Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41681 Publications

Small-scale functional fatigue of a Ni-Mn-Ga Heusler alloy

Fareed, A.; Rosalie, J. M.; Kar, S.; Fähler, S.; Maaß, R.

Abstract

Functional fatigue of shape-memory alloys is a considerable threat to reliable service of actuation devices. Here, we demonstrate the essentially degradation-free cyclic phase-transformation behavior of Ni-Mn-Ga microcrystals up to one million stress-driven superelastic cycles. Cyclic dissipation amounts to about 1/5 of the bulk counterpart and remains unaffected during cycling, even after the introduction of dislocation structures via plastic straining. Plastic yielding and the transformation stress largely exceed the known bulk values. However, the transformation-stress is found to strongly depend on plastic pre-straining, which suggests that the size-affected transformation stress is sensitive to the initial defect structure and that it can be tuned by a targeted introduction of dislocations. These findings demonstrate the high suitability of Ni-Mn-Ga as a robust shape-memory alloy in small-scale functional device engineering.

Keywords: Functional fatigue; Magnetic shape memory alloys; Deformation

Permalink: https://www.hzdr.de/publications/Publ-38745


Surface-symmetry-driven phenomena in magnetoelectric Cr2O3

Pylypovskyi, O.; Weber, S.; Makushko, P.; Veremchuk, I.; Spaldin, N.; Makarov, D.

Abstract

Antiferromagnetic (AFM) Cr$_2$O$_3$ is a unique collinear magnetoelectric material at room temperature. The bulk properties stemming from its magnetic symmetry render chromia of high interest for fundamentals and applications [1]. Features of the chromia surface remain much less explored. Here, we consider nominally compensated surfaces ($m$~and $a$~planes) of Cr$_2$O$_3$ [2]. We show that they provide a sizeable Dzyaloshinskii--Moriya interaction (DMI) determined by the surface magnetic symmetry point group and quantify it to be about 1\,mJ/m$^2$ by means of \textit{ab initio} and micromagnetic approaches. The DMI leads to the development of nonzero surface magnetization $\vec{M}$ whose sign is uniquely determined by the AFM state. The $m$ and $a$ planes of Cr$_2$O$_3$ behave as the canted ferrimagnet and canted 4-sublattice antiferromagnet, respectively. The coupling of $\vec{M}$ to the direction of the N\'{e}el vector is shown by magnetotransport measurements.

[1] P. Makushko et al., Nat. Comm. 13, 6745 (2022). [2] O.V. Pylypovskyi, S. F. Weber et al., ArXiv:2310.13438 (2023).

Keywords: Cr2O3; antiferromagnetism; single crystal; symmetry

  • Lecture (Conference)
    DPG Spring Meeting, 17.-22.03.2024, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-38738


Probing the Long- and Short-Range Structural Chemistry in the C-Type Bixbyite Oxides Th0.40Nd0.48Ce0.12O1.76, Th0.47Nd0.43Ce0.10O1.785 and Th0.45Nd0.37Ce0.18O1.815 via Synchrotron X-ray Diffraction and Absorption Spectroscopy

Murphy, G. L.; Bazarkina, E.; Svitlyk, V.; Roßberg, A.; Potts, S.; Hennig, C.; Henkes, M.; Kvashnina, K.; Huittinen, N. M.

Abstract

The long- and short- range structural chemistry of the C-type bixbyite compounds Th0.40Nd0.48Ce0.12O1.76, Th0.47Nd0.43Ce0.10O1.785 and Th0.45Nd0.37Ce0.18O1.815 is systematically examined using synchrotron X-ray powder diffraction (S-PXRD), high energy resolution fluorescence detection X-ray absorption near edge (HERFD-XANES) and extended absorption fine structure spectroscopy (EXAFS) measurements supported by electronic structure calculations. S-PXRD measurements revealed the title compounds all form classical C-type bixbyite structures in space group Ia3 ̅ that have disordered cationic crystallographic sites with further observation of characteristic superlattice reflections corresponding to oxygen vacancies. Despite the occurrence of oxygen vacancies, HERFD-XANES measurements on the Ce L3-edge revealed that Ce incorporates as Ce+4 into the structures but involves significant local distortion akin to cluster behavior and loss of nearest-neighbors. In comparison, HERFD-XANES measurements on the Nd+3 L3-edge supported by electronic structure calculations reveal that Nd+3 adopts a local coordination environment similar to the long-range C-type structure whilst providing charge balancing for the formation of oxygen defects. Th L3-edge EXAFS analysis reveals shorter average Th-O distances in the title compounds in comparison to pristine ThO2 in addition to shorter Th-O and Th-Ce distances compared to Th-Th or Ce-Ce in corresponding F-type binary oxides (ThO2 and CeO2). These distances are further found to decrease with the increased Nd content of the structures despite simultaneous observation of the overall lattice structure progressively expanding. Linear combination calculations of the M-O bond lengths are used to explain these observations, where the role of oxygen defects, via Nd+3 incorporation, induces local bond contraction and enhanced Th+4 cation valence leading to the observed increased lattice expansion with progressive Nd+3 incorporation. Overall, the investigation points to the significance of dissimilar cations exhibiting variable short-range chemical behavior and how it can affect long-range structural chemistry of complex oxides.

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  • Secondary publication expected from 30.05.2025

Permalink: https://www.hzdr.de/publications/Publ-38737


Investigation of cerium as a surrogate for tetravalent actinides in monazite-type compounds

Lender, T.; Bazarkina, E.; Kvashnina, K.; Huittinen, N. M.; Peters, L.

Abstract

The incorporation of tetravalent cerium into the monazite structure via Ca(II)-coupled substitution was investigated using a solid state and a co-precipitation route. Based on powder XRD measurements and elemental mappings an optimised synthesis procedure was developed that averts the formation of secondary phases and allows the stabilisation of tetravalent cerium with a ratio of up to 0.21 Ce(IV)/Ce(III). In-situ HERFD-XANES measurements at the Ce L3 edge at up to 800 °C were performed to study the cerium oxidation state during the phase transformation from rhabdophane to monazite and the sintering process, revealing an unexpected non-linear behaviour as well as a charge-directing effect of the lanthanum cation.

Keywords: monazite; coupled substitution; solid solution; X-ray diffraction; in-situ XANES

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  • Secondary publication expected from 24.05.2025

Permalink: https://www.hzdr.de/publications/Publ-38736


Heavy metal stabilization of DNA origami nanostructures

Kemper, U.; Weizenmann, N.; Kielar, C.; Erbe, A.; Seidel, R.

Abstract

DNA origami is a powerful tool to fold 3-dimensional DNA structures with nanometer precision. Its usage, however, is limited as high ionic strength, temperatures below ~60 °C and pH values between 5 to 10 are required to ensure the structural integrity of DNA origami nanostructures. Here, we demonstrate a simple and effective method to stabilize DNA origami nanostructures against harsh buffer conditions using [PdCl4]2-. It provided the stabilization of different DNA origami nanostructures against mechanical compression, temperatures up to 100 °C, double-distilled water and pH values between 4 to 12. Additionally, DNA origami superstructures and bound cargos are stabilized with a yield of 98 %. To demonstrate the general applicability of our approach, we employed our protocol to a Pd metallization procedure at elevated temperatures. In the future, we think that our method opens up new possibilities for applications of DNA origami nanostructures beyond their usual reaction conditions.

Keywords: DNA nanostructures; DNA origami; DNA metal interaction; seeded growth; DNA metallization

Permalink: https://www.hzdr.de/publications/Publ-38734


A didactical dataset to learn supervised classification with candy

Sinichenko, V. A.; Bähr, M.; Maximilian, M.; Philip, N.; Gabriele, N.; Ihor, T.; Jessica, A.; Florian, L. C.; Martina, R.; Franziska, B.; Yashkumar, P. F.; Anna, S.; Satyam, S. G.; Dora, H.; Asma, W.; Nico, B.; Tim, Q.; Muhammad, H. K.; Benjamin, B.; Roland, N.; Laura, M.; Marius, P.; Siddhartha, J.; Tom, G.; Yaqian, Z.; Yan, A.; Lena, S.; Hamdaan, A. F.; Florens, K.; Shayan, P.; Lukas, P.; Steinbach, P.

Abstract

A didactical dataset to learn supervised classification

It was obtained from university level students measuring candy that was mixed and distributed in bowls to them. The goal of this dataset creation was to expose the students to the data taking process. Further, the dataset is meant for classificatio

Keywords: Data Science; machine learning

Permalink: https://www.hzdr.de/publications/Publ-38732


Development of [¹⁸F]AG-120 as radiotracer for the detection by positron emission tomography (PET) of the mutant isocitrate dehydrogenase 1 in glioma:

Toussaint, M.; Lai, T. H.; Dukic-Stefanovic, S.; Teodoro, R.; Arnaud, L.; Maisonial-Besset, A.; Weber, V.; Moldovan, R.-P.; Meister, S.; Pietzsch, J.; Kopka, K.; Juratli, T. A.; Wenzel, B.; Deuther-Conrad, W.

Abstract

Background: Mutations of isocitrate dehydrogenase (IDH) enzymes are frequent alterations in glioma - the most common being the IDH1R132H - and their identification has become essential for patient stratification. Here, we propose a transdisciplinary approach to develop an ¹⁸F-labeled ligand to detect the IDH1R132H protein directly and non-invasively by PET.
Material and Methods: Radiosynthesis was performed using the TRACERlab FX2 N automated radiosynthesizer. In vitro evaluation of inhibitory potency, binding affinity, and cell uptake of [¹⁸F]AG-120 was performed using U251 human glioblastoma cells stably transfected with IDH1 or IDH1R132H. In vivo metabolism was investigated in CD-1 mice, and dynamic PET scans (NanoScan®PET/CT) were performed in nude rats bearing U251-IDH1 or U251-IDH1R132H glioblastoma.
Results: AG-120 shows a high inhibitory potency toward IDH1R132H (IC50=5.11 nM). Diastereomerically pure [¹⁸F]AG-120 was produced by an automated copper-mediated radiofluorination. Internalization studies showed a higher uptake of [18F]AG-120 in U251-IDH1R132H cells compared to that in U251-IDH1 cells (0.4 vs. 0.013% ID/μg protein at 120 min), which was suppressed by self-blocking (0.009% ID/μg protein at 120 min). Excellent metabolic stability in vivo was demonstrated (parent fractions in plasma and brain at 30 min p.i.: 85% and 91%, respectively). Low initial uptake in tumors of both models (TAC-peak value ~0.4 SUV) was observed. A slightly higher retention in IDH1R132H- compared to IDH1-tumors (Tumor-to-Background Ratio[30-60min]: ~1.6 vs. ~1.1) was detected.
Conclusion: We have successfully automated the production of [¹⁸F]AG-120 and gained valuable insights into its interactions with IDH1 and IDH1R132H. [¹⁸F]AG-120 will serve as a reference compound for future evaluations of mIDH inhibitors/radioligands and may have applications in peripheral tumors, such as chondrosarcoma.
Acknowledgements: This work was funded by the the European-Regional-Development-Fund and the Sächsische-Aufbaubank (project no. 100364142). We thank Dr. Jacqueline Kessler and Prof. Dirk Vordermark, Department of Radiotherapy, Martin Luther University Halle-Wittenberg, Halle, Germany, for providing the cells.

Keywords: IDH mutation; Preclinical imaging; ¹⁸F-labeled ligand

  • Lecture (Conference)
    Nuclear Medicine and Neurooncology Symposium: Precision Medicine, 26.-27.04.2024, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-38730


Inverting the Kohn-Sham equations with physics-informed machine learning

Martinetto, V.; Shah, K.; Cangi, A.; Pribram-Jones, A.

Abstract

This data repository contains the datasets used in the paper "Inverting the Kohn-Sham equations with physics-informed machine learning". 

It contains the data generation scripts, datasets for the systems used in the paper (Single Well - 1D atom, Double Well - 1D diatomic molecule) and output potentials generated by the physics-informed machine learning models (physics-informed neural networks and Fourier neural operators).

Keywords: density functional theory; machine learning

Involved research facilities

  • Data Center

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Permalink: https://www.hzdr.de/publications/Publ-38725


Complexation of Cm(III) and Eu(III) with phosphates: an experimental and theoretical study

Jordan, N.; Jessat, I.; Huittinen, N. M.; Réal, F.; Vallet, V.

Abstract

The environmental fate of radionuclides (RN), such as actinides and fission products, disposed of in underground nuclear waste repositories is a major concern. Long-term safety assessments of these disposal sites depend on the ability of geochemical models and thermodynamic databases (TDBs) to predict the mobility of RNs over very long time scales. One example where TDBs still have large data gaps is related to the complexation of trivalent actinides and lanthanides with aqueous phosphates. Indeed, solid phosphate monazites are one of the candidate phases for the immobilization of specific high-level waste streams for future safe storage in deep underground disposal facilities, therefore potentially and locally increasing the presence of phosphate at the final disposal site.

Recent work [1-3] obtained reliable complexation constants at 25 °C and at elevated temperatures and thus, closed some knowledge gaps. Laser-induced luminescence spectroscopy was used to study the complexation of Cm(III) and Eu(III) as a function of total phosphate concentration in the temperature regime 25-90 °C, using NaClO4 as a background electrolyte. These studies have been conducted in the acidic pH-range to avoid precipitation of solid Cm and Eu rhabdophane. In addition to the presence of the CmH2PO4 2+/EuH2PO4 2+ species [1-3], the formation of Cm(H2PO4)2 + [2] and Eu(H2PO4)2 + [3] was unambiguously established from the collected luminescence spectroscopic data. The conditional complexation constants of all aqueous complexes were extrapolated to infinite dilution by applying the Specific ion Interaction Theory. Using the integrated van´t Hoff equation, both the molar enthalpy of reaction ΔrHm° and entropy of reaction ΔrSm° values were derived.

Depending on the concentration of phosphate, monodentate or bidentate Cm(III)/Eu(III)-phosphate complexes form with different overall coordination numbers (8,9), but obtaining such information from spectroscopic data only is often challenging. Thus, the structural properties, electronic structures, and thermodynamics of the 1:1 and 1:2 Cm(III) and Eu(III) phosphate complexes were solved using state-of-the-art relativistic quantum chemical (QC) calculations. In particular, the QC methods allowed i) to investigate the complexation strength of Cm(III) and Eu(III) with aqueous phosphate, ii) to understand the possible change of the coordination number with increasing temperature and iii) to investigate the nature (ionic/covalent) of the Cm/Eu bonds with water and phosphate.

Combining the information obtained from quantum chemical calculations with the observed spectral changes facilitates the decisive determination of the structures of the formed phosphate complexes and their overall coordination [2,3].

References
[1] N. Jordan et al., Inorganic Chemistry 57, 7015 (2018).
[2] N. Huittinen et al., Inorganic Chemistry 60, 10656 (2021).
[3] I. Jessat et al., Inorganic Chemistry (in preparation).

Keywords: europium; curium; complexation; SIT; phosphate; ab initio

  • Contribution to proceedings
    53rd Journées des Actinides, 15.-18.04.2024, Lille, France
  • Lecture (Conference)
    53rd Journées des Actinides, 15.-18.04.2024, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-38724


Retrained Models and Scripts for Aluminum at 298K and 933K

Fiedler, L.; Cangi, A.

Abstract

Retrained Models and Scripts for Aluminum at 298K and 933K

Authors

- Fiedler, Lenz (HZDR/CASUS)
- Cangi, Attila (HZDR/CASUS)

Affiliations:

HZDR - Helmholtz-Zentrum Dresden-Rossendorf
CASUS - Center for Advanced Systems Understanding

Data set description

This data sets contains models, scripts and inference results for aluminum at room temperature and the melting point. Training data, hyperparameters and general methodology follow Ref. [1]. The models here are retrained versions of the ones discussed in this publication, and therefore retrained versions of the models contained in Ref. [2]. As such, data from Ref. [2] has been used. Only a subset of models contained in Ref. [1] have been retrained, namely the room temperature model, one liquid and one solid melting point model with four training snapshot each, and the final melting point hybrid model (six training snapshots per phase). Furthermore, for both the hybrid melting temperature model and the room temperature model, multiple models with different initializations were trained.

All models were trained with the MALA code [3] version 1.2.1. They show better accuracy than their original counterparts, as they were trained using the inter-snapshot shuffling algorithm first discussed for the MALA code in Ref. [4].

[1] - "Accelerating finite-temperature Kohn-Sham density functional theory with deep neural networks", Physical Review B, doi.org/10.1103/PhysRevB.104.035120
[2] - "RODARE", doi.org/10.14278/rodare.2485 (v1.0.0)
[3] - "MALA", Zenodo, doi.org/10.5281/zenodo.5557254
[4] - "Machine learning the electronic structure of matter across temperatures", Physical Review B, doi.org/10.1103/PhysRevB.108.125146

Contents

- The models themselves, labeled as either Al298K or Al933K, given as one .zip file per model
    - For 933K, additionally "liquid", "solid" and "hybrid" denotes the training data set
    - For ensembles, a running index denotes the number in the ensemble
- Inference results, given as a single .zip file
    - For all models, band energy and total free energy results are given in the .csv format
        - The columns in these files correspond to "Calculated via DFT LDOS", "Calculated via ML-DFT LDOS", "Calculated via Kohn-Sham system", respectively
    - For some models, additionally the predicted electronic density and density of states on select snapshots is given
- Shuffling, training and testing scripts, given as a single .zip file
    - Scripts are ready-to-use with suitable MALA installation, however, correct data paths have to be filled in
    
   

Keywords: Data set; DFT

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Permalink: https://www.hzdr.de/publications/Publ-38719


High-field magnetization of KEr(MoO4)2

Kutko, K.; Bernáth, B.; Khrustalyov, V.; Young, O.; Engelkamp, H.; Christianen, P. C. M.; Prodan, L.; Skourski, Y.; Pourovskii, L. V.; Khmelevskyi, S.; Kamenskyi, D.

Abstract

We report a magnetization study of the rare-earth-based paramagnet KEr(MoO4)2 in a magnetic field up to 50 T. A recent observation of massive magnetostriction and rotational magnetocaloric effects in this compound triggered interest in the microscopic mechanism behind these phenomena. We combine several experimental techniques to investigate the magnetization behavior up to its saturation along three main crystallographic directions. The synergy of magnetic torque measurements and vibrating sample magnetometry allowed us to reconstruct parallel and perpendicular components of the magnetization vector, enabling us to trace its evolution up to 30 T. Our experiments reveal the magnetization saturation along all principle axes well below the value, expected from crystal electric field calculations. We argue that an externally applied magnetic field induces a distortion of the local environment of Er3+ ions and affects its crystal electric field splitting.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-38714


Templates of expected measurement uncertainties for neutron-induced capture and charged-particle production cross section observables

Lewis, A. M.; Neudecker, D.; Carlson, A. D.; Smith, D. L.; Thompson, I.; Wallner, A.; Barry, D. P.; Bernstein, L. A.; Block, R. C.; Stephen Croft, Y. D.; Drosg, M.; Haight, R. C.; Herman, M. W.; Young Lee, H.; Otuka, N.; Sjöstrand, H.; Sobes, V.

Abstract

This paper provides a template of expected uncertainties and correlations for measurements
of neutron-induced capture and charged-particle production cross sections. Measurements performed in-
beam include total absorption spectroscopy, total energy detection, gamma-ray spectroscopy, and direct charged-
particle detection. Offine measurements include activation analysis and accelerator mass spectrometry. The
information needed for proper use of the datasets in resonance region and high energy region evaluations is
described, and recommended uncertainties are provided when specific values are not available for a dataset.

Permalink: https://www.hzdr.de/publications/Publ-38712


Templates of expected measurement uncertainties

Neudecker, D.; Lewis, A. M.; Matthews, E. F.; Vanhoy, J.; Haight, R. C.; Smith, D. L.; Talou, P.; Croft, S.; Carlson, A. D.; Pierson, B.; Wallner, A.; Al-Adili, A.; Bernstein, L.; Capote, R.; Devlin, M.; Drosg, M.; Duke, D. L.; Finch, S.; Herman, M. W.; Kelly, K. J.; Koning, A.; Lovell, A. E.; Marini, P.; Montoya, K.; Nobre, G. P. A.; Paris, M.; Pritychenko, B.; Sjöstrand, H.; Snyder, L.; Sobes, V.; Solders, A.; Taieb, J.

Abstract

The covariance committee of CSEWG (Cross Section Evaluation Working Group) estab-
lished templates of expected measurement uncertainties for neutron-induced total, (n,γ), neutron-induced
charged-particle, and (n,xn) reaction cross sections as well as prompt fission neutron spectra, average
prompt and total fission neutron multiplicities, and fission yields. Templates provide a list of what uncer-
tainty sources are expected for each measurement type and observable, and suggest typical ranges of these
uncertainties and correlations based on a survey of experimental data, associated literature, and feedback
from experimenters. Information needed to faithfully include the experimental data in the nuclear-data
evaluation process is also provided. These templates could assist (a) experimenters and EXFOR compilers
in delivering more complete uncertainties and measurement information relevant for evaluations of new
experimental data, and (b) evaluators in achieving a more comprehensive uncertainty quantification for
evaluation purposes. This effort might ultimately lead to more realistic evaluated covariances for nuclear-
data applications. In this topical issue, we cover the templates coming out of this CSEWG effort–typically,
one observable per paper. This paper here prefaces this topical issue by introducing the concept and
mathematical framework of templates, discussing potential use cases, and giving an example of how they
can be applied (estimating missing experimental uncertainties of 235U(n,f) average prompt fission neutron
multiplicities), and their impact on nuclear-data evaluations.

Permalink: https://www.hzdr.de/publications/Publ-38711


Time-resolved nanospectroscopy on Si-doped GaAs-InGaAs core-shell nanowires

Luferau, A.; Obst, M.; Kehr, S.; Eng, L.; Winnerl, S.; Pashkin, O.; Dimakis, E.; Helm, M.

Abstract

High-quality epitaxial nanowires (NWs) based on III-V semiconductors offer the possibility to fabricate ultrafast optical devices due to their direct bandgap and the high electron mobility. Contactless investigation of photoexcited carriers within single NWs is enabled by optical-pump THz-probe scanning near-filed optical microscopy (SNOM) experiment. Here we report on first THz-pump MIR-probe SNOM studies on Si-doped GaAs-InGaAs core-shell NWs utilizing THz radiation from the free-electron laser FELBE. The experiment was carried out with SNOM setup from Neaspec equipped with nanoFTIR module, where a broadband MIR source (5-15μm) serves as a probe. Upon intraband THz-pump (25μm) we observed a red shift of amplitude and phase of the NW plasma resonance, while control interband optical pumping (780nm) induced a blue shift of the resonance, and in both cases an exponential decay with a time constant of 4-5ps is seen. We attribute the blue shift to the contribution of photogenerated carriers. The red shift is assigned to the heating of the electrons in the conduction band and the subsequent increase of the effective mass in the nonparabolic Γ-valley due to high peak electric fields of THz pulses.

Keywords: s-SNOM; nanowires; nanospectroscopy

Involved research facilities

  • F-ELBE
  • Contribution to proceedings
    DPG Spring Meeting of the Condensed Matter Section 2023, 26.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-38710


THz-pump / MIR-probe nanospectroscopy on Si-doped GaAs-InGaAs core-shell nanowires

Luferau, A.; Obst, M.; Winnerl, S.; Kehr, S. C.; Dimakis, E.; Pashkin, O.; Kaps, F.; Eng, L. M.; Helm, M.

Abstract

We report on first THz-pump / MIR-probe SNOM studies on Si-doped GaAs-InGaAs core-shell NWs utilizing THz radiation from the free-electron laser FELBE. Upon intraband THz-pump we observe a red shift of the NW plasma resonance in both amplitude and phase spectra, while a controlled interband optical pumping induces a blue shift of the resonance. In both cases, the signal exponentially decays with a time constant of 4-5 ps. We attribute the blue shift to the contribution of photogenerated charge carriers, while the red shift is assigned to the heating of electrons in the conduction band accelerated by the THz electric field of the pump pulses and the subsequent increase of their effective mass due to the nonparabolic Γ-valley dispersion.

Keywords: s-SNOM; nanowires; nanospectroscopy; FEL

Involved research facilities

  • F-ELBE
  • Contribution to proceedings
    2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 17.09.-31.10.2023, Montreal, Canada

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Permalink: https://www.hzdr.de/publications/Publ-38709


Data publication: Significant Resistance Reduction in Modulation-Doped Silicon Nanowires via Aluminum-Induced Acceptor States in SiO2

Ratschinski, I.; Nagarajan, S.; Trommer, J.; Luferau, A.; Khan, M. B.; Erbe, A.; Georgiev, Y.; Mikolajick, T.; Smith, S. C.; König, D.; Hiller, D.

Abstract

Measured resistance as a function of nanowire (NW) width for different modulation doped Si NWs.

Keywords: electrical properties; modulation doping; resistance; silicon nanowires

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Permalink: https://www.hzdr.de/publications/Publ-38708


Significant Resistance Reduction in Modulation-Doped Silicon Nanowires via Aluminum-Induced Acceptor States in SiO2

Ratschinski, I.; Nagarajan, S.; Trommer, J.; Luferau, A.; Khan, M. B.; Erbe, A.; Georgiev, Y.; Mikolajick, T.; Smith, S. C.; König, D.; Hiller, D.

Abstract

Silicon nanowires (Si NWs) like structures in the form of nanosheets are the building blocks for future transistors in the most advanced complementary metal–oxide–semiconductor technologies. However, Si NWs with few nanometers in diameter suffer from severe difficulties with respect to efficient impurity doping. These difficulties can be overcome by a novel doping concept for Si NWs comparable to the modulation doping approach known from III–V semiconductors. Modulation doping means that the parent dopant atoms are spatially separated from the volume that is to be doped by embedding them into an adjacent material with a higher bandgap. Herein, Al-doped SiO2 shells around the Si NWs are used for the experimental realization of modulation doping. In two independent experiments, a significant reduction of the electrical resistance of Si NWs by several orders of magnitude is measured, when compared to the resistance of Si NWs with undoped SiO2 shells. The results are discussed in the context of modulation doping by the surface functionalization with SiO2:Al shells.

Keywords: electrical properties; modulation doping; resistance; silicon nanowires

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Permalink: https://www.hzdr.de/publications/Publ-38707


Data publication: A quantitative analysis of the effect of box size in N-body simulations of the matter power spectrum

Eingorn, M.; Yilmaz, E.; Yukselci, A. E.; Zhuk, O.

Abstract

The dataset consists of the matter power spectra at four redshifts (z=80,50,15,0) generated by simulating Lambda-Cold Dark Matter cosmology within the cosmic screening approach as described in the associated paper. Outputs of six distinct runs are available for boxes with L= 280, 560, 1680, 4480, 5120, 5632 Mpc/h comoving sizes, each with 2 Mpc/h resolution.

Keywords: inhomogeneous Universe; large-scale structure; cosmic screening; cosmological perturbations; N-body simulations; power spectrum

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Permalink: https://www.hzdr.de/publications/Publ-38704


Analyse, Planung und Umsetzung einer verteilten Informationsarchitektur für ein New Work Konzept am HZDR

Schwabe, J.

Abstract

Im Zuge der zunehmenden Digitalisierung bleibt auch die Arbeitswelt von Veränderungen auf diesem Gebiet nicht unberührt.
Wechselnde Arbeitszeitmodelle und flexible sowie hybride Arbeitsplätze stellen eine Herausforderung für das klassische Flächenmanagement und die Erreichbarkeit von Mitarbeitenden dar.
Um eine veränderliche Belegung von Büroräumen für Beschäftigte zu vereinfachen, werden zunehmend verschiedene Smart Office Solutions entwickelt.
Dazu zählt auch eine flexible Informationsanzeige, um Mitarbeitende auch bei zeitlich und räumlich wechselnden Arbeitsplätzen auffinden zu können.
Am Beispiel eines am Helmholtz-Zentrum Dresden - Rossendorf (HZDR) neu entstehenden Bürogebäudes wird im Rahmen dieser Arbeit ein verteiltes Informationssytem konzipiert und ein Prototyp dessen mit den Basis-Funktionalitäten implementiert.
Dabei kommuniziert ein digitales, kabelloses Türschild in einem drahtlosen Netzwerk mit einem zentralen Server, welcher Informationen aus bestehenden Datenbanken zu aktuellen Raumbelegungen ausliest.
Diese Informationen werden automatisiert auf dem ePaper-Display des Türschildes angezeigt.
Im Vordergrund steht dabei ein möglichst geringer Energiebedarf der über eine mobile Spannungsquelle mit Strom zu versorgenden Türschilder.

Keywords: Data Science; Data Management; Electronic Door Sign; E-Paper; New Work; Smart Office; Python; Arduino; ESP8266

Related publications

  • Bachelor thesis
    Berufsakademie Sachsen, Staatliche Studienakademie Dresden, 2023
    Mentor: Dr.-Ing. Oliver Knodel, Dr. rer. nat. Dietbert Gütter

Permalink: https://www.hzdr.de/publications/Publ-38703


Evaluating the quality of pure mineral extraction during luminescence sample preparation

Melo Girón, A. M.; Fuchs, M.; Gloaguen, R.; Dornich, K.; Heitmann, J.

Abstract

Through the last 50 years, Optically Stimulated Luminescence (OSL) dating has been applied to get absolute age estimates for the last exposure of minerals like quartz or feldspar to light or heat. The method provides manifold applications for unraveling the geochronological scale of surface processes and related sediment archives. Over time, technology and techniques improved creating new ways to get a more accurate age. However, ensuring the quality of dating results commenceswith sample preparation and accurate extraction of the dosimeter (quartz or feldspar). Standard separation procedures for quartz-based OSL dating involve a series of steps to enrich the quartz. Due different wettability of feldspar and quartz is possible
to separate them through froth flotation. Our goal is to determine the quality of quartz separation of one poly-mineral sample of fluvial sediments from Pamir applying feldspar flotation. This froth-type method showed in past experiments quartz concentrations of 95-100 %. Using X-ray diffraction analysis, we trace the chemical composition of each step of the process to illustrate the advantage of this froth method in getting high-purity quartz extracts.

Keywords: Luminescence

Permalink: https://www.hzdr.de/publications/Publ-38701


Luminescence dating of active faults in New Zealand: first insights from pIRIR225

Melo Girón, A. M.; Tsukamoto, S.; Fuchs, M.; Tanner, D.; Brandes, C.; Kroner, U.; Gloaguen, R.

Abstract

We aim to test the potential of luminescence dating to determine the relative activity of three active faults in New Zealand. To this end, we collected four dark-gray, fine to very fine grain-size samples classified as cataclasite and gouge from outcrops situated along the fault traces of the Alpine Fault, Hope Fault, and Hundalee Fault. Through sample processing, we obtained polymineral fine grains, ranging from 4 to 11 µm, to conduct post-infrared infrared stimulated luminescence (pIRIR225) dating. In this work, we show the first insights into the Luminescence properties, in the first attend to record ages in active faults in New Zealand using direct dating on gouge and cataclasites.

Keywords: Earthquakes

Permalink: https://www.hzdr.de/publications/Publ-38700


Data publication: Microstructure-informed prediction of hardening in ion-irradiated reactor pressure vessel steels

Lai, L.; Brandenburg, J.-E.; Chekhonin, P.; Duplessi, A.; Cuvilly, F.; Etienne, A.; Radiguet, B.; Rafaja, D.; Bergner, F.

Abstract

Mainly the original data for model establishment.

Keywords: reactor pressure vessel steels; ion irradiation; microstructure characterization; transmission electron microscopy; atom probe tomography; nanoindentation; hardening

Involved research facilities

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-38698


Microstructure-informed prediction of hardening in ion-irradiated reactor pressure vessel steels

Lai, L.; Brandenburg, J.-E.; Chekhonin, P.; Duplessi, A.; Cuvilly, F.; Etienne, A.; Radiguet, B.; Rafaja, D.; Bergner, F.

Abstract

Ion irradiation combined with nanoindentation is a promising tool to study irradiation-induced hardening of nuclear materials including reactor pressure vessel (RPV) steels. For RPV steels, the major sources of hardening are nm-sized irradiation-induced dislocation loops and solute atom clusters, both representing barriers for dislocation glide. The dispersed barrier hardening (DBH) model provides a link between the irradiation-induced nanofeatures and hardening. However, a number of details of the DBH model still require consideration. These include the role of the unirradiated microstructure, the proper treatment of the indentation size effect (ISE), and the appropriate superposition rule of individual hardening contributions. In the present study, two well characterized RPV steels, each ion-irradiated up to two different levels of displacement damage, were investigated. Dislocation loops and solute atom clusters were characterized by transmission electron microscopy and atom probe tomography, respectively. Nanoindentation with a Berkovich indenter was used to measure indentation hardness as a function of the contact depth. In the present paper, the measured hardening profiles are compared with predictions based on different DBH models. Conclusions about the appropriate superposition rule and the consideration of the ISE (in terms of geometrically necessary dislocations) are drawn.

Keywords: reactor pressure vessel steels; ion irradiation; microstructure characterization; transmission electron microscopy; atom probe tomography; nanoindentation; hardening

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-38696


Wechselwirkungen von Technetium mit Mikroorganismen, Metaboliten und an der Mineral-Wasser-Grenzfläche – Radioökologische Betrachtungen

Börner, C.; Müller, K.; Mayordomo, N.

Abstract

Technetium-99 (⁹⁹Tc) ist ein langlebiges Spaltprodukt (2,13∙10⁵ Jahre) von Uran-235 (²³⁵U) und Plutonium-239 (²³⁹Pu) und daher von großer Bedeutung für die langfristig sichere Entsorgung von radioaktiven Abfällen aus Kern-kraftwerken. Die Migration von Tc in der Umwelt wird stark von den Redoxbedingungen beeinflusst, da Tc in verschiedenen Oxidationsstufen vorliegen kann. In der Umgebung eines Endlagers dürfte Tc unter oxidierenden Bedingungen hauptsächlich als Tc(VII) und unter reduzierenden Bedin-gungen als Tc(IV) auftreten. Es ist bekannt, dass das Anion Pertechnetat (Tc(VII)O₄ ⁻) kaum mit mineralischen Oberflächen interagiert, was wiederum seine Migration im Grundwasser und seinen Eintritt in die Biosphäre begünstigt. Im Gegensatz dazu schränkt die Bildung von Tc(IV) die Migration von Tc ein, da es einen schwerlöslichen Feststoff (TcO₂) und/oder Spezies bildet, deren Wechselwirkung mit Mineralien günstiger ist. In vergangenen Untersuchungen lag der Fokus auf der Reduktion von Tc(VII) zu Tc(IV) durch verschiedene Reduktionsmittel wie Fe(II), Sn(II) oder S(-II), die entweder in Lösung vorliegen, an mineralischen Strukturen beteiligt sind (Pearce et al.) oder metabolisch durch mikrobielle Kaskaden induziert werden (Newsome et al.).
Die meisten der veröffentlichten Studien konzentrierten sich auf binäre Systeme, d. h. auf die Untersuchung der Wechselwirkung von Tc mit einem bestimmten Reduktionsmittel. Die Umwelt ist jedoch ein komplexes System, in dem verschiedene Komponenten oft voneinander abhängen und sich gegenseitig beeinflussen. Daher ist die Tc-Migration anfällig und variiert je nach Umweltbedingungen und sollte nicht isoliert untersucht werden. Die Arbeiten der vom BMBF geförderte Nachwuchsforschungsgruppe TecRad (TecRad 2023) zielen darauf ab die Tc-Chemie aus einer breiteren Perspektive zu analysieren. Daher untersuchen wir das biogeochemische Verhalten von Tc mit i) Mikroorganismen, ii) Metaboliten, und iii) Fe(II)-Mineralen. Weiterhin möchten wir die Wechselwirkungen zwischen Fe(II)-Mineralen in Gegenwart von Metaboliten besser verstehen.
Ein wichtiger Teil dieses Projekts befasst sich mit der Anwendung neuer spektro-elektrochemischer Methoden zur In-situ-Überwachung des Verhaltens von Tc in Lösung und an Grenzflächen in Abhängigkeit vom Redoxpotential. Mit diesen Instrumenten wollen wir die molekularen Strukturen der Tc-Spezies unter verschiedenen Redox-Bedingungen charakterisieren, um das Verständnis für das chemische Verhalten des Schadstoffs zu erweitern.

Unser Ziel ist es, wertvolle thermodynamische Daten (komplexe Bildungskonstanten, Löslichkeitskonstanten von Mineralen, Redoxpotentiale und Tc-Verteilungskoeffizienten) zu generieren, die wir zur Imple-mentierung einer geochemischen Modellierung verwenden werden, die das Verhalten von Tc in der Umwelt auch unter verschiedenen Redoxbedingungen erklären kann.

III. DANKSAGUNGEN
Die Autoren danken dem Bundesministerium für Bildung und Forschung (BMBF) für die finanzielle Unterstützung der NukSiFutur TecRad Nachwuchsgruppe (02NUK072).

IV. LITERATURVERZEICHNIS
[1] Pearce, C. et al. (2020). Sci. Total Env. 132849.
[2] Newsome, L. et al. (2014). Chem. Geol. 164-184.
[3] TecRad webpage: https://www.hzdr.de/db/Cms?pNid=1375

Keywords: Technetium; Vivianite; Reduction; Minerals; Iron

  • Poster
    Tage der Standortauswahl 2024, 18.-19.04.2024, Goslar, Deutschland
    DOI: 10.21268/20240416-1

Permalink: https://www.hzdr.de/publications/Publ-38695


In operando visualization of mass transfer in a sodium-zinc molten salt battery with liquid electrolyte

Sarma, M.; Nash, W.; Weber, N.; Weier, T.

Abstract

To bring the novel Na-Zn molten salt battery to market, many unresolved issues – such as self-discharge, migration of Na away from the current collector, and electrolyte “creeping” – must be resolved. Within the framework of the Horizon 2020 project SOLSTICE, a working battery prototype must be delivered. To support this objective, a small-scale experimental cell that can be used for fundamental research has been built. The cell has been designed to permit in situ radiographic imaging of its interior. The aim is to charge and discharge this cell in a neutron beamline and an X-ray source, to observe mass transfer of electroactive species and any flow that occurs during cycling. Of most interest are how these phenomena depend on the geometry and chemical composition of the different cell components, e.g. the positive and negative current collectors.
With a completely liquid interior, all the cell’s components must retain their performance characteristics at its 600oC operating temperature. Besides thermal stress, the cell’s walls and current collectors must resist corrosion by liquid Zn, Na, and the molten salt electrolyte (as well as their vapors). Maintenance of this high internal temperature also requires sufficient thermal insulation, and – in an isolated test cell – an external heating system, and neither of these should interfere with the imaging techniques.
Preliminary attempts to cycle the cell for an extended period of time (>4 weeks) have been successful. Pilot imaging tests using neutron and X-ray radiography have confirmed that the different layers (the electrodes and electrolyte) can be distinguished from one another, and spatial variations in the chemical composition of the electrolyte can be resolved. However, corrosion remains a limitation for long-term structural stability, so optimization of the cell’s components is ongoing. Long-term cycling data and X-ray/neutron images will be presented in this talk, and their implications for improvements to the cell design will be discussed.

  • Lecture (Conference)
    4th International Sodium Battery Symposium (SBS4), 04.09.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38694


Mass transport and solutal convection in a sodium-zinc molten salt battery with liquid electrolyte: comparison of modelling and experiments

Sarma, M.; Duczek, C.; Nash, W.; Weber, N.; Weier, T.

Abstract

Within the Horizon 2020 project SOLSTICE, a molten salt battery has been developed. The battery employs sodium and zinc as anode and cathode respectively and operates at around 600 oC with a completely liquid interior. The primary advantage of this design is its low materials’ cost. However, multiple challenges must be overcome if it is to become commercially viable. These include corrosion of metallic components by the molten salt electrolyte, and self-discharge promoted by transport of cathode materials (Zn2+ ions) to the anode. Efforts to suppress the latter especially benefit from modelling, as the rate of self-discharge is primarily determined by mass transport processes in the electrolyte. Such models require experimental validation, thus, a small-scale experimental cell has been constructed for this purpose. It has been designed specifically for operation during analysis by radiographic methods (neutron beam and X-ray imaging). The distribution of the active materials can be observed at different stages of the charging-discharging cycle. This presentation will provide an overview of current modelling activities at HZDR related to the sodium-zinc battery, together with first (preliminary) experimental results and the most recent progress towards designing a “transparent” cell.

  • Lecture (Conference)
    9th International Scientific Colloquium "Modelling for Materials Processing" 2023, 18.09.2023, Riga, Latvija

Permalink: https://www.hzdr.de/publications/Publ-38693


Magnetocaloric effect in the Laves phases RCo2 (R = Er, Ho, Dy, and Tb) in high magnetic fields

Bykov, E.; Karpenkov, A.; Liu, W.; Straßheim, M.; Niehoff, T.; Skokov, K.; Scheibel, F.; Gutfleisch, O.; Salazar Mejia, C.; Wosnitza, J.; Gottschall, T.

Abstract

The heavy rare-earth-based Laves phases are well-studied intermetallic materials that stand out for their remarkably high magnetocaloric effects, particularly at cryogenic temperatures. In this study, we present the findings of our comprehensive investigation of cobalt Laves phases RCo2 with R standing for erbium, holmium, dysprosium, and terbium. This includes the determination of the magnetocaloric effect by indirect methods using calorimetric and magnetization data. Furthermore, for the first time in these materials, we directly measured the adiabatic temperature change at high magnetic fields up to 20 T. The largest ΔTad value of 17 K, we obtained for ErCo2. Because the order of the transition significantly impacts the efficiency of thermodynamic cycles, we have also focused on determining the transition order in these materials. This was done through the application of established methods and a recently proposed quantitative criterion including the value of the local exponent n. Further, we compare our results with other materials using a straightforward material-based figure of merit - the temperature-averaged entropy change (TEC). Our results demonstrate the great potential of these materials for applications such as for magnetic hydrogen liquefaction.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-38692


Data publication: How to verify the precision of density-functional-theory implementations via reproducible and universal workflows

Bosoni, E.; Beal, L.; Bercx, M.; Blaha, P.; Blugel, S.; Broder, J.; Callsen, M.; Cottenier, S.; Degomme, A.; Dikan, V.; Eimre, K.; Flage-Larsen, E.; Fornari, M.; Garcia, A.; Genovese, L.; Giantomassi, M.; Huber, S. P.; Janssen, H.; Kastlunger, G.; Krack, M.; Kresse, G.; Kühne, T. D.-S.; Lejaeghere, K.; Madsen, G. K. H.; Marsman, M.; Marzari, N.; Michalicek, G.; Mirhosseini, H.; Muller, T. M. A.; Petretto, G.; Pickard, C. J.; Ponce, S.; Rignanese, G.-M.; Rubel, O.; Ruh, T.; Sluydts, M.; Vanpoucke, D. E. P.; Vijay, S.; Wolloch, M.; Wortmann, D.; Yakutovich, A. V.; Yu, J.; Zadoks, A.; Zhu, B.; Pizzi, G.

Abstract

In this Expert Recommendation, we list a set of guiding principles to perform new verification studies of DFT calculations, and we illustrate examples of verification by using a curated reference set of highly converged results for the EOS of 960 crystals, with two independent state-of-the-art all-electron (AE) DFT codes (FLEUR and WIEN2k).

Keywords: Density-functional theory; Verification; pseudopotential codes

Related publications

  • Reseach data in external data repository
    Publication year 2023
    License: CC-BY-4.0
    Hosted on materials cloud: Link to location

Permalink: https://www.hzdr.de/publications/Publ-38691


Laterally resolved polymorph conversion in Ga2O3 using FIBs

Bektas, U.; Klingner, N.; Hübner, R.; Chekhonin, P.; Liedke, M. O.; Hlawacek, G.

Abstract

Laterally resolved polymoprh conversion in Galliumoxide
using Focused Ion Beams

Keywords: FIB

Involved research facilities

Related publications

  • Lecture (Conference) (Online presentation)
    Defect Engineering in SiC and Other Wide Bandgap Semiconductor, 22.-24.10.2023, Erlangen, Shenzen, Deutschaldn, China

Permalink: https://www.hzdr.de/publications/Publ-38690


Materials Science with Fibs across Applications and Fluencies at the HZDR Ion Beam Center.

Hlawacek, G.

Abstract

Materials Science with Fibs across Applications and Fluencies at the HZDR Ion Beam Center.

Keywords: FIB

Involved research facilities

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  • Invited lecture (Conferences)
    CINT User meeting, 19.-20.09.2023, Santa Fe, USA

Permalink: https://www.hzdr.de/publications/Publ-38689


Applications of unconventional focused ion beams in quantum and semiconductor technology

Hlawacek, G.

Abstract

Applications of unconventional focused ion beams in
quantum and semiconductor technology

Keywords: FIB

Involved research facilities

Related publications

  • Lecture (others)
    Institutsseminar, 10.05.2023, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38688


Application of gas field ion source and liquid metal alloy ion source based focused ion beams

Hlawacek, G.

Abstract

I will present recent results obtained in our group using gas field ion sources (GFIS)1 and liquid metal alloy ion
source (LMAIS)2 based focused ion beams (FIB). I will briefly explain the source technology and our efforts
in developing new and unconventional ion sources for their application in FIB instruments. A few selected
examples will include the LMAIS based fabrication of single photon emitters (SPE) which are fundamental
building blocks for future quantum technology applications. I will present a method to fabricate at will placed
single or few SPEs emitting in the telecom O-band in Silicon3 . The successful integration of these telecom
quantum emitters into photonic structures such as micro-resonators, nanopillars and photonic crystals with
sub-micrometer precision paves the way toward a monolithic, all-silicon-based semiconductor-superconductor
quantum circuit for which this work lays the foundations. To achieve our goal we employ home built AuSi
and a unique CeC LMAIS both operated in an Orsay Physics CANION M31Z+ FIB. Silicon-on-insulator
substrates from different fabrication methods have been irradiated with a spot pattern. The achieved lateral
SPE placement accuracy is below 100 nm in both cases and the success rate of SPE formation is more than
50%. In addition I will present recent results obtained on the helium ion microscope using FIB and He ion
extracted from a GFIS source. These examples will include the epitaxial over growth of Sn spheres during He
ion beam irradiation. This more fundamental experiment show cases the importance of the ion beam driven
generation of interstitials and their diffusion during the ion beam irradiation4 . Finally, I’d like to demonstrate
how GFIS based HIM can be used to generate electrically controlled magnetic landscapes in spin orbit torque
(SOT) materials. Here, we use in-situ controlled irradiation to identify the best irradiation conditions for the
preparation of µm sized areas which will switch magnetization direction at different SOT currents5 .
Financial support by the COST Action CA19140 is acknowledged. http://www.fit4nano.eu/

Keywords: FIB

Involved research facilities

Related publications

  • Lecture (others)
    Department Seminar, 13.04.2023, Pasadena, USA

Permalink: https://www.hzdr.de/publications/Publ-38687


High fluence He irradiation of materials using Helium Ion Microscopy

Hlawacek, G.; Klingner, N.; Lohmann, S.; Hübner, R.; Gandy, A.

Abstract

I will present some recent results on the high fluence irradiation of metals using gas field ion source (GFIS) based
helium ion microscope (HIM)1 .
High entropy alloys (HEAs) are a relatively new class of metal alloys composed of several principal elements, usually
at (near) equiatomic ratios. Here, our goal is to understand how such a multicomponent alloy behaves under irradiation.
The FeCoCrNiV HEA exhibits both a face-centred cubic (fcc) and a body-centred tetragonal (bct) phase, thus allowing
us to specifically study the influence of crystalline structure at very similar chemical composition. We irradiated both
phases with a focussed He beam provided by a HIM at temperatures between room temperature and 500 ∘ C. The
irradiation fluence was varied between 6 × 1017 ions cm−2 to 1 × 1020 ions cm−2 . High-resolution images of the irradiated
areas were taken with the same HIM. Selected irradiated areas were additionally studied by transmission electron
microscopy (TEM) in combination with energy dispersive X-ray spectroscopy (EDXS). Under irradiation, pores start
to be generated in the material with pore sizes differing significantly between the two phases. At higher fluences and
above a critical temperature, a tendril structure forms in both phases. We found that the critical temperature depends
on the phase and is lower for fcc. TEM images reveal that the tendrils span the whole depth of the irradiated area, and
are accompanied by bubbles of various sizes. Scanning TEM-based EDXS of these structures indicates a He-induced
change in composition.
In the second part I want to present an intriguing observation shedding light on the fundamental processes related
to interstitial diffusion during irradiation. I will show how epitaxial growth of tin extrusions on tin-oxide-covered tin
spheres can be induced and simultaneously observed by implanting helium using a HIM2 . Calculations of collision
cascades based on the binary collision approximation (BCA) and 3D-lattice-kinetic Monte Carlo (3D-lkMC) simulations
show that the implanted helium will occupy vacancy sites, leading to a tin interstitial excess. Sputtering and phase
separation of the tin oxide skin, which is impermeable for tin atoms, create holes and will allow the epitaxial overgrowth
to start. Simultaneously, helium accumulates inside the irradiated spheres. Fitting the simulations to the experimentally
observed morphology allows us to estimate the tin to tin-oxide interface energy to be 1.98 J m−2 .
Both approach have in common that they employ spatially resolved irradiation and in-situ observation of defect
diffusion-driven effects to improve the understanding of the formation mechanism of ion induced structures.
Financial support by the COST Action CA19140 is acknowledged. http://www.fit4nano.eu/

Keywords: FIB

Involved research facilities

Related publications

  • Lecture (others)
    Department Seminar, 11.04.2023, Berkeley, USA

Permalink: https://www.hzdr.de/publications/Publ-38686


Gallium Oxide Fabrication with Ion Beams

Hlawacek, G.; Klingner, N.; Bektas, U.; Chekhonin, P.; Erb, D.; Kuznetsov, A.; Azarov, A.; García Fernández, J.; Zhao, J.; Djurabekova, F.

Abstract

Gallium oxide is a novel ultra-wide band gap material, and the rationale for the current research project
is that its thin film fabrication technology is immature. In particular, the metastability conditions are
difficult to control during sequential deposition of different polymorphs with existing techniques. However, the
polymorphism may turn into a significant advantage if one can gain control over the polymorph multilayer
and nanostructure design. Our objective is to develop a method for the controllable solid state polymorph
conversion of gallium oxide assisted by ion irradiation. This fabrication method may pave the way for several
potential applications (e.g. in power electronics, optoelectronics, thermoelectricity batteries) and we will test
the corresponding functionalities during the project. Thus, we envisage multiple positive impacts and potential
benefits across a wide range of stakeholders.
I will introduce the aims and objectives of project paying specific attention to the planned methodology to
gain spatial control over the polymorph conversion. In the second half I will present the first results obtained
in the last 5 month. This includes broad beam irradiation which confirms the successful polymorph conversion
independent of primary ion species and the related exceptional radiation tolerance of the formed g-Ga2 O3 layer.
Further I will report the first spatially resolved focused ion beam (FIB) induced b- to g-Ga2 O3 polymorph
conversion. For this result different FIBs—available at the Ion Beam Center—have been used. These are in
particular the Helium Ion Microscope (HIM) using Neon ions, a conventional Gallium liquid metal ion source
(LMIS) based FIB as well as a liquid metal alloy ion source (LMAIS) FIB using Co ions. The confirmation of
the latter result also required the test and optimization of an electron backscatter diffraction (EBSD) based
analysis method.
I will end with an outlook on experiments foreseen for the rest of the project duration.
Support by the State of Saxony via Project 100629936 GoFIB—Gallium Oxide Fabrication with Ion Beams
and the COST Action 19140 FIT4NANO is acknowledged.

Keywords: FIB

Involved research facilities

Related publications

  • Lecture (others)
    Infineon InnoTalk, 05.04.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38685


PCB-Vision: A Multiscene RGB-Hyperspectral Benchmark Dataset of Printed Circuit Boards

Arbash, E.; Fuchs, M.; Rasti, B.; Lorenz, S.; Ghamisi, P.; Gloaguen, R.

Abstract

PCB-Vision Dataset

Description:

The PCB-Vision dataset is a multiscene RGB-Hyperspectral benchmark dataset comprising 53 Printed Circuit Boards (PCBs). The RGB images are collected using a Teledyne Dalsa C4020 camera on a conveyor belt, while hyperspectral images (HSI) are acquired with a Specim FX10 spectrometer. The HSI data contains 224 bands in the VNIR range [400 - 1000]nm.

Data Format

  • RGB Images: .png files
  • PCB Masks: .jpg files
  • HSI Data: Each hyperspectral data cube is accompanied by a data file and a .hdr file.

Folder Organization

  • PCBVision
    • HSI/
      • 53 subfolders (one for each PCB)
      • 'General_masks' folder for 'General' segmentation ground truth
      • 'Monoseg_masks' folder for 'Monoseg' segmentation ground truth
      • 'PCB_Masks' folder for masks of the 53 PCBs in the hyperspectral cube
    • RGB/
      • 53 .jpg images
      • 'General' folder for RGB images 'General' segmentation ground truth
      • 'Monoseg_masks' folder for RGB images 'Monoseg' segmentation ground truth

Data Classes in Masks

  • Masks (both 'General' and 'Monoseg') contain 1 to 4 segmentation classes:
    • 0: "Others"
    • 1: "IC"
    • 2: "Capacitors"
    • 3: "Connectors"

Code Repository

To facilitate reading and working with the data, Python codes are available on the GitHub repository:

https://github.com/hifexplo/PCBVision

Citation

If you use this dataset, please cite the following article:

Word:

Arbash, Elias, Fuchs, Margret, Rasti, Behnood, Lorenz, Sandra, Ghamisi, Pedram, & Gloaguen, Richard. (2024). PCB-Vision: A Multiscene RGB-Hyperspectral Benchmark Dataset of Printed Circuit Boards (Version 1) [Data set]. Rodare. http://doi.org/10.14278/rodare.2704

Latex:

@article{arbash2024pcb, title={PCB-Vision: A Multiscene RGB-Hyperspectral Benchmark Dataset of Printed Circuit Boards}, author={Arbash, Elias and Fuchs, Margret and Rasti, Behnood and Lorenz, Sandra and Ghamisi, Pedram and Gloaguen, Richard}, journal={arXiv preprint arXiv:2401.06528}, year={2024} }

Contact

For further information or inquiries, please visit our website:

https://www.iexplo.space/

Contact Email: e.arbash@hzdr.de

Keywords: circular economy; automated data processing; optical sensors; recycling; e-waste; printed circuit board; hyperspectral; dataset; RGB; conveyor belt; sensors; machine learning; deep learning; PCBVision; open-source data; digitalization

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-38684


Spatially Resolved Polymorph Conversion in Ga2O3

Bektas, U.; Chekhonin, P.; Heller, R.; Hübner, R.; Liedke, M. O.; Klingner, N.; Hlawacek, G.

Abstract

Monoclinic galliumoxide (β-Ga2O3) is a promising wideband gap
semiconductor with a bandgap of 4.7 eV and a high breakdown voltage.
However, the existence of several metastable polymorphs and the
immature fabrication technology limits its applications. The research is
based on the recent observation that β-Ga2O3 can reliable be converted
into γ-Ga2O3 using high energy ion beams [1,2]. It could also be shown that
the resulting γ-Ga2O3 layer exhibits an exceptional tolerance towards high
fluence ion beam irradiation [3].
Here, we use focused ion beam (FIB) induced processing to convert β-Ga2O3
into γ-Ga2O3 in a spatially controlled way. We employ focused Ne ions from
a helium ion microscope (HIM) and liquid metal alloy ion sources (LMAIS)
based FIB with Co, Si, and In to induce the polymorph conversion. Electron
backscatter diffraction (EBSD), transmission electron microscopy (TEM) and
atomic force microscopy (AFM) are used to confirm, in a spatially resolved
way, the successful polymorph conversion. From the obtained EBSD data
the orientation relationship between the irradiated and unirradiated
material is resolved. Broadbeam irradiated reference samples have been
used to corroborate these results with channeling Rutherford
backscattering spectrometry (c-RBS), X-ray diffraction (XRD) and Doppler
broadening variable energy positron annihilation spectroscopy (DB-VEPAS)
results. The obtained crystal structure and defect distribution data supports
the model suggested for the conversion mechanism [3].
This research is supported by the tax funds on the basis of the budget
passed by the Saxonian state parliament in Germany and the COST Action
CA19140 FIT4NANO https://www.fit4nano.eu/.
[1] A. Azarov, C. Bazioti, Disorder-Induced Ordering in Gallium Oxide
Polymorphs, Phys. Rev. Lett. 128 (2022), 015704.
[2] J. Garcia-Fernandez, S.B. KJeldby, Formation of γ-Ga2O3 by ion
implantation: Polymorphic phase transformation of β- Ga2O3, Appl. Phys.
Lett. 121 (2022), 191601.
[3] A. Azarov, J. G. Fernández, J. Zhao, F. Djurabekova, H. He, R. He, Ø. Prytz,
L. Vines, U. Bektas, P. Chekhonin, N. Klingner, G. Hlawacek, A. Kuznetsov,
Universal radiation tolerant semiconductor (2023),
doi:10.48550/ARXIV.2303.13114.

Keywords: FIB

Involved research facilities

Related publications

  • Lecture (Conference)
    AVS 69, 05.-10.11.2023, Portland, OR, USA

Permalink: https://www.hzdr.de/publications/Publ-38683


Influence of crystal structure on helium-induced tendril formation in an FeCoCrNiV high-entropy alloy

Lohmann, S.; Goodall, R.; Hlawacek, G.; Hübner, R.; Ma, L.; Gandy, A. S.

Abstract

High-entropy alloys (HEAs) are a relatively new class of metal alloys
composed of several principal elements, usually at (near) equiatomic
ratios. Our goal is to understand how such a multicomponent alloy
behaves under irradiation. The FeCoCrNiV HEA exhibits both a face-
centred cubic (fcc) and a body-centred tetragonal (bct) phase, thus
allowing us to specifically study the influence of crystalline structure
at very similar chemical composition. We irradiated both phases with
a focussed He beam provided by a helium ion microscope (HIM) at
temperatures between room temperature and 500∘ C. The irradiation
fluence was varied between 6 × 1017 ions/cm2 and 1 × 1020 ions/cm2 .
High-resolution images of the irradiated areas were taken with the same
HIM. Selected irradiated areas were additionally studied by TEM in
combination with EDXS. Under irradiation, pores start to be generated
in the material with pore sizes differing significantly between the two
phases. At higher fluences and above a critical temperature, a tendril
structure forms in both phases. We found that the critical tempera-
ture depends on the phase and is lower for fcc. TEM images reveal
that the tendrils span the whole depth of the irradiated area, and are
accompanied by bubbles of various sizes. Scanning TEM-based EDXS
of these structures indicates a He-induced change in composition.

Keywords: FIB

Involved research facilities

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

Permalink: https://www.hzdr.de/publications/Publ-38682


Influence of Crystal Structure on Helium-induced Nano-tendril Formation in a Multiphase, Multicomponent Alloy

Gandy, A.; Lohmann, S.; Hlawacek, G.; Hübner, R.; Ma, L.; Goodall, R.

Abstract

Plasma-facing materials (PFMs) for magnetic fusion will experience a unique set of challenges, including plasma-surface interactions. In tungsten, helium ions diffuse through the surface resulting in the formation of nano-tendrils which may contaminate the fusion plasma. Multicomponent alloys are being considered as alternative PFMs though little is known about how they will behave in a plasma environment. Using a focused helium beam provided by a helium ion microscope (HIM), we irradiated equiatomic FeCoCrNiV, which comprises FCC and BCT crystal structures with similar compositions, enabling us to determine the influence of crystal structure on the formation of nano-tendrils. Irradiations were performed up to 500°C, and fluences between 6x1017 and 1x1020 He ions/cm2. Here, we present HIM images from the irradiated regions, and cross-sectional TEM/EDX images on selected samples. The data reveals a critical temperature for tendril formation dependant on crystal structure, helium bubbles, and helium-induced changes in composition.

Keywords: FIB

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  • Lecture (Conference)
    TMS 2023 - 152nd Annual Meeting & Exhibition, 19.-23.03.2023, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-38680


Creep strength boosted by a high-density of stable nanoprecipitates in high-chromium steels

Vivas, J.; De-Castro, D.; Poplawsky, J. D.; Altstadt, E.; Houska, M.; Urones-Garrote, E.; San Martín, D.; Caballero, F. G.; Serrano, M.; Capdevila, C.

Abstract

there is a need worldwide to develop materials for advanced power plants with steam temperatures of 700°c and above that will achieve long-term creep-rupture strength and low cO2 emissions. the creep resistance of actual 9-12cr steels is not enough to fulfil the engineering requirements above 600°c. in this paper, the authors report their advances in the improvement of creep properties of this type of steels by the microstructural optimization through nano-precipitation using two methodologies. 1) Applying a high temperature austenitization cycle followed by an ausforming step (thermomechanical treatment, tMt ) to G91 steel, to increase the martensite dislocation density and, thus, the number density of MX precipitates (M = v,Nb; X = c,N) but at the expense of deteriorating the ductility. 2) compositional adjustments, guided by computational thermodynamics, combined with a conventional heat treatment (no tMt ), to design novel steels with a good ductility while still possessing a high number density of MX precipitates, similar to the one obtained after the tMt in G91. the microstructures have been characterized by optical, scanning and transmission electron microscopy, eBSD and atom probe tomog- raphy. the creep behaviour at 700°c has been eval- uated under a load of 200 N using small punch creep tests.

Keywords: creep resistant steels; thermomechanical treatment; creep fracture behaviour; microstructural degradation; small punch creep tests; ausforming

Permalink: https://www.hzdr.de/publications/Publ-38678


Nanoparticle depressants in froth flotation – the effect of colloidal silica with different size and surface modifications on the selective separation of semi-soluble salt type minerals

Ben Said, B.; Rudolph, M.; Ebert, D.; Daniel, G.; Pereira, L.

Abstract

Colloidal silica has been presented as a selective depressant in froth flotation separation of scheelite and calcite by our group in 2020. Here we analyze the effects of colloidal silica dosage, specific surface area (i.e. size) and modification with microflotation on pure scheelite, calcite, fluorite, and apatite minerals. In a reagents scale-up procedure batch flotation experiments were conducted on a low-grade scheelite ore using statistical experimental design methodology. Microflotation experiments showed colloidal silica selectively depressing calcite flotation with an increasing intensity with reduced size of colloidal silica. The nanoparticulate depressant did not affect the recoveries of scheelite, apatite, and fluorite – typical ore minerals that occur associated to calcite. Batch flotation of a low-grade scheelite ore confirmed the observations made at the microscale: colloidal silica significantly improves the scheelite-calcite selectivity index. Here, we observe a series of relations between colloidal silica specific surface area and modification on different process indicators such as scheelite-calcite selectivity index, recoveries, and froth properties. These relations are assumed to be due to the different aggregation mechanisms of the colloidal silica dispersions. The aluminate-modified colloidal silica, which tends to form a coherent gel network in presence of 〖Ca〗^(2+), shows the strongest effect on reducing calcite recovery accompanied by a significant reduction in scheelite recovery compared to the non-functionalised and silane-modified colloidal silica.

Keywords: scheelite; calcite; hornblende; design of experiments; surface charge; hallimond tube; batch flotation

Permalink: https://www.hzdr.de/publications/Publ-38676


Nanoparticle depressants - The effect of colloidal silica in the froth flotation of calcium minerals

Ben Said, B.; Pereira, L.; Rudolph, M.

Abstract

Colloidal silica is investigated as a potential selective nanoparticle depressant in the flotation process of calcium minerals. The micro particle separation of calcium minerals by selective froth flotation is a challenging task. The difficulty arises from the similar surface properties of the minerals and thus similar responses to different known families of flotation collectors (selectively adsorbing surfactants). The effect of colloidal silica and its interactions with the reagent system were investigated by varying its modification and specific surface area/particle size. Microflotation of scheelite (calcium tungstate), fluorite (calcium fluoride), calcite (calcium carbonate) and apatite (calcium fluorophosphate) was used to investigate whether colloidal silica has an effect on the minerals. Initial results show that colloidal silica prevents calcite from floating, while scheelite, fluorite and apatite are not affected by the presence of the reagent, regardless of the dosage. Moreover, batch flotation tests have shown significant differences between the three modifications (Sodium stabilized colloidal silica, sodium stabilized modified with aluminate and sodium stabilized modified with silane) in terms of the significant effect on the selectivity. Fundamental investigations have been carried out to figure out how the different modifications perform and at which phase of the flotation process. The upscaling of the technology was then investigated on a pilot and industrial scale.

Keywords: Froth Flotation; Nanoparticles; Adsorption; Bubble Attachment; Particle Interactions

  • Poster
    Flotation23, 05.-09.11.2023, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-38675


Data publication: MRF timing system characterization and 1-wire sensor calibration using a climate chamber

Zenker, K.; Kuntzsch, M.

Abstract

This data was taken at DSEY (04-08.12.2023) using a climate chamber.

Multiple temperature and humidity sensors were put into the climate chamber.

Due to problems with the ChimeraTK server not all data was collected by a single ChimeraTK server,

but the sensors were grouped and read by different 1-wire servers (`1-wire_1`, `1-wire_2`, `1-wire_3`, `1-wire_4`, `1-wire_5`). Each sensor identification is listed in the owfs.xlmap file. First sensor in owfs.xlmap corresponds e.g. to DS18B20/0. Data is available as HDF5 and ROOT file.

In addition the MRF timing system was running. Two EVRs (EVR2, EVR3) were connected via long fibers (100m) to the EVM. The fibers routed through the climate chamber, such that most of the fiber was inside the chamber. A Rhode&Schwartz oscilloscope was used to measure the delay of the timing output signals with respect to a third EVR (EVR1), that was connected via a short cable outside the climate chamber. That data is included in timing-data.root, which includes:

  • Delay of EVR2 with respect to EVR1 -> Delay_C1C2
  • Delay of EVR3 with respect to EVR1 -> Delay_C1C3
  • Delay compensation (actual, correction) for each EVR

The intended measurement, was to use active delay compensation for EVR2 and deactivated delay compensation for EVR3. However, the measurement was spoiled by periodic delay shifts in case of EVR2. On 07.12. 10:20 the delay compensation was also activated for EVR3.

For technical reasons not all timing related data is included in rs-data.root. The delay compensation data (actual, correction) should be taken from the aggregated raw data. It includes basically all data (temperature, humidity, oscilloscope data), but in the beginning the actual delay measurement was missing (which should be taken from timing-data.root).

Selected data periods are listed in the file data.ods.

Some analysis results are already included here for convenience:

  • Plots includes:
    • Temperature calibration
    • Humidity calibration
    • Delay measurements
  • Calibration.root includes calibration constants for humidity/temperature calibration and graphs/plots

Keywords: ELBE; Timing System

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Permalink: https://www.hzdr.de/publications/Publ-38668


How to verify the precision of density-functional-theory implementations via reproducible and universal workflows

Bosoni, E.; Beal, L.; Bercx, M.; Blaha, P.; Blugel, S.; Broder, J.; Callsen, M.; Cottenier, S.; Degomme, A.; Dikan, V.; Eimre, K.; Flage-Larsen, E.; Fornari, M.; Garcia, A.; Genovese, L.; Giantomassi, M.; Huber, S. P.; Janssen, H.; Kastlunger, G.; Krack, M.; Kresse, G.; Kühne, T. D.-S.; Lejaeghere, K.; Madsen, G. K. H.; Marsman, M.; Marzari, N.; Michalicek, G.; Mirhosseini, H.; Muller, T. M. A.; Petretto, G.; Pickard, C. J.; Ponce, S.; Rignanese, G.-M.; Rubel, O.; Ruh, T.; Sluydts, M.; Vanpoucke, D. E. P.; Vijay, S.; Wolloch, M.; Wortmann, D.; Yakutovich, A. V.; Yu, J.; Zadoks, A.; Zhu, B.; Pizzi, G.

Abstract

Density-functional theory methods and codes adopting periodic boundary conditions are extensively used in condensed matter physics and materials science research. In 2016, their precision (how well properties computed with different codes agree among each other) was systematically assessed on elemental crystals: a first crucial step to evaluate the reliability of such computations. In this Expert Recommendation, we discuss recommendations for verification studies aiming at further testing precision and transferability of density-functional-theory computational approaches and codes. We illustrate such recommendations using a greatly expanded protocol covering the whole periodic table from Z = 1 to 96 and characterizing 10 prototypical cubic compounds for each element: four unaries and six oxides, spanning a wide range of coordination numbers and oxidation states. The primary outcome is a reference dataset of 960 equations of state cross-checked between two all-electron codes, then used to verify and improve nine pseudopotential-based approaches. Finally, we discuss the extent to which the current results for total energies can be reused for different goals.

Keywords: Density-functional theory; Verification; pseudopotential codes

Related publications

Permalink: https://www.hzdr.de/publications/Publ-38667


Triply Bonded Pancake π-Dimers Stabilized by Tetravalent Actinides

Barluzzi, L.; Ogilvie, S. P.; Dalton, A. B.; Kaden, P.; Gericke, R.; Mansikkamäki, A.; Giblin, S. R.; Layfield, R. A.

Abstract

Aromatic π-stacking is a weakly attractive, non-covalent interaction often found in biological macromolecules and synthetic supramolecular chemistry. The weak non-directional nature of π-stacking can present challenges in the design of materials owing to their weak, non-directional nature. However, when aromatic π-systems contain an unpaired electron, stronger attraction involving face-to-face π-orbital overlap is possible, resulting in covalent so-called ‘pancake’ bonds. Two-electron, multicentre single pancake bonds are well-known whereas four-electron double pancake bonds are rare. Higherorder
pancake bonds have been predicted, but experimental systems are unknown. Here, we show that six-electron triple pancake bonds can be synthesized by threefold reduction of hexaazatrinaphthylene (HAN) and subsequent stacking of the [HAN]³‾ tri-radicals. Our analysis reveals a multicentre covalent triple pancake bond consisting of a π-orbital and two equivalent π-orbitals. An electrostatic stabilizing role is established for tetravalent thorium and uranium ions in these systems. We also show that the electronic absorption spectrum of the triple pancake bonds closely matches computational predictions, providing experimental verification of these unique interactions. The discovery of conductivity in thin films of the triply bonded π-dimers presents new opportunities for the discovery of single-component molecular conductors and other spinbased molecular materials.

Keywords: actinides; triply bonded pancake; stabilization; magnetism; EPR; quantum chemistry

Permalink: https://www.hzdr.de/publications/Publ-38655


Impact of Viscosity on Human Hepatoma Spheroids in Soft Core-Shell Microcapsules

Peng, X.; Janićijević, Ž.; Lemm, S.; Hauser, S.; Knobel, M.; Pietzsch, J.; Bachmann, M.; Baraban, L.

Abstract

The extracellular environment regulates the structures and functions of cells, from the molecular to the tissue level. However, the underlying mechanisms influencing the organization and adaptation of cancer in three-dimensional (3D) environments are not yet fully understood. In this study, the influence of the viscosity of the environment is investigated on the mechanical adaptability of human hepatoma cell (HepG2) spheroids in vitro, using 3D microcapsule reactors formed with droplet-based microfluidics. To mimic the environment with different mechanical properties, HepG2 cells are encapsulated in alginate core–shell reservoirs (i.e., microcapsules) with different core viscosities tuned by incorporating carboxymethylcellulose. The significant changes in cell and spheroid distribution, proliferation, and cytoskeleton are observed and quantified. Importantly, changes in the expression and distribution of F-actin and keratin 8 indicate the relation between spheroid stiffness and viscosity of the surrounding medium. The increase of F-actin levels in the viscous medium can indicate an enhanced ability of tumor cells to traverse dense tissue. These results demonstrate the ability of cancer cells to dynamically adapt to the changes in extracellular viscosity, which is an important physical cue regulating tumor development, and thus of relevance in cancer biology.

Keywords: hepatoma spheroids; cell adaptation; cytoskeleton; tumor microenvironment; hydrogel microcapsule

Permalink: https://www.hzdr.de/publications/Publ-38654


Data publication: AFLOW-CCE for the thermodynamics of ionic materials

Friedrich, R.; Curtarolo, S.

Abstract

The data set contains the calculated results from which the formation enthalpies have been calculated.

Involved research facilities

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  • Reseach data in external data repository
    Publication year 2024
    License: CC BY; Creative Commons Attribution 4.0 International
    Hosted on aflow.org: Link to location
    DOI: 10.1063/5.0184917

Permalink: https://www.hzdr.de/publications/Publ-38653


AFLOW-CCE for the thermodynamics of ionic materials

Friedrich, R.; Curtarolo, S.

Abstract

Accurate thermodynamic stability predictions enable data-driven computational materials design. Standard density functional theory
(DFT) approximations have limited accuracy with average errors of a few hundred meV/atom for ionic materials, such as oxides
and nitrides. Thus, insightful correction schemes as given by the coordination corrected enthalpies (CCE) method, based on an intuitive
parametrization of DFT errors with respect to coordination numbers and cation oxidation states, present a simple, yet accurate
solution to enable materials stability assessments. Here, we illustrate the computational capabilities of our AFLOW-CCE software by
utilizing our previous results for oxides and introducing new results for nitrides. The implementation reduces the deviations between
theory and experiment to the order of the room temperature thermal energy scale, i.e., ∼25 meV/atom. The automated corrections
for both materials classes are freely available within the AFLOW ecosystem via the AFLOW-CCE module, requiring only structural
inputs.

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Permalink: https://www.hzdr.de/publications/Publ-38652


Predicting the electronic structure of matter at scale with machine learning

Cangi, A.

Abstract

In this talk, I will present our recent advancements in utilizing machine learning to significantly enhance the efficiency of electronic structure calculations [1]. In particular, I will focus on our efforts to accelerate Kohn-Sham density functional theory calculations by incorporating deep neural networks within the Materials Learning Algorithms framework [2,3]. Our results demonstrate substantial gains in calculation speed for metals across their melting point. Furthermore, our implementation of automated machine learning has resulted in significant savings in computational resources when identifying optimal neural network architectures, thereby laying the foundation for large-scale investigations [4]. I will also showcase our most recent breakthrough, which enables neural-network-driven electronic structure calculations for systems containing over 100,000 atoms [5].

References
[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials, 6, 040301 (2022)
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, Phys. Rev. B 104, 035120 (2021). [3] J. Ellis, L. Fiedler, G. Popoola, N. Modine, J. Stephens, A. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B, 104, 035120 (2021)
[4] L. Fiedler, N. Hoffmann, P. Mohammed, G. Popoola, T. Yovell, V. Oles, J. Austin Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol., 3, 045008 (2022)
[5] L. Fiedler, N. Modine, S. Schmerler, D. Vogel, G. Popoola, A. Thompson, S. Rajamanickam, A. Cangi, npj. Comput. Mater., 9, 115 (2023)

Keywords: Electronic structure theory; Density functional theory; Artificial intelligence; Machine learning; Neural networks; Materials science

  • Invited lecture (Conferences)
    APS March Meeting 2024, 04.-08.03.2024, Minneapolis, United States

Permalink: https://www.hzdr.de/publications/Publ-38651


Scalable Machine Learning for Predicting the Electronic Structure of Matter

Cangi, A.

Abstract

I will present our recent progress in significantly scaling up density functional theory calculations with machine learning [1], for which we have developed the Materials Learning Algorithms (MALA) framework [2]. We have demonstrated the transferability of our machine learning model across phase boundaries, such as metals at their melting point [3] and electronic temperature [4]. In addition, our use of automated machine learning has led to a significant reduction in the computational resources required to identify optimal neural network architectures [5]. Most importantly, I will present our recent breakthrough in enabling fast neural-network driven electronic structure calculations for ultra-large systems unattainable by conventional density functional theory calculations [6]. I will mention in passing our other efforts in solving the Kohn-Sham equations of time-dependent density functional theory in terms of physics-informed neural networks [7], and in developing a robust framework for inverting the Kohn-Sham equations in terms of Fourier neural operators [8].

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials, 6, 040301 (2022).
[2] A. Cangi, S. Rajamanickam, B. Brzoza, T. J. Callow, J. A. Ellis, O. Faruk, L. Fiedler, J. Fox, N. Hoffmann, K. D. Miller, D. Kotik, S. Kulkarni, N. Modine, P. Mohammed, V. Oles, G. A. Popoola, F. Pöschel, J. Romero, S. Schmerler, J. A. Stephens, H. Tahmasbi, A. P. Thompson, S. Verma, D. J. Vogel, Materials Learning Algorithms (MALA), doi.org/10.5281/zenodo.5557254, (2023).
[3] J. Ellis, L. Fiedler, G. Popoola, N. Modine, J. Stephens, A. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B, 104, 035120 (2021).
[4] L. Fiedler, N. A. Modine, K. D. Miller, A. Cangi, Phys. Rev. B 108, 125146 (2023).
[5] L. Fiedler, N. Hoffmann, P. Mohammed, G. Popoola, T. Yovell, V. Oles, J. Austin Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol., 3, 045008 (2022).
[6] L. Fiedler, N. Modine, S. Schmerler, D. Vogel, G. Popoola, A. Thompson, S. Rajamanickam, A. Cangi, npj. Comput. Mater., 9, 115 (2023).
[7] K. Shah, P. Stiller, N. Hoffmann, A. Cangi, Physics-Informed Neural Networks as Solvers for the Time-Dependent Schrödinger Equation, NeurIPS Workshop Machine Learning and the Physical Sciences, arXiv:2210.12522 (2022).
[8] V. Martinetto, K. Shah, A. Cangi, A. Pribram-Jones, Inverting the Kohn-Sham equations with physics-informed machine learning, arXiv:2312.15301 (2023).

Keywords: Electronic structure theory; Density functional theory; Artificial intelligence; Machine learning; Neural networks; Materials science; Condensed-matter physics

  • Invited lecture (Conferences)
    Machine Learning in Electronic-Structure Theory, 25.-29.03.2024, Chicago, United States
  • Lecture (Conference)
    Jahrestagung/Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 17.-22.03.2024, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38650


A survey of practice patterns for real-time intrafractional motion-management in particle therapy

Zhang, Y.; Trnkova, P.; Toshito, T.; Heijmen, B.; Richter, C.; Aznar, M.; Albertini, F.; Bolsi, A.; Daartz, J.; Bertholet, J.; Knopf, A.

Abstract

Background and purpose: Organ motion compromises accurate particle therapy delivery. This study reports on the practice patterns for real-time intrafractional motion-management in particle therapy to evaluate current clinical practice and wishes and barriers to implementation.
Materials and methods: An institutional questionnaire was distributed to particle therapy centres worldwide (7/ 2020–6/2021) asking which type(s) of real-time respiratory motion management (RRMM) methods were used, for which treatment sites, and what were the wishes and barriers to implementation. This was followed by a three-round DELPHI consensus analysis (10/2022) to define recommendations on required actions and future vision. With 70 responses from 17 countries, response rate was 100% for Europe (23/23 centres), 96% for Japan (22/23) and 53% for USA (20/38).
Results: Of the 68 clinically operational centres, 85% used RRMM, with 41% using both rescanning and active methods. Sixty-four percent used active-RRMM for at least one treatment site, mostly with gating guided by an external marker. Forty-eight percent of active-RRMM users wished to expand or change their RRMM technique. The main barriers were technical limitations and limited resources. From the DELPHI analysis, optimisation of rescanning parameters, improvement of motion models, and pre-treatment 4D evaluation were unanimously
considered clinically important future focus. 4D dose calculation was identified as the top requirement for future commercial treatment planning software.
Conclusion: A majority of particle therapy centres have implemented RRMM. Still, further development and clinical integration were desired by most centres. Joint industry, clinical and research efforts are needed to translate innovation into efficient workflows for broad-scale implementation.

Keywords: Particle/proton therapy; Intrafraction motion; Real-time respiratory motion management; Image-guided particle therapy; Rescanning

Involved research facilities

  • OncoRay

Permalink: https://www.hzdr.de/publications/Publ-38649


A survey of practice patterns for adaptive particle therapy for interfractional changes

Trnkova, P.; Zhang, Y.; Toshito, T.; Heijmen, B.; Richter, C.; Aznar, M. C.; Albertini, F.; Bolsi, A.; Daartz, J.; Knopf, A. C.; Bertholet, J.

Abstract

Background and purpose: Anatomical changes may compromise the planned target coverage and organs-at-risk dose in particle therapy. This study reports on the practice patterns for adaptive particle therapy (APT) to evaluate current clinical practice and wishes and barriers to further implementation. Materials and methods: An institutional questionnaire was distributed to PT centres worldwide (7/2020–6/2021) asking which type of APT was used, details of the workflow, and what the wishes and barriers to implementation were. Seventy centres from 17 countries participated. A three-round Delphi consensus analysis (10/2022) among the authors followed to define recommendations on required actions and future vision.
Results: Out of the 68 clinically operational centres, 84% were users of APT for at least one treatment site with head and neck being most common. APT was mostly performed offline with only two online APT users (plan-library). No centre used online daily re-planning. Daily 3D imaging was used for APT by 19% of users. Sixty-eight percent of users had plans to increase their use or change their technique for APT. The main barrier was “lack of integrated and efficient workflows”. Automation and speed, reliable dose deformation for dose accumulation and
higher quality of in-room volumetric imaging were identified as the most urgent task for clinical implementation of online daily APT.
Conclusion: Offline APT was implemented by the majority of PT centres. Joint efforts between industry research and clinics are needed to translate innovations into efficient and clinically feasible workflows for broad-scale implementation of online APT.

Keywords: Particle/proton therapy; Adaptive radiotherapy (ART); Interfraction anatomical variation; Image guided particle therapy; Adaptive treatment planning

Permalink: https://www.hzdr.de/publications/Publ-38648


DNA-Methylome–Based Tumor Hypoxia Classifier Identifies HPV-Negative Head and Neck Cancer Patients at Risk for Locoregional Recurrence after Primary Radiochemotherapy

Tawk, B.; Rein, K.; Schwager, C.; Knoll, M.; Wirkner, U.; Hörner-Rieber, J.; Liermann, J.; Kurth, I.; Balermpas, P.; Rödel, C.; Linge, A.; Löck, S.; Lohaus, F.; Tinhofer, I.; Krause, M.; Stuschke, M.; Ligia Grosu, A.; Zips, D.; Combs, S. E.; Belka, C.; Stenzinger, A.; Herold-Mende, C.; Baumann, M.; Schirmacher, P.; Debus, J.; Abdollahi, A.

Abstract

Purpose: Tumor hypoxia is a paradigmatic negative prognosticator of treatment resistance in head and neck squamous cell carcinoma (HNSCC). The lack of robust and reliable hypoxia
classifiers limits the adaptation of stratified therapies. We hypothesized that the tumor DNA methylation landscape might indicate epigenetic reprogramming induced by chronic intratumoral hypoxia. Experimental Design: A DNA-methylome–based tumor hypoxia classifier (Hypoxia-M) was trained in the TCGA (The Cancer Genome Atlas)-HNSCC cohort based on matched assignments using gene expression–based signatures of hypoxia (Hypoxia-GES). Hypoxia-M was validated in a multicenter DKTK-ROG trial consisting of human papillomavirus (HPV)–negative patients with HNSCC treated with primary radiochemotherapy (RCHT).

Results: Although hypoxia-GES failed to stratify patients in the DKTK-ROG, Hypoxia-M was independently prognostic for local recurrence (HR, 4.3; P ¼0.001) and overall survival (HR, 2.34; P ¼ 0.03) but not distant metastasis after RCHT in both cohorts. Hypoxia-M status was inversely associated with CD8 T-cell infiltration in both cohorts. Hypoxia-M was further prognostic in the TCGA-PanCancer cohort (HR, 1.83; P ¼0.04), underscoring the breadth of this classifier for predicting tumor hypoxia status.

Conclusions: Our findings highlight an unexplored avenue for DNA methylation–based classifiers as biomarkers of tumoral hypoxia for identifying high-risk features in patients with HNSCC
tumors.

Permalink: https://www.hzdr.de/publications/Publ-38647


Consensus guide on CT-based prediction of stopping-power ratio using a Hounsfield look-up table for proton therapy

Peters, N.; Trier Taasti, V.; Ackermann, B.; Bolsi, A.; Vallhagen Dahlgren, C.; Ellerbrock, M.; Fracchiolla, F.; Gomà, C.; Góra, J.; Cambraia Lopes, P.; Rinaldi, I.; Salvo, K.; Sojat Tarp, I.; Vai, A.; Bortfeld, T.; Lomax, A.; Richter, C.; Wohlfahrt, P.

Abstract

Background and purpose: Studies have shown large variations in stopping-power ratio (SPR) prediction from computed tomography (CT) across European proton centres. To standardise this process, a step-by-step guide on specifying a Hounsfield look-up table (HLUT) is presented here. Materials and methods: The HLUT specification process is divided into six steps: Phantom setup, CT acquisition, CT number extraction, SPR determination, HLUT specification, and HLUT validation. Appropriate CT phantoms have a head- and body-sized part, with tissue-equivalent inserts in regard to X-ray and proton interactions. CT numbers are extracted from a region-of-interest covering the inner 70% of each insert in-plane and several axial CT slices in scan direction. For optimal HLUT specification, the SPR of phantom inserts is measured in a proton beam and the SPR of tabulated human tissues is computed stoichiometrically at 100 MeV. Including both phantom inserts and tabulated human tissues increases HLUT stability. Piecewise linear regressions are performed between CT numbers and SPRs for four tissue groups (lung, adipose, soft tissue, and bone) and then connected with straight lines. Finally, a thorough but simple validation is performed. Results: The best practices and individual challenges are explained comprehensively for each step. A well-defined strategy for specifying the connection points between the individual line segments of the HLUT is presented. The guide was tested exemplarily on three CT scanners from different vendors, proving its feasibility. Conclusion: The presented step-by-step guide for CT-based HLUT specification with recommendations and examples can contribute to reduce inter-centre variations in SPR prediction.

Keywords: Hounsfield look-up table; Proton therapy; Single-energy CT; Stoichiometric calibration; Stopping-power ratio; Proton range prediction

Permalink: https://www.hzdr.de/publications/Publ-38646


The role of ESTRO guidelines in achieving consistency and quality in clinical radiation oncology practice

Vrou Offersen, B.; Aznar, M. C.; Bacchus, C.; Coppes, R. P.; Deutsch, E.; Georg, D.; Haustermans, K.; Hoskin, P.; Krause, M.; Lartigau, E. F.; Lee, A. W. M.; Löck, S.; Thwaites, D. I.; van der Kogel, A. J.; van der Heide, U.; Valentini, V.; Overgaard, J.; Baumann, M.

Abstract

Editorial
In summary, ESTRO clinical and other guidelines are soundly based, but always require validation, careful and consistent implementation, and focused education and training on their use, as well as local monitoring of that. As guidelines develop and older ones become superseded, there should be a clear mechanism to inform the community of the status of specific guidelines, especially when they have been replaced by new or updated versions. An important scientific aim for the future is to further advance guidelines and their individual statements into fully evidence-based instruments. These, in principle, could be directly linked to growing data-bases, allowing feedback mechanisms and thus continuous optimization. Another challenging research topic is the interplay of guidelines with growing opportunities and demands of personalized approaches of treatment.

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Permalink: https://www.hzdr.de/publications/Publ-38645


Influence of Bruton’s Tyrosine Kinase (BTK) on Epithelial–Mesenchymal Transition (EMT) Processes and Cancer Stem Cell (CSC) Enrichment in Head and Neck Squamous Cell Carcinoma (HNSCC)

Leichtle, F.; Betzler, A. C.; Eizenberger, C.; Lesakova, K.; Ezic, J.; Drees, R.; Greve, J.; Schuler, P. J.; Laban, S.; Hoffmann, T. K.; Cordes, N.; Lavitrano, M.; Grassilli, E.; Brunner, C.

Abstract

Constitutively active kinases play a crucial role in carcinogenesis, and their inhibition is a common target for molecular tumor therapy. We recently discovered the expression of two oncogenic isoforms of Bruton’s Tyrosine Kinase (BTK) in head and neck squamous cell carcinoma (HNSCC), Btk-p80 and BTK-p65. However, the precise role of BTK in HNSCC remains unclear. Analyses of a tissue microarray containing benign and malignant as well as inflammatory tissue samples of the head and neck region revealed the preferential expression of BTK-p80 in malignant tissue, whereas BTK-p65 expression was confirmed in over 80% of analyzed metastatic head and neck tumor cases. Therefore, processes associated with metastasis, like cancer stem cell (CSC) enrichment and the epithelial–mesenchymal transition (EMT), which in turn depend on an appropriate cytokine milieu, were analyzed. Treatment of HNSCC-derived cell lines cultured under 3D conditions with the BTK inhibitor AVL-292 caused reduced sphere formation, which was accompanied by reduced numbers of ALDH1A1+ CSCs as well as biological changes associated with the EMT. Moreover, we observed reduced NF-κB expression as well as altered NF-κB dependent pro-tumorigenic and EMT-associated cytokine release of IL-6, IFNγ, and TNFα when BTK activity was dampened. Therefore, an autocrine regulation of the oncogenic BTK-dependent process in HNSCC can be suggested, with BTK inhibition
expected to be an effective treatment option for HNSCC.

Keywords: BTK; CSC; EMT; HNSCC

Involved research facilities

  • OncoRay

Permalink: https://www.hzdr.de/publications/Publ-38644


Prognostic biomarkers for the response to the radiosensitizer nimorazole combined with RCTx: a pre-clinical trial in HNSCC xenografts

Koi, L.; Bitto, V.; Weise, C.; Möbius, L.; Linge, A.; Löck, S.; Yaromina, A.; José Besso, M.; Valentini, C.; Pfeifer, M.; Overgaard, J.; Zips, D.; Kurth, I.; Krause, M.; Baumann, M.

Abstract

Background Tumor hypoxia is associated with resistance to radiotherapy and chemotherapy. In head and neck squamous cell carcinoma (HNSCC), nimorazole, an oxygen mimic, combined with radiotherapy (RT) enabled to improve loco-regional control (LRC) in some patients with hypoxic tumors but it is unknown whether this holds also for radio-
chemotherapy (RCTx). Here, we investigated the impact of nimorazole combined with RCTx in HNSCC xenografts and explored molecular biomarkers for its targeted use.
Methods Irradiations were performed with 30 fractions in 6 weeks combined with weekly cisplatin. Nimorazole was applied before each fraction, beginning with the first or after ten fractions. Effect of RCTx with or without addition of nimorazole was quantified as permanent local control after irradiation. For histological evaluation and targeted gene expression analysis, tumors were excised untreated or after ten fractions. Using quantitative image analysis, micromilieu parameters were determined. Results Nimorazole combined with RCTx significantly improved permanent local control in two tumor models, and showed a potential improvement in two additional models. In these four models, pimonidazole hypoxic volume (pHV) was significantly reduced after ten fractions of RCTx alone. Our results suggest that nimorazole combined with RCTx might improve TCR compared to RCTx alone if hypoxia is decreased during the course of RCTx but further experiments are warranted to verify this association. Differential gene expression analysis revealed 12 genes as potential for RCTx response. When evaluated in patients with HNSCC who were treated with primary RCTx, these genes were predictive for LRC. Conclusions Nimorazole combined with RCTx improved local tumor control in some but not in all HNSCC xeno-grafts. We identified prognostic biomarkers with the potential for translation to patients with HNSCC.

Keywords: HNSCC; Biom; Nimorazole; Radiosensitizer; Radiochemotherapy; Radiotherapy; Radioresistance; Hypoxia

Permalink: https://www.hzdr.de/publications/Publ-38643


Dynamics of CXCR4 positive circulating tumor cells in prostate cancer patients during radiotherapy

Klusa, D.; Lohaus, F.; Franken, A.; Baumbach, M.; Cojoc, M.; Dowling, P.; Linge, A.; Offermann, A.; Löck, S.; Husman, D.; Rivandi, M.; Polzer, B.; Freytag, V.; Lange, T.; Neubauer, H.; Kücken, M.; Perner, S.; Hölscher, T.; Dubrovska, A.; Krause, M.; Kurth, I.; Baumann, M.; Peitzsch, C.

Abstract

Ablative radiotherapy is a highly efficient treatment modality for patients with metastatic prostate cancer (PCa). However, a subset of patients does not respond. Currently, this subgroup with bad prognosis cannot be identified before disease progression. We hypothesize that markers indicative of radioresistance, stemness and/or bone tropism may have a prognostic potential to identify patients profiting from metastases-directed radiotherapy. Therefore, circulating tumor cells (CTCs) were analyzed in patients with metastatic PCa (n = 24) during radiotherapy with Cell-Search, multicolor flow cytometry and imaging cytometry. Analysis of copy-number alteration indicates a polyclonal CTC population that changes after radiotherapy.
CTCs were found in 8 out of 24 patients (33.3%) and were associated with a shorter time to biochemical progression after radiotherapy. Whereas the total CTC count dropped after radiotherapy, a chemokine receptor CXCR4-expressing subpopulation representing 28.6% of the total CTC population remained stable up to 3 months. At once, we observed higher chemokine CCL2 plasma concentrations and proinflammatory monocytes. Additional functional analyses demonstrated key roles of CXCR4 and CCL2 for cellular radiosensitivity, tumorigenicity and stem-like potential in vitro and in vivo. Moreover, a high CXCR4 and CCL2 expression was found in bone metastasis biopsies of PCa patients. In summary, panCK+CXCR4+ CTCs may have a prognostic potential in patients with metastatic PCa treated with metastasis-directed radiotherapy.

Keywords: bone metastasis; radiotherapy; prostate cancer; CXCR4; circulating tumor cells

Permalink: https://www.hzdr.de/publications/Publ-38640


Direct visualization of proton beam irradiation effects in liquids by MRI

Gantz, S.; Karsch, L.; Pawelke, J.; Schieferecke, J.; Schellhammer, S.; Smeets, J.; Van Der Kraaij, E.; Hoffmann, A. L.

Abstract

The main advantage proton beams offer over photon beams in radiation therapy of cancer patients is the dose maximum at their finite range, yielding a reduction in the dose deposited in healthy tissues surrounding the tumor. Since no direct method exists to measure the beam’s range during dose delivery, safety margins around the tumor are applied, compromising the dose conformality and reducing the targeting accuracy. Here, we demonstrate that online MRI can visualize the proton beam and reveal its range during irradiation of liquid-filled phantoms. A clear dependence on beam energy and current was found. These results stimulate research into novel MRI-detectable beam signatures and already find application in the geometric quality assurance for magnetic resonance-integrated proton therapy systems currently under development.

Keywords: cancer radiation treatment; proton beam therapy; MRI; beam visualization

Involved research facilities

  • OncoRay

Permalink: https://www.hzdr.de/publications/Publ-38638


Efficient Radial-Shell Model for 3D Tumor Spheroid Dynamics with Radiotherapy

Franke, F.; Michlikova, S.; Aland, S.; Kunz-Schughart, L. A.; Voss-Böhme, A.; Lange, S.

Abstract

Understanding the complex dynamics of tumor growth to develop more efficient therapeutic strategies is one of the most challenging problems in biomedicine. Three-dimensional (3D) tumor spheroids, reflecting avascular microregions within a tumor, are an advanced in vitro model system to assess the curative effect of combinatorial radio(chemo)therapy. Tumor spheroids exhibit particular crucial pathophysiological characteristics such as a radial oxygen gradient that critically affect the sensitivity of the malignant cell population to treatment. However, spheroid experiments remain laborious, and determining long-term radio(chemo)therapy outcomes is challenging. Mathematical models of spheroid dynamics have the potential to enhance the informative value of experimental data, and can support study design; however, they typically face one of two limitations: while non-spatial models are computationally cheap, they lack the spatial resolution to predict oxygen-dependent radioresponse, whereas models that describe spatial cell dynamics are computationally expensive and often heavily parameterized, impeding the required calibration to experimental data. Here, we present an effectively one-dimensional mathematical model based on the cell dynamics within and across radial spheres which fully incorporates the 3D dynamics of tumor spheroids by exploiting their approximate rotational symmetry. We demonstrate that this radial-shell (RS) model reproduces experimental spheroid growth curves of several cell lines with and without radiotherapy, showing equal or better performance than published models such as 3D agent-based models. Notably, the RS model is sufficiently efficient to enable multi-parametric optimization within previously reported and/or physiologically reasonable ranges based on experimental data. Analysis of the model reveals that the characteristic change of dynamics observed in experiments at small spheroid volume originates from the spatial scale of cell interactions. Based on the calibrated parameters, we predict the spheroid volumes at which this behavior should be observable. Finally, we demonstrate how the generic parameterization of the model allows direct parameter transfer to 3D agent-based models.

Keywords: spheroids; spatio-temporal mathematical modelling; minimal model; tumor relapse; systems biology; simulation; radiation therapy; 3D growth; growth curve; radial shell model; cellular automaton

Permalink: https://www.hzdr.de/publications/Publ-38637


Artificial intelligence in cancer research and precision medicine: Applications, limitations and priorities to drive transformation in the delivery of equitable and unbiased care

Corti, C.; Cobanaj, M.; Dee, E. C.; Criscitiello, C.; Tolaney, S. M.; Celi, L. A.; Curigliano, G.

Abstract

Artificial intelligence (AI) has experienced explosive growth in oncology and related specialties in recent years. The improved expertise in data capture, the increased capacity for data aggregation and analytic power, along with decreasing costs of genome sequencing and related biologic “omics”, set the foundation and need for novel tools that can meaningfully process these data from multiple sources and of varying types. These advances provide value across biomedical discovery, diagnosis, prognosis, treatment, and prevention, in a multimodal
fashion. However, while big data and AI tools have already revolutionized many fields, medicine has partially lagged due to its complexity and multi-dimensionality, leading to technical challenges in developing and validating solutions that generalize to diverse populations. Indeed, inner biases and miseducation of algorithms, in view of their implementation in daily clinical practice, are increasingly relevant concerns; critically, it is possible for AI to mirror the unconscious biases of the humans who generated these algorithms. Therefore, to avoid worsening existing health disparities, it is critical to employ a thoughtful, transparent, and inclusive approach that involves addressing bias in algorithm design and implementation along the cancer care continuum.
In this review, a broad landscape of major applications of AI in cancer care is provided, with a focus on cancer
research and precision medicine. Major challenges posed by the implementation of AI in the clinical setting will
be discussed. Potentially feasible solutions for mitigating bias are provided, in the light of promoting cancer
health equity.

Keywords: Artificial intelligence; Precision medicine; Equity; Outcome prediction; Decision support; Bias

Permalink: https://www.hzdr.de/publications/Publ-38636


Are hybrid conferences the new standard?

Baumann, M.; Bacchus, C.; Aznar, M. C.; Coppes, R. P.; Deutsch, E.; Georg, D.; Haustermans, K.; Hoskin, P.; Krause, M.; Lartigau, E. F.; Lee, A. W. M.; Löck, S.; Offersen, B. V.; Overgaard, J.; Thwaites, D. I.; van der Kogel, A. J.; van der Heide, U. A.; Valentini, V.

Abstract

This issue includes a perspective contribution by Lefresne et al. [1] on face-to-face scientific conferences versus virtual meetings and the implications for climate change. Generally, it is the policy of the Green Journal not to publish contributions with non-scientific content. In this specific case, the editors believe that the contribution by Lefresne and colleagues raises an important point that needs careful consideration and discussion in our scientific community. As scientists, we are at the forefront of research and strive to positively shape the future for humankind. Therefore, it is of key importance that the environmental impact of scientific activities is considered, and that our community develops and contributes to solutions to prevent further exacerbation of climate change with its substantial impact on health-related issues. This includes that pros and cons of face-to-face scientific meetings are carefully weighed.

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Permalink: https://www.hzdr.de/publications/Publ-38635


Fabrication, defect chemistry and microstructure of Mn‑doped UO2

Smith, H.; Townsend, L. T.; Mohun, R.; Mosselmans, J. F. W.; Kvashnina, K.; Neil, C. H.; Corkhill, C. L.

Abstract

Mn-doped UO2 is under consideration for use as an accident tolerant nuclear fuel. We detail the
synthesis of Mn-doped UO2 prepared via a wet co-precipitation method, which was refned to
improve the yield of incorporated Mn. To verify the Mn-doped UO2 defect chemistry, X-ray absorption
spectroscopy at the Mn K-edge was performed, in addition to X-ray difraction, Raman spectroscopy
and high-energy resolved fuorescence detection X-ray absorption near edge spectroscopy at the
U M4-edge. It was established that Mn2+ directly substitutes for U4+ in the UO2 lattice, accompanied
by oxygen vacancy (Ov) charge compensation. In contrast to other divalent-element doped UO2
materials, compelling evidence for U5+ in a charge compensating role was not found. This work
furthers understanding of the structure and crystal chemistry of Mn-doped UO2, which could show
potential advantages as a novel efcient advanced nuclear fuel.

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Permalink: https://www.hzdr.de/publications/Publ-38634


Long-term, sustainable solutions to radioactive waste management

Kvashnina, K.; Claret, F.; Clavier, N.; Levitskaia, T. G.; Wainwright, H.; Yao, T.

Abstract

Nuclear power plays a pivotal role in ensuring a scalable, affordable, and reliable low-carbon electricity supply. Along with other low-carbon energy technologies, nuclear energy is essential for reducing our reliance on fossil fuels, addressing climate change and air pollution, and achieving a sustainable economy. Whilst significant progress has been made in reducing the volume of final radioactive waste, its management remains one of the most important challenges when considering the continued use and expansion of nuclear energy. This recently published collection highlights the latest technological and scientific advances aimed to improve the safe, long-term, and sustainable management of wastes produced from nuclear power generation

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Permalink: https://www.hzdr.de/publications/Publ-38633


Precession, Nutation, and Libration Driven Flows

Noir, J.; Meunier, P.; Giesecke, A.

Abstract

Precession and nutation (periodic changes in the orientation of the rotation axis) as well as libration (variations of the orientation of the principal moments of inertia) of a rotating fluid cavity are of interest in a broad range of applications. These span from planetary cores, atmospheres, oceans dynamics, and planetary and laboratory magnetic field generation to mixing in industrial processes and trajectory stabilization of satellites with a liquid payload. This special topic aims to provide a state of the fluid dynamics fundamental research in the field, and welcomes all theoretical, numerical, and experimental investigations.

Keywords: Precession

Involved research facilities

  • DRESDYN

Permalink: https://www.hzdr.de/publications/Publ-38632


Order-parameter evolution in the Fulde-Ferrell-Larkin-Ovchinnikov phase

Molatta, S.; Kotte, T.; Opherden, D.; Koutroulakis, G.; Schlueter, J. A.; Zwicknagl, G.; Brown, S. E.; Wosnitza, J.; Kühne, H.

Abstract

We report on the temperature dependence of the spatially modulated spin-polarization amplitude ΔKspin, which is a hallmark of the superconducting Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. For that, we use 13C nuclear magnetic resonance (NMR) spectroscopy performed on the organic conductor β''-(ET)2SF5CH2CF2SO3. From a comparison of our experimental results to a comprehensive modeling of the 13C NMR spectra, we determine the evolution of ΔKspin upon condensation of the FFLO state. Further, the modeling of the spectra in the superconducting phase allows to quantify the decrease of the average spin susceptibility, stemming from the spin-singlet coupling of the superconducting electron pairs in the FFLO state of β''-(ET)SF5CH2CF2SO3.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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  • Secondary publication expected from 22.01.2025

Permalink: https://www.hzdr.de/publications/Publ-38631


The lattice contraction of UO2 from Cr doping as determined via high resolution synchrotron X-ray powder diffraction

Murphy, G. L.; Svitlyk, V.; Henkes, M.; Sirochii, D.; Hennig, C.; Kegler, P.; Bosbach, D.; Bukaemskiy, A.

Abstract

High resolution synchrotron powder X-ray diffraction analysis of Cr-doped UO2 powder samples with additions of Cr2O3 as 0, 500, 1000, 1500, 2500 to 3500 ppm that were prepared under sintering conditions of -420 kJ/mol and 1700 oC is reported. The lattice dependence of Cr doping is precisely established through the Rietveld method where the rate of linear lattice parameter contraction from Cr doping, Δacr, was found to be considerably smaller and much more subtle than previously described by literature. This investigation demonstrates the critical need for high resolution and precise specimen preparation when experimentally measuring and interpreting results from subtle changes to nuclear fuel material crystal structures due to trace doping.

Keywords: Diffraction; Rietveld; Synchrotron; Cr-doped UO2; X-ray; Nuclear fuel

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Permalink: https://www.hzdr.de/publications/Publ-38630


Controlling magneto-ionics by defect engineering through light ion implantation

Ma, Z.; Martins, S.; Tan, Z.; Chen, S.; Monteblanco, E.; Liedke, M. O.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.; Herrera Diez, L.; Pellicer, E.; Ravelosona, D.; Sort, J.; Menéndez, E.

Abstract

Magneto-ionics relies on the voltage-driven transport of ions to modify magnetic properties. As a diffusion-controlled mechanism, defects play a central role in determining ion motion and, hence, magneto-ionic response. Here we exploit the potential of ion implantation to engineer depth-resolved defect density and type with the aim to control the magneto-ionic behavior of Co3O4 thin films. We demonstrate that through a single implantation process of light ions (He+) at 5 keV, the magneto-ionic response of a highly nanostructured 50 nm thick Co3O4 film, in terms of rate and amount of generated magnetization, at short-, mid-, and long-term voltage actuation, can be controlled by varying the generated collisional damage through the ion fluence. These results constitute a proof-of-principle that paves the way to further use ion implantation (tuning the ion nature, energy, fluence, target temperature, or using multiple implantations) to enhance performance in magneto-ionic systems.

Keywords: magneto-ionics; Co3O4; positron annihilation spectroscopy; ion irradiation; defects

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Permalink: https://www.hzdr.de/publications/Publ-38629


Tracing the dynamics of superconducting order via transient terahertz third harmonic generation

Kim, M.-J.; Kovalev, S.; Udina, M.; Haenel, R.; Kim, G.; Puviani, M.; Cristiani, G.; Ilyakov, I.; de Oliveira, T.; Ponomaryov, O.; Deinert, J.-C.; Logvenov, G.; Keimer, B.; Manske, D.; Benfatto, L.; Kaiser, S.

Abstract

Ultrafast optical control of quantum systems is an emerging field of physics. In particular, the possibility of light-driven superconductivity has attracted much of attention. To identify non-equilibrium superconductivity, it is necessary to measure fingerprints of superconductivity on ultrafast timescales. Recently non-linear THz third harmonic generation (THG) was shown to directly probe the collective degrees of freedoms of the superconducting condensate, including the Higgs mode. Here we extend this idea to light-driven non-equilibrium states in superconducting La2-xSrxCuO4 establishing an optical pump-THz-THG drive protocol to access the transient superconducting (SC) order-parameter quench and recovering on few-picosecond timescales. We show in particular the ability of two-dimensional (2D) TH spectroscopy to disentangle the effects of optically-excited quasiparticles from the pure order-parameter dynamics, that are unavoidably mixed in the pump-driven linear THz response. Benchmarking the gap dynamics to existing experiments shows the ability of driven THG spectroscopy to overcome these limitations in ordinary pump-probe protocols.

Keywords: Ultrafast; Terahertz; Superconductor; Higgs-spectroscopy; Harmonic Generation; Transient THG

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Permalink: https://www.hzdr.de/publications/Publ-38628


Defect nanostructure and its impact on magnetism of α-Cr2O3 thin films

Veremchuk, I.; Liedke, M. O.; Makushko, P.; Kosub, T.; Hedrich, N.; Pylypovskyi, O.; Ganss, F.; Butterling, M.; Hübner, R.; Hirschmann, E.; Elsherif, A. G. A.; Wagner, A.; Wagner, K.; Shields, B.; Maletinsky, P.; Faßbender, J.; Makarov, D.

Abstract

Thin films of the magnetoelectric insulator α-Cr2O3 are technologically relevant for energy-efficient magnetic memory devices controlled by electric fields [1-3]. In contrast to single crystals, the quality of thin Cr2O3 films is usually compromised by the presence of point defects and their agglomerations at grain boundaries, putting into question their application potential. We experimentally investigated the defect nanostructure of magneton-sputtered 250-nm-thick Cr2O3 thin films prepared under different conditions on single crystals of Al2O3 (0001) and correlate it with the integral and local magnetic properties of the samples [4]. We evaluated the type and relative concentration of defects. For this purpose, positron annihilation spectroscopy (PAS) was used as a unique probe for open-volume defects in thin films. The results obtained for the thin-film samples are compared to single crystal data. Our analysis reveals that the Cr2O3 thin films are characterized by the presence of complex defects at grain boundaries, formed by groups of monovacancies, coexisting with monovacancies and dislocations. The concentration of complex defects can be controlled by the sample fabrication conditions. The defect nanostructure strongly affects the magnitude of the electrical readout, which is measured of the Cr2O3 samples capped with a thin layer of Pt relying on spin Hall effect [5]. Furthermore, the presence of larger defects like grain boundaries has a strong influence on the pinning of magnetic domain walls in thin films. Independent of these findings, we showed that the Néel temperature, which is one of the important technological metrics, is hardly affected by the formed defects in a broad range of deposition parameters.

References
[1] X. He, Y. Wang, N. Wu, A. N. Caruso, E. Vescovo, K. D. Belashchenko, P. A. Dowben, C. Binek, Nature Mater. 9, 579 (2010).
[2] T. Kosub, M. Kopte, R. Hühne, P. Appel, B. Shields, P. Maletinsky, R. Hübner, M. O. Liedke, J. Fassbender, O. G. Schmidt, D. Makarov, Nature Commun. 8, 13985 (2017).
[3] N. Hedrich, K. Wagner, O. V. Pylypovskyi, B. J. Shields, T. Kosub, D. D. Sheka, D. Makarov, P. Maletinsky, Nature Phys. 17, 574 (2021).
[4] I. Veremchuk, M. O. Liedke, P. Makushko, T. Kosub, N. Hedrich, O. V. Pylypovskyi, F. Ganss, M. Butterling, R. Hübner, E. Hirschmann, A. G. Attallah, A. Wagner, K. Wagner, B. Shields, P. Maletinsky, J. Fassbender, D. Makarov, Small 18, 2201228 (2022).
[5] R. Schlitz, T. Kosub, A. Thomas, S. Fabretti, K. Nielsch, D. Makarov, S. T. B. Goennenwein, Appl. Phys. Lett. 112, 132401 (2018).

Involved research facilities

  • P-ELBE
  • Poster
    776. WE-Heraeus-Seminar: Re-thinking Spintronics: From Unconventional Materials to Novel Technologies, 04.-06.01.2023, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-38627


NeXus and openPMD: Relevant data structures for Laser-plasma experiments and low-hanging fruits

Debus, A.

Abstract

* NeXus provides a plethora of data structures that can be immediately used.
* openPMD provides scalability to bigdata workflows and flexibility with respect to data format used.
* Vocabulary extensions for describing meta-data for laser-plasma experiments mainly require Lasers, Targetry and Timing.
* Candidate NeXus/H5 software packages for early openPMD migration:
** NeXus-API: NeXpy
** NeXus-Validator: punx
** NeXus-data source for browsing: h5wasm
* To achieve critical mass: Provide value for Laser-Plasma experiments, stay pragmatic with design discussions,
do small steps, but with an idea where to go.

Keywords: data standard; metadata; NeXus; openPMD; data management

  • Lecture (Conference)
    HELPMI Workshop, 13.-14.11.2023, GSI, Darmstadt-Wixhausen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38625


Better Understanding of Laser Particle Accelerators with PIConGPU simulations

Marre, B. E.

Abstract

Getting Simulation and Experiment Closer: Understanding Laser Plasma Interactions with PIConGPU and FLYonPIC

PIConGPU is performance portable and scales up to exascale machines (Summit and Frontier). "Matching" the new model demands large parameter space of complex experimental designs to simulations
needs to be understood and further constrained.

In-situ synthetic diagnostics in particle-in-cell simulations (PIConGPU), such as few-cycle shadowgraphy, coherent transition radiation and Liénard-Wiechert far-field radiation facilitate direct and quantitative comparison to experimental data.

FLYonPIC is an novel addition to PIConGPU, an in-situ rate equation solver, modeling time-dependent atomic physics including excited states, without temperature assumptions.
* Quantitative physics tests show encouraging results.
* Runtime tests show that including atomic physics at scale will require post-exascale systems.

Keywords: PIConGPU; FLYonPIC; atomic physics; Summit; Frontier; exascale; synthetic diagnostic; shadowgraphy

Involved research facilities

  • Data Center
  • Lecture (Conference)
    9. Annual MT Meeting, 09.-11.10.2023, KIT, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38624


Single-shot CTR spectroscopy to unravel fs-scale, electron bunch profiles -- a window to LWFA injection dynamics

Debus, A.; Zarini, O.; La Berge, M.; Schöbel, S.; Tiebel, J.; Pausch, R.; Couperus Cabadağ, J. P.; Köhler, A.; Kurz, T.; Zgadzaj, R.; Chang, Y.-Y.; Bussmann, M.; Downer, M.; Irman, A.; Schramm, U.

Abstract

Laser wakefield accelerators (LWFA) feature unique electron bunch characteristics, namely micrometer beam size with duration ranging from a few fs to tens of fs. The longitudinal profile of such ultra-short electron bunches intricately depends on the ultrafast injection dynamics and laser-electron beam interaction during acceleration. Detailed knowledge of the electron bunch temporal profile is critical for the design of future table-top x-ray light-sources from laser- plasma accelerators, as well as for the characterization of ultrashort electron beam probes or CTR-based THz sources.

Spectral measurements of broadband transition radiation from LWFA electron bunches passing through a metal foil are especially promising for non-destructively analyzing ultrashort longitudinal bunch characteristics with single-shot capability. Our broadband, single-shot spectrometer combines the transition radiation (TR) spectrum in UV/VIS (250-1000nm), NIR (0.9-1.7μm) and mid-IR (1.6-11.35μm). The spectrometer is able to characterize electron bunches with charges as low as 1 pC and resolve time-scales from 0.4 to >20 fs.

We present recent experimental results of different LWFA injection mechanisms, such as self-truncated ionization-injection, density-shock-assisted injection and self-injection. By analyzing the transition radiation spectra and reconstructing electron bunch profiles including error analysis, we determine electron bunch profiles including sub-fs beam micro-structure of the respective injection regimes. Based on hundreds of LWFA shots, we show systematic statistics on bunch duration and peak currents with respect to electron injection-method, gas density and nitrogen-doping concentrations.

In the outlook, we put these results in context of complementary results achieved using multi-spectral near-field images of CTR which are more sensitive to the transverse than the longitudinal electron bunch distribution. We outline steps needed to tackle the challenges of analyzing more complex beams, with the goal of characterizing the 3D distibution of LWFA bunches.

Keywords: longitudinal bunch diagnostics; CTR spectroscopy; coherent transition radiation; injection scheme; Laser wakefield accelerators; LWFA

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  • Draco
  • Data Center
  • Poster
    9. Annual MT Meeting, 09.-11.10.2023, KIT, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38623


Diagnosing longitudinal electron bunch profiles by single-shot CTR spectrometry -- a window to LWFA injection dynamics

Debus, A.; Zarini, O.; La Berge, M.; Couperus Cabadağ, J. P.; Köhler, A.; Kurz, T.; Schöbel, S.; Tiebel, J.; Pausch, R.; Zgadzaj, R.; Chang, Y.-Y.; Bussmann, M.; Downer, M.; Irman, A.; Schramm, U.

Abstract

The longitudinal profile of ultra-short electron bunches from Laser wakefield accelerators (LWFA) intricately depends on the ultrafast injection dynamics and laser-electron beam interaction during acceleration. Detailed knowledge of these electron bunch temporal profile is critical for the design of future table-top x-ray light-sources, as well as for the characterization of ultrashort electron beam probes or THz sources.

We present experimental results based on spectral single-shot measurements of broadband coherent transition radiation (UV to mid-IR, 250nm-11.35μm) from LWFA electron bunches passing through a metal foil. In particular, we examine different LWFA injection mechanisms, such as self-truncated ionization-injection, density-shock-assisted injection and self-injection. By analyzing the transition radiation spectra, we reconstruct electron bunch profiles including sensitivity and uniqueness properties. The electron bunch profiles of the respective injection regimes show a broad range of bunch durations, while individual shots feature complex longitudinal electron pulse profiles that stretch accross several time scales, covering the bunch envelope, its microstructures to below sub-µm, both on top of temporally more extended charge-pedestals and tails. Based on hundreds of LWFA shots, we present systematic statistics and correlations on bunch duration, peak currents with respect to electron injection-method, gas-density, as well as bunch energy, energy spread and charge.

Keywords: Longitudinal bunch diagnostics; CTR spectroscopy; coherent transition radiation

Involved research facilities

  • Draco
  • Data Center
  • Lecture (Conference)
    6th European Advanced Accelerator Concepts (EAAC) Workshop, 17.-23.09.2023, Isola d'Elba, Italien

Permalink: https://www.hzdr.de/publications/Publ-38622


Unravelling ultrashort dynamics of plasma-based accelerators -- leveraging synthetic diagnostics to match PIC simulations with experimental data

Debus, A.; Pausch, R.; Steiniger, K.; Carstens, F.-O.; Tiebel, J.; Widera, R.; Narwal, T.; Pöschel, F.; Willmann, A.; Kelling, J.; La Berge, M.; Schöbel, S.; Chang, Y.-Y.; Vescovi Pinochet, M. A.; Kluge, T.; Gutta, V.; Hernandez Arreguin, B.; Rogers, D.; Young, J.; Joubert, W.; Hoffmann, N.; Juckeland, G.; Irman, A.; Chandrasekaran, S.; Schramm, U.; Bussmann, M.

Abstract

Exascale computing has recently become a reality. PIConGPU has paved the way to accelerating plasma simulations across compute platforms using the Alpaka framework. These capabilities not only enables conducting high-fidelity parameter scans of start-to-end simulations modeling experiments at full 3D3V geometry, but also make it possible to include additional physics.

However, experience has shown that the real challenges are of a different nature. Not only has the increasing quality of experiments put more demand on simulation quality, but more and more the need for fast analysis has grown. Based on recent experiment-driven simulation campaigns, we present results elucidating the LWFA bunch evolution within complex gas targets with plasma lensing, the injection dynamics of micro-structured LWFA bunches from CTR measurements and the pre-plasma dynamics in solid-density targets, correlating proton energies with reflected HHG radiation spectra. Here, we put an emphasis on synthetic diagnostics for radiation processes (HHG, CTR and scattered probe lasers) and atomic physics beyond the thermal equilibrium. We discuss I/O, code coupling, visual analytics and large-scale data analytics workflows to match experiment and provide an outlook on how feedback loops between experiment and simulation can be optimized.

Keywords: synthetic diagnostics; exascale workflows; plasma-based accelerators

Involved research facilities

  • Draco
  • Data Center
  • Lecture (Conference)
    6th European Advanced Accelerator Concepts (EAAC) Workshop, 17.-23.09.2023, Isola d'Elba, Italien

Permalink: https://www.hzdr.de/publications/Publ-38621


From laser-plasma accelerator experiments to digital twins: Exploit machine learning methods to tighten the links between theory and experiment

Bethke, F.; Willmann, A.; Stiller, P.; Couperus Cabadağ, J. P.; Chang, Y.-Y.; Pausch, R.; Ghaith, A.; Irman, A.; Bussmann, M.; Schramm, U.; Debus, A.; Hoffmann, N.

Abstract

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

Live-visualization for experimental data aquisition
Providing data integration for laser-plasma accelerator experiments requires a flexible infrastructure that is easily extendable and can be accessed straight-forward. This not only eases the everyday operations of experimentalists, but also enables fast development and deployment of machine learning methods. Therefore, we propose a novel combination of several existing components such as mongoDB, Grafana, and Kafka, to approach this task. The data, which is ingested live during the experiments, is visualized using interactive plots in an easy-to-access Grafana dashboard.

Surrogate model to identify electron injection
The plasma dynamics in laser-plasma accelerators are in most cases inaccessible to direct measurements. The emitted radiation from the electrons inside the plasma, however, contains information about the electron motion and thus about the relevant plasma dynamics but is hard to interpret and thus does not allow for direct interpretation. We propose an invertible-neural-network (INN) based method, radINN, that is capable of translating the emitted radiation spectra to the amount of injected charge over time. The model was trained using synthetic radiation spectra from large-scale particle-in-cell simulations. Its capabilities in identifying the injection process using "wave-breaking radiation" already exceed the capability of human domain experts.

Towards digital twins of LPA driven FELs
Understanding and control of Laser-driven Free Electron Lasers remain to be difficult problems that require highly intensive experimental and theoretical research. The gap between simulated and experimentally collected data might complicate studies and interpretation of obtained results. In this work we developed a deep learning based surrogate that could help to fill in this gap. We introduce a surrogate model based on normalising flows for conditional phase-space representation of electron clouds in a FEL beamline. Achieved results let us discuss further benefits and limitations in exploitability of the models to gain deeper understanding of fundamental processes within a beamline.

Keywords: laser-plasma accelerators; digital twin; surrogate models; machine learning; invertible-neural-network; normalising flows

Involved research facilities

  • Draco
  • Data Center
  • Lecture (Conference)
    Laser and Plasma Accelerators Workshop (LPAW) 2023, 06.-10.03.2023, Lagos, Portugal

Permalink: https://www.hzdr.de/publications/Publ-38620


Impact of LWFA injection schemes on longitudinal electron bunch properties diagnosed by single-shot CTR spectrometry

Debus, A.; Zarini, O.; La Berge, M.; Couperus Cabadağ, J. P.; Köhler, A.; Kurz, T.; Schöbel, S.; Krämer, J.; Hannasch, A. J.; Zgadzaj, R.; Mewes, H.; Meißner, H.; Pausch, R.; Bussmann, M.; Downer, M.; Schramm, U.; Irman, A.

Abstract

Laser wakefield accelerators (LWFA) feature unique electron bunch characteristics, namely micrometer beam size with duration ranging from a few fs to tens of fs. The longitudinal profile of such ultra-short electron bunches intricately depends on the ultrafast injection dynamics and laser-electron beam interaction during acceleration. Detailed knowledge of the electron bunch temporal profile is critical for the design of future table-top x-ray light-sources from laser-
plasma accelerators, as well as for the characterization of ultrashort electron beam probes or CTR-based THz sources.

Spectral measurements of broadband transition radiation from LWFA electron bunches passing through a metal foil are especially promising for non-destructively analyzing ultrashort longitudinal bunch characteristics with single-shot capability. Our broadband, single-shot spectrometer combines the transition radiation (TR) spectrum in UV/VIS (250-1000nm), NIR (0.9-1.7μm) and mid-IR (1.6-11.35μm) [1]. The spectrometer is able to characterize electron
bunches with charges as low as 1 pC and resolve time-scales from 0.4 to >20 fs.

We present recent experimental results of different LWFA injection mechanisms, such as self-truncated ionization-injection, density-shock-assisted injection and self-injection. By analyzing the transition radiation spectra and reconstructing electron bunch profiles including error analysis, we determine electron bunch profiles including sub-fs beam micro-structure of the respective injection regimes. Based on hundreds of LWFA shots, we show systematic statistics on bunch duration and peak currents with respect to electron injection-method, gas density and nitrogen-doping concentrations.

In the outlook, we put these results in context of complementary results achieved using multi-spectral near-field images of CTR which are more sensitive to the transverse than the longitudinal electron bunch distribution. We outline steps needed to tackle the challenges of analyzing more complex beams, with the goal of characterizing the 3D distibution of LWFA bunches.

References
[1] Zarini, O. et al. (2022), Physical Review Accelerators and Beams, 25(1), p. 012801.

Keywords: LWFA; Laser-wakefield acceleration; peak current; injection scheme; broadband spectrometer; single-shot bunch length measurement; coherent transition radiation; electron bunch duration; longitudinal profile

Involved research facilities

  • Draco
  • Data Center
  • Poster
    Laser and Plasma Accelerators Workshop (LPAW) 2023, 06.-10.03.2023, Lagos, Portugal

Permalink: https://www.hzdr.de/publications/Publ-38619


Advancing Atomic Physics at Gbar Pressure

Dornheim, T.; Döppner, T.; Böhme, M.; Moldabekov, Z.; Gawne, T. D.; Vorberger, J.; Kraus, D.

Abstract

We present new concepts for the experimental and theoretical study of atomic physics of Be at GBar pressure at the National Ignition Facility.

  • Invited lecture (Conferences)
    NIF User Meeting, 30.01.-01.02.2024, Livermore, USA

Permalink: https://www.hzdr.de/publications/Publ-38618


Efficient Flotation of Engineered Artificial Minerals from Metallurgical Slags by Exploiting Interaction Scanning

Strube, F.; Rudolph, M.

Abstract

FlotEnAMIS as part of SPP 2315 focuses on a novel functional atomic force microscopy (AFM) / atomic force spectroscopy and interface engineering based interaction scanning technology to understand the surface properties of engineered artificial minerals (EnAMs) in slags and find suitable flotation reagent regimes (including adsorption of collectors and modifiers/regulators/depressants) for an efficient flotation separation of fine particles from liberated fine grained engineered slags.

Keywords: interaction scanning; slags; atomic force microscopy; lithium

  • Lecture (others) (Online presentation)
    AG Grenzflächen, 23.08.2023, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38617


Zur flotativen Trennung von Lithium haltigen Mineralphasen in "engineered slag systems"

Strube, F.; Rudolph, M.

Abstract

Die zunehmende Nutzung von Batterien für das Vorantreiben der Energiewende führt zu einem immer steigenden Bedarf an Lithium, welches bereits jetzt als kritischer Rohstoff gelistet ist. Die Sicherung vorhandener Lithiumquellen stellt jedoch noch eine Herausforderung dar. Lithium kann in Form von künstlichen Mineralien (EnAM – engineered aritifical minerals) in Schlacken angereichert und wiedergewonnen werden, welche beim pyrometallurgischen Recycling von Batterien anfallen. Durch die Anwendung bestimmter Temperatur- und Additivregime während des Recyclings lässt sich die Anreicherung von Lithium in EnAMs gezielt steuern (bspw. Kristallform, -größe und Phasenzusammensetzung). Das bekannteste Li-haltige EnAM ist Lithiumaluminat, welches unter anderem in das Gangmineral Gehlenit eingebettet ist. Die Trennung dieser EnAM-Phasen vom Gang kann durch Schaumflotation erreicht werden.
Im vorgestellten Projekt FlotEnAMIS, welches Teil des Schwerpunktprogramms 2315 der DFG ist, werden die Bestimmung der Phasenzusammensetzung und physikalisch-chemischen Eigenschaften von EnAMs in unterschiedlich behandelten Schlacken als wichtige Parameter für die Schaumflotation untersucht. Für die Charakterisierung der häufig fein verteilten Phasen werden Ergebnisse von Röntgendiffraktometrie (XRD), Röntgenfloureszenz (XRF), automatisierte Mineralogie (MLA) und Rasterkraftmikroskopie (AFM) miteinander in Verbindung gesetzt. Zur Beurteilung verschiedener wichtiger Oberflächenwechselwirkungen von Flotationsreagenzien in Abhängigkeit von Oberflächenpotentialen werden verschiedene AFM-Messungen mit hydrophilen und hydrophoben kolloidalen Sonden im Trocken- und Flüssigkeitsmodus an einem repräsentativen Modell durchgeführt und mit Ergebnissen aus Mikroflotationsexperimenten korreliert.

Keywords: Flotation; Lithium; Slag; Schlacke

  • Lecture (Conference)
    Tagung Aufbereitung und Recycling, 16.-17.11.2023, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38616


Development of Atomic Force Microscopy based interaction scanning modalities for the assessment of the flotation separation of Lithium bearing engineered artificial minerals in slags

Strube, F.; Rudolph, M.

Abstract

Froth flotation is a widely established heterocoagulation separation process for the raw materials industry that is most efficient for particles in the size range of 20 μm – 200 μm. It is becoming even more important in upgrading critical materials. The key selection criterion is the difference in (de)wett(ing)ability of the surfaces of particulate phases. It has always been a grant challenge to quantitatively asses this complex physicochemical surface property. Most typically single mineral microflotation tests are found practical. They are further applied to find suitable reagent regimes necessary to condition the suspended particles in order to make selective separation possible. This involves various different suits of chemicals referred to as collectors and regulators. It is challenging if not impossible to obtain enough sample materials of pure individual phases to perform those conventional microflotation tests with unconventional resources, such as slags containing engineered artificial mineral (EnAM) phases enriched with critical elements. A prominent Li-containing EnAM is Lithiumaluminate and engineered in Al2O3-CaO-Li2O-MgO-(MnO)-SiO2 slag systems from battery recycling. We propose and develop an Atomic Force Microscopy based Interaction Scanning approach to be able to obtain surface interaction parameters at high resolution which are decisive for the particle-bubble-(non)attachments related to the dewettingability contrast.

As typical artificial phases in the mentioned slag system, we synthesize the valuable Lithiumaluminate and the gangue Gehlenite with high temperature sintering for evaluating interaction parameters and performing conventional microflotation tests of pure EnAM specimen. For assessing different key surface interactions from reagent regime depending surface potentials and surface hydrophizations we perform different hydrophilic and hydrophobic colloidal probe AFM measurements in dry and liquid mode on a representative model system with the valuable Lithium bearing mineral Spodumene and the representative gangue phase Quartz as substrates. This model system occurs in nature and is suitable to study reagents for efficient separation of Li-bearing minerals by flotation and to relate them to artificial phases such as EnAMs. The AFM studies are set in context with common micro flotation experiments and further characterization techniques. With this we will showcase and discuss the potentials of an Atomic Force Microscopy based approach to flotability assessment.
This project is part of the priority program PP2315 on engineered artificial minerals and their processing of the DFG (German Research Foundation).

Keywords: flotation; interaction scanning; atomic force microscopy; lithium

  • Poster
    International Congress on Particle Technology PARTEC, 26.-28.09.2023, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38615


Efficient Flotation of Engineered Artificial Minerals from Metallurgical Slags by Exploiting Interaction Scanning, SPP2315, Yearly Meeting 2023

Strube, F.; Rudolph, M.

Abstract

FlotEnAMIS as part of SPP 2315 focuses on a novel functional atomic force microscopy (AFM) / atomic force spectroscopy and interface engineering based interaction scanning technology to understand the surface properties of engineered artificial minerals (EnAMs) in slags and find suitable flotation reagent regimes (including adsorption of collectors and modifiers/regulators/depressants) for an efficient flotation separation of fine particles from liberated fine grained engineered slags.

Keywords: interaction scanning; flotation; slags; engineered artifical minerals; lithium

  • Lecture (others)
    SPP2315 annual meeting, 05.-06.07.2023, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38614


Data publication: Tunable Crystallinity and Electron Conduction in Wavy 2D Conjugated Metal-Organic Frameworks via Halogen Substitution

Jastrzembski, K.; Zhang, Y.; Lu, Y.; Sporrer, L.; Pohl, D.; Rellinghaus, B.; Waentig, A. L.; Zhang, H.; Mücke, D.; Fu, S.; Polozij, M.; Li, X.; Zhang, J.; Wang, M.; Morag, A.; Yu, M.; Mateo-Alonso, A.; Wang, H. I.; Bonn, M.; Kaiser, U.; Heine, T.; Dong, R.; Feng, X.

Abstract

SinglePoint + band structure calculations for Cu3(HF-HH-cHBC)2 material using VASP software.

Keywords: 2D conjugated MOFs; conductive MOFs; halogen substitution; tunable crystallinity; wavy structure

Related publications

Permalink: https://www.hzdr.de/publications/Publ-38613


The use of AFM to study flotation parameters of Li bearing Engineered Artificial Minerals represented in slags

Strube, F.; Rudolph, M.

Abstract

Due to the developments in electric mobility and the increased utilization of batteries, lithium has been classified as a critical raw material. It is a challenge to save and recycle existing lithium sources and the development of new recycling routes is a key area of research. A common method for the recycling of lithium ion batteries involves a pyrometallurgical high temperature treatment which concentrates critical elements in an alloy, whereas ignoble valuable metals such as lithium are concentrated in slags or dust. In order to use these Li-bearing slags as a promising lithium source, the priority programme PP2315 promotes the enrichment of lithium as engineered artificial mineral (EnAM). The most prominent Li-bearing EnAM is lithium aluminate which is found to be embedded in the gangue mineral gehlenite. The separation of these EnAM phases can be achieved via froth flotation, which is addressed in the presented project FlotEnAMIS as a part of the PP2315.
Froth flotation is a widely established separation process in the mining industry that is most efficient for particles in the size range of 20 μm – 200 μm. It is driven by the differences in the particle wettability and the attractive hydrophobic interaction between bubbles and particles at the solid-gas interface. This wettability difference can be controlled by selective adsorption of chemical reagents, such as collectors or depressants. Atomic force microscopy (AFM) can examine the differences in important driving forces of flotation acting between phases of certain hydrophobicity. For instance, colloidal probe AFM (CP-AFM) can be used as a model method to study the interaction of a sphere mimicking a bubble and a mineral surface.
The adsorption of surfactants on Li-EnAMs and the important sub-processes such as wettability, reagent adsorption, inter-particle interaction and bubble-particle interaction is investigated in this study by means of different AFM methods. The information obtained on the particle-reagent interaction is put in context with results of micro flotation studies. Based on this, suitable reagent regimes can be developed for the efficient recovery of lithium bearing minerals via flotation.

Keywords: slag; lithium; hydrophobicity; atomic force microscopy

  • Poster
    ProcessNet, 08.-10.03.2023, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38612


Magnetic Modelling of the Bjerkreim-Sokndal Layered Intrusion, Southern Norway

Lee, M.; Pastore, Z.; Church, N.; Madriz Diaz, Y. C.; Gloaguen, R.; McEnroe, S. A.

Abstract

The Proterozoic Bjerkreim-Sokndal (BKS) is a 230 km2 layered intrusion in the Rogaland Anorthosite Province, Norway. BKS has been extensively explored for its critical mineral potential. The BKS has also been used as an analogue for planetary studies due to the presence of strong magnetic remanence, which has resulted in anomalies of up to 20 µT below background in airborne surveys. The BKS has five megacyclic lithological units, which are subdivided into zones based on specific mineralogy. The surficial location of these zones has been mapped based on limited outcrops due to difficult accessibility and regional airborne magnetics. However, review of recent high-resolution magnetic surveys suggests that the geologic map should be reassessed and used in conjunction with petrophysical data to better understand subsurface geometry. To address this challenge, we are developing a 3D geologic model that integrates multiscale geophysical data, from microscale lab measurements to regional airborne surveys. This includes data from a novel 2021 multicopter drone magnetic survey. A master ground sample database that includes over 3000 samples with in-situ and in-lab petrophysical measurements was compiled. The petrophysical database was analysed using Principal Component Analysis (PCA) clustering to distinguish relevant lithological units. PCA was performed using the variables: Density, Susceptibility, Natural Remanent Magnetization, Induced Magnetization, Koenigsberger Ratio, Declination, Inclination, Vx, Vy, Vz, and Residual Magnetic Field.

A combination of 2D forward and inversion modelling was implemented in Geosoft Oasis Montaj GM-SYS. The model was based on dense survey profiles orthogonal to geological strike along the eastern margin of the Bjerkreim lobe. Airborne magnetic data was used as the regional constraint and the petrophysical clusters as input data for the modelled blocks. The results were integrated into a 3D visualisation framework and used to refine the geometry of the main geological units. Visualisation of the high-resolution drone data shows complex structures beneath local lakes that were unmapped during previous geophysical surveys.

Keywords: Remanent Magnetization; Magnetics

  • Lecture (Conference)
    AGU23, 11.-15.12.2023, San Francisco, CA, United States of America

Permalink: https://www.hzdr.de/publications/Publ-38611


UAV geophysical surveys for mineral exploration in challenging environments

Madriz Diaz, Y. C.; Shaik Fareedh, J.; Gloaguen, R.; Dana Lee, M.; McEnroe, S. A.

Abstract

Uncrewed aerial vehicles (UAVs) equipped with geophysical sensors have brought numerous advancements to modern geophysics, enabling cost-effective exploration and high-resolution analysis of geological anomalies. Integrating multiple sensors through UAV platforms proves especially advantageous in prospecting for mineral resources. Over the last years, our team has developed and rigorously tested in-house UAV systems carrying magnetometers, gamma-spectrometers, LiDAR, and hyperspectral sensors. Ensuring good data quality presents several challenges specific to UAVs. One significant challenge arises during aeromagnetic surveys conducted in regions with remarkably high magnetic gradients. These gradients have a substantial impact on the UAV’s essential navigation instruments, endangering the aircraft and leading to data disturbances. To showcase the potential of our approach, we have successfully deployed the systems in various challenging environments worldwide, including areas with high magnetic gradients, low GPS coverage, sharp topographic variations, extreme temperatures, and strong wind gusts.

We introduce a robust workflow designed to acquire and process UAV aeromagnetic data effectively. For the surveys, we employ the Sensys MagDrone R3 magnetometer strategically positioned at a 2m distance from the UAV using an extensible arm, eliminating magnetic interferences from the carrier. Additionally, data grids are meticulously designed based on the geological target, unraveling geological complexities. Data processing is performed through a Python toolbox, allowing us to promptly assess data quality during survey operations and to make well-informed decisions on-site. This approach has been validated across contrasting environments to tailor the acquisition strategy to local conditions, leading to the most optimal dataset possible at each location.

Through multiple case studies, we successfully demonstrate the capabilities of UAV magnetic surveys, often providing the highest resolution airborne survey data in the regions to date. The level of detail and accuracy achieved with UAV magnetic surveys opens up new possibilities for gaining deeper insights into complex structures and accurately pinpointing promising
mineral deposits with unprecedented precision.

Keywords: UAV; magnetics; magnetometer

  • Invited lecture (Conferences) (Online presentation)
    AGU23, 11.-15.12.2023, San Francisco, CA, United States

Permalink: https://www.hzdr.de/publications/Publ-38610


Positrons enable analysis of defects in functional materials

Liedke, M. O.; Butterling, M.; Hirschmann, E.; Elsherif, A. G. A.; Wagner, A.

Abstract

Positron annihilation spectroscopy (PAS) is an advanced experimental technique that allows to study of extended and point defects and their agglomeration down to the atomic scale. The main strength of PAS is its excellent resolution to detect low concentrations (0.1 to 100 ppm) of vacancy-like defects. Using our slow positron beams at the positron ELBE (pELBE) facility, not only volumetric capability is achieved, but also defect profilometry over the depth of the sample in the sub-micron range. The other advantage of PAS is the interaction of positrons with core electrons, which carry information about the local atomic environment. The combination of all these characteristics allows the successful analysis of defect nanostructures in many classes of materials. Some research highlights will be presented, including investigations of the role of defects in heavily doped semiconductors, magneto-ionic oxides and nitrides, and superconductors. An overview of current collaborations within the HZDR and with external users will be given, as well as an outlook on future positron activities, including the increasing focus on kinematic pump-and-probe experiments associated with intense lasers and electric fields, and perspectives related to the upcoming DALI project.

Keywords: point defects; pores; positron annihilation spectroscopy

Involved research facilities

Related publications

  • Lecture (Conference)
    2023 HZDR Science Conference, 15.11.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-38609


Defect landscape in TiO2 after ms-range annealing and resulting photocatalytic efficiency

Liedke, M. O.; Prucnal, S.; Butterling, M.; Hirschmann, E.; Gago, R.; David, G. C.; Rebohle, L.; Helm, M.; Zhou, S.; Wagner, A.

Abstract

Transition metal oxides, particularly TiO2, are photoactive materials, which can be utilized to clean the air from pollutants and to produce green hydrogen for clean energy at the same time. They are one of the most promising candidates for high-performance photocatalysis. In this work, we investigate the effect of 20 ms flash lamp annealing (FLA) of sputter deposited TiO2, where arising from the light irradiation structural modifications of the films facilitates the photocatalytic (PC) degradation of two chemical compounds, namely methyl blue and methyl orange, once they interact with the surface of TiO2. The precise control of the flash energy input enables tuning of the TiO2 phase formation starting from pure anatase to mixed anatase/rutile phases, the latter associated with increased PC effect. Scanning electron microscopy and X-ray diffraction studies show that the crystal size and film quality increase with increasing annealing temperature. Further, the evolution of structural defects after FLA has been assessed by positron annihilation spectroscopy (PAS) and photoluminescence. Positron annihilation lifetime characteristics, i.e., positron lifetimes and their relative intensities profoundly sketch a transition between pure anatase and emerging rutile phase as a function of flash energy. Vacancy complexes close to the size of trivacancy dominate the anatase phase, whereas in the mixed anatase/rutile phase smaller open volume is evidenced, likely as a direct consequence of annealing. Finally, Doppler broadening PAS indicates the overall reduction of defect density exhibiting a similar transient phase region at the intermediate flash energies.

Keywords: transition metal oxides; photoactive materials; photocatalysis; flash lamp annealing; sputter deposition; positron annihilation spectroscopy

Involved research facilities

Related publications

  • Lecture (Conference)
    SLOPOS-16, The sixteenth International Workshop on Slow Positron Beam Techniques and applications, 16.07.2023, Orléans, France

Permalink: https://www.hzdr.de/publications/Publ-38608


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.

Abstract

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

Involved research facilities

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


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.

Abstract

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

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


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

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

Abstract

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


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.

Abstract

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


Quasi-particle propagation across semiconductor-Mott insulator interfaces

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

Abstract

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


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

Bernhard, S.; Krause, J.

Abstract

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


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

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

Abstract

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


Higher-harmonic generation in the driven Mott-Hubbard model

Queißer, F.; Schützhold, R.

Abstract

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


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

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

Abstract

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


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.

Abstract

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


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

Schramm, U.

Abstract

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


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

Schramm, U.

Abstract

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

Involved research facilities

  • HIBEF
  • ATHENA
  • Draco
  • Penelope
  • 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


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.

Abstract

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


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