Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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39109 Publications

Atom Probe Tomography: Basics and applications on complex sulphides

Krause, J.

Atom Probe Tomography combines the three dimensional reconstruction of the lattice in real space with a time–of–flight mass spectrometer. The result is a tomographic image of the chemical composition of a solid sample making it a powerful technique to determine the chemical composition of nanostructures in 3-D with sub-nanoscale spatial resolution. It is a powerful technique to study processes on the near-atomic scale such as diffusion, exsolution, or the formation of nano-scale inclusions.

  • Invited lecture (Conferences)
    Vortragsreihe der Österreichischen Mineralogischen Gesellschaft, 16.03.2022, Montanuniversität Leoben, Österreich

Permalink: https://www.hzdr.de/publications/Publ-36319
Publ.-Id: 36319


Atom Probe Tomography: Basics and applications on complex sulphides

Krause, J.

Atom Probe Tomography combines the three dimensional reconstruction of the lattice in real space with a time–of–flight mass spectrometer. The result is a tomographic image of the chemical composition of a solid sample making it a powerful technique to determine the chemical composition of nanostructures in 3-D with sub-nanoscale spatial resolution. It is a powerful technique to study processes on the near-atomic scale such as diffusion, exsolution, or the formation of nano-scale inclusions.

  • Invited lecture (Conferences)
    Vortragsreihe der Österreichischen Mineralogischen Gesellschaft, 14.03.2022, Universität Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-36318
Publ.-Id: 36318


Helmholtz AI: Diversity in Teaching Machine Learning supports democratising AI

Cea, D.; Hoffmann, H.; Weiel, M.; Steinbach, P.; Kesselheim, S.

“Democratising AI” – that is the motto for the Helmholtz AI consultants. With our scientific consulting, we enable Helmholtz researchers from all domains to leverage AI for their datasets by providing comprehensive support with AI methods, tools, and software engineering. And this does not only apply to scientists working on their own research projects. We also offer courses, workshops, lectures, and challenges on various AI-related topics. On our poster, you can find an overview of past teaching experiences from the different consultant teams. These include an in-depth introductory course to deep learning using the flipped classroom approach, advanced courses on AutoML and explainable AI with multiple hands-on sessions, data challenges introducing the learners to domain adaptation tasks and making them experiment and search for personal solutions to complex and current problems, and crash courses on AI for a broader and less technical audience.
You are curious to learn more? Then drop by our poster and let’s have a chat.

Keywords: machine learning; community; learning; diversity; inclusion

  • Open Access Logo Poster
    TEACH2, 09.11.2022, zoom, Germany

Downloads

Permalink: https://www.hzdr.de/publications/Publ-36317
Publ.-Id: 36317


Know your learners to adapt teaching early - a discussion of pre-workshop surveys

Hoffmann, H.; Steinbach, P.

During the process of composing teaching material and preparing for a lesson, an instructor typically bears in mind an expected composition of his/her audience with respect to prior knowledge, speed of learning, and expectations. In this discussion, we would like to present our approaches to assessing these 3 dimensions before a workshop starts in order to prepare the teacher for his/her students. We will share some typical questions we survey with and explain how it helps us to target our content better. Moreover, it can provide a solid baseline for teachers with respect to preparing group activities to foster a community of learners in the classroom. The largest part of the discussion will be devoted to an exchange of experiences by the participants on assessing learner communities before they meet in class and on how to improve for future workshops.

Keywords: machine learning; teaching; interactive

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    TEACH2, 09.11.2022, zoom, Germany

Downloads

Permalink: https://www.hzdr.de/publications/Publ-36316
Publ.-Id: 36316


Spectroscopy of XFEL heated Cu and x-ray absorption in laser-produced Warm Dense Cu a pár dalších témat

Smid, M.

Warm Dense Matter (WDM) is a transitional state between solid and ideal plasmas. It can contain highly charged ions and moderate electron temperatures, while retaining rest of crystalline-like structure. In experimental conditions it can be typically created in a dynamical way by irradiation of solid targets with ultra-short pulse lasers. The x-ray spectroscopy of plasma is a great way of studying this transitional state of matter, by using either a broadband x-ray beam as a backlighter for absorption measurement, or self-emission to observe the radiation of various charge states of present ions.

In this talk I will present two different experiments studying warm dense Copper with their results and a minimum of underlying theory. In the first case, the matter is heated by direct irradiation by optical laser (Draco, Dresden), and probed variable delay later by a 'Laser wakefield accelerated' (LWFA) betatron beam. From the x-ray absorption techniques we can infer both the electron and ion temperatures, therefore observing the heating and melting of the material. In the second case, the matter is created ('pumped') and probed simultaneously by the same pulse of the X-ray Free Electron Laser (European XFEL, Hamburg). Moderately charged ions are created within the duration of the pulse (~30 fs) and their Kα emission is stimulated by the beam. The self-emission spectra in this well described environment serves as a road map of various atomic transitions and non-equilibrium atomic-physics effects of those ions.

  • Open Access Logo Invited lecture (Conferences)
    15th Student Workshop - Winter school on Plasma Physics, 16.-20.01.2023, Marianska, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-36314
Publ.-Id: 36314


Neptunium(V) and uranium(VI) sorption onto the zircaloy corrosion product zirconia (ZrO₂)

Jessat, I.

The interactions of long-lived radionuclides, such as uranium and the transuranium element
neptunium, with corroded phases in the near-field of a repository are crucial processes that
have to be taken into account in the safety assessment of a repository. Neptunium(V) and
uranium(VI) were chosen as representatives of pentavalent and hexavalent actinides,
respectively. Zirconia (ZrO₂) is the main corrosion product of the zircaloy cladding material of
spent nuclear fuel rods and constitutes as one of the first barriers encountered by mobilized
radionuclides. A comprehensive, multi-method approach was pursued to obtain a detailed
understanding of the Np(V)/U(VI) interactions at the zirconia-water interface. pH-dependent
batch sorption studies and isotherm experiments as well as spectroscopic techniques (EXAFS,
IR) were employed to gain information on the macroscopic and the molecular scale,
respectively. The derived information about Np(V)/U(VI) binding sites as well as number and
structure of the formed surface species were then used to constrain the parametrization of a
thermodynamic surface complexation model. The results of this work will contribute to more
reliable predictions about the environmental fate of Np(V)/U(VI) surrounding the near-field of
a repository.

Keywords: uranium(VI); neptunium(V); zirconia; ZrO₂; EXAFS; IR; sorption

  • Lecture (others)
    Presentation PhD topic, 09.11.2022, Veldhoven, Netherlands

Permalink: https://www.hzdr.de/publications/Publ-36313
Publ.-Id: 36313


Introduction to kernel methods and Gaussian processes

Schmerler, S.

Introduction to kernel methods and Gaussian processes

  • Open Access Logo Lecture (others) (Online presentation)
    Institute Seminar, 08.11.2022, Görlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-36308
Publ.-Id: 36308


Radiative particle-in-cell simulations of the beam hosing instability -- an analysis by components

Lebedev, A.; Pausch, R.; Widera, R.; Bastrakov, S.; Bussmann, M.; Schramm, U.; Debus, A.

We present first results and analyses of radiation spectra expected to be produced by highly relativistic particle beams propagating through a plasma medium experiencing the hosing instability. We determine these spectra in particle-in-cell simulations by in-situ computation of coherent and incoherent radiation based on Liénard-Wiechert potentials, emitted by all simulated particles (>10^9) of the beam and plasma for over 160 distinct detectors distributed across half a solid angle. Our code allows us to distinguish radiation emitted by plasma particles from that of the bunch, thereby enabling us to infer the origin of the spectral features.
In the simulation campaign, conducted at the JUWELS Booster cluster at JSC, we considered linear and non-linear regimes of the instability for highly relativistic electron beams of varying emittance impacting a homogeneous electron plasma.
We further show a preliminary analysis of the data relating observed characteristics of the spectra to the characteristics of the instability.
A goal of these studies is to open up new experimental avenues for better understanding the beam instability evolution by identifying quantitative radiation signatures of the instability that can be measured in experiments.

Keywords: Firehose Instability; PIConGPU; High-Performance Computing; Plasma-Wakefield Accelerators; Plasma Instabilities; Radiation Signatures

  • Lecture (Conference) (Online presentation)
    DPG Spring Meeting of the Divisions Hadronic and Nucleonic Physics, Plasma Physics and the Working Group Accelerator Physics, 28.03.-1.04.2022, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36307
Publ.-Id: 36307


Radiative particle-in-cell simulations of the beam hosing instability

Lebedev, A.; Pausch, R.; Bastrakov, S.; Widera, R.; Bussmann, M.; Schramm, U.; Steiniger, K.; Debus, A.

We present the results and analyses of radiation spectra expected to be
produced by highly relativistic particle beams propagating through a
plasma medium and experiencing the hosing instability.
Coherent and incoherent contributions to the spectra are determined
in-situ for all simulated particles (>10^9) of the particle cloud and
ambient plasma for a lage assembly of detectors.
With the help of our particle-in-cell code we are able to distinguish
radiation emitted by plasma particles from that of the bunch.
In the simulation campaign, conducted at the JUWELS Booster cluster at
JSC, we consider linear and non-linear regimes of the instability for
highly relativistic electron beams impacting a homogeneous electron plasma.
We show an updated analysis of the data relating observed
characteristics of the spectra to the features of the bunch and ambient
plasma, thereby identifying first features indicative of the hosing
instability in PWFA.
A goal of these studies is to open up new experimental avenues for
better understanding the beam instability evolution by identifying
quantitative radiation signatures of the instability that can be
measured in experiments.

Keywords: Firehose Instability; High-Performance Computing; PIConGPU; Plasma-Wakefield Accelerator

  • Open Access Logo Lecture (Conference)
    8th Annual Matter and Technologies Student Retreat, 27.-28.09.2022, DESY Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36306
Publ.-Id: 36306


Precipitation stripping of nanometrical particles for the recovery of metal vanadates

Sánchez-Loredo, M. G.; Ebert, D.; Chekhonin, P.; Labrada Delgado, G. J.; Kelly, N.

Transition metal vanadates have shown potential in applications as sensors, in photocatalysis, and recently, because of their high theoretical capacity, safety, easy preparation, and low cost, as electrode materials for primary and rechargeable batteries. Motivated by these relevant applications, much research work has been done on the synthesis and electrochemical studies of various 1D transition metal vanadates. Metal vanadates are normally synthesized by hydrothermal methods at high temperatures and pressures, making the synthesis expensive, and the control of the microstructure and composition difficult to achieve.
Vanadium can currently be found in the slag by-products of certain steel production processes, and the development of hydrometallurgical processes for the recovery and purification is relevant, mostly from alkaline media. Various methods are being investigated for separation of the metal value from alkaline leach feeds, including solvent extraction.
In case of the recovery of vanadium an interesting modification of the conventional solvent extraction process is the addition of a crystallization operation (precipitation stripping). In this work, the extraction was carried out using an Aliquat 336 solution in n-octanol/kerosene as extractant. Precipitation stripping was carried out using several metal salts dissolved in a concentrated chloride solution. For some experiments, polyvinylpyrrolidone was used as stabilizer in order to avoid agglomeration and to control growth. The structural characteristics of the crystallized products were studied. From the results, the synthesis of nanostructured vanadates is a simple and versatile method for the fabrication of valuable vanadium compounds.

  • Poster
    Jahrestreffen der ProcessNet Fachgruppen Extraktion, Phytoextrakte und Membrantechnik, 23.-24.05.2022, Frankfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36305
Publ.-Id: 36305


The Extraction of HREES and LREES with Primene JM-T in Sulphate Media

Bastürkcü, E.; Kelly, N.; Stelter, M.; Yüce, A. E.; Timur, S. İ.

The number of studies on the separation process of rare earth elements (REEs) has been studied intensively because REEs are playing a very critical role of high-tech products. Due to the restriction of export from China which has a dominating position in terms of reserve and production of REEs, other countries have investigated potential reserves and production techniques of rare earths. In case of Turkiye a high potential REE deposit is located in Eskisehir-Beylikova. In the presented study, the separation of heavy rare earth elements (HREEs) from light rare earth elements (LREEs) from the model solution was studied with solvent extraction. The solution was produced based on dissolution of pre-concentrate of Eskisehir-Beylikova ore by water leaching after acid baking. Primene JM-T was selected as an extractant which has not been studied in the separation of HREEs and LREEs. The key parameters pH, extractant concentration and A/O ratio were optimized. The optimum conditions were determined to be 10% concentration of extractant, pH 1 and A:O ratio, 1:1. The extraction for LREEs was 75-80% while HREEs had lower extraction rates of only 45-70%.

Keywords: REE; PrimeneJM-T; solvent extraction; sulphate media

  • Lecture (Conference)
    International Mineral Processing Symposium, 15.-17.12.2022, Istanbul, Türkiye
  • Contribution to proceedings
    International Mineral Processing Symposium, 15.-17.12.2022, Istanbul, Türkiye

Permalink: https://www.hzdr.de/publications/Publ-36304
Publ.-Id: 36304


Precipitation stripping of V(V) as a novel approach for the preparation of transition metal vanadates

Kelly, N.; Ebert, D.; Möckel, R.; Labrada-Delgado, G. J.; Sánchez-Loredo, M. G.

Transition metal vanadates, and particularly copper vanadates (CVO), have shown potential in applications as sensors, in photocatalysis, and recently, because of their high theoretical capacity, safety, easy preparation, and low cost, as electrode materials for primary and rechargeable lithium-ion batteries (LIBs). During discharge, the Cu2+ is reduced, and, more than one lithium ion per vanadium react, giving a high theoretical discharge capacity. Motivated by this relevant application, much research work has been done on the synthesis and electrochemical studies of various 1D transition metal vanadates. Among them, particularly Cu3V2O7(OH)2.2H2O has been studied as an electrode for primary lithium batteries with a high storage capacity. CVO and other metal vanadates are normally synthesized by hydrothermal methods at high temperatures and pressures, making the synthesis expensive, and the control of the microstructure and composition difficult to achieve.
An interesting modification of the conventional solvent extraction process is the addition of a crystallization operation, where low-solubility metal salts such as oxalates, oxides, or sulfides can be precipitated (precipitation stripping). In this work, copper vanadate nanoparticles have been synthesized by a simple synthetic route by solvent extraction and precipitation stripping. The extraction was carried out by ion exchange using a 20% (v/v) Aliquat 336 solution in n-octanol/kerosene as extractant, and an alkaline aqueous solution (0.1 M NaOH) prepared using vanadium pentoxide (V(V) concentration 2 g/L). Precipitation stripping was carried out using copper sulphate (0.01, 0.05 and 1 mol/L) dissolved in a concentrated chloride solution (4 mol/L). For some experiments, polyvinylpyrrolidone (PVP, Sigma Aldrich, ~44,000 g/mol) was used as stabilizer in order to avoid agglomeration and control growth. The prepared materials were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (FTIR), and X-Ray Fluorescence (XRF). The obtained diffractograms could be indexed to the Cu3V2O7(OH)2.2H2O phase, space group: C2/m(12), JCPDS Card No. 46-1443, corresponding to volborthite, an uncommon secondary mineral formed in the oxidized zone of vanadium-bearing hydrothermal mineral deposits, monoclinic or pseudohexagonal and forms normally rosette-like aggregates of scaly crystals. The copper vanadate particles are nanometrical in size, with morphologies varying from nanowires to spherical particles (in presence of PVP)

  • Lecture (Conference)
    International solvent extraction conference (ISEC), 26.-30.09.2022, Göteborg, Sweden

Permalink: https://www.hzdr.de/publications/Publ-36303
Publ.-Id: 36303


Selektive Extraktion von Molybdän mit Cyanex 272 und Cyanex 600: Charakterisierung der organischen Phase zur optimierten Prozessführung

Helbig, T.; Tasker, P.; Kaden, P.; Foerstendorf, H.; Lehmann, F.; Kelly, N.

Der steigende Bedarf an Metallen für moderne technische Anwendungen erfordert die Entwicklung und Optimierung von Verfahren zur Rückgewinnung und zum Recycling dieser wertvollen Metalle. Die Bedeutung hydrometallurgischer Verfahren, z. B. unter Einsatz der Flüssig-Flüssig-Extraktion, aus Rohstoffquellen mit niedrig konzentrierten Wertelementen nimmt dabei stetig zu. Sie ermöglichen eine effiziente Rückgewinnung von Metallen sowohl aus industriellen Abwässern oder aber auch aus festen Sekundärrohstoffen und tragen zudem zu einer Reduzierung der Umweltbelastung durch alte Haldenmaterialien bei. Ein typisches Beispiel für diese Materialien stellt der Theisenschlamm dar, welcher bis 1990 im Rahmen der Aufbereitung von Kupferschiefer im Schachtofen als Abfallprodukt (220000 t) anfiel. Dieser enthält neben Elementen wie Kupfer und Zink auch signifikante Mengen an anderen Wertmetallen (Molybdän, Rhenium, Cobalt). Die komplexe Zusammensetzung des Materials, die Anwesenheit von umweltrelevanten Störelementen und der hohe Anteil an organischen Verbindungen erfordert ein mehrstufiges Verfahren, um die Metalle aufzukonzentrieren und mit notwendiger chemischer Reinheit zu gewinnen.
Im vorliegenden Beitrag wird die selektive Extraktion von Molybdän aus sauren Lösungen unter Einsatz der kommerziellen Extraktionsmittel Cyanex 272 und Cyanex 600 betrachtet. Dabei werden die in der organischen Phase gebildeten Komplexe durch vielseitige moderne, analytische Methoden (NMR, FTIR, Raman, MS) charakterisiert und diskutiert. Ein besseres Verständnis für diese bisher unzureichend untersuchten Extraktionssysteme ist ebenso hinsichtlich des Auftretens dritter Phasen hilfreich. In Kombination mit den optimierten technischen Parametern zur selektiven Abtrennung und Anreicherung des Molybdäns erfolgt eine Übertragung in einen kontinuierlich geführten Prozess.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet Fachgruppen Extraktion, Phytoextrakte und Membrantechnik, 23.-24.05.2022, Frankfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36302
Publ.-Id: 36302


Synthetic shadowgrams of laser-plasma accelerators computed by a PIConGPU in-situ plugin

Carstens, F.-O.; Steiniger, K.; Pausch, R.; Chang, Y.-Y.; Schöbel, S.; Couperus Cabadağ, J. P.; Irman, A.; Lehmann, M.; Widera, R.; Bussmann, M.; Schramm, U.; Cowan, T.; Debus, A.

Few-cycle shadowgraphy is a valuable diagnostic for laser-plasma accelerators to obtain insight into the µm- and fs-scale relativistic plasma dynamics. To enhance the understanding of experimental shadowgrams we developed a synthetic shadowgram diagnostic within the fully relativistic particle-in-cell code PIConGPU.

In an initial version of the synthetic shadowgraphy diagnostic, the probe laser is propagated through the plasma using PIConGPU, and then extracted and propagated onto a virtual CCD using a post-processing code based on Fourier optics. However, the latter step requires 3D-FFTs, which results in performance and scaling limitations in large-scale simulations. To circumvent this, we develop an in-situ plugin for PIConGPU, in which we extract the probe laser slice-wise to obtain the synthetic shadowgrams during the simulation without post-processing.

In this talk, we present the development of the PIConGPU plugin and show preliminary results of synthetic shadowgrams for laser and plasma wakefield accelerators.

Keywords: Shadowgraphy; Synthetic Diagnostics; PIConGPU; Laser-Electron Acceleration

  • Lecture (Conference) (Online presentation)
    Virtuelle DPG-Frühjahrstagung, 28.03.-01.04.2022, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36299
Publ.-Id: 36299


Dissipation losses limiting first-order phase transition materials in cryogenic caloric cooling: A case study on all-d-metal Ni(-Co)-Mn-Ti Heusler alloys

Beckmann, B.; Koch, D.; Pfeuffer, L.; Gottschall, T.; Taubel, A.; Adabifiroozjaei, E.; Miroshkina, O. N.; Riegg, S.; Niehoff, T.; Kani, N. A.; Gruner, M. E.; Molina-Luna, L.; Skokov, K. P.; Gutfleisch, O.

Ni-Mn-based Heusler alloys, in particular all-d-metal Ni(-Co)-Mn-Ti, are highly promising materials for energy-efficient solid-state refrigeration as large multicaloric effects can be achieved across their magnetostructural martensitic transformation. However, no comprehensive study on the crucially important transition entropy change Δs exists so far for Ni(-Co)-Mn-Ti. Here, we present a systematic study analyzing the composition and temperature dependence of Δst. Our results reveal a substantial structural entropy change contribution of approximately 65 J(kgK)-1, which is compensated at lower temperatures by an increasingly negative entropy change associated with the magnetic subsystem. This leads to compensation temperatures Tcomp of 75 K and 300 K in Ni35Co15Mn50-yTiy and Ni33Co17Mn50-yTiy, respectively, below which the martensitic transformations are arrested. In addition, we simultaneously measured the responses of the magnetic, structural and electronic subsystems to the temperature- and field-induced martensitic transformation near Tcomp, showing an abnormal increase of hysteresis and consequently dissipation energy at cryogenic temperatures. Simultaneous measurements of magnetization and adiabatic temperature change ΔTad in pulsed magnetic fields reveal a change in sign of ΔTad and a substantial positive and irreversible ΔTad up to 15 K at 15 K as a consequence of increased dissipation losses and decreased heat capacity. Most importantly, this phenomenon is universal, it applies to any first-order material with non-negligible hysteresis and any stimulus, effectively limiting the utilization of their caloric effects for gas liquefaction at cryogenic temperatures.

Downloads

Permalink: https://www.hzdr.de/publications/Publ-36298
Publ.-Id: 36298


From laser-plasma accelerator experiments to digital twins

Debus, A.

Building high-fidelity digital twins through start-to-end models to better understand and control advanced laser-plasma accelerators, as well as compact free-electron laser beamlines, requires direct comparison to experimental data. We highlight recent results in start-to-end simulations and developments with a focus on their connection to experiment, such as by synthetic diagnostics and experimental data reconstruction analyses.

Keywords: digital twins; machine learning; laser-plasma accelerators; free-electron laser

  • Invited lecture (Conferences)
    8. Annual MT meeting, 26.-27.9.2022, DESY, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36296
Publ.-Id: 36296


PIConGPU: Getting Particle-in-cell Plasma Simulations Ready for Exascale

Debus, A.; Widera, R.; Lebedev, A.; Bastrakov, S.; Pausch, R.; Steiniger, K.; Pöschel, F.; Stephan, J.; Bussmann, M.

No official abstract here. We present an overview talk on laser-particle acceleration research with the challenges of modeling laser-plasma interactions using PIConGPU on latest exascale machines (JUWELS BOOSTER, Perlmutter,Summit and early-access systems for Frontier).We show the softwarestack of the particle-in-cell code PIConGPU (alpaka,openPMD, ...) with an emphasis on performance-portability and I/O at exascale. Furthermore we showed in an example how detailed performance benchmarking and profiling (together with JSC) helped improving code performance.

Keywords: particle-in-cell code; PIConGPU

  • Invited lecture (Conferences) (Online presentation)
    10 Year Anniversary Workshop of NVIDIA Application Lab at Jülich, 21.-22.6.2022, Jülich, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36295
Publ.-Id: 36295


Traveling-wave electron accelerators -- Getting PIConGPU simulations ready for exascale

Debus, A.; Chandrasekaran, S.; Steiniger, K.; Widera, R.; Bastrakov, S.; Meyer, F.; Pausch, R.; Garten, M.; Kluge, T.; Kelling, J.; Hernandez Arreguin, B.; Leinhauser, M.; Young, J.; Pöschel, F.; Hübl, A.; Rogers, D.; Juckeland, G.; Bussmann, M.

Traveling-wave electron acceleration (TWEAC) is an advanced laser-plasma accelerators scheme, which is neither limited by dephasing, nor by pump depletion or diffraction. Such accelerators are scalable to energies beyond 10 GeV without the need for staging and are candidates for future compact electron-positron colliders.

TWEAC simulations to high energies require exascale compute resources. Within the early-access program (CAAR) for the upcoming exascale Frontier cluster at ORNL, we prepare PIConGPU, a 3D3V particle-in-cell code, for large-scale TWEAC simulations, including tuning and refining PIConGPU to run on the latest AMD GPUs. In this talk we present progress in TWEAC simulations and the technical advances in PIConGPU that enable running on Frontier.

Keywords: Traveling-wave electron acceleration; TWEAC; exascale; Laser-plasma accelerator; PIConGPU; particle-in-cell code

  • Lecture (Conference) (Online presentation)
    Virtuelle DPG-Frühjahrstagung in "Mainz" 2022, 28.03.-01.04.2022, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36294
Publ.-Id: 36294


Influence of Underlayer Quality and Sputter Gas Pressure on Structural and Magnetic Properties of Co/Pt Multilayers

Ehrler, R.; Uhlig, T.; Hellwig, O.

Influence of Underlayer Quality and Sputter Gas Pressure on Structural and Magnetic Properties of Co/Pt Multilayers

  • Lecture (Conference)
    AVS 68th International Symposium & Exhibition, 07.-11.11.2022, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-36292
Publ.-Id: 36292


Exploring Magnetic Reversal Behavior and Domain Structure in Perpendicular Anisotropy Layered Synthetic Antiferromagnets

Hellwig, O.

Exploring Magnetic Reversal Behavior and Domain Structure in Perpendicular Anisotropy Layered Synthetic Antiferromagnets

  • Lecture (Conference)
    AVS 68th International Symposium & Exhibition, 07.-11.11.2022, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-36291
Publ.-Id: 36291


Designing Antiferromagnetic Domain Landscapes via Focused Ion Beam Irradiation

Samad, F.; Hlawacek, G.; Koch, L.; Hellwig, O.; Xu, X.

Designing
Antiferromagnetic Domain Landscapes
via
Focussed Ion Beam Irradiation

  • Lecture (Conference)
    AVS 68th International Symposium & Exhibition, 09.11.2022, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-36290
Publ.-Id: 36290


Positrons in Material Sciences: Intense Beams for Defect Characterizations and Porosimetry

Wagner, A.

The Helmholtz-Center Dresden - Rossendorf operates a superconducting electron linear accelerator as a driver for secondary radiation sources, which include two IR-FEL, a broadband high-field THz radiation source, high-energy X-rays, neutrons and positrons. The accelerator runs in continuous-wave (CW) mode and in a 24/7 regime serving an international user community.
Electron-bremsstrahlung is being converted into an intense beam of positrons by means of pair production. After moderation to thermal energies, positrons are re-accelerated to form a mono-energetic positron beam with variable kinetic energies ranging from 0.5 to 18 keV for depth profiling of atomic defects and porosities on nm-scales in thin films. High timing resolutions ( < 100 ps) at high average rates (105 s-1) and adjustable beam repetition rates allow performing high-throughput experiments of positron annihilation lifetimes.
The accelerator-based positron source is complemented by a several radioisotope-driven setups for conventional annihilation lifetime measurements (defect characterizations) and Doppler-broadening spectroscopy, which is sensitive to the defect’s chemical surroundings.
In my presentation, I will highlight some of the unique features of the experimental facilities and I will show various experimental results obtained with positrons in defect characterizations of materials and porosimetry due to their sensitivity on open-volume defects ranging from sub-nm to µm scales.

Keywords: material sciences; positron; positron annihilation spectroscopy; positron lifetime spectroscopy

Related publications

  • Invited lecture (Conferences)
    Department seminar, 12.01.2023, Bowling Green, Ohio, USA
  • Invited lecture (Conferences)
    Materials Science Laboratory Seminar, 19.01.2023, Los Alamos, New Mexico, USA

Permalink: https://www.hzdr.de/publications/Publ-36287
Publ.-Id: 36287


Out-of-field measurements and simulations of a proton pencil beam in a wide range of dose rates using a Timepix3 detector: Dose rate, flux and LET

Oancea, C.; Granja, C.; Marek, L.; Jakubek, J.; Solc, J.; Bodenstein, E.; Gantz, S.; Pawelke, J.; Pivec, J.

Stray radiation produced by ultra-high dose-rates (UHDR) proton pencil beams is characterized using ASIC-chip semiconductor pixel detectors. A proton pencil beam with an energy of 220 MeV was utilized to deliver dose rates (DR) ranging from conventional radiotherapy DRs up to 270 Gy/s. A MiniPIX Timepix3 detector equipped with a silicon sensor and integrated readout electronics was used. The chip-sensor assembly and chipboard on water-equivalent backing were detached and immersed in the water-phantom. The deposited energy, particle flux, DR, and the linear energy transfer (LET(Si)) spectra were measured in the silicon sensor at different positions both laterally, at different depths, and behind the Bragg peak. At low-intensity beams, the detector is operated in the event-by-event data-driven mode for high-resolution spectral tracking of individual particles. This technique provides precise energy loss response and LET(Si) spectra with radiation field composition resolving power. At higher beam intensities a rescaling of LET(Si) can be performed as the distribution of the LET (Si) spectra exhibits the same characteristics regardless of the delivered DR. The integrated deposited energy and the absorbed dose can be thus measured in a wide range. A linear response of measured absorbed dose was obtained by gradually increasing the delivered DR to reach UHDR beams. Particle tracking of scattered radiation in data-driven mode could be performed at DRs up to 0.27 Gy/s. In integrated mode, the saturation limits were not reached at the measured out-of-field locations up to the delivered DR of over 270 Gy/s. A good agreement was found between measured and simulated absorbed doses.

Keywords: Out-of-field proton therapy; Timepix3; Particle tracking; LET(Si) spectra; UHDpulse; Flash radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-36286
Publ.-Id: 36286


Non-linearity induced contrast degradation in high-power lasers

Bock, S.; Oksenhendler, T.; Püschel, T.; Gebhardt, R.; Helbig, U.; Ziegler, T.; Zeil, K.; Pausch, R.; Toncian, T.; Nishiuchi, M.; Kiriyama, H.; Schramm, U.

The characteristics of high power lasers applied for relativistic plasma experiments are a matter of constant research and improvement for supporting highest possible performance. Especially the temporal contrast is crucial, while different mechanisms can lead to its degradation. One prominent effect is the non-linear B-integral induced pulse coupling from a post pulse generating a pre-pulse, generally described by Didenko, et.al. [1]. Recent measurements showed a more complex behavior with delayed pre-pulse generation and complex temporal shapes [2]. We applied an improved SRSI-ETE [3] setup to measure the non-linear pulse coupling at the DRACO Petawatt facility [4], revealing the spectral-temporal structure of the generated pulses. To assist the understanding of the observed non-linear effects a model was developed [5], covering the principle B-integral induced pulse generation, as well as the generation of the additional pulse structures, by means of non-resonant and resonant non-linear optical effects. The performed study allows a full understanding of the non-linear processes generating the pre-pulse and subsequent structures.

  • Lecture (Conference)
    ICUIL 2022, 19.-23.09.2022, Jeju Island, Korea

Permalink: https://www.hzdr.de/publications/Publ-36284
Publ.-Id: 36284


High-content multi-spectral fluorescence microscopy sample preparation artefacts

Sharma, V.; Yakimovich, A.

Sample preparation artefacts represent a significant source of errors in high-content screening datasets leading to misinterpretation of results in drug discovery. To address this we have created a multispectral high-content imaging dataset with typical sample preparation artefacts added to the samples. This dataset consists of high-content images of cultured HeLa ATCC cells in the presence of typical sample preparation artefacts. The aim of this dataset. HeLa cells imaged in this dataset were cultured in a black 96-well (rows A to H and columns 1 to 12) polystyrene imaging plate (Corning, Sigma).

To obtain a dataset similar to the experimental setup of a high-content image-based screening we have used a 96-well (rows A to H and columns 1 to 12) black polystyrene imaging plate (Corning, Sigma). HeLa cells were seeded a day prior to the experiment in 200 µL volume (per well) containing 250000 cells per mL in Dulbecco’s Modified Eagle’s Medium (Sigma) containing 10% fetal calf serum (Sigma) 4500 mg/L glucose (Sigma), sodium bicarbonate (Sigma), L-glutamine (Sigma), sodium pyruvate (Sigma), and non-essential amino acids (Sigma). To obtain a gradient of cell density, the cell suspension was stepwise diluted at 1:2 ratio during seeding (columns 2 to 12). The first column was reserved as no-cells control. Upon seeding, the HeLa cells were incubated overnight at 37° C in a 5% CO2 atmosphere with humidity control. The next day after seeding, cells were fixed with 4% paraformaldehyde (Sigma) solution prepared in phosphate buffer saline (PBS, Sigma). Upon fixation, HeLa cell nuclei were stained with Hoechst 33342 dye (Sigma) at 40 µg/mL concentration prepared in PBS. Row A was kept unstained as the control without Hoechst dye. Upon preparation of the bona fide artefact-free experimental plate, we have collected samples of dust across the approximately 100 m2 laboratory and prepared a suspension of these dust samples in PBS. Next, we added this suspension to rows A to G of the 96-well plate, leaving row H as an artefact-free control.

The dataset consists of images obtained with 4x and 10x objectives using fluorescence cube assemblies for DAPI, CFP, GFP, TRITC and Cy5 channels. For hardware reasons, images with the CFP filter cube were obtained separately from images with DAPI, CFP, GFP, TRITC and Cy5 filter cubes. Furthermore, CFP images (and in some cases DAPI images) were obtained with varying exposure times corresponding to “_w1”, “_w2” and so on filename suffixes. Images were obtained using ImageXpress Micro XL high-content microscope (Molecular Devices). Images are organised into the following folders:

  1. 4x-cfp

  2. 4x-dapi-gfp-tritc-cy5

  3. 10x-6cfp

  4. 10x-6dapi

  5. 10x-cfp

  6. dapi-gfp-tritc-cy5

  7. filters_spectra

Here, folders A and B correspond to 4x magnification and contain images obtained with the CFP (folder A) and the other filter cubes respectively (folder B). Each folder contains “TimePoint_1” subfolder containing the raw images. In the case of 4x images, each field of view (“site” designed with “_s1”, “_s2” etc. suffixes) corresponds to a nearly perfect quarter of a 96-well plate well. In addition to the raw images in the “TimePoint_1”, a subfolder “Stitched” contains images of the entire wells. In the case of folder B containing all other fluorescence channels, “_w1”, “_w2”, “_w3”, and “_w4” correspond to a single optimal exposure time of DAPI, GFP, TRITC and Cy5 filters respectively.

Similarly, folders C - F correspond to 10x magnification and contain images of multiple exposures of CFP and DAPI (folders C and D) and single exposures of CFP and other channels (folders E and F). In the case of CFP and DAPI multiple exposures folders, varying exposure times correspond to “_w1”, “_w2” etc. Finally, folder G contains metadata on filter cubes used in the dataset, including the emission and excitation filters spectra for each filter cube.

Keywords: fluorescence microscopy; high-content microscopy; sample preparation artefacts

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Permalink: https://www.hzdr.de/publications/Publ-36282
Publ.-Id: 36282


Catalytic Activity of Defect-Engineered Transition Metal Dichalcogenides Mapped with Atomic Scale Precision by Electrochemical Scanning Tunneling Microscopy

Lunardon, M.; Kosmala, T.; Ghorbani Asl, M.; Krasheninnikov, A.; Kolekar, S.; Durante, C.; Batzill, M.; Agnoli, S.; Granozzi, G.

Unraveling structure–activity relationships is a key objective of catalysis. Unfortunately, the intrinsic complexity and structural heterogeneity of materials stand in the way of this goal, mainly because the activity measurements are area-averaged and therefore contain information coming from different surface sites. This limitation can be surpassed by the analysis of the noise in the current of electrochemical scanning tunneling microscopy (EC-STM). Herein, we apply this strategy to investigate the catalytic activity toward the hydrogen evolution reaction of monolayer films of MoSe₂. Thanks to atomically resolved potentiodynamic experiments, we can evaluate individually the catalytic activity of the MoSe₂ basal plane, selenium vacancies, and different point defects produced by the intersections of metallic twin boundaries. The activity trend deduced by EC-STM is independently confirmed by density functional theory calculations, which also indicate that, on the metallic twin boundary crossings, the hydrogen adsorption energy is almost thermoneutral. The micro- and macroscopic measurements are combined to extract the turnover frequency of different sites, obtaining for the most active ones a value of 30 s⁻¹ at −136 mV vs RHE.

Keywords: green hydrogen; two-dimensional materials; transition metal dichalcogenides; catalyst; hydrogen evolution reaction; defect; scanning tunneling microscopy

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36281
Publ.-Id: 36281


Generalized Gelfand-Dikii equation for fermionic Schwinger pair production

Ahmadiniaz, N.; Pyo Kim, S.; Schubert, C.

Generalized Gelfand-Dikii equation for fermionic Schwinger pair production

Keywords: Schwinger pair production; Gelfand-Dikii equation

  • Open Access Logo Contribution to proceedings
    29th annual International Laser Physics Workshop (LPHYS'21), 19.-23.07.2022, virtual, virtual
    Journal of Physics: Conference Series 2249 (2022), 012020
    DOI: 10.1088/1742-6596/2249/1/012020
    arXiv: https://arxiv.org/pdf/2205.15945.pdf

Permalink: https://www.hzdr.de/publications/Publ-36280
Publ.-Id: 36280


Generalized Gelfand-Dikii equation and solitonic electric fields for fermionic Schwinger pair production

Ahmadiniaz, N.; Fedotov, A. M.; Gelfer, E. G.; Pyo Kim, S.; Schubert, C.

Schwinger pair creation in a purely time-dependent electric field can be reduced to an effective quantum mechanical problem using a variety of formalisms. Here we develop an approach based on the Gelfand-Dikii equation for scalar QED, and extent it to spinor QED. We discuss some solvable special cases from this point of view. It was previously shown how to use the well-known solitonic solutions of the KdV equation to construct “solitonic” electric fields that do not create scalar pairs with an arbitrary fixed momentum. We show that this construction can be adapted to the fermionic case in two inequivalent ways, both leading to the vanishing of the pair-creation rate at certain values of the P ̈oschl-Teller like index of the associated Schr ̈odinger equation. Thus for any given momentum, we can construct electric fields that create scalar particles but not spinor particles, and also the other way round. Therefore, while often spin is even neglected in Schwingerpair creation, in such cases it becomes decisive.

Keywords: Schwinger mechanism; Pair production; Gelfand-Dikii equation

Permalink: https://www.hzdr.de/publications/Publ-36279
Publ.-Id: 36279


Summing Feynman diagrams in the worldline formalism

Ahmadiniaz, N.; Edwards, J. P.; Lopez-Arcos, C.; Lopez-Lopez, M. A.; Moctezuma Mata, C.; Nicasio, J.; Schubert, C.

The worldline formalism shares with string theory the property that it allows one to write down master integrals that effectively combine the contributions of many Feynman diagrams. While at the one-loop level, these diagrams differ only by the position of the external legs along a fixed line or loop, at multiloop they generally involve different topologies. Here we summarize various efforts that have been made over the years to exploit this property in a computationally meaningful way. As a first example, we show how to generalize the Landau-Khalatnikov-Fradkin formula for the non-perturbative gauge transformation of the fermion propagator in QED to the general2𝑛- point case by pure manipulations at the path-integral level. At the parameter-integral level, we show how to integrate out individual photons in the low-energy expansion and then sketch a recently introduced general framework for the analytical evaluation of such worldline integrals involving a reduction to quantum mechanics on the circle and the relation between inverse derivatives and Bernoulli polynomials

Keywords: Woldline formalism; Feynman diagrams; QED

  • Open Access Logo Contribution to proceedings
    Loops and Legs in Quantum Field Theory - LL2022, 25.-30.04.2022, Ettal, Germany
    Proceedings of Science (LL2022), 052
    DOI: 10.22323/1.416.0052
    arXiv: https://arxiv.org/pdf/2208.06585.pdf

Permalink: https://www.hzdr.de/publications/Publ-36277
Publ.-Id: 36277


Spin-wave study of magnetic perpendicular surface anisotropy in single crystalline MgO/Fe/MgO films

Solano, J.; Gladii, O.; Kuntz, P.; Henry, Y.; Halley, D.; Bailleul, M.

Broadband ferromagnetic resonance is measured in single crystalline Fe films of varying thickness sandwiched between
MgO layers. An exhaustive magnetic characterization of the films (exchange constant, cubic, uniaxial and surface
anisotropies) is enabled by the study of the uniform and the first perpendicular standing spin wave modes as a function of
applied magnetic field and film thickness. Additional measurements of nonreciprocal spin-wave propagation allow us to
separate each of the two interface contributions to the total surface anisotropy. The results are consistent with the model of a
quasi-bulk film interior and two magnetically different top and bottom interfaces, a difference ascribed to different oxidation
states

Keywords: Interface states; spin wave; Magnetic anisotropy; Broadband ferromagnetic resonance

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Permalink: https://www.hzdr.de/publications/Publ-36276
Publ.-Id: 36276


Coupled thermo-fluid-mechanical FEM simulations for thermoelastic harvesting of low-grade waste heat

Neumann, B.; Eckert, K.; Fähler, S.

COMSOL-Multiphysics file for the FEM-Simulations of the paper. The attached version was used to generate plot data. The extracted plot data is attached as well.

Keywords: Energy; FEM; Thermoelastic Energy Harvesting; Simulation

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Permalink: https://www.hzdr.de/publications/Publ-36275
Publ.-Id: 36275


Field-assisted birefringent Compton scattering

Ahmadiniaz, N.; Cowan, T.; Ding, M.; Lopez Lopez, M. A.; Sauerbrey, R.; Shaisultanov, R.; Schützhold, R.

Motivated by experimental initiatives such as the Helmholtz International Beamline for ExtremeFields (HIBEF), we study Compton scattering of x-rays at electrons in a strong external field (e.g., a strong optical laser) with special emphasis on the polarization-changing (i.e., birefringent) contribution on the amplitude level. Apart from being a potential background process for the planned vacuum birefringence experiments, this effect could be used for diagnostic purposes. Since the birefringent signal from free electrons (i.e., without the external field) vanishes in forward direction, the ratio of the birefringent and the normal (polarization conserving) contribution yields information about the field strength at the interaction point.

Keywords: Vacuum birefringent; Compton scattering; HIBEF

Permalink: https://www.hzdr.de/publications/Publ-36274
Publ.-Id: 36274


Solid-Phase Parallel Synthesis of Dual Histone Deacetylase-Cyclooxygenase Inhibitors

Bachmann, L. M.; Hanl, M.; Feller, F.; Sinatra, L.; Schöler, A.; Pietzsch, J.; Laube, M.; Hansen, F. K.

Multi-target drugs (MTDs) are emerging alternatives to combination therapies. Since both his-tone deacetylases (HDACs) and cyclooxygenase-2 (COX-2) are known to be overexpressed in several cancer types, we herein report the design, synthesis, and biological evaluation of a li-brary of dual HDAC-COX inhibitors. The designed compounds were synthesized via an efficient parallel synthesis approach using preloaded solid-phase resins. Biological in vitro assays demon-strated that several of the synthesized compounds possess pronounced inhibitory activities against HDAC and COX isoforms. The membrane permeability and inhibition of cellular HDAC activity of selected compounds were confirmed by whole-cell HDAC inhibition assays and western blot experiments. The most promising dual inhibitors C3 and C4 evoked antiprolifera-tive effects in the low micromolar concentration range and caused a significant increase in apoptotic cells. In contrast to previous reports, the simultaneous inhibition of HDAC and COX activity by dual HDAC-COX inhibitors or combination treatment with vorinostat and celecoxib did not result in additive or synergistic anticancer activities.

Keywords: COX; HDAC; multi-target drugs; cancer; solid-phase synthesis

Permalink: https://www.hzdr.de/publications/Publ-36271
Publ.-Id: 36271


Data publication: Core-shell structured MCM-48-type silica-polymer hybrid material synthesis and characterization

Yismaw, S.; Wenze, M.; Attallah, A. G.; Zaleski, R.; Matysik, J.; Poppitz, D.; Gläser, R.; Ebbinghaus, S. G.; Enke, D.

In the current study, a core-shell structured material of MCM-48-type mesoporous silica nanoparticles (MSNs) and cross-linked poly(N-isopropylacrylamide) homopolymer and its copolymer with methacrylic acid was synthesized. The polymer was preferentially grafted on the outer surface of silane linker-functionalized MSNs based on free radical polymerization. The successful chemical grafting of the polymer on the silica surface was confrmed by FTIR, NMR, TG, and elemental analyses. The polymer contents of the hybrid particles vary from 18 to 40 % as determined by thermogravimetric and elemental analyses. The polymer content was tailored by varying diferent reaction parameters including monomer concentration, linker content/type, and reaction time. Well-defned uniform core-shell structured spherical particles with an average particle size of 367 ± 25 nm and shell thickness of 29 ± 8 nm were observed in TEM analysis. According to XRD and nitrogen physisorption studies, the ordered mesopore structure of the core MCM-48-type MSNs was maintained after an extended polymer grafting process and surface coverage with a high content of polymer. No signifcant pore blockage was observed in porosimetry analysis. More than 75% of specifc surface area, 68% of total pore volume, and the mean mesopore diameter were retained after successful grating of polymer on the outer silica surface. The pore volume thus can provide enough space to encapsulate high contents of cargo molecules for applications. The narrow pore width distribution of the main mesopores of silica determined by PALS analysis corresponds to the N2 sorption analysis and further confrms the uniformity of the mesopores.

Keywords: MCM-48-type mesoporous silica nanoparticles; Hybrid material; Core-shell structure; Polymer; Grafting; Synthesis

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Permalink: https://www.hzdr.de/publications/Publ-36269
Publ.-Id: 36269


Modelling based approach for the identification of germanium- and indium - binding siderophores

Hintersatz, C.; Tsushima, S.; Jain, R.; Pollmann, K.

Density functional theory was used in order to screen for siderophores selective for gallium, indium, and germanium, respectively.

  • Lecture (Conference) (Online presentation)
    BioCuInGe Workshop on Waste to Wealth, 25.-26.11.2022, Delhi, Indien

Permalink: https://www.hzdr.de/publications/Publ-36265
Publ.-Id: 36265


Selection and production of siderophores suitable germanium-, indium and gallium - recovery

Hintersatz, C.; Rojas, L. A.; Kutschke, S.; Jain, R.; Tsushima, S.; Pollmann, K.

Siderophores are a diverse group of small iron-chelating molecules that are synthesized by a vast number of bacteria, fungi and graminaceous plants in order to sequester the essential metal under iron-limited conditions. Their capability to complex other metals as well makes them possibly suited compounds for the usage in bio-based recycling technologies.
The aim of this work is to find siderophores, which selectively bind the critical elements indium, gallium and germanium. Due to the vast number of different known siderophores the complete experimental evaluation is impractical, though. Hence, density functional theory (DFT) is used to simulate the chelation reaction in order to estimate the affinities of various siderophores towards gallium and indium as well as the stability of the resulting coordination complexes. Additionally, environmental samples from lagoons of the Atacama Desert are screened for novel siderophore-producing organisms. The siderophores excreted by those organisms might possess unique binding abilities due to the highly saline and alkaline conditions of the isolation sites. Siderophores selected via DFT as well as those produced by isolated microorganisms are tested experimentally for their affinity towards the metals of interest.
Proving the applicability of siderophores in the recovery of indium and gallium from low concentrated waste waters would create a vast amount of further possible applications of the biomolecules to aid securing the future supply of not just said energy-critical elements, but all strategic metals.

  • Lecture (Conference) (Online presentation)
    ACS Spring 2022, 20.-24.03.2022, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-36263
Publ.-Id: 36263


Chlorine doping of MoSe2 flakes by ion implantation

Prucnal, S.; Li, Y.; Ghorbani Asl, M.; Hübner, R.; Ziegenrücker, R.; Kentsch, U.; Krasheninnikov, A.; Helm, M.; Zahn, D. R. T.; Zhou, S.

The efficient integration of transition metal dichalcogenides (TMDs) into the current electronic device technology requires mastering the techniques of effective tuning of their optoelectronic properties. Specifically, controllable doping is essential. For conventional bulk semiconductors, ion implantation is the most developed method offering stable and tunable doping. In this work, we demonstrate n-type doping in MoSe2 flakes realized by low-energy ion implantation of Cl+ ions followed by millisecond-range flash lamp annealing (FLA). We further show that FLA for 3 ms with a peak temperature of about 1000 °C is enough to recrystallize implanted MoSe2. The Cl distribution in few-layer-thick MoSe2 is measured by secondary ion mass spectrometry. An increase in the electron concentration with increasing Cl fluence is determined from the softening and red shift of the Raman-active A1g phonon mode due to the Fano effect. The electrical measurements confirm the n-type doping of Cl-implanted MoSe2. A comparison of the results of our density functional theory calculations and experimental temperature-dependent micro-Raman spectroscopy data indicates that Cl atoms are incorporated into the atomic network of MoSe2 as substitutional donor impurities.

Related publications

  • Poster
    German Conference for Research with Synchrotron Radiation, Neutrons and Ion Beams at Large Facilities, 05.-07.09.2022, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-36262
Publ.-Id: 36262


Data publication: A network-based approach to identifying correlations between phylogeny, morphological traits and occurrence of fish species in US river basins.

Tripathi, R.; Reza, A.; Su, G.; Mertel, A.; Calabrese, J.

There are three primary datasets used in this work.These were obtained for Dr. Guohuan Su (co-author on the paper) . 1. Phylogenetic distance data sets between all fish species in the US. 2. Morphological traits dataset that list 10 traits information of fish species. 3. Occurrence dataset that list occurrence information of fish species in HUC8 regions of the US There is one dataset that lists exotic species in the US. The entries for exotic species are removed from about datasets before analysis.

Keywords: Complex Networks; Phylogenetic Distance; Morphological Traits; Species Co-occurrence

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Permalink: https://www.hzdr.de/publications/Publ-36260
Publ.-Id: 36260


Animal movement as a cross-cutting theme at CASUS

Calabrese, J.; Simoes Silva, I. M.; Alston, J.; Fleming, C.

The movement of animals through landscapes worldwide drives ecological processes, influences disease transmission, and governs how humans and wildlife interact. High resolution animal tracking data have transformed our ability to understand when, where, how, and why animals move. However, these data come with formidable statistical challenges including strong autocorrelation and context-dependent location errors and fix rates. Overcoming these hurdles requires an interdisciplinary effort that combines ecology, physics, geostatistics, signal processing, and computer science.

In this talk, I detail ongoing work at CASUS in animal movement research, covering statistical methods and software development as well as applications in ecology, wildlife management, and autonomous vehicles research. I also highlight the role that aggregated, multispecies tracking datasets play in understanding animal movement and its consequences at the global scale. Finally, I discuss future directions for this research program, outlining potential points of collaboration with researchers coming from different disciplines.

  • Invited lecture (Conferences)
    Big data analytical methods for complex systems, 06.10.2022, Wroclaw, Poland
  • Invited lecture (Conferences)
    CASUSCON, 14.07.2022, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-36258
Publ.-Id: 36258


Spaceborne GNSS-Receiver Evolution – From Classical HiRel to NewSpace Constellation

Schütz, M.; Zehetmayer, S.; Zajac, K.; Laabs, M.; Borany, J.; Zangl, R.; Sust, M.

Spaceborne Global Navigation Satellite System (GNSS) receivers have become indispensable components of satellites, in particular for real-time navigation as part of the attitude and orbit control system and for precise orbit determination in support of highly accurate earth observation instruments. In cooperation with the project partners TU Dresden and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Beyond Gravity (formerly RUAG Space) has developed a flexible GNSS receiver platform targeting NewSpace applications but leveraging the performance of the current gold standards with respect to spaceborne GNSS-receiver technology. A novel radiation test environment was introduced, and selected components were radiation tested to ensure a consistent reliability.

  • Lecture (Conference)
    Deutscher Luft- und Raumfahrtkongress (DLRK 2022), 27.-29.09.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36256
Publ.-Id: 36256


Species invasiveness and community invasibility of US freshwater fish fauna revealed via trait-based analysis

Su, G.; Mertel, A.; Brosse, S.; Calabrese, J.

While biological invasions are recognized as a major threat to global biodiversity, determining species’ abilities to invade new areas (species invasiveness) and the vulnerability of those areas to invasions (community invasibility) are still poorly understood. Here, we used trait-based analysis to profile invasive species and quantify the community invasibility for >1,800 North American freshwater fish communities. We show that species with higher reproduction rates, longer life spans and larger sizes tend to be more invasive. Community invasibility peaked when the functional distance among native species was high, leaving unoccupied functional space for the establishment of potential invaders. Invasion success is therefore governed by both the functional traits of non-native species determining their invasiveness, and by the functional characteristics of the invaded community determining its invasibility. Considering those two determinants together will allow better predictions of invasions.

Permalink: https://www.hzdr.de/publications/Publ-36255
Publ.-Id: 36255


Using mini-CT specimens for the fracture characterization of ferritic steels within the ductile to brittle transition range: a review

Sánchez, M.; Cicero, S.; Kirk, M.; Altstadt, E.; Server, W.; Yamamoto, M.

The use of mini-CT specimens for the fracture characterization of structural steels is currently a topic of great interest from both scientific and technical points of view, mainly driven by the needs and requirements of the nuclear industry. In fact, the long-term operation of nuclear plants requires accurate characterization of the reactor pressure vessel materials and evaluation of the embrittlement caused by neutron irradiation without applying excessive conservatism. However, the amount of material placed inside the surveillance capsules used to characterize the resulting degradation is generally small. Consequently, in order to increase the reliability of fracture toughness measurements and reduce the volume of material needed for the tests, it is necessary to develop innovative characterization techniques, among which the use of mini-CT specimens stands out. In this context, this paper provides a review of the use of mini-CT specimens for the fracture characterization of ferritic steels, with particular emphasis on those used by the nuclear industry. The main results obtained so far, revealing the potential of this technique, together with the main scientific and technical issues will be thoroughly discussed. Recommendations for several key topics for future research are also provided.

Keywords: mini-CT; ductile-to-brittle transition range; reference temperature; master curve

Permalink: https://www.hzdr.de/publications/Publ-36253
Publ.-Id: 36253


PIConGPU -- High-Fidelity Plasma Simulations on Desktop Computers up to Exascale Compute Systems and a View on its Recent Applications

Debus, A.; Steiniger, K.; Bastrakov, S.; Bastrakova, K.; Bussmann, M.; Carstens, F.-O.; Chandrasekaran, S.; Garten, M.; Gruber, B. M.; Hernandez Arreguin, B.; Hübl, A.; Juckeland, G.; Kelling, J.; Lebedev, A.; Leinhauser, M.; Marre, B. E.; Meyer, F.; Ordyna, P.; Pausch, R.; Pöschel, F.; Rogers, D.; Schramm, U.; Sprenger, L.; Starke, S.; Thévenet, M.; Trojok, J.; Wang, M.; Widera, R.; Young, J.

PIConGPU’s latest release 0.6.0 in December 2021 brought a number of new features. Among these are an arbitrary-order Maxwell solver, the Higuera-Cary pusher, collisions, and incident field generation via the total field/scattered field technique enhancing its numerical stability and predictive capabilities.
Furthermore, there are various technical advances, most notably support of the HIP computational backend allowing to run on AMD GPUs. These advances are mainly driven by our participation in OLCF’s Frontier Center for Accelerated Application Readiness providing access to the hardware platform of the Frontier exascale supercomputer scheduled for deployment in 2022. We show performance data and present recent applications of PIConGPU profiting from these developments. To these applications belongs the advanced laser-plasma accelerator scheme Traveling-wave electron acceleration (TWEAC), providing scalability to energies beyond 10 GeV while avoiding staging. We further present simulation campaigns modeling and delivering valuable insight into the micrometer and femtosecond plasma dynamics of existing experimental
campaigns.

Keywords: particle-in-cell code; TWEAC; PIConGPU; performance portable

  • Poster
    767. WE-Heraeus-Seminar: Science and Applications of Plasma‐Based Accelerators, 15.-18.05.2022, Physikzentrum, Bad Honnef, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36252
Publ.-Id: 36252


minterpy: Multivariate Interpolation in Python

Schreiber, J.; Wicaksono, D. C.; Thekke Veettil, S. K.; Hajizade, A.; Zavalani, G.; Suarez Cardona, J. E.; Hernandez Acosta, U.; Hecht, M.

Many solutions to the computational challenges arising in the fields of computational science and engineering rely on solving interpolation tasks of highly-varying sparse and scattered data. The tasks include surrogate modeling, sparse data regression, global black-box optimization, model inference, as well as solutions for partial differential equations (PDE) on complex geometries.

Interpolation tasks in multi-dimensional space typically suffer from the curse of dimensionality in which the computational cost of interpolation scales exponentially with the number of dimensions.

The open-source Python package minterpy developed and maintained by the Hecht-Lab, CASUS, aims to lift the curse of dimensionality from a brand field of interpolation tasks arising across scientific disciplines.

Keywords: interpolation; multivariate interpolation; surrogate modeling; sparse data regression; global black-box optimization; model inference; partial differential equations (PDE)

  • Open Access Logo Poster
    Big data analytical methods for complex systems, 06.-07.10.2022, Wroclaw, Poland

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Permalink: https://www.hzdr.de/publications/Publ-36251
Publ.-Id: 36251


Transverse Emittance Measurements and Optimization for a Superconducting RF Photon Injector

Ma, S.

As one of the most promising continuous wave (CW) injectors for high brightness electron
beams, ELBE superconducting radio-frequency (SRF) gun has been developed and optimized.
This gun can provide beams with good quality for the ELBE user facility. One important
aspect is to measure the transverse emittance accurately and efficiently. This thesis contributes
to the progress in this field and focuses on measuring and optimizing the transverse emittance
for ELBE SRF gun. The slit-scan, quadrupole scan, and an advanced thermal emittance
measurement method, called single shot cathode transverse momentum imaging, have been
studied and applied at this SRF gun.
A fast slit-scan emittance measurement system consisting of a continuously moving slit and
a yttrium aluminium garnet (YAG) screen has been developed. During the beamlet image
processing, the machine learning (ML) algorithms have been integrated in order to improve
the signal-to-noise ratio effectively. This is the first time to successfully apply the ML in such
diagnostic methods. The measurement speed is improved about ten times and accuracy is also
better than before. The errors of slit-scan emittance measurement, arising from slit position,
beamlet intensity, center position and root mean square (RMS) width uncertainties, have been
analyzed. The quadrupole scan emittance measurement method has been studied too. The
influence of the space charge effect on quadrupole scan results has been revealed. The error of
the quadrupole scan measurement has also been analyzed.
To compensate the transverse emittance due to space charge effect, a superconducting (SC)
solenoid is placed as close as possible to the exit of the SRF cavity. Another important part in
this thesis is the investigation and optimization of the SC solenoid. The spherical aberration
of the SC solenoid has been analyzed. In order to decrease it, a new yoke geometry of SC
solenoid for the next generation SRF gun has been designed. The multipole transverse field
modes of the solenoid caused by an axis tilt have bean analyzed by means of simulations and
experimental investigations using a formalism fitting method. The influences of the multipole
modes, especially the quadrupole and sextupole fields on transverse emittance have been
calculated. A pair of a normal quadrupole and a skew quadrupole, called correctors, have been
adopted to compensate the influence of the quadrupole field on the emittance.
The cathode intrinsic emittance can contribute a non-negligible part to the transverse emittance.
So in this thesis the cathode intrinsic emitttance is measured too. The single shot transverse
momentum imaging method has been used to measure the cathode intrinsic emittance. A
further advantage is that this method allows to determine the transverse momentum locally at
different positions on the cathode.

Keywords: accelerator; superconducting RF photo injector; beam dynamic; emittance measurement

Related publications

  • Doctoral thesis
    Universität Hamburg, 2022
    125 Seiten

Permalink: https://www.hzdr.de/publications/Publ-36250
Publ.-Id: 36250


Tracer diffusion in proton-exchanged congruent LiNbO3 crystals as a function of hydrogen content

Dörrer, L.; Heller, R.; Schmidt, H.

The proton-exchange process is an effective method of fabricating low-loss waveguides based on
LiNbO3 crystals. During proton-exchange, lithium is replaced by hydrogen and Li1 xHxNbO3 is formed.
Currently, mechanisms and kinetics of the proton-exchange process are unclear, primarily due to a lack
in reliable tracer diffusion data. We studied lithium and hydrogen tracer diffusion in proton-exchanged
congruent LiNbO3 single crystals in the temperature range between 130–230 1C. Proton-exchange was
done in benzoic acid with 0, 1, 2, or 3.6 mol% lithium benzoate added, resulting in micrometre thick
surface layers where Li is substituted by H with relative fractions between x = 0.45 and 0.85 as
determined by Nuclear Reaction Analysis. For the diffusion experiments, ion-beam sputtered isotope
enriched 6LiNbO3 was used as a Li tracer source and deuterated benzoic acid as a H tracer source.
Isotope depth profile analysis was carried out by secondary ion mass spectrometry. From the
experimental results, effective diffusivities governing the lithium/hydrogen exchange as well as individual
hydrogen and lithium tracer diffusivities are extracted. All three types of diffusivities can be described by
the Arrhenius law with an activation enthalpy of about 1.0–1.2 eV and increase as a function of hydrogen
content nearly independent of temperature. The effective diffusivities and the lithium tracer diffusivities
are identical within a factor of two to five, while the hydrogen diffusivities are higher by three orders of
magnitude. The results show that the diffusion of Li is the rate determining step governing the protonexchange
process. Exponential dependencies between diffusivities and hydrogen concentrations are
determined. The observed increase of Li tracer diffusivities and effective diffusivities as a function of
hydrogen concentration is attributed to a continuous reduction of the migration enthalpy of diffusion by
a maximum factor of about 0.2 eV. Simulations based on the determined diffusivities can reproduce the
step-like profile of hydrogen penetration during proton-exchange.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36243
Publ.-Id: 36243


Investigation of matrix independent calibration of oxygen in glow discharge optical emission spectrometry

Hoffmann, V.; Gebel, B.; Heller, R.; Gemming, T.

The performance of glow discharge optical emission spectrometry for matrix independent oxygen determination was
investigated using the spectral lines of atomic oxygen at 130 nm and 777 nm and standard conditions for dc discharge with a
4 mm anode (700 V, 20 mA). Using hot-pressed calibration samples of Cu-, Al- and Mg-powder mixed with their oxides, at
130 nm the dependence of the emission yield on these matrices was confirmed. However, at 777 nm oxygen has the same
emission yield in these matrices. In order to compare the emission yield of oxygen with the emission yield in iron a thick 43
μm FeO-layer was prepared and characterized by Rutherford backscattering spectrometry, X-ray diffraction and glow
discharge optical emission spectrometry. At 130 nm, the emission yield of oxygen in FeO is most similar to that in an Almatrix.
At 777 nm, the calibration revealed a higher emission yield of oxygen in FeO in comparison to the common emission
yield of oxygen in Cu-, Al- and Mg-matrices. © 2022 The Royal Society of Chemistry

Keywords: glow discharge; optical emission spectroscopy; material science

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36241
Publ.-Id: 36241


Survey of spatio-temporal couplings throughout high-power ultrashort lasers

Jeandet, A.; Jolly, S. W.; Borot, A.; Bussière, B.; Dumont, P.; Gautier, J.; Gobert, O.; Goddet, J.-P.; Gonsalves, A.; Irman, A.; Leemans, W. P.; Lopez-Martens, R.; Mennerat, G.; Nakamura, K.; Ouillé, M.; Pariente, G.; Pittman, M.; Püschel, T.; Sanson, F.; Sylla, F.; Thaury, C.; Zeil, K.; Fabien Quéré, A.

The investigation of spatio-temporal couplings (STCs) of broadband light beams is
becoming a key topic for the optimization as well as applications of ultrashort laser systems.
This calls for accurate measurements of STCs. Yet, it is only recently that such complete
spatio-temporal or spatio-spectral characterization has become possible, and it has so far mostly
been implemented at the output of the laser systems, where experiments take place. In this survey,
we present for the first time STC measurements at different stages of a collection of high-power
ultrashort laser systems, all based on the chirped-pulse amplification (CPA) technique, but with
very different output characteristics. This measurement campaign reveals spatio-temporal effects
with various sources, and motivates the expanded use of STC characterization throughout CPA
laser chains, as well as in a wider range of types of ultrafast laser systems. In this way knowledge
will be gained not only about potential defects, but also about the fundamental dynamics and
operating regimes of advanced ultrashort laser systems.

Permalink: https://www.hzdr.de/publications/Publ-36238
Publ.-Id: 36238


Characterization of the plasma mirror system at the J-KAREN-P facility

Kon, A.; Nishiuchi, M.; Fukuda, Y.; Kondo, K.; Ogura, K.; Sagisaka, A.; Miyasaka, Y.; Dover, N. P.; Kando, M.; Pirozhkov, A. S.; Daito, I.; Chang, L.; Woo Choi, I.; Hee Nam, C.; Ziegler, T.; Schlenvoigt, H.-P.; Zeil, K.; Schramm, U.; Kiriyama, H.

We report on the design and characterization of the plasma mirror system installed on the J-KAREN-P laser at the Kansai
Photon Science Institute, National Institutes for Quantum Science and Technology. The reflectivity of the single plasma
mirror system exceeded 80%. In addition, the temporal contrast was improved by two orders of magnitude at 1 ps before
the main pulse. Furthermore, the laser near-field spatial distribution after the plasma mirror was kept constant at plasma
mirror fluence of less than 100 kJ/cm2. We also present the results of investigating the difference and the fluctuation in
energy, pulse width and pointing stability with and without the plasma mirror system.

Permalink: https://www.hzdr.de/publications/Publ-36237
Publ.-Id: 36237


High energy proton acceleration at DRACO-PW and radio-biological applications

Zeil, K.

Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power laser driven compact plasma accelerators can generate short, high-intensity pulses of high energy ions with special beam properties. By that they may expand the portfolio of conventional machines in many application areas. The maturation of laser driven ion accelerators from physics experiments to turn-key sources for these applications will rely on breakthroughs in both, generated beam parameters (kinetic energy, flux), as well as increased reproducibility, robustness and scalability to high repetition rate.
Recent developments at the high-power laser facility DRACO-PW enabled the production of polychromatic proton beams with unprecedented stability [1]. This allowed the first in vivo radiobiological study to be conducted using a laser-driven proton source [2]. Yet, the ability to achieve energies beyond the 100 MeV frontier is matter of ongoing research, mainly addressed by exploring advanced acceleration schemes like the relativistically induced transparency (RIT) regime.
In this talk we report on experimental proton acceleration studies at the onset of relativistic transparency using pre-expanded plastic foils. Combined hydrodynamic and 3D particle-in-cell (PIC) simulations helped to identify the most promising target parameter range matched to the prevailing laser contrast conditions carefully mapped out in great detail beforehand. A complex suite of particle and optical diagnostics allowed characterization of spatial and spectral proton beam parameters and the stability of the regime of best acceleration performance, yielding cut-off energies larger than 100 MeV in the best shots.

  • Invited lecture (Conferences)
    20th Advanced Accelerator Concepts Workshop (AAC’22), 07.11.2022, Long Island, USA

Permalink: https://www.hzdr.de/publications/Publ-36236
Publ.-Id: 36236


Laser-plasma ion accelerators for radio-biological research

Zeil, K.

Particle accelerators have always been fundamental engines of discovery and drivers of innovations in industry, basic research, and life sciences. Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power laser-driven compact plasma accelerators can generate short, high-intensity pulses of high energy electrons and ions with special beam properties. By that they may expand the portfolio of conventional machines in many application areas.

For laser-driven ion accelerators, the full application in ultra-high dose rate radiotherapy (RT) research marks one of the most important research objectives and is perfectly timed with the emerging interest on ultra-high dose rate RT. Laser proton accelerators are ideal instruments to investigate ultra-high dose rate effects, yet their ability to provide radiobiological in-vivo data comparable in quality to a clinical reference standard has called for demonstration for a long time.

The talk will introduce the concept of laser-driven ion accelerators and challenges of this technology. For the example of the high power laser source DRACO operated at HZDR, key developments for the production of reliable polychromatic proton beams with maximum energies of around 60 MeV are presented. Most recently, these achievements enabled the first successful small animal pilot study on radiation-induced tumor growth delay in mice using a laser-driven proton source and a clinical reference.

  • Invited lecture (Conferences) (Online presentation)
    Virtual DPG Spring Meeting - Symposium Plasma Induced Accelerators, 31.03.2022, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36235
Publ.-Id: 36235


Laser driven proton accelerators with solid hydrogen jets for application

Zeil, K.

Laser plasma-based particle accelerators attract great interest in fields where conventional accelerators reach limits based on size, cost or beam parameters. However, despite the fact that first principles particle in cell simulations have predicted several advantageous ion acceleration schemes,
laser accelerators have not yet reached their full potential in producing simultaneous high-radiation
doses at high particle energies. The most stringent limitation is the lack of a suitable high-repetition
rate target that also provides a high degree of control of the plasma conditions which is required
to access these advanced regimes. Here, we demonstrate that the interaction of petawatt-class laser
pulses with a pre-formed micrometer-sized cryogenic hydrogen jet plasma overcomes these limitations. Controlled pre-expansion of the initially solid target by low intensity pre-pulses allowed for tailored density scans from the solid to the underdense regime. Our experiment demonstrates that
the near-critical plasma density profile produces proton energies of 80 MeV. This energy presents
more than a factor of two increase compared to the solid hydrogen target. Our three-dimensional
particle in cell simulations show the transition between different acceleration mechanisms and suggest enhanced proton acceleration at the relativistic transparency front for the optimal case.

  • Invited lecture (Conferences)
    13th International Particle Accelerator Conference (IPAC’22), 15.06.2022, Bangkok, Thailand

Permalink: https://www.hzdr.de/publications/Publ-36234
Publ.-Id: 36234


High energy proton detection in Draco PW experiments

Zeil, K.; Assenbaum, S.; Bernert, C.; Brack, F.-E.; Cowan, T.; Garten, M.; Gaus, L.; Göthel, I.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Reimold, M.; Rehwald, M.; Schlenvoigt, H.-P.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Ziegler, T.; Schramm, U.

Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power
laser driven compact plasma accelerators can generate short, high-intensity pulses of high
energy ions with special beam properties interesting for many application areas. The transition
of laser driven ion accelerators from physics experiments to turn-key sources for these
applications relies on improvement of generated beam parameters (kinetic energy, flux), as
well as increased reproducibility, robustness and scalability to high repetition rate.
Recent developments at the high-power laser facility DRACO-PW enabled the production
of polychromatic proton beams with unprecedented stability [1] which enabled the first in vivo
radiobiological study to be conducted using a laser-driven proton source [2]. Yet, the ability to
achieve highest energies around or even beyond the 100 MeV frontier is matter of ongoing
research, mainly addressed by exploring advanced acceleration schemes.
In parallel to the testing of these schemes an important challenge is to provide convincing
evidence that these very high energies could be reached at all for a significant number of
particles. Occurring complications are due to the nature of the multi-species beams with
typically exponentially decaying spectra and low shot statistics of laser-plasma experiments
at the necessary laser pulse energy levels. The latter is in particular complicated for highly
non-linear acceleration regimes with intrinsically low reproducibility.
In this talk we summarize our approaches for the spatial and spectral characterization of our
proton beam parameters with cut-off energies larger than 80 MeV. Key is the combination of
a multitude of different methods based on different detection principles established for single
shot measurements. Time-of-flight methods are discussed for energy cross-calibration of our
Thomson parabola spectrometers and the use of different screen types for on-shot particle
number calibration is presented.

  • Lecture (Conference)
    BLIN5 Workshop 2022, 14.10.2022, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36233
Publ.-Id: 36233


Preliminary results from the x-ray spectrometers at Draco PW laser facility

Stefanikova, R.; Pan, X.; Smid, M.; Schlenvoigt, H.-P.; Prencipe, I.; Gaus, L.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Reimold, M.; Ziegler, T.; Kroll, F.; Kraft, S.; Schramm, U.; Zeil, K.; Metzkes-Ng, J.; Falk, K.

A large amount of complex processes within laser-produced plasmas put a huge demand for precise diagnostics methods. For example, x-ray emission spectroscopy can be used to study atomic physics and plasma conditions. Here, we introduce two new x-ray spectrometers installed in the Ion acceleration lab at the Draco PW laser facility. Availability of such diagnostics at the Draco PW Ti:sapphire 30 fs laser system (i.e. ultra-short pulse system) allows not only for studying unique plasma conditions driving the ion acceleration, but also exploring new possibilities for x-ray backlighters suitable for high energy density experiments.
Both spectrometers are utilized for acquisition of Ti spectral lines, but offer different spectral resolution and range. Quartz crystal spectrometer has wider spectral range, including Ti K-α and He-α emission lines in the spectrum, whereas Ge crystal spectrometer focuses on K-α emission lines and offers 1D spatial imaging. We present first results demonstrating the capabilities of both spectrometers.
The first spectroscopic measurements include the emission spectra measurements from flat Ti targets used for proton acceleration calibration and optimization with and without laser pre-pulse and the use of structured targets for enhanced x-ray emission as well as tailoring of the electron spectra for optimization of the proton acceleration process.

Keywords: x-ray spectrometer; laser-produced plasma; characteristic emission lines

  • Poster
    17th International Conference on the Physics of Non-Ideal Plasmas, 22.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36232
Publ.-Id: 36232


Fabrication of highly n-type-doped germanium nanowires and Ohmic contacts using ion implantation and flash lamp annealing

Echresh, A.; Prucnal, S.; Li, Z.; Hübner, R.; Ganss, F.; Steuer, O.; Bärwolf, F.; Jazavandi Ghamsari, S.; Helm, M.; Zhou, S.; Erbe, A.; Rebohle, L.; Georgiev, Y.

Accurate control of doping and fabrication of metal contacts on n-type germanium nanowires (GeNWs) with low resistance and linear characteristics remain a major challenge in germanium-based nanoelectronics. Here, we present a combined approach to fabricate Ohmic contacts on n-type-doped GeNWs. Phosphorus (P) implantation followed by millisecond rear-side flash lamp annealing was used to produce highly n-type doped Ge with an electron concentration in the order of 10^19 − 10^20 cm^(−3). Electron beam lithography, inductively coupled plasma reactive ion etching, and nickel (Ni) deposition were used to fabricate GeNW-based devices with symmetric Hall bar configuration, which allows detailed electrical characterization of the NWs. Afterward, rear-side flash lamp annealing was applied to form Ni germanide at the Ni-GeNWs contacts to reduce the Schottky barrier height. The two-probe current-voltage measurements on n-type-doped GeNWs exhibit linear Ohmic behavior. Also, the size-dependent electrical measurements showed that carrier scattering near the NW surfaces and reduction of the effective NW cross-section dominate the charge transport in the GeNWs.

Keywords: Germanium nanowires; ion implantation; flash lamp annealing; n-type doped; Ohmic contacts; Hall bar configuration

Related publications

Downloads

  • Secondary publication expected from 02.11.2023

Permalink: https://www.hzdr.de/publications/Publ-36230
Publ.-Id: 36230


Impact of pre-plasma tailoring on K-ɑ emission and proton acceleration

Stefanikova, R.; Pan, X.; Smid, M.; Gaus, L.; Kraft, S.; Kroll, F.; Kozlová, M.; Prencipe, I.; Reimold, M.; Schlenvoigt, H.-P.; Umlandt, M. E. P.; Schramm, U.; Zeil, K.; Metzkes-Ng, J.; Falk, K.

Laser-produced plasmas are widely studied complex systems. In order to get better understanding of their inner processes, advanced diagnostics methods have to be used to get a valuable insight – for example, x-ray emission spectroscopy has the capability to unfold atomic processes and plasma conditions and reveal information about the hot electron population.
Recently, two x-ray crystal spectrometers were installed in the Ion Acceleration Lab at Draco PW laser facility, which allows to acquire characteristic emission spectra including Ti K-α and He-α lines from Ti targets. While quartz spectrometer offers wide spectral range and excellent spectral resolution of ∼ 0.3 eV, Ge spectrometer focuses on Ti K-α emission lines and provides 1D spatial imaging with resolution below 10 μm.
Here, we present the first results from the x-ray spectroscopic measurements from proton acceleration targets at the DRACO PW laser facility uncovering the plasma conditions and electron dynamics for various target and laser configurations including inclusion artificial pre-pulse or the use of reduced mass targets.

  • Poster (Online presentation)
    The 48th European Conference on Plasma Physics (2022), 01.07.2022, Maastricht (online), Netherlands

Permalink: https://www.hzdr.de/publications/Publ-36229
Publ.-Id: 36229


Clarifying space use concepts in ecology: range vs. occurrence distributions

Alston, J.; Fleming, C.; Noonan, M.; Tucker, M.; Silva, I.; Folta, C.; Akre, T.; Ali, A.; Belant, J.; Beyer, D.; Blaum, N.; Boehning-Gaese, K.; Cunha De Paula, R.; Dekker, J.; Drescher-Lehman, J.; Farwig, N.; Fichtel, C.; Fischer, C.; Ford, A.; Janssen, R.; Jeltsch, F.; Kappeler, P.; Lapoint, S.; Markham, A.; Medici, P.; Morato, R.; Nathan, R.; Olson, K.; Patterson, B.; Petroelje, T.; Ramalho, E.; Roesner, S.; Santos, L.; Schabo, D.; Selva, N.; Sergiel, A.; Spiegel, O.; Ullman, W.; Zieba, F.; Zwijacz-Kozica, T.; Wittemyer, G.; Fagan, W.; Mueller, T.; Calabrese, J.

Quantifying animal movements is necessary for answering a wide array of research questions in ecology and conservation biology. Consequently, ecologists have made considerable efforts to identify the best way to estimate an animal’s home range, and many methods of estimating home ranges have arisen over the past half century. Most of these methods fall into two distinct categories of estimators that have only recently been described in statistical detail: those that measure range distributions (methods such as Kernel Density Estimation that quantify the long-run behavior of a movement process that features restricted space use) and those that measure occurrence distributions (methods such as Brownian Bridge Movement Models and the Correlated Random Walk Library that quantify uncertainty in an animal movement path during a specific period of observation). In this paper, we use theory, simulations, and empirical analysis to demonstrate the importance of applying these two classes of space use estimators appropriately and distinctly. Conflating range and occurrence distributions can have serious consequences for ecological inference and conservation practice. For example, in most situations, home-range estimates quantified using occurrence estimators are too small, and this problem is exacerbated by ongoing improvements in tracking technology that enable more frequent and more accurate data on animal movements. We encourage researchers to use range estimators to estimate the area of home ranges and occurrence estimators to answer other questions in movement ecology, such as when and where an animal crosses a linear feature, visits a location of interest, or interacts with other animals.

Permalink: https://www.hzdr.de/publications/Publ-36228
Publ.-Id: 36228


Study of x-ray emission from proton acceleration targets at Draco PW laser facility

Stefanikova, R.; Pan, X.; Meckel, N.; Smid, M.; Schlenvoigt, H.-P.; Prencipe, I.; Kozlová, M.; Gaus, L.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Reimold, M.; Ziegler, T.; Kroll, F.; Kraft, S.; Schramm, U.; Zeil, K.; Metzkes-Ng, J.; Falk, K.

Laser plasma-based ion accelerators are very promising candidates for many applications. In order to ensure the reliability of such accelerators a comprehensive set of diagnostics is required. X-ray emission spectroscopy allows us to directly measure the plasma conditions of the laser-plasma interaction and also provides information about the hot electron population through the cold K-α emission production.
Here, we present preliminary results from two new x-ray spectrometers used to study interaction regimes relevant for laser-driven ion acceleration at ultra-short pulse PW-class laser facility. We acquired the emission spectra from flat Ti targets for a range of target thicknesses and laser energies. Additionally, artificial laser pre-pulses were added to alter the laser absorption efficiency.

Keywords: x-ray spectroscopy; laser-produced plasma; characteristic emission lines; laser-plasma ion acceleration

  • Lecture (Conference) (Online presentation)
    DPG-Frühjahrstagung, 28.03.2022, Mainz, online, Germany

Permalink: https://www.hzdr.de/publications/Publ-36227
Publ.-Id: 36227


Study of the influence of various pre-plasma conditions on laser-proton acceleration via x-ray spectroscopy

Stefanikova, R.; Pan, X.; Smid, M.; Gaus, L.; Kozlová, M.; Kraft, S.; Kroll, F.; Prencipe, I.; Reimold, M.; Schlenvoigt, H.-P.; Umlandt, M. E. P.; Schramm, U.; Zeil, K.; Metzkes-Ng, J.; Falk, K.

Laser driven ion acceleration is a fast growing field, where understanding of the internal processes of laser-plasma interaction is crucial for optimization of such ion sources. Namely, x-ray spectroscopy offers a unique in-situ view at plasma conditions and electron signatures from within the target, which can help to identify important parameters for optimization of the laser-driven acceleration process.
Here, we present an x-ray spectroscopy platform installed at the Draco PW laser facility (Ti:sapphire 30 fs laser system) and how the addition of x-
ray spectroscopy reveals the suprathermal electron population, which provides insight into the energy conversion from laser to the proton-accelerating sheath.
As an example, we study the impact of pre-plasma tailoring on characteristic x-ray emission and proton acceleration via controlled introduction of various pre-pulses on the Ti 2 μm thick target that precede the arrival of the main laser pulse by 2.5 − 30 ps. Based on our data from x-ray spectroscopy combined with proton diagnostics we then gain understand-
ing of the underlying processes in proton acceleration and the influence of pre-plasma formation.

Keywords: x-ray spectrometer; laser-produced plasma; characteristic emission lines

  • Lecture (Conference) (Online presentation)
    64th Annual Meeting of the APS Division of Plasma Physics, 20.10.2022, Spokane, USA

Permalink: https://www.hzdr.de/publications/Publ-36226
Publ.-Id: 36226


The relationship between controllability, optimal testing resource allocation, and incubation-latent period mismatch as revealed by COVID-19

Demers, J.; Fagan, W.; Potluri, S.; Calabrese, J.

The severe shortfall in testing supplies during the initial phases of the COVID-19 pandemic and ensuing struggle to control disease spread have affirmed the need to plan rigorous optimized supply-constrained resource allocation strategies for the next inevitable novel disease epidemic. To address the challenge of optimizing limited resource usage in the face of complicated disease dynamics, we develop an integro partial differential equation disease model which incorporates realistic latent, incubation, and infectious period distributions along with limited testing supplies for identifying and quarantining infected individuals, and we analyze the influence of these ele- ments on controllability and optimal resource allocation between two testing strategies, ‘clinical’ targeting symptomatic individuals and ‘non-clinical’ targeting non-symptomatic individuals, for reducing total infection sizes. We apply our model to not only the original, delta, and omicron COVID-19 variants, but also to generic diseases which have different offsets between latent and incubation period distributions which allow for or prevent varying degrees of presymptomatic transmission or preinfectiousness symptom onset. We find that factors which reduce control- lability generally call for reduced levels of non-clinical testing, while the relationship between symptom onset, controllability, and optimal strategies is complicated. Although greater degrees of presymptomatic transmission reduce disease controllability, they may enhance or reduce the role of non-clinical testing in optimal strategies depending on other disease factors like overall transmissibility and latent period length. Our model allows a spectrum of diseases to be com- pared under the same lens such that the lessons learned from COVID-19 can be adapted to resource constraints in the next emerging epidemic and analyzed for optimal strategies under a consistent mathematical framework.

Permalink: https://www.hzdr.de/publications/Publ-36225
Publ.-Id: 36225


Characterization of low-density rear-driven collisional plasma jets from thin foil targets

Perez-Martin, P.; Smid, M.; Hronová, L.; Bouffetier, V.; Brack, F.-E.; Cagas, P.; Červenák, M.; Gajdos, P.; He, Z.; Holec, M.; Kagan, G.; Kaniz, K.; Kozlová, M.; Kroll, F.; Liu, H.; Pan, X.; Prencipe, I.; Schaumann, G.; Singh, S.; Sobiella, M.; Srinivasan, B.; Stafford, J.; Xie, Z.; Xiong, J.; Suzuki-Vidal, F.; Krůs, M.; Ren, L.; Kang, N.; Falk, K.

Magnetized low density, collisional plasma jets are found in astrophysical systems, such as accretion
discs or polars, and they also show potential as a platform to study transport properties in
astrophysical plasmas. However, no systematic study of their properties has been conducted yet.
Through experiments in kilojoule laser facilities, we aim to benchmark a range of rear-driven
jets from foils of different thicknesses and materials.
We studied free propagation of jets, their collisions with a static object and the collisions
between two counterpropagating jets. The setup was also placed inside a split pair coil, which
provides an external magnetic field of 5-10 T. A streak camera was used to track jet velocity
and density was measured with 4-frame interferometry and x-ray radiography.
The results can be used to plan experiments with focus on specific jet properties, as well as
providing a benchmark for hydrodynamic codes. The data on collisions and magnetized jets
provides insight into compression waves and the effects of strong external magnetic fields,
which are used for the study of transport properties of plasmas.

Keywords: Plasma flows; Laboratory astrophysics; Magnetized plasma; High magnetic fields; Interferometry

  • Lecture (Conference) (Online presentation)
    48th EPS Conference on Plasma Physics, 28.06.-01.07.2022, Online, N/A

Permalink: https://www.hzdr.de/publications/Publ-36224
Publ.-Id: 36224


Modeling of magnetized astrophysical objects through the study of magnetized rear-driven plasma jets from thin foil targets

Perez-Martin, P.; Smid, M.; Hronová, L.; Bouffetier, V.; Bott, A.; Brack, F.-E.; Červenák, M.; Donat, F.; Gajdoš, P.; Kozlová, M.; Kroll, F.; Manuel, M.; Pan, X.; Prencipe, I.; Singh, S.; Sobiella, M.; Krus, M.; Falk, K.

Plasma jets can be found in astrophysical systems (Accretion disks[1][2], Polars [3] or Young
Stellar Objects [4]), but they are also useful as a platform to study plasma properties and transport
effects. On a experiment at the PALS facility, we have studied the formation and propagation
of rear-driven, collisional plasma jets from different foil thicknesses and materials when
subject to an intense external magnetic field.
Magnetic fields were generated using a pair of Helmholtz coils that provide 5-10 T in the
direction perpendicular to the jet propagation. The diagnostics used were the streaked optical
self-emission as a measurement of jet velocity, and 4-frame interferometry as a measurement of
the jet density.
With the right scaling factors, this data can help model the accretion of matter into magnetized
astrophysical systems, such as the surface of Young Stellar Objects, as well as the role that
instabilities play in this process [4].
The work was supported by the Helmholtz Association under Grant No. VH-NG-1338
[1] G. Revet et al., Science Advances 3, 11 (2017)
[2] Kulkarni, A. K. & Romanova, M. M. , Monthly Notices RAS 386, (2008)
[3] E. Falize, et al., Astrophysics and Space Science 336, 81 (2011)
[4] Burdonov, K. et al., A&A 657, A112 (2022)

Keywords: Plasma flows; Laboratory astrophysics; Magnetized plasma; High magnetic fields; Magnetosphere physics; Young Stellar Objects

  • Lecture (Conference)
    64th Annual Meeting of the APS Division of Plasma Physics, 16.-21.10.2022, Spokane, United States of America

Permalink: https://www.hzdr.de/publications/Publ-36223
Publ.-Id: 36223


Atomic Layer Etching of Nanowires Using Conventional RIE Tool

Khan, M. B.; Shakeel, S.; Richter, K.; Ghosh, S.; Erbe, A.; Georgiev, Y.

Innovative material and processing concepts are needed to further enhance the performance of complementary metal-oxide-semiconductor (CMOS) transistors-based circuits as the scaling limits are being reached. To achieve that, we report on the development of an atomic layer etching (ALE) [1] process to fabricate smooth and thin nanowires using a conventional dry etching tool. Firstly, a negative tone resist (hydrogen silsesquioxane) is spin-coated on SiGe-on-insulator (SiGeOI) samples and electron beam lithography performed to create nano-patterns. These patterns act as an etch mask and are transferred into the SiGeOI layer using an inductively-coupled plasma reactive ion etching (ICP-RIE) process. Subsequently, an SF6 and Ar+ based ALE process is employed to smoothen the nanowires and reduce their widths. SF6 modifies the surface of the samples, while in the next step Ar+ removes the modified surface. The ALE cycle sequence is surface modification with 60 sccm SF6 for 20 s, 60 sccm Ar purge for 15 s, removal of the layer with 60 sccm Ar for 10 s at 25 W platen power, and 40 sccm Ar purge for 10 s.
To investigate the effect of ALE on the nanowire roughness and width, several ALE cycles are performed. The surface of the etched features is studied using scanning electron microscopy and atomic force microscopy. With the increasing number of ALE cycles, a reduction in the width of the nanowires, as well as surface roughness, is observed. The roughness reduced from ca. 6 nm to 1 nm (the resolution of the AFM tip) as the number of ALE cycles is increased from 78 to 102.
An etch per cycle of 1.1 Å is obtained. Sub-12 nm nanowires with smooth sidewalls were achieved after performing 63 ALE cycles. This process, developed on a conventional ICP-RIE tool, can be used to further down-scale semiconductor nanowires.

1. Kanarik, Keren J., et al. "Overview of atomic layer etching in the semiconductor industry." Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 33.2 (2015): 020802.

Related publications

  • Lecture (Conference)
    14th EBT 2022 International conference, 26.06.-01.07.2022, Varna, Bulgaria

Permalink: https://www.hzdr.de/publications/Publ-36222
Publ.-Id: 36222


Partial Reduction in BRCA1 Gene Dose Modulates DNA Replication Stress Level and Thereby Contributes to Sensitivity or Resistance

Classen, S.; Rahlf, E.; Jungwirth, J.; Albers, N.; Hebestreit, L.; Zielinski, A.; Poole, L.; Groth, M.; Koch, P.; Liehr, T.; Kankel, S.; Cordes, N.; Petersen, C.; Rothkamm, K.; Pospiech, H.; Borgmann, K.

BRCA1 is a well-known breast cancer risk gene, involved in DNA damage repair via homologous recombination (HR) and replication fork protection. Therapy resistance was linked to loss and amplification of the BRCA1 gene causing inferior survival of breast cancer patients. Most studies have focused on the analysis of complete loss or mutations in functional domains of BRCA1. How mutations in non-functional domains contribute to resistance mechanisms remains elusive and was the focus of this study. Therefore, clones of the breast cancer cell line MCF7 with indels in BRCA1 exon 9 and 14 were generated using CRISPR/Cas9. Clones with successful introduced BRCA1 mutations were evaluated regarding their capacity to perform HR, how they handle DNA replication stress (RS), and the consequences on the sensitivity to MMC, PARP1 inhibition, and ionizing radiation. Unexpectedly, BRCA1 mutations resulted in both increased sensitivity and resistance to exogenous DNA damage, despite a reduction of HR capacity in all clones. Resistance was associated with improved DNA double-strand break repair and reduction in replication stress (RS). Lower RS was accompanied by increased activation and interaction of proteins essential for the S phase-specific DNA damage response consisting of HR proteins, FANCD2, and CHK1.

Keywords: Breast cancer; BRCA1; DNA repair

Permalink: https://www.hzdr.de/publications/Publ-36221
Publ.-Id: 36221


Chemical Vapor Deposition and High-Resolution Patterning of a Highly Conductive Two-Dimensional Coordination Polymer Film

Rubio-Giménez, V.; Arnauts, G.; Wang, M.; Oliveros Mata, E. S.; Huang, X.; Lan, T.; Tietze, M. L.; Kravchenko, D. E.; Smets, J.; Wauteraerts, N.; Khadiev, A.; Novikov, D. V.; Makarov, D.; Dong, R.; Ameloot, R.

Crystalline coordination polymers with high electrical conductivities and charge carrier mobilities might open new opportunities for electronic devices. However, current solvent-based synthesis methods hinder compatibility with microfabrication standards. Here, we describe a solvent-free chemical vapor deposition method to prepare high-quality films of the two-dimensional conjugated coordination polymer Cu-BHT (BHT = benzenehexanothiolate). This approach involves the conversion of a metal oxide precursor into Cu-BHT nanofilms with a controllable thickness (20–85 nm) and low roughness (<10 nm) through exposure to the vaporized organic linker. Moreover, the restricted metal ion mobility during the vapor–solid reaction enables high-resolution patterning via both bottom-up lithography, including the fabrication of micron-sized Hall bar and electrode patterns to accurately evaluate the conductivity and mobility values of the Cu-BHT films.

  • Open Access Logo Journal of the American Chemical Society 145(2023)1, 152-159
    Online First (2022) DOI: 10.1021/jacs.2c09007

Permalink: https://www.hzdr.de/publications/Publ-36220
Publ.-Id: 36220


Defect-assisted ion transport in magneto-ionic nitrides probed by positrons

Liedke, M. O.; Butterling, M.; de Rojas, J.; Quintana, A.; Lopeandía, A.; Menéndez, E.; Costa-Krämer, J. L.; Hirschmann, E.; Elsherif, A. G. A.; Sort, J.; Wagner, A.

Magneto-ionics deals with a class of spintronic materials where the external electrical field induces ion migration and leads to a raise of magnetization, a consequence of magnetic species local segregations or increased magnetic interactions between them. Since this ion transport is activated by the voltage actuation, no large electrical currents are required and heat dissipation processes are mostly negligible. In addition, simply reversing the direction of the voltage bias, the generated ferromagnetic state returns to its original magnetic configuration, which realizes the magnetic switch concept. Using magnetometry and electron microscopy supported with positron annihilation spectroscopy techniques different nitrides (CoN, FeN, NiN) have been investigated. CoN and FeN are promising candidates for fast magneto-ionic switching, whereas NiN clearly underperforms. Positron annihilation spectroscopy provides a unique probe of open volume defects, e.g. dislocations, vacancies and their agglomerations at grain boundaries, and it was successfully utilized to study the defect nanostructure here. As a reference, we first present electrolyte-gated and defect-mediated oxygen migration in single-layer, paramagnetic Co3O4 at room temperature, which allows voltage-controlled ON-OFF magnetic switching via internal reduction/oxidation processes [1]. Here, the bias-induced motion of oxygen ions was caused by dominant vacancy clusters, with oxygen motion promoted at grain boundaries and assisted by the development of O-rich diffusion channels and Co-rich grain inner regions. In the case of nitrides, on the other hand, nitrogen transport is found to occur uniformly throughout the film, creating a plane-wave-like migration front (Fig. 1), without assistance of diffusion channels [2,3]. Using positrons as a probe, we will show that the initial average open volume is larger in nitrides compared to oxides, which likely governs the migration process and allows for enhanced switching rates and cyclability as well as lowers threshold voltages. We will try to propose factors playing a role in case of hindered ionic migration in NiN, too.

Figure 1: Depth profile of the S-parameter as a function of increasing electrical field.

[1] A. Quintana, E. Menéndez, M. O. Liedke et al., ACS Nano, 12, 10291 (2018)
[2] J. de Rojas, A. Quintana, A. Lopeandía et al., Nature Communications, 11, 5871 (2020)
[3] J. de Rojas, J. Salguero, F. Ibrahim et al. ACS Appl. Mater. Interfaces, 13, 30826 (2021)

Keywords: magneto-ionics; Co3O4; CoN; NiN; positron annihilation spectroscopy; defects

Related publications

  • Poster (Online presentation)
    ICPA-19 (International Conference on Positron Annihilation), 22.-26.08.2022, Helsinki, Finnland

Permalink: https://www.hzdr.de/publications/Publ-36219
Publ.-Id: 36219


Defect-assisted ion transport in magneto-ionic functional oxides and nitrides probed by positrons

Liedke, M. O.; Butterling, M.; de Rojas, J.; Quintana, A.; Lopeandía, A.; Menéndez, E.; Costa-Krämer, J. L.; Hirschmann, E.; Sort, J.; Wagner, A.

Magneto-ionics deals with a class of spintronic materials where the external electrical field induces ion migration and leads to a raise of magnetization as a consequence of magnetic species local segregations or increased magnetic interactions between them. Since this ion transport is activated by the voltage actuation, no large electrical currents are required and heat dissipation processes are mostly negligible. Moreover, by simply reversing the direction of the voltage bias, the generated ferromagnetic state is brought back to its original magnetic configuration, which realizes the magnetic switch concept. Using magnetometry and electron microscopy supported with positron annihilation spectroscopy techniques, oxides (Co3O4) and different nitrides (CoN and FeN) have been investigated, which are promising candidates for fast magneto-ionic switching. Positron annihilation spectroscopy provides a unique probe of open volume defects, e.g. dislocations, vacancies within crystal and at interfaces, vacancy agglomerations at grain boundaries, macro- and mesopores and it was successfully utilized to study the defect nanostructure here. We first present electrolyte-gated and defect-mediated oxygen migration in single-layer, paramagnetic Co3O4 at room temperature, which allows voltage-controlled ON-OFF magnetic switching via internal reduction/oxidation processes [1]. Here, the bias-induced motion of oxygen ions is caused by dominant vacancy clusters, with oxygen motion promoted at grain boundaries and assisted by the development of O-rich diffusion channels and Co-rich grain inner regions. In the case of nitrides, on the other hand, nitrogen transport is found to occur uniformly throughout the film, creating a plane-wave-like migration front, without assistance of diffusion channels [2,3]. Using positrons as a probe, we will show that the initial average open volume is larger compared to oxides, which likely governs the migration process and allows, moreover, for enhanced switching rates and cyclability as well as lower threshold voltages.
[1] A. Quintana, E. Menéndez, M. O. Liedke et al., ACS Nano, Vol. 12, p. 10291 (2018)
[2] J. de Rojas, A. Quintana, A. Lopeandía et al., Nature Communications, Vol. 11, p. 5871 (2020)
[3] J. de Rojas, J. Salguero, F. Ibrahim et al. ACS Appl. Mater. Interfaces Vol. 13, p. 30826 (2021)

Keywords: magneto-ionics; Co3O4; CoN; FeN; positron annihilation spectroscopy; defects

Related publications

  • Lecture (Conference)
    E-MRS Fall Meeting 2022, 19.-22.09.2022, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-36218
Publ.-Id: 36218


Data publication : Tailoring crosstalk between localized 1D spin-wave nanochannels using focused ion beams

Iurchuk, V.; Pablo-Navarro, J.; Hula, T.; Narkowicz, R.; Hlawacek, G.; Koerber, L.; Kakay, A.; Schultheiss, H.; Fassbender, J.; Lenz, K.; Lindner, J.

This dataset contains raw data (SEM images, AFM, FMR, BLS, TetraX) used to study the dynamical edge modes in closely spaced permalloy microstrips.

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-36217
Publ.-Id: 36217


Investigation of laser reflectivity and transmissivity of laser-plasma interaction with thin foil targets

Umlandt, M. E. P.; Ziegler, T.; Bernert, C.; Garten, M.; Gaus, L.; Göthel, I.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Prencipe, I.; Rehwald, M.; Reimold, M.; Schlenvoigt, H.-P.; Vescovi Pinochet, M. A.; Zeil, K.; Schramm, U.

Ion acceleration by compact laser-plasma sources promises a variety of applications ranging from medical relevance to fusion experiments.Reaching the required beam quality parameters for those applications demands a very high level of understanding and control over the laserplasma interaction process. Central components in this context are the absorption of the electromagnetic laser field by the plasma and the quality of the resulting acceleration field structure.
Measuring and analyzing unabsorbed light - as transmitted and/or specularly reflected parts - thus allows insight into properties of the underlying laser-plasma interaction. We experimentally investigate these interactions for high and low-contrast laser pulses with thin solid density foil targets at the Draco PW laser system (HZDR). The results of spectral, spatial, and energy analysis of transmitted and reflected light indicate changes in the plasma interaction and will be presented.

Keywords: laser plasma; laser proton acceleration; high power laser

  • Lecture (Conference) (Online presentation)
    DPG-Frühjahrstagung 2022, 28.03.-01.04.2022, Mainz / virtuell, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36216
Publ.-Id: 36216


Data publication: Underground hyperspectral outcrop scanning for automated mine-face mapping — the Lithium deposit of Zinnwald/Cínovec

Kirsch, M.; Mavroudi, M.; Thiele, S. T.; Lorenz, S.; Tusa, L.; Booysen, R.; Herrmann, E.; Fatihi, A.; Möckel, R.; Dittrich, T.; Gloaguen, R.

As part of a project on the development of hyperspectral scanning to support geological mapping in underground mines, we acquired hyperspectral data from three adjacent outcrops of Sn-W-Li greisen rocks in the visitor’s mine of Zinnwald, Germany. The hyperspectral scans were pre-processed and then back-projected onto photogrammetric, three-dimensional digital outcrop models resulting in so-called "hyperclouds". The here presented hyperclouds from the three outcrops (Z1, Z2, and Z3) contain the following attributes:

ZX_Absorbance.ply
RGB colours: Mica/clay-zinnwaldite-topaz abundance based on absorbance (1 – hull-corrected reflectance) at 2200 nm (red), 2250 nm (green), and 2085 nm (blue)
Scalars: Absorbance at 2086.88 nm, 2160.69 nm, 2197.53 nm, 2209.8 nm, 2252.7 nm, and 2338.31 nm

ZX_Iron.ply
RGB colours: Composite (Fe3+ Fe2+ FeOH) iron index (red: 600/570 nm, green:(920 nm + 1650 nm)/ (1035 nm 1230 nm), blue: (2230 nm 2290 nm)/(2245 nm + 2260 nm)
Scalars: Fe3+ = 600/570 nm, Fe2+ = (920 nm + 1650 nm)/ (1035 nm + 1230 nm), FeOH = (2230 nm + 2290 nm)/(2245 nm + 2260 nm)

ZX_MNF.ply
RGB colours: Minimum noise fraction false colour (red: band 4, green: band 7, blue: band 5)
Scalars: Minimum noise fraction bands 4, 7, 5)

ZX_RGB_mineralogy_Li.ply
RGB colours: True colour RGB from photogrammetric outcrop model
Scalars: Mineral abundances derived by combining sample mineralogy from quantitative XRD measurements and hyperspectral unmixing approaches: Quartz/Feldspar, Zinnwaldite, Muscovite/Illite, Kaolinite, Topaz, Lithium (by multiplying the zinnwaldite abundance by its average lithium content of 1.7%)

Keywords: hyperspectral; underground mining; point cloud; lithium; mineral mapping

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Permalink: https://www.hzdr.de/publications/Publ-36215
Publ.-Id: 36215


Wild herbivores enhance resistance to invasion by exotic cacti in an African savanna

Wells, H. B. M.; Crego, R. D.; Alston, J.; Ndungu, S. K.; Khasoha, L. M.; Reed, C. G.; Hassan, A. A.; Kurukura, S.; Ekadeli, J.; Namoni, M.; Stewart, P. S.; Kimuyu, D. M.; Wolf, A. A.; Young, T. P.; Kartzinel, T. R.; Palmer, T. M.; Goheen, J. R.; Pringle, R. M.

Whether wild herbivores confer biotic resistance to invasion by exotic plants remains a key question in ecology. There is evidence that wild herbivores can impede invasion by exotic plants, but it is unclear whether and how this generalises across ecosystems with varying wild herbivore diversity and functional groups of plants, particularly over long-term (decadal) time frames. Using data from three long-term (13- to 26-year) exclosure experiments in central Kenya, we tested the effects of wild herbivores on the density of exotic invasive cacti, Opuntia stricta and O. ficus-indica (collectively, Opuntia), which are among the worst invasive species globally. We also examined relationships between wild herbivore richness and elephant occurrence probability with the probability of O. stricta presence at the landscape level (6150 km2). Opuntia densities were 74% to 99% lower in almost all plots accessible to wild herbivores compared to exclosure plots. Opuntia densities also increased more rapidly across time in plots excluding wild herbivores. These effects were largely driven by megaherbivores (≥1000 kg), particularly elephants. At the landscape level, modelled Opuntia stricta occurrence probability was negatively correlated with estimated species richness of wild herbivores and elephant occurrence probability. On average, O. stricta occurrence probability fell from ~0.56 to ~0.45 as wild herbivore richness increased from 6 to 10 species and fell from ~0.57 to ~0.40 as elephant occurrence probability increased from ~0.41 to ~0.84. These multi-scale results suggest that any facilitative effects of Opuntia by wild herbivores (e.g. seed/vegetative dispersal) are overridden by suppression (e.g. consumption, uprooting, trampling). Synthesis. Our experimental and observational findings that wild herbivores confer resistance to invasion by exotic cacti add to evidence that conserving and restoring native herbivore assemblages (particularly megaherbivores) can increase community resistance to plant invasions. © 2022 The Authors. Journal of Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.

Keywords: biotic resistance; elephants; invasion ecology; long-term exclosure experiments; megaherbivores; multi-trophic interactions; Opuntia stricta; prickly pear

Permalink: https://www.hzdr.de/publications/Publ-36214
Publ.-Id: 36214


Foam Targets as Extreme Magnetic Field Drivers

Laso García, A.; Toncian, T.; Habibi, M.; Prencipe, I.; Cowan, T.; Rinderknecht, H. G.; Wei, M. S.; Bruhaug, G.; Arefiev, A.; Wang, T.; Doria, D.; Crăciun, V.; Ghenuche, P.; Năstasă, V.

Structured foam targets are of great interest for the laser-plasma community. Recent studies have shown how low density foams could be used to generate extreme magnetic fields in the MegaTesla range. A result of the interaction of the fields with the accelerated electrons in the foam is a large increase in the electron kinetic energy, and the generation of bright flashes of synchrotron radiation in the MeV range.

In this talk we introduce experimental results obtained at HED/HiBEF at the European XFEL on the structural changes and homogenization of the foam during the laser interaction. Then we will show results on synchrotron emission at Texas Petawatt. Finally we will provide an overview of our roadmap towards implementing foam experiments at the 10 PW level at ELI-NP

Keywords: laser-plasma; foams; HiBEF; XFEL; ELI-NP; texas PW; synchrotron; bright gamma flashes

  • Invited lecture (Conferences)
    Foam Target Workshop, 02.11.2022, Dolní Břežany, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-36213
Publ.-Id: 36213


Towards High-Field Experiments in Existing and Upcoming Laser Facilities

Laso García, A.; Toncian, T.; Habibi, M.; Prencipe, I.; Rinderknecht, H. G.; Wei, M. S.; Bruhaug, G.; Arefiev, A.; Wang, T.; Doria, D.; Crăciun, V.; Ghenuche, P.; Năstasă, V.; Cernăianu, M.; Dreghici, D.-B.; Talposi, A.-M.; Quevedo, H.; Ditmire, T.; Schlenvoigt, H.-P.; Smid, M.; Cowan, T.

The Helmholtz International Beamline for Extreme Fields is a user consortium providing drivers for high-energy density and high-field science at the HED station of EuXFEL. This presentation will give an overview of the current implementation and commissioning results as well as future plans and exemplary science cases.
In parallel, new exciting opportunities for high-field science are opening with the first user call at the ELI facilities. Here, we will discuss first results on Megatesla magnetic field generation in overdense plasmas. We will also discuss future plans to exploit the high intensities, up to 10 PW, to be delivered at ELI-NP.

Keywords: Extreme fields; Laser-plasmas; HiBEF; XFEL; bright gamma flashes; high energy density

  • Invited lecture (Conferences)
    QED Laser Plasmas, 26.-30.09.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36212
Publ.-Id: 36212


Combined Phase Contrast Imaging and Small-Angle X-Ray Scattering Diagnostic of Relativistic Plasmas at the High Energy Density Instrument at European XFEL

Laso García, A.; Arefiev, A.; Kemp, A.; Allen, C. H.; Bähtz, C.; Nagler, B.; Palmer, C. A. J.; Murphy, C. D.; Spindloe, C.; Brown, C. R. D.; Neely, D.; Kraus, D.; Marley, E.; Hartouni, E. P.; Fiuza, F.; Grim, G. P.; Cochran, G. E.; Schlenvoigt, H.-P.; Prencipe, I.; Williams, J.; Green, J.; Eggert, J. H.; Zeil, K.; Lancaster, K. L.; Divol, L.; Gaus, L.; Huang, L.; Schoelmerich, M.; Rehwald, M.; Oliver, M.; Rödel, M.; Macdonald, M.; Smid, M.; Makita, M.; Nakatsutsumi, M.; Humphries, O. S.; Neumayer, P. B.; Mabey, P.; Shepherd, R. L.; Gray, R.; Wilks, S. C.; Le Pape, S.; Kerr, S. M.; Glenzer, S. H.; Funk, S.; Gales, S. G.; Cowan, T.; White, T. G.; Kluge, T.; Doeppner, T.; Toncian, T.; Zastrau, U.; Schramm, U.; Ping, Y.; He, Z.; Höppner, H.; Pelka, A.

The High Energy Density (HED) instrument at the European XFEL provides a platform to study hot and warm dense matter. The Helmholtz International Beamline for Extreme Fields (HiBEF) is a User Consortium supplying HED with two laser systems (the high-intensity ReLaX laser, by Amplitude Technologies, and the high-energy Dipole-100X laser, by STFC), Diamond Anvil Cells setup and high-pulsed magnetic fields. These tools in combination with the XFEL beam enable the investigation of relativistic laser plasmas, strong-field QED phenomena, high-pressure astro- and planetary physics as well as magnetic phenomena in condensed matter. The successful commissioning of the ultra-short pulse high-intensity ReLaX laser, provides new unique opportunities in the plasma and high-field physics fields [1].
ReLaX is a double CPA Ti:Sa laser capable of delivering up to 300 TW pulses on target. In the first commissioning phase, 100 TW pulses were used, reaching
intensities up to 1020 W/cm2. Small-Angle X-Ray Scattering (SAXS) without the need of a beamstop was first commissioned at HED in September 2019. Two highly annealed pyrolytic graphite (HAPG) crystals were used to reflect the SAXS photons onto a detector while allowing the main XFEL beam to go through [2]. In April and May 2021, Small Angle X-Ray Scattering and Phase Contrast Imaging (PCI) were simultaneously demonstrated in pump-probe experiments at HED in a community experiment involving 15 institutions from all over the world. In this talk we will present the preliminary results of this community experiment probing ultrafast phenomena in a wide array of target configurations: hole boring in wires, shockwave generation in CH blocks, buried heating of a wire inside a CH medium, foam ionization and collective effects in heated foils.

[1] A. Laso Garcia, H. Hoeppner, A. Pelka et al., “ReLaX: the HiBEF high-intensity short-pulse laser driver for relativistic laser-matter interaction and strong-field science at the HED instrument at EuXFEL”. High Power Laser Science and Engineering, 1-15. doi:10.1017/hpl.2021.47
[2] M. Šmíd, et al., "Mirror to measure small angle x-ray scattering signal in high energy density experiments", Review of Scientific Instruments 91, 123501 (2020). doi:10.1063/5.0021691

Keywords: Laser-plasma; High energy density; XFEL; HiBEF; ReLaX; SAXS; PCI

  • Invited lecture (Conferences)
    DPG-Frühjahrstagung Mainz 2022, 01.04.2022, Mainz, Germany

Permalink: https://www.hzdr.de/publications/Publ-36211
Publ.-Id: 36211


Commissioning and First User Experiments with ReLaX and XFEL Beam

Laso García, A.; Arefiev, A.; Kemp, A.; Allen, C. H.; Bähtz, C.; Nagler, B.; Palmer, C. A. J.; Murphy, C. D.; Spindloe, C.; Brown, C. R. D.; Neely, D.; Kraus, D.; Marley, E.; Hartouni, E. P.; Fiuza, F.; Grim, G. P.; Cochran, G. E.; Schlenvoigt, H.-P.; Prencipe, I.; Williams, J.; Green, J.; Eggert, J. H.; Zeil, K.; Lancaster, K. L.; Divol, L.; Gaus, L.; Huang, L.; Schoelmerich, M.; Rehwald, M.; Oliver, M.; Rödel, M.; Macdonald, M.; Smid, M.; Makita, M.; Nakatsutsumi, M.; Humphries, O. S.; Neumayer, P. B.; Mabey, P.; Shepherd, R. L.; Gray, R.; Wilks, S. C.; Le Pape, S.; Kerr, S. M.; Glenzer, S. H.; Funk, S.; Gales, S. G.; Cowan, T.; White, T. G.; Kluge, T.; Doeppner, T.; Toncian, T.; Zastrau, U.; Schramm, U.; Ping, Y.; He, Z.; Höppner, H.; Pelka, A.

In this presentation we provide an overview of the commissioning and first user experiment of ReLaX in combination with the XFEL beam. We will introduce the setup and laser parameters. We will show the established standard setup combining small-angle x-ray scattering (SAXS), phase-contrast imaging (PCI) and spectroscopy techniques. Finally we will show examples of the data obtained in the interaction of the ReLaX laser with targets of interested for the short-pulse laser community.

Keywords: Laser-plasma; HiBEF; XFEL; SAXS; PCI

  • Lecture (Conference)
    Current status and future completion of the HED instrument and the HIBEF contributions, 25.01.2022, European XFEL, Germany

Permalink: https://www.hzdr.de/publications/Publ-36210
Publ.-Id: 36210


Influence of substrate composition on size and chemical state of ion beam synthesised Co nanoparticles – Towards fabrication of electrodes for energy devices

Gupta, P.; Jovic, V.; Hübner, R.; Anquillare, E.; Suschke, K.; Smith, K. E.; Markwitz, A.; Waterhouse, G. I. N.; Kennedy, J.

A one-step approach to synthesize ultrafine transition metal particles (size < 5 nm) in carbon substrates is highly desirable for fabricating electrodes for energy devices. Herein, cobalt ion implantation into amorphous carbon films (a:C) and hydrogenated amorphous carbon films (a:CH) was explored, with the aim of synthesizing ultrafine metallic cobalt nanoparticles at room temperature. Co ions of 30 keV energy were implanted into the carbon films to achieve a Co areal density of 1.0 ± 0.1 × 1017 atoms cm-2. Rutherford backscattering measurements revealed that hydrogenated amorphous carbon films gave a broader Co depth distribution compared to the amorphous carbon films. Further, cross-sectional TEM analysis revealed that hydrogenated carbon films suppressed metallic Co nanoparticle aggregation, leading to the creation of ultrafine Co nanoparticles (size < 5 nm). Co L-edge X-ray absorption spectroscopy measurements confirmed the formation of predominantly metallic Co nanoparticles by ion implantation. Results conclusively demonstrate that the presence of hydrogen (~ 28 at %) in the carbon matrix facilitates the synthesis of ultrafine metallic Co nanoparticles during Co ion implantation.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36209
Publ.-Id: 36209


Energy-chirp compensation of laser-driven ion beams enabled by structured targets

Gong, Z.; Bulanov, S. S.; Toncian, T.; Arefiev, A.

We show using three-dimensional (3D) simulations that the challenge of generating dense monoenergetic laser-driven ion beams with low angular divergence can be overcome by utilizing structured targets with a relativistically transparent channel and an overdense wall. In contrast to a uniform target that produces a chirped ion beam, the target structure facilitates the formation of a dense electron bunch whose longitudinal electric field reverses the energy chirp. This approach works in conjunction with existing acceleration mechanisms, augmenting the ion spectra. For example, our 3D simulations predict a significant improvement for a 2 PW laser pulse with a peak intensity of 5×1022 W/cm2. The simulations show a monoenergetic proton peak in a highly desirable energy range of 200 MeV with an unprecedented charge of several nC and a relatively low divergence that is below 10°.

Keywords: Acceleration; Electric fields; Ions; 3D simulations; Acceleration mechanisms; Angular divergence; Chirp compensation; Electron bunch; Energy; Ion spectrum; Monoenergetic; Target structure; Three-dimensional (3-D) simulation; Ion beams

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Permalink: https://www.hzdr.de/publications/Publ-36208
Publ.-Id: 36208


Ultra-high dose rate radiobiology and dosimetry at the laser-driven proton accelerator Draco-PW

Brack, F.-E.; Reimold, M.; Kroll, F.; Beyreuther, E.; Karsch, L.; Kraft, S.; Leßmann, E.; Pawelke, J.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Ziegler, T.; Zeil, K.; Metzkes-Ng, J.

Background and Aims
Laser-plasma accelerators (LPA) are a viable addition to the ultra-high dose rate accelerator portfolio, as they generate extremely intense proton bunches of several 10 MeV kinetic energy. Efficiently transported and spectrally shaped, a single LPA proton bunch enables homogeneous dose delivery above 20 Gy to mm-scale volumes with a dose rate well above 108 Gy/s. At Draco PW we have recently shown the successful establishment of a proton LPA research platform for small animal studies employing a multi-shot accumulated dose delivery for a mouse model pilot study. [Kroll et al, Nature Physics 2022].
Methods
Reaching the range of FLASH-associated parameters at an LPA proton source requires single-shot irradiation. We performed such irradiations with zebrafish embryos and dosimeters using the pulsed beamline at Draco PW. Since LPA based accelerators are prone to inherent fluctuations of the source, to measure the applied dose, a minimally invasive, online spectral characterization of the delivered proton bunches is necessary. Clinically used ionization chambers saturate under LPA beam conditions. Therefore, we present a scintillator-based time-of-flight (ToF) beam monitoring system for the recording of kinetic energy spectra of single LPA proton bunches. The deduced spectra are used as an input for Monte-Carlo simulations to predict the delivered dose to the irradiated sample.
Results
The ToF ansatz enabled the reconstruction of the kinetic energy spectrum of the transported protons with a relative energy uncertainty down to ca. 11% (2σ). Subsequent Monte-Carlo simulations predict the applied depth dose distribution with an uncertainty of ca. 6% (2σ).
Conclusions
We present a laser-based proton irradiation platform at the Draco PW facility that enables systematic radiobiological studies within an unprecedented range of beam parameters and demonstrate a solution for minimally invasive volumetric dosimetry at ultra-high dose rates.

  • Lecture (Conference)
    Flash Radiotherapy and Particle Therapy Conference - FRPT 2022, 29.11.-02.12.2022, Barcelona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-36207
Publ.-Id: 36207


Machine learning-based quantum accurate interatomic potentials for warm dense matter

Kumar, S.; Tahmasbi, H.; Lokamani, M.; Ramakrishna, K.; Cangi, A.

Modeling warm dense matter is relevant for various applications including the interior of gas giants and exoplanets, inertial confinement fusion, and ablation of metals. Ongoing and upcoming experimental campaigns in photon sources around the globe rely on numerical simulations that are accurate on the level of electronic structures. In that regard, density functional theory molecular dynamics (DFT-MD) simulations [1] have been widely used to compute thermodynamical properties of warm dense matter. However, two challenges impede further progress: (1) DFT-MD becomes computationally infeasible with increasing temperature (2) finite-size effects render many computational observables inaccurate because DFT-MD is limited to a few hundred atoms on current HPC platforms. Recently, molecular dynamics simulations using machine learning-based interatomic potentials (ML-IAP) could overcome these computational limitations. Here, we propose a method to construct ML-IAPs from DFT data based on SNAP descriptors [2]. We investigate the transferability of ML-IAPs over a large range of temperatures (1,000 to 100,000 K) which currently is a topic of active research.

References:

[1] G. Kresse and J. Hafner, Physical Review B 47, 558 (1993).
[2] A. P. Thompson, L. P. Swiler, C. R. Trott, S. M. Foiles, and G. J. Tucker, Journal of Computational Physics, 285, 316-330, 2015.

Keywords: Computational Physics; Warm Dense Matter; Machine Learning; Transport Coefficients; Molecular Dynamics

  • Open Access Logo Lecture (Conference)
    APS March Meeting 2023, 08.03.2023, Las Vegas, Nevada, USA

Permalink: https://www.hzdr.de/publications/Publ-36206
Publ.-Id: 36206


Data publication: Modification of Porous Ultralow‑k Film by Vacuum Ultraviolet Emission

Zotovich, A. I.; Zyryanov, S. M.; Lopaev, D. V.; Rezvanov, A. A.; Attallah, A. G.; Liedke, M. O.; Butterling, M.; Bogdanova, M. A.; Vishnevskiy, A. S.; Seregin, D. S.; Vorotyntsev, D. A. V.; Palov, A. P.; Hirschmann, E.; Wagner, A.; Naumov, S.; Vorotilov, K. A.; Rakhimova, T. V.; Rakhimov, A. T. R.; Baklanov, M.

Modification of spin-on-deposited porous PMO (periodic mesoporous organosilica) ultralow-k (ULK) SiCOH films (k = 2.33) containing both methyl terminal and methylene bridging groups by vacuum ultraviolet (VUV) emission from Xe plasma is studied. The temporal evolution of chemical composition, internal defects, and morphological properties (pore structure transformation) is studied by using Fourier transform infrared spectroscopy, in situ laser ellipsometry, spectroscopic ellipsometry, ellipsometric porosimetry (EP), positron-annihilation lifetime spectroscopy (PALS), and Doppler broadening positron-annihilation spectroscopy. Application of the different advanced diagnostics allows making conclusions on the dynamics of the chemical composition and pore structure. The time frame of the VUV exposure in the current investigation can be divided into two phases. During the first short phase, film loses almost all of its surface methyl and matrix bridging groups. An increase of material porosity due to removal of methyl groups with simultaneous matrix shrinkage is found by in situ ellipsometry. The removal of bridging bonds leads to an increase of matrix intrinsic porosity. Nevertheless, when the treated material is exposed to the ambient air, the sizes of micro- and mesopores and pores interconnectivity decrease with the VUV exposure time according to PAS and EP data. The last is the result of the additional film shrinkage caused by atmosphere exposure. During the second phase the increase of mesopore size is detected by both EP and PAS. The increase of mesopore size goes all the time as it is expected from in situ ellipsometry, but it is masked by the air exposure.

Keywords: ultralow-k materials; vacuum ultraviolet emission; porosimetry; positron-annihilation spectroscopy; in situ ellipsometry

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Permalink: https://www.hzdr.de/publications/Publ-36205
Publ.-Id: 36205


Radiopharmazie

Kopka, K.

kein Abstrakt verfügbar

  • Invited lecture (Conferences)
    Branchendialog zur Resilienz pharmazeutischer Lieferketten, 19.07.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36204
Publ.-Id: 36204


Optical Fingerprints of Unconventional Carriers in Kagome Metals

Uykur, E.

Kagome metals are the newly emerging class of quantum materials, where the peculiar kagome structure along with the itinerant character of the electrons give rise to a non-trivial combination of entangled magnetic states, electronic correlations, and topological orders. Two dissimilar features of massive, localized carriers at dispersionless flat bands and the massless Dirac fermions at the linearly dispersing bands coexist in their electronic structure, giving rise to various exotic phenomena. While the magnetic kagome metals are at the center of interest due to the proximity of the flatband magnetism, newly discovered non-magnetic counterparts possess a peculiar density wave order along with the unconventional superconductivity.

Optical spectroscopy is a useful method that shows excellent sensitivity to both linear and flat bands. Furthermore, (partial)gaps at the density of state at Fermi energy can be identified with clear signatures in optical spectra and the energy scale can be discussed. The opportunity to combine with other external stimuli such as magnetic field and pressure offers a viable route to disentangle different contributions. In this talk, I will highlight the optical fingerprints of unconventional carriers in these unique materials.

  • Invited lecture (Conferences)
    APS March Meeting, 14.-18.03.2022, Chicago, USA

Permalink: https://www.hzdr.de/publications/Publ-36203
Publ.-Id: 36203


Core-Shell Nanostructures of Tungsten Oxide and Hydrogen Titanate for H2Gas Adsorption

Rajbhar, M.; Das, P.; Möller, W.; Chatterjee, S.

Nanostructured tungsten oxide is a promising material for sensing reducing gases such as hydrogen. However, this material exhibits limitations due to a poor response toward sensing at room temperature, incomplete recovery to the initial state, long response time, and a low response factor, which is not desired for explosive gases like hydrogen. In this work, we, for the first time, demonstrate that these limitations can be significantly overcome using the core-shell structure of tungsten oxide (WO3) nanorods and hydrogen titanate (H2Ti3O7) nanotubes developed and suitably defect-engineered by low-energy ion irradiation. The sensor based on the pristine core-shell heterostructure of tungsten oxide nanorods and hydrogen titanate nanotubes exhibits excellent response and selectivity to different concentrations of H2 ranging from 10 to 500 ppm. However, it requires a quite high temperature of 300 °C with response and recovery times of about 38 and 99.8 s, respectively. After irradiation, the hybrid form shows a similar level of response and selectivity, however, at a much lower temperature of about 120 °C with significantly faster response and recovery times of about 16 and 18 s, respectively. Such an ion beam-modified structure addresses critical issues of developing a gas-sensing device, such as the effects of moisture and power consumption. The experimental observations are very well in agreement with the predictions of the state-of-the-art Monte Carlo-based TRI3DYN ion-solid interaction simulation, and the gas-sensing mechanism was explained using first principles-based calculation. The study reveals that low-energy ion-induced defect engineering yields better charge transport, better binding of the gas with the surface, as well as the superior moisture-repelling ability of the surface, leading to better sensing performance than the pristine core-shell structure. This heterostructure between two nanomaterials carries complementary advantages in various aspects, such as the surface area, conductivity, and sensitivity toward a wide range and mixture of gases. Additionally, the wrapping yields good mechanical strength and flexibility, making it possible to use as a flexible sensing device made through a bottom-up fabrication technique.

Keywords: core-shell heterostructure; DFT simulation; gas sensing; H2adsorption; ion beam irradiation; TRI3DYN

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Permalink: https://www.hzdr.de/publications/Publ-36202
Publ.-Id: 36202


Facile and scalable preparation of cage-like mesoporous carbon from lignin-based phenolic resin and its application in supercapacitor electrodes

Li, W.; Wang, G.; Sui, W.; Xu, T.; Li, Z.; Rumpel, A.; Si, C.; Parvez, A. M.

Due to the similarity in chemical structure, lignin has presented great potential in the synthesis of bio-based phenolic resin. Herein, a facile and scalable synthesis strategy for a novel cage-like lignin-based phenolic resin was proposed through direct spray drying of the mixture of phenolic resin and unmodified lignin. The as-prepared lignin-based phenolic resin was pre-carbonized and carbonized using KOH to produce mesoporous carbon materials (LPRAC) that were further employed as supercapacitor electrodes. The results revealed that the lignin addition led to the noticeable change of the resin shape from perfect sphere to cage-like structure owing to the surfactivity and hydrophilicity of lignin. The cage-like structure promoted the KOH-activated pore generation and expansion in the carbonization process, resulting in the significantly increased specific surface area of the phenolic carbon and the intensified mesoporous formation. The electrochemical performance determination indicated that the specific capacitance of LPRAC-20% (20% lignin addition) was 217.3 F/g at 0.5 A/g, which was considerably higher than that of the lignin-free phenolic carbon (122.6 F/g). Moreover, the LPRAC-20% also exhibited preferable capacitance retention and excellent cycling stability. Accordingly, the present work offers a simple and scalable approach to prepare cage-like mesoporous carbon with excellent electrochemical performance from lignin-based phenolic resin and thus provides a promising route for lignin valorization in energy storage materials.

Keywords: Lignin-based phenolic resin; Cage-like mesoporous carbon; KOH activation; Supercapacitor electrodes

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  • Secondary publication expected from 30.08.2023

Permalink: https://www.hzdr.de/publications/Publ-36201
Publ.-Id: 36201


Reduction of lignin heterogeneity for improved catalytic performance of lignin nanosphere supported Pd nanoparticles

Hao, S.; Guanhua, W.; Jing, G.; Ni, W.; Wenjie, S.; Zicheng, C.; Hongyu, J.; Parvez, A. M.; Chuanling, S.

Lignin heterogeneity, including molecular weight polydispersity and structural complexity, causes undesirable properties of lignin in its valorization. In this regard, the current work focuses on the effect of lignin heterogeneity on the green synthesis of lignin nanosphere (LNS) supported Pd nanoparticles (Pd@LNS) and their catalytic performance. Three lignin fractions with reduced heterogeneity (F1, F2, and F3) were used for LNS fabrication and the as-prepared LNSs were further applied as carriers for Pd nanoparticles (Pd NPs) synthesized using lignin as an in-situ reducer. It was found that the three LNSs exhibited a gradually decreased particle size from F1 to F3, while all of them revealed improved particle size uniformity compared to that from the initial lignin. Owing to the superior reducing power of F1, the LNS prepared from F1 presented the highest loading amount of Pd NPs among the three LNSs. Moreover, these Pd NPs had the smallest particle size and they were dispersed in a much more uniform way than those on the LNSs from F2 and F3. Therefore, the Pd@LNS prepared from F1 exhibited significantly increased catalytic activity in the Cr(VI) reduction compared with those from F2 and F3, as well as the initial lignin. Consequently, the work implies that lignin heterogeneity has considerable influences on the green formation of Pd NPs on LNS, and the catalytic performance of Pd@LNS can be substantially improved using low molecular weight lignin fraction as the feedstock.

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  • Secondary publication expected from 18.06.2023

Permalink: https://www.hzdr.de/publications/Publ-36200
Publ.-Id: 36200


Effects of surface microbubbles on the adhesion between air bubble/oil droplet and graphite surfaces

Ming, L.; Xu, M.; Lijuan, S.; Chunyun, Z.; Jincheng, L.; Qinshan, L.; Yaowen, X.; Xiahui, G.

The surface microbubbles (SMBs) induced by air nucleation on mineral surfaces exert a powerful influence over enhancing the adhesion of air bubbles or oil droplets on mineral surfaces in flotation. The contact angles and TPLs were characterized by captive-bubble/oil droplet on the graphite surfaces. They were combined with dynamic bubble/oil droplet-graphite surface attachment and detachment visualization and force measurements using a microbalance system equipped with a camera to demonstrate the role of SMBs in bubble/oil dropletgraphite surface adhesion. The results show that after depressurization, the dissolved air in water nucleates on both hydrophobic and oxidized graphite surfaces, resulting in SMBs formation, which can enhance the adhesion of bubbles/oil droplets with the different graphite surfaces. For bubble-solid adhesion, these enhancements are attributed to the bridging effect of the SMBs coalescing with the large bubble increasing threephrase contact lines (TPLs) and with this the adhesion forces. For oil-solid interactions, SMBs induce the attachment and spreading of the oil droplet on the graphite surfaces, as the TPLs and spreading forces are increased. SMBs also result in a more stable oil droplet-graphite interface, as the adhesion forces are improved. Therefore, SMBs are efficient for improving graphite flotation by increasing the stability of the mineralized bubble and promoting the spreading and adhesion of dodecane oil. Hence, SMBs coupled with the modification of the surface hydrophobicity may be more beneficial for flotation separation.

Keywords: Surface microbubbles; Adhesion; Graphite; Depressurization; Air bubble/oil droplet

Permalink: https://www.hzdr.de/publications/Publ-36199
Publ.-Id: 36199


Controllable fabrication of nanofibrillated cellulose supported HKUST-1 hierarchically porous membranes for highly efficient removal of formaldehyde in air

Zicheng, C.; Xiangyang, H.; Jing, G.; Guangyuan, F.; Lanhe, Z.; Parvez, A. M.; Guanhua, W.

Nanofibrillated cellulose (NFC) has presented great potential as supports for functional membrane materials owing to its unique advantages. In this work, NFC-supported MOF hierarchically porous membranes were synthesized by anchoring HKUST-1 (copper 1,3,5-benzenetricarboxylate open-framework) on NFC membrane through a green DMF-free (N,N-Dimethylformamide) method at room temperature and afterward, the as-prepared composite membrane was used to remove formaldehyde from the air. The addition of HKUST-1 particles significantly increased the specific surface area of NFC membrane without affecting the NFC properties. Meanwhile, the nucleation and growth process of HKUST-1 on the NFC membrane could be effectively regulated, which further controlled the morphology of HKUST-1 as well as the anchored position of HKUST-1. When HKUST-1 was anchored on the interior and surface of the membrane, HKUST-1 reduced the compactness of the arrangement between fibers, which resulted in a hierarchical porous structure and then exposed more active adsorption sites of HKUST-1 particles. Thus, the flexible composite membranes exhibited effective formaldehyde adsorption from a low formaldehyde concentration environment (3.0 mg/m3). Under the optimum conditions, the maximum adsorption capacity of the HKUST-1@NFC-1 for formaldehyde reached 378.09 mg/g (based on HKUST-1 wt), which was considerably higher than support-free HKUST-1 powders. Consequently, the present work offers a green and controllable route to prepare NFC-supported MOF composite membranes with highly effective formaldehyde adsorption capacity and thus provides a promising option for NFC application as a flexible adsorbent support.

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  • Secondary publication expected from 15.10.2023

Permalink: https://www.hzdr.de/publications/Publ-36198
Publ.-Id: 36198


Acid-promoted lignin reductive depolymerization under mild conditions via a condensation minimizing approach: From organosolv lignin to woody biomass

Ni, W.; Shuang, Q.; Guanhua, W.; Jing, G.; Wenjie, S.; Hao, S.; Parvez, A. M.; Hongyu, J.; Chuanling, S.

Lignin reductive depolymerization into phenolic monomers is a critical step for the scale-conversion of lignin into liquid fuels but its scale-up is still compromised by harsh reaction conditions (e.g. high temperature and high external H2 pressure) and inevitable condensations. Herein, we present an efficient acid-promoted reductive depolymerization of lignin over Ni/C without external H2 via a condensation minimizing approach using lignin monomer analogue (p-hydroxybenzyl alcohol, HBA) as the capping agent. With addition of 0.4 % H2SO4 and 0.4 mmol/g HBA, 20.42 % of phenolic monomer yield along with 31.70 % oligomer yield was achieved at 160 °C while the condensated/undepolymerized lignin yield was less than 10 %. HBA inhibited the acid-induced condensation by competitive reaction with the nucleophilic C6 in guaiacyl unit. When the approach was applied in lignin-first reductive fractionation of poplar, 32.72 % of phenolic monomer yield and 76.59 % of delignification were achieved at 160 °C in the presence of acid and HBA. Additionally, xylan was dissociated concurrently owing to the acid-catalyzed hydrolysis, resulting in a cellulose-rich solid residue. Consequently, this work proposes an efficient approach for lignin reductive depolymerization and lignin-first biomass fractionation under mild conditions through the synergism of acid and capping agent.

Keywords: Lignin reductive depolymerization; Liquid fuels; Condensation minimizing; Oligomer characterization

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  • Secondary publication expected from 15.04.2024

Permalink: https://www.hzdr.de/publications/Publ-36197
Publ.-Id: 36197


Proton, deuteron and triton flow measurements in Au+Au collisions at √sNN=2.4 GeV

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; ...; Dreyer, J.; Kämpfer, B.; Kotte, R.; Naumann, L.; HADES Collaboration

High precision measurements of flow coefficients vn (n=1−4) for protons, deuterons and tritons relative to the first-order spectator plane have been performed in Au+Au collisions at √sNN=2.4 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at the SIS18/GSI. Flow coefficients are studied as a function of transverse momentum pt and rapidity ycm over a large region of phase space and for several classes of collision centrality. A clear mass hierarchy is found for the slope of v1, dv1/dy′|y′=0 where y′ is the scaled rapidity, and for v2 at mid-rapidity. Scaling with the number of nucleons is observed for the pt dependence of v2 and v4 at mid-rapidity, which is indicative for nuclear coalescence as the main process responsible for light nuclei formation. v2 is found to scale with the initial eccentricity ⟨ϵ2⟩, while v4 scales with ⟨ϵ2⟩2 and ⟨ϵ4⟩. The multi-differential high-precision data on v1, v2, v3, and v4 provides important constraints on the equation-of-state of compressed baryonic matter.

Permalink: https://www.hzdr.de/publications/Publ-36196
Publ.-Id: 36196


First measurement of massive virtual photon emission from N* baryon resonances

Abou Yassine, R.; Adamczewski-Musch, J.; Arnold, O.; ...; Dreyer, J.; Kämpfer, B.; Kotte, R.; Naumann, L.; HADES Collaboration

First information on the timelike electromagnetic structure of baryons in the second resonance region has been obtained from measurements of invariant mass and angular distributions in the quasi-free reaction π−p→nee at sπ−p−−−−√ = 1.49 GeV with the High Acceptance Di-Electron Spectrometer (HADES) detector at GSI using the pion beam impinging on a CH2 target. We find a total cross section σ(π−p→nee)=2.97±0.07data±0.21acc±0.31Zeffμb. Combined with the Partial Wave Analysis of the concurrently measured two-pion channel, these data sets provide a crucial test of Vector Meson Dominance (VMD) inspired models. The commonly used "strict VMD" approach strongly overestimates the e+e− yield. Instead, approaches based on a VMD amplitude vanishing at small e+e− invariant masses supplemented coherently by a direct photon amplitude provide a better agreement. A good description of the data is also obtained using a calculation of electromagnetic timelike baryon transition form factors in a covariant spectator-quark model, demonstrating the dominance of meson cloud effects. The angular distributions of e+e− pairs demonstrate the contributions of virtual photons with longitudinal polarization, in contrast to real photons. The virtual photon angular dependence supports the dominance of J=3/2, I=1/2 contributions observed in both the γ⋆n and the ππn channels.

Permalink: https://www.hzdr.de/publications/Publ-36195
Publ.-Id: 36195


New results on light nuclei, hyperons and hypernuclei from HADES

Abou Yassine, R.; Adamczewski-Musch, J.; Asal, C.; ...; Dreyer, J.; Kämpfer, B.; Kotte, R.; Naumann, L.; Hades, Collaboration

In March 2019 the HADES experiment recorded 14 billion Ag+Ag collisions at √sNN = 2.55 GeV as a part of the FAIR phase-0 physics program. In this contribution, we present and investigate our capabilities to reconstruct and analyze weakly decaying strange hadrons and hypernuclei emerging from these collisions. The focus is put on measuring the mean lifetimes of these particles.

Permalink: https://www.hzdr.de/publications/Publ-36193
Publ.-Id: 36193


Measurement of global polarization of Λ hyperons in few-GeV heavy-ion collisions

Abou Yassine, R.; Adamczewski-Musch, J.; Asal, C.; ...; Dreyer, J.; Kämpfer, B.; Kotte, R.; Naumann, L.; HADES Collaboration

The global polarization of Λ hyperons along the total orbital angular momentum of a relativistic heavy-ion collision is presented based on the high statistics data samples collected in Au+Au collisions at sqr(SNN)=2.4 GeV and Ag+Ag at 2.55 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at GSI, Darmstadt. This is the first measurement below the strangeness production threshold in nucleon-nucleon collisions. Results are reported as a function of the collision centrality as well as a function of the hyperon's transverse momentum () and rapidity () for the range of centrality 0–40%. We observe a strong centrality dependence of the polarization with an increasing signal towards peripheral collisions. For mid-central (20 – 40%) collisions the polarization magnitudes are (PΛ)(%) = 6.8 ± 1.3 (stat.) ±
2.1 (syst.) for Au+Au and (PΛ)(%) = 6.2 ± 0.4 (stat.) ± 0.6 (syst.) for Ag+Ag, which are the largest values observed so far. This observation thus provides a continuation of the increasing trend previously observed by STAR and contrasts expectations from recent theoretical calculations predicting a maximum in the region of collision energies about 3 GeV. The observed polarization is of a similar magnitude as predicted by 3D-fluid-dynamics and the UrQMD plus thermal vorticity model and significantly above results from the AMPT model.

Permalink: https://www.hzdr.de/publications/Publ-36191
Publ.-Id: 36191


Source-to-sample characterization of laser-driven proton beams for radiobiological applications

Reimold, M.; Assenbaum, S.; Bernert, C.; Beyreuther, E.; Brack, F.-E.; Corvino, A.; Kraft, S.; Kroll, F.; Löser, M.; Pawelke, J.; Püschel, T.; Schlenvoigt, H.-P.; Schneider, M.; Schramm, U.; Umlandt, M. E. P.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

Laser-driven plasma accelerators (LPA) are compact sources of ultra-short, intense proton pulses in the multi-10-MeV energy range. These unique parameters predestine LPAs as powerful tools for ultra-high dose rate radiobiology research. The sources’ capabilities were recently demonstrated in the first successful small animal pilot study on radiation-induced tumor growth delay in mice using an LPA proton source [1].
To promote further sophisticated radiobiological studies at LPAs, adapted approaches for primary LPA source characterization, beam monitoring and dosimeters are required. Here, most prominent challenges are LPA-inherent pulse-to-pulse fluctuation in terms of intensity as well as proton energy distribution, the ultra-high pulse dose rate and the harsh plasma environment, featuring a strong electromagnetic pulse (EMP) and an intense mixed radiation background. These conditions call for robust online monitoring solutions.
We present the solutions for source-to-sample characterization implemented at the ALBUS-2S beamline [2] at the Draco Petawatt laser system [3] at Helmholtz-Zentrum Dresden-Rossendorf. These include firstly an online beam monitoring system based on a time-of-flight spectrometer (ToF BMS). A core feature of the ToF BMS method is a precise spectrum-based forward-calculation of the corresponding volumetric dose distribution via Monte-Carlo simulation. Secondly, a dosimetric system for volumetric mm-scale sample irradiations was conceptualized and tested during an in vivo irradiation study, showing a solution for precise dosimetric characterization of ultra-high dose rate pulses at the ~500 mGy pulse dose range.
Lastly, with the OCTOPOD and MiniSCIDOM, two devices for online, single pulse characterization of volumetric dose distributions are presented, applicable for the primary LPA source and mm-scale dose distributions at the sample site, respectively. Both devices are based on volumetric scintillators as active detector material and rely on tomographic reconstruction for signal retrieval.

[1] F. Kroll, et al., Tumour irradiation in mice with a laser-accelerated proton beam, Nat Phys, 18, (2022), 316.
[2] F.-E. Brack, et al., Spectral and spatial shaping of laser-driven proton beams using a pulsed high-field magnet beamline, Sci Rep, 10, (2020), 9118.
[3] U. Schramm, et al., First results with the novel petawatt laser acceleration facility in Dresden, J. Physics: Conf. Ser, 874, (2017), 012028.

  • Lecture (Conference) (Online presentation)
    BLIN5, 12.-14.10.2022, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36190
Publ.-Id: 36190


Development of a peptides-based approach for metal recovery

Schönberger, N.

Here we demonstrate how a peptide-based material can be obtained for the biosorptive recovery of metals from contaminated industrial wastewater, starting with Phage surface display for the initial identification and optimization of gallium-binding peptides.
Two chromatography-based biopanning methods for the identification of gallium-binding peptides from a commercial phage display library were developed. Five gallium-binding peptide sequences were identified and evaluated to show good gallium-binding properties.
Furthermore, the biosorption of free gallium and arsenic by gallium-binding bacteriophage clones was investigated. A large influence of the pH-value on the respective interactions was demonstrated.
Mutagenesis experiments were also carried out for a bacteriophage clone expressed peptide, in which a cysteine pair systematically replaced amino acids. Biosorption experiments with the resulting seven different bacteriophage mutants suggested a relationship between the rigidity of the peptide structure and the gallium-binding properties.
In isothermal titration experiments, the thermodynamics of the interaction between gallium and the peptides as chemically synthesized derivatives were characterized, independent of the bacteriophage. The peptides differed strongly in their interaction with gallium, and in some cases, the complex formation with gallium depended strongly on the surrounding buffer conditions.
The peptide with the amino acid sequence NYLPHQSSSPSR has particularly promising gallium-binding properties. Computer modeling suggests the probable structure of the peptide in aqueous solution and postulates a possible binding site for gallium.
The side-selective and covalent immobilization of the peptides on a polystyrene matrix led to the creation of a biocomposite for the biosorptive recovery of gallium. The sorption performance and desorbability of the peptide-based biosorption materials were determined in studies with model solutions and real waters from the semiconductor industry.

  • Lecture (others) (Online presentation)
    BioCuInGe Workshop on Waste to Wealth, 25.-26.11.2022, New Delhi, India

Permalink: https://www.hzdr.de/publications/Publ-36189
Publ.-Id: 36189


Laser-plasma based proton accelerators for small animal pre-clinical radiation research

Kroll, F.; Brack, F.-E.; Bernert, C.; Bock, S.; Bodenstein, E.; Brüchner, K.; Cowan, T.; Gaus, L.; Gebhardt, R.; Helbig, U.; Karsch, L.; Kluge, T.; Kraft, S.; Krause, M.; Leßmann, E.; Masood, U.; Meister, S.; Nossula, A.; Pawelke, J.; Pietzsch, J.; Püschel, T.; Reimold, M.; Rehwald, M.; Richter, C.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Ziegler, T.; Zeil, K.; Beyreuther, E.; Metzkes-Ng, J.

Laser-plasma based proton accelerators as a novel accelerator technology have matured to a level at which laboratory-scale setups for the emerging topic of image-guided precision small animal irradiation studies come into reach [Bra2019]. Providing a high proton energy bandwidth [Sch2016] which is filtered in a tunable pulsed magnet beam transport, these accelerators enable flexibility in terms of scattering-free irradiation field formation [Mas2014, Mas2015]. Regarding temporal dose delivery, with single pulse doses reaching the Gy level at unprecedented peak dose rates of up to 1012 Gy/s [Sch2016], laser-plasma based proton accelerator setups can give access to the dose rate regime of FLASH [Fav2014, Voz2019].
The realization of a full-scale setup for image-guided precision radiobiological studies for small animals focusing on dose rate dependent effects is currently prepared at the PENELOPE laser-plasma based proton accelerator at HZDR and will be presented with a focus on the technological requirements and solutions for dose delivery at laser-plasma based sources.
This development relies on our experience in performing dose-controlled radiobiological in vitro studies [Kra2010, Zei2013] and first in vivo irradiation experiments at the DRACO laser-plasma based proton accelerator at HZDR, where we have established a pulsed solenoid beamline for 3D irradiation field formation, yielding a (5 mm)³ homogeneous volumetric dose distribution at a Gy single pulse dose level [8].
[Bra2019] F.-E. Brack, F. Kroll, L. Gaus, C. Bernert, E. Beyreuther, T. E. Cowan, L. Karsch, S. D. Kraft, L. A. Kunz-Schughart, E. Lessmann, J. Metzkes-Ng, L. Obst-Hübl, J. Pawelke, M. Rehwald, H.-P. Schlenvoigt, U. Schramm, M. Sobiella, E. R. Szabó, T. Ziegler, K. Zeil, Spectral and spatial shaping of laser-driven proton beams using a pulsed high-field magnet beamline. arXiv:1910.08430 (2019)
[Sch2016] J. Schreiber, P. Bolton, K. Parodi, “Hands-on” laser-driven ion acceleration: A primer for laser-driven source development and potential applications, Rev. Sci. Instr. 87, 071101 (2016)

  • Lecture (Conference) (Online presentation)
    5th Conference on Smal animal Precision Image-Guided Radiotherapy, 21.-23.03.2022, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36188
Publ.-Id: 36188


Directed evolution biology in resource technology – From the identification of novel inorganic-binding biomolecules to their provision in future resource recovery and recycling processes

Braun, R.; Kießlich, T.; Schönberger, N.; Matys, S.; Lederer, F.; Pollmann, K.

This work focuses on the identification and characterization of inorganic-binding peptidic biomolecules for resource recovery. Manifold biological molecules are used in pharmaceutical and nutrition industries but have so far only limited use in resource technology. Geopolitical tensions, decreasing ore grades combined with increasing demand due to the development of new products and markets result in resource scarcity and the need for new (green) innovative recycling and recovery technologies. Here, we present a novel approach for the design and construction of tailor-made selective target-specific proteinaceous molecules for the creation of innovative bio-based resource recovery applications. Novel peptides with high affinity towards minerals, metals and metalloids such as cobalt, nickel, gallium, arsenic and recently plastics have been identified in our working group using directed evolution phage display technology based on large peptide libraries. Until recently, identification of novel peptides was solely based on ten to hundreds of sequences out of libraries consisting of billions of peptides. As of late, next-generation sequencing (NGS) high throughput analysis of phage display libraries allowed for unprecedented insight into said libraries and accelerated identification of target-specific molecules. Here, we present the NGS-guided phage display-based identification of novel metal- and plastic-binding peptides for surface modification including new findings to the underlying selection process. The characterization of said sequences was successfully achieved in nanomolar ranges with solution- and surface interaction technologies such as isothermal titration calorimetry and quartz crystal microbalance with dissipation monitoring. The here presented results and approaches indicate possibilities for the design and the future provision of innovative bio-based recovery and recycling processes.

Keywords: adsorption; ITC Isothermal Titration Calorimetry; metal recovery; next generation sequencing; peptide; peptide-inorganic interaction; phage display; QCM Quartz Crystal Microbalance

  • Lecture (Conference) (Online presentation)
    24th International Biohydrometallurgy Symposium IBS, 20.-23.11.2022, Perth, Australia

Permalink: https://www.hzdr.de/publications/Publ-36185
Publ.-Id: 36185


A Decade of Electrocatalysis with Metal Aerogels: A Perspective

Li, W.; Weng, B.; Sun, X.; Cai, B.; Hübner, R.; Luo, Y.; Du, R.

Nowadays, great efforts have been spent on addressing concerns over energy and environmental crises. Among these efforts, electrocatalysis is widely recognized and studied for its high efficiency and easy processability. As a class of emerging electrocatalysts, metal aerogels (MAs) stand out in the last decade. In virtue of their three‐dimensional conductive pathways, their library of catalytically/optically active sites, and their robust network structures, MAs have unique advantages in electrocatalysis. However, due to the short history of MAs, there is insufficient research on them, leaving significant room for material design and performance optimization. This perspective will mainly focus on electrocatalysis with MAs, aiming to summarize the state‐of‐the‐art progress and to guide the on‐target design of efficient MAs‐based electrocatalysts towards energy‐ and environment‐related applications.

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Permalink: https://www.hzdr.de/publications/Publ-36184
Publ.-Id: 36184


GaLIOphore technology for Metal Recovery from Primary and Secondary Resources

Jain, R.

GaLIOphore technology for Metal Recovery from Primary and Secondary Resources

Keywords: GaLIophore; Gallium; Wastewater; IPGP

  • Lecture (others)
    Internal IPGP meeting, 08.07.2022, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-36183
Publ.-Id: 36183


Recovery of critical metals from the low concentrated wastewater and wastes

Jain, R.

Recovery of critical metals from the low concentrated wastewater and wastes

Keywords: Critical metals; GaLIophore; Upscaling; Commercialization

  • Invited lecture (Conferences)
    Securing sustainable treatment for drinking water production and water recycling with focus on anionic contaminants, 20.-22.07.2022, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-36182
Publ.-Id: 36182


Biotechnology for the recovery of germanium, indium and copper from industrial copper dust waste

Jain, R.; Pollmann, K.; Sarvanan, G. V.; Pinka, J.; Ahammad, S. Z.

Biotechnology for the recovery of germanium, indium and copper from industrial copper dust waste

Keywords: Indo-German; IGSTC; Critical metals; Siderophores

  • Lecture (others)
    IGSTC Partners Meet: 14-15 June 2022, 13.-15.06.2022, Frankfurt, Germany

Permalink: https://www.hzdr.de/publications/Publ-36181
Publ.-Id: 36181


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