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Improved 242Pu(n,γ) thermal cross section combining activation and prompt gamma analysis
Lerendegui-Marco, J.; Guerrero, C.; Belgya, T.; Maróti, B.; Eberhardt, K.; Düllmann, C. E.; Junghans, A. R.; Mokry, C.; Quesada, J. M.; Runke, J.; Thörle-Pospiech, P.
A good knowledge of the radiative capture cross section of 242Pu is required for innovative nuclear reactor studies, especially for MoX fuel reactors. However, the experimental data available show discrepancies in the energy regions of interest: the thermal point and the keV region. Previous experimental results of the thermal cross section deviate from each other by 20% and these discrepancies are reflected also in the evaluated libraries, each of them giving more credit to different data sets. A recent measurement by Genreith et al. did not succeed to solve the existing discrepancy due to the large uncertainties and correction factors in the analysis. This work presents a new measurement of the thermal capture cross section of 242Pu carried out in the Budapest Research Reactor using the same thin targets of a previous measurement at n_TOF-EAR1, each containing 30mg of 99.995% pure 242Pu . The combined analysis of the full prompt γ-ray spectrum and the 243Pu decay has led to three compatible values for the thermal cross section. Their average value, 18.9(9)b, has an improved accuracy compared to recent measurements. Leaving aside the activation value of Genreith using an outdated intensity value for the 84 keV decay line of 243Pu , our average result is in very good agreement with the JEFF-3.2 evaluation and all the previous measurements, with the exception of the highest value 22.5(11)b reported by Marie et al., which has a strong influence in the ENDF evaluation.242
Keywords: neutron capture cross section; 242Pu; thermal neutron spectrum
European Physical Journal A 55(2019), 63
Analysis of studies and research projects regarding the detection of nanomaterials in different environmental compartments and deduction of need for action regarding method development
Hildebrand, H.; Franke, K.; Fischer, C.; Schymura, S.
Exertengespräch und Präsentation der Ergebnisse aus der Literaturstudie zum Nachweis von Nanomaterialien in den verschiedenen Umweltkompartimenten, Projekt NanoExperte
Keywords: nanomaterials in environemtal media; detection; quantification
Invited lecture (Conferences)
Abschlusspräsentation des Sachverständigengutachtens „NanoExperte“, 17.04.2019, Dessau-Roßlau, Deutschland
Specific ion effects directed noble metal aerogels: Versatile manipulation for electrocatalysis and beyond
Du, R.; Hu, Y.; Hübner, R.; Joswig, J.-O.; Fan, X.; Schneider, K.; Eychmüller, A.
Noble metal foams (NMFs) are a new class of functional materials featuring properties of both noble metals and monolithic porous materials, providing impressive prospects in diverse fields. Among reported synthetic methods, the sol-gel approach manifests overwhelming advantages for versatile synthesis of nanostructured NMFs (i.e., noble metal aerogels) under mild conditions. However, limited gelation methods and elusive formation mechanisms retard structure/composition manipulation, hampering on-demand design for practical applications. Here, highly tunable NMFs are fabricated by activating specific ion effects, enabling various single/alloy aerogels with adjustable composition (Au, Ag, Pd, and Pt), ligament sizes (3.1 to 142.0 nm), and special morphologies. Their superior performance in programmable self-propulsion devices and electrocatalytic alcohol oxidation is also demonstrated. This study provides a conceptually new approach to fabricate and manipulate NMFs and an overall framework for understanding the gelation mechanism, paving the way for on-target design of NMFs and investigating structure-performance
relationships for versatile applications.
Science Advances 5(2019), eaaw4590
Dose-volume predictors of early esophageal toxicity in non-small cell lung cancer patients treated with accelerated-hyperfractionated radiotherapy
Bütof, R.; Löck, S.; Soliman, M.; Haase, R.; Perrin, R.; Richter, C.; Appold, S.; Krause, M.; Baumann, M.
Background and purpose: Early radiation-induced esophageal toxicity (RIET) is one of the major side effects in patients with non-small cell lung cancer (NSCLC) and can be a reason for treatment interruptions. As the age of patients with NSCLC and corresponding comorbidities continue to increase, primary radiotherapy alone is a commonly used alternative treatment in these cases. The aim of the present study is to compare dosimetric and clinical parameters from the previously reported CHARTWEL trial for their ability to predict esophagitis and investigate potential differences in the accelerated and conventional fractionation arm.
Material and methods: 146 patients of the Dresden cohort of the randomized phase III CHARTWEL trial were included in this post-hoc analysis. Side effects were prospectively scored weekly during the first 8 weeks from start of radiotherapy. To compare both treatment arms, recorded dose-volume parameters were adjusted for the different fractionation schedules. Logistic regression was performed to predict early RIET for the entire study group as well as for the individual treatment arms. Differentdosimetric and clinical parameters were tested.
Results: Patients receiving the accelerated CHARTWEL schedule experienced earlier and more severe esophagitis (e.g. 20.5% v . 9.6% ≤ grade 2 at week 3, respectively). In contrast, the median time period for recovery of grade 1 esophagitis was significantly longer for patients with conventional fractionation compared to the CHARTWEL group (median [range]: 21 [12-49] days vs. 15 [7-84] days, p=0.028). In univariable logistic regression none of the dose-volume parameters showed a significant correlation with early RIET grade 2 in the conventional irradiation group. In contrast, for patients receiving CHARTWEL, the physical dose-volumes parameters V40 and V50; and re-scaled values VEQD2,50 and VEQD2,60 were significant predictors of early RIET grade 2. Dose-volume parameters remained different between CHARTWEL and conventional fractionation even after biological rescaling.
Conclusion: Our results show a more dominant dose-volume effect in the CHARTWEL arm compared to conventional fractionation, especially for higher esophageal doses. These findings support the notion that dose-volume parameters for radiation esophagitis determined in a specific and time dependent setting of field arrangements can not be easily transferred to another setting. In clinical practice esophageal volumes receiving 40 Gy or more should be strictly limited in hyperfractionated accelerated fraction schemes.
Keywords: Dose-volume parameters; esophagitis; radiotherapy; accelerated; prediction; non-small cell lung cancer; CHARTWEL
Radiotherapy and Oncology 143(2020), 44-50
Eu3+ incorporation into xenotime LnPO4: the effect of local distortion on long term stability
Ceramic matrices are considered for the immobilization of specific nuclear waste streams. Recently, our group has studied the suitability of orthophosphates with monazite structure for this purpose, and found generally good exchangeability between host and guest cation and a corresponding high stability of the materials. Nonetheless, it was evident that both bulk structure and the local coordination environment of the guest cation need to be studied in order to assess the structural strain in the ceramic
material on the molecular level. Here, we present an in-depth study of the incorporation of Eu3+ as a luminescent homologue for the trivalent actinides, such as Am3+, into xenotime orthophosphates. We combine XRD with laser-induced luminescence spectroscopy (TRLFS) as a method to probe the local structure, to understand the impact of the substitution process.
Polarization-dependent TRLFS studies with single crystalline materials show that Eu3+ occupies identical lattice sites in Tb, Y, Ho, Er, and YbPO4. The site has a distinct lower symmetry than the crystallographic cation lattice site, indicating local distortion. In LuPO4, the material with the smallest host cation, this distortion is no longer viable and Eu3+ occupies a less distorted site with similar geometry to the crystallographic lattice site. The very small site enforces a strong overlap of ligand and metal orbitals, inducing strong spectral shifts as well as coupling to lattice phonons. Characterization of polycrystalline materials reveals a more complex mineralogy, including an anhydrite-type phase and monazite in addition to xenotime. Eu3+ distribution indicates a clear aversion for the xenotime lattice when other phases are present. In the absence of other phases, Eu3+ is incorporated into xenotime initially, but long term studies reveal a complex unmixing process.
 Xiao, B. et al., (2018), Chem Eur J., 24, 13368-77.
 Lösch, H. et al., (2019), Front. Chem., 7, 94.
Keywords: xenotime; TRLFS; luminescence; lanthanides
Goldschmidt 2019, 18.-23.08.2019, Barcelona, Espana
Uranium toxicity on plant cells: Isothermal microcalorimetric studies for the differentiation between chemotoxic and radiotoxic effects of uranium
Sachs, S.; Oertel, J.; Fahmy, K.
The transfer of radionuclides into the food chain is a central concern in the safety assessment of both nuclear waste repositories and remediation strategies in radioactively contaminated sites, such as legacies of the former uranium mining. The uptake and translocation of radionuclides, e.g., uranium, is speciation dependent and induces several stress response reactions, which changes the plant metabolism. Correlating molecular information on radionuclide speciation and biomolecular interactions with physiological performance is a major challenge for radioecology.
In our previous work we applied isothermal microcalorimetry as a sensitive real-time monitor to study the interaction of U(VI) with canola (Brassica napus) cells (Sachs et al., 2017). Applying this method we were able to monitor the metabolic activity of the cells in the presence of U(VI) and to determine the U(VI) toxicity in B. napus cells. Those was correlated with the oxidoreductase activity of the cells and the U(VI) speciation in solution. Based on this work we are currently investigating the differentiation between chemotoxic and radiotoxic effects of uranium on B. napus cells applying natural uranium as well as 233U as alpha emitter. To discriminate between these effects, the metabolic heat flow of the cells at a constant total uranium concentration of 50 µmol/L is monitored by isothermal microcalorimetry applying increasing concentrations of 233U (1-15 µmol/L), which correspond to increasing radiation doses. Applying liquid scintillation counting (LSC) we determine the amount of uranium that is bioassociated to the plant cells and estimate the respective 233U doses for the cells.
Mc values provide a quantitative ranking of metabolic activities that is independent of cell number and largely unaffected by normal variations between experiments (Sachs et al., 2017). Our data are normalized to Mc values of B. napus cells that were exposed to natural uranium only. In the presence of 2 µM 233U a slight increase in the Mc values was observed, which indicates a slightly higher metabolic activity of the cells. Probably, this is an indication for a stress response of the cells to the radiotoxic effect of 233U. With increasing 233U concentration only a slight decrease of the Mc values was observed. This indicates only a slight effect of the alpha radiation on the cells compared to those cells that were exposed to natural uranium, which exhibits a predominant chemotoxic effect. These first results point to a high resistance of B. napus cells to the radiotoxicity of 233U.
This presentation will demonstrate the potential of life cell microcalorimetry for radioecological studies. We will present the calorimetric determination of the U(VI) toxicity in B. napus cells that correlates with oxidoreductase activity and U(VI) speciation and will focus on the differentiation between chemotoxic and radiotoxic effects of uranium.
Sachs, S., Geipel, G., Bok, F., Oertel, J., Fahmy, K. 2017. Calorimetrically determined U(VI) toxicity in Brassica napus correlates with oxidoreductase activity and U(VI) speciation. Environ. Sci. Technol. 51, 10843-10849.
Keywords: uranium; plant cells; toxicity; isothermal microcalorimetry
ENVIRA 2019, 5th International Conference on Environmental Radioactivity, 08.-13.09.2019, Prague, Czech Republic
Influence of local magnification effects in the atom probe for silicon nanocrystals doped by indium
Nomoto, K.; Hiller, D.; Rebohle, L.; Ringer, S.
Atom probe tomography (APT) is a powerful tool to study the 3-dimensional structure of materials with sub-nanometer spatial resolution. This allows us to study the location of atoms such as dopant positions in nanocrystals (NCs) with high accuracy. However, one of the limitations for the spatial resolution are the effects of local magnification when there are multiple elements with different evaporation rates in the atom probe specimen. For example, in the system of silicon (Si) NCs embedded in SiO2, the difference in the local evaporation field between Si NCs and SiO2 results in a non-uniform sequence of evaporation and this affects the accuracy of the 3-dimensional reconstruction of the atom probe experiment (i.e. over/under estimation of the number of doped atoms in the Si NCs). In this study, we use indium (In) as a dopant to investigate the local magnification effects. Due to the very low solubility of In-atoms in Si, the detected In-atoms inside of Si NCs can be attributed to the local magnification effects and we can quantitatively estimate the number of atoms which are projected inside of Si NCs due to the trajectory artefact. This approach provides a model system to quantify and correct local magnification effects which allows a more precise and advanced study of Si nanostructures.
Keywords: Atom probe tomography; Si nanocrystals; ion implantation
European Material Research Society Spring Meeting 2019, 27.-31.05.2019, Nice, France
Radiobiology of high dose-rate particle beams
Beyreuther, E.; Karsch, L.; Pawelke, J.
In the past few years, the normal tissue protecting effect of Flash electron irradiation was shown for several endpoints and in different species , . Contrary to conventional, clinical beam delivery over minutes, the therapeutic dose is administered within less than 0.5 s by Flash irradiation. Hence, this treatment regime is linked to high mean dose rates of ~100 Gy/s and high pulse dose rates of ≥105 Gy/s, clearly exceeding the parameters of a few Gy/min on time average and of ~ 102 Gy/s within one pulse of conventional, clinical Linacs. Of note, tumors were cured by electron Flash as efficient as by conventional electron beam treatment over minutes . Moreover, the protecting Flash effect was recently validated for photons , which promises a general validity of this effect also for other types of clinically used radiation.
First attempts testing the feasibility of proton Flash were conducted at clinical proton beam facilities in France  and at the University Proton Therapy Dresden (UPTD), Germany. At UPTD, a setup was established that allows for the irradiation of zebrafish embryo either with dose rates of 100 Gy/s for Flash or of 5 Gy/min for conventional reference. The zebrafish embryo were treated with graded doses up to 40 Gy and embryonic survival as well as the manifestation of morphological abnormalities were followed for up to four days. However, analysing the different endpoints, a clear dependency on dose but no significant dependence on proton dose rate was revealed.
This unexpected result implies, that more studies are needed to resolve the influence on beam time structure for the induction of a protective Flash effect. Here, research facilities like FAIR with a broader parameter space regarding ion species, particle fluence, LET, pulsing and beam time structure provide the possibility to study the physical limits of Flash in more detail. Therewith also questions on a potential influence or interaction of high dose-rate particle beam, high LET and oxygen level of the irradiated tissue could be investigated systematically. The results obtained therein could help to further develop dedicated clinical accelerators, like superconducting or heavy ion synchrotrons, to make clinical use of the Flash effect.
 V. Favaudon et al., “Ultrahigh dose-rate FLASH irradiation increases the differential response between normal and tumor tissue in mice,” Sci. Transl. Med., vol. 6, no. 245, p. 245ra93, Jul. 2014.
 P. Montay-Gruel et al., “Irradiation in a flash: Unique sparing of memory in mice after whole brain irradiation with dose rates above 100Gy/s,” Radiother. Oncol. J. Eur. Soc. Ther. Radiol. Oncol., vol. 124, no. 3, pp. 365–369, 2017.
 P. Montay-Gruel et al., “X-rays can trigger the FLASH effect: Ultra-high dose-rate synchrotron light source prevents normal brain injury after whole brain irradiation in mice,” Radiother. Oncol. J. Eur. Soc. Ther. Radiol. Oncol., vol. 129, no. 3, pp. 582–588, Dec. 2018.
 A. Patriarca et al., “Experimental Set-up for FLASH Proton Irradiation of Small Animals Using a Clinical System,” Int. J. Radiat. Oncol. Biol. Phys., vol. 102, no. 3, pp. 619–626, Nov. 2018.
Contribution to proceedings
International Biophysics Collaboration Meeting, 20.-22.05.2019, Darmstadt, Deutschland
International Biophysics Collaboration Meeting, 20.-22.05.2019, Darmstadt, Deutschland
‘Box-Profile’ Ion Implants as Geochemical Reference Materials for Electron Probe Microanalysis and Secondary Ion Mass Spectrometry
EPMA (Electron Probe Microanalysis) and SIMS (Secondary Ion Mass Spectrometry) are widely used analytical techniques for geochemical and mineralogical applications. Nevertheless, metrologically rigorous quantification remains a major challenge for these methods. SIMS in particular is a matrix-sensitive method; for SIMS the use of matrix-matched reference materials (RMs) is essential in order to avoid significant analytical bias. A major problem is that the list of available RMs for SIMS is vanishingly short compared to the needs of the analyst. One approach for the production of matrix-specific RMs is the use of high-energy ion implantation that introduces a known amount of a selected isotope into a material. We chose the more elaborate way of implanting a so-called ‘box profile’ to generate a quasi-homogeneous concentration of the implanted isotope in three dimensions, which allows RMs not only to be used for ion beam analysis but also makes them suitable for EPMA. For proof of concept, we used the thoroughly studied mineralogically and chemically ‘simple’ SiO2 system, which addresses many interesting scientific challenges, such as the Ti-in-quartz geothermometer (Wark et al. 2006, Thomas et al. 2010). We implanted either 47Ti or 48Ti into synthetic, ultra-high purity silica glass. Several ‘box profiles’ with concentrations between 10 and 1000 µg g-1 Ti and maximum depths of homogeneous Ti distribution between 200 nm and 3 µm were produced at the Institute of Ion Beam Physics and Materials Research of Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Multiple implantation steps using varying ion energies and ion doses were simulated with the SRIM (Stopping and Range of Ions in Matter) software (Ziegler et al. 2008), optimizing for the target concentrations, implantation-depths and technical limits of the implanter.
We characterized several implant test-samples having different concentrations and maximum implantation depths by means of SIMS and other analytical techniques. The results show that the implant samples are suitable for use as reference materials for SIMS measurements. The multi-energy ion implantation technique also looks to be very promising procedure for the production of EPMA-suitable reference materials.
Keywords: ‘box-profile’; multi-energy ion implantation; EPMA; SIMS; synthetic reference material
Geostandards and Geoanalytical Research 43(2019)4, 531-541
- Final Draft PDF 1,9 MB Secondary publication
Multi-Sensor Spectral Imaging of Geological Samples: A Data Fusion Approach using Spatio-Spectral Feature Extraction
Spectral imaging or hyperspectral reflectance mapping for mineral exploration sample analysis has evolved rapidly in the recent decade. A wide range of deployable sensors is available nowadays, providing high flexibility in spectral as well as in spatial resolution and coverage. However, the fusion of data from different customized setups and sensors is challenging and usually not conducted. In the following study, the integration of such multi-sensor datasets is demonstrated on data acquired from five commercially available hyperspectral sensors and a pair of RGB cameras. We present a workflow for the integrated image analyses using advanced machine learning methods and evaluate the procedure on a representative set of geological samples. Detailed mineralogical and spectral validation affirms the approach. The suggested workflow provides a new way for the integration of multi-source data, e.g., it allows a straight-forward integration of visible/near-infrared (VNIR), short-wave infrared (SWIR) and long-wave infrared (LWIR) data for sensors with highly different spatial and spectral resolution. Finally, we evaluate the benefits of different multi-sensor combinations for potential applications in mineral exploration.
Keywords: hyperspectral; spectral imaging; multi-sensor data; data fusion; feature extraction; Support Vector Machine (SVM); Orthogonal Total Variation Component Analysis (OTVCA); mineral exploration
Sensors 19(2019), 2787
Focused ion beam modification of non-local magnon-based transport in yttrium iron garnet/platinum heterostructures
We study the impact of Ga ion exposure on the local and non-local magnetotransport response in heterostructures of the ferrimagnetic insulator yttrium iron garnet and platinum. In particular, we cut the yttrium iron garnet layer in between two electrically separated wires of platinum using a Ga ion beam, and study the ensuing changes in the magnetoresistive response. between the Pt wires is fully cut, although the local spin Hall magnetoresistance signal remains finite. This observation corroborates the notion that pure spin currents carried by magnons are crucial for the non-local magnetotransport effects observed in magnetic insulator/metal nanostructures and that possible substrate contributions to the non-local transport can be ruled out.
Keywords: nano magnetism; spin transport; focussed ion beam
Applied Physics Letters 114(2019), 252401
Superconductivity in single-crystalline aluminum- and gallium-hyperdoped germanium
Superconductivity in group IV semiconductors is desired for hybrid devices combining both semiconducting and superconducting properties. Following boron-doped diamond and Si, superconductivity has been observed in gallium-doped Ge; however, the obtained specimen is in polycrystalline form [Phys. Rev. Lett. 102, 217003 (2009)]. Here we present superconducting single-crystalline Ge hyperdoped with gallium or aluminum by ion implantation and rear-side flash lamp annealing. The maximum concentration of Al and Ga incorporated into substitutional positions in Ge is 8 times higher than the equilibrium solid solubility. This corresponds to a hole concentration above 1021 cm−3. Using density functional theory in the local-density approximation and pseudopotential plane-wave approach, we show that the superconductivity in p-type Ge is phonon mediated. According to the ab initio calculations, the critical superconducting temperature for Al- and Ga-doped Ge is in the range of 0.45 K for 6.25at.% of dopant concentration, being in qualitative agreement with experimentally obtained values.
Keywords: superconductivity; ion implantation; Germanium; flash lamp annealing
Physical Review Materials 3(2019), 054802
- Original PDF 1,7 MB Secondary publication
Antimonite binding to natural organic matter: Spectroscopic evidence from a mine water impacted peatland
Besold, J.; Eberle, A.; Noël, V.; Kujala, K.; Kumar, N.; Scheinost, A.; Lezama Pacheco, J.; Fendorf, S.; Planer-Friedrich, B.
Peatlands and other wetlands are sinks for antimony (Sb). Solid natural organic matter (NOM) has thus been suggested to play an important role in controlling Sb binding in wetland sediments. However, direct spectroscopic evidence for this sequestration mechanism in natural peat samples is still lacking. In order to investigate Sb binding in peat, we sampled and characterized three profiles up to a depth of 80 cm in an Sb-impacted peatland in northern Finland. We used bulk K-edge X-ray absorption spectroscopy to study the speciation of Fe, S and Sb in the peat solid phase. Additionally, we determined the aqueous speciation of Sb in surface and pore waters. Based on linear combination fittings of extended X-ray absorption fine structure spectra, we found that Sb associated to the solid-phase is up to 100% coordinated to organic phenol and/or thiol groups. Even in the presence of iron, organically-bound Sb(III) was the dominant fraction in all peat profiles and across all depths. While aqueous antimonite concentrations were low, Sb(III) species were dominating solid-phase speciation, suggesting a high reactivity of Sb(III) towards peat surfaces. Our findings therefore confirm that Sb binding to solid NOM acts as an important sequestration mechanism under reducing conditions in NOM-rich wetlands.
Keywords: EXAFS; sulfur; iron; antimony; peat
Environmental Science & Technology 53(2019), 10782-10802
- Final Draft PDF 1,2 MB Secondary publication
Monolithic waveguide laser mode-locked by embedded Ag nanoparticles operating at 1 μm
Monolithic waveguide laser devices are required to achieve on-chip lasing. In this work, a new design of a monolithic device with embedded Ag nanoparticles (NPs) plus the Nd:YAG ridge waveguide has been proposed and implemented. By using Ag+ ion implantation, the embedded Ag NPs are synthesized on the near-surface region of the Nd:YAG crystal, resulting in the significant enhancement of the optical nonlinearity of Nd:YAG and offering saturable absorption properties of the crystal at a wide wavelength band. The subsequent processing of the O5+ ion implantation and diamond saw dicing of crystal finally leads to the fabrication of monolithic waveguide with embedded Ag NPs. Under an optical pump, the Q-switched mode-locked waveguide lasers operating at 1 μm is realized with the pulse duration of 29.5 ps and fundamental repetition rate of 10.53 GHz, owing to the modulation of Ag NPs through evanescent field interaction with waveguide modes. This work introduces a new approach in the application of monolithic ultrafast laser devices by using embedded metallic NPs.
Nanophotonics 8(2019), 859-868
Ion acceleration from ultra-thin foil targets with on-shot monitored temporal contrast
Laser-driven ion acceleration promises to provide a compact solution for demanding applications like particle therapy, proton radiography or inertial confinement research. Controlling the particle beam parameters to achieve these goals is currently pushing the frontier of laser driven particle accelerators.
The performance of the plasma acceleration is strongly dependent on the complex pre-plasma formation process at the target front surface which is determined by the temporal intensity contrast. Particularly low-density targets require an enhanced temporal contrast to remain overcritical until the main pulse arrives. Plasma mirror setups have proven to significantly improve the temporal contrast by reducing pre-pulse intensity and steepening the rising edge of the main laser pulse, enabling the investigation of laser proton acceleration and proton energy scaling using ultra-thin targets.
We present new experimental results on the interaction of the DRACO Petawatt ultra-short pulse laser with ultra-thin foil targets. Efficient and on-demand contrast cleaning established through a re-collimating plasma mirror setup facilitated thickness scans from the µm range down to several tens of nm. The combination of a complex set of diagnostics, consisting of proton detectors in target normal, laser forward and laser backward axis, laser pulse transmission and reflection diagnostics as well as detection of front surface electrons, delivered concrete indicators for the acceleration conditions. Furthermore, tremendous progress has been achieved by successfully implementing a novel laser contrast diagnostic by means of self-referenced spectral interferometry with extended time excursion (SRSI-ETE), allowing to characterize the temporal contrast in the experimental area on a single-shot base with unprecedented dynamic and temporal range.
Laser-Plasma Accelerator Workshop 2019, 05.-10.05.2019, Split, Kroatien
Beam quality optimization in a beam loaded nanocoulomb-class laser wakefield accelerator
Here we report on optimization of both energy spread and beam divergence in a laser wakefield accelerator (LWFA) operating in the beam loading regime. The self-truncated ionization injection scheme is employed, enabling a precise control over the amount of injected electrons with charges up to 0.5 nC (FWHM) at a quasi-monoenergetic peak.
By employing the optimal beam loading condition, the accelerating gradient is flattened and we eliminate additional energy spread contribution from the acceleration process1,2. This point of minimized finite energy spread is used to limit the betatron oscillations of bunch electrons, leading to a decrease of the normalized beam divergence. Meanwhile, an ultrafast single-shot electron beam diagnostic based on Coherent Transition Radiation reveals ~10 femtosecond bunch lengths yielding peak currents of over 10 kA. Such peak currents are one to two orders of magnitude larger than those found in conventional RF accelerators. Control of the energy spread and beam divergence of LWFA beams with the beam loading condition together with the scaling to high peak currents paves the road for driving secondary superradiant lights sources.
1. J.P. Couperus, et.al., “Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator”, Nature Communication, 8, 487 (2017)
2. A. Irman et al., “Improved performance of laser wakefield acceleration by tailored self-truncation ionization injection”, Plasma Physics and Controlled Fusion, 60, 044015 (2018)
Keywords: beam loading; plasma acceleration; electron acceleration; LWFA; laser wakefield acceleration; LPA; betatron
Laser-Plasma Accelerator Workshop (LPAW) 2019, 05.-10.05.2019, Split, Republika Hrvatska
4th European Advanced Accelerator Concepts Workshop, 15.-21.09.2019, Isola d'Elba, Repubblica Italiana
Laser-driven proton beam profiles in ultra-high fields
Obst-Hübl, L.; Bernert, C.; Brack, F.-E.; Branco, J.; Bussmann, M.; Cochran, G.; Cowan, T.; Curry, C. B.; Gaus, L.; Fiuza, F.; Garten, M.; Gauthier, M.; Glenzer, S. H.; Göde, S.; Hübl, A.; Irman, A.; Kim, J. B.; Kluge, T.; Kraft, S.; Kroll, F.; Macdonald, M. J.; Metzkes-Ng, J.; Mishra, R.; Pausch, R.; Poole, P.; Prencipe, I.; Rehwald, M.; Rödel, C.; Ruyer, C.; Schlenvoigt, H.-P.; Sommer, P.; Schoenwalder, C.; Schumaker, W.; Ziegler, T.; Schramm, U.; Schumacher, D. W.; Zeil, K.
Extreme field gradients intrinsic to relativistic laser-interactions with thin solid targets enable compact multi-MeV proton accelerators with unique bunch characteristics. Protons are accelerated in TV/m fields that are established within the micrometer-scale vicinity of the high-power laser focus. This initial acceleration phase is followed by ballistic proton bunch propagation with negligible space-charge effects over millimeters to hundreds of centimeters to the particle detector or a proton target at a dedicated irradiation site. The detected proton emission distribution can be influenced by the spatio-temporal intensity distribution in the laser focus, electron transport through the target, potential plasma instabilities, as well as local and global target geometry and surface properties.
Substantially extending this picture, our recent results show a critical influence of the milimeter scale vacuum environment on the accelerated proton bunch, where residual gas molecules are ionized by the remnant laser light that is not absorbed into the target plasma but reflected or transmitted. In an experiment with µm-sized hydrogen jet targets, this effect lead to the counter-intuitive observation of laser near-field feature imprints in the detected proton beam profiles. Our results show that the remnant laser pulse induces a quasi-static deflecting field map in the ionized residual background gas that serves as a memorizing medium and allows for asynchronous information transfer to the naturally delayed proton bunch. Occurring under typical experimental laser, target and vacuum conditions, all-optical imprinting needs to be taken into account for sensible interpretation of modulated proton beam profiles.
Keywords: laser-driven plasmas; high-power lasers; novel accelerator concepts; laser-ion acceleration; plasma mirrors
Invited lecture (Conferences)
Laser Plasma Accelerator Workshop 2019, 05.-10.05.2019, Split, Kroatien
Seminar talk, 27.06.2019, London, United Kingdom
First demonstration of a hybrid laser-electron-beam driven plasma wakefield accelerator
Kurz, T.; Heinemann, T.; Schöbel, S.; Couperus Cabadağ, J. P.; Kononenko, O.; Chang, Y.-Y.; Bussmann, M.; Corde, S.; Debus, A.; Ding, H.; Döpp, A.; Gilljohann, M. F.; Hidding, B.; Karsch, S.; Köhler, A.; Pausch, R.; Zarini, O.; Schramm, U.; Martinez De La Ossa, A.; Irman, A.
Plasma based electron acceleration is widely considered as a promising concept for a compact electron accelerator with broad range of future applications from high energy physics to photon science.
These accelerators can be powered by either ultra-intense laser beams (LWFA) or relativistic high-current-density particle beams (PWFA).
Here, we report on a novel approach which combines both schemes in a truly compact experimental setup.
In our “LWFA + PWFA” hybrid accelerator, the electron beam generated by a LWFA stage drives a subsequent PWFA stage where a witness beam is trapped and accelerated.
This strategy aims to combine the unique features of both plasma acceleration techniques, the LWFA stage provides with a compact source of high-current electron beams required as PWFA drivers, while the PWFA stage acts as an energy and brightness transformer for the LWFA output.
In this work, we show the first experimental evidence of accelerating a distinct witness bunch in a LWFA-driven PWFA (LPWFA), within only about one millimeter acceleration distance.
In the beam self-ionizing case, we observe witness energies of around 50 MeV.
By utilizing a counter-propagating pre-ionization laser, the interaction with the plasma becomes stronger, increasing the final energies to around 120 MeV.
Thus, yielding a field gradient of (46+-11) GeV/m which is comparable to what has been shown at large scale facilities.
Keywords: Laser; Plasma Accelerator; Hybrid; Electron beam; Peak Current
Laser-Plasma Accelerator Workshop 2019, 05.-10.05.2019, Split, Kroatien
Synthetic radiation diagnostics as a pathway for studying plasma dynamics from advanced accelerators to astrophysical observations
In this thesis, two novel diagnostic techniques for the identi1cation of plasma dynamics and thequanti cation of essential parameters of the dynamics by means of electromagnetic plasmaradiation are presented. Based on particle-in-cell simulations, both the radiation signatures of micrometer-sized laser plasma accelerators and light-year-sized plasma jets are simulated with the same highly parallel radiation simulation framework, in-situ to the plasma simulation.
The basics and limits of classical radiation calculation, as well as the theoretical and technical foundation of modern plasma simulation using the particle-in-cell method, are brie2y introduced. The combination of previously independent methods in an in-situ analysis code as well as its validation and extension with newly developed algorithms for the simultaneous quantitative prediction of both coherent and incoherent radiation and the prevention of numerical artifacts is outlined in the initial chapters.
For laser wake1eld acceleration, a hitherto unknown off-axis beam signature is observed,which can be used to identify the so-called blowout regime during laser defocusing. Since signi cant radiation is emitted only after the minimum spot size is reached, this signature is ideally suited to determine the laser focus position itself in the plasma to below 100 _m and thus to quantify the in2uence of relativistic self-focusing. A simple semi-analytical scattering model was developed to explain the blowout radiation signature. The spectral signature predicted by the model is veri1ed using both a large-scale explorative simulation and a simulation parameter study, based on an experiment conducted at the HZDR. Identi1ed by the simulations, a temporal asymmetry in the scattered laser light, which cannot be described by state of the art quasi-static models of the blowout regime, makes it possible to determine the focus position precisely by using this radiation signature.
For the so-called Kelvin-Helmholtz instability, a polarization signature is identi1ed that allows both identifying the linear phase of the instability and quantifying its most important parameter, the growth rate. This plasma instability is suspected to occur in the shear region between plasma jets of active galactic nuclei or supernova remnants and the surrounding plasma and causes strong magnetic 1elds to grow along the shear surface. The measurement of the growth rate of these elds allows deducing the internal structure and dynamics of these jets and gaining an insight into previously inaccessible regions. A microscopic model of the electron dynamics was developed which describes the main radiation properties. With an unprecedentedly large and accurate simulation of the relativistic Kelvin-Helmholtz instability, the microscopic model was validated. The discovered polarization signature can be clearly identi1ed even under arbitrary Lorentz transformations for observers on Earth and poses thus an ideal method for astronomical observations.
These very different physical scenarios clearly exemplify the possibilities of synthetic radiation diagnostics and represent the 1rst step towards future explorative studies of plasmas and their radiation in other scenarios using simulations.
Keywords: PhD defense
Disputation, 25.03.2019, Dresden, Deutschland
TU Dresden / HZDR, 2019
Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-107 2019
ISSN: 2191-8708, eISSN: 2191-8716
Modeling hybrid plasma accelerator experiments with PIConGPU
Pausch, R.; Bussmann, M.; Garten, M.; Hübl, A.; Steiniger, K.; Widera, R.; Kurz, T.; Schöbel, S.; Chang, Y.-Y.; Couperus Cabadağ, J. P.; Köhler, A.; Zarini, O.; Heinemann, T.; Ding, H.; Döpp, A.; Gilljohann, M. F.; Kononeko, O.; Raj, G.; Corde, S.; Hidding, B.; Karsch, S.; Martinez De La Ossa, A.; Irman, A.; Schramm, U.; Debus, A.
Utilizing laser-wakefield accelerated (LWFA) electrons to drive aplasma-wakefield accelerator (PWFA) holds great promise for realizingcentimeter-scale electron accelerators providing ultra-high brightnessbeams. Recent experiments at HZDR could demonstrate for the first timesuch an electron acceleration in a nonlinear PWFA plasma wakefield. Fordriving this compact hybrid accelerator setup, high-charge electronbunches from LWFA self-truncated ionization injection were used.In this talk, we present recent results of the accompanying simulationcampaign performed with the 3D3V particle-in-cell code PIConGPU. Thesesimulations model the geometry, density distributions, laser modes, andgas dopings as determined in the experiments. The simulation conditionsresemble the experiment to a very high degree and thus provide goodcomparability between experiment and simulation. Additionally, thewealth of information provided by the in-situ data analysis of PIConGPU provides insight into the plasma dynamics, otherwise inaccessible inexperiments.From an algorithmic and computational perspective, we modeled the hybridaccelerator from start to end in a single simulation scenario. Wediscuss the associated challenges in maintaining numerical stability andexperimental comparability of these long-duration simulations.
Keywords: LPWFA; hybrid; PIConGPU
Laser-Plasma AcceleratorWorkshop 2019, 05.-10.05.2019, Split, Croatia
Hybrid plasma accelerators - LWFA-PWFA simulations with PIConGPU
Utilizing laser-wakefield accelerated (LWFA) electrons to drive a plasma-wakefield accelerator (PWFA) holds great promise for realizing centimeter-scale electron accelerators providing ultra-high brightness beams. Recent experiments at HZDR could demonstrate for the first time such an electron acceleration in a nonlinear PWFA plasma wakefield using this compact setup.
On this poster, we show recent results of the accompanying simulation campaign performed with the 3D3V particle-in-cell code PIConGPU. These simulations model the geometry, density distributions, laser modes, and gas dopings as determined in the experiments. The simulation conditions resemble the experiment to a very high degree and thus provide precise comparability between experiment and simulation. Additionally, the wealth of information provided by the in-situ data analysis of PIConGPU provides insight into the plasma dynamic, otherwise inaccessible in experiments. Algorithmic and computational challenges essential for the numerical stability of these long-duration simulations will be presented as well.
Keywords: PIConGPU; LPWFA; hybrid; ISAAC
The fifth annual meeting of the programme "Matter and Technologies", 05.-07.03.2019, Jena, Deutschland
Approaching predictive capabilities for LWFA experiments with PIConGPU
State-of-the-art particle-in-cell simulations are becoming faster in terms of time to solution by utilizing modern hardware accelerators like GPUs and more accurate by improving the underlying algorithms. However, in order to model experiments, methods to include realistic laser pulses and gas distributions as well as efficient techniques to predict experimental observables, so-called synthetic diagnostics, need to be included in these simulations.
In this talk, we present extensions to the particle-in-cell code PIConGPU that were essential to accurately model LWFA experiments based on self-truncated ionization injection performed at HZDR. We discuss the significant impact of the implementation of higher order laser modes on the plasma dynamics and the resulting acceleration process. Furthermore, we discuss in detail the advantage of efficient in situ data analysis on the example of studying electron phase space evolution and of predicting spectrally and directionally radiation emission by all particles.
These improvements set the stage for quantitatively predicting the results of experiments in the near future.
Keywords: PIConGPU; LWFA; radiation; synthetic diagnostics
DPG-Frühjahrstagung der Sektion Materie und Kosmos (SMuK), 18.-22.03.2019, München, Deutschland
Radiation imprint of ultra-intense laser heating of solids
Laser-accelerated ions are increasingly recognized as a promising alternative to conventionally accelerated ion beams. Possible applications range from fast ignition in laser fusion to ion tumor therapy as well as studies of transient high-current and high-field phenomena in laboratory astrophysics and material science. A combination of ultra-short duration and very high charge density is the most sought-after characteristic of these beams which are produced in the violent interaction of an ultra-intense short pulse laser with a solid target. We have performed the – to our knowledge – very first full 3D particle-in-cell simulations of this interaction that includes the picosecond time span prior to the arrival of the main laser pulse. This time period is thought to be decisive for the following main pulse interaction, yet it is poorly explored – partly due to the immense computational needs to resolve the plasma kinetically with full precision. Here, we bridge scales hitherto inaccessible, from attosecond plasma oscillations over few-femtosecond laser oscillations and transient, non-equilibrium plasma dynamics on the tens of femtosecond laser duration to picosecond pre-plasma development. We study the influence of pre-pulse laser conditions and material on the ion acceleration performance. Additionally, we aim to infer radiative signatures of the plasma dynamics and link them to isochoric heating, instability development, and other complex dynamics. Beyond gaining a fundamental understanding of the governing fundamental principle plasma dynamics, the results will be used in the ongoing development of novel diagnostics analyzing the bremsstrahlung and synchrotron radiation in order to experimentally probe the sub-ps interaction. The simulations have been performed at Piz Daint at CSCS, Switzerland, using the 3D particle-in-cell code PIConGPU developed at HZDR.
Keywords: laser ion acceleration; laser-driven proton sources; particle-in-cell; PIConGPU; openPMD; HPC; throughput; PRACE; CSCS; Piz Daint
Invited lecture (Conferences)
EuroHPC Summit Week 2019 / PRACEdays19, 13.-17.05.2019, Poznań, Polska
Synthetic radiation simulations as a path to study the relativistic Kelvin-Helmholtz instability in interstellar jets
The relativistic Kelvin-Helmholtz instability (KHI) is expected in shear flow regions of astrophysical plasma jets originating from AGNs and SNR. It generates magnetic fields that influence the jet dynamics significantly.
We present 3D3V particle-in-cell simulations of unprecedented resolution and extent that not only allow studying the plasma dynamics during the KHI but also making quantitative predictions on the emitted radiation. We present a diagnostic method that allows identifying the linear phase of the instability via a polarization anisotropy observable light years away on Earth and to quantify the growth rate of the instability.
A microscopic model, that describes the fundamental origin of the radiation signature, will be covered in detail during the talk. Technical aspects relevant for performing these large-scale simulations with the particle-in-cell code PIConGPU and for making quantitative predictions with synthetic radiation diagnostics, based on Liénard-Wiechert potentials, will be discussed, and observation limits both for interstellar jets and in lab astrophysics experiments will be covered.
Keywords: KHI; PIConGPU; radiation; synthetic diagnostics; polarization; AGN; SNR
Invited lecture (Conferences)
DPG-Frühjahrstagung der Sektion Materie und Kosmos (SMuK), 18.-22.03.2019, München, Deutschland
Large-scale simulations of plasma acceleration
A brief presentation of the MuT/DMA activities of the Computational radiation group and solutions that might be of interest for the Matter in the Universe community.
Keywords: DMA; MUT; ARD; PIConGPU; alpaka
"Matter and the Universe" Days 2019, 14.-15.02.2019, Hamburg, Deutschland
From studying the self-truncated ionization injection during LWFA to hybrid LPWFA simulations
This talk gives a brief summary of the current status of the start-to-end simulations of the hybrid LPWFA setup using PIConGPU.
Keywords: PIConGPU; hybrid; LPWFA; LWFA; PWFA
hybrid collaboration meeting, 09.-11.01.2019, Hamburg, Deutschland
T cells engrafted with a UniCAR 28/ζ outperform UniCAR BB/ζ-transduced T cells in the face of regulatory T cell-mediated immunosuppression
Adoptive transfer of chimeric antigen receptor (CAR)-equipped T cells has demonstrated astonishing clinical efficacy in hematological malignancies recently culminating in the approval of two CAR T cell products. Despite this tremendous success, CAR T cell approaches have still achieved only moderate efficacy against solid tumors. As major obstacle, engineered conventional T cells (Tconvs) face an anti-inflammatory, hostile tumor microenvironment often infiltrated by highly suppressive regulatory T cells (Tregs). Thus, potent CAR T cell treatment of solid tumors requires efficient activation of Tconvs via their engrafted CAR to overcome Treg-mediated immunosuppression. In that regard, selecting an optimal intracellular signaling domain might represent a crucial step to achieve best clinical efficiency. To shed light on this issue and to investigate responsiveness to Treg inhibition, we engrafted Tconvs with switchable universal CARs (UniCARs) harboring intracellularly the CD3ζ domain alone or in combination with costimulatory CD28 or 4-1BB. Our studies reveal that UniCAR ζ- and UniCAR BB/ζ-engineered Tconvs are strongly impaired by activated Tregs, whereas UniCARs providing CD28 costimulation overcome Treg-mediated suppression both in vitro and in vivo. Compared to UniCAR ζ- and UniCAR BB/ζ-modified cells, UniCAR 28/ζ-armed Tconvs secrete significantly higher amounts of Th1-related cytokines and, furthermore, levels of these cytokines are elevated even upon exposure to Tregs. Thus, in contrast to 4-1BB costimulation, CD28 signaling in UniCAR-transduced Tconvs seems to foster a pro-inflammatory milieu, which contributes to enhanced resistance to Treg suppression. Overall, our results may have significant implications for CAR T cell-based immunotherapies of solid tumors strongly invaded by Tregs.
OncoImmunology 8(2019)9, e1621676
Investigations on stationary measurements at COSMEA-I facility - CT part
Bieberle, A.; Beyer, M.; Pietruske, H.; Hampel, U.; Boden, S.
DataManager: Beyer, Matthias; Project Member: Pietruske, Heiko; RelatedPerson: Boden, Stephan; DataCollector: Szalinski, Lutz; DataManager: Bieberle, André; ContactPerson: Hampel, Uwe
This repository contains reconstructed and analysed CT data obtained from the COSMEA-I test facility that is operated under stationary operating conditions. Furthermore, a full CAD drawing set is provided.
Keywords: Passive Heat Transfer; Stream Condensation; Heat Flux Probe; Process Computed Tomography
- Flow morphology and heat transfer analysis during … (Id 29452) is supplemented by this (Id 29250) publication
Reseach data in the HZDR data repository RODARE
Publication date: 2019-05-20
Thallium contamination, health risk assessment and source apportionment in common vegetables
As an element with well-known toxicity, excessive thallium (Tl) in farmland soils may threaten food security and induce extreme risks to human health. Identification of key contamination sources is a prerequisite for remediation technologies. This study aims to examine the contamination level, health risks and source apportionment of Tl in common vegetables from typical farmlands distributed over a densely populated residential area in a pyrite mine city, which has been exploiting Tl-bearing pyrite minerals for over 50 years. Results showed excessive Tl levels in most of the vegetables (0.16-20.33 mg/kg) and alarming health risks induced by the vegetables via the food chain. Source apportionment of Tl contamination in vegetables was then evaluated by using the Pb isotope fingerprinting technique. Both vegetables and soils were characterized by overall low 206Pb/207Pb ratios. This indicated that a significant contribution may be ascribed to anthropogenic activities for pyrite deposit exploitation, whose raw material and slags were featured with lower 206Pb/207Pb ratios. Further calculations by the binary mixing model suggested that pyrite mining and smelting activities contributed 54-88% to the thallium contamination in vegetables. The results highlighted that Pb isotope tracing is a suitable technique for source apportionment of Tl contamination in vegetables and that contamination from pyrite mining/smelting activities urges authorities to initiate proper practices of remediation.
Keywords: Metal contamination; Isotopic analysis; Source apportionment; Food safety; Plant uptake
Science of the Total Environment 703(2020), 135547
Nitric oxide-releasing selective estrogen receptor modulators (NO-SERMs): a bifunctional approach to improve the therapeutic index
When using selective estrogen receptor modulators (SERMs) in cancer therapy adverse effects such as endothelial dysfunction have to be considered. Estrogens and, consequently, SERMs regulate the synthesis of vasoactive nitric oxide (•NO). We hypothesized that a bifunctional approach combining the antagonistic action of SERMs with a targeted NO-release could diminish vascular side effects. We synthesized a series of NO-releasing SERMs (NO-SERMs) and the corresponding SERMs (after NO-release) derived from a triaryl olefin lead. Compounds showed antagonistic activity for ERβ (IC50(ERβ)=0.2–2.7µM), but no interaction with ERα. Growth of ERβpositive breast cancer and melanoma cells was significantly decreased by treatment with SERM 5d. This anti-proliferative effect was diminished by the additional release of •NO by the corresponding NO-SERM 4d. Moreover, targeted release of •NO by 4d counteracted the antiproliferative effect of 5d in normal vascular tissue cells. Summarizing, the therapeutic index of SERMs might be improved by this bifunctional approach.
Journal of Medicinal Chemistry 62(2019), 6525-6539
- Final Draft PDF 3 MB Secondary publication
Breaking the Doping Limit in Silicon by Deep Impurities
n-type doping in Si by shallow impurities, such as P, As, and Sb, exhibits an intrinsic limit due to the Fermi-level pinning via defect complexes at high doping concentrations. Here, we demonstrate that doping Si with the deep chalcogen donor Te by nonequilibrium processing can exceed this limit and yield higher electron concentrations. In contrast to shallow impurities, the interstitial Te fraction decreases with increasing doping concentration and substitutional Te dimers become the dominant configuration as effective donors, leading to a nonsaturating carrier concentration as well as to an insulator-to-metal transition. First-principles calculations reveal that the Te dimers possess the lowest formation energy and donate two electrons per dimer to the conduction band. These results provide an alternative insight into the physics of deep impurities and lead to a possible solution for the ultrahigh electron concentration needed in today’s Si-based nanoelectronics.
Physical Review Applied 11(2019), 054039
Nano-sandwiched metal hexacyanoferrate/graphene hybrid thin films for in-plane asymmetric micro-supercapacitors with ultrahigh energy density
In-plane micro-supercapacitors (MSCs) with high power density, remarkable rate capability, and long cycling stability, exhibit promising application potential in modern electronic devices. To satisfy the fast-growing energy demands for the next-generation advanced micro-devices, increasing the energy density of MSCs is urgently desirable but still remains a great challenge. In this work, a series of in-plane asymmetric MSCs (AMSCs) are rationally constructed using a family of nano-sandwiched metal hexacyanoferrate/graphene hybrid thin films with interdigital patterns. The voltage output window of the resultant AMSCs is able to reach up to 1.8 V, delivering superior areal capacitances of up to 19.84 mF cm-2, and ultrahigh energy density of 44.6 mW h cm-3 which is among the best performances of the state-of-the-art MSCs. Moreover, the achieved AMSCs show outstanding mechanical flexibility and integration capability. Thus, this work will promote the development of novel high-performance AMSCs.
Materials Horizons 6(2019), 1041-1049
Interface stability, mechanical and corrosion properties of AlCrMoNbZr/(AlCrMoNbZr)N high-entropy alloy multilayer coatings under helium ion irradiation
High entropy alloy (HEA) coatings are promising for use as accident-tolerant fuel cladding due to their outstanding high-temperature corrosion resistance. In this work, we investigated the interface stability, mechanical properties and corrosion resistance of AlCrMoNbZr/(AlCrMoNbZr)N multilayer coatings with individual layer thickness of 5 nm, 10 nm and 50 nm, subjected to helium (He) ion irradiations: 400 keV He+ ions with fluences of 8×1015 ion/cm2 and 8×1016 ion/cm2. We determined that He bubbles are not observed in any of the multilayer coatings after a helium ion irradiation process with 400 keV He ions and a fluence as high as 8×1016 ion/cm2. Although intermixing and chemical reaction in the peak damage region of the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with 5 nm monolayer thickness are induced by the high fluence He ion irradiation, the FCC structure remained, and no intermetallic compounds are detected. Moreover, we found that the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with the monolayer thickness of 50 nm has better interface stability during the irradiation process. Nanoindentation tests reveal that the hardness of all multilayer coatings decreased for low and high fluences, which is mainly due to the thermal effect caused by irradiation. In addition, the electrochemical corrosion test show that AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating 50 nm coatings has better corrosion resistance than AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating 5 nm coatings under high fluence He irradiation. The corrosion resistance of the multilayer coating depends on the stability of the multilayer interface. Our results show that the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with a monolayer thickness of 50 nm had better interface stability, mechanical properties and corrosion resistance than the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with a per layer thickness of 5 nm under high fluence He irradiation. This work reveals that high-entropy alloy multilayer coatings have potential applications as an accident-tolerant fuel cladding coating in light water reactors.
Keywords: AlCrMoNbZr/(AlCrMoNbZr)N; Multilayer coating; High-entropy alloy; Ion irradiation; Interfaces; Nanoindentation; Electrochemical corrosion; Accident-tolerant fuel (ATF)
Applied Surface Science 485(2019), 108-118
Cortical microinfarcts in memory clinic patients are associated with reduced cerebral perfusion
Cerebral cortical microinfarcts (CMIs) are small ischemic lesions associated with cognitive impairment and dementia. CMIs are frequently observed in cortical watershed areas suggesting that hypoperfusion contributes to their development. We investigated if presence of CMIs was related to a decrease in cerebral perfusion, globally or specifically in cortex surrounding CMIs. In181 memory clinic patients (mean age 72 ± 9 years, 51% male) CMI presence was rated on 3 T-MRI. Cerebral perfusion was assessed from cortical gray matter of the anterior circulation using pseudo-continuous arterial spin labeling parameters cerebral blood flow (CBF) (perfusion in mL blood/100g tissue/minute) and spatial coefficient of variation (CoV) (reflecting arterial transit time (ATT)) . Patients with CMIs had a 12% lower CBF (beta=-.20) and 22% higher spatial CoV (beta= .20) (both p<.05) without a specific regional pattern on voxel based CBF analysis. CBF in a 2 cm region-of-interest around the CMIs did not differ from CBF in a reference zone in the contralateral hemisphere. These findings show that CMIs in memory clinic patients are primarily related to global reductions in cerebral perfusion, thus shedding new light on the etiology of vascular brain injury in dementia.
Journal of Cerebral Blood Flow and Metabolism 40(2020)9, 1869-1878
Interaction of curium(III) with plant cells (Brassica napus)
The accumulation of radionuclides and toxic heavy metals into plants and thus into the food chain represents a potential pathway for human exposure. Hence, detailed knowledge of the fate of these elements in the ecosphere including the food chain is required for a reliable assessment of the resulting risk potential for humans and wildlife. Our aim is to explore the complex interaction of trivalent actinides with plant cells on a molecular level using curium(III) as an excellent luminescence probe.
We studied the response of canola (Brassica napus) cells to curium(III) exposure (0.7 µM). TRLFS was used as direct speciation technique to explore the Cm(III) speciation on the cells and in the supernatants. Liquid scintillation counting (LSC) was applied to measure the Cm(III) content in the supernatants. The possible release of plant cell metabolites was probed by solid phase extraction (SPE) with subsequent HPLC analysis.
The bioassociation experiments were performed in 0.154 M NaCl in a glove box over a time period up to 168 h. After defined time steps the Cm(III) concentration in the supernatants was determined as well as luminescence spectra from washed cells and the supernatants were taken. The Cm(III) concentration in the supernatants as a function of time points to a multi-stage bioassociation process on the plant cells. Red shifted Cm(III) luminescence spectra (+8.6 nm compared to Cm3+(aq)) in the supernatants indicated a Cm(III) complexation by substances that were released by the plant cells already after an exposure time of 5 h. Cell metabolites could be enriched and extracted by SPE. TRLFS studies (spectra and lifetime) showed a different Cm(III) speciation on cells compared to those found in the supernatants. To further describe the spectroscopic Cm(III) speciation in the B. napus system all spectra were evaluated with iterative transformation factor analysis (ITFA, Roßberg et al. 2003). The so obtained results (single component spectra and time-dependent species distributions) will be discussed in order to describe the fate of Cm(III) in the presence of plant cells (B. napus).
This new knowledge contributes to an improved understanding of trivalent actinide interactions with plants on a molecular level.
The authors are indebted to the U.S. Department of Energy, Office of Basic Energy Sciences, for the use of 248Cm via the transplutonium element production facilities at Oak Ridge National Laboratory; 248Cm was made available as part of collaboration between HZDR and the Lawrence Berkeley National Laboratory (LBNL). This study is part of the project TRANS-LARA which is funded by the Federal Ministry of Education and Research under contract number 02NUK051B.
Roßberg, A., Reich, T., Bernhard, G. 2003. Complexation of uranium(VI) with protocatechuic acid –
application of iterative transformation factor analysis
to EXAFS spectroscopy. Anal. Bioanal. Chem. 376, 631–638.
Keywords: curium; plant cells; Brassica napus; luminescence spectroscopy
Envira 2019, 08.-13.09.2019, Prague, Czech Republic
Targeting Cyclooxygenase-2 in Pheochromocytoma and Paraganglioma: Focus on Genetic Background
Cyclooxygenase 2 (COX-2) is a key enzyme of the tumorigenesis-inflammation interface and can be induced by hypoxia. A pseudohypoxic transcriptional signature characterizes pheochromocytomas and paragangliomas (PPGLs) of the cluster I, mainly represented by tumors with mutations in von Hippel-Lindau (VHL), endothelial PAS domain-containing protein 1 (EPAS1), or succinate dehydrogenase (SDH) subunit genes. The aim of this study was to investigate a possible association between underlying tumor driver mutations and COX-2 in PPGLs. COX-2 gene expression and immunoreactivity were examined in clinical specimens with documented mutations as well as in spheroids and allografts derived from mouse pheochromocytoma (MPC) cells. COX-2 in vivo imaging was performed in allograft mice. We observed significantly higher COX-2 expression in cluster I, especially in VHL-mutant PPGLs, however, no specific association between COX-2 mRNA levels and a hypoxia-related transcriptional signature was found. COX-2 immunoreactivity was present in about 60 % of clinical specimens as well as in MPC spheroids and allografts. A selective COX-2 tracer specifically accumulated in MPC allografts. This study demonstrates that, although, pseudohypoxia is not the major determinant for high COX-2 levels in PPGLs, COX-2 is a relevant molecular target. This potentially allows for employing selective COX-2 inhibitors as targeted chemotherapeutic agents and radiosensitizers. Moreover, available models are suitable for preclinical testing of these treatments.
Keywords: VHL; NF1; EPAS1; hypoxia-inducible factor; inflammation; radiosensitization; succinate dehydrogenase; mouse pheochromocytoma cells; immunohistochemistry; fluorescence imaging
Cancers 11(2019), 743
Radiumdotierte Bariumsulfat-Nanopartikel für die zukünftige Alphatherapie
1. Zielstellung: Durch die Alterung der Bevölkerung ist eine stetige Zunahme an Tumorneuerkrankungen zu verzeichnen und die Therapieoptimierung daher unabdingbar. Ein diskutierter Ansatz ist die Therapie mit Alphaemittern. Radionuklide wie 223/224Ra sind in der Lage, Tumorgewebe aufgrund ihres hohen linearen Energietransfers infolge einer Kaskade von Alpha-Zerfällen effizient zu zerstören ohne Beinflussung des gesunden Gewebes. Die stabile Fixierung von Barium- und Radiumionen kann durch Co-Fällung radiomarkierter [133Ba223/224Ra]Ba(Ra)SO4 Nanopartikel (NP) erfolgen, welche mit Alendronat funktionalisiert und anschließend mit einer targetspezifischen Einheit modifiziert werden.
Die Synthese der BaSO4-NP wurde durch Fällung realisiert. Die Partikelgröße wurde in Abhängigkeit der Reaktionsparameter (Lösungsmittelsystem, Verhältnis der Reaktanden, Fließgeschwindigkeit bei der Zugabe des zweiten Reaktanden) untersucht. NP-Größenverteilungen wurden mittels Dynamic Light Scattering (DLS) ermittelt. Radiomarkierungen wurden unter analogen Bedingungen unter Zugabe von [133Ba]Ba2+ und [224Ra]Ra2+ durchgeführt. 224Ra wurde als [224Ra]Ra(NO3)2 aus einer 228Th-Quelle durch Ionenaustauschchromatographie separiert. 133Ba wurde als [133Ba]BaCl2 kommerziell bezogen.
Nach Auswertung aller Syntheseansätze wurde die Fällung der Partikel mit einem sechsfachen Bariumüberschuss in einer Ethanol/Wasser-Mischung (1/11) bei Raumtemperatur als beste Methode identifiziert. Die Einlagerung von [133Ba]Ba2+- und [224Ra]Ra2+-Ionen konnte nachgewiesen werden. Die radiomarkierten NP zeigten über 7 Tage keinen relevanten Release. Die Modifikation der Partikel mit Alendronat konnte mittels IR-Spektroskopie, EDXS-Analyse und UV/Vis-Spektroskopie nachgewiesen werden. Die Partikelgröße wurde mittels DLS (140 ± 50 nm) analysiert und durch TEM verifiziert. Die weitere Funktionalisierung der NP wurde mittels Aktivesterkupplung eines fluoreszierenden NBD-Derivates und Fluoreszenzspektroskopie nachgewiesen.
Die Co-Fällung von Barium- und Radiumisotopen zur Gewinnung von NP definierter Größe ist ein Ausgangspunkt zukünftiger Therapieansätze. Die Funktionalisierung mit biologischen Targetmolekülen ermöglicht das zielgerichtete Aufspüren von Tumorzellen. Zukünftige Arbeiten fokussieren die Optimierung der Synthesemethode hinsichtlich der Verringerung der Partikelgröße und Ausbeute bei der Radiomarkierung sowie die anschließende Oberflächenmodifikationen bezüglich verschiedener biologischer Targets.
Keywords: Barium; Radium; Bariumsulfat; Nanopartikel
Jahrestagung der GDCh-Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland
Damage accumulation and implanted Gd and Au position in a- and c-plane GaN
Macková, A.; Malinský, P.; Jagerová, A.; Mikšová, R.; Sofer, Z.; Klímová, K.; Mikulics, M.; Böttger, R.; Akhmadaliev, S.; Oswald, J.
(0001) c-plane and (11−20) a-plane GaN epitaxial layers were implanted with 400 keV Au+ and Gd+ ions using ion implantation fluences of 5×1014, 1×1015 and 5×1015 cm-2. Rutherford Back-Scattering spectrometry in channelling mode (RBS/C) was used to follow the dopant depth profiles and the introduced disorder; the angular dependence of the backscattered ions (angular scans) in c- and a-plane GaN was measured to get insight into structural modification and dopant position in various crystallographic orientations. Defect-accumulation depth profiles exhibited differences for a- and c-plane GaN, with a-plane showing significantly lower accumulated disorder in the buried layer, accompanied by the shift of the maximum damage accumulation into the deeper layer with respect to the theoretical prediction, than c-plane GaN. Angular scans showed channelling preservation in as-implanted samples and better channelling recovery in the annealed a-plane GaN compared to cplane GaN. The angular scan widths were simulated by FLUX code as well as the half-width modifications of angular scans were discussed in connection to the damage accumulation. Photoluminescence measurement followed in detail yellow band and band edge luminescence decline after the implantation and the recovery of luminescence spectra features after annealing.
Keywords: Implanted (0001) and (11–20) GaN; Damage accumulation asymmetry in GaN; Ion implantation in semiconductors; RBS channelling; Damage-depth profiling
Thin Solid Films 680(2019), 102-113
Tc immobilization by Fe(II)-Al(III)-Cl layered double hydroxide phase
⁹⁹Tc is a long half-life isotope (2.13×10⁵ years) that can be found in the environment due to anthropogenic sources - nuclear energy production, tests of nuclear weapons and radiopharmacy - as it is a fission product from ²³⁵U and ²³⁹Pu and the daughter of 99mTc, used for diagnosis .
Although Tc has several oxidation states, Tc(VII) and Tc(IV) are the more stable ones found under oxidizing and reducing conditions, respectively, but their chemical behavior differs. While the Tc(VII) main species (TcO₄⁻) is a highly mobile anion that hardly interacts with minerals, Tc(IV) is usually found as a low soluble solid (TcO₂) whose precipitation avoids the Tc migration . Therefore, in order to reduce Tc mobility it is essential to understand the conditions that favor the three electrons donation step switching between these two oxidation states.
Several works report that Fe²⁺ promotes the Tc reduction, especially when found in Fe(II)-minerals or sorbed on mineral surfaces , .
If corrosion of the nuclear waste canisters occurs, Fe²⁺ will be present in the near-field of a deep geological repository. In that case, Fe²⁺ could not only act as reducing agent but also interact with different minerals, getting sorbed or forming new mineral phases.
In fact, it has been observed that when Fe²⁺ interacts with Al₂O₃, it forms Fe(II)-Al(III)-Cl, a layered double hydroxide (LDH) . The LDH phases are known to retain pollutants by different mechanisms: anion exchange, incorporation, surface complexation and, in Fe(II)-Al(III)-Cl, reduction promoted by the structural Fe²⁺ .
Therefore, we analysed the ⁹⁹Tc retention by Fe(II)-Al(III)-Cl LDH phase under different conditions (pH, ionic strength and Tc concentration). We observed that the affinity of the Fe(II)-Al(III)-Cl LDH phase for Tc has two different trends. For pH < 6.5, Tc retention increases with increasing pH and decreasing ionic strength, being complete in water, suggesting anion exchange as the main retention mechanism. At pH > 6.5, Tc uptake is complete and independent from the ionic strength and the pH value, suggesting Tc reduction as main uptake mechanism.
This work has been performed in the frame of VESPA II project (02E11607B), supported by the German Federal Ministry for Economic Affairs and Energy (BMWi).
 A. H. Meena and Y. Arai, Environ. Chem. Lett., vol. 15, no. 2, pp. 241–263, 2017.
 K. H. Lieser and C. Bauscher, Radiochim. Acta, vol. 42, pp. 205–213, 1987.
 T. Peretyazhko et al., Geochim. Cosmochim. Acta, vol. 72, no. 6, pp. 1521–1539, 2008.
 D. Cui and T. E. Eriksen, Environ. Sci. Technol., vol. 30, no. 7, pp. 2263–2269, 1996.
 E. J. Elzinga, Environ. Sci. Technol., vol. 46, no. 9, pp. 4894–4901, 2012.
 C. Forano, et al , Layered double hydroxides (LDH), vol. 5. 2013.
Keywords: Technetium; immobilization; LDH; reduction
Gesellschaft Deutscher Chemiker Nuclearchemie 2019, 25.-27.09.2019, Dresden, Germany
⁹⁹Tc retention on Fe(II)Al(III)-Cl layered double hydroxides
To assess the safety of nuclear waste repositories, possible incidents have to be considered like canister corrosion and as a consequence the release of radionuclides.Among them,the fission product ⁹⁹Tc is of high concern due to its long half-life (2.13∙10⁵years) and the high mobility of the Tc(VII)O₄⁻ oxoanion that is barely adsorbed by common mineral phases. However, Tc migration decreases under reducing conditions due to formation of Tc(IV), whose main species is a highly insoluble solid TcO₂.Under the reducing and corrosive conditions in the near-field of the repository, Fe²⁺ will act as a reducing agent for redox sensitive radionuclides (when present in the groundwater or sorbed on mineral surfaces). Furthermore,secondary mineral phases like Fe(II)-Al(III)-Cl, a layered double hydroxide (LDH),can be formed when Fe²⁺ interacts with Al₂O₃ at circumneutral-alkaline pH . LDH phases are so-called anionic clays and they are known to retain pollutants by anion exchange, incorporation, surface complexation and in the case of Fe(II)-Al(III)-Cl via reduction promoted by the structural Fe²⁺ . We have analysed the ⁹⁹Tc uptake by Fe(II)-Al(III)-Cl LDH under varying pH (4 to 11), ionic strength (0 to 0.1 M) and Tc concentration(10⁻⁹to 10⁻³ M). At pH < 6.5, the solid to liquid distribution coefficient, (log Kd in mL/g),ranges from (2 to 6) and increases with decreasing ionic strength and increasing pH. At pH > 6.5, log Kd (6.5±0.3) are independent of pH and ionic strength.Tc K-edge X-ray absorption spectroscopy showed in all cases a reduction to Tc(IV) and enabled us to elucidate the surface bound speciation of Tc on a molecular level.
E. J. Elzinga,”Environ. Sci. Technol., vol. 46, no. 9, pp. 4894–4901, 2012.
C. Forano, U. Costantino, V. Prévot, and C. T. Gueho, Layered double hydroxides (LDH), vol. 5. 2013.
Keywords: Technetium; retention; LDH; reduction
Goldschmidt 2019, 18.-23.08.2019, Barcelona, Spain
A Quantitative and Comparative Analysis of X-ray Computed Tomography, X-ray diffraction, and Mineral Liberation Analysis
A precise characterization of ores from mine to concentration plants is a long-standing aim of geometallurgical surveys. However, only limited number of studies have focused on prediction of materials properties from rock-size to downstream processes (i.e. ground-size) using combined characterization techniques. Additionally, individual uncertainty of most common characterization methods i.e. 3D X-ray Computed Tomography (CT), X-ray diffraction (XRD) and Mineral Liberation Analysis (MLA) and their quantification cannot be directly measured. Thus, validation of results requires a constructive comparison amongst these methods.
This work aims to validate CT as a reliable technique to characterize ore grains from 3D images for a parisite-bearing sample and its processed one in two comminution stages (i.e. crushing and milling). With this purpose, the amount and grain size distribution of parisite (Ca(Ce,La)2(CO3)3F2) in a carbonate sample was measured in three forms: uncrushed rock, after crushing, and after milling, using CT. After milling, the sample was sieved into five size fractions and each fraction was analysed by XRD, MLA and CT. The amount of each fraction was used to back calculate the initial mass of parisite in the initial uncrushed sample. It is found that the mass of parisite estimated from grain mounts and the mass directly measured in the entire sample as measured using CT are in good agreement. CT yields more consistent results for coarser grain size fractions, e.g. >56 µm, but significantly underestimates the mass % and PSD of finer size fractions. Above 56 µm, MLA shows inconsistencies, possibly due to sampling representability of grain mounts. For particles bellow 56 µm, MLA values are more representative although seemingly overestimate the content of parisite. Finally, CT is validated as complementary to traditional techniques commonly used for ore characterization when the grain size is sufficiently large relative to the voxel size.
Keywords: X-ray Computed Tomography; X-ray diffraction; Mineral Liberation Analysis; geometallurgical analysis; communition
Contribution to proceedings
Procemin-Geomet 2019, 20.-22.11.2019, Santiago, Chile
Uncovering the Origin of the Emitting States in Bi³⁺-Activated CaMO₃ (M=Zr, Sn, Ti) Perovskites: Metal-to-Metal Charge Transfer versus s-p Transitions
After more than a century of studies on the optical properties of Bi³⁺ ion, the assignment of the nature of the emissions and the bands of the absorption spectra remain ambiguous. Here we report an insight into the spectroscopy of Bi³⁺-activated CaMO₃ perovskites (M=Zr, Sn, Ti), discussing the factors driving the metal-to-metal charge transfer and sp → s2 transitions. With the aim to figure out the whole scenario, a combined experimental and theoretical approach is employed. The comparison between the temperature dependence of the PL emissions with the temperature dependence of the exciton energy of the systems has led to an unprecedent evidence of the charge transfer character of the emitting states in Bi³⁺-activated phosphors. Low temperature VUV spectroscopy together with the design of the vacuum referred binding energy diagram of the luminescent center are exploited to shed light on the origin of the absorption bands. In addition, the X-ray absorption near edge structure, unambiguously confirmed the stabilization of Bi³⁺ in Ca²⁺ site in both CaSnO₃ and CaZrO₃ perovskites. This breakthrough into the understanding of the excited state origin of Bi3+ could pave the way towards the design of a new generation of effective Bi³⁺-activated phosphors.
Journal of Physical Chemistry C 123(2019)23, 14677-14688
- Final Draft PDF 3,5 MB Secondary publication
Plutonium retention mechanisms by magnetite under anoxic conditions: Entrapment versus sorption
The reliable prediction of possible plutonium migration into the geological environment is crucial for the safety assessment of radioactive waste repositories. Fe(II)-bearing corrosion products like magnetite, which form on the surface of steel waste containers, can effectively contribute to the retardation of the potential radionuclide release by sorption and redox reactions, eventually followed by formation of secondary precipitates. A retardation process even more efficient - especially when considering the required long time scales for nuclear waste reposition - is structural incorporation by magnetite, as has been demonstrated for Tc and U. Here we show that this mechanism might not be as relevant for Pu retention: after a rapid reduction of Pu(V) to Pu(III) in acidic Fe(II)/Fe(III) solution, base-induced magnetite precipitation (pHexp ≈ 12.5) leads only to a partial (≈ 50%) incorporation, while the other half remains at the surface by forming tridentate sorption complexes. Neither solid nor sorbed Pu(IV) species were observed in the starting solution and after precipitation. With Fe(II)-inforced re-crystallization at pHexp = 6.5, a process potentially mimicking long-term, thermodynamically controlled aging, the equilibrium between both Pu species is even further shifted towards the sorption complex. A detailed analysis of the incorporated species by Pu LIII-edge X-ray absorption fine-structure (XAFS) spectroscopy shows a pyrochlore-like coordination environment (split eight-fold oxygen coordination shell with Pu-O distances of 2.22 and 2.45 Å, and an edge-sharing linkage to Fe-octahedra with Pu-Fe distances of 3.68 Å), which is embedded in the magnetite matrix (Pu-Fe distances of 3.93, 5.17 and 5.47 Å). This suggests that the reason for the partial incorporation is the structural incompatibility of the large Pu(III) ion for the octahedral Fe site in magnetite. The adoption of a pyrochlore-like local environment within the magnetite long-range structure might be induced by the rapid coprecipitation rather than being a thermodynamically stable state (kinetic entrapment). For the sake of conservatism, safety assessments should rely on the formation of the Pu(III) sorption complex only.
Keywords: solid solutions; radioactive waste disposal; plutonium; magnetite; EXAFS; XANES; XPS
ACS Earth and Space Chemistry 3(2019)10, 2197-2206
- Final Draft PDF 580 kB Secondary publication
Selection of Microwave’s Local Position in Mineral Processing Circuit: Part I- Grindability of Copper Porphyry Ore
Improvement in materials’ grindabilities and energy consumptions using microwave pretreatment have been broadly reported in the literature. However, the impact of microwave’s local position in communition circuits has not been addressed yet. The present work aims to study the influence of microwave’s location (prior to jaw crusher (BC) and after the crusher (AC)), exposure time (15-150s) and grinding time (13, 15 and 17min) on particle size distribution (PSD), mineral liberation degree (LD) and energy consumption for a porphyry copper complex deposit. For this purpose, given samples (1kg) were pretreated under 900W with various time intervals. Semi-quantitative X-ray diffraction technique (SQ-XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and optic microscopic techniques were used for elemental, surface and mineralogical analyses. Comparative work index (RWI), standard Bond work index (Wi), and grindability index (GI) together with breakage and selection functions were utilized to assess the grinding efficiency and its kinetics. Thermal anomalies in the presence and absence of MW-heating were quantified by Testo portable thermal infrared imager. The results revealed that the microwave’s effect in lower grinding time (13min) was more evident while by increasing it to 15 and 17min, its impacts became relatively insignificant. It was also found that at 13min grinding time, the product size (P80) of MW-treated crushed sample for 150s had improvements of 27% and 17% compared to the un-microwaved and MW-treated uncrushed sample. The comparative GIs in the entire spectrum of fraction sizes were reasonably greater if the microwave was located at AC particularly for coarser sizes. The Wis were obtained 13.70, 13.04 and 10.86kWh/t for the untreated, MW-treated uncrushed and crushed samples, respectively. Chalcopyrite’s LD was examined in three fractions and the results showed a significant improvement in -150+74μm and -74+44μm fraction sizes and a reduction in -44μm. We found the interrelation between particle sizes, LDs and heat adsorptions inconsistence in the literature. Finally, it was concluded that MW-pretreatment of the samples before crushing stage could considerably improve the material’s grindability and its kinetics.
Keywords: Microwave irradiation; grindability; copper complex ore; exposure time; uncrushed and crushed samples
Contribution to proceedings
Phsical Separation 19, 12.-14.06.2019, Falmouth, UK
Experiments on the magnetic enrichment of rare-earth metal ions in aqueous solutions in a microflow device
An attempt is made to achieve a continuous enrichment of rare-earth metal ions from aqueous solutions in a microflow device by applying magnetic forcing. An aqueous solution containing holmium(III) ions is pumped through a small channel which was exposed to a strong inhomogeneous magnetic field. At the outflow, the near- and far-field parts of the flow are separated and analyzed using UV-Vis spectroscopy. The relative change of ion concentration is determined from the measured absorbance. Results are reported for three different types of flow cells at different flow rates and magnetic field strengths and for a cascaded application of cells. The change of concentration is found to be small, and no clear trend can currently be stated due to the error margin of the concentration measurement.
Keywords: microflow; spectrophotometry; rare-earth elements; magnetic field; continuous separation
Journal of Flow Chemistry 9(2019)3, 175-185
Impact of mıcrowave treatment’s locatıon on flotabılıty of chalcopyrıte and pyrıt: a case study of Sarcheshmeh copper complex ore
This work aims to investigate the effect of microwave-assisted flotation on chalcopyrite and pyrite’s floatabilities in a porphyry copper complex ore by varying microwave’s local position before crushing (BC), after crushing (AC) and after milling (AM). Indivuduals given samples for each state were pre-treated with a variable power microwave at power levels of 90, 180, 360, 600, and 900W for 15, 30, and 60s. Furthermore, 45 rougher floatation experiments were carried out using a laboratory mechanical Denver flotation cell on both microwave-treated and untreated samples. Particle surface properties were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses. It was found that chalcopyrite and pyrite’s floatabilities monotonically increased by increasing the exposure time and power level for uncrushed preconditioned samples owing to an enhancement on mineral liberation degrees together with the formation of sulphide species and polysulphides on the mineral surfaces. However, flotation results of treated samples for crushed one (AC) revealed an optimum range where chalcopyrite and pyrite’s recoveries improved by increasing power level and exposure time to 30s while thereafter dropped down significantly. Finally, the formation of intensive oxide layers on mineral surfaces of milled samples led to a substantial reduction in the recoveries by increasing the power level and exposure time for AM-sample. Finaly, it was concluded that microwave’s local position at BC induced the best separation efficiencies in flotation section compared to the untreated and microwave-treated samples (crushed and milled).
Keywords: Microwave Treatment; Liberation Distribution; Chalcopyrite; Pyrite; Flotation
Contribution to proceedings
XVIII Balkan Mineral Processing Congress, 23.-26.05.2019, Durres, Albania
Proceedings of th XVIII Balkan Mineral Processing Congress
Surface nanobubbles on the rare earth fluorcarbonate mineral synchysite
Surface nanobubbles have been identified to play an important role in a range of industries from mineral processing to food science. The formation of surface nanobubbles is of importance for mineral processing in the extraction of complex ores, such as those containing rare earth elements. This is due to the way minerals are extracted utilising froth flotation. In this study, surface nanobubbles were imaged using non-contact atomic force microscopy on a polished cross section containing rare earth minerals. Nanobubbles were found on synchysite under reagent conditions expected to induce hydrophobicity in rare earth minerals, which is required for efficient processing.
Synchysite –(Ce) is a rare earth fluorcarbonate mineral containing over 30% rare earth elements. Relatively little research has been conducted on synchysite, with only a few papers on its surface behaviour and flotation. The resulting nanobubbles were analysed and showed an average contact angle of 24 degrees± 8. These are in line with contact angles found on dolomite and galena by previous studies.
Keywords: non-contact atomic force microscopy; synchysite; bastnäsite; rare earth elements; fluorcarbonate; surface nanobubbles; carbonatite
Journal of Colloid and Interface Science 552(2019), 66-71
Refinement of the Hounsfield look‐up table by retrospective application of patient‐specific direct proton stopping‐power prediction from dual‐energy CT
Background and Purpose:
Proton treatment planning relies on an accurate determination of stopping-power ratio (SPR) from x-ray computed tomography (CT). A clinically applicable refinement of the heuristic CT-based SPR prediction using a state-of-the-art Hounsfield look-up table (HLUT) is proposed, which incorporates patient-specific SPR information obtained from dual-energy CT (DECT) in a retrospective patient-cohort analysis.
Material and Methods:
SPR datasets of 25 brain-tumor, 25 prostate-cancer and three non-small cell lung-cancer (NSCLC) patients were directly derived from clinical DECT scans with the DirectSPR approach. Based on the median frequency distribution of voxelwise correlations between CT number and SPR within the irradiated volume, a piecewise linear function was specified (DirectSPR-based adapted HLUT). Differences in dose distribution and proton range were assessed for the non-adapted and adapted HLUT compared with the DirectSPR method.
The application of the DirectSPR-based adapted HLUT instead of the non-adapted one reduced systematic range deviations from 1.2% (1.1 mm) to -0.1% (0.0 mm) for brain-tumor, 1.7% (4.1 mm) to 0.2% (0.5 mm) for prostate-cancer and 2.0% (2.9 mm) to -0.1% (0.0 mm) for NSCLC patients. Due to the intra- and inter-patient tissue variability, range deviations larger than 1% are still present for the adapted HLUT.
The incorporation of patient-specific correlations between CT number and SPR, derived from a retrospective application of DirectSPR to a broad patient cohort, improves the accuracy of the current state-of-the-art HLUT approach. The DirectSPR-based adapted HLUT has been clinically implemented at our institution, which represents a further step toward full integration of the DECT-based DirectSPR method for treatment planning in proton therapy.
Keywords: dual-energy CT; proton range prediction; proton therapy
Medical Physics 47(2020)4, 1796-1806
- Final Draft PDF 2,3 MB Secondary publication
Synthesis of Mg and Zn diolates and their use in metal oxide deposition
Frenzel, P.; Preuß, A.; Bankwitz, J.; Georgi, C.; Ganss, F.; Mertens, L.; Schulz, S.; Hellwig, O.; Mehring, M.; Lang, H.
The synthesis of complexes [M(OCHMeCH₂NMeCH₂)₂] (5, M = Mg; 7, M = Zn) is described. Treatment of MeHNCH2CH2NMeH (1) with 2-methyloxirane (2) gave diol (HOCHMeCH₂NMeCH₂)₂ (3), which upon reaction with equimolar amounts of MR₂ (4, M = Mg, R = Bu; 6, M = Zn, R = Et) gave 5 and 7. The thermal behavior and vapor pressure of 5 and 7 were investigated to show whether they are suited as CVD (= chemical vapor deposition) and/or spin-coating precursors for MgO or ZnO layer formation. Thermogravimetric (TG) studies revealed that 5 and 7 decompose between 80–530 °C forming MgO and ZnO as evidenced by PXRD studies. In addition, TG-MS-coupled experiments were carried out with 7 proving that decomposition occurs by M–O, C–O, C–N and C–C bond cleavages, as evidenced from the detection of fragments such as CH𔔢N+, C₂H𔔢N+, C₂H₅N+, CH₂O+, C₂H₂O+ and C₂H₃O+. The vapor pressure of 7 was measured at 10.4 mbar at 160 °C, while 5 is non-volatile. The layers obtained by CVD are dense and conformal with a somewhat granulated surface morphology as evidenced by SEM studies. In addition, spin–coating experiments using 5 and 7 as precursors were applied. The corresponding MO layer thicknesses are between 7–140 nm (CVD) or 80 nm and 65 nm (5, 7; spin-coating). EDX and XPS measurements confirm the formation of MgO and ZnO films, however, containing 12–24 mol% (CVD) or 5–9 mol% (spin-coating) carbon. GIXRD studies verify the crystalline character of the deposited layers obtained by CVD and the spin-coating processes.
RSC Advances 9(2019)19, 10657-10669
Residual gammaH2AX foci in head and neck squamous cell carcinomas as predictors for tumour radiosensitivity: Evaluation in pre-clinical xenograft models and clinical specimens
Background and purpose: Predictive biomarkers can be instrumental to treatment individualisation of cancer patients and improve therapy outcome. Residual γH2AX foci represent a promising biomarker to predict tumour radiosensitivity. In this pre-clinical study, the slope of the dose–response curve was evaluated for its predictive relevance in head and neck squamous cell carcinoma xenografts (HNSCC). Additionally, the feasibility of the translated assay was tested in a clinical setting in patient derived HNSCC samples, and associations between residual γH2AX foci and clinical parameters were analysed. Materials and methods: Seven HNSCC xenografts models (FaDu, SAS, SKX, UT-SCC-5, UT-SCC-14, UT-SCC-45, XF354)were used. Tumour bearing NMRI nude mice were randomly distributed to five treatment arms (0–8 Gy). Residual γH2AX foci (24 h post irradiation)were counted by visual scoring in a micromilieu dependent manner (assessed with BrdU and pimonidazole). The local tumour control values measured as TCD 50 (tumour control dose 50%)have previously been published. Patient derived HNSCC biopsies were cultivated ex vivo for 24 h including 4 h of pimonidazole and BrdU treatment, subsequently irradiated with 0–8 Gy and fixed after 24 h. Results: In the pre-clinical study, the dose–response curve slopes negatively correlated with the tumour control dose after fractionated irradiation (TCD 50,fx , R 2 = 0.63, p = 0.032)and after single dose irradiation under homogeneous hypoxia (TCD 50,SD,clamp , R 2 = 0.66, p = 0.027). The γH2AX assay in clinical HNSCC samples showed a dose–response relationship, with the values of the slopes ranging from 0.099 Gy −1 to 0.920 Gy −1 (coefficient of variation = 52.8%). Slopes derived from patients were in the same ranges as the sensitive, moderate and resistant models of the pre-clinical study. Statistical analysis revealed a significant negative correlation between the slope and the patients’ age (R 2 = 0.65, p = 0.001). Conclusion: These results further support the promise of the slope of the residual γH2AX foci dose–response as a biomarker for radiosensitivity. In the clinical samples, the variation in the slopes reveals patients’ specific repair capacities, which could hold potential value for treatment individualisation. © 2019 Elsevier B.V.
Keywords: Clinical specimens; HNSCC; Predictive biomarker; Radiosensitivity; Xenograft modelsγH2AX
Radiotherapy and Oncology 137(2019), 24-31
Cancer stem cells in radiation response: current views and future perspectives in radiation oncology
Peitzsch, C.; Kurth, I.; Ebert, N.; Dubrovska, A.; Baumann, M.
Purpose: Despite technological improvement and advances in biology-driven patient stratification, many patients still fail radiotherapy resulting in loco-regional and distant recurrence. Tumor heterogeneity remains a key challenge to effective cancer treatment, and reliable stratification of cancer patients for prediction of outcomes is highly important. Intratumoral heterogeneity is manifested at the different levels, including different tumorigenic properties of cancer cells. Since John Dick et al. isolated leukemia initiating cells in 1990, the populations of tumor initiating or cancer stem cells (CSCs) were identified and characterized also for a broad spectrum of solid tumor types. The properties of CSCs are of considerable clinical relevance: CSCs have self-renewal and tumor initiating potential, and the metastases are initiated by the CSC clones with the ability to disseminate from the primary tumor site. Conclusion: Evidence from both, experimental and clinical studies demonstrates that the probability of achieving local tumor control by radiation therapy depends on the complete eradication of CSC populations. The number, properties and molecular signature of CSCs are highly predictive for clinical outcome of radiotherapy, whereas targeted therapies against CSCs combined with conventional treatment are expected to provide an improved clinical response and prevent tumor relapse. In this review, we discuss the modern methods to study CSCs in radiation biology, the role of CSCs in personalized cancer therapy as well as future directions for CSC research in translational radiooncology.
Keywords: Cancer stem cells; model systems; radiosensitivity
International Journal of Radiation Biology 95(2019)7, 900-911
Widely tunable GaAs bandgap via strain engineering in core/shell nanowires with large lattice mismatch
Balaghi, L.; Bussone, G.; Grifone, R.; Hübner, R.; Grenzer, J.; Ghorbani-Asl, M.; Krasheninnikov, A.; Schneider, H.; Helm, M.; Dimakis, E.
The realization of photonic devices for different energy ranges demands materials with different bandgaps, sometimes combined even within the same device as in multi-junction photovoltaic cells. The optimal solution in terms of integration, device performance and device economics would be a simple material system with widely tunable bandgap and compatible with the mainstream silicon technology. Here, we show that gallium arsenide nanowires grown epitaxially on silicon substrates exhibit a sizeable reduction of their bandgap by up to 40% when overgrown with lattice-mismatched indium gallium arsenide or indium aluminium arsenide shells. Specifically, we demonstrate that the gallium arsenide core sustains unusually large tensile strain with hydrostatic character and its magnitude can be engineered via the composition and the thickness of the shell. The resulted bandgap reduction renders gallium arsenide nanowires suitable for photonic devices across the near-infrared range, including telecom photonics at 1.3 and potentially 1.55 μm, with the additional possibility of monolithic integration in silicon-CMOS chips.
Nature Communications 10(2019), 2793
Advanced Methods for Temporal Reconstruction of Modulated Electron Bunches
We describe optimizations of phase-retrieval algorithms for the reconstruction of the temporal structure of highly modulated electron bunches from coherent transition radiation (CTR) spectra. Synthetic data is used to quantitatively analyze capabilities and limitations of the approach taking into account realistic bandwidth constraints of ultra-broadband spectrometers. Established algorithms are combined with information from independent channels as charge calibrated electron spectra and absolute intensity calibration of the spectrometer. With this set of data, in principle available in experiments, we demonstrate a promising fidelity for the detailed analysis of substructured laser wakefield accelerated electron bunches.
Keywords: Electron bunch duration; reconstruction algorithm; transition radiation
Contribution to proceedings
Advanced Accelerator Concepts Workshop (AAC2018), 12.-17.08.2018, Breckenridge, Colorado, USA: IEEE, 978-1-5386-7721-6
Synthesis and in vitro evaluation of 8-pyridinyl substituted benzo[e]imidazo[2,1-c][1,2,4]triazines as phosphodiesterase 2A (PDE2A) inhibitors
Phosphodiesterase 2A (PDE2A) is highly expressed in distinct areas of the brain which are known to be related to neuropsychiatric diseases. The development of suitable PDE2A tracers for Positron Emission Tomography (PET) would permit the in vivo imaging of the PDE2A and evaluation of disease- mediated alterations of its expression. A series of novel fluorinated PDE2A inhibitors on the basis of a benzoimidazotriazine (BIT) scaffold was prepared leading to a promising inhibitor for further development of a PDE2A PET imaging agent. BIT derivatives (BIT1-9) were obtained by a seven-step synthesis route and their inhibitory potency towards PDE2A and selectivity over other PDEs have been evaluated. BIT1 demonstrated much higher inhibition than other BIT derivatives (82.9% inhibition of PDE2A at 10 nM). BIT1 displayed an IC50 for PDE2A of 3.33 nM with 16-fold selectivity over PDE10A. This finding revealed that a derivative bearing both a 2-fluoro-pyridin-4-yl and 2-chloro-5-methoxy-phenyl unit at 8- and 1-position, respectively, appeared to be the most potent inhibitor. In vitro studies of BIT1 using mouse liver microsomes (MLM) disclosed BIT1 as a suitable ligand for 18F-labeling. Nevertheless, future in vivo metabolism studies are required.
Keywords: Phosphodiesterase 2A (PDE2A); positron emission tomography (PET); benzoimidazotriazine (BIT); fluorinated; mouse liver microsomes (MLM)
Molecules 24(2019)15, 2791
Experimental investigations of bubble chains in a liquid metal under the influence of a horizontal magnetic field
We present an experimental study on bubble chains ascending in the eutectic GaInSn alloy under the influence of a horizontal magnetic field. Argon gas bubbles are injected through a single nozzle positioned in the middle at the bottom of a flat Plexiglas vessel. Bubble size distribution, shape deformation, velocities, etc. are obtained by post-processing of X-ray radiographs measured with a high-speed video-camera for a wide range of Argon gas flow rates. In the case without a magnetic field, the typical zigzag movement of the rising bubbles is observed. This movement and the integrity of the bubble chain are significantly disturbed with increasing gas flow by the turbulent flow in the liquid metal. The main effect of the magnetic field consists in a stabilization of the bubble trajectories. The application of a magnetic field at moderate field strength dampens the turbulent fluctuations in the bubble wake and stabilizes the zigzag movement. The application of a sufficiently strong magnetic field suppresses the zig-zag motion of the bubbles and forces them to follow a straight path. The rising velocity is gradually reduced with increasing magnetic field strength. The motion of the individual bubbles within the chain becomes highly correlated. Ellipsoidal bubbles tend to align their major axes along the magnetic field lines.
Keywords: Liquid metal; Two-phase flow; Bubble chain; Horizontal magnetic field; X-ray radiography
International Journal of Multiphase Flow 121(2019), 103111
- Final Draft PDF 1,2 MB Secondary publication
Measuring sub-femtosecond temporal structures in multi-ten kiloampere electron beams
In laser wakefield acceleration, an ultra-short high-intensity laser pulse excites a plasma wave, which can sustain accelerating electric fields of several hundred GV/m.
This scheme advances a novel concept for compact and less expensive electron accelerators, which can be hosted in a typical university size laboratory. Furthermore, laser wakefield accelerators (LWFA) feature unique electron bunch characteristics, namely micrometer size with duration ranging from several fs to tens of fs. Precise knowledge of the longitudinal profile of such ultra-short electron bunches is essential for the design of future table-top X-ray light-sources and remains a big challenge due to the resolution limit of existing diagnostic techniques.
Spectral measurement of broadband coherent and incoherent transition radiation (TR) produced when electron bunches passing through a metal foil is a promising way to analyze longitudinal characteristics of these bunches. Due to the limited reproducibility of the electron source this measurement highly requires single-shot capability.
An ultra-broadband spectrometer combines the TR spectrum in UV/NIR (200-1000 nm), NIR (0.9-1.7 µm) and mid-IR (1.6-12 µm). A high spectral sensitivity, dynamic bandwidth and spectral resolution are realized by three optimized dispersion and detection systems integrated into a single-shot spectrometer.
A complete characterization and calibration of the spectrometer have been done concerning wavelengths, relative spectral sensitivities, and absolute photometric sensitivities, also taking into account for the light polarization.
The TR spectrometer is able to characterize electron bunches with charges as low as 1pC and can resolve time-scales of 0.4 fs. Electron bunches up to 16 fs (rms width) can be reconstructed from their TR spectrum.
In the presented work, the self-truncated ionization induced injection (STII) scheme has been explored to study the relevant beam parameters especially its longitudinal bunch profile and the resulting peak current.
Proper focusing of a high power laser pulse into a supersonic gas-jet target and tailoring the conditional laser and plasma density and taking advantage of the relativistic self-focusing effects are investigated in this PhD thesis in order to study the final beam parameters as well as the consequent beam loading effects by producing nC-class mono-energetic electron beams.
In the experiment at HZDR, the DRACO 100TW Ti:Sa based laser system is used in conjunction with a He-N₂ mixed, supersonic gas-jet target. Under optimized conditions, mono-energetic electron bunches are accelerated, which are massively loaded up to several 100 pC at 300 MeV peak energy with a narrow energy spread of a few 10 MeV. Reconstruction results of TR spectra, measured by TR spectrometer, show that the shortest electron bunch duration is at about 13 fs FWHM corresponding to a peak current as high as 20 kA.
Such peak current is about one order of magnitude higher than those generated by conventional RF linear accelerator. This landmarks a significant finding of this thesis.
Keywords: Laser wakefield acceleration; laser plasma accelerator; self-truncated ionization injection; high peak current; high bunch charge; beam loading; bunch duration measurement; coherent transition radiation; broadband spectrometer; infrared spectrometer; prism spectrometer; echelle spectrometer; phase reconstruction algorithm; Foldwrap reconstruction algorithm; PIConGPU
Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-100 2019
ISSN: 2191-8708, eISSN: 2191-8716
Recent application of the solid targetry system
Mansel, A.; Franke, K.
The solid targetry system was used both, at port 4 directly mounted at the yoke and at the beamline at port 3. We will give an overview about the purification or separation of n.c.a. radionuclides like Sr-85, V-48, Cu-64, Cr-51, Co-56, Y-88, La-135, Zr-89, Ce-139 and Pb-203.
14th CYCLEUR workshop 2019, 08.-10.05.2019, Dresden, Germany
Competence Center for Ion Beams in Materials Research and Medicine
Competence Center for Ion Beams in Materials Research and Medicine
Keywords: ion beams; high-energy; materials research; user facility
Invited lecture (Conferences)
Competence Center for Ion Beams in Materials Research and Medicine, 02.05.2019, München, Deutschland
Pool CFD Modelling: Lessons from the SESAME Project
Moreau, V.; Profir, M.; Alamberti, A.; Frignani, M.; Merli, F.; Belka, M.; Frybort, O.; Melichar, T.; Tarantino, M.; Franke, S.; Eckert, S.; Class, A.; Yanez, J.; Grishchenko, D.; Jeltsov, M.; Kudinov, P.; Roelofs, F.; Zwijsen, K.; Visser, D. C.; Badillo, A.; Niceno, B.; Martelli, D.
The Computational Fluid-Dynamics (CFD) modelling of Heavy Liquid Metal (HLM) flows in pool configuration is investigated.
We describe how the argument is treated within the SESAME project in its specific work package. The work package structure, based on a systematic approach of redundancy and diversification, is explained along with its motivation. The main achievements obtained and the main lessons learned are illustrated.
The paper focuses on the strong coupling between experimental activity and CFD simulation performed within the SESAME project. Two HLM fluids are contemplated: pure lead and Lead-Bismuth Eutectic. The objective is to make CFD a valid instrument in support to the design of safe and innovative Gen-IV nuclear plants.
Some effort has also been devoted to a highly challenging and innovative approach, the Proper Orthogonal Decomposition (POD) with Galerkin projection modelling, potentially able to cover some CFD applications at a much lower computational cost.
To reach sufficient maturity, the method requires however input from sufficiently complex CFD simulations such as those produced in the present context.
Dedicated experimental campaigns on heavily instrumented facilities have been conceived with the specific objective to build a series of datasets suited for the calibration and CFD modelling validation. In pool configuration, the attention is focused on the balance between conductive and convective heat transfer phenomena, on transients representative of incidental scenarios and on the possible occurrence of solidification phenomena. Four test sections have been selected for the dataset production: (i) the CIRCE facility from ENEA, (ii) the TALL-3D pool test section from KTH, (iii) the TALL-3D Solidification Test Section (STS) from KTH and (iv) the SESAME Stand facility from CVR. While CIRCE and TALL-3D were existing facilities, the STS and SESAME Stand facility have been conceived, built and operated within the project, heavily relying on the use of CFD support. We give an outlook on the work performed, the results achieved and remaining or new uncovered issues.
Keywords: GenIV reactors; Pool-type configuration; Heavy liquid metals; CFD
Nuclear Engineering and Design 355(2019), 110343
- Final Draft PDF 3,5 MB Secondary publication
Adjuvant drug-assisted bone healing: Part III – Further strategies for local and systemic modulation
In this third in a series of reviews on adjuvant drug-assisted bone healing, further approaches aiming at influencing the healing process are discussed. Local and systemic modulation of bone metabolism is persued with use of a number of drugs with completely different indications, which are characterized by a pleiotropic spectrum of action. These include drugs used to treat lipid disorders (HMG-CoA reductase inhibitors), hypertension (ACE inhibitors), osteoporosis (bisphosphonates), cancer (proteasome inhibitors) and others. Potential applications to enhance bone healing are discussed.
Keywords: bisphosphonates; bone metabolism; critical-size bone defects; small molecules; statins; strontium; Wnt signaling
Clinical Hemorheology and Microcirculation 73(2019), 439-488
- Secondary publication expected
Adjuvant drug-assisted bone healing: Part II – Modulation of angiogenesis
The treatment of critical-size bone defects following complicated fractures, infections or tumor resections is a major challenge. The same applies to fractures in patients with impaired bone healing due to systemic inflammatory and metabolic diseases. Despite considerable progress in the development and establishment of new surgical techniques, the design of bone graft substitutes and imaging techniques, these scenarios still represent unresolved clinical problems. However, the development of new active substances gives cause for hope. This work discusses therapeutic approaches that influence angiogenesis or hypoxic situations in healing bone and surrounding tissue. In particular, the literature on sphingosine-1-phosphate receptor modulators and nitric oxide (NO•) donors, including bi-functional (hybrid) compounds like NO•-releasing cyclooxygenase-2 inhibitors, was critically reviewed with regard to their local and systemic mode of action.
Keywords: critical-size bone defects; neovascularization; nitric oxide donors; signaling; small molecules; sphingosine-1-phosphate receptor
Clinical Hemorheology and Microcirculation 73(2019), 409-438
- Final Draft PDF 1,1 MB Secondary publication
Adjuvant drug-assisted bone healing: Part I – Modulation of inflammation
Critical-size bone defects after compound fractures, infection, or tumor resection are challenging to treat. The same is true for fractures in patients with impaired bone healing due to metabolic diseases and cancer. Despite considerable progress over the last decade in surgical techniques, material design, and dedicated imaging approaches, these scenarios represent unsolved clinical problems. The high socioeconomic burden of such conditions justifies increasing interest in novel osteoinductive drugs for adjuvant therapeutic approaches. There is an increasing body of experimental and clinical literature on potentially promising effects of growth factors, anti-resorptive, and anabolic agents. The true clinical efficacy of these, however, is discussed controversially. Therefore, we aimed to critically examine the hypothesis that targeted adjuvant therapies have the potential to enhance bone regeneration in critical-size bone defects and under systemic conditions that impair bone healing. This first approach to the topic deals with small molecule drugs and compounds that influence the immune response and inflammatory processes. In particular, literature reporting on selective cyclooxygenase-2 inhibitors has been reviewed with respect to their local and systemic mode of action and to stimulate further research on bone healing under critical conditions.
Keywords: biomaterials; critical-size bone defects; cyclooxygenase-2; innate immunity; prostanoids; signaling; small molecules
Clinical Hemorheology and Microcirculation 73(2019), 381-408
- Secondary publication expected
Experimental and computational studies of the influence of grain boundaries and temperature on the radiation-induced damage and hydrogen behavior in tungsten
We study the influence of grain boundaries on radiation-induced vacancies, as well as, on the hydrogen (H) behavior in tungsten (W) samples with different grain sizes in the temperature range from 300 K to 573 K, both experimentally and by computer simulations. For this purpose, coarse-grained and nanostructured W samples were sequentially irradiated with carbon (C) and H ions at energies of 665 keV and 170 keV, respectively. A first set of the implanted samples was annealed at 473 K and a second set at 573 K. Object kinetic Monte Carlo simulations were performed to account for experimental outcomes. Results show that the number of vacancies for nanostructured W is always larger than for single crystal W samples in the whole studied temperature range and that the number of vacancies is only reduced in samples with a large density of grain boundaries and at temperatures high enough to activate the vacancy motion (around 573 K). Results also indicate that the migration of H along vacancy free grain boundaries is more effective than along the bulk, and that the retained H is trapped in vacancies located within the grains. These results are used to explain the experimental outcomes.
Nuclear Fusion 59(2019), 086055
Improvement of UniCAR T cell effectiveness against EGFR+ tumor cells by using different αEGFR targeting module formats
Since epithelial growth factor receptor (EGFR) mutations or overexpression is linked with variety of malignancies, including lung, breast, stomach, colorectal, head and neck, and pancreatic carcinomas as well as glioblastomas it is an attractive target for tailored treatment of solid cancer. Thus over the last twenty years many strategies targeting EGFR were developed and even clinically approved, including disrupting intracellular signalling involving tyrosine kinase inhibitors (TKIs) or the inhibition of ligand binding using therapeutic monoclonal antibodies like e.g. Cetuximab, Panitumumab or Necitumumab. Unfortunately, cancers treated with these targeted drugs commonly become resistant to them. These limitations justify the need of more efficient therapy options. As chimeric antigen receptor (CAR) engineered T cells highly effectively eliminate hematological malignancies already in the clinics, one idea is to redirect CAR T cells also against EGFR expressing solid cancers. However, CAR T cell therapy can lead to severe even life-threatening side effects and its effectiveness against solid tumors is still limited. Particular worrying is that EGFR is a widespread antigen commonly expressed also on healthy tissues bearing a high risk of severe on-target/off-tumor side effects due to EGFR-targeted therapies, which cannot be controlled in patients. In order to overcome these challenges our UniCAR technology might be an appropriate answer combining high anti-tumor effectiveness, tumor specificity, flexibility, and safety control mechanisms. In contrast to conventional CARs, UniCAR T cells are per se inert because UniCARs are directed against a small peptide epitope, which is not present on living cells. The redirection of UniCAR T cells to tumor cells occurs only in the presence of a tumor specific targeting module (TM). TMs, on one hand carry the specificity for a certain tumor antigen and on the other hand contain the UniCAR peptide epitope recognized by UniCARs mediating the cross-linkage of UniCAR T cells and antigen presenting tumor cells. As TMs have a very short half-life in vivo they can be used as a switch to control UniCAR T cell activity on demand in patients. In detail, UniCAR T cells are only switched on in the presence of antigen specific TMs realized by permanent TM infusion, but could be rapidly switched off when the application of the TM is stopped and the TM is eliminated. Meanwhile we successfully generated a series of different TMs against different tumor antigens and entities. Interestingly, TMs can be made of different molecules showing various structures and can flexible be exchanged in order to target any tumor antigen and overcome tumor escape variants. Commonly our TMs consist of a humanized single-chain variable fragment (scFv) derived from the variable heavy and light chain domains of a murine monoclonal antibody. In addition, we successfully generated TMs based on different monovalent and bivalent antibody derivatives, nanobodies derived from one variable camelid antibody domain, affibodies and even small peptide molecules.
Recently we demonstrated proof-of-concept for the redirection of UniCAR T cells to EGFR expressing tumor cells by a nanobody based αEGFR TM derived from the camelid αEGFR antibody 7C12. Considering that the affinity and anti-tumor efficiency of the eucaryotically expressed αEGFR nanobody based TM was limited, we therefore asked the question, whether we could further improve the therapeutic effect against EGFR positive tumor cells using the UniCAR technology. In order to answer this question, we generated a novel TM based on a scFv derived from the clinically used chimeric monoclonal antibody Cetuximab (IMC C-225). In detail, we designed a murine and humanized αEGFR scFv TM, successfully expressed them in mammalian cell lines and compared their functionality with the eucaryotic αEGFR nanobody-based TM in vitro and in vivo. In principle, we observed that both TM formats, the αEGFR nanobody as well as the scFv-based TM, are able to redirect UniCAR T cells eliminate EGFR-expressing tumor cells in an antigen-specific and TM-dependent manner. As both the murine and humanized scFv TM variants worked equally well, obviously humanization of the αEGFR scFv does not affect its functionality. However most interestingly, the tumor killing efficiency of the αEGFR scFv TM was significantly superior in comparison to the αEGFR nanobody based TM. Here, the half maximal effective TM concentration (EC50) value of scFv based TM was improved 1000-fold, from nM to pM range. Consequently, UniCAR T cells in combination with the scFv based TM efficiently eliminate also target cells expressing a low EGFR density level, while UniCAR T cells redirected by the nb based TM clearly attack only highly EGFR expressing tumor cells. Furthermore, the high anti-tumor efficacy of the αEGFR scFv TM over nb TM was manifested in experimental mice.
In summary, we successfully established different αEGFR TM formats that are able to redirect UniCAR T cells to eliminate EGFR-positive tumor cells. However, the analysed αEGFR TM formats differ with respect to their anti-tumor efficiency, which might decide whether UniCAR T cells attack target cells showing different EGFR density levels.
Tumor immunology meets oncology (TIMO XV), 25.-27.04.2019, Halle, Deutschland
Engineering human T cells with a novel switchable CAR technology for tumor immunotherapy
With the first approvals of chimeric antigen receptor (CAR) T cell therapies by the FDA the use of genetically modified T cells in the immunotherapy of tumors has recently become a very promising approach. CAR T cells are able to recognize tumor-associated antigens (TAAs) via specific single-chain variable fragments (scFvs) in a major histocompatibility-complex (MHC)-independent manner. Although highly efficient, the inability to regulate the activity of CAR T cells can cause severe even
life-threatening side effects such as cytokine-release syndrome (CRS) and on-target, off-tumor toxicities. Modular CAR systems may overcome these limitations allowing to switch the activity of CAR T cells repeatedly “ON” and “OFF”. Alternatively or in addition, the safety of CAR T cells could also be improved by “gated” targeting strategies e.g. by splitting the signaling and costimulatory motifs to independent CARs of different specificities. Theoretically, the idea of gated targeting could be extended to include further e.g. inhibitory signals. However, the size of current CARs limit the number of specificities that can be simultaneously transduced into a T cell. We therefore developed a novel switchable modular universal artificial receptor having a minimal size. The platform was termed RevCAR system.
In order to reduce the size of the artificial receptor the original idea was to replace the extracellular scFv domain of a conventional CAR with a small peptide epitope and to engage the resulting RevCAR T cell via a bispecific target module which we termed RevTM. For proof of concept two small peptide epitopes were selected and the respective RevCARs constructed. In addition, a series of different RevTMs were constructed. On the one hand the RevTM recognized one of the two peptide epitopes on the other hand the RevTM was directed to a potential tumor associated antigen (TAA). Until now a series of such pairs of RevTMs were constructed and functionally analyzed. RevCAR T cells armed via the respective RevTM were able to specifically lyse their respective target cell in a peptide epitope specific and target specific as well as target dependent manner. These data are supported by analysis of cytokine secretion. We only observed a specific cytokine release from RevCAR T cells in the presence of both target cells and the respective RevTM. Released cytokines detected were IFN-gamma, GM-CSF, TNF, and IL-2.
Taken together these results demonstrate the high anti-tumor efficiency of the novel RevCAR platform which is characterized by a small size, an improved safety, easy controllability as well as high flexibility.
Tumor immunology meets oncology (TIMO XV), 25.-27.04.2019, Halle, Deutschland
Dockerfiles which provide environments for building and running Cupla applications.
Keywords: Docker; Cupla; Alpaka
Reseach data in external data repository
Publication year 2019
License: ISC-Lizenz (Link to license text)
Hosted on https://gitlab.com/hzdr/cupla-docker: Link to location
Thermal expansion of magnetron sputtered TiCxN1-x coatings studied by high-temperature X-ray diffraction
The coefficient of thermal expansion (CTE) of TiCxN1-x can be adjusted by changing the value x between 0 (i.e. pure TiN) and 1 (pure TiC), which makes this material exceptionally useful as base layer to adapt the mismatch between the CTEs of substrate and coating. However, no comprehensive data on the CTE of sputtered TiCxN1-x has been reported up to now. Thus, in this work eleven coatings with compositions ranging from pure TiN to pure TiC were deposited using non-reactive magnetron sputtering. The elemental and phase composition were obtained by elastic recoil detection analysis and Raman spectroscopy, respectively. Powders of the coating material were analyzed using high-temperature X-ray diffraction between room temperature and up to 1000 °C to determine the temperature dependent lattice parameters. Subsequently, these lattice parameters were fitted using second order polynomials with coefficients linearly depending on the carbon content. Thus, a formula for the CTE of TiCxN1-x valid between 25 and 1000 °C was deduced which showed that at room temperature TiN has the highest CTE of 8.12 × 10-6 K-1. The CTE gradually decreases with increasing carbon content to 7.55 × 10-6 K-1 for pure TiC. While the value for TiC only shows a small increase with temperature, the CTE of TiN increases strongly up to 11.1 × 10-6 K-1 at 1000 °C. The presented formula for the temperature dependent CTE of sputtered TiCxN1-x coatings allows to calculate the required composition for TiCxN1-x base layers, in order to tune their thermal expansion for the use in complex multilayered coatings.
Keywords: Thermal expansion; Titanium carbonitride; High-temperature X-ray diffraction; Physical vapor deposition; Hard coatings
Thin Solid Films 688(2019), 137307
Modeling of the FFTF isothermal physics tests with the Serpent and DYN3D codes
In this study, the isothermal physics tests performed on the fully loaded core of the Fast Flux Test Facility (FFTF) are analyzed with the Monte Carlo code Serpent and with the deterministic core simulator DYN3D. The selected tests comprise two neutron spectra measurements and a multitude of reactivity effect measurements (32 cases with control rod movements and one case for isothermal temperature coefficient). While the flux spectra are calculated only with the Monte Carlo code, the reactivity effects are evaluated with both codes, Serpent and DYN3D. The homogenized few-group cross sections for DYN3D calculations are generated with Serpent. The obtained numerical results are in a very good agreement as compared to the experimental data. Additionally, a comparison of radial power distributions is presented between DYN3D and Serpent calculations, demonstrating an adequate performance of the nodal code DYN3D. This paper provides an additional contribution to the validation of both codes for neutronic analyses of Sodium cooled Fast Reactor cores.
Keywords: Group constant generation; SFR; nodal diffusion; Monte Carlo; SPH; Serpent; DYN3D
Annals of Nuclear Energy 132(2019), 679-685
The UniCAR system: A modular CAR T cell approach to improve the safety of CAR T cells
The idea to eliminate tumor cells via our own immune system is more than a hundred years old. However, a real break through came first with the development of check point inhibitors, bispecific antibodies (bsAbs) and T cells genetically modified to express Chimeric Antigen Receptors (CARs). Eventhough the clinical application of T cells equipped with CARs can lead to a complete remission, unfortunately, their application can also cause severe or even life threatening side effects as their activity can no more be adjusted once given to the patient. For targeting of tumor cells expressing tumor associated antigens (TAAs) which are not limited to tumor cells but also accessible on healthy tissues CAR T cells should not be permanently in a killing mode but be equipped with some kind of a switch whereby the activity of CAR T cells can reversely be turned “on and off “. Moreover, in case of cytokine release syndrome (CRS), tumor lysis syndrome (TLS), or other deadly side effects the possibility of an emergency shut down of the CAR T cell activity should exist. Modular CAR variants such as the UniCAR system may fulfill these requirements.
Keywords: Immunotherapy; Chimeric antigen receptor; T cells; UniCAR; BiTE; Bispecific antibody
Immunology Letters 211(2019), 13-22
Formation of calixarenes with acyloxycarboxylate functions
Calixarenes are an exciting class of multifunctional compounds. Their ability to bind small molecules and ions actively make them useful tools in many scopes of application. While looking for a suitable chelating agent, a particular modification of the calixarene lead to an unexpected side reaction. In this work, we will describe the selective formation of the observed acyloxy-acetate derivatives, which can be tuned by the choice of wet solvents. This side reaction is not described in the literature so far. All new compound were obtained in yields >45% and fully characterized by NMR, MS, and X-ray crystallography. Using the monomeric derivatives of calixarenes and X-ray data, an explanation for the reaction mechanism was postulated. Further, we report on different reaction conditions that were investigated to verify and elaborate this type of reaction. Finally, two additional derivatives of this class were synthesized according to this mechanism to support our considerations.
Keywords: Calixarenes; Esterification; O-alkylation; Complexation; Selective bromination
Tetrahedron 76(2020), 131395
- Secondary publication expected from 21.08.2021
Reconstruction of the Landscape Evolution of South Central Africa: A Case Study on Waterfalls of Northern Zambia and South-Eastern D.R. Congo
Northern Zambia and the south-eastern Katanga Province of D.R. Congo lie within the southwest extension of the East African Rift System, which is one of the most significant present-day examples of active tectonics. Seismotectonic research in the area has been scarce, despite the fundamental impacts of neotectonics, which controls landscape evolution southwest of the Tanganyika graben. Nevertheless, the formation of the Congo-Zambezi watershed has been constrained from the combination of geological and biological evidence at ~2 Ma (Cotterill & de Wit 2011).
A preliminary Google Earth mapping has revealed two major sets of fault systems (Mweru and Upemba). Analysis of the seismicity patterns recorded within the two fault systems during the last 35 years provides indications for fault interactions over earthquake timescales, highlighting the fact that they are currently active.
This study is part of an interdisciplinary project combining DNA sequencing of selected fish groups to define molecular clocks together with surface exposure dating of key landforms using in-situ produced cosmogenic nuclides. This technique can be applied to quantify how long rocks have been exposed at “knickpoints” since they were first formed (Burbank & Anderson 2012). For that purpose, quartz-rich samples were collected from selected waterfalls with the aim of quantifying exposure ages and erosion/retreat rates. Expecting complex exposure scenarios both radionuclides ¹⁰Be and ²⁶Al and the stable noble gas ²¹Ne were combined in all samples.
Preliminary results from Northern Zambia indicate burial for at least several hundred thousand years. This specific burial may confirm the existence of a significantly deeper and larger Paleo-Lake Mweru before the modern drainage evolved (Dixey, 1944). More results are expected soon to confirm or dismiss this hypothesis. Furthermore, samples taken at different distances below the Kiubo and Luvilombo Waterfalls (D.R.C.) yield preliminary ages between ~7 and 40 ka, increasing with distance from the falls and thus reflecting waterfall retreat. Extrapolating to the original knickpoint location should enable us to estimate the age of its formation.
Burbank D.W. & Anderson R.S. 2012. Tectonic Geomorphology. Second Edition. Wiley‐Blackwell, Chichester.
Cotterill F.P.D. & de Wit M.J. 2011. South African Geographical Journal 114: 489-514.
Dixey F. 1944. South African Geographical Journal 47, 01: 9-45.
GeoMünster 2019 "Earth! Past, Present, Future", 22.-25.09.2019, Münster, Deutschland
Bulk analysis of meteorites using INAA at FRM II
In March 2017, the 49th German meteorite was found lying on top of a rock pile on the side of a potato field, near the city of Cloppenburg, Lower Saxony, Germany [1,2]. With two other meteorites (Oldenburg (fall in 1930), Benthullen (find in 1948 or 1951)) from the same region and meteorites from other countries, we started a program to analyze extraterrestrial samples in 2017. We have analyzed in total three chondrites, three achondrites of the HED
group (Howardite-Eucrite-Diogenite) (Dhofar 1675, NWA 2690, NWA 2698), a lunar and a Martian meteorite (NWA 7986, NWA 4925), two iron meteorites (Gibeon, yet unnamed new find from Libya/Chad in 2019) and six potential micrometeorites. The bigger samples (10-20 mg) were normally irradiated twice: for 3-5 min and for a long time up to 1 h in the rabbit position. The much smaller micrometeorites (9-38 μg) were irradiated for 24 h in the high-flux capsule irradiation position (Φth>1E14 cm-2s-1). We used the k0-method for the analysis .
With the high and pure thermal neutron flux at the FRM II, up to 45 elements could be determined in most samples . According to the element compositions, the meteorites could be classified or earlier classifications could be confirmed. Although, the sample weights of the micrometeorites are very small and manipulating them was challenging, we could determine up to 16 elements. All of them show a rather high Fe concentration, i.e. 55-70 weight-%. However, for Ni and Ir, we can only give a detection limit of about 0.4% and 2 ng/g, respectively. Their potential origin are under discussion.
We thank A. Muszynski and M. Szyszko (Poznan, PL), A. Bischoff (Uni. Münster), D. Heinlein, J. Feige (TU Berlin) and A. Gärtner (Senckenberg Dresden) for providing and preparation of samples and the TUM-Kolleg program for financial supports.
1. J. Gattacceca et al., Meteorit. Planet. Sci., 2019, 54, 469-471.
2. J. Storz et al., www.paneth.eu/PanethKolloquium/2017/0075.pdf (Jan. 2019)
3. X. Li et al., J. Radioanal. Nucl. Chem. 2014, 300, 457-463.
Keywords: INAA; k0-method; meteorite; micrometeorite
2nd International Conference on Radioanalytical and Nuclear Chemistry (RANC 2019), 05.-10.05.2019, Budapest, Hungary
Preliminary Report on the Study of Beam-induced Background Effects at a Muon Collider
Physics at a multi-TeV muon collider needs a change of perspective for the detector design due to the large amount of background induced by muon beam decays. Preliminary studies, based on simulated data, on the composition and the characteristics of the particles originated from the muon decays and reaching the detectors are presented here. The reconstruction performance of the physics processes H→bb¯ and Z→bb¯ has been investigated for the time being without the effect of the machine induced background. A preliminary study of the environment hazard due to the radiation induced by neutrino interactions with the matter is presented using the FLUKA simulation program.
Keywords: Detectors in high-intensity environments; future accelerators; muon beams; neutrino-induced radiation
Contribution to WWW
arXiv: 1905.03725v1: https://arxiv.org/pdf/1905.03725.pdf
Vertical Organic Thin-Film Transistors with an Anodized Permeable Base for Very Low Leakage Current
Dollinger, F.; Lim, K.-G.; Li, Y.; Guo, E.; Formánek, P.; Hübner, R.; Fischer, A.; Kleemann, H.; Leo, K.
The organic permeable base transistor (OPBT) is currently the fastest organic transistor with a transition frequency of 40 MHz. It relies on a thin aluminum base electrode to control the transistor current. This electrode is surrounded by a native oxide layer for passivation, currently created by oxidation in air. However, this process is not reliable and leads to large performance variations between samples, slow production, and relatively high leakage currents. Here, for the first time it is demonstrated that electrochemical anodization can be conveniently employed for the fabrication of high-performance OPBTs with vastly reduced leakage currents and more controlled process parameters. Very large transmission factors of 99.9996 % are achieved, while excellent on/off ratios of 5 × 105 and high on-currents greater than 300 mA cm−2 show that the C60 semiconductor layer can withstand the electrochemical anodization. These results make anodization an intriguing option for innovative organic transistor design.
Keywords: aluminum oxide; anodization; organic permeable base transistors (OPBTs); organic transistors; organic thin-film transistors (OTFTs); vertical transistors
Advanced Materials 31(2019), 1900917
The influence of microstructure on the fracture behaviour of ferritic ODS steels
Oxide dispersion strengthened (ODS) steels are candidate materials for cladding tube and structural components in Generation IV nuclear fission reactors and as candidate materials for structural components in fusion devices. Fracture toughness is an important parameter required for the structural integrity and workability of a material. Despite having high strength at high temperatures and high irradiation swelling resistance, ODS steels have been known to possess lower fracture toughness than non-ODS ferritic martensitic steels, their immediate competitor. They also exhibit anisotropic fracture behaviour, especially for the hot-rolled and hot-extruded variants. In addition, ODS steels tend to form secondary cracks, which absorb energy but can lead to design problems.
In the present work, the microstructural features which cause low fracture toughness, anisotropic fracture behaviour and secondary cracking are investigated. This information can help manufacturers develop ODS steels with better fracture properties. Fracture toughness testing on three different batches of ODS steels are performed using miniature fracture toughness C(T) specimens using the unloading compliance method. The basic microstructure, fracture surfaces and crack propagation are investigated using techniques such as SEM, TEM and EBSD and compared with the fracture behaviour. A quantitative assessment of the microstructural parameters affecting fracture toughness is made using a critical strain based fracture toughness expression.
It was observed that the low fracture toughness of ODS steels is predominantly affected by the bond strength between the void initiating particle and the matrix. The size and inter-particle spacing of void initiating particles along with the yield stress did not dominantly affect the fracture toughness. The anisotropic fracture behaviour in ODS steels was found to be predominantly affected by the anisotropic grain morphology. Crystallographic anisotropy and anisotropy in void initiating particle distribution did not dominantly affect the fracture anisotropy. Secondary cracking favoured hot-rolled over hot-extruded specimens due to higher degree of microstructural anisotropy. Secondary cracks could stabilize primary crack propagation as well as prevent cleavage fracture at low temperatures. However, the drawback with secondary cracks was that they initiated earlier or at lower loads than the primary crack.
Keywords: fracture; fracture toughness; microstructure-mechanical property correlation; ODS steels; material characterization
University of Siegen, 2019
Mentor: Prof. Dr.-Ing. habil. H.-J. Christ
Wave-shaped polycyclic hydrocarbons with controlled aromaticity
Controlling the aromaticity and electronic properties of curved π-conjugated systems has been increasingly attractive for the development of novel functional materials for organic electronics. Herein, we demonstrate an efficient synthesis of two novel wave-shaped polycyclic hydrocarbons (PHs) 1 and 2 with 64 π-electrons. Among them, the wave-shaped π-conjugated carbon skeleton of 2 is unambiguously revealed by single-crystal X-ray crystallography analysis. The wave-shaped geometry is induced by steric congestion in the cove and fjord regions. Remarkably, the aromaticity of these two structural isomers can be tailored by the annulated direction of cyclopenta[b]fluorene units. Isomer 1 (Eoptg = 1.13 eV) behaves as a closed-shell compound with weakly antiaromatic feature, whereas its structural isomer 2 displays a highly stable tetraradical character (y0 = 0.23; y1 = 0.22; t1/2 = 91 days) with a narrow optical energy gap of 0.96 eV. Moreover, the curved PH 2 exhibits remarkable ambipolar charge transport in solution-processed organic thin-film transistors. Our research provides a new insight into the design and synthesis of stable functional curved aromatics with multiradical characters.
Chemical Science 10(2019), 4025-4031
Flash Lamp Annealing: From Basics to Applications
Rebohle, L.; Prucnal, S.; Reichel, D.
The work gives a detailed introduction to the technology of flash lamp annealing, the corresponding physical background and an overview of the various applications of flash lamp annealing found in literature. It discusses a couple of issues which are relevant for process management with the focus on temperature measurement and temperature simulation. The application-related chapters include, inter alia, ultra-shallow junctions and hyperdoping in silicon, doping and superconductivity in germanium, silicon carbide, III-V semiconductors, diluted magnetic semiconductors, the crystallization of thin amorphous silicon films, semiconductor nanostructures, high-k materials, flash lamp annealing for monocrystalline, polycrystalline and thin film solar cells, transparent conducting oxides and flexible substrates.
Keywords: Thermal processing; semiconductors; flash lamp annealing; thin films; millisecond annealing
Cham: Springer, 2019
Measurement-Protocol Dependence of the Magnetocaloric Effect in Ni-Co-Mn-Sb Heusler Alloys
Salazar Mejia, C.; Kumar, V.; Felser, C.; Skourski, Y.; Wosnitza, J.; Nayak, A. K.
Ni-Co-Mn-Sb-based Heusler shape-memory alloys that undergo a martensitic-structural transition around room temperature are well known for exhibiting large magnetic entropy change and elastocaloric effect. Here, we report the observation of a large adiabatic temperature change of −11 K in a Ni-Co-Mn-Sb system by using direct adiabatic temperature-change measurements in pulsed magnetic fields. We show that a large magnetic cooling can be achieved in a wide temperature range spanning from 120 to 270 K by purposefully varying the chemical composition. The temperature- and field-dependent irreversibility of the effect is analyzed through a detailed experimental study of the protocol-dependent magnetocaloric effect. The present study is an important contribution towards the understanding of irreversible magnetocaloric effects in materials with magnetostructural transition.
Physical Review Applied 11(2019), 054006
- Original PDF 923 kB Secondary publication
Magnetocaloric effect of gadolinium in high magnetic fields
The magnetocaloric effect of gadolinium has been measured directly in pulsed magnetic fields up to 62 T. The maximum observed adiabatic temperature change is ΔTad = 60.5 K, the initial temperature T0 being just above 300 K. The field dependence of ΔTad is found to follow the usual H2/3 law, with a small correction in H4/3. However, as H is increased, a radical change is observed in the dependence of ΔTad on T0, at H = const. The familiar caret-shaped peak situated at T0 = TC becomes distinctly asymmetric, its high-temperature slope becoming more gentle and evolving into a broad plateau. For yet higher magnetic fields, μ0H ≥ 140 T, calculations predict a complete disappearance of the maximum near TC and an emergence of a new very broad maximum far above TC.
Physical Review B 99(2019), 134429
- Original PDF 739 kB Secondary publication
Field-induced instability of the quantum spin liquid ground state in the Jeff = 1/2 triangular-lattice compound NaYbO2
Ranjith, K. M.; Opherden, D.; Khim, S.; Sichelschmidt, J.; Luther, S.; Ehlers, D.; Yasuoka, H.; Wosnitza, J.; Tsirlin, A. A.; Kühne, H.; Baenitz, M.
Polycrystalline samples of NaYbO2 are investigated by bulk agnetization and specific-heat measurements, as well as by nuclear magnetic resonance (NMR) and electron spin resonance (ESR) as local probes. No signatures of long-range magnetic order are found down to 0.3 K, evidencing a highly frustrated spin-liquid-like ground state in zero field. Above 2 T, signatures of magnetic order are observed in thermodynamic measurements, suggesting the possibility of a field-induced quantum phase transition. The 23Na NMR relaxation rates reveal the absence of magnetic order and persistent fluctuations down to 0.3 K at very low fields and confirm the bulk magnetic order above 2 T. The H-T phase diagram is obtained and discussed along with the existing theoretical concepts for layered spin- 1/2 triangular-lattice antiferromagnets.
Physical Review B 99(2019), 180401 (R)
Contribution to WWW
Electronic Properties of Defective MoS2 Monolayers Subject to Mechanical Deformations: A First-Principles Approach
Monolayers (MLs) of group-6 transition-metal dichalcogenides (TMDs) are semiconducting 2D materials with direct bandgap, showing promising applications in various fields of science and technology, such as nanoelectronics and optoelectronics. These MLs can undergo strong elastic deformations, up to about 10%, without any bond breaking. Moreover, the electronic structure and transport properties, which define the performance of these TMD MLs in nanoelectronic devices, can be strongly affected by the presence of point defects, which are often present in the synthetic samples. Thus, it is important to understand both effects on the electronic properties of such MLs. Herein, the electronic structure and energetic properties of defective MoS2 MLs are investigated as subject to various strains, using density functional theory simulations. The results indicate that strain leads to strong modifications of the defect levels inside the bandgap and their orbital characteristics. Strain also splits the degenerate defect levels up to an amount of 450 meV, proposing novel applications.
Physica Status Solidi (B) 257(2020)5, 1900541
Single Plane Compton Imaging for Radionuclide and Prompt Gamma-Ray Imaging
The contribution reports on first attempts to prove the concept of Single Plane Compton Imaging (SPCI), which was recently proposed in . SPCI combines electronic collimation as known from conventional Compton cameras with a much simpler detector design: Multiple scintillator pixels are arranged alongside in a single detection plane. Imaging information is encoded in a set of ‘conditional’ spectra meaning energy deposition distributions in single pixels obliged with the condition of a coincident detection in another (adjacent) pixel. The activity distribution is iteratively reconstructed from the measured projections (the bin contents of the conditional spectra) by using the Maximum Likelihood Expectation Maximization (MLEM) algorithm.
This concept has been approached experimentally with three distinct setups addressing the application fields of radionuclide imaging in nuclear medicine, and of prompt-gamma based range verification in radiooncology with proton beams.
The first setup consists of two Directional Gamma-Ray Detectors , each consisting of two monolithic CeBr3 scintillators of 2”x1” and 2”x2”, arranged facing each other in close geometry. Those were exposed to prompt gamma radiation produced by a 90 MeV proton beam in a beam-stopping polymethyl acrylate (PMMA) target.
The third setup, aiming to be applied in radionuclide imaging, is a combination of a 4×4 pixel array of about 7 × 7 × 20 mm3 GAGG scintillator pixels read out with a Philips STEK module comprising 4×4 digital silicon photomultiplier dies. Data were taken with radioactive point sources arranged in few-cm distance from the scintillator pixels. Though data analyses are not yet finished, the effects enabling imaging are clearly visible. Preliminary plots exemplify the applicability of SPCI in both applications. The experimental activities have been closely accompanied with appropriate imaging methods and modeling using the Geant4 toolkit.
 G. Pausch, C. Golnik, A. Schulz and W. Enghardt, "A Novel Scheme of Compton Imaging for Nuclear Medicine," in IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD), Strasbourg, 2016.
 A. Gueorguiev, J. Preston, l. Hoy, G. Pausch, C. Herbach and J. Stein, "A novel method to determine the directionality of radiation sources with two detectors based on coincidence measurements," in IEEE Nuclear Science Symposuim & Medical Imaging Conference, Knoxville, 2010.
Keywords: proton therapy; radiotherapy; range verification; single plane Compton imaging
Invited lecture (Conferences)
International Conference on Nuclear Data for Science and Technology 2019, 19.-24.05.2019, Beijing, China
Proton-induced Prompt Gamma-Ray Yield of Carbon for Range Verification in Hadron Therapy
With particle therapy, more and more patients around the world are benefiting from precise dose deposition in the tumor. Due to the characteristic depth dose distribution, however, hadron therapy is particularly susceptible to range inaccuracies. Particle range verification is the subject of current research, but not yet a clinical standard. To circumvent this problem, safety margins are currently being defined around the tumor volume, which nullify the potential precision of particle compared to conventional photon therapy.
The use of the prompt gamma radiation resulting from the deceleration of hadrons in tissue for range verification is a promising approach here. At present, various methods exist (for example, prompt gamma-ray imaging, prompt gamma-ray spectroscopy, prompt gamma-ray timing, prompt gamma-ray peak integration), which attempt to obtain information regarding the range from the temporal and / or spatial distribution of these high-energy photons. However, all methods are based directly or indirectly on the results of particle transport calculations. But their results show significant discrepancies compared to the experimental data  - .
Photon production cross sections are particularly important for range verification with prompt gamma radiation, although there is hardly any experimental data for the clinically relevant isotopes to check and optimize the underlying models. The importance of prompt photon yields in clinical research was therefore also the subject of the 2nd ESTRO Physics Workshop Science and Development "Improving Range Accuracy in Particle Therapy" and will soon be emphasized again in a position paper of the society.
At the University Proton Therapy Dresden, the prompt emission spectrum of homogeneous graphite targets of different thickness was determined by irradiation with 90, 150 and 226 MeV protons. The detector response of the CeBr3 scintillation detectors (placed below 55 °, 90 ° and 125 ° with respect to the beam axis) was determined by Geant 4 simulations and verified by measurements with radioactive emitters. The emission spectrum was then obtained by unfolding the detector response using two different deconvolution algorithms (gold deconvolution and spectrum stripping). Scattered protons, which were detected in a YAP / BGO-Phoswich detector below 35°, were used to determine the incident proton fluence. The yields thus obtained are in good agreement with the available experimental data.
 J. Berthold, Single Plane Compton Imaging for Range Verification in Proton Therapy - A Proof-of-Principle Study, Dresden: Technische Universität Dresden, 2018.
 L. Kelleter, A. Wronska, J. Besuglow, A. Konefał, K. Laihem, J. Leidner und A. Magiera, „Spectroscopic study of prompt-gamma emission for range verification in proton therapy,“ Physica Med., Bd. 34, pp. 7-17, 2017.
 M. Pinto, D. Dauvergne, N. Freud, J. Krimmer, J. Létang und E. Testa, „Assessment of Geant4 Prompt-Gamma Emission Yields in the Context of Proton Therapy Monitoring,“ Frontiers in Oncology, Bd. 6, 2016.
 J. Jeyasugiththan und S. Peterson, „Evaluation of proton inelastic reaction models in Geant4 for prompt gamma production during proton radiotherapy,“ Phys. Med. Biol., Bd. 60, p. 7617–7635, 2015.
 A. Schumann, J. Petzoldt, P. Dendooven, W. Enghardt, C. Golnik, F. Hueso-González, T. Kormoll, G. Pausch, K. Roemer und F. Fiedler, „Simulation and experimental verification of prompt gamma-ray emissions during proton irradiation,“ Phys. Med. Biol., Bd. 60, pp. 4197-4207, 2015.
 J. Verburg, Reducing Range Uncertainty In Proton Thearpy, Eindhoven: Technische Universiteit Eindhoven, 2015.
 J. Dudouet, D. Cussol, D. Durand und M. Labalme, „Benchmarking Geant4 nuclear models for hadron therapy with 95 MeV/nucleon carbon ions,“ Phys. Rev. C, Bd. 89, p. 054616, 2014.
Keywords: proton therapy; range verification; prompt gamma yield; spectrum stripping; gold deconvolution
International Conference on Nuclear Data for Science and Technology 2019, 19.-24.05.2019, Beijing, China
Solubility of Se in saline solutions – towards a consistent polythermal Pitzer dataset
Bok, F.; Moog, H. C.
Selenium (with the isotope Se-79 being an important fission product) can occur in oxidation states varying between +VI and –II. Most often negatively charged species are formed rendering them extraordinarily mobile in groundwater systems. For a correct calculation of the solubilities of Se(VI) and Se(IV) phases, the Pitzer ion-ion interaction model is essential for solutions with high ionic strengths.
Beside solubility calculations – mostly relevant for low soluble earth alkali selenites – reliable thermodynamic data sets for selenium are also of importance for chemotoxicity estimations or as boundary system in S-Se-solid solutions.
The state-of-the-art thermodynamic data for Selenium are given in the OECD/NEA Chemical Thermodynamics. This compilation does not address the Pitzer ion-ion interaction model. A polythermal set of Pitzer interaction parameters was compiled by GRS. However, both compilations hold solubility data for T = 25 °C only.
Here, to enable the calculation of selenium solubility at various temperatures in high saline solutions, temperature functions for the solubility products of alkaline and earth alkaline selenium phases are presented.
The experimental solubility data of various alkaline and earth alkaline selenates and selenites have been collected. The temperature function’s parameters of the solubility products were fitted to these solubility data using the geochemical speciation code PHREEQC in combination with the parameter estimation software Ucode2014.
Beside the solubility data, also temperature function’s parameters for the relevant redox reactions have been determined. The THEREDA database was used for all auxiliary reactions. Thus, the obtained data are consistent with their actual Pitzer model.
Temperature function’s parameters for the solubility products of seven selenate and four selenite mineral phases as well as for the relevant redox reactions could be obtained. In all cases, simplified functions with only two parameters were sufficient to fit the data within the range of experimental uncertainty.
With this new temperature-dependent parameter set, the solubility of selenium(IV) and (VI) an be calculated over the temperature range (T = 0 – 100 °C) relevant for a nuclear waste disposal.
The literature on directly measured selenide solubility data is very limited and not sufficient to derive solubility products or Pitzer interaction parameters – even at 25 °C. Thus, for the Se(−II) system the solubility data for alkaline and earth alkaline solid phases were taken from thermochemical measurements. For the Pitzer interaction coefficients data from chemical analogs have been used (Br− or H2S). For the selenide system, this dataset is valid for T = 25 °C only.
The new temperature functions provide a redox-enabled and self-consistent dataset for the solubility calculations of selenium within the oceanic salt system including carbonates from the binary up to ternary and some quaternary systems.
For oxidizing to light reducing conditions, this dataset is valid between T = 0 – 100 °C, for stronger reducing conditions, the dataset is valid at T = 25 °C only.
Keywords: THEREDA; Selenium; Solubility; Löslichkeit; Pitzer
Workshop on Actinide-Brine-Chemistry and Workshop on High Temperature Aqueous Chemistry, 25.-27.06.2019, Karlsruhe, Deutschland
Size effects in nanocrystalline thoria
The facile chemical precipitation method and subsequent thermal treatment were shown to be suitable for preparation of crystalline ThO2 nanoparticles (NPs) in a wide range of particle sizes (from 2.5 to 34.3 nm). The obtained NPs were investigated with X-ray diffraction, high-resolution transmission electron microscopy and X-ray absorption techniques to find out the possible size effects associated with nanocrystalline thoria. The lattice parameter of ThO2 was found to increase by up to 1.1 %, in comparison with the bulk material whose particle size decreased to 2.5 nm. The decrease in the particle size was also accompanied by a significant decrease in the Th-Th coordination number
Journal of Physical Chemistry C 123(2019)37, 23167-23176
- Final Draft PDF 1018 kB Secondary publication
New insights into the mechanism of graphene oxide and radionuclide interaction through vacancy defects
The sorption of U(VI), Am(III)/Eu(III) and Cs(I) radionuclides by graphene oxides (GOs) synthesized by Hummers’s, Brodie’s and Tour’s methods was studied through a combination of batch experiments with characterization by microscopic and spectroscopic techniques such as XPS, ATR-FTIR, HERFD-XANES, EXAFS and HRTEM. Remarkably different sorption capacity and affinity of radionuclides was found towards GOs synthesized by Hummers’s and Brodie’s methods reflecting different structure and oxidation state of these materials. Mechanism underlying GO –radionuclide interaction is determined using variety of experimental techniques. For the first time it is shown here that GO - radionuclides interaction takes place on the small holes or vacancy defects in the GO sheets. Mechanism of GO’s interaction with radionuclides was analysed and specific functional groups responsible for this interaction were identified. Therefore, new strategy to produce improved materials with high capacity for radionuclides suggests to use perforated and highly defected GO with larger proportion of carboxylic functional groups
Carbon 158(2020), 291-302
- Final Draft PDF 1,9 MB Secondary publication
Ion Sources for Focused Ion Beams – Present Status and Prospective Developments
Focused Ion Beam (FIB) processing has been developed into a well-established, irreplaceable and still promising technique in nearly all fields of nano-technology in particular for direct patterning and proto-typing on the μm scale and well below as well as sample preparation for further investigations, using SEM or TEM.
At the moment nearly exclusively gallium Liquid Metal Ion Sources (LMIS) are used for ion beam generation. Therefore, the Liquid Metal Alloy Ion Sources (LMAIS) represent a promising new alternative research area to expand the global FIB application fields. Here, especially, IBL (Ion Beam Lithography) - a direct, resistless and threedimensional patterning - enables a simultaneous in-situ process control by crosssectioning and inspection. Thanks to this, nearly half of the elements of the periodic table are made available in the FIB technology as a result of continuous research in this area during the last forty years . Key features of a LMAIS are long life-time, high brightness and stable ion current. Recent developments could make these sources as an alternative technology feasible for nano patterning challenges e.g. to tune electrical, optical, magnetic or mechanic properties. In this contribution the operation principle, the preparation and testing
technology as well as prospective domains for modern FIB applications will be presented. As an example we will introduce a Ga35Bi60Li5 LMAIS in detail. It enables high resolution imaging with light Li ions, obtained with a VELION FIB/SEM system (Raith GmbH), as well as heavy Bi ions or polyatomic clusters, all coming from one ion source . Additionally, also new ion source developments based on gas field emission (GFIS), on ionic liquids (ILIS), on magneto-optical traps (MOTIS) or on ICP or ECR high current sources for Xe-FIB are presented. Combined with an optimized FIB optics design they can open a bright field of new employments. These alternative ion sources will be introduced and briefly described.
 L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources - An Alternative
for Focused Ion Beam Technology, Appl. Phys. Rev. 3 (2016) 021101.
 W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium Ion Beams from Liquid Metal
Alloy Ion Sources, J. Vac. Sci. Technol. B 37 (2019) 021802-1.
Keywords: Ion sources; Focused Ion Beam; Nanopatterning
Invited lecture (Conferences)
European FIB Network, 3rd EuFN Workshop 2019, 12.-14.06.2019, Dresden, Germany
Studying of plutonium nanoparticles with various synchrotron metods
Plutonium is one of the most significant elements among actinides due to its high radiotoxicity and long period of high-decay. The migration of plutonium in the environment is a challenging and global problem. Plutonium migrates at scale of kilometers from previously contaminated sites in the form of intrinsic colloids or “pseudocolloids”.1-2 In the last few years it was found that so called “colloidal Pu(IV) polymers” actually represents as aggregates of PuO2 nanoparticles with size ~ 2 nm.3-5 The revealing of the mechanism of these particles formation (including the consideration of different factors which may have an influence), as well as their characterization is a key to understanding the conditions for long-term storages for the nuclear waste.
With the combination of different laboratory and synchrotron techniques it was found that small (2 nm) nanoparticles are formed from Pu(III), Pu(IV), Pu(V) aqueous solutions at pH 8-12, with the crystal structure close to PuO2, and with only Pu(IV) oxidation state present. Any other Pu-O contributions except Pu(IV)-O (in oxide) were not revealed.
XXI Mendeleev Congress on General and Applied Chemistry, 09.-13.09.2019, Saint Petersburg, Russia
Minimizing betatron coupling of energy spread and divergence in laser-wakefield accelerated electron beams
Matched beam loading in laser wakefield acceleration (LWFA), characterizing the state of flattening of the accelerating electric field along the bunch, leads to the minimization of energy spread at high bunch charges. Here, we demonstrate by independently controlling injected charge and accelerating gradients, using the self-truncated ionization injection scheme, that minimal energy spread coincides with a reduction of the normalized beam divergence. With the simultaneous confirmation of a constant beam radius at the plasma exit, deduced from betatron radiation spectroscopy, we attribute this effect to the reduction of chromatic betatron decoherence. Thus, beam loaded LWFA enables highest longitudinal and transverse phase space densities.
Keywords: Laser wakefield acceleration; laser plasma accelerator; high bunch charge; beam loading; bunch size measurement; betatron radiation; betatron spectroscopy; Transverse phase space dynamic; beam divergence; beam decoherence; betatron phase mixing; betatron decoherence
- Transverse electron beam dynamics in the beam loading regime (Id 29299) references this (Id 29188) publication
4th European Advanced Accelerator Concepts Workshop, 15.-21.09.2019, Isola d'Elba, Italia
Contribution to WWW
arXiv:1905.02240 [physics.acc-ph]: https://arxiv.org/abs/1905.02240
Geometry description in the FLUKA MC transport code
Geometry description in the FLUKA MC transport code
Keywords: FLUKA; MU2E; CLFV
MU2E SimWG meeting, 11.04.2019, Fermilab, Batavia, USA
Ultrafast Anisotropic Disordering in Graphite Driven by Intense Hard X-ray Pulses
Hartley, N.; Grenzer, J.; Lu, W.; Huang, L.; Inubushi, Y.; Kamimura, N.; Katagiri, K.; Kodama, R.; Kon, A.; Lipp, V.; Makita, M.; Matsuoka, T.; Medvedev, N.; Nakajima, S.; Ozaki, N.; Pikuz, T.; Rode, A. V.; Rohatsch, K.; Sagae, D.; Schuster, A.; Tono, K.; Vorberger, J.; Yabuuchi, T.; Kraus, D.
We present results from the SPring-8 Angstrom Compact free electron LAser (SACLA) X-ray free electron laser (XFEL) facility, using an X-ray pump, X-ray probe scheme to observe ultrafast changes in the structure of heated graphite. The 9.8 keV XFEL beam was focused to give an intensity on the order of 10^19 W/cm2, and the evolution of the diffraction pattern observed up to delays of 300 fs. The interplanar diffraction peaks weaken significantly within 10s of femtoseconds, but in-plane diffraction orders i.e. those with Miller Index (hk0), persist up to 300 fs, with the observed signal increasing. We interpret this as nonthermal damage through the breaking of interplanar bonds, which at longer timescales leads to ablation by removal of intact graphite sheets. Post-experiment examination of the graphite samples shows damage which is comparable in size to the range of the excited photoelectrons. These results highlight the challenges of accurately modelling X-ray driven heating, as it becomes a routine approach to generating high energy density states.
High Energy Density Physics 32(2019), 63-69
Tunable disorder and localization in the rare-earth nickelates
We demonstrate that transport in metallic rare-earth nickelates can be engineered by directly tuning the electronic mean free path. Using irradiation as a tool to induce disorder, we drive this system from a metallic phase into an Anderson insulator. This proceeds via an intermediate regime which shows a thermal crossover from insulating to metallic behavior. We argue that this phase falls within the paradigm of weak localization in three dimensions. We develop a theoretical model for the temperature dependence of resistivity which shows good agreement with our data. The three-dimensional weak localization picture is supported by magnetoconductivity, which scales as ∼B2 up to several tesla. Interestingly, our data indicate that this phase lies in the Mott-Ioffe-Regel regime with the mean free path approaching the lattice constant. Upon further increasing disorder, the charge carriers are localized, leading to insulating behavior at all temperatures. Our results show that irradiation provides a “clean” tuning knob for the mean free path, without altering other system parameters. This suggests promising directions for studies of Anderson localization.
Keywords: Anderson localization; Metal-insulator transition; Weak localization; Magnetoresistance
Physical Review Materials 3(2019)053801
26th International Workshop on Oxide Electronics, 29.09.-02.10.2019, Kyoto, Japan
Light and Heavy Ions from New Non-classical Liquid Metal Ion Sources for Advanced Nanofabrication
Nanofabrication requirements for FIB technologies are specifically demanding in terms of patterning resolution, stability and the support of new processing techniques. Moreover the type of ion defines the nature of the interaction mechanism with the sample and thus has significant consequences on the resulting nanostructures . Therefore, we have extended the technology towards the stable delivery of multiple ion species selectable into a nanometer scale focused ion beam by employing a liquid metal alloy ion source (LMAIS) . This provides single and multiple charged species of different masses, resulting in significantly different interaction mechanisms. Nearly half of the elements of the periodic table are made available in the FIB technology as a result of continuous research in this area . This range of ion species with different mass or charge can be beneficial for various nanofabrication applications. Recent developments could make these sources to an alternative technology feasible for nanopatterning challenges. In this contribution the operation principle, the preparation and testing process as well as prospective domains for modern FIB applications will be presented. As example we will introduce a GaBiLi LMAIS . It enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from one ion source. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB or the AuSiGe-FIB could benefit of providing additional ion species in a mass separated FIB without changing the ion source.
 L. Bruchhaus, P. Mazarov, L. Bischoff, J. Gierak, A. D. Wieck, and H. Hövel, Comparison of technologies for nano device prototyping with a special focus on ion beams: A review, Appl. Phys. Rev. 4, 011302 (2017).
 L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative for
Focused Ion Beam Technology, Appl. Phys. Rev. 3 (2016) 021101.
 J. Gierak, P. Mazarov, L. Bruchhaus, R. Jede, L. Bischoff, Review of electrohydrodynamical ion sources and their applications to focused ion beam technology, JVSTB 36, 06J101 (2018).
 W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium ion beams from liquid metal alloy ion sources, JVSTB 37, 021802 (2019).
Keywords: Nanofabrication; FIB technology; Liquid Metal Alloy Ion Source
Invited lecture (Conferences)
AVS 66th International Symposium & Exhibition, 20.-25.10.2019, Columbus, Ohio, USA
Numerical simulation of an electromagnetic flow excitation in a liquid metal volume using OpenFOAM
To prepare an experiment on the potential resonance effect between the Rayleigh-Bénard convection and weak tidal forcing in a liquid metal, the influence of electromagnetic forcing on the eutectic metal Ga-In-Sn simulated in OpenFOAM will be the main topic of this work .
A modulated tidal m=2 Lorentz forcing will be produced by two opposing Helmholtz-like coils outside a Ga-In-Sn filled cylinder with an aspect ratio of one. Considering future analyses with additional Rayleigh-Bénard convection two Cu-plates installed at the bottom and the top of the volume are also taken into account for the simulation of the AC magnetic field. With a small magnetic flux density of a few mT a flow speed up to several centimeters per second can be produced. The results of the numerical simulations will be compared with experimental data.
Keywords: Magnetohydrodynamics; OpenFOAM; Rayleigh-Bénard convection; electromagnetic forcing; liquid metal
9th European Postgraduate Fluid Dynamics Conference, 16.-19.07.2019, Ilmenau, Deutschland
Electromagnetic flow excitation in a liquid metal volume using a Helmholtz-like coil setup
We present first results of our experiment involving electromagnetic forcing of a liquid metal volume. The experiment consist of a cylinder filled with eutectic GaInSn alloy and two magnetic coils placed on opposite sides of the cylinder. An alternating current in the coils excites Lorentz forces in the fluid, generating a flow field. Using ultrasound doppler velocimetry (UDV), we mapped this flow field. Maximum velocities of a few centimetres per second were reached. Numerical studies of the problem were also conducted and show good agreement. As a next step, the experimental setup shall be used to periodically disturb a Rayleigh-Bénard convection. The Rayleigh-Bénard flow structure occurs, when a layer of fluid is heated from below. The resulting flow is a convection roll about a horizontal axis. Point of interest is a possible resonance effect between the introduced forces and this flow structure.
Keywords: Electromagnetic forcing; liquid metal; Rayleigh-Bénard convection; resonance
9th European Postgraduate Fluid Dynamics Conference, 16.07.2019, Ilmenau, Deutschland
Experimental investigation of magnetorotational instability in hydromagnetic Taylor-Couette flows
Magnetorotational instability (MRI) is believed to be largely responsible for the formation of protostars and black holes by introducing turbulence and facilitating an outward angular momentum transport in accretion disks. MRI is replicable in Taylor-Couette flows of electrically conducting fluids in the presence of externally applied magnetic fields. The Potsdam Rossendorf Magnetic Instability Experiment (PROMISE) at Helmholtz-Zentrum Dresden-Rossendorf is one of several existing facilities where an experimental approach towards understanding MRI takes place. PROMISE creates a magnetized Taylor-Couette flow of GaInSn alloy between concentric copper cylinders. Using PROMISE, the azimuthal MRI (AMRI), which is obtained when an azimuthal magnetic field is applied to the flow, have been demonstrated. The azimuthal magnetic field is induced by a strong central current along the cylinder axis. PROMISE has also shown evidence of the helical MRI (HMRI), which is obtained when an axial magnetic field is applied in addition to the azimuthal magnetic field. The axial magnetic field is induced by current through a coil wound around the outer cylinder. Recently, a symmetry breaking of AMRI due to thermal convection in the GaInSn alloy was discovered. In future, the transition from AMRI to HMRI will be investigated.
Keywords: Magnetorotational instability; Taylor-Couette flows; hydromagnetic flows
9th European Postgraduate Fluid Dynamics Conference, 16.-19.07.2019, Ilmenau, Deutschland
Solid target irradiation at the cyclotron Cyclone 18/9® at the HZDR in Leipzig
Franke, K.; Mansel, A.
Different research projects within the fields of resource ecology and neuroradiopharamceutical research make use of the cyclotron Cyclone 18/9® (IBA RadioPharma Solutions) at the HZDR in Leipzig. Aside liquid (2x F-18) and gas targets ([C-14]CH4, [C-14]CO2, [O-15]O2) two Nirta® Solid irradiation systems (IBA RadioPharma Solutions) are used. A broad spectrum of radionuclides (Ti-45, V-48, Cr-51, Co-56, Cu-64, Sr-85, Y-86, Zr-89, La-135, Ce-139, Au-194) is produced with these Nirta® Solid irradiation systems. Here we give an overview about the used target designs, irradiation parameters and target processing.
The Nirta® Solid irradiation system 1 (SIS1) is mounted at a 2m beam transfer line at port 3 of the cyclotron. The second irradiation system (SIS2) is mounted at port 4 of the cyclotron via a short tube. The cyclotron Cyclone 18/9 provides protons with an energy of 18 MeV and deuterons with energy of 9 MeV. The required energy of the incident particle for the nuclear reaction is set by the appropriate choice of the vacuum (Ti) and the entrance window (Al) of the target. SIS2 can hold coin like target disks (Ø 24 mm x 2mm). The maximal effective target size is Ø 12 mm x 1 mm. The SIS2 is used for the irradiation of metal foils, which are crimped inside the disk in between a cover and a backing plate. SIS1 can operate target capsules with a maximal effective target size of Ø 12 mm x 4 mm. This enables the irradiation of powders and pellets aside its use for metal foils. Both irradiation systems can be pre-loaded with 3 targets for consecutive irradiations. Different target materials are used for irradiation, like metal foils (Sc-45(p,n)Ti-45, Ti-48(p,n)V-48, V-nat(p,n)Cr-51, Ni-64(p,n)Cu-64, Y 89(p,n)Zr-89), metal powders (Ti-48(p,n)V-48, Pt-nat(p,n)Au-194), oxides (La-139(p,n)Ce-139), carbonates (Sr 86(p,n)Y-86) and chlorides (Rb-85(p,n)Sr-85). If required electroplating or pellet pressing is applied for target preparation. After irradiation the targets are transferred out of the vault by a conveyer system. Different techniques, like liquid/liquid extraction, liquid/solid extraction and chromatography are applied for target processing and the recovery of the enriched target material. Gamma-ray spectrometry is used to prove the radionuclidical purity of the product. The presented methods allow a straightforward and reliable production of n.c.a. radionuclides for research purposes. Irradiation parameters, target preparation and processing are easily adaptable to the experimental needs.
Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland
AMS at Big Accelerators: 53Mn and 60Fe in Meteorites
Rugel, G.; Faestermann, T.; Fimiani, L.; Korschinek, G.; Leya, I.; Ludwig, P.; Pavetich, S.; Smith, T.; Wallner, A.
The poster describes that big tandem accelerators are essential to measure 53Mn and 60Fe in meteorites.
Keywords: AMS Accelerator Fe-60 Mn-53 Meteorites
KIMM Workshop 2019, 02.05.2019, München, Deutschland
Interaction of O-Y and O-Y-Ti clusters embedded in bcc Fe with He, vacancies and self-interstitial atoms
Calculations based on Density Functional Theory are performed to investigate the interaction of O-Y and O-Y-Ti clusters in bcc Fe with He atoms, vacancies (V) and self-interstitial atoms (SIA). The four different cluster structures studied in our previous work (J Phys Condens Matter 31 095701) are considered. He, V and SIA are inserted on different positions inside and in the environment of the clusters, the total energy of the corresponding supercell is minimized and the binding and incorporation energy of the three kinds of defects is determined. He in the center of a cage-like (CL) cluster is more stable than on interfacial vacant sites (IVS). In CL O-Y clusters He on an IVS is more stable than in the cluster structure with oxygen in the center (OC), whereas there is no significant difference between the two kinds for clusters with Ti. Up to a distance of 1.5 times the iron lattice constant from the cluster center He is not stable on most of the octahedral and tetrahedral interstitial sites in the Fe matrix near the interface. Instead He is shifted towards positions closer to the cluster. Relaxation occurs to known IVS as well as to previously unknown interfacial interstitial sites (IIS). Moreover, two or three He atoms are placed on sites found to be stable after adding a single He. The corresponding binding and incorporation energies obtained after relaxation are nearly equal to the sum of the values for the interaction with a single He atom. However, placing He dimers or trimers in the environment of a vacancy may also lead to relatively low values of the incorporation energy. Also, barriers for jumps of He atoms between interfacial sites and the center of CL clusters are determined. In the CL O-Y cluster the barriers are lower than in the CL O-Y-Ti cluster, i.e. trapping and release of He is easier in the former than in the latter. V and SIA interaction with the clusters is also attractive. The binding energy of V strongly depends on the site where V is inserted while in all the studied cases the SIA is annihilated at the cluster-iron interface. Present results clearly demonstrate that the oxide-based nanoclusters are strong traps for irradiation induced defects which is in agreement with experimental findings.
Keywords: density functional theory calculations; oxide dispersion strengthened steels; interaction with He; vacancies and self-interstitial atoms
Journal of Physics: Condensed Matter 31(2019), 485702
Magnetic Orders and Origin of Exchange Bias in Co Clusters Embedded Oxide Nanocomposite Films
Magnetic nanoparticles embedded oxide semiconductors are interesting candidates for spintronics in view of combining ferromagnetic (FM) and semiconducting properties. Co-ZnO and Co-V2O3 nanocomposite thin films are synthesized by Co ion implantation in crystalline thin films. Magnetic order varies with the implantation fluence in Co-ZnO, where the superparamagnetic (SPM) order appears in the low-fluence films (2×1016 and 4×1016 ions/cm2) while the FM order coexists with the SPM phase in high-fluence ones (1×1017 ions/cm2). The exchange bias (EB) effect is evident in high-fluence films, which gives an EB field of about 100 Oe at 2 K and a blocking temperature of around 100 K. In parallel, 3.5×1016 ions/cm2 Co-V2O3 hybrid thin film exhibits a clear antiferromagnetic (AFM) coupling at low temperature with a weak EB effect. The different magnetic behaviors in the two Co-implanted systems lead us to believe on one hand, that the observed EB effect in the Co-ZnO system is the result of the FM/AFM coupling between large Co nanoparticles and their CoO/Co3O4 surroundings in the (Zn,Co)O matrix. While, on the other hand, the EB effect in Co-V2O3 system originates from the interaction between FM Co nanoparticles and AFM V2O3 matrix. Detailed studies of magnetic orders as well as EB effect in magnetic nanocomposite semiconductors pave the way for their application in spintronics.
Keywords: nanocomposite; exchange bias; antiferromagnetic; superparamagnetic
Journal of Physics: Condensed Matter 31(2019), 155301
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