Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31738 Publications
Open Science with openPMD
Huebl, A.ORC; Lehe, R.; Vay, J.-L.ORC; Grote, D. P.; Sbalzarini, I. F.ORC; Kuschel, S.; Bussmann, M.ORC
Nobody needs yet an other data format for HPC. But why have so-called self-describing data formats never provided out-of-the-box cross application portability? Why are most open-access datasets not self-describing for both the domain scientist and after-use? And why do communities need to implement their data readers in various post-processing, visualization and analysis frameworks over and over again?

We present the open meta data format openPMD for data format agnostic markup of particle-mesh data. Based on a minimal kernel of meta information and enriched with domain-specific extensions, we develop an open ecosystem of interoperable simulations and data processing frameworks from the domains of laser-plasma interaction, X-ray photon sciences, astrophysics up to systems biology. This poster presents our efforts to enable & establish workflows suitable to frictionless transposition between those domains, using highly scalable I/O methods (e.g. ADIOS BP or HDF5), a truly self-describing data markup and peer reviewed participation.
Keywords: I/O OpenScience OpenData HPC OpenAccess HDF5 ADIOS metadata
  • Poster
    Platform for Advanced Scientific Computing (PASC) Conference 2017, 26.-28.06.2017, Lugano, Schweiz
    DOI: 10.5281/zenodo.822396

Publ.-Id: 25686 - Permalink


Data Management in Small Animal Imaging: Conceptual and Technical Considerations
Maus, J.ORC; Hofheinz, F.
Small animal imaging in general and multimodal tomographic imaging in particular generate a substantial amount of heterogeneous data that can be challenging to handle. Besides computed tomographic images, there are also the primarily acquired raw data such as listmode data in positron emission tomography (PET), projection data in X-ray computed tomography (CT), or even k-space data in magnetic resonance imaging (MRI). Additionally, further image data might be created by postprocessing (e.g., filtering) or by using alternative image reconstruction methods. All these data have to be stored; thus, the required disk space can easily exceed several terabyte (TB) over time. Therefore, good data storage planning and management strategies are required. In this context, data management obviously does not just mean storing the data. Rather, the data have to be easily accessible for all involved researchers, they also have to remain accessible years after the measurement, and the data have to be backed up in a save and secured place.
Keywords: PET, Small Animal Imaging
  • Book chapter
    Fabian Kiessling, Bernd J. Pichler, Peter Hauff: Small Animal Imaging: Basics and Practical Guide, Heidelberg: Springer International Publishing, 2017, 978-3-319-42200-8, 581-590
    DOI: 10.1007/978-3-319-42202-2_22

Publ.-Id: 25685 - Permalink


Range verification in proton therapy and related activities at OncoRay
Pausch, G.ORC
Range verification with millimeter accuracy is considered to be a key for improving the precision and for reducing side effects of radiotherapy with ion beams. The detection and analysis of prompt gamma rays with respect to their emission points, emission time, and emission energy can provide appropriate means for range verification in situ and in real time. The research group “In-vivo Dosimetry” at Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology - OncoRay, has focused considerable efforts on developing and testing prompt-gamma based techniques of range verification in under treatment conditions in proton therapy. The talk reviews complementary approaches and presents recent results of corresponding research activities.
Keywords: Particle therapy; proton therapy; treatment verification; range verification; prompt gamma rays; prompt gamma imaging; prompt gamma timing; gamma spectroscopy
  • Invited lecture (Conferences)
    Annual Meeting of the Gilbert H. Fletcher Society, 21.-22.06.2017, Dresden, Germany

Publ.-Id: 25684 - Permalink


Towards probing THz-driven transient electronic states with time-resolved ARPES
Deinert, J.-C.ORC; Green, B. W.; Kovalev, S.; Gensch, M.
In this contribution, we present the concept for a novel experimental setup at the THz facility TELBE at Helmholtz-Zentrum Dresden-Rossendorf [1], which combines THz excitation with intrinsically surface-sensitive time- and angle-resolved photoelectron spectroscopy (tr-ARPES). THz excitation provides resonant access to a multitude of fundamental modes, e.g., lattice vibrations, molecular rotations, spin precession and the motion of free electrons. Thereby it can be a handle to control highly relevant transient material properties, from metal-insulator-transitions [2] to superconductivity [3] and catalytic activity [4]. The obvious way of probing these THz-driven dynamics is tr-ARPES which enables direct access to the surface electronic states on a femtosecond timescale, thereby complementing current purely optical techniques. However, the implementation of THz pump – tr-ARPES probe experiments (cf. Fig. 1) has been impeded, because of the unmet requirement for high duty cycle THz sources (>> 10 kHz repetition rate quasi-cw) to provide sufficient statistics for tr-ARPES.
This limitation is overcome at TELBE which offers tunable and CEP-stable THz pulses at a repetition rate of 100 kHz based on superradiant emission, and timing stability of < 30 fs due to a novel pulse-to-pulse diagnostics scheme [5]. Over the next three years, a tr-ARPES setup shall hence be implemented at the THz facility TELBE which aims at establishing feasibility and dynamic range despite obvious obstacles such as residual streaking of the photoelectrons by the high THz excitation fields.
This contribution discusses the challenges and the opportunities of tr-ARPES in first THz control experiments and will outline the current design of the planned tr-ARPES endstation.

[1] B. Green et al., Sci. Rep. 6, 22256 (2016).
[2]T. Kampfrath et al., Nature Photonics 7, 680-690 (2013)
[3]D. Nicoletti and A. Cavalleri, Adv. Opt. Photon. 8, 401 (2016).
[4]L. A. Pellouchoud and E. J. Reed, Phys. Rev. A 91, 052706 (2015).
[5]S. Kovalev et al., Struct. Dyn. (2017) (under review).
  • Poster
    Ultrafast Surface Dynamics 10, 11.-16.06.2017, Inzell, Deutschland

Publ.-Id: 25683 - Permalink


Hyperdoping silicon with tellurium by ion implantation and ultra-short annealing for optoelectronics
Wang, M.; Liu, F.; Yuan, Y.; Prucnal, S.; Berencén, Y.; Rebohle, L.; Skorupa, W.; Helm, M.; Zhou, S.;
Hyperdoping silicon with chalcogen atoms is a topic of increasing interest due to the strong sub-band gap absorption exhibited by the resulting materials, which can be exploited to develop infrared photodectectors and intermediate band solar cells [1-3]. In our work, tellurium-hyperdoped silicon layers have been fabricated by ion implantation followed by flash lamp annealing (FLA) or pulsed-laser melting (PLM). The Rutherford backscattering spectrometry / Channeling (RBS/C) results reveal the high-quality recrystallization of tellurium implanted silicon by both FLA and PLM. From the transport measurements, an insulator-to-metal transition is observed with increasing tellurium concentration. Moreover, the ellipsometry measurements show that the band gap narrows with increasing doping concentration. And the Fourier transform infrared (FTIR) spectroscopy show that tellurium hyperdoped Si has strong infrared absorption. All these results give us a signal that hyperdoped silicon with tellurium could enable silicon-based optoelectronics in the infrared band.

[1] Kim, T. G., et al., Appl. Phys. Lett. 88, 241902 (2006)
[2] Tabbal, M., et al., Appl. Phys. A 98, 589–594 (2010)
[3] Umezu, I., et al., J. Appl. Phys. 113, 213501 (2013)
Keywords: Hyperdoping silicon, infrared absorption, ion implantation
  • Lecture (Conference)
    DPG-Frühjahrstagung (DPG Spring Meeting), 19.-24.03.2017, Dresden, Germany, Germany

Publ.-Id: 25682 - Permalink


Bentonite - geotechnical barrier and source for microbial life
Matschiavelli, N.; Steglich, J.; Kluge, S.; Cherkouk, A.;
The safe storage of high-level radioactive waste is a challenging task for our society. For a deep geological deposition of the waste, a multi-barrier concept is favoured, which combines a technical barrier (canister), a geotechnical barrier (e.g. Bentonite) and the geological barrier (host rock). Due to their properties, namely a high swelling capacity and a low hydraulic conductivity, Bentonites fulfil in this system a sealing and buffering function. Depending on the mineral composition, Bentonites contain many suitable electron-donors and -acceptors, enabling potential microbial life. For the potential repository of nuclear waste, the microbial mediated transformation of Bentonite could influence its properties as a barrier material. To elucidate the microbial potential within selected Bentonites, microcosms were set up containing 20g of Bentonite and 40ml anaerobic synthetic Opalinus-clay-pore water solution under an N2/CO2-gas-atmosphere. Substrates like acetate, lactate and H2 were supplemented to stimulate microbial activity. Microcosms were incubated in the dark, without shaking at 30°C and 60°C. Within a year, samples were taken at six different time-points and were analysed regarding geochemical parameters like pH, O2-concentration, redox potential, iron-concentration and sulphate-concentration as well as biological parameters like the consumption and formation of metabolites. Our results show that indigenous microbes from Bentonite are active and could therefore facilitate diverse transformations within the respective Bentonite.
Keywords: Bentonite, anaerobic metabolism, storage of high-level radioactive waste
  • Lecture (Conference)
    Goldschmidt 2017, 13.-17.08.2017, Paris, Frankreich

Publ.-Id: 25681 - Permalink


Bentonite – geotechnical barrier and source for microbial life
Matschiavelli, N.; Kluge, S.; Cherkouk, A.;
Due to their properties, namely a high swelling capacity and a low hydraulic conductivity, bentonites fulfil as geotechnical barrier a sealing and buffering function in a high-level waste repository. Depending on the mineral composition, bentonites contain many suitable electron-donors and –acceptors, enabling potential microbial life. For the potential repository of highly radioactive waste, the microbial mediated transformation of bentonite could influence its properties as a barrier material. Microcosms were set up containing bentonite and anaerobic synthetic Opalinus-clay pore water solution under an N2/CO2 gas atmosphere to elucidate the microbial potential within selected bentonites. Substrates like acetate, lactate and hydrogen were supplemented as electron donors to stimulate potential microbial activity. First results show that bentonites represent a source for microbial life, demonstrated by the consumption of lactate and the formation of pyruvate and hydrogen sulphide.
Keywords: bentonite, sulfate reduction, redox potential
  • Lecture (Conference)
    PETRUS-ANNETTE PhD Conference, 23.-30.06.2017, Lissabon, Portugal

Publ.-Id: 25680 - Permalink


Microbial processes in bentonite transformation
Steglich, J.; Matschiavelli, N.; Kluge, S.; Cherkouk, A.;
A safe and long-term storage of highly radioactive waste in deep geological layers should be achieved by a multi-barrier concept consisting of geological (host rock), geotechnical (e.g. bentonite) and technical barriers (canister including the highly radioactive waste). Suitable materials for a geotechnical barrier are the so-called bentonites. These clay minerals have due to their mineralogical composition a high swelling capacity and a low solvent permeability and can therefore fulfil in this system a sealing and buffering function.
Like in all natural materials, different microorganisms inhabit bentonites. These microorganisms can influence the conditions in a potential nuclear repository by microbial transformation of bentonite. To elucidate the microbial potential within a selected bentonite, microcosms were set up, which contain 20 g bentonite and 40 ml anaerobic synthetic Opalinus-clay-pore water solution under N2/CO2-gas-atmosphere. Substrates like acetate and lactate were added for the stimulation of the potential microbial activity and anthraquinone-2,6-disulfonate was added as an electron shuttle. Microcosms were incubated in the dark, without shaking at 30°C for 98 days. The samples were taken at different time points of incubation and were analysed regarding geochemical parameters like pH, O2-concentration, redox potential, iron concentration and sulphate concentration as well as biological parameters like the consumption and formation of metabolites.
The results confirm the presence of microbial life in the selected bentonite for example by consumption of lactate and the formation of acetate and pyruvate. Moreover, a fast microbial reduction of iron was detected. The results show the importance of the selection of suitable bentonites for a safe storage of highly radioactive waste in order to avoid the transformation of bentonite by microorganisms, which could cause the loss of its barrier function.
  • Poster
    GDCh-Wissenschaftsforum Chemie 2017 Interdisziplinäre Symposien Jahrestagung Nuklearchemie, 10.-14.09.2017, Berlin, Deutschland

Publ.-Id: 25679 - Permalink


Properties and application perspectives of S-layer protein self-assembly
Raff, J.;
Nature develops different strategies to allow microorganisms to successfully interact with their environment, which encompasses diverse aspects such as nutrition, protection and communication. One strategy realized in case of bacteria and archaea is the formation of multilayered cell envelopes. The oldest known cell component of such multifunctional cell structures is the so-called surface layer (S-layer). S-layers are composed of proteins being able to self-assemble in highly regular layers forming oblique, square or hexagonal lattices on the surface of cells. These layers protect especially bacteria living in extreme habitats against diverse harmful environmental influences. In case of uranium mining waste pile isolates belonging to the genera Lysinibacillus and Bacillus it was proven that these S-layers act as scavenger for reactive oxygen species and as selective binding matrix for toxic elements and heavy metals. Based on these interesting natural functions and by combining S-layers with layer-by-layer techniques the development of various materials being interesting for an industrial application is possible. Thus, new metals selective filter materials, diverse nano-particular catalysts and sensor materials were successfully produced and tested for their applicability.
Keywords: S-layer, self-assembly, functional coating
  • Invited lecture (Conferences)
    18. Wörlitzer Workshop "Selbstorganisierende Schichtstrukturen, 19.-20.06.2017, Wörlitz, Deutschland

Publ.-Id: 25678 - Permalink


Quantum criticality in the coupled two-leg spin ladder Ba2CuTeO6
Glamazda, A.; Choi, Y. S.; Do, S.-H.; Lee, S.; Lemmens, P.; Ponomaryov, A. N.; Zvyagin, S. A.; Wosnitza, J.; Sari, D. P.; Watanabe, I.;
We report on zero-field muon spin rotation, electron-spin resonance, and polarized Raman scattering measurements of the coupled quantum spin ladder Ba2CuTeO6. Zero-field muon spin rotation and electron spin resonance probes disclose a successive crossover from a paramagnetic through a spin-liquid-like into a magnetically ordered state with decreasing temperature. More significantly, the two-magnon Raman response obeys a T -linear scaling relation in its peak energy, linewidth, and intensity. This critical scaling behavior presents an experimental signature of proximity to a quantum-critical point from an ordered side in Ba2CuTeO6.

Publ.-Id: 25676 - Permalink


Bose-Einstein condensation of triplons in the S = 1 tetramer antiferromagnet K2Ni2(MoO4)3: A compound close to a quantum critical point
Koteswararao, B.; Khuntia, P.; Kumar, R.; Mahajan, A. V.; Yogi, A.; Baenitz, M.; Skourski, Y.; Chou, F. C.;
The structure of K2Ni2(MoO4)3 consists of S = 1 tetramers formed by Ni2+ ions. The magnetic susceptibility χ(T ) and specific heat CP (T ) data on a single crystal show a broad maximum due to the low dimensionality of the system with short-range spin correlations. A sharp peak is seen in χ(T ) and CP (T ) at about 1.13 K, well below the broad maximum. This is an indication of magnetic long-range order, i.e., the absence of spin gap in the ground state. Interestingly, the application of a small magnetic field (H >0.1 T) induces magnetic behavior akin to the Bose-Einstein condensation (BEC) of triplon excitations observed in some spin-gap materials. Our results demonstrate that the temperature-field (T -H) phase boundary follows a power law (T − TN) ∝ H1/α with the exponent 1/α close to 2/3 , as predicted for the BEC scenario. The observation of BEC of triplon excitations in small H infers that K2Ni2(MoO4)3 is located in the proximity of a quantum critical point, which separates the magnetically ordered and spin-gap regions of the phase diagram.

Publ.-Id: 25675 - Permalink


Forced-ferromagnetic state in a Tm2Fe17H5 single crystal
Tereshina, E. A.; Kuz´Min, M. D.; Skourski, Y.; Doerr, M.; Iwasieczko, W.; Wosnitza, J.; Tereshina, I. S.;
We report the attainment of the ferromagnetic state in an interstitially modified heavy rareearth-iron intermetallic compound in an external magnetic field. The starting composition is E2Fe17, which is the RE–Fe binary richest in iron. We concentrate on the Tm–Fe compound, which is the most sensitive to magnetic field. The maximum possible amount of hydrogen (5 at.H/f.u.) is inserted into a Tm2Fe17 single crystal. We demonstrate that in a magnetic field of 57 T Tm2Fe17H5 reaches the ferromagnetic state with an enviably high polarization of 2.25 T.
Keywords: single crystal, hydride, forced-ferromagnetic state, rare-earth-iron intermetallic, compound

Publ.-Id: 25674 - Permalink


Narrow band tunable spintronic THz emission from ferrimagnetic nanofilms
Awari, N.; Kovalev, S.; Fowley, C.; Rode, K.; Lau, Y.-C.; Betto, D.; Thiyagarajah, N.; Green, B.; Yildrim, O.; Lindner, J.; Fassbender, J.ORC; Coey, M.; Deac, A.; Gensch, M.
we report on narrow band THz emission from ferrimagnetic Mn3-xGa nanofilms based. The emission originates from coherently excited spin precession. The central frequency of the emitted radiation is determined by the anisotropy field, while the bandwidth relates to Gilbert damping. It is shown how THz emission spectroscopy can be used for the material characterization of ultra-thin magnetic films. We furthermore discuss the potential of these types of films as efficient on-chip spintronic THz emitters.
Keywords: THz Emitter, Spintronics, Ferrimagnetic
  • Lecture (Conference)
    INTERMAG 2017, 24.-28.04.2017, Dublin, Ireland

Publ.-Id: 25673 - Permalink


OpenACC for Programmers - Concepts and Strategies
Chandrasekaran, S.ORC; Juckeland, G.ORC
Klappentext noch nicht vorhanden
  • Book (Editorship)
    New York, USA: Addison-Wesley Professional, 2017
    320 Seiten
    ISBN: 978-0134694283

Publ.-Id: 25672 - Permalink


Analyzing Offloading Inefficiencies in Scalable Heterogeneous Applications
Dietrich, R.ORC; Tschüter, R.; Juckeland, G.ORC; Knüpfer, A.
With the rise of accelerators in high performance computing, programming models for the development of heterogeneous applications have evolved and are continuously being improved to increase program performance and programmer productivity. The concept of computation offloading to massively parallel compute devices has established itself as a new layer of parallelism in scientific applications, next to message passing and multi-threading. To optimize the execution of a respective parallel heterogeneous program for a specific platform, performance analysis is crucial. This work abstracts from specific offloading APIs such as available with CUDA, OpenCL, OpenACC, and OpenMP and summarizes common inefficiencies for offloading. Based on the definition of inefficiency patterns, the offloading concept can be included in generic analysis techniques such as critical-path and root-cause analysis. We implemented the detection and evaluation of inefficiency patterns as a post-mortem trace analysis, which finally highlights program activities with a high potential to reduce the total program runtime.
Keywords: performance analysis computation offloading heterogeneous applications critical path
  • Contribution to proceedings
    2nd International Workshop on Performance Portable Programming Models for Accelerators (P^3MA), colocated with the ISC High Performance Conference in Frankfurt, Germany, 22.06.2017, Frankfurt/Main, Deutschland
    High Performance Computing. ISC High Performance 2017. Lecture Notes in Computer Science, vol 10524, Cham: Springer, 978-3-319-67630-2, 457-476
    DOI: 10.1007/978-3-319-67630-2_34

Publ.-Id: 25671 - Permalink


Narrow band tunable spintronic THz emission from ferrimagnetic nanofilms
Awari, N.ORC; Kovalev, S.; Fowley, C.; Rode, K.; Lau, Y.-C.; Betto, D.; Thiyagarajah, N.; Green, B.; Yildrim, O.; Lindner, J.; Fassbender, J.ORC; Coey, M.; Deac, A.; Gensch, M.
we report on narrow band THz emission from ferrimagnetic Mn3-xGa nanofilms based. The emission originates from coherently excited spin precession. The central frequency of the emitted radiation is determined by the anisotropy field, while the bandwidth relates to Gilbert damping. It is shown how THz emission can be used for the characterization dynamical properties of ultra-thin magnetic films. We furthermore discuss the potential of these types of films as efficient on-chip spintronic THz emitter.
Keywords: THz emission, Ferrimagnetic, Spin precession
  • Poster
    IRMMW 2016 - 41st International Conference on Infrared, Millimeter and Terahertz Waves, 26.-30.09.2016, Copenhagen, Denmark

Publ.-Id: 25670 - Permalink


Advanced Data Processing for Full-Field PIXE Imaging
Buchriegler, J.ORC; Klingner, N.ORC; Hanf, D.; Munnik, F.; Nowak, S. H.ORC; Scharf, O.; Ziegenrücker, R.; Renno, A. D.; von Borany, J.
The combination of a pnCCD-based detector with a poly-capillary X-ray optics was installed and examined at HZDR [1]. The set-up is intended for PIXE imaging with protons (2-4 MeV) to survey large, polished geological samples with respect to their trace elemental composition. The X-ray optics is used to guide the emitted photons towards the pnCCD-chip divided into nearly 70000 pixels with dimensions of 48 × 48 µm². By applying a dedicated sub-pixel algorithm to recalculate the footprint of the photon’s electron cloud in the chip [2], this limitation can be bypassed and the resolution is then mainly determined by the capillary’s diameter of 20 µm.
Nevertheless, all images gathered with this kind of set-up from are superimposed by patterns of the X-ray optics. The optics’ capillaries are grouped in hexagonal bundles during the fabrication process and these bundles are grouped together again. This process results in a reduced efficiency in the regions where the bundles are joined making the hexagonal pattern visible. This influence can be removed by the technique of multi-frame super-resolution combining several short measurements with slightly shifted positions. The optics pattern is averaged out and in addition the shifting allows further increase of the lateral resolution. The total measurement time can be kept similar by dividing the single measurement time by the number of “shots” without reducing the sampling size.
This approach of multi-frame super-resolution in combination with a sub-pixel correction algorithm will be illustrated and shown on experimental data. Additionally, a flat-field correction attempt is shown to remove general imaging inhomogeneity. Descriptive image-sets will be presented to demonstrate the potential of such techniques for full-field PIXE imaging [3].
[1] D. Hanf, J. Buchriegler, A. D. Renno, S. Merchel, F. Munnik, R. Ziegenrücker, O. Scharf, S. H. Nowak, J. von Borany, NIM B 377, pp. 17-24 (2016).
[2] S. H. Nowak, A. Bjeoumikhov, J. von Borany, J. Buchriegler, F. Munnik, M. Petric, A. D. Renno, M. Radtke, U. Reinholz, O. Scharf, L. Strüder, R. Wedell, R. Ziegenrücker, X-ray Spectrometry 44 (3), pp. 135-140 (2015).
[3] J. Buchriegler, N. Klingner, D. Hanf, F. Munnik, S. H. Nowak, O. Scharf, R. Ziegenrücker, A. D. Renno, J. von Borany, submitted to Journal of Analytical Atomic Spectrometry (2017)

This work has been supported by BMBF (INTRA r3 033R070) and by Marie Curie Actions - Initial Training Network (ITN) as an Integrating Activity Supporting Postgraduate Research with Internships in Industry and Training Excellence (SPRITE) under EC contract no. 317169.
  • Poster
    23rd International Conference on Ion Beam Analysis IBA-2017, 08.-13.10.2017, Shanghai, China

Publ.-Id: 25669 - Permalink


Backscattering Spectrometry with Ultimate Lateral Resolution: keV Nanoprobes vs. MeV Microprobes
Klingner, N.ORC; Heller, R.; Hlawacek, G.; Munnik, F.; Facsko, S.
Rutherford Backscattering Spectrometry with a MeV nuclear microprobe is a versatile tool for compositional and structural analysis in material science, micro-electronics and geology. The continuous shrinking of object dimensions lead to an enhanced demand on spatial resolution and surface sensitivity of modern analysis techniques.
Microprobe setups have been optimized for small beam spots below 1 µm, large solid angles and good energy resolution [1]. However, their performance is limited by the ion source’s brightness and the corresponding beam spot size, sample damage, as well as by the interaction volume of the incident ions.
Recently, we implemented Time-of-Flight Backscattering Spectrometry into a Helium Ion Microscope [2, 3]. The enormous brightness of its Gas Field Ionization Source and the sharp primary ion energy of 30 keV enable an ion beam focus below 1 nm. Due to this very small probe size the achievable lateral resolution for bulk samples is limited by sample damage and the size of the collision cascade.
Different binary collision codes were utilized to simulate the ion-solid interaction for various beam and sample parameters. The origin of backscattered particles, surface sputtering and the intermixing behavior has been studied.
In this contribution we will discuss which primary ion energy, ion species and setup can reach ultimate lateral resolution in Backscattering Spectrometry. Besides simulation results and considerations about advantages and disadvantages we will show practical examples of both - classical MeV nuclear microprobes and focused ion beam keV nanoprobes.

[1] N.Klingner, J.Vogt, D.Spemann, NIMB 306, 44 (2013).
[2] N.Klingner, R.Heller, G.Hlawacek, J.vonBorany, J.Notte, J.Huang, S.Facsko, Ultramicroscopy 162, 91 (2016).
[3] R.Heller, N.Klingner, G.Hlawacek. Helium Ion Microscopy, Chapter 12, Springer International Publishing 2016, ISBN 978-3-319-41988-6
  • Poster
    23rd International Conference on Ion Beam Analysis IBA-2017, 08.-13.10.2017, Shanghai, China

Publ.-Id: 25668 - Permalink


SIMS using gas field ion sources to approach ultimate spatial resolution
Klingner, N.ORC; Heller, R.; Hlawacek, G.; Facsko, S.
Continuously shrinking object dimensions lead to an enhanced demand on spatial resolution and surface sensitivity of modern analysis techniques. Secondary Ion Mass Spectrometry (SIMS), as one of the most powerful technique for surface analysis, performed on nanometer scale may comply with this challenge. The mass of sputtered ions directly serves elemental and molecular information and even allows measuring isotope concentrations.

During last decades, primary ion species used in SIMS have optimized in terms of best ionization probabilities and small molecule fragmentation. Thereby, highest mass-resolution has been one of the biggest design goals in the development of new SIMS spectrometers. In contrast to former developments, our approach aims for ultimate spatial resolution.

Typically the lateral resolution is limited by the probe size of the primary ion beam. Minimal probe sizes below 1 nm can be achieved using Gas Field Ionization Sources (GFIS) in a Helium Ion Microscope (HIM). Recently, SIMS has been achieved by implementing Time-of-Flight (TOF) spectrometry to the HIM [1, 2] as well by adding of a sophisticated magnetic sector field analyzer [3]. In this way SIMS could be performed with unprecedented spot sizes.

We will discuss constrains, limits, benefits and drawbacks of the approach. The technical realization will be shown as well as first results and derived conclusions for the practical use of this promising technique.
  • Lecture (Conference)
    22nd International Workshop on Inelastic Ion-Surface Collisions IISC22, 17.-22.09.2017, Dresden, Deutschland

Publ.-Id: 25667 - Permalink


Individualized risk assessment in neuroblastoma: Prediction of outcome based on metabolic activity in I-123-MIBG-SPECT
Rogasch, J.; Schatka, I.; Hundsdoerfer, P.; Furth, C.; Wedel, F.; Steffen, I.; Hofheinz, F.; Brenner, W.; Eggert, A.; Amthauer, H.;
Objectives: Risk-adapted treatment in children with neuroblastoma (NB) follows clinical and genetic factors. This study evaluated the metabolic tumor volume (MTV) and its asphericity (ASP) in pre-therapeutic I-123-MIBG-SPECT (IMS) for individualized image-based prediction of outcome.

Methods: Retrospective analysis of 22 consecutive children with newly diagnosed NB (f:10; m:12; median age, 1.7 [0.3-6.8] years) undergoing pretherapeutic IMS. MTV and asphericity as the relative deviation of the MTV surface from an isovolumetric sphere were defined for each primary tumor using semi-automatic, background-adapted thresholds. Cox regression, ROC analysis (cut-off determination) and Kaplan-Meier analyses with log-rank test were performed regarding event-free survival (EFS) and overall survival (OS). Analyzed parameters included ASP, MTV, laboratory parameters (such as urinary homovanillic acid-to-creatinine ratio [HVA/C] or serum lactate dehydrogenase [LDH]), age, tumor stage and genetic factors. The predictive accuracy of the optimal multifactorial models was determined by Harrell’s C and the χ2.



Results: Median follow-up was 37 [6-102] months (disease progression / relapse, n=8; death, n=4). Only ASP (p=0.034; hazard ratio [HR], 1.03 for one-unit increase) and MTV (p=0.031; HR, 1.012) were significant predictors of EFS in univariate Cox, only ASP was predictive in multivariate analysis (p=0.024; HR, 1.041). Mean EFS for high (>31.6%) vs. low ASP was 20 vs. 82 months (p=0.022), EFS for high (>46.7 ml) vs. low MTV was 18 vs. 83 months (p=0.008). A combined risk model of high ASP and high HVA/C predicted EFS with the highest accuracy. In Kaplan-Meier analysis, shorter OS was predicted by high ASP (p=0.003), MTV (p<0.001; cut-off, >82.5 ml), HVA/C (>215 µmol/g; p=0.021), LDH (p<0.001) and MYCN amplification (p=0.001). A combination of high MTV and high HVA/C predicted OS with the highest accuracy.

Conclusion: In this explorative study, pre-therapeutic markers of tumor metabolic activity in neuroblastoma (ASP, MTV, urinary HVA-to-creatinine ratio) allowed to separate children with high and low risk for progression / relapse or shorter OS under current therapy regimens. Research Support: No external funding. Figure:Kaplan-Meier curves with log-rank test are displayed for patients with 0, 1 or 2 risk factors according to the predictive model regarding EFS (ASP, HVA/C) or OS (MTV, HVA/C), respectively. Log-rank test was performed for the overall model.
  • Contribution to proceedings
    SNMMI 2017 Annual Meeting, 11.06.2017, Denver, USA
    Journal of Nuclear Medicine 58(2017)

Publ.-Id: 25666 - Permalink


Relativistic Electron Streaming Instabilities Modulate Proton Beams Accelerated in Laser-Plasma Interactions
Göde, S.; Rödel, C.; Zeil, K.; Mishra, R.; Gauthier, M.; Brack, F.-E.; Kluge, T.; Macdonald, M. J.; Metzkes, J.; Obst, L.ORC; Rehwald, M.; Ruyer, C.; Schlenvoigt, H.-P.; Schumaker, W.; Sommer, P.; Cowan, T. E.; Schramm, U.; Glenzer, S.; Fiuza, F.
We report experimental evidence that multi-MeV protons accelerated in relativistic laser-plasma interactions are modulated by strong filamentary electromagnetic fields. Modulations are observed when a preplasma is developed on the rear side of a μm-scale solid-density hydrogen target. Under such conditions, electromagnetic fields are amplified by the relativistic electron Weibel instability and are maximized at the critical density region of the target. The analysis of the spatial profile of the protons indicates the generation of B>10  MG and E>0.1  MV/μm fields with a μm-scale wavelength. These results are in good agreement with three-dimensional particle-in-cell simulations and analytical estimates, which further confirm that this process is dominant for different target materials provided that a preplasma is formed on the rear side with scale length ≳0.13λ0√a0. These findings impose important constraints on the preplasma levels required for high-quality proton acceleration for multipurpose applications.

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Publ.-Id: 25665 - Permalink


Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets
Obst, L.ORC; Göde, S.; Rehwald, M.; Brack, F.-E.; Branco, J.; Bock, S.; Bussmann, M.; Cowan, T.; Curry, C.; Fiuza, F.; Gauthier, M.; Gebhardt, R.; Helbig, U.; Huebl, A.; Hübner, U.; Irman, A.; Kazak, L.; Kim, J.; Kluge, T.; Kraft, S.; Loeser, M.; Metzkes, J.; Mishra, R.; Roedel, C.; Schlenvoigt, H.-P.; Siebold, M.; Tiggesbäumker, J.; Wolter, S.; Ziegler, T.; Schramm, U.; Glenzer, S.; Zeil, K.
We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (diameter 5 μm) and planar (20 μm × 2 μm). In both cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. This is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions.
Keywords: Laser-produced plasmas, Plasma-based accelerators
  • Open Access LogoScientific Reports 7(2017), 10248
    DOI: 10.1038/s41598-017-10589-3
  • Lecture (Conference)
    European Physical Society Conference on Plasma Physics, 26.-30.6.2017, Belfast, United Kingdom
  • Lecture (Conference)
    3rd European Advanced Accelerator Concepts Workshop, 25.-29.9.2017, La Biodola, Isola d'Elba, Italien
  • Lecture (Conference)
    DPG Beschleunigerphysik Tagung, 19.03.2018, Würzburg, Deutschland

Publ.-Id: 25664 - Permalink


Potential proton and photon dose degradation in advanced head and neck cancer patients by intra-therapy changes
Stützer, K.; Jakobi, A.; Bandurska-Luque, A.; Barczyk, S.; Arnsmeyer, C.; Löck, S.; Richter, C.;
Purpose: Evaluation of dose degradation by anatomic changes for head-and-neck cancer (HNC) intensity-modulated proton therapy (IMPT) relative to intensity-modulated photon therapy (IMRT) and identification of potential indicators for IMPT treatment plan adaptation.

Methods: For 31 advanced HNC datasets, IMPT and IMRT plans were recalculated on a computed tomography scan (CT) taken after about four weeks of therapy. Dose parameter changes were determined for the organs at risk (OARs) spinal cord, brain stem, parotid glands, brachial plexus and mandible, for the clinical target volume (CTV) and the healthy tissue outside planning target volume (PTV). Correlation of dose degradation with target volume changes and quality of rigid CT matching was investigated.

Results: Recalculated IMPT dose distributions showed stronger degradation than the IMRT doses. OAR analysis revealed significant changes in parotid median dose (IMPT) and near maximum dose (D1ml) of spinal cord (IMPT, IMRT) and mandible (IMPT). OAR dose parameters remained lower in IMPT cases. CTV coverage (V95%) and overdose (V107%) deteriorated for IMPT plans to (93.4±5.4)% and (10.6±12.5)%, while those for IMRT plans remained acceptable. Recalculated plans showed similarly decreased PTV conformity, but considerable hotspots, also outside the PTV, emerged in IMPT cases. Lower CT matching quality was significantly correlated with loss of PTV conformity (IMPT, IMRT), CTV homogeneity and coverage (IMPT). Target shrinkage correlated with increased dose in brachial plexus (IMRT, IMPT), hotspot generation outside the PTV (IMPT) and lower PTV conformity (IMRT).

Conclusions: The study underlines the necessity of precise positioning and monitoring of anatomy changes, especially in IMPT which might require adaptation more often. Since OAR doses remained typically below constraints, IMPT plan adaptation might be indicated by target dose degradations.
Keywords: IMPT; IMRT; Interfractional changes; Head-and-neck cancer; Setup error; Dose degradation

Publ.-Id: 25663 - Permalink


Optimization of liquid metal flow pattern generated by rotating magnetic field and the effect on solidification structure of wrought aluminium alloys
Räbiger, D.; Willers, B.; Eckert, S.; Rosefort, M.; Dang, T.; Koch, H.;
AC magnetic fields provide a contactless method to control the flow inside a liquid metal. Many studies have shown that beneficial effects like a distinct grain refinement or the promotion of a transition from a columnar to an equiaxed dendritic growth (CET) can be obtained. However, melt convection may also produce segregation freckles on the macroscale. The achievement of superior casting structures needs a well-aimed control of melt convection during solidification. Previous investigations considered the use of time-modulated AC magnetic fields to control the heat and mass transfer at the solidification front. It has been shown that an accurate tuning of the magnetic field parameters can avoid segregation effects. The present study examines the directional solidification of wrought aluminium alloys from a water-cooled copper chill. Rotating magnetic fields were used to agitate the melt.
  • Lecture (Conference)
    XVIII International UIE-Congress on Electrotechnologies for Material Processing, 06.-09.06.2017, Hannover, Deutschland
  • Contribution to proceedings
    XVIII International UIE-Congress on Electrotechnologies for Material Processing, 06.-09.06.2017, Hannover, Deutschland
    XVIII International UIE-Congress Electrotechnologies for Material Processing: Vulkan-Verlag GmbH, 978-3-8027-3095-5, 255-260

Publ.-Id: 25662 - Permalink


Impact of forced flow on the solidification structure of wrought aluminium alloys by means of AC magnetic
Räbiger, D.; Willers, B.; Eckert, S.; Rosefort, M.; Dang, T.; Koch, H.;
AC magnetic fields provide a contactless method to control the flow inside a liquid metal and the grain size of the solidified ingot. Many studies have shown that beneficial effects like a distinct grain refinement or the promotion of a transition from a columnar to an equiaxed dendritic growth (CET) can be obtained. However, electromagnetically-driven melt convection may also produce segregation freckles on the macroscale. The achievement of superior casting structures needs a well-aimed control of melt convection during solidification. Previous investigations considered the use of time-modulated AC magnetic fields to control the heat and mass transfer at the solidification front. It has been shown recently under laboratory conditions, that an accurate tuning of the magnetic field parameters can avoid segregation effects and homogenize the mechanical properties. The present study examines the directional solidification of commercial wrought aluminium alloys from a water-cooled copper chill. Rotating magnetic fields were used to agitate the melt.
Our results demonstrate the potential of magnetic fields to control the grain size, the formation of segregation freckle and the morphology and distribution of pores, especially for use time modulated rotating fields.
Keywords: wrought aluminium alloys, grain size control, time modulated magnetic field
  • Lecture (Conference)
    6th Decennial International Conference on Solidification Processing, 25.-28.07.2017, Beaumont Estate, Old Windsor, UK
  • Contribution to proceedings
    6th Decennial International Conference on Solidification Processing, 25.-28.07.2017, Beaumont Estate, Old Windsor, UK
    SP17 - Solidification Processing 2017: Brunel University London, 978 1 908549 29 7, 638-641

Publ.-Id: 25661 - Permalink


Bulk production and evaluation of high specific activity 186gRe for cancer therapy using enriched 186WO3 targets in a proton beam
Mastren, T.; Radchenko, V.; Bach, H.; Balkin, E.; Birnbaum, E.; Brugh, M.; Engle, J.; Gott, M.; Guthrie, J.; Hennkens, H.; John, K.; Ketring, A.; Kuchuk, M.; Maassen, J.; Naranjo, C.; Nortier, M.; Phelps, T.; Jurisson, S.; Wilbur, S.; Fassbender, M.;
Introduction

Rhenium-186g (t1/2 = 3.72 d) is a β− emitting isotope suitable for theranostic applications. Current production methods rely on reactor production by way of the reaction 185Re(n,γ)186gRe, which results in low specific activities limiting its use for cancer therapy. Production via charged particle activation of enriched 186W results in a 186gRe product with a higher specific activity, allowing it to be used more broadly for targeted radiotherapy applications. This targets the unmet clinical need for more efficient radiotherapeutics.

Methods

A target consisting of highly enriched, pressed 186WO3 was irradiated with protons at the Los Alamos National Laboratory Isotope Production Facility (LANL-IPF) to evaluate 186gRe product yield and quality. LANL-IPF was operated in a dedicated nominal 40 MeV mode. Alkaline dissolution followed by anion exchange chromatography was used to isolate 186gRe from the target material. Phantom and radiolabeling studies were conducted with the produced 186gRe activity.

Results

A 186gRe batch yield of 1.38 ± 0.09 MBq/μAh or 384.9 ± 27.3 MBq/C was obtained after 16.5 h in a 205 μA average/230μA maximum current proton beam. The chemical recovery yield was 93% and radiolabeling was achieved with efficiencies ranging from 60–80%. True specific activity of 186gRe at EOB was determined via ICP-AES and amounted to 0.788 ± 0.089 GBq/μg (0.146 ± 0.017 GBq/nmol), which is approximately seven times higher than the product obtained from neutron capture in a reactor. Phantom studies show similar imaging quality to the gold standard 99mTc.

Conclusions

We report a preliminary study of the large-scale production and novel anion exchange based chemical recovery of high specific activity 186gRe from enriched 186WO3 targets in a high-intensity proton beam with exceptional chemical recovery and radiochemical purity.
Keywords: Theranostic; 186gRe; 186WO3 target; High specific activity; Radiolabeling; SPECT phantom images

Publ.-Id: 25659 - Permalink


Application of Photothermal Expansion for Optical Absorption Mapping at the Nanoscale
Madeira, T. I.; Rodriguez, R. D.; Ravikumar, Y.; Shah, H.; Bortchagovsky, E.; Zahn, D. R. T.;
In this work we demonstrate that photothermal expansion can be used to obtain images of nanostructured semiconductor materials such as GaSe flakes on graphite and carbon nanotubes on SiO2 in ambient conditions with high sensitivity and spatial resolution. The principle behind is the detection of the mechanical force exerted on an atomic force microscopy (AFM) tip by the thermal expansion of the materials excited with pulses of optical radiation, taking advantage of the different absorption properties between substrate and sample. Characterization of semiconductor nanostructures, with a bandgap in the optical range enables the use of cw lasers chopped and synchronized with the resonance frequency of custom-made fully metallic cantilever AFM Au tips. The spatial resolution achieved by the synchronization procedure described is indeed in the nanometer range below 60 nm, and by taking advantage of the difference between optical absorption and thermal coefficients material contrast can be achieved.
Keywords: photothermal expansion, AFM, TERS, semiconductor nanostructures
  • Invited lecture (Conferences)
    Seminar at the Academy of Sciences in Prague - Department of Thin Films and Nanostructures, 27.05.2016, Prague, Czech Republic

Publ.-Id: 25658 - Permalink


Breaking the Electrical Barrier between Copper and Carbon Nanotubes
Milowska, K. Z.; Ghorbani-Asl, M.ORC; Burda, M.; Wolanicka, L.; Catic, N.; Bristowe, P. D.; Kozioł, K. K. K.
Improving the interface between copper and carbon nanotubes (CNTs) offers a straightforward strategy for the effective manufacturing and utilisation of Cu-CNT composite material that could be used in various industries including microelectronics, aerospace and transportation. Motivated by a combination of structural and electrical measurements on Cu-M-CNT bimetal systems (M = Ni, Cr) we show, using first principles calculations, that the conductance of this composite can exceed that of a pure Cu-CNT system and that the current density can even reach 10 11 A/cm2 . The results show that the proper choice of alloying element (M) and type of contact facilitate the fabrication of ultra-conductive Cu-M-CNT systems by creating a favourable interface geometry, increasing the interface electronic density of states and reducing the contact resistance. In particular, a small concentration of Ni between the Cu matrix and the CNT using either an "end contact" and or a "dot contact" can significantly improve the electrical performance of the composite. Furthermore the predicted conductance of Ni-doped Cu-CNT "carpets" exceeds that of an undoped system by ∼200%. Cr is shown to improve CNT integration and composite conductance over a wide temperature range while Al, at low voltages, can enhance the conductance beyond that of Cr.
Keywords: carbon nanotubes, copper, composite, electrical properties

Publ.-Id: 25657 - Permalink


Froth flotation of scheelite - a review
Kupka, N.; Rudolph, M.;
Froth flotation of scheelite has regained new focus since the 2010s and research regarding floatability and reagents has made great progress over the years. The main objective was and remains the selective flotation of scheelite from other calcium-bearing minerals, in particular calcite, fluorite and apatite. Due to similar properties, most attempts have limited success or only specific application (linked to a type of ore or a location). This article aims at reviewing all general physical-chemical information on froth flotation of scheelite, including electrokinetic properties, influence of pH and already existing reagents as well as ones still under examination. It appears that chelating or mixed collectors and modified versions of sodium silicate and quebracho hold great promise for scheelite flotation, while the use of said depressants and/or promoters seems inevitable.
Keywords: scheelite; froth flotation; calcium-bearing minerals

Publ.-Id: 25656 - Permalink


Holographic Entanglement Entropy in the QCD Phase Diagram with a Critical Point
Knaute, J.; Kämpfer, B.;
We calculate the holographic entanglement entropy for the holographic QCD phase diagram in [Knaute, Yaresko, Kämpfer (2017), arXiv:1702.06731] and explore the resulting qualitative behavior over the temperature-chemical potential plane. In agreement with the thermodynamic result, the phase diagram exhibits the same critical point as the starting point of a first-order phase transition curve. We compare the phase diagram of the entanglement entropy to that of the thermodynamic entropy density and find a striking agreement in the vicinity of the critical point. Thus, the holographic entanglement entropy qualifies to characterize different phase structures. The scaling behavior near the critical point is analyzed through the calculation of critical exponents.

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Publ.-Id: 25655 - Permalink


A Bayesian Approach for Measurements of Stray Neutrons at Proton Therapy Facilities: Quantifying Neutron Dose Uncertainty
Dommert, M.; Reginatto, M.; Zboril, M.; Fiedler, F.; Helmbrecht, S.; Enghardt, W.; Lutz, B.;
The analysis of Bonner sphere measurements is typically done using unfolding codes. However, it is very difficult to implement reliable uncertainty propagation in standard unfolding procedures. An alternative approach, which does provide reliable estimates of the uncertainties of neutron spectra leading to rigorous estimates of uncertainties of the dose, is to analyze the data using Bayesian parameter estimation. In this work, we extend previous approaches and apply this method to secondary neutrons from radiation therapy proton beams. This requires introducing a parameterized model which can describe the main features of the neutron spectra. We choose the parameterization based on information that is available from measurements and detailed Monte Carlo simulations. To demonstrate the validity of this approach, we consider the results of an experiment carried out at the experimental hall at the OncoRay proton therapy facility in Dresden.
Keywords: Neutron measurement, proton therapy

Publ.-Id: 25654 - Permalink


Efficient Parallel Monte-Carlo Simulations for Large-Scale Studies of Surface Growth Processes
Kelling, J.;
Lattice Monte Carlo methods are used to investigate far from and out-of-equilibrium systems, including surface growth, spin systems and solid mixtures. Such studies require observations of large systems over long times scales, to allow structures to grow over orders of magnitude, which necessitates massively parallel simulations. This talk presents work done to address the problem of parallel processing introducing correlations in Monte Carlo updates. Studies of the effect of correlations on scaling and dynamical properties of surface growth systems and related lattice gases is investigated further by comparing results obtained by correlation-free and intrinsically correlated but highly efficient simulations using a stochastic cellular automaton. The primary subject of study is the Kardar-Parisi-Zhang surface growth in (2+1) dimensions. Key physical insights about this universality class, like precise universal exponent values and exponent relations, obtained from large-scale simulations are presented.
Keywords: Lattice Monte Carlo, GPU, Surface Growth, Kardar-Parisi-Zhang
  • Lecture (others)
    Seminar Topical Problems, 14.06.2017, Chemnitz, Deutschland

Publ.-Id: 25653 - Permalink


Magnesium photocathodes in the SRF photo-injector at HZDR
Teichert, J.; Arnold, A.; Lu, P.; Murcek, P.; Vennekate, H.; Xiang, R.;
Magnesium photocathodes in the SRF photo-injector at HZDR
Keywords: Magnesium photocathode, SRF photoinjector
  • Poster
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Germany

Publ.-Id: 25652 - Permalink


Improvements of the photoemission efficiency of magnesium photocathodes
Xiang, R.; Arnold, A.; Michel, P.; Murcek, P.; Teichert, J.; Lu, P.; Vennekate, H.; Patra, P.;
To improve the quality of photocathodes is one of the critical issues in enhancing the stability and reliability of photo-injector systems. Presently the primary choice is to use metallic photocathodes for the ELBE SRF Gun II to reduce the risk of contamination of the superconducting cavity. Magnesium has a low work function (3.6 eV) and shows high quantum efficiency (QE) up to 0.3 % after laser cleaning. The SRF Gun II with an Mg photocathode has successfully provided electron beam for ELBE users. However, the present cleaning process with a high intensi-ty laser (activation) is time consuming and generates unwanted surface roughness. This paper presents the investigation of alternative surface cleaning procedures, such as thermal treatment. The QE and topography of Mg samples after treatment are reported.
Keywords: magnesium photocathodes, quantum efficiency, SRF photoinjector
  • Open Access LogoContribution to proceedings
    The 8th International Particle Accelerator Conference (IPAC’17), 14.-19.05.2017, Copenhagen, Danmark
    Proceedings of IPAC'17
  • Poster
    The 8th International Particle Accelerator Conference (IPAC’17), 14.-19.05.2017, Copenhagen, Denmark

Publ.-Id: 25651 - Permalink


Tailoring Optical Properties of Atomically-Thin WS2 via Ion Irradiation
Tan, L. N.; Tan, Y.; Ghorbani-Asl, M.ORC; Boettger, R.; Kretschmer, S.; Zhou, S. Q.; Huang, Z. Y.; Krasheninnikov, A. V.ORC; Chen, F.
Two-dimensional transition metal dichalcogenides (TMDCs) exhibit excellent optoelectronic properties. However, the large band gaps in many semiconducting TMDCs make optical absorption in the near-infrared (NIR) wavelength regime impossible, which prevents applications of these materials in optical communications. In this work, we demonstrate that Ar+ ion irradiation is a powerful post-synthesis technique to tailor the optical properties of the semiconducting tungsten disulfide (WS2) by creating S vacancies and thus controlling material stoichiometry. First-principles calculations reveal that the S-vacancies give rise to deep states in the band gap, which determine the NIR optical absorption of the WS2 monolayer. As the density of the S-vacancies increases, the enhanced NIR linear and saturable absorption of WS2 is observed, which is explained by the results of first-principles calculations. We further demonstrate that by using the irradiated WS2 as a saturable absorber in a waveguide system, the passively Q-switched laser operations can be optimized, opening thus new avenues for tailoring the optical response of TMDCs by defect-engineering through ion irradiation.
Keywords: Ion irradiation, WS2, optical properties

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Publ.-Id: 25650 - Permalink


Laser-Ablation-Based Ion Source Characterization and Manipulation for Laser-Driven Ion Acceleration
Sommer, P.; Metzkes, J.; Brack, F.-E.; Cowan, T. E.; Kraft, S. D.; Obst, L.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.;
For laser-driven ion acceleration from thin foils (~10 µm- 100 nm) in the target normal sheath acceleration (TNSA) regime, the hydro-carbon contaminant layer at the target surface generally serves as the ion source and hence determines the accelerated ion species, i.e. mainly protons, carbon and oxygen ions. The specific characteristics of the source layer - thickness and relevant lateral extent - as well as its manipulation have both been investigated since the first experiments on laser-driven ion acceleration using a variety of techniques from direct source imaging to knife-edge or mesh imaging.
In this publication, we present an experimental study in which laser ablation in two fluence regimes (low: F~0.6 J/cm², high: F~4 J/cm²) was applied to characterize and manipulate the hydro-carbon source layer. The high-fluence ablation in combination with a timed laser pulse for particle acceleration allowed for an estimation of the relevant source layer thickness for proton acceleration. Moreover, from these data and independently from the low-fluence regime, the lateral extent of the ion source layer became accessible.

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Publ.-Id: 25649 - Permalink


Enhancements in full-field PIXE imaging - large area elemental mapping with increased lateral resolution devoid of optics artefacts
Buchriegler, J.ORC; Klingner, N.ORC; Hanf, D.; Munnik, F.; Nowak, S. H.ORC; Scharf, O.; Ziegenrücker, R.; Renno, A. D.; von Borany, J.
The combination of a pnCCD-based pixel detector with a poly-capillary X-ray optics was installed and examined at the Helmholtz-Zentrum Dresden-Rossendorf. The set-up is intended for Particle Induced X-ray Emission imaging to survey the trace elemental composition of flat/polished geological samples. In the standard configuration a straight X-ray optics (20 µm capillary diameter) is used to guide the emitted photons from the sample towards the detector with nearly 70000 pixels. Their dimensions of 48×48 µm2 are the main limitation of the lateral resolution. This limitation can be bypassed by applying a dedicated sub-pixel algorithm to recalculate the footprint of the photon’s electron cloud in the detector. The lateral resolution is then mainly determined by the capillary’s diameter. Nevertheless, images are still superimposed by the X-ray optics pattern. The optics’ capillaries are grouped in hexagonal bundles resulting in a reduced transmission of X-rays in the boundary regions. This influence can be largely suppressed by combining a series of short measurements at slightly shifted positions using a precision stage and correcting the image-data for this shifting. The use of a sub-pixel grid for the image reconstruction allows a further increase of the spatial resolution. This approach of multi-frame super-resolution in combination with the sub-pixel correction algorithm is presented and illustrated with experimental data. Additionally, a flat-field correction is shown to remove the remaining imaging inhomogeneity caused by non-uniform X-ray transmission. The described techniques can be used for all X-ray spectrometry methods using an X-ray camera to obtain high quality elemental images.
Keywords: Color X-ray camera, full-field imaging, image stacking, multi-frame super-resolution, flat-field correction

Publ.-Id: 25648 - Permalink


Road to micron resolution with a color X-ray camera – polycapillary optics characterization
Nowak, S. H.ORC; Petric, M.; Buchriegler, J.ORC; Bjeoumikhov, A.; Bjeoumikhov, Z.; von Borany, J.; Munnik, F.; Radtke, M.; Renno, A. D.; Reinholz, U.; Scharf, O.; Tilgner, J.; Wedell, R.
In a color X-ray camera spatial resolution is achieved by means of a polycapillary optic conducting X-ray photons from small regions on a sample to distinct energy dispersive pixels on a CCD matrix. At present, the resolution limit of color X-ray camera systems can go down to several microns and is mainly restricted by pixel dimensions. The recent development of an efficient subpixel resolution algorithm allows a release from pixel size, limiting the resolution only to the quality of the optics. In this work polycapillary properties that influence the spatial resolution are systematized and assessed both theoretically and experimentally. It is demonstrated that with the current technological level reaching one micron resolution is challenging, but possible.
Keywords: color X-ray camera, polycapillary optics, lateral resolution

Publ.-Id: 25647 - Permalink


Asymmetric spin-wave dispersion in ferromagnetic nanotubes induced by surface curvature
Otálora, J. A.; Yan, M.; Schultheiss, H.; Hertel, R.; Kákay, A.;
We present a detailed analytical derivation of the spin wave (SW) dispersion relation in magnetic nanotubes with magnetization along the azimuthal direction. The obtained formula can be used to calculate the dispersion relation for any longitudinal and azimuthal mode. The obtained dispersion is asymmetric for all azimuthal modes traveling along the axial direction. As reported in our recent publication [Phys. Rev. Lett. 117, 227203 (2016)], the asymmetry is a curvature-induced effect originating from the dipole-dipole interaction. Here, we discuss the asymmetry of the dispersion for azimuthal modes by analyzing the SW asymmetry deltaf (kz) = fn(kz) − fn(−kz), where fn(kz) is the eigenfrequency of a magnon with a longitudinal and azimuthal wave vectors, kz and n, respectively; and the dependence of the maximum asymmetry with the nanotube radius R. The analytical results are in perfect agreement with micromagnetic simulations. Furthermore, we show that the dispersion relation simplifies to the thin-film dispersion relation with in-plane magnetization when analyzing the three limiting cases: (i) kz = 0, (ii) kz>>1/R, and (iii) kz<<1/R. In the first case, for the zeroth-order modes the thin-film Kittel formula is obtained. For modeswith higher order the dispersion relation for the Backward-Volume geometry is recovered. In the second case, for the zeroth-order mode the exchange dominated dispersion relation for SW in Damon-Esbach configuration is obtained. For the case kz<<1/R, we find that the dispersion relation can be reduced to a formula similar to the Kalinikos-Slavin [J. Phys. C: Sol. State Phys. 19, 7013 (1986)] type.
Keywords: Spin waves, curvature, mangnonics

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Publ.-Id: 25646 - Permalink


TELBE: High-field high-repetition-rate photonics facility for coherent terahertz control of Matter
Wang, Z.; Deinert, J.-C.; Green, B.; Awari, N.; Chen, M.; Kovalev, S.; Gensch, M.;
The TELBE user facility at Helmholtz-Zentrum Dresden-Rossendorf is based on the new class of accelerator-driven terahertz (THz) radiation sources. Superradiant THz radiation is generated from relativistic electron bunches in a compact MeV level superconducting radiofrequency electron accelerator. Compared to the laser-based table-top THz sources with moderate repetition rates of a few kHz, the superradiant THz facility TELBE provides high repetition rates (quasi-cw) up to several 100 kHz, peak electric fields of 1 GV/m, and flexibility of tuning the THz pulse form. Time resolved experiments can be performed with time resolution down to 30 fs using the novel pulse-resolved diagnostics. We will present the results from first benchmarking THz control experiments, and discuss the possibility of various pump-probe experiments for friendly users, especially at low temperatures and in magnetic fields.
  • Poster
    International Conference on Quantum Criticality and Novel Phases (QCNP 2017), 26.02.-01.03.2017, Berlin, Germany

Publ.-Id: 25645 - Permalink


Nanometer probing of ultrahigh intensity ultrashort pulse laser interaction with solid density plasmas, by Small Angle X-Ray Scattering using XFELs
Kluge, T.; Rödel, M.; Metzkes, J.; Pelka, A.; Laso Garcia, A.; Prencipe, I.; Hartley, N.; Nakatsutsumi, M.; Gutt, C.; Galtier, E.; Nam, I.; Lee, H. J.; Zacharias, M.; Garten, M.; Bussmann, M.; Zeil, K.; Rödel, C.; Mcbride, E.; Schramm, U.; Cowan, T. E.;
Nanometer probing of ultrahigh intensity ultrashort pulse laser interaction with solid density plasmas, by Small Angle X-Ray Scattering using XFELs
  • Lecture (Conference)
    2017 European XFEL Users' Meeting and Satellite Meetings, Satellite Meeting: Status of the HED science instrument & Meeting of the HIBEF user consortium, 24.01.2017, Hamburg, Deutschland
  • Invited lecture (Conferences)
    International Conference on Extreme Light, 06.-09.11.2017, Szeged, Ungarn
  • Lecture (others)
    Plasmaphysik Seminar GSI, 17.01.2017, Darstadt, Deutschland

Publ.-Id: 25644 - Permalink


SAXS on ultrashort laser pulse experiments
Kluge, T.; Pelka, A.; Metzkes, J.; Rödel, M.; Laso Garcia, A.; Prencipe, I.; Gutt, C.; Schramm, U.; Cowan, T. E.;
Nanometer probing of ultrahigh intensity short pulse laser interaction with solid density plasmas, by Small Angle X-Ray Scattering using XFELs
  • Lecture (Conference)
    High Intensity Laser Matter Science at The HED Instrument at The European XFEL, 05.-06.04.2017, Hamburg, Deutschland

Publ.-Id: 25643 - Permalink


Start-to-end simulations for photon interaction in ultra-high intensity short pulse laser experiments with solids
Kluge, T.; Burau, H.; Garten, M.; Grund, A.; Huebl, A.; Matthes, A.; Jung, F.; Widera, R.; Zacharias, M.; Fortmann-Grote, C.; Bussmann, M.;
EUCALL annual meeting poster
  • Poster
    EUCALL annual meeting 2017, 07.-09.06.2017, Grenoble, Frankreich

Publ.-Id: 25642 - Permalink


The need for detailed scattering simulations for Small Angle X-Ray Scattering on laser driven solids
Thomas Kluge; Burau, H.; Garten, M.; Grund, A.; Huebl, A.; Matthes, A.; Jung, F.; Widera, R.; Zacharias, M.; Fortmann-Grote, C.; Bussmann, M.;
SIMEX progress report June 2017
  • Lecture (Conference)
    EUCALL annual meeting 2017, 07.-09.06.2017, Grenoble, Frankreich

Publ.-Id: 25641 - Permalink


1‑(4‑[18F]Fluorobenzyl)-4-[(tetrahydrofuran-2-yl)methyl]piperazine: A Novel Suitable Radioligand with Low Lipophilicity for Imaging σ1 Receptors in the Brain
He, Y.; Xie, F.; Ye, J.; Deuther-Conrad, W.; Cui, B.; Wang, L.; Lu, J.; Steinbach, J.; Brust, P.; Huang, Y.; Lu, J.; Jia, H.;
We have designed and synthesized novel piperazine compounds with low lipophilicity as σ1 receptor ligands. 1-(4-Fluorobenzyl)-4-[(tetrahydrofuran-2-yl)methyl]piperazine (10) possessed a low nanomolar σ1 receptor affinity and a high selectivity toward the vesicular acetylcholine transporter (>2000-fold), σ2 receptors (52-fold), and adenosine A2A, adrenergic α2, cannabinoid CB1, dopamine D1, D2L, γ-aminobutyric acid A (GABAA), NMDA, melatonin MT1, MT2, and serotonin 5-HT1 receptors. The corresponding radiotracer [18F]10 demonstrated high brain uptake and extremely high brain-to-blood ratios in biodistribution studies in mice. Pretreatment with the selective σ1 receptor agonist SA4503 significantly reduced the level of accumulation of the radiotracer in the brain. No radiometabolite of [18F]10 was observed to enter the brain. Positron emission tomography and magnetic resonance imaging confirmed suitable kinetics and a high specific binding of [18F]10 to σ1 receptors in rat brain. Ex vivo autoradiography showed a reduced level of binding of [18F]10 in the cortex and hippocampus of the senescence-accelerated prone (SAMP8) compared to that of the senescence-accelerated resistant (SAMR1) mice, indicating the potential dysfunction of σ1 receptors in Alzheimer’s disease.

Publ.-Id: 25640 - Permalink


test20
Henrion, K.;
alles nur ein Test
  • AAPG Bulletin (2017)

Publ.-Id: 25639 - Permalink


Noble gas ion beams in materials science for future applications and devices
Belianinov, A.; Burch, M. J.; Kim, S.; Tan, S.; Hlawacek, G.; Ovchinnikova, O.;
Helium ion microscopy (HIM), enabled by a gas field ion source (GFIS), is an emerging imaging and nanofabrication technique compatible with many applications in materials science. The scanning electron microscope (SEM) has become ubiquitous in materials science for high-resolution imaging of materials. However, due to the fundamental limitation in focusing of electron beams, ion-beam microscopy is now being developed (e.g., at 20 kV the SEM beam diameter ranges from 0.5 to 1 nm, whereas the HIM offers 0.35 nm). The key technological advantage of the HIM is in its multipurpose design that excels in a variety of disciplines. The HIM offers higher resolution than the best available SEMs as well as the traditional gallium liquid-metal ion source (LMISs) focused ion beams (FIBs), and is capable of imaging untreated biological or other insulating samples with unprecedented resolution, depth of field, materials contrast, and image quality. GFIS FIBs also offer a direct path to defect engineering via ion implantation, three-dimensional direct write using gaseous and liquid precursors, and chemical-imaging options with secondary ion mass spectrometry. HIM covers a wide range of tasks that otherwise would require multiple tools or specialized sample preparation. In this article, we describe the underlying technology, present materials, relevant applications, and offer an outlook for the potential of FIB technology in processing materials.
Keywords: Helium Ion Microscopy, Nanofabrication, defect engineering, 2D materials, Focused Ion Beam Induced Deposition

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Publ.-Id: 25638 - Permalink


Disentangling magnetic order on nanostructured surfaces
Erb, D.; Schlage, K.; Bocklage, L.; Hübner, R.; Merkel, D. G.; Rüffer, R.; Wille, H.-C.; Röhlsberger, R.;
We present a synchrotron-based X-ray scattering technique which allows disentangling magnetic properties of heterogeneous systems with nanopatterned surfaces. This technique combines the nm-range spatial resolution of surface morphology features provided by Grazing Incidence Small Angle X-ray Scattering and the high sensitivity of Nuclear Resonant Scattering to magnetic order. A single experiment thus allows attributing magnetic properties to structural features of the sample; chemical and structural properties may be correlated analogously. We demonstrate how this technique shows the correlation between structural growth and evolution of magnetic properties for the case of a remarkable magnetization reversal in a structurally and magnetically nanopatterned sample system.

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Publ.-Id: 25637 - Permalink


Quantifying the relative availability of high-tech by-product metals – The cases of gallium, germanium and indium
Frenzel, M.; Mikolajczak, C.; Reuther, M. A.; Gutzmer, J.;
There are considerable concerns about the supply security of certain high-tech elements produced as by-products. To determine in how far these concerns are justified by the actual availability of these elements, we compare the supply potentials for three particularly relevant examples – gallium, germanium and indium – to current and historic production volumes. Our assessment is based on detailed estimates of the amounts extractable from various raw materials given contemporary market prices and technologies. While the estimate for gallium is taken from a previous publication, the estimate for germanium is recalculated from an earlier estimate of recoverable germanium in reserves and resources, and the estimate for indium is compiled as part of this article.

We find that the supply potentials of all three elements significantly exceed current primary production. However, the degree to which this is the case varies from element to element. While both the supply potentials of gallium and germanium are ~10 times higher than primary production, the supply potential of indium is ~3 times higher.

Differences also exist in historic growth trends, with indium showing the fastest growth rate of the utilised supply potential. This makes it the most likely of the three to reach its maximum production level in the future. Based on these considerations we propose a new quantitative indicator for the future availability of by-products, time-to-maximum extraction as a by-product (TMEB), and show its utility in discriminating between the different supply situations of the three by-product elements.
Keywords: Scarcity; Critical raw materials; Indium; Companion metals; By-products; Supply potential

Publ.-Id: 25636 - Permalink


PIConGPU Particle-in-Cell Simulations of Transient High Energy Density Plasmas
Huebl, A.ORC; Kluge, T.; Garten, M.; Grund, A.; Pausch, R.; Widera, R.ORC; Matthes, A.ORC; Debus, A.; Vorberger, J.; Fortmann-Grote, C.ORC; Chung, H.-K.; Bussmann, M.ORC
This talk shows the progress of PIConGPU on modeling transient high-energy density plasmas for the EUCALL annual workshop. We report on new features in PIConGPU, challenges in HPC-scale I/O for PIC simulations and how we interact with simex_platform and our approach for collisional-radiative non-LTE modeling within the scope of particle-in-cell.
Keywords: PIConGPU EUCALL non-LTE HPC I/O transient plasma processes
  • Lecture (Conference)
    EUCALL Annual Meeting 2017, 07.-09.06.2017, Grenoble, Frankreich

Publ.-Id: 25635 - Permalink


Studying tracer metabolism by LC-MS: (+)-[18F]flubatine and (S)-[18F]fluspidine – two different radioligands showing similar metabolic pathways in vitro and in vivo
Ludwig, F.-A.; Fischer, S.; Smits, R.; Hoepping, A.; Houska, R.; Patt, M.; Hesse, S.; Wünsch, B.; Sabri, O.; Brust, P.; Steinbach, J.;
Objectives: Radiometabolites can affect PET imaging dramatically due to their expected different properties. Therefore identification of radiometabolites is an important step to understand the metabolic fate of a radioligand. The approach presented demonstrates how LC-MS supports in vitro experiments and contributes to explore the metabolic profile of two tracers recently studied in human brain [1, 2].
Methods: (+)-[18F]Flubatine ([18F]1) and (S)-[18F]Fluspidine ([18F]2) (Figure 1), as well as nonradioactive references were incubated with human liver microsomes (HLM) in presence of NADPH and/or activated glucuronic acid (UDPGA) at 37°C. Radiometabolite patterns were monitored by radio-HPLC and structures were identified by LC-MS of non-radioactive incubations using different MS-methods (EPI, MS3). Plasma (30 min p.i.) and urine (90 min p.i.) from human subjects receiving [18F]1 or [18F]2 during clinical studies were investigated and compared with results von microsomal incubations.
Results: During HLM incubations in presence of NADPH, mono-hydroxylation was predominant for both, 1 and 2, beside debenzylation of 2. In presence of UDPGA 1 and 2 underwent glucuronidation, but only after previous hydroxylation. Corresponding in vitro radiometabolites were detected by radio-HPLC and assigned regarding their structure. Samples obtained from humans showed high stability of both tracers, whereby [18F]1 (97.0% in plasma 30 min p.i, n=6) proved to be more stable than [18F]2 (85.3% in plasma 30 min p.i, n=3). However, hydroxylation and subsequent glucuronidation was found to be the major metabolic pathway of both tracers.
Conclusions: Using in vitro studies and LC-MS, in vivo radiometabolites could be identified. Beside high metabolic stability, [18F]1 and [18F]2 show similar major pathways, namely glucuronidation after previous hydroxylation.
Acknowledgements: Supported by the Helmholtz Validation Fund (HVF) and the German Research Foundation (DFG).
References: [1] Sattler et al. (2015), J Nucl Med, 56, suppl. 3, 1020; [2] Sattler et al. (2016), J Nucl Med, 57, suppl. 2, 1022.
Keywords: PET, LC-MS, Microsomes, Flubatine, Fluspidine, Metabolism, Fluorine-18
  • Lecture (Conference)
    XIV Turku PET symposium, 27.-30.5.2017, Turku, Finnland

Publ.-Id: 25633 - Permalink


Orthotopic Transplantation of Cancer Cells into Mice Lung Using a Stereotactic Technique
Aktar, R.; Bütof, R.; Tillner, F.; Baumann, M.; Krause, M.; Dietrich, A.;
Primary radiotherapy is the treatment of choice for patients with locally advanced non-small cell lung carcinoma where surgery is unable to perform. Orthotopic tumor models, where tumor material is transplanted into the corresponding organ of origin, are used in preclinical studies to predict the clinical efficacy of newly developed treatment options. For radiooncological research, orthotopic lung tumor models should have the characteristics of growing locally and spread in a manner that resembles the growth and metastasis of a real clinical situation.

In light of these respects, luciferases expressing human lung carcinoma cells (A549) were used for orthotopic transplantation. Different transplantation techniques were tested: (i) injection of small tumor pieces (< 1 mm) of subcutaneous source tumors, (ii) percutaneous injection of cell suspensions in matrigel between two ribs or (iii) stereotactic-guided injection of few microliters of cell suspensions with matrigel. Tumor development was imaged twice weekly by optical imaging using IVIS Spectrum and cone beam CT integrated in the Small-Animal Image-Guided Radiotherapy (SAIGRT) platform, developed in our institute. Tumor histology was analyzed via staining with hematoxylin and eosin and human origin of tumors were verified by a specific anti-human Ki-67 antibody. Our experiments revealed a multifocal, early metastatic spreading after percutaneous injection of cell suspensions while the transplantation of small tumor pieces lead to a defined tumor mass after quite a long period of time. In contrast, our new stereotactic approach resulted in early solitary lung lesions mimicking a clinical scenario which will allow us to start image-guided radiotherapy treatment at an appropriate time point.

In the future different lung carcinoma cell lines will be orthotopically transplanted using the stereotactic technique and corresponding growth and metastatic potential will be compared in order to improve the selection of models for preclinical radiooncological experiments.
  • Lecture (Conference)
    ERRS and GBS 2017, 17.-21.09.2017, Essen, Deutschland

Publ.-Id: 25632 - Permalink


DOs and DON’Ts of applying for an ERC starting grant
Makarov, D.;
In this special open door Seminar at the FU Berlin I will address the following aspects:
•outline my Research Topic: flexible interactive electronics based on magnetic field sensors
•challenges of carrying out basic and applied research
•‘DOs’ and ‘DON’Ts’ of applying for an ERC starting grant, based on my personal experience
Keywords: shapeable magnetic field sensorics
  • Invited lecture (Conferences)
    Special Open Door Talk "Do's and Dont's of Appyling for an ERC Starting Grant" at the FU Berlin, 29.06.2017, Berlin, Germany

Publ.-Id: 25630 - Permalink


Flexible and ultrathin magnetic field sensorics
Makarov, D.;
Erst vor kurzem haben wir flexible Magnetoelektronik (Hall-Elemente und Magnetoresistive Sensoren) entwickelt. Die Kernidee der Technologie beruht auf der Kombination flexibler Polymermembranen und magnetisch hochempfindlicher metallischer Dünnschichten. Diese Synergie führt zu einzigartigen Eigenschaften und erlaubt die Gestaltung einer neuen Klasse von Magnetfeldsensoren mit einer neuartigen Funktionaltät der Verformbarkeit. Die Technologie erlaubt es, dass die magnetoelektronischen Elemente auch nach der Herstellung beliebige Formen durch Biegen, Verdrehen und Dehnen annehmen und somit auf gekrümmten Oberflächen integriert werden können.

Die formbare Magnetoelektronik weist zugleich mehrere kundenspezifische Vorteile hinsichtlich ereichbarer Sensorbauhöhen und –aktivflächen sowie Flexibilität im Vergleich zu konventioneller starrer Magnetfeldsensorik auf:

Verformbarkeit: Die Technologie erlaubt es, dass die magnetoelektronischen Elemente auch nach der Herstellung beliebige Formen durch Biegen, Verdrehen und Dehnen annehmen und somit auf gekrümmten Oberflächen integriert werden können.

Sensoraktivfläche: Es besteht die einzigartige Möglichkeit formbare magnetische Sensoren neben einer kleinflächigen Realisierung ebenso als grossflächige Sensoren, z.B. zur vorteilhaften Erfassung der mittleren magnetischen Flussdichte über eine planare oder beliebig gekrümmte Messoberfläche, kostengünstig herzustellen.

Geringe Bauhöhe: Unsere Technologieplatform ermöglicht Sensorbauhöhen von weniger als 150 μm. Das stellt eine Bauhöhereduktion von ca. 60% in Vergleich zu starrer Magnetfeldsensorik dar.
Keywords: flexible magnetic field sensors
  • Invited lecture (Conferences)
    12. Silicon Saxony Day, 20.06.2017, Dresden, Germany

Publ.-Id: 25629 - Permalink


Flexible und ultradünne Magnetfeldsensorik
Makarov, D.;
Neuartige magnetische Sensoren, die sich noch nach ihrer Herstellung beliebig verformen lassen, bieten entscheidende Vorteile gegenüber herkömmlichen in starrer Architektur. Sie können in kleinsten Luftspalten elektrischer Werkzeugmaschinen eingesetzt werden und so deren Leistungsfähigkeit deutlich erhöhen. Darüber hinaus ergeben sich neue, spektakuläre Anwendungen, wie z.B. „Internet of Things“.
Keywords: flexible magnetic field sensors
  • Invited lecture (Conferences)
    Science Match: Future Technologies, 26.01.2017, Dresden, Germany

Publ.-Id: 25628 - Permalink


Flexible electronics: from interactive on-skin devices to in vivo applications
Makarov, D.;
The portable consumer electronics necessitates functional elements to be lightweight, flexible, and wearable [1-4]. The unique possibility to adjust the shape of the devices offered by this alternative formulation of the electronics provides vast advantages over the conventional rigid devices particularly in medicine and consumer electronics. There is already a remarkable number of available flexible devices starting from interconnects, sensing elements towards complex platforms consisting of communication and diagnostic components.
We developed shapeable magnetoelectronics [5] – namely, flexible [6-8], printable [9,10], stretchable [11,12] and even imperceptible [13] magnetosensitive large area elements, which were completely missing in the family of flexible electronics. The unique mechanical properties open up new application potentials for smart skins, allowing to equip the recipient with a “sixth sense” providing new experiences in sensing and manipulating the objects of the surrounding us physical as well as digital world [7,13]. On the other hand, we realized self-assembled compact tubular microchannels based on strain engineering [14] with integrated passive sensory elements [15-17] and communication antenna devices [18] for on-chip and bio-medical applications, e.g. smart implants [19,20].
Combining these two research directions carried out at different length scales into a single truly interdisciplinary topic opens up the novel field of smart biomimetics [20]. In this respect, we demonstrated mechanically and electrically active compact biomimetic microelectronics, which can serve as a base for realization of novel regenerative neuronal cuff implants with unmatched functionalities. The biomimetic microelectronics can mechanically adapt to and impact the environment possessing the possibility to assess, adopt and communicate the environmental changes and even stimulate the environment electrically.
In my talk, these recent developments will be covered.

[1] M. G. Lagally, MRS Bull., 32, 57 (2007).
[2] J. A. Rogers et al., Nature, 477, 45 (2011).
[3] S. Bauer et al., Adv. Mater., 26, 149 (2014).
[4] M. Kaltenbrunner et al., Nature, 499, 458 (2013).
[5] D. Makarov et al., Appl. Phys. Rev., 3, 011101 (2016).
[6] G. Lin, D. Makarov et al., Lab Chip, 14, 4050 (2014).
[7] M. Melzer, D. Makarov et al., Adv. Mater., 27, 1274 (2015).
[8] N. Münzenrieder, D. Makarov et al., Adv. Electron. Mater., 2, 1600188 (2016).
[9] D. Karnaushenko, D. Makarov et al., Adv. Mater., 27, 880 (2015).
[10] D. Karnaushenko, D. Makarov et al., Adv. Mater., 24, 4518 (2012).
[11] M. Melzer, D. Makarov et al., Adv. Mater., 27, 1333 (2015).
[12] M. Melzer, D. Makarov et al., Nano Lett., 11, 2522 (2011).
[13] M. Melzer, D. Makarov et al., Nat. Commun., 6, 6080 (2015).
[14] O. G. Schmidt et al., Nature, 410, 168 (2001).
[15] I. Mönch, D. Makarov et al., ACS Nano, 5, 7436 (2011).
[16] C. Müller, D. Makarov et al., Appl. Phys. Lett., 100, 022409 (2012).
[17] E. J. Smith, D. Makarov et al., Lab Chip, 12, 1917 (2012).
[18] D. D. Karnaushenko, D. Makarov et al., NPG Asia Materials, 7, e188 (2015).
[19] D. Karnaushenko, D. Makarov et al., Adv. Mater., 27, 6582 (2015).
[20] D. Karnaushenko, D. Makarov et al., Adv. Mater., 27, 6797 (2015).
Keywords: flexible magnetic field sensors, GMR effect, shapeable magnetoelectronics
  • Invited lecture (Conferences)
    LII Zakopane School of Physics, 26.05.2017, Zakopane, Poland

Publ.-Id: 25627 - Permalink


ERC grant SMaRT at the Helmholtz-Zentrum Dresden-Rossendorf
Makarov, D.;
In this invited talk I presented the HZDR as a user facility. The activities of the FWIN-I Group was Reviewed. Beside the scientific part, I shared my experience in applying / handling the ERC starting grant.
Keywords: flexible electronics, ERC
  • Invited lecture (Conferences)
    Eastern Partnership PLUS Workshop “Science Connects”, 15.05.2017, Kyiv, Ukraine

Publ.-Id: 25626 - Permalink


Intelligent materials and devices
Makarov, D.;
In this invited talk I discussed the activities of the Group FWIN-I on flexible interactive electronics. The summary of the fabrication of mechanically flexible magnetic field sensors was given. The prospective application directions were outlined. The fundamental Background behind the electrical and magnetic Responses of curved magnetic thin films was given.
Keywords: curved magnetic thin films, flexible electronics, magnetic field sensors
  • Invited lecture (Conferences)
    Special workshop at the Institute of Mathematics, National Academy of Sciences of Ukraine, 14.05.2017, Kyiv, Ukraine

Publ.-Id: 25625 - Permalink


Prompt-gamma based range verification with a slit camera: Sensitivity and first clinical experiences
Richter, C.;
Overview of PGI slit camera activities in Dresden
  • Invited lecture (Conferences)
    ENLIGHT Annual Meeting 2017, 12.-13.06.2017, Aarhus, Danmark

Publ.-Id: 25624 - Permalink


Following our DREAMS (DREsden Accelerator Mass Spectrometry)
Merchel, S.; DREAMS-Team (S. Pavetich, G. Rugel, A. Scharf, R. Ziegenrücker,...); DREAMS-Users; DREAMS-Friends;
no abstract necessary
Keywords: AMS
  • Poster
    Workshop on Nuclear Astrophysics at the Dresden Felsenkeller, 26.-28.06.2017, Dresden, Deutschland

Publ.-Id: 25623 - Permalink


From Space to Earth to Accelerator Mass Spectrometry: Applications at Dresden AMS
Rugel, G.; Merchel, S.; DREAMS; Cooperation partners;
no abstract necessary
Keywords: AMS, astrophysics
  • Poster
    Workshop on Nuclear Astrophysics at the Dresden Felsenkeller, 26.-28.06.2017, Dresden, Deutschland

Publ.-Id: 25622 - Permalink


Low-cost production of a beryllium-7 tracer from rainwater and purification: preliminary results
Querfeld, R.; Merchel, S.; Steinhauser, G.;
7Be with its relatively short half-life (53.22 days) is a possibly suitable radionuclide for radiotracer experiments. Low-level activities of natural 7Be can be found in rainwater and might be available as a tracer after radiochemical isolation. Herein, beryllium was first concentrated by evaporation of rainwater and/or iron(III) hydroxide co-precipitation. Afterwards, several separation schemes have been tested including various ion exchange resins in order to remove interfering other elements. Characterization was done by gamma spectrometry and inductively coupled plasma atomic emission spectrometry, respectively. With further optimizations of our methodology, rainwater may become a suitable low-cost and easily accessible 7Be tracer source.
Keywords: 7Be, tracer, gamma spectroscopy, Actinide resin, LN resin, Diphonix resin, DOWEX

Publ.-Id: 25621 - Permalink


Strain and particle size analysis in ion beam synthesized SiC nanoparticles using Raman scattering studies
Saravanan, K.; Jayalakshmi, G.; Panigrahi, B. K.; Hübner, R.;
We study the strain and particle size analysis of ion beam synthesized SiC nanoparticles (NPs) embedded in Si matrix using Raman and low-frequency Raman scattering (LFRS). 300 keV C+ ions with the fluence of 2 × 1017 ions/cm2 were implanted on Si substrate at three different substrate temperatures (300, 500 and 650 °C). Raman scattering analyses confirm the formation of 3C-SiC NPs in Si matrix. Relative strain in 3C-SiC NPs estimated from Raman scattering was found to decrease with increase of substrate temperature. The particle size distribution of 3C-SiC NPs was estimated from the signature of localized acoustic phonon modes observed in the low frequency region (ω<40cm-1) of LFRS spectra. The estimated particle size of the SiC is found to be in good agreement with the TEM analysis.
Keywords: Acoustic phonon modes; Ion beam synthesis; SiC nanoparticles; Strain

Publ.-Id: 25620 - Permalink


Including Atomic Physics in Simulations of Transient Plasma Processes with PIConGPU & simex_platform
Huebl, A.ORC; Garten, M.ORC; Chung, H.-K.; Vorberger, J.; Kluge, T.; Bussmann, M.ORC
Particle-in-Cell (PIC) codes are the the working horses of computational modeling in plasma physics, as they describe even the most turbulent kinetic processes from first-principles. But great applicability comes with great computational demand, requiring leadership-scale HPC systems in order to model full 3D geometries with solid-density. This poster shows the open software architecture of the world's fastest PIC code PIConGPU which is addressing these demands for the community. With a blazingly short time-to-solution, GPU-powered high-performance computing opens unique opportunities for studying transient plasma processes, e.g. by including XFEL photon distributions from simex_platform. Trading speed for enhanced predictive capabilities, we including collisional-radiative non-LTE models from SCFLY into the electro-magnetic PIC cycle.
Keywords: PIC modeling transient plasma GPU laser-matter non-LTE collisional-radiative PIConGPU
  • Poster
    EUCALL Annual Meeting 2017, 07.-09.06.2017, Grenoble, Frankreich

Publ.-Id: 25619 - Permalink


Kreislaufwirtschaft 4.0 - Was bedeutet die Digitalisierung für die kommunale Abfallwirtschaft?
Reuter, M. A.;
Metallurgy is a key enabler of a circular economy (CE), its digitalization is the metallurgical Internet of Things (m-IoT). In short: Metallurgy is at the heart of a CE, as metals all have strong intrinsic recycling potentials. Process metallurgy, as a key enabler for a CE, will help much to deliver its goals. The first-principles models of process engineering help quantify the resource efficiency (RE) of the CE system, connecting all stakeholders via digitalization. This provides well-argued and first-principles environmental information to empower a tax paying consumer society, policy, legislators, and environmentalists. It provides the details of capital expenditure and operational expenditure estimates. Through this path, the opportunities and limits of a CE, recycling, and its technology can be estimated. The true boundaries of sustainability can be determined in addition to the techno-economic evaluation of RE. The integration of metallurgical reactor technology and systems digitally, not only on one site but linking different sites globally via hardware, is the basis for describing CE systems as dynamic feedback control loops, i.e., the m-IoT. It is the linkage of the global carrier metallurgical processing system infrastructure that maximizes the recovery of all minor and technology elements in its associated refining metallurgical infrastructure.
  • Invited lecture (Conferences)
    Ressourcenschutz und -effizienz: Die kommunale Abfallwirtschaft zwischen Politik und Potenzial / 2. Bundeskongress der kommunalen Abfallwirtschaft und Stadtreinigung 2017, 31.05.2017, Berlin, Deutschland

Publ.-Id: 25618 - Permalink


Recycling 4.0
Reuter, M. A.;
Metallurgy is a key enabler of a circular economy (CE), its digitalization is the metallurgical Internet of Things (m-IoT). In short: Metallurgy is at the heart of a CE, as metals all have strong intrinsic recycling potentials. Process metallurgy, as a key enabler for a CE, will help much to deliver its goals. The first-principles models of process engineering help quantify the resource efficiency (RE) of the CE system, connecting all stakeholders via digitalization. This provides well-argued and first-principles environmental information to empower a tax paying consumer society, policy, legislators, and environmentalists. It provides the details of capital expenditure and operational expenditure estimates. Through this path, the opportunities and limits of a CE, recycling, and its technology can be estimated. The true boundaries of sustainability can be determined in addition to the techno-economic evaluation of RE. The integration of metallurgical reactor technology and systems digitally, not only on one site but linking different sites globally via hardware, is the basis for describing CE systems as dynamic feedback control loops, i.e., the m-IoT. It is the linkage of the global carrier metallurgical processing system infrastructure that maximizes the recovery of all minor and technology elements in its associated refining metallurgical infrastructure.
  • Invited lecture (Conferences)
    Mitgliederversammlung des Landesverbandes der Recyclingwirtschaft Sachsen e.V. und der LVR-Entsorgergemeinschaft Sachsen e.V., 09.05.2017, Dresden, Deutschland

Publ.-Id: 25617 - Permalink


The effect of a Lorentz-force-driven rotating flow on the detachment of gas bubbles from the electrode surface
Weier, T.; Baczyzmalski, D.; Massing, J.; Landgraf, S.; Cierpka, C.;
Water electrolysis is a promising technique for energy conversion and is one of the key technologies to ensure an efficient and clean energy management in the future. However, the efficiency of this process is limited by overpotentials arising from - among other things - the high bubble coverage at the electrode surface. The influence of a magnetic field on the bubble behavior during electrolysis, in particular the bubble detachment from the electrodes, shows great potential for improving the efficiency of the process. In this study experiments and numerical simulations were carried out to investigate the effect of an electrode-normal magnetic field on the bubble detachment. Astigmatism Particle Tracking Velocimetry (APTV) was used to measure the magnetohydrodynamic (MHD) flow field around a magnetized sphere mimicking an electrolytic bubble. Complementary simulations gave further insight into the corresponding pressure field. The experimental and numerical results demonstrate that the pressure reduction formerly assumed to be responsible for the accelerated bubble detachment in the magnetic field is too weak to cause this effect. However, the flow over an arrangement of magnets was additionally measured by Particle Image Velocimetry (PIV), showing that the formation of bubble groups on the electrode surface gives rise to a stronger global flow which may have a substantial influence on the bubble behavior.
Keywords: electrolysis, magnetohydrodynamics

Downloads:

Publ.-Id: 25616 - Permalink


Physical modelling of Czochralski crystal growth in horizontal magnetic field
Grants, I.; Pal, J.; Gerbeth, G.;
This study addresses experimentally the heat transfer, the temperature azimuthal non-uniformity and the onset of oscillations in a low temperature physical model of a medium-sized Czochralski Crystal growth process with a strong horizontal magnetic field (HMF). It is observed that under certain conditions the integral heat flux may decrease with increasing magnetic field strength at the same time as the flow velocity increases. The azimuthal non-uniformity of the temperature field in the melt near the crystal model rim is only little influenced by its rotation rate outside of a narrow range where the centrifugal force balances the buoyant one. The flow oscillation onset has been observed for two values of the HMF strength. Conditions of this onset are little influenced by the crystal rotation. The critical temperature difference of the oscillation onset considerably exceeds that of the Rayleigh–Bénard (RB) cell in a strong HMF.
Keywords: Fluid flows, Heat Transfer, Magnetic field assisted Czochralski method, Semiconducting materials

Downloads:

  • Secondary publication expected

Publ.-Id: 25615 - Permalink


A round robin program of Master Curve evaluation using miniature C(T) specimens (comparison of T0 for a weld metal)
Yamamoto, M.; Carter, R.; Viehrig, H.-W.; Lambrecht, M.;
The Master Curve approach for the fracture toughness evaluation is expected to be a powerful tool to ensure the reliability of long-term used RPV steels. In order to get sufficient number of data for the Master Curve approach coexistent with the present surveillance program for RPVs, the utilization of miniature specimens, which can be taken from broken halves of surveillance Charpy specimens, is important. CRIEPI has been working on applying the miniature C(T) specimens (Mini-C(T)), whose dimensions are 4 x 10 x 9.6 mm, on the Master Curve fracture toughness evaluation. Miura (2010) had verified the basic applicability of Mini-C(T) specimens for typical Japanese RPV steels. Subsequently, an international round robin activity by Yamamoto (2012, 2013, 2014) assured the robustness of the testing procedure to the difference in testing machines or operators. Similar activity is being carried out for the weld metal materials and the basic applicability of Mini-C(T) was confirmed by Yamamoto (2015). The present paper describes the round robin activity for an un-irradiated weld metal, which is used for the weld filler of PRV plate steels. Four institutes are involved with the round robin tests and 78 fracture toughness data points in total were generated in conformity with ASTM E1921-10e1 (ASTM (2010)). All the participants successfully evaluated the valid reference temperature, To, with their own data set. The discrepancy among the 4 data sets was at the most 14 oC, which is considered as the acceptable scatter range specified in ASTM E1921-10e1. Weibull distribution of the 78 data points suggests that the tested material is in good agreement with the assumption of the Master Curve method, where the Weibull exponent is 4, the minimum fracture toughness is 20 MPa√m. From overall examination results, it was concluded that the miniature C(T) specimen can be used for the Master Curve evaluation of tested PRV weld metal.
Keywords: miniature specimens, fracture toughness, Master Curve, weld metal, reactor pressure vessel
  • Contribution to proceedings
    SMiRT-24 BEXCO, Division II, 20.-24.08.2017, Busan, Korea
    Transactions, SMiRT-24 BEXCO, Busan, Korea

Publ.-Id: 25614 - Permalink


[UO2Cl2(phen)2], a Simple Uranium(VI) Compound with a Significantly Bent Uranyl Unit (phen = 1,10-phenanthroline)
Schöne, S.ORC; Radoske, T.; März, J.; Stumpf, T.; Patzschke, M.; Ikeda-Ohno, A.ORC
A simple synthesis based on UO2Cl2·n(H2O) and 1,10-phenanthroline (phen) resulted in the formation of a new uranyl(VI) complex [UO2Cl2(phen)2] (1), revealing a unique snub disphenoid coordination geometry around the uranium centre with significant bending of the robust linear arrangement of the uranyl (O─U─O) unit. Quantum chemical calculations on complex 1 indicated that the weak but distinct interactions between the uranyl oxygens and the adjacent hydrogens of phen molecules play an important role in forming the snub disphenoid geometry that fits to the crystal structure of 1, resulting in the bending the uranyl unit. The uranyl oxygens in 1 are highly activated as compared with those in the linear uranyl unit and, hence, complex 1 is anticipated to be one of the rare uranyl(VI) complexes with readily reactive uranyl oxygens.
Keywords: uranium, uranyl(VI), phenanthroline, n-donor, crystal structure, quantum chemical calculations

Publ.-Id: 25613 - Permalink


Dynamics of rectal balloon implant shrinkage in prostate VMAT: Influence on anorectal dose and late rectal complication risk
Vanneste, B.; van Wijk, Y.; Lutgens, L.; van Limbergen, E.; van Lin, E.; van de Beek, K.; Lambin, P.; Hoffmann, A.;
Background and Purpose:
To assess the effect of a shrinking rectal balloon implant (RBI) on the anorectal dose and complication risk during the course of prostate radiotherapy.

Material/Methods:
In 15 patients with localized prostate cancer an RBI was implanted. A weekly kilovolt cone-beam computed tomography (CBCT) scan was acquired to measure the dynamics of RBI volume and prostate-rectum separation. The absolute anorectal volume encompassed by the 75 Gy isodose (V75Gy) was calculated as well as the mean anorectal dose. The increase in risk of grade 2-3 late rectal bleeding (LRB) between the start and end of treatment was predicted.

Results:
A significant shrinkage of RBI volumes was observed, with an average volume of 70.4% of baseline at the end of the treatment. Although the prostate–rectum separation significantly decreased over time, it remained at least 1 cm. No correlation between mean anorectal dose and balloon deflation was found. No significant increase in V75Gy and increase in LRB risk over time was observed, except in one patient whose RBI had completely deflated in the third week of treatment.

Conclusions:
Despite significant decrease in RBI volume the high-dose rectal volume and the predicted LRB risk were unaffected due to a persistent spacing between the prostate and the anterior rectal wall.
Keywords: Prostate cancer; Radiotherapy; Rectal Balloon Implant; Volume stability; Rectal Dose; Rectal Toxicity

Publ.-Id: 25612 - Permalink


Bewertung von drei Verwertungsoptionen für das Fairphone und Übertragbarkeit auf weitere ressourcenrelevante Altgeräte
Reuter, M. A.;
Metallurgy is a key enabler of a circular economy (CE), its digitalization is the metallurgical Internet of Things (m-IoT). In short: Metallurgy is at the heart of a CE, as metals all have strong intrinsic recycling potentials. Process metallurgy, as a key enabler for a CE, will help much to deliver its goals. The first-principles models of process engineering help quantify the resource efficiency (RE) of the CE system, connecting all stakeholders via digitalization. This provides well-argued and first-principles environmental information to empower a tax paying consumer society, policy, legislators, and environmentalists. It provides the details of capital expenditure and operational expenditure estimates. Through this path, the opportunities and limits of a CE, recycling, and its technology can be estimated. The true boundaries of sustainability can be determined in addition to the techno-economic evaluation of RE. The integration of metallurgical reactor technology and systems digitally, not only on one site but linking different sites globally via hardware, is the basis for describing CE systems as dynamic feedback control loops, i.e., the m-IoT. It is the linkage of the global carrier metallurgical processing system infrastructure that maximizes the recovery of all minor and technology elements in its associated refining metallurgical infrastructure.
  • Invited lecture (Conferences)
    2. Treffen AG 1 - Leiterplatten und ressourcenrelevante Bauteile, 19.05.2017, Berlin, Deutschland

Publ.-Id: 25611 - Permalink


Structural transformations in two-dimensional transition-metal dichalcogenide MoS₂ under electron beam: insights from first-principles calculations
Kretschmer, S.ORC; Komsa, H.-P.ORC; Bøggild, P.ORC; Krasheninnikov, A. V.ORC
The polymorphism of two-dimensional (2D) transition metal dichalcogenides (TMDs) and different electronic properties of the polymorphs make TMDs particularly promising materials in the context of the applications in electronics. Recently, local transformations from the hexagonal H to trigonal distorted T’ phase in 2D MoS₂ have been induced by electron irradiation [Nat. Nanotech. 9 (2014) 391], but the mechanism of the transformations remains elusive. Using density functional theory calculations, we study the energetics of the stable and metastable phases of 2D MoS₂ when additional charge, mechanical strain and vacancies are present. We also investigate the role of finite temperatures, which appear to be critical for the transformations. Based on the results of our calculations, we propose an explanation for the beam-induced transformations which are likely promoted by charge redistribution in the monolayer due to electronic excitations combined with formation of vacancies under electron beam and build-up of the associated mechanical strain in the sample. As this mechanism should be relevant to other 2D TMDs, our results provide hints for further development and optimization of electron-beam-mediated engineering of the atomic structure and electronic properties of 2D TMDs with sub-nanometer resolution.
Keywords: 2D materials, transition-metal dichalcogenides, phase transition, electron beam, first-principles calculations

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Publ.-Id: 25610 - Permalink


Coupling and stability of interfacial waves in liquid metal batteries
Horstmann, G. M.; Weber, N.; Weier, T.;
Liquid metal batteries (LMBs) are discussed today as a cheap grid scale energy storage, as required for the deployment of fluctuating renewable energies. LMBs incorporate stratified three-layer fluid systems consisting of two liquid metal electrodes separated by a thin molten salt electrolyte (see sketch below). Due to the large electrical conductivities of the liquid metals, LMBs are highly susceptible to become unstable by interactions of induced or external magnetic fields with internal cell currents. Several different types of instabilities have been identified as to be crucial for the LMB operation. Besides the Tayler instability and electrovortex flows, the metal pad roll (MPR) instability, originally known from aluminium reductions cells (ARCs), emerged as a key instability mechanism capable to cause short-circuits by exciting interfacial gravity-capillary waves. The MPR instability can be induced only by the interaction of a homogeneous vertical magnetic field with horizontal compensation currents arising due to small perturbations of the interfaces. While this mechanism is well understood in the case of ARCs, in LMBs an additional interface is present that may strongly influence the global stability depending on several parameters. Both interfaces can be closely coupled for thin salt-layers such that they both may excite each other and may be connected by different oscillating modes. The analysis of the coupling behavior is the main target of this study.
As the main part of this talk I will present an analytical analysis using linear wave theory describing coupled gravity-capillary waves enclosed in cylindrical containers. We have derived a fourth-order dispersion relation containing two different coupling modes. Further, we found that the global coupling behavior can be completely described by only two dimensionless parameters. On this basis, we suggest a coupling criterion predicting for which parameter regimes both interfaces can be considered as to be fully decoupled such that two-layer stability analysis becomes sufficient. Our study is further accompanied by both numerical simulations and experiments. For highly coupled cases we discovered different kinds of interface displacements not known from ARCs.
Some of the found states cannot be explained by the MPR instability mechanism alone and probably involve some new physical aspects.
Keywords: Liquid Metal Battery, MHD, Metal Pad Roll Instability, Wave Coupling
  • Lecture (Conference)
    International workshop on liquid metal battery fluid dynamics (LMBFD2017), 16.-17.05.2017, Dresden, Deutschland

Publ.-Id: 25608 - Permalink


Analysing methods of animal irradiation experiments with deviations from prescribed dose
Beyreuther, E.ORC; Eger Passos, D.; Karsch, L.; Löck, S.; Pawelke, J.
Introduction: The development of new radiotherapy technologies is a long time process which requires proving the general concept although clinical requirements with respect to beam quality and controlled dose delivery may not yet be fulfilled. Exemplarily, the necessary radiobiological experiments with laser-accelerated ion beams, which promise to compact ion radiotherapy facilities, are challenged by low particle energy and fluctuating beam intensities delivered by currently available laser systems. The first issue was handled by establishing a small tumour model on mouse ear that allows full penetration by ~25 MeV proton beams [1], whereas the latter, i.e. the subsequent deviations of the delivered from the prescribed dose, should be considered mathematically.

Methods: Based on tumour growth data and dose values obtained in a preceding in vivo trial comparing the biological efficacy of laser-driven and conventional LINAC electrons [2], different mathematical approaches to determine corresponding dose-response relationships were compared. During this experiment, the beam intensity fluctuations were not fully gathered by online dosimetry, which results in deviations of more than 10 % from scheduled dose as measured by retrospective absolute film dosimetry. Instead of classical averaging-per-dose point, which excludes animals with high dose deviations, multivariate linear regression, Cox regression and a Monte Carlo based approach were tested as alternatives to include all animals in statistical analysis.

Results: The application of different mathematical approaches to the same set of experimental tumour growth data and dose values led to similar results, revealing a comparable radiobiological efficacy of laser-driven and conventional LINAC electrons. Although the inclusion of those animals that were previously excluded because of more than 10% dose deviation did not change the experimental conclusion, the new mathematical approaches allowed for including all animals in the analysis. Comparing the different approaches, multivariate linear regression and Cox regression were considered as most feasible for future analysis, since they were already implemented in commercial statistical software, like SPSS (IBM).

Conclusion: The previously established small animal tumour model on mouse ear [1] together with the recently tested regression methods enable the investigation and evaluation of beams at new accelerators relative to their conventional equivalents despite their still limited beam stability, like laser-driven particle beams. The tested mathematical approaches allow for increasing the number of animals in analysis and therewith reduce the total number of animals in experiment with respect to the 3R of animal experimentation.

Acknowledgement: The work was supported by the German Government, Federal Ministry of Education and Research, grant nos. 03ZIK445 and 03Z1N511.

[1] Beyreuther et al. An optimized small animal tumour model for experimentation with low energy protons. PLOS One,2017; 12: e0177428.
[2] Oppelt et al. Comparison study of in vivo dose response to laser-driven versus conventional electron beam. Radiat Environ Biophys, 2015; 54:155-166.
  • Contribution to proceedings
    ERRS & GBS 2017, 17.-21.09.2017, Essen, Germany
  • Lecture (Conference)
    ERRS & GBS 2017, 17.-21.09.2017, Essen, Germany

Publ.-Id: 25607 - Permalink


Dual-energy CT based proton range prediction in head and pelvic tumor patients
Wohlfahrt, P.ORC; Möhler, C.ORC; Stützer, K.; Greilich, S.; Richter, C.
Background and Purpose:
To reduce range uncertainty in particle therapy, an accurate computation of stopping-power ratios (SPRs) based on computed tomography (CT) is crucial. Here, we assess range differences between the state-of-the-art CT-number-to-SPR conversion using a generic Hounsfield look-up table (HLUT) and a direct patient-specific SPR prediction (RhoSigma) based on dual-energy CT (DECT) in 100 proton treatment fields.

Material and Methods:
For 25 head-tumor and 25 prostate-cancer patients, the clinically applied treatment plan, optimized using a HLUT, was recalculated with RhoSigma as CT-number-to-SPR conversion.
Depth-dose curves in beam direction were extracted for both dose distributions in a regular grid and range deviations were determined and correlated to SPR differences within the irradiated volume.

Results:
Absolute (relative) mean water-equivalent range shifts of 1.1mm (1.2%) and 4.1mm (1.7%) were observed in the head-tumor and prostate-cancer cohort, respectively. Due to the case dependency of a generic HLUT, range deviations within treatment fields strongly depend on the tissues traversed leading to a larger variation within one patient than between patients.

Conclusions:
The magnitude of patient-specific range deviations between HLUT and the more accurate DECT-based SPR prediction is clinically relevant. A clinical application of the latter seems feasible as demonstrated in this study using medically approved systems from CT acquisition to treatment planning.
Keywords: dual-energy CT range uncertainty proton therapy

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  • Secondary publication expected

Publ.-Id: 25606 - Permalink


Sensitivity of a prompt-gamma slit-camera to detect range shifts for proton treatment verification
Nenoff, L.; Priegnitz, M.; Janssens, G.; Petzoldt, J.; Trezza, A.; Smeets, J.; Pausch, G.; Richter, C.;
Background and Purpose: Prompt-gamma imaging (PGI) was recently applied successfully in first clinical patient treatments in pencil beam scanning (PBS) and double scattering (DS). Still, systematic evaluations on its capability in clinical conditions are desirable. Here, the performance of the slit-camera is systematically assessed in well-defined error scenarios using realistic treatment deliveries to an anthropomorphic phantom.
Materials and Methods: The sensitivity to detect global and local range shifts with the slit camera was investigated in PBS and DS irradiations of a head phantom. For PBS, measured PGI information for shifted geometries was compared spot-wise with either simulated or measured un-shifted PGI-information to evaluate the sensitivity to detect deviations from the treatment plan and interfractional shifts, respectively.
Results: Deviations from the treatment plan can be detected with an accuracy of 1.5 and 3 mm for global and local shifts in PBS, respectively. Interfractional comparisons are more affected by noise in the measurements. Evaluation of the average PGI signal of the whole field allows the detection of global shifts also in DS mode.
Conclusions: PGI-based detection of global and local range shifts under clinical conditions is possible. Especially for PBS treatments, both high sensitivity and high accuracy in shift detection were found.
Keywords: range verification, prompt gamma imaging, slit camera, proton therapy, PGI

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Publ.-Id: 25605 - Permalink


Experimental setup to measure magnetic field effects of proton dose distributions: simulation study
Schellhammer, S. M.ORC; Oborn, B.; Lühr, A.; Gantz, S.; Bussmann, M.; Hoffmann, A. L.
Background and Purpose: As an initial step towards MR-integrated proton therapy, a setup is introduced capable to measure thedose deposited by a proton beam within a magnetic field in tissue-equivalent material. Simulations are performed predicting the experimental outcome and radiation-induced risk effects on the magnet.
Material and Methods: The setup comprises proton pencil beams (80-180 MeV; Ø10 mm) passing through a transverse magnetic field of a permanent dipole magnet (0.95 T) while being stopped inside a PMMA phantom. Using a combined Monte Carlo and finite-element model validated by reference measurements of magnetic flux density, depth-dose distributions and beam profiles, 2D dose distributions of the central plane are simulated.
Depth-dose curves and beam trajectories are extracted. A worst-case estimate of radioactivation and demagnetization of the magnet is made.
Results: The model shows excellent agreement with the reference measurements. Mean dose to the magnets is below 2 μGy, and the initial activation below 12 kBq for a dose of 1 Gy in the film. The predicted deflection of the Bragg peak ranges from 1 mm to 9 mm.
Conclusions: The magnetic field induced beam deflections are measurable with the presented setup and radiation-induced magnet damage is expected to be manageable. This demonstrates the feasibility of a benchmarking experiment.
Keywords: proton therapy, MR-guided radiotherapy, beam deflection, dose measurement, Monte Carlo simulation

Publ.-Id: 25604 - Permalink


Melanoma Brain Metastases
Brütting, J.; Rauschenberg, R.; Troost, E. G. C.; Meier, F.; Garzarolli, M.;
The majority of melanoma patients with metastatic disease stage IV is also affected by brain metastases, which are the main cause of death. If there is suspicion of brain metastases, staging diagnostics including cranial magnetic resonance imaging (cMRI) and a neurological examination are indicated. Prognostic factors, such as the number and symptoms of brain metastases, serum LDH and S100, existence of extracerebral metastases and ECOG status, should be considered in treatment planning. In addition, therapeutic interventions should be based on an interdisciplinary and multimodal approach. In case of a single brain metastasis, treatment by neurosurgical resection or stereotactic radiotherapy is standard of care. Until recently, the sole option for controlling brain metastases was local treatment. However, the spectrum of therapies has significantly expanded by approval of effective immune checkpoint (CTLA-4 and PD-1 antibody) and targeted therapies (BRAF and MEK inhibitors). In case of multiple symptomatic brain metastases, palliative whole-brain radiotherapy is used although there is no significant prolongation of overall survival (OS) but only some improvement of neurological symptoms and quality of life. Corticosteroids and anticonvulsants are indicated for increased intracranial pressure and epileptic seizures. New treatment options in melanoma with brain metastasis such as PD-1 antibodies and several combination strategies (e.g. ipilimumab plus nivolumab, BRAF inhibitors plus MEK inhibitors, or stereotactic radiotherapy plus immune or targeted therapy) will be evaluated in ongoing clinical trials.

Publ.-Id: 25603 - Permalink


Modification of structural and magnetic properties in Fe/Pt (111)-oriented multilayers with ion beam irradiation
Marynowska, A.; Misiuna, P.; Lewińska, S.; Dynowska, E.; Wawro, A.; Ślawska-Waniewska, A.; Böttger, R.; Fassbender, J.ORC; Baczewski, L. T.
This paper reports on structural and magnetic properties changes that occur after irradiation of Fe/Pt (1 1 1) multilayers with Ne+ ions. Multilayer samples of Al2O3 (0 0 0 1)/Pt 100 Å/(Fe X Å/Pt X Å)n/Pt 100 Å structure with different individual layer thickness X (5 or 10 Å) and different number of bilayers n (5, 10 or 15) were irradiated with Ne+ ions of 10 to 25 keV energy and 1 × 1014 ÷ 1 × 1016 ions cm−2 dose range at room temperature. Irradiation parameters were estimated a priori using Tridyn software. As-deposited samples revealed presence of sharp interfaces. Structural properties changes were investigated using symmetrical and asymmetrical X-ray diffraction methods and magnetic properties changes were examined using vibrating sample magnetometer. Ion beam induced mixing of multilayers resulted in formation of disordered face centered cubic (fcc) FePt alloys of two different compositions (quasi-50:50 in the initial multilayer volume and Pt-rich in initial cover-layer volume). Non-regular changes in magnetic properties after ion irradiation were observed whilst retaining in-plane orientation of magnetization easy axis.
Keywords: Magnetic metallic thin films; Multilayers; Magnetic and structural properties; Ion irradiation

Publ.-Id: 25602 - Permalink


Local formation of InAs nanocrystals in Si by masked ion implantation and flash lamp annealing
Rebohle, L.; Wutzler, R.; Prucnal, S.; Hübner, R.; Böttger, R.; Georgiev, Y. M.; Erbe, A.; Helm, M.; Skorupa, W.;
The integration of high-mobility III-V compound semiconductors emerges as a promising route for Si device technologies to overcome the limits of further down-scaling. In this work we investigate the possibilities to form InAs nanocrystals in a thin Si layer at laterally defined positions with the help of masked ion beam implantation and flash lamp annealing. In detail, after thinning of the device layer of a SOI wafer a cladding layer was deposited and patterned by electron beam lithography in order to serve as an implantation mask. The wafer was subsequently implanted with As and In, followed by flash lamp annealing leading to the formation of InAs nanocrystals in the implanted areas. The structures were investigated by Raman spectroscopy, scanning and transmission electron microscopy as well as energy-dispersive X-ray spectroscopy. Depending on the size of the implantation window, several, one or no nanocrystal is formed. Finally, the perspectives for using this technique for the local modification of Si nanowires are discussed.
Keywords: Blitzlampenausheilung, Ionenimplantation, Elektronstrahllithographie, InAs Nanokristalle, flash lamp annealing, ion implantation, electron beam lithography, InAs Nanocrystals
  • Lecture (Conference)
    EMRS Spring Meeting, 21.-26.05.2017, Strasbourg, France

Publ.-Id: 25599 - Permalink


Evidence for self-organized formation of logarithmic spirals during explosive crystallization of amorphous Ge:Mn layers
Bürger, D.; Baunack, S.; Thomas, J.; Oswald, S.; Wendrock, H.; Rebohle, L.; Schumann, T.; Skorupa, W.; Blaschke, D.; Gemming, T.; Schmidt, O. G.; Schmidt, H.;
Logarithmic spirals are found on different length scales in nature, e.g. in nautilus shells, cyclones, and galaxies. The underlying formation laws can be related with different growth mechanisms, pressure gradients, and density waves. Here we report on the self-organized formation of symmetric logarithmic crystallization spirals in a solid material on the micrometer length scale, namely in an amorphous Ge:Mn layer on a Ge substrate. After exposure to a single light pulse of a flash lamp array, the Ge:Mn layer is crystallized and reveals a partially rippled surface and logarithmic microspirals. Finally, we present a model describing the formation of the crystallization spirals by directional explosive crystallization of the amorphous Ge:Mn layer which is triggered by the flash lamp light pulse.
Keywords: Logarithmische Spiralen, Selbstorganisation, Explosivkristallisation, Blitzlampenausheilung, logarithmic spirals, self-organization, explosive crystallization, flash lamp annealing

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Publ.-Id: 25598 - Permalink


Photons, protons or carbon ions for stage I non-small cell lung cancer - results of the multicentric ROCOCO in silico study
Wink, K. C. J.; Roelofs, E.; Simone, C. B.; Dechambre, D.; Santiago, A.; van der Stoep, J.; Dries, W.; Smits, J.; Avery, S.; Ammazzalorso, F.; Jansen, N.; Jelen, U.; Solberg, T.; de Ruysscher, D.; Troost, E. G. C.;
Purpose: To compare dose to organs at risk (OARs) and dose-escalation possibility for 24 stage I nonsmall cell lung cancer (NSCLC) patients in a ROCOCO (Radiation Oncology Collaborative Comparison) trial.
Methods: For each patient, 3 photon plans [Intensity-modulated rad 5 iotherapy (IMRT), volumetric modulated arc therapy (VMAT) and CyberKnife], a double scattered proton (DSP) and an intensitymodulated carbon-ion (IMIT) therapy plan were created. Dose prescription was 60Gy (equivalent) in 8 fractions.
Results: The mean dose and dose to 2% of the clinical target volume (CTV) were lower for protons 10 and ions compared with IMRT (p<0.01). Doses to the lungs, heart, and mediastinal structures were lowest with IMIT (p<0.01), doses to the spinal cord were lowest with DSP (p<0.01). VMAT and CyberKnife allowed for reduced doses to most OARs compared with IMRT. Dose escalation was possible for 8 patients. Generally, the mediastinum was the primary dose-limiting organ.
Conclusion: On average, the doses to the OARs were lowest using particles, with more homogenous 15 CTV doses. Given the ability of VMAT and CyberKnife to limit doses to OARs compared with IMRT, the additional benefit of particles may only be clinically relevant in selected patients and thus should be carefully weighed for every individual patient.
Keywords: stage I NSCLC, radiotherapy, particle therapy, in silico planning study, multicentric trial

Publ.-Id: 25597 - Permalink


Testing the NURESIM platform on a PWR main steam line break benchmark
Kliem, S.ORC; Kozmenkov, Y.; Hadek, J.; Perin, Y.; Fouquet, F.; Bernard, F.; Sargeni, A.; Cuervo, D.; Sabater, A.; Sanchez-Cervera, S.; Garcia-Herranz, N.; Zerkak, O.; Ferroukhi, H.; Mala, P.
Within the NURESAFE project, a main steam line break benchmark has been defined and solved by codes integrated into the European code platform NURESIM. The paper describes the results of the calculations for this benchmark. Six different solutions using different codes and code systems are provided for the comparison. The quantitative differences in the results are dominated by the differences in the secondary system parameters during the depressurization. The source of these differences comes mainly from the application of different models for the two-phase leak flow available in the system codes. The use of two different thermal hydraulic system codes influences the results more than expected when the benchmark was created. The codes integrated into the NURESIM platform showed their applicability to a challenging transient like a main steam line break.

Publ.-Id: 25595 - Permalink


Variation in platinum group mineral and base metal sulfide assemblages in the Lower Group chromitites of the western Bushveld Complex, South Africa
Bachmann, K.; Osbahr, I.; Tolosana-Delgado, R.; Chetty, D.; Gutzmer, J.;
The Lower Group chromitites of the Bushveld Igneous Complex are mined for chromite as a primary product. The recovery of platinum group elements and base metals (Ni, Cu) as by-products has the potential to add value to the chromite resources. This study focuses on the LG-6 and LG-6A chromitite seams at the Thaba mine located on the western limb of the Bushveld Complex. Platinum group minerals and base-metal sulfides are studied by mineral liberation analysis and electron microprobe analysis to define distinct assemblages and to evaluate the potential for beneficiation. Based on the results two distinct major mineral assemblages are defined: The first assemblage is rich in platinum group element-sulfides, along with variable proportions of malanite/cuprorhodsite and alloys of Fe and Sn. The associated base metal sulfides are dominated by chalcopyrite, pentlandite, but also pyrite and subordinate millerite/violarite. Associated silicates are mainly primary magmatic orthopyroxene and plagioclase. The second assemblage is rich in platinum group element-sulfarsenides and -arsenides and -alloys of Sb and Bi, which are associated with a base metal sulfide assemblage dominated by pentlandite and Co-rich pentlandite. Silicates in this assemblage are marked by an abundance of alteration minerals, such as talc, serpentine and/or carbonates, which are closely associated with the platinum group minerals. Geostatistical evaluation reveals that these two mineral assemblages are not attributable to the origin of samples from different chromitite seams, but document the effects of pervasive hydrothermal alteration. Alteration evidently had similar effects on the different chromitite seams. Occurrence and distribution of these two characteristic assemblages has important implications for beneficiation. Assemblages rich in platinum group element-sulfides associated with base metal sulfides are known to respond well to flotation, different to alteration assemblages rich in arsenides and alloys. The nature of the gangue minerals will also impact platinum group mineral recovery as high phyllosilicate abundances, such as those noted in the alteration assemblage may cause problems during flotation and lead to poor recoveries.
Keywords: EPMA, SEM-based image analysis, ANOVA, Cluster Analysis, PGM, Thaba Mine

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  • Secondary publication expected from 01.09.2019

Publ.-Id: 25594 - Permalink


New solar-selective CSP receiver coatings studied by environmental in situ methods
Krause, M.; Wenisch, R.; Heras, I.; Lungwitz, F.; Janke, D.; Guillén, E.; Erbe, A.; Gemming, S.; Escobar Galindo, R.;
The development of solar-selective CSP receiver coatings with high-temperature and environmental stability requires new concepts of design and in operando monitoring. Solar receiver tubes are a key component of solar thermal power plants. The increase of their operation temperature from today’s maximum of 550°C to about 800°C could increase the CSP efficiency by approximately 15 to 20% and improve the competiveness of this technology compared to other ones of carbon-free electricity generation. Potential alternatives to fast degrading state-of-the-art pigment paint receiver tube coatings are based on refractive metal carbides, nitrides, and oxides because of their high thermal stability and oxidation resistance. New types of solar-selective coatings were studied in situ at temperatures of up to 830°C by Rutherford backscattering spectrometry, Raman spectroscopy, and spectroscopic ellipsometry within a cluster tool. They include carbon- and oxynitride-absorber based multilayers as well as a solarselective transmitter based on a transparent conductive oxide.

Financial support by the EU, grant No. 645725, project FRIENDS2, and the HGF via the W3 program (S.G.) is gratefully acknowledged.
Keywords: Concentrated solar power, in situ analysis, cluster tool, solar-selective coatings
  • Invited lecture (Conferences)
    12th Pacific Rim Conference on Ceramic and Glass Technology including Glass & Optical Materials Division Meeting 2017, 21.-26.05.2017, Waikoloa, USA

Publ.-Id: 25592 - Permalink


Design of Solar Selective Coatings Based on Aluminium Titanium AlTi(OxN1-x) Oxynitrides for High-Temperature CSP Applications
Heras, I.; Krause, M.; Lungwitz, F.; Rincon, G.; Alcon-Camas, M.; Azkona, I.; Guillén, E.; Escobar-Galindo, R.;
Aluminium titanium oxynitrides were studied as candidate materials for high temperature solar-selective coatings due to their excellent stability and their tuneable optical behaviour. A set of individual AlyTi1-y(OxN1-x) layers with different oxygen content was prepared by cathodic vacuum arc (CVA) deposition. The composition, morphology, phase structure and microstructure of the films were characterized by elastic recoil detection (ERD), scanning and transmission electron microscopy and X-ray diffraction.
Keywords: Concentrated solar power, solar-selective coatings, optical simulation
  • Lecture (Conference)
    2017 MRS Spring Meeting & Exhibit, 17.-21.04.2017, Phoenix, USA

Publ.-Id: 25591 - Permalink


Verlängerte Hirnmetastasenkontrolle bei geringer Toxizität nach einer Radiatio (SRS/WBR) in Kombination mit einer Systemtherapie bei zerebral metastasierten Melanompatienten
Rauschenberg, R.; Bruns, J.; Daubner, D.; Garzarolli, M.; Beissert, S.; Linn, J.; Troost, E. G. C.; Meier, F.;
Das mediane Überleben von Patienten mit Hirnmetastasen des malignen Melanoms beträgt ohne Therapie 2 Monate [1]. Neben etablierten lokalen Behandlungsmodalitäten wie der Resektion, stereotaktischen Radiatio (SRS) oder Ganzhirnbestrahlung (WBR) stehen innovative Immuntherapien (CTLA-4- und PD-1-Antikörper) und zielgerichtete Behandlungen (BRAF- +/- MEK-Inhibitoren) zur Verfügung. Prospektive Studiendaten zur Wirksamkeit und Toxizität der Kombination dieser Systemtherapien mit einer Bestrahlung stehen aus.
Wir führten eine retrospektive Datenanalyse der im Zeitraum von März 2014 bis März 2016 im Universitätsklinikum Dresden behandelten Melanompatienten mit Hirnmetastasen durch, die eine zerebrale Bestrahlung und bis zu 5 Wochen davor, danach oder währenddessen eine der oben genannten Systemtherapien erhalten hatten. Ein klinisches Follow-Up wurde monatlich durchgeführt – zusätzlich zum vierteljährlichen Staging (Schädel-MRT/CT). Eine detaillierte neuroradiologische Auswertung erfolgte. Primäre Endpunkte der Studie waren Toxizität, Hirnmetastasenkontrolle und Gesamtüberleben.
Insgesamt erhielten 22 Patienten mit zerebral metastasiertem Melanom eine SRS (10) oder WBR (12) plus 5 Wochen davor, danach oder währenddessen eine Systemtherapie mit BRAF-/MEK-Inhibitoren (5) oder CTLA-4-/PD-1-Antikörpern (17). Abgesehen von Übelkeit (1) wurden keine CTCAE-Grad 3/4-Nebenwirkungen der Bestrahlung beobachtet. Insbesondere die Rate an Radionekrosen und Einblutungen war nach Kombinationstherapie im Vergleich zur alleinigen SRS nicht erhöht. 6 Monate nach der Radiatio waren bei 75 % (SRS) beziehungsweise 70 % der Patienten (WBR) keine neuen Hirnmetastasen aufgetreten. Kaplan-Meier-Schätzungen ergaben ein medianes Gesamtüberleben mit Hirnmetastasen von 20 (SRS) respektive 14 Monaten (WBR).
Die Kombination einer zerebralen Bestrahlung mit einer Systemtherapie wurde gut toleriert. Die retrospektiven Daten sprechen für eine Verlängerung der Hirnmetastasenkontrolle sowie des Überlebens und propagieren prospektive Studien. Aktuell wird die retrospektive Analyse in 15 weiteren deutschen Hauttumorzentren durchgeführt.
[1] Fife KM et al (2004) Determinants of outcome in melanoma patients with cerebral metastases. J Clin Oncol 22(7):1293-1300
Keywords: SRS, WBRT, CTLA-4, PD-1
  • Contribution to proceedings
    27. Deutschen Hautkrebskongress, 21.-23.09.2017, Mainz, Deutschland
    Journal der Deutschen Dermatologischen Gesellschaft 15, Suppl. 3, 11-12

Publ.-Id: 25590 - Permalink


Visual observation and charge/discharge behavior of liquid metal cells
Nimtz, M.; Landgraf, S.;
Over the last years, several experiments on liquid metal battery (LMB) materials and different electrode and electrolyte systems were performed at HZDR. The presentation will give an overview on experimental equipment and setup, preparation steps of cell and container materials and cell charge/discharge behaviour. Main focus lies on the visual observation of several chemical incompatibilities and/or mechanical processes in LMB cells and liquid metal - molten salt - container material systems.
Keywords: liquid metal battery, molten salts
  • Lecture (Conference)
    International Workshop on Liquid Metal Battery Fluid Dynamics (LMBFD2017), 16.-17.05.2017, Dresden, Deutschland

Publ.-Id: 25589 - Permalink


X-Ray Diffraction and X-Ray Spectroscopy Studies of Cobalt-Doped Anatase TiO2:Co Nanopowders
Mesilov, V. V.; Galakhov, V. R.; Gubkin, A. F.; Sherstobitova, E. A.; Zakharova, G. S.; Uimin, M. A.; Yermakov, A. E.; Kvashnina, K. O.; Smirnov, D. A.;
Cobalt-doped anatase Ti0.97Co0.03O2 nanopowders with a particle size of about 100 °A were produced by a microwave-hydrothermal method. The obtained samples were characterized by means of X-ray diffraction, X-ray absorption (Ti L2,3, Co L2,3, and Co K), and 1s3p resonant inelastic X-ray scattering spectroscopies. Co2+ ions tetrahedrally coordinated by oxygen ions in nanoparticles were found to be located on the surface of agglomerates. Titanium ions were found to be in a tetravalent state (Ti4+). All the samples before the thermal treatment contain an amorphous phase of titanium dioxide on the surface. After annealing in vacuum or hydrogen anatase structure of Ti0.97Co0.03O2 remains and the amorphous phase disappears. Annealing the samples in vacuum or hydrogen leads to clustering metal cobalt at the particles from the bulk of agglomerates.

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Publ.-Id: 25588 - Permalink


Experimental determination of gold speciation in sulfide-rich hydrothermal fluids from reduced to oxidized
Trigub, A. L.; Tagirov, B. R.; Kvashnina, K. O.; Lafuerza, S.; Filmonova, O. N.; Nickolsky, M. S.;
The oxidation state of hydrothermal fluids, which form economic deposits of noble metals, varies in wide limits – from oxidized ones typical for porphyry mineralization to reduced which formed volcanogenic massive sulfide deposits. Sulfur-bearing species, along with chloride, are the most important ligands that form stable aqueous complexes with Au and determine Au concentration in natural ore-generating fluids. Depending on the f(O2) value, in high-temperature fluids (t > 300 °C) the dominant forms of sulfur are sulfides (H2S, HS-), sulfites (SO2, HSO3-, SO32-), sulfates (HSO4-, SO42-), and the radical species (S3-). Here we report an investigation of Au complexation in high-temperature sulfide-bearing fluids of contrasting oxidation states. The solubility of Au was measured in “oxidized” sulfide fluid (H2S/SO42- buffer controls the Red/Ox state) at 450 °C, 1000 bar, and compared with the Au solubility in “reduced” sulfide systems (H2S/HS- predominate) reported in the literature. The measured values of the Au solubility matches best the model of the formation of Au(HS)2- at near-neutral to weakly acidic pH, and AuHS° in acidic solutions. The solubility constants have been determined for the reactions,
Au(cr) + H2S°(aq) + HS- = Au(HS)2- + 0.5 H2(g) log KAu(HS)2- = -0.9 ± 0.1 ,
Au(cr) + H2S°(aq) = AuHS°(aq) + 0.5 H2(g) log KAuHS = -6.5 ± 0.1 .
The average value of log KAu(HS)2- = -1.3 ± 0.5 was calculated for 450 °C (P = 500 – 1500 bar) using all the available Au solubility constants obtained in both “reduced” and “oxidized” sulfide systems. The local atomic environment of Au in high-temperature hydrothermal fluids has been studied using X-ray absorption fine structure spectroscopy (XAFS) in high energy resolution fluorescence detection (HERFD) mode in combination with ab initio molecular dynamics (AIMD) and Reverse Monte Carlo (RMC) simulations. Interpretation of Au L3-edge EXAFS spectra showed that, independently of the Red/Ox (sulfide or sulfide/sulfate systems) and PT – conditions (350 – 450 °C, 500 bar) two S atoms are located in the first coordination shell of Au at 2.29±0.02Å. Comparison of the experimental spectra with those simulated by means of AIMD revealed that EXAFS spectroscopy is not sensitive to the presence of light atoms like S in a distant coordination shell of Au. However, theoretical calculations indicated that the shape of Au L3-edge HERFD-XANES spectra depends upon the composition of the distant coordination shell and, therefore, can be used to discriminate between Au(HS)2-, Au-(HS)-S3- and, probably, other complexes with distant-coordination-shell anions. Experimental Au L3-edge HERFD-XANES spectra are identical for all studied PT- and Red/Ox-parameters. These results allowed us to conclude that Au(HS)2- complex predominates Au speciation in weakly acidic to weakly alkaline pH independently from the oxidation state of the fluid. Besides that, XAFS experiment demonstrated that the formation of mixed Au-HS-Cl complex can be neglected. With increasing pressure (to nkbar) or decreasing temperature (to < 300 °C), due to increasing of concentration of S species in intermediate oxidation states, formation of the Au-HS complexes can be accompanied by the formation of other species with (hydro)sulfite, thiosulfate, (hydro)polysulfide, and sulfur radicals, which would enhance the hydrothermal Au mobility. Stability of these complexes needs further experimental and theoretical examination.
Keywords: gold, solubility, hydrothermal fluids, hydrosulfide complexes, stability constants, X-ray absorption spectroscopy, HERFD-XAS, ab initio molecular dynamics

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Publ.-Id: 25587 - Permalink


Indium-bearing sulphides from the Hämmerlein skarn deposit, Erzgebirge, Germany - Evidence for late stage diffusion of indium into sphalerite
Bauer, M. E.; Seifert, T.; Burisch, M.; Krause, J.; Richter, N.; Gutzmer, J.;
At the Hämmerlein skarn deposit, located in the Western Erzgebirge (Germany), a major cassiterite-dominated Sn mineralization stage is spatially associated with a younger Zn-Cu-In sulphide mineralization stage. In this contribution, we provide the first detailed description of the Zn-Cu-In sulphide mineralization stage, based on field geological observations combined with detailed petrographic studies and electron probe micro analysis data. Indium-rich sulphide mineralization occurs as irregular, semi-massive lenses or as infill of short, discontinuous veinlets that crosscut the cassiterite-bearing skarn assemblage. Indium-and Cu-rich sphalerite and roquesite are found to be closely associated with In-bearing chalcopyrite. The highest In concentrations occur at rims and along cracks of sphalerite grains. The distribution resembles diffusion profiles, suggesting that In enrichment is due to an hydrothermal overprint that postdates the initial formation of both sphalerite and chalcopyrite. Textural relations illustrate that the diffusion fronts in sphalerite grains are thicker where they are in contact to anhedral masses of hematite and magnetite. Our observations suggest that indium enrichment in sphalerite at the Hämmerlein skarn deposit is due to the decomposition of In-bearing chalcopyrite. The resultant release of Fe led to the formation of hematite and magnetite, whereas Cu and In were incorporated into sphalerite along grain boundaries and micro-fractures. Incorporation into the sphalerite lattice took place by coupled substitution of Cu+ + In3+ ↔ 2 Zn2+, suggesting that the concurrent availability of Cu and In may be an essential factor to enrich In in sphalerite in hydrothermal ore-forming environments.
Keywords: Indium, sphalerite group minerals, chalcopyrite, roquesite, diffusion, skarn

Publ.-Id: 25586 - Permalink


Efficient Correlation-Free Many-States Lattice Monte Carlo on GPUs
Kelling, J.; Ódor, G.; Weigel, M.; Gemming, S.;
We'll present a method for highly efficient lattice Monte Carlo simulations with correlation-free updates. Achieving freedom from erroneous correlations requires random selection of lattice sites for updates, which must be restricted by suitable domain decomposition to create parallelism. While approaches based on caching limit the number of allowed states, the multisurface-type approach presented here allows arbitrarily complex states. The effectiveness of the method is illustrated in the fact that it allowed us to solve a long-standing dispute around surface growth under random kinetic deposition in the KPZ-universality class. The method has also been applied to Potts models and is suitable for spin-glass simulations, such as those required to test quantum annealers, like D-Wave.
Keywords: Lattice Monte Carlo, GPU, Surface Growth, Kardar-Parisi-Zhang

Publ.-Id: 25585 - Permalink


Classification at 10Hz: Protecting High-Power Lasers with Deep Learning
Kelling, J.; Gebhardt, R.; Helbig, U.; Bock, S.; Schramm, U.; Juckeland, G.;
In this talk we present our approach to automatic detection of critical failure states in pulsed Petawatt laser systems, used for investigations of exotic states of matter and medical applications. The beam shape is controlled to avoid high destructive energy densities. However, randomly occurring states threatening the device must be detected between pulses and trigger an interlock in the device firing at 10Hz.

Our automation approach, presented here, uses deep learning via the Caffe framework. The states we are aiming to detect are rare; thus, training data for this category is scarce. We address this by identifying regions of interest based on physical properties of the system.
Keywords: image classification, deep learning, smart laser operation, OpenCV
  • Lecture (Conference)
    Minds Mastering Machines [M³], 09.-11.10.2017, London, United Kingdom

Publ.-Id: 25584 - Permalink


Strahlenbiologische Experimente im Experimentalraum der Universitäts Protonentherapie Dresden
Beyreuther, E.ORC
No Abstract available
  • Invited lecture (Conferences)
    Seminar Nuklearmedizin, Medizinische Fakultät Carl Gustav Carus, TU Dresden, 30.05.2017, Dresden, Deutschland

Publ.-Id: 25582 - Permalink


Radiation dose rate: a factor of importance in laser-radiooncology?
Beyreuther, E.ORC
no abstract available
  • Invited lecture (Conferences)
    Preparation of scientific collaborations on medical applications with laser plasma accelerators, 09.05.2017, Berlin, Deutschland

Publ.-Id: 25581 - Permalink


Experimental animal models for radiobiological studies with low penetrating beams
Beyreuther, E.ORC; Brüchner, K.; Hideghety, K.; Karsch, L.; Krause, M.; Leßmann, E.; Schmidt, M.; Schürer, M.; Szabo, R.; Pawelke, J.
The development of new radiotherapeutic approaches is a long-time process where the general concept should be proven from time to time even though clinical requirements, i.e. on particle energy, are not yet fulfilled. Examples are laser accelerated particle beams, which are promised to replace classical ion radiotherapy, and proton and X-ray micro beams. For these low penetrating beams in vivo models are required that allow for full penetration, e.g. by ~25 MeV proton beams with a penetration depth of ~4 mm, currently available at laser driven accelerators. As the standard tumour model on mice leg cannot be applied for this purpose a new small animal tumour model on mice ear was established for the investigation of tumour response, whereas for the study of normal tissue toxicity Zebrafish embryos were applied.

For the mouse ear tumour model, human tumour cells of three different entities (HNSCC FaDu, LN229 glioblastoma, A549 adenocarcinoma) were injected subcutaneously in the right ear of NMRI nude mice and growing tumours were characterized with respect to growth parameters, histology and 200 kV X-ray dose dependent tumour growth delay. Histological analyses reveal bordered tumours at treatment size (~10 mm³) that interact with the surrounding tissue and activate endothelial cells to form vessels. By X-ray treatment optimised dose ranges for inducing tumour growth delay but not tumour control were determined and a full scale radiobiological experiment at a clinical and a laser-accelerator was performed with FaDu tumours.

In order to quantify the normal tissue toxicity after irradiation with low energy beams wildtype Zebrafish embryos were applied whose size of ~1 mm allow for the full penetration, e.g. by ~10 MeV proton beams. Measurements of the radiobiological response to high (150 MeV) and low energy protons from a conventional therapy facility provide comparative data on survival and immune response for further studies with laser driven beams.

The results obtained during the establishment of the mouse ear tumour model and the Zebrafish embryo normal tissue model will be presented together with first findings of experiments with conventional and laser driven particle beams.

Acknowledgement: The work was supported by German BMBF, grant nos. 03ZIK445 and 03Z1N511 and ELI-ALPS project (GINOP-2.3.6-15-2015-00001).
  • Contribution to proceedings
    63rd Annual Radiation Research Society Meeting, 15.-18.10.2017, Cancun, Mexico
    Proceedings of the 63rd Annual Radiation Research Society Meeting

Publ.-Id: 25580 - Permalink


Interaction between magnetic moments and itinerant carriers in d0 ferromagnetic SiC
Liu, Y.; Yuan, Y.; Liu, F.; Böttger, R.; Anwand, W.; Wang, Y.; Semisalova, A.; Ponomaryov, A.; Lu, X.; N’Diaye, A. T.; Arenholz, E.; Heera, V.; Skorupa, W.; Helm, M.; Zhou, S.ORC
Elucidating the interaction between magnetic moments and itinerant carriers is an important step to spintronic applications. Here, we investigate magnetic and transport properties in d0 ferromagnetic SiC single crystals prepared by postimplantation pulsed laser annealing. Magnetic moments are contributed by the p states of carbon atoms, but their magnetic circular dichroism is different from that in semi-insulating SiC samples. The anomalous Hall effect and negative magnetoresistance indicate the influence of d0 spin order on free carriers. The ferromagnetism is relatively weak in N-implanted SiC compared with that in Al-implanted SiC after annealing. The results suggest that d0 magnetic moments and itinerant carriers can interact with each other, which will facilitate the development of SiC spintronic devices with d0 ferromagnetism.

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Publ.-Id: 25579 - Permalink


Current-driven flow in a liquid-metal-battery-like geometry
Starace, M.; Weber, N.; Weier, T.; Ashour, R.; Kelley, D.; Salas, A.;
Introduction
Fluid flow can be both a boon and a curse for liquid metal batteries. One one hand, it may promote mixing of the anode metal into the cathode, preventing it from lingering on the electrolyte-cathode interface. On the other hand, it could momentarily displace part of the electrolyte layer and thus cause a short circuit. The experiment presented here consists of a cylindrical container filled with GaInSn bounded by copper current collectors on the top and bottom, which are attached a power supply unit. The current collector is electrically insulated except for a circular surface whose area is 100 times smaller than that of the bottom current collector. This geometry emulates that of a battery whose cathode consists of a liquid metal drop attached to the top current collector dipped into the electrolyte layer while the anode extends throughout the bottom part of the container. An ultrasound Doppler array was used to perform velocimetry measurements of the electro-vortex flow perpendicularly to the cylindrical axis. In addition, the fluid flow of this setup was also simulated numerically.

Results
While currents ranging from 10 A to 100 A are supplied to the system, the flow pattern appears to consists of multiple stationary swirls, which is in general agreement with numerical results. Additional UDV measurements that are parallel to the cylindrical axis will be performed to obtain a better understanding of the flow structure.

Fig. 1: Velocity profile of the electro-vortex experiment while 100 A are flowing through it. The ultrasound transducers in the array are arranged along the height of the cylinder on the left hand side and measure the radial component of the velocity within one plane.
Keywords: liquid metal battery, electro-vortex flow, ultrasound Doppler velocimetry.
  • Lecture (Conference)
    International workshop on liquid metal battery fluid dynamics (LMBFD 2017), 16.-17.05.2017, Dresden, Deutschland

Publ.-Id: 25578 - Permalink


Liquid metal batteries: activities at the Helmholtz-Zentrum Dresden - Rossendorf
Weier, T.; Galindo, V.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Salas, A.; Starace, M.; Stefani, F.; Weber, N.;
The talk will provide an overview of the liquid metal battery (LMB) related activities at Helmholtz-Zentrum Dresden - Rossendorf (HZDR) with a focus on magnetohydrodynamic aspects of future large scale LMBs. High current densities in the range of 4 up to 130 kA/m-2, as typical for LMBs, together with cells of large cross section will result in substantial currents accompanied by considerable magnetic fields. Thus electromagnetically driven flows and instabilities should be of concern for large enough installations, especially when the thin electrolyte layers necessitated by the limited open circuit voltages are taken into account. Beneficial effects of mild electromagnetically driven flows are to be expected for the cathodes were mixing should improve cell performance.

The Tayler instability (TI) can be understood as a generic case of a current driven instability under perfectly uniform current, i.e., ideal conditions. In this sense it constitutes sort of an upper bound for a current bearing fluid to remain at rest. Modifying the magnetic field distribution in the cell is an effective means to suppress the TI. Different field configurations to achieve TI suppression and their relative merits will be discussed and related to TI saturation mechanisms. Non-uniform current distributions are more typical for real settings. They give rise to rotational Lorentz force distributions and will thereby also generate electro-vortex flows (EVFs). In terms of LMBs the concrete shape of the current collectors plays a crucial role in whether EVFs exist and how they might interact with the TI. We will conclude with a discussion of electromagnetically exited interface instabilities quite similar to the sloshing modes known from aluminium reduction cells.
Keywords: liquid metal batteries, Tayler instability, electro-vortex flows, metal pad roll instability, sloshing
  • Lecture (Conference)
    International Workshop on Liquid Metal Battery Fluid Dynamics (LMBFD2017), 16.-17.05.2017, Dresden, Deutschland

Publ.-Id: 25577 - Permalink


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