Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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28621 Publications
Extremely high magnetoresistance and conductivity in the type-II Weyl semimetals WP2 and MoP2
Kumar, N.; Sun, Y.; Xu, N.; Manna, K.; Yao, M.; Süss, V.; Leermakers, I.; Young, O.; Förster, T.; Schmidt, M.; Borrmann, H.; Yan, B.; Zeitler, U.; Shi, M.; Felser, C.; Shekhar, C.
Corresponding author: Felser, C. Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
Abstract: The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings can lead to spectacular electronic properties such as large mobilities accompanied by extremely high magnetoresistance. In particular, two closely neighboring Weyl points of the same chirality are protected from annihilation by structural distortions or defects, thereby significantly reducing the scattering probability between them. Here we present the electronic properties of the transition metal diphosphides, WP2 and MoP2, which are type-II Weyl semimetals with robust Weyl points by transport, angle resolved photoemission spectroscopy and first principles calculations. Our single crystals of WP2 display an extremely low residual low-temperature resistivity of 3 nΩ cm accompanied by an enormous and highly anisotropic magnetoresistance above 200 million % at 63 T and 2.5 K. We observe a large suppression of charge carrier backscattering in WP2 from transport measurements. These properties are likely a consequence of the novel Weyl fermions expressed in this compound.

Registration No. 26376 - Permalink


Coupling of ferromagnetism and structural phase transition in V2O3/Co bilayers
Wang, C.; Xu, C.; Wang, M.; Yuan, Y.; Liu, H.; Dillemans, L.; Homm, P.; Menghini, M.; Locquet, J.-P.; Haesendonck, C. V.; Zhou, S.; Ruan, S.; Zeng, Y.-J.
Abstract: Interfacial coupling in hybrid magnetic heterostructures is being considered as a unique opportunity for functional material design. Here, we present the temperature dependence of magnetic properties of V2O3/Co bilayers influenced by the structural phase transition that is accompanied by a metal–insulator transition in V2O3. Both the coercivity and the magnetization of Co layer are strongly affected by the interfacial stress due to the magnetostrictive effect in the ferromagnetic film. The observed change in coercivity is as large as 59% in a narrow temperature range. The changes in the magnetic properties are reproducible and reversible, which are of importance for potential applications.
Keywords: metal–insulator transition, magnetostrictive coupling, structural phase transition, heterostructure

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  • Secondary publication expected from 14.11.2018

Registration No. 26371 - Permalink


Feasible device architectures for ultra-scaled CNTFETs
Pacheco-Sanchez, A.; Fuchs, F.; Mothes, S.; Zienert, A.; Schuster, J.; Gemming, S.; Claus, M.
Corresponding author: Pacheco-Sanchez, A. TUD, cfaed
Abstract: Feasible device architectures for ultra-scaled CNTFETs are studied down to 5.9 nm using a multiscale simulation approach covering electronic quantum transport simulations and TCAD numerical device simulations. Schottky-like and ohmic-like contacts are considered. The simplified approach employed in the numerical device simulator is critically evaluated and verified by means of comparing the results with electronic quantum simulation results of an identical device. Different performance indicators such as the switching speed, switching energy, the subthreshold slope, Ion/Ioff-ratio, among others, are extracted for different device architectures. These values guide the evaluation of the technology for different application scenarios. For high-performance logic applications, the buried gate CNTFET is claimed to be the most suitable structure.
Keywords: CNTFETs, Logic gates, Numerical models, Computer architecture, Performance evaluation, Electric potential, Effective mass

Registration No. 26363 - Permalink


Novel Humanized and Highly Efficient Bispecific Antibodies Mediate Killing of Prostate Stem Cell Antigen-Expressing Tumor Cells by CD8+ and CD4+ T Cells
Feldmann, A.; Arndt, C.; Töpfer, K.; Stamova, S.; Krone, F.; Cartellieri, M.; Koristka, S.; Michalk, I.; Lindemann, D.; Schmitz, M.; Temme, A.; Bornhäuser, M.; Ehninger, G.; Bachmann, M.
Abstract: Prostate cancer is the most common noncutaneous malignancy in men. The prostate stem cell Ag (PSCA) is a promising target for immunotherapy of advanced disease. Based on a novel mAb directed to PSCA, we established and compared a series of murine and humanized anti-CD3–anti-PSCA single-chain bispecific Abs. Their capability to redirect T cells for killing of tumor cells was analyzed. During these studies, we identified a novel bispecific humanized Ab that efficiently retargets T cells to tumor cells in a strictly Ag-dependent manner and at femtomolar concentrations. T cell activation, cytokine release, and lysis of target cells depend on a cross-linkage of redirected T cells with tumor cells, whereas binding of the anti-CD3 domain alone does not lead to an activation or cytokine release. Interestingly, both CD8+ and CD4+ T cells are activated in parallel and can efficiently mediate the lysis of tumor cells. However, the onset of killing via CD4+ T cells is delayed. Furthermore, redirecting T cells via the novel humanized bispecific Abs results in a delay of tumor growth in xenografted nude mice.

Registration No. 26359 - Permalink


Retargeting of T Cells to Prostate Stem Cell Antigen ExpressingTumor Cells: Comparison of Different Antibody Formats
Feldmann, A.; Stamova, S.; Bippes, C. C.; Bartsch, H.; Wehner, R.; Schmitz, M.; Temme, A.; Cartellieri, M.; Bachmann, M.
Abstract: BACKGROUND. Prostate cancer (PCa) is the most common malignant disease in men. Novel treatment options are needed for patients after development of metastatic, hormone-refractory disease or for those who have failed a local treatment. The prostate stem cell antigen (PSCA) is expressed in >80% of primary PCa samples and bone metastases. Its expression is increased both in androgen-dependent and independent prostate tumors, particularly in carcinomas of high stages and Gleason scores. Therefore, PSCA is an attractive target for immunotherapy of PCa by retargeting of T cells to tumor cells.
METHODS. Aseries of different bispecific antibody formats for retargeting of T cells to tumor cells were described but, only very limited data obtained by side by side comparison of the different antibody formats are available. We established two novel bispecific antibodies in different formats. The functionality of both constructs was analyzed by FACS and chromium release assays. In parallel, the release of pro-inflammatory cytokines was determined by ELISA.
RESULTS AND CONCLUSIONS. Irrespective of the underlying antibody format, both novel bispecific antibodies cause an efficient killing of PSCA-positive tumor cells by preand non-pre-activated T cells. Killing and release of pro-inflammatory cytokines requires an antigen specific cross-linkage of the T cells with the target cells.
Keywords: single chain bispecific antibodies; prostate cancer; T cell targeting; immunotherapy

Registration No. 26358 - Permalink


Retargeting of Human Regulatory T Cells by Single-Chain Bispecific Antibodies
Koristka, S.; Cartellieri, M.; Theil, A.; Feldmann, A.; Arndt, C.; Stamova, S.; Michalk, I.; Töpfer, K.; Temme, A.; Kretschmer, K.; Bornhäuser, M.; Ehninger, G.; Schmitz, M.; Bachmann, M.
Abstract: Bispecific Abs hold great potential for immunotherapy of malignant diseases. Because the first components of this new drug class are now entering clinical trials, all aspects of their mode of action should be well understood. Several studies proved that CD8+ and CD4+ effector T cells can be successfully redirected and activated against tumor cells by bispecific Abs both in vitro and in vivo. To our knowledge, this study provides the first evidence that bispecific Abs can also redirect and activate regulatory T cells against a surface Ag, independently of their TCR specificity. After cross-linking, via a bispecific Ab, redirected regulatory T cells upregulate the activation markers CD69 and CD25, as well as regulatory T cell-associated markers, like CTLA-4 and FOXP3. The activated regulatory T cells secrete the immunosuppressive cytokine IL-10, but, in contrast to CD8+ and CD4+ effector T cells, almost no inflammatory cytokines. In addition, the redirected regulatory T cells are able to suppress effector functions of activated autologous CD4+ T cells both in vitro and in vivo. Therefore, the potential risk for activation of regulatory T cells should be taken into consideration when bispecific Abs are applied for the treatment of malignant diseases. In contrast, an Ag/tissue-specific redirection of regulatory T cells with bispecific Abs holds great potential for the treatment of autoimmune diseases and graft rejection.

Registration No. 26357 - Permalink


Retargeting of regulatory T cells to surface-inducible autoantigen La/SS-B
Koristka, S.; Cartellieri, M.; Arndt, C.; Bippes, C. C.; Feldmann, A.; Michalk, I.; Wiefel, K.; Stamova, S.; Schmitz, M.; Ehninger, G.; Bornhäuser, M.; Bachmann, M.
Abstract: The nuclear autoantigen La can be detected on the surface of dying cells. Here we present an assay which enables us to show that La protein is not limited to the surface of dying cells but will be released upon stress-induced cell death. As released La protein tightly binds to the surface of neighboring intact cells we asked the question whether or not La protein could serve as a stress-inducible target e.g. for redirecting of regulatory T cells (Tregs) into damaged tissues to downregulate an immune response. In order to provide first proof of concept we developed a novel fully humanized single-chain bispecific antibody (bsAb) which on the one hand is directed to the La antigen and on the other hand to the CD3 complex of T cells. A cross-linkage of Tregs with La-decorated target cells mediated by this bsAb resulted indeed in the activation of the Tregs in a target-dependent manner. Moreover, such bsAb activated Tregs displayed a potent suppressive capacity and negatively influenced proliferation, expansion and cytokine production of autologous CD4+ and CD8+ Teff cells.
Keywords: La/SS-B, Regulatory T cells, Single-chain bispecific antibodies, Immunotherapy

Registration No. 26356 - Permalink


Combinatorial antigen recognition with balanced signaling promotes selective tumor eradication by engineered T cells
Kloss, C. C.; Condomines, M.; Cartellieri, M.; Bachmann, M.; Sadelain, M.
Abstract: Current T-cell engineering approaches redirect patient T cells to tumors by transducing them with antigen-specific T-cell receptors (TCRs) or chimeric antigen receptors (CARs) that target a single antigen. However, few truly tumor-specific antigens have been identified, and healthy tissues that express the targeted antigen may undergo T cell–mediated damage. Here we present a strategy to render T cells specific for a tumor in the absence of a truly tumor-restricted antigen. T cells are transduced with both a CAR that provides suboptimal activation upon binding of one antigen and a chimeric costimulatory receptor (CCR) that recognizes a second antigen. Using the prostate tumor antigens PSMA and PSCA, we show that co-transduced T cells destroy tumors that express both antigens but do not affect tumors expressing either antigen alone. This ‘tumor-sensing’ strategy may help broaden the applicability and avoid some of the side effects of targeted T-cell therapies.

Registration No. 26353 - Permalink


Redirection of T cells with a first fully humanized bispecific CD33–CD3 antibody efficiently eliminates AML blasts without harming hematopoietic stem cells
Arndt, C.; von Bonin, M.; Cartellieri, M.; Feldmann, A.; Koristka, S.; Michalk, I.; Stamova, S.; Bornhäuser, M.; Schmitz, M.; Ehninger, G.; Bachmann, M.
Corresponding author: Bachmann, Michael Institute of Immunology, Medical Faculty ‘Carl Gustav Carus’, TU Dresden, Dresden, Germany
Abstract: Redirection of T cells with a first fully humanized bispecific
CD33–CD3 antibody efficiently eliminates AML blasts without
harming hematopoietic stem cells

Registration No. 26352 - Permalink


Magnetohydrodynamic instabilites in aluminium reduction cells
Weber, N.; Herreman, W.; Horstmann, G.; Nore, C.; Weier, T.
Abstract: Übersicht über Theorie und numerische Simulation von Aluminium-Reduktionszellen.
  • Lecture (others)
    Aluminium-Reduktions-Treffen, 16.11.2017, Wuppertal, Deutschland

Registration No. 26350 - Permalink


Magnetic nanomaterials
Josten, E.; Glavic, A.; Meertens, D.; Wetterskog, E.; Bersgtröm, L.; Brückel, T.; Lindner, J.
Abstract: Magnetic nanomaterials and their assembly in highly correlated structures are of great interest for future applications as e.g. spin-based data storage media or as material for magnon-spintronics. These systems exhibit unique physical properties like superparamagnetism or symmetry breaking emerging due to their limited size. Individual nanomaterials can be combined as building blocks for so called superstructures where the combination of the different functionalities creates a novel multi-functional system.
Recently, more and more well-defined nanoobjects became available and the advances in measurement methods allow a characterization of these systems. For example, single micrometer-sized three-dimensional magnetic nanoparticle assemblies are available, exhibiting a high degree of structural order close to that of an atomic crystal [1,2]. These systems provide a good basis for the magnetic investigation of nanoparticle superstructures.
The work to be presented focuses on the fundamental structural and magnetic research on such objects and their functionalization. For the investigation we make use of different complementary measurement methods like small angle x-ray and neutron scattering or using microresonators, which provide the necessary sensitivity for the investigation of magnetic properties of a single nano- or micrometer-sized object using ferromagnetic resonance (FMR) [3].
Keywords: nanoparticles, scattering
  • Invited lecture (Conferences)
    JCNS Workshop 2017, 10.-13.10.2017, Tutzing, Deutschland

Registration No. 26349 - Permalink


Highly ordered 3D nanoparticle superlattices investigated by microresonator ferromagnetic resonance
Josten, E.; Narkowicz, R.; Kakay, A.; Meertens, D.; Lennart, B.; Brückel, T.; Fassbender, J.; Lindner, L.
Abstract: Magnetic nanoparticles and their assembly into highly correlated superstructures are of great interest for future applications, e.g. as material for magnon-spintronic. These systems are not only distinguished by the obvious miniaturization but by their novel physical properties emerging due to their limited size and ordered arrangement. These superstructures are formed from nanometer-sized building blocks ordered like atoms in a crystal, which render them a new class of materials.
Recently, single micrometer-sized three-dimensional magnetic nanoparticle assemblies became available, exhibiting a high degree of structural order close to that of an atomic crystal. These systems provide a good basis for the magnetic investigation of nanoparticle superstructures.

Novel microresonators, provide the necessary sensitivity for the investigation of magnetic properties of nano- and micrometer-sized objects using ferromagnetic resonance (FMR) [1,2]. Due to the much higher filling factor as compared to conventional microwave cavities, they offer several orders of magnitude increased sensitivity gain. A focused ion beam was used to isolate an individual 3D mesocrystal from an ensemble and to transfer it into the microresonator loop (Fig. 1). The FMR study reveals the magnetic anisotropy of the single mesocrystal (Fig. 2), which is corroborated by micromagnetic simulations. It was possible for us to functionalize the system and to set the magnetic easy axis of the mesocrystal via pre-defining their shape.
Keywords: nanoparticle
  • Lecture (Conference)
    INTERMAG Europe 2017, 24.-28.04.2017, Dublin, Irland

Registration No. 26348 - Permalink


Felsenkeller 5 MV underground accelerator: Towards the Holy Grail of Nuclear Astrophysics 12C(α,γ)16O
Bemmerer, D.
Abstract: Underground ion accelerator laboratories such as the LUNA 0.4 MV accelerator in Italy are indispensable in order to precisely measure charged particle induced nuclear reaction cross sections. The rock overburden attenuates the cosmic ray induced background and enables the measurement of very low interaction rates. The first of the new generation of higher-energy underground accelerators is the Felsenkeller 5 MV machine in Dresden/Germany, under construction and due to open late 2017. The cross sections of several nuclear reactions relevant to nucleosynthesis in a supernova and/or its precursor are not well known, with effects on the nucleosynthetic output of these events. Of these reactions, it is planned to study the 12C(alpha,gamma), 22Ne(alpha,gamma), 40Ca(alpha,gamma), and several other cases at Felsenkeller. The scientific motivation and state of work will be reviewed. It is hoped that the Felsenkeller accelerator will be widely used, including researchers from as many German universities as possible.
Keywords: Underground nuclear astrophysics Felsenkeller Helium burning
  • Invited lecture (Conferences)
    Arbeitstreffen Kernphysik, 02.-09.03.2017, Schleching, Deutschland
  • Lecture (Conference)
    Workshop on Nuclear Astrophysics at the Dresden Felsenkeller, 26.-28.06.2017, Dresden, Deutschland
  • Lecture (Conference)
    Nuclear Physics in Astrophysics VIII, 20.06.2017, Catania, Italien
  • Invited lecture (Conferences)
    16th International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS16), 19.09.2017, Shanghai, China

Registration No. 26346 - Permalink


Felsenkeller 5 MV underground accelerator: Muon, neutron, 𝛾-ray background and project status
Bemmerer, D.
Abstract: Motivated by the success of the world's only underground ion accelerator, LUNA 0.4 MV in Italy, a project for a higher-energy underground accelerator is underway in Dresden. A 5\,MV Pelletron accelerator with double charging chains and provision for intensive ^1H^+, ^4He^+, and ^{12}C^+ beams based on external and internal ion sources is currently being installed in the Felsenkeller underground site in Dresden. Civil construction work in Felsenkeller will be completed in August 2017. The nine Felsenkeller tunnels are shielded from cosmic rays by 45\,m rock overburden, attenuating the background in radiation detectors. New data on the muon, neutron, and $\gamma$ background in Felsenkeller will be shown, and used for a discussion on the feasibility of low-background experiments there. The new accelerator will be open for outside users, and its most important experimental capabilities will be summarized.
Keywords: Underground Nuclear Astrophysics Felsenkeller
  • Lecture (Conference)
    Frühjahrstagung, 30.03.2017, Münster, Deutschland

Registration No. 26344 - Permalink


Recent progress on hydrogen and helium burning at the LUNA 400 kV underground accelerator
Bemmerer, D.
Abstract: n-beam radiative-capture experiments at low astrophysical energies require experiments in ultra-low background conditions. The Laboratory for Underground Nuclear Astrophysics (LUNA) 0.4\,MV accelerator at INFN Gran Sasso, Italy, is so far the only underground ion accelerator in the world. Recent progress at LUNA regarding the $^{22}$Ne(p,$\gamma$)$^{23}$Na [1,2], $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg, and $^{17}$O(p,$\alpha$)$^{14}$N [3] reactions will be reviewed. The project for the new, 3.5 MV LUNA-MV accelerator is on track and will be summarized.
Keywords: Nuclear Astrophysics Hydrogen burning
  • Lecture (Conference)
    Frühjahrstagung, 27.03.2017, Münster, Deutschland

Registration No. 26343 - Permalink


LUNA: Status and Prospects
Broggini, C.; Bemmerer, D.; Caciolli, A.; Trezzi, D.
Abstract: The essential ingredients of nuclear astrophysics are the thermonuclear reactions which shape the life and death of stars and which are responsible for the synthesis of the chemical elements in the Universe. Deep underground in the Gran Sasso Laboratory the cross sections of the key reactions responsible for the hydrogen burning in stars have been measured with two accelerators of 50 and 400 kV voltage right down to the energies of astrophysical interest. As a matter of fact, the main advantage of the underground laboratory is the reduction of the background. Such a reduction has allowed, for the first time, to measure relevant cross sections at the Gamow energy. The qualifying features of underground nuclear astrophysics are exhaustively reviewed before discussing the current LUNA program which is mainly devoted to the study of the Big-Bang nucleosynthesis and of the synthesis of the light elements in AGB stars and classical novae. The main results obtained during the study of reactions relevant to the Sun are also reviewed and their influence on our understanding of the properties of the neutrino, of the Sun and of the Universe itself is discussed. Finally, the future of LUNA during the next decade is outlined. It will be mainly focused on the study of the nuclear burning stages after hydrogen burning: helium and carbon burning. All this will be accomplished thanks to a new 3.5 MV accelerator able to deliver high current beams of proton, helium and carbon which will start running under Gran Sasso in 2019. In particular, we will discuss the first phase of the scientific case of the 3.5 MV accelerator focused on the study of 12C+12C and of the two reactions which generate free neutrons inside stars: 13C(α,n)16O and 22Ne(α,n)25Mg.
Keywords: Nuclear Astrophysics LUNA Laboratory Underground for Nuclear Astrophysics

Registration No. 26341 - Permalink


Modification of surface properties of solids by femtosecond LIPSS writing: comparative studies on silicon and stainless steel
Varlamova, O.; Hoefner, K.; Ratzke, M.; Reif, J.; Sarker, D.
Corresponding author: Varlamova, O. LS Experimentalphysik II, Brandenburg University of Technology Cottbus-Senftenberg, Cottbus
Abstract: We investigate the implication of modified surface morphology on wettability of stainless steel (AISI 304) and silicon (100) targets covered by laser-induced periodic surface structures (LIPSS) on extended areas (10 × 10 mm2). Using multiple pulses from a Ti: Sapphire laser (790 nm/100 fs/1 kHz) at a fluence in the range of 0.35–2.1 J/cm2 on a spot of 1.13 × 10− 4 cm2, we scanned the target under the spot to cover a large area. A systematical variation of the irradiation dose by changing the scanning speed and thus dwelling time per spot results in the formation of surface patterns ranging from very regular linear structures with a lateral period of about 500–600 nm to complex patterns of 3D microstructures with several-µm feature size, hierarchically covered by nano-ripples.

Registration No. 26340 - Permalink


Surface modifications of crystal-ion-sliced LiNbO3 thin films by low energy ion irradiations
Bai, X.; Shuai, Y.; Gong, C.; Wu, C.; Luo, W.; Böttger, R.; Zhou, S.; Zhang, W.
Corresponding author: Wu, C. State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
Abstract: Single crystalline 128°Y-cut LiNbO3 thin films with a thickness of 670 nm are fabricated onto Si substrates by means of crystal ion slicing (CIS) technique, adhesive wafer bonding using BCB as the medium layer to alleviate the large thermal coefficient mismatch between LiNbO3 and Si, and the X-ray diffraction pattern indicates the exfoliated thin films have good crystalline quality. The LiNbO3 thin films are modified by low energy Ar+ irradiation, and the surface roughness of the films is decreased from 8.7 nm to 3.4 nm. The sputtering of the Ar+ irradiation is studied by scanning electron microscope, atomic force microscope and X-ray photoelectron spectroscopy, and the results show that an amorphous layer exists at the surface of the exfoliated film, which can be quickly removed by Ar+ irradiation. A two-stage etching mechanism by Ar+ irradiation is demonstrated, which not only establishes a new non-contact surface polishing method for the CIS-fabricated single crystalline thin films, but also is potentially useful to remove the residue damage layer produced during the CIS process.
Keywords: 128°Y-cut LiNbO3; Single crystalline thin films; Crystal ion slicing; BCB bonding; Ar+ irradiation

Registration No. 26339 - Permalink


Die Bestimmung des neutroneninduzierten Spaltquerschnitts von ²⁴²Pu
Kögler, T.
Abstract: Präzise neutroneninduzierte Spaltquerschnitte von Actinoiden wie den Plutoniumisotopen haben für die Entwicklung zukünftiger Transmutationstechnologien eine große Bedeutung. Die Unsicherheiten des ²⁴²Pu-Spaltquerschnitts im schnellen Bereich des Spektrums betragen derzeit etwa 21 %. Aktuelle Sensitivitätsstudien haben gezeigt, dass nur eine Reduzierung dieser Unsicherheiten auf unter 5 % verlässliche neutronenphysikalische Simulationen zulässt.
Diese anspruchsvolle Aufgabe konnte im Rahmen der vorliegenden Arbeit an der Neutronen-Flugzeitanlage nELBE durchgeführt werden. Dünne, homogene und großflächige Actinoiden-Proben wurden dem Helmholtz-Zentrum Dresden - Rossendorf innerhalb des TRAKULA-Verbundprojektes zur Verfügung gestellt. Eingesetzt in eine neu entwickelte Spaltionisationskammer ermöglichten sie eine akkurate Bestimmung des Spaltquerschnitts relativ zu ²³⁵U. Die Flächendichten der Plutoniumschichten wurden anhand der spontanen Spaltrate von ²⁴²Pu bestimmt. Aufwändige Teilchentransportsimula-
tionen (durchgeführt mit Geant 4, MCNP 6 und FLUKA) wurden genutzt, um die auftretende Neutronenstreuung zu korrigieren. Die gewonnenen Ergebnisse sind im Rahmen ihrer Unsicherheiten in guter Übereinstimmung mit aktuellen Kerndatenevaluierungen. /
Neutron induced fission cross sections of actinides like the Pu-isotopes are of relevance for the development of nuclear transmutation technologies. For ²⁴²Pu, current uncertainties are of around 21 \%. Sensitivity studies show that the total
uncertainty has to be reduced to below 5\% to allow for reliable neutron physics simulations. This challenging task was performed at the neutron time-of-flight facility of the new German National Center for High Power Radiation Sources at HZDR, Dresden. Within the TRAKULA project, thin, large and homogeneous deposits of ²³⁵U and ²⁴²Pu have been produced successfully. Using two consecutively placed fission chambers allowed the determination of the neutron induced fission cross section of ²⁴²Pu relative to ²³⁵U. The areal density of the Plutonium targets was calculated using the measured spontaneous fission rate. Experimental results of the fast neutron induced fission of ²⁴²Pu acquired at nELBE will be presented and compared to recent experiments and evaluated data. Corrections addressing the neutron scattering are discussed by using
results of different neutron transport simulations (Geant4, MCNP6 and FLUKA).
Keywords: Kernspaltung, Wirkungsquerschnitt, schnelle Neutronen, nELBE, Spaltionisationskammern/ fission, cross section, fast neutrons, nELBE, fission ionization chambers
  • Doctoral thesis
    TU Dresden, 2017
    Mentor: Dr. Arnd R. Junghans
    187 Seiten

Registration No. 26338 - Permalink


Determination of the γ-Ray-Angular Distribution in the Inelastic Scattering of Fast Neutrons on ⁵⁶Fe at nELBE
Dietz, M.
Abstract: The inelastic neutron scattering reaction on 56Fe was studied at the nELBE time-of-flight facility of HZDR. The incoming neutron energy ranges in the fast neutron spectrum from 100 keV to 10 MeV, where high precision nuclear data are needed. Regarding the recent CIELO evaluation on 56Fe, there is a great interest in improving the knowledge of inelastic scattering angular distribution and increasing the resolution on the few literature data of gamma-ray-angular distribution.
To investigate angular distributions of the emitted gamma-rays, a new detector setup has been installed. It contains five HPGe detectors and five LaBr3 scintillation detectors, which can be set under different angles. For this measurement they were positioned under 30°; 55°; 90°; 125° and 150°, relative to the beam axis. By cyclical measurement with and without the natural Fe-target the intrinsic and the neutron induced background from the setup, except the target, has been subtracted. Corrections for gamma-self-absorption inside the target and extended source effciency were achieved using GEANT4 simulations.
The gamma-ray-angular distribution data measured with the HPGe detectors are compared with data from D. L. Smith, Argonne, 1976. Due to the much better time resolution in LaBr3 detectors high resolution data have been obtained and very interesting resonant structures have been observed for the gamma-ray-angular distribution. In the end, the influence of angular distribution coeffcient a4 is demonstrated by a anisotropy correction factor for experiments, using only one detector under an angle of 125°.
Keywords: nELBE, inelastic neutron scattering, Fe-56, angular distribution
  • Master thesis
    TU Dresden, 2016
    Mentor: Arnd R. Junghans

Registration No. 26336 - Permalink


Orca for computational actinide chemistry
Patzschke, M.
Abstract: The program package Orca will be introduced and the use in computational actinide chemistry will be demonstrated.
Keywords: computational chemistry, ab initio, DFT, relativistic effects
  • Invited lecture (Conferences)
    ThUL School 2017, 16.-20.10.2017, Jülich, Deutschland

Registration No. 26334 - Permalink


Computational Spectroscopy
Patzschke, M.
Abstract: In the contribution we discuss the application of computational chemistry to calculate spectroscopical parameters. We first present the foundations of computational chemistry in a very short form. We will show problems and advantages of DFT. Then we will show how spectroscopical parameters (IR,UV-VIS,NMR) can be calculated and what accuracy can be expected.
Keywords: computational chemistry, DFT, ab initio, actinides, spin-orbit coupling, relativistic effects
  • Invited lecture (Conferences)
    ThUL School 2017, 16.-20.10.2017, Jülich, Deutschland

Registration No. 26333 - Permalink


VVER-1000 RPV lower head model related to late in-vessel phenomena in case of hypothetical severe accident
Gencheva, R.; Grudev, P.; Stefanova, A.; Jobst, M.; Wilhelm, P.
Abstract: This work discusses the progress in the development of an ASTEC computational model for investigation of molten corium pool behaviour in the lower head of a VVER-1000 reactor in case of a hypothetical accident with core degradation. The model was tested with variation of characterizing parameters which could have an influence on the molten pool behaviour and respectively the response behaviour of the reactor pressure vessel wall. An accident scenario with external cooling of the RPV wall was analysed. The preliminary code results give an estimation of the thermal load on the RPV wall. The sensitivity of the model depending on RPV wall nodalization was investigated. The analysis is performed in support to the numerical investigations realized within the frames of the EU HORIZON 2020 IVMR project (grant agreement number 662157).
Keywords: VVER-1000, severe accident, RPV, lower head, in-vessel
  • Lecture (Conference)
    27th Symposium of AER on VVER Reactor Physics and Reactor Safety, 17.-20.10.2017, München, Deutschland

Registration No. 26332 - Permalink


The influence of bentonite colloids on neptunium(V) migration in granitic rock
Elo, O.; Hölttä, P.; Huittinen, N.
Abstract: In Finland, the repository for spent nuclear fuel (SNF) will be excavated at a depth of about 500 meters in the fractured crystalline bedrock in Olkiluoto at Eurajoki implemented by Posiva Oy. The engineered barrier systems (EBS), consisting of a solid fuel capsule, a copper-iron canister and the bentonite buffer should prevent the migration of radionuclides to the biosphere. Montmorillonite, the main mineral of bentonite, is like other aluminosilicates known to retain radionuclides, thus, preventing them from migrating from the repository with the groundwater. Bentonite erosion resulting in the formation of colloids may have a direct impact on the overall performance of the bentonite buffer. The potential relevance of colloids for radionuclide transport is highly dependent on the formation of colloids, the stability and mobility of colloids in different chemical environments, and their interaction with radionuclides [1]. Stable and mobile bentonite colloids can be formed when the glacial meltwater dilutes the groundwater. In these mildly oxic conditions, neptunium(V) will be present in its pentavalent oxidation state as the neptunyl cation (NpO2+), which is rather soluble, highly mobile and poorly adsorbed. Due to the long half-life of Np-237 (2.144·106 y), it will be a major dose contributor after 100,000 years in the SNF repository.
In our previous study, the interaction of Np(V) with Na-montmorillonite purified from MX-80 bentonite and corundum was investigated [2]. Corundum was used as a reference mineral in order to study the aluminol surface sites present on clay minerals, which are regarded as the main adsorption sites for radionuclide attachment [3]. This study aimed at investigating two processes: retardation of Np(V) on the bentonite colloids and granitic rock and the effect of the stable and mobile bentonite colloids on the migration of Np(V) in intact and crushed granitic rock columns.
The materials used in this study were colloids prepared from MX-80 Volclay type bentonite (76% montmorillonite) and Kuru Grey granite. Np(V) sorption on these materials under stagnant conditions was studied as a function of pH, solid concentration, time, and Np(V) concentration. The sorption experiments as a function of pH (3-11), were performed at a constant Np(V) concentration of 10-6 M. The sorption isotherms as a function of Np(V) concentration were conducted at concentration from 10-9 to 5·10-6 M at pH 8, 9, and 10. Solid concentrations were 0.08 g/L and 0.8 g/L for colloids and 40 g/L for granite. The samples were prepared by adding a small aliquot of colloid stock solution or crushed granite, Np-237 tracer and the background electrolyte in 20 ml polypropylene vials. The solution was buffered to the desired pH and after one week equilibration time the solid phase was separated from the liquid by centrifugation and 1 ml aliquots were taken immediately for liquid scintillation counting (Perkin Elmer Tri-Carb 3100 TR or Quantulus liquid scintillation counter). All the batch sorption studies were conducted in 10 mM NaClO4 either in carbonate-free N2-atmosphere (bentonite colloids, 0.08 g/L) or under ambient air conditions (granite and bentonite colloids 0.8 g/L).
The effect of bentonite colloids on Np(V) migration was studied in column experiments, where the column material was either crushed granite (grain size 0.01-0.1 mm) or an intact drill core of the Kuru Grey granite. The crushed granite column diameter was 1.5 cm and the length 15 cm. Drill core columns were constructed from Kuru grey granite cores which were placed inside a tube to form a flow channel (L = 28 cm, w = 4.4 cm) representing an artificial fracture formed by the 0.5 mm gap between the core and the tube [3]. In the experiments, colloid solution was injected into the water flow and the colloid breakthrough was detected by photon correlation spectroscopy (PCS) measurements. The column experiments were performed under ambient air conditions in 10 mM NaClO4 solution using flowrates of 1.5 mL/h, 0.8 mL/h, and 0.3 mL/h. The Np-tracer was injected into the flow, through an injection loop of known volume. The flow conditions in the columns were determined using chloride (36Cl-) as a conservative tracer. The effect of bentonite colloids on Np(V) transport at pH 8 and pH 10 was determined in the absence and presence of colloids (0.7 and 0.9 g/L). The colloid concentration in the collected fractions was determined by PCS and the Np(V) concentration was determined after PCS measurements from the same samples by liquid scintillation counting.
Np(V) adsorption onto MX-80 bentonite colloids and crushed Kuru Grey granite in 10 mM NaClO4 is shown as a function of pH in Figure 1a and as a function of Np concentration in Figure 1b. Sorption onto colloids was rather weak (20%) at pH 8 and higher adsorption occurred only above pH 10. According to the pH-edge results, the sorption isotherms for bentonite colloids are as expected, linear and the slopes are close to one another. The weak sorption of Np(V) on the colloids indicates that Np(V) will be mobilized as a neptunyl cation in solution. Despite the low uptake of Np(V) by the bentonite colloids, the obtained column results show that Np(V) breakthrough from the granite columns is enhanced in the presence of colloids (Figure 2).
  • Poster
    16th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barcelona, Spain

Registration No. 26330 - Permalink


Complexation of trivalent actinides and lanthanides with aqueous phosphates at elevated temperatures (25-80°C)
Huittinen, N.; Jordan, N.; Lösch, H.
Abstract: The incorporation of actinides in solid lanthanide phosphates crystallizing in the monazite structure has been intensely investigated in the past decades due to the relevance of these monazites as potential ceramic phases for the immobilization of specific high level radioactive waste (HLW) streams [1-3]. In recent years, understanding the incorporation behaviour of trivalent dopants in the LnPO4×nH2O rhabdophane structure, which is the hydrated phosphate precursor in the synthesis of monazites through precipitation routes and a potential secondary mineral controlling actinide solubility in dissolution and re-precipitation reactions of monazite host-phases, has been given more attention [4,5]. Despite the large interest in lanthanide phosphates and the interaction of actinides with these solids, very little data is available on the complexation of lanthanides and actinides with aqueous phosphates, even though these complexation reactions precede any aqueous synthesis of monazite ceramics and are expected to occur in natural waters as well as in the proximity of monazite-containing HLW repositories. It also suffers from an almost systematic absence of independent spectroscopic validation of the stoichiometry of the proposed complexes. Both from the perspective of aqueous rhabdophane synthesis, which is often carried out at elevated temperatures, and heat-generating HLW immobilization in monazites, the lanthanide and actinide complexation reactions with aqueous phosphates under ambient conditions should be complemented with data obtained at higher temperatures.

In the present work, time-resolved laser fluorescence spectroscopy (TRLFS) has been employed to study the phosphate complexation of Eu3+ (5×10-6 M) and Cm3+ (5×10-7 M) as a function of total phosphate concentration (0-1 M ΣPO4) in the temperature regime 25-80°C, using NaClO4 as a background electrolyte. These studies have, in a first step, been conducted in the acidic pH-range (pH = 1) to avoid precipitation of solid Eu or Cm rhabdophane. Both trivalent metal cations form a complex with the anionic H2PO4- species, i.e. EuH2PO42+ and CmH2PO42+. As expected, the complexation reaction occurs at lower total phosphate concentration when increasing the temperature. In addition, our preliminary results show the presence of a second Eu-phosphate species which is tentatively assigned to Eu(H2PO4)2+. The presence of this species will be verified with mass-spectrometric methods.
Temperature-dependent complexation constants for the identified species will be derived from the recorded luminescence emission spectra. These will be recalculated to standard conditions with the van´t Hoff equation and the Specific Ion Interaction Theory. For this, the required ion interaction coefficients have been preliminary determined at 25 °C by varying the ionic strength (0.6 to 3 M).
  • Poster
    16th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barcelona, Spain

Registration No. 26329 - Permalink


Charaterization of actinide(IV) complexes with imine type ligands
Radoske, T.
Abstract: The progress on the PhD thesis is presented in an oral talk. The results include complexes of tetradentate and hexadentate salen complexes with several actinides in tetravalent state.
Keywords: actinide, salen, complex, thorium, uranium, SC-XRD
  • Lecture (others)
    FENABIUM Projekttreffen, 10.05.2017, Leipzig, Deutschland

Registration No. 26328 - Permalink


European standard on small punch testing of metallic materials
Bruchhausen, M.; Holmström, S.; Altstadt, E.; Dymacek, P.; Jeffs, S.; Lancaster, R.; Lacalle, R.; Matocha, K.; Petzova, J.
Abstract: Life extension of aging nuclear power plant components requires knowledge of the properties of the service-exposed materials. For instance, in long term service the tensile and creep properties might decline and the ductile-to-brittle transition temperature (DBTT) might shift towards higher temperatures. Monitoring of structural components in nuclear power plants receives much attention – in particular in the context of lifetime extension of current plants, where the amount of material available for destructive testing is limited. Much effort has therefore been invested in the development of miniature testing techniques that allow characterizing structural materials with small amounts of material. The small punch (SP) test is one of the most widely used of these techniques. It has been developed for nuclear applications but its use is spreading to other industries.
Keywords: small punch test; tensile properties; fracture; creep; standardization
  • Contribution to proceedings
    ASME 2017 Pressure Vessels and Piping Conference PVP2017, 16.-20.07.2017, Hawaii, USA
    Proceedings of the ASME 2017 Pressure Vessels and Piping Conference PVP2017
    DOI-Link: http://dx.doi.org/10.1115/PVP2017-65396

Registration No. 26327 - Permalink


Structure Analysis of Pipe Section Reactor for Pipe-Wall Reaction: A Computational Fluid Dynamics Analysis Approach
Hua, P.; Ma, S.; Ding, W.; Zhang, J.
Corresponding author: Zhang, J. Tech Univ Dresden, Inst Urban Water Management, D-01062 Dresden, Germany
Abstract: Pipe section reactor (PSR) is a well-controlled laboratory reactor, which is used to simulate the water quality variations in drinking water distribution systems. However, the hydraulics condition within PSR, which is an essential prerequisite of the water quality studies, still remains unclear. Consequently, the objective of this study is to analyze the hydraulic conditions within PSR by means of a computational fluid dynamics (CFD) approach. The influences of configuration parameters on the hydraulic conditions were tested including propeller diameter, inclined angle of the propeller, distance between the top and inner cylinder, distance between the bottom and inner cylinder, outer cylinder length, baffle length, number of the baffles, rotational speed of the propeller, and inner and outer cylinder diameters. According to the CFD analysis, an optimal structure of PSR was suggested. The data presented here could facilitate the PSR application and improve the simulation of water quality in distribution systems
Keywords: Chlorine decay; Computational fluid dynamics; Pipe section reactor; Structure optimization

Registration No. 26325 - Permalink


On the Role of the Electrical Field in Spark Plasma Sintering of UO2+x
Tyrpekl, V.; Najii, M.; Holzhäuser, M.; Freis, D.; Prieur, D.; Martin, P.; Cremer, B.; Murray-Farthing, M.; Cologna, M.
Corresponding author: Tyrpekl, Vaclav JRC
Abstract: The electric field has a large effect on the stoichiometry and grain growth of UO2+x during Spark Plasma Sintering. UO2+x is gradually reduced to UO2.00 as a function of sintering temperature and time. A gradient in the oxidation state within the pellets is observed in intermediate conditions. The shape of the gradient depends unequivocally on the direction of the electrical field. The positive surface of the pellet shows a higher oxidation state compared to the negative one. An area with larger grain size is found close to the positive electrode, but not in contact with it. We interpret these findings with the redistribution of defects under an electric field, which affect the stoichiometry of UO2+x and thus the cation diffusivity. The results bear implications for understanding the electric field assisted sintering of UO2 and non-stoichiometric oxides in general.
Keywords: UO2, SPS, XANES

Registration No. 26323 - Permalink


Serpent-DYN3D solution of the X2 benchmark: fresh core at HZP
Bilodid, Y.; Fridman, E.
Abstract: In this work, the hot zero power experiments conducted during the startup of the fresh core of Khmelnitsky-2 NPP are modelled with the Serpent and DYN3D codes.
  • Lecture (Conference)
    7th International Serpent User Group Meeting, 06.-09.11.2017, Gainesville, FL, USA

Registration No. 26322 - Permalink


Nuclear data uncertainty quantification for the FREYA fast critical experiments
Fridman, E.; Aufiero, M.
Abstract: This study summarizes some initial results of nuclear data uncertainty quantification for the FREYA fast critical experiments
  • Lecture (Conference)
    7th International Serpent User Group Meeting, 06.-09.11.2017, Gainesville, FL, USA

Registration No. 26321 - Permalink


Modeling of Phenix EOL experiments with Serpent-DYN3D
Nikitin, E.; Fridman, E.
Abstract: This study presents the Serpent-DYN3D solution of the Phenix EOL benchmark
Keywords: Serpent, DYN3D, SFR, Phenix
  • Lecture (Conference)
    7th International Serpent User Group Meeting, 06.-09.11.2017, Gainesville, FL, USA

Registration No. 26320 - Permalink


Evaluation of gamma-ray strength functions
Schwengner, R.
Abstract: Gamma-ray strength functions deduced from nuclear resonance fluorescence (NRF) and from light-ion induced reactions are compared.
Model assumptions in the analysis and differences in the reaction mechanisms and their influence on the results are considered.
New results from NRF experiments at ELBE and from calculations within the shell model are presented.
Keywords: Nuclear resonance fluorescence, light-ion induced reactions, absorption cross sections, dipole strength functions.
  • Invited lecture (Conferences)
    2nd Research Coordination Meeting of the Coordinated Research Project on Updating the Photonuclear Data Library and generating a Reference Database for Photon Strength Functions, 16.-20.10.2017, Wien, Österreich

Registration No. 26317 - Permalink


FFLO States in Layered Organic Superconductors
Wosnitza, J.
Corresponding author: Wosnitza, J. Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
Abstract: In this short review, the recently found experimental evidence that Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) states are realized in quasi-two-dimensional (2D) organic superconductors is reported. At low temperatures and when a high magnetic field is aligned parallel to the conducting organic layers, an upturn of the upper critical field much beyond the Pauli limit is observed, as proven by thermodynamic measurements. Under certain conditions, a second thermodynamic transition emerges inside the FFLO state. Nuclear magnetic resonance (NMR) work has added strong microscopic support for the realization of the FFLO state. The NMR spectra in the FFLO phase can very well be explained by a nonuniform one-dimensionally modulated superconducting order parameter. All These features, appearing only in a very narrow angular region close to parallel-field orientation, give robust evidence for the realization of the FFLO state in organic superconductors.

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  • Secondary publication expected from 03.11.2018

Registration No. 26310 - Permalink


Pt and Au bimetallic and monometallic nanostructured amperometric sensors for direct detection of hydrogen peroxide: Influences of bimetallic effect and silica support
Liu, W.; Hiekel, K.; Hübner, R.; Sun, H.; Ferancova, A.; Sillanpää, M.
Corresponding author: Liu, W. TU Dresden
Abstract: The non-enzyme direct electrochemical sensing of hydrogen peroxide (H2O2) by nanostructured electrodes of Pt- and Au-containing bimetallic or monometallic nanocatalysts including paramecium-like nanostructures of PtAu supported on silica nanorods, Pt and Au nanoparticles supported on silica nanorods, and the non-supported Pt and Au nanoparticles (NPs) is reported. The nanocatalysts modified electrodes were fabricated by simple self-assembling on 3-aminopropyl-trimethoxysilane (APTMS) modified glassy carbon. The cyclic voltammetric and amperometric results showed that PtAu supported on silica nanorods has superior performance over the corresponding monometallic counterparts, with a broad linear range from 5.0 µM to 72000 µM for H2O2, a detection limit of 2.6 µM, a sensitivity of 46.7 µA mM-1cm-2 at a lower working potential of -0.20 V vs SCE, and has good stability and reproducibility. In addition, a systematic test showed that the non-supported Pt NPs sensor has a surprisingly high performance, even better than the paramecium-like nanostructure of PtAu supported on silica nanorods, where the existence of silica nanorod templates in the nanocatalysts retards the electrocatalytic reduction/oxidation of H2O2. Among the nanocatalysts tested in this work, the Pt NPs sensor showed fastest response within 3 s, a broad linear response from 5 µM to 58000 µM, a detection limit of 4.2 µM, and the highest sensitivity of 110.3 µA mM-1cm-2 at the lowest working potential of -0.08 V vs SCE. Notably, the performance of the Pt NPs sensor is also among the best Pt-containing monometallic or bimetallic nanostructured electrochemical sensors toward H2O2 reported so far. This work shows a simple method to fabricate H2O2 electrochemical sensors of high performance and indicates the importance of considering not only bimetallic effects but also the influences of the nanostructure of nanocatalysts on the electrocatalytic performance and electrochemical sensing property.
Keywords: Platinum, Bimetallic effect, Support material, Electrocatalyst, Amperometric sensor, Hydrogen peroxide
  • Sensors and Actuators B 255(2018), 1325-1334

Registration No. 26307 - Permalink


Fast neutron measurements at the nELBE time-of-flight facility
Junghans, A. R.; Beyer, R.; Grosse, E.; Hannaske, R.; Kögler, T.; Massarczyk, R.; Schwengner, R.; Wagner, A.
Abstract: The compact neutron-time-of-flight facility nELBE at the superconducting electron accelerator ELBE of Helmholtz-Zentrum Dresden-Rossendorf has been rebuilt. A new enlarged experimental hall with a flight path of up to 10 m is available for neutron time-of-flight experiments in the fast energy range from about 50 keV to 10 MeV.
nELBE is intended to deliver nuclear data of fast neutron nuclear interactions e.g. for the transmutation of nuclear waste and improvement of neutron physical simulations of innovative nuclear systems. The experimental programme consists of transmission measurements of neutron total cross sections, elastic and inelastic scattering cross section measurements, and neutron induced fission cross sections. The inelastic scattering to the first few excited states in 56Fe was investigated by measuring the gamma production cross section with an HPGe detector. The neutron induced fission of 242Pu was studied using fast ionisation chambers with large homogeneous actinide deposits.
Keywords: nELBE, neutron time of flight, transmission, total cross section, inelastic scattering, fission

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Registration No. 26306 - Permalink


Generation of high-avidity, WT1-reactive CD8+ cytotoxic T cell clones with anti-leukemic activity by streptamer technology
Tunger, A.; Wehner, R.; von Bonin, M.; Kühn, D.; Heidenreich, F.; Matko, S.; Nauerth, M.; Rücker-Braun, E.; Dietz, S.; Link, C. S.; Eugster, A.; Odendahl, M.; Busch, D. H.; Tonn, T.; Bonifacio, E.; Germeroth, L.; Schetelig, J.; Bachmann, M. P.; Bornhäuser, M.; Schmitz, M.
Abstract: Summary: In summary, we demonstrated that the expansion of WT1 peptide-specific CD8+ T cells by peptide-loaded MoDCs followed by streptamer-based selection represents an attractive strategy to significantly enrich such T cells prior to cloning. By using this technology, we generated high-avidity, WT1 peptide-reactive CD8+T cell clones with anti-leukemic activity. This strategy may be particular useful for the generation of CD8+T cell clones from healthy donors, in which blood circulating T cells recognizing tumor-associated antigens are rare or not detectable.
Keywords: WT1, CD8+ cytotoxic T cell clones, streptamer technology

Registration No. 26305 - Permalink


Exploratory investigation of PSCA-protein expression in primary breast cancer patients reveals a link to HER2/neu overexpression.
Link, T.; Kuithan, F.; Ehninger, A.; Kuhlmann, J. D.; Kramer, M.; Werner, A.; Gatzweiler, A.; Richter, B.; Ehninger, G.; Baretton, G.; Bachmann, M.; Wimberger, P.; Friedrich, K.
Corresponding author: Kuhlmann, J. D. Department of Gynecology and Obstetrics, Medical Faculty and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
Abstract: Background: Prostate stem cell antigen (PSCA) has been suggested as biomarker and therapeutic target for prostate cancer. Recent advances showed that PSCA is upregulated in other cancer entities, such as bladder or pancreatic cancer. However, the clinical relevance of PSCA-expression in breast cancer patients has not yet been established and is therefore addressed by the current study.
Methods: PSCA-protein expression was assessed in 405 breast cancer patients, using immunohistochemistry (PSCA antibody MB1) and tissue microarrays.
Results: PSCA-expression was detected in 94/405 patients (23%) and correlated with unfavorable histopathological grade (p=0.011) and increased Ki67 proliferation index (p=0.006). We observed a strong positive correlation between PSCA-protein expression and HER2/neu receptor status (p<0.001). PSCA did not provide prognostic information in the analyzed cohort. Interestingly, the distribution of PSCA-expression among triple negative patients was comparable to the total population.
Conclusion: We identified a subgroup of PSCA-positive breast cancer patients, which could be amenable for a PSCA-targeted therapy. Moreover, given that we found a strong positive correlation between PSCA- and HER/neu expression, targeting PSCA may provide an alternative therapeutic option in case of trastuzumab resistance.
Keywords: breast cancer, PSCA, HER2/neu, therapeutic target

Registration No. 26302 - Permalink


Deposition and properties of Fe(Se,Te) thin films on vicinal CaF2 substrates
Bryja, H.; Hühne, R.; Iida, K.; Molatta, S.; Sala, A.; Putti, M.; Schultz, L.; Nielsch, K.; Hänisch, J.
Corresponding author: Bryja, H. Institute for Metallic Materials, IFW Dresden & Institute of Materials Science, TU Dresden, Dresden, Germany
Abstract: We report on the growth of epitaxial Fe1+δSe0.5Te0.5 thin films on 0°, 5°, 10°, 15° and 20° vicinal cut CaF2 single crystals by pulsed laser deposition. In situ electron and ex situ x-ray diffraction studies reveal a tilted growth of the Fe1+δSe0.5Te0.5 films, whereby under optimized deposition conditions the c-axis alignment coincides with the substrate [001] tilted axis up to a vicinal angle of 10°. Atomic force microscopy shows a flat island growth for all films. From resistivity measurements in longitudinal and transversal directions, the ab- and c-axis components of resistivity are derived and the mass anisotropy parameter is determined. Analysis of the critical current density indicates that no effective c-axis correlated defects are generated by vicinal growth, and pinning by normal point core defects dominates. However, for H||ab the effective pinning centers change from surface defects to point core defects near the superconducting transition due to the vicinal cut. Furthermore, we show in angular-dependent critical current density data a shift of the ab-planes maxima position with the magnetic field strength.

Registration No. 26300 - Permalink


Acoustic Properties of Crystals with Jahn–Teller Impurities: Elastic Moduli and Relaxation Time. Application to SrF2:Cr2+
Averkiev, N. S.; Bersuker, I. B.; Gudkov, V. V.; Zhevstovskikh, I. V.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Shakurov, G. S.; Ulanov, V. A.; Surikov, V. T.
Corresponding author: Gudkov, V. V. Ural Federal University, Ekaterinburg, Russia
Abstract: A new approach to evaluate the relaxation contribution to the total elastic moduli for crystals with Jahn–Teller (JT) impurities is worked out and applied to the analysis of the experimentally measured ultrasound velocity and attenuation in SrF2:Cr2+. Distinguished from previous work, the background adiabatic contribution to the moduli, important for revealing the impurity relaxation contribution, is taken into account. The temperature dependence of the relaxation time for transitions between the equivalent configurations of the JT centers has been obtained, and the activation energy for the latter in SrF2:Cr2+. as well as the linear vibronic coupling constant have been evaluated.

Registration No. 26299 - Permalink


Mass spectrometry-based identification of a naturally presented receptor tyrosine kinase-like orphan receptor 1-derived epitope recognized by CD8+ cytotoxic T cells
Heidenreich, F.; Rücker-Braun, E.; Walz, J. S.; Eugster, A.; Kühn, D.; Dietz, S.; Nelde, A.; Tunger, A.; Wehner, R.; Link, C. S.; Middeke, J. M.; Stölzel, F.; Tonn, T.; Stevanovic, S.; Rammensee, H. G.; Bonifacio, E.; Bachmann, M.; Zeis, M.; Ehninger, G.; Bornhäuser, M.; Schetelig, J.; Schmitz, M.
Corresponding author: Heidenreich, F. DKMS German Bone Marrow Donor Center, Clinical Trials Unit, Dresden, Germany; Department of Medicine I, University Hospital of Dresden, Germany
Abstract: Mass spectrometry-based identification of a naturally presented receptor tyrosine kinase-like orphan receptor 1-derived epitope recognized by CD8+ cytotoxic T cells

Registration No. 26298 - Permalink


Microstructure and charge trapping in in ZrO2- and Si3N4-based superlattice layer systems with Ge nanoparticles
Seidel, S.; Rebohle, L.; Prucnal, S.; Lehninger, D.; Hübner, R.; Klemm, V.; Skorupa, W.; Heitmann, J.
Corresponding author: Seidel, S.
Abstract: Ge was deposited on silicon as a superlattice with 10 layers of Ge embedded in Si3N4 or ZrO2 matrices via plasma enhanced chemical vapor deposition or RF-sputtering, respectively. Raman spectroscopy, transmission electron microscopy and capacitance-voltage (CV) measurements were performed in order to investigate the structural and electrical properties of the superlattices. It will be shown that, in contrast to furnace annealing, flash lamp annealing of Ge-ZrO2-superlattices leads to crystalline Ge nanoparticles in an amorphous matrix. As revealed by CV measurements, these layers show excellent charge storage capabilities. In comparison, a higher thermal budget is needed to crystallize Ge in case of Si3N4-based superlattices, and no significant charge trapping could be detected during CV measurements.
Keywords: Ge nanocrystals, zirconium oxide, silicon nitride, superlattice, flash lamp annealing

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Registration No. 26291 - Permalink


Topological Hall Effect in an Artificial Skyrmion Lattice
Murray, P.; Chen, Z.; Gilbert, D. A.; Zang, J.; Stuckler, T.; Lenz, K.; Maranville, B. B.; Fassbender, J.; Yu, H.; Borchers, J. A.; Liu, K.
Abstract: Magnetic skyrmions have exciting potential for future device applications in low dissipation information storage [1-3]. While much research has been focused on DMI-stabilized skyrmions in bulk crystals or multilayers, we recently realized Bloch-type artificial skyrmion lattices which are stable at room temperature under zero magnetic field [4], offering a convenient platform for investigating transport characteristics such as the Topological Hall Effect (THE). Here, we report a study of the THE in a different type of planar skyrmion lattice, without any protruding magnetic dots on top.
Keywords: skyrmions, DMI, magnetism, topological hall effect
  • Poster
    62nd Annual Conference on Magnetism and Magnetic Materials, MMM 2017, 06.-10.11.2017, Pittsburgh, USA

Registration No. 26289 - Permalink


Synthesis and characterization of tetravalent actinide complexes with benzamidinates
Schöne, S.ORC; März, J.; Kaden, P.
Abstract: The synthesis and characterization of tetravalent actinide complexes with different amidinates is presented. The synthesized thorium and uranium amidinates were characterized in solution with NMR and UV-Visible spectroscopy and in solid state with SC-XRD and IR spectroscopy. The molecular structures were discussed in detail showing differences between the coordination behavior of different amidinates.
  • Lecture (others)
    FENABIUM Projekttreffen, 10.05.2017, Leipzig, Deutschland

Registration No. 26288 - Permalink


Novel Radiolabeled Bisphosphonates for PET Diagnosis and Endoradiotherapy of Bone Metastases
Pfannkuchen, N.; Meckel, M.; Bergmann, R.; Bachmann, M.; Bal, C.; Sathekge, M.; Mohnike, W.; Baum, R. P.; Rösch, F. .
Corresponding author: Rösch, Frank . Institute of Nuclear Chemistry, Johannes Gutenberg University Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz, Germany
Abstract: Bone metastases, often a consequence of breast, prostate, and lung carcinomas, are characterized by an increased bone turnover, which can be visualized by positron emission tomography (PET), as well as single-photon emission computed tomography (SPECT). Bisphosphonate complexes of 99mTc are predominantly used as SPECT tracers. In contrast to SPECT, PET offers a higher spatial resolution and, owing to the 68Ge/68Ga generator, an analog to the established 99mTc generator exists. Complexation of Ga(III) requires the use of chelators. Therefore, DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), NOTA (1,4,7-triazacyclododecane-1,4,7-triacetic acid), and their derivatives, are often used. The combination of these macrocyclic chelators and bisphosphonates is currently studied worldwide. The use of DOTA offers the possibility of a therapeutic application by complexing the β-emitter 177Lu. This overview describes the possibility of diagnosing bone metastases using [68Ga]Ga-BPAMD (68Ga-labeled (4-{[bis-(phosphonomethyl))carbamoyl]methyl}-7,10-bis(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl)acetic acid) as well as the successful application of [177Lu]Lu-BPAMD for therapy and the development of new diagnostic and therapeutic tools based on this structure. Improvements concerning both the chelator and the bisphosphonate structure are illustrated providing new 68Ga- and 177Lu-labeled bisphosphonates offering improved pharmacological properties.
Keywords: bisphosphonates; bone metastases; diagnosis; therapy; 68Ga; 177Lu

Registration No. 26287 - Permalink


Biological characterization of novel nitroimidazole-peptide conjugates in vitro and in vivo.
Bergmann, R.; Splith, K.; Pietzsch, J.; Bachmann, M.; Neundorf, I.
Corresponding author: Neundorf, Ines Department für Chemie, Institut für Biochemie, Mathematisch-Naturwissenschaftliche Fakultät, Universität zu Köln, Köln, Germany
Abstract: Recently, we reported on the design of a multimodal peptide conjugate useful as delivery platform for targeting hypoxic cells. A nitroimidazole (2-(2-nitroimidazol-1-yl)acetic acid, NIA) moiety, which is selectively entrapped in hypoxic cells, was coupled to a cell-penetrating peptide serving as the transporter. Furthermore, attachment of a bifunctional linker allowed the introduction of a diagnostic or therapeutic radiometal. However, although selective tumor accumulation could be detected in vivo, a fast renal clearance of the compound was observed. The present study aims to improve the system by using the more proteolytically stable all-d version of the peptide carrier (DsC18), by attaching two NIA moieties instead of one (DsC18(NIA)2 ) to enhance the tumor uptake, and by incorporating the bifunctional chelator NODAGA instead of DOTA (NODAGA-DsC18(NIA)2 ) to optimize labeling chemistry. First, we characterized in vitro the novel all-d peptide compared with its parent l-version. Then, in order to investigate and compare the pharmacological profiles of the peptides, these were radiolabeled with 64 CuII and 68 GaIII , and the biodistribution and kinetics were evaluated in vivo. Our results show the versatility of the d-peptide as cell-penetrating peptide and transporter. However, attaching two NIA groups modified the system in such a way that no selective tumor uptake could be observed compared with the peptide without NIA moieties. Still, this work highlights new pharmacokinetic data on the biodistribution of such compounds in vivo.
Keywords: cell-penetrating peptides; drug delivery; positron emission tomography (PET); proteolytic stability; tumor hypoxia; tumor theranostics

Registration No. 26286 - Permalink


Characterization of a switchable chimeric antigen receptor platform in a pre-clinical solid tumor model
Bejestani, E. P.; Cartellieri, M.; Bergmann, R.; Ehninger, A.; Loff, S.; Kramer, M.; Spehr, J.; Dietrich, A.; Feldmann, A.; Albert, S.; Wermke, M.; Baumann, M.; Krause, M.; Bornhäuser, M.; Ehninger, G.; Bachmann, M.; von Bonin, M.
Corresponding author: Bonin, Malte Von Medical Department I, University Hospital Carl Gustav Carus, Technische Universität Dresden, Germany
Abstract: The universal modular chimeric antigen receptor (UniCAR) platform redirects CAR-T cells using a separated, soluble targeting module with a short half-life. This segregation allows precise controllability and flexibility. Herein we show that the UniCAR platform can be used to efficiently target solid cancers in vitro and in vivo using a pre-clinical prostate cancer model which overexpresses prostate stem cell antigen (PSCA). Short-term administration of the targeting module to tumor bearing immunocompromised mice engrafted with human UniCAR-T cells significantly delayed tumor growth and prolonged survival of recipient mice both in a low and high tumor burden model. In addition, we analyzed phenotypic and functional changes of cancer cells and UniCAR-T cells in association with the administration of the targeting module to reveal potential immunoevasive mechanisms. Most notably, UniCAR-T cell activation induced upregulation of immune-inhibitory molecules such as programmed death ligands. In conclusion, this work illustrates that the UniCAR platform mediates potent anti-tumor activity in a relevant in vitro and in vivo solid tumor model.
Keywords: Chimeric antigen receptors, immune checkpoints, immunoevasion, prostate stem cell antigen, solid tumors, targeting module

Registration No. 26282 - Permalink


Monovacancy paramagnetism in neutronirradiated graphite probed by 13C NMR
Zhang, Z. T.; Xu, C.; Dmytriieva, D.; Molatta, S.; Wosnitza, J.; Wang, Y. T.; Helm, M.; Zhou, S.; Kühne, H.
Corresponding author: Zhang, Z. T. Institute of Ion Beam Physics and Materials Research & Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
Abstract: We report on the magnetic properties of monovacancy defects in neutron-irradiated graphite, probed by 13C nuclear magnetic resonance spectroscopy. The bulk paramagnetism of the defect moments is revealed by the temperature dependence of the NMR frequency shift and spectral linewidth, both of which follow a Curie behavior, in agreement with measurements of the macroscopic magnetization. Compared to pristine graphite, the fluctuating hyperfine fields generated by the defect moments lead to an enhancement of the 13C nuclear spin-lattice relaxation rate 1/T1 by about two orders of magnitude. With an applied magnetic field of 7.1 T, the temperature dependence of 1/T1 below about 10 K can well be described by a thermally activated form, 1/T1 α exp(−Δ/kBT), yielding a singular Zeeman energy of (0.41 ± 0.01) meV, in excellent agreement with the sole presence of polarized, non-interacting defect moments.

Registration No. 26279 - Permalink


Magnetic Properties of the Nanocrystalline Nd-Ho-Fe-Co-B Alloy at Low Temperatures: The Influence of Time and Annealing
Tereshina, I. S.; Kudrevatykh, N. V.; Ivanov, L. A.; Politova, G. A.; Tereshina, E. A.; Gorbunov, D.; Doerr, M.; Rogackie, K.
Corresponding author: Tereshina, I. S. Faculty of Physics, Lomonosov Moscow State University, Moscow, Russia and International Laboratory of High Magnetic Fields and Low Temperature, Wroclaw, Poland
Abstract: A study is made of the effects of various factors such as time (7 years), temperature, high magnetic field up to 580 kOe and heat treatment (HT) on the morphological structure and magnetic hysteresis properties of a high-coercive nanocrystalline (Nd0.55Ho0.45)2.7(Fe0.8Co0.2)14B1.2 alloy with a low temperature coefficient of remanence. We find a rather weak time effect on (Nd0.55Ho0.45)2.7(Fe0.8Co0.2)14B1.2. After 7 years, the loss in the maximum magnetic energy product (BH)max is no more than 5%. Annealing of the sample at 250 °C for 30 min decreases the amount of amorphous phase from 7.2 to 1.7%, while the grains’ size of the 2-14-1 phase increases from 83 to 109 nm. For the HT alloy, a magnetization jump is observed at H ~ 500 kOe. It can be attributed to the first-order magnetization process or a spin-flip magnetic transition. Rectangularity of the hysteresis loop degrades after annealing. In case of the short-time heat treatment, losses in (BH)maxare ~ 10%.

Registration No. 26278 - Permalink


Influence of Co on the magnetism of HoFe5Al7
Andreev, A. V.; Gorbunov, D. I.; Sebek, J.; Nehnakhin, D. S.
Corresponding author: Andreev, A. V. Institute of Physics, Academy of Sciences, Prague, Czech Republic
Abstract: Effects of the Co substitution for Fe on the strongly anisotropic ferrimagnet HoFe5Al7 are studied on single-crystalline samples with a tetragonal crystal structure of the ThMn12-type. For HoFe5-xCoxAl7, we found the homogeneity range up to x = 2.5. The Co substitution results in a shrinkage of the tetragonal lattice within the basal plane, whereas the c parameter does not change. The exchange interactions and magnetic anisotropy are strongly affected by the Co substitution. The detrimental effect of Co on the Curie temperature TC in HoFe5-xCoxAl7 compounds is very unusual. The Curie temperature linearly falls from 216 K for x = 0-67 K for x = 2.5, which is unexpected because the Co substitution for Fe in 3d-4f intermetallic compounds usually increases the magnetic ordering temperatures due to the strengthening of exchange interactions. At the same time, the compensation temperature changes very little between 65 K and 72 K. At 2 K, spontaneous magnetic moment increases from 2 µB at x = 0-4.2 µB at x = 2.5. Magnetization measurements have been performed in pulsed magnetic fields up to 58 T. The compounds exhibit a high magnetic anisotropy of the easy-plane type with the [110] axis as the easy-magnetization direction. Along the easy axis, two first-order field-induced magnetic transitions (at 17 T and 37 T) are observed for HoFe5Al7 and one transition at 27 T for HoFe4CoAl7. The magnetization curve has an S-shape for HoFe3Co2Al7.

Registration No. 26273 - Permalink


Meniscus Asymmetry and Chemo-Marangoni Convection in Capillaries
Eckert, K.; Shi, Q.; Seidel, K.; Schwarzenberger, K.
Corresponding author: Eckert, Kerstin
Abstract: A liquid-liquid system inside a capillary in which an interfacial reaction leads to in situ production of a surfactant was studied experimentally. The resulting chemo-Marangoni convection induces periodic spreading-dewetting cycles in laboratory experiments. By selected experiments in microgravity, the individual phenomena of the system dynamics could be isolated. The spreading-dewetting cycles result from a complex interplay between the decrease in interfacial tension due to the production of surfactant, the chemo-Marangoni convection, and the gravity-driven deformation of the meniscus shape.
Keywords: Capillaries, Interfacial reactions, Marangoni convection, Meniscus deformation, Microgravity

Registration No. 26272 - Permalink


Magnetic and acoustic properties of CoCrS4
Felea, V.; Cong, P. T.; Prodan, L.; Gritsenko, Y.; Wosnitza, J.; Zherlitsyn, S.; Tsurkan, V.
Corresponding author: Zherlitsyn, S. Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
Abstract: We report results of magnetic and ultrasound studies of the sulfide spinel CoCr2S4, for which the multiferroicity has recently been suggested. Clear anomalies in the magnetic and acoustic properties have been observed at TN = 222 K and in applied magnetic fields evidencing the important role of magnetoelastic interac-tions in this material. In contrast, no anomalies have been detected at TC = 28 K, where a spontaneous electric polarization and isostructural distortions have been reported. We have extracted the H–T phase diagram of CoCr2S4 from our experiments for magnetic fields applied along the <111> direction. We discuss our observa-tions in relation to our earlier results obtained for the oxide multiferroic spinel CoCr2O4.
  • Low Temperature Physics 43(2017), 1618-1621

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  • Secondary publication expected

Registration No. 26269 - Permalink


Bulk Fermi surface of the Weyl type-II semimetallic candidate γ -MoTe2
Rhodes, D.; Schönemann, R.; Aryal, N.; Zhou, Q.; Zhang, Q. R.; Kampert, E.; Chiu, Y.-C.; Lai, Y.; Shimura, Y.; Mccandless, G. T.; Chan, J. Y.; Paley, D. W.; Lee, J.; Finke, A. D.; Ruff, J. P. C.; Das, S.; Manousakis, E.; Balicas, L.
Corresponding author: Balicas, L. National High Magnetic Field Laboratory, Florida State University, Tallahassee & Department of Physics, Florida State University, Tallahassee, Florida, USA
Abstract: The electronic structure of semimetallic transition-metal dichalcogenides, such as WTe2 and orthorhombic γ-MoTe2, are claimed to contain pairs of Weyl points or linearly touching electron and hole pockets associated with a nontrivial Chern number. For this reason, these compounds were recently claimed to conform to a new class, deemed type-II, of Weyl semimetallic systems. A series of angle-resolved photoemission experiments (ARPES) claim a broad agreem nt with these predictions detecting, for example, Fermi arcs at the surface of these crystals. We synthesized single crystals of semimetallic MoTe2 through a Te flux method to validate these predictions through measurements of its bulk Fermi surface (FS) via quantum oscillatory phenomena.We find that the superconducting transition temperature of γ-MoTe2 depends on disorder as quantified by the ratio between the room- and low-temperature resistivities, suggesting the possibility of an unconventional superconducting pairing symmetry. Similarly to WTe2, the magnetoresistivity of γ-MoTe2 does not saturate at high magnetic fields and can easily surpass 106%. Remarkably, the analysis of the de Haas–van Alphen (dHvA) signal superimposed onto the magnetic torque indicates that the geometry of its FS is markedly distinct from the calculated one. The dHvA signal also reveals that the FS is affected by the Zeeman effect precluding the extraction of the Berry phase. A direct comparison between the previous ARPES studies and density-functional-theory (DFT) calculations reveals a disagreement in the position of the valence bands relative to the Fermi level εF . Here, we show that a shift of the DFT valence bands relative to εF , in order to match the ARPES observations, and of the DFT electron bands to explain some of the observed dHvA frequencies, leads to a good agreement between the calculations and the angular dependence of the FS cross-sectional areas observed experimentally. However, this relative displacement between electron and hole bands eliminates their crossings and, therefore, the Weyl type-II points predicted for γ-MoTe2.

Registration No. 26268 - Permalink


Methods of dilatometric investigations under extreme conditions and the case of spin-ice compounds
Doerr, M.; Granovsky, S.; Rotter, M.; Stöter, T.; Wang, Z.-S.; Zherlitsyn, S.; Wosnitza, J.
Corresponding author: Doerr, M. Technische Universität Dresden, Institut für Festkörperphysik, Dresden, Germany
Abstract: We give an overview on how dilatometric methods have been developed in the last decade. The concept of capacitive dilatometry was successfully adapted to dilution refrigerators with a resolution of 10-9. Miniaturized dilatometers with an overall diameter of 18 mm or less are optimally suited for measuring longitudinal and transversal components of the striction tensor. Going to another extreme, to the highest (pulsed) fields, optical methods, such as the FBG technology, were developed for investigations up to 100 T.
As examples for utilizing dilatometry at low temperatures we show results for the spin-ice materials Dy2Ti2O7 and Ho2Ti2O7. To characterise the magneto-elastic coupling in these materials, we investigated the thermal expansion and magnetostriction between 80 mK and 15 K and in magnetic fields aligned along the [111] direction and found field-induced phases and strong correlations below 500 mK. Our data demonstrate, that the formation of the field-induced phase is strongly influenced by lattice distortions: any change in interatomic distances will result in a variation of the exchange couplings.

Registration No. 26267 - Permalink


High Temperature Stability of BaZrO3: An Ab Initio Thermodynamic Study
Raja, N.; Murali, D.; Posselt, M.; Satyanarayana, S. V. M.
Corresponding author: Raja, Nadarajan Department of Physics, Pondicherry University, Puducherry 605 014, India
Abstract: BaZrO3 exhibits excellent proton conductivity and good high-temperature stability. It is therefore a promising electrolyte material for solid oxide fuel cells. The stability of BaZrO3 at high temperatures is generally explained by the low diffusivity of O vacancy. Present first principle density functional theory calculations show that the slow migration of the doubly charged O vacancy at high temperature cannot be solely caused by the ground-state migration energy but by the contribution of phonon excitations to the free migration energy. With increasing temperature, the effective barrier for oxygen vacancy migration increases. At about 1000 K, which is the operating temperature of fuel cells, the calculated O vacancy diffusivity is more than one order of magnitude lower than that determined using ground-state migration barrier. The calculated diffusivity data agree well with experimental results from literature. The present work reveals that the high-temperature stability of BaZrO3 is mainly due to the phonon contribution to the free migration energy of the O vacancy.
Keywords: perovskite, high-temperature stability, ab-initio calculation, O vacancy

Registration No. 26262 - Permalink


Achievement of a table-like magnetocaloric effect in the dual-phase ErZn2/ErZn composite
Li, L.; Yuan, Y.; Qi, Y.; Wang, Q.; Zhou, S.
Corresponding author: Li, L. Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, China
Abstract: Dual-phase ErZn2/ErZn composite was obtained by induction-melting method. The composite crystallizes in the phases of ErZn2 and ErZn with the weight ratio of 53.8:46.2. The composite undergoes two successive magnetic phase transitions. And accordingly two peaks (partly overlapped) are appeared in the temperature dependence of magnetic part of entropy change SM(T) curves which resulting in a table-like magnetocaloric effect (MCE) and large refrigerant capacity (RC). The MCE parameters are comparable or even larger than most of the recently reported potential magnetic refrigerant materials at similar temperature region, making the dual-phase ErZn2/ErZn composite attractive for low-temperature magnetic refrigeration.

Registration No. 26261 - Permalink


Ion beams for the creation of magnonic circuits
Fassbender, J.ORC
Abstract: Ion beams for the Creation of magnonic circuits
Keywords: ions, magnetism, magnonics
  • Invited lecture (Conferences)
    Magnonics - quo vadis?, 27.10.2017, Kaiserslautern, Deutschland

Registration No. 26260 - Permalink


Temperature measurement of hohlraum radiation for energy loss experiments in indirectly laser heated carbon plasma
Schumacher, D.; Bedacht, S.; Blazevic, A.; Busold, S.; Cayzac, W.; Frank, A.; Heßling, T.; Kraus, D.; Ortner, A.; Schaumann, G.; Roth, M.
Abstract: For ion energy loss measurements in plasmas with near solid densities, an indirect laser heating scheme for carbon foils has been developed at GSI Helmholtzzentrum für Schwerionenforschung GmbH (Darmstadt, Germany). To achieve an electron density of 10^22 cm^3 and an electron temperature of 10–30 eV, two carbon foils with an areal density of 100 μg/cm^2 heated in a double-hohlraum configuration have been chosen. In this paper we present the results of temperature measurements of both primary and secondary hohlraums for two different hohlraum designs. They were heated by the PHELIX laser with a wavelength of 527 nm and an energy of 150 J in 1.5 ns. For this purpose the temperature has been investigated by an x-ray streak camera with a transmission grating as the dispersive element.

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Registration No. 26259 - Permalink


Residual tumour hypoxia in head-and-neck cancer patients undergoing primary radiochemotherapy, final results of a prospective trial on repeat FMISO-PET imaging
Löck, S.; Perrin, R.; Seidlitz, A.; Bandurska-Luque, A.; Zschaeck, S.; Zöphel, K.; Krause, M.; Steinbach, J.; Kotzerke, J.; Zips, D.; Troost, E. G. C.; Baumann, M.
Corresponding author: Krause, M.
Abstract: BACKGROUND:

Hypoxia is a well recognised parameter of tumour resistance to radiotherapy, a number of anticancer drugs and potentially immunotherapy. In a previously published exploration cohort of 25 head and neck squamous cell carcinoma (HNSCC) patients on [18F]fluoromisonidazole positron emission tomography (FMISO-PET) we identified residual tumour hypoxia during radiochemotherapy, not before start of treatment, as the driving mechanism of hypoxia-mediated therapy resistance. Several quantitative FMISO-PET parameters were identified as potential prognostic biomarkers. Here we present the results of the prospective validation cohort, and the overall results of the study.
METHODS:

FMISO-PET/CT images of further 25 HNSCC patients were acquired at four time-points before and during radiochemotherapy (RCHT). Peak standardised uptake value, tumour-to-background ratio, and hypoxic volume were analysed. The impact of the potential prognostic parameters on loco-regional tumour control (LRC) was validated by the concordance index (ci) using univariable and multivariable Cox models based on the exploration cohort. Log-rank tests were employed to compare the endpoint between risk groups.
RESULTS:

The two cohorts differed significantly in several baseline parameters, e.g., tumour volume, hypoxic volume, HPV status, and intercurrent death. Validation was successful for several FMISO-PET parameters and showed the highest performance (ci=0.77-0.81) after weeks 1 and 2 of treatment. Cut-off values for the FMISO-PET parameters could be validated after week 2 of RCHT. Median values for the residual hypoxic volume, defined as the ratio of the hypoxic volume in week 2 of RCHT and at baseline, stratified patients into groups of significantly different LRC when applied to the respective other cohort.
CONCLUSION:

Our study validates that residual tumour hypoxia during radiochemotherapy is a major driver of therapy resistance of HNSCC, and that hypoxia after the second week of treatment measured by FMISO-PET may serve as biomarker for selection of patients at high risk of loco-regional recurrence after state-of-the art radiochemotherapy.

Copyright © 2017 Elsevier B.V. All rights reserved.
Keywords: Advanced stage HNSCC; FMISO-PET; Hypoxia; Prognostic biomarker; Radiochemotherapy

Registration No. 26256 - Permalink


Quality assessment of delineation and dose planning of early breast cancer patients included in the randomized Skagen Trial 1
Francolini, G.; Thomsen, M. S.; Yates, E. S.; Kirkove, C.; Jensen, I.; Blix, E. S.; Kamby, C.; Nielsen, M. H.; Krause, M.; Berg, M.; Mjaaland, I.; Schreiber, A.; Kasti, U. M.; Boye, K.; Offersen, B. V.
Corresponding author: Krause, M.
Abstract: BACKGROUND AND PURPOSE:

To report on a Quality assessment (QA) of Skagen Trial 1, exploring hypofractionation for breast cancer patients with indication for regional nodal radiotherapy.
MATERIAL AND METHODS:

Deviations from protocol regarding target volume delineations and dose parameters (Dmin, Dmax, D98%, D95% and D2%) from randomly selected dose plans were assessed. Target volume delineation according to ESTRO guidelines was obtained through atlas based automated segmentation and centrally approved as gold standard (GS). Dice similarity scores (DSC) with original delineations were measured. Dose parameters measured in the two delineations were reported to assess their dosimetric outcome.
RESULTS:

Assessment included 88 plans from 12 centres in 4 countries. DSC showed high agreement in contouring, 99% and 96% of the patients had a complete delineation of target volumes and organs at risk. No deviations in the dosimetric outcome were found in 76% of the patients, 82% and 95% of the patients had successful coverage of breast/chestwall and CTVn_L2-4-interpectoral. Dosimetric outcomes of original delineation and GS were comparable.
CONCLUSIONS:

QA showed high protocol compliance and adequate dose coverage in most patients. Inter-observer variability in contouring was low. Dose parameters were in harmony with protocol regardless original or GS segmentation.
Keywords: Delineation; Quality assessment; Skagen Trial 1

Registration No. 26255 - Permalink


Beam operation with ELBE SRF gun using Mg photo cathodes
Xiang, R.; Teichert, J.; Arnold, A.; Murcek, P.; Lu, P.; Vennekate, H.
Abstract: In this presentation the latest results of SRF gun-II with Mg photocathode is overviewed. The stable beam from SRF gun was guided into ELBE linac for a whole week of neutron beam time and THz beam time without unexperted breakdown.
  • Lecture (Conference)
    The 3rd annual meeting of Matter and Technologies, 31.01.-02.02.2017, Darmstadt, Germany

Registration No. 26253 - Permalink


Status of SRF-gun-II and Photocathodes at HZDR
Xiang, R.
Abstract: In this presentation the latest results of ELBE SRF gun-II with Mg photocathodes are overviewed. And the status of Cs2Te photocathode for SRF gun is also summaried.
  • Invited lecture (Conferences)
    HOPE-II annual meeting, 11.10.2017, Rostock, Germany

Registration No. 26252 - Permalink


Cs2Te and metallic photocathodes for SRF gun at HZDR
Xiang, R.; Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.
Abstract: Quality of photocathode is one of the critical issues for the stability and reliability of the photoinjector system. SRF Gun II with Mg photocathode has successfully provided stable electron beams for ELBE users at HZDR. In this work, we present the various cleaning processes (activation) for Mg photocathodes, e.g. high intensity laser cleaning and thermal treatment. Furthermore, we show the first result of the photoemission study on the alternative metallic cathode, for instance MgY alloy.

To generate higher bunch charge up to 0.5nC, Cs2Te photocathode is planned for SRF gun II. Up to now three Cs2Te photocathodes have been used in SRF gun II, however, they show abnormal phenomena and unwanted contamination for the superconducting cavity.
  • Poster
    European Workshop on Photocathodes for Particle Accelerator Applications (EWPAA 2017), 20.-22.09.2017, Berlin, Germany

Registration No. 26251 - Permalink


Compatibility of SC cavity and "foreigner" photocathodes in SRF gun
Xiang, R.
Abstract: More and more electron accelerator projects ask for “super” electron beams with high brightness, low emittance, and high average current. Under this background, much attention is paid on the research and development of new electron sources potentially providing electron beams with better quality. Superconducting RF photoinjectors allow CW operation and meanwhile provide high E-field on cathode to generator high bunch charge and low emittance beam, thus it is a promising candidate for such kind of high current and high brightness electron source.

However, because Nb itself has too low quantum efficiency, the normal conducting photocathodes, such as alkali photocathodes, are the best photoemitter with high quantum efficiency for SRF gun. The compatibility of photocathodes made of ‘foreigner materials’ inside the sensitive Nb cavity is of the biggest difficulty for the designer of SRF gun. One has to solve a lot of unwanted problems like compatibility, particle contamination, multipacting, dark current etc.

In this presentation we collect the running results of SRF guns with normal conducting photocathodes at HZDR and BNL, share the experience gained during the long term development experiments, and discuss the relative problems in the future development.
  • Invited lecture (Conferences)
    Workshop "Operating SRF in a "dirty" machine", 14.-15.09.2017, Berlin, Germany

Registration No. 26250 - Permalink


Multiphase CFD with OpenFOAM at HZDR
Schlegel, F.
Abstract: Presentation of the activities at HZDR in the field of simulation of multiphase flows with OpenFOAM.
Keywords: OpenFOAM, Multiphase, CFD, Simulation
  • Lecture (Conference)
    OpenFuelCell Workshop, 24.-25.10.2017, Jülich, Deutschland

Registration No. 26248 - Permalink


Hyperdoping of silicon: A last niche of defect engineering?
Berencen, Y.; Liu, F.; Wang, M.; Prucnal, S.; Rebohle, L.; Zhou, S.; Helm, M.; Skorupa, W.
Abstract: Hyperdoping of silicon using ion implantation and short time annealing of chalcogen atoms and transition metals (e.g. S, Se, Te, Au and Ti) appears as a challenging and promising research topic for developing Si-based infrared photodetectors and intermediate band solar cells [i.e.1-3].
The specific physical properties, such as a near-unity broadband absorption (particularly below the Si bandgap), a large enhancement of sub-band-gap photocurrent generation, and the insulator-to-metal transition, are based on this type of doping much above the solid solubility limit of dopants in Si. We have recently been demonstrated that both, laser annealing via the liquid phase and flash lamp annealing via the solid phase can be used to process such high-dose chalcogen-implanted layers [2]. Such kind of non-equilibrium processing needs a careful adjustment of the processing parameters, especially in regard to the “thermal engineering” with processing times at or below the millisecond range, to optimize the defect engineering of this specific type of hyperdoped material. We will report on the microstructural, optical and electrical properties of this new type of silicon material as well as first applications for room-temperature extended infrared Si p-n photodiodes.
[1] J. P. Mailoa, A. J. Akey, C. B. Simmons, D. Hutchinson, J. Mathews, J. T. Sullivan, D. Recht, M. T. Winkler, J. S. Williams, J. M. Warrender, P. D. Persans, M. J. Aziz, and T. Buonassisi, Nat. Commun. 5, 3011 (2014).
[2] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015).
[3] F. Liu, S Prucnal, R. Hübner, Ye Yuan, W Skorupa, M Helm, and S. Zhou, J.Phys.D: Appl.Phys. 49 (2016) 245104.
Keywords: hyperdoping, silicon, ion implantation, flash lamp annealing, chalcogen atoms, transition metals
  • Lecture (Conference)
    17th Conference on Gettering and Defect Engineering in Semiconductor Technology (GADEST 2017), 01.-06.10.2017, Tbilisi, Georgia

Registration No. 26247 - Permalink


Ge/Si core/shell quantum dots in alumina: Tuning the optical absorption by the core and shell size(Article)
Nekić, N.; Sancho-Parramon, J.; Bogdanović-Radović, I.; Grenzer, J.; Hübner, R.; Bernstorff, S.; Ivanda, M.; Buljan, M.
Corresponding author: Nekić, N. Ruer Boškoviæ Institute, Bijenièka cesta 54, Zagreb, Croatia
Abstract: Ge/Si core/shell quantum dots (QDs) recently received extensive attention due to their specific properties induced by the confinement effects of the core and shell structure. They have a type II confinement resulting in spatially separated charge carriers, the electronic structure strongly dependent on the core and shell size. Herein, the experimental realization of Ge/Si core/shell QDs with strongly tunable optical properties is demonstrated. QDs embedded in an amorphous alumina glass matrix are produced by simple magnetron sputtering deposition. In addition, they are regularly arranged within the matrix due to their self-assembled growth regime. QDs with different Ge core and Si shell sizes are made. These core/shell structures have a significantly stronger absorption compared to pure Ge QDs and a highly tunable absorption peak dependent on the size of the core and shell. The optical properties are in agreement with recent theoretical predictions showing the dramatic influence of the shell size on optical gap, resulting in 0.7 eV blue shift for only 0.4 nm decrease at the shell thickness. Therefore, these materials are very promising for light-harvesting applications.
Keywords: absorption, Ge/Si core/shell quantum dots, quantum confinement, self-assembly

Registration No. 26244 - Permalink


Effect of broken axial symmetry on the electric dipole strength and the collective enhancement of level densities in heavy nuclei
Grosse, E.; Junghans, A. R.; Wilson, J. N.
Corresponding author: Grosse, E. Institut für Kern- und Teilchenphysik, TU Dresden
Abstract: The basic parameters for calculations of radiative neutron capture, photon strength functions and nuclear level densities near the neutron separation energy are determined based on experimental data without an ad hoc assumption about axial symmetry—at variance to previous analysis. Surprisingly few global fit parameters are needed in addition to information on nuclear deformation, taken from Hartree Fock Bogolyubov calculations with the Gogny force, and the generator coordinator method assures properly defined angular momentum. For a large number of nuclei the GDR shapes and the photon strength are described by the sum of three Lorentzians, extrapolated to low energies and normalised in accordance to the dipole sum rule. Level densities are influenced strongly by the significant collective enhancement based on the breaking of shape symmetry. The replacement of axial symmetry by the less stringent requirement of invariance against rotation by 180° leads to a novel prediction for radiative neutron capture. It compares well to recent compilations of average radiative widths and Maxwellian average cross sections for neutron capture by even target nuclei. An extension to higher spin promises a reliable prediction for various compound nuclear reactions also outside the valley of stability. Such predictions are of high importance for future nuclear energy systems and waste transmutation as well as for the understanding of the cosmic synthesis of heavy elements.
Keywords: nuclear structure, nuclear level density, giant resonances, nuclear astrophysics, nuclear waste transmutation

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  • Secondary publication expected from 16.10.2018

Registration No. 26243 - Permalink


Trapping of hydrogen and helium at dislocations in tungsten: an ab initio study
Bakaev, A.; Grigorev, P.; Terentyev, D.; Bakaeva, A.; Zhurkin, E. E.; Mastrikov, Y. A.
Corresponding author: Bakaev, A.
Abstract: The interaction of H or He atoms with a core of edge and screw dislocations (SDs), with Burgers vector a0/2 < 111 > s are stronger traps for H and He compared to the SDs, while the H/He affinity to both types of dislocation is significantly weaker than to a single vacancy. The lowest energy atomic configurations are rationalized on the basis of the charge density distribution and elasticity theory considerations. The results obtained contribute to the rationalization of the thermal desorption spectroscopy analysis by attributing certain peaks of the release of plasma components to the detrapping from dislocations. Complementary molecular statics (MS) calculations are performed to validate the accuracy of the recently developed W-H-He embedded atom method (EAM) and bond-order potentials. It is revealed that the EAM potential can reproduce correctly the magnitude of the interaction of H with both dislocations as compared to the ab initio results. All the potentials underestimate significantly the He-dislocation interaction and cannot describe correctly the lowest energy positions for H and He around the dislocation core. The reason for the discrepancy between ab initio and the MS results is rationalized by the analysis of the fully relaxed atomic configurations.
Keywords: tungsten; plasma; hydrogen; helium; dislocations; ab initio; molecular statics

Registration No. 26241 - Permalink


Excitations and relaxation dynamics in multiferroic GeV4S8 studied by terahertz and dielectric spectroscopy
Reschke, S.; Wang, Z.; Mayr, F.; Ruff, E.; Lunkenheimer, P.; Tsurkan, V.; Loidl, A.
Corresponding author: Loidl, A. Uni Augsburg
Abstract: We report on THz time-domain spectroscopy on multiferroic GeV4S8, which undergoes orbital ordering at a Jahn-Teller transition at 30.5 K and exhibits antiferromagnetic order below 14.6 K. The THz experiments are complemented by dielectric experiments at audio and radio frequencies. We identify a low-lying excitation close to 0.5 THz, which is only weakly temperature dependent and probably corresponds to a molecular excitation within the electronic level scheme of the V4 clusters. In addition, we detect complex temperature-dependent behavior of a low-lying phononic excitation, closely linked to the onset of orbitally driven ferroelectricity. In the high-temperature cubic phase, which is paramagnetic and orbitally disordered, this excitation is of relaxational character becomes an overdamped Lorentzian mode in the orbitally ordered phase below the Jahn-Teller transition, and finally appears as well-defined phonon excitation in the antiferromagnetic state. Abrupt changes in the real and imaginary parts of the complex dielectric permittivity show that orbital ordering appears via a structural phase transition with strong first-order character and that the onset of antiferromagnetic order is accompanied by significant structural changes, which are of first-order character, too. Dielectric spectroscopy documents that at low frequencies, significant dipolar relaxations are present in the orbitally ordered, paramagnetic phase only. In contrast to the closely related GaV4S8, this relaxation dynamics that most likely mirrors coupled orbital and polar fluctuations does not seem to be related to the dynamic processes detected in the THz regime.

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Registration No. 26239 - Permalink


Serpent solution of X2 benchmark: fresh core at HZP conditions
Bilodid, Y.; Fridman, E.
Abstract: The X2 benchmark, published in AER conference proceedings, describes first 4 fuel cycles of the Khmelnitsky NPP 2nd unit (KhNPP-2) with VVER-1000 reactor. The benchmark specifications contain description of the reactor core and operational history supplemented by measured operational data. In this work, the HZP experiments conducted in the KhNPP-2 fresh core are modelled with the Serpent-2 Monte Carlo code. The numerical results are validated against the available measured core data.
Keywords: Serpent, VVER-1000, X2 benchmark
  • Contribution to proceedings
    The 27th Symposium of AER on VVER Reactor Physics and Reactor Safety, 17.-20.10.2017, Munich, Germany
    Proceedings of the 27th Symposium of AER on VVER Reactor Physics and Reactor Safety
  • Lecture (Conference)
    The 27th Symposium of AER on VVER Reactor Physics and Reactor Safety, 17.-20.10.2017, Munich, Germany

Registration No. 26237 - Permalink


Nanometer-scale characterization of laser-driven compression, shocks, and phase transitions, by x-ray scattering using free electron lasers
Kluge, T.; Rödel, C.; Rödel, M.; Pelka, A.; Mcbride, E. E.; Fletcher, L. B.; Harmand, M.; Krygier, A.; Higginbotham, A.; Bussmann, M.; Galtier, E.; Gamboa, E.; Garcia, A. L.; Garten, M.; Glenzer, S. H.; Granados, E.; Gutt, C.; Lee, H. J.; Nagler, B.; Schumaker, W.; Tavella, F.; Zacharias, M.; Schramm, U.; Cowan, T. E.
Corresponding author: Kluge, T. HZDR
Abstract: We study the feasibility of using small angle X-ray scattering (SAXS) as a new experimental diagnostic for intense laser-solid interactions. By using X-ray pulses from a hard X-ray free electron laser, we can simultaneously achieve nanometer and femtosecond resolution of laser-driven samples. This is an important new capability for the Helmholtz international beamline for extreme fields at the high energy density endstation currently built at the European X-ray free electron laser. We review the relevant SAXS theory and its application to transient processes in solid density plasmas and report on first experimental results that confirm the feasibility of the method. We present results of two test experiments where the first experiment employs ultra-short laser pulses for studying relativistic laser plasma interactions, and the second one focuses on shock compression studies with a nanosecond laser system.

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Registration No. 26231 - Permalink


In situ ohmic contact formation for n-type Ge via non-equilibrium processing
Prucnal, S.; Frigerio, J.; Napolitani, E.; Ballabio, A.; Berencén, Y.; Rebohle, L.; Wang, M.; Böttger, R.; Voelskow, M.; Isella, G.; Hübner, R.; Helm, M.; Zhou, S.; Skorupa, W.
Corresponding author: Prucnal, S.
Abstract: Highly scaled nanoelectronics requires effective channel doping above 5×10^19 /cm3 together with ohmic contacts with extremely low specific contact resistivity. Nowadays, Ge becomes very attractive for modern optoelectronics due to the high carrier mobility and the quasi-direct bandgap, but n-type Ge doped above 5×10^19 /cm3 is metastable and thus difficult to be achieved. In this letter, we report on the formation of low-resistivity ohmic contacts in highly n-type doped Ge via non-equilibrium thermal processing consisting of millisecond-range flash lamp annealing. This is a single-step process that allows for the formation of a 90 nm thick NiGe layer with a very sharp interface between NiGe and Ge. The measured carrier concentration in Ge is above 9×10^19 /cm3 with a specific contact resistivity of 1.2×10^(−6) Ω cm2.
Simultaneously, both the diffusion and the electrical deactivation of P are fully suppressed.
Keywords: germanium, flash lamp annealing, ion implantation, NiGe, ohmic contact

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  • Secondary publication expected from 04.10.2018

Registration No. 26223 - Permalink


Thermal convection in liquid metal batteries
Personnettaz, P.; Weber, N.; Koellner, T.; Nimtz, M.; Weier, T.
Abstract: Liquid Metal Batteries ( LMBs ) are a promising electrochemical energy storage technology, built as a stable density stratification of two liquid metals separated by a molten salt. In this work, we focus our attention on thermal convection that appear inside Li||Bi LMBs. The chemistry of the cell is first presented. Then all possible thermal phenomena are discussed, with a continuum mechanics approach. The temperature profile is first defined in the hypothesis of pure conduction. Moreover, in order to take into account thermal convection inside the cell, the multiphase solver multiphaseInterFOAM is extended. The results of this solver are compared to the one of a pseudo-spectral code. Finally the first result of thermal convection in Li||Bi LMB is presented. The future work on transport phenomena in LMBs is also briefly summarized.
Keywords: thermal convection, transport phenomena, liquid metal battery, numerical model, OpenFOAM.
  • Lecture (Conference)
    openFuelCell workshop, 24.10.2017, Jülich, Deutschland

Registration No. 26218 - Permalink


Multiscaled experimental investigations of corrosion and precipitation processes after loss-of-coolant accidents in pressurized water reactors
Renger, S.; Alt, S.; Gocht, U.; Kästner, W.; Seeliger, A.; Kryk, H.; Harm, U.
Abstract: In a joint research project of the Zittau/Goerlitz University of Applied Sciences (HSZG), the Technische Universitaet Dresden (TUD) and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the main emphasis is the time-related assignment of simultaneous and interacting mechanisms at zinc sources and zinc sinks at boundary conditions of a loss-of-coolant accident (LOCA) in German pressurized water reactors (PWR). The according experiments are carried out at semi-technical as well as at laboratory scale.
Zinc is used as a protective coating, e.g. for gratings in the containment, showing high corrosion resistance due to a gradual formation of passivating layers. In contrast, its long-term behaviour during LOCA changes significantly under the influence of the coolant chemistry of German PWR. As a consequence, according installations in the containment act as zinc sources due to corrosion. Released zinc ions change the chemical properties of the coolant and could e.g. lead to layer-forming depositions of zinc borates in the core, which increase the possibility of a hindered heat dissipation. For experimental and methodical investigations of these phenomena, the test rig “Zittau Flow Tray” (ZFT), a scaled sump model of a German PWR, was equipped with a full-length 3×3 fuel assembly (FA) dummy acting as core model, a preheater and a cooler component. Nine 4.4 m long fuel rod dummies simulate the decay heat by internal heating cartridges. This rig design enables experimental investigation of physico-chemical mechanisms considering coolant containing boric acid and zinc and their influence on the thermo-hydraulic processes in the reactor core at post-LOCA boundary conditions.
The time depending zinc release at hot-dip galvanized gratings (HGG) was investigated regarding their position (e.g. inside or near the leaking jet, freely suspended or submerged in the coolant) and their surface area as well as temperature and flow rate of the coolant. The experimental database allows the approximation of corrosion rates in dependence of HGG position and the accident-specific coolant leakage rate as well as the development of first mathematical approaches for the modelling of zinc sources.
Keywords: pressurized water reactor, PWR, corrosion, LOCA, loss-of-coolant accident, experiment, zinc, zinc borate, debris, deposition, precipitation, particle formation, chemical effects
  • Lecture (Conference)
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi'an, China
  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi'an, China
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17)

Registration No. 26214 - Permalink


Speziation trivalenter Actinide/Lanthanide im Verdauungssystem
Barkleit, A.ORC; Wilke, C.
Abstract: Im Falle einer Inkorporation radioaktiver Stoffe entstehen ernsthafte gesundheitliche Risiken durch deren Chemo- und Radiotoxizität. Um die möglichen toxischen Effekte besser abschätzen und letztendlich verhindern zu können, ist es notwendig, die Speziation dieser Elemente im menschlichen Organismus auf molekularer Ebene zu verstehen. Die Speziation beeinflusst die Aufnahme, den Transport, den Metabolismus, die Einlagerung und die Ausscheidung der Elemente.
Die Gefahr einer oralen Aufnahme von Radionukliden besteht durch kontaminierte Lebensmittel oder Trinkwasser. Deshalb haben wir die Speziation von ausgewählten dreiwertigen Actiniden und Lanthaniden (Cm(III) und Eu(III)) in den Biofluiden des Verdauungstraktes näher untersucht [1]. Die Biofluide wurden nach einer international anerkannten Methode (Unified Bioaccessibility Method, UBM) der Bioaccessibility Research Group of Europe (BARGE) synthetisch hergestellt [2]. Parallel dazu wurden natürliche menschliche Speichelproben zum Vergleich in die Untersuchungen einbezogen [3].
Die Speziatonsuntersuchungen von Cm(III) und Eu(III) in den Verdauungsfluiden wurden mit Hilfe der zeitaufgelösten laserinduzierten Fluoreszenzspektroskopie (Time-Resolved Laser-induced Fluorescence Spectroscopy, TRLFS) durchgeführt. Für Speichel wurde ermittelt, dass sich zum größten Teil (60-90%) anorganische Komplexe bilden, darunter dominiert ein ternärer Komplex mit Phosphat und Carbonat als Liganden und Calcium als weiterem Kation zum Ladungsausgleich. Organische Komplexe, hauptsächlich mit dem Verdauungsenzym α-Amylase, wurden ebenfalls nachgewiesen. Wenn die Speichelmischung den Magen erreicht, findet aufgrund des niedrigen pH-Wertes im Magen (pH<2) eine Dissoziation der Komplexe statt, Cm(III) und Eu(III) liegen dann hauptsächlich in Form ihrer Aquo-Komplexe vor. Aber ein kleiner Teil der Metallionen (ca. 20%) bildet trotz des niedrigen pH-Wertes Komplexe mit dem Verdauungsenzym Pepsin. Im Dünndarm, wo die eigentliche Verdauung und die Absorption der (Nähr-, aber auch Gift-)Stoffe in den Blutkreislauf stattfindet, werden die Metallionen hauptsächlich (ca. 65%) von dem Protein Muzin komplexiert, welches Hauptbestandteil der schützenden Schleimhaut (Mucosa) ist, und ca. 35% liegen als anorganische Spezies mit Phosphat und Carbonat als Liganden vor.

[1] C. Wilke et al., J. Inorg. Biochem. 175, 2017, 248-258
[2] J. Wragg et al., British Geological Survey Open Report OR/07/027, Keyworth, Nottingham, 2009, 90 pp.
[3] A. Barkleit et al., Dalton Trans. 46, 2017, 1593-1605.
Keywords: digestive media, speciation, europium, curium
  • Invited lecture (Conferences)
    2. Workshop - Helmholtz Cross Program Activity, Querschnittsthema Strahlenforschung "Transportprozesse in Mensch und Umwelt", 24.-25.10.2017, Darmstadt, Deutschland

Registration No. 26213 - Permalink


Chemische Effekte bei Kühlmittelverluststörfällen in Druckwasserreaktoren - Arbeiten des Kompetenzzentrums Ost für Kerntechnik
Kryk, H.; Kästner, W.; Hampel, U.; Seeliger, A.
Abstract: Zur Abfuhr der Nachzerfallswärme in der Spätphase eines Kühlmittelverluststörfalles in Druckwasserreaktoren wird das aus den Leck im Primärkreislauf austretende Kühlwasser aus dem Reaktorsumpf im sog. Sumpfumwälzbetrieb mittels der Niederdruckeinspeisepumpen in den Reaktorkern rezirkuliert. Im Containment kommt das Kühlmittel dabei in Kontakt mit Fremdstoffen, wie z.B. Isoliermaterialfasern, Staub und korrosiven Materialien, welche einerseits die Kühlmittelchemie und andererseits die Performance der den Pumpen vorgeschalteten Sumpfsiebe beeinflussen können. Weiterhin haben Studien gezeigt, dass feuerverzinkte Containment-Einbauten (z.B. Lichtgitterroste, Stützgitter von Sumpfsieben, Kanäle) einer beschleunigten Korrosion durch das borsäurehaltige Kühlmittel unterliegen. Die daraus resultierenden thermohydraulischen Effekte hängen in hohem Maße vom Löslichkeitsverhalten der Korrosionsprodukte ab. So können unlösliche Korrosionspartikel zu einem erhöhten Differenzdruck an den bereits mit Isoliermaterialfasern beladenen Sumpfsieben führen, während lösliche Korrosionsprodukte nicht zurückgehalten werden und somit in den Kern gelangen, was unter Umständen in Ausfällungsprozessen durch Temperaturänderungen resultiert.
Da ein Einfluss dieser Effekte auf die Kernkühlung nicht ausgeschlossen werden kann, ist die Untersuchung der zugrundeliegenden physikochemischen Korrosions-, Ausfällungs- und Ablagerungsprozesse sowie deren thermohydraulischen Folgen Gegenstand von gemeinsamen Forschungsvorhaben des Helmholtz-Zentrums Dresden-Rossendorf, der TU Dresden sowie der Hochschule Zittau-Görlitz. Der Vortrag gibt einen Überblick über die bisherigen Forschungsarbeiten der o.g. Institutionen sowie die wesentlichen Ergebnisse der entsprechenden BMWi-Forschungsvorhaben im Kontext der Reaktorsicherheitsforschung.
Keywords: Kühlmittelverluststörfall, KMV, Druckwasserreaktor, DWR, Korrosion, Zink, Zinkborat, Reaktorsicherheitsforschung, Loss-of-coolant Accident, LOCA, Pressurized Water Reactor, PWR, Corrosion, Zinc, Zinc Borate, Nuclear Safety Research, Chemical Effects
  • Invited lecture (Conferences)
    49. Kraftwerkstechnisches Kolloquium 2017, 17.-18.10.2017, Dresden, Deutschland
  • Contribution to proceedings
    49. Kraftwerkstechnisches Kolloquium 2017, 17.-18.10.2017, Dresden, Deutschland
    Kraftwerkstechnik 2017 - Strategien, Anlagentechnik und Betrieb, Freiberg: SAXONIA, 978-3-934409-79-8, 101-115

Registration No. 26208 - Permalink


Research Data Management to increase research quality
Konrad, U.
Abstract: The publication is an invited plenary lecture at the national workshop on documentation and information in Jakarta, Indonesia.
Research data play a fundamental role in todays open science driven research. In addition the software used to generate, process or analyse the data has to be considered for the whole research and publication process to ensure, that results are findable, accessible, interoperable, re-usable and re-producible. The lecture describes the challenges, tasks, solutions and organization structures to meet the challenges for the library and data center at the Helmholtz-Center Dresden-Rossendorf and beyond.
Keywords: Open Science, Research Data Management, Software Management, Data Center, Library
  • Invited lecture (Conferences)
    National Workshop on Documentation and Information Data, Information and Knowledge, 25.-26.10.2017, Jakarta, Indonesia
    DOI: 10.5281/zenodo.1040289
    DOI-Link: http://dx.doi.org/10.5281/zenodo.1040289

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Registration No. 26206 - Permalink


Population balance modeling using class and quadrature-based moment methods with application to bubbly flows
Oertel, R.; Li, D.; Pollack, M.; Saalenbauch, S.; Schlegel, F.; Hasse, C.; Lucas, D.
Abstract: Multi-phase flows with a continuous and a distinct disperse phase are essential in a variety of industrial applications, e.g., in chemical engineering or in nuclear safety research. These flows are usually polydisperse, i.e., the disperse phase exhibits a size distribution. In case of bubbly flows, the size distribution and its statistical moments are highly influenced by the overall heat- and mass transfer rates as well as the flow structure, e.g., during the transition from the homogeneous to the heterogeneous regime in bubble columns. Temporal and spatial changes of the size distribution can be described with a transport equation for the number density function (NDF), i.e., the population balance equation (PBE). Two popular Eulerian methods to solve the PBE are the method of classes and the family of Quadrature Based Methods of Moments (QBMM). Both approaches have been applied in CFD before, e.g., for simulations of stirred tanks, spray behavior or soot formation. However, OpenFOAM offers no capabilities in this regard. While the Quadrature Method of Moments (QMOM) - the basic QBMM approach - tracks only the moments of the NDF, class methods track the shape of the NDF directly by means of discretization. An extended version of QMOM, called EQMOM, allows reconstructing the NDF using a set of kernel density functions. All three approaches are implemented into the OpenFOAM library and validated against analytical solutions. A comparison for pipe flow and bubble column cases using appropriate coalescence and breakup models shows the accuracy and performance of each method. Furthermore, it is known for bubbly flows that the velocity of the disperse phase is generally size dependent and the bubbles may separate spatially. An extreme case is the lift force, which governs the lateral migration of bubbles in a liquid shear field and changes its sign at a critical diameter. This effect is not covered by the general two-fluid or Euler-Euler approach. Partially, this can be taken into account using a multi-fluid solver, by splitting the disperse phase into velocity groups with fixed boundaries. An alternative approach is to include the velocity as an internal coordinate into the PBE, which gives the generalized PBE (GBPE). Using a size-conditioned velocity approach, the GBPE can be solved within the QBMM framework. Thereby, a continuous information about the dependency of velocity on size can be obtained. The work presents first results and comparisons between the two approaches.
  • Invited lecture (Conferences)
    5th OpenFOAM User Conference, 17.-18.10.2017, Wiesbaden, Deutschland

Registration No. 26203 - Permalink


Sb-related defects in Sb-doped ZnO thin film grown by pulsed laser deposition
Luo, C.; Ping, H. L.; Azad, F.; Anwand, W.; Butterling, M.; Wagner, A.; Kuznetsov, A.; Zhu, H.; Su, S. C.; Ling, F. C. C.
Corresponding author: Ling, F. C. C. Department of Physics, The University of Hong Kong, Hong Kong, China
Abstract: Sb-doped ZnO films were fabricated on c-plane sapphire using the pulsed laser deposition method and characterized by the Hall effect measurement, X-ray photoelectron spectroscopy, X-ray diffraction, photoluminescence and positron annihilation spectroscopy. Systematic studies on the growth conditions with different Sb composition, oxygen pressure and post-growth annealing were conducted. If the Sb doping concentration is lower than the threshold ~8×E20 cm-3, the as-grown films grown with appropriate oxygen pressure could be n~4×E20 cm-3. The shallow donor was attributed to the SbZn related defect. Annealing these samples lead to the formation of the SbZn-2VZn shallow acceptor which subsequently compensated the free carrier. For samples with Sb concentration exceeding the threshold, the yielded as-grown samples were highly resistive. X-ray diffraction results showed that the Sb dopant occupied the O site rather than the Zn site as the Sb doping exceeded the threshold, whereas the SbO related deep acceptor was responsible for the high resistivity of the samples.
Keywords: ZnO, Sb-doping, shallow donors, shallow acceptors, compensating defects

Registration No. 26200 - Permalink


Magnetohydrodynamic flow simulation in liquid metal batteries
Weber, N.; Personnettaz, P.; Stefani, F.; Weier, T.
Abstract: Overview about numerical simulation of liquid metal batteries at HZDR
  • Lecture (Conference)
    OpenFuelCell Workshop, 24.10.2017, Forschungszentrum Jülich, Deutschland

Registration No. 26199 - Permalink


Radionuclides in living organisms – Calorimetric determination of the radionuclide toxicity
Sachs, S.; Fahmy, K.ORC; Oertel, J.; Geipel, G.; Bok, F.
Abstract: Quantification of radionuclide transfer within the environment and to the food chain is required for the reliable human risk assessment. The uptake of radionuclides by plants is typically described phenomenologically by transfer factors. However, investigations on a molecular level are necessary to understand the underlying processes. We studied the interaction of U(VI) with canola cells (Brassica napus) focusing on the concentration-dependent impact of U(VI) on the cell metabolism. Isothermal microcalorimetry was used to monitor the metabolic heat flow of the cells, which was compared to the cell viability. The speciation of U(VI) in the medium was determined by time-resolved laser-induced fluorescence spectroscopy and thermodynamic modeling. The data reveal the correlation of U(VI) hydroxo species with metabolic heat release and general oxidoreductase on a quantitative toxicity scale [1].

[1] Sachs, S., Geipel, G., Bok, F., Oertel, J., Fahmy, K., Calorimetrically determined U(VI) toxicity in Brassica napus correlates with oxidoreductase activity and U(VI) speciation. Env. Sci. Technol. 51 (2017) 10843.
Keywords: plant cells, uranium, cell metabolisms, isothermal microcalorimetry, cell viability, speciation, TRLFS, thermodynamic modeling, speciation
  • Invited lecture (Conferences)
    2. Workshop - Helmholtz Cross Program Activity, Querschnittsthema Strahlenforschung "Transportprozesse in Mensch und Umwelt", 24.-25.10.2017, Darmstadt, Deutschland

Registration No. 26197 - Permalink


In-chip microstructures and photonic devices fabricated by nonlinear laser lithography deep inside silicon
Tokel, O.; Turnalı, A.; Makey, G.; Elahi, P.; Çolakoğlu, T.; Ergeçen, E.; Yavuz, Ö.; Hübner, R.; Zolfaghari Borra, M.; Pavlov, I.; Bek, A.; Turan, R.; Koray Kesim, D.; Tozburun, S.; Ilday, S.; Ilday, F. Ö.
Corresponding author: Tokel, O. Bilkent University
Abstract: Silicon is an excellent material for microelectronics and integrated photonics, with untapped potential for mid-infrared optics. Despite broad recognition of the importance of the third dimension, current lithography methods do not allow the fabrication of photonic devices and functional microelements directly inside silicon chips. Even relatively simple curved geometries cannot be realized with techniques like reactive ion etching. Embedded optical elements, electronic devices and better electronic–photonic integration are lacking. Here, we demonstrate laser-based fabrication of complex 3D structures deep inside silicon using 1-μm-sized dots and rod-like structures of adjustable length as basic building blocks. The laser-modified Si has an optical index different to that in unmodified parts, enabling the creation of numerous photonic devices. Optionally, these parts can be chemically etched to produce desired 3D shapes. We exemplify a plethora of subsurface - that is, ‘in-chip’ - microstructures for microfluidic cooling of chips, vias, micro-electromechanical systems, photovoltaic applications and photonic devices that match or surpass corresponding state-of-the-art device performances.

Registration No. 26192 - Permalink


Nanomagnet fabrication by ion beams
Fassbender, J.
Abstract: In recent years the tailoring of magnetic properties by means of ion irradiation and implantation techniques has become fashionable. Early investigations relied on the fact that the perpendicular magnetic anisotropy of Co/Pt multilayers depend sensitively on the interface sharpness [1]. Subsequently also the ion induced modification of exchange bias phenomena as well as interlayer exchange coupling have been investigated [2]. For single magnetic films ion implantation has been used to reduce the Curie temperature and hence the saturation magnetization [3]. Nowadays also the reverse process, i.e. the creation of nanomagnets within special binary alloys is employed [4,5]. In combination with lithography or with focused ion beams a pure magnetic patterning becomes possible [6] leading to hybrid magnetic materials [7] with properties different from both, the ion irradiated as well as the untreated material. Even ion induced chemical reduction can be employed to create a nanomagnetic pattern [8,9].
An overview of the present status in this research field will be given.
[1] C. Chappert et al., Science, 280 (1998) 1919.
[2] J. Fassbender, D. Ravelosona, Y. Samson, J. Phys. D, 37 (2004) R179. [3] J. Fassbender, J. McCord, Appl. Phys. Lett., 88 (2006) 252501.
[4] E. Menendez et al., Small, 5 (2009) 229.
[5] R. Bali et al., Nano Lett., 14 (2014) 435.
[6] J. Fassbender and J. McCord, J. Magn. Magn. Mater., 320 (2008) 579. [7] J. McCord, L. Schultz, J. Fassbender, Adv. Mater., 20 (2008) 2090.
[8] S. Kim et al., Nature Nanotechnology, 7 (2012) 567.
[9] J. Fassbender, Nature Nanotechnology, 7 (2012) 554.
Keywords: magnetism, ion irradiation, magnetic patterning
  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism, 01.-05.07.2017, Moscow, Russia

Registration No. 26191 - Permalink


Gefüge und Eigenschaften des warmfesten Chromstahls P91
Kohlar, S.
Abstract: Aufgabenstellung:
Aus einem Rohrstück des Materials P91 soll nach der Erarbeitung eines Probenplans zunächst das Gefüge in allen 3 Orientierungen metallographisch charakterisiert werden. Anschließend wird das Material mechanisch - technologisch sowie bruchmechanisch und fraktographisch untersucht. Die daraus erhaltenen Werkstoffkennwerte sollen mit dem Gefüge und dem fraktographischen Befund in Beziehung gesetzt werden.
Großer Beleg, angefertigt 2009
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-082 2017

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Registration No. 26190 - Permalink


Interaction between Double Diffusive Convection and Solidification in Ammonium-Chloride Solutions
Anders, S.; Eckert, S.
Abstract: This paper presents an experimental investigation of thermally and chemically driven convection with simultaneous crystallisation in a concentrated aqueous ammonium-chloride solution. Measurements were performed in a transparent Hele-Shaw cell (200·100·10mm3) between two massive copper blocks equipped with internal water channels controlling the thermal boundary conditions at the upper and lower horizontal boundaries. The temperatures were regulated by thermostats in a range between -20°C and +40°C giving Rayleigh numbers up to around 0.2·10 9 . A double-wall construction with climatisation was implemented in order to avoid thermal losses through the side walls. Temperatures were monitored by thermocouples calibrated to an accuracy better than 0.05K.
Various flow regimes were studied by choosing different temperature boundary conditions.
The focus was on configurations with negative vertical temperature gradients where thermal convection occurs once a critical temperature difference is exceeded. At sufficient supercooling free crystals nucleate in the upper part of the cell, grow and descend due to their higher density compared to the ambient fluid.
The flow field in the liquid was measured by PIV using fluorescent tracer-particles and laser illumination. PTV with LED-background lighting was used to determine the size-evolution and the trajectories of the free-moving crystals. The application of alternating lighting methods and advanced digital image filtering allows for simultaneous operation of PIV and PTV. This approach enables a quantitative study of the interplay of different convection regimes and the solidification process. For example the relation between drag-coefficient, crystal size and crystal growth was investigated.
As a reference case a stable stratification resulting from parallel cooling of the top and bottom walls was investigated. The following solidification phenomena were observed during the experiments: columnar growth at the walls, nucleation and growth of equiaxed crystals in the bulk, chimney-formation in the mushy layer as well as the remelting of columnar and equiaxed dendrites.
Keywords: equiaxed solidification, double diffusive convection, dual phase velocimetry, PTV, PIV
  • Lecture (Conference)
    SP17, Solidification Processing 2017, 25.-28.07.2017, Beaumont Estate, Old Windsor, United Kingdom
  • Contribution to proceedings
    SP17, Solidification Processing 2017, 25.-28.07.2017, Beaumont Estate, Old Windsor, United Kingdom
    Proceedings of the 6th Decennial International Conference on Solidification Processing, London: BCAST, Brunel University London, 978-1-908549-29-7, 350-353

Registration No. 26185 - Permalink


Combined experimental and numerical analysis of a bubbly liquid metal flow
Krull, B.; Strumpf, E.; Keplinger, O.; Shevchenko, N.; Fröhlich, J.; Eckert, S.; Gerbeth, G.
Corresponding author: Krull, B. TU Dresden
Abstract: The paper proposes a combined experimental and numerical procedure for the investigation of bubbly liquid-metal flows. It describes the application to a model configuration consisting of a recirculating GaInSn flow driven by an argon bubble chain. The experimental methods involve X-ray measurements to detect the bubbles and UDV measurements to gain velocity information about the liquid metal. The chosen numerical method is an immersed boundary method extended to deformable bubbles. The model configuration includes typical phenomena occurring in industrial applications and allows insight into the physics of bubbly liquid-metal flows. It constitutes an attractive test case for assessing further experimental and numerical methods.
Keywords: Bubbly liquid-metal flows, Xray radiography, UDV, GaInSn

Registration No. 26184 - Permalink


Investigating spin-transfer torques induced by thermal gradients on magnetic tunnel junctions using microcavity ferromagnetic resonance
Cansever, H.; Fowley, C.; Narkovic, R.; Lenz, K.; Kowalska, E.; Yildirim, O.; Aleksandrov, Y.; Lindner, J.; Fassbender, J.; Deac, A. M.
Abstract: Similar to electrical currents flowing through magnetic multilayers [1], it has been predicted that thermal gradients applied across the spacer of a spin-valve or a magnetic tunnel junction may induce pure spin currents and generate ‘thermal’ spin-transfer torques (T-STTs) large enough to induce magnetization dynamics [2-3]. Nevertheless, providing detailed experimental studies in this direction has so far proved elusive, due to difficulties in generating sufficiently large thermal gradients for such effects to be observed. Here, we describe a different approach, which focuses on observing and quantifying spin-transfer torques induced by thermal gradients in magnetic multilayers by means of ferromagnetic resonance (FMR) response under open circuit conditions. The FMR response is measured using specially designed planar microresonators, which generate ac fields perpendicular to the plane of the layers [4]. Such microresonators, with loop diameters of 10 and 20 μm were optimized at a fixed frequency of 14 GHz. Magnetic multilayers with different compositions were patterned using electron-beam lithography into micron-sized pillars with different cross-sections. Microresonators were fabricated using UV lithography such that the magnetic device lies in the center of the loop. An example is shown in Fig 1. For laser heating, we used a diode laser with 51 mW power (5-10 μm focus in diameter). Fig 2 shows a set of FMR measurements performed on an 8x10 μm elliptical shape Py/Cu/Py magnetic multilayer under laser heating, with different laser powers. A clear change is observed at higher than 30 mW laser power, with the FMR line exhibiting changes in resonance field and linewidth. These changes likely arise from a combination of the induced TSTT and the heating of the whole device. The results are analyzed by means of conventional FMR modeling and the thermal gradients are estimated from COMSOL simulations.This project is funded by DFG Priority Programme SPP 1538 Spincaloritronics (SpinCat) and supported by the Nanofabrication Facilities at Ion Beam Center.
Keywords: thermal spin transfer torque, microresonator, ferromagnetic resonance, magnetic tunnel junction.
  • Lecture (Conference)
    Magnetism and Magnetic Materials MMM 2017, 06.-10.11.2017, Pittsburgh, PA, USA

Registration No. 26175 - Permalink


Decoupling the two roles of Ga droplets in the self-catalyzed growth of GaAs nanowires on SiOx/Si(111) substrates
Tauchnitz, T.ORC; Nurmamytov, T.; Hübner, R.; Engler, M.ORC; Facsko, S.; Schneider, H.; Helm, M.; Dimakis, E.ORC
Corresponding author: Dimakis, Emmanouil
Abstract: Liquid Ga droplets play a double role in the self-catalyzed growth of GaAs nanowires on Si(111) substrates covered with a native SiOx layer: they induce the formation of nano-sized holes in SiOx and then drive the uniaxial nanowire growth directly onto the underlying Si. The independent control of the two mechanisms is a prerequisite for mastering the growth of nanowires, but it is challenging in a conventional growth procedure where they both take place under the same droplets. To that end, we have developed an in situ procedure where the Ga droplets used for the formation of SiOx holes are removed before new Ga droplets drive the growth of GaAs nanowires. In that way, it was made possible to study the interaction between Ga droplets and SiOx, to create holes in SiOx with controlled number density and size and, finally, to grow GaAs nanowires only within those holes. Our results show unprecedented control of the nanowire nucleation with unique possibilities: (1) deliberate control of the number density of nanowires within three orders of magnitude (106-109 cm-2) without patterning the substrate and without changing the growth conditions, (2) highly synchronous nucleation events and, thus, exceptionally narrow nanowire length distributions (standard deviation < 1 % for 3 mm long nanowires), (3) high yield of vertical nanowires up to 80 % (against GaAs islands), (4) highly reproducible results, and (5) independent control of the nanowire diameter from the number density. We anticipate that our methodology could be also exploited for different materials or other types of nanostructures.

Registration No. 26174 - Permalink


AER Working Group D on VVER Safety Analysis – Report of the 2017 Meeting
Kliem, S.ORC
Abstract: The AER Working Group D on VVER reactor safety analysis held its 26th meeting in Erlan-gen, Germany, during the period 10-11 May, 2017. The meeting was hosted by AREVA Germany and was held in conjunction with the 11th workshop on the OECD Benchmark for Uncertainty Analysis in Best-Estimate Modelling (UAM) for Design, Operation and Safety Analysis of LWRs. Altogether 11 participants attended the meeting of the working group D, all 11 from AER member organizations. The co-ordinator of the working group, Mr. S. Kliem, served as chairman of the meeting.
The meeting started with a general information exchange about the recent activities in the participating organizations.
The given presentations and the discussions can be attributed to the following topics:
• Safety analyses methods and results
• Code development and benchmarking
• Future activities
A list of the participants and a list of the handouts distributed at the meeting are attached to the report. The corresponding PDF-files of the handouts can be obtained from the chairman.
  • Lecture (Conference)
    27th Symposium of AER on VVER Reactor Physics and Reactor Safety, 17.-20.10.2017, München, Deutschland

Registration No. 26173 - Permalink


Bioflotation with amphiphilic siderophores
Schrader, S.; Kutschke, S.; Pollmann, K.; Rudolph, M.
Abstract: Siderophores are small organic molecules with a high affinity for binding Fe(III) and the ability to form strong complexes. They are produced by microorganisms (aerobic bacteria and fungi) and some plants to equalize the low bioavailability of iron in their environment.
The biotechnological production of siderophores offers the application in very different fields. For example, they are used as medicine against iron or heavy metal poisoning. Other applications are their utilization for the extraction, recovery and treating of iron as well as other elements, that also can be bound by siderophores. In addition, their application in froth flotation processes could be an attractive novel approach. Molecules produced by the chemical industry with functional groups like hydroxamates have been already applied successfully in this processing method. It can be suggested that siderophores carrying the same functional groups should also work well as collectors. Particularly the group of amphiphilic siderophores that have both hydrophilic and hydrophobic areas are very interesting. The natural hydrophobic property of these chelating agents could avoid additional chemicals and further working steps for making the target mineral particles hydrophobic for an efficient flotation process.
The main advantage of using biotechnology for the production of siderophores is the wide natural diversity of the structures. A lot of microorganisms and their produced siderophores have already been identified and analyzed in detail. So there is an enormous variety of different molecules available. The aim of this study is to test for the first time, whether it is possible to use siderophores in flotation processes. In addition optimized processes for both the biotechnological production and the froth flotation have to be developed. This presupposes also the investigation and characterization of the binding properties during these procedures.
  • Lecture (Conference)
    Mineral Engineering Conference 2017, 20.-23.09.2017, Wisła, Poland

Registration No. 26171 - Permalink


Production of amphiphilic hydroxamate siderophore marinobactin by Marinobacter sp. DS40M6 for bioflotation process
Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.
Abstract: Siderophores are small biomolecules (400-1500 Da) with the ability to form strong complexes with Fe(III) and other metals. A wide range of siderophore structures are already well-known.
The biotechnological production of these organic compounds with bacteria enables them to be used for extracting and recycling metals.
The application of siderophores in traditional froth flotation process enables the development of a sustained bioflotation.
Keywords: siderophores; marinobactin; bioflotation
  • Poster
    22. International Biohydrometallurgy Symposium 2017, 24.-27.09.2017, Freiberg, Deutschland

Registration No. 26169 - Permalink


Variability in crystal surface reactivity: A critical constraint for reactive transport modeling
Fischer, C.
Abstract: Reactive transport modeling of fluid-solid interactions relies on (i) contrasts in fluid flow velocity and (ii) variability of surface reactivity. The first point is based on data from, e.g., PET and µCT techniques. The second point, however, is usually addressed by simple kinetic data only. Thus, it neglects information about the intrinsic variability of crystal surface reactivity that often results in a rate range of 2-3 orders of magnitude (1). Such variability is however an important constraint for the evolution of surface roughness and porosity pattern in crystalline matter (2). Here, we highlight important sources of the intrinsic variability of crystal surface reactivity and their impact on surface reaction rates. Rate maps (3) and rate spectra (4) provide critical information about the spatial and temporal variability of surface reactivity that is required to predict the evolution of porosity pattern in crystalline matter (5).

1. Luttge A, Arvidson RS, & Fischer C (2013) A Stochastic Treatment of Crystal Dissolution Kinetics. Elements 9(3):183-188.
2. Fischer C, Kurganskaya I, Schäfer T, & Luttge A (2014) Variability of Crystal Surface Reactivity: What do we know? (Review Article). Applied Geochemistry 43:132-157.
3. Fischer C & Luttge A (2017) Beyond the conventional understanding of water–rock reactivity. Earth and Planetary Science Letters 457:100-105.
4. Fischer C, Arvidson RS, & Luttge A (2012) How predictable are dissolution rates of crystalline material? Geochimica et Cosmochimica Acta 98:177-185.
5. Michaelis M, Fischer C, Colombi Ciacchi L, & Luttge A (2017) Variability of Zinc Oxide Dissolution Rates. Environmental Science & Technology 51(8):4297-4305.
  • Poster
    Reactive Transport in the Earth and Environmental Sciences in the 21st Century, 02.-05.10.2017, Amboise, Frankreich

Registration No. 26168 - Permalink


Manipulation of antiferromagnetic domain distribution in Mn2Au by ultrahigh magnetic fields and by strain
A. A. Sapozhnik, A. A.; Abrudan, R.; Skourski, Y.; Jourdan, M.; Zabel, H.; Kläui, M.; Elmers, H. J.
Corresponding author: A. A. Sapozhnik, A. A. Institute of Physics, Johannes Gutenberg-University Mainz and Graduate School of Excellence, Materials Science in Mainz (MAINZ), Mainz, Germany
Abstract: Evidence for a spin reorientation in antiferromagnetic (AFM) Mn2Au thin films induced by high magnetic fields as well as by the application of in-plane mechanical stress is provided. The AFM domain population in the samples was investigated by resonant X-ray Magnetic Linear Dichroism (XMLD) measurements at the L3 edge of Mn using a variable linear polarization of the incident photon beam. As grown samples show no XMLD signal due to averaging over a random AFM domain distribution. After the exposure to a 70 T in-plane magnetic field a clear XMLD signal indicating the generation of a preferential AFM domain orientation is obtained. The same type of XMLD signal is observed when the thin films are strained, demonstrating the feasibility of AFM Domain manipulation by magnetic fields and stress in Mn2Au.

Registration No. 26167 - Permalink


Magnetic structure in a U(Ru0.92Rh0.08)2Si2 single crystal studied by neutron diffraction in static magnetic fields up to 24 T
Prokes, K.; Bartkowiak, M.; Rivin, O.; Prokhnenko, O.; Förster, T.; Gerischer, S.; Wahle, R.; Huang, Y.-K.; Mydosh, J. A.
Corresponding author: Prokes, K. Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
Abstract: We report a high-field-induced magnetic phase in a single crystal of U(Ru0.92Rh0.08)2Si2. Our neutron study, combined with high-field magnetization, shows that the magnetic phase above the first metamagnetic transition at μ0H = 21.6 T has an uncompensated commensurate antiferromagnetic structure with a propagation vector Q2 = (2/3 0 0) possessing two single-Q domains. U moments of 1.45(9)μB directed along the c axis are arranged in an up-up-down sequence propagating along the a axis, in agreement with bulk measurements. The U magnetic form factor at high fields is consistent with both the U3+ and U4+ types. The low-field short-range order that emerges from pure URu2Si2 due to Rh doping is initially strengthened by the field but disappears in the field-induced phase. The tetragonal symmetry is preserved across the transition, but the a-axis lattice parameter increases already at low fields. Our results are in agreement with an itinerant electron model with 5f states forming bands pinned in the vicinity of the Fermi surface that is significantly reconstructed by the applied magnetic field.

Registration No. 26166 - Permalink


Magnetic field induced tunneling and relaxation between orthogonal configurations in solids and molecular systems
Averkiev, N. S.; Bersuker, I. B.; Gudkov, V. V.; Zhevstovskikh, I. V.; Baryshnikov, K. A.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Korostelin, Y. V.
Corresponding author: Averkiev, N. S. Ioffe Institute, St. Petersburg, Russia
Abstract: We report the effect of magnetic field induced quantum tunneling and relaxation transitions between orthogonal configurations in polyatomic systems where no tunneling is expected. Typical situations of this kind occur in molecular systems and local centers in crystals in ground and excited electronic T states, subject to the T⊗e problem of the Jahn-Teller effect, where the wave functions of the three tetragonally distorted configurations are orthogonal. A detailed microscopic theory of this effect shows how the magnetic field violates the orthogonality between the latter allowing for tunneling and relaxations, which decrease in strong fields due to the induced decoherence. The novel effect is demonstrated experimentally as a big, sharp peak in ultrasound attenuation by Cr2+ centers in ZnSe:Cr2+ in the magnetic field B = 0.15 T at the temperature below 8 K. It may influence a variety of magnetic, electronic, and photonic properties of any system in an electronic T state.

Registration No. 26165 - Permalink


Structural and thermodynamic investigation of AnIVLI(O)HOPO(Article)
Aupiais, J.; Younes, A.; Moisy, P.; Hennig, C.; Rossberg, A.; Brunel, B.; Kerbaa, M.; Vidaud, C.; Den Auwer, C.
Corresponding author: Den Auwer, C. Université Côte d'Azur, CNRS, Institut de Chimie de Nice, France
Abstract: For the first time, capillary electrophoresis coupled with inductively coupled plasma mass spectrometry has been used to determine the stability constants of PuIV with the multidentate hydroxypyridinonate chelating agents 3,4,3-LI(1,2-HOPO) and 5-LIO(Me-3,2-HOPO) in 0.1 M NaNO3 solution, pcH = 1.395 at 25 °C through competition with the NTA ligand. The limiting electrophoretic mobility was found to be zero for AnIV[5-LIO(Me-3,2-HOPO)] and slightly positive for AnIV[3,4,3-LI(1,2-HOPO)] (AnIV = Th, Pu). They were respectively assigned to the formation of the 1:2 neutral species An[5-LIO(Me-3,2-HOPO)]2 and a mixture of the neutral species AnIV[3,4,3-LI(1,2-HOPO)] and its protonated form AnIVH[3,4,3-LI(1,2-HOPO)]+. The corresponding stability constants of ThIV with both chelators were evaluated through the same experiments for the sake of comparison. The stability of both PuIV-HOPOs was about ten orders of magnitude better than that of the equivalent ThIV complexes. To complement these thermodynamic data, structural parameters of Pu[3,4,3-LI(1,2-HOPO)] and Th[3,4,3-LI(1,2-HOPO)] complexes in solution have been derived from EXAFS experiments and compared to previously reported crystallographic structures.

Registration No. 26162 - Permalink


Calibration of scintillation screens for ultrashort electron bunch detection
Kurz, T.; Couperus, J. P.ORC; Krämer, J. M.; Ding, H.; Kuschel, S.; Köhler, A.; Zarini, O.; Hollatz, D.; Schinkel, D.; D‘Arcy, R.; Schwinkendorf, J. P.; Irman, A.; Schramm, U.; Karsch, S.
Abstract: This work reports on the calibration of scintillating screens for diagnoses of high-charge density electron beams origination from laser plasma accelerators (LPA). Our setup at the conventional ELBE accelerator is cross-calibrated with an integrating current transformer (ICT) and allows for calibration over a large charge density range, thus enabling the study both the linear and non-linear scintillating screen response, as well as long-term stability tests of the screens. In contrast to previous works, the calibration presented here is performed under conditions with a close mimic to real experimental LPA conditions.
A linear response of the scintillator to the applied electron charge was found, followed by a saturation process starting in the range of nC/mm^2. Mimicking a 1-Hz LPA, long–term stability tests showed a significant decrease of the scintillation efficiency over time.
Finally, we present a method where a LED-based constant light source provides an easy method for absolute calibration of charge diagnostic systems at LPAs. This method eliminates many potential error sources existing in currently used methods and enables the transfer of absolute charge calibrations between laboratories.
  • Poster
    3rd European Advanced Accelerator Concepts Workshop, 24.-30.09.2017, Isola d'Elba, Italy

Registration No. 26161 - Permalink


Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator
Couperus, J. P.ORC; Pausch, R.; Köhler, A.; Zarini, O.; Krämer, J. M.; Kurz, T.; Garten, M.; Huebl, A.; Gebhardt, R.; Helbig, U.; Bock, S.; Zeil, K.; Debus, A.; Bussmann, M.; Schramm, U.; Irman, A.
Abstract: Laser-plasma wakefield acceleration is capable of producing quasi-monoenergetic electron beams reaching into the GeV range with few-femtoseconds bunch duration. Scaling the charge to the nanocoulomb range would yield hundreds of kiloamperes peak-current and stimulate the next generation of radiation sources covering high-field THz, high-brightness X-ray and γ-ray sources, compact FELs and laboratory-size beam-driven plasma accelerators. Laser-plasma accelerators generating such high currents operate in the beam loading regime where the accelerating field is strongly modified by the self-fields of the injected bunch, improving the final beam quality if appropriately controlled. Here we experimentally investigate the effects of beam loading at the theoretically predicted limit by loading unprecedented charges of about 0.5 nC within a mono-energetic peak into the first plasma cavity. As the energy balance is reached, the final energy spread is minimized. We show that the beam quality is maintained up to an estimated peak-current of 50 kA, an order of magnitude larger than in state-of-the-art conventional and laser-plasma accelerators.
  • Lecture (Conference)
    3rd European Advanced Accelerator Concepts Workshop, 24.-30.09.2017, Isola d'Elba, Italy

Registration No. 26160 - Permalink


Research on the chemistry of f-elements at HZDR - A general overview of the division Chemistry of the f-Elements
Ikeda-Ohno, A.ORC
Abstract: Established in June 2014, the division Chemistry of the f-Elements at the Institute of Resource Ecology (IRE) is conducting research on the fundamental physics/chemistry of f-elements, i.e. actinides and lanthanides. This presentation intends to provide a general overview of the recent research activities in the division, in order to possible research overlapping between HZDR-IRE and CEA-Marcoule for future collaborations.
Keywords: actinides, f-elements, coordination, chemistry
  • Lecture (others)
    Internal colloquium, 05.10.2017, CEA-Marcoule, France

Registration No. 26159 - Permalink


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