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41662 Publications

Data publication: Electrical Conductivity of Iron in Earth's Core from Microscopic Ohm's Law

Ramakrishna, K.; Lokamani, M.; Baczweski, A. D.; Vorberger, J.; Cangi, A.

Abstract

Simulation and literature data on the electrical and thermal conductivity of iron. The raw simulation data was generated from time-dependent density functional theory calculations. Post-processing was applied to obtain the transport properties (conductivities) as described in the associated journal publication. The literature data was compiled from available publication data as referenced in the associated journal publication.

Keywords: transport properties; time-dependent density functional theory; Kubo-Greenwood; electrical conductivity; thermal conductivity; electronic structure theory; materials science

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Permalink: https://www.hzdr.de/publications/Publ-36755


Current state of Na-Zn battery research

Weber, N.

Abstract

Within the Horizon 2020 project SOLSTICE, two molten salt battery concepts, based on sodium and zinc, are developed. The first cell relies on a solid Na-beta’’-alumina membrane, and is very similar to the commercially available ZEBRA batteries. Operating at 300°C, this design benefits from a wide range of knowledge available from these existing batteries. The second cell concept, a fully liquid battery, operates around 600°C. Due to its novelty, this design presents a larger number of challenges, such as corrosion, sealing and self-discharge. Once these are solved, the sodium-zinc battery can be employed as a very competitive and sustainable stationary energy storage device due to the lower costs, abundance and recyclability of the active materials. The talk will give an overview on the current state of research in the SOLSTICE consortium, the achievements and the remaining challenges in Na-Zn battery development.

  • Lecture (Conference)
    SUPHER23 (SUstainable PolyEnergy generation and HaRvesting), 06.-08.09.2023, Savona, Italy

Permalink: https://www.hzdr.de/publications/Publ-36754


Vermeidung von Flüssigkeitsfehlverteilungen in RPBs durch den Einsatz von 3D-gedruckten Zickzack-Packungen

Loll, R.; Bieberle, A.; Schubert, M.; Koop, J.; Held, C.; Schembecker, G.

Abstract

Poster zum Thema: Vermeidung von Flüssigkeitsfehlverteilungen in RPBs durch Einsatz 3D-gedruckter Zickzack-Packungen

Keywords: Zickzack-Packungen; Trennprozesse; Gammastrahlen-Computertomographie

Involved research facilities

  • TOPFLOW Facility

Related publications

  • Poster
    Jahrestreffen Fachgruppe Fluidverfahrenstechnik, 21.-23.03.2023, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36753


Neues Konzept zur Flüssigkeitsverteilung für Rotating Packed Beds

Pyka, T.; Koop, J.; Bieberle, A.; Schubert, M.; Held, C.; Schembecker, G.

Abstract

Vorstellung eines neuen Konzepts zur Flüssigkeitsverteilung für Rotating Packed Beds

Keywords: Rotating Packed Beds; Trennprozesse; Gammastrahlen-Computertomographie

Involved research facilities

  • TOPFLOW Facility

Related publications

  • Lecture (Conference)
    Jahrestreffen Fachgruppe Fluidverfahrenstechnik, 21.-23.03.2023, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36752


OCTOPOD: single bunch tomography for angular-spectral characterization of laser-driven protons

Reimold, M.; Assenbaum, S.; Beyreuther, E.; Bodenstein, E.; Brack, F.-E.; Eisenmann, C.; Englbrecht, F.; Kroll, F.; Lindner, F.; Masood, U.; Pawelke, J.; Schramm, U.; Schneider, M.; Sobiella, M.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

Abstract

Laser-plasma accelerated (LPA) proton bunches are now prepared and provided for research fields ranging from ultra-high dose rate radiobiology to material science and probing of extreme states of matter. Yet, the capabilities to fully characterize the spectrally and angularly broad LPA bunches lag behind the rapidly evolving applications. The Optical Cone beam TOmograph for Proton Online Dosimetry - short OCTOPOD - translates the angularly resolved spectral characterization of LPA proton bunches into the spatially resolved detection of the volumetric dose distribution deposited in a liquid scintillator. Up to 24 multi-pinhole arrays record projections of the volumetric scintillation light distribution and allow for tomographic reconstruction of the volumetric dose deposition pattern, from which proton spectra may be retrieved in arbitrary directions by spectral deconvolution.
Applying the OCTOPOD at a cyclotron, we show the reliable retrieval of various spatial dose deposition patterns and detector sensitivity over a broad dose range from less than 1 Gy to more than 100 Gy, as required for LPA proton bunch characterization. With a dedicated vacuum housing, the OCTOPOD was installed at a LPA proton source, providing real-time data on proton acceleration performance for various laser-target interaction parameters and attesting the system optimal performance in the harsh laser plasma environment.

Keywords: laser-plasma acceleration of protons; proton detector; tomographic reconstruction

Involved research facilities

  • OncoRay
  • Draco

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Permalink: https://www.hzdr.de/publications/Publ-36751


Direct numerical simulation of a flexible fiber interacting with a fluidic interface

Lecrivain, G.

Abstract

The dynamics of fibers at a fluidic interface is of significant importance in various processes, among which stand out textile flotation, stabilization of emulsions, micro-folding of elastic structures, and clogging of feather fibers by oil droplets. A consistent formulation for the direct numerical simulation of a flexible fiber interacting with a fluidic interface is presently suggested. The fiber is geometrically decomposed into a chain of spherical beads, which undergo stretching, bending, and twisting interactions. The capillary force, acting at the three-phase contact line, is calculated using a ternary diffuse-interface model. Each ingredient of the model was validated against theoretical solutions. Partial and complete wrapping of an immersed three-dimensional drop is successfully simulated. The results show that the fiber curvature increases linearly with the square of the elasto-capillary length, for both low and large structural deformation, in-line with previously experimental observations

Keywords: Simulation; Particle at interface

  • Invited lecture (Conferences)
    Final Conference - MSCA-ITN-EID COMETE, 28.-29.03.2023, Udine, Italy

Permalink: https://www.hzdr.de/publications/Publ-36750


Effect of helium ion implantation on nanomechanical resonators in 3C-SiC

Jagtap, N.; Klaß, Y.; David, F.; Bredol, P.; Weig, E.; Helm, M.; Astakhov, G.; Erbe, A.

Abstract

Silicon carbide (SiC) is a suitable candidate for nanoelectromechanical systems due to its superior mechanical properties. It is also an interesting material platform to study the coupling of mechanical modes with localized spins associated with irradiation-induced defects. Such a spin-mechanical system can be used for quantum sensing applications [1].
The nanomechanical resonators in 3C-SiC are fabricated by standard semiconductor processing techniques such as electron beam lithography and reactive ion etching. They are characterized using Fabry-Pérot interferometer. In the preliminary experiments, we focus on the material modification by helium ion broad beam implantation on strained 3C-SiC resonators. The effect of varying fluence on resonance frequencies and quality factors is studied. With the fluence of 1 X 10^14 /cm^2 we observe decrease in resonant frequencies (~ 15%) and quality factors.

[1] A. V. Poshakinskiy and G. V. Astakhov, "Optically detected spin-mechanical resonance in silicon carbide membranes”, PhysRevB.100.094104 (2019)

Involved research facilities

Related publications

  • Poster
    Frontiers of Nanomechanical Systems (FNS) workshop, 06.-09.06.2023, Art Center Delft, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-36749


New Cross Section Data for Radiative Proton Capture on Carbon for Nuclear Astrophysics at LUNA

Boeltzig, A.; Skowronski, J.

Abstract

The observable ratio of 12C/13C can be used as a probe for stellar nucleosynthesis as well as for mixing processes during hydrogen burning, provided that the reaction rates of 12C(p,γ)13N and 13C(p,γ)14N are known. To obtain direct cross section measurements at low energies, which are required to better constrain these rates in astrophysical scenarios, both reactions were studied in a series of experiments at the LUNA-400 accelerator. Different targets and complementary detector setups were employed for a systematic study, and the sensitivity afforded by the low-background underground environment allowed for precise measurements at lower energies than previously available. We will present these experiments and their results for both reactions.

  • Lecture (Conference)
    DPG-Frühjahrstagung, 20.-24.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36748


MetroPOEM – Metrology for the harmonisation of measurements of environmental pollutants in Europe

Arnold, D.; Eberhardt, J.; Flierl, L.; Rienitz, O.; Pramann, A.; Zapata, D.; Vogl, J.; Prem, P. S.; Lourenço, V.; Chambon, L.; Isnard, H.; Mazánová, M.; Sochorová, J.; Zuliani, T.; Goltnik, T.; Rovan, L.; Štrok, M.; Noireaux, J.; Kamarainen, M.; Engin, B. A.; Can, S. Z.; Cankur, O.; İşleyen, A.; Hansen, V.; Ulrich, T.; Andreasen, R.; Hou, X.; Qiao, J.; Pröfrock, D.; Wippermann, D.; Zimmermann, T.; Winkler, S.; Fichter, S.; Wallner, A.; Schöpke, C.; Johansen, I.; Yasin, V.; Ioan, M.-R.; Virgolici, M.; Olaru, C.; Badea, R.; Walther, C.; Irrgeher, J.; Lancaster, S.; Epov, A.; Chernonozhkin, S.; Wagner, S.; Jerome, S.; Skipperud, L.; Jensen, K.-A.; Salminen-Paatero, S.; Vukanac, I.; Čeliković, I.; Rajačić, I.; Djurašević, M.; Nikolić, J. K.; Christl, M.; Tribouillier, H. P.; Malinovskiy, D.; Hil, S.; Goenaga-Infante, H.; Strekopytov, S.; Russell, B.; Mohamud, H.; Thompkins, H.

Abstract

Summary

The European Green Deal’s ambition for zero pollution requires the development of highly sensitive techniques to detect ultra-low amounts of pollutants. This requirement will be delivered via strategies described by the two European Metrology Network (EMN) on Pollution Monitoring (PolMo) and the EMN on Radiation Protection, supporting the Basic Safety Standards directive. Implicit in these strategies is a strong need to improve data quality for monitoring and reporting pollution in the air, water, and soil. To detect radioactive isotopes and stable polluting elements in the environment, fast, sensitive, and inexpensive analytical procedures are needed. Mass spectrometry is a key method for determination of non-radioactive polluting elements and of increasing importance for long-lived radionuclides, however, application of single collector ICP-MS, this potential cannot be fully realised unless techniques are validated with traceable multi-element reference materials. However, multi-element certified reference materials are usually not available and single-element certified reference materials are limited to very few elements. Nevertheless, these reference materials are urgently needed to calibrate mass spectrometric measurements, to overcome mass bias effects occurring during the measurements in mass spectrometers. The MetroPOEM project (21GRD09) is designed to address these problems. MetroPOEM, coordinated by the Physikalisch-Technische Bundesanstalt of Germany, will be delivered by a consortium of 22 partners from 13 countries throughout Europe.

Objectives

The overall aim of MetroPOEM is to bridge the gap between radiometric techniques and mass spectrometry for the characterisation and detection of polluting long-lived radionuclides and stable elements and element tracers by comparing and linking both techniques, thus significantly improving measurement uncertainties and detection limits. These aims and objectives will be delivered through four technical work packages, supported by project and impact management activities:

  • Establish and compare (inter-laboratory) the selectivity and detection limits of diverse types of mass spectrometers for selected radioactive pollutants (e.g., U, Np, Pu, Am) using isotope reference materials and/or activity standards. This includes assessing relative instrument performance with respect to current measurement challenges and establishing detection limits in relation to environmental regulations.
  • Develop measurement methods for isotope ratios that are traceable to the SI by using multi-collector ICP-MS and apply these methods on more commonly available techniques (ICP-MS/MS, ICP-QMS) by providing suitable operating procedures focussing on stable polluting elements (e.g., Li, B, Cr, Cd, Ni, Sb, Pb, U). To produce recommendations for sample processing, treatment, uncertainty budgets, and if feasible, the quantification of the so-called mass bias.
  • Develop two radioactive reference materials with the sample matrix containing radioactive pollutants (e.g., U, Np, Pu, Am) for use in an inter-laboratory comparison employing techniques used WP1, which will demonstrate the variations in parameters including detection limits, sample preparation, sample introduction methods, total procedural time, and uncertainty budgets.
  • Implement and validate the methods for isotope ratio measurements established in objective 2 by the development of one aqueous certified reference material that is certified for the same stable polluting elements with lowest possible uncertainties using multi-collector instruments, to facilitate the calibration of single collector ICP-MS, instrument validation, as well as quality control.
  • Facilitate the acceptance of the technology and measurement infrastructure developed in the project by the measurement supply chain (e.g., accredited laboratories), standards developing organisations and international organisations and end users (e.g., environmental monitoring agencies).

Involved research facilities

Related publications

  • Poster
    10. RCA-Workshop, 12.-14.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36747


Comparison of different CFD approaches for the simulation of developing free surface two-phase flow in straight and bent pipes

Döß, A.; Höhne, T.; Schubert, M.; Hampel, U.

Abstract

Two-phase flows in feed pipes of thermal separation columns have complex flow patterns and are difficult to predict during sizing and design for geometries with non-straight pipes. Numerical simulation codes have only been validated for very few pipe geometries. This work benchmarks the state-of-the-art Volume-of-Fluid model (VoF) and the Algebraic Interfacial Area Density model (AIAD) for the simulation of two-phase flows with the Eulerian/Eulerian CFD approach for straight pipes and horizontal bends as well as for different pipe diameters and flow rates. Both models are compared and shortcomings of the predicted velocity fields from AIAD in the vicinity of horizontal bends are highlighted. Predicted average phase fractions agree reasonably with experimental data. From the numerical results, recommendations for the selection of feed inlet devices are derived.

Keywords: Horizontal two-phase feeds; Flow morphology; Numerical simulation; VoF; AIAD; CFD; Wire-mesh sensors

Involved research facilities

  • TOPFLOW Facility

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  • Secondary publication expected from 18.07.2024

Permalink: https://www.hzdr.de/publications/Publ-36746


Exploring the lowest levels of environmental 90Sr in carbonates and seawater using a new, highly sensitive Accelerator Mass Spectrometry technique

Winkler, S.; Martschini, M.; Merchel, S.; Steier, P.; Golser, R.

Abstract

1 Introduction

Strontium-90 (90Sr) is an anthropogenic radionuclide, which, due to its radiological relevance, has been most intensively monitored in the past. In terms of initial activity, over 630 PBb of this radioisotope have been distributed globally from stratospheric fallout of bomb-testing, and there are more localized contributions from test, accidents, and releases from reprocessing plants.[1] Despite of the massive spike of 90Sr from global fall-out has been very difficult to measure in the ocean, due to the massive dilution in the oceans and the low atom detection efficiency of decay counting measurements. Massive sample sizes (up to 100 l of seawater or 100 g of coral aragonite) were required even right after the peak period of global fall-out from bomb testing. On the other hand, the high amount of strontium dissolved in seawater complicates the use of mass spectrometric methods, as an isotopic abundance sensitivity of at least 1·10-15 is required to detect the estimated main signal. Here we report on the results of successful measurements of such samples using a new Accelerator Mass Spectrometry (AMS) technique [2].

2 Samples and Methods

Our interest in this study lies in the determination of 90Sr as geochemical and ocean current tracer in conjunction with another anthropogenic tracer isotope, 236U. Both the respective elements both get build into marine carbonates such a coral samples, and both are present in significant amounts in seawater. While 236U is a well-established isotope and can be measured at very low levels (<10-13 236U/U) with AMS, only recent advances in isobar separation technique in AMS at the University of Vienna have opened possibility to measure 90Sr at the required level. The new technique uses an ion-cooler and laser-photo-detachment to suppress the stable isobar 90Zr. Besides the isobar suppression in the mass spectrometer system, we also gain a boost in suppression using ion-exchange columns. Since we are interested in measuring 90Sr against 236U we developed a sample preparation technique to extract both efficiently from a calcium carbonate matrix, while suppressing 90Zr, and avoiding pre-concentration steps. In principle, this could also be applied to seawater samples, although the efficiency of uranium co-precipitation in with carbonates still needs investigation. In this study we relied on separate procedures in the case of sea water samples.

3 Results

With initial test samples we could confirm a detection limit for the method corresponding to 0.03 mBq (or better) and a 90Sr/Sr isotopic abundance sensitivity of <8·10-16. We will present results from contemporary coral skeleton material, the methods, requirements, and impact of sample preparation. Further, we explain our sample preparation scheme to extract 236U, another important anthropogenic radionuclide, simultaneously with 90Sr for multi-isotope applications of both. Finally, the sample preparation and blank levels for ocean water samples and the results will be shown.

  • Lecture (Conference)
    RCA-Workshop, 12.-14.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36745


Porous Magnesium Oxide by Twin Polymerization: From Hybrid Materials to Catalysis

Scharf, S.; Notz, S.; Thomas, R.; Mehring, M.; Tegenkamp, C.; Formánek, P.; Hübner, R.; Lang, H.

Abstract

Twin monomers [Mg(2-OCH2-cC6H4O)][L]0.8 (2, L=diglyme) and [Mg(2-OCH2-cC6H4O)][L]0.66 (3, L=tmeda) form by their thermal polymerization interpenetrating organic-inorganic hybrid materials in a straightforward manner. Carbonization (Ar) followed by calcination gave porous MgO (2: surface area 200 m2g-1, 3: 400 m2g-1), which showed in catalytic studies towards Meerwein-Ponndorf-Verley reductions excellent yields and complete conversions for cyclohexanone and benzaldehyde. However, with crotonaldehyde a mixture of C4–C8 compounds was obtained. When MgO was exposed to air then primarily crotyl alcohol was formed. The range of applications could be easily extended by twin polymerization of 3 in presence of [Cu-(O2CCH2O(CH2CH2O)2Me)2] (4) or [Ag(O2CCH2-cC4H3S)(PPh3)] (5), resulting in the formation of nanoparticle-decorated porous CuO@MgO or Ag@MgO materials, which showed high catalytic reactivity towards the reduction of methylene blue.

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Permalink: https://www.hzdr.de/publications/Publ-36744


How tobacco (Nicotiana tabacum) BY-2 cells cope with Eu(III) – A microspectroscopic study.

Klotzsche, M.; Vogel, M.; Sachs, S.; Raff, J.; Stumpf, T.; Drobot, B.; Steudtner, R.

Abstract

Herein, Eu(III) was representatively used as luminescent probe to study the chemical environment and to elucidate the molecular interactions of lanthanides with a suspension cell culture of Nicotiana tabacum BY-2. Biochemical methods were combined with luminescence spectroscopy, two-dimensional microspectroscopic mappings, and data deconvolution methods to resolve bioassociation behavior and spatial distribution of Eu(III) in plant cells.

Keywords: Europium; Tobacco BY-2; Luminescence; Chemical microscopy; Raman microscopy; Plant cells; Species analysis; Lanthanides; Bioassociation

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  • Secondary publication expected from 30.08.2024

Permalink: https://www.hzdr.de/publications/Publ-36743


Data publication: Experimental and numerical investigation of a density-driven instability during a horizontal miscible displacement

Stergiou, Y.; Papp, P.; Horvath, D.; Toth, A.; Eckert, K.; Schwarzenberger, K.

Abstract

Data from flow visualization experiments, results of numerical simulations and Particle Image Velocimetry image data

Keywords: instabilities : buoyancy-driven; computational fluid dynamics; vortex flows; buoyancy; convection

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Permalink: https://www.hzdr.de/publications/Publ-36742


Laser Transmission in the Relativistically Induced Transparency Regime for High Performance Proton Acceleration at PW Laser Systems

Umlandt, M. E. P.; Assenbaum, S.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Ditter, E. J.; Dover, N. P.; Garten, M.; Gaus, L.; Göthel, I.; Hicks, G. S.; Kiriyama, H.; Kluge, T.; Koga, J. K.; Kon, A.; Kondo, K.; Kraft, S.; Kroll, F.; Lowe, H. F.; Metzkes-Ng, J.; Miyatake, T.; Najmudin, Z.; Nishiuchi, M.; Püschel, T.; Rehwald, M.; Reimold, M.; Sakaki, H.; Schlenvoigt, H.-P.; Shiokawa, K.; Zeil, K.; Ziegler, T.; Schramm, U.

Abstract

Ion acceleration by laser-plasma sources promises many applications, but reaching the required beam quality parameters demands a high level of understanding and control over the interaction process. Several advanced schemes, including the Relativistically Induced Transparency (RIT) regime, have been proposed and investigated in search of a stable acceleration for proton energies beyond 100 MeV. In the RIT scheme, the absorption of the electromagnetic laser field by the target and the generated plasma is critical. In joint experiments at the DRACO PW (HZDR) and J-KAREN (KPSI) lasers, we use transmission diagnostics to study the onset of transparency and learn about the sensitivity of the laser input to improve the process’s robustness. Using ultra-short pulses on thin solid density foil targets, we observe high performance proton beams in an expanded foil case. Our analysis of the effects on the transmission and its correlation with the acceleration performance indicates changes in the plasma interaction process.

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

Involved research facilities

  • Draco
  • Lecture (Conference)
    DPG-Frühjahrstagung 2023; SMuK2023, 20.-24.03.2023, Dresden, Deutschland
  • Lecture (Conference)
    SPIE Optics + Optoelectronics, 24.-27.04.2023, Praha, Česká republika

Permalink: https://www.hzdr.de/publications/Publ-36740


Revisiting power-law distributions in empirical outage data of power systems

Hartmann, B.; Deng, S.; Ódor, G.; Kelling, J.

Abstract

The size distribution of planned and forced outages in power systems have been studied for
almost two decades and has drawn great interest as they display heavy tails. Understanding of this
phenomenon has been done by various threshold models, which are self-tuned at their critical points,
but as many papers pointed out, explanations are intuitive, and more empirical data is needed to
support hypotheses. In this paper, the authors analyze outage data collected from various public
sources to calculate the outage energy and outage duration exponents of possible power-law fits.
Temporal thresholds are applied to identify crossovers from initial short-time behavior to power-
law tails. We revisit and add to the possible explanations of the uniformness of these exponents.
By performing power spectral analyses on the outage event time series and the outage duration
time series, it is found that, on the one hand, while being overwhelmed by white noise, outage
events show traits of self-organized criticality (SOC), which may be modeled by a crossover from
random percolation to directed percolation branching process with dissipation. On the other hand,
in responses to outages, the heavy tails in outage duration distributions could be a consequence of
the highly optimized tolerance (HOT) mechanism, based on the optimized allocation of maintenance
resources.

Keywords: power grid; self-organized criticality; highly optimized tolerance

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Permalink: https://www.hzdr.de/publications/Publ-36739


Optimizing PW Laser-Driven Proton Acceleration by Characterizing Laser Transmission of Relativistically Transparent Targets

Umlandt, M. E. P.; Assenbaum, S.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Ditter, E. J.; Dover, N. P.; Garten, M.; Gaus, L.; Göthel, I.; Hicks, G. S.; Kiriyama, H.; Kluge, T.; Koga, J. K.; Kon, A.; Kondo, K.; Kraft, S.; Kroll, F.; Lowe, H. F.; Metzkes-Ng, J.; Miyatake, T.; Najmudin, Z.; Nishiuchi, M.; Püschel, T.; Rehwald, M.; Reimold, M.; Sakaki, H.; Schlenvoigt, H.-P.; Shiokawa, K.; Zeil, K.; Ziegler, T.; Schramm, U.

Abstract

Ion acceleration by compact laser-plasma sources has great potential for a range of applications, including those with medical relevance and fusion experiments. However, in order to achieve the necessary beam quality parameters for these applications, a thorough understanding and control over the laser-plasma interaction process is required.
Therefore, we are exploring laser plasma acceleration around the promising regime of Relativistically Induced Transparency (RIT) through joint studies at DRACO PW (HZDR) and the J-KAREN-P laser system at KPSI. We have performed thickness scans to investigate the relation between proton acceleration performance and target transparency, revealing high-performance proton beams (> 60 MeV) in an expanded foil case, with an optimum at the onset of target transparency. [1] Subsequent experiments showed even higher proton energies.
Clearly, the relationship between the transparency onset time and the acceleration performance is crucial for achieving optimal beam parameters, improving our understanding of the sensitivity of laser input parameters, and increasing the process’s robustness. Thus, we are using a combination of particle and laser diagnostics to investigate this correlation. In this contribution, we present a summary of our studies in which we use spectral interferometry with the unperturbed laser beam as a reference to evaluate the output of reflected and transmitted light diagnostics. Obtaining features like shown in Bagnoud et al. [2] and Williamson et al. [3], we additionally correlate these measures with the proton acceleration performance and show first results of spectral, spatial, and energy analysis of the effects on the laser transmission through the target.

References
[1] Dover, N. P. et al.: Enhanced ion acceleration from transparency-driven foils demonstrated at two ultraintense laser facilities. Light Sci. Appl. in press (2023).
[2] Bagnoud, V. et al.: Studying the Dynamics of Relativistic Laser-Plasma Interaction on Thin Foils by Means of Fourier-Transform Spectral Interferometry. Phys. Rev. Lett. 118, 255003 (2017).
[3] Williamson, S. D. R. et al.: Self-Referencing Spectral Interferometric Probing of the Onset Time of Relativistic Transparency in Intense Laser-Foil Interactions. Phys. Rev. Appl. 14, 034018 (2020).

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

Involved research facilities

  • Draco
  • Poster
    Laser and Plasma Accelerators Workshop 2023, 06.-10.03.2023, Lagos, Portugal

Permalink: https://www.hzdr.de/publications/Publ-36738


State-of-the-Art Room Temperature Operable Zero-Bias Schottky Diode-Based Terahertz Detector up to 5.56 THz

Yadav, R.; Ludwig, F.; Faridi, F. R.; Klopf, J. M.; Roskos, H. G.; Preu, S.; Penirschke, A.

Abstract

We present the characterization of a Zero-bias Schottky diode-based Terahertz (THz) detector up to 5.56 THz. The detector was operated with both a table-top system until 1.2 THz and at a Free-Electron Laser (FEL) facility at singular frequencies from 1.9 to 5.56 THz. We used two measurement techniques in order to discriminate the sub-ns-scale (via a 20 GHz oscilloscope) and the ms-scale (using the lock-in technique) responsivity. While the lock-in measurements basically contain all rectification effects, the sub-ns-scale detection with the oscilloscope is not sensitive to slow bolometric effects caused by changes of the IV characteristic due to temperature. The noise equivalent power (NEP) is 10 pW/√Hz in the frequency range from 0.2 to 0.6 THz and 17 pW/√Hz at 1.2 THz and increases to 0.9 μW/√Hz at 5.56 THz, which is at the state of the art for room temperature zero-bias Schottky diode-based THz detectors with non-resonant antennas. The voltage and current responsivity of ∼500 kV/W and ∼100 mA/W, respectively, is demonstrated over a frequency range of 0.2 to 1.2 THz with the table-top system.

Keywords: FELBE; THz detectors; FEL; Schottky; ultrafast

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Permalink: https://www.hzdr.de/publications/Publ-36737


Experimental and numerical investigation of a density-driven instability during a horizontal miscible displacement

Stergiou, Y.; Papp, P.; Horvath, D.; Toth, A.; Eckert, K.; Schwarzenberger, K.

Abstract

We performed an experimental and numerical investigation of a convective buoyancy-driven instability that arises during the injection of a denser miscible fluid into a less dense one in a rectilinear geometry. We visualized the instability using a shadowgraph technique and we obtained quantitative information using micro-Paricle Image Velocimetry. Numerical simulations provided further insights into the 3D velocity field. We suggest scalings of the critical time, TC and dimensionless wavelength, λ/h of the instability by using the Péclet and Rayleigh numbers. Finally, we investigated the interactions of the instability vortices with each other and the geometry boundaries.

Keywords: instabilities : buoyancy-driven; computational fluid dynamics; vortex flows; buoyancy; convection

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Permalink: https://www.hzdr.de/publications/Publ-36736


Positron beams for materials research

Wagner, A.; Butterling, M.; Hirschmann, E.; Liedke, M. O.; Krause-Rehberg, R.

Abstract

The Helmholtz-Center Dresden - Rossendorf operates several user beamlines for materials research using positron-annihilation energy and lifetime spectroscopy. The superconducting electron linear accelerator ELBE drives several secondary beams including hard X-ray production from electron-bremsstrahlung, which serves as an intense source of positrons by means of pair production. The Mono-energetic Positron Source MePS [1] utilizes positrons 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 (σt ≈100 ps) at high average rates (105 s-1) and adjustable beam repetition rates allow performing high-throughput experiments.
The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). AIDA was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox) and by the Helmholtz Energy Materials Characterization Platform.
[1] A. Wagner, et al., AIP Conference Proceedings, 1970, 040003 (2018).

Keywords: positron annihilation; lifetime spectroscopy; superconducting linear accelerator; defect characterization; porosity; vacancies

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  • Lecture (Conference)
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 26.-31.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36735


Quasi-2D FCC lithium crystals inside defective bi-layer graphene: insights from first-principles calculations

Zhang, X.; Ghorbani Asl, M.; Zhang, Y.; Krasheninnikov, A.

Abstract

Quasi-2D crystals inside bilayer graphene have been observed in in-situ TEM experiments [Nature 564 (2018) 234]. It was also revealed that Li crystals have the FCC structure, nucleate at point defects in graphene and contain impurity atoms. Using first-principles calculations, we systematically study the interaction of isolated Li atoms and those assembled in FCC crystals with vacancy-type defects in graphene and show that quasi-2D Li crystals encapsulated between graphene sheets must indeed nucleate at the defects and that the interaction of not only isolated Li atoms but also Li crystals with the defects in graphene is strong. We further demonstrate that a moiré pattern develops at the graphene/Li interface. Finally, we investigate the behavior of impurities most likely to be found in the encapsulated Li crystals, such as O, N, S, and F and show that all impurity atoms take octahedral interstitial positions and strongly interact with atoms in Li crystals, thus impeding the de-lithiation process. Our theoretical work focused on the fundamental aspects of the behavior of Li inside bilayer graphene should help rationalize the results of in-situ TEM experiments and shed light on the role of impurities in the degradation of anode materials during Li-ion battery operation.

Keywords: Li intercalation; graphene; defects; first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-36733


Hydrodynamics in a bubble column – Part 1: Two-phase flow

Sommer, A.-E.; Draw, M.; Wang, L.; Schmidtpeter, J.; Gatter, J.; Nam, H.; Eckert, K.; Rzehak, R.

Abstract

Multiphase computational fluid dynamics (CFD) simulation is a useful tool to study the hydrodynamics in a bubble column, if appropriate closure models are known. Systematic assessment of different models is an ongoing venture that benefits from improved validation data. The present study accumulates a database on two-phase flow experiments in a bubble column. This is achieved by using a combination of Particle Image Velocimetry and Shadowgraphy to measure the liquid velocity field and gas dispersion properties simultaneously. This methodology is applied for different needle diameters and gas flow rates.

A detailed description of the experimental

The experimental data (Table 1) described in this repository is structured into different folders and files as follows:
Level 1: Folders classified by measurement configuration: TX_Jg_Y_Di_ZZZ as outlined in Table 1

  • TX = Identifier
  • Jg_Y = Superficial gas velocity in mm/s
  • Di_ZZZ = Inner diameter of the needle in µm

Level 2: Folders classified by measurement height: Z_XXX

  • Z_XXX = Measurement height in mm

Level 3: csv files classified by their analysis parameter:

  • Gas_Eg_ub_over_x.csv: Each csv file consists of five columns, namely the x-coordinate (in m), the gas holdup, the uncertainty of the gas holdup, the averaged bubble rising velocity (in m/s) and the corresponding uncertainty (in m/s).
  • Liquid_v_z_over_x.csv: Each csv file consists of three columns, namely the x-coordinate (in m), the averaged liquid velocity (in m/s) and the corresponding uncertainty (in m/s).

Table 1: Overview of the measurement cases in this repository.

| ID | Diameter of needle orifice in µm | Superficial gas velocity in mm/s |
|----|----------------------------------|----------------------------------|
| T1 | 200                              | 2                                |
| T2 | 200                              | 4                                |
| T3 | 200                              | 6                                |
| T4 | 600                              | 2                                |
| T5 | 600                              | 4                                |
| T6 | 600                              | 6                                |

Keywords: Particle Image Velocimetry (PIV); Shadowgraphy; Two-phase bubble column

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Permalink: https://www.hzdr.de/publications/Publ-36732


Data publication: Deconvoluting Cr States in Cr-Doped UO2 Nuclear Fuels via Bulk and Single Crystal Spectroscopic Studies

Murphy, G. L.; Gericke, R.; Gilson, S.; Bazarkina, E.; Roßberg, A.; Kaden, P.; Thümmler, R.; Klinkenberg, M.; Henkes, M.; Kegler, P.; Svitlyk, V.; Marquardt, J.; Lender, T.; Hennig, C.; Kvashnina, K.; Huittinen, N. M.

Abstract

Experimental and fitted EPR data of Cr-UO2 single crystal grains, EXAFS data Cr-UO2 single crystal grain and powder with Cr redox standards, XANES data Cr-UO2 single crystal grain and powder with Cr redox standards

Keywords: Cr-doped UO2; Nuclear Fuel; Uranium; EPR; HERFD-XANES; EXAFS

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Permalink: https://www.hzdr.de/publications/Publ-36731


StarDist Models for "Hydrodynamics in a bubble column – Part 1: Two-phase flow"

Sommer, A.-E.; Draw, M.; Wang, L.; Schmidtpeter, J.; Hessenkemper, H.; Gatter, J.; Nam, H.; Eckert, K.; Rzehak, R.

Abstract

This package contains the software and the trained models described in the publication "Hydrodynamics in a bubble column – Part 1: Two-phase flow". Please refer to the readme.md for installation instructions and to the Prediction_demo.ipynb for usage demonstration.

Keywords: StarDist; Bubble detection; Shadowgraphy

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Permalink: https://www.hzdr.de/publications/Publ-36730


Klassifikation von Pulsdaten mit neuronalen Netzwerken auf einer FPGA Accelerator Card

Ufer, R.; Auer, B.; Hoffmann, H.; Knodel, O.; Lokamani, M.; Müller, S.

Abstract

Zur Analyse der entstehenden Detektordaten bei dem Mu2e Experiment am Fermilab soll die Datenauswertung mit Field Programmable Gate Array (FPGA) erfolgen. Diese übernehmen die notwendige Vorverarbeitung und Reduktion der Messdaten, noch während der Durchführung der Messung. Die dabei ausgeführten Anwendungen werden standardmäßig durch Algorithmen realisiert. Eine dieser Anwendungen führt die Klassifikation der ermittelten Pulsdaten durch. Mit den Testläufen an der gELBE Bremstrahlungs-Beamline am Helmholtz-Zentrum Dresden-Rossendorf (HZDR) konnte für das zukünftige Experiment eine große Menge dieser Datensätze erfasst werden. Diese dienen zur Charakterisierung des Detektorsystems und wurden mit einem Lanthanbromid (LaBr) Detektor gemessen. Für die Pulsdatenklassifikation wird auf der Basis des Algorithmus und der erfassten Datensätze, ein neuronales Netzwerk erstellt, trainiert und validiert. Um bei diesen Schritten etablierte Machine Learning Frameworks zu verwenden, wird für die Portierung des Netzwerks in eine High-Level Synthese (HLS) Sprache die Software hls4ml verwendet. Dabei werden verschiedene Konfigurationen genutzt, um unterschiedlich optimierte Implementierungen zu generieren. Zum Evaluieren erfolgt die Ausführung der Implementierungen auf einer Xilinx Alveo Accelerator Card.

Keywords: FPGA; ML; CI; Mu2e

  • Lecture (Conference)
    86. Jahrestagung der DPG und DPG-Frühjahrstagung, 20.-24.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36729


Investigation of contrast mechanisms for MRI phase signal-based proton beam visualization in water phantoms

Schieferecke, J.; Gantz, S.; Hoffmann, A. L.; Pawelke, J.

Abstract

Purpose: The low sensitivity and limitation to water phantoms of convection-dependent MRI
magnitude signal-based proton beam visualization hinder its in-vivo applicability in MR-integrated
proton beam therapy. The purpose of the present study was therefore to assess possible contrast
mechanisms for MRI phase signal-based proton beam visualization that can potentially be exploited
to enhance the sensitivity of the method and extend its applicability to tissue materials.
Methods: To assess whether proton beam-induced magnetic field perturbations, changes in material
susceptibility or convection result in detectable changes in the MRI phase signal, water phantom
characteristics, experiment timing and imaging parameters were varied in combined irradiation and
imaging experiments using a time-of-flight angiography pulse sequence on a prototype in-beam MRI
scanner. Velocity encoding was used to further probe and quantify beam-induced convection.
Results: MRI phase signal-based proton beam visualization proved feasible. The observed phase
difference contrast was evoked by beam-induced buoyant convection with flow velocities in the mm/s
range. Proton beam-induced magnetic field perturbations or changes in magnetic susceptibility did not
influence the MRI phase signal. Velocity encoding was identified as a means to further enhance the
detection sensitivity.
Conclusion: Because the MRI phase difference contrast observed during proton beam irradiation of water phantoms is caused by beam-induced convection, this method will unlikely be transferable to tightly compartmentalized tissue wherein flow effects are restricted. Strongly velocity encoded pulse
sequences, however, were identified as promising candidates for the future development of MRI-
based methods for water phantom-based geometric quality assurance in MR-integrated proton beam
therapy.

Keywords: in-beam MRI; proton therapy; proton beam visualization; phase difference imaging; velocity encoding; convection

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  • OncoRay

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Permalink: https://www.hzdr.de/publications/Publ-36728


Characterization of defect microstructure in MgRE (RE=Ce, Nd) alloys after processing by High-Pressure Torsion using Positron Annihilation Spectroscopy and a High Resolution X-ray Diffraction

Bibimoune, I.; Bourezg, Y. I.; Abib, K.; Liedke, M. O.; Wagner, A.; Matej, Z.; Huang, Y.; Langdon, T. G.; Bradai, D.

Abstract

Two MgRE (RE=Ce, Nd) alloys with ultrafine-grain (UFG) microstructures were prepared by high-pressure torsion (HPT) at room temperature. The in-depth distribution of defects was
characterized by Doppler broadening –variable energy positron annihilation spectroscopy (DBVEPAS). The characteristic S parameter increases in bulk after HPT processing relative to an
as-received sample and shows a relative stability between ½ and 10 turns, which suggests a rise in the open volume defect density. However, a theoretical analysis of the S(E) depth profile reveals an increase in the positron diffusion length from ~115 nm for the as-received state to ~207 nm after 10 HPT turns. Almost all the open volume defect consisted of dislocations
(positron lifetime of τ = 260 ps). The dislocation density deduced from high-resolution X-ray diffraction in the HPT disc radial direction was reasonably homogeneous (around 4 - 6e14 m-2).

Keywords: Mg; rare earthhtp; dislocations; positron annihilation spectroscopy; VEPfit

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36727


Techno-economic assessment of PEM electrolysis for O2 supply in activated sludge systems – a simulation study based on the BSM2 wastewater treatment plant

Parra Ramirez, M. A.; Fogel, S.; Reinecke, S.; Hampel, U.

Abstract

The conversion of renewable energy into hydrogen (H2) by power-to-gas technologies involving electrolysis is seen today as a key element in the transition to a renewable energy sector. Wastewater treatment plants (WWTP) could make use of oxygen (O2) produced alongside H2 in biological treatment steps, however, production costs of electrolysis O2 should be competitive with respect to those of conventional O2 production processes. In this study, mathematical models of a polymer electrolyte membrane electrolyser (PEME) plant and the WWTP of the Benchmark Simulation Model Nr. 2 (BSM2) were used to simulate electrolysis O2 supply to an activated sludge (AS) system and estimate net costs of production (NCP) via a techno-economic assessment (TEA). Assuming that produced H2 is sold to a nearby industry, NCPs for O2 were calculated for two scenarios regarding PEME plant dimensions, which correspond to average (scenario 1) and optimal (scenario 2) electricity availability, i.e. medium and high number of full load hours per year. For each scenario, estimations were made for four alternatives for electricity supply and costs, namely conventional sources, photovoltaic (PV), and on/off shore wind energy, and using sets of optimistic, neutral and pessimistic data regarding system performance and market conditions. The analyses were done for 2020 as reference year and again for 2030 based on forecasts of relevant data. The results of the dimensioning of the PEME plant in scenario 1 show that a 6.4 MW PEME operated for 4,073 full load hours per year is able to cover the O2 demand of the AS system during more than 99% of the simulated period. The same is true for a 4.8 MW PEME operated for 6,259 full load hours per year in scenario 2. The TEA shows that investment costs for the PEME stacks and the operational costs for electricity make up most of the NCP of electrolysis O2. Although NCP for electrolysis O2 are always higher than those of conventional O2 sources for the year 2020, in 2030 estimated NCPs for the smaller PEME plant of scenario 2 become competitive for PV and wind on shore electricity supply under optimistic market conditions. Potential minimum selling prices were also calculated for the produced O2, however, they were above those of conventional O2 sources both in 2020 and 2030. The approach described in this study can be applied to analyse O2 supply to biological wastewater treatment in WWTPs with different characteristics, in processes different to conventional AS, and under different assumptions regarding economic conditions.

Keywords: Wastewater treatment; Activated sludge; PEM electrolysis; Techno-economic assessment

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Permalink: https://www.hzdr.de/publications/Publ-36725


Influence of Eu(III) and U(VI) on rat and human kidney cells

Butscher, D.; Senwitz, C.; Heller, A.; Stumpf, T.; Barkleit, A.

Abstract

Radionuclides (RNs) that enter the human body, for example through ingestion or inhalation, pose a potential health risk due to their radio- and chemotoxicity. The kidneys are especially exposed to the incorporated RNs, as they are mainly responsible for the excretion of toxic substances from the blood stream. Therefore, the effect of uranium(VI) and europium(III), an analogue for trivalent actinides such as Am or Cm, on rat (NRK-52E) and human (HEK-293) kidney cells was studied in vitro at the cellular and molecular levels.
Exposure experiments were carried out in which cells were incubated with these metal ions (10−9 – 10−3 M) for 7, 24 and 48 hours. The cell viability after exposure to the metal ions was measured using the XTT-assay. The half-maximum effective concentration (EC50) was calculated on the basis of the dose-response curves. In addition, morphological changes due to metal ion exposure were investigated by staining selected cell compartments and intracellular uptake was determined by ICP-MS. The speciation of a metal determines its bioavailability, influencing both the effect on cells and its uptake into cells. Therefore, time resolved laser-induced fluorescence spectroscopy (TRLFS) was used to investigate the speciation of Eu(III) and U(VI) in the cell culture medium, in the cell-exposed medium and in cell suspension. The obtained results on the cellular and molecular level contribute to a better understanding of the toxic effects of RNs.
This work is funded in the frame of the RADEKOR project by the German Federal Ministry of Education and Research (BMBF, grant number: 02NUK057A and 02NUK057B).

Keywords: Cytotoxicity; Kidney cells; Uranium; Europium; EC50; Speciation

  • Lecture (Conference)
    7th International Conference on Environmental Radioactivity (ENVIRA), 17.-22.09.2023, Seville, España

Permalink: https://www.hzdr.de/publications/Publ-36723


Theorien und Experimente zur Entstehung und Wirkung kosmischer Magnetfelder

Stefani, F.

Abstract

Der Vortrag beschäftigt sich mit Theorien und Experimenten zur Entstehung und Wirkung kosmischer Magnetfelder. Ein besonderer Schwerpunkt liegt auf der Vorstellung des DRESDYN-Experiments am HZDR.

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  • DRESDYN
  • Invited lecture (Conferences)
    Öffentlicher Vortrag im Palitzsch-Museum Dresden, 23.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36720


Finite Elemente Simulation der Aufschlusszerkleinerung von Verbundstrukturen im Recycling

Heibeck, M.; Richter, J.; Mütze, T.; Filippatos, A.

Abstract

Die Kombination von Materialien wie Metallen und Kunststoffen in Verbundstrukturen ermöglicht funktionsintegrative Designs. Im Recycling müssen die unterschiedlichen Materialien jedoch wieder aufgeschlossen werden, um materialspezifisch hohe Recyclingraten zu erzielen. Typischerweise erfolgt der Aufschluss durch mechanische Zerkleinerungsprozesse. Derzeit gibt es keine adäquate Beschreibung dieser Prozesse, die zu einer recyclingorientierten Produktgestaltung beitragen könnte. Im Beitrag wird ein Ansatz zu physikalisch basierten numerischen Simulationen mit der Finite-Elemente-Methode (FEM) vorgestellt.

Keywords: FEM; Aufschluss; Zerkleinerung; Rotorreißer; Verbundwerkstoff

  • Lecture (Conference)
    DECHEMA - Fachgruppentreffen Zerkleinern & Klassieren 2023, 21.-22.03.2023, Braunschweig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36719


Hands-on training on machine learning

Fiedler, L.

Abstract

Hands-on training on machine learning and the MALA library.

  • Lecture (others)
    Theoretical Chemistry Seminar, 21.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36718


Demonstrating temperature transferability of neural network models replacing modern density functional theory

Fiedler, L.; Cangi, A.

Abstract

Due to its balance between accuracy and computational cost, Density Functional Theory (DFT) is one of the most important computational methods within materials science and chemistry. However, current research efforts such as the modeling of matter under extreme conditions demand the application of DFT to larger length scales as well as higher temperatures. Such investigations are currently prohibited due to the computational scaling of DFT.

We have recently introduced a machine-learning workflow that replaces modern DFT calculations [1,2,3]. This workflow uses neural networks to predict the electronic structure locally. We show that by employing such an approach, models can be trained to predict the electronic structure of matter across temperature ranges. This paves the way for large-scale simulations of thermodynamically sampled observables relevant to modeling technologically important phenomena such as radiation damage in fusion reactor walls.

Keywords: Density Functional Theory; Surrogate Models; Machine Learning

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 27.03.2023, Dresden, Deutschland
  • Invited lecture (Conferences)
    Electronic Structure Workshop, 13.-16.06.2023, Merced, USA

Permalink: https://www.hzdr.de/publications/Publ-36717


Monte Carlo simulation studies of background contributions in the Mu2e experiment

Rachamin, R.; Di Falco, S.; Ferrari, A.; Giusti, V.; Müller, S. E.; Pronskikh, V. S.

Abstract

The Mu2e experiment is currently being constructed at Fermilab to search for the direct conversion of muons into electrons in the field of a nucleus without the emission of neutrinos. The experiment aims at a sensitivity of four orders of magnitude higher than previous related experiments, which implies highly demanding accuracy requirements both in the design and during the operation. Hence, it is essential to estimate precisely the backgrounds that could mimic the monoenergetic conversion electron signal and the particle yields relevant to the experiment sensitivity. In that regard, Monte Carlo simulations were performed to investigate key yields and beam-related and cosmic rays-related backgrounds. The investigation includes: (I) an evaluation of the antiproton and charged pion yields from an 8 GeV proton pencil beam impinging on a tungsten cylindrical target, (II) an evaluation of the transmission of cosmic neutrons and neutral kaons in a block of concrete. The simulations were performed using the FLUKA2021, MCNP6, GEANT4, PHITS, and MARS15 codes. The presentation will show the simulation results with a focus on the prediction obtained from each code and their impact on the experiment.

Keywords: Charged Lepton Flavor Violation; Muon to Electron conversion; Mu2e experiment; Monte Carlo; GEANT4; PHITS; MARS15; FLUKA; MCNP

  • Lecture (Conference)
    86th Annual Conference of the DPG and DPG Spring Meeting, 20.-24.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36716


The Stopping Target Monitor of the Mu2e experiment

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

Abstract

The Mu2e experiment, currently under construction at the Fermi National Accelerator Laboratory near Chicago, will search for the neutrinoless direct conversion of a muon to an electron in the field of an aluminum nucleus, aiming for a sensitivity four orders of magnitude better than previous experiments. The observation of a clear signal would imply Charged Lepton Flavor Violation, and hint at physics beyond the Standard Model.

The normalization of the signal events will be done by monitoring the rate of muons stopping on aluminum target discs. This will be accomplished with a detector system made of an HPGe detector and a Lanthanum Bromide detector, which detect the characteristic X- and γ-rays of energies up to 1809 keV produced when the muons are stopped or captured on the aluminum.

At the Helmholtz-Zentrum Dresden-Rossendorf, we have used a pulsed Bremsstrahlung photon beam at the ELBE radiation facility to study the performance of the detectors under conditions very similar to the ones expected at Mu2e.

In the presentation, a short overview of design and status of the Mu2e experiment and its detectors will be given, and results of the ELBE beamtime campaigns will be presented.

Keywords: Mu2e; STM; CLFV; FNAL

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  • Lecture (Conference)
    DPG Meeting SMuK, 20.-24.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36715


Activation calculations for decommissioning planning of NPPs

Rachamin, R.; Konheiser, J.; Barkleit, A.; Seidl, M.

Abstract

By the middle of 2023, all German nuclear power plants (NPPs) will have been shut down. The final shutdown is followed by a post-operational phase in which measures can be carried out to prepare for the NPPs dismantling and decommissioning. One of the essential tasks in planning and preparing an NPP for decommissioning is to obtain precise knowledge of the activation levels in its reactor pressure vessel (RPV), the biological shielding, and other internal components. In that regard, a novel method based on the combined use of two Monte Carlo codes, MCNP6 and FLUKA2021, was developed to serve as a non-destructive tool for evaluating the activation in an NPP. The presentation will give an overview of the methodology and demonstrate its application through the activation calculations of selected components of a German pressurized water reactor (PWR), which is the most common NPP type in Germany.

Keywords: German PWR; Decommissioning; Neutron fluence; Activation; MCNP; FLUKA

  • Invited lecture (Conferences)
    86th Annual Conference of the DPG and DPG Spring Meeting, 20.-24.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36714


Sensing strategies for determining the axial gas dispersion coefficient in bubble columns via gas flow modulation technique

Marchini, S.; Bieberle, A.; Schleicher, E.; Schubert, M.; Hampel, U.

Abstract

The gas flow modulation technique (GFM) is a recently proposed approach for measuring the axial gas dispersion coefficient in bubble columns. It bases on a time-resolved measurement of the modulated gas holdup at different axial positions in the column and a subsequent calculation of the axial dispersion coefficient from amplitude damping and the phase lag of a gas holdup wave. In recent studies holdup has been measured with gamma-ray densitometry, which is advantageous in terms of measurement accuracy. However, the application of radiative measurement techniques in industrial settings poses several logistical and safety challenges. This study investigates the potential of non-radiative measurement techniques in the context of GFM. In particular, differential pressure sensors, conductivity needle probes and optical probes are considered. The results obtained using these alternative techniques are compared with gamma-ray measurements. The comparison qualifies differential pressure sensors as a particular viable alternative to gamma-ray densitometry.

Keywords: gas flow modulation; axial dispersion coefficient; bubble columns; conductivity needle probes; transmittance optical probes

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  • TOPFLOW Facility

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Permalink: https://www.hzdr.de/publications/Publ-36713


Determining the axial gas dispersion coefficient in bubble columns via gas flow modulation technique and several sensing strategies

Marchini, S.; Bieberle, A.; Schleicher, E.; Schubert, M.; Hampel, U.

Abstract

Collected data refer to gas flow modulation measurements in a D=100 mm bubble column. The axial holdup wave is determined at three axial positions using different sensing stategies (gamma-ray densitometry, differential pressure sensors, transmittance optical probes and conductivity needle probes). Average gas holdup as well as amplitude damping and phase-shift have been determined at three different gas flow rates in the homogeneous regime. A description of the experimental setup is provided in the file "Experimental_setup.pdf". An overview of the performed experiments is provided in the Excel file "DataDescription.xlsx"

Keywords: gas flow modulation; axial dispersion coefficient; bubble columns; conductivity needle probes; transmittance optical probes

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  • TOPFLOW Facility

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Permalink: https://www.hzdr.de/publications/Publ-36712


Halomonas gemina sp. nov. and Halomonas llamarensis sp. nov., two siderophore-producing organisms isolated from high-altitude salars of the Atacama Desert

Hintersatz, C.; Singh, S.; Antonio Rojas, L.; Kretzschmar, J.; Wei, T.-S.; Khambhati, K.; Kutschke, S.; Lehmann, F.; Singh, V.; Jain, R.; Pollmann, K.

Abstract

This study aimed to discover novel siderophore-producing organisms with the ability to produce high amounts of the iron-binding compounds. In the course of this, two not yet reported halophilic strains designated ATCHAT and ATCH28T were isolated from hypersaline, alkaline surface waters of Salar de Llamará and Laguna Lejía, respectively. As an alkaline milieu greatly reduces the bioavailability of iron, organisms native to those environments were suspected to produce greater amounts of siderophores to sequester the essential element. Both strains were characterized utilizing a polyphasic approach and further investigated to assess their ability to secrete siderophores. Comparative analysis of the 16S rRNA gene sequences revealed that the isolates belonged to the genus Halomonas. ATCHAT was closely related to Halomonas. salicampi and Halomonas vilamensis, while ATCH28T was related closest to Halomonas ventosae and Halomonas salina. Utilizing the chromeazurol S liquid assay, both strains were shown to produce iron-binding compounds. Via NMR and genomic analysis, the siderophore synthesized by strain ATCH28T has been determined to be desferrioxamine E (DFOE). Although this siderophore is common for various terrestrial microorganisms, it has not yet been reported to occur within Halomonas, making strain ATCH28T first member of the genus to produce a non-amphiphilic siderophore. Furthermore, the effect of various media components on the secretion of DFOE was investigated and obtained concentrations could be increased to more than 1000 µM of the compound. Genomic analysis of strain ATCHAT revealed the presence of a not yet reported NRPS-dependant gene cluster responsible for the secretion of siderophore. However, the strain only secreted small amounts of the iron-binding compound and therefore its siderophore was not investigated exhaustively within the scope of this study. Based on their phenotypic and genotypic characteristics, both strains unambiguously differed from other described members of the genus Halomonas. Average nucleotide identity (ANI) values and levels of DNA-DNA relatedness clearly indicated that the strains represented two novel species. Hence, both species should be added as new representatives of the genus Halomonas, for which the designations Halomonas llamarensis sp. nov. (type strain ATCHAT=DSM 114476=LMG 32709) and Halomonas gemina sp. nov. (type strain ATCH28T=DSM 114418=LMG 32708) are proposed.

Keywords: Halophilic bacteria; siderophores; polyphasic taxonomic; desferrioxamine E; Atacama Desert

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Permalink: https://www.hzdr.de/publications/Publ-36711


Concepts of statistical entropy for the evaluation of comminution and separation processes

Tolosana Delgado, R.; Schach, E.; Peuker, U.

Abstract

Statistical entropy, corresponding to Shannon entropy in information theory or Gibbs entropy in physical thermodynamics, can be used to evaluate the additional disorder in a system induced by its subdivision in components or subsystems. Several variations of this concept have been introduced in the last 20 years to quantify the efficiency of a separation process (or a chain of it) within the context of minerals processing both in mining and recycling. This contribution presents a coherent frame connecting these concepts, and extends them to evaluate comminution processes, in such a way that joint thermoeconomic zoptimization of whole beneficiation plants becomes possible.

The main idea is to split the system simultaneously into three dimensions: (1) mineral or chemical components, (2) particles or particle classes, and (3) output streams. In each of these dimensions, a different ratio can be defined to describe the way the mass (or volume or matter) of the system is split into the subsystems: (1) a composition; (2) a particle-wise distribution; a (3) set of partition coefficients. Entropy contributions can then be defined for each of these dimensions at different levels of integration, e.g. (1) component-wise or for a total, (2) particle-wise or bulk-wise, (3) per stream or per stage feed.

By systematically considering all possible entropy decompositions, the following results were found. Total stage entropy does not depend on the ordering of integration through the three dimensions. Comminution cannot decrease the stage entropy; a comminution that would generate perfectly liberated particles without overgrinding would keep the stage entropy constant. A separation process cannot decrease stage entropy, and perfect separation would keep it constant. However, once the masses of the output streams are measured, the output entropy does indeed decrease for any moderately good separation process. The difference between the stage entropy with and without controlling output masses can then be understood as the information value of the output mass flow measurements.

  • Open Access Logo Contribution to proceedings
    22nd Annual Conference of the International Association for Mathematical Geosciences, 05.-12.08.2023, Trondheim, Norway

Permalink: https://www.hzdr.de/publications/Publ-36710


In-situ flow visualization with Geo-Positron-Emission-Tomography in a granite fracture from Soultz-sous-Forêts, France

Pingel, J. L.; Kulenkampff, J.; Jara-Heredia, D.; Zhou, W.; Fischer, C.; Schäfer, T.

Abstract

We investigate the fluid flow field in a fractured granite core sample. Sequential imaging with Positron-Emission-Tomography (PET) allows direct reconstruction of flow streamlines, thus providing a unique insight into the fluid dynamics of complex fractured crystalline materials. Pulse migration experiments using the positron-emitting radionuclide 18F- as tracer were conducted on a fractured granitic drill core, originating from a depth of 1958 m of the Enhanced Geothermal System (EGS) reference site at Soultz-sous-Forêts, France. The flow field was analyzed as a function of in- and outlet positions across the fracture, as well as applied flow rates. Different flow path characteristics were identified. Both the fracture aperture variation and the topography of the fracture surface affect the flow field with consequences on flow channeling and preferential flow paths. Furthermore, pulse migration experiments were also numerically simulated with a 2.5D model using COMSOL Multiphysics®.
While the higher flow rate experiments show wider and higher dispersion of the flow path, lower velocity results in more localized flow and channeling behavior. This type of study thus yields enhanced experimental insights into the hydrodynamics of fracture flow and its relation to the rough structure of natural single fractures, compared to input‑output experiments. It can help to validate model simulations and experimentally determine hydrodynamic parameters needed for reactive transport modeling that are otherwise estimated with a high degree of uncertainty.

Keywords: Positron Emission Tomography; single fracture; fluid flow; flow channeling; fracture aperture; COMSOL

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Permalink: https://www.hzdr.de/publications/Publ-36709


Influence of soil microbiology on radionuclide transport and uptake into plants

Linares Jimenez, R. E.; Flemming, K.; Matschiavelli, N.; Cherkouk, A.; Raff, J.; Stumpf, T.; Sachs, S.

Abstract

Deep geological repositories (DGR) will be used for the final disposal of highly radioactive waste. For the safety assessment of the DGR, it is important to consider accident scenarios such as the ingress of water, which might lead to a release of radionuclides (RNs) from the repository into the groundwater. RNs in groundwater can migrate to the surface soil where they can interact with indigenous microorganisms and plants, entering the food chain and posing a health risk to humans. The reliable modelling of the RN uptake into plants requires more than just transfer factors. A more detailed process understanding of the RN uptake into plants, including the effects of soil microorganisms, is necessary. RNs may affect the soil microbial community altering the natural community composition and interactions. Root exudates from plants and microorganisms can alter the speciation of RNs, affecting their bioavailability and mobility.
We study the impact of soil microorganisms on the RN transport and uptake into plants at the molecular level. The experiments discussed focus on studying the modulation of soil microbial diversity in the presence of RNs and selected root exudates. In addition, radiation-resistant soil microorganisms will be isolated to study their interaction with RNs and their effect on the degradation of root exudates. This will include characterization of the degradation products and their interactions with RNs. These findings will be used to elaborate radioecological models for the assessment of the RN transport and uptake into the food chain.

Keywords: Soil; Radionuclides; Microbial diversity; Root exudates; Plants

  • Poster
    ENVIRA 2023 - 7th International Conference on Environmental Radioactivity, 17.-22.09.2023, Sevilla, España

Permalink: https://www.hzdr.de/publications/Publ-36708


A continuous multiphase model for liquid metal batteries

Godinez-Brizuela, O. E.; Duczek, C.; Weber, N.; Nash, W.; Sarma, M.; Einarsrud, K. E.

Abstract

Liquid metal batteries (LMBs) are a promising candidate for large-scale stationary storage of renewably generated energy. Their Earth-abundant electrode materials and highly conductive molten salt electrolytes confer the low costs and high power densities required for grid-scale storage. LMB operation involves a complex interplay between mass transport mechanisms, and as a result their performance potential and operational limits are not fully understood. In this study, a multiphase numerical model is presented that simulates the charge and discharge processes of an LMB based on the Na-Zn couple. The model computes the changes in electrode and electrolyte volume, and resolves the spatial variations in the chemistry of the electrolyte that accompany the interfacial reactions. Volume change and species redistribution were found to be important in predicting the maximum theoretical capacity of the cell when neglecting other transport mechanisms.

Keywords: liquid metal battery; energy storage; multiphase flow; Na-Zn

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Permalink: https://www.hzdr.de/publications/Publ-36707


Multiobjective tuning technique for MPC in grinding circuits

Yamashita, A. S.; Martins, W. T.; Pinto, T.; Raffo, G. V.; Melo Euzebio, T. A.

Abstract

We investigate the control challenges in grinding circuits---slow dynamics, long dead times, variable coupling--- and the controller tuning challenge, that is, the difficulty in translating operating goals into tuning goals and closed-loop performance. A tuning algorithm for DMC (dynamic matrix control), suitable for the mineral processing industry, is proposed. The tuning problem is posed as a multiobjective optimization problem, in which the tuning goals are directly related to the desired closed-loop performance of process variables. The problem is solved using a compromise optimization, which minimizes the Euclidian distance between a feasible solution and the Utopia solution. Three case studies are presented, which validate the tuning algorithm for DMC in linear and non-linear grinding circuit models. The closed-loop performance obtained with the proposed tuning algorithm is compared to the one obtained through a benchmark tuning technique from the literature. The proposed tuning method has the following features: i) it shapes the closed-loop response according to the goal definitions for linear systems; ii) it requires tailored initial guesses and search spaces to converge to a stabilizing solution in non-linear applications; and iii) it allows the user to specify the desired closed-loop performance behavior in the tuning procedure, allowing the implementation of an adequate controller for each situation.

Keywords: grinding circuit; model predictive control; dynamic matrix control; controller tuning; multiobjective optimization; compromise optimization

Permalink: https://www.hzdr.de/publications/Publ-36706


Superconducting radio frequency Photoinjectors for CW-XFEL

Xiang, R.; Arnold, A.; Lewellen, J. W.

Abstract

A dependable and consistent electron source is a crucial requirement for the achievement of high-power free electron lasers (FELs). Over the past two decades, it has been demonstrated that photoinjectors based on SRF technology (SRF guns) are suitable for continuous wave (CW) beam generation. SRF guns possess both the high accelerating field gradients of normal conducting RF photoinjectors and the low power dissipation thanks to mature SRF cavity technology, and therefore have the potential to provide the high-brightness, high-current beams required for CW-XFELs.
After the demonstration of the first SRF gun in Dresden-Rossendorf, several SRF gun programs based on different approaches have achieved promising progress and even succeeded in routine operation. SRF guns are expected to play an important role in XFEL facilities in the near future. In this paper, we give an overview of design concepts, important parameters and development status of the worldwide SRF gun projects.

Keywords: CW; FEL; SRF gun; low emittance

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-36705


Corrosion of Cast Iron for High-Level Nuclear Waste Containers in the Presence of Bentonite or the SRB Desulfosporosinus burensis

Kirsch, K.; Matschiavelli, N.; Stumpf, T.; Koerdt, A.

Abstract

Cast iron containers are currently used for the temporary storage of nuclear waste. At the current stage of research, it is not clear whether cast iron, together with coating materials, also is an option for long-time storage. In this study, we want to investigate its potential as a container material for the disposal of high-level nuclear waste in deep geological repositories (DGR) in claystone bedrock. The dynamic corrosion process depends on the conditions present in the DGR which are influenced and/or controlled by geochemical parameters (e.g., redox potential, pH, the ionic composition of the pore-water), physical parameters (e.g., pressure), and the influence of metabolically active microorganisms. Corrosion of cast iron will occur at the interface of the container surface and the bentonite backfill material, which contains natural microbial populations. In the investigated worst-case scenario, water would reach the container and introduce microorganisms inherent in the bedrock, such as sulfate-reducing bacteria (SRB).
The conditions in a DGR were simulated in microcosm experiments to investigate the impact of microbiologically influenced corrosion (MIC) on cast iron. The anaerobic microcosms contained artificial Opalinus Clay pore water, N2, cast iron coupons, as well as a Wyoming bentonite or the SRB Desulfosporosinus burensis (DSM 24089) (isolated at the Andra Underground Research Laboratory in Buré, France).
After incubation at 25°C for 50 days, the microcosms were analysed for bio- and geochemical parameters, i.e., pH, Fe(II):Fe(III), changes in their microbial populations, as well as SEM-EDX and Raman spectroscopy to identify secondary iron phases and corrosion products. The coupons showed surface corrosion and various mineral phases on their surfaces. Additionally, the coupons from the D. burensis microcosms showed an increased concentration of carbon on their surface, i.e., an indication of a biofilm.
Furthermore, the interaction of technetium-99 with the corroded coupons was investigated to assess the immobilisation of Tc by exposed and corroded cast iron

  • Poster
    Goldschmidt, 09.-14.07.2023, Lyon, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-36704


Corrosion of Container Material for High-Level Nuclear Waste in the Presence of Bentonite or the SRB Desulfosporosinus burensis

Kirsch, K.; Matschiavelli, N.; Stumpf, T.; Koerdt, A.

Abstract

Ductile cast iron is investigated as a potential container material for the disposal of high-level nuclear waste in deep geological repositories (DGR) in claystone bedrock. The dynamic corrosion process depends on the conditions present in the DGR which are influenced and/or controlled by geochemical parameters (e.g., redox potential, pH, the ionic composition of the pore-water), physical parameters (e.g., pressure), and the influence of metabolically active microorganisms. Corrosion of cast iron will occur at the interface of the container surface and the bentonite backfill material, which contains natural microbial populations. In the investigated worst-case scenario, water would reach the container and introduce microorganisms inherent in the bedrock, such as sulfate-reducing bacteria (SRB).
The conditions in a DGR were simulated in microcosm experiments to investigate the impact of microbiologically influenced corrosion (MIC) on a potential container material. The anaerobic microcosms contained artificial Opalinus Clay pore water, N2 atmosphere, cast iron coupons, as well as a Wyoming bentonite or the SRB Desulfosporosinus burensis (DSM 24089) (isolated at the Andra Underground Research Laboratory in Buré, France).
After incubation at 25°C for 50 days, the microcosms were analysed for bio- and geochemical parameters, i.e., pH, Fe(II):Fe(III), changes in their microbial populations, as well as SEM-EDX and Raman spectroscopy to identify secondary iron phases and corrosion products. The coupon showed mild to severe pitting corrosion and various mineral phases on their surfaces. Additionally, the coupons from the D. burensis microcosms showed an increased concentration of carbon on their surface, i.e., an indication of a biofilm.
Furthermore, the interaction of technetium-99 with the corroded coupons was investigated to assess the immobilisation of Tc by exposed and corroded cast iron.

  • Poster
    EUROCORR, 27.-31.08.2023, Brüssel, Belgien

Permalink: https://www.hzdr.de/publications/Publ-36703


Fostering quality improvement for RSE projects through consulting offers

Förster, T.

Abstract

To promote FAIR principles and to improve the value and knowledge from data innovation, HIFIS – a Helmholtz IT platform, provides a wide variety of services. This talk focuses on the lessons learned and the impact of integrating a variety of RSE offers, including educational resources and consulting on the research community in Helmholtz. We discuss the structure of the HIFIS consulting service and the resources needed to provide a good and fruitful environment for improving our clients’ software projects.

Keywords: RSE; consulting; software development

Permalink: https://www.hzdr.de/publications/Publ-36702


Fracture mechanics investigation of reactor pressure vessel steels by means of sub-sized specimens (KLEINPROBEN)

Das, A.; Altstadt, E.; Chekhonin, P.; Houska, M.

Abstract

The embrittlement of reactor pressure vessel (RPV) steels due to neutron irradiation restricts the operating lifetime of nuclear reactors. The reference temperature 𝑇0, obtained from fracture mechanics testing using the Master Curve concept, is a good indicator of the irradiation resistance of a material. The measurement of the shift in 𝑇0 after neutron irradiation, which accompanies the embrittlement of the material, using the Master Curve concept, enables the
assessment of the reactor materials. In the context of worldwide life time extensions of nuclear power plants, the limited availability of neutron irradiated materials (surveillance materials) is a challenge. Testing of miniaturized 0.16T C(T) specimens manufactured from already tested standard Charpy-sized specimens helps to solve the material shortage problem. In this work, four different reactor pressure vessel steels with different compositions were
investigated in the unirradiated and in the neutron-irradiated condition. A total number of 189 mini-C(T) samples were fabricated and tested. An important component of this study is the transferability of fracture mechanics data from mini-C(T) to standard Charpy-sized specimen. Our results demonstrate good agreement of the reference temperatures from the mini-C(T) specimens with those from standard Charpy-sized specimens. RPV steels containing higher Cu and P contents exhibit a higher increase in 𝑇0 after irradiation. The fracture surfaces were investigated using SEM in order to record the location of the fracture initiators. The fracture modes were also determined. A large number of test results formed the basis for a censoring probability function, which was
used to optimally select the testing temperature in Master Curve testing. The effect of the slow stable crack growth censoring criteria from ASTM E1921 on the determination of 𝑇0 was analysed and found to have a minor effect. Our results demonstrate the validity of mini-C(T) specimen testing and confirm the role of the impurity elements Cu and P in neutron embrittlement. We anticipate further research linking microstructure to the fracture properties of materials before and after neutron irradiation and the optimization of Master Curve testing using the results from our statistical analysis.

Keywords: reactor pressure vessel steel; neutron embrittlement; Master Curve testing; mini-CT specimens; small specimen test technology

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-125 2023
    ISSN: 2191-8708, eISSN: 2191-8716
    ISSN: 2191-8708

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Permalink: https://www.hzdr.de/publications/Publ-36701


Visualizing Ultrafast Kinetic Instabilities in Laser-Driven Solids using X-ray Scattering

Ordyna, P.; Bussmann, M.; Gaus, L.; Grenzer, J.; Gutt, C.; Huang, L.; Laso García, A.; Garten, M.; Höppner, H.; Humpries, O.; Marre, B. E.; Metzkes-Ng, J.; Nakatsutsumi, M.; Öztürk, Ö.; Pan, X.; Paschke-Brühl, F.-L.; Pelka, A.; Prencipe, I.; Randolph, L.; Schlenvoigt, H.-P.; Smid, M.; Stefanikova, R.; Thiessenhusen, E.; Toncian, T.; Zeil, K.; Schramm, U.; Cowan, T.; Kluge, T.

Abstract

Ultra-intense lasers that ionize and accelerate electrons in solids to near the speed of light can lead to kinetic instabilities that alter the laser absorption and subsequent electron transport, isochoric heating, and ion acceleration.
These instabilities can be difficult to characterize, but a novel approach using X-ray scattering at keV energies allows for their visualization with femtosecond temporal resolution on the few nanometer mesoscale.
Our experiments on laser-driven flat silicon membranes show the development of structure with a dominant scale of $~60\unit{nm}$ in the plane of the laser axis and laser polarization, and $~95\unit{nm}$ in the vertical direction with a growth rate faster than $0.1/\mathrm{fs}$.
Combining the XFEL experiments with simulations provides a complete picture of the structural evolution of ultra-fast laser-induced instability development, indicating the excitation of surface plasmons and the growth of a new type of filamentation instability.
These findings provide new insight into the ultra-fast instability processes in solids under extreme conditions at the nanometer level with important implications for inertial confinement fusion and laboratory astrophysics.

Keywords: laser; proton; ion; acceleration; HIBEF; HED; European; XFEL; SAXS

Involved research facilities

  • HIBEF

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Permalink: https://www.hzdr.de/publications/Publ-36700


Dataset: Basic verification of an industrial type of wire-mesh sensor

Wiedemann, P.; Trepte, M.

Abstract

The experimental data presented here was recorded with an industrial type of wire-mesh sensor and additional equipment. The experiments aim at verifying the main functionalities of the developed sensor and include tests of

  • Temperature compensation
  • Flow pattern identification in vertical gas-liquid flow
  • Flow pattern identification in horizontal gas-liquid flow

The experimental procedure and the results are described in detail in Wiedemann et al.: Towards Real-Time Analysis of Gas-Liquid Pipe Flow: A Wire-Mesh Sensor for Industrial Applications, Sensors 23 (2023) 4067, https://doi.org/10.3390/s23084067

Keywords: wire-mesh sensor; indWMS; two-phase flow

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Permalink: https://www.hzdr.de/publications/Publ-36699


International Standardization of Basic Industrial Radiotracer and Radiation Applications – Current State

Jentsch, T.; Thereska, J.; Jin, J.-H.; Brisset, P.

Abstract

The International Atomic Energy Agency (IAEA) in cooperation with the International Society for Tracer and Radiation Applications (ISTRA) promotes the international standardization of basic industrial radiotracer and radiation applications. On behalf of IAEA and ISTRA experts from many countries employed in leading research centers and renowned industrial companies analyze existing international standards regarding the necessity of their update or amendment as well as the need for new standards in this field.
In June 2020, a new international standard on “Non-destructive testing - Gamma ray scanning method on process columns” was published as ISO 23159. About three years before, the experts detected the need to standardize this method, which is widely used in petrochemical and chemical plants to identify and locate the cause of malfunction inside various process columns.
In the field of flow rate measurements of fluids in conduits using radioactive tracers, a proposal for a new international standard was prepared in 2021. It united several old international standards in this technical field: measurement of water flow in closed conduits (ISO 2975), measurement of gas flow in conduits (ISO 4053) and measurement of liquid flow in open channels (ISO 9555). The new international standard with the title “Measurement of Fluid Flow Rate in Closed Conduits – Radioactive Tracer Methods” has now the state of a Draft International Standard (DIS) and will be published as ISO 24460 in this year.
Furthermore, two other international standards using radioactive tracer methods are under development. One of them is on leak testing in pressured vessels and underground pipelines, another one is on determination of concentration or density of suspended and deposited sediment in water bodies by radiometric methods. Both has already passed the New Work Item Proposal (NWIP) stage. The first one is being edited in ISO Technical Committee 135, Sub Committee 6, Working Group 1 (ISO TC 135/SC 6/WG 1), has the stage of a Committee Draft (CD) now and will be published as ISO 6640 in the middle of next year. The second one is being edited in ISO TC 113/SC 6/WG 5, has still the stage of a Working Draft (WD) and will be published as ISO 6366 also next year.
ISO standards are part of accreditation of radiotracer and radiation applications groups, facilitating the promotion and implementation of these competitive technologies in national, regional and international scale.

Keywords: International standards; ISO; radioactive tracers; radiometric methods

  • Lecture (Conference)
    NUTECH 2023 International Conference on Development and Applications of Nuclear Technologies, 20.-22.09.2023, Krakow, Polska

Permalink: https://www.hzdr.de/publications/Publ-36698


Trimorphic TaCrP – A diffraction and 31P solid state NMR spectroscopic study

Paulsen, C.; Maximilian Gerdes, J.; Svitlyk, V.; Kai Reimann, M.; Rabenbauer, A.; Nilges, T.; Ryan Hansen, M.; Pöttgen, R.

Abstract

The metal-rich phosphide TaCrP forms from the elements by step-wise solid state reaction in an alumina crucible (maximum annealing temperature 1180 K). TaCrP is trimorphic. The structural data of the hexagonal ZrNiAl high-temperature phase (space group P¯62m) was deduced from a Rietveld refinement. At room temperature TaCrP crystallizes with the TiNiSi type (Pnma, a = 623.86(5), b = 349.12(3), c = 736.78(6) pm, wR = 0.0419, 401 F2 values, 20 variables) and shows a Peierls type transition below ca. 280 K to the monoclinic low-temperature modification (P121/c1, a = 630.09(3), b = 740.3(4), c = 928.94(4) pm, β = 132.589(5)°, wR = 0.0580, 1378 F2 values, 57 variables). The latter phase transition is driven by pairwise Cr–Cr bond formation out of an equidistant chain in o-TaCrP. The phase transition was monitored via different analytical tools: differential scanning calorimetry, powder synchrotron X-ray diffraction, magnetic susceptibility measurements and 31P solid state NMR spectroscopy.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36697


A van der Waals Heterostructure with an Electronically Textured Moiré Pattern: PtSe₂/PtTe₂

Li, J.; Ghorbani Asl, M.; Lasek, K.; Pathirage, V.; Krasheninnikov, A.; Batzill, M.

Abstract

The interlayer interaction in Pt-dichalcogenides strongly affects their electronic structures. The modulations of the interlayer atom-coordination in vertical heterostructures based on these materials are expected to laterally modify these interlayer interactions and thus provide an opportunity to texture the electronic structure. To determine the effects of local variation of the interlayer atom coordination on the electronic structure of PtSe₂, van der Waals heterostructures of PtSe₂ and PtTe₂ have been synthesized by molecular beam epitaxy. The heterostructure forms a coincidence lattice with 13-unit cells of PtSe₂ matching 12-unit cells of PtTe₂, forming a moiré superstructure. The interaction with PtTe₂ reduces the band gap of PtSe₂ monolayers from 1.8 to 0.5 eV. While the band gap is uniform across the moiré unit cell, STS and dI/dV mapping identify gap states that are localized within certain regions of the moiré unit cell. Deep states associated with chalcogen pz-orbitals at binding energies of ~-2 eV also exhibit lateral variation within the moiré unit cell, indicative of varying interlayer chalcogen interactions. Density functional theory calculations indicate that local variations in atom coordination in the moiré unit cell causes variations in the charge transfer from PtTe2 to PtSe2 thus affecting the value of the interface dipole. Experimentally this is confirmed by measuring the local work function by field emission resonance spectroscopy, which reveals a large work function modulation of ~0.5 eV within the moiré structure. These results show that the local coordination variation of the chalcogen atoms in the PtSe2/PtTe2 van der Waals heterostructure induces a nanoscale electronic structure texture in PtSe₂.

Keywords: platinum dichalcogenides; van der Waals heterostructure; work function modulation; scanning tunneling microscopy; density functional theory

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Permalink: https://www.hzdr.de/publications/Publ-36696


Event generation in Julia and the path to GPUs

Hernandez Acosta, U.; Steiniger, K.; Reinhard, A.; Jungnickel, T.; Ehrig, S.; Bussmann, M.

Abstract

The inventors of the Julia programming language proclaim, that one can use high-level syntax to solve demanding numerical tasks. In order to evaluate this claim, we present possible applications of Julia by using it for the implementation of our Monte-Carlo event generator for laser-matter interaction. Especially the possible deployment of modern GPUs for demanding computing tasks during several stages of the event generation is discussed. In order to elaborate on these GPU capabilities, we show benchmarks of Julia's main programming interface for NVIDIA CUDA GPUs, namely `CUDA.jl`, and compare them with native CUDA-C++ implementations. Finally, Julia's capabilities for high-level abstraction for computations on heterogenous architectures are discussed and compared to low-level solutions like the `alpaka` library for C++.

Keywords: Julia programming language

  • Invited lecture (Conferences) (Online presentation)
    Compute Accelerator Forum, 08.03.2023, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-36695


Biogenic minerals formation by an Fe(III)-reducing Desulfitobacterium sp. isolate

Cardaio, I.; Kluge, S.; Cherkouk, A.; Müller, K.; Stumpf, T.; Mayordomo, N.

Abstract

Dissimilatory iron reduction is an anaerobic respiratory pathway, wherein ferric (Fe(III)) reducers couple the oxidation of organic acids, sugars and aromatic hydrocarbons to the reduction of Fe(III)-species [1]. This may lead to the formation of minerals such as magnetite (Fe(II)Fe(III)₂O₄) and siderite (Fe(II)CO₃) [2], which, in turn, can mediate the reduction of soluble pollutants as pertechnetate (Tc(VII)O₄⁻) to insoluble oxides (Tc(IV)O₂) [3].
The genus Desulfitobacterium contains obligate anaerobic bacteria that are capable of utilizing a wide range of electron acceptors, including nitrite, sulfite, metals, humic acids and halogenated organic compounds [4].
In this work, the Fe(III) reduction of a Desulfitobacterium species was examined. The microorganism has been isolated from bentonite, which is potentially used as geotechnical barrier in deep geological repositories for radioactive waste [5].
The cultivation conditions included DSMZ 579 medium with Na-acetate as electron donor to reduce Fe(III) citrate [6]. During cultivation, the formation of white precipitates was observed. The phases were collected both under aerobic and anaerobic conditions and repeatedly investigated by using Raman microscopy and powder X-ray diffraction (pXRD). It was noticed that the phases turned immediately to blue-greenish overnight under oxic conditions. Both Raman spectra and pXRD diffractograms can be attributed to vivianite (Fe(II)₃(PO₄)₂). Moreover, Raman spectra revealed the possible presence of pyrite (Fe(II)S₂), siderite, magnetite and hematite (FeIII₂O₃). These results suggest the ability of the bacterium of forming different Fe(II)-minerals. Notwithstanding, both methods indicate the change of the chemistry of the precipitates according to environmental factors. The Fe(II)-minerals formation by this microorganism depending on Fe(III)-compounds and background electrolytes is currently ongoing. The biogenic ferrous minerals will be studied regarding the reduction of Tc(VII)O₄⁻.

The authors acknowledge the German Federal Ministry of Education and Research (BMBF) for the financial support of NukSiFutur TecRad young investigator group (02NUK072).

[1] Lovley, 1993, Annual Review of Microbiology, 47:263-290
[2] Lee, et al., 2007, Geomicrobiology Journal, 24:1, 31-41
[3] Lloyd, et al., 2000, Appl Environ Microbiol., 66(9):3743-9
[4] Villemur et al., 2006, FEMS Microbiol Rev. 2006, 30(5):706-33
[5] Drozdowski J., et al., 2018, HZDR Annual Report, pp. 40, ISSN 2191-870
[6] https://www.dsmz.de/microorganisms/medium/pdf/DSMZ_Medium579.pdf. Accessed on 27.02.23

Keywords: iron reducing bacteria; technetium; biogenic minerals; Raman microscopy; X-ray diffraction

  • Open Access Logo Poster
    Goldschmidt 2023, 09.-14.07.2023, Lyon, Frankreich

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Permalink: https://www.hzdr.de/publications/Publ-36694


Messebericht ACHEMA 2022: Klassieren und Sortieren

Mütze, T.

Abstract

Auf der ACHEMA 2022 waren in Frankfurt 25 Anbieter von Klassierer-, Sortier-, Recycling- oder Aufbereitungsanlagen im engeren Sinne vertreten. Der vorliegende Bericht fasst kurz zusammen, welche Aussteller ihr Portfolio im Bereich der Mechanischen Prozesse vorstellten und was an Neuerungen gezeigt wurde. Schwerpunkte stellten u. a. Plan- und Taumelsiebmaschinen sowie Technologien für schnelle Siebbelagswechsel und zum Entfernen von Körnern außerhalb der Produktspezifikation dar.

Keywords: Automatische Klaubung; Hydrozyklone; Klassieren; Magnetscheidung; Sichter; Siebe; Sortieren

Permalink: https://www.hzdr.de/publications/Publ-36693


Messebericht ACHEMA 2022: Zerkleinern

Mütze, T.

Abstract

Auf der ACHEMA 2022 waren in Frankfurt 38 Anbieter von Zerkleinerungstechnik vertreten. Der vorliegende Bericht fasst kurz zusammen, welche Aussteller vertreten waren und was – vor allem an Neuerungen – gezeigt wurde. Schwerpunkte waren einerseits Maschinen zum Dispergieren verklumpter bzw. sehr feinkörniger Pulver zur besseren Verarbeitbarkeit oder zum Einmischen in Flüssigkeiten sowie andererseits Mahlkörpermühlen zur Fein- und Feinstmahlung.

Keywords: Zerkleinern; Brecher; Mühlen

Permalink: https://www.hzdr.de/publications/Publ-36692


Fluctuation Electron Microscopy on Amorphous Silicon and Amorphous Germanium

Radić, D.; Peterlechner, M.; Posselt, M.; Bracht, H.

Abstract

Variable resolution fluctuation electron microscopy experiments were performed on self-ion implanted amorphous silicon and amorphous germanium to analyze the medium-range order. The results highlight that the commonly used pair-persistence analysis is influenced by the experimental conditions. Precisely, the structural correlation length Λ, a metric for the medium-range order length scale in the material, obtained from this particular evaluation varies depending on whether energy filtering is used to acquire the data. In addition, Λ depends on the sample thickness. Both observations can be explained by the fact that the pair-persistence analysis utilizes the experimentally susceptible absolute value of the normalized variance obtained from fluctuation electron microscopy data. Instead, plotting the normalized variance peak magnitude over the electron beam size offers more robust results. This evaluation yields medium-range order with an extent of approximately (1.50± 0.50)nm for the analyzed amorphous germanium and around (1.10±0.20)nm for amorphous silicon

Keywords: amorphous germanium; amorphous silicon; fluctuation electron microscopy; medium-range order

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Permalink: https://www.hzdr.de/publications/Publ-36691


An experimental study of boiling two-phase flow in a vertical rod bundle with a spacer grid-Part 2: Effects of vane angle

Tas-Köhler, S.; Boden, S.; Franz, R.; Liao, Y.; Hampel, U.

Abstract

We performed boiling flow experiments and measured the void fraction in a 3 x 3 rod bundle including a spacer grid with split type vanes using X-ray computed tomography, which provides high-resolution time-averaged void data without disturbing the flow. We studied the effects of mixing vanes with different vane angles, namely, 20°, 29° and 40°, for a mass flux between 535 and 1950 kg/m2 s and the central rod being heated giving a heat flux of 85.7 kW/m2. The presence of vanes leads to an increase of the cross-sectional averaged void fraction up to an axial position of Z≈〖0.8D〗_h. After that, the void fraction decreases until 3D_h

Involved research facilities

  • TOPFLOW Facility

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  • Secondary publication expected from 01.07.2024

Permalink: https://www.hzdr.de/publications/Publ-36690


Frontiers of challenging studies utilizing accelerator mass spectrometry in geoscience

Honda, M.; Martschini, M.; Lachner, J.; Wieser, A.; Marchhart, O.; Steier, P.; Golser, R.; Sakaguchi, A.

Abstract

The fission-product 90Sr (half-life 28.9 years) and 135Cs (half-life 2.3×106 years) are present in the environment. Strontium-90 is one of the most concerning nuclides in the assessment of internal exposure of residents because it can accumulate in bones and cause health problems. Therefore, it is essential to study the distribution of 90Sr in the environment and its temporal variation (90Sr enrichment in organisms and plants). On the other hand, 135Cs, which has a longer physical half-life than 137Cs (30.1 years), is expected to be utilized as a tracer to follow the long-term environmental fate of 137Cs, which is difficult to measure due to decay. These studies require high-throughput multi-sample analysis. However, as 90Sr and 135Cs are pure β-emitters, other β-emitters in the environmental samples (e.g., Ra isotopes, 137Cs, and 210Pb) must be entirely removed, which would interfere with β-ray detection. While this is impossible for the conventional β-ray detection method of 135Cs, it does work for 90Sr. Still, it requires a large sample volume due to the low concentrations of 90Sr in general environmental samples1). Therefore, the chemical separation of the target nuclide is very time-consuming and challenging for reliable quantification.
This study addressed solving these problems using accelerator mass spectrometry (AMS) for sensitive analysis of 90Sr and 135Cs in environmental samples2,3). AMS has the advantage of allowing more precise analysis of small sample volumes. However, the most concerning aspect of AMS for 90Sr and 135Cs is the interference of the isobars 90Zr and 135Ba. Therefore, the measurements of 90Sr and 135Cs were carried out at the University of Vienna (VERA). The AMS system is equipped with an "Ion cooler" that can effectively separate the isobars. For 90Sr, various molecular ions such as SrFn− and ZrFn− (n ≥ 1) were extracted from the target (a mixture of SrF2 and PbF2 in a weight ratio of 1:8) by Cs sputtering, and then the molecular ions with an m/q of 147 (90SrF3− and 90ZrF3−) were selectively passed through a 90° bending magnet. The ion beam (200-300 nA) was decelerated to ~30 eV and injected into the Ion cooler, an isobaric separation system with built-in radio-frequency quadrupole (RFQ). Collisions with a buffer gas mixture of He and O2 gas inside the RFQ reduced the ion energy to <1 eV. In addition, the O2 gas produces oxide ions and separated Zr. Here, a 12 W laser (532 nm) further suppressed Zr (neutralized 90ZrF3− by photo-detachment). In this isobaric separation system, Zr was suppressed by >107 for Sr (current ratio), and the overall Zr suppression is >1012 (ion source >105). The overall transmission efficiency of Sr was 0.4‰. Meanwhile, a simple chemical separation scheme was developed which efficiently separates Zr to maximize the isobaric separation performance of AMS: acid leaching → two-step chromatography with crown ether and anion exchange → SrF2 precipitation (2 days for the precipitation) to environmental reference materials (soil, beef bones, fish meat) with known 90Sr concentrations. The results showed that the 90Sr concentrations quantified by the AMS method agreed with the nominal values (quantified by the β-ray detection method) within a margin of error. Furthermore, based on the measurements of 1 mg of Sr carrier treated in the same manner as environmental samples, the detection limit of 90Sr by the AMS method achieved 1/10 (< 0.1 mBq, 90Sr/88Sr = 2.5×10-15) of the general detection limit of the β-ray detection method4). The highly sensitive analysis of 90Sr by AMS is promising for studies on the detailed distribution of 90Sr in individual (and even site-specific) corals and fishes with limited sample volumes. As for 135Cs, significant issues remain, such as efficient Ba separation in chemical separation, cross-contamination between samples in AMS ion sources, and preparing 135Cs reference materials. However, the detection limit for 135C was 0.3 µBq (135Cs/Cs atomic ratio was 7×10-12), demonstrating excellent results. Therefore, this study showed that the 135Cs AMS has the potential to apply geoscience.

Keywords: Accelerator Mass Spectrometry; Isobar; Chemical Separation; Laser photo-detachment; 90Sr; 135Cs

  • Invited lecture (Conferences)
    71st Annual Conference on Mass Spectrometry, Japan, 15.-17.05.2023, Osaka, Japan

Permalink: https://www.hzdr.de/publications/Publ-36689


Immunotargeting of Cancer Stem Cells.

Köseer, A. S.; Di Gaetano, S.; Arndt, C.; Bachmann, M.; Dubrovska, A.

Abstract

The generally accepted view is that CSCs hijack the signaling pathways attributed to normal stem cells that regulate the self-renewal and differentiation processes. Therefore, the development of selective targeting strategies for CSC, although clinically meaningful, is associated with significant challenges because CSC and normal stem cells share many important signaling mechanisms for their maintenance and survival. Furthermore, the efficacy of this therapy is opposed by tumor heterogeneity and CSC plasticity. While there have been considerable efforts to target CSC populations by the chemical inhibition of the developmental pathways such as Notch, Hedgehog (Hh), and Wnt/β-catenin, noticeably fewer attempts were focused on the stimulation of the immune response by CSC-specific antigens, including cell-surface targets. Cancer immunotherapies are based on triggering the anti-tumor immune response by specific activation and targeted redirecting of immune cells toward tumor cells. This review is focused on CSC-directed immunotherapeutic approaches such as bispecific antibodies and antibody-drug candidates, CSC-targeted cellular immunotherapies, and immune-based vaccines. We discuss the strategies to improve the safety and efficacy of the different immunotherapeutic approaches and describe the current state of their clinical development.

Keywords: CAR-T cells; CSC; bsAB; cancer stem cells; cancer vaccines; immunotherapy

Permalink: https://www.hzdr.de/publications/Publ-36685


Synthesis and Characterization of a Masked Terminal Nickel-Oxide Complex

Heim, P.; Spedalotto, G.; Lovisari, M.; Gericke, R.; O’Brien, J.; Farquhar, E. R.; McDonald, A. R.

Abstract

In exploring terminal nickel-oxo complexes, postulated to be the active oxidant in natural and non-natural oxidation reactions, we report the synthesis of the pseudo-trigonal bipyramidal Ni(II) complexes (K)[Ni(II)(LPh)(DMF)] (1[DMF]) and (NMe₄)₂[Ni(II)(LPh)(OAc)] (1[OAc]) (LPh = 2,2’,2’’-nitrilo-tris-(N-phenylacetamide); DMF = N,N-dimethylformamide; OAc = acetate). Both complexes were characterized using NMR, FTIR, ESI-MS, and X-ray crystallography, showing the LPh ligand to bind in a tetradentate fashion, together with an ancillary donor. The reaction of 1[OAc] with peroxyphenyl acetic acid (PPAA) resulted in the formation of [(LPh)Ni(III)-O-H···OAc]²-, 2, that displays many of the characteristics of a terminal Ni=O species. 2 was characterized by UV-Vis, EPR, and XAS spectroscopies and ESI-MS. 2 decayed to yield a Ni(II)-phenolate complex 3 (through aromatic electrophilic substitution) that was characterized by NMR, FTIR, ESI-MS, and X-ray crystallography. 2 was capable of hydroxylation of hydrocarbons and epoxidation of olefins, as well as oxygen atom transfer oxidation of phosphines at exceptional rates. While the oxo-wall remains standing, this complex represents an excellent example of a masked metal-oxide that displays all of the properties expected of the ever elusive terminal M=O beyond the oxo-wall.

Keywords: bioinorganic chemistry; high-valent nickel; hydrocarbon oxidation; oxo-wall; peracid activation

Permalink: https://www.hzdr.de/publications/Publ-36684


High-Throughput Gel Microbeads as Incubators for Bacterial Competition Study

Nguyen Le, T. A.; Zhao, X.; Bachmann, M.; Ruelens, P.; de Visser, J. A. G. M.; Baraban, L.

Abstract

Bacteria primarily live in structured environments, such as colonies and biofilms, attached to surfaces or growing within soft tissues. They are engaged in local competitive and cooperative interactions impacting our health and well-being, for example, by affecting population-level drug resistance. Our knowledge of bacterial competition and cooperation within soft matrices is in-complete, partly because we lack high-throughput tools to quantitatively study their interactions. Here, we introduce a method to generate a large amount of agarose microbeads that mimic the natural culture conditions experienced by bacteria to co-encapsulate two strains of fluores-cence-labeled Escherichia coli. Focusing specifically on low bacterial inoculum (1–100 cells/capsule), we demonstrate a study on the formation of colonies of both strains within these 3D scaffolds and follow their growth kinetics and interaction using fluorescence microscopy in highly replicated experiments. We confirmed that the average final colony size is inversely proportional to the inoculum size in this semi-solid environment as a result of limited available resources. Further-more, the colony shape and fluorescence intensity per colony are distinctly different in mono-culture and co-culture. The experimental observations in mono- and co-culture are compared with predictions from a simple growth model. We suggest that our high throughput and small foot-print microbead system is an excellent platform for future investigation of competitive and co-operative interactions in bacterial communities under diverse conditions, including antibiotics stress.

Keywords: millifluidic; high-throughput; agarose microbeads; co-culture; bacterial co-existence; fluorescence

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Permalink: https://www.hzdr.de/publications/Publ-36682


Unraveling the Np(V) Sorption on the Nuclear Fuel Cladding Corrosion Product ZrO₂: a Batch, Spectroscopic and Modeling Combined Approach

Jessat, I.; Foerstendorf, H.; Roßberg, A.; Scheinost, A.; Lützenkirchen, J.; Heim, K.; Stumpf, T.; Jordan, N.

Abstract

Zirconia (ZrO₂), the main corrosion product of the zircaloy cladding material of nuclear fuel rods, might potentially act as the first barrier for radionuclides. Thus, the interactions of radionuclides, such as the long-lived actinide neptunium, with zirconia have to be considered in the safety assessment process of a repository for radioactive waste. The sorption of Np(V) onto zirconia (ZrO₂) was investigated in the absence of carbonate at the macroscopic and molecular scale. For the macroscopic description, pH-dependent batch sorption experiments under varying ionic strength (0.1 and 0.01 mol∙L⁻¹ NaCl), Np(V) concentration (1∙10⁻⁶ or 6∙10⁻⁶ mol∙L⁻¹) and solid-to-liquid ratio (m/V = 0.5 or 4 g∙L⁻¹ ZrO₂) were conducted. Np(V) sorption isotherms at pH 4.5 and 6.0 were additionally obtained at 0.01 mol∙L⁻¹ NaCl. The Np(V) uptake on zirconia strongly depends on pH, with sorption starting from acidic pH and maximum sorption was reached at pH 6 and above. Increasing the m/V ratio caused a significant shift of the sorption edge towards lower pH values. This indicates the presence of different kinds of sorption sites, which was supported by the results of the Np(V) sorption isotherms, where the shape of the isotherm suggested the presence of strong and weak sorption sites. The Np(V) uptake was independent of ionic strength, suggesting the presence of inner-sphere Np(V) surface complexes on zirconia. This was also supported by zeta potential measurements where a shift of the isoelectric point of the pristine zirconia towards higher pH values in the presence of Np(V) was observed.
Molecular level investigations by means of spectroscopic techniques, namely in situ attenuated total reflection Fourier transform Infrared Spectroscopy (ATR FT-IR) and extended X-ray absorption fine structure spectroscopy (EXAFS), confirmed the predominant presence of Np(V) inner-sphere complexes on the zirconia surface. EXAFS experiments conducted in the weak sorption site regime revealed the formation of one Np(V) bidentate inner-sphere surface complex. Spectroscopic techniques could not be applied to gain information about the presence and structure of Np(V) surface species at such low Np(V) concentrations, where the strong site regimes could be investigated.
The derived information at the macroscopic and molecular levels were used to parameterize a surface complexation model. The Np(V) sorption edges and isotherms could be described with a 1-pK three plane CD-MUSIC model. The derived thermodynamic constants are expected to help to better predict the environmental fate of Np(V) in the context of nuclear waste repository assessments and will also support the appraisal of safety-relevant scenarios for the extended interim storage of spent nuclear fuel.

Keywords: neptunium(V); zirconia; sorption; IR; EXAFS; SCM; ZrO₂; spectroscopy; modelling

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-36679


Data publication: Membrane-free alkali metal-iodide battery with a molten salt

Lee, J.; Monrrabal Marquez, G.; Sarma, M.; Lappan, T.; Hofstettet, Y. J.; Trtik, P.; Landgraf, S.; Ding, W.; Kumar, S.; Vaynzof, Y.; Weber, N.; Weier, T.

Abstract

Raw data from experiments with membrane-free alkali metal-iodide cells containing XPS results, phase-diagram calculations, neutron radiography images, electrochemical cycling data, and electron microscope images of the carbon felt used.

Keywords: liquid metal batteries; alkali metal-iodide batteries; liquid metal electrodes; low-temperature molten salt; membrane-free energy storage; neutron radiography

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Permalink: https://www.hzdr.de/publications/Publ-36678


Band-to-band tunneling switches based on two-dimensional van der Waals heterojunctions

Chava, P.; Fekri, Z.; Vekariya, Y. N.; Mikolajick, T.; Erbe, A.

Abstract

Quantum mechanical band-to-band tunneling (BTBT) is a type of carrier injection mechanism that is responsible for the electronic transport in devices like tunnel field effect transistors (TFETs), which hold great promise in reducing the subthreshold swing below the Boltzmann limit. This allows scaling down the operating voltage and the off-state leakage current at the same time, and thus reducing the power consumption of metal oxide semiconductor transistors. Conventional group IV or compound semiconductor materials suffer from interface and bulk traps, which hinders the device performance owing to the increased trap induced parasitics. Alternatives like two-dimensional materials (2DMs) are beneficial for realizing such devices due to their ultra-thin body and atomically sharp interfaces with van der Waals interactions, which significantly reduce the trap density, compared to their bulk counterparts, and hold the promise to finally achieve the desired low voltage operation. In this review, we summarize the recent progress on such devices, with a major focus on heterojunctions made of different 2DMs. We review different types of emerging device concepts, architectures and the tunneling mechanisms involved by analytically studying various simulations and experimental devices. We present our detailed perspective on the current developments, major roadblocks and key strategies for further improvements of the TFET technology based on 2D heterojunctions to match industry requirements. The main goal of this paper is to introduce the reader to the concept of tunneling especially in van der Waals devices and provide an overview of the recent progress and challenges in the field.

Keywords: 2D materials; heterojunctions; band-to-band tunneling; tunnel field effect transistor; tunnel diode

Permalink: https://www.hzdr.de/publications/Publ-36676


Generalized Laguerre Mosaics as versatile toolbox for microstructure modelling

van den Boogaart, K. G.; Tolosana Delgado, R.; Ballani, F.

Abstract

The particle based simulation of minerals processing often requires
models of 3D particles, while only insufficiently resolved 3D
information from CT or sufficiently resolved 2D information on the
structure of the material is available. Fitted and simulated
microstructure models can support us with relevant 3D microstructures.

The contribution proposes several steps to generalize 3D
Laguerre mosaics that allow to recreate various typical features of
microstructures with meaningful parameters to the simulation process:
Multiple phases with different abundance, preferred contacts, different
grain sizes, spatial variation of properties, flattened crystallites,
preferred orientation, flat and rounded boundaries, etc.

A special feature of the model is the possibility to change the parameters
gradually for the same simulation, such that one can track the effect
of the parameters visually and for estimation algorithms with lower
variability than with a resimulation.

The same microstructure can be computed for 3D voxel spaces, in 2D
sections and on MPS type patterns for estimation of high order
statistics.

Keywords: Geometallurgy; Stochastic Geometry; Microstructure Simulation

  • Lecture (Conference)
    IAMG2023, 05.-12.08.2023, Trontheim, Kongeriket Noreg

Permalink: https://www.hzdr.de/publications/Publ-36675


Structural MATerias research on parameters influencing the material properties of RPV steels for safe long-term operation of PWR NPPs

Kolluri, M.; Martin, O.; Naziris, F.; D’Agata, E.; Gillemot, F.; Brumovsky, M.; Ulbricht, A.; Autio, J.-M.; Shugailo, O.; Horvath, A.

Abstract

This article provides a comprehensive overview of the STRUMAT-LTO project. Embrittlement of the reactor pressure vessel (RPV) due to neutron irradiation and high temperature conditions impose critical challenges for long-term operation (LTO) of pressurized water reactors (PWRs). Significant amount of past research conducted on RPV ageing phenomena has helped to enhance the understanding of the flux effect and the impact of chemical/microstructural heterogeneities on RPV embrittlement. Nonetheless, several unresolved questions regarding RPV embrittlement persist, such as the conflicting viewpoints on the underlying mechanisms that lead to accelerated embrittlement at high fluence conditions in certain low-copper (Cu) RPV steels and the synergistic
effect between nickel, manganese, and silicon (Ni-Mn-Si). Also, the accuracy of embrittlement trend curves (ETCs) for LTO beyond 60 years and the applicability of the master curve approach at high fluences for small/sub-sized specimens require further study. The aim of the STRUMAT-LTO is to address the above-mentioned scientific gaps in RPV embrittlement by employing a unique set of RPV steel specimens constituting systematic variations in Ni, Mn, and Si content, which are irradiated to high fluences resembling reactor operation beyond 60 years within the LYRA-10 experiment at high flux reactor (HFR) in Petten. The STRUMAT-LTO project has received funding from the Euratom research and training programme 2019–2020 under grant agreement
n◦945272. The project has a duration of 48 months.

Keywords: STRUMAT-LTO; RPV embrittlement; LYRA-10; HFR; mini-CT; LWRs; Long term operation; Embrittlement trent curve

Permalink: https://www.hzdr.de/publications/Publ-36674


Vacancy complexes in Cd3As2

Rice, A. D.; Liedke, M. O.; Butterling, M.; Hirschmann, E.; Wagner, A.; Haegel, N. M.; Alberi, K.

Abstract

Epitaxial growth of the three-dimensional topological semimetal Cd3As2 on semiconductor substrates enables its use and integration in device applications. Epitaxy also provides an avenue for varying and controlling point defects through modification of the chemical potential during growth. In turn, knowledge of the point defects that are generated in Cd3As2 epilayers will aid the interpretation of electron transport behavior and guide growth efforts to produce material with low defect densities. Point defects in Cd3As2 epilayers grown by molecular beam epitaxy with varying As/Cd flux ratios are probed by positron annihilation spectroscopy. We find that lower As/Cd flux ratios produce higher concentrations of point defects. Remarkably, the measurements indicate that the average defect size is larger than a monovacancy. The data presented here contribute to an evolving picture of vacancy point defects in Cd3As2 and can be used to direct future investigation of the defect-transport relationships in this emerging electronic material.

Keywords: Cd3As2; semiconductors; defects; positron annihilation spectroscopy

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-36673


Chirality coupling in topological magnetic textures with multiple magnetochiral parameters

Volkov, O.; Wolf, D.; Pylypovskyi, O.; Kakay, A.; Sheka, D. D.; Büchner, B.; Faßbender, J.; Lubk, A.; Makarov, D.

Abstract

Chiral effects originate from the lack of inversion symmetry within the lattice unit cell or sample’s shape. Being mapped onto magnetic ordering, chirality enables topologically non-trivial textures with a given handedness. Here, we demonstrate the existence of a static 3D texture characterized by two magnetochiral parameters being magnetic helicity of the vortex and geometrical chirality of the core string itself in geometrically curved asymmetric permalloy cap with a size of 80 nm and a vortex ground state. We experimentally validate the nonlocal chiral symmetry breaking effect in this object, which leads to the geometric deformation of the vortex string into a helix with curvature 3 μm−1 and torsion 11 μm−1. The geometric chirality of the vortex string is determined by the magnetic helicity of the vortex texture, constituting coupling of two chiral parameters within the same texture. Beyond the vortex state, we anticipate that complex curvilinear objects hosting 3D magnetic textures like curved skyrmion tubes and hopfions can be characterized by multiple coupled magnetochiral parameters, that influence their statics and field- or current-driven dynamics for spin-orbitronics and magnonics.

Keywords: Non-local chiral symmetry breaking; Magnetic vortex

Permalink: https://www.hzdr.de/publications/Publ-36672


Eine Infrastruktur zur Harmonisierung von Datenstrukturen und Semantik

Steinmeier, L.; Ballani, F.; Rau, F.

Abstract

Derzeit wird viel daran geforscht, wie Forschungsdaten im Sinne der FAIR-Prinzipien publiziert werden können. Diese Prinzipien bereits während der Erfassung und Bearbeitung der Daten, also zu einem frühen Zeitpunkt im Forschungsdatenlebenszyklus anzuwenden, bringt viele Vorteile mit sich. Wir stellen eine Softwareinfrastruktur vor, die dies unterstützen soll. Hierbei legen wir den Schwerpunkt auf die Aspekte des Austausches und der Harmonisierung von Datenstrukturen und Semantik und beschreiben auch, wie eine angebundene Endnutzersoftware aussehen kann.

Die Infrastruktur basiert auf folgender Top-Level-Architektur: Teilnehmende Parteien können eigene Instanzen von Datenstruktur- und Semantik-"Warehouses" mit privaten und öffentlichen Teilen betreiben. Ein globaler Index macht dann die öffentlichen Teile aller Warehouses auffindbar und zugänglich. Diese Infrastruktur muss die Anbindung beliebiger Endnutzersoftware durch einen gemeinsamen Kommunikationsstandard ermöglichen, da die Anforderungen an Dateneingabe und -bearbeitung zwischen verschiedenen Forschungsfeldern sehr unterschiedlich ausfallen können. Die Kommunikation soll grundsätzlich über Graphdaten erfolgen, da diese besonders geeignet sind, um vernetzte Inhalte abzubilden.

Eine solche Infrastruktur kann u. a. folgende Funktionen in Endnutzersoftware unterstützen: Bei der Eingabe von Daten können automatisch bestehende Datenstrukturen und Semantiken zur Verwendung vorgeschlagen werden; bestehende Daten, die gleiche oder ähnliche Strukturen und Semantiken verwenden, können gefunden und verglichen werden; Datenstrukturen und Semantiken können öffentlich diskutiert werden, um sie von und für die jeweiligen Nutzergemeinschaften weiter zu harmonisieren und zu entwickeln.

Zur Demonstration der Funktionen und Vorteile einer derartigen Infrastruktur entwickeln wir eine Proof-of-Concept-Endnutzersoftware in Form eines Graphdateneditors. Dieser Editor wird Forschende beim FAIRen Erfassen von Daten durch die folgenden Funktionalitäten unterstützen: Zu domänenunabhängigen Themen (z. B. Einheiten) stellt er ihnen Standards für Strukturen und Semantik zur Verfügung. Er ermöglicht ihnen, bestehende Ressourcen wie Geräte oder Datensätze mit ihrer Arbeit zu verknüpfen. Und er fördert unter Verwendung eines Prototypen der skizzierten Infrastruktur die Harmonisierung von Datenstrukturen und Semantik mit anderen Nutzer:innen.

Keywords: FAIR; Semantik; Datenstruktur; Harmonisierung; Graphdaten; Editor; Infrastruktur

  • Poster
    Datenräume in Deutschland und Europa gestalten - Impulse der Wissenschaft, 24.-25.04.2023, Hannover, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36670


Helmholtz Metadata Collaboration - Datenräume innerhalb und mit der Helmholtz-Gemeinschaft gestalten

Ballani, F.; Curdt, C.; Lorenz, S.; Süß, W.

Abstract

Daten sind ein essentieller Bestandteil heutiger Forschungsaktivitäten. Ein leistungsfähiges und zukunftsorientiertes Forschungsdatenmanagement kann die Effizienz von Forschung, die langfristige Verfügbarkeit generierter Daten und die Reproduzierbarkeit entsprechender Ergebnisse verbessern. Ein wesentlicher Baustein, wie er in den FAIR-Prinzipien umrissen wird, sind dabei Metadaten. Um dieses Thema aufzugreifen, hat die Helmholtz-Gemeinschaft Deutscher Forschungszentren die Plattform "Helmholtz Metadata Collaboration (HMC)" ins Leben gerufen und mit der Aufgabe betraut, Beratungsangebote, Informationen und Werkzeuge für einen effizienten Umgang mit Metadaten und damit zur Verbesserung der FAIRness von Helmholtz-Forschungsdaten zur Verfügung zu stellen.
Von großer Bedeutung für den Erfolg von HMC ist die Vernetzung in den Communities der Helmholtz-Forschungsbereiche Energie, Erde und Umwelt, Gesundheit, Materie, Information sowie Luft- und Raumfahrt und Verkehr. HMC stützt sich daher auf eine verteilte Struktur von sechs disziplinspezifischen Metadaten-Hubs, die innerhalb ihrer Communities Kompetenzen aktivieren, Ideen fördern und Anforderungen sammeln, um daraus Lösungen für die aktuellen Herausforderungen im Bereich der Metadaten zu entwickeln. Ein mit den technischen Entwicklungen beauftragtes, zentral verankertes Team wirkt unterstützend bei der Implementierung empfohlener Lösungen, Dienste und Werkzeuge mit. Derartige technische Lösungen, allgemein verwendbare Prozesse sowie Angebote zu Schulung, Weiterbildung und Beratung werden fortlaufend erweitert und zur Verfügung gestellt.
HMC ist Teil eines größeren Helmholtz-Förderprogramms, das sich mit unterschiedlichen Herausforderungen der Digitalisierung von Forschung auseinandersetzt, und steht in engem Kontakt mit Helmholtz Open Science. Darüber hinaus sind die Aktivitäten von HMC in den nationalen und internationalen Kontext (z. B. RDA, EOSC, NFDI) und entlang der wissenschaftlichen Disziplinen sowie der Informations- und Datenwissenschaft eingebettet, um die Kompatibilität mit der größeren Wissenschaftsgemeinschaft zu gewährleisten.
Ziel ist neben der Gestaltung einer internen Helmholtz-Plattform, die Etablierung eines öffentlichen, offenen und langfristig verfügbaren Gemeinschaftsdienstes für den Umgang mit Metadaten in der Wissenschaft.

Keywords: Helmholtz Metadata Collaboration

  • Poster
    Herrenhäuser Konferenz "Datenräume in Deutschland und Europa gestalten - Impulse der Wissenschaft", 24.-25.04.2023, Hannover, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36669


Rollen und Strukturen für eine vollständige Erfassung und Publikation von Forschungsdaten

Rau, F.; Ballani, F.; Steinmeier, L.; van den Boogaart, K. G.

Abstract

Ein Datensatz gilt als vollständig, wenn neben den reinen Daten (z. B. Messwerte) auch weiterführende Informationen, wie Entstehung und Nutzungslizenz, vorliegen. Dies erfordert neben der vollständigen Erfassung der Daten und Metadaten auch Hilfestelllungen bzw. Instruktionen für die Erfassung und Nutzung sowie einer Infrastruktur zur Speicherung, Publikation und eindeutigen Identifikation. Eine solche "Wertschöpfungskette" setzt sich aus verschiedenartigen Prozessen zusammen, die von Personen in definierten Rollen bearbeitet werden sollten. Auch gilt es, eine Infrastruktur bereitzustellen, die zum einen eine präzise Eingabemaske für den konkreten Fall des Anwenders generiert, aber zum anderen allgemeine Suchanfragen zielgerichtet auf die richtigen Datensätze lenken muss. Und natürlich ist dieses gesamte Konstrukt nicht ohne Regeln und Dokumentation beherrschbar und muss mit einem angepassten Schulungsangebot und einer intuitiven Benutzeroberfläche ausgestattet sein. Das Schulungsangebot richtet sich auch an Personen mit Rollen bzw. zugewiesenen Aufgaben im Datenmanagementsystem um sicherzustellen, dass die Rollen durch die Definition von notwendigen Qualifikationen mit der notwendigen Qualität ausgeführt werden. Eine Plausibilitätsprüfung, die die erwartete Flexibilität des Systems berücksichtigt, garantiert die Konsistenz der Datensätze. In einer der höchsten Ausbaustufen folgt der Plausibilitätsprüfung eine Art Selbstheilungsmechanismus, der dem Anwender einen Datensatz gemäß den Vorgaben vorschlägt oder dessen erneutes Eingreifen gänzlich obsolet macht.
In diesem Beitrag soll der Fokus auf den Rollen und auf der Interaktion mit dem Datenmanagementsystem liegen. Alle notwendigen Qualifikationen und Aufgabenfelder werden dabei den Rollen zugeordnet. Der Vorteil der Unterteilung in Rollen ist es, dass offenbleibt, ob die zusätzlichen Aufgaben durch bestehendes oder neues Personal abgedeckt werden oder ob nicht eine Person mehrere Rollen innehat. Damit kann der konkrete Personalansatz an die eigenen Bedürfnisse angepasst werden.

  • Poster
    Datenräume in Deutschland und Europa gestalten - Impulse der Wissenschaft, 24.-25.04.2023, Hannover, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36668


Advances and new ideas for neutron-capture astrophysics experiments at CERN n_TOF

Domingo-Pardo, C.; Babiano-Suarez, V.; Balibrea-Correa, J.; Caballero, L.; Ladarescu, I.; Lerendegui-Marco, J.; Tain, J. L.; Tarifeño-Saldivia, A.; Aberle, O.; Alcayne, V.; Altieri, S.; Amaducci, S.; Andrzejewski, J.; Bacak, M.; Beltrami, C.; Bennett, S.; Bernardes, A. P.; Berthoumieux, E.; Boromiza, M.; Bosnar, D.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Casanovas, A.; Cerutti, F.; Cescutti, G.; Chasapoglou, S.; Chiaveri, E.; Chiera, N. M.; Colombetti, P.; Colonna, N.; Camprini, P. C.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Dellmann, S.; Di, C. M.; Di, M. S.; Diakaki, M.; Dietz, M.; Dressler, R.; Dupont, E.; Durán, I.; Eleme, Z.; Fargier, S.; Fernández, B.; Fernández-Domínguez, B.; Finocchiaro, P.; Fiore, S.; García-Infantes, F.; Gawlik-Ramięga, A.; Gervino, G.; Gilardoni, S.; González-Romero, E.; Guerrero, C.; Gunsing, F.; Gustavino, C.; Heyse, J.; Hillman, W.; Jenkins, D. G.; Jericha, E.; Junghans, A.; Kadi, Y.; Kaperoni, K.; Käppeler, F.; Kaur, G.; Kimura, A.; Knapová, I.; Köster, U.; Kokkoris, M.; Krtička, M.; Kyritsis, N.; Lederer-Woods, C.; Lerner, G.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Maugeri, E. A.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Mönch, I.; Mucciola, R.; Murtas, F.; Musacchio-Gonzalez, E.; Musumarra, A.; Negret, A.; Pérez, D. R. A.; Pérez-Maroto, P.; Patronis, N.; Pavón-Rodríguez, J. A.; Pellegriti, M. G.; Perkowski, J.; Petrone, C.; Pirovano, E.; Plaza, J.; Pomp, S.; Porras, I.; Praena, J.; Quesada, J. M.; Reifarth, R.; Rochman, D.; Romanets, Y.; Rubbia, C.; Sánchez, A.; Sabaté-Gilarte, M.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N. V.; Stamati, M.; Sturniolo, A.; Tagliente, G.; Tarrío, D.; Torres-Sánchez, P.; Turko, J. A. B.; Urlass, S.; Vagena, E.; Valenta, S.; Variale, V.; Vaz, P.; Vecchio, G.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T.; Zarrella, R.; Žugec, P.

Abstract

This article presents a few selected developments and future ideas related to the measurement of (n,γ) data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with γ-ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate i neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area.

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Experimental and theoretical study on the production of carbide-rich composite nano-coatings

Fogarassy, Z.; Kentsch, U.; Panjan, P.; Racz, A. S.

Abstract

Carbides are known for high hardness and corrosion resistance and therefore applicable as protective coatings. C/Si and C/W multilayers (the individual layer thicknesses were between 10 and 20 nm) have been irradiated at room temperature by argon and xenon ions. The energies varied between 40 and 120 keV while the fluences were in the range of 0.07 - 6 × 10¹⁶ ions/cm². The SRIM simulation was applied to have the proper ion energy. The irradiation induced intermixing and carbide (SiC and WC) formation at the interfaces already for the lowest irradiation fluence. The component in-depth distribution has been determined by AES depth profiling which showed that it varied greatly as a function of the irradiation conditions and layer structure. In both material pair the thickness of the produced carbide increased with square root of fluence but the mixing mechanism were different: local spike for C/W and ballistic for C/Si. The mixing efficiency was lower for the C/Si than for the C/ W.

Keywords: WC; SiC; Carbide; Irradiation; Multilayer; Mixing

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Efficient Production of the PET Radionuclide Lanthanum-133

Brühlmann, S. A.; Kreller, M.; Pietzsch, H.-J.; Kopka, K.; Mamat, C.; Walther, M.; Reissig, F.

Abstract

Ziel/Aim:

Targeted Alpha Therapy is a research field of highest interest in specialized radionuclide therapy. In particular the radionuclide actinium-225 provides all necessary physical and chemical properties for a successful clinical application. Although the macropa chelator has shown beneficial properties regarding labeling and stability in vivo as compared with DOTA, the former lacks an imaging counterpart to actinium-225. On the other hand, lanthanum is a perfect surrogate for actinium. The imaging properties of the β+-emitter lanthanum-133 makes it an attractive candidate as a theranostic matched pair to actinium-225. This project aims at the cyclotron-based production of lanthanum-133 with high radionuclidic purity for theranostic purposes.
Methodik/Methods:
Silver discs were filled with [Ba-134]BaCO3 and capped with a platinum foil. One-hour proton irradiations (18.6 MeV, 15 µA) were performed with the HZDR TR-FLEX (ACSI) cyclotron. The powder target was then opened and the dry solid dissolved in HNO3. Separation was carried out with branched DGA cartridge, although other anion-exchange resins are also under investigation. The fractions containing Ba were collected for recovery. Test radiolabeling of macropa-derived PSMA inhibitors previously published by our group was performed in the MBq/nmol range.
Ergebnisse/Results:
Activity yields of 1.8 GBq lanthanum-133 (decay-corrected to EOB) were achieved, with corresponding lanthanum-135 impurities below 0.4 % and no other La radionuclides detected. The product was collected in diluted HCl, with ca. 80 % activity eluted in the second mL. Quantitative radiolabeling was achieved with ligand concentrations down to the µM range.
Schlussfolgerungen/Conclusions:
Lanthanum-133 with high radionuclidic purity was produced for the first time. Considering future medical demands, the scale up to radioactivity amounts that are needed for clinical application purposes could be achieved by increasing the target mass, beam current and irradiation time.

  • Contribution to proceedings
    NuklearMedizin 2023, 19.-22.04.2023, Leipzig, Deutschland

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Nanoscale mineral/contaminant redox reaction processes: impact on oxyanion contaminant fate in oscillating anoxic environments

Charlet, L.; Guida, C.; Poulain, A.; Ding, R.; Ramothe, V.; Maria Papaslioti, E.; Kirsch, R.; Fernandez-Martinez, A.; Scheinost, A.; Marc Greneche, J.; Menguy, N.; Rosso, K. M.

Abstract

Oscillating oxic/anoxic conditions induces processes at mineral-Kuid
interfaces aeecting the speciation and fate of redox active elements. Such
Kuctuations occur in natural environments (at watershed and delta water
table or in lake water chemocline) and in engineered systems (in oil reDnery
drainage water peatbogs or nuclear waste repository). In presence of aqueous
sulDde or ferrous iron ions, Se, Sb, Pu and Re undergo heterogeneous
reductive precipitation. At the nanosecond scale, selenate adsorption onto
the net pyrite surface is shown by ab-initio computations to proceed via the
formation of a chemical bond between the oxyanion oxygen atom and a
surface Fe atom, weakening the other Se-O bonds and reducing Se atom
oxydation state. At hour-to-day scale, mobile Se(VI), Se(IV), Sb(V), Pu(V) and
Re(VII) oxyanions are shown by strictly anoxic wet chemistry experiments,
XAFS and Mossbauer spectroscopy [1] to be reduced, in presence of
nanosized particles (iron sulDdes (mackinawite or pyrite) [2], oxides
(magnetite) [3] [4] [5] or clays [6]) and aqueous iron (II) or S(-II), to solids (Se(0),
Sb O , PuO , Re0 , ReS or Re(0)) or to highly speciDc Sb(III) [7] and Pu(III) [8]
sorption complexes. STEM-HAADF microscopy demonstrates the formation of
Se(0) trigonal gray selenium nanowires after co-adsorption of selenate and
ferrous iron ions on 10 nm nanomagnetite [4], a reaction which results from a
complex, kinetically controlled interplay of intermediate reduced surface
complexes and transport of these reduced species to the tip of the nanowires.
These processes in far-from-equilibrium conditions are of prime importance
in the safety assessment of petroleum industry and geological repositories, as
well as in the bioavailability to crop or human beings.
[1] Charlet et al., 2022, J. Mat. Res. DOI: 10.1557/s43578-022-00823-8 [2] Son et
al., 2022, Geochim. Cosmochim. Acta 338 : 220–228. [3] Goberna-Feron et al.,
2021, Env. Sci. & Tech. 55, 3021−3031. [4] Poulain et al., 2022, Env. Sci. & Tech 56
: 14817-14827 [5] Wang et al., 2022, Environ. Sci. Technol. 2022, 56, 9. [6]
Charlet et al., Geochim. Cosmochim. Acta 71: 5731-49. [7] Kirsch et al., 2008,
Mineral Mag, 72, 185-189. [8] Kirsch et al, 2011, Environ. Sci. Technol. 45 :
7267–7274

Keywords: oxyanion; redox

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    Goldschmidt Conference 2023, 09.-14.07.2023, Lyon, France

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Coordination chemistry of the early actinides

März, J.

Abstract

The actinides (An) are located at the bottom of the periodic table. These elements are exclusively radioactive, highly chemo-toxic, and play an important role in chemical engineering and environmental science related to the nuclear industry or nuclear waste repositories. In contrast to the strongly shielded 4f electrons of the lanthanides, 5f electrons of particularly the early An are found to participate in bonding, e.g. to organic ligands. Another characteristic of the An is their huge variety of possible oxidation states, typically ranging from +II to +VII for early actinides, making their chemistry complex but interesting. A suitable approach to explore fundamental physico-chemical properties of the actinides is to study series
of isostructural An compounds in which the An is in the same oxidation state. Observed changes in e.g. the binding situation or magnetic effects among the An series may deliver insight into their unique electronic properties mainly originating from the f-electrons. A question still remaining in the field of An chemistry is the degree of “covalency” in compounds across the actinide series, which may be addressed by systematic studies on series of An compounds, including transuranium (TRU) elements.
We investigate the coordination chemistry of low-valent actinides using organic N-, O-, or S-donor ligands. Information on covalency trends as well as mutual ligand influences can be obtained by the analysis of solid-state structures derived by SC-XRD in combination with quantum chemical calculations (QCC) and high-energy-resolution fluorescence detection X-ray absorption near edge spectroscopy (HERFD-XANES). In solution, NMR spectroscopy permits to draw conclusions about the complex speciation in solution, the intrinsic magnetic properties of the actinides, or subtle changes in covalency in the ligand-actinide-bonding.

Keywords: actinides; coordination chemistry; covalency; bonding analyses

  • Invited lecture (Conferences)
    AC-Kolloquium, 18.01.2023, Leipzig, Deutschland

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Reductive immobilization of 99Tc(VII) by pyrite and marcasite

Rodríguez, D. M.; Mayordomo, N.; Brendler, V.; Scheinost, A.; Schild, D.; Müller, K.

Abstract

99Tc is a fission product with a long half-life of 2.14 × 105 years. Its migration and bioavailability strongly depend on its oxidation state and speciation in aqueous solution. Under oxidizing conditions, Tc mainly exists as pertechnetate, TcVIIO4, a highly water-soluble anion with s negligible sorption to most minerals. Under reducing conditions, TcIV prevails, whose main species, TcO2 xH2O, is a polymer of low solubility. As the presence of reductants like Fe2+ in the near-field of a nuclear waste repository is expected due to canister corrosion, several studies consider 99TcVII reductive immobilization by minerals containing reductant moieties, such as magnetite (FeIIFe2IIIO4) or mackinawite (FeS) [1]

Pyrite (cubic FeS2) is a redox sensitive sulfide mineral that has been identified as a good sorbent for TcVII from soil and groundwater [2]. Under repository conditions, both pyrite and marcasite (orthorhombic FeS2) are expected to form by corrosion processes and microbial interaction [3]. Moreover, both iron sulfides are also accessory minerals in granitic and argillaceous rocks. Therefore, reliable data on 99TcVII retention by both minerals and their mixtures is relevant for the safe disposal of nuclear waste.

We have studied the Tc retention by pure pyrite and by a mixture of marcasite and pyrite (60:40) using a combination of batch experiments and spectroscopy (Raman microscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy) at pH 6 and 10. [4, 5]. We confirm the 99TcVII reduction and subsequent 99TcIV retention on the mineral surfaces and shed new light on different retention mechanisms for pyrite and marcasite at pH 10.

We acknowledge funding from the German Federal Ministry of Economic Affairs and Energy (BMWi) for VESPA II project (02E11607B), and from the German Federal Ministry of Education and Research (BMBF) for the NukSiFutur TecRad young investigator group (02NUK072).

[1] Yalçıntaş E, et al. 2016 Dalton Trans. 45 17874
[2] Huo L, et al. 2017 Chemosphere 174 456
[3] Roberts W M B, et al. 1969 Mineralium Deposita 4 18
[4] Rodríguez D M, et al. 2020 Environ. Sci. Technol. 54 2678
[5] Rodríguez D M, et al. 2021 Chemosphere 281 130904

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    Goldschmidt 2023 Conference, 09.-14.07.2023, Lyon, France

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Proton dosimetry in a magnetic field: measurement and calculation of correction factors for a plane-parallel ionization chamber

Gebauer, B.; Baumann, K.-S.; Fuchs, H.; Georg, D.; Oborn, B.; Looe, H.-K.; Lühr, A.

Abstract

Purpose: In magnetic resonance imaging-integrated proton therapy (MRiPT), the magnetic field-dependent change in the dosage of ionization chambers is considered by the correction factor k ⃗ B,M,Q, which needs to be determined experimentally or computed via Monte Carlo (MC) simulations. In this study, k ⃗B,M,Q was both measured and simulated with high accuracy for a plane-parallel ionization chamber at different clinical relevant proton energies andmagnetic field strengths.

Material&Methods: The dose-response of the Advanced Markus chamber (TM34045, PTW, Freiburg, Germany) irradiated with homogeneous 10×10 cm2 mono-energetic fields, using 103.3, 128.4, 153.1, 223.1, and 252.7 MeV proton beams was measured in a water phantom placed in the magnetic field (MF) of an electromagnet with MF strengths of 0.32, 0.5, and 1 T. The detector was positioned at a depth of 2 g/cm2, with chamber electrodes
parallel to the MF lines and perpendicular to the proton beam incidence direction. The measurements were compared with TOPAS MC simulations utilizing COMSOL-calculated 0.32, 0.5, and 1 T MF maps of the electromagnet. k ⃗B,M,Q was calculated for the measurements for all energies and MF strengths based on the equation: k ⃗B,M,Q = MQ/M ⃗ BQ , where MQ and M ⃗ BQ were the temperature and air-pressure corrected detector readings with and without the MF, respectively. MC-based correction factors were determined as k ⃗B,M,Q = Ddet/D ⃗ Bdet , where Ddet and D ⃗ Bdet were the doses deposited in the air cavity of the ionization chamber model without and
with the MF, respectively.

Results: The detector showed a reduced dose-response for all measured energies and MF strengths, resulting in experimentally determined k ⃗B,M,Q values larger than unity. k ⃗B,M,Q increased with proton energy and MF strength, except for 0.5 T and 252.7 MeV. Overall, k ⃗B,M,Q ranged between 1.0065 and 1.0205 for all energies and MF strengths examined and the strongest dependence on energy was observed at 1 T. The MC simulated k ⃗B,M,Q values for all MF strengths showed a good agreement with the experimentally determined correction factors with a maximum deviation of 0.6% and trends within their standard deviations.

Conclusion: For the first time, measurements and simulations were compared for an Advanced Markus chamber for proton dosimetry within MFs. For all MF strengths, there was a good agreement of k ⃗B,M,Q between experimentally determined and MC calculated values in this study. By benchmarking the MC code for the calculation of k ⃗B,M,Q it can be used to calculate k ⃗B,M,Q for various ionization chamber models, MF strengths and proton energies to generate the data needed for a dosimetry protocol for MRiPT.

Keywords: dosimetry; MC simulation; advanced Markus chamber; proton; magnetic fields; MR integrated proton therapy; MRiPT

Permalink: https://www.hzdr.de/publications/Publ-36661


Results of a round robin test on surface energy analysis of silica and lactose by inverse gas chromatography

Sandbrink, J.; Duempelmann, R.; Meyer, R.; Adamska, K.; Strzemiecka, B.; Enke, D.; Rudolph, M.; Brendlé, E.

Abstract

Inverse gas chromatography (IGC) has become a popular technique for the analysis of particulate materials. By injecting certain probe molecules through a column containing the sample as the stationary phase and measuring the retention time of said probe molecules, information on a range of different physicochemical properties, such as surface energy or Hansen-solubility parameters can be obtained. A proper understanding of these physicochemical properties is significant for many industrial processes (e.g. formulation, miscibility of polymer blends, agglomeration), as said processes are often driven by surface properties.
Though, IGC analysis has many benefits and is widely used nowadays, the comparability of results that are reported and measured by different operators using different IGC devices has not been investigated yet. Therefore, a round robin test was conducted, where eight organisations analysed two standard materials, silica and lactose, according to a jointly defined protocol using IGC devices that either have a valve-based or a syringe-based dosing system. The results are evaluated based on standard IGC theories and the same mathematical operations are applied to all datasets in order to obtain the specific retention volume and the dispersive surface energy component for the two materials. The resulting values of the calculated parameters vary quite significantly, which is a rather unexpected and a very unpleasant finding for this highly sensitive analytical device. Measurements that are conducted individually by the same operator on the same IGC device report similar results, whereas results obtained by different operators with different types of IGC devices are significantly different. Potential factors for the differences, such as the injected quantity of the probe molecules, are presented and discussed.
This round robin test therefore raises some questions on the reproducibility of results obtained via inverse gas chromatography. Furthermore, it demonstrates the need for a standard powder and protocol in order to have a common ground for an objective judgment of results.

Keywords: Inverse gas chromatography; surface energy; physicochemical properties; silica; lactose

  • Poster
    Jahrestreffen der DECHEMA-Fachgruppen Kristallisation, Grenzflächenbestimmte Systeme und Prozesse und Mechanische Flüssigkeitsabtrennung, 09.-10.03.2023, Frankfurt, Deutschland

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Redox reactivity of selenium (VI) in the presence of Fe(II) and S(−II) bearing mineral phases under the conditions of Callovo-Oxfordian pore water

Saini, D.; Fernandez-Martinez, A.; Jordan, N.; Madé, B.

Abstract

⁷⁹Se with a half-life of 3.27 × 10⁵ y [1] is presently considered as a key mobile radionuclide for the disposal of spent fuel and high-level waste [2]. The solubility of selenium (Se) is largely controlled by its oxidation state, and hence depends on the redox conditions present in soils, sediments, bedrock and aquifers. The −II, −I, and 0 oxidation states are commonly predominant in “reducing” anoxic environments, while the +IV and +VI states predominate in more “oxidizing” environments [2]. The interactions with Fe(II) and S(–II)-bearing redox active solids- mediate the oxido-reduction kinetics of Se oxyanions, playing an important role in the control of Se speciation [3]. Regarding Se(VI), it was found to be metastable (far from thermodynamic equilibrium) and potentially selenium could coexist in different oxidation states in the Callovo-Oxfordian pore waters [4]. The reduction of Se(VI) by magnetite, much slower than for Se(IV), include different steps (adsorption, reduction to Se(IV), and further reduction to less soluble Se phases: Se⁰(s), FeSe₂(s), FeSe(s)), each of them imposing a kinetic barrier for the whole reduction process. At present it is not clear whether the Se(VI) initial adsorption or its reduction to Se(IV) are concomitant or not, and extra work needs to be done in this direction to establish the reduction pathway. Furthermore, little is known about the potential competition with ubiquitous ions in porewater such as carbonate or sulfate and especially about their capability to limit the contact of selenate molecules with the Fe(II)-bearing solids, and thus to inhibit the electron transfer.
The redox reactions Se(VI) with magnetite and pyrite under neutral pH conditions will be deciphered at both macroscopic and molecular levels by combining batch sorption studies and advanced spectroscopic techniques (XAS, XPS). In addition, the influence of sulfate ions will be investigated.

[1] Jörg, G. et al., Appl. Radiat. Isot. (2010), 68 (12), 2339−2351.
[2] Fernandez-Martinez, A. and Charlet, L., Rev. Environ. Sci. Biotechnol. (2009), 8, 81–110.
[3] Scheinost, A. C. et al., J Contam Hydrol (2008), 102, 228-45.
[4] Savoye, S. et al., Appl. Geochemistry (2021), 128, 104932.

  • Contribution to proceedings
    Goldschmidt2023, 09.-14.07.2023, Lyon, France
  • Poster
    Goldschmidt2023, 09.-14.07.2023, Lyon, France

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Wave Function Extent in multilayer van der Waals Heterostructures: A First-Principles Study

Umm-E.-Hani; Muhammad, S. R.; Kuc, A. B.

Abstract

A good understanding of interlayer coupling is crucial to designing novel van der Waals heterostructures. The present study examines two types of multilayer heterostructures based on 2D transition-metal dichalcogenides (TMDCs). ABC or ABBC stackings consist of three layers (A - MoS2, B - MoSe2, C - WSe2). By doing so, MoSe2 spatially separates the electron layer (MoS2) from the hole layer (WSe2). TMDCs are stacked in one of three ways in the second type: ABA, ABBA, or AABAA. Depending on stoichiometry, the electrons or holes are localized in the middle part of the heterostructure or delocalized to the outer layers. The majority of the materials studied here are direct gap semiconductors with transitions at K. A type II band alignment is found in all of them. We predict that indirect excitons will be evident in all materials.

  • Poster
    Chem2Dmat2023, 15.-18.05.2023, Bologna, Italy

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Reduction of pertechnetate by magnetite - influence of pH and time

Zimmermann, T.; Faria Oliveira, A.; Mayordomo, N.; Scheinost, A.

Abstract

Magnetite is arguably the most relevant corrosion product when steel canisters corrode anaerobically in future deep geological radioactive waste repositories. 99Tc is of great concern for the safety assessment of these repositories, due to its long half-life (t1/2 = 2.1∙105 years). Under oxidative conditions Tc forms an anionic species, pertechnetate (TcVIIO4−), which is highly mobile due to its high solubility and weak sorption on most minerals. Under anaerobic conditions, TcVII can be reduced to TcIV, which strongly interacts with minerals by sorption, structural incorporation and formation of insoluble oxides like TcO2. FeII-minerals, and among them magnetite, have shown to effectively reduce pertechnetate and play thereby a critical role.[1]
Previous studies by Yalcintas et al.[2] suggested that TcVII reduction by magnetite resulted in the precipitation and surface adsorption of TcO2-like oligomers at pH 9, i.e. close to the pH of magnetite solubility minimum. In contrast at pH 6-7, the reduction resulted in a partial incorporation of TcIV in octahedral Fe-sites of magnetite.[3] Our initial working hypothesis was that the incorporation is linked to magnetite solubility. To test this, we investigated Tc reaction with magnetite nanoparticles in a wide range of pH (3 - 13), reaction time (1 - 210 days) and varied initial Tc concentration (μM - mM).
To characterize the oxidation state of Tc and its molecular structure, we employed a range of methods including Tc K-edge (21 044 eV) X-ray absorption spectroscopy (XAS) at the Rossendorf Beamline at the ESRF in Grenoble. XANES analysis revealed the predominance of TcIV at all evaluated pH values, supporting that reductive Tc immobilization is the main retention mechanism. EXAFS analysis suggests that two species are formed. At pH 5 and short equilibration times, Tc is retained by forming TcO2∙xH2O polymers, showing the recently reported “zig-zag-chain” structure[4]. In contrast, TcIV substituted magnetite forms within a few hours at pH 7 and 10. At pH 5, it forms only after a few days with the proportion of the Tc-magnetite phase growing at the expense of the TcO2∙xH2O polymers. Therefore, across the pH range 5 to 10, Tc-magnetite seems to be the thermodynamically preferred phase. The initial formation of TcO2∙xH2O polymers at low pH seems to be linked to the release of Fe2+ from magnetite (reductive maghemitization)[5], which leads to substantial Fe2+ concentrations in solution due to the lacking re-adsorption at this pH. The mechanism behind the fast incorporation of TcIV in magnetite, now observed for the first time within days across a wide pH range, remains unsolved. The structural stability of cubic spinel magnetite and the absence of strong evidence for structural uptake of other elements with similar coordination number and ionic
Fig. 1: Schematic process of the interaction of pertechnetate (TcVIIO4−) with magnetite radius like Co, Ni and other 3d metals, point to a complex coupled sorption/redox/incorporation mechanism.
In order to better understand the Tc incorporation into by magnetite, we also conducted density functional theory (DFT) calculations using the PBE[6] functional implemented in AMS/BAND 2022[7], with full optimization of atomic coordinates and lattice parameters. For the finite structures, solvent effects were included with the COSMO[8]. Three charge compensation mechanisms were considered. The calculated incorporation energies and comparison of the Tc coordination structure with experimental EXAFS data indicate that Tc incorporation is most likely to occur either by substitution of two octahedral FeIII sites with a TcIV/FeII pair (Fig. 2, left), or by substitution of two FeII sites with a single TcIV, thus forming a vacancy (Fig. 2, right). The last mechanism, where three TcIV replace four octahedral FeIII (Fig. 2, center), could be excluded.

Keywords: magnetite; technetium; XAFS; ROBL; redox

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    Migration Conference, 24.-29.09.2023, Nantes, France

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Understanding uranium fate in wetland soils: a speciation and labile behavior study in the former extraction mine of Rophin (France)

Nivesse, A.-L.; Landesman, C.; Arnold, T.; Sachs, S.; Stumpf, T.; Scheinost, A.; Coppin, F.; Fevrier, L.; Den Auwer, C.; Gourgiotis, A.; Del Nero, M.; Montavon, G.

Abstract

Uranium (U) mining and milling activities, as well as mineral processing plants, raise environmental concerns due to the possible release of radioactive and other potentially toxic elements. To understand their fate in the environment and evaluate their potential impact, the main scientific challenge calls for identifying their solubility, mobility and bioavailability in the environment. Around former U mining and processing plants, wetlands prove to be specific zones with significant amounts of U. This is partly explained by the reduction of the mobile U(VI) into U(IV) due to strongly reducing conditions related to the microbial activity and/or by complexation with the organic matter occurring with high concentrations in wetlands.
At the center of the ancient mining district of Lachaux in France (45.994°N, 3.596°E), the site of Rophin (within the ZATU: Uranium Working Zone = Long Term Socio-Ecological Research Tool of CNRS, Fig.1.a) is characterized by a wetland area with large U concentrations up to 16 g.kg-1 of dry mass of soil [1]. Several cross-analyses indicate that U was transported in particulate forms into the wetland during the exploitation of U(VI) phosphate minerals [1]. The Rophin site therefore provides the opportunity to study the stability of these U minerals over almost 70 years in a non-manipulated wetland since the closure of the mine. In this context, the main challenge is to describe the behavior of U (and decay products of interest) in the wetland using a predictive model that combines transport and chemical speciation. The overall adopted scientific approach is to propose a mechanistic description of the mobility of these elements, from the molecular scale (speciation) to in natura behavior (lability), by coupling field investigations and laboratory experiments.
A simplified three-layer model describes the soil profile of the Rophin wetland, with variable U concentrations and specific physico-chemical soil properties (Fig.1.b). Analyses carried out by X-absorption spectroscopy on in natura soil samples mainly indicate the presence of an adsorbed form of U(IV) in the highly contaminated layer, while both U(IV) and U(VI) are identified in the organically rich part at the surface. Additional SEM-EDX and μ-XRF mapping measurements also indicate that U minerals transported into the wetland were partially dissolved and re-adsorbed in soils.
The objective was to determine which fraction is finally labile, i.e. the fraction that is adsorbed and whose resupply in solution is rapid. This was assessed by desorption experiments under representative site conditions with two complementary approaches [2,3]. Overall, the available fraction is very low (3 to 10 % for the highly contaminated layer and less than 1% for the surface layer) and is characterized by distribution coefficient (Kd) values of the order of 102 L.kg-1. These results were then compared with field data using DGT/DET techniques coupling (Diffusive Gradient in Thin-films/ Diffusive Equilibrium in Thin-Films) [4]. We found an available fraction in the whitish zone, which is rapidly eliminated with time, whereas a labile U fraction is almost undetectable in the surface layer. Combined with time-dependent deployment DGT/DET coupling, results highlighted the predominance of a kinetic parameter and thus, the expected key role of the organic matter in the U mobile behavior in the surface soil.
This study provides access to the input data (labile quantity and (Kd) values) for the establishment of a reactive transport model at the scale of the Rophin mining-affected wetland, but also allows to determine significant information on U interactions in soils. As such, this multi-scale and interdisciplinary study contributes to the improvement of the global understanding of U migration and fate in wetland soils.

Keywords: uranium; soils; ROBL; mining

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  • Lecture (Conference)
    Migration Conference, 24.-29.09.2023, Nantes, France

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From FineFuture to FINEST towards a more sustainable circular economy

Dirlich, S.; Renno, A.; Engelhardt, J.; Rudolph, M.; Stemmermann, P.; Heipieper, H.

Abstract

The EU-funded H2020 project FineFuture successfully tackled the recovery of fine particles for an increased resource efficiency, and an improved pneumatic flotation technology was one of the key outcomes with the very realistic option of bringing it to industry. Though being potentially suitable for secondary material as well, the focus was on primary ores such as manganese, magnesite or iron. Nevertheless, feeding the pneumatic flotation cell with tailings material was also conducted in some experiments, and resulted in satisfactory recovery rates of the target elements.
However, due to resource depletion and the paradigm of climate-neutrality economy needs to be transformed into a more circular one, making use of sustainable value chains and keeping resources longer in the loop. Therefore, the research goes further with the project FINEST, and tackles finest particulate matter of anthropogenic origin such as shredder waste from WEEE or cars, fine ashes, etc. The target elements considered from these waste materials are microplastics, mineral additives and disperse metals. The idea is to combine different waste streams by blending them in order to stimulate improved process behavior, and an increase of the recovery rate of valuable elements such as copper, iron etc. Most of the waste streams considered in FINEST are currently not utilized, resulting in a great benefit for circularity and simultaneously reducing environmental harm through the reduction of the amount of material that needs to be disposed of. The unavoidable residuals are treated in a way that all compounds are inert, and allow for a safe disposal.
The project is largely oriented towards transdisciplinarity, and the FINEST Research School is additionally embedded into the research project. The school aims to train postgraduate students in a structured way to allow them to become transfer experts in resource management. While offering training at industry during the PhD phase, the school follows the concept of “transfer via brains“, which means to aim for an excellent education of the PhD’s, who will enter industry afterwards with the goal to manage a transformation from inside into more circular thinking.

Keywords: finest particles; resource recovery; sustainable value chains; circular economy; microplastics; mineral additives; disperse metals

  • Open Access Logo Lecture (Conference)
    World Resources Forum'23, 04.-6.9.2023, Genf, Schweiz

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From FineFuture to FINEST: Resource Supply for the Energy Transition and Sustainable Value Chains

Dirlich, S.; Schlosser, D.; Stapf, D.; Renno, A.; Gutzmer, J.

Abstract

One of the biggest threats to humankind and the planet is the climate change that is propelled by excessive carbon dioxide emissions mainly being generated through combustion of fossil fuels in industry, transportation, building, etc. In order to keep the increase of the global temperature below 2K compared to pre-industrialization level, climate-neutrality becomes more and more important for nations, societies, regions, cities and companies in response to this development. In addition, a sustainable circular economy that keeps material streams in the loop as far as possible contributes to this goal. However, the transformation of the society and economy towards more sustainability requires a vast amount of resources in itself. Though resource depletion may actually not really be a challenge for many elements, in particular those elements that are required for high technology applications such as batteries for electro mobility, wind turbines, etc. are scarce, and might become even scarcer in view of the pursued expansion of sustainable and climate-neutral technologies. This is the case for example for lithium as an important raw material for batteries, but also for rare earth elements like neodymium that are required for magnets in wind turbines.
In addition, the extraction of primary ores becomes also more and more difficult due to decreasing concentrations of valuable minerals in the ore bodies in turn leading to even larger amounts of mining waste compared to the recovery of the target element. Often, a considerable part of the minerals cannot be recovered as the particles are too fine for the conventional processing technologies currently in place. In order to tackle this challenge, the Horizon 2020 project FineFuture was conducted in which experts from all over Europe collaborated to find ways to unlock the fine-grained mineral and critical raw materials resources through innovative technologies and concepts for fine particle flotation. Beside advancements in the fundamental understanding of the underlying processes in the interphases as well as the modelling of the particle flows, the pneumatic flotation technology was improved through a new design and more suitable selection of frothers and collectors resulting in higher recovery rates for certain minerals such as manganese and magnesite.
Current research going on is intended to utilize and manage finest particulate matters of anthropogenic origin. The types of finest materials considered in the FINEST project jointly conducted by HZB, HZDR, KIT, UFZ, TUBAF and UG are microplastics, mineral additives and disperse metals, which are found in waste streams such as plastics waste, external thermal insulation composite systems, light-weight shredder fractions (e.g. from electronic scrap and/or automotive recycling), etc.
The sub-project FINEST Microplastics deals with biotechnological solutions for the utilization of the microplastics fraction. Biocatalysts are to convert the plastics fraction to yield specific mono-/oligomers for product synthesis, microbial biomass amenable to further microbial fermentation and inert residues for a safe deposition.
The sub-project FINEST Mineral Additives is dedicated to finest minerals with the aim to recover mineral additives like fillers, flame retardants, pigments or heat stabilizers during chemical recycling processes. By means of pyrolysis, part of the mineral additives from external thermal insulation composite systems shall be recovered while non-separable additives shall be safely stored in recycling cement and low-grade plastics may be utilized by feeding them back into the plastics fraction.
The sub-project FINEST Disperse Metals targets at a blending and agglomeration of complex residues composing of finest particles. The pellets produced from the blended waste shall be further processed through thermal treatment in a furnace aiming at the recovery of the metallic content. The remaining residues shall be disposed of in an inert form.
These innovative approaches need to be assessed in terms of their technological, ecological, economic, and social impact in comparison to the conventional processing, but also in comparison to a mere storage, which is regularly the case for the finest particle waste up-to-date.
Finally, the transdisciplinary approach of the project shall enable a transformation of industry through “transfer via brains” in order to contribute to a circular economy and enable more sustainable value chains.

Keywords: finest particles; resource recovery; sustainable value chains; circular economy; microplastics; mineral additives; disperse metals

  • Open Access Logo Lecture (Conference)
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Deutschland

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Data publication: Small-angle neutron scattering study of neutron-irradiated and post-irradiation annealed VVER-1000 reactor pressure vessel weld material

Ulbricht, A.; Dykas, J.; Chekhonin, P.; Altstadt, E.; Bergner, F.

Abstract

messdaten und auswertedaten

Keywords: reactor pressure vessel; weld; neutron irradiation; annealing; small-angle neutron scattering; Vickers hardness; solute-rich clusters; recovery

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Data publication: Experimental characterization of four-magnon scattering processes in ferromagnetic conduits

Hula, T.

Abstract

All Raw and Processed Data + written Thesis. Data and Figures are stored in the 'Figures_and_Data' Directory. Experimental Measurements were done by means of BLS Microscopy (group of H. Schultheiß at HZDR). Micromagnetic Simulations were done at the Hemera Cluster (Dr. A. Kakay at HZDR). Data Analysis was done in Python or Jupyter Notebooks (Open Source). All scripts are included. Graphics were done using OmniGraffle and Blender. Plotting was done using Python and 'Plot2' (Mac Only!). All Files/Data/Skripts are sorted by Figure! The entire Latex Package is stored under 'Thesis_Hula' - Dissertation.tex is the main file and shows all required dependencies.

Keywords: Magnonics; Spin waves; Brillouin spectroscopy; light scattering; nonlinear phenomena; scattering

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Experimental characterization of four-magnon scattering processes in ferromagnetic conduits

Hula, T.

Abstract

PhD Thesis:

Experimental characterization of four-magnon scattering processes in ferromagnetic
conduits

Keywords: Magnonics; Spin waves; Brillouin spectroscopy; light scattering; nonlinear phenomena; scattering

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  • Doctoral thesis
    TU Chemnitz, 2023
    Mentor: Prof. Olav Hellwig / Dr. Helmut Schultheiß
    140 Seiten

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Clinical Significance of Tumor-Infiltrating Conventional and Plasmacytoid Dendritic Cells in Pancreatic Ductal Adenocarcinoma

Plesca, I.; Benešová, I.; Beer, C.; Sommer, U.; Müller, L.; Wehner, R.; Heiduk, M.; Aust, D.; Baretton, G.; Bachmann, M.; Feldmann, A.; Weitz, J.; Seifert, L.; Seifert, A. M.; Schmitz, M.

Abstract

Dendritic cells (DCs) play a key role in the orchestration of antitumor immunity. Activated DCs efficiently enhance antitumor effects mediated by natural killer cells and T lymphocytes. Conversely, tolerogenic DCs essentially contribute to an immunosuppressive tumor microenvironment. Thus, DCs can profoundly influence tumor progression and clinical outcome of tumor patients. To gain novel insights into the role of human DCs in pancreatic ductal adenocarcinoma (PDAC), we explored the frequency, spatial organization, and clinical significance of conventional DCs type 1 (cDC1s) and type 2 (cDC2s) and plasmacytoid DCs (pDCs) in primary PDAC tissues. A higher density of whole tumor area (WTA)- and tumor stroma (TS)-infiltrating cDC1s was significantly associated with better disease-free survival (DFS). In addition, an increased frequency of intraepithelial tumor-infiltrating cDC2s was linked to better DFS and overall survival (OS). Furthermore, an increased density of WTA- and TS-infiltrating pDCs tended to improve DFS. Moreover, a higher frequency of WTA- and TS-infiltrating cDC1s and pDCs emerged as an independent prognostic factor for better DFS and OS. These findings indicate that tumor-infiltrating DCs can significantly influence the clinical outcome of PDAC patients and may contribute to the design of novel treatment options that target PDAC-infiltrating DCs.

Keywords: dendritic cells; neoadjuvant chemotherapy; pancreatic cancer; tumor microenvironment

Permalink: https://www.hzdr.de/publications/Publ-36650


Curvilinear Magnetic Architectures for Biomedical Engineering

Baraban, L.; Huang, T.; Chen, X.; Santiago Herrera Restrepo, R.; Ignés Mullol, J.; Puigmartí-Luis, J.; Pané, S.

Abstract

The field of autonomous motile micro/nanomotors that can propel in the liquid environment strongly benefits from the use of magnetic materials, winning in the long-time deterministic locomotion and controllability of such microscopic objects. This chapter reviews the applications of curved magnetic micro/nanostructures to be employed for biomedical and environmental applications. In this respect, after introducing the basic principle and examples of the self-propelled micro-objects, we further focus here on the locomotion of the magnetically decorated microscopic objects and the influence of their shape on the character and pattern of the motion. Namely, we consider the properties of magnetically capped spherical Janus particles, rod-like, tubular, and other asymmetric objects, e.g., microhelices, with magnetic functionalization. Finally, we describe the applications of such magnetic objects in environmental remediation, biosensing and drug delivery, etc.

  • Book chapter
    Denis D. Sheka, Denys Makarov: Curvilinear Micromagnetism, Springer Cham: Springer, 2023, 978-3-031-09088-2
    DOI: 10.1007/978-3-031-09086-8

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Molecular scale understanding of Ni2+ adsorption on swelling clay minerals

Stotskyi, V.; Di Lorenzo, F.; Marques Fernandes, M.; Krack, M.; Scheinost, A.; Lanson, M.; Lanson, B.; Churakov, S. V.

Abstract

Sorption of hazardous metals on clay minerals is a key process contributing to the safety of repository sys-tems. The existence of high- and low-affinity adsorption sites on smectites edge surfaces, responsible for met-als uptake has been revealed in previous studies [1,2]. The exact molecular nature of these adsorption sites has not been fully resolved.
Similar to the adsorption of Ni2+ on montmorillonite [1], Ni2+ on saponite shows a non-linear adsorption be-havior, which, by analogy, suggests the existence of strong and weak sorption sites (Fig.1). Based on the sorp-tion isotherms obtained on saponite, self-oriented clay films were prepared, with Ni loadings corresponding to adsorption dominated by strong and weak sites, and then polarized Ni K-edge EXAFS spectra were recorded.
For samples with low Ni2+ loadings (below 4 mmol/kg), P-EXAFS results confirmed the existence of strong sorption sites. An increase of Ni loading (up to 40 mmol/kg) leads to decreasing in Ni-Mg bond length and an increase in Ni-Si coordination number, indicating the formation of a secondary phase. The exact structure of the new phase is still under evaluation, but this solid phase will certainly mask Ni sorbed to weak sites.
The molecular structure of cations adsorbed on the water-edge interfaces for the most stable surfaces was modeled using ab initio MD, which enable us to obtain a theoretical estimation of the free energies of Zn-Ni cation exchange reactions between weak and strong sites on (100) and (130) edges of saponite. Theoretical values obtained for Zn-Ni exchange are equal to 13.5±0.4 and 5.50±0.03 kJ/mol for (100) and (130) surfaces, respectively. These results are in a good agreement with experimental results for montmorillonite (9.1 kJ/mol) – a trustworthy proxy and suggest a stronger affinity of Zn to strong sites than Ni.

Keywords: Montmorillonite; Saponite; Nickel; Sorption; ROBL

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Thick as thieves: Antimony sequestration during ferrous iron oxidation

Wegner, L.; Scheinost, A.; Peiffer, S.; Hockmann, K.

Abstract

The geochemical behavior of antimony (Sb), a priority pollutant of increasing concern, is closely linked to the redox cycling of iron (Fe). Microbial reduction of Fe(III) oxides and production of soluble Fe(II) under anoxic conditions has been shown to release co-associated Sb (occurring as Sb(V) and/or Sb(III)). In redox-dynamic environments, Fe(II) can be re-oxidized and precipitate as Fe(III) oxides. The extent to which these processes affect Sb mobility, however, is still poorly understood and likely depends on an array of factors such as pH, Sb species and the nature of the newly formed Fe(III) oxides.

Here, we investigated the effect of Fe(II) oxidation on Sb sequestration and on the mineralogy of the resulting Fe(III) precipitates in a pH range typical of Sb-contaminated systems (i.e. pH 6, 6.5, and 7). To initiate the oxidation reaction, 0.5 mmol L-1 Fe(II) was added to an oxygen-saturated electrolyte solution containing 0 – 50 µmol L-1 Sb(V) or Sb(III). Changes in aqueous Sb and Fe(II) were tracked during the experiments, and solid phase samples were collected at the end of the oxidation reaction for characterization by diffractometric, spectroscopic, and microscopic techniques.

Iron(II) oxidation kinetics and Sb sequestration were a function of pH and Sb species, with Sb(III) retarding the oxidation reaction. In the absence of Sb, Fe K-edge extended X-ray absorption fine structure (EXAFS) analysis revealed lepidocrocite as the only solid-phase product. In presence of Sb, feroxyhyte and goethite formed instead of lepidocrocite. The shift in Fe oxide assemblage was more pronounced when Sb was present as Sb(V) and at a lower pH. Antimony EXAFS analyses showed an almost complete oxidation of Sb(III) to Sb(V) followed by the incorporation of Sb(V) into the structure of the Fe oxides precipitates.

Our results allow for a better understanding of Sb geochemistry in redox-dynamic environments as they demonstrate that Sb itself can influence the pathways of secondary Fe oxide formation. Our study also provides important information for the development of adequate remediation practices of Sb-contaminated soils and sediments that are subject to changes in redox conditions as induced by flooding or waterlogging.

Keywords: Antimony; EXAFS; ROBL; Iron oxides; lepidocrocite

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  • Open Access Logo Lecture (Conference)
    Goldschmidt Conference 2023, 09.-14.07.2023, Lyon, France

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Small-angle neutron scattering study of neutron-irradiated and post-irradiation annealed VVER-1000 reactor pressure vessel weld material

Ulbricht, A.; Dykas, J.; Chekhonin, P.; Altstadt, E.; Bergner, F.

Abstract

Post-irradiation annealing of neutron-irradiated reactor pressure vessel steels is a matter of both technical and scientific interest. Small-angle neutron scattering (SANS), while being sensitive to nm-sized irradiation-induced solute-atom clusters, provides macroscopically representative and statistically reliable measures of cluster volume fraction, number density and size. In the present study, SANS was applied to uncover the size distribution of clusters in as-irradiated samples of a VVER-1000 weld and their gradual dissolution as function of the post-irradiation annealing temperature. The same samples were used to measure Vickers hardness. The results are consistent with Mn-Ni-Si-rich clusters of less than 2 nm radius to be the dominant source of both scattering and hardening. Annealing gave rise to small but significant partial recovery at 350 °C and almost complete recovery at 475 °C. The dispersed-barrier hardening model was applied to bridge the gap between the characteristics of nano-features and macro-hardness.

Keywords: reactor pressure vessel; weld; neutron irradiation; annealing; small-angle neutron scattering; Vickers hardness; solute-rich clusters; recovery

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Field-Tunable Berezinskii-Kosterlitz-Thouless Correlations in a Heisenberg Magnet

Opherden, D.; Tepaske, M. S. J.; Bärtl, F.; Weber, M.; Turnbull, M. M.; Lancaster, T.; Blundell, S. J.; Baenitz, M.; Wosnitza, J.; Landee, C. P.; Moessner, R.; Luitz, D. J.; Kühne, H.

Abstract

We report the manifestation of field-induced Berezinskii-Kosterlitz-Thouless (BKT) correlations in the weakly coupled spin-1/2 Heisenberg layers of the molecular-based bulk material [Cu(pz)2(2-HOpy]2)(PF6)2. At zero field, a transition to long-range order occurs at 1.38 K, caused by a weak intrinsic easy-plane anisotropy and an interlayer exchange of J´/kB ≈ 1 mK. Because of the moderate intralayer exchange coupling of J/kB = 6.8 K, the application of laboratory magnetic fields induces a substantial XY anisotropy of the spin correlations. Crucially, this provides a significant BKT regime, as the tiny interlayer exchange J0 only induces 3D correlations upon close approach to the BKT transition with its exponential growth in the spin-correlation length. We employ nuclear magnetic resonance measurements to probe the spin correlations that determine the critical temperatures of the BKT transition as well as that of the onset of long-range order. Further, we perform stochastic series expansion quantum Monte Carlo simulations based on the experimentally determined model parameters. Finite-size scaling of the in-plane spin stiffness yields excellent agreement of critical temperatures between theory and experiment, providing clear evidence that the nonmonotonic magnetic phase diagram of [Cu(pz)2(2-HOpy]2)(PF6)2 is determined by the field-tuned XY anisotropy and the concomitant BKT physics.

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  • High Magnetic Field Laboratory (HLD)

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Uranium(VI) reduction by iron- and sulfate-reducing bacteria in pure culture and in artificial multispecies bio-constructs

Hilpmann, S.; Jeschke, I.; Deev, D.; Zugan, M.; Lapanje, A.; Rijavec, T.; Steudtner, R.; Hübner, R.; Schymura, S.; Cherkouk, A.

Abstract

The microbial reduction of U(VI) to U(IV) can decrease the mobility of U contaminants in the environment and may have a significant impact on the safety of a nuclear waste repository, as well as, the potential to serve as a component in bioremediation strategies for U-contaminated environments. In this study, we show significant differences in the reduction mechanisms for iron- and sulfate-reducing bacteria, highlighting the importance of investigating microbe-uranium interaction of different bacterial genera. Moreover, we introduce the use of artificial bio-constructs to study U reduction by microbial communities to gain insights into the complex interactions in a multi-species environment. To gain molecular process understanding regarding microbial U reduction Desulfosporosinus and Desulfitobacterium spp. were chosen as important representatives of sulfate- and iron-reducing bacteria in anaerobic environments. Furthermore, their U reduction capabilities were investigated using artificial bio-constructs with different other microbial species.
Time-dependent experiments of pure cultures in bicarbonate buffer (30 mM, 100 µM U(VI), 10 mM lactate) showed a decrease of U concentrations in the supernatant of Desulfitobacterium sp. G1-2, whereas no changes occurred for Desulfosporosinus hippei DSM 8344T. In contrast, in artificial Opalinus Clay pore water (100 µM U(VI), pH 5.5, 10 mM lactate) up to 80% of the radionuclide got removed by both microorganisms. UV/Vis studies verified the reduction of U(VI) to U(IV) in the cell pellets. STEM-EDXX revealed the presence of two different U-containing aggregates inside the cells of Desulfitobacterium sp. G1-2, while cells of Desulfosporosinus hippei DSM 8344T showed almost no U uptake but U-aggregates on the cell surface.
First experiments with artificial bio-constructs that were formed from different bacterial genera using polyelectrolyte-controlled aggregation showed a promising U reduction capacity. Such artificial biostructures, in the form of aggregates or artificial biofilms, have a potential in investigating the complex interactions in multi-species environments and to utilize beneficial microbes in remediation strategies, even if they do not form biofilms themselves.

Keywords: Uranium(VI) reduction; bio-aggregates; anaerobic bacteria

  • Lecture (Conference) (Online presentation)
    ACS Spring 2023, 26.-30.03.2023, Indianapolis, USA

Permalink: https://www.hzdr.de/publications/Publ-36642


Complexation of neptunium(V) with aqueous phosphate using a dual experimental and quantum chemical approach

Miladi, E.; Réal, F.; Vallet, V.; Jordan, N.; Huittinen, N. M.

Abstract

Understanding and quantifying the chemistry of actinides with strong complexing ligands found in the environment is of key importance for predicting their mobility in the subsurface, especially with respect to the safety of high-level nuclear waste disposal. Phosphate ligands are present in the environment as they originate from the natural decomposition or microbially mediated solubilization processes of phosphate containing rocks and minerals. They can also be produced by anthropogenic activities such as fertilizers spread on the fields or phosphate-based detergents. Furthermore, phosphates are constituents of glasses and ceramics that may be used to immobilize high-level wastes.

Current thermodynamic databases contain very little data on actinide-phosphate complexes [1]. For the trivalent actinide curium, a recent study combining luminescence spectroscopy, thermodynamics, and quantum chemical (QC) calculations could unambiguously establish the formation of 1:1 and 1:2 phosphate complexes with the H₂PO₄⁻ ligand [2]. Complexation constants for both species were derived and extrapolated to standard conditions using the specific ion interaction theory. By combining the data obtained in the luminescence spectroscopic investigations, such as the crystal-field splitting of the emitting excited states and the luminescence lifetimes, with quantum chemical calculations, the coordination number of the complexes could be determined. At room temperature, both the 1:1 and 1:2 complexes are coordinated by 9 ligands. At elevated temperature, only the 1:1 complex retains a coordination number of 9, while one water molecule is released from the 1:2 complex, thereby reducing its coordination number to 8.

In this study, a similar combined experimental and computational approach will be applied to bridge the gaps in the databases for neptunium(V)-phosphate complexes. The complexation reaction will be studied with UV-vis and infrared (IR) spectroscopies at varying ionic strengths and temperatures under acidic pH conditions. Thereby, complexation constants and thermodynamic parameters for Np(V) aqua ion with phosphate can be derived for the formed Np(V)-H₂PO₄⁻ complex(es) (Figure 1). However, the experimental data alone, do neither hold information on the coordination of phosphate to the NpO₂⁺ cation (mono or bidentate binding), nor on the overall coordination number. This calls for relativistic QC calculations that will help characterizing the stoichiometry and geometries of the complexes. Indeed, QC methods can quantify the relative stability of these structures as well as the complexation strengths with aqueous phosphate through potential change of the coordination number with increasing temperature. The calculated vibrational frequency supports the assignment of bands within the measured IR spectra. In addition, the electronic structures at fundamental and excited states will be computed in order to predict the absorption bands of Np(V) – phosphate complexes in acidic solution. Ultimately, by using the quantum theory of atoms in molecules (QTAIM), the topology of the neptunyl-ligand bonds can be scrutinized to i) discuss the evolution of its character as additional phosphate ligands bind neptunyl and ii) to complement the evolution of the complexation constants determined experimentally.

[1] Grenthe, I. Gaona, X. Plyasunov, A. Rao, L. Runde, W.H. Grambow, B. Konings, R.J.M. Smith, A.L. Moore, E.E. (2020). Second Update on the Chemical Thermodynamics of Uranium, Neptunium, Plutonium, Americium and Technetium. Chemical Thermodynamics Volume 14, OECD Publications, Paris.
[2] Huittinen, N., Jessat, I., Réal, F., Vallet, V., Starke, S., Eibl, M., and Jordan, N. (2021). Revisiting the complexation of Cm(III) with aqueous phosphates: new insights from luminescence spectroscopy and ab initio simulations. Inorg. Chem. 60:10656−10673.

  • Poster
    Migration 2023, 24.-29.09.2023, Nantes, France

Permalink: https://www.hzdr.de/publications/Publ-36641


Annual Report 2022 - Institute of Ion Beam Physics and Materials Research

Faßbender, J.; Helm, M.; Zahn, P.; Zahn, M.

Abstract

Preface
Selected publications
Statistics (Publications and patents, Concluded scientific degrees; Appointments and honors; Invited conference contributions, colloquia, lectures and talks; Conferences, workshops, colloquia and seminars; Exchange of researchers; Projects)
Doctoral training programme
Experimental equipment
User facilities and services
Organization chart and personnel

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  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-123 2023
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-36640


Pages: [1.] [2.] [3.] [4.] [5.] [6.] [7.] [8.] [9.] [10.] [11.] [12.] [13.] [14.] [15.] [16.] [17.] [18.] [19.] [20.] [21.] [22.] [23.] [24.] [25.] [26.] [27.] [28.] [29.] [30.] [31.] [32.] [33.] [34.] [35.] [36.] [37.] [38.] [39.] [40.] [41.] [42.] [43.] [44.] [45.] [46.] [47.] [48.] [49.] [50.] [51.] [52.] [53.] [54.] [55.] [56.] [57.] [58.] [59.] [60.] [61.] [62.] [63.] [64.] [65.] [66.] [67.] [68.] [69.] [70.] [71.] [72.] [73.] [74.] [75.] [76.] [77.] [78.] [79.] [80.] [81.] [82.] [83.] [84.] [85.] [86.] [87.] [88.] [89.] [90.] [91.] [92.] [93.] [94.] [95.] [96.] [97.] [98.] [99.] [100.] [101.] [102.] [103.] [104.] [105.] [106.] [107.] [108.] [109.] [110.] [111.] [112.] [113.] [114.] [115.] [116.] [117.] [118.] [119.] [120.] [121.] [122.] [123.] [124.] [125.] [126.] [127.] [128.] [129.] [130.] [131.] [132.] [133.] [134.] [135.] [136.] [137.] [138.] [139.] [140.] [141.] [142.] [143.] [144.] [145.] [146.] [147.] [148.] [149.] [150.] [151.] [152.] [153.] [154.] [155.] [156.] [157.] [158.] [159.] [160.] [161.] [162.] [163.] [164.] [165.] [166.] [167.] [168.] [169.] [170.] [171.] [172.] [173.] [174.] [175.] [176.] [177.] [178.] [179.] [180.] [181.] [182.] [183.] [184.] [185.] [186.] [187.] [188.] [189.] [190.] [191.] [192.] [193.] [194.] [195.] [196.] [197.] [198.] [199.] [200.] [201.] [202.] [203.] [204.] [205.] [206.] [207.] [208.] [209.] [210.] [211.] [212.] [213.] [214.] [215.] [216.] [217.] [218.] [219.] [220.] [221.] [222.] [223.] [224.] [225.] [226.] [227.] [228.] [229.] [230.] [231.] [232.] [233.] [234.] [235.] [236.] [237.] [238.] [239.] [240.] [241.] [242.] [243.] [244.] [245.] [246.] [247.] [248.] [249.] [250.] [251.] [252.] [253.] [254.] [255.] [256.] [257.] [258.] [259.] [260.] [261.] [262.] [263.] [264.] [265.] [266.] [267.] [268.] [269.] [270.] [271.] [272.] [273.] [274.] [275.] [276.] [277.] [278.] [279.] [280.] [281.] [282.] [283.] [284.] [285.] [286.] [287.] [288.] [289.] [290.] [291.] [292.] [293.] [294.] [295.] [296.] [297.] [298.] [299.] [300.] [301.] [302.] [303.] [304.] [305.] [306.] [307.] [308.] [309.] [310.] [311.] [312.] [313.] [314.] [315.] [316.] [317.] [318.] [319.] [320.] [321.] [322.] [323.] [324.] [325.] [326.] [327.] [328.] [329.] [330.] [331.] [332.] [333.] [334.] [335.] [336.] [337.] [338.] [339.] [340.] [341.] [342.] [343.] [344.] [345.] [346.] [347.] [348.] [349.] [350.] [351.]