Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Benefitting from the rapid expansion of consumer electronics (CE), plenty of new electronic products are introduced into the market annually. At the same time, due to the short life span of such products and the rapid emergence of new generations, large quantities of electronic waste are produced. The objective of this thesis is obtaining information on printed circuit boards (PCB) composition through non-invasive analysis using RGB (red, green and blue) and hyperspectral data to aid in recycling precious metals from recycled PCBs. The obtained information will be useful in more efficient processing of E-waste by harnessing deep learning networks. The goal of the thesis is to identify the surface mounted devices of a PCB such as the integrated circuits, connectors, capacitors, resistors etc. through the spatial information available in RGB images. The information obtained will be used in conjunction with HSI (Hyperspectral Images) to localise the detection area to recognise the composition of the PCB. We utilize spectral signatures of materials derived from HSI's and combining the spectral and spatial information to obtain a more precise recognition of the composition of a PCB. While hyperspectral data finds its use mostly in the remote sensing community to aid geological exploration, the application of this technology in the area of PCB recycling shows promise. The RGB images and HSI are collected by the multi-sensor system at the Helmholtz Institute Freiberg for Resource Technology (HIF) and supplements the training of the neural networks with the public data sets available from analogous research to localize the area of analysis for HSI based recognition. The neural network chosen for the application is the Faster Regional Convolutional Networks (Faster-RCNN) and we propose a guided anchoring method that utilizes Hyperspectral data to further improve the detection accuracy of the RGB based Faster RCNN, thereby including both spatial and spectral information of the PCBs. The results are then shown in comparison to demonstrate that the cross modal guided anchoring has a pronounced effect on the detection accuracy of the object detection network.

Neben dem Problem des Schimmelpilzbefalls in Orgel-Instrumenten existiert das Problem der Korrosion von metallischen Orgelbestandteilen aus Blei/Zinn- sowie Kupfer/Zink (Messing)-Legierungen. Dabei werden die labialen Orgelpfeifen aus den Blei/Zinn-Legierungen gefertigt, während Messingteile für die Tonerzeugung in Zungenpfeifen verwendet werden. Die Korrosion erfolgt vor allem durch Ausdiffusion von Gerb-bzw. Ameisensäure aus dem in Orgeln verbauten Holz, wobei die Luftfeuchtigkeit der Umgebung eine katalytisch verstärkende Wirkung hat. Legierungen mit hohem Bleigehalt (>95%) sind dabei besonders gefährdet. Unsere Experimente konzentrierten sich auf Laborexperimente zur Korrosion entsprechender Legierungsproben aus dem Orgelbau mittels verdünnter Essigsäure (2–5 v/v%). Zuvor waren die Proben mit zwei verschiedenen Verfahren zur Erzeugung einer nanoskaligen Schutzschicht behandelt worden: (1) Gepulste Laserabscheidung bzw. Sputtern von Al2O3 -oder Al-Schichten gefolgt von Stickstoffbestrahlung mittels Plasmaimmersion, und (2) plasma-gestützte chemische Dampfphasenabscheidung (CVD) von SiOx. Während das erstere Verfahren ein Vakuumprozess ist, erfolgt das zweitgenannte Verfahren bei Atmosphärendruck. Die Barriere-Schichten wurden erfolgreich im Labor erprobt. Messing-Proben, beschichtet nach Verfahren 1, wurden in einem Feldexperiment in einer Mecklenburger Kirche mit besonders hohem Korrosionspotential für 15 Monate nach Einbau in reale Pfeifen ebenso erfolgreich getestet.

Vortrag anläßlich der Inauguration von Prof. Thoralf Gebel an der Hochschule Mittweida - (University of Applied Science), Fakultät Wirtschaftsingenieurwesen, Lehrstuhl Industrial Management mit den Schwerpunkten Innovationsmanagement und Consulting

Pipe organs with their unique musical sound are important objects of the cultural heritage. Such instruments consist of a number of pipes (flute and reed), which are prone to heavy corrosion attack, getting finally voiceless. The atmospheric corrosion of reed (CuZn alloys) and flute pipes (PbSn alloys) is strongly enhanced by traces of volatile organic compounds (VOCs) and the alloy’s instability. Moreover, there is a strong impact of humidity in the corrosion process. Experiments have been undertaken to explore the suppression of an aqueous corrosion with acetic acid concentration (2–5 v/v%) of CuZn and PbSn alloys, by deposition of nanocoating using two different methods: (i) Pulsed laser- or Magnetron sputtering deposition of Al2O3 or Al followed by plasma immersion ion implantation of nitrogen as a vacuum technology, and (ii) Plasma enhanced CVD of SiOx films at atmospheric pressure. The nanocoating is then able to withstand acoustic vibrations of organ pipes, and it produces a barrier to VOCs and water vapor. The laboratory corrosion tests were combined with field studies to approach environmental conditions. Some of the samples were exposed for 15 months to harmful indoor environment in North-German church. Surface modification of metallic alloys based on ion-solid interactions as well as plasma-based processing creates new paths in restoration and conservation technologies to protect our historical and modern cultural heritage against environmental attacks.

The mechanical and chemical properties of a compound material are determined by the fractional abundances of its components. In this work, we present a spectral unmixing technique to estimate the fractional abundances of the components of mixed and compound materials from hyperspectral images. The estimation of fractional abundances in mixed materials faces the main challenge of intimate mixing. In compound materials, the mixing with water causes changes in chemical properties resulting in spectral variability and non-linearity. To address these challenges, a supervised method is proposed that learns a mapping from the hyperspectral data to spectra that follow the linear mixing model. Then, a linear unmixing technique is applied on the mapped spectra to estimate the fractional abundances. To demonstrate the potential of the proposed method, experiments are conducted on hyperspectral images from mixtures of red and yellow clay powders and hardened mortar samples with varying water to cement ratios.

The imbalance between the (often limited) number of available training samples and the high data dimensionality, together with the presence of mixed pixels, often complicates the classification of remotely sensed hyperspectral data. In this paper, we tackle these problems by developing a new method that combines spectral unmixing and classification techniques in a subspace-based approach. The proposed method is developed under the assumption that the spectral signature of a land cover class is associated with a given set of pure spectral signatures (called endmembers in spectral unmixing terminology), which define a low-dimensional subspace with clear physical meaning. We aim to exploit this relationship to learn the class-dependent subspaces and integrate them with a multinomial logistic regression procedure. Experiments on synthetic datasets and real hyperspectral images show that our method is able to obtain competitive performances in comparison with other approaches, particularly when very limited training sets are available.

Non-covalent nanohybrids composed of cationic 5,10,15,20-tetra(4-trimethylammoniophenyl)porphyrintetra(p-toluenesul-fonate) (TMAP) and the graphene oxide sheets were prepared under two pH values (6.2 vs. 1.8).The TMAP molecule was positively charged, regardless of the pH value during preparation. However, protonation of the iminonitrogens increased the overall charge of the porphyrin molecule from +4 to +6 (TMAP4+ and TMAP6+). It was found that at acidic pH,interaction of TMAP6+ with GO was largely suppressed. On the other hand,results of FTIR, Raman spectroscopy, thermogravimetric analysis, atomic force microscopy (AFM) and elemental analysis confirmed effective non-covalent functionalization of graphene oxide with cationic porphyrinat pH 6.2. The TMAP4+-GO hybrids exhibited well defined structure with a monolayer of TMAP4+ on the GO sheets as confirmed by AFM.Formation of the ground-stateTMAP4+-GO complex in solution was monitored by the red-shift of the porphyrin Soret absorption band.This ground-state interaction between TMAP4+ and GO is responsible for the static quenching of the porphyrin emission.Fluorescence was not detected for the nanohybrid which indicated that a very fast deactivation process had to take place.Ultrafast time-resolved transient absorption spectroscopy clearly demonstrated the occurrence of electron transfer from the photoexcited TMAP4+ singlet state to GO sheets,as proven by the formation of a porphyrin radical cation.

A theoretician of the first water, Axel Brandenburg has always been interested in experimental MHD as well. Anecdotal evidence has it that he is the only person who witnessed in operation the three successful dynamo experiments in Riga, Karlsruhe and Cadarache. Axel’s theoretical work, in turn, has inspired experimentalists more often than not. One case in point is his early work on nonlinear and highly supercritical dynamos which has motivated investigations into the common mechanism underlying the field reversals of the geodynamo and the VKS dynamo. These efforts lead to the complementary explanations of reversals in terms of spectral exceptional points of non-selfadjoint dynamo operators, or via saddle-node bifurcations. In this context, we shortly report the construction progress of the DRESDYN precession driven dynamo, the set-up of which was partly motivated by the signature of Milankovic cycles in the reversal statistics of the geodynamo.
The second part of the talk refers to Axel’s work on massively non-linear, “self-creating” dynamos, such as the MRI dynamo or the Tayler-Spruit dynamo. Here we summarize some previous experiments on the magnetorotational instability (MRI) and the Tayler instability (TI), and present some recent results on double-diffusive instabilities for rotating flows with positive shear. The talk will close with a highly speculative idea which connects the oscillatory behaviour of the TI-related alpha-effect to the persistent synchronization of the solar dynamo with the 11.07 years periodic alignments of the tidally dominant planets Venus, Earth and Jupiter.

Due to the complex interaction of light with the Earth’s surface, reflectance spectra can be described as highly nonlinear mixtures of the reflectances of the material constituents occurring in a given resolution cell of hyperspectral data. Our aim is to estimate the fractional abundance maps of the materials from the nonlinear hyperspectral data. The main disadvantage of using nonlinear mixing models is that the model parameters are not properly interpretable in terms of fractional abundances. Moreover, not all spectra of a hyperspectral dataset necessarily follow the same particular mixing model. In this work, we present a supervised method for nonlinear spectral unmixing. The method learns a mapping from a true hyperspectral dataset to corresponding linear spectra, composed of the same fractional abundances. A simple linear unmixing then reveals the fractional abundances. To learn this mapping, ground truth information is required, in the form of actual spectra and corresponding fractional abundances, along with spectra of the pure materials, obtained from a spectral library or available in the dataset. Three methods are presented for learning nonlinear mapping, based on Gaussian processes, kernel ridge regression, and feedforward neural networks. Experimental results conducted on an artificial dataset, a data set obtained by ray tracing, and a drill core hyperspectral dataset shows that this novel methodology is very promising.

Noncovalent nanohybrids between meso-(p-hydroxyphenyl)porphyrin (TPPH) and graphene oxide (GO)sheets were studied as a function of pH. The overall charge of theTPPH molecule changes between negative (−4), neutral, and positive (+2) depending on the pH of the solution. Results of Fourier transform infrared spectroscopy, thermogravimetricanalysis, and elemental analysis confirm successful noncovalent functionalization of GO sheets with TPPH. We applied a numberof methods to probe the ground-state as well as the excited-state interaction between the components of the new material. The experimental results were additionally supported by theoretical calculations that included optimizations of the ground-state structures of TPPH and TPPH2+and their complexes with amolecular model of GO. It was demonstrated that both TPPHand TPPH2+molecules can be assembled onto the surface of GO, but it was clearly shown that the stronger interaction with GO occurs for TPPH2+. The stronger interaction in the acidic environment can be rationalized by the electrostatic attraction between positively charged TPPH2+ and negatively charged GO, whereas the interaction between TPPH4−and GO at basic pH was largely suppressed. Our comprehensive analysis of the emission quenching led to the conclusion that it was solely attributed to static quenching of the porphyrin by GO. Surprisingly,fluorescence was not detected for the nanohybrid, which indicates thata very fast deactivation process must take place. Ultrafast time-resolved transient absorption spectroscopy demonstrated that although the singlet excited-state lifetime of TPPH2+adsorbed on the GO sheets was decreased in the presence of GO from 1.4ns to 12 ps, no electron-transfer products were detected. It is highly plausible that electron transfer takes place and is followed by fast back electron transfer.

We study the intercalation of alkali metals, namely lithium and sodium, between graphene and MoS2 sheets using density functional theory calculations with the van der Waals correction. The structures and energetics of a different number of alkali layers with closed packed structures have been investigated for various stacking sequences of bilayer graphene. The intercalation energies suggested that the AA stacking is more favorable for the single-layer intercalation but it has no considerable effect on multilayer storage. Our calculations showed that there is a clear correlation between the intercalation energy and the electron transfer between alkali atoms and layered material. While the higher values of charge transfer observed for the single-layer intercalation, the charge transfer is noticeable only for the outer alkali layers in the multi-layer case. As a result, the intercalation energy reduces with increasing the number of the lithium and sodium layers but reduces for potassium. In the case of lithium intercalation between MoS2 bilayers, a 2H-1T phase transition was observed due to the
significant charge transfer. The present study can shed light on the design of high storage alkali batteries using two-dimensional layered materials as reported recently.

Ion irradiation techniques have been extensively used for material modification, post-synthesis engineering and imaging purposes. Although the response of bulk targets to ion irradiation has been studied at length, including simulations, much less is known about the effects of ion bombardment on two-dimensional (2D) materials. 2D transition metal dichalcogenides (TMDs) have shown outstanding physical properties which make them intriguing candidates for various nanoelectronic and optoelectronic applications. We have studied the effects of ion irradiation on freestanding and supported 2D TMDs by using analytical potential molecular dynamics combined with Monte Carlo simulations. We characterized the types and assess the abundance of point defects in our structures as a function of ion energy, mass and incident angle. Furthermore, we studied the irradiation with highly charged ions (HCIs) for the fabrication of well-defined pores in MoS2 monolayer. The simulations indicated a dependence of the pore size on the potential energy of the projectile and suggested enrichment in molybdenum in the vicinity of the pore edges. These findings help to understand the fundamental physical mechanisms underlying ion irradiation of low-dimensional materials and finding optimum parameters for defect engineering of 2D TMDs with optimized properties

Two-dimensional (2D) materials feature exceptional electronic and optoelectronic properties controlled by the strong confinement in the third dimension. Here, we present calculations within the framework of density functional theory (DFT) to assess the change of 2D materials and their properties under the influence of deviations from the purely 2D nature.
Significant changes to the electronic and optical properties have been monitored already in free-standing 2D layers when comparing structurally perfect monolayers and slightly thicker multilayer structures of the same material, although the multilayer still obeys the same ideal 2D periodicity as the monolayer does. This effect becomes more pronounced once the in-plane symmetry is reduced by rotational stacking faults between the layers of a single 2D material, in van-der-Waals bound heterostructures with other 2D materials, or in the proximity of the substrate. If the adjacent 2D crystal lattices are (nearly) commensurate, such structures still obey periodic boundary conditions in-plane, but with larger superlattice vectors. In that case, the electronic structure undergoes additional modulations within the supercell, which are then periodically repeated in 2D. From a symmetry point of view, the decoration of 2D materials with two-dimensionally periodic assembled organic films may lead to very similar lateral superlattice features, although the interaction of the 2D layer and the individual molecules of the film is local. That provides the possibility to use molecular functionalization for enhancing or suppressing such superlattice features in a predefined way. Finally, decoration can also be employed to heal local structural and electronic defects, which occur depending on the synthesis conditions and break the ideal 2D periodicity of realistic samples. Electronic confinements along 1D boundary lines or localized states at intrinsic defects on the faces cause rather strong local and non-periodic changes of the 2D properties. Calculations suggest that in the limit of low defect density, i.e., below the percolation threshold, the long-range properties of such systems still maintain their 2D nature, but additional effects, such as scattering may result from the interaction with the defects.
Molybdenum sulfide is a well-studied binary 2D material, which exhibits all those effects without the need to add additional elements, e.g. hydrogen, to saturate dangling bonds at termination sites. The implications for other, electronically more complex materials such as graphene will be discussed.

Grazing Incidence Small Angle X-ray Scattering (GISAXS) has been established as a versatile tool for comprehensive morphological characterization of surfaces on the nanometer scale. As a contact-less technique it lends itself especially to in-situ monitoring of surface nanopattern development or the growth of supported nanostructures under various conditions such as reactive atmospheres, high temperatures, applied fields, or ion irradiation. A GISAXS intensity pattern is a representation of the shapes, sizes, as well as lateral and vertical arrangements of three-dimensional structures in reciprocal space, in dependence of the direction of the incident X-ray beam. Complementary to local imaging techniques such as atomic force microscopy (AFM), it provides information on the average surface morphology of the extended area covered by the footprint of the X-ray beam. We implemented an in-situ ultra-high vacuum setup at the ISR beamline of the NSLS-II synchrotron combining GISAXS with low-energy broad-beam ion irradiation, providing sample rotation as well as heating to several hundred degrees Celsius. This setup allows us to observe the nanoscale pattern formation kinetics on crystalline semiconductors in-situ under ion irradiation. We studied the pattern formation on Ge(001) surfaces, where the crystallinity of the surface under ion irradiation is ensured by heating the sample above its recrystallization temperature. The Ge(001) surface is known to develop a pit-and-mound pattern of faceted pyramidal structures under irradiation with 1 keV Ar+ ions. The edges of the pyramidal structures are aligned along the <100> and <010> direction, while their sidewall facets have a uniform polar tilt from the <001> direction. Such a regular surface morphology results in a distinct GISAXS intensity pattern. From the development of the GISAXS pattern features with ion fluence, we can conclude on the corresponding development of the surface morphology. Using this technique, we monitor the lateral correlation length as well as the polar facet angle and the azimuthal pattern orientation as indicators of the kinetics of this ion-induced self-assembly process.

MULSEDRO is an EIT RawMaterials project of a consortium of Finnish, German, Danish and Swedish institutions and companies that aims to develop multi-sensor drone systems for mineral exploration. In September 2018, a field campaign was performed to test the newly designed UAS systems at the Otanmäki Fe–Ti–V deposit in central Finland. In this report, the acquisition and processing of UAS-based magnetic, multi- and hyperspectral datasets in Otanmäki are described. In order to validate the drone-borne data, a ground magnetic survey was acquired and in situ measurements with hhXRF and VNIR-SWIR spectrometers, as well as magnetic susceptibility meter measurements, were performed. A strategy for integrating all the data is introduced, aiming to improve the mapping and evaluation of the near-surface oxide ore distributions.
The survey area was covered with four magnetic UAS surveys using both multi- copter and fixed-wing drones equipped with fluxgate magnetometers. The drones op- erated at different altitude levels (15, 40 and 65 m a.g.l.) and line spacings (7, 20, 35 and 40 m), resulting in magnetic information with very different scales of resolution. An equivalent layer modelling (ELM) procedure was jointly applied to all the magnetic datasets to present the magnetic surveys with very different acquisition parameters in one consistent total magnetic intensity plot and to evaluate the consistency of data from the different magnetic surveys. Multi- and hyperspectral data were acquired at a high resolution and geolocated with precisely spatially surveyed control points. Although the lichen and vegetation coverage reduced the total number of visible bare ground pixels by roughly 30%, the application of different band ratios and classification algorithms made it generally possible to adequately map iron-bearing alteration minerals such as hematite and goethite from the UAS-based datasets.
The combination of lightweight UAS technologies and ground truthing measurements was demonstrated to be advantageous in rapidly mapping ore-rich outcrops and created a multi-parameter and multi-scale dataset well suited to data integration. The magnetic maps correlated well with both susceptibility values from profiling and ore occurrences visible at the surface, and the iron-bearing phases could be successfully mapped by UAS-borne multi- and hyperspectral sensors in the VNIR. The acquired datasets partly complement each other, e.g. UAS-borne magnetic anomalies can be associated with ore lenses in areas where spectral features are hidden by lichen or vegetation.

The talk investigates the formation of interlayer excitons as a function of heterostack composition for MoS2 and GaSe.
The composition of the stack has a large influence of the exciton binding energy.
As experimentally fabricated stacks are large, theoretical data need to be extrapolated slightly.
This finally results in a theoretical prediction closer to experimental observations of the interlayer excitons.

Low-energy ion-irradiation of semiconductors above their recrystallization temperature has been shown to induce regular nanoscale patterning of the crystalline surface. The mechanism is called reverse epitaxy in analogy to epitaxy in growth: ion-induced mobile vacancies and ad-atoms on the crystalline surface encounter the Ehrlich-Schwoebel energy barrier for crossing terrace steps and exhibit preferential diffusion along specific in-plane directions. This can lead to the formation of well-defined faceted surface structures with morphologies strongly dependent on crystalline structure and surface orientation. For instance, GaAs(001) and InAs(001) develop periodic ripple structures with a saw tooth profile.
We have studied the topological defects in ion-induced patterns on GaAs(001) and InAs(001), i.e. ripple junctions, and present results from both experiments and simulations on the following aspects:
-- defect morphology and the influence of polar and azimuthal ion incidence angles thereon
-- dependence of the defect density on sample temperature and ion energy
-- temporal evolution of the defect density
-- defect motion and annihilation processes
We find strong dependencies on the easily controllable external process parameters, which is crucial information when preparing ion-induced surface patterns for specific applications.

Computational modeling is an important aspect of the research on nuclear waste materials. In particular, atomistic simulations, when used complementary to experimental efforts, contribute to the scientific basis of safety case for nuclear waste repositories.
Here we discuss the state-of-the-art and perspectives of atomistic modeling for nuclear waste management on a few cases of successful synergy of atomistic simulations and experiments. In particular, we discuss here: (1) the potential of atomistic simulations to investigate the uranium oxidation state in mixedvalence uranium oxides and (2) the ability of cementitious barrier materials to retain radionuclides such as 226Ra and 90Sr, and of studtite/metastudtite secondary peroxide phases to incorporate actinides such as Np and Am. The new contribution we make here is the computation of the incorporation of Sr by C-S-H (calcium silicate hydrate) phases

Terahertz (THz) frequency range contains wave-lengths between 3 mm to 30 µm that corresponds to the energies between 0.4 meV to 40 meV. Spectroscopy in this range plays very important role in an understanding the solid state physics as there are multiple low energy excitations (phonons, magnons, Higgs mode etc.) that determine numerous physical parameters of the matter. Not only to perform THz spectroscopy but to coherently manipulate the phase of matter through these excitations it is required to develop high field narrow band THz radi-ation sources with very sensitive probing techniques.
THz user facility TELBE at Helmholtz-Zentrum Dresden-Rossendorf provides quasi CW SRF accelerator based narrowband THz radiation at high repetition rates. The source is based on superradiant principle that ena-bles high degree of CEP stability, operation in deep THz frequencies tunable between 100 GHz to 3 THz and rep-etition rates up to MHz range [1]. The bandwidth of radi-ation is 10-15 % with pulse energies up to 2-3 µJ in a fundamental band (up to 100 µJ as design parameter) that results in few 100 kV/cm peak field strength. Using pulse-resolved technique we can reach few femto-second synchronization with ultra-fast laser system that is crucial for studying ultrafast dynamics [2]. The listed above parameters outperform state of the art high repeti-tion rates laser based THz sources and are important for observing novel high field THz phenomena. In this con-tribution we present concept of superradiant THz sources and our recent results on observing novel high field te-rahertz phenomena making use of such sources. Among the experimental results we will present THz high har-monic generation in Dirac materials, Higgs spectroscopy of high TC superconductors and spintronic based THz oscillators.

From the perspective of wafer-level integration technologies, this work presents theoretical and experimental insights on fundamental device properties of single-walled carbon nanotubes (SWCNTs) based giant piezoresistive transducers. The role of contacts in such devices and their contribution to a significant tunneling-related sensitivity enhancement is demonstrated. The origin of this phenomenon is the strain dependence of the effective Schottky barrier (SB) width which is modulated by a drain-source voltage (VDS) dependent large built-in electric field F at the Schottky-barrier (SB), which defines the effective SB width and can be controlled via VDS. Moreover, perspectives for forthcoming sensor generations exposing operation regimes beyond intrinsic sensitivity are revealed.

Quantum bit or qubit is a two-level system, which builds the foundation for quantum computation, simulation, communication and sensing. Quantum states of higher dimension, i.e., qutrits (D = 3) and especially qudits (D = 4 or higher), offer significant advantages. Particularly, they can provide noise-resistant quantum cryptography, simplify quantum logic and improve quantum metrology. Flying and solid-state qudits have been implemented on the basis of photonic chips and superconducting circuits, respectively. However, there is still a lack of room-temperature qudits with long coherence time and high spectral resolution. The silicon vacancy centers in silicon carbide (SiC) with spin S = 3/2 are quite promising in this respect. Here, we report a two-frequency protocol to excite and image multiple qudit modes in a SiC spin ensemble under ambient conditions. Strikingly, their spectral width is about one order of magnitude narrower than the inhomogeneous broadening of the corresponding spin resonance. By applying Ramsey interferometry to these spin qudits, a spectral selectivity of 600 kHz and a spectral resolution of 30 kHz are achieved. As a practical consequence, we demonstrate absolute DC magnetometry insensitive to thermal noise and strain fluctuations.

One of the challenges in the field of quantum sensing and information processing is to selectively address and coherently manipulate highly homogeneous qubits subject to external perturbations. Here, we present room-temperature coherent control of high-dimensional quantum bits, the so-called qudits, associated with vacancy-related spins in silicon carbide enriched with nuclear spin-free isotopes. In addition to the excitation of a spectrally narrow qudit mode at the pump frequency, several other modes are excited in the electron spin resonance spectra. We demonstrate selective quantum control of homogeneous spin packets with sub-MHz spectral resolution. Furthermore, we perform two-frequency Ramsey interferometry to demonstrate absolute DC magnetometry, which is immune to thermal noise and strain inhomogeneity.

The atomistic-level understanding of iron speciation and the probable oxidative behavior of iron (Feaq 2+→Fesurf 3+ ) in clay minerals is fundamental for environmental geochemistry of redox reactions. Thermodynamics analysis of wet chemistry data suggests that iron adsorbs on the edge surfaces of clay minerals at distinct structural sites commonly referred as strong- and weak-sites (with high and low affinity, respectively). In this study, we applied ab initio molecular dynamics simulation to investigate the structure and stability of edge surfaces of trans- and cis-vacant montmorillonites. These structures were further used to evaluate the surface complexation energy and to calculate reference ab initio X-ray absorption spectra (XAS) for distinct inner-sphere complexes of Fe. The combination of ab initio simulations and XAS allowed us to reveal the Fe-complexation mechanism and to quantify the Fe partitioning between the high and low affinity sites as function of the oxidation state and loadings.
Although, iron is mostly present in Fe3+ form, Fe2+ increasingly co-adsorb with increasing loadings. Ab initio structure relaxations of several different clay structures with substituted Fe2+/Fe3+ in the bulk or at the surface site showed that the oxidative sorption of ferrous iron is an energetically favored process at several edge surfaces of Fe-bearing montmorillonite.

We explore saturable absorption and terahertz photoluminescence emission in a set of n-doped Ge/SiGe asymmetric coupled quantum wells, designed as three-level systems (i.e., quantum fountain emitter). We generate a non-equilibrium population by optical pumping at the 1→3 transition energy using picosecond pulses from a free-electron laser and characterize this effect by measuring absorption as a function of the pump intensity. In the emission experiment we observe weak emission peaks in the 14-25 meV range (3-6 THz) corresponding to the two intermediate intersubband transition energies. The results represent a step towards silicon-based integrated terahertz emitters.

We report third-harmonic generation (THG) of terahertz free-electron laser (FEL) pulses in Si:B at cryogenic temperatures. The physical mechanism of THG is attributed to the free-carrier χ(3) nonlinearity due to the non-parabolicity of the valence band. The value of χ(3) increases as a function of the carrier density, which are generated via impact ionization of the boron dopants under irradiation by the FEL pulses. By positioning the Si:B in a one-dimensional photonic crystal (1D PC) cavity, the measured THG intensity increases by a factor of about 200.

The modification of solids by ion irradiation is a longstanding research objective driven by the urge for controlled defect engineering. By incorporating defects in a host material, the electronic, optical and magnetic properties of a solid can be modified. Especially in low-dimensional materials, like 2D layers, the presence of defects may significantly change their performance in applications. Highly charged ions (HCIs) are an effective tool for nanostructure formation on surfaces [1,2]. For HCI impact on a surface, nanostructure formation is driven by the deposition of the potential energy in very shallow depths in the order of nanometers. Recently, pore formation in 2D materials, like carbon nanomembranes [1] or MoS₂ [2], was observed by HCI impact despite the fact that their atomic thickness is limiting the amount of energy, which can be deposited. By measuring the charge exchange of HCIs transmitted through a monolayer of MoS₂, we can provide an upper estimate for the energy transferred to the layer available for pore formation in MoS₂. Additionally, we can gain insights into non equilibrium charge state effects, i.e. the neutralization behavior of the projectile and the charge state dependent kinetic energy loss.
The exit charge state of the ions transmitted through a suspended monolayer of MoS₂ placed on a TEM grid is measured simultaneously with their time-of-flight (TOF) [3].
A two-dimensional charge state and scattering angle resolved spectrum is measured. Two distinct exit charge state distributions at high and low charge states are observed. The distribution at high charge states is accompanied by small scattering angles, which indicates collision events taking place at large impact parameters. On the contrary, the distribution at low charge states is characterized by larger scattering angles pointing to collisions occurring at small impact parameters. We can associate both exit charge state distributions with two well separated peaks in the TOF signal corresponding to slow and fast transmitted ions, i.e. high and low energy loss, respectively. The low exit charge state distribution was already observed for HCI interaction with graphene. Neutralization times of a few femtoseconds were determined previously [4], which could only be explained by ion de-excitation via an Interatomic Coulombic Decay process. This common neutralization behavior for graphene and MoS₂ implies a common de-excitation mechanism for HCI interaction for both target materials. The additional high exit charge state distribution for MoS₂ is interpreted as a feature related to the different crystalline structure of the material in contrast to graphene. Our experimental results are supported by computer simulations using the Monte-Carlo code TDPot [5], which also reveals two distinct interaction regimes of the incident ions within the unit cell of MoS₂.
[1] R. A. Wilhelm et al., 2D Mater. 2, 035009 (2015).
[2] R. Kozubek et al., J. Phys. Chem. Lett. 10, 904-910 (2019).
[3] J. Schwestka et al., Rev. Sci Instrum. 89, 085101 (2018).
[4] R. A. Wilhelm et al., Phys. Rev. Lett. 119, 103401 (2017).
[5] R. A. Wilhelm and P. L. Grande, Commun. Phys. 2, 89 (2019).

Highly charged ions (HCIs) are an efficient tool for the perforation of suspended 2D materials. Only a fraction of their potential energy is transferred to the atomically thin target during the very short interaction time and is available for pore formation. Charge exchange spectra were measured for highly charged xenon ions transmitted through suspended, single layer MoS₂ in order to determine the deposited potential energy available for pore formation. Additionally, charge exchange dependent ion stopping responsible for kinetic sputtering was measured simultaneously.

High energy ion beams as a powerful tool for the surface analysis of the elemental composition of almost any sample.

2D materials offer extraordinary optical, electronic and mechanical properties, which make them interesting for future applications. Modification techniques, like ion irradiation, allow to alter their properties to specific applications. However, because of their atomic thickness applied techniques have to address mainly the surface region. Highly charged ions are a novel tool for nanostructure formation. They carry potential energies up to tens of keV, which trigger the process of nanostructure formation due to the energy deposition in shallow depths in close vicinity of the surface region. Recently, HCI impact induced nanoholes in carbon nanomembranes [1] and in suspended monolayer MoS₂ [2] have been observed despite their atomic thickness limiting the amount of potential energy to be transferred. Here, we investigate the charge exchange of highly charged xenon ions passing a monolayer of MoS₂, from which we can obtain an upper estimate of the deposited energy. The exit charge states of transmitted ions are measured simultaneously with their scattering angle as well as with their time-of-flights [3]. Two distinct distributions at high and low charge states are visible. The different scattering angles indicate the existence of two impact parameter regimes leading to two (exit charge state) distributions. Our experimental results are supported by computer simulations using the Monte-Carlo code TDPot [4].
[1] R. A. Wilhelm et al., 2D Mater. 2, 035009 (2015).
[2] R. Kozubek et al., J. Phys. Chem. Lett. 10, 904-910 (2019).
[3] J. Schwestka et al., Rev. Sci Instrum. 89, 085101 (2018).
[4] R. A. Wilhelm and P. L. Grande, Commun. Phys. 2, 89 (2019).

We investigate the effect of a static, horizontal magnetic field on a liquid metal Rayleigh-Bénard convection by means of laboratory experiments. Although a static magnetic field acts as a stabilizing force on the fluid, we find that self organized convective flow structures reach an optimal state where the heat transport significantly increases and convective velocities perpendicular to the magnetic field reach the theoretical free-fall limit. Our measurements show that the application of the magnetic field leads to an anisotropic, highly ordered flow structure and a decrease of the turbulent fluctuations. When the magnetic field strength is increased beyond the optimum, Hartmann braking becomes dominant and leads to a reduction of the heat and momentum transport. The results are relevant for the understanding of magneto-hydrodynamic convective flows in planetary cores and stellar interiors in regions with strong toroidal magnetic fields oriented perpendicular to the temperature gradient.

2D materials are promising candidates for electronic and photonic applications in future devices. Their properties can be tailored by surface sensitive modification techniques, like ion irradiation. Usually single charged ions are used, which deposit the main part of their kinetic energy in depths well below the surface. Only a tiny fraction is converted into the sputtering of target atoms. In contrast, highly charged ions (HCIs) carry additional potential energy in the keV regime, which may even exceed their kinetic energy. The deposition of the potential energy causes intense excitation and ionization of the electronic system of the target atoms in a shallow surface region. The high density of electronic excitations may lead to local temperatures above the sublimation point and finally to the creation of nanostructures. Even for freestanding 2D materials, like carbon nanomembranes, which consist of only a few atomic layers, pore formation induced by HCIs was observed. The small thickness of 2D materials enables spectroscopic measurements of the HCIs after transmission with respect to their charge state and kinetic energy. From our data we can estimate the amount of energy deposited in the material and therefore available for pore formation. In the present study, the influence of target properties on the charge exchange and on the neutralization dynamics is investigated. Spectroscopic measurements of the charge state of transmitted ions were performed using monolayers consisting of graphene, MoS₂ and hBN, which show different band gap energies between 0 and 6 eV, conductance properties (semi-metallic, semi-conducting and insulating) and layer structures.

The neutralisation of ions due to their interaction with matter deals with fundamental aspects of ion-solid interaction, e.g.: How does the kinetic energy loss depend on the charge exchange? In order to investigate the neutralisation behaviour, classical ion beam foil experiments were performed using ultimately thin 2D materials as target. Because of their low thickness, an ion with a sufficiently high incident charge state does not reach charge equilibrium, which enables the measurement of the non-equilibrium exit charge state distribution. The influence of target material properties on the charge exchange is investigated for 2D materials consisting of graphene, MoS₂ and hBN, which show different band gap energies between 0 and 6 eV, conductance properties (metallic, semi-conducting and insulating) and layer structures.

The main origin of the chiral symmetry breaking and, thus, for the magnetochiral effects in magnetic materials is associated with an antisymmetric exchange interaction, the intrinsic Dzyaloshinskii-Moriya interaction (DMI). Recently, numerous inspiring theoretical works predict that the bending of a thin film to a curved surface is often sufficient to induce similar chiral effects. However, these originate from the exchange or magnetostatic interactions and can stabilize noncollinear magnetic structures or influence spin-wave propagation. Here, we demonstrate that curvature-induced chiral effects are experimentally observable rather than theoretical abstraction and are present even in conventional soft ferromagnetic materials. We show that, by measuring the depinning field of domain walls in the simplest possible curve, a flat parabolic stripe, the effective exchange-driven DMI interaction constant can be quantified. Remarkably, its value can be as high as the interfacial DMI constant for thin films and can be tuned by the parabola’s curvature.

Acting at high speed enables creatures to survive in their harsh natural environments. They developed strategies for fast actuation that inspire technological embodiments like soft robots. Here, we demonstrate a series of simulation-guided lightweight, durable, and untethered soft-bodied robots performing large-degree deformations at unprecedentedly high frequencies of up to 200 Hz, driven at very low magnetic fields down to 0.5 mT, and exhibit a record high specific energy density of 10.8 kJ/m3/mT. Unforeseen nonlinear behavior of our robots is observed in experiments and analyzed by simulation, guiding future designs of soft-bodied robots. Our robots walk, swim, levitate, transport cargo, and can even catch a living fly unharmed. Such ultrafast soft robots with high-frequency oscillations can rapidly adapt to varying environmental conditions, inspire biomedical applications in confined environment, and serve as model systems to develop complex movements inspired by nature.

The recent development of dedicated prostate-specific membrane antigen (PSMA) targeted radioligands shows the potential to change and improve the diagnosis and therapy of prostate cancer. There is an increasing number of prospective trials to further establish these tracers in the clinical setting. We analyzed data from the ClinicalTrials.gov registry including all listed prospective trials with PSMA-ligands for prostate cancer as of October 2019 concerning the different tracers and study characteristics. We found n = 104 eligible studies with a total of n = 25 different tracers in use: most frequently [68Ga] Ga-PSMA-11 (32%), followed by [18F] DCFPyL (24%) and [177Lu] Lu-PSMA-617 (10%). 85% are single-center, 15% multi-center studies. 95% national and 5% international studies. 34% are phase-II, 24% phase-I, 13% phase-I/-II, 12% phase-II/-III and phase-III and 7% early-phase-I. The primary purpose was classified as diagnostic in 72% of cases and therapeutic in 23% of cases. Most studies were executed in the USA (70%), followed by Canada (13%) and France (6%). This quantitative descriptive registry analysis indicates the rapid and global clinical developments and current status of PSMA-radioligands with emphasis on radiopharmaceutical and organizational aspects. It will be very interesting to see which tracers will prevail in the clinical setting.

Thermodynamic properties, in particular, the temperature dependencies of magnetization of asymmetrically sandwiched ultrathin cobalt films with perpendicular anisotropy are investigated. The experimental results are described theoretically in the frame of magnon thermodynamics consistently accounting for the finite thickness of the films. The analysis includes both three-dimensional (Bloch’s T3/2 law) and two-dimensional (the 2D Bloch law) theories as limiting cases. By fitting the experimental temperature dependencies of magnetization to the theoretical model, the exchange stiffness parameter is extracted. This approach provides access to the exchange stiffness without the need to know the strength of the Dzyaloshinskii-Moriya interaction in the stack. The exchange stiffness of sub-nm-thick Co films is found to be about three times smaller compared to the case of bulk cobalt. In the temperature range T<170±30 K the temperature dependencies of magnetization follow the 2D Bloch law. The applicability of Bloch’s T3/2 law and analysis of the Curie temperature (two-dimensional and three-dimensional pictures) to extract the exchange stiffness for sub-nm-thick Co films are tested as well. The closest value of the exchange stiffness to the magnon thermodynamics turned out to be within the analysis of the Curie temperature in the three-dimensional picture.

We present a micromagnetic theory of curvilinear ferromagnetic shells. We show the appearance of new chiral effects, originating from the magnetostatic interaction. They manifest themselves even in statics and are essentially nonlocal. This is in contrast to conventional Dzyaloshinskii--Moriya interaction (material intrinsic or curvature-induced, stemming from the exchange). The physical origin is in a non-zero mean curvature of a shell and non-equivalence between the top and bottom surfaces of the shell. To describe the new effects, we split a conventional volume magnetostatic charge into two terms: (i) magnetostatic charge, governed by the tangent to the sample's surface, and (ii) geometrical charge, given by the normal component of magnetization and the mean curvature. We classify the interplay between the symmetry of the shell, its local curvature and magnetic textures and apply the proposed formalism to analyse magnetic textures in corrugated shells with perpendicular anisotropy.

Radioimmunotherapy (RIT) has the potential to reduce the incidence of relapse after allogeneic hematopoietic cell transplantation (allo-HCT) in patients with advanced-stage multiple myeloma (MM). In this study, we evaluated the efficacy of RIT in combination with chemotherapy-based reduced-intensity conditioning (RIC). RIT was based on the coupling of an anti-CD66 antibody to the beta emitter 188-rhenium (188-re) for targeted bone marrow irradiation. Between 2012 and 2018, 30 patients with MM, most of them heavily pretreated with various therapies including proteasome inhibitors, immunomodulatory drugs, anti-CD38 antibodies, and autologous hematopoietic cell transplantation (auto-HCT), were treated with a RIT-RIC combination before allo-HCT. In addition to a fludarabine plus melphalan- or treosulfan-based RIC, a median dose of 18.1 Gy (interquartile range [IQR], 14.6 to 24.1 Gy) was applied to the bone marrow. After a median duration of follow-up for surviving patients of 2.1 years (IQR, 1.3 to 3.0 years), the 2-year progression-free survival and overall survival rates were 43% (95% confidence interval [CI], 26% to 73%) and 55% (95% CI, 38% to 79%), respectively. The 2-year nonrelapse mortality and cumulative incidence of progression were 17% (95% CI, 3% to 30%) and 46% (95% CI, 25% to 67%), respectively. Renal toxicity and mucositis were the most frequent extramedullary side effects. In conclusion, the addition of RIT to RIC was safe and feasible and resulted in promising outcomes compared with those previously reported for RIC-based allo-HCT without the addition of RIT in patients with relapsed/refractory MM. Nevertheless, despite the addition of RIT, relapse after allo-HCT remained a major determinant of therapeutic failure. Therefore, the development of novel RIT strategies (eg, dual targeting strategies or combinations with adapter chimeric antigen receptor T cell-based therapies) is needed.

The orientation of a chiral magnetic domain wall in a racetrack determines its dynamical properties. In equilibrium, magnetic domain walls are expected to be oriented perpendicular to the stripe axis. We demonstrate the appearance of a unidirectional domain wall tilt in an out-of-plane magnetized stripes with biaxial anisotropy (the firsrt easy axis is perpendicular to the plane and the second one is tilted with respect to the stripe axis) and interfacial Dzyaloshinskii--Moriya interaction (DMI). The tilt is a result of the interplay between the in-plane easy-axis anisotropy and DMI. We show that the additional anisotropy and DMI prefer different domain wall structure: anisotropy links the magnetization azimuthal angle inside the domain wall with the stripe main axis in contrast to DMI, which prefers the magnetization perpendicular to the domain wall plane. Their balance with the energy gain due to domain wall extension defines the equilibrium magnetization and domain wall tilt angles. We demonstrate that the Walker field and the corresponding Walker velocity of the domain wall can be enhanced in the system supporting tilted walls.

Antiferromagnetic nanostructures as objects with ultrahigh eigenfrequencies and low sensitivity to demagnetizing fields are promising candidates for applications in data storage and information processing. Three-dimensional architectures enable new ways for tuning magnetic responses and extend ideas of spintronic devices. Here, we analyze anitferromagnetically ordered curvilinear spin chains and derive a Lagrangian taking into account the exchange interaction and effective anisotropy arising from the dipolar interaction. The static and dynamic properties of the spin system are influenced by emergent geometry-induced anisotropies and Dzyaloshinskii--Moriya interaction, which are illustrated by ring and helix geometries as case studies. Ground states and coupling of spin wave modes due to curvilinear geometry are described.

Background: Chimeric antigen receptor (CAR) T cells are powerful living drugs to fight against cancer. However, they also possess the capacity to elicit moderate to severe toxicities that might be even fatal. Thus, one major issue of CAR T cell engineering is to reduce the risk for side effects while maintaining high anti-tumor activity. In order to improve the safety profile of CAR, we developed the so-called UniCAR system. In this modular platform technology, soluble, tumor-specific target modules (TM) act as molecular switches of per se inactive universal (Uni)CAR T cells. TM consist of tumor-specific binding domains fused to the E5B9 peptide epitope that is recognized by the UniCAR. All so far developed TMs have a low molecular weight and are therefore rapidly eliminated. This allows to specifically and repeatedly turn on/off UniCAR T cell activity via TM dosing.
Aims: Tumor patients with bulky disease present the highest risk for CAR T cell-related toxicities. At this stage, a high level of safety and therefore controllability of (Uni)CAR T cells is required. However, for convenient treatment of patients with lower tumor burden, we intended to develop extended half-life TM to foster anti-tumor responses and to ease the clinical TM administration at later stages of tumor therapy.
Methods: Based on the human IgG4 Fc-domain, we engineered a set of novel extended half-life TM each consisting of tumor-specific single-chain fragments variable (scFv), the IgG4 hinge and Fc domain as well as the E5B9 peptide epitope. Functionality of these IgG4-based TMs was analyzed in vitro and in vivo in comparison to originally developed scFv-based TM. Pharmacokinetic properties were studied in experimental mice.
Results: In presence of extended half-life TM, UniCAR T cells are able to efficiently mediate tumor cell lysis in vitro and in vivo. Anti-tumor responses are comparable or even improved in comparison to smaller TM, whereas bioavailability and plasma half-life are prolonged.
Summary: Overall, combination of both short-lived and longer lasting (IgG4-based) TM is a highly promising approach for redirection of UniCAR T cells to various cancer cells. At the beginning of tumor treatment, rapidly eliminated TM should be chosen to provide a fast safety switch. After significant reduction in tumor burden, IgG4-based TM with increased serum half-lives could be administered to avoid continuous TM infusions and to improve the elimination of residual tumor cells. This strategy might allow a more convenient, individualized and safe treatment of cancer patients.

The concept of curvature and chirality in space and time are foundational for the understanding of the organic life and formation of matter in the Universe. Chiral interactions but also curvature effects are tacitly accepted to be local. A prototypical condensed matter example is a local spin-orbit- or curvature-induced Rashba or Dzyaloshinskii-Moriya interactions. Here, we introduce a chiral effect, which is essentially non-local and resembles itself even in static spin textures living in curvilinear magnetic nanoshells. Its physical origin is the non-local magnetostatic interaction. To identify this interaction, we put forth a self-consistent micromagnetic framework of curvilinear magnetism. Understanding of the non-local physics of curved magnetic shells requires a curvature-induced geometrical charge, which couples the magnetic sub-system with the curvilinear geometry. The chiral interaction brings about a non-local chiral symmetry breaking effect: it introduces handedness in an intrinsically achiral material and enables the design of magnetolectric and ferrotoroidic responses.

Background: Chimeric antigen receptor (CAR) T cell therapy has demonstrated impressive clinical efficiency, but can also cause moderate to severe adverse effects that might be even fatal. Thus, preventing or managing CAR T cell toxicity is still an important issue for successful treatment of tumor patients. In order to provide a novel CAR technology platform with an improved safety profile, we established the switchable UniCAR system. This platform consists of (I) universal CAR (UniCAR) T cells that are per se inactive. Their anti-tumor activity can be specifically and repeatedly turned on/off in dependence of soluble tumor-binding target modules (TM).e.g.1-4 TMs are constructed by fusing an antigen-specific binding moiety with the E5B9 peptide epitope recognized by UniCARs. As these molecules are rapidly eliminated, UniCAR T cells can be easily controlled by TM dosing.
Aims: As the risk for CAR T cell-related toxicities will also decrease with reduction of tumor burden, we intended to develop TMs with prolonged half-life that might ease clinical application and improve elimination of residual tumor cells in late phase of tumor therapy.
Methods: We constructed a set of novel, longer lasting TMs by fusion of different tumor-specific single-chain fragment variables (scFv) and the E5B9 peptide epitope to the Fc domain of human IgG4 antibodies. The resulting IgG4-based TMs were functionally compared with smaller, scFv-based TMs in vitro and characterized for their pharmacokinetic properties in experimental mice.
Results: The novel IgG4-based TMs are able to efficiently activate UniCAR T cells for killing of various tumor cell lines. In comparison to short-lived TMs, they are characterized by a comparable or increased efficiency at low TM concentrations. Pharmacokinetic studies in tumor-bearing mice further revealed that IgG4-based TM have a prolonged plasma half-life and enhanced bioavailability.
Summary: Our data demonstrate that IgG4-based TMs in combination with smaller TMs are highly promising tools for redirection of UniCAR T cells to various cancer cells. Once the tumor burden is reduced, UniCAR T cells can be combined with IgG4-based TMs instead of small TMs. This is more convenient for patients as IgG4-based TM have not to be continuously infused due to their prolonged serum half-lives. Overall, the combination of UniCAR T cells with TMs of different size and specificity should allow a more convenient, individualized and safe treatment regimen of cancer patients.

An introduction of spectroscopy with f-elements (actinides/lanthanides)

Thin film antiferromagnets (AF) have potential to revolutionize spintronics due to their inherently magnetic-field stable magnetic order and high-frequency operation. To explore their application potential, it is necessary to understand modifications of the magnetic properties and magnetoelectric responses of AF thin films with respect to their bulk counterparts. Considering grainy morphology of thin films, questions regarding the change of the intergranular exchange, criticality behavior and switching of the order parameter need to be addressed.
Our approach is based on the electron transport characterization of magnetic responses of thin film antiferromagnets [1-3]. This task is difficult as minute uncompensated surface magnetization of antiferromagnets needs to be detected, which imposes strict requirements to the sensitivity of the method. I will outline our developments of zero-offset anomalous Hall magnetometry [2] applied to study the physics of conventional metallic IrMn and insulating magnetoelectric Cr2O3 antiferromagnets. To build a reliable description of the material properties, the analysis of the transport data is backed up by structural characterization and real space imaging of AF domain patterns using NV microscopy [1,4].
The fundamental understanding of the magnetic microstructure of magnetoelectric α-Cr2O3 thin films and the possibility to read-out its antiferromagnetic order parameter all-electrically enabled the entirely new recording concept where a magnetoelectric memory cell can be addressed without using a ferromagnet. With this approach, we opened an appealing topic of purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) [1].

[1] T. Kosub, D. Makarov et al., Nat. Commun. 8, 13985 (2017).
[2] T. Kosub, D. Makarov et al., Phys. Rev. Lett. 115, 097201 (2015).
[3] R. Schlitz, D. Makarov et al., Appl. Phys. Lett. 112, 132401 (2018).
[4] P. Appel, D. Makarov et al., Nano Lett. 19, 1682 (2019).

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We explore the potential of these 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [Makarov et al., Appl. Phys. Rev. 3, 011101 (2016)] for automotive applications [Melzer et al., Adv. Mater. 27, 1274 (2015)], point-of-care diagnostics [Lin et al, Lab Chip 14, 4050 (2014)], virtual and augmented reality appliances [Canon et al., Nature Electronics 1, 589 (2018) & Science Advances 4, eaao2623 (2018); Granell et al., npj Flexible Electronics 3, 3 (2019)]. Combining compliant magnetic field sensors with soft (magnetic) actuators allows realizing ultrafast soft robots with embedded cognition and feedback. These developments pave the way towards intelligent soft robots, autonomous and responsive soft devices, and novel human-machine interfaces.

Extending 2D structures into 3D space has become a general trend in multiple disciplines including electronics, photonics, and magnetics. This approach provides means to enrich conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-3]. On the other hand, we explore the application potential of 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [4] for automotive but also virtual and augmented reality appliances [5-7]. To advance in this research field, we develop novel theoretical methods and fabrication/characterization techniques [8-10]. In this talk, recent fundamental and technological advancements in this research field will be reviewed.

[1] R. Streubel, DM et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander, DM et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov, DM et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] D. Makarov et al., Shapeable magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[5] G. S. Cañón Bermúdez, DM et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[6] G. S. Cañón Bermúdez, DM et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[7] J. Ge, DM et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[8] R. Streubel, DM et al., Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies. Nature Communications 6, 7612 (2015).
[9] T. Kosub, DM et al., All-electric access to the magnetic-field-invariant magnetization of antiferromagnets. Phys. Rev. Lett. 115, 097201 (2015).
[10] T. Kosub, DM et al., Purely antiferromagnetic magnetoelectric random access memory. Nature Communications 8, 13985 (2017).

The development of highly selective and active electrocatalysts promoting the CO2 reduction reaction (CO2RR) is highly desirable to address current environmental challenges and to produce value-added chemicals and carbon-based fuels. Herein, we develop a layer-stacked, bimetallic two-dimensional conjugated metal-organic framework (2D c-MOF) with copper-phthalocyanine as ligand (CuN4) and zinc-bis(dihydroxy) complex (ZnO4) as linkage, named as PcCu-O8-Zn. The PcCu-O8-Zn exhibits high CO selectivity of 88%, a TOF of 1408 h1 and long-term durability (> 10 h), which surpasses thus by far the reported MOF-based electrocatalysts. The molar H2/CO ratio can be tuned by varying the metal centers and the applied potential rendering the 2D c-MOFs highly relevant for syngas industry applications. The contrast experiments combined with operando surface-enhanced IR-absorption spectroelectrochemistry and theoretical calculation unveil a synergistic catalytic mechanism; the ZnO4 complexes act as catalytic sites for the CO2 conversion while the CuN4 centers promote the protonation of adsorbed CO2 during the CO2RR. This work offers a strategy on developing bimetallic MOF electrocatalysts for synergistically catalyzing CO2RR toward syngas synthesis.

Engineering the magnetic properties (Gilbert damping, saturation magnetization, exchange stiffness, and
magnetic anisotropy) of multicomponent magnetic compounds plays a key role in fundamental magnetism
and its applications. Here, we perform a systematic study of (Ni81Fe19 )100−xGdx films with x = 0%, 5%, 9%,
and 13% using ferromagnetic resonance (FMR), element-specific time-resolved x-ray magnetic resonance, and
femtosecond time-resolved magneto-optical pump-probe techniques. The comparative analysis of field and
time domain FMR methods, with complimentary information extracted from the dynamics of high-frequency
exchange magnons in ferromagnetic thin films, is used to investigate the dependence of Gilbert damping on the
Gd concentration.

The current establishment of stretchable electronics to form a seamless link between soft or
even living materials and the digital world is at the forefront of multidisciplinary research
efforts, bridging physics, engineering and materials science. Magnetic functionalities can
provide a sense of displacement, orientation or proximity to this novel formulation of
electronics. This work reviews the recent development of stretchable magnetic field sensorics
relying on the combination of metallic thin films revealing a giant magnetoresistance effect
with elastomeric materials. Stretchability of the magnetic nanomembranes is achieved
by specific morphologic features (e.g. wrinkles or microcracks), which accommodate the
applied tensile deformation while maintaining the electrical and magnetic integrity of the
sensor device. The entire development, from the demonstration of the world’s first elastically
stretchable magnetic sensor to the realization of a technology platform for robust, ready-touse
elastic magnetosensorics is described. Soft giant magnetoresistive elements exhibiting the
same sensing performance as on conventional rigid supports, but with fully strain invariant
properties up to 270% stretching have been demonstrated. With their unique mechanical
properties, these sensor elements readily conform to ubiquitous objects of arbitrary shapes
including the human skin. Stretchable magnetoelectronic sensors can equip soft and epidermal
electronic systems with navigation, orientation, motion tracking and touchless control
capabilities. A variety of novel technologies, like electronic skins, smart textiles, soft robotics
and actuators, active medical implants and soft consumer electronics will benefit from these
new magnetic functionalities.

Presentation at AAA Workshop 02.12.2019

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-3]. On the other hand, we explore the application potential of these 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [4] for automotive but also virtual and augmented reality appliances [5-8]. The balance between the fundamental and applied inputs stimulates even further the development of new theoretical methods and novel fabrication/characterization techniques [9-11].
In this talk, recent fundamental and technological advancements in this exciting research field will be reviewed.

[1] R. Streubel et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] D. Makarov et al., Shapeable Magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[5] G. S. Cañón Bermúdez et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[6] G. S. Cañón Bermúdez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[7] P. N. Granell et al., Highly compliant planar Hall effect sensor with sub 200 nT sensitivity. npj Flexible Electronics 3, 3 (2019).
[8] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[9] R. Streubel et al., Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies. Nature Communications 6, 7612 (2015).
[10] T. Kosub et al., All-electric access to the magnetic-field-invariant magnetization of antiferromagnets. Phys. Rev. Lett. 115, 097201 (2015).
[11] T. Kosub et al., Purely antiferromagnetic magnetoelectric random access memory. Nature Communications 8, 13985 (2017).

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-3]. On the other hand, we explore the application potential of these 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [4] for automotive but also virtual and augmented reality appliances [5-8]. The balance between the fundamental and applied inputs stimulates even further the development of new theoretical methods and novel fabrication/characterization techniques [9-11].
In this talk, recent fundamental and technological advancements in this exciting research field will be reviewed.

[1] R. Streubel et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] D. Makarov et al., Shapeable Magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[5] G. S. Cañón Bermúdez et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[6] G. S. Cañón Bermúdez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[7] P. N. Granell et al., Highly compliant planar Hall effect sensor with sub 200 nT sensitivity. npj Flexible Electronics 3, 3 (2019).
[8] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[9] R. Streubel et al., Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies. Nature Communications 6, 7612 (2015).
[10] T. Kosub et al., All-electric access to the magnetic-field-invariant magnetization of antiferromagnets. Phys. Rev. Lett. 115, 097201 (2015).
[11] T. Kosub et al., Purely antiferromagnetic magnetoelectric random access memory. Nature Communications 8, 13985 (2017).

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study fundamentals of 3D curved magnetic thin films [1] and explore their application potential for flexible electronics, eMobility and health. We put forth the concept of shapeable magnetoelectronics [2] for various applications ranging from automotive [3] through consumer electronics to virtual and augmented reality [4-7] applications. These activities impact several emerging research fields of smart skins, soft robotics and human-machine interfaces.
Highly compliant functional elements are exceptionally suited for bio/medical applications. Very recently we realized an implantable, multifunctional and highly compliant device for targeted thermal treatment of cancer [8]. We fabricated a flexible light weight diagnostic platform based on highly sensitive Si nanowire field effect transistors revealing remarkable limit of detection at 40 pM for Avian Influenza Virus (AIV) subtype H1N1 DNA sequences [9].
For the emerging field of biosensing technologies, we developed droplet-based magnetofluidic platforms encompassing integrated novel functionalities [10] including analytics in a flow cytometry format [11], magnetic barcoding and sorting of magnetically encoded emulsion droplets using flexible microfluidic devices [12]. These features are crucial to address the needs of modern medical research, e.g. drug discovery.

[1] R. Streubel et al., J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016)
[2] D. Makarov et al., Appl. Phys. Rev. (Review) 3, 011101 (2016).
[3] M. Melzer et al., Adv. Mater. 27, 1274 (2015).
[4] G. S. Cañón Bermúdez et al., Science Advances 4, eaao2623 (2018).
[5] G. S. Cañón Bermúdez et al., Nature Electronics 1, 589 (2018).
[6] P. N. Granell et al., npj Flexible Electronics 3, 3 (2019).
[7] J. Ge et al., Nature Communications 10, 4405 (2019).
[8] G. S. Cañón Bermúdez et al., Adv. Eng. Mater. 21, 1900407 (2019).
[9] D. Karnaushenko et al., Adv. Healthcare Mater. 4, 1517 (2015).
[10] G. Lin, D. Makarov et al., Lab Chip (Review) 17, 1884 (2017).
[11] G. Lin, D. Makarov et al., Small 12, 4553 (2016).
[12] G. Lin, D. Makarov et al., Lab Chip 14, 4050 (2014).

The intentional merging of epitaxial Ge on Si(001) quantum dots with optically active defect sites promises low-cost applications such as room temperature (RT)light emitters in Si photonics. Despite recent progress in this field, important benchmarks, for example, the thermal stability of such a combination of low-dimensional nanosystems, as well as the curing of parasitic charge-carrier recombination channels, have been barely investigated thus far. Herein, the structural robustness of defect-enhanced quantum dots (DEQDs) is examined under millisecond flash lamp annealing (FLA), carried out at sample temperatures up to 800oC. Changes in the optical DEQD properties are investigated using photoluminescence spectroscopy performed in a sample temperature range from10 to 300 K. It is demonstrated that FLA—in contrast to in situ thermal annealing—leads to only negligible modifications of the electronic band alignment. Moreover, upon proper conditions of FLA, the RT emission intensity of DEQDs is improved by almost 50% with respect to untreated reference samples.

The two-dimensional materials with direct band gap are attractive for optoelectronics operated in the visible and near infrared spectral range. The number of new van der Waals crystals increases systematically but the doping and the modification of their optoelectronic properties remain challenging. Here we present the tuning of the fundamental properties of different 2D mono- and dichalcogenides using millisecond range flash lamp annealing (FLA) in the controlled atmosphere. Those investigated 2D flakes are made by mechanical exfoliation onto the SiN/Si substrates. The change of internal properties of 2D chalcogenides is monitored by micro-Raman, photoluminescence and photoreflectance spectroscopies as well as conductive atomic force microscope (c-AFM). Using ms-range FLA in N2 ambient the transition metal dichalcogenides are stable up to the annealing at 1200 oC, while upon high temperature annealing the group IV-dichalcogenides can be reduced to monochalcogenides which opens new route for the fabrication of heterostructures. The formation of SnSe/SnSe2 heterostructures is proven by micro-Raman spectroscopy and current-voltage characteristic obtained by c-AFM measurements.

Semiconducting metal oxides often exhibit high photocatalytic efficiency (PE) and, among them, the anatase-TiO2 (A-TiO2) is the most promising material for the water splitting under sun light illumination. The PE of TiO2-based materials mainly depends on the surface state density, Fermi level position, band gap and crystalline structure (anatase, rutile, brookite). Here, we present the optical, electrical and structural properties of A-TiO2 thin films made by RT magnetron sputtering followed by ms-range flash lamp annealing (FLA) in N2 ambient. X-ray diffraction (XRD), X-ray absorption near-edge structure, and Raman spectroscopies reveal the transformation from amorphous to single-phase A-TiO2 during FLA for 20 ms. The FLA energy density was in the range of 65 to 110 Jcm-2, corresponding to peak temperatures in the range of 500oC to 1100 oC, respectively. XRD and scanning electron microscopy shows that with increasing FLA energy the average crystal size of the A-TiO2 increases from a few nm?s up to ~200 nm after annealing at energy density of 110 Jcm-2. On the other hand, the optical band-gap, as determined by spectroscopic ellipsometry, remains at ~3.4 eV. The bleaching of methylene blue under irradiation with a high-intensity light-emitting-diode (4.5 W/cm2) at 365 nm has been used to test the photoactivity of the samples after FLA. The PE of the samples is enhanced with increasing the annealing temperature, which we assign to the engineering of surface states and carrier lifetime upon FLA in N2 ambient.

The last missing piece of puzzle for the full functionalization of group IV optoelectronic devices is the direct band gap semiconductor made by CMOS compatible technology. Here we report on the fabrication of GeSn alloys with a Sn concentration of up to 6 % using ion implantation followed by ms-range explosive solid phase epitaxy. The n-type single crystalline GeSn alloys are made by co-doping of Sn and P into Ge. Both the activation of P and the formation of GeSn are performed during a single-step flash lamp annealing for 3 ms. The band gap engineering in ultra-doped n-type Ge and GeSn alloys is theoretically predicted by density functional theory and experimentally verified using ellipsometric spectroscopy. We demonstrate that both the diffusion and the segregation of Sn and P atoms in Ge are fully supressed by ms-range non-equilibrium thermal processing.

The demand for strategic metals such as chromium and vanadium is predicted to rise in the future. These metals can currently be found in the slag by-products of certain steel production processes. We are developing a solvent extraction process for the separation and purification of these valuable resources from alkaline oxidative leach feed streams. This process shows potential to be applicable to alternative feed streams in addition. The extractant phase used is commercially available Aliquat 336 with kerosene as diluent and long-chain alcohol or ketone as phase modifiers. The use of the radiotracer technique allows simple and precise measurement of the metal concentration at each step of the process. Chromium-51 and vanadium-48 radionuclides are produced in-house at the HZDR cyclotron facility. Early results have shown that this process effectively removes chromium and vanadium together from model feed streams, indicating the need for a further separation step of the two species. To this end, a chromate scrub step is suggested.

The n-type doping of Ge and Ge-based alloys is a self-limiting process due to the formation of vacancy-donor complexes (DnV with n ≤ 4) that deactivate the donors. This work clearly demonstrates that the dissolution of the DnV clusters in a heavily n-doped Ge, GeSn and SiGeSn layers can be achieved by millisecond-flash lamp annealing. This DnV cluster dissolution results in a considerable increase of the electrical activation together with a suppression of donor diffusion. Using electrical measurements and positron annihilation lifetime spectroscopy, combined with theoretical calculations, it is possible to address, understand and solve the fundamental problem of achieving ultra-high doping level in Ge, that has hindered so far the full integration of Ge and Ge-based alloys with complementary-metal-oxide-semiconductor technology.

To address the projected requirements of future technology and ecology, and move towards a circular economy, a comprehensive consideration of the sources, processing methods, and life cycles of natural resources is needed. Certain important metal resources, such as chromium and vanadium, are currently available but unexploited in the slag by-products of steel production processes. This represents a significant potential source of these elements for European enterprise. To help meet the rising demand, the CHROMIC project seeks to develop a hydrometallurgical process for the recovery and purification of these valuable resources. By utilising an oxidative, high-alkaline leaching method, the process aims to avoid the destruction of the saleable slag matrix, as well as the presence of Si or Fe in the leachate solution. Various methods are being investigated for separation of the metal value from the resulting alkaline leach feeds, including solvent extraction (SX) which is the focus of this work.
In developing this SX process, the radiotracer technique has been employed, utilising chromium-51 and vanadium-48 radionuclides produced in-house at the HZDR cyclotron facility. The use of this technique, in combination with more conventional methods such as ICP-OES, allows for precise and powerful analysis of the process with minimal workup after experiments.
Aliquat 336, a quaternary ammonium based IL, is suitable for the separation of oxoanions from such alkaline solutions due to the presence of the organic cation species, independently of pH. This extractant is mostly used in its commercially available chloride form, although experiments involving alternative anions (e.g. OCl⁻, OH⁻, S₂O₈²⁻, CO₃²⁻) are also necessary to investigate the influence of competing anions (arising from the leaching conditions) on the SX process. Scrubbing and back extraction of the loaded IL phase has been demonstrated, using solutions of sodium chromate and sodium chloride. Experiments have now begun on the real leaching solutions of steel slags relevant to the CHROMIC project.

The n-type doping of Ge is self-limiting process due to formation of the vacancy-donor complexes (Dn V with n≤4). Here we report on experiments and density functional theory (DFT) calculations solving the basic problem of donor deactivation in heavily doped Ge. The self-healing process of heavily doped n-type Ge is achieved by rear-side flash lamp annealing (r-FLA) for 20 ms with the peak temperature of about 1050 K. The positron-annihilation lifetime spectroscopy (PALS) reveals that the P4V clusters are main defects in the as-grown Ge:P samples. Millisecond range high-temperature treatment dissociates the phosphorus-vacancy cluster (P4V) and, as shown by SIMS, fully supress the P diffusion. The electrochemical capacitance-voltage (ECV) profiling shows that the effective carrier concentration in P doped Ge (P concentration - 1×1020 cm-3) increases from about 3×1019 cm-3 in as-grown sample to above 8×1019 cm-3 after r-FLA. For the first time using structural (PALS, SIMS) and electrical (ECV) characterization combined with DFT calculations we were able to addressed, explained and solved the fundamental problem hindering the full integration of Ge with CMOS technology.

Reichweiteverifikation ist ein wesentlicher Baustein zur Reduzierung der Sicherheitssäume in der Partikeltherapie. Da eine direkte Messung der Reichweite schwerer geladener Teilchen im menschlichen Gewebe schwierig ist, ist man derzeit auf den Informationsgehalt von Sekundärstrahlung angewiesen, die bei der Abbremsung der primären Teilchen im Körper entstehen.
Die durch Kernwechselwirkungen entstehende prompte Gammastrahlung ist hierfür ein vielversprechende Sonde.
Mehrere Ansätze zur Verifikation der Reichweite von therapeutischen Protonen mittels prompter Gammastrahlung wurden in den vergangenen Jahren untersucht. Bisher wurde erst eine, das Prompt Gamma Ray Timing, erfolgreich am Patienten angewendet. Andere Methoden befinden sich kurz vor den ersten klinischen Anwendungen.
Auf dem Weg von der Idee eines Reichweiteverifikationsverfahrens bis hin zu dessen klinischer Implementierung ist es jedoch ein langer und schwieriger Weg. Dieser Beitrag zeigt welche Schwierigkeiten bei der erfolgreichen Einführung eines derartigen Systems in den klinischen Alltag existieren und geht dabei auf mehrere konkrete Beispiele ein.

In Uranus and Neptune methane and other hydrocarbons are highly abundant. Their planetary interior conditions can be mimicked using high intensity lasers in the laboratory on a nanosecond timescale. Nanodiamond formation from shock-compressed polystyrene (~150GPa, ~5000K) was demonstrated via in situ X-ray diffraction with a XFEL. The lower size estimate is 4nm. 60% of the carbon atoms in the plastic are
transferred to a diamond lattice. However, in total a maximum of ~16μg of nanodiamonds are expected from a 125nm CH foil and a 500μm focal spot. In order to understand the underlying hydrocarbon separation mechanism the physical recovery of nanodiamonds is pursued to learn from their shape, size, surface modifications and defects.

In an experimental study with a stainless steel heater (surface with maximum roughness Rt = 0.82 µm and contact angle hysteresis θhys = 53°), we investigated the bubble growth and motion during nucleation and departure. Complementary to that we analysed the formation of microlayer during the bubble growth and motion with computational fluid dynamics (CFD) simulation. From the simulations we found that the bubble motion leads to an expansion of the microlayer. From the experiments we obtained the drag coefficient on the bubble during bubble growth with an assumption of the absence of the wall surface tension force. From the comparison of this drag coefficient and the proposed values from the literature, we conclude that the vapour bubble does not directly contact the solid wall during the sliding. Using well-known mechanistic bubble growth models for further analysis of available microlayer area with the experimental data we conclude that a microlayer exists and the bubble must slide completely on this microlayer after leaving its originating cavity. From the change of microlayer size we can also explain the bubble regrowth after departure.

In sickle cell disease (SCD), oxygen delivery is impaired due to anemia, especially during times of increased metabolic demand, and cerebral blood flow (CBF) must increase to meet changing physiologic needs. But hyperemia limits cerebrovascular reserve (CVR) and ischemic risk prevails despite elevated CBF. The cerebral metabolic rate of oxygen (CMRO 2 ) reflects oxygen supply and consumption so may be more insightful than flow-based CVR measures for ischemic risk in SCD. We hypothesized that adults with SCD have impaired CMRO 2 at rest and that a vasodilatory challenge with acetazolamide would improve CMRO 2 . CMRO 2 was calculated from CBF and oxygen extraction fraction (OEF), measured with arterial spin labeling and T 2 -prepared tissue relaxation with inversion recovery (T 2 -TRIR) MRI. We studied 36 adults with SCD without a clinical history of overt stroke and 9 healthy controls. As expected, CBF was higher in patients with SCD versus controls (mean ± standard deviation: 74±16 vs 46±5 mL/100g/min, P<.001), resulting in similar oxygen delivery (SCD: 377±67 vs controls: 368±42 μmol O 2 /100g/min, P=.69). OEF was lower in patients versus controls (27±4 vs 35±4 %, P<.001), resulting in lower CMRO 2 in patients versus controls (102±24 vs 127±20 μmol O 2 /100g/min, P=.002). After acetazolamide, CMRO 2 declined further in patients (P<.01) and did not decline significantly in controls (P=.78), indicating that forcing higher CBF worsened oxygen utilization in SCD patients. This lower CMRO 2 could reflect variation between healthy and unhealthy vascular beds in terms of dilatory capacity and resistance whereby dysfunctional vessels become more oxygen-deprived, hence increasing the risk of localized ischemia.

The chemically ordered B2 Fe50Rh50 alloy is antiferromagnetic. By inducing chemical disorder its structure can be changed to the ferromagnetic A2 structure. Following the laser writing method published here [1] we used a pulsed laser to induce ferromagnetism locally in Fe50Rh50 thin films of 10, 20, and 30nm thickness. XMCD measurements on the laser-treated region revealed the formation of an annulus of FM contrast and a non-FM center. Transmission electron microscopy (TEM) on a section through the annulus found the FM region to be A2 and the enclosed non-contrast region of the fcc A1 structure. The surrounding untreated region remained in the B2 structure.

Discovery and delineation of new ore deposits require substantial investment into diamond-drilling. Traditionally, the extracted drill-cores are visually analysed by site geologists and subjected to geochemical analyses for metal grade evaluation. Frequently, the geochemical information is insufficient for the evaluation of the mineralization and system morphology, mineralogical information being therefore required. Traditional mineralogical analyses such as optical microscopy, scanning electron microscopy, and X-ray diffraction are time consuming, require extensive sample preparation and deliver non-continuous point information. Due to its fast acquisition time, low sample handling requirements, and non-invasive character hyperspectral drill-core scanning has recently become an efficient tool for lithological / alteration drill core logging. Most commonly used for drill core scanning are visible to near-infrared (VNIR) and short-wave infrared (SWIR) hyperspectral sensors. These sensors allow the identification of mineral groups that show a specific signature as they absorb parts of the incoming light between 400 and 2500 nm. Many of the spectrally active minerals such as white micas, chlorites, epidotes or gypsum play an important role in exploration mapping as they have specific associations with the ore minerals and strong zonality in their distribution within the deposit. They can, therefore, be used as proxies for exploration vectoring and ore deposit modelling. Their compositional analysis and quantification has thus become an important tool for exploration. Commonly used methods for mineral abundance estimation from hyperspectral data consist in unmixing algorithms, which strongly rely on endmember extraction techniques. However, the obtained endmembers in hyperspectral drill-core data using conventional tools usually consist of mineral mixtures due to the spatial resolution of most hyperspectral sensors; the unmixing results will thus only define abundances of mixed compositions.
We propose a supervised machine learning-based methodology that uses the abundance of SWIR active mineral groups in selected representative known areas of the drill-core samples for predicting the content of these groups at the drill-core scale.
The training data consists of high-resolution scanning electron microscopy-based mineral maps resampled to the resolution of the hyperspectral image. As a result, the resampled image contains in each pixel the abundance of each selected mineral or mineral group. An artificial neural network-based regression is used in order to upscale the mineral abundances from the training set to the entire drill-core sample. Preliminary results show a great potential for automation and allow for the evaluation of the individual abundance of each mineral or mineral group.

Sensor-based sorting is increasingly used for the concentration of ores. To assess the sorting performance for a specific ore type, the raw materials industry currently conducts trial-and-error batch tests. In this study, a new methodology to assess the potential of hyperspectral visible to near-infrared (VNIR) and short-wave infrared (SWIR) sensors, combined with machine-learning routines to improve the sorting potential evaluation, is pre- sented. The methodology is tested on two complex ores. The first is a tin ore in which cassiterite—the target mineral—is variable in grain size, heterogeneously distributed and has no diagnostic response in the VNIR-SWIR range of the electromagnetic spectrum. However, cassiterite is intimately associated with SWIR active minerals, such as chlorite and fluorite, which can be used as proxies for its presence. The second case study consists of a copper-gold porphyry, where copper occurs mainly in chalcopyrite, bornite, covellite and chalcocite, while gold is present as inclusions in the copper minerals and in pyrite. Machine-learning techniques such as Random Forest and Support Vector Machine applied to the hyperspectral data predict excellent sorting results in terms of grade and recovery. The approach can be adjusted to optimize sorting for a variety of ore types and thus could increase the attractivity of VNIR-SWIR sensor sorting in the minerals industry.

The rapid mapping and characterization of specific porphyry vein types in geological samples represent a challenge for the mineral exploration and mining industry. In this paper, a methodology to integrate mineralogical and structural data extracted from hyperspectral drill-core scans is proposed. The workflow allows for the identification of vein types based on minerals having significant absorption features in the short-wave infrared. The method not only targets alteration halos of known compositions but also allows for the identification of any vein-like structure. The results consist of vein distribution maps, quantified vein abundances, and their azimuths. Three drill-cores from the Bolcana porphyry system hosting veins of variable density, composition, orientation, and thickness are analysed for this purpose. The results are validated using high-resolution scanning electron microscopy-based mineral mapping techniques. We demonstrate that the use of hyperspectral scanning allows for faster, non-invasive and more efficient drill-core mapping, providing a useful tool for complementing core-logging performed by on-site geologists.

Noble-metal aerogels are emerging functional porous materials that have been applied in diverse fields. Among them, gold (Au) aerogels have displayed grand potentials in a wide range of catalytic processes. However, current fabrication methods fall short in obtaining Au gels with small ligament sizes and controlled surface valence states, which hinder the study of the underlying catalytic mechanisms. Here, a new approach of producing Au aerogels is reported. Via a two-phase ligand exchange, the long-chain ligands (oleylamine) of the as-prepared Au nanoparticles were replaced by short sulfide ions and subsequently self-assembled into three-dimensional gels. As a result, Au aerogels with small ligament sizes (ca. 3−4 nm) and tunable surface valence states are acquired. Taking the application for peroxidase mimics as an example, by correlating the surface valence with the catalytic properties, Au(I) is found to be the active site for H₂O₂ and substrate-binding site for 3,3′,5,5′-tetramethylbenzidine, paving a new avenue for on-target devising Au-based catalysts.

We carry out a linear stability analysis of a magnetized relativistic rotating cylindrical jet flow using the approximation of zero thermal pressure. We identify several modes of instability in the jet: Kelvin-Helmholtz, current-driven and two kinds of centrifugal-buoyancy modes - toroidal and poloidal. The Kelvin-Helmholtz mode is found at low magnetization and its growth rate depends very weakly on the pitch parameter of the background magnetic field and on rotation. The current-driven mode is found at high magnetization, the values of its growth rate and the wavenumber, corresponding to the maximum growth, increase as we decrease the pitch parameter of the background magnetic field. This mode is stabilized by rotation, especially, at high magnetization. The centrifugal-buoyancy modes, arising due to rotation, tend also to be more stable when magnetization is increased. Overall, relativistic jet flows appear to be more stable with respect to their non-relativistic counterpart.

Silicon (Si) nanowires (NWs) have potential applications in various areas including electronics, opto-electronics and biochemical sensing. These wires are used to fabricate electronic devices with new architectures to complement the scaling down of electronic circuits. Our work focuses on one such architecture called Reconfigurable field effect transistors (RFET). An RFET is a Nickel(Ni)Si2-Si-NiSi2 Schottky junctions based device, which has an intrinsic Si channel. To fabricate an RFET, SiNWs are silicided at both ends to form Schottky junctions with the Si channel. Typically, it has two gates placed on each of the two Schottky junctions. It can be tuned to p- or n- polarity by applying appropriate electrostatic potential at one of the gates. Therefore, functional complexity and performance of electronic circuits can be enhanced using such FETs. Formation of NiSi2 is a pre-requisite for proper operation of these devices because metal work function of NiSi2 aligns itself near the mid-bandgap of Si. This enables band bending by application of an appropriate electrostatic potential for the operation of devices either as p- or as n- FET. We report our results on Ni silicidation using flash lamp annealing. By optimizing the silicidation process, control over the diffusion of Ni into the nanowire and proper silicide phase formation is achieved.

To complement scaling of field effect transistors, new device concepts were introduced recently. One such concept is the reconfigurable field effect transistor (RFET). These transistors are based on nickel silicide-Si-nickel silicide Schottky junctions and their polarity can be switched between p- and n- type at runtime by the application of an electrostatic potential [1]. Control over silicide length and phase is important for scaling and proper functioning of these devices [2]. NiSi2 is the desirable silicide phase as its metal work function aligns itself near mid bandgap of Si, which enables reconfigurability of the device [1, 3].
We report on fabrication and electrical characterization results of RFETs. Si nanowires (SiNWs) are fabricated on undoped silicon-on-insulator (SOI) substrates by a top-down process based on electron beam lithography and inductively coupled plasma etching. Then, Ni is placed at both ends of the SiNWs by metal evaporation and lift-off processes. Afterwards, flash lamp annealing (FLA) is performed for silicidation of the NWs.
FLA has enabled better control over silicidation length since flash times are much shorter (of the order of milli-seconds) than rapid thermal annealing (RTA) times. Transmission electron microscopy (TEM) shows the formation of the desired NiSi2 phase near the silicide-Si interface. Electrical characterization of the devices with back gating shows ambipolar behaviour. For unipolar behaviour, top gates need to be fabricated, results of which will be presented at the conference.

In recent days, due to increased use of hadron therapy for cancer and tumor treatment, precise online dose monitoring is an important issue for safety purpose. Regarding hadron therapy, recently carbon ion beam with high Linear Energy Transfer (LET) is found to be more effective than the photon beams. Among several known TL/OSL oxides phosphors, C-doped alumina (Al₂O₃) is favorable for radiation dosimetry, especially in medical field due to its tissue equivalent in terms of radiation absorption, simple glow curve, and high sensitivity. A facile approach to improve thermoluminescence sensitivity of electrochemically anodized porous Al₂O₃ (AAO) is presented by introducing carbon ions for ion beam dosimetry. Initially, ion implantation technique has been carried out for Carbon doping in AAO in controlled manner. HAADF-STEM, EDS mapping, SEM studies reveal the evolution of a porous structure followed by the carbon distribution up to 200 nm. However, the evolution of optically active F⁺ centres with increasing ion fluence has been examined by photoluminescence investigation at room temperature and thermoluminescence (TL) measurement while the chemical nature of such defect centres has been extracted by depth dependent XPS analysis.

Adenosine is an essential neuromodulatory molecule that acts via four G-protein coupled receptors (A1R, A2AR, A2BR, A3R). In the central nervous system (CNS), the A2AR is highly concentrated in the striatum. The A2AR is a promising target for positron emission tomography (PET) imaging of neurodegenerative diseases, such as Huntington’s disease (HD), Alzheimer’s disease (AD) and Parkinson’s disease (PD). Istradefylline is the first A2AR antagonist that is approved by the U.S. Food and Drug Administration (FDA) for adjunctive treatment in patients with PD. So far, [18F]MNI-444 [Ki (hA2AR) = 2.8 nM] is the only 18F-labelled A2AR radiotracer evaluated in healthy subjects.

Aiming at the development of A2AR radiotracers with improved molecular imaging properties, this study is based on three recently published lead compounds with a pyrazolo[3,4-d]pyridine, a morpholinobenzo[d]thiazol-2-amine and a pyrazolo[4,3‑e]‑1,2,4-triazolo[1,5‑ c]-pyrimidine scaffold. Herein, a series of 30 fluorinated derivatives was developed by systematic modification of selected lead compounds. The binding affinities torwards the A2AR and the adenosine A1 receptor (A1R) subtypes were determined by in vitro radioligand binding assays. Regarding the binding affinity and selectivity, PYP1 [Ki (hA2AR) = 5.29 nM, Ki (hA1R) = 220 nM)], PYP2 [Ki (hA2AR) = 2.13 nM, Ki (hA1R) = 147 nM)] und TOZ1 [Ki (hA2AR) = 1.00 nM, Ki (hA1R) = 618 nM)] were radiolabelled as the most suitable A2AR ligands in order to perform first preclinical studies in mice. Additionally, FLUDA [Ki (hA2AR) = 0.61 nM, Ki (hA1R) = 767 nM] was developed and radiolabelled based on the known PET radiotracer [18F]FESCH. [18F]FESCH was selected as reference compound and thus, its radio-synthesis was established as well as optimised in our laboratories.

Three different labelling strategies have been investigated in the frame of this work: (i) two-step one-pot radiolabelling procedures using 18F-labelled prosthetic groups, (ii) alcohol-enhanced copper-mediated one-step radiolabelling procedures starting from boronic acid pinacol ester precursors and (iii) conventional one-step radiolabelling procedures starting from nitro precursors. After the successful radiosynthesis, all five A2AR radiotracers were evaluated by in vitro and in vivo experiments. In vitro autoradiography on mice brain slices revealed specific binding of [18F]PPY2, [18F]TOZ1 and [18F]FLUDA in the region of interest (striatum). Metabolism studies in mice showed a fast metabolic degradation of [18F]PPY1 and [18F]PPY2 with the formation of brain penetrating radiometabolites. In contrast, [18F]TOZ1 and [18F]FLUDA displayed a higher metabolic stability in vivo as the reference [18F]FESCH. PET studies of [18F]PPY1, [18F]PPY1 and [18F]TOZ1 in CD-1 mice revealed no specific accumulation in striatum which would be non-consistent with the known A2AR distribution pattern. The findings indicate that these radiotracers may not demonstrate sufficient affinity in vivo for PET imaging of the A2AR in the brain. In contrast to the previous results, striatum was clearly visualized in PET studies with [18F]FLUDA. Altogether [18F]FLUDA revealed improved molecular imaging properties compared [18F]FESCH which might be a result of the introduction of deuterium atoms in the [18F]fluoroethyl chain, thus resulting in an increased metabolic stability.

In conclusion, the preclinical evaluation of the new developed radiotracers demonstrated that [18F]FLUDA has the highest potential to provide information about the A2AR expression by PET imaging of the brain. Hence, we focus on the clinical translation of [18F]FLUDA to study the A2AR expression in patients with Parkinson’s disease.

Introduction
The adenosine A2A receptor (A2AR) is related to the pathogenesis of several brain diseases and is assumed to mediate immunsuppressive processes related to cancer pathology. Thus, A2AR radiotracers for PET imaging are promising candidates for the differential diagnosis of neurodegenerative diseases, in particular Parkinson’s disease, and to study the A2AR within the tumor environment. We developed [18F]FLUDA based on the deuteration of the [18F]fluoroethoxy chain of [18F]FESCH [1,2] to improve imaging properties in mice. [18F]FLUDA was evaluated pre-clinically prior to a first-in-human trial.

Methods
Binding affinities of FLUDA towards the human A2AR and A1R subtypes were estimated in vitro by competitive radioligand binding assays. [18F]FLUDA was synthesized by a two-step one-pot approach. In vitro autoradiography of [18F]FLUDA was performed on mice brain cryosections. In vivo evaluation of [18F]FLUDA was carried out in a CD-1 mouse by radio-HPLC analysis of plasma and brain samples (15 min p.i.) and dynamic PET/MR studies under baseline (n = 4) and blocking conditions (2.5 mg tozadenant per kg, 15 min before tracer, n = 4). The cerebellum was used as a reference tissue. The time-activity curves were obtained and the SUV ratio (SUVR) of striatum over cerebellum were used as measure for specific uptake.

Results/discussion
In vitro binding studies revealed no influence of deuteration on the estimated binding affinities with Ki values of FLUDA and FESCH towards human A2AR of 0.60 nM and 0.61 nM, respectively. The radiosynthesis of [18F]FLUDA was successfully established (Fig.1). A single experiment indicates that [18F]FLUDA is metabolically more stable in mouse than [18F]FESCH. While no radiometabolites were found for [18F]FLUDA in plasma and brain samples at 15 min p.i., for [18F]FESCH the percentages of intact radiotracer were 71% and 41% in brain and plasma samples, respectively. By in vitro autoradiography [18F]FLUDA demonstrated a specific accumulation in the striatum, which is characterized by the binding parameters KD = 4.3 ± 0.7 nM and Bmax = 556 ± 143 fmol/mg wet weight (Fig.2A). PET scans revealed a selective binding of [18F]FLUDA in striatum (SUVR15 30 min p.i. >8), which was significantly reduced by tozadenant pre-treatment by 30% (p<0.05, Fig.2B/C).

Conclusion
The two-step one-pot radiosynthesis of [18F]FLUDA was successfully implemented for preclinical studies. Due to the promising preclinical results in mice, we focus on the clinical translation of [18F]FLUDA. Based on the performed single dose toxicity study of FLUDA we don’t expect any adverse effects. Currently, we are working on the radiation dosimetry of [18F]FLUDA in piglets and its implementation for clinical application.

Acknowledgments
The authors thank the European Regional Development Fund and Sächsische Aufbaubank (SAB) for financial support (project no. 100226753).

References
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Taking the advancing of accelerator technologies, a variety of ions (all stable elements and some radioactive elements) in a wide energy range from eV to GeV can be produced and injected into targets. Using the chemical effect of injected ions, “ion implantation" has been well established to dope semiconductors and integrated into the standard microelectronics production line in Si-chip technology. Ion irradiation refers to using other effects rather than the doping effect in materials and has been used for defect (or lifetime) engineering in microelectronics. Moreover, ion beams are also instrument for the analysis of solid state surfaces to get the information about the composition and impurity lattice location. In this talk, I will give some examples for the application of ion beams in information technologies. The following topics will be included: (1) Doping semiconductors well above the solid solidity limits: by doing so the semiconductors can be ferromagnetic or superconducting [1-5]. (2) Defect engineering in SiC: defects can carry magnetic moments giving possibilities for ferromagnetic coupling in SiC as well as for manipulating single defect center for quantum technology [6, 7]. (3) Defect engineering in oxides: it can introduce uniaxial strain and change the properties rather than by choosing different growth substrates [8, 9]. It is worthy to note that ion beam technology has been well developed for applications at wafer (450 mm) scale. Once the proof-of-concept is done, these applications mentioned above can be easily transferred to industries.

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[8] P. Pandey, et al., APL Materials 6, 066109 (2018).
[9] C. Wang, et al., Topological Hall effect in single thick SrRuO3 layers induced by defect engineering, submitted (2019).

Presently, silicon photonics requires photodetectors that are sensitive in a broad infrared range, can operate at room temperature, and are suitable for integration with the existing Si technology process. Here, we demonstrate strong room-temperature sub-bandgap photoresponse of photodiodes based on Si hyperdoped with chacolgen ions. The epitaxially recrystallized hyperdoped Si layers are developed by ion implantation combined with pulsed laser melting and incorporate Se/Te dopant concentrations several orders of magnitude above the solid solubility limit. With increasing the impurity concentration, the hyperdoped Si is changed from insulating to quasi-metallic with a finite conductivity as the temperature tends to zero. The optical absorptance is found to increase monotonically with increasing dopant concentration and extends well into the mid-infrared range. Temperature-dependent optoelectronic photoresponse unambiguously demonstrates that the extended infrared photoresponsivity from hyperdoped Si p-n photodiodes is mediated by an impurity band within the upper half of the Si bandgap. This work contributes to pave the way towards establishing a Si-based broadband infrared photonic system operating at room temperature.
References: Sci. Reports 7, 43688 (2017), Phys. Rev. Appl. 10, 024054 (2018) and Adv. Mater. Inter. 5, 1800101 (2018), Phys. Rev. Applied 11, 054039 (2019).

Inter-relations among charge, spin, orbital and lattice parameters are largely demonstrated in multi-functional oxide materials, which exhibit a variety of exotic properties, ranging from superconductivity, insulator-metal transition, colossal magnetoresistance, charge ordering, and orbital ordering, etc. In particular, tilting a delicate energy balance in lattice interactions and kinetics, achieved by temperature, pressure or chemical control, may result in exotic phenomena in these systems. However, fine-tailoring such interactions has proven difficult. In this context, defect engineering by ion irradiation, which can introduce strain and electronic disorder, has emerged as a powerful technique to fine tune complex phases of oxide thin films. In this contribution, we show that ion irradiation can modify the magnetic and electrical transport properties in a broad variety of materials, including spinel NiCo2O4, perovskite BiFeO3, SrRuO3 and LaNiO3 [1-4]. Diverse magnetic, structure and magneto-transport modifications, which are inaccessible by conventional film growth methods, have been obtained. For instance, the transport in LaNiO3 can be driven from metallic phase into an Anderson insulator by directly tuning the electronic mean free path via irradiation-induced disorder [4]. In BiFeO3, we have obtained a super-tetragonal phase with the largest c/a ratio ~ 1.3 that has ever been experimentally achieved in BiFeO3 [2]. This may lead to strong polarization enhancement. By comparing the effect in different materials, we will also point out the complexity in understanding the tailoring of oxides by ion beams.

Reference
[1] P. Pandey, Y. Bitla, M. Zschornak, M. Wang, C. Xu, J. Grenzer, D. C. Meyer, Y. Y. Chin, H. J. Lin, C. T. Chen, S. Gemming, M. Helm, Y. H. Chu, S. Zhou, Enhancing the Magnetic Moment of Ferrimagnetic NiCo2O4 via Ion Irradiation driven Oxygen Vacancies, APL Materials 6, 066109 (2018)
[2] C. Chen, C. Wang, X. Cai, C. Xu, C. Li, J. Zhou, Z. Luo, Z. Fan, M. Qin, M. Zeng, X. Lu, X. Gao, U. Kentsch, P. Yang, G. Zhou, N. Wang, Y. Zhu, S. Zhou, D. Chen, J. Liu, Controllable defect driven symmetry change and domain structure evolution in BiFeO3 with enhanced tetragonality, Nanoscale 11, 8110 (2019)
[3] C. Wang, C. Chen, C.-H. Chang, H.-S. Tsai, P. Pandey, C. Xu, R. Böttger, D. Chen, Y.-J. Zeng, X. Gao, M. Helm, S. Zhou, Defect-induced exchange bias in a single SrRuO3 layer, ACS Appl. Mater. Interfaces, 27472 (2018).
[4] C. Wang, C.-H. Chang, A. Huang, P.-C. Wang, P.-C. Wu, L. Yang, C. Xu, P. Pandey, M. Zeng, R. Böttger, H.-T. Jeng, Y.-J. Zeng, M. Helm, Y.-H. Chu, R. Ganesh, S. Zhou, Tunable disorder and localization in the rare-earth nickelates, Phys. Rev. Materials 3, 053801 (2019)

We report on the experimental observation and theoretical studies of a self-assembled Fe-rich (In,Fe)As nano-lamellar structure that is driven by anisotropic spinodal decomposition at the growth front during laser heating-induced recrystallization of Fe-implanted InAs [1]. Pseudomorphically embedded in the InAs lattice, those Fe-rich nano-lamellae are perpendicular to the (001) surface and parallel to the in-plane [110] crystallographic direction. The Fe atoms are substitutionally incorporated at the indium sites. Magnetic measurements indicate a typical blocked superparamagnetic behavior suggesting strong ferromagnetic orderings inside the Fe-rich nanostructures, but weak coupling between the nano-lamellae. Our findings explain the surprisingly high apparent Curie temperatures and unexpected eight-fold symmetry of crystalline anisotropic magnetoresistance found previously in Be-doped n-type (In,Fe)As grown by molecular beam epitaxy [2]. Prompted by these results we discuss how a different d-level electronic configuration of Fe in InAs and Mn in GaAs [3] affects the magnetic ion incorporation and spatial distribution and, thus, magnetism and anisotropy. Our results also indicate that the directional distribution of impurities or alloy components setting in during the growth may account for the observed nematicity in other classes of correlated systems.

Reference
[1] Y. Yuan, R. Hübner, M. Birowska, C. Xu, M. Wang, S. Prucnal, R. Jakiela, K. Potzger, R. Böttger, S. Facsko, J.A. Majewski, M. Helm, M. Sawicki, S. Zhou, T. Dietl, Nematicity of correlated systems driven by anisotropic chemical phase separation, in Phys. Rev. Materials 2, 114601 (2018).
[2] Pham Nam Hai, D. Sasaki, Le Duc Anh, and M. Tanaka, Crystalline anisotropic magnetoresistance with twofold and eight-fold symmetry in (In,Fe)As ferromagnetic semiconductor, Appl. Phys. Lett. 100, 262409 (2012).
[3] M. Birowska, C. Śliwa, J. A. Majewski, and T. Dietl, Origin of Bulk Uniaxial Anisotropy in Zinc-Blende Dilute Magnetic Semiconductors, Phys. Rev. Lett. 108, 237203 (2012).

Magnetic nanoclusters in amorphous carbon have promising applications for highly responsive magnetic sensors, where decreasing the size of the nanoclusters can lead to superparamagnetism and therefore low remanence. The insulating properties (wide bandgap) of amorphous carbon are also potentially useful for designing high frequency components. Both these properties are crucial to achieve ultra-high density magnetic data storage.

High fluence (1.2×10¹⁷ Co/cm²) near-surface implantation of 30 keV Co ions into amorphous carbon results in the formation of complex magnetic nanostructures and multiple magnetic phases. Next to small segregated cobalt carbide nanoclusters, starting forming at a depth of 25 nm within the amorphous carbon film, a nearly continuous network of cobalt carbide thin nanocrystalline regions can be observed at a depth of 8 nm. On the surface a 3 nm thin cobalt oxide nanostructured layer is seen separated from the cobalt carbide by a 1 nm thin Co-depleted region. TEM and magnetic measurements show superparamagnetic nanoclusters with a blocking temperature of 5 K. However, a small proportion of larger cobalt carbide nanoclusters exhibits magnetic hysteresis even at room-temperature. The magnetic saturation moment is as high as 0.51 µB/Co at 2 K and 0.32 µB/Co at room temperature - ten times larger than previously reported on hydrogenated amorphous carbon [1]. The structural disorder of the nanoparticles results in a spin glass behaviour with a range of transition temperatures below ~70 K, suggesting a spin disordered shell model [2]. Thus high fluence Co-implantation into amorphous carbon at room temperature created complex magnetic nanostructures consisting of cobalt oxide and cobalt carbide. Multiple magnetic phases such as superparamagnetism, spin glass, ferromagnetism and also antiferromagnetism can be observed.

References:

1. P.G. Sridhar Gupta, G.V.M. Williams and A. Markwitz, Journal of Physics D: Applied Physics, 2016, 49, 5, 055002.
2. T. Prakash, G.V.M. Williams, J. Kennedy and S. Rubanov, Materials Research Express, 2016, 3, 12, 126102.

We introduce a complex image processing scheme for the simultaneous application of liquid crystal thermometry (LCT), in addition to the previously established method in Anders et al. (Exp Fluids 60(4):68, 2019. https ://doi.org/10.1007/s00348-019-2703-8) for particle tracking velocimetry and particle image velocimetry. This scheme was developed for an experimental study on the double-diffusive convection in an aqueous ammonium chloride solution NH4Cl(aq) during crystallization. The use of thermochromic liquid crystals (TLC) enables to visualize the flow and temperature field simultaneously. We present a color interpolation method that enhances the accuracy of the LCT by yielding RGB images only representative of the TLC’s coloration. An artificial neural network (ANN) which processes RGB triplets and spatial color dependencies transforms these images into temperature fields. The combination of the ANN system and a corresponding calibration procedure enhances the accuracy and measurable temperature range of the LCT compared to state-of-the-art procedures. By using the here established measurement scheme, quantitative global studies of the mutual influence between solidification and convection are enabled and exemplary results are presented.

Rhenium ist ein sehr seltenes Element. Die Häufigkeit in der Lithosphäre liegt in der Größenordnung von Gold. Als Hochtechnologiemetall erfährt Rhenium insbesondere zur Fertigung hochwarmfester Superlegierungen steigende Nachfrage. Sowohl in den natürlichen Lagerstätten, als auch in Sekundärrohstoffen, liegt Rhenium häufig gemeinsam mit Molybdän vor.
Im Rahmen der Solventextraktion von Re(VII) und Mo(VI) aus saurer Lösung mittels aliphatischer Amine wurde bereits in den 1980er Jahren ein Effekt beschrieben, der bei Zusatz von Organophosphorderivaten eine selektive Trennung von Re(VII) und Mo(VI) bei der Reextraktion ermöglicht. Die vorliegende Arbeit nutzt FTIR-Spektroskopie und mehrdimensionale NMR-Experimente, um die Ursachen für die selektive Trennung der beiden Elemente zu belegen und Wege zu ihrer Optimierung aufzuzeigen.
Die Ergebnisse der selektiven Reextraktion (Stripping) werden in Übereinstimmung mit den spektroskopischen Befunden vor dem Hintergrund ihrer supramolekularen Ursachen präsentiert.

The electronic structure and optical spectra of anatase titanium dioxide is computed by combining state-of-the-art density functional theory (DFT) and many-body perturbation theory (MBPT). Excitonic optical spectra is computed by solving Bethe-SalpeterEquation (BSE). From the solution of BSE and also from the analysis of charge distribution the photo-generated excitons in anatase is shown to be strongly bound and localized. Such typical behavior of intrinsic excitons in bulk anatase makes it a material which shows superior performance in photo catalysis, photovoltaics, optoelectronics and in nonlinear optical regime.

Correlative microscopy combining light and electron microscopy (CLEM) has become one of the important and unmissable tools in various investigations of complex biological systems revealing high-resolution structural and highly-specific functional information [1]. In the last years more combinations of other advanced techniques have been developed, such as combining optical microscopy with atomic force spectroscopy/microscopy (AFM) or with magnetic resonance imaging, etc [2] whereas in our study multimodal optical microscopy has been correlated with ion and electron based techniques such as is helium ion microscopy (HIM) [3]. The purpose for using combination of the complementary techniques was to elucidate or better interpret specific biological problems which could not be explained just by one technique lacking of whether resolution, sensitivity of specificity. We focused on toxicology related scientific questions of how inhaled nanoparticles interact with lung epithelial cells/tissue once get into direct contact and why interactions can eventually lead to diseases and potentially persistent inflammation [4,5]. In order to better understand the interaction on nanometer scales we first developed proper lung in-vitro model which was followed by proper sample preparation for efficient correlative microscopy using multimodal optical microscopy and high resolution HIM microscopy. By latter we managed to image single metal oxide nanoparticles on cell surfaces interacting with cell membranes, while functional information of the same events was prior measured with confocal and super-resolution optical microscopy. Besides, we implemented described correlative microscopies also for scientific problem related to rejection of hip implants where material debris is found everywhere in the surrounding periprosthetic tissue with lack of knowledge what happens on a molecular scale. The latest findings of both ongoing studies will be presented.

References:

1. P. de Boer, JP Hoogenboom, BNG Giepmans, Nature Methods 12, 503-513 (2015).
2. T Ando, et. Al, Journal of Physics D: Applied physics 44, (2018)
3. G Hlawacek. et Al. Helium Ion Microscopy. J. Vac. Sci. Technol. 32, (2014)
4. Li, X., Jin, L. & Kan, H. Air pollution: a global problem needs local fixes. Nature 570, 437–439 (2019).
5. E Underwood. The polluted brain. Science 355, 342–345 (2017).

In this paper, we propose a supervised learning method for estimating mineral quantities in drill core hyperspectral data. Our proposed method links the high-resolution mineralogical analyses and hyperspectral data to learn a dictionary. The learned dictionary is then used for linear unmixing and estimating mineral abundances of the entire drill core sample. To evaluate the performance of the proposed method, we use a drill core data set, which is composed of the VNIR-SWIR hyperspectral data and high-resolution mineralogical analyses performed by a Scanning Electron Microscopy (SEM) instrument equipped with the Mineral Liberation Analysis (MLA) software. The quantitative and qualitative analysis of the experimental results shows that the proposed method provides reliable mineral quantity estimates.

Bis ein Endlager in tiefen geologischen Formationen zur Verfügung steht, besteht in Deutschland Bedarf für die sichere Zwischenlagerung abgebrannter Brennelemente an den Kraftwerksstandorten. Es wird davon ausgegangen, dass erhebliche Zeiträume von mehr als 50 Jahren zu berücksichtigen sind. Dadurch ergeben sich verschiedene regulatorische und sicherheitstechnische Fragestellungen. Eine davon ist die nach der Langzeitintegrität der Brennelemente in den Behältern. Ihre Beantwortung hat direkte Relevanz für den späteren Transport zum Endlager und die Umladung des abgebrannten Kernbrennstoffs in andere Behälter. Im Rahmen des vom BMWi geförderten Vorhabens DCS-MONITOR untersuchen wir Potenziale und Grenzen von nichtinvasiven Verfahren zur Überwachung des Zustands des radioaktiven Inventars von Trockenlagerbehältern. Als solche betrachten wir die Thermographie, strahlungsbasierte Messverfahren sowie akustische Messverfahren.

We investigated the suitability of thermography for detecting a potential relocation of the inventory of dry storage containers of type CASTOR V/19. We used numerical simulations of the heat transfer in the container to determine the sensitivity of the wall temperature distribution to such changes. We conducted an analysis for three different hypothetical damage cases: a 9 cm compaction of the fuel in all fuel rods of a single fuel assembly, the same compaction in all fuel assemblies and a compaction of all fuel assemblies by 50 %. The analysis shows that the temperature difference between intact case and all three damage cases after 40 years is too low for an accurate detection becoming even lower for longer storage periods. Temporal thermal insulation of the containers may increase the temperature gradients but reducing the spatial resolution.

The combined structural, magnetic and thermoelectric study of polycrystalline ternary MIn2S4 (M = Mn, Fe, Co, Ni) thiospinels is presented. All compounds crystallize with MgAl2O4-type structure. Rietveld refinement analysis confirmed that the preferred crystallographic position of transition metal element changes from mainly tetrahedral 8a for Mn to exclusively octahedral 16d for Ni (i.e. increase of the inversion parameter). The magnetic susceptibility measurements revealed M-elements to possess 2+ oxidation state in MIn2S4. All these compounds order antiferromagnetic with Néel temperature TN ranging from 5–13 K. Studied thiospinels are n-type semiconductors with large values of electrical resistivity ρ > 0.6 Ω∙m at RT. An increase of inversion parameter leads to reduction of determined activation energies, as well as to the more disorder-like behavior of thermal conductivity. The highest thermoelectric figure of merit ZT was observed for MIn2S4 with M = Fe, Ni, which adopt inverse spinel structure.

In our project we are developing methods for the detection of the anthropogenic radionuclide 99-Technetium by Accelerator Mass Spectrometry (AMS). For environmental samples, a highly effective chemical sample preparation method was developed, that removes a large fraction of the interfering elements Ruthenium and Molybdenum and embeds the Tc in a Niobium matrix. The samples were measured at the AMS setup of the Maier-Leibnitz-Laboratory in Munich by extraction of 99TcO− from the ion source, stripping to 99Tc12+ and normalizing to the 93Nb11+ current. A particle energy of 150 MeV in combination with the detection via a Time-of-Flight path and the Gas-filled Analyzing Magnet System (GAMS) allows for a sensitivity of 5·1E6 atoms per sample. The method is discussed together with results from environmental samples. In particular, 99Tc concentrations along a water column from the Pacific Ocean, as well as in porewater from an Austrian peat-bog are presented.

The fission product 90Sr (T1/2 = 28.9 a) is of interest in environmental sciences for its radiotoxicity as well as a potential tracer. Limits of detection (LoD) of mass spectrometric methods such as ICP-MS, RIMS or conventional AMS are close to the radiometric limit of 3 mBq.
The main problem in AMS of 90Sr is the strong interference of the stable isobar 90Zr. This problem can be overcome with the new Ion Laser InterAction Mass Spectrometry (ILIAMS) setup at the Vienna Environmental Research Accelerator (VERA). It provides near complete suppression of elemental or molecular isobars via selective laser photodetachment inside a gas-filled radiofrequency quadrupole (RFQ). With 10W of laser power from a 532nm cw-laser and a He+O2 mixture as buffer gas, ILIAMS achieves a suppression factor for 90Zr of 10⁷. Extracting SrF₃^− out of the ion source and elemental separation inside an ionization chamber gives an additional Zr suppression of 10⁵.
Measurements with dilution series of reference materials were successfully conducted. The overall Sr detection efficiency is 0.4 %₀ and the
blank level 90Sr/Sr=(4.5 ± 3.2)×10^−15. This corresponds to a more than tenfold improved LoD of 0.1 mBq.

At the Grimsel Test Site (Switzerland), several in situ tracer tests aim at studying the possible radionuclide release from the bentonite engineered barrier system and the processes which may lead to their subsequent migration though the granodiorite host rock. We investigate the diffusion of Tc-99 and actinides (AN) through bentonite and the remobilization over a time period of several years of the AN tracers employed in previous in situ tests. AMS is the ultra-trace analysis method of choice for studying the behaviour of Tc-99 and AN with concentration at and below fg/g levels in such dedicated long-term in situ tests, providing results that contribute to the safety evaluation of future nuclear waste repositories.

The recently developed GENTOP (Generalized Two Phase Flow) concept which bases on the multi-field Euler-Euler approach was applied to model a free-surface vortex - a flow situation which is relevant for hydraulic intake. A new bubble entrainment model has been developed and implemented in the concept. In general a satisfying agreement with the experimental data can be achieved. However, the gas entrainment can be largely affected by several parameters or models used in the CFD (Computational Fluid Dynamics) simulation. The scale of curvature correction C_scale in the turbulence model, the coefficient in the entrainment model C_ent and the assigned bubble size to be entrained has significant influence on the gas entrainment rate. The gas entrainment increases with higher C_scale which can be attributed to the stronger rotation captured by the simulation. A smaller bubble size gives higher gas entrainment while a larger bubble size leads to a smaller entrainment with a periodical peak of entrainment in its transient profile. The results also show that the gas entrainment can be controlled by adjusting the entrainment coefficient C_ent. Basing on the modeling framework presented in this paper further improvement on the physical modeling of the entrainment process should be done.

The Ion Laser InterAction Mass Spectrometry (ILIAMS) technique at the Vienna Environmental Research Accelerator (VERA) tackles the problem of elemental selectivity in AMS. It achieves near-complete suppression of isobar contaminants via selective laser photodetachment of decelerated anion beams in a gas-filled radio frequency quadrupole cooler. The technique exploits differences in electron affinities (EA) within elemental or molecular isobaric systems neutralizing anions with EAs smaller than the photon energy. Collisional detachment or chemical reactions with the buffer gas can further enhance anion separation.
In AMS of 36Cl and 26Al, ILIAMS reliably provides isobar suppression of more than 10 orders of magnitude. Furthermore it already enables measurements of 90Sr, 135,137Cs and 182Hf with unprecedented sensitivity at VERA and allows to study anion chemistry at eV energies.
Current research focusses on extending this technique to 41Ca, 53Mn, 59Ni, 99Tc and 107Pd. Exotic species such as double-negatively charged carbon clusters complete the cooler ’guestbook’. This contribution will give an overview over these achievements and prospects of the ILIAMS-technique for the near future.

For the age range from 1.5 to 4 Myr ago we found in deep ocean ferromanganese crusts an excess concentration in terms of 53Mn/Mn of about 4 · 10−14 over that expected for cosmogenic production. We conclude that this 53Mn is of supernova origin because it is detected in the same time window, about 2.5 Myr ago, where 60Fe has been found earlier. This overabundance confirms unambiguously the supernova (SN) origin of that 60Fe. For the first time supernova-formed 53Mn has been detected and it is the second positively verified radioisotope from the same supernovae. The ratio 53Mn/60Fe of about 12 is consistent with that expected for a SN with a 11 - 25 M⊙ progenitor mass and
solar metallicity. A fit over the whole range until 10 Myr shows also a second increase of 53Mn/Mn in the range around 6 Myr matching
recent 60Fe detection in sediments at ANU.

Cancer is one of the main causes of death and represents a worldwide health problem. Most of the cancer-related deaths are associated with the appearance and progression of a solid tumor. Even though effective conventional treatments exist, they share a common drawback, which is their incapacity to strictly distinguish between malignant and healthy cells. Since it was observed that immune cells are capable to eliminate cancer cells, extensive research has been made to retarget immune cells towards malignant cells without damaging healthy tissue. This type of approach is termed as immunotherapy and involves diverse strategies ranging from the use of Abs to engineered immune cells. One of the most attractive immunotherapeutic strategies is based on the engineering of T cells to express chimeric antigen receptors (CARs), which can recognize specific antigens localized on the surface of cancer cells, leading to an activation of the CAR T cells and a subsequently killing of the malignant cells. Even though CAR technology has shown a strong potential in targeting cancer cells during pre-clinical and clinical studies, numerous clinical trials have also revealed that once they are infused into the patient, the activity of the modified T cells becomes uncontrollable, which represents the main safety problem from the system. For this reason, a novel modular and switchable CAR platform, termed as RevCAR system, was developed in the group of Prof. Bachmann. A crucial element of mentioned system is the design of the RevCAR. In contrast to conventional CARs, RevCARs lack an extracellular binding moiety and comprise only a short peptide epitope instead. Thus, RevCAR T cells are per se inert because they cannot bind to any antigen. Only in the presence of target modules (RevTMs), which bind on the one hand to the peptide epitope of RevCARs and on the other hand simultaneously to tumor targets, RevCAR T cells can be redirected and consequently activated against tumor cells. An attractive tumor-associated antigen (TAA) for the development of immunotherapies is the carcinoembryonic antigen (CEA), because it is highly overexpressed on certain cancer types associated with solid tumor formation, such as breast and lung cancer. In order to show the proof of concept that CEA is an optimal TAA to redirect the RevCAR system, two different formats of RevTMs (scFv- or IgG-based) were produced and tested for their functionality. Here we have shown, that both RevTMs were able to efficiently redirect RevCAR T cells to eliminate CEA-expressing tumor cells in an antigenand epitope-specific as well as TM-dependent manner. Moreover, here, the IgG4-based RevTM worked more efficient than the scFv-based RevTM.

High-intensity short-pulse lasers in the Petawatt regime offer the possibility to study new compact accelerator schemes by utilizing high-density targets for the generation of energetic ion beams. The optimization of the acceleration process demands comprehensive exploration of the plasma dynamics involved, for example via optical probing. In particular, experiments using low density cryogenic hydrogen jet targets with µm-scale transverse size are well suited to deliver new results which can then be compared to predictive particle-in-cell simulations. However, strong plasma self-emission and conversion of the plasma’s drive laser wavelength into its harmonics often masks the interaction region and complicates data analysis. Here, we present a stand-alone probe laser system operating at 1030 nm, far off the plasma’s drive laser wavelength of 800 nm and its implementation into an experiment dedicated to laser-proton acceleration from the hydrogen jet target irradiated by the DRACO PW laser at Helmholtz-Zentrum Dresden – Rossendorf. We show that the plasma self-emission in the probe images is significantly suppressed and we are able to measure the pre-expansion of the target by the DRACO PW laser for intrinsic and for plasma mirror enhanced laser contrast. The influence of the plasma pre-expansion on the measured proton acceleration performance is presented.

Extensive research in the last decades has revealed the dynamic role of the immune system in surveillance, recognition and elimination of cancer cells. However, resistant variants can rise and overcome these immune responses by various escape mechanisms. Therefore, huge efforts have been invested in developing of immunotherapies that can overcome these hurdles and allow the specific activation and retargeting of immune cells toward tumor cells. Immunotherapy includes diverse strategies ranging from cytokines to antibodies and their derivatives reaching to engineered immune cells.
One of the very promising immunotherapeutic approaches is based on the engineering of T cells to express chimeric antigen receptors (CARs) which can redirect immune cells to specific antigens leading to T cell activation and subsequent killing of target cells. The CAR technology has shown a strong therapeutic potential in targeting of cancer both in preclinical as well as clinical studies, especially with hematological malignancies, which lead to FDA approval of CD19-specific CAR T cells for the treatment of leukemia. Despite the success of CAR T cells, clinical trials have also revealed various toxicities and adverse events that can be life-threatening for patients. Moreover, the CAR technology still faces many hurdles to achieve an effective targeting of solid tumors due to the structure, immunosuppressive microenvironment and heterogeneity of the disease. Therefore, a novel modular and switchable CAR platform, called the UniCAR system, was developed in the group of Prof. Bachmann in order to address these obstacles. The UniCAR system consists of UniCAR T cells that cannot bind surface antigens. Instead, UniCARs recognize an epitope (E5B9) which is derived from the nuclear protein La-SS/B. Therefore, UniCAR T cells can only be redirected via target modules (TMs) that have the E5B9 tag on one hand and an antigen-binding domain on the other hand. These TMs provide a bridge with tumor cells that allow the activation of UniCAR T cells. Once these TMs are eliminated, the UniCAR T cells can no more be activated, and thus they are switched off. This approach provides not only a safety switch but also a flexible platform for multi-targeting of diverse antigens by using various TMs with different antigen specificities. Alternatively, the UniCAR system can be applied on NK cells or NK cell lines, which have a natural anti-tumor response. Cell lines like NK-92 are of especial interest because they can be used allogenically, and thus provide an off-the-shelf therapy that might reduce the cost and time of therapy development.
For my thesis work, disialoganglioside GD2 was selected as a target for the UniCAR system. GD2 is overexpressed on many tumors including neuroblastoma, Ewing’s sarcoma, melanoma, osteosarcoma and others. In fact, GD2 is considered as one of the priority antigens to be targeted for cancer therapy according to a pilot project of the national cancer institute. Moreover, targeting GD2 with CAR T cells has shown very positive clinical outcome in previously published clinical trials. However, as other tumor-associated antigens, GD2 has also some limited expression on normal tissues including some regions of the central nervous system and peripheral nerves. Therefore, using a safety switch like the UniCAR system emerges as a necessary step to assure better controlling of any on-target/off-tumor side effects.
Driven by these facts, several formats of anti-GD2 TMs were developed in order to redirect UniCAR T cells to GD2-expressing tumors. Three TMs were designed based on a single chain fragment variable (scFv) connected to the E5B9 epitope. However, they differed in the orientation of the variable light and variable heavy chain domains and their linker components in order to find the best functional conformation. In vitro functional assays showed that all of the three TMs were able to redirect UniCAR T cells toward tumor cells leading to efficient tumor cell killing and release of cytokines in an antigen-specific and TM-dependent manner. Furthermore, the TMs showed dose-dependent killing with half-maximal effective concentration (EC50) in the picomolar range. As all the TM formats showed comparable results in vitro, further in vivo studies were restricted to one TM. This anti-GD2 TM was able to activate UniCAR T cells to eradicate GD2-positive tumor cells in experimental mice. Furthermore, the TM was modified and radiolabeled with 64Cu, in order to investigate its pharmacokinetic properties and biodistribution in tumor-bearing mice. PET analysis of the radiolabeled anti-GD2 TM showed enrichment in the GD2-expressing tumors with blood elimination half-life of less than one hour, which makes it a suitable key for a fast safety switch of UniCAR T cells.
In contrast to UniCAR T cells, the UniCAR NK-92 cell line provides an-off-the shelf therapy that can be expanded for allogenic use. Since these cells are usually irradiated before infusion into patients, their life-span as well as the possibility of side effects is reduced. Therefore, we have further created an IgG4-based anti-GD2 TM with an extended half-life that fits to the life-span of irradiated NK-92 cells. PET imaging of the radiolabeled IgG4-based TM showed an increase in the half-life of about 24 folds in comparison to the scFv TM format. Further testing has shown that UniCAR NK-92 cells are functional with both scFv- and IgG4-based TM formats leading to specific killing of GD2-expressing tumor cells as well as secretion of pro-inflammatory cytokines in vitro. In addition, UniCAR NK-92 showed specific killing of tumor cells in vivo when combined with the anti-GD2 TM.
In summary, we have shown that the UniCAR system can be used to redirect both T cells and NK-92 cells against GD2-expressing tumors in vitro as well as in vivo in an antigen-specific and TM-dependent manner. The UniCAR system allows an on/off safety switch as well as fine controlling of the activity of UniCAR T/NK-92 cells via titration (dosing) of the anti-GD2 TMs. Furthermore, it provides a flexible platform that allows the use of several antibody formats for an effective and safe targeting of cancer.

The development of high-intensity short-pulse lasers in the Petawatt regime offers the possibility to design new compact accelerator schemes by utilizing high-density targets for the generation of ion beams with multiple 10 MeV energy per nucleon. The optimization of the acceleration process demands comprehensive exploration of the plasma dynamics involved, for example via spatially and temporally resolved optical probing. Experimental results can then be compared to numerical particle-in-cell simulations, which is particularly sensible in the case of cryogenic hydrogen jet targets. However, strong plasma self-emission and conversion of the plasma’s drive laser wavelength into its harmonics often masks the interaction region and interferes with the data analysis. Recently, the development of a stand-alone and synchronized probe laser system for off-harmonic probing at the DRACO laser operated at the Helmholtz-Zentrum Dresden–Rossendorf showed promising performance.
Here, we present an updated stand-alone probe laser system applying a compact CPA system based on a synchronized fs mode-locked oscillator operating at 1030 nm, far off the plasma’s drive laser wavelength of 800 nm. A chirped volume Bragg grating (Optigrate Corp) is used as a hybrid stretcher and compressor unit. The system delivers 160 fs pulses with a maximum energy of 0.9 mJ. By deploying the upgraded probe laser system in the laser-proton acceleration experiment with the renewable cryogenic hydrogen jet target, the plasma self-emission could be significantly suppressed while studying the temporal evolution of the expanding plasma jet. Recorded probe images resemble those of z-pinch experiments with metal wires and indicate a sausage-like instability along the jet axis, which will be discussed.