Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41709 Publications

Automatic optimization of bilateral filter parameters in clinical PET

Maus, J.; Nikulin, P.; Hofheinz, F.; Braune, A.; Kotzerke, J.; van den Hoff, J.

Abstract

Aim: Gaussian filters are commonly used to improve signal to noise ratio (SNR) of PET images but reduce spatial resolution, thus increasing partial volume effects. Edge preserving filters can alleviate this problem. Especially, the bilateral filter (BF) has shown to have very good performance but requires manual tuning of its two parameters (σS, σI) for optimal results. This is time consuming and hampers clinical use. In this work we, therefore, investigated an automatic method for parameter optimization.

Methods: PET-data from 69 patients were included: 18F-FDG(N=33), 18F-LDOPA(N=25), 68Ga-DOTATATE(N=11). All scans were performed with respiratory gating (8 gates), resulting in 552 low SNR PET volumes. Four 3D ROIs were placed in each volume: one within the liver (to assess noise) and three in areas with elevated focal uptake and various SNR levels. Optimal parameters were determined by a grid search in the (σS,σI) plane aiming at parameters that simultaneously leave SUVmax of the focal uptake mostly unaltered while yielding a noise level comparable to that seen in the sum over all gates. BF with the optimized parameters was then applied and images were visually inspected and analyzed regarding ΔSUVmax and ΔNoise differences (BF vs. unfiltered) in the respective ROIs.

Results: In 19/69 datasets our method failed (over-smoothed background or artifacts). For these images the parameters had to be manually tuned. Overall, optimal parameter values varied over a substantial range (mean±sd: σI=(1.4±1.5) SUV and σS=(5.5±1.7) mm) with σI exhibiting a pronounced tracer dependance. ΔSUVmax of the focal uptake ROIs across all datasets was small (-0.5±0.8) while substantial noise reduction was achieved by (-12.3±3.5) percentage points although detailed behaviour differed between tracers.

Conclusions: Our results demonstrate inter-individual and tracer-specific variability of optimal BF parameters and thus underline the need for careful parameter optimization. In 72% of all investigated cases our automated method was able to perform this optimization without any user intervention. More work is needed to further improve the success rate. However, already in its current form our method does notably reduce workload imposed on the user when considering BF for routine use.

Keywords: positron emission tomography (PET); post-filtering; bilateral filter; optimization

Involved research facilities

  • PET-Center
  • ZRT
  • Open Access Logo Poster
    62. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 11.04.2024, Leipzig, Deutschland
    DOI: 10.1055/s-0044-1782423

Permalink: https://www.hzdr.de/publications/Publ-39212


Deep learning enhanced bilateral post-filtering of noisy PET data

Maus, J.; Nikulin, P.; Hofheinz, F.; Rosin, B.; Braune, A.; Kotzerke, J.; van den Hoff, J.

Abstract

Aim: PET images can exhibit high noise levels which adversely affects qualitative and quantitative image evaluation. Especially challenging are respiratory gated studies and dynamic studies. In such cases, Gaussian filtering is routinely used to improve the signal to noise ratio. However, this degrades the spatial resolution and leads to reduced contrast recovery (CR) in small lesions. Edge preserving bilateral filtering is able to overcome this shortcoming but requires careful tuning of its 2 parameters on a per case basis in order to produce optimal results. In this work we evaluate the potential of using a deep neural network for automatic edge preserving image filtering utilizing a training set of manually filtered PET images.

Methods: We collected unfiltered gated PET data from clinical PET/MR (Philips PET/MR) and PET/CT (Siemens PET/CT) systems and interactively optimized bilateral filtering to achieve the best combination of noise reduction and preservation of spatial resolution. The set of pairs of corresponding unfiltered and filtered images was randomly split into training, validation, and testing sets. The convolutional neural network (CNN) was trained to generate the filtered images from the unfiltered ones. The resulting network model was then evaluated using the ROVER software package regarding its denoising and CR performance and also for presence of artifacts.

Results: With the preliminary data available so far, evaluation of the images filtered with CNN yielded results closely resembling these obtained with manually tuned bilateral filtering in terms of noise level and CR. No apparent image artifacts were found.

Conclusions: Our initial results indicate that the CNN-based post-filtering produces images comparable to interactively optimized filtering. However, more thorough analyses with more image data for testing and training is required to draw definite conclusions about reliably of the proposed solution and will be performed in the coming months. Furthermore, integration of the derived network into a new respiratory motion compensation framework is planned.

Keywords: positron emission tomography (PET); denoising; post-filtering; deep learning

Involved research facilities

  • PET-Center
  • ZRT
  • Open Access Logo Poster (Online presentation)
    60. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 29.04.2022, Leipzig, Deutschland
    DOI: 10.1055/s-0042-1746121

Permalink: https://www.hzdr.de/publications/Publ-39211


Evaluation of effective spatial resolution in reconstructed PET images

Maus, J.; Hofheinz, F.; Meister, S.; Pietzsch, J.; van den Hoff, J.

Abstract

Aim: Spatial resolution is one of the key parameters for assessment of PET scanner performance. However, spatial resolution is usually determined with point or line sources, not allowing to study the finite object size and contrast effects known to affect iterative image reconstruction results. We present an approach to determine the spatial resolution at finite background for extended objects. The method was applied to preclinical PET/CT systems (Bruker PET/CT Si78, Mediso PET/CT).

Methods: Spatial resolution is assessed as the full width at half maximum (FWHM) of the point spread function (PSF, approximated by a 3D Gaussian). FWHM is determined from a fit of the convolution of the considered object (homogeneous sphere or rod) with the PSF to the reconstructed image data. In this process, the full 3D vicinity of each sphere/rod is evaluated by transforming the data to spherical/cylindrical coordinates relative to the respective object center/axis. F-18 measurements were performed with a cylindrical phantom (diameter 3.5cm) with a cylindrical insert (diameter 1cm). Measurements were performed without background and at contrast ratio 3:1, respectively.

Results: Without background, we obtained FWHM=1.3mm for the Mediso system, but severe Gibbs artefacts are present, indicating a too aggressive resolution recovery approach. The Bruker system achieves FWHM=2.1mm while avoiding any Gibbs artefacts. At 3:1 contrast, resolution of both systems decreases (to FWHM=2.6mm and 3.2mm, respectively) while Gibbs artefacts are not visible for the Mediso system, too.

Conclusions: Our preliminary results show that both investigated systems have a strongly contrast dependent spatial resolution. Optimizations of reconstruction parameters are currently underway with the aim of reducing the adverse effects of Gibbs artefacts on quantification and improving reconstructed image resolution at finite background while avoiding any negative effects on potential quantification.

Keywords: positron emission tomography (PET); spatial resolution; preclinical

Involved research facilities

  • PET-Center
  • ZRT
  • Open Access Logo Poster (Online presentation)
    59. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 17.04.2021, digital, Deutschland
    DOI: 10.1055/s-0041-1726820

Permalink: https://www.hzdr.de/publications/Publ-39210


Using advanced measurement techniques for analysis and modelling of multiphase processes

Kipping, R.; Marchini, S.; Wiedemann, P.; Hampel, U.

Abstract

The design of multiphase reaction and separation processes, such as for example catalytic hydrogenations, distillation and absorption processes, extraction processes, wastewater treatment, and many more, require a profound understanding of the multiphase fluid dynamics inside reactors and contactors. As Computational Multiphase Fluid Dynamics is still not fully mature to simulate complex two-phase and three-phase flow with overlaying heat and mass transfer as well as chemical reaction with sufficient accuracy there is a constant need for advanced experimental and measurement techniques; may it be for the provision of operational, design or thermodynamic parameters or for the validation of codes. In this talk we report on three different novel measurement techniques for this purpose. The presentation shall exemplarily demonstrate how advanced measurement and imaging techniques can be used to study opaque two-phase and three-phase flows in lab environment and potentially also in the field. We report on a) the use of ultrafast X-ray tomography and wire-mesh sensors for the study of reactive bubbly flow in a bubble column, b) the application of a large flow profiler in studying two-phase flow on a distillation column tray, and c) a method to obtain gas dispersion parameters in gas-liquid contactors using modulated gas flow.

Involved research facilities

  • TOPFLOW Facility
  • Invited lecture (Conferences)
    Vortrag innerhalb der Session Smart Multiphase Processes bei der ACHEMA, 10.-14.06.2024, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-39205


Driving nanomaterials with a THz free-electron laser

Helm, M.

Abstract

Long-wavelength free-electrons lasers are unique sources of intense, narrowband THz radiation. I will discuss here time-resolved experiments, where intense THz radiation strongly drives and excites charge carriers in two different types of nanomaterials.
In the first experiment a single GaAs/InGaAs core-shell nanowire with a strained GaAs core and a highly doped InGaAs shell is excited with 12-THz radiation near the tip of a Neaspec scattering scanning near-field microscope (s-SNOM). Subsequently the spectrally resolved mid-infrared response (20-60 THz) is probed using a difference-frequency mixing source. Resulting from this intraband pumping we observe a red shift of the nanowire plasma resonance both in amplitude and phase spectra, which is ascribed to a heating of the electron distribution in the nonparabolic band and to electron transfer into the side valleys, resulting in an increase of the average effective mass.
In the second experiment we excite a single 2D layer of MoSe2 with THz radiation of photon energy in the vicinity of the trion binding energy (here 26 meV). A trion is an exciton that binds a second electron; it is known, even from the hydrogen atom, that its binding energy is roughly an order of magnitude smaller than the exciton binding energy. Subsequently the time-resolved photoluminescence is monitored to observe exciton and trion populations for different excitation photon energies. We clearly identify the resonant ionization of the trion and its conversion to an exciton.

Keywords: terahertz; thz; free electron laser; nanowires; 2d materials; trions; excitons; SNOM

Involved research facilities

  • F-ELBE
  • Invited lecture (Conferences)
    6th International Symposium on Microwave/THz Science and Applications (MTSA 2024), 04.-07.06.2024, Copenhagen, Denmark

Permalink: https://www.hzdr.de/publications/Publ-39200


Si1-x-yGeySnx alloy formation by Sn ion implantation and flash lamp annealing

Steuer, O.; Michailow, M.; Hübner, R.; Pyszniak, K.; Turek, M.; Kentsch, U.; Ganss, F.; Khan, M. M.; Rebohle, L.; Zhou, S.; Knoch, J.; Helm, M.; Cuniberti, G.; Georgiev, Y.; Prucnal, S.

Abstract

Bei diesem Datensatz handelt es sich um die im Paper beschriebenen µRaman, RBS und TEM Daten sowie die SRIM Simulationen

Keywords: Implantation; SiGeSn; Si1-x-yGeySnx; Sn; FLA; Flash lamp annealing

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Permalink: https://www.hzdr.de/publications/Publ-39199


Janus Particles in Acoustofluidic Setup: The Interplay between Self-Propulsion and Acoustic Trapping

Marie Benko, L.; Misko, V. R.; Baraban, L.; Makarov, D.; Maisto, A.; de Malsche, W.

Abstract

Acoustic focusing of particle flow in microfluidics has been shown to be an efficient tool for particle separation for various chemical and biomedical applications. The mechanism behind the method is the selective effect of the acoustic radiation force on distinct particles. In this way, they can be selectively focused and separated. The technique can also be applied under stationary conditions, i.e., in the absence of fluid flows. In this study, the manipulation of self-propelled particles, such as Janus particles, in an acoustofluidic setup was investigated. In experiments with self-propelled Janus particles and passive beads, we explored the interplay between self-propulsion and the acoustic radiation force. Our results demonstrated unusual and potentially useful effects such as selective trapping, escape, and assisted escape in binary mixtures of active and passive particles. We also analyzed various aspects related to the behavior of Janus particles in acoustic traps in the presence and absence of flows.

Keywords: acoustofluidics; Janus particles; particle focusing

Permalink: https://www.hzdr.de/publications/Publ-39198


Flash lamp annealing for roll-to-roll applications

Rebohle, L.; Begeza, V.; Cherkouk, C.; Folgner, C.; Prucnal, S.; Zhou, S.

Abstract

The talk gives a short overview about the combination of flash lamp annealing and roll-to-roll applications including the application fields of inkjet printing with nanoparticle inks, transparent conduction oxides, and energy materials.

Keywords: flash lamp annealing; roll-to-roll application; inkjet printing

Involved research facilities

Related publications

  • Lecture (Conference)
    Nutzertreffen "Heissprozesse und RTP", 15.05.2024, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-39197


3D Empirical Dissolution Model (Winardhi 2024)

Da Assuncao Godinho, J. R.; Winardhi, C.

Abstract

 3D empirical dissolution model aimed at examining the time-series evolution of macroscopic features together with the corresponding changes in the dissolution rate under far from equilibrium batch reactor conditions. The developed empirical model is based on the mineral geometry (surface topography and volume) derived from X-ray computed tomography (CT) measurements. The macroscopic features are identified using surface curvature which are then used to generate reactivity maps for dissolution models.

Keywords: dissolution model; 3d

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Permalink: https://www.hzdr.de/publications/Publ-39195


Dynamo action driven by precessional turbulence

Kumar, V.; Pizzi, F.; Mamatsashvili, G.; Giesecke, A.; Stefani, F.; Barker, A. J.

Abstract

We reveal and analyze an efficient magnetic dynamo action due to precession-driven hydrodynamic turbulence in the local model of a precessional flow, focusing on the kinematic stage of this dynamo. The growth rate of the magnetic field monotonically increases with the Poincaré number Po, characterizing precession strength, and the magnetic Prandtl number Pm, equal to the ratio of viscosity to resistivity, for the considered ranges of these parameters. The critical Po for the dynamo onset decreases with increasing Pm. To understand the scale-by-scale evolution (growth) of the precession dynamo and its driving processes, we perform spectral analysis by calculating the spectra of magnetic energy and of different terms in the induction equation in Fourier space. To this end, we decompose the velocity field of precession-driven turbulence into two-dimensional (2D) vortical and three-dimensional (3D) inertial wave modes. It is shown that the dynamo operates across a broad range of scales and exhibits a remarkable transition from a primarily vortex-driven regime at lower Po to a more complex regime at higher Po where it is driven jointly by vortices, inertial waves, and the shear of the background precessional flow. Vortices and shear drive the dynamo mostly at large scales comparable to the flow system size, and at intermediate scales, while at smaller scales it is mainly driven by inertial waves. This study can be important not only for understanding the magnetic dynamo action in precession-driven flows, but also in a general context of flows where vortices emerge and govern the flow dynamics and evolution.

Permalink: https://www.hzdr.de/publications/Publ-39194


Data publication: Tuning the Electronic Characteristics of Monolayer MoS2-Based Transistors by Ion Irradiation: The Role of the Substrate

Fekri, Z.; Chava, P.; Hlawacek, G.; Ghorbani Asl, M.; Kretschmer, S.; Awan, W.; Koladi Mootheri, V.; Sycheva, N.; George, A.; Turchanin, A.; Watanabe, K.; Taniguchi, T.; Helm, M.; Krasheninnikov, A.; Erbe, A.

Abstract

This study explores defect engineering in 2D materials using ion beam irradiation to modify the electrical and optical properties with potential in advancing quantum electronics and photonics. Helium and neon ions ranging from 5 to 7.5 keV are employed to manipulate charge transport in monolayer molybdenum disulfide (MoS2). In situ electrical characterization occurs without vacuum breakage post-irradiation. Raman and photoluminescence spectroscopy quantify ion irradiation’s impact on MoS2. Small doses of helium ion irradiation enhance monolayer MoS2 conductivity in field-effect transistor geometry by inducing doping and substrate charging. Findings reveal a strong correlation between the electrical properties of MoS2 and the primary ion used, as well as the substrate on which the irradiation occurred. Using hexagonal boron nitride (h-BN) as a buffer layer between MoS2 flake and SiO2 substrate yields distinct alterations in electrical behavior subsequent to ion irradiation compared to the MoS2 layer directly interfacing with SiO2. Molecular dynamics simulations and density functional theory provide insight into experimental results, emphasizing substrate influence on measured electrical properties post-ion irradiation.

Keywords: defects; FET; first-principles calculations; ion irradiation; monolayer MoS2

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Permalink: https://www.hzdr.de/publications/Publ-39191


Dataset on WetAnnealing

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

Abstract

This dataset covers test data related to the WetAnnealing Project, in particular the publication "Recovery of neutron-irradiated VVER-440 RPV base metal and weld exposed to isothermal annealing at 343 °C up to 2000 hours" submitted to Frontiers in Nuclear Engineering. The test data have been derived from Vickers hardness (HV10) testing, Small Punch Tests (SPT), Master Curve (MC) fracture mechanics testing of miniaturized compact tension 0.16-C(T) samples, and Small-Ange Neutron Scattering (SANS) experiments. Plots and figures are also included.

Keywords: reactor pressure vessel steel; embrittlement; wet annealing; recovery; hardness; small punch test; fracture mechanics; small-angle neutron scattering

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Permalink: https://www.hzdr.de/publications/Publ-39189


MultiMorph - A Morphology-Adaptive Multifield Two-Fluid Model

Meller, R.; Krull, B.; Tekavcic, M.; Schlegel, F.

Abstract

Industrial multiphase flows are typically characterized by coexisting morphologies. Modern simulation methods are well established for dispersed (e.g., Euler-Euler) or resolved (e.g., Volume-of-Fluid) interfacial structures. A simulation method that requires less knowledge about the flow in advance would be desirable and should allow describing both types of interfacial structures – resolved and dispersed – in a single computational domain. Such methods that combine interface-resolving and non-resolving approaches are called hybrid models. A morphology adaptive multifield two-fluid model, named MultiMorph Model, is proposed, which is able to handle dispersed and resolved interfacial structures coexisting in the computational domain with the same set of equations. For large interfacial structures an interfacial drag formulation is used to describe them in a volume-of-fluid-like manner. For the dispersed structures, the baseline model developed at Helmholtz-Zentrum Dresden - Rossendorf e.V. (HZDR) is applied. The functionality of the framework is demonstrated by several test cases, including a single rising gas bubble in a stagnant water column. Recent developments focus on the transition region, where bubbles are over- or under-resolved for Euler-Euler or for Volume-of-Fluid, respectively. The contribution will focus on an overview about the fundamentals of the MultiMorph Model and recent simulation results for a plunging jet, a stratified counter-current air-water flow and a column tray of a distillation column.

  • Lecture (Conference)
    15th International Conference on Industrial Applications of Computational Fluid Dynamics, 11.-13.06.2024, Trondheim, Norwegen

Permalink: https://www.hzdr.de/publications/Publ-39186


VACVPlaque: mobile photography of Vaccinia virus plaque assay with segmentation masks

De, T.; Urbanski, A.; Thangamani, S.; Wyrzykowska, M.; Yakimovich, A.

Abstract

Data Description

The VACVPlaque dataset comprises spatially correlated objects, specifically virological plaques, which are circular phenotypes indicative of vaccinia virus (VACV) spread, and the wells of the assay plate. The virus plaque assay is a common method performed by infecting a monolayer of host cells (indicator cells) that are grown in the wells of assay plates or dishes. The host cells are infected with varying concentrations of a highly diluted virus inoculum. After an incubation period, typically around 48 hours, the cells are fixed with formaldehyde and stained with a dye to reveal the plaques or areas of cell death. By counting these plaques, researchers can calculate the number of infectious particles present in the original inoculum as described in [1].

This dataset consists of mobile photographs of 6-well tissue culture plates where the VACV plaque assay was conducted. The photographs were taken using two different mobile phones, resulting in 211, 16-bit RGB images with a resolution of 2448 x 3264 pixels. Each plate was photographed from two different perspectives using two different devices, meaning there are two images of the same plate but from different angles and devices.

To aid in the training of machine learning models, the dataset is divided into training, validation, and test subsets in a 70:20:10 ratio. To prevent data leaks, only one perspective of each image is included in the validation and test subsets. The training subset, which includes images from both perspectives, consists of 148 images.

File Description:

VACVPlaque_train.zip -> train holdout

VACVPlaque_validation.zip -> validation holdout

VACVPlaque_test.zip -> test holdout

Each zip file contains:

images -> {filename}.tif

plaque_masks -> {filename}.tif

well_masks -> {filename}.tif

References:

1. Dulbecco, Renato. "Production of plaques in monolayer tissue cultures by single particles of an animal virus." Proceedings of the National Academy of Sciences 38, no. 8 (1952): 747-752.

Keywords: Vaccinia virus; mobile photography; plaque assay

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Permalink: https://www.hzdr.de/publications/Publ-39182


HeLaCytoNuc: fluorescence microscopy dataset with segmentation masks for cell nuclei and cytoplasm

De, T.; Urbanski, A.; Thangamani, S.; Wyrzykowska, M.; Yakimovich, A.

Abstract

Data Description:

This dataset comprises fluorescence micrographs of HeLa cells, specifically labelled to identify nuclei and cell cytoplasm. These images were acquired as a technical calibration for a high-content screening study detailed and published in [1].

The HeLa cell line (ATCC-CCL-2), a widely used immortalised cell line in laboratory research, was cultured under standard conditions. Post-cultivation, the cells were fixed and stained with fluorescent dyes to visualise the nuclei and cytoplasm. The nuclei were stained with DAPI (4',6-diamidino-2-phenylindole), a blue-fluorescent DNA stain, while fluorescent-labeled phalloidin was used to detect actin filaments and delineate the cytoplasm. The entire process of cell culture, fixation, staining, and imaging adhered strictly to the protocols described in [1].

The preprocessed dataset includes 2,676 8-bit RGB images, each with a pixel resolution of 520 x 696 pixels. In these images, only two of the RGB channels are utilized: the red channel represents the cytoplasm, and the blue channel represents the nuclei. The dataset is divided into training, validation, and test subsets in a 70:20:10 ratio. The entire dataset is accompanied by instance segmentation masks for nuclei and cytoplasm objects obtained through a specialised CellProfiler [2] software. Notably, the test subset was annotated manually by a specialist, ensuring high-quality annotations. The original raw images are of a higher resolution, 1040 x 1392 pixels, and have a bit depth of 16 bits, providing more detailed information for advanced analyses.


File Description:

The file structure of the zip files is as follows:

HeLaCytoNuc_{train/validation/test}.zip ->

- images -> {filename}.tif

- nuclei_masks  -> {filename}.tif

- cytoplasm_masks  -> {filename}.tif

HeLaCytoNuc_raw_images.zip -> {filename}.tif

HeLaCytoNuc_test_cellprofiler_masks.zip ->

- nuclei_masks  -> {filename}.tif

- cytoplasm_masks  -> {filename}.tif 

References:

1. Rämö, Pauli, Anna Drewek, Cécile Arrieumerlou, Niko Beerenwinkel, Houchaima Ben-Tekaya, Bettina Cardel, Alain Casanova et al. "Simultaneous analysis of large-scale RNAi screens for pathogen entry." BMC genomics 15 (2014): 1-18.

2. Carpenter, Anne E., Thouis R. Jones, Michael R. Lamprecht, Colin Clarke, In Han Kang, Ola Friman, David A. Guertin et al. "CellProfiler: image analysis software for identifying and quantifying cell phenotypes." Genome biology 7 (2006): 1-11.

Keywords: Fluorescence microscopy; high content microscopy; cytoskeleton; cell nuclei

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Permalink: https://www.hzdr.de/publications/Publ-39181


Nonlinear Z-scan Terahertz Transmission of Protein Solutions

Adams, E.; Thai, Q.-M.; Raj, M.; Dornbusch, D.; Czajkowski, A.

Abstract

The folded structure and stability of proteins emanates from their interaction with the water solvent. Water at the protein surface is strongly impacted, resulting in a region with a perturbed hydrogen bonding network. This region, the solvation shell, has distinct properties from that of bulk water, including retarded dynamics and fewer hydrogen bonds. Changes in the structure and dynamics of solvation water can be both perturbed and reported on by Terahertz radiation. Yet, some fundamental properties of solvation water, such as energy transfer within the hydrogen bonding network, remain largely unexplored.
Here, we utilize the TELBE free electron laser source to investigate the nonlinear transmission of lysozyme protein solutions. Z-scan experiments were performed at 0.5 THz, revealing a large nonlinear transmission of water. The nonlinear transmission of lysozyme solutions had a concentration dependent effect, showing that the amount of available water has a role. For the largest protein concentration measured, an inversion in the sign of the nonlinear transmission was observed. These results indicate that the nonlinear properties of protein solutions depend on the fraction of bulk and solvation water, and suggest that the mechanism of energy transfer changes at a threshold value. This work has implications for the study of nonlinear properties in biological systems.

Involved research facilities

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  • Poster
    Optical Terahertz Science and Technology, 08.-12.04.2024, Marburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-39180


Data and Code: Transforming martensite in NiTi within nanoseconds

Lünser, K.; Neumann, B.; Schmidt, D.; Ge, Y.; Hensel, D.; Khosla, M.; Gaal, P.; Fähler, S.

Abstract

This dataset belongs to the paper "Transforming martensite in NiTi within nanoseconds" and contains all raw data used for the paper. It includes raw data of reciprocal space maps taken at P23 Petra III DESY Synchrotron. It also contains the Python code used to analyze the raw data and the martensite intensities extracted from the raw data. Information about sample, measurement techniques and further data description can be found in README.txt.

Keywords: NiTi; shape memory alloy; speed limit; dynamics of martensitic transformation

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Permalink: https://www.hzdr.de/publications/Publ-39177


Investigations on how the froth height is influencing the flotation of ultrafine particles using the newly developed separation apparatus MultiDimFlot

Erdeneduvchir, N.; Sygusch, J.; Hollenberg, T.; Rudolph, M.

Abstract

Investigations on how the froth height is influencing the flotation of ultrafine particles using the newly developed separation apparatus MultiDimFlot

  • Lecture (Conference)
    SOMP 2023 - The 12th Regional Meeting of the Society of Mining Professors, 22.-23.06.2023, Ulaanbaatar, Mongolia

Permalink: https://www.hzdr.de/publications/Publ-39176


Dislocation-free two-dimensional concentric lateral heterostructures: MoS₂-TaS₂/Au(111)

Mehlich, K.; Ghorbani Asl, M.; Sahm, D.; Chagas, T.; Weber, D.; Grover, C.; Dombrowski, D.; Krasheninnikov, A.; Busse, C.

Abstract

We prepared two-dimensional concentric lateral heterostructures of the monolayer transition metal dichalcogenides (TMDCs) MoS₂ and TaS₂ by reactive molecular beam epitaxy (MBE) on chemically inert and weakly interacting Au(111). The heterostructures are in a size regime where quantum confinement can be expected. Despite large lattice mismatch a seamless interconnection of the two materials has been achieved, confirming that the semiconducting core is fully enclosed by a metallic border around its circumference. The resulting strain is analyzed on the atomic scale using scanning tunneling microscopy (STM), corroborated by calculations based on empirical potentials and compared to results from finite elements simulations.

Keywords: two-dimensional materials; lateral heterostructures; scanning tunneling microscopy; atomistic simulations; molecular beam epitaxy

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Permalink: https://www.hzdr.de/publications/Publ-39172


Source data: Revealing the 3D structure of microbunched plasma-wakefield-accelerated electron beams

La Berge, M.; Bowers, B.; Chang, Y.-Y.; Couperus Cabadag, J.; Debus, A.; Hannasch, A.; Pausch, R.; Schöbel, S.; Tiebel, J.; Ufer, P.; Willmann, A.; Zarini, O.; Zgadzaj, R.; Lumpkin, A.; Irman, A.; Schramm, U.; Downer, M.

Abstract

Source data for the publication titled "Revealing the 3D structure of microbunched plasma-wakefield-accelerated electron beams."

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Permalink: https://www.hzdr.de/publications/Publ-39170


Spectral Characterization of Battery Components from Li-Ion Battery Recycling Processes

Richter, J.; Lorenz, S.; Kaas, A.; Fuchs, M.; Röder, C.; Peuker, U. A.; Heitmann, J.; Gloaguen, R.

Abstract

Considering the increasing demand for Li-ion batteries, there is a need for sophisticated recycling strategies with both high recovery rates and low costs. Applying optical sensors for automating component detection is a very promising approach because of the non-contact, real-time process monitoring and the potential for complete digitization of mechanical sorting processes. In this work, mm-scale particles from shredded end-of-life Li-ion batteries are investigated by five different reflectance sensors, and a range from the visible to long-wave infrared is covered to determine the ideal detection window for major component identification as relevant input signals to sorting technologies. Based on the characterization, a spectral library including Al, Cu, separator foil, inlay foil, and plastic splinters was created, and the visible to near-infrared range (400–1000 nm) was identified as the most suitable spectral range to reliably discriminate between Al, Cu, and other battery components in the recycling material stream of interest. The evaluation of the different sensor types outlines that only imaging sensors meet the requirements of recycling stream monitoring and can deliver sufficient signal quality for subsequent mechanical sorting controls. Requirements for the setup parameters were discussed leading to the setup recommendation of a fast snapshot camera with a sufficiently high spectral resolution and signal-to-noise ratio.

Permalink: https://www.hzdr.de/publications/Publ-39169


Data publication: Fluid mechanics of Na-Zn liquid metal batteries

Duczek, C.; Horstmann, G. M.; Ding, W.; Einarsrud, K. E.; Gelfgat, A. Y.; Godinez-Brizuela, O. E.; Kjos, O. S.; Landgraf, S.; Lappan, T.; Monrrabal Marquez, G.; Nash, W.; Personnettaz, P.; Sarma, M.; Sommerseth, C.; Trtik, P.; Weber, N.; Weier, T.

Abstract

The dataset contains python scripts to reproduce the Turner diagram (double diffusive convection), the image on voltage efficiency and the 1D temperature profile.

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Permalink: https://www.hzdr.de/publications/Publ-39159


Breaking the Vicious Cycle of Warm Dense Matter Diagnostics

Dornheim, T.

Abstract

Matter at extreme densities and temperatures displays a complex quantum behavior that is characterized by Coulomb interactions, thermal excitations, and partial ionization. Such warm dense matter (WDM) is ubiquitous throughout the universe and occurs in a host of astrophysical objects such as giant planet interiors and white dwarf atmospheres. A particularly intriguing application is given by inertial confinement fusion, where both the fuel capsule and the ablator have to traverse the WDM regime in a controlled way to reach ignition.

In practice, rigorously understanding WDM is highly challenging both from experimental measurements and numerical simulations [1]. On the one hand, interpreting and diagnosing experiments with WDM requires a suitable theoretical description. One the other hand, there is no single method that is capable of accurately describing the full range of relevant densities and temperatures, and the interpretation of experiments is, therefore, usually based on a number of de-facto uncontrolled approximations. The result is the vicious cycle of WDM diagnostics: making sense of experimental observations requires theoretical modeling, whereas theoretical models must be benchmarked against experiments to verify their inherent assumptions.

In this work, we outline a strategy to break this vicious cycle by combining the X-ray Thomson scattering (XRTS) technique [2] with new ab initio path integral Monte Carlo (PIMC) capabilities [3,4,5]. As a first step, we have proposed to interpret XRTS experiments in the imaginary-time (Laplace) domain, which allows for the model-free diagnostics of the temperature [6] and normalization [7]. Moreover, by switching to the imaginary-time, we can directly compare our quasi-exact PIMC calculations with the experimental measurement [5]. This opens up novel ways to diagnose the experimental conditions, as we have recently demonstrated for the case of strongly compressed beryllium at the National Ignition Facility.

Our results open up new possibilities for improved XRTS set-ups that are specifically designed to be sensitive to particular parameters of interest [8]. Moreover, the presented PIMC capabilities are important in their own right and will allow for a gamut of applications, including equation-of-state calculations and the estimation of structural properties and linear response functions.

[1] T. Dornheim et al., Phys. Plasmas 30, 032705 (2023) [2] S. Glenzer and R. Redmer, Rev. Mod. Phys. 81, 1625 (2009) [3] T. Dornheim et al., J. Phys. Chem. Lett. 15, 1305-1313 (2024) [4] T. Dornheim et al., arXiv:2403.01979 [5] T. Dornheim et al., arXiv:2402.19113 [6] T. Dornheim et al., Nature Commun. 13, 7911 (2022) [7] T. Dornheim et al., arXiv:2305.15305 [8] Th. Gawne et al., arXiv:2403.02776

  • Invited lecture (Conferences)
    HEDLA-2024: THE 14TH INTERNATIONAL CONFERENCE ON HIGH ENERGY DENSITY LABORATORY ASTROPHYSICS, 20.-24.05.2024, Tallahassee, USA

Permalink: https://www.hzdr.de/publications/Publ-39155


Zirconium Oxynitride Thin Films for Photoelectrochemical Water Splitting

Streibel, V.; Schönecker, J. L.; Wagner, L. I.; Sirotti, E.; Munnik, F.; Kuhl, M.; Jiang, C.-M.; Eichhorn, J.; Santra, S.; Sharp, I. D.

Abstract

Transition metal oxynitrides are a promising class of functional materials for photoelectrochemical (PEC) applications. Although these compounds are most commonly synthesized via ammonolysis of oxide precursors, such synthetic routes often lead to poorly controlled oxygen-to-nitrogen anion ratios, and the harsh nitridation conditions are incompatible with many substrates, including transparent conductive oxides. Here, we report direct reactive sputter deposition of a family of zirconium oxynitride thin films and the comprehensive characterization of their tunable structural, optical, and functional PEC properties. Systematic increases of the oxygen content in the reactive sputter gas mixture enable access to different crystalline structures within the zirconium oxynitride family. Increasing oxygen contents lead to a transition from metallic to semiconducting to insulating phases. In particular, crystalline Zr2ON2-like films have band gaps in the UV−visible range and are n-type semiconductors. These properties, together with a valence band maximum position located favorably relative to the water oxidation potential, make them viable photoanode candidates. Using chopped linear sweep voltammetry, we indeed confirm that our Zr2ON2 films are PEC-active for the oxygen evolution reaction in alkaline electrolytes. We further show that high-vacuum annealing boosts their PEC performance characteristics. Although the observed photocurrents are low compared to state-of-the-art photoanodes, these dense and planar thin films can offer a valuable platform for studying oxynitride photoelectrodes, as well as for future nanostructuring, band gap engineering, and defect engineering efforts.

Keywords: zirconium oxynitride; reactive sputtering; thin film photoanodes; photoelectrochemical water splitting; oxygen evolution reaction; water oxidation

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Permalink: https://www.hzdr.de/publications/Publ-39149


Data publication: Multiferroic Microstructure Created from Invariant Line Constraint

Kar, S.; Ikeda, Y.; Nielsch, K.; Reith, H.; Maaß, R.; Fähler, S.

Abstract

This dataset contains all raw data used for the publication of the paper "Multiferroic Microstructure Created from Invariant Line Constraint" including SEM, TEM, MFM, VSM, RXD data.

Keywords: Multiferroics; Martensite; Magnetic shape memory alloys; Ni-Mn-Ga-based alloys; Epitaxial films; Finite-size effects

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Permalink: https://www.hzdr.de/publications/Publ-39148


Investigating the influence of (de)wetting(ability) heterogeneities using atomic force microscopy on the separation of ultrafine particles via froth flotation

Sygusch, J.; Graebe, K.; Rudolph, M.

Abstract

Froth flotation is an efficient separation process for particles with sizes between 10 μm and 200 μm, which is based on differences in the particle wettabilities, or more precisely dewettingability. Therefore, a fundamental understanding of the interfacial properties is required. Within the project MultiDimFlot, which is part of the priority programme SPP2045, funded by the German research foundation (DFG), the selective separation of ultrafine particles (< 10 μm) according to multiple particle properties (e.g. wettability, shape, size) by flotation is investigated. For this purpose, two ultrafine glass particle fractions with different shapes are used, i.e. glass spheres and fragments, and their wettability is modified via an esterification reaction using alcohols, where the wettability of the esterified particles is controlled by the length of the alkyl chain.
In order to investigate the influence of wetting heterogeneities on the separation via flotation, glass slides with the same chemical composition as the glass particles and that were esterified in the same way, were analysed via atomic force microscopy (AFM). By applying colloidal probe AFM in dry and liquid mode, information on the hydrophobic interactions on the surface of the glass slides with different levels of wettability are obtained. Furthermore, the esterified glass slides are analysed by measuring static and dynamic contact angles against water using the sessile drop method. This information is set into context with the surface energy results of the glass particles, obtained via inverse gas chromatography as well as results obtained by liquid-liquid extraction of particles, which is used to study the behaviour of the particles at the interface.
The correlation of the various methods shed light on the (de)wetting(ability) heterogeneities, how these are changed through esterification and how these results can be transferred to flotation.

Keywords: wettability; wetting heterogeneities; atomic force microscopy; flotation; esterification; ultrafine particles; surface energy; contact angles

  • Poster
    Jahrestreffen der DECHEMA/VDI-Fachgruppen Grenzflächenbestimmte Systeme und Prozesse, Kristallisation, Mechanische Flüssigkeitsabtrennung und Partikelmesstechnik, 27.-28.02.2024, Frankfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-39144


High quantum efficiency magnisum photocathode for photoinjectors

Xiang, R.; Schaber, J.; Teichert, J.; Arnold, A.; Murcek, P.; Niemczyk, R.; Ryzhov, A.

Abstract

To improve the quality of photocathodes is one of the critical issues in enhancing the stability and reliability of photo-injector systems. Magnesium has a low work function (3.6 eV) and shows high quantum efficiency (QE) after proper surface cleaning. This paper presents the investigation of alternative surface cleaning procedures, such as ps laser cleaning, thermal cleaning and ion beam cleaning. The QE is able to be improved two magnitudes after the treatment.

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  • Lecture (Conference)
    87. Jahrestagung der DPG und DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2024, 17.-22.03.2024, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-39138


Partilce-free cathode transfer system for SRF photoinjector

Xiang, R.; Gatzmaga, S.; Murcek, P.; Steinbrueck, R.; Teichert, J.; Arnold, A.; Hoffmann, A.

Abstract

Superconducting radio frequency (SRF) photoinjectors offer advantages for continuous wave (CW) operation and high brightness, high current beam generation. One of the critical components for successful operation of SRF photoinjectors is the photocathode system. HZDR is building a sophisticated cathode exchange system to ensure accurate, particle-free and warm cathode exchange. A novel alignment process aligns the cathode to the gun axis without touching the cathode plug itself. Less than 10 particles as small as 0.3 micrometer are detected
during the cathode load-lock tests.

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  • Lecture (Conference)
    87. Jahrestagung der DPG und DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2024, 17.-22.03.2024, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-39137


Thin Film Lithium-Ion Battery Based on Copper Silicon Anode

Cherkouk, C.; Weigel, T.; Köhler, T.; Stöcker, H.; Ferch, M.; Hahn, R.; Delan, A.; Folgner, C.; Zhou, S.; Rebohle, L.

Abstract

Ongoing miniaturization down to a few nanometers will lead to further significant
reductions in the power consumption of microchips and sensors. The number of
innovative applications immediately arise from the potential of integrating a
microbattery as a power source for flexible electronics, wearables, the Internet of
Things, medical implants and sensor chips.
In this work, a thin film lithium-Ion battery (TF-LIB) is demonstrated. The TF-LIB consists
of a high potential copper silicide anode (CuSi-anode) that can be integrated on a Siwafer
with standard semiconductor technology and a hybrid polymer electrolyte with a
high lithium-ion transference number. Two cathode materials were tested: LiFePO4 and
NCA.
The CuSi-anode is fabricated by Si sputtering followed by flash lamp annealing (FLA).
This anode material replaces metallic lithium for reaching high energy densities and
provides the thermal stability required in microelectronics (> 230 °C for soldering).
The hybrid polymer electrolyte is mechanically stable against the volume change of the
silicon during the lithiation/ delithiathion processes. The electrolyte is unreactive and
thermally stable at high temperatures during operation.

Keywords: Battery; Copper silicide anode; Polymer electrolyte; Thin film battery; All-solid-state battery; Integration on Si-Wafer

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  • Poster
    Advanced Automotive Battery Conference Europe, 13.-16.05.2024, Straßburg, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-39136


A contribution to understanding ion-exchange mechanisms for lithium recovery from industrial effluents of lithium-ion battery recycling operations

Salces, A. M.; Kelly, N.; Streblow, G. J.; Temel, E. T.; Rudolph, M.; Chagnes, A.; Vanderbruggen, A.

Abstract

Industrial effluents or process waters generated from spent lithium-ion batteries (LIBs) recycling operations often contain high concentrations of lithium ions (Li+). This study characterizes the composition of process water obtained from pre-treatment and concentration operations of LIBs recycling. Ion-exchange experiments are conducted using synthetic lithium solutions (1 g/L) and industrial waters to understand Li+ recovery. Employing four commercial cationic resins, fast Li+ exchange kinetics are observed fitting the pseudo-second order model. The equilibrium isotherm data corresponds to the Langmuir adsorption model and reveals a Li capacity of 30 32 mg/g using AmberliteTM IRC 120 H, 70 mg/g using Lewatit® TP 308 H, 37 40 mg/g using Lewatit® TP 208 Na, and 37-41 mg/g using Lewatit® TP 260 Na. While the resins initially demonstrate moderate affinity for Li+, this can be significantly enhanced by increasing the Li+ concentration. Notably, as LIBs recycling operation effluents typically contain minimal competing ions, these results underscore the potential of employing ion exchange as a viable method to recover and concentrate lithium before precipitation into lithium salts.

Keywords: lithium-ion batteries recycling; direct lithium extraction; ion exchange; water re-use

Permalink: https://www.hzdr.de/publications/Publ-39133


Momentum space separation of quantum path interferences between photons and surface plasmon polaritons in nonlinear photoemission microscopy

Dreher, P.; Janoschka, D.; Giessen, H.; Schützhold, R.; Davis, T. J.; Horn-Von Hoegen, M.; Meyer Zu Heringdorf, F.-J.

Abstract

Quantum path interferences occur whenever multiple equivalent and coherent transitions result in a common final state. Such interferences strongly modify the probability of a particle to be found in that final state, a key concept of quantum coherent control. When multiple nonlinear and energy-degenerate transitions occur in a system, the multitude of possible quantum path interferences is hard to disentangle experimentally. Here, we analyze quantum path interferences during the nonlinear emission of electrons from hybrid plasmonic and photonic fields using time-resolved photoemission electron microscopy.We experimentally distinguish quantum path interferences by exploiting the momentum difference between photons and plasmons and through balancing the relative contributions of their respective fields. Our work provides a fundamental understanding of the nonlinear photon–plasmon–electron
interaction. Distinguishing emission processes in momentum space, as introduced here, could allow nano-optical quantum-correlations to be studied without destroying the quantum path interferences.

Keywords: PEEM; surface plasmon polaritons; photoemission

Permalink: https://www.hzdr.de/publications/Publ-39131


Searching for axion resonances in vacuum birefringence with three-beam collisions

Evans, S.; Schützhold, R.

Abstract

We consider birefringent (i.e., polarization changing) scattering of x-ray photons at the superposition of two optical laser beams of ultrahigh intensity and study the resonant contributions of axions or axionlike particles, which could also be short lived. Applying the specifications of the Helmholtz International Beamline for Extreme Fields (HIBEF), we find that this setup can be more sensitive than previous light-bylight scattering (birefringence) or light-shining-through-wall experiments in a certain domain of parameter space. By changing the pump and probe laser orientations and frequencies, one can even scan different axion masses, i.e., chart the axion propagator.

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Permalink: https://www.hzdr.de/publications/Publ-39130


Temperature-Dependent Characteristics of GeSn Waveguide p-i-n Photodetectors: Step Towards Cryogenic Silicon Photonics

Bansal, R.; Jheng, Y.-T.; Lee, K.-C.; Wen, S.; Berencen, Y.; Cheng, H.-H.; Chang, G.-E.

Abstract

This dataset is for noise equivalent power measurements of different GeSn photodetectors

Keywords: GeSn; Photodetectors; Noise

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Permalink: https://www.hzdr.de/publications/Publ-39129


Data publication: Effect of Helium Ion Implantation on 3C-SiC Nanomechanical String Resonators

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

Abstract

The file "figures.hdf5" contains all numbers plotted in the figures of the main manuscript. Each entry in the first hierarchy level of the file, e.g. "Figure 2a", corresponds to one subfigure. Each entry in the second hierarchy level (if existent) corresponds to one of the curve/subset of the the respective figure, e.g. if curves for multiple fluences are plotted. The innermost hierarchy level contains the data arrays. The dataset name corresponds to the axis label and units. The file "analyzed.hdf5" contains frequencies, quality factors, stress and Young's modulus fit results for each measured nanostring device on each measured sample. The first hierarchy level represents the sample (A or B). The second hierarchy level represents the accumulated implantation fluence that the sample has seen before the respective measurements. The third hierarchy level represents the write field, i.e. string array index, on the chip (0-3) and the fourth hierarchy level represents the string length within the write field. Each length exists exactly once in each write field. The innermost hierarchy level contains arrays of mode number, frequency, quality factor and "raw data indices" (see next paragraph) representing each measured resonance. The fields Young's modulus and pre-stress are scalars containing the respective fit result and its uncertainty. The file "raw.hdf5" finally contains all raw spectra. The first hierarchy level corresponds to unique indices of the respective measurement. This is intended as a look up table for the "raw data indices" of the "analyzed.hdf5" file. Using the index found in the "analyzed.hdf5", one can obtain the raw frequency sweep data and metadata. The file "srim-VACANCY.txt" is the vacancy output file of the SRIM simulation discussed in the main manuscript.

Keywords: nanomechanics; defects; ion beam irradiation; quantum sensors

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Permalink: https://www.hzdr.de/publications/Publ-39128


Organic/metallic component analysis of lignocellulosic biomass: A thermochemical-perspective-based study on rice and bamboo waste

Kachroo, H.; Verma, V. K.; Doddapaneni, T. R. K. C.; Kaushal, P.; Jain, R.

Abstract

Thermochemical treatment is significantly impacted by the physiochemical properties of lignocellulosic biomass. Traditional characterization methods lack granularity, requiring advanced analytical techniques for comprehensive biomass characterization. This study analyzed elemental composition and their distribution in untreated rice husk, rice straw, and bamboo chips at micron and sub-micron scales. Results reveal significant variations in composition and spatial distribution of metallic components among agro-residues. Thermogravimetric analysis shows divergent decomposition patterns, while spectroscopic analysis indicates structural complexities and distinct silica content. Surface mapping illustrates prevalent silica and alkali metals on rice husk and rice straw. Atomic force microscopy depicts distinctive surface morphologies, with rice straw exhibiting heightened roughness due to silica bodies. Inductively coupled plasma-mass-spectrometry identified the abundance of alkali and alkaline earth metals in rice waste. Time-of-flight secondary ion mass spectrometry elucidates elemental spatial localization, affirming heterogeneous distribution across rice waste and homogenous distribution across bamboo waste. This study bridges the gap between biomass composition and optimized thermochemical conversion outcomes.

Keywords: Lignocellulosic biomass; Biomass characterization; Comparative biomass study; Tof-SIMS; Inorganics distribution

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Permalink: https://www.hzdr.de/publications/Publ-39126


MRI turbulence in vertically stratified accretion discs at large magnetic Prandtl numbers

Held, L.; Mamatsashvili, G.; Pessah, M. E.

Abstract

The discovery of the first binary neutron star merger, GW170817, has spawned a plethora of global numerical relativity simulations. These simulations are often ideal (with dissipation determined by the grid) and/or axisymmetric (invoking ad hoc mean-field dynamos). However, binary neutron star mergers (similar to X-ray binaries and active galactic nuclei inner discs) are characterized by large magnetic Prandtl numbers, Pm, (the ratio of viscosity to resistivity). Pm is a key parameter determining dynamo action and dissipation but it is ill-defined (and likely of order unity) in ideal simulations. To bridge this gap, we investigate the magnetorotational instability (MRI) and associated dynamo at large magnetic Prandtl numbers using fully compressible, three-dimensional, vertically stratified, isothermal simulations of a local patch of a disc. We find that, within the bulk of the disc (z ≲ 2H, where H is the scale-height), the turbulent intensity (parametrized by the stress-to-thermal-pressure ratio α), and the saturated magnetic field energy density, Emag, produced by the MRI dynamo, both scale as a power with Pm at moderate Pm (4 ≲ Pm ≲ 32): Emag ~ Pm0.74 and α ~ Pm0.71, respectively. At larger Pm (≳ 32), we find deviations from power-law scaling and the onset of a plateau. Compared to our recent unstratified study, this scaling with Pm becomes weaker further away from the disc mid-plane, where the Parker instability dominates. We perform a thorough spectral analysis to understand the underlying dynamics of small-scale MRI-driven turbulence in the mid-plane and of large-scale Parker-unstable structures in the atmosphere.

  • Open Access Logo Monthly Notices of the Royal Astronomical Society 530(2024)2, 2232-2250
    DOI: 10.1093/mnras/stae929
    arXiv: arXiv:2310.00453

Permalink: https://www.hzdr.de/publications/Publ-39124


Is Julia ready to be adopted by HEP?

Gál, T.; Gras, P.; Hegner, B.; Hernandez Acosta, U.; Kluth, S.; Ling, J.; Moreno, A.; Pivarski, J.; Schulz, O.; Stewart, G.; Strube, J.; Vasilev, V.

Abstract

The Julia programming language was created 10 years ago and is now a mature and stable language with a large ecosystem including more than 8,000 third-party packages. It was designed for scientific programming to be a high-level and dynamic language as Python is, while achieving runtime performances comparable to C/C++ or even faster. With this, we ask ourselves if the Julia language and its ecosystem is ready now for its adoption by the High Energy Physics community. We will report on a number of investigations and studies of the Julia language that have been done for various representative HEP applications, ranging from computing intensive initial data processing of experimental data and simulation, to final interactive data analysis and plotting. Aspects of collaborative code development of large software within a HEP experiment has also been investigated: scalability with large development teams, continuous integration and code test, code reuse, language interoperability to enable an adiabatic migration of packages and tools, software installation and distribution, training of the community, benefit from development from industry and academia from other fields.

  • Open Access Logo Contribution to proceedings
    26th International Conference on Computing in High Energy and Nuclear Physics (CHEP 2023), 08.-12.05.2023, Norfolk, VA, United States
    DOI: 10.1051/epjconf/202429505008

Permalink: https://www.hzdr.de/publications/Publ-39120


Critical behavior of the dimerized Si(001) surface: Continuous order-disorder phase transition in the two-dimensional Ising universality class

Brand, C.; Hucht, A.; Mehdipour, H.; Jnawali, G.; Fortmann, J. D.; Tajik, M.; Hild, R.; Sothmann, B.; Kratzer, P.; Schützhold, R.; Horn-Von Hoegen, M.

Abstract

The critical behavior of the order-disorder phase transition in the buckled dimer structure of the Si(001) surface is investigated both theoretically by means of first-principles calculations and experimentally by spot profile analysis low-energy electron diffraction (SPA-LEED). We use density functional theory (DFT) with three different functionals commonly used for Si to determine the coupling constants of an effective lattice Hamiltonian describing the dimer interactions. Experimentally, the phase transition from the low-temperature c(4×2)- to the high-temperature p(2×1)-reconstructed surface is followed through the intensity and width of the superstructure spots within the temperature range 78–400K. Near the critical temperature Tc = 190.6K, we observe universal critical behavior of spot intensities and correlation lengths, which falls into the universality class of the two-dimensional (2D) Ising model. From the ratio of correlation lengths along and across the dimer rows we determine effective nearest-neighbor couplings of an anisotropic 2D Ising model,
J = (−24.9 ± 0.9stat ± 1.3sys )meV and J⊥ = (−0.8 ± 0.1stat )meV.We find that the experimentally determined coupling constants of the Ising model can be reconciled with those of the more complex lattice Hamiltonian
from DFT when the critical behavior is of primary interest. The anisotropy of the interactions derived from the
experimental data via the 2D Ising model is best matched by DFT calculations using the PBEsol functional.
The trends in the calculated anisotropy are consistent with the surface stress anisotropy predicted by the
DFT functionals, pointing towards the role of surface stress reduction as a driving force for establishing the
c(4×2)-reconstructed ground state.

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Permalink: https://www.hzdr.de/publications/Publ-39119


Formulation and application assessment of lignin-based biodegradable composite mulching film with emphasis on lignin enhancement

Zhang, B.; Wang, G.; Sui, W.; Parvez, A. M.; Si, C.

Abstract

Utilization of plastic materials (e.g., polyethylene) in mulching film production has inevitably resulted in nondegradable
pollutants in soil, which accordingly promotes the development of biodegradable mulching film
industry. As a rich renewable, biodegradable aromatic polymer, Lignin exhibits great potential for fabricating
functional biodegradable composite mulching films. In recent years, composite mulching films containing lignin
have garnered more interest for both practical applications and fundamental research, but comprehensive reviews
detailing preparation and application of this rapidly developing composite are still limited. Herein, we
begin with a brief description about the processes used to prepare lignin-based biodegradable mulching film.
Furthermore, the design and application advances of lignin-based biodegradable mulching films are elaborated
based on the polymer materials used, including natural and synthetic biodegradable polymers. Finally, the
remaining challenges and future perspectives of lignin-based biodegradable mulching films are summarized. We
expect that this finding will shed light on the forthcoming research of lignin-based biodegradable mulching film,
and stimulate the development in this research area.

Keywords: Lignin valorization; Lignin-based biodegradable mulching film; Composite film; Application assessment

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  • Secondary publication expected from 04.05.2025

Permalink: https://www.hzdr.de/publications/Publ-39117


Mineralogy and mineral paragenesis of the Palaeoproterozoic manganese ores of the Avontuur deposit of the Kalahari Manganese Field, South Africa

Coetzee, L. L.; Gutzmer, J.; Smith, A. J. B.; Beukes, N. J.

Abstract

This study provides for the first time details of the mineralogy, petrography and mineral paragenetic relationships of manganese ores of the Avontuur deposit, a prominent northern outlier of the Kalahari Manganese Field in the Northern Cape Province of South Africa. Using a combination of light and electron microscopy and X-ray powder diffractometry on an extensive suite of exploration drill core samples, it is shown that the manganese ores comprise an exceptionally fine-grained assemblage of Mn2+-silicates (friedelite, tephroite, gageite), Mn2+/Mn3+-oxides (jacobsite, hausmannite) and Mn2+-carbonates (rhodochrosite, kutnahorite, Mn-dolomite and Mn-calcite). This mineral assemblage is a product of diagenesis and very low-grade regional metamorphism. Locally, this assemblage is overprinted by contact metamorphism or supergene alteration. Despite close geochemical and textural similarities, the manganese ores of the Avontuur deposit are surprisingly different in their mineralogy compared to the carbonate- and braunite-dominated mangano-lutites of the main Kalahari deposit. Distinctly higher concentrations of both SiO2and Fe2O3in the mangano-lutites of the Avontuur deposit as compared to the main Kalahari Deposit provide the reason for the markedly different mineralogy. Such marked differences in bulk chemistry are tentatively attributed to systematic lateral variations in the physicochemical conditions of mineral precipitation during the deposition of the Hotazel Formation.

Keywords: South Africa; Manganese; Paleoproterozoic; Mineralogy; Geology

Permalink: https://www.hzdr.de/publications/Publ-39113


Preparation and characterization of Mn(II)Mn(III) complexes with relevance to class Ib ribonucleotide reductases

Doyle, L. M.; Bienenmann, R. L. M.; Gericke, R.; Xu, S.; Farquhar, E. R.; Que Jr, L.; McDonald, A. R.

Abstract

The Mn₂ complex (Mn(II)₂(TPDP)(O₂CPh)₂)(BPh₄) (1, TPDP = 1,3-bis(bis(pyridin-2-ylmethyl)amino)propan-2-ol, Ph = phenyl) was prepared and subsequently characterized via single-crystal X-ray diffraction, X-ray absorption, electronic absorption, and infrared spectroscopies, and mass spectrometry. 1 was prepared in order to explore its properties as a structural and functional mimic of class Ib ribonucleotide reductases (RNRs). 1 reacted with superoxide anion (O₂(•–)) to generate a peroxido-MnIIMnIII complex, 2. The electronic absorption and electron paramagnetic resonance (EPR) spectra of 2 were similar to previously published peroxido-Mn(II)Mn(III) species. Furthermore, X-ray near edge absorption structure (XANES) studies indicated the conversion of a Mn(II) 2 core in 1 to a Mn(II)Mn(III) state in 2. Treatment of 2 with para-toluenesulfonic acid (p-TsOH) resulted in the conversion to a new Mn(II)Mn(III) species, 3, rather than causing O—O bond scission, as previously encountered. 3 was characterized using electronic absorption, EPR, and X-ray absorption spectroscopies. Unlike other reported peroxido-Mn(II)Mn(III) species, 3 was capable of oxidative O—H activation, mirroring the generation of tyrosyl radical in class Ib RNRs, however without accessing the Mn(III)Mn(IV) state.

Keywords: Bioinorganic; Dimanganese cluster; Ribonucleotide reductase; Dioxygen activation; electron paramagnetic resonance

Permalink: https://www.hzdr.de/publications/Publ-39110


Spremberg Hyperspectral Drillcore Data

Thiele, S. T.; Kirsch, M.; Madriz Diaz, Y. C.; Gloaguen, R.

Abstract

This hyperspectral drillcore dataset (shed) contains 70 drill holes, totalling 383 boxes that cumulatively contain 1323 meters of scanned cores. Hyperspectral data is stored in the widely used ENVI format (.dat and associated .hdr files), which can be opened using e.g., napari-hippo (GUI) and hylite (python). The whole directory structure is compatible with hycore, for easier out-of-core processing and visualisation.

These hyperspectral data and associated visualisations can also be viewed interactively here.

The scanned cores come from the Spremberg–Graustein Kupferschiefer exploration zone, located in Lusatia, Germany. Five extensive and uninterrupted intervals were scanned, from three boreholes and their deviations drilled by Kupferschiefer Lausitz (KSL) between 2009 and 2010. An additional 65 smaller intervals were also scanned from material drilled during the period spanning 1957 to 1979, a component of the Spremberg exploration initiative executed by the former German Democratic Republic (GDR). Further information on the Spremberg–Graustein exporation zone can be found here.

Stratigraphically, the KSL cores intersect the Rotliegend (Permian) sandstones and conglomerates (S1), the overlying Kupferschiefer mudstone (T1), which transitions upwards into the Zechstein marls, carbonates and evaporites. Data from one hole also includes the base of the Buntsandstein.

The GDR drill cores, housed at the drill core repository of the Geological Survey of Brandenburg (LBGR), predominantly cover a few meters around the immediate intersection of the Kupferschiefer mudstones.

These data were acquired as part of the Horizons Europe project Vector. Kupferschiefer Lausitz and the Geological Survey of Brandenburg are thanked for providing access to core material and their support during data acquisition.

Keywords: mineral deposits; kupferschiefer; sedimentary hosted copper; hyperspectral; resources; germany

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Permalink: https://www.hzdr.de/publications/Publ-39109


Collinstown Hyperspectral Drillcore Data

Thiele, S. T.; Kirsch, M.; Madriz Diaz, Y. C.; Gloaguen, R.

Abstract

This hyperspectral drillcore dataset (shed) contains 10 drill holes, totalling 413 boxes that cumulatively contain 2845 meters of scanned cores. Hyperspectral data is stored in the widely used ENVI format (.dat and associated .hdr files), which can be opened using e.g., napari-hippo (GUI) and hylite (python). The whole directory structure is compatible with hycore, for easier out-of-core processing and visualisation.

These hyperspectral data and associated visualisations can also be viewed interactively here.

These cores intersect stratigraphic units of the Lower Carboniferous Irish Midlands, including the Lucan Formation (Upper Dark Limestones), the Feltrim Formation (Boulder Conglomerate), the Slane Castle Formation (Argillaceous Bioclastic Limestone), the Meath Formation (Shaley Pale Limestones unit), the Liscarton Formation (Mixed Beds unit), and Lower Paleozoic basement rocks.

Scanning was conducted on cores such that a variety of lithology, sedimentary facies, proximity to mineralization, alteration intensity, and dolomitization intensity were sampled.

These data were acquired as part of the Horizons Europe project Vector. Teck Ireland is acknowledged for providing access to core material and assisting with the hyperspectral scanning logistics.

Keywords: mineral deposits; hyperspectral; resources; ireland; sediment hosted Pb-Zn

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Permalink: https://www.hzdr.de/publications/Publ-39108


Memory effect in photochromic rare-earth oxyhydride thin films studied by in situ positron annihilation spectroscopy upon photodarkening-bleaching cycling

Wu, Z.; de Wit, L.; Beek, M.; Colombi, G.; Chaykina, D.; Schreuders, H.; Schut, H.; Liedke, M. O.; Butterling, M.; Wagner, A.; Dickmann, M.; Brück, E.; Dam, B.; Eijt, S. W. H.

Abstract

Cycling stability of the photochromic effect in rare-earth oxyhydride thin films is of great importance for longterm applications such as smart windows. However, an increasingly slower bleaching rate upon photochromic cycling was found in yttrium oxyhydride thin films; the origin of this memory effect is yet unclear. In this work, the microstructural changes under six photodarkening-bleaching cycles in YHxOy and GdHxOy thin films are investigated by in situ illumination Doppler broadening positron annihilation spectroscopy, complemented by positron annihilation lifetime spectroscopy (PALS) investigations on YHxOy films before and after one cycle. For the first three cycles, the Doppler broadening S parameter after bleaching increases systematically with photodarkening-bleaching cycle, and correlates with the bleaching time constant extracted from optical transmittance measurements. This suggests that the icrostructural evolution that leads to progressively slower bleaching involves vacancy creation and agglomeration. PALS suggests that during a photodarkening-bleaching cycle, divacancies are formed that are possibly composed of illumination-induced hydrogen vacancies and preexisting yttrium monovacancies, and vacancy clusters grow, which might be due to local removal of hydrogen. If bleaching is a diffusion-related process, the formed vacancy defects induced by illumination might affect the diffusion time by reducing the diffusion coefficient. Hydrogen loss could also be a key factor in the reduced bleaching kinetics. Other microstructural origins including domain growth, or formation of OH−hydroxide groups, are also discussed with respect to the slower bleaching kinetics. During the fourth to sixth photodarkening-bleaching cycle, reversible shifts in the Doppler S and W parameters are seen that are consistent
with the reversible formation of metallic-like domains, previously proposed as a key factor in the mechanism for the photochromic effect.

Keywords: rare-earth oxyhydride; thin films; positron annihilation spectroscopy; smart windows; memory effects; point defects

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  • Secondary publication expected from 15.04.2025

Permalink: https://www.hzdr.de/publications/Publ-39107


Neutron Reflectivity for Testing Graphene Oxide Films Sorption of EuCl3 in Ethanol Solution

Nordenström, A.; Boulanger, N.; Vorobiev, A.; Amidani, L.; Bauters, S.; Galanzew, J.; Kvashnina, K.; Talyzin, A.

Abstract

Neutron reflectivity (NR) was used to study the sorption of Eu(III) by graphene oxide (GO) films exposed to ethanol solution of EuCl3. Most of the earlier sorption studies have been performed using GO dispersed in solution. In contrast, layered structure of GO films imposes limitations for penetration of ions between individual sheets. The analysis of NR data recorded before and after sorption under vacuum demonstrates an increase of GO film thickness due to sorption by 35–40%. The characterization of chemical state of Eu(III) sorbed by GO films by X-ray absorption near-edge structure (XANES) in high-energy resolution fluorescence detection (HERFD) method at the Eu L3 edge reveals that it remains the same as in anhydrous EuCl3. Analysis of all collected data including reference experiments with bulk GO samples allows to conclude that EuCl3 penetrates into GO interlayers with ethanol solution and remains trapped in interlayers after evaporation of ethanol. Sorption of EuCl3 results in nearly complete amorphization of film and likely formation of voids, thus making NR models based on specific volume of unit cell not valid for quantitative evaluation of Eu sorption. Limitations of NR method must be taken into account in future studies of sorption by thin films.

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Permalink: https://www.hzdr.de/publications/Publ-39105


Experimental data for investigating proton bunch monitors for clinical translation of prompt gamma-ray timing

Makarevich, K.; Schellhammer, S.; Pausch, G.; Römer, K.; Tiebel, J.; Turko, J. A. B.; Wagner, A.; Kögler, T.
ResearchGroup: Werner, Rahel-Debora; ResearchGroup: Franke, Anna; ContactPerson: Makarevich, Krystsina; ContactPerson: Kögler, Toni; Project Leader: Kögler, Toni; ResearchGroup: Stach, Daniel; ResearchGroup: Weinberger, David; ResearchGroup: Wolf, Andreas; ResearchGroup: Dreyer, Anne

Abstract

The dataset contains the data reported on https://www.hzdr.de/publications/Publ-39073 where 2 proton bunch monitors (PBMs), namely the diamond detector and the cyclotron monitoring signal Uphi, are established, characterized, and applied for correcting the prompt gamma-ray timing (PGT) data. Experimental setup, irradiation modalities, data acquisition, and data pre- and postprocessing are described there.

The process is summarized in the following:

Experimental setup: A homogeneous cylindrical PMMA phantom was irradiated with a proton beam. Two sets of measurements were considered:

S1) measurements at the horizontal fixed beamline with the control of the beam time structure and current. These data establish the relation between the investigated PBMs and calibrate them to the scattering setup that provides the proton bunch arrival time in the experimental room. The phantom was irradiated with 7 different proton energies Ep = {70, 90, 110, 130, 160, 190, 224} MeV. For each Ep, 3 irradiation modalities were applied:

  • CW-mode represented the continuous beam lasting for 30 s, the beam current Ibeam = 2 nA for all Ep excluding 70 MeV (for 70 MeV, Ibeam = 0.5 nA);
  • Plan I represented a clinically realistic plan with a spot duration of 4 ms and a spot repetition time of 7 ms. The beam current Ibeam = 1 nA for all Ep excluding 70 MeV (for 70 MeV, Ibeam = 0.5 nA);
  • Plan II aimed to reproduce the measurements of Werner et al. (2019) in Phys. Med. Biol. 64 105023, 20pp (https://doi.org/10.1088/1361-6560/ab176d). For that, the spot duration was set to 69 ms, and the repetition time was 72 ms. The beam current Ibeam = 1 nA for all Ep excluding 70 MeV (for 70 MeV, Ibeam = 0.5 nA).

S2) measurements at the pencil beam scanning (PBS) beamline were similar to those at the clinical beam delivery nozzle. The PBS beamline delivers the beam as spots of given intensity (expressed in MU), (x,y)-coordinates, and energy (corresponds to the penetration depth or z-coordinate). These data comprise data from the PGT detector and PBMs and are used to correct the PGT data employing the investigated PBMs. The phantom was irradiated with 8 different proton energies Ep = {70, 90, 110, 130, 162, 180, 200, 220} MeV. For every energy, 2 spot intensities were considered: 0.1 MU per 1 spot (~1e7 protons) and 1 MU per 1 spot (~1e8 protons). For Ep = 162 MeV, an additional spot intensity of 10 MU per 1 spot (~1e9 protons) was applied to reproduce the measurements of Werner et al. (2019) in Phys. Med. Biol. 64 105023, 20pp (https://doi.org/10.1088/1361-6560/ab176d).

Data preprocessing:

The raw data of each measurement were converted from the binary list-mode format to ROOT TTrees. The data were corrected for the photomultiplier gain drift, and digitalization time non-linearities, and the integral signal was converted into deposited energy. For the measurements at the fixed beamline, the coincidence analysis was applied additionally for non-PBM detectors. The data were assigned to individual corresponding spots for the PBS beamline measurements.

Data structure:

The ROOT files are named u100-p00XX-yyyy-mm-dd_HH.MM.SS+TZ.root where p00XX is the detector’s number, yyyy-mm-dd_HH.MM.SS is the time of the measurement, and TZ is the time zone. Here, p0012 and p0019 mean scintillating detectors that were used both at the fixed beamline, and only detector p0012 was used for PGT measurements at the PBS beamline. P0015 is the diamond detector, and p0017 contains data of the Uphi signal.

In general, the data structure inside the ROOT files is different depending on the purpose of the detector. However, there are some general includes:

  • data (TTree) contains list-mode data which comprises
    • uncorrected data: before corrections and calibrations steps;
    • corrected data: after correcations and calibrations steps;
  • meta (TTree) is a measurement metadata (applied detector voltage, the start time of the measurements, etc.);
  • histograms is a directory with selected example histograms (uncorrected);
  • analysis is a directory with histograms with corrected data used for the analysis.

For further questions, please refer to the contact persons stated above.

Keywords: prompt gamma timing; PGT; proton bunch monitor; PBM; proton range verification

Involved research facilities

  • OncoRay

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Permalink: https://www.hzdr.de/publications/Publ-39104


Raw data and data used for figures in "Visualizing Plasmons and Ultrafast Kinetic Instabilities in Laser-Driven Solids using X-ray Scattering"

Kluge, T.; Ordyna, P.

Abstract

Data and visualization scripts for "Visualizing Ultrafast Kinetic Instabilities in Laser-Driven Solids using X-ray Scattering"

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  • HIBEF

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Permalink: https://www.hzdr.de/publications/Publ-39103


Stonepark Hyperspectral Drillcore Data

Thiele, S. T.; Kirsch, M.; Madriz Diaz, Y. C.; Gloaguen, R.; El Alami, S.; Cecilia Contreras Acosta, I.; Saffi, H.

Abstract

This hyperspectral drillcore dataset (shed) contains 14 drill holes, totalling 389 boxes that cumulatively contain 2513 meters of scanned cores. Hyperspectral data is stored in the widely used ENVI format (.dat and associated .hdr files), which can be opened using e.g., napari-hippo (GUI) and hylite (python). The whole directory structure is compatible with hycore, for easier out-of-core processing and visualisation.

These hyperspectral data and associated visualisations can also be viewed interactively here.

The scanned drillcores were selected to cover the main mineralised intervals and key stratigraphic horizons, sedimentary facies, igneous intrusions, brecciation and alteration zones present at Stonepark. These include the Knockroe Fm and Knockseefin Fm, the Lough Gur Formation, the Waulsortian Limestone Formation, and the Ballysteen Formation (Argillaceous Bioclastic Limestone). Drillcore selection was further based on the availability and accessibility of drill core and sought to capture the variations both laterally and vertically, in consultation with geologists from Group Eleven Resources.

These data were acquired as part of the Horizons Europe project Vector. We would also like to acknowledge Group Eleven, for providing access to core material and their support during data acquisition.

Keywords: mineral deposits; hyperspectral; resources; ireland; sediment hosted Pb-Zn

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Permalink: https://www.hzdr.de/publications/Publ-39102


High-count rate photon detection with scintillators coupled to photomultiplier tubes and fast digitizers

García Rivas, I.; Fernández Prieto, A.; Kögler, T.; Römer, K.; Hueso González, F.

Abstract

This repository contains raw experimental data acquired during the gELBE beam time performed in October 2023 under proposal number 23203137-ST, at Helmholtz-Zentrum Dresden - Rossendorf.

In this setup, a bremsstrahlung beam of up to 12.5 MeV energy in 13 MHz pulses irradiates a CeBr3 scintillation detector (by Hilger®) of Ø 1'' x 1'', coupled to a Hamamatsu® R13408-100 PMT, custom voltage divider and shaping electronics, and a commercial digitizer (SFMC01+SIS1160) by Struck®, containing an AD9689 chip that supports a data sampling rate of 2.5 Gsps and 14-bits. This detector is developed in the context of the coaxial prompt gamma-ray monitoring method [1], where very high count rates are expected [2]. The dead-time-free data acquisition is programmed in-house using ROOT [3]. In addition, a plastic scintillation detector (paddle) was placed inbetween the beam and the CeBr3 crystal to serve as reference beam monitor. An Arduino is used to monitor the high-voltage supply for the PMT and active divider electronics in terms of current, voltage and temperature. A Comet Systems® T7310 is used to monitor ambient temperature, humidity and pressure.

The published data consist of the raw signal waveforms acquired during ~450 measurements. Each measurement is stored in a separate folder, its name being the acquisition time start, and lasts between 3 and 20 seconds (16 GiB up to 100 GiB). The data format is little-endian binary. Each sample uses two bytes, being the 14 first bits the digitized signal in a 1.7 Vpp range, and the 15th bit the (negated) logic status of the reference beam monitor (paddle). Samples are stored consecutively, without headers. Sample time separation is 0.4 ns (2.5 Gsps). The digitizer is phase-locked to the accelerator radiofrequency (RF), so that each 2500 stored samples correspond to 13 consecutive periods of 13 MHz.

The data can be directly opened using the open-source pulse visualization software (PulseSurfer) available in this link: https://igit.ific.uv.es/ferhue/pulse-surfer/, with ROOT as a dependency. One just needs to run:

root -l test_gui.cpp+(\"/path-to-folder/chA.bin\") 

and then set 192.307692307692307696 in the "Cycle" box. Use the slider in the bottom to navigate across different consecutive frames. To visualize the paddle counter (negated) logic status, change the "Mask" box from 3FFF to 4000. There is also a checkbox to activate the baseline subtraction.

In addition to the raw waveform data (chA.bin), each folder contains following metadata:

  • log.root a ROOT file storing all the measurement and hardware settings as TObjString. It also contains the T7310 monitoring as a TTree ("pth")
  • chA.root a ROOT file storing a TTree that benchmarks the readout speed of the DAQ for this channel
  • zdt.log a text file storing the output printed by the DAQ software to terminal
  • gui.png Screenshot of the DAQ window
  • hv.txt a test file storing the monitoring of the high-voltage supply and electronics

Keywords: Proton Therapy; Range Verification; High-count rate photon detection; high speed digitizers; pile-up deconvolution

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Permalink: https://www.hzdr.de/publications/Publ-39098


Software engineering for validating finite-temperature XC-functional

Lokamani, M.; Ramakrishna, K.; Hüser, C.; Huste, T.; Cangi, A.; Juckeland, G.

Abstract

In recent years, density functional theory (DFT) has revolutionzed simulations in the domain of warm dense matter (WDM) which focuses on unraveling behavior of matter in fusion reactor, planetary interiors and other areas of high energy physics. The success of DFT relies on accurate approximations of the exchange-correlation (XC) effects based on exact quantum monte carlo (QMC) results. In this contribution, we summarize our recent work toward improving XC at finite temperatures, which is called thermal PBE[1] and incorporting the improvements in LIBXC[2], a library widely used in the material science community. We highlight the software engineering challenges in the field of high performance computing including: (i) deployment of continuous integration (CI) using Gitlab runners, (ii) incorporating containers for CI and reproducibility and (iii) refactoring strategies. We also highlight the importance of research software engineering (RSE) for validating accurate utilization of community high-performance-computing codes.

References

[1] https://doi.org/10.48550/arXiv.2308.03319
[2] https://doi.org/10.1016/j.softx.2017.11.002

Keywords: density functional theory; EVERSE; thermalPBE; research software engineering

  • Open Access Logo Lecture (Conference)
    RSEHPC@ISC24, 12.-16.05.2024, Hamburg, Germany

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Permalink: https://www.hzdr.de/publications/Publ-39096


A Supervised Approach for Estimating Fractional Abundances of Binary Intimate Mixtures

Koirala, B.; Rasti, B.; Scheunders, P.

Abstract

In this work, we propose a supervised framework for spectral unmixing of binary intimate mixtures. The core idea is based on geodesic distance measurements and regression to estimate the fractional abundances. The main assumption is that spectral reflectances of binary mixtures form a curve between the two endmembers, and the mixture's relative position on this curve serves as an indicator of its fractional abundances. We propose four novel approaches to approximate this relative position. From this, the fractional abundances are obtained using Gaussian process regression. The proposed framework simultaneously copes with the spectral variability by hypersphere and high-dimensional simplex projections. The approach is extensively validated on real datasets, including binary mineral mixtures and industrial clay powder mixtures produced in a laboratory setting, comprising 60 binary mixtures derived from five types of clay powders: Kaolin, Roof clay, Red clay, mixed clay, and Calcium hydroxide, measured by a variety of hyperspectral sensors in the VNIR-SWIR and mid-and longwave infrared regions. A comparison with the linear mixing model and several nonlinear mixing models demonstrates the superiority of the proposed approach.

Keywords: Earth; Estimation; Hyperspectral; Hyperspectral imaging; Mathematical models; mineral powder mixture

Permalink: https://www.hzdr.de/publications/Publ-39090


Quantum critical fluctuations in a transverse-field Ising magnet

Hauspurg, A.; Matsuura, K.; Arima, T.; Zherlitsyn, S.; Wosnitza, J.

Abstract

CoNb2O6 is a model system for a spin-1/2 one-dimensional (1D) transverse-field Ising magnet (TFIM) with a rather low three-dimensional (3D) Néel ordering temperature at TN = 2.95 K. We studied CoNb2O6 using ultrasound measurements down to 0.3 K in transverse magnetic fields applied along the b direction. Upon entering the 3D ordered state, we observe pronounced anomalies in the transverse acoustic mode c66. In particular, from 1.3 to 1.5 K and around 4.7 T, this mode reveals an almost diverging softening, which is considerably reduced at lower and higher magnetic fields. We interpret this as an influence of quantum critical fluctuations emerging from the quantum critical point (QCP) of the 1D Ising spin chains at about 4.75 T, which lies below the QCP of the 3D ordering at about 5.4 T. This is clear experimental evidence of the predicted generic phase diagram for a TFIM with superimposed 3D ordering.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-39089


Fractionalized excitations probed by ultrasound

Hauspurg, A.; Zherlitsyn, S.; Helm, T.; Felea, V.; Wosnitza, J.; Tsurkan, V.; Choi, K.-Y.; Do, S.-H.; Ye, M.; Brenig, W.; Perkins, N. B.

Abstract

In this work, we study magnetoelastic interactions by means of ultrasound experiments in α-RuCl3—a prototypical material for the Kitaev spin model on the honeycomb lattice, with a possible spin-liquid state featuring Majorana fermions and Z2-flux excitations. We present results of the temperature and in-plane magnetic-field dependence of the sound velocity and sound attenuation for several longitudinal and transverse phonon modes propagating along high-symmetry crystallographic directions. A comprehensive data analysis above the magnetically ordered state provides strong evidence of phonon scattering by Majorana fermions. This scattering depends sensitively on the value of the phonon velocities relative to the characteristic velocity of the low-energy fermionic excitations describing the spin dynamics of the underlying Kitaev magnet. Moreover, our data displays a distinct reduction of anisotropy of the sound attenuation, consistent with the presence of thermally excited Z2 visons. We demonstrate the potential of phonon dynamics as a promising probe for uncovering fractionalized excitations in α-RuCl3 and provide new insights into the H-T phase diagram of this material.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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Permalink: https://www.hzdr.de/publications/Publ-39088


Narrowly avoided spin-nematic phase in BaCdVO(PO4)2: NMR evidence

Ranjith, K. M.; Povarov, K.; Yan, Z.; Zheludev, A.; Horvatic, M.

Abstract

We present a 31P NMR investigation of BaCdVO(PO4)2 focusing on the nearly saturated regime between μ0Hc1 = 4.05 T and μ0Hc2 = 6.5 T, which used to be considered a promising candidate for a spin-nematic phase. NMR spectra establish the absence of any dipolar order there, whereas the weak field dependence of the magnetization above Hc1 is accounted for by Dzyaloshinskii-Moriya interaction terms. The low-energy spin dynamics (fluctuations), measured by the nuclear spin-lattice relaxation rate T1 −1, confirms the continuity of this phase and the absence of any low-temperature phase transition. Unexpectedly, the spin dynamics above Hc1 is largely dominated by two-magnon processes, which is expected above the saturation field of a spin-nematic phase, but not inside. This shows that BaCdVO(PO4)2 is indeed close to a spin-nematic instability; however, this phase is not stabilized. We thus confirm recent theoretical predictions that the spin-nematic phase can be stabilized, at most, in an extremely narrow field range close to saturation or is rather narrowly avoided [Jiang et al., Phys. Rev. Lett. 130, 116701 (2023)].

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-39087


Data publication: Defect Microstructure Evolution in Immiscible Composite Cu43%Cr Alloy after High-Pressure Torsion and Annealing using Positron Annihilation Spectroscopy

Bibimoune, I.; Hirschmann, E.; Liedke, M. O.; Wagner, A.; Kawasaki, M.; Baudin, T.; Mkinsi, I.; Abib, K.; Huang, Y.; Langdon, T. G.; Bradai, D.

Abstract

This data set contains positron annihilation lifetime spectra and VEPAS-DB spectra. It contains raw data and the corresponding analyzed data.

Keywords: Cu-Cr; immiscible alloys; high-pressure torsion; defects; positron annihilation spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-39080


Multimessenger measurements of the static structure of shock-compressed liquid silicon at 100 GPa

Poole, H.; Ginnane, M. K.; Millot, M.; Bellenbaum, H.; Collins, G. W.; Hu, S. X.; Polsin, D.; Saha, R.; Topp-Mugglestone, J.; White, T. G.; Chapman, D. A.; Rygg, J. R.; Regan, S. P.; Gregori, G.

Abstract

The ionic structure of high-pressure, high-temperature fluids is a challenging theoretical problem with applications to planetary interiors and fusion capsules. Here we report a multimessenger platform using velocimetry and in situ angularly and spectrally resolved x-ray scattering to measure the thermodynamic conditions and ion structure factor of materials at extreme pressures. We document the pressure, density, and temperature of shocked silicon near 100 GPa with uncertainties of 6%, 2%, and 20%, respectively. The measurements are sufficient to distinguish between and rule out some ion screening models.

Permalink: https://www.hzdr.de/publications/Publ-39077


A matter of performance & criticality: a review of rare-earth-based magnetocaloric intermetallic compounds for hydrogen liquefaction

Liu, W.; Gottschall, T.; Scheibel, F.; Bykov, E.; Aubert, A.; Fortunato, N.; Beckmann, B.; Döring, A. M.; Zhang, H.; Skokov, K.; Gutfleisch, O.

Abstract

The low efficiency of conventional liquefaction technologies based on the Joule-Thomson expansion makes liquid hydrogen currently not attractive enough for large-scale energy-related technologies that are important for the transition to a carbon-neutral society. Magnetocaloric hydrogen liquefaction has great potential to achieve higher efficiency and is therefore a crucial enabler for affordable liquid hydrogen. Cost-effective magnetocaloric materials with large magnetic entropy and adiabatic temperature changes in the temperature range of 77 ∼ 20 K under commercially practicable magnetic fields are the foundation for the success of magnetocaloric hydrogen liquefaction. Heavy rare-earth-based magnetocaloric intermetallic compounds generally show excellent magnetocaloric performances, but the heavy rare-earth elements (Gd, Tb, Dy, Ho, Er, and Tm) are highly critical in resources. Yttrium and light rare-earth elements (La, Ce, Pr, and Nd) are relatively abundant, but their alloys generally show less excellent magnetocaloric properties. A dilemma appears: higher performance or lower criticality? In this review, we study how cryogenic temperature influences magnetocaloric performance by first reviewing heavy rare-earth-based intermetallic compounds. Next, we look at light rare-earth-based, "mixed" rare-earth-based, and Gd-based intermetallic compounds with the nature of the phase transition order taken into consideration, and summarize ways to resolve the dilemma.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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Permalink: https://www.hzdr.de/publications/Publ-39076


Data publication: Defectivity of Al:ZnO Thin Films with Different Crystalline Order Probed by Positron Annihilation Spectroscopy

Magrin Maffei, R.; Butterling, M.; Liedke, M. O.; D’Addato, S.; Di Bona, A.; Bertoni, G.; Gazzadi, G. C.; Mariazzi, S.; Wagner, A.; Brusa, R. S.; Benedetti, S.

Abstract

Positronen-Lebensdauer-Messungen gewonnen an der Positronen-Strahlanlage MePS (pELBE), August 2023 Doppler-Verbreiterungs-Messungen gewonnen an der Positronen-Strahlanlage SPONSOR (pELBE), September 2023

Keywords: Positron Annihilation; MePS; SPONSOR; AZO; AlZnO; PALS; VEPALS; VEPAS

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Permalink: https://www.hzdr.de/publications/Publ-39072


Simplified Beam Hardening Correction for Ultrafast X-ray CT Imaging of Binary Granular Mixtures

Bieberle, M.; Nestor Papapetrou, T.; Lecrivain, G.; Windisch, D.; Bieberle, A.; Wagner, M.; Hampel, U.

Abstract

Ultrafast X-ray computed tomography is an advanced imaging technique for multiphase flows. It has been used with great success for studying gas–liquid as well as gas–solid flows. Here, we apply this technique to analyze density-driven particle segregation in a rotating drum as an exemplary use case for analyzing industrial particle mixing systems. As glass particles are used as the denser of two granular species to be mixed, beam hardening artefacts occur and hamper the data analysis. In the general case of a distribution of arbitrary materials, the inverse problem of image reconstruction with energy-dependent attenuation is often ill-posed. Consequently, commonly known beam hardening correction algorithms are often quite complex. In our case, however, the number of materials is limited. We therefore propose a correction algorithm simplified by taking advantage of the known material properties, and demonstrate its ability to improve image quality and subsequent analyses significantly.

Keywords: beam hardening; computed tomography; image reconstruction; ultrafast measurement; granular media; particle mixing; rotating drum

Involved research facilities

  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-39067


Data publication: Revealing the 3D structure of microbunched plasma-wakefield-accelerated electron beams

La Berge, M.; Bowers, B.; Chang, Y.-Y.; Couperus Cabadag, J.; Debus, A.; Hannasch, A.; Pausch, R.; Schöbel, S.; Tiebel, J.; Ufer, P.; Willmann, A.; Zarini, O.; Zgadzaj, R.; Lumpkin, A.; Schramm, U.; Irman, A.; Downer, M.

Abstract

This repository contains data on coherent optical transition radiation (COTR) from laser wakefield accelerated electron beams. This includes raw (COTR) images and electron spectra, as well as analysis code for evaluating the COTR data and using it as an input for a differential-evolution-based reconstruction of the electron bunch.

Keywords: Laser wakefield acceleration; Laser plasma acceleration; Transition radiation; Differential evolution; Coherent transition radiation; Coherent optical transition radiation; Microbunching

Involved research facilities

  • Draco

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Permalink: https://www.hzdr.de/publications/Publ-39065


Control of the Hydroquinone/Benzoquinone Redox State in High-Mobility Semiconducting Conjugated Coordination Polymers

Huang, X.; Li, Y.; Fu, S.; Ma, C.; Lu, Y.; Wang, M.; Zhang, P.; Li, Z.; He, F.; Huang, C.; Liao, Z.; Zou, Y.; Zhou, S.; Helm, M.; Petkov, P. S.; Wang, H. I.; Bonn, M.; Li, J.; Xu, W.; Dong, R.; Feng, X.

Abstract

Conjugated coordination polymers (c-CPs) are unique organic–inorganic hybrid semiconductors with intrinsically high electrical conductivity and excellent charge carrier mobility. However, it remains a challenge in tailoring electronic structures, due to the lack of clear guidelines. Here, we develop a strategy wherein controlling the redox state of hydroquinone/benzoquinone (HQ/BQ) ligands allows for the modulation of the electronic structure of c-CPs while maintaining the structural topology. The redox-state control is achieved by reacting the ligand TTHQ (TTHQ=1,2,4,5-tetrathiolhydroquinone) with silver acetate and silver nitrate, yielding Ag4TTHQ and Ag4TTBQ (TTBQ=1,2,4,5-tetrathiolbenzoquinone), respectively. In spite of sharing the same topology consisting of a two-dimensional Ag−S network and HQ/BQ layer, they exhibit different band gaps (1.5 eV for Ag4TTHQ and 0.5 eV for Ag4TTBQ) and conductivities (0.4 S/cm for Ag4TTHQ and 10 S/cm for Ag4TTBQ). DFT calculations reveal that these differences arise from the ligand oxidation state inhibiting energy band formation near the Fermi level in Ag4TTHQ. Consequently, Ag4TTHQ displays a high Seebeck coefficient of 330 μV/K and a power factor of 10 μW/m ⋅ K2, surpassing Ag4TTBQ and the other reported silver-based c-CPs. Furthermore, terahertz spectroscopy demonstrates high charge mobilities exceeding 130 cm2/V ⋅ s in both Ag4TTHQ and Ag4TTBQ.

Permalink: https://www.hzdr.de/publications/Publ-39064


Data publication: Static and dynamic properties of noncollinear magnetized ferromagnetic films

Jiménez-Bustamante, J.; Lindner, A. A.; Koyun Yücel, H. N.; Salikhov, R.; Lenz, K.; Lindner, J.; Gallardo, R. A.

Abstract

Research data of the publication (FMR, VSM).

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Permalink: https://www.hzdr.de/publications/Publ-39062


Static and dynamic properties of noncollinear magnetized ferromagnetic films

Jiménez-Bustamante, J.; Lindner, A. A.; Koyun Yücel, H. N.; Salikhov, R.; Lenz, K.; Lindner, J.; Gallardo, R. A.

Abstract

The dynamic matrix method was employed to perform theoretical calculations for investigating both static and
dynamic characteristics of thick ferromagnetic films. This approach considers situations where a noncollinear
equilibrium magnetization exists along the thickness due to a thickness-dependent uniaxial anisotropy and inter-
facial interactions in a synthetic antiferromagnet. In the former scenario, the study exposes a correlation between
noncollinear static magnetization and a nonmonotonic dependence of ferromagnetic resonance frequency, where
a frequency decrease is observed at low fields in the unsaturated regime. Regarding the synthetic antiferromagnet
structure, the research demonstrates noncoherent magnetization rotation in the spin-flop regime, with twisted
magnetization states influencing the critical and nucleation fields that define the spin-flop region. The results of
the investigation were compared to the macrospin approach, where the magnetization is assumed to be uniform
along the thickness. The study suggests that the contribution of noncollinear magnetic moments may mimic the
role of the biquadratic interaction in the macrospin model, implying that such a biquadratic term may be over-
estimated in coupled ferromagnetic films with thicknesses exceeding the material’s intrinsic exchange length.
Finally, the model was compared with experimental data obtained from a Py/Ir/Py synthetic antiferromagnet,
demonstrating that the theoretical consideration of a twisting equilibrium state of the magnetization precisely
reproduces the observed dynamic and static properties of the nanostructure.

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  • Secondary publication expected from 04.03.2025

Permalink: https://www.hzdr.de/publications/Publ-39061


ASTM interlaboratory study on tensile testing of AM deposited and wrought steel using miniature specimens

Dzugan, J.; Lucon, E.; Koukolikova, M.; Li, Y.; Rzepa, S.; Yasin, M. S.; Shao, S.; Shamsaei, N.; Seifi, M.; Lodeiro, M.; Lefebvre, F.; Mayer, U.; Olbricht, J.; Houska, M.; Mentl, V.; You, Z.

Abstract

An interlaboratory study, involving eigth international laboratories and coordinated by COMTES FHT (Czech Republic), was conducted to validate tensile measurements obtained using miniature specimens on additively manufactured (AM) components and artifacts. In addition to AM 316L stainless steel (316L SS), a wrought highstrength steel (34CrNiMo6V, equivalent to AISI 4340) was also used. Based on the results, a precision statement in accordance with ASTM E691 standard practice was developed, intended for inclusion in a proposed annex to
the ASTM E8/E8M tension testing method. The primary outcomes of the study highlighted the agreement between yield and tensile strength measured from miniature and standard-sized tensile specimens. Furthermore, most tensile properties exhibited similar standard deviations, offering users insight into the efficacy of miniature specimen applications.

Keywords: 316L stainless steel; Additive manufacturing; High-strength steel; Miniature specimens; Tensile tests

Permalink: https://www.hzdr.de/publications/Publ-39060


Tailoring dielectric permittivity of epitaxial Gd-doped CeO2−x films by ionic defects

Palliotto, A.; Wu, Y.; Rata, A. D.; Herklotz, A.; Zhou, S.; Dörr, K.; Muralt, P.; Park, D.-S.

Abstract

Engineering materials with highly tunable physical properties in response to external stimuli is a cornerstone strategy for advancing energy technology. Among various approaches, engineering ionic defects and understanding their roles are essential in tailoring emergent material properties and functionalities. Here, we demonstrate an effective approach for creating and controlling ionic defects (oxygen vacancies) in epitaxial Gd-doped CeO2−x (CGO)(001) films grown on Nb:SrTiO3(001) single crystal. Our results exhibit a significant limitation in the formation of excess oxygen vacancies in the films during high-temperature film growth. However, we have discovered that managing the oxygen vacancies in the epitaxial CGO(001) films is feasible using a two-step film growth process. Subsequently, our findings show that manipulating excess oxygen vacancies is a key to the emergence of giant apparent dielectric permittivity (e.g. 106) in the epitaxial films under electrical field control. Overall, the strategy of tuning functional ionic defects in CGO and similar oxides is beneficial for various applications such as electromechanical, sensing, and energy storage applications.

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Permalink: https://www.hzdr.de/publications/Publ-39052


Nonaxisymmetric modes of magnetorotational and possible hydrodynamical instabilities in the upcoming DRESDYN-MRI experiments: Linear and nonlinear dynamics

Mishra, A.; Mamatsashvili, G.; Stefani, F.

Abstract

The quest for an unambiguous detection of magnetorotational instability (MRI) in experiments is still ongoing despite recent promising results. To conclusively identify MRI in the laboratory, a large cylindrical Taylor-Couette experiment with liquid sodium is under construction within the DRESDYN project. Recently, we have analyzed the nonlinear dynamics and scaling properties of axisymmetric standard MRI with an axial background magnetic field in the context of the DRESDYN-MRI experiment. In this sequel paper, we investigate the linear and nonlinear dynamics of nonaxisymmetric MRI in the same magnetized Taylor-Couette flow of liquid sodium. We show that the achievable highest Lundquist Lu=10 and magnetic Reynolds Rm=40 numbers in this experiment are large enough for the linear instability of nonaxisymmetric modes with azimuthal wave number |m|=1, although the corresponding critical values of these numbers are usually higher than those for the axisymmetric mode. The structure of the ensuing nonlinear saturated state and its scaling properties with respect to Reynolds number Re are analyzed, which are important for the DRESDYN-MRI experiment having very high Re≳106. It is shown that for Re≲4×104, the nonaxisymmetric MRI modes eventually decay, since the modified shear profile of the mean azimuthal velocity due to the nonlinear axisymmetric MRI appears to be stable against nonaxisymmetric instabilities. By contrast, for larger Re≳4×104, a rapid growth and saturation of the nonaxisymmetric modes of nonmagnetic origin occurs, which are radially localized near the inner cylinder wall, forming a turbulent boundary layer. However, for all the parameters considered, the saturation amplitude of these nonaxisymmetric modes is always a few orders smaller than that of the axisymmetric MRI mode. Therefore, the results of our previous axisymmetric study on the scaling properties of nonlinear MRI states also hold when nonaxisymmetric modes are included.

Keywords: MHD; Taylor-Couette flow; Magnetorotational Instability; Turbulence

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  • DRESDYN

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Permalink: https://www.hzdr.de/publications/Publ-39050


Data publication: Risk assessment for Na-Zn liquid metal batteries

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

Abstract

The dataset contains the risk assessment table as well as certain calculations.

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Permalink: https://www.hzdr.de/publications/Publ-39047


Depth-distribution of resistivity within ion-irradiated semiconductor layers revealed by low-kV scanning electron microscopy

Jóźwik, I.; Jagielski, J.; Ciepielewski, P.; Dumiszewska, E.; Piętak-Jurczak, K.; Kamiński, M.; Kentsch, U.

Abstract

Low-kV scanning electron microscopy imaging was used to visualize the 2D profiles of internal resistivity distribution in 600 keV He2+ ion-irradiated epitaxial GaAs and Al(0.55)Ga(0.45)As. The influence of the dopant concentration on DIVA (damage-induced voltage alteration) contrast formation has been studied in this paper. The threshold irradiation fluencies (the fluencies below which no damage-related contrast is observed) were defined for each studied material. The results show that the same level of damage in the material caused by ion irradiation becomes visible at lower threshold fluence in the case of lower-doped sample of the same composition. The aluminum content in the composition of materials exposed to ion irradiation and subsequent DIVA contrast formation mechanism was considered as well. The carrier concentration in irradiated layers has been studied by Raman spectroscopy and photoluminescence measurements, which confirmed that the increase of the resistivity of the material caused by ion-irradiation damage generation is resulting from the formation of deep states in the bandgap trapping free carriers.

Keywords: AIIIBV; Ion damage; Low-kV SEM

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Permalink: https://www.hzdr.de/publications/Publ-39046


Approaching the Curie temperature of ferromagnetic (Ga,Mn)P prepared by ion implantation and pulsed laser melting

Tian, M.; Yang, Q.; Yuan, Y.; Kentsch, U.; Liu, K.; Tang, M.; Xie, Z.; Li, L.; Wang, M.

Abstract

This work aims to estimate the Curie temperature and critical exponents in the critical regime of III-V ferro- magnetic semiconductor (FS) (Ga,Mn)P film using various methods, including Arrott and Kouvel-Fisher plots, as well as electrical transport measurements. The (Ga,Mn)P film was prepared by implanting Mn ions into an intrinsic (001) GaP wafer, followed by pulsed laser melting (PLM). The magnetic properties of the (Ga,Mn)P layer were systematically investigated. The study investigated the accuracy of four different methods in deter- mining the critical behaviors for the magnetic properties close to TC. The results suggest that the critical ex- ponents are similar to those of the mean-field model, as indicated by the modified Arrot plots and temperature dependent effective critical exponents. However, the accuracy of the temperature-dependent resistance Rₓₓ(T) method and Kouvel-Fisher (K-F) analysis is limited due to the Gaussian distribution of Mn ions in the film.

Keywords: Magnetic properties; Ion implantation; Electrical transport; Ferromagnetic; III-V ferromagnetic semiconductors

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Permalink: https://www.hzdr.de/publications/Publ-39045


Prior implantation of hydrogen as a mechanism to delay helium bubbles, blistering, and exfoliation in titanium

Fink Ilyasafov, S.; Maman, N.; Kentsch, U.; Zenou, V. Y.; Vaknin, M.; Rakita, Y.; Zamir, G.; Dahan, I.; Shneck, R. Z.

Abstract

This study explores the delaying of the formation of helium bubbles and blisters in pure titanium by hydrogen pre-implantation. Titanium, implanted with helium (40 KeV, 5 × 10¹⁷ ions/cm²), exhibited large bubbles that cause exfoliation after heat treatment, whereas hydrogen pre-implantation inhibited bubble growth at room temperature and reduced the exfoliation after heat treatment.
In the samples pre-implanted with hydrogen, we found evidence of helium diffusion delay by: (a) a fourfold reduction in bubble pressure (b) faceted cavities in the samples (c) a smaller increase in titanium lattice pa- rameters (d) a 16-fold reduction in average bubble size and a sixfold reduction in bubble area fraction (e) a more than twofold decrease in exfoliation (f) a tendency toward the formation of larger bubbles as a result of heat treatment. We believe that it is reasonable to assume that the inhibition of helium diffusion between tetrahedral interstitial lattice sites takes place because of the occupation of the intermediate octahedral sites by hydrogen atoms.
Evidence for the opposite effect, that is inhibition of the diffusion of hydrogen in the presence of helium, is found in the retention of hydrogen in the specimens at elevated temperatures. This retention allowed the exis- tence of titanium hydride after heat treatment at 680 °C. The present study sheds light on the intricate interplay between hydrogen and helium in titanium, providing insights into mechanisms that can potentially mitigate helium-induced damage in materials.

Keywords: Bubble formation; Helium implantation; Pre-implantation; Plasma-facing materials (PFMs); Nuclear technology; Irradiation damage; Helium diffusion; Titanium hydride; Blisters; Surface exfoliation; Repulsive interactions; EELS

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  • Secondary publication expected from 13.03.2025

Permalink: https://www.hzdr.de/publications/Publ-39044


Promethium bound

Kvashnina, K.

Abstract

The chemistry of promethium, a rare radioactive element, has been clouded in mystery, owing to its scarcity and the
difficulties involved in working with it. The synthesis of a complex of promethium plugs this knowledge gap

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Permalink: https://www.hzdr.de/publications/Publ-39043


Sublimed fine-grained dysprosium: Significant magnetocaloric effect

Koshkidko, Y. S.; Cwik, J.; Salazar Mejia, C.; Dormidontov, N. A.; Prokofev, P. A.; Bakulina, A. S.; Nikitin, A. A.; Khomich, A. A.; Gimaev, R. R.; Andreenko, A. S.; Burmii, Z. P.; Telitsa, A. A.; Zverev, V. I.; Kolchugina, N. B.

Abstract

As is known, rare-earth metals (REMs) are promising magnetocaloric materials. The magnitude of the magnetocaloric effect (MCE) of REMs significantly depends on their purity. This paper presents results of studies of the magnetic and magnetocaloric properties of sublimed dysprosium, prepared in the course of the present study, with an emphasis on its impurity and structure perfection. The comprehensive analysis of the chemical composition of sublimed dysprosium, which was performed for the first time by atom probe tomography, showed that the metal corresponds to high-purity rare-earth metals (3 N+). The MCE effect was studied using direct measurements of the adiabatic temperature change (ΔTad) in pulsed (up to 50 T) and steady (up to 14 T) magnetic fields. The studies of the MCE of polycrystalline sublimed Dy by direct method showed that the high ΔTad value for sublimed Dy are comparable with those obtained for single-crystal Dy in magnetic fields up to 5 T. The vacuum sublimation, which is more economical and technologically advanced in contrast to single crystal growing, can be used to create magnetocaloric REM-based materials with high MCE values.

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  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-39042


A Co(II)-Hydroxide Complex That Converts Directly to a Co(II)-Acetamide during Catalytic Nitrile Hydration

Heim, P.; Biswas, S.; Lopez, H.; Gericke, R.; Twamley, B.; McDonald, A. R.

Abstract

In exploring structural and functional mimics of nitrile hydratases, we report the synthesis of the pseudo-trigonal bipyramidal Co(II) complexes (K)[Co(II)(DMF)(LPh)] (1(DMF)), (NMe₄)₂[Co(II)(OAc)(LPh)] (1(OAc)), and (NMe₄)₂[Co(II)(OH)(LPh)] (1(OH)) (LPh = 2,2′,2’’-nitrilo-tris-(N-phenylacetamide; DMF = N,N-dimethylformamide; −OAc = acetate)). The complexes were characterized using NMR, FT-IR, ESI-MS, electronic absorption spectroscopy, and X-ray crystallography, showing the LPh ligand to bind in a tetradentate tripodal fashion alongside the respective ancillary donor. One of the complexes, 1(OH), is an unusual structural and functional mimic of the Co active site in Co nitrile hydratases. 1(OH) reacted with acetonitrile to yield the Co(II)-acetamide complex (NMe₄)₂[Co(II)(NHC(O)CH₃)(LPh)], 2, which was also thoroughly characterized. In the presence of excess hydroxide, 1(OH) was found to catalyze quantitative conversion of the added hydroxide into acetamide. Despite the differences in Co oxidation state in nitrile hydratases and 1(OH) (Co(III) versus Co(II), respectively), 1(OH) was nonetheless an effective nitrile hydration catalyst, selectively producing acetamide over multiple turnovers.

Keywords: Anions; Hydration; Ions; Ligands; Nitrogen compounds

Permalink: https://www.hzdr.de/publications/Publ-39041


Irradiation-induced enhancement of Fe and Al magnetic polarizations in Fe60Al40 films

Smekhova, A.; Szyjka, T.; La Torre, E.; Ollefs, K.; Eggert, B.; Cöster, B.; Wilhelm, F.; Bali, R.; Lindner, J.; Rogalev, A.; Többens, D.; Weschke, E.; Luo, C.; Chen, K.; Radu, F.; Schmitz-Antoniak, C.; Wende, H.

Abstract

The rise of Fe magnetic moment, changes in Al electronic structure and a variation of Al magnetic polarization in thin films of transition metal aluminide Fe60Al40 have been probed through the order-disorder phase transition by soft x-ray absorption spectroscopy and x-ray resonant magnetic reflectivity in the extreme ultraviolet regime. In a course of the transition induced by 20 keV Ne+ irradiation with low fluences (∼1014 ions cm−2), x-ray magnetic circular dichroism spectra taken at the Fe L2,3 absorption edges at room and low temperatures revealed a pronounced increase of Fe 3d states spin-polarization. X-ray resonant magnetic reflectivity applied to the Al L2,3 and Fe M2,3 edges allowed to detect the magnetic polarization of Al atoms in the films. The changes in Al electronic structure have been seen by alteration of Al K edge x-ray absorption near edge structure. A difference in anisotropy fields for films before and after irradiation has been observed by element-specific hysteresis loops recorded at low temperatures in absorption and reflection geometries at the Fe L2,3 and M2,3 edges, respectively. An attempt to reduce the top oxide layer by an inductively coupled hydrogen plasma has shown a possibility to recover the chemically ordered
phase.

Keywords: chemical disorder; ion-irradiation; XANES; XMCD; plasma treatment

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Permalink: https://www.hzdr.de/publications/Publ-39038


Chains of atoms embedded into transition metal dichalcogenides as one-dimensional half-metallic magnets

Davies, F. H.; Krasheninnikov, A.

Abstract

Quasi-one-dimensional structures, single chains of Pt and Co atoms embedded into mirror twin boundaries in two-dimensional MoS2, have recently been fabricated [Guo et al., Nat. Synth. 1, 245 (2022)]. Using both collinear and noncollinear first-principles calculations, we predict that other transition metals can form similar structures, and that these systems should possess exciting electronic and magnetic properties and specifically exhibit half-metallic electronic behavior. We further analyze the magnetocrystalline anisotropy of these systems and show that they possess unique easy axes and varying strengths of anisotropy, making thus efficient magneti- zation switching possible. We finally discuss the potentials of using single-atom chains embedded in MoS2 and other transition metal dichalcogenides in spintronic devices.

Keywords: 2D materials; Atomic chains; First-principles calculations

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  • Secondary publication expected from 30.04.2025

Permalink: https://www.hzdr.de/publications/Publ-39036


Robust Magnetoelectric Coupling in FeTiO3/Ga2O3 Non-van der Waals Heterostructures

Jin, C.; Tang, X.; Sun, Q.; Mu, C.; Krasheninnikov, A.; Kou, L.

Abstract

Magnetoelectric coupling represents a significant breakthrough for next-generation electronics, offering the ability to achieve nonvolatile magnetic control via electrical means. In this comprehensive investigation, leveraging first-principles calculations, we unveil a robust magnetoelectric coupling within multiferroic heterostructures (HSs) by ingeniously integrating a non-van der Waals (non-vdW) magnetic FeTiO3 monolayer with the ferroelectric (FE) Ga2O3. Diverging from conventional van der Waals (vdW) multiferroic HSs, the magnetic states of the FeTiO3 monolayer can be efficiently toggled between ferromagnetic (FM) and antiferromagnetic (AFM) configurations by reversing the polarization of the Ga2O3 monolayer. This intriguing phenomenon arises from polarization-dependent substantial interlayer electron transfers and the interplay between superexchange and direct-exchange magnetic couplings of the iron atoms. The carrier-mediated interfacial interactions induce crucial shifts in Fermi level positions, decisively imparting distinct electronic characteristics near the Fermi level of composite systems. These novel findings offer exciting prospects for the future of magnetoelectric technology.

Keywords: 2D materials; Heterostructures; First-principles calculations

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  • Secondary publication expected from 28.02.2025

Permalink: https://www.hzdr.de/publications/Publ-39035


A priori procedure to establish spinodal decomposition in alloys

Divilov, S.; Eckert, H.; Toher, C.; Friedrich, R.; Zettel, A. C.; Brenner, D. W.; Fahrenholtz, W. G.; Wolfe, D. E.; Zurek, E.; Maria, J.-P.; Hotz, N.; Campilongo, X.; Curtarolo, S.

Abstract

Spinodal decomposition can improve a number of essential properties in materials, especially hardness. Yet,
the theoretical prediction of the onset of this phenomenon (e.g., temperature) and its microstructure (e.g.,
wavelength) often requires input parameters coming from costly and time-consuming experimental efforts,
hindering rational materials optimization. Here, we present a procedure where such parameters are not derived
from experiments. First, we calculate the spinodal temperature by modeling nucleation in the solid solution
while approaching the spinode boundary. Then, we compute the spinodal wavelength self-consistently using
a few reasonable approximations. Our results show remarkable agreement with experiments and, for NiRh,
the calculated yield strength due to spinodal microstructures surpasses even those of Ni-based superalloys.
We believe that this procedure will accelerate the exploration of the complex materials experiencing spinodal
decomposition, critical for their macroscopic properties.

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Permalink: https://www.hzdr.de/publications/Publ-39034


Leveraging Automatic Differentiation in Complex Model Fitting

Thiessenhusen, E.; Aguilar, R. A.; Smid, M.; Kluge, T.; Bussmann, M.; Cowan, T.; Hoffmann, N.; Huang, L.; Kelling, J.

Abstract

Understanding laser-solid interactions is important for the development of laser-driven particle and photon sources, e.g., tumor therapy, astrophysics, and fusion. Currently, these interactions can only be modeled by simulations that need to be verified experimentally. Consequently, pump-probe experiments were conducted to examine the laser-plasma interaction that occurs when a high intensity laser hits a solid target. Since we aim for a femtosecond temporal and nanometer spatial resolution at European XFEL, we employ Small-Angle X-ray Scattering (SAXS) and Phase Contrast Imaging (PCI) that can each be approximated by an analytical propagator. In our reconstruction of the target, we employ a gradient descent algorithm that iteratively minimizes the error between experimental and synthetic patterns propagated from proposed target structures. By implementing the propagator in PyTorch we leverage the automatic differentiation capabilities, as well as the speed-up by computing the process on a GPU. We perform a scan of different initial parameters to find the global minimum, which is accelerated by batching multiple parallel reconstructions.

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  • HIBEF
  • Poster
    DPG-Frühjahrstagungen, 17.-22.03.2024, Berlin, Deutschland
  • Poster
    Machine Learning Conference for X-Ray and Neutron-Based Experiments, 08.-10.04.2024, Garching bei München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-39033


Charge Collection Efficiency of Single GaN Core-Shell Wires Assessed by High-Precision Ion-Beam-Induced Charge Measurements

Verheij, D.; Vićentijević, M.; Jakšić, M.; Peres, M.; Cerqueira Alves, L.; Cardoso, S.; Alves, E.; Durand, C.; Eymery, J.; Möller, W.; Lorenz, K.

Abstract

We report on the charge collection efficiency (CCE) of GaN core–shell p–n junction microwires obtained through high-precision ion-beam-induced charge (IBIC) measurements. Single wires are processed into working radiation detectors using a set of microfabrication processes and are irradiated with either 1 MeV or 750 keV Si ions. We show that we are able to accurately probe the microwires and measure structures that have dimensions below 1 μm. CCE maps show that the detectors are efficient in collecting the charge induced by the Si ions, presenting average CCE magnitudes between 20 and 30% when applying a small reverse bias. Additionally, three-dimensional Monte Carlo simulations were carried out to gain a better understanding of the energy deposition in the depletion region of the p–n junction. Comparison between the experimental and simulated data shows good agreement despite also revealing some drawbacks associated with the microwire detectors, namely, the poor collection efficiency of charge carriers generated in the neutral n-GaN core. Nevertheless, the average CCE of the detectors is promising, especially when only considering the energy deposited in the active region of the detector. In this case, depending on the applied bias, we obtain a CCE between 45 and 80%.

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Permalink: https://www.hzdr.de/publications/Publ-39030


Formation and specific contact resistivity of NiGe on polycrystalline Ge made by flash lamp annealing

Begeza, V.; Rebohle, L.; Stöcker, H.; Mehner, E.; Hübner, R.; Zhou, S.

Abstract

Flash lamp annealing (FLA) is an ultra-short annealing method, which excellently meets the requirements of thinfilm processing and microelectronics. Due to the relatively high hole mobility, thin Ge layers are highly interesting as a transistor channel material or generally as a functional layer in CMOS technology and for low-cost electronics. One possibility to realize ohmic contacts with low contact resistance is the use of metal germanides, especially the stoichiometric NiGe phase. In this work, NiGe contacts on thin Ge films were fabricated by magnetron sputtering followed by FLA. The evolution of microstructure was traced by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Electrical measurements focused on the determination of contact resistance by the circular transfer length method. The contacts were fabricated by two different approaches, and the influence of different process steps on the layer morphology and uncertainty of the measurement was studied. Finally, we show that FLA as a thermal treatment with a low thermal budget is able to form NiGe on p-type Ge with a low contact resistance similar to that achieved by other thermal treatments.

Keywords: Germanium; Nickel germanide; Thin films; Sputtering; Flash lamp annealing; Circular transfer length method

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Permalink: https://www.hzdr.de/publications/Publ-39029


Phase retrieval by a conditional Wavelet Flow: applications to near-field X-ray holography

Aguilar, R. A.; Zhang, Y.; Willmann, A.; Thiessenhusen, E.; Dora, J.; Greving, I.; Hagemann, J.; Lopes, A.; Osenberg, M.; Zeller-Plumhoff, B.; Hoffmann, N.; Bussmann, M.; Schramm, U.; Cowan, T.; Kelling, J.

Abstract

Phase retrieval is an ill-posed inverse problem with several applications in the fields of medical imaging and
materials science. Conventional phase retrieval algorithms either simplify the problem by assuming certain
object properties and optical propagation regimes or tuning a large number of free parameters. While the
latter most often leads to good solutions for a wider application range, it is still a time-consuming process,
even for experienced users. One way to circumvent this is by introducing a self-optimizing machine learning-
based algorithm. Basing this on invertible networks such as normalising flows ensures good inversion, effi-
cient sampling, and fast probability density estimation for large images and generally, complex-valued dis-
tributions. Here, complex wavefield datasets are trained and tested on a normalising flows-based machine
learning model for phase retrieval called conditional Wavelet Flow (cWF) and benchmarked against other
conventional algorithms and baseline models. The cWF algorithm adds a conditioning network on top of the
Wavelet Flow algorithm that is able to model the conditional data distribution of high resolution images of up
to 1024 x 1024 pixels, which was not possible in other flow-based models. Additionally, cWF takes advantage
of the parallelized training of different image resolutions, allowing for more efficient and fast training of large
datasets. The trained algorithm is then applied to X-ray holography data wherein fast and high-quality image
reconstruction is made possible.

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  • HIBEF
  • Open Access Logo Poster
    Machine Learning Conference for X-ray and Neutron Scattering, 08.-10.04.2024, Garching, Germany
  • Open Access Logo Poster
    DPG 2024, 17.-22.03.2024, Berlin, Germany

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Permalink: https://www.hzdr.de/publications/Publ-39028


Epigenetic Targeting to Overcome Radioresistance in Head and Neck Cancer

Schniewind, I.; José Besso, M.; Klicker, S.; Maria Schwarz, F.; Wijaya Hadiwikarta, W.; Richter, S.; Löck, S.; Linge, A.; Krause, M.; Dubrovska, A.; Baumann, M.; Kurth, I.; Peitzsch, C.

Abstract

(1) Background: The sensitivity of head and neck squamous cell carcinoma (HNSCC) to ionizing radiation, among others, is determined by the number of cells with high clonogenic potential and stem-like features. These cellular characteristics are dynamically regulated in response to treatment and may lead to an enrichment of radioresistant cells with a cancer stem cell (CSC) phenotype. Epigenetic mechanisms, particularly DNA and histone methylation, are key regulators of gene-specific transcription and cellular plasticity. Therefore, we hypothesized that specific epigenetic targeting may prevent irradiation-induced plasticity and may sensitize HNSCC cells to radiotherapy.
(2) Methods: We compared the DNA methylome and intracellular concentrations of tricarboxylic acid cycle metabolites in radioresistant FaDu and Cal33 cell lines with their parental controls, as well as aldehyde dehydrogenase (ALDH)-positive CSCs with negative controls. Moreover, we conducted a screen of a chemical library targeting enzymes involved in epigenetic regulation in combination with irradiation and analyzed the clonogenic potential, sphere formation, and DNA repair capacity to identify compounds with both radiosensitizing and CSC-targeting potential.
(3) Results: We identified the histone demethylase inhibitor GSK-J1, which targets UTX (KDM6A) and JMJD3 (KDM6B), leading to increased H3K27 trimethylation, heterochromatin formation, and gene silencing. The clonogenic survival assay after siRNA-mediated knock-down of both genes radiosensitized Cal33 and SAS cell lines. Moreover, high KDM6A expression in tissue sections of patients with HNSCC was associated with improved locoregional control after primary (n = 137) and post-operative (n = 187) radio/chemotherapy. Conversely, high KDM6B expression was a prognostic factor for reduced overall survival.
(4) Conclusions: Within this study, we investigated cellular and molecular mechanisms underlying irradiation-induced cellular plasticity, a key inducer of radioresistance, with a focus on
epigenetic alterations. We identified UTX (KDM6A) as a putative prognostic and therapeutic target for HNSCC patients treated with radiotherapy.

Keywords: histone methylation; radioresistance; cellular plasticity; cancer stem cells; head and neck cancer

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  • OncoRay

Permalink: https://www.hzdr.de/publications/Publ-39024


Radiomics for residual tumour detection and prognosis in newly diagnosed glioblastoma based on postoperative [11C] methionine PET and T1c‑w MRI

Shahzadi, I.; Seidlitz, A.; Beuthien‑Baumann, B.; Zwanenburg, A.; Platzek, I.; Kotzerke, J.; Baumann, M.; Krause, M.; Troost, E. G. C.; Löck, S.

Abstract

Personalized treatment strategies based on non‑invasive biomarkers have potential to improve patient management in patients with newly diagnosed glioblastoma (GBM). The residual tumour burden after surgery in GBM patients is a prognostic imaging biomarker. However, in clinical patient management, its assessment is a manual and time‑consuming process that is at risk of inter‑rater variability. Furthermore, the prediction of patient outcome prior to radiotherapy may identify patient subgroups that could benefit from escalated radiotherapy doses. Therefore, in this study, we investigate the capabilities of traditional radiomics and 3D convolutional neural networks for automatic detection of the residual tumour status and to prognosticate time‑to‑recurrence (TTR) and overall survival (OS) in GBM using postoperative [11C] methionine positron emission tomography (MET‑PET) and gadolinium‑enhanced T1‑w magnetic resonance imaging (MRI). On the independent test data, the 3D‑DenseNet model based on MET‑PET achieved the best performance for residual tumour detection, while the logistic regression model with conventional radiomics features performed best for T1c‑w MRI (AUC: MET‑PET 0.95, T1c‑w MRI 0.78). For the prognosis of TTR and OS, the 3D‑DenseNet model based on MET‑PET integrated with age and MGMT status achieved the best performance (Concordance‑Index: TTR 0.68, OS 0.65). In conclusion, we showed that both deep‑
learning and conventional radiomics have potential value for supporting image‑based assessment and prognosis in GBM. After prospective validation, these models may be considered for treatment personalization.

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  • OncoRay

Permalink: https://www.hzdr.de/publications/Publ-39023


Data for: Experimental Analysis of Lifelines in a 15,000 L Bioreactor by Means of Lagrangian Sensor Particles

Hofmann, S.; Buntkiel, L.; Rautenbach, R.; Gaugler, L.; Ma, Y.; Haase, I.; Fitschen, J.; Wucherpfennig, T.; Reinecke, S.; Hoffmann, M.; Takors, R.; Hampel, U.; Schlüter, M.

Abstract

The DaRUS repository entails the raw files, result files and the MATLAB codes for the publication "Experimental Analysis of Lifelines in a 15,000 L Bioreactor by Means of Lagrangian Sensor Particles" in the journal "Chemical Engineering Research and Design".
This study employs Lagrangian Sensor Particles (LSPs) with a diameter of 40 mm equipped with a pressure sensor to investigate cell lifelines in a 15,000 L stirred tank reactor (STR) with three Elephant Ear impellers. The Stokes number of the LSPs is approx. 0.004 on a macro-scale. The vertical probability of presence, axial velocity profiles, circulation time distributions, and residence time distributions are quantified to analyze single-phase mixing heterogeneities, detect hydrodynamic compartments and conduct a Lagrangian regime analysis. Results reveal a similarly distributed probability of presence in the vertical reactor center but emphasize the LSP's sensitivity to fluctuating densities. Axial velocity distributions illustrate characteristic impeller-induced flow patterns, and circulation time distributions identify three compartments with comparatively shorter times in the axial center. Residence time distributions exhibit a similar compartmentalized profile. Moreover, the study estimates a potential oxygen deprivation zone for CHO cells in the upper compartment and demonstrates the LSP's efficacy in characterizing impeller systems. Contrary to literature, the ratio of examined global mixing times to circulation times is 1.0, highlighting macro-scale mixing. The research underscores that LSPs offer crucial insights into industrial-scale STRs, specifically for determining hydrodynamic compartments without having optical access. (2024-04-19)

Keywords: Lagrangian Sensor Particles; Circulation Time Distribution; Residence Time Distribution; Lagrangian Regime Analysis; Elephant Ear Impeller; Industrial Scale

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Permalink: https://www.hzdr.de/publications/Publ-39020


Recent results and future perspectives with solid targets at LUNA

Ananna, C.; Barbieri, L.; Boeltzig, A.; Campostrini, M.; Casaburo, F.; Francesco Ciani, G.; Compagnucci, A.; Maria Gesuè, R.; Marsh, J.; Masha, E.; Mercogliano, D.; Rapagnani, D.; Robb, D.; Singh Sidhu, R.; Skowronski, J.

Abstract

The stellar evolution and chemical make-up of the Universe are determined by nuclear reactions occurring in a wide variety of stellar sites. Precise determinations of the cross sections of these reactions are crucial for the calculation of reaction rates and for the development of stellar evolution models. The Laboratory for Underground Nuclear Astrophysics (LUNA) collaboration has been at the forefront of the direct measurement of nuclear reactions at the low energies of astrophysical interest for the last 35 years. The many significant results achieved at LUNA have been made possible due to the low background conditions uniquely available thanks to its location deep underground at the Laboratori Nazionali del Gran Sasso. Another key aspect of these successes is due to the experience of the LUNA collaboration in the production and characterization of a variety of solid targets used in reaction measurements. In this review, the main production techniques of solid targets are described, as well as the common methods adopted for target degradation monitoring. We also present the results of recent measurements using these targets and the future plans of the LUNA collaboration for measurements using solid targets at the LUNA400 kV and the new Ion Beam Facility (IBF) 3.5 MV are also presented.

Keywords: Nuclear Astrophysics; Solid Targets; Ion Beam Accelerator; Laboratory for Underground Nuclear Astrophysics (LUNA); Gran Sasso National Laboratory

Permalink: https://www.hzdr.de/publications/Publ-39019


Nuclear Physics Mid Term Plan at LNGS

Buompane, R.; Cavanna, F.; Curceanu, C.; D’Onofrio, A.; Di Leva, A.; Formicola, A.; Gialanella, L.; Gustavino, C.; Imbriani, G.; Junker, M.; Marcianò, A.; Marzaioli, F.; Nania, R.; Napolitano, F.; Piscicchia, K.; Straniero, O.; Abia, C.; Aliotta, M.; Bemmerer, D.; Best, A.; Boeltzig, A.; Bruno, C.; Caciolli, A.; Chieffi, A.; Ciani, G.; D’Agata, G.; Deboer, R. J.; de Cesare, M.; Dell’Aquila, D.; Depalo, R.; Dominguez, I.; Ferraro, F.; Garcia Duarte, J.; Guglielmetti, A.; Gyürky, G.; Hayakawa, S.; La Cognata, M.; Lamia, L.; Marcucci, L. E.; Masha, E.; Mazzocco, M.; Morales-Gallegos, E. L.; Palmerini, S.; Passariello, I.; Petraglia, A.; Piatti, D.; Pignatari, M.; Pizzone, R. G.; Porzio, G.; Rapagnani, D.; Rapisarda, G. G.; Romano, S.; Rubino, M.; Santonastaso, C.; Sergi, M. L.; Skowronski, J.; Spartà, R.; Terrasi, F.; Tumino, A.; Turkat, S.; Wiescher, M.; Zavatarelli, S.

Abstract

The Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Gran Sasso (LNGS) is one of the largest underground physics laboratory, a very peculiar environment suited for experiments in Astroparticle Physics, Nuclear Physics and Fundamental Symmetries. The newly established Bellotti Ion Beam facility represents a major advance in the possibilities of studying nuclear processes in an underground environment. A workshop was organized at LNGS in the framework of the Nuclear Physics Mid Term Plan in Italy, an initiative of the Nuclear Physics Division of the Instituto Nazionale di Fisica Nucleare to discuss the opportunities that will be possible to study in the near future by employing state-of-the-art detection systems. In this report, a detailed discussion of the outcome of the workshop is presented.

Keywords: Underground Physics; Gran Sasso National Laboratory; Astroparticle Physics; Nuclear Physics

Permalink: https://www.hzdr.de/publications/Publ-39018


Comparison of three titanium-precursors for atomic-layer-deposited TiO2 for passivating contacts on silicon

Hiller, D.; Munnik, F.; López-Vidrier, J.; Solonenko, D.; Reif, J.; Knaut, M.; Thimm, O.; Grant, N. E.

Abstract

Atomic layer-deposited (ALD) TiO2 thin films on silicon were deposited using titanium tetrachloride (TiCl4), titanium tetraisopropoxide (TTIP), and tetrakis(dimethylamino)titanium (TDMAT) together with water vapor as the oxidant at temperatures ranging between 75 and 250 °C. The Si surface passivation quality of as-deposited and isothermally annealed samples was compared using photoconductance lifetime measurements in order to calculate their effective surface recombination velocities Seff. A low Seff of 3.9 cm/s (J0s = 24 fA/cm2) is achieved for as-deposited TiCl4-TiO2 at 75 °C when a chemically grown (i.e., from RCA cleaning) SiOx interface layer is present. Depositing TTIP-TiO2 at 200 °C on a chemically grown SiOx interface layer yields equivalent Seff values; however, in this case, TTIP-TiO2 requires a 5–15 min postdeposition forming gas anneal at 250 °C. In contrast, TDMAT-TiO2 was not found to provide a similar level of passivation with/without a chemically grown SiOx interface layer and postdeposition anneal. Modeling of the effective lifetime curves was used to determine the magnitude of the effective charge densities Qf in the TiO2 films. In all cases, Qf was found to be of the order of ∼10^11 q cm−2, meaning field-effect passivation arising from ALD TiO2 is relatively weak. By comparing the material properties of the various TiO2 films using ellipsometry, photothermal deflection spectroscopy, Raman spectroscopy, elastic recoil detection analysis, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, we find experimental support for the role of Cl (in conjunction with hydrogen) playing a beneficial role in passivating dangling bond defects at the Si surface. It is concluded that low deposition temperature TiCl4 processes are advantageous, by providing the lowest Seff without any postanneal and a comparatively high growth per cycle (GPC).

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Permalink: https://www.hzdr.de/publications/Publ-39016


Model Analysis

Afzal Chaudhry, A.; Nagel, T.; Zhao, J.; Düsterloh, U.; Zhao, J.; Chen, L.; Wang, J.; Liu, Y.; Cao, S.; Zhang, Q.; Shao, H.; Chen, C.; Yuan, T.; Lu, R.; Fischer, C.; Kolditz, O.

Abstract

Understanding the function and evolution of terrestrial environmental systems is fundamental to many environmental aspects investigated in the geo-and hydro-sciences. The terrestrial environmental systems under investigation here range from the geosphere and its related water cycle to associated matter fluxes and biogeochem-ical transformations. Modelling is important for system characterization and under-standing as well as describing potential paths of terrestrial environmental systems. Benchmarking builds a bridge to experimental studies and provides a methodology for model validation. Moreover, benchmarking and code comparison foster commu-nity efforts. This book series invites contributions in fundamental and applied aspects in terrestrial environmental sciences as well as in other related fields to promote interdisciplinary approaches.

  • Open Access Logo Book chapter
    in: Thermo-Hydro-Mechanical-Chemical (THMC) Processes in Bentonite Barrier Systems, Gewerbestrasse 11, 6330 Cham, Switzerland: Springer, 2024

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Permalink: https://www.hzdr.de/publications/Publ-39014


Inkjet printing of functional materials activated by ms-range flash lamp annealing

Folgner, C.; Zhang, G.; Prucnal, S.; Rebohle, L.; Zhou, S.

Abstract

Currently, we observe a continuous need for innovative flexible optoelectronics that are present in smart homes, smart healthcare products and different sensors like gas or temperature sensors. All those applications require a fast and cheap fabrication process. In the last two decades, flash lamp annealing (FLA or photonic curing) has extended its scope of applications from traditional microelectronics to many other areas where thin film coatings are in use. The layer deposition by inkjet printing followed by FLA, preferably on flexible substrates, features a couple of advantages such as material savings, no need for lithographic structuring processes, a fast adaption to changing design requirements and easy possibility for up-scaling. In the case of nanoparticle-based inks, FLA has not only the task to evaporate remnants of the solvent, the binder and other additives, and to sinter the nanoparticles, but has advantageous in terms of energy and process time saving [1]. Currently, we are putting a roll-to-roll (R2R) tool combining inkjet printing and FLA into operation, and first successful tests to print nanoparticle inks containing transparent conductive oxides for optoelectronic applications (TCOs) like zinc oxide (ZnO), aluminum doped zinc oxide (AZO) and also metal inks like copper oxide/copper (CuO/Cu) followed by ex-situ FLA have been done.
In this poster, we will report some of these first results and discuss the corresponding application cases. In addition, the extension of the palette of available materials will address further application, as we will discuss in the case of Si, which e.g. is of high interest as anode material for LIBs and electronic devices in the area of low-cost or printed electronics.

Keywords: Inkjet printing; flash lamp annealing; roll-to-roll; nanoparticle inks; zinc oxide; metal inks; TCO; photonic curing; sensors; fabrication process

  • Poster
    Microprinting Materials, Methods and Applications, 18.-20.03.2024, Bad Schandau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-39010


Investigation of the Σ Production Mechanism in p(3.5 GeV)+p Collisions

Yassine, R. A.; Arnold, O.; Becker, M.; Kämpfer, B.; Kotte, R.; Naumann, L.; HADES Collaboration

Abstract

The production of Σ hyperons in proton proton collisions at a beam kinetic energy of 3.5 GeV impinging on a liquid hydrogen target was investigated using data collected with the HADES setup. The total production cross section is found to be σ(pK+Σ) = 17.7 ± 1.7 (stat) ± 1.6 (syst) µb. Differential cross section distributions of the exclusive channel pp→ pK+Σ were analyzed in the center-of-mass, Gottfried–Jackson and helicity reference frames for the first time at the excess energy of 556 MeV. The data support the interplay between pion and kaon exchange mechanisms and clearly demonstrate the contribution of interfering nucleon resonances decaying to K +Σ . The Bonn–Gatchina partial wave analysis was employed to analyse the data. Due to the limited statistics, it was not possible to obtain an unambiguous determination of the relative contribution of intermediate nucleon resonances to the final state. However nucleon resonances with masses around 1.710 GeV / c 2 (N ∗(1710)) and 1.900 GeV / c 2 (N ∗(1900) or Δ ∗(1900)) are preferred by the fit.

Permalink: https://www.hzdr.de/publications/Publ-39009


Generation of localized, half-frequency spin waves in micron sized ferromagnetic stripes: Experiments and simulations

Copus, M. G.; Hula, T.; Heins, C.; Flacke, L.; Weiler, M.; Schultheiß, K.; Schultheiß, H.; Camley, 
. E.

Abstract

We demonstrate the nonlinear generation of spin-wave edge modes with half the frequency of the applied oscillating field in a Co25Fe75 ferro- magnetic stripe through micromagnetic simulations and experiments. The generation of half-frequency modes depends on the simultaneous presence of resonances near both the driving frequency and the half-frequency in different regions of the material. The half-frequency genera- tion occurs in a system that is thin enough that typical three-magnon decay would not be allowed in a ferromagnetic resonance experiment in an extended film. We find that a limited range of driving frequencies will produce a half-frequency for a given set of system parameters. This range can be tuned by the strength of the oscillating field and the strength of the static external field. Our experimental results agree well with the findings from the simulations.

Keywords: spin waves; magnons; nonlinearity; Brillouin light scattering; micromagnetic simulations

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  • Secondary publication expected from 10.04.2025

Permalink: https://www.hzdr.de/publications/Publ-39007


Plasma dynamics between laser-induced breakdown and relativistically induced transparency: An investigation of high-intensity laser-solid interactions by time-resolved off-harmonic optical shadowgraphy

Bernert, C.

Abstract

Laser-plasma-based ion accelerators are becoming a versatile platform to drive different fields of applied research and life sciences, for example translational research in radiation oncology. To ensure stable accelerator performance, complete control over the ion source, i.e., the high-intensity laser-solid interaction, is required. However, idealized interaction conditions are almost impossible to reach, as the utilized high-power lasers always feature a non-negligible amount of light preceding the laser peak. This leading edge of the laser pulse usually exceeds the ionization potential of bound electrons much earlier than the arrival of the high-power laser peak and the solid-density target undergoes significant modifications even before the actual high-intensity laser-plasma interaction starts. Control over this so-called target pre-expansion is a key requirement to achieve quantitative agreement between numerical simulations and experiments of high-intensity laser-solid interactions.
This thesis investigates several aspects that are relevant to improve the capability of simulations to model realistic experimental scenarios. The corresponding experiments are conducted with cryogenic hydrogen-jet targets and the DRACO-PW laser at peak intensities between 10^12 W/cm^2 and 10^21 W/cm^2 . The experimental implementation of time-resolved optical-probing diagnostics and technical innovations with respect to the technique of off-harmonic optical probing overcome the disturbances by parasitic plasma self-emission and allow for unprecedented observations of the target evolution during the laser-target interactions. The laser-induced breakdown of solids, i.e., the phase transition from the solid to the plasma state, can be considered as an heuristic starting point of high-intensity laser-solid interactions. As it is highly relevant to simulations of target pre-expansion, Chapter 3 of this thesis presents time-resolved measurements of laser-induced breakdown in laser-target interactions at peak intensities between 0.6 * 10^21 W/cm^2 and 5.7 * 10^21 W/cm^2 . By increasing the peak intensity, a lowering of the applicable threshold intensity of laser-induced breakdown well below the appearance intensity of barrier-suppression ionization occurs. The observation demonstrates the relevance of the pulse-duration dependence of laser-induced breakdown and laser-induced damage threshold to the starting point of high-intensity laser-solid interactions. To apply the results to other laser-target assemblies, we provide a detailed instruction of how to pinpoint the starting point by comparing measurements of the laser contrast with a characterization study of the target-specific thresholds of laser-induced breakdown at low laser intensity. Chapter 4 of this thesis presents an example of how optical-probing diagnostics are able to estimate target pre-expansion as a starting condition for particle-in-cell simulations. The measurement allows to restrict the surface gradient of the pre-expanded plasma density to an exponential scalelength between 0.06 um and 0.13 um. Furthermore, the plasma-expansion dynamics induced by the ultra-relativistic laser peak are computed and post-processed by ray-tracing simulations. A comparison to the experimental results yields that the formation of the measured shadowgrams is governed by refraction in the plasma-density gradients and that the observed volumetric transparency of the target at 1.4 ps after the laser peak is not caused by relativistically induced transparency but by plasma expansion into vacuum instead. Chapter 5 of this thesis shows that a precise adjustment of the target density to the arrival of the ultra-relativistic laser peak by all-optical target-density tailoring in combination with the low solid density of the cryogenic hydrogen-jet target allows to explore the laser-target interaction in the nearcritical density regime. The chapter presents an experimental demonstration of all-optical target-density tailoring by isochoric heating via ultra-short laser pulses with a dimensionless vector potential a_0 ∼ 1. A hybrid of hydrodynamics and ray-tracing simulations allows to determine the evolution of the full target-density distribution after isochoric heating. Finally, the utilization of the method as a testbed platform to experimentally benchmark collisional particle-in-cell simulations is proposed and an experimental exploration of future possibilities of all-optical target-density tailoring is given.

Keywords: high-intensity; laser-solid; laser-induced breakdown; realtivistic transparency; off-harmonic; optical probing; shadowgraphy

Involved research facilities

  • Draco
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-130 2024
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-39006


Radionuclide sorption in the far field: Geostatistical simulation of crystalline rock to assess uncertainties due to heterogeneities

Duckstein, A.; Pospiech, S.; Tolosana Delgado, R.; Brendler, V.

Abstract

In the event of radionuclides leaking from a deep geological repository for radioactive waste, they can reach the ecosphere through fluid migration pathways in the rock and aquifers. Retention mechanisms such as the sorption of radionuclides on the minerals along such pathways influence the migration patterns and are thus an essential part of the safety requirements. Consequently, determining the mineral composition and its spatial distribution of a crystalline host rock is an important task in the safety assessment for potential repositories.

In the SANGUR project (Systematic sensitivity analysis for mechanistic geochemical models using field data from crystalline rock) we aim to determine which parameters and their uncertainties are essential for developing models for the simulation of radionuclide retention in crystalline rock. Radionuclide retention is substantially affected by sorption processes on the mineral surfaces, described by distribution coefficients (Kd values). A subsequent sensitivity analysis will help to identify the most influential parameters.

In addition to the groundwater composition and the thermodynamic sorption data, the mineralogy and its heterogeneity of the host rock play an important role in establishing the model. For the sensitivity analysis, in turn, it is vital to be able to describe the uncertainties of the individual parameters in the model.

To quantify the uncertainties, we simulate crystalline rock based on MLA (Mineral Liberation Analyzer image) data using Multinary Random Fields geostatistics. The focus is not only on the mineral composition of the bulk rock as a function of number of mineral phases and variability in grain sizes, but above all on the determination of the mineral composition of the exposed surfaces with which the aqueous phase comes into contact and on which sorption processes will thus preferentially take place.

Besides the question of how detailed the rock must be modeled in order to adequately capture the heterogeneities, the question of the model scale or the size of the representative volume element is also addressed.

In addition to the discussion of the methodology and the results of the host rock simulations, we show the results of an initial study that enables us to determine what size the representative volume element should have in order to best describe the heterogeneities of the host rock for the subsequent calculation of the Kd values and their uncertainties.

Permalink: https://www.hzdr.de/publications/Publ-39004


Investigation into the metabolic stability of 18F-labeled PSMA inhibitor derivatives bearing aryl-fluorosulfates for PET tracer development applications

Luque Consuegra, G.; Craig, A.; Kogler, J.; Ullrich, M.; Donat, C.; Kopka, K.; Stadlbauer, S.

Abstract

This poster highlights the use of the sulfur [18F]fluoride exchange approach to radiolabel a PSMA inhibitor ([18F]2) and test its radiolabeling, in vitro and in vivo properties.

  • [18F]2 shows good binding kinetics compared to known radiotracers (1 nM) but ~20%
defluorination occurs in human serum after 120 min.
  • [18F]2 binds to LNCaP xenograft sections in a similar pattern as [68Ga]Ga-PSMA-11.
  • PET imaging experiments show defluorination but also accumulation in LNCaP tumor
xenografts (SUVmax = 4.4).
  • Further work: Radiosynthesis of [18F]4 starting from precursor 3 (in poster)

Keywords: sulfur [18F]fluoride exchange approach; Radiolabeling; PET; PSMA; Radiopharmaceuticals

  • Open Access Logo Poster
    21st European Symposium on Radiopharmacy & Radiopharmaceuticals, 18.-21.04.2024, Coimbra, Portugal

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Permalink: https://www.hzdr.de/publications/Publ-39001


Hyperspectral imaging and TRI3DYN simulation study of physical sputtering from a fuzzy surface

Chang, F.; Nishijima, D.; Baldwin, M. J.; Möller, W.; Tynan, G. R.

Abstract

The influence of a fuzzy surface on the physical sputtering of Mo in He plasmas has been studied with hyperspectral imaging (HSI) measurements and simulations that couple the TRI3DYN code with an impurity transport code. The 2D profiles of the Mo I line emission intensity from HSI images reveal that the sputtering yield, Y, is reduced to ∼40 % of the smooth-surface value due to the presence of a fuzz layer, while the angular distribution of the sputtered Mo atoms might not change significantly. The simulations reproduce the Y reduction successfully, but indicate that fuzz causes an increase in the small-angle distribution of sputtered atoms. However, the increase is too small to produce an observable change in the Mo I emission profiles. A simple analytical model that assumes a single collision mean free path for a fuzz layer and considers only the primary sputtering events qualitatively reproduces the Y reduction and the small-angle distribution enhancement, explaining the geometrical effect of fuzz on physical sputtering.

Keywords: Fuzz; Hyperspectral imaging; Physical sputtering; TRI3DYN

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Permalink: https://www.hzdr.de/publications/Publ-38996


Study of (n,α) reactions of interest for nuclear reactors: the case of 19F(n,α)16N with SCALP detector

Chevalier, A.; Lecolley, F.-R.; Lehaut, G.; Lecouey, J.-L.; Marie, N.; Manduci, L.; Ledoux, X.; Beyer, R.; Junghans, A.; Bouland, O.; Serot, O.

Abstract

The 19F(n,α)16N cross section is of great interest for the development of the next generation IV reactors that could potentially use molten fluoride salts. Significant differences (up to a factor of 3) have been observed for this nucleus regarding the (n,α) channel. In view of improving our knowledge on this (n,α) reactions, the GrACE group (Groupe Aval du Cycle Electronucleaire) of the LPC Caen has developed a new detector named SCALP (Scintillating ionization Chamber for ALPha particle detection in neutron induced reactions). This paper deals with the first experiment carried out with this brand new detector at the new NFS facility (GANIL, Caen, France). After discussing the needs for new measurments of the 19F(n,α)16N reaction, the operating procedure of the SCALP detector will be presented, as well as the experiments that have been conducted using it. Furthermore, insights into the data acquired during our experiment, as well as the ongoing data processing and associated multi-channel analysis, will be provided.

Keywords: nELBE; (n,a); 19F(n,a)16N; Generation IV reactor; SCALP; NFS

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Permalink: https://www.hzdr.de/publications/Publ-38994


InvenioRDM at HZDR: Rodare

Knodel, O.

Abstract

The talk will address data publishing and the FAIR data principles by examining the central role of data policies and infrastructure services. On the path to making data findable, accessible, interoperable and reusable (FAIR), the talk will provide insights into the fundamental strategies for creating effective data policies and implementing infrastructure services that support these principles. The HZDR data publication repository RODARE will be presented as well as the underlying software Invenio, which was developed by CERN. Future developments in the context of Rodare, Zenodo and Invenio will be presented. Invenio RDM (Research Data Management) and the content of the joint project InvenioRDM will be presented as well as the first steps towards an InvenioRDM demo instance. Finally, further points such as the SciCat metadata catalogue will be discussed.

Keywords: data management; data publication; FAIR; Invenio; Rodare; InvenioRDM; Data Policy; Zenodo

  • Open Access Logo Lecture (others) (Online presentation)
    MT-DMA Seminar Series 2024, 22.04.2024, online, Germany

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Permalink: https://www.hzdr.de/publications/Publ-38992


Data publication: Ab initio path integral Monte Carlo simulations of warm dense two-component systems without fixed nodes: structural properties

Dornheim, T.

Abstract

This repository contains the raw data for the publication "Ab initio path integral Monte Carlo simulations of warm dense two-component systems without fixed nodes: structural properties". All units as described in the paper / figure captions.

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Permalink: https://www.hzdr.de/publications/Publ-38990


High-Performance Thermochromic VO2-Based Coatings Deposited by Roll-to-Roll High-Power Impulse Magnetron Sputtering

Szelwicka, J.; Fahland, M.; Rezek, J.; Kaufman, M.; Munnik, F.; Vlcek, J.; von Hauff, E.

Abstract

Thermochromic vanadium dioxide (VO2) undergoes a metal-to-semiconductor (MST) transition, a property that can be exploited for energy reduction in buildings in smart windows. We present thermochromic VO2-based films prepared in a roll-to-roll process on ultra-thin glass (0.1 mm) with High Power Impulse Magnetron Sputtering (HiPIMS) without any post annealing. We characterized the film structure with X-ray diffraction, the stoichiometry by Rutherford Backscattering Spectrometry, and the optical properties with spectrophotometry. The selected films (over 2.6 m x 0.3 m), sputtered from a V-metallic tube target doped with 1.2 at.% of W (V-W target), show a transition temperature of 28 °C and 34 °C, a luminous transmittance over 50% and a modulation of the solar energy transmittance of about 7 and 10%. We monitor the deposition control parameters in the roll-to-roll process with optical emission spectroscopy, and show that both the process parameters and target history impact the thermochromic properties. Finally, we extract the charge carrier concentration and mobility by modelling the transmittance and reflectance spectra, which indicates that the VO2-coating has a slight sub-stoichiometric character.

Keywords: vanadium dioxide; thermochromic; roll-to-roll; HiPIMS; ultrathin glass

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Permalink: https://www.hzdr.de/publications/Publ-38989


Laser-driven high-energy proton beams from cascaded acceleration regimes

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

Abstract

Laser-driven ion accelerators can deliver high-energy, high-peak current beams and are thus attracting attention as a compact alternative to conventional accelerators. However, achieving sufficiently high energy levels suitable for applications such as radiation therapy remains a challenge for laser-driven ion accelerators. Here we generate proton beams with a spectrally separated high-energy component of up to 150 MeV by irradiating solid-density plastic foil targets with ultrashort laser pulses from a repetitive petawatt laser. The preceding laser light heats the target, leading to the onset of relativistically induced transparency upon main pulse arrival. The laser peak then penetrates the initially opaque target and triggers proton acceleration through a cascade of different mechanisms, as revealed by three-dimensional particle-in-cell simulations. The transparency of the target can be used to identify the high-performance domain, making it a suitable feedback parameter for automated laser and target optimization to enhance stability of plasma accelerators in the future.

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  • Draco

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Permalink: https://www.hzdr.de/publications/Publ-38987


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