Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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29597 Publications
Results of the stationary measurements at COSMEA-I facility - CT part
Bieberle, A.; Boden, S.; Beyer, M.; Hampel, U.

At the COSMEA-I facility cross-sectional distributions of the condensated steam is measured at five different positions along a slightly inclined condensator-tube using adapted conventional CT imaging technique based on X-ray. This data set contains the reconstructed raw data of the CT imaging scans.

Keywords: Passive heat transfer; Conventional CT imaging; Reconstructed raw data of the CT imaging scan
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-03-20
    DOI: 10.14278/rodare.3


Publ.-Id: 27228 - Permalink

The role of radiative de-excitation in the neutralization process of highly charged ions interacting with a single layer of graphene
Schwestka, J.; Wilhelm, R. A.ORC; Gruber, E.; Heller, R.; Kozubek, R.; Schleberger, M.; Facsko, S.; Aumayr, F.
X-ray emission of slow (<1 a.u.) highly charged Argon and Xenon ions is measured for transmission through a freestanding single layer of graphene. To discriminate against X-ray emission originating from the graphene's support grid a coincidence technique is used. X-ray emission of 75 keV Ar17+ and Ar18+ ions with either one or two K-shell vacancies is recorded. Using a windowless Bruker XFlash detector allows us to measure additionally Ar KLL and KLM Auger electrons and determine the branching ratio of radiative vs. non-radiative decay of Ar K-shell holes. Furthermore, X-ray spectra for 100 keV Xe22+-Xe35+ ions are compared, showing a broad M-line peak for all cases, where M-shell vacancies are present. All these peaks are accompanied by emission lines at still higher energies indicating the presence of a hollow atom during X-ray decay. We report a linear shift of the main M-line peak to higher energies for increasing incident charge state, i.e. increasing number of M-shell holes.
Keywords: Slow highly charged ions; Graphene; X-ray emission


  • Secondary publication expected from 01.05.2019

Publ.-Id: 27223 - Permalink

Intrinsic magnetic properties of hydrided and non-hydrided Nd5Fe17 single crystals
Karpenkov, D. Y.; Skokov, K. P.; Lyakhova, M. B.; Radulov, I. A.; Faske, T.; Skourski, Y.; Gutfleisch, O.
We report on the spontaneous magnetization Ms, the exchange stiffness constant A and the magneto-crystalline anisotropy constants K1, K2, K3 and K4 of Nd5Fe17 and Nd5Fe17H16 single crystals. Field dependencies of magnetization M(H) were measured along a, b' and c principal crystallographic directions within the temperature range of 10-600 K and magnetic fields up to 40 T. Large anisotropies of spontaneous magnetization and high-field susceptibility were revealed for both compounds. The exchange stiffness parameter A was determined using Bloch's T3/2 law. In order to provide high accuracy detection of K1(T), K2(T), K3(T) and K4(T), we used two different approaches: the modified Sucksmith-Thompson technique and the Néel's phase method.

Publ.-Id: 27220 - Permalink

Electrically pumped graphene-based Landau-level laser
Brem, S.; Wendler, F.; Winnerl, S.; Malic, E.
Graphene exhibits a nonequidistant Landau quantization with tunable Landau-level (LL) transitions in the technologically desired terahertz spectral range. Here, we present a strategy for an electrically driven terahertz laser based on Landau-quantized graphene as the gain medium. Performing microscopic modeling of the coupled electron, phonon, and photon dynamics in such a laser, we reveal that an inter-LL population inversion can be achieved resulting in the emission of coherent terahertz radiation. The presented paper provides a concrete recipe for the experimental realization of tunable graphene-based terahertz laser systems.
Keywords: graphene, Landau quantization, laser, Landau-level laser


  • Secondary publication expected

Publ.-Id: 27219 - Permalink

ThMn12-type phases for magnets with low rare-earth content: Crystal-field analysis of the full magnetization process
Tereshina, I. S.; Kostyuchenko, N. V.; Tereshina-Chitrova, E. A.; Skourski, Y.; Doerr, M.; Pelevin, I. A.; Zvezdin, A. K.; Paukov, M.; Havela, L.; Drulis, H.
Rare-earth (R)-iron alloys are a backbone of permanent magnets. Recent increase in price of rare earths has pushed the industry to seek ways to reduce the R-content in the hard magnetic materials. For this reason strong magnets with the ThMn12 type of structure came into focus. Functional properties of R(Fe,T)12 (T-element stabilizes the structure) compounds or their interstitially modified derivatives, R(Fe,T)12-X (X is an atom of hydrogen or nitrogen) are determined by the crystal-electric-field (CEF) and exchange interaction (EI) parameters. We have calculated the parameters using high-field magnetization data. We choose the ferrimagnetic Tm-containing compounds, which are most sensitive to magnetic field and demonstrate that TmFe11Ti-H reaches the ferromagnetic state in the magnetic field of 52 T. Knowledge of exact CEF and EI parameters and their variation in the compounds modified by the interstitial atoms is a cornerstone of the quest for hard magnetic materials with low rare-earth content.

Publ.-Id: 27218 - Permalink

Field-effect transistors as electrically controllable nonlinear rectifiers for the characterization of terahertz pulses
Lisauskas, A.; Ikamas, K.; Massabeau, S.; Bauer, M.; Cibiraité, D.; Matukas, J.; Mangeney, J.; Mittendorff, M.; Winnerl, S.; Krozer, V.; Roskos, H. G.
We propose to exploit rectification in field-effect transistors as an electrically controllable higher-order nonlinear phenomenon for the convenient monitoring of the temporal characteristics of THz pulses, for example, by autocorrelation measurements. This option arises because of the existence of a gate-bias-controlled super-linear response at sub-threshold operation conditions when the devices are subjected to THz radiation. We present measurements for different antenna-coupled transistor-based THz detectors (TeraFETs) employing (i) AlGaN/GaN high-electron-mobility and (ii) silicon CMOS field-effect transistors and show that the super-linear behavior in the sub-threshold bias regime is a universal phenomenon to be expected if the amplitude of the high-frequency voltage oscillations exceeds the thermal voltage. The effect is also employed as a tool for the direct determination of the speed of the intrinsic TeraFET response which allows us to avoid limitations set by the read-out circuitry. In particular, we show that the build-up time of the intrinsic rectification signal of a patch-antenna-coupled CMOS detector changes from 20 ps in the deep sub-threshold voltage regime to below12 ps in the vicinity of the threshold voltage.
Keywords: Terahertz detection, field-effect transistor, nonlinear response, autocorrelation

Publ.-Id: 27217 - Permalink

Infrared/Terahertz Spectra of the Photogalvanic Effect in (Bi,Sb)Te based Three Dimensional Topological Insulators
Plank, H.; Pernul, J.; Gebert, S.; Danilov, S. N.; König-Otto, J.; Winnerl, S.; Lanius, M.; Kampmeier, J.; Mussler, G.; Aguilera, I.; Grützmacher, D.; Ganichev, S. D.
We report on the systematic study of infrared/terahertz spectra of photocurrents in (Bi,Sb)Te
based three dimensional topological insulators. We demonstrate that in a wide range of frequencies, ranging from fractions up to tens of terahertz, the photocurrent is caused by the linear photogalvanic effect (LPGE) excited in the surface states. The photocurrent spectra reveal that at low frequencies the LPGE emerges due to free carrier Drude-like absorption. The spectra allow to determine the room temperature carrier mobilities in the surface states despite the presence of thermally activated residual impurities in the material bulk. In a number of samples we observed an enhancement of the linear photogalvanic effect at frequencies between 30 and 60 THz, which is attributed to the excitation of electrons from helical surface to bulk conduction band states. Under this condition and applying oblique incidence we also observed the circular photogalvanic effect driven by the radiation helicity.
Keywords: Topological insulators, terahertz spectroscopy, photocurrents, photogalvanic effect


  • Secondary publication expected

Publ.-Id: 27216 - Permalink

Shielding and source calculations for the new cyclotron and possible activation in the soil
Konheiser, J.; Ferrari, A.; Naumann, B.; Müller, S.
This presentation summarizes the results of the Monte Carlo simulation of the shielding calculations and estimates of the soil activation for the new cyclotron of the HZDR (Helmholtz-Zentrum Dresden-Rossendorf). The dose values were determined on base of the resulting neutron flux at the 18F production and were carried out with the Monte Carlo code MCNP6. The calculation of the soil activations was performed with FLUKA. The neutron source term was provided by manufacturer. A source check with MCNP6 and FLUKA codes, significant discrepancies were found to the manufacturer supplied data for the neutron source term. For this reason, experiments were carried out on a cyclotron in operation. The comparison confirmed the results of the MCNP/FLUKA calculations.
The estimated dose rate in the public area is about 0.035 μSv/h (28 MeV protons) and thus significantly below the reference value of 0.5 μSv/h(3). After 5 years of continuous beam operation and a subsequent decay time of 30 days, the activity concentration of the soil is about 0.34 Bq/g.
Keywords: shielding calculation, neutron source calculation, cyclotron, MCNP6, FLUKA
  • Lecture (others)
    88. Sitzung des Arbeitskreises Dosimetrie, 20.-21.03.2018, TU Dresden, Deutschland

Publ.-Id: 27215 - Permalink

Anwendung von Anstaupackungen bei der CO2-Absorption in wässrigen Aminlösungen
Flechsig, S.; Sohr, J.; Schubert, M.; Hampel, U.; Kenig, E. Y.
Kolonneneinbauten stellen einen wichtigen Bestandteil fluider Trennprozesse dar und haben einen erheblichen Einfluss auf die Prozessleistung. Anzustrebende Eigenschaften von Einbauten sind eine hohe Trenneffizienz bei gleichzeitig geringem Druckverlust sowie eine hohe Kapazität. In den vergangenen Jahrzehnten konnten erhebliche Fortschritte zur Verbesserung von Einbauten erzielt werden. In diesem Bereich zeigt die Entwicklung von Anstaupackungen (AP) ein wesentliches Potenzial zur Prozessintensivierung auf. Diese bestehen aus zwei alternierenden Lagen strukturierter Packungen mit unterschiedlicher spezifischer Oberfläche. Die untere Anstaulage weist eine geringere Lastgrenze als die darüber angeordnete Abscheidelage auf. AP werden üblicherweise zwischen den Flutpunkten der beiden Lagen betrieben, weshalb ein heterogenes Strömungsmuster entsteht. Dabei bildet sich oberhalb der gefluteten Anstaulage eine Sprudelschicht, die durch eine intensive Vermischung der Phasen geprägt ist und eine hohe Trennleistung erzielt.
Im Rahmen eines DFG-geförderten Forschungsprojekts gilt es nun, die Auswirkungen der einzelnen Strömungsregime von AP auf Fluiddynamik und Stofftransport separat zu untersuchen. Für diesen Zweck werden erstmalig Experimente an einer Absorptions-/ Desorptionsanlage durch bildgebende Messungen der Strömung in AP ergänzt. An der Universität Paderborn werden für verschiedene Design- und Betriebsparameter Technikumsversuche zur CO2-Absorption in einer wässrigen Monethanolamin-Lösung durchgeführt. Die Anlage ermöglicht die Aufnahme von Temperaturprofilen der Gasphase sowie von Konzentrationsprofilen beider Phasen. In Kooperation mit der Technischen Universität Dresden wird mittels ultraschneller Röntgentomographie ein detaillierter Einblick in die Phasenverteilung der verschiedenen Strömungszustände ermöglicht. Die bei beiden Untersuchungen anfallenden Messdaten sollen zur Erarbeitung von Korrelationen für Stoffübergang, Phasengrenzfläche, Holdup und Druckverlust genutzt werden, welche in einem rate-based-Model Verwendung finden. In dieser Arbeit werden neben einer Vorstellung des Vorhabens erste experimentelle Daten zur Absorption mit AP präsentiert.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet Fachgruppen Mechanische Flüssigkeitsabtrennung, Kristallisation, Phytoextrakte, Adsorption, Extraktion, Fluidverfahrenstechnik und Membrantechnik, 06.-10.03.2018, Köln, Deutschland

Publ.-Id: 27212 - Permalink

Rate-based-Modellierung von CO2-Absorptionskolonnen mit Anstaupackungen
Flechsig, S.; Sohr, J.; Schubert, M.; Hampel, U.; Kenig, E. Y.
Eines der am häufigsten eingesetzten Trennverfahren zur Abscheidung von Kohlenstoffdioxid (CO2) aus Kraftwerksabgasen ist die Reaktivabsorption mit wässrigen Aminlösungen. Neben der Entwicklung effektiverer Lösungsmittel weisen die Kolonneneinbauten hinsichtlich Druckverlust, Kapazität und Trennleistung ein wesentliches Potenzial für die Prozessintensivierung und damit die Reduzierung des hohen Ressourcenbedarfs auf.
Eine Verbesserung der Trennleistung kann durch den Einsatz von Anstaupackungen erzielt werden. Diese bestehen aus zwei abwechselnden Lagen von Standardpackungen mit unterschiedlichen spezifischen Oberflächen. Die untere Packungslage (die sogenannte Anstaulage) hat eine geringere Belastungsgrenze im Vergleich zur darüberliegenden Abscheidelage. Anstaupackungen werden typischerweise bei Betriebsbedingungen zwischen den Flutpunkten beider Lagen betrieben. Durch das gezielte Fluten der Anstaulage bildet sich eine in die Abscheidelage hineinreichende Sprudelschicht, in der eine hohe Trennleistung mit intensiver Phasenvermischung erzielt wird. Im oberen Bereich der Abscheidelage können filmähnliche Strömungsmuster, Rinnsale und aus der Sprudelschicht mitgerissene Tropfen beobachtet werden [1]. Obwohl der für Trennverfahren vorteilhafte intensive Phasenkontakts bei dem integrierten Packungstyps bereits nachgewiesen wurde, fehlend validierte Auslegungsgrundlagen für eine breitere Anwendung [2].
Eine genaue Vorhersage der Leistungscharakteristik ist für die Auslegung von Anstaupackungen unerlässlich. In einem von der DFG geförderten Kooperationsprojekt zwischen Universität Paderborn und TU Dresden werden die Auswirkungen der einzelnen Strömungsregime auf die Fluiddynamik und den Stoffaustausch komplementär mit experimentellen und theoretischen Methoden untersucht. Um die Auswirkungen jedes einzelnen Strömungsregimes zu bestimmen, werden Experimente an einer Absorptions-/ Desorptionsanlage durch bildgebende Messungen in Anstaupackungen ergänzt. An der Universität Paderborn wird die CO2-Absorption in einer Pilotanlage für verschiedene Design- und Betriebsparameter untersucht. Die Anlage ermöglicht die Messung von Temperaturprofilen der Gasphase sowie von Konzentrationsprofilen beider Phasen. Mithilfe der ultraschnellen Röntgentomographie wird am Helmholtz-Zentrum Dresden-Rosendorf die Phasenverteilung innerhalb der Anstaupackung untersucht. Die Messdaten aus beiden experimentellen Methoden werden verwendet, um Korrelationen für Stofftransportkoeffizienten, Phasengrenzfläche, Holdup und Druckverlust zu entwickeln, die in einem rate-based-Modell für CO2-Absorptionsverfahren mit wässrigen Aminlösungen eingesetzt werden.
Der rate-based-Ansatz kann die Besonderheiten diverser Kolonneneinbauten durch einbautenspezifische Korrelationen berücksichtigen. Da die verschiedenen Fluiddynamikregime in Anstaupackungen unterschiedliche Auswirkungen auf den Stofftransport aufweisen, werden Absorptionskolonnen mit Anstaupackungen als eine Folge von abwechselnden Segmenten dargestellt und jedes Segment wird durch einen der Fluiddynamik entsprechenden Satz von Korrelationen beschrieben. Im Rahmen dieser Arbeit erfolgt eine Validierung des Modells mit experimentellen Daten zur CO2-Absorption.

[1] U. Brinkmann, B. Kaibel, M. Jödecke, J. Mackowiak, E.Y. Kenig: Beschreibung der Fluiddynamik von Anstaupackungen, Chemie Ingenieur Technik 84: 36-45 (2012).
[2] Ö. Yildirim, E.Y. Kenig: Rate-based modelling and simulation of distillation columns with sandwich packings, Chemical Engineering and Processing: Process Intensification 98, 147-154 (2015).
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppe Fluidverfahrentechnik, 27.-28.02.2018, München, Deutschland

Publ.-Id: 27210 - Permalink

New Phenomena in Gamma-Ray Strength Functions
Schwengner, R.
The excitation and deexcitation of atomic nuclei by electromagnetic radiation are fundamental processes in reactions of this many-body quantum system. At high excitation energy and high level density, statistical models are applied to describe reaction rates, which use $\gamma$-ray strength functions (γSF) to describe the average transition probabilities in a certain range of excitation energy. The experimental determination and the theoretical understanding of the properties of γSF are important for the accurate description of photonuclear reactions and radiative-capture reactions, which play a central role in the synthesis of the elements in various stellar environments.
We report photon-scattering experiments using bremsstrahlung at the γELBE facility (HZDR) and quasi-monoenergetic, polarized γ beams at the HIγS facility (TUNL, Duke Univ., Durham, USA). Systematic studies of the dipole strength revealed new phenomena that are not described by the analytical approximations currently used in reaction codes. The (γ,γ') experiments at high energy show considerable contributions to the γSF from the quasicontinuum of states. Combined with (γ,n) cross sections, the (γ,γ') data provide experimental input γSF for statistical reaction codes.
Keywords: Photonuclear reactions, Nuclear resonance fluorescence, Bremsstrahlung, Monoenergetic gamma rays, Shell Model.
  • Invited lecture (Conferences)
    Frühjahrstagung 2018, 26.02.-02.03.2018, Bochum, Deutschland

Publ.-Id: 27208 - Permalink

Damage accumulation and structural modification in c-plane and a-plane GaN implanted with 400 keV Kr and Gd ions
Mackova, A.; Malinsky, P.; Jágerova, A.; Sofer, Z.; Klímová, K.; Sedmidubský, D.; Mikulics, M.; Böttger, R.; Akhmadaliev, S.
GaN is the most actively studied wide-bandgap material, applicable e.g. in short-wavelength optoelectronic devices, high-electron-mobility transistors, and semiconductor lasers. The crystallographic orientation of an implanted crystal can significantly influence the optical properties of the implanted layer, reflecting the rearrangement of the crystal matrix after annealing. The annealing procedure, influencing dynamic recovery, point defect diffusion and large defect stabilisation, depending on the GaN crystal orientation and the used ion implantation parameters, is still an important issue to be studied. We have studied the structural and compositional changes of the GaN-epitaxial-layers of c-plane and a-plane orientations grown by MOVPE and implanted with Gd and Kr ions using the ion energy of 400 keV and ion fluences of 5 × 1014 cm-2, 1 × 1015 cm-2 and 5 × 1015 cm-2 with subsequent annealing at 800 °C in ammonia. Dopant depth profiling was accomplished by Rutherford backscattering spectrometry (RBS). Induced structure disorder and its recovery during subsequent annealing were characterised by RBS channelling and Raman spectroscopy. Ion-implanted c-plane and a-plane GaN exhibit significant differences in damage accumulation simultaneously with post-implantation annealing, inducing a different structural reorganization of the GaN structure in the buried layer depending on the introduced disorder level, i.e. depending on the ion-implantation fluence and ion mass.
Keywords: GaN damage accumulation, RBS channelling studies of implanted GaN, Structure modification in c-plane and a-plane GaN

Publ.-Id: 27207 - Permalink

Effect of U(VI) aqueous speciation on the binding of uranium by the cell surface of Rhodotorula mucilaginosa, a natural yeast isolate from bentonites
Lopez-Fernandez, M.; Romero-Gonzalez, M.; Günther, A.; Solari, P. L.; Merroun, M. L.
This study presents the effect of aqueous uranium speciation (U-hydroxides and U-hydroxo-carbonates) on the interaction of this radionuclide with the cells of the yeast Rhodotorula mucigilanosa BII-R8. This strain was isolated from Spanish bentonites considered as reference materials for the engineered barrier components of the future deep geological repository of radioactive waste. X-ray absorption and infrared spectroscopy showed that the aqueous uranium speciation has no effect on the uranium binding process by this yeast strain. The cells bind mobile uranium species (U-hydroxides and U-hydroxo-carbonates) from solution via a time-dependent process initiated by the adsorption of uranium species to carboxyl groups. This leads to the subsequent involvement of organic phosphate groups forming uranium complexes with a local coordination similar to that of the uranyl mineral phase meta-autunite. Scanning transmission electron microscopy with high angle annular dark field analysis showed uranium accumulations at the cell surface associated with phosphorus containing ligands. Moreover, the effect of uranium mobile species on the cell viability and metabolic activity was examined by means of flow cytometry techniques, revealing that the cell metabolism is more affected by higher concentrations of uranium than the cell viability.The results obtained in this work provide new insights on the interaction of uranium with bentonite natural yeast from genus Rhodotorula under deep geological repository relevant conditions.
Keywords: Uranium biosorption, cell surface, speciation

Publ.-Id: 27199 - Permalink

A high-efficiency gas target setup for underground experiments, and redetermination of the branching ratio of the 189.5 keV 22Ne(p,γ)23Na resonance
Ferraro, F.; Takács, M. P.; Piatti, D.; Mossa, V.; Aliotta, M.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Cavanna, F.; Chillery, T.; Ciani, G. F.; Corvisiero, P.; Csedreki, L.; Davinson, T.; Depalo, R.; D'Erasmo, G.; Di Leva, A.; Elekes, Z.; Fiore, E. M.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Kochanek, I.; Lugaro, M.; Marcucci, L. E.; Marigo, P.; Menegazzo, R.; Pantaleo, F. R.; Paticchio, V.; Perrino, R.; Prati, P.; Schiavulli, L.; Stöckel, K.; Straniero, O.; Szücs, T.; Trezzi, D.; Zavatarelli, S.
The experimental study of nuclear reactions of astrophysical interest is greatly facilitated by a low-background, high-luminosity setup. The Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator offers ultra-low cosmic-ray induced background due to its location deep underground in the Gran Sasso National Laboratory (INFN-LNGS), Italy, and high intensity, 250-500 μA, proton and α ion beams. In order to fully exploit these features, a high-purity, recirculating gas target system for isotopically enriched gases is coupled to a high-efficiency, six-fold optically segmented bismuth germanate (BGO) γ-ray detector. The beam intensity is measured with a beam calorimeter with constant temperature gradient. Pressure and temperature measurements have been carried out at several positions along the beam path, and the resultant gas density profile has been determined. Calibrated γ-intensity standards and the well-known Ep = 278 keV 14N(p,γ)15O resonance were used to determine the γ-ray detection efficiency and to validate the simulation of the target and detector setup. As an example, the recently measured resonance at Ep = 189.5 keV in the 22Ne(p,γ)23Na reaction has been investigated with high statistics, and the γ-decay branching ratios of the resonance have been determined.

Publ.-Id: 27186 - Permalink

Fluiddynamische Untersuchung von Anstaupackungen mittels ultraschneller Röntgentomographie
Sohr, J.; Schubert, M.; Flechsig, S.; Kenig, E. Y.; Hampel, U.
In Anstaupackungen bilden sich durch die Kombination von Packungslagen unterschiedlicher geometrischer Oberfläche abhängig von den Betriebsbedingungen Filmströmung und Sprudelschicht gleichzeitig aus. Durch die axial stark heterogene Strömungsmorphologie lassen integrale Holdup-Messungen keine Rückschlüsse auf lokale Flüssigkeitsinhalte in einzelnen Packungslagen zu.
Die ultraschnelle Röntgentomographie bietet dank einer Bildrate von bis zu 8000 Schnittbildern pro Sekunde die Möglichkeit, bei den hochdynamischen Zweiphasenströmungen relevante fluiddynamische Parameter in einzelnen Abschnitten der Anstaupackung nichtinvasiv zu bestimmen [1]. Neben der Ermittlung von Phasenanteilen und deren radialer sowie axialer Verteilung werden auch Methoden zur Ermittlung der Gas-Flüssigkeits-Grenzfläche angewandt. Ein weiterer entscheidender Parameter für die hydrodynamische Modellierung von Anstaupackungen ist die Höhe der Sprudelschicht [2]. Deren Bestimmung erfolgt zum einen mithilfe der ultraschnellen Röntgentomographie sowie ergänzend durch eine verteilte Druckverlustmessung mit einer axialen Auflösung von 10 mm. Im Rahmen dieses Beitrags werden sowohl die Messmethoden als auch Messergebnisse der experimentellen Untersuchungen vorgestellt.
Wir danken der DFG für die finanzielle Unterstützung des Kooperationsprojekts "Experimentelle und theoretische Untersuchung der Fluiddynamik und des Stofftrennverhaltens von Anstaupackungen" (KE 837/26-1, HA 3088/10-1).
[1] A. Janzen, M. Schubert, F. Barthel, U. Hampel, E.Y. Kenig, Chemical Engineering and Processing: Process Intensification 66, 20-26 (2013).
[2] U. Brinkmann, B. Kaibel, M. Jödecke, J. Maćkowiak, E.Y. Kenig, Chemie Ingenieur Technik 84: 36-45 (2012).
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppe Fluidverfahrentechnik, 27.-28.02.2018, München, Deutschland

Publ.-Id: 27182 - Permalink

Cluster Formation in the Superconducting Complex Intermetallic Compound Be21Pt5
Amon, A.; Ormeci, A.; Bobnar, M.; Akselrud, L. G.; Avdeev, M.; Gumeniuk, R.; Burkhardt, U.; Prots, Y.; Hennig, C.; Leithe-Jasper, A.; Grin, Y.
Materials with the crystal structure of γ-brass type (Cu5Zn8 type) are typical representatives of intermetallic compounds. From the electronic point of view, they are often interpreted using the valence electron concentration approach of Hume−Rothery, developed previously for transition metals. The γ-brass-type phases of the main-group elements are rather rare. The intermetallic compound Be21Pt5, a new member of this family, was synthesized, and its crystal structure, chemical bonding, and physical properties were characterized. Be21Pt5 crystallizes in the cubic space group F4̅3m with lattice parameter a = 15.90417(3) Å and 416 atoms per unit cell. From the crystallographic point of view, the binary substance represents a special family of intermetallic compounds called complex metallic alloys (CMA). The crystal structure was solved by a combination of synchrotron and neutron powder diffraction data. Besides the large difference in the scattering power of the components, the structure solution was hampered by the systematic presence of very weak reflections mimicking wrong symmetry. The structural motif of Be21Pt5 is described as a 2 × 2 × 2 superstructure of the γ-brass structure (Cu5Zn8 type) or 6 × 6 × 6 superstructure of the simple bcc structural pattern with distinct distribution of defects. The main building elements of the crystal structure are four types of nested polyhedral units (clusters) with the compositions Be22Pt4 and Be20Pt6. Each cluster contains four shells (4 + 4 + 6 + 12 atoms). Clusters with different compositions reveal various occupation of the shells by platinum and beryllium. Polyhedral nested units with the same composition differ by the distance of the shell atoms to the cluster center. Analysis of chemical bonding was made applying the electron localizability approach, a quantum chemical technique operating in real space that is proven to be especially efficient for intermetallic compounds. Evaluations of the calculated electron density and electron localizability indicator (ELI-D) revealed multicenter bonding, being in accordance with the low valence electron count per atom in Be21Pt5. A new type of atomic interactions in intermetallic compounds, cluster bonds involving 8 or even 14 atoms, is found in the clusters with shorter distances between the shell atoms and the cluster centers. In the remaining clusters, four- and five-center bonds characterize the atomic interactions. Multicluster interactions within the polyhedral nested units and threecenter polar intercluster bonds result in a three-dimensional framework resembling the structural pattern of NaCl. Be21Pt5 is a diamagnetic metal and one of rather rare CMA compounds revealing superconductivity (Tc = 2.06 K).

Publ.-Id: 27181 - Permalink

Evidence for a dynamical ground state in the frustrated pyrohafnate Tb2Hf2O7
Anand, V. K.; Opherden, L.; Xu, J.; Adroja, D. T.; Hillier, A. D.; Biswas, P. K.; Herrmannsdörfer, T.; Uhlarz, M.; Hornung, J.; Wosnitza, J.
We report the physical properties of Tb2Hf2O7 based on ac magnetic susceptibility χac(T ), dc magnetic susceptibility χ(T ), isothermal magnetization M(H), and heat capacity C(T ) measurements combined with muon spin relaxation (μSR) and neutron powder diffraction measurements. No evidence for long-range magnetic order is found down to 0.1 K. However, χac(T ) data present a frequency-dependent broad peak (near 0.9 K at 16 Hz) indicating slow spin dynamics. The slow spin dynamics is further evidenced from the μSR data (characterized by a stretched exponential behavior) which show persistent spin fluctuations down to 0.3 K. The neutron powder diffraction data collected at 0.1 K show a broad peak of magnetic origin (diffuse scattering) but no magnetic Bragg peaks. The analysis of the diffuse scattering data reveals a dominant antiferromagnetic interaction in agreement with the negative Weiss temperature. The absence of long-range magnetic order and the presence of slow spin dynamics and persistent spin fluctuations together reflect a dynamical ground state in Tb2Hf2O7.

Publ.-Id: 27179 - Permalink

Increasing stripe-type fluctuations in AFe2As2 (A = K, Rb, Cs) superconductors probed by 75As NMR spectroscopy
Zhang, Z. T.; Dmytriieva, D.; Molatta, S.; Wosnitza, J.; Khim, S.; Gass, S.; Wolter, A. U. B.; Wurmehl, S.; Grafe, H.-J.; Kühne, H.
We report 75As nuclear magnetic resonance measurements on single crystals of RbFe2As2 and CsFe2As2. Taking previously reported results for KFe2As2 into account, we find that the anisotropic electronic correlations evolve towards a magnetic instability in the AFe2As2 series (with A = K, Rb, Cs). Upon isovalent substitution with larger alkali-metal ions, a drastic enhancement of the anisotropic nuclear spin-lattice relaxation rate and decreasing Knight shift reveal the formation of pronounced spin fluctuations with stripe-type modulation. Furthermore, a decreasing power-law exponent of the nuclear spin-lattice relaxation rate (1/T1)HIIab, probing the in-plane spin fluctuations, evidences an emergent deviation from Fermi-liquid behavior. All these findings clearly indicate that the expansion of the lattice in the AFe2As2 series tunes the electronic correlations towards a quantum critical point at the transition to a yet unobserved ordered phase.


Publ.-Id: 27178 - Permalink

Defect induced magnetism in SiC
Zhou, S.ORC
Defect induced magnetism, which can be controllably generated by ion or neutron irradiation, is attracting intensive research interest. It not only challenges the traditional opinions about magnetism, but also has some potential applications in spin-electronics. SiC is a new candidate for the investigation of defect-induced ferromagnetism after graphitic materials and oxides due to its high material purity and crystalline quality [1, 2]. In this contribution, we present a comprehensive investigation on the structural and magnetic properties of ion implanted and neutron irradiated SiC samples. In combination with X-ray absorption spectroscopy, high-resolution transmission electron microscopy and first-principles calculations, we try to understand the mechanism in a microscopic picture.
For neon or xenon ion implanted SiC, we identify a multi-magnetic-phase nature [3]. The magnetization of SiC can be decomposed into paramagnetic, superparamagnetic and ferromagnetic contributions. The ferromagnetic contribution persists well above room temperature and exhibits a pronounced magnetic anisotropy. By combining X-ray magnetic circular dichroism and first-principles calculations, we clarify that p-electrons of the nearest-neighbor carbon atoms around divacancies are mainly responsible for the long-range ferromagnetic coupling [4]. Thus, we provide a correlation between the collective magnetic phenomena and the specific electrons/orbitals. Moreover, a negative magnetoresistance has been observed in ferromagnetic an conducting SiC, indicating the interplay between magnetism and free carriers [5].
With the aim to verify if a sample containing defects through its bulk volume can persist ferromagnetic coupling, we applied neutron irradiation to introduce defects into SiC [6]. Besides a weak ferromagnetic contribution, we observe a strong paramagnetism, scaling up with the neutron fluence. The ferromagnetic contribution only occurs in a narrow fluence window or after annealing. First-principles calculations hint towards a mutually exclusive role of the concentration of defects: Defects favor spin polarization at the expense of magnetic interaction. Moreover, the interaction between the nuclear spin and the paramagnetic defect can effectively tune the spin-lattice relaxation time (T1) as well as the nuclear spin coherent time (T2) [7].

[1] L. Li, et al., Appl. Phys. Lett. 98, 222508 (2011).
[2] Y. Wang, et al., Phys. Rev. B 90, 214435 (2014).
[3] Y. Wang, et al., Phys. Rev. B 89, 014417 (2014).
[4] Y. Wang, et al., Scientific Reports, 5, 8999 (2015).
[5] Y. Liu, et al., Phys. Rev. B 95, 195309 (2017).
[6] Y. Wang, et al., Phys. Rev. B 92, 174409 (2015).
[7] Z. Zhang, et al., Phys. Rev. B 95, 085203 (2017).
  • Invited lecture (Conferences)
    International Workshop: Functionality of Oxide Interfaces, 26.02.-02.03.2018, Benedictine Abbey of Frauenwörth, Germany

Publ.-Id: 27177 - Permalink

Hydrogen-assisted Post-growth Doping of Tellurium into Molybdenum Disulfide Monolayers with Tunable Compositions
Yin, G.; Zhu, D.; Lv, D.; Zhang, Z.; Hashemi, A.; Krasheninnikov, A. V.ORC; Komsa, H.-P.; Jin, C.
Herein we report the successful doping of tellurium (Te) into molybdenum disulfide (MoS2) monolayers to form MoS2xTe2(1−x) alloy with variable compositions via a hydrogen-assisted post-growth chemical vapor deposition process. It is confirmed that H2 plays an indispensable role in the Te substitution into as-grown MoS2 monolayers. Atomic-resolution transmission electron microscopy allows us to determine the lattice sites and the concentration of introduced Te atoms. At a relatively low concentration, tellurium is only substituted in the sulfur sublattice to form monolayer MoS2(1−x)Te2x alloy, while with increasing Te concentration (up to ∼27.6% achieved in this study), local regions with enriched tellurium, large structural distortions, and obvious sulfur deficiency are observed. Statistical analysis of the Te distribution indicates the random substitution. Density functional theory calculations are used to investigate the stability of the alloy structures and their electronic properties. Comparison with experimental results indicate that the samples are unstrained and the Te atoms are predominantly substituted in the top S sublattice. Importantly, such ultimately thin Janus structure of MoS2(1−x)Te2x exhibits properties that are distinct from their constituents. We believe our results will inspire further exploration of the versatile properties of asymmetric 2D TMD alloys.
Keywords: 2D materials, post-growth, tellurium, TMDC, MoS2


  • Secondary publication expected from 16.02.2019

Publ.-Id: 27175 - Permalink

Big Bang Cosmology in the Lab: The 2H(p,γ)3He reaction studied at LUNA
Stöckel, K. For The Luna Collaboration
Recent high-precision measurements of the primordial 2H abundance have opened the path to use Big Bang nucleosynthesis to constrain the primordial baryon to photon ratio with similar precision as the cosmic microwave background. This would provide an independent cross-check on current Big Bang models. However, the interpretation of the abundance is limited by the lack of precise nuclear data, in particular on the main 2H destruction channel, the 2H(p,γ)3He reaction. A new experiment to study the 2H(p,γ)3He cross section directly in the Big Bang energy window is underway at the LUNA 400 kV accelerator, deep underground in the Gran Sasso laboratory, Italy. The progress of experiment and analysis will be summarized. – Supported by DFG (BE 4100/4-1).
  • Lecture (Conference)
    DPG-Frühjahrstagung Bochum 2018, 26.02.-02.03.2018, Bochum, Deutschland

Publ.-Id: 27174 - Permalink

Plasmonic nanoparticles embedded in single crystals synthesized by gold ion implantation for enhanced optical nonlinearity and efficient Q-switched lasing
Nie, W. J.; Zhang, Y. X.; Yu, H. H.; Li, R.; He, R. Y.; Dong, N. N.; Wang, J.; Hübner, R.; Böttger, R.; Zhou, S. Q.; Amekura, H.; Chen, F.
We report on the synthesis of embedded gold (Au) nanoparticles (NPs) in Nd:YAG single crystals using ion implantation and subsequent thermal annealing. Both linear and nonlinear absorption of the Nd:YAG crystals have been enhanced significantly due to the embedded Au NPs, which is induced by the surface plasmon resonance (SPR) effect in the visible light wavelength band. Particularly, through a typical Z-scan system excited by a femtosecond laser at 515 nm within the SPR band, the nonlinear absorption coefficients of crystals with Au NPs have been observed to be nearly 5 orders of magnitude larger than that without Au NPs. This giant enhancement of nonlinear absorption properties is correlated with the saturable absorption (SA) effect, which is the basis of passive Q-switching or mode-locking for pulsed laser generation. In addition, the linear and nonlinear absorption enhancement could be tailored by varying the fluence of implanted Au+ ions, corresponding to the NP size and concentration modulation. Finally, the Nd:YAG wafer with embedded Au NPs has been applied as a saturable absorber in a Pr:LuLiF4 crystal laser cavity, and efficient pulsed laser generation at 639 nm has been realized, which presents superior performance to the MoS2 saturable absorber based system. This work opens an avenue to enhance and modulate the nonlinearities of dielectrics by embedding plasmonic Au NPs for efficient pulsed laser operation.

Publ.-Id: 27165 - Permalink

OpenFOAM – a contributer‘s point of view
Schlegel, F.; Liao, Y.; Oertel, R.; Meller, R.
Der Vortrag behinhaltet einen Überblick über die Arbeiten im Bereich Mehrphasen-Simulation der Abteilung FWDC mit Hilfe der C++-Bibliothek OpenFOAM.
  • Lecture (Conference)
    German CFD Meeting, 06.03.2018, München, Deutschland

Publ.-Id: 27164 - Permalink

Magnetic Properties of Coupled Co/Mo/Co Structures Tailored by Ion Irradiation
Wawro, A.; Kurant, Z.; Jakubowski, M.; Tekielak, M.; Pietruczik, A.; Böttger, R.; Maziewski, A.
Modifications of the magnetic properties of Co=Mo=Co films activated by irradiation with 30-keV Ar and 17-keV Ne ion beams are investigated and compared with the influence of 35-keV Ga ions. This system is magnetized in the sample plane and exhibits a twofold anisotropy. The interlayer coupling of magnetization in as-deposited structures is parallel except for the Mo spacer thickness range between 0.5 and 1.0 nm, where the magnetization of the Co layers is antiparallel oriented. The coupling changes and gradually reduced strength of the ferromagnetic properties are compared for all ion types and discussed as a function of the Mo spacer thickness and the ion fluence. The structural evolution of the studied films with increasing fluence determined from TRIDYN simulations is discussed in relation to the observed magnetic changes.We also propose various types of magnonic crystals that can be fabricated by exploiting the results presented in this work.
Keywords: Ion Irradiation, layered magnetic structures, interlayer coupling, magnetism

Publ.-Id: 27163 - Permalink

Localized ion beam mixing using a focused Neon beam for future SET applicatons
Xu, X.; Hlawacek, G.; Wolf, D.; Engelmann, H.-J.; Prüfer, T.; Hübner, R.; Bischof, L.; von Borany, J.; Facsko, S.; Heinig, K.-H.
The increased use of personal computing devices and the Internet of Things (IoT) is accompanied by a demand for a computation unit with extra low energy dissipation. The Single Electron Transistor (SET), which uses a Coulomb island to manipulate the movement of single electrons, is a candidate device for future low-power electronics. However, so far its development is hindered by low-temperature requirements and the absence of CMOS compatibility. By combining advanced top-down lithography with botom-up self-assembly of Si nano dots (NDs) we will overcome this barrier.
In this work, Si NDs—suitable as RT Coulomb islands—are formed via ion beam mixing followed by thermally stimulated phase separation. Spatial control over the ND formation is achieved by using the highly focused Neon beam with a diameter of only 2 nm available in the helium ion microscope (HIM).
The impinging energetic ions will locally mix excess Si from a top Si-layer and into a buried SiO 2 layer which is grown on a Si wafer. This results in a mixing volume small enough for restricted Ostwald ripening and successful single ND formation. The formation of spatially controlled single NDs with a diameter of only 2.2 nm is confrmed by comparing the energy fltered transmission electron microscopy (EFTEM) Si plasmon-loss intensity with simulated plasmon loss images. The conditions for ND formation, namely the dependence on primary energy, irradiation fuence, layer thickness and thermal budget during rapid thermal annealing (RTA), are optimized based on an extensive survey of this multidimensional parameter space. The investigation is guided by TRIDYN simulations of the Si excess in an SiO 2 layer due to ion beam mixing and 3D Kinetic Monte-Carlo (3DkMC) simulation for the phase separation during the thermal treatment. To achieve a CMOS compatible mass fabrication of individual NDs the results are than transferred to Si + broad beam irradiation and cross checked by EFTEM. In this case localization will be achieved by pre-structuring the sample into narrow pillars using lithography.
This work has been funded by the European Union’s Horizon 2020 Research and Innovation Program under grant agreement No. 688072 “IONS SET”.
Keywords: HIM
  • Lecture (Conference)
    picoFIB, 31.01.2018, Dresden, Germany

Publ.-Id: 27162 - Permalink

From the creation of carbon nanomembranes in a low energy electron microscope to perforation with highly charged ions
Wilhelm, R. A.ORC; Neumann, C.; Küllmer, M.; Winter, A.; Turchanin, A.
Carbon nanomembranes are materials with only nm thickness, which can be used as freestanding membranes in filtration applications. They exhibit interesting properties as they can be e.g. transformed into (semi-)metallic graphene, but are insulating in their pristine phase. Using a Low Energy Electron Microscope allowed us to follow the formation of a carbon nanomembrane by electron-induced cross-linking of a self-assembled monolayer in-situ and in real-time. Releasing the membrane from the substrate and irradiating it with highly chared ions leads finally to regularely sized nanopores.
  • Lecture (others)
    Seminar AG Turchanin, 11.01.2018, Jena, Deutschland

Publ.-Id: 27159 - Permalink

Switching the uniaxial magnetic anisotropy by ion irradiation induced compensation
Yuan, Y.; Amarouche, T.; Xu, C.; Rushforth, A.; Boettger, R.; Edmonds, K.; Campion, R.; Gallagher, B.; Helm, M.; von Bardeleben, H.; Zhou, S. Q.
In the present work, the uniaxial magnetic anisotropy of GaMnAsP is modified by helium ion irradiation. According to the micro-magnetic parameters, e.g. resonance fields and anisotropy constants deduced from ferromagnetic resonance measurements, a rotation of the magnetic easy axis from out-of-plane [001] to in-plane [100] direction is achieved. From the application point of view, our work presents a novel avenue in modifying the uniaxial magnetic anisotropy in GaMnAsP with the possibility of lateral patterning by using lithography or focused ion beam.

Publ.-Id: 27156 - Permalink

Electronic phase separation in insulating (Ga, Mn) As with low compensation: super-paramagnetism and hopping conduction
Yuan, Y.; Wang, M.; Xu, C.; Hübner, R.; Böttger, R.; Jakiela, R.; Helm, M.; Sawicki, M.; Zhou, S.
In the present work, low compensated insulating (Ga,Mn)As with 0.7% Mn is obtained by ion implantation combined with pulsed laser melting. The sample shows variable-range hopping transport behavior with a Coulomb gap in the vicinity of the Fermi energy, and the activation energy is reduced by an external magnetic field. A blocking super-paramagnetism is observed rather than ferromagnetism. Below the blocking temperature, the sample exhibits a colossal negative magnetoresistance. Our studies confirm that the disorder-induced electronic phase separation occurs in (Ga,Mn)As samples with a Mn concentration in the insulator–metal transition regime, and it can account for the observed superparamagnetism and the colossal magnetoresistance.

Publ.-Id: 27155 - Permalink

Investigation of a possible electronic phase separation in the magnetic semiconductors Ga1−xMnxAs and Ga1−xMnxP by means of fluctuation spectroscopy
Lonsky, M.; Teschabai-Oglu, J.; Pierz, K.; Sievers, S.; Schumacher, H. W.; Yuan, Y.; Böttger, B.; Zhou, S.; Müller, J.
We present systematic temperature-dependent resistance noise measurements on a series of ferromagnetic Ga1−xMnxAs epitaxial thin films covering a large parameter space in terms of the Mn content x and other variations regarding sample fabrication. We infer that the electronic noise is dominated by switching processes related to impurities in the entire temperature range. While metallic compounds with x>2% do not exhibit any significant change in the low-frequency resistance noise around the Curie temperature TC, we find indications for an electronic phase separation in films with x<2% in the vicinity of TC, manifesting itself in a maximum in the noise power spectral density. These results are compared with noise measurements on an insulating Ga1−xMnxP reference sample, for which the evidence for an electronic phase separation is even stronger and a possible percolation of bound magnetic polarons is discussed. Another aspect addressed in this work is the effect of ion-irradiation-induced disorder on the electronic properties of Ga1−xMnxAs films and, in particular, whether any electronic inhomogeneities can be observed in this case. Finally, we put our findings into the context of the ongoing debate on the electronic structure and the development of spontaneous magnetization in these materials.

Publ.-Id: 27154 - Permalink

Frust, T.ORC

RODARE (Rossendorf Data Repository) is the institutional data repository at Helmholtz-Zentrum Dresden-Rossendorf. The initial logos of the platform are collected in this upload and are available as Open Access.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-02-28
    DOI: 10.14278/rodare.1
    License: CC-BY-NC-4.0


Publ.-Id: 27151 - Permalink

Probing charged lepton flavor violation with the Mu2e experiment
Mueller, S. E.ORC
The Mu2e experiment, currently under construction at the Fermi National Accelerator Laboratory near Chicago, will search for the neutrinoless conversion of muons to electrons in the field of an aluminum nucleus. This charged lepton flavor-changing process is highly suppressed in the Standard Model and therefore undetectable. There exist however scenarios for physics beyond the Standard Model that predict small but observable rates.The Mu2e experiment aims at a sensitivity four orders of magnitude better than existing experiments. This is achieved by a rigorous control of all backgrounds that could mimic the monoenergetic signal electron.

The design and status of the Mu2e experiment will be presented. In addition, I will highlight the results from several test runs carried out at HZDR's ELBE facility to study the radiation hardness and performance of components for the Mu2e calorimeter and for the detector that monitors the rate of stopped muons in the aluminum target.
Keywords: charged lepton flavor violation muon to electron conversion MU2E ELBE
  • Lecture (Conference)
    DPG Spring Meeting 2018, 26.02.-02.03.2018, Bochum, Germany

Publ.-Id: 27145 - Permalink

Formation and Aggregation of ZrO2 Nanoparticles on Muscovite (001)
Qiu, C.; Eng, P. J.; Hennig, C.ORC; Schmidt, M.ORC
The aggregation of nanoparticles is a key step in the formation of solid phases and a controlling factor for the behavior of suspended nanoparticles in solution. Using a charged mineral surface [muscovite (001)] we apply the surface X-ray diffraction techniques Crystal Truncation Rod (CTR) measurements and Resonant Anomalous X-ray reflectivity (RAXR) to investigate the aggregation process of Zr nanoparticles at the sub-nm scale. The aggregation process was studied as a function of ionic strength (0, 1, 10, and 100 mM NaCl), and the interfacial particles were characterized by CTR/RAXR and AFM. The observations are consistent with an aggregation process that follows a multi-step mechanism, which starts with the 3D aggregation of primary building units to form nanosheets. These sheets continue to grow through addition of building units to their reactive edges at higher ionic strength. Once the size and concentration of aggregates is sufficient, “face-to-face” stacking of nanosheets becomes the preferred aggregation mechanism as this minimizes the electrostatic repulsion of the charge that accumulates along nanosheet edges.
Keywords: Zr, muscovite, X-ray surface diffraction


  • Secondary publication expected from 06.02.2019

Publ.-Id: 27143 - Permalink

High-field magnetoelasticity of Tm2Co17 and comparison with Er2Co17
Andreev, A. V.; Zvyagin, A. A.; Skourski, Y.; Yasin, S.; Zherlitsyn, S.
Acoustic properties (ultrasound velocity and attenuation) and magnetostriction were measured in pulsed fields up to 60 T applied along the c axis of Tm2Co17 single crystal. Similar to Er2Co17, the transition in Tm2Co17 is accompanied by clear anomalies in the sound velocity. The observed 0.3% jump of the sound velocity at the transition is negative in Tm2Co17, whereas it is positive in Er2Co17. The magnetostriction at the transition also differs very much from that in Er2Co17. In Tm2Co17, the transition is accompanied by a smooth minimum of 0.15×10-4 in longitudinal magnetostriction whereas in Er2Co17 by a very sharp expansion of much larger magnitude (1.2×10-4). In the transverse mode, the effect in Tm2Co17 looks as very broad minimum of low amplitude (<0.1×10-4) whereas in Er2Co17 as very sharp and large shrinkage (2.6×10-4). Thus, both the magnetoacoustics and magnetostriction are rather different in Tm2Co17 and Er2Co17. This supports different nature of the field-induced transitions in these compounds.

Publ.-Id: 27141 - Permalink

Unconventional field induced phases in a quantum magnet formed by free radical tetramers
Saúl, A.; Gauthier, N.; Askari, R. M.; Coté, M.; Maris, T.; Reber, C.; Lannes, A.; Luneau, D.; Nicklas, M.; Law, J. M.; Green, E. L.; Wosnitza, J.; Bianchi, A. D.; Feiguin, A.
We report experimental and theoretical studies on themagnetic and thermodynamic properties ofNIT-2Py, a free radical based organic magnet. From magnetization and specific-heat measurements we establish the temperature versus magnetic field phase diagram which includes two Bose-Einstein condensates (BEC) and an infrequent half-magnetization plateau. Calculations based on density functional theory demonstrate that magnetically this system can be mapped to a quasi-two-dimensional structure of weakly coupled tetramers. Density matrix renormalization group calculations show the unusual characteristics of the BECs where the spins forming the low-field condensate are different than those participating in the high-field one.

Publ.-Id: 27140 - Permalink

Multiplet of skyrmion states on a curvilinear defect: Reconfigurable skyrmion lattices
Kravchuk, V. P.; Sheka, D. D.; Kákay, A.; Volkov, O. M.; Rößler, U. K.; van den Brink, J.; Makarov, D.; Gaididei, Y.
Typically, the chiral magnetic Skyrmion is a single-state excitation. Here we propose a system, where multiplet of Skyrmion states appears and one of these states can be the ground one. We show that the presence of a localized curvilinear defect drastically changes the magnetic properties of a thin perpendicularly magnetized ferromagnetic film. For a large enough defect amplitude a discrete set of equilibrium magnetization states appears forming a ladder of energy levels. Each equilibrium state has either a zero or a unit topological charge; i.e., topologically trivial and Skyrmion multiplets generally appear. Transitions between the levels with the same topological charge are allowed and can be utilized to encode and switch a bit of information. There is a wide range of geometrical and material parameters, where the Skyrmion level has the lowest energy. Thus, periodically arranged curvilinear defects can result in a Skyrmion lattice as the ground state.
Keywords: Skyrmions, curvilinear defects


Publ.-Id: 27139 - Permalink

Clinical translation and regulatory aspects of CAR/TCR-based adoptive cell therapies-the German Cancer Consortium approach.
Krackhardt, A. M.; Anliker, B.; Hildebrandt, M.; Bachmann, M.; Eichmüller, S. B.; Nettelbeck, D. M.; Renner, M.; Uharek, L.; Willimsky, G.; Schmitt, M.; Wels, W. S.; Schüssler-Lenz, M.
Adoptive transfer of T cells genetically modified by TCRs or CARs represents a highly attractive novel therapeutic strategy to treat malignant diseases. Various approaches for the development of such gene therapy medicinal products (GTMPs) have been initiated by scientists in recent years. To date, however, the number of clinical trials commenced in Germany and Europe is still low. Several hurdles may contribute to the delay in clinical translation of these therapeutic innovations including the significant complexity of manufacture and non-clinical testing of these novel medicinal products, the limited knowledge about the intricate regulatory requirements of the academic developers as well as limitations of funds for clinical testing. A suitable good manufacturing practice (GMP) environment is a key prerequisite and platform for the development, validation, and manufacture of such cell-based therapies, but may also represent a bottleneck for clinical translation. The German Cancer Consortium (DKTK) and the Paul-Ehrlich-Institut (PEI) have initiated joint efforts of researchers and regulators to facilitate and advance early phase, academia-driven clinical trials. Starting with a workshop held in 2016, stakeholders from academia and regulatory authorities in Germany have entered into continuing discussions on a diversity of scientific, manufacturing, and regulatory aspects, as well as the benefits and risks of clinical application of CAR/TCR-based cell therapies. This review summarizes the current state of discussions of this cooperative approach providing a basis for further policy-making and suitable modification of processes.
Keywords: CAR/TCR-transgenic T cells; Cellular therapy; Clinical translation; Regulatory aspects

Publ.-Id: 27138 - Permalink

Hydrogen burning: Study of the 22Ne(p,gamma)23Na, 3He(alpha,gamma)7Be and 7Be(p, gamma)8B reactions at ultra-low energies
Takács, M. P.
The neon-sodium cycle (NeNa cycle) of hydrogen burning is active in stars of the Asymptotic Giant Branch, in classical novae, and in supernovae of type Ia. The thermonuclear reaction rate of the 22Ne(p,γ)23Na reaction is determined by a large number of resonances, and it represents the most uncertain rate in the NeNa cycle. This PhD thesis reports on an experiment to study tentative 22Ne(p,γ)23Na resonances at Elab = 71 and 105 keV, as well as the direct capture component of the reaction rate for Elab ≤ 400 keV. The measurements were performed deep underground at the Laboratory for Un- derground Nuclear Astrophysics - LUNA (Gran Sasso, Italy), taking advantage of the strong reduction in the cosmic ray induced background. The LUNA-400-kV electrostatic accelerator and a differentially pumped, windowless gas target of iso- topically enriched 22Ne gas were used. The γ-rays from the reaction were detected with a 4π bismuth germanate scintillator. The data show upper limits on the strengths of the resonances at Elab = 71 and 105 keV of 5.8 × 10−11 and 7.0 × 10−11 eV respectively. The resonances at Elab = 156.2, 189.5 and 259.7 keV have been re-studied and show 20% higher strength than the literature. The present experiment did not show any evidence for the direct capture process at the low energies studied. In addition to the experimental work at LUNA, the 3He(α, γ)7Be and 7Be(p, γ)8B reactions were studied using the most recent solar neutrino data available. Based on the standard solar model and the experimentally measured fluxes of solar 7Be and 8B neutrinos, the astrophysical S-factors of both reactions were evaluated directly in the solar Gamow peak.
Keywords: Nuclear Astrophysics Solar Neutrinos LUNA Neon-sodium cycle
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-087 2018


Publ.-Id: 27110 - Permalink

Overexpression of receptor tyrosine kinase EphB4 triggers tumor growth and hypoxia in A375 melanoma xenografts: insights from multitracer small animal imaging experiments
Neuber, C.; Belter, B.; Meister, S.; Hofheinz, F.; Bergmann, R.; Pietzsch, H.-J.; Pietzsch, J.ORC
Experimental evidence has associated receptor tyrosine kinase EphB4 with tumor angiogenesis also in malignant melanoma. Considering the limited in vivo data available, we have conducted a systematic multitracer and multimodal imaging investigation in EphB4-overexpressing and mock-transfected A375 melanoma xenografts. Tumor growth, perfusion, and hypoxia were investigated by positron emission tomography. Vascularization was investigated by fluorescence imaging in vivo and ex vivo. The approach was completed by magnetic resonance imaging, radioluminography ex vivo, and immunohistochemical staining for blood and lymph vessel markers. Results revealed EphB4 to be a positive regulator of A375 melanoma growth, but a negative regulator of tumor vascularization. Resulting in increased hypoxia, this physiological characteristic is considered as highly unfavorable for melanoma prognosis and therapy outcome. Lymphangiogenesis, by contrast, was not influenced by EphB4 overexpression. In order to distinguish between EphB4 forward and EphrinB2, the natural EphB4 ligand, reverse signaling a specific EphB4 kinase inhibitor was applied. Blocking experiments show EphrinB2 reverse signaling rather than EphB4 forward signaling to be responsible for the observed effects. In conclusion, functional expression of EphB4 is considered a promising differentiating characteristic, preferentially determined by non-invasive in vivo imaging, which may improve personalized theranostics of malignant melanoma.
Keywords: Eph receptor tyrosine kinase family; Ephrin ligands; tumor microenvironment; malignant melanoma; small animal positron emission tomography; tumor angiogenesis; tumor hypoxia

Publ.-Id: 27108 - Permalink

Experimentelle Untersuchung der Wärmeübertragung, des Druckverlustes und des Strömungsfeldes an ovalen Rippenrohren unter Variation des Anströmwinkels
Unger, S.; Beyer, M.; Arlit, M.; Hampel, U.
Rippenrohrwärmeübertrager finden in vielen Bereichen der Industrie Anwendung, wie beispielsweise in der Klimatechnik, Kältetechnik, Kraftwerkstechnik und in chemischen Anlagen. Da ca. 90% des gesamten thermischen Widerstandes gasseitig auftreten, werden hier Oberflächenerweiterungen in Form von Rippen genutzt. Bei vielen Anwendungsfällen werden die Rippenrohrwärmeübertrager geneigt installiert, um den benötigten Bauraum zu reduzieren oder um ein Abfließen von Kondensat auf der Rohrinnenseite zu gewährleisten. Daher soll der Einfluss des Anströmwinkels auf die Wärmeübertragungsleistung und Strömungscharakteristik untersucht und beschrieben werden.

Messtechnik, experimenteller Aufbau und Durchführung
Die stationären Messungen wurden in einem ca. 6.5 m langen, senkrechten und transparenten Strömungskanal mit rechteckigem Querschnitt durchgeführt. Im Einströmbereich des Kanals befinden sich drei Sieb- sowie ein Wabengleichrichter zur Strömungsformierung an die sich eine Testsektion mit den zu untersuchenden Rippenrohren anschließt. Es wurden 3 Rippenrohre mit Rippenabständen von 6 mm,11 mm und 16 mm jeweils unter vier Anströmwinkeln (0°,20°,30° und 40°) untersucht. Die Strömung wurde durch einen Kompressor aufgeprägt und die mittlere Strömungsgeschwindigkeit zwischen 0,5 m/s und 3 m/s variiert. Die ovalen Rippenrohre wurden additiv aus 316L Edelstahl (Wärmeleitfähigkeit: 16.2 W/mK) gefertigt und sind durch Haltebuchsen an den Kanalwänden fixiert. Der Austausch von Haltebuchsen und dazugehörigen Kanalwänden ermöglichte die Positionierung der Rippenrohre mit den erforderlichen Winkeln. Im Inneren der Rippenrohre befinden sich drei elektrisch beheizte Heizpatronen. Um eine gute Wärmeleitung zum Rippenrohr zu gewährleisten, sind die Zwischenräume mit Kupferpulver ausgefüllt. Aus jeweils drei stromaufwärts und –abwärts angeordneten Thermoelementen wurde die mittlere Lufttemperatur bestimmt. Das radiale Temperaturprofil der Rippen wurde mithilfe von 12 Thermoelementen entlang der Rippenoberfläche vermessen, um den Rippenwirkungsgrad zu bestimmen. An senkrechten Bohrungen der Kanalwand unter- und oberhalb der Testsektion befinden sich die Anschlüsse der Differenzdruckmessung.
Zur Einstellung der stationären Versuchsrandbedingungen wurde die mittlere Oberflächentemperatur des Rippenrohres, durch Anpassung der elektrischen Leistung in Abhängigkeit von der Anströmgeschwindigkeit konstant bei 60° C gehalten. Die Aufzeichnung der Messdaten erfolgte mit einer zeitlichen Auflösung von 1Hz. Ein Temperaturgittersensor wurde verwendet um in 16 Messstellen stromabwärts der Versuchsstrecke das Temperatur- und Geschwindigkeitsfeld mithilfe von Widerstandstemperaturmessung und thermischer Anemometrie zu bestimmen.

Die Messergebnisse zeigen einen deutlichen Anstieg des Wärmeübergangskoeffizienten mit größerem Rippenabstand. Hintergrund sind die Strömungsgrenzschichten, welche bei niedrigerem Abstand der Rippen schon früher stromabwärts zusammenwachsen und den Wärmeübergangskoeffizient reduzieren. Des Weiteren wurde festgestellt, dass bei einem Rippenabstand von 6 mm der Rippenwirkungsgrad am höchsten und bei 16 mm am kleinsten ist. Generell wurden höhere Temperaturen der Rippe im thermischen Nachlaufgebiet hinter dem Rohr sowie niedrigere Rippentemperaturen im Anströmbereich des Rippenrohres gemessen. Aufgrund der erhöhten Oberfläche ist bei 6 mm Rippenabstand der Druckverlust am höchsten, gefolgt von den Abständen 11 mm und 16 mm.
Durch einen erhöhten Anströmwinkel von 40° nimmt die Turbulenz entlang der Rippenoberfläche zu und der Wärmeübergangskoeffizient erhöht sich um 38 % bei 6 mm Rippenabstand gegenüber der senkrechten Anströmung. Der Druckverlust nimmt mit dem Anströmwinkel stark zu. Somit ist der Druckverlust in der 40° Position gegenüber der senkrechten Anströmung für 6 mm um den Faktor 3.23 größer.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet Fachgruppen Mehrphasenströmungen (MPH), Wärme- und Stoffübertragung (WSUE) und Computional Fluid Dynamics (CFD), 06.-07.03.2018, Bremen, Deutschland

Publ.-Id: 27107 - Permalink

Projektidee KESS Kreislaufwirtschaftliches EntscheidungsSimulationsSystem
van den Boogaart, K. G.
Das Projekt KESS - Kreislaufwirtschaftliches EntscheidungsSimulationsSystem beschäftigt sich mit der Vorhersage von Entscheidungen, Wert- und Stoffströmen einer zukünfigen Kreislaufwirtschaft. Gesucht werden Kooperationspartner aus den Bereichen Psychologie, Wirtschaftsrecht, Wirtschaft, Reuse, Repair, und Recyclingmodellierung, sowie Mathematik und Informatik. Besonders Willkommen sind Wirtschaftsunternehmen mit Fragestellungen zu zukünftigen Geschäftsmodellen im Rahmen der Kreislaufwirtschaft.
Keywords: Kreislaufwirtschaft, Spieltheorie, Entscheidungstheorie, Stoffstrommodellierung
  • Lecture (others)
    Vernetzungs- und Informationsveranstaltung, 22.02.2018, Berlin, Deutschlad

Publ.-Id: 27106 - Permalink

Magnetic stirring and sonication of metal melts
Gerbeth, G.
  • Invited lecture (Conferences)
    XVIII International UIE-Congress, 06.-09.06.2017, Hannover, Germany

Publ.-Id: 27103 - Permalink

Experimental Modelling of Metallurgical Processes
Eckert, G.; Gerbeth, S.
  • Invited lecture (Conferences)
    12th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries - SINTEF, 30.05.-01.06.2017, Trondheim, Norway

Publ.-Id: 27102 - Permalink

Interaction of Stem Cell Properties and DNA Repair determine the Radiosensitizing Effect after Inhibition of CHK1, RAD51 and PARP1 in TNBCs
Meyer, F.; Becker, S.; Niecke, A.; Werner, S.; Peitzsch, C.; Hein, L.; Dubrovska, A.; Goy, Y.; Parplys, A.; Petersen, C.; Riepen, B.; Zielinski, A.; Rothkamm, K.; Borgmann, K.

Publ.-Id: 27100 - Permalink

Recent update on the KLOE ISR-measurements
Keshavarzi, A.; Müller, S. E.ORC; Teubner, T.; Venanzoni, G.
Recent updates on KLOE ISR measurements
  • Invited lecture (Conferences)
    Workshop on hadronic vacuum polarization contributions to muon g-2, 12.-14.02.2018, KEK Tsukuba, Japan

Publ.-Id: 27097 - Permalink

Intratumoral heterogeneity and TERT promoter mutations in progressive/higher-grade meningiomas
Juratli, T. A.; Thiede, C.; Koerner, M. V. A.; Tummala, S. S.; Daubner, D.; Shankar, G. M.; Williams, E. A.; Martinez-Lage, M.; Soucek, S.; Robel, K.; Penson, T.; Krause, M.; Appold, S.; Meinhardt, M.; Pinzer, T.; Miller, J. J.; Krex, D.; Ely, H. A.; Silverman, I. M.; Christiansen, J.; Schackert, G.; Wakimoto, H.; Kirsch, M.; Brastianos, P. K.; Cahill, D. P.
Background: Recent studies have reported mutations in the telomerase reverse transcriptase promoter (TERTp) in meningiomas. We sought to determine the frequency, clonality and clinical significance of telomere gene alterations in a cohort of patients with progressive/higher-grade meningiomas.

Methods: We characterized 64 temporally- and regionally-distinct specimens from 26 WHO grade III meningioma patients. On initial diagnoses, the meningiomas spanned all WHO grades (3 grade I, 13 grade II and 10 grade III). The tumor samples were screened for TERTp and ATRX/DAXX mutations, and TERT rearrangements. Additionally, TERTp was sequenced in a separate cohort of 19 patients with radiation-associated meningiomas. We examined the impact of mutational status on patients’ progression and overall survival.

Results: Somatic TERTp mutations were detected in six patients (6/26 = 23%). Regional intratumoral heterogeneity in TERTp mutation status was noted. In 4 patients, TERTp mutations were detected in recurrent specimens but not in the available specimens of the first surgery. Additionally, a TERT gene fusion (LPCAT1-TERT) was found in one sample. In contrary, none of the investigated samples harbored an ATRX or DAXX mutation. In the cohort of radiation-induced meningiomas, TERTp mutation was detected in two patients (10.5%). Importantly, we found that patients with emergence of TERTp mutations had a substantially shorter OS than their TERTp wild-type counterparts (2.7 years, 95% CI 0.9 – 4.5 years versus 10.8 years, 95% CI 7.8 -12.8 years, p=0.003).

Conclusions: In progressive/higher-grade meningiomas,TERTp mutations are associated with poor survival, supporting a model in which selection of this alteration is a harbinger of aggressive tumor development. In addition, we observe spatial intratumoral heterogeneity of TERTp mutation status, consistent with this model of late emergence in tumor evolution. Thus, early detection of TERTp mutations may define patients with more aggressive meningiomas. Stratification for TERT alterations should be adopted in future clinical trials of progressive/higher-grade meningiomas.

Publ.-Id: 27096 - Permalink

An Image Reconstruction Framework and Camera Prototype Aimed for Compton Imaging for In-vivo Dosimetry of Therapeutic Ion Beams
Schoene, S.; Enghardt, W.; Fiedler, F.; Golnik, C.; Pausch, G.; Rohling, H.; Kormoll, T.
Prompt γ-ray imaging in hadron therapy is a novel approach for range verification. Due to the high energy of prompt γ-rays emitted during therapeutic irradiation in the order of MeV, Compton imaging is a feasible method. In this work, an imaging prototype together with the corresponding data handling and an image reconstruction framework are presented. Data and reconstructed images from laboratory measurements are shown and evaluated. A spatial resolution of 7 mm full width at half maximum in a distance of 7 cm has been achieved. More importantly, current limitations were identified for further work. It has been shown that an assumption on the unknown initial photon energy can considerably improve the imaging result.

Publ.-Id: 27095 - Permalink

Robustness evaluation of single-and multifield optimized proton plans for unilateral head and neck
Cubillos-Mesías, M.; Baumann, M.; Troost, E. G. C.; Appold, S.; Krause, M.; Richter, C.; Stützer, K.

Publ.-Id: 27094 - Permalink

Adhesion- and stress-related adaptation mechanisms eliciting glioblastoma radiochemoresistance can be effectively circumvented by beta1 integrin/JNK co-targeting
Vehlow, A.; Klapproth, E.; Storch, K.; Dickreuter, E.; Seifert, M.; Dietrich, A.; Bütof, R.; Temme, A.; Cordes, N.
Glioblastoma multiforme (GBM) is the most common brain tumor in adults and characterized by poor clinical outcome due to genetic and epigenetic alterations in resistance-mediating genes and destructive infiltration into the normal brain. Upon therapy, malignant tumors show adaptation to maintain their homeostasis. Two critical determinants of this adaptation process are cell adhesion by beta1 integrins and stress signaling via c-Jun N-terminal kinases (JNK). Here, we evaluated the potential of simultaneous beta1 integrin/JNK targeting to overcome GBM adaptation controlling radiochemoresistance and invasion.

Comparative Oncomine data base analysis was performed on the expression of JNK1/2/3 isoforms, beta1 integrin and its ligands in GBM with normal brain. Different human GBM cell populations (patient-derived, stem-like, established) were analyzed for sphere formation, clonogenicity, 3D collagen type-1 invasion, cell cycling, chromatin organization, DNA double strand break (DSB) repair (γH2AX foci assay), broad-spectrum phosphoproteome analysis, FACS analysis and protein expression/phosphorylation upon irradiation (0-6 Gy X-rays) and chemotherapy (Temozolomide) with and without single and simultaneous inhibition of beta1 integrin (AIIB2) and JNK (SP600125, JNKi). The radiochemosensitizing potential of AIIB2/JNKi was also investigated in an orthotopic GBM mouse model using stem-like cells.

In contrast to JNK isoforms, beta1 integrin and col1 showed significant overexpression in GBM compared with normal brain. While single inhibition of beta1 integrin and JNK mediated cytotoxicity, only combined targeting resulted in radiochemosensitization. Intriguingly, double AIIB2/JNKi treatment abrogated GBM cell invasion. Importantly, dual beta1 integrin/JNK inhibition elicited a significant reduction in tumor growth and longer survival of mice concomitantly treated with radiotherapy/Temozolomide. Mechanistically, JNK blocking induced beta1 integrin expression for stimulating diverse signaling pathways controlling cell cycling, invasion and radiochemosensitivity. Radiosensitization by AIIB2/JNKi is caused by enhanced ATM phosphorylation and prolonged G2/M cell cycle arrest as well as impaired DNA double strand break repair in the context of elevated levels of euchromatin.

In summary, our data reveal that dual beta1 integrin/JNK targeting efficiently impairs adhesion and stress-related adaptation mechanisms involved in radiochemoresistance and invasion. More in-depth evaluation is warranted to clarify the potential of this kind of beta1 integrin/JNK multi-targeting strategy administrated concomitantly to standard radiochemotherapy in patients suffering from GBM.

Publ.-Id: 27093 - Permalink

Ein möglicher prognostischer Biomarker für das Therapieansprechen und therapeutisches Zielmolekül zur Strahlensensitivierung in Kopf-Hals-Plattenepithelkarzinomen
Digomann, D.; Kurth, I.; Linge, A.; Hein, L.; Baumann, M.; Dubrovska, A.
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 193(2017), S25-S26

Publ.-Id: 27090 - Permalink

Preparation of small animal irradiation experiments with laser-accelerated protons
Kroll, F.; Beyreuther, E.; Brack, F. E.; Gaus, L.; Karsch, L.; Kraft, S.; Metzkes, J.; Pawelke, J.; Schlenvoigt, H. P.; Schürer, M.; Zeil, K.; Schramm, U.
  • Open Access LogoAbstract in refereed journal
    Biomedical Engineering / Biomedizinische Technik 62(2017)Suppl. 1, S239
    DOI: 10.1515/bmt-2017-5044

Publ.-Id: 27087 - Permalink

Borohydrides oxidation by photoexcited [UO2(CO3)3]4−
Takao, K.ORC; Tsushima, S.ORC
Carbonate ion is an effective quencher of uranyl(VI) luminescence and makes uranyl(VI) tricarbonate barely luminecent and photochemically inactive. We demonstrate here that photoexcited uranyl(VI) tricarbonate, *[UVIO2(CO3)3]4− can yet oxidize borohydrides (BH3X, X = H, CN) to give boric acid and H2 gas, reducing itself to [UVO2(CO3)3]5−. This hypothesis was supported by UV-Vis and NMR spectroscopies as well as quantum chemical calculations. The charge transfer states associated with photoreduction processes were modelled by density functional theory calculations. These results suggest that the mechanism of photoreduction of [UVIO2(CO3)3]4− is similar to that in [[UVIO2(H2O)5]2+ and that it occurs through one–photon reduction process.

Publ.-Id: 27086 - Permalink

Experimental observation of Bethe strings
Wang, Z.ORC; Wu, J.; Yang, W.; Bera, A. K.; Kamenskyi, D.; Islam, A. T. M. N.; Xu, S.; Law, J. M.; Lake, B.; Wu, C.; Loidl, A.
Almost a century ago, string states—complex bound states of magnetic excitations—were predicted to exist in one-dimensional quantum magnets. However, despite many theoretical studies, the experimental realization and identification of string states in a condensed-matter system have yet to be achieved. Here we use high-resolution terahertz spectroscopy to resolve string states in the antiferromagnetic Heisenberg–Ising chain SrCo2V2O8 in strong longitudinal magnetic fields. In the field-induced quantum-critical regime, we identify strings and fractional magnetic excitations that are accurately described by the Bethe ansatz. Close to quantum criticality, the string excitations govern the quantum spin dynamics, whereas the fractional excitations, which are dominant at low energies, reflect the antiferromagnetic quantum fluctuations. Today, Bethe’s result1 is important not only in the field of quantum magnetism but also more broadly, including in the study of cold atoms and in string theory; hence, we anticipate that our work will shed light on the study of complex many-body systems in general.
Keywords: Bethe ansatz, string excitations, Heisenberg-Ising chain, THz/infrared spectroscopy, high magnetic field

Publ.-Id: 27084 - Permalink

Origin of field-induced discontinuous phase transitions in Nd2Fe17
Diop, L. V. B.; Kuz'Min, M. D.; Skokov, K. P.; Skourski, Y.; Gutfleisch, O.
Magnetic properties of a trigonal ferromagnet Nd2Fe17 have been studied on single crystals in steady (14 T) and pulsed (32 T) magnetic fields. The easy-magnetization direction lies close to the [120] axis, deviating from the basal plane by 2.9° (at T = 5 K). Of particular interest is the low-temperature magnetization process along the high-symmetry axis [001], which is the hard direction. This process is discontinuous and involves two first-order phase transitions (FOMPs). One of them (at 20 T) is a symmetry FOMP similar to that observed in Sm2Fe17. The second transition (at 10.4 T) is unusual: as the magnetization turns abruptly toward the applied field, it also changes its azimuthal orientation (the angle ϕ) by 60°. Both transitions can be reasonably accounted for by the presence of a significant sixth-order trigonal anisotropy term.

Publ.-Id: 27083 - Permalink

Radiative neutron capture on 242Pu in the resonance region at the CERN n_TOF-EAR1 facility
Lerendegui-Marco, J.; Guerrero, C.; Mendoza, E.; Quesada, J. M.; Eberhardt, K.; Junghans, A. R.; Krtička, M.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Barros, S.; Bečvář, F.; Beinrucker, C.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brugger, M.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Furman, V.; Göbel, K.; García, A. R.; Gawlik, A.; Glodariu, T.; Gonçalves, I. F.; González-Romero, E.; Goverdovski, A.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heftrich, T.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Katabuchi, T.; Kavrigin, P.; Ketlerov, V.; Khryachkov, V.; Kimura, A.; Kivel, N.; Kokkoris, M.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lo Meo, S.; Lonsdale, S. J.; Losito, R.; Macina, D.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Matteucci, F.; Maugeri, E. A.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Montesano, S.; Musumarra, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, J. I.; Praena, J.; Rajeev, K.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Smith, A. G.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou33, R.; Wallner, A.; Warren, S.; Weigand, M.; Weiss, C.; Wolf, C.; Woods, P. J.; Wright, T.; Žugec, P.
The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with uranium to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. However, an extensive use of MOX fuels, in particular in fast reactors, requires more accurate capture and fission cross sections for some Pu isotopes. In the case of 242Pu there are sizable discrepancies among the existing capture cross-section measurements included in the evaluations (all from the 1970s) resulting in an uncertainty as high as 35% in the fast energy region. Moreover, postirradiation experiments evaluated with JEFF-3.1 indicate an overestimation of 14% in the capture cross section in the fast neutron energy region. In this context, the Nuclear Energy Agency (NEA) requested an accuracy of 8% in this cross section in the energy region between 500 meV and 500 keV. This paper presents a new time-of-flight capture measurement on 242Pu carried out at n_TOF-EAR1 (CERN), focusing on the analysis and statistical properties of the resonance region, below 4 keV. The 242Pu(n,γ) reaction on a sample containing 95(4) mg enriched to 99.959% was measured with an array of four C6D6 detectors and applying the total energy detection technique. The high neutron energy resolution of n_TOF-EAR1 and the good statistics accumulated have allowed us to extend the resonance analysis up to 4 keV, obtaining new individual and average resonance parameters from a capture cross section featuring a systematic uncertainty of 5%, fulfilling the request of the NEA.
Keywords: Neutron physics, nuclear reactions, radiative capture, reactor fuel and coolants, radioactive waste

Publ.-Id: 27080 - Permalink

Electrical properties of surface and interface layers of the N- and In-polar undoped and Mg-doped InN layers grown by PA MBE
Komissarova, T. A.; Kampert, E.; Law, J.; Jmerik, V. N.; Paturi, P.; Wang, X.; Yoshikawa, A.; Ivanov, S. V.
Electrical properties of N-polar undoped and Mg-doped InN layers and In-polar undoped InN layers grown by plasma-assisted molecular beam epitaxy (PA MBE) were studied. Transport parameters of the surface and interface layers were determined from the measurements of the Hall coefficient and resistivity as well as the Shubnikov-de Haas oscillations at magnetic fields up to 60 T. Contributions of the 2D surface, 3D near-interface, and 2D interface layers to the total conductivity of the InN films were defined and discussed to be dependent on InN surface polarity, Mg doping, and PA MBE growth conditions.

Publ.-Id: 27078 - Permalink

ChimeraTK OPC UA Adapter for the Integration of a MicroTCA.4 based digital LLRF
Steinbrück, R.; Kuntzsch, M.; Zenker, K.; Hierholzer, M.; Killenberg, M.; Iatrou, C. P.; Rahm, J.
The superconducting linear accelerator ELBE at Helmholtz-Center Dresden-Rossendorf is a versatile light source operated in continuous wave mode. Currently there is a transition from an analogue low level radio frequency control (LLRF) to a digital MicroTCA.4 based solution developed at DESY, Hamburg. Control system integration is realized collaboratively by DESY, Technische Universität Dresden (TUD) and HZDR with ChimeraTK and the incorporated OPC UA adapter. The poster gives an overview of the variable mapping scheme used to represent LLRF data in the OPC UA server address space, the graphical user interface and first integration test results.
Keywords: ELBE MicroTCA.4 LLRF "OPC UA" ChimeraTK
  • Lecture (others)
    6th MicroTCA Workshop for Industry and Research, 04.-07.12.2017, Hamburg, Deutschland

Publ.-Id: 27072 - Permalink

Control System Integration of a MicroTCA.4 Based Digital LLRF Using the ChimeraTK OPC UA Adapter
Steinbrück, R.; Kuntzsch, M.; Michel, P.; Hierholzer, M.; Killenberg, M.; Schlarb, H.; Iatrou, C. P.; Rahm, J.; Urbas, L.
The superconducting linear electron accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf is a versatile light source. It operates in continuous wave (CW) mode to provide a high average beam current. In order to meet the requirements for future high resolution experiments the analogue low level radio frequency control (LLRF) is currently replaced by a digital MicroTCA.4 LLRF system based on a development at DESY, Hamburg.
Operation and parametrization is realized by a server application implemented by DESY using the ChimeraTK software framework. To interface the WinCC 7.3 based ELBE control system an OPC UA adapter for ChimeraTK has been developed in cooperation of DESY, Technische Universität Dresden (TUD) and HZDR. The contribution gives an overview of the collaborating parties, the variable
mapping scheme used to represent LLRF data in the OPC UA server address space and integration experiences with different industrial OPC UA Clients like WinCC 7.3 and LabVIEW.
Keywords: MicroTCA.4 LLRF "OPC UA" ChimeraTK
  • Poster
    ICALEPCS2017 - 16th International Conference on Accelerator and Large Experimental Physics Control Systems, 03.-13.10.2017, Barcelona, Spain
    DOI: 10.18429/JACoW-ICALEPCS2017-THPHA166
  • Contribution to proceedings
    ICALEPCS2017 - 16th International Conference on Accelerator and Large Experimental Physics Control Systems, 08.-13.10.2017, Barcelona, Spain
    Proceedings of ICALEPCS2017
    DOI: 10.18429/JACoW-ICALEPCS2017-THPHA166

Publ.-Id: 27070 - Permalink

Vertical Nanowire Based Single Electron Transistor Self-Assembled by Ion Beam Mixing and Phase Separation
Heinig, K.-H.; von Borany, J.; Hlawacak, G.; Hübner, R.; Wolf, D.; Engelmann, H.-J.; Bischoff, L.; Xu, X.; Prüfer, T.; Möller, W.; Facsko, S.
Electronics has been dominated by silicon since half a century. Si will dominate electronics another decade, however its functionality might change from classical field-controlled currents through channels (the Field Effect Transistor FET) to quantum mechanical effects like field-controlled hopping of single electrons to a quantum dot (Single Electron Transistor SET). The SET is the champion of low-power consumption. This is attractive for the Internet of Things: more and more devices need batteries and plugs. Together with improved batteries, advanced computation must be delivered at extremely low-power consumption. At low temperatures, the functionality of SETs has been proven. Large-scale use of SETs requires room temperature operation, which can be achieved with tiny Si dots (<4 nm) in SiO2, exactly located between source and drain with distances of ~1…2 nm. Manufacturability of such nanostructures is the roadblock for large-scale use of SETs. Lithography cannot deliver such feature sizes. Therefore, there are currently intense studies to fulfill these requirements by self-organization processes. The ion beam technique is a well-established technology in microelectronics used for doping and amorphization, and even for ion beam mixing [1]. The parameters of ion beam processing are very well controllable. We searched for a self-organization process in a vertical silicon nanowire with an embedded, very thin (~6nm) SiO2 layer. Ion beam mixing transforms this layer to metastable SiOx. If the nanowire is thin enough, a subsequent thermal treatment leads by phase separation to a single Si nanodot (~3nm) self-aligned to the lower and upper Si at distances of <2nm. Here, we present 3D computer simulations on ion beam mixing (TRI3DYN code [2]) and Si nanodot formation (3D kinetic Monte Carlo code [3]). Such simulations predicted successfully the fabrication of non-volatile memories using ion beam mixing [4]. Experimentally, single Si nanodot formation has been proven by local mixing in a c-Si/SiO2/a-Si layer stack. The nanoscale mixing has been performed with a Helium Ion Microscope using an Argon beam of ~2nm diameter. After Rapid Thermal Annealing, the self-organized single Si nanodot has been imaged by cross-section energy-filtered transmission electron microscopy EFTEM. In a vertical nanowire the very small volume of mixed SiO2 is not due to nanoscale ion beams but due to the small diameter of the wire. It will be shown, how a vertical nanowire gate-all-around SETs operating at room temperature can be CMOS-compatibly fabricated by this method.
This work has been funded by the European Union’s Horizon 2020 research and innovation program under grant
agreement No 688072.
[1] K.H. Heinig, T. Müller, B. Schmidt, M. Strobel, W. Möller, Appl. Phys. A77 (2003) 17.
[2] W. Möller, NIM B322 (2014) 23.
[3] M. Strobel, K.-H. Heinig, W. Möller, Phys. Rev. B64 (2001) 245422.
[4] T. Mueller et al., Appl .Phys. Lett. 81 (2002) 3049; ibid 85 (2004) 2373.
Keywords: ion beam mixing, phase separation, computer simulations, manufacturing, single electron transistor
  • Lecture (Conference)
    Symposium “Progress in Developing and Applications of Functional 1D Nanostructiures”, 2017 Fall Meeting of the Materials Research Society, 26.11.-01.12.2017, Boston, USA

Publ.-Id: 27068 - Permalink

Ion-Beam-Induced Self-Organisation of Nanostructures at Interfaces
Heinig, K.-H.; Prüfer, T.; Möller, W.; Hlawacek, G.; Xu, X.; Bischoff, L.; Hübner, R.; Wolf, D.; Facsko, S.; von Borany, J.
Ion irradiation through an interface between the phases A and B causes atomic displacements which results at low temperatures in a diffusion-like concentration profile. Even if phases A and B are immiscible, a metastable layer of an A/B mixture forms at high ion fluence. A subsequent thermal treatment will activate phase separation in this A/B mixture via nucleation and coarsening. This phase separation process has the potential of self-organisation of nanostructures, where the resulting nanostructure can be tailored by understanding and controlling the reaction pathway.
(i) At first, in this presentation it will be shown how the ion beam mixing of a flat infinite interface can be simulated with the SRIM and TRIDYN programs.
(ii) Then, by means of 3D kinetic lattice Monte-Carlo simulations it will be demonstrated how a thermally activated phase separation of the A/B mixture starts either by formation of nuclei of the minority phase or by spinodal decomposition.
(iii) Simulations for long times show that the subsequent nanostructure evolution is driven by interface minimization, i.e. Ostwald ripening of nanocluster ensembles or coarsening of spinodal structures.
At this stage, a self-organisation process governed by Brailsford's diffusional screening length can evolve, which can be eventually controlled. The A/B interface which re-forms during phase separation plays a central role for self-organisation and self-alignment of nanostructures.
These general mechanisms are effective in ion beam mixing of a thin SiO2 layer buried in Si with the following observations: (i) Zones denuded of Si form during annealing at the upper and lower interface. (ii) Additionally, three, two or one layer of Si nanoclusters form and align with the interface. (iii) If only a tiny volume ~(10nm)^3 of metastable SiOx (such as in an ion beam mixed nanopillar of a Si/SiO2/Si stack) becomes phase separated, the reaction pathway leads always to the existence of a single Si dot for a rather long time period.
This single Si nanodot fabrication becomes even more stable if all boundaries of the tiny SiOx volume are sinks for Si diffusing in SiO2, which can be realized by sideways in-diffusion of oxygen into the nanopillar.
Finally it will be shown, how such a single Si nanodot fabrication process can be used for manufactoring of single electron transisrors working at room temperature.
Keywords: Nanostructure fabrication, ion-beam-mixing, phase separation, silicon nanodot, single electron transistor
  • Invited lecture (Conferences)
    FOR3NANO: Formation of 3D Nanostructures by Ion Beams, 28.-30.06.2017, Helsinki, Finland

Publ.-Id: 27067 - Permalink

Underground Nuclear Astrophysics in 2017 at LUNA, LUNA-MV, and Felsenkeller
Bemmerer, D.
The state of the art of underground nuclear astrophysics is reviewed. Starting from recent progress on hydrogen burning and Big Bang nucleosynthesis at LUNA, the upcoming new underground accelerators LUNA-MV and Felsenkeller are discussed.
Keywords: Nuclear Astrophysics underground; LUNA; Felsenkeller
  • Invited lecture (Conferences)
    Strategietreffen "Astroteilchenphysik in Deutschland", 07.-08.12.2017, Bad Honnef, Deutschland

Publ.-Id: 27062 - Permalink

Strahlenschutzaspekte beim neuen Beschleunigerlabor im Dresdner Felsenkeller
Bemmerer, D.
Strahlenschutzaspekte beim neuen Beschleunigerlabor im Dresdner Felsenkeller. Zusätzlich zum klassischen Strahlenschutz am 5 MV Ionenbeschleuniger im Felsenkeller wird auch die Low-Background-Problematik unter Tage diskutiert.
  • Invited lecture (Conferences)
    TÜV Süd Akademie "Strahlenschutz in Medizin, Forschung und Industrie", 06.-07.12.2017, Marburg/Lahn, Deutschland

Publ.-Id: 27061 - Permalink

Nuclear Astrophysics Basics II
Bemmerer, D.
Carbon-nitrogen-oxygen cycle, nuclear cosmology, Felsenkeller underground accelerator
  • Invited lecture (Conferences)
    Lecture Week on Nuclear Structure and Nuclear Astrophysics, 04.-05.12.2017, Zell / Mosel, Deutschland

Publ.-Id: 27060 - Permalink

Nuclear Astrophysics Basics I
Bemmerer, D.
Nuclear Astrophysics Basics I: Cross Section, Gamow Peak, Thermonuclear Reaction Rate, and the Sun.
  • Invited lecture (Conferences)
    Lecture Week on Nuclear Structure and Nuclear Astrophysics, 04.-05.12.2017, Zell / Mosel, Deutschland

Publ.-Id: 27059 - Permalink

Using XFELs to Probe Kilotesla Magnetic Fields inside Solid Density Plasmas Driven by Optical High Power Lasers
Huang, L. G.; Schlenvoigt, H.-P.; Takebe, H.; Cowan, T. E.
The relativistic laser matter interaction is a complex interplay of ionization, extreme current densities, rapidly evolving strong fields and acceleration processes. Understanding the interaction physics is a challenging but highly rewarding endeavor. The unprecedented brightness of XFELs opens a new window for discovering the interior of solid-density plasmas created by relativistic laser interactions with matter, resolving the relevant femtosecond and sub-micrometer scales experimentally.
Here, we focus on discussing the feasibility of probing the magnetic fields by X-Ray polarimetry via Faraday rotation using XFEls.
Keywords: laser,plasmas, magnetic fields,faraday rotation,xfel
  • Poster
    European XFEL Users' Meeting 2018, 23.-26.01.2018, Hamburg, Germany

Publ.-Id: 27055 - Permalink

Quasifree (p,2p) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength
Atar, L.; Paschalis, S.; Barbieri, C.; Bertulani, C.  A.; Díaz Fernández, P.; Holl, M.; Najafi, M.  A.; Panin, V.; Alvarez-Pol, H.; Aumann, T.; Avdeichikov, V.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Boillos, J.  M.; Boretzky, K.; Borge, M.  J.  G.; Caamaño, M.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkall, J.; Chartier, M.; Chulkov, L.; Cortina-Gil, D.; Cravo, E.; Crespo, R.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; Fraile, L.  M.; Freer, M.; Galaviz Redondo, D.; Geissel, H.; Gernhäuser, R.; Golubev, P.; Göbel, K.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Hufnagel, A.; Ignatov, A.; Johansson, H.  T.; Jonson, B.; Kahlbow, J.; Kalantar-Nayestanaki, N.; Kanungo, R.; Kelic-Heil, A.; Knyazev, A.; Kröll, T.; Kurz, N.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lindberg, S.; Machado, J.; Marganiec-Gałązka, J.; Movsesyan, A.; Nacher, E.; Nikolskii, E.  Y.; Nilsson, T.; Nociforo, C.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Reifarth, R.; Ribeiro, G.; Rigollet, C.; Rossi, D.  M.; Röder, M.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Syndikus, I.; Taylor, J.  T.; Tengblad, O.; Thies, R.; Togano, Y.; Vandebrouck, M.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Wheldon, C.; Wilson, G.  L.; Winfield, J.  S.; Woods, P.; Yakorev, D.; Zhukov, M.; Zilges, A.; Zuber, K.
Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the
R3B/LAND setup with incident beam energies in the range of 300–450 MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type AO(p,2p)A−1N have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry

Publ.-Id: 27054 - Permalink

Femtosecond laser-generated high-energydensity states studied by x-ray FELs
Nakatsutsumi, M.; Appel, K.; Baehtz, C.; Chen, B.; Cowan, T. E.; Göde, S.; Konopkova, Z.; Pelka, A.; Priebe, G.; Schmidt, A.; Sukharnikov, K.; Thorpe, I.; Tschentscher, T.; Zastrau, U.
The combination of powerful optical lasers and an x-ray free-electron laser (XFEL) provides unique capabilities to study the transient behaviour of matter in extreme conditions. The high energy density science instrument (HED instrument) at the European XFEL will provide the experimental platform on which an unique x-ray source can be combined with various types of high-power optical lasers. In this paper, we highlight selected scientific examples together with the associated x-ray techniques, with particular emphasis on femtosecond (fs)-timescale pump–probe experiments. Subsequently, we present the current design status of the HED instrument, outlining how the experiments could be performed. First user experiments will start at the beginning of 2018, after which various optical lasers will be commissioned and made available to the international scientific community.
Keywords: x-ray free-electron laser, femtosecond dynamics, relativistic plasma, high-energydensity state

Publ.-Id: 27053 - Permalink

Isothermal differential dilatometry based on X-ray analysis applied to stress relaxation in thin ion-beam-sputtered Pt films
Gruber, W.; Baehtz, C.; Geue, T.; Stahn, J.; Schmidt, H.
Relaxation of stress and point defects in ion-beam-sputtered Pt films with a thickness of 20 and 40 nm during isothermal annealing was investigated. First, isothermal differential dilatometry measurements based on X-ray analysis were carried out between 130 and 400 °C. They show that the relaxation of compressive stress is associated with the formation of vacancies at the surface. From the measurements, an activation enthalpy of 0.14 eV was estimated for the stress relaxation process. In addition, self-diffusion experiments of Pt were carried out on the same type of films using stable 194Pt tracer. From secondary ion mass spectrometry on samples annealed for longer times, an activation enthalpy of 0.5 eV for Pt diffusion in grain boundaries was estimated. The influence of vacancy creation at the surface, vacancy transport, and the annihilation of nonequilibrium
bulk interstitials and thermally created vacancies on stress relaxation is discussed.
Keywords: Thin films Synchrotron X-ray diffraction ion-beam-sputtering

Publ.-Id: 27052 - Permalink

Non-Reciprocal Spin-Wave Emission from Topological Spin Textures
Schneider, T.; Sluka, V.; Kakay, A.; Weigand, M.; Warnatz, T.; Mattheis, R.; Gallardo, R. A.; Roldan-Molina, A.; Landeros, P.; Tiberkevich, V.; Slavin, A.; Erbe, A.; Deac, A.; Lindner, J.; Fassbender, J.; Raabe, J.; Wintz, S.
Investigations of spin waves are of great interest for both fundamental science and applications. For the excitation of spin waves with short wavelengths, it was typically necessary to either use patterned transducers with sizes on the order of the desired wavelengths or to generate such spin waves parametrically.
Here, we will show a combined experimental and theoretical study of spin waves in a stacked vortex pair system formed in a NiFe/Ru/CoFeB trilayer. The magnetization dynamics was imaged by means of time-resolved scanning transmission x-ray microscopy (STXM). Thereby, two different spin wave regimes were identified. For excitation frequencies above 500 MHz, mainly 2D plane waves within the magnetic domains were observed. However, a transition from 2D to 1D wave transport occurs for excitation frequencies below 500 MHz. In this case almost no spin waves were detected within the domains but high amplitudes were found within the 180° domain walls. An analytic and numerical analysis was done for both regimes, resulting in both a qualitative and quantitative understanding of the finite frequency gap in the spin wave dispersion relation for the ferromagnetic domains. Moreover, the dispersion relation was found to exhibit a strong non-reciprocity.
Keywords: Spin-wave, non-reciprocity, spin textures
  • Lecture (Conference)
    APS March Meeting 2018, 05.-09.03.2018, Los Angeles, USA

Publ.-Id: 27051 - Permalink

Chiral-partner D mesons in a heat bath within QCD sum rules
Buchheim, T.; Hilger, T.; Kämpfer, B.; Leupold, S.
Utilizing QCD sum rules, we extract the temperature dependences of the spectral properties of the pseudo-scalar and scalar D mesons regarded as chiral partners. Besides the masses also decay constants are analyzed as the D meson yields in heavy-ion collisions may be sensitive to their altered decay properties in an ambient strongly interacting medium. Our findings are (i) a decreasing scalar D meson mass for growing temperatures while its pseudo-scalar partner meson seems hardly affected, which is in qualitative agreement with hadronic model calculations; (ii) inferring an equally weak temperature dependence of the pseudo-scalar D meson decay properties the decreasing residua and decay constants of the scalar particle point towards partial chiral restoration. As a bonus of our analysis in the pseudo-scalar sector we determine the pseudo-scalar decay constant at vanishing temperature. Due to the connection to particular leptonic branching fractions this decay constant is of great interest allowing for the determination of the off-diagonal CKM matrix element |Vcd| at zero temperature.

Publ.-Id: 27050 - Permalink

Assisted Vacuum Decay by Time Dependent Electric Fields
Otto, A.; Oppitz, H.; Kämpfer, B.
We consider the vacuum decay by electron-positron pair production in spatially homogeneous, time dependent electric fields by means of quantum kinetic equations. Our focus is on the impact of various pulse shapes as envelopes of oscillating fields and the assistance effects in multi-scale fields, which are also seen in photons accompanying the creation and motion of pairs.


  • Secondary publication expected from 19.02.2019

Publ.-Id: 27049 - Permalink

Large scale structures of a turbulent Rayleigh-Bénard convection in a liquid metal layer confined by a moderate aspect ratio box
Akashi, M.; Tasaka, Y.; Yanagisawa, T.; Murai, Y.; Vogt, T.; Eckert, S.
We report laboratory experiments of Rayleigh-Bénard convection with a liquid metal, Prandtl number Pr = 0.03, in a rectangular cell with a moderate aspect ratio. Rayleigh number, Ra, was set at a range from 7.9 × 10^3 to 3.5 × 10^5 at which the thermal turbulence regime is expected. Multiple horizontal velocity profiles in the fluid layer by ultrasonic velocity profiling elucidated formations of several large scale flow structures with periodic oscillations. The flow structure has transitions as increasing Ra from a quasi-two-dimensional roll-like structure to a three-dimensional cell-like structure via unstable intermediate regimes with stepwise increase of its horizontal scale. By using observed Ra dependences of the frequency of oscillation and the velocity of large scale flow, we made up a model to explain the increase of horizontal scale. We evaluated effective viscosities and diffusivities based on the turbulent fluctuations, and found that the morphology of roll-like structure can be understood by using these effective values.
  • Lecture (Conference)
    The 70th Annual Meeting of the American Physical Society Division of Fluid Dynamics, 20.11.2017, Denver, USA

Publ.-Id: 27046 - Permalink

New Heterodinuclear Zn/Ln (Ln = Gd, Tb, Er, Yb) Complexes of Hexadentate N,N'-Bis(3-alkoxy-2-hydroxybenzyl)cyclohexane-1,2-diamines: Synthesis and Structure
Kelly, N.; Schnaars, K.; Gloe, K.; Doert, T.; Weigand, J. J.; Gloe, K.
Two N,N′-bis(3-alkoxy-2-hydroxybenzyl)cyclohexane-1,2-diamine proligands, H₂L¹ (R = OCH₃) and H₂L² (R = OC₂H₅), and five heterodinuclear Znᴵᴵ/Lnᴵᴵᴵ complexes, [Zn(L)(µ-CH₃COO)Ln(NO₃)₂], containing [L¹]²⁻ and Gd³⁺, Tb³⁺, Er³⁺, or Yb³⁺ and [L²]²⁻ and Yb³⁺ have been synthesised and structurally characterised. The complexes are isostructural and crystallise in the P2₁/n monoclinic space group. Zinc(II) is coordinated by the inner N₂O₂ donor set of the ligand and an oxygen of the bridging acetate anion; the lanthanide(III) ions possess an O₉ coordination environment involving the interaction with the ligand’s outer O₄ donor set, two bidentate nitrate ions, and the bridging acetate.

Publ.-Id: 27043 - Permalink

Investigation of heavy metal release at a municipal solid waste incineration facility - an excellent example for the unique potential of intrinsic radiotracer application to the investigation of industrial processes in chemical engineering
Jentsch, T. B. O.
Radiotracers are widespread in use for investigation of material transport processes in industry and environment. Often they are used for the measurement of the residence time distribution in continuously operating chemical engineering facilities and reactors. Mostly intrinsic or physical tracers are used for these purposes.

In case of phase transformation processes are in the focus of interest physical or extrinsic tracers are not the labelling material of choice. Intrinsic or chemical tracers are required in that case.

At example of the heavy metal release investigation at a municipal solid waste incineration facility the unique potential of intrinsic radiotracers will be demonstrated in the given paper.

Goal of the investigation at the municipal solid waste incineration facility reported in this paper was the behaviour study of different heavy metal species at various incineration conditions. With the help of short lived radioisotopes of copper (Cu-64) and zinc (Zn-69m) could be shown at which position of the incinerator and in which amount the heavy metal under investigation was released.

The experimental results of this investigation were an essential contribution for better understanding the processes inside the incinerator and to optimize the processing conditions.
Keywords: heavy metal release, radiotracer, municipal solid waste incineration, copper-64, zinc-69m,
  • Lecture (Conference)
    ICARST 2017 - International Conference on Applications of Radiation Science and Technology, 24.-28.04.2017, Wien, Österreich

Publ.-Id: 27039 - Permalink

PO-0619: Comparison of a nanoString and RNA microarray gene signature predicting LRC after PORT-C in HNSCC
Schmidt, S.; Linge, A.; Zwanenburg, A.; Leger, S.; Lohaus, F.; Gudziol, V.; Nowak, A.; Tinhofer, I.; Budach, V.; Sak, A.; Stuschke, M.; Balermpas, P.; Rödel, C.; Grosu, A. L.; Abdollahi, A.; Debus, J.; Belka, C.; Combs, S. E.; Mönnich, D.; Zips, D.; Baretton, G. B.; Buchholz, F.; Baumann, M.; Krause, M.; Löck, S.
A gene signature predicting loco-regional control (LRC) of locally advanced head and neck squamous cell carcinoma (HNSCC) after postoperative radiochemotherapy (PORTC) will be evaluated using nanoString and RNA microarray data. The prognostic power of the signature as well as the correlation between both methods is evaluated to underline the robustness of the proposed signature.


Publ.-Id: 27038 - Permalink

Pencil beam scanning treatments in free-breathing lung cancer patients–is 5 mm motion a limit?
Jakobi, A.; Perrin, R.; Knopf, A.; Richter, C.
To evaluate the dose degradation when treating lung cancer patie nts with proton pencil beam scanning during free-breathing. We assess if treatments without rescanning are feasible in order to avoid prolonged treatment time, especially for slow scanning facilities.


Publ.-Id: 27034 - Permalink

High-precision radiotherapy–Do we need better pre-treatment CT imaging?
Greilich, S.; Richter, C.
Computed tomography (CT) images from fan-beam medical grade scanners are the current gold standard for treatment planning in radiation oncology: they provide geometrically correct, reliable, and quantitative measures of photon attenuation in the patient. However, this information is not fully identical with the physical quantities needed for dose calculation and optimization and additional uncertainty is introduced by inferring them from the kV images. Also, the low soft tissue contrast in CT impacts delineation accuracy. While additional Imaging modalities are advocated as complementary – sometimes alternative – techniques to CT imaging, uncertainties in image registration can even deteriorate the quality of treatment planning. Dual-energy CT – i.e. using scans from two X-ray spectra or detection in two separate energy ranges – retains the virtues of computed tomography while it opens at the same time the possibility to overcome the restrictions mentioned. It can improve the accuracy of dose calculation and delineation and enables to abandon the use of a general translation rule (“Hounsfield look-up table”) for the photon attenuation (CT numbers) - replacing it by a patient-specific determination of radiological tissue quantities. DECT-derived quantities might additionally provide opportunities in advanced image analysis methods such as radiomics, i.e. the machine-learning-based approach for the prediction of patient outcome and treatment personalization. CT-based radiomics analyses might even be able to uncover information that can so far only be derived from additional multi-modal imaging. Currently, many applications based on innovations in pre-treatment CT imaging and image analysis are investigated that could have the potential to change clinical practice in future. This presentation is intended to set the stage for the focus session which tries to look into the question, which of These applications can find its way into routine clinical application.
  • Open Access LogoAbstract in refereed journal
    Biomedical Engineering / Biomedizinische Technik 62(2017), S292-S297
    DOI: 10.1515/bmt-2017-5057


Publ.-Id: 27032 - Permalink

PO-0819: Robustness evaluation of single-and multifield optimized proton plans for unilateral head and neck.
Cubillos-Mesías, M.; Baumann, M.; Troost, E. G. C.; Appold, S.; Krause, M.; Richter, C.; Stützer, K.
To compare 4 different proton pencil beam scanning (PBS) treatment approaches for unilateral head and neck cancer (HNC) targets in terms of robustness, including anatomical changes during the treatment course.


Publ.-Id: 27030 - Permalink

Modeling patterns of anatomical deformations in prostate patients undergoing radiation therapy with an endorectal ballon
Brion, E.; Richter, C.; Macq, B.; Stützer, K.; Exner, F.; Troost, E.; Hölscher, T.; Bondar, L.
External beam radiation therapy (EBRT) treats cancer by delivering daily fractions of radiation to a target volume. For prostate cancer, the target undergoes day-to-day variations in position, volume, and shape. For stereotactic photon and for proton EBRT, endorectal balloons (ERBs) can be used to limit variations. To date, patterns of non-rigid variations for patients with ERB have not been modeled. We extracted and modeled the patient-specific patterns of variations, using regularly acquired CT-images, non-rigid point cloud registration, and principal component analysis (PCA). For each patient, a non-rigid point-set registration method, called Coherent Point Drift, (CPD) was used to automatically generate landmark correspondences between all target shapes. To ensure accurate registrations, we tested and validated CPD by identifying parameter values leading to the smallest registration errors (surface matching error 0.13±0.09 mm). PCA demonstrated that 88±3.2% of the target motion could be explained using only 4 principal modes. The most dominant component of target motion is a squeezing and stretching in the anterior-posterior and superior-inferior directions. A PCA model of daily landmark displacements, generated using 6 to 10 CT-scans, could explain well the target motion for the CT-scans not included in the model (modeling error decreased from 1.83±0.8 mm for 6 CT-scans to 1.6±0.7 mm for 10 CT-scans). PCA modeling error was smaller than the naive approximation by the mean shape (approximation error 2.66±0.59 mm). Future work will investigate the use of the PCA-model to improve the accuracy of EBRT techniques that are highly susceptible to anatomical variations such as, proton therapy.
  • Abstract in refereed journal
    Proceedings of SPIE 10135(2017), 1013506
    DOI: 10.1117/12.2251933


Publ.-Id: 27028 - Permalink

Combined PET/MRI: Global Warming-Summary Report of the 6th International Workshop on PET/MRI, March 27-29, 2017, Tübingen,
Bailey, D. L.; Pichler, B. J.; Gückel, B.; Antoch, G.; Barthel, H.; Bhujwalla, Z. M.; Biskup, S.; Biswal, S.; Bitzer, M.; Boellaard, R.; Braren, R. F.; Brendle, C.; Brindle, K.; Chiti, A.; La Fougère, C.; Gillies, R.; Goh, V.; Goyen, M.; Hacker, M.; Heukamp, L.; Knudsen, G. M.; Krackhardt, A. M.; Law, I.; Morris, J. C.; Nikolaou, K.; Nuyts, J.; Ordonez, A. A.; Pantel, K.; Quick, H. H.; Riklund, K.; Sabri, O.; Sattler, B.; Troost, E.; Zaiss, M.; Zender, L.; Beyer, T.
The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both clinically and as a research tool, and attempted to chart future directions. The meeting addressed the use of PET/MRI and workflows in oncology, neurosciences, infection, inflammation and chronic pain syndromes, as well as deeper discussions about how best to characterise the tumour microenvironment, optimise the complementary information available from PET and MRI, and how advanced data mining and bioinformatics, as well as information from liquid biomarkers (circulating tumour cells and nucleic acids) and pathology, can be integrated to give a more complete characterisation of disease phenotype. Some issues that have dominated previous meetings, such as the accuracy of MR-based attenuation correction (AC) of the PET scan, were finally put to rest as having been adequately addressed for the majority of clinical situations. Likewise, the ability to standardise PET systems for use in multicentre trials was confirmed, thus removing a perceived barrier to larger clinical imaging trials. The meeting openly questioned whether PET/MRI should, in all cases, be used as a whole-body imaging modality or whether in many circumstances it would best be employed to give an in-depth study of previously identified disease in a single organ or region. The meeting concluded that there is still much work to be done in the integration of data from different fields and in developing a common language for all stakeholders involved. In addition, the participants advocated joint training and education for individuals who engage in routine PET/MRI. It was agreed that PET/MRI can enhance our understanding of normal and disrupted biology, and we are in a position to describe the in vivo nature of disease processes, metabolism, evolution of cancer and the monitoring of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care.

Publ.-Id: 27024 - Permalink

Atomistic Simulation of Interface-Driven Self-Alignment of Si-SiO2 Nanostructures
Prüfer, T.; Heinig, K. H.; Möller, W.; von Borany, J.
Si nanostructures are very promising candidates for optical and electrical applications. Charged nanocluster can be used for data storage [2]; their discrete energy levels can be used for logic operations; sponge nanostructures can be used as the ion conductor in fuel cells. The size-dependency of their energy levels makes them interesting for application in colour displays.
Among a lot of other methods to synthesize nanoclusters or sponges we present an approach which allows a selfalignment of nanostructures at an interface. The basic idea is to bring together Si, SiO2 and SiOx and anneal it to cause phase separation of SiOx. The interfaces between Si/SiOx and SiOx/SiO2 act as driving forces for the selfalignment of the separated Si and SiO2. To create SiOx we consider 2 processes: (i) Deposition of SiOx films by PVD or CVD and (ii) Ion beam Mixing of Si/SiO2 interfaces.
By PVD it’s possible to create arbitrary shapes of Si/SiO2/SiOx layerstacks. The subsequent annealing causes different effects at the interface. Mainly depending on the structure of the layerstack, but also on the annealing time, different reaction pathways can be observed. The system can end up with different numbers of cluster layers or sponge structures, aligned parallel to the interface. Here we show how and why it is possible to control the sizes, densities and distances of these structures.
The ion irradiation through a Si/SiO2 interface causes mixing of both phases and transforms the interface into SiOx.
This method is not that flexible as PVD, but it’s easier to be implemented into common industrial technologies, like the production of CMOS compatible devices. The reformation of the Si/SiO2 interface during heat treatment is again acting as a driving force for the self-alignment and forms a zone between the interface and the resulting nanostructures which is denuded of excess Si. In this case, sizes and density can be controlled by irradiation and annealing parameters.
Earlier studies [1] have proven the reliability of dot formations using ion beam mixing technologies for application as memories [2]. Here, we show simulation results for the formation of Si nanostructures at interfaces in layerstacks of Si, SiOx, SiO2 and basic principles of the driving forces for this kind of self-alignment. Computer simulations using the binary collision approximation (TRIDYN [3]) and the kinetic monte carlo method [4] are employed to subsequently describe the ion irradiation and annealing processes, respectively.
This part of the work is being funded by the European Union’s Horizon 2020 research and innovation program under Grant Agreement No 688072 (Project IONS4SET).
[1] T. Müller et al., Appl. Phys. Lett. 81 (2002) 3049; ibid. 85 (2004) 2373.
[2] K.H. Heinig et al., Appl. Phys. A77 (2003)17.
[3] W. Möller, W. Eckstein, Nucl. Instr. and Meth. in Phys. Res. B2 (1984) 814
[4] M. Strobel et al., Phys. Rev. B64 (2001)245422.
  • Lecture (Conference)
    Material Research Society Fall Meeting 2017, 26.11.-01.12.2017, Boston, United States of America

Publ.-Id: 27018 - Permalink

WTZ Russland - Transientenanalysen für schnelle Reaktoren
Kliem, S.ORC; Nikitin, E.; Rachamin, R.; Glivici-Cotruta, V.
Der Reaktordynamikcode DYN3D wird für Kernanalysen von Natrium-gekühlten schnellen Reaktoren (SFR) erweitert. In diesem Bericht werden neu implementierte thermomechanische Modelle für die adäquate Simulation von SFR-Transienten beschrieben, die die Simulation der axialen Wärmeausdehnung von Brennstäben und die radiale Ausdehnung des Reaktorkerns umfassen. Darüber hinaus wurde das Verfahren zur Erstellung von Querschnittsbibliotheken für DYN3D für SFR-Analysen erweitert. Die Verifizierung der neuen Modelle und der Querschnittserstellung erfolgte auf Vollkern-Ebene mit stationären Experimenten von der BFS-Testanlage des IPPE Obninsk und Daten des großen oxidischen Kerns des OECD/NEA-Benchmark und den Experimenten zum Zyklusende des Phenix-Kerns. Die DYN3D-Ergebnisse wurden mit der Monte-Carlo-Referenzlösung verglichen, die durch den SERPENT-Code berechnet wurde. Die Testergebnisse zeigen, dass die neu entwickelten Modelle die Wärmeausdeh-nungseffekte der Kernstruktur genau berücksichtigen können. Das neu entwickelte Verfahren zur Erstellung von Querschnittsbibliotheken wurde ebenfalls auf der Basis von SERPENT-Ergebnissen erfolgreich verifiziert. Zur Validierung wurden mehrere Tests, die sowohl stationäre als auch transiente Fälle aus den Phenix-Experimenten enthalten, mit DYN3D berechnet. Die DYN3D-Lösungen weisen eine gute Übereinstimmung mit den experimentellen Daten auf, was die Anwendbarkeit der Codes für Kernanalysen von Natrium-gekühlten schnellen Reaktoren bestätigt.
Keywords: DYN3D, SERPENT, Natrium gekühlter Reaktor, thermomechanische Modelle, Validierung
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-086 2018
    ISSN: 2191-8708

Publ.-Id: 27016 - Permalink

Process Simulation of Single Si Quantum Dot Formation for Single Electron Transistors
Prüfer, T.; Heinig, K. H.; Möller, W.; Hlawacek, G.; Xu, X.; Friedlund, C.; Djurabekova, F.; von Borany, J.
Conventional Lithography allows the fabrication of structures down to ~10 nm, being still too large for single electron transistors (SET) operating at room temperature (RT), which requires a tiny quantum dot (<5nm) embedded in SiO2, with tunnel distances to the source and drain <2nm. Here, we predict a fully CMOS-compatible method of self-assembly of a single Si quantum dot. We assume that 10…20nm thin nanopillars of a layer stack c-Si/6nm SiO2/30nm a-Si are made by conventional lithography. We predict that such a single dot is self-organized and self-assembled between the top and bottom silicon layer by phase separation of metastable SiOx. The SiOx is made by collisional mixing in the layer stack, which is simulated by TRI3DYN [1]. The phase separation of SiOx is described by 3D kinetic lattice Monte Carlo simulations [2]. Our results predict that a single Si nanodot forms if the volume of SiOx is smaller than (10nm)^3. This work has been funded by the European Union's Horizon 2020 research and innovation program under grant agreement No 688072.
[1] W. Möller; NIM B, 322, 23–33
[2] M. Strobel, K.H. Heinig, W. Möller, PRB 64, 245422
  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Deutschland

Publ.-Id: 27014 - Permalink

Influence of resistance and spin-torque bias dependence on the output power of MgO-based nano oscillators
Kowalska, E.; Fukushima, A.; Sluka, V.; Fowley, C.; Kákay, A.; Aleksandrov, Y.; Lindner, J.; Fassbender, J.; Yuasa, S.; Deac, A. M.
Spin-transfer torques (STTs) can be exploited in order to manipulate magnetic moments of nanomagnets, allowing for new consumer-oriented devices to be designed, such as tuneable radio-frequency spin-torque nano oscillators (STNOs) for wireless communication. Currently, the structure involving an MgO-based magnetic tunnel junction (MTJ) with hybrid geometry combining an IP reference layer and an out-of-plane free layer is the system of choice [1,2]. This configuration, Fig. 1a, maximizes the output power, reduces the critical current [3], and can allow for stable precession regardless of magnetic or applied current history [1,4,5].

Here, we experimentally observe an unusual curvature of the critical lines on the current-field phase diagram enclosing the region of steady-state dynamics (Fig. 2a) which has never been reported in similar metallic- or MTJ-based devices. Theoretically, we incorporate the angular dependence of the TMR (dRAP/dV) [6-8] and bias dependent spin-transfer torques [9-11] into the in-plane and the perpendicular STT and solve LLGS equation [12]. We find that the angular dependence of TMR introduces an asymmetry in the in-plane STT and gives rise to stable precession. Moreover, including the bias dependence of TMR (Fig. 1b) correctly reproduces the curvature of the dynamical region in the experimental phase diagram (Fig. 2b), gradually suppressing the induced asymmetry, and with it the output power. Therefore, the TMR ratio and its bias dependence are both equally crucial factors governing the performance of MTJ-based STNOs.
Keywords: STNO,MTJ,STT
  • Lecture (Conference)
    MMM 2017 - 62nd Annual Conference on Magnetism and Magnetic Materials, 06.-10.11.2017, Pittsburgh, USA

Publ.-Id: 27010 - Permalink

15 years of CW SRF operation at ELBE
Arnold, A.; Büchner, A.; Büttig, H.; Freitag, M.; Lehnert, U.; Michel, P.; Schneider, C.; Teichert, J.
ELBE is a compact, accelerator-driven photon and particle source. The variety of secondary radiation being offered extends from high-energy gamma rays to infrared and THz radiation as well as from neutrons to positrons and electrons. Since 2001 ELBE is operated as a user facility, providing more than 5500 hours of beamtime with an efficiency of more than 90% each year. The electron accelerator is based on four superconducting 9-cell TESLA cavities that are driven in CW operation to accelerate an average current of 1 mA up to beam energies of 40 MeV. Although these cavities performed well in the vertical test, they were limited by field emission from the very beginning to about 10 MV/m each. The reason is still unknown, but several candidates are being discussed. The prime suspect is particle contamination during cleanroom and beamline assembly but also a mechanism that allows particles to migrate from far away towards the cavity over an extended period of time might be possible. And also outgassing EPDM gaskets that are installed in the entire accelerator are a candidate for deterioration. Nevertheless, to ensure a reliable user operation, the performance of the cavities is determined in regular intervals by Q vs. E measurements and by means of high power RF processing and complete thermal cycling the performance could be partially returned to an earlier state. With the contribution we try to summarize our experiences in operating a superconducting CW LINAC over the last 15 years in an unclassified and probably dirty environment.
Keywords: CW, SRF, operation, ELBE, cryomodule
  • Invited lecture (Conferences)
    Operating SRF systems reliably in a "dirty" accelerator, 14.-15.09.2017, Berlin, Deutschland
  • Invited lecture (Conferences)
    TESLA Technology Collaboration Meeting, 06.-09.02.2018, Mailand, Italien

Publ.-Id: 27009 - Permalink

Cancer stem cells: Radioresistance, prediction of radiotherapy outcome and specific targets for combined treatments.
Krause, M.; Dubrovska, A.; Linge, A.; Baumann, M.
Inactivation of cancer stem cells (CSCs) is of utmost importance for tumor cure after radiotherapy. An increasing body of evidence complies with a higher radioresistance of CSCs compared to the mass of tumor cells, supporting the use of CSC related biomarkers for prediction of radiotherapy outcome. Treatment individualization strategies for patient groups with vastly different risk of recurrence will most likely require application of more than one biomarker. Specifically, inclusion of established biomarkers like tumor size for primary radio(chemo)therapy or human papilloma virus (HPV) infection status in head and neck squamous cell carcinoma seems to be of very high relevance. The high heterogeneity of CSC subclones along with changes of the functional behavior of individual tumors under treatment underlines the importance of the selection of the optimal timepoint(s) of biomarker evaluation, but also provides a potential therapeutic target for combined treatment approaches with irradiation.

Publ.-Id: 27005 - Permalink

PORTAF–postoperative radiotherapy of non-small cell lung cancer: accelerated versus conventional fractionation–study protocol for a randomized controlled trial
Bütof, R.; Simon, M.; Löck, S.; Troost, E.; Appold, S.; Krause, M.; Baumann, M.

In early-stage non-small cell lung cancer (NSCLC) without affected lymph nodes detected at staging, surgical resection is still the mainstay of treatment. However, in patients with metastatic mediastinal lymph nodes (pN2) or non-radically resected primary tumors (R1/R2), postoperative radiotherapy (possibly combined with chemotherapy) is indicated. So far, investigations about time factors affecting postoperative radiotherapy have only examined the waiting time defined as interval between surgery and start of radiotherapy, but not the overall treatment time (OTT) itself. Conversely, results from trials on primary radio(chemo)therapy in NSCLC show that longer OTT correlates with significantly worse local tumor control and overall survival rates. This time factor of primary radio(chemo)therapy is thought to mainly be based on repopulation of surviving tumor cells between irradiation fractions. It remains to be elucidated if such an effect also occurs when patients with NSCLC are treated with postoperative radiotherapy after surgery (and chemotherapy). Our own retrospective data suggest an advantage of shorter OTT also for postoperative radiotherapy in this patient group.

This is a multicenter, prospective randomized trial investigating whether an accelerated course of postoperative radiotherapy with photons or protons (7 fractions per week, 2 Gy fractions) improves locoregional tumor control in NSCLC patients in comparison to conventional fractionation (5 fractions per week, 2 Gy fractions). Target volumes and total radiation doses will be stratified in both treatment arms based on individual risk factors.

For the primary endpoint of the study we postulate an increase in local tumor control from 70% to 85% after 36 months. Secondary endpoints are overall survival of patients; local recurrence-free and distant metastases-free survival after 36 months; acute and late toxicity and quality of life for both treatment methods.

Publ.-Id: 26999 - Permalink

PO-0616: HPV, CSC marker expression and tumor hypoxia as prognosticators for LRC in patients with HNSCC
Linge, A.; Löck, S.; Krenn, C.; Appold, S.; Lohaus, F.; Schneider, M.; Nowak, A.; Gudziol, V.; Baretton, G. B.; Buchholz, F.; Baumann, M.; Krause, M.
PO-0616: HPV, CSC marker expression and tumor hypoxia as prognosticators for LRC in patients with HNSCC

Publ.-Id: 26997 - Permalink

PO-0968: The Role of epithelial to mesenchymal transition (EMT) as Biomarker for Radioresistance in HNSCC
Kurth, I.; Digomann, M.; Hein, L.; Linge, A.; Koi, L.; Loeck, S.; Maebert, K.; Stephan, H.; Peitzsch, C.; Krause, M.; Baumann, M.; Dubrovska, A.
PO-0968: The Role of epithelial to mesenchymal transition (EMT) as Biomarker for Radioresistance in HNSCC

Publ.-Id: 26996 - Permalink

Optimisation and stabilisation of cathepsin B-endopeptidase substrates: Towards a Cathepsin B-activated cell-penetrating peptide
Kuhne, K.; Behring, L.; Belter, B.; Neuber, C.; Wodtke, R.; Pietzsch, J.; Löser, R.
Cathepsin B (CTB), whose expression in tumours correlates with increased metastasis, therapy resistance, and generally poor prognosis, represents an excellent target for molecular imaging using radiotracers [1]. It is our aim to develop a CTB-specifc, substrate-based radiotracer based on activatable, poly-D-arginine-derived cell pentrating peptides [2]. Central prerequisite for such a probe is an endopeptidase substrate for CTB used as an activator sequence that shows efficient cleavage kinetics towards CTB and is stable in circulation and against other relevant cathepsins. After newly identifying the P4' position as major determinant of CTB endopeptidase specificity, we determined Val (kcat/KM=245 mM-1s-1, 16xGly) as the ideal amino acid at this position. In terms of stabilisation, we were able to increase serum half-life from 3.6 min to >1440 min by amino acid exchange at P1 and N2-methylation of a secondary cleavage site, while still retaining good cleavability by CTB. Analysis of cleavage by other relevant ctahepsins is currently ongoing.

[1] Löser & Pietzsch Front. Chem. 2015, 3, 37
[2] Jang et al. PNAS 2004, 101, 17867
  • Poster
    International Sympsosium on Bioorganic Chemistry (ISBOC-11), 27.-29.09.2017, Konstanz, Deutschland

Publ.-Id: 26995 - Permalink

Neutron imaging of particle laden Foam
Heitkam, S.; Lappan, T.; Eckert, S.; Eckert, K.
This presentation reports on the simultaneous measurement of foam structure and attached particles employing neutron imaging. An aqueous foam sample is placed in the NEUTRA beamline at PSI, enables for achieving a spatial resolution of less than 200 μm at a frame rate of more than 1 Hz. A forced drainage setup allows to control the liquid content of the foam. The averaged attenuation of the neutrons is demonstrated to yield the liquid fraction of the foam. Hydrophobized gadolinium particles of 200 μm diameter are added to the foam. Using two surfactants different levels of hydrophobicity are achieved. Depending on the drainage flow and the hydrophobicity, the particles are washed out of the foam with different rates. An avalanche-like motion of particle clusters is observed. The neutron radiography is demonstrated to yield unique insights into the unsteady froth flotation process.
Keywords: Neutron Imaging, Froth, Foam
  • Lecture (others)
    Seminarvortrag, 24.10.2017, Strasbourg, Frankreich

Publ.-Id: 26994 - Permalink

Using Lorentz forces to control the distribution of bubbles in a vertical tube filled with liquid metal
Heitkam, S.; Tschisgale, S.; Krull, B.; Wetzel, T.; Baake, E.; Fröhlich, J.
In this work, a method to increase the residence time of bubbles in tubes or pipes filled with liquid metal is investigated. Imposing a horizontal electric current and a perpendicular horizontal magnetic field generates an upward-directed Lorentz force. This force can counteract gravity and cause floating of bubbles. Even with homogeneous electric fields these float in the mean but fluctuate randomly within the swarm due to mutual interactions.
In the present case the cylindrical shape of the container furthermore creates inhomogeneous electric currents and an inhomogeneous force distribution resulting in a macroscopic convection pattern stirring the bubbles and further homogenising the spatial distribution of the bubbles.
Keywords: Magnetohydrodynamics, Bubbles, Flow

Publ.-Id: 26993 - Permalink

The Role of epithelial to mesenchymal transition (EMT) as Biomarker for Radioresistance in HNSCC
Kurth, I.; Digomann, D.; Hein, L.; Linge, A.; Koi, L.; Loeck, S.; Maebert, K.; Stephan, H.; Peitzsch, C.; Krause, M.; Baumann, M.; Dubrovska, A.
Purpose or Objective
It is described that epithelial – to -mesenchymal transition (EMT) plays an important role in head and neck squamous carcinomas (HNSCC) progression and resistance to therapy. Recent studies suggest that for instance the expression of EMT related microRNAs may cause intrinsic radioresistance in HNSCC. During the process of EMT epithelial cancer cells obtain a more mesenchymal –like motile and invasive phenotype, which has been argued to sustain survival and therapy resistance of those tumor cells and facilitate cancer progression. Radiotherapy is one of the main approaches to treat HNSCC. However, tumor radioresistance often impedes the success of radiotherapy and has been found to drive tumor aggressiveness and expansion. In this study we asked the question, if radioresistant HNSCC populations display EMT features on a molecular as well as on a functional level and whether we can correlate those characteristics to treatment outcome.
Material and Methods
We used multiple irradiated HNSCC lines (IR) as an established model to investigate the traits of radioresistance. Global gene expression analysis in vitro and on xenograft models and functional radiobiological analyis was applied.
Interestingly, global gene expression analysis revealed a negative correlation of genes associated with cell motility and migration in the IR derivatives of two HNSCC cell lines, namely Cal33, FaDu. We functionally validated those findings and screened for known EMT marks from literature by functional migration assays and EMT-related protein expression in several HNSCC model cell lines and established xenografts as well as in their IR derivatives in order to correlate the acquired findings to radiotherapy outcome. The only positive correlation was found for the initial before therapy protein expression in vitro and in vivo for Slug, a zinc - finger protein encoded by the SNAI2 gene and c-Met, a receptor tyrosine kinase encoded by the MET gene. Functional knockdown of Slug or c-Met expression let to radiosensitization in 3-D clonogenic survival assays of several HNSCC cell lines.
Currently the expression of these molecules is scored for clinical outcome to better understand the context of EMT biomarkers for HNSCC progression and the development of a potential well-directed combinational radiochemotherapy.
Keywords: EMT, radiotherapy, HNSCC, migration

Publ.-Id: 26992 - Permalink

Rücker, C.

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-01-30
    DOI: 10.14278/rodare.34


Publ.-Id: 26988 - Permalink

Measurement of foam flow using Ultrasound Doppler Velocimetry + Froth dynamics by Neutron Imaging
Heitkam, S.; Nauber, R.; Büttner, L.; Czarske, J.; Eckert, K.
The flowing behavior of liquid foam and froth is only scarcely investigated. One reason for that is, that no adequate measurement technique exists. Also, industrial flotation applications could be improved by monitoring the froth flow in the process.

In this work, the Ultrasound Doppler Velocimetry has been used to measure the velocity distribution inside liquid foam. To that end, an array of ultrasound transducers sends pulses into the foam and receiving the echoes. Sound pulses are reflected at moving particles and air-liquid interfaces. The echoes reveal the longitudinal velocity distribution on the beam axis. Multiplexing of the array allows for 2D-1C measurement.

Comparing with optical measurement it is demonstrated, that the velocity uncertainty at 2.5 Hz frame rate is below 15 percent and the spatial resolution better than 10 mm. These parameters allow for on-line monitoring of industrial processes as well as scientific investigation of three-dimensional froth and foam flows.
Keywords: Foam, Froth, Flotation, Ultrasound Dopller Velocimetry, Neutron Imaging
  • Lecture (Conference)
    Flotation17, 12.-16.11.2017, Cape Town, South Africa

Publ.-Id: 26982 - Permalink

Profile of European proton and carbon ion therapy centers assessed by the EORTC facility questionnaire.
Weber, D. C.; Abrunhosa-Branquinho, A.; Bolsi, A.; Kacperek, A.; Dendale, R.; Geismar, D.; Bachtiary, B.; Hall, A.; Heufelder, J.; Herfarth, K.; Debus, J.; Amichetti, M.; Krause, M.; Orecchia, R.; Vondracek, V.; Thariat, J.; Kajdrowicz, T.; Nilsson, K.; Grau, C.

We performed a survey using the modified EORTC Facility questionnaire (pFQ) to evaluate the human, technical and organizational resources of particle centers in Europe.

The modified pFQ consisted of 235 questions distributed in 11 sections accessible on line on an EORTC server. Fifteen centers from 8 countries completed the pFQ between May 2015 and December 2015.

The average number of patients treated per year and per particle center was 221 (range, 40-557). The majority (66.7%) of centers had pencil beam or raster scanning capability. Four (27%) centers were dedicated to eye treatment only. An increase in the patients-health professional FTE ratio was observed for eye tumor only centers when compared to other centers. All centers treated routinely chordomas/chondrosarcomas, brain tumors and sarcomas but rarely breast cancer. The majority of centers treated pediatric cases with particles. Only a minority of the queried institutions treated non-static targets.

As the number of particle centers coming online will increase, the experience with this treatment modality will rise in Europe. Children can currently be treated in these facilities in a majority of cases. The majority of these centers provide state of the art particle beam therapy.

Publ.-Id: 26981 - Permalink

Radiation Resistance in KRAS-Mutated Lung Cancer Is Enabled by Stem-like Properties Mediated by an Osteopontin-EGFR Pathway.
Wang, M.; Han, J.; Marcar, L.; Black, J.; Liu, Q.; Li, X.; Nagulapalli, K.; Sequist, L. V.; Mak, R. H.; Benes, C. H.; Hong, T. S.; Gurtner, K.; Krause, M.; Baumann, M.; Kang, J. X.; Whetstine, J. R.; Willers, H.
Lung cancers with activating KRAS mutations are characterized by treatment resistance and poor prognosis. In particular, the basis for their resistance to radiation therapy is poorly understood. Here, we describe a radiation resistance phenotype conferred by a stem-like subpopulation characterized by mitosis-like condensed chromatin (MLCC), high CD133 expression, invasive potential, and tumor-initiating properties. Mechanistic investigations defined a pathway involving osteopontin and the EGFR in promoting this phenotype. Osteopontin/EGFR-dependent MLCC protected cells against radiation-induced DNA double-strand breaks and repressed putative negative regulators of stem-like properties, such as CRMP1 and BIM. The MLCC-positive phenotype defined a subset of KRAS-mutated lung cancers that were enriched for co-occurring genomic alterations in TP53 and CDKN2A. Our results illuminate the basis for the radiation resistance of KRAS-mutated lung cancers, with possible implications for prognostic and therapeutic strategies. Cancer Res; 77(8); 2018-28. ©2017 AACR.

Publ.-Id: 26980 - Permalink

Heat shock protein 70 and tumor-infiltrating NK cells as prognostic indicators for patients with squamous cell carcinoma of the head and neck after radiochemotherapy: A multicentre retrospective study of the German Cancer Consortium
Stangl, S.; Tontcheva, N.; Sievert, W.; Shevtsov, M.; Niu, M.; Schmid, T.; Pigorsch, S.; Combs, S.; Haller, B.; Balermpas, P.; Rödel, F.; Rödel, C.; Fokas, E.; Krause, M.; Linge, A.; Lohaus, F.; Baumann, M.; Tinhofer, I.; Budach, V.; Stuschke, M.; Grosu, A.; Abdollahi, A.; Debus, J.; Belka, C.; Maihöfer, C.; Mönnich, D.; Zips, D.; Multhoff, G.
Tumor cells frequently overexpress heat shock protein 70 (Hsp70) and present it on their cell surface, where it can be recognized by pre-activated NK cells. In our retrospective study the expression of Hsp70 was determined in relation to tumor-infiltrating CD56+ NK cells in formalin-fixed paraffin embedded (FFPE) tumor specimens of patients with SCCHN (N = 145) as potential indicators for survival and disease recurrence. All patients received radical surgery and postoperative cisplatin-based radiochemotherapy (RCT). In general, Hsp70 expression was stronger, but with variable intensities, in tumor compared to normal tissues. Patients with high Hsp70 expressing tumors (scores 3-4) showed significantly decreased overall survival (OS; p = 0.008), local progression-free survival (LPFS; p = 0.034) and distant metastases-free survival (DMFS; p = 0.044), compared to those with low Hsp70 expression (scores 0-2), which remained significant after adjustment for relevant prognostic variables. The adverse prognostic value of a high Hsp70 expression for OS was also observed in patient cohorts with p16- (p = 0.001), p53- (p = 0.0003) and HPV16 DNA-negative (p = 0.001) tumors. The absence or low numbers of tumor-infiltrating CD56+ NK cells also correlated with significantly decreased OS (p = 0.0001), LPFS (p = 0.0009) and DMFS (p = 0.0001). A high Hsp70 expression and low numbers of tumor-infiltrating NK cells have the highest negative predictive value (p = 0.00004). In summary, a strong Hsp70 expression and low numbers of tumor-infiltrating NK cells correlate with unfavorable outcome following surgery and RCT in patients with SCCHN, and thus serve as negative prognostic markers.
Keywords: Hsp70; IHC; NK cells; SCCHN; prognostic biomarker; retrospective trial

Publ.-Id: 26978 - Permalink

Tumor heterogeneity determined with a γH2AX foci assay: A study in human head and neck squamous cell carcinoma (hHNSCC) models
Rassamegevanon, T.; Löck, S.; Range, U.; Krause, M.; Baumann, M.; von Neubeck, C.

This study aimed to analyze the intra-tumoral heterogeneity of γH2AX foci in tumor specimens following ex vivo radiation to evaluate the potential of γH2AX foci as predictors for radiosensitivity.

γH2AX foci were quantified in tumor specimens of 3hHNSCC tumor models with known differences in radiosensitivity after reoxygenation in culture medium (10h, 24h), single dose exposure (0Gy, 4Gy), and fixation 24h post-irradiation. Multiple, equally treated samples of the same tumor were analyzed for foci, normalized and fitted in a linear mixed-effects model.

The ex vivo reoxygenation time had no significant effect on γH2AX foci counts. A significant intra model heterogeneity could be shown for FaDu (p=0.033) but not for SKX (p=0.167) and UT-SCC-5 (p=0.082) tumors, respectively. All tumor models showed a significant intra-tumoral heterogeneity between specimens of the same tumor (p<0.01) or among microscopic fields of a particular tumor specimen (p<0.0001).

Similar results for ex vivo γH2AX foci between 10h and 24h reoxygenation time support the applicability of the assay in a clinical setting. The high intra-tumoral heterogeneity underlines the necessity of multiple analyzable samples per patient and therewith the need for an automated foci analysis.

Copyright © 2017 Elsevier B.V. All rights reserved.
Keywords: Biomarker; Radiosensitivity; Tumor heterogeneity; γH2AX foci

Publ.-Id: 26977 - Permalink

Development of a genetic sensor that eliminates p53 deficient cells
Mircetic, J.; Dietrich, A.; Paszkowski-Rogacz, M.; Krause, M.; Buchholz, F.
The TP53 gene fulfills a central role in protecting cells from genetic insult. Given this crucial role it might be surprising that p53 itself is not essential for cell survival. Indeed, TP53 is the single most mutated gene across different cancer types. Thus, both a theoretical and a question of significant practical applicability arise: can cells be programmed to make TP53 an essential gene? Here we present a genetic p53 sensor, in which the loss of p53 is coupled to the rise of HSV-TK expression. We show that the sensor can distinguish both p53 knockout and cells expressing a common TP53 cancer mutation from otherwise isogenic TP53 wild-type cells. Importantly, the system is sensitive enough to specifically target TP53 loss-of-function cells with the HSV-TK pro-drug Ganciclovir both in vitro and in vivo. Our work opens new ways to programming cell intrinsic transformation protection systems that rely on endogenous components.

Publ.-Id: 26974 - Permalink

Comparison of detection methods for HPV status as a prognostic marker for loco-regional control after radiochemotherapy in patients with HNSCC.
Linge, A.; Schötz, U.; Löck, S.; Lohaus, F.; von Neubeck, C.; Gudziol, V.; Nowak, A.; Tinhofer, I.; Budach, V.; Sak, A.; Stuschke, M.; Balermpas, P.; Rödel, C.; Bunea, H.; Grosu, A.; Abdollahi, A.; Debus, J.; Ganswindt, U.; Lauber, K.; Pigorsch, S.; Combs, S.; Mönnich, D.; Zips, D.; Baretton, G.; Buchholz, F.; Krause, M.; Belka, C.; Baumann, M.

To compare six HPV detection methods in pre-treatment FFPE tumour samples from patients with locally advanced head and neck squamous cell carcinoma (HNSCC) who received postoperative (N = 175) or primary (N = 90) radiochemotherapy.

HPV analyses included detection of (i) HPV16 E6/E7 RNA, (ii) HPV16 DNA (PCR-based arrays, A-PCR), (iii) HPV DNA (GP5+/GP6+ qPCR, (GP-PCR)), (iv) p16 (immunohistochemistry, p16 IHC), (v) combining p16 IHC and the A-PCR result and (vi) combining p16 IHC and the GP-PCR result. Differences between HPV positive and negative subgroups were evaluated for the primary endpoint loco-regional control (LRC) using Cox regression.

Correlation between the HPV detection methods was high (chi-squared test, p < 0.001). While p16 IHC analysis resulted in several false positive classifications, A-PCR, GP-PCR and the combination of p16 IHC and A-PCR or GP-PCR led to results comparable to RNA analysis. In both cohorts, Cox regression analyses revealed significantly prolonged LRC for patients with HPV positive tumours irrespective of the detection method.

The most stringent classification was obtained by detection of HPV16 RNA, or combining p16 IHC with A-PCR or GP-PCR. This approach revealed the lowest rate of recurrence in patients with tumours classified as HPV positive and therefore appears most suited for patient stratification in HPV-based clinical studies.
Keywords: DKTK-ROG; HNSCC; HPV; Loco-regional control; Radiochemotherapy; p16

Publ.-Id: 26970 - Permalink

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