Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35175 Publications

Where do the Actinides go? And why we should care…

Patzschke, M.

Understanding the chemistry of actinides is crucial for the safety guarantees required for final repositories for nuclear waste. Pathways of distribution of actinides in the environment are discussed and calculations on model compounds to understand the bonding of actinides are presented.

Keywords: DFT; Real space analysis; actinide compounds

  • Invited lecture (Conferences)
    X. MMQC Mariapfarr, 06.-10.03.2017, Mariapfarr, Österreich

Permalink: https://www.hzdr.de/publications/Publ-25703
Publ.-Id: 25703


Bond analysis of actinide complexes in real space

Patzschke, M.

Subtle effects are important in the bonding of actinides. Understanding of these effects is crucial for the prediction of the fate of actinides in the environment. In this talk we will focus on QTAIM, NCI and ELI calculations to understand the difference in bonding between actinides and lanthanides.

Keywords: DFT; CASPT2; Real space analysis; QTAIM; ELF/ELI; NCI; actinide complexes

  • Invited lecture (Conferences)
    UCT und IOCB Seminar Prag, 31.03.2017, Prag, Tschechien

Permalink: https://www.hzdr.de/publications/Publ-25702
Publ.-Id: 25702


Real Space Analysis of Ac-Ac bonds, the case of encaged U_2

Patzschke, M.

Real space analysis of the chemical bond is a valuable tool for understanding the bonding in chemical compounds. Especially in the field of actinide complexes and actinide-actinide bonds, there is still much to be learned. In this talk we will shoe how encaged uranium is forced to bond and how the bond depends on the cage size.

Keywords: Real Space Analysis; DFT; CASPT2; Actinides

  • Invited lecture (Conferences)
    Chemical Bonding in Position Space, 27.11.-01.12.2016, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25701
Publ.-Id: 25701


Technetium Complexes with Arylselenolato and Aryltellurolato Ligands

Noschang Cabral, B.; Kirsten, L.; Hagenbach, A.; Piquini, P. C.; Patzschke, M.; Schulz Lang, E.; Abram, U.

Reactions of (NBu4)[TcOCl4] or [TcCl3(PPh3)2(CH3CN)] with in situ-prepared lithium arylselenolates and -tellurolates
give (NBu4)[TcVO(ArE)4] (E = Se, Te; Ar = phenyl) and [TcIII(ArE)3(PPh3)(CH3CN)] (E = Se, Te; Ar = phenyl, 2,6-Me2phenyl,
mesityl) complexes, respectively. The products contain square-pyramidal (TcV compounds) and trigonal bipyramidal (TcIII
complexes) coordinated technetium atoms. Density Functional Theory calculations indicate that the Tc-chalcogen bonds in
the TcIII compounds have greater bond order than in the TcV compounds.

Keywords: Technetium; new compounds; crystal structure; DFT; bond analysis

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Permalink: https://www.hzdr.de/publications/Publ-25700
Publ.-Id: 25700


Towards direct access to THz-driven transient electronic states with time-resolved ARPES

Deinert, J.-C.; Green, B. W.; Kovalev, S.; Stähler, J.; 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 time- and angleresolved photoelectron spectroscopy (tr-ARPES). This challenging combination of two state-of-the-art techniques promises new insights into highly relevant non-equilibrium processes in matter, since 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. Until now, the corresponding changes to the electronic structure of a material can be probed only indirectly, e.g., by measuring the material's optical properties. The obvious method – tr-ARPES – which gives direct access to the electronic states on a femtosecond timescale (cf. Fig. 1) has not been implemented due to the previously unaccomplishable high duty cycle of the THz source (>> 10 kHz repetition rate quasi-cw) to provide sufficient statistics for tr-ARPES. This limitation is overcome at the TELBE which provides 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 [3]. 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 (see, e.g., [2]). This contribution is discussing the challenges and the opportunities of tr-ARPES in THz control experiments and will outline the current design of the planned tr-ARPES endstation.
[1] B. Green et al., Sci. Rep. 6 (2016), 22256.
[2] U. Fruehling et al., Nat. Phot.. 3 (2009), 523.
[3] see poster presentation of S. Kovalev

  • Poster
    Optical Terahertz Science and Technology, 06.04.2017, London, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-25699
Publ.-Id: 25699


Evaluation of Motion Mitigation using Abdominal Compression in the Clinical Implementation of Pencil Beam Scanning Proton Therapy of Liver Tumors

Lin, L.; Souris, K.; Kang, M.; Glick, A.; Lin, H.; Huang, S.; Stützer, K.; Janssens, G.; Sterpin, E.; Lee, J. A.; Solberg, T. D.; Mcdonough, J. E.; Simone Ii, C. B.; Ben-Josef, E.

Purpose: To determine whether individual liver tumor patients can be safely treated with pencil beam scanning proton therapy. This study reports a planning preparation workflow that can be used for beam angle selection and the evaluation of the efficacy of abdominal compression (AC) to mitigate motion.

Methods: Four-dimensional computed tomography scans (4DCT) with and without AC were available from 10 liver tumor patients with fluoroscopy-proven motion reduction by AC. For each scan, the motion amplitudes and the motion-induced variation of water equivalent thickness (ΔWET) in each voxel of the target volume were evaluated during treatment plan preparation. Optimal proton beam angles were selected after volume analysis of the respective beam-specific planning target volume (BSPTV). M₈₀ and ΔWET₈₀ derived from the 80ᵗʰ percentiles of motion amplitude (M) and ΔWET were compared with and without AC. Proton plans were created on the average CT. 4D dynamic dose calculation was performed post plan by synchronizing proton beam delivery timing patterns to the 4DCT phases to assess interplay and fractionation effects, and to determine motion criteria for subsequent patient treatment.

Results: AC resulted in reductions in mean Liver-GTV dose, M, ΔWET, and BSPTV volumes and improved dose degradation (ΔD₉₅ and ΔD₁) within the CTV. For small motion (M₈₀ < 7 mm and ΔWET₈₀ < 5 mm), motion mitigation was not needed. For moderate motion (M₈₀ 7-10 mm or ΔWET₈₀ 5-7 mm), AC produced a modest improvement. For large motion (M₈₀ > 10 mm or ΔWET₈₀ > 7 mm), AC and/or some other form of mitigation strategies were required.

Conclusion: A workflow for screening patients’ motion characteristics and optimizing beam angle selection was established for the pencil beam scanning proton therapy treatment of liver tumors. Abdominal compression was found to be useful at mitigation of moderate and large motion.

  • Poster
    AAPM 59th Annual Meeting & Exhibition, 30.07.-03.08.2017, Denver, Colorado, United States of America

Permalink: https://www.hzdr.de/publications/Publ-25698
Publ.-Id: 25698


Local aspects of hydrogen-induced metallization of the ZnO(10-10) surface

Deinert, J.-C.; Hofmann, O. T.; Meyer, M.; Rinke, P.; Stähler, J.

This study combines surface-sensitive photoemission experiments with density functional theory to give a microscopic description of H-adsorption-induced modifications of the ZnO(10-10) surface electronic structure. We find a complex adsorption behavior caused by a strong coverage dependence of the H adsorption energies: Initially, O-H bond formation is energetically favorable and H acting as an electron donor leads to the formation of a charge accumulation layer and to surface metallization. The increase of the number of O-H bonds leads to a reversal in adsorption energies such that Zn-H bonds become favored at sites close to existing O-H bonds, which results in a gradual extenuation of the metallization. The corresponding surface potential changes are localized within a few nanometers both laterally and normal to the surface. This localized character is experimentally corroborated by using subsurface bound excitons at the ZnO(10-10) surface as a local probe. The pronounced and comparably localized effect of small amounts of hydrogen at this surface strongly suggests metallic character of ZnO surfaces under technologically relevant conditions and may, thus, be of high importance for energy level alignment at ZnO-based junctions in general.

Permalink: https://www.hzdr.de/publications/Publ-25697
Publ.-Id: 25697


Nanoscale Potential Fluctuations in Zirconium Oxide and the Flash Memory Based on Such Fluctuations

Gritsenko, V. A.; Perevalov, T. V.; Kruchinin, V. N.; Aliev, V. S.; Gerasimova, A. K.; Erenburg, S. B.; Trubina, S. V.; Kvashnina, K. O.; Prosvirin, I. P.

X-ray photoelectron spectroscopy, EXAFS, XANES, spectral ellipsometry and quantum-chemistry calculations were used to examine the atomic and electronic structure of non-stoichiometric amorphous ZrOx slightly enriched with zirconium. The experimental data show that the ZrOx material consists of stoichiometric ZrO2, metallic Zr and zirconium suboxides ZrOy. The structure of ZrOx is analyzed using the Random Bonding and Random Mixture models. A model of nanoscale spatial potential fluctuations in ZrOx is substantiated. In this model, the potential fluctuations for electrons and holes arise due to the local fluctuations of bandgap energy in the range from 0 to 5.4 eV. A ZrOx-based flash memory element with giant retention time is proposed

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Permalink: https://www.hzdr.de/publications/Publ-25696
Publ.-Id: 25696


The first six to eight years of DREAMS (DREsden Accelerator Mass Spectrometry): On our way to cloud nine?

Merchel, S.; Rugel, G.; Scharf, A.; Ziegenrücker, R.; DREAMS-Users; DREAMS-Friends

Since 2009, the DREAMS (DREsden Accelerator Mass Spectrometry) facility offers users to do their own sample preparation for producing AMS-targets. Two years after the 6 MV-based tandem accelerator measured the first unknown samples for long-lived radionuclides [1]. AMS reduces background and interfering signals resulting from molecular ions and isobars enormously. Thus, AMS provides much lower detection limits compared to conventional MS or decay counting. DREAMS offers excellent measurement capabilities also for external users [2].
AMS allows thousands of exciting applications, especially within environmental and geosciences. In nature, the so-called cosmogenic nuclides (CNs) are products of nuclear reactions induced by primary and secondary cosmic rays. Hence, they can be found in extraterrestrial material such as meteorites - originating from the asteroid belt, the Moon or Mars - and lunar samples in higher concentrations (e.g. ~1010 10Be atoms/g or < 0.5 mBq/g). A combination of several CNs is used to reconstruct the exposure history of this unique material while in space (irradiation age) and on Earth (terrestrial age).
Though, in terrestrial material the concentrations are typically only on the order of 104-109 atoms/g (i.e. μBq/g - nBq/g) for 10Be produced in the Earth’s atmosphere, then transported to the surface and further absorbed and incorporated at and in e.g. sediments or ice. Some of the lowest 10Be concentrations (~103 atoms/g), produced in-situ by neutron- and muon-induced nuclear reactions from e.g. oxygen and silicon in quartz, can be found in samples taken from the Earth’s surface. The concentrations of atmospheric or in-situ produced CNs record information that is used to reconstruct sudden geomorphological events such as volcanic eruptions, rock avalanches, tsunamis, meteor impacts, earthquakes [e.g. 3] and glacier movements. These movements and data from ice cores give also hints for the reconstruction of historic climate changes and provide information for the validation of climate model predicting future changes. Slower processes such as sedimentation, river incision and erosion rates can also be investigated and indirect dating of bones as old as several Ma’s is possible. Finally, remnants of supernova-produced nuclides can also be found in deep-sea archives (sediment, crust, nodule) [e.g. 4].
Anthropogenic production e.g. by release from nuclear reprocessing, accidents and weapon tests led to increased radionuclide levels in surface water, ice and soil (36Cl, 129I,…). Hence, some nuclides can be used as tracers to follow pathways in oceanography, to date and identify sources of groundwater, to perform retrospective dosimetry and to study aspects in radioecology and pharmacology. Obviously, also nuclear installation materials are radioactive (36Cl, 41Ca,…).

References: [1] G. Rugel et al., Nucl. Instr. Meth. Phys. Res. B. 2016, 370,94. [2] www.hzdr.de/ibc for beam time application. [3] W. Schwanghart et al., Science 2016, 351,147. [4] A. Wallner et al., Nature 2016, 532, 69.

Keywords: AMS; radionuclide

  • Poster
    GDCh-Wissenschaftsforum Chemie 2017 ─ Jubiläumskongress "GDCh - 150 Jahre", Jahrestagung der Fachgruppe Nuklearchemie, 10.-14.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25694
Publ.-Id: 25694


Attempts to understand potential deficiencies in chemical procedures for accelerator mass spectrometry (AMS)

Merchel, S.; Gurlit, S.; Rugel, G.; Scharf, A.; DREAMS-Users; DREAMS-Friends

Since 2009, the DREAMS (DREsden Accelerator Mass Spectrometry) facility offers users to do their own sample preparation for producing AMS-targets. Several projects are aiming at analysing 10Be, 26Al, and 36Cl (as BeO, Al2O3, AgCl). In cooperation with other AMS-facilities, also actinides (coprecipitation as Fe2O3) and 60Fe (as Fe2O3) are investigated.
Hence, essential steps are hydroxide or AgCl precipitation. For the determination of in-situ or atmospheric 26Al in marine and terrestrial sediments, we had sometimes unaccountable low chemical yields, which might be explained by redissolving Al(OH)3 in the last washings. Thus, we investigated these potential losses by ICP-MS as a function of alteration (waiting) times. Indeed, up to 31% of the precipitated Al was redissolved by immediate triple washings. After 2 h of waiting, this could be reduced to 11%. Further waiting (over-night) resulted in losses of 6% of Al (equally for Be) only.
We also tested the behaviour of Fe(III), U(VI) (also as analogue for ~Pu(VI) and Np(VI)), and Er(III) (as analogue for Am(III), Cm(III), Pu(III)) when Fe(OH)3 is washed. Even including the supernatant, total losses of 3-times washing of over-night altered hydroxides are as low as 2.6-3.5%. Thus, repeated washing cycles are very advisable to reduce ions such as NH4 + and Cl- before drying and ignition.
For a single project, we explored the possibility to measure 36Cl and natCl by (isotope dilution) AMS in “dirty” permafrost ice wedge samples as heavy as 1.6 kg. The chemical yield of AgCl was only 20-35% and is a function of total natCl. Thus, we tested preconcentration steps like ion exchange (DOWEX 1x8, 5 ml), which look promising.
Very often DREAMS projects focus at analysing quartz for in-situ-produced 10Be and 26Al. Dissolving quartz only will minimise other troublesome elements such as Al, Be, and Ti from coexisting mineral phases. Obviously, low stable Al leads to higher 26Al/27Al, i.e. better 26Al-statistics. However, low Ti is also helpful for fewer problems in Be-chemistry, i.e. better 10Be-statistics. For correct calculation of exposure ages and erosion rates, “pure quartz”, i.e. similar target elements as the calibration site used for production rates and no natural 9Be, is needed, too. One of the earliest quartz cleaning methods is routinely used at DREAMS: H2SiF6/HCl on a shaker table at room temperature. It produces up to 1.8% residue of the original “quartz” mass with a mean maximum value of 0.6% (values from >100 samples from six different projects). SEM-EDX identified the most prominent minerals to be zircon Zr[SiO4], white sillimanite Al2[O|SiO4], transparent to blue kyanite Al2[O|SiO4], black chromite Fe2+Cr2O4, and orange rutile TiO2. For comparison, we treated 3.5 g of these residues by microwave (MW) digestion resulting in further dissolving 31% of the original residue. SEM-EDX analyses of the MW-residue showed mainly pristine kyanite and heavily-attacked sillimanite only. ICP-MS of the MW-solution validated the dissolution of Al, Ti, Cr, Fe, and Zr. For a typical 50 g-“quartz sample” the MW-method would add more than 3 mg of Ti, over 7 mg of Al and, and, worst of all, about 25 μg of Be to the sample.
Ackn.: Thanks to B. Bookhagen, A. Gärtner, T. Opel, P. Steier, F. Quinto & S. Weiss.

Keywords: AMS; sample preparation; exposure dating; erosion rate

  • Poster
    GDCh-Wissenschaftsforum Chemie 2017 ─ Jubiläumskongress "GDCh - 150 Jahre", Jahrestagung der Fachgruppe Nuklearchemie, 10.-14.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25693
Publ.-Id: 25693


Using cosmogenic 10Be surface exposure dating to constrain the timing of deglaciation on the northern Swiss Plateau

Groos, A. R.; Struck, J.; Wüthrich, L.; Veit, H.; Gnägi, C.; Merchel, S.; Scharf, A.; Rugel, G.; Zech, R.

Keywords: LGM; AMS; 10Be Surface Exposure Dating

  • Poster
    Annual CH-QUAT Meeting Faculty of Science, University of Neuchâtel Topic: "Quaternary topics in the Jura Mountains and the Seeland region", 01.04.2017, Neuchâtel, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-25692
Publ.-Id: 25692


Structural Distortions and Charge Density Waves in Iodine Chains Encapsulated inside Carbon Nanotubes

Komsa, H.-P.; Senga, R.; Suenaga, K.; Krasheninnikov, A. V.

Atomic chains are perfect systems for getting fundamental insights into the electron dynamics and coupling between the electronic and ionic degrees of freedom in one-dimensional metals. Depending on the band filling, they can exhibit Peierls instabilities (or charge density waves), where equally spaced chain of atoms with partially filled band is inherently unstable, exhibiting spontaneous distortion of the lattice that further leads to metal−insulator transition in the system. Here, using high-resolution scanning transmission electron microscopy, we directly image the atomic structures of a chain of iodine atoms confined inside carbon nanotubes. In addition to long equidistant chains, the ones consisting of iodine dimers and trimers were also observed, as well as transitions between them. First-principles calculations reproduce the experimentally observed bond lengths and lattice constants, showing that the ionic movement is largely unconstrained in the longitudinal direction, while naturally confined by the nanotube in the lateral directions. Moreover, the trimerized chain bears the hallmarks of a charge density wave. The transition is driven by changes in the charge transfer between the chain and the nanotube and is enabled by the charge compensation and additional screening provided by the nanotube.

Keywords: carbon nanotubes; Peierls instabilities; charge density waves; TEM; DFT

Permalink: https://www.hzdr.de/publications/Publ-25691
Publ.-Id: 25691


Revisiting hollandites: channels filling by main-group elements together with transition metals in Bi2-yVyV8O16

Lebedev, O. I.; Hébert, S.; Roddatis, V.; Martin, C.; Turner, S.; Krasheninnikov, A. V.; Grin, Y.; Maignan, A.

Starting from the nominal BixV8O16 formula, state-of-the-art transmission electron microscopy investigation has been made to propose the new chemical formula Bi2-yVyV8O16 for this hollandite structure. This results from the filling of the channels by main-group elements together with vanadium (V5+) species, with variable content of Bi and V inside the channels. The influence of the Bi content and of this local disorder on the magnetic and transport properties has been investigated in polycrystalline samples of BixV8O16 with nominal composition x = 1.6 and x = 1.8. The rather x-independent electrical resistivity (≈ 5 m·cm) and Seebeck coefficient at high T (-35 μV·K-1 at 900 K) is discussed in terms of an unchanged V oxidation state resulting from the filling-up of the wide channels with Bi and V. It is proposed that this local disorder hinders the charge/orbital setting below 60 K on the V ions of the V8O16 framework. Hollandites exhibit complex electronic and magnetic properties with potential applications in the field of batteries, photocatalysis or nuclear waste storage, and these results show that a careful and detailed investigation of the nature and content of the cations inside the channels is crucial to better understand the doping and disorder impact on their properties.

Keywords: hollandites; defects; TEM; DFT calculations

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Permalink: https://www.hzdr.de/publications/Publ-25690
Publ.-Id: 25690


Microbial transformation of bentonite

Matschiavelli, N.; Steglich, J.; Kluge, S.; Cherkouk, A.

For the storage of highly radioactive waste in a deep geological repository a multi-barrier concept is favoured, which combines a technical barrier (canister including the highly radioactive waste), 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. 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, which contain 20g Bentonite and 40ml anaerobic synthetic Opalinus-clay-pore water solution under an N2/CO2-gas-atmosphere. Substrates like acetate and lactate were supplemented to stimulate potential microbial activity. Microcosms were incubated in the dark, without shaking at 30°C. Within an indefinite time scale 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. First results show that bentonites represent a source for microbial life, demonstrated by the consumption of lactate and the formation of acetate and pyruvate. Furthermore, microbial iron-reduction was determined. The results reveal the importance of the selection of the best suitable Bentonite in order to avoid transformation of the mineral structure by indigenous microbes.

  • Poster
    16th International Clay Conference - Clays, from the oceans to space - Granada 17-21 July 2017, 17.-21.07.2017, Granada, Spain

Permalink: https://www.hzdr.de/publications/Publ-25689
Publ.-Id: 25689


Interactions of an extremely halophilic archaeon relevant in nuclear waste repositories in rock salt with uranium

Bader, M.; Swanson, J.; Foerstendorf, H.; Müller, K.; Steudtner, R.; Drobot, B.; Schmidt, M.; Cherkouk, A.

Rock salt is a potential host rock for the final storage of radioactive waste in a deep geological formation. Indigenous microorganisms and their interactions with radionuclides must be considered for the safety performance of the repository, considering the worst case scenario, the release and subsequent migration of radionuclides. Therefore, the extremely halophilic microorganism Halobacterium noricense DSM 15987T, which occurs naturally in the potential host formation rock salt, was used to study its interactions with uranium.
A time-dependent sorption experiment showed that bioassociation of uranium onto cells of H. noricense DSM 15987T is not only a sorption process; i.e. fast sorption within the first hours until reaching a stable equilibrium state. The obtained kinetic data showed a multistage process with fast sorption during the first two hours of exposure time. Over the next hours, an increasing amount of uranium was detectable in the supernatant, implying that the uranium already sorbed was again released from the cells. Subsequently, the amount of bioassociated uranium increased very slowly until a maximum sorption of 80% was reached after 48 h. To investigate this multistage bioassociation process on archaeal cells in detail several spectroscopic as well as microscopic methods were applied. With in situ attenuated total reflection fourier-transform infrared spectroscopy the initial sorption process of uranium to cells of H. noricense DSM 15987T within the first two hours was proven. Results showed that the radionuclide binds to carboxylic as well as to phosphate groups simultaneously within the first two hours of incubation time. Additionally, cryo time-resolved laser-induced fluorescence spectroscopic investigations were performed, which showed the involvement of polynuclear carboxylate species and the presence of a meta-autunite like mineral. By using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, uranium could be localized on the cell surface of the halophilic archaeon within the first sorption phase and later in the biomineral-like agglomerates. Hence, our study showed that uranium can be immobilized by halophilic archaea via biomineralization and bioassociation, which might influence the further migration of the actinide.

  • Poster
    GDCh-Wissenschaftsforum Chemie 2017 Interdisziplinäre Symposien Jahrestagung Nuklearchemie, 10.-14.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25688
Publ.-Id: 25688


Beyond Electrodynamics with PIConGPU: Performance Portable, Open Multi-Physics HPC Simulations for Laser-Plasma Experiments at the European XFEL

Huebl, A.; Widera, R.; Pausch, R.; Garten, M.; Burau, H.; Kluge, T.; Vorberger, J.; Debus, A.; Cowan, T. E.; Schramm, U.; Chung, H.-K.; Bussmann, M.

PIConGPU is reportedly the fastest electro-magnetic particle-in-cell code in the world in terms of sustained Flop/s. Its computational power does not only enable 3D3V simulations with unprecedented detail and fast time-to-solution but also allows improving predictive capabilities of simulations by estimating stochastic and systematic errors via repeated simulations. Synthetic in-situ diagnostics drive the exploration of high-detail simulations whose signatures, e.g. emitted radiation spectra, would be inaccessible in post-processing due to sheer data size. Upcoming experiments at the European XFEL require us to take PIConGPU even one step further: modeling XFEL-matter interaction on top of laser-driven particle acceleration processes requires the introduction of non-trivial X-ray photon scattering, photon generation and advanced non-LTE atomic models. Coupled with an open-science centered strategy, from open performance portable source code over open standardized data formats to documented workflows for PByte scale simulation we strive towards a new quality of predictive, reproducible simulations within our community.

Keywords: PIC GPU XFEL Modeling HPC laser-plasma LPA pump-probe HED IO OpenSource OpenData OpenScience

  • Invited lecture (Conferences)
    Platform for Advanced Scientific Computing (PASC) Conference 2017, 26.-28.06.2017, Lugano, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-25687
Publ.-Id: 25687


Open Science with openPMD

Huebl, A.; Lehe, R.; Vay, J.-L.; Grote, D. P.; Sbalzarini, I. F.; Kuschel, S.; Bussmann, M.

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

Permalink: https://www.hzdr.de/publications/Publ-25686
Publ.-Id: 25686


Data Management in Small Animal Imaging: Conceptual and Technical Considerations

Maus, J.; 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

Permalink: https://www.hzdr.de/publications/Publ-25685
Publ.-Id: 25685


Range verification in proton therapy and related activities at OncoRay

Pausch, G.

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

Permalink: https://www.hzdr.de/publications/Publ-25684
Publ.-Id: 25684


Towards probing THz-driven transient electronic states with time-resolved ARPES

Deinert, J.-C.; 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

Permalink: https://www.hzdr.de/publications/Publ-25683
Publ.-Id: 25683


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

Permalink: https://www.hzdr.de/publications/Publ-25682
Publ.-Id: 25682


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

Permalink: https://www.hzdr.de/publications/Publ-25681
Publ.-Id: 25681


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

Permalink: https://www.hzdr.de/publications/Publ-25680
Publ.-Id: 25680


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

Permalink: https://www.hzdr.de/publications/Publ-25679
Publ.-Id: 25679


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

Permalink: https://www.hzdr.de/publications/Publ-25678
Publ.-Id: 25678


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.

Permalink: https://www.hzdr.de/publications/Publ-25676
Publ.-Id: 25676


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.

Permalink: https://www.hzdr.de/publications/Publ-25675
Publ.-Id: 25675


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

Permalink: https://www.hzdr.de/publications/Publ-25674
Publ.-Id: 25674


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.; 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

Permalink: https://www.hzdr.de/publications/Publ-25673
Publ.-Id: 25673


OpenACC for Programmers - Concepts and Strategies

Chandrasekaran, S.; Juckeland, G.

Klappentext noch nicht vorhanden

  • Book (Editorship)
    New York, USA: Addison-Wesley Professional, 2017
    320 Seiten
    ISBN: 978-0134694283

Permalink: https://www.hzdr.de/publications/Publ-25672
Publ.-Id: 25672


Analyzing Offloading Inefficiencies in Scalable Heterogeneous Applications

Dietrich, R.; Tschüter, R.; Juckeland, G.; 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

Permalink: https://www.hzdr.de/publications/Publ-25671
Publ.-Id: 25671


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.; 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

Permalink: https://www.hzdr.de/publications/Publ-25670
Publ.-Id: 25670


Advanced Data Processing for Full-Field PIXE Imaging

Buchriegler, J.; Klingner, N.; Hanf, D.; Munnik, F.; Nowak, S. H.; 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

Permalink: https://www.hzdr.de/publications/Publ-25669
Publ.-Id: 25669


Backscattering Spectrometry with Ultimate Lateral Resolution: keV Nanoprobes vs. MeV Microprobes

Klingner, N.; 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

Permalink: https://www.hzdr.de/publications/Publ-25668
Publ.-Id: 25668


SIMS using gas field ion sources to approach ultimate spatial resolution

Klingner, N.; 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

Permalink: https://www.hzdr.de/publications/Publ-25667
Publ.-Id: 25667


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)

Permalink: https://www.hzdr.de/publications/Publ-25666
Publ.-Id: 25666


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.; 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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Permalink: https://www.hzdr.de/publications/Publ-25665
Publ.-Id: 25665


Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets

Obst, L.; 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 Logo Scientific 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

Permalink: https://www.hzdr.de/publications/Publ-25664
Publ.-Id: 25664


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

Permalink: https://www.hzdr.de/publications/Publ-25663
Publ.-Id: 25663


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

Permalink: https://www.hzdr.de/publications/Publ-25662
Publ.-Id: 25662


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

Permalink: https://www.hzdr.de/publications/Publ-25661
Publ.-Id: 25661


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

Permalink: https://www.hzdr.de/publications/Publ-25659
Publ.-Id: 25659


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

Permalink: https://www.hzdr.de/publications/Publ-25658
Publ.-Id: 25658


Breaking the Electrical Barrier between Copper and Carbon Nanotubes

Milowska, K. Z.; Ghorbani-Asl, M.; 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

Permalink: https://www.hzdr.de/publications/Publ-25657
Publ.-Id: 25657


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

Permalink: https://www.hzdr.de/publications/Publ-25656
Publ.-Id: 25656


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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Permalink: https://www.hzdr.de/publications/Publ-25655
Publ.-Id: 25655


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

Permalink: https://www.hzdr.de/publications/Publ-25654
Publ.-Id: 25654


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

Permalink: https://www.hzdr.de/publications/Publ-25653
Publ.-Id: 25653


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

Permalink: https://www.hzdr.de/publications/Publ-25652
Publ.-Id: 25652


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 Logo Contribution 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

Permalink: https://www.hzdr.de/publications/Publ-25651
Publ.-Id: 25651


Tailoring Optical Properties of Atomically-Thin WS2 via Ion Irradiation

Tan, L. N.; Tan, Y.; Ghorbani-Asl, M.; Boettger, R.; Kretschmer, S.; Zhou, S. Q.; Huang, Z. Y.; Krasheninnikov, A. V.; 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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Permalink: https://www.hzdr.de/publications/Publ-25650
Publ.-Id: 25650


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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Permalink: https://www.hzdr.de/publications/Publ-25649
Publ.-Id: 25649


Enhancements in full-field PIXE imaging - large area elemental mapping with increased lateral resolution devoid of optics artefacts

Buchriegler, J.; Klingner, N.; Hanf, D.; Munnik, F.; Nowak, S. H.; 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

Permalink: https://www.hzdr.de/publications/Publ-25648
Publ.-Id: 25648


Road to micron resolution with a color X-ray camera – polycapillary optics characterization

Nowak, S. H.; Petric, M.; Buchriegler, J.; 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

Permalink: https://www.hzdr.de/publications/Publ-25647
Publ.-Id: 25647


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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Permalink: https://www.hzdr.de/publications/Publ-25646
Publ.-Id: 25646


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

Permalink: https://www.hzdr.de/publications/Publ-25645
Publ.-Id: 25645


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

Permalink: https://www.hzdr.de/publications/Publ-25644
Publ.-Id: 25644


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

Permalink: https://www.hzdr.de/publications/Publ-25643
Publ.-Id: 25643


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

Permalink: https://www.hzdr.de/publications/Publ-25642
Publ.-Id: 25642


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

Permalink: https://www.hzdr.de/publications/Publ-25641
Publ.-Id: 25641


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.

Permalink: https://www.hzdr.de/publications/Publ-25640
Publ.-Id: 25640


test20

Henrion, K.

alles nur ein Test

  • AAPG Bulletin (2017)

Permalink: https://www.hzdr.de/publications/Publ-25639
Publ.-Id: 25639


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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Permalink: https://www.hzdr.de/publications/Publ-25638
Publ.-Id: 25638


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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Permalink: https://www.hzdr.de/publications/Publ-25637
Publ.-Id: 25637


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

Permalink: https://www.hzdr.de/publications/Publ-25636
Publ.-Id: 25636


PIConGPU Particle-in-Cell Simulations of Transient High Energy Density Plasmas

Huebl, A.; Kluge, T.; Garten, M.; Grund, A.; Pausch, R.; Widera, R.; Matthes, A.; Debus, A.; Vorberger, J.; Fortmann-Grote, C.; Chung, H.-K.; Bussmann, M.

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

Permalink: https://www.hzdr.de/publications/Publ-25635
Publ.-Id: 25635


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

Permalink: https://www.hzdr.de/publications/Publ-25633
Publ.-Id: 25633


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

Permalink: https://www.hzdr.de/publications/Publ-25632
Publ.-Id: 25632


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

Permalink: https://www.hzdr.de/publications/Publ-25630
Publ.-Id: 25630


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

Permalink: https://www.hzdr.de/publications/Publ-25629
Publ.-Id: 25629


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

Permalink: https://www.hzdr.de/publications/Publ-25628
Publ.-Id: 25628


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

Permalink: https://www.hzdr.de/publications/Publ-25627
Publ.-Id: 25627


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

Permalink: https://www.hzdr.de/publications/Publ-25626
Publ.-Id: 25626


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

Permalink: https://www.hzdr.de/publications/Publ-25625
Publ.-Id: 25625


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

Permalink: https://www.hzdr.de/publications/Publ-25624
Publ.-Id: 25624


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

Permalink: https://www.hzdr.de/publications/Publ-25623
Publ.-Id: 25623


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

Permalink: https://www.hzdr.de/publications/Publ-25622
Publ.-Id: 25622


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

Permalink: https://www.hzdr.de/publications/Publ-25621
Publ.-Id: 25621


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

Permalink: https://www.hzdr.de/publications/Publ-25620
Publ.-Id: 25620


Including Atomic Physics in Simulations of Transient Plasma Processes with PIConGPU & simex_platform

Huebl, A.; Garten, M.; Chung, H.-K.; Vorberger, J.; Kluge, T.; Bussmann, M.

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

Permalink: https://www.hzdr.de/publications/Publ-25619
Publ.-Id: 25619


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

Permalink: https://www.hzdr.de/publications/Publ-25618
Publ.-Id: 25618


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

Permalink: https://www.hzdr.de/publications/Publ-25617
Publ.-Id: 25617


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:

Permalink: https://www.hzdr.de/publications/Publ-25616
Publ.-Id: 25616


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

Permalink: https://www.hzdr.de/publications/Publ-25615
Publ.-Id: 25615


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

Permalink: https://www.hzdr.de/publications/Publ-25614
Publ.-Id: 25614


[UO2Cl2(phen)2], a Simple Uranium(VI) Compound with a Significantly Bent Uranyl Unit (phen = 1,10-phenanthroline)

Schöne, S.; Radoske, T.; März, J.; Stumpf, T.; Patzschke, M.; Ikeda-Ohno, A.

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

Permalink: https://www.hzdr.de/publications/Publ-25613
Publ.-Id: 25613


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

Permalink: https://www.hzdr.de/publications/Publ-25612
Publ.-Id: 25612


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

Permalink: https://www.hzdr.de/publications/Publ-25611
Publ.-Id: 25611


Structural transformations in two-dimensional transition-metal dichalcogenide MoS₂ under electron beam: insights from first-principles calculations

Kretschmer, S.; Komsa, H.-P.; Bøggild, P.; Krasheninnikov, A. V.

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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Permalink: https://www.hzdr.de/publications/Publ-25610
Publ.-Id: 25610


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

Permalink: https://www.hzdr.de/publications/Publ-25608
Publ.-Id: 25608


Analysing methods of animal irradiation experiments with deviations from prescribed dose

Beyreuther, E.; 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

Permalink: https://www.hzdr.de/publications/Publ-25607
Publ.-Id: 25607


Dual-energy CT based proton range prediction in head and pelvic tumor patients

Wohlfahrt, P.; Möhler, C.; 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

Permalink: https://www.hzdr.de/publications/Publ-25606
Publ.-Id: 25606


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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Permalink: https://www.hzdr.de/publications/Publ-25605
Publ.-Id: 25605


Experimental setup to measure magnetic field effects of proton dose distributions: simulation study

Schellhammer, S. M.; 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

Permalink: https://www.hzdr.de/publications/Publ-25604
Publ.-Id: 25604


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.

Permalink: https://www.hzdr.de/publications/Publ-25603
Publ.-Id: 25603


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.; 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

Permalink: https://www.hzdr.de/publications/Publ-25602
Publ.-Id: 25602


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

Permalink: https://www.hzdr.de/publications/Publ-25599
Publ.-Id: 25599


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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Permalink: https://www.hzdr.de/publications/Publ-25598
Publ.-Id: 25598


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

Permalink: https://www.hzdr.de/publications/Publ-25597
Publ.-Id: 25597


Testing the NURESIM platform on a PWR main steam line break benchmark

Kliem, S.; 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.

Permalink: https://www.hzdr.de/publications/Publ-25595
Publ.-Id: 25595


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