Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

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

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

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

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

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

Oxygen is one of the key reaction partners for many redox reactions also in the context of nuclear waste disposal. Its solubility influences radionuclides’ behavior, corrosion processes and even microbial activity. Therefore, a reliable calculation of the solubility of molecular oxygen in aqueous solutions is relevant for the safety assessment.
In the available geochemical speciation and reactive transport programs, these data are handled very differently. In some data files for such codes the hypothetical equilibrium between dissolved oxygen and water is used to balance redox reactions. Equilibrium constants are given in “temperature grids” for up to 573.15 K. In other cases, temperature functions for the solubility of gaseous oxygen in water are given, without any reference to a valid temperature range.
In some cases, these data were also used in the context of modeling equilibria in high-saline solutions using the Pitzer formalism. This raised the question about the experimental foundation of equilibrium constants given in such data files and their validity for the solubility of molecular oxygen in saline solutions.
For this article a thorough literature review was conducted with respect to the solubility of molecular oxygen in saline solutions. From these primary experimental data Pitzer coefficients were derived. An internally consistent set of thermodynamic data for dissolved oxygen is presented, along with statements about its validity in terms of temperature and, as far as Pitzer coefficients are concerned, of solution composition.

This study presents a comprehensive community data-driven surface complexation modeling framework for simulating potentiometric titration of mineral surfaces. Compiled community data for ferrihydrite, goethite, hematite, and magnetite are fit to produce representative protolysis constants
that can reproduce potentiometric titration data collected from multiple literature sources. Using this framework, the impact of SCM type and surface site density (SSD) on the fit quality and protolysis constants can be readily evaluated. For example, the non-electrostatic model (NEM) yielded a poor
data fit compared to diffuse double layer model (DDLM) and constant capacitance models (CCM) due to the absence of known surface charge effects. Regardless of the choice of iron oxide mineral, pKa1 decreased with increasing SSD while the opposite tendency was observed for pKa2. This newly
developed framework demonstrates a method to reconcile community data-wide potentiometric titration data using FAIR data principles to produce mineral protolysis constants that improve robustness of surface complexation models for applications in metal sorption and reactive transport
modeling. The framework is readily expandable (as community data increase) and extensible (as the number of minerals increase). The framework provides a path forward for developing self-consistent, comprehensive, and updateable surface complexation databases for surface complexation and
reactive transport modeling.

Introduction to kernel methods and Gaussian processes

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

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

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

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

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

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

This work describes the in-situ CTR plugin for the particle-in-cell code PIConGPU. The C++ -plugin calculates coherent transition radiation (CTR) from millions to billions of macro-particles in a PIConGPU plasma simulation. In order to avoid excessive disk output of many GB to TB of data, as well as and extensive post-processing runtimes on only few CPUs, the plugin was parallelized on GPUs and implemented in-situ as part of PIConGPU.
The physics of this plugins was successfully implemented, tested and verified to agree with an initial python implementation, which again was verified using analytical CTR theory, with an average error of less than 1 %. Additionally the plugin was benchmarked, resulting in typical time to solutions for complete transition radiation spectra on the scale of several minutes.
The CTR plugin was then used in several Laser-wakefield accelerator (LWFA) simulations, with self-injected and down-ramp injected electrons respectively. Mimicking the hypothetical placement of successive transition radiaton foils along the LWFA interaction length, the CTR plugin was used multiple times for observing how the electron bunch evolution leads to the characteristic features of transition radiation spectra.
This new tool is a synthetic diagnostic, which enables direct comparison of experi- mentally measured transition radiation data to simulations. In future experiments this can provide insight into LWFA longitudinal electron pulse profiles on the fs-scale, required for future compact LWFA-driven free-electron laser applications.

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

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

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

Ni-Mn-based Heusler alloys, in particular all-d-metal Ni(-Co)-Mn-Ti, are highly promising materials for energy-efficient solid-state refrigeration as large multicaloric effects can be achieved across their magnetostructural martensitic transformation. However, no comprehensive study on the crucially important transition entropy change Δs exists so far for Ni(-Co)-Mn-Ti. Here, we present a systematic study analyzing the composition and temperature dependence of Δs_t. Our results reveal a substantial structural entropy change contribution of approximately 65 J(kgK)^-1, which is compensated at lower temperatures by an increasingly negative entropy change associated with the magnetic subsystem. This leads to compensation temperatures T_comp of 75 K and 300 K in Ni₃₅Co₁₅Mn_50-yTi_y and Ni₃₃Co₁₇Mn_50-yTi_y, respectively, below which the martensitic transformations are arrested. In addition, we simultaneously measured the responses of the magnetic, structural and electronic subsystems to the temperature- and field-induced martensitic transformation near T_comp, showing an abnormal increase of hysteresis and consequently dissipation energy at cryogenic temperatures. Simultaneous measurements of magnetization and adiabatic temperature change ΔT_ad in pulsed magnetic fields reveal a change in sign of ΔT_ad and a substantial positive and irreversible ΔT_ad up to 15 K at 15 K as a consequence of increased dissipation losses and decreased heat capacity. Most importantly, this phenomenon is universal, it applies to any first-order material with non-negligible hysteresis and any stimulus, effectively limiting the utilization of their caloric effects for gas liquefaction at cryogenic temperatures.

The safe disposal of radioactive waste from operation and decommissioning of nuclear power plants in geological repositories requires the application of multiple barriers to isolate the waste from the biosphere. Bentonite and cementitious materials are foreseen as buffer and borehole sealing material or for stabilization purposes. Pore waters of the North German clay deposits are characterized by high ionic strengths up to 4 M [1,2]. The contact of such saline formation waters with concrete will result in an enhanced corrosion of concrete and to the evolution of highly alkaline cement pore waters (10 < pH < 13), which in turn, can react with the bentonite buffer as well as with the clay host rock, changing their retention potential towards radionuclides. Moreover, the role of organics (as admixtures in cement-based materials or waste constituents [3]) on actinide retention has to be studied.
The U(VI) retention on Ca-bentonite in mixed electrolyte solutions (‘diluted Gipshut solution’, I = 2.6 M) was found to be very effective at pH>10, even in the presence of carbonate and despite the prevalence of anionic aqueous uranyl species [4]. By means of luminescence and X-ray absorption spectroscopy, the U(VI) speciation could be clarified. A substantial contribution of calcium (aluminum) silicate hydrates (C-(A-)S-H), formed as secondary phases in the presence of Ca due to partial dissolution of alumosilicates at hyperalkaline conditions, to the retention of anionic actinide species in clayey systems was shown [5]. Citrate and 2-phosphonobutane-1,2,4,-tricarboxylate (PBTC) were found to reduce U(VI) retention only when present at high concentrations.
The U(VI) and Eu(III)/Cm(III) retention by C-A-S-H, formed due to Al-rich additives in cement formulations, was studied applying samples with Ca/Si molar ratios of 0.8, 1.2 and 1.6, representing different alteration stages of concrete, and with increasing Al/Si molar ratios of 0, 0.06 and 0.18 in each series. Furthermore, the impact of temperature (25°C, 100°C, 200°C) on both the C-A-S-H structure and the actinide retention mechanism was studied. Solid-state 27Al and 29Si NMR spectroscopy along with XRD revealed that enhanced temperatures increase the crystallinity of the material with the appearance of neoformed crystalline phases. Surface-sorbed, interlayer-sorbed or incorporated actinide species were detected by luminescence spectroscopy. Actinide mobilization due to high ionic strengths or presence of organics (gluconate, PBTC or nitrilotriacetate (NTA)) was very low [6,7].
The results show that both bentonite and cementitious material constitute an important retention barrier for actinides under hyperalkaline conditions at increased ionic strengths and in presence of organics.

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

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

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

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

In many European countries (e.g., Switzerland, France, Sweden), thick steel casks are foreseen for the containment of high-level radioactive waste in deep geological repositories. In contact with pore-water, steel corrodes forming mixed iron oxides, mainly magnetite at the surface (Fe3O4). After tens of thousands of years, casks may breach allowing for leaching of the radionuclides by pore-water. Magnetite can retard dissolved radionuclides either by adsorption or structural incorporation [1,2]. But since these interaction mechanisms are poorly understood at the atomistic scale, our goal is to better understand them by using computer simulations alongside experiments [3].
In this computational study, we identified the dominant low-index surfaces of magnetite particles and their termination at the relevant conditions based on Kohn-Sham density functional theory (DFT). This was done using the open-source code CP2K. The DFT+U method was employed for the strongly correlated 3d and 5f electrons of Fe and Pu, respectively. After revising our model and determining the Hubbard U parameter [4], we examined the preferential magnetite crystal orientation plane (111) allowing for different surface terminations, water coverage and redox conditions. Comparing the surface energy, the most stable surface can be deduced and we found the most stable magnetite (111) surfaces under real repository conditions. Subsequently, we used ab initio molecular dynamics (MD) to simulate sorption structures on the expected magnetite (111) surfaces.

[1] T. Dumas et al. (2019). Plutonium Retention Mechanisms by Magnetite under Anoxic Conditions: Entrapment versus Sorption. ACS Earth & Space Chemistry, 2019, 3(10), 2197.
[2] R. Kirsch et al. (2011). Oxidation State and Local Structure of Plutonium Reacted with Magnetite, Mackinawite, and Chukanovite. Environmental Science & Technology, 2011, 45(17), 7267.
[3] E. Yalçintaş et al. (2016). Systematic XAS study on the reduction and uptake of Tc by magnetite and mackinawite. Dalton Transactions, 2016, 45(44), 17874.
[4] A. Kéri et al. (2017). Combines XAFS Spectroscopy and Ab Inito Study on the Characterization of Iron Incorporation in Motmorillonite. Environmental Science & Technology, 51(18), 10585.

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

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

Designing
Antiferromagnetic Domain Landscapes
via
Focussed Ion Beam Irradiation

The plasma shutter is a thin solid foil (or series of them) placed in front of the main target irradiated by high intense laser. It can mitigate the prepulse and also shape the main pulse, resulting in the generation of a steep-rising front and local intensity increase of the pulse. We study the application of the shutter for ion acceleration via 3D PIC simulations assuming Si₃N₄ plasma shutter, ultrathin silver target and a PW-class laser. The application of shutter results in increase of maximal ion energy for both linear and circular polarizations. It also significantly reduces the beam divergence for the linear polarization. In the case of circular polarization, the transmitted laser pulse obtains a spiral-like intensity profile. The structure is transferred into the electron density profile of the shutter and the main target behind it. The use of a double-shutter is studied via a combination of 2D PIC and hydrodynamic simulations assuming the laser pulse accompanied by a sub-ns prepulse. We present a prototype of the double-shutter and the design of the whole shutter-target setup. The generated steep-front has also positive effect on different scenario with low-Z double-layer targets. The 3D shutter simulation is also represented via an interactive Virtual Reality visualization.

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

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

We present a method extending scanning third-order correlator temporal pulse14
evolution measurement capabilities of high power short pulse lasers to spectral sensitivity within15
the spectral range exploited by typical chirped pulse amplification systems. Modelling of the16
spectral response achieved by angle tuning of the third harmonic generating crystal is applied17
and experimentally validated. Exemplary measurements of spectrally resolved pulse contrast of a18
Petawatt laser frontend illustrate the importance of full bandwidth coverage for the interpretation19
of relativistic laser target interaction in particular for the case of solid targets.

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

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

Generalized Gelfand-Dikii equation for fermionic Schwinger pair production

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

Electric Dipole Moments (EDM) of particles (leptons, nucleons and light nuclei) are currently deemed one of the best indicators for new physics, i.e. phenomena, which lie outside the Stand-ard Model (SM) of elementary particle physics – so called physics “Beyond-the-Standard-Model” (BSM). Since EDMs of the SM are vanishingly small, a finite permanent EDM would indicate charge-parity symmetry (CP-) violation in addition to the well-known sources of the SM and could explain the baryon asymmetry of the Universe, while an oscillating EDM would hint at a possible Dark Matter (DM) field comprising axions or axion-like particles (ALPs). A new ap-proach exploiting polarized charged particles (proton, deuteron, 3He) in precision storage rings offers the prospect to push current experimental EDM upper limits significantly further includ-ing the possibility of an EDM discovery. In this paper, we describe the scientific background and the steps towards the realization of a precision storage ring, which will make such measure-ments possible.

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

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

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

The M4 edge XANES of actindies acquired in the High-Energy-Resolution Fluorescence Detected (HERFD) mode is very powerful since it porbes directly the 5f manifold with sufficient resolution to resolve the relevant spectral features. Theoretical calculations of such spectra are then fundamental for a correct interpretation and to guide the insight into actinides electronic structure.
We recently explored the use of a DFT-based code for X-ray spectroscopies, i.e. FDMNES,1 to calculate the M4 edge HERFD XANES of U6+ systems.2 The DFT approach is suitable to calculate closed-shell systems and our results are in good agreement with the experimental data. Our findings reveal the high sensitivity of the M4 edge to the local environment of the An ion and the suitability of the DFT approach to reproduce closed-shell systems. In particular, we were able to reproduce the spectral variations observed in 4 different U6+ systems with a local geometry from uranate to uranyl. We are currently expanding our investigation to open-shell systems, in particular to U(III) halides. For this case we are using atomic multiplet theory3 and investigating how scaling of atomic parameters affects the spectra in order to reproduce the effects observed.
We will present the results from both approaches, discuss the assignment of spectral features as emerging from the analysis of the projected density of states (DOS), underline the critical points that suggest further developments in the calculation approach.

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

Liquid metals, such as sodium, have been already successfully used as heat transfer fluids (HTF) in concentrating solar power (CSP) plants up to ~550 °C. Even higher temperatures can be achieved and are envisioned for future CSP plants. The lack of measuring flow rate devices at high temperatures for liquid metals motivated this study. The present paper presents the experimental mock-up and the experimental results obtained with the SOLTEC-2 facility for two test flow sensors, one innovative eddy current flow sensor (ECFM) developed at HZDR, Germany and a built-in permanent magnet fly-wheel sensor for runs up to a sodium temperature of 700 °C. The signals of the sensors are compared also against the power level of the sodium pump.

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

Experimental oxygen K-edge spectra of ThO2 and CeO2 are presented and interpreted based on density functional theory (DFT). The contribution of d and f orbitals to the O K-edge spectrum are identified as well distinguished peaks, the presence of which evidences the strong hybridization of Th and Ce metal centers with O orbitals. The sensitivity of the O K-edge to both f- and d-states in the absence of a core-hole on the metal ion results in an insightful overview of the electronic structure involved in the chemical bond. In particular, the large bandwidth of the Th 5f band as compared to the Ce 4f band is observed as a set of wider and more substantial set of peaks in the O K-edge, confirming the stronger hybridization of the former with O orbitals. The peak ascribed to the 5f band of ThO2 is found at higher energy than the 6d band, as predicted from DFT calculations on actinide dioxides. To highlight the sensitivity and the potential use of the O K-edge for the characterization of ThO2-based systems, the sensitivity of the spectrum to structural changes such as lattice expansion and size reduction are calculated and discussed.

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

Most industrial processes are generating waste heat that can be converted into electrical energy with thermoelectric generators (TEGs). For efficient energy harvesting, it is necessary to significantly improve the properties like Seebeck coefficient, electrical and thermal conductivity of the thermoelectric materials in the TEGs. One promising approach are thermoelectric nanostructures to reduce the thermal conductivity while maintaining constant electrical conductivity and Seebeck coefficient. For that reason, this study investigated the possibility of preparing nanowires of the thermoelectric material iron antimonide (FeSb₂) on crystalline gallium arsenide GaAs(001) substrates with ion-induced surface nanopatterning.
The GaAs(001) substrates were pre-patterned using 1 keV Ar⁺ ion irradiation. By using an ion source with a broad, unfocused ion beam at normal incidence, the patterned area can be scaled to nearly any size. The self-organized surface structure is formed by reverse epitaxy and is characterized by almost perfectly parallel-aligned ripples at the nanometer scale. For the fabrication of FeSb₂ nanowires, iron and antimony were successively deposited on the prepatterned GaAs substrates at grazing incidence and then annealed. They were characterized using transmission electron microscopy (TEM), in particular high-resolution TEM imaging for structure analysis and spectrum imaging analysis based on energy-dispersive X-ray spectroscopy
for element characterization.
With the presented fabrication method, FeSb₂ nanowires were produced successfully on GaAs(001) substrates with an ion-induced nanopatterned surface. The nanowires have a polycristalline structure and a cross-sectional area which is scalable up to 22×22nm². Due to the highly ordered nanostructure of the GaAs substrates, the nanowires have a length of several micrometer. These bottom-up nanofabrication based on ion-induced patterning can be a viable alternative to top-down procedures regarding to efficiency and costs.

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

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

The complex network framework has been successfully used to model interactions between entities in Complex Systems in the Biological Sciences such as Proteomics, Genomics, Neuroscience, and Ecology. Networks of organisms at different spatial scales and in different ecosystems have provided insights into
community assembly patterns and emergent properties of ecological systems. In the present work, we investigate two questions pertaining to fish species assembly rules in US river basins, a) if morphologically similar fish species also tend to be phylogenetically closer, and b) to what extent are co-occurring species that are phylogentically close also morphologically similar? For the first question, we construct a network of Hydrologic Unit Code 8 (HUC8) regions as nodes with interaction strengths (edges) governed by the number of common species. For each of the modules of this network, which are found to be geographically separated, there is differential yet significant evidence that phylogenetic distance predicts morphological distance. For the second question, we construct and analyze nearest neighbor directed networks of species based on their morphological distances and phylogenetic distances. Through module detection on these networks and comparing the module-level mean phylogenetic distance and mean morphological distance with the number of basins of common occurrence of species in modules, we find that both phylogeny and morphology of species have significant roles in governing species co-occurrence, i.e. phylogenetically and morphologically distant species tend to co-exist more. In addition, between the two quantities (morphological distance and phylogentic distance), we find that morphological distance is a stronger determinant of species co-occurrences

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

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

During cooling, conventional martensitic transformation can only be realized from austenite to martensite. Recently, a so-called reentrant martensitic transformation obtained much interest due to an additional transformation from martensite to austenite during further cooling. Obviously, materials with this reentrant transformation will increase the number of physical effects and possible applications. However, until now, only bulk samples are reported available, which are not suitable for applications in micro-devices. In this work, ferromagnetic Co-Cr-Ga-Si films were selected as a model system to explore the reentrant transformation behavior in thin films. We observed that the films grow epitaxially on MgO (100) substrates and exhibit a martensitic transformation if deposited at a sufficiently high temperature or with an additional heat treatment. Film within the austenite state are ferromagnetic while films within the martensitic state just exhibit a very low ferromagnetism order.

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

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

Tracers for bimodal optical imaging and positron emission tomography unite multiple ad-vantages in a single molecule. Their tumor-specific uptake can be visualized after their PET-activation by radiofluorination via PET/CT or PET/MRI allowing for staging or therapy planning, while their non-radioactive moiety additionally facilitates the visualization of malig-nant tissue during intraoperative fluorescence-guided surgery or in histological assessments. The silicon-bridged xanthene core offers the opportunity for radiofluorination with SiFA isotope exchange to obtain a small molecule PET-activatable NIR dye that can be linked to different tar-get vectors. Herein, we demonstrate the PET-activation of a fluorinated silicon pyronine, be-longing to a class of low-molecular weight fluorescence dyes with a large Stokes shift and sol-vent-dependent NIR dye properties, with successful radiochemical conversion. Moreover, a li-brary of unusually functionalized, red-shifted silicon rhodamines was synthesized, which can be easily conjugated by amide bond formation or ‘click-reaction’ approaches.

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

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

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

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

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

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

The morphology adaptive multifield two-fluid model OpenFOAM-Hybrid focuses on the reliable and robust simulation of interfacial two-phase flows in real size industrial applications. This requires to combine the Volume-of-Fluid approach with the Euler-Euler model for large and small scale interfacial structures, respectively. The choice of the local representation of interfacial structures, such as bubbles or droplets, by either the first or the second of the aforementioned basic method strongly depends on the ratio of the length scale of the interface feature to the grid spacing. In case the computational grid gets too coarse to locally resolve an interfacial structure anymore, a morphology transfer is required. Such a transfer process allows to convert resolved fluid into non-resolved one, i.e. changing from a continuous description to a dispersed one. A formulation for such a numerically motivated disintegration process is presented and validated with a case of a two-dimensional single rising bubble on a grid with gradually varying cell size. The model is then applied to two further cases: an oil-water phase inversion and a water jet plunging into a free water surface. Hereby, functionality, robustness and feasibility of the proposed morphology transfer mechanism are demonstrated. This work contributes to a hybrid modelling approach for the simulation of two-phase flows adapting the numerical representation depending on local flow morphology and on available computational resources.

Ion-induced surface patterning has turned out to be a highly versatile technique for many applications where large areas of nanostructured surfaces or thin films are required. Both fundamental and applied research may benefit from in-situ studies revealing the kinetics of the patterning process, yielding further insight into the dominant mechanisms and thus enabling to gain precise process control. The surface-sensitive X-ray scattering technique of Grazing Incidence Small Angle X-Ray Scattering (GISAXS) is a well-suited method for such in-situ investigations, allowing for contact-less examination under various external conditions.

Here, we present a real-time in-situ GISAXS investigation of reverse epitaxy patterning in crystalline Ge(001). From the X-ray scattering pattern we deduce the significant morphological parameters of the surface, thus tracking the development of the surface morphology with time during ion irradiation.

These findings are compared with results from simulations based on a continuum equation of the local surface height. Good agreement of the simulation with both experiment and theory was only achieved when including in the continuum equation an additional term for regulating the pattern anisotropy. We then find that a continuum equation considering only diffusive effects reproduces the experimentally observed surface patterning kinetics well.

Observing the kinetics of pattern formation in the non-linear regime, we find that the temporal evolutions of characteristic length and roughness conform to power laws, their exponents agreeing with scaling laws for conserved continuum equations with four-fold symmetry. Moreover, we find that the facet angle kinetics can be described by the Austin-Rickett equation for diffusion-controlled transformation processes, corroborating our assumption of a predominantly diffusive mechanism of pattern formation.

Intricate topographical patterns can form on the surface of crystalline Ge(001) subject to low-energy ion irradiation in the reverse epitaxy regime, i.e., at elevated temperatures which enable dynamic recrystallization. We compare such nanoscale patterns produced by irradiation from varied polar and azimuthal ion incidence angles with corresponding calculated surface topographies. To this end, we propose a continuum equation including both anisotropic erosive and anisotropic diffusive effects. Molecular dynamics simulations provide the coefficients of angle-dependent sputter erosion for the calculations. By merely changing these coefficients accordingly, the experimentally observed surface morphologies can be reproduced, except for extreme ion incidence angles. Angle-dependent sputter erosion is thereby identified as a dominant mechanism in ion-induced pattern formation on crystalline surfaces under irradiation from off-normal incidence angles.

The role of pool scrubbing in attenuating radioactivity release after severe accidents has been explored extensively. It is known that the scrubbing efficiency is largely determined by the hydrodynamic phenomenology in pools. The aerosol gas forms large globules at the nozzle exit, which subsequently break up to a swarm of stable bubbles, where the change of bubble size can reach over two orders. Furthermore, with the increase of flow rates, the injection regime changes from globule to jet characterized by a continuous gas structure. The flow field in the pool can be divided into injection and rise (swarm) two zones according to the gas-liquid interface morphology. In different zones, the scrubbing is governed by different mechanisms such as inertial impact, diffusion and gravity, and bubble shape, size and velocity in addition to particle size are major influential parameters. So far, numerical analysis of pool scrubbing is routinely based on system codes, which rely on empirical correlations for the determination of these parameters. More recently, owing to the increasing availability of computational resources, the knowledge is improved through three-dimensional computational fluid hydrodynamics simulations. Nevertheless, the morphology and regime change represents still a challenge. The conventional two-fluid model is generally effective for bubble size smaller than the cell size, while interface-tracking (capturing) methods demands dozens of cells per bubble size. The present work aims to capture the complex hydrodynamic process in the pool scrubbing with a hybrid multi-field two-fluid model. By comparing with experimental data, the results are shown to be promising.

Numerical modeling of boiling flow is challenging due to the wide range characteristic lengths of the physics at play: from nano/micrometers bubble nucleus to sub-meters flow pattern, particularly, when the role of the nano/micro surface structure attracts more attention recently. To address this, we present here our activities in multiscale approaches e.g the Euler Euler (EE) of boiling flow considering the bubble void fraction distribution and GEneralized TwO Phase flow (GENTOP) model to simulate the large free surface structure, the Direct Numerical Simulation (DNS) of bubble dynamics considering detailed surface structure, the Molecular Dynamics (MD) simulation of bubble static/dynamics wetting, and also the bridging concept between each scale activities. The works are demonstrated on several problems including the contact line region of a nucleation bubble, microlayer beneath the bubble, bubble dynamics on a structured surface, bubble population balance, interfacial forces between dispersed phases, and free surface. These activities highlight the capability of the developed multiscale concept to enhance the robustness of boiling flow simulation, though whose application in nuclear-related processes should be an industry-oriented theme that should be with low time and computer hardware requirements.

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

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

Dispersion phenomena significantly influence the residence time of the fluid phases in gas-liquid contactors and, thus, their yield. With the axial dispersion model (ADM), the effect of dispersion is considered during the process design. However, this requires a reliable quantification of the axial dispersion coefficients.
A novel non-intrusive approach to determine the axial gas dispersion coefficient in bubble columns was recently pronounced by Hampel [1], called gas flow modulation technique (GFM). This approach is based on an imposed marginal sinusoidal modulation on the constant gas inlet flow. This leads to a modulation of the gas holdup in the bubble column, called holdup wave. Along the column axial direction, the gas dispersion damps the rising holdup wave in amplitude and shifts its phase. Amplitude damping and phase shift can be non-invasively determined, e.g., using gamma-ray densitometry to relate it to the value of the axial dispersion coefficient using the ADM. Figure 1 shows the principle of GFM and a simplified scheme of the experimental setup.
Döß et al. [2] applied the GFM to bubble columns for the first time, although only for a narrow range of operating conditions in a 100 mm ID bubble column. The present study proves the applicability of the GFM to larger columns and for a wider range of gas superficial velocities and liquid properties. Experiments were performed in columns of 100, 150 and 330 mm ID at gas superficial velocities ranging from 17 to 47 mm/s. Air was used as the gas phase. Water, aqueous solutions with 2% wt. ethanol and 30% wt. glycerin were used as the liquid phase. This study, together with the uncertainty analyses recently performed by Marchini et al. [3, 4], qualifies the GFM as a viable non-invasive alternative to traditional tracer studies, for measuring the axial gas dispersion coefficient in bubble columns.

The uniformity of the gas distribution in bubble columns strongly depends on the gas sparger design. For example, not all holes of a perforated plate sparger with relatively high fractional free area are active at the same time. This is true especially at low gas flow rates. Consequently, the random activation of the holes causes gas maldistribution in the radial as well as in the axial directions. Contrary, needle spargers provide rather uniform distribution at the same operating conditions.
Since dispersion phenomena depend on the gas holdup gradient, the gas maldistribution is expected to affect the dispersion. Surprisingly, only few publications address the possible influence of the sparger on gas dispersion. An exception is the study of Kölbel [1]. They measured the axial gas dispersion coefficient in a bubble column using a monolithic type of sparger. Here, the obtained gas dispersion coefficients run through a minimum while increasing the gas superficial velocity. Contrary, literature frequently reports axial dispersion coefficients that increase monotonously with the gas superficial velocity (e.g., [2], [3]).
The objective of the present study was to resolve this discrepancy. Experiments were performed in a 100 mm ID column using three different spargers, namely: a perforated plate sparger with (a) 50 holes of 0.6 mm diameter corresponding to a fractional free area of 0.18%, (b) with 38 holes of 1.0 mm and 12 holes of 1.5 mm corresponding to a fractional free area of 0.66%, and (c) a needle sparger made of 31 needles with 0.8 mm inner diameter each.
Axial dispersion was experimentally measured applying the gas flow modulation technique, which is a tracer-free approach explained by Marchini et al. [4, 5].
The results showed that the above mentioned minimum found by Kölbel [1] is reproducible for spargers with high fractional free area. Figure 1 reports the determined axial dispersion coefficients as a function of the gas superficial velocity for all considered spargers. The minimum is less evident for the considered sparger with lower fractional free area and, finally, it is not identified for the needle sparger.
Considering that dispersion causes back-mixing, which often has a detrimental effect on process yield, the presence of such a dispersion minimum can be considered as an additional option for process optimization in the future. However, more studies are required to reliably predict the occurrence of such dispersion minimum depending on sparger design and operating conditions.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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