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41396 Publications

Evolution of vacancy like defects in heavily doped GaAs

Liedke, M. O.; Prucnal, S.; Butterling, M.; Duan, J.; Hirschmann, E.; Wang, M.; Helm, M.; Zhou, S.; Wagner, A.; Dawidowski, W.; Boyu Young, L.; Hong, M.

N-type doping of GaAs is a self-limiting process where a carrier concentration in the
level of 1019 cm-3 is difficult to achieve. By means of ion implantation sequences with
precisely defined energy, homogenizing the distribution profile of dopants, followed
by non-equilibrium thermal annealing using intense light pulses, a highly doped ntype
GaAs with electron concentration easily exceeding the level of 5×1019 cm-3 was
obtained. Although, the absolute achieved carrier concentration has been
exceptionally large a peculiar variations of its magnitude across the samples
thickness have been observed, which we will regard to the incomplete
recrystallization processes. Moreover, we will discuss the effect of intense pulsed
laser melting and flash lamp annealing on defects distribution and electrical
activation efficiency in chalcogenide-implanted GaAs investigated by means of
positron annihilation spectroscopy, transport measurements, as well as
electrochemical capacitance-voltage techniques. Using positron beams, delivered by
the large scale facility ELBE at HZDR, as a sensitive probe of open volumes and
dedicated DFT calculations, we will highlight the capability of nanosecond pulsed
laser melting to control the type and density of defect complexes across the depth,
e.g. S or Te substitutions of As atoms associated to Ga vacancy, playing a crucial
role for donor deactivation. The distribution of defects and carriers will be discussed
considering the depth distribution of implanted elements and the solidification
velocity during recrystallization. The ultra-doped n-type GaAs is a potential candidate
for plasmonic and photonic applications. The proposed model for the donor-vacancy
formation during the PLM process of highly doped semiconductors is potentially
transferable to the group IV elements and groups III-V compound semiconductors.

Keywords: GaAs; pulsed laser melting; flash lamp annealing; positron annihilation spectroscopy

Related publications

  • Lecture (Conference)
    DPG Spring Meeting 2023, 20.03.2023, Dresden, Germany
  • Lecture (Conference)
    The 2023 Fall Meeting of the European Materials Research Society (E-MRS), 18.09.2023, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-38607
Publ.-Id: 38607


Multi–length scale characterization of point defects in thermally oxidized, proton irradiated iron oxides

Lun Chan, H.; Auguste, R.; Romanovskaia, E.; Lopez Morales, A.; Liedke, M. O.; Schmidt, F.; Butterling, M.; Romanovski, V.; Winkler, C.; Qiu, J.; Wang, Y.; Kaoumi, D.; Selim, F. A.; Uberuaga, B. P.; Hirschmann, E.; Wagner, A.; Hosemann, P.; Scully, J. R.

A key for the success of safe nuclear power generation system is to consider structural materials that are economical, meet mechanical property needs, possess good corrosion resistance, and are radiation tolerant. Nevertheless, fundamental insights that elucidate the details of radiation damage on materials corrosion performance are lacking. This includes the behavior of surface oxides which often regulate corrosion. For example, it is unclear how non-equilibrium point defects, oxide structure, mass transport in oxides, and subsequent oxidation behavior are altered by the radiation. In this work, some of the effects of proton irradiation on the attributes of point defects, iron oxide microstructures, and the physical nature of the oxidation product were correlated with corrosion behavior. Iron oxides, fabricated by thermal oxidation in air at 400°C and 800°C for 1 h, were subjected to 200 keV, 0.03 dpa (displacements per atom) of proton irradiation, and subjected to corrosion reactivity assessment using AC and DC electrochemical methods. Experimental methods that target materials information at different length scales, such as positron annihilation spectroscopy (atomistic), transmission electron microscopy (mesoscopic), and electrochemical methods (macroscopic), were coupled to shed light on the impact of radiation-induced defect modifications and structural changes in oxides on corrosion reactivity which ultimately affects durability in harsh environments.

Keywords: proton irradiation; thermal oxidation; iron; corrosion; positron annihilation spectroscopy; point defects

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  • Secondary publication expected from 30.03.2024

Permalink: https://www.hzdr.de/publications/Publ-38606
Publ.-Id: 38606


UAV magnetics over the Bjerkreim-Sokndal Intrusion, Rogaland, Norway: A first look

Lee, M.; Madriz Diaz, Y. C.; Gloaguen, R.; McEnroe, S.

The Bjerkreim-Sokndal layered intrusion in Rogaland Anorthosite Province in southwestern Norway has been the focus of decades of research due to its complex geology, the presence of prominent remanent magnetic anomalies, and current economic interest in critical minerals. In 2021, collaborative geophysical fieldwork was conducted by the Norwegian University of Science and Technology and Helmholtz Institute Freiberg for Resource Technology. Despite challenging environmental conditions, more than 100 line-km of magnetic data were collected by a custom multirotor unmanned aerial vehicle (UAV) along the eastern margin of the Bjerkreim lobe of the Bjerkreim-Sokndal Intrusion. Data collection was focused over two areas. The first is an area in the south near the prominent Heskestad magnetic anomaly that is associated with large reversed magnetic remanence in a magnetite-ilmenite-gabbronorite unit. The second is an area in the north near Lake Teksevatnet that hosts mineralized zones and the Lauvneset magnetic anomaly. Initial analysis of the UAV-acquired magnetic data shows additional details on the geologic contacts of key units, especially where in-situ measurements are difficult to collect. UAV surveys help in the construction of an anomaly's geometry through incremental source-sensor separations at various flight altitudes above ground. The UAV data set is an intermediate step between ground and airborne surveys for multiscale interpretation and potentially extreme magnetic scales (from microscopic to planetary).

Keywords: airborne survey; magnetics; magnetometer; remanent magnetization

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-38604
Publ.-Id: 38604


Data publication: Thermal twin stars within a hybrid equation of state based on a nonlocal chiral quark model compatible with modern astrophysical observations

Carlomagno, J. P.; Contrera, G.; Grunfeld, A. G.; Blaschke, D.

These data sets characterize the thermodynamics of color superconducting quark matter under neutron star constraints and neutron star sequences at finite temperatures. They concern order parameters chiral condensate and diquark pairing gap as functions of chemical potential and temperature, phase diagrams in the temperature-chemical potential plane, mass-radius diagrams, mass as a function of the central energy density, equation of state, entropy per baryon versus pressure and chemical potential versus pressure.

Keywords: Chiral quark model; Thermal twin stars; QCD phase diagram; Color superconductivity; Multi-messenger astronomy; Quark-hadron phase transition

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Permalink: https://www.hzdr.de/publications/Publ-38593
Publ.-Id: 38593


Quasi-particle propagation across semiconductor-Mott insulator interfaces

Verlage, J.; Queißer, F.; Szpak, N.; König, J.; Kratzer, P.; Schützhold, R.

As a prototypical example for a heterostructure combining a weakly and a strongly interacting quantum many-body system, we study the interface between a semiconductor and a Mott insulator. Via the hierarchy of correlations, we derive and match the propagating or evanescent quasi-particle solutions on both sides. While the propagation is described by a band-like dispersion in both the weakly and the strongly interacting case, the inverse decay length across the interface follows a different dependence on the band gap in the Mott insulator and the semiconductor. As one consequence, tunnelling through a Mott insulating layer behaves quite different from a semiconducting (or band insulating) layer. For example, we find a strong suppression of tunnelling for energies in the middle between the upper and lower Hubbard band of the Mott insulator.

Permalink: https://www.hzdr.de/publications/Publ-38591
Publ.-Id: 38591


Electron probe petrochronology of monazite- and garnet-bearing metamorphic rocks in the Saxothuringian allochthonous domains (Erzgebirge, Granulite and Münchberg massifs)

Bernhard, S.; Krause, J.

In the Saxothuringian Zone, a unique assemblage of high- to ultra-high-pressure and ultra-high-temperature
metamorphic units is associated with medium- to low-pressure and temperature rocks. The units were
studied in a campaign with garnet and monazite petrochronology of gneisses, micaschists and phyllites, and
monazite dating in granites. P–T path segments of garnet crystallization were reconstructed by geothermobarometry
and interpreted in terms of the monazite stability field, EPMA Th–U–Pb monazite ages and garnet Y +
HREE zonations. One can recognize (1) Cambrian plutonism (512–503 Ma) with contact metamorphism in the
Münchberg Massif. Subordinate monazite populations may indicate a (2) widespread but weak Silurian (444–
418 Ma) thermal event. A (3) Devonian (389–360 Ma) high-pressure metamorphism prevails in the Münchberg
and Frankenberg massifs. In the ultra-high-pressure and high-pressure units of the Erzgebirge the predominant
(4) Carboniferous (336–327 Ma) monazites crystallized at the decompression paths. In the Saxonian Granulite
Massif, prograde–retrograde P–T paths of cordierite-garnet gneisses can be related to monazite ages from 339 to
317 Ma. A (5) local hydrothermal overprint at 313–302 Ma coincides partly with post-tectonic (345–307 Ma)
granite intrusions. Such diverse monazite age pattern and P–T time paths characterize the tectono-metamorphic
evolution of each crustal segment involved in the Variscan Orogeny.

Permalink: https://www.hzdr.de/publications/Publ-38590
Publ.-Id: 38590


Doublon-holon pair creation in Mott-Hubbard systems in analogy to QED

Queißer, F.; Krutitsky, K.; Navez, P.; Schützhold, R.

Via the hierarchy of correlations, we study doublon-holon pair creation in the Mott state of the Fermi-Hubbard model induced by a time-dependent electric field. Special emphasis is placed on the analogy to electron-positron pair creation from the vacuum in quantum electrodynamics (QED). We find that the accuracy of this analogy depends on the spin structure of the Mott background. For Ising type anti-ferromagnetic order, we derive an effective Dirac equation. A Mott state without any spin order, on the other hand, does not explicitly display such a quasi-relativistic behavior.

Permalink: https://www.hzdr.de/publications/Publ-38589
Publ.-Id: 38589


Higher-harmonic generation in the driven Mott-Hubbard model

Queißer, F.; Schützhold, R.

Using Floquet theory and the hierarchy of correlations, we study the non-equilibrium dynamics of the Mott insulator state in the Fermi-Hubbard model under the influence of a harmonically oscillating electric field representing the pump laser. After deriving the associated Floquet exponents, we consider higher-harmonic generation where the strongest signal is obtained if the driving frequency equals one third of the Mott gap.

Permalink: https://www.hzdr.de/publications/Publ-38588
Publ.-Id: 38588


In search of lost time: Raman thermochronology of FC‑1 zircon

Härtel, B.; Enkelmann, E.; Jonckheere, R.; Ludwig, T.; Krause, J.; Ratschbacher, L.

Translating thermochronological ages to geological models requires knowledge of the thermal sensitivity of the
applied thermochronometer, i.e. the closure temperature or the partial annealing/retention zone. Zircon Raman dating
is a thermochronometer that uses radiation-damage measurements and matched analyses of actinide contents in zircon.
Experimental work placed its closure temperature at 330–370 °C for the internal ν2(SiO4) and ν3(SiO4) Raman bands at 439
and 1008 cm−
1, and 260–310 °C for the external rotation (ER) band at 356 cm−
1. However, experimental annealing models
also predict partial radiation-damage annealing over a broad temperature range (> 500 °C). We test these closure temperatures
by dating zircon from the U–Pb reference material FC-1. We matched Raman-based radiation-damage measurements with U
and Th concentrations measured with a secondary ion mass spectrometer. The zircon Raman ages for the ν2, ν3, and ER bands
are 942 ± 23 Ma (2 s), 978 ± 38 Ma, and 1033 ± 32 Ma. This is lower than the expected range of 1040–1080 Ma, between the
apatite U–Pb (~ 490 °C) and zircon (U-Th)/He (ZHe; ~ 200 °C) ages. We discuss long-term, low-temperature annealing of
radiation damage during protracted cooling of the sample as a cause of age reduction. This explanation fits both, experimental
annealing models and zircon Raman data from other geological settings. Long-term, low-temperature annealing complicates
the interpretation of standalone zircon Raman data. However, exploiting this effect by combining zircon Raman and ZHe
dating on the same sample provides thermal-history information beyond that revealed by either of them.

Keywords: Zircon Raman dating; Closure temperature; Radiation-damage annealing; (U-Th)/He dating; Thermochronology

Permalink: https://www.hzdr.de/publications/Publ-38587
Publ.-Id: 38587


Preparation of 5‑[131I]iodotubercidin for the detection of adenosine kinase

Bier, D.; Holschbah, M.; Wedekind, F.; Sihver, W.; Drewes, B.; Schulze, A.; Neumaier, F.; Neumaier, B.; Bauer, A.

5-Iodotubercidin is a prototype adenosine kinase (AK) inhibitor with potent anti-seizure activity in rodent epilepsy models.
Using the chloramine-T method for radioiodination of tubercidin with 131I, we prepared no-carrier-added 5-[131I]iodotubercidin
(5-[131I]IT) in a radiochemical yield of 61 ± 13% and with a radiochemical purity of > 99% (molar activity = 10–40 GBq/
μmol). In vitro competition and saturation experiments demonstrated specific binding of 5-[131I]IT in rodent brain slices
(KD ~ 31 nM), but ex vivo autoradiography revealed its accumulation in cerebral vessels. We conclude that 5-[131I]IT could
be a useful tool for the detection and quantification of AK in in vitro studies.

Keywords: nucleoside adenosine kinase inhibitor (AKI); n.c.a. radioiodination; iodotubercidin; in vitro/ex vivo autoradiography

Permalink: https://www.hzdr.de/publications/Publ-38584
Publ.-Id: 38584


Fusion related laser plasma expertise and interests in the German Helmholtz Association

Schramm, U.

Presentation summing up the work of the Helmholtz task force AG Laser - the fusion energy options: Fusion related laser plasma expertise and interests in the German Helmholtz Association

  • Open Access Logo Invited lecture (Conferences)
    ELI Laser induced Fusion Kick-Off, 28.-29.11.2023, Dolni Brezani (Prag), Tschechien

Permalink: https://www.hzdr.de/publications/Publ-38582
Publ.-Id: 38582


Ion acceleration with ultrashort laser pulses: state-of-the-art and perspectives in the multi-PW regime

Schramm, U.

Talk on: Ion acceleration with ultrashort laser pulses: state-of-the-art and perspectives in the multi-PW regime

  • Open Access Logo Invited lecture (Conferences)
    Scientific opportunities with APOLLON facilities: from fundamental physics to societal applications workshop, 29.-30.11.2023, Paris, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-38581
Publ.-Id: 38581


Data publication: LA-ICP-MS U-Pb cassiterite age data of the Sadisdorf deposit link Sn-Li-(W-Cu) mineralization in the eastern Erzgebirge to the collapse of the Altenberg-Teplice Caldera

Leopardi, D.; Gerdes, A.; Albert, R.; Gutzmer, J.; Lehmann, B.; Burisch, M.

This data repository contains sample overview photographs as well as the U-Pb LA-IC-MS measuring conditions, results and Tera-Wasserburg diagrams summarizing those results.

Keywords: U-Pb dating cassiterite; LA-ICP-MS

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Permalink: https://www.hzdr.de/publications/Publ-38580
Publ.-Id: 38580


Exploration of a mining residue from a high-Sulfidation epithermal gold Deposit

Bachmann, K.; Contreras Acosta, I. C.; Tolosana Delgado, R.; Gutzmer, J.

Reevaluating tailings material originating from a high-sulfidation epithermal gold deposit has unveiled the potential for a holistic remining endeavour. The primary objective of this operation would be the mitigation of minerals containing penalty elements, specifically sulphur in pyrrhotite, a major contributor to acid mine water drainage, alongside the concentration of precious elements like gold. Furthermore, exploring the applicability of the silicate fraction for industries such as ceramics, glass, and geopolymer production has been considered.
To accomplish these objectives, an initial drill core campaign featuring six drill holes was executed, accompanied by a thorough material characterization using automated mineralogy, geochemical assays, and hyperspectral analysis. The subsequent step involved a geometallurgical domaining process based on 64 geochemical assays, particle size measurements, and mineralogy assessments. A Mahalanobis distance hierarchical cluster analysis was employed to differentiate domains, and predictions for these domains were extended to all hyperspectral imaging samples.
The outcome of this comprehensive approach revealed the delineation of four distinct domains, each characterized by variations in modal mineralogy and trace elemental contents. This strategic analysis provides valuable insights into the heterogeneity of the tailings material, laying the groundwork for targeted interventions to address environmental concerns and maximize the extraction of valuable resources.

  • Invited lecture (Conferences) (Online presentation)
    Secondary Mineral Resources Characterization workshop, 25.-26.10.2023, Lund, Schweden

Permalink: https://www.hzdr.de/publications/Publ-38579
Publ.-Id: 38579


Evidence of free-bound transitions in warm dense matter

Dornheim, T.

Warm dense matter (WDM) is now routinely created and probed in laboratories around the world,
providing unprecedented insights into conditions achieved in stellar atmospheres, planetary
interiors, and inertial confinement fusion experiments. However, the interpretation of these
experiments is often filtered through models with systematic errors that are difficult to quantify.
Due to the simultaneous presence of quantum degeneracy and thermal excitation, processes in
which free electrons are de-excited into thermally unoccupied bound states transferring momentum
and energy to a scattered x-ray photon become viable [1]. Here we show that such free-bound
transitions are a particular feature of WDM and vanish in the limits of cold and hot temperatures.
The inclusion of these processes into the analysis of recent X-ray Thomson Scattering (XRTS)
experiments on WDM at the National Ignition Facility [2] and the Linac Coherent Light Source [3]
significantly improves model fits, indicating that free-bound transitions have been observed without
previously being identified. This interpretation is corroborated by agreement with a recently
developed model-free thermometry technique [4,5] and presents an important step for precisely
characterizing and understanding the complex WDM state of matter.

[1] M. Böhme et al, arXiv:2306.17653
[2] T. Döppner et al, Nature 618, 270-275 (2023)
[3] D. Kraus et al, Plasma Phys. Control. Fusion 61, 014015 (2019)
[4] T. Dornheim et al, Nature Communications 13, 7911 (2022)
[5] T. Dornheim et al, Phys. Plasmas 30, 042707 (2023)

  • Poster
    NIF User Meeting 2024, 30.01.-01.02.2024, Livermore, USA

Permalink: https://www.hzdr.de/publications/Publ-38573
Publ.-Id: 38573


Deuterium burning measurement at LUNA and its astrophysical and nuclear implications

Cavanna, F.; Ciani, G. F.; Masha, E.; Piatti, D.

The D(p,γ)3He reaction is responsible for the deuterium destruction during the Big Bang Nucleosynthesis (BBN) and affects the primordial deuterium abundance. This latter is sensitive to fundamental cosmological parameters such as the baryon density and the effective number of relativistic species. In this paper, we describe the most precise direct measurement of the D(p,γ)3He reaction in the BBN energy range (Ecm = 30–280 keV) at the LUNA (Laboratory for Underground Nuclear Astrophysics) facility in Gran Sasso National Laboratories. Experimental results, cosmological consequences, and future prospects are reported here.

Keywords: Big bang Nucleosynthesis; deuterium abundance; underground nuclear astrophysics; cosmological constants

Permalink: https://www.hzdr.de/publications/Publ-38572
Publ.-Id: 38572


Distributor Effects on Liquid Hold-Up in Rotating Packed Beds

Pyka, T.; Bieberle, A.; Loll, R.; Held, C.; Schubert, M.; Schembecker, G.

Although it is known that a loss in separation performance is caused by liquid maldistribution, there is only marginal knowledge of liquid distribution in rotating packed beds (RPBs). As a result, the exact influence of the liquid distribution on separation performance in RPBs is not fully understood. Therefore, this study focuses on the influence of different liquid distributors on the liquid hold-up distribution of rotating metal foam packing inside RPBs. Liquid hold-ups were measured noninvasively using γ-ray computed tomography (CT), and water/air was the system under investigation, operated at atmospheric pressure, temperature of 20 °C, liquid flow rate of 60 l h^−1, F-factor of 2.3 Pa^0.5, and rotational speeds up to 900 rpm. For the first time, the liquid hold-up distribution in the axial direction of a rotating metal foam of an RPB could be accessed, which allowed the identification and quantification of occurring liquid accumulation at the rotor plates. Furthermore, the liquid hold-up distribution through the entire opaque packing could be visualized for different operating conditions by synchronizing the CT with the rotational speed of the rotor. The use of a single-point full-jet nozzle was more prone to cause liquid accumulation at the rotor plates than that with a rotating baffle distributor with 36 baffles. For comparison, circumferential liquid maldistribution was also observed by using a rotating baffle distributor with 12 baffles.

Keywords: rotating packed bed; process intensification; gamma-ray computed tomography

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  • Secondary publication expected from 18.01.2025

Permalink: https://www.hzdr.de/publications/Publ-38570
Publ.-Id: 38570


Al-delta-doped ZnO films made by atomic layer deposition and flash-lamp annealing for low-emissivity coating

Zhang, G.; Steuer, O.; Li, R.; Cheng, Y.; Hübner, R.; Helm, M.; Zhou, S.; Liu, Y.; Prucnal, S.

In this work, we have investigated and optimized the Al-delta-doped ZnO (δ -AZO) superlattices for mid-infrared applications. Thin films of δ -AZO are fabricated by atomic layer deposition (ALD) followed by millisecond-range (ms-range) flash-lamp annealing (FLA). During the FLA process, the superlattice structure is preserved and Al is electrically activated. The highest carrier concentration and lowest resistivity estimated from Hall-effect measurements are 2.7 × 1021 cm−3 and 8.8 × 10-4 Ωcm, respectively, for the δ -AZO superlattice with an Al:Zn ratio of 1:20. Moreover, glass substrates coated with the developed δ -AZO superlattice show a reflectance above 60 % in the near- and mid-infrared spectral range, while the transmittance in the visible range maintains above 80 %. The presented δ -AZO superlattice is a good alternative material to replace indium tin oxide films for cost-efficient low-emissivity glazing.

Keywords: Al-doped ZnO; Delta-doping; Flash-lamp Annealing; Low-Emissivity coating

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Permalink: https://www.hzdr.de/publications/Publ-38568
Publ.-Id: 38568


NuScale-like SMR Model Development and Applied Safety Analyses with the Code Chain Serpent-DYN3D-ATHLET

Diaz Pescador, E.; Bilodid, Y.; Jobst, M.; Kliem, S.

NuScale is an integral pressurized water reactor (iPWR) operated with light water driven by natural circulation through two helical coil steam generators (HCSGs). This work reports the safety analyses of a boron dilution and steam line break accidental sequences in a developed plant computational model based on the specifications from the Final Safety Analysis Report (FSAR). Multi-physics calculations are performed with the code chain Serpent-DYN3D-ATHLET. A state-of-the-art multi-dimensional vessel topology is developed with ATHLET for the accurate representation of flow and temperature fields, as well as spatial core power distribution. The static calculation results show agreement with the reference values from the FSAR. The boron dilution sequence shows a homogeneous core power excursion by the boron feedback, and the reactor is tripped upon “high pressurizer pressure” signal. During the steam line break sequence, the affected HCSG depressurizes rapidly and the reactor is tripped upon “low main steam pressure” signal. None of the transients violate safety margins. The adopted 3-D vessel modelling approach and applied multi-physics calculations are able to capture both transient physics within the reactor domain, and conclude that symmetric arrangement of the HCSG tubes enhance coolant mixing and prevent a heterogeneous core power excursion.

Keywords: NuScale-SMR; iPWR; Boron dilution; Steam line break; Serpent-DYN3D-ATHLET

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  • Secondary publication expected from 11.01.2025

Permalink: https://www.hzdr.de/publications/Publ-38564
Publ.-Id: 38564


Excitation of the Gyrotropic Mode in a Magnetic Vortex by Time-Varying Strain

Iurchuk, V.; Lindner, J.; Faßbender, J.; Kakay, A.

We demonstrate excitation of the gyrotropic mode in a magnetostrictive vortex by time-varying strain. The vortex dynamics is driven by a time-varying voltage applied to the piezoelectric substrate and detected electrically by spin rectification at subthreshold values of rf current. When the frequency of the time-varying strain matches the gyrotropic frequency at given in-plane magnetic field, the strain-induced in-plane magnetic anisotropy leads to a resonant excitation of the gyration dynamics in a magnetic vortex. We show that nonlinear gyrotropic dynamics can be excited already for moderate amplitudes of the time-varying strain.

Keywords: Magnetic vortices; Magnetoelastic effect; Spin dynamics; Micromagnetic modeling; Strain engineering

Permalink: https://www.hzdr.de/publications/Publ-38561
Publ.-Id: 38561


The impact of an ultrasonic standing wave on the sorption behavior of proteins: Investigation of the role of acoustically induced non-spherical bubble oscillations

Keshmiri, A.; Keshavarzi, B.; Eftekhari, M.; Heitkam, S.; Eckert, K.

Hypothesis
Protein molecules adsorb on the air/liquid interface due to possessing a hydrophobic side. A full surface coverage is important in many processes such as in protein harvesting by foam fractionation. The adsorption of proteins in low concentration solutions is preceded by a relatively long time lag known as the induction period. This has been attributed to the formation of an adsorbed monolayer, which relies on the reorientation of the protein molecules. The reduction of the induction period can significantly facilitate the sorption process to reach full protein coverage. For this purpose acoustically induced non-spherical bubble oscillations can aid in the formation of the monolayer and enhance the sorption process.

Experiment
In this study, low frequency ultrasound was used to induce non-spherical oscillations on an air bubble attached to a capillary. Profile analysis tensiometry was deployed to examine the effect of these non-spherical oscillations on the sorption dynamics of different proteins.

Findings
We observed that during the initial stages of adsorption, when the bubble surface is almost empty, non-spherical oscillations occur, which were found to significantly expedite the adsorption process. However, during later stages of the adsorption process, despite the continued presence of several sonication phenomena such as the primary radiation force and acoustic streaming, no change in adsorption behavior of the proteins could be noted. The occurrence, duration, and intensity of the non-spherical bubble oscillations appeared to be the sole contributing factors for the change of the sorption dynamics of proteins.

Keywords: Sorption on bubble; Protein sorption; Surface tension; Ultrasound; Non-spherical bubble oscillations; Microstreaming; Tensiometry; Acoustic bubble

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Permalink: https://www.hzdr.de/publications/Publ-38559
Publ.-Id: 38559


Data publication: Hybrid star phenomenology from the properties of the special point

Gärtlein, C.; Ivanytskyi, O.; Sagun, V.; Blaschke, D.

The columns of files EOS_TOV_etaV_etaD.TXT include central values of the baryonic chemical potential [MeV], pressure [MeV/fm^3], baryonic density [1/fm^3], radius [km] and mass [M_solar] of neutron stars modelled with hybrid quark-hadron equations of state constructed for the vector and diquark couplings etaV and etaD specified in the titles. The corresponding mass-radius diagrams are presented in Figs. 6-8 of the paper. The columns of the file etaV-etaD.TXT include diquark coupling and values of the vector coupling corresponding to the boundaries of the region providing the conditions of having the onset of deconfinement above the saturation density and stability of the quark branch of the mass-radius curve obtained as a solution of the TOV equation (see Fig. 7 of the paper).

Keywords: Quark matter in neutron stars; Quark-gluon plasma; Dense nuclear matter; High-mass pulsars; PSR J0952-0607; PSR J0740+6620; PSR J0030+0451; GW170817

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Permalink: https://www.hzdr.de/publications/Publ-38558
Publ.-Id: 38558


Data publication: Thermodynamics of quark matter with multi-quark clusters

Blaschke, D.; Cierniak, M.; Ivanytskyi, O.; Röpke, G.

Results for phase shifts of pions as function of the pion energy at vanishing chemical potential for different temperatures and results for the densities and entropies of different particle species as a function of the temperature for different values of the scaled baryochemical potential mu/T=0, 1, 2, 3. Total pressure as a function of temperature for vanishing baryochemical potential.

Keywords: multi-quark clusters; Beth-Uhlenbeck approach; Mott dissociation; Polyakov-loop; quark matter thermodynamics

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Permalink: https://www.hzdr.de/publications/Publ-38557
Publ.-Id: 38557


Combining Cisplatin with Different Radiation Qualities—Interpretation of Cytotoxic Effects In Vitro by Isobolographic Analysis

Runge, R.; Reissig, F.; Herzog, N.; Oehme, L.; Brogsitter, C.; Kotzerke, J.

Background: The combination of platinum-containing cytostatic drugs with different
radiation qualities has been studied for years. Despite their massive side effects, these drugs still
belong to the therapeutic portfolio in cancer treatment. To overcome the disadvantages of cisplatin,
our study investigated the cytotoxic effects of combining radionuclides with cisplatin. Methods:
FaDu cells were treated with cisplatin (concentration ≈ 2 μM) and additionally irradiated after
two hours with the alpha-emitter 223Ra, the beta-emitter 188Re as well as external X-rays using
dose ranges of 2–6 Gy. Cell survival was followed by colony formation assays and plotted against
cisplatin concentration and radiation dose. The results were interpreted by isobolograms. Results:
Isobolographic analyses revealed a supra-additive cytotoxic effect for the combination of cisplatin
and 223Ra. A sub-additive effect was observed for the combination of cisplatin and 188Re, whereas
a protective effect was found for the combination with X-rays. Conclusions: The combination of
cisplatin and 223Ra may have the potential to create a successfully working therapy scheme for various
therapy approaches, whereas the combination with 188Re as well as single-dose X-ray treatment
did not lead to a detectable radiosensitizing effect. Thus, the combination with alpha-emitters
might be advantageous and, therefore, should be followed in future studies when combined with
cytostatic drugs.

Keywords: cisplatin; radionuclides; alpha-emitter; combined treatment; isobolograms

Permalink: https://www.hzdr.de/publications/Publ-38556
Publ.-Id: 38556


Uloga biofotonike u razvoju potenciometrijskih biosenzora i trodimenzionalnih mikrobioreaktora

Janićijević, Ž.

Kratko predavanje koje obuhvata moja istraživanja u domenu biosenzora i bioreaktora sa osvrtom na primenu fotonike u navedenim kontekstima. Uz diskusiju o samim temama istraživanja i njihovoj povezanosti sa fotonikom pridružena je i priča o krivudavom naučno-istraživačkom putu do trenutne pozicije.

Predavanje je održano na srpskom jeziku (engl. Serbian).

  • Lecture (others) (Online presentation)
    Dani Fotonike, 26.-27.12.2023, Belgrade, Serbia

Permalink: https://www.hzdr.de/publications/Publ-38553
Publ.-Id: 38553


A Multisensor Hyperspectral Benchmark Dataset For Unmixing of Intimate Mixtures

Koirala, B.; Rasti, B.; Bnoulkacem, Z.; de Lima Ribeiro, A.; Madriz Diaz, Y. C.; Herrmann, E.; Gestels, A.; de Kerf, T.; Lorenz, S.; Fuchs, M.; Janssens, K.; Steenackers, G.; Gloaguen, R.; Scheunders, P.

Optical hyperspectral cameras capture the spectral reflectance of materials. Since many materials behave as heterogeneous intimate mixtures with which each photon interacts differently, the relationship between spectral reflectance and material composition is very complex. Quantitative validation of spectral unmixing algorithms requires high-quality ground truth fractional abundance data, which are very difficult to obtain. In this work, we generated a comprehensive laboratory ground truth dataset of intimately mixed mineral powders. For this, five clay powders (Kaolin, Roof clay, Red clay, mixed clay, and Calcium hydroxide) were mixed homogeneously to prepare 325 samples of 60 binary, 150 ternary, 100 quaternary, and 15 quinary mixtures. Thirteen different hyperspectral sensors have been used to acquire the reflectance spectra of these mixtures in the visible, near, short, mid, and long-wavelength infrared regions (350-15385) nm. Overlaps in wavelength regions due to the operational ranges of each sensor and variations in acquisition conditions resulted in a large amount of spectral variability. Ground truth composition is given by construction, but to verify that the generated samples are sufficiently homogeneous, XRD and XRF elemental analysis is performed. We believe these data will be beneficial for validating advanced methods for nonlinear unmixing and material composition estimation, including studying spectral variability and training supervised unmixing approaches. The datasets can be downloaded from the following link: https://github.com/VisionlabHyperspectral/Multisensor_datasets.

Keywords: hyperspectral; intimate mixtures

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Permalink: https://www.hzdr.de/publications/Publ-38552
Publ.-Id: 38552


An Extensive Multisensor Hyperspectral Benchmark Datasets of Intimate Mixtures of Mineral Powders

Koirala, B.; Rasti, B.; Bnoulkacem, Z.; de Lima Ribeiro, A.; Madriz Diaz, Y. C.; Herrmann, E.; Gestels, A.; de Kerf, T.; Janssens, K.; Steenackers, G.; Gloaguen, R.; Scheunders, P.

Since many materials behave as heterogeneous intimate mixtures with which each photon interacts differently, the relationship between spectral reflectance and material composition is very complex. Quantitative validation of spectral unmixing algorithms requires high-quality ground truth fractional abundance data, which are very difficult to obtain.In this work, we generated a comprehensive hyperspectral dataset of intimate mineral powder mixtures by homogeneously mixing five different clay powders (Kaolin, Roof clay, Red clay, mixed clay, and Calcium hydroxide). In total 325 samples were prepared. Among the 325 samples, 60 mixtures were binary, 150 were ternary, 100 were quaternary, and 15 were quinary. For each mixture (and pure clay powder), reflectance spectra are acquired by 13 different sensors, with a broad wavelength range between the visible and the long-wavelength infrared regions (i.e., between 350 nm and 15385 nm) and with a large variation in sensor types, platforms, and acquisition conditions. We will make this dataset public, to be used by the community for the validation of nonlinear unmixing methodologies (https://github.com/VisionlabUA/Multisensor_datasets)

  • Contribution to proceedings
    IGARSS 2023 - 2023 IEEE International Geoscience and Remote Sensing Symposium, 16.-21.07.2023, Pasadena, USA
    DOI: 10.1109/IGARSS52108.2023.10281467

Permalink: https://www.hzdr.de/publications/Publ-38550
Publ.-Id: 38550


Analyzing 3-phase Foams in Batch Flotation - A joint FWD-HIF Study

Marquardt, T.; Jähnigen, P.; Lappan, T.; Heitkam, S.; Eckert, K.; Hassan, A.; Pereira, L.; Rudolph, M.

Froth flotation, widely used in the processing and recycling of ores and raw materials, employs hydrophobic interactions between bubbles and particles to concentrate valuable materials in an overflowing froth phase. The flotation process, and therefore the quality of separation, is affected by the height of the 3-phase foam, called froth, and thus by the foamability. Within a joint European industry doctorate program between the Institute of Fluid Dynamics, HIF and TU Dresden, we have carried out a collaborative measurement campaign to collect data for modeling flotation subprocesses under varying hydrodynamic and reagent conditions using a laboratory scale flotation cell and a binary pyrite-quartz particle system. Froth phase measurements included the recording of the froth height through the transparent side wall of the flotation cell and imaging of the froth surface as well as foamability measurements of feed and tailing samples by means of dynamic foam analysis and measurement of the liquid fraction of the froth based on its electrical conductivity. Preliminary results show a significant change in froth properties during the flotation process from a particle-laden froth to finer bubbles containing fewer particles. Further data analysis is planned to investigate the influence of frother and collector concentrations as well as air flow rate and impeller tip speed on the foamability and froth height, impacting the recovery and grade of minerals. Such joint froth studies between the Institute of Fluid Dynamics and HIF belong to the sciences cases perspectively to be intensified by CeRI2, one of the HZDR research infrastructure projects.

  • Lecture (Conference)
    HZDR Science Conference, 15.-16.11.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38549
Publ.-Id: 38549


How can Raman spectroscopy support optical detection systems for plastic identification in complex recycling streams?

de Lima Ribeiro, A.; Fuchs, M.; Lorenz, S.; Röder, C.; Schüler, N.; Heitmann, J.; Gloaguen, R.

Binary sorting between ABS and PS polymers is a challenge for the recycling industry, particularly when black pigments are present. We propose the sequential application of a hyperspectral sensor in the short-wave infrared (HSI-SWIR) and a Raman sensor unit (532 nm excitation). HSI-SWIR created maps which allowed for initial spectral and spatial assessment of the material stream and Raman point measurements enabled specific identification of ABS (white and black) and PS. The operationalisation of this sensor network requires advanced solutions for fast data acquisition, processing and classification.

Keywords: polymer; hyperspectral imaging; electronic waste; ABS/PS

  • Open Access Logo Contribution to proceedings
    Sensor and Measurement Science International meeting, 08.-11.05.2023, Nürnberg, Deutschland
    DOI: 10.5162/SMSI2023/D3.3

Permalink: https://www.hzdr.de/publications/Publ-38548
Publ.-Id: 38548


How can agile sensing improve recycling stream characterisation and monitoring for e-waste? - news from the HELIOS lab

Fuchs, M.; Lorenz, S.; Madriz Diaz, Y. C.; Abend, T.; Shaik Fareedh, J.; de Lima Ribeiro, A.; Arbash, E.; Rasti, B.; Beyer, J.; Röder, C.; Schüler, N.; Dornich, K.; Heitmann, J.; Gloaguen, R.

Increasing volumes of electrical and electronic waste (e-waste) demand for innovative and efficient recycling solutions to keep materials in the process/recovery loop. The recovery percentage and quality of resulting recycling products depend fundamentally on the ability to accurately identify the constituents of the e-waste stream. Traditionally, recycling is based on sequential enrichment of target components and reduction of hazardous substances with random sampling from an assumed homogeneous mass. E-waste represents in this context a highly heterogeneous, complex waste composed of a variety of different compounds required to meet the high diversity of functional requirements. Tailored sensor-systems can achieve a successful extraction of several target materials such as precious metals or specific polymers, but reach their limits for many low concentrated, critical raw materials. Hazardous substances and additives (e.g. dark pigments in polymers, poisonous oxides) are difficult to remove from the stream and induce risks of down-cycling, quality loss and reduced acceptance of recycling products.

HELIOS lab is an agile solution for non-invasive sensing applied to complex recycling streams such as e-waste suited for conveyor belt operations. We employ hyperspectral imaging technology for the fast and spatially resolved acquisition of information associated with physical material properties. Multiple cameras allow for combining reflectance information from the visible to midwave-infrared wavelengths range to differentiate material classes. Fast data processing routines then allow for generating first order material maps. Such maps suffice for well defined, relatively homogeneous material streams but not for a precise and accurate sorting and process monitoring. For efficient e-waste recycling, further information is required to enhance the component identification, particularly for certain critical raw materials and complex compounds. We suggest additional validation cycles to refine the initial mapping. Several sensors traditionally used for bulk measurements deliver the solution for detailed point validation. Here, Raman spectroscopy, XRF and LIBS provide the needed complementary data for the identification of a wide range of critical raw materials and hazardous e-waste components. Additionally, our in-house developed laser-induced fluorescence (LiF) system contributes a scanning solution for rare-earth element mapping. However, those validation sensors are very sensitive to signal integration times, power and focus distances. We showcase two examples for a combination of Raman spectroscopy and LiF with hyperspectral imaging technology to extract meaningful information from typical e-waste streams such as printed circuit boards and electrolysers in a conveyor belt setting. We discuss the main challenges and give an outlook on additional development needs that we will address in our HELIOS lab in the frame of the EU funded projects RAMSES and inSPECtor (EIT RawMaterials), and the BMBF funded projects High-speed imaging, InfraDatRec, Digisort and H2Giga.

Permalink: https://www.hzdr.de/publications/Publ-38547
Publ.-Id: 38547


Potential of optical sensors for polymer type identification in e- waste recycling streams

de Lima Ribeiro, A.; Fuchs, M.; Röder, C.; Schüler, N.; Lorenz, S.; Sheng, Y. X.; Heitmann, J.; Dornich, K.; Gloaguen, R.

Plastics are major components of waste from electrical and electronic equipment (WEEE, or e- waste) accounting for up to 25% of annual e-waste production. The composition of such plastics varies greatly according to their original function in the electrical and electronic equipment, and may include additives such as dark pigments and brominated compounds. With WEEE becoming the fastest growing waste stream in recent years, the recycling of polymers became a keystone for waste management and closing material loops. Closing the loops in material life cycles requires that type-pure plastics are obtained at the end of the recycling chain. Accordingly, the identification of polymers prior to their sorting in recycling lines is a fundamental prerequisite.
Here, we explore how an innovative combination of optical sensors can aid the identification of plastics in the plastic recycling environment in order to increase recovery rates and quality of recyclates.
We have selected 23 different polymer samples, representative of the plastic types commonly found in e-waste. We investigated the sequential use of high-speed hyperspectral imaging (HSI) and Raman spectroscopic sensors for digitalization of the waste stream and identification of polymer composition. HSI-reflectance sensors in the short-wave infrared (HSI-SWIR, Specim AisaFenix, 970 - 2500 nm) domain acquired simultaneously spatial and spectral information, allowing for mapping and initial identification of certain transparent and light-coloured polymers (PE, PP, PET, and PC). Raman measurements, collected at specific points and with integration times < 2 seconds, allowed for specific identification of all polymer samples, including black plastics. The use of both sensor technologies on conveyor belts has the potential to fully characterise the WEEE plastics stream, generating identification signals serving as input for sorting machines or simulation models. The combination of latest high-speed sensors and data processing opens many further fields of material stream characterisation and monitoring, which come with high data acquisition rates and volumes.
Consequently, a smart selection of sensors along with a tailored and learning data processing will

Keywords: E-waste; WEEE; recycling; sensors; polymers

Permalink: https://www.hzdr.de/publications/Publ-38546
Publ.-Id: 38546


ParticleSeg3D: A scalable out-of-the-box deep learning segmentation solution for individual particle characterization from micro CT images in mineral processing and recycling

Gotkowski, K.; Gupta, S.; Da Assuncao Godinho, J. R.; Tochtrop, C.; Maier-Hein, K. H.; Isensee, F.

Minerals, metals, and plastics are indispensable for a modern society. Yet, their limited supply necessitates optimized extraction and recycling processes, which must be meticulously adapted to the material properties. Current imaging approaches perform material analysis on crushed particles imaged with computed tomography (CT) using segmentation and mass characterization. However, their inability to reliably separate touching particles and need to annotate and retrain on new images, leaves untapped potential. By contrast, particle-level characterization unlocks better understanding of particle properties such as mass, appearance and structure. Here, we propose ParticleSeg3D, an instance segmentation method for particle-level characterization with strongly varying properties from CT images. Our approach is based on the powerful nnU-Net, introduces a particle size normalization, employs a border-core representation, and is trained with a diverse dataset. We demonstrate that ParticleSeg3D can be applied out-of-the-box to a large variety of materials without retraining, including materials and properties not present during training.

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Permalink: https://www.hzdr.de/publications/Publ-38544
Publ.-Id: 38544


Strong Exciton-Phonon Coupling as a Fingerprint of Magnetic Ordering in van der Waals Layered CrSBr

Lin, K.; Sun, X.; Dirnberger, F.; Li, Y.; Qu, J.; Wen, P.; Sofer, Z.; Söll, A.; Winnerl, S.; Helm, M.; Zhou, S.; Dan, Y.; Prucnal, S.

The layered, air-stable van der Waals antiferromagnetic compound CrSBr exhibits pronounced coupling between its optical, electronic, and magnetic properties. As an example, exciton dynamics can be significantly influenced by lattice vibrations through exciton-phonon coupling. Using low-temperature photoluminescence spectroscopy, we demonstrate the effective coupling between excitons and phonons in nanometer-thick CrSBr. By careful analysis, we identify that the satellite peaks predominantly arise from the interaction between the exciton and an optical phonon with a frequency of 118 cm-1 (~14.6 meV) due to the out-of-plane vibration of Br atoms. Power-dependent and temperature-dependent photoluminescence measurements support exciton-phonon coupling and indicate a coupling between magnetic and optical properties, suggesting the possibility of carrier localization in the material. The presence of strong coupling between the exciton and the lattice may have important implications for the design of light-matter interactions in magnetic semiconductors and provide insights into the exciton dynamics in CrSBr. This highlights the potential for exploiting exciton-phonon coupling to control the optical properties of layered antiferromagnetic materials.

Keywords: CrSBr; antiferromagnetic semiconductor; van der Waals materials; exciton-phonon coupling; exciton-photon coupling

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Permalink: https://www.hzdr.de/publications/Publ-38541
Publ.-Id: 38541


Data publication: Electron-phonon coupling in transition metals beyond Wang's approximation

Akhmetov, F.; Milov, I.; Makhotkin, I. A.; Ackermann, M.; Vorberger, J.

All input files and scripts to setup calculations in abinit. Also all output files that were used to generate the figures and tables.

Keywords: plasma; warm dense matter; laser matter interaction; relaxation; DFT; energy transfer; Eliashberg; linear response; Boltzmann

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Permalink: https://www.hzdr.de/publications/Publ-38537
Publ.-Id: 38537


Data publication: An LSC approach for tritium determination in gaseous mixtures optimized with respect to handling, reaction parameters and miniaturization towards microfluidic analysis

Becker, A.; Lippold, H.; Bäcker, J. P.; Belder, D.; Fischer, C.

The data consists of LSC measurements of HTO for different sample volumes as well as HTO and scinitllation cocktail concentrations prepared using a microfluidic chip.

Keywords: tritium; hydrogen isotopes; microfluidics; gas analysis; liquid scintillation counting

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Permalink: https://www.hzdr.de/publications/Publ-38536
Publ.-Id: 38536


Electron-phonon coupling in transition metals beyond Wang’s approximation

Akhmetov, F.; Milov, I.; Makhotkin, I. A.; Ackermann, M.; Vorberger, J.

The electron-phonon coupling is the primary mechanism responsible for material relaxation after ultrafast laser irradiation. However, it remains an elusive variable that is extremely challenging to extract experimentally, especially at high electron temperatures. Various previous theoretical approaches to determine electron-phonon coupling demonstrated large degree of inconsistency. In this paper, we present a first-principles framework for simulating the electron-phonon coupling parameter based on the electron-phonon spectral function, going beyond the approximation introduced by Wang et al. [Phys. Rev. B 50, 8016 (1994)]. Our simulations provide electron-temperature-dependent electron-phonon coupling values for transition metals Ru, Pd, and Au. Our findings reveal significant differences between the values obtained from the exact and approximated spectral functions, thus highlighting the limitations of Wang’s approximation at elevated electron temperatures.

Keywords: plasma; warm dense matter; laser matter interaction; relaxation; DFT; energy transfer; Eliashberg; linear response; Boltzmann

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Permalink: https://www.hzdr.de/publications/Publ-38532
Publ.-Id: 38532


Ore mineralogy and metal deportment of Fe-Ni-Co laterite deposits from Sebuku Island, SE Kalimantan, Indonesia

Giorno, M. A.; Kontonikas-Charos, A.; Ernowo, E.; Krisnanto, Y.; Frenzel, M.

Indonesian laterite deposits are a major source of Ni and Co. Here, we present new geological data on the Sebuku laterites (SE Kalimantan, Indonesia), with a resource of ~390 Mt at 42.5 wt.% Fe, 0.9 wt.% Ni, and 0.15 wt.% Co. The deposits are mostly limonitic, oxide-dominated Fe-Ni-Co-rich horizons, which formed by weathering of Jurassic-Cretaceous ophiolitic units. Although the Fe ore has been mined since 2006, little mineralogical and geochemical data are available, which would allow optimizing beneficiation and recovery of Ni and Co.

Typical laterite profiles at Sebuku consist of: 1) weathered bedrock composed of serpentinized dunites and harzburgites overlain by 2) a 0.2-7 m-thick saprolite zone, 3) a 2-8.5 m-thick yellow limonite zone, and 4) a 1-3.5 m-thick red-limonite zone.

Preliminary XRF, XRD, and mineral liberation analysis (MLA) data show a decrease in Mg and Si and an increase in Fe moving upwards through the laterite profile, corresponding to a transition from silicate- to oxide-rich mineralogy. Oxides and (oxy)-hydroxides comprise goethite, maghemite, hematite, magnetite, chromium spinel, gibbsite/bayerite, and various Mn-minerals, whereas silicates consist of serpentine, chlorite, talc, quartz, pyroxene, olivine, and clay minerals. Ni is hosted by various minerals, which include goethite, Mn-oxides, serpentine, and clays, whereas Co is mainly hosted by Mn-oxides.

Mineral chemical analyses (EPMA) are planned to further understand critical metal variability and distribution within the host minerals and throughout the deposits. Our ultimate goal is to characterize and quantify the distribution of Ni and Co in order to develop more efficient beneficiation processes.

  • Contribution to proceedings
    GeoBerlin 2023 - Geosciences Beyond Boundaries - Research, Society, Future, 03.-07.09.2023, Berlin, Germany
    DOI: 10.48380/1z7q-mk41

Permalink: https://www.hzdr.de/publications/Publ-38528
Publ.-Id: 38528


On-water surface synthesis of electronically coupled 2D polyimide-MoS2 van der Waals heterostructure

Prasoon, A.; Yang, H.; Hambsch, M.; Nguyen, N. N.; Chung, S.; Muller, A.; Wang, Z.; Lan, T.; Fontaine, P.; Kühne, T. D.-S.; Cho, K.; Nia, A. S.; Mannsfeld, S. C. B.; Dong, R.; Feng, X.

The water surface provides a highly effective platform for the synthesis of two-dimensional polymers (2DP). In this study, we present an efficient on-water surface synthesis of crystalline monolayer 2D polyimide (2DPI) through the imidization reaction between tetra (4-aminophenyl) porphyrin (M1) and perylenetracarboxylic dianhydride (M2), resulting in excellent stability and coverage over a large area (tens of cm2). We further fabricate innovative organic-inorganic hybrid van der Waals heterostructures (vdWHs) by combining with exfoliated few-layer molybdenum sulfide (MoS2). High-resolution transmission electron microscopy (HRTEM) reveals face-to-face stacking between MoS2 and 2DPI within the vdWH. This stacking configuration facilitates remarkable charge transfer and noticeable n-type doping effects from monolayer 2DPI to MoS2, as corroborated by Raman spectroscopy, photoluminescence measurements, and field-effect transistor (FET) characterizations. Notably, the 2DPI-MoS2 vdWH exhibits an impressive electron mobility of 50 cm2/V·s, signifying a substantial improvement over pristine MoS2 (8 cm2/V·s). This study unveils the immense potential of integrating 2D polymers to enhance semiconductor device functionality through tailored vdWHs, thereby opening up exciting new avenues for exploring unique interfacial physical phenomena.

Keywords: On-water surface synthesis; MoS2; van der Waals heterostructure

Permalink: https://www.hzdr.de/publications/Publ-38527
Publ.-Id: 38527


Hydrogen addition in methane-oxygen laminar inverse diffusion flames: A study focused on free radical chemiluminescence and soot formation

Runmin, W.; Xudong, S.; Juntao, W.; Yonghui, B.; Jiaofei, W.; Peng, L.; Tianbiao, H.; Parvez, A. M.; Guangsuo, Y.

This study investigates the impact of H2 addition on soot formation in inverse diffusion flame (IDF) and explores the underlying mechanism of flame structure on soot formation. Experimental measurements and simulation kinetic calculations were performed to explore the influence of free radical (OH*/CH*/C2*/CO2*) chemiluminescence on soot formation mechanism. The investigation ultimately determines the relationship between free radical chemiluminescence and soot formation. The findings reveal that similar to the simulation results, the peak soot volume fraction (SVF) is reduced by approximately 60 % when the hydrogenation increases to 40 %, and the initial soot production position moves downstream of the flame. The free-radical chemiluminescence distribution is mainly concentrated at the burner exit, where the increase in hydrogen concentration leads to a decrease in CH* and C2* and an increase in OH* content in the flame. The blue region on the fuel side is consistent with the peak CH* and C2* emission region. In the soot formation, the chemiluminescence signal of free radicals is suppressed, indicating that soot formation and free radical chemiluminescence are antithetical. The results of the component yields indicate that soot formation and chemiluminescence are fueled by gas phase components (CH3, C2H3, C2H2, etc.) and there are generated in opposite pathways, which supports the above statement. Furthermore, the increase of hydrogen content inhibits the production of C2H and CH2, resulting in the decrease of C2*, CH* and CO2* radical chemiluminescence by 77.0 %, 75.1 % and 81.2 %, respectively. The decrease of soot concentration is primarily due to the increase of H2, which hinders the formation of C3H3 and C4H5-2.

Keywords: H2 addition; Chemiluminescence; Soot; Inverse diffusion flame

Permalink: https://www.hzdr.de/publications/Publ-38526
Publ.-Id: 38526


Impedance Cytometry as a Tool for Prognostic Analysis in Prostate Cancer Treated with Radiotherapy

Markl, A. M.; Sandoval Bojorquez, D. I.; Makarov, D.; Baraban, L.; Dubrovska, A.

Introduction:

Metastatic prostate cancer (PCa) is challenging to treat due to a limited understanding of the mechanisms driving metastasis development and the absence of reliable prognostic markers . Liquid biopsy analysis is a clinically approved minimal blood test based on the enumeration of circulating tumor cells (CTC) and used to assess early patient prognosis and response to the treatment, including radiotherapy. Due to the high CTC heterogeneity and plasticity, the currently approved tests need further improvement in terms of accuracy and reliability . Recent studies suggest that the electro-physical properties of cancer cells, such as conductivity (σ) and permittivity (ε), may be utilized as potential prognostic markers. Despite the high clinical demand, a method for distinguishing primary tumor and metastatic PCa cells based on their electrical properties has yet to be reported.
In this study, we will employ nano- and microfabrication techniques to develop an impedance cytometry approach in conjunction with various biological models to train our system. Thanks to the collaboration between biological and engineering research groups, we will have the opportunity to test advanced biological models, including cell culture (in vitro), synergetic mouse models, and patient samples. The increased complexity of these models has the potential to significantly improve the training process of machine learning data analysis.
Materials and methods:
To create the electronic sensing structures, we are utilizing both electron beam lithography (EBL) and ultraviolet (UV) lithography. The interdigitated sensing structures are formed through metal deposition. Additionally, we employ soft lithography to imprint cytometrical microchannels into polydimethylsiloxane (PDMS).
Results:
We are currently developing a detection system that will be used to assess the electro-physical properties of primary tumors, metastases, and CTCs.
Outlook:
In the future, this impedance cytometry system may be used to develop reliable prognostic tests based on the detection and enumeration of CTCs with metastatic properties in patients’ samples. Additionally, analyzing circulating immune cell populations during radiotherapy may help characterize the immune status of patients and predict tumor immune evasion.
Conclusions:
The development of a label-free, sensitive, and reliable non-invasive diagnostic test based on the electric properties of tumor cells is expected to improve the sensitivity and reproducibility of traditional liquid biopsy-based diagnostic approaches and make them more time and labor-efficient.

  • Poster
    NanoBio&Med 2023, 21.-23.11.2023, Barcelona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-38525
Publ.-Id: 38525


Effect of annealing temperature on the structure and optical properties of ZnO thin films

Nimitha, K. V.; Maya, P. N.; Mukherjee, S.; Liedke, M. O.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.; Benoy, M. D.

The effect of annealing temperature on the microstructure, defects and optical properties of ZnO thin films are investigated using sol–gel based spin coating method for a range of annealing temperatures from 200 °C to 500 °C. The correlation among the microstructure, defects, impurity content and the optical band gap of films of thickness about 10–12 nm is elucidated. The particle size increases and the optical band gap reduces with the annealing temperature. At 200 ∘C, amorphous films were formed with particle size less than 10 nm with an optical band gap of about 3.41 eV. As the temperature increases the grain size increases and the defect, impurity content as well as the optical band gap reduces. This could be due to the reduction in the lattice strain. For an average grain size of about 35 nm and above, the band gap asymptotically approaches the theoretical value of ZnO (3.37 eV). The photoluminescence (PL) spectra show a systematic red-shift in the excitonic levels corresponding to the variation in the optical band-gap. The defect emission from Zn-vacancies is observed in the PL spectra and are further supported by the positron annihilation measurements.

Keywords: film growth; band gap; refractive index; refractive index; positron annihilation spectroscopy; exciton emission

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  • Secondary publication expected from 21.12.2024

Permalink: https://www.hzdr.de/publications/Publ-38524
Publ.-Id: 38524


FineFuture: Wird die Zukunft wirklich fein? Europäisches H2020-Projekt FineFuture erfolgreich abgeschlossen.

Dirlich, S.

Das europäische H2020-Projekt FineFuture mit einem Konsortium von 16 Partnern aus ganz Europa wurde erfolgreich abgeschlossen. Es konnten große Fortschritte in der Flotationsforschung erzielt werden, die zum einen das grundlegende Verständnis der zugrundeliegenden Prozesse betreffen, zum anderen die Umsetzung dieser Erkenntnisse in Anlagen im Pilot- und sogar Industriemaßstab.

Keywords: flotation; ultrafine particles; mineral processing; froth flotation; industrial scale; pilot scale; critical raw materials; crm

  • Open Access Logo Acamonta - Zeitschrift für Freunde und Förderer der Technischen Universität Bergakademie Freiberg 30(2023), 20-22
    ISSN: 2193-309X

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Permalink: https://www.hzdr.de/publications/Publ-38523
Publ.-Id: 38523


Bubble dynamics and H2 bubble motion reversals during water electrolysis

Bashkatov, A.; Babich, A.; Yang, X.; Mutschke, G.; Eckert, K.

The dynamics of hydrogen bubbles produced by water electrolysis in an acidic electrolyte is studied using electrochemical and optical methods. A defined cyclic modulation of the electric potential is applied at a microelectrode to produce pairs of interacting H2 bubbles in a controlled manner. Three scenarios of interactions are identified and studied systematically. The most prominent one consists of a sudden reversal in the motion of the first detached bubble, its return to the electrode, and finally its coalescence with the second bubble. Attested by Toepler’s schlieren technique, an explanation of contactless motion reversal is provided by the competition between buoyancy and thermocapillary effects.

Keywords: hydrogen; bubbles; multiphase flow; water electrolysis

  • Invited lecture (Conferences)
    Bubbles & Drops 2023, 12.-16.06.2023, Polen, Lublin

Permalink: https://www.hzdr.de/publications/Publ-38521
Publ.-Id: 38521


Turbulent Multiphase Jets - a contribution to honor Prof. Graeme Jameson

Kamble, V. V.; Rzehak, R.; Zürner, T.; Eckert, K.

Turbulent multiphase jets appear in machines used for enhanced flotation processes like the Concorde Cell and the REFLUX Flotation Cell. Likewise, flow structures generated in conventional mechanically stirred rotor-stator cells bear strong resemblance to jets. In contrast to their single-phase counterparts however, they have not been extensively studied yet. In the invited talk we present experimental and numerical methods that are available for this purpose, specifically shadowgraphy and particle image velocimetry on the experimental side and the Eulerian multi-fluid framework for multiphase CFD simulations. The corresponding numerical approach pursued at HZDR is presented. First preliminary results of both bubbly and particulate two-phase jets as well a three-phase jets are presented.

Keywords: multiphase flow; turbulence; flotation; CFD; Concorde-like cell

  • Invited lecture (Conferences)
    INTERNATIONAL FLOTATION SYMPOSIUM Celebrating Science and Engineering Innovation in honor Prof. Graeme Jameson, 10.-14.07.2023, Newcastle, Austalien

Permalink: https://www.hzdr.de/publications/Publ-38520
Publ.-Id: 38520


New insights on the formation of the Jingchong Cu-Co-Pb-Zn deposit, South China: Evidence from sphalerite mineralogy and muscovite 40Ar-39Ar dating

Peng, E.; Kolb, J.; Walter, B. F.; Frenzel, M.; Patten, C. G. C.; Xu, D.; Wang, Y.; Gan, J.; Beranoaguirre, A.; Wang, Z.

The northeastern Hunan Province hosts numerous hydrothermal Pb-Zn(-Cu-Co) polymetallic deposits. As a representative example, the Jingchong Cu-Co-Pb-Zn deposit is characterized by the lower Cu-Co and upper Pb-Zn mineralization, whereas little is known about Pb-Zn mineralization. In this study, three generations of sphalerite were identified based on their textural and geochemical differences. The Sph-I exhibits the oscillatory zoning that consists of reddish-brown Sph-Ia (poor in chalcopyrite inclusion) alternating with dark Sph-Ib with zoned chalcopyrite inclusion. Sph-II is composed of honey-brown Sph-IIa (abundant chalcopyrite droplets) and white clean Sph-IIb (rare chalcopyrite inclusion). The black Sph-III is characterized by nano- to submicron-sized chalcopyrite inclusions with typical “dusting” or “watermelon” texture and crosscuts all other sphalerite generations in veinlets. The electron microprobe and laser ablation inductively coupled plasma mass spectrometry show that Sph-I has higher Fe and Mn contents, but lower Cd, Cu and Ag contents than Sph-II and Sph-III. Sphalerite geothermometry yields temperatures of 334–346 (±58)°C for Sph-I, 254–289 (±60)°C for Sph-II and 286 (±55) °C for Sph-III. The sulfur fugacity ranges from logfS2 values of −9.03 to −8.26 for Sph-I to −11.77 to −10.63 for Sph-II and −10.82 for Sph-III. The combined textural features and chemical compositions indicate that the self-organized mechanism forms Sph-I, and that the coupled dissolution and precipitation reactions triggered by the influx of Cu-elevated fluids are responsible for the formation of Sph-II and Sph-III. The associated pyrite and pyrrhotite inclusions in sphalerite are produced by the exsolution mechanism, while chalcopyrite inclusions are formed by co-precipitation due to local supersaturation at the interface of sphalerite with fluid. The 40Ar-39Ar dating of muscovite in the Jingchong deposit yields a mineralizing age of ca. 121.1 ± 2 Ma, consistent with the ca. 130–120 Ma Pb-Zn mineralizing events in the northeastern Hunan Province. The sulfur isotopic values (−3.0 to +3.5‰) of the Pb-Zn ores are similar to that of Cu-Co ores, indicating a magmatic sulfur origin. Together with the trace element affinity of sphalerite with magmatic-hydrothermal origin, it was proposed that the Jingchong Pb-Zn and Cu-Co mineralization were formed in the same magmatic-hydrothermal system. The placement of Pb-Zn orebodies at the upward zoning of Cu-Co orebodies could be attributed to the higher solubilities of Pb and Zn chloride complexes in hydrothermal fluids, relative to Cu chloride complex.

Keywords: Sphalerite; 40Ar-39Ar dating; Jingchong polymetallic deposit; Jiangnan Orogen

Permalink: https://www.hzdr.de/publications/Publ-38518
Publ.-Id: 38518


Uncertainty and value: Optimising geometallurgical performance along the mining value chain

Ortiz, J. M.; Avalos, S.; Riquelme, A. I.; Leuangthong, O.; Madani, N.; Frenzel, M.

To maximise the value of a mining operation and minimise its environmental and social impacts, all processes - from the ore deposit to the final product and waste streams - should be optimised together. However, mining and metallurgical processes are inherently variable and uncertain due to the natural heterogeneity of ore deposits and the limited information and incomplete models available on ore behaviour throughout the process chain. Propagating these effects to geometallurgical models is important because they are used to make decisions with potentially large environmental and economic impacts. In this paper, we describe the need for geometallurgical optimisation routines to account for the effects of uncertainties, and the tools needed to manage them, by summarising the routines that already exist and those that are still missing.

Keywords: geometallurgy; raw materials value chain; stochastic modelling; optimisation; uncertainty

Permalink: https://www.hzdr.de/publications/Publ-38516
Publ.-Id: 38516


Making sense of mineral trace-element data - How to avoid common pitfalls in statistical analysis and interpretation

Frenzel, M.

Recent years have seen a sharp increase in the generation and use of mineral trace-element data in geological research. This is largely due to the advent of rapid and affordable laser-ablation inductively coupled plasma mass-spectrometry (LA-ICP-MS). However, while much new data is being generated and published, relatively little work has been done to develop appropriate methods for its statistical analysis and interpretation, and indeed, experimental design. In fact, several characteristic features of the data require careful consideration during evaluation and interpretation to avoid biased results. In particular, the commonly hierarchical structure of mineral trace-element data and its compositional nature must be taken into account to generate meaningful and robust results. Unfortunately, these features are not appropriately considered in most current studies. This review provides a general overview of the special features of mineral trace-element data and their consequences for statistical analysis and interpretation, as well as study design. Specifically, it highlights the need for 1) the use of log- or log-ratio-transformations for statistical analysis, 2) careful preparation of the raw data prior to analysis, including an appropriate treatment of missing values, and 3) the application of statistical methods suited to hierarchical data structures. These points, as well as the consequences of neglecting them, are illustrated with relevant examples from ore geology. However, the general principles described in this review also apply to mineral trace-element datasets collected in other fields of the geosciences, as well as other fields dealing with compositional data.

Keywords: Trace-element signatures; Mineral chemistry; Mineral compositions; LA-ICP-MS; Microanalytical data; Compositional data

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Permalink: https://www.hzdr.de/publications/Publ-38515
Publ.-Id: 38515


Deformation Mechanisms, Microstructures, and Seismic Anisotropy of Wadsleyite in the Earth's Transition Zone

Ledoux, E. E.; Saki, M.; Gay, J. P.; Krug, M.; Castelnau, O.; Zhou, W.-Y.; Zhang, J. S.; Chantel, J.; Hilairet, N.; Bykov, M.; Bykova, E.; Aprilis, G.; Svitlyk, V.; Garbarino, G.; Sanchez-Valle, C.; Thomas, C.; Speziale, S.; Merkel, S.

Wadsleyite is the dominant mineral of the upper portion of the Earth's mantle transition zone (MTZ). As such, understanding plastic deformation of wadsleyite is relevant for the interpretation of observations of seismic signals from this region in terms of mantle flow. Despite its relevance, however, the deformation mechanisms of wadsleyite and their effects on microstructures and anisotropy are still poorly understood. Here, we present the results of new deformation experiments on polycrystalline wadsleyite at temperatures of 1400–1770 K and pressures between 12.3 and 20.3 GPa in the laser-heated diamond anvil cell. We rely on multigrain X-ray crystallography to follow the evolution of individual grain orientations and extract lattice preferred orientations at the sample scale at different steps of the experiments. A comparison of experimental results of our work and the literature with polycrystal plasticity simulations, indicates that 〈111〉{101} is the most active slip system of dislocations in wadsleyite at all investigated conditions. Secondary slip systems such as 001](010), [100, and [100]{0kl}, however, play a critical role in the resulting microstructures and their activity depends on both temperature and water content, from which we extract an updated deformation map of wadsleyite at MTZ conditions. Lastly, we propose several seismic anisotropy models of the upper part of the MTZ, depending on temperature, geophysical context, and levels of hydration that will be useful for the interpretation of seismic signals from the MTZ in terms of mantle flow and water content.

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Permalink: https://www.hzdr.de/publications/Publ-38514
Publ.-Id: 38514


In-situ study of microstructures induced by the olivine to wadsleyite transformation at conditions of the 410 km depth discontinuity

Ledoux, E.; Krug, M.; Gay, J.; Chantel, J.; Hilairet, N.; Bykov, M.; Bykova, E.; Aprilis, G.; Svitlyk, V.; Garbarino, G.; Guignot, N.; Sanchez-Valle, C.; Speziale, S.; Merkel, S.

The olivine-wadsleyite transformation is believed to occur at depths of about 410 km in the Earth, producing a major seismic discontinuity in this region of the Earth’s mantle. The mechanism of this phase transition controls the microstructures of the newly nucleated wadsleyite, the major phase of the upper part of the mantle transition zone, and thus impacts seismic observations in the region. Here, we study the microstructures produced by the olivine-wadsleyite transformation using in situ laboratory experiments at pressures and temperatures relevant for the mantle transition zone. We transform pure olivine samples in laser-heated diamond-anvil cells at pressures ranging from 12.3 to 20.2 GPa and temperatures of 1400–1730 K. At different steps of the transformation we measure the orientation and size distribution of individual sample grains using multigrain crystallography at synchrotron radiation sources. We find that the olivine to wadsleyite transformation is incoherent at the conditions of the mantle transition zone, and is probably dominated by nucleation of wadsleyite at grain boundaries of the parent olivine. Thus, we expect that seismic anisotropy near 410 km would drop significantly due to the randomized lattice preferred orientation of newly nucleated wadsleyite induced by the incoherent transformation.

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Permalink: https://www.hzdr.de/publications/Publ-38513
Publ.-Id: 38513


Masking Hyperspectral Imaging Data with Pretrained Models

Arbash, E.; de Lima Ribeiro, A.; Thiele, S. T.; Gnann, N.; Rasti, B.; Fuchs, M.; Ghamisi, P.; Gloaguen, R.

The presence of undesired background areas associated with potential noise and unknown spectral characteristics degrades the performance of hyperspectral data processing. Masking out unwanted regions is key to addressing this issue. Processing only regions of interest yields notable improvements in terms of computational costs, required memory, and overall performance. The proposed processing pipeline encompasses two fundamental parts: regions of interest mask generation, followed by the application of hyperspectral data processing techniques solely on the newly masked hyperspectral cube. The novelty of our work lies in the methodology adopted for the preliminary image segmentation. We employ the Segment Anything Model (SAM) to extract all objects within the dataset, and subsequently refine the segments with a zero-shot Grounding Dino object detector, followed by intersection and exclusion filtering steps, without the need for fine-tuning or retraining. To illustrate the efficacy of the masking procedure, the proposed method is deployed on three challenging applications scenarios that demand accurate masking; shredded plastics characterization, drill core scanning, and litter monitoring. The numerical evaluation of the proposed masking method on the three applications is provided along with the used hyperparameters. The scripts for the method will be available at this https URL.

Keywords: Hyperspectral Imaging; Classification; Masking; SAM; Grounding Dino

  • Open Access Logo Contribution to proceedings
    Workshop on Hyperspectral Image and Signal Processing, 31.10.-02.11.2023, Athens, Greece
    DOI: 10.48550/arXiv.2311.03053

Permalink: https://www.hzdr.de/publications/Publ-38512
Publ.-Id: 38512


Hydrophobicity-based Grading of Industrial Composite Insulators Images using Cross Attention Vision Transformer with Knowledge Distillation

Das, S.; Chatterjee, S.; Basu, M.

The hydrophobic property of composite insulators is a crucial attribute that prevents the accumulation of significant water content on the surface and ensures smooth operation and prevention of power line surges. However, since the weathering effect gradually reduces the hydrophobicity, periodic monitoring is necessary to ensure the smooth operation of the powerline. Efficient machine learning-based analysis of the composite insulator (CI) images collected by the spray method can potentially achieve very high efficacy. However, inconsistency in the shape and size of droplets, the intricate pattern of the droplets, the lack of color variation of the images, etc. pose a challenge to the prevalent computer vision techniques for categorizing the CIs. This treatise explored a novel, efficient deep learning paradigm, termed cross attention vision transformer (CA-ViT) for grading the CI images. The CA-ViT uses both small and large patches to blend spatial features corresponding to a different scale. The network uses a token fusion module to effectively combine the tokens obtained from small and large patches and understand the visual pattern, and characterize droplets of different shapes and sizes by exchanging cross-attentions, which demonstrates its ability to precisely detect small and large droplets, and accurately classify the droplet images. Further, the work also introduces a knowledge distillation strategy to reduce the computational run time of the model. Exhaustive experimental results have confirmed that our proposed work surpasses state-of-the-art methods.

Keywords: Hydrophobicity

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Permalink: https://www.hzdr.de/publications/Publ-38506
Publ.-Id: 38506


Characterization of organic glass scintillator bars and their potential for a hybrid neutron/gamma ray imaging system for proton radiotherapy range verification

Turko, J. A. B.; Junghans, A.; Meric, I.; Müller, S.; Pausch, G.; Ratliff, H. N.; Römer, K.; Schellhammer, S.; Setterdahl, S. M.; Urlass, S.; Wagner, A.; Kögler, T.

For accurate and simultaneous imaging of fast neutrons (FNs) and prompt gamma rays (PGs) produced during proton therapy, the selection of a highly performant detector material is crucial. In this work, a promising candidate material known as organic glass scintillator (OGS) is characterized for this task. To this end, a precisely-timed source of neutrons and Bremsstrahlung radiation produced by the n ELBE facility was used to study the light output and neutron/gamma ray pulse shape discrimination (PSD) properties of a 1 × 1 × 20 cm 3 OGS bar with double-sided readout. Furthermore, the energy, timing, and depth-of-interaction (DOI) resolutions of 1 × 1 × 10 cm 3 and 1 × 1 × 20 cm 3 OGS and EJ-200 bars were characterized with radioactive sources. For electron-equivalent energies above 0.5 MeVee, OGS was found to have excellent PSD capabilities (figure-of-merit above 1.27), energy resolution (below 12%), coincident time resolution (below 500 ps), and DOI resolution (below 10 mm). This work establishes the data analysis methods required for hybrid FN/PG imaging using OGS, and demonstrates the materials' excellent performance for this application.

Keywords: Gamma detectors; Instrumentation for hadron therapy; Neutron detectors; Scintillators and scintillating fibres and light guides

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Permalink: https://www.hzdr.de/publications/Publ-38505
Publ.-Id: 38505


Adhesion evaluation and interface characterization of 3D printed concrete for automatic repair

Yaxin, T.; Yi, Z.; Xiaoyun, W.; Da Assuncao Godinho, J. R.; Geert, D. S.; Kim, V. T.

3D concrete printing can be used for automatic repair, aiming at increasing efficiency and reducing the use of
manpower, as compared to conventional manual repair. Ensuring strong adhesion of the 3D printed materials
and characterizing the interface is crucial for the success of this approach. To this end, we first evaluated the
adhesion performance of 3D printed concrete based on a low-carbon binder, i.e., calcium sulfoaluminate (CSA)
cement. CSA cement pastes with different re-dispersible polymer powder substitution rates were used as coating
before 3D printing. We used two approaches, X-ray computed tomography (CT) and scanning electron micro-
scopy (SEM), to characterize the interface region. Results indicate that the yield stress of the 3D printing material
and the coating material plays an important role in the adhesion in both the fresh and hardened state. Moreover,
the limited adhesion at the overlay interface can be due to the limited contact at the centimeter and micro scale,
as reflected by CT and SEM, respectively. Applying a coating can fill the air voids at the interface, while the
placement of a coating may not improve the bond strength and can even have a negative impact due to the
limited liquid medium at the interface.

Keywords: Adhesion; 3D concrete printing; Automatic repair; nterface characterization

Permalink: https://www.hzdr.de/publications/Publ-38503
Publ.-Id: 38503


Applying particle-based separation modelling on 3D particle data to better quantify the influence of particle size and shape in the recovery of valuable elements

Guimaraes Da Silva Tochtrop, C.

After the successful application of 2D particle characterisation in the raw materials sector, the transition to 3D particle characterisation methods holds the potential of further improving the efficiency of the sector. The main reason to characterise particles in 3D is to obtain reliable information about their shape and size. Yet, given the complexity of particles in the raw materials field, particle composition should be quantified in the same detail offered by 2D-based techniques. This aspect has only recently started to become a reality for 3D X-ray computed tomography measurements, given innovations dedicated to the raw materials sector. Currently, Xray computed tomography analysis offers the potential to characterise particle microstructures in 3D – essential information for a better understanding of mineral separation processes. Hence, it has a considerable impact on improving the efficiency of the mining industry and potentially reducing technical as well as environmental risks. In this study, the flotation of a sulphide-rich ore is investigated with the goal of quantifying, for individual particles, the relation between their microstructural properties, their behaviour in the process, and the flotation cell hydrodynamic conditions. A combination of 2D mineral liberation analysis and 3D X-ray computed tomography is used for respectively characterising fine and coarse particles. This particle data is then applied to model the process behaviour of individual particles in the flotation experiments. Factors such as particle size, shape, liberation, and association are taken into account. Given the more detailed description of particle geometric properties provided by x-ray computed tomography, a more precise
evaluation of the influence of particle shape in the flotation process, both in the recovery of ore minerals (mostly via true flotation) and of gangue minerals (mostly via entrainment). The research findings out that higher turbulence in the cell results in better recovery of fine particles, whereas the recovery efficiency of coarse particles is negatively impacted by higher energy dissipation within the cell. The methodology applied here, both for characterising individual particles in 3D and for modelling mineral separation processes at the level of single particles, is also applicable to other ores and mineral separation units.

  • Master thesis
    TU Bergakademie Freiberg, Faculty of Geosciences, Geotechnics and Mining, 2023
    Mentor: Carsten Drebenstedt, Nils Hoth, Lucas Pereira

Permalink: https://www.hzdr.de/publications/Publ-38501
Publ.-Id: 38501


Adaptable Research and Data Management Platform for High Data-Rate Experiments

Knodel, O.; Voigt, M.; Pape, D.; Lokamani, M.; Kelling, J.; Müller, S.; Gruber, T.; Juckeland, G.

At the High-Field High-Repetition-Rate Terahertz facility (TELBE) [1] at the Helmholtz-Zentrum Dresden-Rossendorf, ultrafast terahertz-induced dynamics can be probed in various states of matter with highest precision. The TELBE source is available for external users who are not familiar with the experiments's data management pipelines. This is especially a challenge as the measurements at TELBE are data intensive, producing as much as 20GB per experiment over few minutes.

In this contribution, we present the guidance system HELIPORT [3] which manages the metadata of the associated project proposal and integrates systems for workflow management, electronic lab documentation and others. We showcase the integrated workflow for post-processing of the experimental data at TELBE with in-built exchange of metadata between our proposal submission service, the experiment control software and workflows managed and executed using UNICORE [2].

Among other information, HELIPORT integrates documentation, scientific workflows, and the final publication of the research results - all via already established solutions for proposal management, electronic lab notebooks, software development and devops tools, and other additional data sources. The integration is accomplished by presenting the researchers with a high-level overview to keep all aspects of the experiment in mind, and automatically exchanging relevant metadata between the experiment's life cycle steps.

By visualizing all aspects of large-scale research experiments, HELIPORT enables deeper insights into a comprehensible data provenance with the chance of raising awareness for FAIR data management.

[1] https://doi.org/10.1063/1.4978042
[2] https://doi.org/10.1109/HPCSim.2016.7568392
[3] https://doi.org/10.1145/3456287.3465477

Keywords: data management; Heliport; workflows; metadata; HMC

  • Lecture (Conference)
    IT4Science-Days 2023, 26.-28.09.2023, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38500
Publ.-Id: 38500


Thermal twin stars within a hybrid equation of state based on a nonlocal chiral quark model compatible with modern astrophysical observations

Carlomagno, J. P.; Contrera, G.; Grunfeld, A. G.; Blaschke, D.

We investigate the extension to finite temperatures and neutrino chemical potentials of a recently developed nonlocal chiral quark model approach to the equation of state of neutron star matter.
We consider two light quark flavors and current-current interactions in the scalar-pseudoscalar, vector, and diquark pairing channels, where the nonlocality of the currents is taken into account
by a Gaussian form factor that depends on the spatial components of the 4-momentum. Within this framework, we analyze order parameters, critical temperatures, phase diagrams, equation of
state, and mass-radius relations for different temperatures and neutrino chemical potentials. For parameters of the model that are constrained by recent multi-messenger observations of neutron
stars, we find that the mass-radius diagram for isothermal hybrid star sequences exhibits the thermal twin phenomenon for temperatures above 30 MeV.

Keywords: Chiral quark model; Thermal twin stars; QCD phase diagram; Color superconductivity; Multi-messenger astronomy; Quark-hadron phase transition

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Permalink: https://www.hzdr.de/publications/Publ-38499
Publ.-Id: 38499


Evaluation of Cyrene as a sustainable pre treatment solvent for the effective froth flotation-based separation of fine valuables from spent lithium-ion batteries

Salces, A. M.; Henderson, M. S.; Rudolph, M.; Eksteen, J.; Vanderbruggen, A.

Froth flotation is a promising technique to separate the cathode (CAM) and anode active material (AAM) of lithium-ion batteries before downstream recycling processes. However, to ensure effective separation, both CAM and AAM particles must be free of organic binders (i.e., polyvinylidene fluoride) which gives them similar wetabilities. In this work, we propose the green solvent Cyrene dihydroleveglucosenone) as a pre-treatment to remove and possibly recover the polyvinylidene fluoride binder from the NMC-rich black mass. Pristine lithium-nickel-manganese-cobalt oxide (NMC111) and anodic graphite are used to determine the ideal flotation behavior. Pristine powders and black mass were mixed with Cyrene, heated at 100°C for 1 hour, and filtered hot. After flotation, 99.6% of the anodic graphite and only 5% of NMC is recovered in the overflow (O/F) indicating that Cyrene pretreatment does not affect their flotation behavior. For NMC-rich black mass, the NMC recovered in the O/F is reduced to 32.6% from 53.8% in the mechanically pre-treated black mass, demonstrating the potential of Cyrene for effective binder removal.

Keywords: battery recycling; flotation; graphite; CAMs; pyrolysis; Cyrene; dihydroleveglucosenone

  • Lecture (Conference)
    11th International Flotation Conference (Flotation '23), 06.-09.11.2023, Cape Town, South Africa
    DOI: 10.13140/RG.2.2.18199.34722

Permalink: https://www.hzdr.de/publications/Publ-38498
Publ.-Id: 38498


Correlated Widefield-confocal Microscopy Dataset

Li, R.; Della Maggiora Valdes, G. E.; Andriasyan, V.; Petkidis, A.; Yushkevich, A.; Kudryashev, M.; Yakimovich, A.

Dataset

This dataset contains a sample of 600 fluorescently labelled nuclei of cultured cells imaged using widefield fluorescence microscopy and confocal fluorescence microscopy at different focal planes.

Image preprocessing

Notably, the hardware precision of the sectioning process led to variations in the step size when shifting the focal plane between the two devices. This resulted in distinct z-dimensions between the datasets obtained from the two microscopy techniques. The confocal stacks in raw data comprised 92 focal planes, whereas the widefield stacks consisted of only 40 slices. Each focal plane image had a shape [2048, 2048, 1]. Assuming the central slice of each stack to be the in-focus, we performed z-direction registration by downsampling the confocal stacks from the central slice (46th) to match the 40 slices of the widefield stacks. Due to the instrumental limitations, a slight drift was noticeable between images. To address this, we used the phase cross-correlation algorithm [2] to compensate for the offsets on the x-y plane for the z-dimension registered image stacks. Having completed the registration and alignment along three dimensions, we then partitioned the original images into non-overlapping patches with dimensions of [128, 128, 1] in the xy plane. This partitioned dataset serves as the test dataset for validating our blind-deconvolution model, conducted without the specific Point Spread Function (PSF) parameters [3].

Files description

The Widefield-confocal Microscopy Dataset is stored in the '*.npz' format, encompassing the variables 'c_img' and 'w_img.' These handles respectively denote the confocal images and their corresponding widefield microscopy images. Both types of data undergo registration, alignment, and normalization, with values scaled to range between [0.0, 1.0]. For each category, the data has a shape of [600, 128, 128, 40], where the first dimension denotes the individual field of view and the last dimension signifies the z-dimension representing changes in the focal plane for virtual sectioning. The first dimension corresponds to the patch number, each with a patch size of [128, 128].

 

Sample preparation and microscopy

A549 lung carcinoma cell line cells were seeded in 96-well imaging plates a night prior to imaging, then fixed with 4% paraformaldehyde (Sigma) and stained for DNA with Hoechst 33342 fluorescent dye (Sigma). Cell culture was maintained similarly to the procedures described in [1]. Next, stained cell nuclei were imaged using ImageXpress Confocal system (Molecular Devices) in either confocal or widefield mode employing Nikon 20X Plan Apo Lambda objective. To obtain 3D information images in both modes were acquired as Z-stacks with 0.3 µm and 0.7 µm for confocal and widefield modes respectively. Confocal z-stack was Nyquist sampled. The excitation wavelength was 405 nm and the emission was 452 nm. Using these settings, we obtained individual stacks for both modalities, with each stack covering 2048 by 2048 pixels or 699 by 699 µm.

References

  1. Yakimovich, Artur, et al. "Plaque2. 0—a high-throughput analysis framework to score virus-cell transmission and clonal cell expansion." PloS one 10.9 (2015): e0138760.

  2. Alink, Mark S. Oude, et al. "Lowering the SNR wall for energy detection using cross-correlation." IEEE transactions on vehicular technology 60.8 (2011): 3748-3757.

  3. Li, Rui, et al. "Microscopy image reconstruction with physics-informed denoising diffusion probabilistic model." arXiv preprint arXiv:2306.02929 (2023).

Keywords: fluorescence microscopy; widefield; confocal; corelative microscopy

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Publ.-Id: 38497


Refinement of the uranium dispersion corrections from anomalous diffraction

Leinders, G.; Grendal, O. G.; Arts, I.; Bes, R.; Prozheev, I.; Orlat, S.; Fitch, A.; Kvashnina, K.; Verwerft, M.

The evolution of the uranium chemical state in uranium compounds, principally
in the oxides, is of concern in the context of nuclear fuel degradation under
storage and repository conditions, and in accident scenarios. The U–O system
shows complicated phase relations between single-valence uranium dioxide
(UO 2 ) and different mixed-valence compounds (e.g. U 4O 9 , U3 O 7 and U 3 O8 ). To
try resolving the electronic structure associated with unique atomic positions, a
combined application of diffraction and spectroscopic techniques, such as
diffraction anomalous fine structure (DAFS), can be considered. Reported here
is the application of two newly developed routines for assessing a DAFS data
set, with the aim of refining the uranium X-ray dispersion corrections. High-
resolution anomalous diffraction data were acquired from polycrystalline
powder samples of UO 2 (containing tetravalent uranium) and potassium
uranate (KUO 3 , containing pentavalent uranium) using synchrotron radiation in
the vicinity of the U L3 edge (17.17 keV). Both routines are based on an
iterative refinement of the dispersion corrections, but differ in either using the
intensity of a selection of reflections or doing a full-pattern (Rietveld method)
refinement. The uranium dispersion corrections obtained using either method
are in excellent agreement with each other, and they show in great detail the
chemical shifts and differences in fine structure expected for tetravalent and
pentavalent uranium. This approach may open new possibilities for the assess-
ment of other, more complicated, materials such as mixed-valence compounds.
Additionally, the DAFS methodology can offer a significant resource optimi-
zation because each data set contains both structural (diffraction) and chemical
(spectroscopy) information, which can avoid the requirement to use multiple
experimental stations at synchrotron sources

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Permalink: https://www.hzdr.de/publications/Publ-38494
Publ.-Id: 38494


Revealing the Incorporation of Cerium in Fluorapatite

Manceau, A.; Mathon, O.; Lomachenko, K. A.; Rovezzi, M.; Kvashnina, K.; Boiron, M.-C.; Brossier, R.; Steinmann, S. N.

Fluorapatite (FAp, nominally Ca5(PO4)3F) is the most common phosphate mineral at the Earth’s surface and a main host for rare-earth elements (REE) in magmatic and hydrothermal ore deposits and in marine sediments. Our understanding of the enrichment process of REE in FAp rests upon two foundations: (1) being able to elucidate the thermodynamic driving force for their partitioning between Ca1 and Ca2 structural sites and (2) being able to determine how the substitution of REE(III) for Ca(II) is charge-compensated. A main unsolved question is the marked preference of the larger light REE (lanthanum → samarium) for the smaller Ca2 site. We used density functional theory (DFT) and high-energy-resolution fluorescence-detected extended X-ray absorption fine structure (HERFD-EXAFS) spectroscopy to gain detailed insight into the bonding energy, electronic structure, and short-range order of cerium (Ce) in natural magmatic/hydrothermal FAp. Results show that Ce(III) has a marked preference for a Ca2 site where the nearest five-valent phosphorus cation is replaced with a tetravalent silicon cation, thus balancing the charge excess of the Ce impurity locally. Atomic charge calculations show that the Ca2 site is more ionic than the Ca1 site and that the energetics of the site preference are linearly correlated to the ionization energy of the substituent. Cations with a low energy of ionization, such as Ce, preferably occupy the Ca2 site. Novel combination of HERFD-EXAFS spectroscopy and DFT appears to be the most straightforward and reliable way to assess the crystal chemistry of trace elements in compositionally complex natural materials and opens a previously unavailable avenue for mechanistic investigation of metal enrichment in ore deposits.

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Permalink: https://www.hzdr.de/publications/Publ-38493
Publ.-Id: 38493


Data publication: In Situ Heating Positron Annihilation Lifetime Spectroscopy Experiments on an Al–Mg Alloy

Banhart, J.; Yang, Z.; Guo, Q.; Liu, M.; Butterling, M.; Liedke, M. O.; Hirschmann, E.; Wagner, A.

Experimentdaten der Positronen-Annihilationsspektroskopie

Keywords: positron annihilation lifetime spectroscopy; Al-Mg; alloy; ageing; vacancy

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Permalink: https://www.hzdr.de/publications/Publ-38490
Publ.-Id: 38490


In Situ Heating Positron Annihilation Lifetime Spectroscopy Experiments on an Al–Mg Alloy

Banhart, J.; Yang, Z.; Guo, Q.; Liu, M.; Butterling, M.; Liedke, M. O.; Hirschmann, E.; Wagner, A.

The binding between vacancies and Mg atoms in an aluminum solid solution is not fully understood but essential for understanding its role in age hardening of many Al alloys. After annealing and quenching, Mg prevents the loss of excess vacancies during natural ageing and forms complexes containing one, possibly two, vacancies, and various Mg atoms. By heating the alloy after natural ageing, these complexes are dissolved, i.e., natural ageing is reverted. This reversion process is studied by in situ positron annihilation lifetime spectroscopy utilizing the very high count rate at the accelerator driven facility ELBE. Positron spectra are continuously acquired during heating at rates between 3 and 50 K/min. After correcting for the contributions of the oxidized surface and decomposing spectra into components, the process can be followed in detail and is found to take place in distinct stages: first, the number of vacancy–Mg complexes is reduced and then the liberated vacancies agglomerate into clusters that eventually dissolve at even higher temperatures.

Keywords: positron annihilation lifetime spectroscopy; Al-Mg; alloy; ageing; vacancy

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Permalink: https://www.hzdr.de/publications/Publ-38489
Publ.-Id: 38489


Data publication: Metal Deportment in Complex Secondary Raw Materials: The Case of Vanadium in Basic Oxygen Furnace Slags

Renno, A.; Möckel, R.; Frenzel, M.; Ebert, D.; Bachmann, K.; Krause, J.; Gutzmer, J.

Compilation of all available raw data for the publication "Metal Deportment in Complex Secondary Raw Materials: The Case of Vanadium in Basic Oxygen Furnace Slags".
List of Supplementary Information

Table A 1: Compilation of elements analyzed by XRF including lower and upper limits of determination (LoD).
Table A 2: Compilation of the subsample designations of the three BOS samples analyzed for the XRF and XRD as well as the MLA and EPMA analyses. All subsamples correspond to representative subsets of the bulk sample.
Table A 3: Compilation of the EPMA measurement parameters with spectrometer position (Spec), lower background (LB), upper background (UB), dwelltime on peak (DTP) and background (DTB) and the complete list of reference materials.
Table App 4: Compilation of all major and minor element contents determined by XRF recalculated as “water-free” and normalized to 100 wt.-%.
Table A 5: Comparison of LOI values for one sample each of the delivered material "as delivered" and fully hydrated.
Table A 6: Compilation of significant differences between the samples with regard to the chemical composition.
Table A 7: Detailed compilation of the results of the MLA measurements of all investigated samples.
Table A 8: Compilation of the phases predefined for EPMA analyses and the number of measurements performed and usable for further MLA and deportation analyses.
Table A 9: Complete summary of all EPMA data used for the deportment analysis (xls File).

Keywords: Steel slag; Basic oxygen furnace slag; Vanadium-bearing slag; Vanadium; Vanadium deportment

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Permalink: https://www.hzdr.de/publications/Publ-38488
Publ.-Id: 38488


Optimizing synthesis strategies for the production of single-phase zirconates with Ce and Nd co-doping

Richter, S.; Gilson, S.; Braga Ferreira Dos Santos, L.; Huittinen, N. M.

Zirconia-based ceramics are promising host matrices for the immobilization of radionuclides in high-level waste streams due to their high radiation resistance and chemical stability. This study explores coprecipitation and different solid-state synthesis techniques to produce phase-pure zirconia-based ceramics with varying cerium and neodymium co-doping. Varying the dopant concentration enabled the synthesis of zirconates with monoclinic, cubic defect fluorite, and cubic pyrochlore structures. Powder X-ray diffraction was used for phase identification. In the case of coprecipitation, all synthesized compositions were predominantly phase-pure. Solid-state synthesis techniques included manual mixing of metal oxide powders with mortar and pestle, mechanical mixing in a ball mill, and magnetic mixing in a slurry. All solid-state mixing methods produced heterogeneous ceramics, featuring multiple phases, with manual mixing yielding the most phase-pure product. Extending the grinding time, re-sintering of the solid phases, and an increased Nd content were found to enhance the phase purity.

Keywords: Nuclear waste; Zirconate; Pyrochlore; XRD; Synthesis optimization

Permalink: https://www.hzdr.de/publications/Publ-38486
Publ.-Id: 38486


Was sind Quantentechnologien? Grundlagen der Quantenmechanik, Funktionsweise, Beispiele für die Anwendung

Astakhov, G.

Zunächst stelle ich die Grundlagen der Quantenmechanik vor. Dann beschreibe ich das Funktionsprinzip von Qubits. Danach stelle ich Beispiele für Quantenprogrammierung vor. Schließlich diskutiere ich mögliche Anwendungen für Quantentechnologien.

Keywords: Quantum Technologies; Quantum Computing

  • Invited lecture (Conferences)
    Seniorenakademie, 11.01.2024, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-38485
Publ.-Id: 38485


Transport dank Wandmoden

Eckert, S.

Aktuelle Studien illustrieren die Entwicklung von Strömungsmustern der Magnetokonvektion bis hin zu chaotischen Strömungen.

Keywords: Rayleigh Benard Konvektion; Magnetfeld; Wandmoden; Wärmetransport

  • Physik Journal 23(2024)2, 22-23

Permalink: https://www.hzdr.de/publications/Publ-38484
Publ.-Id: 38484


Are applied radiopharmaceutical sciences able to consolidate NextGen radionuclide theranostics?

Kopka, K.

Plenary Lecture: Are applied radiopharmaceutical sciences able to consolidate NextGen radionuclide theranostics?

  • Invited lecture (Conferences)
    31st Dutch society of clinical radiochemistry biannual meeting, 20.01.2023, Amsterdam, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-38483
Publ.-Id: 38483


The Future of Radionuclide Theranostics through Radiopharmaceutical Sciences

Kopka, K.

The Future of Radionuclide Theranostics through Radiopharmaceutical Sciences

  • Invited lecture (Conferences) (Online presentation)
    The 1st International Conference on Molecular Probes for Imaging Research Network on Development of Radiotracers for Medical Imaging and Preclinical Evaluations, 22.-23.02.2023, Bangkok, Thailand

Permalink: https://www.hzdr.de/publications/Publ-38482
Publ.-Id: 38482


Radionuclide Theranostics through Radiopharmaceutical Sciences / Radionuklid Theranostik durch Radiopharmazeutische Wissenschaften

Kopka, K.

Radionuclide Theranostics through Radiopharmaceutical Sciences / Radionuklid Theranostik durch Radiopharmazeutische Wissenschaften

  • Invited lecture (Conferences)
    9. VCI-Innovationskongress Chemie – Beiträge von Wirtschaft und Wissenschaft zur Transformation, 31.05.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38481
Publ.-Id: 38481


Radionuclide Theranostics through Radiopharmaceutical Sciences (Part 2)

Kopka, K.

Radionuclide Theranostics through Radiopharmaceutical Sciences (Part 2)

  • Invited lecture (Conferences)
    Monash-Helmholtz Laboratory for Radio-Immuno-Theranostics (MHELTHERA) School, 08.-10.11.2023, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38480
Publ.-Id: 38480


Towards a Quality Indicator for Research Data publications and Research Software publications –- A vision from the Helmholtz Association

Zu Castell, W.; Dransch, D.; Juckeland, G.; Meistring, M.; Fritzsch, B.; Gey, R.; Höpfner, B.; Köhler, M.; Meeßen, C.; Mehrtens, H.; Mühlbauer, F.; Schindler, S.; Schnicke, T.; Bertelmann, R.

Research data and software are widely accepted as an outcome of scientific work.
However, in comparison to text-based publications, there is not yet an established process to assess and evaluate quality of research data and research software publications.
This paper presents an attempt to fill this gap.
Initiated by the Working Group Open Science of the Helmholtz Association the Task Group Helmholtz Quality Indicators for Data and Software Publications currently develops a quality indicator for research data and research software publications to be used within the Association.
This report summarizes the vision of the group of what all contributes to such an indicator.
The proposed approach relies on generic well-established concepts for quality criteria, such as the FAIR Principles and the COBIT Maturity Model.
It does -- on purpose -- not limit itself to technical implementation possibilities to avoid using an existing metric for a new purpose.
The intention of this paper is to share the current state for further discussion with all stakeholders, particularly with other groups also working on similar metrics but also with entities that use the metrics.

Permalink: https://www.hzdr.de/publications/Publ-38478
Publ.-Id: 38478


Inclusive e+e− production in collisions of pions with protons and nuclei in the second resonance region of baryons

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

Inclusive e+e− production has been studied with HADES in π− + p, π− + C and π−+CH2 reactions, using the GSI pion beam at sπp−−−√ = 1.49 GeV. Invariant mass and transverse momentum distributions have been measured and reveal contributions from Dalitz decays of π0, η mesons and baryon resonances. The transverse momentum distributions are very sensitive to the underlying kinematics of the various processes. The baryon contribution exhibits a deviation up to a factor seven from the QED reference expected for the dielectron decay of a hypothetical point-like baryon with the production cross section constrained from the inverse γ n→π− p reaction. The enhancement is attributed to a strong four-momentum squared dependence of the time-like electromagnetic transition form factors as suggested by Vector Meson Dominance (VMD). Two versions of the VMD, that differ in the photon-baryon coupling, have been applied in simulations and compared to data. VMD1 (or two-component VMD) assumes a coupling via the ρ meson and a direct coupling of the photon, while in VMD2 (or strict VMD) the coupling is only mediated via the ρ meson. The VMD2 model, frequently used in transport calculations for dilepton decays, is found to overestimate the measured dielectron yields, while a good description of the data can be obtained with the VMD1 model assuming no phase difference between the two amplitudes. Similar descriptions have also been obtained using a time-like baryon transition form factor model where the pion cloud plays the major role.

Permalink: https://www.hzdr.de/publications/Publ-38477
Publ.-Id: 38477


Dynamical interplay between superconductivity and charge density waves: A nonlinear terahertz study of coherently driven 2H−NbSe2

Feng, L.; Cao, J.; Priessnitz, T.; Dai, Y.; de Oliveira, T.; Yuan, J.; Oka, R.; Kim, M.-J.; Chen, M.; Ponomaryov, O.; Ilyakov, I.; Zhang, H.; Lv, Y.; Mazzotti, V.; Kim, G.; Christiani, G.; Logvenov, G.; Wu, D.; Huang, Y.; Deinert, J.-C.; Kovalev, S.; Kaiser, S.; Dong, T.; Wang, N.; Chu, H.

2H-NbSe2 is an archetypal system in which superconductivity and charge density wave (CDW) coexist and compete macroscopically with each other. In particular, this interplay also manifests in their dynamical fluctuations. As a result, the superconducting amplitude fluctuation (i.e., Higgs mode) is pushed below the quasiparticle continuum, allowing it to become a coherent excitation observable by Raman scattering. In the present study, we coherently drive the collective oscillations of the two orders and visualize their interplay in the time domain. We find that both collective modes contribute to terahertz third-harmonic generation (THG) and their THG signals interfere below Tc, leading to an antiresonance of the integrated THG signal. The dynamical Ginzburg-Landau model suggests that around the antiresonance a periodic energy transfer between the driven Higgs oscillations and the driven CDW oscillations is possible. Our results illustrate the roles of collective modes in the terahertz THG process, revealing a close connection of this technique to Raman scattering. In systems where the different collective modes are coupled, our experimental scheme also illustrates a paradigm for realizing coherent control via such couplings.

Keywords: Terahertz; Ultrafast; Harmonics; Third Harmonic Generation; Superconductors; Higgs spectroscopy; NbSe2

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Permalink: https://www.hzdr.de/publications/Publ-38476
Publ.-Id: 38476


Higher-harmonic generation in boron-doped silicon from band carriers and bound-dopant photoionization

Meng, F.; Walla, F.; Kovalev, S.; Deinert, J.-C.; Ilyakov, I.; Chen, M.; Ponomaryov, O.; Pavlov, S. G.; Hübers, H.-W.; Abrosimov, N. V.; Jungemann, C.; Roskos, H. G.; Thomson, M. D.

We investigate ultrafast harmonic generation (HG) in Si: B, driven by intense pump pulses with fields reaching∼ 100 kV cm− 1 and a carrier frequency of 300 GHz, at 4 K and 300 K, both experimentally and theoretically. We report several findings concerning the nonlinear charge carrier dynamics in intense sub-THz fields:(i) Harmonics of order up to n= 9 are observed at room temperature, while at low temperature we can resolve harmonics reaching at least n= 11. The susceptibility per charge carrier at moderate field strength is as high as for charge carriers in graphene, considered to be one of the materials with the strongest sub-THz nonlinear response.(ii) For T= 300 K, where the charge carriers bound to acceptors are fully thermally ionized into the valence subbands, the susceptibility values decrease with increasing field strength. Simulations incorporating multi-valence-band Monte Carlo and finite-difference-time-domain (FDTD) propagation show that here, the HG process becomes increasingly dominated by energy-dependent scattering rates over the contribution from band nonparabolicity, due to the onset of optical-phonon emission, which ultimately leads to the saturation at high fields. (iii) At T=4K, where the majority of charges are bound to acceptors, we observe a drastic rise of the HG yields for internal pump fields of ∼30kVcm−1, as one reaches the threshold for tunnel ionization. We disentangle the HG nonlinear response into contributions associated with the initial photoionization and subsequent motion in the bands, and show that intracycle scattering seriously degrades any contribution to HG emission from coherent recollision of the holes with their parent ions.

Keywords: Terahertz; Harmonic generation; Ultrafast; Silicon

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Permalink: https://www.hzdr.de/publications/Publ-38475
Publ.-Id: 38475


Transition from fractal-dendritic to compact islands for the 2D-ferroelectric SnSe on graphene/Ir(111)

Aleksa, P.; Ghorbani Asl, M.; Iqbal, S.; Martuza, M. A.; Bremerich, A.; Wilks, D.; Cai, J.; Chagas, T.; Ohmann, R.; Krasheninnikov, A.; Busse, C.

Epitaxial growth is a versatile method to prepare two-dimensional van der Waals ferroelectrics like group IV monochalcogenides which have potential for novel electronic devices and sensors. We systematically study SnSe monolayer islands grown by molecular beam epitaxy, especially the effect of annealing temperature on shape and morphology of the edges. Characterization of the samples by scanning tunneling microscopy reveals that the shape of the islands changes from fractal-dendritic after deposition at room temperature to a compact rhombic shape through annealing, but ripening processes are absent up to the desorption temperature. A two-step growth process leads to large, epitaxially aligned rhombic islands bounded by well-defined ⟨110⟩-edges (armchair-like), which we claim to be the equilibrium shape of the stoichiometric SnSe monolayer islands. The relaxation of the energetically favorable edges is detected in atomically resolved STM images. The experimental findings are supported by the results of our first-principles calculations, which provide insights into the energetics of the edges, their reconstructions, and yields the equilibrium shapes of the islands which are in good agreement with the experiment.

Keywords: two-dimensional materials; ferroelectric; group IV monochalcogenides; SnSe; scanning tunneling spectroscopy; DFT

Permalink: https://www.hzdr.de/publications/Publ-38474
Publ.-Id: 38474


Shot-to-Shot Detection of the Carrier Envelope Phase Evolution in a THz FEL

Klopf, J. M.; Ilyakov, I.; Ponomaryov, O.; Pashkin, O.; Deinert, J.-C.; de Oliveira, T.; Evtushenko, P.; Helm, M.; Winnerl, S.; Kovalev, S.

The free-electron laser (FEL) is an ideal source of high-power coherent THz radiation for many applications. The FEL provides continuously tunable THz radiation, typically in ultrashort transform limited pulses with very high peak power. One limitation though is that the carrier envelope phase (CEP) of the FEL pulses is not fixed, making measurements of coherent THz-driven processes extremely difficult, if not impossible. We present here, a novel technique that enables shot-to-shot measurement of the CEP of every FEL pulse up to very high repetition rates. This powerful technique enables phase-resolved measurements of the FEL pulses, which opens the door for the study of coherent THz-driven phenomena as well as the advanced FEL diagnostics needed in the pursuit of CEP stable operation of an FEL.

Keywords: THz; FEL; CEP; EOS; phase-resolved; coherent; single-shot

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  • Contribution to proceedings
    2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 17.-22.09.2023, Montreal, Canada: IEEE
    DOI: 10.1109/IRMMW-THz57677.2023.10298908

Permalink: https://www.hzdr.de/publications/Publ-38473
Publ.-Id: 38473


movedesign: Study design of movement ecology studies

Simoes Silva, I. M.; Fleming, C. H.; Noonan, M. J.; Fagan, W. F.; Calabrese, J.

A Shiny R application that aims to assist researchers in designing animal tracking projects related to two main research questions: the estimation of home range and of speed and distance traveled. The application makes use of simulations to assess the degree of estimate precision that may be achieved with a given sampling design; that is, the choices regarding data resolution (sampling interval) and battery life (sampling duration).

Keywords: ecology; conservation; software development; experimental design; biologgers; GPS sampling; GPS tracking; simulations; home range; space use

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Permalink: https://www.hzdr.de/publications/Publ-38472
Publ.-Id: 38472


EMFL user operation

Scurschii, I.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences)
    ISABEL Regional Workshop, 06.-08.09.2023, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-38470
Publ.-Id: 38470


The n_TOF NEAR Station Commissioning and first physics case

Stamati, M. E.; Torres-Sanchez, P.; Perez-Maroto, P.; Junghans, A.; Wallner, A.; The n_TOF Collaboration

The NEAR Station is a new experimental area developed at the n_TOF Facility at CERN. The activation station of NEAR underwent a characterization of the beam following the installation of the new n_TOF Spallation Target. The commissioning of the neutron beam comprises a set of simulations made with the FLUKA code and experimental verification. The experimental determination of the neutron spectrum was made using activation techniques with three separate set-ups. Two set-ups were based on the Multi-foil Activation technique (MAM-1 and MAM-2), and the third set-up relied on the process of neutron moderation and activation of a single material (ANTILoPE). The three set-ups are presented. Also the present plans and future perspectives of the activation station of NEAR are discussed.

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Permalink: https://www.hzdr.de/publications/Publ-38467
Publ.-Id: 38467


Detector set up for the measurements of the neutron-induced fission cross section of 235U relative to n-p scattering up to 150 MeV at CERN-n_TOF

Pirovano, E.; Manna, A.; Colonna, N.; Junghans, A.; Wallner, A.; The n_TOF Collaboration

A new measurement of the 235U(n,f) fission cross section was carried out at n_TOF. The experiment covered the neutron energy range from 10 MeV up to 500 MeV, and it used the 1H(n,n) cross section as normalization for the neutron fluence measurement. In this contribution, the measurements and the characterization of the detectors covering the incident energy range up to 150 MeV are discussed.

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Permalink: https://www.hzdr.de/publications/Publ-38466
Publ.-Id: 38466


Characterisation of the n_TOF 20 m beam line at CERN with the new spallation target

Pavon-Rodriguez, J. A.; Alcayne, V.; Amaducci, S.; Junghans, A.; The n_TOF Collaboration

The n_TOF facility hosts CERN’s pulsed neutron source, comprising two beam lines of different flight paths and one activation station. It is based on a proton beam delivered by the PS accelerator impinging on a lead spallation target. During Long Shutdown 2 (LS2) at CERN (2019-2021), a major upgrade of the spallation target was carried out in order to optimize the performances of the neutron beam. Therefore, the characteristics of n_TOF two experimental areas were investigated in detail. In this work, the focus is on the second experimental area (EAR2), located 20 m above the spallation target. Preliminary results of the neutron energy distribution and beam line energy resolution are presented, compared to previous experimental campaigns and Monte Carlo simulations with the FLUKA code. Moreover, preliminary results of the spatial beam profile measurements are shown.

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Permalink: https://www.hzdr.de/publications/Publ-38465
Publ.-Id: 38465


Neutron capture and total cross-section measurements on 94,95,96Mo at n_TOF and GELINA

Mucciola, R.; Paradela, C.; Manna, A.; Junghans, A.; The n_TOF Collaboration

Capture and total cross section measurements for 94,95,96Mo have been performed at the neutron time-of-flight facilities, n_TOF at CERN and GELINA at JRC-Geel. The measurements were performed using isotopically enriched samples with an enrichment above 95% for each of the 94,95,96Mo isotopes. The capture measurements were performed at n_TOF using C6D6 detectors and a new sTED detector. The transmission measurements were performed at a 10 m station of GELINA using a 6Li glass neutron detector. Preliminary results of these measurements are presented.

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Permalink: https://www.hzdr.de/publications/Publ-38464
Publ.-Id: 38464


Measurement of the 235U(n,f) cross section relative to the 10B(n,α) reaction with Micromegas detectors at the CERN n_TOF facility: First results

Michalopoulou, V.; Diakaki, M.; Vlastou, R.; Junghans, A.; The n_TOF Collaboration

Neutron cross section measurements are often made relative to a neutron cross section standard. Thus, the accuracy of the neutron standards determines the best possible accuracy of the neutron measurements. The 235U(n,f) cross section is widely used as reference, while it is considered a standard at thermal point and between 0.15 to 200 MeV. For this reason, additional cross section data for the 235U(n,f) reaction are useful in order to improve the accuracy and to extend the energy range of the standard. In this work, preliminary results of the measurement of the 235U(n,f) cross-section relative to the standard 10B(n,a) reaction are presented. The high accuracy measurement was performed at the experimental area EAR-1 of the n_TOF facility at CERN, aiming at covering the energy range from the thermal region up to approximately 100 keV. The samples were produced at JRC-Geel in Belgium, while the experimental setup was based on Micromegas detectors.

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Permalink: https://www.hzdr.de/publications/Publ-38463
Publ.-Id: 38463


An LSC approach for tritium determination in gaseous mixtures optimized with respect to handling, reaction parameters and miniaturization towards microfluidic analysis

Becker, A.; Lippold, H.; Bäcker, J. P.; Belder, D.; Fischer, C.

The handling and analysis of gaseous tritium is of interest for hydrogen isotope separation experiments. In this work, we present an easy-to-handle setup for catalytic oxidation to HTO, recovering all of the initially dosed gaseous tritium as determined by LSC, using CuO as a catalyst at a reaction temperature of 900°C. Aiming to reduce cocktail waste, the LSC determination was downscaled to a microfluidic setup. The performance was evaluated based on the counting efficiency, which was shown to decrease significantly, as the sample volume was reduced to μl amounts, while no changes were observed over a wide range of sample-to-cocktail ratios.

Keywords: tritium; hydrogen isotopes; microfluidics; gas analysis; liquid scintillation counting

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  • Secondary publication expected from 13.02.2025

Permalink: https://www.hzdr.de/publications/Publ-38460
Publ.-Id: 38460


Measurement of the 160Gd(n, γ) cross section at n_TOF and its medical implications

Mastromarco, M.; Manna, A.; Garcia-Infantes, F.; Junghans, A.; Wallner, A.; The n_TOF Collaboration

Neutron-capture reactions on gadolinium isotopes play an important role in several fields of physics,in particular in nuclear Astrophysics for the understanding of the nucleosynthesis of heavy elements (beyond iron) in stars via the s- and r-processes [1] and in nuclear technology. Another important application of gadolinium is linked to the production of terbium, that offers a set of clinically interesting isotopes for theranostics, characterized by complementary physical decay characteristics. In particular, the low-energy β −emitter terbium-161 is very similar to lutetium-177 in terms of half-life (6.89 d), β − energy and chemical properties. Being a significant emitter of conversion/Auger electrons, greater therapeutic effect can therefore be expected in comparison to Lu-177 [2, 3]. For this reason, in the last decade, the study of the neutron capture reaction 160Gd(n,γ)161 Gd and the subsequent β − decay in terbium-161 is getting particular attention. As the nuclear data on the Gd-160 neutron capture reaction are quite scarce and inconsistent, a new measurement of the capture cross section of Gd-160 at the CERN neutron Time-Of-Flight facilty was performed in order to provide high resolution, high-accuracy data on this important reaction, in the energy range from thermal to hundreds of keV. In this contribution, the preliminary results of the n_TOF measurement are presented.

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Permalink: https://www.hzdr.de/publications/Publ-38459
Publ.-Id: 38459


Neutron-induced cross section measurements

Massimi, C.; Aberle, O.; Alcayne, V.; Junghans, A.; Urlaß, S.; Wallner, A.; The n_TOF Collaboration

Neutron-induced cross sections represent the main nuclear input to models of stellar and Big-Bang nucleosynthesis. While (n,γ) reactions are relevant for the formation of elements heavier than iron, (n,p) and (n,α) reactions can play an important role in specific cases. The time-of-flight method is routinely used at n_TOF to experimentally determine the cross section data. In addition, recent upgrades of the facility will allow the use of activation techniques as well, possibly opening the way to a systematic study of neutron interaction with radioactive isotopes. In the last 20 years n_TOF has provided a large amount of experimental data for Nuclear Astrophysics. Our plan is to carry on challenging measurements and produce nuclear data in the next decades as well.

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Permalink: https://www.hzdr.de/publications/Publ-38457
Publ.-Id: 38457


Characterization of a detector setup for the measurement of the 235U(n,f) cross section relative to n-p scattering up to 500 MeV at the n_TOF facility at CERN

Manna, A.; Pirovano, E.; Colonna, N.; Junghans, A.; The n_TOF Collaboration

The measurement of the 235U(n,f) reaction cross section in the neutron energy region 10 MeV to 500 MeV was carried out at the CERN n_TOF facility. The experimental campaign, completed in 2018, provided precise and accurate data on the fission reaction relative to neutron-proton elastic scattering. A description and characterization of the used setup for the simultaneous measurement of fission fragments and neutron flux is reported here.

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Permalink: https://www.hzdr.de/publications/Publ-38456
Publ.-Id: 38456


New detection systems for an enhanced sensitivity in key stellar (n,γ) measurements

Lerendegui-Marco, J.; Babiano-Suarez, V.; Balibrea-Correa, J.; Junghans, A.; The n_TOF Collaboration

Neutron capture cross-section measurements are fundamental in the study of astrophysical phenomena, such as the slow neutron capture (s-) process of nucleosynthesis operating in red-giant and massive stars. However, neutron capture measurements via the time-of-flight (TOF) technique on key s-process nuclei are often challenging. Difficulties arise from the limited mass (∼mg) available and the high sample-related background in the case of the unstable s-process branching points. Measurements on neutron magic nuclei, that act as s-process bottlenecks, are affected by low (n,γ) cross sections and a dominant neutron scattering background. Overcoming these experimental challenges requires the combination of facilities with high instantaneous flux, such as n_TOFEAR2, with detection systems with an enhanced detection sensitivity and high counting rate capabilities. This contribution reviews some of the latest detector developments in detection systems for (n,γ) measurements at n_TOF, such as i-TED, an innovative detection system which exploits the Compton imaging technique to reduce the dominant neutron scattering background and s-TED, a highly segmented total energy detector intended for high flux facilities. The discussion will be illustrated with results of the first measurement of key the s-process branching-point reaction 79Se(n,γ).

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Permalink: https://www.hzdr.de/publications/Publ-38455
Publ.-Id: 38455


New perspectives for neutron capture measurements in the upgraded CERN-n_TOF Facility

Lerendegui-Marco, J.; Casanovas, A.; Alcayne, V.; Junghans, A.; The n_TOF Collaboration

The n_TOF facility has just undergone in 2021 a major upgrade with the installation of its third generation spallation target that has been designed to optimize the performance of the two n_TOF time-of-flight lines. This contribution describes the key features and limitations for capture measurements in the two beam lines prior to the target upgrade and presents first results of (n,γ) measurements carried out as part of the commissioning of the upgraded facility. In particular, the energy resolution, a key factor for both increasing the signal-to-background ratio and obtaining accurate resonance parameters, has been clearly improved for the 20 m long vertical beam-line with the new target design while keeping the remarkably high resolution of the long beamline n_TOF-EAR1. The improvements in the n_TOF neutron beam-lines need to be accompanied by improvements in the instrumentation. A review is given on recent detector R&D projects aimed at tackling the existing challenges and further improving the capabilities of this facility.

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Permalink: https://www.hzdr.de/publications/Publ-38454
Publ.-Id: 38454


Resonance region evaluation of 16O for criticality safety and reactor applications

Leal, L.; Leclaire, N.; Plompen, A.; Urlass, S.; Junghans, A.

The intent of this paper is to present the resolved resonance evaluation of 16O in the energy range from thermal to 6 MeV. The newness of the present work is that recent cross-section data for the 16O(n,α) 13C reaction taken at the GELINA time-of-flight facility and transmission data obtained at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR ) were included in the evaluation. The evaluation was carried out with the SAMMY code. The evaluation was used to calculate critical benchmark experiment sensitive to the 16O cross sections.

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Permalink: https://www.hzdr.de/publications/Publ-38453
Publ.-Id: 38453


First high resolution measurement of neutron capture resonances in 176Yb at the n_TOF CERN facility

Garcia-Infantes, F.; Praena, J.; Casanovas, A.; Junghans, A.; The n_TOF Collaboration

Several international agencies recommend the study of new routes and new facilities for producing radioisotopes with application to nuclear medicine. 177Lu is a versatile radioisotope used for therapy and diagnosis (theranostics) of cancer with good success in neuroendocrine tumours that is being studied to be applied to a wider range of tumours. 177Lu is produced in few nuclear reactors mainly by the neutron capture on 176Lu. However, it could be produced at high-intensity celeratorbased neutron facilities. The energy of the neutrons in accelerator-based neutron facilities is higher than in thermal reactors.Thus, experimental data on the 176Yb(n,γ) cross-section in the eV and keV region are mandatory to calculate accurately the production of 177Yb, which beta decays to 177Lu. At present, there are not experimental data available from thermal to 3 keV of the 176Yb(n,γ) cross-section. In addition, there is no data in the resolved resonance region (RRR). This contribution shows the first results of the 176Yb capture measurement performed at the n_TOF facility at CERN.

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Permalink: https://www.hzdr.de/publications/Publ-38452
Publ.-Id: 38452


Backreaction in cosmic screening approach’

Eingorn, M.; O’Briant, B.; Diouf, A.; Zhuk, O.

We investigate the backreaction of nonlinear perturbations on the global evolution of the Universe within the cosmic screening approach. To this end, we have considered the second-order scalar perturbations. An analytical study of these perturbations followed by a numerical evaluation shows that, first, the corresponding average values have a negligible backreaction effect on the Friedmann equations and, second, the second-order correction to the gravitational potential is much less than the first-order quantity. Consequently, the expansion of perturbations into orders of smallness in the cosmic screening approach is correct.

Keywords: Inhomogeneous UniverseCosmological perturbationsBackreactionCosmic screening

Permalink: https://www.hzdr.de/publications/Publ-38451
Publ.-Id: 38451


Experimental and Theoretical Investigations of Photocatalytic H2 activity of 0D, 1D, and 2D CdS Nanostructures

Varma, P.; Sudheer, A. E.; Devaraj, M.; Posselt, M.; Reddy, D. A.

In recent years, we have witnessed a great deal of interest in semiconductor-based photocatalysts due to their potential to address major energy-related problems. Among these, Cadmium Sulfide (CdS) has turned into a well-known choice because of its exceptional photocatalytic properties and cost effectiveness. This work provides a comparison of the photocatalytic activity of CdS in 0D (microspheres), 1D (nanorods), and 2D (nanosheets) structure. Among the three, CdS nanorods exhibited high photocatalytic hydrogen evolution performance of about 2.5 mmol. g-1.h-1. which is nearly 2 and 1.3 times higher compared to 0D and 2D structure respectively. Also, the obtained band edge of each nanostructures lies around 520 to 550 nm emphasize their broad visible light absorption. Furthermore, the electronic structure and band alignment studies using density functional theory (DFT) found to be well in accordance with the experimental outcomes via proving 1D CdS hexagonal is more favourable for water redox reactions compared to cubic (0D) CdS nanostructures.

Keywords: low-dimensional nanostructures; CdS; photocatalysis

  • Poster
    DAE Solid State Physics Symposium (DAE-SSPS 2023), 20.-24.12.2023, Visakhapatnam, India

Permalink: https://www.hzdr.de/publications/Publ-38447
Publ.-Id: 38447


A First Principles Study of 2D-2D CdS/MoS2 van der Waals Heterostructure

Tejaswini, G.; Sudheer, A. E.; Maniprakash, S.; Devaraj, M.; Posselt, M.

Recently 2D heterostructures have attracted much attention in the field of photocatalytic water splitting. Here, we demonstrate 2D-2D van der Waals heterostructure CdS/MoS2 with improved efficiency for the water splitting hydrogen production. We designed and explored the structural properties of CdS and MoS2 monolayers and observed similar hexagonal atomic arrangement for both monolayers. By constructing the heterostructure, we aim to introduce interfacial dipoles inside the material, which will separate the charge carriers efficiently. For the analysis of electronic properties, band structure and density of states calculations were performed for the CdS/MoS2 heterostructure and compared with those of isolated CdS and MoS2 monolayers. The band gap of the heterostructure is indirect and obtained to be 1.19 eV. This Reduced band gap of the heterostructure indicates good visible light absorption, which is favorable for photocatalysis.

Keywords: 2D materials; CdS/MoS2 heterostructure; First-principles study

  • Poster
    DAE Solid State Physics Symposium (DAE-SSPS 2023), 20.-24.12.2023, Visakhapatnam, India

Permalink: https://www.hzdr.de/publications/Publ-38446
Publ.-Id: 38446


DFT Investigation on the Water Reduction Capacity of 001 Slab model of CdX (X= S, Se, Te) Structures

Sudheer, A. E.; Tejaswini, G.; Reddy, D. A.; Devaraj, M.; Posselt, M.

Theoretical investigation were carried out on the water reduction capacity of slab models of Wurtzite CdS, CdSe and CdTe compounds, which is constructed in the 001 direction. For the systematic study, we are intertwining the relation between energetics of redox reactions and water reduction capacity of materials with the help of Density Functional Theory (DFT) calculations. We found polarization along the c axis of every CdX (X= S, Se, Te) unitcell structures due to the unsymmetrical tetrahedral structure, which leads to charge separation and better photocatalytic activity. Understanding this unique property of this wurtzite CdX structures, we constructed slab models along 001 direction and performed free energy analysis. Our findings reveal the inhibition of Cd-terminated surface for the water reduction reaction whereas all the chalcogenide surfaces provide highly favorable water reduction environment. Further, we also noticed the exciting water reduction capacity of S- terminated surface of CdS structures with a negative energy barrier of -1.28 eV, which is very less compared to all other chalcogenide surfaces

Keywords: slab structure; CdX; DFT calculations

  • Poster
    DAE Solid State Physics Symposium (DAE-SSPS 2023), 20.-24.12.2023, Visakhapatnam, India

Permalink: https://www.hzdr.de/publications/Publ-38445
Publ.-Id: 38445


Overview of the dissemination of n_TOF experimental data and resonance parameters

Dupont, E.; Otuka, N.; Rochman, D.; Beyer, R.; The n_TOF collaboration

The n_TOF neutron time-of-flight facility at CERN is used for nuclear data measurements. The n_TOF Collaboration works closely with the Nuclear Reaction Data Centres (NRDC) network to disseminate the experimental data through the international EXFOR library. In addition, the Collaboration helps integrate the results in the evaluated library projects. The present contribution describes the dissemination status of n_TOF results, their impact on evaluated libraries and ongoing efforts to provide n_TOF resonance parameters in ENDF-6 format for further use by evaluation projects.

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Permalink: https://www.hzdr.de/publications/Publ-38444
Publ.-Id: 38444


The neutron time-of-flight facility n_TOF at CERN Recent facility upgrades and detector developments

Domingo-Pardo, C.; Aberle, O.; Alcayne, V.; Junghans, A.; The n_TOF Collaboration

Based on an idea by Carlo Rubbia, the n_TOF facility at CERN has been operating for over 20 years. It is a neutron spallation source, driven by the 20 GeV/c proton beam from the CERN PS accelerator. Neutrons in a very wide energy range (from GeV, down to sub-eV kinetic energy) are generated by a massive Lead spallation target feeding two experimental areas. EAR1, horizonal with respect to the proton beam direction is set at 185 meters from the spallation target. EAR2, on the vertical line from the spallation source, is placed at 20 m. Neutron energies for experiments are selected by the time-of-flight technique (hence the name n_TOF), while the long flight paths ensure a very good energy resolution. Over one hundred experiments have been performed by the n_TOF Collaboration at CERN, with applications ranging from nuclear astrophysics (synthesis of the heavy elements in stars, big bang nucleosynthesis, nuclear cosmo-chronology), to advanced nuclear technologies (nuclear data for applications, nuclear safety), as well as for basic nuclear science (reaction mechanisms, structure and decay of highly excited compound states). During the planned shutdown of the CERN accelerator complex between 2019 and 2021, the facility went through a substantial upgrade with a new target-moderator assembly, refurbishing of the neutron beam lines and experimental areas. An additional measuring and irradiation station (the NEAR Station) has been envisaged and its capabilities for performing material test studies and new physics opportunities are presently explored. An overview of the facility and of the activities performed at CERN is presented in this contribution, with a particular emphasis on the most relevant experiments for nuclear astrophysics.

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Permalink: https://www.hzdr.de/publications/Publ-38441
Publ.-Id: 38441


Compton imaging for enhanced sensitivity (n,γ) cross section TOF experiments: Status and prospects

Domingo-Pardo, C.; Babiano-Suarez, V.; Balibrea-Correa, J.; Junghans, A.; The n_TOF collaboration

Radiative neutron-capture cross sections are of pivotal importance in many fields such as nucle-osynthesis studies or innovative reactor technologies. A large number of isotopes have been measured with high accuracy, but there are still a large number of relevant isotopes whose cross sections could not be experimentally determined yet, at least with sufficient accuracy and completeness, owing to limitations in detection techniques, sample production methods or in the facilities themselves.

In the context of the HYMNS (High-sensitivitY Measurements of key stellar Nucleo-Synthesis reactions) project over the last six years we have developed a novel detection technique aimed at background suppression in radiative neutron-capture time-of-flight measurements. This new technique utilizes a complex detection set-up based on position-sensitive radiation-detectors deployed in a Compton-camera array configuration. The latter enables to implement gamma-ray imaging techniques, which help to disentangle true capture events arising from the sample under study and contaminant background events from the surroundings. A summary on the main developments is given in this contribution together with an update on recent experiments at CERN n_TOF and an outlook on future steps.

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Permalink: https://www.hzdr.de/publications/Publ-38440
Publ.-Id: 38440


Bell test of quantum entanglement in attosecond photoionization

Ruberti, M.; Averbukh, V.; Mintert, F.

Attosecond physics enables the study of ultrafast coherent electron dynamics in matter upon photoexcitation and photoionization, revealing spectacular effects such as hole migration and coherent Auger dynamics in molecules. In the photoionization scenario, there has been a strong focus on probing the physical manifestations of the internal quantum coherence within the individual parent ion and photoelectron systems. However, quantum correlations between these two subsystems emerging from the attosecond photoionization event have thus far remained much more elusive. In this work, we design theoretically and model numerically a direct probe of quantum entanglement in attosecond photoionization in the form of a Bell test. We simulate from first principles a Bell test protocol for the case of noble gas atoms photoionized by ultrashort, circularly polarized infrared laser pulses in the strong-field regime predicting robust violation of the Bell inequality. This theoretical result paves the way to the direct observation of entanglement in the context of ultrafast photoionization of many-electron systems. Our work provides a different perspective on attosecond physics directed towards the detection of quantum correlations between systems born during attosecond photoionization and unravelling the signatures of entanglement in the ultrafast coherent molecular dynamics, including in the chemical decomposition pathways of molecular ions.

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Permalink: https://www.hzdr.de/publications/Publ-38439
Publ.-Id: 38439


Momentum spectrum of nonlinear Breit-Wheeler pair production in space-time fields

Degli Esposti, G.; Torgrimsson, G.

We show how to use a worldline-instanton formalism to calculate, to leading order in the weak-field expansion, the momentum spectrum of nonlinear Breit-Wheeler pair production in fields that depend on time and one spatial coordinate. We find a nontrivial dependence on the width, $\lambda$, of the photon wave packet, and the existence of a critical point $\lambda_c$. For $\lambda<\lambda_c$ and a field with one peak, the spectrum has one peak where the electron and positron have the same energy. For $\lambda>\lambda_c$ this splits into two peaks. We calculate a high-energy ($\Omega\gg1$) expansion, which to leading order agrees with the results obtained by replacing the space-time field with a plane wave and using the well-known Volkov solutions. We also calculate an expansion for $\Omega\sim a_0\gg1$, where the field is strong enough to significantly bend the trajectories of the fermions despite $\Omega\gg1$.

Permalink: https://www.hzdr.de/publications/Publ-38438
Publ.-Id: 38438


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