diaz-Ortega, I. F.; Miyata, A.; Kihara, T.; Kotani, Y.; Nakamura, T.; Mushnikov, N. V.; Andreev, A. V.; Nojiri, H.; Wosnitza, J.

We performed soft x-ray spectroscopic studies of the ferrimagnet TbFe5Al7 with strong easy-plane anisotropy in pulsed magnetic fields up to 29 T along with bulk magnetization and magnetostriction measurements. We observed pronounced amplitude changes of x-ray magnetic circular dichroism and x-ray absorption spectra at the field-induced magnetic transition. This microscopically evidences the simultaneous rotation of the Tb 4 f and Fe 3d magnetic moments from a collinear ferrimagnetic order along the [100] axis to a state with the moments close to [010], the other easy-axis direction of the tetragonal lattice in magnetic fields applied along the [100] axis. We determined the magnetic-anisotropy constant of TbFe5Al7 by simulating the high-field macro- and microscopic magnetization process using a two-sublattice model.

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Permalink: https://www.hzdr.de/publications/Publ-33151
Publ.-Id: 33151


Neutron diffraction of field-induced magnon condensation in the spin-dimerized antiferromagnet Sr3Cr2O8

Gazizulina, A.; Quintero-Castro, D. L.; Wang, Z.; Duc, F.; Bourdarot, F.; Prokes, K.; Schmidt, W.; Daou, R.; Zherlitsyn, S.; Islam, N.; Kolnes, N. H.; Kademane, A. B.; Schilling, A.; Lake, B.

In this work, we investigate the evolution and settling of magnon condensation in the spin-1/2 dimer system Sr3Cr2O8 using a combination of magnetostriction in pulsed fields and inelastic neutron scattering in a continuous magnetic field. The magnetic structure in the Bose-Einstein condensation phase was probed by neutron diffraction in pulsed magnetic fields up to 39 T. The magnetic structure in this phase was confirmed to be an XY-antiferromagnetic structure validated by irreducible representational analysis. The magnetic phase diagram as a function of an applied magnetic field for this system is presented. Furthermore, zero-field neutron diffraction results indicate that dimerization plays an important role in stabilizing the low-temperature crystal structure.

Permalink: https://www.hzdr.de/publications/Publ-33150
Publ.-Id: 33150


Drastic reduction of the R-Fe exchange in interstitially modified (Nd, Ho)2Fe14B compounds probed by megagauss magnetic fields

Kostyuchenko, N. V.; Tereshina, I. S.; Tereshina-Chitrova, E. A.; Ivanov, L. A.; Paukov, M.; Gorbunov, D.; Andreev, A. V.; Doerr, M.; Politova, G. A.; Zvezdin, A. K.; Veselova, S. V.; Pyatakov, A. P.; Miyata, A.; Drachenko, O.; Portugall, O.

In this paper, the full magnetization process demonstrated by the series of ferrimagnetic intermetallic compounds (Nd, Ho)2Fe14B and Ho2FeB and their hydrides with the maximum possible hydrogen content (for the given crystal structure type) is studied theoretically and experimentally using megagauss magnetic fields. We observe field-induced phase transitions from the initial ferrimagnetic to the forced-ferromagnetic state in magnetic fields up to 130 T and describe the magnetization process analytically.We find a drastic decrease of the critical transition fields in the hydrogenated compounds. This is due to extremely strong, nearly twofold reduction of the R-Fe intersublattice exchange interaction because of the combined substitution and hydrogenation effects. A comparative analysis of the magnetization behavior for the system Ho2Fe17-H is also performed.

Permalink: https://www.hzdr.de/publications/Publ-33149
Publ.-Id: 33149


Highly sensitive band structure of the Stoner-enhanced Pauli paramagnet SrCo2P2

Götze, K.; Kraft, I.; Klotz, J.; Förster, T.; Uhlarz, M.; Lorenz, V.; Bergmann, C.; Prots, Y.; Bruin, J. A. N.; McCollam, A.; Sheikin, I.; Wosnitza, J.; Geibel, C.; Rosner, H.

The compound SrCo2P2 is a Pauli paramagnet very close to ferromagnetic order. To study its electronic structure in close vicinity to the Fermi level, we report measurements of the de Haas–van Alphen effect in magnetic fields up to 35 T in combination with density-functional-theory band-structure calculations in different approximations. The resulting electronic band structure not only depends significantly on the choice of the functional, but also crucially on the exact values of the structural parameters that have been determined at low temperatures by synchrotron x-ray diffraction. We find the best correspondence between the measured and the calculated de Haas–van Alphen frequencies for the general gradient approximation functional and the structural parameters that were determined at 10 K. Although SrCo2P2 crystallizes in the uncollapsed tetragonal structure with a large P-P distance between the CoP2 layers, we observe a rather three-dimensional Fermi-surface topology. We obtain a mass-enhancement factor of about 2 deduced from the ratio between experimental and calculated quasiparticle masses. The temperature dependence of the structural parameters leads to a significant reduction of the electronic density of states at the Fermi level and in comparison with the measured Sommerfeld coefficient to an overall mass renormalization in line with our experiment.

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Permalink: https://www.hzdr.de/publications/Publ-33148
Publ.-Id: 33148


Multiple field-induced phases in the frustrated triangular magnet Cs3Fe2Br9

Brüning, D.; Fröhlich, T.; Gorkov, D.; Cisarova, I.; Scurschii, I.; Rossi, L.; Bryant, B.; Wiedmann, S.; Meven, M.; Ushakov, A.; Streltsov, S. V.; Khomskii, D.; Becker, P.; Bohatý, L.; Braden, M.; Lorenz, T.

The recently discovered material Cs3Fe2Br9 contains Fe2Br9 bi-octahedra forming triangular layers with hexagonal stacking along the c axis. In contrast to isostructural Cr-based compounds, the zero-field ground state is not a nonmagnetic S = 0 singlet-dimer state. Instead, the Fe2Br9 bi-octahedra host semiclassical S = 5/2 Fe3+ spins with a pronounced easy-axis anisotropy along c, and interestingly, the intradimer spins are ordered ferromagnetically. The high degree of magnetic frustration due to (various) competing intradimer and interdimer couplings leads to a surprisingly rich magnetic phase diagram. The zero-field ground state is already reached via an intermediate phase, and the high-field magnetization and thermal expansion data for H ǀǀ c identify 10 different ordered phases. Among them are phases with constant magnetization of 1/3 , respectively 1/2, of the saturation value, and several transitions are strongly hysteretic with pronounced length changes, reflecting strong magnetoelastic coupling.

Permalink: https://www.hzdr.de/publications/Publ-33147
Publ.-Id: 33147


Folding of laser-cut templates with plasmonic functionalized surfaces into micro cubes

Lorenz, P.; Yu, Y.; Franz, R.; Petersen, C.; Zajadacz, J.; Ehrhardt, M.; Lecrivain, G.; Kirchner, R.; Zimmer, K.

Functional 3D microstructures offer enhanced functionalities but need specific fabrication schemas. One approach is (self) folding of planar structures that enable to apply traditional microelectronic-based fabrication schemas and allows the cost-effective fabrication of such 3D microstructures. Following this approach we combined templating lithographic techniques for plasmonic gold patterns with laser patterning and subsequent folding of the planar structures. Hence, the nanopattern design and the cut out shape can be separated and optimized independently. The micro cubes were realized in polyimide foil which was attached to a wafer for patterning the plasmonic structures. Thereafter the laser patterning and the folding procedure follows. Two different folding concepts was studied: suction and water droplet supported folding.

  • Poster
    Micro and Nano Engineering Conference, 20.-23.09.2021, Turin, Italy

Permalink: https://www.hzdr.de/publications/Publ-33146
Publ.-Id: 33146


Übertragung von SARS Coronaviren über die Luft – Von der Grundlagenforschung zu effizienten Luftreinigungssystemen

Lecrivain, G.; Hampel, U.

Neben Tröpfchen- und Schmierinfektion ist der nach derzeitiger Kenntnis effektivste Übertragungsweg des Corona-Virus der Aerosoltransport. Diese Formen der Übertragung führen leicht zu sogenannten Superspreading-Ereignissen. Solange keine wirksamen Impfstoffe verfügbar sind, sind strenge Hygieneregeln, wie das Tragen von Masken, Abstandhalten, häufiges Reinigen und Desinfizieren von Händen und Oberflächen sowie ausreichendes Lüften von Räumen, einzig wirksame Maßnahmen gegen eine Virenausbreitung. Da der Erfolg solcher Maßnahmen stark vom Faktor Mensch abhängt, ist eine der wesentlichen Erkenntnisse aus dem bisherigen Pandemieverlauf die, dass es dringend notwendig ist, wirksame, sichere und bezahlbare Technologien zur Verhinderung der Virenausbreitung zu entwickeln. Damit können drastische Maßnahmen, wie öffentliche Schließungen und Quarantäne, verhindert werden. Dies gilt nicht nur für die aktuelle, sondern auch für zukünftige Pandemien dieser Art. Das Vorhaben CORAERO der Helmholtz-Gemeinschaft zielt darauf ab, mittels interdisziplinärer wissenschaftlich-technologischer Zusammenarbeit signifikante Beiträge zum Erkenntnisgewinn bezüglich des aerosolgetriebenen Virustransports sowie zur Entwicklung von Technologien für eine effiziente physikalische Virenbekämpfung zu leisten. Es verbindet Wissenschaftler/innen aus der Virologie, der Medizin, der angewandten Physik, der Chemie, der Materialforschung und des Ingenieurwesens, schafft neues Wissen und entwickelt Technologien entlang der Infektionskette von der Aerosolentstehung im Atemweg bis zur effektiven Zerstörung des Virus durch Luftbehandlung in öffentlichen Räumen wie Schulen, Betrieben, Passagierfahrzeugen oder Konzerthallen

Keywords: Corona-Virus; Tröpfchen; Pandemieverlauf; Aerosolentstehung

  • Poster
    13. Dresdner Kolloquium zur Luftreinhaltung, 14.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33145
Publ.-Id: 33145


Magnetic phase diagram, magnetoelastic coupling, and Grüneisen scaling in CoTiO3

Hoffmann, M.; Dey, K.; Werner, J.; Bag, R.; Kaiser, J.; Wadepohl, H.; Scurschii, I.; Abdel-Hafiez, M.; Singh, S.; Klingeler, R.

High-quality single crystals of CoTiO3 are grown and used to elucidate in detail structural and magnetostructural effects by means of high-resolution capacitance dilatometry studies in fields up to 15 T which are complemented by specific heat and magnetization measurements. In addition, we refine the single-crystal structure of the ilmenite (R¯3) phase. At the antiferromagnetic ordering temperature TN pronounced λ-shaped anomaly in the thermal expansion coefficients signals shrinking of both the c and b axes, indicating strong magnetoelastic coupling with uniaxial pressure along c yielding six times larger effect on TN than pressure applied in-plane. The hydrostatic pressure dependency derived by means of Grüneisen analysis amounts to ∂TN/∂ p ≈ 2.7(4) K/GPa. The high-field magnetization studies in static and pulsed magnetic fields up to 60 T along with high-field thermal expansion measurements facilitate in constructing the complete anisotropic magnetic phase diagram of CoTiO3. While the results confirm the presence of significant magnetodielectric coupling, our data show that magnetism drives the observed structural, dielectric, and magnetic changes both in the short-range ordered regime well above TN as well as in the long-range magnetically ordered phase.

Permalink: https://www.hzdr.de/publications/Publ-33144
Publ.-Id: 33144


Evidence of collision-induced effects in particle resuspension

Banari, A.; Henry, C.; Lecrivain, G.

This study addresses the resuspension of microscopic glass particles from a monolayer bed into a turbulent gas flow. With an intermediate surface coverage, here set to about 10 % of the field of view, we report two distinct detachment mechanisms. At relatively low flow velocities, few loosely adhering particles move on the wall to eventually collide with neighboring particles resulting in a clustered resuspension. At higher fluid velocities, mostly individual particles resuspend due to their interaction with the turbulent flow. The resuspension curve, showing the remaining particle fraction as a function of the flow velocity, exhibits a strong bimodal character, that has not been reported so far.

Keywords: Multiphase flow; Particle resuspension; Collision-propagation

  • Lecture (Conference)
    35th French Aerosol Congress, 26.-27.01.2022, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-33143
Publ.-Id: 33143


Sputter yields of rough surfaces: Importance of the mean surface inclination angle from nano- to microscopic rough regimes

Cupak, C.; Szabo, P. S.; Biber, H.; Stadlmayr, R.; Grave, C.; Fellinger, M.; Brötzner, J.; Wilhelm, R. A.; Möller, W.; Mutzke, A.; Moro, M. V.; Aumayr, F.

The roughness of a surface is known to have a strong influence on the sputtering process. Commonly used 1D Monte Carlo codes for calculating sputter yields show good agreement with experimental data only for comparably flat surfaces, whereas local ion incidence angles, shadowing and redeposition influence the sputter yields in both magnitude and angular dependence on rough surfaces. In the present work, we therefore investigated tungsten samples of largely different roughness, characterised by atomic force and confocal microscopy. A highly sensitive quartz crystal microbalance was used to determine sputter yields during ion irradiation. Low ion fluences were applied to ensure that the surface morphology did not change during irradiation. The results were used to benchmark our new ray-tracing simulation code SPRAY, which can take microscopy images without limitations in size as input. SPRAY was furthermore applied to perform systematic simulations for artificially roughened and computer-generated surfaces. A clear result was that the governing parameter for description of the sputtering behaviour is the mean value of the surface inclination angle distribution, rather than the commonly used root mean square roughness. Our simulations show that this parameter is universally applicable for a wide range of different surface structures.

Keywords: Quartz crystal microbalance; Sputtering; Sputtering simulation; Surface roughness; Tungsten

Permalink: https://www.hzdr.de/publications/Publ-33142
Publ.-Id: 33142


Berechnungsverfahren für Zweiphasenströmungen

Höhne, T.

Two-phase flows occur in many industrial relevant processes in
power plants,
chemical engineering,
oil and gas industries and others.

Reliable predictions of the flow characteristics are important for the design of the facilities, the optimization of processes and safety analyses.

Experimental results are often hardly transferable to modified geometries, flow condition or scales.

need for reliable numerical simulations
In general fluid flow is 3D Computation Fluid Dynamics - CFD

Keywords: CFD; Multiphase flow; AIAD; GENTOP

  • Invited lecture (Conferences) (Online presentation)
    Numerische Methoden in der Lebensmitteltechnologie, Biotechnologie und chemischen Verfahrenstechnik, 27.-29.09.2021, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33138
Publ.-Id: 33138


Data publication: Effects of surface roughness and mineralogy on the sorption of Cm(III) on crystalline rock

Demnitz, M.; Molodtsov, K.; Schymura, S.; Schierz, A.; Müller, K.; Jankovsky, F.; Havlova, V.; Stumpf, T.; Schmidt, M.

In the following we have compiled the data used in publication (mappings, taken pictures and measurements) as well as the used python scripts.

Keywords: curium; luminescence; crystalline rock; granite; sorption; correlative spectroscopy

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-09-21
    DOI: 10.14278/rodare.1190
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33137
Publ.-Id: 33137


Tungsten Oxide/Reduced Graphene Oxide Aerogel with Low-Content Platinum as High-Performance Electrocatalyst for Hydrogen Evolution Reaction

Li, Y.; Jiang, K.; Yang, J.; Zheng, Y.; Hübner, R.; Ou, Z.; Dong, X.; He, L.; Wang, H.; Li, J.; Sun, Y.; Lu, X.; Zhuang, X.; Zheng, Z.; Liu, W.

Designing cost-effective, highly active, and durable platinum (Pt)-based electrocatalysts is a crucial endeavor in electrochemical hydrogen evolution
reaction (HER). Herein, the low-content Pt (0.8 wt%)/tungsten oxide/reduced graphene oxide aerogel (LPWGA) electrocatalyst with excellent HER activity and durability is developed by employing a tungsten oxide/reduced graphene oxide aerogel (WGA) obtained from a facile solvothermal process as a support, followed by electrochemical deposition of Pt nanoparticles. The WGA support with abundant oxygen vacancies and hierarchical pores plays the roles of anchoring the Pt nanoparticles, supplying continuous mass transport and electron transfer channels, and modulating the surface electronic state of Pt, which endow the LPWGA with both high HER activity and durability. Even under a low loading of 0.81 μgPt cm-2, the LPWGA exhibits a high HER activity with an overpotential of 42 mV at 10 mA cm-2, an excellent stability under 10000-cycle cyclic voltammetry and 40 h chronopotentiometry at 10 mA cm-2, a low Tafel slope (30 mV dec-1), and a high turnover frequency of 29.05 s-1 at η = 50 mV, which is much superior to the commercial Pt/C and the low-content Pt/reduced graphene oxide aerogel. This work provides a new strategy to design high-performance Pt-based electrocatalysts with greatly reduced use of Pt.

Permalink: https://www.hzdr.de/publications/Publ-33133
Publ.-Id: 33133


Development and preliminary evaluation of [18F]JHU94620-d8 for PET imaging of cannabinoid receptors type 2

Moldovan, R. P.

The development PET radioligands for imaging of the cannabinoid type 2 receptors (CB2R) has been intensively explored due to their upregulation in various pathological conditions [1]. Recently, we reported the development of [18F]JHU94620 [2], however, this radioligand suffered from low metabolic stability in vivo. Here, we describe the development of the deuterated analogues [18F]JHU94620-d4 and -d8 as well as their biological evaluation (Figure 1). The precursors for radiofluorination were obtained by coupling 4,5-dimethylthiazol-ylidene-2,2,3,3-tetramethylcyclopropane-1-carboxamide with either d4 or d8 1,4-butanediol-bistosylate and radiofluorinated in the presence of Kryptand K2.2.2. and K2CO3. [18F]JHU94620-d4 and -d8 were obtained in 10% radiochemical yield and >99% radiochemical purity. The fraction of radiometabolites was quantified in mice plasma, brain and spleen of CD1 mice at 30 min p.i. Both [18F]JHU94620-d4 and -d8 demonstrated an improved metabolic stability with 80% intact radioligand detected in the brain vs. 36% for [18F]JHU94620. The CB2 affinity and specificity of [18F]JHU94620-d8 was determined by in vitro binding experiments and a KD(rCB2) of 0.36 nM was determined. Additionally, we evaluated the [18F]JHU94620-d8 uptake by PET-studies into the spleen of healthy rats and in a rat model carrying an adeno-associated viral (AAV2/7) vector expressing hCB2R(D80N) at high densities in the right striatum (hCB2-rs) [3, 4]. Our PET study with [18F]JHU94620-d8 revealed a rCB2 specific uptake into the spleen (AUC0-30min = 33 vs. 17 SUV min after blocking with GW405833). In the hCB2-rs model we could show a target specific uptake of [18F]JHU94620-d8 with a constant SUV of 6.7±0.3 from 6 to 60 min p.i. and an SUVr (right striatum-to-cerebellum) of 43±7at 60 min p.i., as well as a reversible binding in displacement studies. Thus, [18F]JHU94620-d8 is a new PET tracer with improved metabolic stability and excellent ability to image the CB2 receptors in-vivo. Its further evaluation is underway.

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    DPhG Annual Meeting 2021 Trends and Perspectives in Pharmaceutical Sciences, 30.09.2021, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-33132
Publ.-Id: 33132


Instantaneous Frequency representation used for CPA laser simulation

Oksenhendler, T.; Bock, S.; Schramm, U.

We present a novel intuitive graphical method for the simulation of non-linear effects on stretched pulses characterized by a large time-bandwidth product. By way of example, it allows precise determination of effects occurring in CPA (chirped pulse amplification) laser chains, such as the pre-pulse generation by the non-linear Kerr effect. This method is not limited to first order dispersion and can handle all resulting distortions of the generated pre-pulse.

Keywords: ultra-short laser pulses; laser pulse contrast; high-power laser

Permalink: https://www.hzdr.de/publications/Publ-33130
Publ.-Id: 33130


Tests of the detector system for the Stopping Target Monitor of the MU2E experiment in a high flux pulsed gamma beam

Alvarez, C.; Chen, J.; Edmonds, A.; Ferrari, A.; Huang, S.; Keshavarzi, A.; Knodel, O.; Koltick, D.; Lancaster, M.; Miller, J. P.; Müller, S.; Popp, J. L.; Rachamin, R.; Simic, M.; Tickle, S.; Ufer, R.; Voigt, M.

This dataset contains data generated with LaBr and Nal detector (DSPEC and oszilloscope data) at the gELBE beam. The gELBE pulsed gamma beam to test the detector system for the Stopping Target Monitor of the MU2E experiment. The gELBE pulsed gamma beam with narrow pulses set to about 600 kHz repetition rate - the choice of the ELBE CW mode with micropulses at 406 kHz or 812.5 kHz is ideal in our case- is the unique facility in the world suited to study the performance of the Stopping Target Monitor detector of the Mu2e Experiment. The STM monitor has the crucial role to normalize the charged lepton flavor muon conversion rate in the Mu2e experiment. The ability to operate at high rate in presence of background is crucial. We have at ELBE the unique possibility to validate the final methodology that will be employed by the STM detector.

Keywords: dataset; detector; Stopping Target Monitor (STM); MU2E; gELBE; Data Management; DAQ; muon conversion

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-09-20
    DOI: 10.14278/rodare.1188

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Permalink: https://www.hzdr.de/publications/Publ-33129
Publ.-Id: 33129


Synthesis and Pharmacological Evaluation of 1,8-Naphythyridin-2(1H)-one-3-carboxamides Derivatives as Cannabinoid Receptor Type 2 (CB2R) Ligands

Kaur, S.

The primary aim of the present work was to develop fluorinated containing CB2R
ligands based on the lead compound 26 (Figure 10), reported by Lucchesi et al. with
a binding affinity of Ki(CB2R)< 0.67 nM and Ki(CB1R)>5140 nM [91]. Although the
lead compound 26 had a remarkable binding activity it has rather unfavorable
pharmacological properties (cLogP = 4.99 and MW = 459.52 g/mol). Most of the
compounds with cLogP>5 and MW >500 g/mol have poor absorption due to low
solubility and are also unable to cross BBB resulting in poor pharmacokinetics.
Therefore, this master thesis was aimed to synthesize new derivatives based on the
lead compound 26 with modifications to retain or further increase the CB2R binding
affinity and selectivity and improve the pharmacological properties by introducing
substituents containing electronegative atom (fluoro pyridine, fluoro alkoxy, etc) to
make them more polar and thereby also reducing their molecular weight. In general,
the research work was primarily aimed to variously functionalize at N-1 position. In
addition, the newly derivatized compounds should contain a fluorine atom at a
position that allows a facile incorporation of the 18F-label. The cLogP of the planned
derivatives was calculated (ChemDraw 19.0 software) to analyze the effect of
various substituents on the lipophilicity. The substitution of furyl group with a Br at
C-6 position was aimed to increase the hydrophilicity of the lead compound 26
leading to the bromo substituted derivatives with cLogP < 4.5. In order to further
decrease the lipophilicity of the lead compound (26), the replacement of the pfluorobenzyl
at N-1 position with pyridine (cLogP= 3.57) and alkoxy derivatives
(cLogP= 3.72) was planned to synthesize new derivatives (X= R1: furyl, R2:
fluoropyridine, fluoroalkoxy).

  • Master thesis
    Universität Leipzig, 2021
    Mentor: Prof. Bachmann
    78 Seiten

Permalink: https://www.hzdr.de/publications/Publ-33128
Publ.-Id: 33128


The Relevance of Electronic Perturbations in the Warm Dense Electron Gas

Moldabekov, Z.; Dornheim, T.; Böhme, M.; Vorberger, J.; Cangi, A.

Warm dense matter (WDM) has emerged as one of the frontiers of both experimental and theoretical physics and is challenging traditional concepts of plasma, atomic, and condensed-matter physics. While it has become common practice to model correlated electrons in WDM within the framework of Kohn-Sham density functional theory, quantitative benchmarks of exchange-correlation (XC) functionals under WDM conditions are yet incomplete. Here, we present the first assessment of common XC functionals against exact path-integral Monte Carlo calculations of the harmonically perturbed thermal electron gas. This system is directly related to the numerical modeling of X-Ray scattering experiments on warm dense samples. Our assessment yields the parameter space where common XC functionals are applicable. More importantly, we pinpoint where the tested XC functionals fail when perturbations on the electronic structure are imposed. We indicate the lack of XC functionals that take into account the needs of WDM physics in terms of perturbed electronic structures.

Keywords: density functional theory; quantum monte-carlo; electronic structures; exchange-correlation; warm dense matter

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33126
Publ.-Id: 33126


Terahertz pump-probe of liquid water at 12.3 THz

Novelli, F.; Hoberg, C.; Adams, E. M.; Klopf, J. M.; Havenith, M.

The dynamical complexity of the hydrogen-bonded water network can be investigated with intense Terahertz (THz) spectroscopy, which can drive the liquid into the nonlinear response regime and probe anharmonicity effects. Here we report single-color and polarization-dependent pump-probe experiments at 12.3 THz on liquid water, exciting the librational mode. By comparing results obtained on a static sample and a free-flowing water jet, we are able to disentangle the distinct contributions by thermal, acoustic, and nonlinear optical effects. We show that the transient transmission by the static water layer on a time scale of hundreds of microseconds can be described by thermal (slow) and acoustic (temperature-dependent) effects. In addition, during pump probe overlap we observe an anisotropic nonlinear optical response. This nonlinear signal is more prominent in the liquid jet than in the static cell, where temperature and density perturbations are more pronounced. Our measurements confirm that the THz excitation resonates with the rotationally-damped motion of water molecules, resulting in enhanced transient anisotropy. This model can be used to explain the non-linear response of water in the frequency range between about 1 and 20 THz.

Keywords: Ultrafast Spectroscopy; THz; FEL

Permalink: https://www.hzdr.de/publications/Publ-33125
Publ.-Id: 33125


Ginzburg effect in a dielectric medium with dispersion and dissipation

Lang, S.; Sauerbrey, R.; Schützhold, R.; Unruh, W.

As a quantum analog of Cherenkov radiation, an inertial photon detector moving through a medium with constant refractive index n may perceive the electromagnetic quantum fluctuations as real photons if its velocity v exceeds the medium speed of light c/n. For dispersive Hopfield type media, we find this Ginzburg effect to extend to much lower v because the phase velocity of light is very small near the medium resonance. In this regime, however, dissipation effects become important. Via an extended Hopfield model, we present a consistent treatment of quantum fluctuations in dispersive and dissipative media and derive the Ginzburg effect in such systems. Finally, we propose an experimental test.

Keywords: dielectric media; dispersion and dissipation; quantum vacuum phenomena; Ginzburg effect; inertial atom; spontaneous excitation

Permalink: https://www.hzdr.de/publications/Publ-33124
Publ.-Id: 33124


LDOS/SNAP data for MALA: Aluminium at 298K and 933K

Ellis, J. A.; Fiedler, L.; Popoola, G. A.; Modine, N. A.; Stephens, J. A.; Thompson, A. P.; Cangi, A.; Rajamanickam, S.

LDOS/SNAP data for MALA: Aluminium at 298K and 933K (liquid+solid).

Code development was done jointly by the authors.

The calculations have mainly been performed by:
DFT-MD snapshots / DFT calculations (LDOS data): N. A. Modine (at SNL)

SNAP data generation: A. P. Thompson (at SNL)

Neural network training: J. A. Ellis (ORNL, formerly SNL), G. A. Popoola (SNL), L. Fiedler (HZDR)

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-07-08
    DOI: 10.14278/rodare.1106
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33121
Publ.-Id: 33121


The H2020 McSAFER project: Main goals, technical work program, and status

Sanchez-Espinoza, V. H.; Gabriel, S.; Suikkanen, H.; Telkkä, J.; Valtavirta, V.; Bencik, M.; Kliem, S.; Queral, C.; Farda, A.; Abéeguilée, F.; Smith, P.; van Uffelen, P.; Ammirabile, L.; Seidl, M.; Schneidesch, C.; Grishchenko, D.; Lestani, H.

This paper describes the main objectives, the technical content and the status of the H2020 project entitled “High-performance advanced methods and experimental investigations for the safety evaluation of generic Small Modular Reactors (McSAFER)”. The main pillars of this project is are the combination of safety-relevant thermal hydraulic experiments and numerical simulations of different approaches for safety evaluations of Small Modular Reactors (SMR). It describes the goals and the consortium first. Then, the involved thermal hydraulic test facilities, e.g. COSMOS-H (KIT), HWAT (KTH), and MOTEL (LUT) including the experimental programs. It also outlines the different safety assessment methodologies applied to four different SMR-designs such as the CAREM (CNEA), SMART (KAERI), F-SMR (CEA) and NuScale e.g. the multiscale thermal hydraulic, conventional, low order and high fidelity neutron physical methods applied to demon-strate the inherent safety features of the SMR-core designs under postulated design-basis-accident conditions. Finally, the status of the investigations is shortly discussed followed by the dissemination activities and an outlook.

Keywords: SMR; Multi-physics; Multi-scale; High fidelity; safety evaluation; experiments

Permalink: https://www.hzdr.de/publications/Publ-33120
Publ.-Id: 33120


Data associated with the publication "The relevance of electronic perturbations in the warm dense electron gas"

Moldabekov, Z.; Dornheim, T.; Böhme, M.; Vorberger, J.; Cangi, A.

This repository contains the Kohn-Sham density functional theory (KS-DFT) and path-integral Monte-Carlo (PIMC) data used in the journal publication "The relevance of electronic perturbations in the warm dense electron gas".

Keywords: Density Functional Theory; Path-Integral Monte-Carlo; Electronic Structure Theory

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-09-15
    DOI: 10.14278/rodare.1186
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33115
Publ.-Id: 33115


Verification of the code DYN3D for calculations of neutron flux fluctuations

Viebach, M.; Lange, C.; Kliem, S.; Demaziere, C.; Rohde, U.; Hennig, D.; Hurtado, A.

Insufficiently explained magnitudes and patterns of flux fluctuation observed mainly in KWU PWRs are recently investigated
by various European institutions. Among the numerical tools used to investigate the neutron flux fluctuations is the time-domain
reactor dynamics code DYN3D. As DYN3D and comparable codes have not been developed with the primary intention to simulate
low-amplitude neutron flux fluctuations, their applicability in this field has to be verified.
In order to contribute to the verification of DYN3D for the simulation of neutron flux fluctuations, two special cases of perturbations
of the neutron flux (a localized absorber of variable/oscillatory strength and a travelling oscillatory perturbation) are considered
with DYN3D on the one hand and with the frequency-domain neutron noise tool CORE SIM as well as analytical frequency-domain
approaches, respectively, on the other hand. The obtained results are compared with respect to the distributions of the amplitude and
the phase of the induced neutron flux fluctuations. The comparisons are repeated with varied amplitudes and frequencies of the
perturbation.
The results agree well both qualitatively and quantitatively for each of the conducted calculations. The remaining deviations
between the DYN3D results and the reference results exhibit a dependence on the perturbation magnitude, which is attributed to the
neglect of higher-order terms (linear theory) of the perturbed quantities in the calculation of the reference solutions.

Keywords: neutron noise; deterministic reactor modeling; DYN3D; CORE SIM

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  • Secondary publication expected from 11.10.2022

Permalink: https://www.hzdr.de/publications/Publ-33114
Publ.-Id: 33114


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.

The formation and time dynamics of hydrogen-induced defects in nickel by room temperature aging was investigated by positron annihilation spectroscopy. Low temperature conventional positron annihilation lifetime spectroscopy and positron lifetime measurements using a high-flux positron beam evidenced the formation of a large number of monovacancy-level defects simply by hydrogen addition at room temperature. Low-temperature coincidence Doppler broadening measurements proved that hydrogen was trapped and bound to these vacancies during the hydrogen charge. Room temperature aging, i.e. below the stage III temperature in Ni, and the concomitant hydrogen desorption induced the agglomeration of those monovacancies into large vacancy clusters which remained even after all the hydrogen had desorbed and hydrides had disappeared. These results demonstrated that vacancy-hydrogen complexes were induced in Ni only by hydrogen charging and that hydrogen has a primary role in the formation and stabilization of vacancies even at room temperature.

Keywords: hydrogen; nickel; vacancies; positron annihilation spectroscopy

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33113
Publ.-Id: 33113


Advancement of Mineral Processing Simulation Platforms for the Integration of Water Quality – Process Performance Interactions in Water Management Systems (Raw Data)

Michaux, B.

Files are containing the raw data of the dissertation:

Title: Advancement of Mineral Processing Simulation Platforms for the Integration of Water Quality – Process Performance Interactions in Water Management Systems

Author: M.Sc. Bruno Benjamin Xavier Michaux

Faculty: Faculty of Mechanical, Process and Energy Engineering of the Technische Universität Bergakademie Freiberg

Year: 2021

It contains 3 Excel sheets:

  • One for the flotation kinetics data
  • One for the water composition data in flotation
  • One for the water composition data in the mill.

Furthermore it contains a student report from 2017 which is describing the preparation of the synthetic water by

Miaad Farhan Fadami
Research Intern
miaad.farhanfadami@mail.mcgill.ca

Keywords: Flotation; Mineral Processing; Mining; Water

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-09-14
    DOI: 10.14278/rodare.1184
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33111
Publ.-Id: 33111


SIMS analytics of quartz

Renno, A.

Secondary ion mass spectrometry (SIMS), as a high-precision, spatially resolved analytical method, is an alternative to the standard LA-ICP-MS and EPMA methods of quartz analysis. Quartz, with its "notoriously low" trace element contents, presented a welcome challenge from the beginning of the routine application of SIMS methods in mineralogy. In the course of instrument development, there has been an increasingly intensive instrumental differentiation of SIMS instruments. Today, it is possible to analyze almost all naturally occurring elements (H-U), isotope ratios as well as molecular ions and molecular fragments with resolutions from the millimeter to the nanometer range using SIMS. In principle, this allows its use in solving a variety of scientific problems closely related to quartz. Examples are the clarification of crystallochemical questions of the incorporation of different ions into the quartz lattice, questions of element diffusion (e.g. Li, Ti or H) in quartz, the determination of causes for certain spectroscopic features (e.g. CL or EPR), the reconstruction of formation conditions via isotope ratios (O, Si, Li or H), the application of geothermometers (e.g. TitaniQ), the mechanical behavior of quartz as a function of hydrogen content, provenance analyses for natural rocks but also archaeological artifacts, exploration-related questions for quartz deposits and in particular for deposits in which quartz occurs as a genetic-critical accompanying mineral, up to problems of quality testing and quality assurance of high-purity quartz and the engineering evaluation of processing technologies in particular flotation for quartz extraction.
The main limitation of SIMS is the extreme matrix dependence of secondary ion yield. This requires the use of meticulously characterized reference materials (Audétat et al., 2015). New promising developments in this field will be presented (Nachlas, 2016; Wu et al., 2019).
New instrumental developments such as the positive ion SIMS-SSAMS (Grabowski et al., 2019), the Super-SIMS (Rugel et al., 2016) or SIMS analysis in specially modified helium microscopes (Wirtz et al., 2019) and associated enhanced analytical capabilities of quartz will be presented.

References:

Audétat, A., Garbe-Schönberg, D., Kronz, A., Pettke, T., Rusk, B., Donovan, J.J. and Lowers, H.A. (2015) Characterisation of a Natural Quartz Crystal as a Reference Material for Microanalytical Determination of Ti, Al, Li, Fe, Mn, Ga and Ge. Geostandards and Geoanalytical Research 39, 171-184.
Grabowski, K.S., Groopman, E.E., Rock, B.Y. and Imam, M.A. (2019) Positive ion SIMS-SSAMS for trace analysis of materials. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 455, 158-164.
Nachlas, W.O. (2016) Precise and Accurate Doping of Nanoporous Silica Gel for the Synthesis of Trace Element Microanalytical Reference Materials. Geostandards and Geoanalytical Research 40, 505-516.
Rugel, G., Pavetich, S., Akhmadaliev, S., Baez, S.M.E., Scharf, A., Ziegenrucker, R. and Merchel, S. (2016) The first four years of the AMS-facility DREAMS: Status and developments for more accurate radionuclide data. Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms 370, 94-100.
Wirtz, T., Castro, O.D., Audinot, J.-N. and Philipp, P. (2019) Imaging and Analytics on the Helium Ion Microscope. Annual Review of Analytical Chemistry 12, 523-543.
Wu, H., Böttger, R., Couffignal, F., Gutzmer, J., Krause, J., Munnik, F., Renno, A.D., Hübner, R., Wiedenbeck, M. and Ziegenrücker, R. (2019) ‘Box-Profile’ Ion Implants as Geochemical Reference Materials for Electron Probe Microanalysis and Secondary Ion Mass Spectrometry. Geostandards and Geoanalytical Research 43, 531-541.

Keywords: SIMS; Mineralogy; Geochemistry; Quartz

  • Lecture (Conference)
    QUARTZ2021 - International Symposium on Quartz, 05.-07.09.2021, Tønsberg, Norge

Permalink: https://www.hzdr.de/publications/Publ-33110
Publ.-Id: 33110


Low-level ¹⁶⁶mHo measurements with AMS for the ECHo-project

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

The Electron Capture in ¹⁶³Ho experiment (ECHo) aims at measuring the mass of νe by analysing the EC spectrum of the long-lived radionuclide ¹⁶³Ho (T1/2=4570 a) with a metallic magnetic calorimeter (MMC). For the determination of a reasonable upper limit for the neutrino mass it is mandatory to keep any contamination with the long-lived radionuclide 166mHo nine orders of magnitude below the ¹⁶³Ho content. The ion-implantation of ultra-pure ¹⁶³Ho into a MMC for the experiment is carried out by the RISIKO mass separator. The separation from ¹⁶⁶mHo, however, cannot be quantified to such low levels as needed. Here we present our approach to determine the corresponding low isotopic ratio with accelerator mass spectrometry (AMS). This requires the formation of negative ions, we find the highest negative ion yield for the anion HoO₂. For first tests ¹⁶⁵Ho was implanted by RISIKO in various metal foils and we obtained results for the Ho detection efficieny. This allows for extrapolations for the expected measurement limit of the ¹⁶⁶mHo/¹⁶³Ho ratio.

  • Open Access Logo Lecture (Conference) (Online presentation)
    DPG-Tagung der Sektion Atome, Moleküle, Quantenoptik und Plasmen (SAMOP) virtuell, https://samop21.dpg-tagungen.de, 20.-24.09.2021, Kaiserslautern, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33108
Publ.-Id: 33108


Temperature determination during Flash Lamp Annealing

Begeza, V.; Rebohle, L.; Schumann, T.

Flash lamp annealing (FLA) is a modern technology for the thermal treatment of materials which currently opens up new application areas. During FLA, an intense pulse of light with a pulse duration of milliseconds and below is applied to the surface of a material. In contrast to traditional methods like furnace annealing, temperature now strongly depends on the material properties and the thickness of the sample. In addition, the short time scale leads to a temperature distribution over depth and makes direct temperature measurements very challenging.
In this work we first review in brief the existing possibilities for a direct temperature measurement during FLA. The main part presents our own concept which is a combination of direct measurements, calibration and thermodynamic simulation. The latter point is of special interest as it allows to get information about the temperature distribution within the material, provided that the relevant material parameters are known. Finally, the impact of such temperature distributions on physical processes like diffusion, crystallization and phase formation is discussed.

Keywords: Flash Lamp Annealing; Short time annealing; Temperature determination

  • Invited lecture (Conferences) (Online presentation)
    CERC 2021, 09.-10.09.2021, Cork, Irland

Permalink: https://www.hzdr.de/publications/Publ-33106
Publ.-Id: 33106


Restoring betatron phase coherence in a beam-loaded laser-wakefield accelerator

Köhler, A.; Pausch, R.; Bussmann, M.; Couperus Cabadağ, J. P.; Debus, A.; Krämer, J. M.; Schöbel, S.; Zarini, O.; Schramm, U.; Irman, A.

Matched beam loading in laser wakefield acceleration (LWFA), characterizing the state of flattening the accelerating electric field along the bunch, leads to the minimization of energy spread at high bunch charges. Here, we experimentally demonstrate by independently controlling injected charge and accelerating gradients, using the self-truncated ionization injection scheme, that minimal energy spread coincides with a reduction of the normalized beam divergence. With the simultaneous confirmation of the micrometer-small beam radius at the plasma exit, deduced from betatron radiation spectroscopy, we attribute this effect to the minimization of chromatic betatron decoherence. These findings are supported by rigorous three-dimensional particle-in-cell simulations tracking self-consistently particle trajectories from injection, acceleration until beam extraction to vacuum. We conclude that beam-loaded LWFA enables highest longitudinal and transverse phase space densities.

Keywords: laser-wakefield acceleration; beam loading; beam coherence restoration; beam decoherence; betatron radiation; ionization injection; particle-in-cell simulations

Permalink: https://www.hzdr.de/publications/Publ-33103
Publ.-Id: 33103


Not just a background: pH buffers do interact with lanthanide ions – a Europium(III) case study

Mandal, P.; Kretzschmar, J.; Drobot, B.

The interaction between Eu(III) ion and different pH buffers, popular in biology and biochemistry viz. HEPES, PIPES, MES, MOPS, and TRIS have been studied by solution nuclear magnetic resonance spectroscopy (NMR) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) techniques. The Good’s buffers reveal non-negligible interaction with Eu(III) as determined from their complex stability constants, where the sites of interaction are the morpholine and piperazine nitrogen atoms, respectively. In contrast, TRIS buffer shows practically no affinity towards Eu(III). Therefore, when investigating lanthanides, TRIS buffer should be preferred over Good’s buffers. 

Keywords: Europium; Buffer; TRLFS; NMR; Stability Constant

  • Software in the HZDR data repository RODARE
    Publication date: 2021-09-09
    DOI: 10.14278/rodare.1147
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33100
Publ.-Id: 33100


Raw data related to publication entitled "Turbulent resuspension of micron particles from a wall surface functionalized with cylindrical micropillars" by Banari, A. et al.

Lecrivain, G.
Project Leader: Lecrivain, Gregory

# 'Flowrate.JPG': Table associating a raw image (see 'org' folder below) with the flow rate (Q) in L/min

# 'Rough': raw data obtained with the rough substrate

# 'Smooth': raw data obtained with the smooth substrate

# "Smooth" and "Rough" folders contain a list of subfolders Mi, with i=0,1,2,... the measurement index. Ex: M1: is a first series of measurements and M2: a second series of measurements. Each Mi folder contains the following data:

## 'org': List of pictures (Acquisition_AAA_-BBBBBB.jpg) taken with the high-resolution camera. With AAA=000,001,002,... is the flow rate association. To associate AAA with the flow rate, see 'Flowrate.JPG'. Ex: '000' -> Q = 0 L/min, '001' -> Q = 20 L/min. BBB=000001,000002 or 000003 are pictures of the same particle bed taken at increasing time interval. These 3 pictures are used to check particle bed equilibrium.

## 'pic_CCC.jpg' with CCC=001, 002, 003: simply a copy of the raw picture in 'org' with bed at equilibrium. The association between the index (CCC) and the  flow rate (Q) is identical to that described in 'org' (AAA).

## 'Particles_CCC.csv' with CCC=001, 002, 003: List of particle positions (called tags in the manuscript) in each respective image.

Keywords: Particle resuspension; Particle adhesion; Turbulent gas flow; Surface functionalization; Surface roughness.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-02-01
    DOI: 10.14278/rodare.1145
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33098
Publ.-Id: 33098


Data Publication: Pump-induced terahertz anisotropy in bilayer graphene

Seidl, A.; Anvari, R.; Dignam, M. M.; Richter, P.; Seyller, T.; Schneider, H.; Helm, M.; Winnerl, S.

The raw data and lab book pages are given in the .zip folders. The results of the theoretical calculations in comparison to the experiment are given in Roozbeh_plot.opju. In the other two Origin files, the differential transmission signals and other relevant values are calculated from the raw data.The 2 THz measurement was performed in 2019, the 3.4 THz measurement in 2020.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-08-26
    DOI: 10.14278/rodare.1136

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Permalink: https://www.hzdr.de/publications/Publ-33093
Publ.-Id: 33093


Data publication: Controlled and deterministic creation of synthetic antiferromagnetic domains by focused ion beam irradiation

Samad, F.; Hlawacek, G.; Arekapudi, S. S. P. K.; Xu, X.; Koch, L.; Lenz, M.; Hellwig, O.

This data contains results from magnetometry and magnetic force microscopy from the irradiated synthetic antiferromagnets.

Keywords: Bubble domains; Focused ion beam; Sputter deposition; Interlayer exchange coupling; Magnetic hysteresis

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-09-06
    DOI: 10.14278/rodare.1142
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33091
Publ.-Id: 33091


Controlled and deterministic creation of synthetic antiferromagnetic domains by focused ion beam irradiation

Samad, F.; Hlawacek, G.; Arekapudi, S. S. P. K.; Xu, X.; Koch, L.; Lenz, M.; Hellwig, O.

We study layered synthetic antiferromagnets (SAFs) with out-of-plane interface anisotropy, where the layer-wise antiferromagnetic (AF)
alignment is induced by interlayer exchange coupling (IEC). By applying low energy He+ focused ion beam irradiation to the SAF, a depth-dependent
reduction of the IEC and anisotropy can be achieved due to layer intermixing. As a consequence, after irradiation, a specific field
reversal sequence of the SAF is energetically preferred. When tuning the pristine SAF to exhibit an inverted field reversal, we are thus able to
create AF domains in the irradiated regions. When irradiated with a fluence gradient, these AF domains can be further deterministically
manipulated by an external magnetic field. Among other applications, this could be utilized for engineering a controllable and local magnetic
stray field landscape, for example, at AF domain walls, within the otherwise stray field free environment provided by the SAF.

Keywords: Bubble domains; Focused ion beam; Sputter deposition; Interlayer exchange coupling; Magnetic hysteresis

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33090
Publ.-Id: 33090


DYN3D and CTF Coupling within a Multiscale and Multiphysics Software Development (Part I)

Davies, S.; Litskevich, D.; Rohde, U.; Detkina, A.; Merk, B.; Bryce, P.; Levers, A.; Ravindra, V.

Understanding and optimizing the relation between nuclear reactor components or physical phenomena allows us to improve the economics and safety of nuclear reactors, deliver new nuclear reactor designs, and educate nuclear staff. Such relation in the case of the reactor core is described by coupled reactor physics as heat transfer depends on energy production while energy production depends on heat transfer with almost none of the available codes providing full coupled reactor physics at the fuel pin level. A Multiscale and Multiphysics nuclear software development between NURESIM and CASL for LWRs has been proposed for the UK. Improved coupled reactor physics at the fuel pin level can be simulated through coupling nodal codes such as DYN3D as well as subchannel codes such as CTF. In this journal article, the first part of the DYN3D and CTF coupling within the Multiscale and Multiphysics software development is presented to evaluate all inner iterations within one outer iteration to provide partially verified improved coupled reactor physics at
the fuel pin level. Such verification has proven that the DYN3D and CTF coupling provides improved feedback distributions over the DYN3D coupling as crossflow and turbulent mixing are present in the former.

Keywords: Nuclear Reactor; Coupled reactor physics; Nodal code; Subchannel code; DYN3D; CTF; KAIST

Permalink: https://www.hzdr.de/publications/Publ-33089
Publ.-Id: 33089


Modulated rotating waves and triadic resonances in spherical fluid systems: The case of magnetized spherical Couette flow

Garcia Gonzalez, F.; Giesecke, A.; Stefani, F.

The existence of triadic resonances in the magnetized spherical Couette system is related to the development of modulated rotating waves, which are quasiperiodic flows understood in terms of bifurcation theory in systems with symmetry. In contrast to previous studies in spherical geometry, the resonant modes are not inertial waves but related to the radial jet instability, which is strongly equatorially antisymmetric. We propose a general framework in which triadic resonances are generated through successive Hopf bifurcations from the base state. The study relies on an accurate frequency analysis of different modes of the flow, for solutions belonging to two different bifurcation scenarios. The azimuthal and latitudinal nonlinear coupling among the resonant modes is analyzed and interpreted using spherical harmonics, and the results are compared with previous studies in spherical geometry.

Keywords: Spherical Couette Flow

Permalink: https://www.hzdr.de/publications/Publ-33087
Publ.-Id: 33087


Size-Tunable Gold Aerogels: A Durable and Misfocus-Tolerant 3D Substrate for Multiplex SERS Detection

Zhou, L.; Peng, Y.; Zhang, N.; Du, R.; Hübner, R.; Wen, X.; Li, D.; Hu, Y.; Eychmüller, A.

The research on surface-enhanced Raman scattering (SERS) continuously draws wide attention because of its high detection sensitivity. However, the commonly investigated 2D SERS substrates cannot fully utilize the 3D active focal volume and require a tight focus on the correct plane, retarding signal enhancement and flexible use. Here, self-supported gold aerogels of centimeter-dimension with tunable ligament sizes are designed as 3D SERS substrates, featuring hot spots throughout the entire network. Unveiling a universal ligament-size-effect, the optimized gold aerogel showcases much larger enhancement factors compared to a 8 nm Au film toward dyes, pesticides, and carcinogens (up to 109). Aside from an excellent reusability and an exceptional stability (> 1 month), an outstanding misfocus tolerance (>300 μm along the z-axis) is also demonstrated for such aerogel-based SERS substrates for multiplex detection. This work may expand the application scope of metal aerogels and lay the foundation for designing next-generation 3D SERS substrates.

Permalink: https://www.hzdr.de/publications/Publ-33086
Publ.-Id: 33086


The Al Doping Effect on Epitaxial (In,Mn)As Dilute Magnetic Semiconductors Prepared by Ion Implantation and Pulsed Laser Melting

Yuan, Y.; Xie, Y.; Yuan, N.; Wang, M.; Heller, R.; Kentsch, U.; Zhai, T.; Wang, X.

One of the most attractive characteristics of diluted ferromagnetic semiconductors is the possibility to modulate their electronic and ferromagnetic properties, coupled by itinerant holes through various means. A prominent example is the modification of Curie temperature and magnetic anisotropy by ion implantation and pulsed laser melting in III–V diluted magnetic semiconductors. In this study, to the best of our knowledge, we performed, for the first time, the co-doping of (In,Mn)As diluted magnetic semiconductors by Al by co-implantation subsequently combined with a pulsed laser annealing technique. Additionally, the structural and magnetic properties were systematically investigated by gradually raising the Al implantation fluence. Unexpectedly, under a well-preserved epitaxial structure, all samples presented weaken Curie temperature, magnetization, as well as uniaxial magnetic anisotropies when more aluminum was involved. Such a phenomenon is probably due to enhanced carrier localization introduced by Al or the suppression of substitutional Mn atoms.

Permalink: https://www.hzdr.de/publications/Publ-33083
Publ.-Id: 33083


Phase evolution of Te-hyperdoped Si upon furnace annealing

Shaikh, M. S.; Wang, M.; Hübner, R.; Liedke, M. O.; Butterling, M.; Solonenko, D.; Madeira, T. I.; Li, Z.; Xie, Y.; Hirschmann, E.; Wagner, A.; Zahn, D. R. T.; Helm, M.; Zhou, S.

Si hyperdoped with chalcogens via ion implantation and pulsed laser melting is known to exhibit strong room-temperature sub-bandgap photoresponse. As a thermodynamically metastable system, an impairment of the optoelectronic properties in hyperdoped Si materials occurs upon subsequent high-temperature thermal treatment (>500 °C). The substitutional Te atoms that cause the sub-bandgap absorption are removed from the Si matrix to form Te-related complexes, which are electrically and optically inactive. In this work, we explore the formation of defects in Te-hyperdoped Si layers which leads to the electrical deactivation upon furnace annealing through the analysis of optical and microstructural properties as well as positron annihilation lifetime spectroscopy. Particularly, Te-rich clusters are observed in samples thermally annealed at temperatures reaching 950 °C and above. Combined with polarized Raman analysis and transmission electron microscopy, the observed crystalline clusters are suggested to be Si2Te3.

Keywords: Defect analysis; Furnace annealing; Ion-implantation; Positron annihilation spectroscopy; Raman spectroscopy; Silicon telluride; Te-hyperdoped Si; Transmission electron microscopy

Permalink: https://www.hzdr.de/publications/Publ-33082
Publ.-Id: 33082


Strain-induced switching between noncollinear and collinear spin configuration in magnetic Mn5Ge3 films

Xie, Y.; Yuan, Y.; Birowska, M.; Zhang, C.; Cao, L.; Wang, M.; Grenzer, J.; Kriegner, D.; Doležal, P.; Zeng, Y.-J.; Zhang, X.; Helm, M.; Zhou, S.; Prucnal, S.

We report the temperature-dependent magnetic and structural properties of epitaxial Mn5Ge3 thin films grown
on Ge substrates. Utilizing density-functional theory (DFT) calculations and various experimental methods, we
reveal mechanisms governing the switching between collinear and noncollinear spin configuration in Mn5Ge3.
The Mn atoms in Mn5Ge3 occupy two distinct Wyckoff positions with fourfold (Mn1) and sixfold (Mn2)
multiplicity. The DFT calculations reveal that below a critical distance of approximately 3.002 Å the coupling
between Mn2 atoms is antiferromagnetic (AFM) while ferromagnetic (FM) above that critical distance. The FM
coupling between Mn1 atoms is weakly affected by the strain. The observed noncollinear spin configuration is
due to the coexistence of AFM and FM coupling at low temperatures. The findings give insight in developing
strain-controlled spintronic devices.

Permalink: https://www.hzdr.de/publications/Publ-33081
Publ.-Id: 33081


Interfacial Synthesis of Layer-Oriented 2D Conjugated Metal-Organic Framework Films toward Directional Charge Transport

Wang, Z.; Walter, L. S.; Wang, M.; Petkov, P. S.; Liang, B.; Qi, H.; Ngan Nguyen, N.; Hambsch, M.; Zhong, H.; Wang, M.; Park, S.; Renn, L.; Watanabe, K.; Taniguchi, T.; Mannsfeld, S. C. B.; Heine, T.; Kaiser, U.; Zhou, S.; Weitz, T. R.; Feng, X.; Dong, R.

The development of layer-oriented two-dimensional conjugated metal-organic frameworks (2D c-MOFs) enables access to direct charge transport, dial-in lateral/vertical electronic devices, and the unveiling of transport mechanisms but remains a significant synthetic challenge. Here we report the novel synthesis of metal-phthalocyanine-based p-type semiconducting 2D c-MOF films (Cu2[PcM-O8], M = Cu or Fe) with an unprecedented edge-on layer orientation at the air/water interface. The edge-on structure formation is guided by the preorganization of metal-phthalocyanine ligands, whose basal plane is perpendicular to the water surface due to their π-πinteraction and hydrophobicity. Benefiting from the unique layer orientation, we are able to investigate the lateral and vertical conductivities by DC methods and thus demonstrate an anisotropic charge transport in the resulting Cu2[PcCu-O8] film. The directional conductivity studies combined with theoretical calculation identify that the intrinsic conductivity is dominated by charge transfer along the interlayer pathway. Moreover, a macroscopic (cm2 size) Hall-effect measurement reveals a Hall mobility of ∼4.4 cm2 V-1 s-1 for the obtained Cu2[PcCu-O8] film. The orientation control in semiconducting 2D c-MOFs will enable the development of various optoelectronic applications and the exploration of unique transport properties.

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Permalink: https://www.hzdr.de/publications/Publ-33080
Publ.-Id: 33080


Physicochemical constraints on indium-, tin-, germanium-, gallium-, gold-, and tellurium-bearing mineralizations in the Pefka and St Philippos polymetallic vein- and breccia-type deposits, Greece

Voudouris, P.; Repstock, A.; Spry, P. G.; Frenzel, M.; Mavrogonatos, C.; Keith, M.; Tarantola, A.; Melfos, V.; Tombros, S.; Zhai, D.; Cook, N. J.; Ciobanu, C. L.; Schaarschmidt, A.; Rieck, B.; Kolitsch, U.; Falkenberg, J. J.

The Pefka Cu-Au-Te-In-Se and nearby St Philippos Pb-Zn-Bi-Sn-Ge-Ga-In vein- and breccia-type deposits in western Thrace, Greece, display strong similarities, but also differences in terms of mineralization style, ore mineralogy, and chemistry, and host rock compositions. The Pefka mineralization consists of two crosscutting vein systems with high sulfidation (HS)- and intermediate-sulfidation (IS) assemblages hosted by andesitic lavas and is unusually enriched in In (up to 700 ppm), Te (>1000 ppm), Se (>100 ppm), and Cu (>1 wt%). The main In-carriers are roquesite (CuInS2) and In-bearing “tennantite-(Cu)” and Cu-rich “tennantite-(In)” which contains up to 6.5 wt% In, substituting into the C site. Roquesite is associated with enargite and arsenosulvanite/colusite, as part of the HS assemblage at Pefka. Selenium-bearing galena and a large suite of tellurides including calaverite, sylvanite, petzite, hessite, kostovite, empressite, tellurantimony, and coloradoite, in addition to native tellurium, account for the marked tellurium and selenium enrichment in the ores from Pefka. Tellurides and native gold at Pefka accompany the precipitation of Te-bearing minerals of the tetrahedrite group, such as “stibiogoldfieldite” and “arsenogoldfieldite”, and Cu-excess varieties of tetrahedrite and tennantite. However, the bulk of telluride deposition is associated with normal, fully substituted tetrahedrite-tennantite varieties.

The St Philippos deposit is associated with a brecciated fault zone hosted by Eocene sandstones and Oligocene quartz-feldspar porphyry dikes. It is enriched in a large suite of incompatible elements, including Bi (>2000 ppm), Sn (>100 ppm), U (up to 200 ppm), Pb (>1 wt%), Zn (>1 wt%), Mo (up to 62 ppm), Ge (>100 ppm), Ga (up to 466 ppm) and In (up to 222 ppm), contrasting with the element suite defining the nearby Pefka deposit. The main carrier of In, Ga, and Ge is sphalerite (and wurtzite) with In-rich zones in sphalerite containing up to 6.1. wt% In. Germanium and Ga in sphalerite reach concentrations of up to 0.27 and 0.32 wt%, respectively. Sphalerite from the St Philippos deposit is extremely Fe-poor (<0.04 wt%), and is associated with an unusual suite of Sn-bearing sulfosalts (kësterite-stannite, Mn-bearing kësterite, unnamed Cu2MnSnS4), and enargite, marking an early HS event. Kësterite also hosts indium (up to 0.6 wt% In). Mn-bearing varieties of tennantite host inclusions of minor tellurides (e.g., hessite, altaite, and tsumoite) and formed later in the paragenetic sequence under transitional HS-IS and IS conditions.

Both deposits are characterized by early high-temperature (>300 °C) and HS fluid conditions, followed by IS assemblages as temperatures waned. Rhyolitic oxidized magmas are considered to be the sources of metals in the St Philippos deposit; however, their anomalous W, Sn, U, and Bi contents suggest a contamination by crustal rocks. The Cu-Au-Te signature of the Pefka deposit is compatible with a genetic relationship to less fractionated andesitic magmas, although a possible contribution of In from rhyolitic magmas could explain the high In contents of the ore. However, other factors, as for example different metal-deposition mechanisms resulting in metal zonation around causative porphyry centers at depth, may also account for the observed metal endowment in these two deposits. The Sn-Te-In-(Ge-Ga) element association at Pefka and St Philippos is unusual in that it has been previously reported from only a few other places in the world (e.g., Capillitas deposit, Argentina, and the Kawazu deposit, Japan). We conclude based on this exotic mineralization-style that the northeastern part of Greece represents an area of great potential for the exploitation of critical metals and metalloids.

Keywords: Critical metals; Greece; High-intermediate sulfidation; Magmatic-hydrothermal

Permalink: https://www.hzdr.de/publications/Publ-33079
Publ.-Id: 33079


Probing charged lepton flavor violation with the Mu2e experiment

Müller, S.; Ferrari, A.; Knodel, O.; Rachamin, R.

Presentation a 2021 DPG meeting (section "Matter & Cosmos"), September1, 2021

Keywords: MU2E; Charged Lepton Flavor Violation; DPG

  • Lecture (Conference) (Online presentation)
    DPG Meeting SMUK, 30.08.-03.09.2021, virtuell, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33077
Publ.-Id: 33077


Checkliste zur Unterstützung der Helmholtz-Zentren bei der Implementierung von Richtlinien für nachhaltige Forschungssoftware

Messerschmidt, R.; Pampel, H.; Bach, F.; Zu Castell, W.; Denker, M.; Finke, A.; Fritzsch, B.; Hammitzsch, M.; Konrad, U.; Leifels, J.; Möhl, C.; Nolden, M.; Scheinert, M.; Schlauch, T.; Schnicke, T.; Steglich, D.

Mit der voranschreitenden Digitalisierung von Forschung und Lehre steigt die Zahl an Software-Lösungen, die an wissenschaftlichen Einrichtungen entstehen und zur Erkenntnisgewinnung genutzt werden. Die – unter dem Stichwort Open Science geforderte – Zugänglichkeit und Nachnutzung von wissenschaftlichen Ergebnissen kann in vielen Fachgebieten nur sichergestellt werden, wenn neben Forschungsdaten auch Programmcode offen zugänglich gemacht wird. Die vorliegende Handreichung richtet sich an Entscheider*innen in den Helmholtz-Zentren, die sich mit der Implementierung von Richtlinien für nachhaltige Forschungssoftware befassen. Sie ergänzt eine Muster-Richtlinie, die den Zentren bereits eine richtungsweisende und nachnutzbare Vorlage zur Erstellung von Regelungen für einen nachhaltigen Umgang mit Forschungssoftware gibt.

Keywords: Research Software; Open Access; Checkliste; Regelung; Software Policy

Permalink: https://www.hzdr.de/publications/Publ-33076
Publ.-Id: 33076


ARIEL - Accelerator and Research reactor Infrastructures for Education and Learning

Beyer, R.; Junghans, A.

Status and news from ARIEL

Keywords: ARIEL; nELBE

  • Invited lecture (Conferences) (Online presentation)
    ENEN Special Event 2021 - Outlook of nuclear ETKM activities, 03.03.2021, Brussels, Belgium

Permalink: https://www.hzdr.de/publications/Publ-33073
Publ.-Id: 33073


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